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12 <title>Debian Policy Manual</title>
13 <author><qref id="authors">The Debian Policy Mailing List</qref></author>
14 <version>version &version;, &date;</version>
17 This manual describes the policy requirements for the Debian
18 distribution. This includes the structure and
19 contents of the Debian archive and several design issues of
20 the operating system, as well as technical requirements that
21 each package must satisfy to be included in the distribution.
26 Copyright © 1996,1997,1998 Ian Jackson
27 and Christian Schwarz.
30 These are the copyright dates of the original Policy manual.
31 Since then, this manual has been updated by many others. No
32 comprehensive collection of copyright notices for subsequent
37 This manual is free software; you may redistribute it and/or
38 modify it under the terms of the GNU General Public License
39 as published by the Free Software Foundation; either version
40 2, or (at your option) any later version.
44 This is distributed in the hope that it will be useful, but
45 <em>without any warranty</em>; without even the implied
46 warranty of merchantability or fitness for a particular
47 purpose. See the GNU General Public License for more
52 A copy of the GNU General Public License is available as
53 <file>/usr/share/common-licenses/GPL</file> in the Debian
54 distribution or on the World Wide Web at
55 <url id="http://www.gnu.org/copyleft/gpl.html"
56 name="the GNU General Public Licence">. You can also
57 obtain it by writing to the Free Software Foundation, Inc.,
58 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
66 <heading>About this manual</heading>
68 <heading>Scope</heading>
70 This manual describes the policy requirements for the Debian
71 distribution. This includes the structure and
72 contents of the Debian archive and several design issues of the
73 operating system, as well as technical requirements that
74 each package must satisfy to be included in the
79 This manual also describes Debian policy as it relates to
80 creating Debian packages. It is not a tutorial on how to build
81 packages, nor is it exhaustive where it comes to describing
82 the behavior of the packaging system. Instead, this manual
83 attempts to define the interface to the package management
84 system that the developers have to be conversant with.<footnote>
85 Informally, the criteria used for inclusion is that the
86 material meet one of the following requirements:
87 <taglist compact="compact">
88 <tag>Standard interfaces</tag>
90 The material presented represents an interface to
91 the packaging system that is mandated for use, and
92 is used by, a significant number of packages, and
93 therefore should not be changed without peer
94 review. Package maintainers can then rely on this
95 interface not changing, and the package management
96 software authors need to ensure compatibility with
97 this interface definition. (Control file and
98 changelog file formats are examples.)
100 <tag>Chosen Convention</tag>
102 If there are a number of technically viable choices
103 that can be made, but one needs to select one of
104 these options for inter-operability. The version
105 number format is one example.
108 Please note that these are not mutually exclusive;
109 selected conventions often become parts of standard
115 The footnotes present in this manual are
116 merely informative, and are not part of Debian policy itself.
120 The appendices to this manual are not necessarily normative,
121 either. Please see <ref id="pkg-scope"> for more information.
125 In the normative part of this manual,
126 the words <em>must</em>, <em>should</em> and
127 <em>may</em>, and the adjectives <em>required</em>,
128 <em>recommended</em> and <em>optional</em>, are used to
129 distinguish the significance of the various guidelines in
130 this policy document. Packages that do not conform to the
131 guidelines denoted by <em>must</em> (or <em>required</em>)
132 will generally not be considered acceptable for the Debian
133 distribution. Non-conformance with guidelines denoted by
134 <em>should</em> (or <em>recommended</em>) will generally be
135 considered a bug, but will not necessarily render a package
136 unsuitable for distribution. Guidelines denoted by
137 <em>may</em> (or <em>optional</em>) are truly optional and
138 adherence is left to the maintainer's discretion.
142 These classifications are roughly equivalent to the bug
143 severities <em>serious</em> (for <em>must</em> or
144 <em>required</em> directive violations), <em>minor</em>,
145 <em>normal</em> or <em>important</em>
146 (for <em>should</em> or <em>recommended</em> directive
147 violations) and <em>wishlist</em> (for <em>optional</em>
150 Compare RFC 2119. Note, however, that these words are
151 used in a different way in this document.
156 Much of the information presented in this manual will be
157 useful even when building a package which is to be
158 distributed in some other way or is intended for local use
164 <heading>New versions of this document</heading>
167 This manual is distributed via the Debian package
168 <package><url name="debian-policy"
169 id="http://packages.debian.org/debian-policy"></package>
170 (<httpsite>packages.debian.org</httpsite>
171 <httppath>/debian-policy</httppath>).
175 The current version of this document is also available from
176 the Debian web mirrors at
177 <tt><url name="/doc/debian-policy/"
178 id="http://www.debian.org/doc/debian-policy/"></tt>.
180 <httpsite>www.debian.org</httpsite>
181 <httppath>/doc/debian-policy/</httppath>)
182 Also available from the same directory are several other
183 formats: <file>policy.html.tar.gz</file>
184 (<httppath>/doc/debian-policy/policy.html.tar.gz</httppath>),
185 <file>policy.pdf.gz</file>
186 (<httppath>/doc/debian-policy/policy.pdf.gz</httppath>)
187 and <file>policy.ps.gz</file>
188 (<httppath>/doc/debian-policy/policy.ps.gz</httppath>).
192 The <package>debian-policy</package> package also includes the file
193 <file>upgrading-checklist.txt.gz</file> which indicates policy
194 changes between versions of this document.
199 <heading>Authors and Maintainers</heading>
202 Originally called "Debian GNU/Linux Policy Manual", this
203 manual was initially written in 1996 by Ian Jackson.
204 It was revised on November 27th, 1996 by David A. Morris.
205 Christian Schwarz added new sections on March 15th, 1997,
206 and reworked/restructured it in April-July 1997.
207 Christoph Lameter contributed the "Web Standard".
208 Julian Gilbey largely restructured it in 2001.
212 Since September 1998, the responsibility for the contents of
213 this document lies on the <url name="debian-policy mailing list"
214 id="mailto:debian-policy@lists.debian.org">. Proposals
215 are discussed there and inserted into policy after a certain
216 consensus is established.
217 <!-- insert shameless policy-process plug here eventually -->
218 The actual editing is done by a group of maintainers that have
219 no editorial powers. These are the current maintainers:
222 <item>Russ Allbery</item>
223 <item>Bill Allombert</item>
224 <item>Andrew McMillan</item>
225 <item>Manoj Srivastava</item>
226 <item>Colin Watson</item>
231 While the authors of this document have tried hard to avoid
232 typos and other errors, these do still occur. If you discover
233 an error in this manual or if you want to give any
234 comments, suggestions, or criticisms please send an email to
235 the Debian Policy List,
236 <email>debian-policy@lists.debian.org</email>, or submit a
237 bug report against the <tt>debian-policy</tt> package.
241 Please do not try to reach the individual authors or maintainers
242 of the Policy Manual regarding changes to the Policy.
247 <heading>Related documents</heading>
250 There are several other documents other than this Policy Manual
251 that are necessary to fully understand some Debian policies and
256 The external "sub-policy" documents are referred to in:
257 <list compact="compact">
258 <item><ref id="fhs"></item>
259 <item><ref id="virtual_pkg"></item>
260 <item><ref id="menus"></item>
261 <item><ref id="perl"></item>
262 <item><ref id="maintscriptprompt"></item>
263 <item><ref id="emacs"></item>
268 In addition to those, which carry the weight of policy, there
269 is the Debian Developer's Reference. This document describes
270 procedures and resources for Debian developers, but it is
271 <em>not</em> normative; rather, it includes things that don't
272 belong in the Policy, such as best practices for developers.
276 The Developer's Reference is available in the
277 <package>developers-reference</package> package.
278 It's also available from the Debian web mirrors at
279 <tt><url name="/doc/developers-reference/"
280 id="http://www.debian.org/doc/developers-reference/"></tt>.
284 Finally, a <qref id="copyrightformat">specification for
285 machine-readable copyright files</qref> is maintained as part of
286 the <package>debian-policy</package> package using the same
287 procedure as the other policy documents. Use of this format is
292 <sect id="definitions">
293 <heading>Definitions</heading>
296 The following terms are used in this Policy Manual:
300 The character encoding specified by ANSI X3.4-1986 and its
301 predecessor standards, referred to in MIME as US-ASCII, and
302 corresponding to an encoding in eight bits per character of
303 the first 128 <url id="http://www.unicode.org/"
304 name="Unicode"> characters, with the eighth bit always zero.
308 The transformation format (sometimes called encoding) of
309 <url id="http://www.unicode.org/" name="Unicode"> defined by
310 <url id="http://www.rfc-editor.org/rfc/rfc3629.txt"
311 name="RFC 3629">. UTF-8 has the useful property of having
312 ASCII as a subset, so any text encoded in ASCII is trivially
322 <heading>The Debian Archive</heading>
325 The Debian system is maintained and distributed as a
326 collection of <em>packages</em>. Since there are so many of
327 them (currently well over 15000), they are split into
328 <em>sections</em> and given <em>priorities</em> to simplify
329 the handling of them.
333 The effort of the Debian project is to build a free operating
334 system, but not every package we want to make accessible is
335 <em>free</em> in our sense (see the Debian Free Software
336 Guidelines, below), or may be imported/exported without
337 restrictions. Thus, the archive is split into areas<footnote>
338 The Debian archive software uses the term "component" internally
339 and in the Release file format to refer to the division of an
340 archive. The Debian Social Contract simply refers to "areas."
341 This document uses terminology similar to the Social Contract.
342 </footnote> based on their licenses and other restrictions.
346 The aims of this are:
348 <list compact="compact">
349 <item>to allow us to make as much software available as we can</item>
350 <item>to allow us to encourage everyone to write free software,
352 <item>to allow us to make it easy for people to produce
353 CD-ROMs of our system without violating any licenses,
354 import/export restrictions, or any other laws.</item>
359 The <em>main</em> archive area forms the <em>Debian distribution</em>.
363 Packages in the other archive areas (<tt>contrib</tt>,
364 <tt>non-free</tt>) are not considered to be part of the Debian
365 distribution, although we support their use and provide
366 infrastructure for them (such as our bug-tracking system and
367 mailing lists). This Debian Policy Manual applies to these
372 <heading>The Debian Free Software Guidelines</heading>
374 The Debian Free Software Guidelines (DFSG) form our
375 definition of "free software". These are:
377 <tag>1. Free Redistribution
380 The license of a Debian component may not restrict any
381 party from selling or giving away the software as a
382 component of an aggregate software distribution
383 containing programs from several different
384 sources. The license may not require a royalty or
385 other fee for such sale.
390 The program must include source code, and must allow
391 distribution in source code as well as compiled form.
393 <tag>3. Derived Works
396 The license must allow modifications and derived
397 works, and must allow them to be distributed under the
398 same terms as the license of the original software.
400 <tag>4. Integrity of The Author's Source Code
403 The license may restrict source-code from being
404 distributed in modified form <em>only</em> if the
405 license allows the distribution of "patch files"
406 with the source code for the purpose of modifying the
407 program at build time. The license must explicitly
408 permit distribution of software built from modified
409 source code. The license may require derived works to
410 carry a different name or version number from the
411 original software. (This is a compromise. The Debian
412 Project encourages all authors to not restrict any
413 files, source or binary, from being modified.)
415 <tag>5. No Discrimination Against Persons or Groups
418 The license must not discriminate against any person
421 <tag>6. No Discrimination Against Fields of Endeavor
424 The license must not restrict anyone from making use
425 of the program in a specific field of endeavor. For
426 example, it may not restrict the program from being
427 used in a business, or from being used for genetic
430 <tag>7. Distribution of License
433 The rights attached to the program must apply to all
434 to whom the program is redistributed without the need
435 for execution of an additional license by those
438 <tag>8. License Must Not Be Specific to Debian
441 The rights attached to the program must not depend on
442 the program's being part of a Debian system. If the
443 program is extracted from Debian and used or
444 distributed without Debian but otherwise within the
445 terms of the program's license, all parties to whom
446 the program is redistributed must have the same
447 rights as those that are granted in conjunction with
450 <tag>9. License Must Not Contaminate Other Software
453 The license must not place restrictions on other
454 software that is distributed along with the licensed
455 software. For example, the license must not insist
456 that all other programs distributed on the same medium
457 must be free software.
459 <tag>10. Example Licenses
462 The "GPL," "BSD," and "Artistic" licenses are examples of
463 licenses that we consider <em>free</em>.
470 <heading>Archive areas</heading>
473 <heading>The main archive area</heading>
476 The <em>main</em> archive area comprises the Debian
477 distribution. Only the packages in this area are considered
478 part of the distribution. None of the packages in
479 the <em>main</em> archive area require software outside of
480 that area to function. Anyone may use, share, modify and
481 redistribute the packages in this archive area
483 See <url id="http://www.debian.org/intro/free"
484 name="What Does Free Mean?"> for
485 more about what we mean by free software.
490 Every package in <em>main</em> must comply with the DFSG
491 (Debian Free Software Guidelines).
495 In addition, the packages in <em>main</em>
496 <list compact="compact">
498 must not require or recommend a package outside
499 of <em>main</em> for compilation or execution (thus, the
500 package must not declare a "Pre-Depends", "Depends",
501 "Recommends", "Build-Depends", or "Build-Depends-Indep"
502 relationship on a non-<em>main</em> package),
505 must not be so buggy that we refuse to support them,
509 must meet all policy requirements presented in this
518 <heading>The contrib archive area</heading>
521 The <em>contrib</em> archive area contains supplemental
522 packages intended to work with the Debian distribution, but
523 which require software outside of the distribution to either
528 Every package in <em>contrib</em> must comply with the DFSG.
532 In addition, the packages in <em>contrib</em>
533 <list compact="compact">
535 must not be so buggy that we refuse to support them,
539 must meet all policy requirements presented in this
546 Examples of packages which would be included in
547 <em>contrib</em> are:
548 <list compact="compact">
550 free packages which require <em>contrib</em>,
551 <em>non-free</em> packages or packages which are not
552 in our archive at all for compilation or execution,
556 wrapper packages or other sorts of free accessories for
563 <sect1 id="non-free">
564 <heading>The non-free archive area</heading>
567 The <em>non-free</em> archive area contains supplemental
568 packages intended to work with the Debian distribution that do
569 not comply with the DFSG or have other problems that make
570 their distribution problematic. They may not comply with all
571 of the policy requirements in this manual due to restrictions
572 on modifications or other limitations.
576 Packages must be placed in <em>non-free</em> if they are
577 not compliant with the DFSG or are encumbered by patents
578 or other legal issues that make their distribution
583 In addition, the packages in <em>non-free</em>
584 <list compact="compact">
586 must not be so buggy that we refuse to support them,
590 must meet all policy requirements presented in this
591 manual that it is possible for them to meet.
593 It is possible that there are policy
594 requirements which the package is unable to
595 meet, for example, if the source is
596 unavailable. These situations will need to be
597 handled on a case-by-case basis.
606 <sect id="pkgcopyright">
607 <heading>Copyright considerations</heading>
610 Every package must be accompanied by a verbatim copy of its
611 copyright information and distribution license in the file
612 <file>/usr/share/doc/<var>package</var>/copyright</file>
613 (see <ref id="copyrightfile"> for further details).
617 We reserve the right to restrict files from being included
618 anywhere in our archives if
619 <list compact="compact">
621 their use or distribution would break a law,
624 there is an ethical conflict in their distribution or
628 we would have to sign a license for them, or
631 their distribution would conflict with other project
638 Programs whose authors encourage the user to make
639 donations are fine for the main distribution, provided
640 that the authors do not claim that not donating is
641 immoral, unethical, illegal or something similar; in such
642 a case they must go in <em>non-free</em>.
646 Packages whose copyright permission notices (or patent
647 problems) do not even allow redistribution of binaries
648 only, and where no special permission has been obtained,
649 must not be placed on the Debian FTP site and its mirrors
654 Note that under international copyright law (this applies
655 in the United States, too), <em>no</em> distribution or
656 modification of a work is allowed without an explicit
657 notice saying so. Therefore a program without a copyright
658 notice <em>is</em> copyrighted and you may not do anything
659 to it without risking being sued! Likewise if a program
660 has a copyright notice but no statement saying what is
661 permitted then nothing is permitted.
665 Many authors are unaware of the problems that restrictive
666 copyrights (or lack of copyright notices) can cause for
667 the users of their supposedly-free software. It is often
668 worthwhile contacting such authors diplomatically to ask
669 them to modify their license terms. However, this can be a
670 politically difficult thing to do and you should ask for
671 advice on the <tt>debian-legal</tt> mailing list first, as
676 When in doubt about a copyright, send mail to
677 <email>debian-legal@lists.debian.org</email>. Be prepared
678 to provide us with the copyright statement. Software
679 covered by the GPL, public domain software and BSD-like
680 copyrights are safe; be wary of the phrases "commercial
681 use prohibited" and "distribution restricted".
685 <sect id="subsections">
686 <heading>Sections</heading>
689 The packages in the archive areas <em>main</em>,
690 <em>contrib</em> and <em>non-free</em> are grouped further into
691 <em>sections</em> to simplify handling.
695 The archive area and section for each package should be
696 specified in the package's <tt>Section</tt> control record (see
697 <ref id="f-Section">). However, the maintainer of the Debian
698 archive may override this selection to ensure the consistency of
699 the Debian distribution. The <tt>Section</tt> field should be
701 <list compact="compact">
703 <em>section</em> if the package is in the
704 <em>main</em> archive area,
707 <em>area/section</em> if the package is in
708 the <em>contrib</em> or <em>non-free</em>
715 The Debian archive maintainers provide the authoritative
716 list of sections. At present, they are:
717 <em>admin</em>, <em>cli-mono</em>, <em>comm</em>, <em>database</em>,
718 <em>devel</em>, <em>debug</em>, <em>doc</em>, <em>editors</em>,
719 <em>education</em>, <em>electronics</em>, <em>embedded</em>,
720 <em>fonts</em>, <em>games</em>, <em>gnome</em>, <em>graphics</em>,
721 <em>gnu-r</em>, <em>gnustep</em>, <em>hamradio</em>, <em>haskell</em>,
722 <em>httpd</em>, <em>interpreters</em>, <em>introspection</em>,
723 <em>java</em>, <em>kde</em>, <em>kernel</em>, <em>libs</em>,
724 <em>libdevel</em>, <em>lisp</em>, <em>localization</em>,
725 <em>mail</em>, <em>math</em>, <em>metapackages</em>, <em>misc</em>,
726 <em>net</em>, <em>news</em>, <em>ocaml</em>, <em>oldlibs</em>,
727 <em>otherosfs</em>, <em>perl</em>, <em>php</em>, <em>python</em>,
728 <em>ruby</em>, <em>science</em>, <em>shells</em>, <em>sound</em>,
729 <em>tex</em>, <em>text</em>, <em>utils</em>, <em>vcs</em>,
730 <em>video</em>, <em>web</em>, <em>x11</em>, <em>xfce</em>,
731 <em>zope</em>. The additional section <em>debian-installer</em>
732 contains special packages used by the installer and is not used
733 for normal Debian packages.
737 For more information about the sections and their definitions,
738 see the <url id="http://packages.debian.org/unstable/"
739 name="list of sections in unstable">.
743 <sect id="priorities">
744 <heading>Priorities</heading>
747 Each package should have a <em>priority</em> value, which is
748 included in the package's <em>control record</em>
749 (see <ref id="f-Priority">).
750 This information is used by the Debian package management tools to
751 separate high-priority packages from less-important packages.
755 The following <em>priority levels</em> are recognized by the
756 Debian package management tools.
758 <tag><tt>required</tt></tag>
760 Packages which are necessary for the proper
761 functioning of the system (usually, this means that
762 dpkg functionality depends on these packages).
763 Removing a <tt>required</tt> package may cause your
764 system to become totally broken and you may not even
765 be able to use <prgn>dpkg</prgn> to put things back,
766 so only do so if you know what you are doing. Systems
767 with only the <tt>required</tt> packages are probably
768 unusable, but they do have enough functionality to
769 allow the sysadmin to boot and install more software.
771 <tag><tt>important</tt></tag>
773 Important programs, including those which one would
774 expect to find on any Unix-like system. If the
775 expectation is that an experienced Unix person who
776 found it missing would say "What on earth is going on,
777 where is <prgn>foo</prgn>?", it must be an
778 <tt>important</tt> package.<footnote>
779 This is an important criterion because we are
780 trying to produce, amongst other things, a free
783 Other packages without which the system will not run
784 well or be usable must also have priority
785 <tt>important</tt>. This does
786 <em>not</em> include Emacs, the X Window System, TeX
787 or any other large applications. The
788 <tt>important</tt> packages are just a bare minimum of
789 commonly-expected and necessary tools.
791 <tag><tt>standard</tt></tag>
793 These packages provide a reasonably small but not too
794 limited character-mode system. This is what will be
795 installed by default if the user doesn't select anything
796 else. It doesn't include many large applications.
798 <tag><tt>optional</tt></tag>
800 (In a sense everything that isn't required is
801 optional, but that's not what is meant here.) This is
802 all the software that you might reasonably want to
803 install if you didn't know what it was and don't have
804 specialized requirements. This is a much larger system
805 and includes the X Window System, a full TeX
806 distribution, and many applications. Note that
807 optional packages should not conflict with each other.
809 <tag><tt>extra</tt></tag>
811 This contains all packages that conflict with others
812 with required, important, standard or optional
813 priorities, or are only likely to be useful if you
814 already know what they are or have specialized
815 requirements (such as packages containing only detached
822 Packages must not depend on packages with lower priority
823 values (excluding build-time dependencies). In order to
824 ensure this, the priorities of one or more packages may need
833 <heading>Binary packages</heading>
836 The Debian distribution is based on the Debian
837 package management system, called <prgn>dpkg</prgn>. Thus,
838 all packages in the Debian distribution must be provided
839 in the <tt>.deb</tt> file format.
843 A <tt>.deb</tt> package contains two sets of files: a set of files
844 to install on the system when the package is installed, and a set
845 of files that provide additional metadata about the package or
846 which are executed when the package is installed or removed. This
847 second set of files is called <em>control information files</em>.
848 Among those files are the package maintainer scripts
849 and <file>control</file>, the <qref id="binarycontrolfiles">binary
850 package control file</qref> that contains the control fields for
851 the package. Other control information files
852 include <qref id="sharedlibs-shlibdeps">the <file>shlibs</file>
853 file</qref> used to store shared library dependency information
854 and the <file>conffiles</file> file that lists the package's
855 configuration files (described in <ref id="config-files">).
859 There is unfortunately a collision of terminology here between
860 control information files and files in the Debian control file
861 format. Throughout this document, a <em>control file</em> refers
862 to a file in the Debian control file format. These files are
863 documented in <ref id="controlfields">. Only files referred to
864 specifically as <em>control information files</em> are the files
865 included in the control information file member of
866 the <file>.deb</file> file format used by binary packages. Most
867 control information files are not in the Debian control file
872 <heading>The package name</heading>
875 Every package must have a name that's unique within the Debian
880 The package name is included in the control field
881 <tt>Package</tt>, the format of which is described
882 in <ref id="f-Package">.
883 The package name is also included as a part of the file name
884 of the <tt>.deb</tt> file.
889 <heading>The version of a package</heading>
892 Every package has a version number recorded in its
893 <tt>Version</tt> control file field, described in
894 <ref id="f-Version">.
898 The package management system imposes an ordering on version
899 numbers, so that it can tell whether packages are being up- or
900 downgraded and so that package system front end applications
901 can tell whether a package it finds available is newer than
902 the one installed on the system. The version number format
903 has the most significant parts (as far as comparison is
904 concerned) at the beginning.
908 If an upstream package has problematic version numbers they
909 should be converted to a sane form for use in the
910 <tt>Version</tt> field.
914 <heading>Version numbers based on dates</heading>
917 In general, Debian packages should use the same version
918 numbers as the upstream sources. However, upstream version
919 numbers based on some date formats (sometimes used for
920 development or "snapshot" releases) will not be ordered
921 correctly by the package management software. For
922 example, <prgn>dpkg</prgn> will consider "96May01" to be
923 greater than "96Dec24".
927 To prevent having to use epochs for every new upstream
928 version, the date-based portion of any upstream version number
929 should be given in a way that sorts correctly: four-digit year
930 first, followed by a two-digit numeric month, followed by a
931 two-digit numeric date, possibly with punctuation between the
936 Native Debian packages (i.e., packages which have been written
937 especially for Debian) whose version numbers include dates
938 should also follow these rules. If punctuation is desired
939 between the date components, remember that hyphen (<tt>-</tt>)
940 cannot be used in native package versions. Period
941 (<tt>.</tt>) is normally a good choice.
947 <sect id="maintainer">
948 <heading>The maintainer of a package</heading>
951 Every package must have a maintainer, except for orphaned
952 packages as described below. The maintainer may be one person
953 or a group of people reachable from a common email address, such
954 as a mailing list. The maintainer is responsible for
955 maintaining the Debian packaging files, evaluating and
956 responding appropriately to reported bugs, uploading new
957 versions of the package (either directly or through a sponsor),
958 ensuring that the package is placed in the appropriate archive
959 area and included in Debian releases as appropriate for the
960 stability and utility of the package, and requesting removal of
961 the package from the Debian distribution if it is no longer
962 useful or maintainable.
966 The maintainer must be specified in the <tt>Maintainer</tt>
967 control field with their correct name and a working email
968 address. The email address given in the <tt>Maintainer</tt>
969 control field must accept mail from those role accounts in
970 Debian used to send automated mails regarding the package. This
971 includes non-spam mail from the bug-tracking system, all mail
972 from the Debian archive maintenance software, and other role
973 accounts or automated processes that are commonly agreed on by
974 the project.<footnote>
975 A sample implementation of such a whitelist written for the
976 Mailman mailing list management software is used for mailing
977 lists hosted by alioth.debian.org.
979 If one person or team maintains several packages, they should
980 use the same form of their name and email address in
981 the <tt>Maintainer</tt> fields of those packages.
985 The format of the <tt>Maintainer</tt> control field is
986 described in <ref id="f-Maintainer">.
990 If the maintainer of the package is a team of people with a
991 shared email address, the <tt>Uploaders</tt> control field must
992 be present and must contain at least one human with their
993 personal email address. See <ref id="f-Uploaders"> for the
994 syntax of that field.
998 An orphaned package is one with no current maintainer. Orphaned
999 packages should have their <tt>Maintainer</tt> control field set
1000 to <tt>Debian QA Group <packages@qa.debian.org></tt>.
1001 These packages are considered maintained by the Debian project
1002 as a whole until someone else volunteers to take over
1003 maintenance.<footnote>
1004 The detailed procedure for gracefully orphaning a package can
1005 be found in the Debian Developer's Reference
1006 (see <ref id="related">).
1011 <sect id="descriptions">
1012 <heading>The description of a package</heading>
1015 Every Debian package must have a <tt>Description</tt> control
1016 field which contains a synopsis and extended description of the
1017 package. Technical information about the format of the
1018 <tt>Description</tt> field is in <ref id="f-Description">.
1022 The description should describe the package (the program) to a
1023 user (system administrator) who has never met it before so that
1024 they have enough information to decide whether they want to
1025 install it. This description should not just be copied verbatim
1026 from the program's documentation.
1030 Put important information first, both in the synopsis and
1031 extended description. Sometimes only the first part of the
1032 synopsis or of the description will be displayed. You can
1033 assume that there will usually be a way to see the whole
1034 extended description.
1038 The description should also give information about the
1039 significant dependencies and conflicts between this package
1040 and others, so that the user knows why these dependencies and
1041 conflicts have been declared.
1045 Instructions for configuring or using the package should
1046 not be included (that is what installation scripts,
1047 manual pages, info files, etc., are for). Copyright
1048 statements and other administrivia should not be included
1049 either (that is what the copyright file is for).
1052 <sect1 id="synopsis"><heading>The single line synopsis</heading>
1055 The single line synopsis should be kept brief - certainly
1056 under 80 characters.
1060 Do not include the package name in the synopsis line. The
1061 display software knows how to display this already, and you
1062 do not need to state it. Remember that in many situations
1063 the user may only see the synopsis line - make it as
1064 informative as you can.
1069 <sect1 id="extendeddesc"><heading>The extended description</heading>
1072 Do not try to continue the single line synopsis into the
1073 extended description. This will not work correctly when
1074 the full description is displayed, and makes no sense
1075 where only the summary (the single line synopsis) is
1080 The extended description should describe what the package
1081 does and how it relates to the rest of the system (in terms
1082 of, for example, which subsystem it is which part of).
1086 The description field needs to make sense to anyone, even
1087 people who have no idea about any of the things the
1088 package deals with.<footnote>
1089 The blurb that comes with a program in its
1090 announcements and/or <prgn>README</prgn> files is
1091 rarely suitable for use in a description. It is
1092 usually aimed at people who are already in the
1093 community where the package is used.
1101 <sect id="dependencies">
1102 <heading>Dependencies</heading>
1105 Every package must specify the dependency information
1106 about other packages that are required for the first to
1111 For example, a dependency entry must be provided for any
1112 shared libraries required by a dynamically-linked executable
1113 binary in a package.
1117 Packages are not required to declare any dependencies they
1118 have on other packages which are marked <tt>Essential</tt>
1119 (see below), and should not do so unless they depend on a
1120 particular version of that package.<footnote>
1122 Essential is needed in part to avoid unresolvable dependency
1123 loops on upgrade. If packages add unnecessary dependencies
1124 on packages in this set, the chances that there
1125 <strong>will</strong> be an unresolvable dependency loop
1126 caused by forcing these Essential packages to be configured
1127 first before they need to be is greatly increased. It also
1128 increases the chances that frontends will be unable to
1129 <strong>calculate</strong> an upgrade path, even if one
1133 Also, functionality is rarely ever removed from the
1134 Essential set, but <em>packages</em> have been removed from
1135 the Essential set when the functionality moved to a
1136 different package. So depending on these packages <em>just
1137 in case</em> they stop being essential does way more harm
1144 Sometimes, unpacking one package requires that another package
1145 be first unpacked <em>and</em> configured. In this case, the
1146 depending package must specify this dependency in
1147 the <tt>Pre-Depends</tt> control field.
1151 You should not specify a <tt>Pre-Depends</tt> entry for a
1152 package before this has been discussed on the
1153 <tt>debian-devel</tt> mailing list and a consensus about
1154 doing that has been reached.
1158 The format of the package interrelationship control fields is
1159 described in <ref id="relationships">.
1163 <sect id="virtual_pkg">
1164 <heading>Virtual packages</heading>
1167 Sometimes, there are several packages which offer
1168 more-or-less the same functionality. In this case, it's
1169 useful to define a <em>virtual package</em> whose name
1170 describes that common functionality. (The virtual
1171 packages only exist logically, not physically; that's why
1172 they are called <em>virtual</em>.) The packages with this
1173 particular function will then <em>provide</em> the virtual
1174 package. Thus, any other package requiring that function
1175 can simply depend on the virtual package without having to
1176 specify all possible packages individually.
1180 All packages should use virtual package names where
1181 appropriate, and arrange to create new ones if necessary.
1182 They should not use virtual package names (except privately,
1183 amongst a cooperating group of packages) unless they have
1184 been agreed upon and appear in the list of virtual package
1185 names. (See also <ref id="virtual">)
1189 The latest version of the authoritative list of virtual
1190 package names can be found in the <tt>debian-policy</tt> package.
1191 It is also available from the Debian web mirrors at
1192 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1193 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1197 The procedure for updating the list is described in the preface
1204 <heading>Base system</heading>
1207 The <tt>base system</tt> is a minimum subset of the Debian
1208 system that is installed before everything else
1209 on a new system. Only very few packages are allowed to form
1210 part of the base system, in order to keep the required disk
1215 The base system consists of all those packages with priority
1216 <tt>required</tt> or <tt>important</tt>. Many of them will
1217 be tagged <tt>essential</tt> (see below).
1222 <heading>Essential packages</heading>
1225 Essential is defined as the minimal set of functionality that
1226 must be available and usable on the system at all times, even
1227 when packages are in an unconfigured (but unpacked) state.
1228 Packages are tagged <tt>essential</tt> for a system using the
1229 <tt>Essential</tt> control field. The format of the
1230 <tt>Essential</tt> control field is described in <ref
1235 Since these packages cannot be easily removed (one has to
1236 specify an extra <em>force option</em> to
1237 <prgn>dpkg</prgn> to do so), this flag must not be used
1238 unless absolutely necessary. A shared library package
1239 must not be tagged <tt>essential</tt>; dependencies will
1240 prevent its premature removal, and we need to be able to
1241 remove it when it has been superseded.
1245 Since dpkg will not prevent upgrading of other packages
1246 while an <tt>essential</tt> package is in an unconfigured
1247 state, all <tt>essential</tt> packages must supply all of
1248 their core functionality even when unconfigured. If the
1249 package cannot satisfy this requirement it must not be
1250 tagged as essential, and any packages depending on this
1251 package must instead have explicit dependency fields as
1256 Maintainers should take great care in adding any programs,
1257 interfaces, or functionality to <tt>essential</tt> packages.
1258 Packages may assume that functionality provided by
1259 <tt>essential</tt> packages is always available without
1260 declaring explicit dependencies, which means that removing
1261 functionality from the Essential set is very difficult and is
1262 almost never done. Any capability added to an
1263 <tt>essential</tt> package therefore creates an obligation to
1264 support that capability as part of the Essential set in
1269 You must not tag any packages <tt>essential</tt> before
1270 this has been discussed on the <tt>debian-devel</tt>
1271 mailing list and a consensus about doing that has been
1276 <sect id="maintscripts">
1277 <heading>Maintainer Scripts</heading>
1280 The package installation scripts should avoid producing
1281 output which is unnecessary for the user to see and
1282 should rely on <prgn>dpkg</prgn> to stave off boredom on
1283 the part of a user installing many packages. This means,
1284 amongst other things, using the <tt>--quiet</tt> option on
1285 <prgn>install-info</prgn>.
1289 Errors which occur during the execution of an installation
1290 script must be checked and the installation must not
1291 continue after an error.
1295 Note that in general <ref id="scripts"> applies to package
1296 maintainer scripts, too.
1300 You should not use <prgn>dpkg-divert</prgn> on a file belonging
1301 to another package without consulting the maintainer of that
1302 package first. When adding or removing diversions, package
1303 maintainer scripts must provide the <tt>--package</tt> flag
1304 to <prgn>dpkg-divert</prgn> and must not use <tt>--local</tt>.
1308 All packages which supply an instance of a common command
1309 name (or, in general, filename) should generally use
1310 <prgn>update-alternatives</prgn>, so that they may be
1311 installed together. If <prgn>update-alternatives</prgn>
1312 is not used, then each package must use
1313 <tt>Conflicts</tt> to ensure that other packages are
1314 de-installed. (In this case, it may be appropriate to
1315 specify a conflict against earlier versions of something
1316 that previously did not use
1317 <prgn>update-alternatives</prgn>; this is an exception to
1318 the usual rule that versioned conflicts should be
1322 <sect1 id="maintscriptprompt">
1323 <heading>Prompting in maintainer scripts</heading>
1325 Package maintainer scripts may prompt the user if
1326 necessary. Prompting must be done by communicating
1327 through a program, such as <prgn>debconf</prgn>, which
1328 conforms to the Debian Configuration Management
1329 Specification, version 2 or higher.
1333 Packages which are essential, or which are dependencies of
1334 essential packages, may fall back on another prompting method
1335 if no such interface is available when they are executed.
1339 The Debian Configuration Management Specification is included
1340 in the <file>debconf_specification</file> files in the
1341 <package>debian-policy</package> package.
1342 It is also available from the Debian web mirrors at
1343 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1344 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1348 Packages which use the Debian Configuration Management
1349 Specification may contain the additional control information
1350 files <file>config</file>
1351 and <file>templates</file>. <file>config</file> is an
1352 additional maintainer script used for package configuration,
1353 and <file>templates</file> contains templates used for user
1354 prompting. The <prgn>config</prgn> script might be run before
1355 the <prgn>preinst</prgn> script and before the package is
1356 unpacked or any of its dependencies or pre-dependencies are
1357 satisfied. Therefore it must work using only the tools
1358 present in <em>essential</em> packages.<footnote>
1359 <package>Debconf</package> or another tool that
1360 implements the Debian Configuration Management
1361 Specification will also be installed, and any
1362 versioned dependencies on it will be satisfied
1363 before preconfiguration begins.
1368 Packages which use the Debian Configuration Management
1369 Specification must allow for translation of their user-visible
1370 messages by using a gettext-based system such as the one
1371 provided by the <package>po-debconf</package> package.
1375 Packages should try to minimize the amount of prompting
1376 they need to do, and they should ensure that the user
1377 will only ever be asked each question once. This means
1378 that packages should try to use appropriate shared
1379 configuration files (such as <file>/etc/papersize</file> and
1380 <file>/etc/news/server</file>), and shared
1381 <package>debconf</package> variables rather than each
1382 prompting for their own list of required pieces of
1387 It also means that an upgrade should not ask the same
1388 questions again, unless the user has used
1389 <tt>dpkg --purge</tt> to remove the package's configuration.
1390 The answers to configuration questions should be stored in an
1391 appropriate place in <file>/etc</file> so that the user can
1392 modify them, and how this has been done should be
1397 If a package has a vitally important piece of
1398 information to pass to the user (such as "don't run me
1399 as I am, you must edit the following configuration files
1400 first or you risk your system emitting badly-formatted
1401 messages"), it should display this in the
1402 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1403 prompt the user to hit return to acknowledge the
1404 message. Copyright messages do not count as vitally
1405 important (they belong in
1406 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1407 neither do instructions on how to use a program (these
1408 should be in on-line documentation, where all the users
1413 Any necessary prompting should almost always be confined
1414 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1415 script. If it is done in the <prgn>postinst</prgn>, it
1416 should be protected with a conditional so that
1417 unnecessary prompting doesn't happen if a package's
1418 installation fails and the <prgn>postinst</prgn> is
1419 called with <tt>abort-upgrade</tt>,
1420 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1430 <heading>Source packages</heading>
1432 <sect id="standardsversion">
1433 <heading>Standards conformance</heading>
1436 Source packages should specify the most recent version number
1437 of this policy document with which your package complied
1438 when it was last updated.
1442 This information may be used to file bug reports
1443 automatically if your package becomes too much out of date.
1447 The version is specified in the <tt>Standards-Version</tt>
1449 The format of the <tt>Standards-Version</tt> field is
1450 described in <ref id="f-Standards-Version">.
1454 You should regularly, and especially if your package has
1455 become out of date, check for the newest Policy Manual
1456 available and update your package, if necessary. When your
1457 package complies with the new standards you should update the
1458 <tt>Standards-Version</tt> source package field and
1459 release it.<footnote>
1460 See the file <file>upgrading-checklist</file> for
1461 information about policy which has changed between
1462 different versions of this document.
1468 <sect id="pkg-relations">
1469 <heading>Package relationships</heading>
1472 Source packages should specify which binary packages they
1473 require to be installed or not to be installed in order to
1474 build correctly. For example, if building a package
1475 requires a certain compiler, then the compiler should be
1476 specified as a build-time dependency.
