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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.
910 <sect id="maintainer">
911 <heading>The maintainer of a package</heading>
914 Every package must have a maintainer. The maintainer may be one
915 person or a group of people reachable from a common email
916 address, such as a mailing list. The maintainer is responsible
917 for maintaining the Debian packaging files, evaluating and
918 responding appropriately to reported bugs, uploading new
919 versions of the package (either directly or through a sponsor),
920 ensuring that the package is placed in the appropriate archive
921 area and included in Debian releases as appropriate for the
922 stability and utility of the package, and requesting removal of
923 the package from the Debian distribution if it is no longer
924 useful or maintainable.
928 The maintainer must be specified in the <tt>Maintainer</tt>
929 control field with their correct name and a working email
930 address. The email address given in the <tt>Maintainer</tt>
931 control field must accept mail from those role accounts in
932 Debian used to send automated mails regarding the package. This
933 includes non-spam mail from the bug-tracking system, all mail
934 from the Debian archive maintenance software, and other role
935 accounts or automated processes that are commonly agreed on by
936 the project.<footnote>
937 A sample implementation of such a whitelist written for the
938 Mailman mailing list management software is used for mailing
939 lists hosted by alioth.debian.org.
941 If one person or team maintains several packages, they should
942 use the same form of their name and email address in
943 the <tt>Maintainer</tt> fields of those packages.
947 The format of the <tt>Maintainer</tt> control field is
948 described in <ref id="f-Maintainer">.
952 If the maintainer of the package is a team of people with a
953 shared email address, the <tt>Uploaders</tt> control field must
954 be present and must contain at least one human with their
955 personal email address. See <ref id="f-Uploaders"> for the
956 syntax of that field.
960 If the maintainer of a package no longer has time or desire to
961 maintain a package, it should be orphaned according to the
962 procedure described in the Debian Developer's Reference
963 (see <ref id="related">). The maintainer then
964 becomes <tt>Debian QA Group <packages@qa.debian.org></tt>.
965 These packages are considered maintained by the Debian project
966 as a whole until someone else volunteers to take over
971 <sect id="descriptions">
972 <heading>The description of a package</heading>
975 Every Debian package must have a <tt>Description</tt> control
976 field which contains a synopsis and extended description of the
977 package. Technical information about the format of the
978 <tt>Description</tt> field is in <ref id="f-Description">.
982 The description should describe the package (the program) to a
983 user (system administrator) who has never met it before so that
984 they have enough information to decide whether they want to
985 install it. This description should not just be copied verbatim
986 from the program's documentation.
990 Put important information first, both in the synopsis and
991 extended description. Sometimes only the first part of the
992 synopsis or of the description will be displayed. You can
993 assume that there will usually be a way to see the whole
994 extended description.
998 The description should also give information about the
999 significant dependencies and conflicts between this package
1000 and others, so that the user knows why these dependencies and
1001 conflicts have been declared.
1005 Instructions for configuring or using the package should
1006 not be included (that is what installation scripts,
1007 manual pages, info files, etc., are for). Copyright
1008 statements and other administrivia should not be included
1009 either (that is what the copyright file is for).
1012 <sect1 id="synopsis"><heading>The single line synopsis</heading>
1015 The single line synopsis should be kept brief - certainly
1016 under 80 characters.
1020 Do not include the package name in the synopsis line. The
1021 display software knows how to display this already, and you
1022 do not need to state it. Remember that in many situations
1023 the user may only see the synopsis line - make it as
1024 informative as you can.
1029 <sect1 id="extendeddesc"><heading>The extended description</heading>
1032 Do not try to continue the single line synopsis into the
1033 extended description. This will not work correctly when
1034 the full description is displayed, and makes no sense
1035 where only the summary (the single line synopsis) is
1040 The extended description should describe what the package
1041 does and how it relates to the rest of the system (in terms
1042 of, for example, which subsystem it is which part of).
1046 The description field needs to make sense to anyone, even
1047 people who have no idea about any of the things the
1048 package deals with.<footnote>
1049 The blurb that comes with a program in its
1050 announcements and/or <prgn>README</prgn> files is
1051 rarely suitable for use in a description. It is
1052 usually aimed at people who are already in the
1053 community where the package is used.
1062 <heading>Dependencies</heading>
1065 Every package must specify the dependency information
1066 about other packages that are required for the first to
1071 For example, a dependency entry must be provided for any
1072 shared libraries required by a dynamically-linked executable
1073 binary in a package.
1077 Packages are not required to declare any dependencies they
1078 have on other packages which are marked <tt>Essential</tt>
1079 (see below), and should not do so unless they depend on a
1080 particular version of that package.<footnote>
1082 Essential is needed in part to avoid unresolvable dependency
1083 loops on upgrade. If packages add unnecessary dependencies
1084 on packages in this set, the chances that there
1085 <strong>will</strong> be an unresolvable dependency loop
1086 caused by forcing these Essential packages to be configured
1087 first before they need to be is greatly increased. It also
1088 increases the chances that frontends will be unable to
1089 <strong>calculate</strong> an upgrade path, even if one
1093 Also, functionality is rarely ever removed from the
1094 Essential set, but <em>packages</em> have been removed from
1095 the Essential set when the functionality moved to a
1096 different package. So depending on these packages <em>just
1097 in case</em> they stop being essential does way more harm
1104 Sometimes, a package requires another package to be installed
1105 <em>and</em> configured before it can be installed. In this
1106 case, you must specify a <tt>Pre-Depends</tt> entry for
1111 You should not specify a <tt>Pre-Depends</tt> entry for a
1112 package before this has been discussed on the
1113 <tt>debian-devel</tt> mailing list and a consensus about
1114 doing that has been reached.
1118 The format of the package interrelationship control fields is
1119 described in <ref id="relationships">.
1123 <sect id="virtual_pkg">
1124 <heading>Virtual packages</heading>
1127 Sometimes, there are several packages which offer
1128 more-or-less the same functionality. In this case, it's
1129 useful to define a <em>virtual package</em> whose name
1130 describes that common functionality. (The virtual
1131 packages only exist logically, not physically; that's why
1132 they are called <em>virtual</em>.) The packages with this
1133 particular function will then <em>provide</em> the virtual
1134 package. Thus, any other package requiring that function
1135 can simply depend on the virtual package without having to
1136 specify all possible packages individually.
1140 All packages should use virtual package names where
1141 appropriate, and arrange to create new ones if necessary.
1142 They should not use virtual package names (except privately,
1143 amongst a cooperating group of packages) unless they have
1144 been agreed upon and appear in the list of virtual package
1145 names. (See also <ref id="virtual">)
1149 The latest version of the authoritative list of virtual
1150 package names can be found in the <tt>debian-policy</tt> package.
1151 It is also available from the Debian web mirrors at
1152 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1153 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1157 The procedure for updating the list is described in the preface
1164 <heading>Base system</heading>
1167 The <tt>base system</tt> is a minimum subset of the Debian
1168 GNU/Linux system that is installed before everything else
1169 on a new system. Only very few packages are allowed to form
1170 part of the base system, in order to keep the required disk
1175 The base system consists of all those packages with priority
1176 <tt>required</tt> or <tt>important</tt>. Many of them will
1177 be tagged <tt>essential</tt> (see below).
1182 <heading>Essential packages</heading>
1185 Essential is defined as the minimal set of functionality that
1186 must be available and usable on the system at all times, even
1187 when packages are in an unconfigured (but unpacked) state.
1188 Packages are tagged <tt>essential</tt> for a system using the
1189 <tt>Essential</tt> control field. The format of the
1190 <tt>Essential</tt> control field is described in <ref
1195 Since these packages cannot be easily removed (one has to
1196 specify an extra <em>force option</em> to
1197 <prgn>dpkg</prgn> to do so), this flag must not be used
1198 unless absolutely necessary. A shared library package
1199 must not be tagged <tt>essential</tt>; dependencies will
1200 prevent its premature removal, and we need to be able to
1201 remove it when it has been superseded.
1205 Since dpkg will not prevent upgrading of other packages
1206 while an <tt>essential</tt> package is in an unconfigured
1207 state, all <tt>essential</tt> packages must supply all of
1208 their core functionality even when unconfigured. If the
1209 package cannot satisfy this requirement it must not be
1210 tagged as essential, and any packages depending on this
1211 package must instead have explicit dependency fields as
1216 Maintainers should take great care in adding any programs,
1217 interfaces, or functionality to <tt>essential</tt> packages.
1218 Packages may assume that functionality provided by
1219 <tt>essential</tt> packages is always available without
1220 declaring explicit dependencies, which means that removing
1221 functionality from the Essential set is very difficult and is
1222 almost never done. Any capability added to an
1223 <tt>essential</tt> package therefore creates an obligation to
1224 support that capability as part of the Essential set in
1229 You must not tag any packages <tt>essential</tt> before
1230 this has been discussed on the <tt>debian-devel</tt>
1231 mailing list and a consensus about doing that has been
1236 <sect id="maintscripts">
1237 <heading>Maintainer Scripts</heading>
1240 The package installation scripts should avoid producing
1241 output which is unnecessary for the user to see and
1242 should rely on <prgn>dpkg</prgn> to stave off boredom on
1243 the part of a user installing many packages. This means,
1244 amongst other things, using the <tt>--quiet</tt> option on
1245 <prgn>install-info</prgn>.
1249 Errors which occur during the execution of an installation
1250 script must be checked and the installation must not
1251 continue after an error.
1255 Note that in general <ref id="scripts"> applies to package
1256 maintainer scripts, too.
1260 You should not use <prgn>dpkg-divert</prgn> on a file belonging
1261 to another package without consulting the maintainer of that
1262 package first. When adding or removing diversions, package
1263 maintainer scripts must provide the <tt>--package</tt> flag
1264 to <prgn>dpkg-divert</prgn> and must not use <tt>--local</tt>.
1268 All packages which supply an instance of a common command
1269 name (or, in general, filename) should generally use
1270 <prgn>update-alternatives</prgn>, so that they may be
1271 installed together. If <prgn>update-alternatives</prgn>
1272 is not used, then each package must use
1273 <tt>Conflicts</tt> to ensure that other packages are
1274 de-installed. (In this case, it may be appropriate to
1275 specify a conflict against earlier versions of something
1276 that previously did not use
1277 <prgn>update-alternatives</prgn>; this is an exception to
1278 the usual rule that versioned conflicts should be
1282 <sect1 id="maintscriptprompt">
1283 <heading>Prompting in maintainer scripts</heading>
1285 Package maintainer scripts may prompt the user if
1286 necessary. Prompting must be done by communicating
1287 through a program, such as <prgn>debconf</prgn>, which
1288 conforms to the Debian Configuration Management
1289 Specification, version 2 or higher.
1293 Packages which are essential, or which are dependencies of
1294 essential packages, may fall back on another prompting method
1295 if no such interface is available when they are executed.
1299 The Debian Configuration Management Specification is included
1300 in the <file>debconf_specification</file> files in the
1301 <package>debian-policy</package> package.
1302 It is also available from the Debian web mirrors at
1303 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1304 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1308 Packages which use the Debian Configuration Management
1309 Specification may contain the additional control information
1310 files <file>config</file>
1311 and <file>templates</file>. <file>config</file> is an
1312 additional maintainer script used for package configuration,
1313 and <file>templates</file> contains templates used for user
1314 prompting. The <prgn>config</prgn> script might be run before
1315 the <prgn>preinst</prgn> script and before the package is
1316 unpacked or any of its dependencies or pre-dependencies are
1317 satisfied. Therefore it must work using only the tools
1318 present in <em>essential</em> packages.<footnote>
1319 <package>Debconf</package> or another tool that
1320 implements the Debian Configuration Management
1321 Specification will also be installed, and any
1322 versioned dependencies on it will be satisfied
1323 before preconfiguration begins.
1328 Packages which use the Debian Configuration Management
1329 Specification must allow for translation of their user-visible
1330 messages by using a gettext-based system such as the one
1331 provided by the <package>po-debconf</package> package.
1335 Packages should try to minimize the amount of prompting
1336 they need to do, and they should ensure that the user
1337 will only ever be asked each question once. This means
1338 that packages should try to use appropriate shared
1339 configuration files (such as <file>/etc/papersize</file> and
1340 <file>/etc/news/server</file>), and shared
1341 <package>debconf</package> variables rather than each
1342 prompting for their own list of required pieces of
1347 It also means that an upgrade should not ask the same
1348 questions again, unless the user has used
1349 <tt>dpkg --purge</tt> to remove the package's configuration.
1350 The answers to configuration questions should be stored in an
1351 appropriate place in <file>/etc</file> so that the user can
1352 modify them, and how this has been done should be
1357 If a package has a vitally important piece of
1358 information to pass to the user (such as "don't run me
1359 as I am, you must edit the following configuration files
1360 first or you risk your system emitting badly-formatted
1361 messages"), it should display this in the
1362 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1363 prompt the user to hit return to acknowledge the
1364 message. Copyright messages do not count as vitally
1365 important (they belong in
1366 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1367 neither do instructions on how to use a program (these
1368 should be in on-line documentation, where all the users
1373 Any necessary prompting should almost always be confined
1374 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1375 script. If it is done in the <prgn>postinst</prgn>, it
1376 should be protected with a conditional so that
1377 unnecessary prompting doesn't happen if a package's
1378 installation fails and the <prgn>postinst</prgn> is
1379 called with <tt>abort-upgrade</tt>,
1380 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1390 <heading>Source packages</heading>
1392 <sect id="standardsversion">
1393 <heading>Standards conformance</heading>
1396 Source packages should specify the most recent version number
1397 of this policy document with which your package complied
1398 when it was last updated.
1402 This information may be used to file bug reports
1403 automatically if your package becomes too much out of date.
1407 The version is specified in the <tt>Standards-Version</tt>
1409 The format of the <tt>Standards-Version</tt> field is
1410 described in <ref id="f-Standards-Version">.
1414 You should regularly, and especially if your package has
1415 become out of date, check for the newest Policy Manual
1416 available and update your package, if necessary. When your
1417 package complies with the new standards you should update the
1418 <tt>Standards-Version</tt> source package field and
1419 release it.<footnote>
1420 See the file <file>upgrading-checklist</file> for
1421 information about policy which has changed between
1422 different versions of this document.
1428 <sect id="pkg-relations">
1429 <heading>Package relationships</heading>
1432 Source packages should specify which binary packages they
1433 require to be installed or not to be installed in order to
1434 build correctly. For example, if building a package
1435 requires a certain compiler, then the compiler should be
1436 specified as a build-time dependency.
1440 It is not necessary to explicitly specify build-time
1441 relationships on a minimal set of packages that are always
1442 needed to compile, link and put in a Debian package a
1443 standard "Hello World!" program written in C or C++. The
1444 required packages are called <em>build-essential</em>, and
1445 an informational list can be found in
1446 <file>/usr/share/doc/build-essential/list</file> (which is
1447 contained in the <tt>build-essential</tt>
1450 <list compact="compact">
1452 This allows maintaining the list separately
1453 from the policy documents (the list does not
1454 need the kind of control that the policy
1458 Having a separate package allows one to install
1459 the build-essential packages on a machine, as
1460 well as allowing other packages such as tasks to
1461 require installation of the build-essential
1462 packages using the depends relation.
1465 The separate package allows bug reports against
1466 the list to be categorized separately from
1467 the policy management process in the BTS.
1474 When specifying the set of build-time dependencies, one
1475 should list only those packages explicitly required by the
1476 build. It is not necessary to list packages which are
1477 required merely because some other package in the list of
1478 build-time dependencies depends on them.<footnote>
1479 The reason for this is that dependencies change, and
1480 you should list all those packages, and <em>only</em>
1481 those packages that <em>you</em> need directly. What
1482 others need is their business. For example, if you
1483 only link against <file>libimlib</file>, you will need to
1484 build-depend on <package>libimlib2-dev</package> but
1485 not against any <tt>libjpeg*</tt> packages, even
1486 though <tt>libimlib2-dev</tt> currently depends on
1487 them: installation of <package>libimlib2-dev</package>
1488 will automatically ensure that all of its run-time
1489 dependencies are satisfied.
1494 If build-time dependencies are specified, it must be
1495 possible to build the package and produce working binaries
1496 on a system with only essential and build-essential
1497 packages installed and also those required to satisfy the
1498 build-time relationships (including any implied
1499 relationships). In particular, this means that version
1500 clauses should be used rigorously in build-time
1501 relationships so that one cannot produce bad or
1502 inconsistently configured packages when the relationships
1503 are properly satisfied.
1507 <ref id="relationships"> explains the technical details.
1512 <heading>Changes to the upstream sources</heading>
1515 If changes to the source code are made that are not
1516 specific to the needs of the Debian system, they should be
1517 sent to the upstream authors in whatever form they prefer
1518 so as to be included in the upstream version of the
1523 If you need to configure the package differently for
1524 Debian or for Linux, and the upstream source doesn't
1525 provide a way to do so, you should add such configuration
1526 facilities (for example, a new <prgn>autoconf</prgn> test
1527 or <tt>#define</tt>) and send the patch to the upstream
1528 authors, with the default set to the way they originally
1529 had it. You can then easily override the default in your
1530 <file>debian/rules</file> or wherever is appropriate.
1534 You should make sure that the <prgn>configure</prgn> utility
1535 detects the correct architecture specification string
1536 (refer to <ref id="arch-spec"> for details).
1540 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1541 <prgn>configure</prgn> scripts are used, you should edit the
1542 <file>.in</file> files rather than editing the
1543 <prgn>Makefile</prgn> directly. This allows the user to
1544 reconfigure the package if necessary. You should
1545 <em>not</em> configure the package and edit the generated
1546 <prgn>Makefile</prgn>! This makes it impossible for someone
1547 else to later reconfigure the package without losing the
1553 <sect id="dpkgchangelog">
1554 <heading>Debian changelog: <file>debian/changelog</file></heading>
1557 Changes in the Debian version of the package should be
1558 briefly explained in the Debian changelog file
1559 <file>debian/changelog</file>.<footnote>
1561 Mistakes in changelogs are usually best rectified by
1562 making a new changelog entry rather than "rewriting
1563 history" by editing old changelog entries.
1566 This includes modifications
1567 made in the Debian package compared to the upstream one
1568 as well as other changes and updates to the package.
1570 Although there is nothing stopping an author who is also
1571 the Debian maintainer from using this changelog for all
1572 their changes, it will have to be renamed if the Debian
1573 and upstream maintainers become different people. In such
1574 a case, however, it might be better to maintain the package
1575 as a non-native package.
1580 The format of the <file>debian/changelog</file> allows the
1581 package building tools to discover which version of the package
1582 is being built and find out other release-specific information.
1586 That format is a series of entries like this:
1588 <example compact="compact">
1589 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1591 [optional blank line(s), stripped]
1593 * <var>change details</var>
1594 <var>more change details</var>
1596 [blank line(s), included in output of dpkg-parsechangelog]
1598 * <var>even more change details</var>
1600 [optional blank line(s), stripped]
1602 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1607 <var>package</var> and <var>version</var> are the source
1608 package name and version number.
1612 <var>distribution(s)</var> lists the distributions where
1613 this version should be installed when it is uploaded - it
1614 is copied to the <tt>Distribution</tt> field in the
1615 <file>.changes</file> file. See <ref id="f-Distribution">.
1619 <var>urgency</var> is the value for the <tt>Urgency</tt>
1620 field in the <file>.changes</file> file for the upload
1621 (see <ref id="f-Urgency">). It is not possible to specify
1622 an urgency containing commas; commas are used to separate
1623 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1624 <prgn>dpkg</prgn> changelog format (though there is
1625 currently only one useful <var>keyword</var>,
1630 The change details may in fact be any series of lines
1631 starting with at least two spaces, but conventionally each
1632 change starts with an asterisk and a separating space and
1633 continuation lines are indented so as to bring them in
1634 line with the start of the text above. Blank lines may be
1635 used here to separate groups of changes, if desired.
1639 If this upload resolves bugs recorded in the Bug Tracking
1640 System (BTS), they may be automatically closed on the
1641 inclusion of this package into the Debian archive by
1642 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1643 in the change details.<footnote>
1644 To be precise, the string should match the following
1645 Perl regular expression:
1647 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1649 Then all of the bug numbers listed will be closed by the
1650 archive maintenance script (<prgn>katie</prgn>) using the
1651 <var>version</var> of the changelog entry.
1653 This information is conveyed via the <tt>Closes</tt> field
1654 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1658 The maintainer name and email address used in the changelog
1659 should be the details of the person uploading <em>this</em>
1660 version. They are <em>not</em> necessarily those of the
1661 usual package maintainer. The information here will be
1662 copied to the <tt>Changed-By</tt> field in the
1663 <tt>.changes</tt> file (see <ref id="f-Changed-By">),
1664 and then later used to send an acknowledgement when the
1665 upload has been installed.
1669 The <var>date</var> has the following format<footnote>
1670 This is the same as the format generated by <tt>date
1672 </footnote> (compatible and with the same semantics of
1673 RFC 2822 and RFC 5322):
1674 <example>day-of-week, dd month yyyy hh:mm:ss +zzzz</example>
1676 <list compact="compact">
1678 day-of week is one of: Mon, Tue, Wed, Thu, Fri, Sat, Sun
1681 dd is a one- or two-digit day of the month (01-31)
1684 month is one of: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug,
1687 <item>yyyy is the four-digit year (e.g. 2010)</item>
1688 <item>hh is the two-digit hour (00-23)</item>
1689 <item>mm is the two-digit minutes (00-59)</item>
1690 <item>ss is the two-digit seconds (00-60)</item>
1692 +zzzz or -zzzz is the the time zone offset from Coordinated
1693 Universal Time (UTC). "+" indicates that the time is ahead
1694 of (i.e., east of) UTC and "-" indicates that the time is
1695 behind (i.e., west of) UTC. The first two digits indicate
1696 the hour difference from UTC and the last two digits
1697 indicate the number of additional minutes difference from
1698 UTC. The last two digits must be in the range 00-59.
1704 The first "title" line with the package name must start
1705 at the left hand margin. The "trailer" line with the
1706 maintainer and date details must be preceded by exactly
1707 one space. The maintainer details and the date must be
1708 separated by exactly two spaces.
1712 The entire changelog must be encoded in UTF-8.
1716 For more information on placement of the changelog files
1717 within binary packages, please see <ref id="changelogs">.
1721 <sect id="dpkgcopyright">
1722 <heading>Copyright: <file>debian/copyright</file></heading>
1724 Every package must be accompanied by a verbatim copy of its
1725 copyright information and distribution license in the file
1726 <file>/usr/share/doc/<var>package</var>/copyright</file>
1727 (see <ref id="copyrightfile"> for further details). Also see
1728 <ref id="pkgcopyright"> for further considerations related
1729 to copyrights for packages.
1733 <heading>Error trapping in makefiles</heading>
1736 When <prgn>make</prgn> invokes a command in a makefile
1737 (including your package's upstream makefiles and
1738 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1739 means that <prgn>sh</prgn>'s usual bad error handling
1740 properties apply: if you include a miniature script as one
1741 of the commands in your makefile you'll find that if you
1742 don't do anything about it then errors are not detected
1743 and <prgn>make</prgn> will blithely continue after
1748 Every time you put more than one shell command (this
1749 includes using a loop) in a makefile command you
1750 must make sure that errors are trapped. For
1751 simple compound commands, such as changing directory and
1752 then running a program, using <tt>&&</tt> rather
1753 than semicolon as a command separator is sufficient. For
1754 more complex commands including most loops and
1755 conditionals you should include a separate <tt>set -e</tt>
1756 command at the start of every makefile command that's
1757 actually one of these miniature shell scripts.
1761 <sect id="timestamps">
1762 <heading>Time Stamps</heading>
1764 Maintainers should preserve the modification times of the
1765 upstream source files in a package, as far as is reasonably
1767 The rationale is that there is some information conveyed
1768 by knowing the age of the file, for example, you could
1769 recognize that some documentation is very old by looking
1770 at the modification time, so it would be nice if the
1771 modification time of the upstream source would be
1777 <sect id="restrictions">
1778 <heading>Restrictions on objects in source packages</heading>
1781 The source package may not contain any hard links<footnote>
1783 This is not currently detected when building source
1784 packages, but only when extracting
1788 Hard links may be permitted at some point in the
1789 future, but would require a fair amount of
1792 </footnote>, device special files, sockets or setuid or
1793 setgid files.<footnote>
1794 Setgid directories are allowed.
1799 <sect id="debianrules">
1800 <heading>Main building script: <file>debian/rules</file></heading>
1803 This file must be an executable makefile, and contains the
1804 package-specific recipes for compiling the package and
1805 building binary package(s) from the source.
1809 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1810 so that it can be invoked by saying its name rather than
1811 invoking <prgn>make</prgn> explicitly. That is, invoking
1812 either of <tt>make -f debian/rules <em>args...</em></tt>
1813 or <tt>./debian/rules <em>args...</em></tt> must result in
1818 Since an interactive <file>debian/rules</file> script makes it
1819 impossible to auto-compile that package and also makes it
1820 hard for other people to reproduce the same binary
1821 package, all <em>required targets</em> must be
1822 non-interactive. At a minimum, required targets are the
1823 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1824 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1825 <em>binary-indep</em>, and <em>build</em>. It also follows
1826 that any target that these targets depend on must also be
1831 The targets are as follows (required unless stated otherwise):
1833 <tag><tt>build</tt></tag>
1836 The <tt>build</tt> target should perform all the
1837 configuration and compilation of the package.
1838 If a package has an interactive pre-build
1839 configuration routine, the Debian source package
1840 must either be built after this has taken place (so
1841 that the binary package can be built without rerunning
1842 the configuration) or the configuration routine
1843 modified to become non-interactive. (The latter is
1844 preferable if there are architecture-specific features
1845 detected by the configuration routine.)
1849 For some packages, notably ones where the same
1850 source tree is compiled in different ways to produce
1851 two binary packages, the <tt>build</tt> target
1852 does not make much sense. For these packages it is
1853 good enough to provide two (or more) targets
1854 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1855 for each of the ways of building the package, and a
1856 <tt>build</tt> target that does nothing. The
1857 <tt>binary</tt> target will have to build the
1858 package in each of the possible ways and make the
1859 binary package out of each.
1863 The <tt>build</tt> target must not do anything
1864 that might require root privilege.
1868 The <tt>build</tt> target may need to run the
1869 <tt>clean</tt> target first - see below.
1873 When a package has a configuration and build routine
1874 which takes a long time, or when the makefiles are
1875 poorly designed, or when <tt>build</tt> needs to
1876 run <tt>clean</tt> first, it is a good idea to
1877 <tt>touch build</tt> when the build process is
1878 complete. This will ensure that if <tt>debian/rules
1879 build</tt> is run again it will not rebuild the whole
1881 Another common way to do this is for <tt>build</tt>
1882 to depend on <prgn>build-stamp</prgn> and to do
1883 nothing else, and for the <prgn>build-stamp</prgn>
1884 target to do the building and to <tt>touch
1885 build-stamp</tt> on completion. This is
1886 especially useful if the build routine creates a
1887 file or directory called <tt>build</tt>; in such a
1888 case, <tt>build</tt> will need to be listed as
1889 a phony target (i.e., as a dependency of the
1890 <tt>.PHONY</tt> target). See the documentation of
1891 <prgn>make</prgn> for more information on phony
1897 <tag><tt>build-arch</tt> (optional),
1898 <tt>build-indep</tt> (optional)
1902 A package may also provide both of the targets
1903 <tt>build-arch</tt> and <tt>build-indep</tt>.
1904 The <tt>build-arch</tt> target, if provided, should
1905 perform all the configuration and compilation required for
1906 producing all architecture-dependant binary packages
1907 (those packages for which the body of the
1908 <tt>Architecture</tt> field in <tt>debian/control</tt> is
1909 not <tt>all</tt>). Similarly, the <tt>build-indep</tt>
1910 target, if provided, should perform all the configuration
1911 and compilation required for producing all
1912 architecture-independent binary packages (those packages
1913 for which the body of the <tt>Architecture</tt> field
1914 in <tt>debian/control</tt> is <tt>all</tt>).
1915 The <tt>build</tt> target should depend on those of the
1916 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1917 are provided in the rules file.<footnote>
1918 The intent of this split is so that binary-only builds
1919 need not install the dependencies required for
1920 the <tt>build-indep</tt> target. However, this is not
1921 yet used in practice since <tt>dpkg-buildpackage
1922 -B</tt>, and therefore the autobuilders,
1923 invoke <tt>build</tt> rather than <tt>build-arch</tt>
1924 due to the difficulties in determining whether the
1925 optional <tt>build-arch</tt> target exists.
1930 If one or both of the targets <tt>build-arch</tt> and
1931 <tt>build-indep</tt> are not provided, then invoking
1932 <file>debian/rules</file> with one of the not-provided
1933 targets as arguments should produce a exit status code
1934 of 2. Usually this is provided automatically by make
1935 if the target is missing.
1939 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1940 must not do anything that might require root privilege.
1944 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1945 <tt>binary-indep</tt>
1949 The <tt>binary</tt> target must be all that is
1950 necessary for the user to build the binary package(s)
1951 produced from this source package. It is
1952 split into two parts: <prgn>binary-arch</prgn> builds
1953 the binary packages which are specific to a particular
1954 architecture, and <tt>binary-indep</tt> builds
1955 those which are not.
1958 <tt>binary</tt> may be (and commonly is) a target with
1959 no commands which simply depends on
1960 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1963 Both <tt>binary-*</tt> targets should depend on the
1964 <tt>build</tt> target, or on the appropriate
1965 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1966 provided, so that the package is built if it has not
1967 been already. It should then create the relevant
1968 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1969 make their control files and <prgn>dpkg-deb</prgn> to
1970 build them and place them in the parent of the top
1975 Both the <tt>binary-arch</tt> and
1976 <tt>binary-indep</tt> targets <em>must</em> exist.
1977 If one of them has nothing to do (which will always be
1978 the case if the source generates only a single binary
1979 package, whether architecture-dependent or not), it
1980 must still exist and must always succeed.
1984 The <tt>binary</tt> targets must be invoked as
1986 The <prgn>fakeroot</prgn> package often allows one
1987 to build a package correctly even without being
1993 <tag><tt>clean</tt></tag>
1996 This must undo any effects that the <tt>build</tt>
1997 and <tt>binary</tt> targets may have had, except
1998 that it should leave alone any output files created in
1999 the parent directory by a run of a <tt>binary</tt>
2004 If a <tt>build</tt> file is touched at the end of
2005 the <tt>build</tt> target, as suggested above, it
2006 should be removed as the first action that
2007 <tt>clean</tt> performs, so that running
2008 <tt>build</tt> again after an interrupted
2009 <tt>clean</tt> doesn't think that everything is
2014 The <tt>clean</tt> target may need to be
2015 invoked as root if <tt>binary</tt> has been
2016 invoked since the last <tt>clean</tt>, or if
2017 <tt>build</tt> has been invoked as root (since
2018 <tt>build</tt> may create directories, for
2023 <tag><tt>get-orig-source</tt> (optional)</tag>
2026 This target fetches the most recent version of the
2027 original source package from a canonical archive site
2028 (via FTP or WWW, for example), does any necessary
2029 rearrangement to turn it into the original source
2030 tar file format described below, and leaves it in the
2035 This target may be invoked in any directory, and
2036 should take care to clean up any temporary files it
2041 This target is optional, but providing it if
2042 possible is a good idea.
2046 <tag><tt>patch</tt> (optional)</tag>
2049 This target performs whatever additional actions are
2050 required to make the source ready for editing (unpacking
2051 additional upstream archives, applying patches, etc.).
2052 It is recommended to be implemented for any package where
2053 <tt>dpkg-source -x</tt> does not result in source ready
2054 for additional modification. See
2055 <ref id="readmesource">.
2061 The <tt>build</tt>, <tt>binary</tt> and
2062 <tt>clean</tt> targets must be invoked with the current
2063 directory being the package's top-level directory.
2068 Additional targets may exist in <file>debian/rules</file>,
2069 either as published or undocumented interfaces or for the
2070 package's internal use.
2074 The architectures we build on and build for are determined
2075 by <prgn>make</prgn> variables using the utility
2076 <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
2077 You can determine the
2078 Debian architecture and the GNU style architecture
2079 specification string for the build machine (the machine type
2080 we are building on) as well as for the host machine (the
2081 machine type we are building for). Here is a list of
2082 supported <prgn>make</prgn> variables:
2083 <list compact="compact">
2085 <tt>DEB_*_ARCH</tt> (the Debian architecture)
2088 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2091 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2094 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2095 specification string)
2098 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2099 <tt>DEB_*_GNU_TYPE</tt>)
2102 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2103 <tt>DEB_*_GNU_TYPE</tt>)
2105 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2106 the build machine or <tt>HOST</tt> for specification of the
2111 Backward compatibility can be provided in the rules file
2112 by setting the needed variables to suitable default
2113 values; please refer to the documentation of
2114 <prgn>dpkg-architecture</prgn> for details.
2118 It is important to understand that the <tt>DEB_*_ARCH</tt>
2119 string only determines which Debian architecture we are
2120 building on or for. It should not be used to get the CPU
2121 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2122 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2123 GNU style variables should generally only be used with upstream
2127 <sect1 id="debianrules-options">
2128 <heading><file>debian/rules</file> and
2129 <tt>DEB_BUILD_OPTIONS</tt></heading>
2132 Supporting the standardized environment variable
2133 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2134 contain several flags to change how a package is compiled and
2135 built. Each flag must be in the form <var>flag</var> or
2136 <var>flag</var>=<var>options</var>. If multiple flags are
2137 given, they must be separated by whitespace.<footnote>
2138 Some packages support any delimiter, but whitespace is the
2139 easiest to parse inside a makefile and avoids ambiguity with
2140 flag values that contain commas.
2142 <var>flag</var> must start with a lowercase letter
2143 (<tt>a-z</tt>) and consist only of lowercase letters,
2144 numbers (<tt>0-9</tt>), and the characters
2145 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2146 <var>options</var> must not contain whitespace. The same
2147 tag should not be given multiple times with conflicting
2148 values. Package maintainers may assume that
2149 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2153 The meaning of the following tags has been standardized:
2157 This tag says to not run any build-time test suite
2158 provided by the package.
