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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 utility
2088 <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
2089 You can determine the
2090 Debian architecture and the GNU style architecture
2091 specification string for the build machine (the machine type
2092 we are building on) as well as for the host machine (the
2093 machine type we are building for). Here is a list of
2094 supported <prgn>make</prgn> variables:
2095 <list compact="compact">
2097 <tt>DEB_*_ARCH</tt> (the Debian architecture)
2100 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2103 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2106 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2107 specification string)
2110 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2111 <tt>DEB_*_GNU_TYPE</tt>)
2114 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2115 <tt>DEB_*_GNU_TYPE</tt>)
2117 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2118 the build machine or <tt>HOST</tt> for specification of the
2123 Backward compatibility can be provided in the rules file
2124 by setting the needed variables to suitable default
2125 values; please refer to the documentation of
2126 <prgn>dpkg-architecture</prgn> for details.
2130 It is important to understand that the <tt>DEB_*_ARCH</tt>
2131 string only determines which Debian architecture we are
2132 building on or for. It should not be used to get the CPU
2133 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2134 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2135 GNU style variables should generally only be used with upstream
2139 <sect1 id="debianrules-options">
2140 <heading><file>debian/rules</file> and
2141 <tt>DEB_BUILD_OPTIONS</tt></heading>
2144 Supporting the standardized environment variable
2145 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2146 contain several flags to change how a package is compiled and
2147 built. Each flag must be in the form <var>flag</var> or
2148 <var>flag</var>=<var>options</var>. If multiple flags are
2149 given, they must be separated by whitespace.<footnote>
2150 Some packages support any delimiter, but whitespace is the
2151 easiest to parse inside a makefile and avoids ambiguity with
2152 flag values that contain commas.
2154 <var>flag</var> must start with a lowercase letter
2155 (<tt>a-z</tt>) and consist only of lowercase letters,
2156 numbers (<tt>0-9</tt>), and the characters
2157 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2158 <var>options</var> must not contain whitespace. The same
2159 tag should not be given multiple times with conflicting
2160 values. Package maintainers may assume that
2161 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2165 The meaning of the following tags has been standardized:
2169 This tag says to not run any build-time test suite
2170 provided by the package.
2174 The presence of this tag means that the package should
2175 be compiled with a minimum of optimization. For C
2176 programs, it is best to add <tt>-O0</tt> to
2177 <tt>CFLAGS</tt> (although this is usually the default).
2178 Some programs might fail to build or run at this level
2179 of optimization; it may be necessary to use
2180 <tt>-O1</tt>, for example.
2184 This tag means that the debugging symbols should not be
2185 stripped from the binary during installation, so that
2186 debugging information may be included in the package.
2188 <tag>parallel=n</tag>
2190 This tag means that the package should be built using up
2191 to <tt>n</tt> parallel processes if the package build
2192 system supports this.<footnote>
2193 Packages built with <tt>make</tt> can often implement
2194 this by passing the <tt>-j</tt><var>n</var> option to
2197 If the package build system does not support parallel
2198 builds, this string must be ignored. If the package
2199 build system only supports a lower level of concurrency
2200 than <var>n</var>, the package should be built using as
2201 many parallel processes as the package build system
2202 supports. It is up to the package maintainer to decide
2203 whether the package build times are long enough and the
2204 package build system is robust enough to make supporting
2205 parallel builds worthwhile.
2211 Unknown flags must be ignored by <file>debian/rules</file>.
2215 The following makefile snippet is an example of how one may
2216 implement the build options; you will probably have to
2217 massage this example in order to make it work for your
2219 <example compact="compact">
2222 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2223 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2224 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2225 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2227 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2232 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2233 INSTALL_PROGRAM += -s
2235 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2236 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2237 MAKEFLAGS += -j$(NUMJOBS)
2242 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2243 # Code to run the package test suite.
2250 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2251 <sect id="substvars">
2252 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2255 When <prgn>dpkg-gencontrol</prgn>
2256 generates <qref id="binarycontrolfiles">binary package control
2257 files</qref> (<file>DEBIAN/control</file>), it performs variable
2258 substitutions on its output just before writing it. Variable
2259 substitutions have the form <tt>${<var>variable</var>}</tt>.
2260 The optional file <file>debian/substvars</file> contains
2261 variable substitutions to be used; variables can also be set
2262 directly from <file>debian/rules</file> using the <tt>-V</tt>
2263 option to the source packaging commands, and certain predefined
2264 variables are also available.
2268 The <file>debian/substvars</file> file is usually generated and
2269 modified dynamically by <file>debian/rules</file> targets, in
2270 which case it must be removed by the <tt>clean</tt> target.
2274 See <manref name="deb-substvars" section="5"> for full
2275 details about source variable substitutions, including the
2276 format of <file>debian/substvars</file>.</p>
2279 <sect id="debianwatch">
2280 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2283 This is an optional, recommended configuration file for the
2284 <tt>uscan</tt> utility which defines how to automatically scan
2285 ftp or http sites for newly available updates of the
2286 package. This is used
2287 by <url id="http://dehs.alioth.debian.org/"> and other Debian QA
2288 tools to help with quality control and maintenance of the
2289 distribution as a whole.
2294 <sect id="debianfiles">
2295 <heading>Generated files list: <file>debian/files</file></heading>
2298 This file is not a permanent part of the source tree; it
2299 is used while building packages to record which files are
2300 being generated. <prgn>dpkg-genchanges</prgn> uses it
2301 when it generates a <file>.changes</file> file.
2305 It should not exist in a shipped source package, and so it
2306 (and any backup files or temporary files such as
2307 <file>files.new</file><footnote>
2308 <file>files.new</file> is used as a temporary file by
2309 <prgn>dpkg-gencontrol</prgn> and
2310 <prgn>dpkg-distaddfile</prgn> - they write a new
2311 version of <tt>files</tt> here before renaming it,
2312 to avoid leaving a corrupted copy if an error
2314 </footnote>) should be removed by the
2315 <tt>clean</tt> target. It may also be wise to
2316 ensure a fresh start by emptying or removing it at the
2317 start of the <tt>binary</tt> target.
2321 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2322 package, it adds an entry to <file>debian/files</file> for the
2323 <file>.deb</file> file that will be created when <tt>dpkg-deb
2324 --build</tt> is run for that binary package. So for most
2325 packages all that needs to be done with this file is to
2326 delete it in the <tt>clean</tt> target.
2330 If a package upload includes files besides the source
2331 package and any binary packages whose control files were
2332 made with <prgn>dpkg-gencontrol</prgn> then they should be
2333 placed in the parent of the package's top-level directory
2334 and <prgn>dpkg-distaddfile</prgn> should be called to add
2335 the file to the list in <file>debian/files</file>.</p>
2338 <sect id="embeddedfiles">
2339 <heading>Convenience copies of code</heading>
2342 Some software packages include in their distribution convenience
2343 copies of code from other software packages, generally so that
2344 users compiling from source don't have to download multiple
2345 packages. Debian packages should not make use of these
2346 convenience copies unless the included package is explicitly
2347 intended to be used in this way.<footnote>
2348 For example, parts of the GNU build system work like this.
2350 If the included code is already in the Debian archive in the
2351 form of a library, the Debian packaging should ensure that
2352 binary packages reference the libraries already in Debian and
2353 the convenience copy is not used. If the included code is not
2354 already in Debian, it should be packaged separately as a
2355 prerequisite if possible.
2357 Having multiple copies of the same code in Debian is
2358 inefficient, often creates either static linking or shared
2359 library conflicts, and, most importantly, increases the
2360 difficulty of handling security vulnerabilities in the
2366 <sect id="readmesource">
2367 <heading>Source package handling:
2368 <file>debian/README.source</file></heading>
2371 If running <prgn>dpkg-source -x</prgn> on a source package
2372 doesn't produce the source of the package, ready for editing,
2373 and allow one to make changes and run
2374 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2375 without taking any additional steps, creating a
2376 <file>debian/README.source</file> documentation file is
2377 recommended. This file should explain how to do all of the
2380 <item>Generate the fully patched source, in a form ready for
2381 editing, that would be built to create Debian
2382 packages. Doing this with a <tt>patch</tt> target in
2383 <file>debian/rules</file> is recommended; see
2384 <ref id="debianrules">.</item>
2385 <item>Modify the source and save those modifications so that
2386 they will be applied when building the package.</item>
2387 <item>Remove source modifications that are currently being
2388 applied when building the package.</item>
2389 <item>Optionally, document what steps are necessary to
2390 upgrade the Debian source package to a new upstream version,
2391 if applicable.</item>
2393 This explanation should include specific commands and mention
2394 any additional required Debian packages. It should not assume
2395 familiarity with any specific Debian packaging system or patch
2400 This explanation may refer to a documentation file installed by
2401 one of the package's build dependencies provided that the
2402 referenced documentation clearly explains these tasks and is not
2403 a general reference manual.
2407 <file>debian/README.source</file> may also include any other
2408 information that would be helpful to someone modifying the
2409 source package. Even if the package doesn't fit the above
2410 description, maintainers are encouraged to document in a
2411 <file>debian/README.source</file> file any source package with a
2412 particularly complex or unintuitive source layout or build
2413 system (for example, a package that builds the same source
2414 multiple times to generate different binary packages).
2420 <chapt id="controlfields">
2421 <heading>Control files and their fields</heading>
2424 The package management system manipulates data represented in
2425 a common format, known as <em>control data</em>, stored in
2426 <em>control files</em>.
2427 Control files are used for source packages, binary packages and
2428 the <file>.changes</file> files which control the installation
2429 of uploaded files<footnote>
2430 <prgn>dpkg</prgn>'s internal databases are in a similar
2435 <sect id="controlsyntax">
2436 <heading>Syntax of control files</heading>
2439 A control file consists of one or more paragraphs of
2441 The paragraphs are also sometimes referred to as stanzas.
2443 The paragraphs are separated by blank lines. Some control
2444 files allow only one paragraph; others allow several, in
2445 which case each paragraph usually refers to a different
2446 package. (For example, in source packages, the first
2447 paragraph refers to the source package, and later paragraphs
2448 refer to binary packages generated from the source.)
2452 Each paragraph consists of a series of data fields; each
2453 field consists of the field name, followed by a colon and
2454 then the data/value associated with that field. It ends at
2455 the end of the (logical) line. Horizontal whitespace
2456 (spaces and tabs) may occur immediately before or after the
2457 value and is ignored there; it is conventional to put a
2458 single space after the colon. For example, a field might
2460 <example compact="compact">
2463 the field name is <tt>Package</tt> and the field value
2468 A paragraph must not contain more than one instance of a
2469 particular field name.
2473 Many fields' values may span several lines; in this case
2474 each continuation line must start with a space or a tab.
2475 Any trailing spaces or tabs at the end of individual
2476 lines of a field value are ignored.
2480 In fields where it is specified that lines may not wrap,
2481 only a single line of data is allowed and whitespace is not
2482 significant in a field body. Whitespace must not appear
2483 inside names (of packages, architectures, files or anything
2484 else) or version numbers, or between the characters of
2485 multi-character version relationships.
2489 Field names are not case-sensitive, but it is usual to
2490 capitalize the field names using mixed case as shown below.
2491 Field values are case-sensitive unless the description of the
2492 field says otherwise.
2496 Blank lines, or lines consisting only of spaces and tabs,
2497 are not allowed within field values or between fields - that
2498 would mean a new paragraph.
2502 All control files must be encoded in UTF-8.
2506 <sect id="sourcecontrolfiles">
2507 <heading>Source package control files -- <file>debian/control</file></heading>
2510 The <file>debian/control</file> file contains the most vital
2511 (and version-independent) information about the source package
2512 and about the binary packages it creates.
2516 The first paragraph of the control file contains information about
2517 the source package in general. The subsequent sets each describe a
2518 binary package that the source tree builds.
2522 The fields in the general paragraph (the first one, for the source
2525 <list compact="compact">
2526 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2527 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2528 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2529 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2530 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2531 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2532 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2533 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2538 The fields in the binary package paragraphs are:
2540 <list compact="compact">
2541 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2542 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2543 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2544 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2545 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2546 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2547 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2548 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2553 The syntax and semantics of the fields are described below.
2557 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2558 generate control files for binary packages (see below), by
2559 <prgn>dpkg-genchanges</prgn> to generate the
2560 <file>.changes</file> file to accompany the upload, and by
2561 <prgn>dpkg-source</prgn> when it creates the
2562 <file>.dsc</file> source control file as part of a source
2563 archive. Many fields are permitted to span multiple lines in
2564 <file>debian/control</file> but not in any other control
2565 file. These tools are responsible for removing the line
2566 breaks from such fields when using fields from
2567 <file>debian/control</file> to generate other control files.
2571 The fields here may contain variable references - their
2572 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2573 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2574 when they generate output control files.
2575 See <ref id="substvars"> for details.
2579 In addition to the control file syntax described <qref
2580 id="controlsyntax">above</qref>, this file may also contain
2581 comment lines starting with <tt>#</tt> without any preceding
2582 whitespace. All such lines are ignored, even in the middle of
2583 continuation lines for a multiline field, and do not end a
2589 <sect id="binarycontrolfiles">
2590 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2593 The <file>DEBIAN/control</file> file contains the most vital
2594 (and version-dependent) information about a binary package. It
2595 consists of a single paragraph.
2599 The fields in this file are:
2601 <list compact="compact">
2602 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2603 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2604 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2605 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2606 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2607 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2608 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2609 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2610 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2611 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2612 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2613 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2618 <sect id="debiansourcecontrolfiles">
2619 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2622 This file consists of a single paragraph, possibly surrounded by
2623 a PGP signature. The fields of that paragraph are listed below.
2624 Their syntax is described above, in <ref id="pkg-controlfields">.
2626 <list compact="compact">
2627 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2628 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2629 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2630 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2631 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2632 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2633 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2634 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2635 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2636 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2637 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2638 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2639 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2644 The source package control file is generated by
2645 <prgn>dpkg-source</prgn> when it builds the source
2646 archive, from other files in the source package,
2647 described above. When unpacking, it is checked against
2648 the files and directories in the other parts of the
2654 <sect id="debianchangesfiles">
2655 <heading>Debian changes files -- <file>.changes</file></heading>
2658 The <file>.changes</file> files are used by the Debian archive
2659 maintenance software to process updates to packages. They
2660 consist of a single paragraph, possibly surrounded by a PGP
2661 signature. That paragraph contains information from the
2662 <file>debian/control</file> file and other data about the
2663 source package gathered via <file>debian/changelog</file>
2664 and <file>debian/rules</file>.
2668 <file>.changes</file> files have a format version that is
2669 incremented whenever the documented fields or their meaning
2670 change. This document describes format &changesversion;.
2674 The fields in this file are:
2676 <list compact="compact">
2677 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2678 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2679 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2680 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2681 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2682 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2683 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2684 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2685 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2686 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2687 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2688 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2689 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2690 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2691 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2692 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2697 <sect id="controlfieldslist">
2698 <heading>List of fields</heading>
2700 <sect1 id="f-Source">
2701 <heading><tt>Source</tt></heading>
2704 This field identifies the source package name.
2708 In <file>debian/control</file> or a <file>.dsc</file> file,
2709 this field must contain only the name of the source package.
2713 In a binary package control file or a <file>.changes</file>
2714 file, the source package name may be followed by a version
2715 number in parentheses<footnote>
2716 It is customary to leave a space after the package name
2717 if a version number is specified.
2719 This version number may be omitted (and is, by
2720 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2721 the <tt>Version</tt> field of the binary package in
2722 question. The field itself may be omitted from a binary
2723 package control file when the source package has the same
2724 name and version as the binary package.
2728 Package names (both source and binary,
2729 see <ref id="f-Package">) must consist only of lower case
2730 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2731 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2732 (<tt>.</tt>). They must be at least two characters long and
2733 must start with an alphanumeric character.
2737 <sect1 id="f-Maintainer">
2738 <heading><tt>Maintainer</tt></heading>
2741 The package maintainer's name and email address. The name
2742 must come first, then the email address inside angle
2743 brackets <tt><></tt> (in RFC822 format).
2747 If the maintainer's name contains a full stop then the
2748 whole field will not work directly as an email address due
2749 to a misfeature in the syntax specified in RFC822; a
2750 program using this field as an address must check for this
2751 and correct the problem if necessary (for example by
2752 putting the name in round brackets and moving it to the
2753 end, and bringing the email address forward).
2757 See <ref id="maintainer"> for additional requirements and
2758 information about package maintainers.
2762 <sect1 id="f-Uploaders">
2763 <heading><tt>Uploaders</tt></heading>
2766 List of the names and email addresses of co-maintainers of the
2767 package, if any. If the package has other maintainers besides
2768 the one named in the <qref id="f-Maintainer">Maintainer
2769 field</qref>, their names and email addresses should be listed
2770 here. The format of each entry is the same as that of the
2771 Maintainer field, and multiple entries must be comma
2776 This is normally an optional field, but if
2777 the <tt>Maintainer</tt> control field names a group of people
2778 and a shared email address, the <tt>Uploaders</tt> field must
2779 be present and must contain at least one human with their
2780 personal email address.
2784 Any parser that interprets the Uploaders field in
2785 <file>debian/control</file> must permit it to span multiple
2786 lines. Line breaks in an Uploaders field that spans multiple
2787 lines are not significant and the semantics of the field are
2788 the same as if the line breaks had not been present.
2792 <sect1 id="f-Changed-By">
2793 <heading><tt>Changed-By</tt></heading>
2796 The name and email address of the person who prepared this
2797 version of the package, usually a maintainer. The syntax is
2798 the same as for the <qref id="f-Maintainer">Maintainer
2803 <sect1 id="f-Section">
2804 <heading><tt>Section</tt></heading>
2807 This field specifies an application area into which the package
2808 has been classified. See <ref id="subsections">.
2812 When it appears in the <file>debian/control</file> file,
2813 it gives the value for the subfield of the same name in
2814 the <tt>Files</tt> field of the <file>.changes</file> file.
2815 It also gives the default for the same field in the binary
2820 <sect1 id="f-Priority">
2821 <heading><tt>Priority</tt></heading>
2824 This field represents how important it is that the user
2825 have the package installed. See <ref id="priorities">.
2829 When it appears in the <file>debian/control</file> file,
2830 it gives the value for the subfield of the same name in
2831 the <tt>Files</tt> field of the <file>.changes</file> file.
2832 It also gives the default for the same field in the binary
2837 <sect1 id="f-Package">
2838 <heading><tt>Package</tt></heading>
2841 The name of the binary package.
2845 Binary package names must follow the same syntax and
2846 restrictions as source package names. See <ref id="f-Source">
2851 <sect1 id="f-Architecture">
2852 <heading><tt>Architecture</tt></heading>
2855 Depending on context and the control file used, the
2856 <tt>Architecture</tt> field can include the following sets of
2860 A unique single word identifying a Debian machine
2861 architecture as described in <ref id="arch-spec">.
2864 An architecture wildcard identifying a set of Debian
2865 machine architectures, see <ref id="arch-wildcard-spec">.
2866 <tt>any</tt> matches all Debian machine architectures
2867 and is the most frequently used.
2870 <tt>all</tt>, which indicates an
2871 architecture-independent package.
2874 <tt>source</tt>, which indicates a source package.
2880 In the main <file>debian/control</file> file in the source
2881 package, this field may contain the special
2882 value <tt>all</tt>, the special architecture
2883 wildcard <tt>any</tt>, or a list of specific and wildcard
2884 architectures separated by spaces. If <tt>all</tt>
2885 or <tt>any</tt> appears, that value must be the entire
2886 contents of the field. Most packages will use
2887 either <tt>all</tt> or <tt>any</tt>.
2891 Specifying a specific list of architectures indicates that the
2892 source will build an architecture-dependent package only on
2893 architectures included in the list. Specifying a list of
2894 architecture wildcards indicates that the source will build an
2895 architecture-dependent package on only those architectures
2896 that match any of the specified architecture wildcards.
2897 Specifying a list of architectures or architecture wildcards
2898 other than <tt>any</tt> is for the minority of cases where a
2899 program is not portable or is not useful on some
2900 architectures. Where possible, the program should be made
2905 In the source package control file <file>.dsc</file>, this
2906 field may contain either the architecture
2907 wildcard <tt>any</tt> or a list of architectures and
2908 architecture wildcards separated by spaces. If a list is
2909 given, it may include (or consist solely of) the special
2910 value <tt>all</tt>. In other words, in <file>.dsc</file>
2911 files unlike the <file>debian/control</file>, <tt>all</tt> may
2912 occur in combination with specific architectures.
2913 The <tt>Architecture</tt> field in the source package control
2914 file <file>.dsc</file> is generally constructed from
2915 the <tt>Architecture</tt> fields in
2916 the <file>debian/control</file> in the source package.
2920 Specifying <tt>any</tt> indicates that the source package
2921 isn't dependent on any particular architecture and should
2922 compile fine on any one. The produced binary package(s)
2923 will either be specific to whatever the current build
2924 architecture is or will be architecture-independent.
2928 Specifying only <tt>all</tt> indicates that the source package
2929 will only build architecture-independent packages. If this is
2930 the case, <tt>all</tt> must be used rather than <tt>any</tt>;
2931 <tt>any</tt> implies that the source package will build at
2932 least one architecture-dependent package.
2936 Specifying a list of architectures or architecture wildcards
2937 indicates that the source will build an architecture-dependent
2938 package, and will only work correctly on the listed or
2939 matching architectures. If the source package also builds at
2940 least one architecture-independent package, <tt>all</tt> will
2941 also be included in the list.
2945 In a <file>.changes</file> file, the <tt>Architecture</tt>
2946 field lists the architecture(s) of the package(s) currently
2947 being uploaded. This will be a list; if the source for the
2948 package is also being uploaded, the special
2949 entry <tt>source</tt> is also present. <tt>all</tt> will be
2950 present if any architecture-independent packages are being
2951 uploaded. Architecture wildcards such as <tt>any</tt> must
2952 never occur in the <tt>Architecture</tt> field in
2953 the <file>.changes</file> file.
2957 See <ref id="debianrules"> for information on how to get
2958 the architecture for the build process.
2962 <sect1 id="f-Essential">
2963 <heading><tt>Essential</tt></heading>
2966 This is a boolean field which may occur only in the
2967 control file of a binary package or in a per-package fields
2968 paragraph of a main source control data file.
2972 If set to <tt>yes</tt> then the package management system
2973 will refuse to remove the package (upgrading and replacing
2974 it is still possible). The other possible value is <tt>no</tt>,
2975 which is the same as not having the field at all.
2980 <heading>Package interrelationship fields:
2981 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2982 <tt>Recommends</tt>, <tt>Suggests</tt>,
2983 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2984 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2988 These fields describe the package's relationships with
2989 other packages. Their syntax and semantics are described
2990 in <ref id="relationships">.</p>
2993 <sect1 id="f-Standards-Version">
2994 <heading><tt>Standards-Version</tt></heading>
2997 The most recent version of the standards (the policy
2998 manual and associated texts) with which the package
3003 The version number has four components: major and minor
3004 version number and major and minor patch level. When the
3005 standards change in a way that requires every package to
3006 change the major number will be changed. Significant
3007 changes that will require work in many packages will be
3008 signaled by a change to the minor number. The major patch
3009 level will be changed for any change to the meaning of the
3010 standards, however small; the minor patch level will be
3011 changed when only cosmetic, typographical or other edits
3012 are made which neither change the meaning of the document
3013 nor affect the contents of packages.
3017 Thus only the first three components of the policy version
3018 are significant in the <em>Standards-Version</em> control
3019 field, and so either these three components or all four
3020 components may be specified.<footnote>
3021 In the past, people specified the full version number
3022 in the Standards-Version field, for example "2.3.0.0".
3023 Since minor patch-level changes don't introduce new
3024 policy, it was thought it would be better to relax
3025 policy and only require the first 3 components to be
3026 specified, in this example "2.3.0". All four
3027 components may still be used if someone wishes to do so.
3033 <sect1 id="f-Version">
3034 <heading><tt>Version</tt></heading>
3037 The version number of a package. The format is:
3038 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
3042 The three components here are:
3044 <tag><var>epoch</var></tag>
3047 This is a single (generally small) unsigned integer. It
3048 may be omitted, in which case zero is assumed. If it is
3049 omitted then the <var>upstream_version</var> may not
3054 It is provided to allow mistakes in the version numbers
3055 of older versions of a package, and also a package's
3056 previous version numbering schemes, to be left behind.
3060 <tag><var>upstream_version</var></tag>
3063 This is the main part of the version number. It is
3064 usually the version number of the original ("upstream")
3065 package from which the <file>.deb</file> file has been made,
3066 if this is applicable. Usually this will be in the same
3067 format as that specified by the upstream author(s);
3068 however, it may need to be reformatted to fit into the
3069 package management system's format and comparison
3074 The comparison behavior of the package management system
3075 with respect to the <var>upstream_version</var> is
3076 described below. The <var>upstream_version</var>
3077 portion of the version number is mandatory.
3081 The <var>upstream_version</var> may contain only
3082 alphanumerics<footnote>
3083 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3085 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3086 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3087 tilde) and should start with a digit. If there is no
3088 <var>debian_revision</var> then hyphens are not allowed;
3089 if there is no <var>epoch</var> then colons are not
3094 <tag><var>debian_revision</var></tag>
3097 This part of the version number specifies the version of
3098 the Debian package based on the upstream version. It
3099 may contain only alphanumerics and the characters
3100 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3101 tilde) and is compared in the same way as the
3102 <var>upstream_version</var> is.
3106 It is optional; if it isn't present then the
3107 <var>upstream_version</var> may not contain a hyphen.
3108 This format represents the case where a piece of
3109 software was written specifically to be a Debian
3110 package, where the Debian package source must always
3111 be identical to the pristine source and therefore no
3112 revision indication is required.
3116 It is conventional to restart the
3117 <var>debian_revision</var> at <tt>1</tt> each time the
3118 <var>upstream_version</var> is increased.
3122 The package management system will break the version
3123 number apart at the last hyphen in the string (if there
3124 is one) to determine the <var>upstream_version</var> and
3125 <var>debian_revision</var>. The absence of a
3126 <var>debian_revision</var> is equivalent to a
3127 <var>debian_revision</var> of <tt>0</tt>.
3134 When comparing two version numbers, first the <var>epoch</var>
3135 of each are compared, then the <var>upstream_version</var> if
3136 <var>epoch</var> is equal, and then <var>debian_revision</var>
3137 if <var>upstream_version</var> is also equal.
3138 <var>epoch</var> is compared numerically. The
3139 <var>upstream_version</var> and <var>debian_revision</var>
3140 parts are compared by the package management system using the
3141 following algorithm:
3145 The strings are compared from left to right.
3149 First the initial part of each string consisting entirely of
3150 non-digit characters is determined. These two parts (one of
3151 which may be empty) are compared lexically. If a difference
3152 is found it is returned. The lexical comparison is a
3153 comparison of ASCII values modified so that all the letters
3154 sort earlier than all the non-letters and so that a tilde
3155 sorts before anything, even the end of a part. For example,
3156 the following parts are in sorted order from earliest to
3157 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3158 <tt>a</tt>.<footnote>
3159 One common use of <tt>~</tt> is for upstream pre-releases.
3160 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3161 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3166 Then the initial part of the remainder of each string which
3167 consists entirely of digit characters is determined. The
3168 numerical values of these two parts are compared, and any
3169 difference found is returned as the result of the comparison.
3170 For these purposes an empty string (which can only occur at
3171 the end of one or both version strings being compared) counts
3176 These two steps (comparing and removing initial non-digit
3177 strings and initial digit strings) are repeated until a
3178 difference is found or both strings are exhausted.
3182 Note that the purpose of epochs is to allow us to leave behind
3183 mistakes in version numbering, and to cope with situations
3184 where the version numbering scheme changes. It is
3185 <em>not</em> intended to cope with version numbers containing
3186 strings of letters which the package management system cannot
3187 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3188 silly orderings.<footnote>
3189 The author of this manual has heard of a package whose
3190 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3191 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3197 <sect1 id="f-Description">
3198 <heading><tt>Description</tt></heading>
3201 In a source or binary control file, the <tt>Description</tt>
3202 field contains a description of the binary package, consisting
3203 of two parts, the synopsis or the short description, and the
3204 long description. The field's format is as follows:
3209 Description: <single line synopsis>
3210 <extended description over several lines>
3215 The lines in the extended description can have these formats:
3221 Those starting with a single space are part of a paragraph.
3222 Successive lines of this form will be word-wrapped when
3223 displayed. The leading space will usually be stripped off.
3227 Those starting with two or more spaces. These will be
3228 displayed verbatim. If the display cannot be panned
3229 horizontally, the displaying program will line wrap them "hard"
3230 (i.e., without taking account of word breaks). If it can they
3231 will be allowed to trail off to the right. None, one or two
3232 initial spaces may be deleted, but the number of spaces
3233 deleted from each line will be the same (so that you can have
3234 indenting work correctly, for example).
3238 Those containing a single space followed by a single full stop
3239 character. These are rendered as blank lines. This is the
3240 <em>only</em> way to get a blank line<footnote>
3241 Completely empty lines will not be rendered as blank lines.
3242 Instead, they will cause the parser to think you're starting
3243 a whole new record in the control file, and will therefore
3244 likely abort with an error.
3249 Those containing a space, a full stop and some more characters.
3250 These are for future expansion. Do not use them.
3256 Do not use tab characters. Their effect is not predictable.
3260 See <ref id="descriptions"> for further information on this.
3264 In a <file>.changes</file> file, the <tt>Description</tt>
3265 field contains a summary of the descriptions for the packages
3266 being uploaded. For this case, the first line of the field
3267 value (the part on the same line as <tt>Description:</tt>) is
3268 always empty. The content of the field is expressed as
3269 continuation lines, one line per package. Each line is
3270 indented by one space and contains the name of a binary
3271 package, a space, a hyphen (<tt>-</tt>), a space, and the
3272 short description line from that package.
3276 <sect1 id="f-Distribution">
3277 <heading><tt>Distribution</tt></heading>
3280 In a <file>.changes</file> file or parsed changelog output
3281 this contains the (space-separated) name(s) of the
3282 distribution(s) where this version of the package should
3283 be installed. Valid distributions are determined by the
3284 archive maintainers.<footnote>
3285 Example distribution names in the Debian archive used in
3286 <file>.changes</file> files are:
3287 <taglist compact="compact">
3288 <tag><em>unstable</em></tag>
3290 This distribution value refers to the
3291 <em>developmental</em> part of the Debian distribution
3292 tree. Most new packages, new upstream versions of
3293 packages and bug fixes go into the <em>unstable</em>
3297 <tag><em>experimental</em></tag>
3299 The packages with this distribution value are deemed
3300 by their maintainers to be high risk. Oftentimes they
3301 represent early beta or developmental packages from
3302 various sources that the maintainers want people to
3303 try, but are not ready to be a part of the other parts
3304 of the Debian distribution tree.
3309 Others are used for updating stable releases or for
3310 security uploads. More information is available in the
3311 Debian Developer's Reference, section "The Debian
3315 The Debian archive software only supports listing a single
3316 distribution. Migration of packages to other distributions is
3317 handled outside of the upload process.