1480 It is not necessary to explicitly specify build-time
1481 relationships on a minimal set of packages that are always
1482 needed to compile, link and put in a Debian package a
1483 standard "Hello World!" program written in C or C++. The
1484 required packages are called <em>build-essential</em>, and
1485 an informational list can be found in
1486 <file>/usr/share/doc/build-essential/list</file> (which is
1487 contained in the <tt>build-essential</tt>
1490 <list compact="compact">
1492 This allows maintaining the list separately
1493 from the policy documents (the list does not
1494 need the kind of control that the policy
1498 Having a separate package allows one to install
1499 the build-essential packages on a machine, as
1500 well as allowing other packages such as tasks to
1501 require installation of the build-essential
1502 packages using the depends relation.
1505 The separate package allows bug reports against
1506 the list to be categorized separately from
1507 the policy management process in the BTS.
1514 When specifying the set of build-time dependencies, one
1515 should list only those packages explicitly required by the
1516 build. It is not necessary to list packages which are
1517 required merely because some other package in the list of
1518 build-time dependencies depends on them.<footnote>
1519 The reason for this is that dependencies change, and
1520 you should list all those packages, and <em>only</em>
1521 those packages that <em>you</em> need directly. What
1522 others need is their business. For example, if you
1523 only link against <file>libimlib</file>, you will need to
1524 build-depend on <package>libimlib2-dev</package> but
1525 not against any <tt>libjpeg*</tt> packages, even
1526 though <tt>libimlib2-dev</tt> currently depends on
1527 them: installation of <package>libimlib2-dev</package>
1528 will automatically ensure that all of its run-time
1529 dependencies are satisfied.
1534 If build-time dependencies are specified, it must be
1535 possible to build the package and produce working binaries
1536 on a system with only essential and build-essential
1537 packages installed and also those required to satisfy the
1538 build-time relationships (including any implied
1539 relationships). In particular, this means that version
1540 clauses should be used rigorously in build-time
1541 relationships so that one cannot produce bad or
1542 inconsistently configured packages when the relationships
1543 are properly satisfied.
1547 <ref id="relationships"> explains the technical details.
1552 <heading>Changes to the upstream sources</heading>
1555 If changes to the source code are made that are not
1556 specific to the needs of the Debian system, they should be
1557 sent to the upstream authors in whatever form they prefer
1558 so as to be included in the upstream version of the
1563 If you need to configure the package differently for
1564 Debian or for Linux, and the upstream source doesn't
1565 provide a way to do so, you should add such configuration
1566 facilities (for example, a new <prgn>autoconf</prgn> test
1567 or <tt>#define</tt>) and send the patch to the upstream
1568 authors, with the default set to the way they originally
1569 had it. You can then easily override the default in your
1570 <file>debian/rules</file> or wherever is appropriate.
1574 You should make sure that the <prgn>configure</prgn> utility
1575 detects the correct architecture specification string
1576 (refer to <ref id="arch-spec"> for details).
1580 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1581 <prgn>configure</prgn> scripts are used, you should edit the
1582 <file>.in</file> files rather than editing the
1583 <prgn>Makefile</prgn> directly. This allows the user to
1584 reconfigure the package if necessary. You should
1585 <em>not</em> configure the package and edit the generated
1586 <prgn>Makefile</prgn>! This makes it impossible for someone
1587 else to later reconfigure the package without losing the
1593 <sect id="dpkgchangelog">
1594 <heading>Debian changelog: <file>debian/changelog</file></heading>
1597 Changes in the Debian version of the package should be
1598 briefly explained in the Debian changelog file
1599 <file>debian/changelog</file>.<footnote>
1601 Mistakes in changelogs are usually best rectified by
1602 making a new changelog entry rather than "rewriting
1603 history" by editing old changelog entries.
1606 This includes modifications
1607 made in the Debian package compared to the upstream one
1608 as well as other changes and updates to the package.
1610 Although there is nothing stopping an author who is also
1611 the Debian maintainer from using this changelog for all
1612 their changes, it will have to be renamed if the Debian
1613 and upstream maintainers become different people. In such
1614 a case, however, it might be better to maintain the package
1615 as a non-native package.
1620 The format of the <file>debian/changelog</file> allows the
1621 package building tools to discover which version of the package
1622 is being built and find out other release-specific information.
1626 That format is a series of entries like this:
1628 <example compact="compact">
1629 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1631 [optional blank line(s), stripped]
1633 * <var>change details</var>
1634 <var>more change details</var>
1636 [blank line(s), included in output of dpkg-parsechangelog]
1638 * <var>even more change details</var>
1640 [optional blank line(s), stripped]
1642 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1647 <var>package</var> and <var>version</var> are the source
1648 package name and version number.
1652 <var>distribution(s)</var> lists the distributions where
1653 this version should be installed when it is uploaded - it
1654 is copied to the <tt>Distribution</tt> field in the
1655 <file>.changes</file> file. See <ref id="f-Distribution">.
1659 <var>urgency</var> is the value for the <tt>Urgency</tt>
1660 field in the <file>.changes</file> file for the upload
1661 (see <ref id="f-Urgency">). It is not possible to specify
1662 an urgency containing commas; commas are used to separate
1663 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1664 <prgn>dpkg</prgn> changelog format (though there is
1665 currently only one useful <var>keyword</var>,
1670 The change details may in fact be any series of lines
1671 starting with at least two spaces, but conventionally each
1672 change starts with an asterisk and a separating space and
1673 continuation lines are indented so as to bring them in
1674 line with the start of the text above. Blank lines may be
1675 used here to separate groups of changes, if desired.
1679 If this upload resolves bugs recorded in the Bug Tracking
1680 System (BTS), they may be automatically closed on the
1681 inclusion of this package into the Debian archive by
1682 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1683 in the change details.<footnote>
1684 To be precise, the string should match the following
1685 Perl regular expression:
1687 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1689 Then all of the bug numbers listed will be closed by the
1690 archive maintenance script (<prgn>katie</prgn>) using the
1691 <var>version</var> of the changelog entry.
1693 This information is conveyed via the <tt>Closes</tt> field
1694 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1698 The maintainer name and email address used in the changelog
1699 should be the details of the person uploading <em>this</em>
1700 version. They are <em>not</em> necessarily those of the
1701 usual package maintainer.<footnote>
1702 If the developer uploading the package is not one of the usual
1703 maintainers of the package (as listed in
1704 the <qref id="f-Maintainer"><tt>Maintainer</tt></qref>
1705 or <qref id="f-Uploaders"><tt>Uploaders</tt></qref> control
1706 fields of the package), the first line of the changelog is
1707 conventionally used to explain why a non-maintainer is
1708 uploading the package. The Debian Developer's Reference
1709 (see <ref id="related">) documents the conventions
1711 The information here will be copied to the <tt>Changed-By</tt>
1712 field in the <tt>.changes</tt> file
1713 (see <ref id="f-Changed-By">), and then later used to send an
1714 acknowledgement when the upload has been installed.
1718 The <var>date</var> has the following format<footnote>
1719 This is the same as the format generated by <tt>date
1721 </footnote> (compatible and with the same semantics of
1722 RFC 2822 and RFC 5322):
1723 <example>day-of-week, dd month yyyy hh:mm:ss +zzzz</example>
1725 <list compact="compact">
1727 day-of week is one of: Mon, Tue, Wed, Thu, Fri, Sat, Sun
1730 dd is a one- or two-digit day of the month (01-31)
1733 month is one of: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug,
1736 <item>yyyy is the four-digit year (e.g. 2010)</item>
1737 <item>hh is the two-digit hour (00-23)</item>
1738 <item>mm is the two-digit minutes (00-59)</item>
1739 <item>ss is the two-digit seconds (00-60)</item>
1741 +zzzz or -zzzz is the the time zone offset from Coordinated
1742 Universal Time (UTC). "+" indicates that the time is ahead
1743 of (i.e., east of) UTC and "-" indicates that the time is
1744 behind (i.e., west of) UTC. The first two digits indicate
1745 the hour difference from UTC and the last two digits
1746 indicate the number of additional minutes difference from
1747 UTC. The last two digits must be in the range 00-59.
1753 The first "title" line with the package name must start
1754 at the left hand margin. The "trailer" line with the
1755 maintainer and date details must be preceded by exactly
1756 one space. The maintainer details and the date must be
1757 separated by exactly two spaces.
1761 The entire changelog must be encoded in UTF-8.
1765 For more information on placement of the changelog files
1766 within binary packages, please see <ref id="changelogs">.
1770 <sect id="dpkgcopyright">
1771 <heading>Copyright: <file>debian/copyright</file></heading>
1773 Every package must be accompanied by a verbatim copy of its
1774 copyright information and distribution license in the file
1775 <file>/usr/share/doc/<var>package</var>/copyright</file>
1776 (see <ref id="copyrightfile"> for further details). Also see
1777 <ref id="pkgcopyright"> for further considerations related
1778 to copyrights for packages.
1782 <heading>Error trapping in makefiles</heading>
1785 When <prgn>make</prgn> invokes a command in a makefile
1786 (including your package's upstream makefiles and
1787 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1788 means that <prgn>sh</prgn>'s usual bad error handling
1789 properties apply: if you include a miniature script as one
1790 of the commands in your makefile you'll find that if you
1791 don't do anything about it then errors are not detected
1792 and <prgn>make</prgn> will blithely continue after
1797 Every time you put more than one shell command (this
1798 includes using a loop) in a makefile command you
1799 must make sure that errors are trapped. For
1800 simple compound commands, such as changing directory and
1801 then running a program, using <tt>&&</tt> rather
1802 than semicolon as a command separator is sufficient. For
1803 more complex commands including most loops and
1804 conditionals you should include a separate <tt>set -e</tt>
1805 command at the start of every makefile command that's
1806 actually one of these miniature shell scripts.
1810 <sect id="timestamps">
1811 <heading>Time Stamps</heading>
1813 Maintainers should preserve the modification times of the
1814 upstream source files in a package, as far as is reasonably
1816 The rationale is that there is some information conveyed
1817 by knowing the age of the file, for example, you could
1818 recognize that some documentation is very old by looking
1819 at the modification time, so it would be nice if the
1820 modification time of the upstream source would be
1826 <sect id="restrictions">
1827 <heading>Restrictions on objects in source packages</heading>
1830 The source package may not contain any hard links<footnote>
1832 This is not currently detected when building source
1833 packages, but only when extracting
1837 Hard links may be permitted at some point in the
1838 future, but would require a fair amount of
1841 </footnote>, device special files, sockets or setuid or
1842 setgid files.<footnote>
1843 Setgid directories are allowed.
1848 <sect id="debianrules">
1849 <heading>Main building script: <file>debian/rules</file></heading>
1852 This file must be an executable makefile, and contains the
1853 package-specific recipes for compiling the package and
1854 building binary package(s) from the source.
1858 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1859 so that it can be invoked by saying its name rather than
1860 invoking <prgn>make</prgn> explicitly. That is, invoking
1861 either of <tt>make -f debian/rules <em>args...</em></tt>
1862 or <tt>./debian/rules <em>args...</em></tt> must result in
1867 The following targets are required and must be implemented
1868 by <file>debian/rules</file>: <tt>clean</tt>, <tt>binary</tt>,
1869 <tt>binary-arch</tt>, <tt>binary-indep</tt>, and <tt>build</tt>.
1870 These are the targets called by <prgn>dpkg-buildpackage</prgn>.
1874 Since an interactive <file>debian/rules</file> script makes it
1875 impossible to auto-compile that package and also makes it hard
1876 for other people to reproduce the same binary package, all
1877 required targets must be non-interactive. It also follows that
1878 any target that these targets depend on must also be
1883 The targets are as follows:
1885 <tag><tt>build</tt> (required)</tag>
1888 The <tt>build</tt> target should perform all the
1889 configuration and compilation of the package.
1890 If a package has an interactive pre-build
1891 configuration routine, the Debian source package
1892 must either be built after this has taken place (so
1893 that the binary package can be built without rerunning
1894 the configuration) or the configuration routine
1895 modified to become non-interactive. (The latter is
1896 preferable if there are architecture-specific features
1897 detected by the configuration routine.)
1901 For some packages, notably ones where the same
1902 source tree is compiled in different ways to produce
1903 two binary packages, the <tt>build</tt> target
1904 does not make much sense. For these packages it is
1905 good enough to provide two (or more) targets
1906 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1907 for each of the ways of building the package, and a
1908 <tt>build</tt> target that does nothing. The
1909 <tt>binary</tt> target will have to build the
1910 package in each of the possible ways and make the
1911 binary package out of each.
1915 The <tt>build</tt> target must not do anything
1916 that might require root privilege.
1920 The <tt>build</tt> target may need to run the
1921 <tt>clean</tt> target first - see below.
1925 When a package has a configuration and build routine
1926 which takes a long time, or when the makefiles are
1927 poorly designed, or when <tt>build</tt> needs to
1928 run <tt>clean</tt> first, it is a good idea to
1929 <tt>touch build</tt> when the build process is
1930 complete. This will ensure that if <tt>debian/rules
1931 build</tt> is run again it will not rebuild the whole
1933 Another common way to do this is for <tt>build</tt>
1934 to depend on <prgn>build-stamp</prgn> and to do
1935 nothing else, and for the <prgn>build-stamp</prgn>
1936 target to do the building and to <tt>touch
1937 build-stamp</tt> on completion. This is
1938 especially useful if the build routine creates a
1939 file or directory called <tt>build</tt>; in such a
1940 case, <tt>build</tt> will need to be listed as
1941 a phony target (i.e., as a dependency of the
1942 <tt>.PHONY</tt> target). See the documentation of
1943 <prgn>make</prgn> for more information on phony
1949 <tag><tt>build-arch</tt> (optional),
1950 <tt>build-indep</tt> (optional)
1954 A package may also provide both of the targets
1955 <tt>build-arch</tt> and <tt>build-indep</tt>.
1956 The <tt>build-arch</tt> target, if provided, should
1957 perform all the configuration and compilation required for
1958 producing all architecture-dependant binary packages
1959 (those packages for which the body of the
1960 <tt>Architecture</tt> field in <tt>debian/control</tt> is
1961 not <tt>all</tt>). Similarly, the <tt>build-indep</tt>
1962 target, if provided, should perform all the configuration
1963 and compilation required for producing all
1964 architecture-independent binary packages (those packages
1965 for which the body of the <tt>Architecture</tt> field
1966 in <tt>debian/control</tt> is <tt>all</tt>).
1967 The <tt>build</tt> target should depend on those of the
1968 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1969 are provided in the rules file.<footnote>
1970 The intent of this split is so that binary-only builds
1971 need not install the dependencies required for
1972 the <tt>build-indep</tt> target. However, this is not
1973 yet used in practice since <tt>dpkg-buildpackage
1974 -B</tt>, and therefore the autobuilders,
1975 invoke <tt>build</tt> rather than <tt>build-arch</tt>
1976 due to the difficulties in determining whether the
1977 optional <tt>build-arch</tt> target exists.
1982 If one or both of the targets <tt>build-arch</tt> and
1983 <tt>build-indep</tt> are not provided, then invoking
1984 <file>debian/rules</file> with one of the not-provided
1985 targets as arguments should produce a exit status code
1986 of 2. Usually this is provided automatically by make
1987 if the target is missing.
1991 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1992 must not do anything that might require root privilege.
1996 <tag><tt>binary</tt> (required), <tt>binary-arch</tt>
1997 (required), <tt>binary-indep</tt> (required)
2001 The <tt>binary</tt> target must be all that is
2002 necessary for the user to build the binary package(s)
2003 produced from this source package. It is
2004 split into two parts: <prgn>binary-arch</prgn> builds
2005 the binary packages which are specific to a particular
2006 architecture, and <tt>binary-indep</tt> builds
2007 those which are not.
2010 <tt>binary</tt> may be (and commonly is) a target with
2011 no commands which simply depends on
2012 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
2015 Both <tt>binary-*</tt> targets should depend on the
2016 <tt>build</tt> target, or on the appropriate
2017 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
2018 provided, so that the package is built if it has not
2019 been already. It should then create the relevant
2020 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
2021 make their control files and <prgn>dpkg-deb</prgn> to
2022 build them and place them in the parent of the top
2027 Both the <tt>binary-arch</tt> and
2028 <tt>binary-indep</tt> targets <em>must</em> exist.
2029 If one of them has nothing to do (which will always be
2030 the case if the source generates only a single binary
2031 package, whether architecture-dependent or not), it
2032 must still exist and must always succeed.
2036 The <tt>binary</tt> targets must be invoked as
2038 The <prgn>fakeroot</prgn> package often allows one
2039 to build a package correctly even without being
2045 <tag><tt>clean</tt> (required)</tag>
2048 This must undo any effects that the <tt>build</tt>
2049 and <tt>binary</tt> targets may have had, except
2050 that it should leave alone any output files created in
2051 the parent directory by a run of a <tt>binary</tt>
2056 If a <tt>build</tt> file is touched at the end of
2057 the <tt>build</tt> target, as suggested above, it
2058 should be removed as the first action that
2059 <tt>clean</tt> performs, so that running
2060 <tt>build</tt> again after an interrupted
2061 <tt>clean</tt> doesn't think that everything is
2066 The <tt>clean</tt> target may need to be
2067 invoked as root if <tt>binary</tt> has been
2068 invoked since the last <tt>clean</tt>, or if
2069 <tt>build</tt> has been invoked as root (since
2070 <tt>build</tt> may create directories, for
2075 <tag><tt>get-orig-source</tt> (optional)</tag>
2078 This target fetches the most recent version of the
2079 original source package from a canonical archive site
2080 (via FTP or WWW, for example), does any necessary
2081 rearrangement to turn it into the original source
2082 tar file format described below, and leaves it in the
2087 This target may be invoked in any directory, and
2088 should take care to clean up any temporary files it
2093 This target is optional, but providing it if
2094 possible is a good idea.
2098 <tag><tt>patch</tt> (optional)</tag>
2101 This target performs whatever additional actions are
2102 required to make the source ready for editing (unpacking
2103 additional upstream archives, applying patches, etc.).
2104 It is recommended to be implemented for any package where
2105 <tt>dpkg-source -x</tt> does not result in source ready
2106 for additional modification. See
2107 <ref id="readmesource">.
2113 The <tt>build</tt>, <tt>binary</tt> and
2114 <tt>clean</tt> targets must be invoked with the current
2115 directory being the package's top-level directory.
2120 Additional targets may exist in <file>debian/rules</file>,
2121 either as published or undocumented interfaces or for the
2122 package's internal use.
2126 The architectures we build on and build for are determined
2127 by <prgn>make</prgn> variables using the
2128 utility <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
2129 You can determine the Debian architecture and the GNU style
2130 architecture specification string for the build architecture as
2131 well as for the host architecture. The build architecture is
2132 the architecture on which <file>debian/rules</file> is run and
2133 the package build is performed. The host architecture is the
2134 architecture on which the resulting package will be installed
2135 and run. These are normally the same, but may be different in
2136 the case of cross-compilation (building packages for one
2137 architecture on machines of a different architecture).
2141 Here is a list of supported <prgn>make</prgn> variables:
2142 <list compact="compact">
2144 <tt>DEB_*_ARCH</tt> (the Debian architecture)
2147 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2150 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2153 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2154 specification string)
2157 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2158 <tt>DEB_*_GNU_TYPE</tt>)
2161 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2162 <tt>DEB_*_GNU_TYPE</tt>)
2164 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2165 the build architecture or <tt>HOST</tt> for specification of the
2170 Backward compatibility can be provided in the rules file
2171 by setting the needed variables to suitable default
2172 values; please refer to the documentation of
2173 <prgn>dpkg-architecture</prgn> for details.
2177 It is important to understand that the <tt>DEB_*_ARCH</tt>
2178 string only determines which Debian architecture we are
2179 building on or for. It should not be used to get the CPU
2180 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2181 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2182 GNU style variables should generally only be used with upstream
2186 <sect1 id="debianrules-options">
2187 <heading><file>debian/rules</file> and
2188 <tt>DEB_BUILD_OPTIONS</tt></heading>
2191 Supporting the standardized environment variable
2192 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2193 contain several flags to change how a package is compiled and
2194 built. Each flag must be in the form <var>flag</var> or
2195 <var>flag</var>=<var>options</var>. If multiple flags are
2196 given, they must be separated by whitespace.<footnote>
2197 Some packages support any delimiter, but whitespace is the
2198 easiest to parse inside a makefile and avoids ambiguity with
2199 flag values that contain commas.
2201 <var>flag</var> must start with a lowercase letter
2202 (<tt>a-z</tt>) and consist only of lowercase letters,
2203 numbers (<tt>0-9</tt>), and the characters
2204 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2205 <var>options</var> must not contain whitespace. The same
2206 tag should not be given multiple times with conflicting
2207 values. Package maintainers may assume that
2208 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2212 The meaning of the following tags has been standardized:
2216 This tag says to not run any build-time test suite
2217 provided by the package.
2221 The presence of this tag means that the package should
2222 be compiled with a minimum of optimization. For C
2223 programs, it is best to add <tt>-O0</tt> to
2224 <tt>CFLAGS</tt> (although this is usually the default).
2225 Some programs might fail to build or run at this level
2226 of optimization; it may be necessary to use
2227 <tt>-O1</tt>, for example.
2231 This tag means that the debugging symbols should not be
2232 stripped from the binary during installation, so that
2233 debugging information may be included in the package.
2235 <tag>parallel=n</tag>
2237 This tag means that the package should be built using up
2238 to <tt>n</tt> parallel processes if the package build
2239 system supports this.<footnote>
2240 Packages built with <tt>make</tt> can often implement
2241 this by passing the <tt>-j</tt><var>n</var> option to
2244 If the package build system does not support parallel
2245 builds, this string must be ignored. If the package
2246 build system only supports a lower level of concurrency
2247 than <var>n</var>, the package should be built using as
2248 many parallel processes as the package build system
2249 supports. It is up to the package maintainer to decide
2250 whether the package build times are long enough and the
2251 package build system is robust enough to make supporting
2252 parallel builds worthwhile.
2258 Unknown flags must be ignored by <file>debian/rules</file>.
2262 The following makefile snippet is an example of how one may
2263 implement the build options; you will probably have to
2264 massage this example in order to make it work for your
2266 <example compact="compact">
2269 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2270 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2271 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2272 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2274 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2279 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2280 INSTALL_PROGRAM += -s
2282 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2283 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2284 MAKEFLAGS += -j$(NUMJOBS)
2289 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2290 # Code to run the package test suite.
2297 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2298 <sect id="substvars">
2299 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2302 When <prgn>dpkg-gencontrol</prgn>
2303 generates <qref id="binarycontrolfiles">binary package control
2304 files</qref> (<file>DEBIAN/control</file>), it performs variable
2305 substitutions on its output just before writing it. Variable
2306 substitutions have the form <tt>${<var>variable</var>}</tt>.
2307 The optional file <file>debian/substvars</file> contains
2308 variable substitutions to be used; variables can also be set
2309 directly from <file>debian/rules</file> using the <tt>-V</tt>
2310 option to the source packaging commands, and certain predefined
2311 variables are also available.
2315 The <file>debian/substvars</file> file is usually generated and
2316 modified dynamically by <file>debian/rules</file> targets, in
2317 which case it must be removed by the <tt>clean</tt> target.
2321 See <manref name="deb-substvars" section="5"> for full
2322 details about source variable substitutions, including the
2323 format of <file>debian/substvars</file>.</p>
2326 <sect id="debianwatch">
2327 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2330 This is an optional, recommended configuration file for the
2331 <tt>uscan</tt> utility which defines how to automatically scan
2332 ftp or http sites for newly available updates of the
2333 package. This is used
2334 by <url id="http://dehs.alioth.debian.org/"> and other Debian QA
2335 tools to help with quality control and maintenance of the
2336 distribution as a whole.
2341 <sect id="debianfiles">
2342 <heading>Generated files list: <file>debian/files</file></heading>
2345 This file is not a permanent part of the source tree; it
2346 is used while building packages to record which files are
2347 being generated. <prgn>dpkg-genchanges</prgn> uses it
2348 when it generates a <file>.changes</file> file.
2352 It should not exist in a shipped source package, and so it
2353 (and any backup files or temporary files such as
2354 <file>files.new</file><footnote>
2355 <file>files.new</file> is used as a temporary file by
2356 <prgn>dpkg-gencontrol</prgn> and
2357 <prgn>dpkg-distaddfile</prgn> - they write a new
2358 version of <tt>files</tt> here before renaming it,
2359 to avoid leaving a corrupted copy if an error
2361 </footnote>) should be removed by the
2362 <tt>clean</tt> target. It may also be wise to
2363 ensure a fresh start by emptying or removing it at the
2364 start of the <tt>binary</tt> target.
2368 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2369 package, it adds an entry to <file>debian/files</file> for the
2370 <file>.deb</file> file that will be created when <tt>dpkg-deb
2371 --build</tt> is run for that binary package. So for most
2372 packages all that needs to be done with this file is to
2373 delete it in the <tt>clean</tt> target.
2377 If a package upload includes files besides the source
2378 package and any binary packages whose control files were
2379 made with <prgn>dpkg-gencontrol</prgn> then they should be
2380 placed in the parent of the package's top-level directory
2381 and <prgn>dpkg-distaddfile</prgn> should be called to add
2382 the file to the list in <file>debian/files</file>.</p>
2385 <sect id="embeddedfiles">
2386 <heading>Convenience copies of code</heading>
2389 Some software packages include in their distribution convenience
2390 copies of code from other software packages, generally so that
2391 users compiling from source don't have to download multiple
2392 packages. Debian packages should not make use of these
2393 convenience copies unless the included package is explicitly
2394 intended to be used in this way.<footnote>
2395 For example, parts of the GNU build system work like this.
2397 If the included code is already in the Debian archive in the
2398 form of a library, the Debian packaging should ensure that
2399 binary packages reference the libraries already in Debian and
2400 the convenience copy is not used. If the included code is not
2401 already in Debian, it should be packaged separately as a
2402 prerequisite if possible.
2404 Having multiple copies of the same code in Debian is
2405 inefficient, often creates either static linking or shared
2406 library conflicts, and, most importantly, increases the
2407 difficulty of handling security vulnerabilities in the
2413 <sect id="readmesource">
2414 <heading>Source package handling:
2415 <file>debian/README.source</file></heading>
2418 If running <prgn>dpkg-source -x</prgn> on a source package
2419 doesn't produce the source of the package, ready for editing,
2420 and allow one to make changes and run
2421 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2422 without taking any additional steps, creating a
2423 <file>debian/README.source</file> documentation file is
2424 recommended. This file should explain how to do all of the
2427 <item>Generate the fully patched source, in a form ready for
2428 editing, that would be built to create Debian
2429 packages. Doing this with a <tt>patch</tt> target in
2430 <file>debian/rules</file> is recommended; see
2431 <ref id="debianrules">.</item>
2432 <item>Modify the source and save those modifications so that
2433 they will be applied when building the package.</item>
2434 <item>Remove source modifications that are currently being
2435 applied when building the package.</item>
2436 <item>Optionally, document what steps are necessary to
2437 upgrade the Debian source package to a new upstream version,
2438 if applicable.</item>
2440 This explanation should include specific commands and mention
2441 any additional required Debian packages. It should not assume
2442 familiarity with any specific Debian packaging system or patch
2447 This explanation may refer to a documentation file installed by
2448 one of the package's build dependencies provided that the
2449 referenced documentation clearly explains these tasks and is not
2450 a general reference manual.
2454 <file>debian/README.source</file> may also include any other
2455 information that would be helpful to someone modifying the
2456 source package. Even if the package doesn't fit the above
2457 description, maintainers are encouraged to document in a
2458 <file>debian/README.source</file> file any source package with a
2459 particularly complex or unintuitive source layout or build
2460 system (for example, a package that builds the same source
2461 multiple times to generate different binary packages).
2467 <chapt id="controlfields">
2468 <heading>Control files and their fields</heading>
2471 The package management system manipulates data represented in
2472 a common format, known as <em>control data</em>, stored in
2473 <em>control files</em>.
2474 Control files are used for source packages, binary packages and
2475 the <file>.changes</file> files which control the installation
2476 of uploaded files<footnote>
2477 <prgn>dpkg</prgn>'s internal databases are in a similar
2482 <sect id="controlsyntax">
2483 <heading>Syntax of control files</heading>
2486 A control file consists of one or more paragraphs of
2488 The paragraphs are also sometimes referred to as stanzas.
2490 The paragraphs are separated by empty lines. Parsers may accept
2491 lines consisting solely of spaces and tabs as paragraph
2492 separators, but control files should use empty lines. Some control
2493 files allow only one paragraph; others allow several, in
2494 which case each paragraph usually refers to a different
2495 package. (For example, in source packages, the first
2496 paragraph refers to the source package, and later paragraphs
2497 refer to binary packages generated from the source.) The
2498 ordering of the paragraphs in control files is significant.
2502 Each paragraph consists of a series of data fields; each
2503 field consists of the field name, followed by a colon and
2504 then the data/value associated with that field. The field
2505 name is composed of printable ASCII characters (i.e.,
2506 characters that have values between 33 and 126, inclusive)
2507 except colon and must not with a begin with #. The
2508 field ends at the end of the line or at the end of the
2509 last continuation line (see below). Horizontal whitespace
2510 (spaces and tabs) may occur immediately before or after the
2511 value and is ignored there; it is conventional to put a
2512 single space after the colon. For example, a field might
2514 <example compact="compact">
2517 the field name is <tt>Package</tt> and the field value
2522 A paragraph must not contain more than one instance of a
2523 particular field name.
2527 There are three types of fields:
2531 The field, including its value, must be a single line. Folding
2532 of the field is not permitted. This is the default field type
2533 if the definition of the field does not specify a different
2538 The value of a folded field is a logical line that may span
2539 several lines. The lines after the first are called
2540 continuation lines and must start with a space or a tab.
2541 Whitespace, including any newlines, is not significant in the
2542 field values of folded fields.<footnote>
2543 This folding method is similar to RFC 5322, allowing control
2544 files that contain only one paragraph and no multiline fields
2545 to be read by parsers written for RFC 5322.
2548 <tag>multiline</tag>
2550 The value of a multiline field may comprise multiple continuation
2551 lines. The first line of the value, the part on the same line as
2552 the field name, often has special significance or may have to be
2553 empty. Other lines are added following the same syntax as the
2554 continuation lines of the folded fields. Whitespace, including newlines,
2555 is significant in the values of multiline fields.
2561 Whitespace must not appear
2562 inside names (of packages, architectures, files or anything
2563 else) or version numbers, or between the characters of
2564 multi-character version relationships.
2568 The presence and purpose of a field, and the syntax of its
2569 value may differ between types of control files.
2573 Field names are not case-sensitive, but it is usual to
2574 capitalize the field names using mixed case as shown below.
2575 Field values are case-sensitive unless the description of the
2576 field says otherwise.
2580 Paragraph separators (empty lines) and lines consisting only of
2581 spaces and tabs are not allowed within field values or between
2582 fields. Empty lines in field values are usually escaped by
2583 representing them by a space followed by a dot.
2587 Lines starting with # without any preceding whitespace are comments
2588 lines that are only permitted in source package control files
2589 (<file>debian/control</file>). These comment lines are ignored, even
2590 between two continuation lines. They do not end logical lines.
2594 All control files must be encoded in UTF-8.
2598 <sect id="sourcecontrolfiles">
2599 <heading>Source package control files -- <file>debian/control</file></heading>
2602 The <file>debian/control</file> file contains the most vital
2603 (and version-independent) information about the source package
2604 and about the binary packages it creates.
2608 The first paragraph of the control file contains information about
2609 the source package in general. The subsequent sets each describe a
2610 binary package that the source tree builds.
2614 The fields in the general paragraph (the first one, for the source
2617 <list compact="compact">
2618 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2619 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2620 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2621 <item><qref id="f-DM-Upload-Allowed"><tt>DM-Upload-Allowed</tt></qref></item>
2622 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2623 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2624 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2625 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2626 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2631 The fields in the binary package paragraphs are:
2633 <list compact="compact">
2634 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2635 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2636 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2637 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2638 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2639 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2640 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2641 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2646 The syntax and semantics of the fields are described below.
2650 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2651 generate control files for binary packages (see below), by
2652 <prgn>dpkg-genchanges</prgn> to generate the
2653 <file>.changes</file> file to accompany the upload, and by
2654 <prgn>dpkg-source</prgn> when it creates the
2655 <file>.dsc</file> source control file as part of a source
2656 archive. Some fields are folded in <file>debian/control</file>,
2657 but not in any other control
2658 file. These tools are responsible for removing the line
2659 breaks from such fields when using fields from
2660 <file>debian/control</file> to generate other control files.
2664 The fields here may contain variable references - their
2665 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2666 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2667 when they generate output control files.
2668 See <ref id="substvars"> for details.
2672 <sect id="binarycontrolfiles">
2673 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2676 The <file>DEBIAN/control</file> file contains the most vital
2677 (and version-dependent) information about a binary package. It
2678 consists of a single paragraph.
2682 The fields in this file are:
2684 <list compact="compact">
2685 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2686 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2687 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2688 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2689 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2690 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2691 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2692 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2693 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2694 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2695 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2696 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2701 <sect id="debiansourcecontrolfiles">
2702 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2705 This file consists of a single paragraph, possibly surrounded by
2706 a PGP signature. The fields of that paragraph are listed below.
2707 Their syntax is described above, in <ref id="controlsyntax">.
2709 <list compact="compact">
2710 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2711 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2712 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2713 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2714 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2715 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2716 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2717 <item><qref id="f-DM-Upload-Allowed"><tt>DM-Upload-Allowed</tt></qref></item>
2718 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2719 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2720 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2721 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2722 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2723 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2728 The Debian source control file is generated by
2729 <prgn>dpkg-source</prgn> when it builds the source
2730 archive, from other files in the source package,
2731 described above. When unpacking, it is checked against
2732 the files and directories in the other parts of the
2738 <sect id="debianchangesfiles">
2739 <heading>Debian changes files -- <file>.changes</file></heading>
2742 The <file>.changes</file> files are used by the Debian archive
2743 maintenance software to process updates to packages. They
2744 consist of a single paragraph, possibly surrounded by a PGP
2745 signature. That paragraph contains information from the
2746 <file>debian/control</file> file and other data about the
2747 source package gathered via <file>debian/changelog</file>
2748 and <file>debian/rules</file>.
2752 <file>.changes</file> files have a format version that is
2753 incremented whenever the documented fields or their meaning
2754 change. This document describes format &changesversion;.
2758 The fields in this file are:
2760 <list compact="compact">
2761 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2762 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2763 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2764 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2765 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2766 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2767 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2768 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2769 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2770 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2771 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2772 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2773 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2774 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2775 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2776 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2781 <sect id="controlfieldslist">
2782 <heading>List of fields</heading>
2784 <sect1 id="f-Source">
2785 <heading><tt>Source</tt></heading>
2788 This field identifies the source package name.
2792 In <file>debian/control</file> or a <file>.dsc</file> file,
2793 this field must contain only the name of the source package.
2797 In a binary package control file or a <file>.changes</file>
2798 file, the source package name may be followed by a version
2799 number in parentheses<footnote>
2800 It is customary to leave a space after the package name
2801 if a version number is specified.
2803 This version number may be omitted (and is, by
2804 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2805 the <tt>Version</tt> field of the binary package in
2806 question. The field itself may be omitted from a binary
2807 package control file when the source package has the same
2808 name and version as the binary package.
2812 Package names (both source and binary,
2813 see <ref id="f-Package">) must consist only of lower case
2814 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2815 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2816 (<tt>.</tt>). They must be at least two characters long and
2817 must start with an alphanumeric character.
2821 <sect1 id="f-Maintainer">
2822 <heading><tt>Maintainer</tt></heading>
2825 The package maintainer's name and email address. The name
2826 must come first, then the email address inside angle
2827 brackets <tt><></tt> (in RFC822 format).
2831 If the maintainer's name contains a full stop then the
2832 whole field will not work directly as an email address due
2833 to a misfeature in the syntax specified in RFC822; a
2834 program using this field as an address must check for this
2835 and correct the problem if necessary (for example by
2836 putting the name in round brackets and moving it to the
2837 end, and bringing the email address forward).
2841 See <ref id="maintainer"> for additional requirements and
2842 information about package maintainers.
2846 <sect1 id="f-Uploaders">
2847 <heading><tt>Uploaders</tt></heading>
2850 List of the names and email addresses of co-maintainers of the
2851 package, if any. If the package has other maintainers besides
2852 the one named in the <qref id="f-Maintainer">Maintainer
2853 field</qref>, their names and email addresses should be listed
2854 here. The format of each entry is the same as that of the
2855 Maintainer field, and multiple entries must be comma
2860 This is normally an optional field, but if
2861 the <tt>Maintainer</tt> control field names a group of people
2862 and a shared email address, the <tt>Uploaders</tt> field must
2863 be present and must contain at least one human with their
2864 personal email address.
2868 The Uploaders field in <file>debian/control</file> can be folded.
2872 <sect1 id="f-Changed-By">
2873 <heading><tt>Changed-By</tt></heading>
2876 The name and email address of the person who prepared this
2877 version of the package, usually a maintainer. The syntax is
2878 the same as for the <qref id="f-Maintainer">Maintainer
2883 <sect1 id="f-Section">
2884 <heading><tt>Section</tt></heading>
2887 This field specifies an application area into which the package
2888 has been classified. See <ref id="subsections">.
2892 When it appears in the <file>debian/control</file> file,
2893 it gives the value for the subfield of the same name in
2894 the <tt>Files</tt> field of the <file>.changes</file> file.
2895 It also gives the default for the same field in the binary
2900 <sect1 id="f-Priority">
2901 <heading><tt>Priority</tt></heading>
2904 This field represents how important it is that the user
2905 have the package installed. See <ref id="priorities">.
2909 When it appears in the <file>debian/control</file> file,
2910 it gives the value for the subfield of the same name in
2911 the <tt>Files</tt> field of the <file>.changes</file> file.
2912 It also gives the default for the same field in the binary
2917 <sect1 id="f-Package">
2918 <heading><tt>Package</tt></heading>
2921 The name of the binary package.
2925 Binary package names must follow the same syntax and
2926 restrictions as source package names. See <ref id="f-Source">
2931 <sect1 id="f-Architecture">
2932 <heading><tt>Architecture</tt></heading>
2935 Depending on context and the control file used, the
2936 <tt>Architecture</tt> field can include the following sets of
2940 A unique single word identifying a Debian machine
2941 architecture as described in <ref id="arch-spec">.
2944 An architecture wildcard identifying a set of Debian
2945 machine architectures, see <ref id="arch-wildcard-spec">.
2946 <tt>any</tt> matches all Debian machine architectures
2947 and is the most frequently used.
2950 <tt>all</tt>, which indicates an
2951 architecture-independent package.
2954 <tt>source</tt>, which indicates a source package.
2960 In the main <file>debian/control</file> file in the source
2961 package, this field may contain the special
2962 value <tt>all</tt>, the special architecture
2963 wildcard <tt>any</tt>, or a list of specific and wildcard
2964 architectures separated by spaces. If <tt>all</tt>
2965 or <tt>any</tt> appears, that value must be the entire
2966 contents of the field. Most packages will use
2967 either <tt>all</tt> or <tt>any</tt>.
2971 Specifying a specific list of architectures indicates that the
2972 source will build an architecture-dependent package only on
2973 architectures included in the list. Specifying a list of
2974 architecture wildcards indicates that the source will build an
2975 architecture-dependent package on only those architectures
2976 that match any of the specified architecture wildcards.
