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12 <title>Debian Policy Manual</title>
13 <author><qref id="authors">The Debian Policy Mailing List</qref></author>
14 <version>version &version;, &date;</version>
17 This manual describes the policy requirements for the Debian
18 GNU/Linux distribution. This includes the structure and
19 contents of the Debian archive and several design issues of
20 the operating system, as well as technical requirements that
21 each package must satisfy to be included in the distribution.
26 Copyright © 1996,1997,1998 Ian Jackson
27 and Christian Schwarz.
30 These are the copyright dates of the original Policy manual.
31 Since then, this manual has been updated by many others. No
32 comprehensive collection of copyright notices for subsequent
37 This manual is free software; you may redistribute it and/or
38 modify it under the terms of the GNU General Public License
39 as published by the Free Software Foundation; either version
40 2, or (at your option) any later version.
44 This is distributed in the hope that it will be useful, but
45 <em>without any warranty</em>; without even the implied
46 warranty of merchantability or fitness for a particular
47 purpose. See the GNU General Public License for more
52 A copy of the GNU General Public License is available as
53 <file>/usr/share/common-licenses/GPL</file> in the Debian GNU/Linux
54 distribution or on the World Wide Web at
55 <url id="http://www.gnu.org/copyleft/gpl.html"
56 name="the GNU General Public Licence">. You can also
57 obtain it by writing to the Free Software Foundation, Inc.,
58 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
66 <heading>About this manual</heading>
68 <heading>Scope</heading>
70 This manual describes the policy requirements for the Debian
71 GNU/Linux distribution. This includes the structure and
72 contents of the Debian archive and several design issues of the
73 operating system, as well as technical requirements that
74 each package must satisfy to be included in the
79 This manual also describes Debian policy as it relates to
80 creating Debian packages. It is not a tutorial on how to build
81 packages, nor is it exhaustive where it comes to describing
82 the behavior of the packaging system. Instead, this manual
83 attempts to define the interface to the package management
84 system that the developers have to be conversant with.<footnote>
85 Informally, the criteria used for inclusion is that the
86 material meet one of the following requirements:
87 <taglist compact="compact">
88 <tag>Standard interfaces</tag>
90 The material presented represents an interface to
91 the packaging system that is mandated for use, and
92 is used by, a significant number of packages, and
93 therefore should not be changed without peer
94 review. Package maintainers can then rely on this
95 interface not changing, and the package management
96 software authors need to ensure compatibility with
97 this interface definition. (Control file and
98 changelog file formats are examples.)
100 <tag>Chosen Convention</tag>
102 If there are a number of technically viable choices
103 that can be made, but one needs to select one of
104 these options for inter-operability. The version
105 number format is one example.
108 Please note that these are not mutually exclusive;
109 selected conventions often become parts of standard
115 The footnotes present in this manual are
116 merely informative, and are not part of Debian policy itself.
120 The appendices to this manual are not necessarily normative,
121 either. Please see <ref id="pkg-scope"> for more information.
125 In the normative part of this manual,
126 the words <em>must</em>, <em>should</em> and
127 <em>may</em>, and the adjectives <em>required</em>,
128 <em>recommended</em> and <em>optional</em>, are used to
129 distinguish the significance of the various guidelines in
130 this policy document. Packages that do not conform to the
131 guidelines denoted by <em>must</em> (or <em>required</em>)
132 will generally not be considered acceptable for the Debian
133 distribution. Non-conformance with guidelines denoted by
134 <em>should</em> (or <em>recommended</em>) will generally be
135 considered a bug, but will not necessarily render a package
136 unsuitable for distribution. Guidelines denoted by
137 <em>may</em> (or <em>optional</em>) are truly optional and
138 adherence is left to the maintainer's discretion.
142 These classifications are roughly equivalent to the bug
143 severities <em>serious</em> (for <em>must</em> or
144 <em>required</em> directive violations), <em>minor</em>,
145 <em>normal</em> or <em>important</em>
146 (for <em>should</em> or <em>recommended</em> directive
147 violations) and <em>wishlist</em> (for <em>optional</em>
150 Compare RFC 2119. Note, however, that these words are
151 used in a different way in this document.
156 Much of the information presented in this manual will be
157 useful even when building a package which is to be
158 distributed in some other way or is intended for local use
164 <heading>New versions of this document</heading>
167 This manual is distributed via the Debian package
168 <package><url name="debian-policy"
169 id="http://packages.debian.org/debian-policy"></package>
170 (<httpsite>packages.debian.org</httpsite>
171 <httppath>/debian-policy</httppath>).
175 The current version of this document is also available from
176 the Debian web mirrors at
177 <tt><url name="/doc/debian-policy/"
178 id="http://www.debian.org/doc/debian-policy/"></tt>.
180 <httpsite>www.debian.org</httpsite>
181 <httppath>/doc/debian-policy/</httppath>)
182 Also available from the same directory are several other
183 formats: <file>policy.html.tar.gz</file>
184 (<httppath>/doc/debian-policy/policy.html.tar.gz</httppath>),
185 <file>policy.pdf.gz</file>
186 (<httppath>/doc/debian-policy/policy.pdf.gz</httppath>)
187 and <file>policy.ps.gz</file>
188 (<httppath>/doc/debian-policy/policy.ps.gz</httppath>).
192 The <package>debian-policy</package> package also includes the file
193 <file>upgrading-checklist.txt.gz</file> which indicates policy
194 changes between versions of this document.
199 <heading>Authors and Maintainers</heading>
202 Originally called "Debian GNU/Linux Policy Manual", this
203 manual was initially written in 1996 by Ian Jackson.
204 It was revised on November 27th, 1996 by David A. Morris.
205 Christian Schwarz added new sections on March 15th, 1997,
206 and reworked/restructured it in April-July 1997.
207 Christoph Lameter contributed the "Web Standard".
208 Julian Gilbey largely restructured it in 2001.
212 Since September 1998, the responsibility for the contents of
213 this document lies on the <url name="debian-policy mailing list"
214 id="mailto:debian-policy@lists.debian.org">. Proposals
215 are discussed there and inserted into policy after a certain
216 consensus is established.
217 <!-- insert shameless policy-process plug here eventually -->
218 The actual editing is done by a group of maintainers that have
219 no editorial powers. These are the current maintainers:
222 <item>Julian Gilbey</item>
223 <item>Branden Robinson</item>
224 <item>Josip Rodin</item>
225 <item>Manoj Srivastava</item>
230 While the authors of this document have tried hard to avoid
231 typos and other errors, these do still occur. If you discover
232 an error in this manual or if you want to give any
233 comments, suggestions, or criticisms please send an email to
234 the Debian Policy List,
235 <email>debian-policy@lists.debian.org</email>, or submit a
236 bug report against the <tt>debian-policy</tt> package.
240 Please do not try to reach the individual authors or maintainers
241 of the Policy Manual regarding changes to the Policy.
246 <heading>Related documents</heading>
249 There are several other documents other than this Policy Manual
250 that are necessary to fully understand some Debian policies and
255 The external "sub-policy" documents are referred to in:
256 <list compact="compact">
257 <item><ref id="fhs"></item>
258 <item><ref id="virtual_pkg"></item>
259 <item><ref id="menus"></item>
260 <item><ref id="mime"></item>
261 <item><ref id="perl"></item>
262 <item><ref id="maintscriptprompt"></item>
263 <item><ref id="emacs"></item>
268 In addition to those, which carry the weight of policy, there
269 is the Debian Developer's Reference. This document describes
270 procedures and resources for Debian developers, but it is
271 <em>not</em> normative; rather, it includes things that don't
272 belong in the Policy, such as best practices for developers.
276 The Developer's Reference is available in the
277 <package>developers-reference</package> package.
278 It's also available from the Debian web mirrors at
279 <tt><url name="/doc/developers-reference/"
280 id="http://www.debian.org/doc/developers-reference/"></tt>.
284 <sect id="definitions">
285 <heading>Definitions</heading>
288 The following terms are used in this Policy Manual:
292 The character encoding specified by ANSI X3.4-1986 and its
293 predecessor standards, referred to in MIME as US-ASCII, and
294 corresponding to an encoding in eight bits per character of
295 the first 128 <url id="http://www.unicode.org/"
296 name="Unicode"> characters, with the eighth bit always zero.
300 The transformation format (sometimes called encoding) of
301 <url id="http://www.unicode.org/" name="Unicode"> defined by
302 <url id="http://www.rfc-editor.org/rfc/rfc3629.txt"
303 name="RFC 3629">. UTF-8 has the useful property of having
304 ASCII as a subset, so any text encoded in ASCII is trivially
314 <heading>The Debian Archive</heading>
317 The Debian GNU/Linux system is maintained and distributed as a
318 collection of <em>packages</em>. Since there are so many of
319 them (currently well over 15000), they are split into
320 <em>sections</em> and given <em>priorities</em> to simplify
321 the handling of them.
325 The effort of the Debian project is to build a free operating
326 system, but not every package we want to make accessible is
327 <em>free</em> in our sense (see the Debian Free Software
328 Guidelines, below), or may be imported/exported without
329 restrictions. Thus, the archive is split into areas<footnote>
330 The Debian archive software uses the term "component" internally
331 and in the Release file format to refer to the division of an
332 archive. The Debian Social Contract simply refers to "areas."
333 This document uses terminology similar to the Social Contract.
334 </footnote> based on their licenses and other restrictions.
338 The aims of this are:
340 <list compact="compact">
341 <item>to allow us to make as much software available as we can</item>
342 <item>to allow us to encourage everyone to write free software,
344 <item>to allow us to make it easy for people to produce
345 CD-ROMs of our system without violating any licenses,
346 import/export restrictions, or any other laws.</item>
351 The <em>main</em> archive area forms the <em>Debian GNU/Linux
356 Packages in the other archive areas (<tt>contrib</tt>,
357 <tt>non-free</tt>) are not considered to be part of the Debian
358 distribution, although we support their use and provide
359 infrastructure for them (such as our bug-tracking system and
360 mailing lists). This Debian Policy Manual applies to these
365 <heading>The Debian Free Software Guidelines</heading>
367 The Debian Free Software Guidelines (DFSG) form our
368 definition of "free software". These are:
370 <tag>1. Free Redistribution
373 The license of a Debian component may not restrict any
374 party from selling or giving away the software as a
375 component of an aggregate software distribution
376 containing programs from several different
377 sources. The license may not require a royalty or
378 other fee for such sale.
383 The program must include source code, and must allow
384 distribution in source code as well as compiled form.
386 <tag>3. Derived Works
389 The license must allow modifications and derived
390 works, and must allow them to be distributed under the
391 same terms as the license of the original software.
393 <tag>4. Integrity of The Author's Source Code
396 The license may restrict source-code from being
397 distributed in modified form <em>only</em> if the
398 license allows the distribution of "patch files"
399 with the source code for the purpose of modifying the
400 program at build time. The license must explicitly
401 permit distribution of software built from modified
402 source code. The license may require derived works to
403 carry a different name or version number from the
404 original software. (This is a compromise. The Debian
405 Project encourages all authors to not restrict any
406 files, source or binary, from being modified.)
408 <tag>5. No Discrimination Against Persons or Groups
411 The license must not discriminate against any person
414 <tag>6. No Discrimination Against Fields of Endeavor
417 The license must not restrict anyone from making use
418 of the program in a specific field of endeavor. For
419 example, it may not restrict the program from being
420 used in a business, or from being used for genetic
423 <tag>7. Distribution of License
426 The rights attached to the program must apply to all
427 to whom the program is redistributed without the need
428 for execution of an additional license by those
431 <tag>8. License Must Not Be Specific to Debian
434 The rights attached to the program must not depend on
435 the program's being part of a Debian system. If the
436 program is extracted from Debian and used or
437 distributed without Debian but otherwise within the
438 terms of the program's license, all parties to whom
439 the program is redistributed must have the same
440 rights as those that are granted in conjunction with
443 <tag>9. License Must Not Contaminate Other Software
446 The license must not place restrictions on other
447 software that is distributed along with the licensed
448 software. For example, the license must not insist
449 that all other programs distributed on the same medium
450 must be free software.
452 <tag>10. Example Licenses
455 The "GPL," "BSD," and "Artistic" licenses are examples of
456 licenses that we consider <em>free</em>.
463 <heading>Archive areas</heading>
466 <heading>The main archive area</heading>
469 Every package in <em>main</em> must comply with the DFSG
470 (Debian Free Software Guidelines).
474 In addition, the packages in <em>main</em>
475 <list compact="compact">
477 must not require a package outside of <em>main</em>
478 for compilation or execution (thus, the package must
479 not declare a "Depends", "Recommends", or
480 "Build-Depends" relationship on a non-<em>main</em>
484 must not be so buggy that we refuse to support them,
488 must meet all policy requirements presented in this
497 <heading>The contrib archive area</heading>
500 Every package in <em>contrib</em> must comply with the DFSG.
504 In addition, the packages in <em>contrib</em>
505 <list compact="compact">
507 must not be so buggy that we refuse to support them,
511 must meet all policy requirements presented in this
519 Examples of packages which would be included in
520 <em>contrib</em> are:
521 <list compact="compact">
523 free packages which require <em>contrib</em>,
524 <em>non-free</em> packages or packages which are not
525 in our archive at all for compilation or execution,
529 wrapper packages or other sorts of free accessories for
536 <sect1 id="non-free">
537 <heading>The non-free archive area</heading>
540 Packages must be placed in <em>non-free</em> if they are
541 not compliant with the DFSG or are encumbered by patents
542 or other legal issues that make their distribution
547 In addition, the packages in <em>non-free</em>
548 <list compact="compact">
550 must not be so buggy that we refuse to support them,
554 must meet all policy requirements presented in this
555 manual that it is possible for them to meet.
557 It is possible that there are policy
558 requirements which the package is unable to
559 meet, for example, if the source is
560 unavailable. These situations will need to be
561 handled on a case-by-case basis.
570 <sect id="pkgcopyright">
571 <heading>Copyright considerations</heading>
574 Every package must be accompanied by a verbatim copy of its
575 copyright information and distribution license in the file
576 <file>/usr/share/doc/<var>package</var>/copyright</file>
577 (see <ref id="copyrightfile"> for further details).
581 We reserve the right to restrict files from being included
582 anywhere in our archives if
583 <list compact="compact">
585 their use or distribution would break a law,
588 there is an ethical conflict in their distribution or
592 we would have to sign a license for them, or
595 their distribution would conflict with other project
602 Programs whose authors encourage the user to make
603 donations are fine for the main distribution, provided
604 that the authors do not claim that not donating is
605 immoral, unethical, illegal or something similar; in such
606 a case they must go in <em>non-free</em>.
610 Packages whose copyright permission notices (or patent
611 problems) do not even allow redistribution of binaries
612 only, and where no special permission has been obtained,
613 must not be placed on the Debian FTP site and its mirrors
618 Note that under international copyright law (this applies
619 in the United States, too), <em>no</em> distribution or
620 modification of a work is allowed without an explicit
621 notice saying so. Therefore a program without a copyright
622 notice <em>is</em> copyrighted and you may not do anything
623 to it without risking being sued! Likewise if a program
624 has a copyright notice but no statement saying what is
625 permitted then nothing is permitted.