2162 The presence of this tag means that the package should
2163 be compiled with a minimum of optimization. For C
2164 programs, it is best to add <tt>-O0</tt> to
2165 <tt>CFLAGS</tt> (although this is usually the default).
2166 Some programs might fail to build or run at this level
2167 of optimization; it may be necessary to use
2168 <tt>-O1</tt>, for example.
2172 This tag means that the debugging symbols should not be
2173 stripped from the binary during installation, so that
2174 debugging information may be included in the package.
2176 <tag>parallel=n</tag>
2178 This tag means that the package should be built using up
2179 to <tt>n</tt> parallel processes if the package build
2180 system supports this.<footnote>
2181 Packages built with <tt>make</tt> can often implement
2182 this by passing the <tt>-j</tt><var>n</var> option to
2185 If the package build system does not support parallel
2186 builds, this string must be ignored. If the package
2187 build system only supports a lower level of concurrency
2188 than <var>n</var>, the package should be built using as
2189 many parallel processes as the package build system
2190 supports. It is up to the package maintainer to decide
2191 whether the package build times are long enough and the
2192 package build system is robust enough to make supporting
2193 parallel builds worthwhile.
2199 Unknown flags must be ignored by <file>debian/rules</file>.
2203 The following makefile snippet is an example of how one may
2204 implement the build options; you will probably have to
2205 massage this example in order to make it work for your
2207 <example compact="compact">
2210 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2211 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2212 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2213 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2215 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2220 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2221 INSTALL_PROGRAM += -s
2223 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2224 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2225 MAKEFLAGS += -j$(NUMJOBS)
2230 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2231 # Code to run the package test suite.
2238 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2239 <sect id="substvars">
2240 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2243 When <prgn>dpkg-gencontrol</prgn>
2244 generates <qref id="binarycontrolfiles">binary package control
2245 files</qref> (<file>DEBIAN/control</file>), it performs variable
2246 substitutions on its output just before writing it. Variable
2247 substitutions have the form <tt>${<var>variable</var>}</tt>.
2248 The optional file <file>debian/substvars</file> contains
2249 variable substitutions to be used; variables can also be set
2250 directly from <file>debian/rules</file> using the <tt>-V</tt>
2251 option to the source packaging commands, and certain predefined
2252 variables are also available.
2256 The <file>debian/substvars</file> file is usually generated and
2257 modified dynamically by <file>debian/rules</file> targets, in
2258 which case it must be removed by the <tt>clean</tt> target.
2262 See <manref name="deb-substvars" section="5"> for full
2263 details about source variable substitutions, including the
2264 format of <file>debian/substvars</file>.</p>
2267 <sect id="debianwatch">
2268 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2271 This is an optional, recommended configuration file for the
2272 <tt>uscan</tt> utility which defines how to automatically scan
2273 ftp or http sites for newly available updates of the
2274 package. This is used
2275 by <url id="http://dehs.alioth.debian.org/"> and other Debian QA
2276 tools to help with quality control and maintenance of the
2277 distribution as a whole.
2282 <sect id="debianfiles">
2283 <heading>Generated files list: <file>debian/files</file></heading>
2286 This file is not a permanent part of the source tree; it
2287 is used while building packages to record which files are
2288 being generated. <prgn>dpkg-genchanges</prgn> uses it
2289 when it generates a <file>.changes</file> file.
2293 It should not exist in a shipped source package, and so it
2294 (and any backup files or temporary files such as
2295 <file>files.new</file><footnote>
2296 <file>files.new</file> is used as a temporary file by
2297 <prgn>dpkg-gencontrol</prgn> and
2298 <prgn>dpkg-distaddfile</prgn> - they write a new
2299 version of <tt>files</tt> here before renaming it,
2300 to avoid leaving a corrupted copy if an error
2302 </footnote>) should be removed by the
2303 <tt>clean</tt> target. It may also be wise to
2304 ensure a fresh start by emptying or removing it at the
2305 start of the <tt>binary</tt> target.
2309 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2310 package, it adds an entry to <file>debian/files</file> for the
2311 <file>.deb</file> file that will be created when <tt>dpkg-deb
2312 --build</tt> is run for that binary package. So for most
2313 packages all that needs to be done with this file is to
2314 delete it in the <tt>clean</tt> target.
2318 If a package upload includes files besides the source
2319 package and any binary packages whose control files were
2320 made with <prgn>dpkg-gencontrol</prgn> then they should be
2321 placed in the parent of the package's top-level directory
2322 and <prgn>dpkg-distaddfile</prgn> should be called to add
2323 the file to the list in <file>debian/files</file>.</p>
2326 <sect id="embeddedfiles">
2327 <heading>Convenience copies of code</heading>
2330 Some software packages include in their distribution convenience
2331 copies of code from other software packages, generally so that
2332 users compiling from source don't have to download multiple
2333 packages. Debian packages should not make use of these
2334 convenience copies unless the included package is explicitly
2335 intended to be used in this way.<footnote>
2336 For example, parts of the GNU build system work like this.
2338 If the included code is already in the Debian archive in the
2339 form of a library, the Debian packaging should ensure that
2340 binary packages reference the libraries already in Debian and
2341 the convenience copy is not used. If the included code is not
2342 already in Debian, it should be packaged separately as a
2343 prerequisite if possible.
2345 Having multiple copies of the same code in Debian is
2346 inefficient, often creates either static linking or shared
2347 library conflicts, and, most importantly, increases the
2348 difficulty of handling security vulnerabilities in the
2354 <sect id="readmesource">
2355 <heading>Source package handling:
2356 <file>debian/README.source</file></heading>
2359 If running <prgn>dpkg-source -x</prgn> on a source package
2360 doesn't produce the source of the package, ready for editing,
2361 and allow one to make changes and run
2362 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2363 without taking any additional steps, creating a
2364 <file>debian/README.source</file> documentation file is
2365 recommended. This file should explain how to do all of the
2368 <item>Generate the fully patched source, in a form ready for
2369 editing, that would be built to create Debian
2370 packages. Doing this with a <tt>patch</tt> target in
2371 <file>debian/rules</file> is recommended; see
2372 <ref id="debianrules">.</item>
2373 <item>Modify the source and save those modifications so that
2374 they will be applied when building the package.</item>
2375 <item>Remove source modifications that are currently being
2376 applied when building the package.</item>
2377 <item>Optionally, document what steps are necessary to
2378 upgrade the Debian source package to a new upstream version,
2379 if applicable.</item>
2381 This explanation should include specific commands and mention
2382 any additional required Debian packages. It should not assume
2383 familiarity with any specific Debian packaging system or patch
2388 This explanation may refer to a documentation file installed by
2389 one of the package's build dependencies provided that the
2390 referenced documentation clearly explains these tasks and is not
2391 a general reference manual.
2395 <file>debian/README.source</file> may also include any other
2396 information that would be helpful to someone modifying the
2397 source package. Even if the package doesn't fit the above
2398 description, maintainers are encouraged to document in a
2399 <file>debian/README.source</file> file any source package with a
2400 particularly complex or unintuitive source layout or build
2401 system (for example, a package that builds the same source
2402 multiple times to generate different binary packages).
2408 <chapt id="controlfields">
2409 <heading>Control files and their fields</heading>
2412 The package management system manipulates data represented in
2413 a common format, known as <em>control data</em>, stored in
2414 <em>control files</em>.
2415 Control files are used for source packages, binary packages and
2416 the <file>.changes</file> files which control the installation
2417 of uploaded files<footnote>
2418 <prgn>dpkg</prgn>'s internal databases are in a similar
2423 <sect id="controlsyntax">
2424 <heading>Syntax of control files</heading>
2427 A control file consists of one or more paragraphs of
2429 The paragraphs are also sometimes referred to as stanzas.
2431 The paragraphs are separated by blank lines. Some control
2432 files allow only one paragraph; others allow several, in
2433 which case each paragraph usually refers to a different
2434 package. (For example, in source packages, the first
2435 paragraph refers to the source package, and later paragraphs
2436 refer to binary packages generated from the source.)
2440 Each paragraph consists of a series of data fields; each
2441 field consists of the field name, followed by a colon and
2442 then the data/value associated with that field. It ends at
2443 the end of the (logical) line. Horizontal whitespace
2444 (spaces and tabs) may occur immediately before or after the
2445 value and is ignored there; it is conventional to put a
2446 single space after the colon. For example, a field might
2448 <example compact="compact">
2451 the field name is <tt>Package</tt> and the field value
2456 A paragraph must not contain more than one instance of a
2457 particular field name.
2461 Many fields' values may span several lines; in this case
2462 each continuation line must start with a space or a tab.
2463 Any trailing spaces or tabs at the end of individual
2464 lines of a field value are ignored.
2468 In fields where it is specified that lines may not wrap,
2469 only a single line of data is allowed and whitespace is not
2470 significant in a field body. Whitespace must not appear
2471 inside names (of packages, architectures, files or anything
2472 else) or version numbers, or between the characters of
2473 multi-character version relationships.
2477 Field names are not case-sensitive, but it is usual to
2478 capitalize the field names using mixed case as shown below.
2479 Field values are case-sensitive unless the description of the
2480 field says otherwise.
2484 Blank lines, or lines consisting only of spaces and tabs,
2485 are not allowed within field values or between fields - that
2486 would mean a new paragraph.
2490 All control files must be encoded in UTF-8.
2494 <sect id="sourcecontrolfiles">
2495 <heading>Source package control files -- <file>debian/control</file></heading>
2498 The <file>debian/control</file> file contains the most vital
2499 (and version-independent) information about the source package
2500 and about the binary packages it creates.
2504 The first paragraph of the control file contains information about
2505 the source package in general. The subsequent sets each describe a
2506 binary package that the source tree builds.
2510 The fields in the general paragraph (the first one, for the source
2513 <list compact="compact">
2514 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2515 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2516 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2517 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2518 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2519 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2520 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2521 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2526 The fields in the binary package paragraphs are:
2528 <list compact="compact">
2529 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2530 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2531 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2532 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2533 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2534 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2535 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2536 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2541 The syntax and semantics of the fields are described below.
2545 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2546 generate control files for binary packages (see below), by
2547 <prgn>dpkg-genchanges</prgn> to generate the
2548 <file>.changes</file> file to accompany the upload, and by
2549 <prgn>dpkg-source</prgn> when it creates the
2550 <file>.dsc</file> source control file as part of a source
2551 archive. Many fields are permitted to span multiple lines in
2552 <file>debian/control</file> but not in any other control
2553 file. These tools are responsible for removing the line
2554 breaks from such fields when using fields from
2555 <file>debian/control</file> to generate other control files.
2559 The fields here may contain variable references - their
2560 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2561 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2562 when they generate output control files.
2563 See <ref id="substvars"> for details.
2567 In addition to the control file syntax described <qref
2568 id="controlsyntax">above</qref>, this file may also contain
2569 comment lines starting with <tt>#</tt> without any preceding
2570 whitespace. All such lines are ignored, even in the middle of
2571 continuation lines for a multiline field, and do not end a
2577 <sect id="binarycontrolfiles">
2578 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2581 The <file>DEBIAN/control</file> file contains the most vital
2582 (and version-dependent) information about a binary package. It
2583 consists of a single paragraph.
2587 The fields in this file are:
2589 <list compact="compact">
2590 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2591 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2592 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2593 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2594 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2595 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2596 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2597 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2598 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2599 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2600 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2601 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2606 <sect id="debiansourcecontrolfiles">
2607 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2610 This file consists of a single paragraph, possibly surrounded by
2611 a PGP signature. The fields of that paragraph are listed below.
2612 Their syntax is described above, in <ref id="pkg-controlfields">.
2614 <list compact="compact">
2615 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2616 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2617 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2618 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2619 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2620 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2621 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2622 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2623 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2624 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2625 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2626 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2627 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2632 The source package control file is generated by
2633 <prgn>dpkg-source</prgn> when it builds the source
2634 archive, from other files in the source package,
2635 described above. When unpacking, it is checked against
2636 the files and directories in the other parts of the
2642 <sect id="debianchangesfiles">
2643 <heading>Debian changes files -- <file>.changes</file></heading>
2646 The <file>.changes</file> files are used by the Debian archive
2647 maintenance software to process updates to packages. They
2648 consist of a single paragraph, possibly surrounded by a PGP
2649 signature. That paragraph contains information from the
2650 <file>debian/control</file> file and other data about the
2651 source package gathered via <file>debian/changelog</file>
2652 and <file>debian/rules</file>.
2656 <file>.changes</file> files have a format version that is
2657 incremented whenever the documented fields or their meaning
2658 change. This document describes format &changesversion;.
2662 The fields in this file are:
2664 <list compact="compact">
2665 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2666 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2667 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2668 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2669 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2670 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2671 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2672 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2673 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2674 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2675 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2676 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2677 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2678 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2679 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2680 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2685 <sect id="controlfieldslist">
2686 <heading>List of fields</heading>
2688 <sect1 id="f-Source">
2689 <heading><tt>Source</tt></heading>
2692 This field identifies the source package name.
2696 In <file>debian/control</file> or a <file>.dsc</file> file,
2697 this field must contain only the name of the source package.
2701 In a binary package control file or a <file>.changes</file>
2702 file, the source package name may be followed by a version
2703 number in parentheses<footnote>
2704 It is customary to leave a space after the package name
2705 if a version number is specified.
2707 This version number may be omitted (and is, by
2708 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2709 the <tt>Version</tt> field of the binary package in
2710 question. The field itself may be omitted from a binary
2711 package control file when the source package has the same
2712 name and version as the binary package.
2716 Package names (both source and binary,
2717 see <ref id="f-Package">) must consist only of lower case
2718 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2719 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2720 (<tt>.</tt>). They must be at least two characters long and
2721 must start with an alphanumeric character.
2725 <sect1 id="f-Maintainer">
2726 <heading><tt>Maintainer</tt></heading>
2729 The package maintainer's name and email address. The name
2730 must come first, then the email address inside angle
2731 brackets <tt><></tt> (in RFC822 format).
2735 If the maintainer's name contains a full stop then the
2736 whole field will not work directly as an email address due
2737 to a misfeature in the syntax specified in RFC822; a
2738 program using this field as an address must check for this
2739 and correct the problem if necessary (for example by
2740 putting the name in round brackets and moving it to the
2741 end, and bringing the email address forward).
2745 See <ref id="maintainer"> for additional requirements and
2746 information about package maintainers.
2750 <sect1 id="f-Uploaders">
2751 <heading><tt>Uploaders</tt></heading>
2754 List of the names and email addresses of co-maintainers of the
2755 package, if any. If the package has other maintainers besides
2756 the one named in the <qref id="f-Maintainer">Maintainer
2757 field</qref>, their names and email addresses should be listed
2758 here. The format of each entry is the same as that of the
2759 Maintainer field, and multiple entries must be comma
2764 This is normally an optional field, but if
2765 the <tt>Maintainer</tt> control field names a group of people
2766 and a shared email address, the <tt>Uploaders</tt> field must
2767 be present and must contain at least one human with their
2768 personal email address.
2772 Any parser that interprets the Uploaders field in
2773 <file>debian/control</file> must permit it to span multiple
2774 lines. Line breaks in an Uploaders field that spans multiple
2775 lines are not significant and the semantics of the field are
2776 the same as if the line breaks had not been present.
2780 <sect1 id="f-Changed-By">
2781 <heading><tt>Changed-By</tt></heading>
2784 The name and email address of the person who prepared this
2785 version of the package, usually a maintainer. The syntax is
2786 the same as for the <qref id="f-Maintainer">Maintainer
2791 <sect1 id="f-Section">
2792 <heading><tt>Section</tt></heading>
2795 This field specifies an application area into which the package
2796 has been classified. See <ref id="subsections">.
2800 When it appears in the <file>debian/control</file> file,
2801 it gives the value for the subfield of the same name in
2802 the <tt>Files</tt> field of the <file>.changes</file> file.
2803 It also gives the default for the same field in the binary
2808 <sect1 id="f-Priority">
2809 <heading><tt>Priority</tt></heading>
2812 This field represents how important it is that the user
2813 have the package installed. See <ref id="priorities">.
2817 When it appears in the <file>debian/control</file> file,
2818 it gives the value for the subfield of the same name in
2819 the <tt>Files</tt> field of the <file>.changes</file> file.
2820 It also gives the default for the same field in the binary
2825 <sect1 id="f-Package">
2826 <heading><tt>Package</tt></heading>
2829 The name of the binary package.
2833 Binary package names must follow the same syntax and
2834 restrictions as source package names. See <ref id="f-Source">
2839 <sect1 id="f-Architecture">
2840 <heading><tt>Architecture</tt></heading>
2843 Depending on context and the control file used, the
2844 <tt>Architecture</tt> field can include the following sets of
2848 A unique single word identifying a Debian machine
2849 architecture as described in <ref id="arch-spec">.
2852 An architecture wildcard identifying a set of Debian
2853 machine architectures, see <ref id="arch-wildcard-spec">.
2854 <tt>any</tt> matches all Debian machine architectures
2855 and is the most frequently used.
2858 <tt>all</tt>, which indicates an
2859 architecture-independent package.
2862 <tt>source</tt>, which indicates a source package.
2868 In the main <file>debian/control</file> file in the source
2869 package, this field may contain the special
2870 value <tt>all</tt>, the special architecture
2871 wildcard <tt>any</tt>, or a list of specific and wildcard
2872 architectures separated by spaces. If <tt>all</tt>
2873 or <tt>any</tt> appears, that value must be the entire
2874 contents of the field. Most packages will use
2875 either <tt>all</tt> or <tt>any</tt>.
2879 Specifying a specific list of architectures indicates that the
2880 source will build an architecture-dependent package only on
2881 architectures included in the list. Specifying a list of
2882 architecture wildcards indicates that the source will build an
2883 architecture-dependent package on only those architectures
2884 that match any of the specified architecture wildcards.
2885 Specifying a list of architectures or architecture wildcards
2886 other than <tt>any</tt> is for the minority of cases where a
2887 program is not portable or is not useful on some
2888 architectures. Where possible, the program should be made
2893 In the source package control file <file>.dsc</file>, this
2894 field may contain either the architecture
2895 wildcard <tt>any</tt> or a list of architectures and
2896 architecture wildcards separated by spaces. If a list is
2897 given, it may include (or consist solely of) the special
2898 value <tt>all</tt>. In other words, in <file>.dsc</file>
2899 files unlike the <file>debian/control</file>, <tt>all</tt> may
2900 occur in combination with specific architectures.
2901 The <tt>Architecture</tt> field in the source package control
2902 file <file>.dsc</file> is generally constructed from
2903 the <tt>Architecture</tt> fields in
2904 the <file>debian/control</file> in the source package.
2908 Specifying <tt>any</tt> indicates that the source package
2909 isn't dependent on any particular architecture and should
2910 compile fine on any one. The produced binary package(s)
2911 will either be specific to whatever the current build
2912 architecture is or will be architecture-independent.
2916 Specifying only <tt>all</tt> indicates that the source package
2917 will only build architecture-independent packages. If this is
2918 the case, <tt>all</tt> must be used rather than <tt>any</tt>;
2919 <tt>any</tt> implies that the source package will build at
2920 least one architecture-dependent package.
2924 Specifying a list of architectures or architecture wildcards
2925 indicates that the source will build an architecture-dependent
2926 package, and will only work correctly on the listed or
2927 matching architectures. If the source package also builds at
2928 least one architecture-independent package, <tt>all</tt> will
2929 also be included in the list.
2933 In a <file>.changes</file> file, the <tt>Architecture</tt>
2934 field lists the architecture(s) of the package(s) currently
2935 being uploaded. This will be a list; if the source for the
2936 package is also being uploaded, the special
2937 entry <tt>source</tt> is also present. <tt>all</tt> will be
2938 present if any architecture-independent packages are being
2939 uploaded. Architecture wildcards such as <tt>any</tt> must
2940 never occur in the <tt>Architecture</tt> field in
2941 the <file>.changes</file> file.
2945 See <ref id="debianrules"> for information on how to get
2946 the architecture for the build process.
2950 <sect1 id="f-Essential">
2951 <heading><tt>Essential</tt></heading>
2954 This is a boolean field which may occur only in the
2955 control file of a binary package or in a per-package fields
2956 paragraph of a main source control data file.
2960 If set to <tt>yes</tt> then the package management system
2961 will refuse to remove the package (upgrading and replacing
2962 it is still possible). The other possible value is <tt>no</tt>,
2963 which is the same as not having the field at all.
2968 <heading>Package interrelationship fields:
2969 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2970 <tt>Recommends</tt>, <tt>Suggests</tt>,
2971 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2972 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2976 These fields describe the package's relationships with
2977 other packages. Their syntax and semantics are described
2978 in <ref id="relationships">.</p>
2981 <sect1 id="f-Standards-Version">
2982 <heading><tt>Standards-Version</tt></heading>
2985 The most recent version of the standards (the policy
2986 manual and associated texts) with which the package
2991 The version number has four components: major and minor
2992 version number and major and minor patch level. When the
2993 standards change in a way that requires every package to
2994 change the major number will be changed. Significant
2995 changes that will require work in many packages will be
2996 signaled by a change to the minor number. The major patch
2997 level will be changed for any change to the meaning of the
2998 standards, however small; the minor patch level will be
2999 changed when only cosmetic, typographical or other edits
3000 are made which neither change the meaning of the document
3001 nor affect the contents of packages.
3005 Thus only the first three components of the policy version
3006 are significant in the <em>Standards-Version</em> control
3007 field, and so either these three components or all four
3008 components may be specified.<footnote>
3009 In the past, people specified the full version number
3010 in the Standards-Version field, for example "2.3.0.0".
3011 Since minor patch-level changes don't introduce new
3012 policy, it was thought it would be better to relax
3013 policy and only require the first 3 components to be
3014 specified, in this example "2.3.0". All four
3015 components may still be used if someone wishes to do so.
3021 <sect1 id="f-Version">
3022 <heading><tt>Version</tt></heading>
3025 The version number of a package. The format is:
3026 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
3030 The three components here are:
3032 <tag><var>epoch</var></tag>
3035 This is a single (generally small) unsigned integer. It
3036 may be omitted, in which case zero is assumed. If it is
3037 omitted then the <var>upstream_version</var> may not
3042 It is provided to allow mistakes in the version numbers
3043 of older versions of a package, and also a package's
3044 previous version numbering schemes, to be left behind.
3048 <tag><var>upstream_version</var></tag>
3051 This is the main part of the version number. It is
3052 usually the version number of the original ("upstream")
3053 package from which the <file>.deb</file> file has been made,
3054 if this is applicable. Usually this will be in the same
3055 format as that specified by the upstream author(s);
3056 however, it may need to be reformatted to fit into the
3057 package management system's format and comparison
3062 The comparison behavior of the package management system
3063 with respect to the <var>upstream_version</var> is
3064 described below. The <var>upstream_version</var>
3065 portion of the version number is mandatory.
3069 The <var>upstream_version</var> may contain only
3070 alphanumerics<footnote>
3071 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3073 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3074 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3075 tilde) and should start with a digit. If there is no
3076 <var>debian_revision</var> then hyphens are not allowed;
3077 if there is no <var>epoch</var> then colons are not
3082 <tag><var>debian_revision</var></tag>
3085 This part of the version number specifies the version of
3086 the Debian package based on the upstream version. It
3087 may contain only alphanumerics and the characters
3088 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3089 tilde) and is compared in the same way as the
3090 <var>upstream_version</var> is.
3094 It is optional; if it isn't present then the
3095 <var>upstream_version</var> may not contain a hyphen.
3096 This format represents the case where a piece of
3097 software was written specifically to be a Debian
3098 package, where the Debian package source must always
3099 be identical to the pristine source and therefore no
3100 revision indication is required.
3104 It is conventional to restart the
3105 <var>debian_revision</var> at <tt>1</tt> each time the
3106 <var>upstream_version</var> is increased.
3110 The package management system will break the version
3111 number apart at the last hyphen in the string (if there
3112 is one) to determine the <var>upstream_version</var> and
3113 <var>debian_revision</var>. The absence of a
3114 <var>debian_revision</var> is equivalent to a
3115 <var>debian_revision</var> of <tt>0</tt>.
3122 When comparing two version numbers, first the <var>epoch</var>
3123 of each are compared, then the <var>upstream_version</var> if
3124 <var>epoch</var> is equal, and then <var>debian_revision</var>
3125 if <var>upstream_version</var> is also equal.
3126 <var>epoch</var> is compared numerically. The
3127 <var>upstream_version</var> and <var>debian_revision</var>
3128 parts are compared by the package management system using the
3129 following algorithm:
3133 The strings are compared from left to right.
3137 First the initial part of each string consisting entirely of
3138 non-digit characters is determined. These two parts (one of
3139 which may be empty) are compared lexically. If a difference
3140 is found it is returned. The lexical comparison is a
3141 comparison of ASCII values modified so that all the letters
3142 sort earlier than all the non-letters and so that a tilde
3143 sorts before anything, even the end of a part. For example,
3144 the following parts are in sorted order from earliest to
3145 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3146 <tt>a</tt>.<footnote>
3147 One common use of <tt>~</tt> is for upstream pre-releases.
3148 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3149 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3154 Then the initial part of the remainder of each string which
3155 consists entirely of digit characters is determined. The
3156 numerical values of these two parts are compared, and any
3157 difference found is returned as the result of the comparison.
3158 For these purposes an empty string (which can only occur at
3159 the end of one or both version strings being compared) counts
3164 These two steps (comparing and removing initial non-digit
3165 strings and initial digit strings) are repeated until a
3166 difference is found or both strings are exhausted.
3170 Note that the purpose of epochs is to allow us to leave behind
3171 mistakes in version numbering, and to cope with situations
3172 where the version numbering scheme changes. It is
3173 <em>not</em> intended to cope with version numbers containing
3174 strings of letters which the package management system cannot
3175 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3176 silly orderings.<footnote>
3177 The author of this manual has heard of a package whose
3178 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3179 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3185 <sect1 id="f-Description">
3186 <heading><tt>Description</tt></heading>
3189 In a source or binary control file, the <tt>Description</tt>
3190 field contains a description of the binary package, consisting
3191 of two parts, the synopsis or the short description, and the
3192 long description. The field's format is as follows:
3197 Description: <single line synopsis>
3198 <extended description over several lines>
3203 The lines in the extended description can have these formats:
3209 Those starting with a single space are part of a paragraph.
3210 Successive lines of this form will be word-wrapped when
3211 displayed. The leading space will usually be stripped off.
3215 Those starting with two or more spaces. These will be
3216 displayed verbatim. If the display cannot be panned
3217 horizontally, the displaying program will line wrap them "hard"
3218 (i.e., without taking account of word breaks). If it can they
3219 will be allowed to trail off to the right. None, one or two
3220 initial spaces may be deleted, but the number of spaces
3221 deleted from each line will be the same (so that you can have
3222 indenting work correctly, for example).
3226 Those containing a single space followed by a single full stop
3227 character. These are rendered as blank lines. This is the
3228 <em>only</em> way to get a blank line<footnote>
3229 Completely empty lines will not be rendered as blank lines.
3230 Instead, they will cause the parser to think you're starting
3231 a whole new record in the control file, and will therefore
3232 likely abort with an error.
3237 Those containing a space, a full stop and some more characters.
3238 These are for future expansion. Do not use them.
3244 Do not use tab characters. Their effect is not predictable.
3248 See <ref id="descriptions"> for further information on this.
3252 In a <file>.changes</file> file, the <tt>Description</tt>
3253 field contains a summary of the descriptions for the packages
3254 being uploaded. For this case, the first line of the field
3255 value (the part on the same line as <tt>Description:</tt>) is
3256 always empty. The content of the field is expressed as
3257 continuation lines, one line per package. Each line is
3258 indented by one space and contains the name of a binary
3259 package, a space, a hyphen (<tt>-</tt>), a space, and the
3260 short description line from that package.
3264 <sect1 id="f-Distribution">
3265 <heading><tt>Distribution</tt></heading>
3268 In a <file>.changes</file> file or parsed changelog output
3269 this contains the (space-separated) name(s) of the
3270 distribution(s) where this version of the package should
3271 be installed. Valid distributions are determined by the
3272 archive maintainers.<footnote>
3273 Example distribution names in the Debian archive used in
3274 <file>.changes</file> files are:
3275 <taglist compact="compact">
3276 <tag><em>unstable</em></tag>
3278 This distribution value refers to the
3279 <em>developmental</em> part of the Debian distribution
3280 tree. Most new packages, new upstream versions of
3281 packages and bug fixes go into the <em>unstable</em>
3285 <tag><em>experimental</em></tag>
3287 The packages with this distribution value are deemed
3288 by their maintainers to be high risk. Oftentimes they
3289 represent early beta or developmental packages from
3290 various sources that the maintainers want people to
3291 try, but are not ready to be a part of the other parts
3292 of the Debian distribution tree.
3297 Others are used for updating stable releases or for
3298 security uploads. More information is available in the
3299 Debian Developer's Reference, section "The Debian
3303 The Debian archive software only supports listing a single
3304 distribution. Migration of packages to other distributions is
3305 handled outside of the upload process.
3310 <heading><tt>Date</tt></heading>
3313 This field includes the date the package was built or last
3314 edited. It must be in the same format as the <var>date</var>
3315 in a <file>debian/changelog</file> entry.
3319 The value of this field is usually extracted from the
3320 <file>debian/changelog</file> file - see
3321 <ref id="dpkgchangelog">).
3325 <sect1 id="f-Format">
3326 <heading><tt>Format</tt></heading>
3329 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3330 files, this field declares the format version of that file.
3331 The syntax of the field value is the same as that of
3332 a <qref id="f-Version">package version number</qref> except
3333 that no epoch or Debian revision is allowed. The format
3334 described in this document is <tt>&changesversion;</tt>.
3338 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3339 Debian source control</qref> files, this field declares the
3340 format of the source package. The field value is used by
3341 programs acting on a source package to interpret the list of
3342 files in the source package and determine how to unpack it.
3343 The syntax of the field value is a numeric major revision, a
3344 period, a numeric minor revision, and then an optional subtype
3345 after whitespace, which if specified is an alphanumeric word
3346 in parentheses. The subtype is optional in the syntax but may
3347 be mandatory for particular source format revisions.
3349 The source formats currently supported by the Debian archive
3350 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3351 and <tt>3.0 (quilt)</tt>.
3356 <sect1 id="f-Urgency">
3357 <heading><tt>Urgency</tt></heading>
3360 This is a description of how important it is to upgrade to
3361 this version from previous ones. It consists of a single
3362 keyword taking one of the values <tt>low</tt>,
3363 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3364 <tt>critical</tt><footnote>
3365 Other urgency values are supported with configuration
3366 changes in the archive software but are not used in Debian.
3367 The urgency affects how quickly a package will be considered
3368 for inclusion into the <tt>testing</tt> distribution and
3369 gives an indication of the importance of any fixes included
3370 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3371 treated as synonymous.
3372 </footnote> (not case-sensitive) followed by an optional
3373 commentary (separated by a space) which is usually in
3374 parentheses. For example:
3377 Urgency: low (HIGH for users of diversions)
3383 The value of this field is usually extracted from the
3384 <file>debian/changelog</file> file - see
3385 <ref id="dpkgchangelog">.
3389 <sect1 id="f-Changes">
3390 <heading><tt>Changes</tt></heading>
3393 This field contains the human-readable changes data, describing
3394 the differences between the last version and the current one.
3398 The first line of the field value (the part on the same line
3399 as <tt>Changes:</tt>) is always empty. The content of the
3400 field is expressed as continuation lines, with each line
3401 indented by at least one space. Blank lines must be
3402 represented by a line consisting only of a space and a full
3407 The value of this field is usually extracted from the
3408 <file>debian/changelog</file> file - see
3409 <ref id="dpkgchangelog">).
3413 Each version's change information should be preceded by a
3414 "title" line giving at least the version, distribution(s)
3415 and urgency, in a human-readable way.
3419 If data from several versions is being returned the entry
3420 for the most recent version should be returned first, and
3421 entries should be separated by the representation of a
3422 blank line (the "title" line may also be followed by the
3423 representation of a blank line).
3427 <sect1 id="f-Binary">
3428 <heading><tt>Binary</tt></heading>
3431 This field is a list of binary packages. Its syntax and
3432 meaning varies depending on the control file in which it
3437 When it appears in the <file>.dsc</file> file, it lists binary
3438 packages which a source package can produce, separated by
3440 A space after each comma is conventional.
3441 </footnote>. It may span multiple lines. The source package
3442 does not necessarily produce all of these binary packages for
3443 every architecture. The source control file doesn't contain
3444 details of which architectures are appropriate for which of
3445 the binary packages.
3449 When it appears in a <file>.changes</file> file, it lists the
3450 names of the binary packages being uploaded, separated by
3451 whitespace (not commas). It may span multiple lines.
3455 <sect1 id="f-Installed-Size">
3456 <heading><tt>Installed-Size</tt></heading>
3459 This field appears in the control files of binary packages,
3460 and in the <file>Packages</file> files. It gives an estimate
3461 of the total amount of disk space required to install the
3462 named package. Actual installed size may vary based on block
3463 size, file system properties, or actions taken by package
3468 The disk space is given as the integer value of the estimated
3469 installed size in bytes, divided by 1024 and rounded up.
3473 <sect1 id="f-Files">
3474 <heading><tt>Files</tt></heading>
3477 This field contains a list of files with information about
3478 each one. The exact information and syntax varies with
3483 In all cases, Files is a multiline field. The first line of
3484 the field value (the part on the same line as <tt>Files:</tt>)
3485 is always empty. The content of the field is expressed as
3486 continuation lines, one line per file. Each line must be
3487 indented by one space and contain a number of sub-fields,
3488 separated by spaces, as described below.
3492 In the <file>.dsc</file> file, each line contains the MD5
3493 checksum, size and filename of the tar file and (if
3494 applicable) diff file which make up the remainder of the
3495 source package<footnote>
3496 That is, the parts which are not the <tt>.dsc</tt>.
3497 </footnote>. For example:
3500 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3501 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3503 The exact forms of the filenames are described
3504 in <ref id="pkg-sourcearchives">.
3508 In the <file>.changes</file> file this contains one line per
3509 file being uploaded. Each line contains the MD5 checksum,
3510 size, section and priority and the filename. For example:
3513 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3514 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3515 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3516 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3518 The <qref id="f-Section">section</qref>
3519 and <qref id="f-Priority">priority</qref> are the values of
3520 the corresponding fields in the main source control file. If
3521 no section or priority is specified then <tt>-</tt> should be
3522 used, though section and priority values must be specified for
3523 new packages to be installed properly.
