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12 <title>Debian Policy Manual</title>
13 <author><qref id="authors">The Debian Policy Mailing List</qref></author>
14 <version>version &version;, &date;</version>
17 This manual describes the policy requirements for the Debian
18 GNU/Linux distribution. This includes the structure and
19 contents of the Debian archive and several design issues of
20 the operating system, as well as technical requirements that
21 each package must satisfy to be included in the distribution.
26 Copyright © 1996,1997,1998 Ian Jackson
27 and Christian Schwarz.
30 These are the copyright dates of the original Policy manual.
31 Since then, this manual has been updated by many others. No
32 comprehensive collection of copyright notices for subsequent
37 This manual is free software; you may redistribute it and/or
38 modify it under the terms of the GNU General Public License
39 as published by the Free Software Foundation; either version
40 2, or (at your option) any later version.
44 This is distributed in the hope that it will be useful, but
45 <em>without any warranty</em>; without even the implied
46 warranty of merchantability or fitness for a particular
47 purpose. See the GNU General Public License for more
52 A copy of the GNU General Public License is available as
53 <file>/usr/share/common-licenses/GPL</file> in the Debian GNU/Linux
54 distribution or on the World Wide Web at
55 <url id="http://www.gnu.org/copyleft/gpl.html"
56 name="the GNU General Public Licence">. You can also
57 obtain it by writing to the Free Software Foundation, Inc.,
58 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
66 <heading>About this manual</heading>
68 <heading>Scope</heading>
70 This manual describes the policy requirements for the Debian
71 GNU/Linux distribution. This includes the structure and
72 contents of the Debian archive and several design issues of the
73 operating system, as well as technical requirements that
74 each package must satisfy to be included in the
79 This manual also describes Debian policy as it relates to
80 creating Debian packages. It is not a tutorial on how to build
81 packages, nor is it exhaustive where it comes to describing
82 the behavior of the packaging system. Instead, this manual
83 attempts to define the interface to the package management
84 system that the developers have to be conversant with.<footnote>
85 Informally, the criteria used for inclusion is that the
86 material meet one of the following requirements:
87 <taglist compact="compact">
88 <tag>Standard interfaces</tag>
90 The material presented represents an interface to
91 the packaging system that is mandated for use, and
92 is used by, a significant number of packages, and
93 therefore should not be changed without peer
94 review. Package maintainers can then rely on this
95 interface not changing, and the package management
96 software authors need to ensure compatibility with
97 this interface definition. (Control file and
98 changelog file formats are examples.)
100 <tag>Chosen Convention</tag>
102 If there are a number of technically viable choices
103 that can be made, but one needs to select one of
104 these options for inter-operability. The version
105 number format is one example.
108 Please note that these are not mutually exclusive;
109 selected conventions often become parts of standard
115 The footnotes present in this manual are
116 merely informative, and are not part of Debian policy itself.
120 The appendices to this manual are not necessarily normative,
121 either. Please see <ref id="pkg-scope"> for more information.
125 In the normative part of this manual,
126 the words <em>must</em>, <em>should</em> and
127 <em>may</em>, and the adjectives <em>required</em>,
128 <em>recommended</em> and <em>optional</em>, are used to
129 distinguish the significance of the various guidelines in
130 this policy document. Packages that do not conform to the
131 guidelines denoted by <em>must</em> (or <em>required</em>)
132 will generally not be considered acceptable for the Debian
133 distribution. Non-conformance with guidelines denoted by
134 <em>should</em> (or <em>recommended</em>) will generally be
135 considered a bug, but will not necessarily render a package
136 unsuitable for distribution. Guidelines denoted by
137 <em>may</em> (or <em>optional</em>) are truly optional and
138 adherence is left to the maintainer's discretion.
142 These classifications are roughly equivalent to the bug
143 severities <em>serious</em> (for <em>must</em> or
144 <em>required</em> directive violations), <em>minor</em>,
145 <em>normal</em> or <em>important</em>
146 (for <em>should</em> or <em>recommended</em> directive
147 violations) and <em>wishlist</em> (for <em>optional</em>
150 Compare RFC 2119. Note, however, that these words are
151 used in a different way in this document.
156 Much of the information presented in this manual will be
157 useful even when building a package which is to be
158 distributed in some other way or is intended for local use
164 <heading>New versions of this document</heading>
167 This manual is distributed via the Debian package
168 <package><url name="debian-policy"
169 id="http://packages.debian.org/debian-policy"></package>
170 (<httpsite>packages.debian.org</httpsite>
171 <httppath>/debian-policy</httppath>).
175 The current version of this document is also available from
176 the Debian web mirrors at
177 <tt><url name="/doc/debian-policy/"
178 id="http://www.debian.org/doc/debian-policy/"></tt>.
180 <httpsite>www.debian.org</httpsite>
181 <httppath>/doc/debian-policy/</httppath>)
182 Also available from the same directory are several other
183 formats: <file>policy.html.tar.gz</file>
184 (<httppath>/doc/debian-policy/policy.html.tar.gz</httppath>),
185 <file>policy.pdf.gz</file>
186 (<httppath>/doc/debian-policy/policy.pdf.gz</httppath>)
187 and <file>policy.ps.gz</file>
188 (<httppath>/doc/debian-policy/policy.ps.gz</httppath>).
192 The <package>debian-policy</package> package also includes the file
193 <file>upgrading-checklist.txt.gz</file> which indicates policy
194 changes between versions of this document.
199 <heading>Authors and Maintainers</heading>
202 Originally called "Debian GNU/Linux Policy Manual", this
203 manual was initially written in 1996 by Ian Jackson.
204 It was revised on November 27th, 1996 by David A. Morris.
205 Christian Schwarz added new sections on March 15th, 1997,
206 and reworked/restructured it in April-July 1997.
207 Christoph Lameter contributed the "Web Standard".
208 Julian Gilbey largely restructured it in 2001.
212 Since September 1998, the responsibility for the contents of
213 this document lies on the <url name="debian-policy mailing list"
214 id="mailto:debian-policy@lists.debian.org">. Proposals
215 are discussed there and inserted into policy after a certain
216 consensus is established.
217 <!-- insert shameless policy-process plug here eventually -->
218 The actual editing is done by a group of maintainers that have
219 no editorial powers. These are the current maintainers:
222 <item>Julian Gilbey</item>
223 <item>Branden Robinson</item>
224 <item>Josip Rodin</item>
225 <item>Manoj Srivastava</item>
230 While the authors of this document have tried hard to avoid
231 typos and other errors, these do still occur. If you discover
232 an error in this manual or if you want to give any
233 comments, suggestions, or criticisms please send an email to
234 the Debian Policy List,
235 <email>debian-policy@lists.debian.org</email>, or submit a
236 bug report against the <tt>debian-policy</tt> package.
240 Please do not try to reach the individual authors or maintainers
241 of the Policy Manual regarding changes to the Policy.
246 <heading>Related documents</heading>
249 There are several other documents other than this Policy Manual
250 that are necessary to fully understand some Debian policies and
255 The external "sub-policy" documents are referred to in:
256 <list compact="compact">
257 <item><ref id="fhs"></item>
258 <item><ref id="virtual_pkg"></item>
259 <item><ref id="menus"></item>
260 <item><ref id="mime"></item>
261 <item><ref id="perl"></item>
262 <item><ref id="maintscriptprompt"></item>
263 <item><ref id="emacs"></item>
268 In addition to those, which carry the weight of policy, there
269 is the Debian Developer's Reference. This document describes
270 procedures and resources for Debian developers, but it is
271 <em>not</em> normative; rather, it includes things that don't
272 belong in the Policy, such as best practices for developers.
276 The Developer's Reference is available in the
277 <package>developers-reference</package> package.
278 It's also available from the Debian web mirrors at
279 <tt><url name="/doc/developers-reference/"
280 id="http://www.debian.org/doc/developers-reference/"></tt>.
284 <sect id="definitions">
285 <heading>Definitions</heading>
288 The following terms are used in this Policy Manual:
292 The character encoding specified by ANSI X3.4-1986 and its
293 predecessor standards, referred to in MIME as US-ASCII, and
294 corresponding to an encoding in eight bits per character of
295 the first 128 <url id="http://www.unicode.org/"
296 name="Unicode"> characters, with the eighth bit always zero.
300 The transformation format (sometimes called encoding) of
301 <url id="http://www.unicode.org/" name="Unicode"> defined by
302 <url id="http://www.rfc-editor.org/rfc/rfc3629.txt"
303 name="RFC 3629">. UTF-8 has the useful property of having
304 ASCII as a subset, so any text encoded in ASCII is trivially
314 <heading>The Debian Archive</heading>
317 The Debian GNU/Linux system is maintained and distributed as a
318 collection of <em>packages</em>. Since there are so many of
319 them (currently well over 15000), they are split into
320 <em>sections</em> and given <em>priorities</em> to simplify
321 the handling of them.
325 The effort of the Debian project is to build a free operating
326 system, but not every package we want to make accessible is
327 <em>free</em> in our sense (see the Debian Free Software
328 Guidelines, below), or may be imported/exported without
329 restrictions. Thus, the archive is split into areas<footnote>
330 The Debian archive software uses the term "component" internally
331 and in the Release file format to refer to the division of an
332 archive. The Debian Social Contract simply refers to "areas."
333 This document uses terminology similar to the Social Contract.
334 </footnote> based on their licenses and other restrictions.
338 The aims of this are:
340 <list compact="compact">
341 <item>to allow us to make as much software available as we can</item>
342 <item>to allow us to encourage everyone to write free software,
344 <item>to allow us to make it easy for people to produce
345 CD-ROMs of our system without violating any licenses,
346 import/export restrictions, or any other laws.</item>
351 The <em>main</em> archive area forms the <em>Debian GNU/Linux
356 Packages in the other archive areas (<tt>contrib</tt>,
357 <tt>non-free</tt>) are not considered to be part of the Debian
358 distribution, although we support their use and provide
359 infrastructure for them (such as our bug-tracking system and
360 mailing lists). This Debian Policy Manual applies to these
365 <heading>The Debian Free Software Guidelines</heading>
367 The Debian Free Software Guidelines (DFSG) form our
368 definition of "free software". These are:
370 <tag>1. Free Redistribution
373 The license of a Debian component may not restrict any
374 party from selling or giving away the software as a
375 component of an aggregate software distribution
376 containing programs from several different
377 sources. The license may not require a royalty or
378 other fee for such sale.
383 The program must include source code, and must allow
384 distribution in source code as well as compiled form.
386 <tag>3. Derived Works
389 The license must allow modifications and derived
390 works, and must allow them to be distributed under the
391 same terms as the license of the original software.
393 <tag>4. Integrity of The Author's Source Code
396 The license may restrict source-code from being
397 distributed in modified form <em>only</em> if the
398 license allows the distribution of "patch files"
399 with the source code for the purpose of modifying the
400 program at build time. The license must explicitly
401 permit distribution of software built from modified
402 source code. The license may require derived works to
403 carry a different name or version number from the
404 original software. (This is a compromise. The Debian
405 Project encourages all authors to not restrict any
406 files, source or binary, from being modified.)
408 <tag>5. No Discrimination Against Persons or Groups
411 The license must not discriminate against any person
414 <tag>6. No Discrimination Against Fields of Endeavor
417 The license must not restrict anyone from making use
418 of the program in a specific field of endeavor. For
419 example, it may not restrict the program from being
420 used in a business, or from being used for genetic
423 <tag>7. Distribution of License
426 The rights attached to the program must apply to all
427 to whom the program is redistributed without the need
428 for execution of an additional license by those
431 <tag>8. License Must Not Be Specific to Debian
434 The rights attached to the program must not depend on
435 the program's being part of a Debian system. If the
436 program is extracted from Debian and used or
437 distributed without Debian but otherwise within the
438 terms of the program's license, all parties to whom
439 the program is redistributed must have the same
440 rights as those that are granted in conjunction with
443 <tag>9. License Must Not Contaminate Other Software
446 The license must not place restrictions on other
447 software that is distributed along with the licensed
448 software. For example, the license must not insist
449 that all other programs distributed on the same medium
450 must be free software.
452 <tag>10. Example Licenses
455 The "GPL," "BSD," and "Artistic" licenses are examples of
456 licenses that we consider <em>free</em>.
463 <heading>Archive areas</heading>
466 <heading>The main archive area</heading>
469 Every package in <em>main</em> must comply with the DFSG
470 (Debian Free Software Guidelines).
474 In addition, the packages in <em>main</em>
475 <list compact="compact">
477 must not require a package outside of <em>main</em>
478 for compilation or execution (thus, the package must
479 not declare a "Depends", "Recommends", or
480 "Build-Depends" relationship on a non-<em>main</em>
484 must not be so buggy that we refuse to support them,
488 must meet all policy requirements presented in this
497 <heading>The contrib archive area</heading>
500 Every package in <em>contrib</em> must comply with the DFSG.
504 In addition, the packages in <em>contrib</em>
505 <list compact="compact">
507 must not be so buggy that we refuse to support them,
511 must meet all policy requirements presented in this
519 Examples of packages which would be included in
520 <em>contrib</em> are:
521 <list compact="compact">
523 free packages which require <em>contrib</em>,
524 <em>non-free</em> packages or packages which are not
525 in our archive at all for compilation or execution,
529 wrapper packages or other sorts of free accessories for
536 <sect1 id="non-free">
537 <heading>The non-free archive area</heading>
540 Packages must be placed in <em>non-free</em> if they are
541 not compliant with the DFSG or are encumbered by patents
542 or other legal issues that make their distribution
547 In addition, the packages in <em>non-free</em>
548 <list compact="compact">
550 must not be so buggy that we refuse to support them,
554 must meet all policy requirements presented in this
555 manual that it is possible for them to meet.
557 It is possible that there are policy
558 requirements which the package is unable to
559 meet, for example, if the source is
560 unavailable. These situations will need to be
561 handled on a case-by-case basis.
570 <sect id="pkgcopyright">
571 <heading>Copyright considerations</heading>
574 Every package must be accompanied by a verbatim copy of its
575 copyright information and distribution license in the file
576 <file>/usr/share/doc/<var>package</var>/copyright</file>
577 (see <ref id="copyrightfile"> for further details).
581 We reserve the right to restrict files from being included
582 anywhere in our archives if
583 <list compact="compact">
585 their use or distribution would break a law,
588 there is an ethical conflict in their distribution or
592 we would have to sign a license for them, or
595 their distribution would conflict with other project
602 Programs whose authors encourage the user to make
603 donations are fine for the main distribution, provided
604 that the authors do not claim that not donating is
605 immoral, unethical, illegal or something similar; in such
606 a case they must go in <em>non-free</em>.
610 Packages whose copyright permission notices (or patent
611 problems) do not even allow redistribution of binaries
612 only, and where no special permission has been obtained,
613 must not be placed on the Debian FTP site and its mirrors
618 Note that under international copyright law (this applies
619 in the United States, too), <em>no</em> distribution or
620 modification of a work is allowed without an explicit
621 notice saying so. Therefore a program without a copyright
622 notice <em>is</em> copyrighted and you may not do anything
623 to it without risking being sued! Likewise if a program
624 has a copyright notice but no statement saying what is
625 permitted then nothing is permitted.
629 Many authors are unaware of the problems that restrictive
630 copyrights (or lack of copyright notices) can cause for
631 the users of their supposedly-free software. It is often
632 worthwhile contacting such authors diplomatically to ask
633 them to modify their license terms. However, this can be a
634 politically difficult thing to do and you should ask for
635 advice on the <tt>debian-legal</tt> mailing list first, as
640 When in doubt about a copyright, send mail to
641 <email>debian-legal@lists.debian.org</email>. Be prepared
642 to provide us with the copyright statement. Software
643 covered by the GPL, public domain software and BSD-like
644 copyrights are safe; be wary of the phrases "commercial
645 use prohibited" and "distribution restricted".
649 <sect id="subsections">
650 <heading>Sections</heading>
653 The packages in the archive areas <em>main</em>,
654 <em>contrib</em> and <em>non-free</em> are grouped further into
655 <em>sections</em> to simplify handling.
659 The archive area and section for each package should be
660 specified in the package's <tt>Section</tt> control record (see
661 <ref id="f-Section">). However, the maintainer of the Debian
662 archive may override this selection to ensure the consistency of
663 the Debian distribution. The <tt>Section</tt> field should be
665 <list compact="compact">
667 <em>section</em> if the package is in the
668 <em>main</em> archive area,
671 <em>area/section</em> if the package is in
672 the <em>contrib</em> or <em>non-free</em>
679 The Debian archive maintainers provide the authoritative
680 list of sections. At present, they are:
681 <em>admin</em>, <em>cli-mono</em>, <em>comm</em>, <em>database</em>,
682 <em>devel</em>, <em>debug</em>, <em>doc</em>, <em>editors</em>,
683 <em>electronics</em>, <em>embedded</em>, <em>fonts</em>,
684 <em>games</em>, <em>gnome</em>, <em>graphics</em>, <em>gnu-r</em>,
685 <em>gnustep</em>, <em>hamradio</em>, <em>haskell</em>,
686 <em>httpd</em>, <em>interpreters</em>, <em>java</em>, <em>kde</em>,
687 <em>kernel</em>, <em>libs</em>, <em>libdevel</em>, <em>lisp</em>,
688 <em>localization</em>, <em>mail</em>, <em>math</em>, <em>misc</em>,
689 <em>net</em>, <em>news</em>, <em>ocaml</em>, <em>oldlibs</em>,
690 <em>otherosfs</em>, <em>perl</em>, <em>php</em>, <em>python</em>,
691 <em>ruby</em>, <em>science</em>, <em>shells</em>, <em>sound</em>,
692 <em>tex</em>, <em>text</em>, <em>utils</em>, <em>vcs</em>,
693 <em>video</em>, <em>web</em>, <em>x11</em>, <em>xfce</em>,
694 <em>zope</em>. The additional section <em>debian-installer</em>
695 contains special packages used by the installer and is not used
696 for normal Debian packages.
700 For more information about the sections and their definitions,
701 see the <url id="http://packages.debian.org/unstable/"
702 name="list of sections in unstable">.
706 <sect id="priorities">
707 <heading>Priorities</heading>
710 Each package should have a <em>priority</em> value, which is
711 included in the package's <em>control record</em>
712 (see <ref id="f-Priority">).
713 This information is used by the Debian package management tools to
714 separate high-priority packages from less-important packages.
718 The following <em>priority levels</em> are recognized by the
719 Debian package management tools.
721 <tag><tt>required</tt></tag>
723 Packages which are necessary for the proper
724 functioning of the system (usually, this means that
725 dpkg functionality depends on these packages).
726 Removing a <tt>required</tt> package may cause your
727 system to become totally broken and you may not even
728 be able to use <prgn>dpkg</prgn> to put things back,
729 so only do so if you know what you are doing. Systems
730 with only the <tt>required</tt> packages are probably
731 unusable, but they do have enough functionality to
732 allow the sysadmin to boot and install more software.
734 <tag><tt>important</tt></tag>
736 Important programs, including those which one would
737 expect to find on any Unix-like system. If the
738 expectation is that an experienced Unix person who
739 found it missing would say "What on earth is going on,
740 where is <prgn>foo</prgn>?", it must be an
741 <tt>important</tt> package.<footnote>
742 This is an important criterion because we are
743 trying to produce, amongst other things, a free
746 Other packages without which the system will not run
747 well or be usable must also have priority
748 <tt>important</tt>. This does
749 <em>not</em> include Emacs, the X Window System, TeX
750 or any other large applications. The
751 <tt>important</tt> packages are just a bare minimum of
752 commonly-expected and necessary tools.
754 <tag><tt>standard</tt></tag>
756 These packages provide a reasonably small but not too
757 limited character-mode system. This is what will be
758 installed by default if the user doesn't select anything
759 else. It doesn't include many large applications.
761 <tag><tt>optional</tt></tag>
763 (In a sense everything that isn't required is
764 optional, but that's not what is meant here.) This is
765 all the software that you might reasonably want to
766 install if you didn't know what it was and don't have
767 specialized requirements. This is a much larger system
768 and includes the X Window System, a full TeX
769 distribution, and many applications. Note that
770 optional packages should not conflict with each other.
772 <tag><tt>extra</tt></tag>
774 This contains all packages that conflict with others
775 with required, important, standard or optional
776 priorities, or are only likely to be useful if you
777 already know what they are or have specialized
778 requirements (such as packages containing only detached
785 Packages must not depend on packages with lower priority
786 values (excluding build-time dependencies). In order to
787 ensure this, the priorities of one or more packages may need
796 <heading>Binary packages</heading>
799 The Debian GNU/Linux distribution is based on the Debian
800 package management system, called <prgn>dpkg</prgn>. Thus,
801 all packages in the Debian distribution must be provided
802 in the <tt>.deb</tt> file format.
806 A <tt>.deb</tt> package contains two sets of files: a set of files
807 to install on the system when the package is installed, and a set
808 of files that provide additional metadata about the package or
809 which are executed when the package is installed or removed. This
810 second set of files is called <em>control information files</em>.
811 Among those files are the package maintainer scripts
812 and <file>control</file>, the <qref id="binarycontrolfiles">binary
813 package control file</qref> that contains the control fields for
814 the package. Other control information files
815 include <qref id="sharedlibs-shlibdeps">the <file>shlibs</file>
816 file</qref> used to store shared library dependency information
817 and the <file>conffiles</file> file that lists the package's
818 configuration files (described in <ref id="config-files">).
822 There is unfortunately a collision of terminology here between
823 control information files and files in the Debian control file
824 format. Throughout this document, a <em>control file</em> refers
825 to a file in the Debian control file format. These files are
826 documented in <ref id="controlfields">. Only files referred to
827 specifically as <em>control information files</em> are the files
828 included in the control information file member of
829 the <file>.deb</file> file format used by binary packages. Most
830 control information files are not in the Debian control file
835 <heading>The package name</heading>
838 Every package must have a name that's unique within the Debian
843 The package name is included in the control field
844 <tt>Package</tt>, the format of which is described
845 in <ref id="f-Package">.
846 The package name is also included as a part of the file name
847 of the <tt>.deb</tt> file.
852 <heading>The version of a package</heading>
855 Every package has a version number recorded in its
856 <tt>Version</tt> control file field, described in
857 <ref id="f-Version">.
861 The package management system imposes an ordering on version
862 numbers, so that it can tell whether packages are being up- or
863 downgraded and so that package system front end applications
864 can tell whether a package it finds available is newer than
865 the one installed on the system. The version number format
866 has the most significant parts (as far as comparison is
867 concerned) at the beginning.
871 If an upstream package has problematic version numbers they
872 should be converted to a sane form for use in the
873 <tt>Version</tt> field.
877 <heading>Version numbers based on dates</heading>
880 In general, Debian packages should use the same version
881 numbers as the upstream sources. However, upstream version
882 numbers based on some date formats (sometimes used for
883 development or "snapshot" releases) will not be ordered
884 correctly by the package management software. For
885 example, <prgn>dpkg</prgn> will consider "96May01" to be
886 greater than "96Dec24".
890 To prevent having to use epochs for every new upstream
891 version, the date-based portion of any upstream version number
892 should be given in a way that sorts correctly: four-digit year
893 first, followed by a two-digit numeric month, followed by a
894 two-digit numeric date, possibly with punctuation between the
899 Native Debian packages (i.e., packages which have been written
900 especially for Debian) whose version numbers include dates
901 should also follow these rules. If punctuation is desired
902 between the date components, remember that hyphen (<tt>-</tt>)
903 cannot be used in native package versions. Period
904 (<tt>.</tt>) is normally a good choice.
911 <heading>The maintainer of a package</heading>
914 Every package must have a Debian maintainer (the
915 maintainer may be one person or a group of people
916 reachable from a common email address, such as a mailing
917 list). The maintainer is responsible for ensuring that
918 the package is placed in the appropriate distributions.
922 The maintainer must be specified in the
923 <tt>Maintainer</tt> control field with their correct name
924 and a working email address. If one person maintains
925 several packages, they should try to avoid having
926 different forms of their name and email address in
927 the <tt>Maintainer</tt> fields of those packages.
931 The format of the <tt>Maintainer</tt> control field is
932 described in <ref id="f-Maintainer">.
936 If the maintainer of a package quits from the Debian
937 project, "Debian QA Group"
938 <email>packages@qa.debian.org</email> takes over the
939 maintainer-ship of the package until someone else
940 volunteers for that task. These packages are called
941 <em>orphaned packages</em>.<footnote>
942 The detailed procedure for doing this gracefully can
943 be found in the Debian Developer's Reference,
944 see <ref id="related">.
949 <sect id="descriptions">
950 <heading>The description of a package</heading>
953 Every Debian package must have a <tt>Description</tt> control
954 field which contains a synopsis and extended description of the
955 package. Technical information about the format of the
956 <tt>Description</tt> field is in <ref id="f-Description">.
960 The description should describe the package (the program) to a
961 user (system administrator) who has never met it before so that
962 they have enough information to decide whether they want to
963 install it. This description should not just be copied verbatim
964 from the program's documentation.
968 Put important information first, both in the synopsis and
969 extended description. Sometimes only the first part of the
970 synopsis or of the description will be displayed. You can
971 assume that there will usually be a way to see the whole
972 extended description.
976 The description should also give information about the
977 significant dependencies and conflicts between this package
978 and others, so that the user knows why these dependencies and
979 conflicts have been declared.
983 Instructions for configuring or using the package should
984 not be included (that is what installation scripts,
985 manual pages, info files, etc., are for). Copyright
986 statements and other administrivia should not be included
987 either (that is what the copyright file is for).
990 <sect1 id="synopsis"><heading>The single line synopsis</heading>
993 The single line synopsis should be kept brief - certainly
998 Do not include the package name in the synopsis line. The
999 display software knows how to display this already, and you
1000 do not need to state it. Remember that in many situations
1001 the user may only see the synopsis line - make it as
1002 informative as you can.
1007 <sect1 id="extendeddesc"><heading>The extended description</heading>
1010 Do not try to continue the single line synopsis into the
1011 extended description. This will not work correctly when
1012 the full description is displayed, and makes no sense
1013 where only the summary (the single line synopsis) is
1018 The extended description should describe what the package
1019 does and how it relates to the rest of the system (in terms
1020 of, for example, which subsystem it is which part of).
1024 The description field needs to make sense to anyone, even
1025 people who have no idea about any of the things the
1026 package deals with.<footnote>
1027 The blurb that comes with a program in its
1028 announcements and/or <prgn>README</prgn> files is
1029 rarely suitable for use in a description. It is
1030 usually aimed at people who are already in the
1031 community where the package is used.
1040 <heading>Dependencies</heading>
1043 Every package must specify the dependency information
1044 about other packages that are required for the first to
1049 For example, a dependency entry must be provided for any
1050 shared libraries required by a dynamically-linked executable
1051 binary in a package.
1055 Packages are not required to declare any dependencies they
1056 have on other packages which are marked <tt>Essential</tt>
1057 (see below), and should not do so unless they depend on a
1058 particular version of that package.<footnote>
1060 Essential is needed in part to avoid unresolvable dependency
1061 loops on upgrade. If packages add unnecessary dependencies
1062 on packages in this set, the chances that there
1063 <strong>will</strong> be an unresolvable dependency loop
1064 caused by forcing these Essential packages to be configured
1065 first before they need to be is greatly increased. It also
1066 increases the chances that frontends will be unable to
1067 <strong>calculate</strong> an upgrade path, even if one
1071 Also, functionality is rarely ever removed from the
1072 Essential set, but <em>packages</em> have been removed from
1073 the Essential set when the functionality moved to a
1074 different package. So depending on these packages <em>just
1075 in case</em> they stop being essential does way more harm
1082 Sometimes, unpacking one package requires that another package
1083 be first unpacked <em>and</em> configured. In this case, the
1084 dependent package must specify this dependency in
1085 the <tt>Pre-Depends</tt> control field.
1089 You should not specify a <tt>Pre-Depends</tt> entry for a
1090 package before this has been discussed on the
1091 <tt>debian-devel</tt> mailing list and a consensus about
1092 doing that has been reached.
1096 The format of the package interrelationship control fields is
1097 described in <ref id="relationships">.
1101 <sect id="virtual_pkg">
1102 <heading>Virtual packages</heading>
1105 Sometimes, there are several packages which offer
1106 more-or-less the same functionality. In this case, it's
1107 useful to define a <em>virtual package</em> whose name
1108 describes that common functionality. (The virtual
1109 packages only exist logically, not physically; that's why
1110 they are called <em>virtual</em>.) The packages with this
1111 particular function will then <em>provide</em> the virtual
1112 package. Thus, any other package requiring that function
1113 can simply depend on the virtual package without having to
1114 specify all possible packages individually.
1118 All packages should use virtual package names where
1119 appropriate, and arrange to create new ones if necessary.
1120 They should not use virtual package names (except privately,
1121 amongst a cooperating group of packages) unless they have
1122 been agreed upon and appear in the list of virtual package
1123 names. (See also <ref id="virtual">)
1127 The latest version of the authoritative list of virtual
1128 package names can be found in the <tt>debian-policy</tt> package.
1129 It is also available from the Debian web mirrors at
1130 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1131 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1135 The procedure for updating the list is described in the preface
1142 <heading>Base system</heading>
1145 The <tt>base system</tt> is a minimum subset of the Debian
1146 GNU/Linux system that is installed before everything else
1147 on a new system. Only very few packages are allowed to form
1148 part of the base system, in order to keep the required disk
1153 The base system consists of all those packages with priority
1154 <tt>required</tt> or <tt>important</tt>. Many of them will
1155 be tagged <tt>essential</tt> (see below).
1160 <heading>Essential packages</heading>
1163 Essential is defined as the minimal set of functionality that
1164 must be available and usable on the system at all times, even
1165 when packages are in an unconfigured (but unpacked) state.
1166 Packages are tagged <tt>essential</tt> for a system using the
1167 <tt>Essential</tt> control field. The format of the
1168 <tt>Essential</tt> control field is described in <ref
1173 Since these packages cannot be easily removed (one has to
1174 specify an extra <em>force option</em> to
1175 <prgn>dpkg</prgn> to do so), this flag must not be used
1176 unless absolutely necessary. A shared library package
1177 must not be tagged <tt>essential</tt>; dependencies will
1178 prevent its premature removal, and we need to be able to
1179 remove it when it has been superseded.
1183 Since dpkg will not prevent upgrading of other packages
1184 while an <tt>essential</tt> package is in an unconfigured
1185 state, all <tt>essential</tt> packages must supply all of
1186 their core functionality even when unconfigured. If the
1187 package cannot satisfy this requirement it must not be
1188 tagged as essential, and any packages depending on this
1189 package must instead have explicit dependency fields as
1194 Maintainers should take great care in adding any programs,
1195 interfaces, or functionality to <tt>essential</tt> packages.
1196 Packages may assume that functionality provided by
1197 <tt>essential</tt> packages is always available without
1198 declaring explicit dependencies, which means that removing
1199 functionality from the Essential set is very difficult and is
1200 almost never done. Any capability added to an
1201 <tt>essential</tt> package therefore creates an obligation to
1202 support that capability as part of the Essential set in
1207 You must not tag any packages <tt>essential</tt> before
1208 this has been discussed on the <tt>debian-devel</tt>
1209 mailing list and a consensus about doing that has been
1214 <sect id="maintscripts">
1215 <heading>Maintainer Scripts</heading>
1218 The package installation scripts should avoid producing
1219 output which is unnecessary for the user to see and
1220 should rely on <prgn>dpkg</prgn> to stave off boredom on
1221 the part of a user installing many packages. This means,
1222 amongst other things, using the <tt>--quiet</tt> option on
1223 <prgn>install-info</prgn>.
1227 Errors which occur during the execution of an installation
1228 script must be checked and the installation must not
1229 continue after an error.
1233 Note that in general <ref id="scripts"> applies to package
1234 maintainer scripts, too.
1238 You should not use <prgn>dpkg-divert</prgn> on a file belonging
1239 to another package without consulting the maintainer of that
1240 package first. When adding or removing diversions, package
1241 maintainer scripts must provide the <tt>--package</tt> flag
1242 to <prgn>dpkg-divert</prgn> and must not use <tt>--local</tt>.
1246 All packages which supply an instance of a common command
1247 name (or, in general, filename) should generally use
1248 <prgn>update-alternatives</prgn>, so that they may be
1249 installed together. If <prgn>update-alternatives</prgn>
1250 is not used, then each package must use
1251 <tt>Conflicts</tt> to ensure that other packages are
1252 de-installed. (In this case, it may be appropriate to
1253 specify a conflict against earlier versions of something
1254 that previously did not use
1255 <prgn>update-alternatives</prgn>; this is an exception to
1256 the usual rule that versioned conflicts should be
1260 <sect1 id="maintscriptprompt">
1261 <heading>Prompting in maintainer scripts</heading>
1263 Package maintainer scripts may prompt the user if
1264 necessary. Prompting must be done by communicating
1265 through a program, such as <prgn>debconf</prgn>, which
1266 conforms to the Debian Configuration Management
1267 Specification, version 2 or higher.
1271 Packages which are essential, or which are dependencies of
1272 essential packages, may fall back on another prompting method
1273 if no such interface is available when they are executed.
1277 The Debian Configuration Management Specification is included
1278 in the <file>debconf_specification</file> files in the
1279 <package>debian-policy</package> package.
1280 It is also available from the Debian web mirrors at
1281 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1282 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1286 Packages which use the Debian Configuration Management
1287 Specification may contain the additional control information
1288 files <file>config</file>
1289 and <file>templates</file>. <file>config</file> is an
1290 additional maintainer script used for package configuration,
1291 and <file>templates</file> contains templates used for user
1292 prompting. The <prgn>config</prgn> script might be run before
1293 the <prgn>preinst</prgn> script and before the package is
1294 unpacked or any of its dependencies or pre-dependencies are
1295 satisfied. Therefore it must work using only the tools
1296 present in <em>essential</em> packages.<footnote>
1297 <package>Debconf</package> or another tool that
1298 implements the Debian Configuration Management
1299 Specification will also be installed, and any
1300 versioned dependencies on it will be satisfied
1301 before preconfiguration begins.
1306 Packages which use the Debian Configuration Management
1307 Specification must allow for translation of their user-visible
1308 messages by using a gettext-based system such as the one
1309 provided by the <package>po-debconf</package> package.
1313 Packages should try to minimize the amount of prompting
1314 they need to do, and they should ensure that the user
1315 will only ever be asked each question once. This means
1316 that packages should try to use appropriate shared
1317 configuration files (such as <file>/etc/papersize</file> and
1318 <file>/etc/news/server</file>), and shared
1319 <package>debconf</package> variables rather than each
1320 prompting for their own list of required pieces of
1325 It also means that an upgrade should not ask the same
1326 questions again, unless the user has used
1327 <tt>dpkg --purge</tt> to remove the package's configuration.
1328 The answers to configuration questions should be stored in an
1329 appropriate place in <file>/etc</file> so that the user can
1330 modify them, and how this has been done should be
1335 If a package has a vitally important piece of
1336 information to pass to the user (such as "don't run me
1337 as I am, you must edit the following configuration files
1338 first or you risk your system emitting badly-formatted
1339 messages"), it should display this in the
1340 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1341 prompt the user to hit return to acknowledge the
1342 message. Copyright messages do not count as vitally
1343 important (they belong in
1344 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1345 neither do instructions on how to use a program (these
1346 should be in on-line documentation, where all the users
1351 Any necessary prompting should almost always be confined
1352 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1353 script. If it is done in the <prgn>postinst</prgn>, it
1354 should be protected with a conditional so that
1355 unnecessary prompting doesn't happen if a package's
1356 installation fails and the <prgn>postinst</prgn> is
1357 called with <tt>abort-upgrade</tt>,
1358 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1368 <heading>Source packages</heading>
1370 <sect id="standardsversion">
1371 <heading>Standards conformance</heading>
1374 Source packages should specify the most recent version number
1375 of this policy document with which your package complied
1376 when it was last updated.
1380 This information may be used to file bug reports
1381 automatically if your package becomes too much out of date.
1385 The version is specified in the <tt>Standards-Version</tt>
1387 The format of the <tt>Standards-Version</tt> field is
1388 described in <ref id="f-Standards-Version">.
1392 You should regularly, and especially if your package has
1393 become out of date, check for the newest Policy Manual
1394 available and update your package, if necessary. When your
1395 package complies with the new standards you should update the
1396 <tt>Standards-Version</tt> source package field and
1397 release it.<footnote>
1398 See the file <file>upgrading-checklist</file> for
1399 information about policy which has changed between
1400 different versions of this document.
1406 <sect id="pkg-relations">
1407 <heading>Package relationships</heading>
1410 Source packages should specify which binary packages they
1411 require to be installed or not to be installed in order to
1412 build correctly. For example, if building a package
1413 requires a certain compiler, then the compiler should be
1414 specified as a build-time dependency.
1418 It is not necessary to explicitly specify build-time
1419 relationships on a minimal set of packages that are always
1420 needed to compile, link and put in a Debian package a
1421 standard "Hello World!" program written in C or C++. The
1422 required packages are called <em>build-essential</em>, and
1423 an informational list can be found in
1424 <file>/usr/share/doc/build-essential/list</file> (which is
1425 contained in the <tt>build-essential</tt>
1428 <list compact="compact">
1430 This allows maintaining the list separately
1431 from the policy documents (the list does not
1432 need the kind of control that the policy
1436 Having a separate package allows one to install
1437 the build-essential packages on a machine, as
1438 well as allowing other packages such as tasks to
1439 require installation of the build-essential
1440 packages using the depends relation.
1443 The separate package allows bug reports against
1444 the list to be categorized separately from
1445 the policy management process in the BTS.