629 Many authors are unaware of the problems that restrictive
630 copyrights (or lack of copyright notices) can cause for
631 the users of their supposedly-free software. It is often
632 worthwhile contacting such authors diplomatically to ask
633 them to modify their license terms. However, this can be a
634 politically difficult thing to do and you should ask for
635 advice on the <tt>debian-legal</tt> mailing list first, as
640 When in doubt about a copyright, send mail to
641 <email>debian-legal@lists.debian.org</email>. Be prepared
642 to provide us with the copyright statement. Software
643 covered by the GPL, public domain software and BSD-like
644 copyrights are safe; be wary of the phrases "commercial
645 use prohibited" and "distribution restricted".
649 <sect id="subsections">
650 <heading>Sections</heading>
653 The packages in the archive areas <em>main</em>,
654 <em>contrib</em> and <em>non-free</em> are grouped further into
655 <em>sections</em> to simplify handling.
659 The archive area and section for each package should be
660 specified in the package's <tt>Section</tt> control record (see
661 <ref id="f-Section">). However, the maintainer of the Debian
662 archive may override this selection to ensure the consistency of
663 the Debian distribution. The <tt>Section</tt> field should be
665 <list compact="compact">
667 <em>section</em> if the package is in the
668 <em>main</em> archive area,
671 <em>area/section</em> if the package is in
672 the <em>contrib</em> or <em>non-free</em>
679 The Debian archive maintainers provide the authoritative
680 list of sections. At present, they are:
681 <em>admin</em>, <em>cli-mono</em>, <em>comm</em>, <em>database</em>,
682 <em>devel</em>, <em>debug</em>, <em>doc</em>, <em>editors</em>,
683 <em>electronics</em>, <em>embedded</em>, <em>fonts</em>,
684 <em>games</em>, <em>gnome</em>, <em>graphics</em>, <em>gnu-r</em>,
685 <em>gnustep</em>, <em>hamradio</em>, <em>haskell</em>,
686 <em>httpd</em>, <em>interpreters</em>, <em>java</em>, <em>kde</em>,
687 <em>kernel</em>, <em>libs</em>, <em>libdevel</em>, <em>lisp</em>,
688 <em>localization</em>, <em>mail</em>, <em>math</em>, <em>misc</em>,
689 <em>net</em>, <em>news</em>, <em>ocaml</em>, <em>oldlibs</em>,
690 <em>otherosfs</em>, <em>perl</em>, <em>php</em>, <em>python</em>,
691 <em>ruby</em>, <em>science</em>, <em>shells</em>, <em>sound</em>,
692 <em>tex</em>, <em>text</em>, <em>utils</em>, <em>vcs</em>,
693 <em>video</em>, <em>web</em>, <em>x11</em>, <em>xfce</em>,
694 <em>zope</em>. The additional section <em>debian-installer</em>
695 contains special packages used by the installer and is not used
696 for normal Debian packages.
700 For more information about the sections and their definitions,
701 see the <url id="http://packages.debian.org/unstable/"
702 name="list of sections in unstable">.
706 <sect id="priorities">
707 <heading>Priorities</heading>
710 Each package should have a <em>priority</em> value, which is
711 included in the package's <em>control record</em>
712 (see <ref id="f-Priority">).
713 This information is used by the Debian package management tools to
714 separate high-priority packages from less-important packages.
718 The following <em>priority levels</em> are recognized by the
719 Debian package management tools.
721 <tag><tt>required</tt></tag>
723 Packages which are necessary for the proper
724 functioning of the system (usually, this means that
725 dpkg functionality depends on these packages).
726 Removing a <tt>required</tt> package may cause your
727 system to become totally broken and you may not even
728 be able to use <prgn>dpkg</prgn> to put things back,
729 so only do so if you know what you are doing. Systems
730 with only the <tt>required</tt> packages are probably
731 unusable, but they do have enough functionality to
732 allow the sysadmin to boot and install more software.
734 <tag><tt>important</tt></tag>
736 Important programs, including those which one would
737 expect to find on any Unix-like system. If the
738 expectation is that an experienced Unix person who
739 found it missing would say "What on earth is going on,
740 where is <prgn>foo</prgn>?", it must be an
741 <tt>important</tt> package.<footnote>
742 This is an important criterion because we are
743 trying to produce, amongst other things, a free
746 Other packages without which the system will not run
747 well or be usable must also have priority
748 <tt>important</tt>. This does
749 <em>not</em> include Emacs, the X Window System, TeX
750 or any other large applications. The
751 <tt>important</tt> packages are just a bare minimum of
752 commonly-expected and necessary tools.
754 <tag><tt>standard</tt></tag>
756 These packages provide a reasonably small but not too
757 limited character-mode system. This is what will be
758 installed by default if the user doesn't select anything
759 else. It doesn't include many large applications.
761 <tag><tt>optional</tt></tag>
763 (In a sense everything that isn't required is
764 optional, but that's not what is meant here.) This is
765 all the software that you might reasonably want to
766 install if you didn't know what it was and don't have
767 specialized requirements. This is a much larger system
768 and includes the X Window System, a full TeX
769 distribution, and many applications. Note that
770 optional packages should not conflict with each other.
772 <tag><tt>extra</tt></tag>
774 This contains all packages that conflict with others
775 with required, important, standard or optional
776 priorities, or are only likely to be useful if you
777 already know what they are or have specialized
778 requirements (such as packages containing only detached
785 Packages must not depend on packages with lower priority
786 values (excluding build-time dependencies). In order to
787 ensure this, the priorities of one or more packages may need
796 <heading>Binary packages</heading>
799 The Debian GNU/Linux distribution is based on the Debian
800 package management system, called <prgn>dpkg</prgn>. Thus,
801 all packages in the Debian distribution must be provided
802 in the <tt>.deb</tt> file format.
806 A <tt>.deb</tt> package contains two sets of files: a set of files
807 to install on the system when the package is installed, and a set
808 of files that provide additional metadata about the package or
809 which are executed when the package is installed or removed. This
810 second set of files is called <em>control information files</em>.
811 Among those files are the package maintainer scripts
812 and <file>control</file>, the <qref id="binarycontrolfiles">binary
813 package control file</qref> that contains the control fields for
814 the package. Other control information files
815 include <qref id="sharedlibs-shlibdeps">the <file>shlibs</file>
816 file</qref> used to store shared library dependency information
817 and the <file>conffiles</file> file that lists the package's
818 configuration files (described in <ref id="config-files">).
822 There is unfortunately a collision of terminology here between
823 control information files and files in the Debian control file
824 format. Throughout this document, a <em>control file</em> refers
825 to a file in the Debian control file format. These files are
826 documented in <ref id="controlfields">. Only files referred to
827 specifically as <em>control information files</em> are the files
828 included in the control information file member of
829 the <file>.deb</file> file format used by binary packages. Most
830 control information files are not in the Debian control file
835 <heading>The package name</heading>
838 Every package must have a name that's unique within the Debian
843 The package name is included in the control field
844 <tt>Package</tt>, the format of which is described
845 in <ref id="f-Package">.
846 The package name is also included as a part of the file name
847 of the <tt>.deb</tt> file.
852 <heading>The version of a package</heading>
855 Every package has a version number recorded in its
856 <tt>Version</tt> control file field, described in
857 <ref id="f-Version">.
861 The package management system imposes an ordering on version
862 numbers, so that it can tell whether packages are being up- or
863 downgraded and so that package system front end applications
864 can tell whether a package it finds available is newer than
865 the one installed on the system. The version number format
866 has the most significant parts (as far as comparison is
867 concerned) at the beginning.
871 If an upstream package has problematic version numbers they
872 should be converted to a sane form for use in the
873 <tt>Version</tt> field.
877 <heading>Version numbers based on dates</heading>
880 In general, Debian packages should use the same version
881 numbers as the upstream sources. However, upstream version
882 numbers based on some date formats (sometimes used for
883 development or "snapshot" releases) will not be ordered
884 correctly by the package management software. For
885 example, <prgn>dpkg</prgn> will consider "96May01" to be
886 greater than "96Dec24".
890 To prevent having to use epochs for every new upstream
891 version, the date-based portion of any upstream version number
892 should be given in a way that sorts correctly: four-digit year
893 first, followed by a two-digit numeric month, followed by a
894 two-digit numeric date, possibly with punctuation between the
899 Native Debian packages (i.e., packages which have been written
900 especially for Debian) whose version numbers include dates
901 should also follow these rules. If punctuation is desired
902 between the date components, remember that hyphen (<tt>-</tt>)
903 cannot be used in native package versions. Period
904 (<tt>.</tt>) is normally a good choice.
910 <sect id="maintainer">
911 <heading>The maintainer of a package</heading>
914 Every package must have a maintainer, except for orphaned
915 packages as described below. The maintainer may be one person
916 or a group of people reachable from a common email address, such
917 as a mailing list. The maintainer is responsible for
918 maintaining the Debian packaging files, evaluating and
919 responding appropriately to reported bugs, uploading new
920 versions of the package (either directly or through a sponsor),
921 ensuring that the package is placed in the appropriate archive
922 area and included in Debian releases as appropriate for the
923 stability and utility of the package, and requesting removal of
924 the package from the Debian distribution if it is no longer
925 useful or maintainable.
929 The maintainer must be specified in the <tt>Maintainer</tt>
930 control field with their correct name and a working email
931 address. The email address given in the <tt>Maintainer</tt>
932 control field must accept mail from those role accounts in
933 Debian used to send automated mails regarding the package. This
934 includes non-spam mail from the bug-tracking system, all mail
935 from the Debian archive maintenance software, and other role
936 accounts or automated processes that are commonly agreed on by
937 the project.<footnote>
938 A sample implementation of such a whitelist written for the
939 Mailman mailing list management software is used for mailing
940 lists hosted by alioth.debian.org.
942 If one person or team maintains several packages, they should
943 use the same form of their name and email address in
944 the <tt>Maintainer</tt> fields of those packages.
948 The format of the <tt>Maintainer</tt> control field is
949 described in <ref id="f-Maintainer">.
953 If the maintainer of the package is a team of people with a
954 shared email address, the <tt>Uploaders</tt> control field must
955 be present and must contain at least one human with their
956 personal email address. See <ref id="f-Uploaders"> for the
957 syntax of that field.
961 An orphaned package is one with no current maintainer. Orphaned
962 packages should have their <tt>Maintainer</tt> control field set
963 to <tt>Debian QA Group <packages@qa.debian.org></tt>.
964 These packages are considered maintained by the Debian project
965 as a whole until someone else volunteers to take over
966 maintenance.<footnote>
967 The detailed procedure for gracefully orphaning a package can
968 be found in the Debian Developer's Reference
969 (see <ref id="related">).
974 <sect id="descriptions">
975 <heading>The description of a package</heading>
978 Every Debian package must have a <tt>Description</tt> control
979 field which contains a synopsis and extended description of the
980 package. Technical information about the format of the
981 <tt>Description</tt> field is in <ref id="f-Description">.
985 The description should describe the package (the program) to a
986 user (system administrator) who has never met it before so that
987 they have enough information to decide whether they want to
988 install it. This description should not just be copied verbatim
989 from the program's documentation.
993 Put important information first, both in the synopsis and
994 extended description. Sometimes only the first part of the
995 synopsis or of the description will be displayed. You can
996 assume that there will usually be a way to see the whole
997 extended description.
1001 The description should also give information about the
1002 significant dependencies and conflicts between this package
1003 and others, so that the user knows why these dependencies and
1004 conflicts have been declared.
1008 Instructions for configuring or using the package should
1009 not be included (that is what installation scripts,
1010 manual pages, info files, etc., are for). Copyright
1011 statements and other administrivia should not be included
1012 either (that is what the copyright file is for).
1015 <sect1 id="synopsis"><heading>The single line synopsis</heading>
1018 The single line synopsis should be kept brief - certainly
1019 under 80 characters.
1023 Do not include the package name in the synopsis line. The
1024 display software knows how to display this already, and you
1025 do not need to state it. Remember that in many situations
1026 the user may only see the synopsis line - make it as
1027 informative as you can.
1032 <sect1 id="extendeddesc"><heading>The extended description</heading>
1035 Do not try to continue the single line synopsis into the
1036 extended description. This will not work correctly when
1037 the full description is displayed, and makes no sense
1038 where only the summary (the single line synopsis) is
1043 The extended description should describe what the package
1044 does and how it relates to the rest of the system (in terms
1045 of, for example, which subsystem it is which part of).
1049 The description field needs to make sense to anyone, even
1050 people who have no idea about any of the things the
1051 package deals with.<footnote>
1052 The blurb that comes with a program in its
1053 announcements and/or <prgn>README</prgn> files is
1054 rarely suitable for use in a description. It is
1055 usually aimed at people who are already in the
1056 community where the package is used.
1065 <heading>Dependencies</heading>
1068 Every package must specify the dependency information
1069 about other packages that are required for the first to
1074 For example, a dependency entry must be provided for any
1075 shared libraries required by a dynamically-linked executable
1076 binary in a package.
1080 Packages are not required to declare any dependencies they
1081 have on other packages which are marked <tt>Essential</tt>
1082 (see below), and should not do so unless they depend on a
1083 particular version of that package.<footnote>
1085 Essential is needed in part to avoid unresolvable dependency
1086 loops on upgrade. If packages add unnecessary dependencies
1087 on packages in this set, the chances that there
1088 <strong>will</strong> be an unresolvable dependency loop
1089 caused by forcing these Essential packages to be configured
1090 first before they need to be is greatly increased. It also
1091 increases the chances that frontends will be unable to
1092 <strong>calculate</strong> an upgrade path, even if one
1096 Also, functionality is rarely ever removed from the
1097 Essential set, but <em>packages</em> have been removed from
1098 the Essential set when the functionality moved to a
1099 different package. So depending on these packages <em>just
1100 in case</em> they stop being essential does way more harm
1107 Sometimes, a package requires another package to be installed
1108 <em>and</em> configured before it can be installed. In this
1109 case, you must specify a <tt>Pre-Depends</tt> entry for
1114 You should not specify a <tt>Pre-Depends</tt> entry for a
1115 package before this has been discussed on the
1116 <tt>debian-devel</tt> mailing list and a consensus about
1117 doing that has been reached.
1121 The format of the package interrelationship control fields is
1122 described in <ref id="relationships">.
1126 <sect id="virtual_pkg">
1127 <heading>Virtual packages</heading>
1130 Sometimes, there are several packages which offer
1131 more-or-less the same functionality. In this case, it's
1132 useful to define a <em>virtual package</em> whose name
1133 describes that common functionality. (The virtual
1134 packages only exist logically, not physically; that's why
1135 they are called <em>virtual</em>.) The packages with this
1136 particular function will then <em>provide</em> the virtual
1137 package. Thus, any other package requiring that function
1138 can simply depend on the virtual package without having to
1139 specify all possible packages individually.
1143 All packages should use virtual package names where
1144 appropriate, and arrange to create new ones if necessary.
1145 They should not use virtual package names (except privately,
1146 amongst a cooperating group of packages) unless they have
1147 been agreed upon and appear in the list of virtual package
1148 names. (See also <ref id="virtual">)
1152 The latest version of the authoritative list of virtual
1153 package names can be found in the <tt>debian-policy</tt> package.