3527 The special value <tt>byhand</tt> for the section in a
3528 <tt>.changes</tt> file indicates that the file in question
3529 is not an ordinary package file and must by installed by
3530 hand by the distribution maintainers. If the section is
3531 <tt>byhand</tt> the priority should be <tt>-</tt>.
3535 If a new Debian revision of a package is being shipped and
3536 no new original source archive is being distributed the
3537 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3538 entry for the original source archive
3539 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3540 but the <file>.changes</file> file should leave it out. In
3541 this case the original source archive on the distribution
3542 site must match exactly, byte-for-byte, the original
3543 source archive which was used to generate the
3544 <file>.dsc</file> file and diff which are being uploaded.</p>
3547 <sect1 id="f-Closes">
3548 <heading><tt>Closes</tt></heading>
3551 A space-separated list of bug report numbers that the upload
3552 governed by the .changes file closes.
3556 <sect1 id="f-Homepage">
3557 <heading><tt>Homepage</tt></heading>
3560 The URL of the web site for this package, preferably (when
3561 applicable) the site from which the original source can be
3562 obtained and any additional upstream documentation or
3563 information may be found. The content of this field is a
3564 simple URL without any surrounding characters such as
3569 <sect1 id="f-Checksums">
3570 <heading><tt>Checksums-Sha1</tt>
3571 and <tt>Checksums-Sha256</tt></heading>
3574 These fields contain a list of files with a checksum and size
3575 for each one. Both <tt>Checksums-Sha1</tt>
3576 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3577 only in the checksum algorithm used: SHA-1
3578 for <tt>Checksums-Sha1</tt> and SHA-256
3579 for <tt>Checksums-Sha256</tt>.
3583 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3584 multiline fields. The first line of the field value (the part
3585 on the same line as <tt>Checksums-Sha1:</tt>
3586 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3587 of the field is expressed as continuation lines, one line per
3588 file. Each line consists of the checksum, a space, the file
3589 size, a space, and the file name. For example (from
3590 a <file>.changes</file> file):
3593 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3594 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3595 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3596 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3598 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3599 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3600 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3601 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3606 In the <file>.dsc</file> file, these fields should list all
3607 files that make up the source package. In
3608 the <file>.changes</file> file, these fields should list all
3609 files being uploaded. The list of files in these fields
3610 must match the list of files in the <tt>Files</tt> field.
3616 <heading>User-defined fields</heading>
3619 Additional user-defined fields may be added to the
3620 source package control file. Such fields will be
3621 ignored, and not copied to (for example) binary or
3622 source package control files or upload control files.
3626 If you wish to add additional unsupported fields to
3627 these output files you should use the mechanism
3632 Fields in the main source control information file with
3633 names starting <tt>X</tt>, followed by one or more of
3634 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3635 be copied to the output files. Only the part of the
3636 field name after the hyphen will be used in the output
3637 file. Where the letter <tt>B</tt> is used the field
3638 will appear in binary package control files, where the
3639 letter <tt>S</tt> is used in source package control
3640 files and where <tt>C</tt> is used in upload control
3641 (<tt>.changes</tt>) files.
3645 For example, if the main source information control file
3648 XBS-Comment: I stand between the candle and the star.
3650 then the binary and source package control files will contain the
3653 Comment: I stand between the candle and the star.
3662 <chapt id="maintainerscripts">
3663 <heading>Package maintainer scripts and installation procedure</heading>
3666 <heading>Introduction to package maintainer scripts</heading>
3669 It is possible to supply scripts as part of a package which
3670 the package management system will run for you when your
3671 package is installed, upgraded or removed.
3675 These scripts are the control information
3676 files <prgn>preinst</prgn>, <prgn>postinst</prgn>, <prgn>prerm</prgn>
3677 and <prgn>postrm</prgn>. They must be proper executable files;
3678 if they are scripts (which is recommended), they must start with
3679 the usual <tt>#!</tt> convention. They should be readable and
3680 executable by anyone, and must not be world-writable.
3684 The package management system looks at the exit status from
3685 these scripts. It is important that they exit with a
3686 non-zero status if there is an error, so that the package
3687 management system can stop its processing. For shell
3688 scripts this means that you <em>almost always</em> need to
3689 use <tt>set -e</tt> (this is usually true when writing shell
3690 scripts, in fact). It is also important, of course, that
3691 they exit with a zero status if everything went well.
3695 Additionally, packages interacting with users
3696 using <prgn>debconf</prgn> in the <prgn>postinst</prgn> script
3697 should install a <prgn>config</prgn> script as a control
3698 information file. See <ref id="maintscriptprompt"> for details.
3702 When a package is upgraded a combination of the scripts from
3703 the old and new packages is called during the upgrade
3704 procedure. If your scripts are going to be at all
3705 complicated you need to be aware of this, and may need to
3706 check the arguments to your scripts.
3710 Broadly speaking the <prgn>preinst</prgn> is called before
3711 (a particular version of) a package is installed, and the
3712 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3713 before (a version of) a package is removed and the
3714 <prgn>postrm</prgn> afterwards.
3718 Programs called from maintainer scripts should not normally
3719 have a path prepended to them. Before installation is
3720 started, the package management system checks to see if the
3721 programs <prgn>ldconfig</prgn>,
3722 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3723 and <prgn>update-rc.d</prgn> can be found via the
3724 <tt>PATH</tt> environment variable. Those programs, and any
3725 other program that one would expect to be in the
3726 <tt>PATH</tt>, should thus be invoked without an absolute
3727 pathname. Maintainer scripts should also not reset the
3728 <tt>PATH</tt>, though they might choose to modify it by
3729 prepending or appending package-specific directories. These
3730 considerations really apply to all shell scripts.</p>
3733 <sect id="idempotency">
3734 <heading>Maintainer scripts idempotency</heading>
3737 It is necessary for the error recovery procedures that the
3738 scripts be idempotent. This means that if it is run
3739 successfully, and then it is called again, it doesn't bomb
3740 out or cause any harm, but just ensures that everything is
3741 the way it ought to be. If the first call failed, or
3742 aborted half way through for some reason, the second call
3743 should merely do the things that were left undone the first
3744 time, if any, and exit with a success status if everything
3746 This is so that if an error occurs, the user interrupts
3747 <prgn>dpkg</prgn> or some other unforeseen circumstance
3748 happens you don't leave the user with a badly-broken
3749 package when <prgn>dpkg</prgn> attempts to repeat the
3755 <sect id="controllingterminal">
3756 <heading>Controlling terminal for maintainer scripts</heading>
3759 Maintainer scripts are not guaranteed to run with a controlling
3760 terminal and may not be able to interact with the user. They
3761 must be able to fall back to noninteractive behavior if no
3762 controlling terminal is available. Maintainer scripts that
3763 prompt via a program conforming to the Debian Configuration
3764 Management Specification (see <ref id="maintscriptprompt">) may
3765 assume that program will handle falling back to noninteractive
3770 For high-priority prompts without a reasonable default answer,
3771 maintainer scripts may abort if there is no controlling
3772 terminal. However, this situation should be avoided if at all
3773 possible, since it prevents automated or unattended installs.
3774 In most cases, users will consider this to be a bug in the
3779 <sect id="exitstatus">
3780 <heading>Exit status</heading>
3783 Each script must return a zero exit status for
3784 success, or a nonzero one for failure, since the package
3785 management system looks for the exit status of these scripts
3786 and determines what action to take next based on that datum.
3790 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3795 <list compact="compact">
3797 <var>new-preinst</var> <tt>install</tt>
3800 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3803 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3806 <var>old-preinst</var> <tt>abort-upgrade</tt>
3807 <var>new-version</var>
3812 <list compact="compact">
3814 <var>postinst</var> <tt>configure</tt>
3815 <var>most-recently-configured-version</var>
3818 <var>old-postinst</var> <tt>abort-upgrade</tt>
3819 <var>new-version</var>
3822 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3823 <tt>in-favour</tt> <var>package</var>
3824 <var>new-version</var>
3827 <var>postinst</var> <tt>abort-remove</tt>
3830 <var>deconfigured's-postinst</var>
3831 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3832 <var>failed-install-package</var> <var>version</var>
3833 [<tt>removing</tt> <var>conflicting-package</var>
3839 <list compact="compact">
3841 <var>prerm</var> <tt>remove</tt>
3844 <var>old-prerm</var> <tt>upgrade</tt>
3845 <var>new-version</var>
3848 <var>new-prerm</var> <tt>failed-upgrade</tt>
3849 <var>old-version</var>
3852 <var>conflictor's-prerm</var> <tt>remove</tt>
3853 <tt>in-favour</tt> <var>package</var>
3854 <var>new-version</var>
3857 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3858 <tt>in-favour</tt> <var>package-being-installed</var>
3859 <var>version</var> [<tt>removing</tt>
3860 <var>conflicting-package</var>
3866 <list compact="compact">
3868 <var>postrm</var> <tt>remove</tt>
3871 <var>postrm</var> <tt>purge</tt>
3874 <var>old-postrm</var> <tt>upgrade</tt>
3875 <var>new-version</var>
3878 <var>new-postrm</var> <tt>failed-upgrade</tt>
3879 <var>old-version</var>
3882 <var>new-postrm</var> <tt>abort-install</tt>
3885 <var>new-postrm</var> <tt>abort-install</tt>
3886 <var>old-version</var>
3889 <var>new-postrm</var> <tt>abort-upgrade</tt>
3890 <var>old-version</var>
3893 <var>disappearer's-postrm</var> <tt>disappear</tt>
3894 <var>overwriter</var>
3895 <var>overwriter-version</var>
3901 <sect id="unpackphase">
3902 <heading>Details of unpack phase of installation or upgrade</heading>
3905 The procedure on installation/upgrade/overwrite/disappear
3906 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3907 stage of <tt>dpkg --install</tt>) is as follows. In each
3908 case, if a major error occurs (unless listed below) the
3909 actions are, in general, run backwards - this means that the
3910 maintainer scripts are run with different arguments in
3911 reverse order. These are the "error unwind" calls listed
3918 If a version of the package is already installed, call
3919 <example compact="compact">
3920 <var>old-prerm</var> upgrade <var>new-version</var>
3924 If the script runs but exits with a non-zero
3925 exit status, <prgn>dpkg</prgn> will attempt:
3926 <example compact="compact">
3927 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3929 If this works, the upgrade continues. If this
3930 does not work, the error unwind:
3931 <example compact="compact">
3932 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3934 If this works, then the old-version is
3935 "Installed", if not, the old version is in a
3936 "Half-Configured" state.
3942 If a "conflicting" package is being removed at the same time,
3943 or if any package will be broken (due to <tt>Breaks</tt>):
3946 If <tt>--auto-deconfigure</tt> is
3947 specified, call, for each package to be deconfigured
3948 due to <tt>Breaks</tt>:
3949 <example compact="compact">
3950 <var>deconfigured's-prerm</var> deconfigure \
3951 in-favour <var>package-being-installed</var> <var>version</var>
3954 <example compact="compact">
3955 <var>deconfigured's-postinst</var> abort-deconfigure \
3956 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3958 The deconfigured packages are marked as
3959 requiring configuration, so that if
3960 <tt>--install</tt> is used they will be
3961 configured again if possible.
3964 If any packages depended on a conflicting
3965 package being removed and <tt>--auto-deconfigure</tt> is
3966 specified, call, for each such package:
3967 <example compact="compact">
3968 <var>deconfigured's-prerm</var> deconfigure \
3969 in-favour <var>package-being-installed</var> <var>version</var> \
3970 removing <var>conflicting-package</var> <var>version</var>
3973 <example compact="compact">
3974 <var>deconfigured's-postinst</var> abort-deconfigure \
3975 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3976 removing <var>conflicting-package</var> <var>version</var>
3978 The deconfigured packages are marked as
3979 requiring configuration, so that if
3980 <tt>--install</tt> is used they will be
3981 configured again if possible.
3984 To prepare for removal of each conflicting package, call:
3985 <example compact="compact">
3986 <var>conflictor's-prerm</var> remove \
3987 in-favour <var>package</var> <var>new-version</var>
3990 <example compact="compact">
3991 <var>conflictor's-postinst</var> abort-remove \
3992 in-favour <var>package</var> <var>new-version</var>
4001 If the package is being upgraded, call:
4002 <example compact="compact">
4003 <var>new-preinst</var> upgrade <var>old-version</var>
4005 If this fails, we call:
4007 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4014 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4016 is called. If this works, then the old version
4017 is in an "Installed" state, or else it is left
4018 in an "Unpacked" state.
4023 If it fails, then the old version is left
4024 in an "Half-Installed" state.
4031 Otherwise, if the package had some configuration
4032 files from a previous version installed (i.e., it
4033 is in the "configuration files only" state):
4034 <example compact="compact">
4035 <var>new-preinst</var> install <var>old-version</var>
4039 <var>new-postrm</var> abort-install <var>old-version</var>
4041 If this fails, the package is left in a
4042 "Half-Installed" state, which requires a
4043 reinstall. If it works, the packages is left in
4044 a "Config-Files" state.
4047 Otherwise (i.e., the package was completely purged):
4048 <example compact="compact">
4049 <var>new-preinst</var> install
4052 <example compact="compact">
4053 <var>new-postrm</var> abort-install
4055 If the error-unwind fails, the package is in a
4056 "Half-Installed" phase, and requires a
4057 reinstall. If the error unwind works, the
4058 package is in a not installed state.
4065 The new package's files are unpacked, overwriting any
4066 that may be on the system already, for example any
4067 from the old version of the same package or from
4068 another package. Backups of the old files are kept
4069 temporarily, and if anything goes wrong the package
4070 management system will attempt to put them back as
4071 part of the error unwind.
4075 It is an error for a package to contain files which
4076 are on the system in another package, unless
4077 <tt>Replaces</tt> is used (see <ref id="replaces">).
4079 The following paragraph is not currently the case:
4080 Currently the <tt>- - force-overwrite</tt> flag is
4081 enabled, downgrading it to a warning, but this may not
4087 It is a more serious error for a package to contain a
4088 plain file or other kind of non-directory where another
4089 package has a directory (again, unless
4090 <tt>Replaces</tt> is used). This error can be
4091 overridden if desired using
4092 <tt>--force-overwrite-dir</tt>, but this is not
4097 Packages which overwrite each other's files produce
4098 behavior which, though deterministic, is hard for the
4099 system administrator to understand. It can easily
4100 lead to "missing" programs if, for example, a package
4101 is installed which overwrites a file from another
4102 package, and is then removed again.<footnote>
4103 Part of the problem is due to what is arguably a
4104 bug in <prgn>dpkg</prgn>.
4109 A directory will never be replaced by a symbolic link
4110 to a directory or vice versa; instead, the existing
4111 state (symlink or not) will be left alone and
4112 <prgn>dpkg</prgn> will follow the symlink if there is
4121 If the package is being upgraded, call
4122 <example compact="compact">
4123 <var>old-postrm</var> upgrade <var>new-version</var>
4127 If this fails, <prgn>dpkg</prgn> will attempt:
4128 <example compact="compact">
4129 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4131 If this works, installation continues. If not,
4133 <example compact="compact">
4134 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4136 If this fails, the old version is left in a
4137 "Half-Installed" state. If it works, dpkg now
4139 <example compact="compact">
4140 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4142 If this fails, the old version is left in a
4143 "Half-Installed" state. If it works, dpkg now
4145 <example compact="compact">
4146 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4148 If this fails, the old version is in an
4155 This is the point of no return - if
4156 <prgn>dpkg</prgn> gets this far, it won't back off
4157 past this point if an error occurs. This will
4158 leave the package in a fairly bad state, which
4159 will require a successful re-installation to clear
4160 up, but it's when <prgn>dpkg</prgn> starts doing
4161 things that are irreversible.
4166 Any files which were in the old version of the package
4167 but not in the new are removed.
4171 The new file list replaces the old.
4175 The new maintainer scripts replace the old.
4179 Any packages all of whose files have been overwritten
4180 during the installation, and which aren't required for
4181 dependencies, are considered to have been removed.
4182 For each such package
4185 <prgn>dpkg</prgn> calls:
4186 <example compact="compact">
4187 <var>disappearer's-postrm</var> disappear \
4188 <var>overwriter</var> <var>overwriter-version</var>
4192 The package's maintainer scripts are removed.
4195 It is noted in the status database as being in a
4196 sane state, namely not installed (any conffiles
4197 it may have are ignored, rather than being
4198 removed by <prgn>dpkg</prgn>). Note that
4199 disappearing packages do not have their prerm
4200 called, because <prgn>dpkg</prgn> doesn't know
4201 in advance that the package is going to
4208 Any files in the package we're unpacking that are also
4209 listed in the file lists of other packages are removed
4210 from those lists. (This will lobotomize the file list
4211 of the "conflicting" package if there is one.)
4215 The backup files made during installation, above, are
4221 The new package's status is now sane, and recorded as
4226 Here is another point of no return - if the
4227 conflicting package's removal fails we do not unwind
4228 the rest of the installation; the conflicting package
4229 is left in a half-removed limbo.
4234 If there was a conflicting package we go and do the
4235 removal actions (described below), starting with the
4236 removal of the conflicting package's files (any that
4237 are also in the package being installed have already
4238 been removed from the conflicting package's file list,
4239 and so do not get removed now).
4245 <sect id="configdetails"><heading>Details of configuration</heading>
4248 When we configure a package (this happens with <tt>dpkg
4249 --install</tt> and <tt>dpkg --configure</tt>), we first
4250 update any <tt>conffile</tt>s and then call:
4251 <example compact="compact">
4252 <var>postinst</var> configure <var>most-recently-configured-version</var>
4257 No attempt is made to unwind after errors during
4258 configuration. If the configuration fails, the package is in
4259 a "Failed Config" state, and an error message is generated.
4263 If there is no most recently configured version
4264 <prgn>dpkg</prgn> will pass a null argument.
4267 Historical note: Truly ancient (pre-1997) versions of
4268 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4269 (including the angle brackets) in this case. Even older
4270 ones did not pass a second argument at all, under any
4271 circumstance. Note that upgrades using such an old dpkg
4272 version are unlikely to work for other reasons, even if
4273 this old argument behavior is handled by your postinst script.
4279 <sect id="removedetails"><heading>Details of removal and/or
4280 configuration purging</heading>
4286 <example compact="compact">
4287 <var>prerm</var> remove
4291 If prerm fails during replacement due to conflict
4293 <var>conflictor's-postinst</var> abort-remove \
4294 in-favour <var>package</var> <var>new-version</var>
4298 <var>postinst</var> abort-remove
4302 If this fails, the package is in a "Half-Configured"
4303 state, or else it remains "Installed".
4307 The package's files are removed (except <tt>conffile</tt>s).
4310 <example compact="compact">
4311 <var>postrm</var> remove
4315 If it fails, there's no error unwind, and the package is in
4316 an "Half-Installed" state.
4321 All the maintainer scripts except the <prgn>postrm</prgn>
4326 If we aren't purging the package we stop here. Note
4327 that packages which have no <prgn>postrm</prgn> and no
4328 <tt>conffile</tt>s are automatically purged when
4329 removed, as there is no difference except for the
4330 <prgn>dpkg</prgn> status.
4334 The <tt>conffile</tt>s and any backup files
4335 (<tt>~</tt>-files, <tt>#*#</tt> files,
4336 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4341 <example compact="compact">
4342 <var>postrm</var> purge
4346 If this fails, the package remains in a "Config-Files"
4351 The package's file list is removed.
4360 <chapt id="relationships">
4361 <heading>Declaring relationships between packages</heading>
4363 <sect id="depsyntax">
4364 <heading>Syntax of relationship fields</heading>
4367 These fields all have a uniform syntax. They are a list of
4368 package names separated by commas.
4372 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4373 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4374 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4375 control fields of the package, which declare
4376 dependencies on other packages, the package names listed may
4377 also include lists of alternative package names, separated
4378 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4379 if any one of the alternative packages is installed, that
4380 part of the dependency is considered to be satisfied.
4384 All of the fields except for <tt>Provides</tt> may restrict
4385 their applicability to particular versions of each named
4386 package. This is done in parentheses after each individual
4387 package name; the parentheses should contain a relation from
4388 the list below followed by a version number, in the format
4389 described in <ref id="f-Version">.
4393 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4394 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4395 strictly earlier, earlier or equal, exactly equal, later or
4396 equal and strictly later, respectively. The deprecated
4397 forms <tt><</tt> and <tt>></tt> were used to mean
4398 earlier/later or equal, rather than strictly earlier/later,
4399 so they should not appear in new packages (though
4400 <prgn>dpkg</prgn> still supports them).
4404 Whitespace may appear at any point in the version
4405 specification subject to the rules in <ref
4406 id="controlsyntax">, and must appear where it's necessary to
4407 disambiguate; it is not otherwise significant. All of the
4408 relationship fields may span multiple lines. For
4409 consistency and in case of future changes to
4410 <prgn>dpkg</prgn> it is recommended that a single space be
4411 used after a version relationship and before a version
4412 number; it is also conventional to put a single space after
4413 each comma, on either side of each vertical bar, and before
4414 each open parenthesis. When wrapping a relationship field, it
4415 is conventional to do so after a comma and before the space
4416 following that comma.
4420 For example, a list of dependencies might appear as:
4421 <example compact="compact">
4424 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4429 Relationships may be restricted to a certain set of
4430 architectures. This is indicated in brackets after each
4431 individual package name and the optional version specification.
4432 The brackets enclose a list of Debian architecture names
4433 separated by whitespace. Exclamation marks may be prepended to
4434 each of the names. (It is not permitted for some names to be
4435 prepended with exclamation marks while others aren't.)
4439 For build relationship fields
4440 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4441 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>), if
4442 the current Debian host architecture is not in this list and
4443 there are no exclamation marks in the list, or it is in the list
4444 with a prepended exclamation mark, the package name and the
4445 associated version specification are ignored completely for the
4446 purposes of defining the relationships.
4451 <example compact="compact">
4453 Build-Depends-Indep: texinfo
4454 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4455 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4457 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4458 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4459 <tt>gnumach-dev</tt> only on hurd-i386.
4463 For binary relationship fields, the architecture restriction
4464 syntax is only supported in the source package control
4465 file <file>debian/control</file>. When the corresponding binary
4466 package control file is generated, the relationship will either
4467 be omitted or included without the architecture restriction
4468 based on the architecture of the binary package. This means
4469 that architecture restrictions must not be used in binary
4470 relationship fields for architecture-independent packages
4471 (<tt>Architecture: all</tt>).
4476 <example compact="compact">
4477 Depends: foo [i386], bar [amd64]
4479 becomes <tt>Depends: foo</tt> when the package is built on
4480 the <tt>i386</tt> architecture, <tt>Depends: bar</tt> when the
4481 package is built on the <tt>amd64</tt> architecture, and omitted
4482 entirely in binary packages built on all other architectures.
4486 If the architecture-restricted dependency is part of a set of
4487 alternatives using <tt>|</tt>, that alternative is ignored
4488 completely on architectures that do not match the restriction.
4490 <example compact="compact">
4491 Build-Depends: foo [!i386] | bar [!amd64]
4493 is equivalent to <tt>bar</tt> on the i386 architecture, to
4494 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4495 bar</tt> on all other architectures.
4499 Relationships may also be restricted to a certain set of
4500 architectures using architecture wildcards. The syntax for
4501 declaring such restrictions is the same as declaring
4502 restrictions using a certain set of architectures without
4503 architecture wildcards. For example:
4504 <example compact="compact">
4505 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4507 is equivalent to <tt>foo</tt> on architectures using the Linux
4508 kernel and any cpu, <tt>bar</tt> on architectures using any
4509 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4510 using a kernel other than Linux.
4514 Note that the binary package relationship fields such as
4515 <tt>Depends</tt> appear in one of the binary package
4516 sections of the control file, whereas the build-time
4517 relationships such as <tt>Build-Depends</tt> appear in the
4518 source package section of the control file (which is the
4523 <sect id="binarydeps">
4524 <heading>Binary Dependencies - <tt>Depends</tt>,
4525 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4526 <tt>Pre-Depends</tt>
4530 Packages can declare in their control file that they have
4531 certain relationships to other packages - for example, that
4532 they may not be installed at the same time as certain other
4533 packages, and/or that they depend on the presence of others.
4537 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4538 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4539 <tt>Breaks</tt> and <tt>Conflicts</tt> control fields.
4540 <tt>Breaks</tt> is described in <ref id="breaks">, and
4541 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4542 rest are described below.
4546 These seven fields are used to declare a dependency
4547 relationship by one package on another. Except for
4548 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4549 depending (binary) package's control file.
4550 (<tt>Enhances</tt> appears in the recommending package's
4551 control file, and <tt>Breaks</tt> appears in the version of
4552 depended-on package which causes the named package to
4557 A <tt>Depends</tt> field takes effect <em>only</em> when a
4558 package is to be configured. It does not prevent a package
4559 being on the system in an unconfigured state while its
4560 dependencies are unsatisfied, and it is possible to replace
4561 a package whose dependencies are satisfied and which is
4562 properly installed with a different version whose
4563 dependencies are not and cannot be satisfied; when this is
4564 done the depending package will be left unconfigured (since
4565 attempts to configure it will give errors) and will not
4566 function properly. If it is necessary, a
4567 <tt>Pre-Depends</tt> field can be used, which has a partial
4568 effect even when a package is being unpacked, as explained
4569 in detail below. (The other three dependency fields,
4570 <tt>Recommends</tt>, <tt>Suggests</tt> and
4571 <tt>Enhances</tt>, are only used by the various front-ends
4572 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4573 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4577 For this reason packages in an installation run are usually
4578 all unpacked first and all configured later; this gives
4579 later versions of packages with dependencies on later
4580 versions of other packages the opportunity to have their
4581 dependencies satisfied.
4585 In case of circular dependencies, since installation or
4586 removal order honoring the dependency order can't be
4587 established, dependency loops are broken at some point
4588 (based on rules below), and some packages may not be able to
4589 rely on their dependencies being present when being
4590 installed or removed, depending on which side of the break
4591 of the circular dependency loop they happen to be on. If one
4592 of the packages in the loop has no postinst script, then the
4593 cycle will be broken at that package, so as to ensure that
4594 all postinst scripts run with the dependencies properly
4595 configured if this is possible. Otherwise the breaking point
4600 The <tt>Depends</tt> field thus allows package maintainers
4601 to impose an order in which packages should be configured.
4605 The meaning of the five dependency fields is as follows:
4607 <tag><tt>Depends</tt></tag>
4610 This declares an absolute dependency. A package will
4611 not be configured unless all of the packages listed in
4612 its <tt>Depends</tt> field have been correctly
4617 The <tt>Depends</tt> field should be used if the
4618 depended-on package is required for the depending
4619 package to provide a significant amount of
4624 The <tt>Depends</tt> field should also be used if the
4625 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4626 <prgn>postrm</prgn> scripts require the package to be
4627 present in order to run. Note, however, that the
4628 <prgn>postrm</prgn> cannot rely on any non-essential
4629 packages to be present during the <tt>purge</tt>
4633 <tag><tt>Recommends</tt></tag>
4636 This declares a strong, but not absolute, dependency.
4640 The <tt>Recommends</tt> field should list packages
4641 that would be found together with this one in all but
4642 unusual installations.
4646 <tag><tt>Suggests</tt></tag>
4648 This is used to declare that one package may be more
4649 useful with one or more others. Using this field
4650 tells the packaging system and the user that the
4651 listed packages are related to this one and can
4652 perhaps enhance its usefulness, but that installing
4653 this one without them is perfectly reasonable.
4656 <tag><tt>Enhances</tt></tag>
4658 This field is similar to Suggests but works in the
4659 opposite direction. It is used to declare that a
4660 package can enhance the functionality of another
4664 <tag><tt>Pre-Depends</tt></tag>
4667 This field is like <tt>Depends</tt>, except that it
4668 also forces <prgn>dpkg</prgn> to complete installation
4669 of the packages named before even starting the
4670 installation of the package which declares the
4671 pre-dependency, as follows:
4675 When a package declaring a pre-dependency is about to
4676 be <em>unpacked</em> the pre-dependency can be
4677 satisfied if the depended-on package is either fully
4678 configured, <em>or even if</em> the depended-on
4679 package(s) are only unpacked or in the "Half-Configured"
4680 state, provided that they have been configured
4681 correctly at some point in the past (and not removed
4682 or partially removed since). In this case, both the
4683 previously-configured and currently unpacked or
4684 "Half-Configured" versions must satisfy any version
4685 clause in the <tt>Pre-Depends</tt> field.
4689 When the package declaring a pre-dependency is about
4690 to be <em>configured</em>, the pre-dependency will be
4691 treated as a normal <tt>Depends</tt>, that is, it will
4692 be considered satisfied only if the depended-on
4693 package has been correctly configured.
4697 <tt>Pre-Depends</tt> should be used sparingly,
4698 preferably only by packages whose premature upgrade or
4699 installation would hamper the ability of the system to
4700 continue with any upgrade that might be in progress.
4704 <tt>Pre-Depends</tt> are also required if the
4705 <prgn>preinst</prgn> script depends on the named
4706 package. It is best to avoid this situation if
4714 When selecting which level of dependency to use you should
4715 consider how important the depended-on package is to the
4716 functionality of the one declaring the dependency. Some
4717 packages are composed of components of varying degrees of
4718 importance. Such a package should list using
4719 <tt>Depends</tt> the package(s) which are required by the
4720 more important components. The other components'
4721 requirements may be mentioned as Suggestions or
4722 Recommendations, as appropriate to the components' relative
4728 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4731 When one binary package declares that it breaks another,
4732 <prgn>dpkg</prgn> will refuse to allow the package which
4733 declares <tt>Breaks</tt> be installed unless the broken
4734 package is deconfigured first, and it will refuse to
4735 allow the broken package to be reconfigured.
4739 A package will not be regarded as causing breakage merely
4740 because its configuration files are still installed; it must
4741 be at least "Half-Installed".
4745 A special exception is made for packages which declare that
4746 they break their own package name or a virtual package which
4747 they provide (see below): this does not count as a real
4752 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4753 version clause; such a <tt>Breaks</tt> is introduced in the
4754 version of an (implicit or explicit) dependency which violates
4755 an assumption or reveals a bug in earlier versions of the broken
4756 package, or which takes over a file from earlier versions of the
4757 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
4758 will inform higher-level package management tools that the
4759 broken package must be upgraded before the new one.
4763 If the breaking package also overwrites some files from the
4764 older package, it should use <tt>Replaces</tt> to ensure this
4765 goes smoothly. See <ref id="replaces"> for a full discussion
4766 of taking over files from other packages, including how to
4767 use <tt>Breaks</tt> in those cases.
4771 Many of the cases where <tt>Breaks</tt> should be used were
4772 previously handled with <tt>Conflicts</tt>
4773 because <tt>Breaks</tt> did not yet exist.
4774 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
4775 See <ref id="conflicts"> for more information about the
4780 <sect id="conflicts">
4781 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4784 When one binary package declares a conflict with another
4785 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4786 refuse to allow them to be installed on the system at the
4787 same time. This is a stronger restriction than <tt>Breaks</tt>,
4788 which just prevents both packages from being configured at the
4789 same time. Conflicting packages cannot be unpacked on the
4790 system at the same time.
4794 If one package is to be installed, the other must be removed
4795 first. If the package being installed is marked as replacing
4796 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
4797 normally be used in this case) the one on the system, or the one
4798 on the system is marked as deselected, or both packages are
4799 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
4800 automatically remove the package which is causing the conflict.
4801 Otherwise, it will halt the installation of the new package with
4802 an error. This mechanism is specifically designed to produce an
4803 error when the installed package is <tt>Essential</tt>, but the
4808 A package will not cause a conflict merely because its
4809 configuration files are still installed; it must be at least
4814 A special exception is made for packages which declare a
4815 conflict with their own package name, or with a virtual
4816 package which they provide (see below): this does not
4817 prevent their installation, and allows a package to conflict
4818 with others providing a replacement for it. You use this
4819 feature when you want the package in question to be the only
4820 package providing some feature.
4824 Normally, <tt>Breaks</tt> should be used instead
4825 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
4826 stronger restriction on the ordering of package installation or
4827 upgrade and can make it more difficult for the package manager
4828 to find a correct solution to an upgrade or installation
4829 problem. <tt>Breaks</tt> should be used
4831 <item>when moving a file from one package to another (see
4832 <ref id="replaces">),</item>
4833 <item>when splitting a package (a special case of the previous
4835 <item>when the breaking package exposes a bug in or interacts
4836 badly with particular versions of the broken
4839 <tt>Conflicts</tt> should be used
4841 <item>when two packages provide the same file and will
4842 continue to do so,</item>
4843 <item>in conjunction with <tt>Provides</tt> when only one
4844 package providing a given virtual facility may be installed
4845 at a time (see <ref id="virtual">),</item>
4846 <item>in other cases where one must prevent simultaneous
4847 installation of two packages for reasons that are ongoing
4848 (not fixed in a later version of one of the packages) or
4849 that must prevent both packages from being unpacked at the
4850 same time, not just configured.</item>
4852 Be aware that adding <tt>Conflicts</tt> is normally not the best
4853 solution when two packages provide the same files. Depending on
4854 the reason for that conflict, using alternatives or renaming the
4855 files is often a better approach. See, for
4856 example, <ref id="binaries">.
4860 Neither <tt>Breaks</tt> nor <tt>Conflicts</tt> should be used
4861 unless two packages cannot be installed at the same time or
4862 installing them both causes one of them to be broken or
4863 unusable. Having similar functionality or performing the same
4864 tasks as another package is not sufficient reason to
4865 declare <tt>Breaks</tt> or <tt>Conflicts</tt> with that package.
4869 A <tt>Conflicts</tt> entry may have an "earlier than" version
4870 clause if the reason for the conflict is corrected in a later
4871 version of one of the packages. However, normally the presence
4872 of an "earlier than" version clause is a sign
4873 that <tt>Breaks</tt> should have been used instead. An "earlier
4874 than" version clause in <tt>Conflicts</tt>
4875 prevents <prgn>dpkg</prgn> from upgrading or installing the
4876 package which declares such a conflict until the upgrade or
4877 removal of the conflicted-with package has been completed, which
4878 is a strong restriction.