2977 Specifying a list of architectures or architecture wildcards
2978 other than <tt>any</tt> is for the minority of cases where a
2979 program is not portable or is not useful on some
2980 architectures. Where possible, the program should be made
2985 In the Debian source control file <file>.dsc</file>, this
2986 field contains a list of architectures and architecture
2987 wildcards separated by spaces. When the list contains the
2988 architecture wildcard <tt>any</tt>, the only other value
2989 allowed in the list is <tt>all</tt>.
2993 The list may include (or consist solely of) the special
2994 value <tt>all</tt>. In other words, in <file>.dsc</file>
2995 files unlike the <file>debian/control</file>, <tt>all</tt> may
2996 occur in combination with specific architectures.
2997 The <tt>Architecture</tt> field in the Debian source control
2998 file <file>.dsc</file> is generally constructed from
2999 the <tt>Architecture</tt> fields in
3000 the <file>debian/control</file> in the source package.
3004 Specifying only <tt>any</tt> indicates that the source package
3005 isn't dependent on any particular architecture and should
3006 compile fine on any one. The produced binary package(s)
3007 will be specific to whatever the current build architecture is.
3011 Specifying only <tt>all</tt> indicates that the source package
3012 will only build architecture-independent packages.
3016 Specifying <tt>any all</tt> indicates that the source package
3017 isn't dependent on any particular architecture. The set of
3018 produced binary packages will include at least one
3019 architecture-dependant package and one architecture-independent
3024 Specifying a list of architectures or architecture wildcards
3025 indicates that the source will build an architecture-dependent
3026 package, and will only work correctly on the listed or
3027 matching architectures. If the source package also builds at
3028 least one architecture-independent package, <tt>all</tt> will
3029 also be included in the list.
3033 In a <file>.changes</file> file, the <tt>Architecture</tt>
3034 field lists the architecture(s) of the package(s) currently
3035 being uploaded. This will be a list; if the source for the
3036 package is also being uploaded, the special
3037 entry <tt>source</tt> is also present. <tt>all</tt> will be
3038 present if any architecture-independent packages are being
3039 uploaded. Architecture wildcards such as <tt>any</tt> must
3040 never occur in the <tt>Architecture</tt> field in
3041 the <file>.changes</file> file.
3045 See <ref id="debianrules"> for information on how to get
3046 the architecture for the build process.
3050 <sect1 id="f-Essential">
3051 <heading><tt>Essential</tt></heading>
3054 This is a boolean field which may occur only in the
3055 control file of a binary package or in a per-package fields
3056 paragraph of a source package control file.
3060 If set to <tt>yes</tt> then the package management system
3061 will refuse to remove the package (upgrading and replacing
3062 it is still possible). The other possible value is <tt>no</tt>,
3063 which is the same as not having the field at all.
3068 <heading>Package interrelationship fields:
3069 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
3070 <tt>Recommends</tt>, <tt>Suggests</tt>,
3071 <tt>Breaks</tt>, <tt>Conflicts</tt>,
3072 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
3076 These fields describe the package's relationships with
3077 other packages. Their syntax and semantics are described
3078 in <ref id="relationships">.</p>
3081 <sect1 id="f-Standards-Version">
3082 <heading><tt>Standards-Version</tt></heading>
3085 The most recent version of the standards (the policy
3086 manual and associated texts) with which the package
3091 The version number has four components: major and minor
3092 version number and major and minor patch level. When the
3093 standards change in a way that requires every package to
3094 change the major number will be changed. Significant
3095 changes that will require work in many packages will be
3096 signaled by a change to the minor number. The major patch
3097 level will be changed for any change to the meaning of the
3098 standards, however small; the minor patch level will be
3099 changed when only cosmetic, typographical or other edits
3100 are made which neither change the meaning of the document
3101 nor affect the contents of packages.
3105 Thus only the first three components of the policy version
3106 are significant in the <em>Standards-Version</em> control
3107 field, and so either these three components or all four
3108 components may be specified.<footnote>
3109 In the past, people specified the full version number
3110 in the Standards-Version field, for example "2.3.0.0".
3111 Since minor patch-level changes don't introduce new
3112 policy, it was thought it would be better to relax
3113 policy and only require the first 3 components to be
3114 specified, in this example "2.3.0". All four
3115 components may still be used if someone wishes to do so.
3121 <sect1 id="f-Version">
3122 <heading><tt>Version</tt></heading>
3125 The version number of a package. The format is:
3126 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
3130 The three components here are:
3132 <tag><var>epoch</var></tag>
3135 This is a single (generally small) unsigned integer. It
3136 may be omitted, in which case zero is assumed. If it is
3137 omitted then the <var>upstream_version</var> may not
3142 It is provided to allow mistakes in the version numbers
3143 of older versions of a package, and also a package's
3144 previous version numbering schemes, to be left behind.
3148 <tag><var>upstream_version</var></tag>
3151 This is the main part of the version number. It is
3152 usually the version number of the original ("upstream")
3153 package from which the <file>.deb</file> file has been made,
3154 if this is applicable. Usually this will be in the same
3155 format as that specified by the upstream author(s);
3156 however, it may need to be reformatted to fit into the
3157 package management system's format and comparison
3162 The comparison behavior of the package management system
3163 with respect to the <var>upstream_version</var> is
3164 described below. The <var>upstream_version</var>
3165 portion of the version number is mandatory.
3169 The <var>upstream_version</var> may contain only
3170 alphanumerics<footnote>
3171 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3173 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3174 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3175 tilde) and should start with a digit. If there is no
3176 <var>debian_revision</var> then hyphens are not allowed;
3177 if there is no <var>epoch</var> then colons are not
3182 <tag><var>debian_revision</var></tag>
3185 This part of the version number specifies the version of
3186 the Debian package based on the upstream version. It
3187 may contain only alphanumerics and the characters
3188 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3189 tilde) and is compared in the same way as the
3190 <var>upstream_version</var> is.
3194 It is optional; if it isn't present then the
3195 <var>upstream_version</var> may not contain a hyphen.
3196 This format represents the case where a piece of
3197 software was written specifically to be a Debian
3198 package, where the Debian package source must always
3199 be identical to the pristine source and therefore no
3200 revision indication is required.
3204 It is conventional to restart the
3205 <var>debian_revision</var> at <tt>1</tt> each time the
3206 <var>upstream_version</var> is increased.
3210 The package management system will break the version
3211 number apart at the last hyphen in the string (if there
3212 is one) to determine the <var>upstream_version</var> and
3213 <var>debian_revision</var>. The absence of a
3214 <var>debian_revision</var> is equivalent to a
3215 <var>debian_revision</var> of <tt>0</tt>.
3222 When comparing two version numbers, first the <var>epoch</var>
3223 of each are compared, then the <var>upstream_version</var> if
3224 <var>epoch</var> is equal, and then <var>debian_revision</var>
3225 if <var>upstream_version</var> is also equal.
3226 <var>epoch</var> is compared numerically. The
3227 <var>upstream_version</var> and <var>debian_revision</var>
3228 parts are compared by the package management system using the
3229 following algorithm:
3233 The strings are compared from left to right.
3237 First the initial part of each string consisting entirely of
3238 non-digit characters is determined. These two parts (one of
3239 which may be empty) are compared lexically. If a difference
3240 is found it is returned. The lexical comparison is a
3241 comparison of ASCII values modified so that all the letters
3242 sort earlier than all the non-letters and so that a tilde
3243 sorts before anything, even the end of a part. For example,
3244 the following parts are in sorted order from earliest to
3245 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3246 <tt>a</tt>.<footnote>
3247 One common use of <tt>~</tt> is for upstream pre-releases.
3248 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3249 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3254 Then the initial part of the remainder of each string which
3255 consists entirely of digit characters is determined. The
3256 numerical values of these two parts are compared, and any
3257 difference found is returned as the result of the comparison.
3258 For these purposes an empty string (which can only occur at
3259 the end of one or both version strings being compared) counts
3264 These two steps (comparing and removing initial non-digit
3265 strings and initial digit strings) are repeated until a
3266 difference is found or both strings are exhausted.
3270 Note that the purpose of epochs is to allow us to leave behind
3271 mistakes in version numbering, and to cope with situations
3272 where the version numbering scheme changes. It is
3273 <em>not</em> intended to cope with version numbers containing
3274 strings of letters which the package management system cannot
3275 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3276 silly orderings.<footnote>
3277 The author of this manual has heard of a package whose
3278 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3279 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3285 <sect1 id="f-Description">
3286 <heading><tt>Description</tt></heading>
3289 In a source or binary control file, the <tt>Description</tt>
3290 field contains a description of the binary package, consisting
3291 of two parts, the synopsis or the short description, and the
3292 long description. It is a multiline field with the following
3298 Description: <single line synopsis>
3299 <extended description over several lines>
3304 The lines in the extended description can have these formats:
3310 Those starting with a single space are part of a paragraph.
3311 Successive lines of this form will be word-wrapped when
3312 displayed. The leading space will usually be stripped off.
3313 The line must contain at least one non-whitespace character.
3317 Those starting with two or more spaces. These will be
3318 displayed verbatim. If the display cannot be panned
3319 horizontally, the displaying program will line wrap them "hard"
3320 (i.e., without taking account of word breaks). If it can they
3321 will be allowed to trail off to the right. None, one or two
3322 initial spaces may be deleted, but the number of spaces
3323 deleted from each line will be the same (so that you can have
3324 indenting work correctly, for example). The line must
3325 contain at least one non-whitespace character.
3329 Those containing a single space followed by a single full stop
3330 character. These are rendered as blank lines. This is the
3331 <em>only</em> way to get a blank line<footnote>
3332 Completely empty lines will not be rendered as blank lines.
3333 Instead, they will cause the parser to think you're starting
3334 a whole new record in the control file, and will therefore
3335 likely abort with an error.
3340 Those containing a space, a full stop and some more characters.
3341 These are for future expansion. Do not use them.
3347 Do not use tab characters. Their effect is not predictable.
3351 See <ref id="descriptions"> for further information on this.
3355 In a <file>.changes</file> file, the <tt>Description</tt>
3356 field contains a summary of the descriptions for the packages
3357 being uploaded. For this case, the first line of the field
3358 value (the part on the same line as <tt>Description:</tt>) is
3359 always empty. It is a multiline field, with one
3360 line per package. Each line is
3361 indented by one space and contains the name of a binary
3362 package, a space, a hyphen (<tt>-</tt>), a space, and the
3363 short description line from that package.
3367 <sect1 id="f-Distribution">
3368 <heading><tt>Distribution</tt></heading>
3371 In a <file>.changes</file> file or parsed changelog output
3372 this contains the (space-separated) name(s) of the
3373 distribution(s) where this version of the package should
3374 be installed. Valid distributions are determined by the
3375 archive maintainers.<footnote>
3376 Example distribution names in the Debian archive used in
3377 <file>.changes</file> files are:
3378 <taglist compact="compact">
3379 <tag><em>unstable</em></tag>
3381 This distribution value refers to the
3382 <em>developmental</em> part of the Debian distribution
3383 tree. Most new packages, new upstream versions of
3384 packages and bug fixes go into the <em>unstable</em>
3388 <tag><em>experimental</em></tag>
3390 The packages with this distribution value are deemed
3391 by their maintainers to be high risk. Oftentimes they
3392 represent early beta or developmental packages from
3393 various sources that the maintainers want people to
3394 try, but are not ready to be a part of the other parts
3395 of the Debian distribution tree.
3400 Others are used for updating stable releases or for
3401 security uploads. More information is available in the
3402 Debian Developer's Reference, section "The Debian
3406 The Debian archive software only supports listing a single
3407 distribution. Migration of packages to other distributions is
3408 handled outside of the upload process.
3413 <heading><tt>Date</tt></heading>
3416 This field includes the date the package was built or last
3417 edited. It must be in the same format as the <var>date</var>
3418 in a <file>debian/changelog</file> entry.
3422 The value of this field is usually extracted from the
3423 <file>debian/changelog</file> file - see
3424 <ref id="dpkgchangelog">).
3428 <sect1 id="f-Format">
3429 <heading><tt>Format</tt></heading>
3432 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3433 files, this field declares the format version of that file.
3434 The syntax of the field value is the same as that of
3435 a <qref id="f-Version">package version number</qref> except
3436 that no epoch or Debian revision is allowed. The format
3437 described in this document is <tt>&changesversion;</tt>.
3441 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3442 Debian source control</qref> files, this field declares the
3443 format of the source package. The field value is used by
3444 programs acting on a source package to interpret the list of
3445 files in the source package and determine how to unpack it.
3446 The syntax of the field value is a numeric major revision, a
3447 period, a numeric minor revision, and then an optional subtype
3448 after whitespace, which if specified is an alphanumeric word
3449 in parentheses. The subtype is optional in the syntax but may
3450 be mandatory for particular source format revisions.
3452 The source formats currently supported by the Debian archive
3453 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3454 and <tt>3.0 (quilt)</tt>.
3459 <sect1 id="f-Urgency">
3460 <heading><tt>Urgency</tt></heading>
3463 This is a description of how important it is to upgrade to
3464 this version from previous ones. It consists of a single
3465 keyword taking one of the values <tt>low</tt>,
3466 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3467 <tt>critical</tt><footnote>
3468 Other urgency values are supported with configuration
3469 changes in the archive software but are not used in Debian.
3470 The urgency affects how quickly a package will be considered
3471 for inclusion into the <tt>testing</tt> distribution and
3472 gives an indication of the importance of any fixes included
3473 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3474 treated as synonymous.
3475 </footnote> (not case-sensitive) followed by an optional
3476 commentary (separated by a space) which is usually in
3477 parentheses. For example:
3480 Urgency: low (HIGH for users of diversions)
3486 The value of this field is usually extracted from the
3487 <file>debian/changelog</file> file - see
3488 <ref id="dpkgchangelog">.
3492 <sect1 id="f-Changes">
3493 <heading><tt>Changes</tt></heading>
3496 This multiline field contains the human-readable changes data, describing
3497 the differences between the last version and the current one.
3501 The first line of the field value (the part on the same line
3502 as <tt>Changes:</tt>) is always empty. The content of the
3503 field is expressed as continuation lines, with each line
3504 indented by at least one space. Blank lines must be
3505 represented by a line consisting only of a space and a full
3510 The value of this field is usually extracted from the
3511 <file>debian/changelog</file> file - see
3512 <ref id="dpkgchangelog">).
3516 Each version's change information should be preceded by a
3517 "title" line giving at least the version, distribution(s)
3518 and urgency, in a human-readable way.
3522 If data from several versions is being returned the entry
3523 for the most recent version should be returned first, and
3524 entries should be separated by the representation of a
3525 blank line (the "title" line may also be followed by the
3526 representation of a blank line).
3530 <sect1 id="f-Binary">
3531 <heading><tt>Binary</tt></heading>
3534 This folded field is a list of binary packages. Its syntax and
3535 meaning varies depending on the control file in which it
3540 When it appears in the <file>.dsc</file> file, it lists binary
3541 packages which a source package can produce, separated by
3543 A space after each comma is conventional.
3544 </footnote>. The source package
3545 does not necessarily produce all of these binary packages for
3546 every architecture. The source control file doesn't contain
3547 details of which architectures are appropriate for which of
3548 the binary packages.
3552 When it appears in a <file>.changes</file> file, it lists the
3553 names of the binary packages being uploaded, separated by
3554 whitespace (not commas).
3558 <sect1 id="f-Installed-Size">
3559 <heading><tt>Installed-Size</tt></heading>
3562 This field appears in the control files of binary packages,
3563 and in the <file>Packages</file> files. It gives an estimate
3564 of the total amount of disk space required to install the
3565 named package. Actual installed size may vary based on block
3566 size, file system properties, or actions taken by package
3571 The disk space is given as the integer value of the estimated
3572 installed size in bytes, divided by 1024 and rounded up.
3576 <sect1 id="f-Files">
3577 <heading><tt>Files</tt></heading>
3580 This field contains a list of files with information about
3581 each one. The exact information and syntax varies with
3586 In all cases, Files is a multiline field. The first line of
3587 the field value (the part on the same line as <tt>Files:</tt>)
3588 is always empty. The content of the field is expressed as
3589 continuation lines, one line per file. Each line must be
3590 indented by one space and contain a number of sub-fields,
3591 separated by spaces, as described below.
3595 In the <file>.dsc</file> file, each line contains the MD5
3596 checksum, size and filename of the tar file and (if
3597 applicable) diff file which make up the remainder of the
3598 source package<footnote>
3599 That is, the parts which are not the <tt>.dsc</tt>.
3600 </footnote>. For example:
3603 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3604 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3606 The exact forms of the filenames are described
3607 in <ref id="pkg-sourcearchives">.
3611 In the <file>.changes</file> file this contains one line per
3612 file being uploaded. Each line contains the MD5 checksum,
3613 size, section and priority and the filename. For example:
3616 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3617 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3618 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3619 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3621 The <qref id="f-Section">section</qref>
3622 and <qref id="f-Priority">priority</qref> are the values of
3623 the corresponding fields in the main source control file. If
3624 no section or priority is specified then <tt>-</tt> should be
3625 used, though section and priority values must be specified for
3626 new packages to be installed properly.
3630 The special value <tt>byhand</tt> for the section in a
3631 <tt>.changes</tt> file indicates that the file in question
3632 is not an ordinary package file and must by installed by
3633 hand by the distribution maintainers. If the section is
3634 <tt>byhand</tt> the priority should be <tt>-</tt>.
3638 If a new Debian revision of a package is being shipped and
3639 no new original source archive is being distributed the
3640 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3641 entry for the original source archive
3642 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3643 but the <file>.changes</file> file should leave it out. In
3644 this case the original source archive on the distribution
3645 site must match exactly, byte-for-byte, the original
3646 source archive which was used to generate the
3647 <file>.dsc</file> file and diff which are being uploaded.</p>
3650 <sect1 id="f-Closes">
3651 <heading><tt>Closes</tt></heading>
3654 A space-separated list of bug report numbers that the upload
3655 governed by the .changes file closes.
3659 <sect1 id="f-Homepage">
3660 <heading><tt>Homepage</tt></heading>
3663 The URL of the web site for this package, preferably (when
3664 applicable) the site from which the original source can be
3665 obtained and any additional upstream documentation or
3666 information may be found. The content of this field is a
3667 simple URL without any surrounding characters such as
3672 <sect1 id="f-Checksums">
3673 <heading><tt>Checksums-Sha1</tt>
3674 and <tt>Checksums-Sha256</tt></heading>
3677 These multiline fields contain a list of files with a checksum and size
3678 for each one. Both <tt>Checksums-Sha1</tt>
3679 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3680 only in the checksum algorithm used: SHA-1
3681 for <tt>Checksums-Sha1</tt> and SHA-256
3682 for <tt>Checksums-Sha256</tt>.
3686 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3687 multiline fields. The first line of the field value (the part
3688 on the same line as <tt>Checksums-Sha1:</tt>
3689 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3690 of the field is expressed as continuation lines, one line per
3691 file. Each line consists of the checksum, a space, the file
3692 size, a space, and the file name. For example (from
3693 a <file>.changes</file> file):
3696 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3697 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3698 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3699 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3701 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3702 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3703 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3704 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3709 In the <file>.dsc</file> file, these fields should list all
3710 files that make up the source package. In
3711 the <file>.changes</file> file, these fields should list all
3712 files being uploaded. The list of files in these fields
3713 must match the list of files in the <tt>Files</tt> field.
3717 <sect1 id="f-DM-Upload-Allowed">
3718 <heading><tt>DM-Upload-Allowed</tt></heading>
3721 The most recent version of a package uploaded to unstable or
3722 experimental must include the field <tt>DM-Upload-Allowed:
3723 yes</tt> in the source section of its source control file for
3724 the Debian archive to accept uploads signed with a key in the
3725 Debian Maintainer keyring. See the General
3726 Resolution <url id="http://www.debian.org/vote/2007/vote_003"
3727 name="Endorse the concept of Debian Maintainers"> for more
3734 <heading>User-defined fields</heading>
3737 Additional user-defined fields may be added to the
3738 source package control file. Such fields will be
3739 ignored, and not copied to (for example) binary or
3740 Debian source control files or upload control files.
3744 If you wish to add additional unsupported fields to
3745 these output files you should use the mechanism
3750 Fields in the main source control information file with
3751 names starting <tt>X</tt>, followed by one or more of
3752 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3753 be copied to the output files. Only the part of the
3754 field name after the hyphen will be used in the output
3755 file. Where the letter <tt>B</tt> is used the field
3756 will appear in binary package control files, where the
3757 letter <tt>S</tt> is used in Debian source control
3758 files and where <tt>C</tt> is used in upload control
3759 (<tt>.changes</tt>) files.
3763 For example, if the main source information control file
3766 XBS-Comment: I stand between the candle and the star.
3768 then the binary and Debian source control files will contain the
3771 Comment: I stand between the candle and the star.
3780 <chapt id="maintainerscripts">
3781 <heading>Package maintainer scripts and installation procedure</heading>
3784 <heading>Introduction to package maintainer scripts</heading>
3787 It is possible to supply scripts as part of a package which
3788 the package management system will run for you when your
3789 package is installed, upgraded or removed.
3793 These scripts are the control information
3794 files <prgn>preinst</prgn>, <prgn>postinst</prgn>, <prgn>prerm</prgn>
3795 and <prgn>postrm</prgn>. They must be proper executable files;
3796 if they are scripts (which is recommended), they must start with
3797 the usual <tt>#!</tt> convention. They should be readable and
3798 executable by anyone, and must not be world-writable.
3802 The package management system looks at the exit status from
3803 these scripts. It is important that they exit with a
3804 non-zero status if there is an error, so that the package
3805 management system can stop its processing. For shell
3806 scripts this means that you <em>almost always</em> need to
3807 use <tt>set -e</tt> (this is usually true when writing shell
3808 scripts, in fact). It is also important, of course, that
3809 they exit with a zero status if everything went well.
3813 Additionally, packages interacting with users
3814 using <prgn>debconf</prgn> in the <prgn>postinst</prgn> script
3815 should install a <prgn>config</prgn> script as a control
3816 information file. See <ref id="maintscriptprompt"> for details.
3820 When a package is upgraded a combination of the scripts from
3821 the old and new packages is called during the upgrade
3822 procedure. If your scripts are going to be at all
3823 complicated you need to be aware of this, and may need to
3824 check the arguments to your scripts.
3828 Broadly speaking the <prgn>preinst</prgn> is called before
3829 (a particular version of) a package is unpacked, and the
3830 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3831 before (a version of) a package is removed and the
3832 <prgn>postrm</prgn> afterwards.
3836 Programs called from maintainer scripts should not normally
3837 have a path prepended to them. Before installation is
3838 started, the package management system checks to see if the
3839 programs <prgn>ldconfig</prgn>,
3840 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3841 and <prgn>update-rc.d</prgn> can be found via the
3842 <tt>PATH</tt> environment variable. Those programs, and any
3843 other program that one would expect to be in the
3844 <tt>PATH</tt>, should thus be invoked without an absolute
3845 pathname. Maintainer scripts should also not reset the
3846 <tt>PATH</tt>, though they might choose to modify it by
3847 prepending or appending package-specific directories. These
3848 considerations really apply to all shell scripts.</p>
3851 <sect id="idempotency">
3852 <heading>Maintainer scripts idempotency</heading>
3855 It is necessary for the error recovery procedures that the
3856 scripts be idempotent. This means that if it is run
3857 successfully, and then it is called again, it doesn't bomb
3858 out or cause any harm, but just ensures that everything is
3859 the way it ought to be. If the first call failed, or
3860 aborted half way through for some reason, the second call
3861 should merely do the things that were left undone the first
3862 time, if any, and exit with a success status if everything
3864 This is so that if an error occurs, the user interrupts
3865 <prgn>dpkg</prgn> or some other unforeseen circumstance
3866 happens you don't leave the user with a badly-broken
3867 package when <prgn>dpkg</prgn> attempts to repeat the
3873 <sect id="controllingterminal">
3874 <heading>Controlling terminal for maintainer scripts</heading>
3877 Maintainer scripts are not guaranteed to run with a controlling
3878 terminal and may not be able to interact with the user. They
3879 must be able to fall back to noninteractive behavior if no
3880 controlling terminal is available. Maintainer scripts that
3881 prompt via a program conforming to the Debian Configuration
3882 Management Specification (see <ref id="maintscriptprompt">) may
3883 assume that program will handle falling back to noninteractive
3888 For high-priority prompts without a reasonable default answer,
3889 maintainer scripts may abort if there is no controlling
3890 terminal. However, this situation should be avoided if at all
3891 possible, since it prevents automated or unattended installs.
3892 In most cases, users will consider this to be a bug in the
3897 <sect id="exitstatus">
3898 <heading>Exit status</heading>
3901 Each script must return a zero exit status for
3902 success, or a nonzero one for failure, since the package
3903 management system looks for the exit status of these scripts
3904 and determines what action to take next based on that datum.
3908 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3913 What follows is a summary of all the ways in which maintainer
3914 scripts may be called along with what facilities those scripts
3915 may rely on being available at that time. Script names preceded
3916 by <var>new-</var> are the scripts from the new version of a
3917 package being installed, upgraded to, or downgraded to. Script
3918 names preceded by <var>old-</var> are the scripts from the old
3919 version of a package that is being upgraded from or downgraded
3924 The <prgn>preinst</prgn> script may be called in the following
3927 <tag><var>new-preinst</var> <tt>install</tt></tag>
3928 <tag><var>new-preinst</var> <tt>install</tt>
3929 <var>old-version</var></tag>
3930 <tag><var>new-preinst</var> <tt>upgrade</tt>
3931 <var>old-version</var></tag>
3933 The package will not yet be unpacked, so
3934 the <prgn>preinst</prgn> script cannot rely on any files
3935 included in its package. Only essential packages and
3936 pre-dependencies (<tt>Pre-Depends</tt>) may be assumed to be
3937 available. Pre-dependencies will have been configured at
3938 least once, but at the time the <prgn>preinst</prgn> is
3939 called they may only be in an unpacked or "Half-Configured"
3940 state if a previous version of the pre-dependency was
3941 completely configured and has not been removed since then.
3944 <tag><var>old-preinst</var> <tt>abort-upgrade</tt>
3945 <var>new-version</var></tag>
3947 Called during error handling of an upgrade that failed after
3948 unpacking the new package because the <tt>postrm
3949 upgrade</tt> action failed. The unpacked files may be
3950 partly from the new version or partly missing, so the script
3951 cannot rely on files included in the package. Package
3952 dependencies may not be available. Pre-dependencies will be
3953 at least unpacked following the same rules as above, except
3954 they may be only "Half-Installed" if an upgrade of the
3955 pre-dependency failed.<footnote>
3956 This can happen if the new version of the package no
3957 longer pre-depends on a package that had been partially
3965 The <prgn>postinst</prgn> script may be called in the following
3968 <tag><var>postinst</var> <tt>configure</tt>
3969 <var>most-recently-configured-version</var></tag>
3971 The files contained in the package will be unpacked. All
3972 package dependencies will at least be unpacked. If there
3973 are no circular dependencies involved, all package
3974 dependencies will be configured. For behavior in the case
3975 of circular dependencies, see the discussion
3976 in <ref id="binarydeps">.
3979 <tag><var>old-postinst</var> <tt>abort-upgrade</tt>
3980 <var>new-version</var></tag>
3981 <tag><var>conflictor's-postinst</var> <tt>abort-remove</tt>
3982 <tt>in-favour</tt> <var>package</var>
3983 <var>new-version</var></tag>
3984 <tag><var>postinst</var> <tt>abort-remove</tt></tag>
3985 <tag><var>deconfigured's-postinst</var>
3986 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3987 <var>failed-install-package</var> <var>version</var>
3988 [<tt>removing</tt> <var>conflicting-package</var>
3989 <var>version</var>]</tag>
3991 The files contained in the package will be unpacked. All
3992 package dependencies will at least be "Half-Installed" and
3993 will have previously been configured and not removed.
3994 However, dependencies may not be configured or even fully
3995 unpacked in some error situations.<footnote>
3996 For example, suppose packages foo and bar are installed
3997 with foo depending on bar. If an upgrade of bar were
3998 started and then aborted, and then an attempt to remove
3999 foo failed because its <prgn>prerm</prgn> script failed,
4000 foo's <tt>postinst abort-remove</tt> would be called with
4001 bar only "Half-Installed".
4003 The <prgn>postinst</prgn> should still attempt any actions
4004 for which its dependencies are required, since they will
4005 normally be available, but consider the correct error
4006 handling approach if those actions fail. Aborting
4007 the <prgn>postinst</prgn> action if commands or facilities
4008 from the package dependencies are not available is often the
4015 The <prgn>prerm</prgn> script may be called in the following
4018 <tag><var>prerm</var> <tt>remove</tt></tag>
4019 <tag><var>old-prerm</var>
4020 <tt>upgrade</tt><var>new-version</var></tag>
4021 <tag><var>conflictor's-prerm</var> <tt>remove</tt>
4022 <tt>in-favour</tt> <var>package</var>
4023 <var>new-version</var></tag>
4024 <tag><var>deconfigured's-prerm</var> <tt>deconfigure</tt>
4025 <tt>in-favour</tt> <var>package-being-installed</var>
4026 <var>version</var> [<tt>removing</tt>
4027 <var>conflicting-package</var> <var>version</var>]</tag>
4029 The package whose <prgn>prerm</prgn> is being called will be
4030 at least "Half-Installed". All package dependencies will at
4031 least be "Half-Installed" and will have previously been
4032 configured and not removed. If there was no error, all
4033 dependencies will at least be unpacked, but these actions
4034 may be called in various error states where dependencies are
4035 only "Half-Installed" due to a partial upgrade.
4038 <tag><var>new-prerm</var> <tt>failed-upgrade</tt>
4039 <var>old-version</var></tag>
4041 Called during error handling when <tt>prerm upgrade</tt>
4042 fails. The new package will not yet be unpacked, and all
4043 the same constraints as for <tt>preinst upgrade</tt> apply.
4049 The <prgn>postrm</prgn> script may be called in the following
4052 <tag><var>postrm</var> <tt>remove</tt></tag>
4053 <tag><var>postrm</var> <tt>purge</tt></tag>
4054 <tag><var>old-postrm</var> <tt>upgrade</tt>
4055 <var>new-version</var></tag>
4056 <tag><var>disappearer's-postrm</var> <tt>disappear</tt>
4057 <var>overwriter</var> <var>overwriter-version</var></tag>
4059 The <prgn>postrm</prgn> script is called after the package's
4060 files have been removed or replaced. The package
4061 whose <prgn>postrm</prgn> is being called may have
4062 previously been deconfigured and only be unpacked, at which
4063 point subsequent package changes do not consider its
4064 dependencies. Therefore, all <prgn>postrm</prgn> actions
4065 may only rely on essential packages and must gracefully skip
4066 any actions that require the package's dependencies if those
4067 dependencies are unavailable.<footnote>
4068 This is often done by checking whether the command or
4069 facility the <prgn>postrm</prgn> intends to call is
4070 available before calling it. For example:
4072 if [ "$1" = purge ] && [ -e /usr/share/debconf/confmodule ]; then
4073 . /usr/share/debconf/confmodule
4077 in <prgn>postrm</prgn> purges the <prgn>debconf</prgn>
4078 configuration for the package
4079 if <package>debconf</package> is installed.
4083 <tag><var>new-postrm</var> <tt>failed-upgrade</tt>
4084 <var>old-version</var></tag>
4086 Called when the old <tt>postrm upgrade</tt> action fails.
4087 The new package will be unpacked, but only essential
4088 packages and pre-dependencies can be relied on.
4089 Pre-dependencies will either be configured or will be
4090 "Unpacked" or "Half-Configured" but previously had been
4091 configured and was never removed.
4094 <tag><var>new-postrm</var> <tt>abort-install</tt></tag>
4095 <tag><var>new-postrm</var> <tt>abort-install</tt>
4096 <var>old-version</var></tag>
4097 <tag><var>new-postrm</var> <tt>abort-upgrade</tt>
4098 <var>old-version</var></tag>
4100 Called before unpacking the new package as part of the
4101 error handling of <prgn>preinst</prgn> failures. May assume
4102 the same state as <prgn>preinst</prgn> can assume.
4108 <sect id="unpackphase">
4109 <heading>Details of unpack phase of installation or upgrade</heading>
4112 The procedure on installation/upgrade/overwrite/disappear
4113 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
4114 stage of <tt>dpkg --install</tt>) is as follows. In each
4115 case, if a major error occurs (unless listed below) the
4116 actions are, in general, run backwards - this means that the
4117 maintainer scripts are run with different arguments in
4118 reverse order. These are the "error unwind" calls listed
4125 If a version of the package is already installed, call
4126 <example compact="compact">
4127 <var>old-prerm</var> upgrade <var>new-version</var>
4131 If the script runs but exits with a non-zero
4132 exit status, <prgn>dpkg</prgn> will attempt:
4133 <example compact="compact">
4134 <var>new-prerm</var> failed-upgrade <var>old-version</var>
4136 If this works, the upgrade continues. If this
4137 does not work, the error unwind:
4138 <example compact="compact">
4139 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4141 If this works, then the old-version is
4142 "Installed", if not, the old version is in a
4143 "Half-Configured" state.
4149 If a "conflicting" package is being removed at the same time,
4150 or if any package will be broken (due to <tt>Breaks</tt>):
4153 If <tt>--auto-deconfigure</tt> is
4154 specified, call, for each package to be deconfigured
4155 due to <tt>Breaks</tt>:
4156 <example compact="compact">
4157 <var>deconfigured's-prerm</var> deconfigure \
4158 in-favour <var>package-being-installed</var> <var>version</var>
4161 <example compact="compact">
4162 <var>deconfigured's-postinst</var> abort-deconfigure \
4163 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
4165 The deconfigured packages are marked as
4166 requiring configuration, so that if
4167 <tt>--install</tt> is used they will be
4168 configured again if possible.
4171 If any packages depended on a conflicting
4172 package being removed and <tt>--auto-deconfigure</tt> is
4173 specified, call, for each such package:
4174 <example compact="compact">
4175 <var>deconfigured's-prerm</var> deconfigure \
4176 in-favour <var>package-being-installed</var> <var>version</var> \
4177 removing <var>conflicting-package</var> <var>version</var>
4180 <example compact="compact">
4181 <var>deconfigured's-postinst</var> abort-deconfigure \
4182 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
4183 removing <var>conflicting-package</var> <var>version</var>
4185 The deconfigured packages are marked as
4186 requiring configuration, so that if
4187 <tt>--install</tt> is used they will be
4188 configured again if possible.
4191 To prepare for removal of each conflicting package, call:
4192 <example compact="compact">
4193 <var>conflictor's-prerm</var> remove \
4194 in-favour <var>package</var> <var>new-version</var>
4197 <example compact="compact">
4198 <var>conflictor's-postinst</var> abort-remove \
4199 in-favour <var>package</var> <var>new-version</var>
4208 If the package is being upgraded, call:
4209 <example compact="compact">
4210 <var>new-preinst</var> upgrade <var>old-version</var>
4212 If this fails, we call:
4214 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4221 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4223 is called. If this works, then the old version
4224 is in an "Installed" state, or else it is left
4225 in an "Unpacked" state.
4230 If it fails, then the old version is left
4231 in an "Half-Installed" state.
4238 Otherwise, if the package had some configuration
4239 files from a previous version installed (i.e., it
4240 is in the "configuration files only" state):
4241 <example compact="compact">
4242 <var>new-preinst</var> install <var>old-version</var>
4246 <var>new-postrm</var> abort-install <var>old-version</var>
4248 If this fails, the package is left in a
4249 "Half-Installed" state, which requires a
4250 reinstall. If it works, the packages is left in
4251 a "Config-Files" state.
4254 Otherwise (i.e., the package was completely purged):
4255 <example compact="compact">
4256 <var>new-preinst</var> install
4259 <example compact="compact">
4260 <var>new-postrm</var> abort-install
4262 If the error-unwind fails, the package is in a
4263 "Half-Installed" phase, and requires a
4264 reinstall. If the error unwind works, the
4265 package is in a not installed state.
4272 The new package's files are unpacked, overwriting any
4273 that may be on the system already, for example any
4274 from the old version of the same package or from
4275 another package. Backups of the old files are kept
4276 temporarily, and if anything goes wrong the package
4277 management system will attempt to put them back as
4278 part of the error unwind.
4282 It is an error for a package to contain files which
4283 are on the system in another package, unless
4284 <tt>Replaces</tt> is used (see <ref id="replaces">).
4286 The following paragraph is not currently the case:
4287 Currently the <tt>- - force-overwrite</tt> flag is
4288 enabled, downgrading it to a warning, but this may not
4294 It is a more serious error for a package to contain a
4295 plain file or other kind of non-directory where another
4296 package has a directory (again, unless
4297 <tt>Replaces</tt> is used). This error can be
4298 overridden if desired using
4299 <tt>--force-overwrite-dir</tt>, but this is not
4304 Packages which overwrite each other's files produce
4305 behavior which, though deterministic, is hard for the
4306 system administrator to understand. It can easily
4307 lead to "missing" programs if, for example, a package
4308 is unpacked which overwrites a file from another
4309 package, and is then removed again.<footnote>
4310 Part of the problem is due to what is arguably a
4311 bug in <prgn>dpkg</prgn>.
4316 A directory will never be replaced by a symbolic link
4317 to a directory or vice versa; instead, the existing
4318 state (symlink or not) will be left alone and
4319 <prgn>dpkg</prgn> will follow the symlink if there is
4328 If the package is being upgraded, call
4329 <example compact="compact">
4330 <var>old-postrm</var> upgrade <var>new-version</var>
4334 If this fails, <prgn>dpkg</prgn> will attempt:
4335 <example compact="compact">
4336 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4338 If this works, installation continues. If not,
4340 <example compact="compact">
4341 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4343 If this fails, the old version is left in a
4344 "Half-Installed" state. If it works, dpkg now
4346 <example compact="compact">
4347 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4349 If this fails, the old version is left in a
4350 "Half-Installed" state. If it works, dpkg now
4352 <example compact="compact">
4353 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4355 If this fails, the old version is in an
4362 This is the point of no return - if
4363 <prgn>dpkg</prgn> gets this far, it won't back off
4364 past this point if an error occurs. This will
4365 leave the package in a fairly bad state, which
4366 will require a successful re-installation to clear
4367 up, but it's when <prgn>dpkg</prgn> starts doing
4368 things that are irreversible.
4373 Any files which were in the old version of the package
4374 but not in the new are removed.
4378 The new file list replaces the old.
4382 The new maintainer scripts replace the old.
4386 Any packages all of whose files have been overwritten
4387 during the installation, and which aren't required for
4388 dependencies, are considered to have been removed.
4389 For each such package
4392 <prgn>dpkg</prgn> calls:
4393 <example compact="compact">
4394 <var>disappearer's-postrm</var> disappear \
4395 <var>overwriter</var> <var>overwriter-version</var>
4399 The package's maintainer scripts are removed.
4402 It is noted in the status database as being in a
4403 sane state, namely not installed (any conffiles
4404 it may have are ignored, rather than being
4405 removed by <prgn>dpkg</prgn>). Note that
4406 disappearing packages do not have their prerm
4407 called, because <prgn>dpkg</prgn> doesn't know
4408 in advance that the package is going to
4415 Any files in the package we're unpacking that are also
4416 listed in the file lists of other packages are removed
4417 from those lists. (This will lobotomize the file list
4418 of the "conflicting" package if there is one.)
