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12 <title>Debian Policy Manual</title>
13 <author><qref id="authors">The Debian Policy Mailing List</qref></author>
14 <version>version &version;, &date;</version>
17 This manual describes the policy requirements for the Debian
18 GNU/Linux distribution. This includes the structure and
19 contents of the Debian archive and several design issues of
20 the operating system, as well as technical requirements that
21 each package must satisfy to be included in the distribution.
26 Copyright © 1996,1997,1998 Ian Jackson
27 and Christian Schwarz.
30 These are the copyright dates of the original Policy manual.
31 Since then, this manual has been updated by many others. No
32 comprehensive collection of copyright notices for subsequent
37 This manual is free software; you may redistribute it and/or
38 modify it under the terms of the GNU General Public License
39 as published by the Free Software Foundation; either version
40 2, or (at your option) any later version.
44 This is distributed in the hope that it will be useful, but
45 <em>without any warranty</em>; without even the implied
46 warranty of merchantability or fitness for a particular
47 purpose. See the GNU General Public License for more
52 A copy of the GNU General Public License is available as
53 <file>/usr/share/common-licenses/GPL</file> in the Debian GNU/Linux
54 distribution or on the World Wide Web at
55 <url id="http://www.gnu.org/copyleft/gpl.html"
56 name="the GNU General Public Licence">. You can also
57 obtain it by writing to the Free Software Foundation, Inc.,
58 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
66 <heading>About this manual</heading>
68 <heading>Scope</heading>
70 This manual describes the policy requirements for the Debian
71 GNU/Linux distribution. This includes the structure and
72 contents of the Debian archive and several design issues of the
73 operating system, as well as technical requirements that
74 each package must satisfy to be included in the
79 This manual also describes Debian policy as it relates to
80 creating Debian packages. It is not a tutorial on how to build
81 packages, nor is it exhaustive where it comes to describing
82 the behavior of the packaging system. Instead, this manual
83 attempts to define the interface to the package management
84 system that the developers have to be conversant with.<footnote>
85 Informally, the criteria used for inclusion is that the
86 material meet one of the following requirements:
87 <taglist compact="compact">
88 <tag>Standard interfaces</tag>
90 The material presented represents an interface to
91 the packaging system that is mandated for use, and
92 is used by, a significant number of packages, and
93 therefore should not be changed without peer
94 review. Package maintainers can then rely on this
95 interface not changing, and the package management
96 software authors need to ensure compatibility with
97 this interface definition. (Control file and
98 changelog file formats are examples.)
100 <tag>Chosen Convention</tag>
102 If there are a number of technically viable choices
103 that can be made, but one needs to select one of
104 these options for inter-operability. The version
105 number format is one example.
108 Please note that these are not mutually exclusive;
109 selected conventions often become parts of standard
115 The footnotes present in this manual are
116 merely informative, and are not part of Debian policy itself.
120 The appendices to this manual are not necessarily normative,
121 either. Please see <ref id="pkg-scope"> for more information.
125 In the normative part of this manual,
126 the words <em>must</em>, <em>should</em> and
127 <em>may</em>, and the adjectives <em>required</em>,
128 <em>recommended</em> and <em>optional</em>, are used to
129 distinguish the significance of the various guidelines in
130 this policy document. Packages that do not conform to the
131 guidelines denoted by <em>must</em> (or <em>required</em>)
132 will generally not be considered acceptable for the Debian
133 distribution. Non-conformance with guidelines denoted by
134 <em>should</em> (or <em>recommended</em>) will generally be
135 considered a bug, but will not necessarily render a package
136 unsuitable for distribution. Guidelines denoted by
137 <em>may</em> (or <em>optional</em>) are truly optional and
138 adherence is left to the maintainer's discretion.
142 These classifications are roughly equivalent to the bug
143 severities <em>serious</em> (for <em>must</em> or
144 <em>required</em> directive violations), <em>minor</em>,
145 <em>normal</em> or <em>important</em>
146 (for <em>should</em> or <em>recommended</em> directive
147 violations) and <em>wishlist</em> (for <em>optional</em>
150 Compare RFC 2119. Note, however, that these words are
151 used in a different way in this document.
156 Much of the information presented in this manual will be
157 useful even when building a package which is to be
158 distributed in some other way or is intended for local use
164 <heading>New versions of this document</heading>
167 This manual is distributed via the Debian package
168 <package><url name="debian-policy"
169 id="http://packages.debian.org/debian-policy"></package>
170 (<httpsite>packages.debian.org</httpsite>
171 <httppath>/debian-policy</httppath>).
175 The current version of this document is also available from
176 the Debian web mirrors at
177 <tt><url name="/doc/debian-policy/"
178 id="http://www.debian.org/doc/debian-policy/"></tt>.
180 <httpsite>www.debian.org</httpsite>
181 <httppath>/doc/debian-policy/</httppath>)
182 Also available from the same directory are several other
183 formats: <file>policy.html.tar.gz</file>
184 (<httppath>/doc/debian-policy/policy.html.tar.gz</httppath>),
185 <file>policy.pdf.gz</file>
186 (<httppath>/doc/debian-policy/policy.pdf.gz</httppath>)
187 and <file>policy.ps.gz</file>
188 (<httppath>/doc/debian-policy/policy.ps.gz</httppath>).
192 The <package>debian-policy</package> package also includes the file
193 <file>upgrading-checklist.txt.gz</file> which indicates policy
194 changes between versions of this document.
199 <heading>Authors and Maintainers</heading>
202 Originally called "Debian GNU/Linux Policy Manual", this
203 manual was initially written in 1996 by Ian Jackson.
204 It was revised on November 27th, 1996 by David A. Morris.
205 Christian Schwarz added new sections on March 15th, 1997,
206 and reworked/restructured it in April-July 1997.
207 Christoph Lameter contributed the "Web Standard".
208 Julian Gilbey largely restructured it in 2001.
212 Since September 1998, the responsibility for the contents of
213 this document lies on the <url name="debian-policy mailing list"
214 id="mailto:debian-policy@lists.debian.org">. Proposals
215 are discussed there and inserted into policy after a certain
216 consensus is established.
217 <!-- insert shameless policy-process plug here eventually -->
218 The actual editing is done by a group of maintainers that have
219 no editorial powers. These are the current maintainers:
222 <item>Julian Gilbey</item>
223 <item>Branden Robinson</item>
224 <item>Josip Rodin</item>
225 <item>Manoj Srivastava</item>
230 While the authors of this document have tried hard to avoid
231 typos and other errors, these do still occur. If you discover
232 an error in this manual or if you want to give any
233 comments, suggestions, or criticisms please send an email to
234 the Debian Policy List,
235 <email>debian-policy@lists.debian.org</email>, or submit a
236 bug report against the <tt>debian-policy</tt> package.
240 Please do not try to reach the individual authors or maintainers
241 of the Policy Manual regarding changes to the Policy.
246 <heading>Related documents</heading>
249 There are several other documents other than this Policy Manual
250 that are necessary to fully understand some Debian policies and
255 The external "sub-policy" documents are referred to in:
256 <list compact="compact">
257 <item><ref id="fhs"></item>
258 <item><ref id="virtual_pkg"></item>
259 <item><ref id="menus"></item>
260 <item><ref id="mime"></item>
261 <item><ref id="perl"></item>
262 <item><ref id="maintscriptprompt"></item>
263 <item><ref id="emacs"></item>
268 In addition to those, which carry the weight of policy, there
269 is the Debian Developer's Reference. This document describes
270 procedures and resources for Debian developers, but it is
271 <em>not</em> normative; rather, it includes things that don't
272 belong in the Policy, such as best practices for developers.
276 The Developer's Reference is available in the
277 <package>developers-reference</package> package.
278 It's also available from the Debian web mirrors at
279 <tt><url name="/doc/developers-reference/"
280 id="http://www.debian.org/doc/developers-reference/"></tt>.
284 <sect id="definitions">
285 <heading>Definitions</heading>
288 The following terms are used in this Policy Manual:
292 The character encoding specified by ANSI X3.4-1986 and its
293 predecessor standards, referred to in MIME as US-ASCII, and
294 corresponding to an encoding in eight bits per character of
295 the first 128 <url id="http://www.unicode.org/"
296 name="Unicode"> characters, with the eighth bit always zero.
300 The transformation format (sometimes called encoding) of
301 <url id="http://www.unicode.org/" name="Unicode"> defined by
302 <url id="http://www.rfc-editor.org/rfc/rfc3629.txt"
303 name="RFC 3629">. UTF-8 has the useful property of having
304 ASCII as a subset, so any text encoded in ASCII is trivially
314 <heading>The Debian Archive</heading>
317 The Debian GNU/Linux system is maintained and distributed as a
318 collection of <em>packages</em>. Since there are so many of
319 them (currently well over 15000), they are split into
320 <em>sections</em> and given <em>priorities</em> to simplify
321 the handling of them.
325 The effort of the Debian project is to build a free operating
326 system, but not every package we want to make accessible is
327 <em>free</em> in our sense (see the Debian Free Software
328 Guidelines, below), or may be imported/exported without
329 restrictions. Thus, the archive is split into areas<footnote>
330 The Debian archive software uses the term "component" internally
331 and in the Release file format to refer to the division of an
332 archive. The Debian Social Contract simply refers to "areas."
333 This document uses terminology similar to the Social Contract.
334 </footnote> based on their licenses and other restrictions.
338 The aims of this are:
340 <list compact="compact">
341 <item>to allow us to make as much software available as we can</item>
342 <item>to allow us to encourage everyone to write free software,
344 <item>to allow us to make it easy for people to produce
345 CD-ROMs of our system without violating any licenses,
346 import/export restrictions, or any other laws.</item>
351 The <em>main</em> archive area forms the <em>Debian GNU/Linux
356 Packages in the other archive areas (<tt>contrib</tt>,
357 <tt>non-free</tt>) are not considered to be part of the Debian
358 distribution, although we support their use and provide
359 infrastructure for them (such as our bug-tracking system and
360 mailing lists). This Debian Policy Manual applies to these
365 <heading>The Debian Free Software Guidelines</heading>
367 The Debian Free Software Guidelines (DFSG) form our
368 definition of "free software". These are:
370 <tag>1. Free Redistribution
373 The license of a Debian component may not restrict any
374 party from selling or giving away the software as a
375 component of an aggregate software distribution
376 containing programs from several different
377 sources. The license may not require a royalty or
378 other fee for such sale.
383 The program must include source code, and must allow
384 distribution in source code as well as compiled form.
386 <tag>3. Derived Works
389 The license must allow modifications and derived
390 works, and must allow them to be distributed under the
391 same terms as the license of the original software.
393 <tag>4. Integrity of The Author's Source Code
396 The license may restrict source-code from being
397 distributed in modified form <em>only</em> if the
398 license allows the distribution of "patch files"
399 with the source code for the purpose of modifying the
400 program at build time. The license must explicitly
401 permit distribution of software built from modified
402 source code. The license may require derived works to
403 carry a different name or version number from the
404 original software. (This is a compromise. The Debian
405 Project encourages all authors to not restrict any
406 files, source or binary, from being modified.)
408 <tag>5. No Discrimination Against Persons or Groups
411 The license must not discriminate against any person
414 <tag>6. No Discrimination Against Fields of Endeavor
417 The license must not restrict anyone from making use
418 of the program in a specific field of endeavor. For
419 example, it may not restrict the program from being
420 used in a business, or from being used for genetic
423 <tag>7. Distribution of License
426 The rights attached to the program must apply to all
427 to whom the program is redistributed without the need
428 for execution of an additional license by those
431 <tag>8. License Must Not Be Specific to Debian
434 The rights attached to the program must not depend on
435 the program's being part of a Debian system. If the
436 program is extracted from Debian and used or
437 distributed without Debian but otherwise within the
438 terms of the program's license, all parties to whom
439 the program is redistributed must have the same
440 rights as those that are granted in conjunction with
443 <tag>9. License Must Not Contaminate Other Software
446 The license must not place restrictions on other
447 software that is distributed along with the licensed
448 software. For example, the license must not insist
449 that all other programs distributed on the same medium
450 must be free software.
452 <tag>10. Example Licenses
455 The "GPL," "BSD," and "Artistic" licenses are examples of
456 licenses that we consider <em>free</em>.
463 <heading>Archive areas</heading>
466 <heading>The main archive area</heading>
469 Every package in <em>main</em> must comply with the DFSG
470 (Debian Free Software Guidelines).
474 In addition, the packages in <em>main</em>
475 <list compact="compact">
477 must not require a package outside of <em>main</em>
478 for compilation or execution (thus, the package must
479 not declare a "Depends", "Recommends", or
480 "Build-Depends" relationship on a non-<em>main</em>
484 must not be so buggy that we refuse to support them,
488 must meet all policy requirements presented in this
497 <heading>The contrib archive area</heading>
500 Every package in <em>contrib</em> must comply with the DFSG.
504 In addition, the packages in <em>contrib</em>
505 <list compact="compact">
507 must not be so buggy that we refuse to support them,
511 must meet all policy requirements presented in this
519 Examples of packages which would be included in
520 <em>contrib</em> are:
521 <list compact="compact">
523 free packages which require <em>contrib</em>,
524 <em>non-free</em> packages or packages which are not
525 in our archive at all for compilation or execution,
529 wrapper packages or other sorts of free accessories for
536 <sect1 id="non-free">
537 <heading>The non-free archive area</heading>
540 Packages must be placed in <em>non-free</em> if they are
541 not compliant with the DFSG or are encumbered by patents
542 or other legal issues that make their distribution
547 In addition, the packages in <em>non-free</em>
548 <list compact="compact">
550 must not be so buggy that we refuse to support them,
554 must meet all policy requirements presented in this
555 manual that it is possible for them to meet.
557 It is possible that there are policy
558 requirements which the package is unable to
559 meet, for example, if the source is
560 unavailable. These situations will need to be
561 handled on a case-by-case basis.
570 <sect id="pkgcopyright">
571 <heading>Copyright considerations</heading>
574 Every package must be accompanied by a verbatim copy of its
575 copyright information and distribution license in the file
576 <file>/usr/share/doc/<var>package</var>/copyright</file>
577 (see <ref id="copyrightfile"> for further details).
581 We reserve the right to restrict files from being included
582 anywhere in our archives if
583 <list compact="compact">
585 their use or distribution would break a law,
588 there is an ethical conflict in their distribution or
592 we would have to sign a license for them, or
595 their distribution would conflict with other project
602 Programs whose authors encourage the user to make
603 donations are fine for the main distribution, provided
604 that the authors do not claim that not donating is
605 immoral, unethical, illegal or something similar; in such
606 a case they must go in <em>non-free</em>.
610 Packages whose copyright permission notices (or patent
611 problems) do not even allow redistribution of binaries
612 only, and where no special permission has been obtained,
613 must not be placed on the Debian FTP site and its mirrors
618 Note that under international copyright law (this applies
619 in the United States, too), <em>no</em> distribution or
620 modification of a work is allowed without an explicit
621 notice saying so. Therefore a program without a copyright
622 notice <em>is</em> copyrighted and you may not do anything
623 to it without risking being sued! Likewise if a program
624 has a copyright notice but no statement saying what is
625 permitted then nothing is permitted.
629 Many authors are unaware of the problems that restrictive
630 copyrights (or lack of copyright notices) can cause for
631 the users of their supposedly-free software. It is often
632 worthwhile contacting such authors diplomatically to ask
633 them to modify their license terms. However, this can be a
634 politically difficult thing to do and you should ask for
635 advice on the <tt>debian-legal</tt> mailing list first, as
640 When in doubt about a copyright, send mail to
641 <email>debian-legal@lists.debian.org</email>. Be prepared
642 to provide us with the copyright statement. Software
643 covered by the GPL, public domain software and BSD-like
644 copyrights are safe; be wary of the phrases "commercial
645 use prohibited" and "distribution restricted".
649 <sect id="subsections">
650 <heading>Sections</heading>
653 The packages in the archive areas <em>main</em>,
654 <em>contrib</em> and <em>non-free</em> are grouped further into
655 <em>sections</em> to simplify handling.
659 The archive area and section for each package should be
660 specified in the package's <tt>Section</tt> control record (see
661 <ref id="f-Section">). However, the maintainer of the Debian
662 archive may override this selection to ensure the consistency of
663 the Debian distribution. The <tt>Section</tt> field should be
665 <list compact="compact">
667 <em>section</em> if the package is in the
668 <em>main</em> archive area,
671 <em>area/section</em> if the package is in
672 the <em>contrib</em> or <em>non-free</em>
679 The Debian archive maintainers provide the authoritative
680 list of sections. At present, they are:
681 <em>admin</em>, <em>cli-mono</em>, <em>comm</em>, <em>database</em>,
682 <em>devel</em>, <em>debug</em>, <em>doc</em>, <em>editors</em>,
683 <em>electronics</em>, <em>embedded</em>, <em>fonts</em>,
684 <em>games</em>, <em>gnome</em>, <em>graphics</em>, <em>gnu-r</em>,
685 <em>gnustep</em>, <em>hamradio</em>, <em>haskell</em>,
686 <em>httpd</em>, <em>interpreters</em>, <em>java</em>, <em>kde</em>,
687 <em>kernel</em>, <em>libs</em>, <em>libdevel</em>, <em>lisp</em>,
688 <em>localization</em>, <em>mail</em>, <em>math</em>, <em>misc</em>,
689 <em>net</em>, <em>news</em>, <em>ocaml</em>, <em>oldlibs</em>,
690 <em>otherosfs</em>, <em>perl</em>, <em>php</em>, <em>python</em>,
691 <em>ruby</em>, <em>science</em>, <em>shells</em>, <em>sound</em>,
692 <em>tex</em>, <em>text</em>, <em>utils</em>, <em>vcs</em>,
693 <em>video</em>, <em>web</em>, <em>x11</em>, <em>xfce</em>,
694 <em>zope</em>. The additional section <em>debian-installer</em>
695 contains special packages used by the installer and is not used
696 for normal Debian packages.
700 For more information about the sections and their definitions,
701 see the <url id="http://packages.debian.org/unstable/"
702 name="list of sections in unstable">.
706 <sect id="priorities">
707 <heading>Priorities</heading>
710 Each package should have a <em>priority</em> value, which is
711 included in the package's <em>control record</em>
712 (see <ref id="f-Priority">).
713 This information is used by the Debian package management tools to
714 separate high-priority packages from less-important packages.
718 The following <em>priority levels</em> are recognized by the
719 Debian package management tools.
721 <tag><tt>required</tt></tag>
723 Packages which are necessary for the proper
724 functioning of the system (usually, this means that
725 dpkg functionality depends on these packages).
726 Removing a <tt>required</tt> package may cause your
727 system to become totally broken and you may not even
728 be able to use <prgn>dpkg</prgn> to put things back,
729 so only do so if you know what you are doing. Systems
730 with only the <tt>required</tt> packages are probably
731 unusable, but they do have enough functionality to
732 allow the sysadmin to boot and install more software.
734 <tag><tt>important</tt></tag>
736 Important programs, including those which one would
737 expect to find on any Unix-like system. If the
738 expectation is that an experienced Unix person who
739 found it missing would say "What on earth is going on,
740 where is <prgn>foo</prgn>?", it must be an
741 <tt>important</tt> package.<footnote>
742 This is an important criterion because we are
743 trying to produce, amongst other things, a free
746 Other packages without which the system will not run
747 well or be usable must also have priority
748 <tt>important</tt>. This does
749 <em>not</em> include Emacs, the X Window System, TeX
750 or any other large applications. The
751 <tt>important</tt> packages are just a bare minimum of
752 commonly-expected and necessary tools.
754 <tag><tt>standard</tt></tag>
756 These packages provide a reasonably small but not too
757 limited character-mode system. This is what will be
758 installed by default if the user doesn't select anything
759 else. It doesn't include many large applications.
761 <tag><tt>optional</tt></tag>
763 (In a sense everything that isn't required is
764 optional, but that's not what is meant here.) This is
765 all the software that you might reasonably want to
766 install if you didn't know what it was and don't have
767 specialized requirements. This is a much larger system
768 and includes the X Window System, a full TeX
769 distribution, and many applications. Note that
770 optional packages should not conflict with each other.
772 <tag><tt>extra</tt></tag>
774 This contains all packages that conflict with others
775 with required, important, standard or optional
776 priorities, or are only likely to be useful if you
777 already know what they are or have specialized
778 requirements (such as packages containing only detached
785 Packages must not depend on packages with lower priority
786 values (excluding build-time dependencies). In order to
787 ensure this, the priorities of one or more packages may need
796 <heading>Binary packages</heading>
799 The Debian GNU/Linux distribution is based on the Debian
800 package management system, called <prgn>dpkg</prgn>. Thus,
801 all packages in the Debian distribution must be provided
802 in the <tt>.deb</tt> file format.
806 A <tt>.deb</tt> package contains two sets of files: a set of files
807 to install on the system when the package is installed, and a set
808 of files that provide additional metadata about the package or
809 which are executed when the package is installed or removed. This
810 second set of files is called <em>control information files</em>.
811 Among those files are the package maintainer scripts
812 and <file>control</file>, the <qref id="binarycontrolfiles">binary
813 package control file</qref> that contains the control fields for
814 the package. Other control information files
815 include <qref id="sharedlibs-shlibdeps">the <file>shlibs</file>
816 file</qref> used to store shared library dependency information
817 and the <file>conffiles</file> file that lists the package's
818 configuration files (described in <ref id="config-files">).
822 There is unfortunately a collision of terminology here between
823 control information files and files in the Debian control file
824 format. Throughout this document, a <em>control file</em> refers
825 to a file in the Debian control file format. These files are
826 documented in <ref id="controlfields">. Only files referred to
827 specifically as <em>control information files</em> are the files
828 included in the control information file member of
829 the <file>.deb</file> file format used by binary packages. Most
830 control information files are not in the Debian control file
835 <heading>The package name</heading>
838 Every package must have a name that's unique within the Debian
843 The package name is included in the control field
844 <tt>Package</tt>, the format of which is described
845 in <ref id="f-Package">.
846 The package name is also included as a part of the file name
847 of the <tt>.deb</tt> file.
852 <heading>The version of a package</heading>
855 Every package has a version number recorded in its
856 <tt>Version</tt> control file field, described in
857 <ref id="f-Version">.
861 The package management system imposes an ordering on version
862 numbers, so that it can tell whether packages are being up- or
863 downgraded and so that package system front end applications
864 can tell whether a package it finds available is newer than
865 the one installed on the system. The version number format
866 has the most significant parts (as far as comparison is
867 concerned) at the beginning.
871 If an upstream package has problematic version numbers they
872 should be converted to a sane form for use in the
873 <tt>Version</tt> field.
877 <heading>Version numbers based on dates</heading>
880 In general, Debian packages should use the same version
881 numbers as the upstream sources. However, upstream version
882 numbers based on some date formats (sometimes used for
883 development or "snapshot" releases) will not be ordered
884 correctly by the package management software. For
885 example, <prgn>dpkg</prgn> will consider "96May01" to be
886 greater than "96Dec24".
890 To prevent having to use epochs for every new upstream
891 version, the date-based portion of any upstream version number
892 should be given in a way that sorts correctly: four-digit year
893 first, followed by a two-digit numeric month, followed by a
894 two-digit numeric date, possibly with punctuation between the
899 Native Debian packages (i.e., packages which have been written
900 especially for Debian) whose version numbers include dates
901 should also follow these rules. If punctuation is desired
902 between the date components, remember that hyphen (<tt>-</tt>)
903 cannot be used in native package versions. Period
904 (<tt>.</tt>) is normally a good choice.
911 <heading>The maintainer of a package</heading>
914 Every package must have a Debian maintainer (the
915 maintainer may be one person or a group of people
916 reachable from a common email address, such as a mailing
917 list). The maintainer is responsible for ensuring that
918 the package is placed in the appropriate distributions.
922 The maintainer must be specified in the
923 <tt>Maintainer</tt> control field with their correct name
924 and a working email address. If one person maintains
925 several packages, they should try to avoid having
926 different forms of their name and email address in
927 the <tt>Maintainer</tt> fields of those packages.
931 The format of the <tt>Maintainer</tt> control field is
932 described in <ref id="f-Maintainer">.
936 If the maintainer of a package quits from the Debian
937 project, "Debian QA Group"
938 <email>packages@qa.debian.org</email> takes over the
939 maintainer-ship of the package until someone else
940 volunteers for that task. These packages are called
941 <em>orphaned packages</em>.<footnote>
942 The detailed procedure for doing this gracefully can
943 be found in the Debian Developer's Reference,
944 see <ref id="related">.
949 <sect id="descriptions">
950 <heading>The description of a package</heading>
953 Every Debian package must have a <tt>Description</tt> control
954 field which contains a synopsis and extended description of the
955 package. Technical information about the format of the
956 <tt>Description</tt> field is in <ref id="f-Description">.
960 The description should describe the package (the program) to a
961 user (system administrator) who has never met it before so that
962 they have enough information to decide whether they want to
963 install it. This description should not just be copied verbatim
964 from the program's documentation.
968 Put important information first, both in the synopsis and
969 extended description. Sometimes only the first part of the
970 synopsis or of the description will be displayed. You can
971 assume that there will usually be a way to see the whole
972 extended description.
976 The description should also give information about the
977 significant dependencies and conflicts between this package
978 and others, so that the user knows why these dependencies and
979 conflicts have been declared.
983 Instructions for configuring or using the package should
984 not be included (that is what installation scripts,
985 manual pages, info files, etc., are for). Copyright
986 statements and other administrivia should not be included
987 either (that is what the copyright file is for).
990 <sect1 id="synopsis"><heading>The single line synopsis</heading>
993 The single line synopsis should be kept brief - certainly
998 Do not include the package name in the synopsis line. The
999 display software knows how to display this already, and you
1000 do not need to state it. Remember that in many situations
1001 the user may only see the synopsis line - make it as
1002 informative as you can.
1007 <sect1 id="extendeddesc"><heading>The extended description</heading>
1010 Do not try to continue the single line synopsis into the
1011 extended description. This will not work correctly when
1012 the full description is displayed, and makes no sense
1013 where only the summary (the single line synopsis) is
1018 The extended description should describe what the package
1019 does and how it relates to the rest of the system (in terms
1020 of, for example, which subsystem it is which part of).
1024 The description field needs to make sense to anyone, even
1025 people who have no idea about any of the things the
1026 package deals with.<footnote>
1027 The blurb that comes with a program in its
1028 announcements and/or <prgn>README</prgn> files is
1029 rarely suitable for use in a description. It is
1030 usually aimed at people who are already in the
1031 community where the package is used.
1040 <heading>Dependencies</heading>
1043 Every package must specify the dependency information
1044 about other packages that are required for the first to
1049 For example, a dependency entry must be provided for any
1050 shared libraries required by a dynamically-linked executable
1051 binary in a package.
1055 Packages are not required to declare any dependencies they
1056 have on other packages which are marked <tt>Essential</tt>
1057 (see below), and should not do so unless they depend on a
1058 particular version of that package.<footnote>
1060 Essential is needed in part to avoid unresolvable dependency
1061 loops on upgrade. If packages add unnecessary dependencies
1062 on packages in this set, the chances that there
1063 <strong>will</strong> be an unresolvable dependency loop
1064 caused by forcing these Essential packages to be configured
1065 first before they need to be is greatly increased. It also
1066 increases the chances that frontends will be unable to
1067 <strong>calculate</strong> an upgrade path, even if one
1071 Also, functionality is rarely ever removed from the
1072 Essential set, but <em>packages</em> have been removed from
1073 the Essential set when the functionality moved to a
1074 different package. So depending on these packages <em>just
1075 in case</em> they stop being essential does way more harm
1082 Sometimes, a package requires another package to be unpacked
1083 <em>and</em> configured before it can be unpacked. In this
1084 case, you must specify a <tt>Pre-Depends</tt> entry for
1089 You should not specify a <tt>Pre-Depends</tt> entry for a
1090 package before this has been discussed on the
1091 <tt>debian-devel</tt> mailing list and a consensus about
1092 doing that has been reached.
1096 The format of the package interrelationship control fields is
1097 described in <ref id="relationships">.
1101 <sect id="virtual_pkg">
1102 <heading>Virtual packages</heading>
1105 Sometimes, there are several packages which offer
1106 more-or-less the same functionality. In this case, it's
1107 useful to define a <em>virtual package</em> whose name
1108 describes that common functionality. (The virtual
1109 packages only exist logically, not physically; that's why
1110 they are called <em>virtual</em>.) The packages with this
1111 particular function will then <em>provide</em> the virtual
1112 package. Thus, any other package requiring that function
1113 can simply depend on the virtual package without having to
1114 specify all possible packages individually.
1118 All packages should use virtual package names where
1119 appropriate, and arrange to create new ones if necessary.
1120 They should not use virtual package names (except privately,
1121 amongst a cooperating group of packages) unless they have
1122 been agreed upon and appear in the list of virtual package
1123 names. (See also <ref id="virtual">)
1127 The latest version of the authoritative list of virtual
1128 package names can be found in the <tt>debian-policy</tt> package.
1129 It is also available from the Debian web mirrors at
1130 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1131 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1135 The procedure for updating the list is described in the preface
1142 <heading>Base system</heading>
1145 The <tt>base system</tt> is a minimum subset of the Debian
1146 GNU/Linux system that is installed before everything else
1147 on a new system. Only very few packages are allowed to form
1148 part of the base system, in order to keep the required disk
1153 The base system consists of all those packages with priority
1154 <tt>required</tt> or <tt>important</tt>. Many of them will
1155 be tagged <tt>essential</tt> (see below).
1160 <heading>Essential packages</heading>
1163 Essential is defined as the minimal set of functionality that
1164 must be available and usable on the system at all times, even
1165 when packages are in an unconfigured (but unpacked) state.
1166 Packages are tagged <tt>essential</tt> for a system using the
1167 <tt>Essential</tt> control field. The format of the
1168 <tt>Essential</tt> control field is described in <ref
1173 Since these packages cannot be easily removed (one has to
1174 specify an extra <em>force option</em> to
1175 <prgn>dpkg</prgn> to do so), this flag must not be used
1176 unless absolutely necessary. A shared library package
1177 must not be tagged <tt>essential</tt>; dependencies will
1178 prevent its premature removal, and we need to be able to
1179 remove it when it has been superseded.
1183 Since dpkg will not prevent upgrading of other packages
1184 while an <tt>essential</tt> package is in an unconfigured
1185 state, all <tt>essential</tt> packages must supply all of
1186 their core functionality even when unconfigured. If the
1187 package cannot satisfy this requirement it must not be
1188 tagged as essential, and any packages depending on this
1189 package must instead have explicit dependency fields as
1194 Maintainers should take great care in adding any programs,
1195 interfaces, or functionality to <tt>essential</tt> packages.
1196 Packages may assume that functionality provided by
1197 <tt>essential</tt> packages is always available without
1198 declaring explicit dependencies, which means that removing
1199 functionality from the Essential set is very difficult and is
1200 almost never done. Any capability added to an
1201 <tt>essential</tt> package therefore creates an obligation to
1202 support that capability as part of the Essential set in
1207 You must not tag any packages <tt>essential</tt> before
1208 this has been discussed on the <tt>debian-devel</tt>
1209 mailing list and a consensus about doing that has been
1214 <sect id="maintscripts">
1215 <heading>Maintainer Scripts</heading>
1218 The package installation scripts should avoid producing
1219 output which is unnecessary for the user to see and
1220 should rely on <prgn>dpkg</prgn> to stave off boredom on
1221 the part of a user installing many packages. This means,
1222 amongst other things, using the <tt>--quiet</tt> option on
1223 <prgn>install-info</prgn>.
1227 Errors which occur during the execution of an installation
1228 script must be checked and the installation must not
1229 continue after an error.
1233 Note that in general <ref id="scripts"> applies to package
1234 maintainer scripts, too.
1238 You should not use <prgn>dpkg-divert</prgn> on a file belonging
1239 to another package without consulting the maintainer of that
1240 package first. When adding or removing diversions, package
1241 maintainer scripts must provide the <tt>--package</tt> flag
1242 to <prgn>dpkg-divert</prgn> and must not use <tt>--local</tt>.
1246 All packages which supply an instance of a common command
1247 name (or, in general, filename) should generally use
1248 <prgn>update-alternatives</prgn>, so that they may be
1249 installed together. If <prgn>update-alternatives</prgn>
1250 is not used, then each package must use
1251 <tt>Conflicts</tt> to ensure that other packages are
1252 de-installed. (In this case, it may be appropriate to
1253 specify a conflict against earlier versions of something
1254 that previously did not use
1255 <prgn>update-alternatives</prgn>; this is an exception to
1256 the usual rule that versioned conflicts should be
1260 <sect1 id="maintscriptprompt">
1261 <heading>Prompting in maintainer scripts</heading>
1263 Package maintainer scripts may prompt the user if
1264 necessary. Prompting must be done by communicating
1265 through a program, such as <prgn>debconf</prgn>, which
1266 conforms to the Debian Configuration Management
1267 Specification, version 2 or higher.
1271 Packages which are essential, or which are dependencies of
1272 essential packages, may fall back on another prompting method
1273 if no such interface is available when they are executed.
1277 The Debian Configuration Management Specification is included
1278 in the <file>debconf_specification</file> files in the
1279 <package>debian-policy</package> package.
1280 It is also available from the Debian web mirrors at
1281 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1282 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1286 Packages which use the Debian Configuration Management
1287 Specification may contain the additional control information
1288 files <file>config</file>
1289 and <file>templates</file>. <file>config</file> is an
1290 additional maintainer script used for package configuration,
1291 and <file>templates</file> contains templates used for user
1292 prompting. The <prgn>config</prgn> script might be run before
1293 the <prgn>preinst</prgn> script and before the package is
1294 unpacked or any of its dependencies or pre-dependencies are
1295 satisfied. Therefore it must work using only the tools
1296 present in <em>essential</em> packages.<footnote>
1297 <package>Debconf</package> or another tool that
1298 implements the Debian Configuration Management
1299 Specification will also be installed, and any
1300 versioned dependencies on it will be satisfied
1301 before preconfiguration begins.
1306 Packages which use the Debian Configuration Management
1307 Specification must allow for translation of their user-visible
1308 messages by using a gettext-based system such as the one
1309 provided by the <package>po-debconf</package> package.
1313 Packages should try to minimize the amount of prompting
1314 they need to do, and they should ensure that the user
1315 will only ever be asked each question once. This means
1316 that packages should try to use appropriate shared
1317 configuration files (such as <file>/etc/papersize</file> and
1318 <file>/etc/news/server</file>), and shared
1319 <package>debconf</package> variables rather than each
1320 prompting for their own list of required pieces of
1325 It also means that an upgrade should not ask the same
1326 questions again, unless the user has used
1327 <tt>dpkg --purge</tt> to remove the package's configuration.
1328 The answers to configuration questions should be stored in an
1329 appropriate place in <file>/etc</file> so that the user can
1330 modify them, and how this has been done should be
1335 If a package has a vitally important piece of
1336 information to pass to the user (such as "don't run me
1337 as I am, you must edit the following configuration files
1338 first or you risk your system emitting badly-formatted
1339 messages"), it should display this in the
1340 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1341 prompt the user to hit return to acknowledge the
1342 message. Copyright messages do not count as vitally
1343 important (they belong in
1344 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1345 neither do instructions on how to use a program (these
1346 should be in on-line documentation, where all the users
1351 Any necessary prompting should almost always be confined
1352 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1353 script. If it is done in the <prgn>postinst</prgn>, it
1354 should be protected with a conditional so that
1355 unnecessary prompting doesn't happen if a package's
1356 installation fails and the <prgn>postinst</prgn> is
1357 called with <tt>abort-upgrade</tt>,
1358 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1368 <heading>Source packages</heading>
1370 <sect id="standardsversion">
1371 <heading>Standards conformance</heading>
1374 Source packages should specify the most recent version number
1375 of this policy document with which your package complied
1376 when it was last updated.
1380 This information may be used to file bug reports
1381 automatically if your package becomes too much out of date.
1385 The version is specified in the <tt>Standards-Version</tt>
1387 The format of the <tt>Standards-Version</tt> field is
1388 described in <ref id="f-Standards-Version">.
1392 You should regularly, and especially if your package has
1393 become out of date, check for the newest Policy Manual
1394 available and update your package, if necessary. When your
1395 package complies with the new standards you should update the
1396 <tt>Standards-Version</tt> source package field and
1397 release it.<footnote>
1398 See the file <file>upgrading-checklist</file> for
1399 information about policy which has changed between
1400 different versions of this document.
1406 <sect id="pkg-relations">
1407 <heading>Package relationships</heading>
1410 Source packages should specify which binary packages they
1411 require to be installed or not to be installed in order to
1412 build correctly. For example, if building a package
1413 requires a certain compiler, then the compiler should be
1414 specified as a build-time dependency.