1154 It is also available from the Debian web mirrors at
1155 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1156 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1160 The procedure for updating the list is described in the preface
1167 <heading>Base system</heading>
1170 The <tt>base system</tt> is a minimum subset of the Debian
1171 GNU/Linux system that is installed before everything else
1172 on a new system. Only very few packages are allowed to form
1173 part of the base system, in order to keep the required disk
1178 The base system consists of all those packages with priority
1179 <tt>required</tt> or <tt>important</tt>. Many of them will
1180 be tagged <tt>essential</tt> (see below).
1185 <heading>Essential packages</heading>
1188 Essential is defined as the minimal set of functionality that
1189 must be available and usable on the system at all times, even
1190 when packages are in an unconfigured (but unpacked) state.
1191 Packages are tagged <tt>essential</tt> for a system using the
1192 <tt>Essential</tt> control field. The format of the
1193 <tt>Essential</tt> control field is described in <ref
1198 Since these packages cannot be easily removed (one has to
1199 specify an extra <em>force option</em> to
1200 <prgn>dpkg</prgn> to do so), this flag must not be used
1201 unless absolutely necessary. A shared library package
1202 must not be tagged <tt>essential</tt>; dependencies will
1203 prevent its premature removal, and we need to be able to
1204 remove it when it has been superseded.
1208 Since dpkg will not prevent upgrading of other packages
1209 while an <tt>essential</tt> package is in an unconfigured
1210 state, all <tt>essential</tt> packages must supply all of
1211 their core functionality even when unconfigured. If the
1212 package cannot satisfy this requirement it must not be
1213 tagged as essential, and any packages depending on this
1214 package must instead have explicit dependency fields as
1219 Maintainers should take great care in adding any programs,
1220 interfaces, or functionality to <tt>essential</tt> packages.
1221 Packages may assume that functionality provided by
1222 <tt>essential</tt> packages is always available without
1223 declaring explicit dependencies, which means that removing
1224 functionality from the Essential set is very difficult and is
1225 almost never done. Any capability added to an
1226 <tt>essential</tt> package therefore creates an obligation to
1227 support that capability as part of the Essential set in
1232 You must not tag any packages <tt>essential</tt> before
1233 this has been discussed on the <tt>debian-devel</tt>
1234 mailing list and a consensus about doing that has been
1239 <sect id="maintscripts">
1240 <heading>Maintainer Scripts</heading>
1243 The package installation scripts should avoid producing
1244 output which is unnecessary for the user to see and
1245 should rely on <prgn>dpkg</prgn> to stave off boredom on
1246 the part of a user installing many packages. This means,
1247 amongst other things, using the <tt>--quiet</tt> option on
1248 <prgn>install-info</prgn>.
1252 Errors which occur during the execution of an installation
1253 script must be checked and the installation must not
1254 continue after an error.
1258 Note that in general <ref id="scripts"> applies to package
1259 maintainer scripts, too.
1263 You should not use <prgn>dpkg-divert</prgn> on a file belonging
1264 to another package without consulting the maintainer of that
1265 package first. When adding or removing diversions, package
1266 maintainer scripts must provide the <tt>--package</tt> flag
1267 to <prgn>dpkg-divert</prgn> and must not use <tt>--local</tt>.
1271 All packages which supply an instance of a common command
1272 name (or, in general, filename) should generally use
1273 <prgn>update-alternatives</prgn>, so that they may be
1274 installed together. If <prgn>update-alternatives</prgn>
1275 is not used, then each package must use
1276 <tt>Conflicts</tt> to ensure that other packages are
1277 de-installed. (In this case, it may be appropriate to
1278 specify a conflict against earlier versions of something
1279 that previously did not use
1280 <prgn>update-alternatives</prgn>; this is an exception to
1281 the usual rule that versioned conflicts should be
1285 <sect1 id="maintscriptprompt">
1286 <heading>Prompting in maintainer scripts</heading>
1288 Package maintainer scripts may prompt the user if
1289 necessary. Prompting must be done by communicating
1290 through a program, such as <prgn>debconf</prgn>, which
1291 conforms to the Debian Configuration Management
1292 Specification, version 2 or higher.
1296 Packages which are essential, or which are dependencies of
1297 essential packages, may fall back on another prompting method
1298 if no such interface is available when they are executed.
1302 The Debian Configuration Management Specification is included
1303 in the <file>debconf_specification</file> files in the
1304 <package>debian-policy</package> package.
1305 It is also available from the Debian web mirrors at
1306 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1307 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1311 Packages which use the Debian Configuration Management
1312 Specification may contain the additional control information
1313 files <file>config</file>
1314 and <file>templates</file>. <file>config</file> is an
1315 additional maintainer script used for package configuration,
1316 and <file>templates</file> contains templates used for user
1317 prompting. The <prgn>config</prgn> script might be run before
1318 the <prgn>preinst</prgn> script and before the package is
1319 unpacked or any of its dependencies or pre-dependencies are
1320 satisfied. Therefore it must work using only the tools
1321 present in <em>essential</em> packages.<footnote>
1322 <package>Debconf</package> or another tool that
1323 implements the Debian Configuration Management
1324 Specification will also be installed, and any
1325 versioned dependencies on it will be satisfied
1326 before preconfiguration begins.
1331 Packages which use the Debian Configuration Management
1332 Specification must allow for translation of their user-visible
1333 messages by using a gettext-based system such as the one
1334 provided by the <package>po-debconf</package> package.
1338 Packages should try to minimize the amount of prompting
1339 they need to do, and they should ensure that the user
1340 will only ever be asked each question once. This means
1341 that packages should try to use appropriate shared
1342 configuration files (such as <file>/etc/papersize</file> and
1343 <file>/etc/news/server</file>), and shared
1344 <package>debconf</package> variables rather than each
1345 prompting for their own list of required pieces of
1350 It also means that an upgrade should not ask the same
1351 questions again, unless the user has used
1352 <tt>dpkg --purge</tt> to remove the package's configuration.
1353 The answers to configuration questions should be stored in an
1354 appropriate place in <file>/etc</file> so that the user can
1355 modify them, and how this has been done should be
1360 If a package has a vitally important piece of
1361 information to pass to the user (such as "don't run me
1362 as I am, you must edit the following configuration files
1363 first or you risk your system emitting badly-formatted
1364 messages"), it should display this in the
1365 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1366 prompt the user to hit return to acknowledge the
1367 message. Copyright messages do not count as vitally
1368 important (they belong in
1369 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1370 neither do instructions on how to use a program (these
1371 should be in on-line documentation, where all the users
1376 Any necessary prompting should almost always be confined
1377 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1378 script. If it is done in the <prgn>postinst</prgn>, it
1379 should be protected with a conditional so that
1380 unnecessary prompting doesn't happen if a package's
1381 installation fails and the <prgn>postinst</prgn> is
1382 called with <tt>abort-upgrade</tt>,
1383 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1393 <heading>Source packages</heading>
1395 <sect id="standardsversion">
1396 <heading>Standards conformance</heading>
1399 Source packages should specify the most recent version number
1400 of this policy document with which your package complied
1401 when it was last updated.
1405 This information may be used to file bug reports
1406 automatically if your package becomes too much out of date.
1410 The version is specified in the <tt>Standards-Version</tt>
1412 The format of the <tt>Standards-Version</tt> field is
1413 described in <ref id="f-Standards-Version">.
1417 You should regularly, and especially if your package has
1418 become out of date, check for the newest Policy Manual
1419 available and update your package, if necessary. When your
1420 package complies with the new standards you should update the
1421 <tt>Standards-Version</tt> source package field and
1422 release it.<footnote>
1423 See the file <file>upgrading-checklist</file> for
1424 information about policy which has changed between
1425 different versions of this document.
1431 <sect id="pkg-relations">
1432 <heading>Package relationships</heading>
1435 Source packages should specify which binary packages they
1436 require to be installed or not to be installed in order to
1437 build correctly. For example, if building a package
1438 requires a certain compiler, then the compiler should be
1439 specified as a build-time dependency.
1443 It is not necessary to explicitly specify build-time
1444 relationships on a minimal set of packages that are always
1445 needed to compile, link and put in a Debian package a
1446 standard "Hello World!" program written in C or C++. The
1447 required packages are called <em>build-essential</em>, and
1448 an informational list can be found in
1449 <file>/usr/share/doc/build-essential/list</file> (which is
1450 contained in the <tt>build-essential</tt>
1453 <list compact="compact">
1455 This allows maintaining the list separately
1456 from the policy documents (the list does not
1457 need the kind of control that the policy
1461 Having a separate package allows one to install
1462 the build-essential packages on a machine, as
1463 well as allowing other packages such as tasks to
1464 require installation of the build-essential
1465 packages using the depends relation.
1468 The separate package allows bug reports against
1469 the list to be categorized separately from
1470 the policy management process in the BTS.
1477 When specifying the set of build-time dependencies, one
1478 should list only those packages explicitly required by the
1479 build. It is not necessary to list packages which are
1480 required merely because some other package in the list of
1481 build-time dependencies depends on them.<footnote>
1482 The reason for this is that dependencies change, and
1483 you should list all those packages, and <em>only</em>
1484 those packages that <em>you</em> need directly. What
1485 others need is their business. For example, if you
1486 only link against <file>libimlib</file>, you will need to
1487 build-depend on <package>libimlib2-dev</package> but
1488 not against any <tt>libjpeg*</tt> packages, even
1489 though <tt>libimlib2-dev</tt> currently depends on
1490 them: installation of <package>libimlib2-dev</package>
1491 will automatically ensure that all of its run-time
1492 dependencies are satisfied.
1497 If build-time dependencies are specified, it must be
1498 possible to build the package and produce working binaries
1499 on a system with only essential and build-essential
1500 packages installed and also those required to satisfy the
1501 build-time relationships (including any implied
1502 relationships). In particular, this means that version
1503 clauses should be used rigorously in build-time
1504 relationships so that one cannot produce bad or
1505 inconsistently configured packages when the relationships
1506 are properly satisfied.
1510 <ref id="relationships"> explains the technical details.
1515 <heading>Changes to the upstream sources</heading>
1518 If changes to the source code are made that are not
1519 specific to the needs of the Debian system, they should be
1520 sent to the upstream authors in whatever form they prefer
1521 so as to be included in the upstream version of the
1526 If you need to configure the package differently for
1527 Debian or for Linux, and the upstream source doesn't
1528 provide a way to do so, you should add such configuration
1529 facilities (for example, a new <prgn>autoconf</prgn> test
1530 or <tt>#define</tt>) and send the patch to the upstream
1531 authors, with the default set to the way they originally
1532 had it. You can then easily override the default in your
1533 <file>debian/rules</file> or wherever is appropriate.
1537 You should make sure that the <prgn>configure</prgn> utility
1538 detects the correct architecture specification string
1539 (refer to <ref id="arch-spec"> for details).
1543 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1544 <prgn>configure</prgn> scripts are used, you should edit the
1545 <file>.in</file> files rather than editing the
1546 <prgn>Makefile</prgn> directly. This allows the user to
1547 reconfigure the package if necessary. You should
1548 <em>not</em> configure the package and edit the generated
1549 <prgn>Makefile</prgn>! This makes it impossible for someone
1550 else to later reconfigure the package without losing the
1556 <sect id="dpkgchangelog">
1557 <heading>Debian changelog: <file>debian/changelog</file></heading>
1560 Changes in the Debian version of the package should be
1561 briefly explained in the Debian changelog file
1562 <file>debian/changelog</file>.<footnote>
1564 Mistakes in changelogs are usually best rectified by
1565 making a new changelog entry rather than "rewriting
1566 history" by editing old changelog entries.
1569 This includes modifications
1570 made in the Debian package compared to the upstream one
1571 as well as other changes and updates to the package.
1573 Although there is nothing stopping an author who is also
1574 the Debian maintainer from using this changelog for all
1575 their changes, it will have to be renamed if the Debian
1576 and upstream maintainers become different people. In such
1577 a case, however, it might be better to maintain the package
1578 as a non-native package.
1583 The format of the <file>debian/changelog</file> allows the
1584 package building tools to discover which version of the package
1585 is being built and find out other release-specific information.
1589 That format is a series of entries like this:
1591 <example compact="compact">
1592 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1594 [optional blank line(s), stripped]
1596 * <var>change details</var>
1597 <var>more change details</var>
1599 [blank line(s), included in output of dpkg-parsechangelog]
1601 * <var>even more change details</var>
1603 [optional blank line(s), stripped]
1605 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1610 <var>package</var> and <var>version</var> are the source
1611 package name and version number.
1615 <var>distribution(s)</var> lists the distributions where
1616 this version should be installed when it is uploaded - it
1617 is copied to the <tt>Distribution</tt> field in the
1618 <file>.changes</file> file. See <ref id="f-Distribution">.
1622 <var>urgency</var> is the value for the <tt>Urgency</tt>
1623 field in the <file>.changes</file> file for the upload
1624 (see <ref id="f-Urgency">). It is not possible to specify
1625 an urgency containing commas; commas are used to separate
1626 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1627 <prgn>dpkg</prgn> changelog format (though there is
1628 currently only one useful <var>keyword</var>,
1633 The change details may in fact be any series of lines
1634 starting with at least two spaces, but conventionally each
1635 change starts with an asterisk and a separating space and
1636 continuation lines are indented so as to bring them in
1637 line with the start of the text above. Blank lines may be
1638 used here to separate groups of changes, if desired.
1642 If this upload resolves bugs recorded in the Bug Tracking
1643 System (BTS), they may be automatically closed on the
1644 inclusion of this package into the Debian archive by
1645 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1646 in the change details.<footnote>
1647 To be precise, the string should match the following
1648 Perl regular expression:
1650 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1652 Then all of the bug numbers listed will be closed by the
1653 archive maintenance script (<prgn>katie</prgn>) using the
1654 <var>version</var> of the changelog entry.
1656 This information is conveyed via the <tt>Closes</tt> field
1657 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1661 The maintainer name and email address used in the changelog
1662 should be the details of the person uploading <em>this</em>
1663 version. They are <em>not</em> necessarily those of the
1664 usual package maintainer.<footnote>
1665 If the developer uploading the package is not one of the usual
1666 maintainers of the package (as listed in
1667 the <qref id="f-Maintainer"><tt>Maintainer</tt></qref>
1668 or <qref id="f-Uploaders"><tt>Uploaders</tt></qref> control
1669 fields of the package), the first line of the changelog is
1670 conventionally used to explain why a non-maintainer is
1671 uploading the package. The Debian Developer's Reference
1672 (see <ref id="related">) documents the conventions
1674 The information here will be copied to the <tt>Changed-By</tt>
1675 field in the <tt>.changes</tt> file
1676 (see <ref id="f-Changed-By">), and then later used to send an
1677 acknowledgement when the upload has been installed.