4882 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4886 As well as the names of actual ("concrete") packages, the
4887 package relationship fields <tt>Depends</tt>,
4888 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4889 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4890 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4891 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4892 may mention "virtual packages".
4896 A <em>virtual package</em> is one which appears in the
4897 <tt>Provides</tt> control field of another package. The effect
4898 is as if the package(s) which provide a particular virtual
4899 package name had been listed by name everywhere the virtual
4900 package name appears. (See also <ref id="virtual_pkg">)
4904 If there are both concrete and virtual packages of the same
4905 name, then the dependency may be satisfied (or the conflict
4906 caused) by either the concrete package with the name in
4907 question or any other concrete package which provides the
4908 virtual package with the name in question. This is so that,
4909 for example, supposing we have
4910 <example compact="compact">
4913 </example> and someone else releases an enhanced version of
4914 the <tt>bar</tt> package they can say:
4915 <example compact="compact">
4919 and the <tt>bar-plus</tt> package will now also satisfy the
4920 dependency for the <tt>foo</tt> package.
4924 If a relationship field has a version number attached, only real
4925 packages will be considered to see whether the relationship is
4926 satisfied (or the prohibition violated, for a conflict or
4927 breakage). In other words, if a version number is specified,
4928 this is a request to ignore all <tt>Provides</tt> for that
4929 package name and consider only real packages. The package
4930 manager will assume that a package providing that virtual
4931 package is not of the "right" version. A <tt>Provides</tt>
4932 field may not contain version numbers, and the version number of
4933 the concrete package which provides a particular virtual package
4934 will not be considered when considering a dependency on or
4935 conflict with the virtual package name.<footnote>
4936 It is possible that a future release of <prgn>dpkg</prgn> may
4937 add the ability to specify a version number for each virtual
4938 package it provides. This feature is not yet present,
4939 however, and is expected to be used only infrequently.
4944 To specify which of a set of real packages should be the default
4945 to satisfy a particular dependency on a virtual package, list
4946 the real package as an alternative before the virtual one.
4950 If the virtual package represents a facility that can only be
4951 provided by one real package at a time, such as
4952 the <package>mail-transport-agent</package> virtual package that
4953 requires installation of a binary that would conflict with all
4954 other providers of that virtual package (see
4955 <ref id="mail-transport-agents">), all packages providing that
4956 virtual package should also declare a conflict with it
4957 using <tt>Conflicts</tt>. This will ensure that at most one
4958 provider of that virtual package is unpacked or installed at a
4963 <sect id="replaces"><heading>Overwriting files and replacing
4964 packages - <tt>Replaces</tt></heading>
4967 Packages can declare in their control file that they should
4968 overwrite files in certain other packages, or completely replace
4969 other packages. The <tt>Replaces</tt> control field has these
4970 two distinct purposes.
4973 <sect1><heading>Overwriting files in other packages</heading>
4976 It is usually an error for a package to contain files which
4977 are on the system in another package. However, if the
4978 overwriting package declares that it <tt>Replaces</tt> the one
4979 containing the file being overwritten, then <prgn>dpkg</prgn>
4980 will replace the file from the old package with that from the
4981 new. The file will no longer be listed as "owned" by the old
4982 package and will be taken over by the new package.
4983 Normally, <tt>Breaks</tt> should be used in conjunction
4984 with <tt>Replaces</tt>.<footnote>
4985 To see why <tt>Breaks</tt> is normally needed in addition
4986 to <tt>Replaces</tt>, consider the case of a file in the
4987 package <package>foo</package> being taken over by the
4988 package <package>foo-data</package>.
4989 <tt>Replaces</tt> will allow <package>foo-data</package> to
4990 be installed and take over that file. However,
4991 without <tt>Breaks</tt>, nothing
4992 requires <package>foo</package> to be upgraded to a newer
4993 version that knows it does not include that file and instead
4994 depends on <package>foo-data</package>. Nothing would
4995 prevent the new <package>foo-data</package> package from
4996 being installed and then removed, removing the file that it
4997 took over from <package>foo</package>. After that
4998 operation, the package manager would think the system was in
4999 a consistent state, but the <package>foo</package> package
5000 would be missing one of its files.
5005 For example, if a package <package>foo</package> is split
5006 into <package>foo</package> and <package>foo-data</package>
5007 starting at version 1.2-3, <package>foo-data</package> would
5009 <example compact="compact">
5010 Replaces: foo (<< 1.2-3)
5011 Breaks: foo (<< 1.2-3)
5013 in its control file. The new version of the
5014 package <package>foo</package> would normally have the field
5015 <example compact="compact">
5016 Depends: foo-data (>= 1.2-3)
5018 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
5019 the files moved into <package>foo-data</package> are not
5020 required for normal operation).
5024 If a package is completely replaced in this way, so that
5025 <prgn>dpkg</prgn> does not know of any files it still
5026 contains, it is considered to have "disappeared". It will
5027 be marked as not wanted on the system (selected for
5028 removal) and not installed. Any <tt>conffile</tt>s
5029 details noted for the package will be ignored, as they
5030 will have been taken over by the overwriting package. The
5031 package's <prgn>postrm</prgn> script will be run with a
5032 special argument to allow the package to do any final
5033 cleanup required. See <ref id="mscriptsinstact">.
5035 Replaces is a one way relationship. You have to install
5036 the replacing package after the replaced package.
5041 For this usage of <tt>Replaces</tt>, virtual packages (see
5042 <ref id="virtual">) are not considered when looking at a
5043 <tt>Replaces</tt> field. The packages declared as being
5044 replaced must be mentioned by their real names.
5048 This usage of <tt>Replaces</tt> only takes effect when both
5049 packages are at least partially on the system at once. It is
5050 not relevant if the packages conflict unless the conflict has
5055 <sect1><heading>Replacing whole packages, forcing their
5059 Second, <tt>Replaces</tt> allows the packaging system to
5060 resolve which package should be removed when there is a
5061 conflict (see <ref id="conflicts">). This usage only takes
5062 effect when the two packages <em>do</em> conflict, so that the
5063 two usages of this field do not interfere with each other.
5067 In this situation, the package declared as being replaced
5068 can be a virtual package, so for example, all mail
5069 transport agents (MTAs) would have the following fields in
5070 their control files:
5071 <example compact="compact">
5072 Provides: mail-transport-agent
5073 Conflicts: mail-transport-agent
5074 Replaces: mail-transport-agent
5076 ensuring that only one MTA can be installed at any one
5077 time. See <ref id="virtual"> for more information about this
5082 <sect id="sourcebinarydeps">
5083 <heading>Relationships between source and binary packages -
5084 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5085 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5089 Source packages that require certain binary packages to be
5090 installed or absent at the time of building the package
5091 can declare relationships to those binary packages.
5095 This is done using the <tt>Build-Depends</tt>,
5096 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5097 <tt>Build-Conflicts-Indep</tt> control fields.
5101 Build-dependencies on "build-essential" binary packages can be
5102 omitted. Please see <ref id="pkg-relations"> for more information.
5106 The dependencies and conflicts they define must be satisfied
5107 (as defined earlier for binary packages) in order to invoke
5108 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5110 There is no Build-Depends-Arch; this role is essentially
5111 met with Build-Depends. Anyone building the
5112 <tt>build-indep</tt> and <tt>binary-indep</tt> targets is
5113 assumed to be building the whole package, and therefore
5114 installation of all build dependencies is required.
5117 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5118 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5119 not yet know how to check for its existence, and
5120 <tt>binary-arch</tt>. The purpose of the original split
5121 between <tt>Build-Depends</tt> and
5122 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5123 wouldn't need to install extra packages needed only for the
5124 binary-indep targets. But without a build-arch/build-indep
5125 split, this didn't work, since most of the work is done in
5126 the build target, not in the binary target.
5130 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5131 <tt>binary-arch</tt></tag>
5133 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5134 fields must be satisfied when these targets are invoked.
5136 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5137 and <tt>binary-indep</tt></tag>
5139 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5140 <tt>Build-Depends-Indep</tt>, and
5141 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5142 these targets are invoked.
5150 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5153 Packages containing shared libraries must be constructed with
5154 a little care to make sure that the shared library is always
5155 available. This is especially important for packages whose
5156 shared libraries are vitally important, such as the C library
5157 (currently <tt>libc6</tt>).
5161 This section deals only with public shared libraries: shared
5162 libraries that are placed in directories searched by the dynamic
5163 linker by default or which are intended to be linked against
5164 normally and possibly used by other, independent packages. Shared
5165 libraries that are internal to a particular package or that are
5166 only loaded as dynamic modules are not covered by this section and
5167 are not subject to its requirements.
5171 A shared library is identified by the <tt>SONAME</tt> attribute
5172 stored in its dynamic section. When a binary is linked against a
5173 shared library, the <tt>SONAME</tt> of the shared library is
5174 recorded in the binary's <tt>NEEDED</tt> section so that the
5175 dynamic linker knows that library must be loaded at runtime. The
5176 shared library file's full name (which usually contains additional
5177 version information not needed in the <tt>SONAME</tt>) is
5178 therefore normally not referenced directly. Instead, the shared
5179 library is loaded by its <tt>SONAME</tt>, which exists on the file
5180 system as a symlink pointing to the full name of the shared
5181 library. This symlink must be provided by the
5182 package. <ref id="sharedlibs-runtime"> describes how to do this.
5184 This is a convention of shared library versioning, but not a
5185 requirement. Some libraries use the <tt>SONAME</tt> as the full
5186 library file name instead and therefore do not need a symlink.
5187 Most, however, encode additional information about
5188 backwards-compatible revisions as a minor version number in the
5189 file name. The <tt>SONAME</tt> itself only changes when
5190 binaries linked with the earlier version of the shared library
5191 may no longer work, but the filename may change with each
5192 release of the library. See <ref id="sharedlibs-runtime"> for
5198 When linking a binary or another shared library against a shared
5199 library, the <tt>SONAME</tt> for that shared library is not yet
5200 known. Instead, the shared library is found by looking for a file
5201 matching the library name with <tt>.so</tt> appended. This file
5202 exists on the file system as a symlink pointing to the shared
5207 Shared libraries are normally split into several binary packages.
5208 The <tt>SONAME</tt> symlink is installed by the runtime shared
5209 library package, and the bare <tt>.so</tt> symlink is installed in
5210 the development package since it's only used when linking binaries
5211 or shared libraries. However, there are some exceptions for
5212 unusual shared libraries or for shared libraries that are also
5213 loaded as dynamic modules by other programs.
5217 This section is primarily concerned with how the separation of
5218 shared libraries into multiple packages should be done and how
5219 dependencies on and between shared library binary packages are
5220 managed in Debian. <ref id="libraries"> should be read in
5221 conjunction with this section and contains additional rules for
5222 the files contained in the shared library packages.
5225 <sect id="sharedlibs-runtime">
5226 <heading>Run-time shared libraries</heading>
5229 The run-time shared library must be placed in a package
5230 whose name changes whenever the <tt>SONAME</tt> of the shared
5231 library changes. This allows several versions of the shared
5232 library to be installed at the same time, allowing installation
5233 of the new version of the shared library without immediately
5234 breaking binaries that depend on the old version. Normally, the
5235 run-time shared library and its <tt>SONAME</tt> symlink should
5236 be placed in a package named
5237 <package><var>libraryname</var><var>soversion</var></package>,
5238 where <var>soversion</var> is the version number in
5239 the <tt>SONAME</tt> of the shared library.
5240 See <ref id="shlibs"> for detailed information on how to
5241 determine this version. Alternatively, if it would be confusing
5242 to directly append <var>soversion</var>
5243 to <var>libraryname</var> (if, for example, <var>libraryname</var>
5244 itself ends in a number), you should use
5245 <package><var>libraryname</var>-<var>soversion</var></package>
5250 If you have several shared libraries built from the same source
5251 tree, you may lump them all together into a single shared
5252 library package provided that all of their <tt>SONAME</tt>s will
5253 always change together. Be aware that this is not normally the
5254 case, and if the <tt>SONAME</tt>s do not change together,
5255 upgrading such a merged shared library package will be
5256 unnecessarily difficult because of file conflicts with the old
5257 version of the package. When in doubt, always split shared
5258 library packages so that each binary package installs a single
5263 Every time the shared library ABI changes in a way that may
5264 break binaries linked against older versions of the shared
5265 library, the <tt>SONAME</tt> of the library and the
5266 corresponding name for the binary package containing the runtime
5267 shared library should change. Normally, this means
5268 the <tt>SONAME</tt> should change any time an interface is
5269 removed from the shared library or the signature of an interface
5270 (the number of parameters or the types of parameters that it
5271 takes, for example) is changed. This practice is vital to
5272 allowing clean upgrades from older versions of the package and
5273 clean transitions between the old ABI and new ABI without having
5274 to upgrade every affected package simultaneously.
5278 The <tt>SONAME</tt> and binary package name need not, and indeed
5279 normally should not, change if new interfaces are added but none
5280 are removed or changed, since this will not break binaries
5281 linked against the old shared library. Correct versioning of
5282 dependencies on the newer shared library by binaries that use
5283 the new interfaces is handled via
5284 the <qref id="sharedlibs-shlibdeps"><tt>shlibs</tt>
5285 system</qref> or via symbols files (see
5286 <manref name="deb-symbols" section="5">).
5290 The package should install the shared libraries under
5291 their normal names. For example, the <package>libgdbm3</package>
5292 package should install <file>libgdbm.so.3.0.0</file> as
5293 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5294 renamed or re-linked by any <prgn>prerm</prgn> or
5295 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5296 of renaming things safely without affecting running programs,
5297 and attempts to interfere with this are likely to lead to
5302 Shared libraries should not be installed executable, since
5303 the dynamic linker does not require this and trying to
5304 execute a shared library usually results in a core dump.
5308 The run-time library package should include the symbolic link for
5309 the <tt>SONAME</tt> that <prgn>ldconfig</prgn> would create for
5310 the shared libraries. For example,
5311 the <package>libgdbm3</package> package should include a symbolic
5312 link from <file>/usr/lib/libgdbm.so.3</file> to
5313 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5314 linker (for example <prgn>ld.so</prgn> or
5315 <prgn>ld-linux.so.*</prgn>) can find the library between the
5316 time that <prgn>dpkg</prgn> installs it and the time that
5317 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5319 The package management system requires the library to be
5320 placed before the symbolic link pointing to it in the
5321 <file>.deb</file> file. This is so that when
5322 <prgn>dpkg</prgn> comes to install the symlink
5323 (overwriting the previous symlink pointing at an older
5324 version of the library), the new shared library is already
5325 in place. In the past, this was achieved by creating the
5326 library in the temporary packaging directory before
5327 creating the symlink. Unfortunately, this was not always
5328 effective, since the building of the tar file in the
5329 <file>.deb</file> depended on the behavior of the underlying
5330 file system. Some file systems (such as reiserfs) reorder
5331 the files so that the order of creation is forgotten.
5332 Since version 1.7.0, <prgn>dpkg</prgn>
5333 reorders the files itself as necessary when building a
5334 package. Thus it is no longer important to concern
5335 oneself with the order of file creation.
5339 <sect1 id="ldconfig">
5340 <heading><tt>ldconfig</tt></heading>
5343 Any package installing shared libraries in one of the default
5344 library directories of the dynamic linker (which are currently
5345 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5346 listed in <file>/etc/ld.so.conf</file><footnote>
5348 <list compact="compact">
5349 <item>/usr/local/lib</item>
5350 <item>/usr/lib/libc5-compat</item>
5351 <item>/lib/libc5-compat</item>
5354 must use <prgn>ldconfig</prgn> to update the shared library
5359 The package maintainer scripts must only call
5360 <prgn>ldconfig</prgn> under these circumstances:
5361 <list compact="compact">
5362 <item>When the <prgn>postinst</prgn> script is run with a
5363 first argument of <tt>configure</tt>, the script must call
5364 <prgn>ldconfig</prgn>, and may optionally invoke
5365 <prgn>ldconfig</prgn> at other times.
5367 <item>When the <prgn>postrm</prgn> script is run with a
5368 first argument of <tt>remove</tt>, the script should call
5369 <prgn>ldconfig</prgn>.
5374 During install or upgrade, the preinst is called before
5375 the new files are installed, so calling "ldconfig" is
5376 pointless. The preinst of an existing package can also be
5377 called if an upgrade fails. However, this happens during
5378 the critical time when a shared libs may exist on-disk
5379 under a temporary name. Thus, it is dangerous and
5380 forbidden by current policy to call "ldconfig" at this
5385 When a package is installed or upgraded, "postinst
5386 configure" runs after the new files are safely on-disk.
5387 Since it is perfectly safe to invoke ldconfig
5388 unconditionally in a postinst, it is OK for a package to
5389 simply put ldconfig in its postinst without checking the
5390 argument. The postinst can also be called to recover from
5391 a failed upgrade. This happens before any new files are
5392 unpacked, so there is no reason to call "ldconfig" at this
5397 For a package that is being removed, prerm is
5398 called with all the files intact, so calling ldconfig is
5399 useless. The other calls to "prerm" happen in the case of
5400 upgrade at a time when all the files of the old package
5401 are on-disk, so again calling "ldconfig" is pointless.
5405 postrm, on the other hand, is called with the "remove"
5406 argument just after the files are removed, so this is
5407 the proper time to call "ldconfig" to notify the system
5408 of the fact that the shared libraries from the package
5409 are removed. The postrm can be called at several other
5410 times. At the time of "postrm purge", "postrm
5411 abort-install", or "postrm abort-upgrade", calling
5412 "ldconfig" is useless because the shared lib files are
5413 not on-disk. However, when "postrm" is invoked with
5414 arguments "upgrade", "failed-upgrade", or "disappear", a
5415 shared lib may exist on-disk under a temporary filename.
5423 <sect id="sharedlibs-support-files">
5424 <heading>Shared library support files</heading>
5427 If your package contains files whose names do not change with
5428 each change in the library shared object version, you must not
5429 put them in the shared library package. Otherwise, several
5430 versions of the shared library cannot be installed at the same
5431 time without filename clashes, making upgrades and transitions
5432 unnecessarily difficult.
5436 It is recommended that supporting files and run-time support
5437 programs that do not need to be invoked manually by users, but
5438 are nevertheless required for the package to function, be placed
5439 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5440 preferably under <file>/usr/lib/</file><var>package-name</var>.
5441 If the program or file is architecture independent, the
5442 recommendation is for it to be placed in a subdirectory of
5443 <file>/usr/share</file> instead, preferably under
5444 <file>/usr/share/</file><var>package-name</var>. Following the
5445 <var>package-name</var> naming convention ensures that the file
5446 names change when the shared object version changes.
5450 Run-time support programs that use the shared library but are
5451 not required for the library to function or files used by the
5452 shared library that can be used by any version of the shared
5453 library package should instead be put in a separate package.
5454 This package might typically be named
5455 <package><var>libraryname</var>-tools</package>; note the
5456 absence of the <var>soversion</var> in the package name.
5460 Files and support programs only useful when compiling software
5461 against the library should be included in the development
5462 package for the library.<footnote>
5463 For example, a <file><var>package-name</var>-config</file>
5464 script or <package>pkg-config</package> configuration files.
5469 <sect id="sharedlibs-static">
5470 <heading>Static libraries</heading>
5473 The static library (<file><var>libraryname.a</var></file>)
5474 is usually provided in addition to the shared version.
5475 It is placed into the development package (see below).
5479 In some cases, it is acceptable for a library to be
5480 available in static form only; these cases include:
5482 <item>libraries for languages whose shared library support
5483 is immature or unstable</item>
5484 <item>libraries whose interfaces are in flux or under
5485 development (commonly the case when the library's
5486 major version number is zero, or where the ABI breaks
5487 across patchlevels)</item>
5488 <item>libraries which are explicitly intended to be
5489 available only in static form by their upstream
5494 <sect id="sharedlibs-dev">
5495 <heading>Development files</heading>
5498 If there are development files associated with a shared library,
5499 the source package needs to generate a binary development package
5500 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5501 or if you prefer only to support one development version at a
5502 time, <package><var>libraryname</var>-dev</package>. Installing
5503 the development package must result in installation of all the
5504 development files necessary for compiling programs against that
5505 shared library.<footnote>
5506 This wording allows the development files to be split into
5507 several packages, such as a separate architecture-independent
5508 <package><var>libraryname</var>-headers</package>, provided that
5509 the development package depends on all the required additional
5515 In case several development versions of a library exist, you may
5516 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5517 <ref id="conflicts">) to ensure that the user only installs one
5518 development version at a time (as different development versions are
5519 likely to have the same header files in them, which would cause a
5520 filename clash if both were installed).
5524 The development package should contain a symlink for the associated
5525 shared library without a version number. For example, the
5526 <package>libgdbm-dev</package> package should include a symlink
5527 from <file>/usr/lib/libgdbm.so</file> to
5528 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5529 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5530 <file>libgdbm.so</file> when compiling dynamically.
5534 If the package provides Ada Library Information
5535 (<file>*.ali</file>) files for use with GNAT, these files must be
5536 installed read-only (mode 0444) so that GNAT will not attempt to
5537 recompile them. This overrides the normal file mode requirements
5538 given in <ref id="permissions-owners">.
5542 <sect id="sharedlibs-intradeps">
5543 <heading>Dependencies between the packages of the same library</heading>
5546 Typically the development version should have an exact
5547 version dependency on the runtime library, to make sure that
5548 compilation and linking happens correctly. The
5549 <tt>${binary:Version}</tt> substitution variable can be
5550 useful for this purpose.
5552 Previously, <tt>${Source-Version}</tt> was used, but its name
5553 was confusing and it has been deprecated since dpkg 1.13.19.
5558 <sect id="sharedlibs-shlibdeps">
5559 <heading>Dependencies between the library and other packages -
5560 the <tt>shlibs</tt> system</heading>
5563 If a package contains a binary or library which links to a
5564 shared library, we must ensure that when the package is
5565 installed on the system, all of the libraries needed are
5566 also installed. This requirement led to the creation of the
5567 <tt>shlibs</tt> system, which is very simple in its design:
5568 any package which <em>provides</em> a shared library also
5569 provides information on the package dependencies required to
5570 ensure the presence of this library, and any package which
5571 <em>uses</em> a shared library uses this information to
5572 determine the dependencies it requires. The files which
5573 contain the mapping from shared libraries to the necessary
5574 dependency information are called <file>shlibs</file> files.
5578 When a package is built which contains any shared libraries, it
5579 must provide a <file>shlibs</file> file for other packages to
5580 use. When a package is built which contains any shared
5581 libraries or compiled binaries, it must run
5582 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5583 on these to determine the libraries used and hence the
5584 dependencies needed by this package.<footnote>
5586 <prgn>dpkg-shlibdeps</prgn> will use a program
5587 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
5588 the libraries directly needed by the binaries or shared
5589 libraries in the package.
5593 We say that a binary <tt>foo</tt> <em>directly</em> uses
5594 a library <tt>libbar</tt> if it is explicitly linked
5595 with that library (that is, the library is listed in the ELF
5596 <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
5597 to the link line when the binary is created). Other
5598 libraries that are needed by <tt>libbar</tt> are linked
5599 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5600 linker will load them automatically when it loads
5601 <tt>libbar</tt>. A package should depend on the libraries
5602 it directly uses, but not the libraries it indirectly uses.
5603 The dependencies for those libraries will automatically pull
5604 in the other libraries.
5608 A good example of where this helps is the following. We
5609 could update <tt>libimlib</tt> with a new version that
5610 supports a new graphics format called dgf (but retaining the
5611 same major version number) and depends on <tt>libdgf</tt>.
5612 If we used <prgn>ldd</prgn> to add dependencies for every
5613 library directly or indirectly linked with a binary, every
5614 package that uses <tt>libimlib</tt> would need to be
5615 recompiled so it would also depend on <tt>libdgf</tt> or it
5616 wouldn't run due to missing symbols. Since dependencies are
5617 only added based on ELF <tt>NEEDED</tt> attribute, packages
5618 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
5619 having the dependency on <tt>libdgf</tt> and so they would
5620 not need rebuilding.
5626 In the following sections, we will first describe where the
5627 various <tt>shlibs</tt> files are to be found, then how to
5628 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5629 file format and how to create them if your package contains a
5634 <heading>The <tt>shlibs</tt> files present on the system</heading>
5637 There are several places where <tt>shlibs</tt> files are
5638 found. The following list gives them in the order in which
5640 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5641 (The first one which gives the required information is used.)
5647 <p><file>debian/shlibs.local</file></p>
5650 This lists overrides for this package. This file should
5651 normally not be used, but may be needed temporarily in
5652 unusual situations to work around bugs in other packages,
5653 or in unusual cases where the normally declared dependency
5654 information in the installed <file>shlibs</file> file for
5655 a library cannot be used. This file overrides information
5656 obtained from any other source.
5661 <p><file>/etc/dpkg/shlibs.override</file></p>
5664 This lists global overrides. This list is normally
5665 empty. It is maintained by the local system
5671 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5674 When packages are being built,
5675 any <file>debian/shlibs</file> files are copied into the
5676 control information file area of the temporary build
5677 directory and given the name <file>shlibs</file>. These
5678 files give details of any shared libraries included in the
5679 same package.<footnote>
5680 An example may help here. Let us say that the source
5681 package <tt>foo</tt> generates two binary
5682 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
5683 When building the binary packages, the two packages are
5684 created in the directories <file>debian/libfoo2</file>
5685 and <file>debian/foo-runtime</file> respectively.
5686 (<file>debian/tmp</file> could be used instead of one of
5687 these.) Since <tt>libfoo2</tt> provides the
5688 <tt>libfoo</tt> shared library, it will require a
5689 <tt>shlibs</tt> file, which will be installed in
5690 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually to
5691 become <file>/var/lib/dpkg/info/libfoo2.shlibs</file>.
5692 When <prgn>dpkg-shlibdeps</prgn> is run on the
5693 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
5695 the <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5696 determine whether <tt>foo-prog</tt>'s library
5697 dependencies are satisfied by any of the libraries
5698 provided by <tt>libfoo2</tt>. For this reason,
5699 <prgn>dpkg-shlibdeps</prgn> must only be run once all of
5700 the individual binary packages' <tt>shlibs</tt> files
5701 have been installed into the build directory.
5707 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5710 These are the <file>shlibs</file> files corresponding to
5711 all of the packages installed on the system, and are
5712 maintained by the relevant package maintainers.
5717 <p><file>/etc/dpkg/shlibs.default</file></p>
5720 This file lists any shared libraries whose packages
5721 have failed to provide correct <file>shlibs</file> files.
5722 It was used when the <file>shlibs</file> setup was first
5723 introduced, but it is now normally empty. It is
5724 maintained by the <tt>dpkg</tt> maintainer.
5732 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5733 <file>shlibs</file> files</heading>
5737 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5738 into your <file>debian/rules</file> file. If your package
5739 contains only compiled binaries and libraries (but no scripts),
5740 you can use a command such as:
5741 <example compact="compact">
5742 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5743 debian/tmp/usr/lib/*
5745 Otherwise, you will need to explicitly list the compiled
5746 binaries and libraries.<footnote>
5747 If you are using <tt>debhelper</tt>, the
5748 <prgn>dh_shlibdeps</prgn> program will do this work for you.
5749 It will also correctly handle multi-binary packages.
5754 This command puts the dependency information into the
5755 <file>debian/substvars</file> file, which is then used by
5756 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5757 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5758 field in the control file for this to work.
5762 If you have multiple binary packages, you will need to call
5763 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5764 compiled libraries or binaries. In such a case, you will
5765 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5766 utilities to specify a different <file>substvars</file> file.
5770 If you are creating a udeb for use in the Debian Installer,
5771 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
5772 should use the dependency line of type <tt>udeb</tt> by
5773 adding the <tt>-tudeb</tt> option<footnote>
5774 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5775 will automatically add this option if it knows it is
5777 </footnote>. If there is no dependency line of
5778 type <tt>udeb</tt> in the <file>shlibs</file>
5779 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the regular
5784 For more details on <prgn>dpkg-shlibdeps</prgn>, please see
5785 <ref id="pkg-dpkg-shlibdeps"> and
5786 <manref name="dpkg-shlibdeps" section="1">.
5791 <heading>The <file>shlibs</file> File Format</heading>
5794 Each <file>shlibs</file> file has the same format. Lines
5795 beginning with <tt>#</tt> are considered to be comments and
5796 are ignored. Each line is of the form:
5797 <example compact="compact">
5798 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5803 We will explain this by reference to the example of the
5804 <tt>zlib1g</tt> package, which (at the time of writing)
5805 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5809 <var>type</var> is an optional element that indicates the type
5810 of package for which the line is valid. The only type currently
5811 in use is <tt>udeb</tt>. The colon and space after the type are
5816 <var>library-name</var> is the name of the shared library,
5817 in this case <tt>libz</tt>. (This must match the name part
5818 of the soname, see below.)
5822 <var>soname-version</var> is the version part of the soname of
5823 the library. The soname is the thing that must exactly match
5824 for the library to be recognized by the dynamic linker, and is
5826 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5827 example, <tt>libz.so.1</tt>.<footnote>
5828 This can be determined using the command
5829 <example compact="compact">
5830 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5833 The version part is the part which comes after
5834 <tt>.so.</tt>, so in our case, it is <tt>1</tt>. The soname may
5835 instead be of the form
5836 <tt><var>name</var>-<var>major-version</var>.so</tt>, such
5837 as <tt>libdb-4.8.so</tt>, in which case the name would
5838 be <tt>libdb</tt> and the version would be <tt>4.8</tt>.
5842 <var>dependencies</var> has the same syntax as a dependency
5843 field in a binary package control file. It should give
5844 details of which packages are required to satisfy a binary
5845 built against the version of the library contained in the
5846 package. See <ref id="depsyntax"> for details.
5850 In our example, if the first version of the <tt>zlib1g</tt>
5851 package which contained a minor number of at least
5852 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5853 <tt>shlibs</tt> entry for this library could say:
5854 <example compact="compact">
5855 libz 1 zlib1g (>= 1:1.1.3)
5857 The version-specific dependency is to avoid warnings from
5858 the dynamic linker about using older shared libraries with
5863 As zlib1g also provides a udeb containing the shared library,
5864 there would also be a second line:
5865 <example compact="compact">
5866 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5872 <heading>Providing a <file>shlibs</file> file</heading>
5875 If your package provides a shared library, you need to create
5876 a <file>shlibs</file> file following the format described above.
5877 It is usual to call this file <file>debian/shlibs</file> (but if
5878 you have multiple binary packages, you might want to call it
5879 <file>debian/shlibs.<var>package</var></file> instead). Then
5880 let <file>debian/rules</file> install it in the control
5881 information file area:
5882 <example compact="compact">
5883 install -m644 debian/shlibs debian/tmp/DEBIAN
5885 or, in the case of a multi-binary package:
5886 <example compact="compact">
5887 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5889 An alternative way of doing this is to create the
5890 <file>shlibs</file> file in the control information file area
5891 directly from <file>debian/rules</file> without using
5892 a <file>debian/shlibs</file> file at all,<footnote>
5893 This is what <prgn>dh_makeshlibs</prgn> in
5894 the <package>debhelper</package> suite does. If your package
5895 also has a udeb that provides a shared
5896 library, <prgn>dh_makeshlibs</prgn> can automatically generate
5897 the <tt>udeb:</tt> lines if you specify the name of the udeb
5898 with the <tt>--add-udeb</tt> option.
5900 since the <file>debian/shlibs</file> file itself is ignored by
5901 <prgn>dpkg-shlibdeps</prgn>.
5905 As <prgn>dpkg-shlibdeps</prgn> reads the
5906 <file>DEBIAN/shlibs</file> files in all of the binary packages
5907 being built from this source package, all of the
5908 <file>DEBIAN/shlibs</file> files should be installed before
5909 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5917 <chapt id="opersys"><heading>The Operating System</heading>
5920 <heading>File system hierarchy</heading>
5924 <heading>File System Structure</heading>
5927 The location of all installed files and directories must
5928 comply with the Filesystem Hierarchy Standard (FHS),
5929 version 2.3, with the exceptions noted below, and except
5930 where doing so would violate other terms of Debian
5931 Policy. The following exceptions to the FHS apply:
5936 The optional rules related to user specific
5937 configuration files for applications are stored in
5938 the user's home directory are relaxed. It is
5939 recommended that such files start with the
5940 '<tt>.</tt>' character (a "dot file"), and if an
5941 application needs to create more than one dot file
5942 then the preferred placement is in a subdirectory
5943 with a name starting with a '.' character, (a "dot
5944 directory"). In this case it is recommended the
5945 configuration files not start with the '.'
5951 The requirement for amd64 to use <file>/lib64</file>
5952 for 64 bit binaries is removed.
5957 The requirement for object files, internal binaries, and
5958 libraries, including <file>libc.so.*</file>, to be located
5959 directly under <file>/lib{,32}</file> and
5960 <file>/usr/lib{,32}</file> is amended, permitting files
5961 to instead be installed to
5962 <file>/lib/<var>triplet</var></file> and
5963 <file>/usr/lib/<var>triplet</var></file>, where
5964 <tt><var>triplet</var></tt> is the value returned by
5965 <tt>dpkg-architecture -qDEB_HOST_GNU_TYPE</tt> for the
5966 architecture of the package. Packages may <em>not</em>
5967 install files to any <var>triplet</var> path other
5968 than the one matching the architecture of that package;
5969 for instance, an <tt>Architecture: amd64</tt> package
5970 containing 32-bit x86 libraries may not install these
5971 libraries to <file>/usr/lib/i486-linux-gnu</file>.
5973 This is necessary in order to reserve the directories for
5974 use in cross-installation of library packages from other
5975 architectures, as part of the planned deployment of
5980 Applications may also use a single subdirectory under
5981 <file>/usr/lib/<var>triplet</var></file>.
5984 The execution time linker/loader, ld*, must still be made
5985 available in the existing location under /lib or /lib64
5986 since this is part of the ELF ABI for the architecture.
5991 The requirement that
5992 <file>/usr/local/share/man</file> be "synonymous"
5993 with <file>/usr/local/man</file> is relaxed to a
5998 The requirement that windowmanagers with a single
5999 configuration file call it <file>system.*wmrc</file>
6000 is removed, as is the restriction that the window
6001 manager subdirectory be named identically to the
6002 window manager name itself.