1418 It is not necessary to explicitly specify build-time
1419 relationships on a minimal set of packages that are always
1420 needed to compile, link and put in a Debian package a
1421 standard "Hello World!" program written in C or C++. The
1422 required packages are called <em>build-essential</em>, and
1423 an informational list can be found in
1424 <file>/usr/share/doc/build-essential/list</file> (which is
1425 contained in the <tt>build-essential</tt>
1428 <list compact="compact">
1430 This allows maintaining the list separately
1431 from the policy documents (the list does not
1432 need the kind of control that the policy
1436 Having a separate package allows one to install
1437 the build-essential packages on a machine, as
1438 well as allowing other packages such as tasks to
1439 require installation of the build-essential
1440 packages using the depends relation.
1443 The separate package allows bug reports against
1444 the list to be categorized separately from
1445 the policy management process in the BTS.
1452 When specifying the set of build-time dependencies, one
1453 should list only those packages explicitly required by the
1454 build. It is not necessary to list packages which are
1455 required merely because some other package in the list of
1456 build-time dependencies depends on them.<footnote>
1457 The reason for this is that dependencies change, and
1458 you should list all those packages, and <em>only</em>
1459 those packages that <em>you</em> need directly. What
1460 others need is their business. For example, if you
1461 only link against <file>libimlib</file>, you will need to
1462 build-depend on <package>libimlib2-dev</package> but
1463 not against any <tt>libjpeg*</tt> packages, even
1464 though <tt>libimlib2-dev</tt> currently depends on
1465 them: installation of <package>libimlib2-dev</package>
1466 will automatically ensure that all of its run-time
1467 dependencies are satisfied.
1472 If build-time dependencies are specified, it must be
1473 possible to build the package and produce working binaries
1474 on a system with only essential and build-essential
1475 packages installed and also those required to satisfy the
1476 build-time relationships (including any implied
1477 relationships). In particular, this means that version
1478 clauses should be used rigorously in build-time
1479 relationships so that one cannot produce bad or
1480 inconsistently configured packages when the relationships
1481 are properly satisfied.
1485 <ref id="relationships"> explains the technical details.
1490 <heading>Changes to the upstream sources</heading>
1493 If changes to the source code are made that are not
1494 specific to the needs of the Debian system, they should be
1495 sent to the upstream authors in whatever form they prefer
1496 so as to be included in the upstream version of the
1501 If you need to configure the package differently for
1502 Debian or for Linux, and the upstream source doesn't
1503 provide a way to do so, you should add such configuration
1504 facilities (for example, a new <prgn>autoconf</prgn> test
1505 or <tt>#define</tt>) and send the patch to the upstream
1506 authors, with the default set to the way they originally
1507 had it. You can then easily override the default in your
1508 <file>debian/rules</file> or wherever is appropriate.
1512 You should make sure that the <prgn>configure</prgn> utility
1513 detects the correct architecture specification string
1514 (refer to <ref id="arch-spec"> for details).
1518 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1519 <prgn>configure</prgn> scripts are used, you should edit the
1520 <file>.in</file> files rather than editing the
1521 <prgn>Makefile</prgn> directly. This allows the user to
1522 reconfigure the package if necessary. You should
1523 <em>not</em> configure the package and edit the generated
1524 <prgn>Makefile</prgn>! This makes it impossible for someone
1525 else to later reconfigure the package without losing the
1531 <sect id="dpkgchangelog">
1532 <heading>Debian changelog: <file>debian/changelog</file></heading>
1535 Changes in the Debian version of the package should be
1536 briefly explained in the Debian changelog file
1537 <file>debian/changelog</file>.<footnote>
1539 Mistakes in changelogs are usually best rectified by
1540 making a new changelog entry rather than "rewriting
1541 history" by editing old changelog entries.
1544 This includes modifications
1545 made in the Debian package compared to the upstream one
1546 as well as other changes and updates to the package.
1548 Although there is nothing stopping an author who is also
1549 the Debian maintainer from using this changelog for all
1550 their changes, it will have to be renamed if the Debian
1551 and upstream maintainers become different people. In such
1552 a case, however, it might be better to maintain the package
1553 as a non-native package.
1558 The format of the <file>debian/changelog</file> allows the
1559 package building tools to discover which version of the package
1560 is being built and find out other release-specific information.
1564 That format is a series of entries like this:
1566 <example compact="compact">
1567 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1569 [optional blank line(s), stripped]
1571 * <var>change details</var>
1572 <var>more change details</var>
1574 [blank line(s), included in output of dpkg-parsechangelog]
1576 * <var>even more change details</var>
1578 [optional blank line(s), stripped]
1580 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1585 <var>package</var> and <var>version</var> are the source
1586 package name and version number.
1590 <var>distribution(s)</var> lists the distributions where
1591 this version should be installed when it is uploaded - it
1592 is copied to the <tt>Distribution</tt> field in the
1593 <file>.changes</file> file. See <ref id="f-Distribution">.
1597 <var>urgency</var> is the value for the <tt>Urgency</tt>
1598 field in the <file>.changes</file> file for the upload
1599 (see <ref id="f-Urgency">). It is not possible to specify
1600 an urgency containing commas; commas are used to separate
1601 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1602 <prgn>dpkg</prgn> changelog format (though there is
1603 currently only one useful <var>keyword</var>,
1608 The change details may in fact be any series of lines
1609 starting with at least two spaces, but conventionally each
1610 change starts with an asterisk and a separating space and
1611 continuation lines are indented so as to bring them in
1612 line with the start of the text above. Blank lines may be
1613 used here to separate groups of changes, if desired.
1617 If this upload resolves bugs recorded in the Bug Tracking
1618 System (BTS), they may be automatically closed on the
1619 inclusion of this package into the Debian archive by
1620 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1621 in the change details.<footnote>
1622 To be precise, the string should match the following
1623 Perl regular expression:
1625 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1627 Then all of the bug numbers listed will be closed by the
1628 archive maintenance script (<prgn>katie</prgn>) using the
1629 <var>version</var> of the changelog entry.
1631 This information is conveyed via the <tt>Closes</tt> field
1632 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1636 The maintainer name and email address used in the changelog
1637 should be the details of the person uploading <em>this</em>
1638 version. They are <em>not</em> necessarily those of the
1639 usual package maintainer. The information here will be
1640 copied to the <tt>Changed-By</tt> field in the
1641 <tt>.changes</tt> file (see <ref id="f-Changed-By">),
1642 and then later used to send an acknowledgement when the
1643 upload has been installed.
1647 The <var>date</var> has the following format<footnote>
1648 This is the same as the format generated by <tt>date
1650 </footnote> (compatible and with the same semantics of
1651 RFC 2822 and RFC 5322):
1652 <example>day-of-week, dd month yyyy hh:mm:ss +zzzz</example>
1654 <list compact="compact">
1656 day-of week is one of: Mon, Tue, Wed, Thu, Fri, Sat, Sun
1659 dd is a one- or two-digit day of the month (01-31)
1662 month is one of: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug,
1665 <item>yyyy is the four-digit year (e.g. 2010)</item>
1666 <item>hh is the two-digit hour (00-23)</item>
1667 <item>mm is the two-digit minutes (00-59)</item>
1668 <item>ss is the two-digit seconds (00-60)</item>
1670 +zzzz or -zzzz is the the time zone offset from Coordinated
1671 Universal Time (UTC). "+" indicates that the time is ahead
1672 of (i.e., east of) UTC and "-" indicates that the time is
1673 behind (i.e., west of) UTC. The first two digits indicate
1674 the hour difference from UTC and the last two digits
1675 indicate the number of additional minutes difference from
1676 UTC. The last two digits must be in the range 00-59.
1682 The first "title" line with the package name must start
1683 at the left hand margin. The "trailer" line with the
1684 maintainer and date details must be preceded by exactly
1685 one space. The maintainer details and the date must be
1686 separated by exactly two spaces.
1690 The entire changelog must be encoded in UTF-8.
1694 For more information on placement of the changelog files
1695 within binary packages, please see <ref id="changelogs">.
1699 <sect id="dpkgcopyright">
1700 <heading>Copyright: <file>debian/copyright</file></heading>
1702 Every package must be accompanied by a verbatim copy of its
1703 copyright information and distribution license in the file
1704 <file>/usr/share/doc/<var>package</var>/copyright</file>
1705 (see <ref id="copyrightfile"> for further details). Also see
1706 <ref id="pkgcopyright"> for further considerations related
1707 to copyrights for packages.
1711 <heading>Error trapping in makefiles</heading>
1714 When <prgn>make</prgn> invokes a command in a makefile
1715 (including your package's upstream makefiles and
1716 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1717 means that <prgn>sh</prgn>'s usual bad error handling
1718 properties apply: if you include a miniature script as one
1719 of the commands in your makefile you'll find that if you
1720 don't do anything about it then errors are not detected
1721 and <prgn>make</prgn> will blithely continue after
1726 Every time you put more than one shell command (this
1727 includes using a loop) in a makefile command you
1728 must make sure that errors are trapped. For
1729 simple compound commands, such as changing directory and
1730 then running a program, using <tt>&&</tt> rather
1731 than semicolon as a command separator is sufficient. For
1732 more complex commands including most loops and
1733 conditionals you should include a separate <tt>set -e</tt>
1734 command at the start of every makefile command that's
1735 actually one of these miniature shell scripts.
1739 <sect id="timestamps">
1740 <heading>Time Stamps</heading>
1742 Maintainers should preserve the modification times of the
1743 upstream source files in a package, as far as is reasonably
1745 The rationale is that there is some information conveyed
1746 by knowing the age of the file, for example, you could
1747 recognize that some documentation is very old by looking
1748 at the modification time, so it would be nice if the
1749 modification time of the upstream source would be
1755 <sect id="restrictions">
1756 <heading>Restrictions on objects in source packages</heading>
1759 The source package may not contain any hard links<footnote>
1761 This is not currently detected when building source
1762 packages, but only when extracting
1766 Hard links may be permitted at some point in the
1767 future, but would require a fair amount of
1770 </footnote>, device special files, sockets or setuid or
1771 setgid files.<footnote>
1772 Setgid directories are allowed.
1777 <sect id="debianrules">
1778 <heading>Main building script: <file>debian/rules</file></heading>
1781 This file must be an executable makefile, and contains the
1782 package-specific recipes for compiling the package and
1783 building binary package(s) from the source.
1787 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1788 so that it can be invoked by saying its name rather than
1789 invoking <prgn>make</prgn> explicitly. That is, invoking
1790 either of <tt>make -f debian/rules <em>args...</em></tt>
1791 or <tt>./debian/rules <em>args...</em></tt> must result in
1796 Since an interactive <file>debian/rules</file> script makes it
1797 impossible to auto-compile that package and also makes it
1798 hard for other people to reproduce the same binary
1799 package, all <em>required targets</em> must be
1800 non-interactive. At a minimum, required targets are the
1801 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1802 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1803 <em>binary-indep</em>, and <em>build</em>. It also follows
1804 that any target that these targets depend on must also be
1809 The targets are as follows (required unless stated otherwise):
1811 <tag><tt>build</tt></tag>
1814 The <tt>build</tt> target should perform all the
1815 configuration and compilation of the package.
1816 If a package has an interactive pre-build
1817 configuration routine, the Debian source package
1818 must either be built after this has taken place (so
1819 that the binary package can be built without rerunning
1820 the configuration) or the configuration routine
1821 modified to become non-interactive. (The latter is
1822 preferable if there are architecture-specific features
1823 detected by the configuration routine.)
1827 For some packages, notably ones where the same
1828 source tree is compiled in different ways to produce
1829 two binary packages, the <tt>build</tt> target
1830 does not make much sense. For these packages it is
1831 good enough to provide two (or more) targets
1832 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1833 for each of the ways of building the package, and a
1834 <tt>build</tt> target that does nothing. The
1835 <tt>binary</tt> target will have to build the
1836 package in each of the possible ways and make the
1837 binary package out of each.
1841 The <tt>build</tt> target must not do anything
1842 that might require root privilege.
1846 The <tt>build</tt> target may need to run the
1847 <tt>clean</tt> target first - see below.
1851 When a package has a configuration and build routine
1852 which takes a long time, or when the makefiles are
1853 poorly designed, or when <tt>build</tt> needs to
1854 run <tt>clean</tt> first, it is a good idea to
1855 <tt>touch build</tt> when the build process is
1856 complete. This will ensure that if <tt>debian/rules
1857 build</tt> is run again it will not rebuild the whole
1859 Another common way to do this is for <tt>build</tt>
1860 to depend on <prgn>build-stamp</prgn> and to do
1861 nothing else, and for the <prgn>build-stamp</prgn>
1862 target to do the building and to <tt>touch
1863 build-stamp</tt> on completion. This is
1864 especially useful if the build routine creates a
1865 file or directory called <tt>build</tt>; in such a
1866 case, <tt>build</tt> will need to be listed as
1867 a phony target (i.e., as a dependency of the
1868 <tt>.PHONY</tt> target). See the documentation of
1869 <prgn>make</prgn> for more information on phony
1875 <tag><tt>build-arch</tt> (optional),
1876 <tt>build-indep</tt> (optional)
1880 A package may also provide both of the targets
1881 <tt>build-arch</tt> and <tt>build-indep</tt>.
1882 The <tt>build-arch</tt> target, if provided, should
1883 perform all the configuration and compilation required for
1884 producing all architecture-dependant binary packages
1885 (those packages for which the body of the
1886 <tt>Architecture</tt> field in <tt>debian/control</tt> is
1887 not <tt>all</tt>). Similarly, the <tt>build-indep</tt>
1888 target, if provided, should perform all the configuration
1889 and compilation required for producing all
1890 architecture-independent binary packages (those packages
1891 for which the body of the <tt>Architecture</tt> field
1892 in <tt>debian/control</tt> is <tt>all</tt>).
1893 The <tt>build</tt> target should depend on those of the
1894 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1895 are provided in the rules file.<footnote>
1896 The intent of this split is so that binary-only builds
1897 need not install the dependencies required for
1898 the <tt>build-indep</tt> target. However, this is not
1899 yet used in practice since <tt>dpkg-buildpackage
1900 -B</tt>, and therefore the autobuilders,
1901 invoke <tt>build</tt> rather than <tt>build-arch</tt>
1902 due to the difficulties in determining whether the
1903 optional <tt>build-arch</tt> target exists.
1908 If one or both of the targets <tt>build-arch</tt> and
1909 <tt>build-indep</tt> are not provided, then invoking
1910 <file>debian/rules</file> with one of the not-provided
1911 targets as arguments should produce a exit status code
1912 of 2. Usually this is provided automatically by make
1913 if the target is missing.
1917 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1918 must not do anything that might require root privilege.
1922 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1923 <tt>binary-indep</tt>
1927 The <tt>binary</tt> target must be all that is
1928 necessary for the user to build the binary package(s)
1929 produced from this source package. It is
1930 split into two parts: <prgn>binary-arch</prgn> builds
1931 the binary packages which are specific to a particular
1932 architecture, and <tt>binary-indep</tt> builds
1933 those which are not.
1936 <tt>binary</tt> may be (and commonly is) a target with
1937 no commands which simply depends on
1938 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1941 Both <tt>binary-*</tt> targets should depend on the
1942 <tt>build</tt> target, or on the appropriate
1943 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1944 provided, so that the package is built if it has not
1945 been already. It should then create the relevant
1946 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1947 make their control files and <prgn>dpkg-deb</prgn> to
1948 build them and place them in the parent of the top
1953 Both the <tt>binary-arch</tt> and
1954 <tt>binary-indep</tt> targets <em>must</em> exist.
1955 If one of them has nothing to do (which will always be
1956 the case if the source generates only a single binary
1957 package, whether architecture-dependent or not), it
1958 must still exist and must always succeed.
1962 The <tt>binary</tt> targets must be invoked as
1964 The <prgn>fakeroot</prgn> package often allows one
1965 to build a package correctly even without being
1971 <tag><tt>clean</tt></tag>
1974 This must undo any effects that the <tt>build</tt>
1975 and <tt>binary</tt> targets may have had, except
1976 that it should leave alone any output files created in
1977 the parent directory by a run of a <tt>binary</tt>
1982 If a <tt>build</tt> file is touched at the end of
1983 the <tt>build</tt> target, as suggested above, it
1984 should be removed as the first action that
1985 <tt>clean</tt> performs, so that running
1986 <tt>build</tt> again after an interrupted
1987 <tt>clean</tt> doesn't think that everything is
1992 The <tt>clean</tt> target may need to be
1993 invoked as root if <tt>binary</tt> has been
1994 invoked since the last <tt>clean</tt>, or if
1995 <tt>build</tt> has been invoked as root (since
1996 <tt>build</tt> may create directories, for
2001 <tag><tt>get-orig-source</tt> (optional)</tag>
2004 This target fetches the most recent version of the
2005 original source package from a canonical archive site
2006 (via FTP or WWW, for example), does any necessary
2007 rearrangement to turn it into the original source
2008 tar file format described below, and leaves it in the
2013 This target may be invoked in any directory, and
2014 should take care to clean up any temporary files it
2019 This target is optional, but providing it if
2020 possible is a good idea.
2024 <tag><tt>patch</tt> (optional)</tag>
2027 This target performs whatever additional actions are
2028 required to make the source ready for editing (unpacking
2029 additional upstream archives, applying patches, etc.).
2030 It is recommended to be implemented for any package where
2031 <tt>dpkg-source -x</tt> does not result in source ready
2032 for additional modification. See
2033 <ref id="readmesource">.
2039 The <tt>build</tt>, <tt>binary</tt> and
2040 <tt>clean</tt> targets must be invoked with the current
2041 directory being the package's top-level directory.
2046 Additional targets may exist in <file>debian/rules</file>,
2047 either as published or undocumented interfaces or for the
2048 package's internal use.
2052 The architectures we build on and build for are determined
2053 by <prgn>make</prgn> variables using the utility
2054 <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
2055 You can determine the
2056 Debian architecture and the GNU style architecture
2057 specification string for the build machine (the machine type
2058 we are building on) as well as for the host machine (the
2059 machine type we are building for). Here is a list of
2060 supported <prgn>make</prgn> variables:
2061 <list compact="compact">
2063 <tt>DEB_*_ARCH</tt> (the Debian architecture)
2066 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2069 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2072 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2073 specification string)
2076 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2077 <tt>DEB_*_GNU_TYPE</tt>)
2080 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2081 <tt>DEB_*_GNU_TYPE</tt>)
2083 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2084 the build machine or <tt>HOST</tt> for specification of the
2089 Backward compatibility can be provided in the rules file
2090 by setting the needed variables to suitable default
2091 values; please refer to the documentation of
2092 <prgn>dpkg-architecture</prgn> for details.
2096 It is important to understand that the <tt>DEB_*_ARCH</tt>
2097 string only determines which Debian architecture we are
2098 building on or for. It should not be used to get the CPU
2099 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2100 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2101 GNU style variables should generally only be used with upstream
2105 <sect1 id="debianrules-options">
2106 <heading><file>debian/rules</file> and
2107 <tt>DEB_BUILD_OPTIONS</tt></heading>
2110 Supporting the standardized environment variable
2111 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2112 contain several flags to change how a package is compiled and
2113 built. Each flag must be in the form <var>flag</var> or
2114 <var>flag</var>=<var>options</var>. If multiple flags are
2115 given, they must be separated by whitespace.<footnote>
2116 Some packages support any delimiter, but whitespace is the
2117 easiest to parse inside a makefile and avoids ambiguity with
2118 flag values that contain commas.
2120 <var>flag</var> must start with a lowercase letter
2121 (<tt>a-z</tt>) and consist only of lowercase letters,
2122 numbers (<tt>0-9</tt>), and the characters
2123 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2124 <var>options</var> must not contain whitespace. The same
2125 tag should not be given multiple times with conflicting
2126 values. Package maintainers may assume that
2127 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2131 The meaning of the following tags has been standardized:
2135 This tag says to not run any build-time test suite
2136 provided by the package.
2140 The presence of this tag means that the package should
2141 be compiled with a minimum of optimization. For C
2142 programs, it is best to add <tt>-O0</tt> to
2143 <tt>CFLAGS</tt> (although this is usually the default).
2144 Some programs might fail to build or run at this level
2145 of optimization; it may be necessary to use
2146 <tt>-O1</tt>, for example.
2150 This tag means that the debugging symbols should not be
2151 stripped from the binary during installation, so that
2152 debugging information may be included in the package.
2154 <tag>parallel=n</tag>
2156 This tag means that the package should be built using up
2157 to <tt>n</tt> parallel processes if the package build
2158 system supports this.<footnote>
2159 Packages built with <tt>make</tt> can often implement
2160 this by passing the <tt>-j</tt><var>n</var> option to
2163 If the package build system does not support parallel
2164 builds, this string must be ignored. If the package
2165 build system only supports a lower level of concurrency
2166 than <var>n</var>, the package should be built using as
2167 many parallel processes as the package build system
2168 supports. It is up to the package maintainer to decide
2169 whether the package build times are long enough and the
2170 package build system is robust enough to make supporting
2171 parallel builds worthwhile.
2177 Unknown flags must be ignored by <file>debian/rules</file>.
2181 The following makefile snippet is an example of how one may
2182 implement the build options; you will probably have to
2183 massage this example in order to make it work for your
2185 <example compact="compact">
2188 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2189 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2190 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2191 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2193 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2198 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2199 INSTALL_PROGRAM += -s
2201 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2202 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2203 MAKEFLAGS += -j$(NUMJOBS)
2208 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2209 # Code to run the package test suite.
2216 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2217 <sect id="substvars">
2218 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2221 When <prgn>dpkg-gencontrol</prgn>
2222 generates <qref id="binarycontrolfiles">binary package control
2223 files</qref> (<file>DEBIAN/control</file>), it performs variable
2224 substitutions on its output just before writing it. Variable
2225 substitutions have the form <tt>${<var>variable</var>}</tt>.
2226 The optional file <file>debian/substvars</file> contains
2227 variable substitutions to be used; variables can also be set
2228 directly from <file>debian/rules</file> using the <tt>-V</tt>
2229 option to the source packaging commands, and certain predefined
2230 variables are also available.
2234 The <file>debian/substvars</file> file is usually generated and
2235 modified dynamically by <file>debian/rules</file> targets, in
2236 which case it must be removed by the <tt>clean</tt> target.
2240 See <manref name="deb-substvars" section="5"> for full
2241 details about source variable substitutions, including the
2242 format of <file>debian/substvars</file>.</p>
2245 <sect id="debianwatch">
2246 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2249 This is an optional, recommended configuration file for the
2250 <tt>uscan</tt> utility which defines how to automatically scan
2251 ftp or http sites for newly available updates of the
2252 package. This is used
2253 by <url id="http://dehs.alioth.debian.org/"> and other Debian QA
2254 tools to help with quality control and maintenance of the
2255 distribution as a whole.
2260 <sect id="debianfiles">
2261 <heading>Generated files list: <file>debian/files</file></heading>
2264 This file is not a permanent part of the source tree; it
2265 is used while building packages to record which files are
2266 being generated. <prgn>dpkg-genchanges</prgn> uses it
2267 when it generates a <file>.changes</file> file.
2271 It should not exist in a shipped source package, and so it
2272 (and any backup files or temporary files such as
2273 <file>files.new</file><footnote>
2274 <file>files.new</file> is used as a temporary file by
2275 <prgn>dpkg-gencontrol</prgn> and
2276 <prgn>dpkg-distaddfile</prgn> - they write a new
2277 version of <tt>files</tt> here before renaming it,
2278 to avoid leaving a corrupted copy if an error
2280 </footnote>) should be removed by the
2281 <tt>clean</tt> target. It may also be wise to
2282 ensure a fresh start by emptying or removing it at the
2283 start of the <tt>binary</tt> target.
2287 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2288 package, it adds an entry to <file>debian/files</file> for the
2289 <file>.deb</file> file that will be created when <tt>dpkg-deb
2290 --build</tt> is run for that binary package. So for most
2291 packages all that needs to be done with this file is to
2292 delete it in the <tt>clean</tt> target.
2296 If a package upload includes files besides the source
2297 package and any binary packages whose control files were
2298 made with <prgn>dpkg-gencontrol</prgn> then they should be
2299 placed in the parent of the package's top-level directory
2300 and <prgn>dpkg-distaddfile</prgn> should be called to add
2301 the file to the list in <file>debian/files</file>.</p>
2304 <sect id="embeddedfiles">
2305 <heading>Convenience copies of code</heading>
2308 Some software packages include in their distribution convenience
2309 copies of code from other software packages, generally so that
2310 users compiling from source don't have to download multiple
2311 packages. Debian packages should not make use of these
2312 convenience copies unless the included package is explicitly
2313 intended to be used in this way.<footnote>
2314 For example, parts of the GNU build system work like this.
2316 If the included code is already in the Debian archive in the
2317 form of a library, the Debian packaging should ensure that
2318 binary packages reference the libraries already in Debian and
2319 the convenience copy is not used. If the included code is not
2320 already in Debian, it should be packaged separately as a
2321 prerequisite if possible.
2323 Having multiple copies of the same code in Debian is
2324 inefficient, often creates either static linking or shared
2325 library conflicts, and, most importantly, increases the
2326 difficulty of handling security vulnerabilities in the
2332 <sect id="readmesource">
2333 <heading>Source package handling:
2334 <file>debian/README.source</file></heading>
2337 If running <prgn>dpkg-source -x</prgn> on a source package
2338 doesn't produce the source of the package, ready for editing,
2339 and allow one to make changes and run
2340 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2341 without taking any additional steps, creating a
2342 <file>debian/README.source</file> documentation file is
2343 recommended. This file should explain how to do all of the
2346 <item>Generate the fully patched source, in a form ready for
2347 editing, that would be built to create Debian
2348 packages. Doing this with a <tt>patch</tt> target in
2349 <file>debian/rules</file> is recommended; see
2350 <ref id="debianrules">.</item>
2351 <item>Modify the source and save those modifications so that
2352 they will be applied when building the package.</item>
2353 <item>Remove source modifications that are currently being
2354 applied when building the package.</item>
2355 <item>Optionally, document what steps are necessary to
2356 upgrade the Debian source package to a new upstream version,
2357 if applicable.</item>
2359 This explanation should include specific commands and mention
2360 any additional required Debian packages. It should not assume
2361 familiarity with any specific Debian packaging system or patch
2366 This explanation may refer to a documentation file installed by
2367 one of the package's build dependencies provided that the
2368 referenced documentation clearly explains these tasks and is not
2369 a general reference manual.
2373 <file>debian/README.source</file> may also include any other
2374 information that would be helpful to someone modifying the
2375 source package. Even if the package doesn't fit the above
2376 description, maintainers are encouraged to document in a
2377 <file>debian/README.source</file> file any source package with a
2378 particularly complex or unintuitive source layout or build
2379 system (for example, a package that builds the same source
2380 multiple times to generate different binary packages).
2386 <chapt id="controlfields">
2387 <heading>Control files and their fields</heading>
2390 The package management system manipulates data represented in
2391 a common format, known as <em>control data</em>, stored in
2392 <em>control files</em>.
2393 Control files are used for source packages, binary packages and
2394 the <file>.changes</file> files which control the installation
2395 of uploaded files<footnote>
2396 <prgn>dpkg</prgn>'s internal databases are in a similar
2401 <sect id="controlsyntax">
2402 <heading>Syntax of control files</heading>
2405 A control file consists of one or more paragraphs of
2407 The paragraphs are also sometimes referred to as stanzas.
2409 The paragraphs are separated by blank lines. Some control
2410 files allow only one paragraph; others allow several, in
2411 which case each paragraph usually refers to a different
2412 package. (For example, in source packages, the first
2413 paragraph refers to the source package, and later paragraphs
2414 refer to binary packages generated from the source.)
2418 Each paragraph consists of a series of data fields; each
2419 field consists of the field name, followed by a colon and
2420 then the data/value associated with that field. It ends at
2421 the end of the (logical) line. Horizontal whitespace
2422 (spaces and tabs) may occur immediately before or after the
2423 value and is ignored there; it is conventional to put a
2424 single space after the colon. For example, a field might
2426 <example compact="compact">
2429 the field name is <tt>Package</tt> and the field value
2434 A paragraph must not contain more than one instance of a
2435 particular field name.
2439 Many fields' values may span several lines; in this case
2440 each continuation line must start with a space or a tab.
2441 Any trailing spaces or tabs at the end of individual
2442 lines of a field value are ignored.
2446 In fields where it is specified that lines may not wrap,
2447 only a single line of data is allowed and whitespace is not
2448 significant in a field body. Whitespace must not appear
2449 inside names (of packages, architectures, files or anything
2450 else) or version numbers, or between the characters of
2451 multi-character version relationships.
2455 Field names are not case-sensitive, but it is usual to
2456 capitalize the field names using mixed case as shown below.
2457 Field values are case-sensitive unless the description of the
2458 field says otherwise.
2462 Blank lines, or lines consisting only of spaces and tabs,
2463 are not allowed within field values or between fields - that
2464 would mean a new paragraph.
2468 All control files must be encoded in UTF-8.
2472 <sect id="sourcecontrolfiles">
2473 <heading>Source package control files -- <file>debian/control</file></heading>
2476 The <file>debian/control</file> file contains the most vital
2477 (and version-independent) information about the source package
2478 and about the binary packages it creates.
2482 The first paragraph of the control file contains information about
2483 the source package in general. The subsequent sets each describe a
2484 binary package that the source tree builds.
2488 The fields in the general paragraph (the first one, for the source
2491 <list compact="compact">
2492 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2493 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2494 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2495 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2496 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2497 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2498 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2499 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2504 The fields in the binary package paragraphs are:
2506 <list compact="compact">
2507 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2508 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2509 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2510 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2511 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2512 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2513 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2514 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2519 The syntax and semantics of the fields are described below.
2523 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2524 generate control files for binary packages (see below), by
2525 <prgn>dpkg-genchanges</prgn> to generate the
2526 <file>.changes</file> file to accompany the upload, and by
2527 <prgn>dpkg-source</prgn> when it creates the
2528 <file>.dsc</file> source control file as part of a source
2529 archive. Many fields are permitted to span multiple lines in
2530 <file>debian/control</file> but not in any other control
2531 file. These tools are responsible for removing the line
2532 breaks from such fields when using fields from
2533 <file>debian/control</file> to generate other control files.
2537 The fields here may contain variable references - their
2538 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2539 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2540 when they generate output control files.
2541 See <ref id="substvars"> for details.
2545 In addition to the control file syntax described <qref
2546 id="controlsyntax">above</qref>, this file may also contain
2547 comment lines starting with <tt>#</tt> without any preceding
2548 whitespace. All such lines are ignored, even in the middle of
2549 continuation lines for a multiline field, and do not end a
2555 <sect id="binarycontrolfiles">
2556 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2559 The <file>DEBIAN/control</file> file contains the most vital
2560 (and version-dependent) information about a binary package. It
2561 consists of a single paragraph.
2565 The fields in this file are:
2567 <list compact="compact">
2568 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2569 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2570 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2571 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2572 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2573 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2574 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2575 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2576 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2577 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2578 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2579 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2584 <sect id="debiansourcecontrolfiles">
2585 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2588 This file consists of a single paragraph, possibly surrounded by
2589 a PGP signature. The fields of that paragraph are listed below.
2590 Their syntax is described above, in <ref id="pkg-controlfields">.
2592 <list compact="compact">
2593 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2594 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2595 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2596 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2597 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2598 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2599 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2600 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2601 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2602 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2603 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2604 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2605 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2610 The source package control file is generated by
2611 <prgn>dpkg-source</prgn> when it builds the source
2612 archive, from other files in the source package,
2613 described above. When unpacking, it is checked against
2614 the files and directories in the other parts of the
2620 <sect id="debianchangesfiles">
2621 <heading>Debian changes files -- <file>.changes</file></heading>
2624 The <file>.changes</file> files are used by the Debian archive
2625 maintenance software to process updates to packages. They
2626 consist of a single paragraph, possibly surrounded by a PGP
2627 signature. That paragraph contains information from the
2628 <file>debian/control</file> file and other data about the
2629 source package gathered via <file>debian/changelog</file>
2630 and <file>debian/rules</file>.
2634 <file>.changes</file> files have a format version that is
2635 incremented whenever the documented fields or their meaning
2636 change. This document describes format &changesversion;.
2640 The fields in this file are:
2642 <list compact="compact">
2643 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2644 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2645 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2646 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2647 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2648 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2649 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2650 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2651 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2652 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2653 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2654 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2655 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2656 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2657 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2658 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2663 <sect id="controlfieldslist">
2664 <heading>List of fields</heading>
2666 <sect1 id="f-Source">
2667 <heading><tt>Source</tt></heading>
2670 This field identifies the source package name.
2674 In <file>debian/control</file> or a <file>.dsc</file> file,
2675 this field must contain only the name of the source package.
2679 In a binary package control file or a <file>.changes</file>
2680 file, the source package name may be followed by a version
2681 number in parentheses<footnote>
2682 It is customary to leave a space after the package name
2683 if a version number is specified.
2685 This version number may be omitted (and is, by
2686 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2687 the <tt>Version</tt> field of the binary package in
2688 question. The field itself may be omitted from a binary
2689 package control file when the source package has the same
2690 name and version as the binary package.
2694 Package names (both source and binary,
2695 see <ref id="f-Package">) must consist only of lower case
2696 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2697 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2698 (<tt>.</tt>). They must be at least two characters long and
2699 must start with an alphanumeric character.
2703 <sect1 id="f-Maintainer">
2704 <heading><tt>Maintainer</tt></heading>
2707 The package maintainer's name and email address. The name
2708 must come first, then the email address inside angle
2709 brackets <tt><></tt> (in RFC822 format).
2713 If the maintainer's name contains a full stop then the
2714 whole field will not work directly as an email address due
2715 to a misfeature in the syntax specified in RFC822; a
2716 program using this field as an address must check for this
2717 and correct the problem if necessary (for example by
2718 putting the name in round brackets and moving it to the
2719 end, and bringing the email address forward).
2723 <sect1 id="f-Uploaders">
2724 <heading><tt>Uploaders</tt></heading>
2727 List of the names and email addresses of co-maintainers of
2728 the package, if any. If the package has other maintainers
2729 beside the one named in the
2730 <qref id="f-Maintainer">Maintainer field</qref>, their names
2731 and email addresses should be listed here. The format of each
2732 entry is the same as that of the Maintainer field, and
2733 multiple entries must be comma separated. This is an optional
2738 Any parser that interprets the Uploaders field in
2739 <file>debian/control</file> must permit it to span multiple
2740 lines. Line breaks in an Uploaders field that spans multiple
2741 lines are not significant and the semantics of the field are
2742 the same as if the line breaks had not been present.
2746 <sect1 id="f-Changed-By">
2747 <heading><tt>Changed-By</tt></heading>
2750 The name and email address of the person who prepared this
2751 version of the package, usually a maintainer. The syntax is
2752 the same as for the <qref id="f-Maintainer">Maintainer
2757 <sect1 id="f-Section">
2758 <heading><tt>Section</tt></heading>
2761 This field specifies an application area into which the package
2762 has been classified. See <ref id="subsections">.
2766 When it appears in the <file>debian/control</file> file,
2767 it gives the value for the subfield of the same name in
2768 the <tt>Files</tt> field of the <file>.changes</file> file.
2769 It also gives the default for the same field in the binary
2774 <sect1 id="f-Priority">
2775 <heading><tt>Priority</tt></heading>
2778 This field represents how important it is that the user
2779 have the package installed. See <ref id="priorities">.
2783 When it appears in the <file>debian/control</file> file,
2784 it gives the value for the subfield of the same name in
2785 the <tt>Files</tt> field of the <file>.changes</file> file.
2786 It also gives the default for the same field in the binary
2791 <sect1 id="f-Package">
2792 <heading><tt>Package</tt></heading>
2795 The name of the binary package.
2799 Binary package names must follow the same syntax and
2800 restrictions as source package names. See <ref id="f-Source">
2805 <sect1 id="f-Architecture">
2806 <heading><tt>Architecture</tt></heading>
2809 Depending on context and the control file used, the
2810 <tt>Architecture</tt> field can include the following sets of
2814 A unique single word identifying a Debian machine
2815 architecture as described in <ref id="arch-spec">.
2818 An architecture wildcard identifying a set of Debian
2819 machine architectures, see <ref id="arch-wildcard-spec">.
2820 <tt>any</tt> matches all Debian machine architectures
2821 and is the most frequently used.
2824 <tt>all</tt>, which indicates an
2825 architecture-independent package.
2828 <tt>source</tt>, which indicates a source package.
2834 In the main <file>debian/control</file> file in the source
2835 package, this field may contain the special
2836 value <tt>all</tt>, the special architecture
2837 wildcard <tt>any</tt>, or a list of specific and wildcard
2838 architectures separated by spaces. If <tt>all</tt>
2839 or <tt>any</tt> appears, that value must be the entire
2840 contents of the field. Most packages will use
2841 either <tt>all</tt> or <tt>any</tt>.
2845 Specifying a specific list of architectures indicates that the
2846 source will build an architecture-dependent package only on
2847 architectures included in the list. Specifying a list of
2848 architecture wildcards indicates that the source will build an
2849 architecture-dependent package on only those architectures
2850 that match any of the specified architecture wildcards.