1681 The <var>date</var> has the following format<footnote>
1682 This is the same as the format generated by <tt>date
1684 </footnote> (compatible and with the same semantics of
1685 RFC 2822 and RFC 5322):
1686 <example>day-of-week, dd month yyyy hh:mm:ss +zzzz</example>
1688 <list compact="compact">
1690 day-of week is one of: Mon, Tue, Wed, Thu, Fri, Sat, Sun
1693 dd is a one- or two-digit day of the month (01-31)
1696 month is one of: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug,
1699 <item>yyyy is the four-digit year (e.g. 2010)</item>
1700 <item>hh is the two-digit hour (00-23)</item>
1701 <item>mm is the two-digit minutes (00-59)</item>
1702 <item>ss is the two-digit seconds (00-60)</item>
1704 +zzzz or -zzzz is the the time zone offset from Coordinated
1705 Universal Time (UTC). "+" indicates that the time is ahead
1706 of (i.e., east of) UTC and "-" indicates that the time is
1707 behind (i.e., west of) UTC. The first two digits indicate
1708 the hour difference from UTC and the last two digits
1709 indicate the number of additional minutes difference from
1710 UTC. The last two digits must be in the range 00-59.
1716 The first "title" line with the package name must start
1717 at the left hand margin. The "trailer" line with the
1718 maintainer and date details must be preceded by exactly
1719 one space. The maintainer details and the date must be
1720 separated by exactly two spaces.
1724 The entire changelog must be encoded in UTF-8.
1728 For more information on placement of the changelog files
1729 within binary packages, please see <ref id="changelogs">.
1733 <sect id="dpkgcopyright">
1734 <heading>Copyright: <file>debian/copyright</file></heading>
1736 Every package must be accompanied by a verbatim copy of its
1737 copyright information and distribution license in the file
1738 <file>/usr/share/doc/<var>package</var>/copyright</file>
1739 (see <ref id="copyrightfile"> for further details). Also see
1740 <ref id="pkgcopyright"> for further considerations related
1741 to copyrights for packages.
1745 <heading>Error trapping in makefiles</heading>
1748 When <prgn>make</prgn> invokes a command in a makefile
1749 (including your package's upstream makefiles and
1750 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1751 means that <prgn>sh</prgn>'s usual bad error handling
1752 properties apply: if you include a miniature script as one
1753 of the commands in your makefile you'll find that if you
1754 don't do anything about it then errors are not detected
1755 and <prgn>make</prgn> will blithely continue after
1760 Every time you put more than one shell command (this
1761 includes using a loop) in a makefile command you
1762 must make sure that errors are trapped. For
1763 simple compound commands, such as changing directory and
1764 then running a program, using <tt>&&</tt> rather
1765 than semicolon as a command separator is sufficient. For
1766 more complex commands including most loops and
1767 conditionals you should include a separate <tt>set -e</tt>
1768 command at the start of every makefile command that's
1769 actually one of these miniature shell scripts.
1773 <sect id="timestamps">
1774 <heading>Time Stamps</heading>
1776 Maintainers should preserve the modification times of the
1777 upstream source files in a package, as far as is reasonably
1779 The rationale is that there is some information conveyed
1780 by knowing the age of the file, for example, you could
1781 recognize that some documentation is very old by looking
1782 at the modification time, so it would be nice if the
1783 modification time of the upstream source would be
1789 <sect id="restrictions">
1790 <heading>Restrictions on objects in source packages</heading>
1793 The source package may not contain any hard links<footnote>
1795 This is not currently detected when building source
1796 packages, but only when extracting
1800 Hard links may be permitted at some point in the
1801 future, but would require a fair amount of
1804 </footnote>, device special files, sockets or setuid or
1805 setgid files.<footnote>
1806 Setgid directories are allowed.
1811 <sect id="debianrules">
1812 <heading>Main building script: <file>debian/rules</file></heading>
1815 This file must be an executable makefile, and contains the
1816 package-specific recipes for compiling the package and
1817 building binary package(s) from the source.
1821 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1822 so that it can be invoked by saying its name rather than
1823 invoking <prgn>make</prgn> explicitly. That is, invoking
1824 either of <tt>make -f debian/rules <em>args...</em></tt>
1825 or <tt>./debian/rules <em>args...</em></tt> must result in
1830 Since an interactive <file>debian/rules</file> script makes it
1831 impossible to auto-compile that package and also makes it
1832 hard for other people to reproduce the same binary
1833 package, all <em>required targets</em> must be
1834 non-interactive. At a minimum, required targets are the
1835 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1836 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1837 <em>binary-indep</em>, and <em>build</em>. It also follows
1838 that any target that these targets depend on must also be
1843 The targets are as follows (required unless stated otherwise):
1845 <tag><tt>build</tt></tag>
1848 The <tt>build</tt> target should perform all the
1849 configuration and compilation of the package.
1850 If a package has an interactive pre-build
1851 configuration routine, the Debian source package
1852 must either be built after this has taken place (so
1853 that the binary package can be built without rerunning
1854 the configuration) or the configuration routine
1855 modified to become non-interactive. (The latter is
1856 preferable if there are architecture-specific features
1857 detected by the configuration routine.)
1861 For some packages, notably ones where the same
1862 source tree is compiled in different ways to produce
1863 two binary packages, the <tt>build</tt> target
1864 does not make much sense. For these packages it is
1865 good enough to provide two (or more) targets
1866 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1867 for each of the ways of building the package, and a
1868 <tt>build</tt> target that does nothing. The
1869 <tt>binary</tt> target will have to build the
1870 package in each of the possible ways and make the
1871 binary package out of each.
1875 The <tt>build</tt> target must not do anything
1876 that might require root privilege.
1880 The <tt>build</tt> target may need to run the
1881 <tt>clean</tt> target first - see below.
1885 When a package has a configuration and build routine
1886 which takes a long time, or when the makefiles are
1887 poorly designed, or when <tt>build</tt> needs to
1888 run <tt>clean</tt> first, it is a good idea to
1889 <tt>touch build</tt> when the build process is
1890 complete. This will ensure that if <tt>debian/rules
1891 build</tt> is run again it will not rebuild the whole
1893 Another common way to do this is for <tt>build</tt>
1894 to depend on <prgn>build-stamp</prgn> and to do
1895 nothing else, and for the <prgn>build-stamp</prgn>
1896 target to do the building and to <tt>touch
1897 build-stamp</tt> on completion. This is
1898 especially useful if the build routine creates a
1899 file or directory called <tt>build</tt>; in such a
1900 case, <tt>build</tt> will need to be listed as
1901 a phony target (i.e., as a dependency of the
1902 <tt>.PHONY</tt> target). See the documentation of
1903 <prgn>make</prgn> for more information on phony
1909 <tag><tt>build-arch</tt> (optional),
1910 <tt>build-indep</tt> (optional)
1914 A package may also provide both of the targets
1915 <tt>build-arch</tt> and <tt>build-indep</tt>.
1916 The <tt>build-arch</tt> target, if provided, should
1917 perform all the configuration and compilation required for
1918 producing all architecture-dependant binary packages
1919 (those packages for which the body of the
1920 <tt>Architecture</tt> field in <tt>debian/control</tt> is
1921 not <tt>all</tt>). Similarly, the <tt>build-indep</tt>
1922 target, if provided, should perform all the configuration
1923 and compilation required for producing all
1924 architecture-independent binary packages (those packages
1925 for which the body of the <tt>Architecture</tt> field
1926 in <tt>debian/control</tt> is <tt>all</tt>).
1927 The <tt>build</tt> target should depend on those of the
1928 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1929 are provided in the rules file.<footnote>
1930 The intent of this split is so that binary-only builds
1931 need not install the dependencies required for
1932 the <tt>build-indep</tt> target. However, this is not
1933 yet used in practice since <tt>dpkg-buildpackage
1934 -B</tt>, and therefore the autobuilders,
1935 invoke <tt>build</tt> rather than <tt>build-arch</tt>
1936 due to the difficulties in determining whether the
1937 optional <tt>build-arch</tt> target exists.
1942 If one or both of the targets <tt>build-arch</tt> and
1943 <tt>build-indep</tt> are not provided, then invoking
1944 <file>debian/rules</file> with one of the not-provided
1945 targets as arguments should produce a exit status code
1946 of 2. Usually this is provided automatically by make
1947 if the target is missing.
1951 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1952 must not do anything that might require root privilege.
1956 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1957 <tt>binary-indep</tt>
1961 The <tt>binary</tt> target must be all that is
1962 necessary for the user to build the binary package(s)
1963 produced from this source package. It is
1964 split into two parts: <prgn>binary-arch</prgn> builds
1965 the binary packages which are specific to a particular
1966 architecture, and <tt>binary-indep</tt> builds
1967 those which are not.
1970 <tt>binary</tt> may be (and commonly is) a target with
1971 no commands which simply depends on
1972 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1975 Both <tt>binary-*</tt> targets should depend on the
1976 <tt>build</tt> target, or on the appropriate
1977 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1978 provided, so that the package is built if it has not
1979 been already. It should then create the relevant
1980 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1981 make their control files and <prgn>dpkg-deb</prgn> to
1982 build them and place them in the parent of the top
1987 Both the <tt>binary-arch</tt> and
1988 <tt>binary-indep</tt> targets <em>must</em> exist.
1989 If one of them has nothing to do (which will always be
1990 the case if the source generates only a single binary
1991 package, whether architecture-dependent or not), it
1992 must still exist and must always succeed.
1996 The <tt>binary</tt> targets must be invoked as
1998 The <prgn>fakeroot</prgn> package often allows one
1999 to build a package correctly even without being
2005 <tag><tt>clean</tt></tag>
2008 This must undo any effects that the <tt>build</tt>
2009 and <tt>binary</tt> targets may have had, except
2010 that it should leave alone any output files created in
2011 the parent directory by a run of a <tt>binary</tt>
2016 If a <tt>build</tt> file is touched at the end of
2017 the <tt>build</tt> target, as suggested above, it
2018 should be removed as the first action that
2019 <tt>clean</tt> performs, so that running
2020 <tt>build</tt> again after an interrupted
2021 <tt>clean</tt> doesn't think that everything is
2026 The <tt>clean</tt> target may need to be
2027 invoked as root if <tt>binary</tt> has been
2028 invoked since the last <tt>clean</tt>, or if
2029 <tt>build</tt> has been invoked as root (since
2030 <tt>build</tt> may create directories, for
2035 <tag><tt>get-orig-source</tt> (optional)</tag>
2038 This target fetches the most recent version of the
2039 original source package from a canonical archive site
2040 (via FTP or WWW, for example), does any necessary
2041 rearrangement to turn it into the original source
2042 tar file format described below, and leaves it in the
2047 This target may be invoked in any directory, and
2048 should take care to clean up any temporary files it
2053 This target is optional, but providing it if
2054 possible is a good idea.
2058 <tag><tt>patch</tt> (optional)</tag>
2061 This target performs whatever additional actions are
2062 required to make the source ready for editing (unpacking
2063 additional upstream archives, applying patches, etc.).
2064 It is recommended to be implemented for any package where
2065 <tt>dpkg-source -x</tt> does not result in source ready
2066 for additional modification. See
2067 <ref id="readmesource">.
2073 The <tt>build</tt>, <tt>binary</tt> and
2074 <tt>clean</tt> targets must be invoked with the current
2075 directory being the package's top-level directory.
2080 Additional targets may exist in <file>debian/rules</file>,
2081 either as published or undocumented interfaces or for the
2082 package's internal use.
2086 The architectures we build on and build for are determined
2087 by <prgn>make</prgn> variables using the
2088 utility <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
2089 You can determine the Debian architecture and the GNU style
2090 architecture specification string for the build architecture as
2091 well as for the host architecture. The build architecture is
2092 the architecture on which <file>debian/rules</file> is run and
2093 the package build is performed. The host architecture is the
2094 architecture on which the resulting package will be installed
2095 and run. These are normally the same, but may be different in
2096 the case of cross-compilation (building packages for one
2097 architecture on machines of a different architecture).
2101 Here is a list of supported <prgn>make</prgn> variables:
2102 <list compact="compact">
2104 <tt>DEB_*_ARCH</tt> (the Debian architecture)
2107 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2110 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2113 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2114 specification string)
2117 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2118 <tt>DEB_*_GNU_TYPE</tt>)
2121 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2122 <tt>DEB_*_GNU_TYPE</tt>)
2124 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2125 the build architecture or <tt>HOST</tt> for specification of the
2130 Backward compatibility can be provided in the rules file
2131 by setting the needed variables to suitable default
2132 values; please refer to the documentation of
2133 <prgn>dpkg-architecture</prgn> for details.
2137 It is important to understand that the <tt>DEB_*_ARCH</tt>
2138 string only determines which Debian architecture we are
2139 building on or for. It should not be used to get the CPU
2140 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2141 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2142 GNU style variables should generally only be used with upstream
2146 <sect1 id="debianrules-options">
2147 <heading><file>debian/rules</file> and
2148 <tt>DEB_BUILD_OPTIONS</tt></heading>
2151 Supporting the standardized environment variable
2152 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2153 contain several flags to change how a package is compiled and
2154 built. Each flag must be in the form <var>flag</var> or
2155 <var>flag</var>=<var>options</var>. If multiple flags are
2156 given, they must be separated by whitespace.<footnote>
2157 Some packages support any delimiter, but whitespace is the
2158 easiest to parse inside a makefile and avoids ambiguity with
2159 flag values that contain commas.
2161 <var>flag</var> must start with a lowercase letter
2162 (<tt>a-z</tt>) and consist only of lowercase letters,
2163 numbers (<tt>0-9</tt>), and the characters
2164 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2165 <var>options</var> must not contain whitespace. The same
2166 tag should not be given multiple times with conflicting
2167 values. Package maintainers may assume that
2168 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2172 The meaning of the following tags has been standardized:
2176 This tag says to not run any build-time test suite
2177 provided by the package.
2181 The presence of this tag means that the package should
2182 be compiled with a minimum of optimization. For C
2183 programs, it is best to add <tt>-O0</tt> to
2184 <tt>CFLAGS</tt> (although this is usually the default).
2185 Some programs might fail to build or run at this level
2186 of optimization; it may be necessary to use
2187 <tt>-O1</tt>, for example.
2191 This tag means that the debugging symbols should not be
2192 stripped from the binary during installation, so that
2193 debugging information may be included in the package.
2195 <tag>parallel=n</tag>
2197 This tag means that the package should be built using up
2198 to <tt>n</tt> parallel processes if the package build
2199 system supports this.<footnote>
2200 Packages built with <tt>make</tt> can often implement
2201 this by passing the <tt>-j</tt><var>n</var> option to
2204 If the package build system does not support parallel
2205 builds, this string must be ignored. If the package
2206 build system only supports a lower level of concurrency
2207 than <var>n</var>, the package should be built using as
2208 many parallel processes as the package build system
2209 supports. It is up to the package maintainer to decide
2210 whether the package build times are long enough and the
2211 package build system is robust enough to make supporting
2212 parallel builds worthwhile.
2218 Unknown flags must be ignored by <file>debian/rules</file>.
2222 The following makefile snippet is an example of how one may
2223 implement the build options; you will probably have to
2224 massage this example in order to make it work for your
2226 <example compact="compact">
2229 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2230 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2231 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2232 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2234 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2239 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2240 INSTALL_PROGRAM += -s
2242 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2243 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2244 MAKEFLAGS += -j$(NUMJOBS)
2249 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2250 # Code to run the package test suite.
