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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, except for orphaned
915 packages as described below. The maintainer may be one person
916 or a group of people reachable from a common email address, such
917 as a mailing list. The maintainer is responsible for
918 maintaining the Debian packaging files, evaluating and
919 responding appropriately to reported bugs, uploading new
920 versions of the package (either directly or through a sponsor),
921 ensuring that the package is placed in the appropriate archive
922 area and included in Debian releases as appropriate for the
923 stability and utility of the package, and requesting removal of
924 the package from the Debian distribution if it is no longer
925 useful or maintainable.
929 The maintainer must be specified in the <tt>Maintainer</tt>
930 control field with their correct name and a working email
931 address. The email address given in the <tt>Maintainer</tt>
932 control field must accept mail from those role accounts in
933 Debian used to send automated mails regarding the package. This
934 includes non-spam mail from the bug-tracking system, all mail
935 from the Debian archive maintenance software, and other role
936 accounts or automated processes that are commonly agreed on by
937 the project.<footnote>
938 A sample implementation of such a whitelist written for the
939 Mailman mailing list management software is used for mailing
940 lists hosted by alioth.debian.org.
942 If one person or team maintains several packages, they should
943 use the same form of their name and email address in
944 the <tt>Maintainer</tt> fields of those packages.
948 The format of the <tt>Maintainer</tt> control field is
949 described in <ref id="f-Maintainer">.
953 If the maintainer of the package is a team of people with a
954 shared email address, the <tt>Uploaders</tt> control field must
955 be present and must contain at least one human with their
956 personal email address. See <ref id="f-Uploaders"> for the
957 syntax of that field.
961 An orphaned package is one with no current maintainer. Orphaned
962 packages should have their <tt>Maintainer</tt> control field set
963 to <tt>Debian QA Group <packages@qa.debian.org></tt>.
964 These packages are considered maintained by the Debian project
965 as a whole until someone else volunteers to take over
966 maintenance.<footnote>
967 The detailed procedure for gracefully orphaning a package can
968 be found in the Debian Developer's Reference
969 (see <ref id="related">).
974 <sect id="descriptions">
975 <heading>The description of a package</heading>
978 Every Debian package must have a <tt>Description</tt> control
979 field which contains a synopsis and extended description of the
980 package. Technical information about the format of the
981 <tt>Description</tt> field is in <ref id="f-Description">.
985 The description should describe the package (the program) to a
986 user (system administrator) who has never met it before so that
987 they have enough information to decide whether they want to
988 install it. This description should not just be copied verbatim
989 from the program's documentation.
993 Put important information first, both in the synopsis and
994 extended description. Sometimes only the first part of the
995 synopsis or of the description will be displayed. You can
996 assume that there will usually be a way to see the whole
997 extended description.
1001 The description should also give information about the
1002 significant dependencies and conflicts between this package
1003 and others, so that the user knows why these dependencies and
1004 conflicts have been declared.
1008 Instructions for configuring or using the package should
1009 not be included (that is what installation scripts,
1010 manual pages, info files, etc., are for). Copyright
1011 statements and other administrivia should not be included
1012 either (that is what the copyright file is for).
1015 <sect1 id="synopsis"><heading>The single line synopsis</heading>
1018 The single line synopsis should be kept brief - certainly
1019 under 80 characters.
1023 Do not include the package name in the synopsis line. The
1024 display software knows how to display this already, and you
1025 do not need to state it. Remember that in many situations
1026 the user may only see the synopsis line - make it as
1027 informative as you can.
1032 <sect1 id="extendeddesc"><heading>The extended description</heading>
1035 Do not try to continue the single line synopsis into the
1036 extended description. This will not work correctly when
1037 the full description is displayed, and makes no sense
1038 where only the summary (the single line synopsis) is
1043 The extended description should describe what the package
1044 does and how it relates to the rest of the system (in terms
1045 of, for example, which subsystem it is which part of).
1049 The description field needs to make sense to anyone, even
1050 people who have no idea about any of the things the
1051 package deals with.<footnote>
1052 The blurb that comes with a program in its
1053 announcements and/or <prgn>README</prgn> files is
1054 rarely suitable for use in a description. It is
1055 usually aimed at people who are already in the
1056 community where the package is used.
1065 <heading>Dependencies</heading>
1068 Every package must specify the dependency information
1069 about other packages that are required for the first to
1074 For example, a dependency entry must be provided for any
1075 shared libraries required by a dynamically-linked executable
1076 binary in a package.
1080 Packages are not required to declare any dependencies they
1081 have on other packages which are marked <tt>Essential</tt>
1082 (see below), and should not do so unless they depend on a
1083 particular version of that package.<footnote>
1085 Essential is needed in part to avoid unresolvable dependency
1086 loops on upgrade. If packages add unnecessary dependencies
1087 on packages in this set, the chances that there
1088 <strong>will</strong> be an unresolvable dependency loop
1089 caused by forcing these Essential packages to be configured
1090 first before they need to be is greatly increased. It also
1091 increases the chances that frontends will be unable to
1092 <strong>calculate</strong> an upgrade path, even if one
1096 Also, functionality is rarely ever removed from the
1097 Essential set, but <em>packages</em> have been removed from
1098 the Essential set when the functionality moved to a
1099 different package. So depending on these packages <em>just
1100 in case</em> they stop being essential does way more harm
1107 Sometimes, unpacking one package requires that another package
1108 be first unpacked <em>and</em> configured. In this case, the
1109 dependent package must specify this dependency in
1110 the <tt>Pre-Depends</tt> control field.
1114 You should not specify a <tt>Pre-Depends</tt> entry for a
1115 package before this has been discussed on the
1116 <tt>debian-devel</tt> mailing list and a consensus about
1117 doing that has been reached.
1121 The format of the package interrelationship control fields is
1122 described in <ref id="relationships">.
1126 <sect id="virtual_pkg">
1127 <heading>Virtual packages</heading>
1130 Sometimes, there are several packages which offer
1131 more-or-less the same functionality. In this case, it's
1132 useful to define a <em>virtual package</em> whose name
1133 describes that common functionality. (The virtual
1134 packages only exist logically, not physically; that's why
1135 they are called <em>virtual</em>.) The packages with this
1136 particular function will then <em>provide</em> the virtual
1137 package. Thus, any other package requiring that function
1138 can simply depend on the virtual package without having to
1139 specify all possible packages individually.
1143 All packages should use virtual package names where
1144 appropriate, and arrange to create new ones if necessary.
1145 They should not use virtual package names (except privately,
1146 amongst a cooperating group of packages) unless they have
1147 been agreed upon and appear in the list of virtual package
1148 names. (See also <ref id="virtual">)
1152 The latest version of the authoritative list of virtual
1153 package names can be found in the <tt>debian-policy</tt> package.
1154 It is also available from the Debian web mirrors at
1155 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1156 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1160 The procedure for updating the list is described in the preface
1167 <heading>Base system</heading>
1170 The <tt>base system</tt> is a minimum subset of the Debian
1171 GNU/Linux system that is installed before everything else
1172 on a new system. Only very few packages are allowed to form
1173 part of the base system, in order to keep the required disk
1178 The base system consists of all those packages with priority
1179 <tt>required</tt> or <tt>important</tt>. Many of them will
1180 be tagged <tt>essential</tt> (see below).
1185 <heading>Essential packages</heading>
1188 Essential is defined as the minimal set of functionality that
1189 must be available and usable on the system at all times, even
1190 when packages are in an unconfigured (but unpacked) state.
1191 Packages are tagged <tt>essential</tt> for a system using the
1192 <tt>Essential</tt> control field. The format of the
1193 <tt>Essential</tt> control field is described in <ref
1198 Since these packages cannot be easily removed (one has to
1199 specify an extra <em>force option</em> to
1200 <prgn>dpkg</prgn> to do so), this flag must not be used
1201 unless absolutely necessary. A shared library package
1202 must not be tagged <tt>essential</tt>; dependencies will
1203 prevent its premature removal, and we need to be able to
1204 remove it when it has been superseded.
1208 Since dpkg will not prevent upgrading of other packages
1209 while an <tt>essential</tt> package is in an unconfigured
1210 state, all <tt>essential</tt> packages must supply all of
1211 their core functionality even when unconfigured. If the
1212 package cannot satisfy this requirement it must not be
1213 tagged as essential, and any packages depending on this
1214 package must instead have explicit dependency fields as
1219 Maintainers should take great care in adding any programs,
1220 interfaces, or functionality to <tt>essential</tt> packages.
1221 Packages may assume that functionality provided by
1222 <tt>essential</tt> packages is always available without
1223 declaring explicit dependencies, which means that removing
1224 functionality from the Essential set is very difficult and is
1225 almost never done. Any capability added to an
1226 <tt>essential</tt> package therefore creates an obligation to
1227 support that capability as part of the Essential set in
1232 You must not tag any packages <tt>essential</tt> before
1233 this has been discussed on the <tt>debian-devel</tt>
1234 mailing list and a consensus about doing that has been
1239 <sect id="maintscripts">
1240 <heading>Maintainer Scripts</heading>
1243 The package installation scripts should avoid producing
1244 output which is unnecessary for the user to see and
1245 should rely on <prgn>dpkg</prgn> to stave off boredom on
1246 the part of a user installing many packages. This means,
1247 amongst other things, using the <tt>--quiet</tt> option on
1248 <prgn>install-info</prgn>.
1252 Errors which occur during the execution of an installation
1253 script must be checked and the installation must not
1254 continue after an error.
1258 Note that in general <ref id="scripts"> applies to package
1259 maintainer scripts, too.
1263 You should not use <prgn>dpkg-divert</prgn> on a file belonging
1264 to another package without consulting the maintainer of that
1265 package first. When adding or removing diversions, package
1266 maintainer scripts must provide the <tt>--package</tt> flag
1267 to <prgn>dpkg-divert</prgn> and must not use <tt>--local</tt>.
1271 All packages which supply an instance of a common command
1272 name (or, in general, filename) should generally use
1273 <prgn>update-alternatives</prgn>, so that they may be
1274 installed together. If <prgn>update-alternatives</prgn>
1275 is not used, then each package must use
1276 <tt>Conflicts</tt> to ensure that other packages are
1277 de-installed. (In this case, it may be appropriate to
1278 specify a conflict against earlier versions of something
1279 that previously did not use
1280 <prgn>update-alternatives</prgn>; this is an exception to
1281 the usual rule that versioned conflicts should be
1285 <sect1 id="maintscriptprompt">
1286 <heading>Prompting in maintainer scripts</heading>
1288 Package maintainer scripts may prompt the user if
1289 necessary. Prompting must be done by communicating
1290 through a program, such as <prgn>debconf</prgn>, which
1291 conforms to the Debian Configuration Management
1292 Specification, version 2 or higher.
1296 Packages which are essential, or which are dependencies of
1297 essential packages, may fall back on another prompting method
1298 if no such interface is available when they are executed.
1302 The Debian Configuration Management Specification is included
1303 in the <file>debconf_specification</file> files in the
1304 <package>debian-policy</package> package.
1305 It is also available from the Debian web mirrors at
1306 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1307 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1311 Packages which use the Debian Configuration Management
1312 Specification may contain the additional control information
1313 files <file>config</file>
1314 and <file>templates</file>. <file>config</file> is an
1315 additional maintainer script used for package configuration,
1316 and <file>templates</file> contains templates used for user
1317 prompting. The <prgn>config</prgn> script might be run before
1318 the <prgn>preinst</prgn> script and before the package is
1319 unpacked or any of its dependencies or pre-dependencies are
1320 satisfied. Therefore it must work using only the tools
1321 present in <em>essential</em> packages.<footnote>
1322 <package>Debconf</package> or another tool that
1323 implements the Debian Configuration Management
1324 Specification will also be installed, and any
1325 versioned dependencies on it will be satisfied
1326 before preconfiguration begins.
1331 Packages which use the Debian Configuration Management
1332 Specification must allow for translation of their user-visible
1333 messages by using a gettext-based system such as the one
1334 provided by the <package>po-debconf</package> package.
1338 Packages should try to minimize the amount of prompting
1339 they need to do, and they should ensure that the user
1340 will only ever be asked each question once. This means
1341 that packages should try to use appropriate shared
1342 configuration files (such as <file>/etc/papersize</file> and
1343 <file>/etc/news/server</file>), and shared
1344 <package>debconf</package> variables rather than each
1345 prompting for their own list of required pieces of
1350 It also means that an upgrade should not ask the same
1351 questions again, unless the user has used
1352 <tt>dpkg --purge</tt> to remove the package's configuration.
1353 The answers to configuration questions should be stored in an
1354 appropriate place in <file>/etc</file> so that the user can
1355 modify them, and how this has been done should be
1360 If a package has a vitally important piece of
1361 information to pass to the user (such as "don't run me
1362 as I am, you must edit the following configuration files
1363 first or you risk your system emitting badly-formatted
1364 messages"), it should display this in the
1365 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1366 prompt the user to hit return to acknowledge the
1367 message. Copyright messages do not count as vitally
1368 important (they belong in
1369 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1370 neither do instructions on how to use a program (these
1371 should be in on-line documentation, where all the users
1376 Any necessary prompting should almost always be confined
1377 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1378 script. If it is done in the <prgn>postinst</prgn>, it
1379 should be protected with a conditional so that
1380 unnecessary prompting doesn't happen if a package's
1381 installation fails and the <prgn>postinst</prgn> is
1382 called with <tt>abort-upgrade</tt>,
1383 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1393 <heading>Source packages</heading>
1395 <sect id="standardsversion">
1396 <heading>Standards conformance</heading>
1399 Source packages should specify the most recent version number
1400 of this policy document with which your package complied
1401 when it was last updated.
1405 This information may be used to file bug reports
1406 automatically if your package becomes too much out of date.
1410 The version is specified in the <tt>Standards-Version</tt>
1412 The format of the <tt>Standards-Version</tt> field is
1413 described in <ref id="f-Standards-Version">.
1417 You should regularly, and especially if your package has
1418 become out of date, check for the newest Policy Manual
1419 available and update your package, if necessary. When your
1420 package complies with the new standards you should update the
1421 <tt>Standards-Version</tt> source package field and
1422 release it.<footnote>
1423 See the file <file>upgrading-checklist</file> for
1424 information about policy which has changed between
1425 different versions of this document.
1431 <sect id="pkg-relations">
1432 <heading>Package relationships</heading>
1435 Source packages should specify which binary packages they
1436 require to be installed or not to be installed in order to
1437 build correctly. For example, if building a package
1438 requires a certain compiler, then the compiler should be
1439 specified as a build-time dependency.
1443 It is not necessary to explicitly specify build-time
1444 relationships on a minimal set of packages that are always
1445 needed to compile, link and put in a Debian package a
1446 standard "Hello World!" program written in C or C++. The
1447 required packages are called <em>build-essential</em>, and
1448 an informational list can be found in
1449 <file>/usr/share/doc/build-essential/list</file> (which is
1450 contained in the <tt>build-essential</tt>
1453 <list compact="compact">
1455 This allows maintaining the list separately
1456 from the policy documents (the list does not
1457 need the kind of control that the policy
1461 Having a separate package allows one to install
1462 the build-essential packages on a machine, as
1463 well as allowing other packages such as tasks to
1464 require installation of the build-essential
1465 packages using the depends relation.
1468 The separate package allows bug reports against
1469 the list to be categorized separately from
1470 the policy management process in the BTS.
1477 When specifying the set of build-time dependencies, one
1478 should list only those packages explicitly required by the
1479 build. It is not necessary to list packages which are
1480 required merely because some other package in the list of
1481 build-time dependencies depends on them.<footnote>
1482 The reason for this is that dependencies change, and
1483 you should list all those packages, and <em>only</em>
1484 those packages that <em>you</em> need directly. What
1485 others need is their business. For example, if you
1486 only link against <file>libimlib</file>, you will need to
1487 build-depend on <package>libimlib2-dev</package> but
1488 not against any <tt>libjpeg*</tt> packages, even
1489 though <tt>libimlib2-dev</tt> currently depends on
1490 them: installation of <package>libimlib2-dev</package>
1491 will automatically ensure that all of its run-time
1492 dependencies are satisfied.
1497 If build-time dependencies are specified, it must be
1498 possible to build the package and produce working binaries
1499 on a system with only essential and build-essential
1500 packages installed and also those required to satisfy the
1501 build-time relationships (including any implied
1502 relationships). In particular, this means that version
1503 clauses should be used rigorously in build-time
1504 relationships so that one cannot produce bad or
1505 inconsistently configured packages when the relationships
1506 are properly satisfied.
1510 <ref id="relationships"> explains the technical details.
1515 <heading>Changes to the upstream sources</heading>
1518 If changes to the source code are made that are not
1519 specific to the needs of the Debian system, they should be
1520 sent to the upstream authors in whatever form they prefer
1521 so as to be included in the upstream version of the
1526 If you need to configure the package differently for
1527 Debian or for Linux, and the upstream source doesn't
1528 provide a way to do so, you should add such configuration
1529 facilities (for example, a new <prgn>autoconf</prgn> test
1530 or <tt>#define</tt>) and send the patch to the upstream
1531 authors, with the default set to the way they originally
1532 had it. You can then easily override the default in your
1533 <file>debian/rules</file> or wherever is appropriate.
1537 You should make sure that the <prgn>configure</prgn> utility
1538 detects the correct architecture specification string
1539 (refer to <ref id="arch-spec"> for details).
1543 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1544 <prgn>configure</prgn> scripts are used, you should edit the
1545 <file>.in</file> files rather than editing the
1546 <prgn>Makefile</prgn> directly. This allows the user to
1547 reconfigure the package if necessary. You should
1548 <em>not</em> configure the package and edit the generated
1549 <prgn>Makefile</prgn>! This makes it impossible for someone
1550 else to later reconfigure the package without losing the
1556 <sect id="dpkgchangelog">
1557 <heading>Debian changelog: <file>debian/changelog</file></heading>
1560 Changes in the Debian version of the package should be
1561 briefly explained in the Debian changelog file
1562 <file>debian/changelog</file>.<footnote>
1564 Mistakes in changelogs are usually best rectified by
1565 making a new changelog entry rather than "rewriting
1566 history" by editing old changelog entries.
1569 This includes modifications
1570 made in the Debian package compared to the upstream one
1571 as well as other changes and updates to the package.
1573 Although there is nothing stopping an author who is also
1574 the Debian maintainer from using this changelog for all
1575 their changes, it will have to be renamed if the Debian
1576 and upstream maintainers become different people. In such
1577 a case, however, it might be better to maintain the package
1578 as a non-native package.
1583 The format of the <file>debian/changelog</file> allows the
1584 package building tools to discover which version of the package
1585 is being built and find out other release-specific information.
1589 That format is a series of entries like this:
1591 <example compact="compact">
1592 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1594 [optional blank line(s), stripped]
1596 * <var>change details</var>
1597 <var>more change details</var>
1599 [blank line(s), included in output of dpkg-parsechangelog]
1601 * <var>even more change details</var>
1603 [optional blank line(s), stripped]
1605 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1610 <var>package</var> and <var>version</var> are the source
1611 package name and version number.
1615 <var>distribution(s)</var> lists the distributions where
1616 this version should be installed when it is uploaded - it
1617 is copied to the <tt>Distribution</tt> field in the
1618 <file>.changes</file> file. See <ref id="f-Distribution">.
1622 <var>urgency</var> is the value for the <tt>Urgency</tt>
1623 field in the <file>.changes</file> file for the upload
1624 (see <ref id="f-Urgency">). It is not possible to specify
1625 an urgency containing commas; commas are used to separate
1626 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1627 <prgn>dpkg</prgn> changelog format (though there is
1628 currently only one useful <var>keyword</var>,
1633 The change details may in fact be any series of lines
1634 starting with at least two spaces, but conventionally each
1635 change starts with an asterisk and a separating space and
1636 continuation lines are indented so as to bring them in
1637 line with the start of the text above. Blank lines may be
1638 used here to separate groups of changes, if desired.
1642 If this upload resolves bugs recorded in the Bug Tracking
1643 System (BTS), they may be automatically closed on the
1644 inclusion of this package into the Debian archive by
1645 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1646 in the change details.<footnote>
1647 To be precise, the string should match the following
1648 Perl regular expression:
1650 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1652 Then all of the bug numbers listed will be closed by the
1653 archive maintenance script (<prgn>katie</prgn>) using the
1654 <var>version</var> of the changelog entry.
1656 This information is conveyed via the <tt>Closes</tt> field
1657 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1661 The maintainer name and email address used in the changelog
1662 should be the details of the person uploading <em>this</em>
1663 version. They are <em>not</em> necessarily those of the
1664 usual package maintainer.<footnote>
1665 If the developer uploading the package is not one of the usual
1666 maintainers of the package (as listed in
1667 the <qref id="f-Maintainer"><tt>Maintainer</tt></qref>
1668 or <qref id="f-Uploaders"><tt>Uploaders</tt></qref> control
1669 fields of the package), the first line of the changelog is
1670 conventionally used to explain why a non-maintainer is
1671 uploading the package. The Debian Developer's Reference
1672 (see <ref id="related">) documents the conventions
1674 The information here will be copied to the <tt>Changed-By</tt>
1675 field in the <tt>.changes</tt> file
1676 (see <ref id="f-Changed-By">), and then later used to send an
1677 acknowledgement when the upload has been installed.
1681 The <var>date</var> has the following format<footnote>
1682 This is the same as the format generated by <tt>date
1684 </footnote> (compatible and with the same semantics of
1685 RFC 2822 and RFC 5322):
1686 <example>day-of-week, dd month yyyy hh:mm:ss +zzzz</example>
1688 <list compact="compact">
1690 day-of week is one of: Mon, Tue, Wed, Thu, Fri, Sat, Sun
1693 dd is a one- or two-digit day of the month (01-31)
1696 month is one of: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug,
1699 <item>yyyy is the four-digit year (e.g. 2010)</item>
1700 <item>hh is the two-digit hour (00-23)</item>
1701 <item>mm is the two-digit minutes (00-59)</item>
1702 <item>ss is the two-digit seconds (00-60)</item>
1704 +zzzz or -zzzz is the the time zone offset from Coordinated
1705 Universal Time (UTC). "+" indicates that the time is ahead
1706 of (i.e., east of) UTC and "-" indicates that the time is
1707 behind (i.e., west of) UTC. The first two digits indicate
1708 the hour difference from UTC and the last two digits
1709 indicate the number of additional minutes difference from
1710 UTC. The last two digits must be in the range 00-59.
1716 The first "title" line with the package name must start
1717 at the left hand margin. The "trailer" line with the
1718 maintainer and date details must be preceded by exactly
1719 one space. The maintainer details and the date must be
1720 separated by exactly two spaces.
1724 The entire changelog must be encoded in UTF-8.
1728 For more information on placement of the changelog files
1729 within binary packages, please see <ref id="changelogs">.
1733 <sect id="dpkgcopyright">
1734 <heading>Copyright: <file>debian/copyright</file></heading>
1736 Every package must be accompanied by a verbatim copy of its
1737 copyright information and distribution license in the file
1738 <file>/usr/share/doc/<var>package</var>/copyright</file>
1739 (see <ref id="copyrightfile"> for further details). Also see
1740 <ref id="pkgcopyright"> for further considerations related
1741 to copyrights for packages.
1745 <heading>Error trapping in makefiles</heading>
1748 When <prgn>make</prgn> invokes a command in a makefile
1749 (including your package's upstream makefiles and
1750 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1751 means that <prgn>sh</prgn>'s usual bad error handling
1752 properties apply: if you include a miniature script as one
1753 of the commands in your makefile you'll find that if you
1754 don't do anything about it then errors are not detected
1755 and <prgn>make</prgn> will blithely continue after
1760 Every time you put more than one shell command (this
1761 includes using a loop) in a makefile command you
1762 must make sure that errors are trapped. For
1763 simple compound commands, such as changing directory and
1764 then running a program, using <tt>&&</tt> rather
1765 than semicolon as a command separator is sufficient. For
1766 more complex commands including most loops and
1767 conditionals you should include a separate <tt>set -e</tt>
1768 command at the start of every makefile command that's
1769 actually one of these miniature shell scripts.
1773 <sect id="timestamps">
1774 <heading>Time Stamps</heading>
1776 Maintainers should preserve the modification times of the
1777 upstream source files in a package, as far as is reasonably
1779 The rationale is that there is some information conveyed
1780 by knowing the age of the file, for example, you could
1781 recognize that some documentation is very old by looking
1782 at the modification time, so it would be nice if the
1783 modification time of the upstream source would be
1789 <sect id="restrictions">
1790 <heading>Restrictions on objects in source packages</heading>
1793 The source package may not contain any hard links<footnote>
1795 This is not currently detected when building source
1796 packages, but only when extracting
1800 Hard links may be permitted at some point in the
1801 future, but would require a fair amount of
1804 </footnote>, device special files, sockets or setuid or
1805 setgid files.<footnote>
1806 Setgid directories are allowed.
1811 <sect id="debianrules">
1812 <heading>Main building script: <file>debian/rules</file></heading>
1815 This file must be an executable makefile, and contains the
1816 package-specific recipes for compiling the package and
1817 building binary package(s) from the source.
1821 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1822 so that it can be invoked by saying its name rather than
1823 invoking <prgn>make</prgn> explicitly. That is, invoking
1824 either of <tt>make -f debian/rules <em>args...</em></tt>
1825 or <tt>./debian/rules <em>args...</em></tt> must result in
1830 Since an interactive <file>debian/rules</file> script makes it
1831 impossible to auto-compile that package and also makes it
1832 hard for other people to reproduce the same binary
1833 package, all <em>required targets</em> must be
1834 non-interactive. At a minimum, required targets are the
1835 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1836 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1837 <em>binary-indep</em>, and <em>build</em>. It also follows
1838 that any target that these targets depend on must also be
1843 The targets are as follows (required unless stated otherwise):
1845 <tag><tt>build</tt></tag>
1848 The <tt>build</tt> target should perform all the
1849 configuration and compilation of the package.
1850 If a package has an interactive pre-build
1851 configuration routine, the Debian source package
1852 must either be built after this has taken place (so
1853 that the binary package can be built without rerunning
1854 the configuration) or the configuration routine
1855 modified to become non-interactive. (The latter is
1856 preferable if there are architecture-specific features
1857 detected by the configuration routine.)
1861 For some packages, notably ones where the same
1862 source tree is compiled in different ways to produce
1863 two binary packages, the <tt>build</tt> target
1864 does not make much sense. For these packages it is
1865 good enough to provide two (or more) targets
1866 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1867 for each of the ways of building the package, and a
1868 <tt>build</tt> target that does nothing. The
1869 <tt>binary</tt> target will have to build the
1870 package in each of the possible ways and make the
1871 binary package out of each.
1875 The <tt>build</tt> target must not do anything
1876 that might require root privilege.
1880 The <tt>build</tt> target may need to run the
1881 <tt>clean</tt> target first - see below.
1885 When a package has a configuration and build routine
1886 which takes a long time, or when the makefiles are
1887 poorly designed, or when <tt>build</tt> needs to
1888 run <tt>clean</tt> first, it is a good idea to
1889 <tt>touch build</tt> when the build process is
1890 complete. This will ensure that if <tt>debian/rules
1891 build</tt> is run again it will not rebuild the whole
1893 Another common way to do this is for <tt>build</tt>
1894 to depend on <prgn>build-stamp</prgn> and to do
1895 nothing else, and for the <prgn>build-stamp</prgn>
1896 target to do the building and to <tt>touch
1897 build-stamp</tt> on completion. This is
1898 especially useful if the build routine creates a
1899 file or directory called <tt>build</tt>; in such a
1900 case, <tt>build</tt> will need to be listed as
1901 a phony target (i.e., as a dependency of the
1902 <tt>.PHONY</tt> target). See the documentation of
1903 <prgn>make</prgn> for more information on phony
1909 <tag><tt>build-arch</tt> (optional),
1910 <tt>build-indep</tt> (optional)
1914 A package may also provide both of the targets
1915 <tt>build-arch</tt> and <tt>build-indep</tt>.
1916 The <tt>build-arch</tt> target, if provided, should
1917 perform all the configuration and compilation required for
1918 producing all architecture-dependant binary packages
1919 (those packages for which the body of the
1920 <tt>Architecture</tt> field in <tt>debian/control</tt> is
1921 not <tt>all</tt>). Similarly, the <tt>build-indep</tt>
1922 target, if provided, should perform all the configuration
1923 and compilation required for producing all
1924 architecture-independent binary packages (those packages
1925 for which the body of the <tt>Architecture</tt> field
1926 in <tt>debian/control</tt> is <tt>all</tt>).
1927 The <tt>build</tt> target should depend on those of the
1928 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1929 are provided in the rules file.<footnote>
1930 The intent of this split is so that binary-only builds
1931 need not install the dependencies required for
1932 the <tt>build-indep</tt> target. However, this is not
1933 yet used in practice since <tt>dpkg-buildpackage
1934 -B</tt>, and therefore the autobuilders,
1935 invoke <tt>build</tt> rather than <tt>build-arch</tt>
1936 due to the difficulties in determining whether the
1937 optional <tt>build-arch</tt> target exists.
1942 If one or both of the targets <tt>build-arch</tt> and
1943 <tt>build-indep</tt> are not provided, then invoking
1944 <file>debian/rules</file> with one of the not-provided
1945 targets as arguments should produce a exit status code
1946 of 2. Usually this is provided automatically by make
1947 if the target is missing.
1951 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1952 must not do anything that might require root privilege.
1956 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1957 <tt>binary-indep</tt>
1961 The <tt>binary</tt> target must be all that is
1962 necessary for the user to build the binary package(s)
1963 produced from this source package. It is
1964 split into two parts: <prgn>binary-arch</prgn> builds
1965 the binary packages which are specific to a particular
1966 architecture, and <tt>binary-indep</tt> builds
1967 those which are not.
1970 <tt>binary</tt> may be (and commonly is) a target with
1971 no commands which simply depends on
1972 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1975 Both <tt>binary-*</tt> targets should depend on the
1976 <tt>build</tt> target, or on the appropriate
1977 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1978 provided, so that the package is built if it has not
1979 been already. It should then create the relevant
1980 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1981 make their control files and <prgn>dpkg-deb</prgn> to
1982 build them and place them in the parent of the top
1987 Both the <tt>binary-arch</tt> and
1988 <tt>binary-indep</tt> targets <em>must</em> exist.
1989 If one of them has nothing to do (which will always be
1990 the case if the source generates only a single binary
1991 package, whether architecture-dependent or not), it
1992 must still exist and must always succeed.
1996 The <tt>binary</tt> targets must be invoked as
1998 The <prgn>fakeroot</prgn> package often allows one
1999 to build a package correctly even without being
2005 <tag><tt>clean</tt></tag>
2008 This must undo any effects that the <tt>build</tt>
2009 and <tt>binary</tt> targets may have had, except
2010 that it should leave alone any output files created in
2011 the parent directory by a run of a <tt>binary</tt>
2016 If a <tt>build</tt> file is touched at the end of
2017 the <tt>build</tt> target, as suggested above, it
2018 should be removed as the first action that
2019 <tt>clean</tt> performs, so that running
2020 <tt>build</tt> again after an interrupted
2021 <tt>clean</tt> doesn't think that everything is
2026 The <tt>clean</tt> target may need to be
2027 invoked as root if <tt>binary</tt> has been
2028 invoked since the last <tt>clean</tt>, or if
2029 <tt>build</tt> has been invoked as root (since
2030 <tt>build</tt> may create directories, for
2035 <tag><tt>get-orig-source</tt> (optional)</tag>
2038 This target fetches the most recent version of the
2039 original source package from a canonical archive site
2040 (via FTP or WWW, for example), does any necessary
2041 rearrangement to turn it into the original source
2042 tar file format described below, and leaves it in the
2047 This target may be invoked in any directory, and
2048 should take care to clean up any temporary files it
2053 This target is optional, but providing it if
2054 possible is a good idea.
2058 <tag><tt>patch</tt> (optional)</tag>
2061 This target performs whatever additional actions are
2062 required to make the source ready for editing (unpacking
2063 additional upstream archives, applying patches, etc.).
2064 It is recommended to be implemented for any package where
2065 <tt>dpkg-source -x</tt> does not result in source ready
2066 for additional modification. See
2067 <ref id="readmesource">.
2073 The <tt>build</tt>, <tt>binary</tt> and
2074 <tt>clean</tt> targets must be invoked with the current
2075 directory being the package's top-level directory.
2080 Additional targets may exist in <file>debian/rules</file>,
2081 either as published or undocumented interfaces or for the
2082 package's internal use.
2086 The architectures we build on and build for are determined
2087 by <prgn>make</prgn> variables using the
2088 utility <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
2089 You can determine the Debian architecture and the GNU style
2090 architecture specification string for the build architecture as
2091 well as for the host architecture. The build architecture is
2092 the architecture on which <file>debian/rules</file> is run and
2093 the package build is performed. The host architecture is the
2094 architecture on which the resulting package will be installed
2095 and run. These are normally the same, but may be different in
2096 the case of cross-compilation (building packages for one
2097 architecture on machines of a different architecture).
2101 Here is a list of supported <prgn>make</prgn> variables:
2102 <list compact="compact">
2104 <tt>DEB_*_ARCH</tt> (the Debian architecture)
2107 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2110 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2113 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2114 specification string)
2117 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2118 <tt>DEB_*_GNU_TYPE</tt>)
2121 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2122 <tt>DEB_*_GNU_TYPE</tt>)
2124 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2125 the build architecture or <tt>HOST</tt> for specification of the
2130 Backward compatibility can be provided in the rules file
2131 by setting the needed variables to suitable default
2132 values; please refer to the documentation of
2133 <prgn>dpkg-architecture</prgn> for details.
2137 It is important to understand that the <tt>DEB_*_ARCH</tt>
2138 string only determines which Debian architecture we are
2139 building on or for. It should not be used to get the CPU
2140 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2141 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2142 GNU style variables should generally only be used with upstream
2146 <sect1 id="debianrules-options">
2147 <heading><file>debian/rules</file> and
2148 <tt>DEB_BUILD_OPTIONS</tt></heading>
2151 Supporting the standardized environment variable
2152 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2153 contain several flags to change how a package is compiled and
2154 built. Each flag must be in the form <var>flag</var> or
2155 <var>flag</var>=<var>options</var>. If multiple flags are
2156 given, they must be separated by whitespace.<footnote>
2157 Some packages support any delimiter, but whitespace is the
2158 easiest to parse inside a makefile and avoids ambiguity with
2159 flag values that contain commas.
2161 <var>flag</var> must start with a lowercase letter
2162 (<tt>a-z</tt>) and consist only of lowercase letters,
2163 numbers (<tt>0-9</tt>), and the characters
2164 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2165 <var>options</var> must not contain whitespace. The same
2166 tag should not be given multiple times with conflicting
2167 values. Package maintainers may assume that
2168 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2172 The meaning of the following tags has been standardized:
2176 This tag says to not run any build-time test suite
2177 provided by the package.
2181 The presence of this tag means that the package should
2182 be compiled with a minimum of optimization. For C
2183 programs, it is best to add <tt>-O0</tt> to
2184 <tt>CFLAGS</tt> (although this is usually the default).
2185 Some programs might fail to build or run at this level
2186 of optimization; it may be necessary to use
2187 <tt>-O1</tt>, for example.