2851 Specifying a list of architectures or architecture wildcards
2852 other than <tt>any</tt> is for the minority of cases where a
2853 program is not portable or is not useful on some
2854 architectures. Where possible, the program should be made
2859 In the source package control file <file>.dsc</file>, this
2860 field may contain either the architecture
2861 wildcard <tt>any</tt> or a list of architectures and
2862 architecture wildcards separated by spaces. If a list is
2863 given, it may include (or consist solely of) the special
2864 value <tt>all</tt>. In other words, in <file>.dsc</file>
2865 files unlike the <file>debian/control</file>, <tt>all</tt> may
2866 occur in combination with specific architectures.
2867 The <tt>Architecture</tt> field in the source package control
2868 file <file>.dsc</file> is generally constructed from
2869 the <tt>Architecture</tt> fields in
2870 the <file>debian/control</file> in the source package.
2874 Specifying <tt>any</tt> indicates that the source package
2875 isn't dependent on any particular architecture and should
2876 compile fine on any one. The produced binary package(s)
2877 will either be specific to whatever the current build
2878 architecture is or will be architecture-independent.
2882 Specifying only <tt>all</tt> indicates that the source package
2883 will only build architecture-independent packages. If this is
2884 the case, <tt>all</tt> must be used rather than <tt>any</tt>;
2885 <tt>any</tt> implies that the source package will build at
2886 least one architecture-dependent package.
2890 Specifying a list of architectures or architecture wildcards
2891 indicates that the source will build an architecture-dependent
2892 package, and will only work correctly on the listed or
2893 matching architectures. If the source package also builds at
2894 least one architecture-independent package, <tt>all</tt> will
2895 also be included in the list.
2899 In a <file>.changes</file> file, the <tt>Architecture</tt>
2900 field lists the architecture(s) of the package(s) currently
2901 being uploaded. This will be a list; if the source for the
2902 package is also being uploaded, the special
2903 entry <tt>source</tt> is also present. <tt>all</tt> will be
2904 present if any architecture-independent packages are being
2905 uploaded. Architecture wildcards such as <tt>any</tt> must
2906 never occur in the <tt>Architecture</tt> field in
2907 the <file>.changes</file> file.
2911 See <ref id="debianrules"> for information on how to get
2912 the architecture for the build process.
2916 <sect1 id="f-Essential">
2917 <heading><tt>Essential</tt></heading>
2920 This is a boolean field which may occur only in the
2921 control file of a binary package or in a per-package fields
2922 paragraph of a main source control data file.
2926 If set to <tt>yes</tt> then the package management system
2927 will refuse to remove the package (upgrading and replacing
2928 it is still possible). The other possible value is <tt>no</tt>,
2929 which is the same as not having the field at all.
2934 <heading>Package interrelationship fields:
2935 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2936 <tt>Recommends</tt>, <tt>Suggests</tt>,
2937 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2938 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2942 These fields describe the package's relationships with
2943 other packages. Their syntax and semantics are described
2944 in <ref id="relationships">.</p>
2947 <sect1 id="f-Standards-Version">
2948 <heading><tt>Standards-Version</tt></heading>
2951 The most recent version of the standards (the policy
2952 manual and associated texts) with which the package
2957 The version number has four components: major and minor
2958 version number and major and minor patch level. When the
2959 standards change in a way that requires every package to
2960 change the major number will be changed. Significant
2961 changes that will require work in many packages will be
2962 signaled by a change to the minor number. The major patch
2963 level will be changed for any change to the meaning of the
2964 standards, however small; the minor patch level will be
2965 changed when only cosmetic, typographical or other edits
2966 are made which neither change the meaning of the document
2967 nor affect the contents of packages.
2971 Thus only the first three components of the policy version
2972 are significant in the <em>Standards-Version</em> control
2973 field, and so either these three components or all four
2974 components may be specified.<footnote>
2975 In the past, people specified the full version number
2976 in the Standards-Version field, for example "2.3.0.0".
2977 Since minor patch-level changes don't introduce new
2978 policy, it was thought it would be better to relax
2979 policy and only require the first 3 components to be
2980 specified, in this example "2.3.0". All four
2981 components may still be used if someone wishes to do so.
2987 <sect1 id="f-Version">
2988 <heading><tt>Version</tt></heading>
2991 The version number of a package. The format is:
2992 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
2996 The three components here are:
2998 <tag><var>epoch</var></tag>
3001 This is a single (generally small) unsigned integer. It
3002 may be omitted, in which case zero is assumed. If it is
3003 omitted then the <var>upstream_version</var> may not
3008 It is provided to allow mistakes in the version numbers
3009 of older versions of a package, and also a package's
3010 previous version numbering schemes, to be left behind.
3014 <tag><var>upstream_version</var></tag>
3017 This is the main part of the version number. It is
3018 usually the version number of the original ("upstream")
3019 package from which the <file>.deb</file> file has been made,
3020 if this is applicable. Usually this will be in the same
3021 format as that specified by the upstream author(s);
3022 however, it may need to be reformatted to fit into the
3023 package management system's format and comparison
3028 The comparison behavior of the package management system
3029 with respect to the <var>upstream_version</var> is
3030 described below. The <var>upstream_version</var>
3031 portion of the version number is mandatory.
3035 The <var>upstream_version</var> may contain only
3036 alphanumerics<footnote>
3037 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3039 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3040 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3041 tilde) and should start with a digit. If there is no
3042 <var>debian_revision</var> then hyphens are not allowed;
3043 if there is no <var>epoch</var> then colons are not
3048 <tag><var>debian_revision</var></tag>
3051 This part of the version number specifies the version of
3052 the Debian package based on the upstream version. It
3053 may contain only alphanumerics and the characters
3054 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3055 tilde) and is compared in the same way as the
3056 <var>upstream_version</var> is.
3060 It is optional; if it isn't present then the
3061 <var>upstream_version</var> may not contain a hyphen.
3062 This format represents the case where a piece of
3063 software was written specifically to be a Debian
3064 package, where the Debian package source must always
3065 be identical to the pristine source and therefore no
3066 revision indication is required.
3070 It is conventional to restart the
3071 <var>debian_revision</var> at <tt>1</tt> each time the
3072 <var>upstream_version</var> is increased.
3076 The package management system will break the version
3077 number apart at the last hyphen in the string (if there
3078 is one) to determine the <var>upstream_version</var> and
3079 <var>debian_revision</var>. The absence of a
3080 <var>debian_revision</var> is equivalent to a
3081 <var>debian_revision</var> of <tt>0</tt>.
3088 When comparing two version numbers, first the <var>epoch</var>
3089 of each are compared, then the <var>upstream_version</var> if
3090 <var>epoch</var> is equal, and then <var>debian_revision</var>
3091 if <var>upstream_version</var> is also equal.
3092 <var>epoch</var> is compared numerically. The
3093 <var>upstream_version</var> and <var>debian_revision</var>
3094 parts are compared by the package management system using the
3095 following algorithm:
3099 The strings are compared from left to right.
3103 First the initial part of each string consisting entirely of
3104 non-digit characters is determined. These two parts (one of
3105 which may be empty) are compared lexically. If a difference
3106 is found it is returned. The lexical comparison is a
3107 comparison of ASCII values modified so that all the letters
3108 sort earlier than all the non-letters and so that a tilde
3109 sorts before anything, even the end of a part. For example,
3110 the following parts are in sorted order from earliest to
3111 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3112 <tt>a</tt>.<footnote>
3113 One common use of <tt>~</tt> is for upstream pre-releases.
3114 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3115 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3120 Then the initial part of the remainder of each string which
3121 consists entirely of digit characters is determined. The
3122 numerical values of these two parts are compared, and any
3123 difference found is returned as the result of the comparison.
3124 For these purposes an empty string (which can only occur at
3125 the end of one or both version strings being compared) counts
3130 These two steps (comparing and removing initial non-digit
3131 strings and initial digit strings) are repeated until a
3132 difference is found or both strings are exhausted.
3136 Note that the purpose of epochs is to allow us to leave behind
3137 mistakes in version numbering, and to cope with situations
3138 where the version numbering scheme changes. It is
3139 <em>not</em> intended to cope with version numbers containing
3140 strings of letters which the package management system cannot
3141 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3142 silly orderings.<footnote>
3143 The author of this manual has heard of a package whose
3144 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3145 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3151 <sect1 id="f-Description">
3152 <heading><tt>Description</tt></heading>
3155 In a source or binary control file, the <tt>Description</tt>
3156 field contains a description of the binary package, consisting
3157 of two parts, the synopsis or the short description, and the
3158 long description. The field's format is as follows:
3163 Description: <single line synopsis>
3164 <extended description over several lines>
3169 The lines in the extended description can have these formats:
3175 Those starting with a single space are part of a paragraph.
3176 Successive lines of this form will be word-wrapped when
3177 displayed. The leading space will usually be stripped off.
3181 Those starting with two or more spaces. These will be
3182 displayed verbatim. If the display cannot be panned
3183 horizontally, the displaying program will line wrap them "hard"
3184 (i.e., without taking account of word breaks). If it can they
3185 will be allowed to trail off to the right. None, one or two
3186 initial spaces may be deleted, but the number of spaces
3187 deleted from each line will be the same (so that you can have
3188 indenting work correctly, for example).
3192 Those containing a single space followed by a single full stop
3193 character. These are rendered as blank lines. This is the
3194 <em>only</em> way to get a blank line<footnote>
3195 Completely empty lines will not be rendered as blank lines.
3196 Instead, they will cause the parser to think you're starting
3197 a whole new record in the control file, and will therefore
3198 likely abort with an error.
3203 Those containing a space, a full stop and some more characters.
3204 These are for future expansion. Do not use them.
3210 Do not use tab characters. Their effect is not predictable.
3214 See <ref id="descriptions"> for further information on this.
3218 In a <file>.changes</file> file, the <tt>Description</tt>
3219 field contains a summary of the descriptions for the packages
3220 being uploaded. For this case, the first line of the field
3221 value (the part on the same line as <tt>Description:</tt>) is
3222 always empty. The content of the field is expressed as
3223 continuation lines, one line per package. Each line is
3224 indented by one space and contains the name of a binary
3225 package, a space, a hyphen (<tt>-</tt>), a space, and the
3226 short description line from that package.
3230 <sect1 id="f-Distribution">
3231 <heading><tt>Distribution</tt></heading>
3234 In a <file>.changes</file> file or parsed changelog output
3235 this contains the (space-separated) name(s) of the
3236 distribution(s) where this version of the package should
3237 be installed. Valid distributions are determined by the
3238 archive maintainers.<footnote>
3239 Example distribution names in the Debian archive used in
3240 <file>.changes</file> files are:
3241 <taglist compact="compact">
3242 <tag><em>unstable</em></tag>
3244 This distribution value refers to the
3245 <em>developmental</em> part of the Debian distribution
3246 tree. Most new packages, new upstream versions of
3247 packages and bug fixes go into the <em>unstable</em>
3251 <tag><em>experimental</em></tag>
3253 The packages with this distribution value are deemed
3254 by their maintainers to be high risk. Oftentimes they
3255 represent early beta or developmental packages from
3256 various sources that the maintainers want people to
3257 try, but are not ready to be a part of the other parts
3258 of the Debian distribution tree.
3263 Others are used for updating stable releases or for
3264 security uploads. More information is available in the
3265 Debian Developer's Reference, section "The Debian
3269 The Debian archive software only supports listing a single
3270 distribution. Migration of packages to other distributions is
3271 handled outside of the upload process.
3276 <heading><tt>Date</tt></heading>
3279 This field includes the date the package was built or last
3280 edited. It must be in the same format as the <var>date</var>
3281 in a <file>debian/changelog</file> entry.
3285 The value of this field is usually extracted from the
3286 <file>debian/changelog</file> file - see
3287 <ref id="dpkgchangelog">).
3291 <sect1 id="f-Format">
3292 <heading><tt>Format</tt></heading>
3295 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3296 files, this field declares the format version of that file.
3297 The syntax of the field value is the same as that of
3298 a <qref id="f-Version">package version number</qref> except
3299 that no epoch or Debian revision is allowed. The format
3300 described in this document is <tt>&changesversion;</tt>.
3304 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3305 Debian source control</qref> files, this field declares the
3306 format of the source package. The field value is used by
3307 programs acting on a source package to interpret the list of
3308 files in the source package and determine how to unpack it.
3309 The syntax of the field value is a numeric major revision, a
3310 period, a numeric minor revision, and then an optional subtype
3311 after whitespace, which if specified is an alphanumeric word
3312 in parentheses. The subtype is optional in the syntax but may
3313 be mandatory for particular source format revisions.
3315 The source formats currently supported by the Debian archive
3316 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3317 and <tt>3.0 (quilt)</tt>.
3322 <sect1 id="f-Urgency">
3323 <heading><tt>Urgency</tt></heading>
3326 This is a description of how important it is to upgrade to
3327 this version from previous ones. It consists of a single
3328 keyword taking one of the values <tt>low</tt>,
3329 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3330 <tt>critical</tt><footnote>
3331 Other urgency values are supported with configuration
3332 changes in the archive software but are not used in Debian.
3333 The urgency affects how quickly a package will be considered
3334 for inclusion into the <tt>testing</tt> distribution and
3335 gives an indication of the importance of any fixes included
3336 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3337 treated as synonymous.
3338 </footnote> (not case-sensitive) followed by an optional
3339 commentary (separated by a space) which is usually in
3340 parentheses. For example:
3343 Urgency: low (HIGH for users of diversions)
3349 The value of this field is usually extracted from the
3350 <file>debian/changelog</file> file - see
3351 <ref id="dpkgchangelog">.
3355 <sect1 id="f-Changes">
3356 <heading><tt>Changes</tt></heading>
3359 This field contains the human-readable changes data, describing
3360 the differences between the last version and the current one.
3364 The first line of the field value (the part on the same line
3365 as <tt>Changes:</tt>) is always empty. The content of the
3366 field is expressed as continuation lines, with each line
3367 indented by at least one space. Blank lines must be
3368 represented by a line consisting only of a space and a full
3373 The value of this field is usually extracted from the
3374 <file>debian/changelog</file> file - see
3375 <ref id="dpkgchangelog">).
3379 Each version's change information should be preceded by a
3380 "title" line giving at least the version, distribution(s)
3381 and urgency, in a human-readable way.
3385 If data from several versions is being returned the entry
3386 for the most recent version should be returned first, and
3387 entries should be separated by the representation of a
3388 blank line (the "title" line may also be followed by the
3389 representation of a blank line).
3393 <sect1 id="f-Binary">
3394 <heading><tt>Binary</tt></heading>
3397 This field is a list of binary packages. Its syntax and
3398 meaning varies depending on the control file in which it
3403 When it appears in the <file>.dsc</file> file, it lists binary
3404 packages which a source package can produce, separated by
3406 A space after each comma is conventional.
3407 </footnote>. It may span multiple lines. The source package
3408 does not necessarily produce all of these binary packages for
3409 every architecture. The source control file doesn't contain
3410 details of which architectures are appropriate for which of
3411 the binary packages.
3415 When it appears in a <file>.changes</file> file, it lists the
3416 names of the binary packages being uploaded, separated by
3417 whitespace (not commas). It may span multiple lines.
3421 <sect1 id="f-Installed-Size">
3422 <heading><tt>Installed-Size</tt></heading>
3425 This field appears in the control files of binary packages,
3426 and in the <file>Packages</file> files. It gives an estimate
3427 of the total amount of disk space required to install the
3428 named package. Actual installed size may vary based on block
3429 size, file system properties, or actions taken by package
3434 The disk space is given as the integer value of the estimated
3435 installed size in bytes, divided by 1024 and rounded up.
3439 <sect1 id="f-Files">
3440 <heading><tt>Files</tt></heading>
3443 This field contains a list of files with information about
3444 each one. The exact information and syntax varies with
3449 In all cases, Files is a multiline field. The first line of
3450 the field value (the part on the same line as <tt>Files:</tt>)
3451 is always empty. The content of the field is expressed as
3452 continuation lines, one line per file. Each line must be
3453 indented by one space and contain a number of sub-fields,
3454 separated by spaces, as described below.
3458 In the <file>.dsc</file> file, each line contains the MD5
3459 checksum, size and filename of the tar file and (if
3460 applicable) diff file which make up the remainder of the
3461 source package<footnote>
3462 That is, the parts which are not the <tt>.dsc</tt>.
3463 </footnote>. For example:
3466 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3467 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3469 The exact forms of the filenames are described
3470 in <ref id="pkg-sourcearchives">.
3474 In the <file>.changes</file> file this contains one line per
3475 file being uploaded. Each line contains the MD5 checksum,
3476 size, section and priority and the filename. For example:
3479 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3480 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3481 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3482 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3484 The <qref id="f-Section">section</qref>
3485 and <qref id="f-Priority">priority</qref> are the values of
3486 the corresponding fields in the main source control file. If
3487 no section or priority is specified then <tt>-</tt> should be
3488 used, though section and priority values must be specified for
3489 new packages to be installed properly.
3493 The special value <tt>byhand</tt> for the section in a
3494 <tt>.changes</tt> file indicates that the file in question
3495 is not an ordinary package file and must by installed by
3496 hand by the distribution maintainers. If the section is
3497 <tt>byhand</tt> the priority should be <tt>-</tt>.
3501 If a new Debian revision of a package is being shipped and
3502 no new original source archive is being distributed the
3503 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3504 entry for the original source archive
3505 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3506 but the <file>.changes</file> file should leave it out. In
3507 this case the original source archive on the distribution
3508 site must match exactly, byte-for-byte, the original
3509 source archive which was used to generate the
3510 <file>.dsc</file> file and diff which are being uploaded.</p>
3513 <sect1 id="f-Closes">
3514 <heading><tt>Closes</tt></heading>
3517 A space-separated list of bug report numbers that the upload
3518 governed by the .changes file closes.
3522 <sect1 id="f-Homepage">
3523 <heading><tt>Homepage</tt></heading>
3526 The URL of the web site for this package, preferably (when
3527 applicable) the site from which the original source can be
3528 obtained and any additional upstream documentation or
3529 information may be found. The content of this field is a
3530 simple URL without any surrounding characters such as
3535 <sect1 id="f-Checksums">
3536 <heading><tt>Checksums-Sha1</tt>
3537 and <tt>Checksums-Sha256</tt></heading>
3540 These fields contain a list of files with a checksum and size
3541 for each one. Both <tt>Checksums-Sha1</tt>
3542 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3543 only in the checksum algorithm used: SHA-1
3544 for <tt>Checksums-Sha1</tt> and SHA-256
3545 for <tt>Checksums-Sha256</tt>.
3549 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3550 multiline fields. The first line of the field value (the part
3551 on the same line as <tt>Checksums-Sha1:</tt>
3552 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3553 of the field is expressed as continuation lines, one line per
3554 file. Each line consists of the checksum, a space, the file
3555 size, a space, and the file name. For example (from
3556 a <file>.changes</file> file):
3559 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3560 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3561 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3562 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3564 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3565 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3566 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3567 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3572 In the <file>.dsc</file> file, these fields should list all
3573 files that make up the source package. In
3574 the <file>.changes</file> file, these fields should list all
3575 files being uploaded. The list of files in these fields
3576 must match the list of files in the <tt>Files</tt> field.
3582 <heading>User-defined fields</heading>
3585 Additional user-defined fields may be added to the
3586 source package control file. Such fields will be
3587 ignored, and not copied to (for example) binary or
3588 source package control files or upload control files.
3592 If you wish to add additional unsupported fields to
3593 these output files you should use the mechanism
3598 Fields in the main source control information file with
3599 names starting <tt>X</tt>, followed by one or more of
3600 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3601 be copied to the output files. Only the part of the
3602 field name after the hyphen will be used in the output
3603 file. Where the letter <tt>B</tt> is used the field
3604 will appear in binary package control files, where the
3605 letter <tt>S</tt> is used in source package control
3606 files and where <tt>C</tt> is used in upload control
3607 (<tt>.changes</tt>) files.
3611 For example, if the main source information control file
3614 XBS-Comment: I stand between the candle and the star.
3616 then the binary and source package control files will contain the
3619 Comment: I stand between the candle and the star.
3628 <chapt id="maintainerscripts">
3629 <heading>Package maintainer scripts and installation procedure</heading>
3632 <heading>Introduction to package maintainer scripts</heading>
3635 It is possible to supply scripts as part of a package which
3636 the package management system will run for you when your
3637 package is installed, upgraded or removed.
3641 These scripts are the control information
3642 files <prgn>preinst</prgn>, <prgn>postinst</prgn>, <prgn>prerm</prgn>
3643 and <prgn>postrm</prgn>. They must be proper executable files;
3644 if they are scripts (which is recommended), they must start with
3645 the usual <tt>#!</tt> convention. They should be readable and
3646 executable by anyone, and must not be world-writable.
3650 The package management system looks at the exit status from
3651 these scripts. It is important that they exit with a
3652 non-zero status if there is an error, so that the package
3653 management system can stop its processing. For shell
3654 scripts this means that you <em>almost always</em> need to
3655 use <tt>set -e</tt> (this is usually true when writing shell
3656 scripts, in fact). It is also important, of course, that
3657 they exit with a zero status if everything went well.
3661 Additionally, packages interacting with users
3662 using <prgn>debconf</prgn> in the <prgn>postinst</prgn> script
3663 should install a <prgn>config</prgn> script as a control
3664 information file. See <ref id="maintscriptprompt"> for details.
3668 When a package is upgraded a combination of the scripts from
3669 the old and new packages is called during the upgrade
3670 procedure. If your scripts are going to be at all
3671 complicated you need to be aware of this, and may need to
3672 check the arguments to your scripts.
3676 Broadly speaking the <prgn>preinst</prgn> is called before
3677 (a particular version of) a package is unpacked, and the
3678 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3679 before (a version of) a package is removed and the
3680 <prgn>postrm</prgn> afterwards.
3684 Programs called from maintainer scripts should not normally
3685 have a path prepended to them. Before installation is
3686 started, the package management system checks to see if the
3687 programs <prgn>ldconfig</prgn>,
3688 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3689 and <prgn>update-rc.d</prgn> can be found via the
3690 <tt>PATH</tt> environment variable. Those programs, and any
3691 other program that one would expect to be in the
3692 <tt>PATH</tt>, should thus be invoked without an absolute
3693 pathname. Maintainer scripts should also not reset the
3694 <tt>PATH</tt>, though they might choose to modify it by
3695 prepending or appending package-specific directories. These
3696 considerations really apply to all shell scripts.</p>
3699 <sect id="idempotency">
3700 <heading>Maintainer scripts idempotency</heading>
3703 It is necessary for the error recovery procedures that the
3704 scripts be idempotent. This means that if it is run
3705 successfully, and then it is called again, it doesn't bomb
3706 out or cause any harm, but just ensures that everything is
3707 the way it ought to be. If the first call failed, or
3708 aborted half way through for some reason, the second call
3709 should merely do the things that were left undone the first
3710 time, if any, and exit with a success status if everything
3712 This is so that if an error occurs, the user interrupts
3713 <prgn>dpkg</prgn> or some other unforeseen circumstance
3714 happens you don't leave the user with a badly-broken
3715 package when <prgn>dpkg</prgn> attempts to repeat the
3721 <sect id="controllingterminal">
3722 <heading>Controlling terminal for maintainer scripts</heading>
3725 Maintainer scripts are not guaranteed to run with a controlling
3726 terminal and may not be able to interact with the user. They
3727 must be able to fall back to noninteractive behavior if no
3728 controlling terminal is available. Maintainer scripts that
3729 prompt via a program conforming to the Debian Configuration
3730 Management Specification (see <ref id="maintscriptprompt">) may
3731 assume that program will handle falling back to noninteractive
3736 For high-priority prompts without a reasonable default answer,
3737 maintainer scripts may abort if there is no controlling
3738 terminal. However, this situation should be avoided if at all
3739 possible, since it prevents automated or unattended installs.
3740 In most cases, users will consider this to be a bug in the
3745 <sect id="exitstatus">
3746 <heading>Exit status</heading>
3749 Each script must return a zero exit status for
3750 success, or a nonzero one for failure, since the package
3751 management system looks for the exit status of these scripts
3752 and determines what action to take next based on that datum.
3756 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3761 <list compact="compact">
3763 <var>new-preinst</var> <tt>install</tt>
3766 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3769 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3772 <var>old-preinst</var> <tt>abort-upgrade</tt>
3773 <var>new-version</var>
3778 <list compact="compact">
3780 <var>postinst</var> <tt>configure</tt>
3781 <var>most-recently-configured-version</var>
3784 <var>old-postinst</var> <tt>abort-upgrade</tt>
3785 <var>new-version</var>
3788 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3789 <tt>in-favour</tt> <var>package</var>
3790 <var>new-version</var>
3793 <var>postinst</var> <tt>abort-remove</tt>
3796 <var>deconfigured's-postinst</var>
3797 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3798 <var>failed-install-package</var> <var>version</var>
3799 [<tt>removing</tt> <var>conflicting-package</var>
3805 <list compact="compact">
3807 <var>prerm</var> <tt>remove</tt>
3810 <var>old-prerm</var> <tt>upgrade</tt>
3811 <var>new-version</var>
3814 <var>new-prerm</var> <tt>failed-upgrade</tt>
3815 <var>old-version</var>
3818 <var>conflictor's-prerm</var> <tt>remove</tt>
3819 <tt>in-favour</tt> <var>package</var>
3820 <var>new-version</var>
3823 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3824 <tt>in-favour</tt> <var>package-being-installed</var>
3825 <var>version</var> [<tt>removing</tt>
3826 <var>conflicting-package</var>
3832 <list compact="compact">
3834 <var>postrm</var> <tt>remove</tt>
3837 <var>postrm</var> <tt>purge</tt>
3840 <var>old-postrm</var> <tt>upgrade</tt>
3841 <var>new-version</var>
3844 <var>new-postrm</var> <tt>failed-upgrade</tt>
3845 <var>old-version</var>
3848 <var>new-postrm</var> <tt>abort-install</tt>
3851 <var>new-postrm</var> <tt>abort-install</tt>
3852 <var>old-version</var>
3855 <var>new-postrm</var> <tt>abort-upgrade</tt>
3856 <var>old-version</var>
3859 <var>disappearer's-postrm</var> <tt>disappear</tt>
3860 <var>overwriter</var>
3861 <var>overwriter-version</var>
3867 <sect id="unpackphase">
3868 <heading>Details of unpack phase of installation or upgrade</heading>
3871 The procedure on installation/upgrade/overwrite/disappear
3872 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3873 stage of <tt>dpkg --install</tt>) is as follows. In each
3874 case, if a major error occurs (unless listed below) the
3875 actions are, in general, run backwards - this means that the
3876 maintainer scripts are run with different arguments in
3877 reverse order. These are the "error unwind" calls listed
3884 If a version of the package is already installed, call
3885 <example compact="compact">
3886 <var>old-prerm</var> upgrade <var>new-version</var>
3890 If the script runs but exits with a non-zero
3891 exit status, <prgn>dpkg</prgn> will attempt:
3892 <example compact="compact">
3893 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3895 If this works, the upgrade continues. If this
3896 does not work, the error unwind:
3897 <example compact="compact">
3898 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3900 If this works, then the old-version is
3901 "Installed", if not, the old version is in a
3902 "Half-Configured" state.
3908 If a "conflicting" package is being removed at the same time,
3909 or if any package will be broken (due to <tt>Breaks</tt>):
3912 If <tt>--auto-deconfigure</tt> is
3913 specified, call, for each package to be deconfigured
3914 due to <tt>Breaks</tt>:
3915 <example compact="compact">
3916 <var>deconfigured's-prerm</var> deconfigure \
3917 in-favour <var>package-being-installed</var> <var>version</var>
3920 <example compact="compact">
3921 <var>deconfigured's-postinst</var> abort-deconfigure \
3922 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3924 The deconfigured packages are marked as
3925 requiring configuration, so that if
3926 <tt>--install</tt> is used they will be
3927 configured again if possible.
3930 If any packages depended on a conflicting
3931 package being removed and <tt>--auto-deconfigure</tt> is
3932 specified, call, for each such package:
3933 <example compact="compact">
3934 <var>deconfigured's-prerm</var> deconfigure \
3935 in-favour <var>package-being-installed</var> <var>version</var> \
3936 removing <var>conflicting-package</var> <var>version</var>
3939 <example compact="compact">
3940 <var>deconfigured's-postinst</var> abort-deconfigure \
3941 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3942 removing <var>conflicting-package</var> <var>version</var>
3944 The deconfigured packages are marked as
3945 requiring configuration, so that if
3946 <tt>--install</tt> is used they will be
3947 configured again if possible.
3950 To prepare for removal of each conflicting package, call:
3951 <example compact="compact">
3952 <var>conflictor's-prerm</var> remove \
3953 in-favour <var>package</var> <var>new-version</var>
3956 <example compact="compact">
3957 <var>conflictor's-postinst</var> abort-remove \
3958 in-favour <var>package</var> <var>new-version</var>
3967 If the package is being upgraded, call:
3968 <example compact="compact">
3969 <var>new-preinst</var> upgrade <var>old-version</var>
3971 If this fails, we call:
3973 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3980 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3982 is called. If this works, then the old version
3983 is in an "Installed" state, or else it is left
3984 in an "Unpacked" state.
3989 If it fails, then the old version is left
3990 in an "Half-Installed" state.
3997 Otherwise, if the package had some configuration
3998 files from a previous version installed (i.e., it
3999 is in the "configuration files only" state):
4000 <example compact="compact">
4001 <var>new-preinst</var> install <var>old-version</var>
4005 <var>new-postrm</var> abort-install <var>old-version</var>
4007 If this fails, the package is left in a
4008 "Half-Installed" state, which requires a
4009 reinstall. If it works, the packages is left in
4010 a "Config-Files" state.
4013 Otherwise (i.e., the package was completely purged):
4014 <example compact="compact">
4015 <var>new-preinst</var> install
4018 <example compact="compact">
4019 <var>new-postrm</var> abort-install
4021 If the error-unwind fails, the package is in a
4022 "Half-Installed" phase, and requires a
4023 reinstall. If the error unwind works, the
4024 package is in a not installed state.
4031 The new package's files are unpacked, overwriting any
4032 that may be on the system already, for example any
4033 from the old version of the same package or from
4034 another package. Backups of the old files are kept
4035 temporarily, and if anything goes wrong the package
4036 management system will attempt to put them back as
4037 part of the error unwind.
4041 It is an error for a package to contain files which
4042 are on the system in another package, unless
4043 <tt>Replaces</tt> is used (see <ref id="replaces">).
4045 The following paragraph is not currently the case:
4046 Currently the <tt>- - force-overwrite</tt> flag is
4047 enabled, downgrading it to a warning, but this may not
4053 It is a more serious error for a package to contain a
4054 plain file or other kind of non-directory where another
4055 package has a directory (again, unless
4056 <tt>Replaces</tt> is used). This error can be
4057 overridden if desired using
4058 <tt>--force-overwrite-dir</tt>, but this is not
4063 Packages which overwrite each other's files produce
4064 behavior which, though deterministic, is hard for the
4065 system administrator to understand. It can easily
4066 lead to "missing" programs if, for example, a package
4067 is unpacked which overwrites a file from another
4068 package, and is then removed again.<footnote>
4069 Part of the problem is due to what is arguably a
4070 bug in <prgn>dpkg</prgn>.
4075 A directory will never be replaced by a symbolic link
4076 to a directory or vice versa; instead, the existing
4077 state (symlink or not) will be left alone and
4078 <prgn>dpkg</prgn> will follow the symlink if there is
4087 If the package is being upgraded, call
4088 <example compact="compact">
4089 <var>old-postrm</var> upgrade <var>new-version</var>
4093 If this fails, <prgn>dpkg</prgn> will attempt:
4094 <example compact="compact">
4095 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4097 If this works, installation continues. If not,
4099 <example compact="compact">
4100 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4102 If this fails, the old version is left in a
4103 "Half-Installed" state. If it works, dpkg now
4105 <example compact="compact">
4106 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4108 If this fails, the old version is left in a
4109 "Half-Installed" state. If it works, dpkg now
4111 <example compact="compact">
4112 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4114 If this fails, the old version is in an
4121 This is the point of no return - if
4122 <prgn>dpkg</prgn> gets this far, it won't back off
4123 past this point if an error occurs. This will
4124 leave the package in a fairly bad state, which
4125 will require a successful re-installation to clear
4126 up, but it's when <prgn>dpkg</prgn> starts doing
4127 things that are irreversible.
4132 Any files which were in the old version of the package
4133 but not in the new are removed.
4137 The new file list replaces the old.
4141 The new maintainer scripts replace the old.
4145 Any packages all of whose files have been overwritten
4146 during the installation, and which aren't required for
4147 dependencies, are considered to have been removed.
4148 For each such package
4151 <prgn>dpkg</prgn> calls:
4152 <example compact="compact">
4153 <var>disappearer's-postrm</var> disappear \
4154 <var>overwriter</var> <var>overwriter-version</var>
4158 The package's maintainer scripts are removed.
4161 It is noted in the status database as being in a
4162 sane state, namely not installed (any conffiles
4163 it may have are ignored, rather than being
4164 removed by <prgn>dpkg</prgn>). Note that
4165 disappearing packages do not have their prerm
4166 called, because <prgn>dpkg</prgn> doesn't know
4167 in advance that the package is going to
4174 Any files in the package we're unpacking that are also
4175 listed in the file lists of other packages are removed
4176 from those lists. (This will lobotomize the file list
4177 of the "conflicting" package if there is one.)
4181 The backup files made during installation, above, are
4187 The new package's status is now sane, and recorded as
4192 Here is another point of no return - if the
4193 conflicting package's removal fails we do not unwind
4194 the rest of the installation; the conflicting package
4195 is left in a half-removed limbo.
4200 If there was a conflicting package we go and do the
4201 removal actions (described below), starting with the
4202 removal of the conflicting package's files (any that
4203 are also in the package being unpacked have already
4204 been removed from the conflicting package's file list,
4205 and so do not get removed now).
4211 <sect id="configdetails"><heading>Details of configuration</heading>
4214 When we configure a package (this happens with <tt>dpkg
4215 --install</tt> and <tt>dpkg --configure</tt>), we first
4216 update any <tt>conffile</tt>s and then call:
4217 <example compact="compact">
4218 <var>postinst</var> configure <var>most-recently-configured-version</var>
4223 No attempt is made to unwind after errors during
4224 configuration. If the configuration fails, the package is in
4225 a "Failed Config" state, and an error message is generated.
4229 If there is no most recently configured version
4230 <prgn>dpkg</prgn> will pass a null argument.
4233 Historical note: Truly ancient (pre-1997) versions of
4234 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4235 (including the angle brackets) in this case. Even older
4236 ones did not pass a second argument at all, under any
4237 circumstance. Note that upgrades using such an old dpkg
4238 version are unlikely to work for other reasons, even if
4239 this old argument behavior is handled by your postinst script.
4245 <sect id="removedetails"><heading>Details of removal and/or
4246 configuration purging</heading>
4252 <example compact="compact">
4253 <var>prerm</var> remove
4257 If prerm fails during replacement due to conflict
4259 <var>conflictor's-postinst</var> abort-remove \
4260 in-favour <var>package</var> <var>new-version</var>
4264 <var>postinst</var> abort-remove
4268 If this fails, the package is in a "Half-Configured"
4269 state, or else it remains "Installed".
4273 The package's files are removed (except <tt>conffile</tt>s).
4276 <example compact="compact">
4277 <var>postrm</var> remove
4281 If it fails, there's no error unwind, and the package is in
4282 an "Half-Installed" state.
4287 All the maintainer scripts except the <prgn>postrm</prgn>
4292 If we aren't purging the package we stop here. Note
4293 that packages which have no <prgn>postrm</prgn> and no
4294 <tt>conffile</tt>s are automatically purged when
4295 removed, as there is no difference except for the
4296 <prgn>dpkg</prgn> status.
4300 The <tt>conffile</tt>s and any backup files
4301 (<tt>~</tt>-files, <tt>#*#</tt> files,
4302 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4307 <example compact="compact">
4308 <var>postrm</var> purge
4312 If this fails, the package remains in a "Config-Files"
4317 The package's file list is removed.
4326 <chapt id="relationships">
4327 <heading>Declaring relationships between packages</heading>
4329 <sect id="depsyntax">
4330 <heading>Syntax of relationship fields</heading>
4333 These fields all have a uniform syntax. They are a list of
4334 package names separated by commas.
4338 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4339 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4340 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4341 control fields of the package, which declare
4342 dependencies on other packages, the package names listed may
4343 also include lists of alternative package names, separated
4344 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4345 if any one of the alternative packages is installed, that
4346 part of the dependency is considered to be satisfied.
4350 All of the fields except for <tt>Provides</tt> may restrict
4351 their applicability to particular versions of each named
4352 package. This is done in parentheses after each individual
4353 package name; the parentheses should contain a relation from
4354 the list below followed by a version number, in the format
4355 described in <ref id="f-Version">.
4359 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4360 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4361 strictly earlier, earlier or equal, exactly equal, later or
4362 equal and strictly later, respectively. The deprecated
4363 forms <tt><</tt> and <tt>></tt> were used to mean
4364 earlier/later or equal, rather than strictly earlier/later,
4365 so they should not appear in new packages (though
4366 <prgn>dpkg</prgn> still supports them).