1452 When specifying the set of build-time dependencies, one
1453 should list only those packages explicitly required by the
1454 build. It is not necessary to list packages which are
1455 required merely because some other package in the list of
1456 build-time dependencies depends on them.<footnote>
1457 The reason for this is that dependencies change, and
1458 you should list all those packages, and <em>only</em>
1459 those packages that <em>you</em> need directly. What
1460 others need is their business. For example, if you
1461 only link against <file>libimlib</file>, you will need to
1462 build-depend on <package>libimlib2-dev</package> but
1463 not against any <tt>libjpeg*</tt> packages, even
1464 though <tt>libimlib2-dev</tt> currently depends on
1465 them: installation of <package>libimlib2-dev</package>
1466 will automatically ensure that all of its run-time
1467 dependencies are satisfied.
1472 If build-time dependencies are specified, it must be
1473 possible to build the package and produce working binaries
1474 on a system with only essential and build-essential
1475 packages installed and also those required to satisfy the
1476 build-time relationships (including any implied
1477 relationships). In particular, this means that version
1478 clauses should be used rigorously in build-time
1479 relationships so that one cannot produce bad or
1480 inconsistently configured packages when the relationships
1481 are properly satisfied.
1485 <ref id="relationships"> explains the technical details.
1490 <heading>Changes to the upstream sources</heading>
1493 If changes to the source code are made that are not
1494 specific to the needs of the Debian system, they should be
1495 sent to the upstream authors in whatever form they prefer
1496 so as to be included in the upstream version of the
1501 If you need to configure the package differently for
1502 Debian or for Linux, and the upstream source doesn't
1503 provide a way to do so, you should add such configuration
1504 facilities (for example, a new <prgn>autoconf</prgn> test
1505 or <tt>#define</tt>) and send the patch to the upstream
1506 authors, with the default set to the way they originally
1507 had it. You can then easily override the default in your
1508 <file>debian/rules</file> or wherever is appropriate.
1512 You should make sure that the <prgn>configure</prgn> utility
1513 detects the correct architecture specification string
1514 (refer to <ref id="arch-spec"> for details).
1518 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1519 <prgn>configure</prgn> scripts are used, you should edit the
1520 <file>.in</file> files rather than editing the
1521 <prgn>Makefile</prgn> directly. This allows the user to
1522 reconfigure the package if necessary. You should
1523 <em>not</em> configure the package and edit the generated
1524 <prgn>Makefile</prgn>! This makes it impossible for someone
1525 else to later reconfigure the package without losing the
1531 <sect id="dpkgchangelog">
1532 <heading>Debian changelog: <file>debian/changelog</file></heading>
1535 Changes in the Debian version of the package should be
1536 briefly explained in the Debian changelog file
1537 <file>debian/changelog</file>.<footnote>
1539 Mistakes in changelogs are usually best rectified by
1540 making a new changelog entry rather than "rewriting
1541 history" by editing old changelog entries.
1544 This includes modifications
1545 made in the Debian package compared to the upstream one
1546 as well as other changes and updates to the package.
1548 Although there is nothing stopping an author who is also
1549 the Debian maintainer from using this changelog for all
1550 their changes, it will have to be renamed if the Debian
1551 and upstream maintainers become different people. In such
1552 a case, however, it might be better to maintain the package
1553 as a non-native package.
1558 The format of the <file>debian/changelog</file> allows the
1559 package building tools to discover which version of the package
1560 is being built and find out other release-specific information.
1564 That format is a series of entries like this:
1566 <example compact="compact">
1567 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1569 [optional blank line(s), stripped]
1571 * <var>change details</var>
1572 <var>more change details</var>
1574 [blank line(s), included in output of dpkg-parsechangelog]
1576 * <var>even more change details</var>
1578 [optional blank line(s), stripped]
1580 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1585 <var>package</var> and <var>version</var> are the source
1586 package name and version number.
1590 <var>distribution(s)</var> lists the distributions where
1591 this version should be installed when it is uploaded - it
1592 is copied to the <tt>Distribution</tt> field in the
1593 <file>.changes</file> file. See <ref id="f-Distribution">.
1597 <var>urgency</var> is the value for the <tt>Urgency</tt>
1598 field in the <file>.changes</file> file for the upload
1599 (see <ref id="f-Urgency">). It is not possible to specify
1600 an urgency containing commas; commas are used to separate
1601 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1602 <prgn>dpkg</prgn> changelog format (though there is
1603 currently only one useful <var>keyword</var>,
1608 The change details may in fact be any series of lines
1609 starting with at least two spaces, but conventionally each
1610 change starts with an asterisk and a separating space and
1611 continuation lines are indented so as to bring them in
1612 line with the start of the text above. Blank lines may be
1613 used here to separate groups of changes, if desired.
1617 If this upload resolves bugs recorded in the Bug Tracking
1618 System (BTS), they may be automatically closed on the
1619 inclusion of this package into the Debian archive by
1620 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1621 in the change details.<footnote>
1622 To be precise, the string should match the following
1623 Perl regular expression:
1625 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1627 Then all of the bug numbers listed will be closed by the
1628 archive maintenance script (<prgn>katie</prgn>) using the
1629 <var>version</var> of the changelog entry.
1631 This information is conveyed via the <tt>Closes</tt> field
1632 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1636 The maintainer name and email address used in the changelog
1637 should be the details of the person uploading <em>this</em>
1638 version. They are <em>not</em> necessarily those of the
1639 usual package maintainer.<footnote>
1640 If the developer uploading the package is not one of the usual
1641 maintainers of the package (as listed in
1642 the <qref id="f-Maintainer"><tt>Maintainer</tt></qref>
1643 or <qref id="f-Uploaders"><tt>Uploaders</tt></qref> control
1644 fields of the package), the first line of the changelog is
1645 conventionally used to explain why a non-maintainer is
1646 uploading the package. The Debian Developer's Reference
1647 (see <ref id="related">) documents the conventions
1649 The information here will be copied to the <tt>Changed-By</tt>
1650 field in the <tt>.changes</tt> file
1651 (see <ref id="f-Changed-By">), and then later used to send an
1652 acknowledgement when the upload has been installed.
1656 The <var>date</var> has the following format<footnote>
1657 This is the same as the format generated by <tt>date
1659 </footnote> (compatible and with the same semantics of
1660 RFC 2822 and RFC 5322):
1661 <example>day-of-week, dd month yyyy hh:mm:ss +zzzz</example>
1663 <list compact="compact">
1665 day-of week is one of: Mon, Tue, Wed, Thu, Fri, Sat, Sun
1668 dd is a one- or two-digit day of the month (01-31)
1671 month is one of: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug,
1674 <item>yyyy is the four-digit year (e.g. 2010)</item>
1675 <item>hh is the two-digit hour (00-23)</item>
1676 <item>mm is the two-digit minutes (00-59)</item>
1677 <item>ss is the two-digit seconds (00-60)</item>
1679 +zzzz or -zzzz is the the time zone offset from Coordinated
1680 Universal Time (UTC). "+" indicates that the time is ahead
1681 of (i.e., east of) UTC and "-" indicates that the time is
1682 behind (i.e., west of) UTC. The first two digits indicate
1683 the hour difference from UTC and the last two digits
1684 indicate the number of additional minutes difference from
1685 UTC. The last two digits must be in the range 00-59.
1691 The first "title" line with the package name must start
1692 at the left hand margin. The "trailer" line with the
1693 maintainer and date details must be preceded by exactly
1694 one space. The maintainer details and the date must be
1695 separated by exactly two spaces.
1699 The entire changelog must be encoded in UTF-8.
1703 For more information on placement of the changelog files
1704 within binary packages, please see <ref id="changelogs">.
1708 <sect id="dpkgcopyright">
1709 <heading>Copyright: <file>debian/copyright</file></heading>
1711 Every package must be accompanied by a verbatim copy of its
1712 copyright information and distribution license in the file
1713 <file>/usr/share/doc/<var>package</var>/copyright</file>
1714 (see <ref id="copyrightfile"> for further details). Also see
1715 <ref id="pkgcopyright"> for further considerations related
1716 to copyrights for packages.
1720 <heading>Error trapping in makefiles</heading>
1723 When <prgn>make</prgn> invokes a command in a makefile
1724 (including your package's upstream makefiles and
1725 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1726 means that <prgn>sh</prgn>'s usual bad error handling
1727 properties apply: if you include a miniature script as one
1728 of the commands in your makefile you'll find that if you
1729 don't do anything about it then errors are not detected
1730 and <prgn>make</prgn> will blithely continue after
1735 Every time you put more than one shell command (this
1736 includes using a loop) in a makefile command you
1737 must make sure that errors are trapped. For
1738 simple compound commands, such as changing directory and
1739 then running a program, using <tt>&&</tt> rather
1740 than semicolon as a command separator is sufficient. For
1741 more complex commands including most loops and
1742 conditionals you should include a separate <tt>set -e</tt>
1743 command at the start of every makefile command that's
1744 actually one of these miniature shell scripts.
1748 <sect id="timestamps">
1749 <heading>Time Stamps</heading>
1751 Maintainers should preserve the modification times of the
1752 upstream source files in a package, as far as is reasonably
1754 The rationale is that there is some information conveyed
1755 by knowing the age of the file, for example, you could
1756 recognize that some documentation is very old by looking
1757 at the modification time, so it would be nice if the
1758 modification time of the upstream source would be
1764 <sect id="restrictions">
1765 <heading>Restrictions on objects in source packages</heading>
1768 The source package may not contain any hard links<footnote>
1770 This is not currently detected when building source
1771 packages, but only when extracting
1775 Hard links may be permitted at some point in the
1776 future, but would require a fair amount of
1779 </footnote>, device special files, sockets or setuid or
1780 setgid files.<footnote>
1781 Setgid directories are allowed.
1786 <sect id="debianrules">
1787 <heading>Main building script: <file>debian/rules</file></heading>
1790 This file must be an executable makefile, and contains the
1791 package-specific recipes for compiling the package and
1792 building binary package(s) from the source.
1796 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1797 so that it can be invoked by saying its name rather than
1798 invoking <prgn>make</prgn> explicitly. That is, invoking
1799 either of <tt>make -f debian/rules <em>args...</em></tt>
1800 or <tt>./debian/rules <em>args...</em></tt> must result in
1805 Since an interactive <file>debian/rules</file> script makes it
1806 impossible to auto-compile that package and also makes it
1807 hard for other people to reproduce the same binary
1808 package, all <em>required targets</em> must be
1809 non-interactive. At a minimum, required targets are the
1810 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1811 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1812 <em>binary-indep</em>, and <em>build</em>. It also follows
1813 that any target that these targets depend on must also be
1818 The targets are as follows (required unless stated otherwise):
1820 <tag><tt>build</tt></tag>
1823 The <tt>build</tt> target should perform all the
1824 configuration and compilation of the package.
1825 If a package has an interactive pre-build
1826 configuration routine, the Debian source package
1827 must either be built after this has taken place (so
1828 that the binary package can be built without rerunning
1829 the configuration) or the configuration routine
1830 modified to become non-interactive. (The latter is
1831 preferable if there are architecture-specific features
1832 detected by the configuration routine.)
1836 For some packages, notably ones where the same
1837 source tree is compiled in different ways to produce
1838 two binary packages, the <tt>build</tt> target
1839 does not make much sense. For these packages it is
1840 good enough to provide two (or more) targets
1841 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1842 for each of the ways of building the package, and a
1843 <tt>build</tt> target that does nothing. The
1844 <tt>binary</tt> target will have to build the
1845 package in each of the possible ways and make the
1846 binary package out of each.
1850 The <tt>build</tt> target must not do anything
1851 that might require root privilege.
1855 The <tt>build</tt> target may need to run the
1856 <tt>clean</tt> target first - see below.
1860 When a package has a configuration and build routine
1861 which takes a long time, or when the makefiles are
1862 poorly designed, or when <tt>build</tt> needs to
1863 run <tt>clean</tt> first, it is a good idea to
1864 <tt>touch build</tt> when the build process is
1865 complete. This will ensure that if <tt>debian/rules
1866 build</tt> is run again it will not rebuild the whole
1868 Another common way to do this is for <tt>build</tt>
1869 to depend on <prgn>build-stamp</prgn> and to do
1870 nothing else, and for the <prgn>build-stamp</prgn>
1871 target to do the building and to <tt>touch
1872 build-stamp</tt> on completion. This is
1873 especially useful if the build routine creates a
1874 file or directory called <tt>build</tt>; in such a
1875 case, <tt>build</tt> will need to be listed as
1876 a phony target (i.e., as a dependency of the
1877 <tt>.PHONY</tt> target). See the documentation of
1878 <prgn>make</prgn> for more information on phony
1884 <tag><tt>build-arch</tt> (optional),
1885 <tt>build-indep</tt> (optional)
1889 A package may also provide both of the targets
1890 <tt>build-arch</tt> and <tt>build-indep</tt>.
1891 The <tt>build-arch</tt> target, if provided, should
1892 perform all the configuration and compilation required for
1893 producing all architecture-dependant binary packages
1894 (those packages for which the body of the
1895 <tt>Architecture</tt> field in <tt>debian/control</tt> is
1896 not <tt>all</tt>). Similarly, the <tt>build-indep</tt>
1897 target, if provided, should perform all the configuration
1898 and compilation required for producing all
1899 architecture-independent binary packages (those packages
1900 for which the body of the <tt>Architecture</tt> field
1901 in <tt>debian/control</tt> is <tt>all</tt>).
1902 The <tt>build</tt> target should depend on those of the
1903 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1904 are provided in the rules file.<footnote>
1905 The intent of this split is so that binary-only builds
1906 need not install the dependencies required for
1907 the <tt>build-indep</tt> target. However, this is not
1908 yet used in practice since <tt>dpkg-buildpackage
1909 -B</tt>, and therefore the autobuilders,
1910 invoke <tt>build</tt> rather than <tt>build-arch</tt>
1911 due to the difficulties in determining whether the
1912 optional <tt>build-arch</tt> target exists.
1917 If one or both of the targets <tt>build-arch</tt> and
1918 <tt>build-indep</tt> are not provided, then invoking
1919 <file>debian/rules</file> with one of the not-provided
1920 targets as arguments should produce a exit status code
1921 of 2. Usually this is provided automatically by make
1922 if the target is missing.
1926 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1927 must not do anything that might require root privilege.
1931 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1932 <tt>binary-indep</tt>
1936 The <tt>binary</tt> target must be all that is
1937 necessary for the user to build the binary package(s)
1938 produced from this source package. It is
1939 split into two parts: <prgn>binary-arch</prgn> builds
1940 the binary packages which are specific to a particular
1941 architecture, and <tt>binary-indep</tt> builds
1942 those which are not.
1945 <tt>binary</tt> may be (and commonly is) a target with
1946 no commands which simply depends on
1947 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1950 Both <tt>binary-*</tt> targets should depend on the
1951 <tt>build</tt> target, or on the appropriate
1952 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1953 provided, so that the package is built if it has not
1954 been already. It should then create the relevant
1955 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1956 make their control files and <prgn>dpkg-deb</prgn> to
1957 build them and place them in the parent of the top
1962 Both the <tt>binary-arch</tt> and
1963 <tt>binary-indep</tt> targets <em>must</em> exist.
1964 If one of them has nothing to do (which will always be
1965 the case if the source generates only a single binary
1966 package, whether architecture-dependent or not), it
1967 must still exist and must always succeed.
1971 The <tt>binary</tt> targets must be invoked as
1973 The <prgn>fakeroot</prgn> package often allows one
1974 to build a package correctly even without being
1980 <tag><tt>clean</tt></tag>
1983 This must undo any effects that the <tt>build</tt>
1984 and <tt>binary</tt> targets may have had, except
1985 that it should leave alone any output files created in
1986 the parent directory by a run of a <tt>binary</tt>
1991 If a <tt>build</tt> file is touched at the end of
1992 the <tt>build</tt> target, as suggested above, it
1993 should be removed as the first action that
1994 <tt>clean</tt> performs, so that running
1995 <tt>build</tt> again after an interrupted
1996 <tt>clean</tt> doesn't think that everything is
2001 The <tt>clean</tt> target may need to be
2002 invoked as root if <tt>binary</tt> has been
2003 invoked since the last <tt>clean</tt>, or if
2004 <tt>build</tt> has been invoked as root (since
2005 <tt>build</tt> may create directories, for
2010 <tag><tt>get-orig-source</tt> (optional)</tag>
2013 This target fetches the most recent version of the
2014 original source package from a canonical archive site
2015 (via FTP or WWW, for example), does any necessary
2016 rearrangement to turn it into the original source
2017 tar file format described below, and leaves it in the
2022 This target may be invoked in any directory, and
2023 should take care to clean up any temporary files it
2028 This target is optional, but providing it if
2029 possible is a good idea.
2033 <tag><tt>patch</tt> (optional)</tag>
2036 This target performs whatever additional actions are
2037 required to make the source ready for editing (unpacking
2038 additional upstream archives, applying patches, etc.).
2039 It is recommended to be implemented for any package where
2040 <tt>dpkg-source -x</tt> does not result in source ready
2041 for additional modification. See
2042 <ref id="readmesource">.
2048 The <tt>build</tt>, <tt>binary</tt> and
2049 <tt>clean</tt> targets must be invoked with the current
2050 directory being the package's top-level directory.
2055 Additional targets may exist in <file>debian/rules</file>,
2056 either as published or undocumented interfaces or for the
2057 package's internal use.
2061 The architectures we build on and build for are determined
2062 by <prgn>make</prgn> variables using the utility
2063 <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
2064 You can determine the
2065 Debian architecture and the GNU style architecture
2066 specification string for the build machine (the machine type
2067 we are building on) as well as for the host machine (the
2068 machine type we are building for). Here is a list of
2069 supported <prgn>make</prgn> variables:
2070 <list compact="compact">
2072 <tt>DEB_*_ARCH</tt> (the Debian architecture)
2075 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2078 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2081 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2082 specification string)
2085 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2086 <tt>DEB_*_GNU_TYPE</tt>)
2089 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2090 <tt>DEB_*_GNU_TYPE</tt>)
2092 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2093 the build machine or <tt>HOST</tt> for specification of the
2098 Backward compatibility can be provided in the rules file
2099 by setting the needed variables to suitable default
2100 values; please refer to the documentation of
2101 <prgn>dpkg-architecture</prgn> for details.
2105 It is important to understand that the <tt>DEB_*_ARCH</tt>
2106 string only determines which Debian architecture we are
2107 building on or for. It should not be used to get the CPU
2108 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2109 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2110 GNU style variables should generally only be used with upstream
2114 <sect1 id="debianrules-options">
2115 <heading><file>debian/rules</file> and
2116 <tt>DEB_BUILD_OPTIONS</tt></heading>
2119 Supporting the standardized environment variable
2120 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2121 contain several flags to change how a package is compiled and
2122 built. Each flag must be in the form <var>flag</var> or
2123 <var>flag</var>=<var>options</var>. If multiple flags are
2124 given, they must be separated by whitespace.<footnote>
2125 Some packages support any delimiter, but whitespace is the
2126 easiest to parse inside a makefile and avoids ambiguity with
2127 flag values that contain commas.
2129 <var>flag</var> must start with a lowercase letter
2130 (<tt>a-z</tt>) and consist only of lowercase letters,
2131 numbers (<tt>0-9</tt>), and the characters
2132 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2133 <var>options</var> must not contain whitespace. The same
2134 tag should not be given multiple times with conflicting
2135 values. Package maintainers may assume that
2136 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2140 The meaning of the following tags has been standardized:
2144 This tag says to not run any build-time test suite
2145 provided by the package.
2149 The presence of this tag means that the package should
2150 be compiled with a minimum of optimization. For C
2151 programs, it is best to add <tt>-O0</tt> to
2152 <tt>CFLAGS</tt> (although this is usually the default).
2153 Some programs might fail to build or run at this level
2154 of optimization; it may be necessary to use
2155 <tt>-O1</tt>, for example.
2159 This tag means that the debugging symbols should not be
2160 stripped from the binary during installation, so that
2161 debugging information may be included in the package.
2163 <tag>parallel=n</tag>
2165 This tag means that the package should be built using up
2166 to <tt>n</tt> parallel processes if the package build
2167 system supports this.<footnote>
2168 Packages built with <tt>make</tt> can often implement
2169 this by passing the <tt>-j</tt><var>n</var> option to
2172 If the package build system does not support parallel
2173 builds, this string must be ignored. If the package
2174 build system only supports a lower level of concurrency
2175 than <var>n</var>, the package should be built using as
2176 many parallel processes as the package build system
2177 supports. It is up to the package maintainer to decide
2178 whether the package build times are long enough and the
2179 package build system is robust enough to make supporting
2180 parallel builds worthwhile.
2186 Unknown flags must be ignored by <file>debian/rules</file>.
2190 The following makefile snippet is an example of how one may
2191 implement the build options; you will probably have to
2192 massage this example in order to make it work for your
2194 <example compact="compact">
2197 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2198 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2199 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2200 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2202 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2207 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2208 INSTALL_PROGRAM += -s
2210 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2211 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2212 MAKEFLAGS += -j$(NUMJOBS)
2217 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2218 # Code to run the package test suite.
2225 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2226 <sect id="substvars">
2227 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2230 When <prgn>dpkg-gencontrol</prgn>
2231 generates <qref id="binarycontrolfiles">binary package control
2232 files</qref> (<file>DEBIAN/control</file>), it performs variable
2233 substitutions on its output just before writing it. Variable
2234 substitutions have the form <tt>${<var>variable</var>}</tt>.
2235 The optional file <file>debian/substvars</file> contains
2236 variable substitutions to be used; variables can also be set
2237 directly from <file>debian/rules</file> using the <tt>-V</tt>
2238 option to the source packaging commands, and certain predefined
2239 variables are also available.
2243 The <file>debian/substvars</file> file is usually generated and
2244 modified dynamically by <file>debian/rules</file> targets, in
2245 which case it must be removed by the <tt>clean</tt> target.
2249 See <manref name="deb-substvars" section="5"> for full
2250 details about source variable substitutions, including the
2251 format of <file>debian/substvars</file>.</p>
2254 <sect id="debianwatch">
2255 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2258 This is an optional, recommended configuration file for the
2259 <tt>uscan</tt> utility which defines how to automatically scan
2260 ftp or http sites for newly available updates of the
2261 package. This is used
2262 by <url id="http://dehs.alioth.debian.org/"> and other Debian QA
2263 tools to help with quality control and maintenance of the
2264 distribution as a whole.
2269 <sect id="debianfiles">
2270 <heading>Generated files list: <file>debian/files</file></heading>
2273 This file is not a permanent part of the source tree; it
2274 is used while building packages to record which files are
2275 being generated. <prgn>dpkg-genchanges</prgn> uses it
2276 when it generates a <file>.changes</file> file.
2280 It should not exist in a shipped source package, and so it
2281 (and any backup files or temporary files such as
2282 <file>files.new</file><footnote>
2283 <file>files.new</file> is used as a temporary file by
2284 <prgn>dpkg-gencontrol</prgn> and
2285 <prgn>dpkg-distaddfile</prgn> - they write a new
2286 version of <tt>files</tt> here before renaming it,
2287 to avoid leaving a corrupted copy if an error
2289 </footnote>) should be removed by the
2290 <tt>clean</tt> target. It may also be wise to
2291 ensure a fresh start by emptying or removing it at the
2292 start of the <tt>binary</tt> target.
2296 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2297 package, it adds an entry to <file>debian/files</file> for the
2298 <file>.deb</file> file that will be created when <tt>dpkg-deb
2299 --build</tt> is run for that binary package. So for most
2300 packages all that needs to be done with this file is to
2301 delete it in the <tt>clean</tt> target.
2305 If a package upload includes files besides the source
2306 package and any binary packages whose control files were
2307 made with <prgn>dpkg-gencontrol</prgn> then they should be
2308 placed in the parent of the package's top-level directory
2309 and <prgn>dpkg-distaddfile</prgn> should be called to add
2310 the file to the list in <file>debian/files</file>.</p>
2313 <sect id="embeddedfiles">
2314 <heading>Convenience copies of code</heading>
2317 Some software packages include in their distribution convenience
2318 copies of code from other software packages, generally so that
2319 users compiling from source don't have to download multiple
2320 packages. Debian packages should not make use of these
2321 convenience copies unless the included package is explicitly
2322 intended to be used in this way.<footnote>
2323 For example, parts of the GNU build system work like this.
2325 If the included code is already in the Debian archive in the
2326 form of a library, the Debian packaging should ensure that
2327 binary packages reference the libraries already in Debian and
2328 the convenience copy is not used. If the included code is not
2329 already in Debian, it should be packaged separately as a
2330 prerequisite if possible.
2332 Having multiple copies of the same code in Debian is
2333 inefficient, often creates either static linking or shared
2334 library conflicts, and, most importantly, increases the
2335 difficulty of handling security vulnerabilities in the
2341 <sect id="readmesource">
2342 <heading>Source package handling:
2343 <file>debian/README.source</file></heading>
2346 If running <prgn>dpkg-source -x</prgn> on a source package
2347 doesn't produce the source of the package, ready for editing,
2348 and allow one to make changes and run
2349 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2350 without taking any additional steps, creating a
2351 <file>debian/README.source</file> documentation file is
2352 recommended. This file should explain how to do all of the
2355 <item>Generate the fully patched source, in a form ready for
2356 editing, that would be built to create Debian
2357 packages. Doing this with a <tt>patch</tt> target in
2358 <file>debian/rules</file> is recommended; see
2359 <ref id="debianrules">.</item>
2360 <item>Modify the source and save those modifications so that
2361 they will be applied when building the package.</item>
2362 <item>Remove source modifications that are currently being
2363 applied when building the package.</item>
2364 <item>Optionally, document what steps are necessary to
2365 upgrade the Debian source package to a new upstream version,
2366 if applicable.</item>
2368 This explanation should include specific commands and mention
2369 any additional required Debian packages. It should not assume
2370 familiarity with any specific Debian packaging system or patch
2375 This explanation may refer to a documentation file installed by
2376 one of the package's build dependencies provided that the
2377 referenced documentation clearly explains these tasks and is not
2378 a general reference manual.
2382 <file>debian/README.source</file> may also include any other
2383 information that would be helpful to someone modifying the
2384 source package. Even if the package doesn't fit the above
2385 description, maintainers are encouraged to document in a
2386 <file>debian/README.source</file> file any source package with a
2387 particularly complex or unintuitive source layout or build
2388 system (for example, a package that builds the same source
2389 multiple times to generate different binary packages).
2395 <chapt id="controlfields">
2396 <heading>Control files and their fields</heading>
2399 The package management system manipulates data represented in
2400 a common format, known as <em>control data</em>, stored in
2401 <em>control files</em>.
2402 Control files are used for source packages, binary packages and
2403 the <file>.changes</file> files which control the installation
2404 of uploaded files<footnote>
2405 <prgn>dpkg</prgn>'s internal databases are in a similar
2410 <sect id="controlsyntax">
2411 <heading>Syntax of control files</heading>
2414 A control file consists of one or more paragraphs of
2416 The paragraphs are also sometimes referred to as stanzas.
2418 The paragraphs are separated by blank lines. Some control
2419 files allow only one paragraph; others allow several, in
2420 which case each paragraph usually refers to a different
2421 package. (For example, in source packages, the first
2422 paragraph refers to the source package, and later paragraphs
2423 refer to binary packages generated from the source.)
2427 Each paragraph consists of a series of data fields; each
2428 field consists of the field name, followed by a colon and
2429 then the data/value associated with that field. It ends at
2430 the end of the (logical) line. Horizontal whitespace
2431 (spaces and tabs) may occur immediately before or after the
2432 value and is ignored there; it is conventional to put a
2433 single space after the colon. For example, a field might
2435 <example compact="compact">
2438 the field name is <tt>Package</tt> and the field value
2443 A paragraph must not contain more than one instance of a
2444 particular field name.
2448 Many fields' values may span several lines; in this case
2449 each continuation line must start with a space or a tab.
2450 Any trailing spaces or tabs at the end of individual
2451 lines of a field value are ignored.
2455 In fields where it is specified that lines may not wrap,
2456 only a single line of data is allowed and whitespace is not
2457 significant in a field body. Whitespace must not appear
2458 inside names (of packages, architectures, files or anything
2459 else) or version numbers, or between the characters of
2460 multi-character version relationships.
2464 Field names are not case-sensitive, but it is usual to
2465 capitalize the field names using mixed case as shown below.
2466 Field values are case-sensitive unless the description of the
2467 field says otherwise.
2471 Blank lines, or lines consisting only of spaces and tabs,
2472 are not allowed within field values or between fields - that
2473 would mean a new paragraph.
2477 All control files must be encoded in UTF-8.
2481 <sect id="sourcecontrolfiles">
2482 <heading>Source package control files -- <file>debian/control</file></heading>
2485 The <file>debian/control</file> file contains the most vital
2486 (and version-independent) information about the source package
2487 and about the binary packages it creates.
2491 The first paragraph of the control file contains information about
2492 the source package in general. The subsequent sets each describe a
2493 binary package that the source tree builds.
2497 The fields in the general paragraph (the first one, for the source
2500 <list compact="compact">
2501 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2502 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2503 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2504 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2505 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2506 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2507 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2508 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2513 The fields in the binary package paragraphs are:
2515 <list compact="compact">
2516 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2517 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2518 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2519 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2520 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2521 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2522 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2523 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2528 The syntax and semantics of the fields are described below.
2532 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2533 generate control files for binary packages (see below), by
2534 <prgn>dpkg-genchanges</prgn> to generate the
2535 <file>.changes</file> file to accompany the upload, and by
2536 <prgn>dpkg-source</prgn> when it creates the
2537 <file>.dsc</file> source control file as part of a source
2538 archive. Many fields are permitted to span multiple lines in
2539 <file>debian/control</file> but not in any other control
2540 file. These tools are responsible for removing the line
2541 breaks from such fields when using fields from
2542 <file>debian/control</file> to generate other control files.
2546 The fields here may contain variable references - their
2547 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2548 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2549 when they generate output control files.
2550 See <ref id="substvars"> for details.
2554 In addition to the control file syntax described <qref
2555 id="controlsyntax">above</qref>, this file may also contain
2556 comment lines starting with <tt>#</tt> without any preceding
2557 whitespace. All such lines are ignored, even in the middle of
2558 continuation lines for a multiline field, and do not end a
2564 <sect id="binarycontrolfiles">
2565 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2568 The <file>DEBIAN/control</file> file contains the most vital
2569 (and version-dependent) information about a binary package. It
2570 consists of a single paragraph.
2574 The fields in this file are:
2576 <list compact="compact">
2577 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2578 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2579 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2580 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2581 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2582 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2583 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2584 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2585 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2586 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2587 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2588 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2593 <sect id="debiansourcecontrolfiles">
2594 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2597 This file consists of a single paragraph, possibly surrounded by
2598 a PGP signature. The fields of that paragraph are listed below.
2599 Their syntax is described above, in <ref id="pkg-controlfields">.
2601 <list compact="compact">
2602 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2603 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2604 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2605 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2606 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2607 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2608 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2609 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2610 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2611 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2612 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2613 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2614 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2619 The source package control file is generated by
2620 <prgn>dpkg-source</prgn> when it builds the source
2621 archive, from other files in the source package,
2622 described above. When unpacking, it is checked against
2623 the files and directories in the other parts of the
2629 <sect id="debianchangesfiles">
2630 <heading>Debian changes files -- <file>.changes</file></heading>
2633 The <file>.changes</file> files are used by the Debian archive
2634 maintenance software to process updates to packages. They
2635 consist of a single paragraph, possibly surrounded by a PGP
2636 signature. That paragraph contains information from the
2637 <file>debian/control</file> file and other data about the
2638 source package gathered via <file>debian/changelog</file>
2639 and <file>debian/rules</file>.
2643 <file>.changes</file> files have a format version that is
2644 incremented whenever the documented fields or their meaning
2645 change. This document describes format &changesversion;.
2649 The fields in this file are:
2651 <list compact="compact">
2652 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2653 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2654 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2655 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2656 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2657 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2658 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2659 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2660 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2661 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2662 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2663 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2664 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2665 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2666 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2667 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2672 <sect id="controlfieldslist">
2673 <heading>List of fields</heading>
2675 <sect1 id="f-Source">
2676 <heading><tt>Source</tt></heading>
2679 This field identifies the source package name.
2683 In <file>debian/control</file> or a <file>.dsc</file> file,
2684 this field must contain only the name of the source package.
2688 In a binary package control file or a <file>.changes</file>
2689 file, the source package name may be followed by a version
2690 number in parentheses<footnote>
2691 It is customary to leave a space after the package name
2692 if a version number is specified.
2694 This version number may be omitted (and is, by
2695 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2696 the <tt>Version</tt> field of the binary package in
2697 question. The field itself may be omitted from a binary
2698 package control file when the source package has the same
2699 name and version as the binary package.
2703 Package names (both source and binary,
2704 see <ref id="f-Package">) must consist only of lower case
2705 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2706 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2707 (<tt>.</tt>). They must be at least two characters long and
2708 must start with an alphanumeric character.
2712 <sect1 id="f-Maintainer">
2713 <heading><tt>Maintainer</tt></heading>
2716 The package maintainer's name and email address. The name
2717 must come first, then the email address inside angle
2718 brackets <tt><></tt> (in RFC822 format).
2722 If the maintainer's name contains a full stop then the
2723 whole field will not work directly as an email address due
2724 to a misfeature in the syntax specified in RFC822; a
2725 program using this field as an address must check for this
2726 and correct the problem if necessary (for example by
2727 putting the name in round brackets and moving it to the
2728 end, and bringing the email address forward).
2732 <sect1 id="f-Uploaders">
2733 <heading><tt>Uploaders</tt></heading>
2736 List of the names and email addresses of co-maintainers of
2737 the package, if any. If the package has other maintainers
2738 beside the one named in the
2739 <qref id="f-Maintainer">Maintainer field</qref>, their names
2740 and email addresses should be listed here. The format of each
2741 entry is the same as that of the Maintainer field, and
2742 multiple entries must be comma separated. This is an optional
2747 Any parser that interprets the Uploaders field in
2748 <file>debian/control</file> must permit it to span multiple
2749 lines. Line breaks in an Uploaders field that spans multiple
2750 lines are not significant and the semantics of the field are
2751 the same as if the line breaks had not been present.
2755 <sect1 id="f-Changed-By">
2756 <heading><tt>Changed-By</tt></heading>
2759 The name and email address of the person who prepared this
2760 version of the package, usually a maintainer. The syntax is
2761 the same as for the <qref id="f-Maintainer">Maintainer
2766 <sect1 id="f-Section">
2767 <heading><tt>Section</tt></heading>
2770 This field specifies an application area into which the package
2771 has been classified. See <ref id="subsections">.
2775 When it appears in the <file>debian/control</file> file,
2776 it gives the value for the subfield of the same name in
2777 the <tt>Files</tt> field of the <file>.changes</file> file.
2778 It also gives the default for the same field in the binary
2783 <sect1 id="f-Priority">
2784 <heading><tt>Priority</tt></heading>
2787 This field represents how important it is that the user
2788 have the package installed. See <ref id="priorities">.
2792 When it appears in the <file>debian/control</file> file,
2793 it gives the value for the subfield of the same name in
2794 the <tt>Files</tt> field of the <file>.changes</file> file.
2795 It also gives the default for the same field in the binary
2800 <sect1 id="f-Package">
2801 <heading><tt>Package</tt></heading>
2804 The name of the binary package.
2808 Binary package names must follow the same syntax and
2809 restrictions as source package names. See <ref id="f-Source">
2814 <sect1 id="f-Architecture">
2815 <heading><tt>Architecture</tt></heading>
2818 Depending on context and the control file used, the
2819 <tt>Architecture</tt> field can include the following sets of
2823 A unique single word identifying a Debian machine
2824 architecture as described in <ref id="arch-spec">.
2827 An architecture wildcard identifying a set of Debian
2828 machine architectures, see <ref id="arch-wildcard-spec">.
2829 <tt>any</tt> matches all Debian machine architectures
2830 and is the most frequently used.
2833 <tt>all</tt>, which indicates an
2834 architecture-independent package.
2837 <tt>source</tt>, which indicates a source package.
2843 In the main <file>debian/control</file> file in the source
2844 package, this field may contain the special
2845 value <tt>all</tt>, the special architecture
2846 wildcard <tt>any</tt>, or a list of specific and wildcard
2847 architectures separated by spaces. If <tt>all</tt>
2848 or <tt>any</tt> appears, that value must be the entire
2849 contents of the field. Most packages will use
2850 either <tt>all</tt> or <tt>any</tt>.
2854 Specifying a specific list of architectures indicates that the
2855 source will build an architecture-dependent package only on
2856 architectures included in the list. Specifying a list of
2857 architecture wildcards indicates that the source will build an
2858 architecture-dependent package on only those architectures
2859 that match any of the specified architecture wildcards.
2860 Specifying a list of architectures or architecture wildcards
2861 other than <tt>any</tt> is for the minority of cases where a
2862 program is not portable or is not useful on some
2863 architectures. Where possible, the program should be made
2868 In the source package control file <file>.dsc</file>, this
2869 field may contain either the architecture
2870 wildcard <tt>any</tt> or a list of architectures and
2871 architecture wildcards separated by spaces. If a list is
2872 given, it may include (or consist solely of) the special
2873 value <tt>all</tt>. In other words, in <file>.dsc</file>
2874 files unlike the <file>debian/control</file>, <tt>all</tt> may
2875 occur in combination with specific architectures.
2876 The <tt>Architecture</tt> field in the source package control
2877 file <file>.dsc</file> is generally constructed from
2878 the <tt>Architecture</tt> fields in
2879 the <file>debian/control</file> in the source package.
2883 Specifying <tt>any</tt> indicates that the source package
2884 isn't dependent on any particular architecture and should
2885 compile fine on any one. The produced binary package(s)
2886 will either be specific to whatever the current build
2887 architecture is or will be architecture-independent.
2891 Specifying only <tt>all</tt> indicates that the source package
2892 will only build architecture-independent packages. If this is
2893 the case, <tt>all</tt> must be used rather than <tt>any</tt>;
2894 <tt>any</tt> implies that the source package will build at
2895 least one architecture-dependent package.
