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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. The information here will be
1640 copied to the <tt>Changed-By</tt> field in the
1641 <tt>.changes</tt> file (see <ref id="f-Changed-By">),
1642 and then later used to send an acknowledgement when the
1643 upload has been installed.
1647 The <var>date</var> has the following format<footnote>
1648 This is the same as the format generated by <tt>date
1650 </footnote> (compatible and with the same semantics of
1651 RFC 2822 and RFC 5322):
1652 <example>day-of-week, dd month yyyy hh:mm:ss +zzzz</example>
1654 <list compact="compact">
1656 day-of week is one of: Mon, Tue, Wed, Thu, Fri, Sat, Sun
1659 dd is a one- or two-digit day of the month (01-31)
1662 month is one of: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug,
1665 <item>yyyy is the four-digit year (e.g. 2010)</item>
1666 <item>hh is the two-digit hour (00-23)</item>
1667 <item>mm is the two-digit minutes (00-59)</item>
1668 <item>ss is the two-digit seconds (00-60)</item>
1670 +zzzz or -zzzz is the the time zone offset from Coordinated
1671 Universal Time (UTC). "+" indicates that the time is ahead
1672 of (i.e., east of) UTC and "-" indicates that the time is
1673 behind (i.e., west of) UTC. The first two digits indicate
1674 the hour difference from UTC and the last two digits
1675 indicate the number of additional minutes difference from
1676 UTC. The last two digits must be in the range 00-59.
1682 The first "title" line with the package name must start
1683 at the left hand margin. The "trailer" line with the
1684 maintainer and date details must be preceded by exactly
1685 one space. The maintainer details and the date must be
1686 separated by exactly two spaces.
1690 The entire changelog must be encoded in UTF-8.
1694 For more information on placement of the changelog files
1695 within binary packages, please see <ref id="changelogs">.
1699 <sect id="dpkgcopyright">
1700 <heading>Copyright: <file>debian/copyright</file></heading>
1702 Every package must be accompanied by a verbatim copy of its
1703 copyright information and distribution license in the file
1704 <file>/usr/share/doc/<var>package</var>/copyright</file>
1705 (see <ref id="copyrightfile"> for further details). Also see
1706 <ref id="pkgcopyright"> for further considerations related
1707 to copyrights for packages.
1711 <heading>Error trapping in makefiles</heading>
1714 When <prgn>make</prgn> invokes a command in a makefile
1715 (including your package's upstream makefiles and
1716 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1717 means that <prgn>sh</prgn>'s usual bad error handling
1718 properties apply: if you include a miniature script as one
1719 of the commands in your makefile you'll find that if you
1720 don't do anything about it then errors are not detected
1721 and <prgn>make</prgn> will blithely continue after
1726 Every time you put more than one shell command (this
1727 includes using a loop) in a makefile command you
1728 must make sure that errors are trapped. For
1729 simple compound commands, such as changing directory and
1730 then running a program, using <tt>&&</tt> rather
1731 than semicolon as a command separator is sufficient. For
1732 more complex commands including most loops and
1733 conditionals you should include a separate <tt>set -e</tt>
1734 command at the start of every makefile command that's
1735 actually one of these miniature shell scripts.
1739 <sect id="timestamps">
1740 <heading>Time Stamps</heading>
1742 Maintainers should preserve the modification times of the
1743 upstream source files in a package, as far as is reasonably
1745 The rationale is that there is some information conveyed
1746 by knowing the age of the file, for example, you could
1747 recognize that some documentation is very old by looking
1748 at the modification time, so it would be nice if the
1749 modification time of the upstream source would be
1755 <sect id="restrictions">
1756 <heading>Restrictions on objects in source packages</heading>
1759 The source package may not contain any hard links<footnote>
1761 This is not currently detected when building source
1762 packages, but only when extracting
1766 Hard links may be permitted at some point in the
1767 future, but would require a fair amount of
1770 </footnote>, device special files, sockets or setuid or
1771 setgid files.<footnote>
1772 Setgid directories are allowed.
1777 <sect id="debianrules">
1778 <heading>Main building script: <file>debian/rules</file></heading>
1781 This file must be an executable makefile, and contains the
1782 package-specific recipes for compiling the package and
1783 building binary package(s) from the source.
1787 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1788 so that it can be invoked by saying its name rather than
1789 invoking <prgn>make</prgn> explicitly. That is, invoking
1790 either of <tt>make -f debian/rules <em>args...</em></tt>
1791 or <tt>./debian/rules <em>args...</em></tt> must result in
1796 Since an interactive <file>debian/rules</file> script makes it
1797 impossible to auto-compile that package and also makes it
1798 hard for other people to reproduce the same binary
1799 package, all <em>required targets</em> must be
1800 non-interactive. At a minimum, required targets are the
1801 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1802 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1803 <em>binary-indep</em>, and <em>build</em>. It also follows
1804 that any target that these targets depend on must also be
1809 The targets are as follows (required unless stated otherwise):
1811 <tag><tt>build</tt></tag>
1814 The <tt>build</tt> target should perform all the
1815 configuration and compilation of the package.
1816 If a package has an interactive pre-build
1817 configuration routine, the Debian source package
1818 must either be built after this has taken place (so
1819 that the binary package can be built without rerunning
1820 the configuration) or the configuration routine
1821 modified to become non-interactive. (The latter is
1822 preferable if there are architecture-specific features
1823 detected by the configuration routine.)
1827 For some packages, notably ones where the same
1828 source tree is compiled in different ways to produce
1829 two binary packages, the <tt>build</tt> target
1830 does not make much sense. For these packages it is
1831 good enough to provide two (or more) targets
1832 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1833 for each of the ways of building the package, and a
1834 <tt>build</tt> target that does nothing. The
1835 <tt>binary</tt> target will have to build the
1836 package in each of the possible ways and make the
1837 binary package out of each.
1841 The <tt>build</tt> target must not do anything
1842 that might require root privilege.
1846 The <tt>build</tt> target may need to run the
1847 <tt>clean</tt> target first - see below.
1851 When a package has a configuration and build routine
1852 which takes a long time, or when the makefiles are
1853 poorly designed, or when <tt>build</tt> needs to
1854 run <tt>clean</tt> first, it is a good idea to
1855 <tt>touch build</tt> when the build process is
1856 complete. This will ensure that if <tt>debian/rules
1857 build</tt> is run again it will not rebuild the whole
1859 Another common way to do this is for <tt>build</tt>
1860 to depend on <prgn>build-stamp</prgn> and to do
1861 nothing else, and for the <prgn>build-stamp</prgn>
1862 target to do the building and to <tt>touch
1863 build-stamp</tt> on completion. This is
1864 especially useful if the build routine creates a
1865 file or directory called <tt>build</tt>; in such a
1866 case, <tt>build</tt> will need to be listed as
1867 a phony target (i.e., as a dependency of the
1868 <tt>.PHONY</tt> target). See the documentation of
1869 <prgn>make</prgn> for more information on phony
1875 <tag><tt>build-arch</tt> (optional),
1876 <tt>build-indep</tt> (optional)
1880 A package may also provide both of the targets
1881 <tt>build-arch</tt> and <tt>build-indep</tt>.
1882 The <tt>build-arch</tt> target, if provided, should
1883 perform all the configuration and compilation required for
1884 producing all architecture-dependant binary packages
1885 (those packages for which the body of the
1886 <tt>Architecture</tt> field in <tt>debian/control</tt> is
1887 not <tt>all</tt>). Similarly, the <tt>build-indep</tt>
1888 target, if provided, should perform all the configuration
1889 and compilation required for producing all
1890 architecture-independent binary packages (those packages
1891 for which the body of the <tt>Architecture</tt> field
1892 in <tt>debian/control</tt> is <tt>all</tt>).
1893 The <tt>build</tt> target should depend on those of the
1894 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1895 are provided in the rules file.<footnote>
1896 The intent of this split is so that binary-only builds
1897 need not install the dependencies required for
1898 the <tt>build-indep</tt> target. However, this is not
1899 yet used in practice since <tt>dpkg-buildpackage
1900 -B</tt>, and therefore the autobuilders,
1901 invoke <tt>build</tt> rather than <tt>build-arch</tt>
1902 due to the difficulties in determining whether the
1903 optional <tt>build-arch</tt> target exists.
1908 If one or both of the targets <tt>build-arch</tt> and
1909 <tt>build-indep</tt> are not provided, then invoking
1910 <file>debian/rules</file> with one of the not-provided
1911 targets as arguments should produce a exit status code
1912 of 2. Usually this is provided automatically by make
1913 if the target is missing.
1917 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1918 must not do anything that might require root privilege.
1922 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1923 <tt>binary-indep</tt>
1927 The <tt>binary</tt> target must be all that is
1928 necessary for the user to build the binary package(s)
1929 produced from this source package. It is
1930 split into two parts: <prgn>binary-arch</prgn> builds
1931 the binary packages which are specific to a particular
1932 architecture, and <tt>binary-indep</tt> builds
1933 those which are not.
1936 <tt>binary</tt> may be (and commonly is) a target with
1937 no commands which simply depends on
1938 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1941 Both <tt>binary-*</tt> targets should depend on the
1942 <tt>build</tt> target, or on the appropriate
1943 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1944 provided, so that the package is built if it has not
1945 been already. It should then create the relevant
1946 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1947 make their control files and <prgn>dpkg-deb</prgn> to
1948 build them and place them in the parent of the top
1953 Both the <tt>binary-arch</tt> and
1954 <tt>binary-indep</tt> targets <em>must</em> exist.
1955 If one of them has nothing to do (which will always be
1956 the case if the source generates only a single binary
1957 package, whether architecture-dependent or not), it
1958 must still exist and must always succeed.
1962 The <tt>binary</tt> targets must be invoked as
1964 The <prgn>fakeroot</prgn> package often allows one
1965 to build a package correctly even without being
1971 <tag><tt>clean</tt></tag>
1974 This must undo any effects that the <tt>build</tt>
1975 and <tt>binary</tt> targets may have had, except
1976 that it should leave alone any output files created in
1977 the parent directory by a run of a <tt>binary</tt>
1982 If a <tt>build</tt> file is touched at the end of
1983 the <tt>build</tt> target, as suggested above, it
1984 should be removed as the first action that
1985 <tt>clean</tt> performs, so that running
1986 <tt>build</tt> again after an interrupted
1987 <tt>clean</tt> doesn't think that everything is
1992 The <tt>clean</tt> target may need to be
1993 invoked as root if <tt>binary</tt> has been
1994 invoked since the last <tt>clean</tt>, or if
1995 <tt>build</tt> has been invoked as root (since
1996 <tt>build</tt> may create directories, for
2001 <tag><tt>get-orig-source</tt> (optional)</tag>
2004 This target fetches the most recent version of the
2005 original source package from a canonical archive site
2006 (via FTP or WWW, for example), does any necessary
2007 rearrangement to turn it into the original source
2008 tar file format described below, and leaves it in the
2013 This target may be invoked in any directory, and
2014 should take care to clean up any temporary files it
2019 This target is optional, but providing it if
2020 possible is a good idea.
2024 <tag><tt>patch</tt> (optional)</tag>
2027 This target performs whatever additional actions are
2028 required to make the source ready for editing (unpacking
2029 additional upstream archives, applying patches, etc.).
2030 It is recommended to be implemented for any package where
2031 <tt>dpkg-source -x</tt> does not result in source ready
2032 for additional modification. See
2033 <ref id="readmesource">.
2039 The <tt>build</tt>, <tt>binary</tt> and
2040 <tt>clean</tt> targets must be invoked with the current
2041 directory being the package's top-level directory.
2046 Additional targets may exist in <file>debian/rules</file>,
2047 either as published or undocumented interfaces or for the
2048 package's internal use.
2052 The architectures we build on and build for are determined
2053 by <prgn>make</prgn> variables using the utility
2054 <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
2055 You can determine the
2056 Debian architecture and the GNU style architecture
2057 specification string for the build machine (the machine type
2058 we are building on) as well as for the host machine (the
2059 machine type we are building for). Here is a list of
2060 supported <prgn>make</prgn> variables:
2061 <list compact="compact">
2063 <tt>DEB_*_ARCH</tt> (the Debian architecture)
2066 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2069 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2072 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2073 specification string)
2076 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2077 <tt>DEB_*_GNU_TYPE</tt>)
2080 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2081 <tt>DEB_*_GNU_TYPE</tt>)
2083 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2084 the build machine or <tt>HOST</tt> for specification of the
2089 Backward compatibility can be provided in the rules file
2090 by setting the needed variables to suitable default
2091 values; please refer to the documentation of
2092 <prgn>dpkg-architecture</prgn> for details.
2096 It is important to understand that the <tt>DEB_*_ARCH</tt>
2097 string only determines which Debian architecture we are
2098 building on or for. It should not be used to get the CPU
2099 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2100 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2101 GNU style variables should generally only be used with upstream
2105 <sect1 id="debianrules-options">
2106 <heading><file>debian/rules</file> and
2107 <tt>DEB_BUILD_OPTIONS</tt></heading>
2110 Supporting the standardized environment variable
2111 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2112 contain several flags to change how a package is compiled and
2113 built. Each flag must be in the form <var>flag</var> or
2114 <var>flag</var>=<var>options</var>. If multiple flags are
2115 given, they must be separated by whitespace.<footnote>
2116 Some packages support any delimiter, but whitespace is the
2117 easiest to parse inside a makefile and avoids ambiguity with
2118 flag values that contain commas.
2120 <var>flag</var> must start with a lowercase letter
2121 (<tt>a-z</tt>) and consist only of lowercase letters,
2122 numbers (<tt>0-9</tt>), and the characters
2123 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2124 <var>options</var> must not contain whitespace. The same
2125 tag should not be given multiple times with conflicting
2126 values. Package maintainers may assume that
2127 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2131 The meaning of the following tags has been standardized:
2135 This tag says to not run any build-time test suite
2136 provided by the package.
2140 The presence of this tag means that the package should
2141 be compiled with a minimum of optimization. For C
2142 programs, it is best to add <tt>-O0</tt> to
2143 <tt>CFLAGS</tt> (although this is usually the default).
2144 Some programs might fail to build or run at this level
2145 of optimization; it may be necessary to use
2146 <tt>-O1</tt>, for example.
2150 This tag means that the debugging symbols should not be
2151 stripped from the binary during installation, so that
2152 debugging information may be included in the package.
2154 <tag>parallel=n</tag>
2156 This tag means that the package should be built using up
2157 to <tt>n</tt> parallel processes if the package build
2158 system supports this.<footnote>
2159 Packages built with <tt>make</tt> can often implement
2160 this by passing the <tt>-j</tt><var>n</var> option to
2163 If the package build system does not support parallel
2164 builds, this string must be ignored. If the package
2165 build system only supports a lower level of concurrency
2166 than <var>n</var>, the package should be built using as
2167 many parallel processes as the package build system
2168 supports. It is up to the package maintainer to decide
2169 whether the package build times are long enough and the
2170 package build system is robust enough to make supporting
2171 parallel builds worthwhile.
2177 Unknown flags must be ignored by <file>debian/rules</file>.
2181 The following makefile snippet is an example of how one may
2182 implement the build options; you will probably have to
2183 massage this example in order to make it work for your
2185 <example compact="compact">
2188 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2189 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2190 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2191 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2193 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2198 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2199 INSTALL_PROGRAM += -s
2201 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2202 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2203 MAKEFLAGS += -j$(NUMJOBS)
2208 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2209 # Code to run the package test suite.
2216 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2217 <sect id="substvars">
2218 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2221 When <prgn>dpkg-gencontrol</prgn>,
2222 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
2223 generate control files, they perform variable substitutions
2224 on their output just before writing it. Variable
2225 substitutions have the form <tt>${<var>variable</var>}</tt>.
2226 The optional file <file>debian/substvars</file> contains
2227 variable substitutions to be used; variables can also be set
2228 directly from <file>debian/rules</file> using the <tt>-V</tt>
2229 option to the source packaging commands, and certain
2230 predefined variables are also available.
2234 The <file>debian/substvars</file> file is usually generated and
2235 modified dynamically by <file>debian/rules</file> targets, in
2236 which case it must be removed by the <tt>clean</tt> target.
2240 See <manref name="deb-substvars" section="5"> for full
2241 details about source variable substitutions, including the
2242 format of <file>debian/substvars</file>.</p>
2245 <sect id="debianwatch">
2246 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2249 This is an optional, recommended configuration file for the
2250 <tt>uscan</tt> utility which defines how to automatically scan
2251 ftp or http sites for newly available updates of the
2252 package. This is used
2253 by <url id="http://dehs.alioth.debian.org/"> and other Debian QA
2254 tools to help with quality control and maintenance of the
2255 distribution as a whole.
2260 <sect id="debianfiles">
2261 <heading>Generated files list: <file>debian/files</file></heading>
2264 This file is not a permanent part of the source tree; it
2265 is used while building packages to record which files are
2266 being generated. <prgn>dpkg-genchanges</prgn> uses it
2267 when it generates a <file>.changes</file> file.
2271 It should not exist in a shipped source package, and so it
2272 (and any backup files or temporary files such as
2273 <file>files.new</file><footnote>
2274 <file>files.new</file> is used as a temporary file by
2275 <prgn>dpkg-gencontrol</prgn> and
2276 <prgn>dpkg-distaddfile</prgn> - they write a new
2277 version of <tt>files</tt> here before renaming it,
2278 to avoid leaving a corrupted copy if an error
2280 </footnote>) should be removed by the
2281 <tt>clean</tt> target. It may also be wise to
2282 ensure a fresh start by emptying or removing it at the
2283 start of the <tt>binary</tt> target.
2287 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2288 package, it adds an entry to <file>debian/files</file> for the
2289 <file>.deb</file> file that will be created when <tt>dpkg-deb
2290 --build</tt> is run for that binary package. So for most
2291 packages all that needs to be done with this file is to
2292 delete it in the <tt>clean</tt> target.
2296 If a package upload includes files besides the source
2297 package and any binary packages whose control files were
2298 made with <prgn>dpkg-gencontrol</prgn> then they should be
2299 placed in the parent of the package's top-level directory
2300 and <prgn>dpkg-distaddfile</prgn> should be called to add
2301 the file to the list in <file>debian/files</file>.</p>
2304 <sect id="embeddedfiles">
2305 <heading>Convenience copies of code</heading>
2308 Some software packages include in their distribution convenience
2309 copies of code from other software packages, generally so that
2310 users compiling from source don't have to download multiple
2311 packages. Debian packages should not make use of these
2312 convenience copies unless the included package is explicitly
2313 intended to be used in this way.<footnote>
2314 For example, parts of the GNU build system work like this.
2316 If the included code is already in the Debian archive in the
2317 form of a library, the Debian packaging should ensure that
2318 binary packages reference the libraries already in Debian and
2319 the convenience copy is not used. If the included code is not
2320 already in Debian, it should be packaged separately as a
2321 prerequisite if possible.
2323 Having multiple copies of the same code in Debian is
2324 inefficient, often creates either static linking or shared
2325 library conflicts, and, most importantly, increases the
2326 difficulty of handling security vulnerabilities in the
2332 <sect id="readmesource">
2333 <heading>Source package handling:
2334 <file>debian/README.source</file></heading>
2337 If running <prgn>dpkg-source -x</prgn> on a source package
2338 doesn't produce the source of the package, ready for editing,
2339 and allow one to make changes and run
2340 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2341 without taking any additional steps, creating a
2342 <file>debian/README.source</file> documentation file is
2343 recommended. This file should explain how to do all of the
2346 <item>Generate the fully patched source, in a form ready for
2347 editing, that would be built to create Debian
2348 packages. Doing this with a <tt>patch</tt> target in
2349 <file>debian/rules</file> is recommended; see
2350 <ref id="debianrules">.</item>
2351 <item>Modify the source and save those modifications so that
2352 they will be applied when building the package.</item>
2353 <item>Remove source modifications that are currently being
2354 applied when building the package.</item>
2355 <item>Optionally, document what steps are necessary to
2356 upgrade the Debian source package to a new upstream version,
2357 if applicable.</item>
2359 This explanation should include specific commands and mention
2360 any additional required Debian packages. It should not assume
2361 familiarity with any specific Debian packaging system or patch
2366 This explanation may refer to a documentation file installed by
2367 one of the package's build dependencies provided that the
2368 referenced documentation clearly explains these tasks and is not
2369 a general reference manual.
2373 <file>debian/README.source</file> may also include any other
2374 information that would be helpful to someone modifying the
2375 source package. Even if the package doesn't fit the above
2376 description, maintainers are encouraged to document in a
2377 <file>debian/README.source</file> file any source package with a
2378 particularly complex or unintuitive source layout or build
2379 system (for example, a package that builds the same source
2380 multiple times to generate different binary packages).
2386 <chapt id="controlfields">
2387 <heading>Control files and their fields</heading>
2390 The package management system manipulates data represented in
2391 a common format, known as <em>control data</em>, stored in
2392 <em>control files</em>.
2393 Control files are used for source packages, binary packages and
2394 the <file>.changes</file> files which control the installation
2395 of uploaded files<footnote>
2396 <prgn>dpkg</prgn>'s internal databases are in a similar
2401 <sect id="controlsyntax">
2402 <heading>Syntax of control files</heading>
2405 A control file consists of one or more paragraphs of
2407 The paragraphs are also sometimes referred to as stanzas.
2409 The paragraphs are separated by blank lines. Some control
2410 files allow only one paragraph; others allow several, in
2411 which case each paragraph usually refers to a different
2412 package. (For example, in source packages, the first
2413 paragraph refers to the source package, and later paragraphs
2414 refer to binary packages generated from the source.)
2418 Each paragraph consists of a series of data fields; each
2419 field consists of the field name, followed by a colon and
2420 then the data/value associated with that field. It ends at
2421 the end of the (logical) line. Horizontal whitespace
2422 (spaces and tabs) may occur immediately before or after the
2423 value and is ignored there; it is conventional to put a
2424 single space after the colon. For example, a field might
2426 <example compact="compact">
2429 the field name is <tt>Package</tt> and the field value
2434 A paragraph must not contain more than one instance of a
2435 particular field name.
2439 Many fields' values may span several lines; in this case
2440 each continuation line must start with a space or a tab.
2441 Any trailing spaces or tabs at the end of individual
2442 lines of a field value are ignored.
2446 In fields where it is specified that lines may not wrap,
2447 only a single line of data is allowed and whitespace is not
2448 significant in a field body. Whitespace must not appear
2449 inside names (of packages, architectures, files or anything
2450 else) or version numbers, or between the characters of
2451 multi-character version relationships.
2455 Field names are not case-sensitive, but it is usual to
2456 capitalize the field names using mixed case as shown below.
2457 Field values are case-sensitive unless the description of the
2458 field says otherwise.
2462 Blank lines, or lines consisting only of spaces and tabs,
2463 are not allowed within field values or between fields - that
2464 would mean a new paragraph.
2468 All control files must be encoded in UTF-8.
2472 <sect id="sourcecontrolfiles">
2473 <heading>Source package control files -- <file>debian/control</file></heading>
2476 The <file>debian/control</file> file contains the most vital
2477 (and version-independent) information about the source package
2478 and about the binary packages it creates.
2482 The first paragraph of the control file contains information about
2483 the source package in general. The subsequent sets each describe a
2484 binary package that the source tree builds.
2488 The fields in the general paragraph (the first one, for the source
2491 <list compact="compact">
2492 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2493 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2494 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2495 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2496 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2497 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2498 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2499 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2504 The fields in the binary package paragraphs are:
2506 <list compact="compact">
2507 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2508 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2509 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2510 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2511 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2512 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2513 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2514 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2519 The syntax and semantics of the fields are described below.
2523 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2524 generate control files for binary packages (see below), by
2525 <prgn>dpkg-genchanges</prgn> to generate the
2526 <file>.changes</file> file to accompany the upload, and by
2527 <prgn>dpkg-source</prgn> when it creates the
2528 <file>.dsc</file> source control file as part of a source
2529 archive. Many fields are permitted to span multiple lines in
2530 <file>debian/control</file> but not in any other control
2531 file. These tools are responsible for removing the line
2532 breaks from such fields when using fields from
2533 <file>debian/control</file> to generate other control files.
2537 The fields here may contain variable references - their
2538 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2539 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2540 when they generate output control files.
2541 See <ref id="substvars"> for details.
2545 In addition to the control file syntax described <qref
2546 id="controlsyntax">above</qref>, this file may also contain
2547 comment lines starting with <tt>#</tt> without any preceding
2548 whitespace. All such lines are ignored, even in the middle of
2549 continuation lines for a multiline field, and do not end a
2555 <sect id="binarycontrolfiles">
2556 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2559 The <file>DEBIAN/control</file> file contains the most vital
2560 (and version-dependent) information about a binary package. It
2561 consists of a single paragraph.
2565 The fields in this file are:
2567 <list compact="compact">
2568 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2569 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2570 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2571 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2572 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2573 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2574 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2575 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2576 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2577 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2578 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2579 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2584 <sect id="debiansourcecontrolfiles">
2585 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2588 This file consists of a single paragraph, possibly surrounded by
2589 a PGP signature. The fields of that paragraph are listed below.
2590 Their syntax is described above, in <ref id="pkg-controlfields">.
2592 <list compact="compact">
2593 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2594 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2595 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2596 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2597 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2598 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2599 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2600 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2601 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2602 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2603 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2604 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2605 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2610 The source package control file is generated by
2611 <prgn>dpkg-source</prgn> when it builds the source
2612 archive, from other files in the source package,
2613 described above. When unpacking, it is checked against
2614 the files and directories in the other parts of the
2620 <sect id="debianchangesfiles">
2621 <heading>Debian changes files -- <file>.changes</file></heading>
2624 The <file>.changes</file> files are used by the Debian archive
2625 maintenance software to process updates to packages. They
2626 consist of a single paragraph, possibly surrounded by a PGP
2627 signature. That paragraph contains information from the
2628 <file>debian/control</file> file and other data about the
2629 source package gathered via <file>debian/changelog</file>
2630 and <file>debian/rules</file>.
2634 <file>.changes</file> files have a format version that is
2635 incremented whenever the documented fields or their meaning
2636 change. This document describes format &changesversion;.
2640 The fields in this file are:
2642 <list compact="compact">
2643 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2644 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2645 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2646 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2647 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2648 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2649 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2650 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2651 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2652 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2653 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2654 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2655 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2656 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2657 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2658 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2663 <sect id="controlfieldslist">
2664 <heading>List of fields</heading>
2666 <sect1 id="f-Source">
2667 <heading><tt>Source</tt></heading>
2670 This field identifies the source package name.
2674 In <file>debian/control</file> or a <file>.dsc</file> file,
2675 this field must contain only the name of the source package.
2679 In a binary package control file or a <file>.changes</file>
2680 file, the source package name may be followed by a version
2681 number in parentheses<footnote>
2682 It is customary to leave a space after the package name
2683 if a version number is specified.
2685 This version number may be omitted (and is, by
2686 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2687 the <tt>Version</tt> field of the binary package in
2688 question. The field itself may be omitted from a binary
2689 package control file when the source package has the same
2690 name and version as the binary package.
2694 Package names (both source and binary,
2695 see <ref id="f-Package">) must consist only of lower case
2696 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2697 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2698 (<tt>.</tt>). They must be at least two characters long and
2699 must start with an alphanumeric character.
2703 <sect1 id="f-Maintainer">
2704 <heading><tt>Maintainer</tt></heading>
2707 The package maintainer's name and email address. The name
2708 must come first, then the email address inside angle
2709 brackets <tt><></tt> (in RFC822 format).
2713 If the maintainer's name contains a full stop then the
2714 whole field will not work directly as an email address due
2715 to a misfeature in the syntax specified in RFC822; a
2716 program using this field as an address must check for this
2717 and correct the problem if necessary (for example by
2718 putting the name in round brackets and moving it to the
2719 end, and bringing the email address forward).
2723 <sect1 id="f-Uploaders">
2724 <heading><tt>Uploaders</tt></heading>
2727 List of the names and email addresses of co-maintainers of
2728 the package, if any. If the package has other maintainers
2729 beside the one named in the
2730 <qref id="f-Maintainer">Maintainer field</qref>, their names
2731 and email addresses should be listed here. The format of each
2732 entry is the same as that of the Maintainer field, and
2733 multiple entries must be comma separated. This is an optional
2738 Any parser that interprets the Uploaders field in
2739 <file>debian/control</file> must permit it to span multiple
2740 lines. Line breaks in an Uploaders field that spans multiple
2741 lines are not significant and the semantics of the field are
2742 the same as if the line breaks had not been present.
2746 <sect1 id="f-Changed-By">
2747 <heading><tt>Changed-By</tt></heading>
2750 The name and email address of the person who prepared this
2751 version of the package, usually a maintainer. The syntax is
2752 the same as for the <qref id="f-Maintainer">Maintainer
2757 <sect1 id="f-Section">
2758 <heading><tt>Section</tt></heading>
2761 This field specifies an application area into which the package
2762 has been classified. See <ref id="subsections">.
2766 When it appears in the <file>debian/control</file> file,
2767 it gives the value for the subfield of the same name in
2768 the <tt>Files</tt> field of the <file>.changes</file> file.
2769 It also gives the default for the same field in the binary
2774 <sect1 id="f-Priority">
2775 <heading><tt>Priority</tt></heading>
2778 This field represents how important it is that the user
2779 have the package installed. See <ref id="priorities">.
2783 When it appears in the <file>debian/control</file> file,
2784 it gives the value for the subfield of the same name in
2785 the <tt>Files</tt> field of the <file>.changes</file> file.
2786 It also gives the default for the same field in the binary
2791 <sect1 id="f-Package">
2792 <heading><tt>Package</tt></heading>
2795 The name of the binary package.
2799 Binary package names must follow the same syntax and
2800 restrictions as source package names. See <ref id="f-Source">
2805 <sect1 id="f-Architecture">
2806 <heading><tt>Architecture</tt></heading>
2809 Depending on context and the control file used, the
2810 <tt>Architecture</tt> field can include the following sets of
2814 A unique single word identifying a Debian machine
2815 architecture as described in <ref id="arch-spec">.
2818 An architecture wildcard identifying a set of Debian
2819 machine architectures, see <ref id="arch-wildcard-spec">.
2820 <tt>any</tt> matches all Debian machine architectures
2821 and is the most frequently used.
2824 <tt>all</tt>, which indicates an
2825 architecture-independent package.
2828 <tt>source</tt>, which indicates a source package.
2834 In the main <file>debian/control</file> file in the source
2835 package, this field may contain the special
2836 value <tt>all</tt>, the special architecture
2837 wildcard <tt>any</tt>, or a list of specific and wildcard
2838 architectures separated by spaces. If <tt>all</tt>
2839 or <tt>any</tt> appears, that value must be the entire
2840 contents of the field. Most packages will use
2841 either <tt>all</tt> or <tt>any</tt>.
2845 Specifying a specific list of architectures indicates that the
2846 source will build an architecture-dependent package only on
2847 architectures included in the list. Specifying a list of
2848 architecture wildcards indicates that the source will build an
2849 architecture-dependent package on only those architectures
2850 that match any of the specified architecture wildcards.
2851 Specifying a list of architectures or architecture wildcards
2852 other than <tt>any</tt> is for the minority of cases where a
2853 program is not portable or is not useful on some
2854 architectures. Where possible, the program should be made
2859 In the source package control file <file>.dsc</file>, this
2860 field may contain either the architecture
2861 wildcard <tt>any</tt> or a list of architectures and
2862 architecture wildcards separated by spaces. If a list is
2863 given, it may include (or consist solely of) the special
2864 value <tt>all</tt>. In other words, in <file>.dsc</file>
2865 files unlike the <file>debian/control</file>, <tt>all</tt> may
2866 occur in combination with specific architectures.