4370 Whitespace may appear at any point in the version
4371 specification subject to the rules in <ref
4372 id="controlsyntax">, and must appear where it's necessary to
4373 disambiguate; it is not otherwise significant. All of the
4374 relationship fields may span multiple lines. For
4375 consistency and in case of future changes to
4376 <prgn>dpkg</prgn> it is recommended that a single space be
4377 used after a version relationship and before a version
4378 number; it is also conventional to put a single space after
4379 each comma, on either side of each vertical bar, and before
4380 each open parenthesis. When wrapping a relationship field, it
4381 is conventional to do so after a comma and before the space
4382 following that comma.
4386 For example, a list of dependencies might appear as:
4387 <example compact="compact">
4390 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4395 Relationships may be restricted to a certain set of
4396 architectures. This is indicated in brackets after each
4397 individual package name and the optional version specification.
4398 The brackets enclose a list of Debian architecture names
4399 separated by whitespace. Exclamation marks may be prepended to
4400 each of the names. (It is not permitted for some names to be
4401 prepended with exclamation marks while others aren't.)
4405 For build relationship fields
4406 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4407 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>), if
4408 the current Debian host architecture is not in this list and
4409 there are no exclamation marks in the list, or it is in the list
4410 with a prepended exclamation mark, the package name and the
4411 associated version specification are ignored completely for the
4412 purposes of defining the relationships.
4417 <example compact="compact">
4419 Build-Depends-Indep: texinfo
4420 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4421 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4423 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4424 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4425 <tt>gnumach-dev</tt> only on hurd-i386.
4429 For binary relationship fields, the architecture restriction
4430 syntax is only supported in the source package control
4431 file <file>debian/control</file>. When the corresponding binary
4432 package control file is generated, the relationship will either
4433 be omitted or included without the architecture restriction
4434 based on the architecture of the binary package. This means
4435 that architecture restrictions must not be used in binary
4436 relationship fields for architecture-independent packages
4437 (<tt>Architecture: all</tt>).
4442 <example compact="compact">
4443 Depends: foo [i386], bar [amd64]
4445 becomes <tt>Depends: foo</tt> when the package is built on
4446 the <tt>i386</tt> architecture, <tt>Depends: bar</tt> when the
4447 package is built on the <tt>amd64</tt> architecture, and omitted
4448 entirely in binary packages built on all other architectures.
4452 If the architecture-restricted dependency is part of a set of
4453 alternatives using <tt>|</tt>, that alternative is ignored
4454 completely on architectures that do not match the restriction.
4456 <example compact="compact">
4457 Build-Depends: foo [!i386] | bar [!amd64]
4459 is equivalent to <tt>bar</tt> on the i386 architecture, to
4460 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4461 bar</tt> on all other architectures.
4465 Relationships may also be restricted to a certain set of
4466 architectures using architecture wildcards. The syntax for
4467 declaring such restrictions is the same as declaring
4468 restrictions using a certain set of architectures without
4469 architecture wildcards. For example:
4470 <example compact="compact">
4471 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4473 is equivalent to <tt>foo</tt> on architectures using the Linux
4474 kernel and any cpu, <tt>bar</tt> on architectures using any
4475 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4476 using a kernel other than Linux.
4480 Note that the binary package relationship fields such as
4481 <tt>Depends</tt> appear in one of the binary package
4482 sections of the control file, whereas the build-time
4483 relationships such as <tt>Build-Depends</tt> appear in the
4484 source package section of the control file (which is the
4489 <sect id="binarydeps">
4490 <heading>Binary Dependencies - <tt>Depends</tt>,
4491 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4492 <tt>Pre-Depends</tt>
4496 Packages can declare in their control file that they have
4497 certain relationships to other packages - for example, that
4498 they may not be installed at the same time as certain other
4499 packages, and/or that they depend on the presence of others.
4503 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4504 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4505 <tt>Breaks</tt> and <tt>Conflicts</tt> control fields.
4506 <tt>Breaks</tt> is described in <ref id="breaks">, and
4507 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4508 rest are described below.
4512 These seven fields are used to declare a dependency
4513 relationship by one package on another. Except for
4514 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4515 depending (binary) package's control file.
4516 (<tt>Enhances</tt> appears in the recommending package's
4517 control file, and <tt>Breaks</tt> appears in the version of
4518 depended-on package which causes the named package to
4523 A <tt>Depends</tt> field takes effect <em>only</em> when a
4524 package is to be configured. It does not prevent a package
4525 being on the system in an unconfigured state while its
4526 dependencies are unsatisfied, and it is possible to replace
4527 a package whose dependencies are satisfied and which is
4528 properly installed with a different version whose
4529 dependencies are not and cannot be satisfied; when this is
4530 done the depending package will be left unconfigured (since
4531 attempts to configure it will give errors) and will not
4532 function properly. If it is necessary, a
4533 <tt>Pre-Depends</tt> field can be used, which has a partial
4534 effect even when a package is being unpacked, as explained
4535 in detail below. (The other three dependency fields,
4536 <tt>Recommends</tt>, <tt>Suggests</tt> and
4537 <tt>Enhances</tt>, are only used by the various front-ends
4538 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4539 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4543 Since <tt>Depends</tt> only places requirements on the
4544 configuration step, packages in an installation run are usually
4545 all unpacked first and all configured later. This makes it
4546 easier to satisfy all dependencies when multiple packages are
4551 If there is a circular dependency among packages being installed
4552 or removed, installation or removal order honoring the
4553 dependency order is impossible, requiring the dependency loop be
4554 broken at some point and the dependency requirements violated
4555 for at least one package. Packages involved in circular
4556 dependencies may not be able to rely on their dependencies being
4557 configured when being configured or removed depending on which
4558 side of the break of the circular dependency loop they happen to
4559 be on. If one of the packages in the loop has no
4560 <prgn>postinst</prgn> script, then the cycle will be broken at
4561 that package; this ensures that all <prgn>postinst</prgn>
4562 scripts are run with their dependencies properly configured if
4563 this is possible. Otherwise the breaking point is arbitrary.
4564 Packages should therefore avoid circular dependencies where
4565 possible, particularly if they have <prgn>postinst</prgn>
4570 The meaning of the five dependency fields is as follows:
4572 <tag><tt>Depends</tt></tag>
4575 This declares an absolute dependency. A package will
4576 not be configured unless all of the packages listed in
4577 its <tt>Depends</tt> field have been correctly
4578 configured (unless there is a circular dependency as
4583 The <tt>Depends</tt> field should be used if the
4584 depended-on package is required for the depending
4585 package to provide a significant amount of
4590 The <tt>Depends</tt> field should also be used if the
4591 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4592 <prgn>postrm</prgn> scripts require the package to be
4593 present in order to run. (If both packages are involved
4594 in a dependency loop, this might not work as expected; see
4595 the explanation a few paragraphs back.) In the case of
4596 <prgn>postinst</prgn> and <prgn>postrm</prgn>, the
4597 depended-on packages will be unpacked and configured
4598 first. (Note, however, that the <prgn>postrm</prgn>
4599 cannot rely on any non-essential packages to be present
4600 during the <tt>purge</tt> phase.) In the case of
4601 <prgn>prerm</prgn>, the depended-on package will at least
4602 be unpacked (it might be configured too, but you can't
4603 rely on this unless you use <tt>Pre-Depends</tt>).
4606 <tag><tt>Recommends</tt></tag>
4609 This declares a strong, but not absolute, dependency.
4613 The <tt>Recommends</tt> field should list packages
4614 that would be found together with this one in all but
4615 unusual installations.
4619 <tag><tt>Suggests</tt></tag>
4621 This is used to declare that one package may be more
4622 useful with one or more others. Using this field
4623 tells the packaging system and the user that the
4624 listed packages are related to this one and can
4625 perhaps enhance its usefulness, but that installing
4626 this one without them is perfectly reasonable.
4629 <tag><tt>Enhances</tt></tag>
4631 This field is similar to Suggests but works in the
4632 opposite direction. It is used to declare that a
4633 package can enhance the functionality of another
4637 <tag><tt>Pre-Depends</tt></tag>
4640 This field is like <tt>Depends</tt>, except that it
4641 also forces <prgn>dpkg</prgn> to complete installation
4642 of the packages named before even starting the
4643 installation of the package which declares the
4644 pre-dependency, as follows:
4648 When a package declaring a pre-dependency is about to
4649 be <em>unpacked</em> the pre-dependency can be
4650 satisfied if the depended-on package is either fully
4651 configured, <em>or even if</em> the depended-on
4652 package(s) are only unpacked or in the "Half-Configured"
4653 state, provided that they have been configured
4654 correctly at some point in the past (and not removed
4655 or partially removed since). In this case, both the
4656 previously-configured and currently unpacked or
4657 "Half-Configured" versions must satisfy any version
4658 clause in the <tt>Pre-Depends</tt> field.
4662 When the package declaring a pre-dependency is about
4663 to be <em>configured</em>, the pre-dependency will be
4664 treated as a normal <tt>Depends</tt>, that is, it will
4665 be considered satisfied only if the depended-on
4666 package has been correctly configured. However, unlike
4667 with <tt>Depends</tt>, <tt>Pre-Depends</tt> does not
4668 permit circular dependencies to be broken. If a circular
4669 dependency is encountered while attempting to honor
4670 <tt>Pre-Depends</tt>, the installation will be aborted.
4674 <tt>Pre-Depends</tt> are also required if the
4675 <prgn>preinst</prgn> script depends on the named package.
4676 It is best to avoid this situation if possible.
4680 <tt>Pre-Depends</tt> should be used sparingly,
4681 preferably only by packages whose premature upgrade or
4682 installation would hamper the ability of the system to
4683 continue with any upgrade that might be in progress.
4690 When selecting which level of dependency to use you should
4691 consider how important the depended-on package is to the
4692 functionality of the one declaring the dependency. Some
4693 packages are composed of components of varying degrees of
4694 importance. Such a package should list using
4695 <tt>Depends</tt> the package(s) which are required by the
4696 more important components. The other components'
4697 requirements may be mentioned as Suggestions or
4698 Recommendations, as appropriate to the components' relative
4704 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4707 When one binary package declares that it breaks another,
4708 <prgn>dpkg</prgn> will refuse to allow the package which
4709 declares <tt>Breaks</tt> be unpacked unless the broken
4710 package is deconfigured first, and it will refuse to
4711 allow the broken package to be reconfigured.
4715 A package will not be regarded as causing breakage merely
4716 because its configuration files are still installed; it must
4717 be at least "Half-Installed".
4721 A special exception is made for packages which declare that
4722 they break their own package name or a virtual package which
4723 they provide (see below): this does not count as a real
4728 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4729 version clause; such a <tt>Breaks</tt> is introduced in the
4730 version of an (implicit or explicit) dependency which violates
4731 an assumption or reveals a bug in earlier versions of the broken
4732 package, or which takes over a file from earlier versions of the
4733 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
4734 will inform higher-level package management tools that the
4735 broken package must be upgraded before the new one.
4739 If the breaking package also overwrites some files from the
4740 older package, it should use <tt>Replaces</tt> to ensure this
4741 goes smoothly. See <ref id="replaces"> for a full discussion
4742 of taking over files from other packages, including how to
4743 use <tt>Breaks</tt> in those cases.
4747 Many of the cases where <tt>Breaks</tt> should be used were
4748 previously handled with <tt>Conflicts</tt>
4749 because <tt>Breaks</tt> did not yet exist.
4750 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
4751 See <ref id="conflicts"> for more information about the
4756 <sect id="conflicts">
4757 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4760 When one binary package declares a conflict with another
4761 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4762 refuse to allow them to be unpacked on the system at the
4763 same time. This is a stronger restriction than <tt>Breaks</tt>,
4764 which just prevents both packages from being configured at the
4765 same time. Conflicting packages cannot be unpacked on the
4766 system at the same time.
4770 If one package is to be unpacked, the other must be removed
4771 first. If the package being unpacked is marked as replacing
4772 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
4773 normally be used in this case) the one on the system, or the one
4774 on the system is marked as deselected, or both packages are
4775 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
4776 automatically remove the package which is causing the conflict.
4777 Otherwise, it will halt the installation of the new package with
4778 an error. This mechanism is specifically designed to produce an
4779 error when the installed package is <tt>Essential</tt>, but the
4784 A package will not cause a conflict merely because its
4785 configuration files are still installed; it must be at least
4790 A special exception is made for packages which declare a
4791 conflict with their own package name, or with a virtual
4792 package which they provide (see below): this does not
4793 prevent their installation, and allows a package to conflict
4794 with others providing a replacement for it. You use this
4795 feature when you want the package in question to be the only
4796 package providing some feature.
4800 Normally, <tt>Breaks</tt> should be used instead
4801 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
4802 stronger restriction on the ordering of package installation or
4803 upgrade and can make it more difficult for the package manager
4804 to find a correct solution to an upgrade or installation
4805 problem. <tt>Breaks</tt> should be used
4807 <item>when moving a file from one package to another (see
4808 <ref id="replaces">),</item>
4809 <item>when splitting a package (a special case of the previous
4811 <item>when the breaking package exposes a bug in or interacts
4812 badly with particular versions of the broken
4815 <tt>Conflicts</tt> should be used
4817 <item>when two packages provide the same file and will
4818 continue to do so,</item>
4819 <item>in conjunction with <tt>Provides</tt> when only one
4820 package providing a given virtual facility may be installed
4821 at a time (see <ref id="virtual">),</item>
4822 <item>in other cases where one must prevent simultaneous
4823 installation of two packages for reasons that are ongoing
4824 (not fixed in a later version of one of the packages) or
4825 that must prevent both packages from being unpacked at the
4826 same time, not just configured.</item>
4828 Be aware that adding <tt>Conflicts</tt> is normally not the best
4829 solution when two packages provide the same files. Depending on
4830 the reason for that conflict, using alternatives or renaming the
4831 files is often a better approach. See, for
4832 example, <ref id="binaries">.
4836 Neither <tt>Breaks</tt> nor <tt>Conflicts</tt> should be used
4837 unless two packages cannot be installed at the same time or
4838 installing them both causes one of them to be broken or
4839 unusable. Having similar functionality or performing the same
4840 tasks as another package is not sufficient reason to
4841 declare <tt>Breaks</tt> or <tt>Conflicts</tt> with that package.
4845 A <tt>Conflicts</tt> entry may have an "earlier than" version
4846 clause if the reason for the conflict is corrected in a later
4847 version of one of the packages. However, normally the presence
4848 of an "earlier than" version clause is a sign
4849 that <tt>Breaks</tt> should have been used instead. An "earlier
4850 than" version clause in <tt>Conflicts</tt>
4851 prevents <prgn>dpkg</prgn> from upgrading or installing the
4852 package which declares such a conflict until the upgrade or
4853 removal of the conflicted-with package has been completed, which
4854 is a strong restriction.
4858 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4862 As well as the names of actual ("concrete") packages, the
4863 package relationship fields <tt>Depends</tt>,
4864 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4865 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4866 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4867 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4868 may mention "virtual packages".
4872 A <em>virtual package</em> is one which appears in the
4873 <tt>Provides</tt> control field of another package. The effect
4874 is as if the package(s) which provide a particular virtual
4875 package name had been listed by name everywhere the virtual
4876 package name appears. (See also <ref id="virtual_pkg">)
4880 If there are both concrete and virtual packages of the same
4881 name, then the dependency may be satisfied (or the conflict
4882 caused) by either the concrete package with the name in
4883 question or any other concrete package which provides the
4884 virtual package with the name in question. This is so that,
4885 for example, supposing we have
4886 <example compact="compact">
4889 </example> and someone else releases an enhanced version of
4890 the <tt>bar</tt> package they can say:
4891 <example compact="compact">
4895 and the <tt>bar-plus</tt> package will now also satisfy the
4896 dependency for the <tt>foo</tt> package.
4900 If a relationship field has a version number attached, only real
4901 packages will be considered to see whether the relationship is
4902 satisfied (or the prohibition violated, for a conflict or
4903 breakage). In other words, if a version number is specified,
4904 this is a request to ignore all <tt>Provides</tt> for that
4905 package name and consider only real packages. The package
4906 manager will assume that a package providing that virtual
4907 package is not of the "right" version. A <tt>Provides</tt>
4908 field may not contain version numbers, and the version number of
4909 the concrete package which provides a particular virtual package
4910 will not be considered when considering a dependency on or
4911 conflict with the virtual package name.<footnote>
4912 It is possible that a future release of <prgn>dpkg</prgn> may
4913 add the ability to specify a version number for each virtual
4914 package it provides. This feature is not yet present,
4915 however, and is expected to be used only infrequently.
4920 To specify which of a set of real packages should be the default
4921 to satisfy a particular dependency on a virtual package, list
4922 the real package as an alternative before the virtual one.
4926 If the virtual package represents a facility that can only be
4927 provided by one real package at a time, such as
4928 the <package>mail-transport-agent</package> virtual package that
4929 requires installation of a binary that would conflict with all
4930 other providers of that virtual package (see
4931 <ref id="mail-transport-agents">), all packages providing that
4932 virtual package should also declare a conflict with it
4933 using <tt>Conflicts</tt>. This will ensure that at most one
4934 provider of that virtual package is unpacked or installed at a
4939 <sect id="replaces"><heading>Overwriting files and replacing
4940 packages - <tt>Replaces</tt></heading>
4943 Packages can declare in their control file that they should
4944 overwrite files in certain other packages, or completely replace
4945 other packages. The <tt>Replaces</tt> control field has these
4946 two distinct purposes.
4949 <sect1><heading>Overwriting files in other packages</heading>
4952 It is usually an error for a package to contain files which
4953 are on the system in another package. However, if the
4954 overwriting package declares that it <tt>Replaces</tt> the one
4955 containing the file being overwritten, then <prgn>dpkg</prgn>
4956 will replace the file from the old package with that from the
4957 new. The file will no longer be listed as "owned" by the old
4958 package and will be taken over by the new package.
4959 Normally, <tt>Breaks</tt> should be used in conjunction
4960 with <tt>Replaces</tt>.<footnote>
4961 To see why <tt>Breaks</tt> is normally needed in addition
4962 to <tt>Replaces</tt>, consider the case of a file in the
4963 package <package>foo</package> being taken over by the
4964 package <package>foo-data</package>.
4965 <tt>Replaces</tt> will allow <package>foo-data</package> to
4966 be installed and take over that file. However,
4967 without <tt>Breaks</tt>, nothing
4968 requires <package>foo</package> to be upgraded to a newer
4969 version that knows it does not include that file and instead
4970 depends on <package>foo-data</package>. Nothing would
4971 prevent the new <package>foo-data</package> package from
4972 being installed and then removed, removing the file that it
4973 took over from <package>foo</package>. After that
4974 operation, the package manager would think the system was in
4975 a consistent state, but the <package>foo</package> package
4976 would be missing one of its files.
4981 For example, if a package <package>foo</package> is split
4982 into <package>foo</package> and <package>foo-data</package>
4983 starting at version 1.2-3, <package>foo-data</package> would
4985 <example compact="compact">
4986 Replaces: foo (<< 1.2-3)
4987 Breaks: foo (<< 1.2-3)
4989 in its control file. The new version of the
4990 package <package>foo</package> would normally have the field
4991 <example compact="compact">
4992 Depends: foo-data (>= 1.2-3)
4994 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
4995 the files moved into <package>foo-data</package> are not
4996 required for normal operation).
5000 If a package is completely replaced in this way, so that
5001 <prgn>dpkg</prgn> does not know of any files it still
5002 contains, it is considered to have "disappeared". It will
5003 be marked as not wanted on the system (selected for
5004 removal) and not installed. Any <tt>conffile</tt>s
5005 details noted for the package will be ignored, as they
5006 will have been taken over by the overwriting package. The
5007 package's <prgn>postrm</prgn> script will be run with a
5008 special argument to allow the package to do any final
5009 cleanup required. See <ref id="mscriptsinstact">.
5011 Replaces is a one way relationship. You have to install
5012 the replacing package after the replaced package.
5017 For this usage of <tt>Replaces</tt>, virtual packages (see
5018 <ref id="virtual">) are not considered when looking at a
5019 <tt>Replaces</tt> field. The packages declared as being
5020 replaced must be mentioned by their real names.
5024 This usage of <tt>Replaces</tt> only takes effect when both
5025 packages are at least partially on the system at once. It is
5026 not relevant if the packages conflict unless the conflict has
5031 <sect1><heading>Replacing whole packages, forcing their
5035 Second, <tt>Replaces</tt> allows the packaging system to
5036 resolve which package should be removed when there is a
5037 conflict (see <ref id="conflicts">). This usage only takes
5038 effect when the two packages <em>do</em> conflict, so that the
5039 two usages of this field do not interfere with each other.
5043 In this situation, the package declared as being replaced
5044 can be a virtual package, so for example, all mail
5045 transport agents (MTAs) would have the following fields in
5046 their control files:
5047 <example compact="compact">
5048 Provides: mail-transport-agent
5049 Conflicts: mail-transport-agent
5050 Replaces: mail-transport-agent
5052 ensuring that only one MTA can be unpacked at any one
5053 time. See <ref id="virtual"> for more information about this
5058 <sect id="sourcebinarydeps">
5059 <heading>Relationships between source and binary packages -
5060 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5061 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5065 Source packages that require certain binary packages to be
5066 installed or absent at the time of building the package
5067 can declare relationships to those binary packages.
5071 This is done using the <tt>Build-Depends</tt>,
5072 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5073 <tt>Build-Conflicts-Indep</tt> control fields.
5077 Build-dependencies on "build-essential" binary packages can be
5078 omitted. Please see <ref id="pkg-relations"> for more information.
5082 The dependencies and conflicts they define must be satisfied
5083 (as defined earlier for binary packages) in order to invoke
5084 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5086 There is no Build-Depends-Arch; this role is essentially
5087 met with Build-Depends. Anyone building the
5088 <tt>build-indep</tt> and <tt>binary-indep</tt> targets is
5089 assumed to be building the whole package, and therefore
5090 installation of all build dependencies is required.
5093 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5094 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5095 not yet know how to check for its existence, and
5096 <tt>binary-arch</tt>. The purpose of the original split
5097 between <tt>Build-Depends</tt> and
5098 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5099 wouldn't need to install extra packages needed only for the
5100 binary-indep targets. But without a build-arch/build-indep
5101 split, this didn't work, since most of the work is done in
5102 the build target, not in the binary target.
5106 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5107 <tt>binary-arch</tt></tag>
5109 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5110 fields must be satisfied when these targets are invoked.
5112 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5113 and <tt>binary-indep</tt></tag>
5115 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5116 <tt>Build-Depends-Indep</tt>, and
5117 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5118 these targets are invoked.
5126 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5129 Packages containing shared libraries must be constructed with
5130 a little care to make sure that the shared library is always
5131 available. This is especially important for packages whose
5132 shared libraries are vitally important, such as the C library
5133 (currently <tt>libc6</tt>).
5137 This section deals only with public shared libraries: shared
5138 libraries that are placed in directories searched by the dynamic
5139 linker by default or which are intended to be linked against
5140 normally and possibly used by other, independent packages. Shared
5141 libraries that are internal to a particular package or that are
5142 only loaded as dynamic modules are not covered by this section and
5143 are not subject to its requirements.
5147 A shared library is identified by the <tt>SONAME</tt> attribute
5148 stored in its dynamic section. When a binary is linked against a
5149 shared library, the <tt>SONAME</tt> of the shared library is
5150 recorded in the binary's <tt>NEEDED</tt> section so that the
5151 dynamic linker knows that library must be loaded at runtime. The
5152 shared library file's full name (which usually contains additional
5153 version information not needed in the <tt>SONAME</tt>) is
5154 therefore normally not referenced directly. Instead, the shared
5155 library is loaded by its <tt>SONAME</tt>, which exists on the file
5156 system as a symlink pointing to the full name of the shared
5157 library. This symlink must be provided by the
5158 package. <ref id="sharedlibs-runtime"> describes how to do this.
5160 This is a convention of shared library versioning, but not a
5161 requirement. Some libraries use the <tt>SONAME</tt> as the full
5162 library file name instead and therefore do not need a symlink.
5163 Most, however, encode additional information about
5164 backwards-compatible revisions as a minor version number in the
5165 file name. The <tt>SONAME</tt> itself only changes when
5166 binaries linked with the earlier version of the shared library
5167 may no longer work, but the filename may change with each
5168 release of the library. See <ref id="sharedlibs-runtime"> for
5174 When linking a binary or another shared library against a shared
5175 library, the <tt>SONAME</tt> for that shared library is not yet
5176 known. Instead, the shared library is found by looking for a file
5177 matching the library name with <tt>.so</tt> appended. This file
5178 exists on the file system as a symlink pointing to the shared
5183 Shared libraries are normally split into several binary packages.
5184 The <tt>SONAME</tt> symlink is installed by the runtime shared
5185 library package, and the bare <tt>.so</tt> symlink is installed in
5186 the development package since it's only used when linking binaries
5187 or shared libraries. However, there are some exceptions for
5188 unusual shared libraries or for shared libraries that are also
5189 loaded as dynamic modules by other programs.
5193 This section is primarily concerned with how the separation of
5194 shared libraries into multiple packages should be done and how
5195 dependencies on and between shared library binary packages are
5196 managed in Debian. <ref id="libraries"> should be read in
5197 conjunction with this section and contains additional rules for
5198 the files contained in the shared library packages.
5201 <sect id="sharedlibs-runtime">
5202 <heading>Run-time shared libraries</heading>
5205 The run-time shared library must be placed in a package
5206 whose name changes whenever the <tt>SONAME</tt> of the shared
5207 library changes. This allows several versions of the shared
5208 library to be installed at the same time, allowing installation
5209 of the new version of the shared library without immediately
5210 breaking binaries that depend on the old version. Normally, the
5211 run-time shared library and its <tt>SONAME</tt> symlink should
5212 be placed in a package named
5213 <package><var>libraryname</var><var>soversion</var></package>,
5214 where <var>soversion</var> is the version number in
5215 the <tt>SONAME</tt> of the shared library.
5216 See <ref id="shlibs"> for detailed information on how to
5217 determine this version. Alternatively, if it would be confusing
5218 to directly append <var>soversion</var>
5219 to <var>libraryname</var> (if, for example, <var>libraryname</var>
5220 itself ends in a number), you should use
5221 <package><var>libraryname</var>-<var>soversion</var></package>
5226 If you have several shared libraries built from the same source
5227 tree, you may lump them all together into a single shared
5228 library package provided that all of their <tt>SONAME</tt>s will
5229 always change together. Be aware that this is not normally the
5230 case, and if the <tt>SONAME</tt>s do not change together,
5231 upgrading such a merged shared library package will be
5232 unnecessarily difficult because of file conflicts with the old
5233 version of the package. When in doubt, always split shared
5234 library packages so that each binary package installs a single
5239 Every time the shared library ABI changes in a way that may
5240 break binaries linked against older versions of the shared
5241 library, the <tt>SONAME</tt> of the library and the
5242 corresponding name for the binary package containing the runtime
5243 shared library should change. Normally, this means
5244 the <tt>SONAME</tt> should change any time an interface is
5245 removed from the shared library or the signature of an interface
5246 (the number of parameters or the types of parameters that it
5247 takes, for example) is changed. This practice is vital to
5248 allowing clean upgrades from older versions of the package and
5249 clean transitions between the old ABI and new ABI without having
5250 to upgrade every affected package simultaneously.
5254 The <tt>SONAME</tt> and binary package name need not, and indeed
5255 normally should not, change if new interfaces are added but none
5256 are removed or changed, since this will not break binaries
5257 linked against the old shared library. Correct versioning of
5258 dependencies on the newer shared library by binaries that use
5259 the new interfaces is handled via
5260 the <qref id="sharedlibs-shlibdeps"><tt>shlibs</tt>
5261 system</qref> or via symbols files (see
5262 <manref name="deb-symbols" section="5">).
5266 The package should install the shared libraries under
5267 their normal names. For example, the <package>libgdbm3</package>
5268 package should install <file>libgdbm.so.3.0.0</file> as
5269 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5270 renamed or re-linked by any <prgn>prerm</prgn> or
5271 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5272 of renaming things safely without affecting running programs,
5273 and attempts to interfere with this are likely to lead to
5278 Shared libraries should not be installed executable, since
5279 the dynamic linker does not require this and trying to
5280 execute a shared library usually results in a core dump.
5284 The run-time library package should include the symbolic link for
5285 the <tt>SONAME</tt> that <prgn>ldconfig</prgn> would create for
5286 the shared libraries. For example,
5287 the <package>libgdbm3</package> package should include a symbolic
5288 link from <file>/usr/lib/libgdbm.so.3</file> to
5289 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5290 linker (for example <prgn>ld.so</prgn> or
5291 <prgn>ld-linux.so.*</prgn>) can find the library between the
5292 time that <prgn>dpkg</prgn> installs it and the time that
5293 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5295 The package management system requires the library to be
5296 placed before the symbolic link pointing to it in the
5297 <file>.deb</file> file. This is so that when
5298 <prgn>dpkg</prgn> comes to install the symlink
5299 (overwriting the previous symlink pointing at an older
5300 version of the library), the new shared library is already
5301 in place. In the past, this was achieved by creating the
5302 library in the temporary packaging directory before
5303 creating the symlink. Unfortunately, this was not always
5304 effective, since the building of the tar file in the
5305 <file>.deb</file> depended on the behavior of the underlying
5306 file system. Some file systems (such as reiserfs) reorder
5307 the files so that the order of creation is forgotten.
5308 Since version 1.7.0, <prgn>dpkg</prgn>
5309 reorders the files itself as necessary when building a
5310 package. Thus it is no longer important to concern
5311 oneself with the order of file creation.
5315 <sect1 id="ldconfig">
5316 <heading><tt>ldconfig</tt></heading>
5319 Any package installing shared libraries in one of the default
5320 library directories of the dynamic linker (which are currently
5321 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5322 listed in <file>/etc/ld.so.conf</file><footnote>
5324 <list compact="compact">
5325 <item>/usr/local/lib</item>
5326 <item>/usr/lib/libc5-compat</item>
5327 <item>/lib/libc5-compat</item>
5330 must use <prgn>ldconfig</prgn> to update the shared library
5335 The package maintainer scripts must only call
5336 <prgn>ldconfig</prgn> under these circumstances:
5337 <list compact="compact">
5338 <item>When the <prgn>postinst</prgn> script is run with a
5339 first argument of <tt>configure</tt>, the script must call
5340 <prgn>ldconfig</prgn>, and may optionally invoke
5341 <prgn>ldconfig</prgn> at other times.
5343 <item>When the <prgn>postrm</prgn> script is run with a
5344 first argument of <tt>remove</tt>, the script should call
5345 <prgn>ldconfig</prgn>.
5350 During install or upgrade, the preinst is called before
5351 the new files are unpacked, so calling "ldconfig" is
5352 pointless. The preinst of an existing package can also be
5353 called if an upgrade fails. However, this happens during
5354 the critical time when a shared libs may exist on-disk
5355 under a temporary name. Thus, it is dangerous and
5356 forbidden by current policy to call "ldconfig" at this
5361 When a package is installed or upgraded, "postinst
5362 configure" runs after the new files are safely on-disk.
5363 Since it is perfectly safe to invoke ldconfig
5364 unconditionally in a postinst, it is OK for a package to
5365 simply put ldconfig in its postinst without checking the
5366 argument. The postinst can also be called to recover from
5367 a failed upgrade. This happens before any new files are
5368 unpacked, so there is no reason to call "ldconfig" at this
5373 For a package that is being removed, prerm is
5374 called with all the files intact, so calling ldconfig is
5375 useless. The other calls to "prerm" happen in the case of
5376 upgrade at a time when all the files of the old package
5377 are on-disk, so again calling "ldconfig" is pointless.
5381 postrm, on the other hand, is called with the "remove"
5382 argument just after the files are removed, so this is
5383 the proper time to call "ldconfig" to notify the system
5384 of the fact that the shared libraries from the package
5385 are removed. The postrm can be called at several other
5386 times. At the time of "postrm purge", "postrm
5387 abort-install", or "postrm abort-upgrade", calling
5388 "ldconfig" is useless because the shared lib files are
5389 not on-disk. However, when "postrm" is invoked with
5390 arguments "upgrade", "failed-upgrade", or "disappear", a
5391 shared lib may exist on-disk under a temporary filename.
5399 <sect id="sharedlibs-support-files">
5400 <heading>Shared library support files</heading>
5403 If your package contains files whose names do not change with
5404 each change in the library shared object version, you must not
5405 put them in the shared library package. Otherwise, several
5406 versions of the shared library cannot be installed at the same
5407 time without filename clashes, making upgrades and transitions
5408 unnecessarily difficult.
5412 It is recommended that supporting files and run-time support
5413 programs that do not need to be invoked manually by users, but
5414 are nevertheless required for the package to function, be placed
5415 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5416 preferably under <file>/usr/lib/</file><var>package-name</var>.
5417 If the program or file is architecture independent, the
5418 recommendation is for it to be placed in a subdirectory of
5419 <file>/usr/share</file> instead, preferably under
5420 <file>/usr/share/</file><var>package-name</var>. Following the
5421 <var>package-name</var> naming convention ensures that the file
5422 names change when the shared object version changes.
5426 Run-time support programs that use the shared library but are
5427 not required for the library to function or files used by the
5428 shared library that can be used by any version of the shared
5429 library package should instead be put in a separate package.
5430 This package might typically be named
5431 <package><var>libraryname</var>-tools</package>; note the
5432 absence of the <var>soversion</var> in the package name.
5436 Files and support programs only useful when compiling software
5437 against the library should be included in the development
5438 package for the library.<footnote>
5439 For example, a <file><var>package-name</var>-config</file>
5440 script or <package>pkg-config</package> configuration files.
5445 <sect id="sharedlibs-static">
5446 <heading>Static libraries</heading>
5449 The static library (<file><var>libraryname.a</var></file>)
5450 is usually provided in addition to the shared version.
5451 It is placed into the development package (see below).
5455 In some cases, it is acceptable for a library to be
5456 available in static form only; these cases include:
5458 <item>libraries for languages whose shared library support
5459 is immature or unstable</item>
5460 <item>libraries whose interfaces are in flux or under
5461 development (commonly the case when the library's
5462 major version number is zero, or where the ABI breaks
5463 across patchlevels)</item>
5464 <item>libraries which are explicitly intended to be
5465 available only in static form by their upstream
5470 <sect id="sharedlibs-dev">
5471 <heading>Development files</heading>
5474 If there are development files associated with a shared library,
5475 the source package needs to generate a binary development package
5476 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5477 or if you prefer only to support one development version at a
5478 time, <package><var>libraryname</var>-dev</package>. Installing
5479 the development package must result in installation of all the
5480 development files necessary for compiling programs against that
5481 shared library.<footnote>
5482 This wording allows the development files to be split into
5483 several packages, such as a separate architecture-independent
5484 <package><var>libraryname</var>-headers</package>, provided that
5485 the development package depends on all the required additional
5491 In case several development versions of a library exist, you may
5492 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5493 <ref id="conflicts">) to ensure that the user only installs one
5494 development version at a time (as different development versions are
5495 likely to have the same header files in them, which would cause a
5496 filename clash if both were unpacked).
5500 The development package should contain a symlink for the associated
5501 shared library without a version number. For example, the
5502 <package>libgdbm-dev</package> package should include a symlink
5503 from <file>/usr/lib/libgdbm.so</file> to
5504 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5505 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5506 <file>libgdbm.so</file> when compiling dynamically.
5510 <sect id="sharedlibs-intradeps">
5511 <heading>Dependencies between the packages of the same library</heading>
5514 Typically the development version should have an exact
5515 version dependency on the runtime library, to make sure that
5516 compilation and linking happens correctly. The
5517 <tt>${binary:Version}</tt> substitution variable can be
5518 useful for this purpose.
5520 Previously, <tt>${Source-Version}</tt> was used, but its name
5521 was confusing and it has been deprecated since dpkg 1.13.19.
5526 <sect id="sharedlibs-shlibdeps">
5527 <heading>Dependencies between the library and other packages -
5528 the <tt>shlibs</tt> system</heading>
5531 If a package contains a binary or library which links to a
5532 shared library, we must ensure that when the package is
5533 installed on the system, all of the libraries needed are
5534 also installed. This requirement led to the creation of the
5535 <tt>shlibs</tt> system, which is very simple in its design:
5536 any package which <em>provides</em> a shared library also
5537 provides information on the package dependencies required to
5538 ensure the presence of this library, and any package which
5539 <em>uses</em> a shared library uses this information to
5540 determine the dependencies it requires. The files which
5541 contain the mapping from shared libraries to the necessary
5542 dependency information are called <file>shlibs</file> files.
5546 When a package is built which contains any shared libraries, it
5547 must provide a <file>shlibs</file> file for other packages to
5548 use. When a package is built which contains any shared
5549 libraries or compiled binaries, it must run
5550 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5551 on these to determine the libraries used and hence the
5552 dependencies needed by this package.<footnote>
5554 <prgn>dpkg-shlibdeps</prgn> will use a program
5555 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
5556 the libraries directly needed by the binaries or shared
5557 libraries in the package.