2899 Specifying a list of architectures or architecture wildcards
2900 indicates that the source will build an architecture-dependent
2901 package, and will only work correctly on the listed or
2902 matching architectures. If the source package also builds at
2903 least one architecture-independent package, <tt>all</tt> will
2904 also be included in the list.
2908 In a <file>.changes</file> file, the <tt>Architecture</tt>
2909 field lists the architecture(s) of the package(s) currently
2910 being uploaded. This will be a list; if the source for the
2911 package is also being uploaded, the special
2912 entry <tt>source</tt> is also present. <tt>all</tt> will be
2913 present if any architecture-independent packages are being
2914 uploaded. Architecture wildcards such as <tt>any</tt> must
2915 never occur in the <tt>Architecture</tt> field in
2916 the <file>.changes</file> file.
2920 See <ref id="debianrules"> for information on how to get
2921 the architecture for the build process.
2925 <sect1 id="f-Essential">
2926 <heading><tt>Essential</tt></heading>
2929 This is a boolean field which may occur only in the
2930 control file of a binary package or in a per-package fields
2931 paragraph of a main source control data file.
2935 If set to <tt>yes</tt> then the package management system
2936 will refuse to remove the package (upgrading and replacing
2937 it is still possible). The other possible value is <tt>no</tt>,
2938 which is the same as not having the field at all.
2943 <heading>Package interrelationship fields:
2944 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2945 <tt>Recommends</tt>, <tt>Suggests</tt>,
2946 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2947 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2951 These fields describe the package's relationships with
2952 other packages. Their syntax and semantics are described
2953 in <ref id="relationships">.</p>
2956 <sect1 id="f-Standards-Version">
2957 <heading><tt>Standards-Version</tt></heading>
2960 The most recent version of the standards (the policy
2961 manual and associated texts) with which the package
2966 The version number has four components: major and minor
2967 version number and major and minor patch level. When the
2968 standards change in a way that requires every package to
2969 change the major number will be changed. Significant
2970 changes that will require work in many packages will be
2971 signaled by a change to the minor number. The major patch
2972 level will be changed for any change to the meaning of the
2973 standards, however small; the minor patch level will be
2974 changed when only cosmetic, typographical or other edits
2975 are made which neither change the meaning of the document
2976 nor affect the contents of packages.
2980 Thus only the first three components of the policy version
2981 are significant in the <em>Standards-Version</em> control
2982 field, and so either these three components or all four
2983 components may be specified.<footnote>
2984 In the past, people specified the full version number
2985 in the Standards-Version field, for example "2.3.0.0".
2986 Since minor patch-level changes don't introduce new
2987 policy, it was thought it would be better to relax
2988 policy and only require the first 3 components to be
2989 specified, in this example "2.3.0". All four
2990 components may still be used if someone wishes to do so.
2996 <sect1 id="f-Version">
2997 <heading><tt>Version</tt></heading>
3000 The version number of a package. The format is:
3001 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
3005 The three components here are:
3007 <tag><var>epoch</var></tag>
3010 This is a single (generally small) unsigned integer. It
3011 may be omitted, in which case zero is assumed. If it is
3012 omitted then the <var>upstream_version</var> may not
3017 It is provided to allow mistakes in the version numbers
3018 of older versions of a package, and also a package's
3019 previous version numbering schemes, to be left behind.
3023 <tag><var>upstream_version</var></tag>
3026 This is the main part of the version number. It is
3027 usually the version number of the original ("upstream")
3028 package from which the <file>.deb</file> file has been made,
3029 if this is applicable. Usually this will be in the same
3030 format as that specified by the upstream author(s);
3031 however, it may need to be reformatted to fit into the
3032 package management system's format and comparison
3037 The comparison behavior of the package management system
3038 with respect to the <var>upstream_version</var> is
3039 described below. The <var>upstream_version</var>
3040 portion of the version number is mandatory.
3044 The <var>upstream_version</var> may contain only
3045 alphanumerics<footnote>
3046 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3048 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3049 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3050 tilde) and should start with a digit. If there is no
3051 <var>debian_revision</var> then hyphens are not allowed;
3052 if there is no <var>epoch</var> then colons are not
3057 <tag><var>debian_revision</var></tag>
3060 This part of the version number specifies the version of
3061 the Debian package based on the upstream version. It
3062 may contain only alphanumerics and the characters
3063 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3064 tilde) and is compared in the same way as the
3065 <var>upstream_version</var> is.
3069 It is optional; if it isn't present then the
3070 <var>upstream_version</var> may not contain a hyphen.
3071 This format represents the case where a piece of
3072 software was written specifically to be a Debian
3073 package, where the Debian package source must always
3074 be identical to the pristine source and therefore no
3075 revision indication is required.
3079 It is conventional to restart the
3080 <var>debian_revision</var> at <tt>1</tt> each time the
3081 <var>upstream_version</var> is increased.
3085 The package management system will break the version
3086 number apart at the last hyphen in the string (if there
3087 is one) to determine the <var>upstream_version</var> and
3088 <var>debian_revision</var>. The absence of a
3089 <var>debian_revision</var> is equivalent to a
3090 <var>debian_revision</var> of <tt>0</tt>.
3097 When comparing two version numbers, first the <var>epoch</var>
3098 of each are compared, then the <var>upstream_version</var> if
3099 <var>epoch</var> is equal, and then <var>debian_revision</var>
3100 if <var>upstream_version</var> is also equal.
3101 <var>epoch</var> is compared numerically. The
3102 <var>upstream_version</var> and <var>debian_revision</var>
3103 parts are compared by the package management system using the
3104 following algorithm:
3108 The strings are compared from left to right.
3112 First the initial part of each string consisting entirely of
3113 non-digit characters is determined. These two parts (one of
3114 which may be empty) are compared lexically. If a difference
3115 is found it is returned. The lexical comparison is a
3116 comparison of ASCII values modified so that all the letters
3117 sort earlier than all the non-letters and so that a tilde
3118 sorts before anything, even the end of a part. For example,
3119 the following parts are in sorted order from earliest to
3120 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3121 <tt>a</tt>.<footnote>
3122 One common use of <tt>~</tt> is for upstream pre-releases.
3123 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3124 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3129 Then the initial part of the remainder of each string which
3130 consists entirely of digit characters is determined. The
3131 numerical values of these two parts are compared, and any
3132 difference found is returned as the result of the comparison.
3133 For these purposes an empty string (which can only occur at
3134 the end of one or both version strings being compared) counts
3139 These two steps (comparing and removing initial non-digit
3140 strings and initial digit strings) are repeated until a
3141 difference is found or both strings are exhausted.
3145 Note that the purpose of epochs is to allow us to leave behind
3146 mistakes in version numbering, and to cope with situations
3147 where the version numbering scheme changes. It is
3148 <em>not</em> intended to cope with version numbers containing
3149 strings of letters which the package management system cannot
3150 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3151 silly orderings.<footnote>
3152 The author of this manual has heard of a package whose
3153 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3154 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3160 <sect1 id="f-Description">
3161 <heading><tt>Description</tt></heading>
3164 In a source or binary control file, the <tt>Description</tt>
3165 field contains a description of the binary package, consisting
3166 of two parts, the synopsis or the short description, and the
3167 long description. The field's format is as follows:
3172 Description: <single line synopsis>
3173 <extended description over several lines>
3178 The lines in the extended description can have these formats:
3184 Those starting with a single space are part of a paragraph.
3185 Successive lines of this form will be word-wrapped when
3186 displayed. The leading space will usually be stripped off.
3190 Those starting with two or more spaces. These will be
3191 displayed verbatim. If the display cannot be panned
3192 horizontally, the displaying program will line wrap them "hard"
3193 (i.e., without taking account of word breaks). If it can they
3194 will be allowed to trail off to the right. None, one or two
3195 initial spaces may be deleted, but the number of spaces
3196 deleted from each line will be the same (so that you can have
3197 indenting work correctly, for example).
3201 Those containing a single space followed by a single full stop
3202 character. These are rendered as blank lines. This is the
3203 <em>only</em> way to get a blank line<footnote>
3204 Completely empty lines will not be rendered as blank lines.
3205 Instead, they will cause the parser to think you're starting
3206 a whole new record in the control file, and will therefore
3207 likely abort with an error.
3212 Those containing a space, a full stop and some more characters.
3213 These are for future expansion. Do not use them.
3219 Do not use tab characters. Their effect is not predictable.
3223 See <ref id="descriptions"> for further information on this.
3227 In a <file>.changes</file> file, the <tt>Description</tt>
3228 field contains a summary of the descriptions for the packages
3229 being uploaded. For this case, the first line of the field
3230 value (the part on the same line as <tt>Description:</tt>) is
3231 always empty. The content of the field is expressed as
3232 continuation lines, one line per package. Each line is
3233 indented by one space and contains the name of a binary
3234 package, a space, a hyphen (<tt>-</tt>), a space, and the
3235 short description line from that package.
3239 <sect1 id="f-Distribution">
3240 <heading><tt>Distribution</tt></heading>
3243 In a <file>.changes</file> file or parsed changelog output
3244 this contains the (space-separated) name(s) of the
3245 distribution(s) where this version of the package should
3246 be installed. Valid distributions are determined by the
3247 archive maintainers.<footnote>
3248 Example distribution names in the Debian archive used in
3249 <file>.changes</file> files are:
3250 <taglist compact="compact">
3251 <tag><em>unstable</em></tag>
3253 This distribution value refers to the
3254 <em>developmental</em> part of the Debian distribution
3255 tree. Most new packages, new upstream versions of
3256 packages and bug fixes go into the <em>unstable</em>
3260 <tag><em>experimental</em></tag>
3262 The packages with this distribution value are deemed
3263 by their maintainers to be high risk. Oftentimes they
3264 represent early beta or developmental packages from
3265 various sources that the maintainers want people to
3266 try, but are not ready to be a part of the other parts
3267 of the Debian distribution tree.
3272 Others are used for updating stable releases or for
3273 security uploads. More information is available in the
3274 Debian Developer's Reference, section "The Debian
3278 The Debian archive software only supports listing a single
3279 distribution. Migration of packages to other distributions is
3280 handled outside of the upload process.
3285 <heading><tt>Date</tt></heading>
3288 This field includes the date the package was built or last
3289 edited. It must be in the same format as the <var>date</var>
3290 in a <file>debian/changelog</file> entry.
3294 The value of this field is usually extracted from the
3295 <file>debian/changelog</file> file - see
3296 <ref id="dpkgchangelog">).
3300 <sect1 id="f-Format">
3301 <heading><tt>Format</tt></heading>
3304 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3305 files, this field declares the format version of that file.
3306 The syntax of the field value is the same as that of
3307 a <qref id="f-Version">package version number</qref> except
3308 that no epoch or Debian revision is allowed. The format
3309 described in this document is <tt>&changesversion;</tt>.
3313 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3314 Debian source control</qref> files, this field declares the
3315 format of the source package. The field value is used by
3316 programs acting on a source package to interpret the list of
3317 files in the source package and determine how to unpack it.
3318 The syntax of the field value is a numeric major revision, a
3319 period, a numeric minor revision, and then an optional subtype
3320 after whitespace, which if specified is an alphanumeric word
3321 in parentheses. The subtype is optional in the syntax but may
3322 be mandatory for particular source format revisions.
3324 The source formats currently supported by the Debian archive
3325 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3326 and <tt>3.0 (quilt)</tt>.
3331 <sect1 id="f-Urgency">
3332 <heading><tt>Urgency</tt></heading>
3335 This is a description of how important it is to upgrade to
3336 this version from previous ones. It consists of a single
3337 keyword taking one of the values <tt>low</tt>,
3338 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3339 <tt>critical</tt><footnote>
3340 Other urgency values are supported with configuration
3341 changes in the archive software but are not used in Debian.
3342 The urgency affects how quickly a package will be considered
3343 for inclusion into the <tt>testing</tt> distribution and
3344 gives an indication of the importance of any fixes included
3345 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3346 treated as synonymous.
3347 </footnote> (not case-sensitive) followed by an optional
3348 commentary (separated by a space) which is usually in
3349 parentheses. For example:
3352 Urgency: low (HIGH for users of diversions)
3358 The value of this field is usually extracted from the
3359 <file>debian/changelog</file> file - see
3360 <ref id="dpkgchangelog">.
3364 <sect1 id="f-Changes">
3365 <heading><tt>Changes</tt></heading>
3368 This field contains the human-readable changes data, describing
3369 the differences between the last version and the current one.
3373 The first line of the field value (the part on the same line
3374 as <tt>Changes:</tt>) is always empty. The content of the
3375 field is expressed as continuation lines, with each line
3376 indented by at least one space. Blank lines must be
3377 represented by a line consisting only of a space and a full
3382 The value of this field is usually extracted from the
3383 <file>debian/changelog</file> file - see
3384 <ref id="dpkgchangelog">).
3388 Each version's change information should be preceded by a
3389 "title" line giving at least the version, distribution(s)
3390 and urgency, in a human-readable way.
3394 If data from several versions is being returned the entry
3395 for the most recent version should be returned first, and
3396 entries should be separated by the representation of a
3397 blank line (the "title" line may also be followed by the
3398 representation of a blank line).
3402 <sect1 id="f-Binary">
3403 <heading><tt>Binary</tt></heading>
3406 This field is a list of binary packages. Its syntax and
3407 meaning varies depending on the control file in which it
3412 When it appears in the <file>.dsc</file> file, it lists binary
3413 packages which a source package can produce, separated by
3415 A space after each comma is conventional.
3416 </footnote>. It may span multiple lines. The source package
3417 does not necessarily produce all of these binary packages for
3418 every architecture. The source control file doesn't contain
3419 details of which architectures are appropriate for which of
3420 the binary packages.
3424 When it appears in a <file>.changes</file> file, it lists the
3425 names of the binary packages being uploaded, separated by
3426 whitespace (not commas). It may span multiple lines.
3430 <sect1 id="f-Installed-Size">
3431 <heading><tt>Installed-Size</tt></heading>
3434 This field appears in the control files of binary packages,
3435 and in the <file>Packages</file> files. It gives an estimate
3436 of the total amount of disk space required to install the
3437 named package. Actual installed size may vary based on block
3438 size, file system properties, or actions taken by package
3443 The disk space is given as the integer value of the estimated
3444 installed size in bytes, divided by 1024 and rounded up.
3448 <sect1 id="f-Files">
3449 <heading><tt>Files</tt></heading>
3452 This field contains a list of files with information about
3453 each one. The exact information and syntax varies with
3458 In all cases, Files is a multiline field. The first line of
3459 the field value (the part on the same line as <tt>Files:</tt>)
3460 is always empty. The content of the field is expressed as
3461 continuation lines, one line per file. Each line must be
3462 indented by one space and contain a number of sub-fields,
3463 separated by spaces, as described below.
3467 In the <file>.dsc</file> file, each line contains the MD5
3468 checksum, size and filename of the tar file and (if
3469 applicable) diff file which make up the remainder of the
3470 source package<footnote>
3471 That is, the parts which are not the <tt>.dsc</tt>.
3472 </footnote>. For example:
3475 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3476 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3478 The exact forms of the filenames are described
3479 in <ref id="pkg-sourcearchives">.
3483 In the <file>.changes</file> file this contains one line per
3484 file being uploaded. Each line contains the MD5 checksum,
3485 size, section and priority and the filename. For example:
3488 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3489 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3490 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3491 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3493 The <qref id="f-Section">section</qref>
3494 and <qref id="f-Priority">priority</qref> are the values of
3495 the corresponding fields in the main source control file. If
3496 no section or priority is specified then <tt>-</tt> should be
3497 used, though section and priority values must be specified for
3498 new packages to be installed properly.
3502 The special value <tt>byhand</tt> for the section in a
3503 <tt>.changes</tt> file indicates that the file in question
3504 is not an ordinary package file and must by installed by
3505 hand by the distribution maintainers. If the section is
3506 <tt>byhand</tt> the priority should be <tt>-</tt>.
3510 If a new Debian revision of a package is being shipped and
3511 no new original source archive is being distributed the
3512 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3513 entry for the original source archive
3514 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3515 but the <file>.changes</file> file should leave it out. In
3516 this case the original source archive on the distribution
3517 site must match exactly, byte-for-byte, the original
3518 source archive which was used to generate the
3519 <file>.dsc</file> file and diff which are being uploaded.</p>
3522 <sect1 id="f-Closes">
3523 <heading><tt>Closes</tt></heading>
3526 A space-separated list of bug report numbers that the upload
3527 governed by the .changes file closes.
3531 <sect1 id="f-Homepage">
3532 <heading><tt>Homepage</tt></heading>
3535 The URL of the web site for this package, preferably (when
3536 applicable) the site from which the original source can be
3537 obtained and any additional upstream documentation or
3538 information may be found. The content of this field is a
3539 simple URL without any surrounding characters such as
3544 <sect1 id="f-Checksums">
3545 <heading><tt>Checksums-Sha1</tt>
3546 and <tt>Checksums-Sha256</tt></heading>
3549 These fields contain a list of files with a checksum and size
3550 for each one. Both <tt>Checksums-Sha1</tt>
3551 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3552 only in the checksum algorithm used: SHA-1
3553 for <tt>Checksums-Sha1</tt> and SHA-256
3554 for <tt>Checksums-Sha256</tt>.
3558 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3559 multiline fields. The first line of the field value (the part
3560 on the same line as <tt>Checksums-Sha1:</tt>
3561 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3562 of the field is expressed as continuation lines, one line per
3563 file. Each line consists of the checksum, a space, the file
3564 size, a space, and the file name. For example (from
3565 a <file>.changes</file> file):
3568 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3569 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3570 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3571 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3573 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3574 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3575 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3576 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3581 In the <file>.dsc</file> file, these fields should list all
3582 files that make up the source package. In
3583 the <file>.changes</file> file, these fields should list all
3584 files being uploaded. The list of files in these fields
3585 must match the list of files in the <tt>Files</tt> field.
3591 <heading>User-defined fields</heading>
3594 Additional user-defined fields may be added to the
3595 source package control file. Such fields will be
3596 ignored, and not copied to (for example) binary or
3597 source package control files or upload control files.
3601 If you wish to add additional unsupported fields to
3602 these output files you should use the mechanism
3607 Fields in the main source control information file with
3608 names starting <tt>X</tt>, followed by one or more of
3609 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3610 be copied to the output files. Only the part of the
3611 field name after the hyphen will be used in the output
3612 file. Where the letter <tt>B</tt> is used the field
3613 will appear in binary package control files, where the
3614 letter <tt>S</tt> is used in source package control
3615 files and where <tt>C</tt> is used in upload control
3616 (<tt>.changes</tt>) files.
3620 For example, if the main source information control file
3623 XBS-Comment: I stand between the candle and the star.
3625 then the binary and source package control files will contain the
3628 Comment: I stand between the candle and the star.
3637 <chapt id="maintainerscripts">
3638 <heading>Package maintainer scripts and installation procedure</heading>
3641 <heading>Introduction to package maintainer scripts</heading>
3644 It is possible to supply scripts as part of a package which
3645 the package management system will run for you when your
3646 package is installed, upgraded or removed.
3650 These scripts are the control information
3651 files <prgn>preinst</prgn>, <prgn>postinst</prgn>, <prgn>prerm</prgn>
3652 and <prgn>postrm</prgn>. They must be proper executable files;
3653 if they are scripts (which is recommended), they must start with
3654 the usual <tt>#!</tt> convention. They should be readable and
3655 executable by anyone, and must not be world-writable.
3659 The package management system looks at the exit status from
3660 these scripts. It is important that they exit with a
3661 non-zero status if there is an error, so that the package
3662 management system can stop its processing. For shell
3663 scripts this means that you <em>almost always</em> need to
3664 use <tt>set -e</tt> (this is usually true when writing shell
3665 scripts, in fact). It is also important, of course, that
3666 they exit with a zero status if everything went well.
3670 Additionally, packages interacting with users
3671 using <prgn>debconf</prgn> in the <prgn>postinst</prgn> script
3672 should install a <prgn>config</prgn> script as a control
3673 information file. See <ref id="maintscriptprompt"> for details.
3677 When a package is upgraded a combination of the scripts from
3678 the old and new packages is called during the upgrade
3679 procedure. If your scripts are going to be at all
3680 complicated you need to be aware of this, and may need to
3681 check the arguments to your scripts.
3685 Broadly speaking the <prgn>preinst</prgn> is called before
3686 (a particular version of) a package is unpacked, and the
3687 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3688 before (a version of) a package is removed and the
3689 <prgn>postrm</prgn> afterwards.
3693 Programs called from maintainer scripts should not normally
3694 have a path prepended to them. Before installation is
3695 started, the package management system checks to see if the
3696 programs <prgn>ldconfig</prgn>,
3697 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3698 and <prgn>update-rc.d</prgn> can be found via the
3699 <tt>PATH</tt> environment variable. Those programs, and any
3700 other program that one would expect to be in the
3701 <tt>PATH</tt>, should thus be invoked without an absolute
3702 pathname. Maintainer scripts should also not reset the
3703 <tt>PATH</tt>, though they might choose to modify it by
3704 prepending or appending package-specific directories. These
3705 considerations really apply to all shell scripts.</p>
3708 <sect id="idempotency">
3709 <heading>Maintainer scripts idempotency</heading>
3712 It is necessary for the error recovery procedures that the
3713 scripts be idempotent. This means that if it is run
3714 successfully, and then it is called again, it doesn't bomb
3715 out or cause any harm, but just ensures that everything is
3716 the way it ought to be. If the first call failed, or
3717 aborted half way through for some reason, the second call
3718 should merely do the things that were left undone the first
3719 time, if any, and exit with a success status if everything
3721 This is so that if an error occurs, the user interrupts
3722 <prgn>dpkg</prgn> or some other unforeseen circumstance
3723 happens you don't leave the user with a badly-broken
3724 package when <prgn>dpkg</prgn> attempts to repeat the
3730 <sect id="controllingterminal">
3731 <heading>Controlling terminal for maintainer scripts</heading>
3734 Maintainer scripts are not guaranteed to run with a controlling
3735 terminal and may not be able to interact with the user. They
3736 must be able to fall back to noninteractive behavior if no
3737 controlling terminal is available. Maintainer scripts that
3738 prompt via a program conforming to the Debian Configuration
3739 Management Specification (see <ref id="maintscriptprompt">) may
3740 assume that program will handle falling back to noninteractive
3745 For high-priority prompts without a reasonable default answer,
3746 maintainer scripts may abort if there is no controlling
3747 terminal. However, this situation should be avoided if at all
3748 possible, since it prevents automated or unattended installs.
3749 In most cases, users will consider this to be a bug in the
3754 <sect id="exitstatus">
3755 <heading>Exit status</heading>
3758 Each script must return a zero exit status for
3759 success, or a nonzero one for failure, since the package
3760 management system looks for the exit status of these scripts
3761 and determines what action to take next based on that datum.
3765 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3770 What follows is a summary of all the ways in which maintainer
3771 scripts may be called along with what facilities those scripts
3772 may rely on being available at that time. Script names preceded
3773 by <var>new-</var> are the scripts from the new version of a
3774 package being installed, upgraded to, or downgraded to. Script
3775 names preceded by <var>old-</var> are the scripts from the old
3776 version of a package that is being upgraded from or downgraded
3781 The <prgn>preinst</prgn> script may be called in the following
3784 <tag><var>new-preinst</var> <tt>install</tt></tag>
3785 <tag><var>new-preinst</var> <tt>install</tt>
3786 <var>old-version</var></tag>
3787 <tag><var>new-preinst</var> <tt>upgrade</tt>
3788 <var>old-version</var></tag>
3790 The package will not yet be unpacked, so
3791 the <prgn>preinst</prgn> script cannot rely on any files
3792 included in its package. Only essential packages and
3793 pre-dependencies (<tt>Pre-Depends</tt>) may be assumed to be
3794 available. Pre-dependencies will be at least unpacked.
3795 They may be only unpacked or "Half-Configured", not
3796 completely configured, but only if a previous version of the
3797 pre-dependency was completely configured and the
3798 pre-dependency had not been removed since then.
3801 <tag><var>old-preinst</var> <tt>abort-upgrade</tt>
3802 <var>new-version</var></tag>
3804 Called during error handling of an upgrade that failed after
3805 unpacking the new package because the <tt>postrm
3806 upgrade</tt> action failed. The unpacked files may be
3807 partly from the new version or partly missing, so the script
3808 cannot not rely on files included in the package. Package
3809 dependencies may not be available. Pre-dependencies will be
3810 at least unpacked following the same rules as above, except
3811 they may be only "Half-Installed" if an upgrade of the
3812 pre-dependency failed.<footnote>
3813 This can happen if the new version of the package no
3814 longer pre-depends on a package that had been partially
3822 The <prgn>postinst</prgn> script may be called in the following
3825 <tag><var>postinst</var> <tt>configure</tt>
3826 <var>most-recently-configured-version</var></tag>
3828 The files contained in the package will be unpacked. All
3829 package dependencies will at least be unpacked. If there
3830 are no circular dependencies involved, all package
3831 dependencies will be configured.
3834 <tag><var>old-postinst</var> <tt>abort-upgrade</tt>
3835 <var>new-version</var></tag>
3836 <tag><var>conflictor's-postinst</var> <tt>abort-remove</tt>
3837 <tt>in-favour</tt> <var>package</var>
3838 <var>new-version</var></tag>
3839 <tag><var>postinst</var> <tt>abort-remove</tt></tag>
3840 <tag><var>deconfigured's-postinst</var>
3841 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3842 <var>failed-install-package</var> <var>version</var>
3843 [<tt>removing</tt> <var>conflicting-package</var>
3844 <var>version</var>]</tag>
3846 The files contained in the package will be unpacked. All
3847 package dependencies will at least be "Half-Installed" and
3848 will have previously been configured and not removed.
3849 However, dependencies may not be configured or even fully
3850 unpacked in some error situations.<footnote>
3851 For example, suppose packages foo and bar are installed
3852 with foo depending on bar. If an upgrade of bar were
3853 started and then aborted, and then an attempt to remove
3854 foo failed because its <prgn>prerm</prgn> script failed,
3855 foo's <tt>postinst abort-remove</tt> would be called with
3856 bar only "Half-Installed".
3863 The <prgn>prerm</prgn> script may be called in the following
3866 <tag><var>prerm</var> <tt>remove</tt></tag>
3867 <tag><var>old-prerm</var>
3868 <tt>upgrade</tt><var>new-version</var></tag>
3869 <tag><var>conflictor's-prerm</var> <tt>remove</tt>
3870 <tt>in-favour</tt> <var>package</var>
3871 <var>new-version</var></tag>
3872 <tag><var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3873 <tt>in-favour</tt> <var>package-being-installed</var>
3874 <var>version</var> [<tt>removing</tt>
3875 <var>conflicting-package</var> <var>version</var>]</tag>
3877 The package whose <prgn>prerm</prgn> is being called will be
3878 at least "Half-Installed". All package dependencies will at
3879 least be "Half-Installed" and will have previously been
3880 configured and not removed. If there was no error, all
3881 dependencies will at least be unpacked, but these actions
3882 may be called in various error states where dependencies are
3883 only "Half-Installed" due to a partial upgrade.
3886 <tag><var>new-prerm</var> <tt>failed-upgrade</tt>
3887 <var>old-version</var></tag>
3889 Called during error handling when <tt>prerm upgrade</tt>
3890 fails. The new package will not yet be unpacked, and all
3891 the same constraints as for <tt>preinst upgrade</tt> apply.
3897 The <prgn>postrm</prgn> script may be called in the following
3900 <tag><var>postrm</var> <tt>remove</tt></tag>
3901 <tag><var>postrm</var> <tt>purge</tt></tag>
3902 <tag><var>old-postrm</var> <tt>upgrade</tt>
3903 <var>new-version</var></tag>
3904 <tag><var>disappearer's-postrm</var> <tt>disappear</tt>
3905 <var>overwriter</var> <var>overwriter-version</var></tag>
3907 The <prgn>postrm</prgn> script is called after the package's
3908 files have been removed or replaced. The package
3909 whose <prgn>postrm</prgn> is being called may have
3910 previously been deconfigured and only be unpacked, at which
3911 point subsequent package changes do not consider its
3912 dependencies. Therefore, all <prgn>postrm</prgn> actions
3913 may only rely on essential packages and cannot assume that
3914 the package's dependencies are available.
3917 <tag><var>new-postrm</var> <tt>failed-upgrade</tt>
3918 <var>old-version</var></tag>
3920 Called when the old <tt>postrm upgrade</tt> action fails.
3921 The new package will be unpacked, but only essential
3922 packages and pre-dependencies can be relied on.
3923 Pre-dependencies will either be configured or will be
3924 "Unpacked" or "Half-Configured" but previously had been
3925 configured and was never removed.
3928 <tag><var>new-postrm</var> <tt>abort-install</tt></tag>
3929 <tag><var>new-postrm</var> <tt>abort-install</tt>
3930 <var>old-version</var></tag>
3931 <tag><var>new-postrm</var> <tt>abort-upgrade</tt>
3932 <var>old-version</var></tag>
3934 Called before unpackaging the new package as part of the
3935 error handling of <prgn>preinst</prgn> failures. May assume
3936 the same state as <prgn>preinst</prgn> can assume.
3942 <sect id="unpackphase">
3943 <heading>Details of unpack phase of installation or upgrade</heading>
3946 The procedure on installation/upgrade/overwrite/disappear
3947 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3948 stage of <tt>dpkg --install</tt>) is as follows. In each
3949 case, if a major error occurs (unless listed below) the
3950 actions are, in general, run backwards - this means that the
3951 maintainer scripts are run with different arguments in
3952 reverse order. These are the "error unwind" calls listed
3959 If a version of the package is already installed, call
3960 <example compact="compact">
3961 <var>old-prerm</var> upgrade <var>new-version</var>
3965 If the script runs but exits with a non-zero
3966 exit status, <prgn>dpkg</prgn> will attempt:
3967 <example compact="compact">
3968 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3970 If this works, the upgrade continues. If this
3971 does not work, the error unwind:
3972 <example compact="compact">
3973 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3975 If this works, then the old-version is
3976 "Installed", if not, the old version is in a
3977 "Half-Configured" state.
3983 If a "conflicting" package is being removed at the same time,
3984 or if any package will be broken (due to <tt>Breaks</tt>):
3987 If <tt>--auto-deconfigure</tt> is
3988 specified, call, for each package to be deconfigured
3989 due to <tt>Breaks</tt>:
3990 <example compact="compact">
3991 <var>deconfigured's-prerm</var> deconfigure \
3992 in-favour <var>package-being-installed</var> <var>version</var>
3995 <example compact="compact">
3996 <var>deconfigured's-postinst</var> abort-deconfigure \
3997 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3999 The deconfigured packages are marked as
4000 requiring configuration, so that if
4001 <tt>--install</tt> is used they will be
4002 configured again if possible.
4005 If any packages depended on a conflicting
4006 package being removed and <tt>--auto-deconfigure</tt> is
4007 specified, call, for each such package:
4008 <example compact="compact">
4009 <var>deconfigured's-prerm</var> deconfigure \
4010 in-favour <var>package-being-installed</var> <var>version</var> \
4011 removing <var>conflicting-package</var> <var>version</var>
4014 <example compact="compact">
4015 <var>deconfigured's-postinst</var> abort-deconfigure \
4016 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
4017 removing <var>conflicting-package</var> <var>version</var>
4019 The deconfigured packages are marked as
4020 requiring configuration, so that if
4021 <tt>--install</tt> is used they will be
4022 configured again if possible.
4025 To prepare for removal of each conflicting package, call:
4026 <example compact="compact">
4027 <var>conflictor's-prerm</var> remove \
4028 in-favour <var>package</var> <var>new-version</var>
4031 <example compact="compact">
4032 <var>conflictor's-postinst</var> abort-remove \
4033 in-favour <var>package</var> <var>new-version</var>
4042 If the package is being upgraded, call:
4043 <example compact="compact">
4044 <var>new-preinst</var> upgrade <var>old-version</var>
4046 If this fails, we call:
4048 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4055 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4057 is called. If this works, then the old version
4058 is in an "Installed" state, or else it is left
4059 in an "Unpacked" state.
4064 If it fails, then the old version is left
4065 in an "Half-Installed" state.
4072 Otherwise, if the package had some configuration
4073 files from a previous version installed (i.e., it
4074 is in the "configuration files only" state):
4075 <example compact="compact">
4076 <var>new-preinst</var> install <var>old-version</var>
4080 <var>new-postrm</var> abort-install <var>old-version</var>
4082 If this fails, the package is left in a
4083 "Half-Installed" state, which requires a
4084 reinstall. If it works, the packages is left in
4085 a "Config-Files" state.
4088 Otherwise (i.e., the package was completely purged):
4089 <example compact="compact">
4090 <var>new-preinst</var> install
4093 <example compact="compact">
4094 <var>new-postrm</var> abort-install
4096 If the error-unwind fails, the package is in a
4097 "Half-Installed" phase, and requires a
4098 reinstall. If the error unwind works, the
4099 package is in a not installed state.
4106 The new package's files are unpacked, overwriting any
4107 that may be on the system already, for example any
4108 from the old version of the same package or from
4109 another package. Backups of the old files are kept
4110 temporarily, and if anything goes wrong the package
4111 management system will attempt to put them back as
4112 part of the error unwind.
4116 It is an error for a package to contain files which
4117 are on the system in another package, unless
4118 <tt>Replaces</tt> is used (see <ref id="replaces">).
4120 The following paragraph is not currently the case:
4121 Currently the <tt>- - force-overwrite</tt> flag is
4122 enabled, downgrading it to a warning, but this may not
4128 It is a more serious error for a package to contain a
4129 plain file or other kind of non-directory where another
4130 package has a directory (again, unless
4131 <tt>Replaces</tt> is used). This error can be
4132 overridden if desired using
4133 <tt>--force-overwrite-dir</tt>, but this is not
4138 Packages which overwrite each other's files produce
4139 behavior which, though deterministic, is hard for the
4140 system administrator to understand. It can easily
4141 lead to "missing" programs if, for example, a package
4142 is unpacked which overwrites a file from another
4143 package, and is then removed again.<footnote>
4144 Part of the problem is due to what is arguably a
4145 bug in <prgn>dpkg</prgn>.
4150 A directory will never be replaced by a symbolic link
4151 to a directory or vice versa; instead, the existing
4152 state (symlink or not) will be left alone and
4153 <prgn>dpkg</prgn> will follow the symlink if there is
4162 If the package is being upgraded, call
4163 <example compact="compact">
4164 <var>old-postrm</var> upgrade <var>new-version</var>
4168 If this fails, <prgn>dpkg</prgn> will attempt:
4169 <example compact="compact">
4170 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4172 If this works, installation continues. If not,
4174 <example compact="compact">
4175 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4177 If this fails, the old version is left in a
4178 "Half-Installed" state. If it works, dpkg now
4180 <example compact="compact">
4181 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4183 If this fails, the old version is left in a
4184 "Half-Installed" state. If it works, dpkg now
4186 <example compact="compact">
4187 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4189 If this fails, the old version is in an
4196 This is the point of no return - if
4197 <prgn>dpkg</prgn> gets this far, it won't back off
4198 past this point if an error occurs. This will
4199 leave the package in a fairly bad state, which
4200 will require a successful re-installation to clear
4201 up, but it's when <prgn>dpkg</prgn> starts doing
4202 things that are irreversible.
4207 Any files which were in the old version of the package
4208 but not in the new are removed.
4212 The new file list replaces the old.
4216 The new maintainer scripts replace the old.
4220 Any packages all of whose files have been overwritten
4221 during the installation, and which aren't required for
4222 dependencies, are considered to have been removed.
4223 For each such package
4226 <prgn>dpkg</prgn> calls:
4227 <example compact="compact">
4228 <var>disappearer's-postrm</var> disappear \
4229 <var>overwriter</var> <var>overwriter-version</var>
4233 The package's maintainer scripts are removed.
4236 It is noted in the status database as being in a
4237 sane state, namely not installed (any conffiles
4238 it may have are ignored, rather than being
4239 removed by <prgn>dpkg</prgn>). Note that
4240 disappearing packages do not have their prerm
4241 called, because <prgn>dpkg</prgn> doesn't know
4242 in advance that the package is going to
4249 Any files in the package we're unpacking that are also
4250 listed in the file lists of other packages are removed
4251 from those lists. (This will lobotomize the file list
4252 of the "conflicting" package if there is one.)
4256 The backup files made during installation, above, are
4262 The new package's status is now sane, and recorded as
4267 Here is another point of no return - if the
4268 conflicting package's removal fails we do not unwind
4269 the rest of the installation; the conflicting package
4270 is left in a half-removed limbo.
4275 If there was a conflicting package we go and do the
4276 removal actions (described below), starting with the
4277 removal of the conflicting package's files (any that
4278 are also in the package being unpacked have already
4279 been removed from the conflicting package's file list,
4280 and so do not get removed now).
4286 <sect id="configdetails"><heading>Details of configuration</heading>
4289 When we configure a package (this happens with <tt>dpkg
4290 --install</tt> and <tt>dpkg --configure</tt>), we first
4291 update any <tt>conffile</tt>s and then call:
4292 <example compact="compact">
4293 <var>postinst</var> configure <var>most-recently-configured-version</var>
4298 No attempt is made to unwind after errors during
4299 configuration. If the configuration fails, the package is in
4300 a "Failed Config" state, and an error message is generated.
4304 If there is no most recently configured version
4305 <prgn>dpkg</prgn> will pass a null argument.
4308 Historical note: Truly ancient (pre-1997) versions of
4309 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4310 (including the angle brackets) in this case. Even older
4311 ones did not pass a second argument at all, under any
4312 circumstance. Note that upgrades using such an old dpkg
4313 version are unlikely to work for other reasons, even if
4314 this old argument behavior is handled by your postinst script.
4320 <sect id="removedetails"><heading>Details of removal and/or
4321 configuration purging</heading>
4327 <example compact="compact">
4328 <var>prerm</var> remove
4332 If prerm fails during replacement due to conflict
4334 <var>conflictor's-postinst</var> abort-remove \
4335 in-favour <var>package</var> <var>new-version</var>
4339 <var>postinst</var> abort-remove
4343 If this fails, the package is in a "Half-Configured"
4344 state, or else it remains "Installed".