2257 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2258 <sect id="substvars">
2259 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2262 When <prgn>dpkg-gencontrol</prgn>
2263 generates <qref id="binarycontrolfiles">binary package control
2264 files</qref> (<file>DEBIAN/control</file>), it performs variable
2265 substitutions on its output just before writing it. Variable
2266 substitutions have the form <tt>${<var>variable</var>}</tt>.
2267 The optional file <file>debian/substvars</file> contains
2268 variable substitutions to be used; variables can also be set
2269 directly from <file>debian/rules</file> using the <tt>-V</tt>
2270 option to the source packaging commands, and certain predefined
2271 variables are also available.
2275 The <file>debian/substvars</file> file is usually generated and
2276 modified dynamically by <file>debian/rules</file> targets, in
2277 which case it must be removed by the <tt>clean</tt> target.
2281 See <manref name="deb-substvars" section="5"> for full
2282 details about source variable substitutions, including the
2283 format of <file>debian/substvars</file>.</p>
2286 <sect id="debianwatch">
2287 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2290 This is an optional, recommended configuration file for the
2291 <tt>uscan</tt> utility which defines how to automatically scan
2292 ftp or http sites for newly available updates of the
2293 package. This is used
2294 by <url id="http://dehs.alioth.debian.org/"> and other Debian QA
2295 tools to help with quality control and maintenance of the
2296 distribution as a whole.
2301 <sect id="debianfiles">
2302 <heading>Generated files list: <file>debian/files</file></heading>
2305 This file is not a permanent part of the source tree; it
2306 is used while building packages to record which files are
2307 being generated. <prgn>dpkg-genchanges</prgn> uses it
2308 when it generates a <file>.changes</file> file.
2312 It should not exist in a shipped source package, and so it
2313 (and any backup files or temporary files such as
2314 <file>files.new</file><footnote>
2315 <file>files.new</file> is used as a temporary file by
2316 <prgn>dpkg-gencontrol</prgn> and
2317 <prgn>dpkg-distaddfile</prgn> - they write a new
2318 version of <tt>files</tt> here before renaming it,
2319 to avoid leaving a corrupted copy if an error
2321 </footnote>) should be removed by the
2322 <tt>clean</tt> target. It may also be wise to
2323 ensure a fresh start by emptying or removing it at the
2324 start of the <tt>binary</tt> target.
2328 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2329 package, it adds an entry to <file>debian/files</file> for the
2330 <file>.deb</file> file that will be created when <tt>dpkg-deb
2331 --build</tt> is run for that binary package. So for most
2332 packages all that needs to be done with this file is to
2333 delete it in the <tt>clean</tt> target.
2337 If a package upload includes files besides the source
2338 package and any binary packages whose control files were
2339 made with <prgn>dpkg-gencontrol</prgn> then they should be
2340 placed in the parent of the package's top-level directory
2341 and <prgn>dpkg-distaddfile</prgn> should be called to add
2342 the file to the list in <file>debian/files</file>.</p>
2345 <sect id="embeddedfiles">
2346 <heading>Convenience copies of code</heading>
2349 Some software packages include in their distribution convenience
2350 copies of code from other software packages, generally so that
2351 users compiling from source don't have to download multiple
2352 packages. Debian packages should not make use of these
2353 convenience copies unless the included package is explicitly
2354 intended to be used in this way.<footnote>
2355 For example, parts of the GNU build system work like this.
2357 If the included code is already in the Debian archive in the
2358 form of a library, the Debian packaging should ensure that
2359 binary packages reference the libraries already in Debian and
2360 the convenience copy is not used. If the included code is not
2361 already in Debian, it should be packaged separately as a
2362 prerequisite if possible.
2364 Having multiple copies of the same code in Debian is
2365 inefficient, often creates either static linking or shared
2366 library conflicts, and, most importantly, increases the
2367 difficulty of handling security vulnerabilities in the
2373 <sect id="readmesource">
2374 <heading>Source package handling:
2375 <file>debian/README.source</file></heading>
2378 If running <prgn>dpkg-source -x</prgn> on a source package
2379 doesn't produce the source of the package, ready for editing,
2380 and allow one to make changes and run
2381 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2382 without taking any additional steps, creating a
2383 <file>debian/README.source</file> documentation file is
2384 recommended. This file should explain how to do all of the
2387 <item>Generate the fully patched source, in a form ready for
2388 editing, that would be built to create Debian
2389 packages. Doing this with a <tt>patch</tt> target in
2390 <file>debian/rules</file> is recommended; see
2391 <ref id="debianrules">.</item>
2392 <item>Modify the source and save those modifications so that
2393 they will be applied when building the package.</item>
2394 <item>Remove source modifications that are currently being
2395 applied when building the package.</item>
2396 <item>Optionally, document what steps are necessary to
2397 upgrade the Debian source package to a new upstream version,
2398 if applicable.</item>
2400 This explanation should include specific commands and mention
2401 any additional required Debian packages. It should not assume
2402 familiarity with any specific Debian packaging system or patch
2407 This explanation may refer to a documentation file installed by
2408 one of the package's build dependencies provided that the
2409 referenced documentation clearly explains these tasks and is not
2410 a general reference manual.
2414 <file>debian/README.source</file> may also include any other
2415 information that would be helpful to someone modifying the
2416 source package. Even if the package doesn't fit the above
2417 description, maintainers are encouraged to document in a
2418 <file>debian/README.source</file> file any source package with a
2419 particularly complex or unintuitive source layout or build
2420 system (for example, a package that builds the same source
2421 multiple times to generate different binary packages).
2427 <chapt id="controlfields">
2428 <heading>Control files and their fields</heading>
2431 The package management system manipulates data represented in
2432 a common format, known as <em>control data</em>, stored in
2433 <em>control files</em>.
2434 Control files are used for source packages, binary packages and
2435 the <file>.changes</file> files which control the installation
2436 of uploaded files<footnote>
2437 <prgn>dpkg</prgn>'s internal databases are in a similar
2442 <sect id="controlsyntax">
2443 <heading>Syntax of control files</heading>
2446 A control file consists of one or more paragraphs of
2448 The paragraphs are also sometimes referred to as stanzas.
2450 The paragraphs are separated by blank lines. Some control
2451 files allow only one paragraph; others allow several, in
2452 which case each paragraph usually refers to a different
2453 package. (For example, in source packages, the first
2454 paragraph refers to the source package, and later paragraphs
2455 refer to binary packages generated from the source.)
2459 Each paragraph consists of a series of data fields; each
2460 field consists of the field name, followed by a colon and
2461 then the data/value associated with that field. It ends at
2462 the end of the (logical) line. Horizontal whitespace
2463 (spaces and tabs) may occur immediately before or after the
2464 value and is ignored there; it is conventional to put a
2465 single space after the colon. For example, a field might
2467 <example compact="compact">
2470 the field name is <tt>Package</tt> and the field value
2475 A paragraph must not contain more than one instance of a
2476 particular field name.
2480 Many fields' values may span several lines; in this case
2481 each continuation line must start with a space or a tab.
2482 Any trailing spaces or tabs at the end of individual
2483 lines of a field value are ignored.
2487 In fields where it is specified that lines may not wrap,
2488 only a single line of data is allowed and whitespace is not
2489 significant in a field body. Whitespace must not appear
2490 inside names (of packages, architectures, files or anything
2491 else) or version numbers, or between the characters of
2492 multi-character version relationships.
2496 Field names are not case-sensitive, but it is usual to
2497 capitalize the field names using mixed case as shown below.
2498 Field values are case-sensitive unless the description of the
2499 field says otherwise.
2503 Blank lines, or lines consisting only of spaces and tabs,
2504 are not allowed within field values or between fields - that
2505 would mean a new paragraph.
2509 All control files must be encoded in UTF-8.
2513 <sect id="sourcecontrolfiles">
2514 <heading>Source package control files -- <file>debian/control</file></heading>
2517 The <file>debian/control</file> file contains the most vital
2518 (and version-independent) information about the source package
2519 and about the binary packages it creates.
2523 The first paragraph of the control file contains information about
2524 the source package in general. The subsequent sets each describe a
2525 binary package that the source tree builds.
2529 The fields in the general paragraph (the first one, for the source
2532 <list compact="compact">
2533 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2534 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2535 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2536 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2537 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2538 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2539 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2540 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2545 The fields in the binary package paragraphs are:
2547 <list compact="compact">
2548 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2549 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2550 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2551 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2552 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2553 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2554 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2555 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2560 The syntax and semantics of the fields are described below.
2564 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2565 generate control files for binary packages (see below), by
2566 <prgn>dpkg-genchanges</prgn> to generate the
2567 <file>.changes</file> file to accompany the upload, and by
2568 <prgn>dpkg-source</prgn> when it creates the
2569 <file>.dsc</file> source control file as part of a source
2570 archive. Many fields are permitted to span multiple lines in
2571 <file>debian/control</file> but not in any other control
2572 file. These tools are responsible for removing the line
2573 breaks from such fields when using fields from
2574 <file>debian/control</file> to generate other control files.
2578 The fields here may contain variable references - their
2579 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2580 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2581 when they generate output control files.
2582 See <ref id="substvars"> for details.
2586 In addition to the control file syntax described <qref
2587 id="controlsyntax">above</qref>, this file may also contain
2588 comment lines starting with <tt>#</tt> without any preceding
2589 whitespace. All such lines are ignored, even in the middle of
2590 continuation lines for a multiline field, and do not end a
2596 <sect id="binarycontrolfiles">
2597 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2600 The <file>DEBIAN/control</file> file contains the most vital
2601 (and version-dependent) information about a binary package. It
2602 consists of a single paragraph.
2606 The fields in this file are:
2608 <list compact="compact">
2609 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2610 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2611 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2612 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2613 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2614 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2615 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2616 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2617 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2618 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2619 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2620 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2625 <sect id="debiansourcecontrolfiles">
2626 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2629 This file consists of a single paragraph, possibly surrounded by
2630 a PGP signature. The fields of that paragraph are listed below.
2631 Their syntax is described above, in <ref id="pkg-controlfields">.
2633 <list compact="compact">
2634 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2635 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2636 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2637 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2638 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2639 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2640 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2641 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2642 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2643 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2644 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2645 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2646 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2651 The source package control file is generated by
2652 <prgn>dpkg-source</prgn> when it builds the source
2653 archive, from other files in the source package,
2654 described above. When unpacking, it is checked against
2655 the files and directories in the other parts of the
2661 <sect id="debianchangesfiles">
2662 <heading>Debian changes files -- <file>.changes</file></heading>
2665 The <file>.changes</file> files are used by the Debian archive
2666 maintenance software to process updates to packages. They
2667 consist of a single paragraph, possibly surrounded by a PGP
2668 signature. That paragraph contains information from the
2669 <file>debian/control</file> file and other data about the
2670 source package gathered via <file>debian/changelog</file>
2671 and <file>debian/rules</file>.
2675 <file>.changes</file> files have a format version that is
2676 incremented whenever the documented fields or their meaning
2677 change. This document describes format &changesversion;.
2681 The fields in this file are:
2683 <list compact="compact">
2684 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2685 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2686 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2687 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2688 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2689 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2690 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2691 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2692 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2693 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2694 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2695 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2696 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2697 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2698 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2699 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2704 <sect id="controlfieldslist">
2705 <heading>List of fields</heading>
2707 <sect1 id="f-Source">
2708 <heading><tt>Source</tt></heading>
2711 This field identifies the source package name.
2715 In <file>debian/control</file> or a <file>.dsc</file> file,
2716 this field must contain only the name of the source package.
2720 In a binary package control file or a <file>.changes</file>
2721 file, the source package name may be followed by a version
2722 number in parentheses<footnote>
2723 It is customary to leave a space after the package name
2724 if a version number is specified.
2726 This version number may be omitted (and is, by
2727 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2728 the <tt>Version</tt> field of the binary package in
2729 question. The field itself may be omitted from a binary
2730 package control file when the source package has the same
2731 name and version as the binary package.
2735 Package names (both source and binary,
2736 see <ref id="f-Package">) must consist only of lower case
2737 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2738 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2739 (<tt>.</tt>). They must be at least two characters long and
2740 must start with an alphanumeric character.
2744 <sect1 id="f-Maintainer">
2745 <heading><tt>Maintainer</tt></heading>
2748 The package maintainer's name and email address. The name
2749 must come first, then the email address inside angle
2750 brackets <tt><></tt> (in RFC822 format).
2754 If the maintainer's name contains a full stop then the
2755 whole field will not work directly as an email address due
2756 to a misfeature in the syntax specified in RFC822; a
2757 program using this field as an address must check for this
2758 and correct the problem if necessary (for example by
2759 putting the name in round brackets and moving it to the
2760 end, and bringing the email address forward).
2764 See <ref id="maintainer"> for additional requirements and
2765 information about package maintainers.
2769 <sect1 id="f-Uploaders">
2770 <heading><tt>Uploaders</tt></heading>
2773 List of the names and email addresses of co-maintainers of the
2774 package, if any. If the package has other maintainers besides
2775 the one named in the <qref id="f-Maintainer">Maintainer
2776 field</qref>, their names and email addresses should be listed
2777 here. The format of each entry is the same as that of the
2778 Maintainer field, and multiple entries must be comma
2783 This is normally an optional field, but if
2784 the <tt>Maintainer</tt> control field names a group of people
2785 and a shared email address, the <tt>Uploaders</tt> field must
2786 be present and must contain at least one human with their
2787 personal email address.
2791 Any parser that interprets the Uploaders field in
2792 <file>debian/control</file> must permit it to span multiple
2793 lines. Line breaks in an Uploaders field that spans multiple
2794 lines are not significant and the semantics of the field are
2795 the same as if the line breaks had not been present.
2799 <sect1 id="f-Changed-By">
2800 <heading><tt>Changed-By</tt></heading>
2803 The name and email address of the person who prepared this
2804 version of the package, usually a maintainer. The syntax is
2805 the same as for the <qref id="f-Maintainer">Maintainer
2810 <sect1 id="f-Section">
2811 <heading><tt>Section</tt></heading>
2814 This field specifies an application area into which the package
2815 has been classified. See <ref id="subsections">.
2819 When it appears in the <file>debian/control</file> file,
2820 it gives the value for the subfield of the same name in
2821 the <tt>Files</tt> field of the <file>.changes</file> file.
2822 It also gives the default for the same field in the binary
2827 <sect1 id="f-Priority">
2828 <heading><tt>Priority</tt></heading>
2831 This field represents how important it is that the user
2832 have the package installed. See <ref id="priorities">.
2836 When it appears in the <file>debian/control</file> file,
2837 it gives the value for the subfield of the same name in
2838 the <tt>Files</tt> field of the <file>.changes</file> file.
2839 It also gives the default for the same field in the binary
2844 <sect1 id="f-Package">
2845 <heading><tt>Package</tt></heading>
2848 The name of the binary package.
2852 Binary package names must follow the same syntax and
2853 restrictions as source package names. See <ref id="f-Source">
2858 <sect1 id="f-Architecture">
2859 <heading><tt>Architecture</tt></heading>
2862 Depending on context and the control file used, the
2863 <tt>Architecture</tt> field can include the following sets of
2867 A unique single word identifying a Debian machine
2868 architecture as described in <ref id="arch-spec">.