6007 The requirement that boot manager configuration
6008 files live in <file>/etc</file>, or at least are
6009 symlinked there, is relaxed to a recommendation.
6014 The following directories in the root filesystem are
6015 additionally allowed: <file>/sys</file> and
6016 <file>/selinux</file>. <footnote>These directories
6017 are used as mount points to mount virtual filesystems
6018 to get access to kernel information.</footnote>
6025 The version of this document referred here can be
6026 found in the <tt>debian-policy</tt> package or on <url
6027 id="http://www.debian.org/doc/packaging-manuals/fhs/"
6028 name="FHS (Debian copy)"> alongside this manual (or, if
6029 you have the <package>debian-policy</package> installed,
6031 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
6032 (local copy)">). The
6033 latest version, which may be a more recent version, may
6035 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
6036 Specific questions about following the standard may be
6037 asked on the <tt>debian-devel</tt> mailing list, or
6038 referred to the FHS mailing list (see the
6039 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
6045 <heading>Site-specific programs</heading>
6048 As mandated by the FHS, packages must not place any
6049 files in <file>/usr/local</file>, either by putting them in
6050 the file system archive to be unpacked by <prgn>dpkg</prgn>
6051 or by manipulating them in their maintainer scripts.
6055 However, the package may create empty directories below
6056 <file>/usr/local</file> so that the system administrator knows
6057 where to place site-specific files. These are not
6058 directories <em>in</em> <file>/usr/local</file>, but are
6059 children of directories in <file>/usr/local</file>. These
6060 directories (<file>/usr/local/*/dir/</file>)
6061 should be removed on package removal if they are
6066 Note that this applies only to
6067 directories <em>below</em> <file>/usr/local</file>,
6068 not <em>in</em> <file>/usr/local</file>. Packages must
6069 not create sub-directories in the
6070 directory <file>/usr/local</file> itself, except those
6071 listed in FHS, section 4.5. However, you may create
6072 directories below them as you wish. You must not remove
6073 any of the directories listed in 4.5, even if you created
6078 Since <file>/usr/local</file> can be mounted read-only from a
6079 remote server, these directories must be created and
6080 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
6081 maintainer scripts and not be included in the
6082 <file>.deb</file> archive. These scripts must not fail if
6083 either of these operations fail.
6087 For example, the <tt>emacsen-common</tt> package could
6088 contain something like
6089 <example compact="compact">
6090 if [ ! -e /usr/local/share/emacs ]
6092 if mkdir /usr/local/share/emacs 2>/dev/null
6094 chown root:staff /usr/local/share/emacs
6095 chmod 2775 /usr/local/share/emacs
6099 in its <prgn>postinst</prgn> script, and
6100 <example compact="compact">
6101 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
6102 rmdir /usr/local/share/emacs 2>/dev/null || true
6104 in the <prgn>prerm</prgn> script. (Note that this form is
6105 used to ensure that if the script is interrupted, the
6106 directory <file>/usr/local/share/emacs</file> will still be
6111 If you do create a directory in <file>/usr/local</file> for
6112 local additions to a package, you should ensure that
6113 settings in <file>/usr/local</file> take precedence over the
6114 equivalents in <file>/usr</file>.
6118 However, because <file>/usr/local</file> and its contents are
6119 for exclusive use of the local administrator, a package
6120 must not rely on the presence or absence of files or
6121 directories in <file>/usr/local</file> for normal operation.
6125 The <file>/usr/local</file> directory itself and all the
6126 subdirectories created by the package should (by default) have
6127 permissions 2775 (group-writable and set-group-id) and be
6128 owned by <tt>root:staff</tt>.
6133 <heading>The system-wide mail directory</heading>
6135 The system-wide mail directory
6136 is <file>/var/mail</file>. This directory is part of the
6137 base system and should not be owned by any particular mail
6138 agents. The use of the old
6139 location <file>/var/spool/mail</file> is deprecated, even
6140 though the spool may still be physically located there.
6146 <heading>Users and groups</heading>
6149 <heading>Introduction</heading>
6151 The Debian system can be configured to use either plain or
6156 Some user ids (UIDs) and group ids (GIDs) are reserved
6157 globally for use by certain packages. Because some
6158 packages need to include files which are owned by these
6159 users or groups, or need the ids compiled into binaries,
6160 these ids must be used on any Debian system only for the
6161 purpose for which they are allocated. This is a serious
6162 restriction, and we should avoid getting in the way of
6163 local administration policies. In particular, many sites
6164 allocate users and/or local system groups starting at 100.
6168 Apart from this we should have dynamically allocated ids,
6169 which should by default be arranged in some sensible
6170 order, but the behavior should be configurable.
6174 Packages other than <tt>base-passwd</tt> must not modify
6175 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
6176 <file>/etc/group</file> or <file>/etc/gshadow</file>.
6181 <heading>UID and GID classes</heading>
6183 The UID and GID numbers are divided into classes as
6189 Globally allocated by the Debian project, the same
6190 on every Debian system. These ids will appear in
6191 the <file>passwd</file> and <file>group</file> files of all
6192 Debian systems, new ids in this range being added
6193 automatically as the <tt>base-passwd</tt> package is
6198 Packages which need a single statically allocated
6199 uid or gid should use one of these; their
6200 maintainers should ask the <tt>base-passwd</tt>
6208 Dynamically allocated system users and groups.
6209 Packages which need a user or group, but can have
6210 this user or group allocated dynamically and
6211 differently on each system, should use <tt>adduser
6212 --system</tt> to create the group and/or user.
6213 <prgn>adduser</prgn> will check for the existence of
6214 the user or group, and if necessary choose an unused
6215 id based on the ranges specified in
6216 <file>adduser.conf</file>.
6220 <tag>1000-59999:</tag>
6223 Dynamically allocated user accounts. By default
6224 <prgn>adduser</prgn> will choose UIDs and GIDs for
6225 user accounts in this range, though
6226 <file>adduser.conf</file> may be used to modify this
6231 <tag>60000-64999:</tag>
6234 Globally allocated by the Debian project, but only
6235 created on demand. The ids are allocated centrally
6236 and statically, but the actual accounts are only
6237 created on users' systems on demand.
6241 These ids are for packages which are obscure or
6242 which require many statically-allocated ids. These
6243 packages should check for and create the accounts in
6244 <file>/etc/passwd</file> or <file>/etc/group</file> (using
6245 <prgn>adduser</prgn> if it has this facility) if
6246 necessary. Packages which are likely to require
6247 further allocations should have a "hole" left after
6248 them in the allocation, to give them room to
6253 <tag>65000-65533:</tag>
6261 User <tt>nobody</tt>. The corresponding gid refers
6262 to the group <tt>nogroup</tt>.
6269 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
6270 not</em> be used, because it is the error return
6279 <sect id="sysvinit">
6280 <heading>System run levels and <file>init.d</file> scripts</heading>
6282 <sect1 id="/etc/init.d">
6283 <heading>Introduction</heading>
6286 The <file>/etc/init.d</file> directory contains the scripts
6287 executed by <prgn>init</prgn> at boot time and when the
6288 init state (or "runlevel") is changed (see <manref
6289 name="init" section="8">).
6293 There are at least two different, yet functionally
6294 equivalent, ways of handling these scripts. For the sake
6295 of simplicity, this document describes only the symbolic
6296 link method. However, it must not be assumed by maintainer
6297 scripts that this method is being used, and any automated
6298 manipulation of the various runlevel behaviors by
6299 maintainer scripts must be performed using
6300 <prgn>update-rc.d</prgn> as described below and not by
6301 manually installing or removing symlinks. For information
6302 on the implementation details of the other method,
6303 implemented in the <tt>file-rc</tt> package, please refer
6304 to the documentation of that package.
6308 These scripts are referenced by symbolic links in the
6309 <file>/etc/rc<var>n</var>.d</file> directories. When changing
6310 runlevels, <prgn>init</prgn> looks in the directory
6311 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
6312 execute, where <tt><var>n</var></tt> is the runlevel that
6313 is being changed to, or <tt>S</tt> for the boot-up
6318 The names of the links all have the form
6319 <file>S<var>mm</var><var>script</var></file> or
6320 <file>K<var>mm</var><var>script</var></file> where
6321 <var>mm</var> is a two-digit number and <var>script</var>
6322 is the name of the script (this should be the same as the
6323 name of the actual script in <file>/etc/init.d</file>).
6327 When <prgn>init</prgn> changes runlevel first the targets
6328 of the links whose names start with a <tt>K</tt> are
6329 executed, each with the single argument <tt>stop</tt>,
6330 followed by the scripts prefixed with an <tt>S</tt>, each
6331 with the single argument <tt>start</tt>. (The links are
6332 those in the <file>/etc/rc<var>n</var>.d</file> directory
6333 corresponding to the new runlevel.) The <tt>K</tt> links
6334 are responsible for killing services and the <tt>S</tt>
6335 link for starting services upon entering the runlevel.
6339 For example, if we are changing from runlevel 2 to
6340 runlevel 3, init will first execute all of the <tt>K</tt>
6341 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
6342 all of the <tt>S</tt> prefixed scripts in that directory.
6343 The links starting with <tt>K</tt> will cause the
6344 referred-to file to be executed with an argument of
6345 <tt>stop</tt>, and the <tt>S</tt> links with an argument
6350 The two-digit number <var>mm</var> is used to determine
6351 the order in which to run the scripts: low-numbered links
6352 have their scripts run first. For example, the
6353 <tt>K20</tt> scripts will be executed before the
6354 <tt>K30</tt> scripts. This is used when a certain service
6355 must be started before another. For example, the name
6356 server <prgn>bind</prgn> might need to be started before
6357 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
6358 can set up its access lists. In this case, the script
6359 that starts <prgn>bind</prgn> would have a lower number
6360 than the script that starts <prgn>inn</prgn> so that it
6362 <example compact="compact">
6369 The two runlevels 0 (halt) and 6 (reboot) are slightly
6370 different. In these runlevels, the links with an
6371 <tt>S</tt> prefix are still called after those with a
6372 <tt>K</tt> prefix, but they too are called with the single
6373 argument <tt>stop</tt>.
6377 <sect1 id="writing-init">
6378 <heading>Writing the scripts</heading>
6381 Packages that include daemons for system services should
6382 place scripts in <file>/etc/init.d</file> to start or stop
6383 services at boot time or during a change of runlevel.
6384 These scripts should be named
6385 <file>/etc/init.d/<var>package</var></file>, and they should
6386 accept one argument, saying what to do:
6389 <tag><tt>start</tt></tag>
6390 <item>start the service,</item>
6392 <tag><tt>stop</tt></tag>
6393 <item>stop the service,</item>
6395 <tag><tt>restart</tt></tag>
6396 <item>stop and restart the service if it's already running,
6397 otherwise start the service</item>
6399 <tag><tt>reload</tt></tag>
6400 <item><p>cause the configuration of the service to be
6401 reloaded without actually stopping and restarting
6404 <tag><tt>force-reload</tt></tag>
6405 <item>cause the configuration to be reloaded if the
6406 service supports this, otherwise restart the
6410 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
6411 <tt>force-reload</tt> options should be supported by all
6412 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
6417 The <file>init.d</file> scripts must ensure that they will
6418 behave sensibly (i.e., returning success and not starting
6419 multiple copies of a service) if invoked with <tt>start</tt>
6420 when the service is already running, or with <tt>stop</tt>
6421 when it isn't, and that they don't kill unfortunately-named
6422 user processes. The best way to achieve this is usually to
6423 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
6428 Be careful of using <tt>set -e</tt> in <file>init.d</file>
6429 scripts. Writing correct <file>init.d</file> scripts requires
6430 accepting various error exit statuses when daemons are already
6431 running or already stopped without aborting
6432 the <file>init.d</file> script, and common <file>init.d</file>
6433 function libraries are not safe to call with <tt>set -e</tt>
6435 <tt>/lib/lsb/init-functions</tt>, which assists in writing
6436 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
6437 in effect and echoing status messages to the console fails,
6439 </footnote>. For <tt>init.d</tt> scripts, it's often easier
6440 to not use <tt>set -e</tt> and instead check the result of
6441 each command separately.
6445 If a service reloads its configuration automatically (as
6446 in the case of <prgn>cron</prgn>, for example), the
6447 <tt>reload</tt> option of the <file>init.d</file> script
6448 should behave as if the configuration has been reloaded
6453 The <file>/etc/init.d</file> scripts must be treated as
6454 configuration files, either (if they are present in the
6455 package, that is, in the .deb file) by marking them as
6456 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6457 by managing them correctly in the maintainer scripts (see
6458 <ref id="config-files">). This is important since we want
6459 to give the local system administrator the chance to adapt
6460 the scripts to the local system, e.g., to disable a
6461 service without de-installing the package, or to specify
6462 some special command line options when starting a service,
6463 while making sure their changes aren't lost during the next
6468 These scripts should not fail obscurely when the
6469 configuration files remain but the package has been
6470 removed, as configuration files remain on the system after
6471 the package has been removed. Only when <prgn>dpkg</prgn>
6472 is executed with the <tt>--purge</tt> option will
6473 configuration files be removed. In particular, as the
6474 <file>/etc/init.d/<var>package</var></file> script itself is
6475 usually a <tt>conffile</tt>, it will remain on the system
6476 if the package is removed but not purged. Therefore, you
6477 should include a <tt>test</tt> statement at the top of the
6479 <example compact="compact">
6480 test -f <var>program-executed-later-in-script</var> || exit 0
6485 Often there are some variables in the <file>init.d</file>
6486 scripts whose values control the behavior of the scripts,
6487 and which a system administrator is likely to want to
6488 change. As the scripts themselves are frequently
6489 <tt>conffile</tt>s, modifying them requires that the
6490 administrator merge in their changes each time the package
6491 is upgraded and the <tt>conffile</tt> changes. To ease
6492 the burden on the system administrator, such configurable
6493 values should not be placed directly in the script.
6494 Instead, they should be placed in a file in
6495 <file>/etc/default</file>, which typically will have the same
6496 base name as the <file>init.d</file> script. This extra file
6497 should be sourced by the script when the script runs. It
6498 must contain only variable settings and comments in SUSv3
6499 <prgn>sh</prgn> format. It may either be a
6500 <tt>conffile</tt> or a configuration file maintained by
6501 the package maintainer scripts. See <ref id="config-files">
6506 To ensure that vital configurable values are always
6507 available, the <file>init.d</file> script should set default
6508 values for each of the shell variables it uses, either
6509 before sourcing the <file>/etc/default/</file> file or
6510 afterwards using something like the <tt>:
6511 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6512 script must behave sensibly and not fail if the
6513 <file>/etc/default</file> file is deleted.
6517 <file>/var/run</file> and <file>/var/lock</file> may be mounted
6518 as temporary filesystems<footnote>
6519 For example, using the <tt>RAMRUN</tt> and <tt>RAMLOCK</tt>
6520 options in <file>/etc/default/rcS</file>.
6521 </footnote>, so the <file>init.d</file> scripts must handle this
6522 correctly. This will typically amount to creating any required
6523 subdirectories dynamically when the <file>init.d</file> script
6524 is run, rather than including them in the package and relying on
6525 <prgn>dpkg</prgn> to create them.
6530 <heading>Interfacing with the initscript system</heading>
6533 Maintainers should use the abstraction layer provided by
6534 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6535 programs to deal with initscripts in their packages'
6536 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6537 and <prgn>postrm</prgn>.
6541 Directly managing the /etc/rc?.d links and directly
6542 invoking the <file>/etc/init.d/</file> initscripts should
6543 be done only by packages providing the initscript
6544 subsystem (such as <prgn>sysv-rc</prgn> and
6545 <prgn>file-rc</prgn>).
6549 <heading>Managing the links</heading>
6552 The program <prgn>update-rc.d</prgn> is provided for
6553 package maintainers to arrange for the proper creation and
6554 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6555 or their functional equivalent if another method is being
6556 used. This may be used by maintainers in their packages'
6557 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6561 You must not include any <file>/etc/rc<var>n</var>.d</file>
6562 symbolic links in the actual archive or manually create or
6563 remove the symbolic links in maintainer scripts; you must
6564 use the <prgn>update-rc.d</prgn> program instead. (The
6565 former will fail if an alternative method of maintaining
6566 runlevel information is being used.) You must not include
6567 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6568 in the archive either. (Only the <tt>sysvinit</tt>
6573 By default <prgn>update-rc.d</prgn> will start services in
6574 each of the multi-user state runlevels (2, 3, 4, and 5)
6575 and stop them in the halt runlevel (0), the single-user
6576 runlevel (1) and the reboot runlevel (6). The system
6577 administrator will have the opportunity to customize
6578 runlevels by simply adding, moving, or removing the
6579 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6580 symbolic links are being used, or by modifying
6581 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6586 To get the default behavior for your package, put in your
6587 <prgn>postinst</prgn> script
6588 <example compact="compact">
6589 update-rc.d <var>package</var> defaults
6591 and in your <prgn>postrm</prgn>
6592 <example compact="compact">
6593 if [ "$1" = purge ]; then
6594 update-rc.d <var>package</var> remove
6596 </example>. Note that if your package changes runlevels
6597 or priority, you may have to remove and recreate the links,
6598 since otherwise the old links may persist. Refer to the
6599 documentation of <prgn>update-rc.d</prgn>.
6603 This will use a default sequence number of 20. If it does
6604 not matter when or in which order the <file>init.d</file>
6605 script is run, use this default. If it does, then you
6606 should talk to the maintainer of the <prgn>sysvinit</prgn>
6607 package or post to <tt>debian-devel</tt>, and they will
6608 help you choose a number.
6612 For more information about using <tt>update-rc.d</tt>,
6613 please consult its man page <manref name="update-rc.d"
6619 <heading>Running initscripts</heading>
6621 The program <prgn>invoke-rc.d</prgn> is provided to make
6622 it easier for package maintainers to properly invoke an
6623 initscript, obeying runlevel and other locally-defined
6624 constraints that might limit a package's right to start,
6625 stop and otherwise manage services. This program may be
6626 used by maintainers in their packages' scripts.
6630 The package maintainer scripts must use
6631 <prgn>invoke-rc.d</prgn> to invoke the
6632 <file>/etc/init.d/*</file> initscripts, instead of
6633 calling them directly.
6637 By default, <prgn>invoke-rc.d</prgn> will pass any
6638 action requests (start, stop, reload, restart...) to the
6639 <file>/etc/init.d</file> script, filtering out requests
6640 to start or restart a service out of its intended
6645 Most packages will simply need to change:
6646 <example compact="compact">/etc/init.d/<package>
6647 <action></example> in their <prgn>postinst</prgn>
6648 and <prgn>prerm</prgn> scripts to:
6649 <example compact="compact">
6650 if which invoke-rc.d >/dev/null 2>&1; then
6651 invoke-rc.d <var>package</var> <action>
6653 /etc/init.d/<var>package</var> <action>
6659 A package should register its initscript services using
6660 <prgn>update-rc.d</prgn> before it tries to invoke them
6661 using <prgn>invoke-rc.d</prgn>. Invocation of
6662 unregistered services may fail.
6666 For more information about using
6667 <prgn>invoke-rc.d</prgn>, please consult its man page
6668 <manref name="invoke-rc.d" section="8">.
6674 <heading>Boot-time initialization</heading>
6677 There used to be another directory, <file>/etc/rc.boot</file>,
6678 which contained scripts which were run once per machine
6679 boot. This has been deprecated in favour of links from
6680 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6681 described in <ref id="/etc/init.d">. Packages must not
6682 place files in <file>/etc/rc.boot</file>.
6687 <heading>Example</heading>
6690 An example on which you can base your
6691 <file>/etc/init.d</file> scripts is found in
6692 <file>/etc/init.d/skeleton</file>.
6699 <heading>Console messages from <file>init.d</file> scripts</heading>
6702 This section describes the formats to be used for messages
6703 written to standard output by the <file>/etc/init.d</file>
6704 scripts. The intent is to improve the consistency of
6705 Debian's startup and shutdown look and feel. For this
6706 reason, please look very carefully at the details. We want
6707 the messages to have the same format in terms of wording,
6708 spaces, punctuation and case of letters.
6712 Here is a list of overall rules that should be used for
6713 messages generated by <file>/etc/init.d</file> scripts.
6719 The message should fit in one line (fewer than 80
6720 characters), start with a capital letter and end with
6721 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6725 If the script is performing some time consuming task in
6726 the background (not merely starting or stopping a
6727 program, for instance), an ellipsis (three dots:
6728 <tt>...</tt>) should be output to the screen, with no
6729 leading or tailing whitespace or line feeds.
6733 The messages should appear as if the computer is telling
6734 the user what it is doing (politely :-), but should not
6735 mention "it" directly. For example, instead of:
6736 <example compact="compact">
6737 I'm starting network daemons: nfsd mountd.
6739 the message should say
6740 <example compact="compact">
6741 Starting network daemons: nfsd mountd.
6748 <tt>init.d</tt> script should use the following standard
6749 message formats for the situations enumerated below.
6755 <p>When daemons are started</p>
6758 If the script starts one or more daemons, the output
6759 should look like this (a single line, no leading
6761 <example compact="compact">
6762 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6764 The <var>description</var> should describe the
6765 subsystem the daemon or set of daemons are part of,
6766 while <var>daemon-1</var> up to <var>daemon-n</var>
6767 denote each daemon's name (typically the file name of
6772 For example, the output of <file>/etc/init.d/lpd</file>
6774 <example compact="compact">
6775 Starting printer spooler: lpd.
6780 This can be achieved by saying
6781 <example compact="compact">
6782 echo -n "Starting printer spooler: lpd"
6783 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6786 in the script. If there are more than one daemon to
6787 start, the output should look like this:
6788 <example compact="compact">
6789 echo -n "Starting remote file system services:"
6790 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6791 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6792 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6795 This makes it possible for the user to see what is
6796 happening and when the final daemon has been started.
6797 Care should be taken in the placement of white spaces:
6798 in the example above the system administrators can
6799 easily comment out a line if they don't want to start
6800 a specific daemon, while the displayed message still
6806 <p>When a system parameter is being set</p>
6809 If you have to set up different system parameters
6810 during the system boot, you should use this format:
6811 <example compact="compact">
6812 Setting <var>parameter</var> to "<var>value</var>".
6817 You can use a statement such as the following to get
6819 <example compact="compact">
6820 echo "Setting DNS domainname to \"$domainname\"."
6825 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
6826 for the left and right quotation marks. A grave accent
6827 (<tt>`</tt>) is not a quote character; neither is an
6828 apostrophe (<tt>'</tt>).
6833 <p>When a daemon is stopped or restarted</p>
6836 When you stop or restart a daemon, you should issue a
6837 message identical to the startup message, except that
6838 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6839 or <tt>Restarting</tt> respectively.
6843 For example, stopping the printer daemon will look like
6845 <example compact="compact">
6846 Stopping printer spooler: lpd.
6852 <p>When something is executed</p>
6855 There are several examples where you have to run a
6856 program at system startup or shutdown to perform a
6857 specific task, for example, setting the system's clock
6858 using <prgn>netdate</prgn> or killing all processes
6859 when the system shuts down. Your message should look
6861 <example compact="compact">
6862 Doing something very useful...done.
6864 You should print the <tt>done.</tt> immediately after
6865 the job has been completed, so that the user is
6866 informed why they have to wait. You can get this
6868 <example compact="compact">
6869 echo -n "Doing something very useful..."
6878 <p>When the configuration is reloaded</p>
6881 When a daemon is forced to reload its configuration
6882 files you should use the following format:
6883 <example compact="compact">
6884 Reloading <var>description</var> configuration...done.
6886 where <var>description</var> is the same as in the
6887 daemon starting message.
6895 <heading>Cron jobs</heading>
6898 Packages must not modify the configuration file
6899 <file>/etc/crontab</file>, and they must not modify the files in
6900 <file>/var/spool/cron/crontabs</file>.</p>
6903 If a package wants to install a job that has to be executed
6904 via cron, it should place a file with the name of the
6905 package in one or more of the following directories:
6906 <example compact="compact">
6912 As these directory names imply, the files within them are
6913 executed on an hourly, daily, weekly, or monthly basis,
6914 respectively. The exact times are listed in
6915 <file>/etc/crontab</file>.</p>
6918 All files installed in any of these directories must be
6919 scripts (e.g., shell scripts or Perl scripts) so that they
6920 can easily be modified by the local system administrator.
6921 In addition, they must be treated as configuration files.
6925 If a certain job has to be executed at some other frequency or
6926 at a specific time, the package should install a file
6927 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6928 same syntax as <file>/etc/crontab</file> and is processed by
6929 <prgn>cron</prgn> automatically. The file must also be
6930 treated as a configuration file. (Note that entries in the
6931 <file>/etc/cron.d</file> directory are not handled by
6932 <prgn>anacron</prgn>. Thus, you should only use this
6933 directory for jobs which may be skipped if the system is not
6936 Unlike <file>crontab</file> files described in the IEEE Std
6937 1003.1-2008 (POSIX.1) available from
6938 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
6939 name="The Open Group">, the files in
6940 <file>/etc/cron.d</file> and the file
6941 <file>/etc/crontab</file> have seven fields; namely:
6943 <item>Minute [0,59]</item>
6944 <item>Hour [0,23]</item>
6945 <item>Day of the month [1,31]</item>
6946 <item>Month of the year [1,12]</item>
6947 <item>Day of the week ([0,6] with 0=Sunday)</item>
6948 <item>Username</item>
6949 <item>Command to be run</item>
6951 Ranges of numbers are allowed. Ranges are two numbers
6952 separated with a hyphen. The specified range is inclusive.
6953 Lists are allowed. A list is a set of numbers (or ranges)
6954 separated by commas. Step values can be used in conjunction
6959 The scripts or <tt>crontab</tt> entries in these directories should
6960 check if all necessary programs are installed before they
6961 try to execute them. Otherwise, problems will arise when a
6962 package was removed but not purged since configuration files
6963 are kept on the system in this situation.
6967 Any <tt>cron</tt> daemon must provide
6968 <file>/usr/bin/crontab</file> and support normal
6969 <tt>crontab</tt> entries as specified in POSIX. The daemon
6970 must also support names for days and months, ranges, and
6971 step values. It has to support <file>/etc/crontab</file>,
6972 and correctly execute the scripts in
6973 <file>/etc/cron.d</file>. The daemon must also correctly
6975 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
6980 <heading>Menus</heading>
6983 The Debian <tt>menu</tt> package provides a standard
6984 interface between packages providing applications and
6985 <em>menu programs</em> (either X window managers or
6986 text-based menu programs such as <prgn>pdmenu</prgn>).
6990 All packages that provide applications that need not be
6991 passed any special command line arguments for normal
6992 operation should register a menu entry for those
6993 applications, so that users of the <tt>menu</tt> package
6994 will automatically get menu entries in their window
6995 managers, as well in shells like <tt>pdmenu</tt>.
6999 Menu entries should follow the current menu policy.
7003 The menu policy can be found in the <tt>menu-policy</tt>
7004 files in the <tt>debian-policy</tt> package.
7005 It is also available from the Debian web mirrors at
7006 <tt><url name="/doc/packaging-manuals/menu-policy/"
7007 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
7011 Please also refer to the <em>Debian Menu System</em>
7012 documentation that comes with the <package>menu</package>
7013 package for information about how to register your
7019 <heading>Multimedia handlers</heading>
7022 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
7023 is a mechanism for encoding files and data streams and
7024 providing meta-information about them, in particular their
7025 type (e.g. audio or video) and format (e.g. PNG, HTML,
7030 Registration of MIME type handlers allows programs like mail
7031 user agents and web browsers to invoke these handlers to
7032 view, edit or display MIME types they don't support directly.
7036 Packages which provide the ability to view/show/play,
7037 compose, edit or print MIME types should register themselves
7038 as such following the current MIME support policy.
7042 The MIME support policy can be found in the <tt>mime-policy</tt>
7043 files in the <tt>debian-policy</tt> package.
7044 It is also available from the Debian web mirrors at
7045 <tt><url name="/doc/packaging-manuals/mime-policy/"
7046 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
7052 <heading>Keyboard configuration</heading>
7055 To achieve a consistent keyboard configuration so that all
7056 applications interpret a keyboard event the same way, all
7057 programs in the Debian distribution must be configured to
7058 comply with the following guidelines.
7062 The following keys must have the specified interpretations:
7065 <tag><tt><--</tt></tag>
7066 <item>delete the character to the left of the cursor</item>
7068 <tag><tt>Delete</tt></tag>
7069 <item>delete the character to the right of the cursor</item>
7071 <tag><tt>Control+H</tt></tag>
7072 <item>emacs: the help prefix</item>
7075 The interpretation of any keyboard events should be
7076 independent of the terminal that is used, be it a virtual
7077 console, an X terminal emulator, an rlogin/telnet session,
7082 The following list explains how the different programs
7083 should be set up to achieve this:
7089 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
7093 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
7097 X translations are set up to make
7098 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
7099 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
7100 is the vt220 escape code for the "delete character"
7101 key). This must be done by loading the X resources
7102 using <prgn>xrdb</prgn> on all local X displays, not
7103 using the application defaults, so that the
7104 translation resources used correspond to the
7105 <prgn>xmodmap</prgn> settings.
7109 The Linux console is configured to make
7110 <tt><--</tt> generate DEL, and <tt>Delete</tt>
7111 generate <tt>ESC [ 3 ~</tt>.
7115 X applications are configured so that <tt><</tt>
7116 deletes left, and <tt>Delete</tt> deletes right. Motif
7117 applications already work like this.
7121 Terminals should have <tt>stty erase ^?</tt> .
7125 The <tt>xterm</tt> terminfo entry should have <tt>ESC
7126 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
7127 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
7131 Emacs is programmed to map <tt>KB_Backspace</tt> or
7132 the <tt>stty erase</tt> character to
7133 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
7134 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
7135 <tt>^H</tt> to <tt>help</tt> as always.
7139 Other applications use the <tt>stty erase</tt>
7140 character and <tt>kdch1</tt> for the two delete keys,
7141 with ASCII DEL being "delete previous character" and
7142 <tt>kdch1</tt> being "delete character under
7150 This will solve the problem except for the following
7157 Some terminals have a <tt><--</tt> key that cannot
7158 be made to produce anything except <tt>^H</tt>. On
7159 these terminals Emacs help will be unavailable on
7160 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
7161 character takes precedence in Emacs, and has been set
7162 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
7163 available) can be used instead.
7167 Some operating systems use <tt>^H</tt> for <tt>stty
7168 erase</tt>. However, modern telnet versions and all
7169 rlogin versions propagate <tt>stty</tt> settings, and
7170 almost all UNIX versions honour <tt>stty erase</tt>.
7171 Where the <tt>stty</tt> settings are not propagated
7172 correctly, things can be made to work by using
7173 <tt>stty</tt> manually.
7177 Some systems (including previous Debian versions) use
7178 <prgn>xmodmap</prgn> to arrange for both
7179 <tt><--</tt> and <tt>Delete</tt> to generate
7180 <tt>KB_Delete</tt>. We can change the behavior of
7181 their X clients using the same X resources that we use
7182 to do it for our own clients, or configure our clients
7183 using their resources when things are the other way
7184 around. On displays configured like this
7185 <tt>Delete</tt> will not work, but <tt><--</tt>
7190 Some operating systems have different <tt>kdch1</tt>
7191 settings in their <tt>terminfo</tt> database for
7192 <tt>xterm</tt> and others. On these systems the
7193 <tt>Delete</tt> key will not work correctly when you
7194 log in from a system conforming to our policy, but
7195 <tt><--</tt> will.
7202 <heading>Environment variables</heading>
7205 A program must not depend on environment variables to get
7206 reasonable defaults. (That's because these environment
7207 variables would have to be set in a system-wide
7208 configuration file like <file>/etc/profile</file>, which is not
7209 supported by all shells.)
7213 If a program usually depends on environment variables for its
7214 configuration, the program should be changed to fall back to
7215 a reasonable default configuration if these environment
7216 variables are not present. If this cannot be done easily
7217 (e.g., if the source code of a non-free program is not
7218 available), the program must be replaced by a small
7219 "wrapper" shell script which sets the environment variables
7220 if they are not already defined, and calls the original program.
7224 Here is an example of a wrapper script for this purpose:
7226 <example compact="compact">
7228 BAR=${BAR:-/var/lib/fubar}
7230 exec /usr/lib/foo/foo "$@"
7235 Furthermore, as <file>/etc/profile</file> is a configuration
7236 file of the <prgn>base-files</prgn> package, other packages must
7237 not put any environment variables or other commands into that
7242 <sect id="doc-base">
7243 <heading>Registering Documents using doc-base</heading>
7246 The <package>doc-base</package> package implements a
7247 flexible mechanism for handling and presenting
7248 documentation. The recommended practice is for every Debian
7249 package that provides online documentation (other than just
7250 manual pages) to register these documents with
7251 <package>doc-base</package> by installing a
7252 <package>doc-base</package> control file via the
7253 <prgn/install-docs/ script at installation time and
7254 de-register the manuals again when the package is removed.
7257 Please refer to the documentation that comes with the
7258 <package>doc-base</package> package for information and
7267 <heading>Files</heading>
7269 <sect id="binaries">
7270 <heading>Binaries</heading>
7273 Two different packages must not install programs with
7274 different functionality but with the same filenames. (The
7275 case of two programs having the same functionality but
7276 different implementations is handled via "alternatives" or
7277 the "Conflicts" mechanism. See <ref id="maintscripts"> and
7278 <ref id="conflicts"> respectively.) If this case happens,
7279 one of the programs must be renamed. The maintainers should
7280 report this to the <tt>debian-devel</tt> mailing list and
7281 try to find a consensus about which program will have to be
7282 renamed. If a consensus cannot be reached, <em>both</em>
7283 programs must be renamed.
7287 By default, when a package is being built, any binaries
7288 created should include debugging information, as well as
7289 being compiled with optimization. You should also turn on
7290 as many reasonable compilation warnings as possible; this
7291 makes life easier for porters, who can then look at build
7292 logs for possible problems. For the C programming language,
7293 this means the following compilation parameters should be
7295 <example compact="compact">
7297 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
7299 INSTALL = install -s # (or use strip on the files in debian/tmp)
7304 Note that by default all installed binaries should be stripped,
7305 either by using the <tt>-s</tt> flag to
7306 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
7307 the binaries after they have been copied into
7308 <file>debian/tmp</file> but before the tree is made into a
7313 Although binaries in the build tree should be compiled with
7314 debugging information by default, it can often be difficult to
7315 debug programs if they are also subjected to compiler
7316 optimization. For this reason, it is recommended to support the
7317 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
7318 (see <ref id="debianrules-options">). This variable can contain
7319 several flags to change how a package is compiled and built.