2191 This tag means that the debugging symbols should not be
2192 stripped from the binary during installation, so that
2193 debugging information may be included in the package.
2195 <tag>parallel=n</tag>
2197 This tag means that the package should be built using up
2198 to <tt>n</tt> parallel processes if the package build
2199 system supports this.<footnote>
2200 Packages built with <tt>make</tt> can often implement
2201 this by passing the <tt>-j</tt><var>n</var> option to
2204 If the package build system does not support parallel
2205 builds, this string must be ignored. If the package
2206 build system only supports a lower level of concurrency
2207 than <var>n</var>, the package should be built using as
2208 many parallel processes as the package build system
2209 supports. It is up to the package maintainer to decide
2210 whether the package build times are long enough and the
2211 package build system is robust enough to make supporting
2212 parallel builds worthwhile.
2218 Unknown flags must be ignored by <file>debian/rules</file>.
2222 The following makefile snippet is an example of how one may
2223 implement the build options; you will probably have to
2224 massage this example in order to make it work for your
2226 <example compact="compact">
2229 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2230 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2231 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2232 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2234 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2239 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2240 INSTALL_PROGRAM += -s
2242 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2243 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2244 MAKEFLAGS += -j$(NUMJOBS)
2249 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2250 # Code to run the package test suite.
2257 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2258 <sect id="substvars">
2259 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2262 When <prgn>dpkg-gencontrol</prgn>
2263 generates <qref id="binarycontrolfiles">binary package control
2264 files</qref> (<file>DEBIAN/control</file>), it performs variable
2265 substitutions on its output just before writing it. Variable
2266 substitutions have the form <tt>${<var>variable</var>}</tt>.
2267 The optional file <file>debian/substvars</file> contains
2268 variable substitutions to be used; variables can also be set
2269 directly from <file>debian/rules</file> using the <tt>-V</tt>
2270 option to the source packaging commands, and certain predefined
2271 variables are also available.
2275 The <file>debian/substvars</file> file is usually generated and
2276 modified dynamically by <file>debian/rules</file> targets, in
2277 which case it must be removed by the <tt>clean</tt> target.
2281 See <manref name="deb-substvars" section="5"> for full
2282 details about source variable substitutions, including the
2283 format of <file>debian/substvars</file>.</p>
2286 <sect id="debianwatch">
2287 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2290 This is an optional, recommended configuration file for the
2291 <tt>uscan</tt> utility which defines how to automatically scan
2292 ftp or http sites for newly available updates of the
2293 package. This is used
2294 by <url id="http://dehs.alioth.debian.org/"> and other Debian QA
2295 tools to help with quality control and maintenance of the
2296 distribution as a whole.
2301 <sect id="debianfiles">
2302 <heading>Generated files list: <file>debian/files</file></heading>
2305 This file is not a permanent part of the source tree; it
2306 is used while building packages to record which files are
2307 being generated. <prgn>dpkg-genchanges</prgn> uses it
2308 when it generates a <file>.changes</file> file.
2312 It should not exist in a shipped source package, and so it
2313 (and any backup files or temporary files such as
2314 <file>files.new</file><footnote>
2315 <file>files.new</file> is used as a temporary file by
2316 <prgn>dpkg-gencontrol</prgn> and
2317 <prgn>dpkg-distaddfile</prgn> - they write a new
2318 version of <tt>files</tt> here before renaming it,
2319 to avoid leaving a corrupted copy if an error
2321 </footnote>) should be removed by the
2322 <tt>clean</tt> target. It may also be wise to
2323 ensure a fresh start by emptying or removing it at the
2324 start of the <tt>binary</tt> target.
2328 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2329 package, it adds an entry to <file>debian/files</file> for the
2330 <file>.deb</file> file that will be created when <tt>dpkg-deb
2331 --build</tt> is run for that binary package. So for most
2332 packages all that needs to be done with this file is to
2333 delete it in the <tt>clean</tt> target.
2337 If a package upload includes files besides the source
2338 package and any binary packages whose control files were
2339 made with <prgn>dpkg-gencontrol</prgn> then they should be
2340 placed in the parent of the package's top-level directory
2341 and <prgn>dpkg-distaddfile</prgn> should be called to add
2342 the file to the list in <file>debian/files</file>.</p>
2345 <sect id="embeddedfiles">
2346 <heading>Convenience copies of code</heading>
2349 Some software packages include in their distribution convenience
2350 copies of code from other software packages, generally so that
2351 users compiling from source don't have to download multiple
2352 packages. Debian packages should not make use of these
2353 convenience copies unless the included package is explicitly
2354 intended to be used in this way.<footnote>
2355 For example, parts of the GNU build system work like this.
2357 If the included code is already in the Debian archive in the
2358 form of a library, the Debian packaging should ensure that
2359 binary packages reference the libraries already in Debian and
2360 the convenience copy is not used. If the included code is not
2361 already in Debian, it should be packaged separately as a
2362 prerequisite if possible.
2364 Having multiple copies of the same code in Debian is
2365 inefficient, often creates either static linking or shared
2366 library conflicts, and, most importantly, increases the
2367 difficulty of handling security vulnerabilities in the
2373 <sect id="readmesource">
2374 <heading>Source package handling:
2375 <file>debian/README.source</file></heading>
2378 If running <prgn>dpkg-source -x</prgn> on a source package
2379 doesn't produce the source of the package, ready for editing,
2380 and allow one to make changes and run
2381 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2382 without taking any additional steps, creating a
2383 <file>debian/README.source</file> documentation file is
2384 recommended. This file should explain how to do all of the
2387 <item>Generate the fully patched source, in a form ready for
2388 editing, that would be built to create Debian
2389 packages. Doing this with a <tt>patch</tt> target in
2390 <file>debian/rules</file> is recommended; see
2391 <ref id="debianrules">.</item>
2392 <item>Modify the source and save those modifications so that
2393 they will be applied when building the package.</item>
2394 <item>Remove source modifications that are currently being
2395 applied when building the package.</item>
2396 <item>Optionally, document what steps are necessary to
2397 upgrade the Debian source package to a new upstream version,
2398 if applicable.</item>
2400 This explanation should include specific commands and mention
2401 any additional required Debian packages. It should not assume
2402 familiarity with any specific Debian packaging system or patch
2407 This explanation may refer to a documentation file installed by
2408 one of the package's build dependencies provided that the
2409 referenced documentation clearly explains these tasks and is not
2410 a general reference manual.
2414 <file>debian/README.source</file> may also include any other
2415 information that would be helpful to someone modifying the
2416 source package. Even if the package doesn't fit the above
2417 description, maintainers are encouraged to document in a
2418 <file>debian/README.source</file> file any source package with a
2419 particularly complex or unintuitive source layout or build
2420 system (for example, a package that builds the same source
2421 multiple times to generate different binary packages).
2427 <chapt id="controlfields">
2428 <heading>Control files and their fields</heading>
2431 The package management system manipulates data represented in
2432 a common format, known as <em>control data</em>, stored in
2433 <em>control files</em>.
2434 Control files are used for source packages, binary packages and
2435 the <file>.changes</file> files which control the installation
2436 of uploaded files<footnote>
2437 <prgn>dpkg</prgn>'s internal databases are in a similar
2442 <sect id="controlsyntax">
2443 <heading>Syntax of control files</heading>
2446 A control file consists of one or more paragraphs of
2448 The paragraphs are also sometimes referred to as stanzas.
2450 The paragraphs are separated by blank lines. Some control
2451 files allow only one paragraph; others allow several, in
2452 which case each paragraph usually refers to a different
2453 package. (For example, in source packages, the first
2454 paragraph refers to the source package, and later paragraphs
2455 refer to binary packages generated from the source.)
2459 Each paragraph consists of a series of data fields; each
2460 field consists of the field name, followed by a colon and
2461 then the data/value associated with that field. It ends at
2462 the end of the (logical) line. Horizontal whitespace
2463 (spaces and tabs) may occur immediately before or after the
2464 value and is ignored there; it is conventional to put a
2465 single space after the colon. For example, a field might
2467 <example compact="compact">
2470 the field name is <tt>Package</tt> and the field value
2475 A paragraph must not contain more than one instance of a
2476 particular field name.
2480 Many fields' values may span several lines; in this case
2481 each continuation line must start with a space or a tab.
2482 Any trailing spaces or tabs at the end of individual
2483 lines of a field value are ignored.
2487 In fields where it is specified that lines may not wrap,
2488 only a single line of data is allowed and whitespace is not
2489 significant in a field body. Whitespace must not appear
2490 inside names (of packages, architectures, files or anything
2491 else) or version numbers, or between the characters of
2492 multi-character version relationships.
2496 Field names are not case-sensitive, but it is usual to
2497 capitalize the field names using mixed case as shown below.
2498 Field values are case-sensitive unless the description of the
2499 field says otherwise.
2503 Blank lines, or lines consisting only of spaces and tabs,
2504 are not allowed within field values or between fields - that
2505 would mean a new paragraph.
2509 All control files must be encoded in UTF-8.
2513 <sect id="sourcecontrolfiles">
2514 <heading>Source package control files -- <file>debian/control</file></heading>
2517 The <file>debian/control</file> file contains the most vital
2518 (and version-independent) information about the source package
2519 and about the binary packages it creates.
2523 The first paragraph of the control file contains information about
2524 the source package in general. The subsequent sets each describe a
2525 binary package that the source tree builds.
2529 The fields in the general paragraph (the first one, for the source
2532 <list compact="compact">
2533 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2534 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2535 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2536 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2537 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2538 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2539 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2540 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2545 The fields in the binary package paragraphs are:
2547 <list compact="compact">
2548 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2549 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2550 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2551 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2552 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2553 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2554 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2555 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2560 The syntax and semantics of the fields are described below.
2564 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2565 generate control files for binary packages (see below), by
2566 <prgn>dpkg-genchanges</prgn> to generate the
2567 <file>.changes</file> file to accompany the upload, and by
2568 <prgn>dpkg-source</prgn> when it creates the
2569 <file>.dsc</file> source control file as part of a source
2570 archive. Many fields are permitted to span multiple lines in
2571 <file>debian/control</file> but not in any other control
2572 file. These tools are responsible for removing the line
2573 breaks from such fields when using fields from
2574 <file>debian/control</file> to generate other control files.
2578 The fields here may contain variable references - their
2579 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2580 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2581 when they generate output control files.
2582 See <ref id="substvars"> for details.
2586 In addition to the control file syntax described <qref
2587 id="controlsyntax">above</qref>, this file may also contain
2588 comment lines starting with <tt>#</tt> without any preceding
2589 whitespace. All such lines are ignored, even in the middle of
2590 continuation lines for a multiline field, and do not end a
2596 <sect id="binarycontrolfiles">
2597 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2600 The <file>DEBIAN/control</file> file contains the most vital
2601 (and version-dependent) information about a binary package. It
2602 consists of a single paragraph.
2606 The fields in this file are:
2608 <list compact="compact">
2609 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2610 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2611 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2612 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2613 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2614 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2615 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2616 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2617 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2618 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2619 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2620 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2625 <sect id="debiansourcecontrolfiles">
2626 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2629 This file consists of a single paragraph, possibly surrounded by
2630 a PGP signature. The fields of that paragraph are listed below.
2631 Their syntax is described above, in <ref id="pkg-controlfields">.
2633 <list compact="compact">
2634 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2635 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2636 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2637 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2638 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2639 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2640 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2641 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2642 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2643 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2644 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2645 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2646 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2651 The source package control file is generated by
2652 <prgn>dpkg-source</prgn> when it builds the source
2653 archive, from other files in the source package,
2654 described above. When unpacking, it is checked against
2655 the files and directories in the other parts of the
2661 <sect id="debianchangesfiles">
2662 <heading>Debian changes files -- <file>.changes</file></heading>
2665 The <file>.changes</file> files are used by the Debian archive
2666 maintenance software to process updates to packages. They
2667 consist of a single paragraph, possibly surrounded by a PGP
2668 signature. That paragraph contains information from the
2669 <file>debian/control</file> file and other data about the
2670 source package gathered via <file>debian/changelog</file>
2671 and <file>debian/rules</file>.
2675 <file>.changes</file> files have a format version that is
2676 incremented whenever the documented fields or their meaning
2677 change. This document describes format &changesversion;.
2681 The fields in this file are:
2683 <list compact="compact">
2684 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2685 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2686 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2687 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2688 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2689 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2690 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2691 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2692 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2693 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2694 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2695 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2696 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2697 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2698 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2699 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2704 <sect id="controlfieldslist">
2705 <heading>List of fields</heading>
2707 <sect1 id="f-Source">
2708 <heading><tt>Source</tt></heading>
2711 This field identifies the source package name.
2715 In <file>debian/control</file> or a <file>.dsc</file> file,
2716 this field must contain only the name of the source package.
2720 In a binary package control file or a <file>.changes</file>
2721 file, the source package name may be followed by a version
2722 number in parentheses<footnote>
2723 It is customary to leave a space after the package name
2724 if a version number is specified.
2726 This version number may be omitted (and is, by
2727 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2728 the <tt>Version</tt> field of the binary package in
2729 question. The field itself may be omitted from a binary
2730 package control file when the source package has the same
2731 name and version as the binary package.
2735 Package names (both source and binary,
2736 see <ref id="f-Package">) must consist only of lower case
2737 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2738 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2739 (<tt>.</tt>). They must be at least two characters long and
2740 must start with an alphanumeric character.
2744 <sect1 id="f-Maintainer">
2745 <heading><tt>Maintainer</tt></heading>
2748 The package maintainer's name and email address. The name
2749 must come first, then the email address inside angle
2750 brackets <tt><></tt> (in RFC822 format).
2754 If the maintainer's name contains a full stop then the
2755 whole field will not work directly as an email address due
2756 to a misfeature in the syntax specified in RFC822; a
2757 program using this field as an address must check for this
2758 and correct the problem if necessary (for example by
2759 putting the name in round brackets and moving it to the
2760 end, and bringing the email address forward).
2764 See <ref id="maintainer"> for additional requirements and
2765 information about package maintainers.
2769 <sect1 id="f-Uploaders">
2770 <heading><tt>Uploaders</tt></heading>
2773 List of the names and email addresses of co-maintainers of the
2774 package, if any. If the package has other maintainers besides
2775 the one named in the <qref id="f-Maintainer">Maintainer
2776 field</qref>, their names and email addresses should be listed
2777 here. The format of each entry is the same as that of the
2778 Maintainer field, and multiple entries must be comma
2783 This is normally an optional field, but if
2784 the <tt>Maintainer</tt> control field names a group of people
2785 and a shared email address, the <tt>Uploaders</tt> field must
2786 be present and must contain at least one human with their
2787 personal email address.
2791 Any parser that interprets the Uploaders field in
2792 <file>debian/control</file> must permit it to span multiple
2793 lines. Line breaks in an Uploaders field that spans multiple
2794 lines are not significant and the semantics of the field are
2795 the same as if the line breaks had not been present.
2799 <sect1 id="f-Changed-By">
2800 <heading><tt>Changed-By</tt></heading>
2803 The name and email address of the person who prepared this
2804 version of the package, usually a maintainer. The syntax is
2805 the same as for the <qref id="f-Maintainer">Maintainer
2810 <sect1 id="f-Section">
2811 <heading><tt>Section</tt></heading>
2814 This field specifies an application area into which the package
2815 has been classified. See <ref id="subsections">.
2819 When it appears in the <file>debian/control</file> file,
2820 it gives the value for the subfield of the same name in
2821 the <tt>Files</tt> field of the <file>.changes</file> file.
2822 It also gives the default for the same field in the binary
2827 <sect1 id="f-Priority">
2828 <heading><tt>Priority</tt></heading>
2831 This field represents how important it is that the user
2832 have the package installed. See <ref id="priorities">.
2836 When it appears in the <file>debian/control</file> file,
2837 it gives the value for the subfield of the same name in
2838 the <tt>Files</tt> field of the <file>.changes</file> file.
2839 It also gives the default for the same field in the binary
2844 <sect1 id="f-Package">
2845 <heading><tt>Package</tt></heading>
2848 The name of the binary package.
2852 Binary package names must follow the same syntax and
2853 restrictions as source package names. See <ref id="f-Source">
2858 <sect1 id="f-Architecture">
2859 <heading><tt>Architecture</tt></heading>
2862 Depending on context and the control file used, the
2863 <tt>Architecture</tt> field can include the following sets of
2867 A unique single word identifying a Debian machine
2868 architecture as described in <ref id="arch-spec">.
2871 An architecture wildcard identifying a set of Debian
2872 machine architectures, see <ref id="arch-wildcard-spec">.
2873 <tt>any</tt> matches all Debian machine architectures
2874 and is the most frequently used.
2877 <tt>all</tt>, which indicates an
2878 architecture-independent package.
2881 <tt>source</tt>, which indicates a source package.
2887 In the main <file>debian/control</file> file in the source
2888 package, this field may contain the special
2889 value <tt>all</tt>, the special architecture
2890 wildcard <tt>any</tt>, or a list of specific and wildcard
2891 architectures separated by spaces. If <tt>all</tt>
2892 or <tt>any</tt> appears, that value must be the entire
2893 contents of the field. Most packages will use
2894 either <tt>all</tt> or <tt>any</tt>.
2898 Specifying a specific list of architectures indicates that the
2899 source will build an architecture-dependent package only on
2900 architectures included in the list. Specifying a list of
2901 architecture wildcards indicates that the source will build an
2902 architecture-dependent package on only those architectures
2903 that match any of the specified architecture wildcards.
2904 Specifying a list of architectures or architecture wildcards
2905 other than <tt>any</tt> is for the minority of cases where a
2906 program is not portable or is not useful on some
2907 architectures. Where possible, the program should be made
2912 In the source package control file <file>.dsc</file>, this
2913 field may contain either the architecture
2914 wildcard <tt>any</tt> or a list of architectures and
2915 architecture wildcards separated by spaces. If a list is
2916 given, it may include (or consist solely of) the special
2917 value <tt>all</tt>. In other words, in <file>.dsc</file>
2918 files unlike the <file>debian/control</file>, <tt>all</tt> may
2919 occur in combination with specific architectures.
2920 The <tt>Architecture</tt> field in the source package control
2921 file <file>.dsc</file> is generally constructed from
2922 the <tt>Architecture</tt> fields in
2923 the <file>debian/control</file> in the source package.
2927 Specifying <tt>any</tt> indicates that the source package
2928 isn't dependent on any particular architecture and should
2929 compile fine on any one. The produced binary package(s)
2930 will either be specific to whatever the current build
2931 architecture is or will be architecture-independent.
2935 Specifying only <tt>all</tt> indicates that the source package
2936 will only build architecture-independent packages. If this is
2937 the case, <tt>all</tt> must be used rather than <tt>any</tt>;
2938 <tt>any</tt> implies that the source package will build at
2939 least one architecture-dependent package.
2943 Specifying a list of architectures or architecture wildcards
2944 indicates that the source will build an architecture-dependent
2945 package, and will only work correctly on the listed or
2946 matching architectures. If the source package also builds at
2947 least one architecture-independent package, <tt>all</tt> will
2948 also be included in the list.
2952 In a <file>.changes</file> file, the <tt>Architecture</tt>
2953 field lists the architecture(s) of the package(s) currently
2954 being uploaded. This will be a list; if the source for the
2955 package is also being uploaded, the special
2956 entry <tt>source</tt> is also present. <tt>all</tt> will be
2957 present if any architecture-independent packages are being
2958 uploaded. Architecture wildcards such as <tt>any</tt> must
2959 never occur in the <tt>Architecture</tt> field in
2960 the <file>.changes</file> file.
2964 See <ref id="debianrules"> for information on how to get
2965 the architecture for the build process.
2969 <sect1 id="f-Essential">
2970 <heading><tt>Essential</tt></heading>
2973 This is a boolean field which may occur only in the
2974 control file of a binary package or in a per-package fields
2975 paragraph of a main source control data file.
2979 If set to <tt>yes</tt> then the package management system
2980 will refuse to remove the package (upgrading and replacing
2981 it is still possible). The other possible value is <tt>no</tt>,
2982 which is the same as not having the field at all.
2987 <heading>Package interrelationship fields:
2988 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2989 <tt>Recommends</tt>, <tt>Suggests</tt>,
2990 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2991 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2995 These fields describe the package's relationships with
2996 other packages. Their syntax and semantics are described
2997 in <ref id="relationships">.</p>
3000 <sect1 id="f-Standards-Version">
3001 <heading><tt>Standards-Version</tt></heading>
3004 The most recent version of the standards (the policy
3005 manual and associated texts) with which the package
3010 The version number has four components: major and minor
3011 version number and major and minor patch level. When the
3012 standards change in a way that requires every package to
3013 change the major number will be changed. Significant
3014 changes that will require work in many packages will be
3015 signaled by a change to the minor number. The major patch
3016 level will be changed for any change to the meaning of the
3017 standards, however small; the minor patch level will be
3018 changed when only cosmetic, typographical or other edits
3019 are made which neither change the meaning of the document
3020 nor affect the contents of packages.
3024 Thus only the first three components of the policy version
3025 are significant in the <em>Standards-Version</em> control
3026 field, and so either these three components or all four
3027 components may be specified.<footnote>
3028 In the past, people specified the full version number
3029 in the Standards-Version field, for example "2.3.0.0".
3030 Since minor patch-level changes don't introduce new
3031 policy, it was thought it would be better to relax
3032 policy and only require the first 3 components to be
3033 specified, in this example "2.3.0". All four
3034 components may still be used if someone wishes to do so.
3040 <sect1 id="f-Version">
3041 <heading><tt>Version</tt></heading>
3044 The version number of a package. The format is:
3045 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
3049 The three components here are:
3051 <tag><var>epoch</var></tag>
3054 This is a single (generally small) unsigned integer. It
3055 may be omitted, in which case zero is assumed. If it is
3056 omitted then the <var>upstream_version</var> may not
3061 It is provided to allow mistakes in the version numbers
3062 of older versions of a package, and also a package's
3063 previous version numbering schemes, to be left behind.
3067 <tag><var>upstream_version</var></tag>
3070 This is the main part of the version number. It is
3071 usually the version number of the original ("upstream")
3072 package from which the <file>.deb</file> file has been made,
3073 if this is applicable. Usually this will be in the same
3074 format as that specified by the upstream author(s);
3075 however, it may need to be reformatted to fit into the
3076 package management system's format and comparison
3081 The comparison behavior of the package management system
3082 with respect to the <var>upstream_version</var> is
3083 described below. The <var>upstream_version</var>
3084 portion of the version number is mandatory.
3088 The <var>upstream_version</var> may contain only
3089 alphanumerics<footnote>
3090 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3092 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3093 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3094 tilde) and should start with a digit. If there is no
3095 <var>debian_revision</var> then hyphens are not allowed;
3096 if there is no <var>epoch</var> then colons are not
3101 <tag><var>debian_revision</var></tag>
3104 This part of the version number specifies the version of
3105 the Debian package based on the upstream version. It
3106 may contain only alphanumerics and the characters
3107 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3108 tilde) and is compared in the same way as the
3109 <var>upstream_version</var> is.
3113 It is optional; if it isn't present then the
3114 <var>upstream_version</var> may not contain a hyphen.
3115 This format represents the case where a piece of
3116 software was written specifically to be a Debian
3117 package, where the Debian package source must always
3118 be identical to the pristine source and therefore no
3119 revision indication is required.
3123 It is conventional to restart the
3124 <var>debian_revision</var> at <tt>1</tt> each time the
3125 <var>upstream_version</var> is increased.
3129 The package management system will break the version
3130 number apart at the last hyphen in the string (if there
3131 is one) to determine the <var>upstream_version</var> and
3132 <var>debian_revision</var>. The absence of a
3133 <var>debian_revision</var> is equivalent to a
3134 <var>debian_revision</var> of <tt>0</tt>.
3141 When comparing two version numbers, first the <var>epoch</var>
3142 of each are compared, then the <var>upstream_version</var> if
3143 <var>epoch</var> is equal, and then <var>debian_revision</var>
3144 if <var>upstream_version</var> is also equal.
3145 <var>epoch</var> is compared numerically. The
3146 <var>upstream_version</var> and <var>debian_revision</var>
3147 parts are compared by the package management system using the
3148 following algorithm:
3152 The strings are compared from left to right.
3156 First the initial part of each string consisting entirely of
3157 non-digit characters is determined. These two parts (one of
3158 which may be empty) are compared lexically. If a difference
3159 is found it is returned. The lexical comparison is a
3160 comparison of ASCII values modified so that all the letters
3161 sort earlier than all the non-letters and so that a tilde
3162 sorts before anything, even the end of a part. For example,
3163 the following parts are in sorted order from earliest to
3164 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3165 <tt>a</tt>.<footnote>
3166 One common use of <tt>~</tt> is for upstream pre-releases.
3167 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3168 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3173 Then the initial part of the remainder of each string which
3174 consists entirely of digit characters is determined. The
3175 numerical values of these two parts are compared, and any
3176 difference found is returned as the result of the comparison.
3177 For these purposes an empty string (which can only occur at
3178 the end of one or both version strings being compared) counts
3183 These two steps (comparing and removing initial non-digit
3184 strings and initial digit strings) are repeated until a
3185 difference is found or both strings are exhausted.
3189 Note that the purpose of epochs is to allow us to leave behind
3190 mistakes in version numbering, and to cope with situations
3191 where the version numbering scheme changes. It is
3192 <em>not</em> intended to cope with version numbers containing
3193 strings of letters which the package management system cannot
3194 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3195 silly orderings.<footnote>
3196 The author of this manual has heard of a package whose
3197 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3198 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3204 <sect1 id="f-Description">
3205 <heading><tt>Description</tt></heading>
3208 In a source or binary control file, the <tt>Description</tt>
3209 field contains a description of the binary package, consisting
3210 of two parts, the synopsis or the short description, and the
3211 long description. The field's format is as follows:
3216 Description: <single line synopsis>
3217 <extended description over several lines>
3222 The lines in the extended description can have these formats:
3228 Those starting with a single space are part of a paragraph.
3229 Successive lines of this form will be word-wrapped when
3230 displayed. The leading space will usually be stripped off.
3234 Those starting with two or more spaces. These will be
3235 displayed verbatim. If the display cannot be panned
3236 horizontally, the displaying program will line wrap them "hard"
3237 (i.e., without taking account of word breaks). If it can they
3238 will be allowed to trail off to the right. None, one or two
3239 initial spaces may be deleted, but the number of spaces
3240 deleted from each line will be the same (so that you can have
3241 indenting work correctly, for example).
3245 Those containing a single space followed by a single full stop
3246 character. These are rendered as blank lines. This is the
3247 <em>only</em> way to get a blank line<footnote>
3248 Completely empty lines will not be rendered as blank lines.
3249 Instead, they will cause the parser to think you're starting
3250 a whole new record in the control file, and will therefore
3251 likely abort with an error.
3256 Those containing a space, a full stop and some more characters.
3257 These are for future expansion. Do not use them.
3263 Do not use tab characters. Their effect is not predictable.
3267 See <ref id="descriptions"> for further information on this.
3271 In a <file>.changes</file> file, the <tt>Description</tt>
3272 field contains a summary of the descriptions for the packages
3273 being uploaded. For this case, the first line of the field
3274 value (the part on the same line as <tt>Description:</tt>) is
3275 always empty. The content of the field is expressed as
3276 continuation lines, one line per package. Each line is
3277 indented by one space and contains the name of a binary
3278 package, a space, a hyphen (<tt>-</tt>), a space, and the
3279 short description line from that package.
3283 <sect1 id="f-Distribution">
3284 <heading><tt>Distribution</tt></heading>
3287 In a <file>.changes</file> file or parsed changelog output
3288 this contains the (space-separated) name(s) of the
3289 distribution(s) where this version of the package should
3290 be installed. Valid distributions are determined by the
3291 archive maintainers.<footnote>
3292 Example distribution names in the Debian archive used in
3293 <file>.changes</file> files are:
3294 <taglist compact="compact">
3295 <tag><em>unstable</em></tag>
3297 This distribution value refers to the
3298 <em>developmental</em> part of the Debian distribution
3299 tree. Most new packages, new upstream versions of
3300 packages and bug fixes go into the <em>unstable</em>
3304 <tag><em>experimental</em></tag>
3306 The packages with this distribution value are deemed
3307 by their maintainers to be high risk. Oftentimes they
3308 represent early beta or developmental packages from
3309 various sources that the maintainers want people to
3310 try, but are not ready to be a part of the other parts
3311 of the Debian distribution tree.
3316 Others are used for updating stable releases or for
3317 security uploads. More information is available in the
3318 Debian Developer's Reference, section "The Debian
3322 The Debian archive software only supports listing a single
3323 distribution. Migration of packages to other distributions is
3324 handled outside of the upload process.
3329 <heading><tt>Date</tt></heading>
3332 This field includes the date the package was built or last
3333 edited. It must be in the same format as the <var>date</var>
3334 in a <file>debian/changelog</file> entry.
3338 The value of this field is usually extracted from the
3339 <file>debian/changelog</file> file - see
3340 <ref id="dpkgchangelog">).
3344 <sect1 id="f-Format">
3345 <heading><tt>Format</tt></heading>
3348 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3349 files, this field declares the format version of that file.
3350 The syntax of the field value is the same as that of
3351 a <qref id="f-Version">package version number</qref> except
3352 that no epoch or Debian revision is allowed. The format
3353 described in this document is <tt>&changesversion;</tt>.
3357 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3358 Debian source control</qref> files, this field declares the
3359 format of the source package. The field value is used by
3360 programs acting on a source package to interpret the list of
3361 files in the source package and determine how to unpack it.
3362 The syntax of the field value is a numeric major revision, a
3363 period, a numeric minor revision, and then an optional subtype
3364 after whitespace, which if specified is an alphanumeric word
3365 in parentheses. The subtype is optional in the syntax but may
3366 be mandatory for particular source format revisions.
3368 The source formats currently supported by the Debian archive
3369 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3370 and <tt>3.0 (quilt)</tt>.
3375 <sect1 id="f-Urgency">
3376 <heading><tt>Urgency</tt></heading>
3379 This is a description of how important it is to upgrade to
3380 this version from previous ones. It consists of a single
3381 keyword taking one of the values <tt>low</tt>,
3382 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3383 <tt>critical</tt><footnote>
3384 Other urgency values are supported with configuration
3385 changes in the archive software but are not used in Debian.
3386 The urgency affects how quickly a package will be considered
3387 for inclusion into the <tt>testing</tt> distribution and
3388 gives an indication of the importance of any fixes included
3389 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3390 treated as synonymous.
3391 </footnote> (not case-sensitive) followed by an optional
3392 commentary (separated by a space) which is usually in
3393 parentheses. For example:
3396 Urgency: low (HIGH for users of diversions)
3402 The value of this field is usually extracted from the
3403 <file>debian/changelog</file> file - see
3404 <ref id="dpkgchangelog">.
3408 <sect1 id="f-Changes">
3409 <heading><tt>Changes</tt></heading>
3412 This field contains the human-readable changes data, describing
3413 the differences between the last version and the current one.
3417 The first line of the field value (the part on the same line
3418 as <tt>Changes:</tt>) is always empty. The content of the
3419 field is expressed as continuation lines, with each line
3420 indented by at least one space. Blank lines must be
3421 represented by a line consisting only of a space and a full
3426 The value of this field is usually extracted from the
3427 <file>debian/changelog</file> file - see
3428 <ref id="dpkgchangelog">).
3432 Each version's change information should be preceded by a
3433 "title" line giving at least the version, distribution(s)
3434 and urgency, in a human-readable way.
3438 If data from several versions is being returned the entry
3439 for the most recent version should be returned first, and
3440 entries should be separated by the representation of a
3441 blank line (the "title" line may also be followed by the
3442 representation of a blank line).
3446 <sect1 id="f-Binary">
3447 <heading><tt>Binary</tt></heading>
3450 This field is a list of binary packages. Its syntax and
3451 meaning varies depending on the control file in which it
3456 When it appears in the <file>.dsc</file> file, it lists binary
3457 packages which a source package can produce, separated by
3459 A space after each comma is conventional.
3460 </footnote>. It may span multiple lines. The source package
3461 does not necessarily produce all of these binary packages for
3462 every architecture. The source control file doesn't contain
3463 details of which architectures are appropriate for which of
3464 the binary packages.
3468 When it appears in a <file>.changes</file> file, it lists the
3469 names of the binary packages being uploaded, separated by
3470 whitespace (not commas). It may span multiple lines.
3474 <sect1 id="f-Installed-Size">
3475 <heading><tt>Installed-Size</tt></heading>
3478 This field appears in the control files of binary packages,
3479 and in the <file>Packages</file> files. It gives an estimate
3480 of the total amount of disk space required to install the
3481 named package. Actual installed size may vary based on block
3482 size, file system properties, or actions taken by package
3487 The disk space is given as the integer value of the estimated
3488 installed size in bytes, divided by 1024 and rounded up.
3492 <sect1 id="f-Files">
3493 <heading><tt>Files</tt></heading>
3496 This field contains a list of files with information about
3497 each one. The exact information and syntax varies with
3502 In all cases, Files is a multiline field. The first line of
3503 the field value (the part on the same line as <tt>Files:</tt>)
3504 is always empty. The content of the field is expressed as
3505 continuation lines, one line per file. Each line must be
3506 indented by one space and contain a number of sub-fields,
3507 separated by spaces, as described below.
3511 In the <file>.dsc</file> file, each line contains the MD5
3512 checksum, size and filename of the tar file and (if
3513 applicable) diff file which make up the remainder of the
3514 source package<footnote>
3515 That is, the parts which are not the <tt>.dsc</tt>.
3516 </footnote>. For example:
3519 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3520 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3522 The exact forms of the filenames are described
3523 in <ref id="pkg-sourcearchives">.
3527 In the <file>.changes</file> file this contains one line per
3528 file being uploaded. Each line contains the MD5 checksum,
3529 size, section and priority and the filename. For example:
3532 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3533 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3534 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3535 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3537 The <qref id="f-Section">section</qref>
3538 and <qref id="f-Priority">priority</qref> are the values of
3539 the corresponding fields in the main source control file. If
3540 no section or priority is specified then <tt>-</tt> should be
3541 used, though section and priority values must be specified for
3542 new packages to be installed properly.
3546 The special value <tt>byhand</tt> for the section in a
3547 <tt>.changes</tt> file indicates that the file in question
3548 is not an ordinary package file and must by installed by
3549 hand by the distribution maintainers. If the section is
3550 <tt>byhand</tt> the priority should be <tt>-</tt>.
3554 If a new Debian revision of a package is being shipped and
3555 no new original source archive is being distributed the
3556 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3557 entry for the original source archive
3558 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3559 but the <file>.changes</file> file should leave it out. In
3560 this case the original source archive on the distribution
3561 site must match exactly, byte-for-byte, the original
3562 source archive which was used to generate the
3563 <file>.dsc</file> file and diff which are being uploaded.</p>
3566 <sect1 id="f-Closes">
3567 <heading><tt>Closes</tt></heading>
3570 A space-separated list of bug report numbers that the upload
3571 governed by the .changes file closes.
