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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 GNU/Linux 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 GNU/Linux
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 GNU/Linux 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>Julian Gilbey</item>
223 <item>Branden Robinson</item>
224 <item>Josip Rodin</item>
225 <item>Manoj Srivastava</item>
230 While the authors of this document have tried hard to avoid
231 typos and other errors, these do still occur. If you discover
232 an error in this manual or if you want to give any
233 comments, suggestions, or criticisms please send an email to
234 the Debian Policy List,
235 <email>debian-policy@lists.debian.org</email>, or submit a
236 bug report against the <tt>debian-policy</tt> package.
240 Please do not try to reach the individual authors or maintainers
241 of the Policy Manual regarding changes to the Policy.
246 <heading>Related documents</heading>
249 There are several other documents other than this Policy Manual
250 that are necessary to fully understand some Debian policies and
255 The external "sub-policy" documents are referred to in:
256 <list compact="compact">
257 <item><ref id="fhs"></item>
258 <item><ref id="virtual_pkg"></item>
259 <item><ref id="menus"></item>
260 <item><ref id="mime"></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 <sect id="definitions">
285 <heading>Definitions</heading>
288 The following terms are used in this Policy Manual:
292 The character encoding specified by ANSI X3.4-1986 and its
293 predecessor standards, referred to in MIME as US-ASCII, and
294 corresponding to an encoding in eight bits per character of
295 the first 128 <url id="http://www.unicode.org/"
296 name="Unicode"> characters, with the eighth bit always zero.
300 The transformation format (sometimes called encoding) of
301 <url id="http://www.unicode.org/" name="Unicode"> defined by
302 <url id="http://www.rfc-editor.org/rfc/rfc3629.txt"
303 name="RFC 3629">. UTF-8 has the useful property of having
304 ASCII as a subset, so any text encoded in ASCII is trivially
314 <heading>The Debian Archive</heading>
317 The Debian GNU/Linux system is maintained and distributed as a
318 collection of <em>packages</em>. Since there are so many of
319 them (currently well over 15000), they are split into
320 <em>sections</em> and given <em>priorities</em> to simplify
321 the handling of them.
325 The effort of the Debian project is to build a free operating
326 system, but not every package we want to make accessible is
327 <em>free</em> in our sense (see the Debian Free Software
328 Guidelines, below), or may be imported/exported without
329 restrictions. Thus, the archive is split into areas<footnote>
330 The Debian archive software uses the term "component" internally
331 and in the Release file format to refer to the division of an
332 archive. The Debian Social Contract simply refers to "areas."
333 This document uses terminology similar to the Social Contract.
334 </footnote> based on their licenses and other restrictions.
338 The aims of this are:
340 <list compact="compact">
341 <item>to allow us to make as much software available as we can</item>
342 <item>to allow us to encourage everyone to write free software,
344 <item>to allow us to make it easy for people to produce
345 CD-ROMs of our system without violating any licenses,
346 import/export restrictions, or any other laws.</item>
351 The <em>main</em> archive area forms the <em>Debian GNU/Linux
356 Packages in the other archive areas (<tt>contrib</tt>,
357 <tt>non-free</tt>) are not considered to be part of the Debian
358 distribution, although we support their use and provide
359 infrastructure for them (such as our bug-tracking system and
360 mailing lists). This Debian Policy Manual applies to these
365 <heading>The Debian Free Software Guidelines</heading>
367 The Debian Free Software Guidelines (DFSG) form our
368 definition of "free software". These are:
370 <tag>1. Free Redistribution
373 The license of a Debian component may not restrict any
374 party from selling or giving away the software as a
375 component of an aggregate software distribution
376 containing programs from several different
377 sources. The license may not require a royalty or
378 other fee for such sale.
383 The program must include source code, and must allow
384 distribution in source code as well as compiled form.
386 <tag>3. Derived Works
389 The license must allow modifications and derived
390 works, and must allow them to be distributed under the
391 same terms as the license of the original software.
393 <tag>4. Integrity of The Author's Source Code
396 The license may restrict source-code from being
397 distributed in modified form <em>only</em> if the
398 license allows the distribution of "patch files"
399 with the source code for the purpose of modifying the
400 program at build time. The license must explicitly
401 permit distribution of software built from modified
402 source code. The license may require derived works to
403 carry a different name or version number from the
404 original software. (This is a compromise. The Debian
405 Project encourages all authors to not restrict any
406 files, source or binary, from being modified.)
408 <tag>5. No Discrimination Against Persons or Groups
411 The license must not discriminate against any person
414 <tag>6. No Discrimination Against Fields of Endeavor
417 The license must not restrict anyone from making use
418 of the program in a specific field of endeavor. For
419 example, it may not restrict the program from being
420 used in a business, or from being used for genetic
423 <tag>7. Distribution of License
426 The rights attached to the program must apply to all
427 to whom the program is redistributed without the need
428 for execution of an additional license by those
431 <tag>8. License Must Not Be Specific to Debian
434 The rights attached to the program must not depend on
435 the program's being part of a Debian system. If the
436 program is extracted from Debian and used or
437 distributed without Debian but otherwise within the
438 terms of the program's license, all parties to whom
439 the program is redistributed must have the same
440 rights as those that are granted in conjunction with
443 <tag>9. License Must Not Contaminate Other Software
446 The license must not place restrictions on other
447 software that is distributed along with the licensed
448 software. For example, the license must not insist
449 that all other programs distributed on the same medium
450 must be free software.
452 <tag>10. Example Licenses
455 The "GPL," "BSD," and "Artistic" licenses are examples of
456 licenses that we consider <em>free</em>.
463 <heading>Archive areas</heading>
466 <heading>The main archive area</heading>
469 Every package in <em>main</em> must comply with the DFSG
470 (Debian Free Software Guidelines).
474 In addition, the packages in <em>main</em>
475 <list compact="compact">
477 must not require a package outside of <em>main</em>
478 for compilation or execution (thus, the package must
479 not declare a "Depends", "Recommends", or
480 "Build-Depends" relationship on a non-<em>main</em>
484 must not be so buggy that we refuse to support them,
488 must meet all policy requirements presented in this
497 <heading>The contrib archive area</heading>
500 Every package in <em>contrib</em> must comply with the DFSG.
504 In addition, the packages in <em>contrib</em>
505 <list compact="compact">
507 must not be so buggy that we refuse to support them,
511 must meet all policy requirements presented in this
519 Examples of packages which would be included in
520 <em>contrib</em> are:
521 <list compact="compact">
523 free packages which require <em>contrib</em>,
524 <em>non-free</em> packages or packages which are not
525 in our archive at all for compilation or execution,
529 wrapper packages or other sorts of free accessories for
536 <sect1 id="non-free">
537 <heading>The non-free archive area</heading>
540 Packages must be placed in <em>non-free</em> if they are
541 not compliant with the DFSG or are encumbered by patents
542 or other legal issues that make their distribution
547 In addition, the packages in <em>non-free</em>
548 <list compact="compact">
550 must not be so buggy that we refuse to support them,
554 must meet all policy requirements presented in this
555 manual that it is possible for them to meet.
557 It is possible that there are policy
558 requirements which the package is unable to
559 meet, for example, if the source is
560 unavailable. These situations will need to be
561 handled on a case-by-case basis.
570 <sect id="pkgcopyright">
571 <heading>Copyright considerations</heading>
574 Every package must be accompanied by a verbatim copy of its
575 copyright information and distribution license in the file
576 <file>/usr/share/doc/<var>package</var>/copyright</file>
577 (see <ref id="copyrightfile"> for further details).
581 We reserve the right to restrict files from being included
582 anywhere in our archives if
583 <list compact="compact">
585 their use or distribution would break a law,
588 there is an ethical conflict in their distribution or
592 we would have to sign a license for them, or
595 their distribution would conflict with other project
602 Programs whose authors encourage the user to make
603 donations are fine for the main distribution, provided
604 that the authors do not claim that not donating is
605 immoral, unethical, illegal or something similar; in such
606 a case they must go in <em>non-free</em>.
610 Packages whose copyright permission notices (or patent
611 problems) do not even allow redistribution of binaries
612 only, and where no special permission has been obtained,
613 must not be placed on the Debian FTP site and its mirrors
618 Note that under international copyright law (this applies
619 in the United States, too), <em>no</em> distribution or
620 modification of a work is allowed without an explicit
621 notice saying so. Therefore a program without a copyright
622 notice <em>is</em> copyrighted and you may not do anything
623 to it without risking being sued! Likewise if a program
624 has a copyright notice but no statement saying what is
625 permitted then nothing is permitted.
629 Many authors are unaware of the problems that restrictive
630 copyrights (or lack of copyright notices) can cause for
631 the users of their supposedly-free software. It is often
632 worthwhile contacting such authors diplomatically to ask
633 them to modify their license terms. However, this can be a
634 politically difficult thing to do and you should ask for
635 advice on the <tt>debian-legal</tt> mailing list first, as
640 When in doubt about a copyright, send mail to
641 <email>debian-legal@lists.debian.org</email>. Be prepared
642 to provide us with the copyright statement. Software
643 covered by the GPL, public domain software and BSD-like
644 copyrights are safe; be wary of the phrases "commercial
645 use prohibited" and "distribution restricted".
649 <sect id="subsections">
650 <heading>Sections</heading>
653 The packages in the archive areas <em>main</em>,
654 <em>contrib</em> and <em>non-free</em> are grouped further into
655 <em>sections</em> to simplify handling.
659 The archive area and section for each package should be
660 specified in the package's <tt>Section</tt> control record (see
661 <ref id="f-Section">). However, the maintainer of the Debian
662 archive may override this selection to ensure the consistency of
663 the Debian distribution. The <tt>Section</tt> field should be
665 <list compact="compact">
667 <em>section</em> if the package is in the
668 <em>main</em> archive area,
671 <em>area/section</em> if the package is in
672 the <em>contrib</em> or <em>non-free</em>
679 The Debian archive maintainers provide the authoritative
680 list of sections. At present, they are:
681 <em>admin</em>, <em>cli-mono</em>, <em>comm</em>, <em>database</em>,
682 <em>devel</em>, <em>debug</em>, <em>doc</em>, <em>editors</em>,
683 <em>electronics</em>, <em>embedded</em>, <em>fonts</em>,
684 <em>games</em>, <em>gnome</em>, <em>graphics</em>, <em>gnu-r</em>,
685 <em>gnustep</em>, <em>hamradio</em>, <em>haskell</em>,
686 <em>httpd</em>, <em>interpreters</em>, <em>java</em>, <em>kde</em>,
687 <em>kernel</em>, <em>libs</em>, <em>libdevel</em>, <em>lisp</em>,
688 <em>localization</em>, <em>mail</em>, <em>math</em>, <em>misc</em>,
689 <em>net</em>, <em>news</em>, <em>ocaml</em>, <em>oldlibs</em>,
690 <em>otherosfs</em>, <em>perl</em>, <em>php</em>, <em>python</em>,
691 <em>ruby</em>, <em>science</em>, <em>shells</em>, <em>sound</em>,
692 <em>tex</em>, <em>text</em>, <em>utils</em>, <em>vcs</em>,
693 <em>video</em>, <em>web</em>, <em>x11</em>, <em>xfce</em>,
694 <em>zope</em>. The additional section <em>debian-installer</em>
695 contains special packages used by the installer and is not used
696 for normal Debian packages.
700 For more information about the sections and their definitions,
701 see the <url id="http://packages.debian.org/unstable/"
702 name="list of sections in unstable">.
706 <sect id="priorities">
707 <heading>Priorities</heading>
710 Each package should have a <em>priority</em> value, which is
711 included in the package's <em>control record</em>
712 (see <ref id="f-Priority">).
713 This information is used by the Debian package management tools to
714 separate high-priority packages from less-important packages.
718 The following <em>priority levels</em> are recognized by the
719 Debian package management tools.
721 <tag><tt>required</tt></tag>
723 Packages which are necessary for the proper
724 functioning of the system (usually, this means that
725 dpkg functionality depends on these packages).
726 Removing a <tt>required</tt> package may cause your
727 system to become totally broken and you may not even
728 be able to use <prgn>dpkg</prgn> to put things back,
729 so only do so if you know what you are doing. Systems
730 with only the <tt>required</tt> packages are probably
731 unusable, but they do have enough functionality to
732 allow the sysadmin to boot and install more software.
734 <tag><tt>important</tt></tag>
736 Important programs, including those which one would
737 expect to find on any Unix-like system. If the
738 expectation is that an experienced Unix person who
739 found it missing would say "What on earth is going on,
740 where is <prgn>foo</prgn>?", it must be an
741 <tt>important</tt> package.<footnote>
742 This is an important criterion because we are
743 trying to produce, amongst other things, a free
746 Other packages without which the system will not run
747 well or be usable must also have priority
748 <tt>important</tt>. This does
749 <em>not</em> include Emacs, the X Window System, TeX
750 or any other large applications. The
751 <tt>important</tt> packages are just a bare minimum of
752 commonly-expected and necessary tools.
754 <tag><tt>standard</tt></tag>
756 These packages provide a reasonably small but not too
757 limited character-mode system. This is what will be
758 installed by default if the user doesn't select anything
759 else. It doesn't include many large applications.
761 <tag><tt>optional</tt></tag>
763 (In a sense everything that isn't required is
764 optional, but that's not what is meant here.) This is
765 all the software that you might reasonably want to
766 install if you didn't know what it was and don't have
767 specialized requirements. This is a much larger system
768 and includes the X Window System, a full TeX
769 distribution, and many applications. Note that
770 optional packages should not conflict with each other.
772 <tag><tt>extra</tt></tag>
774 This contains all packages that conflict with others
775 with required, important, standard or optional
776 priorities, or are only likely to be useful if you
777 already know what they are or have specialized
778 requirements (such as packages containing only detached
785 Packages must not depend on packages with lower priority
786 values (excluding build-time dependencies). In order to
787 ensure this, the priorities of one or more packages may need
796 <heading>Binary packages</heading>
799 The Debian GNU/Linux distribution is based on the Debian
800 package management system, called <prgn>dpkg</prgn>. Thus,
801 all packages in the Debian distribution must be provided
802 in the <tt>.deb</tt> file format.
806 A <tt>.deb</tt> package contains two sets of files: a set of files
807 to install on the system when the package is installed, and a set
808 of files that provide additional metadata about the package or
809 which are executed when the package is installed or removed. This
810 second set of files is called <em>control information files</em>.
811 Among those files are the package maintainer scripts
812 and <file>control</file>, the <qref id="binarycontrolfiles">binary
813 package control file</qref> that contains the control fields for
814 the package. Other control information files
815 include <qref id="sharedlibs-shlibdeps">the <file>shlibs</file>
816 file</qref> used to store shared library dependency information
817 and the <file>conffiles</file> file that lists the package's
818 configuration files (described in <ref id="config-files">).
822 There is unfortunately a collision of terminology here between
823 control information files and files in the Debian control file
824 format. Throughout this document, a <em>control file</em> refers
825 to a file in the Debian control file format. These files are
826 documented in <ref id="controlfields">. Only files referred to
827 specifically as <em>control information files</em> are the files
828 included in the control information file member of
829 the <file>.deb</file> file format used by binary packages. Most
830 control information files are not in the Debian control file
835 <heading>The package name</heading>
838 Every package must have a name that's unique within the Debian
843 The package name is included in the control field
844 <tt>Package</tt>, the format of which is described
845 in <ref id="f-Package">.
846 The package name is also included as a part of the file name
847 of the <tt>.deb</tt> file.
852 <heading>The version of a package</heading>
855 Every package has a version number recorded in its
856 <tt>Version</tt> control file field, described in
857 <ref id="f-Version">.
861 The package management system imposes an ordering on version
862 numbers, so that it can tell whether packages are being up- or
863 downgraded and so that package system front end applications
864 can tell whether a package it finds available is newer than
865 the one installed on the system. The version number format
866 has the most significant parts (as far as comparison is
867 concerned) at the beginning.
871 If an upstream package has problematic version numbers they
872 should be converted to a sane form for use in the
873 <tt>Version</tt> field.
877 <heading>Version numbers based on dates</heading>
880 In general, Debian packages should use the same version
881 numbers as the upstream sources. However, upstream version
882 numbers based on some date formats (sometimes used for
883 development or "snapshot" releases) will not be ordered
884 correctly by the package management software. For
885 example, <prgn>dpkg</prgn> will consider "96May01" to be
886 greater than "96Dec24".
890 To prevent having to use epochs for every new upstream
891 version, the date-based portion of any upstream version number
892 should be given in a way that sorts correctly: four-digit year
893 first, followed by a two-digit numeric month, followed by a
894 two-digit numeric date, possibly with punctuation between the
899 Native Debian packages (i.e., packages which have been written
900 especially for Debian) whose version numbers include dates
901 should also follow these rules. If punctuation is desired
902 between the date components, remember that hyphen (<tt>-</tt>)
903 cannot be used in native package versions. Period
904 (<tt>.</tt>) is normally a good choice.
911 <heading>The maintainer of a package</heading>
914 Every package must have a Debian maintainer (the
915 maintainer may be one person or a group of people
916 reachable from a common email address, such as a mailing
917 list). The maintainer is responsible for ensuring that
918 the package is placed in the appropriate distributions.
922 The maintainer must be specified in the
923 <tt>Maintainer</tt> control field with their correct name
924 and a working email address. If one person maintains
925 several packages, they should try to avoid having
926 different forms of their name and email address in
927 the <tt>Maintainer</tt> fields of those packages.
931 The format of the <tt>Maintainer</tt> control field is
932 described in <ref id="f-Maintainer">.
936 If the maintainer of a package quits from the Debian
937 project, "Debian QA Group"
938 <email>packages@qa.debian.org</email> takes over the
939 maintainer-ship of the package until someone else
940 volunteers for that task. These packages are called
941 <em>orphaned packages</em>.<footnote>
942 The detailed procedure for doing this gracefully can
943 be found in the Debian Developer's Reference,
944 see <ref id="related">.
949 <sect id="descriptions">
950 <heading>The description of a package</heading>
953 Every Debian package must have a <tt>Description</tt> control
954 field which contains a synopsis and extended description of the
955 package. Technical information about the format of the
956 <tt>Description</tt> field is in <ref id="f-Description">.
960 The description should describe the package (the program) to a
961 user (system administrator) who has never met it before so that
962 they have enough information to decide whether they want to
963 install it. This description should not just be copied verbatim
964 from the program's documentation.
968 Put important information first, both in the synopsis and
969 extended description. Sometimes only the first part of the
970 synopsis or of the description will be displayed. You can
971 assume that there will usually be a way to see the whole
972 extended description.
976 The description should also give information about the
977 significant dependencies and conflicts between this package
978 and others, so that the user knows why these dependencies and
979 conflicts have been declared.
983 Instructions for configuring or using the package should
984 not be included (that is what installation scripts,
985 manual pages, info files, etc., are for). Copyright
986 statements and other administrivia should not be included
987 either (that is what the copyright file is for).
990 <sect1 id="synopsis"><heading>The single line synopsis</heading>
993 The single line synopsis should be kept brief - certainly
998 Do not include the package name in the synopsis line. The
999 display software knows how to display this already, and you
1000 do not need to state it. Remember that in many situations
1001 the user may only see the synopsis line - make it as
1002 informative as you can.
1007 <sect1 id="extendeddesc"><heading>The extended description</heading>
1010 Do not try to continue the single line synopsis into the
1011 extended description. This will not work correctly when
1012 the full description is displayed, and makes no sense
1013 where only the summary (the single line synopsis) is
1018 The extended description should describe what the package
1019 does and how it relates to the rest of the system (in terms
1020 of, for example, which subsystem it is which part of).
1024 The description field needs to make sense to anyone, even
1025 people who have no idea about any of the things the
1026 package deals with.<footnote>
1027 The blurb that comes with a program in its
1028 announcements and/or <prgn>README</prgn> files is
1029 rarely suitable for use in a description. It is
1030 usually aimed at people who are already in the
1031 community where the package is used.
1040 <heading>Dependencies</heading>
1043 Every package must specify the dependency information
1044 about other packages that are required for the first to
1049 For example, a dependency entry must be provided for any
1050 shared libraries required by a dynamically-linked executable
1051 binary in a package.
1055 Packages are not required to declare any dependencies they
1056 have on other packages which are marked <tt>Essential</tt>
1057 (see below), and should not do so unless they depend on a
1058 particular version of that package.<footnote>
1060 Essential is needed in part to avoid unresolvable dependency
1061 loops on upgrade. If packages add unnecessary dependencies
1062 on packages in this set, the chances that there
1063 <strong>will</strong> be an unresolvable dependency loop
1064 caused by forcing these Essential packages to be configured
1065 first before they need to be is greatly increased. It also
1066 increases the chances that frontends will be unable to
1067 <strong>calculate</strong> an upgrade path, even if one
1071 Also, functionality is rarely ever removed from the
1072 Essential set, but <em>packages</em> have been removed from
1073 the Essential set when the functionality moved to a
1074 different package. So depending on these packages <em>just
1075 in case</em> they stop being essential does way more harm
1082 Sometimes, a package requires another package to be installed
1083 <em>and</em> configured before it can be installed. In this
1084 case, you must specify a <tt>Pre-Depends</tt> entry for
1089 You should not specify a <tt>Pre-Depends</tt> entry for a
1090 package before this has been discussed on the
1091 <tt>debian-devel</tt> mailing list and a consensus about
1092 doing that has been reached.
1096 The format of the package interrelationship control fields is
1097 described in <ref id="relationships">.
1101 <sect id="virtual_pkg">
1102 <heading>Virtual packages</heading>
1105 Sometimes, there are several packages which offer
1106 more-or-less the same functionality. In this case, it's
1107 useful to define a <em>virtual package</em> whose name
1108 describes that common functionality. (The virtual
1109 packages only exist logically, not physically; that's why
1110 they are called <em>virtual</em>.) The packages with this
1111 particular function will then <em>provide</em> the virtual
1112 package. Thus, any other package requiring that function
1113 can simply depend on the virtual package without having to
1114 specify all possible packages individually.
1118 All packages should use virtual package names where
1119 appropriate, and arrange to create new ones if necessary.
1120 They should not use virtual package names (except privately,
1121 amongst a cooperating group of packages) unless they have
1122 been agreed upon and appear in the list of virtual package
1123 names. (See also <ref id="virtual">)
1127 The latest version of the authoritative list of virtual
1128 package names can be found in the <tt>debian-policy</tt> package.
1129 It is also available from the Debian web mirrors at
1130 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1131 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1135 The procedure for updating the list is described in the preface
1142 <heading>Base system</heading>
1145 The <tt>base system</tt> is a minimum subset of the Debian
1146 GNU/Linux system that is installed before everything else
1147 on a new system. Only very few packages are allowed to form
1148 part of the base system, in order to keep the required disk
1153 The base system consists of all those packages with priority
1154 <tt>required</tt> or <tt>important</tt>. Many of them will
1155 be tagged <tt>essential</tt> (see below).
1160 <heading>Essential packages</heading>
1163 Essential is defined as the minimal set of functionality that
1164 must be available and usable on the system at all times, even
1165 when packages are in an unconfigured (but unpacked) state.
1166 Packages are tagged <tt>essential</tt> for a system using the
1167 <tt>Essential</tt> control field. The format of the
1168 <tt>Essential</tt> control field is described in <ref
1173 Since these packages cannot be easily removed (one has to
1174 specify an extra <em>force option</em> to
1175 <prgn>dpkg</prgn> to do so), this flag must not be used
1176 unless absolutely necessary. A shared library package
1177 must not be tagged <tt>essential</tt>; dependencies will
1178 prevent its premature removal, and we need to be able to
1179 remove it when it has been superseded.
1183 Since dpkg will not prevent upgrading of other packages
1184 while an <tt>essential</tt> package is in an unconfigured
1185 state, all <tt>essential</tt> packages must supply all of
1186 their core functionality even when unconfigured. If the
1187 package cannot satisfy this requirement it must not be
1188 tagged as essential, and any packages depending on this
1189 package must instead have explicit dependency fields as
1194 Maintainers should take great care in adding any programs,
1195 interfaces, or functionality to <tt>essential</tt> packages.
1196 Packages may assume that functionality provided by
1197 <tt>essential</tt> packages is always available without
1198 declaring explicit dependencies, which means that removing
1199 functionality from the Essential set is very difficult and is
1200 almost never done. Any capability added to an
1201 <tt>essential</tt> package therefore creates an obligation to
1202 support that capability as part of the Essential set in
1207 You must not tag any packages <tt>essential</tt> before
1208 this has been discussed on the <tt>debian-devel</tt>
1209 mailing list and a consensus about doing that has been
1214 <sect id="maintscripts">
1215 <heading>Maintainer Scripts</heading>
1218 The package installation scripts should avoid producing
1219 output which is unnecessary for the user to see and
1220 should rely on <prgn>dpkg</prgn> to stave off boredom on
1221 the part of a user installing many packages. This means,
1222 amongst other things, using the <tt>--quiet</tt> option on
1223 <prgn>install-info</prgn>.
1227 Errors which occur during the execution of an installation
1228 script must be checked and the installation must not
1229 continue after an error.
1233 Note that in general <ref id="scripts"> applies to package
1234 maintainer scripts, too.
1238 You should not use <prgn>dpkg-divert</prgn> on a file belonging
1239 to another package without consulting the maintainer of that
1240 package first. When adding or removing diversions, package
1241 maintainer scripts must provide the <tt>--package</tt> flag
1242 to <prgn>dpkg-divert</prgn> and must not use <tt>--local</tt>.
1246 All packages which supply an instance of a common command
1247 name (or, in general, filename) should generally use
1248 <prgn>update-alternatives</prgn>, so that they may be
1249 installed together. If <prgn>update-alternatives</prgn>
1250 is not used, then each package must use
1251 <tt>Conflicts</tt> to ensure that other packages are
1252 de-installed. (In this case, it may be appropriate to
1253 specify a conflict against earlier versions of something
1254 that previously did not use
1255 <prgn>update-alternatives</prgn>; this is an exception to
1256 the usual rule that versioned conflicts should be
1260 <sect1 id="maintscriptprompt">
1261 <heading>Prompting in maintainer scripts</heading>
1263 Package maintainer scripts may prompt the user if
1264 necessary. Prompting must be done by communicating
1265 through a program, such as <prgn>debconf</prgn>, which
1266 conforms to the Debian Configuration Management
1267 Specification, version 2 or higher.
1271 Packages which are essential, or which are dependencies of
1272 essential packages, may fall back on another prompting method
1273 if no such interface is available when they are executed.
1277 The Debian Configuration Management Specification is included
1278 in the <file>debconf_specification</file> files in the
1279 <package>debian-policy</package> package.
1280 It is also available from the Debian web mirrors at
1281 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1282 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1286 Packages which use the Debian Configuration Management
1287 Specification may contain the additional control information
1288 files <file>config</file>
1289 and <file>templates</file>. <file>config</file> is an
1290 additional maintainer script used for package configuration,
1291 and <file>templates</file> contains templates used for user
1292 prompting. The <prgn>config</prgn> script might be run before
1293 the <prgn>preinst</prgn> script and before the package is
1294 unpacked or any of its dependencies or pre-dependencies are
1295 satisfied. Therefore it must work using only the tools
1296 present in <em>essential</em> packages.<footnote>
1297 <package>Debconf</package> or another tool that
1298 implements the Debian Configuration Management
1299 Specification will also be installed, and any
1300 versioned dependencies on it will be satisfied
1301 before preconfiguration begins.
1306 Packages which use the Debian Configuration Management
1307 Specification must allow for translation of their user-visible
1308 messages by using a gettext-based system such as the one
1309 provided by the <package>po-debconf</package> package.
1313 Packages should try to minimize the amount of prompting
1314 they need to do, and they should ensure that the user
1315 will only ever be asked each question once. This means
1316 that packages should try to use appropriate shared
1317 configuration files (such as <file>/etc/papersize</file> and
1318 <file>/etc/news/server</file>), and shared
1319 <package>debconf</package> variables rather than each
1320 prompting for their own list of required pieces of
1325 It also means that an upgrade should not ask the same
1326 questions again, unless the user has used
1327 <tt>dpkg --purge</tt> to remove the package's configuration.
1328 The answers to configuration questions should be stored in an
1329 appropriate place in <file>/etc</file> so that the user can
1330 modify them, and how this has been done should be
1335 If a package has a vitally important piece of
1336 information to pass to the user (such as "don't run me
1337 as I am, you must edit the following configuration files
1338 first or you risk your system emitting badly-formatted
1339 messages"), it should display this in the
1340 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1341 prompt the user to hit return to acknowledge the
1342 message. Copyright messages do not count as vitally
1343 important (they belong in
1344 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1345 neither do instructions on how to use a program (these
1346 should be in on-line documentation, where all the users
1351 Any necessary prompting should almost always be confined
1352 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1353 script. If it is done in the <prgn>postinst</prgn>, it
1354 should be protected with a conditional so that
1355 unnecessary prompting doesn't happen if a package's
1356 installation fails and the <prgn>postinst</prgn> is
1357 called with <tt>abort-upgrade</tt>,
1358 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1368 <heading>Source packages</heading>
1370 <sect id="standardsversion">
1371 <heading>Standards conformance</heading>
1374 Source packages should specify the most recent version number
1375 of this policy document with which your package complied
1376 when it was last updated.
1380 This information may be used to file bug reports
1381 automatically if your package becomes too much out of date.
1385 The version is specified in the <tt>Standards-Version</tt>
1387 The format of the <tt>Standards-Version</tt> field is
1388 described in <ref id="f-Standards-Version">.
1392 You should regularly, and especially if your package has
1393 become out of date, check for the newest Policy Manual
1394 available and update your package, if necessary. When your
1395 package complies with the new standards you should update the
1396 <tt>Standards-Version</tt> source package field and
1397 release it.<footnote>
1398 See the file <file>upgrading-checklist</file> for
1399 information about policy which has changed between
1400 different versions of this document.
1406 <sect id="pkg-relations">
1407 <heading>Package relationships</heading>
1410 Source packages should specify which binary packages they
1411 require to be installed or not to be installed in order to
1412 build correctly. For example, if building a package
1413 requires a certain compiler, then the compiler should be
1414 specified as a build-time dependency.
1418 It is not necessary to explicitly specify build-time
1419 relationships on a minimal set of packages that are always
1420 needed to compile, link and put in a Debian package a
1421 standard "Hello World!" program written in C or C++. The
1422 required packages are called <em>build-essential</em>, and
1423 an informational list can be found in
1424 <file>/usr/share/doc/build-essential/list</file> (which is
1425 contained in the <tt>build-essential</tt>
1428 <list compact="compact">
1430 This allows maintaining the list separately
1431 from the policy documents (the list does not
1432 need the kind of control that the policy
1436 Having a separate package allows one to install
1437 the build-essential packages on a machine, as
1438 well as allowing other packages such as tasks to
1439 require installation of the build-essential
1440 packages using the depends relation.
1443 The separate package allows bug reports against
1444 the list to be categorized separately from
1445 the policy management process in the BTS.
1452 When specifying the set of build-time dependencies, one
1453 should list only those packages explicitly required by the
1454 build. It is not necessary to list packages which are
1455 required merely because some other package in the list of
1456 build-time dependencies depends on them.<footnote>
1457 The reason for this is that dependencies change, and
1458 you should list all those packages, and <em>only</em>
1459 those packages that <em>you</em> need directly. What
1460 others need is their business. For example, if you
1461 only link against <file>libimlib</file>, you will need to
1462 build-depend on <package>libimlib2-dev</package> but
1463 not against any <tt>libjpeg*</tt> packages, even
1464 though <tt>libimlib2-dev</tt> currently depends on
1465 them: installation of <package>libimlib2-dev</package>
1466 will automatically ensure that all of its run-time
1467 dependencies are satisfied.
1472 If build-time dependencies are specified, it must be
1473 possible to build the package and produce working binaries
1474 on a system with only essential and build-essential
1475 packages installed and also those required to satisfy the
1476 build-time relationships (including any implied
1477 relationships). In particular, this means that version
1478 clauses should be used rigorously in build-time
1479 relationships so that one cannot produce bad or
1480 inconsistently configured packages when the relationships
1481 are properly satisfied.
1485 <ref id="relationships"> explains the technical details.
1490 <heading>Changes to the upstream sources</heading>
1493 If changes to the source code are made that are not
1494 specific to the needs of the Debian system, they should be
1495 sent to the upstream authors in whatever form they prefer
1496 so as to be included in the upstream version of the
1501 If you need to configure the package differently for
1502 Debian or for Linux, and the upstream source doesn't
1503 provide a way to do so, you should add such configuration
1504 facilities (for example, a new <prgn>autoconf</prgn> test
1505 or <tt>#define</tt>) and send the patch to the upstream
1506 authors, with the default set to the way they originally
1507 had it. You can then easily override the default in your
1508 <file>debian/rules</file> or wherever is appropriate.
1512 You should make sure that the <prgn>configure</prgn> utility
1513 detects the correct architecture specification string
1514 (refer to <ref id="arch-spec"> for details).
1518 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1519 <prgn>configure</prgn> scripts are used, you should edit the
1520 <file>.in</file> files rather than editing the
1521 <prgn>Makefile</prgn> directly. This allows the user to
1522 reconfigure the package if necessary. You should
1523 <em>not</em> configure the package and edit the generated
1524 <prgn>Makefile</prgn>! This makes it impossible for someone
1525 else to later reconfigure the package without losing the
1531 <sect id="dpkgchangelog">
1532 <heading>Debian changelog: <file>debian/changelog</file></heading>
1535 Changes in the Debian version of the package should be
1536 briefly explained in the Debian changelog file
1537 <file>debian/changelog</file>.<footnote>
1539 Mistakes in changelogs are usually best rectified by
1540 making a new changelog entry rather than "rewriting
1541 history" by editing old changelog entries.
1544 This includes modifications
1545 made in the Debian package compared to the upstream one
1546 as well as other changes and updates to the package.
1548 Although there is nothing stopping an author who is also
1549 the Debian maintainer from using this changelog for all
1550 their changes, it will have to be renamed if the Debian
1551 and upstream maintainers become different people. In such
1552 a case, however, it might be better to maintain the package
1553 as a non-native package.
1558 The format of the <file>debian/changelog</file> allows the
1559 package building tools to discover which version of the package
1560 is being built and find out other release-specific information.
1564 That format is a series of entries like this:
1566 <example compact="compact">
1567 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1569 [optional blank line(s), stripped]
1571 * <var>change details</var>
1572 <var>more change details</var>
1574 [blank line(s), included in output of dpkg-parsechangelog]
1576 * <var>even more change details</var>
1578 [optional blank line(s), stripped]
1580 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1585 <var>package</var> and <var>version</var> are the source
1586 package name and version number.
1590 <var>distribution(s)</var> lists the distributions where
1591 this version should be installed when it is uploaded - it
1592 is copied to the <tt>Distribution</tt> field in the
1593 <file>.changes</file> file. See <ref id="f-Distribution">.
1597 <var>urgency</var> is the value for the <tt>Urgency</tt>
1598 field in the <file>.changes</file> file for the upload
1599 (see <ref id="f-Urgency">). It is not possible to specify
1600 an urgency containing commas; commas are used to separate
1601 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1602 <prgn>dpkg</prgn> changelog format (though there is
1603 currently only one useful <var>keyword</var>,
1608 The change details may in fact be any series of lines
1609 starting with at least two spaces, but conventionally each
1610 change starts with an asterisk and a separating space and
1611 continuation lines are indented so as to bring them in
1612 line with the start of the text above. Blank lines may be
1613 used here to separate groups of changes, if desired.
1617 If this upload resolves bugs recorded in the Bug Tracking
1618 System (BTS), they may be automatically closed on the
1619 inclusion of this package into the Debian archive by
1620 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1621 in the change details.<footnote>
1622 To be precise, the string should match the following
1623 Perl regular expression:
1625 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1627 Then all of the bug numbers listed will be closed by the
1628 archive maintenance script (<prgn>katie</prgn>) using the
1629 <var>version</var> of the changelog entry.