2871 An architecture wildcard identifying a set of Debian
2872 machine architectures, see <ref id="arch-wildcard-spec">.
2873 <tt>any</tt> matches all Debian machine architectures
2874 and is the most frequently used.
2877 <tt>all</tt>, which indicates an
2878 architecture-independent package.
2881 <tt>source</tt>, which indicates a source package.
2887 In the main <file>debian/control</file> file in the source
2888 package, this field may contain the special
2889 value <tt>all</tt>, the special architecture
2890 wildcard <tt>any</tt>, or a list of specific and wildcard
2891 architectures separated by spaces. If <tt>all</tt>
2892 or <tt>any</tt> appears, that value must be the entire
2893 contents of the field. Most packages will use
2894 either <tt>all</tt> or <tt>any</tt>.
2898 Specifying a specific list of architectures indicates that the
2899 source will build an architecture-dependent package only on
2900 architectures included in the list. Specifying a list of
2901 architecture wildcards indicates that the source will build an
2902 architecture-dependent package on only those architectures
2903 that match any of the specified architecture wildcards.
2904 Specifying a list of architectures or architecture wildcards
2905 other than <tt>any</tt> is for the minority of cases where a
2906 program is not portable or is not useful on some
2907 architectures. Where possible, the program should be made
2912 In the source package control file <file>.dsc</file>, this
2913 field may contain either the architecture
2914 wildcard <tt>any</tt> or a list of architectures and
2915 architecture wildcards separated by spaces. If a list is
2916 given, it may include (or consist solely of) the special
2917 value <tt>all</tt>. In other words, in <file>.dsc</file>
2918 files unlike the <file>debian/control</file>, <tt>all</tt> may
2919 occur in combination with specific architectures.
2920 The <tt>Architecture</tt> field in the source package control
2921 file <file>.dsc</file> is generally constructed from
2922 the <tt>Architecture</tt> fields in
2923 the <file>debian/control</file> in the source package.
2927 Specifying <tt>any</tt> indicates that the source package
2928 isn't dependent on any particular architecture and should
2929 compile fine on any one. The produced binary package(s)
2930 will either be specific to whatever the current build
2931 architecture is or will be architecture-independent.
2935 Specifying only <tt>all</tt> indicates that the source package
2936 will only build architecture-independent packages. If this is
2937 the case, <tt>all</tt> must be used rather than <tt>any</tt>;
2938 <tt>any</tt> implies that the source package will build at
2939 least one architecture-dependent package.
2943 Specifying a list of architectures or architecture wildcards
2944 indicates that the source will build an architecture-dependent
2945 package, and will only work correctly on the listed or
2946 matching architectures. If the source package also builds at
2947 least one architecture-independent package, <tt>all</tt> will
2948 also be included in the list.
2952 In a <file>.changes</file> file, the <tt>Architecture</tt>
2953 field lists the architecture(s) of the package(s) currently
2954 being uploaded. This will be a list; if the source for the
2955 package is also being uploaded, the special
2956 entry <tt>source</tt> is also present. <tt>all</tt> will be
2957 present if any architecture-independent packages are being
2958 uploaded. Architecture wildcards such as <tt>any</tt> must
2959 never occur in the <tt>Architecture</tt> field in
2960 the <file>.changes</file> file.
2964 See <ref id="debianrules"> for information on how to get
2965 the architecture for the build process.
2969 <sect1 id="f-Essential">
2970 <heading><tt>Essential</tt></heading>
2973 This is a boolean field which may occur only in the
2974 control file of a binary package or in a per-package fields
2975 paragraph of a main source control data file.
2979 If set to <tt>yes</tt> then the package management system
2980 will refuse to remove the package (upgrading and replacing
2981 it is still possible). The other possible value is <tt>no</tt>,
2982 which is the same as not having the field at all.
2987 <heading>Package interrelationship fields:
2988 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2989 <tt>Recommends</tt>, <tt>Suggests</tt>,
2990 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2991 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2995 These fields describe the package's relationships with
2996 other packages. Their syntax and semantics are described
2997 in <ref id="relationships">.</p>
3000 <sect1 id="f-Standards-Version">
3001 <heading><tt>Standards-Version</tt></heading>
3004 The most recent version of the standards (the policy
3005 manual and associated texts) with which the package
3010 The version number has four components: major and minor
3011 version number and major and minor patch level. When the
3012 standards change in a way that requires every package to
3013 change the major number will be changed. Significant
3014 changes that will require work in many packages will be
3015 signaled by a change to the minor number. The major patch
3016 level will be changed for any change to the meaning of the
3017 standards, however small; the minor patch level will be
3018 changed when only cosmetic, typographical or other edits
3019 are made which neither change the meaning of the document
3020 nor affect the contents of packages.
3024 Thus only the first three components of the policy version
3025 are significant in the <em>Standards-Version</em> control
3026 field, and so either these three components or all four
3027 components may be specified.<footnote>
3028 In the past, people specified the full version number
3029 in the Standards-Version field, for example "2.3.0.0".
3030 Since minor patch-level changes don't introduce new
3031 policy, it was thought it would be better to relax
3032 policy and only require the first 3 components to be
3033 specified, in this example "2.3.0". All four
3034 components may still be used if someone wishes to do so.
3040 <sect1 id="f-Version">
3041 <heading><tt>Version</tt></heading>
3044 The version number of a package. The format is:
3045 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
3049 The three components here are:
3051 <tag><var>epoch</var></tag>
3054 This is a single (generally small) unsigned integer. It
3055 may be omitted, in which case zero is assumed. If it is
3056 omitted then the <var>upstream_version</var> may not
3061 It is provided to allow mistakes in the version numbers
3062 of older versions of a package, and also a package's
3063 previous version numbering schemes, to be left behind.
3067 <tag><var>upstream_version</var></tag>
3070 This is the main part of the version number. It is
3071 usually the version number of the original ("upstream")
3072 package from which the <file>.deb</file> file has been made,
3073 if this is applicable. Usually this will be in the same
3074 format as that specified by the upstream author(s);
3075 however, it may need to be reformatted to fit into the
3076 package management system's format and comparison
3081 The comparison behavior of the package management system
3082 with respect to the <var>upstream_version</var> is
3083 described below. The <var>upstream_version</var>
3084 portion of the version number is mandatory.
3088 The <var>upstream_version</var> may contain only
3089 alphanumerics<footnote>
3090 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3092 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3093 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3094 tilde) and should start with a digit. If there is no
3095 <var>debian_revision</var> then hyphens are not allowed;
3096 if there is no <var>epoch</var> then colons are not
3101 <tag><var>debian_revision</var></tag>
3104 This part of the version number specifies the version of
3105 the Debian package based on the upstream version. It
3106 may contain only alphanumerics and the characters
3107 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3108 tilde) and is compared in the same way as the
3109 <var>upstream_version</var> is.
3113 It is optional; if it isn't present then the
3114 <var>upstream_version</var> may not contain a hyphen.
3115 This format represents the case where a piece of
3116 software was written specifically to be a Debian
3117 package, where the Debian package source must always
3118 be identical to the pristine source and therefore no
3119 revision indication is required.
3123 It is conventional to restart the
3124 <var>debian_revision</var> at <tt>1</tt> each time the
3125 <var>upstream_version</var> is increased.
3129 The package management system will break the version
3130 number apart at the last hyphen in the string (if there
3131 is one) to determine the <var>upstream_version</var> and
3132 <var>debian_revision</var>. The absence of a
3133 <var>debian_revision</var> is equivalent to a
3134 <var>debian_revision</var> of <tt>0</tt>.
3141 When comparing two version numbers, first the <var>epoch</var>
3142 of each are compared, then the <var>upstream_version</var> if
3143 <var>epoch</var> is equal, and then <var>debian_revision</var>
3144 if <var>upstream_version</var> is also equal.
3145 <var>epoch</var> is compared numerically. The
3146 <var>upstream_version</var> and <var>debian_revision</var>
3147 parts are compared by the package management system using the
3148 following algorithm:
3152 The strings are compared from left to right.
3156 First the initial part of each string consisting entirely of
3157 non-digit characters is determined. These two parts (one of
3158 which may be empty) are compared lexically. If a difference
3159 is found it is returned. The lexical comparison is a
3160 comparison of ASCII values modified so that all the letters
3161 sort earlier than all the non-letters and so that a tilde
3162 sorts before anything, even the end of a part. For example,
3163 the following parts are in sorted order from earliest to
3164 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3165 <tt>a</tt>.<footnote>
3166 One common use of <tt>~</tt> is for upstream pre-releases.
3167 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3168 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3173 Then the initial part of the remainder of each string which
3174 consists entirely of digit characters is determined. The
3175 numerical values of these two parts are compared, and any
3176 difference found is returned as the result of the comparison.
3177 For these purposes an empty string (which can only occur at
3178 the end of one or both version strings being compared) counts
3183 These two steps (comparing and removing initial non-digit
3184 strings and initial digit strings) are repeated until a
3185 difference is found or both strings are exhausted.
3189 Note that the purpose of epochs is to allow us to leave behind
3190 mistakes in version numbering, and to cope with situations
3191 where the version numbering scheme changes. It is
3192 <em>not</em> intended to cope with version numbers containing
3193 strings of letters which the package management system cannot
3194 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3195 silly orderings.<footnote>
3196 The author of this manual has heard of a package whose
3197 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3198 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3204 <sect1 id="f-Description">
3205 <heading><tt>Description</tt></heading>
3208 In a source or binary control file, the <tt>Description</tt>
3209 field contains a description of the binary package, consisting
3210 of two parts, the synopsis or the short description, and the
3211 long description. The field's format is as follows:
3216 Description: <single line synopsis>
3217 <extended description over several lines>
3222 The lines in the extended description can have these formats:
3228 Those starting with a single space are part of a paragraph.
3229 Successive lines of this form will be word-wrapped when
3230 displayed. The leading space will usually be stripped off.
3234 Those starting with two or more spaces. These will be
3235 displayed verbatim. If the display cannot be panned
3236 horizontally, the displaying program will line wrap them "hard"
3237 (i.e., without taking account of word breaks). If it can they
3238 will be allowed to trail off to the right. None, one or two
3239 initial spaces may be deleted, but the number of spaces
3240 deleted from each line will be the same (so that you can have
3241 indenting work correctly, for example).
3245 Those containing a single space followed by a single full stop
3246 character. These are rendered as blank lines. This is the
3247 <em>only</em> way to get a blank line<footnote>
3248 Completely empty lines will not be rendered as blank lines.
3249 Instead, they will cause the parser to think you're starting
3250 a whole new record in the control file, and will therefore
3251 likely abort with an error.
3256 Those containing a space, a full stop and some more characters.
3257 These are for future expansion. Do not use them.
3263 Do not use tab characters. Their effect is not predictable.
3267 See <ref id="descriptions"> for further information on this.
3271 In a <file>.changes</file> file, the <tt>Description</tt>
3272 field contains a summary of the descriptions for the packages
3273 being uploaded. For this case, the first line of the field
3274 value (the part on the same line as <tt>Description:</tt>) is
3275 always empty. The content of the field is expressed as
3276 continuation lines, one line per package. Each line is
3277 indented by one space and contains the name of a binary
3278 package, a space, a hyphen (<tt>-</tt>), a space, and the
3279 short description line from that package.
3283 <sect1 id="f-Distribution">
3284 <heading><tt>Distribution</tt></heading>
3287 In a <file>.changes</file> file or parsed changelog output
3288 this contains the (space-separated) name(s) of the
3289 distribution(s) where this version of the package should
3290 be installed. Valid distributions are determined by the
3291 archive maintainers.<footnote>
3292 Example distribution names in the Debian archive used in
3293 <file>.changes</file> files are:
3294 <taglist compact="compact">
3295 <tag><em>unstable</em></tag>
3297 This distribution value refers to the
3298 <em>developmental</em> part of the Debian distribution
3299 tree. Most new packages, new upstream versions of
3300 packages and bug fixes go into the <em>unstable</em>
3304 <tag><em>experimental</em></tag>
3306 The packages with this distribution value are deemed
3307 by their maintainers to be high risk. Oftentimes they
3308 represent early beta or developmental packages from
3309 various sources that the maintainers want people to
3310 try, but are not ready to be a part of the other parts
3311 of the Debian distribution tree.
3316 Others are used for updating stable releases or for
3317 security uploads. More information is available in the
3318 Debian Developer's Reference, section "The Debian
3322 The Debian archive software only supports listing a single
3323 distribution. Migration of packages to other distributions is
3324 handled outside of the upload process.
3329 <heading><tt>Date</tt></heading>
3332 This field includes the date the package was built or last
3333 edited. It must be in the same format as the <var>date</var>
3334 in a <file>debian/changelog</file> entry.
3338 The value of this field is usually extracted from the
3339 <file>debian/changelog</file> file - see
3340 <ref id="dpkgchangelog">).
3344 <sect1 id="f-Format">
3345 <heading><tt>Format</tt></heading>
3348 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3349 files, this field declares the format version of that file.
3350 The syntax of the field value is the same as that of
3351 a <qref id="f-Version">package version number</qref> except
3352 that no epoch or Debian revision is allowed. The format
3353 described in this document is <tt>&changesversion;</tt>.
3357 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3358 Debian source control</qref> files, this field declares the
3359 format of the source package. The field value is used by
3360 programs acting on a source package to interpret the list of
3361 files in the source package and determine how to unpack it.
3362 The syntax of the field value is a numeric major revision, a
3363 period, a numeric minor revision, and then an optional subtype
3364 after whitespace, which if specified is an alphanumeric word
3365 in parentheses. The subtype is optional in the syntax but may
3366 be mandatory for particular source format revisions.
3368 The source formats currently supported by the Debian archive
3369 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3370 and <tt>3.0 (quilt)</tt>.
3375 <sect1 id="f-Urgency">
3376 <heading><tt>Urgency</tt></heading>
3379 This is a description of how important it is to upgrade to
3380 this version from previous ones. It consists of a single
3381 keyword taking one of the values <tt>low</tt>,
3382 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3383 <tt>critical</tt><footnote>
3384 Other urgency values are supported with configuration
3385 changes in the archive software but are not used in Debian.
3386 The urgency affects how quickly a package will be considered
3387 for inclusion into the <tt>testing</tt> distribution and
3388 gives an indication of the importance of any fixes included
3389 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3390 treated as synonymous.
3391 </footnote> (not case-sensitive) followed by an optional
3392 commentary (separated by a space) which is usually in
3393 parentheses. For example:
3396 Urgency: low (HIGH for users of diversions)
3402 The value of this field is usually extracted from the
3403 <file>debian/changelog</file> file - see
3404 <ref id="dpkgchangelog">.
3408 <sect1 id="f-Changes">
3409 <heading><tt>Changes</tt></heading>
3412 This field contains the human-readable changes data, describing
3413 the differences between the last version and the current one.
3417 The first line of the field value (the part on the same line
3418 as <tt>Changes:</tt>) is always empty. The content of the
3419 field is expressed as continuation lines, with each line
3420 indented by at least one space. Blank lines must be
3421 represented by a line consisting only of a space and a full
3426 The value of this field is usually extracted from the
3427 <file>debian/changelog</file> file - see
3428 <ref id="dpkgchangelog">).