5561 We say that a binary <tt>foo</tt> <em>directly</em> uses
5562 a library <tt>libbar</tt> if it is explicitly linked
5563 with that library (that is, the library is listed in the ELF
5564 <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
5565 to the link line when the binary is created). Other
5566 libraries that are needed by <tt>libbar</tt> are linked
5567 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5568 linker will load them automatically when it loads
5569 <tt>libbar</tt>. A package should depend on the libraries
5570 it directly uses, but not the libraries it indirectly uses.
5571 The dependencies for those libraries will automatically pull
5572 in the other libraries.
5576 A good example of where this helps is the following. We
5577 could update <tt>libimlib</tt> with a new version that
5578 supports a new graphics format called dgf (but retaining the
5579 same major version number) and depends on <tt>libdgf</tt>.
5580 If we used <prgn>ldd</prgn> to add dependencies for every
5581 library directly or indirectly linked with a binary, every
5582 package that uses <tt>libimlib</tt> would need to be
5583 recompiled so it would also depend on <tt>libdgf</tt> or it
5584 wouldn't run due to missing symbols. Since dependencies are
5585 only added based on ELF <tt>NEEDED</tt> attribute, packages
5586 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
5587 having the dependency on <tt>libdgf</tt> and so they would
5588 not need rebuilding.
5594 In the following sections, we will first describe where the
5595 various <tt>shlibs</tt> files are to be found, then how to
5596 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5597 file format and how to create them if your package contains a
5602 <heading>The <tt>shlibs</tt> files present on the system</heading>
5605 There are several places where <tt>shlibs</tt> files are
5606 found. The following list gives them in the order in which
5608 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5609 (The first one which gives the required information is used.)
5615 <p><file>debian/shlibs.local</file></p>
5618 This lists overrides for this package. This file should
5619 normally not be used, but may be needed temporarily in
5620 unusual situations to work around bugs in other packages,
5621 or in unusual cases where the normally declared dependency
5622 information in the installed <file>shlibs</file> file for
5623 a library cannot be used. This file overrides information
5624 obtained from any other source.
5629 <p><file>/etc/dpkg/shlibs.override</file></p>
5632 This lists global overrides. This list is normally
5633 empty. It is maintained by the local system
5639 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5642 When packages are being built,
5643 any <file>debian/shlibs</file> files are copied into the
5644 control information file area of the temporary build
5645 directory and given the name <file>shlibs</file>. These
5646 files give details of any shared libraries included in the
5647 same package.<footnote>
5648 An example may help here. Let us say that the source
5649 package <tt>foo</tt> generates two binary
5650 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
5651 When building the binary packages, the two packages are
5652 created in the directories <file>debian/libfoo2</file>
5653 and <file>debian/foo-runtime</file> respectively.
5654 (<file>debian/tmp</file> could be used instead of one of
5655 these.) Since <tt>libfoo2</tt> provides the
5656 <tt>libfoo</tt> shared library, it will require a
5657 <tt>shlibs</tt> file, which will be installed in
5658 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually to
5659 become <file>/var/lib/dpkg/info/libfoo2.shlibs</file>.
5660 When <prgn>dpkg-shlibdeps</prgn> is run on the
5661 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
5663 the <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5664 determine whether <tt>foo-prog</tt>'s library
5665 dependencies are satisfied by any of the libraries
5666 provided by <tt>libfoo2</tt>. For this reason,
5667 <prgn>dpkg-shlibdeps</prgn> must only be run once all of
5668 the individual binary packages' <tt>shlibs</tt> files
5669 have been installed into the build directory.
5675 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5678 These are the <file>shlibs</file> files corresponding to
5679 all of the packages installed on the system, and are
5680 maintained by the relevant package maintainers.
5685 <p><file>/etc/dpkg/shlibs.default</file></p>
5688 This file lists any shared libraries whose packages
5689 have failed to provide correct <file>shlibs</file> files.
5690 It was used when the <file>shlibs</file> setup was first
5691 introduced, but it is now normally empty. It is
5692 maintained by the <tt>dpkg</tt> maintainer.
5700 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5701 <file>shlibs</file> files</heading>
5705 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5706 into your <file>debian/rules</file> file. If your package
5707 contains only compiled binaries and libraries (but no scripts),
5708 you can use a command such as:
5709 <example compact="compact">
5710 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5711 debian/tmp/usr/lib/*
5713 Otherwise, you will need to explicitly list the compiled
5714 binaries and libraries.<footnote>
5715 If you are using <tt>debhelper</tt>, the
5716 <prgn>dh_shlibdeps</prgn> program will do this work for you.
5717 It will also correctly handle multi-binary packages.
5722 This command puts the dependency information into the
5723 <file>debian/substvars</file> file, which is then used by
5724 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5725 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5726 field in the control file for this to work.
5730 If you have multiple binary packages, you will need to call
5731 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5732 compiled libraries or binaries. In such a case, you will
5733 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5734 utilities to specify a different <file>substvars</file> file.
5738 If you are creating a udeb for use in the Debian Installer,
5739 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
5740 should use the dependency line of type <tt>udeb</tt> by
5741 adding the <tt>-tudeb</tt> option<footnote>
5742 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5743 will automatically add this option if it knows it is
5745 </footnote>. If there is no dependency line of
5746 type <tt>udeb</tt> in the <file>shlibs</file>
5747 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the regular
5752 For more details on <prgn>dpkg-shlibdeps</prgn>, please see
5753 <ref id="pkg-dpkg-shlibdeps"> and
5754 <manref name="dpkg-shlibdeps" section="1">.
5759 <heading>The <file>shlibs</file> File Format</heading>
5762 Each <file>shlibs</file> file has the same format. Lines
5763 beginning with <tt>#</tt> are considered to be comments and
5764 are ignored. Each line is of the form:
5765 <example compact="compact">
5766 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5771 We will explain this by reference to the example of the
5772 <tt>zlib1g</tt> package, which (at the time of writing)
5773 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5777 <var>type</var> is an optional element that indicates the type
5778 of package for which the line is valid. The only type currently
5779 in use is <tt>udeb</tt>. The colon and space after the type are
5784 <var>library-name</var> is the name of the shared library,
5785 in this case <tt>libz</tt>. (This must match the name part
5786 of the soname, see below.)
5790 <var>soname-version</var> is the version part of the soname of
5791 the library. The soname is the thing that must exactly match
5792 for the library to be recognized by the dynamic linker, and is
5794 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5795 example, <tt>libz.so.1</tt>.<footnote>
5796 This can be determined using the command
5797 <example compact="compact">
5798 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5801 The version part is the part which comes after
5802 <tt>.so.</tt>, so in our case, it is <tt>1</tt>. The soname may
5803 instead be of the form
5804 <tt><var>name</var>-<var>major-version</var>.so</tt>, such
5805 as <tt>libdb-4.8.so</tt>, in which case the name would
5806 be <tt>libdb</tt> and the version would be <tt>4.8</tt>.
5810 <var>dependencies</var> has the same syntax as a dependency
5811 field in a binary package control file. It should give
5812 details of which packages are required to satisfy a binary
5813 built against the version of the library contained in the
5814 package. See <ref id="depsyntax"> for details.
5818 In our example, if the first version of the <tt>zlib1g</tt>
5819 package which contained a minor number of at least
5820 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5821 <tt>shlibs</tt> entry for this library could say:
5822 <example compact="compact">
5823 libz 1 zlib1g (>= 1:1.1.3)
5825 The version-specific dependency is to avoid warnings from
5826 the dynamic linker about using older shared libraries with
5831 As zlib1g also provides a udeb containing the shared library,
5832 there would also be a second line:
5833 <example compact="compact">
5834 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5840 <heading>Providing a <file>shlibs</file> file</heading>
5843 If your package provides a shared library, you need to create
5844 a <file>shlibs</file> file following the format described above.
5845 It is usual to call this file <file>debian/shlibs</file> (but if
5846 you have multiple binary packages, you might want to call it
5847 <file>debian/shlibs.<var>package</var></file> instead). Then
5848 let <file>debian/rules</file> install it in the control
5849 information file area:
5850 <example compact="compact">
5851 install -m644 debian/shlibs debian/tmp/DEBIAN
5853 or, in the case of a multi-binary package:
5854 <example compact="compact">
5855 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5857 An alternative way of doing this is to create the
5858 <file>shlibs</file> file in the control information file area
5859 directly from <file>debian/rules</file> without using
5860 a <file>debian/shlibs</file> file at all,<footnote>
5861 This is what <prgn>dh_makeshlibs</prgn> in
5862 the <package>debhelper</package> suite does. If your package
5863 also has a udeb that provides a shared
5864 library, <prgn>dh_makeshlibs</prgn> can automatically generate
5865 the <tt>udeb:</tt> lines if you specify the name of the udeb
5866 with the <tt>--add-udeb</tt> option.
5868 since the <file>debian/shlibs</file> file itself is ignored by
5869 <prgn>dpkg-shlibdeps</prgn>.
5873 As <prgn>dpkg-shlibdeps</prgn> reads the
5874 <file>DEBIAN/shlibs</file> files in all of the binary packages
5875 being built from this source package, all of the
5876 <file>DEBIAN/shlibs</file> files should be installed before
5877 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5885 <chapt id="opersys"><heading>The Operating System</heading>
5888 <heading>File system hierarchy</heading>
5892 <heading>File System Structure</heading>
5895 The location of all installed files and directories must
5896 comply with the Filesystem Hierarchy Standard (FHS),
5897 version 2.3, with the exceptions noted below, and except
5898 where doing so would violate other terms of Debian
5899 Policy. The following exceptions to the FHS apply:
5904 The optional rules related to user specific
5905 configuration files for applications are stored in
5906 the user's home directory are relaxed. It is
5907 recommended that such files start with the
5908 '<tt>.</tt>' character (a "dot file"), and if an
5909 application needs to create more than one dot file
5910 then the preferred placement is in a subdirectory
5911 with a name starting with a '.' character, (a "dot
5912 directory"). In this case it is recommended the
5913 configuration files not start with the '.'
5919 The requirement for amd64 to use <file>/lib64</file>
5920 for 64 bit binaries is removed.
5925 The requirement for object files, internal binaries, and
5926 libraries, including <file>libc.so.*</file>, to be located
5927 directly under <file>/lib{,32}</file> and
5928 <file>/usr/lib{,32}</file> is amended, permitting files
5929 to instead be installed to
5930 <file>/lib/<var>triplet</var></file> and
5931 <file>/usr/lib/<var>triplet</var></file>, where
5932 <tt><var>triplet</var></tt> is the value returned by
5933 <tt>dpkg-architecture -qDEB_HOST_GNU_TYPE</tt> for the
5934 architecture of the package. Packages may <em>not</em>
5935 install files to any <var>triplet</var> path other
5936 than the one matching the architecture of that package;
5937 for instance, an <tt>Architecture: amd64</tt> package
5938 containing 32-bit x86 libraries may not install these
5939 libraries to <file>/usr/lib/i486-linux-gnu</file>.
5941 This is necessary in order to reserve the directories for
5942 use in cross-installation of library packages from other
5943 architectures, as part of the planned deployment of
5948 Applications may also use a single subdirectory under
5949 <file>/usr/lib/<var>triplet</var></file>.
5952 The execution time linker/loader, ld*, must still be made
5953 available in the existing location under /lib or /lib64
5954 since this is part of the ELF ABI for the architecture.
5959 The requirement that
5960 <file>/usr/local/share/man</file> be "synonymous"
5961 with <file>/usr/local/man</file> is relaxed to a
5966 The requirement that windowmanagers with a single
5967 configuration file call it <file>system.*wmrc</file>
5968 is removed, as is the restriction that the window
5969 manager subdirectory be named identically to the
5970 window manager name itself.
5975 The requirement that boot manager configuration
5976 files live in <file>/etc</file>, or at least are
5977 symlinked there, is relaxed to a recommendation.
5982 The following directories in the root filesystem are
5983 additionally allowed: <file>/sys</file> and
5984 <file>/selinux</file>. <footnote>These directories
5985 are used as mount points to mount virtual filesystems
5986 to get access to kernel information.</footnote>
5993 The version of this document referred here can be
5994 found in the <tt>debian-policy</tt> package or on <url
5995 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5996 name="FHS (Debian copy)"> alongside this manual (or, if
5997 you have the <package>debian-policy</package> installed,
5999 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
6000 (local copy)">). The
6001 latest version, which may be a more recent version, may
6003 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
6004 Specific questions about following the standard may be
6005 asked on the <tt>debian-devel</tt> mailing list, or
6006 referred to the FHS mailing list (see the
6007 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
6013 <heading>Site-specific programs</heading>
6016 As mandated by the FHS, packages must not place any
6017 files in <file>/usr/local</file>, either by putting them in
6018 the file system archive to be unpacked by <prgn>dpkg</prgn>
6019 or by manipulating them in their maintainer scripts.
6023 However, the package may create empty directories below
6024 <file>/usr/local</file> so that the system administrator knows
6025 where to place site-specific files. These are not
6026 directories <em>in</em> <file>/usr/local</file>, but are
6027 children of directories in <file>/usr/local</file>. These
6028 directories (<file>/usr/local/*/dir/</file>)
6029 should be removed on package removal if they are
6034 Note that this applies only to
6035 directories <em>below</em> <file>/usr/local</file>,
6036 not <em>in</em> <file>/usr/local</file>. Packages must
6037 not create sub-directories in the
6038 directory <file>/usr/local</file> itself, except those
6039 listed in FHS, section 4.5. However, you may create
6040 directories below them as you wish. You must not remove
6041 any of the directories listed in 4.5, even if you created
6046 Since <file>/usr/local</file> can be mounted read-only from a
6047 remote server, these directories must be created and
6048 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
6049 maintainer scripts and not be included in the
6050 <file>.deb</file> archive. These scripts must not fail if
6051 either of these operations fail.
6055 For example, the <tt>emacsen-common</tt> package could
6056 contain something like
6057 <example compact="compact">
6058 if [ ! -e /usr/local/share/emacs ]
6060 if mkdir /usr/local/share/emacs 2>/dev/null
6062 chown root:staff /usr/local/share/emacs
6063 chmod 2775 /usr/local/share/emacs
6067 in its <prgn>postinst</prgn> script, and
6068 <example compact="compact">
6069 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
6070 rmdir /usr/local/share/emacs 2>/dev/null || true
6072 in the <prgn>prerm</prgn> script. (Note that this form is
6073 used to ensure that if the script is interrupted, the
6074 directory <file>/usr/local/share/emacs</file> will still be
6079 If you do create a directory in <file>/usr/local</file> for
6080 local additions to a package, you should ensure that
6081 settings in <file>/usr/local</file> take precedence over the
6082 equivalents in <file>/usr</file>.
6086 However, because <file>/usr/local</file> and its contents are
6087 for exclusive use of the local administrator, a package
6088 must not rely on the presence or absence of files or
6089 directories in <file>/usr/local</file> for normal operation.
6093 The <file>/usr/local</file> directory itself and all the
6094 subdirectories created by the package should (by default) have
6095 permissions 2775 (group-writable and set-group-id) and be
6096 owned by <tt>root:staff</tt>.
6101 <heading>The system-wide mail directory</heading>
6103 The system-wide mail directory
6104 is <file>/var/mail</file>. This directory is part of the
6105 base system and should not be owned by any particular mail
6106 agents. The use of the old
6107 location <file>/var/spool/mail</file> is deprecated, even
6108 though the spool may still be physically located there.
6114 <heading>Users and groups</heading>
6117 <heading>Introduction</heading>
6119 The Debian system can be configured to use either plain or
6124 Some user ids (UIDs) and group ids (GIDs) are reserved
6125 globally for use by certain packages. Because some
6126 packages need to include files which are owned by these
6127 users or groups, or need the ids compiled into binaries,
6128 these ids must be used on any Debian system only for the
6129 purpose for which they are allocated. This is a serious
6130 restriction, and we should avoid getting in the way of
6131 local administration policies. In particular, many sites
6132 allocate users and/or local system groups starting at 100.
6136 Apart from this we should have dynamically allocated ids,
6137 which should by default be arranged in some sensible
6138 order, but the behavior should be configurable.
6142 Packages other than <tt>base-passwd</tt> must not modify
6143 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
6144 <file>/etc/group</file> or <file>/etc/gshadow</file>.
6149 <heading>UID and GID classes</heading>
6151 The UID and GID numbers are divided into classes as
6157 Globally allocated by the Debian project, the same
6158 on every Debian system. These ids will appear in
6159 the <file>passwd</file> and <file>group</file> files of all
6160 Debian systems, new ids in this range being added
6161 automatically as the <tt>base-passwd</tt> package is
6166 Packages which need a single statically allocated
6167 uid or gid should use one of these; their
6168 maintainers should ask the <tt>base-passwd</tt>
6176 Dynamically allocated system users and groups.
6177 Packages which need a user or group, but can have
6178 this user or group allocated dynamically and
6179 differently on each system, should use <tt>adduser
6180 --system</tt> to create the group and/or user.
6181 <prgn>adduser</prgn> will check for the existence of
6182 the user or group, and if necessary choose an unused
6183 id based on the ranges specified in
6184 <file>adduser.conf</file>.
6188 <tag>1000-59999:</tag>
6191 Dynamically allocated user accounts. By default
6192 <prgn>adduser</prgn> will choose UIDs and GIDs for
6193 user accounts in this range, though
6194 <file>adduser.conf</file> may be used to modify this
6199 <tag>60000-64999:</tag>
6202 Globally allocated by the Debian project, but only
6203 created on demand. The ids are allocated centrally
6204 and statically, but the actual accounts are only
6205 created on users' systems on demand.
6209 These ids are for packages which are obscure or
6210 which require many statically-allocated ids. These
6211 packages should check for and create the accounts in
6212 <file>/etc/passwd</file> or <file>/etc/group</file> (using
6213 <prgn>adduser</prgn> if it has this facility) if
6214 necessary. Packages which are likely to require
6215 further allocations should have a "hole" left after
6216 them in the allocation, to give them room to
6221 <tag>65000-65533:</tag>
6229 User <tt>nobody</tt>. The corresponding gid refers
6230 to the group <tt>nogroup</tt>.
6237 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
6238 not</em> be used, because it is the error return
6247 <sect id="sysvinit">
6248 <heading>System run levels and <file>init.d</file> scripts</heading>
6250 <sect1 id="/etc/init.d">
6251 <heading>Introduction</heading>
6254 The <file>/etc/init.d</file> directory contains the scripts
6255 executed by <prgn>init</prgn> at boot time and when the
6256 init state (or "runlevel") is changed (see <manref
6257 name="init" section="8">).
6261 There are at least two different, yet functionally
6262 equivalent, ways of handling these scripts. For the sake
6263 of simplicity, this document describes only the symbolic
6264 link method. However, it must not be assumed by maintainer
6265 scripts that this method is being used, and any automated
6266 manipulation of the various runlevel behaviors by
6267 maintainer scripts must be performed using
6268 <prgn>update-rc.d</prgn> as described below and not by
6269 manually installing or removing symlinks. For information
6270 on the implementation details of the other method,
6271 implemented in the <tt>file-rc</tt> package, please refer
6272 to the documentation of that package.
6276 These scripts are referenced by symbolic links in the
6277 <file>/etc/rc<var>n</var>.d</file> directories. When changing
6278 runlevels, <prgn>init</prgn> looks in the directory
6279 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
6280 execute, where <tt><var>n</var></tt> is the runlevel that
6281 is being changed to, or <tt>S</tt> for the boot-up
6286 The names of the links all have the form
6287 <file>S<var>mm</var><var>script</var></file> or
6288 <file>K<var>mm</var><var>script</var></file> where
6289 <var>mm</var> is a two-digit number and <var>script</var>
6290 is the name of the script (this should be the same as the
6291 name of the actual script in <file>/etc/init.d</file>).
6295 When <prgn>init</prgn> changes runlevel first the targets
6296 of the links whose names start with a <tt>K</tt> are
6297 executed, each with the single argument <tt>stop</tt>,
6298 followed by the scripts prefixed with an <tt>S</tt>, each
6299 with the single argument <tt>start</tt>. (The links are
6300 those in the <file>/etc/rc<var>n</var>.d</file> directory
6301 corresponding to the new runlevel.) The <tt>K</tt> links
6302 are responsible for killing services and the <tt>S</tt>
6303 link for starting services upon entering the runlevel.
6307 For example, if we are changing from runlevel 2 to
6308 runlevel 3, init will first execute all of the <tt>K</tt>
6309 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
6310 all of the <tt>S</tt> prefixed scripts in that directory.
6311 The links starting with <tt>K</tt> will cause the
6312 referred-to file to be executed with an argument of
6313 <tt>stop</tt>, and the <tt>S</tt> links with an argument
6318 The two-digit number <var>mm</var> is used to determine
6319 the order in which to run the scripts: low-numbered links
6320 have their scripts run first. For example, the
6321 <tt>K20</tt> scripts will be executed before the
6322 <tt>K30</tt> scripts. This is used when a certain service
6323 must be started before another. For example, the name
6324 server <prgn>bind</prgn> might need to be started before
6325 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
6326 can set up its access lists. In this case, the script
6327 that starts <prgn>bind</prgn> would have a lower number
6328 than the script that starts <prgn>inn</prgn> so that it
6330 <example compact="compact">
6337 The two runlevels 0 (halt) and 6 (reboot) are slightly
6338 different. In these runlevels, the links with an
6339 <tt>S</tt> prefix are still called after those with a
6340 <tt>K</tt> prefix, but they too are called with the single
6341 argument <tt>stop</tt>.
6345 <sect1 id="writing-init">
6346 <heading>Writing the scripts</heading>
6349 Packages that include daemons for system services should
6350 place scripts in <file>/etc/init.d</file> to start or stop
6351 services at boot time or during a change of runlevel.
6352 These scripts should be named
6353 <file>/etc/init.d/<var>package</var></file>, and they should
6354 accept one argument, saying what to do:
6357 <tag><tt>start</tt></tag>
6358 <item>start the service,</item>
6360 <tag><tt>stop</tt></tag>
6361 <item>stop the service,</item>
6363 <tag><tt>restart</tt></tag>
6364 <item>stop and restart the service if it's already running,
6365 otherwise start the service</item>
6367 <tag><tt>reload</tt></tag>
6368 <item><p>cause the configuration of the service to be
6369 reloaded without actually stopping and restarting
6372 <tag><tt>force-reload</tt></tag>
6373 <item>cause the configuration to be reloaded if the
6374 service supports this, otherwise restart the
6378 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
6379 <tt>force-reload</tt> options should be supported by all
6380 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
6385 The <file>init.d</file> scripts must ensure that they will
6386 behave sensibly (i.e., returning success and not starting
6387 multiple copies of a service) if invoked with <tt>start</tt>
6388 when the service is already running, or with <tt>stop</tt>
6389 when it isn't, and that they don't kill unfortunately-named
6390 user processes. The best way to achieve this is usually to
6391 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
6396 Be careful of using <tt>set -e</tt> in <file>init.d</file>
6397 scripts. Writing correct <file>init.d</file> scripts requires
6398 accepting various error exit statuses when daemons are already
6399 running or already stopped without aborting
6400 the <file>init.d</file> script, and common <file>init.d</file>
6401 function libraries are not safe to call with <tt>set -e</tt>
6403 <tt>/lib/lsb/init-functions</tt>, which assists in writing
6404 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
6405 in effect and echoing status messages to the console fails,
6407 </footnote>. For <tt>init.d</tt> scripts, it's often easier
6408 to not use <tt>set -e</tt> and instead check the result of
6409 each command separately.
6413 If a service reloads its configuration automatically (as
6414 in the case of <prgn>cron</prgn>, for example), the
6415 <tt>reload</tt> option of the <file>init.d</file> script
6416 should behave as if the configuration has been reloaded
6421 The <file>/etc/init.d</file> scripts must be treated as
6422 configuration files, either (if they are present in the
6423 package, that is, in the .deb file) by marking them as
6424 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6425 by managing them correctly in the maintainer scripts (see
6426 <ref id="config-files">). This is important since we want
6427 to give the local system administrator the chance to adapt
6428 the scripts to the local system, e.g., to disable a
6429 service without de-installing the package, or to specify
6430 some special command line options when starting a service,
6431 while making sure their changes aren't lost during the next
6436 These scripts should not fail obscurely when the
6437 configuration files remain but the package has been
6438 removed, as configuration files remain on the system after
6439 the package has been removed. Only when <prgn>dpkg</prgn>
6440 is executed with the <tt>--purge</tt> option will
6441 configuration files be removed. In particular, as the
6442 <file>/etc/init.d/<var>package</var></file> script itself is
6443 usually a <tt>conffile</tt>, it will remain on the system
6444 if the package is removed but not purged. Therefore, you
6445 should include a <tt>test</tt> statement at the top of the
6447 <example compact="compact">
6448 test -f <var>program-executed-later-in-script</var> || exit 0
6453 Often there are some variables in the <file>init.d</file>
6454 scripts whose values control the behavior of the scripts,
6455 and which a system administrator is likely to want to
6456 change. As the scripts themselves are frequently
6457 <tt>conffile</tt>s, modifying them requires that the
6458 administrator merge in their changes each time the package
6459 is upgraded and the <tt>conffile</tt> changes. To ease
6460 the burden on the system administrator, such configurable
6461 values should not be placed directly in the script.
6462 Instead, they should be placed in a file in
6463 <file>/etc/default</file>, which typically will have the same
6464 base name as the <file>init.d</file> script. This extra file
6465 should be sourced by the script when the script runs. It
6466 must contain only variable settings and comments in SUSv3
6467 <prgn>sh</prgn> format. It may either be a
6468 <tt>conffile</tt> or a configuration file maintained by
6469 the package maintainer scripts. See <ref id="config-files">
6474 To ensure that vital configurable values are always
6475 available, the <file>init.d</file> script should set default
6476 values for each of the shell variables it uses, either
6477 before sourcing the <file>/etc/default/</file> file or
6478 afterwards using something like the <tt>:
6479 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6480 script must behave sensibly and not fail if the
6481 <file>/etc/default</file> file is deleted.
6485 <file>/var/run</file> and <file>/var/lock</file> may be mounted
6486 as temporary filesystems<footnote>
6487 For example, using the <tt>RAMRUN</tt> and <tt>RAMLOCK</tt>
6488 options in <file>/etc/default/rcS</file>.
6489 </footnote>, so the <file>init.d</file> scripts must handle this
6490 correctly. This will typically amount to creating any required
6491 subdirectories dynamically when the <file>init.d</file> script
6492 is run, rather than including them in the package and relying on
6493 <prgn>dpkg</prgn> to create them.
6498 <heading>Interfacing with the initscript system</heading>
6501 Maintainers should use the abstraction layer provided by
6502 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6503 programs to deal with initscripts in their packages'
6504 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6505 and <prgn>postrm</prgn>.
6509 Directly managing the /etc/rc?.d links and directly
6510 invoking the <file>/etc/init.d/</file> initscripts should
6511 be done only by packages providing the initscript
6512 subsystem (such as <prgn>sysv-rc</prgn> and
6513 <prgn>file-rc</prgn>).
6517 <heading>Managing the links</heading>
6520 The program <prgn>update-rc.d</prgn> is provided for
6521 package maintainers to arrange for the proper creation and
6522 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6523 or their functional equivalent if another method is being
6524 used. This may be used by maintainers in their packages'
6525 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6529 You must not include any <file>/etc/rc<var>n</var>.d</file>
6530 symbolic links in the actual archive or manually create or
6531 remove the symbolic links in maintainer scripts; you must
6532 use the <prgn>update-rc.d</prgn> program instead. (The
6533 former will fail if an alternative method of maintaining
6534 runlevel information is being used.) You must not include
6535 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6536 in the archive either. (Only the <tt>sysvinit</tt>
6541 By default <prgn>update-rc.d</prgn> will start services in
6542 each of the multi-user state runlevels (2, 3, 4, and 5)
6543 and stop them in the halt runlevel (0), the single-user
6544 runlevel (1) and the reboot runlevel (6). The system
6545 administrator will have the opportunity to customize
6546 runlevels by simply adding, moving, or removing the
6547 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6548 symbolic links are being used, or by modifying
6549 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6554 To get the default behavior for your package, put in your
6555 <prgn>postinst</prgn> script
6556 <example compact="compact">
6557 update-rc.d <var>package</var> defaults
6559 and in your <prgn>postrm</prgn>
6560 <example compact="compact">
6561 if [ "$1" = purge ]; then
6562 update-rc.d <var>package</var> remove
6564 </example>. Note that if your package changes runlevels
6565 or priority, you may have to remove and recreate the links,
6566 since otherwise the old links may persist. Refer to the
6567 documentation of <prgn>update-rc.d</prgn>.
6571 This will use a default sequence number of 20. If it does
6572 not matter when or in which order the <file>init.d</file>
6573 script is run, use this default. If it does, then you
6574 should talk to the maintainer of the <prgn>sysvinit</prgn>
6575 package or post to <tt>debian-devel</tt>, and they will
6576 help you choose a number.
6580 For more information about using <tt>update-rc.d</tt>,
6581 please consult its man page <manref name="update-rc.d"
6587 <heading>Running initscripts</heading>
6589 The program <prgn>invoke-rc.d</prgn> is provided to make
6590 it easier for package maintainers to properly invoke an
6591 initscript, obeying runlevel and other locally-defined
6592 constraints that might limit a package's right to start,
6593 stop and otherwise manage services. This program may be
6594 used by maintainers in their packages' scripts.
6598 The package maintainer scripts must use
6599 <prgn>invoke-rc.d</prgn> to invoke the
6600 <file>/etc/init.d/*</file> initscripts, instead of
6601 calling them directly.
6605 By default, <prgn>invoke-rc.d</prgn> will pass any
6606 action requests (start, stop, reload, restart...) to the
6607 <file>/etc/init.d</file> script, filtering out requests
6608 to start or restart a service out of its intended
6613 Most packages will simply need to change:
6614 <example compact="compact">/etc/init.d/<package>
6615 <action></example> in their <prgn>postinst</prgn>
6616 and <prgn>prerm</prgn> scripts to:
6617 <example compact="compact">
6618 if which invoke-rc.d >/dev/null 2>&1; then
6619 invoke-rc.d <var>package</var> <action>
6621 /etc/init.d/<var>package</var> <action>
6627 A package should register its initscript services using
6628 <prgn>update-rc.d</prgn> before it tries to invoke them
6629 using <prgn>invoke-rc.d</prgn>. Invocation of
6630 unregistered services may fail.
6634 For more information about using
6635 <prgn>invoke-rc.d</prgn>, please consult its man page
6636 <manref name="invoke-rc.d" section="8">.
6642 <heading>Boot-time initialization</heading>
6645 There used to be another directory, <file>/etc/rc.boot</file>,
6646 which contained scripts which were run once per machine
6647 boot. This has been deprecated in favour of links from
6648 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6649 described in <ref id="/etc/init.d">. Packages must not
6650 place files in <file>/etc/rc.boot</file>.
6655 <heading>Example</heading>
6658 An example on which you can base your
6659 <file>/etc/init.d</file> scripts is found in
6660 <file>/etc/init.d/skeleton</file>.
6667 <heading>Console messages from <file>init.d</file> scripts</heading>
6670 This section describes the formats to be used for messages
6671 written to standard output by the <file>/etc/init.d</file>
6672 scripts. The intent is to improve the consistency of
6673 Debian's startup and shutdown look and feel. For this
6674 reason, please look very carefully at the details. We want
6675 the messages to have the same format in terms of wording,
6676 spaces, punctuation and case of letters.
6680 Here is a list of overall rules that should be used for
6681 messages generated by <file>/etc/init.d</file> scripts.
6687 The message should fit in one line (fewer than 80
6688 characters), start with a capital letter and end with
6689 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6693 If the script is performing some time consuming task in
6694 the background (not merely starting or stopping a
6695 program, for instance), an ellipsis (three dots:
6696 <tt>...</tt>) should be output to the screen, with no
6697 leading or tailing whitespace or line feeds.
6701 The messages should appear as if the computer is telling
6702 the user what it is doing (politely :-), but should not
6703 mention "it" directly. For example, instead of:
6704 <example compact="compact">
6705 I'm starting network daemons: nfsd mountd.
6707 the message should say
6708 <example compact="compact">
6709 Starting network daemons: nfsd mountd.
6716 <tt>init.d</tt> script should use the following standard
6717 message formats for the situations enumerated below.
6723 <p>When daemons are started</p>
6726 If the script starts one or more daemons, the output
6727 should look like this (a single line, no leading
6729 <example compact="compact">
6730 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6732 The <var>description</var> should describe the
6733 subsystem the daemon or set of daemons are part of,
6734 while <var>daemon-1</var> up to <var>daemon-n</var>
6735 denote each daemon's name (typically the file name of
6740 For example, the output of <file>/etc/init.d/lpd</file>
6742 <example compact="compact">
6743 Starting printer spooler: lpd.
6748 This can be achieved by saying
6749 <example compact="compact">
6750 echo -n "Starting printer spooler: lpd"
6751 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6754 in the script. If there are more than one daemon to
6755 start, the output should look like this:
6756 <example compact="compact">
6757 echo -n "Starting remote file system services:"
6758 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6759 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6760 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6763 This makes it possible for the user to see what is
6764 happening and when the final daemon has been started.
6765 Care should be taken in the placement of white spaces:
6766 in the example above the system administrators can
6767 easily comment out a line if they don't want to start
6768 a specific daemon, while the displayed message still
6774 <p>When a system parameter is being set</p>
6777 If you have to set up different system parameters
6778 during the system boot, you should use this format:
6779 <example compact="compact">
6780 Setting <var>parameter</var> to "<var>value</var>".
6785 You can use a statement such as the following to get
6787 <example compact="compact">
6788 echo "Setting DNS domainname to \"$domainname\"."
6793 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
6794 for the left and right quotation marks. A grave accent
6795 (<tt>`</tt>) is not a quote character; neither is an
6796 apostrophe (<tt>'</tt>).
6801 <p>When a daemon is stopped or restarted</p>
6804 When you stop or restart a daemon, you should issue a
6805 message identical to the startup message, except that
6806 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6807 or <tt>Restarting</tt> respectively.
6811 For example, stopping the printer daemon will look like
6813 <example compact="compact">
6814 Stopping printer spooler: lpd.
6820 <p>When something is executed</p>
6823 There are several examples where you have to run a
6824 program at system startup or shutdown to perform a
6825 specific task, for example, setting the system's clock
6826 using <prgn>netdate</prgn> or killing all processes
6827 when the system shuts down. Your message should look
6829 <example compact="compact">
6830 Doing something very useful...done.
6832 You should print the <tt>done.</tt> immediately after
6833 the job has been completed, so that the user is
6834 informed why they have to wait. You can get this
6836 <example compact="compact">
6837 echo -n "Doing something very useful..."
6846 <p>When the configuration is reloaded</p>
6849 When a daemon is forced to reload its configuration
6850 files you should use the following format:
6851 <example compact="compact">
6852 Reloading <var>description</var> configuration...done.
6854 where <var>description</var> is the same as in the
6855 daemon starting message.
6863 <heading>Cron jobs</heading>
6866 Packages must not modify the configuration file
6867 <file>/etc/crontab</file>, and they must not modify the files in
6868 <file>/var/spool/cron/crontabs</file>.</p>
6871 If a package wants to install a job that has to be executed
6872 via cron, it should place a file with the name of the
6873 package in one or more of the following directories:
6874 <example compact="compact">
6880 As these directory names imply, the files within them are
6881 executed on an hourly, daily, weekly, or monthly basis,
6882 respectively. The exact times are listed in
6883 <file>/etc/crontab</file>.</p>
6886 All files installed in any of these directories must be
6887 scripts (e.g., shell scripts or Perl scripts) so that they
6888 can easily be modified by the local system administrator.
6889 In addition, they must be treated as configuration files.
6893 If a certain job has to be executed at some other frequency or
6894 at a specific time, the package should install a file
6895 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6896 same syntax as <file>/etc/crontab</file> and is processed by
6897 <prgn>cron</prgn> automatically. The file must also be
6898 treated as a configuration file. (Note that entries in the
6899 <file>/etc/cron.d</file> directory are not handled by
6900 <prgn>anacron</prgn>. Thus, you should only use this
6901 directory for jobs which may be skipped if the system is not
6904 Unlike <file>crontab</file> files described in the IEEE Std
6905 1003.1-2008 (POSIX.1) available from
6906 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
6907 name="The Open Group">, the files in
6908 <file>/etc/cron.d</file> and the file
6909 <file>/etc/crontab</file> have seven fields; namely:
6911 <item>Minute [0,59]</item>
6912 <item>Hour [0,23]</item>
6913 <item>Day of the month [1,31]</item>
6914 <item>Month of the year [1,12]</item>
6915 <item>Day of the week ([0,6] with 0=Sunday)</item>
6916 <item>Username</item>
6917 <item>Command to be run</item>
6919 Ranges of numbers are allowed. Ranges are two numbers
6920 separated with a hyphen. The specified range is inclusive.
6921 Lists are allowed. A list is a set of numbers (or ranges)
6922 separated by commas. Step values can be used in conjunction
6927 The scripts or <tt>crontab</tt> entries in these directories should
6928 check if all necessary programs are installed before they
6929 try to execute them. Otherwise, problems will arise when a
6930 package was removed but not purged since configuration files
6931 are kept on the system in this situation.