3322 <heading><tt>Date</tt></heading>
3325 This field includes the date the package was built or last
3326 edited. It must be in the same format as the <var>date</var>
3327 in a <file>debian/changelog</file> entry.
3331 The value of this field is usually extracted from the
3332 <file>debian/changelog</file> file - see
3333 <ref id="dpkgchangelog">).
3337 <sect1 id="f-Format">
3338 <heading><tt>Format</tt></heading>
3341 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3342 files, this field declares the format version of that file.
3343 The syntax of the field value is the same as that of
3344 a <qref id="f-Version">package version number</qref> except
3345 that no epoch or Debian revision is allowed. The format
3346 described in this document is <tt>&changesversion;</tt>.
3350 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3351 Debian source control</qref> files, this field declares the
3352 format of the source package. The field value is used by
3353 programs acting on a source package to interpret the list of
3354 files in the source package and determine how to unpack it.
3355 The syntax of the field value is a numeric major revision, a
3356 period, a numeric minor revision, and then an optional subtype
3357 after whitespace, which if specified is an alphanumeric word
3358 in parentheses. The subtype is optional in the syntax but may
3359 be mandatory for particular source format revisions.
3361 The source formats currently supported by the Debian archive
3362 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3363 and <tt>3.0 (quilt)</tt>.
3368 <sect1 id="f-Urgency">
3369 <heading><tt>Urgency</tt></heading>
3372 This is a description of how important it is to upgrade to
3373 this version from previous ones. It consists of a single
3374 keyword taking one of the values <tt>low</tt>,
3375 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3376 <tt>critical</tt><footnote>
3377 Other urgency values are supported with configuration
3378 changes in the archive software but are not used in Debian.
3379 The urgency affects how quickly a package will be considered
3380 for inclusion into the <tt>testing</tt> distribution and
3381 gives an indication of the importance of any fixes included
3382 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3383 treated as synonymous.
3384 </footnote> (not case-sensitive) followed by an optional
3385 commentary (separated by a space) which is usually in
3386 parentheses. For example:
3389 Urgency: low (HIGH for users of diversions)
3395 The value of this field is usually extracted from the
3396 <file>debian/changelog</file> file - see
3397 <ref id="dpkgchangelog">.
3401 <sect1 id="f-Changes">
3402 <heading><tt>Changes</tt></heading>
3405 This field contains the human-readable changes data, describing
3406 the differences between the last version and the current one.
3410 The first line of the field value (the part on the same line
3411 as <tt>Changes:</tt>) is always empty. The content of the
3412 field is expressed as continuation lines, with each line
3413 indented by at least one space. Blank lines must be
3414 represented by a line consisting only of a space and a full
3419 The value of this field is usually extracted from the
3420 <file>debian/changelog</file> file - see
3421 <ref id="dpkgchangelog">).
3425 Each version's change information should be preceded by a
3426 "title" line giving at least the version, distribution(s)
3427 and urgency, in a human-readable way.
3431 If data from several versions is being returned the entry
3432 for the most recent version should be returned first, and
3433 entries should be separated by the representation of a
3434 blank line (the "title" line may also be followed by the
3435 representation of a blank line).
3439 <sect1 id="f-Binary">
3440 <heading><tt>Binary</tt></heading>
3443 This field is a list of binary packages. Its syntax and
3444 meaning varies depending on the control file in which it
3449 When it appears in the <file>.dsc</file> file, it lists binary
3450 packages which a source package can produce, separated by
3452 A space after each comma is conventional.
3453 </footnote>. It may span multiple lines. The source package
3454 does not necessarily produce all of these binary packages for
3455 every architecture. The source control file doesn't contain
3456 details of which architectures are appropriate for which of
3457 the binary packages.
3461 When it appears in a <file>.changes</file> file, it lists the
3462 names of the binary packages being uploaded, separated by
3463 whitespace (not commas). It may span multiple lines.
3467 <sect1 id="f-Installed-Size">
3468 <heading><tt>Installed-Size</tt></heading>
3471 This field appears in the control files of binary packages,
3472 and in the <file>Packages</file> files. It gives an estimate
3473 of the total amount of disk space required to install the
3474 named package. Actual installed size may vary based on block
3475 size, file system properties, or actions taken by package
3480 The disk space is given as the integer value of the estimated
3481 installed size in bytes, divided by 1024 and rounded up.
3485 <sect1 id="f-Files">
3486 <heading><tt>Files</tt></heading>
3489 This field contains a list of files with information about
3490 each one. The exact information and syntax varies with
3495 In all cases, Files is a multiline field. The first line of
3496 the field value (the part on the same line as <tt>Files:</tt>)
3497 is always empty. The content of the field is expressed as
3498 continuation lines, one line per file. Each line must be
3499 indented by one space and contain a number of sub-fields,
3500 separated by spaces, as described below.
3504 In the <file>.dsc</file> file, each line contains the MD5
3505 checksum, size and filename of the tar file and (if
3506 applicable) diff file which make up the remainder of the
3507 source package<footnote>
3508 That is, the parts which are not the <tt>.dsc</tt>.
3509 </footnote>. For example:
3512 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3513 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3515 The exact forms of the filenames are described
3516 in <ref id="pkg-sourcearchives">.
3520 In the <file>.changes</file> file this contains one line per
3521 file being uploaded. Each line contains the MD5 checksum,
3522 size, section and priority and the filename. For example:
3525 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3526 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3527 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3528 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3530 The <qref id="f-Section">section</qref>
3531 and <qref id="f-Priority">priority</qref> are the values of
3532 the corresponding fields in the main source control file. If
3533 no section or priority is specified then <tt>-</tt> should be
3534 used, though section and priority values must be specified for
3535 new packages to be installed properly.
3539 The special value <tt>byhand</tt> for the section in a
3540 <tt>.changes</tt> file indicates that the file in question
3541 is not an ordinary package file and must by installed by
3542 hand by the distribution maintainers. If the section is
3543 <tt>byhand</tt> the priority should be <tt>-</tt>.
3547 If a new Debian revision of a package is being shipped and
3548 no new original source archive is being distributed the
3549 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3550 entry for the original source archive
3551 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3552 but the <file>.changes</file> file should leave it out. In
3553 this case the original source archive on the distribution
3554 site must match exactly, byte-for-byte, the original
3555 source archive which was used to generate the
3556 <file>.dsc</file> file and diff which are being uploaded.</p>
3559 <sect1 id="f-Closes">
3560 <heading><tt>Closes</tt></heading>
3563 A space-separated list of bug report numbers that the upload
3564 governed by the .changes file closes.
3568 <sect1 id="f-Homepage">
3569 <heading><tt>Homepage</tt></heading>
3572 The URL of the web site for this package, preferably (when
3573 applicable) the site from which the original source can be
3574 obtained and any additional upstream documentation or
3575 information may be found. The content of this field is a
3576 simple URL without any surrounding characters such as
3581 <sect1 id="f-Checksums">
3582 <heading><tt>Checksums-Sha1</tt>
3583 and <tt>Checksums-Sha256</tt></heading>
3586 These fields contain a list of files with a checksum and size
3587 for each one. Both <tt>Checksums-Sha1</tt>
3588 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3589 only in the checksum algorithm used: SHA-1
3590 for <tt>Checksums-Sha1</tt> and SHA-256
3591 for <tt>Checksums-Sha256</tt>.
3595 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3596 multiline fields. The first line of the field value (the part
3597 on the same line as <tt>Checksums-Sha1:</tt>
3598 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3599 of the field is expressed as continuation lines, one line per
3600 file. Each line consists of the checksum, a space, the file
3601 size, a space, and the file name. For example (from
3602 a <file>.changes</file> file):
3605 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3606 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3607 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3608 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3610 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3611 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3612 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3613 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3618 In the <file>.dsc</file> file, these fields should list all
3619 files that make up the source package. In
3620 the <file>.changes</file> file, these fields should list all
3621 files being uploaded. The list of files in these fields
3622 must match the list of files in the <tt>Files</tt> field.
3628 <heading>User-defined fields</heading>
3631 Additional user-defined fields may be added to the
3632 source package control file. Such fields will be
3633 ignored, and not copied to (for example) binary or
3634 source package control files or upload control files.
3638 If you wish to add additional unsupported fields to
3639 these output files you should use the mechanism
3644 Fields in the main source control information file with
3645 names starting <tt>X</tt>, followed by one or more of
3646 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3647 be copied to the output files. Only the part of the
3648 field name after the hyphen will be used in the output
3649 file. Where the letter <tt>B</tt> is used the field
3650 will appear in binary package control files, where the
3651 letter <tt>S</tt> is used in source package control
3652 files and where <tt>C</tt> is used in upload control
3653 (<tt>.changes</tt>) files.
3657 For example, if the main source information control file
3660 XBS-Comment: I stand between the candle and the star.
3662 then the binary and source package control files will contain the
3665 Comment: I stand between the candle and the star.
3674 <chapt id="maintainerscripts">
3675 <heading>Package maintainer scripts and installation procedure</heading>
3678 <heading>Introduction to package maintainer scripts</heading>
3681 It is possible to supply scripts as part of a package which
3682 the package management system will run for you when your
3683 package is installed, upgraded or removed.
3687 These scripts are the control information
3688 files <prgn>preinst</prgn>, <prgn>postinst</prgn>, <prgn>prerm</prgn>
3689 and <prgn>postrm</prgn>. They must be proper executable files;
3690 if they are scripts (which is recommended), they must start with
3691 the usual <tt>#!</tt> convention. They should be readable and
3692 executable by anyone, and must not be world-writable.
3696 The package management system looks at the exit status from
3697 these scripts. It is important that they exit with a
3698 non-zero status if there is an error, so that the package
3699 management system can stop its processing. For shell
3700 scripts this means that you <em>almost always</em> need to
3701 use <tt>set -e</tt> (this is usually true when writing shell
3702 scripts, in fact). It is also important, of course, that
3703 they exit with a zero status if everything went well.
3707 Additionally, packages interacting with users
3708 using <prgn>debconf</prgn> in the <prgn>postinst</prgn> script
3709 should install a <prgn>config</prgn> script as a control
3710 information file. See <ref id="maintscriptprompt"> for details.
3714 When a package is upgraded a combination of the scripts from
3715 the old and new packages is called during the upgrade
3716 procedure. If your scripts are going to be at all
3717 complicated you need to be aware of this, and may need to
3718 check the arguments to your scripts.
3722 Broadly speaking the <prgn>preinst</prgn> is called before
3723 (a particular version of) a package is unpacked, and the
3724 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3725 before (a version of) a package is removed and the
3726 <prgn>postrm</prgn> afterwards.
3730 Programs called from maintainer scripts should not normally
3731 have a path prepended to them. Before installation is
3732 started, the package management system checks to see if the
3733 programs <prgn>ldconfig</prgn>,
3734 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3735 and <prgn>update-rc.d</prgn> can be found via the
3736 <tt>PATH</tt> environment variable. Those programs, and any
3737 other program that one would expect to be in the
3738 <tt>PATH</tt>, should thus be invoked without an absolute
3739 pathname. Maintainer scripts should also not reset the
3740 <tt>PATH</tt>, though they might choose to modify it by
3741 prepending or appending package-specific directories. These
3742 considerations really apply to all shell scripts.</p>
3745 <sect id="idempotency">
3746 <heading>Maintainer scripts idempotency</heading>
3749 It is necessary for the error recovery procedures that the
3750 scripts be idempotent. This means that if it is run
3751 successfully, and then it is called again, it doesn't bomb
3752 out or cause any harm, but just ensures that everything is
3753 the way it ought to be. If the first call failed, or
3754 aborted half way through for some reason, the second call
3755 should merely do the things that were left undone the first
3756 time, if any, and exit with a success status if everything
3758 This is so that if an error occurs, the user interrupts
3759 <prgn>dpkg</prgn> or some other unforeseen circumstance
3760 happens you don't leave the user with a badly-broken
3761 package when <prgn>dpkg</prgn> attempts to repeat the
3767 <sect id="controllingterminal">
3768 <heading>Controlling terminal for maintainer scripts</heading>
3771 Maintainer scripts are not guaranteed to run with a controlling
3772 terminal and may not be able to interact with the user. They
3773 must be able to fall back to noninteractive behavior if no
3774 controlling terminal is available. Maintainer scripts that
3775 prompt via a program conforming to the Debian Configuration
3776 Management Specification (see <ref id="maintscriptprompt">) may
3777 assume that program will handle falling back to noninteractive
3782 For high-priority prompts without a reasonable default answer,
3783 maintainer scripts may abort if there is no controlling
3784 terminal. However, this situation should be avoided if at all
3785 possible, since it prevents automated or unattended installs.
3786 In most cases, users will consider this to be a bug in the
3791 <sect id="exitstatus">
3792 <heading>Exit status</heading>
3795 Each script must return a zero exit status for
3796 success, or a nonzero one for failure, since the package
3797 management system looks for the exit status of these scripts
3798 and determines what action to take next based on that datum.
3802 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3807 What follows is a summary of all the ways in which maintainer
3808 scripts may be called along with what facilities those scripts
3809 may rely on being available at that time. Script names preceded
3810 by <var>new-</var> are the scripts from the new version of a
3811 package being installed, upgraded to, or downgraded to. Script
3812 names preceded by <var>old-</var> are the scripts from the old
3813 version of a package that is being upgraded from or downgraded
3818 The <prgn>preinst</prgn> script may be called in the following
3821 <tag><var>new-preinst</var> <tt>install</tt></tag>
3822 <tag><var>new-preinst</var> <tt>install</tt>
3823 <var>old-version</var></tag>
3824 <tag><var>new-preinst</var> <tt>upgrade</tt>
3825 <var>old-version</var></tag>
3827 The package will not yet be unpacked, so
3828 the <prgn>preinst</prgn> script cannot rely on any files
3829 included in its package. Only essential packages and
3830 pre-dependencies (<tt>Pre-Depends</tt>) may be assumed to be
3831 available. Pre-dependencies will be at least unpacked.
3832 They may be only unpacked or "Half-Configured", not
3833 completely configured, but only if a previous version of the
3834 pre-dependency was completely configured and the
3835 pre-dependency had not been removed since then.
3838 <tag><var>old-preinst</var> <tt>abort-upgrade</tt>
3839 <var>new-version</var></tag>
3841 Called during error handling of an upgrade that failed after
3842 unpacking the new package because the <tt>postrm
3843 upgrade</tt> action failed. The unpacked files may be
3844 partly from the new version or partly missing, so the script
3845 cannot rely on files included in the package. Package
3846 dependencies may not be available. Pre-dependencies will be
3847 at least unpacked following the same rules as above, except
3848 they may be only "Half-Installed" if an upgrade of the
3849 pre-dependency failed.<footnote>
3850 This can happen if the new version of the package no
3851 longer pre-depends on a package that had been partially
3859 The <prgn>postinst</prgn> script may be called in the following
3862 <tag><var>postinst</var> <tt>configure</tt>
3863 <var>most-recently-configured-version</var></tag>
3865 The files contained in the package will be unpacked. All
3866 package dependencies will at least be unpacked. If there
3867 are no circular dependencies involved, all package
3868 dependencies will be configured.
3871 <tag><var>old-postinst</var> <tt>abort-upgrade</tt>
3872 <var>new-version</var></tag>
3873 <tag><var>conflictor's-postinst</var> <tt>abort-remove</tt>
3874 <tt>in-favour</tt> <var>package</var>
3875 <var>new-version</var></tag>
3876 <tag><var>postinst</var> <tt>abort-remove</tt></tag>
3877 <tag><var>deconfigured's-postinst</var>
3878 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3879 <var>failed-install-package</var> <var>version</var>
3880 [<tt>removing</tt> <var>conflicting-package</var>
3881 <var>version</var>]</tag>
3883 The files contained in the package will be unpacked. All
3884 package dependencies will at least be "Half-Installed" and
3885 will have previously been configured and not removed.
3886 However, dependencies may not be configured or even fully
3887 unpacked in some error situations.<footnote>
3888 For example, suppose packages foo and bar are installed
3889 with foo depending on bar. If an upgrade of bar were
3890 started and then aborted, and then an attempt to remove
3891 foo failed because its <prgn>prerm</prgn> script failed,
3892 foo's <tt>postinst abort-remove</tt> would be called with
3893 bar only "Half-Installed".
3900 The <prgn>prerm</prgn> script may be called in the following
3903 <tag><var>prerm</var> <tt>remove</tt></tag>
3904 <tag><var>old-prerm</var>
3905 <tt>upgrade</tt><var>new-version</var></tag>
3906 <tag><var>conflictor's-prerm</var> <tt>remove</tt>
3907 <tt>in-favour</tt> <var>package</var>
3908 <var>new-version</var></tag>
3909 <tag><var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3910 <tt>in-favour</tt> <var>package-being-installed</var>
3911 <var>version</var> [<tt>removing</tt>
3912 <var>conflicting-package</var> <var>version</var>]</tag>
3914 The package whose <prgn>prerm</prgn> is being called will be
3915 at least "Half-Installed". All package dependencies will at
3916 least be "Half-Installed" and will have previously been
3917 configured and not removed. If there was no error, all
3918 dependencies will at least be unpacked, but these actions
3919 may be called in various error states where dependencies are
3920 only "Half-Installed" due to a partial upgrade.
3923 <tag><var>new-prerm</var> <tt>failed-upgrade</tt>
3924 <var>old-version</var></tag>
3926 Called during error handling when <tt>prerm upgrade</tt>
3927 fails. The new package will not yet be unpacked, and all
3928 the same constraints as for <tt>preinst upgrade</tt> apply.
3934 The <prgn>postrm</prgn> script may be called in the following
3937 <tag><var>postrm</var> <tt>remove</tt></tag>
3938 <tag><var>postrm</var> <tt>purge</tt></tag>
3939 <tag><var>old-postrm</var> <tt>upgrade</tt>
3940 <var>new-version</var></tag>
3941 <tag><var>disappearer's-postrm</var> <tt>disappear</tt>
3942 <var>overwriter</var> <var>overwriter-version</var></tag>
3944 The <prgn>postrm</prgn> script is called after the package's
3945 files have been removed or replaced. The package
3946 whose <prgn>postrm</prgn> is being called may have
3947 previously been deconfigured and only be unpacked, at which
3948 point subsequent package changes do not consider its
3949 dependencies. Therefore, all <prgn>postrm</prgn> actions
3950 may only rely on essential packages and cannot assume that
3951 the package's dependencies are available.
3954 <tag><var>new-postrm</var> <tt>failed-upgrade</tt>
3955 <var>old-version</var></tag>
3957 Called when the old <tt>postrm upgrade</tt> action fails.
3958 The new package will be unpacked, but only essential
3959 packages and pre-dependencies can be relied on.
3960 Pre-dependencies will either be configured or will be
3961 "Unpacked" or "Half-Configured" but previously had been
3962 configured and was never removed.
3965 <tag><var>new-postrm</var> <tt>abort-install</tt></tag>
3966 <tag><var>new-postrm</var> <tt>abort-install</tt>
3967 <var>old-version</var></tag>
3968 <tag><var>new-postrm</var> <tt>abort-upgrade</tt>
3969 <var>old-version</var></tag>
3971 Called before unpacking the new package as part of the
3972 error handling of <prgn>preinst</prgn> failures. May assume
3973 the same state as <prgn>preinst</prgn> can assume.
3979 <sect id="unpackphase">
3980 <heading>Details of unpack phase of installation or upgrade</heading>
3983 The procedure on installation/upgrade/overwrite/disappear
3984 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3985 stage of <tt>dpkg --install</tt>) is as follows. In each
3986 case, if a major error occurs (unless listed below) the
3987 actions are, in general, run backwards - this means that the
3988 maintainer scripts are run with different arguments in
3989 reverse order. These are the "error unwind" calls listed
3996 If a version of the package is already installed, call
3997 <example compact="compact">
3998 <var>old-prerm</var> upgrade <var>new-version</var>
4002 If the script runs but exits with a non-zero
4003 exit status, <prgn>dpkg</prgn> will attempt:
4004 <example compact="compact">
4005 <var>new-prerm</var> failed-upgrade <var>old-version</var>
4007 If this works, the upgrade continues. If this
4008 does not work, the error unwind:
4009 <example compact="compact">
4010 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4012 If this works, then the old-version is
4013 "Installed", if not, the old version is in a
4014 "Half-Configured" state.
4020 If a "conflicting" package is being removed at the same time,
4021 or if any package will be broken (due to <tt>Breaks</tt>):
4024 If <tt>--auto-deconfigure</tt> is
4025 specified, call, for each package to be deconfigured
4026 due to <tt>Breaks</tt>:
4027 <example compact="compact">
4028 <var>deconfigured's-prerm</var> deconfigure \
4029 in-favour <var>package-being-installed</var> <var>version</var>
4032 <example compact="compact">
4033 <var>deconfigured's-postinst</var> abort-deconfigure \
4034 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
4036 The deconfigured packages are marked as
4037 requiring configuration, so that if
4038 <tt>--install</tt> is used they will be
4039 configured again if possible.
4042 If any packages depended on a conflicting
4043 package being removed and <tt>--auto-deconfigure</tt> is
4044 specified, call, for each such package:
4045 <example compact="compact">
4046 <var>deconfigured's-prerm</var> deconfigure \
4047 in-favour <var>package-being-installed</var> <var>version</var> \
4048 removing <var>conflicting-package</var> <var>version</var>
4051 <example compact="compact">
4052 <var>deconfigured's-postinst</var> abort-deconfigure \
4053 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
4054 removing <var>conflicting-package</var> <var>version</var>
4056 The deconfigured packages are marked as
4057 requiring configuration, so that if
4058 <tt>--install</tt> is used they will be
4059 configured again if possible.
4062 To prepare for removal of each conflicting package, call:
4063 <example compact="compact">
4064 <var>conflictor's-prerm</var> remove \
4065 in-favour <var>package</var> <var>new-version</var>
4068 <example compact="compact">
4069 <var>conflictor's-postinst</var> abort-remove \
4070 in-favour <var>package</var> <var>new-version</var>
4079 If the package is being upgraded, call:
4080 <example compact="compact">
4081 <var>new-preinst</var> upgrade <var>old-version</var>
4083 If this fails, we call:
4085 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4092 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4094 is called. If this works, then the old version
4095 is in an "Installed" state, or else it is left
4096 in an "Unpacked" state.
4101 If it fails, then the old version is left
4102 in an "Half-Installed" state.
4109 Otherwise, if the package had some configuration
4110 files from a previous version installed (i.e., it
4111 is in the "configuration files only" state):
4112 <example compact="compact">
4113 <var>new-preinst</var> install <var>old-version</var>
4117 <var>new-postrm</var> abort-install <var>old-version</var>
4119 If this fails, the package is left in a
4120 "Half-Installed" state, which requires a
4121 reinstall. If it works, the packages is left in
4122 a "Config-Files" state.
4125 Otherwise (i.e., the package was completely purged):
4126 <example compact="compact">
4127 <var>new-preinst</var> install
4130 <example compact="compact">
4131 <var>new-postrm</var> abort-install
4133 If the error-unwind fails, the package is in a
4134 "Half-Installed" phase, and requires a
4135 reinstall. If the error unwind works, the
4136 package is in a not installed state.
4143 The new package's files are unpacked, overwriting any
4144 that may be on the system already, for example any
4145 from the old version of the same package or from
4146 another package. Backups of the old files are kept
4147 temporarily, and if anything goes wrong the package
4148 management system will attempt to put them back as
4149 part of the error unwind.
4153 It is an error for a package to contain files which
4154 are on the system in another package, unless
4155 <tt>Replaces</tt> is used (see <ref id="replaces">).
4157 The following paragraph is not currently the case:
4158 Currently the <tt>- - force-overwrite</tt> flag is
4159 enabled, downgrading it to a warning, but this may not
4165 It is a more serious error for a package to contain a
4166 plain file or other kind of non-directory where another
4167 package has a directory (again, unless
4168 <tt>Replaces</tt> is used). This error can be
4169 overridden if desired using
4170 <tt>--force-overwrite-dir</tt>, but this is not
4175 Packages which overwrite each other's files produce
4176 behavior which, though deterministic, is hard for the
4177 system administrator to understand. It can easily
4178 lead to "missing" programs if, for example, a package
4179 is unpacked which overwrites a file from another
4180 package, and is then removed again.<footnote>
4181 Part of the problem is due to what is arguably a
4182 bug in <prgn>dpkg</prgn>.
4187 A directory will never be replaced by a symbolic link
4188 to a directory or vice versa; instead, the existing
4189 state (symlink or not) will be left alone and
4190 <prgn>dpkg</prgn> will follow the symlink if there is
4199 If the package is being upgraded, call
4200 <example compact="compact">
4201 <var>old-postrm</var> upgrade <var>new-version</var>
4205 If this fails, <prgn>dpkg</prgn> will attempt:
4206 <example compact="compact">
4207 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4209 If this works, installation continues. If not,
4211 <example compact="compact">
4212 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4214 If this fails, the old version is left in a
4215 "Half-Installed" state. If it works, dpkg now
4217 <example compact="compact">
4218 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4220 If this fails, the old version is left in a
4221 "Half-Installed" state. If it works, dpkg now
4223 <example compact="compact">
4224 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4226 If this fails, the old version is in an
4233 This is the point of no return - if
4234 <prgn>dpkg</prgn> gets this far, it won't back off
4235 past this point if an error occurs. This will
4236 leave the package in a fairly bad state, which
4237 will require a successful re-installation to clear
4238 up, but it's when <prgn>dpkg</prgn> starts doing
4239 things that are irreversible.
4244 Any files which were in the old version of the package
4245 but not in the new are removed.
4249 The new file list replaces the old.
4253 The new maintainer scripts replace the old.
4257 Any packages all of whose files have been overwritten
4258 during the installation, and which aren't required for
4259 dependencies, are considered to have been removed.
4260 For each such package
4263 <prgn>dpkg</prgn> calls:
4264 <example compact="compact">
4265 <var>disappearer's-postrm</var> disappear \
4266 <var>overwriter</var> <var>overwriter-version</var>
4270 The package's maintainer scripts are removed.
4273 It is noted in the status database as being in a
4274 sane state, namely not installed (any conffiles
4275 it may have are ignored, rather than being
4276 removed by <prgn>dpkg</prgn>). Note that
4277 disappearing packages do not have their prerm
4278 called, because <prgn>dpkg</prgn> doesn't know
4279 in advance that the package is going to
4286 Any files in the package we're unpacking that are also
4287 listed in the file lists of other packages are removed
4288 from those lists. (This will lobotomize the file list
4289 of the "conflicting" package if there is one.)
4293 The backup files made during installation, above, are
4299 The new package's status is now sane, and recorded as
4304 Here is another point of no return - if the
4305 conflicting package's removal fails we do not unwind
4306 the rest of the installation; the conflicting package
4307 is left in a half-removed limbo.
4312 If there was a conflicting package we go and do the
4313 removal actions (described below), starting with the
4314 removal of the conflicting package's files (any that
4315 are also in the package being unpacked have already
4316 been removed from the conflicting package's file list,
4317 and so do not get removed now).
4323 <sect id="configdetails"><heading>Details of configuration</heading>
4326 When we configure a package (this happens with <tt>dpkg
4327 --install</tt> and <tt>dpkg --configure</tt>), we first
4328 update any <tt>conffile</tt>s and then call:
4329 <example compact="compact">
4330 <var>postinst</var> configure <var>most-recently-configured-version</var>
4335 No attempt is made to unwind after errors during
4336 configuration. If the configuration fails, the package is in
4337 a "Failed Config" state, and an error message is generated.
4341 If there is no most recently configured version
4342 <prgn>dpkg</prgn> will pass a null argument.
4345 Historical note: Truly ancient (pre-1997) versions of
4346 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4347 (including the angle brackets) in this case. Even older
4348 ones did not pass a second argument at all, under any
4349 circumstance. Note that upgrades using such an old dpkg
4350 version are unlikely to work for other reasons, even if
4351 this old argument behavior is handled by your postinst script.
4357 <sect id="removedetails"><heading>Details of removal and/or
4358 configuration purging</heading>
4364 <example compact="compact">
4365 <var>prerm</var> remove
4369 If prerm fails during replacement due to conflict
4371 <var>conflictor's-postinst</var> abort-remove \
4372 in-favour <var>package</var> <var>new-version</var>
4376 <var>postinst</var> abort-remove
4380 If this fails, the package is in a "Half-Configured"
4381 state, or else it remains "Installed".
4385 The package's files are removed (except <tt>conffile</tt>s).
4388 <example compact="compact">
4389 <var>postrm</var> remove
4393 If it fails, there's no error unwind, and the package is in
4394 an "Half-Installed" state.
4399 All the maintainer scripts except the <prgn>postrm</prgn>
4404 If we aren't purging the package we stop here. Note
4405 that packages which have no <prgn>postrm</prgn> and no
4406 <tt>conffile</tt>s are automatically purged when
4407 removed, as there is no difference except for the
4408 <prgn>dpkg</prgn> status.
4412 The <tt>conffile</tt>s and any backup files
4413 (<tt>~</tt>-files, <tt>#*#</tt> files,
4414 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4419 <example compact="compact">
4420 <var>postrm</var> purge
4424 If this fails, the package remains in a "Config-Files"
4429 The package's file list is removed.
4438 <chapt id="relationships">
4439 <heading>Declaring relationships between packages</heading>
4441 <sect id="depsyntax">
4442 <heading>Syntax of relationship fields</heading>
4445 These fields all have a uniform syntax. They are a list of
4446 package names separated by commas.
4450 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4451 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4452 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4453 control fields of the package, which declare
4454 dependencies on other packages, the package names listed may
4455 also include lists of alternative package names, separated
4456 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4457 if any one of the alternative packages is installed, that
4458 part of the dependency is considered to be satisfied.
4462 All of the fields except for <tt>Provides</tt> may restrict
4463 their applicability to particular versions of each named
4464 package. This is done in parentheses after each individual
4465 package name; the parentheses should contain a relation from
4466 the list below followed by a version number, in the format
4467 described in <ref id="f-Version">.
4471 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4472 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4473 strictly earlier, earlier or equal, exactly equal, later or
4474 equal and strictly later, respectively. The deprecated
4475 forms <tt><</tt> and <tt>></tt> were used to mean
4476 earlier/later or equal, rather than strictly earlier/later,
4477 so they should not appear in new packages (though
4478 <prgn>dpkg</prgn> still supports them).
4482 Whitespace may appear at any point in the version
4483 specification subject to the rules in <ref
4484 id="controlsyntax">, and must appear where it's necessary to
4485 disambiguate; it is not otherwise significant. All of the
4486 relationship fields may span multiple lines. For
4487 consistency and in case of future changes to
4488 <prgn>dpkg</prgn> it is recommended that a single space be
4489 used after a version relationship and before a version
4490 number; it is also conventional to put a single space after
4491 each comma, on either side of each vertical bar, and before
4492 each open parenthesis. When wrapping a relationship field, it
4493 is conventional to do so after a comma and before the space
4494 following that comma.
4498 For example, a list of dependencies might appear as:
4499 <example compact="compact">
4502 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4507 Relationships may be restricted to a certain set of
4508 architectures. This is indicated in brackets after each
4509 individual package name and the optional version specification.