4422 The backup files made during installation, above, are
4428 The new package's status is now sane, and recorded as
4433 Here is another point of no return - if the
4434 conflicting package's removal fails we do not unwind
4435 the rest of the installation; the conflicting package
4436 is left in a half-removed limbo.
4441 If there was a conflicting package we go and do the
4442 removal actions (described below), starting with the
4443 removal of the conflicting package's files (any that
4444 are also in the package being unpacked have already
4445 been removed from the conflicting package's file list,
4446 and so do not get removed now).
4452 <sect id="configdetails"><heading>Details of configuration</heading>
4455 When we configure a package (this happens with <tt>dpkg
4456 --install</tt> and <tt>dpkg --configure</tt>), we first
4457 update any <tt>conffile</tt>s and then call:
4458 <example compact="compact">
4459 <var>postinst</var> configure <var>most-recently-configured-version</var>
4464 No attempt is made to unwind after errors during
4465 configuration. If the configuration fails, the package is in
4466 a "Failed Config" state, and an error message is generated.
4470 If there is no most recently configured version
4471 <prgn>dpkg</prgn> will pass a null argument.
4474 Historical note: Truly ancient (pre-1997) versions of
4475 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4476 (including the angle brackets) in this case. Even older
4477 ones did not pass a second argument at all, under any
4478 circumstance. Note that upgrades using such an old dpkg
4479 version are unlikely to work for other reasons, even if
4480 this old argument behavior is handled by your postinst script.
4486 <sect id="removedetails"><heading>Details of removal and/or
4487 configuration purging</heading>
4493 <example compact="compact">
4494 <var>prerm</var> remove
4498 If prerm fails during replacement due to conflict
4500 <var>conflictor's-postinst</var> abort-remove \
4501 in-favour <var>package</var> <var>new-version</var>
4505 <var>postinst</var> abort-remove
4509 If this fails, the package is in a "Half-Configured"
4510 state, or else it remains "Installed".
4514 The package's files are removed (except <tt>conffile</tt>s).
4517 <example compact="compact">
4518 <var>postrm</var> remove
4522 If it fails, there's no error unwind, and the package is in
4523 an "Half-Installed" state.
4528 All the maintainer scripts except the <prgn>postrm</prgn>
4533 If we aren't purging the package we stop here. Note
4534 that packages which have no <prgn>postrm</prgn> and no
4535 <tt>conffile</tt>s are automatically purged when
4536 removed, as there is no difference except for the
4537 <prgn>dpkg</prgn> status.
4541 The <tt>conffile</tt>s and any backup files
4542 (<tt>~</tt>-files, <tt>#*#</tt> files,
4543 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4548 <example compact="compact">
4549 <var>postrm</var> purge
4553 If this fails, the package remains in a "Config-Files"
4558 The package's file list is removed.
4567 <chapt id="relationships">
4568 <heading>Declaring relationships between packages</heading>
4570 <sect id="depsyntax">
4571 <heading>Syntax of relationship fields</heading>
4574 These fields all have a uniform syntax. They are a list of
4575 package names separated by commas.
4579 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4580 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4581 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4582 control fields of the package, which declare
4583 dependencies on other packages, the package names listed may
4584 also include lists of alternative package names, separated
4585 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4586 if any one of the alternative packages is installed, that
4587 part of the dependency is considered to be satisfied.
4591 All of the fields except for <tt>Provides</tt> may restrict
4592 their applicability to particular versions of each named
4593 package. This is done in parentheses after each individual
4594 package name; the parentheses should contain a relation from
4595 the list below followed by a version number, in the format
4596 described in <ref id="f-Version">.
4600 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4601 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4602 strictly earlier, earlier or equal, exactly equal, later or
4603 equal and strictly later, respectively. The deprecated
4604 forms <tt><</tt> and <tt>></tt> were used to mean
4605 earlier/later or equal, rather than strictly earlier/later,
4606 so they should not appear in new packages (though
4607 <prgn>dpkg</prgn> still supports them).
4611 Whitespace may appear at any point in the version
4612 specification subject to the rules in <ref
4613 id="controlsyntax">, and must appear where it's necessary to
4614 disambiguate; it is not otherwise significant. All of the
4615 relationship fields can only be folded in source package control files. For
4616 consistency and in case of future changes to
4617 <prgn>dpkg</prgn> it is recommended that a single space be
4618 used after a version relationship and before a version
4619 number; it is also conventional to put a single space after
4620 each comma, on either side of each vertical bar, and before
4621 each open parenthesis. When opening a continuation line in a relationship field, it
4622 is conventional to do so after a comma and before the space
4623 following that comma.
4627 For example, a list of dependencies might appear as:
4628 <example compact="compact">
4631 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4636 Relationships may be restricted to a certain set of
4637 architectures. This is indicated in brackets after each
4638 individual package name and the optional version specification.
4639 The brackets enclose a non-empty list of Debian architecture names
4640 in the format described in <ref id="arch-spec">,
4641 separated by whitespace. Exclamation marks may be prepended to
4642 each of the names. (It is not permitted for some names to be
4643 prepended with exclamation marks while others aren't.)
4647 For build relationship fields
4648 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4649 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>), if
4650 the current Debian host architecture is not in this list and
4651 there are no exclamation marks in the list, or it is in the list
4652 with a prepended exclamation mark, the package name and the
4653 associated version specification are ignored completely for the
4654 purposes of defining the relationships.
4659 <example compact="compact">
4661 Build-Depends-Indep: texinfo
4662 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4663 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4665 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4666 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4667 <tt>gnumach-dev</tt> only on hurd-i386.
4671 For binary relationship fields, the architecture restriction
4672 syntax is only supported in the source package control
4673 file <file>debian/control</file>. When the corresponding binary
4674 package control file is generated, the relationship will either
4675 be omitted or included without the architecture restriction
4676 based on the architecture of the binary package. This means
4677 that architecture restrictions must not be used in binary
4678 relationship fields for architecture-independent packages
4679 (<tt>Architecture: all</tt>).
4684 <example compact="compact">
4685 Depends: foo [i386], bar [amd64]
4687 becomes <tt>Depends: foo</tt> when the package is built on
4688 the <tt>i386</tt> architecture, <tt>Depends: bar</tt> when the
4689 package is built on the <tt>amd64</tt> architecture, and omitted
4690 entirely in binary packages built on all other architectures.
4694 If the architecture-restricted dependency is part of a set of
4695 alternatives using <tt>|</tt>, that alternative is ignored
4696 completely on architectures that do not match the restriction.
4698 <example compact="compact">
4699 Build-Depends: foo [!i386] | bar [!amd64]
4701 is equivalent to <tt>bar</tt> on the i386 architecture, to
4702 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4703 bar</tt> on all other architectures.
4707 Relationships may also be restricted to a certain set of
4708 architectures using architecture wildcards in the format
4709 described in <ref id="arch-wildcard-spec">. The syntax for
4710 declaring such restrictions is the same as declaring
4711 restrictions using a certain set of architectures without
4712 architecture wildcards. For example:
4713 <example compact="compact">
4714 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4716 is equivalent to <tt>foo</tt> on architectures using the Linux
4717 kernel and any cpu, <tt>bar</tt> on architectures using any
4718 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4719 using a kernel other than Linux.
4723 Note that the binary package relationship fields such as
4724 <tt>Depends</tt> appear in one of the binary package
4725 sections of the control file, whereas the build-time
4726 relationships such as <tt>Build-Depends</tt> appear in the
4727 source package section of the control file (which is the
4732 <sect id="binarydeps">
4733 <heading>Binary Dependencies - <tt>Depends</tt>,
4734 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4735 <tt>Pre-Depends</tt>
4739 Packages can declare in their control file that they have
4740 certain relationships to other packages - for example, that
4741 they may not be installed at the same time as certain other
4742 packages, and/or that they depend on the presence of others.
4746 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4747 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4748 <tt>Breaks</tt> and <tt>Conflicts</tt> control fields.
4749 <tt>Breaks</tt> is described in <ref id="breaks">, and
4750 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4751 rest are described below.
4755 These seven fields are used to declare a dependency
4756 relationship by one package on another. Except for
4757 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4758 depending (binary) package's control file.
4759 (<tt>Enhances</tt> appears in the recommending package's
4760 control file, and <tt>Breaks</tt> appears in the version of
4761 depended-on package which causes the named package to
4766 A <tt>Depends</tt> field takes effect <em>only</em> when a
4767 package is to be configured. It does not prevent a package
4768 being on the system in an unconfigured state while its
4769 dependencies are unsatisfied, and it is possible to replace
4770 a package whose dependencies are satisfied and which is
4771 properly installed with a different version whose
4772 dependencies are not and cannot be satisfied; when this is
4773 done the depending package will be left unconfigured (since
4774 attempts to configure it will give errors) and will not
4775 function properly. If it is necessary, a
4776 <tt>Pre-Depends</tt> field can be used, which has a partial
4777 effect even when a package is being unpacked, as explained
4778 in detail below. (The other three dependency fields,
4779 <tt>Recommends</tt>, <tt>Suggests</tt> and
4780 <tt>Enhances</tt>, are only used by the various front-ends
4781 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4782 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4786 Since <tt>Depends</tt> only places requirements on the order in
4787 which packages are configured, packages in an installation run
4788 are usually all unpacked first and all configured later.
4790 This approach makes dependency resolution easier. If two
4791 packages A and B are being upgraded, the installed package A
4792 depends on exactly the installed package B, and the new
4793 package A depends on exactly the new package B (a common
4794 situation when upgrading shared libraries and their
4795 corresponding development packages), satisfying the
4796 dependencies at every stage of the upgrade would be
4797 impossible. This relaxed restriction means that both new
4798 packages can be unpacked together and then configured in their
4804 If there is a circular dependency among packages being installed
4805 or removed, installation or removal order honoring the
4806 dependency order is impossible, requiring the dependency loop be
4807 broken at some point and the dependency requirements violated
4808 for at least one package. Packages involved in circular
4809 dependencies may not be able to rely on their dependencies being
4810 configured before they themselves are configured, depending on
4811 which side of the break of the circular dependency loop they
4812 happen to be on. If one of the packages in the loop has
4813 no <prgn>postinst</prgn> script, then the cycle will be broken
4814 at that package; this ensures that all <prgn>postinst</prgn>
4815 scripts are run with their dependencies properly configured if
4816 this is possible. Otherwise the breaking point is arbitrary.
4817 Packages should therefore avoid circular dependencies where
4818 possible, particularly if they have <prgn>postinst</prgn>
4823 The meaning of the five dependency fields is as follows:
4825 <tag><tt>Depends</tt></tag>
4828 This declares an absolute dependency. A package will
4829 not be configured unless all of the packages listed in
4830 its <tt>Depends</tt> field have been correctly
4831 configured (unless there is a circular dependency as
4836 The <tt>Depends</tt> field should be used if the
4837 depended-on package is required for the depending
4838 package to provide a significant amount of
4843 The <tt>Depends</tt> field should also be used if the
4844 <prgn>postinst</prgn> or <prgn>prerm</prgn> scripts
4845 require the depended-on package to be unpacked or
4846 configured in order to run. In the case of <tt>postinst
4847 configure</tt>, the depended-on packages will be unpacked
4848 and configured first. (If both packages are involved in a
4849 dependency loop, this might not work as expected; see the
4850 explanation a few paragraphs back.) In the case
4851 of <prgn>prerm</prgn> or other <prgn>postinst</prgn>
4852 actions, the package dependencies will normally be at
4853 least unpacked, but they may be only "Half-Installed" if a
4854 previous upgrade of the dependency failed.
4858 Finally, the <tt>Depends</tt> field should be used if the
4859 depended-on package is needed by the <prgn>postrm</prgn>
4860 script to fully clean up after the package removal. There
4861 is no guarantee that package dependencies will be
4862 available when <prgn>postrm</prgn> is run, but the
4863 depended-on package is more likely to be available if the
4864 package declares a dependency (particularly in the case
4865 of <tt>postrm remove</tt>). The <prgn>postrm</prgn>
4866 script must gracefully skip actions that require a
4867 dependency if that dependency isn't available.
4871 <tag><tt>Recommends</tt></tag>
4874 This declares a strong, but not absolute, dependency.
4878 The <tt>Recommends</tt> field should list packages
4879 that would be found together with this one in all but
4880 unusual installations.
4884 <tag><tt>Suggests</tt></tag>
4886 This is used to declare that one package may be more
4887 useful with one or more others. Using this field
4888 tells the packaging system and the user that the
4889 listed packages are related to this one and can
4890 perhaps enhance its usefulness, but that installing
4891 this one without them is perfectly reasonable.
4894 <tag><tt>Enhances</tt></tag>
4896 This field is similar to Suggests but works in the
4897 opposite direction. It is used to declare that a
4898 package can enhance the functionality of another
4902 <tag><tt>Pre-Depends</tt></tag>
4905 This field is like <tt>Depends</tt>, except that it
4906 also forces <prgn>dpkg</prgn> to complete installation
4907 of the packages named before even starting the
4908 installation of the package which declares the
4909 pre-dependency, as follows:
4913 When a package declaring a pre-dependency is about to
4914 be <em>unpacked</em> the pre-dependency can be
4915 satisfied if the depended-on package is either fully
4916 configured, <em>or even if</em> the depended-on
4917 package(s) are only unpacked or in the "Half-Configured"
4918 state, provided that they have been configured
4919 correctly at some point in the past (and not removed
4920 or partially removed since). In this case, both the
4921 previously-configured and currently unpacked or
4922 "Half-Configured" versions must satisfy any version
4923 clause in the <tt>Pre-Depends</tt> field.
4927 When the package declaring a pre-dependency is about to
4928 be <em>configured</em>, the pre-dependency will be treated
4929 as a normal <tt>Depends</tt>. It will be considered
4930 satisfied only if the depended-on package has been
4931 correctly configured. However, unlike
4932 with <tt>Depends</tt>, <tt>Pre-Depends</tt> does not
4933 permit circular dependencies to be broken. If a circular
4934 dependency is encountered while attempting to honor
4935 <tt>Pre-Depends</tt>, the installation will be aborted.
4939 <tt>Pre-Depends</tt> are also required if the
4940 <prgn>preinst</prgn> script depends on the named package.
4941 It is best to avoid this situation if possible.
4945 <tt>Pre-Depends</tt> should be used sparingly,
4946 preferably only by packages whose premature upgrade or
4947 installation would hamper the ability of the system to
4948 continue with any upgrade that might be in progress.
4952 You should not specify a <tt>Pre-Depends</tt> entry for a
4953 package before this has been discussed on the
4954 <tt>debian-devel</tt> mailing list and a consensus about
4955 doing that has been reached. See <ref id="dependencies">.
4962 When selecting which level of dependency to use you should
4963 consider how important the depended-on package is to the
4964 functionality of the one declaring the dependency. Some
4965 packages are composed of components of varying degrees of
4966 importance. Such a package should list using
4967 <tt>Depends</tt> the package(s) which are required by the
4968 more important components. The other components'
4969 requirements may be mentioned as Suggestions or
4970 Recommendations, as appropriate to the components' relative
4976 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4979 When one binary package declares that it breaks another,
4980 <prgn>dpkg</prgn> will refuse to allow the package which
4981 declares <tt>Breaks</tt> to be unpacked unless the broken
4982 package is deconfigured first, and it will refuse to
4983 allow the broken package to be reconfigured.
4987 A package will not be regarded as causing breakage merely
4988 because its configuration files are still installed; it must
4989 be at least "Half-Installed".
4993 A special exception is made for packages which declare that
4994 they break their own package name or a virtual package which
4995 they provide (see below): this does not count as a real
5000 Normally a <tt>Breaks</tt> entry will have an "earlier than"
5001 version clause; such a <tt>Breaks</tt> is introduced in the
5002 version of an (implicit or explicit) dependency which violates
5003 an assumption or reveals a bug in earlier versions of the broken
5004 package, or which takes over a file from earlier versions of the
5005 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
5006 will inform higher-level package management tools that the
5007 broken package must be upgraded before the new one.
5011 If the breaking package also overwrites some files from the
5012 older package, it should use <tt>Replaces</tt> to ensure this
5013 goes smoothly. See <ref id="replaces"> for a full discussion
5014 of taking over files from other packages, including how to
5015 use <tt>Breaks</tt> in those cases.
5019 Many of the cases where <tt>Breaks</tt> should be used were
5020 previously handled with <tt>Conflicts</tt>
5021 because <tt>Breaks</tt> did not yet exist.
5022 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
5023 See <ref id="conflicts"> for more information about the
5028 <sect id="conflicts">
5029 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
5032 When one binary package declares a conflict with another using
5033 a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will refuse to
5034 allow them to be unpacked on the system at the same time. This
5035 is a stronger restriction than <tt>Breaks</tt>, which prevents
5036 the broken package from being configured while the breaking
5037 package is in the "Unpacked" state but allows both packages to
5038 be unpacked at the same time.
5042 If one package is to be unpacked, the other must be removed
5043 first. If the package being unpacked is marked as replacing
5044 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
5045 normally be used in this case) the one on the system, or the one
5046 on the system is marked as deselected, or both packages are
5047 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
5048 automatically remove the package which is causing the conflict.
5049 Otherwise, it will halt the installation of the new package with
5050 an error. This mechanism is specifically designed to produce an
5051 error when the installed package is <tt>Essential</tt>, but the
5056 A package will not cause a conflict merely because its
5057 configuration files are still installed; it must be at least
5062 A special exception is made for packages which declare a
5063 conflict with their own package name, or with a virtual
5064 package which they provide (see below): this does not
5065 prevent their installation, and allows a package to conflict
5066 with others providing a replacement for it. You use this
5067 feature when you want the package in question to be the only
5068 package providing some feature.
5072 Normally, <tt>Breaks</tt> should be used instead
5073 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
5074 stronger restriction on the ordering of package installation or
5075 upgrade and can make it more difficult for the package manager
5076 to find a correct solution to an upgrade or installation
5077 problem. <tt>Breaks</tt> should be used
5079 <item>when moving a file from one package to another (see
5080 <ref id="replaces">),</item>
5081 <item>when splitting a package (a special case of the previous
5083 <item>when the breaking package exposes a bug in or interacts
5084 badly with particular versions of the broken
5087 <tt>Conflicts</tt> should be used
5089 <item>when two packages provide the same file and will
5090 continue to do so,</item>
5091 <item>in conjunction with <tt>Provides</tt> when only one
5092 package providing a given virtual facility may be unpacked
5093 at a time (see <ref id="virtual">),</item>
5094 <item>in other cases where one must prevent simultaneous
5095 installation of two packages for reasons that are ongoing
5096 (not fixed in a later version of one of the packages) or
5097 that must prevent both packages from being unpacked at the
5098 same time, not just configured.</item>
5100 Be aware that adding <tt>Conflicts</tt> is normally not the best
5101 solution when two packages provide the same files. Depending on
5102 the reason for that conflict, using alternatives or renaming the
5103 files is often a better approach. See, for
5104 example, <ref id="binaries">.
5108 Neither <tt>Breaks</tt> nor <tt>Conflicts</tt> should be used
5109 unless two packages cannot be installed at the same time or
5110 installing them both causes one of them to be broken or
5111 unusable. Having similar functionality or performing the same
5112 tasks as another package is not sufficient reason to
5113 declare <tt>Breaks</tt> or <tt>Conflicts</tt> with that package.
5117 A <tt>Conflicts</tt> entry may have an "earlier than" version
5118 clause if the reason for the conflict is corrected in a later
5119 version of one of the packages. However, normally the presence
5120 of an "earlier than" version clause is a sign
5121 that <tt>Breaks</tt> should have been used instead. An "earlier
5122 than" version clause in <tt>Conflicts</tt>
5123 prevents <prgn>dpkg</prgn> from upgrading or installing the
5124 package which declares such a conflict until the upgrade or
5125 removal of the conflicted-with package has been completed, which
5126 is a strong restriction.
5130 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
5134 As well as the names of actual ("concrete") packages, the
5135 package relationship fields <tt>Depends</tt>,
5136 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
5137 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
5138 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5139 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
5140 may mention "virtual packages".
5144 A <em>virtual package</em> is one which appears in the
5145 <tt>Provides</tt> control field of another package. The effect
5146 is as if the package(s) which provide a particular virtual
5147 package name had been listed by name everywhere the virtual
5148 package name appears. (See also <ref id="virtual_pkg">)
5152 If there are both concrete and virtual packages of the same
5153 name, then the dependency may be satisfied (or the conflict
5154 caused) by either the concrete package with the name in
5155 question or any other concrete package which provides the
5156 virtual package with the name in question. This is so that,
5157 for example, supposing we have
5158 <example compact="compact">
5161 </example> and someone else releases an enhanced version of
5162 the <tt>bar</tt> package they can say:
5163 <example compact="compact">
5167 and the <tt>bar-plus</tt> package will now also satisfy the
5168 dependency for the <tt>foo</tt> package.
5172 If a relationship field has a version number attached, only real
5173 packages will be considered to see whether the relationship is
5174 satisfied (or the prohibition violated, for a conflict or
5175 breakage). In other words, if a version number is specified,
5176 this is a request to ignore all <tt>Provides</tt> for that
5177 package name and consider only real packages. The package
5178 manager will assume that a package providing that virtual
5179 package is not of the "right" version. A <tt>Provides</tt>
5180 field may not contain version numbers, and the version number of
5181 the concrete package which provides a particular virtual package
5182 will not be considered when considering a dependency on or
5183 conflict with the virtual package name.<footnote>
5184 It is possible that a future release of <prgn>dpkg</prgn> may
5185 add the ability to specify a version number for each virtual
5186 package it provides. This feature is not yet present,
5187 however, and is expected to be used only infrequently.
5192 To specify which of a set of real packages should be the default
5193 to satisfy a particular dependency on a virtual package, list
5194 the real package as an alternative before the virtual one.
5198 If the virtual package represents a facility that can only be
5199 provided by one real package at a time, such as
5200 the <package>mail-transport-agent</package> virtual package that
5201 requires installation of a binary that would conflict with all
5202 other providers of that virtual package (see
5203 <ref id="mail-transport-agents">), all packages providing that
5204 virtual package should also declare a conflict with it
5205 using <tt>Conflicts</tt>. This will ensure that at most one
5206 provider of that virtual package is unpacked or installed at a
5211 <sect id="replaces"><heading>Overwriting files and replacing
5212 packages - <tt>Replaces</tt></heading>
5215 Packages can declare in their control file that they should
5216 overwrite files in certain other packages, or completely replace
5217 other packages. The <tt>Replaces</tt> control field has these
5218 two distinct purposes.
5221 <sect1><heading>Overwriting files in other packages</heading>
5224 It is usually an error for a package to contain files which
5225 are on the system in another package. However, if the
5226 overwriting package declares that it <tt>Replaces</tt> the one
5227 containing the file being overwritten, then <prgn>dpkg</prgn>
5228 will replace the file from the old package with that from the
5229 new. The file will no longer be listed as "owned" by the old
5230 package and will be taken over by the new package.
5231 Normally, <tt>Breaks</tt> should be used in conjunction
5232 with <tt>Replaces</tt>.<footnote>
5233 To see why <tt>Breaks</tt> is normally needed in addition
5234 to <tt>Replaces</tt>, consider the case of a file in the
5235 package <package>foo</package> being taken over by the
5236 package <package>foo-data</package>.
5237 <tt>Replaces</tt> will allow <package>foo-data</package> to
5238 be installed and take over that file. However,
5239 without <tt>Breaks</tt>, nothing
5240 requires <package>foo</package> to be upgraded to a newer
5241 version that knows it does not include that file and instead
5242 depends on <package>foo-data</package>. Nothing would
5243 prevent the new <package>foo-data</package> package from
5244 being installed and then removed, removing the file that it
5245 took over from <package>foo</package>. After that
5246 operation, the package manager would think the system was in
5247 a consistent state, but the <package>foo</package> package
5248 would be missing one of its files.
5253 For example, if a package <package>foo</package> is split
5254 into <package>foo</package> and <package>foo-data</package>
5255 starting at version 1.2-3, <package>foo-data</package> would
5257 <example compact="compact">
5258 Replaces: foo (<< 1.2-3)
5259 Breaks: foo (<< 1.2-3)
5261 in its control file. The new version of the
5262 package <package>foo</package> would normally have the field
5263 <example compact="compact">
5264 Depends: foo-data (>= 1.2-3)
5266 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
5267 the files moved into <package>foo-data</package> are not
5268 required for normal operation).
5272 If a package is completely replaced in this way, so that
5273 <prgn>dpkg</prgn> does not know of any files it still
5274 contains, it is considered to have "disappeared". It will
5275 be marked as not wanted on the system (selected for
5276 removal) and not installed. Any <tt>conffile</tt>s
5277 details noted for the package will be ignored, as they
5278 will have been taken over by the overwriting package. The
5279 package's <prgn>postrm</prgn> script will be run with a
5280 special argument to allow the package to do any final
5281 cleanup required. See <ref id="mscriptsinstact">.
5283 Replaces is a one way relationship. You have to install
5284 the replacing package after the replaced package.
5289 For this usage of <tt>Replaces</tt>, virtual packages (see
5290 <ref id="virtual">) are not considered when looking at a
5291 <tt>Replaces</tt> field. The packages declared as being
5292 replaced must be mentioned by their real names.
5296 This usage of <tt>Replaces</tt> only takes effect when both
5297 packages are at least partially on the system at once. It is
5298 not relevant if the packages conflict unless the conflict has
5303 <sect1><heading>Replacing whole packages, forcing their
5307 Second, <tt>Replaces</tt> allows the packaging system to
5308 resolve which package should be removed when there is a
5309 conflict (see <ref id="conflicts">). This usage only takes
5310 effect when the two packages <em>do</em> conflict, so that the
5311 two usages of this field do not interfere with each other.
5315 In this situation, the package declared as being replaced
5316 can be a virtual package, so for example, all mail
5317 transport agents (MTAs) would have the following fields in
5318 their control files:
5319 <example compact="compact">
5320 Provides: mail-transport-agent
5321 Conflicts: mail-transport-agent
5322 Replaces: mail-transport-agent
5324 ensuring that only one MTA can be unpacked at any one
5325 time. See <ref id="virtual"> for more information about this
5330 <sect id="sourcebinarydeps">
5331 <heading>Relationships between source and binary packages -
5332 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5333 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5337 Source packages that require certain binary packages to be
5338 installed or absent at the time of building the package
5339 can declare relationships to those binary packages.
5343 This is done using the <tt>Build-Depends</tt>,
5344 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5345 <tt>Build-Conflicts-Indep</tt> control fields.
5349 Build-dependencies on "build-essential" binary packages can be
5350 omitted. Please see <ref id="pkg-relations"> for more information.
5354 The dependencies and conflicts they define must be satisfied
5355 (as defined earlier for binary packages) in order to invoke
5356 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5358 There is no Build-Depends-Arch; this role is essentially
5359 met with Build-Depends. Anyone building the
5360 <tt>build-indep</tt> and <tt>binary-indep</tt> targets is
5361 assumed to be building the whole package, and therefore
5362 installation of all build dependencies is required.
5365 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5366 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5367 not yet know how to check for its existence, and
5368 <tt>binary-arch</tt>. The purpose of the original split
5369 between <tt>Build-Depends</tt> and
5370 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5371 wouldn't need to install extra packages needed only for the
5372 binary-indep targets. But without a build-arch/build-indep
5373 split, this didn't work, since most of the work is done in
5374 the build target, not in the binary target.
5378 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5379 <tt>binary-arch</tt></tag>
5381 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5382 fields must be satisfied when these targets are invoked.
5384 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5385 and <tt>binary-indep</tt></tag>
5387 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5388 <tt>Build-Depends-Indep</tt>, and
5389 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5390 these targets are invoked.
5398 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5401 Packages containing shared libraries must be constructed with
5402 a little care to make sure that the shared library is always
5403 available. This is especially important for packages whose
5404 shared libraries are vitally important, such as the C library
5405 (currently <tt>libc6</tt>).
5409 This section deals only with public shared libraries: shared
5410 libraries that are placed in directories searched by the dynamic
5411 linker by default or which are intended to be linked against
5412 normally and possibly used by other, independent packages. Shared
5413 libraries that are internal to a particular package or that are
5414 only loaded as dynamic modules are not covered by this section and
5415 are not subject to its requirements.
5419 A shared library is identified by the <tt>SONAME</tt> attribute
5420 stored in its dynamic section. When a binary is linked against a
5421 shared library, the <tt>SONAME</tt> of the shared library is
5422 recorded in the binary's <tt>NEEDED</tt> section so that the
5423 dynamic linker knows that library must be loaded at runtime. The
5424 shared library file's full name (which usually contains additional
5425 version information not needed in the <tt>SONAME</tt>) is
5426 therefore normally not referenced directly. Instead, the shared
5427 library is loaded by its <tt>SONAME</tt>, which exists on the file
5428 system as a symlink pointing to the full name of the shared
5429 library. This symlink must be provided by the
5430 package. <ref id="sharedlibs-runtime"> describes how to do this.
5432 This is a convention of shared library versioning, but not a
5433 requirement. Some libraries use the <tt>SONAME</tt> as the full
5434 library file name instead and therefore do not need a symlink.
5435 Most, however, encode additional information about
5436 backwards-compatible revisions as a minor version number in the
5437 file name. The <tt>SONAME</tt> itself only changes when
5438 binaries linked with the earlier version of the shared library
5439 may no longer work, but the filename may change with each
5440 release of the library. See <ref id="sharedlibs-runtime"> for
5446 When linking a binary or another shared library against a shared
5447 library, the <tt>SONAME</tt> for that shared library is not yet
5448 known. Instead, the shared library is found by looking for a file
5449 matching the library name with <tt>.so</tt> appended. This file
5450 exists on the file system as a symlink pointing to the shared
5455 Shared libraries are normally split into several binary packages.
5456 The <tt>SONAME</tt> symlink is installed by the runtime shared
5457 library package, and the bare <tt>.so</tt> symlink is installed in
5458 the development package since it's only used when linking binaries
5459 or shared libraries. However, there are some exceptions for
5460 unusual shared libraries or for shared libraries that are also
5461 loaded as dynamic modules by other programs.
5465 This section is primarily concerned with how the separation of
5466 shared libraries into multiple packages should be done and how
5467 dependencies on and between shared library binary packages are
5468 managed in Debian. <ref id="libraries"> should be read in
5469 conjunction with this section and contains additional rules for
5470 the files contained in the shared library packages.
5473 <sect id="sharedlibs-runtime">
5474 <heading>Run-time shared libraries</heading>
5477 The run-time shared library must be placed in a package
5478 whose name changes whenever the <tt>SONAME</tt> of the shared
5479 library changes. This allows several versions of the shared
5480 library to be installed at the same time, allowing installation
5481 of the new version of the shared library without immediately
5482 breaking binaries that depend on the old version. Normally, the
5483 run-time shared library and its <tt>SONAME</tt> symlink should
5484 be placed in a package named
5485 <package><var>libraryname</var><var>soversion</var></package>,
5486 where <var>soversion</var> is the version number in
5487 the <tt>SONAME</tt> of the shared library.
5488 See <ref id="shlibs"> for detailed information on how to
5489 determine this version. Alternatively, if it would be confusing
5490 to directly append <var>soversion</var>
5491 to <var>libraryname</var> (if, for example, <var>libraryname</var>
5492 itself ends in a number), you should use
5493 <package><var>libraryname</var>-<var>soversion</var></package>
5498 If you have several shared libraries built from the same source
5499 tree, you may lump them all together into a single shared
5500 library package provided that all of their <tt>SONAME</tt>s will
5501 always change together. Be aware that this is not normally the
5502 case, and if the <tt>SONAME</tt>s do not change together,
5503 upgrading such a merged shared library package will be
5504 unnecessarily difficult because of file conflicts with the old
5505 version of the package. When in doubt, always split shared
5506 library packages so that each binary package installs a single
5511 Every time the shared library ABI changes in a way that may
5512 break binaries linked against older versions of the shared
5513 library, the <tt>SONAME</tt> of the library and the
5514 corresponding name for the binary package containing the runtime
5515 shared library should change. Normally, this means
5516 the <tt>SONAME</tt> should change any time an interface is
5517 removed from the shared library or the signature of an interface
5518 (the number of parameters or the types of parameters that it
5519 takes, for example) is changed. This practice is vital to
5520 allowing clean upgrades from older versions of the package and
5521 clean transitions between the old ABI and new ABI without having
5522 to upgrade every affected package simultaneously.
5526 The <tt>SONAME</tt> and binary package name need not, and indeed
5527 normally should not, change if new interfaces are added but none
5528 are removed or changed, since this will not break binaries
5529 linked against the old shared library. Correct versioning of
5530 dependencies on the newer shared library by binaries that use
5531 the new interfaces is handled via
5532 the <qref id="sharedlibs-shlibdeps"><tt>shlibs</tt>
5533 system</qref> or via symbols files (see
5534 <manref name="deb-symbols" section="5">).
5538 The package should install the shared libraries under
5539 their normal names. For example, the <package>libgdbm3</package>
5540 package should install <file>libgdbm.so.3.0.0</file> as
5541 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5542 renamed or re-linked by any <prgn>prerm</prgn> or
5543 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5544 of renaming things safely without affecting running programs,
5545 and attempts to interfere with this are likely to lead to
5550 Shared libraries should not be installed executable, since
5551 the dynamic linker does not require this and trying to
5552 execute a shared library usually results in a core dump.
5556 The run-time library package should include the symbolic link for
5557 the <tt>SONAME</tt> that <prgn>ldconfig</prgn> would create for
5558 the shared libraries. For example,
5559 the <package>libgdbm3</package> package should include a symbolic
5560 link from <file>/usr/lib/libgdbm.so.3</file> to
5561 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5562 linker (for example <prgn>ld.so</prgn> or
5563 <prgn>ld-linux.so.*</prgn>) can find the library between the
5564 time that <prgn>dpkg</prgn> installs it and the time that
5565 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5567 The package management system requires the library to be
5568 placed before the symbolic link pointing to it in the
5569 <file>.deb</file> file. This is so that when
5570 <prgn>dpkg</prgn> comes to install the symlink
5571 (overwriting the previous symlink pointing at an older
5572 version of the library), the new shared library is already
5573 in place. In the past, this was achieved by creating the
5574 library in the temporary packaging directory before
5575 creating the symlink. Unfortunately, this was not always
5576 effective, since the building of the tar file in the
5577 <file>.deb</file> depended on the behavior of the underlying
5578 file system. Some file systems (such as reiserfs) reorder
5579 the files so that the order of creation is forgotten.
5580 Since version 1.7.0, <prgn>dpkg</prgn>
5581 reorders the files itself as necessary when building a
5582 package. Thus it is no longer important to concern
5583 oneself with the order of file creation.
5587 <sect1 id="ldconfig">
5588 <heading><tt>ldconfig</tt></heading>
5591 Any package installing shared libraries in one of the default
5592 library directories of the dynamic linker (which are currently
5593 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5594 listed in <file>/etc/ld.so.conf</file><footnote>
5595 These are currently <file>/usr/local/lib</file> plus
5596 directories under <file>/lib</file> and <file>/usr/lib</file>
5597 matching the multiarch triplet for the system architecture.
5599 must use <prgn>ldconfig</prgn> to update the shared library
5604 The package maintainer scripts must only call
5605 <prgn>ldconfig</prgn> under these circumstances:
5606 <list compact="compact">
5607 <item>When the <prgn>postinst</prgn> script is run with a
5608 first argument of <tt>configure</tt>, the script must call
5609 <prgn>ldconfig</prgn>, and may optionally invoke
5610 <prgn>ldconfig</prgn> at other times.
5612 <item>When the <prgn>postrm</prgn> script is run with a
5613 first argument of <tt>remove</tt>, the script should call
5614 <prgn>ldconfig</prgn>.
5619 During install or upgrade, the preinst is called before
5620 the new files are unpacked, so calling "ldconfig" is
5621 pointless. The preinst of an existing package can also be
5622 called if an upgrade fails. However, this happens during
5623 the critical time when a shared libs may exist on-disk
5624 under a temporary name. Thus, it is dangerous and
5625 forbidden by current policy to call "ldconfig" at this
5630 When a package is installed or upgraded, "postinst
5631 configure" runs after the new files are safely on-disk.
5632 Since it is perfectly safe to invoke ldconfig
5633 unconditionally in a postinst, it is OK for a package to
5634 simply put ldconfig in its postinst without checking the
5635 argument. The postinst can also be called to recover from
5636 a failed upgrade. This happens before any new files are
5637 unpacked, so there is no reason to call "ldconfig" at this
5642 For a package that is being removed, prerm is
5643 called with all the files intact, so calling ldconfig is
5644 useless. The other calls to "prerm" happen in the case of
5645 upgrade at a time when all the files of the old package
5646 are on-disk, so again calling "ldconfig" is pointless.
5650 postrm, on the other hand, is called with the "remove"
5651 argument just after the files are removed, so this is
5652 the proper time to call "ldconfig" to notify the system
5653 of the fact that the shared libraries from the package
5654 are removed. The postrm can be called at several other
5655 times. At the time of "postrm purge", "postrm
5656 abort-install", or "postrm abort-upgrade", calling
5657 "ldconfig" is useless because the shared lib files are
5658 not on-disk. However, when "postrm" is invoked with
5659 arguments "upgrade", "failed-upgrade", or "disappear", a
5660 shared lib may exist on-disk under a temporary filename.
5668 <sect id="sharedlibs-support-files">
5669 <heading>Shared library support files</heading>
5672 If your package contains files whose names do not change with
5673 each change in the library shared object version, you must not
5674 put them in the shared library package. Otherwise, several
5675 versions of the shared library cannot be installed at the same
5676 time without filename clashes, making upgrades and transitions
5677 unnecessarily difficult.
5681 It is recommended that supporting files and run-time support
5682 programs that do not need to be invoked manually by users, but
5683 are nevertheless required for the package to function, be placed
5684 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5685 preferably under <file>/usr/lib/</file><var>package-name</var>.
5686 If the program or file is architecture independent, the
5687 recommendation is for it to be placed in a subdirectory of
5688 <file>/usr/share</file> instead, preferably under
5689 <file>/usr/share/</file><var>package-name</var>. Following the
5690 <var>package-name</var> naming convention ensures that the file
5691 names change when the shared object version changes.
5695 Run-time support programs that use the shared library but are
5696 not required for the library to function or files used by the
5697 shared library that can be used by any version of the shared
5698 library package should instead be put in a separate package.
5699 This package might typically be named
5700 <package><var>libraryname</var>-tools</package>; note the
5701 absence of the <var>soversion</var> in the package name.
5705 Files and support programs only useful when compiling software
5706 against the library should be included in the development
5707 package for the library.<footnote>
5708 For example, a <file><var>package-name</var>-config</file>
5709 script or <package>pkg-config</package> configuration files.
5714 <sect id="sharedlibs-static">
5715 <heading>Static libraries</heading>
5718 The static library (<file><var>libraryname.a</var></file>)
5719 is usually provided in addition to the shared version.