6935 Any <tt>cron</tt> daemon must provide
6936 <file>/usr/bin/crontab</file> and support normal
6937 <tt>crontab</tt> entries as specified in POSIX. The daemon
6938 must also support names for days and months, ranges, and
6939 step values. It has to support <file>/etc/crontab</file>,
6940 and correctly execute the scripts in
6941 <file>/etc/cron.d</file>. The daemon must also correctly
6943 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
6948 <heading>Menus</heading>
6951 The Debian <tt>menu</tt> package provides a standard
6952 interface between packages providing applications and
6953 <em>menu programs</em> (either X window managers or
6954 text-based menu programs such as <prgn>pdmenu</prgn>).
6958 All packages that provide applications that need not be
6959 passed any special command line arguments for normal
6960 operation should register a menu entry for those
6961 applications, so that users of the <tt>menu</tt> package
6962 will automatically get menu entries in their window
6963 managers, as well in shells like <tt>pdmenu</tt>.
6967 Menu entries should follow the current menu policy.
6971 The menu policy can be found in the <tt>menu-policy</tt>
6972 files in the <tt>debian-policy</tt> package.
6973 It is also available from the Debian web mirrors at
6974 <tt><url name="/doc/packaging-manuals/menu-policy/"
6975 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6979 Please also refer to the <em>Debian Menu System</em>
6980 documentation that comes with the <package>menu</package>
6981 package for information about how to register your
6987 <heading>Multimedia handlers</heading>
6990 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6991 is a mechanism for encoding files and data streams and
6992 providing meta-information about them, in particular their
6993 type (e.g. audio or video) and format (e.g. PNG, HTML,
6998 Registration of MIME type handlers allows programs like mail
6999 user agents and web browsers to invoke these handlers to
7000 view, edit or display MIME types they don't support directly.
7004 Packages which provide the ability to view/show/play,
7005 compose, edit or print MIME types should register themselves
7006 as such following the current MIME support policy.
7010 The MIME support policy can be found in the <tt>mime-policy</tt>
7011 files in the <tt>debian-policy</tt> package.
7012 It is also available from the Debian web mirrors at
7013 <tt><url name="/doc/packaging-manuals/mime-policy/"
7014 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
7020 <heading>Keyboard configuration</heading>
7023 To achieve a consistent keyboard configuration so that all
7024 applications interpret a keyboard event the same way, all
7025 programs in the Debian distribution must be configured to
7026 comply with the following guidelines.
7030 The following keys must have the specified interpretations:
7033 <tag><tt><--</tt></tag>
7034 <item>delete the character to the left of the cursor</item>
7036 <tag><tt>Delete</tt></tag>
7037 <item>delete the character to the right of the cursor</item>
7039 <tag><tt>Control+H</tt></tag>
7040 <item>emacs: the help prefix</item>
7043 The interpretation of any keyboard events should be
7044 independent of the terminal that is used, be it a virtual
7045 console, an X terminal emulator, an rlogin/telnet session,
7050 The following list explains how the different programs
7051 should be set up to achieve this:
7057 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
7061 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
7065 X translations are set up to make
7066 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
7067 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
7068 is the vt220 escape code for the "delete character"
7069 key). This must be done by loading the X resources
7070 using <prgn>xrdb</prgn> on all local X displays, not
7071 using the application defaults, so that the
7072 translation resources used correspond to the
7073 <prgn>xmodmap</prgn> settings.
7077 The Linux console is configured to make
7078 <tt><--</tt> generate DEL, and <tt>Delete</tt>
7079 generate <tt>ESC [ 3 ~</tt>.
7083 X applications are configured so that <tt><</tt>
7084 deletes left, and <tt>Delete</tt> deletes right. Motif
7085 applications already work like this.
7089 Terminals should have <tt>stty erase ^?</tt> .
7093 The <tt>xterm</tt> terminfo entry should have <tt>ESC
7094 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
7095 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
7099 Emacs is programmed to map <tt>KB_Backspace</tt> or
7100 the <tt>stty erase</tt> character to
7101 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
7102 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
7103 <tt>^H</tt> to <tt>help</tt> as always.
7107 Other applications use the <tt>stty erase</tt>
7108 character and <tt>kdch1</tt> for the two delete keys,
7109 with ASCII DEL being "delete previous character" and
7110 <tt>kdch1</tt> being "delete character under
7118 This will solve the problem except for the following
7125 Some terminals have a <tt><--</tt> key that cannot
7126 be made to produce anything except <tt>^H</tt>. On
7127 these terminals Emacs help will be unavailable on
7128 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
7129 character takes precedence in Emacs, and has been set
7130 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
7131 available) can be used instead.
7135 Some operating systems use <tt>^H</tt> for <tt>stty
7136 erase</tt>. However, modern telnet versions and all
7137 rlogin versions propagate <tt>stty</tt> settings, and
7138 almost all UNIX versions honour <tt>stty erase</tt>.
7139 Where the <tt>stty</tt> settings are not propagated
7140 correctly, things can be made to work by using
7141 <tt>stty</tt> manually.
7145 Some systems (including previous Debian versions) use
7146 <prgn>xmodmap</prgn> to arrange for both
7147 <tt><--</tt> and <tt>Delete</tt> to generate
7148 <tt>KB_Delete</tt>. We can change the behavior of
7149 their X clients using the same X resources that we use
7150 to do it for our own clients, or configure our clients
7151 using their resources when things are the other way
7152 around. On displays configured like this
7153 <tt>Delete</tt> will not work, but <tt><--</tt>
7158 Some operating systems have different <tt>kdch1</tt>
7159 settings in their <tt>terminfo</tt> database for
7160 <tt>xterm</tt> and others. On these systems the
7161 <tt>Delete</tt> key will not work correctly when you
7162 log in from a system conforming to our policy, but
7163 <tt><--</tt> will.
7170 <heading>Environment variables</heading>
7173 A program must not depend on environment variables to get
7174 reasonable defaults. (That's because these environment
7175 variables would have to be set in a system-wide
7176 configuration file like <file>/etc/profile</file>, which is not
7177 supported by all shells.)
7181 If a program usually depends on environment variables for its
7182 configuration, the program should be changed to fall back to
7183 a reasonable default configuration if these environment
7184 variables are not present. If this cannot be done easily
7185 (e.g., if the source code of a non-free program is not
7186 available), the program must be replaced by a small
7187 "wrapper" shell script which sets the environment variables
7188 if they are not already defined, and calls the original program.
7192 Here is an example of a wrapper script for this purpose:
7194 <example compact="compact">
7196 BAR=${BAR:-/var/lib/fubar}
7198 exec /usr/lib/foo/foo "$@"
7203 Furthermore, as <file>/etc/profile</file> is a configuration
7204 file of the <prgn>base-files</prgn> package, other packages must
7205 not put any environment variables or other commands into that
7210 <sect id="doc-base">
7211 <heading>Registering Documents using doc-base</heading>
7214 The <package>doc-base</package> package implements a
7215 flexible mechanism for handling and presenting
7216 documentation. The recommended practice is for every Debian
7217 package that provides online documentation (other than just
7218 manual pages) to register these documents with
7219 <package>doc-base</package> by installing a
7220 <package>doc-base</package> control file via the
7221 <prgn/install-docs/ script at installation time and
7222 de-register the manuals again when the package is removed.
7225 Please refer to the documentation that comes with the
7226 <package>doc-base</package> package for information and
7235 <heading>Files</heading>
7237 <sect id="binaries">
7238 <heading>Binaries</heading>
7241 Two different packages must not install programs with
7242 different functionality but with the same filenames. (The
7243 case of two programs having the same functionality but
7244 different implementations is handled via "alternatives" or
7245 the "Conflicts" mechanism. See <ref id="maintscripts"> and
7246 <ref id="conflicts"> respectively.) If this case happens,
7247 one of the programs must be renamed. The maintainers should
7248 report this to the <tt>debian-devel</tt> mailing list and
7249 try to find a consensus about which program will have to be
7250 renamed. If a consensus cannot be reached, <em>both</em>
7251 programs must be renamed.
7255 By default, when a package is being built, any binaries
7256 created should include debugging information, as well as
7257 being compiled with optimization. You should also turn on
7258 as many reasonable compilation warnings as possible; this
7259 makes life easier for porters, who can then look at build
7260 logs for possible problems. For the C programming language,
7261 this means the following compilation parameters should be
7263 <example compact="compact">
7265 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
7267 INSTALL = install -s # (or use strip on the files in debian/tmp)
7272 Note that by default all installed binaries should be stripped,
7273 either by using the <tt>-s</tt> flag to
7274 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
7275 the binaries after they have been copied into
7276 <file>debian/tmp</file> but before the tree is made into a
7281 Although binaries in the build tree should be compiled with
7282 debugging information by default, it can often be difficult to
7283 debug programs if they are also subjected to compiler
7284 optimization. For this reason, it is recommended to support the
7285 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
7286 (see <ref id="debianrules-options">). This variable can contain
7287 several flags to change how a package is compiled and built.
7291 It is up to the package maintainer to decide what
7292 compilation options are best for the package. Certain
7293 binaries (such as computationally-intensive programs) will
7294 function better with certain flags (<tt>-O3</tt>, for
7295 example); feel free to use them. Please use good judgment
7296 here. Don't use flags for the sake of it; only use them
7297 if there is good reason to do so. Feel free to override
7298 the upstream author's ideas about which compilation
7299 options are best: they are often inappropriate for our
7305 <sect id="libraries">
7306 <heading>Libraries</heading>
7309 If the package is <strong>architecture: any</strong>, then
7310 the shared library compilation and linking flags must have
7311 <tt>-fPIC</tt>, or the package shall not build on some of
7312 the supported architectures<footnote>
7314 If you are using GCC, <tt>-fPIC</tt> produces code with
7315 relocatable position independent code, which is required for
7316 most architectures to create a shared library, with i386 and
7317 perhaps some others where non position independent code is
7318 permitted in a shared library.
7321 Position independent code may have a performance penalty,
7322 especially on <tt>i386</tt>. However, in most cases the
7323 speed penalty must be measured against the memory wasted on
7324 the few architectures where non position independent code is
7327 </footnote>. Any exception to this rule must be discussed on
7328 the mailing list <em>debian-devel@lists.debian.org</em>, and
7329 a rough consensus obtained. The reasons for not compiling
7330 with <tt>-fPIC</tt> flag must be recorded in the file
7331 <tt>README.Debian</tt>, and care must be taken to either
7332 restrict the architecture or arrange for <tt>-fPIC</tt> to
7333 be used on architectures where it is required.<footnote>
7335 Some of the reasons why this might be required is if the
7336 library contains hand crafted assembly code that is not
7337 relocatable, the speed penalty is excessive for compute
7338 intensive libs, and similar reasons.
7343 As to the static libraries, the common case is not to have
7344 relocatable code, since there is no benefit, unless in specific
7345 cases; therefore the static version must not be compiled
7346 with the <tt>-fPIC</tt> flag. Any exception to this rule
7347 should be discussed on the mailing list
7348 <em>debian-devel@lists.debian.org</em>, and the reasons for
7349 compiling with the <tt>-fPIC</tt> flag must be recorded in
7350 the file <tt>README.Debian</tt>. <footnote>
7352 Some of the reasons for linking static libraries with
7353 the <tt>-fPIC</tt> flag are if, for example, one needs a
7354 Perl API for a library that is under rapid development,
7355 and has an unstable API, so shared libraries are
7356 pointless at this phase of the library's development. In
7357 that case, since Perl needs a library with relocatable
7358 code, it may make sense to create a static library with
7359 relocatable code. Another reason cited is if you are
7360 distilling various libraries into a common shared
7361 library, like <tt>mklibs</tt> does in the Debian
7367 In other words, if both a shared and a static library is
7368 being built, each source unit (<tt>*.c</tt>, for example,
7369 for C files) will need to be compiled twice, for the normal
7374 Libraries should be built with threading support and to be
7375 thread-safe if the library supports this.
7379 Although not enforced by the build tools, shared libraries
7380 must be linked against all libraries that they use symbols from
7381 in the same way that binaries are. This ensures the correct
7382 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
7383 system and guarantees that all libraries can be safely opened
7384 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
7385 option <tt>-Wl,-z,defs</tt> when building a shared library.
7386 Since this option enforces symbol resolution at build time,
7387 a missing library reference will be caught early as a fatal
7392 All installed shared libraries should be stripped with
7393 <example compact="compact">
7394 strip --strip-unneeded <var>your-lib</var>
7396 (The option <tt>--strip-unneeded</tt> makes
7397 <prgn>strip</prgn> remove only the symbols which aren't
7398 needed for relocation processing.) Shared libraries can
7399 function perfectly well when stripped, since the symbols for
7400 dynamic linking are in a separate part of the ELF object
7402 You might also want to use the options
7403 <tt>--remove-section=.comment</tt> and
7404 <tt>--remove-section=.note</tt> on both shared libraries
7405 and executables, and <tt>--strip-debug</tt> on static
7411 Note that under some circumstances it may be useful to
7412 install a shared library unstripped, for example when
7413 building a separate package to support debugging.
7417 Shared object files (often <file>.so</file> files) that are not
7418 public libraries, that is, they are not meant to be linked
7419 to by third party executables (binaries of other packages),
7420 should be installed in subdirectories of the
7421 <file>/usr/lib</file> directory. Such files are exempt from the
7422 rules that govern ordinary shared libraries, except that
7423 they must not be installed executable and should be
7425 A common example are the so-called "plug-ins",
7426 internal shared objects that are dynamically loaded by
7427 programs using <manref name="dlopen" section="3">.
7432 Packages that use <prgn>libtool</prgn> to create and install
7433 their shared libraries install a file containing additional
7434 metadata (ending in <file>.la</file>) alongside the library.
7435 For public libraries intended for use by other packages, these
7436 files normally should not be included in the Debian package,
7437 since the information they include is not necessary to link with
7438 the shared library on Debian and can add unnecessary additional
7439 dependencies to other programs or libraries.<footnote>
7440 These files store, among other things, all libraries on which
7441 that shared library depends. Unfortunately, if
7442 the <file>.la</file> file is present and contains that
7443 dependency information, using <prgn>libtool</prgn> when
7444 linking against that library will cause the resulting program
7445 or library to be linked against those dependencies as well,
7446 even if this is unnecessary. This can create unneeded
7447 dependencies on shared library packages that would otherwise
7448 be hidden behind the library ABI, and can make library
7449 transitions to new SONAMEs unnecessarily complicated and
7450 difficult to manage.
7452 If the <file>.la</file> file is required for that library (if,
7453 for instance, it's loaded via <tt>libltdl</tt> in a way that
7454 requires that meta-information), the <tt>dependency_libs</tt>
7455 setting in the <file>.la</file> file should normally be set to
7456 the empty string. If the shared library development package has
7457 historically included the <file>.la</file>, it must be retained
7458 in the development package (with <tt>dependency_libs</tt>
7459 emptied) until all libraries that depend on it have removed or
7460 emptied <tt>dependency_libs</tt> in their <file>.la</file>
7461 files to prevent linking with those other libraries
7462 using <prgn>libtool</prgn> from failing.
7466 If the <file>.la</file> must be included, it should be included
7467 in the development (<tt>-dev</tt>) package, unless the library
7468 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
7469 library. If it is intended for use with <tt>libltdl</tt>,
7470 the <file>.la</file> files must go in the run-time library
7475 These requirements for handling of <file>.la</file> files do not
7476 apply to loadable modules or libraries not installed in
7477 directories searched by default by the dynamic linker. Packages
7478 installing loadable modules will frequently need to install
7479 the <file>.la</file> files alongside the modules so that they
7480 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
7481 does not need to be modified for libraries or modules that are
7482 not installed in directories searched by the dynamic linker by
7483 default and not intended for use by other packages.
7487 You must make sure that you use only released versions of
7488 shared libraries to build your packages; otherwise other
7489 users will not be able to run your binaries
7490 properly. Producing source packages that depend on
7491 unreleased compilers is also usually a bad
7498 <heading>Shared libraries</heading>
7500 This section has moved to <ref id="sharedlibs">.
7506 <heading>Scripts</heading>
7509 All command scripts, including the package maintainer
7510 scripts inside the package and used by <prgn>dpkg</prgn>,
7511 should have a <tt>#!</tt> line naming the shell to be used
7516 In the case of Perl scripts this should be
7517 <tt>#!/usr/bin/perl</tt>.
7521 When scripts are installed into a directory in the system
7522 PATH, the script name should not include an extension such
7523 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7524 language currently used to implement it.
7527 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
7528 <file>init.d</file> scripts should almost certainly start
7529 with <tt>set -e</tt> so that errors are detected.
7530 <file>init.d</file> scripts are something of a special case, due
7531 to how frequently they need to call commands that are allowed to
7532 fail, and it may instead be easier to check the exit status of
7533 commands directly. See <ref id="writing-init"> for more
7534 information about writing <file>init.d</file> scripts.
7537 Every script should use <tt>set -e</tt> or check the exit status
7538 of <em>every</em> command.
7541 Scripts may assume that <file>/bin/sh</file> implements the
7542 SUSv3 Shell Command Language<footnote>
7543 Single UNIX Specification, version 3, which is also IEEE
7544 1003.1-2004 (POSIX), and is available on the World Wide Web
7545 from <url id="http://www.unix.org/version3/online.html"
7546 name="The Open Group"> after free
7547 registration.</footnote>
7548 plus the following additional features not mandated by
7550 These features are in widespread use in the Linux community
7551 and are implemented in all of bash, dash, and ksh, the most
7552 common shells users may wish to use as <file>/bin/sh</file>.
7555 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7556 must not generate a newline.</item>
7557 <item><tt>test</tt>, if implemented as a shell built-in, must
7558 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7560 <item><tt>local</tt> to create a scoped variable must be
7561 supported, including listing multiple variables in a single
7562 local command and assigning a value to a variable at the
7563 same time as localizing it. <tt>local</tt> may or
7564 may not preserve the variable value from an outer scope if
7565 no assignment is present. Uses such as:
7569 # ... use a, b, c, d ...
7572 must be supported and must set the value of <tt>c</tt> to
7576 If a shell script requires non-SUSv3 features from the shell
7577 interpreter other than those listed above, the appropriate shell
7578 must be specified in the first line of the script (e.g.,
7579 <tt>#!/bin/bash</tt>) and the package must depend on the package
7580 providing the shell (unless the shell package is marked
7581 "Essential", as in the case of <prgn>bash</prgn>).
7585 You may wish to restrict your script to SUSv3 features plus the
7586 above set when possible so that it may use <file>/bin/sh</file>
7587 as its interpreter. If your script works with <prgn>dash</prgn>
7588 (originally called <prgn>ash</prgn>), it probably complies with
7589 the above requirements, but if you are in doubt, use
7590 <file>/bin/bash</file>.
7594 Perl scripts should check for errors when making any
7595 system calls, including <tt>open</tt>, <tt>print</tt>,
7596 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7600 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7601 scripting languages. See <em>Csh Programming Considered
7602 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7603 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7604 If an upstream package comes with <prgn>csh</prgn> scripts
7605 then you must make sure that they start with
7606 <tt>#!/bin/csh</tt> and make your package depend on the
7607 <prgn>c-shell</prgn> virtual package.
7611 Any scripts which create files in world-writeable
7612 directories (e.g., in <file>/tmp</file>) must use a
7613 mechanism which will fail atomically if a file with the same
7614 name already exists.
7618 The Debian base system provides the <prgn>tempfile</prgn>
7619 and <prgn>mktemp</prgn> utilities for use by scripts for
7626 <heading>Symbolic links</heading>
7629 In general, symbolic links within a top-level directory
7630 should be relative, and symbolic links pointing from one
7631 top-level directory into another should be absolute. (A
7632 top-level directory is a sub-directory of the root
7633 directory <file>/</file>.)
7637 In addition, symbolic links should be specified as short as
7638 possible, i.e., link targets like <file>foo/../bar</file> are
7643 Note that when creating a relative link using
7644 <prgn>ln</prgn> it is not necessary for the target of the
7645 link to exist relative to the working directory you're
7646 running <prgn>ln</prgn> from, nor is it necessary to change
7647 directory to the directory where the link is to be made.
7648 Simply include the string that should appear as the target
7649 of the link (this will be a pathname relative to the
7650 directory in which the link resides) as the first argument
7655 For example, in your <prgn>Makefile</prgn> or
7656 <file>debian/rules</file>, you can do things like:
7657 <example compact="compact">
7658 ln -fs gcc $(prefix)/bin/cc
7659 ln -fs gcc debian/tmp/usr/bin/cc
7660 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7661 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7666 A symbolic link pointing to a compressed file should always
7667 have the same file extension as the referenced file. (For
7668 example, if a file <file>foo.gz</file> is referenced by a
7669 symbolic link, the filename of the link has to end with
7670 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7675 <heading>Device files</heading>
7678 Packages must not include device files or named pipes in the
7683 If a package needs any special device files that are not
7684 included in the base system, it must call
7685 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7686 after notifying the user<footnote>
7687 This notification could be done via a (low-priority)
7688 debconf message, or an echo (printf) statement.
7693 Packages must not remove any device files in the
7694 <prgn>postrm</prgn> or any other script. This is left to the
7695 system administrator.
7699 Debian uses the serial devices
7700 <file>/dev/ttyS*</file>. Programs using the old
7701 <file>/dev/cu*</file> devices should be changed to use
7702 <file>/dev/ttyS*</file>.
7706 Named pipes needed by the package must be created in
7707 the <prgn>postinst</prgn> script<footnote>
7708 It's better to use <prgn>mkfifo</prgn> rather
7709 than <prgn>mknod</prgn> to create named pipes so that
7710 automated checks for packages incorrectly creating device
7711 files with <prgn>mknod</prgn> won't have false positives.
7712 </footnote> and removed in
7713 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
7718 <sect id="config-files">
7719 <heading>Configuration files</heading>
7722 <heading>Definitions</heading>
7726 <tag>configuration file</tag>
7728 A file that affects the operation of a program, or
7729 provides site- or host-specific information, or
7730 otherwise customizes the behavior of a program.
7731 Typically, configuration files are intended to be
7732 modified by the system administrator (if needed or
7733 desired) to conform to local policy or to provide
7734 more useful site-specific behavior.
7737 <tag><tt>conffile</tt></tag>
7739 A file listed in a package's <tt>conffiles</tt>
7740 file, and is treated specially by <prgn>dpkg</prgn>
7741 (see <ref id="configdetails">).
7747 The distinction between these two is important; they are
7748 not interchangeable concepts. Almost all
7749 <tt>conffile</tt>s are configuration files, but many
7750 configuration files are not <tt>conffiles</tt>.
7754 As noted elsewhere, <file>/etc/init.d</file> scripts,
7755 <file>/etc/default</file> files, scripts installed in
7756 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7757 configuration installed in <file>/etc/cron.d</file> must be
7758 treated as configuration files. In general, any script that
7759 embeds configuration information is de-facto a configuration
7760 file and should be treated as such.
7765 <heading>Location</heading>
7768 Any configuration files created or used by your package
7769 must reside in <file>/etc</file>. If there are several,
7770 consider creating a subdirectory of <file>/etc</file>
7771 named after your package.
7775 If your package creates or uses configuration files
7776 outside of <file>/etc</file>, and it is not feasible to modify
7777 the package to use <file>/etc</file> directly, put the files
7778 in <file>/etc</file> and create symbolic links to those files
7779 from the location that the package requires.
7784 <heading>Behavior</heading>
7787 Configuration file handling must conform to the following
7789 <list compact="compact">
7791 local changes must be preserved during a package
7795 configuration files must be preserved when the
7796 package is removed, and only deleted when the
7800 Obsolete configuration files without local changes may be
7801 removed by the package during upgrade.
7805 The easy way to achieve this behavior is to make the
7806 configuration file a <tt>conffile</tt>. This is
7807 appropriate only if it is possible to distribute a default
7808 version that will work for most installations, although
7809 some system administrators may choose to modify it. This
7810 implies that the default version will be part of the
7811 package distribution, and must not be modified by the
7812 maintainer scripts during installation (or at any other
7817 In order to ensure that local changes are preserved
7818 correctly, no package may contain or make hard links to
7819 conffiles.<footnote>
7820 Rationale: There are two problems with hard links.
7821 The first is that some editors break the link while
7822 editing one of the files, so that the two files may
7823 unwittingly become unlinked and different. The second
7824 is that <prgn>dpkg</prgn> might break the hard link
7825 while upgrading <tt>conffile</tt>s.
7830 The other way to do it is via the maintainer scripts. In
7831 this case, the configuration file must not be listed as a
7832 <tt>conffile</tt> and must not be part of the package
7833 distribution. If the existence of a file is required for
7834 the package to be sensibly configured it is the
7835 responsibility of the package maintainer to provide
7836 maintainer scripts which correctly create, update and
7837 maintain the file and remove it on purge. (See <ref
7838 id="maintainerscripts"> for more information.) These
7839 scripts must be idempotent (i.e., must work correctly if
7840 <prgn>dpkg</prgn> needs to re-run them due to errors
7841 during installation or removal), must cope with all the
7842 variety of ways <prgn>dpkg</prgn> can call maintainer
7843 scripts, must not overwrite or otherwise mangle the user's
7844 configuration without asking, must not ask unnecessary
7845 questions (particularly during upgrades), and must
7846 otherwise be good citizens.
7850 The scripts are not required to configure every possible
7851 option for the package, but only those necessary to get
7852 the package running on a given system. Ideally the
7853 sysadmin should not have to do any configuration other
7854 than that done (semi-)automatically by the
7855 <prgn>postinst</prgn> script.
7859 A common practice is to create a script called
7860 <file><var>package</var>-configure</file> and have the
7861 package's <prgn>postinst</prgn> call it if and only if the
7862 configuration file does not already exist. In certain
7863 cases it is useful for there to be an example or template
7864 file which the maintainer scripts use. Such files should
7865 be in <file>/usr/share/<var>package</var></file> or
7866 <file>/usr/lib/<var>package</var></file> (depending on whether
7867 they are architecture-independent or not). There should
7868 be symbolic links to them from
7869 <file>/usr/share/doc/<var>package</var>/examples</file> if
7870 they are examples, and should be perfectly ordinary
7871 <prgn>dpkg</prgn>-handled files (<em>not</em>
7872 configuration files).
7876 These two styles of configuration file handling must
7877 not be mixed, for that way lies madness:
7878 <prgn>dpkg</prgn> will ask about overwriting the file
7879 every time the package is upgraded.
7884 <heading>Sharing configuration files</heading>
7887 Packages which specify the same file as a
7888 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7889 with each other. (This is an instance of the general rule
7890 about not sharing files. Note that neither alternatives
7891 nor diversions are likely to be appropriate in this case;
7892 in particular, <prgn>dpkg</prgn> does not handle diverted
7893 <tt>conffile</tt>s well.)
7897 The maintainer scripts must not alter a <tt>conffile</tt>
7898 of <em>any</em> package, including the one the scripts
7903 If two or more packages use the same configuration file
7904 and it is reasonable for both to be installed at the same
7905 time, one of these packages must be defined as
7906 <em>owner</em> of the configuration file, i.e., it will be
7907 the package which handles that file as a configuration
7908 file. Other packages that use the configuration file must
7909 depend on the owning package if they require the
7910 configuration file to operate. If the other package will
7911 use the configuration file if present, but is capable of
7912 operating without it, no dependency need be declared.
7916 If it is desirable for two or more related packages to
7917 share a configuration file <em>and</em> for all of the
7918 related packages to be able to modify that configuration
7919 file, then the following should be done:
7920 <enumlist compact="compact">
7922 One of the related packages (the "owning" package)
7923 will manage the configuration file with maintainer
7924 scripts as described in the previous section.
7927 The owning package should also provide a program
7928 that the other packages may use to modify the
7932 The related packages must use the provided program
7933 to make any desired modifications to the
7934 configuration file. They should either depend on
7935 the core package to guarantee that the configuration
7936 modifier program is available or accept gracefully
7937 that they cannot modify the configuration file if it
7938 is not. (This is in addition to the fact that the
7939 configuration file may not even be present in the
7946 Sometimes it's appropriate to create a new package which
7947 provides the basic infrastructure for the other packages
7948 and which manages the shared configuration files. (The
7949 <tt>sgml-base</tt> package is a good example.)
7954 <heading>User configuration files ("dotfiles")</heading>
7957 The files in <file>/etc/skel</file> will automatically be
7958 copied into new user accounts by <prgn>adduser</prgn>.
7959 No other program should reference the files in
7960 <file>/etc/skel</file>.
7964 Therefore, if a program needs a dotfile to exist in
7965 advance in <file>$HOME</file> to work sensibly, that dotfile
7966 should be installed in <file>/etc/skel</file> and treated as a
7971 However, programs that require dotfiles in order to
7972 operate sensibly are a bad thing, unless they do create
7973 the dotfiles themselves automatically.
7977 Furthermore, programs should be configured by the Debian
7978 default installation to behave as closely to the upstream
7979 default behavior as possible.
7983 Therefore, if a program in a Debian package needs to be
7984 configured in some way in order to operate sensibly, that
7985 should be done using a site-wide configuration file placed
7986 in <file>/etc</file>. Only if the program doesn't support a
7987 site-wide default configuration and the package maintainer
7988 doesn't have time to add it may a default per-user file be
7989 placed in <file>/etc/skel</file>.
7993 <file>/etc/skel</file> should be as empty as we can make it.
7994 This is particularly true because there is no easy (or
7995 necessarily desirable) mechanism for ensuring that the
7996 appropriate dotfiles are copied into the accounts of
7997 existing users when a package is installed.
8003 <heading>Log files</heading>
8005 Log files should usually be named
8006 <file>/var/log/<var>package</var>.log</file>. If you have many
8007 log files, or need a separate directory for permission
8008 reasons (<file>/var/log</file> is writable only by
8009 <file>root</file>), you should usually create a directory named
8010 <file>/var/log/<var>package</var></file> and place your log
8015 Log files must be rotated occasionally so that they don't
8016 grow indefinitely; the best way to do this is to drop a log
8017 rotation configuration file into the directory
8018 <file>/etc/logrotate.d</file> and use the facilities provided by
8019 logrotate.<footnote>
8021 The traditional approach to log files has been to set up
8022 <em>ad hoc</em> log rotation schemes using simple shell
8023 scripts and cron. While this approach is highly
8024 customizable, it requires quite a lot of sysadmin work.
8025 Even though the original Debian system helped a little
8026 by automatically installing a system which can be used
8027 as a template, this was deemed not enough.
8031 The use of <prgn>logrotate</prgn>, a program developed
8032 by Red Hat, is better, as it centralizes log management.
8033 It has both a configuration file
8034 (<file>/etc/logrotate.conf</file>) and a directory where
8035 packages can drop their individual log rotation
8036 configurations (<file>/etc/logrotate.d</file>).
8039 Here is a good example for a logrotate config
8040 file (for more information see <manref name="logrotate"
8042 <example compact="compact">
8043 /var/log/foo/*.log {
8048 /etc/init.d/foo force-reload
8052 This rotates all files under <file>/var/log/foo</file>, saves 12
8053 compressed generations, and forces the daemon to reload its
8054 configuration information after the log rotation.
8058 Log files should be removed when the package is
8059 purged (but not when it is only removed). This should be
8060 done by the <prgn>postrm</prgn> script when it is called
8061 with the argument <tt>purge</tt> (see <ref
8062 id="removedetails">).
8067 <heading>Permissions and owners</heading>
8070 The rules in this section are guidelines for general use.
8071 If necessary you may deviate from the details below.
8072 However, if you do so you must make sure that what is done
8073 is secure and you should try to be as consistent as possible
8074 with the rest of the system. You should probably also
8075 discuss it on <prgn>debian-devel</prgn> first.
8079 Files should be owned by <tt>root:root</tt>, and made
8080 writable only by the owner and universally readable (and
8081 executable, if appropriate), that is mode 644 or 755.
8085 Directories should be mode 755 or (for group-writability)
8086 mode 2775. The ownership of the directory should be
8087 consistent with its mode: if a directory is mode 2775, it
8088 should be owned by the group that needs write access to
8091 When a package is upgraded, and the owner or permissions
8092 of a file included in the package has changed, dpkg
8093 arranges for the ownership and permissions to be
8094 correctly set upon installation. However, this does not
8095 extend to directories; the permissions and ownership of
8096 directories already on the system does not change on
8097 install or upgrade of packages. This makes sense, since
8098 otherwise common directories like <tt>/usr</tt> would
8099 always be in flux. To correctly change permissions of a
8100 directory the package owns, explicit action is required,
8101 usually in the <tt>postinst</tt> script. Care must be
8102 taken to handle downgrades as well, in that case.
8109 Setuid and setgid executables should be mode 4755 or 2755
8110 respectively, and owned by the appropriate user or group.
8111 They should not be made unreadable (modes like 4711 or
8112 2711 or even 4111); doing so achieves no extra security,
8113 because anyone can find the binary in the freely available
8114 Debian package; it is merely inconvenient. For the same
8115 reason you should not restrict read or execute permissions
8116 on non-set-id executables.
8120 Some setuid programs need to be restricted to particular
8121 sets of users, using file permissions. In this case they
8122 should be owned by the uid to which they are set-id, and by
8123 the group which should be allowed to execute them. They
8124 should have mode 4754; again there is no point in making
8125 them unreadable to those users who must not be allowed to
8130 It is possible to arrange that the system administrator can
8131 reconfigure the package to correspond to their local
8132 security policy by changing the permissions on a binary:
8133 they can do this by using <prgn>dpkg-statoverride</prgn>, as
8134 described below.<footnote>
8135 Ordinary files installed by <prgn>dpkg</prgn> (as
8136 opposed to <tt>conffile</tt>s and other similar objects)
8137 normally have their permissions reset to the distributed
8138 permissions when the package is reinstalled. However,
8139 the use of <prgn>dpkg-statoverride</prgn> overrides this
8142 Another method you should consider is to create a group for
8143 people allowed to use the program(s) and make any setuid
8144 executables executable only by that group.
8148 If you need to create a new user or group for your package
8149 there are two possibilities. Firstly, you may need to
8150 make some files in the binary package be owned by this
8151 user or group, or you may need to compile the user or
8152 group id (rather than just the name) into the binary
8153 (though this latter should be avoided if possible, as in
8154 this case you need a statically allocated id).</p>
8157 If you need a statically allocated id, you must ask for a
8158 user or group id from the <tt>base-passwd</tt> maintainer,
8159 and must not release the package until you have been
8160 allocated one. Once you have been allocated one you must
8161 either make the package depend on a version of the
8162 <tt>base-passwd</tt> package with the id present in
8163 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
8164 your package to create the user or group itself with the
8165 correct id (using <tt>adduser</tt>) in its
8166 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
8167 the <prgn>postinst</prgn> is to be preferred if it is
8168 possible, otherwise a pre-dependency will be needed on the
8169 <tt>adduser</tt> package.)
8173 On the other hand, the program might be able to determine
8174 the uid or gid from the user or group name at runtime, so
8175 that a dynamically allocated id can be used. In this case
8176 you should choose an appropriate user or group name,
8177 discussing this on <prgn>debian-devel</prgn> and checking
8178 with the <package/base-passwd/ maintainer that it is unique and that
8179 they do not wish you to use a statically allocated id
8180 instead. When this has been checked you must arrange for
8181 your package to create the user or group if necessary using
8182 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
8183 <prgn>postinst</prgn> script (again, the latter is to be
8184 preferred if it is possible).
8188 Note that changing the numeric value of an id associated
8189 with a name is very difficult, and involves searching the
8190 file system for all appropriate files. You need to think
8191 carefully whether a static or dynamic id is required, since
8192 changing your mind later will cause problems.
8195 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
8197 This section is not intended as policy, but as a
8198 description of the use of <prgn>dpkg-statoverride</prgn>.
8202 If a system administrator wishes to have a file (or
8203 directory or other such thing) installed with owner and
8204 permissions different from those in the distributed Debian
8205 package, they can use the <prgn>dpkg-statoverride</prgn>
8206 program to instruct <prgn>dpkg</prgn> to use the different
8207 settings every time the file is installed. Thus the
8208 package maintainer should distribute the files with their
8209 normal permissions, and leave it for the system
8210 administrator to make any desired changes. For example, a
8211 daemon which is normally required to be setuid root, but
8212 in certain situations could be used without being setuid,
8213 should be installed setuid in the <tt>.deb</tt>. Then the
8214 local system administrator can change this if they wish.
8215 If there are two standard ways of doing it, the package
8216 maintainer can use <tt>debconf</tt> to find out the
8217 preference, and call <prgn>dpkg-statoverride</prgn> in the
8218 maintainer script if necessary to accommodate the system
8219 administrator's choice. Care must be taken during
8220 upgrades to not override an existing setting.