7323 It is up to the package maintainer to decide what
7324 compilation options are best for the package. Certain
7325 binaries (such as computationally-intensive programs) will
7326 function better with certain flags (<tt>-O3</tt>, for
7327 example); feel free to use them. Please use good judgment
7328 here. Don't use flags for the sake of it; only use them
7329 if there is good reason to do so. Feel free to override
7330 the upstream author's ideas about which compilation
7331 options are best: they are often inappropriate for our
7337 <sect id="libraries">
7338 <heading>Libraries</heading>
7341 If the package is <strong>architecture: any</strong>, then
7342 the shared library compilation and linking flags must have
7343 <tt>-fPIC</tt>, or the package shall not build on some of
7344 the supported architectures<footnote>
7346 If you are using GCC, <tt>-fPIC</tt> produces code with
7347 relocatable position independent code, which is required for
7348 most architectures to create a shared library, with i386 and
7349 perhaps some others where non position independent code is
7350 permitted in a shared library.
7353 Position independent code may have a performance penalty,
7354 especially on <tt>i386</tt>. However, in most cases the
7355 speed penalty must be measured against the memory wasted on
7356 the few architectures where non position independent code is
7359 </footnote>. Any exception to this rule must be discussed on
7360 the mailing list <em>debian-devel@lists.debian.org</em>, and
7361 a rough consensus obtained. The reasons for not compiling
7362 with <tt>-fPIC</tt> flag must be recorded in the file
7363 <tt>README.Debian</tt>, and care must be taken to either
7364 restrict the architecture or arrange for <tt>-fPIC</tt> to
7365 be used on architectures where it is required.<footnote>
7367 Some of the reasons why this might be required is if the
7368 library contains hand crafted assembly code that is not
7369 relocatable, the speed penalty is excessive for compute
7370 intensive libs, and similar reasons.
7375 As to the static libraries, the common case is not to have
7376 relocatable code, since there is no benefit, unless in specific
7377 cases; therefore the static version must not be compiled
7378 with the <tt>-fPIC</tt> flag. Any exception to this rule
7379 should be discussed on the mailing list
7380 <em>debian-devel@lists.debian.org</em>, and the reasons for
7381 compiling with the <tt>-fPIC</tt> flag must be recorded in
7382 the file <tt>README.Debian</tt>. <footnote>
7384 Some of the reasons for linking static libraries with
7385 the <tt>-fPIC</tt> flag are if, for example, one needs a
7386 Perl API for a library that is under rapid development,
7387 and has an unstable API, so shared libraries are
7388 pointless at this phase of the library's development. In
7389 that case, since Perl needs a library with relocatable
7390 code, it may make sense to create a static library with
7391 relocatable code. Another reason cited is if you are
7392 distilling various libraries into a common shared
7393 library, like <tt>mklibs</tt> does in the Debian
7399 In other words, if both a shared and a static library is
7400 being built, each source unit (<tt>*.c</tt>, for example,
7401 for C files) will need to be compiled twice, for the normal
7406 Libraries should be built with threading support and to be
7407 thread-safe if the library supports this.
7411 Although not enforced by the build tools, shared libraries
7412 must be linked against all libraries that they use symbols from
7413 in the same way that binaries are. This ensures the correct
7414 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
7415 system and guarantees that all libraries can be safely opened
7416 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
7417 option <tt>-Wl,-z,defs</tt> when building a shared library.
7418 Since this option enforces symbol resolution at build time,
7419 a missing library reference will be caught early as a fatal
7424 All installed shared libraries should be stripped with
7425 <example compact="compact">
7426 strip --strip-unneeded <var>your-lib</var>
7428 (The option <tt>--strip-unneeded</tt> makes
7429 <prgn>strip</prgn> remove only the symbols which aren't
7430 needed for relocation processing.) Shared libraries can
7431 function perfectly well when stripped, since the symbols for
7432 dynamic linking are in a separate part of the ELF object
7434 You might also want to use the options
7435 <tt>--remove-section=.comment</tt> and
7436 <tt>--remove-section=.note</tt> on both shared libraries
7437 and executables, and <tt>--strip-debug</tt> on static
7443 Note that under some circumstances it may be useful to
7444 install a shared library unstripped, for example when
7445 building a separate package to support debugging.
7449 Shared object files (often <file>.so</file> files) that are not
7450 public libraries, that is, they are not meant to be linked
7451 to by third party executables (binaries of other packages),
7452 should be installed in subdirectories of the
7453 <file>/usr/lib</file> directory. Such files are exempt from the
7454 rules that govern ordinary shared libraries, except that
7455 they must not be installed executable and should be
7457 A common example are the so-called "plug-ins",
7458 internal shared objects that are dynamically loaded by
7459 programs using <manref name="dlopen" section="3">.
7464 Packages that use <prgn>libtool</prgn> to create and install
7465 their shared libraries install a file containing additional
7466 metadata (ending in <file>.la</file>) alongside the library.
7467 For public libraries intended for use by other packages, these
7468 files normally should not be included in the Debian package,
7469 since the information they include is not necessary to link with
7470 the shared library on Debian and can add unnecessary additional
7471 dependencies to other programs or libraries.<footnote>
7472 These files store, among other things, all libraries on which
7473 that shared library depends. Unfortunately, if
7474 the <file>.la</file> file is present and contains that
7475 dependency information, using <prgn>libtool</prgn> when
7476 linking against that library will cause the resulting program
7477 or library to be linked against those dependencies as well,
7478 even if this is unnecessary. This can create unneeded
7479 dependencies on shared library packages that would otherwise
7480 be hidden behind the library ABI, and can make library
7481 transitions to new SONAMEs unnecessarily complicated and
7482 difficult to manage.
7484 If the <file>.la</file> file is required for that library (if,
7485 for instance, it's loaded via <tt>libltdl</tt> in a way that
7486 requires that meta-information), the <tt>dependency_libs</tt>
7487 setting in the <file>.la</file> file should normally be set to
7488 the empty string. If the shared library development package has
7489 historically included the <file>.la</file>, it must be retained
7490 in the development package (with <tt>dependency_libs</tt>
7491 emptied) until all libraries that depend on it have removed or
7492 emptied <tt>dependency_libs</tt> in their <file>.la</file>
7493 files to prevent linking with those other libraries
7494 using <prgn>libtool</prgn> from failing.
7498 If the <file>.la</file> must be included, it should be included
7499 in the development (<tt>-dev</tt>) package, unless the library
7500 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
7501 library. If it is intended for use with <tt>libltdl</tt>,
7502 the <file>.la</file> files must go in the run-time library
7507 These requirements for handling of <file>.la</file> files do not
7508 apply to loadable modules or libraries not installed in
7509 directories searched by default by the dynamic linker. Packages
7510 installing loadable modules will frequently need to install
7511 the <file>.la</file> files alongside the modules so that they
7512 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
7513 does not need to be modified for libraries or modules that are
7514 not installed in directories searched by the dynamic linker by
7515 default and not intended for use by other packages.
7519 You must make sure that you use only released versions of
7520 shared libraries to build your packages; otherwise other
7521 users will not be able to run your binaries
7522 properly. Producing source packages that depend on
7523 unreleased compilers is also usually a bad
7530 <heading>Shared libraries</heading>
7532 This section has moved to <ref id="sharedlibs">.
7538 <heading>Scripts</heading>
7541 All command scripts, including the package maintainer
7542 scripts inside the package and used by <prgn>dpkg</prgn>,
7543 should have a <tt>#!</tt> line naming the shell to be used
7548 In the case of Perl scripts this should be
7549 <tt>#!/usr/bin/perl</tt>.
7553 When scripts are installed into a directory in the system
7554 PATH, the script name should not include an extension such
7555 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7556 language currently used to implement it.
7559 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
7560 <file>init.d</file> scripts should almost certainly start
7561 with <tt>set -e</tt> so that errors are detected.
7562 <file>init.d</file> scripts are something of a special case, due
7563 to how frequently they need to call commands that are allowed to
7564 fail, and it may instead be easier to check the exit status of
7565 commands directly. See <ref id="writing-init"> for more
7566 information about writing <file>init.d</file> scripts.
7569 Every script should use <tt>set -e</tt> or check the exit status
7570 of <em>every</em> command.
7573 Scripts may assume that <file>/bin/sh</file> implements the
7574 SUSv3 Shell Command Language<footnote>
7575 Single UNIX Specification, version 3, which is also IEEE
7576 1003.1-2004 (POSIX), and is available on the World Wide Web
7577 from <url id="http://www.unix.org/version3/online.html"
7578 name="The Open Group"> after free
7579 registration.</footnote>
7580 plus the following additional features not mandated by
7582 These features are in widespread use in the Linux community
7583 and are implemented in all of bash, dash, and ksh, the most
7584 common shells users may wish to use as <file>/bin/sh</file>.
7587 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7588 must not generate a newline.</item>
7589 <item><tt>test</tt>, if implemented as a shell built-in, must
7590 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7592 <item><tt>local</tt> to create a scoped variable must be
7593 supported, including listing multiple variables in a single
7594 local command and assigning a value to a variable at the
7595 same time as localizing it. <tt>local</tt> may or
7596 may not preserve the variable value from an outer scope if
7597 no assignment is present. Uses such as:
7601 # ... use a, b, c, d ...
7604 must be supported and must set the value of <tt>c</tt> to
7608 If a shell script requires non-SUSv3 features from the shell
7609 interpreter other than those listed above, the appropriate shell
7610 must be specified in the first line of the script (e.g.,
7611 <tt>#!/bin/bash</tt>) and the package must depend on the package
7612 providing the shell (unless the shell package is marked
7613 "Essential", as in the case of <prgn>bash</prgn>).
7617 You may wish to restrict your script to SUSv3 features plus the
7618 above set when possible so that it may use <file>/bin/sh</file>
7619 as its interpreter. If your script works with <prgn>dash</prgn>
7620 (originally called <prgn>ash</prgn>), it probably complies with
7621 the above requirements, but if you are in doubt, use
7622 <file>/bin/bash</file>.
7626 Perl scripts should check for errors when making any
7627 system calls, including <tt>open</tt>, <tt>print</tt>,
7628 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7632 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7633 scripting languages. See <em>Csh Programming Considered
7634 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7635 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7636 If an upstream package comes with <prgn>csh</prgn> scripts
7637 then you must make sure that they start with
7638 <tt>#!/bin/csh</tt> and make your package depend on the
7639 <prgn>c-shell</prgn> virtual package.
7643 Any scripts which create files in world-writeable
7644 directories (e.g., in <file>/tmp</file>) must use a
7645 mechanism which will fail atomically if a file with the same
7646 name already exists.
7650 The Debian base system provides the <prgn>tempfile</prgn>
7651 and <prgn>mktemp</prgn> utilities for use by scripts for
7658 <heading>Symbolic links</heading>
7661 In general, symbolic links within a top-level directory
7662 should be relative, and symbolic links pointing from one
7663 top-level directory into another should be absolute. (A
7664 top-level directory is a sub-directory of the root
7665 directory <file>/</file>.)
7669 In addition, symbolic links should be specified as short as
7670 possible, i.e., link targets like <file>foo/../bar</file> are
7675 Note that when creating a relative link using
7676 <prgn>ln</prgn> it is not necessary for the target of the
7677 link to exist relative to the working directory you're
7678 running <prgn>ln</prgn> from, nor is it necessary to change
7679 directory to the directory where the link is to be made.
7680 Simply include the string that should appear as the target
7681 of the link (this will be a pathname relative to the
7682 directory in which the link resides) as the first argument
7687 For example, in your <prgn>Makefile</prgn> or
7688 <file>debian/rules</file>, you can do things like:
7689 <example compact="compact">
7690 ln -fs gcc $(prefix)/bin/cc
7691 ln -fs gcc debian/tmp/usr/bin/cc
7692 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7693 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7698 A symbolic link pointing to a compressed file should always
7699 have the same file extension as the referenced file. (For
7700 example, if a file <file>foo.gz</file> is referenced by a
7701 symbolic link, the filename of the link has to end with
7702 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7707 <heading>Device files</heading>
7710 Packages must not include device files or named pipes in the
7715 If a package needs any special device files that are not
7716 included in the base system, it must call
7717 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7718 after notifying the user<footnote>
7719 This notification could be done via a (low-priority)
7720 debconf message, or an echo (printf) statement.
7725 Packages must not remove any device files in the
7726 <prgn>postrm</prgn> or any other script. This is left to the
7727 system administrator.
7731 Debian uses the serial devices
7732 <file>/dev/ttyS*</file>. Programs using the old
7733 <file>/dev/cu*</file> devices should be changed to use
7734 <file>/dev/ttyS*</file>.
7738 Named pipes needed by the package must be created in
7739 the <prgn>postinst</prgn> script<footnote>
7740 It's better to use <prgn>mkfifo</prgn> rather
7741 than <prgn>mknod</prgn> to create named pipes so that
7742 automated checks for packages incorrectly creating device
7743 files with <prgn>mknod</prgn> won't have false positives.
7744 </footnote> and removed in
7745 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
7750 <sect id="config-files">
7751 <heading>Configuration files</heading>
7754 <heading>Definitions</heading>
7758 <tag>configuration file</tag>
7760 A file that affects the operation of a program, or
7761 provides site- or host-specific information, or
7762 otherwise customizes the behavior of a program.
7763 Typically, configuration files are intended to be
7764 modified by the system administrator (if needed or
7765 desired) to conform to local policy or to provide
7766 more useful site-specific behavior.
7769 <tag><tt>conffile</tt></tag>
7771 A file listed in a package's <tt>conffiles</tt>
7772 file, and is treated specially by <prgn>dpkg</prgn>
7773 (see <ref id="configdetails">).
7779 The distinction between these two is important; they are
7780 not interchangeable concepts. Almost all
7781 <tt>conffile</tt>s are configuration files, but many
7782 configuration files are not <tt>conffiles</tt>.
7786 As noted elsewhere, <file>/etc/init.d</file> scripts,
7787 <file>/etc/default</file> files, scripts installed in
7788 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7789 configuration installed in <file>/etc/cron.d</file> must be
7790 treated as configuration files. In general, any script that
7791 embeds configuration information is de-facto a configuration
7792 file and should be treated as such.
7797 <heading>Location</heading>
7800 Any configuration files created or used by your package
7801 must reside in <file>/etc</file>. If there are several,
7802 consider creating a subdirectory of <file>/etc</file>
7803 named after your package.
7807 If your package creates or uses configuration files
7808 outside of <file>/etc</file>, and it is not feasible to modify
7809 the package to use <file>/etc</file> directly, put the files
7810 in <file>/etc</file> and create symbolic links to those files
7811 from the location that the package requires.
7816 <heading>Behavior</heading>
7819 Configuration file handling must conform to the following
7821 <list compact="compact">
7823 local changes must be preserved during a package
7827 configuration files must be preserved when the
7828 package is removed, and only deleted when the
7832 Obsolete configuration files without local changes may be
7833 removed by the package during upgrade.
7837 The easy way to achieve this behavior is to make the
7838 configuration file a <tt>conffile</tt>. This is
7839 appropriate only if it is possible to distribute a default
7840 version that will work for most installations, although
7841 some system administrators may choose to modify it. This
7842 implies that the default version will be part of the
7843 package distribution, and must not be modified by the
7844 maintainer scripts during installation (or at any other
7849 In order to ensure that local changes are preserved
7850 correctly, no package may contain or make hard links to
7851 conffiles.<footnote>
7852 Rationale: There are two problems with hard links.
7853 The first is that some editors break the link while
7854 editing one of the files, so that the two files may
7855 unwittingly become unlinked and different. The second
7856 is that <prgn>dpkg</prgn> might break the hard link
7857 while upgrading <tt>conffile</tt>s.
7862 The other way to do it is via the maintainer scripts. In
7863 this case, the configuration file must not be listed as a
7864 <tt>conffile</tt> and must not be part of the package
7865 distribution. If the existence of a file is required for
7866 the package to be sensibly configured it is the
7867 responsibility of the package maintainer to provide
7868 maintainer scripts which correctly create, update and
7869 maintain the file and remove it on purge. (See <ref
7870 id="maintainerscripts"> for more information.) These
7871 scripts must be idempotent (i.e., must work correctly if
7872 <prgn>dpkg</prgn> needs to re-run them due to errors
7873 during installation or removal), must cope with all the
7874 variety of ways <prgn>dpkg</prgn> can call maintainer
7875 scripts, must not overwrite or otherwise mangle the user's
7876 configuration without asking, must not ask unnecessary
7877 questions (particularly during upgrades), and must
7878 otherwise be good citizens.
7882 The scripts are not required to configure every possible
7883 option for the package, but only those necessary to get
7884 the package running on a given system. Ideally the
7885 sysadmin should not have to do any configuration other
7886 than that done (semi-)automatically by the
7887 <prgn>postinst</prgn> script.
7891 A common practice is to create a script called
7892 <file><var>package</var>-configure</file> and have the
7893 package's <prgn>postinst</prgn> call it if and only if the
7894 configuration file does not already exist. In certain
7895 cases it is useful for there to be an example or template
7896 file which the maintainer scripts use. Such files should
7897 be in <file>/usr/share/<var>package</var></file> or
7898 <file>/usr/lib/<var>package</var></file> (depending on whether
7899 they are architecture-independent or not). There should
7900 be symbolic links to them from
7901 <file>/usr/share/doc/<var>package</var>/examples</file> if
7902 they are examples, and should be perfectly ordinary
7903 <prgn>dpkg</prgn>-handled files (<em>not</em>
7904 configuration files).
7908 These two styles of configuration file handling must
7909 not be mixed, for that way lies madness:
7910 <prgn>dpkg</prgn> will ask about overwriting the file
7911 every time the package is upgraded.
7916 <heading>Sharing configuration files</heading>
7919 Packages which specify the same file as a
7920 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7921 with each other. (This is an instance of the general rule
7922 about not sharing files. Note that neither alternatives
7923 nor diversions are likely to be appropriate in this case;
7924 in particular, <prgn>dpkg</prgn> does not handle diverted
7925 <tt>conffile</tt>s well.)
7929 The maintainer scripts must not alter a <tt>conffile</tt>
7930 of <em>any</em> package, including the one the scripts
7935 If two or more packages use the same configuration file
7936 and it is reasonable for both to be installed at the same
7937 time, one of these packages must be defined as
7938 <em>owner</em> of the configuration file, i.e., it will be
7939 the package which handles that file as a configuration
7940 file. Other packages that use the configuration file must
7941 depend on the owning package if they require the
7942 configuration file to operate. If the other package will
7943 use the configuration file if present, but is capable of
7944 operating without it, no dependency need be declared.
7948 If it is desirable for two or more related packages to
7949 share a configuration file <em>and</em> for all of the
7950 related packages to be able to modify that configuration
7951 file, then the following should be done:
7952 <enumlist compact="compact">
7954 One of the related packages (the "owning" package)
7955 will manage the configuration file with maintainer
7956 scripts as described in the previous section.
7959 The owning package should also provide a program
7960 that the other packages may use to modify the
7964 The related packages must use the provided program
7965 to make any desired modifications to the
7966 configuration file. They should either depend on
7967 the core package to guarantee that the configuration
7968 modifier program is available or accept gracefully
7969 that they cannot modify the configuration file if it
7970 is not. (This is in addition to the fact that the
7971 configuration file may not even be present in the
7978 Sometimes it's appropriate to create a new package which
7979 provides the basic infrastructure for the other packages
7980 and which manages the shared configuration files. (The
7981 <tt>sgml-base</tt> package is a good example.)
7986 <heading>User configuration files ("dotfiles")</heading>
7989 The files in <file>/etc/skel</file> will automatically be
7990 copied into new user accounts by <prgn>adduser</prgn>.
7991 No other program should reference the files in
7992 <file>/etc/skel</file>.
7996 Therefore, if a program needs a dotfile to exist in
7997 advance in <file>$HOME</file> to work sensibly, that dotfile
7998 should be installed in <file>/etc/skel</file> and treated as a
8003 However, programs that require dotfiles in order to
8004 operate sensibly are a bad thing, unless they do create
8005 the dotfiles themselves automatically.
8009 Furthermore, programs should be configured by the Debian
8010 default installation to behave as closely to the upstream
8011 default behavior as possible.
8015 Therefore, if a program in a Debian package needs to be
8016 configured in some way in order to operate sensibly, that
8017 should be done using a site-wide configuration file placed
8018 in <file>/etc</file>. Only if the program doesn't support a
8019 site-wide default configuration and the package maintainer
8020 doesn't have time to add it may a default per-user file be
8021 placed in <file>/etc/skel</file>.
8025 <file>/etc/skel</file> should be as empty as we can make it.
8026 This is particularly true because there is no easy (or
8027 necessarily desirable) mechanism for ensuring that the
8028 appropriate dotfiles are copied into the accounts of
8029 existing users when a package is installed.
8035 <heading>Log files</heading>
8037 Log files should usually be named
8038 <file>/var/log/<var>package</var>.log</file>. If you have many
8039 log files, or need a separate directory for permission
8040 reasons (<file>/var/log</file> is writable only by
8041 <file>root</file>), you should usually create a directory named
8042 <file>/var/log/<var>package</var></file> and place your log
8047 Log files must be rotated occasionally so that they don't
8048 grow indefinitely; the best way to do this is to drop a log
8049 rotation configuration file into the directory
8050 <file>/etc/logrotate.d</file> and use the facilities provided by
8051 logrotate.<footnote>
8053 The traditional approach to log files has been to set up
8054 <em>ad hoc</em> log rotation schemes using simple shell
8055 scripts and cron. While this approach is highly
8056 customizable, it requires quite a lot of sysadmin work.
8057 Even though the original Debian system helped a little
8058 by automatically installing a system which can be used
8059 as a template, this was deemed not enough.
8063 The use of <prgn>logrotate</prgn>, a program developed
8064 by Red Hat, is better, as it centralizes log management.
8065 It has both a configuration file
8066 (<file>/etc/logrotate.conf</file>) and a directory where
8067 packages can drop their individual log rotation
8068 configurations (<file>/etc/logrotate.d</file>).
8071 Here is a good example for a logrotate config
8072 file (for more information see <manref name="logrotate"
8074 <example compact="compact">
8075 /var/log/foo/*.log {
8080 /etc/init.d/foo force-reload
8084 This rotates all files under <file>/var/log/foo</file>, saves 12
8085 compressed generations, and forces the daemon to reload its
8086 configuration information after the log rotation.
8090 Log files should be removed when the package is
8091 purged (but not when it is only removed). This should be
8092 done by the <prgn>postrm</prgn> script when it is called
8093 with the argument <tt>purge</tt> (see <ref
8094 id="removedetails">).
8098 <sect id="permissions-owners">
8099 <heading>Permissions and owners</heading>
8102 The rules in this section are guidelines for general use.
8103 If necessary you may deviate from the details below.
8104 However, if you do so you must make sure that what is done
8105 is secure and you should try to be as consistent as possible
8106 with the rest of the system. You should probably also
8107 discuss it on <prgn>debian-devel</prgn> first.
8111 Files should be owned by <tt>root:root</tt>, and made
8112 writable only by the owner and universally readable (and
8113 executable, if appropriate), that is mode 644 or 755.
8117 Directories should be mode 755 or (for group-writability)
8118 mode 2775. The ownership of the directory should be
8119 consistent with its mode: if a directory is mode 2775, it
8120 should be owned by the group that needs write access to
8123 When a package is upgraded, and the owner or permissions
8124 of a file included in the package has changed, dpkg
8125 arranges for the ownership and permissions to be
8126 correctly set upon installation. However, this does not
8127 extend to directories; the permissions and ownership of
8128 directories already on the system does not change on
8129 install or upgrade of packages. This makes sense, since
8130 otherwise common directories like <tt>/usr</tt> would
8131 always be in flux. To correctly change permissions of a
8132 directory the package owns, explicit action is required,
8133 usually in the <tt>postinst</tt> script. Care must be
8134 taken to handle downgrades as well, in that case.
8141 Setuid and setgid executables should be mode 4755 or 2755
8142 respectively, and owned by the appropriate user or group.
8143 They should not be made unreadable (modes like 4711 or
8144 2711 or even 4111); doing so achieves no extra security,
8145 because anyone can find the binary in the freely available
8146 Debian package; it is merely inconvenient. For the same
8147 reason you should not restrict read or execute permissions
8148 on non-set-id executables.
8152 Some setuid programs need to be restricted to particular
8153 sets of users, using file permissions. In this case they
8154 should be owned by the uid to which they are set-id, and by
8155 the group which should be allowed to execute them. They
8156 should have mode 4754; again there is no point in making
8157 them unreadable to those users who must not be allowed to
8162 It is possible to arrange that the system administrator can
8163 reconfigure the package to correspond to their local
8164 security policy by changing the permissions on a binary:
8165 they can do this by using <prgn>dpkg-statoverride</prgn>, as
8166 described below.<footnote>
8167 Ordinary files installed by <prgn>dpkg</prgn> (as
8168 opposed to <tt>conffile</tt>s and other similar objects)
8169 normally have their permissions reset to the distributed
8170 permissions when the package is reinstalled. However,
8171 the use of <prgn>dpkg-statoverride</prgn> overrides this
8174 Another method you should consider is to create a group for
8175 people allowed to use the program(s) and make any setuid
8176 executables executable only by that group.
8180 If you need to create a new user or group for your package
8181 there are two possibilities. Firstly, you may need to
8182 make some files in the binary package be owned by this
8183 user or group, or you may need to compile the user or
8184 group id (rather than just the name) into the binary
8185 (though this latter should be avoided if possible, as in
8186 this case you need a statically allocated id).</p>
8189 If you need a statically allocated id, you must ask for a
8190 user or group id from the <tt>base-passwd</tt> maintainer,
8191 and must not release the package until you have been
8192 allocated one. Once you have been allocated one you must
8193 either make the package depend on a version of the
8194 <tt>base-passwd</tt> package with the id present in
8195 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
8196 your package to create the user or group itself with the
8197 correct id (using <tt>adduser</tt>) in its
8198 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
8199 the <prgn>postinst</prgn> is to be preferred if it is
8200 possible, otherwise a pre-dependency will be needed on the
8201 <tt>adduser</tt> package.)
8205 On the other hand, the program might be able to determine
8206 the uid or gid from the user or group name at runtime, so
8207 that a dynamically allocated id can be used. In this case
8208 you should choose an appropriate user or group name,
8209 discussing this on <prgn>debian-devel</prgn> and checking
8210 with the <package/base-passwd/ maintainer that it is unique and that
8211 they do not wish you to use a statically allocated id
8212 instead. When this has been checked you must arrange for
8213 your package to create the user or group if necessary using
8214 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
8215 <prgn>postinst</prgn> script (again, the latter is to be
8216 preferred if it is possible).
8220 Note that changing the numeric value of an id associated
8221 with a name is very difficult, and involves searching the
8222 file system for all appropriate files. You need to think
8223 carefully whether a static or dynamic id is required, since
8224 changing your mind later will cause problems.
8227 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
8229 This section is not intended as policy, but as a
8230 description of the use of <prgn>dpkg-statoverride</prgn>.
8234 If a system administrator wishes to have a file (or
8235 directory or other such thing) installed with owner and
8236 permissions different from those in the distributed Debian
8237 package, they can use the <prgn>dpkg-statoverride</prgn>
8238 program to instruct <prgn>dpkg</prgn> to use the different
8239 settings every time the file is installed. Thus the
8240 package maintainer should distribute the files with their
8241 normal permissions, and leave it for the system
8242 administrator to make any desired changes. For example, a
8243 daemon which is normally required to be setuid root, but
8244 in certain situations could be used without being setuid,
8245 should be installed setuid in the <tt>.deb</tt>. Then the
8246 local system administrator can change this if they wish.
8247 If there are two standard ways of doing it, the package
8248 maintainer can use <tt>debconf</tt> to find out the
8249 preference, and call <prgn>dpkg-statoverride</prgn> in the
8250 maintainer script if necessary to accommodate the system
8251 administrator's choice. Care must be taken during
8252 upgrades to not override an existing setting.
8256 Given the above, <prgn>dpkg-statoverride</prgn> is
8257 essentially a tool for system administrators and would not
8258 normally be needed in the maintainer scripts. There is
8259 one type of situation, though, where calls to
8260 <prgn>dpkg-statoverride</prgn> would be needed in the
8261 maintainer scripts, and that involves packages which use
8262 dynamically allocated user or group ids. In such a
8263 situation, something like the following idiom can be very
8264 helpful in the package's <prgn>postinst</prgn>, where
8265 <tt>sysuser</tt> is a dynamically allocated id:
8267 for i in /usr/bin/foo /usr/sbin/bar
8269 # only do something when no setting exists
8270 if ! dpkg-statoverride --list $i >/dev/null 2>&1
8272 #include: debconf processing, question about foo and bar
8273 if [ "$RET" = "true" ] ; then
8274 dpkg-statoverride --update --add sysuser root 4755 $i
8279 The corresponding code to remove the override when the package
8282 for i in /usr/bin/foo /usr/sbin/bar
8284 if dpkg-statoverride --list $i >/dev/null 2>&1
8286 dpkg-statoverride --remove $i
8296 <chapt id="customized-programs">
8297 <heading>Customized programs</heading>
8299 <sect id="arch-spec">
8300 <heading>Architecture specification strings</heading>
8303 If a program needs to specify an <em>architecture specification
8304 string</em> in some place, it should select one of the strings
8305 provided by <tt>dpkg-architecture -L</tt>. The strings are in
8306 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
8307 part is sometimes elided, as when the OS is Linux.
8311 Note that we don't want to use
8312 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
8313 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
8314 since this would make our programs incompatible with other
8315 Linux distributions. We also don't use something like
8316 <tt><var>arch</var>-unknown-linux</tt>, since the
8317 <tt>unknown</tt> does not look very good.
8320 <sect1 id="arch-wildcard-spec">
8321 <heading>Architecture wildcards</heading>
8324 A package may specify an architecture wildcard. Architecture
8325 wildcards are in the format <tt>any</tt> (which matches every
8326 architecture), <tt><var>os</var></tt>-any, or
8327 any-<tt><var>cpu</var></tt>. <footnote>
8328 Internally, the package system normalizes the GNU triplets
8329 and the Debian arches into Debian arch triplets (which are
8330 kind of inverted GNU triplets), with the first component of
8331 the triplet representing the libc and ABI in use, and then
8332 does matching against those triplets. However, such
8333 triplets are an internal implementation detail that should
8334 not be used by packages directly. The libc and ABI portion
8335 is handled internally by the package system based on
8336 the <var>os</var> and <var>cpu</var>.
8343 <heading>Daemons</heading>
8346 The configuration files <file>/etc/services</file>,
8347 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
8348 by the <prgn>netbase</prgn> package and must not be modified
8353 If a package requires a new entry in one of these files, the
8354 maintainer should get in contact with the
8355 <prgn>netbase</prgn> maintainer, who will add the entries
8356 and release a new version of the <prgn>netbase</prgn>
8361 The configuration file <file>/etc/inetd.conf</file> must not be
8362 modified by the package's scripts except via the
8363 <prgn>update-inetd</prgn> script or the
8364 <file>DebianNet.pm</file> Perl module. See their documentation
8365 for details on how to add entries.
8369 If a package wants to install an example entry into
8370 <file>/etc/inetd.conf</file>, the entry must be preceded with
8371 exactly one hash character (<tt>#</tt>). Such lines are
8372 treated as "commented out by user" by the
8373 <prgn>update-inetd</prgn> script and are not changed or
8374 activated during package updates.
8379 <heading>Using pseudo-ttys and modifying wtmp, utmp and
8383 Some programs need to create pseudo-ttys. This should be done
8384 using Unix98 ptys if the C library supports it. The resulting
8385 program must not be installed setuid root, unless that
8386 is required for other functionality.
8390 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
8391 <file>/var/log/lastlog</file> must be installed writable by
8392 group <tt>utmp</tt>. Programs which need to modify those
8393 files must be installed setgid <tt>utmp</tt>.
8398 <heading>Editors and pagers</heading>
8401 Some programs have the ability to launch an editor or pager
8402 program to edit or display a text document. Since there are
8403 lots of different editors and pagers available in the Debian
8404 distribution, the system administrator and each user should
8405 have the possibility to choose their preferred editor and
8410 In addition, every program should choose a good default
8411 editor/pager if none is selected by the user or system
8416 Thus, every program that launches an editor or pager must
8417 use the EDITOR or PAGER environment variable to determine
8418 the editor or pager the user wishes to use. If these
8419 variables are not set, the programs <file>/usr/bin/editor</file>
8420 and <file>/usr/bin/pager</file> should be used, respectively.
8424 These two files are managed through the <prgn>dpkg</prgn>
8425 "alternatives" mechanism. Every package providing an editor or
8426 pager must call the <prgn>update-alternatives</prgn> script to
8427 register as an alternative for <file>/usr/bin/editor</file>
8428 or <file>/usr/bin/pager</file> as appropriate. The alternative
8429 should have a slave alternative
8430 for <file>/usr/share/man/man1/editor.1.gz</file>
8431 or <file>/usr/share/man/man1/pager.1.gz</file> pointing to the
8432 corresponding manual page.
8436 If it is very hard to adapt a program to make use of the
8437 EDITOR or PAGER variables, that program may be configured to
8438 use <file>/usr/bin/sensible-editor</file> and
8439 <file>/usr/bin/sensible-pager</file> as the editor or pager
8440 program respectively. These are two scripts provided in the
8441 <package>sensible-utils</package> package that check the EDITOR
8442 and PAGER variables and launch the appropriate program, and fall
8443 back to <file>/usr/bin/editor</file>
8444 and <file>/usr/bin/pager</file> if the variable is not set.
8448 A program may also use the VISUAL environment variable to
8449 determine the user's choice of editor. If it exists, it
8450 should take precedence over EDITOR. This is in fact what
8451 <file>/usr/bin/sensible-editor</file> does.