1631 This information is conveyed via the <tt>Closes</tt> field
1632 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1636 The maintainer name and email address used in the changelog
1637 should be the details of the person uploading <em>this</em>
1638 version. They are <em>not</em> necessarily those of the
1639 usual package maintainer.<footnote>
1640 If the developer uploading the package is not one of the usual
1641 maintainers of the package (as listed in
1642 the <qref id="f-Maintainer"><tt>Maintainer</tt></qref>
1643 or <qref id="f-Uploaders"><tt>Uploaders</tt></qref> control
1644 fields of the package), the first line of the changelog is
1645 conventionally used to explain why a non-maintainer is
1646 uploading the package. The Debian Developer's Reference
1647 (see <ref id="related">) documents the conventions
1649 The information here will be copied to the <tt>Changed-By</tt>
1650 field in the <tt>.changes</tt> file
1651 (see <ref id="f-Changed-By">), and then later used to send an
1652 acknowledgement when the upload has been installed.
1656 The <var>date</var> has the following format<footnote>
1657 This is the same as the format generated by <tt>date
1659 </footnote> (compatible and with the same semantics of
1660 RFC 2822 and RFC 5322):
1661 <example>day-of-week, dd month yyyy hh:mm:ss +zzzz</example>
1663 <list compact="compact">
1665 day-of week is one of: Mon, Tue, Wed, Thu, Fri, Sat, Sun
1668 dd is a one- or two-digit day of the month (01-31)
1671 month is one of: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug,
1674 <item>yyyy is the four-digit year (e.g. 2010)</item>
1675 <item>hh is the two-digit hour (00-23)</item>
1676 <item>mm is the two-digit minutes (00-59)</item>
1677 <item>ss is the two-digit seconds (00-60)</item>
1679 +zzzz or -zzzz is the the time zone offset from Coordinated
1680 Universal Time (UTC). "+" indicates that the time is ahead
1681 of (i.e., east of) UTC and "-" indicates that the time is
1682 behind (i.e., west of) UTC. The first two digits indicate
1683 the hour difference from UTC and the last two digits
1684 indicate the number of additional minutes difference from
1685 UTC. The last two digits must be in the range 00-59.
1691 The first "title" line with the package name must start
1692 at the left hand margin. The "trailer" line with the
1693 maintainer and date details must be preceded by exactly
1694 one space. The maintainer details and the date must be
1695 separated by exactly two spaces.
1699 The entire changelog must be encoded in UTF-8.
1703 For more information on placement of the changelog files
1704 within binary packages, please see <ref id="changelogs">.
1708 <sect id="dpkgcopyright">
1709 <heading>Copyright: <file>debian/copyright</file></heading>
1711 Every package must be accompanied by a verbatim copy of its
1712 copyright information and distribution license in the file
1713 <file>/usr/share/doc/<var>package</var>/copyright</file>
1714 (see <ref id="copyrightfile"> for further details). Also see
1715 <ref id="pkgcopyright"> for further considerations related
1716 to copyrights for packages.
1720 <heading>Error trapping in makefiles</heading>
1723 When <prgn>make</prgn> invokes a command in a makefile
1724 (including your package's upstream makefiles and
1725 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1726 means that <prgn>sh</prgn>'s usual bad error handling
1727 properties apply: if you include a miniature script as one
1728 of the commands in your makefile you'll find that if you
1729 don't do anything about it then errors are not detected
1730 and <prgn>make</prgn> will blithely continue after
1735 Every time you put more than one shell command (this
1736 includes using a loop) in a makefile command you
1737 must make sure that errors are trapped. For
1738 simple compound commands, such as changing directory and
1739 then running a program, using <tt>&&</tt> rather
1740 than semicolon as a command separator is sufficient. For
1741 more complex commands including most loops and
1742 conditionals you should include a separate <tt>set -e</tt>
1743 command at the start of every makefile command that's
1744 actually one of these miniature shell scripts.
1748 <sect id="timestamps">
1749 <heading>Time Stamps</heading>
1751 Maintainers should preserve the modification times of the
1752 upstream source files in a package, as far as is reasonably
1754 The rationale is that there is some information conveyed
1755 by knowing the age of the file, for example, you could
1756 recognize that some documentation is very old by looking
1757 at the modification time, so it would be nice if the
1758 modification time of the upstream source would be
1764 <sect id="restrictions">
1765 <heading>Restrictions on objects in source packages</heading>
1768 The source package may not contain any hard links<footnote>
1770 This is not currently detected when building source
1771 packages, but only when extracting
1775 Hard links may be permitted at some point in the
1776 future, but would require a fair amount of
1779 </footnote>, device special files, sockets or setuid or
1780 setgid files.<footnote>
1781 Setgid directories are allowed.
1786 <sect id="debianrules">
1787 <heading>Main building script: <file>debian/rules</file></heading>
1790 This file must be an executable makefile, and contains the
1791 package-specific recipes for compiling the package and
1792 building binary package(s) from the source.
1796 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1797 so that it can be invoked by saying its name rather than
1798 invoking <prgn>make</prgn> explicitly. That is, invoking
1799 either of <tt>make -f debian/rules <em>args...</em></tt>
1800 or <tt>./debian/rules <em>args...</em></tt> must result in
1805 Since an interactive <file>debian/rules</file> script makes it
1806 impossible to auto-compile that package and also makes it
1807 hard for other people to reproduce the same binary
1808 package, all <em>required targets</em> must be
1809 non-interactive. At a minimum, required targets are the
1810 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1811 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1812 <em>binary-indep</em>, and <em>build</em>. It also follows
1813 that any target that these targets depend on must also be
1818 The targets are as follows (required unless stated otherwise):
1820 <tag><tt>build</tt></tag>
1823 The <tt>build</tt> target should perform all the
1824 configuration and compilation of the package.
1825 If a package has an interactive pre-build
1826 configuration routine, the Debian source package
1827 must either be built after this has taken place (so
1828 that the binary package can be built without rerunning
1829 the configuration) or the configuration routine
1830 modified to become non-interactive. (The latter is
1831 preferable if there are architecture-specific features
1832 detected by the configuration routine.)
1836 For some packages, notably ones where the same
1837 source tree is compiled in different ways to produce
1838 two binary packages, the <tt>build</tt> target
1839 does not make much sense. For these packages it is
1840 good enough to provide two (or more) targets
1841 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1842 for each of the ways of building the package, and a
1843 <tt>build</tt> target that does nothing. The
1844 <tt>binary</tt> target will have to build the
1845 package in each of the possible ways and make the
1846 binary package out of each.
1850 The <tt>build</tt> target must not do anything
1851 that might require root privilege.
1855 The <tt>build</tt> target may need to run the
1856 <tt>clean</tt> target first - see below.
1860 When a package has a configuration and build routine
1861 which takes a long time, or when the makefiles are
1862 poorly designed, or when <tt>build</tt> needs to
1863 run <tt>clean</tt> first, it is a good idea to
1864 <tt>touch build</tt> when the build process is
1865 complete. This will ensure that if <tt>debian/rules
1866 build</tt> is run again it will not rebuild the whole
1868 Another common way to do this is for <tt>build</tt>
1869 to depend on <prgn>build-stamp</prgn> and to do
1870 nothing else, and for the <prgn>build-stamp</prgn>
1871 target to do the building and to <tt>touch
1872 build-stamp</tt> on completion. This is
1873 especially useful if the build routine creates a
1874 file or directory called <tt>build</tt>; in such a
1875 case, <tt>build</tt> will need to be listed as
1876 a phony target (i.e., as a dependency of the
1877 <tt>.PHONY</tt> target). See the documentation of
1878 <prgn>make</prgn> for more information on phony
1884 <tag><tt>build-arch</tt> (optional),
1885 <tt>build-indep</tt> (optional)
1889 A package may also provide both of the targets
1890 <tt>build-arch</tt> and <tt>build-indep</tt>.
1891 The <tt>build-arch</tt> target, if provided, should
1892 perform all the configuration and compilation required for
1893 producing all architecture-dependant binary packages
1894 (those packages for which the body of the
1895 <tt>Architecture</tt> field in <tt>debian/control</tt> is
1896 not <tt>all</tt>). Similarly, the <tt>build-indep</tt>
1897 target, if provided, should perform all the configuration
1898 and compilation required for producing all
1899 architecture-independent binary packages (those packages
1900 for which the body of the <tt>Architecture</tt> field
1901 in <tt>debian/control</tt> is <tt>all</tt>).
1902 The <tt>build</tt> target should depend on those of the
1903 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1904 are provided in the rules file.<footnote>
1905 The intent of this split is so that binary-only builds
1906 need not install the dependencies required for
1907 the <tt>build-indep</tt> target. However, this is not
1908 yet used in practice since <tt>dpkg-buildpackage
1909 -B</tt>, and therefore the autobuilders,
1910 invoke <tt>build</tt> rather than <tt>build-arch</tt>
1911 due to the difficulties in determining whether the
1912 optional <tt>build-arch</tt> target exists.
1917 If one or both of the targets <tt>build-arch</tt> and
1918 <tt>build-indep</tt> are not provided, then invoking
1919 <file>debian/rules</file> with one of the not-provided
1920 targets as arguments should produce a exit status code
1921 of 2. Usually this is provided automatically by make
1922 if the target is missing.
1926 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1927 must not do anything that might require root privilege.
1931 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1932 <tt>binary-indep</tt>
1936 The <tt>binary</tt> target must be all that is
1937 necessary for the user to build the binary package(s)
1938 produced from this source package. It is
1939 split into two parts: <prgn>binary-arch</prgn> builds
1940 the binary packages which are specific to a particular
1941 architecture, and <tt>binary-indep</tt> builds
1942 those which are not.
1945 <tt>binary</tt> may be (and commonly is) a target with
1946 no commands which simply depends on
1947 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1950 Both <tt>binary-*</tt> targets should depend on the
1951 <tt>build</tt> target, or on the appropriate
1952 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1953 provided, so that the package is built if it has not
1954 been already. It should then create the relevant
1955 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1956 make their control files and <prgn>dpkg-deb</prgn> to
1957 build them and place them in the parent of the top
1962 Both the <tt>binary-arch</tt> and
1963 <tt>binary-indep</tt> targets <em>must</em> exist.
1964 If one of them has nothing to do (which will always be
1965 the case if the source generates only a single binary
1966 package, whether architecture-dependent or not), it
1967 must still exist and must always succeed.
1971 The <tt>binary</tt> targets must be invoked as
1973 The <prgn>fakeroot</prgn> package often allows one
1974 to build a package correctly even without being
1980 <tag><tt>clean</tt></tag>
1983 This must undo any effects that the <tt>build</tt>
1984 and <tt>binary</tt> targets may have had, except
1985 that it should leave alone any output files created in
1986 the parent directory by a run of a <tt>binary</tt>
1991 If a <tt>build</tt> file is touched at the end of
1992 the <tt>build</tt> target, as suggested above, it
1993 should be removed as the first action that
1994 <tt>clean</tt> performs, so that running
1995 <tt>build</tt> again after an interrupted
1996 <tt>clean</tt> doesn't think that everything is
2001 The <tt>clean</tt> target may need to be
2002 invoked as root if <tt>binary</tt> has been
2003 invoked since the last <tt>clean</tt>, or if
2004 <tt>build</tt> has been invoked as root (since
2005 <tt>build</tt> may create directories, for
2010 <tag><tt>get-orig-source</tt> (optional)</tag>
2013 This target fetches the most recent version of the
2014 original source package from a canonical archive site
2015 (via FTP or WWW, for example), does any necessary
2016 rearrangement to turn it into the original source
2017 tar file format described below, and leaves it in the
2022 This target may be invoked in any directory, and
2023 should take care to clean up any temporary files it
2028 This target is optional, but providing it if
2029 possible is a good idea.
2033 <tag><tt>patch</tt> (optional)</tag>
2036 This target performs whatever additional actions are
2037 required to make the source ready for editing (unpacking
2038 additional upstream archives, applying patches, etc.).
2039 It is recommended to be implemented for any package where
2040 <tt>dpkg-source -x</tt> does not result in source ready
2041 for additional modification. See
2042 <ref id="readmesource">.
2048 The <tt>build</tt>, <tt>binary</tt> and
2049 <tt>clean</tt> targets must be invoked with the current
2050 directory being the package's top-level directory.
2055 Additional targets may exist in <file>debian/rules</file>,
2056 either as published or undocumented interfaces or for the
2057 package's internal use.
2061 The architectures we build on and build for are determined
2062 by <prgn>make</prgn> variables using the utility
2063 <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
2064 You can determine the
2065 Debian architecture and the GNU style architecture
2066 specification string for the build machine (the machine type
2067 we are building on) as well as for the host machine (the
2068 machine type we are building for). Here is a list of
2069 supported <prgn>make</prgn> variables:
2070 <list compact="compact">
2072 <tt>DEB_*_ARCH</tt> (the Debian architecture)
2075 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2078 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2081 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2082 specification string)
2085 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2086 <tt>DEB_*_GNU_TYPE</tt>)
2089 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2090 <tt>DEB_*_GNU_TYPE</tt>)
2092 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2093 the build machine or <tt>HOST</tt> for specification of the
2098 Backward compatibility can be provided in the rules file
2099 by setting the needed variables to suitable default
2100 values; please refer to the documentation of
2101 <prgn>dpkg-architecture</prgn> for details.
2105 It is important to understand that the <tt>DEB_*_ARCH</tt>
2106 string only determines which Debian architecture we are
2107 building on or for. It should not be used to get the CPU
2108 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2109 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2110 GNU style variables should generally only be used with upstream
2114 <sect1 id="debianrules-options">
2115 <heading><file>debian/rules</file> and
2116 <tt>DEB_BUILD_OPTIONS</tt></heading>
2119 Supporting the standardized environment variable
2120 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2121 contain several flags to change how a package is compiled and
2122 built. Each flag must be in the form <var>flag</var> or
2123 <var>flag</var>=<var>options</var>. If multiple flags are
2124 given, they must be separated by whitespace.<footnote>
2125 Some packages support any delimiter, but whitespace is the
2126 easiest to parse inside a makefile and avoids ambiguity with
2127 flag values that contain commas.
2129 <var>flag</var> must start with a lowercase letter
2130 (<tt>a-z</tt>) and consist only of lowercase letters,
2131 numbers (<tt>0-9</tt>), and the characters
2132 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2133 <var>options</var> must not contain whitespace. The same
2134 tag should not be given multiple times with conflicting
2135 values. Package maintainers may assume that
2136 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2140 The meaning of the following tags has been standardized:
2144 This tag says to not run any build-time test suite
2145 provided by the package.
2149 The presence of this tag means that the package should
2150 be compiled with a minimum of optimization. For C
2151 programs, it is best to add <tt>-O0</tt> to
2152 <tt>CFLAGS</tt> (although this is usually the default).
2153 Some programs might fail to build or run at this level
2154 of optimization; it may be necessary to use
2155 <tt>-O1</tt>, for example.
2159 This tag means that the debugging symbols should not be
2160 stripped from the binary during installation, so that
2161 debugging information may be included in the package.
2163 <tag>parallel=n</tag>
2165 This tag means that the package should be built using up
2166 to <tt>n</tt> parallel processes if the package build
2167 system supports this.<footnote>
2168 Packages built with <tt>make</tt> can often implement
2169 this by passing the <tt>-j</tt><var>n</var> option to
2172 If the package build system does not support parallel
2173 builds, this string must be ignored. If the package
2174 build system only supports a lower level of concurrency
2175 than <var>n</var>, the package should be built using as
2176 many parallel processes as the package build system
2177 supports. It is up to the package maintainer to decide
2178 whether the package build times are long enough and the
2179 package build system is robust enough to make supporting
2180 parallel builds worthwhile.
2186 Unknown flags must be ignored by <file>debian/rules</file>.
2190 The following makefile snippet is an example of how one may
2191 implement the build options; you will probably have to
2192 massage this example in order to make it work for your
2194 <example compact="compact">
2197 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2198 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2199 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2200 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2202 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2207 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2208 INSTALL_PROGRAM += -s
2210 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2211 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2212 MAKEFLAGS += -j$(NUMJOBS)
2217 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2218 # Code to run the package test suite.
2225 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2226 <sect id="substvars">
2227 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2230 When <prgn>dpkg-gencontrol</prgn>
2231 generates <qref id="binarycontrolfiles">binary package control
2232 files</qref> (<file>DEBIAN/control</file>), it performs variable
2233 substitutions on its output just before writing it. Variable
2234 substitutions have the form <tt>${<var>variable</var>}</tt>.
2235 The optional file <file>debian/substvars</file> contains
2236 variable substitutions to be used; variables can also be set
2237 directly from <file>debian/rules</file> using the <tt>-V</tt>
2238 option to the source packaging commands, and certain predefined
2239 variables are also available.
2243 The <file>debian/substvars</file> file is usually generated and
2244 modified dynamically by <file>debian/rules</file> targets, in
2245 which case it must be removed by the <tt>clean</tt> target.
2249 See <manref name="deb-substvars" section="5"> for full
2250 details about source variable substitutions, including the
2251 format of <file>debian/substvars</file>.</p>
2254 <sect id="debianwatch">
2255 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2258 This is an optional, recommended configuration file for the
2259 <tt>uscan</tt> utility which defines how to automatically scan
2260 ftp or http sites for newly available updates of the
2261 package. This is used
2262 by <url id="http://dehs.alioth.debian.org/"> and other Debian QA
2263 tools to help with quality control and maintenance of the
2264 distribution as a whole.
2269 <sect id="debianfiles">
2270 <heading>Generated files list: <file>debian/files</file></heading>
2273 This file is not a permanent part of the source tree; it
2274 is used while building packages to record which files are
2275 being generated. <prgn>dpkg-genchanges</prgn> uses it
2276 when it generates a <file>.changes</file> file.
2280 It should not exist in a shipped source package, and so it
2281 (and any backup files or temporary files such as
2282 <file>files.new</file><footnote>
2283 <file>files.new</file> is used as a temporary file by
2284 <prgn>dpkg-gencontrol</prgn> and
2285 <prgn>dpkg-distaddfile</prgn> - they write a new
2286 version of <tt>files</tt> here before renaming it,
2287 to avoid leaving a corrupted copy if an error
2289 </footnote>) should be removed by the
2290 <tt>clean</tt> target. It may also be wise to
2291 ensure a fresh start by emptying or removing it at the
2292 start of the <tt>binary</tt> target.
2296 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2297 package, it adds an entry to <file>debian/files</file> for the
2298 <file>.deb</file> file that will be created when <tt>dpkg-deb
2299 --build</tt> is run for that binary package. So for most
2300 packages all that needs to be done with this file is to
2301 delete it in the <tt>clean</tt> target.
2305 If a package upload includes files besides the source
2306 package and any binary packages whose control files were
2307 made with <prgn>dpkg-gencontrol</prgn> then they should be
2308 placed in the parent of the package's top-level directory
2309 and <prgn>dpkg-distaddfile</prgn> should be called to add
2310 the file to the list in <file>debian/files</file>.</p>
2313 <sect id="embeddedfiles">
2314 <heading>Convenience copies of code</heading>
2317 Some software packages include in their distribution convenience
2318 copies of code from other software packages, generally so that
2319 users compiling from source don't have to download multiple
2320 packages. Debian packages should not make use of these
2321 convenience copies unless the included package is explicitly
2322 intended to be used in this way.<footnote>
2323 For example, parts of the GNU build system work like this.
2325 If the included code is already in the Debian archive in the
2326 form of a library, the Debian packaging should ensure that
2327 binary packages reference the libraries already in Debian and
2328 the convenience copy is not used. If the included code is not
2329 already in Debian, it should be packaged separately as a
2330 prerequisite if possible.
2332 Having multiple copies of the same code in Debian is
2333 inefficient, often creates either static linking or shared
2334 library conflicts, and, most importantly, increases the
2335 difficulty of handling security vulnerabilities in the
2341 <sect id="readmesource">
2342 <heading>Source package handling:
2343 <file>debian/README.source</file></heading>
2346 If running <prgn>dpkg-source -x</prgn> on a source package
2347 doesn't produce the source of the package, ready for editing,
2348 and allow one to make changes and run
2349 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2350 without taking any additional steps, creating a
2351 <file>debian/README.source</file> documentation file is
2352 recommended. This file should explain how to do all of the
2355 <item>Generate the fully patched source, in a form ready for
2356 editing, that would be built to create Debian
2357 packages. Doing this with a <tt>patch</tt> target in
2358 <file>debian/rules</file> is recommended; see
2359 <ref id="debianrules">.</item>
2360 <item>Modify the source and save those modifications so that
2361 they will be applied when building the package.</item>
2362 <item>Remove source modifications that are currently being
2363 applied when building the package.</item>
2364 <item>Optionally, document what steps are necessary to
2365 upgrade the Debian source package to a new upstream version,
2366 if applicable.</item>
2368 This explanation should include specific commands and mention
2369 any additional required Debian packages. It should not assume
2370 familiarity with any specific Debian packaging system or patch
2375 This explanation may refer to a documentation file installed by
2376 one of the package's build dependencies provided that the
2377 referenced documentation clearly explains these tasks and is not
2378 a general reference manual.
2382 <file>debian/README.source</file> may also include any other
2383 information that would be helpful to someone modifying the
2384 source package. Even if the package doesn't fit the above
2385 description, maintainers are encouraged to document in a
2386 <file>debian/README.source</file> file any source package with a
2387 particularly complex or unintuitive source layout or build
2388 system (for example, a package that builds the same source
2389 multiple times to generate different binary packages).
2395 <chapt id="controlfields">
2396 <heading>Control files and their fields</heading>
2399 The package management system manipulates data represented in
2400 a common format, known as <em>control data</em>, stored in
2401 <em>control files</em>.
2402 Control files are used for source packages, binary packages and
2403 the <file>.changes</file> files which control the installation
2404 of uploaded files<footnote>
2405 <prgn>dpkg</prgn>'s internal databases are in a similar
2410 <sect id="controlsyntax">
2411 <heading>Syntax of control files</heading>
2414 A control file consists of one or more paragraphs of
2416 The paragraphs are also sometimes referred to as stanzas.
2418 The paragraphs are separated by blank lines. Some control
2419 files allow only one paragraph; others allow several, in
2420 which case each paragraph usually refers to a different
2421 package. (For example, in source packages, the first
2422 paragraph refers to the source package, and later paragraphs
2423 refer to binary packages generated from the source.)
2427 Each paragraph consists of a series of data fields; each
2428 field consists of the field name, followed by a colon and
2429 then the data/value associated with that field. It ends at
2430 the end of the (logical) line. Horizontal whitespace
2431 (spaces and tabs) may occur immediately before or after the
2432 value and is ignored there; it is conventional to put a
2433 single space after the colon. For example, a field might
2435 <example compact="compact">
2438 the field name is <tt>Package</tt> and the field value
2443 A paragraph must not contain more than one instance of a
2444 particular field name.
2448 Many fields' values may span several lines; in this case
2449 each continuation line must start with a space or a tab.
2450 Any trailing spaces or tabs at the end of individual
2451 lines of a field value are ignored.
2455 In fields where it is specified that lines may not wrap,
2456 only a single line of data is allowed and whitespace is not
2457 significant in a field body. Whitespace must not appear
2458 inside names (of packages, architectures, files or anything
2459 else) or version numbers, or between the characters of
2460 multi-character version relationships.
2464 Field names are not case-sensitive, but it is usual to
2465 capitalize the field names using mixed case as shown below.
2466 Field values are case-sensitive unless the description of the
2467 field says otherwise.
2471 Blank lines, or lines consisting only of spaces and tabs,
2472 are not allowed within field values or between fields - that
2473 would mean a new paragraph.
2477 All control files must be encoded in UTF-8.
2481 <sect id="sourcecontrolfiles">
2482 <heading>Source package control files -- <file>debian/control</file></heading>
2485 The <file>debian/control</file> file contains the most vital
2486 (and version-independent) information about the source package
2487 and about the binary packages it creates.
2491 The first paragraph of the control file contains information about
2492 the source package in general. The subsequent sets each describe a
2493 binary package that the source tree builds.
2497 The fields in the general paragraph (the first one, for the source
2500 <list compact="compact">
2501 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2502 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2503 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2504 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2505 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2506 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2507 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2508 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2513 The fields in the binary package paragraphs are:
2515 <list compact="compact">
2516 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2517 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2518 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2519 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2520 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2521 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2522 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2523 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2528 The syntax and semantics of the fields are described below.
2532 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2533 generate control files for binary packages (see below), by
2534 <prgn>dpkg-genchanges</prgn> to generate the
2535 <file>.changes</file> file to accompany the upload, and by
2536 <prgn>dpkg-source</prgn> when it creates the
2537 <file>.dsc</file> source control file as part of a source
2538 archive. Many fields are permitted to span multiple lines in
2539 <file>debian/control</file> but not in any other control
2540 file. These tools are responsible for removing the line
2541 breaks from such fields when using fields from
2542 <file>debian/control</file> to generate other control files.
2546 The fields here may contain variable references - their
2547 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2548 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2549 when they generate output control files.
2550 See <ref id="substvars"> for details.
2554 In addition to the control file syntax described <qref
2555 id="controlsyntax">above</qref>, this file may also contain
2556 comment lines starting with <tt>#</tt> without any preceding
2557 whitespace. All such lines are ignored, even in the middle of
2558 continuation lines for a multiline field, and do not end a
2564 <sect id="binarycontrolfiles">
2565 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2568 The <file>DEBIAN/control</file> file contains the most vital
2569 (and version-dependent) information about a binary package. It
2570 consists of a single paragraph.
2574 The fields in this file are:
2576 <list compact="compact">
2577 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2578 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2579 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2580 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2581 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2582 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2583 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2584 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2585 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2586 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2587 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2588 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2593 <sect id="debiansourcecontrolfiles">
2594 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2597 This file consists of a single paragraph, possibly surrounded by
2598 a PGP signature. The fields of that paragraph are listed below.
2599 Their syntax is described above, in <ref id="pkg-controlfields">.
2601 <list compact="compact">
2602 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2603 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2604 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2605 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2606 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2607 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2608 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2609 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2610 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2611 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2612 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2613 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2614 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2619 The source package control file is generated by
2620 <prgn>dpkg-source</prgn> when it builds the source
2621 archive, from other files in the source package,
2622 described above. When unpacking, it is checked against
2623 the files and directories in the other parts of the
2629 <sect id="debianchangesfiles">
2630 <heading>Debian changes files -- <file>.changes</file></heading>
2633 The <file>.changes</file> files are used by the Debian archive
2634 maintenance software to process updates to packages. They
2635 consist of a single paragraph, possibly surrounded by a PGP
2636 signature. That paragraph contains information from the
2637 <file>debian/control</file> file and other data about the
2638 source package gathered via <file>debian/changelog</file>
2639 and <file>debian/rules</file>.
2643 <file>.changes</file> files have a format version that is
2644 incremented whenever the documented fields or their meaning
2645 change. This document describes format &changesversion;.
2649 The fields in this file are:
2651 <list compact="compact">
2652 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2653 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2654 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2655 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2656 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2657 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2658 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2659 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2660 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2661 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2662 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2663 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2664 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2665 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2666 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2667 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2672 <sect id="controlfieldslist">
2673 <heading>List of fields</heading>
2675 <sect1 id="f-Source">
2676 <heading><tt>Source</tt></heading>
2679 This field identifies the source package name.
2683 In <file>debian/control</file> or a <file>.dsc</file> file,
2684 this field must contain only the name of the source package.
2688 In a binary package control file or a <file>.changes</file>
2689 file, the source package name may be followed by a version
2690 number in parentheses<footnote>
2691 It is customary to leave a space after the package name
2692 if a version number is specified.
2694 This version number may be omitted (and is, by
2695 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2696 the <tt>Version</tt> field of the binary package in
2697 question. The field itself may be omitted from a binary
2698 package control file when the source package has the same
2699 name and version as the binary package.
2703 Package names (both source and binary,
2704 see <ref id="f-Package">) must consist only of lower case
2705 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2706 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2707 (<tt>.</tt>). They must be at least two characters long and
2708 must start with an alphanumeric character.
2712 <sect1 id="f-Maintainer">
2713 <heading><tt>Maintainer</tt></heading>
2716 The package maintainer's name and email address. The name
2717 must come first, then the email address inside angle
2718 brackets <tt><></tt> (in RFC822 format).
2722 If the maintainer's name contains a full stop then the
2723 whole field will not work directly as an email address due
2724 to a misfeature in the syntax specified in RFC822; a
2725 program using this field as an address must check for this
2726 and correct the problem if necessary (for example by
2727 putting the name in round brackets and moving it to the
2728 end, and bringing the email address forward).
2732 <sect1 id="f-Uploaders">
2733 <heading><tt>Uploaders</tt></heading>
2736 List of the names and email addresses of co-maintainers of
2737 the package, if any. If the package has other maintainers
2738 beside the one named in the
2739 <qref id="f-Maintainer">Maintainer field</qref>, their names
2740 and email addresses should be listed here. The format of each
2741 entry is the same as that of the Maintainer field, and
2742 multiple entries must be comma separated. This is an optional
2747 Any parser that interprets the Uploaders field in
2748 <file>debian/control</file> must permit it to span multiple
2749 lines. Line breaks in an Uploaders field that spans multiple
2750 lines are not significant and the semantics of the field are
2751 the same as if the line breaks had not been present.
2755 <sect1 id="f-Changed-By">
2756 <heading><tt>Changed-By</tt></heading>
2759 The name and email address of the person who prepared this
2760 version of the package, usually a maintainer. The syntax is
2761 the same as for the <qref id="f-Maintainer">Maintainer
2766 <sect1 id="f-Section">
2767 <heading><tt>Section</tt></heading>
2770 This field specifies an application area into which the package
2771 has been classified. See <ref id="subsections">.
2775 When it appears in the <file>debian/control</file> file,
2776 it gives the value for the subfield of the same name in
2777 the <tt>Files</tt> field of the <file>.changes</file> file.
2778 It also gives the default for the same field in the binary
2783 <sect1 id="f-Priority">
2784 <heading><tt>Priority</tt></heading>
2787 This field represents how important it is that the user
2788 have the package installed. See <ref id="priorities">.
2792 When it appears in the <file>debian/control</file> file,
2793 it gives the value for the subfield of the same name in
2794 the <tt>Files</tt> field of the <file>.changes</file> file.
2795 It also gives the default for the same field in the binary
2800 <sect1 id="f-Package">
2801 <heading><tt>Package</tt></heading>
2804 The name of the binary package.
2808 Binary package names must follow the same syntax and
2809 restrictions as source package names. See <ref id="f-Source">
2814 <sect1 id="f-Architecture">
2815 <heading><tt>Architecture</tt></heading>
2818 Depending on context and the control file used, the
2819 <tt>Architecture</tt> field can include the following sets of
2823 A unique single word identifying a Debian machine
2824 architecture as described in <ref id="arch-spec">.
2827 An architecture wildcard identifying a set of Debian
2828 machine architectures, see <ref id="arch-wildcard-spec">.
2829 <tt>any</tt> matches all Debian machine architectures
2830 and is the most frequently used.
2833 <tt>all</tt>, which indicates an
2834 architecture-independent package.
2837 <tt>source</tt>, which indicates a source package.
2843 In the main <file>debian/control</file> file in the source
2844 package, this field may contain the special
2845 value <tt>all</tt>, the special architecture
2846 wildcard <tt>any</tt>, or a list of specific and wildcard
2847 architectures separated by spaces. If <tt>all</tt>
2848 or <tt>any</tt> appears, that value must be the entire
2849 contents of the field. Most packages will use
2850 either <tt>all</tt> or <tt>any</tt>.
2854 Specifying a specific list of architectures indicates that the
2855 source will build an architecture-dependent package only on
2856 architectures included in the list. Specifying a list of
2857 architecture wildcards indicates that the source will build an
2858 architecture-dependent package on only those architectures
2859 that match any of the specified architecture wildcards.
2860 Specifying a list of architectures or architecture wildcards
2861 other than <tt>any</tt> is for the minority of cases where a
2862 program is not portable or is not useful on some
2863 architectures. Where possible, the program should be made
2868 In the source package control file <file>.dsc</file>, this
2869 field may contain either the architecture
2870 wildcard <tt>any</tt> or a list of architectures and
2871 architecture wildcards separated by spaces. If a list is
2872 given, it may include (or consist solely of) the special
2873 value <tt>all</tt>. In other words, in <file>.dsc</file>
2874 files unlike the <file>debian/control</file>, <tt>all</tt> may
2875 occur in combination with specific architectures.
2876 The <tt>Architecture</tt> field in the source package control
2877 file <file>.dsc</file> is generally constructed from
2878 the <tt>Architecture</tt> fields in
2879 the <file>debian/control</file> in the source package.
2883 Specifying <tt>any</tt> indicates that the source package
2884 isn't dependent on any particular architecture and should
2885 compile fine on any one. The produced binary package(s)
2886 will either be specific to whatever the current build
2887 architecture is or will be architecture-independent.
2891 Specifying only <tt>all</tt> indicates that the source package
2892 will only build architecture-independent packages. If this is
2893 the case, <tt>all</tt> must be used rather than <tt>any</tt>;
2894 <tt>any</tt> implies that the source package will build at
2895 least one architecture-dependent package.
2899 Specifying a list of architectures or architecture wildcards
2900 indicates that the source will build an architecture-dependent
2901 package, and will only work correctly on the listed or
2902 matching architectures. If the source package also builds at
2903 least one architecture-independent package, <tt>all</tt> will
2904 also be included in the list.
2908 In a <file>.changes</file> file, the <tt>Architecture</tt>
2909 field lists the architecture(s) of the package(s) currently
2910 being uploaded. This will be a list; if the source for the
2911 package is also being uploaded, the special
2912 entry <tt>source</tt> is also present. <tt>all</tt> will be
2913 present if any architecture-independent packages are being
2914 uploaded. Architecture wildcards such as <tt>any</tt> must
2915 never occur in the <tt>Architecture</tt> field in
2916 the <file>.changes</file> file.
2920 See <ref id="debianrules"> for information on how to get
2921 the architecture for the build process.
2925 <sect1 id="f-Essential">
2926 <heading><tt>Essential</tt></heading>
2929 This is a boolean field which may occur only in the
2930 control file of a binary package or in a per-package fields
2931 paragraph of a main source control data file.
2935 If set to <tt>yes</tt> then the package management system
2936 will refuse to remove the package (upgrading and replacing
2937 it is still possible). The other possible value is <tt>no</tt>,
2938 which is the same as not having the field at all.
2943 <heading>Package interrelationship fields:
2944 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2945 <tt>Recommends</tt>, <tt>Suggests</tt>,
2946 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2947 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2951 These fields describe the package's relationships with
2952 other packages. Their syntax and semantics are described
2953 in <ref id="relationships">.</p>
2956 <sect1 id="f-Standards-Version">
2957 <heading><tt>Standards-Version</tt></heading>
2960 The most recent version of the standards (the policy
2961 manual and associated texts) with which the package
2966 The version number has four components: major and minor
2967 version number and major and minor patch level. When the
2968 standards change in a way that requires every package to
2969 change the major number will be changed. Significant
2970 changes that will require work in many packages will be
2971 signaled by a change to the minor number. The major patch
2972 level will be changed for any change to the meaning of the
2973 standards, however small; the minor patch level will be
2974 changed when only cosmetic, typographical or other edits
2975 are made which neither change the meaning of the document
2976 nor affect the contents of packages.
2980 Thus only the first three components of the policy version
2981 are significant in the <em>Standards-Version</em> control
2982 field, and so either these three components or all four
2983 components may be specified.<footnote>
2984 In the past, people specified the full version number
2985 in the Standards-Version field, for example "2.3.0.0".
2986 Since minor patch-level changes don't introduce new
2987 policy, it was thought it would be better to relax
2988 policy and only require the first 3 components to be
2989 specified, in this example "2.3.0". All four
2990 components may still be used if someone wishes to do so.
2996 <sect1 id="f-Version">
2997 <heading><tt>Version</tt></heading>
3000 The version number of a package. The format is:
3001 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
3005 The three components here are:
3007 <tag><var>epoch</var></tag>
3010 This is a single (generally small) unsigned integer. It
3011 may be omitted, in which case zero is assumed. If it is
3012 omitted then the <var>upstream_version</var> may not
3017 It is provided to allow mistakes in the version numbers
3018 of older versions of a package, and also a package's
3019 previous version numbering schemes, to be left behind.
3023 <tag><var>upstream_version</var></tag>
3026 This is the main part of the version number. It is
3027 usually the version number of the original ("upstream")
3028 package from which the <file>.deb</file> file has been made,
3029 if this is applicable. Usually this will be in the same
3030 format as that specified by the upstream author(s);
3031 however, it may need to be reformatted to fit into the
3032 package management system's format and comparison
3037 The comparison behavior of the package management system
3038 with respect to the <var>upstream_version</var> is
3039 described below. The <var>upstream_version</var>
3040 portion of the version number is mandatory.