3575 <sect1 id="f-Homepage">
3576 <heading><tt>Homepage</tt></heading>
3579 The URL of the web site for this package, preferably (when
3580 applicable) the site from which the original source can be
3581 obtained and any additional upstream documentation or
3582 information may be found. The content of this field is a
3583 simple URL without any surrounding characters such as
3588 <sect1 id="f-Checksums">
3589 <heading><tt>Checksums-Sha1</tt>
3590 and <tt>Checksums-Sha256</tt></heading>
3593 These fields contain a list of files with a checksum and size
3594 for each one. Both <tt>Checksums-Sha1</tt>
3595 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3596 only in the checksum algorithm used: SHA-1
3597 for <tt>Checksums-Sha1</tt> and SHA-256
3598 for <tt>Checksums-Sha256</tt>.
3602 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3603 multiline fields. The first line of the field value (the part
3604 on the same line as <tt>Checksums-Sha1:</tt>
3605 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3606 of the field is expressed as continuation lines, one line per
3607 file. Each line consists of the checksum, a space, the file
3608 size, a space, and the file name. For example (from
3609 a <file>.changes</file> file):
3612 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3613 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3614 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3615 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3617 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3618 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3619 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3620 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3625 In the <file>.dsc</file> file, these fields should list all
3626 files that make up the source package. In
3627 the <file>.changes</file> file, these fields should list all
3628 files being uploaded. The list of files in these fields
3629 must match the list of files in the <tt>Files</tt> field.
3635 <heading>User-defined fields</heading>
3638 Additional user-defined fields may be added to the
3639 source package control file. Such fields will be
3640 ignored, and not copied to (for example) binary or
3641 source package control files or upload control files.
3645 If you wish to add additional unsupported fields to
3646 these output files you should use the mechanism
3651 Fields in the main source control information file with
3652 names starting <tt>X</tt>, followed by one or more of
3653 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3654 be copied to the output files. Only the part of the
3655 field name after the hyphen will be used in the output
3656 file. Where the letter <tt>B</tt> is used the field
3657 will appear in binary package control files, where the
3658 letter <tt>S</tt> is used in source package control
3659 files and where <tt>C</tt> is used in upload control
3660 (<tt>.changes</tt>) files.
3664 For example, if the main source information control file
3667 XBS-Comment: I stand between the candle and the star.
3669 then the binary and source package control files will contain the
3672 Comment: I stand between the candle and the star.
3681 <chapt id="maintainerscripts">
3682 <heading>Package maintainer scripts and installation procedure</heading>
3685 <heading>Introduction to package maintainer scripts</heading>
3688 It is possible to supply scripts as part of a package which
3689 the package management system will run for you when your
3690 package is installed, upgraded or removed.
3694 These scripts are the control information
3695 files <prgn>preinst</prgn>, <prgn>postinst</prgn>, <prgn>prerm</prgn>
3696 and <prgn>postrm</prgn>. They must be proper executable files;
3697 if they are scripts (which is recommended), they must start with
3698 the usual <tt>#!</tt> convention. They should be readable and
3699 executable by anyone, and must not be world-writable.
3703 The package management system looks at the exit status from
3704 these scripts. It is important that they exit with a
3705 non-zero status if there is an error, so that the package
3706 management system can stop its processing. For shell
3707 scripts this means that you <em>almost always</em> need to
3708 use <tt>set -e</tt> (this is usually true when writing shell
3709 scripts, in fact). It is also important, of course, that
3710 they exit with a zero status if everything went well.
3714 Additionally, packages interacting with users
3715 using <prgn>debconf</prgn> in the <prgn>postinst</prgn> script
3716 should install a <prgn>config</prgn> script as a control
3717 information file. See <ref id="maintscriptprompt"> for details.
3721 When a package is upgraded a combination of the scripts from
3722 the old and new packages is called during the upgrade
3723 procedure. If your scripts are going to be at all
3724 complicated you need to be aware of this, and may need to
3725 check the arguments to your scripts.
3729 Broadly speaking the <prgn>preinst</prgn> is called before
3730 (a particular version of) a package is unpacked, and the
3731 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3732 before (a version of) a package is removed and the
3733 <prgn>postrm</prgn> afterwards.
3737 Programs called from maintainer scripts should not normally
3738 have a path prepended to them. Before installation is
3739 started, the package management system checks to see if the
3740 programs <prgn>ldconfig</prgn>,
3741 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3742 and <prgn>update-rc.d</prgn> can be found via the
3743 <tt>PATH</tt> environment variable. Those programs, and any
3744 other program that one would expect to be in the
3745 <tt>PATH</tt>, should thus be invoked without an absolute
3746 pathname. Maintainer scripts should also not reset the
3747 <tt>PATH</tt>, though they might choose to modify it by
3748 prepending or appending package-specific directories. These
3749 considerations really apply to all shell scripts.</p>
3752 <sect id="idempotency">
3753 <heading>Maintainer scripts idempotency</heading>
3756 It is necessary for the error recovery procedures that the
3757 scripts be idempotent. This means that if it is run
3758 successfully, and then it is called again, it doesn't bomb
3759 out or cause any harm, but just ensures that everything is
3760 the way it ought to be. If the first call failed, or
3761 aborted half way through for some reason, the second call
3762 should merely do the things that were left undone the first
3763 time, if any, and exit with a success status if everything
3765 This is so that if an error occurs, the user interrupts
3766 <prgn>dpkg</prgn> or some other unforeseen circumstance
3767 happens you don't leave the user with a badly-broken
3768 package when <prgn>dpkg</prgn> attempts to repeat the
3774 <sect id="controllingterminal">
3775 <heading>Controlling terminal for maintainer scripts</heading>
3778 Maintainer scripts are not guaranteed to run with a controlling
3779 terminal and may not be able to interact with the user. They
3780 must be able to fall back to noninteractive behavior if no
3781 controlling terminal is available. Maintainer scripts that
3782 prompt via a program conforming to the Debian Configuration
3783 Management Specification (see <ref id="maintscriptprompt">) may
3784 assume that program will handle falling back to noninteractive
3789 For high-priority prompts without a reasonable default answer,
3790 maintainer scripts may abort if there is no controlling
3791 terminal. However, this situation should be avoided if at all
3792 possible, since it prevents automated or unattended installs.
3793 In most cases, users will consider this to be a bug in the
3798 <sect id="exitstatus">
3799 <heading>Exit status</heading>
3802 Each script must return a zero exit status for
3803 success, or a nonzero one for failure, since the package
3804 management system looks for the exit status of these scripts
3805 and determines what action to take next based on that datum.
3809 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3814 What follows is a summary of all the ways in which maintainer
3815 scripts may be called along with what facilities those scripts
3816 may rely on being available at that time. Script names preceded
3817 by <var>new-</var> are the scripts from the new version of a
3818 package being installed, upgraded to, or downgraded to. Script
3819 names preceded by <var>old-</var> are the scripts from the old
3820 version of a package that is being upgraded from or downgraded
3825 The <prgn>preinst</prgn> script may be called in the following
3828 <tag><var>new-preinst</var> <tt>install</tt></tag>
3829 <tag><var>new-preinst</var> <tt>install</tt>
3830 <var>old-version</var></tag>
3831 <tag><var>new-preinst</var> <tt>upgrade</tt>
3832 <var>old-version</var></tag>
3834 The package will not yet be unpacked, so
3835 the <prgn>preinst</prgn> script cannot rely on any files
3836 included in its package. Only essential packages and
3837 pre-dependencies (<tt>Pre-Depends</tt>) may be assumed to be
3838 available. Pre-dependencies will be at least unpacked.
3839 They may be only unpacked or "Half-Configured", not
3840 completely configured, but only if a previous version of the
3841 pre-dependency was completely configured and the
3842 pre-dependency had not been removed since then.
3845 <tag><var>old-preinst</var> <tt>abort-upgrade</tt>
3846 <var>new-version</var></tag>
3848 Called during error handling of an upgrade that failed after
3849 unpacking the new package because the <tt>postrm
3850 upgrade</tt> action failed. The unpacked files may be
3851 partly from the new version or partly missing, so the script
3852 cannot rely on files included in the package. Package
3853 dependencies may not be available. Pre-dependencies will be
3854 at least unpacked following the same rules as above, except
3855 they may be only "Half-Installed" if an upgrade of the
3856 pre-dependency failed.<footnote>
3857 This can happen if the new version of the package no
3858 longer pre-depends on a package that had been partially
3866 The <prgn>postinst</prgn> script may be called in the following
3869 <tag><var>postinst</var> <tt>configure</tt>
3870 <var>most-recently-configured-version</var></tag>
3872 The files contained in the package will be unpacked. All
3873 package dependencies will at least be unpacked. If there
3874 are no circular dependencies involved, all package
3875 dependencies will be configured.
3878 <tag><var>old-postinst</var> <tt>abort-upgrade</tt>
3879 <var>new-version</var></tag>
3880 <tag><var>conflictor's-postinst</var> <tt>abort-remove</tt>
3881 <tt>in-favour</tt> <var>package</var>
3882 <var>new-version</var></tag>
3883 <tag><var>postinst</var> <tt>abort-remove</tt></tag>
3884 <tag><var>deconfigured's-postinst</var>
3885 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3886 <var>failed-install-package</var> <var>version</var>
3887 [<tt>removing</tt> <var>conflicting-package</var>
3888 <var>version</var>]</tag>
3890 The files contained in the package will be unpacked. All
3891 package dependencies will at least be "Half-Installed" and
3892 will have previously been configured and not removed.
3893 However, dependencies may not be configured or even fully
3894 unpacked in some error situations.<footnote>
3895 For example, suppose packages foo and bar are installed
3896 with foo depending on bar. If an upgrade of bar were
3897 started and then aborted, and then an attempt to remove
3898 foo failed because its <prgn>prerm</prgn> script failed,
3899 foo's <tt>postinst abort-remove</tt> would be called with
3900 bar only "Half-Installed".
3907 The <prgn>prerm</prgn> script may be called in the following
3910 <tag><var>prerm</var> <tt>remove</tt></tag>
3911 <tag><var>old-prerm</var>
3912 <tt>upgrade</tt><var>new-version</var></tag>
3913 <tag><var>conflictor's-prerm</var> <tt>remove</tt>
3914 <tt>in-favour</tt> <var>package</var>
3915 <var>new-version</var></tag>
3916 <tag><var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3917 <tt>in-favour</tt> <var>package-being-installed</var>
3918 <var>version</var> [<tt>removing</tt>
3919 <var>conflicting-package</var> <var>version</var>]</tag>
3921 The package whose <prgn>prerm</prgn> is being called will be
3922 at least "Half-Installed". All package dependencies will at
3923 least be "Half-Installed" and will have previously been
3924 configured and not removed. If there was no error, all
3925 dependencies will at least be unpacked, but these actions
3926 may be called in various error states where dependencies are
3927 only "Half-Installed" due to a partial upgrade.
3930 <tag><var>new-prerm</var> <tt>failed-upgrade</tt>
3931 <var>old-version</var></tag>
3933 Called during error handling when <tt>prerm upgrade</tt>
3934 fails. The new package will not yet be unpacked, and all
3935 the same constraints as for <tt>preinst upgrade</tt> apply.
3941 The <prgn>postrm</prgn> script may be called in the following
3944 <tag><var>postrm</var> <tt>remove</tt></tag>
3945 <tag><var>postrm</var> <tt>purge</tt></tag>
3946 <tag><var>old-postrm</var> <tt>upgrade</tt>
3947 <var>new-version</var></tag>
3948 <tag><var>disappearer's-postrm</var> <tt>disappear</tt>
3949 <var>overwriter</var> <var>overwriter-version</var></tag>
3951 The <prgn>postrm</prgn> script is called after the package's
3952 files have been removed or replaced. The package
3953 whose <prgn>postrm</prgn> is being called may have
3954 previously been deconfigured and only be unpacked, at which
3955 point subsequent package changes do not consider its
3956 dependencies. Therefore, all <prgn>postrm</prgn> actions
3957 may only rely on essential packages and cannot assume that
3958 the package's dependencies are available.
3961 <tag><var>new-postrm</var> <tt>failed-upgrade</tt>
3962 <var>old-version</var></tag>
3964 Called when the old <tt>postrm upgrade</tt> action fails.
3965 The new package will be unpacked, but only essential
3966 packages and pre-dependencies can be relied on.
3967 Pre-dependencies will either be configured or will be
3968 "Unpacked" or "Half-Configured" but previously had been
3969 configured and was never removed.
3972 <tag><var>new-postrm</var> <tt>abort-install</tt></tag>
3973 <tag><var>new-postrm</var> <tt>abort-install</tt>
3974 <var>old-version</var></tag>
3975 <tag><var>new-postrm</var> <tt>abort-upgrade</tt>
3976 <var>old-version</var></tag>
3978 Called before unpacking the new package as part of the
3979 error handling of <prgn>preinst</prgn> failures. May assume
3980 the same state as <prgn>preinst</prgn> can assume.
3986 <sect id="unpackphase">
3987 <heading>Details of unpack phase of installation or upgrade</heading>
3990 The procedure on installation/upgrade/overwrite/disappear
3991 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3992 stage of <tt>dpkg --install</tt>) is as follows. In each
3993 case, if a major error occurs (unless listed below) the
3994 actions are, in general, run backwards - this means that the
3995 maintainer scripts are run with different arguments in
3996 reverse order. These are the "error unwind" calls listed
4003 If a version of the package is already installed, call
4004 <example compact="compact">
4005 <var>old-prerm</var> upgrade <var>new-version</var>
4009 If the script runs but exits with a non-zero
4010 exit status, <prgn>dpkg</prgn> will attempt:
4011 <example compact="compact">
4012 <var>new-prerm</var> failed-upgrade <var>old-version</var>
4014 If this works, the upgrade continues. If this
4015 does not work, the error unwind:
4016 <example compact="compact">
4017 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4019 If this works, then the old-version is
4020 "Installed", if not, the old version is in a
4021 "Half-Configured" state.
4027 If a "conflicting" package is being removed at the same time,
4028 or if any package will be broken (due to <tt>Breaks</tt>):
4031 If <tt>--auto-deconfigure</tt> is
4032 specified, call, for each package to be deconfigured
4033 due to <tt>Breaks</tt>:
4034 <example compact="compact">
4035 <var>deconfigured's-prerm</var> deconfigure \
4036 in-favour <var>package-being-installed</var> <var>version</var>
4039 <example compact="compact">
4040 <var>deconfigured's-postinst</var> abort-deconfigure \
4041 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
4043 The deconfigured packages are marked as
4044 requiring configuration, so that if
4045 <tt>--install</tt> is used they will be
4046 configured again if possible.
4049 If any packages depended on a conflicting
4050 package being removed and <tt>--auto-deconfigure</tt> is
4051 specified, call, for each such package:
4052 <example compact="compact">
4053 <var>deconfigured's-prerm</var> deconfigure \
4054 in-favour <var>package-being-installed</var> <var>version</var> \
4055 removing <var>conflicting-package</var> <var>version</var>
4058 <example compact="compact">
4059 <var>deconfigured's-postinst</var> abort-deconfigure \
4060 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
4061 removing <var>conflicting-package</var> <var>version</var>
4063 The deconfigured packages are marked as
4064 requiring configuration, so that if
4065 <tt>--install</tt> is used they will be
4066 configured again if possible.
4069 To prepare for removal of each conflicting package, call:
4070 <example compact="compact">
4071 <var>conflictor's-prerm</var> remove \
4072 in-favour <var>package</var> <var>new-version</var>
4075 <example compact="compact">
4076 <var>conflictor's-postinst</var> abort-remove \
4077 in-favour <var>package</var> <var>new-version</var>
4086 If the package is being upgraded, call:
4087 <example compact="compact">
4088 <var>new-preinst</var> upgrade <var>old-version</var>
4090 If this fails, we call:
4092 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4099 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4101 is called. If this works, then the old version
4102 is in an "Installed" state, or else it is left
4103 in an "Unpacked" state.
4108 If it fails, then the old version is left
4109 in an "Half-Installed" state.
4116 Otherwise, if the package had some configuration
4117 files from a previous version installed (i.e., it
4118 is in the "configuration files only" state):
4119 <example compact="compact">
4120 <var>new-preinst</var> install <var>old-version</var>
4124 <var>new-postrm</var> abort-install <var>old-version</var>
4126 If this fails, the package is left in a
4127 "Half-Installed" state, which requires a
4128 reinstall. If it works, the packages is left in
4129 a "Config-Files" state.
4132 Otherwise (i.e., the package was completely purged):
4133 <example compact="compact">
4134 <var>new-preinst</var> install
4137 <example compact="compact">
4138 <var>new-postrm</var> abort-install
4140 If the error-unwind fails, the package is in a
4141 "Half-Installed" phase, and requires a
4142 reinstall. If the error unwind works, the
4143 package is in a not installed state.
4150 The new package's files are unpacked, overwriting any
4151 that may be on the system already, for example any
4152 from the old version of the same package or from
4153 another package. Backups of the old files are kept
4154 temporarily, and if anything goes wrong the package
4155 management system will attempt to put them back as
4156 part of the error unwind.
4160 It is an error for a package to contain files which
4161 are on the system in another package, unless
4162 <tt>Replaces</tt> is used (see <ref id="replaces">).
4164 The following paragraph is not currently the case:
4165 Currently the <tt>- - force-overwrite</tt> flag is
4166 enabled, downgrading it to a warning, but this may not
4172 It is a more serious error for a package to contain a
4173 plain file or other kind of non-directory where another
4174 package has a directory (again, unless
4175 <tt>Replaces</tt> is used). This error can be
4176 overridden if desired using
4177 <tt>--force-overwrite-dir</tt>, but this is not
4182 Packages which overwrite each other's files produce
4183 behavior which, though deterministic, is hard for the
4184 system administrator to understand. It can easily
4185 lead to "missing" programs if, for example, a package
4186 is unpacked which overwrites a file from another
4187 package, and is then removed again.<footnote>
4188 Part of the problem is due to what is arguably a
4189 bug in <prgn>dpkg</prgn>.
4194 A directory will never be replaced by a symbolic link
4195 to a directory or vice versa; instead, the existing
4196 state (symlink or not) will be left alone and
4197 <prgn>dpkg</prgn> will follow the symlink if there is
4206 If the package is being upgraded, call
4207 <example compact="compact">
4208 <var>old-postrm</var> upgrade <var>new-version</var>
4212 If this fails, <prgn>dpkg</prgn> will attempt:
4213 <example compact="compact">
4214 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4216 If this works, installation continues. If not,
4218 <example compact="compact">
4219 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4221 If this fails, the old version is left in a
4222 "Half-Installed" state. If it works, dpkg now
4224 <example compact="compact">
4225 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4227 If this fails, the old version is left in a
4228 "Half-Installed" state. If it works, dpkg now
4230 <example compact="compact">
4231 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4233 If this fails, the old version is in an
4240 This is the point of no return - if
4241 <prgn>dpkg</prgn> gets this far, it won't back off
4242 past this point if an error occurs. This will
4243 leave the package in a fairly bad state, which
4244 will require a successful re-installation to clear
4245 up, but it's when <prgn>dpkg</prgn> starts doing
4246 things that are irreversible.
4251 Any files which were in the old version of the package
4252 but not in the new are removed.
4256 The new file list replaces the old.
4260 The new maintainer scripts replace the old.
4264 Any packages all of whose files have been overwritten
4265 during the installation, and which aren't required for
4266 dependencies, are considered to have been removed.
4267 For each such package
4270 <prgn>dpkg</prgn> calls:
4271 <example compact="compact">
4272 <var>disappearer's-postrm</var> disappear \
4273 <var>overwriter</var> <var>overwriter-version</var>
4277 The package's maintainer scripts are removed.
4280 It is noted in the status database as being in a
4281 sane state, namely not installed (any conffiles
4282 it may have are ignored, rather than being
4283 removed by <prgn>dpkg</prgn>). Note that
4284 disappearing packages do not have their prerm
4285 called, because <prgn>dpkg</prgn> doesn't know
4286 in advance that the package is going to
4293 Any files in the package we're unpacking that are also
4294 listed in the file lists of other packages are removed
4295 from those lists. (This will lobotomize the file list
4296 of the "conflicting" package if there is one.)
4300 The backup files made during installation, above, are
4306 The new package's status is now sane, and recorded as
4311 Here is another point of no return - if the
4312 conflicting package's removal fails we do not unwind
4313 the rest of the installation; the conflicting package
4314 is left in a half-removed limbo.
4319 If there was a conflicting package we go and do the
4320 removal actions (described below), starting with the
4321 removal of the conflicting package's files (any that
4322 are also in the package being unpacked have already
4323 been removed from the conflicting package's file list,
4324 and so do not get removed now).
4330 <sect id="configdetails"><heading>Details of configuration</heading>
4333 When we configure a package (this happens with <tt>dpkg
4334 --install</tt> and <tt>dpkg --configure</tt>), we first
4335 update any <tt>conffile</tt>s and then call:
4336 <example compact="compact">
4337 <var>postinst</var> configure <var>most-recently-configured-version</var>
4342 No attempt is made to unwind after errors during
4343 configuration. If the configuration fails, the package is in
4344 a "Failed Config" state, and an error message is generated.
4348 If there is no most recently configured version
4349 <prgn>dpkg</prgn> will pass a null argument.
4352 Historical note: Truly ancient (pre-1997) versions of
4353 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4354 (including the angle brackets) in this case. Even older
4355 ones did not pass a second argument at all, under any
4356 circumstance. Note that upgrades using such an old dpkg
4357 version are unlikely to work for other reasons, even if
4358 this old argument behavior is handled by your postinst script.
4364 <sect id="removedetails"><heading>Details of removal and/or
4365 configuration purging</heading>
4371 <example compact="compact">
4372 <var>prerm</var> remove
4376 If prerm fails during replacement due to conflict
4378 <var>conflictor's-postinst</var> abort-remove \
4379 in-favour <var>package</var> <var>new-version</var>
4383 <var>postinst</var> abort-remove
4387 If this fails, the package is in a "Half-Configured"
4388 state, or else it remains "Installed".
4392 The package's files are removed (except <tt>conffile</tt>s).
4395 <example compact="compact">
4396 <var>postrm</var> remove
4400 If it fails, there's no error unwind, and the package is in
4401 an "Half-Installed" state.
4406 All the maintainer scripts except the <prgn>postrm</prgn>
4411 If we aren't purging the package we stop here. Note
4412 that packages which have no <prgn>postrm</prgn> and no
4413 <tt>conffile</tt>s are automatically purged when
4414 removed, as there is no difference except for the
4415 <prgn>dpkg</prgn> status.
4419 The <tt>conffile</tt>s and any backup files
4420 (<tt>~</tt>-files, <tt>#*#</tt> files,
4421 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4426 <example compact="compact">
4427 <var>postrm</var> purge
4431 If this fails, the package remains in a "Config-Files"
4436 The package's file list is removed.
4445 <chapt id="relationships">
4446 <heading>Declaring relationships between packages</heading>
4448 <sect id="depsyntax">
4449 <heading>Syntax of relationship fields</heading>
4452 These fields all have a uniform syntax. They are a list of
4453 package names separated by commas.
4457 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4458 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4459 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4460 control fields of the package, which declare
4461 dependencies on other packages, the package names listed may
4462 also include lists of alternative package names, separated
4463 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4464 if any one of the alternative packages is installed, that
4465 part of the dependency is considered to be satisfied.
4469 All of the fields except for <tt>Provides</tt> may restrict
4470 their applicability to particular versions of each named
4471 package. This is done in parentheses after each individual
4472 package name; the parentheses should contain a relation from
4473 the list below followed by a version number, in the format
4474 described in <ref id="f-Version">.
4478 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4479 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4480 strictly earlier, earlier or equal, exactly equal, later or
4481 equal and strictly later, respectively. The deprecated
4482 forms <tt><</tt> and <tt>></tt> were used to mean
4483 earlier/later or equal, rather than strictly earlier/later,
4484 so they should not appear in new packages (though
4485 <prgn>dpkg</prgn> still supports them).
4489 Whitespace may appear at any point in the version
4490 specification subject to the rules in <ref
4491 id="controlsyntax">, and must appear where it's necessary to
4492 disambiguate; it is not otherwise significant. All of the
4493 relationship fields may span multiple lines. For
4494 consistency and in case of future changes to
4495 <prgn>dpkg</prgn> it is recommended that a single space be
4496 used after a version relationship and before a version
4497 number; it is also conventional to put a single space after
4498 each comma, on either side of each vertical bar, and before
4499 each open parenthesis. When wrapping a relationship field, it
4500 is conventional to do so after a comma and before the space
4501 following that comma.
4505 For example, a list of dependencies might appear as:
4506 <example compact="compact">
4509 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4514 Relationships may be restricted to a certain set of
4515 architectures. This is indicated in brackets after each
4516 individual package name and the optional version specification.
4517 The brackets enclose a list of Debian architecture names
4518 separated by whitespace. Exclamation marks may be prepended to
4519 each of the names. (It is not permitted for some names to be
4520 prepended with exclamation marks while others aren't.)
4524 For build relationship fields
4525 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4526 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>), if
4527 the current Debian host architecture is not in this list and
4528 there are no exclamation marks in the list, or it is in the list
4529 with a prepended exclamation mark, the package name and the
4530 associated version specification are ignored completely for the
4531 purposes of defining the relationships.
4536 <example compact="compact">
4538 Build-Depends-Indep: texinfo
4539 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4540 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4542 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4543 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4544 <tt>gnumach-dev</tt> only on hurd-i386.
4548 For binary relationship fields, the architecture restriction
4549 syntax is only supported in the source package control
4550 file <file>debian/control</file>. When the corresponding binary
4551 package control file is generated, the relationship will either
4552 be omitted or included without the architecture restriction
4553 based on the architecture of the binary package. This means
4554 that architecture restrictions must not be used in binary
4555 relationship fields for architecture-independent packages
4556 (<tt>Architecture: all</tt>).
4561 <example compact="compact">
4562 Depends: foo [i386], bar [amd64]
4564 becomes <tt>Depends: foo</tt> when the package is built on
4565 the <tt>i386</tt> architecture, <tt>Depends: bar</tt> when the
4566 package is built on the <tt>amd64</tt> architecture, and omitted
4567 entirely in binary packages built on all other architectures.
4571 If the architecture-restricted dependency is part of a set of
4572 alternatives using <tt>|</tt>, that alternative is ignored
4573 completely on architectures that do not match the restriction.
4575 <example compact="compact">
4576 Build-Depends: foo [!i386] | bar [!amd64]
4578 is equivalent to <tt>bar</tt> on the i386 architecture, to
4579 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4580 bar</tt> on all other architectures.
4584 Relationships may also be restricted to a certain set of
4585 architectures using architecture wildcards. The syntax for
4586 declaring such restrictions is the same as declaring
4587 restrictions using a certain set of architectures without
4588 architecture wildcards. For example:
4589 <example compact="compact">
4590 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4592 is equivalent to <tt>foo</tt> on architectures using the Linux
4593 kernel and any cpu, <tt>bar</tt> on architectures using any
4594 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4595 using a kernel other than Linux.
4599 Note that the binary package relationship fields such as
4600 <tt>Depends</tt> appear in one of the binary package
4601 sections of the control file, whereas the build-time
4602 relationships such as <tt>Build-Depends</tt> appear in the
4603 source package section of the control file (which is the
4608 <sect id="binarydeps">
4609 <heading>Binary Dependencies - <tt>Depends</tt>,
4610 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4611 <tt>Pre-Depends</tt>
4615 Packages can declare in their control file that they have
4616 certain relationships to other packages - for example, that
4617 they may not be installed at the same time as certain other
4618 packages, and/or that they depend on the presence of others.
4622 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4623 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4624 <tt>Breaks</tt> and <tt>Conflicts</tt> control fields.
4625 <tt>Breaks</tt> is described in <ref id="breaks">, and
4626 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4627 rest are described below.
4631 These seven fields are used to declare a dependency
4632 relationship by one package on another. Except for
4633 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4634 depending (binary) package's control file.
4635 (<tt>Enhances</tt> appears in the recommending package's
4636 control file, and <tt>Breaks</tt> appears in the version of
4637 depended-on package which causes the named package to
4642 A <tt>Depends</tt> field takes effect <em>only</em> when a
4643 package is to be configured. It does not prevent a package
4644 being on the system in an unconfigured state while its
4645 dependencies are unsatisfied, and it is possible to replace
4646 a package whose dependencies are satisfied and which is
4647 properly installed with a different version whose
4648 dependencies are not and cannot be satisfied; when this is
4649 done the depending package will be left unconfigured (since
4650 attempts to configure it will give errors) and will not
4651 function properly. If it is necessary, a
4652 <tt>Pre-Depends</tt> field can be used, which has a partial
4653 effect even when a package is being unpacked, as explained
4654 in detail below. (The other three dependency fields,
4655 <tt>Recommends</tt>, <tt>Suggests</tt> and
4656 <tt>Enhances</tt>, are only used by the various front-ends
4657 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4658 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4662 Since <tt>Depends</tt> only places requirements on the order in
4663 which packages are configured, packages in an installation run
4664 are usually all unpacked first and all configured later.
4666 This approach makes dependency resolution easier. If two
4667 packages A and B are being upgraded, the installed package A
4668 depends on exactly the installed package B, and the new
4669 package A depends on exactly the new package B (a common
4670 situation when upgrading shared libraries and their
4671 corresponding development packages), satisfying the
4672 dependencies at every stage of the upgrade would be
4673 impossible. This relaxed restriction means that both new
4674 packages can be unpacked together and then configured in their
4680 If there is a circular dependency among packages being installed
4681 or removed, installation or removal order honoring the
4682 dependency order is impossible, requiring the dependency loop be
4683 broken at some point and the dependency requirements violated
4684 for at least one package. Packages involved in circular
4685 dependencies may not be able to rely on their dependencies being
4686 configured when being configured depending on which side of the
4687 break of the circular dependency loop they happen to be on. If
4688 one of the packages in the loop has no <prgn>postinst</prgn>
4689 script, then the cycle will be broken at that package; this
4690 ensures that all <prgn>postinst</prgn> scripts are run with
4691 their dependencies properly configured if this is possible.
4692 Otherwise the breaking point is arbitrary. Packages should
4693 therefore avoid circular dependencies where possible,
4694 particularly if they have <prgn>postinst</prgn> scripts.
4698 The meaning of the five dependency fields is as follows:
4700 <tag><tt>Depends</tt></tag>
4703 This declares an absolute dependency. A package will
4704 not be configured unless all of the packages listed in
4705 its <tt>Depends</tt> field have been correctly
4706 configured (unless there is a circular dependency as
4711 The <tt>Depends</tt> field should be used if the
4712 depended-on package is required for the depending
4713 package to provide a significant amount of
4718 The <tt>Depends</tt> field should also be used if the
4719 <prgn>postinst</prgn> or <prgn>prerm</prgn> scripts
4720 require the depended-on package to be unpacked or
4721 configured in order to run. In the case of <tt>postinst
4722 configure</tt>, the depended-on packages will be unpacked
4723 and configured first. (If both packages are involved in a
4724 dependency loop, this might not work as expected; see the
4725 explanation a few paragraphs back.) In the case
4726 of <prgn>prerm</prgn> or other <prgn>postinst</prgn>
4727 actions, the package dependencies will normally be at
4728 least unpacked, but they may be only "Half-Installed" if a
4729 previous upgrade of the dependency failed.
4733 <tag><tt>Recommends</tt></tag>
4736 This declares a strong, but not absolute, dependency.
4740 The <tt>Recommends</tt> field should list packages
4741 that would be found together with this one in all but
4742 unusual installations.
4746 <tag><tt>Suggests</tt></tag>
4748 This is used to declare that one package may be more
4749 useful with one or more others. Using this field
4750 tells the packaging system and the user that the
4751 listed packages are related to this one and can
4752 perhaps enhance its usefulness, but that installing
4753 this one without them is perfectly reasonable.
4756 <tag><tt>Enhances</tt></tag>
4758 This field is similar to Suggests but works in the
4759 opposite direction. It is used to declare that a
4760 package can enhance the functionality of another
4764 <tag><tt>Pre-Depends</tt></tag>
4767 This field is like <tt>Depends</tt>, except that it
4768 also forces <prgn>dpkg</prgn> to complete installation
4769 of the packages named before even starting the
4770 installation of the package which declares the
4771 pre-dependency, as follows:
4775 When a package declaring a pre-dependency is about to
4776 be <em>unpacked</em> the pre-dependency can be
4777 satisfied if the depended-on package is either fully
4778 configured, <em>or even if</em> the depended-on
4779 package(s) are only unpacked or in the "Half-Configured"
4780 state, provided that they have been configured
4781 correctly at some point in the past (and not removed
4782 or partially removed since). In this case, both the
4783 previously-configured and currently unpacked or
4784 "Half-Configured" versions must satisfy any version
4785 clause in the <tt>Pre-Depends</tt> field.
4789 When the package declaring a pre-dependency is about to
4790 be <em>configured</em>, the pre-dependency will be treated
4791 as a normal <tt>Depends</tt>. It will be considered
4792 satisfied only if the depended-on package has been
4793 correctly configured. However, unlike
4794 with <tt>Depends</tt>, <tt>Pre-Depends</tt> does not
4795 permit circular dependencies to be broken. If a circular
4796 dependency is encountered while attempting to honor
4797 <tt>Pre-Depends</tt>, the installation will be aborted.
4801 <tt>Pre-Depends</tt> are also required if the
4802 <prgn>preinst</prgn> script depends on the named package.
4803 It is best to avoid this situation if possible.
4807 <tt>Pre-Depends</tt> should be used sparingly,
4808 preferably only by packages whose premature upgrade or
4809 installation would hamper the ability of the system to
4810 continue with any upgrade that might be in progress.
4817 When selecting which level of dependency to use you should
4818 consider how important the depended-on package is to the
4819 functionality of the one declaring the dependency. Some
4820 packages are composed of components of varying degrees of
4821 importance. Such a package should list using
4822 <tt>Depends</tt> the package(s) which are required by the
4823 more important components. The other components'
4824 requirements may be mentioned as Suggestions or
4825 Recommendations, as appropriate to the components' relative
4831 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4834 When one binary package declares that it breaks another,
4835 <prgn>dpkg</prgn> will refuse to allow the package which
4836 declares <tt>Breaks</tt> to be unpacked unless the broken
4837 package is deconfigured first, and it will refuse to
4838 allow the broken package to be reconfigured.
4842 A package will not be regarded as causing breakage merely
4843 because its configuration files are still installed; it must
4844 be at least "Half-Installed".
4848 A special exception is made for packages which declare that
4849 they break their own package name or a virtual package which
4850 they provide (see below): this does not count as a real
4855 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4856 version clause; such a <tt>Breaks</tt> is introduced in the
4857 version of an (implicit or explicit) dependency which violates
4858 an assumption or reveals a bug in earlier versions of the broken
4859 package, or which takes over a file from earlier versions of the
4860 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
4861 will inform higher-level package management tools that the
4862 broken package must be upgraded before the new one.
4866 If the breaking package also overwrites some files from the
4867 older package, it should use <tt>Replaces</tt> to ensure this
4868 goes smoothly. See <ref id="replaces"> for a full discussion
4869 of taking over files from other packages, including how to
4870 use <tt>Breaks</tt> in those cases.
4874 Many of the cases where <tt>Breaks</tt> should be used were
4875 previously handled with <tt>Conflicts</tt>
4876 because <tt>Breaks</tt> did not yet exist.