2867 The <tt>Architecture</tt> field in the source package control
2868 file <file>.dsc</file> is generally constructed from
2869 the <tt>Architecture</tt> fields in
2870 the <file>debian/control</file> in the source package.
2874 Specifying <tt>any</tt> indicates that the source package
2875 isn't dependent on any particular architecture and should
2876 compile fine on any one. The produced binary package(s)
2877 will either be specific to whatever the current build
2878 architecture is or will be architecture-independent.
2882 Specifying only <tt>all</tt> indicates that the source package
2883 will only build architecture-independent packages. If this is
2884 the case, <tt>all</tt> must be used rather than <tt>any</tt>;
2885 <tt>any</tt> implies that the source package will build at
2886 least one architecture-dependent package.
2890 Specifying a list of architectures or architecture wildcards
2891 indicates that the source will build an architecture-dependent
2892 package, and will only work correctly on the listed or
2893 matching architectures. If the source package also builds at
2894 least one architecture-independent package, <tt>all</tt> will
2895 also be included in the list.
2899 In a <file>.changes</file> file, the <tt>Architecture</tt>
2900 field lists the architecture(s) of the package(s) currently
2901 being uploaded. This will be a list; if the source for the
2902 package is also being uploaded, the special
2903 entry <tt>source</tt> is also present. <tt>all</tt> will be
2904 present if any architecture-independent packages are being
2905 uploaded. Architecture wildcards such as <tt>any</tt> must
2906 never occur in the <tt>Architecture</tt> field in
2907 the <file>.changes</file> file.
2911 See <ref id="debianrules"> for information on how to get
2912 the architecture for the build process.
2916 <sect1 id="f-Essential">
2917 <heading><tt>Essential</tt></heading>
2920 This is a boolean field which may occur only in the
2921 control file of a binary package or in a per-package fields
2922 paragraph of a main source control data file.
2926 If set to <tt>yes</tt> then the package management system
2927 will refuse to remove the package (upgrading and replacing
2928 it is still possible). The other possible value is <tt>no</tt>,
2929 which is the same as not having the field at all.
2934 <heading>Package interrelationship fields:
2935 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2936 <tt>Recommends</tt>, <tt>Suggests</tt>,
2937 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2938 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2942 These fields describe the package's relationships with
2943 other packages. Their syntax and semantics are described
2944 in <ref id="relationships">.</p>
2947 <sect1 id="f-Standards-Version">
2948 <heading><tt>Standards-Version</tt></heading>
2951 The most recent version of the standards (the policy
2952 manual and associated texts) with which the package
2957 The version number has four components: major and minor
2958 version number and major and minor patch level. When the
2959 standards change in a way that requires every package to
2960 change the major number will be changed. Significant
2961 changes that will require work in many packages will be
2962 signaled by a change to the minor number. The major patch
2963 level will be changed for any change to the meaning of the
2964 standards, however small; the minor patch level will be
2965 changed when only cosmetic, typographical or other edits
2966 are made which neither change the meaning of the document
2967 nor affect the contents of packages.
2971 Thus only the first three components of the policy version
2972 are significant in the <em>Standards-Version</em> control
2973 field, and so either these three components or all four
2974 components may be specified.<footnote>
2975 In the past, people specified the full version number
2976 in the Standards-Version field, for example "2.3.0.0".
2977 Since minor patch-level changes don't introduce new
2978 policy, it was thought it would be better to relax
2979 policy and only require the first 3 components to be
2980 specified, in this example "2.3.0". All four
2981 components may still be used if someone wishes to do so.
2987 <sect1 id="f-Version">
2988 <heading><tt>Version</tt></heading>
2991 The version number of a package. The format is:
2992 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
2996 The three components here are:
2998 <tag><var>epoch</var></tag>
3001 This is a single (generally small) unsigned integer. It
3002 may be omitted, in which case zero is assumed. If it is
3003 omitted then the <var>upstream_version</var> may not
3008 It is provided to allow mistakes in the version numbers
3009 of older versions of a package, and also a package's
3010 previous version numbering schemes, to be left behind.
3014 <tag><var>upstream_version</var></tag>
3017 This is the main part of the version number. It is
3018 usually the version number of the original ("upstream")
3019 package from which the <file>.deb</file> file has been made,
3020 if this is applicable. Usually this will be in the same
3021 format as that specified by the upstream author(s);
3022 however, it may need to be reformatted to fit into the
3023 package management system's format and comparison
3028 The comparison behavior of the package management system
3029 with respect to the <var>upstream_version</var> is
3030 described below. The <var>upstream_version</var>
3031 portion of the version number is mandatory.
3035 The <var>upstream_version</var> may contain only
3036 alphanumerics<footnote>
3037 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3039 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3040 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3041 tilde) and should start with a digit. If there is no
3042 <var>debian_revision</var> then hyphens are not allowed;
3043 if there is no <var>epoch</var> then colons are not
3048 <tag><var>debian_revision</var></tag>
3051 This part of the version number specifies the version of
3052 the Debian package based on the upstream version. It
3053 may contain only alphanumerics and the characters
3054 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3055 tilde) and is compared in the same way as the
3056 <var>upstream_version</var> is.
3060 It is optional; if it isn't present then the
3061 <var>upstream_version</var> may not contain a hyphen.
3062 This format represents the case where a piece of
3063 software was written specifically to be a Debian
3064 package, where the Debian package source must always
3065 be identical to the pristine source and therefore no
3066 revision indication is required.
3070 It is conventional to restart the
3071 <var>debian_revision</var> at <tt>1</tt> each time the
3072 <var>upstream_version</var> is increased.
3076 The package management system will break the version
3077 number apart at the last hyphen in the string (if there
3078 is one) to determine the <var>upstream_version</var> and
3079 <var>debian_revision</var>. The absence of a
3080 <var>debian_revision</var> is equivalent to a
3081 <var>debian_revision</var> of <tt>0</tt>.
3088 When comparing two version numbers, first the <var>epoch</var>
3089 of each are compared, then the <var>upstream_version</var> if
3090 <var>epoch</var> is equal, and then <var>debian_revision</var>
3091 if <var>upstream_version</var> is also equal.
3092 <var>epoch</var> is compared numerically. The
3093 <var>upstream_version</var> and <var>debian_revision</var>
3094 parts are compared by the package management system using the
3095 following algorithm:
3099 The strings are compared from left to right.
3103 First the initial part of each string consisting entirely of
3104 non-digit characters is determined. These two parts (one of
3105 which may be empty) are compared lexically. If a difference
3106 is found it is returned. The lexical comparison is a
3107 comparison of ASCII values modified so that all the letters
3108 sort earlier than all the non-letters and so that a tilde
3109 sorts before anything, even the end of a part. For example,
3110 the following parts are in sorted order from earliest to
3111 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3112 <tt>a</tt>.<footnote>
3113 One common use of <tt>~</tt> is for upstream pre-releases.
3114 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3115 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3120 Then the initial part of the remainder of each string which
3121 consists entirely of digit characters is determined. The
3122 numerical values of these two parts are compared, and any
3123 difference found is returned as the result of the comparison.
3124 For these purposes an empty string (which can only occur at
3125 the end of one or both version strings being compared) counts
3130 These two steps (comparing and removing initial non-digit
3131 strings and initial digit strings) are repeated until a
3132 difference is found or both strings are exhausted.
3136 Note that the purpose of epochs is to allow us to leave behind
3137 mistakes in version numbering, and to cope with situations
3138 where the version numbering scheme changes. It is
3139 <em>not</em> intended to cope with version numbers containing
3140 strings of letters which the package management system cannot
3141 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3142 silly orderings.<footnote>
3143 The author of this manual has heard of a package whose
3144 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3145 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3151 <sect1 id="f-Description">
3152 <heading><tt>Description</tt></heading>
3155 In a source or binary control file, the <tt>Description</tt>
3156 field contains a description of the binary package, consisting
3157 of two parts, the synopsis or the short description, and the
3158 long description. The field's format is as follows:
3163 Description: <single line synopsis>
3164 <extended description over several lines>
3169 The lines in the extended description can have these formats:
3175 Those starting with a single space are part of a paragraph.
3176 Successive lines of this form will be word-wrapped when
3177 displayed. The leading space will usually be stripped off.
3181 Those starting with two or more spaces. These will be
3182 displayed verbatim. If the display cannot be panned
3183 horizontally, the displaying program will line wrap them "hard"
3184 (i.e., without taking account of word breaks). If it can they
3185 will be allowed to trail off to the right. None, one or two
3186 initial spaces may be deleted, but the number of spaces
3187 deleted from each line will be the same (so that you can have
3188 indenting work correctly, for example).
3192 Those containing a single space followed by a single full stop
3193 character. These are rendered as blank lines. This is the
3194 <em>only</em> way to get a blank line<footnote>
3195 Completely empty lines will not be rendered as blank lines.
3196 Instead, they will cause the parser to think you're starting
3197 a whole new record in the control file, and will therefore
3198 likely abort with an error.
3203 Those containing a space, a full stop and some more characters.
3204 These are for future expansion. Do not use them.
3210 Do not use tab characters. Their effect is not predictable.
3214 See <ref id="descriptions"> for further information on this.
3218 In a <file>.changes</file> file, the <tt>Description</tt>
3219 field contains a summary of the descriptions for the packages
3220 being uploaded. For this case, the first line of the field
3221 value (the part on the same line as <tt>Description:</tt>) is
3222 always empty. The content of the field is expressed as
3223 continuation lines, one line per package. Each line is
3224 indented by one space and contains the name of a binary
3225 package, a space, a hyphen (<tt>-</tt>), a space, and the
3226 short description line from that package.
3230 <sect1 id="f-Distribution">
3231 <heading><tt>Distribution</tt></heading>
3234 In a <file>.changes</file> file or parsed changelog output
3235 this contains the (space-separated) name(s) of the
3236 distribution(s) where this version of the package should
3237 be installed. Valid distributions are determined by the
3238 archive maintainers.<footnote>
3239 Example distribution names in the Debian archive used in
3240 <file>.changes</file> files are:
3241 <taglist compact="compact">
3242 <tag><em>unstable</em></tag>
3244 This distribution value refers to the
3245 <em>developmental</em> part of the Debian distribution
3246 tree. Most new packages, new upstream versions of
3247 packages and bug fixes go into the <em>unstable</em>
3251 <tag><em>experimental</em></tag>
3253 The packages with this distribution value are deemed
3254 by their maintainers to be high risk. Oftentimes they
3255 represent early beta or developmental packages from
3256 various sources that the maintainers want people to
3257 try, but are not ready to be a part of the other parts
3258 of the Debian distribution tree.
3263 Others are used for updating stable releases or for
3264 security uploads. More information is available in the
3265 Debian Developer's Reference, section "The Debian
3269 The Debian archive software only supports listing a single
3270 distribution. Migration of packages to other distributions is
3271 handled outside of the upload process.
3276 <heading><tt>Date</tt></heading>
3279 This field includes the date the package was built or last
3280 edited. It must be in the same format as the <var>date</var>
3281 in a <file>debian/changelog</file> entry.
3285 The value of this field is usually extracted from the
3286 <file>debian/changelog</file> file - see
3287 <ref id="dpkgchangelog">).
3291 <sect1 id="f-Format">
3292 <heading><tt>Format</tt></heading>
3295 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3296 files, this field declares the format version of that file.
3297 The syntax of the field value is the same as that of
3298 a <qref id="f-Version">package version number</qref> except
3299 that no epoch or Debian revision is allowed. The format
3300 described in this document is <tt>&changesversion;</tt>.
3304 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3305 Debian source control</qref> files, this field declares the
3306 format of the source package. The field value is used by
3307 programs acting on a source package to interpret the list of
3308 files in the source package and determine how to unpack it.
3309 The syntax of the field value is a numeric major revision, a
3310 period, a numeric minor revision, and then an optional subtype
3311 after whitespace, which if specified is an alphanumeric word
3312 in parentheses. The subtype is optional in the syntax but may
3313 be mandatory for particular source format revisions.
3315 The source formats currently supported by the Debian archive
3316 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3317 and <tt>3.0 (quilt)</tt>.
3322 <sect1 id="f-Urgency">
3323 <heading><tt>Urgency</tt></heading>
3326 This is a description of how important it is to upgrade to
3327 this version from previous ones. It consists of a single
3328 keyword taking one of the values <tt>low</tt>,
3329 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3330 <tt>critical</tt><footnote>
3331 Other urgency values are supported with configuration
3332 changes in the archive software but are not used in Debian.
3333 The urgency affects how quickly a package will be considered
3334 for inclusion into the <tt>testing</tt> distribution and
3335 gives an indication of the importance of any fixes included
3336 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3337 treated as synonymous.
3338 </footnote> (not case-sensitive) followed by an optional
3339 commentary (separated by a space) which is usually in
3340 parentheses. For example:
3343 Urgency: low (HIGH for users of diversions)
3349 The value of this field is usually extracted from the
3350 <file>debian/changelog</file> file - see
3351 <ref id="dpkgchangelog">.
3355 <sect1 id="f-Changes">
3356 <heading><tt>Changes</tt></heading>
3359 This field contains the human-readable changes data, describing
3360 the differences between the last version and the current one.
3364 The first line of the field value (the part on the same line
3365 as <tt>Changes:</tt>) is always empty. The content of the
3366 field is expressed as continuation lines, with each line
3367 indented by at least one space. Blank lines must be
3368 represented by a line consisting only of a space and a full
3373 The value of this field is usually extracted from the
3374 <file>debian/changelog</file> file - see
3375 <ref id="dpkgchangelog">).
3379 Each version's change information should be preceded by a
3380 "title" line giving at least the version, distribution(s)
3381 and urgency, in a human-readable way.
3385 If data from several versions is being returned the entry
3386 for the most recent version should be returned first, and
3387 entries should be separated by the representation of a
3388 blank line (the "title" line may also be followed by the
3389 representation of a blank line).
3393 <sect1 id="f-Binary">
3394 <heading><tt>Binary</tt></heading>
3397 This field is a list of binary packages. Its syntax and
3398 meaning varies depending on the control file in which it
3403 When it appears in the <file>.dsc</file> file, it lists binary
3404 packages which a source package can produce, separated by
3406 A space after each comma is conventional.
3407 </footnote>. It may span multiple lines. The source package
3408 does not necessarily produce all of these binary packages for
3409 every architecture. The source control file doesn't contain
3410 details of which architectures are appropriate for which of
3411 the binary packages.
3415 When it appears in a <file>.changes</file> file, it lists the
3416 names of the binary packages being uploaded, separated by
3417 whitespace (not commas). It may span multiple lines.
3421 <sect1 id="f-Installed-Size">
3422 <heading><tt>Installed-Size</tt></heading>
3425 This field appears in the control files of binary packages,
3426 and in the <file>Packages</file> files. It gives an estimate
3427 of the total amount of disk space required to install the
3428 named package. Actual installed size may vary based on block
3429 size, file system properties, or actions taken by package
3434 The disk space is given as the integer value of the estimated
3435 installed size in bytes, divided by 1024 and rounded up.
3439 <sect1 id="f-Files">
3440 <heading><tt>Files</tt></heading>
3443 This field contains a list of files with information about
3444 each one. The exact information and syntax varies with
3449 In all cases, Files is a multiline field. The first line of
3450 the field value (the part on the same line as <tt>Files:</tt>)
3451 is always empty. The content of the field is expressed as
3452 continuation lines, one line per file. Each line must be
3453 indented by one space and contain a number of sub-fields,
3454 separated by spaces, as described below.
3458 In the <file>.dsc</file> file, each line contains the MD5
3459 checksum, size and filename of the tar file and (if
3460 applicable) diff file which make up the remainder of the
3461 source package<footnote>
3462 That is, the parts which are not the <tt>.dsc</tt>.
3463 </footnote>. For example:
3466 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3467 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3469 The exact forms of the filenames are described
3470 in <ref id="pkg-sourcearchives">.
3474 In the <file>.changes</file> file this contains one line per
3475 file being uploaded. Each line contains the MD5 checksum,
3476 size, section and priority and the filename. For example:
3479 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3480 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3481 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3482 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3484 The <qref id="f-Section">section</qref>
3485 and <qref id="f-Priority">priority</qref> are the values of
3486 the corresponding fields in the main source control file. If
3487 no section or priority is specified then <tt>-</tt> should be
3488 used, though section and priority values must be specified for
3489 new packages to be installed properly.
3493 The special value <tt>byhand</tt> for the section in a
3494 <tt>.changes</tt> file indicates that the file in question
3495 is not an ordinary package file and must by installed by
3496 hand by the distribution maintainers. If the section is
3497 <tt>byhand</tt> the priority should be <tt>-</tt>.
3501 If a new Debian revision of a package is being shipped and
3502 no new original source archive is being distributed the
3503 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3504 entry for the original source archive
3505 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3506 but the <file>.changes</file> file should leave it out. In
3507 this case the original source archive on the distribution
3508 site must match exactly, byte-for-byte, the original
3509 source archive which was used to generate the
3510 <file>.dsc</file> file and diff which are being uploaded.</p>
3513 <sect1 id="f-Closes">
3514 <heading><tt>Closes</tt></heading>
3517 A space-separated list of bug report numbers that the upload
3518 governed by the .changes file closes.
3522 <sect1 id="f-Homepage">
3523 <heading><tt>Homepage</tt></heading>
3526 The URL of the web site for this package, preferably (when
3527 applicable) the site from which the original source can be
3528 obtained and any additional upstream documentation or
3529 information may be found. The content of this field is a
3530 simple URL without any surrounding characters such as
3535 <sect1 id="f-Checksums">
3536 <heading><tt>Checksums-Sha1</tt>
3537 and <tt>Checksums-Sha256</tt></heading>
3540 These fields contain a list of files with a checksum and size
3541 for each one. Both <tt>Checksums-Sha1</tt>
3542 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3543 only in the checksum algorithm used: SHA-1
3544 for <tt>Checksums-Sha1</tt> and SHA-256
3545 for <tt>Checksums-Sha256</tt>.
3549 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3550 multiline fields. The first line of the field value (the part
3551 on the same line as <tt>Checksums-Sha1:</tt>
3552 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3553 of the field is expressed as continuation lines, one line per
3554 file. Each line consists of the checksum, a space, the file
3555 size, a space, and the file name. For example (from
3556 a <file>.changes</file> file):
3559 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3560 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3561 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3562 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3564 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3565 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3566 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3567 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3572 In the <file>.dsc</file> file, these fields should list all
3573 files that make up the source package. In
3574 the <file>.changes</file> file, these fields should list all
3575 files being uploaded. The list of files in these fields
3576 must match the list of files in the <tt>Files</tt> field.
3582 <heading>User-defined fields</heading>
3585 Additional user-defined fields may be added to the
3586 source package control file. Such fields will be
3587 ignored, and not copied to (for example) binary or
3588 source package control files or upload control files.
3592 If you wish to add additional unsupported fields to
3593 these output files you should use the mechanism
3598 Fields in the main source control information file with
3599 names starting <tt>X</tt>, followed by one or more of
3600 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3601 be copied to the output files. Only the part of the
3602 field name after the hyphen will be used in the output
3603 file. Where the letter <tt>B</tt> is used the field
3604 will appear in binary package control files, where the
3605 letter <tt>S</tt> is used in source package control
3606 files and where <tt>C</tt> is used in upload control
3607 (<tt>.changes</tt>) files.
3611 For example, if the main source information control file
3614 XBS-Comment: I stand between the candle and the star.
3616 then the binary and source package control files will contain the
3619 Comment: I stand between the candle and the star.
3628 <chapt id="maintainerscripts">
3629 <heading>Package maintainer scripts and installation procedure</heading>
3632 <heading>Introduction to package maintainer scripts</heading>
3635 It is possible to supply scripts as part of a package which
3636 the package management system will run for you when your
3637 package is installed, upgraded or removed.
3641 These scripts are the control information
3642 files <prgn>preinst</prgn>, <prgn>postinst</prgn>, <prgn>prerm</prgn>
3643 and <prgn>postrm</prgn>. They must be proper executable files;
3644 if they are scripts (which is recommended), they must start with
3645 the usual <tt>#!</tt> convention. They should be readable and
3646 executable by anyone, and must not be world-writable.
3650 The package management system looks at the exit status from
3651 these scripts. It is important that they exit with a
3652 non-zero status if there is an error, so that the package
3653 management system can stop its processing. For shell
3654 scripts this means that you <em>almost always</em> need to
3655 use <tt>set -e</tt> (this is usually true when writing shell
3656 scripts, in fact). It is also important, of course, that
3657 they exit with a zero status if everything went well.
3661 Additionally, packages interacting with users
3662 using <prgn>debconf</prgn> in the <prgn>postinst</prgn> script
3663 should install a <prgn>config</prgn> script as a control
3664 information file. See <ref id="maintscriptprompt"> for details.
3668 When a package is upgraded a combination of the scripts from
3669 the old and new packages is called during the upgrade
3670 procedure. If your scripts are going to be at all
3671 complicated you need to be aware of this, and may need to
3672 check the arguments to your scripts.
3676 Broadly speaking the <prgn>preinst</prgn> is called before
3677 (a particular version of) a package is installed, and the
3678 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3679 before (a version of) a package is removed and the
3680 <prgn>postrm</prgn> afterwards.
3684 Programs called from maintainer scripts should not normally
3685 have a path prepended to them. Before installation is
3686 started, the package management system checks to see if the
3687 programs <prgn>ldconfig</prgn>,
3688 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3689 and <prgn>update-rc.d</prgn> can be found via the
3690 <tt>PATH</tt> environment variable. Those programs, and any
3691 other program that one would expect to be in the
3692 <tt>PATH</tt>, should thus be invoked without an absolute
3693 pathname. Maintainer scripts should also not reset the
3694 <tt>PATH</tt>, though they might choose to modify it by
3695 prepending or appending package-specific directories. These
3696 considerations really apply to all shell scripts.</p>
3699 <sect id="idempotency">
3700 <heading>Maintainer scripts idempotency</heading>
3703 It is necessary for the error recovery procedures that the
3704 scripts be idempotent. This means that if it is run
3705 successfully, and then it is called again, it doesn't bomb
3706 out or cause any harm, but just ensures that everything is
3707 the way it ought to be. If the first call failed, or
3708 aborted half way through for some reason, the second call
3709 should merely do the things that were left undone the first
3710 time, if any, and exit with a success status if everything
3712 This is so that if an error occurs, the user interrupts
3713 <prgn>dpkg</prgn> or some other unforeseen circumstance
3714 happens you don't leave the user with a badly-broken
3715 package when <prgn>dpkg</prgn> attempts to repeat the
3721 <sect id="controllingterminal">
3722 <heading>Controlling terminal for maintainer scripts</heading>
3725 Maintainer scripts are not guaranteed to run with a controlling
3726 terminal and may not be able to interact with the user. They
3727 must be able to fall back to noninteractive behavior if no
3728 controlling terminal is available. Maintainer scripts that
3729 prompt via a program conforming to the Debian Configuration
3730 Management Specification (see <ref id="maintscriptprompt">) may
3731 assume that program will handle falling back to noninteractive
3736 For high-priority prompts without a reasonable default answer,
3737 maintainer scripts may abort if there is no controlling
3738 terminal. However, this situation should be avoided if at all
3739 possible, since it prevents automated or unattended installs.
3740 In most cases, users will consider this to be a bug in the
3745 <sect id="exitstatus">
3746 <heading>Exit status</heading>
3749 Each script must return a zero exit status for
3750 success, or a nonzero one for failure, since the package
3751 management system looks for the exit status of these scripts
3752 and determines what action to take next based on that datum.
3756 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3761 <list compact="compact">
3763 <var>new-preinst</var> <tt>install</tt>
3766 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3769 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3772 <var>old-preinst</var> <tt>abort-upgrade</tt>
3773 <var>new-version</var>
3778 <list compact="compact">
3780 <var>postinst</var> <tt>configure</tt>
3781 <var>most-recently-configured-version</var>
3784 <var>old-postinst</var> <tt>abort-upgrade</tt>
3785 <var>new-version</var>
3788 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3789 <tt>in-favour</tt> <var>package</var>
3790 <var>new-version</var>
3793 <var>postinst</var> <tt>abort-remove</tt>
3796 <var>deconfigured's-postinst</var>
3797 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3798 <var>failed-install-package</var> <var>version</var>
3799 [<tt>removing</tt> <var>conflicting-package</var>
3805 <list compact="compact">
3807 <var>prerm</var> <tt>remove</tt>
3810 <var>old-prerm</var> <tt>upgrade</tt>
3811 <var>new-version</var>
3814 <var>new-prerm</var> <tt>failed-upgrade</tt>
3815 <var>old-version</var>
3818 <var>conflictor's-prerm</var> <tt>remove</tt>
3819 <tt>in-favour</tt> <var>package</var>
3820 <var>new-version</var>
3823 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3824 <tt>in-favour</tt> <var>package-being-installed</var>
3825 <var>version</var> [<tt>removing</tt>
3826 <var>conflicting-package</var>
3832 <list compact="compact">
3834 <var>postrm</var> <tt>remove</tt>
3837 <var>postrm</var> <tt>purge</tt>
3840 <var>old-postrm</var> <tt>upgrade</tt>
3841 <var>new-version</var>
3844 <var>new-postrm</var> <tt>failed-upgrade</tt>
3845 <var>old-version</var>
3848 <var>new-postrm</var> <tt>abort-install</tt>
3851 <var>new-postrm</var> <tt>abort-install</tt>
3852 <var>old-version</var>
3855 <var>new-postrm</var> <tt>abort-upgrade</tt>
3856 <var>old-version</var>
3859 <var>disappearer's-postrm</var> <tt>disappear</tt>
3860 <var>overwriter</var>
3861 <var>overwriter-version</var>
3867 <sect id="unpackphase">
3868 <heading>Details of unpack phase of installation or upgrade</heading>
3871 The procedure on installation/upgrade/overwrite/disappear
3872 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3873 stage of <tt>dpkg --install</tt>) is as follows. In each
3874 case, if a major error occurs (unless listed below) the
3875 actions are, in general, run backwards - this means that the
3876 maintainer scripts are run with different arguments in
3877 reverse order. These are the "error unwind" calls listed
3884 If a version of the package is already installed, call
3885 <example compact="compact">
3886 <var>old-prerm</var> upgrade <var>new-version</var>
3890 If the script runs but exits with a non-zero
3891 exit status, <prgn>dpkg</prgn> will attempt:
3892 <example compact="compact">
3893 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3895 If this works, the upgrade continues. If this
3896 does not work, the error unwind:
3897 <example compact="compact">
3898 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3900 If this works, then the old-version is
3901 "Installed", if not, the old version is in a
3902 "Half-Configured" state.
3908 If a "conflicting" package is being removed at the same time,
3909 or if any package will be broken (due to <tt>Breaks</tt>):
3912 If <tt>--auto-deconfigure</tt> is
3913 specified, call, for each package to be deconfigured
3914 due to <tt>Breaks</tt>:
3915 <example compact="compact">
3916 <var>deconfigured's-prerm</var> deconfigure \
3917 in-favour <var>package-being-installed</var> <var>version</var>
3920 <example compact="compact">
3921 <var>deconfigured's-postinst</var> abort-deconfigure \
3922 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3924 The deconfigured packages are marked as
3925 requiring configuration, so that if
3926 <tt>--install</tt> is used they will be
3927 configured again if possible.
3930 If any packages depended on a conflicting
3931 package being removed and <tt>--auto-deconfigure</tt> is
3932 specified, call, for each such package:
3933 <example compact="compact">
3934 <var>deconfigured's-prerm</var> deconfigure \
3935 in-favour <var>package-being-installed</var> <var>version</var> \
3936 removing <var>conflicting-package</var> <var>version</var>
3939 <example compact="compact">
3940 <var>deconfigured's-postinst</var> abort-deconfigure \
3941 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3942 removing <var>conflicting-package</var> <var>version</var>
3944 The deconfigured packages are marked as
3945 requiring configuration, so that if
3946 <tt>--install</tt> is used they will be
3947 configured again if possible.
3950 To prepare for removal of each conflicting package, call:
3951 <example compact="compact">
3952 <var>conflictor's-prerm</var> remove \
3953 in-favour <var>package</var> <var>new-version</var>
3956 <example compact="compact">
3957 <var>conflictor's-postinst</var> abort-remove \
3958 in-favour <var>package</var> <var>new-version</var>
3967 If the package is being upgraded, call:
3968 <example compact="compact">
3969 <var>new-preinst</var> upgrade <var>old-version</var>
3971 If this fails, we call:
3973 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3980 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3982 is called. If this works, then the old version
3983 is in an "Installed" state, or else it is left
3984 in an "Unpacked" state.
3989 If it fails, then the old version is left
3990 in an "Half-Installed" state.
3997 Otherwise, if the package had some configuration
3998 files from a previous version installed (i.e., it
3999 is in the "configuration files only" state):
4000 <example compact="compact">
4001 <var>new-preinst</var> install <var>old-version</var>
4005 <var>new-postrm</var> abort-install <var>old-version</var>
4007 If this fails, the package is left in a
4008 "Half-Installed" state, which requires a
4009 reinstall. If it works, the packages is left in
4010 a "Config-Files" state.
4013 Otherwise (i.e., the package was completely purged):
4014 <example compact="compact">
4015 <var>new-preinst</var> install
4018 <example compact="compact">
4019 <var>new-postrm</var> abort-install
4021 If the error-unwind fails, the package is in a
4022 "Half-Installed" phase, and requires a
4023 reinstall. If the error unwind works, the
4024 package is in a not installed state.
4031 The new package's files are unpacked, overwriting any
4032 that may be on the system already, for example any
4033 from the old version of the same package or from
4034 another package. Backups of the old files are kept
4035 temporarily, and if anything goes wrong the package
4036 management system will attempt to put them back as
4037 part of the error unwind.
4041 It is an error for a package to contain files which
4042 are on the system in another package, unless
4043 <tt>Replaces</tt> is used (see <ref id="replaces">).
4045 The following paragraph is not currently the case:
4046 Currently the <tt>- - force-overwrite</tt> flag is
4047 enabled, downgrading it to a warning, but this may not
4053 It is a more serious error for a package to contain a
4054 plain file or other kind of non-directory where another
4055 package has a directory (again, unless
4056 <tt>Replaces</tt> is used). This error can be
4057 overridden if desired using
4058 <tt>--force-overwrite-dir</tt>, but this is not
4063 Packages which overwrite each other's files produce
4064 behavior which, though deterministic, is hard for the
4065 system administrator to understand. It can easily
4066 lead to "missing" programs if, for example, a package
4067 is installed which overwrites a file from another
4068 package, and is then removed again.<footnote>
4069 Part of the problem is due to what is arguably a
4070 bug in <prgn>dpkg</prgn>.
4075 A directory will never be replaced by a symbolic link
4076 to a directory or vice versa; instead, the existing
4077 state (symlink or not) will be left alone and
4078 <prgn>dpkg</prgn> will follow the symlink if there is
4087 If the package is being upgraded, call
4088 <example compact="compact">
4089 <var>old-postrm</var> upgrade <var>new-version</var>
4093 If this fails, <prgn>dpkg</prgn> will attempt:
4094 <example compact="compact">
4095 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4097 If this works, installation continues. If not,
4099 <example compact="compact">
4100 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4102 If this fails, the old version is left in a
4103 "Half-Installed" state. If it works, dpkg now
4105 <example compact="compact">
4106 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4108 If this fails, the old version is left in a
4109 "Half-Installed" state. If it works, dpkg now
4111 <example compact="compact">
4112 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4114 If this fails, the old version is in an
4121 This is the point of no return - if
4122 <prgn>dpkg</prgn> gets this far, it won't back off
4123 past this point if an error occurs. This will
4124 leave the package in a fairly bad state, which
4125 will require a successful re-installation to clear
4126 up, but it's when <prgn>dpkg</prgn> starts doing
4127 things that are irreversible.