8455 It is not required for a package to depend on
8456 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
8457 package to provide such virtual packages.<footnote>
8458 The Debian base system already provides an editor and a
8464 <sect id="web-appl">
8465 <heading>Web servers and applications</heading>
8468 This section describes the locations and URLs that should
8469 be used by all web servers and web applications in the
8476 Cgi-bin executable files are installed in the
8478 <example compact="compact">
8479 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
8481 or a subdirectory of that directory, and should be
8483 <example compact="compact">
8484 http://localhost/cgi-bin/<var>cgi-bin-name</var>
8486 (possibly with a subdirectory name
8487 before <var>cgi-bin-name</var>).
8491 <p>Access to HTML documents</p>
8494 HTML documents for a package are stored in
8495 <file>/usr/share/doc/<var>package</var></file>
8496 and can be referred to as
8497 <example compact="compact">
8498 http://localhost/doc/<var>package</var>/<var>filename</var>
8503 The web server should restrict access to the document
8504 tree so that only clients on the same host can read
8505 the documents. If the web server does not support such
8506 access controls, then it should not provide access at
8507 all, or ask about providing access during installation.
8512 <p>Access to images</p>
8514 It is recommended that images for a package be stored
8515 in <tt>/usr/share/images/<var>package</var></tt> and
8516 may be referred to through an alias <tt>/images/</tt>
8519 http://localhost/images/<package>/<filename>
8526 <p>Web Document Root</p>
8529 Web Applications should try to avoid storing files in
8530 the Web Document Root. Instead they should use the
8531 /usr/share/doc/<var>package</var> directory for
8532 documents and register the Web Application via the
8533 <package>doc-base</package> package. If access to the
8534 web document root is unavoidable then use
8535 <example compact="compact">
8538 as the Document Root. This might be just a symbolic
8539 link to the location where the system administrator
8540 has put the real document root.
8543 <item><p>Providing httpd and/or httpd-cgi</p>
8545 All web servers should provide the virtual package
8546 <tt>httpd</tt>. If a web server has CGI support it should
8547 provide <tt>httpd-cgi</tt> additionally.
8550 All web applications which do not contain CGI scripts should
8551 depend on <tt>httpd</tt>, all those web applications which
8552 <tt>do</tt> contain CGI scripts, should depend on
8560 <sect id="mail-transport-agents">
8561 <heading>Mail transport, delivery and user agents</heading>
8564 Debian packages which process electronic mail, whether mail
8565 user agents (MUAs) or mail transport agents (MTAs), must
8566 ensure that they are compatible with the configuration
8567 decisions below. Failure to do this may result in lost
8568 mail, broken <tt>From:</tt> lines, and other serious brain
8573 The mail spool is <file>/var/mail</file> and the interface to
8574 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8575 the FHS). On older systems, the mail spool may be
8576 physically located in <file>/var/spool/mail</file>, but all
8577 access to the mail spool should be via the
8578 <file>/var/mail</file> symlink. The mail spool is part of the
8579 base system and not part of the MTA package.
8583 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8584 programs (such as IMAP daemons) must lock the mailbox in an
8585 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8586 be combined with dot locking. To avoid deadlocks, a program
8587 should use <tt>fcntl()</tt> first and dot locking after
8588 this, or alternatively implement the two locking methods in
8589 a non blocking way<footnote>
8590 If it is not possible to establish both locks, the
8591 system shouldn't wait for the second lock to be
8592 established, but remove the first lock, wait a (random)
8593 time, and start over locking again.
8594 </footnote>. Using the functions <tt>maillock</tt> and
8595 <tt>mailunlock</tt> provided by the
8596 <tt>liblockfile*</tt><footnote>
8597 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8598 to use these functions.
8599 </footnote> packages is the recommended way to realize this.
8603 Mailboxes are generally either mode 600 and owned by
8604 <var>user</var> or mode 660 and owned by
8605 <tt><var>user</var>:mail</tt><footnote>
8606 There are two traditional permission schemes for mail spools:
8607 mode 600 with all mail delivery done by processes running as
8608 the destination user, or mode 660 and owned by group mail with
8609 mail delivery done by a process running as a system user in
8610 group mail. Historically, Debian required mode 660 mail
8611 spools to enable the latter model, but that model has become
8612 increasingly uncommon and the principle of least privilege
8613 indicates that mail systems that use the first model should
8614 use permissions of 600. If delivery to programs is permitted,
8615 it's easier to keep the mail system secure if the delivery
8616 agent runs as the destination user. Debian Policy therefore
8617 permits either scheme.
8618 </footnote>. The local system administrator may choose a
8619 different permission scheme; packages should not make
8620 assumptions about the permission and ownership of mailboxes
8621 unless required (such as when creating a new mailbox). A MUA
8622 may remove a mailbox (unless it has nonstandard permissions) in
8623 which case the MTA or another MUA must recreate it if needed.
8627 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8628 be setgid mail to do the locking mentioned above (and
8629 must obviously avoid accessing other users' mailboxes
8630 using this privilege).</p>
8633 <file>/etc/aliases</file> is the source file for the system mail
8634 aliases (e.g., postmaster, usenet, etc.), it is the one
8635 which the sysadmin and <prgn>postinst</prgn> scripts may
8636 edit. After <file>/etc/aliases</file> is edited the program or
8637 human editing it must call <prgn>newaliases</prgn>. All MTA
8638 packages must come with a <prgn>newaliases</prgn> program,
8639 even if it does nothing, but older MTA packages did not do
8640 this so programs should not fail if <prgn>newaliases</prgn>
8641 cannot be found. Note that because of this, all MTA
8642 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8643 <tt>Replaces: mail-transport-agent</tt> control fields.
8647 The convention of writing <tt>forward to
8648 <var>address</var></tt> in the mailbox itself is not
8649 supported. Use a <tt>.forward</tt> file instead.</p>
8652 The <prgn>rmail</prgn> program used by UUCP
8653 for incoming mail should be <file>/usr/sbin/rmail</file>.
8654 Likewise, <prgn>rsmtp</prgn>, for receiving
8655 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8659 If your package needs to know what hostname to use on (for
8660 example) outgoing news and mail messages which are generated
8661 locally, you should use the file <file>/etc/mailname</file>. It
8662 will contain the portion after the username and <tt>@</tt>
8663 (at) sign for email addresses of users on the machine
8664 (followed by a newline).
8668 Such a package should check for the existence of this file
8669 when it is being configured. If it exists, it should be
8670 used without comment, although an MTA's configuration script
8671 may wish to prompt the user even if it finds that this file
8672 exists. If the file does not exist, the package should
8673 prompt the user for the value (preferably using
8674 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8675 as well as using it in the package's configuration. The
8676 prompt should make it clear that the name will not just be
8677 used by that package. For example, in this situation the
8678 <tt>inn</tt> package could say something like:
8679 <example compact="compact">
8680 Please enter the "mail name" of your system. This is the
8681 hostname portion of the address to be shown on outgoing
8682 news and mail messages. The default is
8683 <var>syshostname</var>, your system's host name. Mail
8684 name ["<var>syshostname</var>"]:
8686 where <var>syshostname</var> is the output of <tt>hostname
8692 <heading>News system configuration</heading>
8695 All the configuration files related to the NNTP (news)
8696 servers and clients should be located under
8697 <file>/etc/news</file>.</p>
8700 There are some configuration issues that apply to a number
8701 of news clients and server packages on the machine. These
8705 <tag><file>/etc/news/organization</file></tag>
8707 A string which should appear as the
8708 organization header for all messages posted
8709 by NNTP clients on the machine
8712 <tag><file>/etc/news/server</file></tag>
8714 Contains the FQDN of the upstream NNTP
8715 server, or localhost if the local machine is
8720 Other global files may be added as required for cross-package news
8727 <heading>Programs for the X Window System</heading>
8730 <heading>Providing X support and package priorities</heading>
8733 Programs that can be configured with support for the X
8734 Window System must be configured to do so and must declare
8735 any package dependencies necessary to satisfy their
8736 runtime requirements when using the X Window System. If
8737 such a package is of higher priority than the X packages
8738 on which it depends, it is required that either the
8739 X-specific components be split into a separate package, or
8740 that an alternative version of the package, which includes
8741 X support, be provided, or that the package's priority be
8747 <heading>Packages providing an X server</heading>
8750 Packages that provide an X server that, directly or
8751 indirectly, communicates with real input and display
8752 hardware should declare in their <tt>Provides</tt> control
8753 field that they provide the virtual
8754 package <tt>xserver</tt>.<footnote>
8755 This implements current practice, and provides an
8756 actual policy for usage of the <tt>xserver</tt>
8757 virtual package which appears in the virtual packages
8758 list. In a nutshell, X servers that interface
8759 directly with the display and input hardware or via
8760 another subsystem (e.g., GGI) should provide
8761 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8762 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8768 <heading>Packages providing a terminal emulator</heading>
8771 Packages that provide a terminal emulator for the X Window
8772 System which meet the criteria listed below should declare in
8773 their <tt>Provides</tt> control field that they provide the
8774 virtual package <tt>x-terminal-emulator</tt>. They should
8775 also register themselves as an alternative for
8776 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8777 20. That alternative should have a slave alternative
8778 for <file>/usr/share/man/man1/x-terminal-emulator.1.gz</file>
8779 pointing to the corresponding manual page.
8783 To be an <tt>x-terminal-emulator</tt>, a program must:
8784 <list compact="compact">
8786 Be able to emulate a DEC VT100 terminal, or a
8787 compatible terminal.
8791 Support the command-line option <tt>-e
8792 <var>command</var></tt>, which creates a new
8793 terminal window<footnote>
8794 "New terminal window" does not necessarily mean
8795 a new top-level X window directly parented by
8796 the window manager; it could, if the terminal
8797 emulator application were so coded, be a new
8798 "view" in a multiple-document interface (MDI).
8800 and runs the specified <var>command</var>,
8801 interpreting the entirety of the rest of the command
8802 line as a command to pass straight to exec, in the
8803 manner that <tt>xterm</tt> does.
8807 Support the command-line option <tt>-T
8808 <var>title</var></tt>, which creates a new terminal
8809 window with the window title <var>title</var>.
8816 <heading>Packages providing a window manager</heading>
8819 Packages that provide a window manager should declare in
8820 their <tt>Provides</tt> control field that they provide the
8821 virtual package <tt>x-window-manager</tt>. They should also
8822 register themselves as an alternative for
8823 <file>/usr/bin/x-window-manager</file>, with a priority
8824 calculated as follows:
8825 <list compact="compact">
8827 Start with a priority of 20.
8831 If the window manager supports the Debian menu
8832 system, add 20 points if this support is available
8833 in the package's default configuration (i.e., no
8834 configuration files belonging to the system or user
8835 have to be edited to activate the feature); if
8836 configuration files must be modified, add only 10
8842 If the window manager complies with <url
8843 id="http://www.freedesktop.org/Standards/wm-spec"
8844 name="The Window Manager Specification Project">,
8845 written by the <url id="http://www.freedesktop.org/"
8846 name="Free Desktop Group">, add 40 points.
8850 If the window manager permits the X session to be
8851 restarted using a <em>different</em> window manager
8852 (without killing the X server) in its default
8853 configuration, add 10 points; otherwise add none.
8856 That alternative should have a slave alternative
8857 for <file>/usr/share/man/man1/x-window-manager.1.gz</file>
8858 pointing to the corresponding manual page.
8863 <heading>Packages providing fonts</heading>
8866 Packages that provide fonts for the X Window
8868 For the purposes of Debian Policy, a "font for the X
8869 Window System" is one which is accessed via X protocol
8870 requests. Fonts for the Linux console, for PostScript
8871 renderer, or any other purpose, do not fit this
8872 definition. Any tool which makes such fonts available
8873 to the X Window System, however, must abide by this
8876 must do a number of things to ensure that they are both
8877 available without modification of the X or font server
8878 configuration, and that they do not corrupt files used by
8879 other font packages to register information about
8883 Fonts of any type supported by the X Window System
8884 must be in a separate binary package from any
8885 executables, libraries, or documentation (except
8886 that specific to the fonts shipped, such as their
8887 license information). If one or more of the fonts
8888 so packaged are necessary for proper operation of
8889 the package with which they are associated the font
8890 package may be Recommended; if the fonts merely
8891 provide an enhancement, a Suggests relationship may
8892 be used. Packages must not Depend on font
8894 This is because the X server may retrieve fonts
8895 from the local file system or over the network
8896 from an X font server; the Debian package system
8897 is empowered to deal only with the local
8903 BDF fonts must be converted to PCF fonts with the
8904 <prgn>bdftopcf</prgn> utility (available in the
8905 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8906 placed in a directory that corresponds to their
8908 <list compact="compact">
8910 100 dpi fonts must be placed in
8911 <file>/usr/share/fonts/X11/100dpi/</file>.
8915 75 dpi fonts must be placed in
8916 <file>/usr/share/fonts/X11/75dpi/</file>.
8920 Character-cell fonts, cursor fonts, and other
8921 low-resolution fonts must be placed in
8922 <file>/usr/share/fonts/X11/misc/</file>.
8928 Type 1 fonts must be placed in
8929 <file>/usr/share/fonts/X11/Type1/</file>. If font
8930 metric files are available, they must be placed here
8935 Subdirectories of <file>/usr/share/fonts/X11/</file>
8936 other than those listed above must be neither
8937 created nor used. (The <file>PEX</file>, <file>CID</file>,
8938 <file>Speedo</file>, and <file>cyrillic</file> directories
8939 are excepted for historical reasons, but installation of
8940 files into these directories remains discouraged.)
8944 Font packages may, instead of placing files directly
8945 in the X font directories listed above, provide
8946 symbolic links in that font directory pointing to
8947 the files' actual location in the filesystem. Such
8948 a location must comply with the FHS.
8952 Font packages should not contain both 75dpi and
8953 100dpi versions of a font. If both are available,
8954 they should be provided in separate binary packages
8955 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8956 the names of the packages containing the
8957 corresponding fonts.
8961 Fonts destined for the <file>misc</file> subdirectory
8962 should not be included in the same package as 75dpi
8963 or 100dpi fonts; instead, they should be provided in
8964 a separate package with <tt>-misc</tt> appended to
8969 Font packages must not provide the files
8970 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8971 <file>fonts.scale</file> in a font directory:
8974 <file>fonts.dir</file> files must not be provided at all.
8978 <file>fonts.alias</file> and <file>fonts.scale</file>
8979 files, if needed, should be provided in the
8981 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8982 where <var>fontdir</var> is the name of the
8984 <file>/usr/share/fonts/X11/</file> where the
8985 package's corresponding fonts are stored
8986 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8987 <var>package</var> is the name of the package
8988 that provides these fonts, and
8989 <var>extension</var> is either <tt>scale</tt>
8990 or <tt>alias</tt>, whichever corresponds to
8997 Font packages must declare a dependency on
8998 <tt>xfonts-utils</tt> in their <tt>Depends</tt>
8999 or <tt>Pre-Depends</tt> control field.
9003 Font packages that provide one or more
9004 <file>fonts.scale</file> files as described above must
9005 invoke <prgn>update-fonts-scale</prgn> on each
9006 directory into which they installed fonts
9007 <em>before</em> invoking
9008 <prgn>update-fonts-dir</prgn> on that directory.
9009 This invocation must occur in both the
9010 <prgn>postinst</prgn> (for all arguments) and
9011 <prgn>postrm</prgn> (for all arguments except
9012 <tt>upgrade</tt>) scripts.
9016 Font packages that provide one or more
9017 <file>fonts.alias</file> files as described above must
9018 invoke <prgn>update-fonts-alias</prgn> on each
9019 directory into which they installed fonts. This
9020 invocation must occur in both the
9021 <prgn>postinst</prgn> (for all arguments) and
9022 <prgn>postrm</prgn> (for all arguments except
9023 <tt>upgrade</tt>) scripts.
9027 Font packages must invoke
9028 <prgn>update-fonts-dir</prgn> on each directory into
9029 which they installed fonts. This invocation must
9030 occur in both the <prgn>postinst</prgn> (for all
9031 arguments) and <prgn>postrm</prgn> (for all
9032 arguments except <tt>upgrade</tt>) scripts.
9036 Font packages must not provide alias names for the
9037 fonts they include which collide with alias names
9038 already in use by fonts already packaged.
9042 Font packages must not provide fonts with the same
9043 XLFD registry name as another font already packaged.
9049 <sect1 id="appdefaults">
9050 <heading>Application defaults files</heading>
9053 Application defaults files must be installed in the
9054 directory <file>/etc/X11/app-defaults/</file> (use of a
9055 localized subdirectory of <file>/etc/X11/</file> as described
9056 in the <em>X Toolkit Intrinsics - C Language
9057 Interface</em> manual is also permitted). They must be
9058 registered as <tt>conffile</tt>s or handled as
9059 configuration files.
9063 Customization of programs' X resources may also be
9064 supported with the provision of a file with the same name
9065 as that of the package placed in
9066 the <file>/etc/X11/Xresources/</file> directory, which
9067 must be registered as a <tt>conffile</tt> or handled as a
9068 configuration file.<footnote>
9069 Note that this mechanism is not the same as using
9070 app-defaults; app-defaults are tied to the client
9071 binary on the local file system, whereas X resources
9072 are stored in the X server and affect all connecting
9079 <heading>Installation directory issues</heading>
9082 Historically, packages using the X Window System used a
9083 separate set of installation directories from other packages.
9084 This practice has been discontinued and packages using the X
9085 Window System should now generally be installed in the same
9086 directories as any other package. Specifically, packages must
9087 not install files under the <file>/usr/X11R6/</file> directory
9088 and the <file>/usr/X11R6/</file> directory hierarchy should be
9089 regarded as obsolete.
9093 Include files previously installed under
9094 <file>/usr/X11R6/include/X11/</file> should be installed into
9095 <file>/usr/include/X11/</file>. For files previously
9096 installed into subdirectories of
9097 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
9098 determine if subdirectories of <file>/usr/lib/</file> and
9099 <file>/usr/share/</file> can be used. If not, a subdirectory
9100 of <file>/usr/lib/X11/</file> should be used.
9104 Configuration files for window, display, or session managers
9105 or other applications that are tightly integrated with the X
9106 Window System may be placed in a subdirectory
9107 of <file>/etc/X11/</file> corresponding to the package name.
9108 Other X Window System applications should use
9109 the <file>/etc/</file> directory unless otherwise mandated by
9110 policy (such as for <ref id="appdefaults">).
9115 <heading>The OSF/Motif and OpenMotif libraries</heading>
9118 <em>Programs that require the non-DFSG-compliant OSF/Motif or
9119 OpenMotif libraries</em><footnote>
9120 OSF/Motif and OpenMotif are collectively referred to as
9121 "Motif" in this policy document.
9123 should be compiled against and tested with LessTif (a free
9124 re-implementation of Motif) instead. If the maintainer
9125 judges that the program or programs do not work
9126 sufficiently well with LessTif to be distributed and
9127 supported, but do so when compiled against Motif, then two
9128 versions of the package should be created; one linked
9129 statically against Motif and with <tt>-smotif</tt>
9130 appended to the package name, and one linked dynamically
9131 against Motif and with <tt>-dmotif</tt> appended to the
9136 Both Motif-linked versions are dependent
9137 upon non-DFSG-compliant software and thus cannot be
9138 uploaded to the <em>main</em> distribution; if the
9139 software is itself DFSG-compliant it may be uploaded to
9140 the <em>contrib</em> distribution. While known existing
9141 versions of Motif permit unlimited redistribution of
9142 binaries linked against the library (whether statically or
9143 dynamically), it is the package maintainer's
9144 responsibility to determine whether this is permitted by
9145 the license of the copy of Motif in their possession.
9151 <heading>Perl programs and modules</heading>
9154 Perl programs and modules should follow the current Perl policy.
9158 The Perl policy can be found in the <tt>perl-policy</tt>
9159 files in the <tt>debian-policy</tt> package.
9160 It is also available from the Debian web mirrors at
9161 <tt><url name="/doc/packaging-manuals/perl-policy/"
9162 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
9167 <heading>Emacs lisp programs</heading>
9170 Please refer to the "Debian Emacs Policy" for details of how to
9171 package emacs lisp programs.
9175 The Emacs policy is available in
9176 <file>debian-emacs-policy.gz</file> of the
9177 <package>emacsen-common</package> package.
9178 It is also available from the Debian web mirrors at
9179 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
9180 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
9185 <heading>Games</heading>
9188 The permissions on <file>/var/games</file> are mode 755, owner
9189 <tt>root</tt> and group <tt>root</tt>.
9193 Each game decides on its own security policy.</p>
9196 Games which require protected, privileged access to
9197 high-score files, saved games, etc., may be made
9198 set-<em>group</em>-id (mode 2755) and owned by
9199 <tt>root:games</tt>, and use files and directories with
9200 appropriate permissions (770 <tt>root:games</tt>, for
9201 example). They must not be made
9202 set-<em>user</em>-id, as this causes security problems. (If
9203 an attacker can subvert any set-user-id game they can
9204 overwrite the executable of any other, causing other players
9205 of these games to run a Trojan horse program. With a
9206 set-group-id game the attacker only gets access to less
9207 important game data, and if they can get at the other
9208 players' accounts at all it will take considerably more
9212 Some packages, for example some fortune cookie programs, are
9213 configured by the upstream authors to install with their
9214 data files or other static information made unreadable so
9215 that they can only be accessed through set-id programs
9216 provided. You should not do this in a Debian package: anyone can
9217 download the <file>.deb</file> file and read the data from it,
9218 so there is no point making the files unreadable. Not
9219 making the files unreadable also means that you don't have
9220 to make so many programs set-id, which reduces the risk of a
9224 As described in the FHS, binaries of games should be
9225 installed in the directory <file>/usr/games</file>. This also
9226 applies to games that use the X Window System. Manual pages
9227 for games (X and non-X games) should be installed in
9228 <file>/usr/share/man/man6</file>.</p>
9234 <heading>Documentation</heading>
9237 <heading>Manual pages</heading>
9240 You should install manual pages in <prgn>nroff</prgn> source
9241 form, in appropriate places under <file>/usr/share/man</file>.
9242 You should only use sections 1 to 9 (see the FHS for more
9243 details). You must not install a pre-formatted "cat page".
9247 Each program, utility, and function should have an
9248 associated manual page included in the same package. It is
9249 suggested that all configuration files also have a manual
9250 page included as well. Manual pages for protocols and other
9251 auxiliary things are optional.
9255 If no manual page is available, this is considered as a bug
9256 and should be reported to the Debian Bug Tracking System (the
9257 maintainer of the package is allowed to write this bug report
9258 themselves, if they so desire). Do not close the bug report
9259 until a proper man page is available.<footnote>
9260 It is not very hard to write a man page. See the
9261 <url id="http://www.schweikhardt.net/man_page_howto.html"
9262 name="Man-Page-HOWTO">,
9263 <manref name="man" section="7">, the examples
9264 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
9265 the helper program <prgn>help2man</prgn>, or the
9266 directory <file>/usr/share/doc/man-db/examples</file>.
9271 You may forward a complaint about a missing man page to the
9272 upstream authors, and mark the bug as forwarded in the
9273 Debian bug tracking system. Even though the GNU Project do
9274 not in general consider the lack of a man page to be a bug,
9275 we do; if they tell you that they don't consider it a bug
9276 you should leave the bug in our bug tracking system open
9281 Manual pages should be installed compressed using <tt>gzip -9</tt>.
9285 If one man page needs to be accessible via several names it
9286 is better to use a symbolic link than the <file>.so</file>
9287 feature, but there is no need to fiddle with the relevant
9288 parts of the upstream source to change from <file>.so</file> to
9289 symlinks: don't do it unless it's easy. You should not
9290 create hard links in the manual page directories, nor put
9291 absolute filenames in <file>.so</file> directives. The filename
9292 in a <file>.so</file> in a man page should be relative to the
9293 base of the man page tree (usually
9294 <file>/usr/share/man</file>). If you do not create any links
9295 (whether symlinks, hard links, or <tt>.so</tt> directives)
9296 in the file system to the alternate names of the man page,
9297 then you should not rely on <prgn>man</prgn> finding your
9298 man page under those names based solely on the information in
9299 the man page's header.<footnote>
9300 Supporting this in <prgn>man</prgn> often requires
9301 unreasonable processing time to find a manual page or to
9302 report that none exists, and moves knowledge into man's
9303 database that would be better left in the file system.
9304 This support is therefore deprecated and will cease to
9305 be present in the future.
9310 Manual pages in locale-specific subdirectories of
9311 <file>/usr/share/man</file> should use either UTF-8 or the usual
9312 legacy encoding for that language (normally the one corresponding
9313 to the shortest relevant locale name in
9314 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
9315 <file>/usr/share/man/fr</file> should use either UTF-8 or
9316 ISO-8859-1.<footnote>
9317 <prgn>man</prgn> will automatically detect whether UTF-8 is in
9318 use. In future, all manual pages will be required to use
9324 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
9325 included in the subdirectory name unless it indicates a
9326 significant difference in the language, as this excludes
9327 speakers of the language in other countries.<footnote>
9328 At the time of writing, Chinese and Portuguese are the main
9329 languages with such differences, so <file>pt_BR</file>,
9330 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
9335 If a localized version of a manual page is provided, it should
9336 either be up-to-date or it should be obvious to the reader that
9337 it is outdated and the original manual page should be used
9338 instead. This can be done either by a note at the beginning of
9339 the manual page or by showing the missing or changed portions in
9340 the original language instead of the target language.
9345 <heading>Info documents</heading>
9348 Info documents should be installed in <file>/usr/share/info</file>.
9349 They should be compressed with <tt>gzip -9</tt>.
9353 The <prgn>install-info</prgn> program maintains a directory of
9354 installed info documents in <file>/usr/share/info/dir</file> for
9355 the use of info readers.<footnote>
9356 It was previously necessary for packages installing info
9357 documents to run <prgn>install-info</prgn> from maintainer
9358 scripts. This is no longer necessary. The installation
9359 system now uses dpkg triggers.
9361 This file must not be included in packages. Packages containing
9362 info documents should depend on <tt>dpkg (>= 1.15.4) |
9363 install-info</tt> to ensure that the directory file is properly
9364 rebuilt during partial upgrades from Debian 5.0 (lenny) and
9369 Info documents should contain section and directory entry
9370 information in the document for the use
9371 of <prgn>install-info</prgn>. The section should be specified
9372 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
9373 space and the section of this info page. The directory entry or
9374 entries should be included between
9375 a <tt>START-INFO-DIR-ENTRY</tt> line and
9376 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
9378 INFO-DIR-SECTION Individual utilities
9379 START-INFO-DIR-ENTRY
9380 * example: (example). An example info directory entry.
9383 To determine which section to use, you should look
9384 at <file>/usr/share/info/dir</file> on your system and choose
9385 the most relevant (or create a new section if none of the
9386 current sections are relevant).<footnote>
9387 Normally, info documents are generated from Texinfo source.
9388 To include this information in the generated info document, if
9389 it is absent, add commands like:
9391 @dircategory Individual utilities
9393 * example: (example). An example info directory entry.
9396 to the Texinfo source of the document and ensure that the info
9397 documents are rebuilt from source during the package build.
9403 <heading>Additional documentation</heading>
9406 Any additional documentation that comes with the package may
9407 be installed at the discretion of the package maintainer.
9408 Plain text documentation should be installed in the directory
9409 <file>/usr/share/doc/<var>package</var></file>, where
9410 <var>package</var> is the name of the package, and
9411 compressed with <tt>gzip -9</tt> unless it is small.
9415 If a package comes with large amounts of documentation which
9416 many users of the package will not require you should create
9417 a separate binary package to contain it, so that it does not
9418 take up disk space on the machines of users who do not need
9419 or want it installed.</p>
9422 It is often a good idea to put text information files
9423 (<file>README</file>s, changelogs, and so forth) that come with
9424 the source package in <file>/usr/share/doc/<var>package</var></file>
9425 in the binary package. However, you don't need to install
9426 the instructions for building and installing the package, of
9430 Packages must not require the existence of any files in
9431 <file>/usr/share/doc/</file> in order to function
9433 The system administrator should be able to
9434 delete files in <file>/usr/share/doc/</file> without causing
9435 any programs to break.
9437 Any files that are referenced by programs but are also
9438 useful as stand alone documentation should be installed under
9439 <file>/usr/share/<var>package</var>/</file> with symbolic links from
9440 <file>/usr/share/doc/<var>package</var></file>.
9444 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9445 link to another directory in <file>/usr/share/doc</file> only if
9446 the two packages both come from the same source and the
9447 first package Depends on the second.<footnote>
9449 Please note that this does not override the section on
9450 changelog files below, so the file
9451 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
9452 must refer to the changelog for the current version of
9453 <var>package</var> in question. In practice, this means
9454 that the sources of the target and the destination of the
9455 symlink must be the same (same source package and
9462 Former Debian releases placed all additional documentation
9463 in <file>/usr/doc/<var>package</var></file>. This has been
9464 changed to <file>/usr/share/doc/<var>package</var></file>,
9465 and packages must not put documentation in the directory
9466 <file>/usr/doc/<var>package</var></file>. <footnote>
9467 At this phase of the transition, we no longer require a
9468 symbolic link in <file>/usr/doc/</file>. At a later point,
9469 policy shall change to make the symbolic links a bug.
9475 <heading>Preferred documentation formats</heading>
9478 The unification of Debian documentation is being carried out
9482 If your package comes with extensive documentation in a
9483 markup format that can be converted to various other formats
9484 you should if possible ship HTML versions in a binary
9485 package, in the directory
9486 <file>/usr/share/doc/<var>appropriate-package</var></file> or
9487 its subdirectories.<footnote>
9488 The rationale: The important thing here is that HTML
9489 docs should be available in <em>some</em> package, not
9490 necessarily in the main binary package.
9495 Other formats such as PostScript may be provided at the
9496 package maintainer's discretion.
9500 <sect id="copyrightfile">
9501 <heading>Copyright information</heading>
9504 Every package must be accompanied by a verbatim copy of its
9505 copyright information and distribution license in the file
9506 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
9507 file must neither be compressed nor be a symbolic link.
9511 In addition, the copyright file must say where the upstream
9512 sources (if any) were obtained. It should name the original
9513 authors of the package and the Debian maintainer(s) who were
9514 involved with its creation.
9518 Packages in the <em>contrib</em> or <em>non-free</em> archive
9519 areas should state in the copyright file that the package is not
9520 part of the Debian GNU/Linux distribution and briefly explain
9525 A copy of the file which will be installed in
9526 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9527 be in <file>debian/copyright</file> in the source package.
9531 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9532 link to another directory in <file>/usr/share/doc</file> only if
9533 the two packages both come from the same source and the
9534 first package Depends on the second. These rules are
9535 important because copyrights must be extractable by
9540 Packages distributed under the Apache license (version 2.0), the
9541 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
9542 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
9543 1.3) should refer to the corresponding files
9544 under <file>/usr/share/common-licenses</file>,<footnote>
9547 <file>/usr/share/common-licenses/Apache-2.0</file>,
9548 <file>/usr/share/common-licenses/Artistic</file>,
9549 <file>/usr/share/common-licenses/GPL-1</file>,
9550 <file>/usr/share/common-licenses/GPL-2</file>,
9551 <file>/usr/share/common-licenses/GPL-3</file>,
9552 <file>/usr/share/common-licenses/LGPL-2</file>,
9553 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9554 <file>/usr/share/common-licenses/LGPL-3</file>,
9555 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
9556 <file>/usr/share/common-licenses/GFDL-1.3</file>
9557 respectively. The University of California BSD license is
9558 also included in <package>base-files</package> as
9559 <file>/usr/share/common-licenses/BSD</file>, but given the
9560 brevity of this license, its specificity to code whose
9561 copyright is held by the Regents of the University of
9562 California, and the frequency of minor wording changes, its
9563 text should be included in the copyright file rather than
9564 referencing this file.
9566 </footnote> rather than quoting them in the copyright
9571 You should not use the copyright file as a general <file>README</file>
9572 file. If your package has such a file it should be
9573 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9574 <file>README.Debian</file> or some other appropriate place.</p>
9578 <heading>Examples</heading>
9581 Any examples (configurations, source files, whatever),
9582 should be installed in a directory
9583 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9584 files should not be referenced by any program: they're there
9585 for the benefit of the system administrator and users as
9586 documentation only. Architecture-specific example files
9587 should be installed in a directory
9588 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9590 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9591 latter directory itself may be a symbolic link to the
9596 If the purpose of a package is to provide examples, then the
9597 example files may be installed into
9598 <file>/usr/share/doc/<var>package</var></file>.
9602 <sect id="changelogs">
9603 <heading>Changelog files</heading>
9606 Packages that are not Debian-native must contain a
9607 compressed copy of the <file>debian/changelog</file> file from
9608 the Debian source tree in
9609 <file>/usr/share/doc/<var>package</var></file> with the name
9610 <file>changelog.Debian.gz</file>.
9614 If an upstream changelog is available, it should be accessible as
9615 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9616 plain text. If the upstream changelog is distributed in
9617 HTML, it should be made available in that form as
9618 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9619 and a plain text <file>changelog.gz</file> should be generated
9620 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9621 the upstream changelog files do not already conform to this
9622 naming convention, then this may be achieved either by
9623 renaming the files, or by adding a symbolic link, at the
9624 maintainer's discretion.<footnote>
9625 Rationale: People should not have to look in places for
9626 upstream changelogs merely because they are given
9627 different names or are distributed in HTML format.
9632 All of these files should be installed compressed using
9633 <tt>gzip -9</tt>, as they will become large with time even
9634 if they start out small.
9638 If the package has only one changelog which is used both as
9639 the Debian changelog and the upstream one because there is
9640 no separate upstream maintainer then that changelog should
9641 usually be installed as
9642 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9643 there is a separate upstream maintainer, but no upstream
9644 changelog, then the Debian changelog should still be called
9645 <file>changelog.Debian.gz</file>.
9649 For details about the format and contents of the Debian
9650 changelog file, please see <ref id="dpkgchangelog">.
9655 <appendix id="pkg-scope">
9656 <heading>Introduction and scope of these appendices</heading>
9659 These appendices are taken essentially verbatim from the
9660 now-deprecated Packaging Manual, version 3.2.1.0. They are
9661 the chapters which are likely to be of use to package
9662 maintainers and which have not already been included in the
9663 policy document itself. Most of these sections are very likely
9664 not relevant to policy; they should be treated as
9665 documentation for the packaging system. Please note that these
9666 appendices are included for convenience, and for historical
9667 reasons: they used to be part of policy package, and they have
9668 not yet been incorporated into dpkg documentation. However,
9669 they still have value, and hence they are presented here.