3432 Each version's change information should be preceded by a
3433 "title" line giving at least the version, distribution(s)
3434 and urgency, in a human-readable way.
3438 If data from several versions is being returned the entry
3439 for the most recent version should be returned first, and
3440 entries should be separated by the representation of a
3441 blank line (the "title" line may also be followed by the
3442 representation of a blank line).
3446 <sect1 id="f-Binary">
3447 <heading><tt>Binary</tt></heading>
3450 This field is a list of binary packages. Its syntax and
3451 meaning varies depending on the control file in which it
3456 When it appears in the <file>.dsc</file> file, it lists binary
3457 packages which a source package can produce, separated by
3459 A space after each comma is conventional.
3460 </footnote>. It may span multiple lines. The source package
3461 does not necessarily produce all of these binary packages for
3462 every architecture. The source control file doesn't contain
3463 details of which architectures are appropriate for which of
3464 the binary packages.
3468 When it appears in a <file>.changes</file> file, it lists the
3469 names of the binary packages being uploaded, separated by
3470 whitespace (not commas). It may span multiple lines.
3474 <sect1 id="f-Installed-Size">
3475 <heading><tt>Installed-Size</tt></heading>
3478 This field appears in the control files of binary packages,
3479 and in the <file>Packages</file> files. It gives an estimate
3480 of the total amount of disk space required to install the
3481 named package. Actual installed size may vary based on block
3482 size, file system properties, or actions taken by package
3487 The disk space is given as the integer value of the estimated
3488 installed size in bytes, divided by 1024 and rounded up.
3492 <sect1 id="f-Files">
3493 <heading><tt>Files</tt></heading>
3496 This field contains a list of files with information about
3497 each one. The exact information and syntax varies with
3502 In all cases, Files is a multiline field. The first line of
3503 the field value (the part on the same line as <tt>Files:</tt>)
3504 is always empty. The content of the field is expressed as
3505 continuation lines, one line per file. Each line must be
3506 indented by one space and contain a number of sub-fields,
3507 separated by spaces, as described below.
3511 In the <file>.dsc</file> file, each line contains the MD5
3512 checksum, size and filename of the tar file and (if
3513 applicable) diff file which make up the remainder of the
3514 source package<footnote>
3515 That is, the parts which are not the <tt>.dsc</tt>.
3516 </footnote>. For example:
3519 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3520 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3522 The exact forms of the filenames are described
3523 in <ref id="pkg-sourcearchives">.
3527 In the <file>.changes</file> file this contains one line per
3528 file being uploaded. Each line contains the MD5 checksum,
3529 size, section and priority and the filename. For example:
3532 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3533 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3534 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3535 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3537 The <qref id="f-Section">section</qref>
3538 and <qref id="f-Priority">priority</qref> are the values of
3539 the corresponding fields in the main source control file. If
3540 no section or priority is specified then <tt>-</tt> should be
3541 used, though section and priority values must be specified for
3542 new packages to be installed properly.
3546 The special value <tt>byhand</tt> for the section in a
3547 <tt>.changes</tt> file indicates that the file in question
3548 is not an ordinary package file and must by installed by
3549 hand by the distribution maintainers. If the section is
3550 <tt>byhand</tt> the priority should be <tt>-</tt>.
3554 If a new Debian revision of a package is being shipped and
3555 no new original source archive is being distributed the
3556 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3557 entry for the original source archive
3558 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3559 but the <file>.changes</file> file should leave it out. In
3560 this case the original source archive on the distribution
3561 site must match exactly, byte-for-byte, the original
3562 source archive which was used to generate the
3563 <file>.dsc</file> file and diff which are being uploaded.</p>
3566 <sect1 id="f-Closes">
3567 <heading><tt>Closes</tt></heading>
3570 A space-separated list of bug report numbers that the upload
3571 governed by the .changes file closes.
3575 <sect1 id="f-Homepage">
3576 <heading><tt>Homepage</tt></heading>
3579 The URL of the web site for this package, preferably (when
3580 applicable) the site from which the original source can be
3581 obtained and any additional upstream documentation or
3582 information may be found. The content of this field is a
3583 simple URL without any surrounding characters such as
3588 <sect1 id="f-Checksums">
3589 <heading><tt>Checksums-Sha1</tt>
3590 and <tt>Checksums-Sha256</tt></heading>
3593 These fields contain a list of files with a checksum and size
3594 for each one. Both <tt>Checksums-Sha1</tt>
3595 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3596 only in the checksum algorithm used: SHA-1
3597 for <tt>Checksums-Sha1</tt> and SHA-256
3598 for <tt>Checksums-Sha256</tt>.
3602 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3603 multiline fields. The first line of the field value (the part
3604 on the same line as <tt>Checksums-Sha1:</tt>
3605 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3606 of the field is expressed as continuation lines, one line per
3607 file. Each line consists of the checksum, a space, the file
3608 size, a space, and the file name. For example (from
3609 a <file>.changes</file> file):
3612 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3613 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3614 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3615 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3617 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3618 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3619 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3620 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3625 In the <file>.dsc</file> file, these fields should list all
3626 files that make up the source package. In
3627 the <file>.changes</file> file, these fields should list all
3628 files being uploaded. The list of files in these fields
3629 must match the list of files in the <tt>Files</tt> field.
3635 <heading>User-defined fields</heading>
3638 Additional user-defined fields may be added to the
3639 source package control file. Such fields will be
3640 ignored, and not copied to (for example) binary or
3641 source package control files or upload control files.
3645 If you wish to add additional unsupported fields to
3646 these output files you should use the mechanism
3651 Fields in the main source control information file with
3652 names starting <tt>X</tt>, followed by one or more of
3653 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3654 be copied to the output files. Only the part of the
3655 field name after the hyphen will be used in the output
3656 file. Where the letter <tt>B</tt> is used the field
3657 will appear in binary package control files, where the
3658 letter <tt>S</tt> is used in source package control
3659 files and where <tt>C</tt> is used in upload control
3660 (<tt>.changes</tt>) files.
3664 For example, if the main source information control file
3667 XBS-Comment: I stand between the candle and the star.
3669 then the binary and source package control files will contain the
3672 Comment: I stand between the candle and the star.
3681 <chapt id="maintainerscripts">
3682 <heading>Package maintainer scripts and installation procedure</heading>
3685 <heading>Introduction to package maintainer scripts</heading>
3688 It is possible to supply scripts as part of a package which
3689 the package management system will run for you when your
3690 package is installed, upgraded or removed.
3694 These scripts are the control information
3695 files <prgn>preinst</prgn>, <prgn>postinst</prgn>, <prgn>prerm</prgn>
3696 and <prgn>postrm</prgn>. They must be proper executable files;
3697 if they are scripts (which is recommended), they must start with
3698 the usual <tt>#!</tt> convention. They should be readable and
3699 executable by anyone, and must not be world-writable.
3703 The package management system looks at the exit status from
3704 these scripts. It is important that they exit with a
3705 non-zero status if there is an error, so that the package
3706 management system can stop its processing. For shell
3707 scripts this means that you <em>almost always</em> need to
3708 use <tt>set -e</tt> (this is usually true when writing shell
3709 scripts, in fact). It is also important, of course, that
3710 they exit with a zero status if everything went well.
3714 Additionally, packages interacting with users
3715 using <prgn>debconf</prgn> in the <prgn>postinst</prgn> script
3716 should install a <prgn>config</prgn> script as a control
3717 information file. See <ref id="maintscriptprompt"> for details.
3721 When a package is upgraded a combination of the scripts from
3722 the old and new packages is called during the upgrade
3723 procedure. If your scripts are going to be at all
3724 complicated you need to be aware of this, and may need to
3725 check the arguments to your scripts.
3729 Broadly speaking the <prgn>preinst</prgn> is called before
3730 (a particular version of) a package is installed, and the
3731 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3732 before (a version of) a package is removed and the
3733 <prgn>postrm</prgn> afterwards.
3737 Programs called from maintainer scripts should not normally
3738 have a path prepended to them. Before installation is
3739 started, the package management system checks to see if the
3740 programs <prgn>ldconfig</prgn>,
3741 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3742 and <prgn>update-rc.d</prgn> can be found via the
3743 <tt>PATH</tt> environment variable. Those programs, and any
3744 other program that one would expect to be in the
3745 <tt>PATH</tt>, should thus be invoked without an absolute
3746 pathname. Maintainer scripts should also not reset the
3747 <tt>PATH</tt>, though they might choose to modify it by
3748 prepending or appending package-specific directories. These
3749 considerations really apply to all shell scripts.</p>
3752 <sect id="idempotency">
3753 <heading>Maintainer scripts idempotency</heading>
3756 It is necessary for the error recovery procedures that the
3757 scripts be idempotent. This means that if it is run
3758 successfully, and then it is called again, it doesn't bomb
3759 out or cause any harm, but just ensures that everything is
3760 the way it ought to be. If the first call failed, or
3761 aborted half way through for some reason, the second call
3762 should merely do the things that were left undone the first
3763 time, if any, and exit with a success status if everything
3765 This is so that if an error occurs, the user interrupts
3766 <prgn>dpkg</prgn> or some other unforeseen circumstance
3767 happens you don't leave the user with a badly-broken
3768 package when <prgn>dpkg</prgn> attempts to repeat the
3774 <sect id="controllingterminal">
3775 <heading>Controlling terminal for maintainer scripts</heading>
3778 Maintainer scripts are not guaranteed to run with a controlling
3779 terminal and may not be able to interact with the user. They
3780 must be able to fall back to noninteractive behavior if no
3781 controlling terminal is available. Maintainer scripts that
3782 prompt via a program conforming to the Debian Configuration
3783 Management Specification (see <ref id="maintscriptprompt">) may
3784 assume that program will handle falling back to noninteractive
3789 For high-priority prompts without a reasonable default answer,
3790 maintainer scripts may abort if there is no controlling
3791 terminal. However, this situation should be avoided if at all
3792 possible, since it prevents automated or unattended installs.
3793 In most cases, users will consider this to be a bug in the
3798 <sect id="exitstatus">
3799 <heading>Exit status</heading>
3802 Each script must return a zero exit status for
3803 success, or a nonzero one for failure, since the package
3804 management system looks for the exit status of these scripts
3805 and determines what action to take next based on that datum.
3809 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3814 <list compact="compact">
3816 <var>new-preinst</var> <tt>install</tt>
3819 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3822 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3825 <var>old-preinst</var> <tt>abort-upgrade</tt>
3826 <var>new-version</var>
3831 <list compact="compact">
3833 <var>postinst</var> <tt>configure</tt>
3834 <var>most-recently-configured-version</var>
3837 <var>old-postinst</var> <tt>abort-upgrade</tt>
3838 <var>new-version</var>
3841 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3842 <tt>in-favour</tt> <var>package</var>
3843 <var>new-version</var>
3846 <var>postinst</var> <tt>abort-remove</tt>
3849 <var>deconfigured's-postinst</var>
3850 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3851 <var>failed-install-package</var> <var>version</var>
3852 [<tt>removing</tt> <var>conflicting-package</var>
3858 <list compact="compact">
3860 <var>prerm</var> <tt>remove</tt>
3863 <var>old-prerm</var> <tt>upgrade</tt>
3864 <var>new-version</var>
3867 <var>new-prerm</var> <tt>failed-upgrade</tt>
3868 <var>old-version</var>
3871 <var>conflictor's-prerm</var> <tt>remove</tt>
3872 <tt>in-favour</tt> <var>package</var>
3873 <var>new-version</var>
3876 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3877 <tt>in-favour</tt> <var>package-being-installed</var>
3878 <var>version</var> [<tt>removing</tt>
3879 <var>conflicting-package</var>
3885 <list compact="compact">
3887 <var>postrm</var> <tt>remove</tt>
3890 <var>postrm</var> <tt>purge</tt>
3893 <var>old-postrm</var> <tt>upgrade</tt>
3894 <var>new-version</var>
3897 <var>new-postrm</var> <tt>failed-upgrade</tt>
3898 <var>old-version</var>
3901 <var>new-postrm</var> <tt>abort-install</tt>
3904 <var>new-postrm</var> <tt>abort-install</tt>
3905 <var>old-version</var>
3908 <var>new-postrm</var> <tt>abort-upgrade</tt>
3909 <var>old-version</var>
3912 <var>disappearer's-postrm</var> <tt>disappear</tt>
3913 <var>overwriter</var>
3914 <var>overwriter-version</var>
3920 <sect id="unpackphase">
3921 <heading>Details of unpack phase of installation or upgrade</heading>
3924 The procedure on installation/upgrade/overwrite/disappear
3925 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3926 stage of <tt>dpkg --install</tt>) is as follows. In each
3927 case, if a major error occurs (unless listed below) the
3928 actions are, in general, run backwards - this means that the
3929 maintainer scripts are run with different arguments in
3930 reverse order. These are the "error unwind" calls listed
3937 If a version of the package is already installed, call
3938 <example compact="compact">
3939 <var>old-prerm</var> upgrade <var>new-version</var>
3943 If the script runs but exits with a non-zero
3944 exit status, <prgn>dpkg</prgn> will attempt:
3945 <example compact="compact">
3946 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3948 If this works, the upgrade continues. If this
3949 does not work, the error unwind:
3950 <example compact="compact">
3951 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3953 If this works, then the old-version is
3954 "Installed", if not, the old version is in a
3955 "Half-Configured" state.
3961 If a "conflicting" package is being removed at the same time,
3962 or if any package will be broken (due to <tt>Breaks</tt>):
3965 If <tt>--auto-deconfigure</tt> is
3966 specified, call, for each package to be deconfigured
3967 due to <tt>Breaks</tt>:
3968 <example compact="compact">
3969 <var>deconfigured's-prerm</var> deconfigure \
3970 in-favour <var>package-being-installed</var> <var>version</var>
3973 <example compact="compact">
3974 <var>deconfigured's-postinst</var> abort-deconfigure \
3975 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3977 The deconfigured packages are marked as
3978 requiring configuration, so that if
3979 <tt>--install</tt> is used they will be
3980 configured again if possible.
3983 If any packages depended on a conflicting
3984 package being removed and <tt>--auto-deconfigure</tt> is
3985 specified, call, for each such package:
3986 <example compact="compact">
3987 <var>deconfigured's-prerm</var> deconfigure \
3988 in-favour <var>package-being-installed</var> <var>version</var> \
3989 removing <var>conflicting-package</var> <var>version</var>
3992 <example compact="compact">
3993 <var>deconfigured's-postinst</var> abort-deconfigure \
3994 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3995 removing <var>conflicting-package</var> <var>version</var>
3997 The deconfigured packages are marked as
3998 requiring configuration, so that if
3999 <tt>--install</tt> is used they will be
4000 configured again if possible.
4003 To prepare for removal of each conflicting package, call:
4004 <example compact="compact">
4005 <var>conflictor's-prerm</var> remove \
4006 in-favour <var>package</var> <var>new-version</var>
4009 <example compact="compact">
4010 <var>conflictor's-postinst</var> abort-remove \
4011 in-favour <var>package</var> <var>new-version</var>
4020 If the package is being upgraded, call:
4021 <example compact="compact">
4022 <var>new-preinst</var> upgrade <var>old-version</var>
4024 If this fails, we call:
4026 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4033 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4035 is called. If this works, then the old version
4036 is in an "Installed" state, or else it is left
4037 in an "Unpacked" state.