5720 It is placed into the development package (see below).
5724 In some cases, it is acceptable for a library to be
5725 available in static form only; these cases include:
5727 <item>libraries for languages whose shared library support
5728 is immature or unstable</item>
5729 <item>libraries whose interfaces are in flux or under
5730 development (commonly the case when the library's
5731 major version number is zero, or where the ABI breaks
5732 across patchlevels)</item>
5733 <item>libraries which are explicitly intended to be
5734 available only in static form by their upstream
5739 <sect id="sharedlibs-dev">
5740 <heading>Development files</heading>
5743 If there are development files associated with a shared library,
5744 the source package needs to generate a binary development package
5745 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5746 or if you prefer only to support one development version at a
5747 time, <package><var>libraryname</var>-dev</package>. Installing
5748 the development package must result in installation of all the
5749 development files necessary for compiling programs against that
5750 shared library.<footnote>
5751 This wording allows the development files to be split into
5752 several packages, such as a separate architecture-independent
5753 <package><var>libraryname</var>-headers</package>, provided that
5754 the development package depends on all the required additional
5760 In case several development versions of a library exist, you may
5761 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5762 <ref id="conflicts">) to ensure that the user only installs one
5763 development version at a time (as different development versions are
5764 likely to have the same header files in them, which would cause a
5765 filename clash if both were unpacked).
5769 The development package should contain a symlink for the associated
5770 shared library without a version number. For example, the
5771 <package>libgdbm-dev</package> package should include a symlink
5772 from <file>/usr/lib/libgdbm.so</file> to
5773 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5774 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5775 <file>libgdbm.so</file> when compiling dynamically.
5779 If the package provides Ada Library Information
5780 (<file>*.ali</file>) files for use with GNAT, these files must be
5781 installed read-only (mode 0444) so that GNAT will not attempt to
5782 recompile them. This overrides the normal file mode requirements
5783 given in <ref id="permissions-owners">.
5787 <sect id="sharedlibs-intradeps">
5788 <heading>Dependencies between the packages of the same library</heading>
5791 Typically the development version should have an exact
5792 version dependency on the runtime library, to make sure that
5793 compilation and linking happens correctly. The
5794 <tt>${binary:Version}</tt> substitution variable can be
5795 useful for this purpose.
5797 Previously, <tt>${Source-Version}</tt> was used, but its name
5798 was confusing and it has been deprecated since dpkg 1.13.19.
5803 <sect id="sharedlibs-shlibdeps">
5804 <heading>Dependencies between the library and other packages -
5805 the <tt>shlibs</tt> system</heading>
5808 If a package contains a binary or library which links to a
5809 shared library, we must ensure that when the package is
5810 installed on the system, all of the libraries needed are
5811 also installed. This requirement led to the creation of the
5812 <tt>shlibs</tt> system, which is very simple in its design:
5813 any package which <em>provides</em> a shared library also
5814 provides information on the package dependencies required to
5815 ensure the presence of this library, and any package which
5816 <em>uses</em> a shared library uses this information to
5817 determine the dependencies it requires. The files which
5818 contain the mapping from shared libraries to the necessary
5819 dependency information are called <file>shlibs</file> files.
5823 When a package is built which contains any shared libraries, it
5824 must provide a <file>shlibs</file> file for other packages to
5825 use. When a package is built which contains any shared
5826 libraries or compiled binaries, it must run
5827 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5828 on these to determine the libraries used and hence the
5829 dependencies needed by this package.<footnote>
5831 <prgn>dpkg-shlibdeps</prgn> will use a program
5832 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
5833 the libraries directly needed by the binaries or shared
5834 libraries in the package.
5838 We say that a binary <tt>foo</tt> <em>directly</em> uses
5839 a library <tt>libbar</tt> if it is explicitly linked
5840 with that library (that is, the library is listed in the ELF
5841 <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
5842 to the link line when the binary is created). Other
5843 libraries that are needed by <tt>libbar</tt> are linked
5844 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5845 linker will load them automatically when it loads
5846 <tt>libbar</tt>. A package should depend on the libraries
5847 it directly uses, but not the libraries it indirectly uses.
5848 The dependencies for those libraries will automatically pull
5849 in the other libraries.
5853 A good example of where this helps is the following. We
5854 could update <tt>libimlib</tt> with a new version that
5855 supports a new graphics format called dgf (but retaining the
5856 same major version number) and depends on <tt>libdgf</tt>.
5857 If we used <prgn>ldd</prgn> to add dependencies for every
5858 library directly or indirectly linked with a binary, every
5859 package that uses <tt>libimlib</tt> would need to be
5860 recompiled so it would also depend on <tt>libdgf</tt> or it
5861 wouldn't run due to missing symbols. Since dependencies are
5862 only added based on ELF <tt>NEEDED</tt> attribute, packages
5863 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
5864 having the dependency on <tt>libdgf</tt> and so they would
5865 not need rebuilding.
5871 In the following sections, we will first describe where the
5872 various <tt>shlibs</tt> files are to be found, then how to
5873 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5874 file format and how to create them if your package contains a
5879 <heading>The <tt>shlibs</tt> files present on the system</heading>
5882 There are several places where <tt>shlibs</tt> files are
5883 found. The following list gives them in the order in which
5885 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5886 (The first one which gives the required information is used.)
5892 <p><file>debian/shlibs.local</file></p>
5895 This lists overrides for this package. This file should
5896 normally not be used, but may be needed temporarily in
5897 unusual situations to work around bugs in other packages,
5898 or in unusual cases where the normally declared dependency
5899 information in the installed <file>shlibs</file> file for
5900 a library cannot be used. This file overrides information
5901 obtained from any other source.
5906 <p><file>/etc/dpkg/shlibs.override</file></p>
5909 This lists global overrides. This list is normally
5910 empty. It is maintained by the local system
5916 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5919 When packages are being built,
5920 any <file>debian/shlibs</file> files are copied into the
5921 control information file area of the temporary build
5922 directory and given the name <file>shlibs</file>. These
5923 files give details of any shared libraries included in the
5924 same package.<footnote>
5925 An example may help here. Let us say that the source
5926 package <tt>foo</tt> generates two binary
5927 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
5928 When building the binary packages, the two packages are
5929 created in the directories <file>debian/libfoo2</file>
5930 and <file>debian/foo-runtime</file> respectively.
5931 (<file>debian/tmp</file> could be used instead of one of
5932 these.) Since <tt>libfoo2</tt> provides the
5933 <tt>libfoo</tt> shared library, it will require a
5934 <tt>shlibs</tt> file, which will be installed in
5935 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually to
5936 become <file>/var/lib/dpkg/info/libfoo2.shlibs</file>.
5937 When <prgn>dpkg-shlibdeps</prgn> is run on the
5938 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
5940 the <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5941 determine whether <tt>foo-prog</tt>'s library
5942 dependencies are satisfied by any of the libraries
5943 provided by <tt>libfoo2</tt>. For this reason,
5944 <prgn>dpkg-shlibdeps</prgn> must only be run once all of
5945 the individual binary packages' <tt>shlibs</tt> files
5946 have been installed into the build directory.
5952 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5955 These are the <file>shlibs</file> files corresponding to
5956 all of the packages installed on the system, and are
5957 maintained by the relevant package maintainers.
5962 <p><file>/etc/dpkg/shlibs.default</file></p>
5965 This file lists any shared libraries whose packages
5966 have failed to provide correct <file>shlibs</file> files.
5967 It was used when the <file>shlibs</file> setup was first
5968 introduced, but it is now normally empty. It is
5969 maintained by the <tt>dpkg</tt> maintainer.
5977 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5978 <file>shlibs</file> files</heading>
5982 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5983 into your <file>debian/rules</file> file. If your package
5984 contains only compiled binaries and libraries (but no scripts),
5985 you can use a command such as:
5986 <example compact="compact">
5987 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5988 debian/tmp/usr/lib/*
5990 Otherwise, you will need to explicitly list the compiled
5991 binaries and libraries.<footnote>
5992 If you are using <tt>debhelper</tt>, the
5993 <prgn>dh_shlibdeps</prgn> program will do this work for you.
5994 It will also correctly handle multi-binary packages.
5999 This command puts the dependency information into the
6000 <file>debian/substvars</file> file, which is then used by
6001 <prgn>dpkg-gencontrol</prgn>. You will need to place a
6002 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
6003 field in the control file for this to work.
6007 If you have multiple binary packages, you will need to call
6008 <prgn>dpkg-shlibdeps</prgn> on each one which contains
6009 compiled libraries or binaries. In such a case, you will
6010 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
6011 utilities to specify a different <file>substvars</file> file.
6015 If you are creating a udeb for use in the Debian Installer,
6016 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
6017 should use the dependency line of type <tt>udeb</tt> by
6018 adding the <tt>-tudeb</tt> option<footnote>
6019 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
6020 will automatically add this option if it knows it is
6022 </footnote>. If there is no dependency line of
6023 type <tt>udeb</tt> in the <file>shlibs</file>
6024 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the regular
6029 For more details on <prgn>dpkg-shlibdeps</prgn>, please see
6030 <ref id="pkg-dpkg-shlibdeps"> and
6031 <manref name="dpkg-shlibdeps" section="1">.
6036 <heading>The <file>shlibs</file> File Format</heading>
6039 Each <file>shlibs</file> file has the same format. Lines
6040 beginning with <tt>#</tt> are considered to be comments and
6041 are ignored. Each line is of the form:
6042 <example compact="compact">
6043 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
6048 We will explain this by reference to the example of the
6049 <tt>zlib1g</tt> package, which (at the time of writing)
6050 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
6054 <var>type</var> is an optional element that indicates the type
6055 of package for which the line is valid. The only type currently
6056 in use is <tt>udeb</tt>. The colon and space after the type are
6061 <var>library-name</var> is the name of the shared library,
6062 in this case <tt>libz</tt>. (This must match the name part
6063 of the soname, see below.)
6067 <var>soname-version</var> is the version part of the soname of
6068 the library. The soname is the thing that must exactly match
6069 for the library to be recognized by the dynamic linker, and is
6071 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
6072 example, <tt>libz.so.1</tt>.<footnote>
6073 This can be determined using the command
6074 <example compact="compact">
6075 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
6078 The version part is the part which comes after
6079 <tt>.so.</tt>, so in our case, it is <tt>1</tt>. The soname may
6080 instead be of the form
6081 <tt><var>name</var>-<var>major-version</var>.so</tt>, such
6082 as <tt>libdb-4.8.so</tt>, in which case the name would
6083 be <tt>libdb</tt> and the version would be <tt>4.8</tt>.
6087 <var>dependencies</var> has the same syntax as a dependency
6088 field in a binary package control file. It should give
6089 details of which packages are required to satisfy a binary
6090 built against the version of the library contained in the
6091 package. See <ref id="depsyntax"> for details.
6095 In our example, if the first version of the <tt>zlib1g</tt>
6096 package which contained a minor number of at least
6097 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
6098 <tt>shlibs</tt> entry for this library could say:
6099 <example compact="compact">
6100 libz 1 zlib1g (>= 1:1.1.3)
6102 The version-specific dependency is to avoid warnings from
6103 the dynamic linker about using older shared libraries with
6108 As zlib1g also provides a udeb containing the shared library,
6109 there would also be a second line:
6110 <example compact="compact">
6111 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
6117 <heading>Providing a <file>shlibs</file> file</heading>
6120 If your package provides a shared library, you need to create
6121 a <file>shlibs</file> file following the format described above.
6122 It is usual to call this file <file>debian/shlibs</file> (but if
6123 you have multiple binary packages, you might want to call it
6124 <file>debian/shlibs.<var>package</var></file> instead). Then
6125 let <file>debian/rules</file> install it in the control
6126 information file area:
6127 <example compact="compact">
6128 install -m644 debian/shlibs debian/tmp/DEBIAN
6130 or, in the case of a multi-binary package:
6131 <example compact="compact">
6132 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
6134 An alternative way of doing this is to create the
6135 <file>shlibs</file> file in the control information file area
6136 directly from <file>debian/rules</file> without using
6137 a <file>debian/shlibs</file> file at all,<footnote>
6138 This is what <prgn>dh_makeshlibs</prgn> in
6139 the <package>debhelper</package> suite does. If your package
6140 also has a udeb that provides a shared
6141 library, <prgn>dh_makeshlibs</prgn> can automatically generate
6142 the <tt>udeb:</tt> lines if you specify the name of the udeb
6143 with the <tt>--add-udeb</tt> option.
6145 since the <file>debian/shlibs</file> file itself is ignored by
6146 <prgn>dpkg-shlibdeps</prgn>.
6150 As <prgn>dpkg-shlibdeps</prgn> reads the
6151 <file>DEBIAN/shlibs</file> files in all of the binary packages
6152 being built from this source package, all of the
6153 <file>DEBIAN/shlibs</file> files should be installed before
6154 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
6162 <chapt id="opersys"><heading>The Operating System</heading>
6165 <heading>File system hierarchy</heading>
6169 <heading>File System Structure</heading>
6172 The location of all files and directories must comply with the
6173 Filesystem Hierarchy Standard (FHS), version 2.3, with the
6174 exceptions noted below, and except where doing so would
6175 violate other terms of Debian Policy. The following
6176 exceptions to the FHS apply:
6181 The optional rules related to user specific
6182 configuration files for applications are stored in
6183 the user's home directory are relaxed. It is
6184 recommended that such files start with the
6185 '<tt>.</tt>' character (a "dot file"), and if an
6186 application needs to create more than one dot file
6187 then the preferred placement is in a subdirectory
6188 with a name starting with a '.' character, (a "dot
6189 directory"). In this case it is recommended the
6190 configuration files not start with the '.'
6196 The requirement for amd64 to use <file>/lib64</file>
6197 for 64 bit binaries is removed.
6202 The requirement for object files, internal binaries, and
6203 libraries, including <file>libc.so.*</file>, to be located
6204 directly under <file>/lib{,32}</file> and
6205 <file>/usr/lib{,32}</file> is amended, permitting files
6206 to instead be installed to
6207 <file>/lib/<var>triplet</var></file> and
6208 <file>/usr/lib/<var>triplet</var></file>, where
6209 <tt><var>triplet</var></tt> is the value returned by
6210 <tt>dpkg-architecture -qDEB_HOST_MULTIARCH</tt> for the
6211 architecture of the package. Packages may <em>not</em>
6212 install files to any <var>triplet</var> path other
6213 than the one matching the architecture of that package;
6214 for instance, an <tt>Architecture: amd64</tt> package
6215 containing 32-bit x86 libraries may not install these
6216 libraries to <file>/usr/lib/i386-linux-gnu</file>.
6218 This is necessary in order to reserve the directories for
6219 use in cross-installation of library packages from other
6220 architectures, as part of the planned deployment of
6225 Applications may also use a single subdirectory under
6226 <file>/usr/lib/<var>triplet</var></file>.
6229 The execution time linker/loader, ld*, must still be made
6230 available in the existing location under /lib or /lib64
6231 since this is part of the ELF ABI for the architecture.
6236 The requirement that
6237 <file>/usr/local/share/man</file> be "synonymous"
6238 with <file>/usr/local/man</file> is relaxed to a
6243 The requirement that windowmanagers with a single
6244 configuration file call it <file>system.*wmrc</file>
6245 is removed, as is the restriction that the window
6246 manager subdirectory be named identically to the
6247 window manager name itself.
6252 The requirement that boot manager configuration
6253 files live in <file>/etc</file>, or at least are
6254 symlinked there, is relaxed to a recommendation.
6259 The additional directory <file>/run</file> in the root
6260 file system is allowed. <file>/run</file>
6261 replaces <file>/var/run</file>, and the
6262 subdirectory <file>/run/lock</file>
6263 replaces <file>/var/lock</file>, with
6264 the <file>/var</file> directories replaced by symlinks
6265 for backwards compatibility. <file>/run</file>
6266 and <file>/run/lock</file> must follow all of the
6267 requirements in the FHS for <file>/var/run</file>
6268 and <file>/var/lock</file>, respectively, such as file
6269 naming conventions, file format requirements, or the
6270 requirement that files be cleared during the boot
6271 process. Files and directories residing
6272 in <file>/run</file> should be stored on a temporary
6278 The following directories in the root filesystem are
6279 additionally allowed: <file>/sys</file> and
6280 <file>/selinux</file>. <footnote>These directories
6281 are used as mount points to mount virtual filesystems
6282 to get access to kernel information.</footnote>
6287 On GNU/Hurd systems, the following additional
6288 directories are allowed in the root
6289 filesystem: <file>/hurd</file>
6290 and <file>/servers</file>.<footnote>
6291 These directories are used to store translators and as
6292 a set of standard names for mount points,
6301 The version of this document referred here can be
6302 found in the <tt>debian-policy</tt> package or on <url
6303 id="http://www.debian.org/doc/packaging-manuals/fhs/"
6304 name="FHS (Debian copy)"> alongside this manual (or, if
6305 you have the <package>debian-policy</package> installed,
6307 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
6308 (local copy)">). The
6309 latest version, which may be a more recent version, may
6311 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
6312 Specific questions about following the standard may be
6313 asked on the <tt>debian-devel</tt> mailing list, or
6314 referred to the FHS mailing list (see the
6315 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
6321 <heading>Site-specific programs</heading>
6324 As mandated by the FHS, packages must not place any
6325 files in <file>/usr/local</file>, either by putting them in
6326 the file system archive to be unpacked by <prgn>dpkg</prgn>
6327 or by manipulating them in their maintainer scripts.
6331 However, the package may create empty directories below
6332 <file>/usr/local</file> so that the system administrator knows
6333 where to place site-specific files. These are not
6334 directories <em>in</em> <file>/usr/local</file>, but are
6335 children of directories in <file>/usr/local</file>. These
6336 directories (<file>/usr/local/*/dir/</file>)
6337 should be removed on package removal if they are
6342 Note that this applies only to
6343 directories <em>below</em> <file>/usr/local</file>,
6344 not <em>in</em> <file>/usr/local</file>. Packages must
6345 not create sub-directories in the
6346 directory <file>/usr/local</file> itself, except those
6347 listed in FHS, section 4.5. However, you may create
6348 directories below them as you wish. You must not remove
6349 any of the directories listed in 4.5, even if you created
6354 Since <file>/usr/local</file> can be mounted read-only from a
6355 remote server, these directories must be created and
6356 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
6357 maintainer scripts and not be included in the
6358 <file>.deb</file> archive. These scripts must not fail if
6359 either of these operations fail.
6363 For example, the <tt>emacsen-common</tt> package could
6364 contain something like
6365 <example compact="compact">
6366 if [ ! -e /usr/local/share/emacs ]; then
6367 if mkdir /usr/local/share/emacs 2>/dev/null; then
6368 if chown root:staff /usr/local/share/emacs; then
6369 chmod 2775 /usr/local/share/emacs || true
6374 in its <prgn>postinst</prgn> script, and
6375 <example compact="compact">
6376 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
6377 rmdir /usr/local/share/emacs 2>/dev/null || true
6379 in the <prgn>prerm</prgn> script. (Note that this form is
6380 used to ensure that if the script is interrupted, the
6381 directory <file>/usr/local/share/emacs</file> will still be
6386 If you do create a directory in <file>/usr/local</file> for
6387 local additions to a package, you should ensure that
6388 settings in <file>/usr/local</file> take precedence over the
6389 equivalents in <file>/usr</file>.
6393 However, because <file>/usr/local</file> and its contents are
6394 for exclusive use of the local administrator, a package
6395 must not rely on the presence or absence of files or
6396 directories in <file>/usr/local</file> for normal operation.
6400 The <file>/usr/local</file> directory itself and all the
6401 subdirectories created by the package should (by default) have
6402 permissions 2775 (group-writable and set-group-id) and be
6403 owned by <tt>root:staff</tt>.
6408 <heading>The system-wide mail directory</heading>
6410 The system-wide mail directory
6411 is <file>/var/mail</file>. This directory is part of the
6412 base system and should not be owned by any particular mail
6413 agents. The use of the old
6414 location <file>/var/spool/mail</file> is deprecated, even
6415 though the spool may still be physically located there.
6419 <sect1 id="fhs-run">
6420 <heading><file>/run</file> and <file>/run/lock</file></heading>
6423 The directory <file>/run</file> is cleared at boot, normally
6424 by being a mount point for a temporary file system. Packages
6425 therefore must not assume that any files or directories
6426 under <file>/run</file> other than <file>/run/lock</file>
6427 exist unless the package has arranged to create those files or
6428 directories since the last reboot. Normally, this is done by
6429 the package via an init script. See <ref id="writing-init">
6430 for more information.
6434 Packages must not include files or directories
6435 under <file>/run</file>, or under the
6436 older <file>/var/run</file> and <file>/var/lock</file> paths.
6437 The latter paths will normally be symlinks or other
6438 redirections to <file>/run</file> for backwards compatibility.
6444 <heading>Users and groups</heading>
6447 <heading>Introduction</heading>
6449 The Debian system can be configured to use either plain or
6454 Some user ids (UIDs) and group ids (GIDs) are reserved
6455 globally for use by certain packages. Because some
6456 packages need to include files which are owned by these
6457 users or groups, or need the ids compiled into binaries,
6458 these ids must be used on any Debian system only for the
6459 purpose for which they are allocated. This is a serious
6460 restriction, and we should avoid getting in the way of
6461 local administration policies. In particular, many sites
6462 allocate users and/or local system groups starting at 100.
6466 Apart from this we should have dynamically allocated ids,
6467 which should by default be arranged in some sensible
6468 order, but the behavior should be configurable.
6472 Packages other than <tt>base-passwd</tt> must not modify
6473 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
6474 <file>/etc/group</file> or <file>/etc/gshadow</file>.
6479 <heading>UID and GID classes</heading>
6481 The UID and GID numbers are divided into classes as
6487 Globally allocated by the Debian project, the same
6488 on every Debian system. These ids will appear in
6489 the <file>passwd</file> and <file>group</file> files of all
6490 Debian systems, new ids in this range being added
6491 automatically as the <tt>base-passwd</tt> package is
6496 Packages which need a single statically allocated
6497 uid or gid should use one of these; their
6498 maintainers should ask the <tt>base-passwd</tt>
6506 Dynamically allocated system users and groups.
6507 Packages which need a user or group, but can have
6508 this user or group allocated dynamically and
6509 differently on each system, should use <tt>adduser
6510 --system</tt> to create the group and/or user.
6511 <prgn>adduser</prgn> will check for the existence of
6512 the user or group, and if necessary choose an unused
6513 id based on the ranges specified in
6514 <file>adduser.conf</file>.
6518 <tag>1000-59999:</tag>
6521 Dynamically allocated user accounts. By default
6522 <prgn>adduser</prgn> will choose UIDs and GIDs for
6523 user accounts in this range, though
6524 <file>adduser.conf</file> may be used to modify this
6529 <tag>60000-64999:</tag>
6532 Globally allocated by the Debian project, but only
6533 created on demand. The ids are allocated centrally
6534 and statically, but the actual accounts are only
6535 created on users' systems on demand.
6539 These ids are for packages which are obscure or
6540 which require many statically-allocated ids. These
6541 packages should check for and create the accounts in
6542 <file>/etc/passwd</file> or <file>/etc/group</file> (using
6543 <prgn>adduser</prgn> if it has this facility) if
6544 necessary. Packages which are likely to require
6545 further allocations should have a "hole" left after
6546 them in the allocation, to give them room to
6551 <tag>65000-65533:</tag>
6559 User <tt>nobody</tt>. The corresponding gid refers
6560 to the group <tt>nogroup</tt>.
6567 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
6568 not</em> be used, because it is the error return
6577 <sect id="sysvinit">
6578 <heading>System run levels and <file>init.d</file> scripts</heading>
6580 <sect1 id="/etc/init.d">
6581 <heading>Introduction</heading>
6584 The <file>/etc/init.d</file> directory contains the scripts
6585 executed by <prgn>init</prgn> at boot time and when the
6586 init state (or "runlevel") is changed (see <manref
6587 name="init" section="8">).
6591 There are at least two different, yet functionally
6592 equivalent, ways of handling these scripts. For the sake
6593 of simplicity, this document describes only the symbolic
6594 link method. However, it must not be assumed by maintainer
6595 scripts that this method is being used, and any automated
6596 manipulation of the various runlevel behaviors by
6597 maintainer scripts must be performed using
6598 <prgn>update-rc.d</prgn> as described below and not by
6599 manually installing or removing symlinks. For information
6600 on the implementation details of the other method,
6601 implemented in the <tt>file-rc</tt> package, please refer
6602 to the documentation of that package.
6606 These scripts are referenced by symbolic links in the
6607 <file>/etc/rc<var>n</var>.d</file> directories. When changing
6608 runlevels, <prgn>init</prgn> looks in the directory
6609 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
6610 execute, where <tt><var>n</var></tt> is the runlevel that
6611 is being changed to, or <tt>S</tt> for the boot-up
6616 The names of the links all have the form
6617 <file>S<var>mm</var><var>script</var></file> or
6618 <file>K<var>mm</var><var>script</var></file> where
6619 <var>mm</var> is a two-digit number and <var>script</var>
6620 is the name of the script (this should be the same as the
6621 name of the actual script in <file>/etc/init.d</file>).
6625 When <prgn>init</prgn> changes runlevel first the targets
6626 of the links whose names start with a <tt>K</tt> are
6627 executed, each with the single argument <tt>stop</tt>,
6628 followed by the scripts prefixed with an <tt>S</tt>, each
6629 with the single argument <tt>start</tt>. (The links are
6630 those in the <file>/etc/rc<var>n</var>.d</file> directory
6631 corresponding to the new runlevel.) The <tt>K</tt> links
6632 are responsible for killing services and the <tt>S</tt>
6633 link for starting services upon entering the runlevel.
6637 For example, if we are changing from runlevel 2 to
6638 runlevel 3, init will first execute all of the <tt>K</tt>
6639 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
6640 all of the <tt>S</tt> prefixed scripts in that directory.
6641 The links starting with <tt>K</tt> will cause the
6642 referred-to file to be executed with an argument of
6643 <tt>stop</tt>, and the <tt>S</tt> links with an argument
6648 The two-digit number <var>mm</var> is used to determine
6649 the order in which to run the scripts: low-numbered links
6650 have their scripts run first. For example, the
6651 <tt>K20</tt> scripts will be executed before the
6652 <tt>K30</tt> scripts. This is used when a certain service
6653 must be started before another. For example, the name
6654 server <prgn>bind</prgn> might need to be started before
6655 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
6656 can set up its access lists. In this case, the script
6657 that starts <prgn>bind</prgn> would have a lower number
6658 than the script that starts <prgn>inn</prgn> so that it
6660 <example compact="compact">
6667 The two runlevels 0 (halt) and 6 (reboot) are slightly
6668 different. In these runlevels, the links with an
6669 <tt>S</tt> prefix are still called after those with a
6670 <tt>K</tt> prefix, but they too are called with the single
6671 argument <tt>stop</tt>.
6675 <sect1 id="writing-init">
6676 <heading>Writing the scripts</heading>
6679 Packages that include daemons for system services should
6680 place scripts in <file>/etc/init.d</file> to start or stop
6681 services at boot time or during a change of runlevel.
6682 These scripts should be named
6683 <file>/etc/init.d/<var>package</var></file>, and they should
6684 accept one argument, saying what to do:
6687 <tag><tt>start</tt></tag>
6688 <item>start the service,</item>
6690 <tag><tt>stop</tt></tag>
6691 <item>stop the service,</item>
6693 <tag><tt>restart</tt></tag>
6694 <item>stop and restart the service if it's already running,
6695 otherwise start the service</item>
6697 <tag><tt>reload</tt></tag>
6698 <item><p>cause the configuration of the service to be
6699 reloaded without actually stopping and restarting
6702 <tag><tt>force-reload</tt></tag>
6703 <item>cause the configuration to be reloaded if the
6704 service supports this, otherwise restart the
6708 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
6709 <tt>force-reload</tt> options should be supported by all
6710 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
6715 The <file>init.d</file> scripts must ensure that they will
6716 behave sensibly (i.e., returning success and not starting
6717 multiple copies of a service) if invoked with <tt>start</tt>
6718 when the service is already running, or with <tt>stop</tt>
6719 when it isn't, and that they don't kill unfortunately-named
6720 user processes. The best way to achieve this is usually to
6721 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
6726 Be careful of using <tt>set -e</tt> in <file>init.d</file>
6727 scripts. Writing correct <file>init.d</file> scripts requires
6728 accepting various error exit statuses when daemons are already
6729 running or already stopped without aborting
6730 the <file>init.d</file> script, and common <file>init.d</file>
6731 function libraries are not safe to call with <tt>set -e</tt>
6733 <tt>/lib/lsb/init-functions</tt>, which assists in writing
6734 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
6735 in effect and echoing status messages to the console fails,
6737 </footnote>. For <tt>init.d</tt> scripts, it's often easier
6738 to not use <tt>set -e</tt> and instead check the result of
6739 each command separately.
6743 If a service reloads its configuration automatically (as
6744 in the case of <prgn>cron</prgn>, for example), the
6745 <tt>reload</tt> option of the <file>init.d</file> script
6746 should behave as if the configuration has been reloaded
6751 The <file>/etc/init.d</file> scripts must be treated as
6752 configuration files, either (if they are present in the
6753 package, that is, in the .deb file) by marking them as
6754 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6755 by managing them correctly in the maintainer scripts (see
6756 <ref id="config-files">). This is important since we want
6757 to give the local system administrator the chance to adapt
6758 the scripts to the local system, e.g., to disable a
6759 service without de-installing the package, or to specify
6760 some special command line options when starting a service,
6761 while making sure their changes aren't lost during the next
6766 These scripts should not fail obscurely when the
6767 configuration files remain but the package has been
6768 removed, as configuration files remain on the system after
6769 the package has been removed. Only when <prgn>dpkg</prgn>
6770 is executed with the <tt>--purge</tt> option will
6771 configuration files be removed. In particular, as the
6772 <file>/etc/init.d/<var>package</var></file> script itself is
6773 usually a <tt>conffile</tt>, it will remain on the system
6774 if the package is removed but not purged. Therefore, you
6775 should include a <tt>test</tt> statement at the top of the
6777 <example compact="compact">
6778 test -f <var>program-executed-later-in-script</var> || exit 0
6783 Often there are some variables in the <file>init.d</file>
6784 scripts whose values control the behavior of the scripts,
6785 and which a system administrator is likely to want to
6786 change. As the scripts themselves are frequently
6787 <tt>conffile</tt>s, modifying them requires that the
6788 administrator merge in their changes each time the package
6789 is upgraded and the <tt>conffile</tt> changes. To ease
6790 the burden on the system administrator, such configurable
6791 values should not be placed directly in the script.
6792 Instead, they should be placed in a file in
6793 <file>/etc/default</file>, which typically will have the same
6794 base name as the <file>init.d</file> script. This extra file
6795 should be sourced by the script when the script runs. It
6796 must contain only variable settings and comments in SUSv3
6797 <prgn>sh</prgn> format. It may either be a
6798 <tt>conffile</tt> or a configuration file maintained by
6799 the package maintainer scripts. See <ref id="config-files">
6804 To ensure that vital configurable values are always
6805 available, the <file>init.d</file> script should set default
6806 values for each of the shell variables it uses, either
6807 before sourcing the <file>/etc/default/</file> file or
6808 afterwards using something like the <tt>:
6809 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6810 script must behave sensibly and not fail if the
6811 <file>/etc/default</file> file is deleted.
6815 Files and directories under <file>/run</file>, including ones
6816 referred to via the compatibility paths <file>/var/run</file>
6817 and <file>/var/lock</file>, are normally stored on a temporary
6818 filesystem and are normally not persistent across a reboot.
6819 The <file>init.d</file> scripts must handle this correctly.
6820 This will typically mean creating any required subdirectories
6821 dynamically when the <file>init.d</file> script is run.
6822 See <ref id="fhs-run"> for more information.
6827 <heading>Interfacing with the initscript system</heading>
6830 Maintainers should use the abstraction layer provided by
6831 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6832 programs to deal with initscripts in their packages'
6833 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6834 and <prgn>postrm</prgn>.
6838 Directly managing the /etc/rc?.d links and directly
6839 invoking the <file>/etc/init.d/</file> initscripts should
6840 be done only by packages providing the initscript
6841 subsystem (such as <prgn>sysv-rc</prgn> and
6842 <prgn>file-rc</prgn>).
6846 <heading>Managing the links</heading>
6849 The program <prgn>update-rc.d</prgn> is provided for
6850 package maintainers to arrange for the proper creation and
6851 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6852 or their functional equivalent if another method is being
6853 used. This may be used by maintainers in their packages'
6854 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6858 You must not include any <file>/etc/rc<var>n</var>.d</file>
6859 symbolic links in the actual archive or manually create or
6860 remove the symbolic links in maintainer scripts; you must
6861 use the <prgn>update-rc.d</prgn> program instead. (The
6862 former will fail if an alternative method of maintaining
6863 runlevel information is being used.) You must not include
6864 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6865 in the archive either. (Only the <tt>sysvinit</tt>
6870 By default <prgn>update-rc.d</prgn> will start services in
6871 each of the multi-user state runlevels (2, 3, 4, and 5)
6872 and stop them in the halt runlevel (0), the single-user
6873 runlevel (1) and the reboot runlevel (6). The system
6874 administrator will have the opportunity to customize
6875 runlevels by simply adding, moving, or removing the
6876 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6877 symbolic links are being used, or by modifying
6878 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6883 To get the default behavior for your package, put in your
6884 <prgn>postinst</prgn> script
6885 <example compact="compact">
6886 update-rc.d <var>package</var> defaults
6888 and in your <prgn>postrm</prgn>
6889 <example compact="compact">
6890 if [ "$1" = purge ]; then
6891 update-rc.d <var>package</var> remove
6893 </example>. Note that if your package changes runlevels
6894 or priority, you may have to remove and recreate the links,
6895 since otherwise the old links may persist. Refer to the
6896 documentation of <prgn>update-rc.d</prgn>.
6900 This will use a default sequence number of 20. If it does
6901 not matter when or in which order the <file>init.d</file>
6902 script is run, use this default. If it does, then you
6903 should talk to the maintainer of the <prgn>sysvinit</prgn>
6904 package or post to <tt>debian-devel</tt>, and they will
6905 help you choose a number.
6909 For more information about using <tt>update-rc.d</tt>,
6910 please consult its man page <manref name="update-rc.d"
6916 <heading>Running initscripts</heading>
6918 The program <prgn>invoke-rc.d</prgn> is provided to make
6919 it easier for package maintainers to properly invoke an
6920 initscript, obeying runlevel and other locally-defined
6921 constraints that might limit a package's right to start,
6922 stop and otherwise manage services. This program may be
6923 used by maintainers in their packages' scripts.
6927 The package maintainer scripts must use
6928 <prgn>invoke-rc.d</prgn> to invoke the
6929 <file>/etc/init.d/*</file> initscripts, instead of
6930 calling them directly.
6934 By default, <prgn>invoke-rc.d</prgn> will pass any
6935 action requests (start, stop, reload, restart...) to the
6936 <file>/etc/init.d</file> script, filtering out requests
6937 to start or restart a service out of its intended
6942 Most packages will simply need to change:
6943 <example compact="compact">/etc/init.d/<package>
6944 <action></example> in their <prgn>postinst</prgn>
6945 and <prgn>prerm</prgn> scripts to:
6946 <example compact="compact">
6947 if which invoke-rc.d >/dev/null 2>&1; then
6948 invoke-rc.d <var>package</var> <action>
6950 /etc/init.d/<var>package</var> <action>
6956 A package should register its initscript services using
6957 <prgn>update-rc.d</prgn> before it tries to invoke them
6958 using <prgn>invoke-rc.d</prgn>. Invocation of
6959 unregistered services may fail.
6963 For more information about using
6964 <prgn>invoke-rc.d</prgn>, please consult its man page
6965 <manref name="invoke-rc.d" section="8">.
6971 <heading>Boot-time initialization</heading>
6974 There used to be another directory, <file>/etc/rc.boot</file>,
6975 which contained scripts which were run once per machine
6976 boot. This has been deprecated in favour of links from
6977 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6978 described in <ref id="/etc/init.d">. Packages must not
6979 place files in <file>/etc/rc.boot</file>.
6984 <heading>Example</heading>
6987 An example on which you can base your
6988 <file>/etc/init.d</file> scripts is found in
6989 <file>/etc/init.d/skeleton</file>.
6996 <heading>Console messages from <file>init.d</file> scripts</heading>
6999 This section describes the formats to be used for messages
7000 written to standard output by the <file>/etc/init.d</file>
7001 scripts. The intent is to improve the consistency of
7002 Debian's startup and shutdown look and feel. For this
7003 reason, please look very carefully at the details. We want
7004 the messages to have the same format in terms of wording,
7005 spaces, punctuation and case of letters.
7009 Here is a list of overall rules that should be used for
7010 messages generated by <file>/etc/init.d</file> scripts.
7016 The message should fit in one line (fewer than 80
7017 characters), start with a capital letter and end with
7018 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
7022 If the script is performing some time consuming task in
7023 the background (not merely starting or stopping a
7024 program, for instance), an ellipsis (three dots:
7025 <tt>...</tt>) should be output to the screen, with no
7026 leading or tailing whitespace or line feeds.
7030 The messages should appear as if the computer is telling
7031 the user what it is doing (politely :-), but should not
7032 mention "it" directly. For example, instead of:
7033 <example compact="compact">
7034 I'm starting network daemons: nfsd mountd.
7036 the message should say
7037 <example compact="compact">
7038 Starting network daemons: nfsd mountd.
7045 <tt>init.d</tt> script should use the following standard
7046 message formats for the situations enumerated below.
7052 <p>When daemons are started</p>
7055 If the script starts one or more daemons, the output
7056 should look like this (a single line, no leading
7058 <example compact="compact">
7059 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
7061 The <var>description</var> should describe the
7062 subsystem the daemon or set of daemons are part of,
7063 while <var>daemon-1</var> up to <var>daemon-n</var>
7064 denote each daemon's name (typically the file name of
7069 For example, the output of <file>/etc/init.d/lpd</file>
7071 <example compact="compact">
7072 Starting printer spooler: lpd.
7077 This can be achieved by saying
7078 <example compact="compact">
7079 echo -n "Starting printer spooler: lpd"
7080 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
7083 in the script. If there are more than one daemon to
7084 start, the output should look like this:
7085 <example compact="compact">
7086 echo -n "Starting remote file system services:"
7087 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
7088 echo -n " mountd"; start-stop-daemon --start --quiet mountd
7089 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
7092 This makes it possible for the user to see what is
7093 happening and when the final daemon has been started.
7094 Care should be taken in the placement of white spaces:
7095 in the example above the system administrators can
7096 easily comment out a line if they don't want to start
7097 a specific daemon, while the displayed message still
7103 <p>When a system parameter is being set</p>
7106 If you have to set up different system parameters
7107 during the system boot, you should use this format:
7108 <example compact="compact">
7109 Setting <var>parameter</var> to "<var>value</var>".
7114 You can use a statement such as the following to get
7116 <example compact="compact">
7117 echo "Setting DNS domainname to \"$domainname\"."
7122 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
7123 for the left and right quotation marks. A grave accent
7124 (<tt>`</tt>) is not a quote character; neither is an
7125 apostrophe (<tt>'</tt>).