4348 The package's files are removed (except <tt>conffile</tt>s).
4351 <example compact="compact">
4352 <var>postrm</var> remove
4356 If it fails, there's no error unwind, and the package is in
4357 an "Half-Installed" state.
4362 All the maintainer scripts except the <prgn>postrm</prgn>
4367 If we aren't purging the package we stop here. Note
4368 that packages which have no <prgn>postrm</prgn> and no
4369 <tt>conffile</tt>s are automatically purged when
4370 removed, as there is no difference except for the
4371 <prgn>dpkg</prgn> status.
4375 The <tt>conffile</tt>s and any backup files
4376 (<tt>~</tt>-files, <tt>#*#</tt> files,
4377 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4382 <example compact="compact">
4383 <var>postrm</var> purge
4387 If this fails, the package remains in a "Config-Files"
4392 The package's file list is removed.
4401 <chapt id="relationships">
4402 <heading>Declaring relationships between packages</heading>
4404 <sect id="depsyntax">
4405 <heading>Syntax of relationship fields</heading>
4408 These fields all have a uniform syntax. They are a list of
4409 package names separated by commas.
4413 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4414 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4415 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4416 control fields of the package, which declare
4417 dependencies on other packages, the package names listed may
4418 also include lists of alternative package names, separated
4419 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4420 if any one of the alternative packages is installed, that
4421 part of the dependency is considered to be satisfied.
4425 All of the fields except for <tt>Provides</tt> may restrict
4426 their applicability to particular versions of each named
4427 package. This is done in parentheses after each individual
4428 package name; the parentheses should contain a relation from
4429 the list below followed by a version number, in the format
4430 described in <ref id="f-Version">.
4434 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4435 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4436 strictly earlier, earlier or equal, exactly equal, later or
4437 equal and strictly later, respectively. The deprecated
4438 forms <tt><</tt> and <tt>></tt> were used to mean
4439 earlier/later or equal, rather than strictly earlier/later,
4440 so they should not appear in new packages (though
4441 <prgn>dpkg</prgn> still supports them).
4445 Whitespace may appear at any point in the version
4446 specification subject to the rules in <ref
4447 id="controlsyntax">, and must appear where it's necessary to
4448 disambiguate; it is not otherwise significant. All of the
4449 relationship fields may span multiple lines. For
4450 consistency and in case of future changes to
4451 <prgn>dpkg</prgn> it is recommended that a single space be
4452 used after a version relationship and before a version
4453 number; it is also conventional to put a single space after
4454 each comma, on either side of each vertical bar, and before
4455 each open parenthesis. When wrapping a relationship field, it
4456 is conventional to do so after a comma and before the space
4457 following that comma.
4461 For example, a list of dependencies might appear as:
4462 <example compact="compact">
4465 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4470 Relationships may be restricted to a certain set of
4471 architectures. This is indicated in brackets after each
4472 individual package name and the optional version specification.
4473 The brackets enclose a list of Debian architecture names
4474 separated by whitespace. Exclamation marks may be prepended to
4475 each of the names. (It is not permitted for some names to be
4476 prepended with exclamation marks while others aren't.)
4480 For build relationship fields
4481 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4482 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>), if
4483 the current Debian host architecture is not in this list and
4484 there are no exclamation marks in the list, or it is in the list
4485 with a prepended exclamation mark, the package name and the
4486 associated version specification are ignored completely for the
4487 purposes of defining the relationships.
4492 <example compact="compact">
4494 Build-Depends-Indep: texinfo
4495 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4496 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4498 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4499 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4500 <tt>gnumach-dev</tt> only on hurd-i386.
4504 For binary relationship fields, the architecture restriction
4505 syntax is only supported in the source package control
4506 file <file>debian/control</file>. When the corresponding binary
4507 package control file is generated, the relationship will either
4508 be omitted or included without the architecture restriction
4509 based on the architecture of the binary package. This means
4510 that architecture restrictions must not be used in binary
4511 relationship fields for architecture-independent packages
4512 (<tt>Architecture: all</tt>).
4517 <example compact="compact">
4518 Depends: foo [i386], bar [amd64]
4520 becomes <tt>Depends: foo</tt> when the package is built on
4521 the <tt>i386</tt> architecture, <tt>Depends: bar</tt> when the
4522 package is built on the <tt>amd64</tt> architecture, and omitted
4523 entirely in binary packages built on all other architectures.
4527 If the architecture-restricted dependency is part of a set of
4528 alternatives using <tt>|</tt>, that alternative is ignored
4529 completely on architectures that do not match the restriction.
4531 <example compact="compact">
4532 Build-Depends: foo [!i386] | bar [!amd64]
4534 is equivalent to <tt>bar</tt> on the i386 architecture, to
4535 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4536 bar</tt> on all other architectures.
4540 Relationships may also be restricted to a certain set of
4541 architectures using architecture wildcards. The syntax for
4542 declaring such restrictions is the same as declaring
4543 restrictions using a certain set of architectures without
4544 architecture wildcards. For example:
4545 <example compact="compact">
4546 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4548 is equivalent to <tt>foo</tt> on architectures using the Linux
4549 kernel and any cpu, <tt>bar</tt> on architectures using any
4550 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4551 using a kernel other than Linux.
4555 Note that the binary package relationship fields such as
4556 <tt>Depends</tt> appear in one of the binary package
4557 sections of the control file, whereas the build-time
4558 relationships such as <tt>Build-Depends</tt> appear in the
4559 source package section of the control file (which is the
4564 <sect id="binarydeps">
4565 <heading>Binary Dependencies - <tt>Depends</tt>,
4566 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4567 <tt>Pre-Depends</tt>
4571 Packages can declare in their control file that they have
4572 certain relationships to other packages - for example, that
4573 they may not be installed at the same time as certain other
4574 packages, and/or that they depend on the presence of others.
4578 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4579 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4580 <tt>Breaks</tt> and <tt>Conflicts</tt> control fields.
4581 <tt>Breaks</tt> is described in <ref id="breaks">, and
4582 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4583 rest are described below.
4587 These seven fields are used to declare a dependency
4588 relationship by one package on another. Except for
4589 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4590 depending (binary) package's control file.
4591 (<tt>Enhances</tt> appears in the recommending package's
4592 control file, and <tt>Breaks</tt> appears in the version of
4593 depended-on package which causes the named package to
4598 A <tt>Depends</tt> field takes effect <em>only</em> when a
4599 package is to be configured. It does not prevent a package
4600 being on the system in an unconfigured state while its
4601 dependencies are unsatisfied, and it is possible to replace
4602 a package whose dependencies are satisfied and which is
4603 properly installed with a different version whose
4604 dependencies are not and cannot be satisfied; when this is
4605 done the depending package will be left unconfigured (since
4606 attempts to configure it will give errors) and will not
4607 function properly. If it is necessary, a
4608 <tt>Pre-Depends</tt> field can be used, which has a partial
4609 effect even when a package is being unpacked, as explained
4610 in detail below. (The other three dependency fields,
4611 <tt>Recommends</tt>, <tt>Suggests</tt> and
4612 <tt>Enhances</tt>, are only used by the various front-ends
4613 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4614 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4618 Since <tt>Depends</tt> only places requirements on the order in
4619 which packages are configured, packages in an installation run
4620 are usually all unpacked first and all configured later.
4622 This approach makes dependency resolution easier. If two
4623 packages A and B are being upgraded, the installed package A
4624 depends on exactly the installed package B, and the new
4625 package A depends on exactly the new package B (a common
4626 situation when upgrading shared libraries and their
4627 corresponding development packages), satisfying the
4628 dependencies at every stage of the upgrade would be
4629 impossible. This relaxed restriction means that both new
4630 packages can be unpacked together and then configured in their
4636 If there is a circular dependency among packages being installed
4637 or removed, installation or removal order honoring the
4638 dependency order is impossible, requiring the dependency loop be
4639 broken at some point and the dependency requirements violated
4640 for at least one package. Packages involved in circular
4641 dependencies may not be able to rely on their dependencies being
4642 configured when being configured depending on which side of the
4643 break of the circular dependency loop they happen to be on. If
4644 one of the packages in the loop has no <prgn>postinst</prgn>
4645 script, then the cycle will be broken at that package; this
4646 ensures that all <prgn>postinst</prgn> scripts are run with
4647 their dependencies properly configured if this is possible.
4648 Otherwise the breaking point is arbitrary. Packages should
4649 therefore avoid circular dependencies where possible,
4650 particularly if they have <prgn>postinst</prgn> scripts.
4654 The meaning of the five dependency fields is as follows:
4656 <tag><tt>Depends</tt></tag>
4659 This declares an absolute dependency. A package will
4660 not be configured unless all of the packages listed in
4661 its <tt>Depends</tt> field have been correctly
4662 configured (unless there is a circular dependency as
4667 The <tt>Depends</tt> field should be used if the
4668 depended-on package is required for the depending
4669 package to provide a significant amount of
4674 The <tt>Depends</tt> field should also be used if the
4675 <prgn>postinst</prgn> or <prgn>prerm</prgn> scripts
4676 require the depended-on package to be unpacked or
4677 configured in order to run. In the case of <tt>postinst
4678 configure</tt>, the depended-on packages will be unpacked
4679 and configured first. (If both packages are involved in a
4680 dependency loop, this might not work as expected; see the
4681 explanation a few paragraphs back.) In the case
4682 of <prgn>prerm</prgn> or other <prgn>postinst</prgn>
4683 actions, the package dependencies will normally be at
4684 least unpacked, but they may be only "Half-Installed" if a
4685 previous upgrade of the dependency failed.
4689 <tag><tt>Recommends</tt></tag>
4692 This declares a strong, but not absolute, dependency.
4696 The <tt>Recommends</tt> field should list packages
4697 that would be found together with this one in all but
4698 unusual installations.
4702 <tag><tt>Suggests</tt></tag>
4704 This is used to declare that one package may be more
4705 useful with one or more others. Using this field
4706 tells the packaging system and the user that the
4707 listed packages are related to this one and can
4708 perhaps enhance its usefulness, but that installing
4709 this one without them is perfectly reasonable.
4712 <tag><tt>Enhances</tt></tag>
4714 This field is similar to Suggests but works in the
4715 opposite direction. It is used to declare that a
4716 package can enhance the functionality of another
4720 <tag><tt>Pre-Depends</tt></tag>
4723 This field is like <tt>Depends</tt>, except that it
4724 also forces <prgn>dpkg</prgn> to complete installation
4725 of the packages named before even starting the
4726 installation of the package which declares the
4727 pre-dependency, as follows:
4731 When a package declaring a pre-dependency is about to
4732 be <em>unpacked</em> the pre-dependency can be
4733 satisfied if the depended-on package is either fully
4734 configured, <em>or even if</em> the depended-on
4735 package(s) are only unpacked or in the "Half-Configured"
4736 state, provided that they have been configured
4737 correctly at some point in the past (and not removed
4738 or partially removed since). In this case, both the
4739 previously-configured and currently unpacked or
4740 "Half-Configured" versions must satisfy any version
4741 clause in the <tt>Pre-Depends</tt> field.
4745 When the package declaring a pre-dependency is about to
4746 be <em>configured</em>, the pre-dependency will be treated
4747 as a normal <tt>Depends</tt>. It will be considered
4748 satisfied only if the depended-on package has been
4749 correctly configured. However, unlike
4750 with <tt>Depends</tt>, <tt>Pre-Depends</tt> does not
4751 permit circular dependencies to be broken. If a circular
4752 dependency is encountered while attempting to honor
4753 <tt>Pre-Depends</tt>, the installation will be aborted.
4757 <tt>Pre-Depends</tt> are also required if the
4758 <prgn>preinst</prgn> script depends on the named package.
4759 It is best to avoid this situation if possible.
4763 <tt>Pre-Depends</tt> should be used sparingly,
4764 preferably only by packages whose premature upgrade or
4765 installation would hamper the ability of the system to
4766 continue with any upgrade that might be in progress.
4773 When selecting which level of dependency to use you should
4774 consider how important the depended-on package is to the
4775 functionality of the one declaring the dependency. Some
4776 packages are composed of components of varying degrees of
4777 importance. Such a package should list using
4778 <tt>Depends</tt> the package(s) which are required by the
4779 more important components. The other components'
4780 requirements may be mentioned as Suggestions or
4781 Recommendations, as appropriate to the components' relative
4787 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4790 When one binary package declares that it breaks another,
4791 <prgn>dpkg</prgn> will refuse to allow the package which
4792 declares <tt>Breaks</tt> be unpacked unless the broken
4793 package is deconfigured first, and it will refuse to
4794 allow the broken package to be reconfigured.
4798 A package will not be regarded as causing breakage merely
4799 because its configuration files are still installed; it must
4800 be at least "Half-Installed".
4804 A special exception is made for packages which declare that
4805 they break their own package name or a virtual package which
4806 they provide (see below): this does not count as a real
4811 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4812 version clause; such a <tt>Breaks</tt> is introduced in the
4813 version of an (implicit or explicit) dependency which violates
4814 an assumption or reveals a bug in earlier versions of the broken
4815 package, or which takes over a file from earlier versions of the
4816 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
4817 will inform higher-level package management tools that the
4818 broken package must be upgraded before the new one.
4822 If the breaking package also overwrites some files from the
4823 older package, it should use <tt>Replaces</tt> to ensure this
4824 goes smoothly. See <ref id="replaces"> for a full discussion
4825 of taking over files from other packages, including how to
4826 use <tt>Breaks</tt> in those cases.
4830 Many of the cases where <tt>Breaks</tt> should be used were
4831 previously handled with <tt>Conflicts</tt>
4832 because <tt>Breaks</tt> did not yet exist.
4833 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
4834 See <ref id="conflicts"> for more information about the
4839 <sect id="conflicts">
4840 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4843 When one binary package declares a conflict with another using
4844 a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will refuse to
4845 allow them to be unpacked on the system at the same time. This
4846 is a stronger restriction than <tt>Breaks</tt>, which prevents
4847 the broken package from being configured while the breaking
4848 package is in the "Unpacked" state but allows both packages to
4849 be unpacked at the same time.
4853 If one package is to be unpacked, the other must be removed
4854 first. If the package being unpacked is marked as replacing
4855 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
4856 normally be used in this case) the one on the system, or the one
4857 on the system is marked as deselected, or both packages are
4858 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
4859 automatically remove the package which is causing the conflict.
4860 Otherwise, it will halt the installation of the new package with
4861 an error. This mechanism is specifically designed to produce an
4862 error when the installed package is <tt>Essential</tt>, but the
4867 A package will not cause a conflict merely because its
4868 configuration files are still installed; it must be at least
4873 A special exception is made for packages which declare a
4874 conflict with their own package name, or with a virtual
4875 package which they provide (see below): this does not
4876 prevent their installation, and allows a package to conflict
4877 with others providing a replacement for it. You use this
4878 feature when you want the package in question to be the only
4879 package providing some feature.
4883 Normally, <tt>Breaks</tt> should be used instead
4884 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
4885 stronger restriction on the ordering of package installation or
4886 upgrade and can make it more difficult for the package manager
4887 to find a correct solution to an upgrade or installation
4888 problem. <tt>Breaks</tt> should be used
4890 <item>when moving a file from one package to another (see
4891 <ref id="replaces">),</item>
4892 <item>when splitting a package (a special case of the previous
4894 <item>when the breaking package exposes a bug in or interacts
4895 badly with particular versions of the broken
4898 <tt>Conflicts</tt> should be used
4900 <item>when two packages provide the same file and will
4901 continue to do so,</item>
4902 <item>in conjunction with <tt>Provides</tt> when only one
4903 package providing a given virtual facility may be unpacked
4904 at a time (see <ref id="virtual">),</item>
4905 <item>in other cases where one must prevent simultaneous
4906 installation of two packages for reasons that are ongoing
4907 (not fixed in a later version of one of the packages) or
4908 that must prevent both packages from being unpacked at the
4909 same time, not just configured.</item>
4911 Be aware that adding <tt>Conflicts</tt> is normally not the best
4912 solution when two packages provide the same files. Depending on
4913 the reason for that conflict, using alternatives or renaming the
4914 files is often a better approach. See, for
4915 example, <ref id="binaries">.
4919 Neither <tt>Breaks</tt> nor <tt>Conflicts</tt> should be used
4920 unless two packages cannot be installed at the same time or
4921 installing them both causes one of them to be broken or
4922 unusable. Having similar functionality or performing the same
4923 tasks as another package is not sufficient reason to
4924 declare <tt>Breaks</tt> or <tt>Conflicts</tt> with that package.
4928 A <tt>Conflicts</tt> entry may have an "earlier than" version
4929 clause if the reason for the conflict is corrected in a later
4930 version of one of the packages. However, normally the presence
4931 of an "earlier than" version clause is a sign
4932 that <tt>Breaks</tt> should have been used instead. An "earlier
4933 than" version clause in <tt>Conflicts</tt>
4934 prevents <prgn>dpkg</prgn> from upgrading or installing the
4935 package which declares such a conflict until the upgrade or
4936 removal of the conflicted-with package has been completed, which
4937 is a strong restriction.
4941 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4945 As well as the names of actual ("concrete") packages, the
4946 package relationship fields <tt>Depends</tt>,
4947 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4948 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4949 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4950 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4951 may mention "virtual packages".
4955 A <em>virtual package</em> is one which appears in the
4956 <tt>Provides</tt> control field of another package. The effect
4957 is as if the package(s) which provide a particular virtual
4958 package name had been listed by name everywhere the virtual
4959 package name appears. (See also <ref id="virtual_pkg">)
4963 If there are both concrete and virtual packages of the same
4964 name, then the dependency may be satisfied (or the conflict
4965 caused) by either the concrete package with the name in
4966 question or any other concrete package which provides the
4967 virtual package with the name in question. This is so that,
4968 for example, supposing we have
4969 <example compact="compact">
4972 </example> and someone else releases an enhanced version of
4973 the <tt>bar</tt> package they can say:
4974 <example compact="compact">
4978 and the <tt>bar-plus</tt> package will now also satisfy the
4979 dependency for the <tt>foo</tt> package.
4983 If a relationship field has a version number attached, only real
4984 packages will be considered to see whether the relationship is
4985 satisfied (or the prohibition violated, for a conflict or
4986 breakage). In other words, if a version number is specified,
4987 this is a request to ignore all <tt>Provides</tt> for that
4988 package name and consider only real packages. The package
4989 manager will assume that a package providing that virtual
4990 package is not of the "right" version. A <tt>Provides</tt>
4991 field may not contain version numbers, and the version number of
4992 the concrete package which provides a particular virtual package
4993 will not be considered when considering a dependency on or
4994 conflict with the virtual package name.<footnote>
4995 It is possible that a future release of <prgn>dpkg</prgn> may
4996 add the ability to specify a version number for each virtual
4997 package it provides. This feature is not yet present,
4998 however, and is expected to be used only infrequently.
5003 To specify which of a set of real packages should be the default
5004 to satisfy a particular dependency on a virtual package, list
5005 the real package as an alternative before the virtual one.
5009 If the virtual package represents a facility that can only be
5010 provided by one real package at a time, such as
5011 the <package>mail-transport-agent</package> virtual package that
5012 requires installation of a binary that would conflict with all
5013 other providers of that virtual package (see
5014 <ref id="mail-transport-agents">), all packages providing that
5015 virtual package should also declare a conflict with it
5016 using <tt>Conflicts</tt>. This will ensure that at most one
5017 provider of that virtual package is unpacked or installed at a
5022 <sect id="replaces"><heading>Overwriting files and replacing
5023 packages - <tt>Replaces</tt></heading>
5026 Packages can declare in their control file that they should
5027 overwrite files in certain other packages, or completely replace
5028 other packages. The <tt>Replaces</tt> control field has these
5029 two distinct purposes.
5032 <sect1><heading>Overwriting files in other packages</heading>
5035 It is usually an error for a package to contain files which
5036 are on the system in another package. However, if the
5037 overwriting package declares that it <tt>Replaces</tt> the one
5038 containing the file being overwritten, then <prgn>dpkg</prgn>
5039 will replace the file from the old package with that from the
5040 new. The file will no longer be listed as "owned" by the old
5041 package and will be taken over by the new package.
5042 Normally, <tt>Breaks</tt> should be used in conjunction
5043 with <tt>Replaces</tt>.<footnote>
5044 To see why <tt>Breaks</tt> is normally needed in addition
5045 to <tt>Replaces</tt>, consider the case of a file in the
5046 package <package>foo</package> being taken over by the
5047 package <package>foo-data</package>.
5048 <tt>Replaces</tt> will allow <package>foo-data</package> to
5049 be installed and take over that file. However,
5050 without <tt>Breaks</tt>, nothing
5051 requires <package>foo</package> to be upgraded to a newer
5052 version that knows it does not include that file and instead
5053 depends on <package>foo-data</package>. Nothing would
5054 prevent the new <package>foo-data</package> package from
5055 being installed and then removed, removing the file that it
5056 took over from <package>foo</package>. After that
5057 operation, the package manager would think the system was in
5058 a consistent state, but the <package>foo</package> package
5059 would be missing one of its files.
5064 For example, if a package <package>foo</package> is split
5065 into <package>foo</package> and <package>foo-data</package>
5066 starting at version 1.2-3, <package>foo-data</package> would
5068 <example compact="compact">
5069 Replaces: foo (<< 1.2-3)
5070 Breaks: foo (<< 1.2-3)
5072 in its control file. The new version of the
5073 package <package>foo</package> would normally have the field
5074 <example compact="compact">
5075 Depends: foo-data (>= 1.2-3)
5077 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
5078 the files moved into <package>foo-data</package> are not
5079 required for normal operation).
5083 If a package is completely replaced in this way, so that
5084 <prgn>dpkg</prgn> does not know of any files it still
5085 contains, it is considered to have "disappeared". It will
5086 be marked as not wanted on the system (selected for
5087 removal) and not installed. Any <tt>conffile</tt>s
5088 details noted for the package will be ignored, as they
5089 will have been taken over by the overwriting package. The
5090 package's <prgn>postrm</prgn> script will be run with a
5091 special argument to allow the package to do any final
5092 cleanup required. See <ref id="mscriptsinstact">.
5094 Replaces is a one way relationship. You have to install
5095 the replacing package after the replaced package.
5100 For this usage of <tt>Replaces</tt>, virtual packages (see
5101 <ref id="virtual">) are not considered when looking at a
5102 <tt>Replaces</tt> field. The packages declared as being
5103 replaced must be mentioned by their real names.
5107 This usage of <tt>Replaces</tt> only takes effect when both
5108 packages are at least partially on the system at once. It is
5109 not relevant if the packages conflict unless the conflict has
5114 <sect1><heading>Replacing whole packages, forcing their
5118 Second, <tt>Replaces</tt> allows the packaging system to
5119 resolve which package should be removed when there is a
5120 conflict (see <ref id="conflicts">). This usage only takes
5121 effect when the two packages <em>do</em> conflict, so that the
5122 two usages of this field do not interfere with each other.
5126 In this situation, the package declared as being replaced
5127 can be a virtual package, so for example, all mail
5128 transport agents (MTAs) would have the following fields in
5129 their control files:
5130 <example compact="compact">
5131 Provides: mail-transport-agent
5132 Conflicts: mail-transport-agent
5133 Replaces: mail-transport-agent
5135 ensuring that only one MTA can be unpacked at any one
5136 time. See <ref id="virtual"> for more information about this
5141 <sect id="sourcebinarydeps">
5142 <heading>Relationships between source and binary packages -
5143 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5144 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5148 Source packages that require certain binary packages to be
5149 installed or absent at the time of building the package
5150 can declare relationships to those binary packages.
5154 This is done using the <tt>Build-Depends</tt>,
5155 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5156 <tt>Build-Conflicts-Indep</tt> control fields.
5160 Build-dependencies on "build-essential" binary packages can be
5161 omitted. Please see <ref id="pkg-relations"> for more information.
5165 The dependencies and conflicts they define must be satisfied
5166 (as defined earlier for binary packages) in order to invoke
5167 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5169 There is no Build-Depends-Arch; this role is essentially
5170 met with Build-Depends. Anyone building the
5171 <tt>build-indep</tt> and <tt>binary-indep</tt> targets is
5172 assumed to be building the whole package, and therefore
5173 installation of all build dependencies is required.
5176 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5177 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5178 not yet know how to check for its existence, and
5179 <tt>binary-arch</tt>. The purpose of the original split
5180 between <tt>Build-Depends</tt> and
5181 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5182 wouldn't need to install extra packages needed only for the
5183 binary-indep targets. But without a build-arch/build-indep
5184 split, this didn't work, since most of the work is done in
5185 the build target, not in the binary target.
5189 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5190 <tt>binary-arch</tt></tag>
5192 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5193 fields must be satisfied when these targets are invoked.
5195 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5196 and <tt>binary-indep</tt></tag>
5198 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5199 <tt>Build-Depends-Indep</tt>, and
5200 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5201 these targets are invoked.
5209 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5212 Packages containing shared libraries must be constructed with
5213 a little care to make sure that the shared library is always
5214 available. This is especially important for packages whose
5215 shared libraries are vitally important, such as the C library
5216 (currently <tt>libc6</tt>).
5220 This section deals only with public shared libraries: shared
5221 libraries that are placed in directories searched by the dynamic
5222 linker by default or which are intended to be linked against
5223 normally and possibly used by other, independent packages. Shared
5224 libraries that are internal to a particular package or that are
5225 only loaded as dynamic modules are not covered by this section and
5226 are not subject to its requirements.
5230 A shared library is identified by the <tt>SONAME</tt> attribute
5231 stored in its dynamic section. When a binary is linked against a
5232 shared library, the <tt>SONAME</tt> of the shared library is
5233 recorded in the binary's <tt>NEEDED</tt> section so that the
5234 dynamic linker knows that library must be loaded at runtime. The
5235 shared library file's full name (which usually contains additional
5236 version information not needed in the <tt>SONAME</tt>) is
5237 therefore normally not referenced directly. Instead, the shared
5238 library is loaded by its <tt>SONAME</tt>, which exists on the file
5239 system as a symlink pointing to the full name of the shared
5240 library. This symlink must be provided by the
5241 package. <ref id="sharedlibs-runtime"> describes how to do this.
5243 This is a convention of shared library versioning, but not a
5244 requirement. Some libraries use the <tt>SONAME</tt> as the full
5245 library file name instead and therefore do not need a symlink.
5246 Most, however, encode additional information about
5247 backwards-compatible revisions as a minor version number in the
5248 file name. The <tt>SONAME</tt> itself only changes when
5249 binaries linked with the earlier version of the shared library
5250 may no longer work, but the filename may change with each
5251 release of the library. See <ref id="sharedlibs-runtime"> for
5257 When linking a binary or another shared library against a shared
5258 library, the <tt>SONAME</tt> for that shared library is not yet
5259 known. Instead, the shared library is found by looking for a file
5260 matching the library name with <tt>.so</tt> appended. This file
5261 exists on the file system as a symlink pointing to the shared
5266 Shared libraries are normally split into several binary packages.
5267 The <tt>SONAME</tt> symlink is installed by the runtime shared
5268 library package, and the bare <tt>.so</tt> symlink is installed in
5269 the development package since it's only used when linking binaries
5270 or shared libraries. However, there are some exceptions for
5271 unusual shared libraries or for shared libraries that are also
5272 loaded as dynamic modules by other programs.
5276 This section is primarily concerned with how the separation of
5277 shared libraries into multiple packages should be done and how
5278 dependencies on and between shared library binary packages are
5279 managed in Debian. <ref id="libraries"> should be read in
5280 conjunction with this section and contains additional rules for
5281 the files contained in the shared library packages.
5284 <sect id="sharedlibs-runtime">
5285 <heading>Run-time shared libraries</heading>
5288 The run-time shared library must be placed in a package
5289 whose name changes whenever the <tt>SONAME</tt> of the shared
5290 library changes. This allows several versions of the shared
5291 library to be installed at the same time, allowing installation
5292 of the new version of the shared library without immediately
5293 breaking binaries that depend on the old version. Normally, the
5294 run-time shared library and its <tt>SONAME</tt> symlink should
5295 be placed in a package named
5296 <package><var>libraryname</var><var>soversion</var></package>,
5297 where <var>soversion</var> is the version number in
5298 the <tt>SONAME</tt> of the shared library.
5299 See <ref id="shlibs"> for detailed information on how to
5300 determine this version. Alternatively, if it would be confusing
5301 to directly append <var>soversion</var>
5302 to <var>libraryname</var> (if, for example, <var>libraryname</var>
5303 itself ends in a number), you should use
5304 <package><var>libraryname</var>-<var>soversion</var></package>
5309 If you have several shared libraries built from the same source
5310 tree, you may lump them all together into a single shared
5311 library package provided that all of their <tt>SONAME</tt>s will
5312 always change together. Be aware that this is not normally the
5313 case, and if the <tt>SONAME</tt>s do not change together,
5314 upgrading such a merged shared library package will be
5315 unnecessarily difficult because of file conflicts with the old
5316 version of the package. When in doubt, always split shared
5317 library packages so that each binary package installs a single
5322 Every time the shared library ABI changes in a way that may
5323 break binaries linked against older versions of the shared
5324 library, the <tt>SONAME</tt> of the library and the
5325 corresponding name for the binary package containing the runtime
5326 shared library should change. Normally, this means
5327 the <tt>SONAME</tt> should change any time an interface is
5328 removed from the shared library or the signature of an interface
5329 (the number of parameters or the types of parameters that it
5330 takes, for example) is changed. This practice is vital to
5331 allowing clean upgrades from older versions of the package and
5332 clean transitions between the old ABI and new ABI without having
5333 to upgrade every affected package simultaneously.
5337 The <tt>SONAME</tt> and binary package name need not, and indeed
5338 normally should not, change if new interfaces are added but none
5339 are removed or changed, since this will not break binaries
5340 linked against the old shared library. Correct versioning of
5341 dependencies on the newer shared library by binaries that use
5342 the new interfaces is handled via
5343 the <qref id="sharedlibs-shlibdeps"><tt>shlibs</tt>
5344 system</qref> or via symbols files (see
5345 <manref name="deb-symbols" section="5">).
5349 The package should install the shared libraries under
5350 their normal names. For example, the <package>libgdbm3</package>
5351 package should install <file>libgdbm.so.3.0.0</file> as
5352 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5353 renamed or re-linked by any <prgn>prerm</prgn> or
5354 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5355 of renaming things safely without affecting running programs,
5356 and attempts to interfere with this are likely to lead to
5361 Shared libraries should not be installed executable, since
5362 the dynamic linker does not require this and trying to
5363 execute a shared library usually results in a core dump.
5367 The run-time library package should include the symbolic link for
5368 the <tt>SONAME</tt> that <prgn>ldconfig</prgn> would create for
5369 the shared libraries. For example,
5370 the <package>libgdbm3</package> package should include a symbolic
5371 link from <file>/usr/lib/libgdbm.so.3</file> to
5372 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5373 linker (for example <prgn>ld.so</prgn> or
5374 <prgn>ld-linux.so.*</prgn>) can find the library between the
5375 time that <prgn>dpkg</prgn> installs it and the time that
5376 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5378 The package management system requires the library to be
5379 placed before the symbolic link pointing to it in the
5380 <file>.deb</file> file. This is so that when
5381 <prgn>dpkg</prgn> comes to install the symlink
5382 (overwriting the previous symlink pointing at an older
5383 version of the library), the new shared library is already
5384 in place. In the past, this was achieved by creating the
5385 library in the temporary packaging directory before
5386 creating the symlink. Unfortunately, this was not always
5387 effective, since the building of the tar file in the
5388 <file>.deb</file> depended on the behavior of the underlying
5389 file system. Some file systems (such as reiserfs) reorder
5390 the files so that the order of creation is forgotten.
5391 Since version 1.7.0, <prgn>dpkg</prgn>
5392 reorders the files itself as necessary when building a
5393 package. Thus it is no longer important to concern
5394 oneself with the order of file creation.
5398 <sect1 id="ldconfig">
5399 <heading><tt>ldconfig</tt></heading>
5402 Any package installing shared libraries in one of the default
5403 library directories of the dynamic linker (which are currently
5404 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5405 listed in <file>/etc/ld.so.conf</file><footnote>
5407 <list compact="compact">
5408 <item>/usr/local/lib</item>
5409 <item>/usr/lib/libc5-compat</item>
5410 <item>/lib/libc5-compat</item>
5413 must use <prgn>ldconfig</prgn> to update the shared library
5418 The package maintainer scripts must only call
5419 <prgn>ldconfig</prgn> under these circumstances:
5420 <list compact="compact">
5421 <item>When the <prgn>postinst</prgn> script is run with a
5422 first argument of <tt>configure</tt>, the script must call
5423 <prgn>ldconfig</prgn>, and may optionally invoke
5424 <prgn>ldconfig</prgn> at other times.
5426 <item>When the <prgn>postrm</prgn> script is run with a
5427 first argument of <tt>remove</tt>, the script should call
5428 <prgn>ldconfig</prgn>.
5433 During install or upgrade, the preinst is called before
5434 the new files are unpacked, so calling "ldconfig" is
5435 pointless. The preinst of an existing package can also be
5436 called if an upgrade fails. However, this happens during
5437 the critical time when a shared libs may exist on-disk
5438 under a temporary name. Thus, it is dangerous and
5439 forbidden by current policy to call "ldconfig" at this
5444 When a package is installed or upgraded, "postinst
5445 configure" runs after the new files are safely on-disk.
5446 Since it is perfectly safe to invoke ldconfig
5447 unconditionally in a postinst, it is OK for a package to
5448 simply put ldconfig in its postinst without checking the
5449 argument. The postinst can also be called to recover from
5450 a failed upgrade. This happens before any new files are
5451 unpacked, so there is no reason to call "ldconfig" at this
5456 For a package that is being removed, prerm is
5457 called with all the files intact, so calling ldconfig is
5458 useless. The other calls to "prerm" happen in the case of
5459 upgrade at a time when all the files of the old package
5460 are on-disk, so again calling "ldconfig" is pointless.
5464 postrm, on the other hand, is called with the "remove"
5465 argument just after the files are removed, so this is
5466 the proper time to call "ldconfig" to notify the system
5467 of the fact that the shared libraries from the package
5468 are removed. The postrm can be called at several other
5469 times. At the time of "postrm purge", "postrm
5470 abort-install", or "postrm abort-upgrade", calling
5471 "ldconfig" is useless because the shared lib files are
5472 not on-disk. However, when "postrm" is invoked with
5473 arguments "upgrade", "failed-upgrade", or "disappear", a
5474 shared lib may exist on-disk under a temporary filename.
5482 <sect id="sharedlibs-support-files">
5483 <heading>Shared library support files</heading>
5486 If your package contains files whose names do not change with
5487 each change in the library shared object version, you must not
5488 put them in the shared library package. Otherwise, several
5489 versions of the shared library cannot be installed at the same
5490 time without filename clashes, making upgrades and transitions
5491 unnecessarily difficult.
5495 It is recommended that supporting files and run-time support
5496 programs that do not need to be invoked manually by users, but
5497 are nevertheless required for the package to function, be placed
5498 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5499 preferably under <file>/usr/lib/</file><var>package-name</var>.
5500 If the program or file is architecture independent, the
5501 recommendation is for it to be placed in a subdirectory of
5502 <file>/usr/share</file> instead, preferably under
5503 <file>/usr/share/</file><var>package-name</var>. Following the
5504 <var>package-name</var> naming convention ensures that the file
5505 names change when the shared object version changes.
5509 Run-time support programs that use the shared library but are
5510 not required for the library to function or files used by the
5511 shared library that can be used by any version of the shared
5512 library package should instead be put in a separate package.
5513 This package might typically be named
5514 <package><var>libraryname</var>-tools</package>; note the
5515 absence of the <var>soversion</var> in the package name.
5519 Files and support programs only useful when compiling software
5520 against the library should be included in the development
5521 package for the library.<footnote>
5522 For example, a <file><var>package-name</var>-config</file>
5523 script or <package>pkg-config</package> configuration files.
5528 <sect id="sharedlibs-static">
5529 <heading>Static libraries</heading>
5532 The static library (<file><var>libraryname.a</var></file>)
5533 is usually provided in addition to the shared version.
5534 It is placed into the development package (see below).
5538 In some cases, it is acceptable for a library to be
5539 available in static form only; these cases include:
5541 <item>libraries for languages whose shared library support
5542 is immature or unstable</item>
5543 <item>libraries whose interfaces are in flux or under
5544 development (commonly the case when the library's
5545 major version number is zero, or where the ABI breaks
5546 across patchlevels)</item>
5547 <item>libraries which are explicitly intended to be
5548 available only in static form by their upstream
5553 <sect id="sharedlibs-dev">
5554 <heading>Development files</heading>
5557 If there are development files associated with a shared library,
5558 the source package needs to generate a binary development package
5559 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5560 or if you prefer only to support one development version at a
5561 time, <package><var>libraryname</var>-dev</package>. Installing
5562 the development package must result in installation of all the
5563 development files necessary for compiling programs against that
5564 shared library.<footnote>
5565 This wording allows the development files to be split into
5566 several packages, such as a separate architecture-independent
5567 <package><var>libraryname</var>-headers</package>, provided that
5568 the development package depends on all the required additional
5574 In case several development versions of a library exist, you may
5575 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5576 <ref id="conflicts">) to ensure that the user only installs one
5577 development version at a time (as different development versions are
5578 likely to have the same header files in them, which would cause a
5579 filename clash if both were unpacked).
5583 The development package should contain a symlink for the associated
5584 shared library without a version number. For example, the
5585 <package>libgdbm-dev</package> package should include a symlink
5586 from <file>/usr/lib/libgdbm.so</file> to
5587 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5588 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5589 <file>libgdbm.so</file> when compiling dynamically.