4132 Any files which were in the old version of the package
4133 but not in the new are removed.
4137 The new file list replaces the old.
4141 The new maintainer scripts replace the old.
4145 Any packages all of whose files have been overwritten
4146 during the installation, and which aren't required for
4147 dependencies, are considered to have been removed.
4148 For each such package
4151 <prgn>dpkg</prgn> calls:
4152 <example compact="compact">
4153 <var>disappearer's-postrm</var> disappear \
4154 <var>overwriter</var> <var>overwriter-version</var>
4158 The package's maintainer scripts are removed.
4161 It is noted in the status database as being in a
4162 sane state, namely not installed (any conffiles
4163 it may have are ignored, rather than being
4164 removed by <prgn>dpkg</prgn>). Note that
4165 disappearing packages do not have their prerm
4166 called, because <prgn>dpkg</prgn> doesn't know
4167 in advance that the package is going to
4174 Any files in the package we're unpacking that are also
4175 listed in the file lists of other packages are removed
4176 from those lists. (This will lobotomize the file list
4177 of the "conflicting" package if there is one.)
4181 The backup files made during installation, above, are
4187 The new package's status is now sane, and recorded as
4192 Here is another point of no return - if the
4193 conflicting package's removal fails we do not unwind
4194 the rest of the installation; the conflicting package
4195 is left in a half-removed limbo.
4200 If there was a conflicting package we go and do the
4201 removal actions (described below), starting with the
4202 removal of the conflicting package's files (any that
4203 are also in the package being installed have already
4204 been removed from the conflicting package's file list,
4205 and so do not get removed now).
4211 <sect id="configdetails"><heading>Details of configuration</heading>
4214 When we configure a package (this happens with <tt>dpkg
4215 --install</tt> and <tt>dpkg --configure</tt>), we first
4216 update any <tt>conffile</tt>s and then call:
4217 <example compact="compact">
4218 <var>postinst</var> configure <var>most-recently-configured-version</var>
4223 No attempt is made to unwind after errors during
4224 configuration. If the configuration fails, the package is in
4225 a "Failed Config" state, and an error message is generated.
4229 If there is no most recently configured version
4230 <prgn>dpkg</prgn> will pass a null argument.
4233 Historical note: Truly ancient (pre-1997) versions of
4234 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4235 (including the angle brackets) in this case. Even older
4236 ones did not pass a second argument at all, under any
4237 circumstance. Note that upgrades using such an old dpkg
4238 version are unlikely to work for other reasons, even if
4239 this old argument behavior is handled by your postinst script.
4245 <sect id="removedetails"><heading>Details of removal and/or
4246 configuration purging</heading>
4252 <example compact="compact">
4253 <var>prerm</var> remove
4257 If prerm fails during replacement due to conflict
4259 <var>conflictor's-postinst</var> abort-remove \
4260 in-favour <var>package</var> <var>new-version</var>
4264 <var>postinst</var> abort-remove
4268 If this fails, the package is in a "Half-Configured"
4269 state, or else it remains "Installed".
4273 The package's files are removed (except <tt>conffile</tt>s).
4276 <example compact="compact">
4277 <var>postrm</var> remove
4281 If it fails, there's no error unwind, and the package is in
4282 an "Half-Installed" state.
4287 All the maintainer scripts except the <prgn>postrm</prgn>
4292 If we aren't purging the package we stop here. Note
4293 that packages which have no <prgn>postrm</prgn> and no
4294 <tt>conffile</tt>s are automatically purged when
4295 removed, as there is no difference except for the
4296 <prgn>dpkg</prgn> status.
4300 The <tt>conffile</tt>s and any backup files
4301 (<tt>~</tt>-files, <tt>#*#</tt> files,
4302 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4307 <example compact="compact">
4308 <var>postrm</var> purge
4312 If this fails, the package remains in a "Config-Files"
4317 The package's file list is removed.
4326 <chapt id="relationships">
4327 <heading>Declaring relationships between packages</heading>
4329 <sect id="depsyntax">
4330 <heading>Syntax of relationship fields</heading>
4333 These fields all have a uniform syntax. They are a list of
4334 package names separated by commas.
4338 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4339 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4340 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4341 control fields of the package, which declare
4342 dependencies on other packages, the package names listed may
4343 also include lists of alternative package names, separated
4344 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4345 if any one of the alternative packages is installed, that
4346 part of the dependency is considered to be satisfied.
4350 All of the fields except for <tt>Provides</tt> may restrict
4351 their applicability to particular versions of each named
4352 package. This is done in parentheses after each individual
4353 package name; the parentheses should contain a relation from
4354 the list below followed by a version number, in the format
4355 described in <ref id="f-Version">.
4359 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4360 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4361 strictly earlier, earlier or equal, exactly equal, later or
4362 equal and strictly later, respectively. The deprecated
4363 forms <tt><</tt> and <tt>></tt> were used to mean
4364 earlier/later or equal, rather than strictly earlier/later,
4365 so they should not appear in new packages (though
4366 <prgn>dpkg</prgn> still supports them).
4370 Whitespace may appear at any point in the version
4371 specification subject to the rules in <ref
4372 id="controlsyntax">, and must appear where it's necessary to
4373 disambiguate; it is not otherwise significant. All of the
4374 relationship fields may span multiple lines. For
4375 consistency and in case of future changes to
4376 <prgn>dpkg</prgn> it is recommended that a single space be
4377 used after a version relationship and before a version
4378 number; it is also conventional to put a single space after
4379 each comma, on either side of each vertical bar, and before
4380 each open parenthesis. When wrapping a relationship field, it
4381 is conventional to do so after a comma and before the space
4382 following that comma.
4386 For example, a list of dependencies might appear as:
4387 <example compact="compact">
4390 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4395 Relationships may be restricted to a certain set of
4396 architectures. This is indicated in brackets after each
4397 individual package name and the optional version specification.
4398 The brackets enclose a list of Debian architecture names
4399 separated by whitespace. Exclamation marks may be prepended to
4400 each of the names. (It is not permitted for some names to be
4401 prepended with exclamation marks while others aren't.)
4405 For build relationship fields
4406 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4407 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>), if
4408 the current Debian host architecture is not in this list and
4409 there are no exclamation marks in the list, or it is in the list
4410 with a prepended exclamation mark, the package name and the
4411 associated version specification are ignored completely for the
4412 purposes of defining the relationships.
4417 <example compact="compact">
4419 Build-Depends-Indep: texinfo
4420 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4421 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4423 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4424 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4425 <tt>gnumach-dev</tt> only on hurd-i386.
4429 For binary relationship fields, the architecture restriction
4430 syntax is only supported in the source package control
4431 file <file>debian/control</file>. When the corresponding binary
4432 package control file is generated, the relationship will either
4433 be omitted or included without the architecture restriction
4434 based on the architecture of the binary package. This means
4435 that architecture restrictions must not be used in binary
4436 relationship fields for architecture-independent packages
4437 (<tt>Architecture: all</tt>).
4442 <example compact="compact">
4443 Depends: foo [i386], bar [amd64]
4445 becomes <tt>Depends: foo</tt> when the package is built on
4446 the <tt>i386</tt> architecture, <tt>Depends: bar</tt> when the
4447 package is built on the <tt>amd64</tt> architecture, and omitted
4448 entirely in binary packages built on all other architectures.
4452 If the architecture-restricted dependency is part of a set of
4453 alternatives using <tt>|</tt>, that alternative is ignored
4454 completely on architectures that do not match the restriction.
4456 <example compact="compact">
4457 Build-Depends: foo [!i386] | bar [!amd64]
4459 is equivalent to <tt>bar</tt> on the i386 architecture, to
4460 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4461 bar</tt> on all other architectures.
4465 Relationships may also be restricted to a certain set of
4466 architectures using architecture wildcards. The syntax for
4467 declaring such restrictions is the same as declaring
4468 restrictions using a certain set of architectures without
4469 architecture wildcards. For example:
4470 <example compact="compact">
4471 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4473 is equivalent to <tt>foo</tt> on architectures using the Linux
4474 kernel and any cpu, <tt>bar</tt> on architectures using any
4475 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4476 using a kernel other than Linux.
4480 Note that the binary package relationship fields such as
4481 <tt>Depends</tt> appear in one of the binary package
4482 sections of the control file, whereas the build-time
4483 relationships such as <tt>Build-Depends</tt> appear in the
4484 source package section of the control file (which is the
4489 <sect id="binarydeps">
4490 <heading>Binary Dependencies - <tt>Depends</tt>,
4491 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4492 <tt>Pre-Depends</tt>
4496 Packages can declare in their control file that they have
4497 certain relationships to other packages - for example, that
4498 they may not be installed at the same time as certain other
4499 packages, and/or that they depend on the presence of others.
4503 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4504 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4505 <tt>Breaks</tt> and <tt>Conflicts</tt> control fields.
4506 <tt>Breaks</tt> is described in <ref id="breaks">, and
4507 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4508 rest are described below.
4512 These seven fields are used to declare a dependency
4513 relationship by one package on another. Except for
4514 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4515 depending (binary) package's control file.
4516 (<tt>Enhances</tt> appears in the recommending package's
4517 control file, and <tt>Breaks</tt> appears in the version of
4518 depended-on package which causes the named package to
4523 A <tt>Depends</tt> field takes effect <em>only</em> when a
4524 package is to be configured. It does not prevent a package
4525 being on the system in an unconfigured state while its
4526 dependencies are unsatisfied, and it is possible to replace
4527 a package whose dependencies are satisfied and which is
4528 properly installed with a different version whose
4529 dependencies are not and cannot be satisfied; when this is
4530 done the depending package will be left unconfigured (since
4531 attempts to configure it will give errors) and will not
4532 function properly. If it is necessary, a
4533 <tt>Pre-Depends</tt> field can be used, which has a partial
4534 effect even when a package is being unpacked, as explained
4535 in detail below. (The other three dependency fields,
4536 <tt>Recommends</tt>, <tt>Suggests</tt> and
4537 <tt>Enhances</tt>, are only used by the various front-ends
4538 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4539 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4543 For this reason packages in an installation run are usually
4544 all unpacked first and all configured later; this gives
4545 later versions of packages with dependencies on later
4546 versions of other packages the opportunity to have their
4547 dependencies satisfied.
4551 In case of circular dependencies, since installation or
4552 removal order honoring the dependency order can't be
4553 established, dependency loops are broken at some point
4554 (based on rules below), and some packages may not be able to
4555 rely on their dependencies being present when being
4556 installed or removed, depending on which side of the break
4557 of the circular dependency loop they happen to be on. If one
4558 of the packages in the loop has no postinst script, then the
4559 cycle will be broken at that package, so as to ensure that
4560 all postinst scripts run with the dependencies properly
4561 configured if this is possible. Otherwise the breaking point
4566 The <tt>Depends</tt> field thus allows package maintainers
4567 to impose an order in which packages should be configured.
4571 The meaning of the five dependency fields is as follows:
4573 <tag><tt>Depends</tt></tag>
4576 This declares an absolute dependency. A package will
4577 not be configured unless all of the packages listed in
4578 its <tt>Depends</tt> field have been correctly
4583 The <tt>Depends</tt> field should be used if the
4584 depended-on package is required for the depending
4585 package to provide a significant amount of
4590 The <tt>Depends</tt> field should also be used if the
4591 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4592 <prgn>postrm</prgn> scripts require the package to be
4593 present in order to run. Note, however, that the
4594 <prgn>postrm</prgn> cannot rely on any non-essential
4595 packages to be present during the <tt>purge</tt>
4599 <tag><tt>Recommends</tt></tag>
4602 This declares a strong, but not absolute, dependency.
4606 The <tt>Recommends</tt> field should list packages
4607 that would be found together with this one in all but
4608 unusual installations.
4612 <tag><tt>Suggests</tt></tag>
4614 This is used to declare that one package may be more
4615 useful with one or more others. Using this field
4616 tells the packaging system and the user that the
4617 listed packages are related to this one and can
4618 perhaps enhance its usefulness, but that installing
4619 this one without them is perfectly reasonable.
4622 <tag><tt>Enhances</tt></tag>
4624 This field is similar to Suggests but works in the
4625 opposite direction. It is used to declare that a
4626 package can enhance the functionality of another
4630 <tag><tt>Pre-Depends</tt></tag>
4633 This field is like <tt>Depends</tt>, except that it
4634 also forces <prgn>dpkg</prgn> to complete installation
4635 of the packages named before even starting the
4636 installation of the package which declares the
4637 pre-dependency, as follows:
4641 When a package declaring a pre-dependency is about to
4642 be <em>unpacked</em> the pre-dependency can be
4643 satisfied if the depended-on package is either fully
4644 configured, <em>or even if</em> the depended-on
4645 package(s) are only unpacked or in the "Half-Configured"
4646 state, provided that they have been configured
4647 correctly at some point in the past (and not removed
4648 or partially removed since). In this case, both the
4649 previously-configured and currently unpacked or
4650 "Half-Configured" versions must satisfy any version
4651 clause in the <tt>Pre-Depends</tt> field.
4655 When the package declaring a pre-dependency is about
4656 to be <em>configured</em>, the pre-dependency will be
4657 treated as a normal <tt>Depends</tt>, that is, it will
4658 be considered satisfied only if the depended-on
4659 package has been correctly configured.
4663 <tt>Pre-Depends</tt> should be used sparingly,
4664 preferably only by packages whose premature upgrade or
4665 installation would hamper the ability of the system to
4666 continue with any upgrade that might be in progress.
4670 <tt>Pre-Depends</tt> are also required if the
4671 <prgn>preinst</prgn> script depends on the named
4672 package. It is best to avoid this situation if
4680 When selecting which level of dependency to use you should
4681 consider how important the depended-on package is to the
4682 functionality of the one declaring the dependency. Some
4683 packages are composed of components of varying degrees of
4684 importance. Such a package should list using
4685 <tt>Depends</tt> the package(s) which are required by the
4686 more important components. The other components'
4687 requirements may be mentioned as Suggestions or
4688 Recommendations, as appropriate to the components' relative
4694 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4697 When one binary package declares that it breaks another,
4698 <prgn>dpkg</prgn> will refuse to allow the package which
4699 declares <tt>Breaks</tt> be installed unless the broken
4700 package is deconfigured first, and it will refuse to
4701 allow the broken package to be reconfigured.
4705 A package will not be regarded as causing breakage merely
4706 because its configuration files are still installed; it must
4707 be at least "Half-Installed".
4711 A special exception is made for packages which declare that
4712 they break their own package name or a virtual package which
4713 they provide (see below): this does not count as a real
4718 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4719 version clause; such a <tt>Breaks</tt> is introduced in the
4720 version of an (implicit or explicit) dependency which violates
4721 an assumption or reveals a bug in earlier versions of the broken
4722 package, or which takes over a file from earlier versions of the
4723 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
4724 will inform higher-level package management tools that the
4725 broken package must be upgraded before the new one.
4729 If the breaking package also overwrites some files from the
4730 older package, it should use <tt>Replaces</tt> to ensure this
4731 goes smoothly. See <ref id="replaces"> for a full discussion
4732 of taking over files from other packages, including how to
4733 use <tt>Breaks</tt> in those cases.
4737 Many of the cases where <tt>Breaks</tt> should be used were
4738 previously handled with <tt>Conflicts</tt>
4739 because <tt>Breaks</tt> did not yet exist.
4740 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
4741 See <ref id="conflicts"> for more information about the
4746 <sect id="conflicts">
4747 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4750 When one binary package declares a conflict with another
4751 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4752 refuse to allow them to be installed on the system at the
4753 same time. This is a stronger restriction than <tt>Breaks</tt>,
4754 which just prevents both packages from being configured at the
4755 same time. Conflicting packages cannot be unpacked on the
4756 system at the same time.
4760 If one package is to be installed, the other must be removed
4761 first. If the package being installed is marked as replacing
4762 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
4763 normally be used in this case) the one on the system, or the one
4764 on the system is marked as deselected, or both packages are
4765 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
4766 automatically remove the package which is causing the conflict.
4767 Otherwise, it will halt the installation of the new package with
4768 an error. This mechanism is specifically designed to produce an
4769 error when the installed package is <tt>Essential</tt>, but the
4774 A package will not cause a conflict merely because its
4775 configuration files are still installed; it must be at least
4780 A special exception is made for packages which declare a
4781 conflict with their own package name, or with a virtual
4782 package which they provide (see below): this does not
4783 prevent their installation, and allows a package to conflict
4784 with others providing a replacement for it. You use this
4785 feature when you want the package in question to be the only
4786 package providing some feature.
4790 Normally, <tt>Breaks</tt> should be used instead
4791 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
4792 stronger restriction on the ordering of package installation or
4793 upgrade and can make it more difficult for the package manager
4794 to find a correct solution to an upgrade or installation
4795 problem. <tt>Breaks</tt> should be used
4797 <item>when moving a file from one package to another (see
4798 <ref id="replaces">),</item>
4799 <item>when splitting a package (a special case of the previous
4801 <item>when the breaking package exposes a bug in or interacts
4802 badly with particular versions of the broken
4805 <tt>Conflicts</tt> should be used
4807 <item>when two packages provide the same file and will
4808 continue to do so,</item>
4809 <item>in conjunction with <tt>Provides</tt> when only one
4810 package providing a given virtual facility may be installed
4811 at a time (see <ref id="virtual">),</item>
4812 <item>in other cases where one must prevent simultaneous
4813 installation of two packages for reasons that are ongoing
4814 (not fixed in a later version of one of the packages) or
4815 that must prevent both packages from being unpacked at the
4816 same time, not just configured.</item>
4818 Be aware that adding <tt>Conflicts</tt> is normally not the best
4819 solution when two packages provide the same files. Depending on
4820 the reason for that conflict, using alternatives or renaming the
4821 files is often a better approach. See, for
4822 example, <ref id="binaries">.
4826 Neither <tt>Breaks</tt> nor <tt>Conflicts</tt> should be used
4827 unless two packages cannot be installed at the same time or
4828 installing them both causes one of them to be broken or
4829 unusable. Having similar functionality or performing the same
4830 tasks as another package is not sufficient reason to
4831 declare <tt>Breaks</tt> or <tt>Conflicts</tt> with that package.
4835 A <tt>Conflicts</tt> entry may have an "earlier than" version
4836 clause if the reason for the conflict is corrected in a later
4837 version of one of the packages. However, normally the presence
4838 of an "earlier than" version clause is a sign
4839 that <tt>Breaks</tt> should have been used instead. An "earlier
4840 than" version clause in <tt>Conflicts</tt>
4841 prevents <prgn>dpkg</prgn> from upgrading or installing the
4842 package which declares such a conflict until the upgrade or
4843 removal of the conflicted-with package has been completed, which
4844 is a strong restriction.
4848 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4852 As well as the names of actual ("concrete") packages, the
4853 package relationship fields <tt>Depends</tt>,
4854 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4855 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4856 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4857 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4858 may mention "virtual packages".
4862 A <em>virtual package</em> is one which appears in the
4863 <tt>Provides</tt> control field of another package. The effect
4864 is as if the package(s) which provide a particular virtual
4865 package name had been listed by name everywhere the virtual
4866 package name appears. (See also <ref id="virtual_pkg">)
4870 If there are both concrete and virtual packages of the same
4871 name, then the dependency may be satisfied (or the conflict
4872 caused) by either the concrete package with the name in
4873 question or any other concrete package which provides the
4874 virtual package with the name in question. This is so that,
4875 for example, supposing we have
4876 <example compact="compact">
4879 </example> and someone else releases an enhanced version of
4880 the <tt>bar</tt> package they can say:
4881 <example compact="compact">
4885 and the <tt>bar-plus</tt> package will now also satisfy the
4886 dependency for the <tt>foo</tt> package.
4890 If a relationship field has a version number attached, only real
4891 packages will be considered to see whether the relationship is
4892 satisfied (or the prohibition violated, for a conflict or
4893 breakage). In other words, if a version number is specified,
4894 this is a request to ignore all <tt>Provides</tt> for that
4895 package name and consider only real packages. The package
4896 manager will assume that a package providing that virtual
4897 package is not of the "right" version. A <tt>Provides</tt>
4898 field may not contain version numbers, and the version number of
4899 the concrete package which provides a particular virtual package
4900 will not be considered when considering a dependency on or
4901 conflict with the virtual package name.<footnote>
4902 It is possible that a future release of <prgn>dpkg</prgn> may
4903 add the ability to specify a version number for each virtual
4904 package it provides. This feature is not yet present,
4905 however, and is expected to be used only infrequently.
4910 To specify which of a set of real packages should be the default
4911 to satisfy a particular dependency on a virtual package, list
4912 the real package as an alternative before the virtual one.
4916 If the virtual package represents a facility that can only be
4917 provided by one real package at a time, such as
4918 the <package>mail-transport-agent</package> virtual package that
4919 requires installation of a binary that would conflict with all
4920 other providers of that virtual package (see
4921 <ref id="mail-transport-agents">), all packages providing that
4922 virtual package should also declare a conflict with it
4923 using <tt>Conflicts</tt>. This will ensure that at most one
4924 provider of that virtual package is unpacked or installed at a
4929 <sect id="replaces"><heading>Overwriting files and replacing
4930 packages - <tt>Replaces</tt></heading>
4933 Packages can declare in their control file that they should
4934 overwrite files in certain other packages, or completely replace
4935 other packages. The <tt>Replaces</tt> control field has these
4936 two distinct purposes.
4939 <sect1><heading>Overwriting files in other packages</heading>
4942 It is usually an error for a package to contain files which
4943 are on the system in another package. However, if the
4944 overwriting package declares that it <tt>Replaces</tt> the one
4945 containing the file being overwritten, then <prgn>dpkg</prgn>
4946 will replace the file from the old package with that from the
4947 new. The file will no longer be listed as "owned" by the old
4948 package and will be taken over by the new package.
4949 Normally, <tt>Breaks</tt> should be used in conjunction
4950 with <tt>Replaces</tt>.<footnote>
4951 To see why <tt>Breaks</tt> is normally needed in addition
4952 to <tt>Replaces</tt>, consider the case of a file in the
4953 package <package>foo</package> being taken over by the
4954 package <package>foo-data</package>.
4955 <tt>Replaces</tt> will allow <package>foo-data</package> to
4956 be installed and take over that file. However,
4957 without <tt>Breaks</tt>, nothing
4958 requires <package>foo</package> to be upgraded to a newer
4959 version that knows it does not include that file and instead
4960 depends on <package>foo-data</package>. Nothing would
4961 prevent the new <package>foo-data</package> package from
4962 being installed and then removed, removing the file that it
4963 took over from <package>foo</package>. After that
4964 operation, the package manager would think the system was in
4965 a consistent state, but the <package>foo</package> package
4966 would be missing one of its files.
4971 For example, if a package <package>foo</package> is split
4972 into <package>foo</package> and <package>foo-data</package>
4973 starting at version 1.2-3, <package>foo-data</package> would
4975 <example compact="compact">
4976 Replaces: foo (<< 1.2-3)
4977 Breaks: foo (<< 1.2-3)
4979 in its control file. The new version of the
4980 package <package>foo</package> would normally have the field
4981 <example compact="compact">
4982 Depends: foo-data (>= 1.2-3)
4984 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
4985 the files moved into <package>foo-data</package> are not
4986 required for normal operation).
4990 If a package is completely replaced in this way, so that
4991 <prgn>dpkg</prgn> does not know of any files it still
4992 contains, it is considered to have "disappeared". It will
4993 be marked as not wanted on the system (selected for
4994 removal) and not installed. Any <tt>conffile</tt>s
4995 details noted for the package will be ignored, as they
4996 will have been taken over by the overwriting package. The
4997 package's <prgn>postrm</prgn> script will be run with a
4998 special argument to allow the package to do any final
4999 cleanup required. See <ref id="mscriptsinstact">.
5001 Replaces is a one way relationship. You have to install
5002 the replacing package after the replaced package.
5007 For this usage of <tt>Replaces</tt>, virtual packages (see
5008 <ref id="virtual">) are not considered when looking at a
5009 <tt>Replaces</tt> field. The packages declared as being
5010 replaced must be mentioned by their real names.
5014 This usage of <tt>Replaces</tt> only takes effect when both
5015 packages are at least partially on the system at once. It is
5016 not relevant if the packages conflict unless the conflict has
5021 <sect1><heading>Replacing whole packages, forcing their
5025 Second, <tt>Replaces</tt> allows the packaging system to
5026 resolve which package should be removed when there is a
5027 conflict (see <ref id="conflicts">). This usage only takes
5028 effect when the two packages <em>do</em> conflict, so that the
5029 two usages of this field do not interfere with each other.
5033 In this situation, the package declared as being replaced
5034 can be a virtual package, so for example, all mail
5035 transport agents (MTAs) would have the following fields in
5036 their control files:
5037 <example compact="compact">
5038 Provides: mail-transport-agent
5039 Conflicts: mail-transport-agent
5040 Replaces: mail-transport-agent
5042 ensuring that only one MTA can be installed at any one
5043 time. See <ref id="virtual"> for more information about this
5048 <sect id="sourcebinarydeps">
5049 <heading>Relationships between source and binary packages -
5050 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5051 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5055 Source packages that require certain binary packages to be
5056 installed or absent at the time of building the package
5057 can declare relationships to those binary packages.
5061 This is done using the <tt>Build-Depends</tt>,
5062 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5063 <tt>Build-Conflicts-Indep</tt> control fields.
5067 Build-dependencies on "build-essential" binary packages can be
5068 omitted. Please see <ref id="pkg-relations"> for more information.
5072 The dependencies and conflicts they define must be satisfied
5073 (as defined earlier for binary packages) in order to invoke
5074 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5076 There is no Build-Depends-Arch; this role is essentially
5077 met with Build-Depends. Anyone building the
5078 <tt>build-indep</tt> and <tt>binary-indep</tt> targets is
5079 assumed to be building the whole package, and therefore
5080 installation of all build dependencies is required.
5083 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5084 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5085 not yet know how to check for its existence, and
5086 <tt>binary-arch</tt>. The purpose of the original split
5087 between <tt>Build-Depends</tt> and
5088 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5089 wouldn't need to install extra packages needed only for the
5090 binary-indep targets. But without a build-arch/build-indep
5091 split, this didn't work, since most of the work is done in
5092 the build target, not in the binary target.
5096 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5097 <tt>binary-arch</tt></tag>
5099 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5100 fields must be satisfied when these targets are invoked.
5102 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5103 and <tt>binary-indep</tt></tag>
5105 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5106 <tt>Build-Depends-Indep</tt>, and
5107 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5108 these targets are invoked.
5116 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5119 Packages containing shared libraries must be constructed with
5120 a little care to make sure that the shared library is always
5121 available. This is especially important for packages whose
5122 shared libraries are vitally important, such as the C library
5123 (currently <tt>libc6</tt>).
5127 This section deals only with public shared libraries: shared
5128 libraries that are placed in directories searched by the dynamic
5129 linker by default or which are intended to be linked against
5130 normally and possibly used by other, independent packages. Shared
5131 libraries that are internal to a particular package or that are
5132 only loaded as dynamic modules are not covered by this section and
5133 are not subject to its requirements.
5137 A shared library is identified by the <tt>SONAME</tt> attribute
5138 stored in its dynamic section. When a binary is linked against a
5139 shared library, the <tt>SONAME</tt> of the shared library is
5140 recorded in the binary's <tt>NEEDED</tt> section so that the
5141 dynamic linker knows that library must be loaded at runtime. The
5142 shared library file's full name (which usually contains additional
5143 version information not needed in the <tt>SONAME</tt>) is
5144 therefore normally not referenced directly. Instead, the shared
5145 library is loaded by its <tt>SONAME</tt>, which exists on the file
5146 system as a symlink pointing to the full name of the shared
5147 library. This symlink must be provided by the
5148 package. <ref id="sharedlibs-runtime"> describes how to do this.
5150 This is a convention of shared library versioning, but not a
5151 requirement. Some libraries use the <tt>SONAME</tt> as the full
5152 library file name instead and therefore do not need a symlink.
5153 Most, however, encode additional information about
5154 backwards-compatible revisions as a minor version number in the
5155 file name. The <tt>SONAME</tt> itself only changes when
5156 binaries linked with the earlier version of the shared library
5157 may no longer work, but the filename may change with each
5158 release of the library. See <ref id="sharedlibs-runtime"> for
5164 When linking a binary or another shared library against a shared
5165 library, the <tt>SONAME</tt> for that shared library is not yet
5166 known. Instead, the shared library is found by looking for a file
5167 matching the library name with <tt>.so</tt> appended. This file
5168 exists on the file system as a symlink pointing to the shared
5173 Shared libraries are normally split into several binary packages.
5174 The <tt>SONAME</tt> symlink is installed by the runtime shared
5175 library package, and the bare <tt>.so</tt> symlink is installed in
5176 the development package since it's only used when linking binaries
5177 or shared libraries. However, there are some exceptions for
5178 unusual shared libraries or for shared libraries that are also
5179 loaded as dynamic modules by other programs.
5183 This section is primarily concerned with how the separation of
5184 shared libraries into multiple packages should be done and how
5185 dependencies on and between shared library binary packages are
5186 managed in Debian. <ref id="libraries"> should be read in
5187 conjunction with this section and contains additional rules for
5188 the files contained in the shared library packages.
5191 <sect id="sharedlibs-runtime">
5192 <heading>Run-time shared libraries</heading>
5195 The run-time shared library must be placed in a package
5196 whose name changes whenever the <tt>SONAME</tt> of the shared
5197 library changes. This allows several versions of the shared
5198 library to be installed at the same time, allowing installation
5199 of the new version of the shared library without immediately
5200 breaking binaries that depend on the old version. Normally, the
5201 run-time shared library and its <tt>SONAME</tt> symlink should
5202 be placed in a package named
5203 <package><var>libraryname</var><var>soversion</var></package>,
5204 where <var>soversion</var> is the version number in
5205 the <tt>SONAME</tt> of the shared library.
5206 See <ref id="shlibs"> for detailed information on how to
5207 determine this version. Alternatively, if it would be confusing
5208 to directly append <var>soversion</var>
5209 to <var>libraryname</var> (if, for example, <var>libraryname</var>
5210 itself ends in a number), you should use
5211 <package><var>libraryname</var>-<var>soversion</var></package>
5216 If you have several shared libraries built from the same source
5217 tree, you may lump them all together into a single shared
5218 library package provided that all of their <tt>SONAME</tt>s will
5219 always change together. Be aware that this is not normally the
5220 case, and if the <tt>SONAME</tt>s do not change together,
5221 upgrading such a merged shared library package will be
5222 unnecessarily difficult because of file conflicts with the old
5223 version of the package. When in doubt, always split shared
5224 library packages so that each binary package installs a single
5229 Every time the shared library ABI changes in a way that may
5230 break binaries linked against older versions of the shared
5231 library, the <tt>SONAME</tt> of the library and the
5232 corresponding name for the binary package containing the runtime
5233 shared library should change. Normally, this means
5234 the <tt>SONAME</tt> should change any time an interface is
5235 removed from the shared library or the signature of an interface
5236 (the number of parameters or the types of parameters that it
5237 takes, for example) is changed. This practice is vital to
5238 allowing clean upgrades from older versions of the package and
5239 clean transitions between the old ABI and new ABI without having
5240 to upgrade every affected package simultaneously.