7130 <p>When a daemon is stopped or restarted</p>
7133 When you stop or restart a daemon, you should issue a
7134 message identical to the startup message, except that
7135 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
7136 or <tt>Restarting</tt> respectively.
7140 For example, stopping the printer daemon will look like
7142 <example compact="compact">
7143 Stopping printer spooler: lpd.
7149 <p>When something is executed</p>
7152 There are several examples where you have to run a
7153 program at system startup or shutdown to perform a
7154 specific task, for example, setting the system's clock
7155 using <prgn>netdate</prgn> or killing all processes
7156 when the system shuts down. Your message should look
7158 <example compact="compact">
7159 Doing something very useful...done.
7161 You should print the <tt>done.</tt> immediately after
7162 the job has been completed, so that the user is
7163 informed why they have to wait. You can get this
7165 <example compact="compact">
7166 echo -n "Doing something very useful..."
7175 <p>When the configuration is reloaded</p>
7178 When a daemon is forced to reload its configuration
7179 files you should use the following format:
7180 <example compact="compact">
7181 Reloading <var>description</var> configuration...done.
7183 where <var>description</var> is the same as in the
7184 daemon starting message.
7191 <sect id="cron-jobs">
7192 <heading>Cron jobs</heading>
7195 Packages must not modify the configuration file
7196 <file>/etc/crontab</file>, and they must not modify the files in
7197 <file>/var/spool/cron/crontabs</file>.
7201 If a package wants to install a job that has to be executed via
7202 cron, it should place a file named as specified
7203 in <ref id="cron-files"> into one or more of the following
7205 <example compact="compact">
7211 As these directory names imply, the files within them are
7212 executed on an hourly, daily, weekly, or monthly basis,
7213 respectively. The exact times are listed in
7214 <file>/etc/crontab</file>.
7218 All files installed in any of these directories must be
7219 scripts (e.g., shell scripts or Perl scripts) so that they
7220 can easily be modified by the local system administrator.
7221 In addition, they must be treated as configuration files.
7225 If a certain job has to be executed at some other frequency or
7226 at a specific time, the package should install a file in
7227 <file>/etc/cron.d</file> with a name as specified
7228 in <ref id="cron-files">. This file uses the same syntax
7229 as <file>/etc/crontab</file> and is processed
7230 by <prgn>cron</prgn> automatically. The file must also be
7231 treated as a configuration file. (Note that entries in the
7232 <file>/etc/cron.d</file> directory are not handled by
7233 <prgn>anacron</prgn>. Thus, you should only use this
7234 directory for jobs which may be skipped if the system is not
7239 Unlike <file>crontab</file> files described in the IEEE Std
7240 1003.1-2008 (POSIX.1) available from
7241 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
7242 name="The Open Group">, the files in
7243 <file>/etc/cron.d</file> and the file
7244 <file>/etc/crontab</file> have seven fields; namely:
7246 <item>Minute [0,59]</item>
7247 <item>Hour [0,23]</item>
7248 <item>Day of the month [1,31]</item>
7249 <item>Month of the year [1,12]</item>
7250 <item>Day of the week ([0,6] with 0=Sunday)</item>
7251 <item>Username</item>
7252 <item>Command to be run</item>
7254 Ranges of numbers are allowed. Ranges are two numbers
7255 separated with a hyphen. The specified range is inclusive.
7256 Lists are allowed. A list is a set of numbers (or ranges)
7257 separated by commas. Step values can be used in conjunction
7262 The scripts or <tt>crontab</tt> entries in these directories should
7263 check if all necessary programs are installed before they
7264 try to execute them. Otherwise, problems will arise when a
7265 package was removed but not purged since configuration files
7266 are kept on the system in this situation.
7270 Any <tt>cron</tt> daemon must provide
7271 <file>/usr/bin/crontab</file> and support normal
7272 <tt>crontab</tt> entries as specified in POSIX. The daemon
7273 must also support names for days and months, ranges, and
7274 step values. It has to support <file>/etc/crontab</file>,
7275 and correctly execute the scripts in
7276 <file>/etc/cron.d</file>. The daemon must also correctly
7278 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
7281 <sect1 id="cron-files">
7282 <heading>Cron job file names</heading>
7285 The file name of a cron job file should normally match the
7286 name of the package from which it comes.
7290 If a package supplies multiple cron job files files in the
7291 same directory, the file names should all start with the name
7292 of the package (possibly modified as described below) followed
7293 by a hyphen (<tt>-</tt>) and a suitable suffix.
7297 A cron job file name must not include any period or plus
7298 characters (<tt>.</tt> or <tt>+</tt>) characters as this will
7299 cause cron to ignore the file. Underscores (<tt>_</tt>)
7300 should be used instead of <tt>.</tt> and <tt>+</tt>
7307 <heading>Menus</heading>
7310 The Debian <tt>menu</tt> package provides a standard
7311 interface between packages providing applications and
7312 <em>menu programs</em> (either X window managers or
7313 text-based menu programs such as <prgn>pdmenu</prgn>).
7317 All packages that provide applications that need not be
7318 passed any special command line arguments for normal
7319 operation should register a menu entry for those
7320 applications, so that users of the <tt>menu</tt> package
7321 will automatically get menu entries in their window
7322 managers, as well in shells like <tt>pdmenu</tt>.
7326 Menu entries should follow the current menu policy.
7330 The menu policy can be found in the <tt>menu-policy</tt>
7331 files in the <tt>debian-policy</tt> package.
7332 It is also available from the Debian web mirrors at
7333 <tt><url name="/doc/packaging-manuals/menu-policy/"
7334 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
7338 Please also refer to the <em>Debian Menu System</em>
7339 documentation that comes with the <package>menu</package>
7340 package for information about how to register your
7346 <heading>Multimedia handlers</heading>
7349 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
7350 is a mechanism for encoding files and data streams and
7351 providing meta-information about them, in particular their
7352 type (e.g. audio or video) and format (e.g. PNG, HTML,
7357 Registration of MIME type handlers allows programs like mail
7358 user agents and web browsers to invoke these handlers to
7359 view, edit or display MIME types they don't support directly.
7363 Packages which provide the ability to view/show/play,
7364 compose, edit or print MIME types should register themselves
7365 as such following the current MIME support policy.
7369 The <package>mime-support</package> package provides the
7370 <prgn>update-mime</prgn> program which allows packages to
7371 register programs that can show, compose, edit or print
7376 Packages containing such programs must register them
7377 with <prgn>update-mime</prgn> as documented in <manref
7378 name="update-mime" section="8">. They should <em>not</em> depend
7379 on, recommend, or suggest <prgn>mime-support</prgn>. Instead,
7380 they should just put something like the following in the
7381 <tt>postinst</tt> and <tt>postrm</tt> scripts:
7384 if [ -x /usr/sbin/update-mime ]; then
7393 <heading>Keyboard configuration</heading>
7396 To achieve a consistent keyboard configuration so that all
7397 applications interpret a keyboard event the same way, all
7398 programs in the Debian distribution must be configured to
7399 comply with the following guidelines.
7403 The following keys must have the specified interpretations:
7406 <tag><tt><--</tt></tag>
7407 <item>delete the character to the left of the cursor</item>
7409 <tag><tt>Delete</tt></tag>
7410 <item>delete the character to the right of the cursor</item>
7412 <tag><tt>Control+H</tt></tag>
7413 <item>emacs: the help prefix</item>
7416 The interpretation of any keyboard events should be
7417 independent of the terminal that is used, be it a virtual
7418 console, an X terminal emulator, an rlogin/telnet session,
7423 The following list explains how the different programs
7424 should be set up to achieve this:
7430 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
7434 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
7438 X translations are set up to make
7439 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
7440 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
7441 is the vt220 escape code for the "delete character"
7442 key). This must be done by loading the X resources
7443 using <prgn>xrdb</prgn> on all local X displays, not
7444 using the application defaults, so that the
7445 translation resources used correspond to the
7446 <prgn>xmodmap</prgn> settings.
7450 The Linux console is configured to make
7451 <tt><--</tt> generate DEL, and <tt>Delete</tt>
7452 generate <tt>ESC [ 3 ~</tt>.
7456 X applications are configured so that <tt><</tt>
7457 deletes left, and <tt>Delete</tt> deletes right. Motif
7458 applications already work like this.
7462 Terminals should have <tt>stty erase ^?</tt> .
7466 The <tt>xterm</tt> terminfo entry should have <tt>ESC
7467 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
7468 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
7472 Emacs is programmed to map <tt>KB_Backspace</tt> or
7473 the <tt>stty erase</tt> character to
7474 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
7475 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
7476 <tt>^H</tt> to <tt>help</tt> as always.
7480 Other applications use the <tt>stty erase</tt>
7481 character and <tt>kdch1</tt> for the two delete keys,
7482 with ASCII DEL being "delete previous character" and
7483 <tt>kdch1</tt> being "delete character under
7491 This will solve the problem except for the following
7498 Some terminals have a <tt><--</tt> key that cannot
7499 be made to produce anything except <tt>^H</tt>. On
7500 these terminals Emacs help will be unavailable on
7501 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
7502 character takes precedence in Emacs, and has been set
7503 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
7504 available) can be used instead.
7508 Some operating systems use <tt>^H</tt> for <tt>stty
7509 erase</tt>. However, modern telnet versions and all
7510 rlogin versions propagate <tt>stty</tt> settings, and
7511 almost all UNIX versions honour <tt>stty erase</tt>.
7512 Where the <tt>stty</tt> settings are not propagated
7513 correctly, things can be made to work by using
7514 <tt>stty</tt> manually.
7518 Some systems (including previous Debian versions) use
7519 <prgn>xmodmap</prgn> to arrange for both
7520 <tt><--</tt> and <tt>Delete</tt> to generate
7521 <tt>KB_Delete</tt>. We can change the behavior of
7522 their X clients using the same X resources that we use
7523 to do it for our own clients, or configure our clients
7524 using their resources when things are the other way
7525 around. On displays configured like this
7526 <tt>Delete</tt> will not work, but <tt><--</tt>
7531 Some operating systems have different <tt>kdch1</tt>
7532 settings in their <tt>terminfo</tt> database for
7533 <tt>xterm</tt> and others. On these systems the
7534 <tt>Delete</tt> key will not work correctly when you
7535 log in from a system conforming to our policy, but
7536 <tt><--</tt> will.
7543 <heading>Environment variables</heading>
7546 A program must not depend on environment variables to get
7547 reasonable defaults. (That's because these environment
7548 variables would have to be set in a system-wide
7549 configuration file like <file>/etc/profile</file>, which is not
7550 supported by all shells.)
7554 If a program usually depends on environment variables for its
7555 configuration, the program should be changed to fall back to
7556 a reasonable default configuration if these environment
7557 variables are not present. If this cannot be done easily
7558 (e.g., if the source code of a non-free program is not
7559 available), the program must be replaced by a small
7560 "wrapper" shell script which sets the environment variables
7561 if they are not already defined, and calls the original program.
7565 Here is an example of a wrapper script for this purpose:
7567 <example compact="compact">
7569 BAR=${BAR:-/var/lib/fubar}
7571 exec /usr/lib/foo/foo "$@"
7576 Furthermore, as <file>/etc/profile</file> is a configuration
7577 file of the <prgn>base-files</prgn> package, other packages must
7578 not put any environment variables or other commands into that
7583 <sect id="doc-base">
7584 <heading>Registering Documents using doc-base</heading>
7587 The <package>doc-base</package> package implements a
7588 flexible mechanism for handling and presenting
7589 documentation. The recommended practice is for every Debian
7590 package that provides online documentation (other than just
7591 manual pages) to register these documents with
7592 <package>doc-base</package> by installing a
7593 <package>doc-base</package> control file in
7594 <file>/usr/share/doc-base/</file>.
7597 Please refer to the documentation that comes with the
7598 <package>doc-base</package> package for information and
7607 <heading>Files</heading>
7609 <sect id="binaries">
7610 <heading>Binaries</heading>
7613 Two different packages must not install programs with
7614 different functionality but with the same filenames. (The
7615 case of two programs having the same functionality but
7616 different implementations is handled via "alternatives" or
7617 the "Conflicts" mechanism. See <ref id="maintscripts"> and
7618 <ref id="conflicts"> respectively.) If this case happens,
7619 one of the programs must be renamed. The maintainers should
7620 report this to the <tt>debian-devel</tt> mailing list and
7621 try to find a consensus about which program will have to be
7622 renamed. If a consensus cannot be reached, <em>both</em>
7623 programs must be renamed.
7627 By default, when a package is being built, any binaries
7628 created should include debugging information, as well as
7629 being compiled with optimization. You should also turn on
7630 as many reasonable compilation warnings as possible; this
7631 makes life easier for porters, who can then look at build
7632 logs for possible problems. For the C programming language,
7633 this means the following compilation parameters should be
7635 <example compact="compact">
7637 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
7639 INSTALL = install -s # (or use strip on the files in debian/tmp)
7644 Note that by default all installed binaries should be stripped,
7645 either by using the <tt>-s</tt> flag to
7646 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
7647 the binaries after they have been copied into
7648 <file>debian/tmp</file> but before the tree is made into a
7653 Although binaries in the build tree should be compiled with
7654 debugging information by default, it can often be difficult to
7655 debug programs if they are also subjected to compiler
7656 optimization. For this reason, it is recommended to support the
7657 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
7658 (see <ref id="debianrules-options">). This variable can contain
7659 several flags to change how a package is compiled and built.
7663 It is up to the package maintainer to decide what
7664 compilation options are best for the package. Certain
7665 binaries (such as computationally-intensive programs) will
7666 function better with certain flags (<tt>-O3</tt>, for
7667 example); feel free to use them. Please use good judgment
7668 here. Don't use flags for the sake of it; only use them
7669 if there is good reason to do so. Feel free to override
7670 the upstream author's ideas about which compilation
7671 options are best: they are often inappropriate for our
7677 <sect id="libraries">
7678 <heading>Libraries</heading>
7681 If the package is <strong>architecture: any</strong>, then
7682 the shared library compilation and linking flags must have
7683 <tt>-fPIC</tt>, or the package shall not build on some of
7684 the supported architectures<footnote>
7686 If you are using GCC, <tt>-fPIC</tt> produces code with
7687 relocatable position independent code, which is required for
7688 most architectures to create a shared library, with i386 and
7689 perhaps some others where non position independent code is
7690 permitted in a shared library.
7693 Position independent code may have a performance penalty,
7694 especially on <tt>i386</tt>. However, in most cases the
7695 speed penalty must be measured against the memory wasted on
7696 the few architectures where non position independent code is
7699 </footnote>. Any exception to this rule must be discussed on
7700 the mailing list <em>debian-devel@lists.debian.org</em>, and
7701 a rough consensus obtained. The reasons for not compiling
7702 with <tt>-fPIC</tt> flag must be recorded in the file
7703 <tt>README.Debian</tt>, and care must be taken to either
7704 restrict the architecture or arrange for <tt>-fPIC</tt> to
7705 be used on architectures where it is required.<footnote>
7707 Some of the reasons why this might be required is if the
7708 library contains hand crafted assembly code that is not
7709 relocatable, the speed penalty is excessive for compute
7710 intensive libs, and similar reasons.
7715 As to the static libraries, the common case is not to have
7716 relocatable code, since there is no benefit, unless in specific
7717 cases; therefore the static version must not be compiled
7718 with the <tt>-fPIC</tt> flag. Any exception to this rule
7719 should be discussed on the mailing list
7720 <em>debian-devel@lists.debian.org</em>, and the reasons for
7721 compiling with the <tt>-fPIC</tt> flag must be recorded in
7722 the file <tt>README.Debian</tt>. <footnote>
7724 Some of the reasons for linking static libraries with
7725 the <tt>-fPIC</tt> flag are if, for example, one needs a
7726 Perl API for a library that is under rapid development,
7727 and has an unstable API, so shared libraries are
7728 pointless at this phase of the library's development. In
7729 that case, since Perl needs a library with relocatable
7730 code, it may make sense to create a static library with
7731 relocatable code. Another reason cited is if you are
7732 distilling various libraries into a common shared
7733 library, like <tt>mklibs</tt> does in the Debian
7739 In other words, if both a shared and a static library is
7740 being built, each source unit (<tt>*.c</tt>, for example,
7741 for C files) will need to be compiled twice, for the normal
7746 Libraries should be built with threading support and to be
7747 thread-safe if the library supports this.
7751 Although not enforced by the build tools, shared libraries
7752 must be linked against all libraries that they use symbols from
7753 in the same way that binaries are. This ensures the correct
7754 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
7755 system and guarantees that all libraries can be safely opened
7756 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
7757 option <tt>-Wl,-z,defs</tt> when building a shared library.
7758 Since this option enforces symbol resolution at build time,
7759 a missing library reference will be caught early as a fatal
7764 All installed shared libraries should be stripped with
7765 <example compact="compact">
7766 strip --strip-unneeded <var>your-lib</var>
7768 (The option <tt>--strip-unneeded</tt> makes
7769 <prgn>strip</prgn> remove only the symbols which aren't
7770 needed for relocation processing.) Shared libraries can
7771 function perfectly well when stripped, since the symbols for
7772 dynamic linking are in a separate part of the ELF object
7774 You might also want to use the options
7775 <tt>--remove-section=.comment</tt> and
7776 <tt>--remove-section=.note</tt> on both shared libraries
7777 and executables, and <tt>--strip-debug</tt> on static
7783 Note that under some circumstances it may be useful to
7784 install a shared library unstripped, for example when
7785 building a separate package to support debugging.
7789 Shared object files (often <file>.so</file> files) that are not
7790 public libraries, that is, they are not meant to be linked
7791 to by third party executables (binaries of other packages),
7792 should be installed in subdirectories of the
7793 <file>/usr/lib</file> directory. Such files are exempt from the
7794 rules that govern ordinary shared libraries, except that
7795 they must not be installed executable and should be
7797 A common example are the so-called "plug-ins",
7798 internal shared objects that are dynamically loaded by
7799 programs using <manref name="dlopen" section="3">.
7804 Packages that use <prgn>libtool</prgn> to create and install
7805 their shared libraries install a file containing additional
7806 metadata (ending in <file>.la</file>) alongside the library.
7807 For public libraries intended for use by other packages, these
7808 files normally should not be included in the Debian package,
7809 since the information they include is not necessary to link with
7810 the shared library on Debian and can add unnecessary additional
7811 dependencies to other programs or libraries.<footnote>
7812 These files store, among other things, all libraries on which
7813 that shared library depends. Unfortunately, if
7814 the <file>.la</file> file is present and contains that
7815 dependency information, using <prgn>libtool</prgn> when
7816 linking against that library will cause the resulting program
7817 or library to be linked against those dependencies as well,
7818 even if this is unnecessary. This can create unneeded
7819 dependencies on shared library packages that would otherwise
7820 be hidden behind the library ABI, and can make library
7821 transitions to new SONAMEs unnecessarily complicated and
7822 difficult to manage.
7824 If the <file>.la</file> file is required for that library (if,
7825 for instance, it's loaded via <tt>libltdl</tt> in a way that
7826 requires that meta-information), the <tt>dependency_libs</tt>
7827 setting in the <file>.la</file> file should normally be set to
7828 the empty string. If the shared library development package has
7829 historically included the <file>.la</file>, it must be retained
7830 in the development package (with <tt>dependency_libs</tt>
7831 emptied) until all libraries that depend on it have removed or
7832 emptied <tt>dependency_libs</tt> in their <file>.la</file>
7833 files to prevent linking with those other libraries
7834 using <prgn>libtool</prgn> from failing.
7838 If the <file>.la</file> must be included, it should be included
7839 in the development (<tt>-dev</tt>) package, unless the library
7840 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
7841 library. If it is intended for use with <tt>libltdl</tt>,
7842 the <file>.la</file> files must go in the run-time library
7847 These requirements for handling of <file>.la</file> files do not
7848 apply to loadable modules or libraries not installed in
7849 directories searched by default by the dynamic linker. Packages
7850 installing loadable modules will frequently need to install
7851 the <file>.la</file> files alongside the modules so that they
7852 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
7853 does not need to be modified for libraries or modules that are
7854 not installed in directories searched by the dynamic linker by
7855 default and not intended for use by other packages.
7859 You must make sure that you use only released versions of
7860 shared libraries to build your packages; otherwise other
7861 users will not be able to run your binaries
7862 properly. Producing source packages that depend on
7863 unreleased compilers is also usually a bad
7870 <heading>Shared libraries</heading>
7872 This section has moved to <ref id="sharedlibs">.
7878 <heading>Scripts</heading>
7881 All command scripts, including the package maintainer
7882 scripts inside the package and used by <prgn>dpkg</prgn>,
7883 should have a <tt>#!</tt> line naming the shell to be used
7888 In the case of Perl scripts this should be
7889 <tt>#!/usr/bin/perl</tt>.
7893 When scripts are installed into a directory in the system
7894 PATH, the script name should not include an extension such
7895 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7896 language currently used to implement it.
7899 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
7900 <file>init.d</file> scripts should almost certainly start
7901 with <tt>set -e</tt> so that errors are detected.
7902 <file>init.d</file> scripts are something of a special case, due
7903 to how frequently they need to call commands that are allowed to
7904 fail, and it may instead be easier to check the exit status of
7905 commands directly. See <ref id="writing-init"> for more
7906 information about writing <file>init.d</file> scripts.
7909 Every script should use <tt>set -e</tt> or check the exit status
7910 of <em>every</em> command.
7913 Scripts may assume that <file>/bin/sh</file> implements the
7914 SUSv3 Shell Command Language<footnote>
7915 Single UNIX Specification, version 3, which is also IEEE
7916 1003.1-2004 (POSIX), and is available on the World Wide Web
7917 from <url id="http://www.unix.org/version3/online.html"
7918 name="The Open Group"> after free
7919 registration.</footnote>
7920 plus the following additional features not mandated by
7922 These features are in widespread use in the Linux community
7923 and are implemented in all of bash, dash, and ksh, the most
7924 common shells users may wish to use as <file>/bin/sh</file>.
7927 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7928 must not generate a newline.</item>
7929 <item><tt>test</tt>, if implemented as a shell built-in, must
7930 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7932 <item><tt>local</tt> to create a scoped variable must be
7933 supported, including listing multiple variables in a single
7934 local command and assigning a value to a variable at the
7935 same time as localizing it. <tt>local</tt> may or
7936 may not preserve the variable value from an outer scope if
7937 no assignment is present. Uses such as:
7941 # ... use a, b, c, d ...
7944 must be supported and must set the value of <tt>c</tt> to
7947 <item>The XSI extension to <prgn>kill</prgn> allowing <tt>kill
7948 -<var>signal</var></tt>, where <var>signal</var> is either
7949 the name of a signal or one of the numeric signals listed in
7950 the XSI extension (0, 1, 2, 3, 6, 9, 14, and 15), must be
7951 supported if <prgn>kill</prgn> is implemented as a shell
7954 <item>The XSI extension to <prgn>trap</prgn> allowing numeric
7955 signals must be supported. In addition to the signal
7956 numbers listed in the extension, which are the same as for
7957 <prgn>kill</prgn> above, 13 (SIGPIPE) must be allowed.
7960 If a shell script requires non-SUSv3 features from the shell
7961 interpreter other than those listed above, the appropriate shell
7962 must be specified in the first line of the script (e.g.,
7963 <tt>#!/bin/bash</tt>) and the package must depend on the package
7964 providing the shell (unless the shell package is marked
7965 "Essential", as in the case of <prgn>bash</prgn>).
7969 You may wish to restrict your script to SUSv3 features plus the
7970 above set when possible so that it may use <file>/bin/sh</file>
7971 as its interpreter. Checking your script
7972 with <prgn>checkbashisms</prgn> from
7973 the <package>devscripts</package> package or running your script
7974 with <prgn>posh</prgn> may help uncover violations of the above
7975 requirements. If in doubt whether a script complies with these
7976 requirements, use <file>/bin/bash</file>.
7980 Perl scripts should check for errors when making any
7981 system calls, including <tt>open</tt>, <tt>print</tt>,
7982 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7986 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7987 scripting languages. See <em>Csh Programming Considered
7988 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7989 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7990 If an upstream package comes with <prgn>csh</prgn> scripts
7991 then you must make sure that they start with
7992 <tt>#!/bin/csh</tt> and make your package depend on the
7993 <prgn>c-shell</prgn> virtual package.
7997 Any scripts which create files in world-writeable
7998 directories (e.g., in <file>/tmp</file>) must use a
7999 mechanism which will fail atomically if a file with the same
8000 name already exists.
8004 The Debian base system provides the <prgn>tempfile</prgn>
8005 and <prgn>mktemp</prgn> utilities for use by scripts for
8012 <heading>Symbolic links</heading>
8015 In general, symbolic links within a top-level directory should
8016 be relative, and symbolic links pointing from one top-level
8017 directory to or into another should be absolute. (A top-level
8018 directory is a sub-directory of the root
8019 directory <file>/</file>.) For example, a symbolic link
8020 from <file>/usr/lib/foo</file> to <file>/usr/share/bar</file>
8021 should be relative (<file>../share/bar</file>), but a symbolic
8022 link from <file>/var/run</file> to <file>/run</file> should be
8024 This is necessary to allow top-level directories to be
8025 symlinks. If linking <file>/var/run</file>
8026 to <file>/run</file> were done with the relative symbolic
8027 link <file>../run</file>, but <file>/var</file> were a
8028 symbolic link to <file>/srv/disk1</file>, the symbolic link
8029 would point to <file>/srv/run</file> rather than the intended
8035 In addition, symbolic links should be specified as short as
8036 possible, i.e., link targets like <file>foo/../bar</file> are
8041 Note that when creating a relative link using
8042 <prgn>ln</prgn> it is not necessary for the target of the
8043 link to exist relative to the working directory you're
8044 running <prgn>ln</prgn> from, nor is it necessary to change
8045 directory to the directory where the link is to be made.
8046 Simply include the string that should appear as the target
8047 of the link (this will be a pathname relative to the
8048 directory in which the link resides) as the first argument
8053 For example, in your <prgn>Makefile</prgn> or
8054 <file>debian/rules</file>, you can do things like:
8055 <example compact="compact">
8056 ln -fs gcc $(prefix)/bin/cc
8057 ln -fs gcc debian/tmp/usr/bin/cc
8058 ln -fs ../sbin/sendmail $(prefix)/bin/runq
8059 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
8064 A symbolic link pointing to a compressed file should always
8065 have the same file extension as the referenced file. (For
8066 example, if a file <file>foo.gz</file> is referenced by a
8067 symbolic link, the filename of the link has to end with
8068 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
8073 <heading>Device files</heading>
8076 Packages must not include device files or named pipes in the
8081 If a package needs any special device files that are not
8082 included in the base system, it must call
8083 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
8084 after notifying the user<footnote>
8085 This notification could be done via a (low-priority)
8086 debconf message, or an echo (printf) statement.
8091 Packages must not remove any device files in the
8092 <prgn>postrm</prgn> or any other script. This is left to the
8093 system administrator.
8097 Debian uses the serial devices
8098 <file>/dev/ttyS*</file>. Programs using the old
8099 <file>/dev/cu*</file> devices should be changed to use
8100 <file>/dev/ttyS*</file>.
8104 Named pipes needed by the package must be created in
8105 the <prgn>postinst</prgn> script<footnote>
8106 It's better to use <prgn>mkfifo</prgn> rather
8107 than <prgn>mknod</prgn> to create named pipes so that
8108 automated checks for packages incorrectly creating device
8109 files with <prgn>mknod</prgn> won't have false positives.
8110 </footnote> and removed in
8111 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
8116 <sect id="config-files">
8117 <heading>Configuration files</heading>
8120 <heading>Definitions</heading>
8124 <tag>configuration file</tag>
8126 A file that affects the operation of a program, or
8127 provides site- or host-specific information, or
8128 otherwise customizes the behavior of a program.
8129 Typically, configuration files are intended to be
8130 modified by the system administrator (if needed or
8131 desired) to conform to local policy or to provide
8132 more useful site-specific behavior.
8135 <tag><tt>conffile</tt></tag>
8137 A file listed in a package's <tt>conffiles</tt>
8138 file, and is treated specially by <prgn>dpkg</prgn>
8139 (see <ref id="configdetails">).
8145 The distinction between these two is important; they are
8146 not interchangeable concepts. Almost all
8147 <tt>conffile</tt>s are configuration files, but many
8148 configuration files are not <tt>conffiles</tt>.
8152 As noted elsewhere, <file>/etc/init.d</file> scripts,
8153 <file>/etc/default</file> files, scripts installed in
8154 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
8155 configuration installed in <file>/etc/cron.d</file> must be
8156 treated as configuration files. In general, any script that
8157 embeds configuration information is de-facto a configuration
8158 file and should be treated as such.
8163 <heading>Location</heading>
8166 Any configuration files created or used by your package
8167 must reside in <file>/etc</file>. If there are several,
8168 consider creating a subdirectory of <file>/etc</file>
8169 named after your package.
8173 If your package creates or uses configuration files
8174 outside of <file>/etc</file>, and it is not feasible to modify
8175 the package to use <file>/etc</file> directly, put the files
8176 in <file>/etc</file> and create symbolic links to those files
8177 from the location that the package requires.
8182 <heading>Behavior</heading>
8185 Configuration file handling must conform to the following
8187 <list compact="compact">
8189 local changes must be preserved during a package
8193 configuration files must be preserved when the
8194 package is removed, and only deleted when the
8198 Obsolete configuration files without local changes may be
8199 removed by the package during upgrade.
8203 The easy way to achieve this behavior is to make the
8204 configuration file a <tt>conffile</tt>. This is
8205 appropriate only if it is possible to distribute a default
8206 version that will work for most installations, although
8207 some system administrators may choose to modify it. This
8208 implies that the default version will be part of the
8209 package distribution, and must not be modified by the
8210 maintainer scripts during installation (or at any other
8215 In order to ensure that local changes are preserved
8216 correctly, no package may contain or make hard links to
8217 conffiles.<footnote>
8218 Rationale: There are two problems with hard links.
8219 The first is that some editors break the link while
8220 editing one of the files, so that the two files may
8221 unwittingly become unlinked and different. The second
8222 is that <prgn>dpkg</prgn> might break the hard link
8223 while upgrading <tt>conffile</tt>s.
8228 The other way to do it is via the maintainer scripts. In
8229 this case, the configuration file must not be listed as a
8230 <tt>conffile</tt> and must not be part of the package
8231 distribution. If the existence of a file is required for
8232 the package to be sensibly configured it is the
8233 responsibility of the package maintainer to provide
8234 maintainer scripts which correctly create, update and
8235 maintain the file and remove it on purge. (See <ref
8236 id="maintainerscripts"> for more information.) These
8237 scripts must be idempotent (i.e., must work correctly if
8238 <prgn>dpkg</prgn> needs to re-run them due to errors
8239 during installation or removal), must cope with all the
8240 variety of ways <prgn>dpkg</prgn> can call maintainer
8241 scripts, must not overwrite or otherwise mangle the user's
8242 configuration without asking, must not ask unnecessary
8243 questions (particularly during upgrades), and must
8244 otherwise be good citizens.
8248 The scripts are not required to configure every possible
8249 option for the package, but only those necessary to get
8250 the package running on a given system. Ideally the
8251 sysadmin should not have to do any configuration other
8252 than that done (semi-)automatically by the
8253 <prgn>postinst</prgn> script.
8257 A common practice is to create a script called
8258 <file><var>package</var>-configure</file> and have the
8259 package's <prgn>postinst</prgn> call it if and only if the
8260 configuration file does not already exist. In certain
8261 cases it is useful for there to be an example or template
8262 file which the maintainer scripts use. Such files should
8263 be in <file>/usr/share/<var>package</var></file> or
8264 <file>/usr/lib/<var>package</var></file> (depending on whether
8265 they are architecture-independent or not). There should
8266 be symbolic links to them from
8267 <file>/usr/share/doc/<var>package</var>/examples</file> if
8268 they are examples, and should be perfectly ordinary
8269 <prgn>dpkg</prgn>-handled files (<em>not</em>
8270 configuration files).
8274 These two styles of configuration file handling must
8275 not be mixed, for that way lies madness:
8276 <prgn>dpkg</prgn> will ask about overwriting the file
8277 every time the package is upgraded.
8282 <heading>Sharing configuration files</heading>
8285 If two or more packages use the same configuration file
8286 and it is reasonable for both to be installed at the same
8287 time, one of these packages must be defined as
8288 <em>owner</em> of the configuration file, i.e., it will be
8289 the package which handles that file as a configuration
8290 file. Other packages that use the configuration file must
8291 depend on the owning package if they require the
8292 configuration file to operate. If the other package will
8293 use the configuration file if present, but is capable of
8294 operating without it, no dependency need be declared.
8298 If it is desirable for two or more related packages to
8299 share a configuration file <em>and</em> for all of the
8300 related packages to be able to modify that configuration
8301 file, then the following should be done:
8302 <enumlist compact="compact">
8304 One of the related packages (the "owning" package)
8305 will manage the configuration file with maintainer
8306 scripts as described in the previous section.
8309 The owning package should also provide a program
8310 that the other packages may use to modify the
8314 The related packages must use the provided program
8315 to make any desired modifications to the
8316 configuration file. They should either depend on
8317 the core package to guarantee that the configuration
8318 modifier program is available or accept gracefully
8319 that they cannot modify the configuration file if it
8320 is not. (This is in addition to the fact that the
8321 configuration file may not even be present in the
8328 Sometimes it's appropriate to create a new package which
8329 provides the basic infrastructure for the other packages
8330 and which manages the shared configuration files. (The
8331 <tt>sgml-base</tt> package is a good example.)
8335 If the configuration file cannot be shared as described above,
8336 the packages must be marked as conflicting with each other.
8337 Two packages that specify the same file as
8338 a <tt>conffile</tt> must conflict. This is an instance of the
8339 general rule about not sharing files. Neither alternatives
8340 nor diversions are likely to be appropriate in this case; in
8341 particular, <prgn>dpkg</prgn> does not handle diverted
8342 <tt>conffile</tt>s well.
8346 When two packages both declare the same <tt>conffile</tt>, they
8347 may see left-over configuration files from each other even
8348 though they conflict with each other. If a user removes
8349 (without purging) one of the packages and installs the other,
8350 the new package will take over the <tt>conffile</tt> from the
8351 old package. If the file was modified by the user, it will be
8352 treated the same as any other locally
8353 modified <tt>conffile</tt> during an upgrade.
8357 The maintainer scripts must not alter a <tt>conffile</tt>
8358 of <em>any</em> package, including the one the scripts
8364 <heading>User configuration files ("dotfiles")</heading>
8367 The files in <file>/etc/skel</file> will automatically be
8368 copied into new user accounts by <prgn>adduser</prgn>.
8369 No other program should reference the files in
8370 <file>/etc/skel</file>.
8374 Therefore, if a program needs a dotfile to exist in
8375 advance in <file>$HOME</file> to work sensibly, that dotfile
8376 should be installed in <file>/etc/skel</file> and treated as a
8381 However, programs that require dotfiles in order to
8382 operate sensibly are a bad thing, unless they do create
8383 the dotfiles themselves automatically.
8387 Furthermore, programs should be configured by the Debian
8388 default installation to behave as closely to the upstream
8389 default behavior as possible.
8393 Therefore, if a program in a Debian package needs to be
8394 configured in some way in order to operate sensibly, that
8395 should be done using a site-wide configuration file placed
8396 in <file>/etc</file>. Only if the program doesn't support a
8397 site-wide default configuration and the package maintainer
8398 doesn't have time to add it may a default per-user file be
8399 placed in <file>/etc/skel</file>.
8403 <file>/etc/skel</file> should be as empty as we can make it.
8404 This is particularly true because there is no easy (or
8405 necessarily desirable) mechanism for ensuring that the
8406 appropriate dotfiles are copied into the accounts of
8407 existing users when a package is installed.
8413 <heading>Log files</heading>
8415 Log files should usually be named
8416 <file>/var/log/<var>package</var>.log</file>. If you have many
8417 log files, or need a separate directory for permission
8418 reasons (<file>/var/log</file> is writable only by
8419 <file>root</file>), you should usually create a directory named
8420 <file>/var/log/<var>package</var></file> and place your log
8425 Log files must be rotated occasionally so that they don't grow
8426 indefinitely. The best way to do this is to install a log
8427 rotation configuration file in the
8428 directory <file>/etc/logrotate.d</file>, normally
8429 named <file>/etc/logrotate.d/<var>package</var></file>, and use
8430 the facilities provided by <prgn>logrotate</prgn>.
8433 The traditional approach to log files has been to set up
8434 <em>ad hoc</em> log rotation schemes using simple shell
8435 scripts and cron. While this approach is highly
8436 customizable, it requires quite a lot of sysadmin work.
8437 Even though the original Debian system helped a little
8438 by automatically installing a system which can be used
8439 as a template, this was deemed not enough.
8443 The use of <prgn>logrotate</prgn>, a program developed
8444 by Red Hat, is better, as it centralizes log management.
8445 It has both a configuration file
8446 (<file>/etc/logrotate.conf</file>) and a directory where
8447 packages can drop their individual log rotation
8448 configurations (<file>/etc/logrotate.d</file>).
8451 Here is a good example for a logrotate config
8452 file (for more information see <manref name="logrotate"
8454 <example compact="compact">
8455 /var/log/foo/*.log {
8461 start-stop-daemon -K -p /var/run/foo.pid -s HUP -x /usr/sbin/foo -q
8465 This rotates all files under <file>/var/log/foo</file>, saves 12
8466 compressed generations, and tells the daemon to reopen its log
8467 files after the log rotation. It skips this log rotation
8468 (via <tt>missingok</tt>) if no such log file is present, which
8469 avoids errors if the package is removed but not purged.
8473 Log files should be removed when the package is
8474 purged (but not when it is only removed). This should be
8475 done by the <prgn>postrm</prgn> script when it is called
8476 with the argument <tt>purge</tt> (see <ref
8477 id="removedetails">).
8481 <sect id="permissions-owners">
8482 <heading>Permissions and owners</heading>
8485 The rules in this section are guidelines for general use.
8486 If necessary you may deviate from the details below.
8487 However, if you do so you must make sure that what is done
8488 is secure and you should try to be as consistent as possible
8489 with the rest of the system. You should probably also
8490 discuss it on <prgn>debian-devel</prgn> first.
8494 Files should be owned by <tt>root:root</tt>, and made
8495 writable only by the owner and universally readable (and
8496 executable, if appropriate), that is mode 644 or 755.
8500 Directories should be mode 755 or (for group-writability)
8501 mode 2775. The ownership of the directory should be
8502 consistent with its mode: if a directory is mode 2775, it
8503 should be owned by the group that needs write access to
8506 When a package is upgraded, and the owner or permissions
8507 of a file included in the package has changed, dpkg
8508 arranges for the ownership and permissions to be
8509 correctly set upon installation. However, this does not
8510 extend to directories; the permissions and ownership of
8511 directories already on the system does not change on
8512 install or upgrade of packages. This makes sense, since
8513 otherwise common directories like <tt>/usr</tt> would
8514 always be in flux. To correctly change permissions of a
8515 directory the package owns, explicit action is required,
8516 usually in the <tt>postinst</tt> script. Care must be
8517 taken to handle downgrades as well, in that case.