4877 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
4878 See <ref id="conflicts"> for more information about the
4883 <sect id="conflicts">
4884 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4887 When one binary package declares a conflict with another using
4888 a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will refuse to
4889 allow them to be unpacked on the system at the same time. This
4890 is a stronger restriction than <tt>Breaks</tt>, which prevents
4891 the broken package from being configured while the breaking
4892 package is in the "Unpacked" state but allows both packages to
4893 be unpacked at the same time.
4897 If one package is to be unpacked, the other must be removed
4898 first. If the package being unpacked is marked as replacing
4899 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
4900 normally be used in this case) the one on the system, or the one
4901 on the system is marked as deselected, or both packages are
4902 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
4903 automatically remove the package which is causing the conflict.
4904 Otherwise, it will halt the installation of the new package with
4905 an error. This mechanism is specifically designed to produce an
4906 error when the installed package is <tt>Essential</tt>, but the
4911 A package will not cause a conflict merely because its
4912 configuration files are still installed; it must be at least
4917 A special exception is made for packages which declare a
4918 conflict with their own package name, or with a virtual
4919 package which they provide (see below): this does not
4920 prevent their installation, and allows a package to conflict
4921 with others providing a replacement for it. You use this
4922 feature when you want the package in question to be the only
4923 package providing some feature.
4927 Normally, <tt>Breaks</tt> should be used instead
4928 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
4929 stronger restriction on the ordering of package installation or
4930 upgrade and can make it more difficult for the package manager
4931 to find a correct solution to an upgrade or installation
4932 problem. <tt>Breaks</tt> should be used
4934 <item>when moving a file from one package to another (see
4935 <ref id="replaces">),</item>
4936 <item>when splitting a package (a special case of the previous
4938 <item>when the breaking package exposes a bug in or interacts
4939 badly with particular versions of the broken
4942 <tt>Conflicts</tt> should be used
4944 <item>when two packages provide the same file and will
4945 continue to do so,</item>
4946 <item>in conjunction with <tt>Provides</tt> when only one
4947 package providing a given virtual facility may be unpacked
4948 at a time (see <ref id="virtual">),</item>
4949 <item>in other cases where one must prevent simultaneous
4950 installation of two packages for reasons that are ongoing
4951 (not fixed in a later version of one of the packages) or
4952 that must prevent both packages from being unpacked at the
4953 same time, not just configured.</item>
4955 Be aware that adding <tt>Conflicts</tt> is normally not the best
4956 solution when two packages provide the same files. Depending on
4957 the reason for that conflict, using alternatives or renaming the
4958 files is often a better approach. See, for
4959 example, <ref id="binaries">.
4963 Neither <tt>Breaks</tt> nor <tt>Conflicts</tt> should be used
4964 unless two packages cannot be installed at the same time or
4965 installing them both causes one of them to be broken or
4966 unusable. Having similar functionality or performing the same
4967 tasks as another package is not sufficient reason to
4968 declare <tt>Breaks</tt> or <tt>Conflicts</tt> with that package.
4972 A <tt>Conflicts</tt> entry may have an "earlier than" version
4973 clause if the reason for the conflict is corrected in a later
4974 version of one of the packages. However, normally the presence
4975 of an "earlier than" version clause is a sign
4976 that <tt>Breaks</tt> should have been used instead. An "earlier
4977 than" version clause in <tt>Conflicts</tt>
4978 prevents <prgn>dpkg</prgn> from upgrading or installing the
4979 package which declares such a conflict until the upgrade or
4980 removal of the conflicted-with package has been completed, which
4981 is a strong restriction.
4985 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4989 As well as the names of actual ("concrete") packages, the
4990 package relationship fields <tt>Depends</tt>,
4991 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4992 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4993 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4994 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4995 may mention "virtual packages".
4999 A <em>virtual package</em> is one which appears in the
5000 <tt>Provides</tt> control field of another package. The effect
5001 is as if the package(s) which provide a particular virtual
5002 package name had been listed by name everywhere the virtual
5003 package name appears. (See also <ref id="virtual_pkg">)
5007 If there are both concrete and virtual packages of the same
5008 name, then the dependency may be satisfied (or the conflict
5009 caused) by either the concrete package with the name in
5010 question or any other concrete package which provides the
5011 virtual package with the name in question. This is so that,
5012 for example, supposing we have
5013 <example compact="compact">
5016 </example> and someone else releases an enhanced version of
5017 the <tt>bar</tt> package they can say:
5018 <example compact="compact">
5022 and the <tt>bar-plus</tt> package will now also satisfy the
5023 dependency for the <tt>foo</tt> package.
5027 If a relationship field has a version number attached, only real
5028 packages will be considered to see whether the relationship is
5029 satisfied (or the prohibition violated, for a conflict or
5030 breakage). In other words, if a version number is specified,
5031 this is a request to ignore all <tt>Provides</tt> for that
5032 package name and consider only real packages. The package
5033 manager will assume that a package providing that virtual
5034 package is not of the "right" version. A <tt>Provides</tt>
5035 field may not contain version numbers, and the version number of
5036 the concrete package which provides a particular virtual package
5037 will not be considered when considering a dependency on or
5038 conflict with the virtual package name.<footnote>
5039 It is possible that a future release of <prgn>dpkg</prgn> may
5040 add the ability to specify a version number for each virtual
5041 package it provides. This feature is not yet present,
5042 however, and is expected to be used only infrequently.
5047 To specify which of a set of real packages should be the default
5048 to satisfy a particular dependency on a virtual package, list
5049 the real package as an alternative before the virtual one.
5053 If the virtual package represents a facility that can only be
5054 provided by one real package at a time, such as
5055 the <package>mail-transport-agent</package> virtual package that
5056 requires installation of a binary that would conflict with all
5057 other providers of that virtual package (see
5058 <ref id="mail-transport-agents">), all packages providing that
5059 virtual package should also declare a conflict with it
5060 using <tt>Conflicts</tt>. This will ensure that at most one
5061 provider of that virtual package is unpacked or installed at a
5066 <sect id="replaces"><heading>Overwriting files and replacing
5067 packages - <tt>Replaces</tt></heading>
5070 Packages can declare in their control file that they should
5071 overwrite files in certain other packages, or completely replace
5072 other packages. The <tt>Replaces</tt> control field has these
5073 two distinct purposes.
5076 <sect1><heading>Overwriting files in other packages</heading>
5079 It is usually an error for a package to contain files which
5080 are on the system in another package. However, if the
5081 overwriting package declares that it <tt>Replaces</tt> the one
5082 containing the file being overwritten, then <prgn>dpkg</prgn>
5083 will replace the file from the old package with that from the
5084 new. The file will no longer be listed as "owned" by the old
5085 package and will be taken over by the new package.
5086 Normally, <tt>Breaks</tt> should be used in conjunction
5087 with <tt>Replaces</tt>.<footnote>
5088 To see why <tt>Breaks</tt> is normally needed in addition
5089 to <tt>Replaces</tt>, consider the case of a file in the
5090 package <package>foo</package> being taken over by the
5091 package <package>foo-data</package>.
5092 <tt>Replaces</tt> will allow <package>foo-data</package> to
5093 be installed and take over that file. However,
5094 without <tt>Breaks</tt>, nothing
5095 requires <package>foo</package> to be upgraded to a newer
5096 version that knows it does not include that file and instead
5097 depends on <package>foo-data</package>. Nothing would
5098 prevent the new <package>foo-data</package> package from
5099 being installed and then removed, removing the file that it
5100 took over from <package>foo</package>. After that
5101 operation, the package manager would think the system was in
5102 a consistent state, but the <package>foo</package> package
5103 would be missing one of its files.
5108 For example, if a package <package>foo</package> is split
5109 into <package>foo</package> and <package>foo-data</package>
5110 starting at version 1.2-3, <package>foo-data</package> would
5112 <example compact="compact">
5113 Replaces: foo (<< 1.2-3)
5114 Breaks: foo (<< 1.2-3)
5116 in its control file. The new version of the
5117 package <package>foo</package> would normally have the field
5118 <example compact="compact">
5119 Depends: foo-data (>= 1.2-3)
5121 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
5122 the files moved into <package>foo-data</package> are not
5123 required for normal operation).
5127 If a package is completely replaced in this way, so that
5128 <prgn>dpkg</prgn> does not know of any files it still
5129 contains, it is considered to have "disappeared". It will
5130 be marked as not wanted on the system (selected for
5131 removal) and not installed. Any <tt>conffile</tt>s
5132 details noted for the package will be ignored, as they
5133 will have been taken over by the overwriting package. The
5134 package's <prgn>postrm</prgn> script will be run with a
5135 special argument to allow the package to do any final
5136 cleanup required. See <ref id="mscriptsinstact">.
5138 Replaces is a one way relationship. You have to install
5139 the replacing package after the replaced package.
5144 For this usage of <tt>Replaces</tt>, virtual packages (see
5145 <ref id="virtual">) are not considered when looking at a
5146 <tt>Replaces</tt> field. The packages declared as being
5147 replaced must be mentioned by their real names.
5151 This usage of <tt>Replaces</tt> only takes effect when both
5152 packages are at least partially on the system at once. It is
5153 not relevant if the packages conflict unless the conflict has
5158 <sect1><heading>Replacing whole packages, forcing their
5162 Second, <tt>Replaces</tt> allows the packaging system to
5163 resolve which package should be removed when there is a
5164 conflict (see <ref id="conflicts">). This usage only takes
5165 effect when the two packages <em>do</em> conflict, so that the
5166 two usages of this field do not interfere with each other.
5170 In this situation, the package declared as being replaced
5171 can be a virtual package, so for example, all mail
5172 transport agents (MTAs) would have the following fields in
5173 their control files:
5174 <example compact="compact">
5175 Provides: mail-transport-agent
5176 Conflicts: mail-transport-agent
5177 Replaces: mail-transport-agent
5179 ensuring that only one MTA can be unpacked at any one
5180 time. See <ref id="virtual"> for more information about this
5185 <sect id="sourcebinarydeps">
5186 <heading>Relationships between source and binary packages -
5187 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5188 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5192 Source packages that require certain binary packages to be
5193 installed or absent at the time of building the package
5194 can declare relationships to those binary packages.
5198 This is done using the <tt>Build-Depends</tt>,
5199 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5200 <tt>Build-Conflicts-Indep</tt> control fields.
5204 Build-dependencies on "build-essential" binary packages can be
5205 omitted. Please see <ref id="pkg-relations"> for more information.
5209 The dependencies and conflicts they define must be satisfied
5210 (as defined earlier for binary packages) in order to invoke
5211 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5213 There is no Build-Depends-Arch; this role is essentially
5214 met with Build-Depends. Anyone building the
5215 <tt>build-indep</tt> and <tt>binary-indep</tt> targets is
5216 assumed to be building the whole package, and therefore
5217 installation of all build dependencies is required.
5220 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5221 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5222 not yet know how to check for its existence, and
5223 <tt>binary-arch</tt>. The purpose of the original split
5224 between <tt>Build-Depends</tt> and
5225 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5226 wouldn't need to install extra packages needed only for the
5227 binary-indep targets. But without a build-arch/build-indep
5228 split, this didn't work, since most of the work is done in
5229 the build target, not in the binary target.
5233 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5234 <tt>binary-arch</tt></tag>
5236 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5237 fields must be satisfied when these targets are invoked.
5239 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5240 and <tt>binary-indep</tt></tag>
5242 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5243 <tt>Build-Depends-Indep</tt>, and
5244 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5245 these targets are invoked.
5253 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5256 Packages containing shared libraries must be constructed with
5257 a little care to make sure that the shared library is always
5258 available. This is especially important for packages whose
5259 shared libraries are vitally important, such as the C library
5260 (currently <tt>libc6</tt>).
5264 This section deals only with public shared libraries: shared
5265 libraries that are placed in directories searched by the dynamic
5266 linker by default or which are intended to be linked against
5267 normally and possibly used by other, independent packages. Shared
5268 libraries that are internal to a particular package or that are
5269 only loaded as dynamic modules are not covered by this section and
5270 are not subject to its requirements.
5274 A shared library is identified by the <tt>SONAME</tt> attribute
5275 stored in its dynamic section. When a binary is linked against a
5276 shared library, the <tt>SONAME</tt> of the shared library is
5277 recorded in the binary's <tt>NEEDED</tt> section so that the
5278 dynamic linker knows that library must be loaded at runtime. The
5279 shared library file's full name (which usually contains additional
5280 version information not needed in the <tt>SONAME</tt>) is
5281 therefore normally not referenced directly. Instead, the shared
5282 library is loaded by its <tt>SONAME</tt>, which exists on the file
5283 system as a symlink pointing to the full name of the shared
5284 library. This symlink must be provided by the
5285 package. <ref id="sharedlibs-runtime"> describes how to do this.
5287 This is a convention of shared library versioning, but not a
5288 requirement. Some libraries use the <tt>SONAME</tt> as the full
5289 library file name instead and therefore do not need a symlink.
5290 Most, however, encode additional information about
5291 backwards-compatible revisions as a minor version number in the
5292 file name. The <tt>SONAME</tt> itself only changes when
5293 binaries linked with the earlier version of the shared library
5294 may no longer work, but the filename may change with each
5295 release of the library. See <ref id="sharedlibs-runtime"> for
5301 When linking a binary or another shared library against a shared
5302 library, the <tt>SONAME</tt> for that shared library is not yet
5303 known. Instead, the shared library is found by looking for a file
5304 matching the library name with <tt>.so</tt> appended. This file
5305 exists on the file system as a symlink pointing to the shared
5310 Shared libraries are normally split into several binary packages.
5311 The <tt>SONAME</tt> symlink is installed by the runtime shared
5312 library package, and the bare <tt>.so</tt> symlink is installed in
5313 the development package since it's only used when linking binaries
5314 or shared libraries. However, there are some exceptions for
5315 unusual shared libraries or for shared libraries that are also
5316 loaded as dynamic modules by other programs.
5320 This section is primarily concerned with how the separation of
5321 shared libraries into multiple packages should be done and how
5322 dependencies on and between shared library binary packages are
5323 managed in Debian. <ref id="libraries"> should be read in
5324 conjunction with this section and contains additional rules for
5325 the files contained in the shared library packages.
5328 <sect id="sharedlibs-runtime">
5329 <heading>Run-time shared libraries</heading>
5332 The run-time shared library must be placed in a package
5333 whose name changes whenever the <tt>SONAME</tt> of the shared
5334 library changes. This allows several versions of the shared
5335 library to be installed at the same time, allowing installation
5336 of the new version of the shared library without immediately
5337 breaking binaries that depend on the old version. Normally, the
5338 run-time shared library and its <tt>SONAME</tt> symlink should
5339 be placed in a package named
5340 <package><var>libraryname</var><var>soversion</var></package>,
5341 where <var>soversion</var> is the version number in
5342 the <tt>SONAME</tt> of the shared library.
5343 See <ref id="shlibs"> for detailed information on how to
5344 determine this version. Alternatively, if it would be confusing
5345 to directly append <var>soversion</var>
5346 to <var>libraryname</var> (if, for example, <var>libraryname</var>
5347 itself ends in a number), you should use
5348 <package><var>libraryname</var>-<var>soversion</var></package>
5353 If you have several shared libraries built from the same source
5354 tree, you may lump them all together into a single shared
5355 library package provided that all of their <tt>SONAME</tt>s will
5356 always change together. Be aware that this is not normally the
5357 case, and if the <tt>SONAME</tt>s do not change together,
5358 upgrading such a merged shared library package will be
5359 unnecessarily difficult because of file conflicts with the old
5360 version of the package. When in doubt, always split shared
5361 library packages so that each binary package installs a single
5366 Every time the shared library ABI changes in a way that may
5367 break binaries linked against older versions of the shared
5368 library, the <tt>SONAME</tt> of the library and the
5369 corresponding name for the binary package containing the runtime
5370 shared library should change. Normally, this means
5371 the <tt>SONAME</tt> should change any time an interface is
5372 removed from the shared library or the signature of an interface
5373 (the number of parameters or the types of parameters that it
5374 takes, for example) is changed. This practice is vital to
5375 allowing clean upgrades from older versions of the package and
5376 clean transitions between the old ABI and new ABI without having
5377 to upgrade every affected package simultaneously.
5381 The <tt>SONAME</tt> and binary package name need not, and indeed
5382 normally should not, change if new interfaces are added but none
5383 are removed or changed, since this will not break binaries
5384 linked against the old shared library. Correct versioning of
5385 dependencies on the newer shared library by binaries that use
5386 the new interfaces is handled via
5387 the <qref id="sharedlibs-shlibdeps"><tt>shlibs</tt>
5388 system</qref> or via symbols files (see
5389 <manref name="deb-symbols" section="5">).
5393 The package should install the shared libraries under
5394 their normal names. For example, the <package>libgdbm3</package>
5395 package should install <file>libgdbm.so.3.0.0</file> as
5396 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5397 renamed or re-linked by any <prgn>prerm</prgn> or
5398 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5399 of renaming things safely without affecting running programs,
5400 and attempts to interfere with this are likely to lead to
5405 Shared libraries should not be installed executable, since
5406 the dynamic linker does not require this and trying to
5407 execute a shared library usually results in a core dump.
5411 The run-time library package should include the symbolic link for
5412 the <tt>SONAME</tt> that <prgn>ldconfig</prgn> would create for
5413 the shared libraries. For example,
5414 the <package>libgdbm3</package> package should include a symbolic
5415 link from <file>/usr/lib/libgdbm.so.3</file> to
5416 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5417 linker (for example <prgn>ld.so</prgn> or
5418 <prgn>ld-linux.so.*</prgn>) can find the library between the
5419 time that <prgn>dpkg</prgn> installs it and the time that
5420 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5422 The package management system requires the library to be
5423 placed before the symbolic link pointing to it in the
5424 <file>.deb</file> file. This is so that when
5425 <prgn>dpkg</prgn> comes to install the symlink
5426 (overwriting the previous symlink pointing at an older
5427 version of the library), the new shared library is already
5428 in place. In the past, this was achieved by creating the
5429 library in the temporary packaging directory before
5430 creating the symlink. Unfortunately, this was not always
5431 effective, since the building of the tar file in the
5432 <file>.deb</file> depended on the behavior of the underlying
5433 file system. Some file systems (such as reiserfs) reorder
5434 the files so that the order of creation is forgotten.
5435 Since version 1.7.0, <prgn>dpkg</prgn>
5436 reorders the files itself as necessary when building a
5437 package. Thus it is no longer important to concern
5438 oneself with the order of file creation.
5442 <sect1 id="ldconfig">
5443 <heading><tt>ldconfig</tt></heading>
5446 Any package installing shared libraries in one of the default
5447 library directories of the dynamic linker (which are currently
5448 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5449 listed in <file>/etc/ld.so.conf</file><footnote>
5451 <list compact="compact">
5452 <item>/usr/local/lib</item>
5453 <item>/usr/lib/libc5-compat</item>
5454 <item>/lib/libc5-compat</item>
5457 must use <prgn>ldconfig</prgn> to update the shared library
5462 The package maintainer scripts must only call
5463 <prgn>ldconfig</prgn> under these circumstances:
5464 <list compact="compact">
5465 <item>When the <prgn>postinst</prgn> script is run with a
5466 first argument of <tt>configure</tt>, the script must call
5467 <prgn>ldconfig</prgn>, and may optionally invoke
5468 <prgn>ldconfig</prgn> at other times.
5470 <item>When the <prgn>postrm</prgn> script is run with a
5471 first argument of <tt>remove</tt>, the script should call
5472 <prgn>ldconfig</prgn>.
5477 During install or upgrade, the preinst is called before
5478 the new files are unpacked, so calling "ldconfig" is
5479 pointless. The preinst of an existing package can also be
5480 called if an upgrade fails. However, this happens during
5481 the critical time when a shared libs may exist on-disk
5482 under a temporary name. Thus, it is dangerous and
5483 forbidden by current policy to call "ldconfig" at this
5488 When a package is installed or upgraded, "postinst
5489 configure" runs after the new files are safely on-disk.
5490 Since it is perfectly safe to invoke ldconfig
5491 unconditionally in a postinst, it is OK for a package to
5492 simply put ldconfig in its postinst without checking the
5493 argument. The postinst can also be called to recover from
5494 a failed upgrade. This happens before any new files are
5495 unpacked, so there is no reason to call "ldconfig" at this
5500 For a package that is being removed, prerm is
5501 called with all the files intact, so calling ldconfig is
5502 useless. The other calls to "prerm" happen in the case of
5503 upgrade at a time when all the files of the old package
5504 are on-disk, so again calling "ldconfig" is pointless.
5508 postrm, on the other hand, is called with the "remove"
5509 argument just after the files are removed, so this is
5510 the proper time to call "ldconfig" to notify the system
5511 of the fact that the shared libraries from the package
5512 are removed. The postrm can be called at several other
5513 times. At the time of "postrm purge", "postrm
5514 abort-install", or "postrm abort-upgrade", calling
5515 "ldconfig" is useless because the shared lib files are
5516 not on-disk. However, when "postrm" is invoked with
5517 arguments "upgrade", "failed-upgrade", or "disappear", a
5518 shared lib may exist on-disk under a temporary filename.
5526 <sect id="sharedlibs-support-files">
5527 <heading>Shared library support files</heading>
5530 If your package contains files whose names do not change with
5531 each change in the library shared object version, you must not
5532 put them in the shared library package. Otherwise, several
5533 versions of the shared library cannot be installed at the same
5534 time without filename clashes, making upgrades and transitions
5535 unnecessarily difficult.
5539 It is recommended that supporting files and run-time support
5540 programs that do not need to be invoked manually by users, but
5541 are nevertheless required for the package to function, be placed
5542 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5543 preferably under <file>/usr/lib/</file><var>package-name</var>.
5544 If the program or file is architecture independent, the
5545 recommendation is for it to be placed in a subdirectory of
5546 <file>/usr/share</file> instead, preferably under
5547 <file>/usr/share/</file><var>package-name</var>. Following the
5548 <var>package-name</var> naming convention ensures that the file
5549 names change when the shared object version changes.
5553 Run-time support programs that use the shared library but are
5554 not required for the library to function or files used by the
5555 shared library that can be used by any version of the shared
5556 library package should instead be put in a separate package.
5557 This package might typically be named
5558 <package><var>libraryname</var>-tools</package>; note the
5559 absence of the <var>soversion</var> in the package name.
5563 Files and support programs only useful when compiling software
5564 against the library should be included in the development
5565 package for the library.<footnote>
5566 For example, a <file><var>package-name</var>-config</file>
5567 script or <package>pkg-config</package> configuration files.
5572 <sect id="sharedlibs-static">
5573 <heading>Static libraries</heading>
5576 The static library (<file><var>libraryname.a</var></file>)
5577 is usually provided in addition to the shared version.
5578 It is placed into the development package (see below).
5582 In some cases, it is acceptable for a library to be
5583 available in static form only; these cases include:
5585 <item>libraries for languages whose shared library support
5586 is immature or unstable</item>
5587 <item>libraries whose interfaces are in flux or under
5588 development (commonly the case when the library's
5589 major version number is zero, or where the ABI breaks
5590 across patchlevels)</item>
5591 <item>libraries which are explicitly intended to be
5592 available only in static form by their upstream
5597 <sect id="sharedlibs-dev">
5598 <heading>Development files</heading>
5601 If there are development files associated with a shared library,
5602 the source package needs to generate a binary development package
5603 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5604 or if you prefer only to support one development version at a
5605 time, <package><var>libraryname</var>-dev</package>. Installing
5606 the development package must result in installation of all the
5607 development files necessary for compiling programs against that
5608 shared library.<footnote>
5609 This wording allows the development files to be split into
5610 several packages, such as a separate architecture-independent
5611 <package><var>libraryname</var>-headers</package>, provided that
5612 the development package depends on all the required additional
5618 In case several development versions of a library exist, you may
5619 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5620 <ref id="conflicts">) to ensure that the user only installs one
5621 development version at a time (as different development versions are
5622 likely to have the same header files in them, which would cause a
5623 filename clash if both were unpacked).
5627 The development package should contain a symlink for the associated
5628 shared library without a version number. For example, the
5629 <package>libgdbm-dev</package> package should include a symlink
5630 from <file>/usr/lib/libgdbm.so</file> to
5631 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5632 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5633 <file>libgdbm.so</file> when compiling dynamically.
5637 If the package provides Ada Library Information
5638 (<file>*.ali</file>) files for use with GNAT, these files must be
5639 installed read-only (mode 0444) so that GNAT will not attempt to
5640 recompile them. This overrides the normal file mode requirements
5641 given in <ref id="permissions-owners">.
5645 <sect id="sharedlibs-intradeps">
5646 <heading>Dependencies between the packages of the same library</heading>
5649 Typically the development version should have an exact
5650 version dependency on the runtime library, to make sure that
5651 compilation and linking happens correctly. The
5652 <tt>${binary:Version}</tt> substitution variable can be
5653 useful for this purpose.
5655 Previously, <tt>${Source-Version}</tt> was used, but its name
5656 was confusing and it has been deprecated since dpkg 1.13.19.
5661 <sect id="sharedlibs-shlibdeps">
5662 <heading>Dependencies between the library and other packages -
5663 the <tt>shlibs</tt> system</heading>
5666 If a package contains a binary or library which links to a
5667 shared library, we must ensure that when the package is
5668 installed on the system, all of the libraries needed are
5669 also installed. This requirement led to the creation of the
5670 <tt>shlibs</tt> system, which is very simple in its design:
5671 any package which <em>provides</em> a shared library also
5672 provides information on the package dependencies required to
5673 ensure the presence of this library, and any package which
5674 <em>uses</em> a shared library uses this information to
5675 determine the dependencies it requires. The files which
5676 contain the mapping from shared libraries to the necessary
5677 dependency information are called <file>shlibs</file> files.
5681 When a package is built which contains any shared libraries, it
5682 must provide a <file>shlibs</file> file for other packages to
5683 use. When a package is built which contains any shared
5684 libraries or compiled binaries, it must run
5685 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5686 on these to determine the libraries used and hence the
5687 dependencies needed by this package.<footnote>
5689 <prgn>dpkg-shlibdeps</prgn> will use a program
5690 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
5691 the libraries directly needed by the binaries or shared
5692 libraries in the package.
5696 We say that a binary <tt>foo</tt> <em>directly</em> uses
5697 a library <tt>libbar</tt> if it is explicitly linked
5698 with that library (that is, the library is listed in the ELF
5699 <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
5700 to the link line when the binary is created). Other
5701 libraries that are needed by <tt>libbar</tt> are linked
5702 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5703 linker will load them automatically when it loads
5704 <tt>libbar</tt>. A package should depend on the libraries
5705 it directly uses, but not the libraries it indirectly uses.
5706 The dependencies for those libraries will automatically pull
5707 in the other libraries.
5711 A good example of where this helps is the following. We
5712 could update <tt>libimlib</tt> with a new version that
5713 supports a new graphics format called dgf (but retaining the
5714 same major version number) and depends on <tt>libdgf</tt>.
5715 If we used <prgn>ldd</prgn> to add dependencies for every
5716 library directly or indirectly linked with a binary, every
5717 package that uses <tt>libimlib</tt> would need to be
5718 recompiled so it would also depend on <tt>libdgf</tt> or it
5719 wouldn't run due to missing symbols. Since dependencies are
5720 only added based on ELF <tt>NEEDED</tt> attribute, packages
5721 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
5722 having the dependency on <tt>libdgf</tt> and so they would
5723 not need rebuilding.
5729 In the following sections, we will first describe where the
5730 various <tt>shlibs</tt> files are to be found, then how to
5731 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5732 file format and how to create them if your package contains a
5737 <heading>The <tt>shlibs</tt> files present on the system</heading>
5740 There are several places where <tt>shlibs</tt> files are
5741 found. The following list gives them in the order in which
5743 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5744 (The first one which gives the required information is used.)
5750 <p><file>debian/shlibs.local</file></p>
5753 This lists overrides for this package. This file should
5754 normally not be used, but may be needed temporarily in
5755 unusual situations to work around bugs in other packages,
5756 or in unusual cases where the normally declared dependency
5757 information in the installed <file>shlibs</file> file for
5758 a library cannot be used. This file overrides information
5759 obtained from any other source.
5764 <p><file>/etc/dpkg/shlibs.override</file></p>
5767 This lists global overrides. This list is normally
5768 empty. It is maintained by the local system
5774 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5777 When packages are being built,
5778 any <file>debian/shlibs</file> files are copied into the
5779 control information file area of the temporary build
5780 directory and given the name <file>shlibs</file>. These
5781 files give details of any shared libraries included in the
5782 same package.<footnote>
5783 An example may help here. Let us say that the source
5784 package <tt>foo</tt> generates two binary
5785 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
5786 When building the binary packages, the two packages are
5787 created in the directories <file>debian/libfoo2</file>
5788 and <file>debian/foo-runtime</file> respectively.
5789 (<file>debian/tmp</file> could be used instead of one of
5790 these.) Since <tt>libfoo2</tt> provides the
5791 <tt>libfoo</tt> shared library, it will require a
5792 <tt>shlibs</tt> file, which will be installed in
5793 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually to
5794 become <file>/var/lib/dpkg/info/libfoo2.shlibs</file>.
5795 When <prgn>dpkg-shlibdeps</prgn> is run on the
5796 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
5798 the <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5799 determine whether <tt>foo-prog</tt>'s library
5800 dependencies are satisfied by any of the libraries
5801 provided by <tt>libfoo2</tt>. For this reason,
5802 <prgn>dpkg-shlibdeps</prgn> must only be run once all of
5803 the individual binary packages' <tt>shlibs</tt> files
5804 have been installed into the build directory.
5810 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5813 These are the <file>shlibs</file> files corresponding to
5814 all of the packages installed on the system, and are
5815 maintained by the relevant package maintainers.
5820 <p><file>/etc/dpkg/shlibs.default</file></p>
5823 This file lists any shared libraries whose packages
5824 have failed to provide correct <file>shlibs</file> files.
5825 It was used when the <file>shlibs</file> setup was first
5826 introduced, but it is now normally empty. It is
5827 maintained by the <tt>dpkg</tt> maintainer.
5835 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5836 <file>shlibs</file> files</heading>
5840 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5841 into your <file>debian/rules</file> file. If your package
5842 contains only compiled binaries and libraries (but no scripts),
5843 you can use a command such as:
5844 <example compact="compact">
5845 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5846 debian/tmp/usr/lib/*
5848 Otherwise, you will need to explicitly list the compiled
5849 binaries and libraries.<footnote>
5850 If you are using <tt>debhelper</tt>, the
5851 <prgn>dh_shlibdeps</prgn> program will do this work for you.
5852 It will also correctly handle multi-binary packages.
5857 This command puts the dependency information into the
5858 <file>debian/substvars</file> file, which is then used by
5859 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5860 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5861 field in the control file for this to work.
5865 If you have multiple binary packages, you will need to call
5866 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5867 compiled libraries or binaries. In such a case, you will
5868 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5869 utilities to specify a different <file>substvars</file> file.
5873 If you are creating a udeb for use in the Debian Installer,
5874 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
5875 should use the dependency line of type <tt>udeb</tt> by
5876 adding the <tt>-tudeb</tt> option<footnote>
5877 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5878 will automatically add this option if it knows it is
5880 </footnote>. If there is no dependency line of
5881 type <tt>udeb</tt> in the <file>shlibs</file>
5882 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the regular
5887 For more details on <prgn>dpkg-shlibdeps</prgn>, please see
5888 <ref id="pkg-dpkg-shlibdeps"> and
5889 <manref name="dpkg-shlibdeps" section="1">.
5894 <heading>The <file>shlibs</file> File Format</heading>
5897 Each <file>shlibs</file> file has the same format. Lines
5898 beginning with <tt>#</tt> are considered to be comments and
5899 are ignored. Each line is of the form:
5900 <example compact="compact">
5901 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5906 We will explain this by reference to the example of the
5907 <tt>zlib1g</tt> package, which (at the time of writing)
5908 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5912 <var>type</var> is an optional element that indicates the type
5913 of package for which the line is valid. The only type currently
5914 in use is <tt>udeb</tt>. The colon and space after the type are
5919 <var>library-name</var> is the name of the shared library,
5920 in this case <tt>libz</tt>. (This must match the name part
5921 of the soname, see below.)
5925 <var>soname-version</var> is the version part of the soname of
5926 the library. The soname is the thing that must exactly match
5927 for the library to be recognized by the dynamic linker, and is
5929 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5930 example, <tt>libz.so.1</tt>.<footnote>
5931 This can be determined using the command
5932 <example compact="compact">
5933 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5936 The version part is the part which comes after
5937 <tt>.so.</tt>, so in our case, it is <tt>1</tt>. The soname may
5938 instead be of the form
5939 <tt><var>name</var>-<var>major-version</var>.so</tt>, such
5940 as <tt>libdb-4.8.so</tt>, in which case the name would
5941 be <tt>libdb</tt> and the version would be <tt>4.8</tt>.
5945 <var>dependencies</var> has the same syntax as a dependency
5946 field in a binary package control file. It should give
5947 details of which packages are required to satisfy a binary
5948 built against the version of the library contained in the
5949 package. See <ref id="depsyntax"> for details.
5953 In our example, if the first version of the <tt>zlib1g</tt>
5954 package which contained a minor number of at least
5955 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5956 <tt>shlibs</tt> entry for this library could say:
5957 <example compact="compact">
5958 libz 1 zlib1g (>= 1:1.1.3)
5960 The version-specific dependency is to avoid warnings from
5961 the dynamic linker about using older shared libraries with
5966 As zlib1g also provides a udeb containing the shared library,
5967 there would also be a second line:
5968 <example compact="compact">
5969 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5975 <heading>Providing a <file>shlibs</file> file</heading>
5978 If your package provides a shared library, you need to create
5979 a <file>shlibs</file> file following the format described above.
5980 It is usual to call this file <file>debian/shlibs</file> (but if
5981 you have multiple binary packages, you might want to call it
5982 <file>debian/shlibs.<var>package</var></file> instead). Then
5983 let <file>debian/rules</file> install it in the control
5984 information file area:
5985 <example compact="compact">
5986 install -m644 debian/shlibs debian/tmp/DEBIAN
5988 or, in the case of a multi-binary package:
5989 <example compact="compact">
5990 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5992 An alternative way of doing this is to create the
5993 <file>shlibs</file> file in the control information file area
5994 directly from <file>debian/rules</file> without using
5995 a <file>debian/shlibs</file> file at all,<footnote>
5996 This is what <prgn>dh_makeshlibs</prgn> in
5997 the <package>debhelper</package> suite does. If your package
5998 also has a udeb that provides a shared
5999 library, <prgn>dh_makeshlibs</prgn> can automatically generate
6000 the <tt>udeb:</tt> lines if you specify the name of the udeb
6001 with the <tt>--add-udeb</tt> option.
6003 since the <file>debian/shlibs</file> file itself is ignored by
6004 <prgn>dpkg-shlibdeps</prgn>.