5244 The <tt>SONAME</tt> and binary package name need not, and indeed
5245 normally should not, change if new interfaces are added but none
5246 are removed or changed, since this will not break binaries
5247 linked against the old shared library. Correct versioning of
5248 dependencies on the newer shared library by binaries that use
5249 the new interfaces is handled via
5250 the <qref id="sharedlibs-shlibdeps"><tt>shlibs</tt>
5251 system</qref> or via symbols files (see
5252 <manref name="deb-symbols" section="5">).
5256 The package should install the shared libraries under
5257 their normal names. For example, the <package>libgdbm3</package>
5258 package should install <file>libgdbm.so.3.0.0</file> as
5259 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5260 renamed or re-linked by any <prgn>prerm</prgn> or
5261 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5262 of renaming things safely without affecting running programs,
5263 and attempts to interfere with this are likely to lead to
5268 Shared libraries should not be installed executable, since
5269 the dynamic linker does not require this and trying to
5270 execute a shared library usually results in a core dump.
5274 The run-time library package should include the symbolic link for
5275 the <tt>SONAME</tt> that <prgn>ldconfig</prgn> would create for
5276 the shared libraries. For example,
5277 the <package>libgdbm3</package> package should include a symbolic
5278 link from <file>/usr/lib/libgdbm.so.3</file> to
5279 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5280 linker (for example <prgn>ld.so</prgn> or
5281 <prgn>ld-linux.so.*</prgn>) can find the library between the
5282 time that <prgn>dpkg</prgn> installs it and the time that
5283 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5285 The package management system requires the library to be
5286 placed before the symbolic link pointing to it in the
5287 <file>.deb</file> file. This is so that when
5288 <prgn>dpkg</prgn> comes to install the symlink
5289 (overwriting the previous symlink pointing at an older
5290 version of the library), the new shared library is already
5291 in place. In the past, this was achieved by creating the
5292 library in the temporary packaging directory before
5293 creating the symlink. Unfortunately, this was not always
5294 effective, since the building of the tar file in the
5295 <file>.deb</file> depended on the behavior of the underlying
5296 file system. Some file systems (such as reiserfs) reorder
5297 the files so that the order of creation is forgotten.
5298 Since version 1.7.0, <prgn>dpkg</prgn>
5299 reorders the files itself as necessary when building a
5300 package. Thus it is no longer important to concern
5301 oneself with the order of file creation.
5305 <sect1 id="ldconfig">
5306 <heading><tt>ldconfig</tt></heading>
5309 Any package installing shared libraries in one of the default
5310 library directories of the dynamic linker (which are currently
5311 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5312 listed in <file>/etc/ld.so.conf</file><footnote>
5314 <list compact="compact">
5315 <item>/usr/local/lib</item>
5316 <item>/usr/lib/libc5-compat</item>
5317 <item>/lib/libc5-compat</item>
5320 must use <prgn>ldconfig</prgn> to update the shared library
5325 The package maintainer scripts must only call
5326 <prgn>ldconfig</prgn> under these circumstances:
5327 <list compact="compact">
5328 <item>When the <prgn>postinst</prgn> script is run with a
5329 first argument of <tt>configure</tt>, the script must call
5330 <prgn>ldconfig</prgn>, and may optionally invoke
5331 <prgn>ldconfig</prgn> at other times.
5333 <item>When the <prgn>postrm</prgn> script is run with a
5334 first argument of <tt>remove</tt>, the script should call
5335 <prgn>ldconfig</prgn>.
5340 During install or upgrade, the preinst is called before
5341 the new files are installed, so calling "ldconfig" is
5342 pointless. The preinst of an existing package can also be
5343 called if an upgrade fails. However, this happens during
5344 the critical time when a shared libs may exist on-disk
5345 under a temporary name. Thus, it is dangerous and
5346 forbidden by current policy to call "ldconfig" at this
5351 When a package is installed or upgraded, "postinst
5352 configure" runs after the new files are safely on-disk.
5353 Since it is perfectly safe to invoke ldconfig
5354 unconditionally in a postinst, it is OK for a package to
5355 simply put ldconfig in its postinst without checking the
5356 argument. The postinst can also be called to recover from
5357 a failed upgrade. This happens before any new files are
5358 unpacked, so there is no reason to call "ldconfig" at this
5363 For a package that is being removed, prerm is
5364 called with all the files intact, so calling ldconfig is
5365 useless. The other calls to "prerm" happen in the case of
5366 upgrade at a time when all the files of the old package
5367 are on-disk, so again calling "ldconfig" is pointless.
5371 postrm, on the other hand, is called with the "remove"
5372 argument just after the files are removed, so this is
5373 the proper time to call "ldconfig" to notify the system
5374 of the fact that the shared libraries from the package
5375 are removed. The postrm can be called at several other
5376 times. At the time of "postrm purge", "postrm
5377 abort-install", or "postrm abort-upgrade", calling
5378 "ldconfig" is useless because the shared lib files are
5379 not on-disk. However, when "postrm" is invoked with
5380 arguments "upgrade", "failed-upgrade", or "disappear", a
5381 shared lib may exist on-disk under a temporary filename.
5389 <sect id="sharedlibs-support-files">
5390 <heading>Shared library support files</heading>
5393 If your package contains files whose names do not change with
5394 each change in the library shared object version, you must not
5395 put them in the shared library package. Otherwise, several
5396 versions of the shared library cannot be installed at the same
5397 time without filename clashes, making upgrades and transitions
5398 unnecessarily difficult.
5402 It is recommended that supporting files and run-time support
5403 programs that do not need to be invoked manually by users, but
5404 are nevertheless required for the package to function, be placed
5405 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5406 preferably under <file>/usr/lib/</file><var>package-name</var>.
5407 If the program or file is architecture independent, the
5408 recommendation is for it to be placed in a subdirectory of
5409 <file>/usr/share</file> instead, preferably under
5410 <file>/usr/share/</file><var>package-name</var>. Following the
5411 <var>package-name</var> naming convention ensures that the file
5412 names change when the shared object version changes.
5416 Run-time support programs that use the shared library but are
5417 not required for the library to function or files used by the
5418 shared library that can be used by any version of the shared
5419 library package should instead be put in a separate package.
5420 This package might typically be named
5421 <package><var>libraryname</var>-tools</package>; note the
5422 absence of the <var>soversion</var> in the package name.
5426 Files and support programs only useful when compiling software
5427 against the library should be included in the development
5428 package for the library.<footnote>
5429 For example, a <file><var>package-name</var>-config</file>
5430 script or <package>pkg-config</package> configuration files.
5435 <sect id="sharedlibs-static">
5436 <heading>Static libraries</heading>
5439 The static library (<file><var>libraryname.a</var></file>)
5440 is usually provided in addition to the shared version.
5441 It is placed into the development package (see below).
5445 In some cases, it is acceptable for a library to be
5446 available in static form only; these cases include:
5448 <item>libraries for languages whose shared library support
5449 is immature or unstable</item>
5450 <item>libraries whose interfaces are in flux or under
5451 development (commonly the case when the library's
5452 major version number is zero, or where the ABI breaks
5453 across patchlevels)</item>
5454 <item>libraries which are explicitly intended to be
5455 available only in static form by their upstream
5460 <sect id="sharedlibs-dev">
5461 <heading>Development files</heading>
5464 If there are development files associated with a shared library,
5465 the source package needs to generate a binary development package
5466 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5467 or if you prefer only to support one development version at a
5468 time, <package><var>libraryname</var>-dev</package>. Installing
5469 the development package must result in installation of all the
5470 development files necessary for compiling programs against that
5471 shared library.<footnote>
5472 This wording allows the development files to be split into
5473 several packages, such as a separate architecture-independent
5474 <package><var>libraryname</var>-headers</package>, provided that
5475 the development package depends on all the required additional
5481 In case several development versions of a library exist, you may
5482 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5483 <ref id="conflicts">) to ensure that the user only installs one
5484 development version at a time (as different development versions are
5485 likely to have the same header files in them, which would cause a
5486 filename clash if both were installed).
5490 The development package should contain a symlink for the associated
5491 shared library without a version number. For example, the
5492 <package>libgdbm-dev</package> package should include a symlink
5493 from <file>/usr/lib/libgdbm.so</file> to
5494 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5495 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5496 <file>libgdbm.so</file> when compiling dynamically.
5500 <sect id="sharedlibs-intradeps">
5501 <heading>Dependencies between the packages of the same library</heading>
5504 Typically the development version should have an exact
5505 version dependency on the runtime library, to make sure that
5506 compilation and linking happens correctly. The
5507 <tt>${binary:Version}</tt> substitution variable can be
5508 useful for this purpose.
5510 Previously, <tt>${Source-Version}</tt> was used, but its name
5511 was confusing and it has been deprecated since dpkg 1.13.19.
5516 <sect id="sharedlibs-shlibdeps">
5517 <heading>Dependencies between the library and other packages -
5518 the <tt>shlibs</tt> system</heading>
5521 If a package contains a binary or library which links to a
5522 shared library, we must ensure that when the package is
5523 installed on the system, all of the libraries needed are
5524 also installed. This requirement led to the creation of the
5525 <tt>shlibs</tt> system, which is very simple in its design:
5526 any package which <em>provides</em> a shared library also
5527 provides information on the package dependencies required to
5528 ensure the presence of this library, and any package which
5529 <em>uses</em> a shared library uses this information to
5530 determine the dependencies it requires. The files which
5531 contain the mapping from shared libraries to the necessary
5532 dependency information are called <file>shlibs</file> files.
5536 When a package is built which contains any shared libraries, it
5537 must provide a <file>shlibs</file> file for other packages to
5538 use. When a package is built which contains any shared
5539 libraries or compiled binaries, it must run
5540 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5541 on these to determine the libraries used and hence the
5542 dependencies needed by this package.<footnote>
5544 <prgn>dpkg-shlibdeps</prgn> will use a program
5545 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
5546 the libraries directly needed by the binaries or shared
5547 libraries in the package.
5551 We say that a binary <tt>foo</tt> <em>directly</em> uses
5552 a library <tt>libbar</tt> if it is explicitly linked
5553 with that library (that is, the library is listed in the ELF
5554 <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
5555 to the link line when the binary is created). Other
5556 libraries that are needed by <tt>libbar</tt> are linked
5557 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5558 linker will load them automatically when it loads
5559 <tt>libbar</tt>. A package should depend on the libraries
5560 it directly uses, but not the libraries it indirectly uses.
5561 The dependencies for those libraries will automatically pull
5562 in the other libraries.
5566 A good example of where this helps is the following. We
5567 could update <tt>libimlib</tt> with a new version that
5568 supports a new graphics format called dgf (but retaining the
5569 same major version number) and depends on <tt>libdgf</tt>.
5570 If we used <prgn>ldd</prgn> to add dependencies for every
5571 library directly or indirectly linked with a binary, every
5572 package that uses <tt>libimlib</tt> would need to be
5573 recompiled so it would also depend on <tt>libdgf</tt> or it
5574 wouldn't run due to missing symbols. Since dependencies are
5575 only added based on ELF <tt>NEEDED</tt> attribute, packages
5576 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
5577 having the dependency on <tt>libdgf</tt> and so they would
5578 not need rebuilding.
5584 In the following sections, we will first describe where the
5585 various <tt>shlibs</tt> files are to be found, then how to
5586 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5587 file format and how to create them if your package contains a
5592 <heading>The <tt>shlibs</tt> files present on the system</heading>
5595 There are several places where <tt>shlibs</tt> files are
5596 found. The following list gives them in the order in which
5598 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5599 (The first one which gives the required information is used.)
5605 <p><file>debian/shlibs.local</file></p>
5608 This lists overrides for this package. This file should
5609 normally not be used, but may be needed temporarily in
5610 unusual situations to work around bugs in other packages,
5611 or in unusual cases where the normally declared dependency
5612 information in the installed <file>shlibs</file> file for
5613 a library cannot be used. This file overrides information
5614 obtained from any other source.
5619 <p><file>/etc/dpkg/shlibs.override</file></p>
5622 This lists global overrides. This list is normally
5623 empty. It is maintained by the local system
5629 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5632 When packages are being built,
5633 any <file>debian/shlibs</file> files are copied into the
5634 control information file area of the temporary build
5635 directory and given the name <file>shlibs</file>. These
5636 files give details of any shared libraries included in the
5637 same package.<footnote>
5638 An example may help here. Let us say that the source
5639 package <tt>foo</tt> generates two binary
5640 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
5641 When building the binary packages, the two packages are
5642 created in the directories <file>debian/libfoo2</file>
5643 and <file>debian/foo-runtime</file> respectively.
5644 (<file>debian/tmp</file> could be used instead of one of
5645 these.) Since <tt>libfoo2</tt> provides the
5646 <tt>libfoo</tt> shared library, it will require a
5647 <tt>shlibs</tt> file, which will be installed in
5648 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually to
5649 become <file>/var/lib/dpkg/info/libfoo2.shlibs</file>.
5650 When <prgn>dpkg-shlibdeps</prgn> is run on the
5651 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
5653 the <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5654 determine whether <tt>foo-prog</tt>'s library
5655 dependencies are satisfied by any of the libraries
5656 provided by <tt>libfoo2</tt>. For this reason,
5657 <prgn>dpkg-shlibdeps</prgn> must only be run once all of
5658 the individual binary packages' <tt>shlibs</tt> files
5659 have been installed into the build directory.
5665 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5668 These are the <file>shlibs</file> files corresponding to
5669 all of the packages installed on the system, and are
5670 maintained by the relevant package maintainers.
5675 <p><file>/etc/dpkg/shlibs.default</file></p>
5678 This file lists any shared libraries whose packages
5679 have failed to provide correct <file>shlibs</file> files.
5680 It was used when the <file>shlibs</file> setup was first
5681 introduced, but it is now normally empty. It is
5682 maintained by the <tt>dpkg</tt> maintainer.
5690 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5691 <file>shlibs</file> files</heading>
5695 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5696 into your <file>debian/rules</file> file. If your package
5697 contains only compiled binaries and libraries (but no scripts),
5698 you can use a command such as:
5699 <example compact="compact">
5700 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5701 debian/tmp/usr/lib/*
5703 Otherwise, you will need to explicitly list the compiled
5704 binaries and libraries.<footnote>
5705 If you are using <tt>debhelper</tt>, the
5706 <prgn>dh_shlibdeps</prgn> program will do this work for you.
5707 It will also correctly handle multi-binary packages.
5712 This command puts the dependency information into the
5713 <file>debian/substvars</file> file, which is then used by
5714 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5715 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5716 field in the control file for this to work.
5720 If you have multiple binary packages, you will need to call
5721 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5722 compiled libraries or binaries. In such a case, you will
5723 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5724 utilities to specify a different <file>substvars</file> file.
5728 If you are creating a udeb for use in the Debian Installer,
5729 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
5730 should use the dependency line of type <tt>udeb</tt> by
5731 adding the <tt>-tudeb</tt> option<footnote>
5732 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5733 will automatically add this option if it knows it is
5735 </footnote>. If there is no dependency line of
5736 type <tt>udeb</tt> in the <file>shlibs</file>
5737 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the regular
5742 For more details on <prgn>dpkg-shlibdeps</prgn>, please see
5743 <ref id="pkg-dpkg-shlibdeps"> and
5744 <manref name="dpkg-shlibdeps" section="1">.
5749 <heading>The <file>shlibs</file> File Format</heading>
5752 Each <file>shlibs</file> file has the same format. Lines
5753 beginning with <tt>#</tt> are considered to be comments and
5754 are ignored. Each line is of the form:
5755 <example compact="compact">
5756 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5761 We will explain this by reference to the example of the
5762 <tt>zlib1g</tt> package, which (at the time of writing)
5763 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5767 <var>type</var> is an optional element that indicates the type
5768 of package for which the line is valid. The only type currently
5769 in use is <tt>udeb</tt>. The colon and space after the type are
5774 <var>library-name</var> is the name of the shared library,
5775 in this case <tt>libz</tt>. (This must match the name part
5776 of the soname, see below.)
5780 <var>soname-version</var> is the version part of the soname of
5781 the library. The soname is the thing that must exactly match
5782 for the library to be recognized by the dynamic linker, and is
5784 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5785 example, <tt>libz.so.1</tt>.<footnote>
5786 This can be determined using the command
5787 <example compact="compact">
5788 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5791 The version part is the part which comes after
5792 <tt>.so.</tt>, so in our case, it is <tt>1</tt>. The soname may
5793 instead be of the form
5794 <tt><var>name</var>-<var>major-version</var>.so</tt>, such
5795 as <tt>libdb-4.8.so</tt>, in which case the name would
5796 be <tt>libdb</tt> and the version would be <tt>4.8</tt>.
5800 <var>dependencies</var> has the same syntax as a dependency
5801 field in a binary package control file. It should give
5802 details of which packages are required to satisfy a binary
5803 built against the version of the library contained in the
5804 package. See <ref id="depsyntax"> for details.
5808 In our example, if the first version of the <tt>zlib1g</tt>
5809 package which contained a minor number of at least
5810 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5811 <tt>shlibs</tt> entry for this library could say:
5812 <example compact="compact">
5813 libz 1 zlib1g (>= 1:1.1.3)
5815 The version-specific dependency is to avoid warnings from
5816 the dynamic linker about using older shared libraries with
5821 As zlib1g also provides a udeb containing the shared library,
5822 there would also be a second line:
5823 <example compact="compact">
5824 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5830 <heading>Providing a <file>shlibs</file> file</heading>
5833 If your package provides a shared library, you need to create
5834 a <file>shlibs</file> file following the format described above.
5835 It is usual to call this file <file>debian/shlibs</file> (but if
5836 you have multiple binary packages, you might want to call it
5837 <file>debian/shlibs.<var>package</var></file> instead). Then
5838 let <file>debian/rules</file> install it in the control
5839 information file area:
5840 <example compact="compact">
5841 install -m644 debian/shlibs debian/tmp/DEBIAN
5843 or, in the case of a multi-binary package:
5844 <example compact="compact">
5845 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5847 An alternative way of doing this is to create the
5848 <file>shlibs</file> file in the control information file area
5849 directly from <file>debian/rules</file> without using
5850 a <file>debian/shlibs</file> file at all,<footnote>
5851 This is what <prgn>dh_makeshlibs</prgn> in
5852 the <package>debhelper</package> suite does. If your package
5853 also has a udeb that provides a shared
5854 library, <prgn>dh_makeshlibs</prgn> can automatically generate
5855 the <tt>udeb:</tt> lines if you specify the name of the udeb
5856 with the <tt>--add-udeb</tt> option.
5858 since the <file>debian/shlibs</file> file itself is ignored by
5859 <prgn>dpkg-shlibdeps</prgn>.
5863 As <prgn>dpkg-shlibdeps</prgn> reads the
5864 <file>DEBIAN/shlibs</file> files in all of the binary packages
5865 being built from this source package, all of the
5866 <file>DEBIAN/shlibs</file> files should be installed before
5867 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5875 <chapt id="opersys"><heading>The Operating System</heading>
5878 <heading>File system hierarchy</heading>
5882 <heading>File System Structure</heading>
5885 The location of all installed files and directories must
5886 comply with the Filesystem Hierarchy Standard (FHS),
5887 version 2.3, with the exceptions noted below, and except
5888 where doing so would violate other terms of Debian
5889 Policy. The following exceptions to the FHS apply:
5894 The optional rules related to user specific
5895 configuration files for applications are stored in
5896 the user's home directory are relaxed. It is
5897 recommended that such files start with the
5898 '<tt>.</tt>' character (a "dot file"), and if an
5899 application needs to create more than one dot file
5900 then the preferred placement is in a subdirectory
5901 with a name starting with a '.' character, (a "dot
5902 directory"). In this case it is recommended the
5903 configuration files not start with the '.'
5909 The requirement for amd64 to use <file>/lib64</file>
5910 for 64 bit binaries is removed.
5915 The requirement for object files, internal binaries, and
5916 libraries, including <file>libc.so.*</file>, to be located
5917 directly under <file>/lib{,32}</file> and
5918 <file>/usr/lib{,32}</file> is amended, permitting files
5919 to instead be installed to
5920 <file>/lib/<var>triplet</var></file> and
5921 <file>/usr/lib/<var>triplet</var></file>, where
5922 <tt><var>triplet</var></tt> is the value returned by
5923 <tt>dpkg-architecture -qDEB_HOST_GNU_TYPE</tt> for the
5924 architecture of the package. Packages may <em>not</em>
5925 install files to any <var>triplet</var> path other
5926 than the one matching the architecture of that package;
5927 for instance, an <tt>Architecture: amd64</tt> package
5928 containing 32-bit x86 libraries may not install these
5929 libraries to <file>/usr/lib/i486-linux-gnu</file>.
5931 This is necessary in order to reserve the directories for
5932 use in cross-installation of library packages from other
5933 architectures, as part of the planned deployment of
5938 Applications may also use a single subdirectory under
5939 <file>/usr/lib/<var>triplet</var></file>.
5942 The execution time linker/loader, ld*, must still be made
5943 available in the existing location under /lib or /lib64
5944 since this is part of the ELF ABI for the architecture.
5949 The requirement that
5950 <file>/usr/local/share/man</file> be "synonymous"
5951 with <file>/usr/local/man</file> is relaxed to a
5956 The requirement that windowmanagers with a single
5957 configuration file call it <file>system.*wmrc</file>
5958 is removed, as is the restriction that the window
5959 manager subdirectory be named identically to the
5960 window manager name itself.
5965 The requirement that boot manager configuration
5966 files live in <file>/etc</file>, or at least are
5967 symlinked there, is relaxed to a recommendation.
5972 The following directories in the root filesystem are
5973 additionally allowed: <file>/sys</file> and
5974 <file>/selinux</file>. <footnote>These directories
5975 are used as mount points to mount virtual filesystems
5976 to get access to kernel information.</footnote>
5983 The version of this document referred here can be
5984 found in the <tt>debian-policy</tt> package or on <url
5985 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5986 name="FHS (Debian copy)"> alongside this manual (or, if
5987 you have the <package>debian-policy</package> installed,
5989 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5990 (local copy)">). The
5991 latest version, which may be a more recent version, may
5993 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5994 Specific questions about following the standard may be
5995 asked on the <tt>debian-devel</tt> mailing list, or
5996 referred to the FHS mailing list (see the
5997 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
6003 <heading>Site-specific programs</heading>
6006 As mandated by the FHS, packages must not place any
6007 files in <file>/usr/local</file>, either by putting them in
6008 the file system archive to be unpacked by <prgn>dpkg</prgn>
6009 or by manipulating them in their maintainer scripts.
6013 However, the package may create empty directories below
6014 <file>/usr/local</file> so that the system administrator knows
6015 where to place site-specific files. These are not
6016 directories <em>in</em> <file>/usr/local</file>, but are
6017 children of directories in <file>/usr/local</file>. These
6018 directories (<file>/usr/local/*/dir/</file>)
6019 should be removed on package removal if they are
6024 Note that this applies only to
6025 directories <em>below</em> <file>/usr/local</file>,
6026 not <em>in</em> <file>/usr/local</file>. Packages must
6027 not create sub-directories in the
6028 directory <file>/usr/local</file> itself, except those
6029 listed in FHS, section 4.5. However, you may create
6030 directories below them as you wish. You must not remove
6031 any of the directories listed in 4.5, even if you created
6036 Since <file>/usr/local</file> can be mounted read-only from a
6037 remote server, these directories must be created and
6038 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
6039 maintainer scripts and not be included in the
6040 <file>.deb</file> archive. These scripts must not fail if
6041 either of these operations fail.
6045 For example, the <tt>emacsen-common</tt> package could
6046 contain something like
6047 <example compact="compact">
6048 if [ ! -e /usr/local/share/emacs ]
6050 if mkdir /usr/local/share/emacs 2>/dev/null
6052 chown root:staff /usr/local/share/emacs
6053 chmod 2775 /usr/local/share/emacs
6057 in its <prgn>postinst</prgn> script, and
6058 <example compact="compact">
6059 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
6060 rmdir /usr/local/share/emacs 2>/dev/null || true
6062 in the <prgn>prerm</prgn> script. (Note that this form is
6063 used to ensure that if the script is interrupted, the
6064 directory <file>/usr/local/share/emacs</file> will still be
6069 If you do create a directory in <file>/usr/local</file> for
6070 local additions to a package, you should ensure that
6071 settings in <file>/usr/local</file> take precedence over the
6072 equivalents in <file>/usr</file>.
6076 However, because <file>/usr/local</file> and its contents are
6077 for exclusive use of the local administrator, a package
6078 must not rely on the presence or absence of files or
6079 directories in <file>/usr/local</file> for normal operation.
6083 The <file>/usr/local</file> directory itself and all the
6084 subdirectories created by the package should (by default) have
6085 permissions 2775 (group-writable and set-group-id) and be
6086 owned by <tt>root:staff</tt>.
6091 <heading>The system-wide mail directory</heading>
6093 The system-wide mail directory
6094 is <file>/var/mail</file>. This directory is part of the
6095 base system and should not be owned by any particular mail
6096 agents. The use of the old
6097 location <file>/var/spool/mail</file> is deprecated, even
6098 though the spool may still be physically located there.
6104 <heading>Users and groups</heading>
6107 <heading>Introduction</heading>
6109 The Debian system can be configured to use either plain or
6114 Some user ids (UIDs) and group ids (GIDs) are reserved
6115 globally for use by certain packages. Because some
6116 packages need to include files which are owned by these
6117 users or groups, or need the ids compiled into binaries,
6118 these ids must be used on any Debian system only for the
6119 purpose for which they are allocated. This is a serious
6120 restriction, and we should avoid getting in the way of
6121 local administration policies. In particular, many sites
6122 allocate users and/or local system groups starting at 100.
6126 Apart from this we should have dynamically allocated ids,
6127 which should by default be arranged in some sensible
6128 order, but the behavior should be configurable.
6132 Packages other than <tt>base-passwd</tt> must not modify
6133 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
6134 <file>/etc/group</file> or <file>/etc/gshadow</file>.
6139 <heading>UID and GID classes</heading>
6141 The UID and GID numbers are divided into classes as
6147 Globally allocated by the Debian project, the same
6148 on every Debian system. These ids will appear in
6149 the <file>passwd</file> and <file>group</file> files of all
6150 Debian systems, new ids in this range being added
6151 automatically as the <tt>base-passwd</tt> package is
6156 Packages which need a single statically allocated
6157 uid or gid should use one of these; their
6158 maintainers should ask the <tt>base-passwd</tt>
6166 Dynamically allocated system users and groups.
6167 Packages which need a user or group, but can have
6168 this user or group allocated dynamically and
6169 differently on each system, should use <tt>adduser
6170 --system</tt> to create the group and/or user.
6171 <prgn>adduser</prgn> will check for the existence of
6172 the user or group, and if necessary choose an unused
6173 id based on the ranges specified in
6174 <file>adduser.conf</file>.
6178 <tag>1000-59999:</tag>
6181 Dynamically allocated user accounts. By default
6182 <prgn>adduser</prgn> will choose UIDs and GIDs for
6183 user accounts in this range, though
6184 <file>adduser.conf</file> may be used to modify this
6189 <tag>60000-64999:</tag>
6192 Globally allocated by the Debian project, but only
6193 created on demand. The ids are allocated centrally
6194 and statically, but the actual accounts are only
6195 created on users' systems on demand.
6199 These ids are for packages which are obscure or
6200 which require many statically-allocated ids. These
6201 packages should check for and create the accounts in
6202 <file>/etc/passwd</file> or <file>/etc/group</file> (using
6203 <prgn>adduser</prgn> if it has this facility) if
6204 necessary. Packages which are likely to require
6205 further allocations should have a "hole" left after
6206 them in the allocation, to give them room to
6211 <tag>65000-65533:</tag>
6219 User <tt>nobody</tt>. The corresponding gid refers
6220 to the group <tt>nogroup</tt>.
6227 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
6228 not</em> be used, because it is the error return
6237 <sect id="sysvinit">
6238 <heading>System run levels and <file>init.d</file> scripts</heading>
6240 <sect1 id="/etc/init.d">
6241 <heading>Introduction</heading>
6244 The <file>/etc/init.d</file> directory contains the scripts
6245 executed by <prgn>init</prgn> at boot time and when the
6246 init state (or "runlevel") is changed (see <manref
6247 name="init" section="8">).
6251 There are at least two different, yet functionally
6252 equivalent, ways of handling these scripts. For the sake
6253 of simplicity, this document describes only the symbolic
6254 link method. However, it must not be assumed by maintainer
6255 scripts that this method is being used, and any automated
6256 manipulation of the various runlevel behaviors by
6257 maintainer scripts must be performed using
6258 <prgn>update-rc.d</prgn> as described below and not by
6259 manually installing or removing symlinks. For information
6260 on the implementation details of the other method,
6261 implemented in the <tt>file-rc</tt> package, please refer
6262 to the documentation of that package.
6266 These scripts are referenced by symbolic links in the
6267 <file>/etc/rc<var>n</var>.d</file> directories. When changing
6268 runlevels, <prgn>init</prgn> looks in the directory
6269 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
6270 execute, where <tt><var>n</var></tt> is the runlevel that
6271 is being changed to, or <tt>S</tt> for the boot-up
6276 The names of the links all have the form
6277 <file>S<var>mm</var><var>script</var></file> or
6278 <file>K<var>mm</var><var>script</var></file> where
6279 <var>mm</var> is a two-digit number and <var>script</var>
6280 is the name of the script (this should be the same as the
6281 name of the actual script in <file>/etc/init.d</file>).
6285 When <prgn>init</prgn> changes runlevel first the targets
6286 of the links whose names start with a <tt>K</tt> are
6287 executed, each with the single argument <tt>stop</tt>,
6288 followed by the scripts prefixed with an <tt>S</tt>, each
6289 with the single argument <tt>start</tt>. (The links are
6290 those in the <file>/etc/rc<var>n</var>.d</file> directory
6291 corresponding to the new runlevel.) The <tt>K</tt> links
6292 are responsible for killing services and the <tt>S</tt>
6293 link for starting services upon entering the runlevel.
6297 For example, if we are changing from runlevel 2 to
6298 runlevel 3, init will first execute all of the <tt>K</tt>
6299 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
6300 all of the <tt>S</tt> prefixed scripts in that directory.
6301 The links starting with <tt>K</tt> will cause the
6302 referred-to file to be executed with an argument of
6303 <tt>stop</tt>, and the <tt>S</tt> links with an argument
6308 The two-digit number <var>mm</var> is used to determine
6309 the order in which to run the scripts: low-numbered links
6310 have their scripts run first. For example, the
6311 <tt>K20</tt> scripts will be executed before the
6312 <tt>K30</tt> scripts. This is used when a certain service
6313 must be started before another. For example, the name
6314 server <prgn>bind</prgn> might need to be started before
6315 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
6316 can set up its access lists. In this case, the script
6317 that starts <prgn>bind</prgn> would have a lower number
6318 than the script that starts <prgn>inn</prgn> so that it
6320 <example compact="compact">
6327 The two runlevels 0 (halt) and 6 (reboot) are slightly
6328 different. In these runlevels, the links with an
6329 <tt>S</tt> prefix are still called after those with a
6330 <tt>K</tt> prefix, but they too are called with the single
6331 argument <tt>stop</tt>.
6335 <sect1 id="writing-init">
6336 <heading>Writing the scripts</heading>
6339 Packages that include daemons for system services should
6340 place scripts in <file>/etc/init.d</file> to start or stop
6341 services at boot time or during a change of runlevel.