3044 The <var>upstream_version</var> may contain only
3045 alphanumerics<footnote>
3046 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3048 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3049 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3050 tilde) and should start with a digit. If there is no
3051 <var>debian_revision</var> then hyphens are not allowed;
3052 if there is no <var>epoch</var> then colons are not
3057 <tag><var>debian_revision</var></tag>
3060 This part of the version number specifies the version of
3061 the Debian package based on the upstream version. It
3062 may contain only alphanumerics and the characters
3063 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3064 tilde) and is compared in the same way as the
3065 <var>upstream_version</var> is.
3069 It is optional; if it isn't present then the
3070 <var>upstream_version</var> may not contain a hyphen.
3071 This format represents the case where a piece of
3072 software was written specifically to be a Debian
3073 package, where the Debian package source must always
3074 be identical to the pristine source and therefore no
3075 revision indication is required.
3079 It is conventional to restart the
3080 <var>debian_revision</var> at <tt>1</tt> each time the
3081 <var>upstream_version</var> is increased.
3085 The package management system will break the version
3086 number apart at the last hyphen in the string (if there
3087 is one) to determine the <var>upstream_version</var> and
3088 <var>debian_revision</var>. The absence of a
3089 <var>debian_revision</var> is equivalent to a
3090 <var>debian_revision</var> of <tt>0</tt>.
3097 When comparing two version numbers, first the <var>epoch</var>
3098 of each are compared, then the <var>upstream_version</var> if
3099 <var>epoch</var> is equal, and then <var>debian_revision</var>
3100 if <var>upstream_version</var> is also equal.
3101 <var>epoch</var> is compared numerically. The
3102 <var>upstream_version</var> and <var>debian_revision</var>
3103 parts are compared by the package management system using the
3104 following algorithm:
3108 The strings are compared from left to right.
3112 First the initial part of each string consisting entirely of
3113 non-digit characters is determined. These two parts (one of
3114 which may be empty) are compared lexically. If a difference
3115 is found it is returned. The lexical comparison is a
3116 comparison of ASCII values modified so that all the letters
3117 sort earlier than all the non-letters and so that a tilde
3118 sorts before anything, even the end of a part. For example,
3119 the following parts are in sorted order from earliest to
3120 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3121 <tt>a</tt>.<footnote>
3122 One common use of <tt>~</tt> is for upstream pre-releases.
3123 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3124 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3129 Then the initial part of the remainder of each string which
3130 consists entirely of digit characters is determined. The
3131 numerical values of these two parts are compared, and any
3132 difference found is returned as the result of the comparison.
3133 For these purposes an empty string (which can only occur at
3134 the end of one or both version strings being compared) counts
3139 These two steps (comparing and removing initial non-digit
3140 strings and initial digit strings) are repeated until a
3141 difference is found or both strings are exhausted.
3145 Note that the purpose of epochs is to allow us to leave behind
3146 mistakes in version numbering, and to cope with situations
3147 where the version numbering scheme changes. It is
3148 <em>not</em> intended to cope with version numbers containing
3149 strings of letters which the package management system cannot
3150 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3151 silly orderings.<footnote>
3152 The author of this manual has heard of a package whose
3153 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3154 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3160 <sect1 id="f-Description">
3161 <heading><tt>Description</tt></heading>
3164 In a source or binary control file, the <tt>Description</tt>
3165 field contains a description of the binary package, consisting
3166 of two parts, the synopsis or the short description, and the
3167 long description. The field's format is as follows:
3172 Description: <single line synopsis>
3173 <extended description over several lines>
3178 The lines in the extended description can have these formats:
3184 Those starting with a single space are part of a paragraph.
3185 Successive lines of this form will be word-wrapped when
3186 displayed. The leading space will usually be stripped off.
3190 Those starting with two or more spaces. These will be
3191 displayed verbatim. If the display cannot be panned
3192 horizontally, the displaying program will line wrap them "hard"
3193 (i.e., without taking account of word breaks). If it can they
3194 will be allowed to trail off to the right. None, one or two
3195 initial spaces may be deleted, but the number of spaces
3196 deleted from each line will be the same (so that you can have
3197 indenting work correctly, for example).
3201 Those containing a single space followed by a single full stop
3202 character. These are rendered as blank lines. This is the
3203 <em>only</em> way to get a blank line<footnote>
3204 Completely empty lines will not be rendered as blank lines.
3205 Instead, they will cause the parser to think you're starting
3206 a whole new record in the control file, and will therefore
3207 likely abort with an error.
3212 Those containing a space, a full stop and some more characters.
3213 These are for future expansion. Do not use them.
3219 Do not use tab characters. Their effect is not predictable.
3223 See <ref id="descriptions"> for further information on this.
3227 In a <file>.changes</file> file, the <tt>Description</tt>
3228 field contains a summary of the descriptions for the packages
3229 being uploaded. For this case, the first line of the field
3230 value (the part on the same line as <tt>Description:</tt>) is
3231 always empty. The content of the field is expressed as
3232 continuation lines, one line per package. Each line is
3233 indented by one space and contains the name of a binary
3234 package, a space, a hyphen (<tt>-</tt>), a space, and the
3235 short description line from that package.
3239 <sect1 id="f-Distribution">
3240 <heading><tt>Distribution</tt></heading>
3243 In a <file>.changes</file> file or parsed changelog output
3244 this contains the (space-separated) name(s) of the
3245 distribution(s) where this version of the package should
3246 be installed. Valid distributions are determined by the
3247 archive maintainers.<footnote>
3248 Example distribution names in the Debian archive used in
3249 <file>.changes</file> files are:
3250 <taglist compact="compact">
3251 <tag><em>unstable</em></tag>
3253 This distribution value refers to the
3254 <em>developmental</em> part of the Debian distribution
3255 tree. Most new packages, new upstream versions of
3256 packages and bug fixes go into the <em>unstable</em>
3260 <tag><em>experimental</em></tag>
3262 The packages with this distribution value are deemed
3263 by their maintainers to be high risk. Oftentimes they
3264 represent early beta or developmental packages from
3265 various sources that the maintainers want people to
3266 try, but are not ready to be a part of the other parts
3267 of the Debian distribution tree.
3272 Others are used for updating stable releases or for
3273 security uploads. More information is available in the
3274 Debian Developer's Reference, section "The Debian
3278 The Debian archive software only supports listing a single
3279 distribution. Migration of packages to other distributions is
3280 handled outside of the upload process.
3285 <heading><tt>Date</tt></heading>
3288 This field includes the date the package was built or last
3289 edited. It must be in the same format as the <var>date</var>
3290 in a <file>debian/changelog</file> entry.
3294 The value of this field is usually extracted from the
3295 <file>debian/changelog</file> file - see
3296 <ref id="dpkgchangelog">).
3300 <sect1 id="f-Format">
3301 <heading><tt>Format</tt></heading>
3304 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3305 files, this field declares the format version of that file.
3306 The syntax of the field value is the same as that of
3307 a <qref id="f-Version">package version number</qref> except
3308 that no epoch or Debian revision is allowed. The format
3309 described in this document is <tt>&changesversion;</tt>.
3313 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3314 Debian source control</qref> files, this field declares the
3315 format of the source package. The field value is used by
3316 programs acting on a source package to interpret the list of
3317 files in the source package and determine how to unpack it.
3318 The syntax of the field value is a numeric major revision, a
3319 period, a numeric minor revision, and then an optional subtype
3320 after whitespace, which if specified is an alphanumeric word
3321 in parentheses. The subtype is optional in the syntax but may
3322 be mandatory for particular source format revisions.
3324 The source formats currently supported by the Debian archive
3325 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3326 and <tt>3.0 (quilt)</tt>.
3331 <sect1 id="f-Urgency">
3332 <heading><tt>Urgency</tt></heading>
3335 This is a description of how important it is to upgrade to
3336 this version from previous ones. It consists of a single
3337 keyword taking one of the values <tt>low</tt>,
3338 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3339 <tt>critical</tt><footnote>
3340 Other urgency values are supported with configuration
3341 changes in the archive software but are not used in Debian.
3342 The urgency affects how quickly a package will be considered
3343 for inclusion into the <tt>testing</tt> distribution and
3344 gives an indication of the importance of any fixes included
3345 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3346 treated as synonymous.
3347 </footnote> (not case-sensitive) followed by an optional
3348 commentary (separated by a space) which is usually in
3349 parentheses. For example:
3352 Urgency: low (HIGH for users of diversions)
3358 The value of this field is usually extracted from the
3359 <file>debian/changelog</file> file - see
3360 <ref id="dpkgchangelog">.
3364 <sect1 id="f-Changes">
3365 <heading><tt>Changes</tt></heading>
3368 This field contains the human-readable changes data, describing
3369 the differences between the last version and the current one.
3373 The first line of the field value (the part on the same line
3374 as <tt>Changes:</tt>) is always empty. The content of the
3375 field is expressed as continuation lines, with each line
3376 indented by at least one space. Blank lines must be
3377 represented by a line consisting only of a space and a full
3382 The value of this field is usually extracted from the
3383 <file>debian/changelog</file> file - see
3384 <ref id="dpkgchangelog">).
3388 Each version's change information should be preceded by a
3389 "title" line giving at least the version, distribution(s)
3390 and urgency, in a human-readable way.
3394 If data from several versions is being returned the entry
3395 for the most recent version should be returned first, and
3396 entries should be separated by the representation of a
3397 blank line (the "title" line may also be followed by the
3398 representation of a blank line).
3402 <sect1 id="f-Binary">
3403 <heading><tt>Binary</tt></heading>
3406 This field is a list of binary packages. Its syntax and
3407 meaning varies depending on the control file in which it
3412 When it appears in the <file>.dsc</file> file, it lists binary
3413 packages which a source package can produce, separated by
3415 A space after each comma is conventional.
3416 </footnote>. It may span multiple lines. The source package
3417 does not necessarily produce all of these binary packages for
3418 every architecture. The source control file doesn't contain
3419 details of which architectures are appropriate for which of
3420 the binary packages.
3424 When it appears in a <file>.changes</file> file, it lists the
3425 names of the binary packages being uploaded, separated by
3426 whitespace (not commas). It may span multiple lines.
3430 <sect1 id="f-Installed-Size">
3431 <heading><tt>Installed-Size</tt></heading>
3434 This field appears in the control files of binary packages,
3435 and in the <file>Packages</file> files. It gives an estimate
3436 of the total amount of disk space required to install the
3437 named package. Actual installed size may vary based on block
3438 size, file system properties, or actions taken by package
3443 The disk space is given as the integer value of the estimated
3444 installed size in bytes, divided by 1024 and rounded up.
3448 <sect1 id="f-Files">
3449 <heading><tt>Files</tt></heading>
3452 This field contains a list of files with information about
3453 each one. The exact information and syntax varies with
3458 In all cases, Files is a multiline field. The first line of
3459 the field value (the part on the same line as <tt>Files:</tt>)
3460 is always empty. The content of the field is expressed as
3461 continuation lines, one line per file. Each line must be
3462 indented by one space and contain a number of sub-fields,
3463 separated by spaces, as described below.
3467 In the <file>.dsc</file> file, each line contains the MD5
3468 checksum, size and filename of the tar file and (if
3469 applicable) diff file which make up the remainder of the
3470 source package<footnote>
3471 That is, the parts which are not the <tt>.dsc</tt>.
3472 </footnote>. For example:
3475 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3476 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3478 The exact forms of the filenames are described
3479 in <ref id="pkg-sourcearchives">.
3483 In the <file>.changes</file> file this contains one line per
3484 file being uploaded. Each line contains the MD5 checksum,
3485 size, section and priority and the filename. For example:
3488 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3489 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3490 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3491 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3493 The <qref id="f-Section">section</qref>
3494 and <qref id="f-Priority">priority</qref> are the values of
3495 the corresponding fields in the main source control file. If
3496 no section or priority is specified then <tt>-</tt> should be
3497 used, though section and priority values must be specified for
3498 new packages to be installed properly.
3502 The special value <tt>byhand</tt> for the section in a
3503 <tt>.changes</tt> file indicates that the file in question
3504 is not an ordinary package file and must by installed by
3505 hand by the distribution maintainers. If the section is
3506 <tt>byhand</tt> the priority should be <tt>-</tt>.
3510 If a new Debian revision of a package is being shipped and
3511 no new original source archive is being distributed the
3512 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3513 entry for the original source archive
3514 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3515 but the <file>.changes</file> file should leave it out. In
3516 this case the original source archive on the distribution
3517 site must match exactly, byte-for-byte, the original
3518 source archive which was used to generate the
3519 <file>.dsc</file> file and diff which are being uploaded.</p>
3522 <sect1 id="f-Closes">
3523 <heading><tt>Closes</tt></heading>
3526 A space-separated list of bug report numbers that the upload
3527 governed by the .changes file closes.
3531 <sect1 id="f-Homepage">
3532 <heading><tt>Homepage</tt></heading>
3535 The URL of the web site for this package, preferably (when
3536 applicable) the site from which the original source can be
3537 obtained and any additional upstream documentation or
3538 information may be found. The content of this field is a
3539 simple URL without any surrounding characters such as
3544 <sect1 id="f-Checksums">
3545 <heading><tt>Checksums-Sha1</tt>
3546 and <tt>Checksums-Sha256</tt></heading>
3549 These fields contain a list of files with a checksum and size
3550 for each one. Both <tt>Checksums-Sha1</tt>
3551 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3552 only in the checksum algorithm used: SHA-1
3553 for <tt>Checksums-Sha1</tt> and SHA-256
3554 for <tt>Checksums-Sha256</tt>.
3558 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3559 multiline fields. The first line of the field value (the part
3560 on the same line as <tt>Checksums-Sha1:</tt>
3561 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3562 of the field is expressed as continuation lines, one line per
3563 file. Each line consists of the checksum, a space, the file
3564 size, a space, and the file name. For example (from
3565 a <file>.changes</file> file):
3568 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3569 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3570 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3571 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3573 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3574 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3575 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3576 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3581 In the <file>.dsc</file> file, these fields should list all
3582 files that make up the source package. In
3583 the <file>.changes</file> file, these fields should list all
3584 files being uploaded. The list of files in these fields
3585 must match the list of files in the <tt>Files</tt> field.
3591 <heading>User-defined fields</heading>
3594 Additional user-defined fields may be added to the
3595 source package control file. Such fields will be
3596 ignored, and not copied to (for example) binary or
3597 source package control files or upload control files.
3601 If you wish to add additional unsupported fields to
3602 these output files you should use the mechanism
3607 Fields in the main source control information file with
3608 names starting <tt>X</tt>, followed by one or more of
3609 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3610 be copied to the output files. Only the part of the
3611 field name after the hyphen will be used in the output
3612 file. Where the letter <tt>B</tt> is used the field
3613 will appear in binary package control files, where the
3614 letter <tt>S</tt> is used in source package control
3615 files and where <tt>C</tt> is used in upload control
3616 (<tt>.changes</tt>) files.
3620 For example, if the main source information control file
3623 XBS-Comment: I stand between the candle and the star.
3625 then the binary and source package control files will contain the
3628 Comment: I stand between the candle and the star.
3637 <chapt id="maintainerscripts">
3638 <heading>Package maintainer scripts and installation procedure</heading>
3641 <heading>Introduction to package maintainer scripts</heading>
3644 It is possible to supply scripts as part of a package which
3645 the package management system will run for you when your
3646 package is installed, upgraded or removed.
3650 These scripts are the control information
3651 files <prgn>preinst</prgn>, <prgn>postinst</prgn>, <prgn>prerm</prgn>
3652 and <prgn>postrm</prgn>. They must be proper executable files;
3653 if they are scripts (which is recommended), they must start with
3654 the usual <tt>#!</tt> convention. They should be readable and
3655 executable by anyone, and must not be world-writable.
3659 The package management system looks at the exit status from
3660 these scripts. It is important that they exit with a
3661 non-zero status if there is an error, so that the package
3662 management system can stop its processing. For shell
3663 scripts this means that you <em>almost always</em> need to
3664 use <tt>set -e</tt> (this is usually true when writing shell
3665 scripts, in fact). It is also important, of course, that
3666 they exit with a zero status if everything went well.
3670 Additionally, packages interacting with users
3671 using <prgn>debconf</prgn> in the <prgn>postinst</prgn> script
3672 should install a <prgn>config</prgn> script as a control
3673 information file. See <ref id="maintscriptprompt"> for details.
3677 When a package is upgraded a combination of the scripts from
3678 the old and new packages is called during the upgrade
3679 procedure. If your scripts are going to be at all
3680 complicated you need to be aware of this, and may need to
3681 check the arguments to your scripts.
3685 Broadly speaking the <prgn>preinst</prgn> is called before
3686 (a particular version of) a package is installed, and the
3687 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3688 before (a version of) a package is removed and the
3689 <prgn>postrm</prgn> afterwards.
3693 Programs called from maintainer scripts should not normally
3694 have a path prepended to them. Before installation is
3695 started, the package management system checks to see if the
3696 programs <prgn>ldconfig</prgn>,
3697 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3698 and <prgn>update-rc.d</prgn> can be found via the
3699 <tt>PATH</tt> environment variable. Those programs, and any
3700 other program that one would expect to be in the
3701 <tt>PATH</tt>, should thus be invoked without an absolute
3702 pathname. Maintainer scripts should also not reset the
3703 <tt>PATH</tt>, though they might choose to modify it by
3704 prepending or appending package-specific directories. These
3705 considerations really apply to all shell scripts.</p>
3708 <sect id="idempotency">
3709 <heading>Maintainer scripts idempotency</heading>
3712 It is necessary for the error recovery procedures that the
3713 scripts be idempotent. This means that if it is run
3714 successfully, and then it is called again, it doesn't bomb
3715 out or cause any harm, but just ensures that everything is
3716 the way it ought to be. If the first call failed, or
3717 aborted half way through for some reason, the second call
3718 should merely do the things that were left undone the first
3719 time, if any, and exit with a success status if everything
3721 This is so that if an error occurs, the user interrupts
3722 <prgn>dpkg</prgn> or some other unforeseen circumstance
3723 happens you don't leave the user with a badly-broken
3724 package when <prgn>dpkg</prgn> attempts to repeat the
3730 <sect id="controllingterminal">
3731 <heading>Controlling terminal for maintainer scripts</heading>
3734 Maintainer scripts are not guaranteed to run with a controlling
3735 terminal and may not be able to interact with the user. They
3736 must be able to fall back to noninteractive behavior if no
3737 controlling terminal is available. Maintainer scripts that
3738 prompt via a program conforming to the Debian Configuration
3739 Management Specification (see <ref id="maintscriptprompt">) may
3740 assume that program will handle falling back to noninteractive
3745 For high-priority prompts without a reasonable default answer,
3746 maintainer scripts may abort if there is no controlling
3747 terminal. However, this situation should be avoided if at all
3748 possible, since it prevents automated or unattended installs.
3749 In most cases, users will consider this to be a bug in the
3754 <sect id="exitstatus">
3755 <heading>Exit status</heading>
3758 Each script must return a zero exit status for
3759 success, or a nonzero one for failure, since the package
3760 management system looks for the exit status of these scripts
3761 and determines what action to take next based on that datum.
3765 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3770 <list compact="compact">
3772 <var>new-preinst</var> <tt>install</tt>
3775 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3778 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3781 <var>old-preinst</var> <tt>abort-upgrade</tt>
3782 <var>new-version</var>
3787 <list compact="compact">
3789 <var>postinst</var> <tt>configure</tt>
3790 <var>most-recently-configured-version</var>
3793 <var>old-postinst</var> <tt>abort-upgrade</tt>
3794 <var>new-version</var>
3797 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3798 <tt>in-favour</tt> <var>package</var>
3799 <var>new-version</var>
3802 <var>postinst</var> <tt>abort-remove</tt>
3805 <var>deconfigured's-postinst</var>
3806 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3807 <var>failed-install-package</var> <var>version</var>
3808 [<tt>removing</tt> <var>conflicting-package</var>
3814 <list compact="compact">
3816 <var>prerm</var> <tt>remove</tt>
3819 <var>old-prerm</var> <tt>upgrade</tt>
3820 <var>new-version</var>
3823 <var>new-prerm</var> <tt>failed-upgrade</tt>
3824 <var>old-version</var>
3827 <var>conflictor's-prerm</var> <tt>remove</tt>
3828 <tt>in-favour</tt> <var>package</var>
3829 <var>new-version</var>
3832 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3833 <tt>in-favour</tt> <var>package-being-installed</var>
3834 <var>version</var> [<tt>removing</tt>
3835 <var>conflicting-package</var>
3841 <list compact="compact">
3843 <var>postrm</var> <tt>remove</tt>
3846 <var>postrm</var> <tt>purge</tt>
3849 <var>old-postrm</var> <tt>upgrade</tt>
3850 <var>new-version</var>
3853 <var>new-postrm</var> <tt>failed-upgrade</tt>
3854 <var>old-version</var>
3857 <var>new-postrm</var> <tt>abort-install</tt>
3860 <var>new-postrm</var> <tt>abort-install</tt>
3861 <var>old-version</var>
3864 <var>new-postrm</var> <tt>abort-upgrade</tt>
3865 <var>old-version</var>
3868 <var>disappearer's-postrm</var> <tt>disappear</tt>
3869 <var>overwriter</var>
3870 <var>overwriter-version</var>
3876 <sect id="unpackphase">
3877 <heading>Details of unpack phase of installation or upgrade</heading>
3880 The procedure on installation/upgrade/overwrite/disappear
3881 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3882 stage of <tt>dpkg --install</tt>) is as follows. In each
3883 case, if a major error occurs (unless listed below) the
3884 actions are, in general, run backwards - this means that the
3885 maintainer scripts are run with different arguments in
3886 reverse order. These are the "error unwind" calls listed
3893 If a version of the package is already installed, call
3894 <example compact="compact">
3895 <var>old-prerm</var> upgrade <var>new-version</var>
3899 If the script runs but exits with a non-zero
3900 exit status, <prgn>dpkg</prgn> will attempt:
3901 <example compact="compact">
3902 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3904 If this works, the upgrade continues. If this
3905 does not work, the error unwind:
3906 <example compact="compact">
3907 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3909 If this works, then the old-version is
3910 "Installed", if not, the old version is in a
3911 "Half-Configured" state.
3917 If a "conflicting" package is being removed at the same time,
3918 or if any package will be broken (due to <tt>Breaks</tt>):
3921 If <tt>--auto-deconfigure</tt> is
3922 specified, call, for each package to be deconfigured
3923 due to <tt>Breaks</tt>:
3924 <example compact="compact">
3925 <var>deconfigured's-prerm</var> deconfigure \
3926 in-favour <var>package-being-installed</var> <var>version</var>
3929 <example compact="compact">
3930 <var>deconfigured's-postinst</var> abort-deconfigure \
3931 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3933 The deconfigured packages are marked as
3934 requiring configuration, so that if
3935 <tt>--install</tt> is used they will be
3936 configured again if possible.
3939 If any packages depended on a conflicting
3940 package being removed and <tt>--auto-deconfigure</tt> is
3941 specified, call, for each such package:
3942 <example compact="compact">
3943 <var>deconfigured's-prerm</var> deconfigure \
3944 in-favour <var>package-being-installed</var> <var>version</var> \
3945 removing <var>conflicting-package</var> <var>version</var>
3948 <example compact="compact">
3949 <var>deconfigured's-postinst</var> abort-deconfigure \
3950 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3951 removing <var>conflicting-package</var> <var>version</var>
3953 The deconfigured packages are marked as
3954 requiring configuration, so that if
3955 <tt>--install</tt> is used they will be
3956 configured again if possible.
3959 To prepare for removal of each conflicting package, call:
3960 <example compact="compact">
3961 <var>conflictor's-prerm</var> remove \
3962 in-favour <var>package</var> <var>new-version</var>
3965 <example compact="compact">
3966 <var>conflictor's-postinst</var> abort-remove \
3967 in-favour <var>package</var> <var>new-version</var>
3976 If the package is being upgraded, call:
3977 <example compact="compact">
3978 <var>new-preinst</var> upgrade <var>old-version</var>
3980 If this fails, we call:
3982 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3989 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3991 is called. If this works, then the old version
3992 is in an "Installed" state, or else it is left
3993 in an "Unpacked" state.
3998 If it fails, then the old version is left
3999 in an "Half-Installed" state.
4006 Otherwise, if the package had some configuration
4007 files from a previous version installed (i.e., it
4008 is in the "configuration files only" state):
4009 <example compact="compact">
4010 <var>new-preinst</var> install <var>old-version</var>
4014 <var>new-postrm</var> abort-install <var>old-version</var>
4016 If this fails, the package is left in a
4017 "Half-Installed" state, which requires a
4018 reinstall. If it works, the packages is left in
4019 a "Config-Files" state.
4022 Otherwise (i.e., the package was completely purged):
4023 <example compact="compact">
4024 <var>new-preinst</var> install
4027 <example compact="compact">
4028 <var>new-postrm</var> abort-install
4030 If the error-unwind fails, the package is in a
4031 "Half-Installed" phase, and requires a
4032 reinstall. If the error unwind works, the
4033 package is in a not installed state.
4040 The new package's files are unpacked, overwriting any
4041 that may be on the system already, for example any
4042 from the old version of the same package or from
4043 another package. Backups of the old files are kept
4044 temporarily, and if anything goes wrong the package
4045 management system will attempt to put them back as
4046 part of the error unwind.
4050 It is an error for a package to contain files which
4051 are on the system in another package, unless
4052 <tt>Replaces</tt> is used (see <ref id="replaces">).
4054 The following paragraph is not currently the case:
4055 Currently the <tt>- - force-overwrite</tt> flag is
4056 enabled, downgrading it to a warning, but this may not
4062 It is a more serious error for a package to contain a
4063 plain file or other kind of non-directory where another
4064 package has a directory (again, unless
4065 <tt>Replaces</tt> is used). This error can be
4066 overridden if desired using
4067 <tt>--force-overwrite-dir</tt>, but this is not
4072 Packages which overwrite each other's files produce
4073 behavior which, though deterministic, is hard for the
4074 system administrator to understand. It can easily
4075 lead to "missing" programs if, for example, a package
4076 is installed which overwrites a file from another
4077 package, and is then removed again.<footnote>
4078 Part of the problem is due to what is arguably a
4079 bug in <prgn>dpkg</prgn>.
4084 A directory will never be replaced by a symbolic link
4085 to a directory or vice versa; instead, the existing
4086 state (symlink or not) will be left alone and
4087 <prgn>dpkg</prgn> will follow the symlink if there is
4096 If the package is being upgraded, call
4097 <example compact="compact">
4098 <var>old-postrm</var> upgrade <var>new-version</var>
4102 If this fails, <prgn>dpkg</prgn> will attempt:
4103 <example compact="compact">
4104 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4106 If this works, installation continues. If not,
4108 <example compact="compact">
4109 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4111 If this fails, the old version is left in a
4112 "Half-Installed" state. If it works, dpkg now
4114 <example compact="compact">
4115 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4117 If this fails, the old version is left in a
4118 "Half-Installed" state. If it works, dpkg now
4120 <example compact="compact">
4121 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4123 If this fails, the old version is in an
4130 This is the point of no return - if
4131 <prgn>dpkg</prgn> gets this far, it won't back off
4132 past this point if an error occurs. This will
4133 leave the package in a fairly bad state, which
4134 will require a successful re-installation to clear
4135 up, but it's when <prgn>dpkg</prgn> starts doing
4136 things that are irreversible.
4141 Any files which were in the old version of the package
4142 but not in the new are removed.
4146 The new file list replaces the old.
4150 The new maintainer scripts replace the old.
4154 Any packages all of whose files have been overwritten
4155 during the installation, and which aren't required for
4156 dependencies, are considered to have been removed.
4157 For each such package
4160 <prgn>dpkg</prgn> calls:
4161 <example compact="compact">
4162 <var>disappearer's-postrm</var> disappear \
4163 <var>overwriter</var> <var>overwriter-version</var>
4167 The package's maintainer scripts are removed.
4170 It is noted in the status database as being in a
4171 sane state, namely not installed (any conffiles
4172 it may have are ignored, rather than being
4173 removed by <prgn>dpkg</prgn>). Note that
4174 disappearing packages do not have their prerm
4175 called, because <prgn>dpkg</prgn> doesn't know
4176 in advance that the package is going to
4183 Any files in the package we're unpacking that are also
4184 listed in the file lists of other packages are removed
4185 from those lists. (This will lobotomize the file list
4186 of the "conflicting" package if there is one.)
4190 The backup files made during installation, above, are
4196 The new package's status is now sane, and recorded as
4201 Here is another point of no return - if the
4202 conflicting package's removal fails we do not unwind
4203 the rest of the installation; the conflicting package
4204 is left in a half-removed limbo.
4209 If there was a conflicting package we go and do the
4210 removal actions (described below), starting with the
4211 removal of the conflicting package's files (any that
4212 are also in the package being installed have already
4213 been removed from the conflicting package's file list,
4214 and so do not get removed now).
4220 <sect id="configdetails"><heading>Details of configuration</heading>
4223 When we configure a package (this happens with <tt>dpkg
4224 --install</tt> and <tt>dpkg --configure</tt>), we first
4225 update any <tt>conffile</tt>s and then call:
4226 <example compact="compact">
4227 <var>postinst</var> configure <var>most-recently-configured-version</var>
4232 No attempt is made to unwind after errors during
4233 configuration. If the configuration fails, the package is in
4234 a "Failed Config" state, and an error message is generated.
4238 If there is no most recently configured version
4239 <prgn>dpkg</prgn> will pass a null argument.
4242 Historical note: Truly ancient (pre-1997) versions of
4243 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4244 (including the angle brackets) in this case. Even older
4245 ones did not pass a second argument at all, under any
4246 circumstance. Note that upgrades using such an old dpkg
4247 version are unlikely to work for other reasons, even if
4248 this old argument behavior is handled by your postinst script.
4254 <sect id="removedetails"><heading>Details of removal and/or
4255 configuration purging</heading>
4261 <example compact="compact">
4262 <var>prerm</var> remove
4266 If prerm fails during replacement due to conflict
4268 <var>conflictor's-postinst</var> abort-remove \
4269 in-favour <var>package</var> <var>new-version</var>
4273 <var>postinst</var> abort-remove
4277 If this fails, the package is in a "Half-Configured"
4278 state, or else it remains "Installed".
4282 The package's files are removed (except <tt>conffile</tt>s).
4285 <example compact="compact">
4286 <var>postrm</var> remove
4290 If it fails, there's no error unwind, and the package is in
4291 an "Half-Installed" state.
4296 All the maintainer scripts except the <prgn>postrm</prgn>
4301 If we aren't purging the package we stop here. Note
4302 that packages which have no <prgn>postrm</prgn> and no
4303 <tt>conffile</tt>s are automatically purged when
4304 removed, as there is no difference except for the
4305 <prgn>dpkg</prgn> status.
4309 The <tt>conffile</tt>s and any backup files
4310 (<tt>~</tt>-files, <tt>#*#</tt> files,
4311 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4316 <example compact="compact">
4317 <var>postrm</var> purge
4321 If this fails, the package remains in a "Config-Files"
4326 The package's file list is removed.
4335 <chapt id="relationships">
4336 <heading>Declaring relationships between packages</heading>
4338 <sect id="depsyntax">
4339 <heading>Syntax of relationship fields</heading>
4342 These fields all have a uniform syntax. They are a list of
4343 package names separated by commas.
4347 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4348 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4349 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4350 control fields of the package, which declare
4351 dependencies on other packages, the package names listed may
4352 also include lists of alternative package names, separated
4353 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4354 if any one of the alternative packages is installed, that
4355 part of the dependency is considered to be satisfied.
4359 All of the fields except for <tt>Provides</tt> may restrict
4360 their applicability to particular versions of each named
4361 package. This is done in parentheses after each individual
4362 package name; the parentheses should contain a relation from
4363 the list below followed by a version number, in the format
4364 described in <ref id="f-Version">.
4368 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4369 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4370 strictly earlier, earlier or equal, exactly equal, later or
4371 equal and strictly later, respectively. The deprecated
4372 forms <tt><</tt> and <tt>></tt> were used to mean
4373 earlier/later or equal, rather than strictly earlier/later,
4374 so they should not appear in new packages (though
4375 <prgn>dpkg</prgn> still supports them).
4379 Whitespace may appear at any point in the version
4380 specification subject to the rules in <ref
4381 id="controlsyntax">, and must appear where it's necessary to
4382 disambiguate; it is not otherwise significant. All of the
4383 relationship fields may span multiple lines. For
4384 consistency and in case of future changes to
4385 <prgn>dpkg</prgn> it is recommended that a single space be
4386 used after a version relationship and before a version
4387 number; it is also conventional to put a single space after
4388 each comma, on either side of each vertical bar, and before
4389 each open parenthesis. When wrapping a relationship field, it
4390 is conventional to do so after a comma and before the space
4391 following that comma.
4395 For example, a list of dependencies might appear as:
4396 <example compact="compact">
4399 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4404 Relationships may be restricted to a certain set of
4405 architectures. This is indicated in brackets after each
4406 individual package name and the optional version specification.
4407 The brackets enclose a list of Debian architecture names
4408 separated by whitespace. Exclamation marks may be prepended to
4409 each of the names. (It is not permitted for some names to be
4410 prepended with exclamation marks while others aren't.)
4414 For build relationship fields
4415 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4416 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>), if
4417 the current Debian host architecture is not in this list and
4418 there are no exclamation marks in the list, or it is in the list
4419 with a prepended exclamation mark, the package name and the
4420 associated version specification are ignored completely for the
4421 purposes of defining the relationships.
4426 <example compact="compact">
4428 Build-Depends-Indep: texinfo
4429 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4430 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4432 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4433 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4434 <tt>gnumach-dev</tt> only on hurd-i386.
4438 For binary relationship fields, the architecture restriction
4439 syntax is only supported in the source package control
4440 file <file>debian/control</file>. When the corresponding binary
4441 package control file is generated, the relationship will either
4442 be omitted or included without the architecture restriction
4443 based on the architecture of the binary package. This means
4444 that architecture restrictions must not be used in binary
4445 relationship fields for architecture-independent packages
4446 (<tt>Architecture: all</tt>).
4451 <example compact="compact">
4452 Depends: foo [i386], bar [amd64]
4454 becomes <tt>Depends: foo</tt> when the package is built on
4455 the <tt>i386</tt> architecture, <tt>Depends: bar</tt> when the
4456 package is built on the <tt>amd64</tt> architecture, and omitted
4457 entirely in binary packages built on all other architectures.
4461 If the architecture-restricted dependency is part of a set of
4462 alternatives using <tt>|</tt>, that alternative is ignored
4463 completely on architectures that do not match the restriction.
4465 <example compact="compact">
4466 Build-Depends: foo [!i386] | bar [!amd64]
4468 is equivalent to <tt>bar</tt> on the i386 architecture, to
4469 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4470 bar</tt> on all other architectures.
4474 Relationships may also be restricted to a certain set of
4475 architectures using architecture wildcards. The syntax for
4476 declaring such restrictions is the same as declaring
4477 restrictions using a certain set of architectures without
4478 architecture wildcards. For example:
4479 <example compact="compact">
4480 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4482 is equivalent to <tt>foo</tt> on architectures using the Linux
4483 kernel and any cpu, <tt>bar</tt> on architectures using any
4484 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4485 using a kernel other than Linux.
4489 Note that the binary package relationship fields such as
4490 <tt>Depends</tt> appear in one of the binary package
4491 sections of the control file, whereas the build-time
4492 relationships such as <tt>Build-Depends</tt> appear in the
4493 source package section of the control file (which is the
4498 <sect id="binarydeps">
4499 <heading>Binary Dependencies - <tt>Depends</tt>,
4500 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4501 <tt>Pre-Depends</tt>
4505 Packages can declare in their control file that they have
4506 certain relationships to other packages - for example, that
4507 they may not be installed at the same time as certain other
4508 packages, and/or that they depend on the presence of others.
4512 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4513 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4514 <tt>Breaks</tt> and <tt>Conflicts</tt> control fields.
4515 <tt>Breaks</tt> is described in <ref id="breaks">, and
4516 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4517 rest are described below.
4521 These seven fields are used to declare a dependency
4522 relationship by one package on another. Except for
4523 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4524 depending (binary) package's control file.