6008 As <prgn>dpkg-shlibdeps</prgn> reads the
6009 <file>DEBIAN/shlibs</file> files in all of the binary packages
6010 being built from this source package, all of the
6011 <file>DEBIAN/shlibs</file> files should be installed before
6012 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
6020 <chapt id="opersys"><heading>The Operating System</heading>
6023 <heading>File system hierarchy</heading>
6027 <heading>File System Structure</heading>
6030 The location of all installed files and directories must
6031 comply with the Filesystem Hierarchy Standard (FHS),
6032 version 2.3, with the exceptions noted below, and except
6033 where doing so would violate other terms of Debian
6034 Policy. The following exceptions to the FHS apply:
6039 The optional rules related to user specific
6040 configuration files for applications are stored in
6041 the user's home directory are relaxed. It is
6042 recommended that such files start with the
6043 '<tt>.</tt>' character (a "dot file"), and if an
6044 application needs to create more than one dot file
6045 then the preferred placement is in a subdirectory
6046 with a name starting with a '.' character, (a "dot
6047 directory"). In this case it is recommended the
6048 configuration files not start with the '.'
6054 The requirement for amd64 to use <file>/lib64</file>
6055 for 64 bit binaries is removed.
6060 The requirement for object files, internal binaries, and
6061 libraries, including <file>libc.so.*</file>, to be located
6062 directly under <file>/lib{,32}</file> and
6063 <file>/usr/lib{,32}</file> is amended, permitting files
6064 to instead be installed to
6065 <file>/lib/<var>triplet</var></file> and
6066 <file>/usr/lib/<var>triplet</var></file>, where
6067 <tt><var>triplet</var></tt> is the value returned by
6068 <tt>dpkg-architecture -qDEB_HOST_GNU_TYPE</tt> for the
6069 architecture of the package. Packages may <em>not</em>
6070 install files to any <var>triplet</var> path other
6071 than the one matching the architecture of that package;
6072 for instance, an <tt>Architecture: amd64</tt> package
6073 containing 32-bit x86 libraries may not install these
6074 libraries to <file>/usr/lib/i486-linux-gnu</file>.
6076 This is necessary in order to reserve the directories for
6077 use in cross-installation of library packages from other
6078 architectures, as part of the planned deployment of
6083 Applications may also use a single subdirectory under
6084 <file>/usr/lib/<var>triplet</var></file>.
6087 The execution time linker/loader, ld*, must still be made
6088 available in the existing location under /lib or /lib64
6089 since this is part of the ELF ABI for the architecture.
6094 The requirement that
6095 <file>/usr/local/share/man</file> be "synonymous"
6096 with <file>/usr/local/man</file> is relaxed to a
6101 The requirement that windowmanagers with a single
6102 configuration file call it <file>system.*wmrc</file>
6103 is removed, as is the restriction that the window
6104 manager subdirectory be named identically to the
6105 window manager name itself.
6110 The requirement that boot manager configuration
6111 files live in <file>/etc</file>, or at least are
6112 symlinked there, is relaxed to a recommendation.
6117 The following directories in the root filesystem are
6118 additionally allowed: <file>/sys</file> and
6119 <file>/selinux</file>. <footnote>These directories
6120 are used as mount points to mount virtual filesystems
6121 to get access to kernel information.</footnote>
6128 The version of this document referred here can be
6129 found in the <tt>debian-policy</tt> package or on <url
6130 id="http://www.debian.org/doc/packaging-manuals/fhs/"
6131 name="FHS (Debian copy)"> alongside this manual (or, if
6132 you have the <package>debian-policy</package> installed,
6134 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
6135 (local copy)">). The
6136 latest version, which may be a more recent version, may
6138 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
6139 Specific questions about following the standard may be
6140 asked on the <tt>debian-devel</tt> mailing list, or
6141 referred to the FHS mailing list (see the
6142 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
6148 <heading>Site-specific programs</heading>
6151 As mandated by the FHS, packages must not place any
6152 files in <file>/usr/local</file>, either by putting them in
6153 the file system archive to be unpacked by <prgn>dpkg</prgn>
6154 or by manipulating them in their maintainer scripts.
6158 However, the package may create empty directories below
6159 <file>/usr/local</file> so that the system administrator knows
6160 where to place site-specific files. These are not
6161 directories <em>in</em> <file>/usr/local</file>, but are
6162 children of directories in <file>/usr/local</file>. These
6163 directories (<file>/usr/local/*/dir/</file>)
6164 should be removed on package removal if they are
6169 Note that this applies only to
6170 directories <em>below</em> <file>/usr/local</file>,
6171 not <em>in</em> <file>/usr/local</file>. Packages must
6172 not create sub-directories in the
6173 directory <file>/usr/local</file> itself, except those
6174 listed in FHS, section 4.5. However, you may create
6175 directories below them as you wish. You must not remove
6176 any of the directories listed in 4.5, even if you created
6181 Since <file>/usr/local</file> can be mounted read-only from a
6182 remote server, these directories must be created and
6183 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
6184 maintainer scripts and not be included in the
6185 <file>.deb</file> archive. These scripts must not fail if
6186 either of these operations fail.
6190 For example, the <tt>emacsen-common</tt> package could
6191 contain something like
6192 <example compact="compact">
6193 if [ ! -e /usr/local/share/emacs ]
6195 if mkdir /usr/local/share/emacs 2>/dev/null
6197 chown root:staff /usr/local/share/emacs
6198 chmod 2775 /usr/local/share/emacs
6202 in its <prgn>postinst</prgn> script, and
6203 <example compact="compact">
6204 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
6205 rmdir /usr/local/share/emacs 2>/dev/null || true
6207 in the <prgn>prerm</prgn> script. (Note that this form is
6208 used to ensure that if the script is interrupted, the
6209 directory <file>/usr/local/share/emacs</file> will still be
6214 If you do create a directory in <file>/usr/local</file> for
6215 local additions to a package, you should ensure that
6216 settings in <file>/usr/local</file> take precedence over the
6217 equivalents in <file>/usr</file>.
6221 However, because <file>/usr/local</file> and its contents are
6222 for exclusive use of the local administrator, a package
6223 must not rely on the presence or absence of files or
6224 directories in <file>/usr/local</file> for normal operation.
6228 The <file>/usr/local</file> directory itself and all the
6229 subdirectories created by the package should (by default) have
6230 permissions 2775 (group-writable and set-group-id) and be
6231 owned by <tt>root:staff</tt>.
6236 <heading>The system-wide mail directory</heading>
6238 The system-wide mail directory
6239 is <file>/var/mail</file>. This directory is part of the
6240 base system and should not be owned by any particular mail
6241 agents. The use of the old
6242 location <file>/var/spool/mail</file> is deprecated, even
6243 though the spool may still be physically located there.
6249 <heading>Users and groups</heading>
6252 <heading>Introduction</heading>
6254 The Debian system can be configured to use either plain or
6259 Some user ids (UIDs) and group ids (GIDs) are reserved
6260 globally for use by certain packages. Because some
6261 packages need to include files which are owned by these
6262 users or groups, or need the ids compiled into binaries,
6263 these ids must be used on any Debian system only for the
6264 purpose for which they are allocated. This is a serious
6265 restriction, and we should avoid getting in the way of
6266 local administration policies. In particular, many sites
6267 allocate users and/or local system groups starting at 100.
6271 Apart from this we should have dynamically allocated ids,
6272 which should by default be arranged in some sensible
6273 order, but the behavior should be configurable.
6277 Packages other than <tt>base-passwd</tt> must not modify
6278 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
6279 <file>/etc/group</file> or <file>/etc/gshadow</file>.
6284 <heading>UID and GID classes</heading>
6286 The UID and GID numbers are divided into classes as
6292 Globally allocated by the Debian project, the same
6293 on every Debian system. These ids will appear in
6294 the <file>passwd</file> and <file>group</file> files of all
6295 Debian systems, new ids in this range being added
6296 automatically as the <tt>base-passwd</tt> package is
6301 Packages which need a single statically allocated
6302 uid or gid should use one of these; their
6303 maintainers should ask the <tt>base-passwd</tt>
6311 Dynamically allocated system users and groups.
6312 Packages which need a user or group, but can have
6313 this user or group allocated dynamically and
6314 differently on each system, should use <tt>adduser
6315 --system</tt> to create the group and/or user.
6316 <prgn>adduser</prgn> will check for the existence of
6317 the user or group, and if necessary choose an unused
6318 id based on the ranges specified in
6319 <file>adduser.conf</file>.
6323 <tag>1000-59999:</tag>
6326 Dynamically allocated user accounts. By default
6327 <prgn>adduser</prgn> will choose UIDs and GIDs for
6328 user accounts in this range, though
6329 <file>adduser.conf</file> may be used to modify this
6334 <tag>60000-64999:</tag>
6337 Globally allocated by the Debian project, but only
6338 created on demand. The ids are allocated centrally
6339 and statically, but the actual accounts are only
6340 created on users' systems on demand.
6344 These ids are for packages which are obscure or
6345 which require many statically-allocated ids. These
6346 packages should check for and create the accounts in
6347 <file>/etc/passwd</file> or <file>/etc/group</file> (using
6348 <prgn>adduser</prgn> if it has this facility) if
6349 necessary. Packages which are likely to require
6350 further allocations should have a "hole" left after
6351 them in the allocation, to give them room to
6356 <tag>65000-65533:</tag>
6364 User <tt>nobody</tt>. The corresponding gid refers
6365 to the group <tt>nogroup</tt>.
6372 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
6373 not</em> be used, because it is the error return
6382 <sect id="sysvinit">
6383 <heading>System run levels and <file>init.d</file> scripts</heading>
6385 <sect1 id="/etc/init.d">
6386 <heading>Introduction</heading>
6389 The <file>/etc/init.d</file> directory contains the scripts
6390 executed by <prgn>init</prgn> at boot time and when the
6391 init state (or "runlevel") is changed (see <manref
6392 name="init" section="8">).
6396 There are at least two different, yet functionally
6397 equivalent, ways of handling these scripts. For the sake
6398 of simplicity, this document describes only the symbolic
6399 link method. However, it must not be assumed by maintainer
6400 scripts that this method is being used, and any automated
6401 manipulation of the various runlevel behaviors by
6402 maintainer scripts must be performed using
6403 <prgn>update-rc.d</prgn> as described below and not by
6404 manually installing or removing symlinks. For information
6405 on the implementation details of the other method,
6406 implemented in the <tt>file-rc</tt> package, please refer
6407 to the documentation of that package.
6411 These scripts are referenced by symbolic links in the
6412 <file>/etc/rc<var>n</var>.d</file> directories. When changing
6413 runlevels, <prgn>init</prgn> looks in the directory
6414 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
6415 execute, where <tt><var>n</var></tt> is the runlevel that
6416 is being changed to, or <tt>S</tt> for the boot-up
6421 The names of the links all have the form
6422 <file>S<var>mm</var><var>script</var></file> or
6423 <file>K<var>mm</var><var>script</var></file> where
6424 <var>mm</var> is a two-digit number and <var>script</var>
6425 is the name of the script (this should be the same as the
6426 name of the actual script in <file>/etc/init.d</file>).
6430 When <prgn>init</prgn> changes runlevel first the targets
6431 of the links whose names start with a <tt>K</tt> are
6432 executed, each with the single argument <tt>stop</tt>,
6433 followed by the scripts prefixed with an <tt>S</tt>, each
6434 with the single argument <tt>start</tt>. (The links are
6435 those in the <file>/etc/rc<var>n</var>.d</file> directory
6436 corresponding to the new runlevel.) The <tt>K</tt> links
6437 are responsible for killing services and the <tt>S</tt>
6438 link for starting services upon entering the runlevel.
6442 For example, if we are changing from runlevel 2 to
6443 runlevel 3, init will first execute all of the <tt>K</tt>
6444 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
6445 all of the <tt>S</tt> prefixed scripts in that directory.
6446 The links starting with <tt>K</tt> will cause the
6447 referred-to file to be executed with an argument of
6448 <tt>stop</tt>, and the <tt>S</tt> links with an argument
6453 The two-digit number <var>mm</var> is used to determine
6454 the order in which to run the scripts: low-numbered links
6455 have their scripts run first. For example, the
6456 <tt>K20</tt> scripts will be executed before the
6457 <tt>K30</tt> scripts. This is used when a certain service
6458 must be started before another. For example, the name
6459 server <prgn>bind</prgn> might need to be started before
6460 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
6461 can set up its access lists. In this case, the script
6462 that starts <prgn>bind</prgn> would have a lower number
6463 than the script that starts <prgn>inn</prgn> so that it
6465 <example compact="compact">
6472 The two runlevels 0 (halt) and 6 (reboot) are slightly
6473 different. In these runlevels, the links with an
6474 <tt>S</tt> prefix are still called after those with a
6475 <tt>K</tt> prefix, but they too are called with the single
6476 argument <tt>stop</tt>.
6480 <sect1 id="writing-init">
6481 <heading>Writing the scripts</heading>
6484 Packages that include daemons for system services should
6485 place scripts in <file>/etc/init.d</file> to start or stop
6486 services at boot time or during a change of runlevel.
6487 These scripts should be named
6488 <file>/etc/init.d/<var>package</var></file>, and they should
6489 accept one argument, saying what to do:
6492 <tag><tt>start</tt></tag>
6493 <item>start the service,</item>
6495 <tag><tt>stop</tt></tag>
6496 <item>stop the service,</item>
6498 <tag><tt>restart</tt></tag>
6499 <item>stop and restart the service if it's already running,
6500 otherwise start the service</item>
6502 <tag><tt>reload</tt></tag>
6503 <item><p>cause the configuration of the service to be
6504 reloaded without actually stopping and restarting
6507 <tag><tt>force-reload</tt></tag>
6508 <item>cause the configuration to be reloaded if the
6509 service supports this, otherwise restart the
6513 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
6514 <tt>force-reload</tt> options should be supported by all
6515 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
6520 The <file>init.d</file> scripts must ensure that they will
6521 behave sensibly (i.e., returning success and not starting
6522 multiple copies of a service) if invoked with <tt>start</tt>
6523 when the service is already running, or with <tt>stop</tt>
6524 when it isn't, and that they don't kill unfortunately-named
6525 user processes. The best way to achieve this is usually to
6526 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
6531 Be careful of using <tt>set -e</tt> in <file>init.d</file>
6532 scripts. Writing correct <file>init.d</file> scripts requires
6533 accepting various error exit statuses when daemons are already
6534 running or already stopped without aborting
6535 the <file>init.d</file> script, and common <file>init.d</file>
6536 function libraries are not safe to call with <tt>set -e</tt>
6538 <tt>/lib/lsb/init-functions</tt>, which assists in writing
6539 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
6540 in effect and echoing status messages to the console fails,
6542 </footnote>. For <tt>init.d</tt> scripts, it's often easier
6543 to not use <tt>set -e</tt> and instead check the result of
6544 each command separately.
6548 If a service reloads its configuration automatically (as
6549 in the case of <prgn>cron</prgn>, for example), the
6550 <tt>reload</tt> option of the <file>init.d</file> script
6551 should behave as if the configuration has been reloaded
6556 The <file>/etc/init.d</file> scripts must be treated as
6557 configuration files, either (if they are present in the
6558 package, that is, in the .deb file) by marking them as
6559 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6560 by managing them correctly in the maintainer scripts (see
6561 <ref id="config-files">). This is important since we want
6562 to give the local system administrator the chance to adapt
6563 the scripts to the local system, e.g., to disable a
6564 service without de-installing the package, or to specify
6565 some special command line options when starting a service,
6566 while making sure their changes aren't lost during the next
6571 These scripts should not fail obscurely when the
6572 configuration files remain but the package has been
6573 removed, as configuration files remain on the system after
6574 the package has been removed. Only when <prgn>dpkg</prgn>
6575 is executed with the <tt>--purge</tt> option will
6576 configuration files be removed. In particular, as the
6577 <file>/etc/init.d/<var>package</var></file> script itself is
6578 usually a <tt>conffile</tt>, it will remain on the system
6579 if the package is removed but not purged. Therefore, you
6580 should include a <tt>test</tt> statement at the top of the
6582 <example compact="compact">
6583 test -f <var>program-executed-later-in-script</var> || exit 0
6588 Often there are some variables in the <file>init.d</file>
6589 scripts whose values control the behavior of the scripts,
6590 and which a system administrator is likely to want to
6591 change. As the scripts themselves are frequently
6592 <tt>conffile</tt>s, modifying them requires that the
6593 administrator merge in their changes each time the package
6594 is upgraded and the <tt>conffile</tt> changes. To ease
6595 the burden on the system administrator, such configurable
6596 values should not be placed directly in the script.
6597 Instead, they should be placed in a file in
6598 <file>/etc/default</file>, which typically will have the same
6599 base name as the <file>init.d</file> script. This extra file
6600 should be sourced by the script when the script runs. It
6601 must contain only variable settings and comments in SUSv3
6602 <prgn>sh</prgn> format. It may either be a
6603 <tt>conffile</tt> or a configuration file maintained by
6604 the package maintainer scripts. See <ref id="config-files">
6609 To ensure that vital configurable values are always
6610 available, the <file>init.d</file> script should set default
6611 values for each of the shell variables it uses, either
6612 before sourcing the <file>/etc/default/</file> file or
6613 afterwards using something like the <tt>:
6614 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6615 script must behave sensibly and not fail if the
6616 <file>/etc/default</file> file is deleted.
6620 <file>/var/run</file> and <file>/var/lock</file> may be mounted
6621 as temporary filesystems<footnote>
6622 For example, using the <tt>RAMRUN</tt> and <tt>RAMLOCK</tt>
6623 options in <file>/etc/default/rcS</file>.
6624 </footnote>, so the <file>init.d</file> scripts must handle this
6625 correctly. This will typically amount to creating any required
6626 subdirectories dynamically when the <file>init.d</file> script
6627 is run, rather than including them in the package and relying on
6628 <prgn>dpkg</prgn> to create them.
6633 <heading>Interfacing with the initscript system</heading>
6636 Maintainers should use the abstraction layer provided by
6637 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6638 programs to deal with initscripts in their packages'
6639 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6640 and <prgn>postrm</prgn>.
6644 Directly managing the /etc/rc?.d links and directly
6645 invoking the <file>/etc/init.d/</file> initscripts should
6646 be done only by packages providing the initscript
6647 subsystem (such as <prgn>sysv-rc</prgn> and
6648 <prgn>file-rc</prgn>).
6652 <heading>Managing the links</heading>
6655 The program <prgn>update-rc.d</prgn> is provided for
6656 package maintainers to arrange for the proper creation and
6657 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6658 or their functional equivalent if another method is being
6659 used. This may be used by maintainers in their packages'
6660 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6664 You must not include any <file>/etc/rc<var>n</var>.d</file>
6665 symbolic links in the actual archive or manually create or
6666 remove the symbolic links in maintainer scripts; you must
6667 use the <prgn>update-rc.d</prgn> program instead. (The
6668 former will fail if an alternative method of maintaining
6669 runlevel information is being used.) You must not include
6670 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6671 in the archive either. (Only the <tt>sysvinit</tt>
6676 By default <prgn>update-rc.d</prgn> will start services in
6677 each of the multi-user state runlevels (2, 3, 4, and 5)
6678 and stop them in the halt runlevel (0), the single-user
6679 runlevel (1) and the reboot runlevel (6). The system
6680 administrator will have the opportunity to customize
6681 runlevels by simply adding, moving, or removing the
6682 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6683 symbolic links are being used, or by modifying
6684 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6689 To get the default behavior for your package, put in your
6690 <prgn>postinst</prgn> script
6691 <example compact="compact">
6692 update-rc.d <var>package</var> defaults
6694 and in your <prgn>postrm</prgn>
6695 <example compact="compact">
6696 if [ "$1" = purge ]; then
6697 update-rc.d <var>package</var> remove
6699 </example>. Note that if your package changes runlevels
6700 or priority, you may have to remove and recreate the links,
6701 since otherwise the old links may persist. Refer to the
6702 documentation of <prgn>update-rc.d</prgn>.
6706 This will use a default sequence number of 20. If it does
6707 not matter when or in which order the <file>init.d</file>
6708 script is run, use this default. If it does, then you
6709 should talk to the maintainer of the <prgn>sysvinit</prgn>
6710 package or post to <tt>debian-devel</tt>, and they will
6711 help you choose a number.
6715 For more information about using <tt>update-rc.d</tt>,
6716 please consult its man page <manref name="update-rc.d"
6722 <heading>Running initscripts</heading>
6724 The program <prgn>invoke-rc.d</prgn> is provided to make
6725 it easier for package maintainers to properly invoke an
6726 initscript, obeying runlevel and other locally-defined
6727 constraints that might limit a package's right to start,
6728 stop and otherwise manage services. This program may be
6729 used by maintainers in their packages' scripts.
6733 The package maintainer scripts must use
6734 <prgn>invoke-rc.d</prgn> to invoke the
6735 <file>/etc/init.d/*</file> initscripts, instead of
6736 calling them directly.
6740 By default, <prgn>invoke-rc.d</prgn> will pass any
6741 action requests (start, stop, reload, restart...) to the
6742 <file>/etc/init.d</file> script, filtering out requests
6743 to start or restart a service out of its intended
6748 Most packages will simply need to change:
6749 <example compact="compact">/etc/init.d/<package>
6750 <action></example> in their <prgn>postinst</prgn>
6751 and <prgn>prerm</prgn> scripts to:
6752 <example compact="compact">
6753 if which invoke-rc.d >/dev/null 2>&1; then
6754 invoke-rc.d <var>package</var> <action>
6756 /etc/init.d/<var>package</var> <action>
6762 A package should register its initscript services using
6763 <prgn>update-rc.d</prgn> before it tries to invoke them
6764 using <prgn>invoke-rc.d</prgn>. Invocation of
6765 unregistered services may fail.
6769 For more information about using
6770 <prgn>invoke-rc.d</prgn>, please consult its man page
6771 <manref name="invoke-rc.d" section="8">.
6777 <heading>Boot-time initialization</heading>
6780 There used to be another directory, <file>/etc/rc.boot</file>,
6781 which contained scripts which were run once per machine
6782 boot. This has been deprecated in favour of links from
6783 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6784 described in <ref id="/etc/init.d">. Packages must not
6785 place files in <file>/etc/rc.boot</file>.
6790 <heading>Example</heading>
6793 An example on which you can base your
6794 <file>/etc/init.d</file> scripts is found in
6795 <file>/etc/init.d/skeleton</file>.
6802 <heading>Console messages from <file>init.d</file> scripts</heading>
6805 This section describes the formats to be used for messages
6806 written to standard output by the <file>/etc/init.d</file>
6807 scripts. The intent is to improve the consistency of
6808 Debian's startup and shutdown look and feel. For this
6809 reason, please look very carefully at the details. We want
6810 the messages to have the same format in terms of wording,
6811 spaces, punctuation and case of letters.
6815 Here is a list of overall rules that should be used for
6816 messages generated by <file>/etc/init.d</file> scripts.
6822 The message should fit in one line (fewer than 80
6823 characters), start with a capital letter and end with
6824 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6828 If the script is performing some time consuming task in
6829 the background (not merely starting or stopping a
6830 program, for instance), an ellipsis (three dots:
6831 <tt>...</tt>) should be output to the screen, with no
6832 leading or tailing whitespace or line feeds.
6836 The messages should appear as if the computer is telling
6837 the user what it is doing (politely :-), but should not
6838 mention "it" directly. For example, instead of:
6839 <example compact="compact">
6840 I'm starting network daemons: nfsd mountd.
6842 the message should say
6843 <example compact="compact">
6844 Starting network daemons: nfsd mountd.
6851 <tt>init.d</tt> script should use the following standard
6852 message formats for the situations enumerated below.
6858 <p>When daemons are started</p>
6861 If the script starts one or more daemons, the output
6862 should look like this (a single line, no leading
6864 <example compact="compact">
6865 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6867 The <var>description</var> should describe the
6868 subsystem the daemon or set of daemons are part of,
6869 while <var>daemon-1</var> up to <var>daemon-n</var>
6870 denote each daemon's name (typically the file name of
6875 For example, the output of <file>/etc/init.d/lpd</file>
6877 <example compact="compact">
6878 Starting printer spooler: lpd.
6883 This can be achieved by saying
6884 <example compact="compact">
6885 echo -n "Starting printer spooler: lpd"
6886 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6889 in the script. If there are more than one daemon to
6890 start, the output should look like this:
6891 <example compact="compact">
6892 echo -n "Starting remote file system services:"
6893 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6894 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6895 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6898 This makes it possible for the user to see what is
6899 happening and when the final daemon has been started.
6900 Care should be taken in the placement of white spaces:
6901 in the example above the system administrators can
6902 easily comment out a line if they don't want to start
6903 a specific daemon, while the displayed message still
6909 <p>When a system parameter is being set</p>
6912 If you have to set up different system parameters
6913 during the system boot, you should use this format:
6914 <example compact="compact">
6915 Setting <var>parameter</var> to "<var>value</var>".
6920 You can use a statement such as the following to get
6922 <example compact="compact">
6923 echo "Setting DNS domainname to \"$domainname\"."
6928 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
6929 for the left and right quotation marks. A grave accent
6930 (<tt>`</tt>) is not a quote character; neither is an
6931 apostrophe (<tt>'</tt>).
6936 <p>When a daemon is stopped or restarted</p>
6939 When you stop or restart a daemon, you should issue a
6940 message identical to the startup message, except that
6941 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6942 or <tt>Restarting</tt> respectively.
6946 For example, stopping the printer daemon will look like
6948 <example compact="compact">
6949 Stopping printer spooler: lpd.
6955 <p>When something is executed</p>
6958 There are several examples where you have to run a
6959 program at system startup or shutdown to perform a
6960 specific task, for example, setting the system's clock
6961 using <prgn>netdate</prgn> or killing all processes
6962 when the system shuts down. Your message should look
6964 <example compact="compact">
6965 Doing something very useful...done.
6967 You should print the <tt>done.</tt> immediately after
6968 the job has been completed, so that the user is
6969 informed why they have to wait. You can get this
6971 <example compact="compact">
6972 echo -n "Doing something very useful..."
6981 <p>When the configuration is reloaded</p>
6984 When a daemon is forced to reload its configuration
6985 files you should use the following format:
6986 <example compact="compact">
6987 Reloading <var>description</var> configuration...done.
6989 where <var>description</var> is the same as in the
6990 daemon starting message.
6998 <heading>Cron jobs</heading>
7001 Packages must not modify the configuration file
7002 <file>/etc/crontab</file>, and they must not modify the files in
7003 <file>/var/spool/cron/crontabs</file>.</p>
7006 If a package wants to install a job that has to be executed
7007 via cron, it should place a file with the name of the
7008 package in one or more of the following directories:
7009 <example compact="compact">
7015 As these directory names imply, the files within them are
7016 executed on an hourly, daily, weekly, or monthly basis,
7017 respectively. The exact times are listed in
7018 <file>/etc/crontab</file>.</p>
7021 All files installed in any of these directories must be
7022 scripts (e.g., shell scripts or Perl scripts) so that they
7023 can easily be modified by the local system administrator.
7024 In addition, they must be treated as configuration files.
7028 If a certain job has to be executed at some other frequency or
7029 at a specific time, the package should install a file
7030 <file>/etc/cron.d/<var>package</var></file>. This file uses the
7031 same syntax as <file>/etc/crontab</file> and is processed by
7032 <prgn>cron</prgn> automatically. The file must also be
7033 treated as a configuration file. (Note that entries in the
7034 <file>/etc/cron.d</file> directory are not handled by
7035 <prgn>anacron</prgn>. Thus, you should only use this
7036 directory for jobs which may be skipped if the system is not
7039 Unlike <file>crontab</file> files described in the IEEE Std
7040 1003.1-2008 (POSIX.1) available from
7041 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
7042 name="The Open Group">, the files in
7043 <file>/etc/cron.d</file> and the file
7044 <file>/etc/crontab</file> have seven fields; namely:
7046 <item>Minute [0,59]</item>
7047 <item>Hour [0,23]</item>
7048 <item>Day of the month [1,31]</item>
7049 <item>Month of the year [1,12]</item>
7050 <item>Day of the week ([0,6] with 0=Sunday)</item>
7051 <item>Username</item>
7052 <item>Command to be run</item>
7054 Ranges of numbers are allowed. Ranges are two numbers
7055 separated with a hyphen. The specified range is inclusive.
7056 Lists are allowed. A list is a set of numbers (or ranges)
7057 separated by commas. Step values can be used in conjunction
7062 The scripts or <tt>crontab</tt> entries in these directories should
7063 check if all necessary programs are installed before they
7064 try to execute them. Otherwise, problems will arise when a
7065 package was removed but not purged since configuration files
7066 are kept on the system in this situation.
7070 Any <tt>cron</tt> daemon must provide
7071 <file>/usr/bin/crontab</file> and support normal
7072 <tt>crontab</tt> entries as specified in POSIX. The daemon
7073 must also support names for days and months, ranges, and
7074 step values. It has to support <file>/etc/crontab</file>,
7075 and correctly execute the scripts in
7076 <file>/etc/cron.d</file>. The daemon must also correctly
7078 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
7083 <heading>Menus</heading>
7086 The Debian <tt>menu</tt> package provides a standard
7087 interface between packages providing applications and
7088 <em>menu programs</em> (either X window managers or
7089 text-based menu programs such as <prgn>pdmenu</prgn>).
7093 All packages that provide applications that need not be
7094 passed any special command line arguments for normal
7095 operation should register a menu entry for those
7096 applications, so that users of the <tt>menu</tt> package
7097 will automatically get menu entries in their window
7098 managers, as well in shells like <tt>pdmenu</tt>.
7102 Menu entries should follow the current menu policy.
7106 The menu policy can be found in the <tt>menu-policy</tt>
7107 files in the <tt>debian-policy</tt> package.
7108 It is also available from the Debian web mirrors at
7109 <tt><url name="/doc/packaging-manuals/menu-policy/"
7110 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
7114 Please also refer to the <em>Debian Menu System</em>
7115 documentation that comes with the <package>menu</package>
7116 package for information about how to register your
7122 <heading>Multimedia handlers</heading>
7125 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
7126 is a mechanism for encoding files and data streams and
7127 providing meta-information about them, in particular their
7128 type (e.g. audio or video) and format (e.g. PNG, HTML,
7133 Registration of MIME type handlers allows programs like mail
7134 user agents and web browsers to invoke these handlers to
7135 view, edit or display MIME types they don't support directly.
7139 Packages which provide the ability to view/show/play,
7140 compose, edit or print MIME types should register themselves
7141 as such following the current MIME support policy.
7145 The MIME support policy can be found in the <tt>mime-policy</tt>
7146 files in the <tt>debian-policy</tt> package.
7147 It is also available from the Debian web mirrors at
7148 <tt><url name="/doc/packaging-manuals/mime-policy/"
7149 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
7155 <heading>Keyboard configuration</heading>
7158 To achieve a consistent keyboard configuration so that all
7159 applications interpret a keyboard event the same way, all
7160 programs in the Debian distribution must be configured to
7161 comply with the following guidelines.
7165 The following keys must have the specified interpretations:
7168 <tag><tt><--</tt></tag>
7169 <item>delete the character to the left of the cursor</item>
7171 <tag><tt>Delete</tt></tag>
7172 <item>delete the character to the right of the cursor</item>
7174 <tag><tt>Control+H</tt></tag>
7175 <item>emacs: the help prefix</item>
7178 The interpretation of any keyboard events should be
7179 independent of the terminal that is used, be it a virtual
7180 console, an X terminal emulator, an rlogin/telnet session,
7185 The following list explains how the different programs
7186 should be set up to achieve this:
7192 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
7196 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
7200 X translations are set up to make
7201 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
7202 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
7203 is the vt220 escape code for the "delete character"
7204 key). This must be done by loading the X resources
7205 using <prgn>xrdb</prgn> on all local X displays, not
7206 using the application defaults, so that the
7207 translation resources used correspond to the
7208 <prgn>xmodmap</prgn> settings.
7212 The Linux console is configured to make
7213 <tt><--</tt> generate DEL, and <tt>Delete</tt>
7214 generate <tt>ESC [ 3 ~</tt>.
7218 X applications are configured so that <tt><</tt>
7219 deletes left, and <tt>Delete</tt> deletes right. Motif
7220 applications already work like this.
7224 Terminals should have <tt>stty erase ^?</tt> .
7228 The <tt>xterm</tt> terminfo entry should have <tt>ESC
7229 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
7230 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
7234 Emacs is programmed to map <tt>KB_Backspace</tt> or
7235 the <tt>stty erase</tt> character to
7236 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
7237 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
7238 <tt>^H</tt> to <tt>help</tt> as always.
7242 Other applications use the <tt>stty erase</tt>
7243 character and <tt>kdch1</tt> for the two delete keys,
7244 with ASCII DEL being "delete previous character" and
7245 <tt>kdch1</tt> being "delete character under
7253 This will solve the problem except for the following
7260 Some terminals have a <tt><--</tt> key that cannot
7261 be made to produce anything except <tt>^H</tt>. On
7262 these terminals Emacs help will be unavailable on
7263 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
7264 character takes precedence in Emacs, and has been set
7265 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
7266 available) can be used instead.
7270 Some operating systems use <tt>^H</tt> for <tt>stty
7271 erase</tt>. However, modern telnet versions and all
7272 rlogin versions propagate <tt>stty</tt> settings, and
7273 almost all UNIX versions honour <tt>stty erase</tt>.
7274 Where the <tt>stty</tt> settings are not propagated
7275 correctly, things can be made to work by using
7276 <tt>stty</tt> manually.
7280 Some systems (including previous Debian versions) use
7281 <prgn>xmodmap</prgn> to arrange for both
7282 <tt><--</tt> and <tt>Delete</tt> to generate
7283 <tt>KB_Delete</tt>. We can change the behavior of
7284 their X clients using the same X resources that we use
7285 to do it for our own clients, or configure our clients
7286 using their resources when things are the other way
7287 around. On displays configured like this
7288 <tt>Delete</tt> will not work, but <tt><--</tt>
7293 Some operating systems have different <tt>kdch1</tt>
7294 settings in their <tt>terminfo</tt> database for
7295 <tt>xterm</tt> and others. On these systems the
7296 <tt>Delete</tt> key will not work correctly when you
7297 log in from a system conforming to our policy, but
7298 <tt><--</tt> will.
7305 <heading>Environment variables</heading>
7308 A program must not depend on environment variables to get
7309 reasonable defaults. (That's because these environment
7310 variables would have to be set in a system-wide
7311 configuration file like <file>/etc/profile</file>, which is not
7312 supported by all shells.)
7316 If a program usually depends on environment variables for its
7317 configuration, the program should be changed to fall back to
7318 a reasonable default configuration if these environment
7319 variables are not present. If this cannot be done easily
7320 (e.g., if the source code of a non-free program is not
7321 available), the program must be replaced by a small
7322 "wrapper" shell script which sets the environment variables
7323 if they are not already defined, and calls the original program.
7327 Here is an example of a wrapper script for this purpose:
7329 <example compact="compact">
7331 BAR=${BAR:-/var/lib/fubar}
7333 exec /usr/lib/foo/foo "$@"
7338 Furthermore, as <file>/etc/profile</file> is a configuration
7339 file of the <prgn>base-files</prgn> package, other packages must
7340 not put any environment variables or other commands into that
7345 <sect id="doc-base">
7346 <heading>Registering Documents using doc-base</heading>
7349 The <package>doc-base</package> package implements a
7350 flexible mechanism for handling and presenting
7351 documentation. The recommended practice is for every Debian
7352 package that provides online documentation (other than just
7353 manual pages) to register these documents with
7354 <package>doc-base</package> by installing a
7355 <package>doc-base</package> control file via the
7356 <prgn/install-docs/ script at installation time and
7357 de-register the manuals again when the package is removed.