6342 These scripts should be named
6343 <file>/etc/init.d/<var>package</var></file>, and they should
6344 accept one argument, saying what to do:
6347 <tag><tt>start</tt></tag>
6348 <item>start the service,</item>
6350 <tag><tt>stop</tt></tag>
6351 <item>stop the service,</item>
6353 <tag><tt>restart</tt></tag>
6354 <item>stop and restart the service if it's already running,
6355 otherwise start the service</item>
6357 <tag><tt>reload</tt></tag>
6358 <item><p>cause the configuration of the service to be
6359 reloaded without actually stopping and restarting
6362 <tag><tt>force-reload</tt></tag>
6363 <item>cause the configuration to be reloaded if the
6364 service supports this, otherwise restart the
6368 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
6369 <tt>force-reload</tt> options should be supported by all
6370 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
6375 The <file>init.d</file> scripts must ensure that they will
6376 behave sensibly (i.e., returning success and not starting
6377 multiple copies of a service) if invoked with <tt>start</tt>
6378 when the service is already running, or with <tt>stop</tt>
6379 when it isn't, and that they don't kill unfortunately-named
6380 user processes. The best way to achieve this is usually to
6381 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
6386 Be careful of using <tt>set -e</tt> in <file>init.d</file>
6387 scripts. Writing correct <file>init.d</file> scripts requires
6388 accepting various error exit statuses when daemons are already
6389 running or already stopped without aborting
6390 the <file>init.d</file> script, and common <file>init.d</file>
6391 function libraries are not safe to call with <tt>set -e</tt>
6393 <tt>/lib/lsb/init-functions</tt>, which assists in writing
6394 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
6395 in effect and echoing status messages to the console fails,
6397 </footnote>. For <tt>init.d</tt> scripts, it's often easier
6398 to not use <tt>set -e</tt> and instead check the result of
6399 each command separately.
6403 If a service reloads its configuration automatically (as
6404 in the case of <prgn>cron</prgn>, for example), the
6405 <tt>reload</tt> option of the <file>init.d</file> script
6406 should behave as if the configuration has been reloaded
6411 The <file>/etc/init.d</file> scripts must be treated as
6412 configuration files, either (if they are present in the
6413 package, that is, in the .deb file) by marking them as
6414 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6415 by managing them correctly in the maintainer scripts (see
6416 <ref id="config-files">). This is important since we want
6417 to give the local system administrator the chance to adapt
6418 the scripts to the local system, e.g., to disable a
6419 service without de-installing the package, or to specify
6420 some special command line options when starting a service,
6421 while making sure their changes aren't lost during the next
6426 These scripts should not fail obscurely when the
6427 configuration files remain but the package has been
6428 removed, as configuration files remain on the system after
6429 the package has been removed. Only when <prgn>dpkg</prgn>
6430 is executed with the <tt>--purge</tt> option will
6431 configuration files be removed. In particular, as the
6432 <file>/etc/init.d/<var>package</var></file> script itself is
6433 usually a <tt>conffile</tt>, it will remain on the system
6434 if the package is removed but not purged. Therefore, you
6435 should include a <tt>test</tt> statement at the top of the
6437 <example compact="compact">
6438 test -f <var>program-executed-later-in-script</var> || exit 0
6443 Often there are some variables in the <file>init.d</file>
6444 scripts whose values control the behavior of the scripts,
6445 and which a system administrator is likely to want to
6446 change. As the scripts themselves are frequently
6447 <tt>conffile</tt>s, modifying them requires that the
6448 administrator merge in their changes each time the package
6449 is upgraded and the <tt>conffile</tt> changes. To ease
6450 the burden on the system administrator, such configurable
6451 values should not be placed directly in the script.
6452 Instead, they should be placed in a file in
6453 <file>/etc/default</file>, which typically will have the same
6454 base name as the <file>init.d</file> script. This extra file
6455 should be sourced by the script when the script runs. It
6456 must contain only variable settings and comments in SUSv3
6457 <prgn>sh</prgn> format. It may either be a
6458 <tt>conffile</tt> or a configuration file maintained by
6459 the package maintainer scripts. See <ref id="config-files">
6464 To ensure that vital configurable values are always
6465 available, the <file>init.d</file> script should set default
6466 values for each of the shell variables it uses, either
6467 before sourcing the <file>/etc/default/</file> file or
6468 afterwards using something like the <tt>:
6469 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6470 script must behave sensibly and not fail if the
6471 <file>/etc/default</file> file is deleted.
6475 <file>/var/run</file> and <file>/var/lock</file> may be mounted
6476 as temporary filesystems<footnote>
6477 For example, using the <tt>RAMRUN</tt> and <tt>RAMLOCK</tt>
6478 options in <file>/etc/default/rcS</file>.
6479 </footnote>, so the <file>init.d</file> scripts must handle this
6480 correctly. This will typically amount to creating any required
6481 subdirectories dynamically when the <file>init.d</file> script
6482 is run, rather than including them in the package and relying on
6483 <prgn>dpkg</prgn> to create them.
6488 <heading>Interfacing with the initscript system</heading>
6491 Maintainers should use the abstraction layer provided by
6492 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6493 programs to deal with initscripts in their packages'
6494 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6495 and <prgn>postrm</prgn>.
6499 Directly managing the /etc/rc?.d links and directly
6500 invoking the <file>/etc/init.d/</file> initscripts should
6501 be done only by packages providing the initscript
6502 subsystem (such as <prgn>sysv-rc</prgn> and
6503 <prgn>file-rc</prgn>).
6507 <heading>Managing the links</heading>
6510 The program <prgn>update-rc.d</prgn> is provided for
6511 package maintainers to arrange for the proper creation and
6512 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6513 or their functional equivalent if another method is being
6514 used. This may be used by maintainers in their packages'
6515 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6519 You must not include any <file>/etc/rc<var>n</var>.d</file>
6520 symbolic links in the actual archive or manually create or
6521 remove the symbolic links in maintainer scripts; you must
6522 use the <prgn>update-rc.d</prgn> program instead. (The
6523 former will fail if an alternative method of maintaining
6524 runlevel information is being used.) You must not include
6525 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6526 in the archive either. (Only the <tt>sysvinit</tt>
6531 By default <prgn>update-rc.d</prgn> will start services in
6532 each of the multi-user state runlevels (2, 3, 4, and 5)
6533 and stop them in the halt runlevel (0), the single-user
6534 runlevel (1) and the reboot runlevel (6). The system
6535 administrator will have the opportunity to customize
6536 runlevels by simply adding, moving, or removing the
6537 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6538 symbolic links are being used, or by modifying
6539 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6544 To get the default behavior for your package, put in your
6545 <prgn>postinst</prgn> script
6546 <example compact="compact">
6547 update-rc.d <var>package</var> defaults
6549 and in your <prgn>postrm</prgn>
6550 <example compact="compact">
6551 if [ "$1" = purge ]; then
6552 update-rc.d <var>package</var> remove
6554 </example>. Note that if your package changes runlevels
6555 or priority, you may have to remove and recreate the links,
6556 since otherwise the old links may persist. Refer to the
6557 documentation of <prgn>update-rc.d</prgn>.
6561 This will use a default sequence number of 20. If it does
6562 not matter when or in which order the <file>init.d</file>
6563 script is run, use this default. If it does, then you
6564 should talk to the maintainer of the <prgn>sysvinit</prgn>
6565 package or post to <tt>debian-devel</tt>, and they will
6566 help you choose a number.
6570 For more information about using <tt>update-rc.d</tt>,
6571 please consult its man page <manref name="update-rc.d"
6577 <heading>Running initscripts</heading>
6579 The program <prgn>invoke-rc.d</prgn> is provided to make
6580 it easier for package maintainers to properly invoke an
6581 initscript, obeying runlevel and other locally-defined
6582 constraints that might limit a package's right to start,
6583 stop and otherwise manage services. This program may be
6584 used by maintainers in their packages' scripts.
6588 The package maintainer scripts must use
6589 <prgn>invoke-rc.d</prgn> to invoke the
6590 <file>/etc/init.d/*</file> initscripts, instead of
6591 calling them directly.
6595 By default, <prgn>invoke-rc.d</prgn> will pass any
6596 action requests (start, stop, reload, restart...) to the
6597 <file>/etc/init.d</file> script, filtering out requests
6598 to start or restart a service out of its intended
6603 Most packages will simply need to change:
6604 <example compact="compact">/etc/init.d/<package>
6605 <action></example> in their <prgn>postinst</prgn>
6606 and <prgn>prerm</prgn> scripts to:
6607 <example compact="compact">
6608 if which invoke-rc.d >/dev/null 2>&1; then
6609 invoke-rc.d <var>package</var> <action>
6611 /etc/init.d/<var>package</var> <action>
6617 A package should register its initscript services using
6618 <prgn>update-rc.d</prgn> before it tries to invoke them
6619 using <prgn>invoke-rc.d</prgn>. Invocation of
6620 unregistered services may fail.
6624 For more information about using
6625 <prgn>invoke-rc.d</prgn>, please consult its man page
6626 <manref name="invoke-rc.d" section="8">.
6632 <heading>Boot-time initialization</heading>
6635 There used to be another directory, <file>/etc/rc.boot</file>,
6636 which contained scripts which were run once per machine
6637 boot. This has been deprecated in favour of links from
6638 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6639 described in <ref id="/etc/init.d">. Packages must not
6640 place files in <file>/etc/rc.boot</file>.
6645 <heading>Example</heading>
6648 An example on which you can base your
6649 <file>/etc/init.d</file> scripts is found in
6650 <file>/etc/init.d/skeleton</file>.
6657 <heading>Console messages from <file>init.d</file> scripts</heading>
6660 This section describes the formats to be used for messages
6661 written to standard output by the <file>/etc/init.d</file>
6662 scripts. The intent is to improve the consistency of
6663 Debian's startup and shutdown look and feel. For this
6664 reason, please look very carefully at the details. We want
6665 the messages to have the same format in terms of wording,
6666 spaces, punctuation and case of letters.
6670 Here is a list of overall rules that should be used for
6671 messages generated by <file>/etc/init.d</file> scripts.
6677 The message should fit in one line (fewer than 80
6678 characters), start with a capital letter and end with
6679 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6683 If the script is performing some time consuming task in
6684 the background (not merely starting or stopping a
6685 program, for instance), an ellipsis (three dots:
6686 <tt>...</tt>) should be output to the screen, with no
6687 leading or tailing whitespace or line feeds.
6691 The messages should appear as if the computer is telling
6692 the user what it is doing (politely :-), but should not
6693 mention "it" directly. For example, instead of:
6694 <example compact="compact">
6695 I'm starting network daemons: nfsd mountd.
6697 the message should say
6698 <example compact="compact">
6699 Starting network daemons: nfsd mountd.
6706 <tt>init.d</tt> script should use the following standard
6707 message formats for the situations enumerated below.
6713 <p>When daemons are started</p>
6716 If the script starts one or more daemons, the output
6717 should look like this (a single line, no leading
6719 <example compact="compact">
6720 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6722 The <var>description</var> should describe the
6723 subsystem the daemon or set of daemons are part of,
6724 while <var>daemon-1</var> up to <var>daemon-n</var>
6725 denote each daemon's name (typically the file name of
6730 For example, the output of <file>/etc/init.d/lpd</file>
6732 <example compact="compact">
6733 Starting printer spooler: lpd.
6738 This can be achieved by saying
6739 <example compact="compact">
6740 echo -n "Starting printer spooler: lpd"
6741 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6744 in the script. If there are more than one daemon to
6745 start, the output should look like this:
6746 <example compact="compact">
6747 echo -n "Starting remote file system services:"
6748 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6749 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6750 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6753 This makes it possible for the user to see what is
6754 happening and when the final daemon has been started.
6755 Care should be taken in the placement of white spaces:
6756 in the example above the system administrators can
6757 easily comment out a line if they don't want to start
6758 a specific daemon, while the displayed message still
6764 <p>When a system parameter is being set</p>
6767 If you have to set up different system parameters
6768 during the system boot, you should use this format:
6769 <example compact="compact">
6770 Setting <var>parameter</var> to "<var>value</var>".
6775 You can use a statement such as the following to get
6777 <example compact="compact">
6778 echo "Setting DNS domainname to \"$domainname\"."
6783 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
6784 for the left and right quotation marks. A grave accent
6785 (<tt>`</tt>) is not a quote character; neither is an
6786 apostrophe (<tt>'</tt>).
6791 <p>When a daemon is stopped or restarted</p>
6794 When you stop or restart a daemon, you should issue a
6795 message identical to the startup message, except that
6796 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6797 or <tt>Restarting</tt> respectively.
6801 For example, stopping the printer daemon will look like
6803 <example compact="compact">
6804 Stopping printer spooler: lpd.
6810 <p>When something is executed</p>
6813 There are several examples where you have to run a
6814 program at system startup or shutdown to perform a
6815 specific task, for example, setting the system's clock
6816 using <prgn>netdate</prgn> or killing all processes
6817 when the system shuts down. Your message should look
6819 <example compact="compact">
6820 Doing something very useful...done.
6822 You should print the <tt>done.</tt> immediately after
6823 the job has been completed, so that the user is
6824 informed why they have to wait. You can get this
6826 <example compact="compact">
6827 echo -n "Doing something very useful..."
6836 <p>When the configuration is reloaded</p>
6839 When a daemon is forced to reload its configuration
6840 files you should use the following format:
6841 <example compact="compact">
6842 Reloading <var>description</var> configuration...done.
6844 where <var>description</var> is the same as in the
6845 daemon starting message.
6853 <heading>Cron jobs</heading>
6856 Packages must not modify the configuration file
6857 <file>/etc/crontab</file>, and they must not modify the files in
6858 <file>/var/spool/cron/crontabs</file>.</p>
6861 If a package wants to install a job that has to be executed
6862 via cron, it should place a file with the name of the
6863 package in one or more of the following directories:
6864 <example compact="compact">
6870 As these directory names imply, the files within them are
6871 executed on an hourly, daily, weekly, or monthly basis,
6872 respectively. The exact times are listed in
6873 <file>/etc/crontab</file>.</p>
6876 All files installed in any of these directories must be
6877 scripts (e.g., shell scripts or Perl scripts) so that they
6878 can easily be modified by the local system administrator.
6879 In addition, they must be treated as configuration files.
6883 If a certain job has to be executed at some other frequency or
6884 at a specific time, the package should install a file
6885 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6886 same syntax as <file>/etc/crontab</file> and is processed by
6887 <prgn>cron</prgn> automatically. The file must also be
6888 treated as a configuration file. (Note that entries in the
6889 <file>/etc/cron.d</file> directory are not handled by
6890 <prgn>anacron</prgn>. Thus, you should only use this
6891 directory for jobs which may be skipped if the system is not
6894 Unlike <file>crontab</file> files described in the IEEE Std
6895 1003.1-2008 (POSIX.1) available from
6896 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
6897 name="The Open Group">, the files in
6898 <file>/etc/cron.d</file> and the file
6899 <file>/etc/crontab</file> have seven fields; namely:
6901 <item>Minute [0,59]</item>
6902 <item>Hour [0,23]</item>
6903 <item>Day of the month [1,31]</item>
6904 <item>Month of the year [1,12]</item>
6905 <item>Day of the week ([0,6] with 0=Sunday)</item>
6906 <item>Username</item>
6907 <item>Command to be run</item>
6909 Ranges of numbers are allowed. Ranges are two numbers
6910 separated with a hyphen. The specified range is inclusive.
6911 Lists are allowed. A list is a set of numbers (or ranges)
6912 separated by commas. Step values can be used in conjunction
6917 The scripts or <tt>crontab</tt> entries in these directories should
6918 check if all necessary programs are installed before they
6919 try to execute them. Otherwise, problems will arise when a
6920 package was removed but not purged since configuration files
6921 are kept on the system in this situation.
6925 Any <tt>cron</tt> daemon must provide
6926 <file>/usr/bin/crontab</file> and support normal
6927 <tt>crontab</tt> entries as specified in POSIX. The daemon
6928 must also support names for days and months, ranges, and
6929 step values. It has to support <file>/etc/crontab</file>,
6930 and correctly execute the scripts in
6931 <file>/etc/cron.d</file>. The daemon must also correctly
6933 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
6938 <heading>Menus</heading>
6941 The Debian <tt>menu</tt> package provides a standard
6942 interface between packages providing applications and
6943 <em>menu programs</em> (either X window managers or
6944 text-based menu programs such as <prgn>pdmenu</prgn>).
6948 All packages that provide applications that need not be
6949 passed any special command line arguments for normal
6950 operation should register a menu entry for those
6951 applications, so that users of the <tt>menu</tt> package
6952 will automatically get menu entries in their window
6953 managers, as well in shells like <tt>pdmenu</tt>.
6957 Menu entries should follow the current menu policy.
6961 The menu policy can be found in the <tt>menu-policy</tt>
6962 files in the <tt>debian-policy</tt> package.
6963 It is also available from the Debian web mirrors at
6964 <tt><url name="/doc/packaging-manuals/menu-policy/"
6965 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6969 Please also refer to the <em>Debian Menu System</em>
6970 documentation that comes with the <package>menu</package>
6971 package for information about how to register your
6977 <heading>Multimedia handlers</heading>
6980 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6981 is a mechanism for encoding files and data streams and
6982 providing meta-information about them, in particular their
6983 type (e.g. audio or video) and format (e.g. PNG, HTML,
6988 Registration of MIME type handlers allows programs like mail
6989 user agents and web browsers to invoke these handlers to
6990 view, edit or display MIME types they don't support directly.
6994 Packages which provide the ability to view/show/play,
6995 compose, edit or print MIME types should register themselves
6996 as such following the current MIME support policy.
7000 The MIME support policy can be found in the <tt>mime-policy</tt>
7001 files in the <tt>debian-policy</tt> package.
7002 It is also available from the Debian web mirrors at
7003 <tt><url name="/doc/packaging-manuals/mime-policy/"
7004 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
7010 <heading>Keyboard configuration</heading>
7013 To achieve a consistent keyboard configuration so that all
7014 applications interpret a keyboard event the same way, all
7015 programs in the Debian distribution must be configured to
7016 comply with the following guidelines.
7020 The following keys must have the specified interpretations:
7023 <tag><tt><--</tt></tag>
7024 <item>delete the character to the left of the cursor</item>
7026 <tag><tt>Delete</tt></tag>
7027 <item>delete the character to the right of the cursor</item>
7029 <tag><tt>Control+H</tt></tag>
7030 <item>emacs: the help prefix</item>
7033 The interpretation of any keyboard events should be
7034 independent of the terminal that is used, be it a virtual
7035 console, an X terminal emulator, an rlogin/telnet session,
7040 The following list explains how the different programs
7041 should be set up to achieve this:
7047 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
7051 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
7055 X translations are set up to make
7056 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
7057 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
7058 is the vt220 escape code for the "delete character"
7059 key). This must be done by loading the X resources
7060 using <prgn>xrdb</prgn> on all local X displays, not
7061 using the application defaults, so that the
7062 translation resources used correspond to the
7063 <prgn>xmodmap</prgn> settings.
7067 The Linux console is configured to make
7068 <tt><--</tt> generate DEL, and <tt>Delete</tt>
7069 generate <tt>ESC [ 3 ~</tt>.
7073 X applications are configured so that <tt><</tt>
7074 deletes left, and <tt>Delete</tt> deletes right. Motif
7075 applications already work like this.
7079 Terminals should have <tt>stty erase ^?</tt> .
7083 The <tt>xterm</tt> terminfo entry should have <tt>ESC
7084 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
7085 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
7089 Emacs is programmed to map <tt>KB_Backspace</tt> or
7090 the <tt>stty erase</tt> character to
7091 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
7092 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
7093 <tt>^H</tt> to <tt>help</tt> as always.
7097 Other applications use the <tt>stty erase</tt>
7098 character and <tt>kdch1</tt> for the two delete keys,
7099 with ASCII DEL being "delete previous character" and
7100 <tt>kdch1</tt> being "delete character under
7108 This will solve the problem except for the following
7115 Some terminals have a <tt><--</tt> key that cannot
7116 be made to produce anything except <tt>^H</tt>. On
7117 these terminals Emacs help will be unavailable on
7118 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
7119 character takes precedence in Emacs, and has been set
7120 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
7121 available) can be used instead.
7125 Some operating systems use <tt>^H</tt> for <tt>stty
7126 erase</tt>. However, modern telnet versions and all
7127 rlogin versions propagate <tt>stty</tt> settings, and
7128 almost all UNIX versions honour <tt>stty erase</tt>.
7129 Where the <tt>stty</tt> settings are not propagated
7130 correctly, things can be made to work by using
7131 <tt>stty</tt> manually.
7135 Some systems (including previous Debian versions) use
7136 <prgn>xmodmap</prgn> to arrange for both
7137 <tt><--</tt> and <tt>Delete</tt> to generate
7138 <tt>KB_Delete</tt>. We can change the behavior of
7139 their X clients using the same X resources that we use
7140 to do it for our own clients, or configure our clients
7141 using their resources when things are the other way
7142 around. On displays configured like this
7143 <tt>Delete</tt> will not work, but <tt><--</tt>
7148 Some operating systems have different <tt>kdch1</tt>
7149 settings in their <tt>terminfo</tt> database for
7150 <tt>xterm</tt> and others. On these systems the
7151 <tt>Delete</tt> key will not work correctly when you
7152 log in from a system conforming to our policy, but
7153 <tt><--</tt> will.
7160 <heading>Environment variables</heading>
7163 A program must not depend on environment variables to get
7164 reasonable defaults. (That's because these environment
7165 variables would have to be set in a system-wide
7166 configuration file like <file>/etc/profile</file>, which is not
7167 supported by all shells.)
7171 If a program usually depends on environment variables for its
7172 configuration, the program should be changed to fall back to
7173 a reasonable default configuration if these environment
7174 variables are not present. If this cannot be done easily
7175 (e.g., if the source code of a non-free program is not
7176 available), the program must be replaced by a small
7177 "wrapper" shell script which sets the environment variables
7178 if they are not already defined, and calls the original program.
7182 Here is an example of a wrapper script for this purpose:
7184 <example compact="compact">
7186 BAR=${BAR:-/var/lib/fubar}
7188 exec /usr/lib/foo/foo "$@"
7193 Furthermore, as <file>/etc/profile</file> is a configuration
7194 file of the <prgn>base-files</prgn> package, other packages must
7195 not put any environment variables or other commands into that
7200 <sect id="doc-base">
7201 <heading>Registering Documents using doc-base</heading>
7204 The <package>doc-base</package> package implements a
7205 flexible mechanism for handling and presenting
7206 documentation. The recommended practice is for every Debian
7207 package that provides online documentation (other than just
7208 manual pages) to register these documents with
7209 <package>doc-base</package> by installing a
7210 <package>doc-base</package> control file via the
7211 <prgn/install-docs/ script at installation time and
7212 de-register the manuals again when the package is removed.
7215 Please refer to the documentation that comes with the
7216 <package>doc-base</package> package for information and
7225 <heading>Files</heading>
7227 <sect id="binaries">
7228 <heading>Binaries</heading>
7231 Two different packages must not install programs with
7232 different functionality but with the same filenames. (The
7233 case of two programs having the same functionality but
7234 different implementations is handled via "alternatives" or
7235 the "Conflicts" mechanism. See <ref id="maintscripts"> and
7236 <ref id="conflicts"> respectively.) If this case happens,
7237 one of the programs must be renamed. The maintainers should
7238 report this to the <tt>debian-devel</tt> mailing list and
7239 try to find a consensus about which program will have to be
7240 renamed. If a consensus cannot be reached, <em>both</em>
7241 programs must be renamed.
7245 By default, when a package is being built, any binaries
7246 created should include debugging information, as well as
7247 being compiled with optimization. You should also turn on
7248 as many reasonable compilation warnings as possible; this
7249 makes life easier for porters, who can then look at build
7250 logs for possible problems. For the C programming language,
7251 this means the following compilation parameters should be
7253 <example compact="compact">
7255 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
7257 INSTALL = install -s # (or use strip on the files in debian/tmp)
7262 Note that by default all installed binaries should be stripped,
7263 either by using the <tt>-s</tt> flag to
7264 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
7265 the binaries after they have been copied into
7266 <file>debian/tmp</file> but before the tree is made into a
7271 Although binaries in the build tree should be compiled with
7272 debugging information by default, it can often be difficult to
7273 debug programs if they are also subjected to compiler
7274 optimization. For this reason, it is recommended to support the
7275 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
7276 (see <ref id="debianrules-options">). This variable can contain
7277 several flags to change how a package is compiled and built.
7281 It is up to the package maintainer to decide what
7282 compilation options are best for the package. Certain
7283 binaries (such as computationally-intensive programs) will
7284 function better with certain flags (<tt>-O3</tt>, for
7285 example); feel free to use them. Please use good judgment
7286 here. Don't use flags for the sake of it; only use them
7287 if there is good reason to do so. Feel free to override
7288 the upstream author's ideas about which compilation
7289 options are best: they are often inappropriate for our
7295 <sect id="libraries">
7296 <heading>Libraries</heading>
7299 If the package is <strong>architecture: any</strong>, then
7300 the shared library compilation and linking flags must have
7301 <tt>-fPIC</tt>, or the package shall not build on some of
7302 the supported architectures<footnote>
7304 If you are using GCC, <tt>-fPIC</tt> produces code with
7305 relocatable position independent code, which is required for
7306 most architectures to create a shared library, with i386 and
7307 perhaps some others where non position independent code is
7308 permitted in a shared library.
7311 Position independent code may have a performance penalty,
7312 especially on <tt>i386</tt>. However, in most cases the
7313 speed penalty must be measured against the memory wasted on
7314 the few architectures where non position independent code is
7317 </footnote>. Any exception to this rule must be discussed on
7318 the mailing list <em>debian-devel@lists.debian.org</em>, and
7319 a rough consensus obtained. The reasons for not compiling
7320 with <tt>-fPIC</tt> flag must be recorded in the file
7321 <tt>README.Debian</tt>, and care must be taken to either
7322 restrict the architecture or arrange for <tt>-fPIC</tt> to
7323 be used on architectures where it is required.<footnote>
7325 Some of the reasons why this might be required is if the
7326 library contains hand crafted assembly code that is not
7327 relocatable, the speed penalty is excessive for compute
7328 intensive libs, and similar reasons.
7333 As to the static libraries, the common case is not to have
7334 relocatable code, since there is no benefit, unless in specific
7335 cases; therefore the static version must not be compiled
7336 with the <tt>-fPIC</tt> flag. Any exception to this rule
7337 should be discussed on the mailing list
7338 <em>debian-devel@lists.debian.org</em>, and the reasons for
7339 compiling with the <tt>-fPIC</tt> flag must be recorded in
7340 the file <tt>README.Debian</tt>. <footnote>
7342 Some of the reasons for linking static libraries with
7343 the <tt>-fPIC</tt> flag are if, for example, one needs a
7344 Perl API for a library that is under rapid development,
7345 and has an unstable API, so shared libraries are
7346 pointless at this phase of the library's development. In
7347 that case, since Perl needs a library with relocatable
7348 code, it may make sense to create a static library with
7349 relocatable code. Another reason cited is if you are
7350 distilling various libraries into a common shared
7351 library, like <tt>mklibs</tt> does in the Debian
7357 In other words, if both a shared and a static library is
7358 being built, each source unit (<tt>*.c</tt>, for example,
7359 for C files) will need to be compiled twice, for the normal
7364 Libraries should be built with threading support and to be
7365 thread-safe if the library supports this.
7369 Although not enforced by the build tools, shared libraries
7370 must be linked against all libraries that they use symbols from
7371 in the same way that binaries are. This ensures the correct
7372 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
7373 system and guarantees that all libraries can be safely opened
7374 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
7375 option <tt>-Wl,-z,defs</tt> when building a shared library.
7376 Since this option enforces symbol resolution at build time,
7377 a missing library reference will be caught early as a fatal
7382 All installed shared libraries should be stripped with
7383 <example compact="compact">
7384 strip --strip-unneeded <var>your-lib</var>
7386 (The option <tt>--strip-unneeded</tt> makes
7387 <prgn>strip</prgn> remove only the symbols which aren't
7388 needed for relocation processing.) Shared libraries can
7389 function perfectly well when stripped, since the symbols for
7390 dynamic linking are in a separate part of the ELF object
7392 You might also want to use the options
7393 <tt>--remove-section=.comment</tt> and
7394 <tt>--remove-section=.note</tt> on both shared libraries
7395 and executables, and <tt>--strip-debug</tt> on static
7401 Note that under some circumstances it may be useful to
7402 install a shared library unstripped, for example when
7403 building a separate package to support debugging.
7407 Shared object files (often <file>.so</file> files) that are not
7408 public libraries, that is, they are not meant to be linked
7409 to by third party executables (binaries of other packages),
7410 should be installed in subdirectories of the
7411 <file>/usr/lib</file> directory. Such files are exempt from the
7412 rules that govern ordinary shared libraries, except that
7413 they must not be installed executable and should be
7415 A common example are the so-called "plug-ins",
7416 internal shared objects that are dynamically loaded by
7417 programs using <manref name="dlopen" section="3">.
7422 Packages that use <prgn>libtool</prgn> to create and install
7423 their shared libraries install a file containing additional
7424 metadata (ending in <file>.la</file>) alongside the library.
7425 For public libraries intended for use by other packages, these
7426 files normally should not be included in the Debian package,
7427 since the information they include is not necessary to link with
7428 the shared library on Debian and can add unnecessary additional
7429 dependencies to other programs or libraries.<footnote>
7430 These files store, among other things, all libraries on which
7431 that shared library depends. Unfortunately, if
7432 the <file>.la</file> file is present and contains that
7433 dependency information, using <prgn>libtool</prgn> when
7434 linking against that library will cause the resulting program
7435 or library to be linked against those dependencies as well,
7436 even if this is unnecessary. This can create unneeded
7437 dependencies on shared library packages that would otherwise
7438 be hidden behind the library ABI, and can make library
7439 transitions to new SONAMEs unnecessarily complicated and
7440 difficult to manage.
7442 If the <file>.la</file> file is required for that library (if,
7443 for instance, it's loaded via <tt>libltdl</tt> in a way that
7444 requires that meta-information), the <tt>dependency_libs</tt>
7445 setting in the <file>.la</file> file should normally be set to
7446 the empty string. If the shared library development package has
7447 historically included the <file>.la</file>, it must be retained
7448 in the development package (with <tt>dependency_libs</tt>
7449 emptied) until all libraries that depend on it have removed or
7450 emptied <tt>dependency_libs</tt> in their <file>.la</file>
7451 files to prevent linking with those other libraries
7452 using <prgn>libtool</prgn> from failing.
7456 If the <file>.la</file> must be included, it should be included
7457 in the development (<tt>-dev</tt>) package, unless the library
7458 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
7459 library. If it is intended for use with <tt>libltdl</tt>,
7460 the <file>.la</file> files must go in the run-time library
7465 These requirements for handling of <file>.la</file> files do not
7466 apply to loadable modules or libraries not installed in
7467 directories searched by default by the dynamic linker. Packages
7468 installing loadable modules will frequently need to install
7469 the <file>.la</file> files alongside the modules so that they
7470 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
7471 does not need to be modified for libraries or modules that are
7472 not installed in directories searched by the dynamic linker by
7473 default and not intended for use by other packages.
7477 You must make sure that you use only released versions of
7478 shared libraries to build your packages; otherwise other
7479 users will not be able to run your binaries
7480 properly. Producing source packages that depend on
7481 unreleased compilers is also usually a bad
7488 <heading>Shared libraries</heading>
7490 This section has moved to <ref id="sharedlibs">.
7496 <heading>Scripts</heading>
7499 All command scripts, including the package maintainer
7500 scripts inside the package and used by <prgn>dpkg</prgn>,
7501 should have a <tt>#!</tt> line naming the shell to be used
7506 In the case of Perl scripts this should be
7507 <tt>#!/usr/bin/perl</tt>.
7511 When scripts are installed into a directory in the system
7512 PATH, the script name should not include an extension such
7513 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7514 language currently used to implement it.