4510 The brackets enclose a list of Debian architecture names
4511 separated by whitespace. Exclamation marks may be prepended to
4512 each of the names. (It is not permitted for some names to be
4513 prepended with exclamation marks while others aren't.)
4517 For build relationship fields
4518 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4519 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>), if
4520 the current Debian host architecture is not in this list and
4521 there are no exclamation marks in the list, or it is in the list
4522 with a prepended exclamation mark, the package name and the
4523 associated version specification are ignored completely for the
4524 purposes of defining the relationships.
4529 <example compact="compact">
4531 Build-Depends-Indep: texinfo
4532 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4533 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4535 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4536 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4537 <tt>gnumach-dev</tt> only on hurd-i386.
4541 For binary relationship fields, the architecture restriction
4542 syntax is only supported in the source package control
4543 file <file>debian/control</file>. When the corresponding binary
4544 package control file is generated, the relationship will either
4545 be omitted or included without the architecture restriction
4546 based on the architecture of the binary package. This means
4547 that architecture restrictions must not be used in binary
4548 relationship fields for architecture-independent packages
4549 (<tt>Architecture: all</tt>).
4554 <example compact="compact">
4555 Depends: foo [i386], bar [amd64]
4557 becomes <tt>Depends: foo</tt> when the package is built on
4558 the <tt>i386</tt> architecture, <tt>Depends: bar</tt> when the
4559 package is built on the <tt>amd64</tt> architecture, and omitted
4560 entirely in binary packages built on all other architectures.
4564 If the architecture-restricted dependency is part of a set of
4565 alternatives using <tt>|</tt>, that alternative is ignored
4566 completely on architectures that do not match the restriction.
4568 <example compact="compact">
4569 Build-Depends: foo [!i386] | bar [!amd64]
4571 is equivalent to <tt>bar</tt> on the i386 architecture, to
4572 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4573 bar</tt> on all other architectures.
4577 Relationships may also be restricted to a certain set of
4578 architectures using architecture wildcards. The syntax for
4579 declaring such restrictions is the same as declaring
4580 restrictions using a certain set of architectures without
4581 architecture wildcards. For example:
4582 <example compact="compact">
4583 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4585 is equivalent to <tt>foo</tt> on architectures using the Linux
4586 kernel and any cpu, <tt>bar</tt> on architectures using any
4587 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4588 using a kernel other than Linux.
4592 Note that the binary package relationship fields such as
4593 <tt>Depends</tt> appear in one of the binary package
4594 sections of the control file, whereas the build-time
4595 relationships such as <tt>Build-Depends</tt> appear in the
4596 source package section of the control file (which is the
4601 <sect id="binarydeps">
4602 <heading>Binary Dependencies - <tt>Depends</tt>,
4603 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4604 <tt>Pre-Depends</tt>
4608 Packages can declare in their control file that they have
4609 certain relationships to other packages - for example, that
4610 they may not be installed at the same time as certain other
4611 packages, and/or that they depend on the presence of others.
4615 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4616 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4617 <tt>Breaks</tt> and <tt>Conflicts</tt> control fields.
4618 <tt>Breaks</tt> is described in <ref id="breaks">, and
4619 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4620 rest are described below.
4624 These seven fields are used to declare a dependency
4625 relationship by one package on another. Except for
4626 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4627 depending (binary) package's control file.
4628 (<tt>Enhances</tt> appears in the recommending package's
4629 control file, and <tt>Breaks</tt> appears in the version of
4630 depended-on package which causes the named package to
4635 A <tt>Depends</tt> field takes effect <em>only</em> when a
4636 package is to be configured. It does not prevent a package
4637 being on the system in an unconfigured state while its
4638 dependencies are unsatisfied, and it is possible to replace
4639 a package whose dependencies are satisfied and which is
4640 properly installed with a different version whose
4641 dependencies are not and cannot be satisfied; when this is
4642 done the depending package will be left unconfigured (since
4643 attempts to configure it will give errors) and will not
4644 function properly. If it is necessary, a
4645 <tt>Pre-Depends</tt> field can be used, which has a partial
4646 effect even when a package is being unpacked, as explained
4647 in detail below. (The other three dependency fields,
4648 <tt>Recommends</tt>, <tt>Suggests</tt> and
4649 <tt>Enhances</tt>, are only used by the various front-ends
4650 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4651 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4655 Since <tt>Depends</tt> only places requirements on the order in
4656 which packages are configured, packages in an installation run
4657 are usually all unpacked first and all configured later.
4659 This approach makes dependency resolution easier. If two
4660 packages A and B are being upgraded, the installed package A
4661 depends on exactly the installed package B, and the new
4662 package A depends on exactly the new package B (a common
4663 situation when upgrading shared libraries and their
4664 corresponding development packages), satisfying the
4665 dependencies at every stage of the upgrade would be
4666 impossible. This relaxed restriction means that both new
4667 packages can be unpacked together and then configured in their
4673 If there is a circular dependency among packages being installed
4674 or removed, installation or removal order honoring the
4675 dependency order is impossible, requiring the dependency loop be
4676 broken at some point and the dependency requirements violated
4677 for at least one package. Packages involved in circular
4678 dependencies may not be able to rely on their dependencies being
4679 configured when being configured depending on which side of the
4680 break of the circular dependency loop they happen to be on. If
4681 one of the packages in the loop has no <prgn>postinst</prgn>
4682 script, then the cycle will be broken at that package; this
4683 ensures that all <prgn>postinst</prgn> scripts are run with
4684 their dependencies properly configured if this is possible.
4685 Otherwise the breaking point is arbitrary. Packages should
4686 therefore avoid circular dependencies where possible,
4687 particularly if they have <prgn>postinst</prgn> scripts.
4691 The meaning of the five dependency fields is as follows:
4693 <tag><tt>Depends</tt></tag>
4696 This declares an absolute dependency. A package will
4697 not be configured unless all of the packages listed in
4698 its <tt>Depends</tt> field have been correctly
4699 configured (unless there is a circular dependency as
4704 The <tt>Depends</tt> field should be used if the
4705 depended-on package is required for the depending
4706 package to provide a significant amount of
4711 The <tt>Depends</tt> field should also be used if the
4712 <prgn>postinst</prgn> or <prgn>prerm</prgn> scripts
4713 require the depended-on package to be unpacked or
4714 configured in order to run. In the case of <tt>postinst
4715 configure</tt>, the depended-on packages will be unpacked
4716 and configured first. (If both packages are involved in a
4717 dependency loop, this might not work as expected; see the
4718 explanation a few paragraphs back.) In the case
4719 of <prgn>prerm</prgn> or other <prgn>postinst</prgn>
4720 actions, the package dependencies will normally be at
4721 least unpacked, but they may be only "Half-Installed" if a
4722 previous upgrade of the dependency failed.
4726 <tag><tt>Recommends</tt></tag>
4729 This declares a strong, but not absolute, dependency.
4733 The <tt>Recommends</tt> field should list packages
4734 that would be found together with this one in all but
4735 unusual installations.
4739 <tag><tt>Suggests</tt></tag>
4741 This is used to declare that one package may be more
4742 useful with one or more others. Using this field
4743 tells the packaging system and the user that the
4744 listed packages are related to this one and can
4745 perhaps enhance its usefulness, but that installing
4746 this one without them is perfectly reasonable.
4749 <tag><tt>Enhances</tt></tag>
4751 This field is similar to Suggests but works in the
4752 opposite direction. It is used to declare that a
4753 package can enhance the functionality of another
4757 <tag><tt>Pre-Depends</tt></tag>
4760 This field is like <tt>Depends</tt>, except that it
4761 also forces <prgn>dpkg</prgn> to complete installation
4762 of the packages named before even starting the
4763 installation of the package which declares the
4764 pre-dependency, as follows:
4768 When a package declaring a pre-dependency is about to
4769 be <em>unpacked</em> the pre-dependency can be
4770 satisfied if the depended-on package is either fully
4771 configured, <em>or even if</em> the depended-on
4772 package(s) are only unpacked or in the "Half-Configured"
4773 state, provided that they have been configured
4774 correctly at some point in the past (and not removed
4775 or partially removed since). In this case, both the
4776 previously-configured and currently unpacked or
4777 "Half-Configured" versions must satisfy any version
4778 clause in the <tt>Pre-Depends</tt> field.
4782 When the package declaring a pre-dependency is about to
4783 be <em>configured</em>, the pre-dependency will be treated
4784 as a normal <tt>Depends</tt>. It will be considered
4785 satisfied only if the depended-on package has been
4786 correctly configured. However, unlike
4787 with <tt>Depends</tt>, <tt>Pre-Depends</tt> does not
4788 permit circular dependencies to be broken. If a circular
4789 dependency is encountered while attempting to honor
4790 <tt>Pre-Depends</tt>, the installation will be aborted.
4794 <tt>Pre-Depends</tt> are also required if the
4795 <prgn>preinst</prgn> script depends on the named package.
4796 It is best to avoid this situation if possible.
4800 <tt>Pre-Depends</tt> should be used sparingly,
4801 preferably only by packages whose premature upgrade or
4802 installation would hamper the ability of the system to
4803 continue with any upgrade that might be in progress.
4810 When selecting which level of dependency to use you should
4811 consider how important the depended-on package is to the
4812 functionality of the one declaring the dependency. Some
4813 packages are composed of components of varying degrees of
4814 importance. Such a package should list using
4815 <tt>Depends</tt> the package(s) which are required by the
4816 more important components. The other components'
4817 requirements may be mentioned as Suggestions or
4818 Recommendations, as appropriate to the components' relative
4824 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4827 When one binary package declares that it breaks another,
4828 <prgn>dpkg</prgn> will refuse to allow the package which
4829 declares <tt>Breaks</tt> to be unpacked unless the broken
4830 package is deconfigured first, and it will refuse to
4831 allow the broken package to be reconfigured.
4835 A package will not be regarded as causing breakage merely
4836 because its configuration files are still installed; it must
4837 be at least "Half-Installed".
4841 A special exception is made for packages which declare that
4842 they break their own package name or a virtual package which
4843 they provide (see below): this does not count as a real
4848 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4849 version clause; such a <tt>Breaks</tt> is introduced in the
4850 version of an (implicit or explicit) dependency which violates
4851 an assumption or reveals a bug in earlier versions of the broken
4852 package, or which takes over a file from earlier versions of the
4853 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
4854 will inform higher-level package management tools that the
4855 broken package must be upgraded before the new one.
4859 If the breaking package also overwrites some files from the
4860 older package, it should use <tt>Replaces</tt> to ensure this
4861 goes smoothly. See <ref id="replaces"> for a full discussion
4862 of taking over files from other packages, including how to
4863 use <tt>Breaks</tt> in those cases.
4867 Many of the cases where <tt>Breaks</tt> should be used were
4868 previously handled with <tt>Conflicts</tt>
4869 because <tt>Breaks</tt> did not yet exist.
4870 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
4871 See <ref id="conflicts"> for more information about the
4876 <sect id="conflicts">
4877 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4880 When one binary package declares a conflict with another using
4881 a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will refuse to
4882 allow them to be unpacked on the system at the same time. This
4883 is a stronger restriction than <tt>Breaks</tt>, which prevents
4884 the broken package from being configured while the breaking
4885 package is in the "Unpacked" state but allows both packages to
4886 be unpacked at the same time.
4890 If one package is to be unpacked, the other must be removed
4891 first. If the package being unpacked is marked as replacing
4892 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
4893 normally be used in this case) the one on the system, or the one
4894 on the system is marked as deselected, or both packages are
4895 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
4896 automatically remove the package which is causing the conflict.
4897 Otherwise, it will halt the installation of the new package with
4898 an error. This mechanism is specifically designed to produce an
4899 error when the installed package is <tt>Essential</tt>, but the
4904 A package will not cause a conflict merely because its
4905 configuration files are still installed; it must be at least
4910 A special exception is made for packages which declare a
4911 conflict with their own package name, or with a virtual
4912 package which they provide (see below): this does not
4913 prevent their installation, and allows a package to conflict
4914 with others providing a replacement for it. You use this
4915 feature when you want the package in question to be the only
4916 package providing some feature.
4920 Normally, <tt>Breaks</tt> should be used instead
4921 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
4922 stronger restriction on the ordering of package installation or
4923 upgrade and can make it more difficult for the package manager
4924 to find a correct solution to an upgrade or installation
4925 problem. <tt>Breaks</tt> should be used
4927 <item>when moving a file from one package to another (see
4928 <ref id="replaces">),</item>
4929 <item>when splitting a package (a special case of the previous
4931 <item>when the breaking package exposes a bug in or interacts
4932 badly with particular versions of the broken
4935 <tt>Conflicts</tt> should be used
4937 <item>when two packages provide the same file and will
4938 continue to do so,</item>
4939 <item>in conjunction with <tt>Provides</tt> when only one
4940 package providing a given virtual facility may be unpacked
4941 at a time (see <ref id="virtual">),</item>
4942 <item>in other cases where one must prevent simultaneous
4943 installation of two packages for reasons that are ongoing
4944 (not fixed in a later version of one of the packages) or
4945 that must prevent both packages from being unpacked at the
4946 same time, not just configured.</item>
4948 Be aware that adding <tt>Conflicts</tt> is normally not the best
4949 solution when two packages provide the same files. Depending on
4950 the reason for that conflict, using alternatives or renaming the
4951 files is often a better approach. See, for
4952 example, <ref id="binaries">.
4956 Neither <tt>Breaks</tt> nor <tt>Conflicts</tt> should be used
4957 unless two packages cannot be installed at the same time or
4958 installing them both causes one of them to be broken or
4959 unusable. Having similar functionality or performing the same
4960 tasks as another package is not sufficient reason to
4961 declare <tt>Breaks</tt> or <tt>Conflicts</tt> with that package.
4965 A <tt>Conflicts</tt> entry may have an "earlier than" version
4966 clause if the reason for the conflict is corrected in a later
4967 version of one of the packages. However, normally the presence
4968 of an "earlier than" version clause is a sign
4969 that <tt>Breaks</tt> should have been used instead. An "earlier
4970 than" version clause in <tt>Conflicts</tt>
4971 prevents <prgn>dpkg</prgn> from upgrading or installing the
4972 package which declares such a conflict until the upgrade or
4973 removal of the conflicted-with package has been completed, which
4974 is a strong restriction.
4978 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4982 As well as the names of actual ("concrete") packages, the
4983 package relationship fields <tt>Depends</tt>,
4984 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4985 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4986 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4987 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4988 may mention "virtual packages".
4992 A <em>virtual package</em> is one which appears in the
4993 <tt>Provides</tt> control field of another package. The effect
4994 is as if the package(s) which provide a particular virtual
4995 package name had been listed by name everywhere the virtual
4996 package name appears. (See also <ref id="virtual_pkg">)
5000 If there are both concrete and virtual packages of the same
5001 name, then the dependency may be satisfied (or the conflict
5002 caused) by either the concrete package with the name in
5003 question or any other concrete package which provides the
5004 virtual package with the name in question. This is so that,
5005 for example, supposing we have
5006 <example compact="compact">
5009 </example> and someone else releases an enhanced version of
5010 the <tt>bar</tt> package they can say:
5011 <example compact="compact">
5015 and the <tt>bar-plus</tt> package will now also satisfy the
5016 dependency for the <tt>foo</tt> package.
5020 If a relationship field has a version number attached, only real
5021 packages will be considered to see whether the relationship is
5022 satisfied (or the prohibition violated, for a conflict or
5023 breakage). In other words, if a version number is specified,
5024 this is a request to ignore all <tt>Provides</tt> for that
5025 package name and consider only real packages. The package
5026 manager will assume that a package providing that virtual
5027 package is not of the "right" version. A <tt>Provides</tt>
5028 field may not contain version numbers, and the version number of
5029 the concrete package which provides a particular virtual package
5030 will not be considered when considering a dependency on or
5031 conflict with the virtual package name.<footnote>
5032 It is possible that a future release of <prgn>dpkg</prgn> may
5033 add the ability to specify a version number for each virtual
5034 package it provides. This feature is not yet present,
5035 however, and is expected to be used only infrequently.
5040 To specify which of a set of real packages should be the default
5041 to satisfy a particular dependency on a virtual package, list
5042 the real package as an alternative before the virtual one.
5046 If the virtual package represents a facility that can only be
5047 provided by one real package at a time, such as
5048 the <package>mail-transport-agent</package> virtual package that
5049 requires installation of a binary that would conflict with all
5050 other providers of that virtual package (see
5051 <ref id="mail-transport-agents">), all packages providing that
5052 virtual package should also declare a conflict with it
5053 using <tt>Conflicts</tt>. This will ensure that at most one
5054 provider of that virtual package is unpacked or installed at a
5059 <sect id="replaces"><heading>Overwriting files and replacing
5060 packages - <tt>Replaces</tt></heading>
5063 Packages can declare in their control file that they should
5064 overwrite files in certain other packages, or completely replace
5065 other packages. The <tt>Replaces</tt> control field has these
5066 two distinct purposes.
5069 <sect1><heading>Overwriting files in other packages</heading>
5072 It is usually an error for a package to contain files which
5073 are on the system in another package. However, if the
5074 overwriting package declares that it <tt>Replaces</tt> the one
5075 containing the file being overwritten, then <prgn>dpkg</prgn>
5076 will replace the file from the old package with that from the
5077 new. The file will no longer be listed as "owned" by the old
5078 package and will be taken over by the new package.
5079 Normally, <tt>Breaks</tt> should be used in conjunction
5080 with <tt>Replaces</tt>.<footnote>
5081 To see why <tt>Breaks</tt> is normally needed in addition
5082 to <tt>Replaces</tt>, consider the case of a file in the
5083 package <package>foo</package> being taken over by the
5084 package <package>foo-data</package>.
5085 <tt>Replaces</tt> will allow <package>foo-data</package> to
5086 be installed and take over that file. However,
5087 without <tt>Breaks</tt>, nothing
5088 requires <package>foo</package> to be upgraded to a newer
5089 version that knows it does not include that file and instead
5090 depends on <package>foo-data</package>. Nothing would
5091 prevent the new <package>foo-data</package> package from
5092 being installed and then removed, removing the file that it
5093 took over from <package>foo</package>. After that
5094 operation, the package manager would think the system was in
5095 a consistent state, but the <package>foo</package> package
5096 would be missing one of its files.
5101 For example, if a package <package>foo</package> is split
5102 into <package>foo</package> and <package>foo-data</package>
5103 starting at version 1.2-3, <package>foo-data</package> would
5105 <example compact="compact">
5106 Replaces: foo (<< 1.2-3)
5107 Breaks: foo (<< 1.2-3)
5109 in its control file. The new version of the
5110 package <package>foo</package> would normally have the field
5111 <example compact="compact">
5112 Depends: foo-data (>= 1.2-3)
5114 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
5115 the files moved into <package>foo-data</package> are not
5116 required for normal operation).
5120 If a package is completely replaced in this way, so that
5121 <prgn>dpkg</prgn> does not know of any files it still
5122 contains, it is considered to have "disappeared". It will
5123 be marked as not wanted on the system (selected for
5124 removal) and not installed. Any <tt>conffile</tt>s
5125 details noted for the package will be ignored, as they
5126 will have been taken over by the overwriting package. The
5127 package's <prgn>postrm</prgn> script will be run with a
5128 special argument to allow the package to do any final
5129 cleanup required. See <ref id="mscriptsinstact">.
5131 Replaces is a one way relationship. You have to install
5132 the replacing package after the replaced package.
5137 For this usage of <tt>Replaces</tt>, virtual packages (see
5138 <ref id="virtual">) are not considered when looking at a
5139 <tt>Replaces</tt> field. The packages declared as being
5140 replaced must be mentioned by their real names.
5144 This usage of <tt>Replaces</tt> only takes effect when both
5145 packages are at least partially on the system at once. It is
5146 not relevant if the packages conflict unless the conflict has
5151 <sect1><heading>Replacing whole packages, forcing their
5155 Second, <tt>Replaces</tt> allows the packaging system to
5156 resolve which package should be removed when there is a
5157 conflict (see <ref id="conflicts">). This usage only takes
5158 effect when the two packages <em>do</em> conflict, so that the
5159 two usages of this field do not interfere with each other.
5163 In this situation, the package declared as being replaced
5164 can be a virtual package, so for example, all mail
5165 transport agents (MTAs) would have the following fields in
5166 their control files:
5167 <example compact="compact">
5168 Provides: mail-transport-agent
5169 Conflicts: mail-transport-agent
5170 Replaces: mail-transport-agent
5172 ensuring that only one MTA can be unpacked at any one
5173 time. See <ref id="virtual"> for more information about this
5178 <sect id="sourcebinarydeps">
5179 <heading>Relationships between source and binary packages -
5180 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5181 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5185 Source packages that require certain binary packages to be
5186 installed or absent at the time of building the package
5187 can declare relationships to those binary packages.
5191 This is done using the <tt>Build-Depends</tt>,
5192 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5193 <tt>Build-Conflicts-Indep</tt> control fields.
5197 Build-dependencies on "build-essential" binary packages can be
5198 omitted. Please see <ref id="pkg-relations"> for more information.
5202 The dependencies and conflicts they define must be satisfied
5203 (as defined earlier for binary packages) in order to invoke
5204 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5206 There is no Build-Depends-Arch; this role is essentially
5207 met with Build-Depends. Anyone building the
5208 <tt>build-indep</tt> and <tt>binary-indep</tt> targets is
5209 assumed to be building the whole package, and therefore
5210 installation of all build dependencies is required.
5213 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5214 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5215 not yet know how to check for its existence, and
5216 <tt>binary-arch</tt>. The purpose of the original split
5217 between <tt>Build-Depends</tt> and
5218 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5219 wouldn't need to install extra packages needed only for the
5220 binary-indep targets. But without a build-arch/build-indep
5221 split, this didn't work, since most of the work is done in
5222 the build target, not in the binary target.
5226 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5227 <tt>binary-arch</tt></tag>
5229 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5230 fields must be satisfied when these targets are invoked.
5232 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5233 and <tt>binary-indep</tt></tag>
5235 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5236 <tt>Build-Depends-Indep</tt>, and
5237 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5238 these targets are invoked.
5246 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5249 Packages containing shared libraries must be constructed with
5250 a little care to make sure that the shared library is always
5251 available. This is especially important for packages whose
5252 shared libraries are vitally important, such as the C library
5253 (currently <tt>libc6</tt>).
5257 This section deals only with public shared libraries: shared
5258 libraries that are placed in directories searched by the dynamic
5259 linker by default or which are intended to be linked against
5260 normally and possibly used by other, independent packages. Shared
5261 libraries that are internal to a particular package or that are
5262 only loaded as dynamic modules are not covered by this section and
5263 are not subject to its requirements.
5267 A shared library is identified by the <tt>SONAME</tt> attribute
5268 stored in its dynamic section. When a binary is linked against a
5269 shared library, the <tt>SONAME</tt> of the shared library is
5270 recorded in the binary's <tt>NEEDED</tt> section so that the
5271 dynamic linker knows that library must be loaded at runtime. The
5272 shared library file's full name (which usually contains additional
5273 version information not needed in the <tt>SONAME</tt>) is
5274 therefore normally not referenced directly. Instead, the shared
5275 library is loaded by its <tt>SONAME</tt>, which exists on the file
5276 system as a symlink pointing to the full name of the shared
5277 library. This symlink must be provided by the
5278 package. <ref id="sharedlibs-runtime"> describes how to do this.
5280 This is a convention of shared library versioning, but not a
5281 requirement. Some libraries use the <tt>SONAME</tt> as the full
5282 library file name instead and therefore do not need a symlink.
5283 Most, however, encode additional information about
5284 backwards-compatible revisions as a minor version number in the
5285 file name. The <tt>SONAME</tt> itself only changes when
5286 binaries linked with the earlier version of the shared library
5287 may no longer work, but the filename may change with each
5288 release of the library. See <ref id="sharedlibs-runtime"> for
5294 When linking a binary or another shared library against a shared
5295 library, the <tt>SONAME</tt> for that shared library is not yet
5296 known. Instead, the shared library is found by looking for a file
5297 matching the library name with <tt>.so</tt> appended. This file
5298 exists on the file system as a symlink pointing to the shared
5303 Shared libraries are normally split into several binary packages.
5304 The <tt>SONAME</tt> symlink is installed by the runtime shared
5305 library package, and the bare <tt>.so</tt> symlink is installed in
5306 the development package since it's only used when linking binaries
5307 or shared libraries. However, there are some exceptions for
5308 unusual shared libraries or for shared libraries that are also
5309 loaded as dynamic modules by other programs.
5313 This section is primarily concerned with how the separation of
5314 shared libraries into multiple packages should be done and how
5315 dependencies on and between shared library binary packages are
5316 managed in Debian. <ref id="libraries"> should be read in
5317 conjunction with this section and contains additional rules for
5318 the files contained in the shared library packages.
5321 <sect id="sharedlibs-runtime">
5322 <heading>Run-time shared libraries</heading>
5325 The run-time shared library must be placed in a package
5326 whose name changes whenever the <tt>SONAME</tt> of the shared
5327 library changes. This allows several versions of the shared
5328 library to be installed at the same time, allowing installation
5329 of the new version of the shared library without immediately
5330 breaking binaries that depend on the old version. Normally, the
5331 run-time shared library and its <tt>SONAME</tt> symlink should
5332 be placed in a package named
5333 <package><var>libraryname</var><var>soversion</var></package>,
5334 where <var>soversion</var> is the version number in
5335 the <tt>SONAME</tt> of the shared library.
5336 See <ref id="shlibs"> for detailed information on how to
5337 determine this version. Alternatively, if it would be confusing
5338 to directly append <var>soversion</var>
5339 to <var>libraryname</var> (if, for example, <var>libraryname</var>
5340 itself ends in a number), you should use
5341 <package><var>libraryname</var>-<var>soversion</var></package>
5346 If you have several shared libraries built from the same source
5347 tree, you may lump them all together into a single shared
5348 library package provided that all of their <tt>SONAME</tt>s will
5349 always change together. Be aware that this is not normally the
5350 case, and if the <tt>SONAME</tt>s do not change together,
5351 upgrading such a merged shared library package will be
5352 unnecessarily difficult because of file conflicts with the old
5353 version of the package. When in doubt, always split shared
5354 library packages so that each binary package installs a single
5359 Every time the shared library ABI changes in a way that may
5360 break binaries linked against older versions of the shared
5361 library, the <tt>SONAME</tt> of the library and the
5362 corresponding name for the binary package containing the runtime
5363 shared library should change. Normally, this means
5364 the <tt>SONAME</tt> should change any time an interface is
5365 removed from the shared library or the signature of an interface
5366 (the number of parameters or the types of parameters that it
5367 takes, for example) is changed. This practice is vital to
5368 allowing clean upgrades from older versions of the package and
5369 clean transitions between the old ABI and new ABI without having
5370 to upgrade every affected package simultaneously.
5374 The <tt>SONAME</tt> and binary package name need not, and indeed
5375 normally should not, change if new interfaces are added but none
5376 are removed or changed, since this will not break binaries
5377 linked against the old shared library. Correct versioning of
5378 dependencies on the newer shared library by binaries that use
5379 the new interfaces is handled via
5380 the <qref id="sharedlibs-shlibdeps"><tt>shlibs</tt>
5381 system</qref> or via symbols files (see
5382 <manref name="deb-symbols" section="5">).
5386 The package should install the shared libraries under
5387 their normal names. For example, the <package>libgdbm3</package>
5388 package should install <file>libgdbm.so.3.0.0</file> as
5389 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5390 renamed or re-linked by any <prgn>prerm</prgn> or
5391 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5392 of renaming things safely without affecting running programs,
5393 and attempts to interfere with this are likely to lead to
5398 Shared libraries should not be installed executable, since
5399 the dynamic linker does not require this and trying to
5400 execute a shared library usually results in a core dump.
5404 The run-time library package should include the symbolic link for
5405 the <tt>SONAME</tt> that <prgn>ldconfig</prgn> would create for
5406 the shared libraries. For example,
5407 the <package>libgdbm3</package> package should include a symbolic
5408 link from <file>/usr/lib/libgdbm.so.3</file> to
5409 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5410 linker (for example <prgn>ld.so</prgn> or
5411 <prgn>ld-linux.so.*</prgn>) can find the library between the
5412 time that <prgn>dpkg</prgn> installs it and the time that
5413 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5415 The package management system requires the library to be
5416 placed before the symbolic link pointing to it in the
5417 <file>.deb</file> file. This is so that when
5418 <prgn>dpkg</prgn> comes to install the symlink
5419 (overwriting the previous symlink pointing at an older
5420 version of the library), the new shared library is already
5421 in place. In the past, this was achieved by creating the
5422 library in the temporary packaging directory before
5423 creating the symlink. Unfortunately, this was not always
5424 effective, since the building of the tar file in the
5425 <file>.deb</file> depended on the behavior of the underlying
5426 file system. Some file systems (such as reiserfs) reorder
5427 the files so that the order of creation is forgotten.
5428 Since version 1.7.0, <prgn>dpkg</prgn>
5429 reorders the files itself as necessary when building a
5430 package. Thus it is no longer important to concern
5431 oneself with the order of file creation.
5435 <sect1 id="ldconfig">
5436 <heading><tt>ldconfig</tt></heading>
5439 Any package installing shared libraries in one of the default
5440 library directories of the dynamic linker (which are currently
5441 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5442 listed in <file>/etc/ld.so.conf</file><footnote>
5444 <list compact="compact">
5445 <item>/usr/local/lib</item>
5446 <item>/usr/lib/libc5-compat</item>
5447 <item>/lib/libc5-compat</item>
5450 must use <prgn>ldconfig</prgn> to update the shared library
5455 The package maintainer scripts must only call
5456 <prgn>ldconfig</prgn> under these circumstances:
5457 <list compact="compact">
5458 <item>When the <prgn>postinst</prgn> script is run with a
5459 first argument of <tt>configure</tt>, the script must call
5460 <prgn>ldconfig</prgn>, and may optionally invoke
5461 <prgn>ldconfig</prgn> at other times.
5463 <item>When the <prgn>postrm</prgn> script is run with a
5464 first argument of <tt>remove</tt>, the script should call
5465 <prgn>ldconfig</prgn>.
5470 During install or upgrade, the preinst is called before
5471 the new files are unpacked, so calling "ldconfig" is
5472 pointless. The preinst of an existing package can also be
5473 called if an upgrade fails. However, this happens during
5474 the critical time when a shared libs may exist on-disk
5475 under a temporary name. Thus, it is dangerous and
5476 forbidden by current policy to call "ldconfig" at this
5481 When a package is installed or upgraded, "postinst
5482 configure" runs after the new files are safely on-disk.
5483 Since it is perfectly safe to invoke ldconfig
5484 unconditionally in a postinst, it is OK for a package to
5485 simply put ldconfig in its postinst without checking the
5486 argument. The postinst can also be called to recover from
5487 a failed upgrade. This happens before any new files are
5488 unpacked, so there is no reason to call "ldconfig" at this
5493 For a package that is being removed, prerm is
5494 called with all the files intact, so calling ldconfig is
5495 useless. The other calls to "prerm" happen in the case of
5496 upgrade at a time when all the files of the old package
5497 are on-disk, so again calling "ldconfig" is pointless.