5593 If the package provides Ada Library Information
5594 (<file>*.ali</file>) files for use with GNAT, these files must be
5595 installed read-only (mode 0444) so that GNAT will not attempt to
5596 recompile them. This overrides the normal file mode requirements
5597 given in <ref id="permissions-owners">.
5601 <sect id="sharedlibs-intradeps">
5602 <heading>Dependencies between the packages of the same library</heading>
5605 Typically the development version should have an exact
5606 version dependency on the runtime library, to make sure that
5607 compilation and linking happens correctly. The
5608 <tt>${binary:Version}</tt> substitution variable can be
5609 useful for this purpose.
5611 Previously, <tt>${Source-Version}</tt> was used, but its name
5612 was confusing and it has been deprecated since dpkg 1.13.19.
5617 <sect id="sharedlibs-shlibdeps">
5618 <heading>Dependencies between the library and other packages -
5619 the <tt>shlibs</tt> system</heading>
5622 If a package contains a binary or library which links to a
5623 shared library, we must ensure that when the package is
5624 installed on the system, all of the libraries needed are
5625 also installed. This requirement led to the creation of the
5626 <tt>shlibs</tt> system, which is very simple in its design:
5627 any package which <em>provides</em> a shared library also
5628 provides information on the package dependencies required to
5629 ensure the presence of this library, and any package which
5630 <em>uses</em> a shared library uses this information to
5631 determine the dependencies it requires. The files which
5632 contain the mapping from shared libraries to the necessary
5633 dependency information are called <file>shlibs</file> files.
5637 When a package is built which contains any shared libraries, it
5638 must provide a <file>shlibs</file> file for other packages to
5639 use. When a package is built which contains any shared
5640 libraries or compiled binaries, it must run
5641 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5642 on these to determine the libraries used and hence the
5643 dependencies needed by this package.<footnote>
5645 <prgn>dpkg-shlibdeps</prgn> will use a program
5646 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
5647 the libraries directly needed by the binaries or shared
5648 libraries in the package.
5652 We say that a binary <tt>foo</tt> <em>directly</em> uses
5653 a library <tt>libbar</tt> if it is explicitly linked
5654 with that library (that is, the library is listed in the ELF
5655 <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
5656 to the link line when the binary is created). Other
5657 libraries that are needed by <tt>libbar</tt> are linked
5658 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5659 linker will load them automatically when it loads
5660 <tt>libbar</tt>. A package should depend on the libraries
5661 it directly uses, but not the libraries it indirectly uses.
5662 The dependencies for those libraries will automatically pull
5663 in the other libraries.
5667 A good example of where this helps is the following. We
5668 could update <tt>libimlib</tt> with a new version that
5669 supports a new graphics format called dgf (but retaining the
5670 same major version number) and depends on <tt>libdgf</tt>.
5671 If we used <prgn>ldd</prgn> to add dependencies for every
5672 library directly or indirectly linked with a binary, every
5673 package that uses <tt>libimlib</tt> would need to be
5674 recompiled so it would also depend on <tt>libdgf</tt> or it
5675 wouldn't run due to missing symbols. Since dependencies are
5676 only added based on ELF <tt>NEEDED</tt> attribute, packages
5677 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
5678 having the dependency on <tt>libdgf</tt> and so they would
5679 not need rebuilding.
5685 In the following sections, we will first describe where the
5686 various <tt>shlibs</tt> files are to be found, then how to
5687 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5688 file format and how to create them if your package contains a
5693 <heading>The <tt>shlibs</tt> files present on the system</heading>
5696 There are several places where <tt>shlibs</tt> files are
5697 found. The following list gives them in the order in which
5699 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5700 (The first one which gives the required information is used.)
5706 <p><file>debian/shlibs.local</file></p>
5709 This lists overrides for this package. This file should
5710 normally not be used, but may be needed temporarily in
5711 unusual situations to work around bugs in other packages,
5712 or in unusual cases where the normally declared dependency
5713 information in the installed <file>shlibs</file> file for
5714 a library cannot be used. This file overrides information
5715 obtained from any other source.
5720 <p><file>/etc/dpkg/shlibs.override</file></p>
5723 This lists global overrides. This list is normally
5724 empty. It is maintained by the local system
5730 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5733 When packages are being built,
5734 any <file>debian/shlibs</file> files are copied into the
5735 control information file area of the temporary build
5736 directory and given the name <file>shlibs</file>. These
5737 files give details of any shared libraries included in the
5738 same package.<footnote>
5739 An example may help here. Let us say that the source
5740 package <tt>foo</tt> generates two binary
5741 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
5742 When building the binary packages, the two packages are
5743 created in the directories <file>debian/libfoo2</file>
5744 and <file>debian/foo-runtime</file> respectively.
5745 (<file>debian/tmp</file> could be used instead of one of
5746 these.) Since <tt>libfoo2</tt> provides the
5747 <tt>libfoo</tt> shared library, it will require a
5748 <tt>shlibs</tt> file, which will be installed in
5749 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually to
5750 become <file>/var/lib/dpkg/info/libfoo2.shlibs</file>.
5751 When <prgn>dpkg-shlibdeps</prgn> is run on the
5752 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
5754 the <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5755 determine whether <tt>foo-prog</tt>'s library
5756 dependencies are satisfied by any of the libraries
5757 provided by <tt>libfoo2</tt>. For this reason,
5758 <prgn>dpkg-shlibdeps</prgn> must only be run once all of
5759 the individual binary packages' <tt>shlibs</tt> files
5760 have been installed into the build directory.
5766 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5769 These are the <file>shlibs</file> files corresponding to
5770 all of the packages installed on the system, and are
5771 maintained by the relevant package maintainers.
5776 <p><file>/etc/dpkg/shlibs.default</file></p>
5779 This file lists any shared libraries whose packages
5780 have failed to provide correct <file>shlibs</file> files.
5781 It was used when the <file>shlibs</file> setup was first
5782 introduced, but it is now normally empty. It is
5783 maintained by the <tt>dpkg</tt> maintainer.
5791 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5792 <file>shlibs</file> files</heading>
5796 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5797 into your <file>debian/rules</file> file. If your package
5798 contains only compiled binaries and libraries (but no scripts),
5799 you can use a command such as:
5800 <example compact="compact">
5801 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5802 debian/tmp/usr/lib/*
5804 Otherwise, you will need to explicitly list the compiled
5805 binaries and libraries.<footnote>
5806 If you are using <tt>debhelper</tt>, the
5807 <prgn>dh_shlibdeps</prgn> program will do this work for you.
5808 It will also correctly handle multi-binary packages.
5813 This command puts the dependency information into the
5814 <file>debian/substvars</file> file, which is then used by
5815 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5816 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5817 field in the control file for this to work.
5821 If you have multiple binary packages, you will need to call
5822 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5823 compiled libraries or binaries. In such a case, you will
5824 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5825 utilities to specify a different <file>substvars</file> file.
5829 If you are creating a udeb for use in the Debian Installer,
5830 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
5831 should use the dependency line of type <tt>udeb</tt> by
5832 adding the <tt>-tudeb</tt> option<footnote>
5833 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5834 will automatically add this option if it knows it is
5836 </footnote>. If there is no dependency line of
5837 type <tt>udeb</tt> in the <file>shlibs</file>
5838 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the regular
5843 For more details on <prgn>dpkg-shlibdeps</prgn>, please see
5844 <ref id="pkg-dpkg-shlibdeps"> and
5845 <manref name="dpkg-shlibdeps" section="1">.
5850 <heading>The <file>shlibs</file> File Format</heading>
5853 Each <file>shlibs</file> file has the same format. Lines
5854 beginning with <tt>#</tt> are considered to be comments and
5855 are ignored. Each line is of the form:
5856 <example compact="compact">
5857 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5862 We will explain this by reference to the example of the
5863 <tt>zlib1g</tt> package, which (at the time of writing)
5864 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5868 <var>type</var> is an optional element that indicates the type
5869 of package for which the line is valid. The only type currently
5870 in use is <tt>udeb</tt>. The colon and space after the type are
5875 <var>library-name</var> is the name of the shared library,
5876 in this case <tt>libz</tt>. (This must match the name part
5877 of the soname, see below.)
5881 <var>soname-version</var> is the version part of the soname of
5882 the library. The soname is the thing that must exactly match
5883 for the library to be recognized by the dynamic linker, and is
5885 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5886 example, <tt>libz.so.1</tt>.<footnote>
5887 This can be determined using the command
5888 <example compact="compact">
5889 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5892 The version part is the part which comes after
5893 <tt>.so.</tt>, so in our case, it is <tt>1</tt>. The soname may
5894 instead be of the form
5895 <tt><var>name</var>-<var>major-version</var>.so</tt>, such
5896 as <tt>libdb-4.8.so</tt>, in which case the name would
5897 be <tt>libdb</tt> and the version would be <tt>4.8</tt>.
5901 <var>dependencies</var> has the same syntax as a dependency
5902 field in a binary package control file. It should give
5903 details of which packages are required to satisfy a binary
5904 built against the version of the library contained in the
5905 package. See <ref id="depsyntax"> for details.
5909 In our example, if the first version of the <tt>zlib1g</tt>
5910 package which contained a minor number of at least
5911 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5912 <tt>shlibs</tt> entry for this library could say:
5913 <example compact="compact">
5914 libz 1 zlib1g (>= 1:1.1.3)
5916 The version-specific dependency is to avoid warnings from
5917 the dynamic linker about using older shared libraries with
5922 As zlib1g also provides a udeb containing the shared library,
5923 there would also be a second line:
5924 <example compact="compact">
5925 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5931 <heading>Providing a <file>shlibs</file> file</heading>
5934 If your package provides a shared library, you need to create
5935 a <file>shlibs</file> file following the format described above.
5936 It is usual to call this file <file>debian/shlibs</file> (but if
5937 you have multiple binary packages, you might want to call it
5938 <file>debian/shlibs.<var>package</var></file> instead). Then
5939 let <file>debian/rules</file> install it in the control
5940 information file area:
5941 <example compact="compact">
5942 install -m644 debian/shlibs debian/tmp/DEBIAN
5944 or, in the case of a multi-binary package:
5945 <example compact="compact">
5946 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5948 An alternative way of doing this is to create the
5949 <file>shlibs</file> file in the control information file area
5950 directly from <file>debian/rules</file> without using
5951 a <file>debian/shlibs</file> file at all,<footnote>
5952 This is what <prgn>dh_makeshlibs</prgn> in
5953 the <package>debhelper</package> suite does. If your package
5954 also has a udeb that provides a shared
5955 library, <prgn>dh_makeshlibs</prgn> can automatically generate
5956 the <tt>udeb:</tt> lines if you specify the name of the udeb
5957 with the <tt>--add-udeb</tt> option.
5959 since the <file>debian/shlibs</file> file itself is ignored by
5960 <prgn>dpkg-shlibdeps</prgn>.
5964 As <prgn>dpkg-shlibdeps</prgn> reads the
5965 <file>DEBIAN/shlibs</file> files in all of the binary packages
5966 being built from this source package, all of the
5967 <file>DEBIAN/shlibs</file> files should be installed before
5968 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5976 <chapt id="opersys"><heading>The Operating System</heading>
5979 <heading>File system hierarchy</heading>
5983 <heading>File System Structure</heading>
5986 The location of all installed files and directories must
5987 comply with the Filesystem Hierarchy Standard (FHS),
5988 version 2.3, with the exceptions noted below, and except
5989 where doing so would violate other terms of Debian
5990 Policy. The following exceptions to the FHS apply:
5995 The optional rules related to user specific
5996 configuration files for applications are stored in
5997 the user's home directory are relaxed. It is
5998 recommended that such files start with the
5999 '<tt>.</tt>' character (a "dot file"), and if an
6000 application needs to create more than one dot file
6001 then the preferred placement is in a subdirectory
6002 with a name starting with a '.' character, (a "dot
6003 directory"). In this case it is recommended the
6004 configuration files not start with the '.'
6010 The requirement for amd64 to use <file>/lib64</file>
6011 for 64 bit binaries is removed.
6016 The requirement for object files, internal binaries, and
6017 libraries, including <file>libc.so.*</file>, to be located
6018 directly under <file>/lib{,32}</file> and
6019 <file>/usr/lib{,32}</file> is amended, permitting files
6020 to instead be installed to
6021 <file>/lib/<var>triplet</var></file> and
6022 <file>/usr/lib/<var>triplet</var></file>, where
6023 <tt><var>triplet</var></tt> is the value returned by
6024 <tt>dpkg-architecture -qDEB_HOST_GNU_TYPE</tt> for the
6025 architecture of the package. Packages may <em>not</em>
6026 install files to any <var>triplet</var> path other
6027 than the one matching the architecture of that package;
6028 for instance, an <tt>Architecture: amd64</tt> package
6029 containing 32-bit x86 libraries may not install these
6030 libraries to <file>/usr/lib/i486-linux-gnu</file>.
6032 This is necessary in order to reserve the directories for
6033 use in cross-installation of library packages from other
6034 architectures, as part of the planned deployment of
6039 Applications may also use a single subdirectory under
6040 <file>/usr/lib/<var>triplet</var></file>.
6043 The execution time linker/loader, ld*, must still be made
6044 available in the existing location under /lib or /lib64
6045 since this is part of the ELF ABI for the architecture.
6050 The requirement that
6051 <file>/usr/local/share/man</file> be "synonymous"
6052 with <file>/usr/local/man</file> is relaxed to a
6057 The requirement that windowmanagers with a single
6058 configuration file call it <file>system.*wmrc</file>
6059 is removed, as is the restriction that the window
6060 manager subdirectory be named identically to the
6061 window manager name itself.
6066 The requirement that boot manager configuration
6067 files live in <file>/etc</file>, or at least are
6068 symlinked there, is relaxed to a recommendation.
6073 The following directories in the root filesystem are
6074 additionally allowed: <file>/sys</file> and
6075 <file>/selinux</file>. <footnote>These directories
6076 are used as mount points to mount virtual filesystems
6077 to get access to kernel information.</footnote>
6084 The version of this document referred here can be
6085 found in the <tt>debian-policy</tt> package or on <url
6086 id="http://www.debian.org/doc/packaging-manuals/fhs/"
6087 name="FHS (Debian copy)"> alongside this manual (or, if
6088 you have the <package>debian-policy</package> installed,
6090 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
6091 (local copy)">). The
6092 latest version, which may be a more recent version, may
6094 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
6095 Specific questions about following the standard may be
6096 asked on the <tt>debian-devel</tt> mailing list, or
6097 referred to the FHS mailing list (see the
6098 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
6104 <heading>Site-specific programs</heading>
6107 As mandated by the FHS, packages must not place any
6108 files in <file>/usr/local</file>, either by putting them in
6109 the file system archive to be unpacked by <prgn>dpkg</prgn>
6110 or by manipulating them in their maintainer scripts.
6114 However, the package may create empty directories below
6115 <file>/usr/local</file> so that the system administrator knows
6116 where to place site-specific files. These are not
6117 directories <em>in</em> <file>/usr/local</file>, but are
6118 children of directories in <file>/usr/local</file>. These
6119 directories (<file>/usr/local/*/dir/</file>)
6120 should be removed on package removal if they are
6125 Note that this applies only to
6126 directories <em>below</em> <file>/usr/local</file>,
6127 not <em>in</em> <file>/usr/local</file>. Packages must
6128 not create sub-directories in the
6129 directory <file>/usr/local</file> itself, except those
6130 listed in FHS, section 4.5. However, you may create
6131 directories below them as you wish. You must not remove
6132 any of the directories listed in 4.5, even if you created
6137 Since <file>/usr/local</file> can be mounted read-only from a
6138 remote server, these directories must be created and
6139 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
6140 maintainer scripts and not be included in the
6141 <file>.deb</file> archive. These scripts must not fail if
6142 either of these operations fail.
6146 For example, the <tt>emacsen-common</tt> package could
6147 contain something like
6148 <example compact="compact">
6149 if [ ! -e /usr/local/share/emacs ]
6151 if mkdir /usr/local/share/emacs 2>/dev/null
6153 chown root:staff /usr/local/share/emacs
6154 chmod 2775 /usr/local/share/emacs
6158 in its <prgn>postinst</prgn> script, and
6159 <example compact="compact">
6160 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
6161 rmdir /usr/local/share/emacs 2>/dev/null || true
6163 in the <prgn>prerm</prgn> script. (Note that this form is
6164 used to ensure that if the script is interrupted, the
6165 directory <file>/usr/local/share/emacs</file> will still be
6170 If you do create a directory in <file>/usr/local</file> for
6171 local additions to a package, you should ensure that
6172 settings in <file>/usr/local</file> take precedence over the
6173 equivalents in <file>/usr</file>.
6177 However, because <file>/usr/local</file> and its contents are
6178 for exclusive use of the local administrator, a package
6179 must not rely on the presence or absence of files or
6180 directories in <file>/usr/local</file> for normal operation.
6184 The <file>/usr/local</file> directory itself and all the
6185 subdirectories created by the package should (by default) have
6186 permissions 2775 (group-writable and set-group-id) and be
6187 owned by <tt>root:staff</tt>.
6192 <heading>The system-wide mail directory</heading>
6194 The system-wide mail directory
6195 is <file>/var/mail</file>. This directory is part of the
6196 base system and should not be owned by any particular mail
6197 agents. The use of the old
6198 location <file>/var/spool/mail</file> is deprecated, even
6199 though the spool may still be physically located there.
6205 <heading>Users and groups</heading>
6208 <heading>Introduction</heading>
6210 The Debian system can be configured to use either plain or
6215 Some user ids (UIDs) and group ids (GIDs) are reserved
6216 globally for use by certain packages. Because some
6217 packages need to include files which are owned by these
6218 users or groups, or need the ids compiled into binaries,
6219 these ids must be used on any Debian system only for the
6220 purpose for which they are allocated. This is a serious
6221 restriction, and we should avoid getting in the way of
6222 local administration policies. In particular, many sites
6223 allocate users and/or local system groups starting at 100.
6227 Apart from this we should have dynamically allocated ids,
6228 which should by default be arranged in some sensible
6229 order, but the behavior should be configurable.
6233 Packages other than <tt>base-passwd</tt> must not modify
6234 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
6235 <file>/etc/group</file> or <file>/etc/gshadow</file>.
6240 <heading>UID and GID classes</heading>
6242 The UID and GID numbers are divided into classes as
6248 Globally allocated by the Debian project, the same
6249 on every Debian system. These ids will appear in
6250 the <file>passwd</file> and <file>group</file> files of all
6251 Debian systems, new ids in this range being added
6252 automatically as the <tt>base-passwd</tt> package is
6257 Packages which need a single statically allocated
6258 uid or gid should use one of these; their
6259 maintainers should ask the <tt>base-passwd</tt>
6267 Dynamically allocated system users and groups.
6268 Packages which need a user or group, but can have
6269 this user or group allocated dynamically and
6270 differently on each system, should use <tt>adduser
6271 --system</tt> to create the group and/or user.
6272 <prgn>adduser</prgn> will check for the existence of
6273 the user or group, and if necessary choose an unused
6274 id based on the ranges specified in
6275 <file>adduser.conf</file>.
6279 <tag>1000-59999:</tag>
6282 Dynamically allocated user accounts. By default
6283 <prgn>adduser</prgn> will choose UIDs and GIDs for
6284 user accounts in this range, though
6285 <file>adduser.conf</file> may be used to modify this
6290 <tag>60000-64999:</tag>
6293 Globally allocated by the Debian project, but only
6294 created on demand. The ids are allocated centrally
6295 and statically, but the actual accounts are only
6296 created on users' systems on demand.
6300 These ids are for packages which are obscure or
6301 which require many statically-allocated ids. These
6302 packages should check for and create the accounts in
6303 <file>/etc/passwd</file> or <file>/etc/group</file> (using
6304 <prgn>adduser</prgn> if it has this facility) if
6305 necessary. Packages which are likely to require
6306 further allocations should have a "hole" left after
6307 them in the allocation, to give them room to
6312 <tag>65000-65533:</tag>
6320 User <tt>nobody</tt>. The corresponding gid refers
6321 to the group <tt>nogroup</tt>.
6328 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
6329 not</em> be used, because it is the error return
6338 <sect id="sysvinit">
6339 <heading>System run levels and <file>init.d</file> scripts</heading>
6341 <sect1 id="/etc/init.d">
6342 <heading>Introduction</heading>
6345 The <file>/etc/init.d</file> directory contains the scripts
6346 executed by <prgn>init</prgn> at boot time and when the
6347 init state (or "runlevel") is changed (see <manref
6348 name="init" section="8">).
6352 There are at least two different, yet functionally
6353 equivalent, ways of handling these scripts. For the sake
6354 of simplicity, this document describes only the symbolic
6355 link method. However, it must not be assumed by maintainer
6356 scripts that this method is being used, and any automated
6357 manipulation of the various runlevel behaviors by
6358 maintainer scripts must be performed using
6359 <prgn>update-rc.d</prgn> as described below and not by
6360 manually installing or removing symlinks. For information
6361 on the implementation details of the other method,
6362 implemented in the <tt>file-rc</tt> package, please refer
6363 to the documentation of that package.
6367 These scripts are referenced by symbolic links in the
6368 <file>/etc/rc<var>n</var>.d</file> directories. When changing
6369 runlevels, <prgn>init</prgn> looks in the directory
6370 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
6371 execute, where <tt><var>n</var></tt> is the runlevel that
6372 is being changed to, or <tt>S</tt> for the boot-up
6377 The names of the links all have the form
6378 <file>S<var>mm</var><var>script</var></file> or
6379 <file>K<var>mm</var><var>script</var></file> where
6380 <var>mm</var> is a two-digit number and <var>script</var>
6381 is the name of the script (this should be the same as the
6382 name of the actual script in <file>/etc/init.d</file>).
6386 When <prgn>init</prgn> changes runlevel first the targets
6387 of the links whose names start with a <tt>K</tt> are
6388 executed, each with the single argument <tt>stop</tt>,
6389 followed by the scripts prefixed with an <tt>S</tt>, each
6390 with the single argument <tt>start</tt>. (The links are
6391 those in the <file>/etc/rc<var>n</var>.d</file> directory
6392 corresponding to the new runlevel.) The <tt>K</tt> links
6393 are responsible for killing services and the <tt>S</tt>
6394 link for starting services upon entering the runlevel.
6398 For example, if we are changing from runlevel 2 to
6399 runlevel 3, init will first execute all of the <tt>K</tt>
6400 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
6401 all of the <tt>S</tt> prefixed scripts in that directory.
6402 The links starting with <tt>K</tt> will cause the
6403 referred-to file to be executed with an argument of
6404 <tt>stop</tt>, and the <tt>S</tt> links with an argument
6409 The two-digit number <var>mm</var> is used to determine
6410 the order in which to run the scripts: low-numbered links
6411 have their scripts run first. For example, the
6412 <tt>K20</tt> scripts will be executed before the
6413 <tt>K30</tt> scripts. This is used when a certain service
6414 must be started before another. For example, the name
6415 server <prgn>bind</prgn> might need to be started before
6416 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
6417 can set up its access lists. In this case, the script
6418 that starts <prgn>bind</prgn> would have a lower number
6419 than the script that starts <prgn>inn</prgn> so that it
6421 <example compact="compact">
6428 The two runlevels 0 (halt) and 6 (reboot) are slightly
6429 different. In these runlevels, the links with an
6430 <tt>S</tt> prefix are still called after those with a
6431 <tt>K</tt> prefix, but they too are called with the single
6432 argument <tt>stop</tt>.
6436 <sect1 id="writing-init">
6437 <heading>Writing the scripts</heading>
6440 Packages that include daemons for system services should
6441 place scripts in <file>/etc/init.d</file> to start or stop
6442 services at boot time or during a change of runlevel.
6443 These scripts should be named
6444 <file>/etc/init.d/<var>package</var></file>, and they should
6445 accept one argument, saying what to do:
6448 <tag><tt>start</tt></tag>
6449 <item>start the service,</item>
6451 <tag><tt>stop</tt></tag>
6452 <item>stop the service,</item>
6454 <tag><tt>restart</tt></tag>
6455 <item>stop and restart the service if it's already running,
6456 otherwise start the service</item>
6458 <tag><tt>reload</tt></tag>
6459 <item><p>cause the configuration of the service to be
6460 reloaded without actually stopping and restarting
6463 <tag><tt>force-reload</tt></tag>
6464 <item>cause the configuration to be reloaded if the
6465 service supports this, otherwise restart the
6469 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
6470 <tt>force-reload</tt> options should be supported by all
6471 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
6476 The <file>init.d</file> scripts must ensure that they will
6477 behave sensibly (i.e., returning success and not starting
6478 multiple copies of a service) if invoked with <tt>start</tt>
6479 when the service is already running, or with <tt>stop</tt>
6480 when it isn't, and that they don't kill unfortunately-named
6481 user processes. The best way to achieve this is usually to
6482 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
6487 Be careful of using <tt>set -e</tt> in <file>init.d</file>
6488 scripts. Writing correct <file>init.d</file> scripts requires
6489 accepting various error exit statuses when daemons are already
6490 running or already stopped without aborting
6491 the <file>init.d</file> script, and common <file>init.d</file>
6492 function libraries are not safe to call with <tt>set -e</tt>
6494 <tt>/lib/lsb/init-functions</tt>, which assists in writing
6495 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
6496 in effect and echoing status messages to the console fails,
6498 </footnote>. For <tt>init.d</tt> scripts, it's often easier
6499 to not use <tt>set -e</tt> and instead check the result of
6500 each command separately.
6504 If a service reloads its configuration automatically (as
6505 in the case of <prgn>cron</prgn>, for example), the
6506 <tt>reload</tt> option of the <file>init.d</file> script
6507 should behave as if the configuration has been reloaded
6512 The <file>/etc/init.d</file> scripts must be treated as
6513 configuration files, either (if they are present in the
6514 package, that is, in the .deb file) by marking them as
6515 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6516 by managing them correctly in the maintainer scripts (see
6517 <ref id="config-files">). This is important since we want
6518 to give the local system administrator the chance to adapt
6519 the scripts to the local system, e.g., to disable a
6520 service without de-installing the package, or to specify
6521 some special command line options when starting a service,
6522 while making sure their changes aren't lost during the next
6527 These scripts should not fail obscurely when the
6528 configuration files remain but the package has been
6529 removed, as configuration files remain on the system after
6530 the package has been removed. Only when <prgn>dpkg</prgn>
6531 is executed with the <tt>--purge</tt> option will
6532 configuration files be removed. In particular, as the
6533 <file>/etc/init.d/<var>package</var></file> script itself is
6534 usually a <tt>conffile</tt>, it will remain on the system
6535 if the package is removed but not purged. Therefore, you
6536 should include a <tt>test</tt> statement at the top of the
6538 <example compact="compact">
6539 test -f <var>program-executed-later-in-script</var> || exit 0
6544 Often there are some variables in the <file>init.d</file>
6545 scripts whose values control the behavior of the scripts,
6546 and which a system administrator is likely to want to
6547 change. As the scripts themselves are frequently
6548 <tt>conffile</tt>s, modifying them requires that the
6549 administrator merge in their changes each time the package
6550 is upgraded and the <tt>conffile</tt> changes. To ease
6551 the burden on the system administrator, such configurable
6552 values should not be placed directly in the script.
6553 Instead, they should be placed in a file in
6554 <file>/etc/default</file>, which typically will have the same
6555 base name as the <file>init.d</file> script. This extra file
6556 should be sourced by the script when the script runs. It
6557 must contain only variable settings and comments in SUSv3
6558 <prgn>sh</prgn> format. It may either be a
6559 <tt>conffile</tt> or a configuration file maintained by
6560 the package maintainer scripts. See <ref id="config-files">
6565 To ensure that vital configurable values are always
6566 available, the <file>init.d</file> script should set default
6567 values for each of the shell variables it uses, either
6568 before sourcing the <file>/etc/default/</file> file or
6569 afterwards using something like the <tt>:
6570 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6571 script must behave sensibly and not fail if the
6572 <file>/etc/default</file> file is deleted.
6576 <file>/var/run</file> and <file>/var/lock</file> may be mounted
6577 as temporary filesystems<footnote>
6578 For example, using the <tt>RAMRUN</tt> and <tt>RAMLOCK</tt>
6579 options in <file>/etc/default/rcS</file>.
6580 </footnote>, so the <file>init.d</file> scripts must handle this
6581 correctly. This will typically amount to creating any required
6582 subdirectories dynamically when the <file>init.d</file> script
6583 is run, rather than including them in the package and relying on
6584 <prgn>dpkg</prgn> to create them.
6589 <heading>Interfacing with the initscript system</heading>
6592 Maintainers should use the abstraction layer provided by
6593 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6594 programs to deal with initscripts in their packages'
6595 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6596 and <prgn>postrm</prgn>.
6600 Directly managing the /etc/rc?.d links and directly
6601 invoking the <file>/etc/init.d/</file> initscripts should
6602 be done only by packages providing the initscript
6603 subsystem (such as <prgn>sysv-rc</prgn> and
6604 <prgn>file-rc</prgn>).
6608 <heading>Managing the links</heading>
6611 The program <prgn>update-rc.d</prgn> is provided for
6612 package maintainers to arrange for the proper creation and
6613 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6614 or their functional equivalent if another method is being
6615 used. This may be used by maintainers in their packages'
6616 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6620 You must not include any <file>/etc/rc<var>n</var>.d</file>
6621 symbolic links in the actual archive or manually create or
6622 remove the symbolic links in maintainer scripts; you must
6623 use the <prgn>update-rc.d</prgn> program instead. (The
6624 former will fail if an alternative method of maintaining
6625 runlevel information is being used.) You must not include
6626 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6627 in the archive either. (Only the <tt>sysvinit</tt>
6632 By default <prgn>update-rc.d</prgn> will start services in
6633 each of the multi-user state runlevels (2, 3, 4, and 5)
6634 and stop them in the halt runlevel (0), the single-user
6635 runlevel (1) and the reboot runlevel (6). The system
6636 administrator will have the opportunity to customize
6637 runlevels by simply adding, moving, or removing the
6638 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6639 symbolic links are being used, or by modifying
6640 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6645 To get the default behavior for your package, put in your
6646 <prgn>postinst</prgn> script
6647 <example compact="compact">
6648 update-rc.d <var>package</var> defaults
6650 and in your <prgn>postrm</prgn>
6651 <example compact="compact">
6652 if [ "$1" = purge ]; then
6653 update-rc.d <var>package</var> remove
6655 </example>. Note that if your package changes runlevels
6656 or priority, you may have to remove and recreate the links,
6657 since otherwise the old links may persist. Refer to the
6658 documentation of <prgn>update-rc.d</prgn>.
6662 This will use a default sequence number of 20. If it does
6663 not matter when or in which order the <file>init.d</file>
6664 script is run, use this default. If it does, then you
6665 should talk to the maintainer of the <prgn>sysvinit</prgn>
6666 package or post to <tt>debian-devel</tt>, and they will
6667 help you choose a number.
6671 For more information about using <tt>update-rc.d</tt>,
6672 please consult its man page <manref name="update-rc.d"
6678 <heading>Running initscripts</heading>
6680 The program <prgn>invoke-rc.d</prgn> is provided to make
6681 it easier for package maintainers to properly invoke an
6682 initscript, obeying runlevel and other locally-defined
6683 constraints that might limit a package's right to start,
6684 stop and otherwise manage services. This program may be
6685 used by maintainers in their packages' scripts.
6689 The package maintainer scripts must use
6690 <prgn>invoke-rc.d</prgn> to invoke the
6691 <file>/etc/init.d/*</file> initscripts, instead of
6692 calling them directly.
6696 By default, <prgn>invoke-rc.d</prgn> will pass any
6697 action requests (start, stop, reload, restart...) to the
6698 <file>/etc/init.d</file> script, filtering out requests
6699 to start or restart a service out of its intended
6704 Most packages will simply need to change:
6705 <example compact="compact">/etc/init.d/<package>
6706 <action></example> in their <prgn>postinst</prgn>
6707 and <prgn>prerm</prgn> scripts to:
6708 <example compact="compact">
6709 if which invoke-rc.d >/dev/null 2>&1; then
6710 invoke-rc.d <var>package</var> <action>
6712 /etc/init.d/<var>package</var> <action>
6718 A package should register its initscript services using
6719 <prgn>update-rc.d</prgn> before it tries to invoke them
6720 using <prgn>invoke-rc.d</prgn>. Invocation of
6721 unregistered services may fail.
6725 For more information about using
6726 <prgn>invoke-rc.d</prgn>, please consult its man page
6727 <manref name="invoke-rc.d" section="8">.
6733 <heading>Boot-time initialization</heading>
6736 There used to be another directory, <file>/etc/rc.boot</file>,
6737 which contained scripts which were run once per machine
6738 boot. This has been deprecated in favour of links from
6739 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6740 described in <ref id="/etc/init.d">. Packages must not
6741 place files in <file>/etc/rc.boot</file>.
6746 <heading>Example</heading>
6749 An example on which you can base your
6750 <file>/etc/init.d</file> scripts is found in
6751 <file>/etc/init.d/skeleton</file>.
6758 <heading>Console messages from <file>init.d</file> scripts</heading>
6761 This section describes the formats to be used for messages
6762 written to standard output by the <file>/etc/init.d</file>
6763 scripts. The intent is to improve the consistency of
6764 Debian's startup and shutdown look and feel. For this
6765 reason, please look very carefully at the details. We want
6766 the messages to have the same format in terms of wording,
6767 spaces, punctuation and case of letters.
6771 Here is a list of overall rules that should be used for
6772 messages generated by <file>/etc/init.d</file> scripts.
6778 The message should fit in one line (fewer than 80
6779 characters), start with a capital letter and end with
6780 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6784 If the script is performing some time consuming task in
6785 the background (not merely starting or stopping a
6786 program, for instance), an ellipsis (three dots:
6787 <tt>...</tt>) should be output to the screen, with no
6788 leading or tailing whitespace or line feeds.
6792 The messages should appear as if the computer is telling
6793 the user what it is doing (politely :-), but should not
6794 mention "it" directly. For example, instead of:
6795 <example compact="compact">
6796 I'm starting network daemons: nfsd mountd.
6798 the message should say
6799 <example compact="compact">
6800 Starting network daemons: nfsd mountd.
6807 <tt>init.d</tt> script should use the following standard
6808 message formats for the situations enumerated below.
6814 <p>When daemons are started</p>
6817 If the script starts one or more daemons, the output
6818 should look like this (a single line, no leading
6820 <example compact="compact">
6821 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6823 The <var>description</var> should describe the
6824 subsystem the daemon or set of daemons are part of,
6825 while <var>daemon-1</var> up to <var>daemon-n</var>
6826 denote each daemon's name (typically the file name of
6831 For example, the output of <file>/etc/init.d/lpd</file>
6833 <example compact="compact">
6834 Starting printer spooler: lpd.
6839 This can be achieved by saying
6840 <example compact="compact">
6841 echo -n "Starting printer spooler: lpd"
6842 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6845 in the script. If there are more than one daemon to
6846 start, the output should look like this:
6847 <example compact="compact">
6848 echo -n "Starting remote file system services:"
6849 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6850 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6851 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6854 This makes it possible for the user to see what is
6855 happening and when the final daemon has been started.
6856 Care should be taken in the placement of white spaces:
6857 in the example above the system administrators can
6858 easily comment out a line if they don't want to start
6859 a specific daemon, while the displayed message still
6865 <p>When a system parameter is being set</p>
6868 If you have to set up different system parameters
6869 during the system boot, you should use this format:
6870 <example compact="compact">
6871 Setting <var>parameter</var> to "<var>value</var>".
6876 You can use a statement such as the following to get
6878 <example compact="compact">
6879 echo "Setting DNS domainname to \"$domainname\"."
6884 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
6885 for the left and right quotation marks. A grave accent
6886 (<tt>`</tt>) is not a quote character; neither is an
6887 apostrophe (<tt>'</tt>).
6892 <p>When a daemon is stopped or restarted</p>
6895 When you stop or restart a daemon, you should issue a
6896 message identical to the startup message, except that
6897 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6898 or <tt>Restarting</tt> respectively.
6902 For example, stopping the printer daemon will look like
6904 <example compact="compact">
6905 Stopping printer spooler: lpd.
6911 <p>When something is executed</p>
6914 There are several examples where you have to run a
6915 program at system startup or shutdown to perform a
6916 specific task, for example, setting the system's clock
6917 using <prgn>netdate</prgn> or killing all processes
6918 when the system shuts down. Your message should look
6920 <example compact="compact">
6921 Doing something very useful...done.
6923 You should print the <tt>done.</tt> immediately after
6924 the job has been completed, so that the user is
6925 informed why they have to wait. You can get this
6927 <example compact="compact">
6928 echo -n "Doing something very useful..."
6937 <p>When the configuration is reloaded</p>
6940 When a daemon is forced to reload its configuration
6941 files you should use the following format:
6942 <example compact="compact">
6943 Reloading <var>description</var> configuration...done.
6945 where <var>description</var> is the same as in the
6946 daemon starting message.
6954 <heading>Cron jobs</heading>
6957 Packages must not modify the configuration file
6958 <file>/etc/crontab</file>, and they must not modify the files in
6959 <file>/var/spool/cron/crontabs</file>.</p>
6962 If a package wants to install a job that has to be executed
6963 via cron, it should place a file with the name of the
6964 package in one or more of the following directories:
6965 <example compact="compact">
6971 As these directory names imply, the files within them are
6972 executed on an hourly, daily, weekly, or monthly basis,
6973 respectively. The exact times are listed in
6974 <file>/etc/crontab</file>.</p>
6977 All files installed in any of these directories must be
6978 scripts (e.g., shell scripts or Perl scripts) so that they
6979 can easily be modified by the local system administrator.