7517 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
7518 <file>init.d</file> scripts should almost certainly start
7519 with <tt>set -e</tt> so that errors are detected.
7520 <file>init.d</file> scripts are something of a special case, due
7521 to how frequently they need to call commands that are allowed to
7522 fail, and it may instead be easier to check the exit status of
7523 commands directly. See <ref id="writing-init"> for more
7524 information about writing <file>init.d</file> scripts.
7527 Every script should use <tt>set -e</tt> or check the exit status
7528 of <em>every</em> command.
7531 Scripts may assume that <file>/bin/sh</file> implements the
7532 SUSv3 Shell Command Language<footnote>
7533 Single UNIX Specification, version 3, which is also IEEE
7534 1003.1-2004 (POSIX), and is available on the World Wide Web
7535 from <url id="http://www.unix.org/version3/online.html"
7536 name="The Open Group"> after free
7537 registration.</footnote>
7538 plus the following additional features not mandated by
7540 These features are in widespread use in the Linux community
7541 and are implemented in all of bash, dash, and ksh, the most
7542 common shells users may wish to use as <file>/bin/sh</file>.
7545 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7546 must not generate a newline.</item>
7547 <item><tt>test</tt>, if implemented as a shell built-in, must
7548 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7550 <item><tt>local</tt> to create a scoped variable must be
7551 supported, including listing multiple variables in a single
7552 local command and assigning a value to a variable at the
7553 same time as localizing it. <tt>local</tt> may or
7554 may not preserve the variable value from an outer scope if
7555 no assignment is present. Uses such as:
7559 # ... use a, b, c, d ...
7562 must be supported and must set the value of <tt>c</tt> to
7566 If a shell script requires non-SUSv3 features from the shell
7567 interpreter other than those listed above, the appropriate shell
7568 must be specified in the first line of the script (e.g.,
7569 <tt>#!/bin/bash</tt>) and the package must depend on the package
7570 providing the shell (unless the shell package is marked
7571 "Essential", as in the case of <prgn>bash</prgn>).
7575 You may wish to restrict your script to SUSv3 features plus the
7576 above set when possible so that it may use <file>/bin/sh</file>
7577 as its interpreter. If your script works with <prgn>dash</prgn>
7578 (originally called <prgn>ash</prgn>), it probably complies with
7579 the above requirements, but if you are in doubt, use
7580 <file>/bin/bash</file>.
7584 Perl scripts should check for errors when making any
7585 system calls, including <tt>open</tt>, <tt>print</tt>,
7586 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7590 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7591 scripting languages. See <em>Csh Programming Considered
7592 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7593 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7594 If an upstream package comes with <prgn>csh</prgn> scripts
7595 then you must make sure that they start with
7596 <tt>#!/bin/csh</tt> and make your package depend on the
7597 <prgn>c-shell</prgn> virtual package.
7601 Any scripts which create files in world-writeable
7602 directories (e.g., in <file>/tmp</file>) must use a
7603 mechanism which will fail atomically if a file with the same
7604 name already exists.
7608 The Debian base system provides the <prgn>tempfile</prgn>
7609 and <prgn>mktemp</prgn> utilities for use by scripts for
7616 <heading>Symbolic links</heading>
7619 In general, symbolic links within a top-level directory
7620 should be relative, and symbolic links pointing from one
7621 top-level directory into another should be absolute. (A
7622 top-level directory is a sub-directory of the root
7623 directory <file>/</file>.)
7627 In addition, symbolic links should be specified as short as
7628 possible, i.e., link targets like <file>foo/../bar</file> are
7633 Note that when creating a relative link using
7634 <prgn>ln</prgn> it is not necessary for the target of the
7635 link to exist relative to the working directory you're
7636 running <prgn>ln</prgn> from, nor is it necessary to change
7637 directory to the directory where the link is to be made.
7638 Simply include the string that should appear as the target
7639 of the link (this will be a pathname relative to the
7640 directory in which the link resides) as the first argument
7645 For example, in your <prgn>Makefile</prgn> or
7646 <file>debian/rules</file>, you can do things like:
7647 <example compact="compact">
7648 ln -fs gcc $(prefix)/bin/cc
7649 ln -fs gcc debian/tmp/usr/bin/cc
7650 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7651 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7656 A symbolic link pointing to a compressed file should always
7657 have the same file extension as the referenced file. (For
7658 example, if a file <file>foo.gz</file> is referenced by a
7659 symbolic link, the filename of the link has to end with
7660 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7665 <heading>Device files</heading>
7668 Packages must not include device files or named pipes in the
7673 If a package needs any special device files that are not
7674 included in the base system, it must call
7675 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7676 after notifying the user<footnote>
7677 This notification could be done via a (low-priority)
7678 debconf message, or an echo (printf) statement.
7683 Packages must not remove any device files in the
7684 <prgn>postrm</prgn> or any other script. This is left to the
7685 system administrator.
7689 Debian uses the serial devices
7690 <file>/dev/ttyS*</file>. Programs using the old
7691 <file>/dev/cu*</file> devices should be changed to use
7692 <file>/dev/ttyS*</file>.
7696 Named pipes needed by the package must be created in
7697 the <prgn>postinst</prgn> script<footnote>
7698 It's better to use <prgn>mkfifo</prgn> rather
7699 than <prgn>mknod</prgn> to create named pipes so that
7700 automated checks for packages incorrectly creating device
7701 files with <prgn>mknod</prgn> won't have false positives.
7702 </footnote> and removed in
7703 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
7708 <sect id="config-files">
7709 <heading>Configuration files</heading>
7712 <heading>Definitions</heading>
7716 <tag>configuration file</tag>
7718 A file that affects the operation of a program, or
7719 provides site- or host-specific information, or
7720 otherwise customizes the behavior of a program.
7721 Typically, configuration files are intended to be
7722 modified by the system administrator (if needed or
7723 desired) to conform to local policy or to provide
7724 more useful site-specific behavior.
7727 <tag><tt>conffile</tt></tag>
7729 A file listed in a package's <tt>conffiles</tt>
7730 file, and is treated specially by <prgn>dpkg</prgn>
7731 (see <ref id="configdetails">).
7737 The distinction between these two is important; they are
7738 not interchangeable concepts. Almost all
7739 <tt>conffile</tt>s are configuration files, but many
7740 configuration files are not <tt>conffiles</tt>.
7744 As noted elsewhere, <file>/etc/init.d</file> scripts,
7745 <file>/etc/default</file> files, scripts installed in
7746 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7747 configuration installed in <file>/etc/cron.d</file> must be
7748 treated as configuration files. In general, any script that
7749 embeds configuration information is de-facto a configuration
7750 file and should be treated as such.
7755 <heading>Location</heading>
7758 Any configuration files created or used by your package
7759 must reside in <file>/etc</file>. If there are several,
7760 consider creating a subdirectory of <file>/etc</file>
7761 named after your package.
7765 If your package creates or uses configuration files
7766 outside of <file>/etc</file>, and it is not feasible to modify
7767 the package to use <file>/etc</file> directly, put the files
7768 in <file>/etc</file> and create symbolic links to those files
7769 from the location that the package requires.
7774 <heading>Behavior</heading>
7777 Configuration file handling must conform to the following
7779 <list compact="compact">
7781 local changes must be preserved during a package
7785 configuration files must be preserved when the
7786 package is removed, and only deleted when the
7790 Obsolete configuration files without local changes may be
7791 removed by the package during upgrade.
7795 The easy way to achieve this behavior is to make the
7796 configuration file a <tt>conffile</tt>. This is
7797 appropriate only if it is possible to distribute a default
7798 version that will work for most installations, although
7799 some system administrators may choose to modify it. This
7800 implies that the default version will be part of the
7801 package distribution, and must not be modified by the
7802 maintainer scripts during installation (or at any other
7807 In order to ensure that local changes are preserved
7808 correctly, no package may contain or make hard links to
7809 conffiles.<footnote>
7810 Rationale: There are two problems with hard links.
7811 The first is that some editors break the link while
7812 editing one of the files, so that the two files may
7813 unwittingly become unlinked and different. The second
7814 is that <prgn>dpkg</prgn> might break the hard link
7815 while upgrading <tt>conffile</tt>s.
7820 The other way to do it is via the maintainer scripts. In
7821 this case, the configuration file must not be listed as a
7822 <tt>conffile</tt> and must not be part of the package
7823 distribution. If the existence of a file is required for
7824 the package to be sensibly configured it is the
7825 responsibility of the package maintainer to provide
7826 maintainer scripts which correctly create, update and
7827 maintain the file and remove it on purge. (See <ref
7828 id="maintainerscripts"> for more information.) These
7829 scripts must be idempotent (i.e., must work correctly if
7830 <prgn>dpkg</prgn> needs to re-run them due to errors
7831 during installation or removal), must cope with all the
7832 variety of ways <prgn>dpkg</prgn> can call maintainer
7833 scripts, must not overwrite or otherwise mangle the user's
7834 configuration without asking, must not ask unnecessary
7835 questions (particularly during upgrades), and must
7836 otherwise be good citizens.
7840 The scripts are not required to configure every possible
7841 option for the package, but only those necessary to get
7842 the package running on a given system. Ideally the
7843 sysadmin should not have to do any configuration other
7844 than that done (semi-)automatically by the
7845 <prgn>postinst</prgn> script.
7849 A common practice is to create a script called
7850 <file><var>package</var>-configure</file> and have the
7851 package's <prgn>postinst</prgn> call it if and only if the
7852 configuration file does not already exist. In certain
7853 cases it is useful for there to be an example or template
7854 file which the maintainer scripts use. Such files should
7855 be in <file>/usr/share/<var>package</var></file> or
7856 <file>/usr/lib/<var>package</var></file> (depending on whether
7857 they are architecture-independent or not). There should
7858 be symbolic links to them from
7859 <file>/usr/share/doc/<var>package</var>/examples</file> if
7860 they are examples, and should be perfectly ordinary
7861 <prgn>dpkg</prgn>-handled files (<em>not</em>
7862 configuration files).
7866 These two styles of configuration file handling must
7867 not be mixed, for that way lies madness:
7868 <prgn>dpkg</prgn> will ask about overwriting the file
7869 every time the package is upgraded.
7874 <heading>Sharing configuration files</heading>
7877 Packages which specify the same file as a
7878 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7879 with each other. (This is an instance of the general rule
7880 about not sharing files. Note that neither alternatives
7881 nor diversions are likely to be appropriate in this case;
7882 in particular, <prgn>dpkg</prgn> does not handle diverted
7883 <tt>conffile</tt>s well.)
7887 The maintainer scripts must not alter a <tt>conffile</tt>
7888 of <em>any</em> package, including the one the scripts
7893 If two or more packages use the same configuration file
7894 and it is reasonable for both to be installed at the same
7895 time, one of these packages must be defined as
7896 <em>owner</em> of the configuration file, i.e., it will be
7897 the package which handles that file as a configuration
7898 file. Other packages that use the configuration file must
7899 depend on the owning package if they require the
7900 configuration file to operate. If the other package will
7901 use the configuration file if present, but is capable of
7902 operating without it, no dependency need be declared.
7906 If it is desirable for two or more related packages to
7907 share a configuration file <em>and</em> for all of the
7908 related packages to be able to modify that configuration
7909 file, then the following should be done:
7910 <enumlist compact="compact">
7912 One of the related packages (the "owning" package)
7913 will manage the configuration file with maintainer
7914 scripts as described in the previous section.
7917 The owning package should also provide a program
7918 that the other packages may use to modify the
7922 The related packages must use the provided program
7923 to make any desired modifications to the
7924 configuration file. They should either depend on
7925 the core package to guarantee that the configuration
7926 modifier program is available or accept gracefully
7927 that they cannot modify the configuration file if it
7928 is not. (This is in addition to the fact that the
7929 configuration file may not even be present in the
7936 Sometimes it's appropriate to create a new package which
7937 provides the basic infrastructure for the other packages
7938 and which manages the shared configuration files. (The
7939 <tt>sgml-base</tt> package is a good example.)
7944 <heading>User configuration files ("dotfiles")</heading>
7947 The files in <file>/etc/skel</file> will automatically be
7948 copied into new user accounts by <prgn>adduser</prgn>.
7949 No other program should reference the files in
7950 <file>/etc/skel</file>.
7954 Therefore, if a program needs a dotfile to exist in
7955 advance in <file>$HOME</file> to work sensibly, that dotfile
7956 should be installed in <file>/etc/skel</file> and treated as a
7961 However, programs that require dotfiles in order to
7962 operate sensibly are a bad thing, unless they do create
7963 the dotfiles themselves automatically.
7967 Furthermore, programs should be configured by the Debian
7968 default installation to behave as closely to the upstream
7969 default behavior as possible.
7973 Therefore, if a program in a Debian package needs to be
7974 configured in some way in order to operate sensibly, that
7975 should be done using a site-wide configuration file placed
7976 in <file>/etc</file>. Only if the program doesn't support a
7977 site-wide default configuration and the package maintainer
7978 doesn't have time to add it may a default per-user file be
7979 placed in <file>/etc/skel</file>.
7983 <file>/etc/skel</file> should be as empty as we can make it.
7984 This is particularly true because there is no easy (or
7985 necessarily desirable) mechanism for ensuring that the
7986 appropriate dotfiles are copied into the accounts of
7987 existing users when a package is installed.
7993 <heading>Log files</heading>
7995 Log files should usually be named
7996 <file>/var/log/<var>package</var>.log</file>. If you have many
7997 log files, or need a separate directory for permission
7998 reasons (<file>/var/log</file> is writable only by
7999 <file>root</file>), you should usually create a directory named
8000 <file>/var/log/<var>package</var></file> and place your log
8005 Log files must be rotated occasionally so that they don't
8006 grow indefinitely; the best way to do this is to drop a log
8007 rotation configuration file into the directory
8008 <file>/etc/logrotate.d</file> and use the facilities provided by
8009 logrotate.<footnote>
8011 The traditional approach to log files has been to set up
8012 <em>ad hoc</em> log rotation schemes using simple shell
8013 scripts and cron. While this approach is highly
8014 customizable, it requires quite a lot of sysadmin work.
8015 Even though the original Debian system helped a little
8016 by automatically installing a system which can be used
8017 as a template, this was deemed not enough.
8021 The use of <prgn>logrotate</prgn>, a program developed
8022 by Red Hat, is better, as it centralizes log management.
8023 It has both a configuration file
8024 (<file>/etc/logrotate.conf</file>) and a directory where
8025 packages can drop their individual log rotation
8026 configurations (<file>/etc/logrotate.d</file>).
8029 Here is a good example for a logrotate config
8030 file (for more information see <manref name="logrotate"
8032 <example compact="compact">
8033 /var/log/foo/*.log {
8038 /etc/init.d/foo force-reload
8042 This rotates all files under <file>/var/log/foo</file>, saves 12
8043 compressed generations, and forces the daemon to reload its
8044 configuration information after the log rotation.
8048 Log files should be removed when the package is
8049 purged (but not when it is only removed). This should be
8050 done by the <prgn>postrm</prgn> script when it is called
8051 with the argument <tt>purge</tt> (see <ref
8052 id="removedetails">).
8057 <heading>Permissions and owners</heading>
8060 The rules in this section are guidelines for general use.
8061 If necessary you may deviate from the details below.
8062 However, if you do so you must make sure that what is done
8063 is secure and you should try to be as consistent as possible
8064 with the rest of the system. You should probably also
8065 discuss it on <prgn>debian-devel</prgn> first.
8069 Files should be owned by <tt>root:root</tt>, and made
8070 writable only by the owner and universally readable (and
8071 executable, if appropriate), that is mode 644 or 755.
8075 Directories should be mode 755 or (for group-writability)
8076 mode 2775. The ownership of the directory should be
8077 consistent with its mode: if a directory is mode 2775, it
8078 should be owned by the group that needs write access to
8081 When a package is upgraded, and the owner or permissions
8082 of a file included in the package has changed, dpkg
8083 arranges for the ownership and permissions to be
8084 correctly set upon installation. However, this does not
8085 extend to directories; the permissions and ownership of
8086 directories already on the system does not change on
8087 install or upgrade of packages. This makes sense, since
8088 otherwise common directories like <tt>/usr</tt> would
8089 always be in flux. To correctly change permissions of a
8090 directory the package owns, explicit action is required,
8091 usually in the <tt>postinst</tt> script. Care must be
8092 taken to handle downgrades as well, in that case.
8099 Setuid and setgid executables should be mode 4755 or 2755
8100 respectively, and owned by the appropriate user or group.
8101 They should not be made unreadable (modes like 4711 or
8102 2711 or even 4111); doing so achieves no extra security,
8103 because anyone can find the binary in the freely available
8104 Debian package; it is merely inconvenient. For the same
8105 reason you should not restrict read or execute permissions
8106 on non-set-id executables.
8110 Some setuid programs need to be restricted to particular
8111 sets of users, using file permissions. In this case they
8112 should be owned by the uid to which they are set-id, and by
8113 the group which should be allowed to execute them. They
8114 should have mode 4754; again there is no point in making
8115 them unreadable to those users who must not be allowed to
8120 It is possible to arrange that the system administrator can
8121 reconfigure the package to correspond to their local
8122 security policy by changing the permissions on a binary:
8123 they can do this by using <prgn>dpkg-statoverride</prgn>, as
8124 described below.<footnote>
8125 Ordinary files installed by <prgn>dpkg</prgn> (as
8126 opposed to <tt>conffile</tt>s and other similar objects)
8127 normally have their permissions reset to the distributed
8128 permissions when the package is reinstalled. However,
8129 the use of <prgn>dpkg-statoverride</prgn> overrides this
8132 Another method you should consider is to create a group for
8133 people allowed to use the program(s) and make any setuid
8134 executables executable only by that group.
8138 If you need to create a new user or group for your package
8139 there are two possibilities. Firstly, you may need to
8140 make some files in the binary package be owned by this
8141 user or group, or you may need to compile the user or
8142 group id (rather than just the name) into the binary
8143 (though this latter should be avoided if possible, as in
8144 this case you need a statically allocated id).</p>
8147 If you need a statically allocated id, you must ask for a
8148 user or group id from the <tt>base-passwd</tt> maintainer,
8149 and must not release the package until you have been
8150 allocated one. Once you have been allocated one you must
8151 either make the package depend on a version of the
8152 <tt>base-passwd</tt> package with the id present in
8153 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
8154 your package to create the user or group itself with the
8155 correct id (using <tt>adduser</tt>) in its
8156 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
8157 the <prgn>postinst</prgn> is to be preferred if it is
8158 possible, otherwise a pre-dependency will be needed on the
8159 <tt>adduser</tt> package.)
8163 On the other hand, the program might be able to determine
8164 the uid or gid from the user or group name at runtime, so
8165 that a dynamically allocated id can be used. In this case
8166 you should choose an appropriate user or group name,
8167 discussing this on <prgn>debian-devel</prgn> and checking
8168 with the <package/base-passwd/ maintainer that it is unique and that
8169 they do not wish you to use a statically allocated id
8170 instead. When this has been checked you must arrange for
8171 your package to create the user or group if necessary using
8172 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
8173 <prgn>postinst</prgn> script (again, the latter is to be
8174 preferred if it is possible).
8178 Note that changing the numeric value of an id associated
8179 with a name is very difficult, and involves searching the
8180 file system for all appropriate files. You need to think
8181 carefully whether a static or dynamic id is required, since
8182 changing your mind later will cause problems.
8185 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
8187 This section is not intended as policy, but as a
8188 description of the use of <prgn>dpkg-statoverride</prgn>.
8192 If a system administrator wishes to have a file (or
8193 directory or other such thing) installed with owner and
8194 permissions different from those in the distributed Debian
8195 package, they can use the <prgn>dpkg-statoverride</prgn>
8196 program to instruct <prgn>dpkg</prgn> to use the different
8197 settings every time the file is installed. Thus the
8198 package maintainer should distribute the files with their
8199 normal permissions, and leave it for the system
8200 administrator to make any desired changes. For example, a
8201 daemon which is normally required to be setuid root, but
8202 in certain situations could be used without being setuid,
8203 should be installed setuid in the <tt>.deb</tt>. Then the
8204 local system administrator can change this if they wish.
8205 If there are two standard ways of doing it, the package
8206 maintainer can use <tt>debconf</tt> to find out the
8207 preference, and call <prgn>dpkg-statoverride</prgn> in the
8208 maintainer script if necessary to accommodate the system
8209 administrator's choice. Care must be taken during
8210 upgrades to not override an existing setting.
8214 Given the above, <prgn>dpkg-statoverride</prgn> is
8215 essentially a tool for system administrators and would not
8216 normally be needed in the maintainer scripts. There is
8217 one type of situation, though, where calls to
8218 <prgn>dpkg-statoverride</prgn> would be needed in the
8219 maintainer scripts, and that involves packages which use
8220 dynamically allocated user or group ids. In such a
8221 situation, something like the following idiom can be very
8222 helpful in the package's <prgn>postinst</prgn>, where
8223 <tt>sysuser</tt> is a dynamically allocated id:
8225 for i in /usr/bin/foo /usr/sbin/bar
8227 # only do something when no setting exists
8228 if ! dpkg-statoverride --list $i >/dev/null 2>&1
8230 #include: debconf processing, question about foo and bar
8231 if [ "$RET" = "true" ] ; then
8232 dpkg-statoverride --update --add sysuser root 4755 $i
8237 The corresponding code to remove the override when the package
8240 for i in /usr/bin/foo /usr/sbin/bar
8242 if dpkg-statoverride --list $i >/dev/null 2>&1
8244 dpkg-statoverride --remove $i
8254 <chapt id="customized-programs">
8255 <heading>Customized programs</heading>
8257 <sect id="arch-spec">
8258 <heading>Architecture specification strings</heading>
8261 If a program needs to specify an <em>architecture specification
8262 string</em> in some place, it should select one of the strings
8263 provided by <tt>dpkg-architecture -L</tt>. The strings are in
8264 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
8265 part is sometimes elided, as when the OS is Linux.
8269 Note that we don't want to use
8270 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
8271 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
8272 since this would make our programs incompatible with other
8273 Linux distributions. We also don't use something like
8274 <tt><var>arch</var>-unknown-linux</tt>, since the
8275 <tt>unknown</tt> does not look very good.
8278 <sect1 id="arch-wildcard-spec">
8279 <heading>Architecture wildcards</heading>
8282 A package may specify an architecture wildcard. Architecture
8283 wildcards are in the format <tt>any</tt> (which matches every
8284 architecture), <tt><var>os</var></tt>-any, or
8285 any-<tt><var>cpu</var></tt>. <footnote>
8286 Internally, the package system normalizes the GNU triplets
8287 and the Debian arches into Debian arch triplets (which are
8288 kind of inverted GNU triplets), with the first component of
8289 the triplet representing the libc and ABI in use, and then
8290 does matching against those triplets. However, such
8291 triplets are an internal implementation detail that should
8292 not be used by packages directly. The libc and ABI portion
8293 is handled internally by the package system based on
8294 the <var>os</var> and <var>cpu</var>.
8301 <heading>Daemons</heading>
8304 The configuration files <file>/etc/services</file>,
8305 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
8306 by the <prgn>netbase</prgn> package and must not be modified
8311 If a package requires a new entry in one of these files, the
8312 maintainer should get in contact with the
8313 <prgn>netbase</prgn> maintainer, who will add the entries
8314 and release a new version of the <prgn>netbase</prgn>
8319 The configuration file <file>/etc/inetd.conf</file> must not be
8320 modified by the package's scripts except via the
8321 <prgn>update-inetd</prgn> script or the
8322 <file>DebianNet.pm</file> Perl module. See their documentation
8323 for details on how to add entries.
8327 If a package wants to install an example entry into
8328 <file>/etc/inetd.conf</file>, the entry must be preceded with
8329 exactly one hash character (<tt>#</tt>). Such lines are
8330 treated as "commented out by user" by the
8331 <prgn>update-inetd</prgn> script and are not changed or
8332 activated during package updates.
8337 <heading>Using pseudo-ttys and modifying wtmp, utmp and
8341 Some programs need to create pseudo-ttys. This should be done
8342 using Unix98 ptys if the C library supports it. The resulting
8343 program must not be installed setuid root, unless that
8344 is required for other functionality.
8348 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
8349 <file>/var/log/lastlog</file> must be installed writable by
8350 group <tt>utmp</tt>. Programs which need to modify those
8351 files must be installed setgid <tt>utmp</tt>.
8356 <heading>Editors and pagers</heading>
8359 Some programs have the ability to launch an editor or pager
8360 program to edit or display a text document. Since there are
8361 lots of different editors and pagers available in the Debian
8362 distribution, the system administrator and each user should
8363 have the possibility to choose their preferred editor and
8368 In addition, every program should choose a good default
8369 editor/pager if none is selected by the user or system
8374 Thus, every program that launches an editor or pager must
8375 use the EDITOR or PAGER environment variable to determine
8376 the editor or pager the user wishes to use. If these
8377 variables are not set, the programs <file>/usr/bin/editor</file>
8378 and <file>/usr/bin/pager</file> should be used, respectively.
8382 These two files are managed through the <prgn>dpkg</prgn>
8383 "alternatives" mechanism. Every package providing an editor or
8384 pager must call the <prgn>update-alternatives</prgn> script to
8385 register as an alternative for <file>/usr/bin/editor</file>
8386 or <file>/usr/bin/pager</file> as appropriate. The alternative
8387 should have a slave alternative
8388 for <file>/usr/share/man/man1/editor.1.gz</file>
8389 or <file>/usr/share/man/man1/pager.1.gz</file> pointing to the
8390 corresponding manual page.
8394 If it is very hard to adapt a program to make use of the
8395 EDITOR or PAGER variables, that program may be configured to
8396 use <file>/usr/bin/sensible-editor</file> and
8397 <file>/usr/bin/sensible-pager</file> as the editor or pager
8398 program respectively. These are two scripts provided in the
8399 <package>sensible-utils</package> package that check the EDITOR
8400 and PAGER variables and launch the appropriate program, and fall
8401 back to <file>/usr/bin/editor</file>
8402 and <file>/usr/bin/pager</file> if the variable is not set.
8406 A program may also use the VISUAL environment variable to
8407 determine the user's choice of editor. If it exists, it
8408 should take precedence over EDITOR. This is in fact what
8409 <file>/usr/bin/sensible-editor</file> does.
8413 It is not required for a package to depend on
8414 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
8415 package to provide such virtual packages.<footnote>
8416 The Debian base system already provides an editor and a
8422 <sect id="web-appl">
8423 <heading>Web servers and applications</heading>
8426 This section describes the locations and URLs that should
8427 be used by all web servers and web applications in the
8434 Cgi-bin executable files are installed in the
8436 <example compact="compact">
8437 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
8439 or a subdirectory of that directory, and should be
8441 <example compact="compact">
8442 http://localhost/cgi-bin/<var>cgi-bin-name</var>
8444 (possibly with a subdirectory name
8445 before <var>cgi-bin-name</var>).
8449 <p>Access to HTML documents</p>
8452 HTML documents for a package are stored in
8453 <file>/usr/share/doc/<var>package</var></file>
8454 and can be referred to as
8455 <example compact="compact">
8456 http://localhost/doc/<var>package</var>/<var>filename</var>
8461 The web server should restrict access to the document
8462 tree so that only clients on the same host can read
8463 the documents. If the web server does not support such
8464 access controls, then it should not provide access at
8465 all, or ask about providing access during installation.
8470 <p>Access to images</p>
8472 It is recommended that images for a package be stored
8473 in <tt>/usr/share/images/<var>package</var></tt> and
8474 may be referred to through an alias <tt>/images/</tt>
8477 http://localhost/images/<package>/<filename>
8484 <p>Web Document Root</p>
8487 Web Applications should try to avoid storing files in
8488 the Web Document Root. Instead they should use the
8489 /usr/share/doc/<var>package</var> directory for
8490 documents and register the Web Application via the
8491 <package>doc-base</package> package. If access to the
8492 web document root is unavoidable then use
8493 <example compact="compact">
8496 as the Document Root. This might be just a symbolic
8497 link to the location where the system administrator
8498 has put the real document root.
8501 <item><p>Providing httpd and/or httpd-cgi</p>
8503 All web servers should provide the virtual package
8504 <tt>httpd</tt>. If a web server has CGI support it should
8505 provide <tt>httpd-cgi</tt> additionally.
8508 All web applications which do not contain CGI scripts should
8509 depend on <tt>httpd</tt>, all those web applications which
8510 <tt>do</tt> contain CGI scripts, should depend on
8518 <sect id="mail-transport-agents">
8519 <heading>Mail transport, delivery and user agents</heading>
8522 Debian packages which process electronic mail, whether mail
8523 user agents (MUAs) or mail transport agents (MTAs), must
8524 ensure that they are compatible with the configuration
8525 decisions below. Failure to do this may result in lost
8526 mail, broken <tt>From:</tt> lines, and other serious brain
8531 The mail spool is <file>/var/mail</file> and the interface to
8532 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8533 the FHS). On older systems, the mail spool may be
8534 physically located in <file>/var/spool/mail</file>, but all
8535 access to the mail spool should be via the
8536 <file>/var/mail</file> symlink. The mail spool is part of the
8537 base system and not part of the MTA package.
8541 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8542 programs (such as IMAP daemons) must lock the mailbox in an
8543 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8544 be combined with dot locking. To avoid deadlocks, a program
8545 should use <tt>fcntl()</tt> first and dot locking after
8546 this, or alternatively implement the two locking methods in
8547 a non blocking way<footnote>
8548 If it is not possible to establish both locks, the
8549 system shouldn't wait for the second lock to be
8550 established, but remove the first lock, wait a (random)
8551 time, and start over locking again.
8552 </footnote>. Using the functions <tt>maillock</tt> and
8553 <tt>mailunlock</tt> provided by the
8554 <tt>liblockfile*</tt><footnote>
8555 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8556 to use these functions.
8557 </footnote> packages is the recommended way to realize this.
8561 Mailboxes are generally either mode 600 and owned by
8562 <var>user</var> or mode 660 and owned by
8563 <tt><var>user</var>:mail</tt><footnote>
8564 There are two traditional permission schemes for mail spools:
8565 mode 600 with all mail delivery done by processes running as
8566 the destination user, or mode 660 and owned by group mail with
8567 mail delivery done by a process running as a system user in
8568 group mail. Historically, Debian required mode 660 mail
8569 spools to enable the latter model, but that model has become
8570 increasingly uncommon and the principle of least privilege
8571 indicates that mail systems that use the first model should
8572 use permissions of 600. If delivery to programs is permitted,
8573 it's easier to keep the mail system secure if the delivery
8574 agent runs as the destination user. Debian Policy therefore
8575 permits either scheme.
8576 </footnote>. The local system administrator may choose a
8577 different permission scheme; packages should not make
8578 assumptions about the permission and ownership of mailboxes
8579 unless required (such as when creating a new mailbox). A MUA
8580 may remove a mailbox (unless it has nonstandard permissions) in
8581 which case the MTA or another MUA must recreate it if needed.
8585 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8586 be setgid mail to do the locking mentioned above (and
8587 must obviously avoid accessing other users' mailboxes
8588 using this privilege).</p>
8591 <file>/etc/aliases</file> is the source file for the system mail
8592 aliases (e.g., postmaster, usenet, etc.), it is the one
8593 which the sysadmin and <prgn>postinst</prgn> scripts may
8594 edit. After <file>/etc/aliases</file> is edited the program or
8595 human editing it must call <prgn>newaliases</prgn>. All MTA
8596 packages must come with a <prgn>newaliases</prgn> program,
8597 even if it does nothing, but older MTA packages did not do
8598 this so programs should not fail if <prgn>newaliases</prgn>
8599 cannot be found. Note that because of this, all MTA
8600 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8601 <tt>Replaces: mail-transport-agent</tt> control fields.