5501 postrm, on the other hand, is called with the "remove"
5502 argument just after the files are removed, so this is
5503 the proper time to call "ldconfig" to notify the system
5504 of the fact that the shared libraries from the package
5505 are removed. The postrm can be called at several other
5506 times. At the time of "postrm purge", "postrm
5507 abort-install", or "postrm abort-upgrade", calling
5508 "ldconfig" is useless because the shared lib files are
5509 not on-disk. However, when "postrm" is invoked with
5510 arguments "upgrade", "failed-upgrade", or "disappear", a
5511 shared lib may exist on-disk under a temporary filename.
5519 <sect id="sharedlibs-support-files">
5520 <heading>Shared library support files</heading>
5523 If your package contains files whose names do not change with
5524 each change in the library shared object version, you must not
5525 put them in the shared library package. Otherwise, several
5526 versions of the shared library cannot be installed at the same
5527 time without filename clashes, making upgrades and transitions
5528 unnecessarily difficult.
5532 It is recommended that supporting files and run-time support
5533 programs that do not need to be invoked manually by users, but
5534 are nevertheless required for the package to function, be placed
5535 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5536 preferably under <file>/usr/lib/</file><var>package-name</var>.
5537 If the program or file is architecture independent, the
5538 recommendation is for it to be placed in a subdirectory of
5539 <file>/usr/share</file> instead, preferably under
5540 <file>/usr/share/</file><var>package-name</var>. Following the
5541 <var>package-name</var> naming convention ensures that the file
5542 names change when the shared object version changes.
5546 Run-time support programs that use the shared library but are
5547 not required for the library to function or files used by the
5548 shared library that can be used by any version of the shared
5549 library package should instead be put in a separate package.
5550 This package might typically be named
5551 <package><var>libraryname</var>-tools</package>; note the
5552 absence of the <var>soversion</var> in the package name.
5556 Files and support programs only useful when compiling software
5557 against the library should be included in the development
5558 package for the library.<footnote>
5559 For example, a <file><var>package-name</var>-config</file>
5560 script or <package>pkg-config</package> configuration files.
5565 <sect id="sharedlibs-static">
5566 <heading>Static libraries</heading>
5569 The static library (<file><var>libraryname.a</var></file>)
5570 is usually provided in addition to the shared version.
5571 It is placed into the development package (see below).
5575 In some cases, it is acceptable for a library to be
5576 available in static form only; these cases include:
5578 <item>libraries for languages whose shared library support
5579 is immature or unstable</item>
5580 <item>libraries whose interfaces are in flux or under
5581 development (commonly the case when the library's
5582 major version number is zero, or where the ABI breaks
5583 across patchlevels)</item>
5584 <item>libraries which are explicitly intended to be
5585 available only in static form by their upstream
5590 <sect id="sharedlibs-dev">
5591 <heading>Development files</heading>
5594 If there are development files associated with a shared library,
5595 the source package needs to generate a binary development package
5596 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5597 or if you prefer only to support one development version at a
5598 time, <package><var>libraryname</var>-dev</package>. Installing
5599 the development package must result in installation of all the
5600 development files necessary for compiling programs against that
5601 shared library.<footnote>
5602 This wording allows the development files to be split into
5603 several packages, such as a separate architecture-independent
5604 <package><var>libraryname</var>-headers</package>, provided that
5605 the development package depends on all the required additional
5611 In case several development versions of a library exist, you may
5612 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5613 <ref id="conflicts">) to ensure that the user only installs one
5614 development version at a time (as different development versions are
5615 likely to have the same header files in them, which would cause a
5616 filename clash if both were unpacked).
5620 The development package should contain a symlink for the associated
5621 shared library without a version number. For example, the
5622 <package>libgdbm-dev</package> package should include a symlink
5623 from <file>/usr/lib/libgdbm.so</file> to
5624 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5625 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5626 <file>libgdbm.so</file> when compiling dynamically.
5630 If the package provides Ada Library Information
5631 (<file>*.ali</file>) files for use with GNAT, these files must be
5632 installed read-only (mode 0444) so that GNAT will not attempt to
5633 recompile them. This overrides the normal file mode requirements
5634 given in <ref id="permissions-owners">.
5638 <sect id="sharedlibs-intradeps">
5639 <heading>Dependencies between the packages of the same library</heading>
5642 Typically the development version should have an exact
5643 version dependency on the runtime library, to make sure that
5644 compilation and linking happens correctly. The
5645 <tt>${binary:Version}</tt> substitution variable can be
5646 useful for this purpose.
5648 Previously, <tt>${Source-Version}</tt> was used, but its name
5649 was confusing and it has been deprecated since dpkg 1.13.19.
5654 <sect id="sharedlibs-shlibdeps">
5655 <heading>Dependencies between the library and other packages -
5656 the <tt>shlibs</tt> system</heading>
5659 If a package contains a binary or library which links to a
5660 shared library, we must ensure that when the package is
5661 installed on the system, all of the libraries needed are
5662 also installed. This requirement led to the creation of the
5663 <tt>shlibs</tt> system, which is very simple in its design:
5664 any package which <em>provides</em> a shared library also
5665 provides information on the package dependencies required to
5666 ensure the presence of this library, and any package which
5667 <em>uses</em> a shared library uses this information to
5668 determine the dependencies it requires. The files which
5669 contain the mapping from shared libraries to the necessary
5670 dependency information are called <file>shlibs</file> files.
5674 When a package is built which contains any shared libraries, it
5675 must provide a <file>shlibs</file> file for other packages to
5676 use. When a package is built which contains any shared
5677 libraries or compiled binaries, it must run
5678 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5679 on these to determine the libraries used and hence the
5680 dependencies needed by this package.<footnote>
5682 <prgn>dpkg-shlibdeps</prgn> will use a program
5683 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
5684 the libraries directly needed by the binaries or shared
5685 libraries in the package.
5689 We say that a binary <tt>foo</tt> <em>directly</em> uses
5690 a library <tt>libbar</tt> if it is explicitly linked
5691 with that library (that is, the library is listed in the ELF
5692 <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
5693 to the link line when the binary is created). Other
5694 libraries that are needed by <tt>libbar</tt> are linked
5695 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5696 linker will load them automatically when it loads
5697 <tt>libbar</tt>. A package should depend on the libraries
5698 it directly uses, but not the libraries it indirectly uses.
5699 The dependencies for those libraries will automatically pull
5700 in the other libraries.
5704 A good example of where this helps is the following. We
5705 could update <tt>libimlib</tt> with a new version that
5706 supports a new graphics format called dgf (but retaining the
5707 same major version number) and depends on <tt>libdgf</tt>.
5708 If we used <prgn>ldd</prgn> to add dependencies for every
5709 library directly or indirectly linked with a binary, every
5710 package that uses <tt>libimlib</tt> would need to be
5711 recompiled so it would also depend on <tt>libdgf</tt> or it
5712 wouldn't run due to missing symbols. Since dependencies are
5713 only added based on ELF <tt>NEEDED</tt> attribute, packages
5714 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
5715 having the dependency on <tt>libdgf</tt> and so they would
5716 not need rebuilding.
5722 In the following sections, we will first describe where the
5723 various <tt>shlibs</tt> files are to be found, then how to
5724 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5725 file format and how to create them if your package contains a
5730 <heading>The <tt>shlibs</tt> files present on the system</heading>
5733 There are several places where <tt>shlibs</tt> files are
5734 found. The following list gives them in the order in which
5736 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5737 (The first one which gives the required information is used.)
5743 <p><file>debian/shlibs.local</file></p>
5746 This lists overrides for this package. This file should
5747 normally not be used, but may be needed temporarily in
5748 unusual situations to work around bugs in other packages,
5749 or in unusual cases where the normally declared dependency
5750 information in the installed <file>shlibs</file> file for
5751 a library cannot be used. This file overrides information
5752 obtained from any other source.
5757 <p><file>/etc/dpkg/shlibs.override</file></p>
5760 This lists global overrides. This list is normally
5761 empty. It is maintained by the local system
5767 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5770 When packages are being built,
5771 any <file>debian/shlibs</file> files are copied into the
5772 control information file area of the temporary build
5773 directory and given the name <file>shlibs</file>. These
5774 files give details of any shared libraries included in the
5775 same package.<footnote>
5776 An example may help here. Let us say that the source
5777 package <tt>foo</tt> generates two binary
5778 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
5779 When building the binary packages, the two packages are
5780 created in the directories <file>debian/libfoo2</file>
5781 and <file>debian/foo-runtime</file> respectively.
5782 (<file>debian/tmp</file> could be used instead of one of
5783 these.) Since <tt>libfoo2</tt> provides the
5784 <tt>libfoo</tt> shared library, it will require a
5785 <tt>shlibs</tt> file, which will be installed in
5786 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually to
5787 become <file>/var/lib/dpkg/info/libfoo2.shlibs</file>.
5788 When <prgn>dpkg-shlibdeps</prgn> is run on the
5789 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
5791 the <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5792 determine whether <tt>foo-prog</tt>'s library
5793 dependencies are satisfied by any of the libraries
5794 provided by <tt>libfoo2</tt>. For this reason,
5795 <prgn>dpkg-shlibdeps</prgn> must only be run once all of
5796 the individual binary packages' <tt>shlibs</tt> files
5797 have been installed into the build directory.
5803 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5806 These are the <file>shlibs</file> files corresponding to
5807 all of the packages installed on the system, and are
5808 maintained by the relevant package maintainers.
5813 <p><file>/etc/dpkg/shlibs.default</file></p>
5816 This file lists any shared libraries whose packages
5817 have failed to provide correct <file>shlibs</file> files.
5818 It was used when the <file>shlibs</file> setup was first
5819 introduced, but it is now normally empty. It is
5820 maintained by the <tt>dpkg</tt> maintainer.
5828 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5829 <file>shlibs</file> files</heading>
5833 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5834 into your <file>debian/rules</file> file. If your package
5835 contains only compiled binaries and libraries (but no scripts),
5836 you can use a command such as:
5837 <example compact="compact">
5838 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5839 debian/tmp/usr/lib/*
5841 Otherwise, you will need to explicitly list the compiled
5842 binaries and libraries.<footnote>
5843 If you are using <tt>debhelper</tt>, the
5844 <prgn>dh_shlibdeps</prgn> program will do this work for you.
5845 It will also correctly handle multi-binary packages.
5850 This command puts the dependency information into the
5851 <file>debian/substvars</file> file, which is then used by
5852 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5853 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5854 field in the control file for this to work.
5858 If you have multiple binary packages, you will need to call
5859 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5860 compiled libraries or binaries. In such a case, you will
5861 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5862 utilities to specify a different <file>substvars</file> file.
5866 If you are creating a udeb for use in the Debian Installer,
5867 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
5868 should use the dependency line of type <tt>udeb</tt> by
5869 adding the <tt>-tudeb</tt> option<footnote>
5870 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5871 will automatically add this option if it knows it is
5873 </footnote>. If there is no dependency line of
5874 type <tt>udeb</tt> in the <file>shlibs</file>
5875 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the regular
5880 For more details on <prgn>dpkg-shlibdeps</prgn>, please see
5881 <ref id="pkg-dpkg-shlibdeps"> and
5882 <manref name="dpkg-shlibdeps" section="1">.
5887 <heading>The <file>shlibs</file> File Format</heading>
5890 Each <file>shlibs</file> file has the same format. Lines
5891 beginning with <tt>#</tt> are considered to be comments and
5892 are ignored. Each line is of the form:
5893 <example compact="compact">
5894 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5899 We will explain this by reference to the example of the
5900 <tt>zlib1g</tt> package, which (at the time of writing)
5901 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5905 <var>type</var> is an optional element that indicates the type
5906 of package for which the line is valid. The only type currently
5907 in use is <tt>udeb</tt>. The colon and space after the type are
5912 <var>library-name</var> is the name of the shared library,
5913 in this case <tt>libz</tt>. (This must match the name part
5914 of the soname, see below.)
5918 <var>soname-version</var> is the version part of the soname of
5919 the library. The soname is the thing that must exactly match
5920 for the library to be recognized by the dynamic linker, and is
5922 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5923 example, <tt>libz.so.1</tt>.<footnote>
5924 This can be determined using the command
5925 <example compact="compact">
5926 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5929 The version part is the part which comes after
5930 <tt>.so.</tt>, so in our case, it is <tt>1</tt>. The soname may
5931 instead be of the form
5932 <tt><var>name</var>-<var>major-version</var>.so</tt>, such
5933 as <tt>libdb-4.8.so</tt>, in which case the name would
5934 be <tt>libdb</tt> and the version would be <tt>4.8</tt>.
5938 <var>dependencies</var> has the same syntax as a dependency
5939 field in a binary package control file. It should give
5940 details of which packages are required to satisfy a binary
5941 built against the version of the library contained in the
5942 package. See <ref id="depsyntax"> for details.
5946 In our example, if the first version of the <tt>zlib1g</tt>
5947 package which contained a minor number of at least
5948 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5949 <tt>shlibs</tt> entry for this library could say:
5950 <example compact="compact">
5951 libz 1 zlib1g (>= 1:1.1.3)
5953 The version-specific dependency is to avoid warnings from
5954 the dynamic linker about using older shared libraries with
5959 As zlib1g also provides a udeb containing the shared library,
5960 there would also be a second line:
5961 <example compact="compact">
5962 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5968 <heading>Providing a <file>shlibs</file> file</heading>
5971 If your package provides a shared library, you need to create
5972 a <file>shlibs</file> file following the format described above.
5973 It is usual to call this file <file>debian/shlibs</file> (but if
5974 you have multiple binary packages, you might want to call it
5975 <file>debian/shlibs.<var>package</var></file> instead). Then
5976 let <file>debian/rules</file> install it in the control
5977 information file area:
5978 <example compact="compact">
5979 install -m644 debian/shlibs debian/tmp/DEBIAN
5981 or, in the case of a multi-binary package:
5982 <example compact="compact">
5983 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5985 An alternative way of doing this is to create the
5986 <file>shlibs</file> file in the control information file area
5987 directly from <file>debian/rules</file> without using
5988 a <file>debian/shlibs</file> file at all,<footnote>
5989 This is what <prgn>dh_makeshlibs</prgn> in
5990 the <package>debhelper</package> suite does. If your package
5991 also has a udeb that provides a shared
5992 library, <prgn>dh_makeshlibs</prgn> can automatically generate
5993 the <tt>udeb:</tt> lines if you specify the name of the udeb
5994 with the <tt>--add-udeb</tt> option.
5996 since the <file>debian/shlibs</file> file itself is ignored by
5997 <prgn>dpkg-shlibdeps</prgn>.
6001 As <prgn>dpkg-shlibdeps</prgn> reads the
6002 <file>DEBIAN/shlibs</file> files in all of the binary packages
6003 being built from this source package, all of the
6004 <file>DEBIAN/shlibs</file> files should be installed before
6005 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
6013 <chapt id="opersys"><heading>The Operating System</heading>
6016 <heading>File system hierarchy</heading>
6020 <heading>File System Structure</heading>
6023 The location of all installed files and directories must
6024 comply with the Filesystem Hierarchy Standard (FHS),
6025 version 2.3, with the exceptions noted below, and except
6026 where doing so would violate other terms of Debian
6027 Policy. The following exceptions to the FHS apply:
6032 The optional rules related to user specific
6033 configuration files for applications are stored in
6034 the user's home directory are relaxed. It is
6035 recommended that such files start with the
6036 '<tt>.</tt>' character (a "dot file"), and if an
6037 application needs to create more than one dot file
6038 then the preferred placement is in a subdirectory
6039 with a name starting with a '.' character, (a "dot
6040 directory"). In this case it is recommended the
6041 configuration files not start with the '.'
6047 The requirement for amd64 to use <file>/lib64</file>
6048 for 64 bit binaries is removed.
6053 The requirement for object files, internal binaries, and
6054 libraries, including <file>libc.so.*</file>, to be located
6055 directly under <file>/lib{,32}</file> and
6056 <file>/usr/lib{,32}</file> is amended, permitting files
6057 to instead be installed to
6058 <file>/lib/<var>triplet</var></file> and
6059 <file>/usr/lib/<var>triplet</var></file>, where
6060 <tt><var>triplet</var></tt> is the value returned by
6061 <tt>dpkg-architecture -qDEB_HOST_GNU_TYPE</tt> for the
6062 architecture of the package. Packages may <em>not</em>
6063 install files to any <var>triplet</var> path other
6064 than the one matching the architecture of that package;
6065 for instance, an <tt>Architecture: amd64</tt> package
6066 containing 32-bit x86 libraries may not install these
6067 libraries to <file>/usr/lib/i486-linux-gnu</file>.
6069 This is necessary in order to reserve the directories for
6070 use in cross-installation of library packages from other
6071 architectures, as part of the planned deployment of
6076 Applications may also use a single subdirectory under
6077 <file>/usr/lib/<var>triplet</var></file>.
6080 The execution time linker/loader, ld*, must still be made
6081 available in the existing location under /lib or /lib64
6082 since this is part of the ELF ABI for the architecture.
6087 The requirement that
6088 <file>/usr/local/share/man</file> be "synonymous"
6089 with <file>/usr/local/man</file> is relaxed to a
6094 The requirement that windowmanagers with a single
6095 configuration file call it <file>system.*wmrc</file>
6096 is removed, as is the restriction that the window
6097 manager subdirectory be named identically to the
6098 window manager name itself.
6103 The requirement that boot manager configuration
6104 files live in <file>/etc</file>, or at least are
6105 symlinked there, is relaxed to a recommendation.
6110 The following directories in the root filesystem are
6111 additionally allowed: <file>/sys</file> and
6112 <file>/selinux</file>. <footnote>These directories
6113 are used as mount points to mount virtual filesystems
6114 to get access to kernel information.</footnote>
6121 The version of this document referred here can be
6122 found in the <tt>debian-policy</tt> package or on <url
6123 id="http://www.debian.org/doc/packaging-manuals/fhs/"
6124 name="FHS (Debian copy)"> alongside this manual (or, if
6125 you have the <package>debian-policy</package> installed,
6127 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
6128 (local copy)">). The
6129 latest version, which may be a more recent version, may
6131 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
6132 Specific questions about following the standard may be
6133 asked on the <tt>debian-devel</tt> mailing list, or
6134 referred to the FHS mailing list (see the
6135 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
6141 <heading>Site-specific programs</heading>
6144 As mandated by the FHS, packages must not place any
6145 files in <file>/usr/local</file>, either by putting them in
6146 the file system archive to be unpacked by <prgn>dpkg</prgn>
6147 or by manipulating them in their maintainer scripts.
6151 However, the package may create empty directories below
6152 <file>/usr/local</file> so that the system administrator knows
6153 where to place site-specific files. These are not
6154 directories <em>in</em> <file>/usr/local</file>, but are
6155 children of directories in <file>/usr/local</file>. These
6156 directories (<file>/usr/local/*/dir/</file>)
6157 should be removed on package removal if they are
6162 Note that this applies only to
6163 directories <em>below</em> <file>/usr/local</file>,
6164 not <em>in</em> <file>/usr/local</file>. Packages must
6165 not create sub-directories in the
6166 directory <file>/usr/local</file> itself, except those
6167 listed in FHS, section 4.5. However, you may create
6168 directories below them as you wish. You must not remove
6169 any of the directories listed in 4.5, even if you created
6174 Since <file>/usr/local</file> can be mounted read-only from a
6175 remote server, these directories must be created and
6176 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
6177 maintainer scripts and not be included in the
6178 <file>.deb</file> archive. These scripts must not fail if
6179 either of these operations fail.
6183 For example, the <tt>emacsen-common</tt> package could
6184 contain something like
6185 <example compact="compact">
6186 if [ ! -e /usr/local/share/emacs ]
6188 if mkdir /usr/local/share/emacs 2>/dev/null
6190 chown root:staff /usr/local/share/emacs
6191 chmod 2775 /usr/local/share/emacs
6195 in its <prgn>postinst</prgn> script, and
6196 <example compact="compact">
6197 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
6198 rmdir /usr/local/share/emacs 2>/dev/null || true
6200 in the <prgn>prerm</prgn> script. (Note that this form is
6201 used to ensure that if the script is interrupted, the
6202 directory <file>/usr/local/share/emacs</file> will still be
6207 If you do create a directory in <file>/usr/local</file> for
6208 local additions to a package, you should ensure that
6209 settings in <file>/usr/local</file> take precedence over the
6210 equivalents in <file>/usr</file>.
6214 However, because <file>/usr/local</file> and its contents are
6215 for exclusive use of the local administrator, a package
6216 must not rely on the presence or absence of files or
6217 directories in <file>/usr/local</file> for normal operation.
6221 The <file>/usr/local</file> directory itself and all the
6222 subdirectories created by the package should (by default) have
6223 permissions 2775 (group-writable and set-group-id) and be
6224 owned by <tt>root:staff</tt>.
6229 <heading>The system-wide mail directory</heading>
6231 The system-wide mail directory
6232 is <file>/var/mail</file>. This directory is part of the
6233 base system and should not be owned by any particular mail
6234 agents. The use of the old
6235 location <file>/var/spool/mail</file> is deprecated, even
6236 though the spool may still be physically located there.
6242 <heading>Users and groups</heading>
6245 <heading>Introduction</heading>
6247 The Debian system can be configured to use either plain or
6252 Some user ids (UIDs) and group ids (GIDs) are reserved
6253 globally for use by certain packages. Because some
6254 packages need to include files which are owned by these
6255 users or groups, or need the ids compiled into binaries,
6256 these ids must be used on any Debian system only for the
6257 purpose for which they are allocated. This is a serious
6258 restriction, and we should avoid getting in the way of
6259 local administration policies. In particular, many sites
6260 allocate users and/or local system groups starting at 100.
6264 Apart from this we should have dynamically allocated ids,
6265 which should by default be arranged in some sensible
6266 order, but the behavior should be configurable.
6270 Packages other than <tt>base-passwd</tt> must not modify
6271 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
6272 <file>/etc/group</file> or <file>/etc/gshadow</file>.
6277 <heading>UID and GID classes</heading>
6279 The UID and GID numbers are divided into classes as
6285 Globally allocated by the Debian project, the same
6286 on every Debian system. These ids will appear in
6287 the <file>passwd</file> and <file>group</file> files of all
6288 Debian systems, new ids in this range being added
6289 automatically as the <tt>base-passwd</tt> package is
6294 Packages which need a single statically allocated
6295 uid or gid should use one of these; their
6296 maintainers should ask the <tt>base-passwd</tt>
6304 Dynamically allocated system users and groups.
6305 Packages which need a user or group, but can have
6306 this user or group allocated dynamically and
6307 differently on each system, should use <tt>adduser
6308 --system</tt> to create the group and/or user.
6309 <prgn>adduser</prgn> will check for the existence of
6310 the user or group, and if necessary choose an unused
6311 id based on the ranges specified in
6312 <file>adduser.conf</file>.
6316 <tag>1000-59999:</tag>
6319 Dynamically allocated user accounts. By default
6320 <prgn>adduser</prgn> will choose UIDs and GIDs for
6321 user accounts in this range, though
6322 <file>adduser.conf</file> may be used to modify this
6327 <tag>60000-64999:</tag>
6330 Globally allocated by the Debian project, but only
6331 created on demand. The ids are allocated centrally
6332 and statically, but the actual accounts are only
6333 created on users' systems on demand.
6337 These ids are for packages which are obscure or
6338 which require many statically-allocated ids. These
6339 packages should check for and create the accounts in
6340 <file>/etc/passwd</file> or <file>/etc/group</file> (using
6341 <prgn>adduser</prgn> if it has this facility) if
6342 necessary. Packages which are likely to require
6343 further allocations should have a "hole" left after
6344 them in the allocation, to give them room to
6349 <tag>65000-65533:</tag>
6357 User <tt>nobody</tt>. The corresponding gid refers
6358 to the group <tt>nogroup</tt>.
6365 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
6366 not</em> be used, because it is the error return
6375 <sect id="sysvinit">
6376 <heading>System run levels and <file>init.d</file> scripts</heading>
6378 <sect1 id="/etc/init.d">
6379 <heading>Introduction</heading>
6382 The <file>/etc/init.d</file> directory contains the scripts
6383 executed by <prgn>init</prgn> at boot time and when the
6384 init state (or "runlevel") is changed (see <manref
6385 name="init" section="8">).
6389 There are at least two different, yet functionally
6390 equivalent, ways of handling these scripts. For the sake
6391 of simplicity, this document describes only the symbolic
6392 link method. However, it must not be assumed by maintainer
6393 scripts that this method is being used, and any automated
6394 manipulation of the various runlevel behaviors by
6395 maintainer scripts must be performed using
6396 <prgn>update-rc.d</prgn> as described below and not by
6397 manually installing or removing symlinks. For information
6398 on the implementation details of the other method,
6399 implemented in the <tt>file-rc</tt> package, please refer
6400 to the documentation of that package.
6404 These scripts are referenced by symbolic links in the
6405 <file>/etc/rc<var>n</var>.d</file> directories. When changing
6406 runlevels, <prgn>init</prgn> looks in the directory
6407 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
6408 execute, where <tt><var>n</var></tt> is the runlevel that
6409 is being changed to, or <tt>S</tt> for the boot-up
6414 The names of the links all have the form
6415 <file>S<var>mm</var><var>script</var></file> or
6416 <file>K<var>mm</var><var>script</var></file> where
6417 <var>mm</var> is a two-digit number and <var>script</var>
6418 is the name of the script (this should be the same as the
6419 name of the actual script in <file>/etc/init.d</file>).
6423 When <prgn>init</prgn> changes runlevel first the targets
6424 of the links whose names start with a <tt>K</tt> are
6425 executed, each with the single argument <tt>stop</tt>,
6426 followed by the scripts prefixed with an <tt>S</tt>, each
6427 with the single argument <tt>start</tt>. (The links are
6428 those in the <file>/etc/rc<var>n</var>.d</file> directory
6429 corresponding to the new runlevel.) The <tt>K</tt> links
6430 are responsible for killing services and the <tt>S</tt>
6431 link for starting services upon entering the runlevel.
6435 For example, if we are changing from runlevel 2 to
6436 runlevel 3, init will first execute all of the <tt>K</tt>
6437 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
6438 all of the <tt>S</tt> prefixed scripts in that directory.
6439 The links starting with <tt>K</tt> will cause the
6440 referred-to file to be executed with an argument of
6441 <tt>stop</tt>, and the <tt>S</tt> links with an argument
6446 The two-digit number <var>mm</var> is used to determine
6447 the order in which to run the scripts: low-numbered links
6448 have their scripts run first. For example, the
6449 <tt>K20</tt> scripts will be executed before the
6450 <tt>K30</tt> scripts. This is used when a certain service
6451 must be started before another. For example, the name
6452 server <prgn>bind</prgn> might need to be started before
6453 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
6454 can set up its access lists. In this case, the script
6455 that starts <prgn>bind</prgn> would have a lower number
6456 than the script that starts <prgn>inn</prgn> so that it
6458 <example compact="compact">
6465 The two runlevels 0 (halt) and 6 (reboot) are slightly
6466 different. In these runlevels, the links with an
6467 <tt>S</tt> prefix are still called after those with a
6468 <tt>K</tt> prefix, but they too are called with the single
6469 argument <tt>stop</tt>.
6473 <sect1 id="writing-init">
6474 <heading>Writing the scripts</heading>
6477 Packages that include daemons for system services should
6478 place scripts in <file>/etc/init.d</file> to start or stop
6479 services at boot time or during a change of runlevel.
6480 These scripts should be named
6481 <file>/etc/init.d/<var>package</var></file>, and they should
6482 accept one argument, saying what to do:
6485 <tag><tt>start</tt></tag>
6486 <item>start the service,</item>
6488 <tag><tt>stop</tt></tag>
6489 <item>stop the service,</item>
6491 <tag><tt>restart</tt></tag>
6492 <item>stop and restart the service if it's already running,
6493 otherwise start the service</item>
6495 <tag><tt>reload</tt></tag>
6496 <item><p>cause the configuration of the service to be
6497 reloaded without actually stopping and restarting
6500 <tag><tt>force-reload</tt></tag>
6501 <item>cause the configuration to be reloaded if the
6502 service supports this, otherwise restart the
6506 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
6507 <tt>force-reload</tt> options should be supported by all
6508 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
6513 The <file>init.d</file> scripts must ensure that they will
6514 behave sensibly (i.e., returning success and not starting
6515 multiple copies of a service) if invoked with <tt>start</tt>
6516 when the service is already running, or with <tt>stop</tt>
6517 when it isn't, and that they don't kill unfortunately-named
6518 user processes. The best way to achieve this is usually to
6519 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
6524 Be careful of using <tt>set -e</tt> in <file>init.d</file>
6525 scripts. Writing correct <file>init.d</file> scripts requires
6526 accepting various error exit statuses when daemons are already
6527 running or already stopped without aborting
6528 the <file>init.d</file> script, and common <file>init.d</file>
6529 function libraries are not safe to call with <tt>set -e</tt>
6531 <tt>/lib/lsb/init-functions</tt>, which assists in writing
6532 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
6533 in effect and echoing status messages to the console fails,
6535 </footnote>. For <tt>init.d</tt> scripts, it's often easier
6536 to not use <tt>set -e</tt> and instead check the result of
6537 each command separately.
6541 If a service reloads its configuration automatically (as
6542 in the case of <prgn>cron</prgn>, for example), the
6543 <tt>reload</tt> option of the <file>init.d</file> script
6544 should behave as if the configuration has been reloaded
6549 The <file>/etc/init.d</file> scripts must be treated as
6550 configuration files, either (if they are present in the
6551 package, that is, in the .deb file) by marking them as
6552 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6553 by managing them correctly in the maintainer scripts (see
6554 <ref id="config-files">). This is important since we want
6555 to give the local system administrator the chance to adapt
6556 the scripts to the local system, e.g., to disable a
6557 service without de-installing the package, or to specify
6558 some special command line options when starting a service,
6559 while making sure their changes aren't lost during the next
6564 These scripts should not fail obscurely when the
6565 configuration files remain but the package has been
6566 removed, as configuration files remain on the system after
6567 the package has been removed. Only when <prgn>dpkg</prgn>
6568 is executed with the <tt>--purge</tt> option will
6569 configuration files be removed. In particular, as the
6570 <file>/etc/init.d/<var>package</var></file> script itself is
6571 usually a <tt>conffile</tt>, it will remain on the system
6572 if the package is removed but not purged. Therefore, you
6573 should include a <tt>test</tt> statement at the top of the
6575 <example compact="compact">
6576 test -f <var>program-executed-later-in-script</var> || exit 0
6581 Often there are some variables in the <file>init.d</file>
6582 scripts whose values control the behavior of the scripts,
6583 and which a system administrator is likely to want to
6584 change. As the scripts themselves are frequently
6585 <tt>conffile</tt>s, modifying them requires that the
6586 administrator merge in their changes each time the package
6587 is upgraded and the <tt>conffile</tt> changes. To ease
6588 the burden on the system administrator, such configurable
6589 values should not be placed directly in the script.