8523 Control information files should be owned by <tt>root:root</tt>
8524 and either mode 644 (for most files) or mode 755 (for
8525 executables such as <qref id="maintscripts">maintainer
8530 Setuid and setgid executables should be mode 4755 or 2755
8531 respectively, and owned by the appropriate user or group.
8532 They should not be made unreadable (modes like 4711 or
8533 2711 or even 4111); doing so achieves no extra security,
8534 because anyone can find the binary in the freely available
8535 Debian package; it is merely inconvenient. For the same
8536 reason you should not restrict read or execute permissions
8537 on non-set-id executables.
8541 Some setuid programs need to be restricted to particular
8542 sets of users, using file permissions. In this case they
8543 should be owned by the uid to which they are set-id, and by
8544 the group which should be allowed to execute them. They
8545 should have mode 4754; again there is no point in making
8546 them unreadable to those users who must not be allowed to
8551 It is possible to arrange that the system administrator can
8552 reconfigure the package to correspond to their local
8553 security policy by changing the permissions on a binary:
8554 they can do this by using <prgn>dpkg-statoverride</prgn>, as
8555 described below.<footnote>
8556 Ordinary files installed by <prgn>dpkg</prgn> (as
8557 opposed to <tt>conffile</tt>s and other similar objects)
8558 normally have their permissions reset to the distributed
8559 permissions when the package is reinstalled. However,
8560 the use of <prgn>dpkg-statoverride</prgn> overrides this
8563 Another method you should consider is to create a group for
8564 people allowed to use the program(s) and make any setuid
8565 executables executable only by that group.
8569 If you need to create a new user or group for your package
8570 there are two possibilities. Firstly, you may need to
8571 make some files in the binary package be owned by this
8572 user or group, or you may need to compile the user or
8573 group id (rather than just the name) into the binary
8574 (though this latter should be avoided if possible, as in
8575 this case you need a statically allocated id).</p>
8578 If you need a statically allocated id, you must ask for a
8579 user or group id from the <tt>base-passwd</tt> maintainer,
8580 and must not release the package until you have been
8581 allocated one. Once you have been allocated one you must
8582 either make the package depend on a version of the
8583 <tt>base-passwd</tt> package with the id present in
8584 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
8585 your package to create the user or group itself with the
8586 correct id (using <tt>adduser</tt>) in its
8587 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
8588 the <prgn>postinst</prgn> is to be preferred if it is
8589 possible, otherwise a pre-dependency will be needed on the
8590 <tt>adduser</tt> package.)
8594 On the other hand, the program might be able to determine
8595 the uid or gid from the user or group name at runtime, so
8596 that a dynamically allocated id can be used. In this case
8597 you should choose an appropriate user or group name,
8598 discussing this on <prgn>debian-devel</prgn> and checking
8599 with the <package/base-passwd/ maintainer that it is unique and that
8600 they do not wish you to use a statically allocated id
8601 instead. When this has been checked you must arrange for
8602 your package to create the user or group if necessary using
8603 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
8604 <prgn>postinst</prgn> script (again, the latter is to be
8605 preferred if it is possible).
8609 Note that changing the numeric value of an id associated
8610 with a name is very difficult, and involves searching the
8611 file system for all appropriate files. You need to think
8612 carefully whether a static or dynamic id is required, since
8613 changing your mind later will cause problems.
8616 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
8618 This section is not intended as policy, but as a
8619 description of the use of <prgn>dpkg-statoverride</prgn>.
8623 If a system administrator wishes to have a file (or
8624 directory or other such thing) installed with owner and
8625 permissions different from those in the distributed Debian
8626 package, they can use the <prgn>dpkg-statoverride</prgn>
8627 program to instruct <prgn>dpkg</prgn> to use the different
8628 settings every time the file is installed. Thus the
8629 package maintainer should distribute the files with their
8630 normal permissions, and leave it for the system
8631 administrator to make any desired changes. For example, a
8632 daemon which is normally required to be setuid root, but
8633 in certain situations could be used without being setuid,
8634 should be installed setuid in the <tt>.deb</tt>. Then the
8635 local system administrator can change this if they wish.
8636 If there are two standard ways of doing it, the package
8637 maintainer can use <tt>debconf</tt> to find out the
8638 preference, and call <prgn>dpkg-statoverride</prgn> in the
8639 maintainer script if necessary to accommodate the system
8640 administrator's choice. Care must be taken during
8641 upgrades to not override an existing setting.
8645 Given the above, <prgn>dpkg-statoverride</prgn> is
8646 essentially a tool for system administrators and would not
8647 normally be needed in the maintainer scripts. There is
8648 one type of situation, though, where calls to
8649 <prgn>dpkg-statoverride</prgn> would be needed in the
8650 maintainer scripts, and that involves packages which use
8651 dynamically allocated user or group ids. In such a
8652 situation, something like the following idiom can be very
8653 helpful in the package's <prgn>postinst</prgn>, where
8654 <tt>sysuser</tt> is a dynamically allocated id:
8656 for i in /usr/bin/foo /usr/sbin/bar
8658 # only do something when no setting exists
8659 if ! dpkg-statoverride --list $i >/dev/null 2>&1
8661 #include: debconf processing, question about foo and bar
8662 if [ "$RET" = "true" ] ; then
8663 dpkg-statoverride --update --add sysuser root 4755 $i
8668 The corresponding code to remove the override when the package
8671 for i in /usr/bin/foo /usr/sbin/bar
8673 if dpkg-statoverride --list $i >/dev/null 2>&1
8675 dpkg-statoverride --remove $i
8685 <chapt id="customized-programs">
8686 <heading>Customized programs</heading>
8688 <sect id="arch-spec">
8689 <heading>Architecture specification strings</heading>
8692 If a program needs to specify an <em>architecture specification
8693 string</em> in some place, it should select one of the strings
8694 provided by <tt>dpkg-architecture -L</tt>. The strings are in
8695 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
8696 part is sometimes elided, as when the OS is Linux.
8700 Note that we don't want to use
8701 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
8702 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
8703 since this would make our programs incompatible with other
8704 Linux distributions. We also don't use something like
8705 <tt><var>arch</var>-unknown-linux</tt>, since the
8706 <tt>unknown</tt> does not look very good.
8709 <sect1 id="arch-wildcard-spec">
8710 <heading>Architecture wildcards</heading>
8713 A package may specify an architecture wildcard. Architecture
8714 wildcards are in the format <tt>any</tt> (which matches every
8715 architecture), <tt><var>os</var></tt>-any, or
8716 any-<tt><var>cpu</var></tt>. <footnote>
8717 Internally, the package system normalizes the GNU triplets
8718 and the Debian arches into Debian arch triplets (which are
8719 kind of inverted GNU triplets), with the first component of
8720 the triplet representing the libc and ABI in use, and then
8721 does matching against those triplets. However, such
8722 triplets are an internal implementation detail that should
8723 not be used by packages directly. The libc and ABI portion
8724 is handled internally by the package system based on
8725 the <var>os</var> and <var>cpu</var>.
8732 <heading>Daemons</heading>
8735 The configuration files <file>/etc/services</file>,
8736 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
8737 by the <prgn>netbase</prgn> package and must not be modified
8742 If a package requires a new entry in one of these files, the
8743 maintainer should get in contact with the
8744 <prgn>netbase</prgn> maintainer, who will add the entries
8745 and release a new version of the <prgn>netbase</prgn>
8750 The configuration file <file>/etc/inetd.conf</file> must not be
8751 modified by the package's scripts except via the
8752 <prgn>update-inetd</prgn> script or the
8753 <file>DebianNet.pm</file> Perl module. See their documentation
8754 for details on how to add entries.
8758 If a package wants to install an example entry into
8759 <file>/etc/inetd.conf</file>, the entry must be preceded with
8760 exactly one hash character (<tt>#</tt>). Such lines are
8761 treated as "commented out by user" by the
8762 <prgn>update-inetd</prgn> script and are not changed or
8763 activated during package updates.
8768 <heading>Using pseudo-ttys and modifying wtmp, utmp and
8772 Some programs need to create pseudo-ttys. This should be done
8773 using Unix98 ptys if the C library supports it. The resulting
8774 program must not be installed setuid root, unless that
8775 is required for other functionality.
8779 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
8780 <file>/var/log/lastlog</file> must be installed writable by
8781 group <tt>utmp</tt>. Programs which need to modify those
8782 files must be installed setgid <tt>utmp</tt>.
8787 <heading>Editors and pagers</heading>
8790 Some programs have the ability to launch an editor or pager
8791 program to edit or display a text document. Since there are
8792 lots of different editors and pagers available in the Debian
8793 distribution, the system administrator and each user should
8794 have the possibility to choose their preferred editor and
8799 In addition, every program should choose a good default
8800 editor/pager if none is selected by the user or system
8805 Thus, every program that launches an editor or pager must
8806 use the EDITOR or PAGER environment variable to determine
8807 the editor or pager the user wishes to use. If these
8808 variables are not set, the programs <file>/usr/bin/editor</file>
8809 and <file>/usr/bin/pager</file> should be used, respectively.
8813 These two files are managed through the <prgn>dpkg</prgn>
8814 "alternatives" mechanism. Every package providing an editor or
8815 pager must call the <prgn>update-alternatives</prgn> script to
8816 register as an alternative for <file>/usr/bin/editor</file>
8817 or <file>/usr/bin/pager</file> as appropriate. The alternative
8818 should have a slave alternative
8819 for <file>/usr/share/man/man1/editor.1.gz</file>
8820 or <file>/usr/share/man/man1/pager.1.gz</file> pointing to the
8821 corresponding manual page.
8825 If it is very hard to adapt a program to make use of the
8826 EDITOR or PAGER variables, that program may be configured to
8827 use <file>/usr/bin/sensible-editor</file> and
8828 <file>/usr/bin/sensible-pager</file> as the editor or pager
8829 program respectively. These are two scripts provided in the
8830 <package>sensible-utils</package> package that check the EDITOR
8831 and PAGER variables and launch the appropriate program, and fall
8832 back to <file>/usr/bin/editor</file>
8833 and <file>/usr/bin/pager</file> if the variable is not set.
8837 A program may also use the VISUAL environment variable to
8838 determine the user's choice of editor. If it exists, it
8839 should take precedence over EDITOR. This is in fact what
8840 <file>/usr/bin/sensible-editor</file> does.
8844 It is not required for a package to depend on
8845 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
8846 package to provide such virtual packages.<footnote>
8847 The Debian base system already provides an editor and a
8853 <sect id="web-appl">
8854 <heading>Web servers and applications</heading>
8857 This section describes the locations and URLs that should
8858 be used by all web servers and web applications in the
8865 Cgi-bin executable files are installed in the
8867 <example compact="compact">
8868 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
8870 or a subdirectory of that directory, and should be
8872 <example compact="compact">
8873 http://localhost/cgi-bin/<var>cgi-bin-name</var>
8875 (possibly with a subdirectory name
8876 before <var>cgi-bin-name</var>).
8880 <p>Access to HTML documents</p>
8883 HTML documents for a package are stored in
8884 <file>/usr/share/doc/<var>package</var></file>
8885 and can be referred to as
8886 <example compact="compact">
8887 http://localhost/doc/<var>package</var>/<var>filename</var>
8892 The web server should restrict access to the document
8893 tree so that only clients on the same host can read
8894 the documents. If the web server does not support such
8895 access controls, then it should not provide access at
8896 all, or ask about providing access during installation.
8901 <p>Access to images</p>
8903 It is recommended that images for a package be stored
8904 in <tt>/usr/share/images/<var>package</var></tt> and
8905 may be referred to through an alias <tt>/images/</tt>
8908 http://localhost/images/<package>/<filename>
8915 <p>Web Document Root</p>
8918 Web Applications should try to avoid storing files in
8919 the Web Document Root. Instead they should use the
8920 /usr/share/doc/<var>package</var> directory for
8921 documents and register the Web Application via the
8922 <package>doc-base</package> package. If access to the
8923 web document root is unavoidable then use
8924 <example compact="compact">
8927 as the Document Root. This might be just a symbolic
8928 link to the location where the system administrator
8929 has put the real document root.
8932 <item><p>Providing httpd and/or httpd-cgi</p>
8934 All web servers should provide the virtual package
8935 <tt>httpd</tt>. If a web server has CGI support it should
8936 provide <tt>httpd-cgi</tt> additionally.
8939 All web applications which do not contain CGI scripts should
8940 depend on <tt>httpd</tt>, all those web applications which
8941 <tt>do</tt> contain CGI scripts, should depend on
8949 <sect id="mail-transport-agents">
8950 <heading>Mail transport, delivery and user agents</heading>
8953 Debian packages which process electronic mail, whether mail
8954 user agents (MUAs) or mail transport agents (MTAs), must
8955 ensure that they are compatible with the configuration
8956 decisions below. Failure to do this may result in lost
8957 mail, broken <tt>From:</tt> lines, and other serious brain
8962 The mail spool is <file>/var/mail</file> and the interface to
8963 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8964 the FHS). On older systems, the mail spool may be
8965 physically located in <file>/var/spool/mail</file>, but all
8966 access to the mail spool should be via the
8967 <file>/var/mail</file> symlink. The mail spool is part of the
8968 base system and not part of the MTA package.
8972 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8973 programs (such as IMAP daemons) must lock the mailbox in an
8974 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8975 be combined with dot locking. To avoid deadlocks, a program
8976 should use <tt>fcntl()</tt> first and dot locking after
8977 this, or alternatively implement the two locking methods in
8978 a non blocking way<footnote>
8979 If it is not possible to establish both locks, the
8980 system shouldn't wait for the second lock to be
8981 established, but remove the first lock, wait a (random)
8982 time, and start over locking again.
8983 </footnote>. Using the functions <tt>maillock</tt> and
8984 <tt>mailunlock</tt> provided by the
8985 <tt>liblockfile*</tt><footnote>
8986 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8987 to use these functions.
8988 </footnote> packages is the recommended way to realize this.
8992 Mailboxes are generally either mode 600 and owned by
8993 <var>user</var> or mode 660 and owned by
8994 <tt><var>user</var>:mail</tt><footnote>
8995 There are two traditional permission schemes for mail spools:
8996 mode 600 with all mail delivery done by processes running as
8997 the destination user, or mode 660 and owned by group mail with
8998 mail delivery done by a process running as a system user in
8999 group mail. Historically, Debian required mode 660 mail
9000 spools to enable the latter model, but that model has become
9001 increasingly uncommon and the principle of least privilege
9002 indicates that mail systems that use the first model should
9003 use permissions of 600. If delivery to programs is permitted,
9004 it's easier to keep the mail system secure if the delivery
9005 agent runs as the destination user. Debian Policy therefore
9006 permits either scheme.
9007 </footnote>. The local system administrator may choose a
9008 different permission scheme; packages should not make
9009 assumptions about the permission and ownership of mailboxes
9010 unless required (such as when creating a new mailbox). A MUA
9011 may remove a mailbox (unless it has nonstandard permissions) in
9012 which case the MTA or another MUA must recreate it if needed.
9016 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
9017 be setgid mail to do the locking mentioned above (and
9018 must obviously avoid accessing other users' mailboxes
9019 using this privilege).</p>
9022 <file>/etc/aliases</file> is the source file for the system mail
9023 aliases (e.g., postmaster, usenet, etc.), it is the one
9024 which the sysadmin and <prgn>postinst</prgn> scripts may
9025 edit. After <file>/etc/aliases</file> is edited the program or
9026 human editing it must call <prgn>newaliases</prgn>. All MTA
9027 packages must come with a <prgn>newaliases</prgn> program,
9028 even if it does nothing, but older MTA packages did not do
9029 this so programs should not fail if <prgn>newaliases</prgn>
9030 cannot be found. Note that because of this, all MTA
9031 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
9032 <tt>Replaces: mail-transport-agent</tt> control fields.
9036 The convention of writing <tt>forward to
9037 <var>address</var></tt> in the mailbox itself is not
9038 supported. Use a <tt>.forward</tt> file instead.</p>
9041 The <prgn>rmail</prgn> program used by UUCP
9042 for incoming mail should be <file>/usr/sbin/rmail</file>.
9043 Likewise, <prgn>rsmtp</prgn>, for receiving
9044 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
9048 If your package needs to know what hostname to use on (for
9049 example) outgoing news and mail messages which are generated
9050 locally, you should use the file <file>/etc/mailname</file>. It
9051 will contain the portion after the username and <tt>@</tt>
9052 (at) sign for email addresses of users on the machine
9053 (followed by a newline).
9057 Such a package should check for the existence of this file
9058 when it is being configured. If it exists, it should be
9059 used without comment, although an MTA's configuration script
9060 may wish to prompt the user even if it finds that this file
9061 exists. If the file does not exist, the package should
9062 prompt the user for the value (preferably using
9063 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
9064 as well as using it in the package's configuration. The
9065 prompt should make it clear that the name will not just be
9066 used by that package. For example, in this situation the
9067 <tt>inn</tt> package could say something like:
9068 <example compact="compact">
9069 Please enter the "mail name" of your system. This is the
9070 hostname portion of the address to be shown on outgoing
9071 news and mail messages. The default is
9072 <var>syshostname</var>, your system's host name. Mail
9073 name ["<var>syshostname</var>"]:
9075 where <var>syshostname</var> is the output of <tt>hostname
9081 <heading>News system configuration</heading>
9084 All the configuration files related to the NNTP (news)
9085 servers and clients should be located under
9086 <file>/etc/news</file>.</p>
9089 There are some configuration issues that apply to a number
9090 of news clients and server packages on the machine. These
9094 <tag><file>/etc/news/organization</file></tag>
9096 A string which should appear as the
9097 organization header for all messages posted
9098 by NNTP clients on the machine
9101 <tag><file>/etc/news/server</file></tag>
9103 Contains the FQDN of the upstream NNTP
9104 server, or localhost if the local machine is
9109 Other global files may be added as required for cross-package news
9116 <heading>Programs for the X Window System</heading>
9119 <heading>Providing X support and package priorities</heading>
9122 Programs that can be configured with support for the X
9123 Window System must be configured to do so and must declare
9124 any package dependencies necessary to satisfy their
9125 runtime requirements when using the X Window System. If
9126 such a package is of higher priority than the X packages
9127 on which it depends, it is required that either the
9128 X-specific components be split into a separate package, or
9129 that an alternative version of the package, which includes
9130 X support, be provided, or that the package's priority be
9136 <heading>Packages providing an X server</heading>
9139 Packages that provide an X server that, directly or
9140 indirectly, communicates with real input and display
9141 hardware should declare in their <tt>Provides</tt> control
9142 field that they provide the virtual
9143 package <tt>xserver</tt>.<footnote>
9144 This implements current practice, and provides an
9145 actual policy for usage of the <tt>xserver</tt>
9146 virtual package which appears in the virtual packages
9147 list. In a nutshell, X servers that interface
9148 directly with the display and input hardware or via
9149 another subsystem (e.g., GGI) should provide
9150 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
9151 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
9157 <heading>Packages providing a terminal emulator</heading>
9160 Packages that provide a terminal emulator for the X Window
9161 System which meet the criteria listed below should declare in
9162 their <tt>Provides</tt> control field that they provide the
9163 virtual package <tt>x-terminal-emulator</tt>. They should
9164 also register themselves as an alternative for
9165 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
9166 20. That alternative should have a slave alternative
9167 for <file>/usr/share/man/man1/x-terminal-emulator.1.gz</file>
9168 pointing to the corresponding manual page.
9172 To be an <tt>x-terminal-emulator</tt>, a program must:
9173 <list compact="compact">
9175 Be able to emulate a DEC VT100 terminal, or a
9176 compatible terminal.
9180 Support the command-line option <tt>-e
9181 <var>command</var></tt>, which creates a new
9182 terminal window<footnote>
9183 "New terminal window" does not necessarily mean
9184 a new top-level X window directly parented by
9185 the window manager; it could, if the terminal
9186 emulator application were so coded, be a new
9187 "view" in a multiple-document interface (MDI).
9189 and runs the specified <var>command</var>,
9190 interpreting the entirety of the rest of the command
9191 line as a command to pass straight to exec, in the
9192 manner that <tt>xterm</tt> does.
9196 Support the command-line option <tt>-T
9197 <var>title</var></tt>, which creates a new terminal
9198 window with the window title <var>title</var>.
9205 <heading>Packages providing a window manager</heading>
9208 Packages that provide a window manager should declare in
9209 their <tt>Provides</tt> control field that they provide the
9210 virtual package <tt>x-window-manager</tt>. They should also
9211 register themselves as an alternative for
9212 <file>/usr/bin/x-window-manager</file>, with a priority
9213 calculated as follows:
9214 <list compact="compact">
9216 Start with a priority of 20.
9220 If the window manager supports the Debian menu
9221 system, add 20 points if this support is available
9222 in the package's default configuration (i.e., no
9223 configuration files belonging to the system or user
9224 have to be edited to activate the feature); if
9225 configuration files must be modified, add only 10
9231 If the window manager complies with <url
9232 id="http://www.freedesktop.org/wiki/Specifications/wm-spec"
9233 name="The Window Manager Specification Project">,
9234 written by the <url id="http://www.freedesktop.org/wiki/"
9235 name="Free Desktop Group">, add 40 points.
9239 If the window manager permits the X session to be
9240 restarted using a <em>different</em> window manager
9241 (without killing the X server) in its default
9242 configuration, add 10 points; otherwise add none.
9245 That alternative should have a slave alternative
9246 for <file>/usr/share/man/man1/x-window-manager.1.gz</file>
9247 pointing to the corresponding manual page.
9252 <heading>Packages providing fonts</heading>
9255 Packages that provide fonts for the X Window
9257 For the purposes of Debian Policy, a "font for the X
9258 Window System" is one which is accessed via X protocol
9259 requests. Fonts for the Linux console, for PostScript
9260 renderer, or any other purpose, do not fit this
9261 definition. Any tool which makes such fonts available
9262 to the X Window System, however, must abide by this
9265 must do a number of things to ensure that they are both
9266 available without modification of the X or font server
9267 configuration, and that they do not corrupt files used by
9268 other font packages to register information about
9272 Fonts of any type supported by the X Window System
9273 must be in a separate binary package from any
9274 executables, libraries, or documentation (except
9275 that specific to the fonts shipped, such as their
9276 license information). If one or more of the fonts
9277 so packaged are necessary for proper operation of
9278 the package with which they are associated the font
9279 package may be Recommended; if the fonts merely
9280 provide an enhancement, a Suggests relationship may
9281 be used. Packages must not Depend on font
9283 This is because the X server may retrieve fonts
9284 from the local file system or over the network
9285 from an X font server; the Debian package system
9286 is empowered to deal only with the local
9292 BDF fonts must be converted to PCF fonts with the
9293 <prgn>bdftopcf</prgn> utility (available in the
9294 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
9295 placed in a directory that corresponds to their
9297 <list compact="compact">
9299 100 dpi fonts must be placed in
9300 <file>/usr/share/fonts/X11/100dpi/</file>.
9304 75 dpi fonts must be placed in
9305 <file>/usr/share/fonts/X11/75dpi/</file>.
9309 Character-cell fonts, cursor fonts, and other
9310 low-resolution fonts must be placed in
9311 <file>/usr/share/fonts/X11/misc/</file>.
9317 Type 1 fonts must be placed in
9318 <file>/usr/share/fonts/X11/Type1/</file>. If font
9319 metric files are available, they must be placed here
9324 Subdirectories of <file>/usr/share/fonts/X11/</file>
9325 other than those listed above must be neither
9326 created nor used. (The <file>PEX</file>, <file>CID</file>,
9327 <file>Speedo</file>, and <file>cyrillic</file> directories
9328 are excepted for historical reasons, but installation of
9329 files into these directories remains discouraged.)
9333 Font packages may, instead of placing files directly
9334 in the X font directories listed above, provide
9335 symbolic links in that font directory pointing to
9336 the files' actual location in the filesystem. Such
9337 a location must comply with the FHS.
9341 Font packages should not contain both 75dpi and
9342 100dpi versions of a font. If both are available,
9343 they should be provided in separate binary packages
9344 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
9345 the names of the packages containing the
9346 corresponding fonts.
9350 Fonts destined for the <file>misc</file> subdirectory
9351 should not be included in the same package as 75dpi
9352 or 100dpi fonts; instead, they should be provided in
9353 a separate package with <tt>-misc</tt> appended to
9358 Font packages must not provide the files
9359 <file>fonts.dir</file>, <file>fonts.alias</file>, or
9360 <file>fonts.scale</file> in a font directory:
9363 <file>fonts.dir</file> files must not be provided at all.
9367 <file>fonts.alias</file> and <file>fonts.scale</file>
9368 files, if needed, should be provided in the
9370 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
9371 where <var>fontdir</var> is the name of the
9373 <file>/usr/share/fonts/X11/</file> where the
9374 package's corresponding fonts are stored
9375 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
9376 <var>package</var> is the name of the package
9377 that provides these fonts, and
9378 <var>extension</var> is either <tt>scale</tt>
9379 or <tt>alias</tt>, whichever corresponds to
9386 Font packages must declare a dependency on
9387 <tt>xfonts-utils</tt> in their <tt>Depends</tt>
9388 or <tt>Pre-Depends</tt> control field.
9392 Font packages that provide one or more
9393 <file>fonts.scale</file> files as described above must
9394 invoke <prgn>update-fonts-scale</prgn> on each
9395 directory into which they installed fonts
9396 <em>before</em> invoking
9397 <prgn>update-fonts-dir</prgn> on that directory.
9398 This invocation must occur in both the
9399 <prgn>postinst</prgn> (for all arguments) and
9400 <prgn>postrm</prgn> (for all arguments except
9401 <tt>upgrade</tt>) scripts.
9405 Font packages that provide one or more
9406 <file>fonts.alias</file> files as described above must
9407 invoke <prgn>update-fonts-alias</prgn> on each
9408 directory into which they installed fonts. This
9409 invocation must occur in both the
9410 <prgn>postinst</prgn> (for all arguments) and
9411 <prgn>postrm</prgn> (for all arguments except
9412 <tt>upgrade</tt>) scripts.
9416 Font packages must invoke
9417 <prgn>update-fonts-dir</prgn> on each directory into
9418 which they installed fonts. This invocation must
9419 occur in both the <prgn>postinst</prgn> (for all
9420 arguments) and <prgn>postrm</prgn> (for all
9421 arguments except <tt>upgrade</tt>) scripts.
9425 Font packages must not provide alias names for the
9426 fonts they include which collide with alias names
9427 already in use by fonts already packaged.
9431 Font packages must not provide fonts with the same
9432 XLFD registry name as another font already packaged.
9438 <sect1 id="appdefaults">
9439 <heading>Application defaults files</heading>
9442 Application defaults files must be installed in the
9443 directory <file>/etc/X11/app-defaults/</file> (use of a
9444 localized subdirectory of <file>/etc/X11/</file> as described
9445 in the <em>X Toolkit Intrinsics - C Language
9446 Interface</em> manual is also permitted). They must be
9447 registered as <tt>conffile</tt>s or handled as
9448 configuration files.
9452 Customization of programs' X resources may also be
9453 supported with the provision of a file with the same name
9454 as that of the package placed in
9455 the <file>/etc/X11/Xresources/</file> directory, which
9456 must be registered as a <tt>conffile</tt> or handled as a
9457 configuration file.<footnote>
9458 Note that this mechanism is not the same as using
9459 app-defaults; app-defaults are tied to the client
9460 binary on the local file system, whereas X resources
9461 are stored in the X server and affect all connecting
9468 <heading>Installation directory issues</heading>
9471 Historically, packages using the X Window System used a
9472 separate set of installation directories from other packages.
9473 This practice has been discontinued and packages using the X
9474 Window System should now generally be installed in the same
9475 directories as any other package. Specifically, packages must
9476 not install files under the <file>/usr/X11R6/</file> directory
9477 and the <file>/usr/X11R6/</file> directory hierarchy should be
9478 regarded as obsolete.
9482 Include files previously installed under
9483 <file>/usr/X11R6/include/X11/</file> should be installed into
9484 <file>/usr/include/X11/</file>. For files previously
9485 installed into subdirectories of
9486 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
9487 determine if subdirectories of <file>/usr/lib/</file> and
9488 <file>/usr/share/</file> can be used. If not, a subdirectory
9489 of <file>/usr/lib/X11/</file> should be used.
9493 Configuration files for window, display, or session managers
9494 or other applications that are tightly integrated with the X
9495 Window System may be placed in a subdirectory
9496 of <file>/etc/X11/</file> corresponding to the package name.
9497 Other X Window System applications should use
9498 the <file>/etc/</file> directory unless otherwise mandated by
9499 policy (such as for <ref id="appdefaults">).
9505 <heading>Perl programs and modules</heading>
9508 Perl programs and modules should follow the current Perl policy.
9512 The Perl policy can be found in the <tt>perl-policy</tt>
9513 files in the <tt>debian-policy</tt> package.
9514 It is also available from the Debian web mirrors at
9515 <tt><url name="/doc/packaging-manuals/perl-policy/"
9516 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
9521 <heading>Emacs lisp programs</heading>
9524 Please refer to the "Debian Emacs Policy" for details of how to
9525 package emacs lisp programs.
9529 The Emacs policy is available in
9530 <file>debian-emacs-policy.gz</file> of the
9531 <package>emacsen-common</package> package.
9532 It is also available from the Debian web mirrors at
9533 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
9534 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
9539 <heading>Games</heading>
9542 The permissions on <file>/var/games</file> are mode 755, owner
9543 <tt>root</tt> and group <tt>root</tt>.
9547 Each game decides on its own security policy.</p>
9550 Games which require protected, privileged access to
9551 high-score files, saved games, etc., may be made
9552 set-<em>group</em>-id (mode 2755) and owned by
9553 <tt>root:games</tt>, and use files and directories with
9554 appropriate permissions (770 <tt>root:games</tt>, for
9555 example). They must not be made
9556 set-<em>user</em>-id, as this causes security problems. (If
9557 an attacker can subvert any set-user-id game they can
9558 overwrite the executable of any other, causing other players
9559 of these games to run a Trojan horse program. With a
9560 set-group-id game the attacker only gets access to less
9561 important game data, and if they can get at the other
9562 players' accounts at all it will take considerably more
9566 Some packages, for example some fortune cookie programs, are
9567 configured by the upstream authors to install with their
9568 data files or other static information made unreadable so
9569 that they can only be accessed through set-id programs
9570 provided. You should not do this in a Debian package: anyone can
9571 download the <file>.deb</file> file and read the data from it,
9572 so there is no point making the files unreadable. Not
9573 making the files unreadable also means that you don't have
9574 to make so many programs set-id, which reduces the risk of a
9578 As described in the FHS, binaries of games should be
9579 installed in the directory <file>/usr/games</file>. This also
9580 applies to games that use the X Window System. Manual pages
9581 for games (X and non-X games) should be installed in
9582 <file>/usr/share/man/man6</file>.</p>
9588 <heading>Documentation</heading>
9591 <heading>Manual pages</heading>
9594 You should install manual pages in <prgn>nroff</prgn> source
9595 form, in appropriate places under <file>/usr/share/man</file>.
9596 You should only use sections 1 to 9 (see the FHS for more
9597 details). You must not install a pre-formatted "cat page".
9601 Each program, utility, and function should have an
9602 associated manual page included in the same package. It is
9603 suggested that all configuration files also have a manual
9604 page included as well. Manual pages for protocols and other
9605 auxiliary things are optional.
9609 If no manual page is available, this is considered as a bug
9610 and should be reported to the Debian Bug Tracking System (the
9611 maintainer of the package is allowed to write this bug report
9612 themselves, if they so desire). Do not close the bug report
9613 until a proper man page is available.<footnote>
9614 It is not very hard to write a man page. See the
9615 <url id="http://www.schweikhardt.net/man_page_howto.html"
9616 name="Man-Page-HOWTO">,
9617 <manref name="man" section="7">, the examples created
9618 by <prgn>dh_make</prgn>, the helper
9619 program <prgn>help2man</prgn>, or the
9620 directory <file>/usr/share/doc/man-db/examples</file>.
9625 You may forward a complaint about a missing man page to the
9626 upstream authors, and mark the bug as forwarded in the
9627 Debian bug tracking system. Even though the GNU Project do
9628 not in general consider the lack of a man page to be a bug,
9629 we do; if they tell you that they don't consider it a bug
9630 you should leave the bug in our bug tracking system open
9635 Manual pages should be installed compressed using <tt>gzip -9</tt>.
9639 If one man page needs to be accessible via several names it
9640 is better to use a symbolic link than the <file>.so</file>
9641 feature, but there is no need to fiddle with the relevant
9642 parts of the upstream source to change from <file>.so</file> to
9643 symlinks: don't do it unless it's easy. You should not
9644 create hard links in the manual page directories, nor put
9645 absolute filenames in <file>.so</file> directives. The filename
9646 in a <file>.so</file> in a man page should be relative to the
9647 base of the man page tree (usually
9648 <file>/usr/share/man</file>). If you do not create any links
9649 (whether symlinks, hard links, or <tt>.so</tt> directives)
9650 in the file system to the alternate names of the man page,
9651 then you should not rely on <prgn>man</prgn> finding your
9652 man page under those names based solely on the information in
9653 the man page's header.<footnote>
9654 Supporting this in <prgn>man</prgn> often requires
9655 unreasonable processing time to find a manual page or to
9656 report that none exists, and moves knowledge into man's
9657 database that would be better left in the file system.
9658 This support is therefore deprecated and will cease to
9659 be present in the future.
9664 Manual pages in locale-specific subdirectories of
9665 <file>/usr/share/man</file> should use either UTF-8 or the usual
9666 legacy encoding for that language (normally the one corresponding
9667 to the shortest relevant locale name in
9668 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
9669 <file>/usr/share/man/fr</file> should use either UTF-8 or
9670 ISO-8859-1.<footnote>
9671 <prgn>man</prgn> will automatically detect whether UTF-8 is in
9672 use. In future, all manual pages will be required to use
9678 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
9679 included in the subdirectory name unless it indicates a
9680 significant difference in the language, as this excludes
9681 speakers of the language in other countries.<footnote>
9682 At the time of writing, Chinese and Portuguese are the main
9683 languages with such differences, so <file>pt_BR</file>,
9684 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
9689 If a localized version of a manual page is provided, it should
9690 either be up-to-date or it should be obvious to the reader that
9691 it is outdated and the original manual page should be used
9692 instead. This can be done either by a note at the beginning of
9693 the manual page or by showing the missing or changed portions in
9694 the original language instead of the target language.
9699 <heading>Info documents</heading>
9702 Info documents should be installed in <file>/usr/share/info</file>.
9703 They should be compressed with <tt>gzip -9</tt>.
9707 The <prgn>install-info</prgn> program maintains a directory of
9708 installed info documents in <file>/usr/share/info/dir</file> for
9709 the use of info readers.<footnote>
9710 It was previously necessary for packages installing info
9711 documents to run <prgn>install-info</prgn> from maintainer
9712 scripts. This is no longer necessary. The installation
9713 system now uses dpkg triggers.
9715 This file must not be included in packages. Packages containing
9716 info documents should depend on <tt>dpkg (>= 1.15.4) |
9717 install-info</tt> to ensure that the directory file is properly
9718 rebuilt during partial upgrades from Debian 5.0 (lenny) and
9723 Info documents should contain section and directory entry
9724 information in the document for the use
9725 of <prgn>install-info</prgn>. The section should be specified
9726 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
9727 space and the section of this info page. The directory entry or
9728 entries should be included between
9729 a <tt>START-INFO-DIR-ENTRY</tt> line and
9730 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
9732 INFO-DIR-SECTION Individual utilities
9733 START-INFO-DIR-ENTRY
9734 * example: (example). An example info directory entry.
9737 To determine which section to use, you should look
9738 at <file>/usr/share/info/dir</file> on your system and choose
9739 the most relevant (or create a new section if none of the
9740 current sections are relevant).<footnote>
9741 Normally, info documents are generated from Texinfo source.
9742 To include this information in the generated info document, if
9743 it is absent, add commands like:
9745 @dircategory Individual utilities
9747 * example: (example). An example info directory entry.
9750 to the Texinfo source of the document and ensure that the info
9751 documents are rebuilt from source during the package build.
9757 <heading>Additional documentation</heading>
9760 Any additional documentation that comes with the package may
9761 be installed at the discretion of the package maintainer.
9762 Plain text documentation should be installed in the directory
9763 <file>/usr/share/doc/<var>package</var></file>, where
9764 <var>package</var> is the name of the package, and
9765 compressed with <tt>gzip -9</tt> unless it is small.
9769 If a package comes with large amounts of documentation which
9770 many users of the package will not require you should create
9771 a separate binary package to contain it, so that it does not
9772 take up disk space on the machines of users who do not need
9773 or want it installed.</p>
9776 It is often a good idea to put text information files
9777 (<file>README</file>s, changelogs, and so forth) that come with
9778 the source package in <file>/usr/share/doc/<var>package</var></file>
9779 in the binary package. However, you don't need to install
9780 the instructions for building and installing the package, of
9784 Packages must not require the existence of any files in
9785 <file>/usr/share/doc/</file> in order to function
9787 The system administrator should be able to
9788 delete files in <file>/usr/share/doc/</file> without causing
9789 any programs to break.
9791 Any files that are referenced by programs but are also
9792 useful as stand alone documentation should be installed under
9793 <file>/usr/share/<var>package</var>/</file> with symbolic links from
9794 <file>/usr/share/doc/<var>package</var></file>.
9798 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9799 link to another directory in <file>/usr/share/doc</file> only if
9800 the two packages both come from the same source and the
9801 first package Depends on the second.<footnote>
9803 Please note that this does not override the section on
9804 changelog files below, so the file
9805 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
9806 must refer to the changelog for the current version of
9807 <var>package</var> in question. In practice, this means
9808 that the sources of the target and the destination of the
9809 symlink must be the same (same source package and
9816 Former Debian releases placed all additional documentation
9817 in <file>/usr/doc/<var>package</var></file>. This has been
9818 changed to <file>/usr/share/doc/<var>package</var></file>,
9819 and packages must not put documentation in the directory
9820 <file>/usr/doc/<var>package</var></file>. <footnote>
9821 At this phase of the transition, we no longer require a
9822 symbolic link in <file>/usr/doc/</file>. At a later point,
9823 policy shall change to make the symbolic links a bug.
9829 <heading>Preferred documentation formats</heading>
9832 The unification of Debian documentation is being carried out
9836 If your package comes with extensive documentation in a
9837 markup format that can be converted to various other formats
9838 you should if possible ship HTML versions in a binary
9839 package, in the directory
9840 <file>/usr/share/doc/<var>appropriate-package</var></file> or
9841 its subdirectories.<footnote>
9842 The rationale: The important thing here is that HTML
9843 docs should be available in <em>some</em> package, not
9844 necessarily in the main binary package.
9849 Other formats such as PostScript may be provided at the
9850 package maintainer's discretion.
9854 <sect id="copyrightfile">
9855 <heading>Copyright information</heading>
9858 Every package must be accompanied by a verbatim copy of its
9859 copyright information and distribution license in the file
9860 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
9861 file must neither be compressed nor be a symbolic link.