8605 The convention of writing <tt>forward to
8606 <var>address</var></tt> in the mailbox itself is not
8607 supported. Use a <tt>.forward</tt> file instead.</p>
8610 The <prgn>rmail</prgn> program used by UUCP
8611 for incoming mail should be <file>/usr/sbin/rmail</file>.
8612 Likewise, <prgn>rsmtp</prgn>, for receiving
8613 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8617 If your package needs to know what hostname to use on (for
8618 example) outgoing news and mail messages which are generated
8619 locally, you should use the file <file>/etc/mailname</file>. It
8620 will contain the portion after the username and <tt>@</tt>
8621 (at) sign for email addresses of users on the machine
8622 (followed by a newline).
8626 Such a package should check for the existence of this file
8627 when it is being configured. If it exists, it should be
8628 used without comment, although an MTA's configuration script
8629 may wish to prompt the user even if it finds that this file
8630 exists. If the file does not exist, the package should
8631 prompt the user for the value (preferably using
8632 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8633 as well as using it in the package's configuration. The
8634 prompt should make it clear that the name will not just be
8635 used by that package. For example, in this situation the
8636 <tt>inn</tt> package could say something like:
8637 <example compact="compact">
8638 Please enter the "mail name" of your system. This is the
8639 hostname portion of the address to be shown on outgoing
8640 news and mail messages. The default is
8641 <var>syshostname</var>, your system's host name. Mail
8642 name ["<var>syshostname</var>"]:
8644 where <var>syshostname</var> is the output of <tt>hostname
8650 <heading>News system configuration</heading>
8653 All the configuration files related to the NNTP (news)
8654 servers and clients should be located under
8655 <file>/etc/news</file>.</p>
8658 There are some configuration issues that apply to a number
8659 of news clients and server packages on the machine. These
8663 <tag><file>/etc/news/organization</file></tag>
8665 A string which should appear as the
8666 organization header for all messages posted
8667 by NNTP clients on the machine
8670 <tag><file>/etc/news/server</file></tag>
8672 Contains the FQDN of the upstream NNTP
8673 server, or localhost if the local machine is
8678 Other global files may be added as required for cross-package news
8685 <heading>Programs for the X Window System</heading>
8688 <heading>Providing X support and package priorities</heading>
8691 Programs that can be configured with support for the X
8692 Window System must be configured to do so and must declare
8693 any package dependencies necessary to satisfy their
8694 runtime requirements when using the X Window System. If
8695 such a package is of higher priority than the X packages
8696 on which it depends, it is required that either the
8697 X-specific components be split into a separate package, or
8698 that an alternative version of the package, which includes
8699 X support, be provided, or that the package's priority be
8705 <heading>Packages providing an X server</heading>
8708 Packages that provide an X server that, directly or
8709 indirectly, communicates with real input and display
8710 hardware should declare in their <tt>Provides</tt> control
8711 field that they provide the virtual
8712 package <tt>xserver</tt>.<footnote>
8713 This implements current practice, and provides an
8714 actual policy for usage of the <tt>xserver</tt>
8715 virtual package which appears in the virtual packages
8716 list. In a nutshell, X servers that interface
8717 directly with the display and input hardware or via
8718 another subsystem (e.g., GGI) should provide
8719 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8720 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8726 <heading>Packages providing a terminal emulator</heading>
8729 Packages that provide a terminal emulator for the X Window
8730 System which meet the criteria listed below should declare in
8731 their <tt>Provides</tt> control field that they provide the
8732 virtual package <tt>x-terminal-emulator</tt>. They should
8733 also register themselves as an alternative for
8734 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8735 20. That alternative should have a slave alternative
8736 for <file>/usr/share/man/man1/x-terminal-emulator.1.gz</file>
8737 pointing to the corresponding manual page.
8741 To be an <tt>x-terminal-emulator</tt>, a program must:
8742 <list compact="compact">
8744 Be able to emulate a DEC VT100 terminal, or a
8745 compatible terminal.
8749 Support the command-line option <tt>-e
8750 <var>command</var></tt>, which creates a new
8751 terminal window<footnote>
8752 "New terminal window" does not necessarily mean
8753 a new top-level X window directly parented by
8754 the window manager; it could, if the terminal
8755 emulator application were so coded, be a new
8756 "view" in a multiple-document interface (MDI).
8758 and runs the specified <var>command</var>,
8759 interpreting the entirety of the rest of the command
8760 line as a command to pass straight to exec, in the
8761 manner that <tt>xterm</tt> does.
8765 Support the command-line option <tt>-T
8766 <var>title</var></tt>, which creates a new terminal
8767 window with the window title <var>title</var>.
8774 <heading>Packages providing a window manager</heading>
8777 Packages that provide a window manager should declare in
8778 their <tt>Provides</tt> control field that they provide the
8779 virtual package <tt>x-window-manager</tt>. They should also
8780 register themselves as an alternative for
8781 <file>/usr/bin/x-window-manager</file>, with a priority
8782 calculated as follows:
8783 <list compact="compact">
8785 Start with a priority of 20.
8789 If the window manager supports the Debian menu
8790 system, add 20 points if this support is available
8791 in the package's default configuration (i.e., no
8792 configuration files belonging to the system or user
8793 have to be edited to activate the feature); if
8794 configuration files must be modified, add only 10
8800 If the window manager complies with <url
8801 id="http://www.freedesktop.org/Standards/wm-spec"
8802 name="The Window Manager Specification Project">,
8803 written by the <url id="http://www.freedesktop.org/"
8804 name="Free Desktop Group">, add 40 points.
8808 If the window manager permits the X session to be
8809 restarted using a <em>different</em> window manager
8810 (without killing the X server) in its default
8811 configuration, add 10 points; otherwise add none.
8814 That alternative should have a slave alternative
8815 for <file>/usr/share/man/man1/x-window-manager.1.gz</file>
8816 pointing to the corresponding manual page.
8821 <heading>Packages providing fonts</heading>
8824 Packages that provide fonts for the X Window
8826 For the purposes of Debian Policy, a "font for the X
8827 Window System" is one which is accessed via X protocol
8828 requests. Fonts for the Linux console, for PostScript
8829 renderer, or any other purpose, do not fit this
8830 definition. Any tool which makes such fonts available
8831 to the X Window System, however, must abide by this
8834 must do a number of things to ensure that they are both
8835 available without modification of the X or font server
8836 configuration, and that they do not corrupt files used by
8837 other font packages to register information about
8841 Fonts of any type supported by the X Window System
8842 must be in a separate binary package from any
8843 executables, libraries, or documentation (except
8844 that specific to the fonts shipped, such as their
8845 license information). If one or more of the fonts
8846 so packaged are necessary for proper operation of
8847 the package with which they are associated the font
8848 package may be Recommended; if the fonts merely
8849 provide an enhancement, a Suggests relationship may
8850 be used. Packages must not Depend on font
8852 This is because the X server may retrieve fonts
8853 from the local file system or over the network
8854 from an X font server; the Debian package system
8855 is empowered to deal only with the local
8861 BDF fonts must be converted to PCF fonts with the
8862 <prgn>bdftopcf</prgn> utility (available in the
8863 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8864 placed in a directory that corresponds to their
8866 <list compact="compact">
8868 100 dpi fonts must be placed in
8869 <file>/usr/share/fonts/X11/100dpi/</file>.
8873 75 dpi fonts must be placed in
8874 <file>/usr/share/fonts/X11/75dpi/</file>.
8878 Character-cell fonts, cursor fonts, and other
8879 low-resolution fonts must be placed in
8880 <file>/usr/share/fonts/X11/misc/</file>.
8886 Type 1 fonts must be placed in
8887 <file>/usr/share/fonts/X11/Type1/</file>. If font
8888 metric files are available, they must be placed here
8893 Subdirectories of <file>/usr/share/fonts/X11/</file>
8894 other than those listed above must be neither
8895 created nor used. (The <file>PEX</file>, <file>CID</file>,
8896 <file>Speedo</file>, and <file>cyrillic</file> directories
8897 are excepted for historical reasons, but installation of
8898 files into these directories remains discouraged.)
8902 Font packages may, instead of placing files directly
8903 in the X font directories listed above, provide
8904 symbolic links in that font directory pointing to
8905 the files' actual location in the filesystem. Such
8906 a location must comply with the FHS.
8910 Font packages should not contain both 75dpi and
8911 100dpi versions of a font. If both are available,
8912 they should be provided in separate binary packages
8913 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8914 the names of the packages containing the
8915 corresponding fonts.
8919 Fonts destined for the <file>misc</file> subdirectory
8920 should not be included in the same package as 75dpi
8921 or 100dpi fonts; instead, they should be provided in
8922 a separate package with <tt>-misc</tt> appended to
8927 Font packages must not provide the files
8928 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8929 <file>fonts.scale</file> in a font directory:
8932 <file>fonts.dir</file> files must not be provided at all.
8936 <file>fonts.alias</file> and <file>fonts.scale</file>
8937 files, if needed, should be provided in the
8939 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8940 where <var>fontdir</var> is the name of the
8942 <file>/usr/share/fonts/X11/</file> where the
8943 package's corresponding fonts are stored
8944 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8945 <var>package</var> is the name of the package
8946 that provides these fonts, and
8947 <var>extension</var> is either <tt>scale</tt>
8948 or <tt>alias</tt>, whichever corresponds to
8955 Font packages must declare a dependency on
8956 <tt>xfonts-utils</tt> in their <tt>Depends</tt>
8957 or <tt>Pre-Depends</tt> control field.
8961 Font packages that provide one or more
8962 <file>fonts.scale</file> files as described above must
8963 invoke <prgn>update-fonts-scale</prgn> on each
8964 directory into which they installed fonts
8965 <em>before</em> invoking
8966 <prgn>update-fonts-dir</prgn> on that directory.
8967 This invocation must occur in both the
8968 <prgn>postinst</prgn> (for all arguments) and
8969 <prgn>postrm</prgn> (for all arguments except
8970 <tt>upgrade</tt>) scripts.
8974 Font packages that provide one or more
8975 <file>fonts.alias</file> files as described above must
8976 invoke <prgn>update-fonts-alias</prgn> on each
8977 directory into which they installed fonts. This
8978 invocation must occur in both the
8979 <prgn>postinst</prgn> (for all arguments) and
8980 <prgn>postrm</prgn> (for all arguments except
8981 <tt>upgrade</tt>) scripts.
8985 Font packages must invoke
8986 <prgn>update-fonts-dir</prgn> on each directory into
8987 which they installed fonts. This invocation must
8988 occur in both the <prgn>postinst</prgn> (for all
8989 arguments) and <prgn>postrm</prgn> (for all
8990 arguments except <tt>upgrade</tt>) scripts.
8994 Font packages must not provide alias names for the
8995 fonts they include which collide with alias names
8996 already in use by fonts already packaged.
9000 Font packages must not provide fonts with the same
9001 XLFD registry name as another font already packaged.
9007 <sect1 id="appdefaults">
9008 <heading>Application defaults files</heading>
9011 Application defaults files must be installed in the
9012 directory <file>/etc/X11/app-defaults/</file> (use of a
9013 localized subdirectory of <file>/etc/X11/</file> as described
9014 in the <em>X Toolkit Intrinsics - C Language
9015 Interface</em> manual is also permitted). They must be
9016 registered as <tt>conffile</tt>s or handled as
9017 configuration files.
9021 Customization of programs' X resources may also be
9022 supported with the provision of a file with the same name
9023 as that of the package placed in
9024 the <file>/etc/X11/Xresources/</file> directory, which
9025 must be registered as a <tt>conffile</tt> or handled as a
9026 configuration file.<footnote>
9027 Note that this mechanism is not the same as using
9028 app-defaults; app-defaults are tied to the client
9029 binary on the local file system, whereas X resources
9030 are stored in the X server and affect all connecting
9037 <heading>Installation directory issues</heading>
9040 Historically, packages using the X Window System used a
9041 separate set of installation directories from other packages.
9042 This practice has been discontinued and packages using the X
9043 Window System should now generally be installed in the same
9044 directories as any other package. Specifically, packages must
9045 not install files under the <file>/usr/X11R6/</file> directory
9046 and the <file>/usr/X11R6/</file> directory hierarchy should be
9047 regarded as obsolete.
9051 Include files previously installed under
9052 <file>/usr/X11R6/include/X11/</file> should be installed into
9053 <file>/usr/include/X11/</file>. For files previously
9054 installed into subdirectories of
9055 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
9056 determine if subdirectories of <file>/usr/lib/</file> and
9057 <file>/usr/share/</file> can be used. If not, a subdirectory
9058 of <file>/usr/lib/X11/</file> should be used.
9062 Configuration files for window, display, or session managers
9063 or other applications that are tightly integrated with the X
9064 Window System may be placed in a subdirectory
9065 of <file>/etc/X11/</file> corresponding to the package name.
9066 Other X Window System applications should use
9067 the <file>/etc/</file> directory unless otherwise mandated by
9068 policy (such as for <ref id="appdefaults">).
9073 <heading>The OSF/Motif and OpenMotif libraries</heading>
9076 <em>Programs that require the non-DFSG-compliant OSF/Motif or
9077 OpenMotif libraries</em><footnote>
9078 OSF/Motif and OpenMotif are collectively referred to as
9079 "Motif" in this policy document.
9081 should be compiled against and tested with LessTif (a free
9082 re-implementation of Motif) instead. If the maintainer
9083 judges that the program or programs do not work
9084 sufficiently well with LessTif to be distributed and
9085 supported, but do so when compiled against Motif, then two
9086 versions of the package should be created; one linked
9087 statically against Motif and with <tt>-smotif</tt>
9088 appended to the package name, and one linked dynamically
9089 against Motif and with <tt>-dmotif</tt> appended to the
9094 Both Motif-linked versions are dependent
9095 upon non-DFSG-compliant software and thus cannot be
9096 uploaded to the <em>main</em> distribution; if the
9097 software is itself DFSG-compliant it may be uploaded to
9098 the <em>contrib</em> distribution. While known existing
9099 versions of Motif permit unlimited redistribution of
9100 binaries linked against the library (whether statically or
9101 dynamically), it is the package maintainer's
9102 responsibility to determine whether this is permitted by
9103 the license of the copy of Motif in their possession.
9109 <heading>Perl programs and modules</heading>
9112 Perl programs and modules should follow the current Perl policy.
9116 The Perl policy can be found in the <tt>perl-policy</tt>
9117 files in the <tt>debian-policy</tt> package.
9118 It is also available from the Debian web mirrors at
9119 <tt><url name="/doc/packaging-manuals/perl-policy/"
9120 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
9125 <heading>Emacs lisp programs</heading>
9128 Please refer to the "Debian Emacs Policy" for details of how to
9129 package emacs lisp programs.
9133 The Emacs policy is available in
9134 <file>debian-emacs-policy.gz</file> of the
9135 <package>emacsen-common</package> package.
9136 It is also available from the Debian web mirrors at
9137 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
9138 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
9143 <heading>Games</heading>
9146 The permissions on <file>/var/games</file> are mode 755, owner
9147 <tt>root</tt> and group <tt>root</tt>.
9151 Each game decides on its own security policy.</p>
9154 Games which require protected, privileged access to
9155 high-score files, saved games, etc., may be made
9156 set-<em>group</em>-id (mode 2755) and owned by
9157 <tt>root:games</tt>, and use files and directories with
9158 appropriate permissions (770 <tt>root:games</tt>, for
9159 example). They must not be made
9160 set-<em>user</em>-id, as this causes security problems. (If
9161 an attacker can subvert any set-user-id game they can
9162 overwrite the executable of any other, causing other players
9163 of these games to run a Trojan horse program. With a
9164 set-group-id game the attacker only gets access to less
9165 important game data, and if they can get at the other
9166 players' accounts at all it will take considerably more
9170 Some packages, for example some fortune cookie programs, are
9171 configured by the upstream authors to install with their
9172 data files or other static information made unreadable so
9173 that they can only be accessed through set-id programs
9174 provided. You should not do this in a Debian package: anyone can
9175 download the <file>.deb</file> file and read the data from it,
9176 so there is no point making the files unreadable. Not
9177 making the files unreadable also means that you don't have
9178 to make so many programs set-id, which reduces the risk of a
9182 As described in the FHS, binaries of games should be
9183 installed in the directory <file>/usr/games</file>. This also
9184 applies to games that use the X Window System. Manual pages
9185 for games (X and non-X games) should be installed in
9186 <file>/usr/share/man/man6</file>.</p>
9192 <heading>Documentation</heading>
9195 <heading>Manual pages</heading>
9198 You should install manual pages in <prgn>nroff</prgn> source
9199 form, in appropriate places under <file>/usr/share/man</file>.
9200 You should only use sections 1 to 9 (see the FHS for more
9201 details). You must not install a pre-formatted "cat page".
9205 Each program, utility, and function should have an
9206 associated manual page included in the same package. It is
9207 suggested that all configuration files also have a manual
9208 page included as well. Manual pages for protocols and other
9209 auxiliary things are optional.
9213 If no manual page is available, this is considered as a bug
9214 and should be reported to the Debian Bug Tracking System (the
9215 maintainer of the package is allowed to write this bug report
9216 themselves, if they so desire). Do not close the bug report
9217 until a proper man page is available.<footnote>
9218 It is not very hard to write a man page. See the
9219 <url id="http://www.schweikhardt.net/man_page_howto.html"
9220 name="Man-Page-HOWTO">,
9221 <manref name="man" section="7">, the examples
9222 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
9223 the helper program <prgn>help2man</prgn>, or the
9224 directory <file>/usr/share/doc/man-db/examples</file>.
9229 You may forward a complaint about a missing man page to the
9230 upstream authors, and mark the bug as forwarded in the
9231 Debian bug tracking system. Even though the GNU Project do
9232 not in general consider the lack of a man page to be a bug,
9233 we do; if they tell you that they don't consider it a bug
9234 you should leave the bug in our bug tracking system open
9239 Manual pages should be installed compressed using <tt>gzip -9</tt>.
9243 If one man page needs to be accessible via several names it
9244 is better to use a symbolic link than the <file>.so</file>
9245 feature, but there is no need to fiddle with the relevant
9246 parts of the upstream source to change from <file>.so</file> to
9247 symlinks: don't do it unless it's easy. You should not
9248 create hard links in the manual page directories, nor put
9249 absolute filenames in <file>.so</file> directives. The filename
9250 in a <file>.so</file> in a man page should be relative to the
9251 base of the man page tree (usually
9252 <file>/usr/share/man</file>). If you do not create any links
9253 (whether symlinks, hard links, or <tt>.so</tt> directives)
9254 in the file system to the alternate names of the man page,
9255 then you should not rely on <prgn>man</prgn> finding your
9256 man page under those names based solely on the information in
9257 the man page's header.<footnote>
9258 Supporting this in <prgn>man</prgn> often requires
9259 unreasonable processing time to find a manual page or to
9260 report that none exists, and moves knowledge into man's
9261 database that would be better left in the file system.
9262 This support is therefore deprecated and will cease to
9263 be present in the future.
9268 Manual pages in locale-specific subdirectories of
9269 <file>/usr/share/man</file> should use either UTF-8 or the usual
9270 legacy encoding for that language (normally the one corresponding
9271 to the shortest relevant locale name in
9272 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
9273 <file>/usr/share/man/fr</file> should use either UTF-8 or
9274 ISO-8859-1.<footnote>
9275 <prgn>man</prgn> will automatically detect whether UTF-8 is in
9276 use. In future, all manual pages will be required to use
9282 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
9283 included in the subdirectory name unless it indicates a
9284 significant difference in the language, as this excludes
9285 speakers of the language in other countries.<footnote>
9286 At the time of writing, Chinese and Portuguese are the main
9287 languages with such differences, so <file>pt_BR</file>,
9288 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
9293 If a localized version of a manual page is provided, it should
9294 either be up-to-date or it should be obvious to the reader that
9295 it is outdated and the original manual page should be used
9296 instead. This can be done either by a note at the beginning of
9297 the manual page or by showing the missing or changed portions in
9298 the original language instead of the target language.
9303 <heading>Info documents</heading>
9306 Info documents should be installed in <file>/usr/share/info</file>.
9307 They should be compressed with <tt>gzip -9</tt>.
9311 The <prgn>install-info</prgn> program maintains a directory of
9312 installed info documents in <file>/usr/share/info/dir</file> for
9313 the use of info readers.<footnote>
9314 It was previously necessary for packages installing info
9315 documents to run <prgn>install-info</prgn> from maintainer
9316 scripts. This is no longer necessary. The installation
9317 system now uses dpkg triggers.
9319 This file must not be included in packages. Packages containing
9320 info documents should depend on <tt>dpkg (>= 1.15.4) |
9321 install-info</tt> to ensure that the directory file is properly
9322 rebuilt during partial upgrades from Debian 5.0 (lenny) and
9327 Info documents should contain section and directory entry
9328 information in the document for the use
9329 of <prgn>install-info</prgn>. The section should be specified
9330 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
9331 space and the section of this info page. The directory entry or
9332 entries should be included between
9333 a <tt>START-INFO-DIR-ENTRY</tt> line and
9334 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
9336 INFO-DIR-SECTION Individual utilities
9337 START-INFO-DIR-ENTRY
9338 * example: (example). An example info directory entry.
9341 To determine which section to use, you should look
9342 at <file>/usr/share/info/dir</file> on your system and choose
9343 the most relevant (or create a new section if none of the
9344 current sections are relevant).<footnote>
9345 Normally, info documents are generated from Texinfo source.
9346 To include this information in the generated info document, if
9347 it is absent, add commands like:
9349 @dircategory Individual utilities
9351 * example: (example). An example info directory entry.
9354 to the Texinfo source of the document and ensure that the info
9355 documents are rebuilt from source during the package build.
9361 <heading>Additional documentation</heading>
9364 Any additional documentation that comes with the package may
9365 be installed at the discretion of the package maintainer.
9366 Plain text documentation should be installed in the directory
9367 <file>/usr/share/doc/<var>package</var></file>, where
9368 <var>package</var> is the name of the package, and
9369 compressed with <tt>gzip -9</tt> unless it is small.
9373 If a package comes with large amounts of documentation which
9374 many users of the package will not require you should create
9375 a separate binary package to contain it, so that it does not
9376 take up disk space on the machines of users who do not need
9377 or want it installed.</p>
9380 It is often a good idea to put text information files
9381 (<file>README</file>s, changelogs, and so forth) that come with
9382 the source package in <file>/usr/share/doc/<var>package</var></file>
9383 in the binary package. However, you don't need to install
9384 the instructions for building and installing the package, of
9388 Packages must not require the existence of any files in
9389 <file>/usr/share/doc/</file> in order to function
9391 The system administrator should be able to
9392 delete files in <file>/usr/share/doc/</file> without causing
9393 any programs to break.
9395 Any files that are referenced by programs but are also
9396 useful as stand alone documentation should be installed under
9397 <file>/usr/share/<var>package</var>/</file> with symbolic links from
9398 <file>/usr/share/doc/<var>package</var></file>.
9402 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9403 link to another directory in <file>/usr/share/doc</file> only if
9404 the two packages both come from the same source and the
9405 first package Depends on the second.<footnote>
9407 Please note that this does not override the section on
9408 changelog files below, so the file
9409 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
9410 must refer to the changelog for the current version of
9411 <var>package</var> in question. In practice, this means
9412 that the sources of the target and the destination of the
9413 symlink must be the same (same source package and
9420 Former Debian releases placed all additional documentation
9421 in <file>/usr/doc/<var>package</var></file>. This has been
9422 changed to <file>/usr/share/doc/<var>package</var></file>,
9423 and packages must not put documentation in the directory
9424 <file>/usr/doc/<var>package</var></file>. <footnote>
9425 At this phase of the transition, we no longer require a
9426 symbolic link in <file>/usr/doc/</file>. At a later point,
9427 policy shall change to make the symbolic links a bug.
9433 <heading>Preferred documentation formats</heading>
9436 The unification of Debian documentation is being carried out
9440 If your package comes with extensive documentation in a
9441 markup format that can be converted to various other formats
9442 you should if possible ship HTML versions in a binary
9443 package, in the directory
9444 <file>/usr/share/doc/<var>appropriate-package</var></file> or
9445 its subdirectories.<footnote>
9446 The rationale: The important thing here is that HTML
9447 docs should be available in <em>some</em> package, not
9448 necessarily in the main binary package.
9453 Other formats such as PostScript may be provided at the
9454 package maintainer's discretion.
9458 <sect id="copyrightfile">
9459 <heading>Copyright information</heading>
9462 Every package must be accompanied by a verbatim copy of its
9463 copyright information and distribution license in the file
9464 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
9465 file must neither be compressed nor be a symbolic link.
9469 In addition, the copyright file must say where the upstream
9470 sources (if any) were obtained. It should name the original
9471 authors of the package and the Debian maintainer(s) who were
9472 involved with its creation.
9476 Packages in the <em>contrib</em> or <em>non-free</em> archive
9477 areas should state in the copyright file that the package is not
9478 part of the Debian GNU/Linux distribution and briefly explain
9483 A copy of the file which will be installed in
9484 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9485 be in <file>debian/copyright</file> in the source package.
9489 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9490 link to another directory in <file>/usr/share/doc</file> only if
9491 the two packages both come from the same source and the
9492 first package Depends on the second. These rules are
9493 important because copyrights must be extractable by
9498 Packages distributed under the Apache license (version 2.0), the
9499 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
9500 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
9501 1.3) should refer to the corresponding files
9502 under <file>/usr/share/common-licenses</file>,<footnote>
9505 <file>/usr/share/common-licenses/Apache-2.0</file>,
9506 <file>/usr/share/common-licenses/Artistic</file>,
9507 <file>/usr/share/common-licenses/GPL-1</file>,
9508 <file>/usr/share/common-licenses/GPL-2</file>,
9509 <file>/usr/share/common-licenses/GPL-3</file>,
9510 <file>/usr/share/common-licenses/LGPL-2</file>,
9511 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9512 <file>/usr/share/common-licenses/LGPL-3</file>,
9513 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
9514 <file>/usr/share/common-licenses/GFDL-1.3</file>
9515 respectively. The University of California BSD license is
9516 also included in <package>base-files</package> as
9517 <file>/usr/share/common-licenses/BSD</file>, but given the
9518 brevity of this license, its specificity to code whose
9519 copyright is held by the Regents of the University of
9520 California, and the frequency of minor wording changes, its
9521 text should be included in the copyright file rather than
9522 referencing this file.
9524 </footnote> rather than quoting them in the copyright
9529 You should not use the copyright file as a general <file>README</file>
9530 file. If your package has such a file it should be
9531 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9532 <file>README.Debian</file> or some other appropriate place.</p>
9536 <heading>Examples</heading>
9539 Any examples (configurations, source files, whatever),
9540 should be installed in a directory
9541 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9542 files should not be referenced by any program: they're there
9543 for the benefit of the system administrator and users as
9544 documentation only. Architecture-specific example files
9545 should be installed in a directory
9546 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9548 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9549 latter directory itself may be a symbolic link to the
9554 If the purpose of a package is to provide examples, then the
9555 example files may be installed into
9556 <file>/usr/share/doc/<var>package</var></file>.
9560 <sect id="changelogs">
9561 <heading>Changelog files</heading>
9564 Packages that are not Debian-native must contain a
9565 compressed copy of the <file>debian/changelog</file> file from
9566 the Debian source tree in
9567 <file>/usr/share/doc/<var>package</var></file> with the name
9568 <file>changelog.Debian.gz</file>.
9572 If an upstream changelog is available, it should be accessible as
9573 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9574 plain text. If the upstream changelog is distributed in
9575 HTML, it should be made available in that form as
9576 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9577 and a plain text <file>changelog.gz</file> should be generated
9578 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9579 the upstream changelog files do not already conform to this
9580 naming convention, then this may be achieved either by
9581 renaming the files, or by adding a symbolic link, at the
9582 maintainer's discretion.<footnote>
9583 Rationale: People should not have to look in places for
9584 upstream changelogs merely because they are given
9585 different names or are distributed in HTML format.
9590 All of these files should be installed compressed using
9591 <tt>gzip -9</tt>, as they will become large with time even
9592 if they start out small.
9596 If the package has only one changelog which is used both as
9597 the Debian changelog and the upstream one because there is
9598 no separate upstream maintainer then that changelog should
9599 usually be installed as
9600 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9601 there is a separate upstream maintainer, but no upstream
9602 changelog, then the Debian changelog should still be called
9603 <file>changelog.Debian.gz</file>.
9607 For details about the format and contents of the Debian
9608 changelog file, please see <ref id="dpkgchangelog">.
9613 <appendix id="pkg-scope">
9614 <heading>Introduction and scope of these appendices</heading>
9617 These appendices are taken essentially verbatim from the
9618 now-deprecated Packaging Manual, version 3.2.1.0. They are
9619 the chapters which are likely to be of use to package
9620 maintainers and which have not already been included in the
9621 policy document itself. Most of these sections are very likely
9622 not relevant to policy; they should be treated as
9623 documentation for the packaging system. Please note that these
9624 appendices are included for convenience, and for historical
9625 reasons: they used to be part of policy package, and they have
9626 not yet been incorporated into dpkg documentation. However,
9627 they still have value, and hence they are presented here.
9631 They have not yet been checked to ensure that they are
9632 compatible with the contents of policy, and if there are any
9633 contradictions, the version in the main policy document takes
9634 precedence. The remaining chapters of the old Packaging
9635 Manual have also not been read in detail to ensure that there
9636 are not parts which have been left out. Both of these will be
9641 Certain parts of the Packaging manual were integrated into the
9642 Policy Manual proper, and removed from the appendices. Links
9643 have been placed from the old locations to the new ones.
9647 <prgn>dpkg</prgn> is a suite of programs for creating binary
9648 package files and installing and removing them on Unix
9650 <prgn>dpkg</prgn> is targeted primarily at Debian
9651 GNU/Linux, but may work on or be ported to other
9657 The binary packages are designed for the management of
9658 installed executable programs (usually compiled binaries) and
9659 their associated data, though source code examples and
9660 documentation are provided as part of some packages.</p>
9663 This manual describes the technical aspects of creating Debian
9664 binary packages (<file>.deb</file> files). It documents the
9665 behavior of the package management programs
9666 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9667 they interact with packages.</p>
9670 It also documents the interaction between
9671 <prgn>dselect</prgn>'s core and the access method scripts it
9672 uses to actually install the selected packages, and describes
9673 how to create a new access method.</p>
9676 This manual does not go into detail about the options and
9677 usage of the package building and installation tools. It
9678 should therefore be read in conjunction with those programs'
9683 The utility programs which are provided with <prgn>dpkg</prgn>
9684 for managing various system configuration and similar issues,
9685 such as <prgn>update-rc.d</prgn> and
9686 <prgn>install-info</prgn>, are not described in detail here -
9687 please see their man pages.
9691 It is assumed that the reader is reasonably familiar with the
9692 <prgn>dpkg</prgn> System Administrators' manual.
9693 Unfortunately this manual does not yet exist.
9697 The Debian version of the FSF's GNU hello program is provided
9698 as an example for people wishing to create Debian
9699 packages. The Debian <prgn>debmake</prgn> package is
9700 recommended as a very helpful tool in creating and maintaining
9701 Debian packages. However, while the tools and examples are
9702 helpful, they do not replace the need to read and follow the
9703 Policy and Programmer's Manual.</p>
9706 <appendix id="pkg-binarypkg">
9707 <heading>Binary packages (from old Packaging Manual)</heading>
9710 The binary package has two main sections. The first part
9711 consists of various control information files and scripts used
9712 by <prgn>dpkg</prgn> when installing and removing. See <ref
9713 id="pkg-controlarea">.