6590 Instead, they should be placed in a file in
6591 <file>/etc/default</file>, which typically will have the same
6592 base name as the <file>init.d</file> script. This extra file
6593 should be sourced by the script when the script runs. It
6594 must contain only variable settings and comments in SUSv3
6595 <prgn>sh</prgn> format. It may either be a
6596 <tt>conffile</tt> or a configuration file maintained by
6597 the package maintainer scripts. See <ref id="config-files">
6602 To ensure that vital configurable values are always
6603 available, the <file>init.d</file> script should set default
6604 values for each of the shell variables it uses, either
6605 before sourcing the <file>/etc/default/</file> file or
6606 afterwards using something like the <tt>:
6607 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6608 script must behave sensibly and not fail if the
6609 <file>/etc/default</file> file is deleted.
6613 <file>/var/run</file> and <file>/var/lock</file> may be mounted
6614 as temporary filesystems<footnote>
6615 For example, using the <tt>RAMRUN</tt> and <tt>RAMLOCK</tt>
6616 options in <file>/etc/default/rcS</file>.
6617 </footnote>, so the <file>init.d</file> scripts must handle this
6618 correctly. This will typically amount to creating any required
6619 subdirectories dynamically when the <file>init.d</file> script
6620 is run, rather than including them in the package and relying on
6621 <prgn>dpkg</prgn> to create them.
6626 <heading>Interfacing with the initscript system</heading>
6629 Maintainers should use the abstraction layer provided by
6630 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6631 programs to deal with initscripts in their packages'
6632 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6633 and <prgn>postrm</prgn>.
6637 Directly managing the /etc/rc?.d links and directly
6638 invoking the <file>/etc/init.d/</file> initscripts should
6639 be done only by packages providing the initscript
6640 subsystem (such as <prgn>sysv-rc</prgn> and
6641 <prgn>file-rc</prgn>).
6645 <heading>Managing the links</heading>
6648 The program <prgn>update-rc.d</prgn> is provided for
6649 package maintainers to arrange for the proper creation and
6650 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6651 or their functional equivalent if another method is being
6652 used. This may be used by maintainers in their packages'
6653 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6657 You must not include any <file>/etc/rc<var>n</var>.d</file>
6658 symbolic links in the actual archive or manually create or
6659 remove the symbolic links in maintainer scripts; you must
6660 use the <prgn>update-rc.d</prgn> program instead. (The
6661 former will fail if an alternative method of maintaining
6662 runlevel information is being used.) You must not include
6663 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6664 in the archive either. (Only the <tt>sysvinit</tt>
6669 By default <prgn>update-rc.d</prgn> will start services in
6670 each of the multi-user state runlevels (2, 3, 4, and 5)
6671 and stop them in the halt runlevel (0), the single-user
6672 runlevel (1) and the reboot runlevel (6). The system
6673 administrator will have the opportunity to customize
6674 runlevels by simply adding, moving, or removing the
6675 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6676 symbolic links are being used, or by modifying
6677 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6682 To get the default behavior for your package, put in your
6683 <prgn>postinst</prgn> script
6684 <example compact="compact">
6685 update-rc.d <var>package</var> defaults
6687 and in your <prgn>postrm</prgn>
6688 <example compact="compact">
6689 if [ "$1" = purge ]; then
6690 update-rc.d <var>package</var> remove
6692 </example>. Note that if your package changes runlevels
6693 or priority, you may have to remove and recreate the links,
6694 since otherwise the old links may persist. Refer to the
6695 documentation of <prgn>update-rc.d</prgn>.
6699 This will use a default sequence number of 20. If it does
6700 not matter when or in which order the <file>init.d</file>
6701 script is run, use this default. If it does, then you
6702 should talk to the maintainer of the <prgn>sysvinit</prgn>
6703 package or post to <tt>debian-devel</tt>, and they will
6704 help you choose a number.
6708 For more information about using <tt>update-rc.d</tt>,
6709 please consult its man page <manref name="update-rc.d"
6715 <heading>Running initscripts</heading>
6717 The program <prgn>invoke-rc.d</prgn> is provided to make
6718 it easier for package maintainers to properly invoke an
6719 initscript, obeying runlevel and other locally-defined
6720 constraints that might limit a package's right to start,
6721 stop and otherwise manage services. This program may be
6722 used by maintainers in their packages' scripts.
6726 The package maintainer scripts must use
6727 <prgn>invoke-rc.d</prgn> to invoke the
6728 <file>/etc/init.d/*</file> initscripts, instead of
6729 calling them directly.
6733 By default, <prgn>invoke-rc.d</prgn> will pass any
6734 action requests (start, stop, reload, restart...) to the
6735 <file>/etc/init.d</file> script, filtering out requests
6736 to start or restart a service out of its intended
6741 Most packages will simply need to change:
6742 <example compact="compact">/etc/init.d/<package>
6743 <action></example> in their <prgn>postinst</prgn>
6744 and <prgn>prerm</prgn> scripts to:
6745 <example compact="compact">
6746 if which invoke-rc.d >/dev/null 2>&1; then
6747 invoke-rc.d <var>package</var> <action>
6749 /etc/init.d/<var>package</var> <action>
6755 A package should register its initscript services using
6756 <prgn>update-rc.d</prgn> before it tries to invoke them
6757 using <prgn>invoke-rc.d</prgn>. Invocation of
6758 unregistered services may fail.
6762 For more information about using
6763 <prgn>invoke-rc.d</prgn>, please consult its man page
6764 <manref name="invoke-rc.d" section="8">.
6770 <heading>Boot-time initialization</heading>
6773 There used to be another directory, <file>/etc/rc.boot</file>,
6774 which contained scripts which were run once per machine
6775 boot. This has been deprecated in favour of links from
6776 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6777 described in <ref id="/etc/init.d">. Packages must not
6778 place files in <file>/etc/rc.boot</file>.
6783 <heading>Example</heading>
6786 An example on which you can base your
6787 <file>/etc/init.d</file> scripts is found in
6788 <file>/etc/init.d/skeleton</file>.
6795 <heading>Console messages from <file>init.d</file> scripts</heading>
6798 This section describes the formats to be used for messages
6799 written to standard output by the <file>/etc/init.d</file>
6800 scripts. The intent is to improve the consistency of
6801 Debian's startup and shutdown look and feel. For this
6802 reason, please look very carefully at the details. We want
6803 the messages to have the same format in terms of wording,
6804 spaces, punctuation and case of letters.
6808 Here is a list of overall rules that should be used for
6809 messages generated by <file>/etc/init.d</file> scripts.
6815 The message should fit in one line (fewer than 80
6816 characters), start with a capital letter and end with
6817 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6821 If the script is performing some time consuming task in
6822 the background (not merely starting or stopping a
6823 program, for instance), an ellipsis (three dots:
6824 <tt>...</tt>) should be output to the screen, with no
6825 leading or tailing whitespace or line feeds.
6829 The messages should appear as if the computer is telling
6830 the user what it is doing (politely :-), but should not
6831 mention "it" directly. For example, instead of:
6832 <example compact="compact">
6833 I'm starting network daemons: nfsd mountd.
6835 the message should say
6836 <example compact="compact">
6837 Starting network daemons: nfsd mountd.
6844 <tt>init.d</tt> script should use the following standard
6845 message formats for the situations enumerated below.
6851 <p>When daemons are started</p>
6854 If the script starts one or more daemons, the output
6855 should look like this (a single line, no leading
6857 <example compact="compact">
6858 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6860 The <var>description</var> should describe the
6861 subsystem the daemon or set of daemons are part of,
6862 while <var>daemon-1</var> up to <var>daemon-n</var>
6863 denote each daemon's name (typically the file name of
6868 For example, the output of <file>/etc/init.d/lpd</file>
6870 <example compact="compact">
6871 Starting printer spooler: lpd.
6876 This can be achieved by saying
6877 <example compact="compact">
6878 echo -n "Starting printer spooler: lpd"
6879 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6882 in the script. If there are more than one daemon to
6883 start, the output should look like this:
6884 <example compact="compact">
6885 echo -n "Starting remote file system services:"
6886 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6887 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6888 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6891 This makes it possible for the user to see what is
6892 happening and when the final daemon has been started.
6893 Care should be taken in the placement of white spaces:
6894 in the example above the system administrators can
6895 easily comment out a line if they don't want to start
6896 a specific daemon, while the displayed message still
6902 <p>When a system parameter is being set</p>
6905 If you have to set up different system parameters
6906 during the system boot, you should use this format:
6907 <example compact="compact">
6908 Setting <var>parameter</var> to "<var>value</var>".
6913 You can use a statement such as the following to get
6915 <example compact="compact">
6916 echo "Setting DNS domainname to \"$domainname\"."
6921 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
6922 for the left and right quotation marks. A grave accent
6923 (<tt>`</tt>) is not a quote character; neither is an
6924 apostrophe (<tt>'</tt>).
6929 <p>When a daemon is stopped or restarted</p>
6932 When you stop or restart a daemon, you should issue a
6933 message identical to the startup message, except that
6934 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6935 or <tt>Restarting</tt> respectively.
6939 For example, stopping the printer daemon will look like
6941 <example compact="compact">
6942 Stopping printer spooler: lpd.
6948 <p>When something is executed</p>
6951 There are several examples where you have to run a
6952 program at system startup or shutdown to perform a
6953 specific task, for example, setting the system's clock
6954 using <prgn>netdate</prgn> or killing all processes
6955 when the system shuts down. Your message should look
6957 <example compact="compact">
6958 Doing something very useful...done.
6960 You should print the <tt>done.</tt> immediately after
6961 the job has been completed, so that the user is
6962 informed why they have to wait. You can get this
6964 <example compact="compact">
6965 echo -n "Doing something very useful..."
6974 <p>When the configuration is reloaded</p>
6977 When a daemon is forced to reload its configuration
6978 files you should use the following format:
6979 <example compact="compact">
6980 Reloading <var>description</var> configuration...done.
6982 where <var>description</var> is the same as in the
6983 daemon starting message.
6991 <heading>Cron jobs</heading>
6994 Packages must not modify the configuration file
6995 <file>/etc/crontab</file>, and they must not modify the files in
6996 <file>/var/spool/cron/crontabs</file>.</p>
6999 If a package wants to install a job that has to be executed
7000 via cron, it should place a file with the name of the
7001 package in one or more of the following directories:
7002 <example compact="compact">
7008 As these directory names imply, the files within them are
7009 executed on an hourly, daily, weekly, or monthly basis,
7010 respectively. The exact times are listed in
7011 <file>/etc/crontab</file>.</p>
7014 All files installed in any of these directories must be
7015 scripts (e.g., shell scripts or Perl scripts) so that they
7016 can easily be modified by the local system administrator.
7017 In addition, they must be treated as configuration files.
7021 If a certain job has to be executed at some other frequency or
7022 at a specific time, the package should install a file
7023 <file>/etc/cron.d/<var>package</var></file>. This file uses the
7024 same syntax as <file>/etc/crontab</file> and is processed by
7025 <prgn>cron</prgn> automatically. The file must also be
7026 treated as a configuration file. (Note that entries in the
7027 <file>/etc/cron.d</file> directory are not handled by
7028 <prgn>anacron</prgn>. Thus, you should only use this
7029 directory for jobs which may be skipped if the system is not
7032 Unlike <file>crontab</file> files described in the IEEE Std
7033 1003.1-2008 (POSIX.1) available from
7034 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
7035 name="The Open Group">, the files in
7036 <file>/etc/cron.d</file> and the file
7037 <file>/etc/crontab</file> have seven fields; namely:
7039 <item>Minute [0,59]</item>
7040 <item>Hour [0,23]</item>
7041 <item>Day of the month [1,31]</item>
7042 <item>Month of the year [1,12]</item>
7043 <item>Day of the week ([0,6] with 0=Sunday)</item>
7044 <item>Username</item>
7045 <item>Command to be run</item>
7047 Ranges of numbers are allowed. Ranges are two numbers
7048 separated with a hyphen. The specified range is inclusive.
7049 Lists are allowed. A list is a set of numbers (or ranges)
7050 separated by commas. Step values can be used in conjunction
7055 The scripts or <tt>crontab</tt> entries in these directories should
7056 check if all necessary programs are installed before they
7057 try to execute them. Otherwise, problems will arise when a
7058 package was removed but not purged since configuration files
7059 are kept on the system in this situation.
7063 Any <tt>cron</tt> daemon must provide
7064 <file>/usr/bin/crontab</file> and support normal
7065 <tt>crontab</tt> entries as specified in POSIX. The daemon
7066 must also support names for days and months, ranges, and
7067 step values. It has to support <file>/etc/crontab</file>,
7068 and correctly execute the scripts in
7069 <file>/etc/cron.d</file>. The daemon must also correctly
7071 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
7076 <heading>Menus</heading>
7079 The Debian <tt>menu</tt> package provides a standard
7080 interface between packages providing applications and
7081 <em>menu programs</em> (either X window managers or
7082 text-based menu programs such as <prgn>pdmenu</prgn>).
7086 All packages that provide applications that need not be
7087 passed any special command line arguments for normal
7088 operation should register a menu entry for those
7089 applications, so that users of the <tt>menu</tt> package
7090 will automatically get menu entries in their window
7091 managers, as well in shells like <tt>pdmenu</tt>.
7095 Menu entries should follow the current menu policy.
7099 The menu policy can be found in the <tt>menu-policy</tt>
7100 files in the <tt>debian-policy</tt> package.
7101 It is also available from the Debian web mirrors at
7102 <tt><url name="/doc/packaging-manuals/menu-policy/"
7103 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
7107 Please also refer to the <em>Debian Menu System</em>
7108 documentation that comes with the <package>menu</package>
7109 package for information about how to register your
7115 <heading>Multimedia handlers</heading>
7118 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
7119 is a mechanism for encoding files and data streams and
7120 providing meta-information about them, in particular their
7121 type (e.g. audio or video) and format (e.g. PNG, HTML,
7126 Registration of MIME type handlers allows programs like mail
7127 user agents and web browsers to invoke these handlers to
7128 view, edit or display MIME types they don't support directly.
7132 Packages which provide the ability to view/show/play,
7133 compose, edit or print MIME types should register themselves
7134 as such following the current MIME support policy.
7138 The MIME support policy can be found in the <tt>mime-policy</tt>
7139 files in the <tt>debian-policy</tt> package.
7140 It is also available from the Debian web mirrors at
7141 <tt><url name="/doc/packaging-manuals/mime-policy/"
7142 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
7148 <heading>Keyboard configuration</heading>
7151 To achieve a consistent keyboard configuration so that all
7152 applications interpret a keyboard event the same way, all
7153 programs in the Debian distribution must be configured to
7154 comply with the following guidelines.
7158 The following keys must have the specified interpretations:
7161 <tag><tt><--</tt></tag>
7162 <item>delete the character to the left of the cursor</item>
7164 <tag><tt>Delete</tt></tag>
7165 <item>delete the character to the right of the cursor</item>
7167 <tag><tt>Control+H</tt></tag>
7168 <item>emacs: the help prefix</item>
7171 The interpretation of any keyboard events should be
7172 independent of the terminal that is used, be it a virtual
7173 console, an X terminal emulator, an rlogin/telnet session,
7178 The following list explains how the different programs
7179 should be set up to achieve this:
7185 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
7189 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
7193 X translations are set up to make
7194 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
7195 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
7196 is the vt220 escape code for the "delete character"
7197 key). This must be done by loading the X resources
7198 using <prgn>xrdb</prgn> on all local X displays, not
7199 using the application defaults, so that the
7200 translation resources used correspond to the
7201 <prgn>xmodmap</prgn> settings.
7205 The Linux console is configured to make
7206 <tt><--</tt> generate DEL, and <tt>Delete</tt>
7207 generate <tt>ESC [ 3 ~</tt>.
7211 X applications are configured so that <tt><</tt>
7212 deletes left, and <tt>Delete</tt> deletes right. Motif
7213 applications already work like this.
7217 Terminals should have <tt>stty erase ^?</tt> .
7221 The <tt>xterm</tt> terminfo entry should have <tt>ESC
7222 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
7223 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
7227 Emacs is programmed to map <tt>KB_Backspace</tt> or
7228 the <tt>stty erase</tt> character to
7229 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
7230 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
7231 <tt>^H</tt> to <tt>help</tt> as always.
7235 Other applications use the <tt>stty erase</tt>
7236 character and <tt>kdch1</tt> for the two delete keys,
7237 with ASCII DEL being "delete previous character" and
7238 <tt>kdch1</tt> being "delete character under
7246 This will solve the problem except for the following
7253 Some terminals have a <tt><--</tt> key that cannot
7254 be made to produce anything except <tt>^H</tt>. On
7255 these terminals Emacs help will be unavailable on
7256 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
7257 character takes precedence in Emacs, and has been set
7258 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
7259 available) can be used instead.
7263 Some operating systems use <tt>^H</tt> for <tt>stty
7264 erase</tt>. However, modern telnet versions and all
7265 rlogin versions propagate <tt>stty</tt> settings, and
7266 almost all UNIX versions honour <tt>stty erase</tt>.
7267 Where the <tt>stty</tt> settings are not propagated
7268 correctly, things can be made to work by using
7269 <tt>stty</tt> manually.
7273 Some systems (including previous Debian versions) use
7274 <prgn>xmodmap</prgn> to arrange for both
7275 <tt><--</tt> and <tt>Delete</tt> to generate
7276 <tt>KB_Delete</tt>. We can change the behavior of
7277 their X clients using the same X resources that we use
7278 to do it for our own clients, or configure our clients
7279 using their resources when things are the other way
7280 around. On displays configured like this
7281 <tt>Delete</tt> will not work, but <tt><--</tt>
7286 Some operating systems have different <tt>kdch1</tt>
7287 settings in their <tt>terminfo</tt> database for
7288 <tt>xterm</tt> and others. On these systems the
7289 <tt>Delete</tt> key will not work correctly when you
7290 log in from a system conforming to our policy, but
7291 <tt><--</tt> will.
7298 <heading>Environment variables</heading>
7301 A program must not depend on environment variables to get
7302 reasonable defaults. (That's because these environment
7303 variables would have to be set in a system-wide
7304 configuration file like <file>/etc/profile</file>, which is not
7305 supported by all shells.)
7309 If a program usually depends on environment variables for its
7310 configuration, the program should be changed to fall back to
7311 a reasonable default configuration if these environment
7312 variables are not present. If this cannot be done easily
7313 (e.g., if the source code of a non-free program is not
7314 available), the program must be replaced by a small
7315 "wrapper" shell script which sets the environment variables
7316 if they are not already defined, and calls the original program.
7320 Here is an example of a wrapper script for this purpose:
7322 <example compact="compact">
7324 BAR=${BAR:-/var/lib/fubar}
7326 exec /usr/lib/foo/foo "$@"
7331 Furthermore, as <file>/etc/profile</file> is a configuration
7332 file of the <prgn>base-files</prgn> package, other packages must
7333 not put any environment variables or other commands into that
7338 <sect id="doc-base">
7339 <heading>Registering Documents using doc-base</heading>
7342 The <package>doc-base</package> package implements a
7343 flexible mechanism for handling and presenting
7344 documentation. The recommended practice is for every Debian
7345 package that provides online documentation (other than just
7346 manual pages) to register these documents with
7347 <package>doc-base</package> by installing a
7348 <package>doc-base</package> control file via the
7349 <prgn/install-docs/ script at installation time and
7350 de-register the manuals again when the package is removed.
7353 Please refer to the documentation that comes with the
7354 <package>doc-base</package> package for information and
7363 <heading>Files</heading>
7365 <sect id="binaries">
7366 <heading>Binaries</heading>
7369 Two different packages must not install programs with
7370 different functionality but with the same filenames. (The
7371 case of two programs having the same functionality but
7372 different implementations is handled via "alternatives" or
7373 the "Conflicts" mechanism. See <ref id="maintscripts"> and
7374 <ref id="conflicts"> respectively.) If this case happens,
7375 one of the programs must be renamed. The maintainers should
7376 report this to the <tt>debian-devel</tt> mailing list and
7377 try to find a consensus about which program will have to be
7378 renamed. If a consensus cannot be reached, <em>both</em>
7379 programs must be renamed.
7383 By default, when a package is being built, any binaries
7384 created should include debugging information, as well as
7385 being compiled with optimization. You should also turn on
7386 as many reasonable compilation warnings as possible; this
7387 makes life easier for porters, who can then look at build
7388 logs for possible problems. For the C programming language,
7389 this means the following compilation parameters should be
7391 <example compact="compact">
7393 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
7395 INSTALL = install -s # (or use strip on the files in debian/tmp)
7400 Note that by default all installed binaries should be stripped,
7401 either by using the <tt>-s</tt> flag to
7402 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
7403 the binaries after they have been copied into
7404 <file>debian/tmp</file> but before the tree is made into a
7409 Although binaries in the build tree should be compiled with
7410 debugging information by default, it can often be difficult to
7411 debug programs if they are also subjected to compiler
7412 optimization. For this reason, it is recommended to support the
7413 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
7414 (see <ref id="debianrules-options">). This variable can contain
7415 several flags to change how a package is compiled and built.
7419 It is up to the package maintainer to decide what
7420 compilation options are best for the package. Certain
7421 binaries (such as computationally-intensive programs) will
7422 function better with certain flags (<tt>-O3</tt>, for
7423 example); feel free to use them. Please use good judgment
7424 here. Don't use flags for the sake of it; only use them
7425 if there is good reason to do so. Feel free to override
7426 the upstream author's ideas about which compilation
7427 options are best: they are often inappropriate for our
7433 <sect id="libraries">
7434 <heading>Libraries</heading>
7437 If the package is <strong>architecture: any</strong>, then
7438 the shared library compilation and linking flags must have
7439 <tt>-fPIC</tt>, or the package shall not build on some of
7440 the supported architectures<footnote>
7442 If you are using GCC, <tt>-fPIC</tt> produces code with
7443 relocatable position independent code, which is required for
7444 most architectures to create a shared library, with i386 and
7445 perhaps some others where non position independent code is
7446 permitted in a shared library.
7449 Position independent code may have a performance penalty,
7450 especially on <tt>i386</tt>. However, in most cases the
7451 speed penalty must be measured against the memory wasted on
7452 the few architectures where non position independent code is
7455 </footnote>. Any exception to this rule must be discussed on
7456 the mailing list <em>debian-devel@lists.debian.org</em>, and
7457 a rough consensus obtained. The reasons for not compiling
7458 with <tt>-fPIC</tt> flag must be recorded in the file
7459 <tt>README.Debian</tt>, and care must be taken to either
7460 restrict the architecture or arrange for <tt>-fPIC</tt> to
7461 be used on architectures where it is required.<footnote>
7463 Some of the reasons why this might be required is if the
7464 library contains hand crafted assembly code that is not
7465 relocatable, the speed penalty is excessive for compute
7466 intensive libs, and similar reasons.
7471 As to the static libraries, the common case is not to have
7472 relocatable code, since there is no benefit, unless in specific
7473 cases; therefore the static version must not be compiled
7474 with the <tt>-fPIC</tt> flag. Any exception to this rule
7475 should be discussed on the mailing list
7476 <em>debian-devel@lists.debian.org</em>, and the reasons for
7477 compiling with the <tt>-fPIC</tt> flag must be recorded in
7478 the file <tt>README.Debian</tt>. <footnote>
7480 Some of the reasons for linking static libraries with
7481 the <tt>-fPIC</tt> flag are if, for example, one needs a
7482 Perl API for a library that is under rapid development,
7483 and has an unstable API, so shared libraries are
7484 pointless at this phase of the library's development. In
7485 that case, since Perl needs a library with relocatable
7486 code, it may make sense to create a static library with
7487 relocatable code. Another reason cited is if you are
7488 distilling various libraries into a common shared
7489 library, like <tt>mklibs</tt> does in the Debian
7495 In other words, if both a shared and a static library is
7496 being built, each source unit (<tt>*.c</tt>, for example,
7497 for C files) will need to be compiled twice, for the normal
7502 Libraries should be built with threading support and to be
7503 thread-safe if the library supports this.
7507 Although not enforced by the build tools, shared libraries
7508 must be linked against all libraries that they use symbols from
7509 in the same way that binaries are. This ensures the correct
7510 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
7511 system and guarantees that all libraries can be safely opened
7512 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
7513 option <tt>-Wl,-z,defs</tt> when building a shared library.
7514 Since this option enforces symbol resolution at build time,
7515 a missing library reference will be caught early as a fatal
7520 All installed shared libraries should be stripped with
7521 <example compact="compact">
7522 strip --strip-unneeded <var>your-lib</var>
7524 (The option <tt>--strip-unneeded</tt> makes
7525 <prgn>strip</prgn> remove only the symbols which aren't
7526 needed for relocation processing.) Shared libraries can
7527 function perfectly well when stripped, since the symbols for
7528 dynamic linking are in a separate part of the ELF object
7530 You might also want to use the options
7531 <tt>--remove-section=.comment</tt> and
7532 <tt>--remove-section=.note</tt> on both shared libraries
7533 and executables, and <tt>--strip-debug</tt> on static
7539 Note that under some circumstances it may be useful to
7540 install a shared library unstripped, for example when
7541 building a separate package to support debugging.
7545 Shared object files (often <file>.so</file> files) that are not
7546 public libraries, that is, they are not meant to be linked
7547 to by third party executables (binaries of other packages),
7548 should be installed in subdirectories of the
7549 <file>/usr/lib</file> directory. Such files are exempt from the
7550 rules that govern ordinary shared libraries, except that
7551 they must not be installed executable and should be
7553 A common example are the so-called "plug-ins",
7554 internal shared objects that are dynamically loaded by
7555 programs using <manref name="dlopen" section="3">.
7560 Packages that use <prgn>libtool</prgn> to create and install
7561 their shared libraries install a file containing additional
7562 metadata (ending in <file>.la</file>) alongside the library.
7563 For public libraries intended for use by other packages, these
7564 files normally should not be included in the Debian package,
7565 since the information they include is not necessary to link with
7566 the shared library on Debian and can add unnecessary additional
7567 dependencies to other programs or libraries.<footnote>
7568 These files store, among other things, all libraries on which
7569 that shared library depends. Unfortunately, if
7570 the <file>.la</file> file is present and contains that
7571 dependency information, using <prgn>libtool</prgn> when
7572 linking against that library will cause the resulting program
7573 or library to be linked against those dependencies as well,
7574 even if this is unnecessary. This can create unneeded
7575 dependencies on shared library packages that would otherwise
7576 be hidden behind the library ABI, and can make library
7577 transitions to new SONAMEs unnecessarily complicated and
7578 difficult to manage.
7580 If the <file>.la</file> file is required for that library (if,
7581 for instance, it's loaded via <tt>libltdl</tt> in a way that
7582 requires that meta-information), the <tt>dependency_libs</tt>
7583 setting in the <file>.la</file> file should normally be set to
7584 the empty string. If the shared library development package has
7585 historically included the <file>.la</file>, it must be retained
7586 in the development package (with <tt>dependency_libs</tt>
7587 emptied) until all libraries that depend on it have removed or
7588 emptied <tt>dependency_libs</tt> in their <file>.la</file>
7589 files to prevent linking with those other libraries
7590 using <prgn>libtool</prgn> from failing.
7594 If the <file>.la</file> must be included, it should be included
7595 in the development (<tt>-dev</tt>) package, unless the library
7596 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
7597 library. If it is intended for use with <tt>libltdl</tt>,
7598 the <file>.la</file> files must go in the run-time library
7603 These requirements for handling of <file>.la</file> files do not
7604 apply to loadable modules or libraries not installed in
7605 directories searched by default by the dynamic linker. Packages
7606 installing loadable modules will frequently need to install
7607 the <file>.la</file> files alongside the modules so that they
7608 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
7609 does not need to be modified for libraries or modules that are
7610 not installed in directories searched by the dynamic linker by
7611 default and not intended for use by other packages.
7615 You must make sure that you use only released versions of
7616 shared libraries to build your packages; otherwise other
7617 users will not be able to run your binaries
7618 properly. Producing source packages that depend on
7619 unreleased compilers is also usually a bad
7626 <heading>Shared libraries</heading>
7628 This section has moved to <ref id="sharedlibs">.
7634 <heading>Scripts</heading>
7637 All command scripts, including the package maintainer
7638 scripts inside the package and used by <prgn>dpkg</prgn>,
7639 should have a <tt>#!</tt> line naming the shell to be used
7644 In the case of Perl scripts this should be
7645 <tt>#!/usr/bin/perl</tt>.
7649 When scripts are installed into a directory in the system
7650 PATH, the script name should not include an extension such
7651 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7652 language currently used to implement it.
7655 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
7656 <file>init.d</file> scripts should almost certainly start
7657 with <tt>set -e</tt> so that errors are detected.
7658 <file>init.d</file> scripts are something of a special case, due
7659 to how frequently they need to call commands that are allowed to
7660 fail, and it may instead be easier to check the exit status of
7661 commands directly. See <ref id="writing-init"> for more
7662 information about writing <file>init.d</file> scripts.
7665 Every script should use <tt>set -e</tt> or check the exit status
7666 of <em>every</em> command.
7669 Scripts may assume that <file>/bin/sh</file> implements the
7670 SUSv3 Shell Command Language<footnote>
7671 Single UNIX Specification, version 3, which is also IEEE
7672 1003.1-2004 (POSIX), and is available on the World Wide Web
7673 from <url id="http://www.unix.org/version3/online.html"
7674 name="The Open Group"> after free
7675 registration.</footnote>
7676 plus the following additional features not mandated by
7678 These features are in widespread use in the Linux community
7679 and are implemented in all of bash, dash, and ksh, the most
7680 common shells users may wish to use as <file>/bin/sh</file>.
7683 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7684 must not generate a newline.</item>
7685 <item><tt>test</tt>, if implemented as a shell built-in, must
7686 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7688 <item><tt>local</tt> to create a scoped variable must be
7689 supported, including listing multiple variables in a single
7690 local command and assigning a value to a variable at the
7691 same time as localizing it. <tt>local</tt> may or
7692 may not preserve the variable value from an outer scope if
7693 no assignment is present. Uses such as:
7697 # ... use a, b, c, d ...
7700 must be supported and must set the value of <tt>c</tt> to
7703 <item>The XSI extension to <prgn>kill</prgn> allowing <tt>kill
7704 -<var>signal</var></tt>, where <var>signal</var> is either
7705 the name of a signal or one of the numeric signals listed in
7706 the XSI extension (0, 1, 2, 3, 6, 9, 14, and 15), must be
7707 supported if <prgn>kill</prgn> is implemented as a shell
7710 <item>The XSI extension to <prgn>trap</prgn> allowing numeric
7711 signals must be supported. In addition to the signal
7712 numbers listed in the extension, which are the same as for
7713 <prgn>kill</prgn> above, 13 (SIGPIPE) must be allowed.
7716 If a shell script requires non-SUSv3 features from the shell
7717 interpreter other than those listed above, the appropriate shell
7718 must be specified in the first line of the script (e.g.,
7719 <tt>#!/bin/bash</tt>) and the package must depend on the package
7720 providing the shell (unless the shell package is marked
7721 "Essential", as in the case of <prgn>bash</prgn>).
7725 You may wish to restrict your script to SUSv3 features plus the
7726 above set when possible so that it may use <file>/bin/sh</file>
7727 as its interpreter. If your script works with <prgn>dash</prgn>
7728 (originally called <prgn>ash</prgn>), it probably complies with
7729 the above requirements, but if you are in doubt, use
7730 <file>/bin/bash</file>.