9673 They have not yet been checked to ensure that they are
9674 compatible with the contents of policy, and if there are any
9675 contradictions, the version in the main policy document takes
9676 precedence. The remaining chapters of the old Packaging
9677 Manual have also not been read in detail to ensure that there
9678 are not parts which have been left out. Both of these will be
9683 Certain parts of the Packaging manual were integrated into the
9684 Policy Manual proper, and removed from the appendices. Links
9685 have been placed from the old locations to the new ones.
9689 <prgn>dpkg</prgn> is a suite of programs for creating binary
9690 package files and installing and removing them on Unix
9692 <prgn>dpkg</prgn> is targeted primarily at Debian
9693 GNU/Linux, but may work on or be ported to other
9699 The binary packages are designed for the management of
9700 installed executable programs (usually compiled binaries) and
9701 their associated data, though source code examples and
9702 documentation are provided as part of some packages.</p>
9705 This manual describes the technical aspects of creating Debian
9706 binary packages (<file>.deb</file> files). It documents the
9707 behavior of the package management programs
9708 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9709 they interact with packages.</p>
9712 It also documents the interaction between
9713 <prgn>dselect</prgn>'s core and the access method scripts it
9714 uses to actually install the selected packages, and describes
9715 how to create a new access method.</p>
9718 This manual does not go into detail about the options and
9719 usage of the package building and installation tools. It
9720 should therefore be read in conjunction with those programs'
9725 The utility programs which are provided with <prgn>dpkg</prgn>
9726 for managing various system configuration and similar issues,
9727 such as <prgn>update-rc.d</prgn> and
9728 <prgn>install-info</prgn>, are not described in detail here -
9729 please see their man pages.
9733 It is assumed that the reader is reasonably familiar with the
9734 <prgn>dpkg</prgn> System Administrators' manual.
9735 Unfortunately this manual does not yet exist.
9739 The Debian version of the FSF's GNU hello program is provided
9740 as an example for people wishing to create Debian
9741 packages. The Debian <prgn>debmake</prgn> package is
9742 recommended as a very helpful tool in creating and maintaining
9743 Debian packages. However, while the tools and examples are
9744 helpful, they do not replace the need to read and follow the
9745 Policy and Programmer's Manual.</p>
9748 <appendix id="pkg-binarypkg">
9749 <heading>Binary packages (from old Packaging Manual)</heading>
9752 The binary package has two main sections. The first part
9753 consists of various control information files and scripts used
9754 by <prgn>dpkg</prgn> when installing and removing. See <ref
9755 id="pkg-controlarea">.
9759 The second part is an archive containing the files and
9760 directories to be installed.
9764 In the future binary packages may also contain other
9765 components, such as checksums and digital signatures. The
9766 format for the archive is described in full in the
9767 <file>deb(5)</file> man page.
9771 <sect id="pkg-bincreating"><heading>Creating package files -
9772 <prgn>dpkg-deb</prgn>
9776 All manipulation of binary package files is done by
9777 <prgn>dpkg-deb</prgn>; it's the only program that has
9778 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9779 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9780 will spot that the options requested are appropriate to
9781 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9786 In order to create a binary package you must make a
9787 directory tree which contains all the files and directories
9788 you want to have in the file system data part of the package.
9789 In Debian-format source packages this directory is usually
9790 <file>debian/tmp</file>, relative to the top of the package's
9795 They should have the locations (relative to the root of the
9796 directory tree you're constructing) ownerships and
9797 permissions which you want them to have on the system when
9802 With current versions of <prgn>dpkg</prgn> the uid/username
9803 and gid/groupname mappings for the users and groups being
9804 used should be the same on the system where the package is
9805 built and the one where it is installed.
9809 You need to add one special directory to the root of the
9810 miniature file system tree you're creating:
9811 <prgn>DEBIAN</prgn>. It should contain the control
9812 information files, notably the binary package control file
9813 (see <ref id="pkg-controlfile">).
9817 The <prgn>DEBIAN</prgn> directory will not appear in the
9818 file system archive of the package, and so won't be installed
9819 by <prgn>dpkg</prgn> when the package is installed.
9823 When you've prepared the package, you should invoke:
9825 dpkg --build <var>directory</var>
9830 This will build the package in
9831 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9832 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9833 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9838 See the man page <manref name="dpkg-deb" section="8"> for details of how
9839 to examine the contents of this newly-created file. You may find the
9840 output of following commands enlightening:
9842 dpkg-deb --info <var>filename</var>.deb
9843 dpkg-deb --contents <var>filename</var>.deb
9844 dpkg --contents <var>filename</var>.deb
9846 To view the copyright file for a package you could use this command:
9848 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
9853 <sect id="pkg-controlarea">
9854 <heading>Package control information files</heading>
9857 The control information portion of a binary package is a
9858 collection of files with names known to <prgn>dpkg</prgn>.
9859 It will treat the contents of these files specially - some
9860 of them contain information used by <prgn>dpkg</prgn> when
9861 installing or removing the package; others are scripts which
9862 the package maintainer wants <prgn>dpkg</prgn> to run.
9866 It is possible to put other files in the package control
9867 information file area, but this is not generally a good idea
9868 (though they will largely be ignored).
9872 Here is a brief list of the control information files supported
9873 by <prgn>dpkg</prgn> and a summary of what they're used for.
9878 <tag><tt>control</tt>
9881 This is the key description file used by
9882 <prgn>dpkg</prgn>. It specifies the package's name
9883 and version, gives its description for the user,
9884 states its relationships with other packages, and so
9885 forth. See <ref id="sourcecontrolfiles"> and
9886 <ref id="binarycontrolfiles">.
9890 It is usually generated automatically from information
9891 in the source package by the
9892 <prgn>dpkg-gencontrol</prgn> program, and with
9893 assistance from <prgn>dpkg-shlibdeps</prgn>.
9894 See <ref id="pkg-sourcetools">.
9898 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9903 These are executable files (usually scripts) which
9904 <prgn>dpkg</prgn> runs during installation, upgrade
9905 and removal of packages. They allow the package to
9906 deal with matters which are particular to that package
9907 or require more complicated processing than that
9908 provided by <prgn>dpkg</prgn>. Details of when and
9909 how they are called are in <ref id="maintainerscripts">.
9913 It is very important to make these scripts idempotent.
9914 See <ref id="idempotency">.
9918 The maintainer scripts are not guaranteed to run with a
9919 controlling terminal and may not be able to interact with
9920 the user. See <ref id="controllingterminal">.
9924 <tag><tt>conffiles</tt>
9927 This file contains a list of configuration files which
9928 are to be handled automatically by <prgn>dpkg</prgn>
9929 (see <ref id="pkg-conffiles">). Note that not necessarily
9930 every configuration file should be listed here.
9933 <tag><tt>shlibs</tt>
9936 This file contains a list of the shared libraries
9937 supplied by the package, with dependency details for
9938 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9939 when it determines what dependencies are required in a
9940 package control file. The <tt>shlibs</tt> file format
9941 is described on <ref id="shlibs">.
9946 <sect id="pkg-controlfile">
9947 <heading>The main control information file: <tt>control</tt></heading>
9950 The most important control information file used by
9951 <prgn>dpkg</prgn> when it installs a package is
9952 <tt>control</tt>. It contains all the package's "vital
9957 The binary package control files of packages built from
9958 Debian sources are made by a special tool,
9959 <prgn>dpkg-gencontrol</prgn>, which reads
9960 <file>debian/control</file> and <file>debian/changelog</file> to
9961 find the information it needs. See <ref id="pkg-sourcepkg"> for
9966 The fields in binary package control files are listed in
9967 <ref id="binarycontrolfiles">.
9971 A description of the syntax of control files and the purpose
9972 of the fields is available in <ref id="controlfields">.
9977 <heading>Time Stamps</heading>
9980 See <ref id="timestamps">.
9985 <appendix id="pkg-sourcepkg">
9986 <heading>Source packages (from old Packaging Manual) </heading>
9989 The Debian binary packages in the distribution are generated
9990 from Debian sources, which are in a special format to assist
9991 the easy and automatic building of binaries.
9994 <sect id="pkg-sourcetools">
9995 <heading>Tools for processing source packages</heading>
9998 Various tools are provided for manipulating source packages;
9999 they pack and unpack sources and help build of binary
10000 packages and help manage the distribution of new versions.
10004 They are introduced and typical uses described here; see
10005 <manref name="dpkg-source" section="1"> for full
10006 documentation about their arguments and operation.
10010 For examples of how to construct a Debian source package,
10011 and how to use those utilities that are used by Debian
10012 source packages, please see the <prgn>hello</prgn> example
10016 <sect1 id="pkg-dpkg-source">
10018 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
10023 This program is frequently used by hand, and is also
10024 called from package-independent automated building scripts
10025 such as <prgn>dpkg-buildpackage</prgn>.
10029 To unpack a package it is typically invoked with
10031 dpkg-source -x <var>.../path/to/filename</var>.dsc
10036 with the <file><var>filename</var>.tar.gz</file> and
10037 <file><var>filename</var>.diff.gz</file> (if applicable) in
10038 the same directory. It unpacks into
10039 <file><var>package</var>-<var>version</var></file>, and if
10041 <file><var>package</var>-<var>version</var>.orig</file>, in
10042 the current directory.
10046 To create a packed source archive it is typically invoked:
10048 dpkg-source -b <var>package</var>-<var>version</var>
10053 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
10054 <file>.diff.gz</file> (if appropriate) in the current
10055 directory. <prgn>dpkg-source</prgn> does not clean the
10056 source tree first - this must be done separately if it is
10061 See also <ref id="pkg-sourcearchives">.</p>
10065 <sect1 id="pkg-dpkg-buildpackage">
10067 <prgn>dpkg-buildpackage</prgn> - overall package-building
10072 <prgn>dpkg-buildpackage</prgn> is a script which invokes
10073 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
10074 targets <tt>clean</tt>, <tt>build</tt> and
10075 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
10076 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
10077 source and binary package upload.
10081 It is usually invoked by hand from the top level of the
10082 built or unbuilt source directory. It may be invoked with
10083 no arguments; useful arguments include:
10084 <taglist compact="compact">
10085 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
10088 Do not sign the <tt>.changes</tt> file or the
10089 source package <tt>.dsc</tt> file, respectively.</p>
10091 <tag><tt>-p<var>sign-command</var></tt></tag>
10094 Invoke <var>sign-command</var> instead of finding
10095 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
10096 <var>sign-command</var> must behave just like
10097 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
10099 <tag><tt>-r<var>root-command</var></tt></tag>
10102 When root privilege is required, invoke the command
10103 <var>root-command</var>. <var>root-command</var>
10104 should invoke its first argument as a command, from
10105 the <prgn>PATH</prgn> if necessary, and pass its
10106 second and subsequent arguments to the command it
10107 calls. If no <var>root-command</var> is supplied
10108 then <var>dpkg-buildpackage</var> will take no
10109 special action to gain root privilege, so that for
10110 most packages it will have to be invoked as root to
10113 <tag><tt>-b</tt>, <tt>-B</tt></tag>
10116 Two types of binary-only build and upload - see
10117 <manref name="dpkg-source" section="1">.
10124 <sect1 id="pkg-dpkg-gencontrol">
10126 <prgn>dpkg-gencontrol</prgn> - generates binary package
10131 This program is usually called from <file>debian/rules</file>
10132 (see <ref id="pkg-sourcetree">) in the top level of the source
10137 This is usually done just before the files and directories in the
10138 temporary directory tree where the package is being built have their
10139 permissions and ownerships set and the package is constructed using
10140 <prgn>dpkg-deb/</prgn>
10142 This is so that the control file which is produced has
10143 the right permissions
10148 <prgn>dpkg-gencontrol</prgn> must be called after all the
10149 files which are to go into the package have been placed in
10150 the temporary build directory, so that its calculation of
10151 the installed size of a package is correct.
10155 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
10156 be run after <prgn>dpkg-shlibdeps</prgn> so that the
10157 variable substitutions created by
10158 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
10163 For a package which generates only one binary package, and
10164 which builds it in <file>debian/tmp</file> relative to the top
10165 of the source package, it is usually sufficient to call
10166 <prgn>dpkg-gencontrol</prgn>.
10170 Sources which build several binaries will typically need
10173 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
10174 </example> The <tt>-P</tt> tells
10175 <prgn>dpkg-gencontrol</prgn> that the package is being
10176 built in a non-default directory, and the <tt>-p</tt>
10177 tells it which package's control file should be generated.
10181 <prgn>dpkg-gencontrol</prgn> also adds information to the
10182 list of files in <file>debian/files</file>, for the benefit of
10183 (for example) a future invocation of
10184 <prgn>dpkg-genchanges</prgn>.</p>
10187 <sect1 id="pkg-dpkg-shlibdeps">
10189 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
10194 This program is usually called from <file>debian/rules</file>
10195 just before <prgn>dpkg-gencontrol</prgn> (see <ref
10196 id="pkg-sourcetree">), in the top level of the source tree.
10200 Its arguments are executables and shared libraries
10203 They may be specified either in the locations in the
10204 source tree where they are created or in the locations
10205 in the temporary build tree where they are installed
10206 prior to binary package creation.
10208 </footnote> for which shared library dependencies should
10209 be included in the binary package's control file.
10213 If some of the found shared libraries should only
10214 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
10215 some warrant a <tt>Pre-Depends</tt>, this can be achieved
10216 by using the <tt>-d<var>dependency-field</var></tt> option
10217 before those executable(s). (Each <tt>-d</tt> option
10218 takes effect until the next <tt>-d</tt>.)
10222 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
10223 output control file to be modified. Instead by default it
10224 adds to the <file>debian/substvars</file> file variable
10225 settings like <tt>shlibs:Depends</tt>. These variable
10226 settings must be referenced in dependency fields in the
10227 appropriate per-binary-package sections of the source
10232 For example, a package that generates an essential part
10233 which requires dependencies, and optional parts that
10234 which only require a recommendation, would separate those
10235 two sets of dependencies into two different fields.<footnote>
10236 At the time of writing, an example for this was the
10237 <package/xmms/ package, with Depends used for the xmms
10238 executable, Recommends for the plug-ins and Suggests for
10239 even more optional features provided by unzip.
10241 It can say in its <file>debian/rules</file>:
10243 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
10244 -dRecommends <var>optionalpart anotheroptionalpart</var>
10246 and then in its main control file <file>debian/control</file>:
10249 Depends: ${shlibs:Depends}
10250 Recommends: ${shlibs:Recommends}
10256 Sources which produce several binary packages with
10257 different shared library dependency requirements can use
10258 the <tt>-p<var>varnameprefix</var></tt> option to override
10259 the default <tt>shlibs:</tt> prefix (one invocation of
10260 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
10261 They can thus produce several sets of dependency
10262 variables, each of the form
10263 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
10264 which can be referred to in the appropriate parts of the
10265 binary package control files.
10270 <sect1 id="pkg-dpkg-distaddfile">
10272 <prgn>dpkg-distaddfile</prgn> - adds a file to
10273 <file>debian/files</file>
10277 Some packages' uploads need to include files other than
10278 the source and binary package files.
10282 <prgn>dpkg-distaddfile</prgn> adds a file to the
10283 <file>debian/files</file> file so that it will be included in
10284 the <file>.changes</file> file when
10285 <prgn>dpkg-genchanges</prgn> is run.
10289 It is usually invoked from the <tt>binary</tt> target of
10290 <file>debian/rules</file>:
10292 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
10294 The <var>filename</var> is relative to the directory where
10295 <prgn>dpkg-genchanges</prgn> will expect to find it - this
10296 is usually the directory above the top level of the source
10297 tree. The <file>debian/rules</file> target should put the
10298 file there just before or just after calling
10299 <prgn>dpkg-distaddfile</prgn>.
10303 The <var>section</var> and <var>priority</var> are passed
10304 unchanged into the resulting <file>.changes</file> file.
10309 <sect1 id="pkg-dpkg-genchanges">
10311 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
10312 upload control file
10316 This program is usually called by package-independent
10317 automatic building scripts such as
10318 <prgn>dpkg-buildpackage</prgn>, but it may also be called
10323 It is usually called in the top level of a built source
10324 tree, and when invoked with no arguments will print out a
10325 straightforward <file>.changes</file> file based on the
10326 information in the source package's changelog and control
10327 file and the binary and source packages which should have
10333 <sect1 id="pkg-dpkg-parsechangelog">
10335 <prgn>dpkg-parsechangelog</prgn> - produces parsed
10336 representation of a changelog
10340 This program is used internally by
10341 <prgn>dpkg-source</prgn> et al. It may also occasionally
10342 be useful in <file>debian/rules</file> and elsewhere. It
10343 parses a changelog, <file>debian/changelog</file> by default,
10344 and prints a control-file format representation of the
10345 information in it to standard output.
10349 <sect1 id="pkg-dpkg-architecture">
10351 <prgn>dpkg-architecture</prgn> - information about the build and
10356 This program can be used manually, but is also invoked by
10357 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
10358 environment or make variables which specify the build and host
10359 architecture for the package building process.
10364 <sect id="pkg-sourcetree">
10365 <heading>The Debian package source tree</heading>
10368 The source archive scheme described later is intended to
10369 allow a Debian package source tree with some associated
10370 control information to be reproduced and transported easily.
10371 The Debian package source tree is a version of the original
10372 program with certain files added for the benefit of the
10373 packaging process, and with any other changes required
10374 made to the rest of the source code and installation
10379 The extra files created for Debian are in the subdirectory
10380 <file>debian</file> of the top level of the Debian package
10381 source tree. They are described below.
10384 <sect1 id="pkg-debianrules">
10385 <heading><file>debian/rules</file> - the main building script</heading>
10388 See <ref id="debianrules">.
10392 <sect1 id="pkg-srcsubstvars">
10393 <heading><file>debian/substvars</file> and variable substitutions</heading>
10396 See <ref id="substvars">.
10402 <heading><file>debian/files</file></heading>
10405 See <ref id="debianfiles">.
10409 <sect1><heading><file>debian/tmp</file>
10413 This is the canonical temporary location for the
10414 construction of binary packages by the <tt>binary</tt>
10415 target. The directory <file>tmp</file> serves as the root of
10416 the file system tree as it is being constructed (for
10417 example, by using the package's upstream makefiles install
10418 targets and redirecting the output there), and it also
10419 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10420 id="pkg-bincreating">.
10424 If several binary packages are generated from the same
10425 source tree it is usual to use several
10426 <file>debian/tmp<var>something</var></file> directories, for
10427 example <file>tmp-a</file> or <file>tmp-doc</file>.
10431 Whatever <file>tmp</file> directories are created and used by
10432 <tt>binary</tt> must of course be removed by the
10433 <tt>clean</tt> target.</p></sect1>
10437 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10441 As it exists on the FTP site, a Debian source package
10442 consists of three related files. You must have the right
10443 versions of all three to be able to use them.
10448 <tag>Debian source control file - <tt>.dsc</tt></tag>
10450 This file is a control file used by <prgn>dpkg-source</prgn>
10451 to extract a source package.
10452 See <ref id="debiansourcecontrolfiles">.
10456 Original source archive -
10458 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10464 This is a compressed (with <tt>gzip -9</tt>)
10465 <prgn>tar</prgn> file containing the source code from
10466 the upstream authors of the program.
10471 Debian package diff -
10473 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10479 This is a unified context diff (<tt>diff -u</tt>)
10480 giving the changes which are required to turn the
10481 original source into the Debian source. These changes
10482 may only include editing and creating plain files.
10483 The permissions of files, the targets of symbolic
10484 links and the characteristics of special files or
10485 pipes may not be changed and no files may be removed
10490 All the directories in the diff must exist, except the
10491 <file>debian</file> subdirectory of the top of the source
10492 tree, which will be created by
10493 <prgn>dpkg-source</prgn> if necessary when unpacking.
10497 The <prgn>dpkg-source</prgn> program will
10498 automatically make the <file>debian/rules</file> file
10499 executable (see below).</p></item>
10504 If there is no original source code - for example, if the
10505 package is specially prepared for Debian or the Debian
10506 maintainer is the same as the upstream maintainer - the
10507 format is slightly different: then there is no diff, and the
10509 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10510 and preferably contains a directory named
10511 <file><var>package</var>-<var>version</var></file>.
10516 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10519 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10520 Debian source package. However, if it is not available it
10521 is possible to unpack a Debian source archive as follows:
10522 <enumlist compact="compact">
10525 Untar the tarfile, which will create a <file>.orig</file>
10529 <p>Rename the <file>.orig</file> directory to
10530 <file><var>package</var>-<var>version</var></file>.</p>
10534 Create the subdirectory <file>debian</file> at the top of
10535 the source tree.</p>
10537 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10539 <item><p>Untar the tarfile again if you want a copy of the original
10540 source code alongside the Debian version.</p>
10545 It is not possible to generate a valid Debian source archive
10546 without using <prgn>dpkg-source</prgn>. In particular,
10547 attempting to use <prgn>diff</prgn> directly to generate the
10548 <file>.diff.gz</file> file will not work.
10552 <heading>Restrictions on objects in source packages</heading>
10555 The source package may not contain any hard links
10557 This is not currently detected when building source
10558 packages, but only when extracting
10562 Hard links may be permitted at some point in the
10563 future, but would require a fair amount of
10565 </footnote>, device special files, sockets or setuid or
10568 Setgid directories are allowed.
10573 The source packaging tools manage the changes between the
10574 original and Debian source using <prgn>diff</prgn> and
10575 <prgn>patch</prgn>. Turning the original source tree as
10576 included in the <file>.orig.tar.gz</file> into the Debian
10577 package source must not involve any changes which cannot be
10578 handled by these tools. Problematic changes which cause
10579 <prgn>dpkg-source</prgn> to halt with an error when
10580 building the source package are:
10581 <list compact="compact">
10582 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10584 <item><p>Changing the targets of symbolic links.</p>
10586 <item><p>Creating directories, other than <file>debian</file>.</p>
10588 <item><p>Changes to the contents of binary files.</p></item>
10589 </list> Changes which cause <prgn>dpkg-source</prgn> to
10590 print a warning but continue anyway are:
10591 <list compact="compact">
10594 Removing files, directories or symlinks.
10596 Renaming a file is not treated specially - it is
10597 seen as the removal of the old file (which
10598 generates a warning, but is otherwise ignored),
10599 and the creation of the new one.
10605 Changed text files which are missing the usual final
10606 newline (either in the original or the modified
10611 Changes which are not represented, but which are not detected by
10612 <prgn>dpkg-source</prgn>, are:
10613 <list compact="compact">
10614 <item><p>Changing the permissions of files (other than
10615 <file>debian/rules</file>) and directories.</p></item>
10620 The <file>debian</file> directory and <file>debian/rules</file>
10621 are handled specially by <prgn>dpkg-source</prgn> - before
10622 applying the changes it will create the <file>debian</file>
10623 directory, and afterwards it will make
10624 <file>debian/rules</file> world-executable.
10630 <appendix id="pkg-controlfields">
10631 <heading>Control files and their fields (from old Packaging Manual)</heading>
10634 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10635 data in a common format, known as control files. Binary and
10636 source packages have control data as do the <file>.changes</file>
10637 files which control the installation of uploaded files, and
10638 <prgn>dpkg</prgn>'s internal databases are in a similar
10643 <heading>Syntax of control files</heading>
10646 See <ref id="controlsyntax">.
10650 It is important to note that there are several fields which
10651 are optional as far as <prgn>dpkg</prgn> and the related
10652 tools are concerned, but which must appear in every Debian
10653 package, or whose omission may cause problems.
10658 <heading>List of fields</heading>
10661 See <ref id="controlfieldslist">.
10665 This section now contains only the fields that didn't belong
10666 to the Policy manual.
10669 <sect1 id="pkg-f-Filename">
10670 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10673 These fields in <tt>Packages</tt> files give the
10674 filename(s) of (the parts of) a package in the
10675 distribution directories, relative to the root of the
10676 Debian hierarchy. If the package has been split into
10677 several parts the parts are all listed in order, separated
10682 <sect1 id="pkg-f-Size">
10683 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10686 These fields in <file>Packages</file> files give the size (in
10687 bytes, expressed in decimal) and MD5 checksum of the
10688 file(s) which make(s) up a binary package in the
10689 distribution. If the package is split into several parts
10690 the values for the parts are listed in order, separated by
10695 <sect1 id="pkg-f-Status">
10696 <heading><tt>Status</tt></heading>
10699 This field in <prgn>dpkg</prgn>'s status file records
10700 whether the user wants a package installed, removed or
10701 left alone, whether it is broken (requiring
10702 re-installation) or not and what its current state on the
10703 system is. Each of these pieces of information is a
10708 <sect1 id="pkg-f-Config-Version">
10709 <heading><tt>Config-Version</tt></heading>
10712 If a package is not installed or not configured, this
10713 field in <prgn>dpkg</prgn>'s status file records the last
10714 version of the package which was successfully
10719 <sect1 id="pkg-f-Conffiles">
10720 <heading><tt>Conffiles</tt></heading>
10723 This field in <prgn>dpkg</prgn>'s status file contains
10724 information about the automatically-managed configuration
10725 files held by a package. This field should <em>not</em>
10726 appear anywhere in a package!
10731 <heading>Obsolete fields</heading>
10734 These are still recognized by <prgn>dpkg</prgn> but should
10735 not appear anywhere any more.
10737 <taglist compact="compact">
10739 <tag><tt>Revision</tt></tag>
10740 <tag><tt>Package-Revision</tt></tag>
10741 <tag><tt>Package_Revision</tt></tag>
10743 The Debian revision part of the package version was
10744 at one point in a separate control field. This
10745 field went through several names.
10748 <tag><tt>Recommended</tt></tag>
10749 <item>Old name for <tt>Recommends</tt>.</item>
10751 <tag><tt>Optional</tt></tag>
10752 <item>Old name for <tt>Suggests</tt>.</item>
10754 <tag><tt>Class</tt></tag>
10755 <item>Old name for <tt>Priority</tt>.</item>
10764 <appendix id="pkg-conffiles">
10765 <heading>Configuration file handling (from old Packaging Manual)</heading>
10768 <prgn>dpkg</prgn> can do a certain amount of automatic
10769 handling of package configuration files.
10773 Whether this mechanism is appropriate depends on a number of
10774 factors, but basically there are two approaches to any
10775 particular configuration file.
10779 The easy method is to ship a best-effort configuration in the
10780 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10781 handle updates. If the user is unlikely to want to edit the
10782 file, but you need them to be able to without losing their
10783 changes, and a new package with a changed version of the file
10784 is only released infrequently, this is a good approach.
10788 The hard method is to build the configuration file from
10789 scratch in the <prgn>postinst</prgn> script, and to take the
10790 responsibility for fixing any mistakes made in earlier
10791 versions of the package automatically. This will be
10792 appropriate if the file is likely to need to be different on
10796 <sect><heading>Automatic handling of configuration files by
10801 A package may contain a control information file called
10802 <tt>conffiles</tt>. This file should be a list of filenames
10803 of configuration files needing automatic handling, separated
10804 by newlines. The filenames should be absolute pathnames,
10805 and the files referred to should actually exist in the
10810 When a package is upgraded <prgn>dpkg</prgn> will process
10811 the configuration files during the configuration stage,
10812 shortly before it runs the package's <prgn>postinst</prgn>
10817 For each file it checks to see whether the version of the
10818 file included in the package is the same as the one that was
10819 included in the last version of the package (the one that is
10820 being upgraded from); it also compares the version currently
10821 installed on the system with the one shipped with the last
10826 If neither the user nor the package maintainer has changed
10827 the file, it is left alone. If one or the other has changed
10828 their version, then the changed version is preferred - i.e.,
10829 if the user edits their file, but the package maintainer
10830 doesn't ship a different version, the user's changes will
10831 stay, silently, but if the maintainer ships a new version
10832 and the user hasn't edited it the new version will be
10833 installed (with an informative message). If both have
10834 changed their version the user is prompted about the problem
10835 and must resolve the differences themselves.
10839 The comparisons are done by calculating the MD5 message
10840 digests of the files, and storing the MD5 of the file as it
10841 was included in the most recent version of the package.
10845 When a package is installed for the first time
10846 <prgn>dpkg</prgn> will install the file that comes with it,
10847 unless that would mean overwriting a file already on the
10852 However, note that <prgn>dpkg</prgn> will <em>not</em>
10853 replace a conffile that was removed by the user (or by a
10854 script). This is necessary because with some programs a
10855 missing file produces an effect hard or impossible to
10856 achieve in another way, so that a missing file needs to be
10857 kept that way if the user did it.
10861 Note that a package should <em>not</em> modify a
10862 <prgn>dpkg</prgn>-handled conffile in its maintainer
10863 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10864 the user confusing and possibly dangerous options for
10865 conffile update when the package is upgraded.</p>
10868 <sect><heading>Fully-featured maintainer script configuration
10873 For files which contain site-specific information such as
10874 the hostname and networking details and so forth, it is
10875 better to create the file in the package's
10876 <prgn>postinst</prgn> script.
10880 This will typically involve examining the state of the rest
10881 of the system to determine values and other information, and
10882 may involve prompting the user for some information which
10883 can't be obtained some other way.
10887 When using this method there are a couple of important
10888 issues which should be considered:
10892 If you discover a bug in the program which generates the
10893 configuration file, or if the format of the file changes
10894 from one version to the next, you will have to arrange for
10895 the postinst script to do something sensible - usually this
10896 will mean editing the installed configuration file to remove
10897 the problem or change the syntax. You will have to do this
10898 very carefully, since the user may have changed the file,
10899 perhaps to fix the very problem that your script is trying
10900 to deal with - you will have to detect these situations and
10901 deal with them correctly.
10905 If you do go down this route it's probably a good idea to
10906 make the program that generates the configuration file(s) a
10907 separate program in <file>/usr/sbin</file>, by convention called
10908 <file><var>package</var>config</file> and then run that if
10909 appropriate from the post-installation script. The
10910 <tt><var>package</var>config</tt> program should not
10911 unquestioningly overwrite an existing configuration - if its
10912 mode of operation is geared towards setting up a package for
10913 the first time (rather than any arbitrary reconfiguration
10914 later) you should have it check whether the configuration
10915 already exists, and require a <tt>--force</tt> flag to
10916 overwrite it.</p></sect>
10919 <appendix id="pkg-alternatives"><heading>Alternative versions of
10920 an interface - <prgn>update-alternatives</prgn> (from old
10925 When several packages all provide different versions of the
10926 same program or file it is useful to have the system select a
10927 default, but to allow the system administrator to change it
10928 and have their decisions respected.
10932 For example, there are several versions of the <prgn>vi</prgn>
10933 editor, and there is no reason to prevent all of them from
10934 being installed at once, each under their own name
10935 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10936 Nevertheless it is desirable to have the name <tt>vi</tt>
10937 refer to something, at least by default.
10941 If all the packages involved cooperate, this can be done with
10942 <prgn>update-alternatives</prgn>.
10946 Each package provides its own version under its own name, and
10947 calls <prgn>update-alternatives</prgn> in its postinst to
10948 register its version (and again in its prerm to deregister
10953 See the man page <manref name="update-alternatives"
10954 section="8"> for details.
10958 If <prgn>update-alternatives</prgn> does not seem appropriate
10959 you may wish to consider using diversions instead.</p>
10962 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10963 package's version of a file (from old Packaging Manual)
10967 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10968 when it reinstalls the package it belongs to, and to have it
10969 put the file from the package somewhere else instead.
10973 This can be used locally to override a package's version of a
10974 file, or by one package to override another's version (or
10975 provide a wrapper for it).
10979 Before deciding to use a diversion, read <ref
10980 id="pkg-alternatives"> to see if you really want a diversion
10981 rather than several alternative versions of a program.
10985 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10986 and updated by a special program <prgn>dpkg-divert</prgn>.
10987 Please see <manref name="dpkg-divert" section="8"> for full
10988 details of its operation.
10992 When a package wishes to divert a file from another, it should
10993 call <prgn>dpkg-divert</prgn> in its preinst to add the
10994 diversion and rename the existing file. For example,
10995 supposing that a <prgn>smailwrapper</prgn> package wishes to
10996 install a wrapper around <file>/usr/sbin/smail</file>:
10998 dpkg-divert --package smailwrapper --add --rename \
10999 --divert /usr/sbin/smail.real /usr/sbin/smail
11000 </example> The <tt>--package smailwrapper</tt> ensures that
11001 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
11002 can bypass the diversion and get installed as the true version.
11003 It's safe to add the diversion unconditionally on upgrades since
11004 it will be left unchanged if it already exists, but
11005 <prgn>dpkg-divert</prgn> will display a message. To suppress that
11006 message, make the command conditional on the version from which
11007 the package is being upgraded:
11009 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
11010 dpkg-divert --package smailwrapper --add --rename \
11011 --divert /usr/sbin/smail.real /usr/sbin/smail
11013 </example> where <tt>1.0-2</tt> is the version at which the
11014 diversion was first added to the package. Running the command
11015 during abort-upgrade is pointless but harmless.
11019 The postrm has to do the reverse:
11021 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
11022 dpkg-divert --package smailwrapper --remove --rename \
11023 --divert /usr/sbin/smail.real /usr/sbin/smail
11025 </example> If the diversion was added at a particular version, the
11026 postrm should also handle the failure case of upgrading from an
11027 older version (unless the older version is so old that direct
11028 upgrades are no longer supported):
11030 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
11031 dpkg-divert --package smailwrapper --remove --rename \
11032 --divert /usr/sbin/smail.real /usr/sbin/smail
11034 </example> where <tt>1.02-2</tt> is the version at which the
11035 diversion was first added to the package. The postrm should not
11036 remove the diversion on upgrades both because there's no reason to
11037 remove the diversion only to immediately re-add it and since the
11038 postrm of the old package is run after unpacking so the removal of
11039 the diversion will fail.
11043 Do not attempt to divert a file which is vitally important for
11044 the system's operation - when using <prgn>dpkg-divert</prgn>
11045 there is a time, after it has been diverted but before
11046 <prgn>dpkg</prgn> has installed the new version, when the file
11047 does not exist.</p>
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