9717 The second part is an archive containing the files and
9718 directories to be installed.
9722 In the future binary packages may also contain other
9723 components, such as checksums and digital signatures. The
9724 format for the archive is described in full in the
9725 <file>deb(5)</file> man page.
9729 <sect id="pkg-bincreating"><heading>Creating package files -
9730 <prgn>dpkg-deb</prgn>
9734 All manipulation of binary package files is done by
9735 <prgn>dpkg-deb</prgn>; it's the only program that has
9736 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9737 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9738 will spot that the options requested are appropriate to
9739 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9744 In order to create a binary package you must make a
9745 directory tree which contains all the files and directories
9746 you want to have in the file system data part of the package.
9747 In Debian-format source packages this directory is usually
9748 <file>debian/tmp</file>, relative to the top of the package's
9753 They should have the locations (relative to the root of the
9754 directory tree you're constructing) ownerships and
9755 permissions which you want them to have on the system when
9760 With current versions of <prgn>dpkg</prgn> the uid/username
9761 and gid/groupname mappings for the users and groups being
9762 used should be the same on the system where the package is
9763 built and the one where it is installed.
9767 You need to add one special directory to the root of the
9768 miniature file system tree you're creating:
9769 <prgn>DEBIAN</prgn>. It should contain the control
9770 information files, notably the binary package control file
9771 (see <ref id="pkg-controlfile">).
9775 The <prgn>DEBIAN</prgn> directory will not appear in the
9776 file system archive of the package, and so won't be installed
9777 by <prgn>dpkg</prgn> when the package is installed.
9781 When you've prepared the package, you should invoke:
9783 dpkg --build <var>directory</var>
9788 This will build the package in
9789 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9790 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9791 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9796 See the man page <manref name="dpkg-deb" section="8"> for details of how
9797 to examine the contents of this newly-created file. You may find the
9798 output of following commands enlightening:
9800 dpkg-deb --info <var>filename</var>.deb
9801 dpkg-deb --contents <var>filename</var>.deb
9802 dpkg --contents <var>filename</var>.deb
9804 To view the copyright file for a package you could use this command:
9806 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
9811 <sect id="pkg-controlarea">
9812 <heading>Package control information files</heading>
9815 The control information portion of a binary package is a
9816 collection of files with names known to <prgn>dpkg</prgn>.
9817 It will treat the contents of these files specially - some
9818 of them contain information used by <prgn>dpkg</prgn> when
9819 installing or removing the package; others are scripts which
9820 the package maintainer wants <prgn>dpkg</prgn> to run.
9824 It is possible to put other files in the package control
9825 information file area, but this is not generally a good idea
9826 (though they will largely be ignored).
9830 Here is a brief list of the control information files supported
9831 by <prgn>dpkg</prgn> and a summary of what they're used for.
9836 <tag><tt>control</tt>
9839 This is the key description file used by
9840 <prgn>dpkg</prgn>. It specifies the package's name
9841 and version, gives its description for the user,
9842 states its relationships with other packages, and so
9843 forth. See <ref id="sourcecontrolfiles"> and
9844 <ref id="binarycontrolfiles">.
9848 It is usually generated automatically from information
9849 in the source package by the
9850 <prgn>dpkg-gencontrol</prgn> program, and with
9851 assistance from <prgn>dpkg-shlibdeps</prgn>.
9852 See <ref id="pkg-sourcetools">.
9856 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9861 These are executable files (usually scripts) which
9862 <prgn>dpkg</prgn> runs during installation, upgrade
9863 and removal of packages. They allow the package to
9864 deal with matters which are particular to that package
9865 or require more complicated processing than that
9866 provided by <prgn>dpkg</prgn>. Details of when and
9867 how they are called are in <ref id="maintainerscripts">.
9871 It is very important to make these scripts idempotent.
9872 See <ref id="idempotency">.
9876 The maintainer scripts are not guaranteed to run with a
9877 controlling terminal and may not be able to interact with
9878 the user. See <ref id="controllingterminal">.
9882 <tag><tt>conffiles</tt>
9885 This file contains a list of configuration files which
9886 are to be handled automatically by <prgn>dpkg</prgn>
9887 (see <ref id="pkg-conffiles">). Note that not necessarily
9888 every configuration file should be listed here.
9891 <tag><tt>shlibs</tt>
9894 This file contains a list of the shared libraries
9895 supplied by the package, with dependency details for
9896 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9897 when it determines what dependencies are required in a
9898 package control file. The <tt>shlibs</tt> file format
9899 is described on <ref id="shlibs">.
9904 <sect id="pkg-controlfile">
9905 <heading>The main control information file: <tt>control</tt></heading>
9908 The most important control information file used by
9909 <prgn>dpkg</prgn> when it installs a package is
9910 <tt>control</tt>. It contains all the package's "vital
9915 The binary package control files of packages built from
9916 Debian sources are made by a special tool,
9917 <prgn>dpkg-gencontrol</prgn>, which reads
9918 <file>debian/control</file> and <file>debian/changelog</file> to
9919 find the information it needs. See <ref id="pkg-sourcepkg"> for
9924 The fields in binary package control files are listed in
9925 <ref id="binarycontrolfiles">.
9929 A description of the syntax of control files and the purpose
9930 of the fields is available in <ref id="controlfields">.
9935 <heading>Time Stamps</heading>
9938 See <ref id="timestamps">.
9943 <appendix id="pkg-sourcepkg">
9944 <heading>Source packages (from old Packaging Manual) </heading>
9947 The Debian binary packages in the distribution are generated
9948 from Debian sources, which are in a special format to assist
9949 the easy and automatic building of binaries.
9952 <sect id="pkg-sourcetools">
9953 <heading>Tools for processing source packages</heading>
9956 Various tools are provided for manipulating source packages;
9957 they pack and unpack sources and help build of binary
9958 packages and help manage the distribution of new versions.
9962 They are introduced and typical uses described here; see
9963 <manref name="dpkg-source" section="1"> for full
9964 documentation about their arguments and operation.
9968 For examples of how to construct a Debian source package,
9969 and how to use those utilities that are used by Debian
9970 source packages, please see the <prgn>hello</prgn> example
9974 <sect1 id="pkg-dpkg-source">
9976 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9981 This program is frequently used by hand, and is also
9982 called from package-independent automated building scripts
9983 such as <prgn>dpkg-buildpackage</prgn>.
9987 To unpack a package it is typically invoked with
9989 dpkg-source -x <var>.../path/to/filename</var>.dsc
9994 with the <file><var>filename</var>.tar.gz</file> and
9995 <file><var>filename</var>.diff.gz</file> (if applicable) in
9996 the same directory. It unpacks into
9997 <file><var>package</var>-<var>version</var></file>, and if
9999 <file><var>package</var>-<var>version</var>.orig</file>, in
10000 the current directory.
10004 To create a packed source archive it is typically invoked:
10006 dpkg-source -b <var>package</var>-<var>version</var>
10011 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
10012 <file>.diff.gz</file> (if appropriate) in the current
10013 directory. <prgn>dpkg-source</prgn> does not clean the
10014 source tree first - this must be done separately if it is
10019 See also <ref id="pkg-sourcearchives">.</p>
10023 <sect1 id="pkg-dpkg-buildpackage">
10025 <prgn>dpkg-buildpackage</prgn> - overall package-building
10030 <prgn>dpkg-buildpackage</prgn> is a script which invokes
10031 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
10032 targets <tt>clean</tt>, <tt>build</tt> and
10033 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
10034 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
10035 source and binary package upload.
10039 It is usually invoked by hand from the top level of the
10040 built or unbuilt source directory. It may be invoked with
10041 no arguments; useful arguments include:
10042 <taglist compact="compact">
10043 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
10046 Do not sign the <tt>.changes</tt> file or the
10047 source package <tt>.dsc</tt> file, respectively.</p>
10049 <tag><tt>-p<var>sign-command</var></tt></tag>
10052 Invoke <var>sign-command</var> instead of finding
10053 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
10054 <var>sign-command</var> must behave just like
10055 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
10057 <tag><tt>-r<var>root-command</var></tt></tag>
10060 When root privilege is required, invoke the command
10061 <var>root-command</var>. <var>root-command</var>
10062 should invoke its first argument as a command, from
10063 the <prgn>PATH</prgn> if necessary, and pass its
10064 second and subsequent arguments to the command it
10065 calls. If no <var>root-command</var> is supplied
10066 then <var>dpkg-buildpackage</var> will take no
10067 special action to gain root privilege, so that for
10068 most packages it will have to be invoked as root to
10071 <tag><tt>-b</tt>, <tt>-B</tt></tag>
10074 Two types of binary-only build and upload - see
10075 <manref name="dpkg-source" section="1">.
10082 <sect1 id="pkg-dpkg-gencontrol">
10084 <prgn>dpkg-gencontrol</prgn> - generates binary package
10089 This program is usually called from <file>debian/rules</file>
10090 (see <ref id="pkg-sourcetree">) in the top level of the source
10095 This is usually done just before the files and directories in the
10096 temporary directory tree where the package is being built have their
10097 permissions and ownerships set and the package is constructed using
10098 <prgn>dpkg-deb/</prgn>
10100 This is so that the control file which is produced has
10101 the right permissions
10106 <prgn>dpkg-gencontrol</prgn> must be called after all the
10107 files which are to go into the package have been placed in
10108 the temporary build directory, so that its calculation of
10109 the installed size of a package is correct.
10113 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
10114 be run after <prgn>dpkg-shlibdeps</prgn> so that the
10115 variable substitutions created by
10116 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
10121 For a package which generates only one binary package, and
10122 which builds it in <file>debian/tmp</file> relative to the top
10123 of the source package, it is usually sufficient to call
10124 <prgn>dpkg-gencontrol</prgn>.
10128 Sources which build several binaries will typically need
10131 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
10132 </example> The <tt>-P</tt> tells
10133 <prgn>dpkg-gencontrol</prgn> that the package is being
10134 built in a non-default directory, and the <tt>-p</tt>
10135 tells it which package's control file should be generated.
10139 <prgn>dpkg-gencontrol</prgn> also adds information to the
10140 list of files in <file>debian/files</file>, for the benefit of
10141 (for example) a future invocation of
10142 <prgn>dpkg-genchanges</prgn>.</p>
10145 <sect1 id="pkg-dpkg-shlibdeps">
10147 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
10152 This program is usually called from <file>debian/rules</file>
10153 just before <prgn>dpkg-gencontrol</prgn> (see <ref
10154 id="pkg-sourcetree">), in the top level of the source tree.
10158 Its arguments are executables and shared libraries
10161 They may be specified either in the locations in the
10162 source tree where they are created or in the locations
10163 in the temporary build tree where they are installed
10164 prior to binary package creation.
10166 </footnote> for which shared library dependencies should
10167 be included in the binary package's control file.
10171 If some of the found shared libraries should only
10172 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
10173 some warrant a <tt>Pre-Depends</tt>, this can be achieved
10174 by using the <tt>-d<var>dependency-field</var></tt> option
10175 before those executable(s). (Each <tt>-d</tt> option
10176 takes effect until the next <tt>-d</tt>.)
10180 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
10181 output control file to be modified. Instead by default it
10182 adds to the <file>debian/substvars</file> file variable
10183 settings like <tt>shlibs:Depends</tt>. These variable
10184 settings must be referenced in dependency fields in the
10185 appropriate per-binary-package sections of the source
10190 For example, a package that generates an essential part
10191 which requires dependencies, and optional parts that
10192 which only require a recommendation, would separate those
10193 two sets of dependencies into two different fields.<footnote>
10194 At the time of writing, an example for this was the
10195 <package/xmms/ package, with Depends used for the xmms
10196 executable, Recommends for the plug-ins and Suggests for
10197 even more optional features provided by unzip.
10199 It can say in its <file>debian/rules</file>:
10201 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
10202 -dRecommends <var>optionalpart anotheroptionalpart</var>
10204 and then in its main control file <file>debian/control</file>:
10207 Depends: ${shlibs:Depends}
10208 Recommends: ${shlibs:Recommends}
10214 Sources which produce several binary packages with
10215 different shared library dependency requirements can use
10216 the <tt>-p<var>varnameprefix</var></tt> option to override
10217 the default <tt>shlibs:</tt> prefix (one invocation of
10218 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
10219 They can thus produce several sets of dependency
10220 variables, each of the form
10221 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
10222 which can be referred to in the appropriate parts of the
10223 binary package control files.
10228 <sect1 id="pkg-dpkg-distaddfile">
10230 <prgn>dpkg-distaddfile</prgn> - adds a file to
10231 <file>debian/files</file>
10235 Some packages' uploads need to include files other than
10236 the source and binary package files.
10240 <prgn>dpkg-distaddfile</prgn> adds a file to the
10241 <file>debian/files</file> file so that it will be included in
10242 the <file>.changes</file> file when
10243 <prgn>dpkg-genchanges</prgn> is run.
10247 It is usually invoked from the <tt>binary</tt> target of
10248 <file>debian/rules</file>:
10250 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
10252 The <var>filename</var> is relative to the directory where
10253 <prgn>dpkg-genchanges</prgn> will expect to find it - this
10254 is usually the directory above the top level of the source
10255 tree. The <file>debian/rules</file> target should put the
10256 file there just before or just after calling
10257 <prgn>dpkg-distaddfile</prgn>.
10261 The <var>section</var> and <var>priority</var> are passed
10262 unchanged into the resulting <file>.changes</file> file.
10267 <sect1 id="pkg-dpkg-genchanges">
10269 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
10270 upload control file
10274 This program is usually called by package-independent
10275 automatic building scripts such as
10276 <prgn>dpkg-buildpackage</prgn>, but it may also be called
10281 It is usually called in the top level of a built source
10282 tree, and when invoked with no arguments will print out a
10283 straightforward <file>.changes</file> file based on the
10284 information in the source package's changelog and control
10285 file and the binary and source packages which should have
10291 <sect1 id="pkg-dpkg-parsechangelog">
10293 <prgn>dpkg-parsechangelog</prgn> - produces parsed
10294 representation of a changelog
10298 This program is used internally by
10299 <prgn>dpkg-source</prgn> et al. It may also occasionally
10300 be useful in <file>debian/rules</file> and elsewhere. It
10301 parses a changelog, <file>debian/changelog</file> by default,
10302 and prints a control-file format representation of the
10303 information in it to standard output.
10307 <sect1 id="pkg-dpkg-architecture">
10309 <prgn>dpkg-architecture</prgn> - information about the build and
10314 This program can be used manually, but is also invoked by
10315 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
10316 environment or make variables which specify the build and host
10317 architecture for the package building process.
10322 <sect id="pkg-sourcetree">
10323 <heading>The Debian package source tree</heading>
10326 The source archive scheme described later is intended to
10327 allow a Debian package source tree with some associated
10328 control information to be reproduced and transported easily.
10329 The Debian package source tree is a version of the original
10330 program with certain files added for the benefit of the
10331 packaging process, and with any other changes required
10332 made to the rest of the source code and installation
10337 The extra files created for Debian are in the subdirectory
10338 <file>debian</file> of the top level of the Debian package
10339 source tree. They are described below.
10342 <sect1 id="pkg-debianrules">
10343 <heading><file>debian/rules</file> - the main building script</heading>
10346 See <ref id="debianrules">.
10350 <sect1 id="pkg-srcsubstvars">
10351 <heading><file>debian/substvars</file> and variable substitutions</heading>
10354 See <ref id="substvars">.
10360 <heading><file>debian/files</file></heading>
10363 See <ref id="debianfiles">.
10367 <sect1><heading><file>debian/tmp</file>
10371 This is the canonical temporary location for the
10372 construction of binary packages by the <tt>binary</tt>
10373 target. The directory <file>tmp</file> serves as the root of
10374 the file system tree as it is being constructed (for
10375 example, by using the package's upstream makefiles install
10376 targets and redirecting the output there), and it also
10377 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10378 id="pkg-bincreating">.
10382 If several binary packages are generated from the same
10383 source tree it is usual to use several
10384 <file>debian/tmp<var>something</var></file> directories, for
10385 example <file>tmp-a</file> or <file>tmp-doc</file>.
10389 Whatever <file>tmp</file> directories are created and used by
10390 <tt>binary</tt> must of course be removed by the
10391 <tt>clean</tt> target.</p></sect1>
10395 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10399 As it exists on the FTP site, a Debian source package
10400 consists of three related files. You must have the right
10401 versions of all three to be able to use them.
10406 <tag>Debian source control file - <tt>.dsc</tt></tag>
10408 This file is a control file used by <prgn>dpkg-source</prgn>
10409 to extract a source package.
10410 See <ref id="debiansourcecontrolfiles">.
10414 Original source archive -
10416 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10422 This is a compressed (with <tt>gzip -9</tt>)
10423 <prgn>tar</prgn> file containing the source code from
10424 the upstream authors of the program.
10429 Debian package diff -
10431 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10437 This is a unified context diff (<tt>diff -u</tt>)
10438 giving the changes which are required to turn the
10439 original source into the Debian source. These changes
10440 may only include editing and creating plain files.
10441 The permissions of files, the targets of symbolic
10442 links and the characteristics of special files or
10443 pipes may not be changed and no files may be removed
10448 All the directories in the diff must exist, except the
10449 <file>debian</file> subdirectory of the top of the source
10450 tree, which will be created by
10451 <prgn>dpkg-source</prgn> if necessary when unpacking.
10455 The <prgn>dpkg-source</prgn> program will
10456 automatically make the <file>debian/rules</file> file
10457 executable (see below).</p></item>
10462 If there is no original source code - for example, if the
10463 package is specially prepared for Debian or the Debian
10464 maintainer is the same as the upstream maintainer - the
10465 format is slightly different: then there is no diff, and the
10467 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10468 and preferably contains a directory named
10469 <file><var>package</var>-<var>version</var></file>.
10474 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10477 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10478 Debian source package. However, if it is not available it
10479 is possible to unpack a Debian source archive as follows:
10480 <enumlist compact="compact">
10483 Untar the tarfile, which will create a <file>.orig</file>
10487 <p>Rename the <file>.orig</file> directory to
10488 <file><var>package</var>-<var>version</var></file>.</p>
10492 Create the subdirectory <file>debian</file> at the top of
10493 the source tree.</p>
10495 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10497 <item><p>Untar the tarfile again if you want a copy of the original
10498 source code alongside the Debian version.</p>
10503 It is not possible to generate a valid Debian source archive
10504 without using <prgn>dpkg-source</prgn>. In particular,
10505 attempting to use <prgn>diff</prgn> directly to generate the
10506 <file>.diff.gz</file> file will not work.
10510 <heading>Restrictions on objects in source packages</heading>
10513 The source package may not contain any hard links
10515 This is not currently detected when building source
10516 packages, but only when extracting
10520 Hard links may be permitted at some point in the
10521 future, but would require a fair amount of
10523 </footnote>, device special files, sockets or setuid or
10526 Setgid directories are allowed.
10531 The source packaging tools manage the changes between the
10532 original and Debian source using <prgn>diff</prgn> and
10533 <prgn>patch</prgn>. Turning the original source tree as
10534 included in the <file>.orig.tar.gz</file> into the Debian
10535 package source must not involve any changes which cannot be
10536 handled by these tools. Problematic changes which cause
10537 <prgn>dpkg-source</prgn> to halt with an error when
10538 building the source package are:
10539 <list compact="compact">
10540 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10542 <item><p>Changing the targets of symbolic links.</p>
10544 <item><p>Creating directories, other than <file>debian</file>.</p>
10546 <item><p>Changes to the contents of binary files.</p></item>
10547 </list> Changes which cause <prgn>dpkg-source</prgn> to
10548 print a warning but continue anyway are:
10549 <list compact="compact">
10552 Removing files, directories or symlinks.
10554 Renaming a file is not treated specially - it is
10555 seen as the removal of the old file (which
10556 generates a warning, but is otherwise ignored),
10557 and the creation of the new one.
10563 Changed text files which are missing the usual final
10564 newline (either in the original or the modified
10569 Changes which are not represented, but which are not detected by
10570 <prgn>dpkg-source</prgn>, are:
10571 <list compact="compact">
10572 <item><p>Changing the permissions of files (other than
10573 <file>debian/rules</file>) and directories.</p></item>
10578 The <file>debian</file> directory and <file>debian/rules</file>
10579 are handled specially by <prgn>dpkg-source</prgn> - before
10580 applying the changes it will create the <file>debian</file>
10581 directory, and afterwards it will make
10582 <file>debian/rules</file> world-executable.
10588 <appendix id="pkg-controlfields">
10589 <heading>Control files and their fields (from old Packaging Manual)</heading>
10592 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10593 data in a common format, known as control files. Binary and
10594 source packages have control data as do the <file>.changes</file>
10595 files which control the installation of uploaded files, and
10596 <prgn>dpkg</prgn>'s internal databases are in a similar
10601 <heading>Syntax of control files</heading>
10604 See <ref id="controlsyntax">.
10608 It is important to note that there are several fields which
10609 are optional as far as <prgn>dpkg</prgn> and the related
10610 tools are concerned, but which must appear in every Debian
10611 package, or whose omission may cause problems.
10616 <heading>List of fields</heading>
10619 See <ref id="controlfieldslist">.
10623 This section now contains only the fields that didn't belong
10624 to the Policy manual.
10627 <sect1 id="pkg-f-Filename">
10628 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10631 These fields in <tt>Packages</tt> files give the
10632 filename(s) of (the parts of) a package in the
10633 distribution directories, relative to the root of the
10634 Debian hierarchy. If the package has been split into
10635 several parts the parts are all listed in order, separated
10640 <sect1 id="pkg-f-Size">
10641 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10644 These fields in <file>Packages</file> files give the size (in
10645 bytes, expressed in decimal) and MD5 checksum of the
10646 file(s) which make(s) up a binary package in the
10647 distribution. If the package is split into several parts
10648 the values for the parts are listed in order, separated by
10653 <sect1 id="pkg-f-Status">
10654 <heading><tt>Status</tt></heading>
10657 This field in <prgn>dpkg</prgn>'s status file records
10658 whether the user wants a package installed, removed or
10659 left alone, whether it is broken (requiring
10660 re-installation) or not and what its current state on the
10661 system is. Each of these pieces of information is a
10666 <sect1 id="pkg-f-Config-Version">
10667 <heading><tt>Config-Version</tt></heading>
10670 If a package is not installed or not configured, this
10671 field in <prgn>dpkg</prgn>'s status file records the last
10672 version of the package which was successfully
10677 <sect1 id="pkg-f-Conffiles">
10678 <heading><tt>Conffiles</tt></heading>
10681 This field in <prgn>dpkg</prgn>'s status file contains
10682 information about the automatically-managed configuration
10683 files held by a package. This field should <em>not</em>
10684 appear anywhere in a package!
10689 <heading>Obsolete fields</heading>
10692 These are still recognized by <prgn>dpkg</prgn> but should
10693 not appear anywhere any more.
10695 <taglist compact="compact">
10697 <tag><tt>Revision</tt></tag>
10698 <tag><tt>Package-Revision</tt></tag>
10699 <tag><tt>Package_Revision</tt></tag>
10701 The Debian revision part of the package version was
10702 at one point in a separate control field. This
10703 field went through several names.
10706 <tag><tt>Recommended</tt></tag>
10707 <item>Old name for <tt>Recommends</tt>.</item>
10709 <tag><tt>Optional</tt></tag>
10710 <item>Old name for <tt>Suggests</tt>.</item>
10712 <tag><tt>Class</tt></tag>
10713 <item>Old name for <tt>Priority</tt>.</item>
10722 <appendix id="pkg-conffiles">
10723 <heading>Configuration file handling (from old Packaging Manual)</heading>
10726 <prgn>dpkg</prgn> can do a certain amount of automatic
10727 handling of package configuration files.
10731 Whether this mechanism is appropriate depends on a number of
10732 factors, but basically there are two approaches to any
10733 particular configuration file.
10737 The easy method is to ship a best-effort configuration in the
10738 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10739 handle updates. If the user is unlikely to want to edit the
10740 file, but you need them to be able to without losing their
10741 changes, and a new package with a changed version of the file
10742 is only released infrequently, this is a good approach.
10746 The hard method is to build the configuration file from
10747 scratch in the <prgn>postinst</prgn> script, and to take the
10748 responsibility for fixing any mistakes made in earlier
10749 versions of the package automatically. This will be
10750 appropriate if the file is likely to need to be different on
10754 <sect><heading>Automatic handling of configuration files by
10759 A package may contain a control information file called
10760 <tt>conffiles</tt>. This file should be a list of filenames
10761 of configuration files needing automatic handling, separated
10762 by newlines. The filenames should be absolute pathnames,
10763 and the files referred to should actually exist in the
10768 When a package is upgraded <prgn>dpkg</prgn> will process
10769 the configuration files during the configuration stage,
10770 shortly before it runs the package's <prgn>postinst</prgn>
10775 For each file it checks to see whether the version of the
10776 file included in the package is the same as the one that was
10777 included in the last version of the package (the one that is
10778 being upgraded from); it also compares the version currently
10779 installed on the system with the one shipped with the last
10784 If neither the user nor the package maintainer has changed
10785 the file, it is left alone. If one or the other has changed
10786 their version, then the changed version is preferred - i.e.,
10787 if the user edits their file, but the package maintainer
10788 doesn't ship a different version, the user's changes will
10789 stay, silently, but if the maintainer ships a new version
10790 and the user hasn't edited it the new version will be
10791 installed (with an informative message). If both have
10792 changed their version the user is prompted about the problem
10793 and must resolve the differences themselves.
10797 The comparisons are done by calculating the MD5 message
10798 digests of the files, and storing the MD5 of the file as it
10799 was included in the most recent version of the package.
10803 When a package is installed for the first time
10804 <prgn>dpkg</prgn> will install the file that comes with it,
10805 unless that would mean overwriting a file already on the
10810 However, note that <prgn>dpkg</prgn> will <em>not</em>
10811 replace a conffile that was removed by the user (or by a
10812 script). This is necessary because with some programs a
10813 missing file produces an effect hard or impossible to
10814 achieve in another way, so that a missing file needs to be
10815 kept that way if the user did it.
10819 Note that a package should <em>not</em> modify a
10820 <prgn>dpkg</prgn>-handled conffile in its maintainer
10821 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10822 the user confusing and possibly dangerous options for
10823 conffile update when the package is upgraded.</p>
10826 <sect><heading>Fully-featured maintainer script configuration
10831 For files which contain site-specific information such as
10832 the hostname and networking details and so forth, it is
10833 better to create the file in the package's
10834 <prgn>postinst</prgn> script.
10838 This will typically involve examining the state of the rest
10839 of the system to determine values and other information, and
10840 may involve prompting the user for some information which
10841 can't be obtained some other way.
10845 When using this method there are a couple of important
10846 issues which should be considered:
10850 If you discover a bug in the program which generates the
10851 configuration file, or if the format of the file changes
10852 from one version to the next, you will have to arrange for
10853 the postinst script to do something sensible - usually this
10854 will mean editing the installed configuration file to remove
10855 the problem or change the syntax. You will have to do this
10856 very carefully, since the user may have changed the file,
10857 perhaps to fix the very problem that your script is trying
10858 to deal with - you will have to detect these situations and
10859 deal with them correctly.
10863 If you do go down this route it's probably a good idea to
10864 make the program that generates the configuration file(s) a
10865 separate program in <file>/usr/sbin</file>, by convention called
10866 <file><var>package</var>config</file> and then run that if
10867 appropriate from the post-installation script. The
10868 <tt><var>package</var>config</tt> program should not
10869 unquestioningly overwrite an existing configuration - if its
10870 mode of operation is geared towards setting up a package for
10871 the first time (rather than any arbitrary reconfiguration
10872 later) you should have it check whether the configuration
10873 already exists, and require a <tt>--force</tt> flag to
10874 overwrite it.</p></sect>
10877 <appendix id="pkg-alternatives"><heading>Alternative versions of
10878 an interface - <prgn>update-alternatives</prgn> (from old
10883 When several packages all provide different versions of the
10884 same program or file it is useful to have the system select a
10885 default, but to allow the system administrator to change it
10886 and have their decisions respected.
10890 For example, there are several versions of the <prgn>vi</prgn>
10891 editor, and there is no reason to prevent all of them from
10892 being installed at once, each under their own name
10893 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10894 Nevertheless it is desirable to have the name <tt>vi</tt>
10895 refer to something, at least by default.
10899 If all the packages involved cooperate, this can be done with
10900 <prgn>update-alternatives</prgn>.
10904 Each package provides its own version under its own name, and
10905 calls <prgn>update-alternatives</prgn> in its postinst to
10906 register its version (and again in its prerm to deregister
10911 See the man page <manref name="update-alternatives"
10912 section="8"> for details.
10916 If <prgn>update-alternatives</prgn> does not seem appropriate
10917 you may wish to consider using diversions instead.</p>
10920 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10921 package's version of a file (from old Packaging Manual)
10925 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10926 when it reinstalls the package it belongs to, and to have it
10927 put the file from the package somewhere else instead.
10931 This can be used locally to override a package's version of a
10932 file, or by one package to override another's version (or
10933 provide a wrapper for it).
10937 Before deciding to use a diversion, read <ref
10938 id="pkg-alternatives"> to see if you really want a diversion
10939 rather than several alternative versions of a program.
10943 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10944 and updated by a special program <prgn>dpkg-divert</prgn>.
10945 Please see <manref name="dpkg-divert" section="8"> for full
10946 details of its operation.
10950 When a package wishes to divert a file from another, it should
10951 call <prgn>dpkg-divert</prgn> in its preinst to add the
10952 diversion and rename the existing file. For example,
10953 supposing that a <prgn>smailwrapper</prgn> package wishes to
10954 install a wrapper around <file>/usr/sbin/smail</file>:
10956 dpkg-divert --package smailwrapper --add --rename \
10957 --divert /usr/sbin/smail.real /usr/sbin/smail
10958 </example> The <tt>--package smailwrapper</tt> ensures that
10959 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
10960 can bypass the diversion and get installed as the true version.
10961 It's safe to add the diversion unconditionally on upgrades since
10962 it will be left unchanged if it already exists, but
10963 <prgn>dpkg-divert</prgn> will display a message. To suppress that
10964 message, make the command conditional on the version from which
10965 the package is being upgraded:
10967 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
10968 dpkg-divert --package smailwrapper --add --rename \
10969 --divert /usr/sbin/smail.real /usr/sbin/smail
10971 </example> where <tt>1.0-2</tt> is the version at which the
10972 diversion was first added to the package. Running the command
10973 during abort-upgrade is pointless but harmless.
10977 The postrm has to do the reverse:
10979 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
10980 dpkg-divert --package smailwrapper --remove --rename \
10981 --divert /usr/sbin/smail.real /usr/sbin/smail
10983 </example> If the diversion was added at a particular version, the
10984 postrm should also handle the failure case of upgrading from an
10985 older version (unless the older version is so old that direct
10986 upgrades are no longer supported):
10988 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
10989 dpkg-divert --package smailwrapper --remove --rename \
10990 --divert /usr/sbin/smail.real /usr/sbin/smail
10992 </example> where <tt>1.02-2</tt> is the version at which the
10993 diversion was first added to the package. The postrm should not
10994 remove the diversion on upgrades both because there's no reason to
10995 remove the diversion only to immediately re-add it and since the
10996 postrm of the old package is run after unpacking so the removal of
10997 the diversion will fail.
11001 Do not attempt to divert a file which is vitally important for
11002 the system's operation - when using <prgn>dpkg-divert</prgn>
11003 there is a time, after it has been diverted but before
11004 <prgn>dpkg</prgn> has installed the new version, when the file
11005 does not exist.</p>
11010 <!-- Local variables: -->
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