6980 In addition, they must be treated as configuration files.
6984 If a certain job has to be executed at some other frequency or
6985 at a specific time, the package should install a file
6986 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6987 same syntax as <file>/etc/crontab</file> and is processed by
6988 <prgn>cron</prgn> automatically. The file must also be
6989 treated as a configuration file. (Note that entries in the
6990 <file>/etc/cron.d</file> directory are not handled by
6991 <prgn>anacron</prgn>. Thus, you should only use this
6992 directory for jobs which may be skipped if the system is not
6995 Unlike <file>crontab</file> files described in the IEEE Std
6996 1003.1-2008 (POSIX.1) available from
6997 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
6998 name="The Open Group">, the files in
6999 <file>/etc/cron.d</file> and the file
7000 <file>/etc/crontab</file> have seven fields; namely:
7002 <item>Minute [0,59]</item>
7003 <item>Hour [0,23]</item>
7004 <item>Day of the month [1,31]</item>
7005 <item>Month of the year [1,12]</item>
7006 <item>Day of the week ([0,6] with 0=Sunday)</item>
7007 <item>Username</item>
7008 <item>Command to be run</item>
7010 Ranges of numbers are allowed. Ranges are two numbers
7011 separated with a hyphen. The specified range is inclusive.
7012 Lists are allowed. A list is a set of numbers (or ranges)
7013 separated by commas. Step values can be used in conjunction
7018 The scripts or <tt>crontab</tt> entries in these directories should
7019 check if all necessary programs are installed before they
7020 try to execute them. Otherwise, problems will arise when a
7021 package was removed but not purged since configuration files
7022 are kept on the system in this situation.
7026 Any <tt>cron</tt> daemon must provide
7027 <file>/usr/bin/crontab</file> and support normal
7028 <tt>crontab</tt> entries as specified in POSIX. The daemon
7029 must also support names for days and months, ranges, and
7030 step values. It has to support <file>/etc/crontab</file>,
7031 and correctly execute the scripts in
7032 <file>/etc/cron.d</file>. The daemon must also correctly
7034 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
7039 <heading>Menus</heading>
7042 The Debian <tt>menu</tt> package provides a standard
7043 interface between packages providing applications and
7044 <em>menu programs</em> (either X window managers or
7045 text-based menu programs such as <prgn>pdmenu</prgn>).
7049 All packages that provide applications that need not be
7050 passed any special command line arguments for normal
7051 operation should register a menu entry for those
7052 applications, so that users of the <tt>menu</tt> package
7053 will automatically get menu entries in their window
7054 managers, as well in shells like <tt>pdmenu</tt>.
7058 Menu entries should follow the current menu policy.
7062 The menu policy can be found in the <tt>menu-policy</tt>
7063 files in the <tt>debian-policy</tt> package.
7064 It is also available from the Debian web mirrors at
7065 <tt><url name="/doc/packaging-manuals/menu-policy/"
7066 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
7070 Please also refer to the <em>Debian Menu System</em>
7071 documentation that comes with the <package>menu</package>
7072 package for information about how to register your
7078 <heading>Multimedia handlers</heading>
7081 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
7082 is a mechanism for encoding files and data streams and
7083 providing meta-information about them, in particular their
7084 type (e.g. audio or video) and format (e.g. PNG, HTML,
7089 Registration of MIME type handlers allows programs like mail
7090 user agents and web browsers to invoke these handlers to
7091 view, edit or display MIME types they don't support directly.
7095 Packages which provide the ability to view/show/play,
7096 compose, edit or print MIME types should register themselves
7097 as such following the current MIME support policy.
7101 The MIME support policy can be found in the <tt>mime-policy</tt>
7102 files in the <tt>debian-policy</tt> package.
7103 It is also available from the Debian web mirrors at
7104 <tt><url name="/doc/packaging-manuals/mime-policy/"
7105 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
7111 <heading>Keyboard configuration</heading>
7114 To achieve a consistent keyboard configuration so that all
7115 applications interpret a keyboard event the same way, all
7116 programs in the Debian distribution must be configured to
7117 comply with the following guidelines.
7121 The following keys must have the specified interpretations:
7124 <tag><tt><--</tt></tag>
7125 <item>delete the character to the left of the cursor</item>
7127 <tag><tt>Delete</tt></tag>
7128 <item>delete the character to the right of the cursor</item>
7130 <tag><tt>Control+H</tt></tag>
7131 <item>emacs: the help prefix</item>
7134 The interpretation of any keyboard events should be
7135 independent of the terminal that is used, be it a virtual
7136 console, an X terminal emulator, an rlogin/telnet session,
7141 The following list explains how the different programs
7142 should be set up to achieve this:
7148 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
7152 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
7156 X translations are set up to make
7157 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
7158 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
7159 is the vt220 escape code for the "delete character"
7160 key). This must be done by loading the X resources
7161 using <prgn>xrdb</prgn> on all local X displays, not
7162 using the application defaults, so that the
7163 translation resources used correspond to the
7164 <prgn>xmodmap</prgn> settings.
7168 The Linux console is configured to make
7169 <tt><--</tt> generate DEL, and <tt>Delete</tt>
7170 generate <tt>ESC [ 3 ~</tt>.
7174 X applications are configured so that <tt><</tt>
7175 deletes left, and <tt>Delete</tt> deletes right. Motif
7176 applications already work like this.
7180 Terminals should have <tt>stty erase ^?</tt> .
7184 The <tt>xterm</tt> terminfo entry should have <tt>ESC
7185 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
7186 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
7190 Emacs is programmed to map <tt>KB_Backspace</tt> or
7191 the <tt>stty erase</tt> character to
7192 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
7193 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
7194 <tt>^H</tt> to <tt>help</tt> as always.
7198 Other applications use the <tt>stty erase</tt>
7199 character and <tt>kdch1</tt> for the two delete keys,
7200 with ASCII DEL being "delete previous character" and
7201 <tt>kdch1</tt> being "delete character under
7209 This will solve the problem except for the following
7216 Some terminals have a <tt><--</tt> key that cannot
7217 be made to produce anything except <tt>^H</tt>. On
7218 these terminals Emacs help will be unavailable on
7219 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
7220 character takes precedence in Emacs, and has been set
7221 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
7222 available) can be used instead.
7226 Some operating systems use <tt>^H</tt> for <tt>stty
7227 erase</tt>. However, modern telnet versions and all
7228 rlogin versions propagate <tt>stty</tt> settings, and
7229 almost all UNIX versions honour <tt>stty erase</tt>.
7230 Where the <tt>stty</tt> settings are not propagated
7231 correctly, things can be made to work by using
7232 <tt>stty</tt> manually.
7236 Some systems (including previous Debian versions) use
7237 <prgn>xmodmap</prgn> to arrange for both
7238 <tt><--</tt> and <tt>Delete</tt> to generate
7239 <tt>KB_Delete</tt>. We can change the behavior of
7240 their X clients using the same X resources that we use
7241 to do it for our own clients, or configure our clients
7242 using their resources when things are the other way
7243 around. On displays configured like this
7244 <tt>Delete</tt> will not work, but <tt><--</tt>
7249 Some operating systems have different <tt>kdch1</tt>
7250 settings in their <tt>terminfo</tt> database for
7251 <tt>xterm</tt> and others. On these systems the
7252 <tt>Delete</tt> key will not work correctly when you
7253 log in from a system conforming to our policy, but
7254 <tt><--</tt> will.
7261 <heading>Environment variables</heading>
7264 A program must not depend on environment variables to get
7265 reasonable defaults. (That's because these environment
7266 variables would have to be set in a system-wide
7267 configuration file like <file>/etc/profile</file>, which is not
7268 supported by all shells.)
7272 If a program usually depends on environment variables for its
7273 configuration, the program should be changed to fall back to
7274 a reasonable default configuration if these environment
7275 variables are not present. If this cannot be done easily
7276 (e.g., if the source code of a non-free program is not
7277 available), the program must be replaced by a small
7278 "wrapper" shell script which sets the environment variables
7279 if they are not already defined, and calls the original program.
7283 Here is an example of a wrapper script for this purpose:
7285 <example compact="compact">
7287 BAR=${BAR:-/var/lib/fubar}
7289 exec /usr/lib/foo/foo "$@"
7294 Furthermore, as <file>/etc/profile</file> is a configuration
7295 file of the <prgn>base-files</prgn> package, other packages must
7296 not put any environment variables or other commands into that
7301 <sect id="doc-base">
7302 <heading>Registering Documents using doc-base</heading>
7305 The <package>doc-base</package> package implements a
7306 flexible mechanism for handling and presenting
7307 documentation. The recommended practice is for every Debian
7308 package that provides online documentation (other than just
7309 manual pages) to register these documents with
7310 <package>doc-base</package> by installing a
7311 <package>doc-base</package> control file via the
7312 <prgn/install-docs/ script at installation time and
7313 de-register the manuals again when the package is removed.
7316 Please refer to the documentation that comes with the
7317 <package>doc-base</package> package for information and
7326 <heading>Files</heading>
7328 <sect id="binaries">
7329 <heading>Binaries</heading>
7332 Two different packages must not install programs with
7333 different functionality but with the same filenames. (The
7334 case of two programs having the same functionality but
7335 different implementations is handled via "alternatives" or
7336 the "Conflicts" mechanism. See <ref id="maintscripts"> and
7337 <ref id="conflicts"> respectively.) If this case happens,
7338 one of the programs must be renamed. The maintainers should
7339 report this to the <tt>debian-devel</tt> mailing list and
7340 try to find a consensus about which program will have to be
7341 renamed. If a consensus cannot be reached, <em>both</em>
7342 programs must be renamed.
7346 By default, when a package is being built, any binaries
7347 created should include debugging information, as well as
7348 being compiled with optimization. You should also turn on
7349 as many reasonable compilation warnings as possible; this
7350 makes life easier for porters, who can then look at build
7351 logs for possible problems. For the C programming language,
7352 this means the following compilation parameters should be
7354 <example compact="compact">
7356 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
7358 INSTALL = install -s # (or use strip on the files in debian/tmp)
7363 Note that by default all installed binaries should be stripped,
7364 either by using the <tt>-s</tt> flag to
7365 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
7366 the binaries after they have been copied into
7367 <file>debian/tmp</file> but before the tree is made into a
7372 Although binaries in the build tree should be compiled with
7373 debugging information by default, it can often be difficult to
7374 debug programs if they are also subjected to compiler
7375 optimization. For this reason, it is recommended to support the
7376 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
7377 (see <ref id="debianrules-options">). This variable can contain
7378 several flags to change how a package is compiled and built.
7382 It is up to the package maintainer to decide what
7383 compilation options are best for the package. Certain
7384 binaries (such as computationally-intensive programs) will
7385 function better with certain flags (<tt>-O3</tt>, for
7386 example); feel free to use them. Please use good judgment
7387 here. Don't use flags for the sake of it; only use them
7388 if there is good reason to do so. Feel free to override
7389 the upstream author's ideas about which compilation
7390 options are best: they are often inappropriate for our
7396 <sect id="libraries">
7397 <heading>Libraries</heading>
7400 If the package is <strong>architecture: any</strong>, then
7401 the shared library compilation and linking flags must have
7402 <tt>-fPIC</tt>, or the package shall not build on some of
7403 the supported architectures<footnote>
7405 If you are using GCC, <tt>-fPIC</tt> produces code with
7406 relocatable position independent code, which is required for
7407 most architectures to create a shared library, with i386 and
7408 perhaps some others where non position independent code is
7409 permitted in a shared library.
7412 Position independent code may have a performance penalty,
7413 especially on <tt>i386</tt>. However, in most cases the
7414 speed penalty must be measured against the memory wasted on
7415 the few architectures where non position independent code is
7418 </footnote>. Any exception to this rule must be discussed on
7419 the mailing list <em>debian-devel@lists.debian.org</em>, and
7420 a rough consensus obtained. The reasons for not compiling
7421 with <tt>-fPIC</tt> flag must be recorded in the file
7422 <tt>README.Debian</tt>, and care must be taken to either
7423 restrict the architecture or arrange for <tt>-fPIC</tt> to
7424 be used on architectures where it is required.<footnote>
7426 Some of the reasons why this might be required is if the
7427 library contains hand crafted assembly code that is not
7428 relocatable, the speed penalty is excessive for compute
7429 intensive libs, and similar reasons.
7434 As to the static libraries, the common case is not to have
7435 relocatable code, since there is no benefit, unless in specific
7436 cases; therefore the static version must not be compiled
7437 with the <tt>-fPIC</tt> flag. Any exception to this rule
7438 should be discussed on the mailing list
7439 <em>debian-devel@lists.debian.org</em>, and the reasons for
7440 compiling with the <tt>-fPIC</tt> flag must be recorded in
7441 the file <tt>README.Debian</tt>. <footnote>
7443 Some of the reasons for linking static libraries with
7444 the <tt>-fPIC</tt> flag are if, for example, one needs a
7445 Perl API for a library that is under rapid development,
7446 and has an unstable API, so shared libraries are
7447 pointless at this phase of the library's development. In
7448 that case, since Perl needs a library with relocatable
7449 code, it may make sense to create a static library with
7450 relocatable code. Another reason cited is if you are
7451 distilling various libraries into a common shared
7452 library, like <tt>mklibs</tt> does in the Debian
7458 In other words, if both a shared and a static library is
7459 being built, each source unit (<tt>*.c</tt>, for example,
7460 for C files) will need to be compiled twice, for the normal
7465 Libraries should be built with threading support and to be
7466 thread-safe if the library supports this.
7470 Although not enforced by the build tools, shared libraries
7471 must be linked against all libraries that they use symbols from
7472 in the same way that binaries are. This ensures the correct
7473 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
7474 system and guarantees that all libraries can be safely opened
7475 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
7476 option <tt>-Wl,-z,defs</tt> when building a shared library.
7477 Since this option enforces symbol resolution at build time,
7478 a missing library reference will be caught early as a fatal
7483 All installed shared libraries should be stripped with
7484 <example compact="compact">
7485 strip --strip-unneeded <var>your-lib</var>
7487 (The option <tt>--strip-unneeded</tt> makes
7488 <prgn>strip</prgn> remove only the symbols which aren't
7489 needed for relocation processing.) Shared libraries can
7490 function perfectly well when stripped, since the symbols for
7491 dynamic linking are in a separate part of the ELF object
7493 You might also want to use the options
7494 <tt>--remove-section=.comment</tt> and
7495 <tt>--remove-section=.note</tt> on both shared libraries
7496 and executables, and <tt>--strip-debug</tt> on static
7502 Note that under some circumstances it may be useful to
7503 install a shared library unstripped, for example when
7504 building a separate package to support debugging.
7508 Shared object files (often <file>.so</file> files) that are not
7509 public libraries, that is, they are not meant to be linked
7510 to by third party executables (binaries of other packages),
7511 should be installed in subdirectories of the
7512 <file>/usr/lib</file> directory. Such files are exempt from the
7513 rules that govern ordinary shared libraries, except that
7514 they must not be installed executable and should be
7516 A common example are the so-called "plug-ins",
7517 internal shared objects that are dynamically loaded by
7518 programs using <manref name="dlopen" section="3">.
7523 Packages that use <prgn>libtool</prgn> to create and install
7524 their shared libraries install a file containing additional
7525 metadata (ending in <file>.la</file>) alongside the library.
7526 For public libraries intended for use by other packages, these
7527 files normally should not be included in the Debian package,
7528 since the information they include is not necessary to link with
7529 the shared library on Debian and can add unnecessary additional
7530 dependencies to other programs or libraries.<footnote>
7531 These files store, among other things, all libraries on which
7532 that shared library depends. Unfortunately, if
7533 the <file>.la</file> file is present and contains that
7534 dependency information, using <prgn>libtool</prgn> when
7535 linking against that library will cause the resulting program
7536 or library to be linked against those dependencies as well,
7537 even if this is unnecessary. This can create unneeded
7538 dependencies on shared library packages that would otherwise
7539 be hidden behind the library ABI, and can make library
7540 transitions to new SONAMEs unnecessarily complicated and
7541 difficult to manage.
7543 If the <file>.la</file> file is required for that library (if,
7544 for instance, it's loaded via <tt>libltdl</tt> in a way that
7545 requires that meta-information), the <tt>dependency_libs</tt>
7546 setting in the <file>.la</file> file should normally be set to
7547 the empty string. If the shared library development package has
7548 historically included the <file>.la</file>, it must be retained
7549 in the development package (with <tt>dependency_libs</tt>
7550 emptied) until all libraries that depend on it have removed or
7551 emptied <tt>dependency_libs</tt> in their <file>.la</file>
7552 files to prevent linking with those other libraries
7553 using <prgn>libtool</prgn> from failing.
7557 If the <file>.la</file> must be included, it should be included
7558 in the development (<tt>-dev</tt>) package, unless the library
7559 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
7560 library. If it is intended for use with <tt>libltdl</tt>,
7561 the <file>.la</file> files must go in the run-time library
7566 These requirements for handling of <file>.la</file> files do not
7567 apply to loadable modules or libraries not installed in
7568 directories searched by default by the dynamic linker. Packages
7569 installing loadable modules will frequently need to install
7570 the <file>.la</file> files alongside the modules so that they
7571 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
7572 does not need to be modified for libraries or modules that are
7573 not installed in directories searched by the dynamic linker by
7574 default and not intended for use by other packages.
7578 You must make sure that you use only released versions of
7579 shared libraries to build your packages; otherwise other
7580 users will not be able to run your binaries
7581 properly. Producing source packages that depend on
7582 unreleased compilers is also usually a bad
7589 <heading>Shared libraries</heading>
7591 This section has moved to <ref id="sharedlibs">.
7597 <heading>Scripts</heading>
7600 All command scripts, including the package maintainer
7601 scripts inside the package and used by <prgn>dpkg</prgn>,
7602 should have a <tt>#!</tt> line naming the shell to be used
7607 In the case of Perl scripts this should be
7608 <tt>#!/usr/bin/perl</tt>.
7612 When scripts are installed into a directory in the system
7613 PATH, the script name should not include an extension such
7614 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7615 language currently used to implement it.
7618 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
7619 <file>init.d</file> scripts should almost certainly start
7620 with <tt>set -e</tt> so that errors are detected.
7621 <file>init.d</file> scripts are something of a special case, due
7622 to how frequently they need to call commands that are allowed to
7623 fail, and it may instead be easier to check the exit status of
7624 commands directly. See <ref id="writing-init"> for more
7625 information about writing <file>init.d</file> scripts.
7628 Every script should use <tt>set -e</tt> or check the exit status
7629 of <em>every</em> command.
7632 Scripts may assume that <file>/bin/sh</file> implements the
7633 SUSv3 Shell Command Language<footnote>
7634 Single UNIX Specification, version 3, which is also IEEE
7635 1003.1-2004 (POSIX), and is available on the World Wide Web
7636 from <url id="http://www.unix.org/version3/online.html"
7637 name="The Open Group"> after free
7638 registration.</footnote>
7639 plus the following additional features not mandated by
7641 These features are in widespread use in the Linux community
7642 and are implemented in all of bash, dash, and ksh, the most
7643 common shells users may wish to use as <file>/bin/sh</file>.
7646 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7647 must not generate a newline.</item>
7648 <item><tt>test</tt>, if implemented as a shell built-in, must
7649 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7651 <item><tt>local</tt> to create a scoped variable must be
7652 supported, including listing multiple variables in a single
7653 local command and assigning a value to a variable at the
7654 same time as localizing it. <tt>local</tt> may or
7655 may not preserve the variable value from an outer scope if
7656 no assignment is present. Uses such as:
7660 # ... use a, b, c, d ...
7663 must be supported and must set the value of <tt>c</tt> to
7666 <item>The XSI extension to <prgn>kill</prgn> allowing <tt>kill
7667 -<var>signal</var></tt>, where <var>signal</var> is either
7668 the name of a signal or one of the numeric signals listed in
7669 the XSI extension (0, 1, 2, 3, 6, 9, 14, and 15), must be
7670 supported if <prgn>kill</prgn> is implemented as a shell
7673 <item>The XSI extension to <prgn>trap</prgn> allowing numeric
7674 signals must be supported. In addition to the signal
7675 numbers listed in the extension, which are the same as for
7676 <prgn>kill</prgn> above, 13 (SIGPIPE) must be allowed.
7679 If a shell script requires non-SUSv3 features from the shell
7680 interpreter other than those listed above, the appropriate shell
7681 must be specified in the first line of the script (e.g.,
7682 <tt>#!/bin/bash</tt>) and the package must depend on the package
7683 providing the shell (unless the shell package is marked
7684 "Essential", as in the case of <prgn>bash</prgn>).
7688 You may wish to restrict your script to SUSv3 features plus the
7689 above set when possible so that it may use <file>/bin/sh</file>
7690 as its interpreter. If your script works with <prgn>dash</prgn>
7691 (originally called <prgn>ash</prgn>), it probably complies with
7692 the above requirements, but if you are in doubt, use
7693 <file>/bin/bash</file>.
7697 Perl scripts should check for errors when making any
7698 system calls, including <tt>open</tt>, <tt>print</tt>,
7699 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7703 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7704 scripting languages. See <em>Csh Programming Considered
7705 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7706 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7707 If an upstream package comes with <prgn>csh</prgn> scripts
7708 then you must make sure that they start with
7709 <tt>#!/bin/csh</tt> and make your package depend on the
7710 <prgn>c-shell</prgn> virtual package.
7714 Any scripts which create files in world-writeable
7715 directories (e.g., in <file>/tmp</file>) must use a
7716 mechanism which will fail atomically if a file with the same
7717 name already exists.
7721 The Debian base system provides the <prgn>tempfile</prgn>
7722 and <prgn>mktemp</prgn> utilities for use by scripts for
7729 <heading>Symbolic links</heading>
7732 In general, symbolic links within a top-level directory
7733 should be relative, and symbolic links pointing from one
7734 top-level directory into another should be absolute. (A
7735 top-level directory is a sub-directory of the root
7736 directory <file>/</file>.)
7740 In addition, symbolic links should be specified as short as
7741 possible, i.e., link targets like <file>foo/../bar</file> are
7746 Note that when creating a relative link using
7747 <prgn>ln</prgn> it is not necessary for the target of the
7748 link to exist relative to the working directory you're
7749 running <prgn>ln</prgn> from, nor is it necessary to change
7750 directory to the directory where the link is to be made.
7751 Simply include the string that should appear as the target
7752 of the link (this will be a pathname relative to the
7753 directory in which the link resides) as the first argument
7758 For example, in your <prgn>Makefile</prgn> or
7759 <file>debian/rules</file>, you can do things like:
7760 <example compact="compact">
7761 ln -fs gcc $(prefix)/bin/cc
7762 ln -fs gcc debian/tmp/usr/bin/cc
7763 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7764 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7769 A symbolic link pointing to a compressed file should always
7770 have the same file extension as the referenced file. (For
7771 example, if a file <file>foo.gz</file> is referenced by a
7772 symbolic link, the filename of the link has to end with
7773 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7778 <heading>Device files</heading>
7781 Packages must not include device files or named pipes in the
7786 If a package needs any special device files that are not
7787 included in the base system, it must call
7788 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7789 after notifying the user<footnote>
7790 This notification could be done via a (low-priority)
7791 debconf message, or an echo (printf) statement.
7796 Packages must not remove any device files in the
7797 <prgn>postrm</prgn> or any other script. This is left to the
7798 system administrator.
7802 Debian uses the serial devices
7803 <file>/dev/ttyS*</file>. Programs using the old
7804 <file>/dev/cu*</file> devices should be changed to use
7805 <file>/dev/ttyS*</file>.
7809 Named pipes needed by the package must be created in
7810 the <prgn>postinst</prgn> script<footnote>
7811 It's better to use <prgn>mkfifo</prgn> rather
7812 than <prgn>mknod</prgn> to create named pipes so that
7813 automated checks for packages incorrectly creating device
7814 files with <prgn>mknod</prgn> won't have false positives.
7815 </footnote> and removed in
7816 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
7821 <sect id="config-files">
7822 <heading>Configuration files</heading>
7825 <heading>Definitions</heading>
7829 <tag>configuration file</tag>
7831 A file that affects the operation of a program, or
7832 provides site- or host-specific information, or
7833 otherwise customizes the behavior of a program.
7834 Typically, configuration files are intended to be
7835 modified by the system administrator (if needed or
7836 desired) to conform to local policy or to provide
7837 more useful site-specific behavior.
7840 <tag><tt>conffile</tt></tag>
7842 A file listed in a package's <tt>conffiles</tt>
7843 file, and is treated specially by <prgn>dpkg</prgn>
7844 (see <ref id="configdetails">).
7850 The distinction between these two is important; they are
7851 not interchangeable concepts. Almost all
7852 <tt>conffile</tt>s are configuration files, but many
7853 configuration files are not <tt>conffiles</tt>.
7857 As noted elsewhere, <file>/etc/init.d</file> scripts,
7858 <file>/etc/default</file> files, scripts installed in
7859 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7860 configuration installed in <file>/etc/cron.d</file> must be
7861 treated as configuration files. In general, any script that
7862 embeds configuration information is de-facto a configuration
7863 file and should be treated as such.
7868 <heading>Location</heading>
7871 Any configuration files created or used by your package
7872 must reside in <file>/etc</file>. If there are several,
7873 consider creating a subdirectory of <file>/etc</file>
7874 named after your package.
7878 If your package creates or uses configuration files
7879 outside of <file>/etc</file>, and it is not feasible to modify
7880 the package to use <file>/etc</file> directly, put the files
7881 in <file>/etc</file> and create symbolic links to those files
7882 from the location that the package requires.
7887 <heading>Behavior</heading>
7890 Configuration file handling must conform to the following
7892 <list compact="compact">
7894 local changes must be preserved during a package
7898 configuration files must be preserved when the
7899 package is removed, and only deleted when the
7903 Obsolete configuration files without local changes may be
7904 removed by the package during upgrade.
7908 The easy way to achieve this behavior is to make the
7909 configuration file a <tt>conffile</tt>. This is
7910 appropriate only if it is possible to distribute a default
7911 version that will work for most installations, although
7912 some system administrators may choose to modify it. This
7913 implies that the default version will be part of the
7914 package distribution, and must not be modified by the
7915 maintainer scripts during installation (or at any other
7920 In order to ensure that local changes are preserved
7921 correctly, no package may contain or make hard links to
7922 conffiles.<footnote>
7923 Rationale: There are two problems with hard links.
7924 The first is that some editors break the link while
7925 editing one of the files, so that the two files may
7926 unwittingly become unlinked and different. The second
7927 is that <prgn>dpkg</prgn> might break the hard link
7928 while upgrading <tt>conffile</tt>s.
7933 The other way to do it is via the maintainer scripts. In
7934 this case, the configuration file must not be listed as a
7935 <tt>conffile</tt> and must not be part of the package
7936 distribution. If the existence of a file is required for
7937 the package to be sensibly configured it is the
7938 responsibility of the package maintainer to provide
7939 maintainer scripts which correctly create, update and
7940 maintain the file and remove it on purge. (See <ref
7941 id="maintainerscripts"> for more information.) These
7942 scripts must be idempotent (i.e., must work correctly if
7943 <prgn>dpkg</prgn> needs to re-run them due to errors
7944 during installation or removal), must cope with all the
7945 variety of ways <prgn>dpkg</prgn> can call maintainer
7946 scripts, must not overwrite or otherwise mangle the user's
7947 configuration without asking, must not ask unnecessary
7948 questions (particularly during upgrades), and must
7949 otherwise be good citizens.
7953 The scripts are not required to configure every possible
7954 option for the package, but only those necessary to get
7955 the package running on a given system. Ideally the
7956 sysadmin should not have to do any configuration other
7957 than that done (semi-)automatically by the
7958 <prgn>postinst</prgn> script.
7962 A common practice is to create a script called
7963 <file><var>package</var>-configure</file> and have the
7964 package's <prgn>postinst</prgn> call it if and only if the
7965 configuration file does not already exist. In certain
7966 cases it is useful for there to be an example or template
7967 file which the maintainer scripts use. Such files should
7968 be in <file>/usr/share/<var>package</var></file> or
7969 <file>/usr/lib/<var>package</var></file> (depending on whether
7970 they are architecture-independent or not). There should
7971 be symbolic links to them from
7972 <file>/usr/share/doc/<var>package</var>/examples</file> if
7973 they are examples, and should be perfectly ordinary
7974 <prgn>dpkg</prgn>-handled files (<em>not</em>
7975 configuration files).
7979 These two styles of configuration file handling must
7980 not be mixed, for that way lies madness:
7981 <prgn>dpkg</prgn> will ask about overwriting the file
7982 every time the package is upgraded.
7987 <heading>Sharing configuration files</heading>
7990 Packages which specify the same file as a
7991 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7992 with each other. (This is an instance of the general rule
7993 about not sharing files. Note that neither alternatives
7994 nor diversions are likely to be appropriate in this case;
7995 in particular, <prgn>dpkg</prgn> does not handle diverted
7996 <tt>conffile</tt>s well.)
8000 The maintainer scripts must not alter a <tt>conffile</tt>
8001 of <em>any</em> package, including the one the scripts
8006 If two or more packages use the same configuration file
8007 and it is reasonable for both to be installed at the same
8008 time, one of these packages must be defined as
8009 <em>owner</em> of the configuration file, i.e., it will be
8010 the package which handles that file as a configuration
8011 file. Other packages that use the configuration file must
8012 depend on the owning package if they require the
8013 configuration file to operate. If the other package will
8014 use the configuration file if present, but is capable of
8015 operating without it, no dependency need be declared.
8019 If it is desirable for two or more related packages to
8020 share a configuration file <em>and</em> for all of the
8021 related packages to be able to modify that configuration
8022 file, then the following should be done:
8023 <enumlist compact="compact">
8025 One of the related packages (the "owning" package)
8026 will manage the configuration file with maintainer
8027 scripts as described in the previous section.
8030 The owning package should also provide a program
8031 that the other packages may use to modify the
8035 The related packages must use the provided program
8036 to make any desired modifications to the
8037 configuration file. They should either depend on
8038 the core package to guarantee that the configuration
8039 modifier program is available or accept gracefully
8040 that they cannot modify the configuration file if it
8041 is not. (This is in addition to the fact that the
8042 configuration file may not even be present in the
8049 Sometimes it's appropriate to create a new package which
8050 provides the basic infrastructure for the other packages
8051 and which manages the shared configuration files. (The
8052 <tt>sgml-base</tt> package is a good example.)
8057 <heading>User configuration files ("dotfiles")</heading>
8060 The files in <file>/etc/skel</file> will automatically be
8061 copied into new user accounts by <prgn>adduser</prgn>.
8062 No other program should reference the files in
8063 <file>/etc/skel</file>.
8067 Therefore, if a program needs a dotfile to exist in
8068 advance in <file>$HOME</file> to work sensibly, that dotfile
8069 should be installed in <file>/etc/skel</file> and treated as a
8074 However, programs that require dotfiles in order to
8075 operate sensibly are a bad thing, unless they do create
8076 the dotfiles themselves automatically.
8080 Furthermore, programs should be configured by the Debian
8081 default installation to behave as closely to the upstream
8082 default behavior as possible.
8086 Therefore, if a program in a Debian package needs to be
8087 configured in some way in order to operate sensibly, that
8088 should be done using a site-wide configuration file placed
8089 in <file>/etc</file>. Only if the program doesn't support a
8090 site-wide default configuration and the package maintainer
8091 doesn't have time to add it may a default per-user file be
8092 placed in <file>/etc/skel</file>.
8096 <file>/etc/skel</file> should be as empty as we can make it.
8097 This is particularly true because there is no easy (or
8098 necessarily desirable) mechanism for ensuring that the
8099 appropriate dotfiles are copied into the accounts of
8100 existing users when a package is installed.
8106 <heading>Log files</heading>
8108 Log files should usually be named
8109 <file>/var/log/<var>package</var>.log</file>. If you have many
8110 log files, or need a separate directory for permission
8111 reasons (<file>/var/log</file> is writable only by
8112 <file>root</file>), you should usually create a directory named
8113 <file>/var/log/<var>package</var></file> and place your log
8118 Log files must be rotated occasionally so that they don't grow
8119 indefinitely. The best way to do this is to install a log
8120 rotation configuration file in the
8121 directory <file>/etc/logrotate.d</file>, normally
8122 named <file>/etc/logrotate.d/<var>package</var></file>, and use
8123 the facilities provided by <prgn>logrotate</prgn>.
8126 The traditional approach to log files has been to set up
8127 <em>ad hoc</em> log rotation schemes using simple shell
8128 scripts and cron. While this approach is highly
8129 customizable, it requires quite a lot of sysadmin work.
8130 Even though the original Debian system helped a little
8131 by automatically installing a system which can be used
8132 as a template, this was deemed not enough.
8136 The use of <prgn>logrotate</prgn>, a program developed
8137 by Red Hat, is better, as it centralizes log management.
8138 It has both a configuration file
8139 (<file>/etc/logrotate.conf</file>) and a directory where
8140 packages can drop their individual log rotation
8141 configurations (<file>/etc/logrotate.d</file>).
8144 Here is a good example for a logrotate config
8145 file (for more information see <manref name="logrotate"
8147 <example compact="compact">
8148 /var/log/foo/*.log {
8154 start-stop-daemon -K -p /var/run/foo.pid -s HUP -x /usr/sbin/foo -q
8158 This rotates all files under <file>/var/log/foo</file>, saves 12
8159 compressed generations, and tells the daemon to reopen its log
8160 files after the log rotation. It skips this log rotation
8161 (via <tt>missingok</tt>) if no such log file is present, which
8162 avoids errors if the package is removed but not purged.
8166 Log files should be removed when the package is
8167 purged (but not when it is only removed). This should be
8168 done by the <prgn>postrm</prgn> script when it is called
8169 with the argument <tt>purge</tt> (see <ref
8170 id="removedetails">).
8174 <sect id="permissions-owners">
8175 <heading>Permissions and owners</heading>
8178 The rules in this section are guidelines for general use.
8179 If necessary you may deviate from the details below.
8180 However, if you do so you must make sure that what is done
8181 is secure and you should try to be as consistent as possible
8182 with the rest of the system. You should probably also
8183 discuss it on <prgn>debian-devel</prgn> first.
8187 Files should be owned by <tt>root:root</tt>, and made
8188 writable only by the owner and universally readable (and
8189 executable, if appropriate), that is mode 644 or 755.
8193 Directories should be mode 755 or (for group-writability)
8194 mode 2775. The ownership of the directory should be
8195 consistent with its mode: if a directory is mode 2775, it
8196 should be owned by the group that needs write access to
8199 When a package is upgraded, and the owner or permissions
8200 of a file included in the package has changed, dpkg
8201 arranges for the ownership and permissions to be
8202 correctly set upon installation. However, this does not
8203 extend to directories; the permissions and ownership of
8204 directories already on the system does not change on
8205 install or upgrade of packages. This makes sense, since
8206 otherwise common directories like <tt>/usr</tt> would
8207 always be in flux. To correctly change permissions of a
8208 directory the package owns, explicit action is required,
8209 usually in the <tt>postinst</tt> script. Care must be
8210 taken to handle downgrades as well, in that case.
8216 Control information files should be owned by <tt>root:root</tt>
8217 and either mode 644 (for most files) or mode 755 (for
8218 executables such as <qref id="maintscripts">maintainer
8223 Setuid and setgid executables should be mode 4755 or 2755
8224 respectively, and owned by the appropriate user or group.
8225 They should not be made unreadable (modes like 4711 or
8226 2711 or even 4111); doing so achieves no extra security,
8227 because anyone can find the binary in the freely available
8228 Debian package; it is merely inconvenient. For the same
8229 reason you should not restrict read or execute permissions
8230 on non-set-id executables.
8234 Some setuid programs need to be restricted to particular
8235 sets of users, using file permissions. In this case they
8236 should be owned by the uid to which they are set-id, and by
8237 the group which should be allowed to execute them. They
8238 should have mode 4754; again there is no point in making
8239 them unreadable to those users who must not be allowed to
8244 It is possible to arrange that the system administrator can
8245 reconfigure the package to correspond to their local
8246 security policy by changing the permissions on a binary:
8247 they can do this by using <prgn>dpkg-statoverride</prgn>, as
8248 described below.<footnote>
8249 Ordinary files installed by <prgn>dpkg</prgn> (as
8250 opposed to <tt>conffile</tt>s and other similar objects)
8251 normally have their permissions reset to the distributed
8252 permissions when the package is reinstalled. However,
8253 the use of <prgn>dpkg-statoverride</prgn> overrides this
8256 Another method you should consider is to create a group for
8257 people allowed to use the program(s) and make any setuid
8258 executables executable only by that group.
8262 If you need to create a new user or group for your package
8263 there are two possibilities. Firstly, you may need to
8264 make some files in the binary package be owned by this
8265 user or group, or you may need to compile the user or
8266 group id (rather than just the name) into the binary
8267 (though this latter should be avoided if possible, as in
8268 this case you need a statically allocated id).</p>
8271 If you need a statically allocated id, you must ask for a
8272 user or group id from the <tt>base-passwd</tt> maintainer,
8273 and must not release the package until you have been
8274 allocated one. Once you have been allocated one you must
8275 either make the package depend on a version of the
8276 <tt>base-passwd</tt> package with the id present in
8277 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
8278 your package to create the user or group itself with the
8279 correct id (using <tt>adduser</tt>) in its
8280 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
8281 the <prgn>postinst</prgn> is to be preferred if it is
8282 possible, otherwise a pre-dependency will be needed on the
8283 <tt>adduser</tt> package.)
8287 On the other hand, the program might be able to determine
8288 the uid or gid from the user or group name at runtime, so
8289 that a dynamically allocated id can be used. In this case
8290 you should choose an appropriate user or group name,
8291 discussing this on <prgn>debian-devel</prgn> and checking
8292 with the <package/base-passwd/ maintainer that it is unique and that
8293 they do not wish you to use a statically allocated id
8294 instead. When this has been checked you must arrange for
8295 your package to create the user or group if necessary using
8296 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
8297 <prgn>postinst</prgn> script (again, the latter is to be
8298 preferred if it is possible).
8302 Note that changing the numeric value of an id associated
8303 with a name is very difficult, and involves searching the
8304 file system for all appropriate files. You need to think
8305 carefully whether a static or dynamic id is required, since
8306 changing your mind later will cause problems.