7360 Please refer to the documentation that comes with the
7361 <package>doc-base</package> package for information and
7370 <heading>Files</heading>
7372 <sect id="binaries">
7373 <heading>Binaries</heading>
7376 Two different packages must not install programs with
7377 different functionality but with the same filenames. (The
7378 case of two programs having the same functionality but
7379 different implementations is handled via "alternatives" or
7380 the "Conflicts" mechanism. See <ref id="maintscripts"> and
7381 <ref id="conflicts"> respectively.) If this case happens,
7382 one of the programs must be renamed. The maintainers should
7383 report this to the <tt>debian-devel</tt> mailing list and
7384 try to find a consensus about which program will have to be
7385 renamed. If a consensus cannot be reached, <em>both</em>
7386 programs must be renamed.
7390 By default, when a package is being built, any binaries
7391 created should include debugging information, as well as
7392 being compiled with optimization. You should also turn on
7393 as many reasonable compilation warnings as possible; this
7394 makes life easier for porters, who can then look at build
7395 logs for possible problems. For the C programming language,
7396 this means the following compilation parameters should be
7398 <example compact="compact">
7400 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
7402 INSTALL = install -s # (or use strip on the files in debian/tmp)
7407 Note that by default all installed binaries should be stripped,
7408 either by using the <tt>-s</tt> flag to
7409 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
7410 the binaries after they have been copied into
7411 <file>debian/tmp</file> but before the tree is made into a
7416 Although binaries in the build tree should be compiled with
7417 debugging information by default, it can often be difficult to
7418 debug programs if they are also subjected to compiler
7419 optimization. For this reason, it is recommended to support the
7420 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
7421 (see <ref id="debianrules-options">). This variable can contain
7422 several flags to change how a package is compiled and built.
7426 It is up to the package maintainer to decide what
7427 compilation options are best for the package. Certain
7428 binaries (such as computationally-intensive programs) will
7429 function better with certain flags (<tt>-O3</tt>, for
7430 example); feel free to use them. Please use good judgment
7431 here. Don't use flags for the sake of it; only use them
7432 if there is good reason to do so. Feel free to override
7433 the upstream author's ideas about which compilation
7434 options are best: they are often inappropriate for our
7440 <sect id="libraries">
7441 <heading>Libraries</heading>
7444 If the package is <strong>architecture: any</strong>, then
7445 the shared library compilation and linking flags must have
7446 <tt>-fPIC</tt>, or the package shall not build on some of
7447 the supported architectures<footnote>
7449 If you are using GCC, <tt>-fPIC</tt> produces code with
7450 relocatable position independent code, which is required for
7451 most architectures to create a shared library, with i386 and
7452 perhaps some others where non position independent code is
7453 permitted in a shared library.
7456 Position independent code may have a performance penalty,
7457 especially on <tt>i386</tt>. However, in most cases the
7458 speed penalty must be measured against the memory wasted on
7459 the few architectures where non position independent code is
7462 </footnote>. Any exception to this rule must be discussed on
7463 the mailing list <em>debian-devel@lists.debian.org</em>, and
7464 a rough consensus obtained. The reasons for not compiling
7465 with <tt>-fPIC</tt> flag must be recorded in the file
7466 <tt>README.Debian</tt>, and care must be taken to either
7467 restrict the architecture or arrange for <tt>-fPIC</tt> to
7468 be used on architectures where it is required.<footnote>
7470 Some of the reasons why this might be required is if the
7471 library contains hand crafted assembly code that is not
7472 relocatable, the speed penalty is excessive for compute
7473 intensive libs, and similar reasons.
7478 As to the static libraries, the common case is not to have
7479 relocatable code, since there is no benefit, unless in specific
7480 cases; therefore the static version must not be compiled
7481 with the <tt>-fPIC</tt> flag. Any exception to this rule
7482 should be discussed on the mailing list
7483 <em>debian-devel@lists.debian.org</em>, and the reasons for
7484 compiling with the <tt>-fPIC</tt> flag must be recorded in
7485 the file <tt>README.Debian</tt>. <footnote>
7487 Some of the reasons for linking static libraries with
7488 the <tt>-fPIC</tt> flag are if, for example, one needs a
7489 Perl API for a library that is under rapid development,
7490 and has an unstable API, so shared libraries are
7491 pointless at this phase of the library's development. In
7492 that case, since Perl needs a library with relocatable
7493 code, it may make sense to create a static library with
7494 relocatable code. Another reason cited is if you are
7495 distilling various libraries into a common shared
7496 library, like <tt>mklibs</tt> does in the Debian
7502 In other words, if both a shared and a static library is
7503 being built, each source unit (<tt>*.c</tt>, for example,
7504 for C files) will need to be compiled twice, for the normal
7509 Libraries should be built with threading support and to be
7510 thread-safe if the library supports this.
7514 Although not enforced by the build tools, shared libraries
7515 must be linked against all libraries that they use symbols from
7516 in the same way that binaries are. This ensures the correct
7517 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
7518 system and guarantees that all libraries can be safely opened
7519 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
7520 option <tt>-Wl,-z,defs</tt> when building a shared library.
7521 Since this option enforces symbol resolution at build time,
7522 a missing library reference will be caught early as a fatal
7527 All installed shared libraries should be stripped with
7528 <example compact="compact">
7529 strip --strip-unneeded <var>your-lib</var>
7531 (The option <tt>--strip-unneeded</tt> makes
7532 <prgn>strip</prgn> remove only the symbols which aren't
7533 needed for relocation processing.) Shared libraries can
7534 function perfectly well when stripped, since the symbols for
7535 dynamic linking are in a separate part of the ELF object
7537 You might also want to use the options
7538 <tt>--remove-section=.comment</tt> and
7539 <tt>--remove-section=.note</tt> on both shared libraries
7540 and executables, and <tt>--strip-debug</tt> on static
7546 Note that under some circumstances it may be useful to
7547 install a shared library unstripped, for example when
7548 building a separate package to support debugging.
7552 Shared object files (often <file>.so</file> files) that are not
7553 public libraries, that is, they are not meant to be linked
7554 to by third party executables (binaries of other packages),
7555 should be installed in subdirectories of the
7556 <file>/usr/lib</file> directory. Such files are exempt from the
7557 rules that govern ordinary shared libraries, except that
7558 they must not be installed executable and should be
7560 A common example are the so-called "plug-ins",
7561 internal shared objects that are dynamically loaded by
7562 programs using <manref name="dlopen" section="3">.
7567 Packages that use <prgn>libtool</prgn> to create and install
7568 their shared libraries install a file containing additional
7569 metadata (ending in <file>.la</file>) alongside the library.
7570 For public libraries intended for use by other packages, these
7571 files normally should not be included in the Debian package,
7572 since the information they include is not necessary to link with
7573 the shared library on Debian and can add unnecessary additional
7574 dependencies to other programs or libraries.<footnote>
7575 These files store, among other things, all libraries on which
7576 that shared library depends. Unfortunately, if
7577 the <file>.la</file> file is present and contains that
7578 dependency information, using <prgn>libtool</prgn> when
7579 linking against that library will cause the resulting program
7580 or library to be linked against those dependencies as well,
7581 even if this is unnecessary. This can create unneeded
7582 dependencies on shared library packages that would otherwise
7583 be hidden behind the library ABI, and can make library
7584 transitions to new SONAMEs unnecessarily complicated and
7585 difficult to manage.
7587 If the <file>.la</file> file is required for that library (if,
7588 for instance, it's loaded via <tt>libltdl</tt> in a way that
7589 requires that meta-information), the <tt>dependency_libs</tt>
7590 setting in the <file>.la</file> file should normally be set to
7591 the empty string. If the shared library development package has
7592 historically included the <file>.la</file>, it must be retained
7593 in the development package (with <tt>dependency_libs</tt>
7594 emptied) until all libraries that depend on it have removed or
7595 emptied <tt>dependency_libs</tt> in their <file>.la</file>
7596 files to prevent linking with those other libraries
7597 using <prgn>libtool</prgn> from failing.
7601 If the <file>.la</file> must be included, it should be included
7602 in the development (<tt>-dev</tt>) package, unless the library
7603 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
7604 library. If it is intended for use with <tt>libltdl</tt>,
7605 the <file>.la</file> files must go in the run-time library
7610 These requirements for handling of <file>.la</file> files do not
7611 apply to loadable modules or libraries not installed in
7612 directories searched by default by the dynamic linker. Packages
7613 installing loadable modules will frequently need to install
7614 the <file>.la</file> files alongside the modules so that they
7615 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
7616 does not need to be modified for libraries or modules that are
7617 not installed in directories searched by the dynamic linker by
7618 default and not intended for use by other packages.
7622 You must make sure that you use only released versions of
7623 shared libraries to build your packages; otherwise other
7624 users will not be able to run your binaries
7625 properly. Producing source packages that depend on
7626 unreleased compilers is also usually a bad
7633 <heading>Shared libraries</heading>
7635 This section has moved to <ref id="sharedlibs">.
7641 <heading>Scripts</heading>
7644 All command scripts, including the package maintainer
7645 scripts inside the package and used by <prgn>dpkg</prgn>,
7646 should have a <tt>#!</tt> line naming the shell to be used
7651 In the case of Perl scripts this should be
7652 <tt>#!/usr/bin/perl</tt>.
7656 When scripts are installed into a directory in the system
7657 PATH, the script name should not include an extension such
7658 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7659 language currently used to implement it.
7662 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
7663 <file>init.d</file> scripts should almost certainly start
7664 with <tt>set -e</tt> so that errors are detected.
7665 <file>init.d</file> scripts are something of a special case, due
7666 to how frequently they need to call commands that are allowed to
7667 fail, and it may instead be easier to check the exit status of
7668 commands directly. See <ref id="writing-init"> for more
7669 information about writing <file>init.d</file> scripts.
7672 Every script should use <tt>set -e</tt> or check the exit status
7673 of <em>every</em> command.
7676 Scripts may assume that <file>/bin/sh</file> implements the
7677 SUSv3 Shell Command Language<footnote>
7678 Single UNIX Specification, version 3, which is also IEEE
7679 1003.1-2004 (POSIX), and is available on the World Wide Web
7680 from <url id="http://www.unix.org/version3/online.html"
7681 name="The Open Group"> after free
7682 registration.</footnote>
7683 plus the following additional features not mandated by
7685 These features are in widespread use in the Linux community
7686 and are implemented in all of bash, dash, and ksh, the most
7687 common shells users may wish to use as <file>/bin/sh</file>.
7690 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7691 must not generate a newline.</item>
7692 <item><tt>test</tt>, if implemented as a shell built-in, must
7693 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7695 <item><tt>local</tt> to create a scoped variable must be
7696 supported, including listing multiple variables in a single
7697 local command and assigning a value to a variable at the
7698 same time as localizing it. <tt>local</tt> may or
7699 may not preserve the variable value from an outer scope if
7700 no assignment is present. Uses such as:
7704 # ... use a, b, c, d ...
7707 must be supported and must set the value of <tt>c</tt> to
7710 <item>The XSI extension to <prgn>kill</prgn> allowing <tt>kill
7711 -<var>signal</var></tt>, where <var>signal</var> is either
7712 the name of a signal or one of the numeric signals listed in
7713 the XSI extension (0, 1, 2, 3, 6, 9, 14, and 15), must be
7714 supported if <prgn>kill</prgn> is implemented as a shell
7717 <item>The XSI extension to <prgn>trap</prgn> allowing numeric
7718 signals must be supported. In addition to the signal
7719 numbers listed in the extension, which are the same as for
7720 <prgn>kill</prgn> above, 13 (SIGPIPE) must be allowed.
7723 If a shell script requires non-SUSv3 features from the shell
7724 interpreter other than those listed above, the appropriate shell
7725 must be specified in the first line of the script (e.g.,
7726 <tt>#!/bin/bash</tt>) and the package must depend on the package
7727 providing the shell (unless the shell package is marked
7728 "Essential", as in the case of <prgn>bash</prgn>).
7732 You may wish to restrict your script to SUSv3 features plus the
7733 above set when possible so that it may use <file>/bin/sh</file>
7734 as its interpreter. If your script works with <prgn>dash</prgn>
7735 (originally called <prgn>ash</prgn>), it probably complies with
7736 the above requirements, but if you are in doubt, use
7737 <file>/bin/bash</file>.
7741 Perl scripts should check for errors when making any
7742 system calls, including <tt>open</tt>, <tt>print</tt>,
7743 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7747 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7748 scripting languages. See <em>Csh Programming Considered
7749 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7750 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7751 If an upstream package comes with <prgn>csh</prgn> scripts
7752 then you must make sure that they start with
7753 <tt>#!/bin/csh</tt> and make your package depend on the
7754 <prgn>c-shell</prgn> virtual package.
7758 Any scripts which create files in world-writeable
7759 directories (e.g., in <file>/tmp</file>) must use a
7760 mechanism which will fail atomically if a file with the same
7761 name already exists.
7765 The Debian base system provides the <prgn>tempfile</prgn>
7766 and <prgn>mktemp</prgn> utilities for use by scripts for
7773 <heading>Symbolic links</heading>
7776 In general, symbolic links within a top-level directory
7777 should be relative, and symbolic links pointing from one
7778 top-level directory into another should be absolute. (A
7779 top-level directory is a sub-directory of the root
7780 directory <file>/</file>.)
7784 In addition, symbolic links should be specified as short as
7785 possible, i.e., link targets like <file>foo/../bar</file> are
7790 Note that when creating a relative link using
7791 <prgn>ln</prgn> it is not necessary for the target of the
7792 link to exist relative to the working directory you're
7793 running <prgn>ln</prgn> from, nor is it necessary to change
7794 directory to the directory where the link is to be made.
7795 Simply include the string that should appear as the target
7796 of the link (this will be a pathname relative to the
7797 directory in which the link resides) as the first argument
7802 For example, in your <prgn>Makefile</prgn> or
7803 <file>debian/rules</file>, you can do things like:
7804 <example compact="compact">
7805 ln -fs gcc $(prefix)/bin/cc
7806 ln -fs gcc debian/tmp/usr/bin/cc
7807 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7808 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7813 A symbolic link pointing to a compressed file should always
7814 have the same file extension as the referenced file. (For
7815 example, if a file <file>foo.gz</file> is referenced by a
7816 symbolic link, the filename of the link has to end with
7817 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7822 <heading>Device files</heading>
7825 Packages must not include device files or named pipes in the
7830 If a package needs any special device files that are not
7831 included in the base system, it must call
7832 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7833 after notifying the user<footnote>
7834 This notification could be done via a (low-priority)
7835 debconf message, or an echo (printf) statement.
7840 Packages must not remove any device files in the
7841 <prgn>postrm</prgn> or any other script. This is left to the
7842 system administrator.
7846 Debian uses the serial devices
7847 <file>/dev/ttyS*</file>. Programs using the old
7848 <file>/dev/cu*</file> devices should be changed to use
7849 <file>/dev/ttyS*</file>.
7853 Named pipes needed by the package must be created in
7854 the <prgn>postinst</prgn> script<footnote>
7855 It's better to use <prgn>mkfifo</prgn> rather
7856 than <prgn>mknod</prgn> to create named pipes so that
7857 automated checks for packages incorrectly creating device
7858 files with <prgn>mknod</prgn> won't have false positives.
7859 </footnote> and removed in
7860 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
7865 <sect id="config-files">
7866 <heading>Configuration files</heading>
7869 <heading>Definitions</heading>
7873 <tag>configuration file</tag>
7875 A file that affects the operation of a program, or
7876 provides site- or host-specific information, or
7877 otherwise customizes the behavior of a program.
7878 Typically, configuration files are intended to be
7879 modified by the system administrator (if needed or
7880 desired) to conform to local policy or to provide
7881 more useful site-specific behavior.
7884 <tag><tt>conffile</tt></tag>
7886 A file listed in a package's <tt>conffiles</tt>
7887 file, and is treated specially by <prgn>dpkg</prgn>
7888 (see <ref id="configdetails">).
7894 The distinction between these two is important; they are
7895 not interchangeable concepts. Almost all
7896 <tt>conffile</tt>s are configuration files, but many
7897 configuration files are not <tt>conffiles</tt>.
7901 As noted elsewhere, <file>/etc/init.d</file> scripts,
7902 <file>/etc/default</file> files, scripts installed in
7903 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7904 configuration installed in <file>/etc/cron.d</file> must be
7905 treated as configuration files. In general, any script that
7906 embeds configuration information is de-facto a configuration
7907 file and should be treated as such.
7912 <heading>Location</heading>
7915 Any configuration files created or used by your package
7916 must reside in <file>/etc</file>. If there are several,
7917 consider creating a subdirectory of <file>/etc</file>
7918 named after your package.
7922 If your package creates or uses configuration files
7923 outside of <file>/etc</file>, and it is not feasible to modify
7924 the package to use <file>/etc</file> directly, put the files
7925 in <file>/etc</file> and create symbolic links to those files
7926 from the location that the package requires.
7931 <heading>Behavior</heading>
7934 Configuration file handling must conform to the following
7936 <list compact="compact">
7938 local changes must be preserved during a package
7942 configuration files must be preserved when the
7943 package is removed, and only deleted when the
7947 Obsolete configuration files without local changes may be
7948 removed by the package during upgrade.
7952 The easy way to achieve this behavior is to make the
7953 configuration file a <tt>conffile</tt>. This is
7954 appropriate only if it is possible to distribute a default
7955 version that will work for most installations, although
7956 some system administrators may choose to modify it. This
7957 implies that the default version will be part of the
7958 package distribution, and must not be modified by the
7959 maintainer scripts during installation (or at any other
7964 In order to ensure that local changes are preserved
7965 correctly, no package may contain or make hard links to
7966 conffiles.<footnote>
7967 Rationale: There are two problems with hard links.
7968 The first is that some editors break the link while
7969 editing one of the files, so that the two files may
7970 unwittingly become unlinked and different. The second
7971 is that <prgn>dpkg</prgn> might break the hard link
7972 while upgrading <tt>conffile</tt>s.
7977 The other way to do it is via the maintainer scripts. In
7978 this case, the configuration file must not be listed as a
7979 <tt>conffile</tt> and must not be part of the package
7980 distribution. If the existence of a file is required for
7981 the package to be sensibly configured it is the
7982 responsibility of the package maintainer to provide
7983 maintainer scripts which correctly create, update and
7984 maintain the file and remove it on purge. (See <ref
7985 id="maintainerscripts"> for more information.) These
7986 scripts must be idempotent (i.e., must work correctly if
7987 <prgn>dpkg</prgn> needs to re-run them due to errors
7988 during installation or removal), must cope with all the
7989 variety of ways <prgn>dpkg</prgn> can call maintainer
7990 scripts, must not overwrite or otherwise mangle the user's
7991 configuration without asking, must not ask unnecessary
7992 questions (particularly during upgrades), and must
7993 otherwise be good citizens.
7997 The scripts are not required to configure every possible
7998 option for the package, but only those necessary to get
7999 the package running on a given system. Ideally the
8000 sysadmin should not have to do any configuration other
8001 than that done (semi-)automatically by the
8002 <prgn>postinst</prgn> script.
8006 A common practice is to create a script called
8007 <file><var>package</var>-configure</file> and have the
8008 package's <prgn>postinst</prgn> call it if and only if the
8009 configuration file does not already exist. In certain
8010 cases it is useful for there to be an example or template
8011 file which the maintainer scripts use. Such files should
8012 be in <file>/usr/share/<var>package</var></file> or
8013 <file>/usr/lib/<var>package</var></file> (depending on whether
8014 they are architecture-independent or not). There should
8015 be symbolic links to them from
8016 <file>/usr/share/doc/<var>package</var>/examples</file> if
8017 they are examples, and should be perfectly ordinary
8018 <prgn>dpkg</prgn>-handled files (<em>not</em>
8019 configuration files).
8023 These two styles of configuration file handling must
8024 not be mixed, for that way lies madness:
8025 <prgn>dpkg</prgn> will ask about overwriting the file
8026 every time the package is upgraded.
8031 <heading>Sharing configuration files</heading>
8034 Packages which specify the same file as a
8035 <tt>conffile</tt> must be tagged as <em>conflicting</em>
8036 with each other. (This is an instance of the general rule
8037 about not sharing files. Note that neither alternatives
8038 nor diversions are likely to be appropriate in this case;
8039 in particular, <prgn>dpkg</prgn> does not handle diverted
8040 <tt>conffile</tt>s well.)
8044 The maintainer scripts must not alter a <tt>conffile</tt>
8045 of <em>any</em> package, including the one the scripts
8050 If two or more packages use the same configuration file
8051 and it is reasonable for both to be installed at the same
8052 time, one of these packages must be defined as
8053 <em>owner</em> of the configuration file, i.e., it will be
8054 the package which handles that file as a configuration
8055 file. Other packages that use the configuration file must
8056 depend on the owning package if they require the
8057 configuration file to operate. If the other package will
8058 use the configuration file if present, but is capable of
8059 operating without it, no dependency need be declared.
8063 If it is desirable for two or more related packages to
8064 share a configuration file <em>and</em> for all of the
8065 related packages to be able to modify that configuration
8066 file, then the following should be done:
8067 <enumlist compact="compact">
8069 One of the related packages (the "owning" package)
8070 will manage the configuration file with maintainer
8071 scripts as described in the previous section.
8074 The owning package should also provide a program
8075 that the other packages may use to modify the
8079 The related packages must use the provided program
8080 to make any desired modifications to the
8081 configuration file. They should either depend on
8082 the core package to guarantee that the configuration
8083 modifier program is available or accept gracefully
8084 that they cannot modify the configuration file if it
8085 is not. (This is in addition to the fact that the
8086 configuration file may not even be present in the
8093 Sometimes it's appropriate to create a new package which
8094 provides the basic infrastructure for the other packages
8095 and which manages the shared configuration files. (The
8096 <tt>sgml-base</tt> package is a good example.)
8101 <heading>User configuration files ("dotfiles")</heading>
8104 The files in <file>/etc/skel</file> will automatically be
8105 copied into new user accounts by <prgn>adduser</prgn>.
8106 No other program should reference the files in
8107 <file>/etc/skel</file>.
8111 Therefore, if a program needs a dotfile to exist in
8112 advance in <file>$HOME</file> to work sensibly, that dotfile
8113 should be installed in <file>/etc/skel</file> and treated as a
8118 However, programs that require dotfiles in order to
8119 operate sensibly are a bad thing, unless they do create
8120 the dotfiles themselves automatically.
8124 Furthermore, programs should be configured by the Debian
8125 default installation to behave as closely to the upstream
8126 default behavior as possible.
8130 Therefore, if a program in a Debian package needs to be
8131 configured in some way in order to operate sensibly, that
8132 should be done using a site-wide configuration file placed
8133 in <file>/etc</file>. Only if the program doesn't support a
8134 site-wide default configuration and the package maintainer
8135 doesn't have time to add it may a default per-user file be
8136 placed in <file>/etc/skel</file>.
8140 <file>/etc/skel</file> should be as empty as we can make it.
8141 This is particularly true because there is no easy (or
8142 necessarily desirable) mechanism for ensuring that the
8143 appropriate dotfiles are copied into the accounts of
8144 existing users when a package is installed.
8150 <heading>Log files</heading>
8152 Log files should usually be named
8153 <file>/var/log/<var>package</var>.log</file>. If you have many
8154 log files, or need a separate directory for permission
8155 reasons (<file>/var/log</file> is writable only by
8156 <file>root</file>), you should usually create a directory named
8157 <file>/var/log/<var>package</var></file> and place your log
8162 Log files must be rotated occasionally so that they don't grow
8163 indefinitely. The best way to do this is to install a log
8164 rotation configuration file in the
8165 directory <file>/etc/logrotate.d</file>, normally
8166 named <file>/etc/logrotate.d/<var>package</var></file>, and use
8167 the facilities provided by <prgn>logrotate</prgn>.
8170 The traditional approach to log files has been to set up
8171 <em>ad hoc</em> log rotation schemes using simple shell
8172 scripts and cron. While this approach is highly
8173 customizable, it requires quite a lot of sysadmin work.
8174 Even though the original Debian system helped a little
8175 by automatically installing a system which can be used
8176 as a template, this was deemed not enough.
8180 The use of <prgn>logrotate</prgn>, a program developed
8181 by Red Hat, is better, as it centralizes log management.
8182 It has both a configuration file
8183 (<file>/etc/logrotate.conf</file>) and a directory where
8184 packages can drop their individual log rotation
8185 configurations (<file>/etc/logrotate.d</file>).
8188 Here is a good example for a logrotate config
8189 file (for more information see <manref name="logrotate"
8191 <example compact="compact">
8192 /var/log/foo/*.log {
8198 start-stop-daemon -K -p /var/run/foo.pid -s HUP -x /usr/sbin/foo -q
8202 This rotates all files under <file>/var/log/foo</file>, saves 12
8203 compressed generations, and tells the daemon to reopen its log
8204 files after the log rotation. It skips this log rotation
8205 (via <tt>missingok</tt>) if no such log file is present, which
8206 avoids errors if the package is removed but not purged.
8210 Log files should be removed when the package is
8211 purged (but not when it is only removed). This should be
8212 done by the <prgn>postrm</prgn> script when it is called
8213 with the argument <tt>purge</tt> (see <ref
8214 id="removedetails">).
8218 <sect id="permissions-owners">
8219 <heading>Permissions and owners</heading>
8222 The rules in this section are guidelines for general use.
8223 If necessary you may deviate from the details below.
8224 However, if you do so you must make sure that what is done
8225 is secure and you should try to be as consistent as possible
8226 with the rest of the system. You should probably also
8227 discuss it on <prgn>debian-devel</prgn> first.
8231 Files should be owned by <tt>root:root</tt>, and made
8232 writable only by the owner and universally readable (and
8233 executable, if appropriate), that is mode 644 or 755.
8237 Directories should be mode 755 or (for group-writability)
8238 mode 2775. The ownership of the directory should be
8239 consistent with its mode: if a directory is mode 2775, it
8240 should be owned by the group that needs write access to
8243 When a package is upgraded, and the owner or permissions
8244 of a file included in the package has changed, dpkg
8245 arranges for the ownership and permissions to be
8246 correctly set upon installation. However, this does not
8247 extend to directories; the permissions and ownership of
8248 directories already on the system does not change on
8249 install or upgrade of packages. This makes sense, since
8250 otherwise common directories like <tt>/usr</tt> would
8251 always be in flux. To correctly change permissions of a
8252 directory the package owns, explicit action is required,
8253 usually in the <tt>postinst</tt> script. Care must be
8254 taken to handle downgrades as well, in that case.
8260 Control information files should be owned by <tt>root:root</tt>
8261 and either mode 644 (for most files) or mode 755 (for
8262 executables such as <qref id="maintscripts">maintainer
8267 Setuid and setgid executables should be mode 4755 or 2755
8268 respectively, and owned by the appropriate user or group.
8269 They should not be made unreadable (modes like 4711 or
8270 2711 or even 4111); doing so achieves no extra security,
8271 because anyone can find the binary in the freely available
8272 Debian package; it is merely inconvenient. For the same
8273 reason you should not restrict read or execute permissions
8274 on non-set-id executables.
8278 Some setuid programs need to be restricted to particular
8279 sets of users, using file permissions. In this case they
8280 should be owned by the uid to which they are set-id, and by
8281 the group which should be allowed to execute them. They
8282 should have mode 4754; again there is no point in making
8283 them unreadable to those users who must not be allowed to
8288 It is possible to arrange that the system administrator can
8289 reconfigure the package to correspond to their local
8290 security policy by changing the permissions on a binary:
8291 they can do this by using <prgn>dpkg-statoverride</prgn>, as
8292 described below.<footnote>
8293 Ordinary files installed by <prgn>dpkg</prgn> (as
8294 opposed to <tt>conffile</tt>s and other similar objects)
8295 normally have their permissions reset to the distributed
8296 permissions when the package is reinstalled. However,
8297 the use of <prgn>dpkg-statoverride</prgn> overrides this
8300 Another method you should consider is to create a group for
8301 people allowed to use the program(s) and make any setuid
8302 executables executable only by that group.
8306 If you need to create a new user or group for your package
8307 there are two possibilities. Firstly, you may need to
8308 make some files in the binary package be owned by this
8309 user or group, or you may need to compile the user or
8310 group id (rather than just the name) into the binary
8311 (though this latter should be avoided if possible, as in
8312 this case you need a statically allocated id).</p>
8315 If you need a statically allocated id, you must ask for a
8316 user or group id from the <tt>base-passwd</tt> maintainer,
8317 and must not release the package until you have been
8318 allocated one. Once you have been allocated one you must
8319 either make the package depend on a version of the
8320 <tt>base-passwd</tt> package with the id present in
8321 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
8322 your package to create the user or group itself with the
8323 correct id (using <tt>adduser</tt>) in its
8324 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
8325 the <prgn>postinst</prgn> is to be preferred if it is
8326 possible, otherwise a pre-dependency will be needed on the
8327 <tt>adduser</tt> package.)
8331 On the other hand, the program might be able to determine
8332 the uid or gid from the user or group name at runtime, so
8333 that a dynamically allocated id can be used. In this case
8334 you should choose an appropriate user or group name,
8335 discussing this on <prgn>debian-devel</prgn> and checking
8336 with the <package/base-passwd/ maintainer that it is unique and that
8337 they do not wish you to use a statically allocated id
8338 instead. When this has been checked you must arrange for
8339 your package to create the user or group if necessary using
8340 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
8341 <prgn>postinst</prgn> script (again, the latter is to be
8342 preferred if it is possible).
8346 Note that changing the numeric value of an id associated
8347 with a name is very difficult, and involves searching the
8348 file system for all appropriate files. You need to think
8349 carefully whether a static or dynamic id is required, since
8350 changing your mind later will cause problems.
8353 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
8355 This section is not intended as policy, but as a
8356 description of the use of <prgn>dpkg-statoverride</prgn>.
8360 If a system administrator wishes to have a file (or
8361 directory or other such thing) installed with owner and
8362 permissions different from those in the distributed Debian
8363 package, they can use the <prgn>dpkg-statoverride</prgn>
8364 program to instruct <prgn>dpkg</prgn> to use the different
8365 settings every time the file is installed. Thus the
8366 package maintainer should distribute the files with their
8367 normal permissions, and leave it for the system
8368 administrator to make any desired changes. For example, a
8369 daemon which is normally required to be setuid root, but
8370 in certain situations could be used without being setuid,
8371 should be installed setuid in the <tt>.deb</tt>. Then the
8372 local system administrator can change this if they wish.
8373 If there are two standard ways of doing it, the package
8374 maintainer can use <tt>debconf</tt> to find out the
8375 preference, and call <prgn>dpkg-statoverride</prgn> in the
8376 maintainer script if necessary to accommodate the system
8377 administrator's choice. Care must be taken during
8378 upgrades to not override an existing setting.
8382 Given the above, <prgn>dpkg-statoverride</prgn> is
8383 essentially a tool for system administrators and would not
8384 normally be needed in the maintainer scripts. There is
8385 one type of situation, though, where calls to
8386 <prgn>dpkg-statoverride</prgn> would be needed in the
8387 maintainer scripts, and that involves packages which use
8388 dynamically allocated user or group ids. In such a
8389 situation, something like the following idiom can be very
8390 helpful in the package's <prgn>postinst</prgn>, where
8391 <tt>sysuser</tt> is a dynamically allocated id:
8393 for i in /usr/bin/foo /usr/sbin/bar
8395 # only do something when no setting exists
8396 if ! dpkg-statoverride --list $i >/dev/null 2>&1
8398 #include: debconf processing, question about foo and bar
8399 if [ "$RET" = "true" ] ; then
8400 dpkg-statoverride --update --add sysuser root 4755 $i
8405 The corresponding code to remove the override when the package
8408 for i in /usr/bin/foo /usr/sbin/bar
8410 if dpkg-statoverride --list $i >/dev/null 2>&1
8412 dpkg-statoverride --remove $i
8422 <chapt id="customized-programs">
8423 <heading>Customized programs</heading>
8425 <sect id="arch-spec">
8426 <heading>Architecture specification strings</heading>
8429 If a program needs to specify an <em>architecture specification
8430 string</em> in some place, it should select one of the strings
8431 provided by <tt>dpkg-architecture -L</tt>. The strings are in
8432 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
8433 part is sometimes elided, as when the OS is Linux.
8437 Note that we don't want to use
8438 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
8439 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
8440 since this would make our programs incompatible with other
8441 Linux distributions. We also don't use something like
8442 <tt><var>arch</var>-unknown-linux</tt>, since the
8443 <tt>unknown</tt> does not look very good.
8446 <sect1 id="arch-wildcard-spec">
8447 <heading>Architecture wildcards</heading>
8450 A package may specify an architecture wildcard. Architecture
8451 wildcards are in the format <tt>any</tt> (which matches every
8452 architecture), <tt><var>os</var></tt>-any, or
8453 any-<tt><var>cpu</var></tt>. <footnote>
8454 Internally, the package system normalizes the GNU triplets
8455 and the Debian arches into Debian arch triplets (which are
8456 kind of inverted GNU triplets), with the first component of
8457 the triplet representing the libc and ABI in use, and then
8458 does matching against those triplets. However, such
8459 triplets are an internal implementation detail that should
8460 not be used by packages directly. The libc and ABI portion
8461 is handled internally by the package system based on
8462 the <var>os</var> and <var>cpu</var>.
8469 <heading>Daemons</heading>
8472 The configuration files <file>/etc/services</file>,
8473 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
8474 by the <prgn>netbase</prgn> package and must not be modified
8479 If a package requires a new entry in one of these files, the
8480 maintainer should get in contact with the
8481 <prgn>netbase</prgn> maintainer, who will add the entries
8482 and release a new version of the <prgn>netbase</prgn>
8487 The configuration file <file>/etc/inetd.conf</file> must not be
8488 modified by the package's scripts except via the
8489 <prgn>update-inetd</prgn> script or the
8490 <file>DebianNet.pm</file> Perl module. See their documentation
8491 for details on how to add entries.
8495 If a package wants to install an example entry into
8496 <file>/etc/inetd.conf</file>, the entry must be preceded with
8497 exactly one hash character (<tt>#</tt>). Such lines are
8498 treated as "commented out by user" by the
8499 <prgn>update-inetd</prgn> script and are not changed or
8500 activated during package updates.
8505 <heading>Using pseudo-ttys and modifying wtmp, utmp and
8509 Some programs need to create pseudo-ttys. This should be done
8510 using Unix98 ptys if the C library supports it. The resulting
8511 program must not be installed setuid root, unless that
8512 is required for other functionality.
8516 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
8517 <file>/var/log/lastlog</file> must be installed writable by
8518 group <tt>utmp</tt>. Programs which need to modify those
8519 files must be installed setgid <tt>utmp</tt>.
8524 <heading>Editors and pagers</heading>
8527 Some programs have the ability to launch an editor or pager
8528 program to edit or display a text document. Since there are
8529 lots of different editors and pagers available in the Debian
8530 distribution, the system administrator and each user should
8531 have the possibility to choose their preferred editor and
8536 In addition, every program should choose a good default
8537 editor/pager if none is selected by the user or system
8542 Thus, every program that launches an editor or pager must
8543 use the EDITOR or PAGER environment variable to determine
8544 the editor or pager the user wishes to use. If these
8545 variables are not set, the programs <file>/usr/bin/editor</file>
8546 and <file>/usr/bin/pager</file> should be used, respectively.