7734 Perl scripts should check for errors when making any
7735 system calls, including <tt>open</tt>, <tt>print</tt>,
7736 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7740 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7741 scripting languages. See <em>Csh Programming Considered
7742 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7743 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7744 If an upstream package comes with <prgn>csh</prgn> scripts
7745 then you must make sure that they start with
7746 <tt>#!/bin/csh</tt> and make your package depend on the
7747 <prgn>c-shell</prgn> virtual package.
7751 Any scripts which create files in world-writeable
7752 directories (e.g., in <file>/tmp</file>) must use a
7753 mechanism which will fail atomically if a file with the same
7754 name already exists.
7758 The Debian base system provides the <prgn>tempfile</prgn>
7759 and <prgn>mktemp</prgn> utilities for use by scripts for
7766 <heading>Symbolic links</heading>
7769 In general, symbolic links within a top-level directory
7770 should be relative, and symbolic links pointing from one
7771 top-level directory into another should be absolute. (A
7772 top-level directory is a sub-directory of the root
7773 directory <file>/</file>.)
7777 In addition, symbolic links should be specified as short as
7778 possible, i.e., link targets like <file>foo/../bar</file> are
7783 Note that when creating a relative link using
7784 <prgn>ln</prgn> it is not necessary for the target of the
7785 link to exist relative to the working directory you're
7786 running <prgn>ln</prgn> from, nor is it necessary to change
7787 directory to the directory where the link is to be made.
7788 Simply include the string that should appear as the target
7789 of the link (this will be a pathname relative to the
7790 directory in which the link resides) as the first argument
7795 For example, in your <prgn>Makefile</prgn> or
7796 <file>debian/rules</file>, you can do things like:
7797 <example compact="compact">
7798 ln -fs gcc $(prefix)/bin/cc
7799 ln -fs gcc debian/tmp/usr/bin/cc
7800 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7801 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7806 A symbolic link pointing to a compressed file should always
7807 have the same file extension as the referenced file. (For
7808 example, if a file <file>foo.gz</file> is referenced by a
7809 symbolic link, the filename of the link has to end with
7810 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7815 <heading>Device files</heading>
7818 Packages must not include device files or named pipes in the
7823 If a package needs any special device files that are not
7824 included in the base system, it must call
7825 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7826 after notifying the user<footnote>
7827 This notification could be done via a (low-priority)
7828 debconf message, or an echo (printf) statement.
7833 Packages must not remove any device files in the
7834 <prgn>postrm</prgn> or any other script. This is left to the
7835 system administrator.
7839 Debian uses the serial devices
7840 <file>/dev/ttyS*</file>. Programs using the old
7841 <file>/dev/cu*</file> devices should be changed to use
7842 <file>/dev/ttyS*</file>.
7846 Named pipes needed by the package must be created in
7847 the <prgn>postinst</prgn> script<footnote>
7848 It's better to use <prgn>mkfifo</prgn> rather
7849 than <prgn>mknod</prgn> to create named pipes so that
7850 automated checks for packages incorrectly creating device
7851 files with <prgn>mknod</prgn> won't have false positives.
7852 </footnote> and removed in
7853 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
7858 <sect id="config-files">
7859 <heading>Configuration files</heading>
7862 <heading>Definitions</heading>
7866 <tag>configuration file</tag>
7868 A file that affects the operation of a program, or
7869 provides site- or host-specific information, or
7870 otherwise customizes the behavior of a program.
7871 Typically, configuration files are intended to be
7872 modified by the system administrator (if needed or
7873 desired) to conform to local policy or to provide
7874 more useful site-specific behavior.
7877 <tag><tt>conffile</tt></tag>
7879 A file listed in a package's <tt>conffiles</tt>
7880 file, and is treated specially by <prgn>dpkg</prgn>
7881 (see <ref id="configdetails">).
7887 The distinction between these two is important; they are
7888 not interchangeable concepts. Almost all
7889 <tt>conffile</tt>s are configuration files, but many
7890 configuration files are not <tt>conffiles</tt>.
7894 As noted elsewhere, <file>/etc/init.d</file> scripts,
7895 <file>/etc/default</file> files, scripts installed in
7896 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7897 configuration installed in <file>/etc/cron.d</file> must be
7898 treated as configuration files. In general, any script that
7899 embeds configuration information is de-facto a configuration
7900 file and should be treated as such.
7905 <heading>Location</heading>
7908 Any configuration files created or used by your package
7909 must reside in <file>/etc</file>. If there are several,
7910 consider creating a subdirectory of <file>/etc</file>
7911 named after your package.
7915 If your package creates or uses configuration files
7916 outside of <file>/etc</file>, and it is not feasible to modify
7917 the package to use <file>/etc</file> directly, put the files
7918 in <file>/etc</file> and create symbolic links to those files
7919 from the location that the package requires.
7924 <heading>Behavior</heading>
7927 Configuration file handling must conform to the following
7929 <list compact="compact">
7931 local changes must be preserved during a package
7935 configuration files must be preserved when the
7936 package is removed, and only deleted when the
7940 Obsolete configuration files without local changes may be
7941 removed by the package during upgrade.
7945 The easy way to achieve this behavior is to make the
7946 configuration file a <tt>conffile</tt>. This is
7947 appropriate only if it is possible to distribute a default
7948 version that will work for most installations, although
7949 some system administrators may choose to modify it. This
7950 implies that the default version will be part of the
7951 package distribution, and must not be modified by the
7952 maintainer scripts during installation (or at any other
7957 In order to ensure that local changes are preserved
7958 correctly, no package may contain or make hard links to
7959 conffiles.<footnote>
7960 Rationale: There are two problems with hard links.
7961 The first is that some editors break the link while
7962 editing one of the files, so that the two files may
7963 unwittingly become unlinked and different. The second
7964 is that <prgn>dpkg</prgn> might break the hard link
7965 while upgrading <tt>conffile</tt>s.
7970 The other way to do it is via the maintainer scripts. In
7971 this case, the configuration file must not be listed as a
7972 <tt>conffile</tt> and must not be part of the package
7973 distribution. If the existence of a file is required for
7974 the package to be sensibly configured it is the
7975 responsibility of the package maintainer to provide
7976 maintainer scripts which correctly create, update and
7977 maintain the file and remove it on purge. (See <ref
7978 id="maintainerscripts"> for more information.) These
7979 scripts must be idempotent (i.e., must work correctly if
7980 <prgn>dpkg</prgn> needs to re-run them due to errors
7981 during installation or removal), must cope with all the
7982 variety of ways <prgn>dpkg</prgn> can call maintainer
7983 scripts, must not overwrite or otherwise mangle the user's
7984 configuration without asking, must not ask unnecessary
7985 questions (particularly during upgrades), and must
7986 otherwise be good citizens.
7990 The scripts are not required to configure every possible
7991 option for the package, but only those necessary to get
7992 the package running on a given system. Ideally the
7993 sysadmin should not have to do any configuration other
7994 than that done (semi-)automatically by the
7995 <prgn>postinst</prgn> script.
7999 A common practice is to create a script called
8000 <file><var>package</var>-configure</file> and have the
8001 package's <prgn>postinst</prgn> call it if and only if the
8002 configuration file does not already exist. In certain
8003 cases it is useful for there to be an example or template
8004 file which the maintainer scripts use. Such files should
8005 be in <file>/usr/share/<var>package</var></file> or
8006 <file>/usr/lib/<var>package</var></file> (depending on whether
8007 they are architecture-independent or not). There should
8008 be symbolic links to them from
8009 <file>/usr/share/doc/<var>package</var>/examples</file> if
8010 they are examples, and should be perfectly ordinary
8011 <prgn>dpkg</prgn>-handled files (<em>not</em>
8012 configuration files).
8016 These two styles of configuration file handling must
8017 not be mixed, for that way lies madness:
8018 <prgn>dpkg</prgn> will ask about overwriting the file
8019 every time the package is upgraded.
8024 <heading>Sharing configuration files</heading>
8027 Packages which specify the same file as a
8028 <tt>conffile</tt> must be tagged as <em>conflicting</em>
8029 with each other. (This is an instance of the general rule
8030 about not sharing files. Note that neither alternatives
8031 nor diversions are likely to be appropriate in this case;
8032 in particular, <prgn>dpkg</prgn> does not handle diverted
8033 <tt>conffile</tt>s well.)
8037 The maintainer scripts must not alter a <tt>conffile</tt>
8038 of <em>any</em> package, including the one the scripts
8043 If two or more packages use the same configuration file
8044 and it is reasonable for both to be installed at the same
8045 time, one of these packages must be defined as
8046 <em>owner</em> of the configuration file, i.e., it will be
8047 the package which handles that file as a configuration
8048 file. Other packages that use the configuration file must
8049 depend on the owning package if they require the
8050 configuration file to operate. If the other package will
8051 use the configuration file if present, but is capable of
8052 operating without it, no dependency need be declared.
8056 If it is desirable for two or more related packages to
8057 share a configuration file <em>and</em> for all of the
8058 related packages to be able to modify that configuration
8059 file, then the following should be done:
8060 <enumlist compact="compact">
8062 One of the related packages (the "owning" package)
8063 will manage the configuration file with maintainer
8064 scripts as described in the previous section.
8067 The owning package should also provide a program
8068 that the other packages may use to modify the
8072 The related packages must use the provided program
8073 to make any desired modifications to the
8074 configuration file. They should either depend on
8075 the core package to guarantee that the configuration
8076 modifier program is available or accept gracefully
8077 that they cannot modify the configuration file if it
8078 is not. (This is in addition to the fact that the
8079 configuration file may not even be present in the
8086 Sometimes it's appropriate to create a new package which
8087 provides the basic infrastructure for the other packages
8088 and which manages the shared configuration files. (The
8089 <tt>sgml-base</tt> package is a good example.)
8094 <heading>User configuration files ("dotfiles")</heading>
8097 The files in <file>/etc/skel</file> will automatically be
8098 copied into new user accounts by <prgn>adduser</prgn>.
8099 No other program should reference the files in
8100 <file>/etc/skel</file>.
8104 Therefore, if a program needs a dotfile to exist in
8105 advance in <file>$HOME</file> to work sensibly, that dotfile
8106 should be installed in <file>/etc/skel</file> and treated as a
8111 However, programs that require dotfiles in order to
8112 operate sensibly are a bad thing, unless they do create
8113 the dotfiles themselves automatically.
8117 Furthermore, programs should be configured by the Debian
8118 default installation to behave as closely to the upstream
8119 default behavior as possible.
8123 Therefore, if a program in a Debian package needs to be
8124 configured in some way in order to operate sensibly, that
8125 should be done using a site-wide configuration file placed
8126 in <file>/etc</file>. Only if the program doesn't support a
8127 site-wide default configuration and the package maintainer
8128 doesn't have time to add it may a default per-user file be
8129 placed in <file>/etc/skel</file>.
8133 <file>/etc/skel</file> should be as empty as we can make it.
8134 This is particularly true because there is no easy (or
8135 necessarily desirable) mechanism for ensuring that the
8136 appropriate dotfiles are copied into the accounts of
8137 existing users when a package is installed.
8143 <heading>Log files</heading>
8145 Log files should usually be named
8146 <file>/var/log/<var>package</var>.log</file>. If you have many
8147 log files, or need a separate directory for permission
8148 reasons (<file>/var/log</file> is writable only by
8149 <file>root</file>), you should usually create a directory named
8150 <file>/var/log/<var>package</var></file> and place your log
8155 Log files must be rotated occasionally so that they don't grow
8156 indefinitely. The best way to do this is to install a log
8157 rotation configuration file in the
8158 directory <file>/etc/logrotate.d</file>, normally
8159 named <file>/etc/logrotate.d/<var>package</var></file>, and use
8160 the facilities provided by <prgn>logrotate</prgn>.
8163 The traditional approach to log files has been to set up
8164 <em>ad hoc</em> log rotation schemes using simple shell
8165 scripts and cron. While this approach is highly
8166 customizable, it requires quite a lot of sysadmin work.
8167 Even though the original Debian system helped a little
8168 by automatically installing a system which can be used
8169 as a template, this was deemed not enough.
8173 The use of <prgn>logrotate</prgn>, a program developed
8174 by Red Hat, is better, as it centralizes log management.
8175 It has both a configuration file
8176 (<file>/etc/logrotate.conf</file>) and a directory where
8177 packages can drop their individual log rotation
8178 configurations (<file>/etc/logrotate.d</file>).
8181 Here is a good example for a logrotate config
8182 file (for more information see <manref name="logrotate"
8184 <example compact="compact">
8185 /var/log/foo/*.log {
8191 start-stop-daemon -K -p /var/run/foo.pid -s HUP -x /usr/sbin/foo -q
8195 This rotates all files under <file>/var/log/foo</file>, saves 12
8196 compressed generations, and tells the daemon to reopen its log
8197 files after the log rotation. It skips this log rotation
8198 (via <tt>missingok</tt>) if no such log file is present, which
8199 avoids errors if the package is removed but not purged.
8203 Log files should be removed when the package is
8204 purged (but not when it is only removed). This should be
8205 done by the <prgn>postrm</prgn> script when it is called
8206 with the argument <tt>purge</tt> (see <ref
8207 id="removedetails">).
8211 <sect id="permissions-owners">
8212 <heading>Permissions and owners</heading>
8215 The rules in this section are guidelines for general use.
8216 If necessary you may deviate from the details below.
8217 However, if you do so you must make sure that what is done
8218 is secure and you should try to be as consistent as possible
8219 with the rest of the system. You should probably also
8220 discuss it on <prgn>debian-devel</prgn> first.
8224 Files should be owned by <tt>root:root</tt>, and made
8225 writable only by the owner and universally readable (and
8226 executable, if appropriate), that is mode 644 or 755.
8230 Directories should be mode 755 or (for group-writability)
8231 mode 2775. The ownership of the directory should be
8232 consistent with its mode: if a directory is mode 2775, it
8233 should be owned by the group that needs write access to
8236 When a package is upgraded, and the owner or permissions
8237 of a file included in the package has changed, dpkg
8238 arranges for the ownership and permissions to be
8239 correctly set upon installation. However, this does not
8240 extend to directories; the permissions and ownership of
8241 directories already on the system does not change on
8242 install or upgrade of packages. This makes sense, since
8243 otherwise common directories like <tt>/usr</tt> would
8244 always be in flux. To correctly change permissions of a
8245 directory the package owns, explicit action is required,
8246 usually in the <tt>postinst</tt> script. Care must be
8247 taken to handle downgrades as well, in that case.
8253 Control information files should be owned by <tt>root:root</tt>
8254 and either mode 644 (for most files) or mode 755 (for
8255 executables such as <qref id="maintscripts">maintainer
8260 Setuid and setgid executables should be mode 4755 or 2755
8261 respectively, and owned by the appropriate user or group.
8262 They should not be made unreadable (modes like 4711 or
8263 2711 or even 4111); doing so achieves no extra security,
8264 because anyone can find the binary in the freely available
8265 Debian package; it is merely inconvenient. For the same
8266 reason you should not restrict read or execute permissions
8267 on non-set-id executables.
8271 Some setuid programs need to be restricted to particular
8272 sets of users, using file permissions. In this case they
8273 should be owned by the uid to which they are set-id, and by
8274 the group which should be allowed to execute them. They
8275 should have mode 4754; again there is no point in making
8276 them unreadable to those users who must not be allowed to
8281 It is possible to arrange that the system administrator can
8282 reconfigure the package to correspond to their local
8283 security policy by changing the permissions on a binary:
8284 they can do this by using <prgn>dpkg-statoverride</prgn>, as
8285 described below.<footnote>
8286 Ordinary files installed by <prgn>dpkg</prgn> (as
8287 opposed to <tt>conffile</tt>s and other similar objects)
8288 normally have their permissions reset to the distributed
8289 permissions when the package is reinstalled. However,
8290 the use of <prgn>dpkg-statoverride</prgn> overrides this
8293 Another method you should consider is to create a group for
8294 people allowed to use the program(s) and make any setuid
8295 executables executable only by that group.
8299 If you need to create a new user or group for your package
8300 there are two possibilities. Firstly, you may need to
8301 make some files in the binary package be owned by this
8302 user or group, or you may need to compile the user or
8303 group id (rather than just the name) into the binary
8304 (though this latter should be avoided if possible, as in
8305 this case you need a statically allocated id).</p>
8308 If you need a statically allocated id, you must ask for a
8309 user or group id from the <tt>base-passwd</tt> maintainer,
8310 and must not release the package until you have been
8311 allocated one. Once you have been allocated one you must
8312 either make the package depend on a version of the
8313 <tt>base-passwd</tt> package with the id present in
8314 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
8315 your package to create the user or group itself with the
8316 correct id (using <tt>adduser</tt>) in its
8317 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
8318 the <prgn>postinst</prgn> is to be preferred if it is
8319 possible, otherwise a pre-dependency will be needed on the
8320 <tt>adduser</tt> package.)
8324 On the other hand, the program might be able to determine
8325 the uid or gid from the user or group name at runtime, so
8326 that a dynamically allocated id can be used. In this case
8327 you should choose an appropriate user or group name,
8328 discussing this on <prgn>debian-devel</prgn> and checking
8329 with the <package/base-passwd/ maintainer that it is unique and that
8330 they do not wish you to use a statically allocated id
8331 instead. When this has been checked you must arrange for
8332 your package to create the user or group if necessary using
8333 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
8334 <prgn>postinst</prgn> script (again, the latter is to be
8335 preferred if it is possible).
8339 Note that changing the numeric value of an id associated
8340 with a name is very difficult, and involves searching the
8341 file system for all appropriate files. You need to think
8342 carefully whether a static or dynamic id is required, since
8343 changing your mind later will cause problems.
8346 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
8348 This section is not intended as policy, but as a
8349 description of the use of <prgn>dpkg-statoverride</prgn>.
8353 If a system administrator wishes to have a file (or
8354 directory or other such thing) installed with owner and
8355 permissions different from those in the distributed Debian
8356 package, they can use the <prgn>dpkg-statoverride</prgn>
8357 program to instruct <prgn>dpkg</prgn> to use the different
8358 settings every time the file is installed. Thus the
8359 package maintainer should distribute the files with their
8360 normal permissions, and leave it for the system
8361 administrator to make any desired changes. For example, a
8362 daemon which is normally required to be setuid root, but
8363 in certain situations could be used without being setuid,
8364 should be installed setuid in the <tt>.deb</tt>. Then the
8365 local system administrator can change this if they wish.
8366 If there are two standard ways of doing it, the package
8367 maintainer can use <tt>debconf</tt> to find out the
8368 preference, and call <prgn>dpkg-statoverride</prgn> in the
8369 maintainer script if necessary to accommodate the system
8370 administrator's choice. Care must be taken during
8371 upgrades to not override an existing setting.
8375 Given the above, <prgn>dpkg-statoverride</prgn> is
8376 essentially a tool for system administrators and would not
8377 normally be needed in the maintainer scripts. There is
8378 one type of situation, though, where calls to
8379 <prgn>dpkg-statoverride</prgn> would be needed in the
8380 maintainer scripts, and that involves packages which use
8381 dynamically allocated user or group ids. In such a
8382 situation, something like the following idiom can be very
8383 helpful in the package's <prgn>postinst</prgn>, where
8384 <tt>sysuser</tt> is a dynamically allocated id:
8386 for i in /usr/bin/foo /usr/sbin/bar
8388 # only do something when no setting exists
8389 if ! dpkg-statoverride --list $i >/dev/null 2>&1
8391 #include: debconf processing, question about foo and bar
8392 if [ "$RET" = "true" ] ; then
8393 dpkg-statoverride --update --add sysuser root 4755 $i
8398 The corresponding code to remove the override when the package
8401 for i in /usr/bin/foo /usr/sbin/bar
8403 if dpkg-statoverride --list $i >/dev/null 2>&1
8405 dpkg-statoverride --remove $i
8415 <chapt id="customized-programs">
8416 <heading>Customized programs</heading>
8418 <sect id="arch-spec">
8419 <heading>Architecture specification strings</heading>
8422 If a program needs to specify an <em>architecture specification
8423 string</em> in some place, it should select one of the strings
8424 provided by <tt>dpkg-architecture -L</tt>. The strings are in
8425 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
8426 part is sometimes elided, as when the OS is Linux.
8430 Note that we don't want to use
8431 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
8432 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
8433 since this would make our programs incompatible with other
8434 Linux distributions. We also don't use something like
8435 <tt><var>arch</var>-unknown-linux</tt>, since the
8436 <tt>unknown</tt> does not look very good.
8439 <sect1 id="arch-wildcard-spec">
8440 <heading>Architecture wildcards</heading>
8443 A package may specify an architecture wildcard. Architecture
8444 wildcards are in the format <tt>any</tt> (which matches every
8445 architecture), <tt><var>os</var></tt>-any, or
8446 any-<tt><var>cpu</var></tt>. <footnote>
8447 Internally, the package system normalizes the GNU triplets
8448 and the Debian arches into Debian arch triplets (which are
8449 kind of inverted GNU triplets), with the first component of
8450 the triplet representing the libc and ABI in use, and then
8451 does matching against those triplets. However, such
8452 triplets are an internal implementation detail that should
8453 not be used by packages directly. The libc and ABI portion
8454 is handled internally by the package system based on
8455 the <var>os</var> and <var>cpu</var>.
8462 <heading>Daemons</heading>
8465 The configuration files <file>/etc/services</file>,
8466 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
8467 by the <prgn>netbase</prgn> package and must not be modified
8472 If a package requires a new entry in one of these files, the
8473 maintainer should get in contact with the
8474 <prgn>netbase</prgn> maintainer, who will add the entries
8475 and release a new version of the <prgn>netbase</prgn>
8480 The configuration file <file>/etc/inetd.conf</file> must not be
8481 modified by the package's scripts except via the
8482 <prgn>update-inetd</prgn> script or the
8483 <file>DebianNet.pm</file> Perl module. See their documentation
8484 for details on how to add entries.
8488 If a package wants to install an example entry into
8489 <file>/etc/inetd.conf</file>, the entry must be preceded with
8490 exactly one hash character (<tt>#</tt>). Such lines are
8491 treated as "commented out by user" by the
8492 <prgn>update-inetd</prgn> script and are not changed or
8493 activated during package updates.
8498 <heading>Using pseudo-ttys and modifying wtmp, utmp and
8502 Some programs need to create pseudo-ttys. This should be done
8503 using Unix98 ptys if the C library supports it. The resulting
8504 program must not be installed setuid root, unless that
8505 is required for other functionality.
8509 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
8510 <file>/var/log/lastlog</file> must be installed writable by
8511 group <tt>utmp</tt>. Programs which need to modify those
8512 files must be installed setgid <tt>utmp</tt>.
8517 <heading>Editors and pagers</heading>
8520 Some programs have the ability to launch an editor or pager
8521 program to edit or display a text document. Since there are
8522 lots of different editors and pagers available in the Debian
8523 distribution, the system administrator and each user should
8524 have the possibility to choose their preferred editor and
8529 In addition, every program should choose a good default
8530 editor/pager if none is selected by the user or system
8535 Thus, every program that launches an editor or pager must
8536 use the EDITOR or PAGER environment variable to determine
8537 the editor or pager the user wishes to use. If these
8538 variables are not set, the programs <file>/usr/bin/editor</file>
8539 and <file>/usr/bin/pager</file> should be used, respectively.
8543 These two files are managed through the <prgn>dpkg</prgn>
8544 "alternatives" mechanism. Every package providing an editor or
8545 pager must call the <prgn>update-alternatives</prgn> script to
8546 register as an alternative for <file>/usr/bin/editor</file>
8547 or <file>/usr/bin/pager</file> as appropriate. The alternative
8548 should have a slave alternative
8549 for <file>/usr/share/man/man1/editor.1.gz</file>
8550 or <file>/usr/share/man/man1/pager.1.gz</file> pointing to the
8551 corresponding manual page.
8555 If it is very hard to adapt a program to make use of the
8556 EDITOR or PAGER variables, that program may be configured to
8557 use <file>/usr/bin/sensible-editor</file> and
8558 <file>/usr/bin/sensible-pager</file> as the editor or pager
8559 program respectively. These are two scripts provided in the
8560 <package>sensible-utils</package> package that check the EDITOR
8561 and PAGER variables and launch the appropriate program, and fall
8562 back to <file>/usr/bin/editor</file>
8563 and <file>/usr/bin/pager</file> if the variable is not set.
8567 A program may also use the VISUAL environment variable to
8568 determine the user's choice of editor. If it exists, it
8569 should take precedence over EDITOR. This is in fact what
8570 <file>/usr/bin/sensible-editor</file> does.
8574 It is not required for a package to depend on
8575 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
8576 package to provide such virtual packages.<footnote>
8577 The Debian base system already provides an editor and a
8583 <sect id="web-appl">
8584 <heading>Web servers and applications</heading>
8587 This section describes the locations and URLs that should
8588 be used by all web servers and web applications in the
8595 Cgi-bin executable files are installed in the
8597 <example compact="compact">
8598 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
8600 or a subdirectory of that directory, and should be
8602 <example compact="compact">
8603 http://localhost/cgi-bin/<var>cgi-bin-name</var>
8605 (possibly with a subdirectory name
8606 before <var>cgi-bin-name</var>).
8610 <p>Access to HTML documents</p>
8613 HTML documents for a package are stored in
8614 <file>/usr/share/doc/<var>package</var></file>
8615 and can be referred to as
8616 <example compact="compact">
8617 http://localhost/doc/<var>package</var>/<var>filename</var>
8622 The web server should restrict access to the document
8623 tree so that only clients on the same host can read
8624 the documents. If the web server does not support such
8625 access controls, then it should not provide access at
8626 all, or ask about providing access during installation.
8631 <p>Access to images</p>
8633 It is recommended that images for a package be stored
8634 in <tt>/usr/share/images/<var>package</var></tt> and
8635 may be referred to through an alias <tt>/images/</tt>
8638 http://localhost/images/<package>/<filename>
8645 <p>Web Document Root</p>
8648 Web Applications should try to avoid storing files in
8649 the Web Document Root. Instead they should use the
8650 /usr/share/doc/<var>package</var> directory for
8651 documents and register the Web Application via the
8652 <package>doc-base</package> package. If access to the
8653 web document root is unavoidable then use
8654 <example compact="compact">
8657 as the Document Root. This might be just a symbolic
8658 link to the location where the system administrator
8659 has put the real document root.
8662 <item><p>Providing httpd and/or httpd-cgi</p>
8664 All web servers should provide the virtual package
8665 <tt>httpd</tt>. If a web server has CGI support it should
8666 provide <tt>httpd-cgi</tt> additionally.
8669 All web applications which do not contain CGI scripts should
8670 depend on <tt>httpd</tt>, all those web applications which
8671 <tt>do</tt> contain CGI scripts, should depend on
8679 <sect id="mail-transport-agents">
8680 <heading>Mail transport, delivery and user agents</heading>
8683 Debian packages which process electronic mail, whether mail
8684 user agents (MUAs) or mail transport agents (MTAs), must
8685 ensure that they are compatible with the configuration
8686 decisions below. Failure to do this may result in lost
8687 mail, broken <tt>From:</tt> lines, and other serious brain
8692 The mail spool is <file>/var/mail</file> and the interface to
8693 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8694 the FHS). On older systems, the mail spool may be
8695 physically located in <file>/var/spool/mail</file>, but all
8696 access to the mail spool should be via the
8697 <file>/var/mail</file> symlink. The mail spool is part of the
8698 base system and not part of the MTA package.
8702 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8703 programs (such as IMAP daemons) must lock the mailbox in an
8704 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8705 be combined with dot locking. To avoid deadlocks, a program
8706 should use <tt>fcntl()</tt> first and dot locking after
8707 this, or alternatively implement the two locking methods in
8708 a non blocking way<footnote>
8709 If it is not possible to establish both locks, the
8710 system shouldn't wait for the second lock to be
8711 established, but remove the first lock, wait a (random)
8712 time, and start over locking again.
8713 </footnote>. Using the functions <tt>maillock</tt> and
8714 <tt>mailunlock</tt> provided by the
8715 <tt>liblockfile*</tt><footnote>
8716 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8717 to use these functions.
8718 </footnote> packages is the recommended way to realize this.
8722 Mailboxes are generally either mode 600 and owned by
8723 <var>user</var> or mode 660 and owned by
8724 <tt><var>user</var>:mail</tt><footnote>
8725 There are two traditional permission schemes for mail spools:
8726 mode 600 with all mail delivery done by processes running as
8727 the destination user, or mode 660 and owned by group mail with
8728 mail delivery done by a process running as a system user in
8729 group mail. Historically, Debian required mode 660 mail
8730 spools to enable the latter model, but that model has become
8731 increasingly uncommon and the principle of least privilege
8732 indicates that mail systems that use the first model should
8733 use permissions of 600. If delivery to programs is permitted,
8734 it's easier to keep the mail system secure if the delivery
8735 agent runs as the destination user. Debian Policy therefore
8736 permits either scheme.
8737 </footnote>. The local system administrator may choose a
8738 different permission scheme; packages should not make
8739 assumptions about the permission and ownership of mailboxes
8740 unless required (such as when creating a new mailbox). A MUA
8741 may remove a mailbox (unless it has nonstandard permissions) in
8742 which case the MTA or another MUA must recreate it if needed.
8746 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8747 be setgid mail to do the locking mentioned above (and
8748 must obviously avoid accessing other users' mailboxes
8749 using this privilege).</p>
8752 <file>/etc/aliases</file> is the source file for the system mail
8753 aliases (e.g., postmaster, usenet, etc.), it is the one
8754 which the sysadmin and <prgn>postinst</prgn> scripts may
8755 edit. After <file>/etc/aliases</file> is edited the program or
8756 human editing it must call <prgn>newaliases</prgn>. All MTA
8757 packages must come with a <prgn>newaliases</prgn> program,
8758 even if it does nothing, but older MTA packages did not do
8759 this so programs should not fail if <prgn>newaliases</prgn>
8760 cannot be found. Note that because of this, all MTA
8761 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8762 <tt>Replaces: mail-transport-agent</tt> control fields.
8766 The convention of writing <tt>forward to
8767 <var>address</var></tt> in the mailbox itself is not
8768 supported. Use a <tt>.forward</tt> file instead.</p>
8771 The <prgn>rmail</prgn> program used by UUCP
8772 for incoming mail should be <file>/usr/sbin/rmail</file>.
8773 Likewise, <prgn>rsmtp</prgn>, for receiving
8774 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8778 If your package needs to know what hostname to use on (for
8779 example) outgoing news and mail messages which are generated
8780 locally, you should use the file <file>/etc/mailname</file>. It
8781 will contain the portion after the username and <tt>@</tt>
8782 (at) sign for email addresses of users on the machine
8783 (followed by a newline).