8309 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
8311 This section is not intended as policy, but as a
8312 description of the use of <prgn>dpkg-statoverride</prgn>.
8316 If a system administrator wishes to have a file (or
8317 directory or other such thing) installed with owner and
8318 permissions different from those in the distributed Debian
8319 package, they can use the <prgn>dpkg-statoverride</prgn>
8320 program to instruct <prgn>dpkg</prgn> to use the different
8321 settings every time the file is installed. Thus the
8322 package maintainer should distribute the files with their
8323 normal permissions, and leave it for the system
8324 administrator to make any desired changes. For example, a
8325 daemon which is normally required to be setuid root, but
8326 in certain situations could be used without being setuid,
8327 should be installed setuid in the <tt>.deb</tt>. Then the
8328 local system administrator can change this if they wish.
8329 If there are two standard ways of doing it, the package
8330 maintainer can use <tt>debconf</tt> to find out the
8331 preference, and call <prgn>dpkg-statoverride</prgn> in the
8332 maintainer script if necessary to accommodate the system
8333 administrator's choice. Care must be taken during
8334 upgrades to not override an existing setting.
8338 Given the above, <prgn>dpkg-statoverride</prgn> is
8339 essentially a tool for system administrators and would not
8340 normally be needed in the maintainer scripts. There is
8341 one type of situation, though, where calls to
8342 <prgn>dpkg-statoverride</prgn> would be needed in the
8343 maintainer scripts, and that involves packages which use
8344 dynamically allocated user or group ids. In such a
8345 situation, something like the following idiom can be very
8346 helpful in the package's <prgn>postinst</prgn>, where
8347 <tt>sysuser</tt> is a dynamically allocated id:
8349 for i in /usr/bin/foo /usr/sbin/bar
8351 # only do something when no setting exists
8352 if ! dpkg-statoverride --list $i >/dev/null 2>&1
8354 #include: debconf processing, question about foo and bar
8355 if [ "$RET" = "true" ] ; then
8356 dpkg-statoverride --update --add sysuser root 4755 $i
8361 The corresponding code to remove the override when the package
8364 for i in /usr/bin/foo /usr/sbin/bar
8366 if dpkg-statoverride --list $i >/dev/null 2>&1
8368 dpkg-statoverride --remove $i
8378 <chapt id="customized-programs">
8379 <heading>Customized programs</heading>
8381 <sect id="arch-spec">
8382 <heading>Architecture specification strings</heading>
8385 If a program needs to specify an <em>architecture specification
8386 string</em> in some place, it should select one of the strings
8387 provided by <tt>dpkg-architecture -L</tt>. The strings are in
8388 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
8389 part is sometimes elided, as when the OS is Linux.
8393 Note that we don't want to use
8394 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
8395 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
8396 since this would make our programs incompatible with other
8397 Linux distributions. We also don't use something like
8398 <tt><var>arch</var>-unknown-linux</tt>, since the
8399 <tt>unknown</tt> does not look very good.
8402 <sect1 id="arch-wildcard-spec">
8403 <heading>Architecture wildcards</heading>
8406 A package may specify an architecture wildcard. Architecture
8407 wildcards are in the format <tt>any</tt> (which matches every
8408 architecture), <tt><var>os</var></tt>-any, or
8409 any-<tt><var>cpu</var></tt>. <footnote>
8410 Internally, the package system normalizes the GNU triplets
8411 and the Debian arches into Debian arch triplets (which are
8412 kind of inverted GNU triplets), with the first component of
8413 the triplet representing the libc and ABI in use, and then
8414 does matching against those triplets. However, such
8415 triplets are an internal implementation detail that should
8416 not be used by packages directly. The libc and ABI portion
8417 is handled internally by the package system based on
8418 the <var>os</var> and <var>cpu</var>.
8425 <heading>Daemons</heading>
8428 The configuration files <file>/etc/services</file>,
8429 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
8430 by the <prgn>netbase</prgn> package and must not be modified
8435 If a package requires a new entry in one of these files, the
8436 maintainer should get in contact with the
8437 <prgn>netbase</prgn> maintainer, who will add the entries
8438 and release a new version of the <prgn>netbase</prgn>
8443 The configuration file <file>/etc/inetd.conf</file> must not be
8444 modified by the package's scripts except via the
8445 <prgn>update-inetd</prgn> script or the
8446 <file>DebianNet.pm</file> Perl module. See their documentation
8447 for details on how to add entries.
8451 If a package wants to install an example entry into
8452 <file>/etc/inetd.conf</file>, the entry must be preceded with
8453 exactly one hash character (<tt>#</tt>). Such lines are
8454 treated as "commented out by user" by the
8455 <prgn>update-inetd</prgn> script and are not changed or
8456 activated during package updates.
8461 <heading>Using pseudo-ttys and modifying wtmp, utmp and
8465 Some programs need to create pseudo-ttys. This should be done
8466 using Unix98 ptys if the C library supports it. The resulting
8467 program must not be installed setuid root, unless that
8468 is required for other functionality.
8472 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
8473 <file>/var/log/lastlog</file> must be installed writable by
8474 group <tt>utmp</tt>. Programs which need to modify those
8475 files must be installed setgid <tt>utmp</tt>.
8480 <heading>Editors and pagers</heading>
8483 Some programs have the ability to launch an editor or pager
8484 program to edit or display a text document. Since there are
8485 lots of different editors and pagers available in the Debian
8486 distribution, the system administrator and each user should
8487 have the possibility to choose their preferred editor and
8492 In addition, every program should choose a good default
8493 editor/pager if none is selected by the user or system
8498 Thus, every program that launches an editor or pager must
8499 use the EDITOR or PAGER environment variable to determine
8500 the editor or pager the user wishes to use. If these
8501 variables are not set, the programs <file>/usr/bin/editor</file>
8502 and <file>/usr/bin/pager</file> should be used, respectively.
8506 These two files are managed through the <prgn>dpkg</prgn>
8507 "alternatives" mechanism. Every package providing an editor or
8508 pager must call the <prgn>update-alternatives</prgn> script to
8509 register as an alternative for <file>/usr/bin/editor</file>
8510 or <file>/usr/bin/pager</file> as appropriate. The alternative
8511 should have a slave alternative
8512 for <file>/usr/share/man/man1/editor.1.gz</file>
8513 or <file>/usr/share/man/man1/pager.1.gz</file> pointing to the
8514 corresponding manual page.
8518 If it is very hard to adapt a program to make use of the
8519 EDITOR or PAGER variables, that program may be configured to
8520 use <file>/usr/bin/sensible-editor</file> and
8521 <file>/usr/bin/sensible-pager</file> as the editor or pager
8522 program respectively. These are two scripts provided in the
8523 <package>sensible-utils</package> package that check the EDITOR
8524 and PAGER variables and launch the appropriate program, and fall
8525 back to <file>/usr/bin/editor</file>
8526 and <file>/usr/bin/pager</file> if the variable is not set.
8530 A program may also use the VISUAL environment variable to
8531 determine the user's choice of editor. If it exists, it
8532 should take precedence over EDITOR. This is in fact what
8533 <file>/usr/bin/sensible-editor</file> does.
8537 It is not required for a package to depend on
8538 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
8539 package to provide such virtual packages.<footnote>
8540 The Debian base system already provides an editor and a
8546 <sect id="web-appl">
8547 <heading>Web servers and applications</heading>
8550 This section describes the locations and URLs that should
8551 be used by all web servers and web applications in the
8558 Cgi-bin executable files are installed in the
8560 <example compact="compact">
8561 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
8563 or a subdirectory of that directory, and should be
8565 <example compact="compact">
8566 http://localhost/cgi-bin/<var>cgi-bin-name</var>
8568 (possibly with a subdirectory name
8569 before <var>cgi-bin-name</var>).
8573 <p>Access to HTML documents</p>
8576 HTML documents for a package are stored in
8577 <file>/usr/share/doc/<var>package</var></file>
8578 and can be referred to as
8579 <example compact="compact">
8580 http://localhost/doc/<var>package</var>/<var>filename</var>
8585 The web server should restrict access to the document
8586 tree so that only clients on the same host can read
8587 the documents. If the web server does not support such
8588 access controls, then it should not provide access at
8589 all, or ask about providing access during installation.
8594 <p>Access to images</p>
8596 It is recommended that images for a package be stored
8597 in <tt>/usr/share/images/<var>package</var></tt> and
8598 may be referred to through an alias <tt>/images/</tt>
8601 http://localhost/images/<package>/<filename>
8608 <p>Web Document Root</p>
8611 Web Applications should try to avoid storing files in
8612 the Web Document Root. Instead they should use the
8613 /usr/share/doc/<var>package</var> directory for
8614 documents and register the Web Application via the
8615 <package>doc-base</package> package. If access to the
8616 web document root is unavoidable then use
8617 <example compact="compact">
8620 as the Document Root. This might be just a symbolic
8621 link to the location where the system administrator
8622 has put the real document root.
8625 <item><p>Providing httpd and/or httpd-cgi</p>
8627 All web servers should provide the virtual package
8628 <tt>httpd</tt>. If a web server has CGI support it should
8629 provide <tt>httpd-cgi</tt> additionally.
8632 All web applications which do not contain CGI scripts should
8633 depend on <tt>httpd</tt>, all those web applications which
8634 <tt>do</tt> contain CGI scripts, should depend on
8642 <sect id="mail-transport-agents">
8643 <heading>Mail transport, delivery and user agents</heading>
8646 Debian packages which process electronic mail, whether mail
8647 user agents (MUAs) or mail transport agents (MTAs), must
8648 ensure that they are compatible with the configuration
8649 decisions below. Failure to do this may result in lost
8650 mail, broken <tt>From:</tt> lines, and other serious brain
8655 The mail spool is <file>/var/mail</file> and the interface to
8656 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8657 the FHS). On older systems, the mail spool may be
8658 physically located in <file>/var/spool/mail</file>, but all
8659 access to the mail spool should be via the
8660 <file>/var/mail</file> symlink. The mail spool is part of the
8661 base system and not part of the MTA package.
8665 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8666 programs (such as IMAP daemons) must lock the mailbox in an
8667 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8668 be combined with dot locking. To avoid deadlocks, a program
8669 should use <tt>fcntl()</tt> first and dot locking after
8670 this, or alternatively implement the two locking methods in
8671 a non blocking way<footnote>
8672 If it is not possible to establish both locks, the
8673 system shouldn't wait for the second lock to be
8674 established, but remove the first lock, wait a (random)
8675 time, and start over locking again.
8676 </footnote>. Using the functions <tt>maillock</tt> and
8677 <tt>mailunlock</tt> provided by the
8678 <tt>liblockfile*</tt><footnote>
8679 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8680 to use these functions.
8681 </footnote> packages is the recommended way to realize this.
8685 Mailboxes are generally either mode 600 and owned by
8686 <var>user</var> or mode 660 and owned by
8687 <tt><var>user</var>:mail</tt><footnote>
8688 There are two traditional permission schemes for mail spools:
8689 mode 600 with all mail delivery done by processes running as
8690 the destination user, or mode 660 and owned by group mail with
8691 mail delivery done by a process running as a system user in
8692 group mail. Historically, Debian required mode 660 mail
8693 spools to enable the latter model, but that model has become
8694 increasingly uncommon and the principle of least privilege
8695 indicates that mail systems that use the first model should
8696 use permissions of 600. If delivery to programs is permitted,
8697 it's easier to keep the mail system secure if the delivery
8698 agent runs as the destination user. Debian Policy therefore
8699 permits either scheme.
8700 </footnote>. The local system administrator may choose a
8701 different permission scheme; packages should not make
8702 assumptions about the permission and ownership of mailboxes
8703 unless required (such as when creating a new mailbox). A MUA
8704 may remove a mailbox (unless it has nonstandard permissions) in
8705 which case the MTA or another MUA must recreate it if needed.
8709 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8710 be setgid mail to do the locking mentioned above (and
8711 must obviously avoid accessing other users' mailboxes
8712 using this privilege).</p>
8715 <file>/etc/aliases</file> is the source file for the system mail
8716 aliases (e.g., postmaster, usenet, etc.), it is the one
8717 which the sysadmin and <prgn>postinst</prgn> scripts may
8718 edit. After <file>/etc/aliases</file> is edited the program or
8719 human editing it must call <prgn>newaliases</prgn>. All MTA
8720 packages must come with a <prgn>newaliases</prgn> program,
8721 even if it does nothing, but older MTA packages did not do
8722 this so programs should not fail if <prgn>newaliases</prgn>
8723 cannot be found. Note that because of this, all MTA
8724 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8725 <tt>Replaces: mail-transport-agent</tt> control fields.
8729 The convention of writing <tt>forward to
8730 <var>address</var></tt> in the mailbox itself is not
8731 supported. Use a <tt>.forward</tt> file instead.</p>
8734 The <prgn>rmail</prgn> program used by UUCP
8735 for incoming mail should be <file>/usr/sbin/rmail</file>.
8736 Likewise, <prgn>rsmtp</prgn>, for receiving
8737 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8741 If your package needs to know what hostname to use on (for
8742 example) outgoing news and mail messages which are generated
8743 locally, you should use the file <file>/etc/mailname</file>. It
8744 will contain the portion after the username and <tt>@</tt>
8745 (at) sign for email addresses of users on the machine
8746 (followed by a newline).
8750 Such a package should check for the existence of this file
8751 when it is being configured. If it exists, it should be
8752 used without comment, although an MTA's configuration script
8753 may wish to prompt the user even if it finds that this file
8754 exists. If the file does not exist, the package should
8755 prompt the user for the value (preferably using
8756 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8757 as well as using it in the package's configuration. The
8758 prompt should make it clear that the name will not just be
8759 used by that package. For example, in this situation the
8760 <tt>inn</tt> package could say something like:
8761 <example compact="compact">
8762 Please enter the "mail name" of your system. This is the
8763 hostname portion of the address to be shown on outgoing
8764 news and mail messages. The default is
8765 <var>syshostname</var>, your system's host name. Mail
8766 name ["<var>syshostname</var>"]:
8768 where <var>syshostname</var> is the output of <tt>hostname
8774 <heading>News system configuration</heading>
8777 All the configuration files related to the NNTP (news)
8778 servers and clients should be located under
8779 <file>/etc/news</file>.</p>
8782 There are some configuration issues that apply to a number
8783 of news clients and server packages on the machine. These
8787 <tag><file>/etc/news/organization</file></tag>
8789 A string which should appear as the
8790 organization header for all messages posted
8791 by NNTP clients on the machine
8794 <tag><file>/etc/news/server</file></tag>
8796 Contains the FQDN of the upstream NNTP
8797 server, or localhost if the local machine is
8802 Other global files may be added as required for cross-package news
8809 <heading>Programs for the X Window System</heading>
8812 <heading>Providing X support and package priorities</heading>
8815 Programs that can be configured with support for the X
8816 Window System must be configured to do so and must declare
8817 any package dependencies necessary to satisfy their
8818 runtime requirements when using the X Window System. If
8819 such a package is of higher priority than the X packages
8820 on which it depends, it is required that either the
8821 X-specific components be split into a separate package, or
8822 that an alternative version of the package, which includes
8823 X support, be provided, or that the package's priority be
8829 <heading>Packages providing an X server</heading>
8832 Packages that provide an X server that, directly or
8833 indirectly, communicates with real input and display
8834 hardware should declare in their <tt>Provides</tt> control
8835 field that they provide the virtual
8836 package <tt>xserver</tt>.<footnote>
8837 This implements current practice, and provides an
8838 actual policy for usage of the <tt>xserver</tt>
8839 virtual package which appears in the virtual packages
8840 list. In a nutshell, X servers that interface
8841 directly with the display and input hardware or via
8842 another subsystem (e.g., GGI) should provide
8843 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8844 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8850 <heading>Packages providing a terminal emulator</heading>
8853 Packages that provide a terminal emulator for the X Window
8854 System which meet the criteria listed below should declare in
8855 their <tt>Provides</tt> control field that they provide the
8856 virtual package <tt>x-terminal-emulator</tt>. They should
8857 also register themselves as an alternative for
8858 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8859 20. That alternative should have a slave alternative
8860 for <file>/usr/share/man/man1/x-terminal-emulator.1.gz</file>
8861 pointing to the corresponding manual page.
8865 To be an <tt>x-terminal-emulator</tt>, a program must:
8866 <list compact="compact">
8868 Be able to emulate a DEC VT100 terminal, or a
8869 compatible terminal.
8873 Support the command-line option <tt>-e
8874 <var>command</var></tt>, which creates a new
8875 terminal window<footnote>
8876 "New terminal window" does not necessarily mean
8877 a new top-level X window directly parented by
8878 the window manager; it could, if the terminal
8879 emulator application were so coded, be a new
8880 "view" in a multiple-document interface (MDI).
8882 and runs the specified <var>command</var>,
8883 interpreting the entirety of the rest of the command
8884 line as a command to pass straight to exec, in the
8885 manner that <tt>xterm</tt> does.
8889 Support the command-line option <tt>-T
8890 <var>title</var></tt>, which creates a new terminal
8891 window with the window title <var>title</var>.
8898 <heading>Packages providing a window manager</heading>
8901 Packages that provide a window manager should declare in
8902 their <tt>Provides</tt> control field that they provide the
8903 virtual package <tt>x-window-manager</tt>. They should also
8904 register themselves as an alternative for
8905 <file>/usr/bin/x-window-manager</file>, with a priority
8906 calculated as follows:
8907 <list compact="compact">
8909 Start with a priority of 20.
8913 If the window manager supports the Debian menu
8914 system, add 20 points if this support is available
8915 in the package's default configuration (i.e., no
8916 configuration files belonging to the system or user
8917 have to be edited to activate the feature); if
8918 configuration files must be modified, add only 10
8924 If the window manager complies with <url
8925 id="http://www.freedesktop.org/Standards/wm-spec"
8926 name="The Window Manager Specification Project">,
8927 written by the <url id="http://www.freedesktop.org/"
8928 name="Free Desktop Group">, add 40 points.
8932 If the window manager permits the X session to be
8933 restarted using a <em>different</em> window manager
8934 (without killing the X server) in its default
8935 configuration, add 10 points; otherwise add none.
8938 That alternative should have a slave alternative
8939 for <file>/usr/share/man/man1/x-window-manager.1.gz</file>
8940 pointing to the corresponding manual page.
8945 <heading>Packages providing fonts</heading>
8948 Packages that provide fonts for the X Window
8950 For the purposes of Debian Policy, a "font for the X
8951 Window System" is one which is accessed via X protocol
8952 requests. Fonts for the Linux console, for PostScript
8953 renderer, or any other purpose, do not fit this
8954 definition. Any tool which makes such fonts available
8955 to the X Window System, however, must abide by this
8958 must do a number of things to ensure that they are both
8959 available without modification of the X or font server
8960 configuration, and that they do not corrupt files used by
8961 other font packages to register information about
8965 Fonts of any type supported by the X Window System
8966 must be in a separate binary package from any
8967 executables, libraries, or documentation (except
8968 that specific to the fonts shipped, such as their
8969 license information). If one or more of the fonts
8970 so packaged are necessary for proper operation of
8971 the package with which they are associated the font
8972 package may be Recommended; if the fonts merely
8973 provide an enhancement, a Suggests relationship may
8974 be used. Packages must not Depend on font
8976 This is because the X server may retrieve fonts
8977 from the local file system or over the network
8978 from an X font server; the Debian package system
8979 is empowered to deal only with the local
8985 BDF fonts must be converted to PCF fonts with the
8986 <prgn>bdftopcf</prgn> utility (available in the
8987 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8988 placed in a directory that corresponds to their
8990 <list compact="compact">
8992 100 dpi fonts must be placed in
8993 <file>/usr/share/fonts/X11/100dpi/</file>.
8997 75 dpi fonts must be placed in
8998 <file>/usr/share/fonts/X11/75dpi/</file>.
9002 Character-cell fonts, cursor fonts, and other
9003 low-resolution fonts must be placed in
9004 <file>/usr/share/fonts/X11/misc/</file>.
9010 Type 1 fonts must be placed in
9011 <file>/usr/share/fonts/X11/Type1/</file>. If font
9012 metric files are available, they must be placed here
9017 Subdirectories of <file>/usr/share/fonts/X11/</file>
9018 other than those listed above must be neither
9019 created nor used. (The <file>PEX</file>, <file>CID</file>,
9020 <file>Speedo</file>, and <file>cyrillic</file> directories
9021 are excepted for historical reasons, but installation of
9022 files into these directories remains discouraged.)
9026 Font packages may, instead of placing files directly
9027 in the X font directories listed above, provide
9028 symbolic links in that font directory pointing to
9029 the files' actual location in the filesystem. Such
9030 a location must comply with the FHS.
9034 Font packages should not contain both 75dpi and
9035 100dpi versions of a font. If both are available,
9036 they should be provided in separate binary packages
9037 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
9038 the names of the packages containing the
9039 corresponding fonts.
9043 Fonts destined for the <file>misc</file> subdirectory
9044 should not be included in the same package as 75dpi
9045 or 100dpi fonts; instead, they should be provided in
9046 a separate package with <tt>-misc</tt> appended to
9051 Font packages must not provide the files
9052 <file>fonts.dir</file>, <file>fonts.alias</file>, or
9053 <file>fonts.scale</file> in a font directory:
9056 <file>fonts.dir</file> files must not be provided at all.
9060 <file>fonts.alias</file> and <file>fonts.scale</file>
9061 files, if needed, should be provided in the
9063 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
9064 where <var>fontdir</var> is the name of the
9066 <file>/usr/share/fonts/X11/</file> where the
9067 package's corresponding fonts are stored
9068 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
9069 <var>package</var> is the name of the package
9070 that provides these fonts, and
9071 <var>extension</var> is either <tt>scale</tt>
9072 or <tt>alias</tt>, whichever corresponds to
9079 Font packages must declare a dependency on
9080 <tt>xfonts-utils</tt> in their <tt>Depends</tt>
9081 or <tt>Pre-Depends</tt> control field.
9085 Font packages that provide one or more
9086 <file>fonts.scale</file> files as described above must
9087 invoke <prgn>update-fonts-scale</prgn> on each
9088 directory into which they installed fonts
9089 <em>before</em> invoking
9090 <prgn>update-fonts-dir</prgn> on that directory.
9091 This invocation must occur in both the
9092 <prgn>postinst</prgn> (for all arguments) and
9093 <prgn>postrm</prgn> (for all arguments except
9094 <tt>upgrade</tt>) scripts.
9098 Font packages that provide one or more
9099 <file>fonts.alias</file> files as described above must
9100 invoke <prgn>update-fonts-alias</prgn> on each
9101 directory into which they installed fonts. This
9102 invocation must occur in both the
9103 <prgn>postinst</prgn> (for all arguments) and
9104 <prgn>postrm</prgn> (for all arguments except
9105 <tt>upgrade</tt>) scripts.
9109 Font packages must invoke
9110 <prgn>update-fonts-dir</prgn> on each directory into
9111 which they installed fonts. This invocation must
9112 occur in both the <prgn>postinst</prgn> (for all
9113 arguments) and <prgn>postrm</prgn> (for all
9114 arguments except <tt>upgrade</tt>) scripts.
9118 Font packages must not provide alias names for the
9119 fonts they include which collide with alias names
9120 already in use by fonts already packaged.
9124 Font packages must not provide fonts with the same
9125 XLFD registry name as another font already packaged.
9131 <sect1 id="appdefaults">
9132 <heading>Application defaults files</heading>
9135 Application defaults files must be installed in the
9136 directory <file>/etc/X11/app-defaults/</file> (use of a
9137 localized subdirectory of <file>/etc/X11/</file> as described
9138 in the <em>X Toolkit Intrinsics - C Language
9139 Interface</em> manual is also permitted). They must be
9140 registered as <tt>conffile</tt>s or handled as
9141 configuration files.
9145 Customization of programs' X resources may also be
9146 supported with the provision of a file with the same name
9147 as that of the package placed in
9148 the <file>/etc/X11/Xresources/</file> directory, which
9149 must be registered as a <tt>conffile</tt> or handled as a
9150 configuration file.<footnote>
9151 Note that this mechanism is not the same as using
9152 app-defaults; app-defaults are tied to the client
9153 binary on the local file system, whereas X resources
9154 are stored in the X server and affect all connecting
9161 <heading>Installation directory issues</heading>
9164 Historically, packages using the X Window System used a
9165 separate set of installation directories from other packages.
9166 This practice has been discontinued and packages using the X
9167 Window System should now generally be installed in the same
9168 directories as any other package. Specifically, packages must
9169 not install files under the <file>/usr/X11R6/</file> directory
9170 and the <file>/usr/X11R6/</file> directory hierarchy should be
9171 regarded as obsolete.
9175 Include files previously installed under
9176 <file>/usr/X11R6/include/X11/</file> should be installed into
9177 <file>/usr/include/X11/</file>. For files previously
9178 installed into subdirectories of
9179 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
9180 determine if subdirectories of <file>/usr/lib/</file> and
9181 <file>/usr/share/</file> can be used. If not, a subdirectory
9182 of <file>/usr/lib/X11/</file> should be used.
9186 Configuration files for window, display, or session managers
9187 or other applications that are tightly integrated with the X
9188 Window System may be placed in a subdirectory
9189 of <file>/etc/X11/</file> corresponding to the package name.
9190 Other X Window System applications should use
9191 the <file>/etc/</file> directory unless otherwise mandated by
9192 policy (such as for <ref id="appdefaults">).
9197 <heading>The OSF/Motif and OpenMotif libraries</heading>
9200 <em>Programs that require the non-DFSG-compliant OSF/Motif or
9201 OpenMotif libraries</em><footnote>
9202 OSF/Motif and OpenMotif are collectively referred to as
9203 "Motif" in this policy document.
9205 should be compiled against and tested with LessTif (a free
9206 re-implementation of Motif) instead. If the maintainer
9207 judges that the program or programs do not work
9208 sufficiently well with LessTif to be distributed and
9209 supported, but do so when compiled against Motif, then two
9210 versions of the package should be created; one linked
9211 statically against Motif and with <tt>-smotif</tt>
9212 appended to the package name, and one linked dynamically
9213 against Motif and with <tt>-dmotif</tt> appended to the
9218 Both Motif-linked versions are dependent
9219 upon non-DFSG-compliant software and thus cannot be
9220 uploaded to the <em>main</em> distribution; if the
9221 software is itself DFSG-compliant it may be uploaded to
9222 the <em>contrib</em> distribution. While known existing
9223 versions of Motif permit unlimited redistribution of
9224 binaries linked against the library (whether statically or
9225 dynamically), it is the package maintainer's
9226 responsibility to determine whether this is permitted by
9227 the license of the copy of Motif in their possession.
9233 <heading>Perl programs and modules</heading>
9236 Perl programs and modules should follow the current Perl policy.
9240 The Perl policy can be found in the <tt>perl-policy</tt>
9241 files in the <tt>debian-policy</tt> package.
9242 It is also available from the Debian web mirrors at
9243 <tt><url name="/doc/packaging-manuals/perl-policy/"
9244 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
9249 <heading>Emacs lisp programs</heading>
9252 Please refer to the "Debian Emacs Policy" for details of how to
9253 package emacs lisp programs.
9257 The Emacs policy is available in
9258 <file>debian-emacs-policy.gz</file> of the
9259 <package>emacsen-common</package> package.
9260 It is also available from the Debian web mirrors at
9261 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
9262 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
9267 <heading>Games</heading>
9270 The permissions on <file>/var/games</file> are mode 755, owner
9271 <tt>root</tt> and group <tt>root</tt>.
9275 Each game decides on its own security policy.</p>
9278 Games which require protected, privileged access to
9279 high-score files, saved games, etc., may be made
9280 set-<em>group</em>-id (mode 2755) and owned by
9281 <tt>root:games</tt>, and use files and directories with
9282 appropriate permissions (770 <tt>root:games</tt>, for
9283 example). They must not be made
9284 set-<em>user</em>-id, as this causes security problems. (If
9285 an attacker can subvert any set-user-id game they can
9286 overwrite the executable of any other, causing other players
9287 of these games to run a Trojan horse program. With a
9288 set-group-id game the attacker only gets access to less
9289 important game data, and if they can get at the other
9290 players' accounts at all it will take considerably more
9294 Some packages, for example some fortune cookie programs, are
9295 configured by the upstream authors to install with their
9296 data files or other static information made unreadable so
9297 that they can only be accessed through set-id programs
9298 provided. You should not do this in a Debian package: anyone can
9299 download the <file>.deb</file> file and read the data from it,
9300 so there is no point making the files unreadable. Not
9301 making the files unreadable also means that you don't have
9302 to make so many programs set-id, which reduces the risk of a
9306 As described in the FHS, binaries of games should be
9307 installed in the directory <file>/usr/games</file>. This also
9308 applies to games that use the X Window System. Manual pages
9309 for games (X and non-X games) should be installed in
9310 <file>/usr/share/man/man6</file>.</p>
9316 <heading>Documentation</heading>
9319 <heading>Manual pages</heading>
9322 You should install manual pages in <prgn>nroff</prgn> source
9323 form, in appropriate places under <file>/usr/share/man</file>.
9324 You should only use sections 1 to 9 (see the FHS for more
9325 details). You must not install a pre-formatted "cat page".
9329 Each program, utility, and function should have an
9330 associated manual page included in the same package. It is
9331 suggested that all configuration files also have a manual
9332 page included as well. Manual pages for protocols and other
9333 auxiliary things are optional.
9337 If no manual page is available, this is considered as a bug
9338 and should be reported to the Debian Bug Tracking System (the
9339 maintainer of the package is allowed to write this bug report
9340 themselves, if they so desire). Do not close the bug report
9341 until a proper man page is available.<footnote>
9342 It is not very hard to write a man page. See the
9343 <url id="http://www.schweikhardt.net/man_page_howto.html"
9344 name="Man-Page-HOWTO">,
9345 <manref name="man" section="7">, the examples
9346 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
9347 the helper program <prgn>help2man</prgn>, or the
9348 directory <file>/usr/share/doc/man-db/examples</file>.
9353 You may forward a complaint about a missing man page to the
9354 upstream authors, and mark the bug as forwarded in the
9355 Debian bug tracking system. Even though the GNU Project do
9356 not in general consider the lack of a man page to be a bug,
9357 we do; if they tell you that they don't consider it a bug
9358 you should leave the bug in our bug tracking system open
9363 Manual pages should be installed compressed using <tt>gzip -9</tt>.
9367 If one man page needs to be accessible via several names it
9368 is better to use a symbolic link than the <file>.so</file>
9369 feature, but there is no need to fiddle with the relevant
9370 parts of the upstream source to change from <file>.so</file> to
9371 symlinks: don't do it unless it's easy. You should not
9372 create hard links in the manual page directories, nor put
9373 absolute filenames in <file>.so</file> directives. The filename
9374 in a <file>.so</file> in a man page should be relative to the
9375 base of the man page tree (usually
9376 <file>/usr/share/man</file>). If you do not create any links
9377 (whether symlinks, hard links, or <tt>.so</tt> directives)
9378 in the file system to the alternate names of the man page,
9379 then you should not rely on <prgn>man</prgn> finding your
9380 man page under those names based solely on the information in
9381 the man page's header.<footnote>
9382 Supporting this in <prgn>man</prgn> often requires
9383 unreasonable processing time to find a manual page or to
9384 report that none exists, and moves knowledge into man's
9385 database that would be better left in the file system.
9386 This support is therefore deprecated and will cease to
9387 be present in the future.
9392 Manual pages in locale-specific subdirectories of
9393 <file>/usr/share/man</file> should use either UTF-8 or the usual
9394 legacy encoding for that language (normally the one corresponding
9395 to the shortest relevant locale name in
9396 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
9397 <file>/usr/share/man/fr</file> should use either UTF-8 or
9398 ISO-8859-1.<footnote>
9399 <prgn>man</prgn> will automatically detect whether UTF-8 is in
9400 use. In future, all manual pages will be required to use
9406 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
9407 included in the subdirectory name unless it indicates a
9408 significant difference in the language, as this excludes
9409 speakers of the language in other countries.<footnote>
9410 At the time of writing, Chinese and Portuguese are the main
9411 languages with such differences, so <file>pt_BR</file>,
9412 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
9417 If a localized version of a manual page is provided, it should
9418 either be up-to-date or it should be obvious to the reader that
9419 it is outdated and the original manual page should be used
9420 instead. This can be done either by a note at the beginning of
9421 the manual page or by showing the missing or changed portions in
9422 the original language instead of the target language.
9427 <heading>Info documents</heading>
9430 Info documents should be installed in <file>/usr/share/info</file>.
9431 They should be compressed with <tt>gzip -9</tt>.
9435 The <prgn>install-info</prgn> program maintains a directory of
9436 installed info documents in <file>/usr/share/info/dir</file> for
9437 the use of info readers.<footnote>
9438 It was previously necessary for packages installing info
9439 documents to run <prgn>install-info</prgn> from maintainer
9440 scripts. This is no longer necessary. The installation
9441 system now uses dpkg triggers.
9443 This file must not be included in packages. Packages containing
9444 info documents should depend on <tt>dpkg (>= 1.15.4) |
9445 install-info</tt> to ensure that the directory file is properly
9446 rebuilt during partial upgrades from Debian 5.0 (lenny) and
9451 Info documents should contain section and directory entry
9452 information in the document for the use
9453 of <prgn>install-info</prgn>. The section should be specified
9454 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
9455 space and the section of this info page. The directory entry or
9456 entries should be included between
9457 a <tt>START-INFO-DIR-ENTRY</tt> line and
9458 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
9460 INFO-DIR-SECTION Individual utilities
9461 START-INFO-DIR-ENTRY
9462 * example: (example). An example info directory entry.
9465 To determine which section to use, you should look
9466 at <file>/usr/share/info/dir</file> on your system and choose
9467 the most relevant (or create a new section if none of the
9468 current sections are relevant).<footnote>
9469 Normally, info documents are generated from Texinfo source.
9470 To include this information in the generated info document, if
9471 it is absent, add commands like:
9473 @dircategory Individual utilities
9475 * example: (example). An example info directory entry.
9478 to the Texinfo source of the document and ensure that the info
9479 documents are rebuilt from source during the package build.
9485 <heading>Additional documentation</heading>
9488 Any additional documentation that comes with the package may
9489 be installed at the discretion of the package maintainer.
9490 Plain text documentation should be installed in the directory
9491 <file>/usr/share/doc/<var>package</var></file>, where
9492 <var>package</var> is the name of the package, and
9493 compressed with <tt>gzip -9</tt> unless it is small.
9497 If a package comes with large amounts of documentation which
9498 many users of the package will not require you should create
9499 a separate binary package to contain it, so that it does not
9500 take up disk space on the machines of users who do not need
9501 or want it installed.</p>
9504 It is often a good idea to put text information files
9505 (<file>README</file>s, changelogs, and so forth) that come with
9506 the source package in <file>/usr/share/doc/<var>package</var></file>
9507 in the binary package. However, you don't need to install
9508 the instructions for building and installing the package, of
9512 Packages must not require the existence of any files in
9513 <file>/usr/share/doc/</file> in order to function
9515 The system administrator should be able to
9516 delete files in <file>/usr/share/doc/</file> without causing
9517 any programs to break.
9519 Any files that are referenced by programs but are also
9520 useful as stand alone documentation should be installed under
9521 <file>/usr/share/<var>package</var>/</file> with symbolic links from
9522 <file>/usr/share/doc/<var>package</var></file>.
9526 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9527 link to another directory in <file>/usr/share/doc</file> only if
9528 the two packages both come from the same source and the
9529 first package Depends on the second.<footnote>
9531 Please note that this does not override the section on
9532 changelog files below, so the file
9533 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
9534 must refer to the changelog for the current version of
9535 <var>package</var> in question. In practice, this means
9536 that the sources of the target and the destination of the
9537 symlink must be the same (same source package and
9544 Former Debian releases placed all additional documentation
9545 in <file>/usr/doc/<var>package</var></file>. This has been
9546 changed to <file>/usr/share/doc/<var>package</var></file>,
9547 and packages must not put documentation in the directory
9548 <file>/usr/doc/<var>package</var></file>. <footnote>
9549 At this phase of the transition, we no longer require a
9550 symbolic link in <file>/usr/doc/</file>. At a later point,
9551 policy shall change to make the symbolic links a bug.
9557 <heading>Preferred documentation formats</heading>
9560 The unification of Debian documentation is being carried out
9564 If your package comes with extensive documentation in a
9565 markup format that can be converted to various other formats
9566 you should if possible ship HTML versions in a binary
9567 package, in the directory
9568 <file>/usr/share/doc/<var>appropriate-package</var></file> or
9569 its subdirectories.<footnote>
9570 The rationale: The important thing here is that HTML
9571 docs should be available in <em>some</em> package, not
9572 necessarily in the main binary package.
9577 Other formats such as PostScript may be provided at the
9578 package maintainer's discretion.
9582 <sect id="copyrightfile">
9583 <heading>Copyright information</heading>
9586 Every package must be accompanied by a verbatim copy of its
9587 copyright information and distribution license in the file
9588 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
9589 file must neither be compressed nor be a symbolic link.
9593 In addition, the copyright file must say where the upstream
9594 sources (if any) were obtained. It should name the original
9595 authors of the package and the Debian maintainer(s) who were
9596 involved with its creation.
9600 Packages in the <em>contrib</em> or <em>non-free</em> archive
9601 areas should state in the copyright file that the package is not
9602 part of the Debian GNU/Linux distribution and briefly explain
9607 A copy of the file which will be installed in
9608 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9609 be in <file>debian/copyright</file> in the source package.