8224 Given the above, <prgn>dpkg-statoverride</prgn> is
8225 essentially a tool for system administrators and would not
8226 normally be needed in the maintainer scripts. There is
8227 one type of situation, though, where calls to
8228 <prgn>dpkg-statoverride</prgn> would be needed in the
8229 maintainer scripts, and that involves packages which use
8230 dynamically allocated user or group ids. In such a
8231 situation, something like the following idiom can be very
8232 helpful in the package's <prgn>postinst</prgn>, where
8233 <tt>sysuser</tt> is a dynamically allocated id:
8235 for i in /usr/bin/foo /usr/sbin/bar
8237 # only do something when no setting exists
8238 if ! dpkg-statoverride --list $i >/dev/null 2>&1
8240 #include: debconf processing, question about foo and bar
8241 if [ "$RET" = "true" ] ; then
8242 dpkg-statoverride --update --add sysuser root 4755 $i
8247 The corresponding code to remove the override when the package
8250 for i in /usr/bin/foo /usr/sbin/bar
8252 if dpkg-statoverride --list $i >/dev/null 2>&1
8254 dpkg-statoverride --remove $i
8264 <chapt id="customized-programs">
8265 <heading>Customized programs</heading>
8267 <sect id="arch-spec">
8268 <heading>Architecture specification strings</heading>
8271 If a program needs to specify an <em>architecture specification
8272 string</em> in some place, it should select one of the strings
8273 provided by <tt>dpkg-architecture -L</tt>. The strings are in
8274 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
8275 part is sometimes elided, as when the OS is Linux.
8279 Note that we don't want to use
8280 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
8281 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
8282 since this would make our programs incompatible with other
8283 Linux distributions. We also don't use something like
8284 <tt><var>arch</var>-unknown-linux</tt>, since the
8285 <tt>unknown</tt> does not look very good.
8288 <sect1 id="arch-wildcard-spec">
8289 <heading>Architecture wildcards</heading>
8292 A package may specify an architecture wildcard. Architecture
8293 wildcards are in the format <tt>any</tt> (which matches every
8294 architecture), <tt><var>os</var></tt>-any, or
8295 any-<tt><var>cpu</var></tt>. <footnote>
8296 Internally, the package system normalizes the GNU triplets
8297 and the Debian arches into Debian arch triplets (which are
8298 kind of inverted GNU triplets), with the first component of
8299 the triplet representing the libc and ABI in use, and then
8300 does matching against those triplets. However, such
8301 triplets are an internal implementation detail that should
8302 not be used by packages directly. The libc and ABI portion
8303 is handled internally by the package system based on
8304 the <var>os</var> and <var>cpu</var>.
8311 <heading>Daemons</heading>
8314 The configuration files <file>/etc/services</file>,
8315 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
8316 by the <prgn>netbase</prgn> package and must not be modified
8321 If a package requires a new entry in one of these files, the
8322 maintainer should get in contact with the
8323 <prgn>netbase</prgn> maintainer, who will add the entries
8324 and release a new version of the <prgn>netbase</prgn>
8329 The configuration file <file>/etc/inetd.conf</file> must not be
8330 modified by the package's scripts except via the
8331 <prgn>update-inetd</prgn> script or the
8332 <file>DebianNet.pm</file> Perl module. See their documentation
8333 for details on how to add entries.
8337 If a package wants to install an example entry into
8338 <file>/etc/inetd.conf</file>, the entry must be preceded with
8339 exactly one hash character (<tt>#</tt>). Such lines are
8340 treated as "commented out by user" by the
8341 <prgn>update-inetd</prgn> script and are not changed or
8342 activated during package updates.
8347 <heading>Using pseudo-ttys and modifying wtmp, utmp and
8351 Some programs need to create pseudo-ttys. This should be done
8352 using Unix98 ptys if the C library supports it. The resulting
8353 program must not be installed setuid root, unless that
8354 is required for other functionality.
8358 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
8359 <file>/var/log/lastlog</file> must be installed writable by
8360 group <tt>utmp</tt>. Programs which need to modify those
8361 files must be installed setgid <tt>utmp</tt>.
8366 <heading>Editors and pagers</heading>
8369 Some programs have the ability to launch an editor or pager
8370 program to edit or display a text document. Since there are
8371 lots of different editors and pagers available in the Debian
8372 distribution, the system administrator and each user should
8373 have the possibility to choose their preferred editor and
8378 In addition, every program should choose a good default
8379 editor/pager if none is selected by the user or system
8384 Thus, every program that launches an editor or pager must
8385 use the EDITOR or PAGER environment variable to determine
8386 the editor or pager the user wishes to use. If these
8387 variables are not set, the programs <file>/usr/bin/editor</file>
8388 and <file>/usr/bin/pager</file> should be used, respectively.
8392 These two files are managed through the <prgn>dpkg</prgn>
8393 "alternatives" mechanism. Every package providing an editor or
8394 pager must call the <prgn>update-alternatives</prgn> script to
8395 register as an alternative for <file>/usr/bin/editor</file>
8396 or <file>/usr/bin/pager</file> as appropriate. The alternative
8397 should have a slave alternative
8398 for <file>/usr/share/man/man1/editor.1.gz</file>
8399 or <file>/usr/share/man/man1/pager.1.gz</file> pointing to the
8400 corresponding manual page.
8404 If it is very hard to adapt a program to make use of the
8405 EDITOR or PAGER variables, that program may be configured to
8406 use <file>/usr/bin/sensible-editor</file> and
8407 <file>/usr/bin/sensible-pager</file> as the editor or pager
8408 program respectively. These are two scripts provided in the
8409 <package>sensible-utils</package> package that check the EDITOR
8410 and PAGER variables and launch the appropriate program, and fall
8411 back to <file>/usr/bin/editor</file>
8412 and <file>/usr/bin/pager</file> if the variable is not set.
8416 A program may also use the VISUAL environment variable to
8417 determine the user's choice of editor. If it exists, it
8418 should take precedence over EDITOR. This is in fact what
8419 <file>/usr/bin/sensible-editor</file> does.
8423 It is not required for a package to depend on
8424 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
8425 package to provide such virtual packages.<footnote>
8426 The Debian base system already provides an editor and a
8432 <sect id="web-appl">
8433 <heading>Web servers and applications</heading>
8436 This section describes the locations and URLs that should
8437 be used by all web servers and web applications in the
8444 Cgi-bin executable files are installed in the
8446 <example compact="compact">
8447 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
8449 or a subdirectory of that directory, and should be
8451 <example compact="compact">
8452 http://localhost/cgi-bin/<var>cgi-bin-name</var>
8454 (possibly with a subdirectory name
8455 before <var>cgi-bin-name</var>).
8459 <p>Access to HTML documents</p>
8462 HTML documents for a package are stored in
8463 <file>/usr/share/doc/<var>package</var></file>
8464 and can be referred to as
8465 <example compact="compact">
8466 http://localhost/doc/<var>package</var>/<var>filename</var>
8471 The web server should restrict access to the document
8472 tree so that only clients on the same host can read
8473 the documents. If the web server does not support such
8474 access controls, then it should not provide access at
8475 all, or ask about providing access during installation.
8480 <p>Access to images</p>
8482 It is recommended that images for a package be stored
8483 in <tt>/usr/share/images/<var>package</var></tt> and
8484 may be referred to through an alias <tt>/images/</tt>
8487 http://localhost/images/<package>/<filename>
8494 <p>Web Document Root</p>
8497 Web Applications should try to avoid storing files in
8498 the Web Document Root. Instead they should use the
8499 /usr/share/doc/<var>package</var> directory for
8500 documents and register the Web Application via the
8501 <package>doc-base</package> package. If access to the
8502 web document root is unavoidable then use
8503 <example compact="compact">
8506 as the Document Root. This might be just a symbolic
8507 link to the location where the system administrator
8508 has put the real document root.
8511 <item><p>Providing httpd and/or httpd-cgi</p>
8513 All web servers should provide the virtual package
8514 <tt>httpd</tt>. If a web server has CGI support it should
8515 provide <tt>httpd-cgi</tt> additionally.
8518 All web applications which do not contain CGI scripts should
8519 depend on <tt>httpd</tt>, all those web applications which
8520 <tt>do</tt> contain CGI scripts, should depend on
8528 <sect id="mail-transport-agents">
8529 <heading>Mail transport, delivery and user agents</heading>
8532 Debian packages which process electronic mail, whether mail
8533 user agents (MUAs) or mail transport agents (MTAs), must
8534 ensure that they are compatible with the configuration
8535 decisions below. Failure to do this may result in lost
8536 mail, broken <tt>From:</tt> lines, and other serious brain
8541 The mail spool is <file>/var/mail</file> and the interface to
8542 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8543 the FHS). On older systems, the mail spool may be
8544 physically located in <file>/var/spool/mail</file>, but all
8545 access to the mail spool should be via the
8546 <file>/var/mail</file> symlink. The mail spool is part of the
8547 base system and not part of the MTA package.
8551 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8552 programs (such as IMAP daemons) must lock the mailbox in an
8553 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8554 be combined with dot locking. To avoid deadlocks, a program
8555 should use <tt>fcntl()</tt> first and dot locking after
8556 this, or alternatively implement the two locking methods in
8557 a non blocking way<footnote>
8558 If it is not possible to establish both locks, the
8559 system shouldn't wait for the second lock to be
8560 established, but remove the first lock, wait a (random)
8561 time, and start over locking again.
8562 </footnote>. Using the functions <tt>maillock</tt> and
8563 <tt>mailunlock</tt> provided by the
8564 <tt>liblockfile*</tt><footnote>
8565 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8566 to use these functions.
8567 </footnote> packages is the recommended way to realize this.
8571 Mailboxes are generally either mode 600 and owned by
8572 <var>user</var> or mode 660 and owned by
8573 <tt><var>user</var>:mail</tt><footnote>
8574 There are two traditional permission schemes for mail spools:
8575 mode 600 with all mail delivery done by processes running as
8576 the destination user, or mode 660 and owned by group mail with
8577 mail delivery done by a process running as a system user in
8578 group mail. Historically, Debian required mode 660 mail
8579 spools to enable the latter model, but that model has become
8580 increasingly uncommon and the principle of least privilege
8581 indicates that mail systems that use the first model should
8582 use permissions of 600. If delivery to programs is permitted,
8583 it's easier to keep the mail system secure if the delivery
8584 agent runs as the destination user. Debian Policy therefore
8585 permits either scheme.
8586 </footnote>. The local system administrator may choose a
8587 different permission scheme; packages should not make
8588 assumptions about the permission and ownership of mailboxes
8589 unless required (such as when creating a new mailbox). A MUA
8590 may remove a mailbox (unless it has nonstandard permissions) in
8591 which case the MTA or another MUA must recreate it if needed.
8595 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8596 be setgid mail to do the locking mentioned above (and
8597 must obviously avoid accessing other users' mailboxes
8598 using this privilege).</p>
8601 <file>/etc/aliases</file> is the source file for the system mail
8602 aliases (e.g., postmaster, usenet, etc.), it is the one
8603 which the sysadmin and <prgn>postinst</prgn> scripts may
8604 edit. After <file>/etc/aliases</file> is edited the program or
8605 human editing it must call <prgn>newaliases</prgn>. All MTA
8606 packages must come with a <prgn>newaliases</prgn> program,
8607 even if it does nothing, but older MTA packages did not do
8608 this so programs should not fail if <prgn>newaliases</prgn>
8609 cannot be found. Note that because of this, all MTA
8610 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8611 <tt>Replaces: mail-transport-agent</tt> control fields.
8615 The convention of writing <tt>forward to
8616 <var>address</var></tt> in the mailbox itself is not
8617 supported. Use a <tt>.forward</tt> file instead.</p>
8620 The <prgn>rmail</prgn> program used by UUCP
8621 for incoming mail should be <file>/usr/sbin/rmail</file>.
8622 Likewise, <prgn>rsmtp</prgn>, for receiving
8623 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8627 If your package needs to know what hostname to use on (for
8628 example) outgoing news and mail messages which are generated
8629 locally, you should use the file <file>/etc/mailname</file>. It
8630 will contain the portion after the username and <tt>@</tt>
8631 (at) sign for email addresses of users on the machine
8632 (followed by a newline).
8636 Such a package should check for the existence of this file
8637 when it is being configured. If it exists, it should be
8638 used without comment, although an MTA's configuration script
8639 may wish to prompt the user even if it finds that this file
8640 exists. If the file does not exist, the package should
8641 prompt the user for the value (preferably using
8642 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8643 as well as using it in the package's configuration. The
8644 prompt should make it clear that the name will not just be
8645 used by that package. For example, in this situation the
8646 <tt>inn</tt> package could say something like:
8647 <example compact="compact">
8648 Please enter the "mail name" of your system. This is the
8649 hostname portion of the address to be shown on outgoing
8650 news and mail messages. The default is
8651 <var>syshostname</var>, your system's host name. Mail
8652 name ["<var>syshostname</var>"]:
8654 where <var>syshostname</var> is the output of <tt>hostname
8660 <heading>News system configuration</heading>
8663 All the configuration files related to the NNTP (news)
8664 servers and clients should be located under
8665 <file>/etc/news</file>.</p>
8668 There are some configuration issues that apply to a number
8669 of news clients and server packages on the machine. These
8673 <tag><file>/etc/news/organization</file></tag>
8675 A string which should appear as the
8676 organization header for all messages posted
8677 by NNTP clients on the machine
8680 <tag><file>/etc/news/server</file></tag>
8682 Contains the FQDN of the upstream NNTP
8683 server, or localhost if the local machine is
8688 Other global files may be added as required for cross-package news
8695 <heading>Programs for the X Window System</heading>
8698 <heading>Providing X support and package priorities</heading>
8701 Programs that can be configured with support for the X
8702 Window System must be configured to do so and must declare
8703 any package dependencies necessary to satisfy their
8704 runtime requirements when using the X Window System. If
8705 such a package is of higher priority than the X packages
8706 on which it depends, it is required that either the
8707 X-specific components be split into a separate package, or
8708 that an alternative version of the package, which includes
8709 X support, be provided, or that the package's priority be
8715 <heading>Packages providing an X server</heading>
8718 Packages that provide an X server that, directly or
8719 indirectly, communicates with real input and display
8720 hardware should declare in their <tt>Provides</tt> control
8721 field that they provide the virtual
8722 package <tt>xserver</tt>.<footnote>
8723 This implements current practice, and provides an
8724 actual policy for usage of the <tt>xserver</tt>
8725 virtual package which appears in the virtual packages
8726 list. In a nutshell, X servers that interface
8727 directly with the display and input hardware or via
8728 another subsystem (e.g., GGI) should provide
8729 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8730 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8736 <heading>Packages providing a terminal emulator</heading>
8739 Packages that provide a terminal emulator for the X Window
8740 System which meet the criteria listed below should declare in
8741 their <tt>Provides</tt> control field that they provide the
8742 virtual package <tt>x-terminal-emulator</tt>. They should
8743 also register themselves as an alternative for
8744 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8745 20. That alternative should have a slave alternative
8746 for <file>/usr/share/man/man1/x-terminal-emulator.1.gz</file>
8747 pointing to the corresponding manual page.
8751 To be an <tt>x-terminal-emulator</tt>, a program must:
8752 <list compact="compact">
8754 Be able to emulate a DEC VT100 terminal, or a
8755 compatible terminal.
8759 Support the command-line option <tt>-e
8760 <var>command</var></tt>, which creates a new
8761 terminal window<footnote>
8762 "New terminal window" does not necessarily mean
8763 a new top-level X window directly parented by
8764 the window manager; it could, if the terminal
8765 emulator application were so coded, be a new
8766 "view" in a multiple-document interface (MDI).
8768 and runs the specified <var>command</var>,
8769 interpreting the entirety of the rest of the command
8770 line as a command to pass straight to exec, in the
8771 manner that <tt>xterm</tt> does.
8775 Support the command-line option <tt>-T
8776 <var>title</var></tt>, which creates a new terminal
8777 window with the window title <var>title</var>.
8784 <heading>Packages providing a window manager</heading>
8787 Packages that provide a window manager should declare in
8788 their <tt>Provides</tt> control field that they provide the
8789 virtual package <tt>x-window-manager</tt>. They should also
8790 register themselves as an alternative for
8791 <file>/usr/bin/x-window-manager</file>, with a priority
8792 calculated as follows:
8793 <list compact="compact">
8795 Start with a priority of 20.
8799 If the window manager supports the Debian menu
8800 system, add 20 points if this support is available
8801 in the package's default configuration (i.e., no
8802 configuration files belonging to the system or user
8803 have to be edited to activate the feature); if
8804 configuration files must be modified, add only 10
8810 If the window manager complies with <url
8811 id="http://www.freedesktop.org/Standards/wm-spec"
8812 name="The Window Manager Specification Project">,
8813 written by the <url id="http://www.freedesktop.org/"
8814 name="Free Desktop Group">, add 40 points.
8818 If the window manager permits the X session to be
8819 restarted using a <em>different</em> window manager
8820 (without killing the X server) in its default
8821 configuration, add 10 points; otherwise add none.
8824 That alternative should have a slave alternative
8825 for <file>/usr/share/man/man1/x-window-manager.1.gz</file>
8826 pointing to the corresponding manual page.
8831 <heading>Packages providing fonts</heading>
8834 Packages that provide fonts for the X Window
8836 For the purposes of Debian Policy, a "font for the X
8837 Window System" is one which is accessed via X protocol
8838 requests. Fonts for the Linux console, for PostScript
8839 renderer, or any other purpose, do not fit this
8840 definition. Any tool which makes such fonts available
8841 to the X Window System, however, must abide by this
8844 must do a number of things to ensure that they are both
8845 available without modification of the X or font server
8846 configuration, and that they do not corrupt files used by
8847 other font packages to register information about
8851 Fonts of any type supported by the X Window System
8852 must be in a separate binary package from any
8853 executables, libraries, or documentation (except
8854 that specific to the fonts shipped, such as their
8855 license information). If one or more of the fonts
8856 so packaged are necessary for proper operation of
8857 the package with which they are associated the font
8858 package may be Recommended; if the fonts merely
8859 provide an enhancement, a Suggests relationship may
8860 be used. Packages must not Depend on font
8862 This is because the X server may retrieve fonts
8863 from the local file system or over the network
8864 from an X font server; the Debian package system
8865 is empowered to deal only with the local
8871 BDF fonts must be converted to PCF fonts with the
8872 <prgn>bdftopcf</prgn> utility (available in the
8873 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8874 placed in a directory that corresponds to their
8876 <list compact="compact">
8878 100 dpi fonts must be placed in
8879 <file>/usr/share/fonts/X11/100dpi/</file>.
8883 75 dpi fonts must be placed in
8884 <file>/usr/share/fonts/X11/75dpi/</file>.
8888 Character-cell fonts, cursor fonts, and other
8889 low-resolution fonts must be placed in
8890 <file>/usr/share/fonts/X11/misc/</file>.
8896 Type 1 fonts must be placed in
8897 <file>/usr/share/fonts/X11/Type1/</file>. If font
8898 metric files are available, they must be placed here
8903 Subdirectories of <file>/usr/share/fonts/X11/</file>
8904 other than those listed above must be neither
8905 created nor used. (The <file>PEX</file>, <file>CID</file>,
8906 <file>Speedo</file>, and <file>cyrillic</file> directories
8907 are excepted for historical reasons, but installation of
8908 files into these directories remains discouraged.)
8912 Font packages may, instead of placing files directly
8913 in the X font directories listed above, provide
8914 symbolic links in that font directory pointing to
8915 the files' actual location in the filesystem. Such
8916 a location must comply with the FHS.
8920 Font packages should not contain both 75dpi and
8921 100dpi versions of a font. If both are available,
8922 they should be provided in separate binary packages
8923 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8924 the names of the packages containing the
8925 corresponding fonts.
8929 Fonts destined for the <file>misc</file> subdirectory
8930 should not be included in the same package as 75dpi
8931 or 100dpi fonts; instead, they should be provided in
8932 a separate package with <tt>-misc</tt> appended to
8937 Font packages must not provide the files
8938 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8939 <file>fonts.scale</file> in a font directory:
8942 <file>fonts.dir</file> files must not be provided at all.
8946 <file>fonts.alias</file> and <file>fonts.scale</file>
8947 files, if needed, should be provided in the
8949 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8950 where <var>fontdir</var> is the name of the
8952 <file>/usr/share/fonts/X11/</file> where the
8953 package's corresponding fonts are stored
8954 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8955 <var>package</var> is the name of the package
8956 that provides these fonts, and
8957 <var>extension</var> is either <tt>scale</tt>
8958 or <tt>alias</tt>, whichever corresponds to
8965 Font packages must declare a dependency on
8966 <tt>xfonts-utils</tt> in their <tt>Depends</tt>
8967 or <tt>Pre-Depends</tt> control field.
8971 Font packages that provide one or more
8972 <file>fonts.scale</file> files as described above must
8973 invoke <prgn>update-fonts-scale</prgn> on each
8974 directory into which they installed fonts
8975 <em>before</em> invoking
8976 <prgn>update-fonts-dir</prgn> on that directory.
8977 This invocation must occur in both the
8978 <prgn>postinst</prgn> (for all arguments) and
8979 <prgn>postrm</prgn> (for all arguments except
8980 <tt>upgrade</tt>) scripts.
8984 Font packages that provide one or more
8985 <file>fonts.alias</file> files as described above must
8986 invoke <prgn>update-fonts-alias</prgn> on each
8987 directory into which they installed fonts. This
8988 invocation must occur in both the
8989 <prgn>postinst</prgn> (for all arguments) and
8990 <prgn>postrm</prgn> (for all arguments except
8991 <tt>upgrade</tt>) scripts.
8995 Font packages must invoke
8996 <prgn>update-fonts-dir</prgn> on each directory into
8997 which they installed fonts. This invocation must
8998 occur in both the <prgn>postinst</prgn> (for all
8999 arguments) and <prgn>postrm</prgn> (for all
9000 arguments except <tt>upgrade</tt>) scripts.
9004 Font packages must not provide alias names for the
9005 fonts they include which collide with alias names
9006 already in use by fonts already packaged.
9010 Font packages must not provide fonts with the same
9011 XLFD registry name as another font already packaged.
9017 <sect1 id="appdefaults">
9018 <heading>Application defaults files</heading>
9021 Application defaults files must be installed in the
9022 directory <file>/etc/X11/app-defaults/</file> (use of a
9023 localized subdirectory of <file>/etc/X11/</file> as described
9024 in the <em>X Toolkit Intrinsics - C Language
9025 Interface</em> manual is also permitted). They must be
9026 registered as <tt>conffile</tt>s or handled as
9027 configuration files.
9031 Customization of programs' X resources may also be
9032 supported with the provision of a file with the same name
9033 as that of the package placed in
9034 the <file>/etc/X11/Xresources/</file> directory, which
9035 must be registered as a <tt>conffile</tt> or handled as a
9036 configuration file.<footnote>
9037 Note that this mechanism is not the same as using
9038 app-defaults; app-defaults are tied to the client
9039 binary on the local file system, whereas X resources
9040 are stored in the X server and affect all connecting
9047 <heading>Installation directory issues</heading>
9050 Historically, packages using the X Window System used a
9051 separate set of installation directories from other packages.
9052 This practice has been discontinued and packages using the X
9053 Window System should now generally be installed in the same
9054 directories as any other package. Specifically, packages must
9055 not install files under the <file>/usr/X11R6/</file> directory
9056 and the <file>/usr/X11R6/</file> directory hierarchy should be
9057 regarded as obsolete.
9061 Include files previously installed under
9062 <file>/usr/X11R6/include/X11/</file> should be installed into
9063 <file>/usr/include/X11/</file>. For files previously
9064 installed into subdirectories of
9065 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
9066 determine if subdirectories of <file>/usr/lib/</file> and
9067 <file>/usr/share/</file> can be used. If not, a subdirectory
9068 of <file>/usr/lib/X11/</file> should be used.
9072 Configuration files for window, display, or session managers
9073 or other applications that are tightly integrated with the X
9074 Window System may be placed in a subdirectory
9075 of <file>/etc/X11/</file> corresponding to the package name.
9076 Other X Window System applications should use
9077 the <file>/etc/</file> directory unless otherwise mandated by
9078 policy (such as for <ref id="appdefaults">).
9083 <heading>The OSF/Motif and OpenMotif libraries</heading>
9086 <em>Programs that require the non-DFSG-compliant OSF/Motif or
9087 OpenMotif libraries</em><footnote>
9088 OSF/Motif and OpenMotif are collectively referred to as
9089 "Motif" in this policy document.
9091 should be compiled against and tested with LessTif (a free
9092 re-implementation of Motif) instead. If the maintainer
9093 judges that the program or programs do not work
9094 sufficiently well with LessTif to be distributed and
9095 supported, but do so when compiled against Motif, then two
9096 versions of the package should be created; one linked
9097 statically against Motif and with <tt>-smotif</tt>
9098 appended to the package name, and one linked dynamically
9099 against Motif and with <tt>-dmotif</tt> appended to the
9104 Both Motif-linked versions are dependent
9105 upon non-DFSG-compliant software and thus cannot be
9106 uploaded to the <em>main</em> distribution; if the
9107 software is itself DFSG-compliant it may be uploaded to
9108 the <em>contrib</em> distribution. While known existing
9109 versions of Motif permit unlimited redistribution of
9110 binaries linked against the library (whether statically or
9111 dynamically), it is the package maintainer's
9112 responsibility to determine whether this is permitted by
9113 the license of the copy of Motif in their possession.
9119 <heading>Perl programs and modules</heading>
9122 Perl programs and modules should follow the current Perl policy.
9126 The Perl policy can be found in the <tt>perl-policy</tt>
9127 files in the <tt>debian-policy</tt> package.
9128 It is also available from the Debian web mirrors at
9129 <tt><url name="/doc/packaging-manuals/perl-policy/"
9130 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
9135 <heading>Emacs lisp programs</heading>
9138 Please refer to the "Debian Emacs Policy" for details of how to
9139 package emacs lisp programs.
9143 The Emacs policy is available in
9144 <file>debian-emacs-policy.gz</file> of the
9145 <package>emacsen-common</package> package.
9146 It is also available from the Debian web mirrors at
9147 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
9148 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
9153 <heading>Games</heading>
9156 The permissions on <file>/var/games</file> are mode 755, owner
9157 <tt>root</tt> and group <tt>root</tt>.
9161 Each game decides on its own security policy.</p>
9164 Games which require protected, privileged access to
9165 high-score files, saved games, etc., may be made
9166 set-<em>group</em>-id (mode 2755) and owned by
9167 <tt>root:games</tt>, and use files and directories with
9168 appropriate permissions (770 <tt>root:games</tt>, for
9169 example). They must not be made
9170 set-<em>user</em>-id, as this causes security problems. (If
9171 an attacker can subvert any set-user-id game they can
9172 overwrite the executable of any other, causing other players
9173 of these games to run a Trojan horse program. With a
9174 set-group-id game the attacker only gets access to less
9175 important game data, and if they can get at the other
9176 players' accounts at all it will take considerably more
9180 Some packages, for example some fortune cookie programs, are
9181 configured by the upstream authors to install with their
9182 data files or other static information made unreadable so
9183 that they can only be accessed through set-id programs
9184 provided. You should not do this in a Debian package: anyone can
9185 download the <file>.deb</file> file and read the data from it,
9186 so there is no point making the files unreadable. Not
9187 making the files unreadable also means that you don't have
9188 to make so many programs set-id, which reduces the risk of a
9192 As described in the FHS, binaries of games should be
9193 installed in the directory <file>/usr/games</file>. This also
9194 applies to games that use the X Window System. Manual pages
9195 for games (X and non-X games) should be installed in
9196 <file>/usr/share/man/man6</file>.</p>
9202 <heading>Documentation</heading>
9205 <heading>Manual pages</heading>
9208 You should install manual pages in <prgn>nroff</prgn> source
9209 form, in appropriate places under <file>/usr/share/man</file>.
9210 You should only use sections 1 to 9 (see the FHS for more
9211 details). You must not install a pre-formatted "cat page".
9215 Each program, utility, and function should have an
9216 associated manual page included in the same package. It is
9217 suggested that all configuration files also have a manual
9218 page included as well. Manual pages for protocols and other
9219 auxiliary things are optional.
9223 If no manual page is available, this is considered as a bug
9224 and should be reported to the Debian Bug Tracking System (the
9225 maintainer of the package is allowed to write this bug report
9226 themselves, if they so desire). Do not close the bug report
9227 until a proper man page is available.<footnote>
9228 It is not very hard to write a man page. See the
9229 <url id="http://www.schweikhardt.net/man_page_howto.html"
9230 name="Man-Page-HOWTO">,
9231 <manref name="man" section="7">, the examples
9232 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
9233 the helper program <prgn>help2man</prgn>, or the
9234 directory <file>/usr/share/doc/man-db/examples</file>.
9239 You may forward a complaint about a missing man page to the
9240 upstream authors, and mark the bug as forwarded in the
9241 Debian bug tracking system. Even though the GNU Project do
9242 not in general consider the lack of a man page to be a bug,
9243 we do; if they tell you that they don't consider it a bug
9244 you should leave the bug in our bug tracking system open
9249 Manual pages should be installed compressed using <tt>gzip -9</tt>.
9253 If one man page needs to be accessible via several names it
9254 is better to use a symbolic link than the <file>.so</file>
9255 feature, but there is no need to fiddle with the relevant
9256 parts of the upstream source to change from <file>.so</file> to
9257 symlinks: don't do it unless it's easy. You should not
9258 create hard links in the manual page directories, nor put
9259 absolute filenames in <file>.so</file> directives. The filename
9260 in a <file>.so</file> in a man page should be relative to the
9261 base of the man page tree (usually
9262 <file>/usr/share/man</file>). If you do not create any links
9263 (whether symlinks, hard links, or <tt>.so</tt> directives)
9264 in the file system to the alternate names of the man page,
9265 then you should not rely on <prgn>man</prgn> finding your
9266 man page under those names based solely on the information in
9267 the man page's header.<footnote>
9268 Supporting this in <prgn>man</prgn> often requires
9269 unreasonable processing time to find a manual page or to
9270 report that none exists, and moves knowledge into man's
9271 database that would be better left in the file system.
9272 This support is therefore deprecated and will cease to
9273 be present in the future.
9278 Manual pages in locale-specific subdirectories of
9279 <file>/usr/share/man</file> should use either UTF-8 or the usual
9280 legacy encoding for that language (normally the one corresponding
9281 to the shortest relevant locale name in
9282 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
9283 <file>/usr/share/man/fr</file> should use either UTF-8 or
9284 ISO-8859-1.<footnote>
9285 <prgn>man</prgn> will automatically detect whether UTF-8 is in
9286 use. In future, all manual pages will be required to use
9292 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
9293 included in the subdirectory name unless it indicates a
9294 significant difference in the language, as this excludes
9295 speakers of the language in other countries.<footnote>
9296 At the time of writing, Chinese and Portuguese are the main
9297 languages with such differences, so <file>pt_BR</file>,
9298 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
9303 If a localized version of a manual page is provided, it should
9304 either be up-to-date or it should be obvious to the reader that
9305 it is outdated and the original manual page should be used
9306 instead. This can be done either by a note at the beginning of
9307 the manual page or by showing the missing or changed portions in
9308 the original language instead of the target language.
9313 <heading>Info documents</heading>
9316 Info documents should be installed in <file>/usr/share/info</file>.
9317 They should be compressed with <tt>gzip -9</tt>.
9321 The <prgn>install-info</prgn> program maintains a directory of
9322 installed info documents in <file>/usr/share/info/dir</file> for
9323 the use of info readers.<footnote>
9324 It was previously necessary for packages installing info
9325 documents to run <prgn>install-info</prgn> from maintainer
9326 scripts. This is no longer necessary. The installation
9327 system now uses dpkg triggers.
9329 This file must not be included in packages. Packages containing
9330 info documents should depend on <tt>dpkg (>= 1.15.4) |
9331 install-info</tt> to ensure that the directory file is properly
9332 rebuilt during partial upgrades from Debian 5.0 (lenny) and
9337 Info documents should contain section and directory entry
9338 information in the document for the use
9339 of <prgn>install-info</prgn>. The section should be specified
9340 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
9341 space and the section of this info page. The directory entry or
9342 entries should be included between
9343 a <tt>START-INFO-DIR-ENTRY</tt> line and
9344 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
9346 INFO-DIR-SECTION Individual utilities
9347 START-INFO-DIR-ENTRY
9348 * example: (example). An example info directory entry.
9351 To determine which section to use, you should look
9352 at <file>/usr/share/info/dir</file> on your system and choose
9353 the most relevant (or create a new section if none of the
9354 current sections are relevant).<footnote>
9355 Normally, info documents are generated from Texinfo source.
9356 To include this information in the generated info document, if
9357 it is absent, add commands like:
9359 @dircategory Individual utilities
9361 * example: (example). An example info directory entry.
9364 to the Texinfo source of the document and ensure that the info
9365 documents are rebuilt from source during the package build.
9371 <heading>Additional documentation</heading>
9374 Any additional documentation that comes with the package may
9375 be installed at the discretion of the package maintainer.
9376 Plain text documentation should be installed in the directory
9377 <file>/usr/share/doc/<var>package</var></file>, where
9378 <var>package</var> is the name of the package, and
9379 compressed with <tt>gzip -9</tt> unless it is small.
9383 If a package comes with large amounts of documentation which
9384 many users of the package will not require you should create
9385 a separate binary package to contain it, so that it does not
9386 take up disk space on the machines of users who do not need
9387 or want it installed.</p>
9390 It is often a good idea to put text information files
9391 (<file>README</file>s, changelogs, and so forth) that come with
9392 the source package in <file>/usr/share/doc/<var>package</var></file>
9393 in the binary package. However, you don't need to install
9394 the instructions for building and installing the package, of
9398 Packages must not require the existence of any files in
9399 <file>/usr/share/doc/</file> in order to function
9401 The system administrator should be able to
9402 delete files in <file>/usr/share/doc/</file> without causing
9403 any programs to break.
9405 Any files that are referenced by programs but are also
9406 useful as stand alone documentation should be installed under
9407 <file>/usr/share/<var>package</var>/</file> with symbolic links from
9408 <file>/usr/share/doc/<var>package</var></file>.
9412 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9413 link to another directory in <file>/usr/share/doc</file> only if
9414 the two packages both come from the same source and the
9415 first package Depends on the second.<footnote>
9417 Please note that this does not override the section on
9418 changelog files below, so the file
9419 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
9420 must refer to the changelog for the current version of
9421 <var>package</var> in question. In practice, this means
9422 that the sources of the target and the destination of the
9423 symlink must be the same (same source package and
9430 Former Debian releases placed all additional documentation
9431 in <file>/usr/doc/<var>package</var></file>. This has been
9432 changed to <file>/usr/share/doc/<var>package</var></file>,
9433 and packages must not put documentation in the directory
9434 <file>/usr/doc/<var>package</var></file>. <footnote>
9435 At this phase of the transition, we no longer require a
9436 symbolic link in <file>/usr/doc/</file>. At a later point,
9437 policy shall change to make the symbolic links a bug.
9443 <heading>Preferred documentation formats</heading>
9446 The unification of Debian documentation is being carried out
9450 If your package comes with extensive documentation in a
9451 markup format that can be converted to various other formats
9452 you should if possible ship HTML versions in a binary
9453 package, in the directory
9454 <file>/usr/share/doc/<var>appropriate-package</var></file> or
9455 its subdirectories.<footnote>
9456 The rationale: The important thing here is that HTML
9457 docs should be available in <em>some</em> package, not
9458 necessarily in the main binary package.
9463 Other formats such as PostScript may be provided at the
9464 package maintainer's discretion.
9468 <sect id="copyrightfile">
9469 <heading>Copyright information</heading>
9472 Every package must be accompanied by a verbatim copy of its
9473 copyright information and distribution license in the file
9474 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
9475 file must neither be compressed nor be a symbolic link.
9479 In addition, the copyright file must say where the upstream
9480 sources (if any) were obtained. It should name the original
9481 authors of the package and the Debian maintainer(s) who were
9482 involved with its creation.
9486 Packages in the <em>contrib</em> or <em>non-free</em> archive
9487 areas should state in the copyright file that the package is not
9488 part of the Debian GNU/Linux distribution and briefly explain
9493 A copy of the file which will be installed in
9494 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9495 be in <file>debian/copyright</file> in the source package.
9499 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9500 link to another directory in <file>/usr/share/doc</file> only if
9501 the two packages both come from the same source and the
9502 first package Depends on the second. These rules are
9503 important because copyrights must be extractable by
9508 Packages distributed under the Apache license (version 2.0), the
9509 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
9510 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
9511 1.3) should refer to the corresponding files
9512 under <file>/usr/share/common-licenses</file>,<footnote>
9515 <file>/usr/share/common-licenses/Apache-2.0</file>,
9516 <file>/usr/share/common-licenses/Artistic</file>,
9517 <file>/usr/share/common-licenses/GPL-1</file>,
9518 <file>/usr/share/common-licenses/GPL-2</file>,
9519 <file>/usr/share/common-licenses/GPL-3</file>,
9520 <file>/usr/share/common-licenses/LGPL-2</file>,
9521 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9522 <file>/usr/share/common-licenses/LGPL-3</file>,
9523 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
9524 <file>/usr/share/common-licenses/GFDL-1.3</file>
9525 respectively. The University of California BSD license is
9526 also included in <package>base-files</package> as
9527 <file>/usr/share/common-licenses/BSD</file>, but given the
9528 brevity of this license, its specificity to code whose
9529 copyright is held by the Regents of the University of
9530 California, and the frequency of minor wording changes, its
9531 text should be included in the copyright file rather than
9532 referencing this file.