4525 (<tt>Enhances</tt> appears in the recommending package's
4526 control file, and <tt>Breaks</tt> appears in the version of
4527 depended-on package which causes the named package to
4532 A <tt>Depends</tt> field takes effect <em>only</em> when a
4533 package is to be configured. It does not prevent a package
4534 being on the system in an unconfigured state while its
4535 dependencies are unsatisfied, and it is possible to replace
4536 a package whose dependencies are satisfied and which is
4537 properly installed with a different version whose
4538 dependencies are not and cannot be satisfied; when this is
4539 done the depending package will be left unconfigured (since
4540 attempts to configure it will give errors) and will not
4541 function properly. If it is necessary, a
4542 <tt>Pre-Depends</tt> field can be used, which has a partial
4543 effect even when a package is being unpacked, as explained
4544 in detail below. (The other three dependency fields,
4545 <tt>Recommends</tt>, <tt>Suggests</tt> and
4546 <tt>Enhances</tt>, are only used by the various front-ends
4547 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4548 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4552 For this reason packages in an installation run are usually
4553 all unpacked first and all configured later; this gives
4554 later versions of packages with dependencies on later
4555 versions of other packages the opportunity to have their
4556 dependencies satisfied.
4560 In case of circular dependencies, since installation or
4561 removal order honoring the dependency order can't be
4562 established, dependency loops are broken at some point
4563 (based on rules below), and some packages may not be able to
4564 rely on their dependencies being present when being
4565 installed or removed, depending on which side of the break
4566 of the circular dependency loop they happen to be on. If one
4567 of the packages in the loop has no postinst script, then the
4568 cycle will be broken at that package, so as to ensure that
4569 all postinst scripts run with the dependencies properly
4570 configured if this is possible. Otherwise the breaking point
4575 The <tt>Depends</tt> field thus allows package maintainers
4576 to impose an order in which packages should be configured.
4580 The meaning of the five dependency fields is as follows:
4582 <tag><tt>Depends</tt></tag>
4585 This declares an absolute dependency. A package will
4586 not be configured unless all of the packages listed in
4587 its <tt>Depends</tt> field have been correctly
4592 The <tt>Depends</tt> field should be used if the
4593 depended-on package is required for the depending
4594 package to provide a significant amount of
4599 The <tt>Depends</tt> field should also be used if the
4600 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4601 <prgn>postrm</prgn> scripts require the package to be
4602 present in order to run. Note, however, that the
4603 <prgn>postrm</prgn> cannot rely on any non-essential
4604 packages to be present during the <tt>purge</tt>
4608 <tag><tt>Recommends</tt></tag>
4611 This declares a strong, but not absolute, dependency.
4615 The <tt>Recommends</tt> field should list packages
4616 that would be found together with this one in all but
4617 unusual installations.
4621 <tag><tt>Suggests</tt></tag>
4623 This is used to declare that one package may be more
4624 useful with one or more others. Using this field
4625 tells the packaging system and the user that the
4626 listed packages are related to this one and can
4627 perhaps enhance its usefulness, but that installing
4628 this one without them is perfectly reasonable.
4631 <tag><tt>Enhances</tt></tag>
4633 This field is similar to Suggests but works in the
4634 opposite direction. It is used to declare that a
4635 package can enhance the functionality of another
4639 <tag><tt>Pre-Depends</tt></tag>
4642 This field is like <tt>Depends</tt>, except that it
4643 also forces <prgn>dpkg</prgn> to complete installation
4644 of the packages named before even starting the
4645 installation of the package which declares the
4646 pre-dependency, as follows:
4650 When a package declaring a pre-dependency is about to
4651 be <em>unpacked</em> the pre-dependency can be
4652 satisfied if the depended-on package is either fully
4653 configured, <em>or even if</em> the depended-on
4654 package(s) are only unpacked or in the "Half-Configured"
4655 state, provided that they have been configured
4656 correctly at some point in the past (and not removed
4657 or partially removed since). In this case, both the
4658 previously-configured and currently unpacked or
4659 "Half-Configured" versions must satisfy any version
4660 clause in the <tt>Pre-Depends</tt> field.
4664 When the package declaring a pre-dependency is about
4665 to be <em>configured</em>, the pre-dependency will be
4666 treated as a normal <tt>Depends</tt>, that is, it will
4667 be considered satisfied only if the depended-on
4668 package has been correctly configured.
4672 <tt>Pre-Depends</tt> should be used sparingly,
4673 preferably only by packages whose premature upgrade or
4674 installation would hamper the ability of the system to
4675 continue with any upgrade that might be in progress.
4679 <tt>Pre-Depends</tt> are also required if the
4680 <prgn>preinst</prgn> script depends on the named
4681 package. It is best to avoid this situation if
4689 When selecting which level of dependency to use you should
4690 consider how important the depended-on package is to the
4691 functionality of the one declaring the dependency. Some
4692 packages are composed of components of varying degrees of
4693 importance. Such a package should list using
4694 <tt>Depends</tt> the package(s) which are required by the
4695 more important components. The other components'
4696 requirements may be mentioned as Suggestions or
4697 Recommendations, as appropriate to the components' relative
4703 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4706 When one binary package declares that it breaks another,
4707 <prgn>dpkg</prgn> will refuse to allow the package which
4708 declares <tt>Breaks</tt> be installed unless the broken
4709 package is deconfigured first, and it will refuse to
4710 allow the broken package to be reconfigured.
4714 A package will not be regarded as causing breakage merely
4715 because its configuration files are still installed; it must
4716 be at least "Half-Installed".
4720 A special exception is made for packages which declare that
4721 they break their own package name or a virtual package which
4722 they provide (see below): this does not count as a real
4727 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4728 version clause; such a <tt>Breaks</tt> is introduced in the
4729 version of an (implicit or explicit) dependency which violates
4730 an assumption or reveals a bug in earlier versions of the broken
4731 package, or which takes over a file from earlier versions of the
4732 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
4733 will inform higher-level package management tools that the
4734 broken package must be upgraded before the new one.
4738 If the breaking package also overwrites some files from the
4739 older package, it should use <tt>Replaces</tt> to ensure this
4740 goes smoothly. See <ref id="replaces"> for a full discussion
4741 of taking over files from other packages, including how to
4742 use <tt>Breaks</tt> in those cases.
4746 Many of the cases where <tt>Breaks</tt> should be used were
4747 previously handled with <tt>Conflicts</tt>
4748 because <tt>Breaks</tt> did not yet exist.
4749 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
4750 See <ref id="conflicts"> for more information about the
4755 <sect id="conflicts">
4756 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4759 When one binary package declares a conflict with another
4760 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4761 refuse to allow them to be installed on the system at the
4762 same time. This is a stronger restriction than <tt>Breaks</tt>,
4763 which just prevents both packages from being configured at the
4764 same time. Conflicting packages cannot be unpacked on the
4765 system at the same time.
4769 If one package is to be installed, the other must be removed
4770 first. If the package being installed is marked as replacing
4771 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
4772 normally be used in this case) the one on the system, or the one
4773 on the system is marked as deselected, or both packages are
4774 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
4775 automatically remove the package which is causing the conflict.
4776 Otherwise, it will halt the installation of the new package with
4777 an error. This mechanism is specifically designed to produce an
4778 error when the installed package is <tt>Essential</tt>, but the
4783 A package will not cause a conflict merely because its
4784 configuration files are still installed; it must be at least
4789 A special exception is made for packages which declare a
4790 conflict with their own package name, or with a virtual
4791 package which they provide (see below): this does not
4792 prevent their installation, and allows a package to conflict
4793 with others providing a replacement for it. You use this
4794 feature when you want the package in question to be the only
4795 package providing some feature.
4799 Normally, <tt>Breaks</tt> should be used instead
4800 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
4801 stronger restriction on the ordering of package installation or
4802 upgrade and can make it more difficult for the package manager
4803 to find a correct solution to an upgrade or installation
4804 problem. <tt>Breaks</tt> should be used
4806 <item>when moving a file from one package to another (see
4807 <ref id="replaces">),</item>
4808 <item>when splitting a package (a special case of the previous
4810 <item>when the breaking package exposes a bug in or interacts
4811 badly with particular versions of the broken
4814 <tt>Conflicts</tt> should be used
4816 <item>when two packages provide the same file and will
4817 continue to do so,</item>
4818 <item>in conjunction with <tt>Provides</tt> when only one
4819 package providing a given virtual facility may be installed
4820 at a time (see <ref id="virtual">),</item>
4821 <item>in other cases where one must prevent simultaneous
4822 installation of two packages for reasons that are ongoing
4823 (not fixed in a later version of one of the packages) or
4824 that must prevent both packages from being unpacked at the
4825 same time, not just configured.</item>
4827 Be aware that adding <tt>Conflicts</tt> is normally not the best
4828 solution when two packages provide the same files. Depending on
4829 the reason for that conflict, using alternatives or renaming the
4830 files is often a better approach. See, for
4831 example, <ref id="binaries">.
4835 Neither <tt>Breaks</tt> nor <tt>Conflicts</tt> should be used
4836 unless two packages cannot be installed at the same time or
4837 installing them both causes one of them to be broken or
4838 unusable. Having similar functionality or performing the same
4839 tasks as another package is not sufficient reason to
4840 declare <tt>Breaks</tt> or <tt>Conflicts</tt> with that package.
4844 A <tt>Conflicts</tt> entry may have an "earlier than" version
4845 clause if the reason for the conflict is corrected in a later
4846 version of one of the packages. However, normally the presence
4847 of an "earlier than" version clause is a sign
4848 that <tt>Breaks</tt> should have been used instead. An "earlier
4849 than" version clause in <tt>Conflicts</tt>
4850 prevents <prgn>dpkg</prgn> from upgrading or installing the
4851 package which declares such a conflict until the upgrade or
4852 removal of the conflicted-with package has been completed, which
4853 is a strong restriction.
4857 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4861 As well as the names of actual ("concrete") packages, the
4862 package relationship fields <tt>Depends</tt>,
4863 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4864 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4865 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4866 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4867 may mention "virtual packages".
4871 A <em>virtual package</em> is one which appears in the
4872 <tt>Provides</tt> control field of another package. The effect
4873 is as if the package(s) which provide a particular virtual
4874 package name had been listed by name everywhere the virtual
4875 package name appears. (See also <ref id="virtual_pkg">)
4879 If there are both concrete and virtual packages of the same
4880 name, then the dependency may be satisfied (or the conflict
4881 caused) by either the concrete package with the name in
4882 question or any other concrete package which provides the
4883 virtual package with the name in question. This is so that,
4884 for example, supposing we have
4885 <example compact="compact">
4888 </example> and someone else releases an enhanced version of
4889 the <tt>bar</tt> package they can say:
4890 <example compact="compact">
4894 and the <tt>bar-plus</tt> package will now also satisfy the
4895 dependency for the <tt>foo</tt> package.
4899 If a relationship field has a version number attached, only real
4900 packages will be considered to see whether the relationship is
4901 satisfied (or the prohibition violated, for a conflict or
4902 breakage). In other words, if a version number is specified,
4903 this is a request to ignore all <tt>Provides</tt> for that
4904 package name and consider only real packages. The package
4905 manager will assume that a package providing that virtual
4906 package is not of the "right" version. A <tt>Provides</tt>
4907 field may not contain version numbers, and the version number of
4908 the concrete package which provides a particular virtual package
4909 will not be considered when considering a dependency on or
4910 conflict with the virtual package name.<footnote>
4911 It is possible that a future release of <prgn>dpkg</prgn> may
4912 add the ability to specify a version number for each virtual
4913 package it provides. This feature is not yet present,
4914 however, and is expected to be used only infrequently.
4919 To specify which of a set of real packages should be the default
4920 to satisfy a particular dependency on a virtual package, list
4921 the real package as an alternative before the virtual one.
4925 If the virtual package represents a facility that can only be
4926 provided by one real package at a time, such as
4927 the <package>mail-transport-agent</package> virtual package that
4928 requires installation of a binary that would conflict with all
4929 other providers of that virtual package (see
4930 <ref id="mail-transport-agents">), all packages providing that
4931 virtual package should also declare a conflict with it
4932 using <tt>Conflicts</tt>. This will ensure that at most one
4933 provider of that virtual package is unpacked or installed at a
4938 <sect id="replaces"><heading>Overwriting files and replacing
4939 packages - <tt>Replaces</tt></heading>
4942 Packages can declare in their control file that they should
4943 overwrite files in certain other packages, or completely replace
4944 other packages. The <tt>Replaces</tt> control field has these
4945 two distinct purposes.
4948 <sect1><heading>Overwriting files in other packages</heading>
4951 It is usually an error for a package to contain files which
4952 are on the system in another package. However, if the
4953 overwriting package declares that it <tt>Replaces</tt> the one
4954 containing the file being overwritten, then <prgn>dpkg</prgn>
4955 will replace the file from the old package with that from the
4956 new. The file will no longer be listed as "owned" by the old
4957 package and will be taken over by the new package.
4958 Normally, <tt>Breaks</tt> should be used in conjunction
4959 with <tt>Replaces</tt>.<footnote>
4960 To see why <tt>Breaks</tt> is normally needed in addition
4961 to <tt>Replaces</tt>, consider the case of a file in the
4962 package <package>foo</package> being taken over by the
4963 package <package>foo-data</package>.
4964 <tt>Replaces</tt> will allow <package>foo-data</package> to
4965 be installed and take over that file. However,
4966 without <tt>Breaks</tt>, nothing
4967 requires <package>foo</package> to be upgraded to a newer
4968 version that knows it does not include that file and instead
4969 depends on <package>foo-data</package>. Nothing would
4970 prevent the new <package>foo-data</package> package from
4971 being installed and then removed, removing the file that it
4972 took over from <package>foo</package>. After that
4973 operation, the package manager would think the system was in
4974 a consistent state, but the <package>foo</package> package
4975 would be missing one of its files.
4980 For example, if a package <package>foo</package> is split
4981 into <package>foo</package> and <package>foo-data</package>
4982 starting at version 1.2-3, <package>foo-data</package> would
4984 <example compact="compact">
4985 Replaces: foo (<< 1.2-3)
4986 Breaks: foo (<< 1.2-3)
4988 in its control file. The new version of the
4989 package <package>foo</package> would normally have the field
4990 <example compact="compact">
4991 Depends: foo-data (>= 1.2-3)
4993 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
4994 the files moved into <package>foo-data</package> are not
4995 required for normal operation).
4999 If a package is completely replaced in this way, so that
5000 <prgn>dpkg</prgn> does not know of any files it still
5001 contains, it is considered to have "disappeared". It will
5002 be marked as not wanted on the system (selected for
5003 removal) and not installed. Any <tt>conffile</tt>s
5004 details noted for the package will be ignored, as they
5005 will have been taken over by the overwriting package. The
5006 package's <prgn>postrm</prgn> script will be run with a
5007 special argument to allow the package to do any final
5008 cleanup required. See <ref id="mscriptsinstact">.
5010 Replaces is a one way relationship. You have to install
5011 the replacing package after the replaced package.
5016 For this usage of <tt>Replaces</tt>, virtual packages (see
5017 <ref id="virtual">) are not considered when looking at a
5018 <tt>Replaces</tt> field. The packages declared as being
5019 replaced must be mentioned by their real names.
5023 This usage of <tt>Replaces</tt> only takes effect when both
5024 packages are at least partially on the system at once. It is
5025 not relevant if the packages conflict unless the conflict has
5030 <sect1><heading>Replacing whole packages, forcing their
5034 Second, <tt>Replaces</tt> allows the packaging system to
5035 resolve which package should be removed when there is a
5036 conflict (see <ref id="conflicts">). This usage only takes
5037 effect when the two packages <em>do</em> conflict, so that the
5038 two usages of this field do not interfere with each other.
5042 In this situation, the package declared as being replaced
5043 can be a virtual package, so for example, all mail
5044 transport agents (MTAs) would have the following fields in
5045 their control files:
5046 <example compact="compact">
5047 Provides: mail-transport-agent
5048 Conflicts: mail-transport-agent
5049 Replaces: mail-transport-agent
5051 ensuring that only one MTA can be installed at any one
5052 time. See <ref id="virtual"> for more information about this
5057 <sect id="sourcebinarydeps">
5058 <heading>Relationships between source and binary packages -
5059 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5060 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5064 Source packages that require certain binary packages to be
5065 installed or absent at the time of building the package
5066 can declare relationships to those binary packages.
5070 This is done using the <tt>Build-Depends</tt>,
5071 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5072 <tt>Build-Conflicts-Indep</tt> control fields.
5076 Build-dependencies on "build-essential" binary packages can be
5077 omitted. Please see <ref id="pkg-relations"> for more information.
5081 The dependencies and conflicts they define must be satisfied
5082 (as defined earlier for binary packages) in order to invoke
5083 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5085 There is no Build-Depends-Arch; this role is essentially
5086 met with Build-Depends. Anyone building the
5087 <tt>build-indep</tt> and <tt>binary-indep</tt> targets is
5088 assumed to be building the whole package, and therefore
5089 installation of all build dependencies is required.
5092 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5093 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5094 not yet know how to check for its existence, and
5095 <tt>binary-arch</tt>. The purpose of the original split
5096 between <tt>Build-Depends</tt> and
5097 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5098 wouldn't need to install extra packages needed only for the
5099 binary-indep targets. But without a build-arch/build-indep
5100 split, this didn't work, since most of the work is done in
5101 the build target, not in the binary target.
5105 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5106 <tt>binary-arch</tt></tag>
5108 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5109 fields must be satisfied when these targets are invoked.
5111 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5112 and <tt>binary-indep</tt></tag>
5114 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5115 <tt>Build-Depends-Indep</tt>, and
5116 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5117 these targets are invoked.
5125 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5128 Packages containing shared libraries must be constructed with
5129 a little care to make sure that the shared library is always
5130 available. This is especially important for packages whose
5131 shared libraries are vitally important, such as the C library
5132 (currently <tt>libc6</tt>).
5136 This section deals only with public shared libraries: shared
5137 libraries that are placed in directories searched by the dynamic
5138 linker by default or which are intended to be linked against
5139 normally and possibly used by other, independent packages. Shared
5140 libraries that are internal to a particular package or that are
5141 only loaded as dynamic modules are not covered by this section and
5142 are not subject to its requirements.
5146 A shared library is identified by the <tt>SONAME</tt> attribute
5147 stored in its dynamic section. When a binary is linked against a
5148 shared library, the <tt>SONAME</tt> of the shared library is
5149 recorded in the binary's <tt>NEEDED</tt> section so that the
5150 dynamic linker knows that library must be loaded at runtime. The
5151 shared library file's full name (which usually contains additional
5152 version information not needed in the <tt>SONAME</tt>) is
5153 therefore normally not referenced directly. Instead, the shared
5154 library is loaded by its <tt>SONAME</tt>, which exists on the file
5155 system as a symlink pointing to the full name of the shared
5156 library. This symlink must be provided by the
5157 package. <ref id="sharedlibs-runtime"> describes how to do this.
5159 This is a convention of shared library versioning, but not a
5160 requirement. Some libraries use the <tt>SONAME</tt> as the full
5161 library file name instead and therefore do not need a symlink.
5162 Most, however, encode additional information about
5163 backwards-compatible revisions as a minor version number in the
5164 file name. The <tt>SONAME</tt> itself only changes when
5165 binaries linked with the earlier version of the shared library
5166 may no longer work, but the filename may change with each
5167 release of the library. See <ref id="sharedlibs-runtime"> for
5173 When linking a binary or another shared library against a shared
5174 library, the <tt>SONAME</tt> for that shared library is not yet
5175 known. Instead, the shared library is found by looking for a file
5176 matching the library name with <tt>.so</tt> appended. This file
5177 exists on the file system as a symlink pointing to the shared
5182 Shared libraries are normally split into several binary packages.
5183 The <tt>SONAME</tt> symlink is installed by the runtime shared
5184 library package, and the bare <tt>.so</tt> symlink is installed in
5185 the development package since it's only used when linking binaries
5186 or shared libraries. However, there are some exceptions for
5187 unusual shared libraries or for shared libraries that are also
5188 loaded as dynamic modules by other programs.
5192 This section is primarily concerned with how the separation of
5193 shared libraries into multiple packages should be done and how
5194 dependencies on and between shared library binary packages are
5195 managed in Debian. <ref id="libraries"> should be read in
5196 conjunction with this section and contains additional rules for
5197 the files contained in the shared library packages.
5200 <sect id="sharedlibs-runtime">
5201 <heading>Run-time shared libraries</heading>
5204 The run-time shared library must be placed in a package
5205 whose name changes whenever the <tt>SONAME</tt> of the shared
5206 library changes. This allows several versions of the shared
5207 library to be installed at the same time, allowing installation
5208 of the new version of the shared library without immediately
5209 breaking binaries that depend on the old version. Normally, the
5210 run-time shared library and its <tt>SONAME</tt> symlink should
5211 be placed in a package named
5212 <package><var>libraryname</var><var>soversion</var></package>,
5213 where <var>soversion</var> is the version number in
5214 the <tt>SONAME</tt> of the shared library.
5215 See <ref id="shlibs"> for detailed information on how to
5216 determine this version. Alternatively, if it would be confusing
5217 to directly append <var>soversion</var>
5218 to <var>libraryname</var> (if, for example, <var>libraryname</var>
5219 itself ends in a number), you should use
5220 <package><var>libraryname</var>-<var>soversion</var></package>
5225 If you have several shared libraries built from the same source
5226 tree, you may lump them all together into a single shared
5227 library package provided that all of their <tt>SONAME</tt>s will
5228 always change together. Be aware that this is not normally the
5229 case, and if the <tt>SONAME</tt>s do not change together,
5230 upgrading such a merged shared library package will be
5231 unnecessarily difficult because of file conflicts with the old
5232 version of the package. When in doubt, always split shared
5233 library packages so that each binary package installs a single
5238 Every time the shared library ABI changes in a way that may
5239 break binaries linked against older versions of the shared
5240 library, the <tt>SONAME</tt> of the library and the
5241 corresponding name for the binary package containing the runtime
5242 shared library should change. Normally, this means
5243 the <tt>SONAME</tt> should change any time an interface is
5244 removed from the shared library or the signature of an interface
5245 (the number of parameters or the types of parameters that it
5246 takes, for example) is changed. This practice is vital to
5247 allowing clean upgrades from older versions of the package and
5248 clean transitions between the old ABI and new ABI without having
5249 to upgrade every affected package simultaneously.
5253 The <tt>SONAME</tt> and binary package name need not, and indeed
5254 normally should not, change if new interfaces are added but none
5255 are removed or changed, since this will not break binaries
5256 linked against the old shared library. Correct versioning of
5257 dependencies on the newer shared library by binaries that use
5258 the new interfaces is handled via
5259 the <qref id="sharedlibs-shlibdeps"><tt>shlibs</tt>
5260 system</qref> or via symbols files (see
5261 <manref name="deb-symbols" section="5">).
5265 The package should install the shared libraries under
5266 their normal names. For example, the <package>libgdbm3</package>
5267 package should install <file>libgdbm.so.3.0.0</file> as
5268 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5269 renamed or re-linked by any <prgn>prerm</prgn> or
5270 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5271 of renaming things safely without affecting running programs,
5272 and attempts to interfere with this are likely to lead to
5277 Shared libraries should not be installed executable, since
5278 the dynamic linker does not require this and trying to
5279 execute a shared library usually results in a core dump.
5283 The run-time library package should include the symbolic link for
5284 the <tt>SONAME</tt> that <prgn>ldconfig</prgn> would create for
5285 the shared libraries. For example,
5286 the <package>libgdbm3</package> package should include a symbolic
5287 link from <file>/usr/lib/libgdbm.so.3</file> to
5288 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5289 linker (for example <prgn>ld.so</prgn> or
5290 <prgn>ld-linux.so.*</prgn>) can find the library between the
5291 time that <prgn>dpkg</prgn> installs it and the time that
5292 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5294 The package management system requires the library to be
5295 placed before the symbolic link pointing to it in the
5296 <file>.deb</file> file. This is so that when
5297 <prgn>dpkg</prgn> comes to install the symlink
5298 (overwriting the previous symlink pointing at an older
5299 version of the library), the new shared library is already
5300 in place. In the past, this was achieved by creating the
5301 library in the temporary packaging directory before
5302 creating the symlink. Unfortunately, this was not always
5303 effective, since the building of the tar file in the
5304 <file>.deb</file> depended on the behavior of the underlying
5305 file system. Some file systems (such as reiserfs) reorder
5306 the files so that the order of creation is forgotten.
5307 Since version 1.7.0, <prgn>dpkg</prgn>
5308 reorders the files itself as necessary when building a
5309 package. Thus it is no longer important to concern
5310 oneself with the order of file creation.
5314 <sect1 id="ldconfig">
5315 <heading><tt>ldconfig</tt></heading>
5318 Any package installing shared libraries in one of the default
5319 library directories of the dynamic linker (which are currently
5320 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5321 listed in <file>/etc/ld.so.conf</file><footnote>
5323 <list compact="compact">
5324 <item>/usr/local/lib</item>
5325 <item>/usr/lib/libc5-compat</item>
5326 <item>/lib/libc5-compat</item>
5329 must use <prgn>ldconfig</prgn> to update the shared library
5334 The package maintainer scripts must only call
5335 <prgn>ldconfig</prgn> under these circumstances:
5336 <list compact="compact">
5337 <item>When the <prgn>postinst</prgn> script is run with a
5338 first argument of <tt>configure</tt>, the script must call
5339 <prgn>ldconfig</prgn>, and may optionally invoke
5340 <prgn>ldconfig</prgn> at other times.
5342 <item>When the <prgn>postrm</prgn> script is run with a
5343 first argument of <tt>remove</tt>, the script should call
5344 <prgn>ldconfig</prgn>.
5349 During install or upgrade, the preinst is called before
5350 the new files are installed, so calling "ldconfig" is
5351 pointless. The preinst of an existing package can also be
5352 called if an upgrade fails. However, this happens during
5353 the critical time when a shared libs may exist on-disk
5354 under a temporary name. Thus, it is dangerous and
5355 forbidden by current policy to call "ldconfig" at this
5360 When a package is installed or upgraded, "postinst
5361 configure" runs after the new files are safely on-disk.
5362 Since it is perfectly safe to invoke ldconfig
5363 unconditionally in a postinst, it is OK for a package to
5364 simply put ldconfig in its postinst without checking the
5365 argument. The postinst can also be called to recover from
5366 a failed upgrade. This happens before any new files are
5367 unpacked, so there is no reason to call "ldconfig" at this
5372 For a package that is being removed, prerm is
5373 called with all the files intact, so calling ldconfig is
5374 useless. The other calls to "prerm" happen in the case of
5375 upgrade at a time when all the files of the old package
5376 are on-disk, so again calling "ldconfig" is pointless.
5380 postrm, on the other hand, is called with the "remove"
5381 argument just after the files are removed, so this is
5382 the proper time to call "ldconfig" to notify the system
5383 of the fact that the shared libraries from the package
5384 are removed. The postrm can be called at several other
5385 times. At the time of "postrm purge", "postrm
5386 abort-install", or "postrm abort-upgrade", calling
5387 "ldconfig" is useless because the shared lib files are
5388 not on-disk. However, when "postrm" is invoked with
5389 arguments "upgrade", "failed-upgrade", or "disappear", a
5390 shared lib may exist on-disk under a temporary filename.
5398 <sect id="sharedlibs-support-files">
5399 <heading>Shared library support files</heading>
5402 If your package contains files whose names do not change with
5403 each change in the library shared object version, you must not
5404 put them in the shared library package. Otherwise, several
5405 versions of the shared library cannot be installed at the same
5406 time without filename clashes, making upgrades and transitions
5407 unnecessarily difficult.
5411 It is recommended that supporting files and run-time support
5412 programs that do not need to be invoked manually by users, but
5413 are nevertheless required for the package to function, be placed
5414 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5415 preferably under <file>/usr/lib/</file><var>package-name</var>.
5416 If the program or file is architecture independent, the
5417 recommendation is for it to be placed in a subdirectory of
5418 <file>/usr/share</file> instead, preferably under
5419 <file>/usr/share/</file><var>package-name</var>. Following the
5420 <var>package-name</var> naming convention ensures that the file
5421 names change when the shared object version changes.
5425 Run-time support programs that use the shared library but are
5426 not required for the library to function or files used by the
5427 shared library that can be used by any version of the shared
5428 library package should instead be put in a separate package.
5429 This package might typically be named
5430 <package><var>libraryname</var>-tools</package>; note the
5431 absence of the <var>soversion</var> in the package name.
5435 Files and support programs only useful when compiling software
5436 against the library should be included in the development
5437 package for the library.<footnote>
5438 For example, a <file><var>package-name</var>-config</file>
5439 script or <package>pkg-config</package> configuration files.
5444 <sect id="sharedlibs-static">
5445 <heading>Static libraries</heading>
5448 The static library (<file><var>libraryname.a</var></file>)
5449 is usually provided in addition to the shared version.
5450 It is placed into the development package (see below).
5454 In some cases, it is acceptable for a library to be
5455 available in static form only; these cases include:
5457 <item>libraries for languages whose shared library support
5458 is immature or unstable</item>
5459 <item>libraries whose interfaces are in flux or under
5460 development (commonly the case when the library's
5461 major version number is zero, or where the ABI breaks
5462 across patchlevels)</item>
5463 <item>libraries which are explicitly intended to be
5464 available only in static form by their upstream
5469 <sect id="sharedlibs-dev">
5470 <heading>Development files</heading>
5473 If there are development files associated with a shared library,
5474 the source package needs to generate a binary development package
5475 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5476 or if you prefer only to support one development version at a
5477 time, <package><var>libraryname</var>-dev</package>. Installing
5478 the development package must result in installation of all the
5479 development files necessary for compiling programs against that
5480 shared library.<footnote>
5481 This wording allows the development files to be split into
5482 several packages, such as a separate architecture-independent
5483 <package><var>libraryname</var>-headers</package>, provided that
5484 the development package depends on all the required additional
5490 In case several development versions of a library exist, you may
5491 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5492 <ref id="conflicts">) to ensure that the user only installs one
5493 development version at a time (as different development versions are
5494 likely to have the same header files in them, which would cause a
5495 filename clash if both were installed).
5499 The development package should contain a symlink for the associated
5500 shared library without a version number. For example, the
5501 <package>libgdbm-dev</package> package should include a symlink
5502 from <file>/usr/lib/libgdbm.so</file> to
5503 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5504 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5505 <file>libgdbm.so</file> when compiling dynamically.
5509 If the package provides Ada Library Information
5510 (<file>*.ali</file>) files for use with GNAT, these files must be
5511 installed read-only (mode 0444) so that GNAT will not attempt to
5512 recompile them. This overrides the normal file mode requirements
5513 given in <ref id="permissions-owners">.
5517 <sect id="sharedlibs-intradeps">
5518 <heading>Dependencies between the packages of the same library</heading>
5521 Typically the development version should have an exact
5522 version dependency on the runtime library, to make sure that
5523 compilation and linking happens correctly. The
5524 <tt>${binary:Version}</tt> substitution variable can be
5525 useful for this purpose.
5527 Previously, <tt>${Source-Version}</tt> was used, but its name
5528 was confusing and it has been deprecated since dpkg 1.13.19.
5533 <sect id="sharedlibs-shlibdeps">
5534 <heading>Dependencies between the library and other packages -
5535 the <tt>shlibs</tt> system</heading>
5538 If a package contains a binary or library which links to a
5539 shared library, we must ensure that when the package is
5540 installed on the system, all of the libraries needed are
5541 also installed. This requirement led to the creation of the
5542 <tt>shlibs</tt> system, which is very simple in its design:
5543 any package which <em>provides</em> a shared library also
5544 provides information on the package dependencies required to
5545 ensure the presence of this library, and any package which
5546 <em>uses</em> a shared library uses this information to
5547 determine the dependencies it requires. The files which
5548 contain the mapping from shared libraries to the necessary
5549 dependency information are called <file>shlibs</file> files.
5553 When a package is built which contains any shared libraries, it
5554 must provide a <file>shlibs</file> file for other packages to
5555 use. When a package is built which contains any shared
5556 libraries or compiled binaries, it must run
5557 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5558 on these to determine the libraries used and hence the
5559 dependencies needed by this package.<footnote>
5561 <prgn>dpkg-shlibdeps</prgn> will use a program
5562 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
5563 the libraries directly needed by the binaries or shared
5564 libraries in the package.
5568 We say that a binary <tt>foo</tt> <em>directly</em> uses
5569 a library <tt>libbar</tt> if it is explicitly linked
5570 with that library (that is, the library is listed in the ELF
5571 <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
5572 to the link line when the binary is created). Other
5573 libraries that are needed by <tt>libbar</tt> are linked
5574 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5575 linker will load them automatically when it loads
5576 <tt>libbar</tt>. A package should depend on the libraries
5577 it directly uses, but not the libraries it indirectly uses.
5578 The dependencies for those libraries will automatically pull
5579 in the other libraries.
5583 A good example of where this helps is the following. We
5584 could update <tt>libimlib</tt> with a new version that
5585 supports a new graphics format called dgf (but retaining the
5586 same major version number) and depends on <tt>libdgf</tt>.
5587 If we used <prgn>ldd</prgn> to add dependencies for every
5588 library directly or indirectly linked with a binary, every
5589 package that uses <tt>libimlib</tt> would need to be
5590 recompiled so it would also depend on <tt>libdgf</tt> or it
5591 wouldn't run due to missing symbols. Since dependencies are
5592 only added based on ELF <tt>NEEDED</tt> attribute, packages
5593 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
5594 having the dependency on <tt>libdgf</tt> and so they would
5595 not need rebuilding.
5601 In the following sections, we will first describe where the
5602 various <tt>shlibs</tt> files are to be found, then how to
5603 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5604 file format and how to create them if your package contains a
5609 <heading>The <tt>shlibs</tt> files present on the system</heading>
5612 There are several places where <tt>shlibs</tt> files are
5613 found. The following list gives them in the order in which
5615 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5616 (The first one which gives the required information is used.)
5622 <p><file>debian/shlibs.local</file></p>
5625 This lists overrides for this package. This file should
5626 normally not be used, but may be needed temporarily in
5627 unusual situations to work around bugs in other packages,
5628 or in unusual cases where the normally declared dependency
5629 information in the installed <file>shlibs</file> file for
5630 a library cannot be used. This file overrides information
5631 obtained from any other source.
5636 <p><file>/etc/dpkg/shlibs.override</file></p>
5639 This lists global overrides. This list is normally
5640 empty. It is maintained by the local system
5646 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5649 When packages are being built,
5650 any <file>debian/shlibs</file> files are copied into the
5651 control information file area of the temporary build
5652 directory and given the name <file>shlibs</file>. These
5653 files give details of any shared libraries included in the
5654 same package.<footnote>
5655 An example may help here. Let us say that the source
5656 package <tt>foo</tt> generates two binary
5657 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
5658 When building the binary packages, the two packages are
5659 created in the directories <file>debian/libfoo2</file>
5660 and <file>debian/foo-runtime</file> respectively.
5661 (<file>debian/tmp</file> could be used instead of one of
5662 these.) Since <tt>libfoo2</tt> provides the
5663 <tt>libfoo</tt> shared library, it will require a
5664 <tt>shlibs</tt> file, which will be installed in
5665 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually to
5666 become <file>/var/lib/dpkg/info/libfoo2.shlibs</file>.
5667 When <prgn>dpkg-shlibdeps</prgn> is run on the
5668 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
5670 the <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5671 determine whether <tt>foo-prog</tt>'s library
5672 dependencies are satisfied by any of the libraries
5673 provided by <tt>libfoo2</tt>. For this reason,
5674 <prgn>dpkg-shlibdeps</prgn> must only be run once all of
5675 the individual binary packages' <tt>shlibs</tt> files
5676 have been installed into the build directory.
5682 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5685 These are the <file>shlibs</file> files corresponding to
5686 all of the packages installed on the system, and are
5687 maintained by the relevant package maintainers.
5692 <p><file>/etc/dpkg/shlibs.default</file></p>
5695 This file lists any shared libraries whose packages
5696 have failed to provide correct <file>shlibs</file> files.
5697 It was used when the <file>shlibs</file> setup was first
5698 introduced, but it is now normally empty. It is
5699 maintained by the <tt>dpkg</tt> maintainer.