9613 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9614 link to another directory in <file>/usr/share/doc</file> only if
9615 the two packages both come from the same source and the
9616 first package Depends on the second. These rules are
9617 important because copyrights must be extractable by
9622 Packages distributed under the Apache license (version 2.0), the
9623 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
9624 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
9625 1.3) should refer to the corresponding files
9626 under <file>/usr/share/common-licenses</file>,<footnote>
9629 <file>/usr/share/common-licenses/Apache-2.0</file>,
9630 <file>/usr/share/common-licenses/Artistic</file>,
9631 <file>/usr/share/common-licenses/GPL-1</file>,
9632 <file>/usr/share/common-licenses/GPL-2</file>,
9633 <file>/usr/share/common-licenses/GPL-3</file>,
9634 <file>/usr/share/common-licenses/LGPL-2</file>,
9635 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9636 <file>/usr/share/common-licenses/LGPL-3</file>,
9637 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
9638 <file>/usr/share/common-licenses/GFDL-1.3</file>
9639 respectively. The University of California BSD license is
9640 also included in <package>base-files</package> as
9641 <file>/usr/share/common-licenses/BSD</file>, but given the
9642 brevity of this license, its specificity to code whose
9643 copyright is held by the Regents of the University of
9644 California, and the frequency of minor wording changes, its
9645 text should be included in the copyright file rather than
9646 referencing this file.
9648 </footnote> rather than quoting them in the copyright
9653 You should not use the copyright file as a general <file>README</file>
9654 file. If your package has such a file it should be
9655 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9656 <file>README.Debian</file> or some other appropriate place.</p>
9660 <heading>Examples</heading>
9663 Any examples (configurations, source files, whatever),
9664 should be installed in a directory
9665 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9666 files should not be referenced by any program: they're there
9667 for the benefit of the system administrator and users as
9668 documentation only. Architecture-specific example files
9669 should be installed in a directory
9670 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9672 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9673 latter directory itself may be a symbolic link to the
9678 If the purpose of a package is to provide examples, then the
9679 example files may be installed into
9680 <file>/usr/share/doc/<var>package</var></file>.
9684 <sect id="changelogs">
9685 <heading>Changelog files</heading>
9688 Packages that are not Debian-native must contain a
9689 compressed copy of the <file>debian/changelog</file> file from
9690 the Debian source tree in
9691 <file>/usr/share/doc/<var>package</var></file> with the name
9692 <file>changelog.Debian.gz</file>.
9696 If an upstream changelog is available, it should be accessible as
9697 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9698 plain text. If the upstream changelog is distributed in
9699 HTML, it should be made available in that form as
9700 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9701 and a plain text <file>changelog.gz</file> should be generated
9702 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9703 the upstream changelog files do not already conform to this
9704 naming convention, then this may be achieved either by
9705 renaming the files, or by adding a symbolic link, at the
9706 maintainer's discretion.<footnote>
9707 Rationale: People should not have to look in places for
9708 upstream changelogs merely because they are given
9709 different names or are distributed in HTML format.
9714 All of these files should be installed compressed using
9715 <tt>gzip -9</tt>, as they will become large with time even
9716 if they start out small.
9720 If the package has only one changelog which is used both as
9721 the Debian changelog and the upstream one because there is
9722 no separate upstream maintainer then that changelog should
9723 usually be installed as
9724 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9725 there is a separate upstream maintainer, but no upstream
9726 changelog, then the Debian changelog should still be called
9727 <file>changelog.Debian.gz</file>.
9731 For details about the format and contents of the Debian
9732 changelog file, please see <ref id="dpkgchangelog">.
9737 <appendix id="pkg-scope">
9738 <heading>Introduction and scope of these appendices</heading>
9741 These appendices are taken essentially verbatim from the
9742 now-deprecated Packaging Manual, version 3.2.1.0. They are
9743 the chapters which are likely to be of use to package
9744 maintainers and which have not already been included in the
9745 policy document itself. Most of these sections are very likely
9746 not relevant to policy; they should be treated as
9747 documentation for the packaging system. Please note that these
9748 appendices are included for convenience, and for historical
9749 reasons: they used to be part of policy package, and they have
9750 not yet been incorporated into dpkg documentation. However,
9751 they still have value, and hence they are presented here.
9755 They have not yet been checked to ensure that they are
9756 compatible with the contents of policy, and if there are any
9757 contradictions, the version in the main policy document takes
9758 precedence. The remaining chapters of the old Packaging
9759 Manual have also not been read in detail to ensure that there
9760 are not parts which have been left out. Both of these will be
9765 Certain parts of the Packaging manual were integrated into the
9766 Policy Manual proper, and removed from the appendices. Links
9767 have been placed from the old locations to the new ones.
9771 <prgn>dpkg</prgn> is a suite of programs for creating binary
9772 package files and installing and removing them on Unix
9774 <prgn>dpkg</prgn> is targeted primarily at Debian
9775 GNU/Linux, but may work on or be ported to other
9781 The binary packages are designed for the management of
9782 installed executable programs (usually compiled binaries) and
9783 their associated data, though source code examples and
9784 documentation are provided as part of some packages.</p>
9787 This manual describes the technical aspects of creating Debian
9788 binary packages (<file>.deb</file> files). It documents the
9789 behavior of the package management programs
9790 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9791 they interact with packages.</p>
9794 It also documents the interaction between
9795 <prgn>dselect</prgn>'s core and the access method scripts it
9796 uses to actually install the selected packages, and describes
9797 how to create a new access method.</p>
9800 This manual does not go into detail about the options and
9801 usage of the package building and installation tools. It
9802 should therefore be read in conjunction with those programs'
9807 The utility programs which are provided with <prgn>dpkg</prgn>
9808 for managing various system configuration and similar issues,
9809 such as <prgn>update-rc.d</prgn> and
9810 <prgn>install-info</prgn>, are not described in detail here -
9811 please see their man pages.
9815 It is assumed that the reader is reasonably familiar with the
9816 <prgn>dpkg</prgn> System Administrators' manual.
9817 Unfortunately this manual does not yet exist.
9821 The Debian version of the FSF's GNU hello program is provided
9822 as an example for people wishing to create Debian
9823 packages. The Debian <prgn>debmake</prgn> package is
9824 recommended as a very helpful tool in creating and maintaining
9825 Debian packages. However, while the tools and examples are
9826 helpful, they do not replace the need to read and follow the
9827 Policy and Programmer's Manual.</p>
9830 <appendix id="pkg-binarypkg">
9831 <heading>Binary packages (from old Packaging Manual)</heading>
9834 The binary package has two main sections. The first part
9835 consists of various control information files and scripts used
9836 by <prgn>dpkg</prgn> when installing and removing. See <ref
9837 id="pkg-controlarea">.
9841 The second part is an archive containing the files and
9842 directories to be installed.
9846 In the future binary packages may also contain other
9847 components, such as checksums and digital signatures. The
9848 format for the archive is described in full in the
9849 <file>deb(5)</file> man page.
9853 <sect id="pkg-bincreating"><heading>Creating package files -
9854 <prgn>dpkg-deb</prgn>
9858 All manipulation of binary package files is done by
9859 <prgn>dpkg-deb</prgn>; it's the only program that has
9860 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9861 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9862 will spot that the options requested are appropriate to
9863 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9868 In order to create a binary package you must make a
9869 directory tree which contains all the files and directories
9870 you want to have in the file system data part of the package.
9871 In Debian-format source packages this directory is usually
9872 <file>debian/tmp</file>, relative to the top of the package's
9877 They should have the locations (relative to the root of the
9878 directory tree you're constructing) ownerships and
9879 permissions which you want them to have on the system when
9884 With current versions of <prgn>dpkg</prgn> the uid/username
9885 and gid/groupname mappings for the users and groups being
9886 used should be the same on the system where the package is
9887 built and the one where it is installed.
9891 You need to add one special directory to the root of the
9892 miniature file system tree you're creating:
9893 <prgn>DEBIAN</prgn>. It should contain the control
9894 information files, notably the binary package control file
9895 (see <ref id="pkg-controlfile">).
9899 The <prgn>DEBIAN</prgn> directory will not appear in the
9900 file system archive of the package, and so won't be installed
9901 by <prgn>dpkg</prgn> when the package is unpacked.
9905 When you've prepared the package, you should invoke:
9907 dpkg --build <var>directory</var>
9912 This will build the package in
9913 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9914 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9915 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9920 See the man page <manref name="dpkg-deb" section="8"> for details of how
9921 to examine the contents of this newly-created file. You may find the
9922 output of following commands enlightening:
9924 dpkg-deb --info <var>filename</var>.deb
9925 dpkg-deb --contents <var>filename</var>.deb
9926 dpkg --contents <var>filename</var>.deb
9928 To view the copyright file for a package you could use this command:
9930 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
9935 <sect id="pkg-controlarea">
9936 <heading>Package control information files</heading>
9939 The control information portion of a binary package is a
9940 collection of files with names known to <prgn>dpkg</prgn>.
9941 It will treat the contents of these files specially - some
9942 of them contain information used by <prgn>dpkg</prgn> when
9943 installing or removing the package; others are scripts which
9944 the package maintainer wants <prgn>dpkg</prgn> to run.
9948 It is possible to put other files in the package control
9949 information file area, but this is not generally a good idea
9950 (though they will largely be ignored).
9954 Here is a brief list of the control information files supported
9955 by <prgn>dpkg</prgn> and a summary of what they're used for.
9960 <tag><tt>control</tt>
9963 This is the key description file used by
9964 <prgn>dpkg</prgn>. It specifies the package's name
9965 and version, gives its description for the user,
9966 states its relationships with other packages, and so
9967 forth. See <ref id="sourcecontrolfiles"> and
9968 <ref id="binarycontrolfiles">.
9972 It is usually generated automatically from information
9973 in the source package by the
9974 <prgn>dpkg-gencontrol</prgn> program, and with
9975 assistance from <prgn>dpkg-shlibdeps</prgn>.
9976 See <ref id="pkg-sourcetools">.
9980 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9985 These are executable files (usually scripts) which
9986 <prgn>dpkg</prgn> runs during installation, upgrade
9987 and removal of packages. They allow the package to
9988 deal with matters which are particular to that package
9989 or require more complicated processing than that
9990 provided by <prgn>dpkg</prgn>. Details of when and
9991 how they are called are in <ref id="maintainerscripts">.
9995 It is very important to make these scripts idempotent.
9996 See <ref id="idempotency">.
10000 The maintainer scripts are not guaranteed to run with a
10001 controlling terminal and may not be able to interact with
10002 the user. See <ref id="controllingterminal">.
10006 <tag><tt>conffiles</tt>
10009 This file contains a list of configuration files which
10010 are to be handled automatically by <prgn>dpkg</prgn>
10011 (see <ref id="pkg-conffiles">). Note that not necessarily
10012 every configuration file should be listed here.
10015 <tag><tt>shlibs</tt>
10018 This file contains a list of the shared libraries
10019 supplied by the package, with dependency details for
10020 each. This is used by <prgn>dpkg-shlibdeps</prgn>
10021 when it determines what dependencies are required in a
10022 package control file. The <tt>shlibs</tt> file format
10023 is described on <ref id="shlibs">.
10028 <sect id="pkg-controlfile">
10029 <heading>The main control information file: <tt>control</tt></heading>
10032 The most important control information file used by
10033 <prgn>dpkg</prgn> when it installs a package is
10034 <tt>control</tt>. It contains all the package's "vital
10039 The binary package control files of packages built from
10040 Debian sources are made by a special tool,
10041 <prgn>dpkg-gencontrol</prgn>, which reads
10042 <file>debian/control</file> and <file>debian/changelog</file> to
10043 find the information it needs. See <ref id="pkg-sourcepkg"> for
10048 The fields in binary package control files are listed in
10049 <ref id="binarycontrolfiles">.
10053 A description of the syntax of control files and the purpose
10054 of the fields is available in <ref id="controlfields">.
10059 <heading>Time Stamps</heading>
10062 See <ref id="timestamps">.
10067 <appendix id="pkg-sourcepkg">
10068 <heading>Source packages (from old Packaging Manual) </heading>
10071 The Debian binary packages in the distribution are generated
10072 from Debian sources, which are in a special format to assist
10073 the easy and automatic building of binaries.
10076 <sect id="pkg-sourcetools">
10077 <heading>Tools for processing source packages</heading>
10080 Various tools are provided for manipulating source packages;
10081 they pack and unpack sources and help build of binary
10082 packages and help manage the distribution of new versions.
10086 They are introduced and typical uses described here; see
10087 <manref name="dpkg-source" section="1"> for full
10088 documentation about their arguments and operation.
10092 For examples of how to construct a Debian source package,
10093 and how to use those utilities that are used by Debian
10094 source packages, please see the <prgn>hello</prgn> example
10098 <sect1 id="pkg-dpkg-source">
10100 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
10105 This program is frequently used by hand, and is also
10106 called from package-independent automated building scripts
10107 such as <prgn>dpkg-buildpackage</prgn>.
10111 To unpack a package it is typically invoked with
10113 dpkg-source -x <var>.../path/to/filename</var>.dsc
10118 with the <file><var>filename</var>.tar.gz</file> and
10119 <file><var>filename</var>.diff.gz</file> (if applicable) in
10120 the same directory. It unpacks into
10121 <file><var>package</var>-<var>version</var></file>, and if
10123 <file><var>package</var>-<var>version</var>.orig</file>, in
10124 the current directory.
10128 To create a packed source archive it is typically invoked:
10130 dpkg-source -b <var>package</var>-<var>version</var>
10135 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
10136 <file>.diff.gz</file> (if appropriate) in the current
10137 directory. <prgn>dpkg-source</prgn> does not clean the
10138 source tree first - this must be done separately if it is
10143 See also <ref id="pkg-sourcearchives">.</p>
10147 <sect1 id="pkg-dpkg-buildpackage">
10149 <prgn>dpkg-buildpackage</prgn> - overall package-building
10154 <prgn>dpkg-buildpackage</prgn> is a script which invokes
10155 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
10156 targets <tt>clean</tt>, <tt>build</tt> and
10157 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
10158 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
10159 source and binary package upload.
10163 It is usually invoked by hand from the top level of the
10164 built or unbuilt source directory. It may be invoked with
10165 no arguments; useful arguments include:
10166 <taglist compact="compact">
10167 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
10170 Do not sign the <tt>.changes</tt> file or the
10171 source package <tt>.dsc</tt> file, respectively.</p>
10173 <tag><tt>-p<var>sign-command</var></tt></tag>
10176 Invoke <var>sign-command</var> instead of finding
10177 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
10178 <var>sign-command</var> must behave just like
10179 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
10181 <tag><tt>-r<var>root-command</var></tt></tag>
10184 When root privilege is required, invoke the command
10185 <var>root-command</var>. <var>root-command</var>
10186 should invoke its first argument as a command, from
10187 the <prgn>PATH</prgn> if necessary, and pass its
10188 second and subsequent arguments to the command it
10189 calls. If no <var>root-command</var> is supplied
10190 then <var>dpkg-buildpackage</var> will take no
10191 special action to gain root privilege, so that for
10192 most packages it will have to be invoked as root to
10195 <tag><tt>-b</tt>, <tt>-B</tt></tag>
10198 Two types of binary-only build and upload - see
10199 <manref name="dpkg-source" section="1">.
10206 <sect1 id="pkg-dpkg-gencontrol">
10208 <prgn>dpkg-gencontrol</prgn> - generates binary package
10213 This program is usually called from <file>debian/rules</file>
10214 (see <ref id="pkg-sourcetree">) in the top level of the source
10219 This is usually done just before the files and directories in the
10220 temporary directory tree where the package is being built have their
10221 permissions and ownerships set and the package is constructed using
10222 <prgn>dpkg-deb/</prgn>
10224 This is so that the control file which is produced has
10225 the right permissions
10230 <prgn>dpkg-gencontrol</prgn> must be called after all the
10231 files which are to go into the package have been placed in
10232 the temporary build directory, so that its calculation of
10233 the installed size of a package is correct.
10237 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
10238 be run after <prgn>dpkg-shlibdeps</prgn> so that the
10239 variable substitutions created by
10240 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
10245 For a package which generates only one binary package, and
10246 which builds it in <file>debian/tmp</file> relative to the top
10247 of the source package, it is usually sufficient to call
10248 <prgn>dpkg-gencontrol</prgn>.
10252 Sources which build several binaries will typically need
10255 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
10256 </example> The <tt>-P</tt> tells
10257 <prgn>dpkg-gencontrol</prgn> that the package is being
10258 built in a non-default directory, and the <tt>-p</tt>
10259 tells it which package's control file should be generated.
10263 <prgn>dpkg-gencontrol</prgn> also adds information to the
10264 list of files in <file>debian/files</file>, for the benefit of
10265 (for example) a future invocation of
10266 <prgn>dpkg-genchanges</prgn>.</p>
10269 <sect1 id="pkg-dpkg-shlibdeps">
10271 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
10276 This program is usually called from <file>debian/rules</file>
10277 just before <prgn>dpkg-gencontrol</prgn> (see <ref
10278 id="pkg-sourcetree">), in the top level of the source tree.
10282 Its arguments are executables and shared libraries
10285 They may be specified either in the locations in the
10286 source tree where they are created or in the locations
10287 in the temporary build tree where they are installed
10288 prior to binary package creation.
10290 </footnote> for which shared library dependencies should
10291 be included in the binary package's control file.
10295 If some of the found shared libraries should only
10296 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
10297 some warrant a <tt>Pre-Depends</tt>, this can be achieved
10298 by using the <tt>-d<var>dependency-field</var></tt> option
10299 before those executable(s). (Each <tt>-d</tt> option
10300 takes effect until the next <tt>-d</tt>.)
10304 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
10305 output control file to be modified. Instead by default it
10306 adds to the <file>debian/substvars</file> file variable
10307 settings like <tt>shlibs:Depends</tt>. These variable
10308 settings must be referenced in dependency fields in the
10309 appropriate per-binary-package sections of the source
10314 For example, a package that generates an essential part
10315 which requires dependencies, and optional parts that
10316 which only require a recommendation, would separate those
10317 two sets of dependencies into two different fields.<footnote>
10318 At the time of writing, an example for this was the
10319 <package/xmms/ package, with Depends used for the xmms
10320 executable, Recommends for the plug-ins and Suggests for
10321 even more optional features provided by unzip.
10323 It can say in its <file>debian/rules</file>:
10325 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
10326 -dRecommends <var>optionalpart anotheroptionalpart</var>
10328 and then in its main control file <file>debian/control</file>:
10331 Depends: ${shlibs:Depends}
10332 Recommends: ${shlibs:Recommends}
10338 Sources which produce several binary packages with
10339 different shared library dependency requirements can use
10340 the <tt>-p<var>varnameprefix</var></tt> option to override
10341 the default <tt>shlibs:</tt> prefix (one invocation of
10342 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
10343 They can thus produce several sets of dependency
10344 variables, each of the form
10345 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
10346 which can be referred to in the appropriate parts of the
10347 binary package control files.
10352 <sect1 id="pkg-dpkg-distaddfile">
10354 <prgn>dpkg-distaddfile</prgn> - adds a file to
10355 <file>debian/files</file>
10359 Some packages' uploads need to include files other than
10360 the source and binary package files.
10364 <prgn>dpkg-distaddfile</prgn> adds a file to the
10365 <file>debian/files</file> file so that it will be included in
10366 the <file>.changes</file> file when
10367 <prgn>dpkg-genchanges</prgn> is run.
10371 It is usually invoked from the <tt>binary</tt> target of
10372 <file>debian/rules</file>:
10374 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
10376 The <var>filename</var> is relative to the directory where
10377 <prgn>dpkg-genchanges</prgn> will expect to find it - this
10378 is usually the directory above the top level of the source
10379 tree. The <file>debian/rules</file> target should put the
10380 file there just before or just after calling
10381 <prgn>dpkg-distaddfile</prgn>.
10385 The <var>section</var> and <var>priority</var> are passed
10386 unchanged into the resulting <file>.changes</file> file.
10391 <sect1 id="pkg-dpkg-genchanges">
10393 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
10394 upload control file
10398 This program is usually called by package-independent
10399 automatic building scripts such as
10400 <prgn>dpkg-buildpackage</prgn>, but it may also be called
10405 It is usually called in the top level of a built source
10406 tree, and when invoked with no arguments will print out a
10407 straightforward <file>.changes</file> file based on the
10408 information in the source package's changelog and control
10409 file and the binary and source packages which should have
10415 <sect1 id="pkg-dpkg-parsechangelog">
10417 <prgn>dpkg-parsechangelog</prgn> - produces parsed
10418 representation of a changelog
10422 This program is used internally by
10423 <prgn>dpkg-source</prgn> et al. It may also occasionally
10424 be useful in <file>debian/rules</file> and elsewhere. It
10425 parses a changelog, <file>debian/changelog</file> by default,
10426 and prints a control-file format representation of the
10427 information in it to standard output.
10431 <sect1 id="pkg-dpkg-architecture">
10433 <prgn>dpkg-architecture</prgn> - information about the build and
10438 This program can be used manually, but is also invoked by
10439 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
10440 environment or make variables which specify the build and host
10441 architecture for the package building process.
10446 <sect id="pkg-sourcetree">
10447 <heading>The Debian package source tree</heading>
10450 The source archive scheme described later is intended to
10451 allow a Debian package source tree with some associated
10452 control information to be reproduced and transported easily.
10453 The Debian package source tree is a version of the original
10454 program with certain files added for the benefit of the
10455 packaging process, and with any other changes required
10456 made to the rest of the source code and installation
10461 The extra files created for Debian are in the subdirectory
10462 <file>debian</file> of the top level of the Debian package
10463 source tree. They are described below.
10466 <sect1 id="pkg-debianrules">
10467 <heading><file>debian/rules</file> - the main building script</heading>
10470 See <ref id="debianrules">.
10474 <sect1 id="pkg-srcsubstvars">
10475 <heading><file>debian/substvars</file> and variable substitutions</heading>
10478 See <ref id="substvars">.
10484 <heading><file>debian/files</file></heading>
10487 See <ref id="debianfiles">.
10491 <sect1><heading><file>debian/tmp</file>
10495 This is the canonical temporary location for the
10496 construction of binary packages by the <tt>binary</tt>
10497 target. The directory <file>tmp</file> serves as the root of
10498 the file system tree as it is being constructed (for
10499 example, by using the package's upstream makefiles install
10500 targets and redirecting the output there), and it also
10501 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10502 id="pkg-bincreating">.
10506 If several binary packages are generated from the same
10507 source tree it is usual to use several
10508 <file>debian/tmp<var>something</var></file> directories, for
10509 example <file>tmp-a</file> or <file>tmp-doc</file>.
10513 Whatever <file>tmp</file> directories are created and used by
10514 <tt>binary</tt> must of course be removed by the
10515 <tt>clean</tt> target.</p></sect1>
10519 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10523 As it exists on the FTP site, a Debian source package
10524 consists of three related files. You must have the right
10525 versions of all three to be able to use them.
10530 <tag>Debian source control file - <tt>.dsc</tt></tag>
10532 This file is a control file used by <prgn>dpkg-source</prgn>
10533 to extract a source package.
10534 See <ref id="debiansourcecontrolfiles">.
10538 Original source archive -
10540 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10546 This is a compressed (with <tt>gzip -9</tt>)
10547 <prgn>tar</prgn> file containing the source code from
10548 the upstream authors of the program.
10553 Debian package diff -
10555 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10561 This is a unified context diff (<tt>diff -u</tt>)
10562 giving the changes which are required to turn the
10563 original source into the Debian source. These changes
10564 may only include editing and creating plain files.
10565 The permissions of files, the targets of symbolic
10566 links and the characteristics of special files or
10567 pipes may not be changed and no files may be removed
10572 All the directories in the diff must exist, except the
10573 <file>debian</file> subdirectory of the top of the source
10574 tree, which will be created by
10575 <prgn>dpkg-source</prgn> if necessary when unpacking.
10579 The <prgn>dpkg-source</prgn> program will
10580 automatically make the <file>debian/rules</file> file
10581 executable (see below).</p></item>
10586 If there is no original source code - for example, if the
10587 package is specially prepared for Debian or the Debian
10588 maintainer is the same as the upstream maintainer - the
10589 format is slightly different: then there is no diff, and the
10591 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10592 and preferably contains a directory named
10593 <file><var>package</var>-<var>version</var></file>.
10598 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10601 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10602 Debian source package. However, if it is not available it
10603 is possible to unpack a Debian source archive as follows:
10604 <enumlist compact="compact">
10607 Untar the tarfile, which will create a <file>.orig</file>
10611 <p>Rename the <file>.orig</file> directory to
10612 <file><var>package</var>-<var>version</var></file>.</p>
10616 Create the subdirectory <file>debian</file> at the top of
10617 the source tree.</p>
10619 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10621 <item><p>Untar the tarfile again if you want a copy of the original
10622 source code alongside the Debian version.</p>
10627 It is not possible to generate a valid Debian source archive
10628 without using <prgn>dpkg-source</prgn>. In particular,
10629 attempting to use <prgn>diff</prgn> directly to generate the
10630 <file>.diff.gz</file> file will not work.
10634 <heading>Restrictions on objects in source packages</heading>
10637 The source package may not contain any hard links
10639 This is not currently detected when building source
10640 packages, but only when extracting
10644 Hard links may be permitted at some point in the
10645 future, but would require a fair amount of
10647 </footnote>, device special files, sockets or setuid or
10650 Setgid directories are allowed.
10655 The source packaging tools manage the changes between the
10656 original and Debian source using <prgn>diff</prgn> and
10657 <prgn>patch</prgn>. Turning the original source tree as
10658 included in the <file>.orig.tar.gz</file> into the Debian
10659 package source must not involve any changes which cannot be
10660 handled by these tools. Problematic changes which cause
10661 <prgn>dpkg-source</prgn> to halt with an error when
10662 building the source package are:
10663 <list compact="compact">
10664 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10666 <item><p>Changing the targets of symbolic links.</p>
10668 <item><p>Creating directories, other than <file>debian</file>.</p>
10670 <item><p>Changes to the contents of binary files.</p></item>
10671 </list> Changes which cause <prgn>dpkg-source</prgn> to
10672 print a warning but continue anyway are:
10673 <list compact="compact">
10676 Removing files, directories or symlinks.
10678 Renaming a file is not treated specially - it is
10679 seen as the removal of the old file (which
10680 generates a warning, but is otherwise ignored),
10681 and the creation of the new one.
10687 Changed text files which are missing the usual final
10688 newline (either in the original or the modified
10693 Changes which are not represented, but which are not detected by
10694 <prgn>dpkg-source</prgn>, are:
10695 <list compact="compact">
10696 <item><p>Changing the permissions of files (other than
10697 <file>debian/rules</file>) and directories.</p></item>
10702 The <file>debian</file> directory and <file>debian/rules</file>
10703 are handled specially by <prgn>dpkg-source</prgn> - before
10704 applying the changes it will create the <file>debian</file>
10705 directory, and afterwards it will make
10706 <file>debian/rules</file> world-executable.
10712 <appendix id="pkg-controlfields">
10713 <heading>Control files and their fields (from old Packaging Manual)</heading>
10716 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10717 data in a common format, known as control files. Binary and
10718 source packages have control data as do the <file>.changes</file>
10719 files which control the installation of uploaded files, and
10720 <prgn>dpkg</prgn>'s internal databases are in a similar
10725 <heading>Syntax of control files</heading>
10728 See <ref id="controlsyntax">.
10732 It is important to note that there are several fields which
10733 are optional as far as <prgn>dpkg</prgn> and the related
10734 tools are concerned, but which must appear in every Debian
10735 package, or whose omission may cause problems.
10740 <heading>List of fields</heading>
10743 See <ref id="controlfieldslist">.
10747 This section now contains only the fields that didn't belong
10748 to the Policy manual.
10751 <sect1 id="pkg-f-Filename">
10752 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10755 These fields in <tt>Packages</tt> files give the
10756 filename(s) of (the parts of) a package in the
10757 distribution directories, relative to the root of the
10758 Debian hierarchy. If the package has been split into
10759 several parts the parts are all listed in order, separated
10764 <sect1 id="pkg-f-Size">
10765 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10768 These fields in <file>Packages</file> files give the size (in
10769 bytes, expressed in decimal) and MD5 checksum of the
10770 file(s) which make(s) up a binary package in the
10771 distribution. If the package is split into several parts
10772 the values for the parts are listed in order, separated by
10777 <sect1 id="pkg-f-Status">
10778 <heading><tt>Status</tt></heading>
10781 This field in <prgn>dpkg</prgn>'s status file records
10782 whether the user wants a package installed, removed or
10783 left alone, whether it is broken (requiring
10784 re-installation) or not and what its current state on the
10785 system is. Each of these pieces of information is a
10790 <sect1 id="pkg-f-Config-Version">
10791 <heading><tt>Config-Version</tt></heading>
10794 If a package is not installed or not configured, this
10795 field in <prgn>dpkg</prgn>'s status file records the last
10796 version of the package which was successfully
10801 <sect1 id="pkg-f-Conffiles">
10802 <heading><tt>Conffiles</tt></heading>
10805 This field in <prgn>dpkg</prgn>'s status file contains
10806 information about the automatically-managed configuration
10807 files held by a package. This field should <em>not</em>
10808 appear anywhere in a package!
10813 <heading>Obsolete fields</heading>
10816 These are still recognized by <prgn>dpkg</prgn> but should
10817 not appear anywhere any more.
10819 <taglist compact="compact">
10821 <tag><tt>Revision</tt></tag>
10822 <tag><tt>Package-Revision</tt></tag>
10823 <tag><tt>Package_Revision</tt></tag>
10825 The Debian revision part of the package version was
10826 at one point in a separate control field. This
10827 field went through several names.
10830 <tag><tt>Recommended</tt></tag>
10831 <item>Old name for <tt>Recommends</tt>.</item>
10833 <tag><tt>Optional</tt></tag>
10834 <item>Old name for <tt>Suggests</tt>.</item>
10836 <tag><tt>Class</tt></tag>
10837 <item>Old name for <tt>Priority</tt>.</item>
10846 <appendix id="pkg-conffiles">
10847 <heading>Configuration file handling (from old Packaging Manual)</heading>
10850 <prgn>dpkg</prgn> can do a certain amount of automatic
10851 handling of package configuration files.
10855 Whether this mechanism is appropriate depends on a number of
10856 factors, but basically there are two approaches to any
10857 particular configuration file.
10861 The easy method is to ship a best-effort configuration in the
10862 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10863 handle updates. If the user is unlikely to want to edit the
10864 file, but you need them to be able to without losing their
10865 changes, and a new package with a changed version of the file
10866 is only released infrequently, this is a good approach.
10870 The hard method is to build the configuration file from
10871 scratch in the <prgn>postinst</prgn> script, and to take the
10872 responsibility for fixing any mistakes made in earlier
10873 versions of the package automatically. This will be
10874 appropriate if the file is likely to need to be different on
10878 <sect><heading>Automatic handling of configuration files by
10883 A package may contain a control information file called
10884 <tt>conffiles</tt>. This file should be a list of filenames
10885 of configuration files needing automatic handling, separated
10886 by newlines. The filenames should be absolute pathnames,
10887 and the files referred to should actually exist in the
10892 When a package is upgraded <prgn>dpkg</prgn> will process
10893 the configuration files during the configuration stage,
10894 shortly before it runs the package's <prgn>postinst</prgn>
10899 For each file it checks to see whether the version of the
10900 file included in the package is the same as the one that was
10901 included in the last version of the package (the one that is
10902 being upgraded from); it also compares the version currently
10903 installed on the system with the one shipped with the last
10908 If neither the user nor the package maintainer has changed
10909 the file, it is left alone. If one or the other has changed
10910 their version, then the changed version is preferred - i.e.,
10911 if the user edits their file, but the package maintainer
10912 doesn't ship a different version, the user's changes will
10913 stay, silently, but if the maintainer ships a new version
10914 and the user hasn't edited it the new version will be
10915 installed (with an informative message). If both have
10916 changed their version the user is prompted about the problem
10917 and must resolve the differences themselves.
10921 The comparisons are done by calculating the MD5 message
10922 digests of the files, and storing the MD5 of the file as it
10923 was included in the most recent version of the package.
10927 When a package is installed for the first time
10928 <prgn>dpkg</prgn> will install the file that comes with it,
10929 unless that would mean overwriting a file already on the
10934 However, note that <prgn>dpkg</prgn> will <em>not</em>
10935 replace a conffile that was removed by the user (or by a
10936 script). This is necessary because with some programs a
10937 missing file produces an effect hard or impossible to
10938 achieve in another way, so that a missing file needs to be
10939 kept that way if the user did it.
10943 Note that a package should <em>not</em> modify a
10944 <prgn>dpkg</prgn>-handled conffile in its maintainer
10945 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10946 the user confusing and possibly dangerous options for
10947 conffile update when the package is upgraded.</p>
10950 <sect><heading>Fully-featured maintainer script configuration
10955 For files which contain site-specific information such as
10956 the hostname and networking details and so forth, it is
10957 better to create the file in the package's
10958 <prgn>postinst</prgn> script.
10962 This will typically involve examining the state of the rest
10963 of the system to determine values and other information, and
10964 may involve prompting the user for some information which
10965 can't be obtained some other way.
10969 When using this method there are a couple of important
10970 issues which should be considered:
10974 If you discover a bug in the program which generates the
10975 configuration file, or if the format of the file changes
10976 from one version to the next, you will have to arrange for
10977 the postinst script to do something sensible - usually this
10978 will mean editing the installed configuration file to remove
10979 the problem or change the syntax. You will have to do this
10980 very carefully, since the user may have changed the file,
10981 perhaps to fix the very problem that your script is trying
10982 to deal with - you will have to detect these situations and
10983 deal with them correctly.
10987 If you do go down this route it's probably a good idea to
10988 make the program that generates the configuration file(s) a
10989 separate program in <file>/usr/sbin</file>, by convention called
10990 <file><var>package</var>config</file> and then run that if
10991 appropriate from the post-installation script. The
10992 <tt><var>package</var>config</tt> program should not
10993 unquestioningly overwrite an existing configuration - if its
10994 mode of operation is geared towards setting up a package for
10995 the first time (rather than any arbitrary reconfiguration
10996 later) you should have it check whether the configuration
10997 already exists, and require a <tt>--force</tt> flag to
10998 overwrite it.</p></sect>
11001 <appendix id="pkg-alternatives"><heading>Alternative versions of
11002 an interface - <prgn>update-alternatives</prgn> (from old
11007 When several packages all provide different versions of the
11008 same program or file it is useful to have the system select a
11009 default, but to allow the system administrator to change it
11010 and have their decisions respected.
11014 For example, there are several versions of the <prgn>vi</prgn>
11015 editor, and there is no reason to prevent all of them from
11016 being installed at once, each under their own name
11017 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
11018 Nevertheless it is desirable to have the name <tt>vi</tt>
11019 refer to something, at least by default.
11023 If all the packages involved cooperate, this can be done with
11024 <prgn>update-alternatives</prgn>.
11028 Each package provides its own version under its own name, and
11029 calls <prgn>update-alternatives</prgn> in its postinst to
11030 register its version (and again in its prerm to deregister
11035 See the man page <manref name="update-alternatives"
11036 section="8"> for details.
11040 If <prgn>update-alternatives</prgn> does not seem appropriate
11041 you may wish to consider using diversions instead.</p>
11044 <appendix id="pkg-diversions"><heading>Diversions - overriding a
11045 package's version of a file (from old Packaging Manual)
11049 It is possible to have <prgn>dpkg</prgn> not overwrite a file
11050 when it reinstalls the package it belongs to, and to have it
11051 put the file from the package somewhere else instead.
11055 This can be used locally to override a package's version of a
11056 file, or by one package to override another's version (or
11057 provide a wrapper for it).
11061 Before deciding to use a diversion, read <ref
11062 id="pkg-alternatives"> to see if you really want a diversion
11063 rather than several alternative versions of a program.
11067 There is a diversion list, which is read by <prgn>dpkg</prgn>,
11068 and updated by a special program <prgn>dpkg-divert</prgn>.
11069 Please see <manref name="dpkg-divert" section="8"> for full
11070 details of its operation.
11074 When a package wishes to divert a file from another, it should
11075 call <prgn>dpkg-divert</prgn> in its preinst to add the
11076 diversion and rename the existing file. For example,
11077 supposing that a <prgn>smailwrapper</prgn> package wishes to
11078 install a wrapper around <file>/usr/sbin/smail</file>:
11080 dpkg-divert --package smailwrapper --add --rename \
11081 --divert /usr/sbin/smail.real /usr/sbin/smail
11082 </example> The <tt>--package smailwrapper</tt> ensures that
11083 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
11084 can bypass the diversion and get installed as the true version.
11085 It's safe to add the diversion unconditionally on upgrades since
11086 it will be left unchanged if it already exists, but
11087 <prgn>dpkg-divert</prgn> will display a message. To suppress that
11088 message, make the command conditional on the version from which
11089 the package is being upgraded:
11091 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
11092 dpkg-divert --package smailwrapper --add --rename \
11093 --divert /usr/sbin/smail.real /usr/sbin/smail
11095 </example> where <tt>1.0-2</tt> is the version at which the
11096 diversion was first added to the package. Running the command
11097 during abort-upgrade is pointless but harmless.
11101 The postrm has to do the reverse:
11103 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
11104 dpkg-divert --package smailwrapper --remove --rename \
11105 --divert /usr/sbin/smail.real /usr/sbin/smail
11107 </example> If the diversion was added at a particular version, the
11108 postrm should also handle the failure case of upgrading from an
11109 older version (unless the older version is so old that direct
11110 upgrades are no longer supported):
11112 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
11113 dpkg-divert --package smailwrapper --remove --rename \
11114 --divert /usr/sbin/smail.real /usr/sbin/smail
11116 </example> where <tt>1.02-2</tt> is the version at which the
11117 diversion was first added to the package. The postrm should not
11118 remove the diversion on upgrades both because there's no reason to
11119 remove the diversion only to immediately re-add it and since the
11120 postrm of the old package is run after unpacking so the removal of
11121 the diversion will fail.
11125 Do not attempt to divert a file which is vitally important for
11126 the system's operation - when using <prgn>dpkg-divert</prgn>
11127 there is a time, after it has been diverted but before
11128 <prgn>dpkg</prgn> has installed the new version, when the file
11129 does not exist.</p>
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