9865 In addition, the copyright file must say where the upstream
9866 sources (if any) were obtained, and should name the original
9871 Packages in the <em>contrib</em> or <em>non-free</em> archive
9872 areas should state in the copyright file that the package is not
9873 part of the Debian distribution and briefly explain why.
9877 A copy of the file which will be installed in
9878 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9879 be in <file>debian/copyright</file> in the source package.
9883 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9884 link to another directory in <file>/usr/share/doc</file> only if
9885 the two packages both come from the same source and the
9886 first package Depends on the second. These rules are important
9887 because <file>copyright</file> files must be extractable by
9892 Packages distributed under the Apache license (version 2.0), the
9893 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
9894 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
9895 1.3) should refer to the corresponding files
9896 under <file>/usr/share/common-licenses</file>,<footnote>
9899 <file>/usr/share/common-licenses/Apache-2.0</file>,
9900 <file>/usr/share/common-licenses/Artistic</file>,
9901 <file>/usr/share/common-licenses/GPL-1</file>,
9902 <file>/usr/share/common-licenses/GPL-2</file>,
9903 <file>/usr/share/common-licenses/GPL-3</file>,
9904 <file>/usr/share/common-licenses/LGPL-2</file>,
9905 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9906 <file>/usr/share/common-licenses/LGPL-3</file>,
9907 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
9908 <file>/usr/share/common-licenses/GFDL-1.3</file>
9909 respectively. The University of California BSD license is
9910 also included in <package>base-files</package> as
9911 <file>/usr/share/common-licenses/BSD</file>, but given the
9912 brevity of this license, its specificity to code whose
9913 copyright is held by the Regents of the University of
9914 California, and the frequency of minor wording changes, its
9915 text should be included in the copyright file rather than
9916 referencing this file.
9918 </footnote> rather than quoting them in the copyright
9923 You should not use the copyright file as a general <file>README</file>
9924 file. If your package has such a file it should be
9925 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9926 <file>README.Debian</file> or some other appropriate place.
9929 <sect1 id="copyrightformat">
9930 <heading>Machine-readable copyright information</heading>
9933 A specification for a standard, machine-readable format
9934 for <file>debian/copyright</file> files is maintained as part
9935 of the <package>debian-policy</package> package. This
9936 document may be found in the <file>copyright-format</file>
9937 files in the <package>debian-policy</package> package. It is
9938 also available from the Debian web mirrors at
9939 <tt><url name="/doc/packaging-manuals/copyright-format/1.0/"
9940 id="http://www.debian.org/doc/packaging-manuals/copyright-format/1.0/"></tt>.
9944 Use of this format is optional.
9950 <heading>Examples</heading>
9953 Any examples (configurations, source files, whatever),
9954 should be installed in a directory
9955 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9956 files should not be referenced by any program: they're there
9957 for the benefit of the system administrator and users as
9958 documentation only. Architecture-specific example files
9959 should be installed in a directory
9960 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9962 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9963 latter directory itself may be a symbolic link to the
9968 If the purpose of a package is to provide examples, then the
9969 example files may be installed into
9970 <file>/usr/share/doc/<var>package</var></file>.
9974 <sect id="changelogs">
9975 <heading>Changelog files</heading>
9978 Packages that are not Debian-native must contain a
9979 compressed copy of the <file>debian/changelog</file> file from
9980 the Debian source tree in
9981 <file>/usr/share/doc/<var>package</var></file> with the name
9982 <file>changelog.Debian.gz</file>.
9986 If an upstream changelog is available, it should be accessible as
9987 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9988 plain text. If the upstream changelog is distributed in
9989 HTML, it should be made available in that form as
9990 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9991 and a plain text <file>changelog.gz</file> should be generated
9992 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9993 the upstream changelog files do not already conform to this
9994 naming convention, then this may be achieved either by
9995 renaming the files, or by adding a symbolic link, at the
9996 maintainer's discretion.<footnote>
9997 Rationale: People should not have to look in places for
9998 upstream changelogs merely because they are given
9999 different names or are distributed in HTML format.
10004 All of these files should be installed compressed using
10005 <tt>gzip -9</tt>, as they will become large with time even
10006 if they start out small.
10010 If the package has only one changelog which is used both as
10011 the Debian changelog and the upstream one because there is
10012 no separate upstream maintainer then that changelog should
10013 usually be installed as
10014 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
10015 there is a separate upstream maintainer, but no upstream
10016 changelog, then the Debian changelog should still be called
10017 <file>changelog.Debian.gz</file>.
10021 For details about the format and contents of the Debian
10022 changelog file, please see <ref id="dpkgchangelog">.
10027 <appendix id="pkg-scope">
10028 <heading>Introduction and scope of these appendices</heading>
10031 These appendices are taken essentially verbatim from the
10032 now-deprecated Packaging Manual, version 3.2.1.0. They are
10033 the chapters which are likely to be of use to package
10034 maintainers and which have not already been included in the
10035 policy document itself. Most of these sections are very likely
10036 not relevant to policy; they should be treated as
10037 documentation for the packaging system. Please note that these
10038 appendices are included for convenience, and for historical
10039 reasons: they used to be part of policy package, and they have
10040 not yet been incorporated into dpkg documentation. However,
10041 they still have value, and hence they are presented here.
10045 They have not yet been checked to ensure that they are
10046 compatible with the contents of policy, and if there are any
10047 contradictions, the version in the main policy document takes
10048 precedence. The remaining chapters of the old Packaging
10049 Manual have also not been read in detail to ensure that there
10050 are not parts which have been left out. Both of these will be
10051 done in due course.
10055 Certain parts of the Packaging manual were integrated into the
10056 Policy Manual proper, and removed from the appendices. Links
10057 have been placed from the old locations to the new ones.
10061 <prgn>dpkg</prgn> is a suite of programs for creating binary
10062 package files and installing and removing them on Unix
10064 <prgn>dpkg</prgn> is targeted primarily at Debian, but may
10065 work on or be ported to other systems.
10070 The binary packages are designed for the management of
10071 installed executable programs (usually compiled binaries) and
10072 their associated data, though source code examples and
10073 documentation are provided as part of some packages.</p>
10076 This manual describes the technical aspects of creating Debian
10077 binary packages (<file>.deb</file> files). It documents the
10078 behavior of the package management programs
10079 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
10080 they interact with packages.</p>
10083 It also documents the interaction between
10084 <prgn>dselect</prgn>'s core and the access method scripts it
10085 uses to actually install the selected packages, and describes
10086 how to create a new access method.</p>
10089 This manual does not go into detail about the options and
10090 usage of the package building and installation tools. It
10091 should therefore be read in conjunction with those programs'
10096 The utility programs which are provided with <prgn>dpkg</prgn>
10097 for managing various system configuration and similar issues,
10098 such as <prgn>update-rc.d</prgn> and
10099 <prgn>install-info</prgn>, are not described in detail here -
10100 please see their man pages.
10104 It is assumed that the reader is reasonably familiar with the
10105 <prgn>dpkg</prgn> System Administrators' manual.
10106 Unfortunately this manual does not yet exist.
10110 The Debian version of the FSF's GNU hello program is provided as
10111 an example for people wishing to create Debian packages. However,
10112 while the examples are helpful, they do not replace the need to
10113 read and follow the Policy and Programmer's Manual.</p>
10116 <appendix id="pkg-binarypkg">
10117 <heading>Binary packages (from old Packaging Manual)</heading>
10120 The binary package has two main sections. The first part
10121 consists of various control information files and scripts used
10122 by <prgn>dpkg</prgn> when installing and removing. See <ref
10123 id="pkg-controlarea">.
10127 The second part is an archive containing the files and
10128 directories to be installed.
10132 In the future binary packages may also contain other
10133 components, such as checksums and digital signatures. The
10134 format for the archive is described in full in the
10135 <file>deb(5)</file> man page.
10139 <sect id="pkg-bincreating"><heading>Creating package files -
10140 <prgn>dpkg-deb</prgn>
10144 All manipulation of binary package files is done by
10145 <prgn>dpkg-deb</prgn>; it's the only program that has
10146 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
10147 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
10148 will spot that the options requested are appropriate to
10149 <prgn>dpkg-deb</prgn> and invoke that instead with the same
10154 In order to create a binary package you must make a
10155 directory tree which contains all the files and directories
10156 you want to have in the file system data part of the package.
10157 In Debian-format source packages this directory is usually
10158 <file>debian/tmp</file>, relative to the top of the package's
10163 They should have the locations (relative to the root of the
10164 directory tree you're constructing) ownerships and
10165 permissions which you want them to have on the system when
10166 they are installed.
10170 With current versions of <prgn>dpkg</prgn> the uid/username
10171 and gid/groupname mappings for the users and groups being
10172 used should be the same on the system where the package is
10173 built and the one where it is installed.
10177 You need to add one special directory to the root of the
10178 miniature file system tree you're creating:
10179 <prgn>DEBIAN</prgn>. It should contain the control
10180 information files, notably the binary package control file
10181 (see <ref id="pkg-controlfile">).
10185 The <prgn>DEBIAN</prgn> directory will not appear in the
10186 file system archive of the package, and so won't be installed
10187 by <prgn>dpkg</prgn> when the package is unpacked.
10191 When you've prepared the package, you should invoke:
10193 dpkg --build <var>directory</var>
10198 This will build the package in
10199 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
10200 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
10201 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
10202 build the package.)
10206 See the man page <manref name="dpkg-deb" section="8"> for details of how
10207 to examine the contents of this newly-created file. You may find the
10208 output of following commands enlightening:
10210 dpkg-deb --info <var>filename</var>.deb
10211 dpkg-deb --contents <var>filename</var>.deb
10212 dpkg --contents <var>filename</var>.deb
10214 To view the copyright file for a package you could use this command:
10216 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
10221 <sect id="pkg-controlarea">
10222 <heading>Package control information files</heading>
10225 The control information portion of a binary package is a
10226 collection of files with names known to <prgn>dpkg</prgn>.
10227 It will treat the contents of these files specially - some
10228 of them contain information used by <prgn>dpkg</prgn> when
10229 installing or removing the package; others are scripts which
10230 the package maintainer wants <prgn>dpkg</prgn> to run.
10234 It is possible to put other files in the package control
10235 information file area, but this is not generally a good idea
10236 (though they will largely be ignored).
10240 Here is a brief list of the control information files supported
10241 by <prgn>dpkg</prgn> and a summary of what they're used for.
10246 <tag><tt>control</tt>
10249 This is the key description file used by
10250 <prgn>dpkg</prgn>. It specifies the package's name
10251 and version, gives its description for the user,
10252 states its relationships with other packages, and so
10253 forth. See <ref id="sourcecontrolfiles"> and
10254 <ref id="binarycontrolfiles">.
10258 It is usually generated automatically from information
10259 in the source package by the
10260 <prgn>dpkg-gencontrol</prgn> program, and with
10261 assistance from <prgn>dpkg-shlibdeps</prgn>.
10262 See <ref id="pkg-sourcetools">.
10266 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
10271 These are executable files (usually scripts) which
10272 <prgn>dpkg</prgn> runs during installation, upgrade
10273 and removal of packages. They allow the package to
10274 deal with matters which are particular to that package
10275 or require more complicated processing than that
10276 provided by <prgn>dpkg</prgn>. Details of when and
10277 how they are called are in <ref id="maintainerscripts">.
10281 It is very important to make these scripts idempotent.
10282 See <ref id="idempotency">.
10286 The maintainer scripts are not guaranteed to run with a
10287 controlling terminal and may not be able to interact with
10288 the user. See <ref id="controllingterminal">.
10292 <tag><tt>conffiles</tt>
10295 This file contains a list of configuration files which
10296 are to be handled automatically by <prgn>dpkg</prgn>
10297 (see <ref id="pkg-conffiles">). Note that not necessarily
10298 every configuration file should be listed here.
10301 <tag><tt>shlibs</tt>
10304 This file contains a list of the shared libraries
10305 supplied by the package, with dependency details for
10306 each. This is used by <prgn>dpkg-shlibdeps</prgn>
10307 when it determines what dependencies are required in a
10308 package control file. The <tt>shlibs</tt> file format
10309 is described on <ref id="shlibs">.
10314 <sect id="pkg-controlfile">
10315 <heading>The main control information file: <tt>control</tt></heading>
10318 The most important control information file used by
10319 <prgn>dpkg</prgn> when it installs a package is
10320 <tt>control</tt>. It contains all the package's "vital
10325 The binary package control files of packages built from
10326 Debian sources are made by a special tool,
10327 <prgn>dpkg-gencontrol</prgn>, which reads
10328 <file>debian/control</file> and <file>debian/changelog</file> to
10329 find the information it needs. See <ref id="pkg-sourcepkg"> for
10334 The fields in binary package control files are listed in
10335 <ref id="binarycontrolfiles">.
10339 A description of the syntax of control files and the purpose
10340 of the fields is available in <ref id="controlfields">.
10345 <heading>Time Stamps</heading>
10348 See <ref id="timestamps">.
10353 <appendix id="pkg-sourcepkg">
10354 <heading>Source packages (from old Packaging Manual) </heading>
10357 The Debian binary packages in the distribution are generated
10358 from Debian sources, which are in a special format to assist
10359 the easy and automatic building of binaries.
10362 <sect id="pkg-sourcetools">
10363 <heading>Tools for processing source packages</heading>
10366 Various tools are provided for manipulating source packages;
10367 they pack and unpack sources and help build of binary
10368 packages and help manage the distribution of new versions.
10372 They are introduced and typical uses described here; see
10373 <manref name="dpkg-source" section="1"> for full
10374 documentation about their arguments and operation.
10378 For examples of how to construct a Debian source package,
10379 and how to use those utilities that are used by Debian
10380 source packages, please see the <prgn>hello</prgn> example
10384 <sect1 id="pkg-dpkg-source">
10386 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
10391 This program is frequently used by hand, and is also
10392 called from package-independent automated building scripts
10393 such as <prgn>dpkg-buildpackage</prgn>.
10397 To unpack a package it is typically invoked with
10399 dpkg-source -x <var>.../path/to/filename</var>.dsc
10404 with the <file><var>filename</var>.tar.gz</file> and
10405 <file><var>filename</var>.diff.gz</file> (if applicable) in
10406 the same directory. It unpacks into
10407 <file><var>package</var>-<var>version</var></file>, and if
10409 <file><var>package</var>-<var>version</var>.orig</file>, in
10410 the current directory.
10414 To create a packed source archive it is typically invoked:
10416 dpkg-source -b <var>package</var>-<var>version</var>
10421 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
10422 <file>.diff.gz</file> (if appropriate) in the current
10423 directory. <prgn>dpkg-source</prgn> does not clean the
10424 source tree first - this must be done separately if it is
10429 See also <ref id="pkg-sourcearchives">.</p>
10433 <sect1 id="pkg-dpkg-buildpackage">
10435 <prgn>dpkg-buildpackage</prgn> - overall package-building
10440 <prgn>dpkg-buildpackage</prgn> is a script which invokes
10441 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
10442 targets <tt>clean</tt>, <tt>build</tt> and
10443 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
10444 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
10445 source and binary package upload.
10449 It is usually invoked by hand from the top level of the
10450 built or unbuilt source directory. It may be invoked with
10451 no arguments; useful arguments include:
10452 <taglist compact="compact">
10453 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
10456 Do not sign the <tt>.changes</tt> file or the
10457 source package <tt>.dsc</tt> file, respectively.</p>
10459 <tag><tt>-p<var>sign-command</var></tt></tag>
10462 Invoke <var>sign-command</var> instead of finding
10463 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
10464 <var>sign-command</var> must behave just like
10465 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
10467 <tag><tt>-r<var>root-command</var></tt></tag>
10470 When root privilege is required, invoke the command
10471 <var>root-command</var>. <var>root-command</var>
10472 should invoke its first argument as a command, from
10473 the <prgn>PATH</prgn> if necessary, and pass its
10474 second and subsequent arguments to the command it
10475 calls. If no <var>root-command</var> is supplied
10476 then <var>dpkg-buildpackage</var> will take no
10477 special action to gain root privilege, so that for
10478 most packages it will have to be invoked as root to
10481 <tag><tt>-b</tt>, <tt>-B</tt></tag>
10484 Two types of binary-only build and upload - see
10485 <manref name="dpkg-source" section="1">.
10492 <sect1 id="pkg-dpkg-gencontrol">
10494 <prgn>dpkg-gencontrol</prgn> - generates binary package
10499 This program is usually called from <file>debian/rules</file>
10500 (see <ref id="pkg-sourcetree">) in the top level of the source
10505 This is usually done just before the files and directories in the
10506 temporary directory tree where the package is being built have their
10507 permissions and ownerships set and the package is constructed using
10508 <prgn>dpkg-deb/</prgn>
10510 This is so that the control file which is produced has
10511 the right permissions
10516 <prgn>dpkg-gencontrol</prgn> must be called after all the
10517 files which are to go into the package have been placed in
10518 the temporary build directory, so that its calculation of
10519 the installed size of a package is correct.
10523 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
10524 be run after <prgn>dpkg-shlibdeps</prgn> so that the
10525 variable substitutions created by
10526 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
10531 For a package which generates only one binary package, and
10532 which builds it in <file>debian/tmp</file> relative to the top
10533 of the source package, it is usually sufficient to call
10534 <prgn>dpkg-gencontrol</prgn>.
10538 Sources which build several binaries will typically need
10541 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
10542 </example> The <tt>-P</tt> tells
10543 <prgn>dpkg-gencontrol</prgn> that the package is being
10544 built in a non-default directory, and the <tt>-p</tt>
10545 tells it which package's control file should be generated.
10549 <prgn>dpkg-gencontrol</prgn> also adds information to the
10550 list of files in <file>debian/files</file>, for the benefit of
10551 (for example) a future invocation of
10552 <prgn>dpkg-genchanges</prgn>.</p>
10555 <sect1 id="pkg-dpkg-shlibdeps">
10557 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
10562 This program is usually called from <file>debian/rules</file>
10563 just before <prgn>dpkg-gencontrol</prgn> (see <ref
10564 id="pkg-sourcetree">), in the top level of the source tree.
10568 Its arguments are executables and shared libraries
10571 They may be specified either in the locations in the
10572 source tree where they are created or in the locations
10573 in the temporary build tree where they are installed
10574 prior to binary package creation.
10576 </footnote> for which shared library dependencies should
10577 be included in the binary package's control file.
10581 If some of the found shared libraries should only
10582 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
10583 some warrant a <tt>Pre-Depends</tt>, this can be achieved
10584 by using the <tt>-d<var>dependency-field</var></tt> option
10585 before those executable(s). (Each <tt>-d</tt> option
10586 takes effect until the next <tt>-d</tt>.)
10590 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
10591 output control file to be modified. Instead by default it
10592 adds to the <file>debian/substvars</file> file variable
10593 settings like <tt>shlibs:Depends</tt>. These variable
10594 settings must be referenced in dependency fields in the
10595 appropriate per-binary-package sections of the source
10600 For example, a package that generates an essential part
10601 which requires dependencies, and optional parts that
10602 which only require a recommendation, would separate those
10603 two sets of dependencies into two different fields.<footnote>
10604 At the time of writing, an example for this was the
10605 <package/xmms/ package, with Depends used for the xmms
10606 executable, Recommends for the plug-ins and Suggests for
10607 even more optional features provided by unzip.
10609 It can say in its <file>debian/rules</file>:
10611 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
10612 -dRecommends <var>optionalpart anotheroptionalpart</var>
10614 and then in its main control file <file>debian/control</file>:
10617 Depends: ${shlibs:Depends}
10618 Recommends: ${shlibs:Recommends}
10624 Sources which produce several binary packages with
10625 different shared library dependency requirements can use
10626 the <tt>-p<var>varnameprefix</var></tt> option to override
10627 the default <tt>shlibs:</tt> prefix (one invocation of
10628 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
10629 They can thus produce several sets of dependency
10630 variables, each of the form
10631 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
10632 which can be referred to in the appropriate parts of the
10633 binary package control files.
10638 <sect1 id="pkg-dpkg-distaddfile">
10640 <prgn>dpkg-distaddfile</prgn> - adds a file to
10641 <file>debian/files</file>
10645 Some packages' uploads need to include files other than
10646 the source and binary package files.
10650 <prgn>dpkg-distaddfile</prgn> adds a file to the
10651 <file>debian/files</file> file so that it will be included in
10652 the <file>.changes</file> file when
10653 <prgn>dpkg-genchanges</prgn> is run.
10657 It is usually invoked from the <tt>binary</tt> target of
10658 <file>debian/rules</file>:
10660 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
10662 The <var>filename</var> is relative to the directory where
10663 <prgn>dpkg-genchanges</prgn> will expect to find it - this
10664 is usually the directory above the top level of the source
10665 tree. The <file>debian/rules</file> target should put the
10666 file there just before or just after calling
10667 <prgn>dpkg-distaddfile</prgn>.
10671 The <var>section</var> and <var>priority</var> are passed
10672 unchanged into the resulting <file>.changes</file> file.
10677 <sect1 id="pkg-dpkg-genchanges">
10679 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
10680 upload control file
10684 This program is usually called by package-independent
10685 automatic building scripts such as
10686 <prgn>dpkg-buildpackage</prgn>, but it may also be called
10691 It is usually called in the top level of a built source
10692 tree, and when invoked with no arguments will print out a
10693 straightforward <file>.changes</file> file based on the
10694 information in the source package's changelog and control
10695 file and the binary and source packages which should have
10701 <sect1 id="pkg-dpkg-parsechangelog">
10703 <prgn>dpkg-parsechangelog</prgn> - produces parsed
10704 representation of a changelog
10708 This program is used internally by
10709 <prgn>dpkg-source</prgn> et al. It may also occasionally
10710 be useful in <file>debian/rules</file> and elsewhere. It
10711 parses a changelog, <file>debian/changelog</file> by default,
10712 and prints a control-file format representation of the
10713 information in it to standard output.
10717 <sect1 id="pkg-dpkg-architecture">
10719 <prgn>dpkg-architecture</prgn> - information about the build and
10724 This program can be used manually, but is also invoked by
10725 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
10726 environment or make variables which specify the build and host
10727 architecture for the package building process.
10732 <sect id="pkg-sourcetree">
10733 <heading>The Debian package source tree</heading>
10736 The source archive scheme described later is intended to
10737 allow a Debian package source tree with some associated
10738 control information to be reproduced and transported easily.
10739 The Debian package source tree is a version of the original
10740 program with certain files added for the benefit of the
10741 packaging process, and with any other changes required
10742 made to the rest of the source code and installation
10747 The extra files created for Debian are in the subdirectory
10748 <file>debian</file> of the top level of the Debian package
10749 source tree. They are described below.
10752 <sect1 id="pkg-debianrules">
10753 <heading><file>debian/rules</file> - the main building script</heading>
10756 See <ref id="debianrules">.
10760 <sect1 id="pkg-srcsubstvars">
10761 <heading><file>debian/substvars</file> and variable substitutions</heading>
10764 See <ref id="substvars">.
10770 <heading><file>debian/files</file></heading>
10773 See <ref id="debianfiles">.
10777 <sect1><heading><file>debian/tmp</file>
10781 This is the canonical temporary location for the
10782 construction of binary packages by the <tt>binary</tt>
10783 target. The directory <file>tmp</file> serves as the root of
10784 the file system tree as it is being constructed (for
10785 example, by using the package's upstream makefiles install
10786 targets and redirecting the output there), and it also
10787 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10788 id="pkg-bincreating">.
10792 If several binary packages are generated from the same
10793 source tree it is usual to use several
10794 <file>debian/tmp<var>something</var></file> directories, for
10795 example <file>tmp-a</file> or <file>tmp-doc</file>.
10799 Whatever <file>tmp</file> directories are created and used by
10800 <tt>binary</tt> must of course be removed by the
10801 <tt>clean</tt> target.</p></sect1>
10805 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10809 As it exists on the FTP site, a Debian source package
10810 consists of three related files. You must have the right
10811 versions of all three to be able to use them.
10816 <tag>Debian source control file - <tt>.dsc</tt></tag>
10818 This file is a control file used by <prgn>dpkg-source</prgn>
10819 to extract a source package.
10820 See <ref id="debiansourcecontrolfiles">.
10824 Original source archive -
10826 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10832 This is a compressed (with <tt>gzip -9</tt>)
10833 <prgn>tar</prgn> file containing the source code from
10834 the upstream authors of the program.
10839 Debian package diff -
10841 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10847 This is a unified context diff (<tt>diff -u</tt>)
10848 giving the changes which are required to turn the
10849 original source into the Debian source. These changes
10850 may only include editing and creating plain files.
10851 The permissions of files, the targets of symbolic
10852 links and the characteristics of special files or
10853 pipes may not be changed and no files may be removed
10858 All the directories in the diff must exist, except the
10859 <file>debian</file> subdirectory of the top of the source
10860 tree, which will be created by
10861 <prgn>dpkg-source</prgn> if necessary when unpacking.
10865 The <prgn>dpkg-source</prgn> program will
10866 automatically make the <file>debian/rules</file> file
10867 executable (see below).</p></item>
10872 If there is no original source code - for example, if the
10873 package is specially prepared for Debian or the Debian
10874 maintainer is the same as the upstream maintainer - the
10875 format is slightly different: then there is no diff, and the
10877 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10878 and preferably contains a directory named
10879 <file><var>package</var>-<var>version</var></file>.
10884 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10887 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10888 Debian source package. However, if it is not available it
10889 is possible to unpack a Debian source archive as follows:
10890 <enumlist compact="compact">
10893 Untar the tarfile, which will create a <file>.orig</file>
10897 <p>Rename the <file>.orig</file> directory to
10898 <file><var>package</var>-<var>version</var></file>.</p>
10902 Create the subdirectory <file>debian</file> at the top of
10903 the source tree.</p>
10905 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10907 <item><p>Untar the tarfile again if you want a copy of the original
10908 source code alongside the Debian version.</p>
10913 It is not possible to generate a valid Debian source archive
10914 without using <prgn>dpkg-source</prgn>. In particular,
10915 attempting to use <prgn>diff</prgn> directly to generate the
10916 <file>.diff.gz</file> file will not work.
10920 <heading>Restrictions on objects in source packages</heading>
10923 The source package may not contain any hard links
10925 This is not currently detected when building source
10926 packages, but only when extracting
10930 Hard links may be permitted at some point in the
10931 future, but would require a fair amount of
10933 </footnote>, device special files, sockets or setuid or
10936 Setgid directories are allowed.
10941 The source packaging tools manage the changes between the
10942 original and Debian source using <prgn>diff</prgn> and
10943 <prgn>patch</prgn>. Turning the original source tree as
10944 included in the <file>.orig.tar.gz</file> into the Debian
10945 package source must not involve any changes which cannot be
10946 handled by these tools. Problematic changes which cause
10947 <prgn>dpkg-source</prgn> to halt with an error when
10948 building the source package are:
10949 <list compact="compact">
10950 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10952 <item><p>Changing the targets of symbolic links.</p>
10954 <item><p>Creating directories, other than <file>debian</file>.</p>
10956 <item><p>Changes to the contents of binary files.</p></item>
10957 </list> Changes which cause <prgn>dpkg-source</prgn> to
10958 print a warning but continue anyway are:
10959 <list compact="compact">
10962 Removing files, directories or symlinks.
10964 Renaming a file is not treated specially - it is
10965 seen as the removal of the old file (which
10966 generates a warning, but is otherwise ignored),
10967 and the creation of the new one.
10973 Changed text files which are missing the usual final
10974 newline (either in the original or the modified
10979 Changes which are not represented, but which are not detected by
10980 <prgn>dpkg-source</prgn>, are:
10981 <list compact="compact">
10982 <item><p>Changing the permissions of files (other than
10983 <file>debian/rules</file>) and directories.</p></item>
10988 The <file>debian</file> directory and <file>debian/rules</file>
10989 are handled specially by <prgn>dpkg-source</prgn> - before
10990 applying the changes it will create the <file>debian</file>
10991 directory, and afterwards it will make
10992 <file>debian/rules</file> world-executable.
10998 <appendix id="pkg-controlfields">
10999 <heading>Control files and their fields (from old Packaging Manual)</heading>
11002 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
11003 data in a common format, known as control files. Binary and
11004 source packages have control data as do the <file>.changes</file>
11005 files which control the installation of uploaded files, and
11006 <prgn>dpkg</prgn>'s internal databases are in a similar
11011 <heading>Syntax of control files</heading>
11014 See <ref id="controlsyntax">.
11018 It is important to note that there are several fields which
11019 are optional as far as <prgn>dpkg</prgn> and the related
11020 tools are concerned, but which must appear in every Debian
11021 package, or whose omission may cause problems.
11026 <heading>List of fields</heading>
11029 See <ref id="controlfieldslist">.
11033 This section now contains only the fields that didn't belong
11034 to the Policy manual.
11037 <sect1 id="pkg-f-Filename">
11038 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
11041 These fields in <tt>Packages</tt> files give the
11042 filename(s) of (the parts of) a package in the
11043 distribution directories, relative to the root of the
11044 Debian hierarchy. If the package has been split into
11045 several parts the parts are all listed in order, separated
11050 <sect1 id="pkg-f-Size">
11051 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
11054 These fields in <file>Packages</file> files give the size (in
11055 bytes, expressed in decimal) and MD5 checksum of the
11056 file(s) which make(s) up a binary package in the
11057 distribution. If the package is split into several parts
11058 the values for the parts are listed in order, separated by
11063 <sect1 id="pkg-f-Status">
11064 <heading><tt>Status</tt></heading>
11067 This field in <prgn>dpkg</prgn>'s status file records
11068 whether the user wants a package installed, removed or
11069 left alone, whether it is broken (requiring
11070 re-installation) or not and what its current state on the
11071 system is. Each of these pieces of information is a
11076 <sect1 id="pkg-f-Config-Version">
11077 <heading><tt>Config-Version</tt></heading>
11080 If a package is not installed or not configured, this
11081 field in <prgn>dpkg</prgn>'s status file records the last
11082 version of the package which was successfully
11087 <sect1 id="pkg-f-Conffiles">
11088 <heading><tt>Conffiles</tt></heading>
11091 This field in <prgn>dpkg</prgn>'s status file contains
11092 information about the automatically-managed configuration
11093 files held by a package. This field should <em>not</em>
11094 appear anywhere in a package!
11099 <heading>Obsolete fields</heading>
11102 These are still recognized by <prgn>dpkg</prgn> but should
11103 not appear anywhere any more.
11105 <taglist compact="compact">
11107 <tag><tt>Revision</tt></tag>
11108 <tag><tt>Package-Revision</tt></tag>
11109 <tag><tt>Package_Revision</tt></tag>
11111 The Debian revision part of the package version was
11112 at one point in a separate control field. This
11113 field went through several names.
11116 <tag><tt>Recommended</tt></tag>
11117 <item>Old name for <tt>Recommends</tt>.</item>
11119 <tag><tt>Optional</tt></tag>
11120 <item>Old name for <tt>Suggests</tt>.</item>
11122 <tag><tt>Class</tt></tag>
11123 <item>Old name for <tt>Priority</tt>.</item>
11132 <appendix id="pkg-conffiles">
11133 <heading>Configuration file handling (from old Packaging Manual)</heading>
11136 <prgn>dpkg</prgn> can do a certain amount of automatic
11137 handling of package configuration files.
11141 Whether this mechanism is appropriate depends on a number of
11142 factors, but basically there are two approaches to any
11143 particular configuration file.
11147 The easy method is to ship a best-effort configuration in the
11148 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
11149 handle updates. If the user is unlikely to want to edit the
11150 file, but you need them to be able to without losing their
11151 changes, and a new package with a changed version of the file
11152 is only released infrequently, this is a good approach.
11156 The hard method is to build the configuration file from
11157 scratch in the <prgn>postinst</prgn> script, and to take the
11158 responsibility for fixing any mistakes made in earlier
11159 versions of the package automatically. This will be
11160 appropriate if the file is likely to need to be different on
11164 <sect><heading>Automatic handling of configuration files by
11169 A package may contain a control information file called
11170 <tt>conffiles</tt>. This file should be a list of filenames
11171 of configuration files needing automatic handling, separated
11172 by newlines. The filenames should be absolute pathnames,
11173 and the files referred to should actually exist in the
11178 When a package is upgraded <prgn>dpkg</prgn> will process
11179 the configuration files during the configuration stage,
11180 shortly before it runs the package's <prgn>postinst</prgn>
11185 For each file it checks to see whether the version of the
11186 file included in the package is the same as the one that was
11187 included in the last version of the package (the one that is
11188 being upgraded from); it also compares the version currently
11189 installed on the system with the one shipped with the last
11194 If neither the user nor the package maintainer has changed
11195 the file, it is left alone. If one or the other has changed
11196 their version, then the changed version is preferred - i.e.,
11197 if the user edits their file, but the package maintainer
11198 doesn't ship a different version, the user's changes will
11199 stay, silently, but if the maintainer ships a new version
11200 and the user hasn't edited it the new version will be
11201 installed (with an informative message). If both have
11202 changed their version the user is prompted about the problem
11203 and must resolve the differences themselves.
11207 The comparisons are done by calculating the MD5 message
11208 digests of the files, and storing the MD5 of the file as it
11209 was included in the most recent version of the package.
11213 When a package is installed for the first time
11214 <prgn>dpkg</prgn> will install the file that comes with it,
11215 unless that would mean overwriting a file already on the
11220 However, note that <prgn>dpkg</prgn> will <em>not</em>
11221 replace a conffile that was removed by the user (or by a
11222 script). This is necessary because with some programs a
11223 missing file produces an effect hard or impossible to
11224 achieve in another way, so that a missing file needs to be
11225 kept that way if the user did it.
11229 Note that a package should <em>not</em> modify a
11230 <prgn>dpkg</prgn>-handled conffile in its maintainer
11231 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
11232 the user confusing and possibly dangerous options for
11233 conffile update when the package is upgraded.</p>
11236 <sect><heading>Fully-featured maintainer script configuration
11241 For files which contain site-specific information such as
11242 the hostname and networking details and so forth, it is
11243 better to create the file in the package's
11244 <prgn>postinst</prgn> script.
11248 This will typically involve examining the state of the rest
11249 of the system to determine values and other information, and
11250 may involve prompting the user for some information which
11251 can't be obtained some other way.
11255 When using this method there are a couple of important
11256 issues which should be considered:
11260 If you discover a bug in the program which generates the
11261 configuration file, or if the format of the file changes
11262 from one version to the next, you will have to arrange for
11263 the postinst script to do something sensible - usually this
11264 will mean editing the installed configuration file to remove
11265 the problem or change the syntax. You will have to do this
11266 very carefully, since the user may have changed the file,
11267 perhaps to fix the very problem that your script is trying
11268 to deal with - you will have to detect these situations and
11269 deal with them correctly.
11273 If you do go down this route it's probably a good idea to
11274 make the program that generates the configuration file(s) a
11275 separate program in <file>/usr/sbin</file>, by convention called
11276 <file><var>package</var>config</file> and then run that if
11277 appropriate from the post-installation script. The
11278 <tt><var>package</var>config</tt> program should not
11279 unquestioningly overwrite an existing configuration - if its
11280 mode of operation is geared towards setting up a package for
11281 the first time (rather than any arbitrary reconfiguration
11282 later) you should have it check whether the configuration
11283 already exists, and require a <tt>--force</tt> flag to
11284 overwrite it.</p></sect>
11287 <appendix id="pkg-alternatives"><heading>Alternative versions of
11288 an interface - <prgn>update-alternatives</prgn> (from old
11293 When several packages all provide different versions of the
11294 same program or file it is useful to have the system select a
11295 default, but to allow the system administrator to change it
11296 and have their decisions respected.
11300 For example, there are several versions of the <prgn>vi</prgn>
11301 editor, and there is no reason to prevent all of them from
11302 being installed at once, each under their own name
11303 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
11304 Nevertheless it is desirable to have the name <tt>vi</tt>
11305 refer to something, at least by default.
11309 If all the packages involved cooperate, this can be done with
11310 <prgn>update-alternatives</prgn>.
11314 Each package provides its own version under its own name, and
11315 calls <prgn>update-alternatives</prgn> in its postinst to
11316 register its version (and again in its prerm to deregister
11321 See the man page <manref name="update-alternatives"
11322 section="8"> for details.
11326 If <prgn>update-alternatives</prgn> does not seem appropriate
11327 you may wish to consider using diversions instead.</p>
11330 <appendix id="pkg-diversions"><heading>Diversions - overriding a
11331 package's version of a file (from old Packaging Manual)
11335 It is possible to have <prgn>dpkg</prgn> not overwrite a file
11336 when it reinstalls the package it belongs to, and to have it
11337 put the file from the package somewhere else instead.
11341 This can be used locally to override a package's version of a
11342 file, or by one package to override another's version (or
11343 provide a wrapper for it).
11347 Before deciding to use a diversion, read <ref
11348 id="pkg-alternatives"> to see if you really want a diversion
11349 rather than several alternative versions of a program.
11353 There is a diversion list, which is read by <prgn>dpkg</prgn>,
11354 and updated by a special program <prgn>dpkg-divert</prgn>.
11355 Please see <manref name="dpkg-divert" section="8"> for full
11356 details of its operation.
11360 When a package wishes to divert a file from another, it should
11361 call <prgn>dpkg-divert</prgn> in its preinst to add the
11362 diversion and rename the existing file. For example,
11363 supposing that a <prgn>smailwrapper</prgn> package wishes to
11364 install a wrapper around <file>/usr/sbin/smail</file>:
11366 dpkg-divert --package smailwrapper --add --rename \
11367 --divert /usr/sbin/smail.real /usr/sbin/smail
11368 </example> The <tt>--package smailwrapper</tt> ensures that
11369 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
11370 can bypass the diversion and get installed as the true version.
11371 It's safe to add the diversion unconditionally on upgrades since
11372 it will be left unchanged if it already exists, but
11373 <prgn>dpkg-divert</prgn> will display a message. To suppress that
11374 message, make the command conditional on the version from which
11375 the package is being upgraded:
11377 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
11378 dpkg-divert --package smailwrapper --add --rename \
11379 --divert /usr/sbin/smail.real /usr/sbin/smail
11381 </example> where <tt>1.0-2</tt> is the version at which the
11382 diversion was first added to the package. Running the command
11383 during abort-upgrade is pointless but harmless.
11387 The postrm has to do the reverse:
11389 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
11390 dpkg-divert --package smailwrapper --remove --rename \
11391 --divert /usr/sbin/smail.real /usr/sbin/smail
11393 </example> If the diversion was added at a particular version, the
11394 postrm should also handle the failure case of upgrading from an
11395 older version (unless the older version is so old that direct
11396 upgrades are no longer supported):
11398 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
11399 dpkg-divert --package smailwrapper --remove --rename \
11400 --divert /usr/sbin/smail.real /usr/sbin/smail
11402 </example> where <tt>1.0-2</tt> is the version at which the
11403 diversion was first added to the package. The postrm should not
11404 remove the diversion on upgrades both because there's no reason to
11405 remove the diversion only to immediately re-add it and since the
11406 postrm of the old package is run after unpacking so the removal of
11407 the diversion will fail.
11411 Do not attempt to divert a file which is vitally important for
11412 the system's operation - when using <prgn>dpkg-divert</prgn>
11413 there is a time, after it has been diverted but before
11414 <prgn>dpkg</prgn> has installed the new version, when the file
11415 does not exist.</p>
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