5707 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5708 <file>shlibs</file> files</heading>
5712 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5713 into your <file>debian/rules</file> file. If your package
5714 contains only compiled binaries and libraries (but no scripts),
5715 you can use a command such as:
5716 <example compact="compact">
5717 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5718 debian/tmp/usr/lib/*
5720 Otherwise, you will need to explicitly list the compiled
5721 binaries and libraries.<footnote>
5722 If you are using <tt>debhelper</tt>, the
5723 <prgn>dh_shlibdeps</prgn> program will do this work for you.
5724 It will also correctly handle multi-binary packages.
5729 This command puts the dependency information into the
5730 <file>debian/substvars</file> file, which is then used by
5731 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5732 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5733 field in the control file for this to work.
5737 If you have multiple binary packages, you will need to call
5738 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5739 compiled libraries or binaries. In such a case, you will
5740 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5741 utilities to specify a different <file>substvars</file> file.
5745 If you are creating a udeb for use in the Debian Installer,
5746 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
5747 should use the dependency line of type <tt>udeb</tt> by
5748 adding the <tt>-tudeb</tt> option<footnote>
5749 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5750 will automatically add this option if it knows it is
5752 </footnote>. If there is no dependency line of
5753 type <tt>udeb</tt> in the <file>shlibs</file>
5754 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the regular
5759 For more details on <prgn>dpkg-shlibdeps</prgn>, please see
5760 <ref id="pkg-dpkg-shlibdeps"> and
5761 <manref name="dpkg-shlibdeps" section="1">.
5766 <heading>The <file>shlibs</file> File Format</heading>
5769 Each <file>shlibs</file> file has the same format. Lines
5770 beginning with <tt>#</tt> are considered to be comments and
5771 are ignored. Each line is of the form:
5772 <example compact="compact">
5773 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5778 We will explain this by reference to the example of the
5779 <tt>zlib1g</tt> package, which (at the time of writing)
5780 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5784 <var>type</var> is an optional element that indicates the type
5785 of package for which the line is valid. The only type currently
5786 in use is <tt>udeb</tt>. The colon and space after the type are
5791 <var>library-name</var> is the name of the shared library,
5792 in this case <tt>libz</tt>. (This must match the name part
5793 of the soname, see below.)
5797 <var>soname-version</var> is the version part of the soname of
5798 the library. The soname is the thing that must exactly match
5799 for the library to be recognized by the dynamic linker, and is
5801 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5802 example, <tt>libz.so.1</tt>.<footnote>
5803 This can be determined using the command
5804 <example compact="compact">
5805 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5808 The version part is the part which comes after
5809 <tt>.so.</tt>, so in our case, it is <tt>1</tt>. The soname may
5810 instead be of the form
5811 <tt><var>name</var>-<var>major-version</var>.so</tt>, such
5812 as <tt>libdb-4.8.so</tt>, in which case the name would
5813 be <tt>libdb</tt> and the version would be <tt>4.8</tt>.
5817 <var>dependencies</var> has the same syntax as a dependency
5818 field in a binary package control file. It should give
5819 details of which packages are required to satisfy a binary
5820 built against the version of the library contained in the
5821 package. See <ref id="depsyntax"> for details.
5825 In our example, if the first version of the <tt>zlib1g</tt>
5826 package which contained a minor number of at least
5827 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5828 <tt>shlibs</tt> entry for this library could say:
5829 <example compact="compact">
5830 libz 1 zlib1g (>= 1:1.1.3)
5832 The version-specific dependency is to avoid warnings from
5833 the dynamic linker about using older shared libraries with
5838 As zlib1g also provides a udeb containing the shared library,
5839 there would also be a second line:
5840 <example compact="compact">
5841 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5847 <heading>Providing a <file>shlibs</file> file</heading>
5850 If your package provides a shared library, you need to create
5851 a <file>shlibs</file> file following the format described above.
5852 It is usual to call this file <file>debian/shlibs</file> (but if
5853 you have multiple binary packages, you might want to call it
5854 <file>debian/shlibs.<var>package</var></file> instead). Then
5855 let <file>debian/rules</file> install it in the control
5856 information file area:
5857 <example compact="compact">
5858 install -m644 debian/shlibs debian/tmp/DEBIAN
5860 or, in the case of a multi-binary package:
5861 <example compact="compact">
5862 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5864 An alternative way of doing this is to create the
5865 <file>shlibs</file> file in the control information file area
5866 directly from <file>debian/rules</file> without using
5867 a <file>debian/shlibs</file> file at all,<footnote>
5868 This is what <prgn>dh_makeshlibs</prgn> in
5869 the <package>debhelper</package> suite does. If your package
5870 also has a udeb that provides a shared
5871 library, <prgn>dh_makeshlibs</prgn> can automatically generate
5872 the <tt>udeb:</tt> lines if you specify the name of the udeb
5873 with the <tt>--add-udeb</tt> option.
5875 since the <file>debian/shlibs</file> file itself is ignored by
5876 <prgn>dpkg-shlibdeps</prgn>.
5880 As <prgn>dpkg-shlibdeps</prgn> reads the
5881 <file>DEBIAN/shlibs</file> files in all of the binary packages
5882 being built from this source package, all of the
5883 <file>DEBIAN/shlibs</file> files should be installed before
5884 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5892 <chapt id="opersys"><heading>The Operating System</heading>
5895 <heading>File system hierarchy</heading>
5899 <heading>File System Structure</heading>
5902 The location of all installed files and directories must
5903 comply with the Filesystem Hierarchy Standard (FHS),
5904 version 2.3, with the exceptions noted below, and except
5905 where doing so would violate other terms of Debian
5906 Policy. The following exceptions to the FHS apply:
5911 The optional rules related to user specific
5912 configuration files for applications are stored in
5913 the user's home directory are relaxed. It is
5914 recommended that such files start with the
5915 '<tt>.</tt>' character (a "dot file"), and if an
5916 application needs to create more than one dot file
5917 then the preferred placement is in a subdirectory
5918 with a name starting with a '.' character, (a "dot
5919 directory"). In this case it is recommended the
5920 configuration files not start with the '.'
5926 The requirement for amd64 to use <file>/lib64</file>
5927 for 64 bit binaries is removed.
5932 The requirement for object files, internal binaries, and
5933 libraries, including <file>libc.so.*</file>, to be located
5934 directly under <file>/lib{,32}</file> and
5935 <file>/usr/lib{,32}</file> is amended, permitting files
5936 to instead be installed to
5937 <file>/lib/<var>triplet</var></file> and
5938 <file>/usr/lib/<var>triplet</var></file>, where
5939 <tt><var>triplet</var></tt> is the value returned by
5940 <tt>dpkg-architecture -qDEB_HOST_GNU_TYPE</tt> for the
5941 architecture of the package. Packages may <em>not</em>
5942 install files to any <var>triplet</var> path other
5943 than the one matching the architecture of that package;
5944 for instance, an <tt>Architecture: amd64</tt> package
5945 containing 32-bit x86 libraries may not install these
5946 libraries to <file>/usr/lib/i486-linux-gnu</file>.
5948 This is necessary in order to reserve the directories for
5949 use in cross-installation of library packages from other
5950 architectures, as part of the planned deployment of
5955 Applications may also use a single subdirectory under
5956 <file>/usr/lib/<var>triplet</var></file>.
5959 The execution time linker/loader, ld*, must still be made
5960 available in the existing location under /lib or /lib64
5961 since this is part of the ELF ABI for the architecture.
5966 The requirement that
5967 <file>/usr/local/share/man</file> be "synonymous"
5968 with <file>/usr/local/man</file> is relaxed to a
5973 The requirement that windowmanagers with a single
5974 configuration file call it <file>system.*wmrc</file>
5975 is removed, as is the restriction that the window
5976 manager subdirectory be named identically to the
5977 window manager name itself.
5982 The requirement that boot manager configuration
5983 files live in <file>/etc</file>, or at least are
5984 symlinked there, is relaxed to a recommendation.
5989 The following directories in the root filesystem are
5990 additionally allowed: <file>/sys</file> and
5991 <file>/selinux</file>. <footnote>These directories
5992 are used as mount points to mount virtual filesystems
5993 to get access to kernel information.</footnote>
6000 The version of this document referred here can be
6001 found in the <tt>debian-policy</tt> package or on <url
6002 id="http://www.debian.org/doc/packaging-manuals/fhs/"
6003 name="FHS (Debian copy)"> alongside this manual (or, if
6004 you have the <package>debian-policy</package> installed,
6006 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
6007 (local copy)">). The
6008 latest version, which may be a more recent version, may
6010 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
6011 Specific questions about following the standard may be
6012 asked on the <tt>debian-devel</tt> mailing list, or
6013 referred to the FHS mailing list (see the
6014 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
6020 <heading>Site-specific programs</heading>
6023 As mandated by the FHS, packages must not place any
6024 files in <file>/usr/local</file>, either by putting them in
6025 the file system archive to be unpacked by <prgn>dpkg</prgn>
6026 or by manipulating them in their maintainer scripts.
6030 However, the package may create empty directories below
6031 <file>/usr/local</file> so that the system administrator knows
6032 where to place site-specific files. These are not
6033 directories <em>in</em> <file>/usr/local</file>, but are
6034 children of directories in <file>/usr/local</file>. These
6035 directories (<file>/usr/local/*/dir/</file>)
6036 should be removed on package removal if they are
6041 Note that this applies only to
6042 directories <em>below</em> <file>/usr/local</file>,
6043 not <em>in</em> <file>/usr/local</file>. Packages must
6044 not create sub-directories in the
6045 directory <file>/usr/local</file> itself, except those
6046 listed in FHS, section 4.5. However, you may create
6047 directories below them as you wish. You must not remove
6048 any of the directories listed in 4.5, even if you created
6053 Since <file>/usr/local</file> can be mounted read-only from a
6054 remote server, these directories must be created and
6055 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
6056 maintainer scripts and not be included in the
6057 <file>.deb</file> archive. These scripts must not fail if
6058 either of these operations fail.
6062 For example, the <tt>emacsen-common</tt> package could
6063 contain something like
6064 <example compact="compact">
6065 if [ ! -e /usr/local/share/emacs ]
6067 if mkdir /usr/local/share/emacs 2>/dev/null
6069 chown root:staff /usr/local/share/emacs
6070 chmod 2775 /usr/local/share/emacs
6074 in its <prgn>postinst</prgn> script, and
6075 <example compact="compact">
6076 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
6077 rmdir /usr/local/share/emacs 2>/dev/null || true
6079 in the <prgn>prerm</prgn> script. (Note that this form is
6080 used to ensure that if the script is interrupted, the
6081 directory <file>/usr/local/share/emacs</file> will still be
6086 If you do create a directory in <file>/usr/local</file> for
6087 local additions to a package, you should ensure that
6088 settings in <file>/usr/local</file> take precedence over the
6089 equivalents in <file>/usr</file>.
6093 However, because <file>/usr/local</file> and its contents are
6094 for exclusive use of the local administrator, a package
6095 must not rely on the presence or absence of files or
6096 directories in <file>/usr/local</file> for normal operation.
6100 The <file>/usr/local</file> directory itself and all the
6101 subdirectories created by the package should (by default) have
6102 permissions 2775 (group-writable and set-group-id) and be
6103 owned by <tt>root:staff</tt>.
6108 <heading>The system-wide mail directory</heading>
6110 The system-wide mail directory
6111 is <file>/var/mail</file>. This directory is part of the
6112 base system and should not be owned by any particular mail
6113 agents. The use of the old
6114 location <file>/var/spool/mail</file> is deprecated, even
6115 though the spool may still be physically located there.
6121 <heading>Users and groups</heading>
6124 <heading>Introduction</heading>
6126 The Debian system can be configured to use either plain or
6131 Some user ids (UIDs) and group ids (GIDs) are reserved
6132 globally for use by certain packages. Because some
6133 packages need to include files which are owned by these
6134 users or groups, or need the ids compiled into binaries,
6135 these ids must be used on any Debian system only for the
6136 purpose for which they are allocated. This is a serious
6137 restriction, and we should avoid getting in the way of
6138 local administration policies. In particular, many sites
6139 allocate users and/or local system groups starting at 100.
6143 Apart from this we should have dynamically allocated ids,
6144 which should by default be arranged in some sensible
6145 order, but the behavior should be configurable.
6149 Packages other than <tt>base-passwd</tt> must not modify
6150 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
6151 <file>/etc/group</file> or <file>/etc/gshadow</file>.
6156 <heading>UID and GID classes</heading>
6158 The UID and GID numbers are divided into classes as
6164 Globally allocated by the Debian project, the same
6165 on every Debian system. These ids will appear in
6166 the <file>passwd</file> and <file>group</file> files of all
6167 Debian systems, new ids in this range being added
6168 automatically as the <tt>base-passwd</tt> package is
6173 Packages which need a single statically allocated
6174 uid or gid should use one of these; their
6175 maintainers should ask the <tt>base-passwd</tt>
6183 Dynamically allocated system users and groups.
6184 Packages which need a user or group, but can have
6185 this user or group allocated dynamically and
6186 differently on each system, should use <tt>adduser
6187 --system</tt> to create the group and/or user.
6188 <prgn>adduser</prgn> will check for the existence of
6189 the user or group, and if necessary choose an unused
6190 id based on the ranges specified in
6191 <file>adduser.conf</file>.
6195 <tag>1000-59999:</tag>
6198 Dynamically allocated user accounts. By default
6199 <prgn>adduser</prgn> will choose UIDs and GIDs for
6200 user accounts in this range, though
6201 <file>adduser.conf</file> may be used to modify this
6206 <tag>60000-64999:</tag>
6209 Globally allocated by the Debian project, but only
6210 created on demand. The ids are allocated centrally
6211 and statically, but the actual accounts are only
6212 created on users' systems on demand.
6216 These ids are for packages which are obscure or
6217 which require many statically-allocated ids. These
6218 packages should check for and create the accounts in
6219 <file>/etc/passwd</file> or <file>/etc/group</file> (using
6220 <prgn>adduser</prgn> if it has this facility) if
6221 necessary. Packages which are likely to require
6222 further allocations should have a "hole" left after
6223 them in the allocation, to give them room to
6228 <tag>65000-65533:</tag>
6236 User <tt>nobody</tt>. The corresponding gid refers
6237 to the group <tt>nogroup</tt>.
6244 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
6245 not</em> be used, because it is the error return
6254 <sect id="sysvinit">
6255 <heading>System run levels and <file>init.d</file> scripts</heading>
6257 <sect1 id="/etc/init.d">
6258 <heading>Introduction</heading>
6261 The <file>/etc/init.d</file> directory contains the scripts
6262 executed by <prgn>init</prgn> at boot time and when the
6263 init state (or "runlevel") is changed (see <manref
6264 name="init" section="8">).
6268 There are at least two different, yet functionally
6269 equivalent, ways of handling these scripts. For the sake
6270 of simplicity, this document describes only the symbolic
6271 link method. However, it must not be assumed by maintainer
6272 scripts that this method is being used, and any automated
6273 manipulation of the various runlevel behaviors by
6274 maintainer scripts must be performed using
6275 <prgn>update-rc.d</prgn> as described below and not by
6276 manually installing or removing symlinks. For information
6277 on the implementation details of the other method,
6278 implemented in the <tt>file-rc</tt> package, please refer
6279 to the documentation of that package.
6283 These scripts are referenced by symbolic links in the
6284 <file>/etc/rc<var>n</var>.d</file> directories. When changing
6285 runlevels, <prgn>init</prgn> looks in the directory
6286 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
6287 execute, where <tt><var>n</var></tt> is the runlevel that
6288 is being changed to, or <tt>S</tt> for the boot-up
6293 The names of the links all have the form
6294 <file>S<var>mm</var><var>script</var></file> or
6295 <file>K<var>mm</var><var>script</var></file> where
6296 <var>mm</var> is a two-digit number and <var>script</var>
6297 is the name of the script (this should be the same as the
6298 name of the actual script in <file>/etc/init.d</file>).
6302 When <prgn>init</prgn> changes runlevel first the targets
6303 of the links whose names start with a <tt>K</tt> are
6304 executed, each with the single argument <tt>stop</tt>,
6305 followed by the scripts prefixed with an <tt>S</tt>, each
6306 with the single argument <tt>start</tt>. (The links are
6307 those in the <file>/etc/rc<var>n</var>.d</file> directory
6308 corresponding to the new runlevel.) The <tt>K</tt> links
6309 are responsible for killing services and the <tt>S</tt>
6310 link for starting services upon entering the runlevel.
6314 For example, if we are changing from runlevel 2 to
6315 runlevel 3, init will first execute all of the <tt>K</tt>
6316 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
6317 all of the <tt>S</tt> prefixed scripts in that directory.
6318 The links starting with <tt>K</tt> will cause the
6319 referred-to file to be executed with an argument of
6320 <tt>stop</tt>, and the <tt>S</tt> links with an argument
6325 The two-digit number <var>mm</var> is used to determine
6326 the order in which to run the scripts: low-numbered links
6327 have their scripts run first. For example, the
6328 <tt>K20</tt> scripts will be executed before the
6329 <tt>K30</tt> scripts. This is used when a certain service
6330 must be started before another. For example, the name
6331 server <prgn>bind</prgn> might need to be started before
6332 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
6333 can set up its access lists. In this case, the script
6334 that starts <prgn>bind</prgn> would have a lower number
6335 than the script that starts <prgn>inn</prgn> so that it
6337 <example compact="compact">
6344 The two runlevels 0 (halt) and 6 (reboot) are slightly
6345 different. In these runlevels, the links with an
6346 <tt>S</tt> prefix are still called after those with a
6347 <tt>K</tt> prefix, but they too are called with the single
6348 argument <tt>stop</tt>.
6352 <sect1 id="writing-init">
6353 <heading>Writing the scripts</heading>
6356 Packages that include daemons for system services should
6357 place scripts in <file>/etc/init.d</file> to start or stop
6358 services at boot time or during a change of runlevel.
6359 These scripts should be named
6360 <file>/etc/init.d/<var>package</var></file>, and they should
6361 accept one argument, saying what to do:
6364 <tag><tt>start</tt></tag>
6365 <item>start the service,</item>
6367 <tag><tt>stop</tt></tag>
6368 <item>stop the service,</item>
6370 <tag><tt>restart</tt></tag>
6371 <item>stop and restart the service if it's already running,
6372 otherwise start the service</item>
6374 <tag><tt>reload</tt></tag>
6375 <item><p>cause the configuration of the service to be
6376 reloaded without actually stopping and restarting
6379 <tag><tt>force-reload</tt></tag>
6380 <item>cause the configuration to be reloaded if the
6381 service supports this, otherwise restart the
6385 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
6386 <tt>force-reload</tt> options should be supported by all
6387 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
6392 The <file>init.d</file> scripts must ensure that they will
6393 behave sensibly (i.e., returning success and not starting
6394 multiple copies of a service) if invoked with <tt>start</tt>
6395 when the service is already running, or with <tt>stop</tt>
6396 when it isn't, and that they don't kill unfortunately-named
6397 user processes. The best way to achieve this is usually to
6398 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
6403 Be careful of using <tt>set -e</tt> in <file>init.d</file>
6404 scripts. Writing correct <file>init.d</file> scripts requires
6405 accepting various error exit statuses when daemons are already
6406 running or already stopped without aborting
6407 the <file>init.d</file> script, and common <file>init.d</file>
6408 function libraries are not safe to call with <tt>set -e</tt>
6410 <tt>/lib/lsb/init-functions</tt>, which assists in writing
6411 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
6412 in effect and echoing status messages to the console fails,
6414 </footnote>. For <tt>init.d</tt> scripts, it's often easier
6415 to not use <tt>set -e</tt> and instead check the result of
6416 each command separately.
6420 If a service reloads its configuration automatically (as
6421 in the case of <prgn>cron</prgn>, for example), the
6422 <tt>reload</tt> option of the <file>init.d</file> script
6423 should behave as if the configuration has been reloaded
6428 The <file>/etc/init.d</file> scripts must be treated as
6429 configuration files, either (if they are present in the
6430 package, that is, in the .deb file) by marking them as
6431 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6432 by managing them correctly in the maintainer scripts (see
6433 <ref id="config-files">). This is important since we want
6434 to give the local system administrator the chance to adapt
6435 the scripts to the local system, e.g., to disable a
6436 service without de-installing the package, or to specify
6437 some special command line options when starting a service,
6438 while making sure their changes aren't lost during the next
6443 These scripts should not fail obscurely when the
6444 configuration files remain but the package has been
6445 removed, as configuration files remain on the system after
6446 the package has been removed. Only when <prgn>dpkg</prgn>
6447 is executed with the <tt>--purge</tt> option will
6448 configuration files be removed. In particular, as the
6449 <file>/etc/init.d/<var>package</var></file> script itself is
6450 usually a <tt>conffile</tt>, it will remain on the system
6451 if the package is removed but not purged. Therefore, you
6452 should include a <tt>test</tt> statement at the top of the
6454 <example compact="compact">
6455 test -f <var>program-executed-later-in-script</var> || exit 0
6460 Often there are some variables in the <file>init.d</file>
6461 scripts whose values control the behavior of the scripts,
6462 and which a system administrator is likely to want to
6463 change. As the scripts themselves are frequently
6464 <tt>conffile</tt>s, modifying them requires that the
6465 administrator merge in their changes each time the package
6466 is upgraded and the <tt>conffile</tt> changes. To ease
6467 the burden on the system administrator, such configurable
6468 values should not be placed directly in the script.
6469 Instead, they should be placed in a file in
6470 <file>/etc/default</file>, which typically will have the same
6471 base name as the <file>init.d</file> script. This extra file
6472 should be sourced by the script when the script runs. It
6473 must contain only variable settings and comments in SUSv3
6474 <prgn>sh</prgn> format. It may either be a
6475 <tt>conffile</tt> or a configuration file maintained by
6476 the package maintainer scripts. See <ref id="config-files">
6481 To ensure that vital configurable values are always
6482 available, the <file>init.d</file> script should set default
6483 values for each of the shell variables it uses, either
6484 before sourcing the <file>/etc/default/</file> file or
6485 afterwards using something like the <tt>:
6486 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6487 script must behave sensibly and not fail if the
6488 <file>/etc/default</file> file is deleted.
6492 <file>/var/run</file> and <file>/var/lock</file> may be mounted
6493 as temporary filesystems<footnote>
6494 For example, using the <tt>RAMRUN</tt> and <tt>RAMLOCK</tt>
6495 options in <file>/etc/default/rcS</file>.
6496 </footnote>, so the <file>init.d</file> scripts must handle this
6497 correctly. This will typically amount to creating any required
6498 subdirectories dynamically when the <file>init.d</file> script
6499 is run, rather than including them in the package and relying on
6500 <prgn>dpkg</prgn> to create them.
6505 <heading>Interfacing with the initscript system</heading>
6508 Maintainers should use the abstraction layer provided by
6509 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6510 programs to deal with initscripts in their packages'
6511 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6512 and <prgn>postrm</prgn>.
6516 Directly managing the /etc/rc?.d links and directly
6517 invoking the <file>/etc/init.d/</file> initscripts should
6518 be done only by packages providing the initscript
6519 subsystem (such as <prgn>sysv-rc</prgn> and
6520 <prgn>file-rc</prgn>).
6524 <heading>Managing the links</heading>
6527 The program <prgn>update-rc.d</prgn> is provided for
6528 package maintainers to arrange for the proper creation and
6529 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6530 or their functional equivalent if another method is being
6531 used. This may be used by maintainers in their packages'
6532 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6536 You must not include any <file>/etc/rc<var>n</var>.d</file>
6537 symbolic links in the actual archive or manually create or
6538 remove the symbolic links in maintainer scripts; you must
6539 use the <prgn>update-rc.d</prgn> program instead. (The
6540 former will fail if an alternative method of maintaining
6541 runlevel information is being used.) You must not include
6542 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6543 in the archive either. (Only the <tt>sysvinit</tt>
6548 By default <prgn>update-rc.d</prgn> will start services in
6549 each of the multi-user state runlevels (2, 3, 4, and 5)
6550 and stop them in the halt runlevel (0), the single-user
6551 runlevel (1) and the reboot runlevel (6). The system
6552 administrator will have the opportunity to customize
6553 runlevels by simply adding, moving, or removing the
6554 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6555 symbolic links are being used, or by modifying
6556 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6561 To get the default behavior for your package, put in your
6562 <prgn>postinst</prgn> script
6563 <example compact="compact">
6564 update-rc.d <var>package</var> defaults
6566 and in your <prgn>postrm</prgn>
6567 <example compact="compact">
6568 if [ "$1" = purge ]; then
6569 update-rc.d <var>package</var> remove
6571 </example>. Note that if your package changes runlevels
6572 or priority, you may have to remove and recreate the links,
6573 since otherwise the old links may persist. Refer to the
6574 documentation of <prgn>update-rc.d</prgn>.
6578 This will use a default sequence number of 20. If it does
6579 not matter when or in which order the <file>init.d</file>
6580 script is run, use this default. If it does, then you
6581 should talk to the maintainer of the <prgn>sysvinit</prgn>
6582 package or post to <tt>debian-devel</tt>, and they will
6583 help you choose a number.
6587 For more information about using <tt>update-rc.d</tt>,
6588 please consult its man page <manref name="update-rc.d"
6594 <heading>Running initscripts</heading>
6596 The program <prgn>invoke-rc.d</prgn> is provided to make
6597 it easier for package maintainers to properly invoke an
6598 initscript, obeying runlevel and other locally-defined
6599 constraints that might limit a package's right to start,
6600 stop and otherwise manage services. This program may be
6601 used by maintainers in their packages' scripts.
6605 The package maintainer scripts must use
6606 <prgn>invoke-rc.d</prgn> to invoke the
6607 <file>/etc/init.d/*</file> initscripts, instead of
6608 calling them directly.
6612 By default, <prgn>invoke-rc.d</prgn> will pass any
6613 action requests (start, stop, reload, restart...) to the
6614 <file>/etc/init.d</file> script, filtering out requests
6615 to start or restart a service out of its intended
6620 Most packages will simply need to change:
6621 <example compact="compact">/etc/init.d/<package>
6622 <action></example> in their <prgn>postinst</prgn>
6623 and <prgn>prerm</prgn> scripts to:
6624 <example compact="compact">
6625 if which invoke-rc.d >/dev/null 2>&1; then
6626 invoke-rc.d <var>package</var> <action>
6628 /etc/init.d/<var>package</var> <action>
6634 A package should register its initscript services using
6635 <prgn>update-rc.d</prgn> before it tries to invoke them
6636 using <prgn>invoke-rc.d</prgn>. Invocation of
6637 unregistered services may fail.
6641 For more information about using
6642 <prgn>invoke-rc.d</prgn>, please consult its man page
6643 <manref name="invoke-rc.d" section="8">.
6649 <heading>Boot-time initialization</heading>
6652 There used to be another directory, <file>/etc/rc.boot</file>,
6653 which contained scripts which were run once per machine
6654 boot. This has been deprecated in favour of links from
6655 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6656 described in <ref id="/etc/init.d">. Packages must not
6657 place files in <file>/etc/rc.boot</file>.
6662 <heading>Example</heading>
6665 An example on which you can base your
6666 <file>/etc/init.d</file> scripts is found in
6667 <file>/etc/init.d/skeleton</file>.
6674 <heading>Console messages from <file>init.d</file> scripts</heading>
6677 This section describes the formats to be used for messages
6678 written to standard output by the <file>/etc/init.d</file>
6679 scripts. The intent is to improve the consistency of
6680 Debian's startup and shutdown look and feel. For this
6681 reason, please look very carefully at the details. We want
6682 the messages to have the same format in terms of wording,
6683 spaces, punctuation and case of letters.
6687 Here is a list of overall rules that should be used for
6688 messages generated by <file>/etc/init.d</file> scripts.
6694 The message should fit in one line (fewer than 80
6695 characters), start with a capital letter and end with
6696 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6700 If the script is performing some time consuming task in
6701 the background (not merely starting or stopping a
6702 program, for instance), an ellipsis (three dots:
6703 <tt>...</tt>) should be output to the screen, with no
6704 leading or tailing whitespace or line feeds.
6708 The messages should appear as if the computer is telling
6709 the user what it is doing (politely :-), but should not
6710 mention "it" directly. For example, instead of:
6711 <example compact="compact">
6712 I'm starting network daemons: nfsd mountd.
6714 the message should say
6715 <example compact="compact">
6716 Starting network daemons: nfsd mountd.
6723 <tt>init.d</tt> script should use the following standard
6724 message formats for the situations enumerated below.
6730 <p>When daemons are started</p>
6733 If the script starts one or more daemons, the output
6734 should look like this (a single line, no leading
6736 <example compact="compact">
6737 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6739 The <var>description</var> should describe the
6740 subsystem the daemon or set of daemons are part of,
6741 while <var>daemon-1</var> up to <var>daemon-n</var>
6742 denote each daemon's name (typically the file name of
6747 For example, the output of <file>/etc/init.d/lpd</file>
6749 <example compact="compact">
6750 Starting printer spooler: lpd.
6755 This can be achieved by saying
6756 <example compact="compact">
6757 echo -n "Starting printer spooler: lpd"
6758 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6761 in the script. If there are more than one daemon to
6762 start, the output should look like this:
6763 <example compact="compact">
6764 echo -n "Starting remote file system services:"
6765 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6766 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6767 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6770 This makes it possible for the user to see what is
6771 happening and when the final daemon has been started.
6772 Care should be taken in the placement of white spaces:
6773 in the example above the system administrators can
6774 easily comment out a line if they don't want to start
6775 a specific daemon, while the displayed message still
6781 <p>When a system parameter is being set</p>
6784 If you have to set up different system parameters
6785 during the system boot, you should use this format:
6786 <example compact="compact">
6787 Setting <var>parameter</var> to "<var>value</var>".
6792 You can use a statement such as the following to get
6794 <example compact="compact">
6795 echo "Setting DNS domainname to \"$domainname\"."
6800 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
6801 for the left and right quotation marks. A grave accent
6802 (<tt>`</tt>) is not a quote character; neither is an
6803 apostrophe (<tt>'</tt>).
6808 <p>When a daemon is stopped or restarted</p>
6811 When you stop or restart a daemon, you should issue a
6812 message identical to the startup message, except that
6813 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6814 or <tt>Restarting</tt> respectively.
6818 For example, stopping the printer daemon will look like
6820 <example compact="compact">
6821 Stopping printer spooler: lpd.
6827 <p>When something is executed</p>
6830 There are several examples where you have to run a
6831 program at system startup or shutdown to perform a
6832 specific task, for example, setting the system's clock
6833 using <prgn>netdate</prgn> or killing all processes
6834 when the system shuts down. Your message should look
6836 <example compact="compact">
6837 Doing something very useful...done.
6839 You should print the <tt>done.</tt> immediately after
6840 the job has been completed, so that the user is
6841 informed why they have to wait. You can get this
6843 <example compact="compact">
6844 echo -n "Doing something very useful..."
6853 <p>When the configuration is reloaded</p>
6856 When a daemon is forced to reload its configuration
6857 files you should use the following format:
6858 <example compact="compact">
6859 Reloading <var>description</var> configuration...done.
6861 where <var>description</var> is the same as in the
6862 daemon starting message.
6870 <heading>Cron jobs</heading>
6873 Packages must not modify the configuration file
6874 <file>/etc/crontab</file>, and they must not modify the files in
6875 <file>/var/spool/cron/crontabs</file>.</p>
6878 If a package wants to install a job that has to be executed
6879 via cron, it should place a file with the name of the
6880 package in one or more of the following directories:
6881 <example compact="compact">
6887 As these directory names imply, the files within them are
6888 executed on an hourly, daily, weekly, or monthly basis,
6889 respectively. The exact times are listed in
6890 <file>/etc/crontab</file>.</p>
6893 All files installed in any of these directories must be
6894 scripts (e.g., shell scripts or Perl scripts) so that they
6895 can easily be modified by the local system administrator.
6896 In addition, they must be treated as configuration files.
6900 If a certain job has to be executed at some other frequency or
6901 at a specific time, the package should install a file
6902 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6903 same syntax as <file>/etc/crontab</file> and is processed by
6904 <prgn>cron</prgn> automatically. The file must also be
6905 treated as a configuration file. (Note that entries in the
6906 <file>/etc/cron.d</file> directory are not handled by
6907 <prgn>anacron</prgn>. Thus, you should only use this
6908 directory for jobs which may be skipped if the system is not
6911 Unlike <file>crontab</file> files described in the IEEE Std
6912 1003.1-2008 (POSIX.1) available from
6913 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
6914 name="The Open Group">, the files in
6915 <file>/etc/cron.d</file> and the file
6916 <file>/etc/crontab</file> have seven fields; namely:
6918 <item>Minute [0,59]</item>
6919 <item>Hour [0,23]</item>
6920 <item>Day of the month [1,31]</item>
6921 <item>Month of the year [1,12]</item>
6922 <item>Day of the week ([0,6] with 0=Sunday)</item>
6923 <item>Username</item>
6924 <item>Command to be run</item>
6926 Ranges of numbers are allowed. Ranges are two numbers
6927 separated with a hyphen. The specified range is inclusive.
6928 Lists are allowed. A list is a set of numbers (or ranges)
6929 separated by commas. Step values can be used in conjunction
6934 The scripts or <tt>crontab</tt> entries in these directories should
6935 check if all necessary programs are installed before they
6936 try to execute them. Otherwise, problems will arise when a
6937 package was removed but not purged since configuration files
6938 are kept on the system in this situation.
6942 Any <tt>cron</tt> daemon must provide
6943 <file>/usr/bin/crontab</file> and support normal
6944 <tt>crontab</tt> entries as specified in POSIX. The daemon
6945 must also support names for days and months, ranges, and
6946 step values. It has to support <file>/etc/crontab</file>,
6947 and correctly execute the scripts in
6948 <file>/etc/cron.d</file>. The daemon must also correctly
6950 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
6955 <heading>Menus</heading>
6958 The Debian <tt>menu</tt> package provides a standard
6959 interface between packages providing applications and
6960 <em>menu programs</em> (either X window managers or
6961 text-based menu programs such as <prgn>pdmenu</prgn>).
6965 All packages that provide applications that need not be
6966 passed any special command line arguments for normal
6967 operation should register a menu entry for those
6968 applications, so that users of the <tt>menu</tt> package
6969 will automatically get menu entries in their window
6970 managers, as well in shells like <tt>pdmenu</tt>.
6974 Menu entries should follow the current menu policy.
6978 The menu policy can be found in the <tt>menu-policy</tt>
6979 files in the <tt>debian-policy</tt> package.
6980 It is also available from the Debian web mirrors at
6981 <tt><url name="/doc/packaging-manuals/menu-policy/"
6982 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6986 Please also refer to the <em>Debian Menu System</em>
6987 documentation that comes with the <package>menu</package>
6988 package for information about how to register your
6994 <heading>Multimedia handlers</heading>
6997 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6998 is a mechanism for encoding files and data streams and
6999 providing meta-information about them, in particular their
7000 type (e.g. audio or video) and format (e.g. PNG, HTML,
7005 Registration of MIME type handlers allows programs like mail
7006 user agents and web browsers to invoke these handlers to
7007 view, edit or display MIME types they don't support directly.
7011 Packages which provide the ability to view/show/play,
7012 compose, edit or print MIME types should register themselves
7013 as such following the current MIME support policy.
7017 The MIME support policy can be found in the <tt>mime-policy</tt>
7018 files in the <tt>debian-policy</tt> package.
7019 It is also available from the Debian web mirrors at
7020 <tt><url name="/doc/packaging-manuals/mime-policy/"
7021 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
7027 <heading>Keyboard configuration</heading>
7030 To achieve a consistent keyboard configuration so that all
7031 applications interpret a keyboard event the same way, all
7032 programs in the Debian distribution must be configured to
7033 comply with the following guidelines.
7037 The following keys must have the specified interpretations:
7040 <tag><tt><--</tt></tag>
7041 <item>delete the character to the left of the cursor</item>
7043 <tag><tt>Delete</tt></tag>
7044 <item>delete the character to the right of the cursor</item>
7046 <tag><tt>Control+H</tt></tag>
7047 <item>emacs: the help prefix</item>
7050 The interpretation of any keyboard events should be
7051 independent of the terminal that is used, be it a virtual
7052 console, an X terminal emulator, an rlogin/telnet session,
7057 The following list explains how the different programs
7058 should be set up to achieve this:
7064 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
7068 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
7072 X translations are set up to make
7073 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
7074 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
7075 is the vt220 escape code for the "delete character"
7076 key). This must be done by loading the X resources
7077 using <prgn>xrdb</prgn> on all local X displays, not
7078 using the application defaults, so that the
7079 translation resources used correspond to the
7080 <prgn>xmodmap</prgn> settings.