8550 These two files are managed through the <prgn>dpkg</prgn>
8551 "alternatives" mechanism. Every package providing an editor or
8552 pager must call the <prgn>update-alternatives</prgn> script to
8553 register as an alternative for <file>/usr/bin/editor</file>
8554 or <file>/usr/bin/pager</file> as appropriate. The alternative
8555 should have a slave alternative
8556 for <file>/usr/share/man/man1/editor.1.gz</file>
8557 or <file>/usr/share/man/man1/pager.1.gz</file> pointing to the
8558 corresponding manual page.
8562 If it is very hard to adapt a program to make use of the
8563 EDITOR or PAGER variables, that program may be configured to
8564 use <file>/usr/bin/sensible-editor</file> and
8565 <file>/usr/bin/sensible-pager</file> as the editor or pager
8566 program respectively. These are two scripts provided in the
8567 <package>sensible-utils</package> package that check the EDITOR
8568 and PAGER variables and launch the appropriate program, and fall
8569 back to <file>/usr/bin/editor</file>
8570 and <file>/usr/bin/pager</file> if the variable is not set.
8574 A program may also use the VISUAL environment variable to
8575 determine the user's choice of editor. If it exists, it
8576 should take precedence over EDITOR. This is in fact what
8577 <file>/usr/bin/sensible-editor</file> does.
8581 It is not required for a package to depend on
8582 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
8583 package to provide such virtual packages.<footnote>
8584 The Debian base system already provides an editor and a
8590 <sect id="web-appl">
8591 <heading>Web servers and applications</heading>
8594 This section describes the locations and URLs that should
8595 be used by all web servers and web applications in the
8602 Cgi-bin executable files are installed in the
8604 <example compact="compact">
8605 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
8607 or a subdirectory of that directory, and should be
8609 <example compact="compact">
8610 http://localhost/cgi-bin/<var>cgi-bin-name</var>
8612 (possibly with a subdirectory name
8613 before <var>cgi-bin-name</var>).
8617 <p>Access to HTML documents</p>
8620 HTML documents for a package are stored in
8621 <file>/usr/share/doc/<var>package</var></file>
8622 and can be referred to as
8623 <example compact="compact">
8624 http://localhost/doc/<var>package</var>/<var>filename</var>
8629 The web server should restrict access to the document
8630 tree so that only clients on the same host can read
8631 the documents. If the web server does not support such
8632 access controls, then it should not provide access at
8633 all, or ask about providing access during installation.
8638 <p>Access to images</p>
8640 It is recommended that images for a package be stored
8641 in <tt>/usr/share/images/<var>package</var></tt> and
8642 may be referred to through an alias <tt>/images/</tt>
8645 http://localhost/images/<package>/<filename>
8652 <p>Web Document Root</p>
8655 Web Applications should try to avoid storing files in
8656 the Web Document Root. Instead they should use the
8657 /usr/share/doc/<var>package</var> directory for
8658 documents and register the Web Application via the
8659 <package>doc-base</package> package. If access to the
8660 web document root is unavoidable then use
8661 <example compact="compact">
8664 as the Document Root. This might be just a symbolic
8665 link to the location where the system administrator
8666 has put the real document root.
8669 <item><p>Providing httpd and/or httpd-cgi</p>
8671 All web servers should provide the virtual package
8672 <tt>httpd</tt>. If a web server has CGI support it should
8673 provide <tt>httpd-cgi</tt> additionally.
8676 All web applications which do not contain CGI scripts should
8677 depend on <tt>httpd</tt>, all those web applications which
8678 <tt>do</tt> contain CGI scripts, should depend on
8686 <sect id="mail-transport-agents">
8687 <heading>Mail transport, delivery and user agents</heading>
8690 Debian packages which process electronic mail, whether mail
8691 user agents (MUAs) or mail transport agents (MTAs), must
8692 ensure that they are compatible with the configuration
8693 decisions below. Failure to do this may result in lost
8694 mail, broken <tt>From:</tt> lines, and other serious brain
8699 The mail spool is <file>/var/mail</file> and the interface to
8700 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8701 the FHS). On older systems, the mail spool may be
8702 physically located in <file>/var/spool/mail</file>, but all
8703 access to the mail spool should be via the
8704 <file>/var/mail</file> symlink. The mail spool is part of the
8705 base system and not part of the MTA package.
8709 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8710 programs (such as IMAP daemons) must lock the mailbox in an
8711 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8712 be combined with dot locking. To avoid deadlocks, a program
8713 should use <tt>fcntl()</tt> first and dot locking after
8714 this, or alternatively implement the two locking methods in
8715 a non blocking way<footnote>
8716 If it is not possible to establish both locks, the
8717 system shouldn't wait for the second lock to be
8718 established, but remove the first lock, wait a (random)
8719 time, and start over locking again.
8720 </footnote>. Using the functions <tt>maillock</tt> and
8721 <tt>mailunlock</tt> provided by the
8722 <tt>liblockfile*</tt><footnote>
8723 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8724 to use these functions.
8725 </footnote> packages is the recommended way to realize this.
8729 Mailboxes are generally either mode 600 and owned by
8730 <var>user</var> or mode 660 and owned by
8731 <tt><var>user</var>:mail</tt><footnote>
8732 There are two traditional permission schemes for mail spools:
8733 mode 600 with all mail delivery done by processes running as
8734 the destination user, or mode 660 and owned by group mail with
8735 mail delivery done by a process running as a system user in
8736 group mail. Historically, Debian required mode 660 mail
8737 spools to enable the latter model, but that model has become
8738 increasingly uncommon and the principle of least privilege
8739 indicates that mail systems that use the first model should
8740 use permissions of 600. If delivery to programs is permitted,
8741 it's easier to keep the mail system secure if the delivery
8742 agent runs as the destination user. Debian Policy therefore
8743 permits either scheme.
8744 </footnote>. The local system administrator may choose a
8745 different permission scheme; packages should not make
8746 assumptions about the permission and ownership of mailboxes
8747 unless required (such as when creating a new mailbox). A MUA
8748 may remove a mailbox (unless it has nonstandard permissions) in
8749 which case the MTA or another MUA must recreate it if needed.
8753 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8754 be setgid mail to do the locking mentioned above (and
8755 must obviously avoid accessing other users' mailboxes
8756 using this privilege).</p>
8759 <file>/etc/aliases</file> is the source file for the system mail
8760 aliases (e.g., postmaster, usenet, etc.), it is the one
8761 which the sysadmin and <prgn>postinst</prgn> scripts may
8762 edit. After <file>/etc/aliases</file> is edited the program or
8763 human editing it must call <prgn>newaliases</prgn>. All MTA
8764 packages must come with a <prgn>newaliases</prgn> program,
8765 even if it does nothing, but older MTA packages did not do
8766 this so programs should not fail if <prgn>newaliases</prgn>
8767 cannot be found. Note that because of this, all MTA
8768 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8769 <tt>Replaces: mail-transport-agent</tt> control fields.
8773 The convention of writing <tt>forward to
8774 <var>address</var></tt> in the mailbox itself is not
8775 supported. Use a <tt>.forward</tt> file instead.</p>
8778 The <prgn>rmail</prgn> program used by UUCP
8779 for incoming mail should be <file>/usr/sbin/rmail</file>.
8780 Likewise, <prgn>rsmtp</prgn>, for receiving
8781 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8785 If your package needs to know what hostname to use on (for
8786 example) outgoing news and mail messages which are generated
8787 locally, you should use the file <file>/etc/mailname</file>. It
8788 will contain the portion after the username and <tt>@</tt>
8789 (at) sign for email addresses of users on the machine
8790 (followed by a newline).
8794 Such a package should check for the existence of this file
8795 when it is being configured. If it exists, it should be
8796 used without comment, although an MTA's configuration script
8797 may wish to prompt the user even if it finds that this file
8798 exists. If the file does not exist, the package should
8799 prompt the user for the value (preferably using
8800 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8801 as well as using it in the package's configuration. The
8802 prompt should make it clear that the name will not just be
8803 used by that package. For example, in this situation the
8804 <tt>inn</tt> package could say something like:
8805 <example compact="compact">
8806 Please enter the "mail name" of your system. This is the
8807 hostname portion of the address to be shown on outgoing
8808 news and mail messages. The default is
8809 <var>syshostname</var>, your system's host name. Mail
8810 name ["<var>syshostname</var>"]:
8812 where <var>syshostname</var> is the output of <tt>hostname
8818 <heading>News system configuration</heading>
8821 All the configuration files related to the NNTP (news)
8822 servers and clients should be located under
8823 <file>/etc/news</file>.</p>
8826 There are some configuration issues that apply to a number
8827 of news clients and server packages on the machine. These
8831 <tag><file>/etc/news/organization</file></tag>
8833 A string which should appear as the
8834 organization header for all messages posted
8835 by NNTP clients on the machine
8838 <tag><file>/etc/news/server</file></tag>
8840 Contains the FQDN of the upstream NNTP
8841 server, or localhost if the local machine is
8846 Other global files may be added as required for cross-package news
8853 <heading>Programs for the X Window System</heading>
8856 <heading>Providing X support and package priorities</heading>
8859 Programs that can be configured with support for the X
8860 Window System must be configured to do so and must declare
8861 any package dependencies necessary to satisfy their
8862 runtime requirements when using the X Window System. If
8863 such a package is of higher priority than the X packages
8864 on which it depends, it is required that either the
8865 X-specific components be split into a separate package, or
8866 that an alternative version of the package, which includes
8867 X support, be provided, or that the package's priority be
8873 <heading>Packages providing an X server</heading>
8876 Packages that provide an X server that, directly or
8877 indirectly, communicates with real input and display
8878 hardware should declare in their <tt>Provides</tt> control
8879 field that they provide the virtual
8880 package <tt>xserver</tt>.<footnote>
8881 This implements current practice, and provides an
8882 actual policy for usage of the <tt>xserver</tt>
8883 virtual package which appears in the virtual packages
8884 list. In a nutshell, X servers that interface
8885 directly with the display and input hardware or via
8886 another subsystem (e.g., GGI) should provide
8887 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8888 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8894 <heading>Packages providing a terminal emulator</heading>
8897 Packages that provide a terminal emulator for the X Window
8898 System which meet the criteria listed below should declare in
8899 their <tt>Provides</tt> control field that they provide the
8900 virtual package <tt>x-terminal-emulator</tt>. They should
8901 also register themselves as an alternative for
8902 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8903 20. That alternative should have a slave alternative
8904 for <file>/usr/share/man/man1/x-terminal-emulator.1.gz</file>
8905 pointing to the corresponding manual page.
8909 To be an <tt>x-terminal-emulator</tt>, a program must:
8910 <list compact="compact">
8912 Be able to emulate a DEC VT100 terminal, or a
8913 compatible terminal.
8917 Support the command-line option <tt>-e
8918 <var>command</var></tt>, which creates a new
8919 terminal window<footnote>
8920 "New terminal window" does not necessarily mean
8921 a new top-level X window directly parented by
8922 the window manager; it could, if the terminal
8923 emulator application were so coded, be a new
8924 "view" in a multiple-document interface (MDI).
8926 and runs the specified <var>command</var>,
8927 interpreting the entirety of the rest of the command
8928 line as a command to pass straight to exec, in the
8929 manner that <tt>xterm</tt> does.
8933 Support the command-line option <tt>-T
8934 <var>title</var></tt>, which creates a new terminal
8935 window with the window title <var>title</var>.
8942 <heading>Packages providing a window manager</heading>
8945 Packages that provide a window manager should declare in
8946 their <tt>Provides</tt> control field that they provide the
8947 virtual package <tt>x-window-manager</tt>. They should also
8948 register themselves as an alternative for
8949 <file>/usr/bin/x-window-manager</file>, with a priority
8950 calculated as follows:
8951 <list compact="compact">
8953 Start with a priority of 20.
8957 If the window manager supports the Debian menu
8958 system, add 20 points if this support is available
8959 in the package's default configuration (i.e., no
8960 configuration files belonging to the system or user
8961 have to be edited to activate the feature); if
8962 configuration files must be modified, add only 10
8968 If the window manager complies with <url
8969 id="http://www.freedesktop.org/Standards/wm-spec"
8970 name="The Window Manager Specification Project">,
8971 written by the <url id="http://www.freedesktop.org/"
8972 name="Free Desktop Group">, add 40 points.
8976 If the window manager permits the X session to be
8977 restarted using a <em>different</em> window manager
8978 (without killing the X server) in its default
8979 configuration, add 10 points; otherwise add none.
8982 That alternative should have a slave alternative
8983 for <file>/usr/share/man/man1/x-window-manager.1.gz</file>
8984 pointing to the corresponding manual page.
8989 <heading>Packages providing fonts</heading>
8992 Packages that provide fonts for the X Window
8994 For the purposes of Debian Policy, a "font for the X
8995 Window System" is one which is accessed via X protocol
8996 requests. Fonts for the Linux console, for PostScript
8997 renderer, or any other purpose, do not fit this
8998 definition. Any tool which makes such fonts available
8999 to the X Window System, however, must abide by this
9002 must do a number of things to ensure that they are both
9003 available without modification of the X or font server
9004 configuration, and that they do not corrupt files used by
9005 other font packages to register information about
9009 Fonts of any type supported by the X Window System
9010 must be in a separate binary package from any
9011 executables, libraries, or documentation (except
9012 that specific to the fonts shipped, such as their
9013 license information). If one or more of the fonts
9014 so packaged are necessary for proper operation of
9015 the package with which they are associated the font
9016 package may be Recommended; if the fonts merely
9017 provide an enhancement, a Suggests relationship may
9018 be used. Packages must not Depend on font
9020 This is because the X server may retrieve fonts
9021 from the local file system or over the network
9022 from an X font server; the Debian package system
9023 is empowered to deal only with the local
9029 BDF fonts must be converted to PCF fonts with the
9030 <prgn>bdftopcf</prgn> utility (available in the
9031 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
9032 placed in a directory that corresponds to their
9034 <list compact="compact">
9036 100 dpi fonts must be placed in
9037 <file>/usr/share/fonts/X11/100dpi/</file>.
9041 75 dpi fonts must be placed in
9042 <file>/usr/share/fonts/X11/75dpi/</file>.
9046 Character-cell fonts, cursor fonts, and other
9047 low-resolution fonts must be placed in
9048 <file>/usr/share/fonts/X11/misc/</file>.
9054 Type 1 fonts must be placed in
9055 <file>/usr/share/fonts/X11/Type1/</file>. If font
9056 metric files are available, they must be placed here
9061 Subdirectories of <file>/usr/share/fonts/X11/</file>
9062 other than those listed above must be neither
9063 created nor used. (The <file>PEX</file>, <file>CID</file>,
9064 <file>Speedo</file>, and <file>cyrillic</file> directories
9065 are excepted for historical reasons, but installation of
9066 files into these directories remains discouraged.)
9070 Font packages may, instead of placing files directly
9071 in the X font directories listed above, provide
9072 symbolic links in that font directory pointing to
9073 the files' actual location in the filesystem. Such
9074 a location must comply with the FHS.
9078 Font packages should not contain both 75dpi and
9079 100dpi versions of a font. If both are available,
9080 they should be provided in separate binary packages
9081 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
9082 the names of the packages containing the
9083 corresponding fonts.
9087 Fonts destined for the <file>misc</file> subdirectory
9088 should not be included in the same package as 75dpi
9089 or 100dpi fonts; instead, they should be provided in
9090 a separate package with <tt>-misc</tt> appended to
9095 Font packages must not provide the files
9096 <file>fonts.dir</file>, <file>fonts.alias</file>, or
9097 <file>fonts.scale</file> in a font directory:
9100 <file>fonts.dir</file> files must not be provided at all.
9104 <file>fonts.alias</file> and <file>fonts.scale</file>
9105 files, if needed, should be provided in the
9107 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
9108 where <var>fontdir</var> is the name of the
9110 <file>/usr/share/fonts/X11/</file> where the
9111 package's corresponding fonts are stored
9112 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
9113 <var>package</var> is the name of the package
9114 that provides these fonts, and
9115 <var>extension</var> is either <tt>scale</tt>
9116 or <tt>alias</tt>, whichever corresponds to
9123 Font packages must declare a dependency on
9124 <tt>xfonts-utils</tt> in their <tt>Depends</tt>
9125 or <tt>Pre-Depends</tt> control field.
9129 Font packages that provide one or more
9130 <file>fonts.scale</file> files as described above must
9131 invoke <prgn>update-fonts-scale</prgn> on each
9132 directory into which they installed fonts
9133 <em>before</em> invoking
9134 <prgn>update-fonts-dir</prgn> on that directory.
9135 This invocation must occur in both the
9136 <prgn>postinst</prgn> (for all arguments) and
9137 <prgn>postrm</prgn> (for all arguments except
9138 <tt>upgrade</tt>) scripts.
9142 Font packages that provide one or more
9143 <file>fonts.alias</file> files as described above must
9144 invoke <prgn>update-fonts-alias</prgn> on each
9145 directory into which they installed fonts. This
9146 invocation must occur in both the
9147 <prgn>postinst</prgn> (for all arguments) and
9148 <prgn>postrm</prgn> (for all arguments except
9149 <tt>upgrade</tt>) scripts.
9153 Font packages must invoke
9154 <prgn>update-fonts-dir</prgn> on each directory into
9155 which they installed fonts. This invocation must
9156 occur in both the <prgn>postinst</prgn> (for all
9157 arguments) and <prgn>postrm</prgn> (for all
9158 arguments except <tt>upgrade</tt>) scripts.
9162 Font packages must not provide alias names for the
9163 fonts they include which collide with alias names
9164 already in use by fonts already packaged.
9168 Font packages must not provide fonts with the same
9169 XLFD registry name as another font already packaged.
9175 <sect1 id="appdefaults">
9176 <heading>Application defaults files</heading>
9179 Application defaults files must be installed in the
9180 directory <file>/etc/X11/app-defaults/</file> (use of a
9181 localized subdirectory of <file>/etc/X11/</file> as described
9182 in the <em>X Toolkit Intrinsics - C Language
9183 Interface</em> manual is also permitted). They must be
9184 registered as <tt>conffile</tt>s or handled as
9185 configuration files.
9189 Customization of programs' X resources may also be
9190 supported with the provision of a file with the same name
9191 as that of the package placed in
9192 the <file>/etc/X11/Xresources/</file> directory, which
9193 must be registered as a <tt>conffile</tt> or handled as a
9194 configuration file.<footnote>
9195 Note that this mechanism is not the same as using
9196 app-defaults; app-defaults are tied to the client
9197 binary on the local file system, whereas X resources
9198 are stored in the X server and affect all connecting
9205 <heading>Installation directory issues</heading>
9208 Historically, packages using the X Window System used a
9209 separate set of installation directories from other packages.
9210 This practice has been discontinued and packages using the X
9211 Window System should now generally be installed in the same
9212 directories as any other package. Specifically, packages must
9213 not install files under the <file>/usr/X11R6/</file> directory
9214 and the <file>/usr/X11R6/</file> directory hierarchy should be
9215 regarded as obsolete.
9219 Include files previously installed under
9220 <file>/usr/X11R6/include/X11/</file> should be installed into
9221 <file>/usr/include/X11/</file>. For files previously
9222 installed into subdirectories of
9223 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
9224 determine if subdirectories of <file>/usr/lib/</file> and
9225 <file>/usr/share/</file> can be used. If not, a subdirectory
9226 of <file>/usr/lib/X11/</file> should be used.
9230 Configuration files for window, display, or session managers
9231 or other applications that are tightly integrated with the X
9232 Window System may be placed in a subdirectory
9233 of <file>/etc/X11/</file> corresponding to the package name.
9234 Other X Window System applications should use
9235 the <file>/etc/</file> directory unless otherwise mandated by
9236 policy (such as for <ref id="appdefaults">).
9241 <heading>The OSF/Motif and OpenMotif libraries</heading>
9244 <em>Programs that require the non-DFSG-compliant OSF/Motif or
9245 OpenMotif libraries</em><footnote>
9246 OSF/Motif and OpenMotif are collectively referred to as
9247 "Motif" in this policy document.
9249 should be compiled against and tested with LessTif (a free
9250 re-implementation of Motif) instead. If the maintainer
9251 judges that the program or programs do not work
9252 sufficiently well with LessTif to be distributed and
9253 supported, but do so when compiled against Motif, then two
9254 versions of the package should be created; one linked
9255 statically against Motif and with <tt>-smotif</tt>
9256 appended to the package name, and one linked dynamically
9257 against Motif and with <tt>-dmotif</tt> appended to the
9262 Both Motif-linked versions are dependent
9263 upon non-DFSG-compliant software and thus cannot be
9264 uploaded to the <em>main</em> distribution; if the
9265 software is itself DFSG-compliant it may be uploaded to
9266 the <em>contrib</em> distribution. While known existing
9267 versions of Motif permit unlimited redistribution of
9268 binaries linked against the library (whether statically or
9269 dynamically), it is the package maintainer's
9270 responsibility to determine whether this is permitted by
9271 the license of the copy of Motif in their possession.
9277 <heading>Perl programs and modules</heading>
9280 Perl programs and modules should follow the current Perl policy.
9284 The Perl policy can be found in the <tt>perl-policy</tt>
9285 files in the <tt>debian-policy</tt> package.
9286 It is also available from the Debian web mirrors at
9287 <tt><url name="/doc/packaging-manuals/perl-policy/"
9288 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
9293 <heading>Emacs lisp programs</heading>
9296 Please refer to the "Debian Emacs Policy" for details of how to
9297 package emacs lisp programs.
9301 The Emacs policy is available in
9302 <file>debian-emacs-policy.gz</file> of the
9303 <package>emacsen-common</package> package.
9304 It is also available from the Debian web mirrors at
9305 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
9306 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
9311 <heading>Games</heading>
9314 The permissions on <file>/var/games</file> are mode 755, owner
9315 <tt>root</tt> and group <tt>root</tt>.
9319 Each game decides on its own security policy.</p>
9322 Games which require protected, privileged access to
9323 high-score files, saved games, etc., may be made
9324 set-<em>group</em>-id (mode 2755) and owned by
9325 <tt>root:games</tt>, and use files and directories with
9326 appropriate permissions (770 <tt>root:games</tt>, for
9327 example). They must not be made
9328 set-<em>user</em>-id, as this causes security problems. (If
9329 an attacker can subvert any set-user-id game they can
9330 overwrite the executable of any other, causing other players
9331 of these games to run a Trojan horse program. With a
9332 set-group-id game the attacker only gets access to less
9333 important game data, and if they can get at the other
9334 players' accounts at all it will take considerably more
9338 Some packages, for example some fortune cookie programs, are
9339 configured by the upstream authors to install with their
9340 data files or other static information made unreadable so
9341 that they can only be accessed through set-id programs
9342 provided. You should not do this in a Debian package: anyone can
9343 download the <file>.deb</file> file and read the data from it,
9344 so there is no point making the files unreadable. Not
9345 making the files unreadable also means that you don't have
9346 to make so many programs set-id, which reduces the risk of a
9350 As described in the FHS, binaries of games should be
9351 installed in the directory <file>/usr/games</file>. This also
9352 applies to games that use the X Window System. Manual pages
9353 for games (X and non-X games) should be installed in
9354 <file>/usr/share/man/man6</file>.</p>
9360 <heading>Documentation</heading>
9363 <heading>Manual pages</heading>
9366 You should install manual pages in <prgn>nroff</prgn> source
9367 form, in appropriate places under <file>/usr/share/man</file>.
9368 You should only use sections 1 to 9 (see the FHS for more
9369 details). You must not install a pre-formatted "cat page".
9373 Each program, utility, and function should have an
9374 associated manual page included in the same package. It is
9375 suggested that all configuration files also have a manual
9376 page included as well. Manual pages for protocols and other
9377 auxiliary things are optional.
9381 If no manual page is available, this is considered as a bug
9382 and should be reported to the Debian Bug Tracking System (the
9383 maintainer of the package is allowed to write this bug report
9384 themselves, if they so desire). Do not close the bug report
9385 until a proper man page is available.<footnote>
9386 It is not very hard to write a man page. See the
9387 <url id="http://www.schweikhardt.net/man_page_howto.html"
9388 name="Man-Page-HOWTO">,
9389 <manref name="man" section="7">, the examples
9390 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
9391 the helper program <prgn>help2man</prgn>, or the
9392 directory <file>/usr/share/doc/man-db/examples</file>.
9397 You may forward a complaint about a missing man page to the
9398 upstream authors, and mark the bug as forwarded in the
9399 Debian bug tracking system. Even though the GNU Project do
9400 not in general consider the lack of a man page to be a bug,
9401 we do; if they tell you that they don't consider it a bug
9402 you should leave the bug in our bug tracking system open
9407 Manual pages should be installed compressed using <tt>gzip -9</tt>.
9411 If one man page needs to be accessible via several names it
9412 is better to use a symbolic link than the <file>.so</file>
9413 feature, but there is no need to fiddle with the relevant
9414 parts of the upstream source to change from <file>.so</file> to
9415 symlinks: don't do it unless it's easy. You should not
9416 create hard links in the manual page directories, nor put
9417 absolute filenames in <file>.so</file> directives. The filename
9418 in a <file>.so</file> in a man page should be relative to the
9419 base of the man page tree (usually
9420 <file>/usr/share/man</file>). If you do not create any links
9421 (whether symlinks, hard links, or <tt>.so</tt> directives)
9422 in the file system to the alternate names of the man page,
9423 then you should not rely on <prgn>man</prgn> finding your
9424 man page under those names based solely on the information in
9425 the man page's header.<footnote>
9426 Supporting this in <prgn>man</prgn> often requires
9427 unreasonable processing time to find a manual page or to
9428 report that none exists, and moves knowledge into man's
9429 database that would be better left in the file system.
9430 This support is therefore deprecated and will cease to
9431 be present in the future.
9436 Manual pages in locale-specific subdirectories of
9437 <file>/usr/share/man</file> should use either UTF-8 or the usual
9438 legacy encoding for that language (normally the one corresponding
9439 to the shortest relevant locale name in
9440 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
9441 <file>/usr/share/man/fr</file> should use either UTF-8 or
9442 ISO-8859-1.<footnote>
9443 <prgn>man</prgn> will automatically detect whether UTF-8 is in
9444 use. In future, all manual pages will be required to use
9450 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
9451 included in the subdirectory name unless it indicates a
9452 significant difference in the language, as this excludes
9453 speakers of the language in other countries.<footnote>
9454 At the time of writing, Chinese and Portuguese are the main
9455 languages with such differences, so <file>pt_BR</file>,
9456 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
9461 If a localized version of a manual page is provided, it should
9462 either be up-to-date or it should be obvious to the reader that
9463 it is outdated and the original manual page should be used
9464 instead. This can be done either by a note at the beginning of
9465 the manual page or by showing the missing or changed portions in
9466 the original language instead of the target language.
9471 <heading>Info documents</heading>
9474 Info documents should be installed in <file>/usr/share/info</file>.
9475 They should be compressed with <tt>gzip -9</tt>.
9479 The <prgn>install-info</prgn> program maintains a directory of
9480 installed info documents in <file>/usr/share/info/dir</file> for
9481 the use of info readers.<footnote>
9482 It was previously necessary for packages installing info
9483 documents to run <prgn>install-info</prgn> from maintainer
9484 scripts. This is no longer necessary. The installation
9485 system now uses dpkg triggers.
9487 This file must not be included in packages. Packages containing
9488 info documents should depend on <tt>dpkg (>= 1.15.4) |
9489 install-info</tt> to ensure that the directory file is properly
9490 rebuilt during partial upgrades from Debian 5.0 (lenny) and
9495 Info documents should contain section and directory entry
9496 information in the document for the use
9497 of <prgn>install-info</prgn>. The section should be specified
9498 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
9499 space and the section of this info page. The directory entry or
9500 entries should be included between
9501 a <tt>START-INFO-DIR-ENTRY</tt> line and
9502 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
9504 INFO-DIR-SECTION Individual utilities
9505 START-INFO-DIR-ENTRY
9506 * example: (example). An example info directory entry.
9509 To determine which section to use, you should look
9510 at <file>/usr/share/info/dir</file> on your system and choose
9511 the most relevant (or create a new section if none of the
9512 current sections are relevant).<footnote>
9513 Normally, info documents are generated from Texinfo source.
9514 To include this information in the generated info document, if
9515 it is absent, add commands like:
9517 @dircategory Individual utilities
9519 * example: (example). An example info directory entry.
9522 to the Texinfo source of the document and ensure that the info
9523 documents are rebuilt from source during the package build.
9529 <heading>Additional documentation</heading>
9532 Any additional documentation that comes with the package may
9533 be installed at the discretion of the package maintainer.
9534 Plain text documentation should be installed in the directory
9535 <file>/usr/share/doc/<var>package</var></file>, where
9536 <var>package</var> is the name of the package, and
9537 compressed with <tt>gzip -9</tt> unless it is small.
9541 If a package comes with large amounts of documentation which
9542 many users of the package will not require you should create
9543 a separate binary package to contain it, so that it does not
9544 take up disk space on the machines of users who do not need
9545 or want it installed.</p>
9548 It is often a good idea to put text information files
9549 (<file>README</file>s, changelogs, and so forth) that come with
9550 the source package in <file>/usr/share/doc/<var>package</var></file>
9551 in the binary package. However, you don't need to install
9552 the instructions for building and installing the package, of
9556 Packages must not require the existence of any files in
9557 <file>/usr/share/doc/</file> in order to function
9559 The system administrator should be able to
9560 delete files in <file>/usr/share/doc/</file> without causing
9561 any programs to break.
9563 Any files that are referenced by programs but are also
9564 useful as stand alone documentation should be installed under
9565 <file>/usr/share/<var>package</var>/</file> with symbolic links from
9566 <file>/usr/share/doc/<var>package</var></file>.
9570 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9571 link to another directory in <file>/usr/share/doc</file> only if
9572 the two packages both come from the same source and the
9573 first package Depends on the second.<footnote>
9575 Please note that this does not override the section on
9576 changelog files below, so the file
9577 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
9578 must refer to the changelog for the current version of
9579 <var>package</var> in question. In practice, this means
9580 that the sources of the target and the destination of the
9581 symlink must be the same (same source package and
9588 Former Debian releases placed all additional documentation
9589 in <file>/usr/doc/<var>package</var></file>. This has been
9590 changed to <file>/usr/share/doc/<var>package</var></file>,
9591 and packages must not put documentation in the directory
9592 <file>/usr/doc/<var>package</var></file>. <footnote>
9593 At this phase of the transition, we no longer require a
9594 symbolic link in <file>/usr/doc/</file>. At a later point,
9595 policy shall change to make the symbolic links a bug.
9601 <heading>Preferred documentation formats</heading>
9604 The unification of Debian documentation is being carried out
9608 If your package comes with extensive documentation in a
9609 markup format that can be converted to various other formats
9610 you should if possible ship HTML versions in a binary
9611 package, in the directory
9612 <file>/usr/share/doc/<var>appropriate-package</var></file> or
9613 its subdirectories.<footnote>
9614 The rationale: The important thing here is that HTML
9615 docs should be available in <em>some</em> package, not
9616 necessarily in the main binary package.
9621 Other formats such as PostScript may be provided at the
9622 package maintainer's discretion.
9626 <sect id="copyrightfile">
9627 <heading>Copyright information</heading>
9630 Every package must be accompanied by a verbatim copy of its
9631 copyright information and distribution license in the file
9632 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
9633 file must neither be compressed nor be a symbolic link.
9637 In addition, the copyright file must say where the upstream
9638 sources (if any) were obtained. It should name the original
9639 authors of the package and the Debian maintainer(s) who were
9640 involved with its creation.
9644 Packages in the <em>contrib</em> or <em>non-free</em> archive
9645 areas should state in the copyright file that the package is not
9646 part of the Debian GNU/Linux distribution and briefly explain
9651 A copy of the file which will be installed in
9652 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9653 be in <file>debian/copyright</file> in the source package.
9657 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9658 link to another directory in <file>/usr/share/doc</file> only if
9659 the two packages both come from the same source and the
9660 first package Depends on the second. These rules are
9661 important because copyrights must be extractable by
9666 Packages distributed under the Apache license (version 2.0), the
9667 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
9668 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
9669 1.3) should refer to the corresponding files
9670 under <file>/usr/share/common-licenses</file>,<footnote>
9673 <file>/usr/share/common-licenses/Apache-2.0</file>,
9674 <file>/usr/share/common-licenses/Artistic</file>,
9675 <file>/usr/share/common-licenses/GPL-1</file>,
9676 <file>/usr/share/common-licenses/GPL-2</file>,
9677 <file>/usr/share/common-licenses/GPL-3</file>,
9678 <file>/usr/share/common-licenses/LGPL-2</file>,
9679 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9680 <file>/usr/share/common-licenses/LGPL-3</file>,
9681 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
9682 <file>/usr/share/common-licenses/GFDL-1.3</file>
9683 respectively. The University of California BSD license is
9684 also included in <package>base-files</package> as
9685 <file>/usr/share/common-licenses/BSD</file>, but given the
9686 brevity of this license, its specificity to code whose
9687 copyright is held by the Regents of the University of
9688 California, and the frequency of minor wording changes, its
9689 text should be included in the copyright file rather than
9690 referencing this file.
9692 </footnote> rather than quoting them in the copyright
9697 You should not use the copyright file as a general <file>README</file>
9698 file. If your package has such a file it should be
9699 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9700 <file>README.Debian</file> or some other appropriate place.</p>
9704 <heading>Examples</heading>
9707 Any examples (configurations, source files, whatever),
9708 should be installed in a directory
9709 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9710 files should not be referenced by any program: they're there
9711 for the benefit of the system administrator and users as
9712 documentation only. Architecture-specific example files
9713 should be installed in a directory
9714 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9716 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9717 latter directory itself may be a symbolic link to the
9722 If the purpose of a package is to provide examples, then the
9723 example files may be installed into
9724 <file>/usr/share/doc/<var>package</var></file>.
9728 <sect id="changelogs">
9729 <heading>Changelog files</heading>
9732 Packages that are not Debian-native must contain a
9733 compressed copy of the <file>debian/changelog</file> file from
9734 the Debian source tree in
9735 <file>/usr/share/doc/<var>package</var></file> with the name
9736 <file>changelog.Debian.gz</file>.
9740 If an upstream changelog is available, it should be accessible as
9741 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9742 plain text. If the upstream changelog is distributed in
9743 HTML, it should be made available in that form as
9744 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9745 and a plain text <file>changelog.gz</file> should be generated
9746 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9747 the upstream changelog files do not already conform to this
9748 naming convention, then this may be achieved either by
9749 renaming the files, or by adding a symbolic link, at the
9750 maintainer's discretion.<footnote>
9751 Rationale: People should not have to look in places for
9752 upstream changelogs merely because they are given
9753 different names or are distributed in HTML format.
9758 All of these files should be installed compressed using
9759 <tt>gzip -9</tt>, as they will become large with time even
9760 if they start out small.