8787 Such a package should check for the existence of this file
8788 when it is being configured. If it exists, it should be
8789 used without comment, although an MTA's configuration script
8790 may wish to prompt the user even if it finds that this file
8791 exists. If the file does not exist, the package should
8792 prompt the user for the value (preferably using
8793 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8794 as well as using it in the package's configuration. The
8795 prompt should make it clear that the name will not just be
8796 used by that package. For example, in this situation the
8797 <tt>inn</tt> package could say something like:
8798 <example compact="compact">
8799 Please enter the "mail name" of your system. This is the
8800 hostname portion of the address to be shown on outgoing
8801 news and mail messages. The default is
8802 <var>syshostname</var>, your system's host name. Mail
8803 name ["<var>syshostname</var>"]:
8805 where <var>syshostname</var> is the output of <tt>hostname
8811 <heading>News system configuration</heading>
8814 All the configuration files related to the NNTP (news)
8815 servers and clients should be located under
8816 <file>/etc/news</file>.</p>
8819 There are some configuration issues that apply to a number
8820 of news clients and server packages on the machine. These
8824 <tag><file>/etc/news/organization</file></tag>
8826 A string which should appear as the
8827 organization header for all messages posted
8828 by NNTP clients on the machine
8831 <tag><file>/etc/news/server</file></tag>
8833 Contains the FQDN of the upstream NNTP
8834 server, or localhost if the local machine is
8839 Other global files may be added as required for cross-package news
8846 <heading>Programs for the X Window System</heading>
8849 <heading>Providing X support and package priorities</heading>
8852 Programs that can be configured with support for the X
8853 Window System must be configured to do so and must declare
8854 any package dependencies necessary to satisfy their
8855 runtime requirements when using the X Window System. If
8856 such a package is of higher priority than the X packages
8857 on which it depends, it is required that either the
8858 X-specific components be split into a separate package, or
8859 that an alternative version of the package, which includes
8860 X support, be provided, or that the package's priority be
8866 <heading>Packages providing an X server</heading>
8869 Packages that provide an X server that, directly or
8870 indirectly, communicates with real input and display
8871 hardware should declare in their <tt>Provides</tt> control
8872 field that they provide the virtual
8873 package <tt>xserver</tt>.<footnote>
8874 This implements current practice, and provides an
8875 actual policy for usage of the <tt>xserver</tt>
8876 virtual package which appears in the virtual packages
8877 list. In a nutshell, X servers that interface
8878 directly with the display and input hardware or via
8879 another subsystem (e.g., GGI) should provide
8880 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8881 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8887 <heading>Packages providing a terminal emulator</heading>
8890 Packages that provide a terminal emulator for the X Window
8891 System which meet the criteria listed below should declare in
8892 their <tt>Provides</tt> control field that they provide the
8893 virtual package <tt>x-terminal-emulator</tt>. They should
8894 also register themselves as an alternative for
8895 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8896 20. That alternative should have a slave alternative
8897 for <file>/usr/share/man/man1/x-terminal-emulator.1.gz</file>
8898 pointing to the corresponding manual page.
8902 To be an <tt>x-terminal-emulator</tt>, a program must:
8903 <list compact="compact">
8905 Be able to emulate a DEC VT100 terminal, or a
8906 compatible terminal.
8910 Support the command-line option <tt>-e
8911 <var>command</var></tt>, which creates a new
8912 terminal window<footnote>
8913 "New terminal window" does not necessarily mean
8914 a new top-level X window directly parented by
8915 the window manager; it could, if the terminal
8916 emulator application were so coded, be a new
8917 "view" in a multiple-document interface (MDI).
8919 and runs the specified <var>command</var>,
8920 interpreting the entirety of the rest of the command
8921 line as a command to pass straight to exec, in the
8922 manner that <tt>xterm</tt> does.
8926 Support the command-line option <tt>-T
8927 <var>title</var></tt>, which creates a new terminal
8928 window with the window title <var>title</var>.
8935 <heading>Packages providing a window manager</heading>
8938 Packages that provide a window manager should declare in
8939 their <tt>Provides</tt> control field that they provide the
8940 virtual package <tt>x-window-manager</tt>. They should also
8941 register themselves as an alternative for
8942 <file>/usr/bin/x-window-manager</file>, with a priority
8943 calculated as follows:
8944 <list compact="compact">
8946 Start with a priority of 20.
8950 If the window manager supports the Debian menu
8951 system, add 20 points if this support is available
8952 in the package's default configuration (i.e., no
8953 configuration files belonging to the system or user
8954 have to be edited to activate the feature); if
8955 configuration files must be modified, add only 10
8961 If the window manager complies with <url
8962 id="http://www.freedesktop.org/Standards/wm-spec"
8963 name="The Window Manager Specification Project">,
8964 written by the <url id="http://www.freedesktop.org/"
8965 name="Free Desktop Group">, add 40 points.
8969 If the window manager permits the X session to be
8970 restarted using a <em>different</em> window manager
8971 (without killing the X server) in its default
8972 configuration, add 10 points; otherwise add none.
8975 That alternative should have a slave alternative
8976 for <file>/usr/share/man/man1/x-window-manager.1.gz</file>
8977 pointing to the corresponding manual page.
8982 <heading>Packages providing fonts</heading>
8985 Packages that provide fonts for the X Window
8987 For the purposes of Debian Policy, a "font for the X
8988 Window System" is one which is accessed via X protocol
8989 requests. Fonts for the Linux console, for PostScript
8990 renderer, or any other purpose, do not fit this
8991 definition. Any tool which makes such fonts available
8992 to the X Window System, however, must abide by this
8995 must do a number of things to ensure that they are both
8996 available without modification of the X or font server
8997 configuration, and that they do not corrupt files used by
8998 other font packages to register information about
9002 Fonts of any type supported by the X Window System
9003 must be in a separate binary package from any
9004 executables, libraries, or documentation (except
9005 that specific to the fonts shipped, such as their
9006 license information). If one or more of the fonts
9007 so packaged are necessary for proper operation of
9008 the package with which they are associated the font
9009 package may be Recommended; if the fonts merely
9010 provide an enhancement, a Suggests relationship may
9011 be used. Packages must not Depend on font
9013 This is because the X server may retrieve fonts
9014 from the local file system or over the network
9015 from an X font server; the Debian package system
9016 is empowered to deal only with the local
9022 BDF fonts must be converted to PCF fonts with the
9023 <prgn>bdftopcf</prgn> utility (available in the
9024 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
9025 placed in a directory that corresponds to their
9027 <list compact="compact">
9029 100 dpi fonts must be placed in
9030 <file>/usr/share/fonts/X11/100dpi/</file>.
9034 75 dpi fonts must be placed in
9035 <file>/usr/share/fonts/X11/75dpi/</file>.
9039 Character-cell fonts, cursor fonts, and other
9040 low-resolution fonts must be placed in
9041 <file>/usr/share/fonts/X11/misc/</file>.
9047 Type 1 fonts must be placed in
9048 <file>/usr/share/fonts/X11/Type1/</file>. If font
9049 metric files are available, they must be placed here
9054 Subdirectories of <file>/usr/share/fonts/X11/</file>
9055 other than those listed above must be neither
9056 created nor used. (The <file>PEX</file>, <file>CID</file>,
9057 <file>Speedo</file>, and <file>cyrillic</file> directories
9058 are excepted for historical reasons, but installation of
9059 files into these directories remains discouraged.)
9063 Font packages may, instead of placing files directly
9064 in the X font directories listed above, provide
9065 symbolic links in that font directory pointing to
9066 the files' actual location in the filesystem. Such
9067 a location must comply with the FHS.
9071 Font packages should not contain both 75dpi and
9072 100dpi versions of a font. If both are available,
9073 they should be provided in separate binary packages
9074 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
9075 the names of the packages containing the
9076 corresponding fonts.
9080 Fonts destined for the <file>misc</file> subdirectory
9081 should not be included in the same package as 75dpi
9082 or 100dpi fonts; instead, they should be provided in
9083 a separate package with <tt>-misc</tt> appended to
9088 Font packages must not provide the files
9089 <file>fonts.dir</file>, <file>fonts.alias</file>, or
9090 <file>fonts.scale</file> in a font directory:
9093 <file>fonts.dir</file> files must not be provided at all.
9097 <file>fonts.alias</file> and <file>fonts.scale</file>
9098 files, if needed, should be provided in the
9100 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
9101 where <var>fontdir</var> is the name of the
9103 <file>/usr/share/fonts/X11/</file> where the
9104 package's corresponding fonts are stored
9105 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
9106 <var>package</var> is the name of the package
9107 that provides these fonts, and
9108 <var>extension</var> is either <tt>scale</tt>
9109 or <tt>alias</tt>, whichever corresponds to
9116 Font packages must declare a dependency on
9117 <tt>xfonts-utils</tt> in their <tt>Depends</tt>
9118 or <tt>Pre-Depends</tt> control field.
9122 Font packages that provide one or more
9123 <file>fonts.scale</file> files as described above must
9124 invoke <prgn>update-fonts-scale</prgn> on each
9125 directory into which they installed fonts
9126 <em>before</em> invoking
9127 <prgn>update-fonts-dir</prgn> on that directory.
9128 This invocation must occur in both the
9129 <prgn>postinst</prgn> (for all arguments) and
9130 <prgn>postrm</prgn> (for all arguments except
9131 <tt>upgrade</tt>) scripts.
9135 Font packages that provide one or more
9136 <file>fonts.alias</file> files as described above must
9137 invoke <prgn>update-fonts-alias</prgn> on each
9138 directory into which they installed fonts. This
9139 invocation must occur in both the
9140 <prgn>postinst</prgn> (for all arguments) and
9141 <prgn>postrm</prgn> (for all arguments except
9142 <tt>upgrade</tt>) scripts.
9146 Font packages must invoke
9147 <prgn>update-fonts-dir</prgn> on each directory into
9148 which they installed fonts. This invocation must
9149 occur in both the <prgn>postinst</prgn> (for all
9150 arguments) and <prgn>postrm</prgn> (for all
9151 arguments except <tt>upgrade</tt>) scripts.
9155 Font packages must not provide alias names for the
9156 fonts they include which collide with alias names
9157 already in use by fonts already packaged.
9161 Font packages must not provide fonts with the same
9162 XLFD registry name as another font already packaged.
9168 <sect1 id="appdefaults">
9169 <heading>Application defaults files</heading>
9172 Application defaults files must be installed in the
9173 directory <file>/etc/X11/app-defaults/</file> (use of a
9174 localized subdirectory of <file>/etc/X11/</file> as described
9175 in the <em>X Toolkit Intrinsics - C Language
9176 Interface</em> manual is also permitted). They must be
9177 registered as <tt>conffile</tt>s or handled as
9178 configuration files.
9182 Customization of programs' X resources may also be
9183 supported with the provision of a file with the same name
9184 as that of the package placed in
9185 the <file>/etc/X11/Xresources/</file> directory, which
9186 must be registered as a <tt>conffile</tt> or handled as a
9187 configuration file.<footnote>
9188 Note that this mechanism is not the same as using
9189 app-defaults; app-defaults are tied to the client
9190 binary on the local file system, whereas X resources
9191 are stored in the X server and affect all connecting
9198 <heading>Installation directory issues</heading>
9201 Historically, packages using the X Window System used a
9202 separate set of installation directories from other packages.
9203 This practice has been discontinued and packages using the X
9204 Window System should now generally be installed in the same
9205 directories as any other package. Specifically, packages must
9206 not install files under the <file>/usr/X11R6/</file> directory
9207 and the <file>/usr/X11R6/</file> directory hierarchy should be
9208 regarded as obsolete.
9212 Include files previously installed under
9213 <file>/usr/X11R6/include/X11/</file> should be installed into
9214 <file>/usr/include/X11/</file>. For files previously
9215 installed into subdirectories of
9216 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
9217 determine if subdirectories of <file>/usr/lib/</file> and
9218 <file>/usr/share/</file> can be used. If not, a subdirectory
9219 of <file>/usr/lib/X11/</file> should be used.
9223 Configuration files for window, display, or session managers
9224 or other applications that are tightly integrated with the X
9225 Window System may be placed in a subdirectory
9226 of <file>/etc/X11/</file> corresponding to the package name.
9227 Other X Window System applications should use
9228 the <file>/etc/</file> directory unless otherwise mandated by
9229 policy (such as for <ref id="appdefaults">).
9234 <heading>The OSF/Motif and OpenMotif libraries</heading>
9237 <em>Programs that require the non-DFSG-compliant OSF/Motif or
9238 OpenMotif libraries</em><footnote>
9239 OSF/Motif and OpenMotif are collectively referred to as
9240 "Motif" in this policy document.
9242 should be compiled against and tested with LessTif (a free
9243 re-implementation of Motif) instead. If the maintainer
9244 judges that the program or programs do not work
9245 sufficiently well with LessTif to be distributed and
9246 supported, but do so when compiled against Motif, then two
9247 versions of the package should be created; one linked
9248 statically against Motif and with <tt>-smotif</tt>
9249 appended to the package name, and one linked dynamically
9250 against Motif and with <tt>-dmotif</tt> appended to the
9255 Both Motif-linked versions are dependent
9256 upon non-DFSG-compliant software and thus cannot be
9257 uploaded to the <em>main</em> distribution; if the
9258 software is itself DFSG-compliant it may be uploaded to
9259 the <em>contrib</em> distribution. While known existing
9260 versions of Motif permit unlimited redistribution of
9261 binaries linked against the library (whether statically or
9262 dynamically), it is the package maintainer's
9263 responsibility to determine whether this is permitted by
9264 the license of the copy of Motif in their possession.
9270 <heading>Perl programs and modules</heading>
9273 Perl programs and modules should follow the current Perl policy.
9277 The Perl policy can be found in the <tt>perl-policy</tt>
9278 files in the <tt>debian-policy</tt> package.
9279 It is also available from the Debian web mirrors at
9280 <tt><url name="/doc/packaging-manuals/perl-policy/"
9281 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
9286 <heading>Emacs lisp programs</heading>
9289 Please refer to the "Debian Emacs Policy" for details of how to
9290 package emacs lisp programs.
9294 The Emacs policy is available in
9295 <file>debian-emacs-policy.gz</file> of the
9296 <package>emacsen-common</package> package.
9297 It is also available from the Debian web mirrors at
9298 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
9299 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
9304 <heading>Games</heading>
9307 The permissions on <file>/var/games</file> are mode 755, owner
9308 <tt>root</tt> and group <tt>root</tt>.
9312 Each game decides on its own security policy.</p>
9315 Games which require protected, privileged access to
9316 high-score files, saved games, etc., may be made
9317 set-<em>group</em>-id (mode 2755) and owned by
9318 <tt>root:games</tt>, and use files and directories with
9319 appropriate permissions (770 <tt>root:games</tt>, for
9320 example). They must not be made
9321 set-<em>user</em>-id, as this causes security problems. (If
9322 an attacker can subvert any set-user-id game they can
9323 overwrite the executable of any other, causing other players
9324 of these games to run a Trojan horse program. With a
9325 set-group-id game the attacker only gets access to less
9326 important game data, and if they can get at the other
9327 players' accounts at all it will take considerably more
9331 Some packages, for example some fortune cookie programs, are
9332 configured by the upstream authors to install with their
9333 data files or other static information made unreadable so
9334 that they can only be accessed through set-id programs
9335 provided. You should not do this in a Debian package: anyone can
9336 download the <file>.deb</file> file and read the data from it,
9337 so there is no point making the files unreadable. Not
9338 making the files unreadable also means that you don't have
9339 to make so many programs set-id, which reduces the risk of a
9343 As described in the FHS, binaries of games should be
9344 installed in the directory <file>/usr/games</file>. This also
9345 applies to games that use the X Window System. Manual pages
9346 for games (X and non-X games) should be installed in
9347 <file>/usr/share/man/man6</file>.</p>
9353 <heading>Documentation</heading>
9356 <heading>Manual pages</heading>
9359 You should install manual pages in <prgn>nroff</prgn> source
9360 form, in appropriate places under <file>/usr/share/man</file>.
9361 You should only use sections 1 to 9 (see the FHS for more
9362 details). You must not install a pre-formatted "cat page".
9366 Each program, utility, and function should have an
9367 associated manual page included in the same package. It is
9368 suggested that all configuration files also have a manual
9369 page included as well. Manual pages for protocols and other
9370 auxiliary things are optional.
9374 If no manual page is available, this is considered as a bug
9375 and should be reported to the Debian Bug Tracking System (the
9376 maintainer of the package is allowed to write this bug report
9377 themselves, if they so desire). Do not close the bug report
9378 until a proper man page is available.<footnote>
9379 It is not very hard to write a man page. See the
9380 <url id="http://www.schweikhardt.net/man_page_howto.html"
9381 name="Man-Page-HOWTO">,
9382 <manref name="man" section="7">, the examples
9383 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
9384 the helper program <prgn>help2man</prgn>, or the
9385 directory <file>/usr/share/doc/man-db/examples</file>.
9390 You may forward a complaint about a missing man page to the
9391 upstream authors, and mark the bug as forwarded in the
9392 Debian bug tracking system. Even though the GNU Project do
9393 not in general consider the lack of a man page to be a bug,
9394 we do; if they tell you that they don't consider it a bug
9395 you should leave the bug in our bug tracking system open
9400 Manual pages should be installed compressed using <tt>gzip -9</tt>.
9404 If one man page needs to be accessible via several names it
9405 is better to use a symbolic link than the <file>.so</file>
9406 feature, but there is no need to fiddle with the relevant
9407 parts of the upstream source to change from <file>.so</file> to
9408 symlinks: don't do it unless it's easy. You should not
9409 create hard links in the manual page directories, nor put
9410 absolute filenames in <file>.so</file> directives. The filename
9411 in a <file>.so</file> in a man page should be relative to the
9412 base of the man page tree (usually
9413 <file>/usr/share/man</file>). If you do not create any links
9414 (whether symlinks, hard links, or <tt>.so</tt> directives)
9415 in the file system to the alternate names of the man page,
9416 then you should not rely on <prgn>man</prgn> finding your
9417 man page under those names based solely on the information in
9418 the man page's header.<footnote>
9419 Supporting this in <prgn>man</prgn> often requires
9420 unreasonable processing time to find a manual page or to
9421 report that none exists, and moves knowledge into man's
9422 database that would be better left in the file system.
9423 This support is therefore deprecated and will cease to
9424 be present in the future.
9429 Manual pages in locale-specific subdirectories of
9430 <file>/usr/share/man</file> should use either UTF-8 or the usual
9431 legacy encoding for that language (normally the one corresponding
9432 to the shortest relevant locale name in
9433 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
9434 <file>/usr/share/man/fr</file> should use either UTF-8 or
9435 ISO-8859-1.<footnote>
9436 <prgn>man</prgn> will automatically detect whether UTF-8 is in
9437 use. In future, all manual pages will be required to use
9443 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
9444 included in the subdirectory name unless it indicates a
9445 significant difference in the language, as this excludes
9446 speakers of the language in other countries.<footnote>
9447 At the time of writing, Chinese and Portuguese are the main
9448 languages with such differences, so <file>pt_BR</file>,
9449 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
9454 If a localized version of a manual page is provided, it should
9455 either be up-to-date or it should be obvious to the reader that
9456 it is outdated and the original manual page should be used
9457 instead. This can be done either by a note at the beginning of
9458 the manual page or by showing the missing or changed portions in
9459 the original language instead of the target language.
9464 <heading>Info documents</heading>
9467 Info documents should be installed in <file>/usr/share/info</file>.
9468 They should be compressed with <tt>gzip -9</tt>.
9472 The <prgn>install-info</prgn> program maintains a directory of
9473 installed info documents in <file>/usr/share/info/dir</file> for
9474 the use of info readers.<footnote>
9475 It was previously necessary for packages installing info
9476 documents to run <prgn>install-info</prgn> from maintainer
9477 scripts. This is no longer necessary. The installation
9478 system now uses dpkg triggers.
9480 This file must not be included in packages. Packages containing
9481 info documents should depend on <tt>dpkg (>= 1.15.4) |
9482 install-info</tt> to ensure that the directory file is properly
9483 rebuilt during partial upgrades from Debian 5.0 (lenny) and
9488 Info documents should contain section and directory entry
9489 information in the document for the use
9490 of <prgn>install-info</prgn>. The section should be specified
9491 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
9492 space and the section of this info page. The directory entry or
9493 entries should be included between
9494 a <tt>START-INFO-DIR-ENTRY</tt> line and
9495 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
9497 INFO-DIR-SECTION Individual utilities
9498 START-INFO-DIR-ENTRY
9499 * example: (example). An example info directory entry.
9502 To determine which section to use, you should look
9503 at <file>/usr/share/info/dir</file> on your system and choose
9504 the most relevant (or create a new section if none of the
9505 current sections are relevant).<footnote>
9506 Normally, info documents are generated from Texinfo source.
9507 To include this information in the generated info document, if
9508 it is absent, add commands like:
9510 @dircategory Individual utilities
9512 * example: (example). An example info directory entry.
9515 to the Texinfo source of the document and ensure that the info
9516 documents are rebuilt from source during the package build.
9522 <heading>Additional documentation</heading>
9525 Any additional documentation that comes with the package may
9526 be installed at the discretion of the package maintainer.
9527 Plain text documentation should be installed in the directory
9528 <file>/usr/share/doc/<var>package</var></file>, where
9529 <var>package</var> is the name of the package, and
9530 compressed with <tt>gzip -9</tt> unless it is small.
9534 If a package comes with large amounts of documentation which
9535 many users of the package will not require you should create
9536 a separate binary package to contain it, so that it does not
9537 take up disk space on the machines of users who do not need
9538 or want it installed.</p>
9541 It is often a good idea to put text information files
9542 (<file>README</file>s, changelogs, and so forth) that come with
9543 the source package in <file>/usr/share/doc/<var>package</var></file>
9544 in the binary package. However, you don't need to install
9545 the instructions for building and installing the package, of
9549 Packages must not require the existence of any files in
9550 <file>/usr/share/doc/</file> in order to function
9552 The system administrator should be able to
9553 delete files in <file>/usr/share/doc/</file> without causing
9554 any programs to break.
9556 Any files that are referenced by programs but are also
9557 useful as stand alone documentation should be installed under
9558 <file>/usr/share/<var>package</var>/</file> with symbolic links from
9559 <file>/usr/share/doc/<var>package</var></file>.
9563 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9564 link to another directory in <file>/usr/share/doc</file> only if
9565 the two packages both come from the same source and the
9566 first package Depends on the second.<footnote>
9568 Please note that this does not override the section on
9569 changelog files below, so the file
9570 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
9571 must refer to the changelog for the current version of
9572 <var>package</var> in question. In practice, this means
9573 that the sources of the target and the destination of the
9574 symlink must be the same (same source package and
9581 Former Debian releases placed all additional documentation
9582 in <file>/usr/doc/<var>package</var></file>. This has been
9583 changed to <file>/usr/share/doc/<var>package</var></file>,
9584 and packages must not put documentation in the directory
9585 <file>/usr/doc/<var>package</var></file>. <footnote>
9586 At this phase of the transition, we no longer require a
9587 symbolic link in <file>/usr/doc/</file>. At a later point,
9588 policy shall change to make the symbolic links a bug.
9594 <heading>Preferred documentation formats</heading>
9597 The unification of Debian documentation is being carried out
9601 If your package comes with extensive documentation in a
9602 markup format that can be converted to various other formats
9603 you should if possible ship HTML versions in a binary
9604 package, in the directory
9605 <file>/usr/share/doc/<var>appropriate-package</var></file> or
9606 its subdirectories.<footnote>
9607 The rationale: The important thing here is that HTML
9608 docs should be available in <em>some</em> package, not
9609 necessarily in the main binary package.
9614 Other formats such as PostScript may be provided at the
9615 package maintainer's discretion.
9619 <sect id="copyrightfile">
9620 <heading>Copyright information</heading>
9623 Every package must be accompanied by a verbatim copy of its
9624 copyright information and distribution license in the file
9625 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
9626 file must neither be compressed nor be a symbolic link.
9630 In addition, the copyright file must say where the upstream
9631 sources (if any) were obtained. It should name the original
9632 authors of the package and the Debian maintainer(s) who were
9633 involved with its creation.
9637 Packages in the <em>contrib</em> or <em>non-free</em> archive
9638 areas should state in the copyright file that the package is not
9639 part of the Debian GNU/Linux distribution and briefly explain
9644 A copy of the file which will be installed in
9645 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9646 be in <file>debian/copyright</file> in the source package.
9650 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9651 link to another directory in <file>/usr/share/doc</file> only if
9652 the two packages both come from the same source and the
9653 first package Depends on the second. These rules are
9654 important because copyrights must be extractable by
9659 Packages distributed under the Apache license (version 2.0), the
9660 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
9661 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
9662 1.3) should refer to the corresponding files
9663 under <file>/usr/share/common-licenses</file>,<footnote>
9666 <file>/usr/share/common-licenses/Apache-2.0</file>,
9667 <file>/usr/share/common-licenses/Artistic</file>,
9668 <file>/usr/share/common-licenses/GPL-1</file>,
9669 <file>/usr/share/common-licenses/GPL-2</file>,
9670 <file>/usr/share/common-licenses/GPL-3</file>,
9671 <file>/usr/share/common-licenses/LGPL-2</file>,
9672 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9673 <file>/usr/share/common-licenses/LGPL-3</file>,
9674 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
9675 <file>/usr/share/common-licenses/GFDL-1.3</file>
9676 respectively. The University of California BSD license is
9677 also included in <package>base-files</package> as
9678 <file>/usr/share/common-licenses/BSD</file>, but given the
9679 brevity of this license, its specificity to code whose
9680 copyright is held by the Regents of the University of
9681 California, and the frequency of minor wording changes, its
9682 text should be included in the copyright file rather than
9683 referencing this file.
9685 </footnote> rather than quoting them in the copyright
9690 You should not use the copyright file as a general <file>README</file>
9691 file. If your package has such a file it should be
9692 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9693 <file>README.Debian</file> or some other appropriate place.</p>
9697 <heading>Examples</heading>
9700 Any examples (configurations, source files, whatever),
9701 should be installed in a directory
9702 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9703 files should not be referenced by any program: they're there
9704 for the benefit of the system administrator and users as
9705 documentation only. Architecture-specific example files
9706 should be installed in a directory
9707 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9709 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9710 latter directory itself may be a symbolic link to the
9715 If the purpose of a package is to provide examples, then the
9716 example files may be installed into
9717 <file>/usr/share/doc/<var>package</var></file>.
9721 <sect id="changelogs">
9722 <heading>Changelog files</heading>
9725 Packages that are not Debian-native must contain a
9726 compressed copy of the <file>debian/changelog</file> file from
9727 the Debian source tree in
9728 <file>/usr/share/doc/<var>package</var></file> with the name
9729 <file>changelog.Debian.gz</file>.
9733 If an upstream changelog is available, it should be accessible as
9734 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9735 plain text. If the upstream changelog is distributed in
9736 HTML, it should be made available in that form as
9737 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9738 and a plain text <file>changelog.gz</file> should be generated
9739 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9740 the upstream changelog files do not already conform to this
9741 naming convention, then this may be achieved either by
9742 renaming the files, or by adding a symbolic link, at the
9743 maintainer's discretion.<footnote>
9744 Rationale: People should not have to look in places for
9745 upstream changelogs merely because they are given
9746 different names or are distributed in HTML format.
9751 All of these files should be installed compressed using
9752 <tt>gzip -9</tt>, as they will become large with time even
9753 if they start out small.
9757 If the package has only one changelog which is used both as
9758 the Debian changelog and the upstream one because there is
9759 no separate upstream maintainer then that changelog should
9760 usually be installed as
9761 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9762 there is a separate upstream maintainer, but no upstream
9763 changelog, then the Debian changelog should still be called
9764 <file>changelog.Debian.gz</file>.
9768 For details about the format and contents of the Debian
9769 changelog file, please see <ref id="dpkgchangelog">.
9774 <appendix id="pkg-scope">
9775 <heading>Introduction and scope of these appendices</heading>
9778 These appendices are taken essentially verbatim from the
9779 now-deprecated Packaging Manual, version 3.2.1.0. They are
9780 the chapters which are likely to be of use to package
9781 maintainers and which have not already been included in the
9782 policy document itself. Most of these sections are very likely
9783 not relevant to policy; they should be treated as
9784 documentation for the packaging system. Please note that these
9785 appendices are included for convenience, and for historical
9786 reasons: they used to be part of policy package, and they have
9787 not yet been incorporated into dpkg documentation. However,
9788 they still have value, and hence they are presented here.
9792 They have not yet been checked to ensure that they are
9793 compatible with the contents of policy, and if there are any
9794 contradictions, the version in the main policy document takes
9795 precedence. The remaining chapters of the old Packaging
9796 Manual have also not been read in detail to ensure that there
9797 are not parts which have been left out. Both of these will be
9802 Certain parts of the Packaging manual were integrated into the
9803 Policy Manual proper, and removed from the appendices. Links
9804 have been placed from the old locations to the new ones.
9808 <prgn>dpkg</prgn> is a suite of programs for creating binary
9809 package files and installing and removing them on Unix
9811 <prgn>dpkg</prgn> is targeted primarily at Debian
9812 GNU/Linux, but may work on or be ported to other
9818 The binary packages are designed for the management of
9819 installed executable programs (usually compiled binaries) and
9820 their associated data, though source code examples and
9821 documentation are provided as part of some packages.</p>
9824 This manual describes the technical aspects of creating Debian
9825 binary packages (<file>.deb</file> files). It documents the
9826 behavior of the package management programs
9827 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9828 they interact with packages.</p>
9831 It also documents the interaction between
9832 <prgn>dselect</prgn>'s core and the access method scripts it
9833 uses to actually install the selected packages, and describes
9834 how to create a new access method.</p>
9837 This manual does not go into detail about the options and
9838 usage of the package building and installation tools. It
9839 should therefore be read in conjunction with those programs'
9844 The utility programs which are provided with <prgn>dpkg</prgn>
9845 for managing various system configuration and similar issues,
9846 such as <prgn>update-rc.d</prgn> and
9847 <prgn>install-info</prgn>, are not described in detail here -
9848 please see their man pages.
9852 It is assumed that the reader is reasonably familiar with the
9853 <prgn>dpkg</prgn> System Administrators' manual.
9854 Unfortunately this manual does not yet exist.
9858 The Debian version of the FSF's GNU hello program is provided
9859 as an example for people wishing to create Debian
9860 packages. The Debian <prgn>debmake</prgn> package is
9861 recommended as a very helpful tool in creating and maintaining
9862 Debian packages. However, while the tools and examples are
9863 helpful, they do not replace the need to read and follow the
9864 Policy and Programmer's Manual.</p>
9867 <appendix id="pkg-binarypkg">
9868 <heading>Binary packages (from old Packaging Manual)</heading>
9871 The binary package has two main sections. The first part
9872 consists of various control information files and scripts used
9873 by <prgn>dpkg</prgn> when installing and removing. See <ref
9874 id="pkg-controlarea">.
9878 The second part is an archive containing the files and
9879 directories to be installed.
9883 In the future binary packages may also contain other
9884 components, such as checksums and digital signatures. The
9885 format for the archive is described in full in the
9886 <file>deb(5)</file> man page.
9890 <sect id="pkg-bincreating"><heading>Creating package files -
9891 <prgn>dpkg-deb</prgn>
9895 All manipulation of binary package files is done by
9896 <prgn>dpkg-deb</prgn>; it's the only program that has
9897 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9898 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9899 will spot that the options requested are appropriate to
9900 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9905 In order to create a binary package you must make a
9906 directory tree which contains all the files and directories
9907 you want to have in the file system data part of the package.