7084 The Linux console is configured to make
7085 <tt><--</tt> generate DEL, and <tt>Delete</tt>
7086 generate <tt>ESC [ 3 ~</tt>.
7090 X applications are configured so that <tt><</tt>
7091 deletes left, and <tt>Delete</tt> deletes right. Motif
7092 applications already work like this.
7096 Terminals should have <tt>stty erase ^?</tt> .
7100 The <tt>xterm</tt> terminfo entry should have <tt>ESC
7101 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
7102 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
7106 Emacs is programmed to map <tt>KB_Backspace</tt> or
7107 the <tt>stty erase</tt> character to
7108 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
7109 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
7110 <tt>^H</tt> to <tt>help</tt> as always.
7114 Other applications use the <tt>stty erase</tt>
7115 character and <tt>kdch1</tt> for the two delete keys,
7116 with ASCII DEL being "delete previous character" and
7117 <tt>kdch1</tt> being "delete character under
7125 This will solve the problem except for the following
7132 Some terminals have a <tt><--</tt> key that cannot
7133 be made to produce anything except <tt>^H</tt>. On
7134 these terminals Emacs help will be unavailable on
7135 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
7136 character takes precedence in Emacs, and has been set
7137 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
7138 available) can be used instead.
7142 Some operating systems use <tt>^H</tt> for <tt>stty
7143 erase</tt>. However, modern telnet versions and all
7144 rlogin versions propagate <tt>stty</tt> settings, and
7145 almost all UNIX versions honour <tt>stty erase</tt>.
7146 Where the <tt>stty</tt> settings are not propagated
7147 correctly, things can be made to work by using
7148 <tt>stty</tt> manually.
7152 Some systems (including previous Debian versions) use
7153 <prgn>xmodmap</prgn> to arrange for both
7154 <tt><--</tt> and <tt>Delete</tt> to generate
7155 <tt>KB_Delete</tt>. We can change the behavior of
7156 their X clients using the same X resources that we use
7157 to do it for our own clients, or configure our clients
7158 using their resources when things are the other way
7159 around. On displays configured like this
7160 <tt>Delete</tt> will not work, but <tt><--</tt>
7165 Some operating systems have different <tt>kdch1</tt>
7166 settings in their <tt>terminfo</tt> database for
7167 <tt>xterm</tt> and others. On these systems the
7168 <tt>Delete</tt> key will not work correctly when you
7169 log in from a system conforming to our policy, but
7170 <tt><--</tt> will.
7177 <heading>Environment variables</heading>
7180 A program must not depend on environment variables to get
7181 reasonable defaults. (That's because these environment
7182 variables would have to be set in a system-wide
7183 configuration file like <file>/etc/profile</file>, which is not
7184 supported by all shells.)
7188 If a program usually depends on environment variables for its
7189 configuration, the program should be changed to fall back to
7190 a reasonable default configuration if these environment
7191 variables are not present. If this cannot be done easily
7192 (e.g., if the source code of a non-free program is not
7193 available), the program must be replaced by a small
7194 "wrapper" shell script which sets the environment variables
7195 if they are not already defined, and calls the original program.
7199 Here is an example of a wrapper script for this purpose:
7201 <example compact="compact">
7203 BAR=${BAR:-/var/lib/fubar}
7205 exec /usr/lib/foo/foo "$@"
7210 Furthermore, as <file>/etc/profile</file> is a configuration
7211 file of the <prgn>base-files</prgn> package, other packages must
7212 not put any environment variables or other commands into that
7217 <sect id="doc-base">
7218 <heading>Registering Documents using doc-base</heading>
7221 The <package>doc-base</package> package implements a
7222 flexible mechanism for handling and presenting
7223 documentation. The recommended practice is for every Debian
7224 package that provides online documentation (other than just
7225 manual pages) to register these documents with
7226 <package>doc-base</package> by installing a
7227 <package>doc-base</package> control file via the
7228 <prgn/install-docs/ script at installation time and
7229 de-register the manuals again when the package is removed.
7232 Please refer to the documentation that comes with the
7233 <package>doc-base</package> package for information and
7242 <heading>Files</heading>
7244 <sect id="binaries">
7245 <heading>Binaries</heading>
7248 Two different packages must not install programs with
7249 different functionality but with the same filenames. (The
7250 case of two programs having the same functionality but
7251 different implementations is handled via "alternatives" or
7252 the "Conflicts" mechanism. See <ref id="maintscripts"> and
7253 <ref id="conflicts"> respectively.) If this case happens,
7254 one of the programs must be renamed. The maintainers should
7255 report this to the <tt>debian-devel</tt> mailing list and
7256 try to find a consensus about which program will have to be
7257 renamed. If a consensus cannot be reached, <em>both</em>
7258 programs must be renamed.
7262 By default, when a package is being built, any binaries
7263 created should include debugging information, as well as
7264 being compiled with optimization. You should also turn on
7265 as many reasonable compilation warnings as possible; this
7266 makes life easier for porters, who can then look at build
7267 logs for possible problems. For the C programming language,
7268 this means the following compilation parameters should be
7270 <example compact="compact">
7272 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
7274 INSTALL = install -s # (or use strip on the files in debian/tmp)
7279 Note that by default all installed binaries should be stripped,
7280 either by using the <tt>-s</tt> flag to
7281 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
7282 the binaries after they have been copied into
7283 <file>debian/tmp</file> but before the tree is made into a
7288 Although binaries in the build tree should be compiled with
7289 debugging information by default, it can often be difficult to
7290 debug programs if they are also subjected to compiler
7291 optimization. For this reason, it is recommended to support the
7292 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
7293 (see <ref id="debianrules-options">). This variable can contain
7294 several flags to change how a package is compiled and built.
7298 It is up to the package maintainer to decide what
7299 compilation options are best for the package. Certain
7300 binaries (such as computationally-intensive programs) will
7301 function better with certain flags (<tt>-O3</tt>, for
7302 example); feel free to use them. Please use good judgment
7303 here. Don't use flags for the sake of it; only use them
7304 if there is good reason to do so. Feel free to override
7305 the upstream author's ideas about which compilation
7306 options are best: they are often inappropriate for our
7312 <sect id="libraries">
7313 <heading>Libraries</heading>
7316 If the package is <strong>architecture: any</strong>, then
7317 the shared library compilation and linking flags must have
7318 <tt>-fPIC</tt>, or the package shall not build on some of
7319 the supported architectures<footnote>
7321 If you are using GCC, <tt>-fPIC</tt> produces code with
7322 relocatable position independent code, which is required for
7323 most architectures to create a shared library, with i386 and
7324 perhaps some others where non position independent code is
7325 permitted in a shared library.
7328 Position independent code may have a performance penalty,
7329 especially on <tt>i386</tt>. However, in most cases the
7330 speed penalty must be measured against the memory wasted on
7331 the few architectures where non position independent code is
7334 </footnote>. Any exception to this rule must be discussed on
7335 the mailing list <em>debian-devel@lists.debian.org</em>, and
7336 a rough consensus obtained. The reasons for not compiling
7337 with <tt>-fPIC</tt> flag must be recorded in the file
7338 <tt>README.Debian</tt>, and care must be taken to either
7339 restrict the architecture or arrange for <tt>-fPIC</tt> to
7340 be used on architectures where it is required.<footnote>
7342 Some of the reasons why this might be required is if the
7343 library contains hand crafted assembly code that is not
7344 relocatable, the speed penalty is excessive for compute
7345 intensive libs, and similar reasons.
7350 As to the static libraries, the common case is not to have
7351 relocatable code, since there is no benefit, unless in specific
7352 cases; therefore the static version must not be compiled
7353 with the <tt>-fPIC</tt> flag. Any exception to this rule
7354 should be discussed on the mailing list
7355 <em>debian-devel@lists.debian.org</em>, and the reasons for
7356 compiling with the <tt>-fPIC</tt> flag must be recorded in
7357 the file <tt>README.Debian</tt>. <footnote>
7359 Some of the reasons for linking static libraries with
7360 the <tt>-fPIC</tt> flag are if, for example, one needs a
7361 Perl API for a library that is under rapid development,
7362 and has an unstable API, so shared libraries are
7363 pointless at this phase of the library's development. In
7364 that case, since Perl needs a library with relocatable
7365 code, it may make sense to create a static library with
7366 relocatable code. Another reason cited is if you are
7367 distilling various libraries into a common shared
7368 library, like <tt>mklibs</tt> does in the Debian
7374 In other words, if both a shared and a static library is
7375 being built, each source unit (<tt>*.c</tt>, for example,
7376 for C files) will need to be compiled twice, for the normal
7381 Libraries should be built with threading support and to be
7382 thread-safe if the library supports this.
7386 Although not enforced by the build tools, shared libraries
7387 must be linked against all libraries that they use symbols from
7388 in the same way that binaries are. This ensures the correct
7389 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
7390 system and guarantees that all libraries can be safely opened
7391 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
7392 option <tt>-Wl,-z,defs</tt> when building a shared library.
7393 Since this option enforces symbol resolution at build time,
7394 a missing library reference will be caught early as a fatal
7399 All installed shared libraries should be stripped with
7400 <example compact="compact">
7401 strip --strip-unneeded <var>your-lib</var>
7403 (The option <tt>--strip-unneeded</tt> makes
7404 <prgn>strip</prgn> remove only the symbols which aren't
7405 needed for relocation processing.) Shared libraries can
7406 function perfectly well when stripped, since the symbols for
7407 dynamic linking are in a separate part of the ELF object
7409 You might also want to use the options
7410 <tt>--remove-section=.comment</tt> and
7411 <tt>--remove-section=.note</tt> on both shared libraries
7412 and executables, and <tt>--strip-debug</tt> on static
7418 Note that under some circumstances it may be useful to
7419 install a shared library unstripped, for example when
7420 building a separate package to support debugging.
7424 Shared object files (often <file>.so</file> files) that are not
7425 public libraries, that is, they are not meant to be linked
7426 to by third party executables (binaries of other packages),
7427 should be installed in subdirectories of the
7428 <file>/usr/lib</file> directory. Such files are exempt from the
7429 rules that govern ordinary shared libraries, except that
7430 they must not be installed executable and should be
7432 A common example are the so-called "plug-ins",
7433 internal shared objects that are dynamically loaded by
7434 programs using <manref name="dlopen" section="3">.
7439 Packages that use <prgn>libtool</prgn> to create and install
7440 their shared libraries install a file containing additional
7441 metadata (ending in <file>.la</file>) alongside the library.
7442 For public libraries intended for use by other packages, these
7443 files normally should not be included in the Debian package,
7444 since the information they include is not necessary to link with
7445 the shared library on Debian and can add unnecessary additional
7446 dependencies to other programs or libraries.<footnote>
7447 These files store, among other things, all libraries on which
7448 that shared library depends. Unfortunately, if
7449 the <file>.la</file> file is present and contains that
7450 dependency information, using <prgn>libtool</prgn> when
7451 linking against that library will cause the resulting program
7452 or library to be linked against those dependencies as well,
7453 even if this is unnecessary. This can create unneeded
7454 dependencies on shared library packages that would otherwise
7455 be hidden behind the library ABI, and can make library
7456 transitions to new SONAMEs unnecessarily complicated and
7457 difficult to manage.
7459 If the <file>.la</file> file is required for that library (if,
7460 for instance, it's loaded via <tt>libltdl</tt> in a way that
7461 requires that meta-information), the <tt>dependency_libs</tt>
7462 setting in the <file>.la</file> file should normally be set to
7463 the empty string. If the shared library development package has
7464 historically included the <file>.la</file>, it must be retained
7465 in the development package (with <tt>dependency_libs</tt>
7466 emptied) until all libraries that depend on it have removed or
7467 emptied <tt>dependency_libs</tt> in their <file>.la</file>
7468 files to prevent linking with those other libraries
7469 using <prgn>libtool</prgn> from failing.
7473 If the <file>.la</file> must be included, it should be included
7474 in the development (<tt>-dev</tt>) package, unless the library
7475 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
7476 library. If it is intended for use with <tt>libltdl</tt>,
7477 the <file>.la</file> files must go in the run-time library
7482 These requirements for handling of <file>.la</file> files do not
7483 apply to loadable modules or libraries not installed in
7484 directories searched by default by the dynamic linker. Packages
7485 installing loadable modules will frequently need to install
7486 the <file>.la</file> files alongside the modules so that they
7487 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
7488 does not need to be modified for libraries or modules that are
7489 not installed in directories searched by the dynamic linker by
7490 default and not intended for use by other packages.
7494 You must make sure that you use only released versions of
7495 shared libraries to build your packages; otherwise other
7496 users will not be able to run your binaries
7497 properly. Producing source packages that depend on
7498 unreleased compilers is also usually a bad
7505 <heading>Shared libraries</heading>
7507 This section has moved to <ref id="sharedlibs">.
7513 <heading>Scripts</heading>
7516 All command scripts, including the package maintainer
7517 scripts inside the package and used by <prgn>dpkg</prgn>,
7518 should have a <tt>#!</tt> line naming the shell to be used
7523 In the case of Perl scripts this should be
7524 <tt>#!/usr/bin/perl</tt>.
7528 When scripts are installed into a directory in the system
7529 PATH, the script name should not include an extension such
7530 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7531 language currently used to implement it.
7534 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
7535 <file>init.d</file> scripts should almost certainly start
7536 with <tt>set -e</tt> so that errors are detected.
7537 <file>init.d</file> scripts are something of a special case, due
7538 to how frequently they need to call commands that are allowed to
7539 fail, and it may instead be easier to check the exit status of
7540 commands directly. See <ref id="writing-init"> for more
7541 information about writing <file>init.d</file> scripts.
7544 Every script should use <tt>set -e</tt> or check the exit status
7545 of <em>every</em> command.
7548 Scripts may assume that <file>/bin/sh</file> implements the
7549 SUSv3 Shell Command Language<footnote>
7550 Single UNIX Specification, version 3, which is also IEEE
7551 1003.1-2004 (POSIX), and is available on the World Wide Web
7552 from <url id="http://www.unix.org/version3/online.html"
7553 name="The Open Group"> after free
7554 registration.</footnote>
7555 plus the following additional features not mandated by
7557 These features are in widespread use in the Linux community
7558 and are implemented in all of bash, dash, and ksh, the most
7559 common shells users may wish to use as <file>/bin/sh</file>.
7562 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7563 must not generate a newline.</item>
7564 <item><tt>test</tt>, if implemented as a shell built-in, must
7565 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7567 <item><tt>local</tt> to create a scoped variable must be
7568 supported, including listing multiple variables in a single
7569 local command and assigning a value to a variable at the
7570 same time as localizing it. <tt>local</tt> may or
7571 may not preserve the variable value from an outer scope if
7572 no assignment is present. Uses such as:
7576 # ... use a, b, c, d ...
7579 must be supported and must set the value of <tt>c</tt> to
7582 <item>The XSI extension to <prgn>kill</prgn> allowing <tt>kill
7583 -<var>signal</var></tt>, where <var>signal</var> is either
7584 the name of a signal or one of the numeric signals listed in
7585 the XSI extension (0, 1, 2, 3, 6, 9, 14, and 15), must be
7586 supported if <prgn>kill</prgn> is implemented as a shell
7589 <item>The XSI extension to <prgn>trap</prgn> allowing numeric
7590 signals must be supported. In addition to the signal
7591 numbers listed in the extension, which are the same as for
7592 <prgn>kill<prgn> above, 13 (SIGPIPE) must be allowed.
7595 If a shell script requires non-SUSv3 features from the shell
7596 interpreter other than those listed above, the appropriate shell
7597 must be specified in the first line of the script (e.g.,
7598 <tt>#!/bin/bash</tt>) and the package must depend on the package
7599 providing the shell (unless the shell package is marked
7600 "Essential", as in the case of <prgn>bash</prgn>).
7604 You may wish to restrict your script to SUSv3 features plus the
7605 above set when possible so that it may use <file>/bin/sh</file>
7606 as its interpreter. If your script works with <prgn>dash</prgn>
7607 (originally called <prgn>ash</prgn>), it probably complies with
7608 the above requirements, but if you are in doubt, use
7609 <file>/bin/bash</file>.
7613 Perl scripts should check for errors when making any
7614 system calls, including <tt>open</tt>, <tt>print</tt>,
7615 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7619 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7620 scripting languages. See <em>Csh Programming Considered
7621 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7622 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7623 If an upstream package comes with <prgn>csh</prgn> scripts
7624 then you must make sure that they start with
7625 <tt>#!/bin/csh</tt> and make your package depend on the
7626 <prgn>c-shell</prgn> virtual package.
7630 Any scripts which create files in world-writeable
7631 directories (e.g., in <file>/tmp</file>) must use a
7632 mechanism which will fail atomically if a file with the same
7633 name already exists.
7637 The Debian base system provides the <prgn>tempfile</prgn>
7638 and <prgn>mktemp</prgn> utilities for use by scripts for
7645 <heading>Symbolic links</heading>
7648 In general, symbolic links within a top-level directory
7649 should be relative, and symbolic links pointing from one
7650 top-level directory into another should be absolute. (A
7651 top-level directory is a sub-directory of the root
7652 directory <file>/</file>.)
7656 In addition, symbolic links should be specified as short as
7657 possible, i.e., link targets like <file>foo/../bar</file> are
7662 Note that when creating a relative link using
7663 <prgn>ln</prgn> it is not necessary for the target of the
7664 link to exist relative to the working directory you're
7665 running <prgn>ln</prgn> from, nor is it necessary to change
7666 directory to the directory where the link is to be made.
7667 Simply include the string that should appear as the target
7668 of the link (this will be a pathname relative to the
7669 directory in which the link resides) as the first argument
7674 For example, in your <prgn>Makefile</prgn> or
7675 <file>debian/rules</file>, you can do things like:
7676 <example compact="compact">
7677 ln -fs gcc $(prefix)/bin/cc
7678 ln -fs gcc debian/tmp/usr/bin/cc
7679 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7680 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7685 A symbolic link pointing to a compressed file should always
7686 have the same file extension as the referenced file. (For
7687 example, if a file <file>foo.gz</file> is referenced by a
7688 symbolic link, the filename of the link has to end with
7689 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7694 <heading>Device files</heading>
7697 Packages must not include device files or named pipes in the
7702 If a package needs any special device files that are not
7703 included in the base system, it must call
7704 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7705 after notifying the user<footnote>
7706 This notification could be done via a (low-priority)
7707 debconf message, or an echo (printf) statement.
7712 Packages must not remove any device files in the
7713 <prgn>postrm</prgn> or any other script. This is left to the
7714 system administrator.
7718 Debian uses the serial devices
7719 <file>/dev/ttyS*</file>. Programs using the old
7720 <file>/dev/cu*</file> devices should be changed to use
7721 <file>/dev/ttyS*</file>.
7725 Named pipes needed by the package must be created in
7726 the <prgn>postinst</prgn> script<footnote>
7727 It's better to use <prgn>mkfifo</prgn> rather
7728 than <prgn>mknod</prgn> to create named pipes so that
7729 automated checks for packages incorrectly creating device
7730 files with <prgn>mknod</prgn> won't have false positives.
7731 </footnote> and removed in
7732 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
7737 <sect id="config-files">
7738 <heading>Configuration files</heading>
7741 <heading>Definitions</heading>
7745 <tag>configuration file</tag>
7747 A file that affects the operation of a program, or
7748 provides site- or host-specific information, or
7749 otherwise customizes the behavior of a program.
7750 Typically, configuration files are intended to be
7751 modified by the system administrator (if needed or
7752 desired) to conform to local policy or to provide
7753 more useful site-specific behavior.
7756 <tag><tt>conffile</tt></tag>
7758 A file listed in a package's <tt>conffiles</tt>
7759 file, and is treated specially by <prgn>dpkg</prgn>
7760 (see <ref id="configdetails">).
7766 The distinction between these two is important; they are
7767 not interchangeable concepts. Almost all
7768 <tt>conffile</tt>s are configuration files, but many
7769 configuration files are not <tt>conffiles</tt>.
7773 As noted elsewhere, <file>/etc/init.d</file> scripts,
7774 <file>/etc/default</file> files, scripts installed in
7775 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7776 configuration installed in <file>/etc/cron.d</file> must be
7777 treated as configuration files. In general, any script that
7778 embeds configuration information is de-facto a configuration
7779 file and should be treated as such.
7784 <heading>Location</heading>
7787 Any configuration files created or used by your package
7788 must reside in <file>/etc</file>. If there are several,
7789 consider creating a subdirectory of <file>/etc</file>
7790 named after your package.
7794 If your package creates or uses configuration files
7795 outside of <file>/etc</file>, and it is not feasible to modify
7796 the package to use <file>/etc</file> directly, put the files
7797 in <file>/etc</file> and create symbolic links to those files
7798 from the location that the package requires.
7803 <heading>Behavior</heading>
7806 Configuration file handling must conform to the following
7808 <list compact="compact">
7810 local changes must be preserved during a package
7814 configuration files must be preserved when the
7815 package is removed, and only deleted when the
7819 Obsolete configuration files without local changes may be
7820 removed by the package during upgrade.
7824 The easy way to achieve this behavior is to make the
7825 configuration file a <tt>conffile</tt>. This is
7826 appropriate only if it is possible to distribute a default
7827 version that will work for most installations, although
7828 some system administrators may choose to modify it. This
7829 implies that the default version will be part of the
7830 package distribution, and must not be modified by the
7831 maintainer scripts during installation (or at any other
7836 In order to ensure that local changes are preserved
7837 correctly, no package may contain or make hard links to
7838 conffiles.<footnote>
7839 Rationale: There are two problems with hard links.
7840 The first is that some editors break the link while
7841 editing one of the files, so that the two files may
7842 unwittingly become unlinked and different. The second
7843 is that <prgn>dpkg</prgn> might break the hard link
7844 while upgrading <tt>conffile</tt>s.
7849 The other way to do it is via the maintainer scripts. In
7850 this case, the configuration file must not be listed as a
7851 <tt>conffile</tt> and must not be part of the package
7852 distribution. If the existence of a file is required for
7853 the package to be sensibly configured it is the
7854 responsibility of the package maintainer to provide
7855 maintainer scripts which correctly create, update and
7856 maintain the file and remove it on purge. (See <ref
7857 id="maintainerscripts"> for more information.) These
7858 scripts must be idempotent (i.e., must work correctly if
7859 <prgn>dpkg</prgn> needs to re-run them due to errors
7860 during installation or removal), must cope with all the
7861 variety of ways <prgn>dpkg</prgn> can call maintainer
7862 scripts, must not overwrite or otherwise mangle the user's
7863 configuration without asking, must not ask unnecessary
7864 questions (particularly during upgrades), and must
7865 otherwise be good citizens.
7869 The scripts are not required to configure every possible
7870 option for the package, but only those necessary to get
7871 the package running on a given system. Ideally the
7872 sysadmin should not have to do any configuration other
7873 than that done (semi-)automatically by the
7874 <prgn>postinst</prgn> script.
7878 A common practice is to create a script called
7879 <file><var>package</var>-configure</file> and have the
7880 package's <prgn>postinst</prgn> call it if and only if the
7881 configuration file does not already exist. In certain
7882 cases it is useful for there to be an example or template
7883 file which the maintainer scripts use. Such files should
7884 be in <file>/usr/share/<var>package</var></file> or
7885 <file>/usr/lib/<var>package</var></file> (depending on whether
7886 they are architecture-independent or not). There should
7887 be symbolic links to them from
7888 <file>/usr/share/doc/<var>package</var>/examples</file> if
7889 they are examples, and should be perfectly ordinary
7890 <prgn>dpkg</prgn>-handled files (<em>not</em>
7891 configuration files).
7895 These two styles of configuration file handling must
7896 not be mixed, for that way lies madness:
7897 <prgn>dpkg</prgn> will ask about overwriting the file
7898 every time the package is upgraded.
7903 <heading>Sharing configuration files</heading>
7906 Packages which specify the same file as a
7907 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7908 with each other. (This is an instance of the general rule
7909 about not sharing files. Note that neither alternatives
7910 nor diversions are likely to be appropriate in this case;
7911 in particular, <prgn>dpkg</prgn> does not handle diverted
7912 <tt>conffile</tt>s well.)
7916 The maintainer scripts must not alter a <tt>conffile</tt>
7917 of <em>any</em> package, including the one the scripts
7922 If two or more packages use the same configuration file
7923 and it is reasonable for both to be installed at the same
7924 time, one of these packages must be defined as
7925 <em>owner</em> of the configuration file, i.e., it will be
7926 the package which handles that file as a configuration
7927 file. Other packages that use the configuration file must
7928 depend on the owning package if they require the
7929 configuration file to operate. If the other package will
7930 use the configuration file if present, but is capable of
7931 operating without it, no dependency need be declared.
7935 If it is desirable for two or more related packages to
7936 share a configuration file <em>and</em> for all of the
7937 related packages to be able to modify that configuration
7938 file, then the following should be done:
7939 <enumlist compact="compact">
7941 One of the related packages (the "owning" package)
7942 will manage the configuration file with maintainer
7943 scripts as described in the previous section.
7946 The owning package should also provide a program
7947 that the other packages may use to modify the
7951 The related packages must use the provided program
7952 to make any desired modifications to the
7953 configuration file. They should either depend on
7954 the core package to guarantee that the configuration
7955 modifier program is available or accept gracefully
7956 that they cannot modify the configuration file if it
7957 is not. (This is in addition to the fact that the
7958 configuration file may not even be present in the
7965 Sometimes it's appropriate to create a new package which
7966 provides the basic infrastructure for the other packages
7967 and which manages the shared configuration files. (The
7968 <tt>sgml-base</tt> package is a good example.)
7973 <heading>User configuration files ("dotfiles")</heading>
7976 The files in <file>/etc/skel</file> will automatically be
7977 copied into new user accounts by <prgn>adduser</prgn>.
7978 No other program should reference the files in
7979 <file>/etc/skel</file>.
7983 Therefore, if a program needs a dotfile to exist in
7984 advance in <file>$HOME</file> to work sensibly, that dotfile
7985 should be installed in <file>/etc/skel</file> and treated as a
7990 However, programs that require dotfiles in order to
7991 operate sensibly are a bad thing, unless they do create
7992 the dotfiles themselves automatically.
7996 Furthermore, programs should be configured by the Debian
7997 default installation to behave as closely to the upstream
7998 default behavior as possible.
8002 Therefore, if a program in a Debian package needs to be
8003 configured in some way in order to operate sensibly, that
8004 should be done using a site-wide configuration file placed
8005 in <file>/etc</file>. Only if the program doesn't support a
8006 site-wide default configuration and the package maintainer
8007 doesn't have time to add it may a default per-user file be
8008 placed in <file>/etc/skel</file>.
8012 <file>/etc/skel</file> should be as empty as we can make it.
8013 This is particularly true because there is no easy (or
8014 necessarily desirable) mechanism for ensuring that the
8015 appropriate dotfiles are copied into the accounts of
8016 existing users when a package is installed.
8022 <heading>Log files</heading>
8024 Log files should usually be named
8025 <file>/var/log/<var>package</var>.log</file>. If you have many
8026 log files, or need a separate directory for permission
8027 reasons (<file>/var/log</file> is writable only by
8028 <file>root</file>), you should usually create a directory named
8029 <file>/var/log/<var>package</var></file> and place your log
8034 Log files must be rotated occasionally so that they don't grow
8035 indefinitely. The best way to do this is to install a log
8036 rotation configuration file in the
8037 directory <file>/etc/logrotate.d</file>, normally
8038 named <file>/etc/logrotate.d/<var>package</var></file>, and use
8039 the facilities provided by <prgn>logrotate</prgn>.
8042 The traditional approach to log files has been to set up
8043 <em>ad hoc</em> log rotation schemes using simple shell
8044 scripts and cron. While this approach is highly
8045 customizable, it requires quite a lot of sysadmin work.
8046 Even though the original Debian system helped a little
8047 by automatically installing a system which can be used
8048 as a template, this was deemed not enough.
8052 The use of <prgn>logrotate</prgn>, a program developed
8053 by Red Hat, is better, as it centralizes log management.
8054 It has both a configuration file
8055 (<file>/etc/logrotate.conf</file>) and a directory where
8056 packages can drop their individual log rotation
8057 configurations (<file>/etc/logrotate.d</file>).
8060 Here is a good example for a logrotate config
8061 file (for more information see <manref name="logrotate"
8063 <example compact="compact">
8064 /var/log/foo/*.log {
8070 start-stop-daemon -K -p /var/run/foo.pid -s HUP -x /usr/sbin/foo -q
8074 This rotates all files under <file>/var/log/foo</file>, saves 12
8075 compressed generations, and tells the daemon to reopen its log
8076 files after the log rotation. It skips this log rotation
8077 (via <tt>missingok</tt>) if no such log file is present, which
8078 avoids errors if the package is removed but not purged.
8082 Log files should be removed when the package is
8083 purged (but not when it is only removed). This should be
8084 done by the <prgn>postrm</prgn> script when it is called
8085 with the argument <tt>purge</tt> (see <ref
8086 id="removedetails">).
8090 <sect id="permissions-owners">
8091 <heading>Permissions and owners</heading>
8094 The rules in this section are guidelines for general use.
8095 If necessary you may deviate from the details below.
8096 However, if you do so you must make sure that what is done
8097 is secure and you should try to be as consistent as possible
8098 with the rest of the system. You should probably also
8099 discuss it on <prgn>debian-devel</prgn> first.
8103 Files should be owned by <tt>root:root</tt>, and made
8104 writable only by the owner and universally readable (and
8105 executable, if appropriate), that is mode 644 or 755.
8109 Directories should be mode 755 or (for group-writability)
8110 mode 2775. The ownership of the directory should be
8111 consistent with its mode: if a directory is mode 2775, it
8112 should be owned by the group that needs write access to
8115 When a package is upgraded, and the owner or permissions
8116 of a file included in the package has changed, dpkg
8117 arranges for the ownership and permissions to be
8118 correctly set upon installation. However, this does not
8119 extend to directories; the permissions and ownership of
8120 directories already on the system does not change on
8121 install or upgrade of packages. This makes sense, since
8122 otherwise common directories like <tt>/usr</tt> would
8123 always be in flux. To correctly change permissions of a
8124 directory the package owns, explicit action is required,
8125 usually in the <tt>postinst</tt> script. Care must be
8126 taken to handle downgrades as well, in that case.
8132 Control information files should be owned by <tt>root:root</tt>
8133 and either mode 644 (for most files) or mode 755 (for
8134 executables such as <qref id="maintscripts">maintainer
8139 Setuid and setgid executables should be mode 4755 or 2755
8140 respectively, and owned by the appropriate user or group.
8141 They should not be made unreadable (modes like 4711 or
8142 2711 or even 4111); doing so achieves no extra security,
8143 because anyone can find the binary in the freely available
8144 Debian package; it is merely inconvenient. For the same
8145 reason you should not restrict read or execute permissions
8146 on non-set-id executables.
8150 Some setuid programs need to be restricted to particular
8151 sets of users, using file permissions. In this case they
8152 should be owned by the uid to which they are set-id, and by
8153 the group which should be allowed to execute them. They
8154 should have mode 4754; again there is no point in making
8155 them unreadable to those users who must not be allowed to
8160 It is possible to arrange that the system administrator can
8161 reconfigure the package to correspond to their local
8162 security policy by changing the permissions on a binary:
8163 they can do this by using <prgn>dpkg-statoverride</prgn>, as
8164 described below.<footnote>
8165 Ordinary files installed by <prgn>dpkg</prgn> (as
8166 opposed to <tt>conffile</tt>s and other similar objects)
8167 normally have their permissions reset to the distributed
8168 permissions when the package is reinstalled. However,
8169 the use of <prgn>dpkg-statoverride</prgn> overrides this
8172 Another method you should consider is to create a group for
8173 people allowed to use the program(s) and make any setuid
8174 executables executable only by that group.
8178 If you need to create a new user or group for your package
8179 there are two possibilities. Firstly, you may need to
8180 make some files in the binary package be owned by this
8181 user or group, or you may need to compile the user or
8182 group id (rather than just the name) into the binary
8183 (though this latter should be avoided if possible, as in
8184 this case you need a statically allocated id).</p>
8187 If you need a statically allocated id, you must ask for a
8188 user or group id from the <tt>base-passwd</tt> maintainer,
8189 and must not release the package until you have been
8190 allocated one. Once you have been allocated one you must
8191 either make the package depend on a version of the
8192 <tt>base-passwd</tt> package with the id present in
8193 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
8194 your package to create the user or group itself with the
8195 correct id (using <tt>adduser</tt>) in its
8196 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
8197 the <prgn>postinst</prgn> is to be preferred if it is
8198 possible, otherwise a pre-dependency will be needed on the
8199 <tt>adduser</tt> package.)
8203 On the other hand, the program might be able to determine
8204 the uid or gid from the user or group name at runtime, so
8205 that a dynamically allocated id can be used. In this case
8206 you should choose an appropriate user or group name,
8207 discussing this on <prgn>debian-devel</prgn> and checking
8208 with the <package/base-passwd/ maintainer that it is unique and that
8209 they do not wish you to use a statically allocated id
8210 instead. When this has been checked you must arrange for
8211 your package to create the user or group if necessary using
8212 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
8213 <prgn>postinst</prgn> script (again, the latter is to be
8214 preferred if it is possible).
8218 Note that changing the numeric value of an id associated
8219 with a name is very difficult, and involves searching the
8220 file system for all appropriate files. You need to think
8221 carefully whether a static or dynamic id is required, since
8222 changing your mind later will cause problems.
8225 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
8227 This section is not intended as policy, but as a
8228 description of the use of <prgn>dpkg-statoverride</prgn>.
8232 If a system administrator wishes to have a file (or
8233 directory or other such thing) installed with owner and
8234 permissions different from those in the distributed Debian
8235 package, they can use the <prgn>dpkg-statoverride</prgn>
8236 program to instruct <prgn>dpkg</prgn> to use the different
8237 settings every time the file is installed. Thus the
8238 package maintainer should distribute the files with their
8239 normal permissions, and leave it for the system
8240 administrator to make any desired changes. For example, a
8241 daemon which is normally required to be setuid root, but
8242 in certain situations could be used without being setuid,
8243 should be installed setuid in the <tt>.deb</tt>. Then the
8244 local system administrator can change this if they wish.
8245 If there are two standard ways of doing it, the package
8246 maintainer can use <tt>debconf</tt> to find out the
8247 preference, and call <prgn>dpkg-statoverride</prgn> in the
8248 maintainer script if necessary to accommodate the system
8249 administrator's choice. Care must be taken during
8250 upgrades to not override an existing setting.
8254 Given the above, <prgn>dpkg-statoverride</prgn> is
8255 essentially a tool for system administrators and would not
8256 normally be needed in the maintainer scripts. There is
8257 one type of situation, though, where calls to
8258 <prgn>dpkg-statoverride</prgn> would be needed in the
8259 maintainer scripts, and that involves packages which use
8260 dynamically allocated user or group ids. In such a
8261 situation, something like the following idiom can be very
8262 helpful in the package's <prgn>postinst</prgn>, where
8263 <tt>sysuser</tt> is a dynamically allocated id:
8265 for i in /usr/bin/foo /usr/sbin/bar
8267 # only do something when no setting exists
8268 if ! dpkg-statoverride --list $i >/dev/null 2>&1
8270 #include: debconf processing, question about foo and bar
8271 if [ "$RET" = "true" ] ; then
8272 dpkg-statoverride --update --add sysuser root 4755 $i
8277 The corresponding code to remove the override when the package
8280 for i in /usr/bin/foo /usr/sbin/bar
8282 if dpkg-statoverride --list $i >/dev/null 2>&1
8284 dpkg-statoverride --remove $i
8294 <chapt id="customized-programs">
8295 <heading>Customized programs</heading>
8297 <sect id="arch-spec">
8298 <heading>Architecture specification strings</heading>
8301 If a program needs to specify an <em>architecture specification
8302 string</em> in some place, it should select one of the strings
8303 provided by <tt>dpkg-architecture -L</tt>. The strings are in
8304 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
8305 part is sometimes elided, as when the OS is Linux.
8309 Note that we don't want to use
8310 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
8311 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
8312 since this would make our programs incompatible with other
8313 Linux distributions. We also don't use something like
8314 <tt><var>arch</var>-unknown-linux</tt>, since the
8315 <tt>unknown</tt> does not look very good.