9534 </footnote> rather than quoting them in the copyright
9539 You should not use the copyright file as a general <file>README</file>
9540 file. If your package has such a file it should be
9541 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9542 <file>README.Debian</file> or some other appropriate place.</p>
9546 <heading>Examples</heading>
9549 Any examples (configurations, source files, whatever),
9550 should be installed in a directory
9551 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9552 files should not be referenced by any program: they're there
9553 for the benefit of the system administrator and users as
9554 documentation only. Architecture-specific example files
9555 should be installed in a directory
9556 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9558 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9559 latter directory itself may be a symbolic link to the
9564 If the purpose of a package is to provide examples, then the
9565 example files may be installed into
9566 <file>/usr/share/doc/<var>package</var></file>.
9570 <sect id="changelogs">
9571 <heading>Changelog files</heading>
9574 Packages that are not Debian-native must contain a
9575 compressed copy of the <file>debian/changelog</file> file from
9576 the Debian source tree in
9577 <file>/usr/share/doc/<var>package</var></file> with the name
9578 <file>changelog.Debian.gz</file>.
9582 If an upstream changelog is available, it should be accessible as
9583 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9584 plain text. If the upstream changelog is distributed in
9585 HTML, it should be made available in that form as
9586 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9587 and a plain text <file>changelog.gz</file> should be generated
9588 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9589 the upstream changelog files do not already conform to this
9590 naming convention, then this may be achieved either by
9591 renaming the files, or by adding a symbolic link, at the
9592 maintainer's discretion.<footnote>
9593 Rationale: People should not have to look in places for
9594 upstream changelogs merely because they are given
9595 different names or are distributed in HTML format.
9600 All of these files should be installed compressed using
9601 <tt>gzip -9</tt>, as they will become large with time even
9602 if they start out small.
9606 If the package has only one changelog which is used both as
9607 the Debian changelog and the upstream one because there is
9608 no separate upstream maintainer then that changelog should
9609 usually be installed as
9610 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9611 there is a separate upstream maintainer, but no upstream
9612 changelog, then the Debian changelog should still be called
9613 <file>changelog.Debian.gz</file>.
9617 For details about the format and contents of the Debian
9618 changelog file, please see <ref id="dpkgchangelog">.
9623 <appendix id="pkg-scope">
9624 <heading>Introduction and scope of these appendices</heading>
9627 These appendices are taken essentially verbatim from the
9628 now-deprecated Packaging Manual, version 3.2.1.0. They are
9629 the chapters which are likely to be of use to package
9630 maintainers and which have not already been included in the
9631 policy document itself. Most of these sections are very likely
9632 not relevant to policy; they should be treated as
9633 documentation for the packaging system. Please note that these
9634 appendices are included for convenience, and for historical
9635 reasons: they used to be part of policy package, and they have
9636 not yet been incorporated into dpkg documentation. However,
9637 they still have value, and hence they are presented here.
9641 They have not yet been checked to ensure that they are
9642 compatible with the contents of policy, and if there are any
9643 contradictions, the version in the main policy document takes
9644 precedence. The remaining chapters of the old Packaging
9645 Manual have also not been read in detail to ensure that there
9646 are not parts which have been left out. Both of these will be
9651 Certain parts of the Packaging manual were integrated into the
9652 Policy Manual proper, and removed from the appendices. Links
9653 have been placed from the old locations to the new ones.
9657 <prgn>dpkg</prgn> is a suite of programs for creating binary
9658 package files and installing and removing them on Unix
9660 <prgn>dpkg</prgn> is targeted primarily at Debian
9661 GNU/Linux, but may work on or be ported to other
9667 The binary packages are designed for the management of
9668 installed executable programs (usually compiled binaries) and
9669 their associated data, though source code examples and
9670 documentation are provided as part of some packages.</p>
9673 This manual describes the technical aspects of creating Debian
9674 binary packages (<file>.deb</file> files). It documents the
9675 behavior of the package management programs
9676 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9677 they interact with packages.</p>
9680 It also documents the interaction between
9681 <prgn>dselect</prgn>'s core and the access method scripts it
9682 uses to actually install the selected packages, and describes
9683 how to create a new access method.</p>
9686 This manual does not go into detail about the options and
9687 usage of the package building and installation tools. It
9688 should therefore be read in conjunction with those programs'
9693 The utility programs which are provided with <prgn>dpkg</prgn>
9694 for managing various system configuration and similar issues,
9695 such as <prgn>update-rc.d</prgn> and
9696 <prgn>install-info</prgn>, are not described in detail here -
9697 please see their man pages.
9701 It is assumed that the reader is reasonably familiar with the
9702 <prgn>dpkg</prgn> System Administrators' manual.
9703 Unfortunately this manual does not yet exist.
9707 The Debian version of the FSF's GNU hello program is provided
9708 as an example for people wishing to create Debian
9709 packages. The Debian <prgn>debmake</prgn> package is
9710 recommended as a very helpful tool in creating and maintaining
9711 Debian packages. However, while the tools and examples are
9712 helpful, they do not replace the need to read and follow the
9713 Policy and Programmer's Manual.</p>
9716 <appendix id="pkg-binarypkg">
9717 <heading>Binary packages (from old Packaging Manual)</heading>
9720 The binary package has two main sections. The first part
9721 consists of various control information files and scripts used
9722 by <prgn>dpkg</prgn> when installing and removing. See <ref
9723 id="pkg-controlarea">.
9727 The second part is an archive containing the files and
9728 directories to be installed.
9732 In the future binary packages may also contain other
9733 components, such as checksums and digital signatures. The
9734 format for the archive is described in full in the
9735 <file>deb(5)</file> man page.
9739 <sect id="pkg-bincreating"><heading>Creating package files -
9740 <prgn>dpkg-deb</prgn>
9744 All manipulation of binary package files is done by
9745 <prgn>dpkg-deb</prgn>; it's the only program that has
9746 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9747 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9748 will spot that the options requested are appropriate to
9749 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9754 In order to create a binary package you must make a
9755 directory tree which contains all the files and directories
9756 you want to have in the file system data part of the package.
9757 In Debian-format source packages this directory is usually
9758 <file>debian/tmp</file>, relative to the top of the package's
9763 They should have the locations (relative to the root of the
9764 directory tree you're constructing) ownerships and
9765 permissions which you want them to have on the system when
9770 With current versions of <prgn>dpkg</prgn> the uid/username
9771 and gid/groupname mappings for the users and groups being
9772 used should be the same on the system where the package is
9773 built and the one where it is installed.
9777 You need to add one special directory to the root of the
9778 miniature file system tree you're creating:
9779 <prgn>DEBIAN</prgn>. It should contain the control
9780 information files, notably the binary package control file
9781 (see <ref id="pkg-controlfile">).
9785 The <prgn>DEBIAN</prgn> directory will not appear in the
9786 file system archive of the package, and so won't be installed
9787 by <prgn>dpkg</prgn> when the package is unpacked.
9791 When you've prepared the package, you should invoke:
9793 dpkg --build <var>directory</var>
9798 This will build the package in
9799 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9800 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9801 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9806 See the man page <manref name="dpkg-deb" section="8"> for details of how
9807 to examine the contents of this newly-created file. You may find the
9808 output of following commands enlightening:
9810 dpkg-deb --info <var>filename</var>.deb
9811 dpkg-deb --contents <var>filename</var>.deb
9812 dpkg --contents <var>filename</var>.deb
9814 To view the copyright file for a package you could use this command:
9816 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
9821 <sect id="pkg-controlarea">
9822 <heading>Package control information files</heading>
9825 The control information portion of a binary package is a
9826 collection of files with names known to <prgn>dpkg</prgn>.
9827 It will treat the contents of these files specially - some
9828 of them contain information used by <prgn>dpkg</prgn> when
9829 installing or removing the package; others are scripts which
9830 the package maintainer wants <prgn>dpkg</prgn> to run.
9834 It is possible to put other files in the package control
9835 information file area, but this is not generally a good idea
9836 (though they will largely be ignored).
9840 Here is a brief list of the control information files supported
9841 by <prgn>dpkg</prgn> and a summary of what they're used for.
9846 <tag><tt>control</tt>
9849 This is the key description file used by
9850 <prgn>dpkg</prgn>. It specifies the package's name
9851 and version, gives its description for the user,
9852 states its relationships with other packages, and so
9853 forth. See <ref id="sourcecontrolfiles"> and
9854 <ref id="binarycontrolfiles">.
9858 It is usually generated automatically from information
9859 in the source package by the
9860 <prgn>dpkg-gencontrol</prgn> program, and with
9861 assistance from <prgn>dpkg-shlibdeps</prgn>.
9862 See <ref id="pkg-sourcetools">.
9866 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9871 These are executable files (usually scripts) which
9872 <prgn>dpkg</prgn> runs during installation, upgrade
9873 and removal of packages. They allow the package to
9874 deal with matters which are particular to that package
9875 or require more complicated processing than that
9876 provided by <prgn>dpkg</prgn>. Details of when and
9877 how they are called are in <ref id="maintainerscripts">.
9881 It is very important to make these scripts idempotent.
9882 See <ref id="idempotency">.
9886 The maintainer scripts are not guaranteed to run with a
9887 controlling terminal and may not be able to interact with
9888 the user. See <ref id="controllingterminal">.
9892 <tag><tt>conffiles</tt>
9895 This file contains a list of configuration files which
9896 are to be handled automatically by <prgn>dpkg</prgn>
9897 (see <ref id="pkg-conffiles">). Note that not necessarily
9898 every configuration file should be listed here.
9901 <tag><tt>shlibs</tt>
9904 This file contains a list of the shared libraries
9905 supplied by the package, with dependency details for
9906 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9907 when it determines what dependencies are required in a
9908 package control file. The <tt>shlibs</tt> file format
9909 is described on <ref id="shlibs">.
9914 <sect id="pkg-controlfile">
9915 <heading>The main control information file: <tt>control</tt></heading>
9918 The most important control information file used by
9919 <prgn>dpkg</prgn> when it installs a package is
9920 <tt>control</tt>. It contains all the package's "vital
9925 The binary package control files of packages built from
9926 Debian sources are made by a special tool,
9927 <prgn>dpkg-gencontrol</prgn>, which reads
9928 <file>debian/control</file> and <file>debian/changelog</file> to
9929 find the information it needs. See <ref id="pkg-sourcepkg"> for
9934 The fields in binary package control files are listed in
9935 <ref id="binarycontrolfiles">.
9939 A description of the syntax of control files and the purpose
9940 of the fields is available in <ref id="controlfields">.
9945 <heading>Time Stamps</heading>
9948 See <ref id="timestamps">.
9953 <appendix id="pkg-sourcepkg">
9954 <heading>Source packages (from old Packaging Manual) </heading>
9957 The Debian binary packages in the distribution are generated
9958 from Debian sources, which are in a special format to assist
9959 the easy and automatic building of binaries.
9962 <sect id="pkg-sourcetools">
9963 <heading>Tools for processing source packages</heading>
9966 Various tools are provided for manipulating source packages;
9967 they pack and unpack sources and help build of binary
9968 packages and help manage the distribution of new versions.
9972 They are introduced and typical uses described here; see
9973 <manref name="dpkg-source" section="1"> for full
9974 documentation about their arguments and operation.
9978 For examples of how to construct a Debian source package,
9979 and how to use those utilities that are used by Debian
9980 source packages, please see the <prgn>hello</prgn> example
9984 <sect1 id="pkg-dpkg-source">
9986 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9991 This program is frequently used by hand, and is also
9992 called from package-independent automated building scripts
9993 such as <prgn>dpkg-buildpackage</prgn>.
9997 To unpack a package it is typically invoked with
9999 dpkg-source -x <var>.../path/to/filename</var>.dsc
10004 with the <file><var>filename</var>.tar.gz</file> and
10005 <file><var>filename</var>.diff.gz</file> (if applicable) in
10006 the same directory. It unpacks into
10007 <file><var>package</var>-<var>version</var></file>, and if
10009 <file><var>package</var>-<var>version</var>.orig</file>, in
10010 the current directory.
10014 To create a packed source archive it is typically invoked:
10016 dpkg-source -b <var>package</var>-<var>version</var>
10021 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
10022 <file>.diff.gz</file> (if appropriate) in the current
10023 directory. <prgn>dpkg-source</prgn> does not clean the
10024 source tree first - this must be done separately if it is
10029 See also <ref id="pkg-sourcearchives">.</p>
10033 <sect1 id="pkg-dpkg-buildpackage">
10035 <prgn>dpkg-buildpackage</prgn> - overall package-building
10040 <prgn>dpkg-buildpackage</prgn> is a script which invokes
10041 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
10042 targets <tt>clean</tt>, <tt>build</tt> and
10043 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
10044 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
10045 source and binary package upload.
10049 It is usually invoked by hand from the top level of the
10050 built or unbuilt source directory. It may be invoked with
10051 no arguments; useful arguments include:
10052 <taglist compact="compact">
10053 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
10056 Do not sign the <tt>.changes</tt> file or the
10057 source package <tt>.dsc</tt> file, respectively.</p>
10059 <tag><tt>-p<var>sign-command</var></tt></tag>
10062 Invoke <var>sign-command</var> instead of finding
10063 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
10064 <var>sign-command</var> must behave just like
10065 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
10067 <tag><tt>-r<var>root-command</var></tt></tag>
10070 When root privilege is required, invoke the command
10071 <var>root-command</var>. <var>root-command</var>
10072 should invoke its first argument as a command, from
10073 the <prgn>PATH</prgn> if necessary, and pass its
10074 second and subsequent arguments to the command it
10075 calls. If no <var>root-command</var> is supplied
10076 then <var>dpkg-buildpackage</var> will take no
10077 special action to gain root privilege, so that for
10078 most packages it will have to be invoked as root to
10081 <tag><tt>-b</tt>, <tt>-B</tt></tag>
10084 Two types of binary-only build and upload - see
10085 <manref name="dpkg-source" section="1">.
10092 <sect1 id="pkg-dpkg-gencontrol">
10094 <prgn>dpkg-gencontrol</prgn> - generates binary package
10099 This program is usually called from <file>debian/rules</file>
10100 (see <ref id="pkg-sourcetree">) in the top level of the source
10105 This is usually done just before the files and directories in the
10106 temporary directory tree where the package is being built have their
10107 permissions and ownerships set and the package is constructed using
10108 <prgn>dpkg-deb/</prgn>
10110 This is so that the control file which is produced has
10111 the right permissions
10116 <prgn>dpkg-gencontrol</prgn> must be called after all the
10117 files which are to go into the package have been placed in
10118 the temporary build directory, so that its calculation of
10119 the installed size of a package is correct.
10123 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
10124 be run after <prgn>dpkg-shlibdeps</prgn> so that the
10125 variable substitutions created by
10126 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
10131 For a package which generates only one binary package, and
10132 which builds it in <file>debian/tmp</file> relative to the top
10133 of the source package, it is usually sufficient to call
10134 <prgn>dpkg-gencontrol</prgn>.
10138 Sources which build several binaries will typically need
10141 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
10142 </example> The <tt>-P</tt> tells
10143 <prgn>dpkg-gencontrol</prgn> that the package is being
10144 built in a non-default directory, and the <tt>-p</tt>
10145 tells it which package's control file should be generated.
10149 <prgn>dpkg-gencontrol</prgn> also adds information to the
10150 list of files in <file>debian/files</file>, for the benefit of
10151 (for example) a future invocation of
10152 <prgn>dpkg-genchanges</prgn>.</p>
10155 <sect1 id="pkg-dpkg-shlibdeps">
10157 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
10162 This program is usually called from <file>debian/rules</file>
10163 just before <prgn>dpkg-gencontrol</prgn> (see <ref
10164 id="pkg-sourcetree">), in the top level of the source tree.
10168 Its arguments are executables and shared libraries
10171 They may be specified either in the locations in the
10172 source tree where they are created or in the locations
10173 in the temporary build tree where they are installed
10174 prior to binary package creation.
10176 </footnote> for which shared library dependencies should
10177 be included in the binary package's control file.
10181 If some of the found shared libraries should only
10182 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
10183 some warrant a <tt>Pre-Depends</tt>, this can be achieved
10184 by using the <tt>-d<var>dependency-field</var></tt> option
10185 before those executable(s). (Each <tt>-d</tt> option
10186 takes effect until the next <tt>-d</tt>.)
10190 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
10191 output control file to be modified. Instead by default it
10192 adds to the <file>debian/substvars</file> file variable
10193 settings like <tt>shlibs:Depends</tt>. These variable
10194 settings must be referenced in dependency fields in the
10195 appropriate per-binary-package sections of the source
10200 For example, a package that generates an essential part
10201 which requires dependencies, and optional parts that
10202 which only require a recommendation, would separate those
10203 two sets of dependencies into two different fields.<footnote>
10204 At the time of writing, an example for this was the
10205 <package/xmms/ package, with Depends used for the xmms
10206 executable, Recommends for the plug-ins and Suggests for
10207 even more optional features provided by unzip.
10209 It can say in its <file>debian/rules</file>:
10211 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
10212 -dRecommends <var>optionalpart anotheroptionalpart</var>
10214 and then in its main control file <file>debian/control</file>:
10217 Depends: ${shlibs:Depends}
10218 Recommends: ${shlibs:Recommends}
10224 Sources which produce several binary packages with
10225 different shared library dependency requirements can use
10226 the <tt>-p<var>varnameprefix</var></tt> option to override
10227 the default <tt>shlibs:</tt> prefix (one invocation of
10228 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
10229 They can thus produce several sets of dependency
10230 variables, each of the form
10231 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
10232 which can be referred to in the appropriate parts of the
10233 binary package control files.
10238 <sect1 id="pkg-dpkg-distaddfile">
10240 <prgn>dpkg-distaddfile</prgn> - adds a file to
10241 <file>debian/files</file>
10245 Some packages' uploads need to include files other than
10246 the source and binary package files.
10250 <prgn>dpkg-distaddfile</prgn> adds a file to the
10251 <file>debian/files</file> file so that it will be included in
10252 the <file>.changes</file> file when
10253 <prgn>dpkg-genchanges</prgn> is run.
10257 It is usually invoked from the <tt>binary</tt> target of
10258 <file>debian/rules</file>:
10260 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
10262 The <var>filename</var> is relative to the directory where
10263 <prgn>dpkg-genchanges</prgn> will expect to find it - this
10264 is usually the directory above the top level of the source
10265 tree. The <file>debian/rules</file> target should put the
10266 file there just before or just after calling
10267 <prgn>dpkg-distaddfile</prgn>.
10271 The <var>section</var> and <var>priority</var> are passed
10272 unchanged into the resulting <file>.changes</file> file.
10277 <sect1 id="pkg-dpkg-genchanges">
10279 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
10280 upload control file
10284 This program is usually called by package-independent
10285 automatic building scripts such as
10286 <prgn>dpkg-buildpackage</prgn>, but it may also be called
10291 It is usually called in the top level of a built source
10292 tree, and when invoked with no arguments will print out a
10293 straightforward <file>.changes</file> file based on the
10294 information in the source package's changelog and control
10295 file and the binary and source packages which should have
10301 <sect1 id="pkg-dpkg-parsechangelog">
10303 <prgn>dpkg-parsechangelog</prgn> - produces parsed
10304 representation of a changelog
10308 This program is used internally by
10309 <prgn>dpkg-source</prgn> et al. It may also occasionally
10310 be useful in <file>debian/rules</file> and elsewhere. It
10311 parses a changelog, <file>debian/changelog</file> by default,
10312 and prints a control-file format representation of the
10313 information in it to standard output.
10317 <sect1 id="pkg-dpkg-architecture">
10319 <prgn>dpkg-architecture</prgn> - information about the build and
10324 This program can be used manually, but is also invoked by
10325 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
10326 environment or make variables which specify the build and host
10327 architecture for the package building process.
10332 <sect id="pkg-sourcetree">
10333 <heading>The Debian package source tree</heading>
10336 The source archive scheme described later is intended to
10337 allow a Debian package source tree with some associated
10338 control information to be reproduced and transported easily.
10339 The Debian package source tree is a version of the original
10340 program with certain files added for the benefit of the
10341 packaging process, and with any other changes required
10342 made to the rest of the source code and installation
10347 The extra files created for Debian are in the subdirectory
10348 <file>debian</file> of the top level of the Debian package
10349 source tree. They are described below.
10352 <sect1 id="pkg-debianrules">
10353 <heading><file>debian/rules</file> - the main building script</heading>
10356 See <ref id="debianrules">.
10360 <sect1 id="pkg-srcsubstvars">
10361 <heading><file>debian/substvars</file> and variable substitutions</heading>
10364 See <ref id="substvars">.
10370 <heading><file>debian/files</file></heading>
10373 See <ref id="debianfiles">.
10377 <sect1><heading><file>debian/tmp</file>
10381 This is the canonical temporary location for the
10382 construction of binary packages by the <tt>binary</tt>
10383 target. The directory <file>tmp</file> serves as the root of
10384 the file system tree as it is being constructed (for
10385 example, by using the package's upstream makefiles install
10386 targets and redirecting the output there), and it also
10387 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10388 id="pkg-bincreating">.
10392 If several binary packages are generated from the same
10393 source tree it is usual to use several
10394 <file>debian/tmp<var>something</var></file> directories, for
10395 example <file>tmp-a</file> or <file>tmp-doc</file>.
10399 Whatever <file>tmp</file> directories are created and used by
10400 <tt>binary</tt> must of course be removed by the
10401 <tt>clean</tt> target.</p></sect1>
10405 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10409 As it exists on the FTP site, a Debian source package
10410 consists of three related files. You must have the right
10411 versions of all three to be able to use them.
10416 <tag>Debian source control file - <tt>.dsc</tt></tag>
10418 This file is a control file used by <prgn>dpkg-source</prgn>
10419 to extract a source package.
10420 See <ref id="debiansourcecontrolfiles">.
10424 Original source archive -
10426 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10432 This is a compressed (with <tt>gzip -9</tt>)
10433 <prgn>tar</prgn> file containing the source code from
10434 the upstream authors of the program.
10439 Debian package diff -
10441 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10447 This is a unified context diff (<tt>diff -u</tt>)
10448 giving the changes which are required to turn the
10449 original source into the Debian source. These changes
10450 may only include editing and creating plain files.
10451 The permissions of files, the targets of symbolic
10452 links and the characteristics of special files or
10453 pipes may not be changed and no files may be removed
10458 All the directories in the diff must exist, except the
10459 <file>debian</file> subdirectory of the top of the source
10460 tree, which will be created by
10461 <prgn>dpkg-source</prgn> if necessary when unpacking.
10465 The <prgn>dpkg-source</prgn> program will
10466 automatically make the <file>debian/rules</file> file
10467 executable (see below).</p></item>
10472 If there is no original source code - for example, if the
10473 package is specially prepared for Debian or the Debian
10474 maintainer is the same as the upstream maintainer - the
10475 format is slightly different: then there is no diff, and the
10477 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10478 and preferably contains a directory named
10479 <file><var>package</var>-<var>version</var></file>.
10484 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10487 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10488 Debian source package. However, if it is not available it
10489 is possible to unpack a Debian source archive as follows:
10490 <enumlist compact="compact">
10493 Untar the tarfile, which will create a <file>.orig</file>
10497 <p>Rename the <file>.orig</file> directory to
10498 <file><var>package</var>-<var>version</var></file>.</p>
10502 Create the subdirectory <file>debian</file> at the top of
10503 the source tree.</p>
10505 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10507 <item><p>Untar the tarfile again if you want a copy of the original
10508 source code alongside the Debian version.</p>
10513 It is not possible to generate a valid Debian source archive
10514 without using <prgn>dpkg-source</prgn>. In particular,
10515 attempting to use <prgn>diff</prgn> directly to generate the
10516 <file>.diff.gz</file> file will not work.
10520 <heading>Restrictions on objects in source packages</heading>
10523 The source package may not contain any hard links
10525 This is not currently detected when building source
10526 packages, but only when extracting
10530 Hard links may be permitted at some point in the
10531 future, but would require a fair amount of
10533 </footnote>, device special files, sockets or setuid or
10536 Setgid directories are allowed.
10541 The source packaging tools manage the changes between the
10542 original and Debian source using <prgn>diff</prgn> and
10543 <prgn>patch</prgn>. Turning the original source tree as
10544 included in the <file>.orig.tar.gz</file> into the Debian
10545 package source must not involve any changes which cannot be
10546 handled by these tools. Problematic changes which cause
10547 <prgn>dpkg-source</prgn> to halt with an error when
10548 building the source package are:
10549 <list compact="compact">
10550 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10552 <item><p>Changing the targets of symbolic links.</p>
10554 <item><p>Creating directories, other than <file>debian</file>.</p>
10556 <item><p>Changes to the contents of binary files.</p></item>
10557 </list> Changes which cause <prgn>dpkg-source</prgn> to
10558 print a warning but continue anyway are:
10559 <list compact="compact">
10562 Removing files, directories or symlinks.
10564 Renaming a file is not treated specially - it is
10565 seen as the removal of the old file (which
10566 generates a warning, but is otherwise ignored),
10567 and the creation of the new one.
10573 Changed text files which are missing the usual final
10574 newline (either in the original or the modified
10579 Changes which are not represented, but which are not detected by
10580 <prgn>dpkg-source</prgn>, are:
10581 <list compact="compact">
10582 <item><p>Changing the permissions of files (other than
10583 <file>debian/rules</file>) and directories.</p></item>
10588 The <file>debian</file> directory and <file>debian/rules</file>
10589 are handled specially by <prgn>dpkg-source</prgn> - before
10590 applying the changes it will create the <file>debian</file>
10591 directory, and afterwards it will make
10592 <file>debian/rules</file> world-executable.
10598 <appendix id="pkg-controlfields">
10599 <heading>Control files and their fields (from old Packaging Manual)</heading>
10602 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10603 data in a common format, known as control files. Binary and
10604 source packages have control data as do the <file>.changes</file>
10605 files which control the installation of uploaded files, and
10606 <prgn>dpkg</prgn>'s internal databases are in a similar
10611 <heading>Syntax of control files</heading>
10614 See <ref id="controlsyntax">.
10618 It is important to note that there are several fields which
10619 are optional as far as <prgn>dpkg</prgn> and the related
10620 tools are concerned, but which must appear in every Debian
10621 package, or whose omission may cause problems.
10626 <heading>List of fields</heading>
10629 See <ref id="controlfieldslist">.
10633 This section now contains only the fields that didn't belong
10634 to the Policy manual.
10637 <sect1 id="pkg-f-Filename">
10638 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10641 These fields in <tt>Packages</tt> files give the
10642 filename(s) of (the parts of) a package in the
10643 distribution directories, relative to the root of the
10644 Debian hierarchy. If the package has been split into
10645 several parts the parts are all listed in order, separated
10650 <sect1 id="pkg-f-Size">
10651 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10654 These fields in <file>Packages</file> files give the size (in
10655 bytes, expressed in decimal) and MD5 checksum of the
10656 file(s) which make(s) up a binary package in the
10657 distribution. If the package is split into several parts
10658 the values for the parts are listed in order, separated by
10663 <sect1 id="pkg-f-Status">
10664 <heading><tt>Status</tt></heading>
10667 This field in <prgn>dpkg</prgn>'s status file records
10668 whether the user wants a package installed, removed or
10669 left alone, whether it is broken (requiring
10670 re-installation) or not and what its current state on the
10671 system is. Each of these pieces of information is a
10676 <sect1 id="pkg-f-Config-Version">
10677 <heading><tt>Config-Version</tt></heading>
10680 If a package is not installed or not configured, this
10681 field in <prgn>dpkg</prgn>'s status file records the last
10682 version of the package which was successfully
10687 <sect1 id="pkg-f-Conffiles">
10688 <heading><tt>Conffiles</tt></heading>
10691 This field in <prgn>dpkg</prgn>'s status file contains
10692 information about the automatically-managed configuration
10693 files held by a package. This field should <em>not</em>
10694 appear anywhere in a package!
10699 <heading>Obsolete fields</heading>
10702 These are still recognized by <prgn>dpkg</prgn> but should
10703 not appear anywhere any more.
10705 <taglist compact="compact">
10707 <tag><tt>Revision</tt></tag>
10708 <tag><tt>Package-Revision</tt></tag>
10709 <tag><tt>Package_Revision</tt></tag>
10711 The Debian revision part of the package version was
10712 at one point in a separate control field. This
10713 field went through several names.
10716 <tag><tt>Recommended</tt></tag>
10717 <item>Old name for <tt>Recommends</tt>.</item>
10719 <tag><tt>Optional</tt></tag>
10720 <item>Old name for <tt>Suggests</tt>.</item>
10722 <tag><tt>Class</tt></tag>
10723 <item>Old name for <tt>Priority</tt>.</item>
10732 <appendix id="pkg-conffiles">
10733 <heading>Configuration file handling (from old Packaging Manual)</heading>
10736 <prgn>dpkg</prgn> can do a certain amount of automatic
10737 handling of package configuration files.
10741 Whether this mechanism is appropriate depends on a number of
10742 factors, but basically there are two approaches to any
10743 particular configuration file.
10747 The easy method is to ship a best-effort configuration in the
10748 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10749 handle updates. If the user is unlikely to want to edit the
10750 file, but you need them to be able to without losing their
10751 changes, and a new package with a changed version of the file
10752 is only released infrequently, this is a good approach.
10756 The hard method is to build the configuration file from
10757 scratch in the <prgn>postinst</prgn> script, and to take the
10758 responsibility for fixing any mistakes made in earlier
10759 versions of the package automatically. This will be
10760 appropriate if the file is likely to need to be different on
10764 <sect><heading>Automatic handling of configuration files by
10769 A package may contain a control information file called
10770 <tt>conffiles</tt>. This file should be a list of filenames
10771 of configuration files needing automatic handling, separated
10772 by newlines. The filenames should be absolute pathnames,
10773 and the files referred to should actually exist in the
10778 When a package is upgraded <prgn>dpkg</prgn> will process
10779 the configuration files during the configuration stage,
10780 shortly before it runs the package's <prgn>postinst</prgn>
10785 For each file it checks to see whether the version of the
10786 file included in the package is the same as the one that was
10787 included in the last version of the package (the one that is
10788 being upgraded from); it also compares the version currently
10789 installed on the system with the one shipped with the last
10794 If neither the user nor the package maintainer has changed
10795 the file, it is left alone. If one or the other has changed
10796 their version, then the changed version is preferred - i.e.,
10797 if the user edits their file, but the package maintainer
10798 doesn't ship a different version, the user's changes will
10799 stay, silently, but if the maintainer ships a new version
10800 and the user hasn't edited it the new version will be
10801 installed (with an informative message). If both have
10802 changed their version the user is prompted about the problem
10803 and must resolve the differences themselves.
10807 The comparisons are done by calculating the MD5 message
10808 digests of the files, and storing the MD5 of the file as it
10809 was included in the most recent version of the package.
10813 When a package is installed for the first time
10814 <prgn>dpkg</prgn> will install the file that comes with it,
10815 unless that would mean overwriting a file already on the
10820 However, note that <prgn>dpkg</prgn> will <em>not</em>
10821 replace a conffile that was removed by the user (or by a
10822 script). This is necessary because with some programs a
10823 missing file produces an effect hard or impossible to
10824 achieve in another way, so that a missing file needs to be
10825 kept that way if the user did it.
10829 Note that a package should <em>not</em> modify a
10830 <prgn>dpkg</prgn>-handled conffile in its maintainer
10831 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10832 the user confusing and possibly dangerous options for
10833 conffile update when the package is upgraded.</p>
10836 <sect><heading>Fully-featured maintainer script configuration
10841 For files which contain site-specific information such as
10842 the hostname and networking details and so forth, it is
10843 better to create the file in the package's
10844 <prgn>postinst</prgn> script.
10848 This will typically involve examining the state of the rest
10849 of the system to determine values and other information, and
10850 may involve prompting the user for some information which
10851 can't be obtained some other way.
10855 When using this method there are a couple of important
10856 issues which should be considered:
10860 If you discover a bug in the program which generates the
10861 configuration file, or if the format of the file changes
10862 from one version to the next, you will have to arrange for
10863 the postinst script to do something sensible - usually this
10864 will mean editing the installed configuration file to remove
10865 the problem or change the syntax. You will have to do this
10866 very carefully, since the user may have changed the file,
10867 perhaps to fix the very problem that your script is trying
10868 to deal with - you will have to detect these situations and
10869 deal with them correctly.
10873 If you do go down this route it's probably a good idea to
10874 make the program that generates the configuration file(s) a
10875 separate program in <file>/usr/sbin</file>, by convention called
10876 <file><var>package</var>config</file> and then run that if
10877 appropriate from the post-installation script. The
10878 <tt><var>package</var>config</tt> program should not
10879 unquestioningly overwrite an existing configuration - if its
10880 mode of operation is geared towards setting up a package for
10881 the first time (rather than any arbitrary reconfiguration
10882 later) you should have it check whether the configuration
10883 already exists, and require a <tt>--force</tt> flag to
10884 overwrite it.</p></sect>
10887 <appendix id="pkg-alternatives"><heading>Alternative versions of
10888 an interface - <prgn>update-alternatives</prgn> (from old
10893 When several packages all provide different versions of the
10894 same program or file it is useful to have the system select a
10895 default, but to allow the system administrator to change it
10896 and have their decisions respected.
10900 For example, there are several versions of the <prgn>vi</prgn>
10901 editor, and there is no reason to prevent all of them from
10902 being installed at once, each under their own name
10903 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10904 Nevertheless it is desirable to have the name <tt>vi</tt>
10905 refer to something, at least by default.
10909 If all the packages involved cooperate, this can be done with
10910 <prgn>update-alternatives</prgn>.
10914 Each package provides its own version under its own name, and
10915 calls <prgn>update-alternatives</prgn> in its postinst to
10916 register its version (and again in its prerm to deregister
10921 See the man page <manref name="update-alternatives"
10922 section="8"> for details.
10926 If <prgn>update-alternatives</prgn> does not seem appropriate
10927 you may wish to consider using diversions instead.</p>
10930 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10931 package's version of a file (from old Packaging Manual)
10935 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10936 when it reinstalls the package it belongs to, and to have it
10937 put the file from the package somewhere else instead.
10941 This can be used locally to override a package's version of a
10942 file, or by one package to override another's version (or
10943 provide a wrapper for it).
10947 Before deciding to use a diversion, read <ref
10948 id="pkg-alternatives"> to see if you really want a diversion
10949 rather than several alternative versions of a program.
10953 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10954 and updated by a special program <prgn>dpkg-divert</prgn>.
10955 Please see <manref name="dpkg-divert" section="8"> for full
10956 details of its operation.
10960 When a package wishes to divert a file from another, it should
10961 call <prgn>dpkg-divert</prgn> in its preinst to add the
10962 diversion and rename the existing file. For example,
10963 supposing that a <prgn>smailwrapper</prgn> package wishes to
10964 install a wrapper around <file>/usr/sbin/smail</file>:
10966 dpkg-divert --package smailwrapper --add --rename \
10967 --divert /usr/sbin/smail.real /usr/sbin/smail
10968 </example> The <tt>--package smailwrapper</tt> ensures that
10969 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
10970 can bypass the diversion and get installed as the true version.
10971 It's safe to add the diversion unconditionally on upgrades since
10972 it will be left unchanged if it already exists, but
10973 <prgn>dpkg-divert</prgn> will display a message. To suppress that
10974 message, make the command conditional on the version from which
10975 the package is being upgraded:
10977 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
10978 dpkg-divert --package smailwrapper --add --rename \
10979 --divert /usr/sbin/smail.real /usr/sbin/smail
10981 </example> where <tt>1.0-2</tt> is the version at which the
10982 diversion was first added to the package. Running the command
10983 during abort-upgrade is pointless but harmless.
10987 The postrm has to do the reverse:
10989 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
10990 dpkg-divert --package smailwrapper --remove --rename \
10991 --divert /usr/sbin/smail.real /usr/sbin/smail
10993 </example> If the diversion was added at a particular version, the
10994 postrm should also handle the failure case of upgrading from an
10995 older version (unless the older version is so old that direct
10996 upgrades are no longer supported):
10998 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
10999 dpkg-divert --package smailwrapper --remove --rename \
11000 --divert /usr/sbin/smail.real /usr/sbin/smail
11002 </example> where <tt>1.02-2</tt> is the version at which the
11003 diversion was first added to the package. The postrm should not
11004 remove the diversion on upgrades both because there's no reason to
11005 remove the diversion only to immediately re-add it and since the
11006 postrm of the old package is run after unpacking so the removal of
11007 the diversion will fail.
11011 Do not attempt to divert a file which is vitally important for
11012 the system's operation - when using <prgn>dpkg-divert</prgn>
11013 there is a time, after it has been diverted but before
11014 <prgn>dpkg</prgn> has installed the new version, when the file
11015 does not exist.</p>
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