9764 If the package has only one changelog which is used both as
9765 the Debian changelog and the upstream one because there is
9766 no separate upstream maintainer then that changelog should
9767 usually be installed as
9768 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9769 there is a separate upstream maintainer, but no upstream
9770 changelog, then the Debian changelog should still be called
9771 <file>changelog.Debian.gz</file>.
9775 For details about the format and contents of the Debian
9776 changelog file, please see <ref id="dpkgchangelog">.
9781 <appendix id="pkg-scope">
9782 <heading>Introduction and scope of these appendices</heading>
9785 These appendices are taken essentially verbatim from the
9786 now-deprecated Packaging Manual, version 3.2.1.0. They are
9787 the chapters which are likely to be of use to package
9788 maintainers and which have not already been included in the
9789 policy document itself. Most of these sections are very likely
9790 not relevant to policy; they should be treated as
9791 documentation for the packaging system. Please note that these
9792 appendices are included for convenience, and for historical
9793 reasons: they used to be part of policy package, and they have
9794 not yet been incorporated into dpkg documentation. However,
9795 they still have value, and hence they are presented here.
9799 They have not yet been checked to ensure that they are
9800 compatible with the contents of policy, and if there are any
9801 contradictions, the version in the main policy document takes
9802 precedence. The remaining chapters of the old Packaging
9803 Manual have also not been read in detail to ensure that there
9804 are not parts which have been left out. Both of these will be
9809 Certain parts of the Packaging manual were integrated into the
9810 Policy Manual proper, and removed from the appendices. Links
9811 have been placed from the old locations to the new ones.
9815 <prgn>dpkg</prgn> is a suite of programs for creating binary
9816 package files and installing and removing them on Unix
9818 <prgn>dpkg</prgn> is targeted primarily at Debian
9819 GNU/Linux, but may work on or be ported to other
9825 The binary packages are designed for the management of
9826 installed executable programs (usually compiled binaries) and
9827 their associated data, though source code examples and
9828 documentation are provided as part of some packages.</p>
9831 This manual describes the technical aspects of creating Debian
9832 binary packages (<file>.deb</file> files). It documents the
9833 behavior of the package management programs
9834 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9835 they interact with packages.</p>
9838 It also documents the interaction between
9839 <prgn>dselect</prgn>'s core and the access method scripts it
9840 uses to actually install the selected packages, and describes
9841 how to create a new access method.</p>
9844 This manual does not go into detail about the options and
9845 usage of the package building and installation tools. It
9846 should therefore be read in conjunction with those programs'
9851 The utility programs which are provided with <prgn>dpkg</prgn>
9852 for managing various system configuration and similar issues,
9853 such as <prgn>update-rc.d</prgn> and
9854 <prgn>install-info</prgn>, are not described in detail here -
9855 please see their man pages.
9859 It is assumed that the reader is reasonably familiar with the
9860 <prgn>dpkg</prgn> System Administrators' manual.
9861 Unfortunately this manual does not yet exist.
9865 The Debian version of the FSF's GNU hello program is provided
9866 as an example for people wishing to create Debian
9867 packages. The Debian <prgn>debmake</prgn> package is
9868 recommended as a very helpful tool in creating and maintaining
9869 Debian packages. However, while the tools and examples are
9870 helpful, they do not replace the need to read and follow the
9871 Policy and Programmer's Manual.</p>
9874 <appendix id="pkg-binarypkg">
9875 <heading>Binary packages (from old Packaging Manual)</heading>
9878 The binary package has two main sections. The first part
9879 consists of various control information files and scripts used
9880 by <prgn>dpkg</prgn> when installing and removing. See <ref
9881 id="pkg-controlarea">.
9885 The second part is an archive containing the files and
9886 directories to be installed.
9890 In the future binary packages may also contain other
9891 components, such as checksums and digital signatures. The
9892 format for the archive is described in full in the
9893 <file>deb(5)</file> man page.
9897 <sect id="pkg-bincreating"><heading>Creating package files -
9898 <prgn>dpkg-deb</prgn>
9902 All manipulation of binary package files is done by
9903 <prgn>dpkg-deb</prgn>; it's the only program that has
9904 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9905 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9906 will spot that the options requested are appropriate to
9907 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9912 In order to create a binary package you must make a
9913 directory tree which contains all the files and directories
9914 you want to have in the file system data part of the package.
9915 In Debian-format source packages this directory is usually
9916 <file>debian/tmp</file>, relative to the top of the package's
9921 They should have the locations (relative to the root of the
9922 directory tree you're constructing) ownerships and
9923 permissions which you want them to have on the system when
9928 With current versions of <prgn>dpkg</prgn> the uid/username
9929 and gid/groupname mappings for the users and groups being
9930 used should be the same on the system where the package is
9931 built and the one where it is installed.
9935 You need to add one special directory to the root of the
9936 miniature file system tree you're creating:
9937 <prgn>DEBIAN</prgn>. It should contain the control
9938 information files, notably the binary package control file
9939 (see <ref id="pkg-controlfile">).
9943 The <prgn>DEBIAN</prgn> directory will not appear in the
9944 file system archive of the package, and so won't be installed
9945 by <prgn>dpkg</prgn> when the package is unpacked.
9949 When you've prepared the package, you should invoke:
9951 dpkg --build <var>directory</var>
9956 This will build the package in
9957 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9958 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9959 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9964 See the man page <manref name="dpkg-deb" section="8"> for details of how
9965 to examine the contents of this newly-created file. You may find the
9966 output of following commands enlightening:
9968 dpkg-deb --info <var>filename</var>.deb
9969 dpkg-deb --contents <var>filename</var>.deb
9970 dpkg --contents <var>filename</var>.deb
9972 To view the copyright file for a package you could use this command:
9974 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
9979 <sect id="pkg-controlarea">
9980 <heading>Package control information files</heading>
9983 The control information portion of a binary package is a
9984 collection of files with names known to <prgn>dpkg</prgn>.
9985 It will treat the contents of these files specially - some
9986 of them contain information used by <prgn>dpkg</prgn> when
9987 installing or removing the package; others are scripts which
9988 the package maintainer wants <prgn>dpkg</prgn> to run.
9992 It is possible to put other files in the package control
9993 information file area, but this is not generally a good idea
9994 (though they will largely be ignored).
9998 Here is a brief list of the control information files supported
9999 by <prgn>dpkg</prgn> and a summary of what they're used for.
10004 <tag><tt>control</tt>
10007 This is the key description file used by
10008 <prgn>dpkg</prgn>. It specifies the package's name
10009 and version, gives its description for the user,
10010 states its relationships with other packages, and so
10011 forth. See <ref id="sourcecontrolfiles"> and
10012 <ref id="binarycontrolfiles">.
10016 It is usually generated automatically from information
10017 in the source package by the
10018 <prgn>dpkg-gencontrol</prgn> program, and with
10019 assistance from <prgn>dpkg-shlibdeps</prgn>.
10020 See <ref id="pkg-sourcetools">.
10024 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
10029 These are executable files (usually scripts) which
10030 <prgn>dpkg</prgn> runs during installation, upgrade
10031 and removal of packages. They allow the package to
10032 deal with matters which are particular to that package
10033 or require more complicated processing than that
10034 provided by <prgn>dpkg</prgn>. Details of when and
10035 how they are called are in <ref id="maintainerscripts">.
10039 It is very important to make these scripts idempotent.
10040 See <ref id="idempotency">.
10044 The maintainer scripts are not guaranteed to run with a
10045 controlling terminal and may not be able to interact with
10046 the user. See <ref id="controllingterminal">.
10050 <tag><tt>conffiles</tt>
10053 This file contains a list of configuration files which
10054 are to be handled automatically by <prgn>dpkg</prgn>
10055 (see <ref id="pkg-conffiles">). Note that not necessarily
10056 every configuration file should be listed here.
10059 <tag><tt>shlibs</tt>
10062 This file contains a list of the shared libraries
10063 supplied by the package, with dependency details for
10064 each. This is used by <prgn>dpkg-shlibdeps</prgn>
10065 when it determines what dependencies are required in a
10066 package control file. The <tt>shlibs</tt> file format
10067 is described on <ref id="shlibs">.
10072 <sect id="pkg-controlfile">
10073 <heading>The main control information file: <tt>control</tt></heading>
10076 The most important control information file used by
10077 <prgn>dpkg</prgn> when it installs a package is
10078 <tt>control</tt>. It contains all the package's "vital
10083 The binary package control files of packages built from
10084 Debian sources are made by a special tool,
10085 <prgn>dpkg-gencontrol</prgn>, which reads
10086 <file>debian/control</file> and <file>debian/changelog</file> to
10087 find the information it needs. See <ref id="pkg-sourcepkg"> for
10092 The fields in binary package control files are listed in
10093 <ref id="binarycontrolfiles">.
10097 A description of the syntax of control files and the purpose
10098 of the fields is available in <ref id="controlfields">.
10103 <heading>Time Stamps</heading>
10106 See <ref id="timestamps">.
10111 <appendix id="pkg-sourcepkg">
10112 <heading>Source packages (from old Packaging Manual) </heading>
10115 The Debian binary packages in the distribution are generated
10116 from Debian sources, which are in a special format to assist
10117 the easy and automatic building of binaries.
10120 <sect id="pkg-sourcetools">
10121 <heading>Tools for processing source packages</heading>
10124 Various tools are provided for manipulating source packages;
10125 they pack and unpack sources and help build of binary
10126 packages and help manage the distribution of new versions.
10130 They are introduced and typical uses described here; see
10131 <manref name="dpkg-source" section="1"> for full
10132 documentation about their arguments and operation.
10136 For examples of how to construct a Debian source package,
10137 and how to use those utilities that are used by Debian
10138 source packages, please see the <prgn>hello</prgn> example
10142 <sect1 id="pkg-dpkg-source">
10144 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
10149 This program is frequently used by hand, and is also
10150 called from package-independent automated building scripts
10151 such as <prgn>dpkg-buildpackage</prgn>.
10155 To unpack a package it is typically invoked with
10157 dpkg-source -x <var>.../path/to/filename</var>.dsc
10162 with the <file><var>filename</var>.tar.gz</file> and
10163 <file><var>filename</var>.diff.gz</file> (if applicable) in
10164 the same directory. It unpacks into
10165 <file><var>package</var>-<var>version</var></file>, and if
10167 <file><var>package</var>-<var>version</var>.orig</file>, in
10168 the current directory.
10172 To create a packed source archive it is typically invoked:
10174 dpkg-source -b <var>package</var>-<var>version</var>
10179 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
10180 <file>.diff.gz</file> (if appropriate) in the current
10181 directory. <prgn>dpkg-source</prgn> does not clean the
10182 source tree first - this must be done separately if it is
10187 See also <ref id="pkg-sourcearchives">.</p>
10191 <sect1 id="pkg-dpkg-buildpackage">
10193 <prgn>dpkg-buildpackage</prgn> - overall package-building
10198 <prgn>dpkg-buildpackage</prgn> is a script which invokes
10199 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
10200 targets <tt>clean</tt>, <tt>build</tt> and
10201 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
10202 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
10203 source and binary package upload.
10207 It is usually invoked by hand from the top level of the
10208 built or unbuilt source directory. It may be invoked with
10209 no arguments; useful arguments include:
10210 <taglist compact="compact">
10211 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
10214 Do not sign the <tt>.changes</tt> file or the
10215 source package <tt>.dsc</tt> file, respectively.</p>
10217 <tag><tt>-p<var>sign-command</var></tt></tag>
10220 Invoke <var>sign-command</var> instead of finding
10221 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
10222 <var>sign-command</var> must behave just like
10223 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
10225 <tag><tt>-r<var>root-command</var></tt></tag>
10228 When root privilege is required, invoke the command
10229 <var>root-command</var>. <var>root-command</var>
10230 should invoke its first argument as a command, from
10231 the <prgn>PATH</prgn> if necessary, and pass its
10232 second and subsequent arguments to the command it
10233 calls. If no <var>root-command</var> is supplied
10234 then <var>dpkg-buildpackage</var> will take no
10235 special action to gain root privilege, so that for
10236 most packages it will have to be invoked as root to
10239 <tag><tt>-b</tt>, <tt>-B</tt></tag>
10242 Two types of binary-only build and upload - see
10243 <manref name="dpkg-source" section="1">.
10250 <sect1 id="pkg-dpkg-gencontrol">
10252 <prgn>dpkg-gencontrol</prgn> - generates binary package
10257 This program is usually called from <file>debian/rules</file>
10258 (see <ref id="pkg-sourcetree">) in the top level of the source
10263 This is usually done just before the files and directories in the
10264 temporary directory tree where the package is being built have their
10265 permissions and ownerships set and the package is constructed using
10266 <prgn>dpkg-deb/</prgn>
10268 This is so that the control file which is produced has
10269 the right permissions
10274 <prgn>dpkg-gencontrol</prgn> must be called after all the
10275 files which are to go into the package have been placed in
10276 the temporary build directory, so that its calculation of
10277 the installed size of a package is correct.
10281 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
10282 be run after <prgn>dpkg-shlibdeps</prgn> so that the
10283 variable substitutions created by
10284 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
10289 For a package which generates only one binary package, and
10290 which builds it in <file>debian/tmp</file> relative to the top
10291 of the source package, it is usually sufficient to call
10292 <prgn>dpkg-gencontrol</prgn>.
10296 Sources which build several binaries will typically need
10299 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
10300 </example> The <tt>-P</tt> tells
10301 <prgn>dpkg-gencontrol</prgn> that the package is being
10302 built in a non-default directory, and the <tt>-p</tt>
10303 tells it which package's control file should be generated.
10307 <prgn>dpkg-gencontrol</prgn> also adds information to the
10308 list of files in <file>debian/files</file>, for the benefit of
10309 (for example) a future invocation of
10310 <prgn>dpkg-genchanges</prgn>.</p>
10313 <sect1 id="pkg-dpkg-shlibdeps">
10315 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
10320 This program is usually called from <file>debian/rules</file>
10321 just before <prgn>dpkg-gencontrol</prgn> (see <ref
10322 id="pkg-sourcetree">), in the top level of the source tree.
10326 Its arguments are executables and shared libraries
10329 They may be specified either in the locations in the
10330 source tree where they are created or in the locations
10331 in the temporary build tree where they are installed
10332 prior to binary package creation.
10334 </footnote> for which shared library dependencies should
10335 be included in the binary package's control file.
10339 If some of the found shared libraries should only
10340 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
10341 some warrant a <tt>Pre-Depends</tt>, this can be achieved
10342 by using the <tt>-d<var>dependency-field</var></tt> option
10343 before those executable(s). (Each <tt>-d</tt> option
10344 takes effect until the next <tt>-d</tt>.)
10348 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
10349 output control file to be modified. Instead by default it
10350 adds to the <file>debian/substvars</file> file variable
10351 settings like <tt>shlibs:Depends</tt>. These variable
10352 settings must be referenced in dependency fields in the
10353 appropriate per-binary-package sections of the source
10358 For example, a package that generates an essential part
10359 which requires dependencies, and optional parts that
10360 which only require a recommendation, would separate those
10361 two sets of dependencies into two different fields.<footnote>
10362 At the time of writing, an example for this was the
10363 <package/xmms/ package, with Depends used for the xmms
10364 executable, Recommends for the plug-ins and Suggests for
10365 even more optional features provided by unzip.
10367 It can say in its <file>debian/rules</file>:
10369 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
10370 -dRecommends <var>optionalpart anotheroptionalpart</var>
10372 and then in its main control file <file>debian/control</file>:
10375 Depends: ${shlibs:Depends}
10376 Recommends: ${shlibs:Recommends}
10382 Sources which produce several binary packages with
10383 different shared library dependency requirements can use
10384 the <tt>-p<var>varnameprefix</var></tt> option to override
10385 the default <tt>shlibs:</tt> prefix (one invocation of
10386 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
10387 They can thus produce several sets of dependency
10388 variables, each of the form
10389 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
10390 which can be referred to in the appropriate parts of the
10391 binary package control files.
10396 <sect1 id="pkg-dpkg-distaddfile">
10398 <prgn>dpkg-distaddfile</prgn> - adds a file to
10399 <file>debian/files</file>
10403 Some packages' uploads need to include files other than
10404 the source and binary package files.
10408 <prgn>dpkg-distaddfile</prgn> adds a file to the
10409 <file>debian/files</file> file so that it will be included in
10410 the <file>.changes</file> file when
10411 <prgn>dpkg-genchanges</prgn> is run.
10415 It is usually invoked from the <tt>binary</tt> target of
10416 <file>debian/rules</file>:
10418 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
10420 The <var>filename</var> is relative to the directory where
10421 <prgn>dpkg-genchanges</prgn> will expect to find it - this
10422 is usually the directory above the top level of the source
10423 tree. The <file>debian/rules</file> target should put the
10424 file there just before or just after calling
10425 <prgn>dpkg-distaddfile</prgn>.
10429 The <var>section</var> and <var>priority</var> are passed
10430 unchanged into the resulting <file>.changes</file> file.
10435 <sect1 id="pkg-dpkg-genchanges">
10437 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
10438 upload control file
10442 This program is usually called by package-independent
10443 automatic building scripts such as
10444 <prgn>dpkg-buildpackage</prgn>, but it may also be called
10449 It is usually called in the top level of a built source
10450 tree, and when invoked with no arguments will print out a
10451 straightforward <file>.changes</file> file based on the
10452 information in the source package's changelog and control
10453 file and the binary and source packages which should have
10459 <sect1 id="pkg-dpkg-parsechangelog">
10461 <prgn>dpkg-parsechangelog</prgn> - produces parsed
10462 representation of a changelog
10466 This program is used internally by
10467 <prgn>dpkg-source</prgn> et al. It may also occasionally
10468 be useful in <file>debian/rules</file> and elsewhere. It
10469 parses a changelog, <file>debian/changelog</file> by default,
10470 and prints a control-file format representation of the
10471 information in it to standard output.
10475 <sect1 id="pkg-dpkg-architecture">
10477 <prgn>dpkg-architecture</prgn> - information about the build and
10482 This program can be used manually, but is also invoked by
10483 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
10484 environment or make variables which specify the build and host
10485 architecture for the package building process.
10490 <sect id="pkg-sourcetree">
10491 <heading>The Debian package source tree</heading>
10494 The source archive scheme described later is intended to
10495 allow a Debian package source tree with some associated
10496 control information to be reproduced and transported easily.
10497 The Debian package source tree is a version of the original
10498 program with certain files added for the benefit of the
10499 packaging process, and with any other changes required
10500 made to the rest of the source code and installation
10505 The extra files created for Debian are in the subdirectory
10506 <file>debian</file> of the top level of the Debian package
10507 source tree. They are described below.
10510 <sect1 id="pkg-debianrules">
10511 <heading><file>debian/rules</file> - the main building script</heading>
10514 See <ref id="debianrules">.
10518 <sect1 id="pkg-srcsubstvars">
10519 <heading><file>debian/substvars</file> and variable substitutions</heading>
10522 See <ref id="substvars">.
10528 <heading><file>debian/files</file></heading>
10531 See <ref id="debianfiles">.
10535 <sect1><heading><file>debian/tmp</file>
10539 This is the canonical temporary location for the
10540 construction of binary packages by the <tt>binary</tt>
10541 target. The directory <file>tmp</file> serves as the root of
10542 the file system tree as it is being constructed (for
10543 example, by using the package's upstream makefiles install
10544 targets and redirecting the output there), and it also
10545 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10546 id="pkg-bincreating">.
10550 If several binary packages are generated from the same
10551 source tree it is usual to use several
10552 <file>debian/tmp<var>something</var></file> directories, for
10553 example <file>tmp-a</file> or <file>tmp-doc</file>.
10557 Whatever <file>tmp</file> directories are created and used by
10558 <tt>binary</tt> must of course be removed by the
10559 <tt>clean</tt> target.</p></sect1>
10563 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10567 As it exists on the FTP site, a Debian source package
10568 consists of three related files. You must have the right
10569 versions of all three to be able to use them.
10574 <tag>Debian source control file - <tt>.dsc</tt></tag>
10576 This file is a control file used by <prgn>dpkg-source</prgn>
10577 to extract a source package.
10578 See <ref id="debiansourcecontrolfiles">.
10582 Original source archive -
10584 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10590 This is a compressed (with <tt>gzip -9</tt>)
10591 <prgn>tar</prgn> file containing the source code from
10592 the upstream authors of the program.
10597 Debian package diff -
10599 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10605 This is a unified context diff (<tt>diff -u</tt>)
10606 giving the changes which are required to turn the
10607 original source into the Debian source. These changes
10608 may only include editing and creating plain files.
10609 The permissions of files, the targets of symbolic
10610 links and the characteristics of special files or
10611 pipes may not be changed and no files may be removed
10616 All the directories in the diff must exist, except the
10617 <file>debian</file> subdirectory of the top of the source
10618 tree, which will be created by
10619 <prgn>dpkg-source</prgn> if necessary when unpacking.
10623 The <prgn>dpkg-source</prgn> program will
10624 automatically make the <file>debian/rules</file> file
10625 executable (see below).</p></item>
10630 If there is no original source code - for example, if the
10631 package is specially prepared for Debian or the Debian
10632 maintainer is the same as the upstream maintainer - the
10633 format is slightly different: then there is no diff, and the
10635 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10636 and preferably contains a directory named
10637 <file><var>package</var>-<var>version</var></file>.
10642 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10645 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10646 Debian source package. However, if it is not available it
10647 is possible to unpack a Debian source archive as follows:
10648 <enumlist compact="compact">
10651 Untar the tarfile, which will create a <file>.orig</file>
10655 <p>Rename the <file>.orig</file> directory to
10656 <file><var>package</var>-<var>version</var></file>.</p>
10660 Create the subdirectory <file>debian</file> at the top of
10661 the source tree.</p>
10663 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10665 <item><p>Untar the tarfile again if you want a copy of the original
10666 source code alongside the Debian version.</p>
10671 It is not possible to generate a valid Debian source archive
10672 without using <prgn>dpkg-source</prgn>. In particular,
10673 attempting to use <prgn>diff</prgn> directly to generate the
10674 <file>.diff.gz</file> file will not work.
10678 <heading>Restrictions on objects in source packages</heading>
10681 The source package may not contain any hard links
10683 This is not currently detected when building source
10684 packages, but only when extracting
10688 Hard links may be permitted at some point in the
10689 future, but would require a fair amount of
10691 </footnote>, device special files, sockets or setuid or
10694 Setgid directories are allowed.
10699 The source packaging tools manage the changes between the
10700 original and Debian source using <prgn>diff</prgn> and
10701 <prgn>patch</prgn>. Turning the original source tree as
10702 included in the <file>.orig.tar.gz</file> into the Debian
10703 package source must not involve any changes which cannot be
10704 handled by these tools. Problematic changes which cause
10705 <prgn>dpkg-source</prgn> to halt with an error when
10706 building the source package are:
10707 <list compact="compact">
10708 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10710 <item><p>Changing the targets of symbolic links.</p>
10712 <item><p>Creating directories, other than <file>debian</file>.</p>
10714 <item><p>Changes to the contents of binary files.</p></item>
10715 </list> Changes which cause <prgn>dpkg-source</prgn> to
10716 print a warning but continue anyway are:
10717 <list compact="compact">
10720 Removing files, directories or symlinks.
10722 Renaming a file is not treated specially - it is
10723 seen as the removal of the old file (which
10724 generates a warning, but is otherwise ignored),
10725 and the creation of the new one.
10731 Changed text files which are missing the usual final
10732 newline (either in the original or the modified
10737 Changes which are not represented, but which are not detected by
10738 <prgn>dpkg-source</prgn>, are:
10739 <list compact="compact">
10740 <item><p>Changing the permissions of files (other than
10741 <file>debian/rules</file>) and directories.</p></item>
10746 The <file>debian</file> directory and <file>debian/rules</file>
10747 are handled specially by <prgn>dpkg-source</prgn> - before
10748 applying the changes it will create the <file>debian</file>
10749 directory, and afterwards it will make
10750 <file>debian/rules</file> world-executable.
10756 <appendix id="pkg-controlfields">
10757 <heading>Control files and their fields (from old Packaging Manual)</heading>
10760 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10761 data in a common format, known as control files. Binary and
10762 source packages have control data as do the <file>.changes</file>
10763 files which control the installation of uploaded files, and
10764 <prgn>dpkg</prgn>'s internal databases are in a similar
10769 <heading>Syntax of control files</heading>
10772 See <ref id="controlsyntax">.
10776 It is important to note that there are several fields which
10777 are optional as far as <prgn>dpkg</prgn> and the related
10778 tools are concerned, but which must appear in every Debian
10779 package, or whose omission may cause problems.
10784 <heading>List of fields</heading>
10787 See <ref id="controlfieldslist">.
10791 This section now contains only the fields that didn't belong
10792 to the Policy manual.
10795 <sect1 id="pkg-f-Filename">
10796 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10799 These fields in <tt>Packages</tt> files give the
10800 filename(s) of (the parts of) a package in the
10801 distribution directories, relative to the root of the
10802 Debian hierarchy. If the package has been split into
10803 several parts the parts are all listed in order, separated
10808 <sect1 id="pkg-f-Size">
10809 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10812 These fields in <file>Packages</file> files give the size (in
10813 bytes, expressed in decimal) and MD5 checksum of the
10814 file(s) which make(s) up a binary package in the
10815 distribution. If the package is split into several parts
10816 the values for the parts are listed in order, separated by
10821 <sect1 id="pkg-f-Status">
10822 <heading><tt>Status</tt></heading>
10825 This field in <prgn>dpkg</prgn>'s status file records
10826 whether the user wants a package installed, removed or
10827 left alone, whether it is broken (requiring
10828 re-installation) or not and what its current state on the
10829 system is. Each of these pieces of information is a
10834 <sect1 id="pkg-f-Config-Version">
10835 <heading><tt>Config-Version</tt></heading>
10838 If a package is not installed or not configured, this
10839 field in <prgn>dpkg</prgn>'s status file records the last
10840 version of the package which was successfully
10845 <sect1 id="pkg-f-Conffiles">
10846 <heading><tt>Conffiles</tt></heading>
10849 This field in <prgn>dpkg</prgn>'s status file contains
10850 information about the automatically-managed configuration
10851 files held by a package. This field should <em>not</em>
10852 appear anywhere in a package!
10857 <heading>Obsolete fields</heading>
10860 These are still recognized by <prgn>dpkg</prgn> but should
10861 not appear anywhere any more.
10863 <taglist compact="compact">
10865 <tag><tt>Revision</tt></tag>
10866 <tag><tt>Package-Revision</tt></tag>
10867 <tag><tt>Package_Revision</tt></tag>
10869 The Debian revision part of the package version was
10870 at one point in a separate control field. This
10871 field went through several names.
10874 <tag><tt>Recommended</tt></tag>
10875 <item>Old name for <tt>Recommends</tt>.</item>
10877 <tag><tt>Optional</tt></tag>
10878 <item>Old name for <tt>Suggests</tt>.</item>
10880 <tag><tt>Class</tt></tag>
10881 <item>Old name for <tt>Priority</tt>.</item>
10890 <appendix id="pkg-conffiles">
10891 <heading>Configuration file handling (from old Packaging Manual)</heading>
10894 <prgn>dpkg</prgn> can do a certain amount of automatic
10895 handling of package configuration files.
10899 Whether this mechanism is appropriate depends on a number of
10900 factors, but basically there are two approaches to any
10901 particular configuration file.
10905 The easy method is to ship a best-effort configuration in the
10906 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10907 handle updates. If the user is unlikely to want to edit the
10908 file, but you need them to be able to without losing their
10909 changes, and a new package with a changed version of the file
10910 is only released infrequently, this is a good approach.
10914 The hard method is to build the configuration file from
10915 scratch in the <prgn>postinst</prgn> script, and to take the
10916 responsibility for fixing any mistakes made in earlier
10917 versions of the package automatically. This will be
10918 appropriate if the file is likely to need to be different on
10922 <sect><heading>Automatic handling of configuration files by
10927 A package may contain a control information file called
10928 <tt>conffiles</tt>. This file should be a list of filenames
10929 of configuration files needing automatic handling, separated
10930 by newlines. The filenames should be absolute pathnames,
10931 and the files referred to should actually exist in the
10936 When a package is upgraded <prgn>dpkg</prgn> will process
10937 the configuration files during the configuration stage,
10938 shortly before it runs the package's <prgn>postinst</prgn>
10943 For each file it checks to see whether the version of the
10944 file included in the package is the same as the one that was
10945 included in the last version of the package (the one that is
10946 being upgraded from); it also compares the version currently
10947 installed on the system with the one shipped with the last
10952 If neither the user nor the package maintainer has changed
10953 the file, it is left alone. If one or the other has changed
10954 their version, then the changed version is preferred - i.e.,
10955 if the user edits their file, but the package maintainer
10956 doesn't ship a different version, the user's changes will
10957 stay, silently, but if the maintainer ships a new version
10958 and the user hasn't edited it the new version will be
10959 installed (with an informative message). If both have
10960 changed their version the user is prompted about the problem
10961 and must resolve the differences themselves.
10965 The comparisons are done by calculating the MD5 message
10966 digests of the files, and storing the MD5 of the file as it
10967 was included in the most recent version of the package.
10971 When a package is installed for the first time
10972 <prgn>dpkg</prgn> will install the file that comes with it,
10973 unless that would mean overwriting a file already on the
10978 However, note that <prgn>dpkg</prgn> will <em>not</em>
10979 replace a conffile that was removed by the user (or by a
10980 script). This is necessary because with some programs a
10981 missing file produces an effect hard or impossible to
10982 achieve in another way, so that a missing file needs to be
10983 kept that way if the user did it.
10987 Note that a package should <em>not</em> modify a
10988 <prgn>dpkg</prgn>-handled conffile in its maintainer
10989 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10990 the user confusing and possibly dangerous options for
10991 conffile update when the package is upgraded.</p>
10994 <sect><heading>Fully-featured maintainer script configuration
10999 For files which contain site-specific information such as
11000 the hostname and networking details and so forth, it is
11001 better to create the file in the package's
11002 <prgn>postinst</prgn> script.
11006 This will typically involve examining the state of the rest
11007 of the system to determine values and other information, and
11008 may involve prompting the user for some information which
11009 can't be obtained some other way.
11013 When using this method there are a couple of important
11014 issues which should be considered:
11018 If you discover a bug in the program which generates the
11019 configuration file, or if the format of the file changes
11020 from one version to the next, you will have to arrange for
11021 the postinst script to do something sensible - usually this
11022 will mean editing the installed configuration file to remove
11023 the problem or change the syntax. You will have to do this
11024 very carefully, since the user may have changed the file,
11025 perhaps to fix the very problem that your script is trying
11026 to deal with - you will have to detect these situations and
11027 deal with them correctly.
11031 If you do go down this route it's probably a good idea to
11032 make the program that generates the configuration file(s) a
11033 separate program in <file>/usr/sbin</file>, by convention called
11034 <file><var>package</var>config</file> and then run that if
11035 appropriate from the post-installation script. The
11036 <tt><var>package</var>config</tt> program should not
11037 unquestioningly overwrite an existing configuration - if its
11038 mode of operation is geared towards setting up a package for
11039 the first time (rather than any arbitrary reconfiguration
11040 later) you should have it check whether the configuration
11041 already exists, and require a <tt>--force</tt> flag to
11042 overwrite it.</p></sect>
11045 <appendix id="pkg-alternatives"><heading>Alternative versions of
11046 an interface - <prgn>update-alternatives</prgn> (from old
11051 When several packages all provide different versions of the
11052 same program or file it is useful to have the system select a
11053 default, but to allow the system administrator to change it
11054 and have their decisions respected.
11058 For example, there are several versions of the <prgn>vi</prgn>
11059 editor, and there is no reason to prevent all of them from
11060 being installed at once, each under their own name
11061 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
11062 Nevertheless it is desirable to have the name <tt>vi</tt>
11063 refer to something, at least by default.
11067 If all the packages involved cooperate, this can be done with
11068 <prgn>update-alternatives</prgn>.
11072 Each package provides its own version under its own name, and
11073 calls <prgn>update-alternatives</prgn> in its postinst to
11074 register its version (and again in its prerm to deregister
11079 See the man page <manref name="update-alternatives"
11080 section="8"> for details.
11084 If <prgn>update-alternatives</prgn> does not seem appropriate
11085 you may wish to consider using diversions instead.</p>
11088 <appendix id="pkg-diversions"><heading>Diversions - overriding a
11089 package's version of a file (from old Packaging Manual)
11093 It is possible to have <prgn>dpkg</prgn> not overwrite a file
11094 when it reinstalls the package it belongs to, and to have it
11095 put the file from the package somewhere else instead.
11099 This can be used locally to override a package's version of a
11100 file, or by one package to override another's version (or
11101 provide a wrapper for it).
11105 Before deciding to use a diversion, read <ref
11106 id="pkg-alternatives"> to see if you really want a diversion
11107 rather than several alternative versions of a program.
11111 There is a diversion list, which is read by <prgn>dpkg</prgn>,
11112 and updated by a special program <prgn>dpkg-divert</prgn>.
11113 Please see <manref name="dpkg-divert" section="8"> for full
11114 details of its operation.
11118 When a package wishes to divert a file from another, it should
11119 call <prgn>dpkg-divert</prgn> in its preinst to add the
11120 diversion and rename the existing file. For example,
11121 supposing that a <prgn>smailwrapper</prgn> package wishes to
11122 install a wrapper around <file>/usr/sbin/smail</file>:
11124 dpkg-divert --package smailwrapper --add --rename \
11125 --divert /usr/sbin/smail.real /usr/sbin/smail
11126 </example> The <tt>--package smailwrapper</tt> ensures that
11127 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
11128 can bypass the diversion and get installed as the true version.
11129 It's safe to add the diversion unconditionally on upgrades since
11130 it will be left unchanged if it already exists, but
11131 <prgn>dpkg-divert</prgn> will display a message. To suppress that
11132 message, make the command conditional on the version from which
11133 the package is being upgraded:
11135 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
11136 dpkg-divert --package smailwrapper --add --rename \
11137 --divert /usr/sbin/smail.real /usr/sbin/smail
11139 </example> where <tt>1.0-2</tt> is the version at which the
11140 diversion was first added to the package. Running the command
11141 during abort-upgrade is pointless but harmless.
11145 The postrm has to do the reverse:
11147 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
11148 dpkg-divert --package smailwrapper --remove --rename \
11149 --divert /usr/sbin/smail.real /usr/sbin/smail
11151 </example> If the diversion was added at a particular version, the
11152 postrm should also handle the failure case of upgrading from an
11153 older version (unless the older version is so old that direct
11154 upgrades are no longer supported):
11156 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
11157 dpkg-divert --package smailwrapper --remove --rename \
11158 --divert /usr/sbin/smail.real /usr/sbin/smail
11160 </example> where <tt>1.02-2</tt> is the version at which the
11161 diversion was first added to the package. The postrm should not
11162 remove the diversion on upgrades both because there's no reason to
11163 remove the diversion only to immediately re-add it and since the
11164 postrm of the old package is run after unpacking so the removal of
11165 the diversion will fail.
11169 Do not attempt to divert a file which is vitally important for
11170 the system's operation - when using <prgn>dpkg-divert</prgn>
11171 there is a time, after it has been diverted but before
11172 <prgn>dpkg</prgn> has installed the new version, when the file
11173 does not exist.</p>
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