8318 <sect1 id="arch-wildcard-spec">
8319 <heading>Architecture wildcards</heading>
8322 A package may specify an architecture wildcard. Architecture
8323 wildcards are in the format <tt>any</tt> (which matches every
8324 architecture), <tt><var>os</var></tt>-any, or
8325 any-<tt><var>cpu</var></tt>. <footnote>
8326 Internally, the package system normalizes the GNU triplets
8327 and the Debian arches into Debian arch triplets (which are
8328 kind of inverted GNU triplets), with the first component of
8329 the triplet representing the libc and ABI in use, and then
8330 does matching against those triplets. However, such
8331 triplets are an internal implementation detail that should
8332 not be used by packages directly. The libc and ABI portion
8333 is handled internally by the package system based on
8334 the <var>os</var> and <var>cpu</var>.
8341 <heading>Daemons</heading>
8344 The configuration files <file>/etc/services</file>,
8345 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
8346 by the <prgn>netbase</prgn> package and must not be modified
8351 If a package requires a new entry in one of these files, the
8352 maintainer should get in contact with the
8353 <prgn>netbase</prgn> maintainer, who will add the entries
8354 and release a new version of the <prgn>netbase</prgn>
8359 The configuration file <file>/etc/inetd.conf</file> must not be
8360 modified by the package's scripts except via the
8361 <prgn>update-inetd</prgn> script or the
8362 <file>DebianNet.pm</file> Perl module. See their documentation
8363 for details on how to add entries.
8367 If a package wants to install an example entry into
8368 <file>/etc/inetd.conf</file>, the entry must be preceded with
8369 exactly one hash character (<tt>#</tt>). Such lines are
8370 treated as "commented out by user" by the
8371 <prgn>update-inetd</prgn> script and are not changed or
8372 activated during package updates.
8377 <heading>Using pseudo-ttys and modifying wtmp, utmp and
8381 Some programs need to create pseudo-ttys. This should be done
8382 using Unix98 ptys if the C library supports it. The resulting
8383 program must not be installed setuid root, unless that
8384 is required for other functionality.
8388 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
8389 <file>/var/log/lastlog</file> must be installed writable by
8390 group <tt>utmp</tt>. Programs which need to modify those
8391 files must be installed setgid <tt>utmp</tt>.
8396 <heading>Editors and pagers</heading>
8399 Some programs have the ability to launch an editor or pager
8400 program to edit or display a text document. Since there are
8401 lots of different editors and pagers available in the Debian
8402 distribution, the system administrator and each user should
8403 have the possibility to choose their preferred editor and
8408 In addition, every program should choose a good default
8409 editor/pager if none is selected by the user or system
8414 Thus, every program that launches an editor or pager must
8415 use the EDITOR or PAGER environment variable to determine
8416 the editor or pager the user wishes to use. If these
8417 variables are not set, the programs <file>/usr/bin/editor</file>
8418 and <file>/usr/bin/pager</file> should be used, respectively.
8422 These two files are managed through the <prgn>dpkg</prgn>
8423 "alternatives" mechanism. Every package providing an editor or
8424 pager must call the <prgn>update-alternatives</prgn> script to
8425 register as an alternative for <file>/usr/bin/editor</file>
8426 or <file>/usr/bin/pager</file> as appropriate. The alternative
8427 should have a slave alternative
8428 for <file>/usr/share/man/man1/editor.1.gz</file>
8429 or <file>/usr/share/man/man1/pager.1.gz</file> pointing to the
8430 corresponding manual page.
8434 If it is very hard to adapt a program to make use of the
8435 EDITOR or PAGER variables, that program may be configured to
8436 use <file>/usr/bin/sensible-editor</file> and
8437 <file>/usr/bin/sensible-pager</file> as the editor or pager
8438 program respectively. These are two scripts provided in the
8439 <package>sensible-utils</package> package that check the EDITOR
8440 and PAGER variables and launch the appropriate program, and fall
8441 back to <file>/usr/bin/editor</file>
8442 and <file>/usr/bin/pager</file> if the variable is not set.
8446 A program may also use the VISUAL environment variable to
8447 determine the user's choice of editor. If it exists, it
8448 should take precedence over EDITOR. This is in fact what
8449 <file>/usr/bin/sensible-editor</file> does.
8453 It is not required for a package to depend on
8454 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
8455 package to provide such virtual packages.<footnote>
8456 The Debian base system already provides an editor and a
8462 <sect id="web-appl">
8463 <heading>Web servers and applications</heading>
8466 This section describes the locations and URLs that should
8467 be used by all web servers and web applications in the
8474 Cgi-bin executable files are installed in the
8476 <example compact="compact">
8477 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
8479 or a subdirectory of that directory, and should be
8481 <example compact="compact">
8482 http://localhost/cgi-bin/<var>cgi-bin-name</var>
8484 (possibly with a subdirectory name
8485 before <var>cgi-bin-name</var>).
8489 <p>Access to HTML documents</p>
8492 HTML documents for a package are stored in
8493 <file>/usr/share/doc/<var>package</var></file>
8494 and can be referred to as
8495 <example compact="compact">
8496 http://localhost/doc/<var>package</var>/<var>filename</var>
8501 The web server should restrict access to the document
8502 tree so that only clients on the same host can read
8503 the documents. If the web server does not support such
8504 access controls, then it should not provide access at
8505 all, or ask about providing access during installation.
8510 <p>Access to images</p>
8512 It is recommended that images for a package be stored
8513 in <tt>/usr/share/images/<var>package</var></tt> and
8514 may be referred to through an alias <tt>/images/</tt>
8517 http://localhost/images/<package>/<filename>
8524 <p>Web Document Root</p>
8527 Web Applications should try to avoid storing files in
8528 the Web Document Root. Instead they should use the
8529 /usr/share/doc/<var>package</var> directory for
8530 documents and register the Web Application via the
8531 <package>doc-base</package> package. If access to the
8532 web document root is unavoidable then use
8533 <example compact="compact">
8536 as the Document Root. This might be just a symbolic
8537 link to the location where the system administrator
8538 has put the real document root.
8541 <item><p>Providing httpd and/or httpd-cgi</p>
8543 All web servers should provide the virtual package
8544 <tt>httpd</tt>. If a web server has CGI support it should
8545 provide <tt>httpd-cgi</tt> additionally.
8548 All web applications which do not contain CGI scripts should
8549 depend on <tt>httpd</tt>, all those web applications which
8550 <tt>do</tt> contain CGI scripts, should depend on
8558 <sect id="mail-transport-agents">
8559 <heading>Mail transport, delivery and user agents</heading>
8562 Debian packages which process electronic mail, whether mail
8563 user agents (MUAs) or mail transport agents (MTAs), must
8564 ensure that they are compatible with the configuration
8565 decisions below. Failure to do this may result in lost
8566 mail, broken <tt>From:</tt> lines, and other serious brain
8571 The mail spool is <file>/var/mail</file> and the interface to
8572 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8573 the FHS). On older systems, the mail spool may be
8574 physically located in <file>/var/spool/mail</file>, but all
8575 access to the mail spool should be via the
8576 <file>/var/mail</file> symlink. The mail spool is part of the
8577 base system and not part of the MTA package.
8581 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8582 programs (such as IMAP daemons) must lock the mailbox in an
8583 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8584 be combined with dot locking. To avoid deadlocks, a program
8585 should use <tt>fcntl()</tt> first and dot locking after
8586 this, or alternatively implement the two locking methods in
8587 a non blocking way<footnote>
8588 If it is not possible to establish both locks, the
8589 system shouldn't wait for the second lock to be
8590 established, but remove the first lock, wait a (random)
8591 time, and start over locking again.
8592 </footnote>. Using the functions <tt>maillock</tt> and
8593 <tt>mailunlock</tt> provided by the
8594 <tt>liblockfile*</tt><footnote>
8595 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8596 to use these functions.
8597 </footnote> packages is the recommended way to realize this.
8601 Mailboxes are generally either mode 600 and owned by
8602 <var>user</var> or mode 660 and owned by
8603 <tt><var>user</var>:mail</tt><footnote>
8604 There are two traditional permission schemes for mail spools:
8605 mode 600 with all mail delivery done by processes running as
8606 the destination user, or mode 660 and owned by group mail with
8607 mail delivery done by a process running as a system user in
8608 group mail. Historically, Debian required mode 660 mail
8609 spools to enable the latter model, but that model has become
8610 increasingly uncommon and the principle of least privilege
8611 indicates that mail systems that use the first model should
8612 use permissions of 600. If delivery to programs is permitted,
8613 it's easier to keep the mail system secure if the delivery
8614 agent runs as the destination user. Debian Policy therefore
8615 permits either scheme.
8616 </footnote>. The local system administrator may choose a
8617 different permission scheme; packages should not make
8618 assumptions about the permission and ownership of mailboxes
8619 unless required (such as when creating a new mailbox). A MUA
8620 may remove a mailbox (unless it has nonstandard permissions) in
8621 which case the MTA or another MUA must recreate it if needed.
8625 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8626 be setgid mail to do the locking mentioned above (and
8627 must obviously avoid accessing other users' mailboxes
8628 using this privilege).</p>
8631 <file>/etc/aliases</file> is the source file for the system mail
8632 aliases (e.g., postmaster, usenet, etc.), it is the one
8633 which the sysadmin and <prgn>postinst</prgn> scripts may
8634 edit. After <file>/etc/aliases</file> is edited the program or
8635 human editing it must call <prgn>newaliases</prgn>. All MTA
8636 packages must come with a <prgn>newaliases</prgn> program,
8637 even if it does nothing, but older MTA packages did not do
8638 this so programs should not fail if <prgn>newaliases</prgn>
8639 cannot be found. Note that because of this, all MTA
8640 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8641 <tt>Replaces: mail-transport-agent</tt> control fields.
8645 The convention of writing <tt>forward to
8646 <var>address</var></tt> in the mailbox itself is not
8647 supported. Use a <tt>.forward</tt> file instead.</p>
8650 The <prgn>rmail</prgn> program used by UUCP
8651 for incoming mail should be <file>/usr/sbin/rmail</file>.
8652 Likewise, <prgn>rsmtp</prgn>, for receiving
8653 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8657 If your package needs to know what hostname to use on (for
8658 example) outgoing news and mail messages which are generated
8659 locally, you should use the file <file>/etc/mailname</file>. It
8660 will contain the portion after the username and <tt>@</tt>
8661 (at) sign for email addresses of users on the machine
8662 (followed by a newline).
8666 Such a package should check for the existence of this file
8667 when it is being configured. If it exists, it should be
8668 used without comment, although an MTA's configuration script
8669 may wish to prompt the user even if it finds that this file
8670 exists. If the file does not exist, the package should
8671 prompt the user for the value (preferably using
8672 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8673 as well as using it in the package's configuration. The
8674 prompt should make it clear that the name will not just be
8675 used by that package. For example, in this situation the
8676 <tt>inn</tt> package could say something like:
8677 <example compact="compact">
8678 Please enter the "mail name" of your system. This is the
8679 hostname portion of the address to be shown on outgoing
8680 news and mail messages. The default is
8681 <var>syshostname</var>, your system's host name. Mail
8682 name ["<var>syshostname</var>"]:
8684 where <var>syshostname</var> is the output of <tt>hostname
8690 <heading>News system configuration</heading>
8693 All the configuration files related to the NNTP (news)
8694 servers and clients should be located under
8695 <file>/etc/news</file>.</p>
8698 There are some configuration issues that apply to a number
8699 of news clients and server packages on the machine. These
8703 <tag><file>/etc/news/organization</file></tag>
8705 A string which should appear as the
8706 organization header for all messages posted
8707 by NNTP clients on the machine
8710 <tag><file>/etc/news/server</file></tag>
8712 Contains the FQDN of the upstream NNTP
8713 server, or localhost if the local machine is
8718 Other global files may be added as required for cross-package news
8725 <heading>Programs for the X Window System</heading>
8728 <heading>Providing X support and package priorities</heading>
8731 Programs that can be configured with support for the X
8732 Window System must be configured to do so and must declare
8733 any package dependencies necessary to satisfy their
8734 runtime requirements when using the X Window System. If
8735 such a package is of higher priority than the X packages
8736 on which it depends, it is required that either the
8737 X-specific components be split into a separate package, or
8738 that an alternative version of the package, which includes
8739 X support, be provided, or that the package's priority be
8745 <heading>Packages providing an X server</heading>
8748 Packages that provide an X server that, directly or
8749 indirectly, communicates with real input and display
8750 hardware should declare in their <tt>Provides</tt> control
8751 field that they provide the virtual
8752 package <tt>xserver</tt>.<footnote>
8753 This implements current practice, and provides an
8754 actual policy for usage of the <tt>xserver</tt>
8755 virtual package which appears in the virtual packages
8756 list. In a nutshell, X servers that interface
8757 directly with the display and input hardware or via
8758 another subsystem (e.g., GGI) should provide
8759 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8760 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8766 <heading>Packages providing a terminal emulator</heading>
8769 Packages that provide a terminal emulator for the X Window
8770 System which meet the criteria listed below should declare in
8771 their <tt>Provides</tt> control field that they provide the
8772 virtual package <tt>x-terminal-emulator</tt>. They should
8773 also register themselves as an alternative for
8774 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8775 20. That alternative should have a slave alternative
8776 for <file>/usr/share/man/man1/x-terminal-emulator.1.gz</file>
8777 pointing to the corresponding manual page.
8781 To be an <tt>x-terminal-emulator</tt>, a program must:
8782 <list compact="compact">
8784 Be able to emulate a DEC VT100 terminal, or a
8785 compatible terminal.
8789 Support the command-line option <tt>-e
8790 <var>command</var></tt>, which creates a new
8791 terminal window<footnote>
8792 "New terminal window" does not necessarily mean
8793 a new top-level X window directly parented by
8794 the window manager; it could, if the terminal
8795 emulator application were so coded, be a new
8796 "view" in a multiple-document interface (MDI).
8798 and runs the specified <var>command</var>,
8799 interpreting the entirety of the rest of the command
8800 line as a command to pass straight to exec, in the
8801 manner that <tt>xterm</tt> does.
8805 Support the command-line option <tt>-T
8806 <var>title</var></tt>, which creates a new terminal
8807 window with the window title <var>title</var>.
8814 <heading>Packages providing a window manager</heading>
8817 Packages that provide a window manager should declare in
8818 their <tt>Provides</tt> control field that they provide the
8819 virtual package <tt>x-window-manager</tt>. They should also
8820 register themselves as an alternative for
8821 <file>/usr/bin/x-window-manager</file>, with a priority
8822 calculated as follows:
8823 <list compact="compact">
8825 Start with a priority of 20.
8829 If the window manager supports the Debian menu
8830 system, add 20 points if this support is available
8831 in the package's default configuration (i.e., no
8832 configuration files belonging to the system or user
8833 have to be edited to activate the feature); if
8834 configuration files must be modified, add only 10
8840 If the window manager complies with <url
8841 id="http://www.freedesktop.org/Standards/wm-spec"
8842 name="The Window Manager Specification Project">,
8843 written by the <url id="http://www.freedesktop.org/"
8844 name="Free Desktop Group">, add 40 points.
8848 If the window manager permits the X session to be
8849 restarted using a <em>different</em> window manager
8850 (without killing the X server) in its default
8851 configuration, add 10 points; otherwise add none.
8854 That alternative should have a slave alternative
8855 for <file>/usr/share/man/man1/x-window-manager.1.gz</file>
8856 pointing to the corresponding manual page.
8861 <heading>Packages providing fonts</heading>
8864 Packages that provide fonts for the X Window
8866 For the purposes of Debian Policy, a "font for the X
8867 Window System" is one which is accessed via X protocol
8868 requests. Fonts for the Linux console, for PostScript
8869 renderer, or any other purpose, do not fit this
8870 definition. Any tool which makes such fonts available
8871 to the X Window System, however, must abide by this
8874 must do a number of things to ensure that they are both
8875 available without modification of the X or font server
8876 configuration, and that they do not corrupt files used by
8877 other font packages to register information about
8881 Fonts of any type supported by the X Window System
8882 must be in a separate binary package from any
8883 executables, libraries, or documentation (except
8884 that specific to the fonts shipped, such as their
8885 license information). If one or more of the fonts
8886 so packaged are necessary for proper operation of
8887 the package with which they are associated the font
8888 package may be Recommended; if the fonts merely
8889 provide an enhancement, a Suggests relationship may
8890 be used. Packages must not Depend on font
8892 This is because the X server may retrieve fonts
8893 from the local file system or over the network
8894 from an X font server; the Debian package system
8895 is empowered to deal only with the local
8901 BDF fonts must be converted to PCF fonts with the
8902 <prgn>bdftopcf</prgn> utility (available in the
8903 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8904 placed in a directory that corresponds to their
8906 <list compact="compact">
8908 100 dpi fonts must be placed in
8909 <file>/usr/share/fonts/X11/100dpi/</file>.
8913 75 dpi fonts must be placed in
8914 <file>/usr/share/fonts/X11/75dpi/</file>.
8918 Character-cell fonts, cursor fonts, and other
8919 low-resolution fonts must be placed in
8920 <file>/usr/share/fonts/X11/misc/</file>.
8926 Type 1 fonts must be placed in
8927 <file>/usr/share/fonts/X11/Type1/</file>. If font
8928 metric files are available, they must be placed here
8933 Subdirectories of <file>/usr/share/fonts/X11/</file>
8934 other than those listed above must be neither
8935 created nor used. (The <file>PEX</file>, <file>CID</file>,
8936 <file>Speedo</file>, and <file>cyrillic</file> directories
8937 are excepted for historical reasons, but installation of
8938 files into these directories remains discouraged.)
8942 Font packages may, instead of placing files directly
8943 in the X font directories listed above, provide
8944 symbolic links in that font directory pointing to
8945 the files' actual location in the filesystem. Such
8946 a location must comply with the FHS.
8950 Font packages should not contain both 75dpi and
8951 100dpi versions of a font. If both are available,
8952 they should be provided in separate binary packages
8953 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8954 the names of the packages containing the
8955 corresponding fonts.
8959 Fonts destined for the <file>misc</file> subdirectory
8960 should not be included in the same package as 75dpi
8961 or 100dpi fonts; instead, they should be provided in
8962 a separate package with <tt>-misc</tt> appended to
8967 Font packages must not provide the files
8968 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8969 <file>fonts.scale</file> in a font directory:
8972 <file>fonts.dir</file> files must not be provided at all.
8976 <file>fonts.alias</file> and <file>fonts.scale</file>
8977 files, if needed, should be provided in the
8979 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8980 where <var>fontdir</var> is the name of the
8982 <file>/usr/share/fonts/X11/</file> where the
8983 package's corresponding fonts are stored
8984 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8985 <var>package</var> is the name of the package
8986 that provides these fonts, and
8987 <var>extension</var> is either <tt>scale</tt>
8988 or <tt>alias</tt>, whichever corresponds to
8995 Font packages must declare a dependency on
8996 <tt>xfonts-utils</tt> in their <tt>Depends</tt>
8997 or <tt>Pre-Depends</tt> control field.
9001 Font packages that provide one or more
9002 <file>fonts.scale</file> files as described above must
9003 invoke <prgn>update-fonts-scale</prgn> on each
9004 directory into which they installed fonts
9005 <em>before</em> invoking
9006 <prgn>update-fonts-dir</prgn> on that directory.
9007 This invocation must occur in both the
9008 <prgn>postinst</prgn> (for all arguments) and
9009 <prgn>postrm</prgn> (for all arguments except
9010 <tt>upgrade</tt>) scripts.
9014 Font packages that provide one or more
9015 <file>fonts.alias</file> files as described above must
9016 invoke <prgn>update-fonts-alias</prgn> on each
9017 directory into which they installed fonts. This
9018 invocation must occur in both the
9019 <prgn>postinst</prgn> (for all arguments) and
9020 <prgn>postrm</prgn> (for all arguments except
9021 <tt>upgrade</tt>) scripts.
9025 Font packages must invoke
9026 <prgn>update-fonts-dir</prgn> on each directory into
9027 which they installed fonts. This invocation must
9028 occur in both the <prgn>postinst</prgn> (for all
9029 arguments) and <prgn>postrm</prgn> (for all
9030 arguments except <tt>upgrade</tt>) scripts.
9034 Font packages must not provide alias names for the
9035 fonts they include which collide with alias names
9036 already in use by fonts already packaged.
9040 Font packages must not provide fonts with the same
9041 XLFD registry name as another font already packaged.
9047 <sect1 id="appdefaults">
9048 <heading>Application defaults files</heading>
9051 Application defaults files must be installed in the
9052 directory <file>/etc/X11/app-defaults/</file> (use of a
9053 localized subdirectory of <file>/etc/X11/</file> as described
9054 in the <em>X Toolkit Intrinsics - C Language
9055 Interface</em> manual is also permitted). They must be
9056 registered as <tt>conffile</tt>s or handled as
9057 configuration files.
9061 Customization of programs' X resources may also be
9062 supported with the provision of a file with the same name
9063 as that of the package placed in
9064 the <file>/etc/X11/Xresources/</file> directory, which
9065 must be registered as a <tt>conffile</tt> or handled as a
9066 configuration file.<footnote>
9067 Note that this mechanism is not the same as using
9068 app-defaults; app-defaults are tied to the client
9069 binary on the local file system, whereas X resources
9070 are stored in the X server and affect all connecting
9077 <heading>Installation directory issues</heading>
9080 Historically, packages using the X Window System used a
9081 separate set of installation directories from other packages.
9082 This practice has been discontinued and packages using the X
9083 Window System should now generally be installed in the same
9084 directories as any other package. Specifically, packages must
9085 not install files under the <file>/usr/X11R6/</file> directory
9086 and the <file>/usr/X11R6/</file> directory hierarchy should be
9087 regarded as obsolete.
9091 Include files previously installed under
9092 <file>/usr/X11R6/include/X11/</file> should be installed into
9093 <file>/usr/include/X11/</file>. For files previously
9094 installed into subdirectories of
9095 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
9096 determine if subdirectories of <file>/usr/lib/</file> and
9097 <file>/usr/share/</file> can be used. If not, a subdirectory
9098 of <file>/usr/lib/X11/</file> should be used.
9102 Configuration files for window, display, or session managers
9103 or other applications that are tightly integrated with the X
9104 Window System may be placed in a subdirectory
9105 of <file>/etc/X11/</file> corresponding to the package name.
9106 Other X Window System applications should use
9107 the <file>/etc/</file> directory unless otherwise mandated by
9108 policy (such as for <ref id="appdefaults">).
9113 <heading>The OSF/Motif and OpenMotif libraries</heading>
9116 <em>Programs that require the non-DFSG-compliant OSF/Motif or
9117 OpenMotif libraries</em><footnote>
9118 OSF/Motif and OpenMotif are collectively referred to as
9119 "Motif" in this policy document.
9121 should be compiled against and tested with LessTif (a free
9122 re-implementation of Motif) instead. If the maintainer
9123 judges that the program or programs do not work
9124 sufficiently well with LessTif to be distributed and
9125 supported, but do so when compiled against Motif, then two
9126 versions of the package should be created; one linked
9127 statically against Motif and with <tt>-smotif</tt>
9128 appended to the package name, and one linked dynamically
9129 against Motif and with <tt>-dmotif</tt> appended to the
9134 Both Motif-linked versions are dependent
9135 upon non-DFSG-compliant software and thus cannot be
9136 uploaded to the <em>main</em> distribution; if the
9137 software is itself DFSG-compliant it may be uploaded to
9138 the <em>contrib</em> distribution. While known existing
9139 versions of Motif permit unlimited redistribution of
9140 binaries linked against the library (whether statically or
9141 dynamically), it is the package maintainer's
9142 responsibility to determine whether this is permitted by
9143 the license of the copy of Motif in their possession.
9149 <heading>Perl programs and modules</heading>
9152 Perl programs and modules should follow the current Perl policy.
9156 The Perl policy can be found in the <tt>perl-policy</tt>
9157 files in the <tt>debian-policy</tt> package.
9158 It is also available from the Debian web mirrors at
9159 <tt><url name="/doc/packaging-manuals/perl-policy/"
9160 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
9165 <heading>Emacs lisp programs</heading>
9168 Please refer to the "Debian Emacs Policy" for details of how to
9169 package emacs lisp programs.
9173 The Emacs policy is available in
9174 <file>debian-emacs-policy.gz</file> of the
9175 <package>emacsen-common</package> package.
9176 It is also available from the Debian web mirrors at
9177 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
9178 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
9183 <heading>Games</heading>
9186 The permissions on <file>/var/games</file> are mode 755, owner
9187 <tt>root</tt> and group <tt>root</tt>.
9191 Each game decides on its own security policy.</p>
9194 Games which require protected, privileged access to
9195 high-score files, saved games, etc., may be made
9196 set-<em>group</em>-id (mode 2755) and owned by
9197 <tt>root:games</tt>, and use files and directories with
9198 appropriate permissions (770 <tt>root:games</tt>, for
9199 example). They must not be made
9200 set-<em>user</em>-id, as this causes security problems. (If
9201 an attacker can subvert any set-user-id game they can
9202 overwrite the executable of any other, causing other players
9203 of these games to run a Trojan horse program. With a
9204 set-group-id game the attacker only gets access to less
9205 important game data, and if they can get at the other
9206 players' accounts at all it will take considerably more
9210 Some packages, for example some fortune cookie programs, are
9211 configured by the upstream authors to install with their
9212 data files or other static information made unreadable so
9213 that they can only be accessed through set-id programs
9214 provided. You should not do this in a Debian package: anyone can
9215 download the <file>.deb</file> file and read the data from it,
9216 so there is no point making the files unreadable. Not
9217 making the files unreadable also means that you don't have
9218 to make so many programs set-id, which reduces the risk of a
9222 As described in the FHS, binaries of games should be
9223 installed in the directory <file>/usr/games</file>. This also
9224 applies to games that use the X Window System. Manual pages
9225 for games (X and non-X games) should be installed in
9226 <file>/usr/share/man/man6</file>.</p>
9232 <heading>Documentation</heading>
9235 <heading>Manual pages</heading>
9238 You should install manual pages in <prgn>nroff</prgn> source
9239 form, in appropriate places under <file>/usr/share/man</file>.
9240 You should only use sections 1 to 9 (see the FHS for more
9241 details). You must not install a pre-formatted "cat page".
9245 Each program, utility, and function should have an
9246 associated manual page included in the same package. It is
9247 suggested that all configuration files also have a manual
9248 page included as well. Manual pages for protocols and other
9249 auxiliary things are optional.
9253 If no manual page is available, this is considered as a bug
9254 and should be reported to the Debian Bug Tracking System (the
9255 maintainer of the package is allowed to write this bug report
9256 themselves, if they so desire). Do not close the bug report
9257 until a proper man page is available.<footnote>
9258 It is not very hard to write a man page. See the
9259 <url id="http://www.schweikhardt.net/man_page_howto.html"
9260 name="Man-Page-HOWTO">,
9261 <manref name="man" section="7">, the examples
9262 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
9263 the helper program <prgn>help2man</prgn>, or the
9264 directory <file>/usr/share/doc/man-db/examples</file>.
9269 You may forward a complaint about a missing man page to the
9270 upstream authors, and mark the bug as forwarded in the
9271 Debian bug tracking system. Even though the GNU Project do
9272 not in general consider the lack of a man page to be a bug,
9273 we do; if they tell you that they don't consider it a bug
9274 you should leave the bug in our bug tracking system open
9279 Manual pages should be installed compressed using <tt>gzip -9</tt>.
9283 If one man page needs to be accessible via several names it
9284 is better to use a symbolic link than the <file>.so</file>
9285 feature, but there is no need to fiddle with the relevant
9286 parts of the upstream source to change from <file>.so</file> to
9287 symlinks: don't do it unless it's easy. You should not
9288 create hard links in the manual page directories, nor put
9289 absolute filenames in <file>.so</file> directives. The filename
9290 in a <file>.so</file> in a man page should be relative to the
9291 base of the man page tree (usually
9292 <file>/usr/share/man</file>). If you do not create any links
9293 (whether symlinks, hard links, or <tt>.so</tt> directives)
9294 in the file system to the alternate names of the man page,
9295 then you should not rely on <prgn>man</prgn> finding your
9296 man page under those names based solely on the information in
9297 the man page's header.<footnote>
9298 Supporting this in <prgn>man</prgn> often requires
9299 unreasonable processing time to find a manual page or to
9300 report that none exists, and moves knowledge into man's
9301 database that would be better left in the file system.
9302 This support is therefore deprecated and will cease to
9303 be present in the future.
9308 Manual pages in locale-specific subdirectories of
9309 <file>/usr/share/man</file> should use either UTF-8 or the usual
9310 legacy encoding for that language (normally the one corresponding
9311 to the shortest relevant locale name in
9312 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
9313 <file>/usr/share/man/fr</file> should use either UTF-8 or
9314 ISO-8859-1.<footnote>
9315 <prgn>man</prgn> will automatically detect whether UTF-8 is in
9316 use. In future, all manual pages will be required to use
9322 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
9323 included in the subdirectory name unless it indicates a
9324 significant difference in the language, as this excludes
9325 speakers of the language in other countries.<footnote>
9326 At the time of writing, Chinese and Portuguese are the main
9327 languages with such differences, so <file>pt_BR</file>,
9328 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
9333 If a localized version of a manual page is provided, it should
9334 either be up-to-date or it should be obvious to the reader that
9335 it is outdated and the original manual page should be used
9336 instead. This can be done either by a note at the beginning of
9337 the manual page or by showing the missing or changed portions in
9338 the original language instead of the target language.
9343 <heading>Info documents</heading>
9346 Info documents should be installed in <file>/usr/share/info</file>.
9347 They should be compressed with <tt>gzip -9</tt>.
9351 The <prgn>install-info</prgn> program maintains a directory of
9352 installed info documents in <file>/usr/share/info/dir</file> for
9353 the use of info readers.<footnote>
9354 It was previously necessary for packages installing info
9355 documents to run <prgn>install-info</prgn> from maintainer
9356 scripts. This is no longer necessary. The installation
9357 system now uses dpkg triggers.
9359 This file must not be included in packages. Packages containing
9360 info documents should depend on <tt>dpkg (>= 1.15.4) |
9361 install-info</tt> to ensure that the directory file is properly
9362 rebuilt during partial upgrades from Debian 5.0 (lenny) and
9367 Info documents should contain section and directory entry
9368 information in the document for the use
9369 of <prgn>install-info</prgn>. The section should be specified
9370 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
9371 space and the section of this info page. The directory entry or
9372 entries should be included between
9373 a <tt>START-INFO-DIR-ENTRY</tt> line and
9374 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
9376 INFO-DIR-SECTION Individual utilities
9377 START-INFO-DIR-ENTRY
9378 * example: (example). An example info directory entry.
9381 To determine which section to use, you should look
9382 at <file>/usr/share/info/dir</file> on your system and choose
9383 the most relevant (or create a new section if none of the
9384 current sections are relevant).<footnote>
9385 Normally, info documents are generated from Texinfo source.
9386 To include this information in the generated info document, if
9387 it is absent, add commands like:
9389 @dircategory Individual utilities
9391 * example: (example). An example info directory entry.
9394 to the Texinfo source of the document and ensure that the info
9395 documents are rebuilt from source during the package build.
9401 <heading>Additional documentation</heading>
9404 Any additional documentation that comes with the package may
9405 be installed at the discretion of the package maintainer.
9406 Plain text documentation should be installed in the directory
9407 <file>/usr/share/doc/<var>package</var></file>, where
9408 <var>package</var> is the name of the package, and
9409 compressed with <tt>gzip -9</tt> unless it is small.
9413 If a package comes with large amounts of documentation which
9414 many users of the package will not require you should create
9415 a separate binary package to contain it, so that it does not
9416 take up disk space on the machines of users who do not need
9417 or want it installed.</p>
9420 It is often a good idea to put text information files
9421 (<file>README</file>s, changelogs, and so forth) that come with
9422 the source package in <file>/usr/share/doc/<var>package</var></file>
9423 in the binary package. However, you don't need to install
9424 the instructions for building and installing the package, of
9428 Packages must not require the existence of any files in
9429 <file>/usr/share/doc/</file> in order to function
9431 The system administrator should be able to
9432 delete files in <file>/usr/share/doc/</file> without causing
9433 any programs to break.
9435 Any files that are referenced by programs but are also
9436 useful as stand alone documentation should be installed under
9437 <file>/usr/share/<var>package</var>/</file> with symbolic links from
9438 <file>/usr/share/doc/<var>package</var></file>.
9442 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9443 link to another directory in <file>/usr/share/doc</file> only if
9444 the two packages both come from the same source and the
9445 first package Depends on the second.<footnote>
9447 Please note that this does not override the section on
9448 changelog files below, so the file
9449 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
9450 must refer to the changelog for the current version of
9451 <var>package</var> in question. In practice, this means
9452 that the sources of the target and the destination of the
9453 symlink must be the same (same source package and
9460 Former Debian releases placed all additional documentation
9461 in <file>/usr/doc/<var>package</var></file>. This has been
9462 changed to <file>/usr/share/doc/<var>package</var></file>,
9463 and packages must not put documentation in the directory
9464 <file>/usr/doc/<var>package</var></file>. <footnote>
9465 At this phase of the transition, we no longer require a
9466 symbolic link in <file>/usr/doc/</file>. At a later point,
9467 policy shall change to make the symbolic links a bug.
9473 <heading>Preferred documentation formats</heading>
9476 The unification of Debian documentation is being carried out
9480 If your package comes with extensive documentation in a
9481 markup format that can be converted to various other formats
9482 you should if possible ship HTML versions in a binary
9483 package, in the directory
9484 <file>/usr/share/doc/<var>appropriate-package</var></file> or
9485 its subdirectories.<footnote>
9486 The rationale: The important thing here is that HTML
9487 docs should be available in <em>some</em> package, not
9488 necessarily in the main binary package.
9493 Other formats such as PostScript may be provided at the
9494 package maintainer's discretion.
9498 <sect id="copyrightfile">
9499 <heading>Copyright information</heading>
9502 Every package must be accompanied by a verbatim copy of its
9503 copyright information and distribution license in the file
9504 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
9505 file must neither be compressed nor be a symbolic link.
9509 In addition, the copyright file must say where the upstream
9510 sources (if any) were obtained. It should name the original
9511 authors of the package and the Debian maintainer(s) who were
9512 involved with its creation.
9516 Packages in the <em>contrib</em> or <em>non-free</em> archive
9517 areas should state in the copyright file that the package is not
9518 part of the Debian GNU/Linux distribution and briefly explain
9523 A copy of the file which will be installed in
9524 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9525 be in <file>debian/copyright</file> in the source package.
9529 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9530 link to another directory in <file>/usr/share/doc</file> only if
9531 the two packages both come from the same source and the
9532 first package Depends on the second. These rules are
9533 important because copyrights must be extractable by
9538 Packages distributed under the Apache license (version 2.0), the
9539 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
9540 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
9541 1.3) should refer to the corresponding files
9542 under <file>/usr/share/common-licenses</file>,<footnote>
9545 <file>/usr/share/common-licenses/Apache-2.0</file>,
9546 <file>/usr/share/common-licenses/Artistic</file>,
9547 <file>/usr/share/common-licenses/GPL-1</file>,
9548 <file>/usr/share/common-licenses/GPL-2</file>,
9549 <file>/usr/share/common-licenses/GPL-3</file>,
9550 <file>/usr/share/common-licenses/LGPL-2</file>,
9551 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9552 <file>/usr/share/common-licenses/LGPL-3</file>,
9553 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
9554 <file>/usr/share/common-licenses/GFDL-1.3</file>
9555 respectively. The University of California BSD license is
9556 also included in <package>base-files</package> as
9557 <file>/usr/share/common-licenses/BSD</file>, but given the
9558 brevity of this license, its specificity to code whose
9559 copyright is held by the Regents of the University of
9560 California, and the frequency of minor wording changes, its
9561 text should be included in the copyright file rather than
9562 referencing this file.
9564 </footnote> rather than quoting them in the copyright
9569 You should not use the copyright file as a general <file>README</file>
9570 file. If your package has such a file it should be
9571 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9572 <file>README.Debian</file> or some other appropriate place.</p>
9576 <heading>Examples</heading>
9579 Any examples (configurations, source files, whatever),
9580 should be installed in a directory
9581 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9582 files should not be referenced by any program: they're there
9583 for the benefit of the system administrator and users as
9584 documentation only. Architecture-specific example files
9585 should be installed in a directory
9586 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9588 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9589 latter directory itself may be a symbolic link to the
9594 If the purpose of a package is to provide examples, then the
9595 example files may be installed into
9596 <file>/usr/share/doc/<var>package</var></file>.