9908 In Debian-format source packages this directory is usually
9909 <file>debian/tmp</file>, relative to the top of the package's
9914 They should have the locations (relative to the root of the
9915 directory tree you're constructing) ownerships and
9916 permissions which you want them to have on the system when
9921 With current versions of <prgn>dpkg</prgn> the uid/username
9922 and gid/groupname mappings for the users and groups being
9923 used should be the same on the system where the package is
9924 built and the one where it is installed.
9928 You need to add one special directory to the root of the
9929 miniature file system tree you're creating:
9930 <prgn>DEBIAN</prgn>. It should contain the control
9931 information files, notably the binary package control file
9932 (see <ref id="pkg-controlfile">).
9936 The <prgn>DEBIAN</prgn> directory will not appear in the
9937 file system archive of the package, and so won't be installed
9938 by <prgn>dpkg</prgn> when the package is unpacked.
9942 When you've prepared the package, you should invoke:
9944 dpkg --build <var>directory</var>
9949 This will build the package in
9950 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9951 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9952 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9957 See the man page <manref name="dpkg-deb" section="8"> for details of how
9958 to examine the contents of this newly-created file. You may find the
9959 output of following commands enlightening:
9961 dpkg-deb --info <var>filename</var>.deb
9962 dpkg-deb --contents <var>filename</var>.deb
9963 dpkg --contents <var>filename</var>.deb
9965 To view the copyright file for a package you could use this command:
9967 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
9972 <sect id="pkg-controlarea">
9973 <heading>Package control information files</heading>
9976 The control information portion of a binary package is a
9977 collection of files with names known to <prgn>dpkg</prgn>.
9978 It will treat the contents of these files specially - some
9979 of them contain information used by <prgn>dpkg</prgn> when
9980 installing or removing the package; others are scripts which
9981 the package maintainer wants <prgn>dpkg</prgn> to run.
9985 It is possible to put other files in the package control
9986 information file area, but this is not generally a good idea
9987 (though they will largely be ignored).
9991 Here is a brief list of the control information files supported
9992 by <prgn>dpkg</prgn> and a summary of what they're used for.
9997 <tag><tt>control</tt>
10000 This is the key description file used by
10001 <prgn>dpkg</prgn>. It specifies the package's name
10002 and version, gives its description for the user,
10003 states its relationships with other packages, and so
10004 forth. See <ref id="sourcecontrolfiles"> and
10005 <ref id="binarycontrolfiles">.
10009 It is usually generated automatically from information
10010 in the source package by the
10011 <prgn>dpkg-gencontrol</prgn> program, and with
10012 assistance from <prgn>dpkg-shlibdeps</prgn>.
10013 See <ref id="pkg-sourcetools">.
10017 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
10022 These are executable files (usually scripts) which
10023 <prgn>dpkg</prgn> runs during installation, upgrade
10024 and removal of packages. They allow the package to
10025 deal with matters which are particular to that package
10026 or require more complicated processing than that
10027 provided by <prgn>dpkg</prgn>. Details of when and
10028 how they are called are in <ref id="maintainerscripts">.
10032 It is very important to make these scripts idempotent.
10033 See <ref id="idempotency">.
10037 The maintainer scripts are not guaranteed to run with a
10038 controlling terminal and may not be able to interact with
10039 the user. See <ref id="controllingterminal">.
10043 <tag><tt>conffiles</tt>
10046 This file contains a list of configuration files which
10047 are to be handled automatically by <prgn>dpkg</prgn>
10048 (see <ref id="pkg-conffiles">). Note that not necessarily
10049 every configuration file should be listed here.
10052 <tag><tt>shlibs</tt>
10055 This file contains a list of the shared libraries
10056 supplied by the package, with dependency details for
10057 each. This is used by <prgn>dpkg-shlibdeps</prgn>
10058 when it determines what dependencies are required in a
10059 package control file. The <tt>shlibs</tt> file format
10060 is described on <ref id="shlibs">.
10065 <sect id="pkg-controlfile">
10066 <heading>The main control information file: <tt>control</tt></heading>
10069 The most important control information file used by
10070 <prgn>dpkg</prgn> when it installs a package is
10071 <tt>control</tt>. It contains all the package's "vital
10076 The binary package control files of packages built from
10077 Debian sources are made by a special tool,
10078 <prgn>dpkg-gencontrol</prgn>, which reads
10079 <file>debian/control</file> and <file>debian/changelog</file> to
10080 find the information it needs. See <ref id="pkg-sourcepkg"> for
10085 The fields in binary package control files are listed in
10086 <ref id="binarycontrolfiles">.
10090 A description of the syntax of control files and the purpose
10091 of the fields is available in <ref id="controlfields">.
10096 <heading>Time Stamps</heading>
10099 See <ref id="timestamps">.
10104 <appendix id="pkg-sourcepkg">
10105 <heading>Source packages (from old Packaging Manual) </heading>
10108 The Debian binary packages in the distribution are generated
10109 from Debian sources, which are in a special format to assist
10110 the easy and automatic building of binaries.
10113 <sect id="pkg-sourcetools">
10114 <heading>Tools for processing source packages</heading>
10117 Various tools are provided for manipulating source packages;
10118 they pack and unpack sources and help build of binary
10119 packages and help manage the distribution of new versions.
10123 They are introduced and typical uses described here; see
10124 <manref name="dpkg-source" section="1"> for full
10125 documentation about their arguments and operation.
10129 For examples of how to construct a Debian source package,
10130 and how to use those utilities that are used by Debian
10131 source packages, please see the <prgn>hello</prgn> example
10135 <sect1 id="pkg-dpkg-source">
10137 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
10142 This program is frequently used by hand, and is also
10143 called from package-independent automated building scripts
10144 such as <prgn>dpkg-buildpackage</prgn>.
10148 To unpack a package it is typically invoked with
10150 dpkg-source -x <var>.../path/to/filename</var>.dsc
10155 with the <file><var>filename</var>.tar.gz</file> and
10156 <file><var>filename</var>.diff.gz</file> (if applicable) in
10157 the same directory. It unpacks into
10158 <file><var>package</var>-<var>version</var></file>, and if
10160 <file><var>package</var>-<var>version</var>.orig</file>, in
10161 the current directory.
10165 To create a packed source archive it is typically invoked:
10167 dpkg-source -b <var>package</var>-<var>version</var>
10172 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
10173 <file>.diff.gz</file> (if appropriate) in the current
10174 directory. <prgn>dpkg-source</prgn> does not clean the
10175 source tree first - this must be done separately if it is
10180 See also <ref id="pkg-sourcearchives">.</p>
10184 <sect1 id="pkg-dpkg-buildpackage">
10186 <prgn>dpkg-buildpackage</prgn> - overall package-building
10191 <prgn>dpkg-buildpackage</prgn> is a script which invokes
10192 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
10193 targets <tt>clean</tt>, <tt>build</tt> and
10194 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
10195 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
10196 source and binary package upload.
10200 It is usually invoked by hand from the top level of the
10201 built or unbuilt source directory. It may be invoked with
10202 no arguments; useful arguments include:
10203 <taglist compact="compact">
10204 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
10207 Do not sign the <tt>.changes</tt> file or the
10208 source package <tt>.dsc</tt> file, respectively.</p>
10210 <tag><tt>-p<var>sign-command</var></tt></tag>
10213 Invoke <var>sign-command</var> instead of finding
10214 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
10215 <var>sign-command</var> must behave just like
10216 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
10218 <tag><tt>-r<var>root-command</var></tt></tag>
10221 When root privilege is required, invoke the command
10222 <var>root-command</var>. <var>root-command</var>
10223 should invoke its first argument as a command, from
10224 the <prgn>PATH</prgn> if necessary, and pass its
10225 second and subsequent arguments to the command it
10226 calls. If no <var>root-command</var> is supplied
10227 then <var>dpkg-buildpackage</var> will take no
10228 special action to gain root privilege, so that for
10229 most packages it will have to be invoked as root to
10232 <tag><tt>-b</tt>, <tt>-B</tt></tag>
10235 Two types of binary-only build and upload - see
10236 <manref name="dpkg-source" section="1">.
10243 <sect1 id="pkg-dpkg-gencontrol">
10245 <prgn>dpkg-gencontrol</prgn> - generates binary package
10250 This program is usually called from <file>debian/rules</file>
10251 (see <ref id="pkg-sourcetree">) in the top level of the source
10256 This is usually done just before the files and directories in the
10257 temporary directory tree where the package is being built have their
10258 permissions and ownerships set and the package is constructed using
10259 <prgn>dpkg-deb/</prgn>
10261 This is so that the control file which is produced has
10262 the right permissions
10267 <prgn>dpkg-gencontrol</prgn> must be called after all the
10268 files which are to go into the package have been placed in
10269 the temporary build directory, so that its calculation of
10270 the installed size of a package is correct.
10274 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
10275 be run after <prgn>dpkg-shlibdeps</prgn> so that the
10276 variable substitutions created by
10277 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
10282 For a package which generates only one binary package, and
10283 which builds it in <file>debian/tmp</file> relative to the top
10284 of the source package, it is usually sufficient to call
10285 <prgn>dpkg-gencontrol</prgn>.
10289 Sources which build several binaries will typically need
10292 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
10293 </example> The <tt>-P</tt> tells
10294 <prgn>dpkg-gencontrol</prgn> that the package is being
10295 built in a non-default directory, and the <tt>-p</tt>
10296 tells it which package's control file should be generated.
10300 <prgn>dpkg-gencontrol</prgn> also adds information to the
10301 list of files in <file>debian/files</file>, for the benefit of
10302 (for example) a future invocation of
10303 <prgn>dpkg-genchanges</prgn>.</p>
10306 <sect1 id="pkg-dpkg-shlibdeps">
10308 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
10313 This program is usually called from <file>debian/rules</file>
10314 just before <prgn>dpkg-gencontrol</prgn> (see <ref
10315 id="pkg-sourcetree">), in the top level of the source tree.
10319 Its arguments are executables and shared libraries
10322 They may be specified either in the locations in the
10323 source tree where they are created or in the locations
10324 in the temporary build tree where they are installed
10325 prior to binary package creation.
10327 </footnote> for which shared library dependencies should
10328 be included in the binary package's control file.
10332 If some of the found shared libraries should only
10333 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
10334 some warrant a <tt>Pre-Depends</tt>, this can be achieved
10335 by using the <tt>-d<var>dependency-field</var></tt> option
10336 before those executable(s). (Each <tt>-d</tt> option
10337 takes effect until the next <tt>-d</tt>.)
10341 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
10342 output control file to be modified. Instead by default it
10343 adds to the <file>debian/substvars</file> file variable
10344 settings like <tt>shlibs:Depends</tt>. These variable
10345 settings must be referenced in dependency fields in the
10346 appropriate per-binary-package sections of the source
10351 For example, a package that generates an essential part
10352 which requires dependencies, and optional parts that
10353 which only require a recommendation, would separate those
10354 two sets of dependencies into two different fields.<footnote>
10355 At the time of writing, an example for this was the
10356 <package/xmms/ package, with Depends used for the xmms
10357 executable, Recommends for the plug-ins and Suggests for
10358 even more optional features provided by unzip.
10360 It can say in its <file>debian/rules</file>:
10362 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
10363 -dRecommends <var>optionalpart anotheroptionalpart</var>
10365 and then in its main control file <file>debian/control</file>:
10368 Depends: ${shlibs:Depends}
10369 Recommends: ${shlibs:Recommends}
10375 Sources which produce several binary packages with
10376 different shared library dependency requirements can use
10377 the <tt>-p<var>varnameprefix</var></tt> option to override
10378 the default <tt>shlibs:</tt> prefix (one invocation of
10379 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
10380 They can thus produce several sets of dependency
10381 variables, each of the form
10382 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
10383 which can be referred to in the appropriate parts of the
10384 binary package control files.
10389 <sect1 id="pkg-dpkg-distaddfile">
10391 <prgn>dpkg-distaddfile</prgn> - adds a file to
10392 <file>debian/files</file>
10396 Some packages' uploads need to include files other than
10397 the source and binary package files.
10401 <prgn>dpkg-distaddfile</prgn> adds a file to the
10402 <file>debian/files</file> file so that it will be included in
10403 the <file>.changes</file> file when
10404 <prgn>dpkg-genchanges</prgn> is run.
10408 It is usually invoked from the <tt>binary</tt> target of
10409 <file>debian/rules</file>:
10411 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
10413 The <var>filename</var> is relative to the directory where
10414 <prgn>dpkg-genchanges</prgn> will expect to find it - this
10415 is usually the directory above the top level of the source
10416 tree. The <file>debian/rules</file> target should put the
10417 file there just before or just after calling
10418 <prgn>dpkg-distaddfile</prgn>.
10422 The <var>section</var> and <var>priority</var> are passed
10423 unchanged into the resulting <file>.changes</file> file.
10428 <sect1 id="pkg-dpkg-genchanges">
10430 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
10431 upload control file
10435 This program is usually called by package-independent
10436 automatic building scripts such as
10437 <prgn>dpkg-buildpackage</prgn>, but it may also be called
10442 It is usually called in the top level of a built source
10443 tree, and when invoked with no arguments will print out a
10444 straightforward <file>.changes</file> file based on the
10445 information in the source package's changelog and control
10446 file and the binary and source packages which should have
10452 <sect1 id="pkg-dpkg-parsechangelog">
10454 <prgn>dpkg-parsechangelog</prgn> - produces parsed
10455 representation of a changelog
10459 This program is used internally by
10460 <prgn>dpkg-source</prgn> et al. It may also occasionally
10461 be useful in <file>debian/rules</file> and elsewhere. It
10462 parses a changelog, <file>debian/changelog</file> by default,
10463 and prints a control-file format representation of the
10464 information in it to standard output.
10468 <sect1 id="pkg-dpkg-architecture">
10470 <prgn>dpkg-architecture</prgn> - information about the build and
10475 This program can be used manually, but is also invoked by
10476 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
10477 environment or make variables which specify the build and host
10478 architecture for the package building process.
10483 <sect id="pkg-sourcetree">
10484 <heading>The Debian package source tree</heading>
10487 The source archive scheme described later is intended to
10488 allow a Debian package source tree with some associated
10489 control information to be reproduced and transported easily.
10490 The Debian package source tree is a version of the original
10491 program with certain files added for the benefit of the
10492 packaging process, and with any other changes required
10493 made to the rest of the source code and installation
10498 The extra files created for Debian are in the subdirectory
10499 <file>debian</file> of the top level of the Debian package
10500 source tree. They are described below.
10503 <sect1 id="pkg-debianrules">
10504 <heading><file>debian/rules</file> - the main building script</heading>
10507 See <ref id="debianrules">.
10511 <sect1 id="pkg-srcsubstvars">
10512 <heading><file>debian/substvars</file> and variable substitutions</heading>
10515 See <ref id="substvars">.
10521 <heading><file>debian/files</file></heading>
10524 See <ref id="debianfiles">.
10528 <sect1><heading><file>debian/tmp</file>
10532 This is the canonical temporary location for the
10533 construction of binary packages by the <tt>binary</tt>
10534 target. The directory <file>tmp</file> serves as the root of
10535 the file system tree as it is being constructed (for
10536 example, by using the package's upstream makefiles install
10537 targets and redirecting the output there), and it also
10538 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10539 id="pkg-bincreating">.
10543 If several binary packages are generated from the same
10544 source tree it is usual to use several
10545 <file>debian/tmp<var>something</var></file> directories, for
10546 example <file>tmp-a</file> or <file>tmp-doc</file>.
10550 Whatever <file>tmp</file> directories are created and used by
10551 <tt>binary</tt> must of course be removed by the
10552 <tt>clean</tt> target.</p></sect1>
10556 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10560 As it exists on the FTP site, a Debian source package
10561 consists of three related files. You must have the right
10562 versions of all three to be able to use them.
10567 <tag>Debian source control file - <tt>.dsc</tt></tag>
10569 This file is a control file used by <prgn>dpkg-source</prgn>
10570 to extract a source package.
10571 See <ref id="debiansourcecontrolfiles">.
10575 Original source archive -
10577 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10583 This is a compressed (with <tt>gzip -9</tt>)
10584 <prgn>tar</prgn> file containing the source code from
10585 the upstream authors of the program.
10590 Debian package diff -
10592 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10598 This is a unified context diff (<tt>diff -u</tt>)
10599 giving the changes which are required to turn the
10600 original source into the Debian source. These changes
10601 may only include editing and creating plain files.
10602 The permissions of files, the targets of symbolic
10603 links and the characteristics of special files or
10604 pipes may not be changed and no files may be removed
10609 All the directories in the diff must exist, except the
10610 <file>debian</file> subdirectory of the top of the source
10611 tree, which will be created by
10612 <prgn>dpkg-source</prgn> if necessary when unpacking.
10616 The <prgn>dpkg-source</prgn> program will
10617 automatically make the <file>debian/rules</file> file
10618 executable (see below).</p></item>
10623 If there is no original source code - for example, if the
10624 package is specially prepared for Debian or the Debian
10625 maintainer is the same as the upstream maintainer - the
10626 format is slightly different: then there is no diff, and the
10628 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10629 and preferably contains a directory named
10630 <file><var>package</var>-<var>version</var></file>.
10635 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10638 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10639 Debian source package. However, if it is not available it
10640 is possible to unpack a Debian source archive as follows:
10641 <enumlist compact="compact">
10644 Untar the tarfile, which will create a <file>.orig</file>
10648 <p>Rename the <file>.orig</file> directory to
10649 <file><var>package</var>-<var>version</var></file>.</p>
10653 Create the subdirectory <file>debian</file> at the top of
10654 the source tree.</p>
10656 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10658 <item><p>Untar the tarfile again if you want a copy of the original
10659 source code alongside the Debian version.</p>
10664 It is not possible to generate a valid Debian source archive
10665 without using <prgn>dpkg-source</prgn>. In particular,
10666 attempting to use <prgn>diff</prgn> directly to generate the
10667 <file>.diff.gz</file> file will not work.
10671 <heading>Restrictions on objects in source packages</heading>
10674 The source package may not contain any hard links
10676 This is not currently detected when building source
10677 packages, but only when extracting
10681 Hard links may be permitted at some point in the
10682 future, but would require a fair amount of
10684 </footnote>, device special files, sockets or setuid or
10687 Setgid directories are allowed.
10692 The source packaging tools manage the changes between the
10693 original and Debian source using <prgn>diff</prgn> and
10694 <prgn>patch</prgn>. Turning the original source tree as
10695 included in the <file>.orig.tar.gz</file> into the Debian
10696 package source must not involve any changes which cannot be
10697 handled by these tools. Problematic changes which cause
10698 <prgn>dpkg-source</prgn> to halt with an error when
10699 building the source package are:
10700 <list compact="compact">
10701 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10703 <item><p>Changing the targets of symbolic links.</p>
10705 <item><p>Creating directories, other than <file>debian</file>.</p>
10707 <item><p>Changes to the contents of binary files.</p></item>
10708 </list> Changes which cause <prgn>dpkg-source</prgn> to
10709 print a warning but continue anyway are:
10710 <list compact="compact">
10713 Removing files, directories or symlinks.
10715 Renaming a file is not treated specially - it is
10716 seen as the removal of the old file (which
10717 generates a warning, but is otherwise ignored),
10718 and the creation of the new one.
10724 Changed text files which are missing the usual final
10725 newline (either in the original or the modified
10730 Changes which are not represented, but which are not detected by
10731 <prgn>dpkg-source</prgn>, are:
10732 <list compact="compact">
10733 <item><p>Changing the permissions of files (other than
10734 <file>debian/rules</file>) and directories.</p></item>
10739 The <file>debian</file> directory and <file>debian/rules</file>
10740 are handled specially by <prgn>dpkg-source</prgn> - before
10741 applying the changes it will create the <file>debian</file>
10742 directory, and afterwards it will make
10743 <file>debian/rules</file> world-executable.
10749 <appendix id="pkg-controlfields">
10750 <heading>Control files and their fields (from old Packaging Manual)</heading>
10753 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10754 data in a common format, known as control files. Binary and
10755 source packages have control data as do the <file>.changes</file>
10756 files which control the installation of uploaded files, and
10757 <prgn>dpkg</prgn>'s internal databases are in a similar
10762 <heading>Syntax of control files</heading>
10765 See <ref id="controlsyntax">.
10769 It is important to note that there are several fields which
10770 are optional as far as <prgn>dpkg</prgn> and the related
10771 tools are concerned, but which must appear in every Debian
10772 package, or whose omission may cause problems.
10777 <heading>List of fields</heading>
10780 See <ref id="controlfieldslist">.
10784 This section now contains only the fields that didn't belong
10785 to the Policy manual.
10788 <sect1 id="pkg-f-Filename">
10789 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10792 These fields in <tt>Packages</tt> files give the
10793 filename(s) of (the parts of) a package in the
10794 distribution directories, relative to the root of the
10795 Debian hierarchy. If the package has been split into
10796 several parts the parts are all listed in order, separated
10801 <sect1 id="pkg-f-Size">
10802 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10805 These fields in <file>Packages</file> files give the size (in
10806 bytes, expressed in decimal) and MD5 checksum of the
10807 file(s) which make(s) up a binary package in the
10808 distribution. If the package is split into several parts
10809 the values for the parts are listed in order, separated by
10814 <sect1 id="pkg-f-Status">
10815 <heading><tt>Status</tt></heading>
10818 This field in <prgn>dpkg</prgn>'s status file records
10819 whether the user wants a package installed, removed or
10820 left alone, whether it is broken (requiring
10821 re-installation) or not and what its current state on the
10822 system is. Each of these pieces of information is a
10827 <sect1 id="pkg-f-Config-Version">
10828 <heading><tt>Config-Version</tt></heading>
10831 If a package is not installed or not configured, this
10832 field in <prgn>dpkg</prgn>'s status file records the last
10833 version of the package which was successfully
10838 <sect1 id="pkg-f-Conffiles">
10839 <heading><tt>Conffiles</tt></heading>
10842 This field in <prgn>dpkg</prgn>'s status file contains
10843 information about the automatically-managed configuration
10844 files held by a package. This field should <em>not</em>
10845 appear anywhere in a package!
10850 <heading>Obsolete fields</heading>
10853 These are still recognized by <prgn>dpkg</prgn> but should
10854 not appear anywhere any more.
10856 <taglist compact="compact">
10858 <tag><tt>Revision</tt></tag>
10859 <tag><tt>Package-Revision</tt></tag>
10860 <tag><tt>Package_Revision</tt></tag>
10862 The Debian revision part of the package version was
10863 at one point in a separate control field. This
10864 field went through several names.
10867 <tag><tt>Recommended</tt></tag>
10868 <item>Old name for <tt>Recommends</tt>.</item>
10870 <tag><tt>Optional</tt></tag>
10871 <item>Old name for <tt>Suggests</tt>.</item>
10873 <tag><tt>Class</tt></tag>
10874 <item>Old name for <tt>Priority</tt>.</item>
10883 <appendix id="pkg-conffiles">
10884 <heading>Configuration file handling (from old Packaging Manual)</heading>
10887 <prgn>dpkg</prgn> can do a certain amount of automatic
10888 handling of package configuration files.
10892 Whether this mechanism is appropriate depends on a number of
10893 factors, but basically there are two approaches to any
10894 particular configuration file.
10898 The easy method is to ship a best-effort configuration in the
10899 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10900 handle updates. If the user is unlikely to want to edit the
10901 file, but you need them to be able to without losing their
10902 changes, and a new package with a changed version of the file
10903 is only released infrequently, this is a good approach.
10907 The hard method is to build the configuration file from
10908 scratch in the <prgn>postinst</prgn> script, and to take the
10909 responsibility for fixing any mistakes made in earlier
10910 versions of the package automatically. This will be
10911 appropriate if the file is likely to need to be different on
10915 <sect><heading>Automatic handling of configuration files by
10920 A package may contain a control information file called
10921 <tt>conffiles</tt>. This file should be a list of filenames
10922 of configuration files needing automatic handling, separated
10923 by newlines. The filenames should be absolute pathnames,
10924 and the files referred to should actually exist in the
10929 When a package is upgraded <prgn>dpkg</prgn> will process
10930 the configuration files during the configuration stage,
10931 shortly before it runs the package's <prgn>postinst</prgn>
10936 For each file it checks to see whether the version of the
10937 file included in the package is the same as the one that was
10938 included in the last version of the package (the one that is
10939 being upgraded from); it also compares the version currently
10940 installed on the system with the one shipped with the last
10945 If neither the user nor the package maintainer has changed
10946 the file, it is left alone. If one or the other has changed
10947 their version, then the changed version is preferred - i.e.,
10948 if the user edits their file, but the package maintainer
10949 doesn't ship a different version, the user's changes will
10950 stay, silently, but if the maintainer ships a new version
10951 and the user hasn't edited it the new version will be
10952 installed (with an informative message). If both have
10953 changed their version the user is prompted about the problem
10954 and must resolve the differences themselves.
10958 The comparisons are done by calculating the MD5 message
10959 digests of the files, and storing the MD5 of the file as it
10960 was included in the most recent version of the package.
10964 When a package is installed for the first time
10965 <prgn>dpkg</prgn> will install the file that comes with it,
10966 unless that would mean overwriting a file already on the
10971 However, note that <prgn>dpkg</prgn> will <em>not</em>
10972 replace a conffile that was removed by the user (or by a
10973 script). This is necessary because with some programs a
10974 missing file produces an effect hard or impossible to
10975 achieve in another way, so that a missing file needs to be
10976 kept that way if the user did it.
10980 Note that a package should <em>not</em> modify a
10981 <prgn>dpkg</prgn>-handled conffile in its maintainer
10982 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10983 the user confusing and possibly dangerous options for
10984 conffile update when the package is upgraded.</p>
10987 <sect><heading>Fully-featured maintainer script configuration
10992 For files which contain site-specific information such as
10993 the hostname and networking details and so forth, it is
10994 better to create the file in the package's
10995 <prgn>postinst</prgn> script.
10999 This will typically involve examining the state of the rest
11000 of the system to determine values and other information, and
11001 may involve prompting the user for some information which
11002 can't be obtained some other way.
11006 When using this method there are a couple of important
11007 issues which should be considered:
11011 If you discover a bug in the program which generates the
11012 configuration file, or if the format of the file changes
11013 from one version to the next, you will have to arrange for
11014 the postinst script to do something sensible - usually this
11015 will mean editing the installed configuration file to remove
11016 the problem or change the syntax. You will have to do this
11017 very carefully, since the user may have changed the file,
11018 perhaps to fix the very problem that your script is trying
11019 to deal with - you will have to detect these situations and
11020 deal with them correctly.
11024 If you do go down this route it's probably a good idea to
11025 make the program that generates the configuration file(s) a
11026 separate program in <file>/usr/sbin</file>, by convention called
11027 <file><var>package</var>config</file> and then run that if
11028 appropriate from the post-installation script. The
11029 <tt><var>package</var>config</tt> program should not
11030 unquestioningly overwrite an existing configuration - if its
11031 mode of operation is geared towards setting up a package for
11032 the first time (rather than any arbitrary reconfiguration
11033 later) you should have it check whether the configuration
11034 already exists, and require a <tt>--force</tt> flag to
11035 overwrite it.</p></sect>
11038 <appendix id="pkg-alternatives"><heading>Alternative versions of
11039 an interface - <prgn>update-alternatives</prgn> (from old
11044 When several packages all provide different versions of the
11045 same program or file it is useful to have the system select a
11046 default, but to allow the system administrator to change it
11047 and have their decisions respected.
11051 For example, there are several versions of the <prgn>vi</prgn>
11052 editor, and there is no reason to prevent all of them from
11053 being installed at once, each under their own name
11054 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
11055 Nevertheless it is desirable to have the name <tt>vi</tt>
11056 refer to something, at least by default.
11060 If all the packages involved cooperate, this can be done with
11061 <prgn>update-alternatives</prgn>.
11065 Each package provides its own version under its own name, and
11066 calls <prgn>update-alternatives</prgn> in its postinst to
11067 register its version (and again in its prerm to deregister
11072 See the man page <manref name="update-alternatives"
11073 section="8"> for details.
11077 If <prgn>update-alternatives</prgn> does not seem appropriate
11078 you may wish to consider using diversions instead.</p>
11081 <appendix id="pkg-diversions"><heading>Diversions - overriding a
11082 package's version of a file (from old Packaging Manual)
11086 It is possible to have <prgn>dpkg</prgn> not overwrite a file
11087 when it reinstalls the package it belongs to, and to have it
11088 put the file from the package somewhere else instead.
11092 This can be used locally to override a package's version of a
11093 file, or by one package to override another's version (or
11094 provide a wrapper for it).
11098 Before deciding to use a diversion, read <ref
11099 id="pkg-alternatives"> to see if you really want a diversion
11100 rather than several alternative versions of a program.
11104 There is a diversion list, which is read by <prgn>dpkg</prgn>,
11105 and updated by a special program <prgn>dpkg-divert</prgn>.
11106 Please see <manref name="dpkg-divert" section="8"> for full
11107 details of its operation.
11111 When a package wishes to divert a file from another, it should
11112 call <prgn>dpkg-divert</prgn> in its preinst to add the
11113 diversion and rename the existing file. For example,
11114 supposing that a <prgn>smailwrapper</prgn> package wishes to
11115 install a wrapper around <file>/usr/sbin/smail</file>:
11117 dpkg-divert --package smailwrapper --add --rename \
11118 --divert /usr/sbin/smail.real /usr/sbin/smail
11119 </example> The <tt>--package smailwrapper</tt> ensures that
11120 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
11121 can bypass the diversion and get installed as the true version.
11122 It's safe to add the diversion unconditionally on upgrades since
11123 it will be left unchanged if it already exists, but
11124 <prgn>dpkg-divert</prgn> will display a message. To suppress that
11125 message, make the command conditional on the version from which
11126 the package is being upgraded:
11128 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
11129 dpkg-divert --package smailwrapper --add --rename \
11130 --divert /usr/sbin/smail.real /usr/sbin/smail
11132 </example> where <tt>1.0-2</tt> is the version at which the
11133 diversion was first added to the package. Running the command
11134 during abort-upgrade is pointless but harmless.
11138 The postrm has to do the reverse:
11140 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
11141 dpkg-divert --package smailwrapper --remove --rename \
11142 --divert /usr/sbin/smail.real /usr/sbin/smail
11144 </example> If the diversion was added at a particular version, the
11145 postrm should also handle the failure case of upgrading from an
11146 older version (unless the older version is so old that direct
11147 upgrades are no longer supported):
11149 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
11150 dpkg-divert --package smailwrapper --remove --rename \
11151 --divert /usr/sbin/smail.real /usr/sbin/smail
11153 </example> where <tt>1.02-2</tt> is the version at which the
11154 diversion was first added to the package. The postrm should not
11155 remove the diversion on upgrades both because there's no reason to
11156 remove the diversion only to immediately re-add it and since the
11157 postrm of the old package is run after unpacking so the removal of
11158 the diversion will fail.
11162 Do not attempt to divert a file which is vitally important for
11163 the system's operation - when using <prgn>dpkg-divert</prgn>
11164 there is a time, after it has been diverted but before
11165 <prgn>dpkg</prgn> has installed the new version, when the file
11166 does not exist.</p>
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