9600 <sect id="changelogs">
9601 <heading>Changelog files</heading>
9604 Packages that are not Debian-native must contain a
9605 compressed copy of the <file>debian/changelog</file> file from
9606 the Debian source tree in
9607 <file>/usr/share/doc/<var>package</var></file> with the name
9608 <file>changelog.Debian.gz</file>.
9612 If an upstream changelog is available, it should be accessible as
9613 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9614 plain text. If the upstream changelog is distributed in
9615 HTML, it should be made available in that form as
9616 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9617 and a plain text <file>changelog.gz</file> should be generated
9618 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9619 the upstream changelog files do not already conform to this
9620 naming convention, then this may be achieved either by
9621 renaming the files, or by adding a symbolic link, at the
9622 maintainer's discretion.<footnote>
9623 Rationale: People should not have to look in places for
9624 upstream changelogs merely because they are given
9625 different names or are distributed in HTML format.
9630 All of these files should be installed compressed using
9631 <tt>gzip -9</tt>, as they will become large with time even
9632 if they start out small.
9636 If the package has only one changelog which is used both as
9637 the Debian changelog and the upstream one because there is
9638 no separate upstream maintainer then that changelog should
9639 usually be installed as
9640 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9641 there is a separate upstream maintainer, but no upstream
9642 changelog, then the Debian changelog should still be called
9643 <file>changelog.Debian.gz</file>.
9647 For details about the format and contents of the Debian
9648 changelog file, please see <ref id="dpkgchangelog">.
9653 <appendix id="pkg-scope">
9654 <heading>Introduction and scope of these appendices</heading>
9657 These appendices are taken essentially verbatim from the
9658 now-deprecated Packaging Manual, version 3.2.1.0. They are
9659 the chapters which are likely to be of use to package
9660 maintainers and which have not already been included in the
9661 policy document itself. Most of these sections are very likely
9662 not relevant to policy; they should be treated as
9663 documentation for the packaging system. Please note that these
9664 appendices are included for convenience, and for historical
9665 reasons: they used to be part of policy package, and they have
9666 not yet been incorporated into dpkg documentation. However,
9667 they still have value, and hence they are presented here.
9671 They have not yet been checked to ensure that they are
9672 compatible with the contents of policy, and if there are any
9673 contradictions, the version in the main policy document takes
9674 precedence. The remaining chapters of the old Packaging
9675 Manual have also not been read in detail to ensure that there
9676 are not parts which have been left out. Both of these will be
9681 Certain parts of the Packaging manual were integrated into the
9682 Policy Manual proper, and removed from the appendices. Links
9683 have been placed from the old locations to the new ones.
9687 <prgn>dpkg</prgn> is a suite of programs for creating binary
9688 package files and installing and removing them on Unix
9690 <prgn>dpkg</prgn> is targeted primarily at Debian
9691 GNU/Linux, but may work on or be ported to other
9697 The binary packages are designed for the management of
9698 installed executable programs (usually compiled binaries) and
9699 their associated data, though source code examples and
9700 documentation are provided as part of some packages.</p>
9703 This manual describes the technical aspects of creating Debian
9704 binary packages (<file>.deb</file> files). It documents the
9705 behavior of the package management programs
9706 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9707 they interact with packages.</p>
9710 It also documents the interaction between
9711 <prgn>dselect</prgn>'s core and the access method scripts it
9712 uses to actually install the selected packages, and describes
9713 how to create a new access method.</p>
9716 This manual does not go into detail about the options and
9717 usage of the package building and installation tools. It
9718 should therefore be read in conjunction with those programs'
9723 The utility programs which are provided with <prgn>dpkg</prgn>
9724 for managing various system configuration and similar issues,
9725 such as <prgn>update-rc.d</prgn> and
9726 <prgn>install-info</prgn>, are not described in detail here -
9727 please see their man pages.
9731 It is assumed that the reader is reasonably familiar with the
9732 <prgn>dpkg</prgn> System Administrators' manual.
9733 Unfortunately this manual does not yet exist.
9737 The Debian version of the FSF's GNU hello program is provided
9738 as an example for people wishing to create Debian
9739 packages. The Debian <prgn>debmake</prgn> package is
9740 recommended as a very helpful tool in creating and maintaining
9741 Debian packages. However, while the tools and examples are
9742 helpful, they do not replace the need to read and follow the
9743 Policy and Programmer's Manual.</p>
9746 <appendix id="pkg-binarypkg">
9747 <heading>Binary packages (from old Packaging Manual)</heading>
9750 The binary package has two main sections. The first part
9751 consists of various control information files and scripts used
9752 by <prgn>dpkg</prgn> when installing and removing. See <ref
9753 id="pkg-controlarea">.
9757 The second part is an archive containing the files and
9758 directories to be installed.
9762 In the future binary packages may also contain other
9763 components, such as checksums and digital signatures. The
9764 format for the archive is described in full in the
9765 <file>deb(5)</file> man page.
9769 <sect id="pkg-bincreating"><heading>Creating package files -
9770 <prgn>dpkg-deb</prgn>
9774 All manipulation of binary package files is done by
9775 <prgn>dpkg-deb</prgn>; it's the only program that has
9776 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9777 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9778 will spot that the options requested are appropriate to
9779 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9784 In order to create a binary package you must make a
9785 directory tree which contains all the files and directories
9786 you want to have in the file system data part of the package.
9787 In Debian-format source packages this directory is usually
9788 <file>debian/tmp</file>, relative to the top of the package's
9793 They should have the locations (relative to the root of the
9794 directory tree you're constructing) ownerships and
9795 permissions which you want them to have on the system when
9800 With current versions of <prgn>dpkg</prgn> the uid/username
9801 and gid/groupname mappings for the users and groups being
9802 used should be the same on the system where the package is
9803 built and the one where it is installed.
9807 You need to add one special directory to the root of the
9808 miniature file system tree you're creating:
9809 <prgn>DEBIAN</prgn>. It should contain the control
9810 information files, notably the binary package control file
9811 (see <ref id="pkg-controlfile">).
9815 The <prgn>DEBIAN</prgn> directory will not appear in the
9816 file system archive of the package, and so won't be installed
9817 by <prgn>dpkg</prgn> when the package is installed.
9821 When you've prepared the package, you should invoke:
9823 dpkg --build <var>directory</var>
9828 This will build the package in
9829 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9830 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9831 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9836 See the man page <manref name="dpkg-deb" section="8"> for details of how
9837 to examine the contents of this newly-created file. You may find the
9838 output of following commands enlightening:
9840 dpkg-deb --info <var>filename</var>.deb
9841 dpkg-deb --contents <var>filename</var>.deb
9842 dpkg --contents <var>filename</var>.deb
9844 To view the copyright file for a package you could use this command:
9846 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
9851 <sect id="pkg-controlarea">
9852 <heading>Package control information files</heading>
9855 The control information portion of a binary package is a
9856 collection of files with names known to <prgn>dpkg</prgn>.
9857 It will treat the contents of these files specially - some
9858 of them contain information used by <prgn>dpkg</prgn> when
9859 installing or removing the package; others are scripts which
9860 the package maintainer wants <prgn>dpkg</prgn> to run.
9864 It is possible to put other files in the package control
9865 information file area, but this is not generally a good idea
9866 (though they will largely be ignored).
9870 Here is a brief list of the control information files supported
9871 by <prgn>dpkg</prgn> and a summary of what they're used for.
9876 <tag><tt>control</tt>
9879 This is the key description file used by
9880 <prgn>dpkg</prgn>. It specifies the package's name
9881 and version, gives its description for the user,
9882 states its relationships with other packages, and so
9883 forth. See <ref id="sourcecontrolfiles"> and
9884 <ref id="binarycontrolfiles">.
9888 It is usually generated automatically from information
9889 in the source package by the
9890 <prgn>dpkg-gencontrol</prgn> program, and with
9891 assistance from <prgn>dpkg-shlibdeps</prgn>.
9892 See <ref id="pkg-sourcetools">.
9896 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9901 These are executable files (usually scripts) which
9902 <prgn>dpkg</prgn> runs during installation, upgrade
9903 and removal of packages. They allow the package to
9904 deal with matters which are particular to that package
9905 or require more complicated processing than that
9906 provided by <prgn>dpkg</prgn>. Details of when and
9907 how they are called are in <ref id="maintainerscripts">.
9911 It is very important to make these scripts idempotent.
9912 See <ref id="idempotency">.
9916 The maintainer scripts are not guaranteed to run with a
9917 controlling terminal and may not be able to interact with
9918 the user. See <ref id="controllingterminal">.
9922 <tag><tt>conffiles</tt>
9925 This file contains a list of configuration files which
9926 are to be handled automatically by <prgn>dpkg</prgn>
9927 (see <ref id="pkg-conffiles">). Note that not necessarily
9928 every configuration file should be listed here.
9931 <tag><tt>shlibs</tt>
9934 This file contains a list of the shared libraries
9935 supplied by the package, with dependency details for
9936 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9937 when it determines what dependencies are required in a
9938 package control file. The <tt>shlibs</tt> file format
9939 is described on <ref id="shlibs">.
9944 <sect id="pkg-controlfile">
9945 <heading>The main control information file: <tt>control</tt></heading>
9948 The most important control information file used by
9949 <prgn>dpkg</prgn> when it installs a package is
9950 <tt>control</tt>. It contains all the package's "vital
9955 The binary package control files of packages built from
9956 Debian sources are made by a special tool,
9957 <prgn>dpkg-gencontrol</prgn>, which reads
9958 <file>debian/control</file> and <file>debian/changelog</file> to
9959 find the information it needs. See <ref id="pkg-sourcepkg"> for
9964 The fields in binary package control files are listed in
9965 <ref id="binarycontrolfiles">.
9969 A description of the syntax of control files and the purpose
9970 of the fields is available in <ref id="controlfields">.
9975 <heading>Time Stamps</heading>
9978 See <ref id="timestamps">.
9983 <appendix id="pkg-sourcepkg">
9984 <heading>Source packages (from old Packaging Manual) </heading>
9987 The Debian binary packages in the distribution are generated
9988 from Debian sources, which are in a special format to assist
9989 the easy and automatic building of binaries.
9992 <sect id="pkg-sourcetools">
9993 <heading>Tools for processing source packages</heading>
9996 Various tools are provided for manipulating source packages;
9997 they pack and unpack sources and help build of binary
9998 packages and help manage the distribution of new versions.
10002 They are introduced and typical uses described here; see
10003 <manref name="dpkg-source" section="1"> for full
10004 documentation about their arguments and operation.
10008 For examples of how to construct a Debian source package,
10009 and how to use those utilities that are used by Debian
10010 source packages, please see the <prgn>hello</prgn> example
10014 <sect1 id="pkg-dpkg-source">
10016 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
10021 This program is frequently used by hand, and is also
10022 called from package-independent automated building scripts
10023 such as <prgn>dpkg-buildpackage</prgn>.
10027 To unpack a package it is typically invoked with
10029 dpkg-source -x <var>.../path/to/filename</var>.dsc
10034 with the <file><var>filename</var>.tar.gz</file> and
10035 <file><var>filename</var>.diff.gz</file> (if applicable) in
10036 the same directory. It unpacks into
10037 <file><var>package</var>-<var>version</var></file>, and if
10039 <file><var>package</var>-<var>version</var>.orig</file>, in
10040 the current directory.
10044 To create a packed source archive it is typically invoked:
10046 dpkg-source -b <var>package</var>-<var>version</var>
10051 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
10052 <file>.diff.gz</file> (if appropriate) in the current
10053 directory. <prgn>dpkg-source</prgn> does not clean the
10054 source tree first - this must be done separately if it is
10059 See also <ref id="pkg-sourcearchives">.</p>
10063 <sect1 id="pkg-dpkg-buildpackage">
10065 <prgn>dpkg-buildpackage</prgn> - overall package-building
10070 <prgn>dpkg-buildpackage</prgn> is a script which invokes
10071 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
10072 targets <tt>clean</tt>, <tt>build</tt> and
10073 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
10074 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
10075 source and binary package upload.
10079 It is usually invoked by hand from the top level of the
10080 built or unbuilt source directory. It may be invoked with
10081 no arguments; useful arguments include:
10082 <taglist compact="compact">
10083 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
10086 Do not sign the <tt>.changes</tt> file or the
10087 source package <tt>.dsc</tt> file, respectively.</p>
10089 <tag><tt>-p<var>sign-command</var></tt></tag>
10092 Invoke <var>sign-command</var> instead of finding
10093 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
10094 <var>sign-command</var> must behave just like
10095 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
10097 <tag><tt>-r<var>root-command</var></tt></tag>
10100 When root privilege is required, invoke the command
10101 <var>root-command</var>. <var>root-command</var>
10102 should invoke its first argument as a command, from
10103 the <prgn>PATH</prgn> if necessary, and pass its
10104 second and subsequent arguments to the command it
10105 calls. If no <var>root-command</var> is supplied
10106 then <var>dpkg-buildpackage</var> will take no
10107 special action to gain root privilege, so that for
10108 most packages it will have to be invoked as root to
10111 <tag><tt>-b</tt>, <tt>-B</tt></tag>
10114 Two types of binary-only build and upload - see
10115 <manref name="dpkg-source" section="1">.
10122 <sect1 id="pkg-dpkg-gencontrol">
10124 <prgn>dpkg-gencontrol</prgn> - generates binary package
10129 This program is usually called from <file>debian/rules</file>
10130 (see <ref id="pkg-sourcetree">) in the top level of the source
10135 This is usually done just before the files and directories in the
10136 temporary directory tree where the package is being built have their
10137 permissions and ownerships set and the package is constructed using
10138 <prgn>dpkg-deb/</prgn>
10140 This is so that the control file which is produced has
10141 the right permissions
10146 <prgn>dpkg-gencontrol</prgn> must be called after all the
10147 files which are to go into the package have been placed in
10148 the temporary build directory, so that its calculation of
10149 the installed size of a package is correct.
10153 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
10154 be run after <prgn>dpkg-shlibdeps</prgn> so that the
10155 variable substitutions created by
10156 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
10161 For a package which generates only one binary package, and
10162 which builds it in <file>debian/tmp</file> relative to the top
10163 of the source package, it is usually sufficient to call
10164 <prgn>dpkg-gencontrol</prgn>.
10168 Sources which build several binaries will typically need
10171 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
10172 </example> The <tt>-P</tt> tells
10173 <prgn>dpkg-gencontrol</prgn> that the package is being
10174 built in a non-default directory, and the <tt>-p</tt>
10175 tells it which package's control file should be generated.
10179 <prgn>dpkg-gencontrol</prgn> also adds information to the
10180 list of files in <file>debian/files</file>, for the benefit of
10181 (for example) a future invocation of
10182 <prgn>dpkg-genchanges</prgn>.</p>
10185 <sect1 id="pkg-dpkg-shlibdeps">
10187 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
10192 This program is usually called from <file>debian/rules</file>
10193 just before <prgn>dpkg-gencontrol</prgn> (see <ref
10194 id="pkg-sourcetree">), in the top level of the source tree.
10198 Its arguments are executables and shared libraries
10201 They may be specified either in the locations in the
10202 source tree where they are created or in the locations
10203 in the temporary build tree where they are installed
10204 prior to binary package creation.
10206 </footnote> for which shared library dependencies should
10207 be included in the binary package's control file.
10211 If some of the found shared libraries should only
10212 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
10213 some warrant a <tt>Pre-Depends</tt>, this can be achieved
10214 by using the <tt>-d<var>dependency-field</var></tt> option
10215 before those executable(s). (Each <tt>-d</tt> option
10216 takes effect until the next <tt>-d</tt>.)
10220 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
10221 output control file to be modified. Instead by default it
10222 adds to the <file>debian/substvars</file> file variable
10223 settings like <tt>shlibs:Depends</tt>. These variable
10224 settings must be referenced in dependency fields in the
10225 appropriate per-binary-package sections of the source
10230 For example, a package that generates an essential part
10231 which requires dependencies, and optional parts that
10232 which only require a recommendation, would separate those
10233 two sets of dependencies into two different fields.<footnote>
10234 At the time of writing, an example for this was the
10235 <package/xmms/ package, with Depends used for the xmms
10236 executable, Recommends for the plug-ins and Suggests for
10237 even more optional features provided by unzip.
10239 It can say in its <file>debian/rules</file>:
10241 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
10242 -dRecommends <var>optionalpart anotheroptionalpart</var>
10244 and then in its main control file <file>debian/control</file>:
10247 Depends: ${shlibs:Depends}
10248 Recommends: ${shlibs:Recommends}
10254 Sources which produce several binary packages with
10255 different shared library dependency requirements can use
10256 the <tt>-p<var>varnameprefix</var></tt> option to override
10257 the default <tt>shlibs:</tt> prefix (one invocation of
10258 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
10259 They can thus produce several sets of dependency
10260 variables, each of the form
10261 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
10262 which can be referred to in the appropriate parts of the
10263 binary package control files.
10268 <sect1 id="pkg-dpkg-distaddfile">
10270 <prgn>dpkg-distaddfile</prgn> - adds a file to
10271 <file>debian/files</file>
10275 Some packages' uploads need to include files other than
10276 the source and binary package files.
10280 <prgn>dpkg-distaddfile</prgn> adds a file to the
10281 <file>debian/files</file> file so that it will be included in
10282 the <file>.changes</file> file when
10283 <prgn>dpkg-genchanges</prgn> is run.
10287 It is usually invoked from the <tt>binary</tt> target of
10288 <file>debian/rules</file>:
10290 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
10292 The <var>filename</var> is relative to the directory where
10293 <prgn>dpkg-genchanges</prgn> will expect to find it - this
10294 is usually the directory above the top level of the source
10295 tree. The <file>debian/rules</file> target should put the
10296 file there just before or just after calling
10297 <prgn>dpkg-distaddfile</prgn>.
10301 The <var>section</var> and <var>priority</var> are passed
10302 unchanged into the resulting <file>.changes</file> file.
10307 <sect1 id="pkg-dpkg-genchanges">
10309 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
10310 upload control file
10314 This program is usually called by package-independent
10315 automatic building scripts such as
10316 <prgn>dpkg-buildpackage</prgn>, but it may also be called
10321 It is usually called in the top level of a built source
10322 tree, and when invoked with no arguments will print out a
10323 straightforward <file>.changes</file> file based on the
10324 information in the source package's changelog and control
10325 file and the binary and source packages which should have
10331 <sect1 id="pkg-dpkg-parsechangelog">
10333 <prgn>dpkg-parsechangelog</prgn> - produces parsed
10334 representation of a changelog
10338 This program is used internally by
10339 <prgn>dpkg-source</prgn> et al. It may also occasionally
10340 be useful in <file>debian/rules</file> and elsewhere. It
10341 parses a changelog, <file>debian/changelog</file> by default,
10342 and prints a control-file format representation of the
10343 information in it to standard output.
10347 <sect1 id="pkg-dpkg-architecture">
10349 <prgn>dpkg-architecture</prgn> - information about the build and
10354 This program can be used manually, but is also invoked by
10355 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
10356 environment or make variables which specify the build and host
10357 architecture for the package building process.
10362 <sect id="pkg-sourcetree">
10363 <heading>The Debian package source tree</heading>
10366 The source archive scheme described later is intended to
10367 allow a Debian package source tree with some associated
10368 control information to be reproduced and transported easily.
10369 The Debian package source tree is a version of the original
10370 program with certain files added for the benefit of the
10371 packaging process, and with any other changes required
10372 made to the rest of the source code and installation
10377 The extra files created for Debian are in the subdirectory
10378 <file>debian</file> of the top level of the Debian package
10379 source tree. They are described below.
10382 <sect1 id="pkg-debianrules">
10383 <heading><file>debian/rules</file> - the main building script</heading>
10386 See <ref id="debianrules">.
10390 <sect1 id="pkg-srcsubstvars">
10391 <heading><file>debian/substvars</file> and variable substitutions</heading>
10394 See <ref id="substvars">.
10400 <heading><file>debian/files</file></heading>
10403 See <ref id="debianfiles">.
10407 <sect1><heading><file>debian/tmp</file>
10411 This is the canonical temporary location for the
10412 construction of binary packages by the <tt>binary</tt>
10413 target. The directory <file>tmp</file> serves as the root of
10414 the file system tree as it is being constructed (for
10415 example, by using the package's upstream makefiles install
10416 targets and redirecting the output there), and it also
10417 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10418 id="pkg-bincreating">.
10422 If several binary packages are generated from the same
10423 source tree it is usual to use several
10424 <file>debian/tmp<var>something</var></file> directories, for
10425 example <file>tmp-a</file> or <file>tmp-doc</file>.
10429 Whatever <file>tmp</file> directories are created and used by
10430 <tt>binary</tt> must of course be removed by the
10431 <tt>clean</tt> target.</p></sect1>
10435 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10439 As it exists on the FTP site, a Debian source package
10440 consists of three related files. You must have the right
10441 versions of all three to be able to use them.
10446 <tag>Debian source control file - <tt>.dsc</tt></tag>
10448 This file is a control file used by <prgn>dpkg-source</prgn>
10449 to extract a source package.
10450 See <ref id="debiansourcecontrolfiles">.
10454 Original source archive -
10456 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10462 This is a compressed (with <tt>gzip -9</tt>)
10463 <prgn>tar</prgn> file containing the source code from
10464 the upstream authors of the program.
10469 Debian package diff -
10471 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10477 This is a unified context diff (<tt>diff -u</tt>)
10478 giving the changes which are required to turn the
10479 original source into the Debian source. These changes
10480 may only include editing and creating plain files.
10481 The permissions of files, the targets of symbolic
10482 links and the characteristics of special files or
10483 pipes may not be changed and no files may be removed
10488 All the directories in the diff must exist, except the
10489 <file>debian</file> subdirectory of the top of the source
10490 tree, which will be created by
10491 <prgn>dpkg-source</prgn> if necessary when unpacking.
10495 The <prgn>dpkg-source</prgn> program will
10496 automatically make the <file>debian/rules</file> file
10497 executable (see below).</p></item>
10502 If there is no original source code - for example, if the
10503 package is specially prepared for Debian or the Debian
10504 maintainer is the same as the upstream maintainer - the
10505 format is slightly different: then there is no diff, and the
10507 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10508 and preferably contains a directory named
10509 <file><var>package</var>-<var>version</var></file>.
10514 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10517 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10518 Debian source package. However, if it is not available it
10519 is possible to unpack a Debian source archive as follows:
10520 <enumlist compact="compact">
10523 Untar the tarfile, which will create a <file>.orig</file>
10527 <p>Rename the <file>.orig</file> directory to
10528 <file><var>package</var>-<var>version</var></file>.</p>
10532 Create the subdirectory <file>debian</file> at the top of
10533 the source tree.</p>
10535 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10537 <item><p>Untar the tarfile again if you want a copy of the original
10538 source code alongside the Debian version.</p>
10543 It is not possible to generate a valid Debian source archive
10544 without using <prgn>dpkg-source</prgn>. In particular,
10545 attempting to use <prgn>diff</prgn> directly to generate the
10546 <file>.diff.gz</file> file will not work.
10550 <heading>Restrictions on objects in source packages</heading>
10553 The source package may not contain any hard links
10555 This is not currently detected when building source
10556 packages, but only when extracting
10560 Hard links may be permitted at some point in the
10561 future, but would require a fair amount of
10563 </footnote>, device special files, sockets or setuid or
10566 Setgid directories are allowed.
10571 The source packaging tools manage the changes between the
10572 original and Debian source using <prgn>diff</prgn> and
10573 <prgn>patch</prgn>. Turning the original source tree as
10574 included in the <file>.orig.tar.gz</file> into the Debian
10575 package source must not involve any changes which cannot be
10576 handled by these tools. Problematic changes which cause
10577 <prgn>dpkg-source</prgn> to halt with an error when
10578 building the source package are:
10579 <list compact="compact">
10580 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10582 <item><p>Changing the targets of symbolic links.</p>
10584 <item><p>Creating directories, other than <file>debian</file>.</p>
10586 <item><p>Changes to the contents of binary files.</p></item>
10587 </list> Changes which cause <prgn>dpkg-source</prgn> to
10588 print a warning but continue anyway are:
10589 <list compact="compact">
10592 Removing files, directories or symlinks.
10594 Renaming a file is not treated specially - it is
10595 seen as the removal of the old file (which
10596 generates a warning, but is otherwise ignored),
10597 and the creation of the new one.
10603 Changed text files which are missing the usual final
10604 newline (either in the original or the modified
10609 Changes which are not represented, but which are not detected by
10610 <prgn>dpkg-source</prgn>, are:
10611 <list compact="compact">
10612 <item><p>Changing the permissions of files (other than
10613 <file>debian/rules</file>) and directories.</p></item>
10618 The <file>debian</file> directory and <file>debian/rules</file>
10619 are handled specially by <prgn>dpkg-source</prgn> - before
10620 applying the changes it will create the <file>debian</file>
10621 directory, and afterwards it will make
10622 <file>debian/rules</file> world-executable.
10628 <appendix id="pkg-controlfields">
10629 <heading>Control files and their fields (from old Packaging Manual)</heading>
10632 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10633 data in a common format, known as control files. Binary and
10634 source packages have control data as do the <file>.changes</file>
10635 files which control the installation of uploaded files, and
10636 <prgn>dpkg</prgn>'s internal databases are in a similar
10641 <heading>Syntax of control files</heading>
10644 See <ref id="controlsyntax">.
10648 It is important to note that there are several fields which
10649 are optional as far as <prgn>dpkg</prgn> and the related
10650 tools are concerned, but which must appear in every Debian
10651 package, or whose omission may cause problems.
10656 <heading>List of fields</heading>
10659 See <ref id="controlfieldslist">.
10663 This section now contains only the fields that didn't belong
10664 to the Policy manual.
10667 <sect1 id="pkg-f-Filename">
10668 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10671 These fields in <tt>Packages</tt> files give the
10672 filename(s) of (the parts of) a package in the
10673 distribution directories, relative to the root of the
10674 Debian hierarchy. If the package has been split into
10675 several parts the parts are all listed in order, separated
10680 <sect1 id="pkg-f-Size">
10681 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10684 These fields in <file>Packages</file> files give the size (in
10685 bytes, expressed in decimal) and MD5 checksum of the
10686 file(s) which make(s) up a binary package in the
10687 distribution. If the package is split into several parts
10688 the values for the parts are listed in order, separated by
10693 <sect1 id="pkg-f-Status">
10694 <heading><tt>Status</tt></heading>
10697 This field in <prgn>dpkg</prgn>'s status file records
10698 whether the user wants a package installed, removed or
10699 left alone, whether it is broken (requiring
10700 re-installation) or not and what its current state on the
10701 system is. Each of these pieces of information is a
10706 <sect1 id="pkg-f-Config-Version">
10707 <heading><tt>Config-Version</tt></heading>
10710 If a package is not installed or not configured, this
10711 field in <prgn>dpkg</prgn>'s status file records the last
10712 version of the package which was successfully
10717 <sect1 id="pkg-f-Conffiles">
10718 <heading><tt>Conffiles</tt></heading>
10721 This field in <prgn>dpkg</prgn>'s status file contains
10722 information about the automatically-managed configuration
10723 files held by a package. This field should <em>not</em>
10724 appear anywhere in a package!
10729 <heading>Obsolete fields</heading>
10732 These are still recognized by <prgn>dpkg</prgn> but should
10733 not appear anywhere any more.
10735 <taglist compact="compact">
10737 <tag><tt>Revision</tt></tag>
10738 <tag><tt>Package-Revision</tt></tag>
10739 <tag><tt>Package_Revision</tt></tag>
10741 The Debian revision part of the package version was
10742 at one point in a separate control field. This
10743 field went through several names.
10746 <tag><tt>Recommended</tt></tag>
10747 <item>Old name for <tt>Recommends</tt>.</item>
10749 <tag><tt>Optional</tt></tag>
10750 <item>Old name for <tt>Suggests</tt>.</item>
10752 <tag><tt>Class</tt></tag>
10753 <item>Old name for <tt>Priority</tt>.</item>
10762 <appendix id="pkg-conffiles">
10763 <heading>Configuration file handling (from old Packaging Manual)</heading>
10766 <prgn>dpkg</prgn> can do a certain amount of automatic
10767 handling of package configuration files.
10771 Whether this mechanism is appropriate depends on a number of
10772 factors, but basically there are two approaches to any
10773 particular configuration file.
10777 The easy method is to ship a best-effort configuration in the
10778 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10779 handle updates. If the user is unlikely to want to edit the
10780 file, but you need them to be able to without losing their
10781 changes, and a new package with a changed version of the file
10782 is only released infrequently, this is a good approach.
10786 The hard method is to build the configuration file from
10787 scratch in the <prgn>postinst</prgn> script, and to take the
10788 responsibility for fixing any mistakes made in earlier
10789 versions of the package automatically. This will be
10790 appropriate if the file is likely to need to be different on
10794 <sect><heading>Automatic handling of configuration files by
10799 A package may contain a control information file called
10800 <tt>conffiles</tt>. This file should be a list of filenames
10801 of configuration files needing automatic handling, separated
10802 by newlines. The filenames should be absolute pathnames,
10803 and the files referred to should actually exist in the
10808 When a package is upgraded <prgn>dpkg</prgn> will process
10809 the configuration files during the configuration stage,
10810 shortly before it runs the package's <prgn>postinst</prgn>
10815 For each file it checks to see whether the version of the
10816 file included in the package is the same as the one that was
10817 included in the last version of the package (the one that is
10818 being upgraded from); it also compares the version currently
10819 installed on the system with the one shipped with the last
10824 If neither the user nor the package maintainer has changed
10825 the file, it is left alone. If one or the other has changed
10826 their version, then the changed version is preferred - i.e.,
10827 if the user edits their file, but the package maintainer
10828 doesn't ship a different version, the user's changes will
10829 stay, silently, but if the maintainer ships a new version
10830 and the user hasn't edited it the new version will be
10831 installed (with an informative message). If both have
10832 changed their version the user is prompted about the problem
10833 and must resolve the differences themselves.
10837 The comparisons are done by calculating the MD5 message
10838 digests of the files, and storing the MD5 of the file as it
10839 was included in the most recent version of the package.
10843 When a package is installed for the first time
10844 <prgn>dpkg</prgn> will install the file that comes with it,
10845 unless that would mean overwriting a file already on the
10850 However, note that <prgn>dpkg</prgn> will <em>not</em>
10851 replace a conffile that was removed by the user (or by a
10852 script). This is necessary because with some programs a
10853 missing file produces an effect hard or impossible to
10854 achieve in another way, so that a missing file needs to be
10855 kept that way if the user did it.
10859 Note that a package should <em>not</em> modify a
10860 <prgn>dpkg</prgn>-handled conffile in its maintainer
10861 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10862 the user confusing and possibly dangerous options for
10863 conffile update when the package is upgraded.</p>
10866 <sect><heading>Fully-featured maintainer script configuration
10871 For files which contain site-specific information such as
10872 the hostname and networking details and so forth, it is
10873 better to create the file in the package's
10874 <prgn>postinst</prgn> script.
10878 This will typically involve examining the state of the rest
10879 of the system to determine values and other information, and
10880 may involve prompting the user for some information which
10881 can't be obtained some other way.
10885 When using this method there are a couple of important
10886 issues which should be considered:
10890 If you discover a bug in the program which generates the
10891 configuration file, or if the format of the file changes
10892 from one version to the next, you will have to arrange for
10893 the postinst script to do something sensible - usually this
10894 will mean editing the installed configuration file to remove
10895 the problem or change the syntax. You will have to do this
10896 very carefully, since the user may have changed the file,
10897 perhaps to fix the very problem that your script is trying
10898 to deal with - you will have to detect these situations and
10899 deal with them correctly.
10903 If you do go down this route it's probably a good idea to
10904 make the program that generates the configuration file(s) a
10905 separate program in <file>/usr/sbin</file>, by convention called
10906 <file><var>package</var>config</file> and then run that if
10907 appropriate from the post-installation script. The
10908 <tt><var>package</var>config</tt> program should not
10909 unquestioningly overwrite an existing configuration - if its
10910 mode of operation is geared towards setting up a package for
10911 the first time (rather than any arbitrary reconfiguration
10912 later) you should have it check whether the configuration
10913 already exists, and require a <tt>--force</tt> flag to
10914 overwrite it.</p></sect>
10917 <appendix id="pkg-alternatives"><heading>Alternative versions of
10918 an interface - <prgn>update-alternatives</prgn> (from old
10923 When several packages all provide different versions of the
10924 same program or file it is useful to have the system select a
10925 default, but to allow the system administrator to change it
10926 and have their decisions respected.
10930 For example, there are several versions of the <prgn>vi</prgn>
10931 editor, and there is no reason to prevent all of them from
10932 being installed at once, each under their own name
10933 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10934 Nevertheless it is desirable to have the name <tt>vi</tt>
10935 refer to something, at least by default.
10939 If all the packages involved cooperate, this can be done with
10940 <prgn>update-alternatives</prgn>.
10944 Each package provides its own version under its own name, and
10945 calls <prgn>update-alternatives</prgn> in its postinst to
10946 register its version (and again in its prerm to deregister
10951 See the man page <manref name="update-alternatives"
10952 section="8"> for details.
10956 If <prgn>update-alternatives</prgn> does not seem appropriate
10957 you may wish to consider using diversions instead.</p>
10960 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10961 package's version of a file (from old Packaging Manual)
10965 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10966 when it reinstalls the package it belongs to, and to have it
10967 put the file from the package somewhere else instead.
10971 This can be used locally to override a package's version of a
10972 file, or by one package to override another's version (or
10973 provide a wrapper for it).
10977 Before deciding to use a diversion, read <ref
10978 id="pkg-alternatives"> to see if you really want a diversion
10979 rather than several alternative versions of a program.
10983 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10984 and updated by a special program <prgn>dpkg-divert</prgn>.
10985 Please see <manref name="dpkg-divert" section="8"> for full
10986 details of its operation.
10990 When a package wishes to divert a file from another, it should
10991 call <prgn>dpkg-divert</prgn> in its preinst to add the
10992 diversion and rename the existing file. For example,
10993 supposing that a <prgn>smailwrapper</prgn> package wishes to
10994 install a wrapper around <file>/usr/sbin/smail</file>:
10996 dpkg-divert --package smailwrapper --add --rename \
10997 --divert /usr/sbin/smail.real /usr/sbin/smail
10998 </example> The <tt>--package smailwrapper</tt> ensures that
10999 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
11000 can bypass the diversion and get installed as the true version.
11001 It's safe to add the diversion unconditionally on upgrades since
11002 it will be left unchanged if it already exists, but
11003 <prgn>dpkg-divert</prgn> will display a message. To suppress that
11004 message, make the command conditional on the version from which
11005 the package is being upgraded:
11007 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
11008 dpkg-divert --package smailwrapper --add --rename \
11009 --divert /usr/sbin/smail.real /usr/sbin/smail
11011 </example> where <tt>1.0-2</tt> is the version at which the
11012 diversion was first added to the package. Running the command
11013 during abort-upgrade is pointless but harmless.
11017 The postrm has to do the reverse:
11019 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
11020 dpkg-divert --package smailwrapper --remove --rename \
11021 --divert /usr/sbin/smail.real /usr/sbin/smail
11023 </example> If the diversion was added at a particular version, the
11024 postrm should also handle the failure case of upgrading from an
11025 older version (unless the older version is so old that direct
11026 upgrades are no longer supported):
11028 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
11029 dpkg-divert --package smailwrapper --remove --rename \
11030 --divert /usr/sbin/smail.real /usr/sbin/smail
11032 </example> where <tt>1.02-2</tt> is the version at which the
11033 diversion was first added to the package. The postrm should not
11034 remove the diversion on upgrades both because there's no reason to
11035 remove the diversion only to immediately re-add it and since the
11036 postrm of the old package is run after unpacking so the removal of
11037 the diversion will fail.
11041 Do not attempt to divert a file which is vitally important for
11042 the system's operation - when using <prgn>dpkg-divert</prgn>
11043 there is a time, after it has been diverted but before
11044 <prgn>dpkg</prgn> has installed the new version, when the file
11045 does not exist.</p>
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