4042 If it fails, then the old version is left
4043 in an "Half-Installed" state.
4050 Otherwise, if the package had some configuration
4051 files from a previous version installed (i.e., it
4052 is in the "configuration files only" state):
4053 <example compact="compact">
4054 <var>new-preinst</var> install <var>old-version</var>
4058 <var>new-postrm</var> abort-install <var>old-version</var>
4060 If this fails, the package is left in a
4061 "Half-Installed" state, which requires a
4062 reinstall. If it works, the packages is left in
4063 a "Config-Files" state.
4066 Otherwise (i.e., the package was completely purged):
4067 <example compact="compact">
4068 <var>new-preinst</var> install
4071 <example compact="compact">
4072 <var>new-postrm</var> abort-install
4074 If the error-unwind fails, the package is in a
4075 "Half-Installed" phase, and requires a
4076 reinstall. If the error unwind works, the
4077 package is in a not installed state.
4084 The new package's files are unpacked, overwriting any
4085 that may be on the system already, for example any
4086 from the old version of the same package or from
4087 another package. Backups of the old files are kept
4088 temporarily, and if anything goes wrong the package
4089 management system will attempt to put them back as
4090 part of the error unwind.
4094 It is an error for a package to contain files which
4095 are on the system in another package, unless
4096 <tt>Replaces</tt> is used (see <ref id="replaces">).
4098 The following paragraph is not currently the case:
4099 Currently the <tt>- - force-overwrite</tt> flag is
4100 enabled, downgrading it to a warning, but this may not
4106 It is a more serious error for a package to contain a
4107 plain file or other kind of non-directory where another
4108 package has a directory (again, unless
4109 <tt>Replaces</tt> is used). This error can be
4110 overridden if desired using
4111 <tt>--force-overwrite-dir</tt>, but this is not
4116 Packages which overwrite each other's files produce
4117 behavior which, though deterministic, is hard for the
4118 system administrator to understand. It can easily
4119 lead to "missing" programs if, for example, a package
4120 is installed which overwrites a file from another
4121 package, and is then removed again.<footnote>
4122 Part of the problem is due to what is arguably a
4123 bug in <prgn>dpkg</prgn>.
4128 A directory will never be replaced by a symbolic link
4129 to a directory or vice versa; instead, the existing
4130 state (symlink or not) will be left alone and
4131 <prgn>dpkg</prgn> will follow the symlink if there is
4140 If the package is being upgraded, call
4141 <example compact="compact">
4142 <var>old-postrm</var> upgrade <var>new-version</var>
4146 If this fails, <prgn>dpkg</prgn> will attempt:
4147 <example compact="compact">
4148 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4150 If this works, installation continues. If not,
4152 <example compact="compact">
4153 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4155 If this fails, the old version is left in a
4156 "Half-Installed" state. If it works, dpkg now
4158 <example compact="compact">
4159 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4161 If this fails, the old version is left in a
4162 "Half-Installed" state. If it works, dpkg now
4164 <example compact="compact">
4165 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4167 If this fails, the old version is in an
4174 This is the point of no return - if
4175 <prgn>dpkg</prgn> gets this far, it won't back off
4176 past this point if an error occurs. This will
4177 leave the package in a fairly bad state, which
4178 will require a successful re-installation to clear
4179 up, but it's when <prgn>dpkg</prgn> starts doing
4180 things that are irreversible.
4185 Any files which were in the old version of the package
4186 but not in the new are removed.
4190 The new file list replaces the old.
4194 The new maintainer scripts replace the old.
4198 Any packages all of whose files have been overwritten
4199 during the installation, and which aren't required for
4200 dependencies, are considered to have been removed.
4201 For each such package
4204 <prgn>dpkg</prgn> calls:
4205 <example compact="compact">
4206 <var>disappearer's-postrm</var> disappear \
4207 <var>overwriter</var> <var>overwriter-version</var>
4211 The package's maintainer scripts are removed.
4214 It is noted in the status database as being in a
4215 sane state, namely not installed (any conffiles
4216 it may have are ignored, rather than being
4217 removed by <prgn>dpkg</prgn>). Note that
4218 disappearing packages do not have their prerm
4219 called, because <prgn>dpkg</prgn> doesn't know
4220 in advance that the package is going to
4227 Any files in the package we're unpacking that are also
4228 listed in the file lists of other packages are removed
4229 from those lists. (This will lobotomize the file list
4230 of the "conflicting" package if there is one.)
4234 The backup files made during installation, above, are
4240 The new package's status is now sane, and recorded as
4245 Here is another point of no return - if the
4246 conflicting package's removal fails we do not unwind
4247 the rest of the installation; the conflicting package
4248 is left in a half-removed limbo.
4253 If there was a conflicting package we go and do the
4254 removal actions (described below), starting with the
4255 removal of the conflicting package's files (any that
4256 are also in the package being installed have already
4257 been removed from the conflicting package's file list,
4258 and so do not get removed now).
4264 <sect id="configdetails"><heading>Details of configuration</heading>
4267 When we configure a package (this happens with <tt>dpkg
4268 --install</tt> and <tt>dpkg --configure</tt>), we first
4269 update any <tt>conffile</tt>s and then call:
4270 <example compact="compact">
4271 <var>postinst</var> configure <var>most-recently-configured-version</var>
4276 No attempt is made to unwind after errors during
4277 configuration. If the configuration fails, the package is in
4278 a "Failed Config" state, and an error message is generated.
4282 If there is no most recently configured version
4283 <prgn>dpkg</prgn> will pass a null argument.
4286 Historical note: Truly ancient (pre-1997) versions of
4287 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4288 (including the angle brackets) in this case. Even older
4289 ones did not pass a second argument at all, under any
4290 circumstance. Note that upgrades using such an old dpkg
4291 version are unlikely to work for other reasons, even if
4292 this old argument behavior is handled by your postinst script.
4298 <sect id="removedetails"><heading>Details of removal and/or
4299 configuration purging</heading>
4305 <example compact="compact">
4306 <var>prerm</var> remove
4310 If prerm fails during replacement due to conflict
4312 <var>conflictor's-postinst</var> abort-remove \
4313 in-favour <var>package</var> <var>new-version</var>
4317 <var>postinst</var> abort-remove
4321 If this fails, the package is in a "Half-Configured"
4322 state, or else it remains "Installed".
4326 The package's files are removed (except <tt>conffile</tt>s).
4329 <example compact="compact">
4330 <var>postrm</var> remove
4334 If it fails, there's no error unwind, and the package is in
4335 an "Half-Installed" state.
4340 All the maintainer scripts except the <prgn>postrm</prgn>
4345 If we aren't purging the package we stop here. Note
4346 that packages which have no <prgn>postrm</prgn> and no
4347 <tt>conffile</tt>s are automatically purged when
4348 removed, as there is no difference except for the
4349 <prgn>dpkg</prgn> status.
4353 The <tt>conffile</tt>s and any backup files
4354 (<tt>~</tt>-files, <tt>#*#</tt> files,
4355 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4360 <example compact="compact">
4361 <var>postrm</var> purge
4365 If this fails, the package remains in a "Config-Files"
4370 The package's file list is removed.
4379 <chapt id="relationships">
4380 <heading>Declaring relationships between packages</heading>
4382 <sect id="depsyntax">
4383 <heading>Syntax of relationship fields</heading>
4386 These fields all have a uniform syntax. They are a list of
4387 package names separated by commas.
4391 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4392 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4393 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4394 control fields of the package, which declare
4395 dependencies on other packages, the package names listed may
4396 also include lists of alternative package names, separated
4397 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4398 if any one of the alternative packages is installed, that
4399 part of the dependency is considered to be satisfied.
4403 All of the fields except for <tt>Provides</tt> may restrict
4404 their applicability to particular versions of each named
4405 package. This is done in parentheses after each individual
4406 package name; the parentheses should contain a relation from
4407 the list below followed by a version number, in the format
4408 described in <ref id="f-Version">.
4412 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4413 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4414 strictly earlier, earlier or equal, exactly equal, later or
4415 equal and strictly later, respectively. The deprecated
4416 forms <tt><</tt> and <tt>></tt> were used to mean
4417 earlier/later or equal, rather than strictly earlier/later,
4418 so they should not appear in new packages (though
4419 <prgn>dpkg</prgn> still supports them).
4423 Whitespace may appear at any point in the version
4424 specification subject to the rules in <ref
4425 id="controlsyntax">, and must appear where it's necessary to
4426 disambiguate; it is not otherwise significant. All of the
4427 relationship fields may span multiple lines. For
4428 consistency and in case of future changes to
4429 <prgn>dpkg</prgn> it is recommended that a single space be
4430 used after a version relationship and before a version
4431 number; it is also conventional to put a single space after
4432 each comma, on either side of each vertical bar, and before
4433 each open parenthesis. When wrapping a relationship field, it
4434 is conventional to do so after a comma and before the space
4435 following that comma.
4439 For example, a list of dependencies might appear as:
4440 <example compact="compact">
4443 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4448 Relationships may be restricted to a certain set of
4449 architectures. This is indicated in brackets after each
4450 individual package name and the optional version specification.
4451 The brackets enclose a list of Debian architecture names
4452 separated by whitespace. Exclamation marks may be prepended to
4453 each of the names. (It is not permitted for some names to be
4454 prepended with exclamation marks while others aren't.)
4458 For build relationship fields
4459 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4460 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>), if
4461 the current Debian host architecture is not in this list and
4462 there are no exclamation marks in the list, or it is in the list
4463 with a prepended exclamation mark, the package name and the
4464 associated version specification are ignored completely for the
4465 purposes of defining the relationships.
4470 <example compact="compact">
4472 Build-Depends-Indep: texinfo
4473 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4474 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4476 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4477 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4478 <tt>gnumach-dev</tt> only on hurd-i386.
4482 For binary relationship fields, the architecture restriction
4483 syntax is only supported in the source package control
4484 file <file>debian/control</file>. When the corresponding binary
4485 package control file is generated, the relationship will either
4486 be omitted or included without the architecture restriction
4487 based on the architecture of the binary package. This means
4488 that architecture restrictions must not be used in binary
4489 relationship fields for architecture-independent packages
4490 (<tt>Architecture: all</tt>).
4495 <example compact="compact">
4496 Depends: foo [i386], bar [amd64]
4498 becomes <tt>Depends: foo</tt> when the package is built on
4499 the <tt>i386</tt> architecture, <tt>Depends: bar</tt> when the
4500 package is built on the <tt>amd64</tt> architecture, and omitted
4501 entirely in binary packages built on all other architectures.
4505 If the architecture-restricted dependency is part of a set of
4506 alternatives using <tt>|</tt>, that alternative is ignored
4507 completely on architectures that do not match the restriction.
4509 <example compact="compact">
4510 Build-Depends: foo [!i386] | bar [!amd64]
4512 is equivalent to <tt>bar</tt> on the i386 architecture, to
4513 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4514 bar</tt> on all other architectures.
4518 Relationships may also be restricted to a certain set of
4519 architectures using architecture wildcards. The syntax for
4520 declaring such restrictions is the same as declaring
4521 restrictions using a certain set of architectures without
4522 architecture wildcards. For example:
4523 <example compact="compact">
4524 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4526 is equivalent to <tt>foo</tt> on architectures using the Linux
4527 kernel and any cpu, <tt>bar</tt> on architectures using any
4528 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4529 using a kernel other than Linux.
4533 Note that the binary package relationship fields such as
4534 <tt>Depends</tt> appear in one of the binary package
4535 sections of the control file, whereas the build-time
4536 relationships such as <tt>Build-Depends</tt> appear in the
4537 source package section of the control file (which is the
4542 <sect id="binarydeps">
4543 <heading>Binary Dependencies - <tt>Depends</tt>,
4544 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4545 <tt>Pre-Depends</tt>
4549 Packages can declare in their control file that they have
4550 certain relationships to other packages - for example, that
4551 they may not be installed at the same time as certain other
4552 packages, and/or that they depend on the presence of others.
4556 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4557 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4558 <tt>Breaks</tt> and <tt>Conflicts</tt> control fields.
4559 <tt>Breaks</tt> is described in <ref id="breaks">, and
4560 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4561 rest are described below.
4565 These seven fields are used to declare a dependency
4566 relationship by one package on another. Except for
4567 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4568 depending (binary) package's control file.
4569 (<tt>Enhances</tt> appears in the recommending package's
4570 control file, and <tt>Breaks</tt> appears in the version of
4571 depended-on package which causes the named package to
4576 A <tt>Depends</tt> field takes effect <em>only</em> when a
4577 package is to be configured. It does not prevent a package
4578 being on the system in an unconfigured state while its
4579 dependencies are unsatisfied, and it is possible to replace
4580 a package whose dependencies are satisfied and which is
4581 properly installed with a different version whose
4582 dependencies are not and cannot be satisfied; when this is
4583 done the depending package will be left unconfigured (since
4584 attempts to configure it will give errors) and will not
4585 function properly. If it is necessary, a
4586 <tt>Pre-Depends</tt> field can be used, which has a partial
4587 effect even when a package is being unpacked, as explained
4588 in detail below. (The other three dependency fields,
4589 <tt>Recommends</tt>, <tt>Suggests</tt> and
4590 <tt>Enhances</tt>, are only used by the various front-ends
4591 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4592 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4596 For this reason packages in an installation run are usually
4597 all unpacked first and all configured later; this gives
4598 later versions of packages with dependencies on later
4599 versions of other packages the opportunity to have their
4600 dependencies satisfied.
4604 In case of circular dependencies, since installation or
4605 removal order honoring the dependency order can't be
4606 established, dependency loops are broken at some point
4607 (based on rules below), and some packages may not be able to
4608 rely on their dependencies being present when being
4609 installed or removed, depending on which side of the break
4610 of the circular dependency loop they happen to be on. If one
4611 of the packages in the loop has no postinst script, then the
4612 cycle will be broken at that package, so as to ensure that
4613 all postinst scripts run with the dependencies properly
4614 configured if this is possible. Otherwise the breaking point
4619 The <tt>Depends</tt> field thus allows package maintainers
4620 to impose an order in which packages should be configured.
4624 The meaning of the five dependency fields is as follows:
4626 <tag><tt>Depends</tt></tag>
4629 This declares an absolute dependency. A package will
4630 not be configured unless all of the packages listed in
4631 its <tt>Depends</tt> field have been correctly
4636 The <tt>Depends</tt> field should be used if the
4637 depended-on package is required for the depending
4638 package to provide a significant amount of
4643 The <tt>Depends</tt> field should also be used if the
4644 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4645 <prgn>postrm</prgn> scripts require the package to be
4646 present in order to run. Note, however, that the
4647 <prgn>postrm</prgn> cannot rely on any non-essential
4648 packages to be present during the <tt>purge</tt>
4652 <tag><tt>Recommends</tt></tag>
4655 This declares a strong, but not absolute, dependency.
4659 The <tt>Recommends</tt> field should list packages
4660 that would be found together with this one in all but
4661 unusual installations.
4665 <tag><tt>Suggests</tt></tag>
4667 This is used to declare that one package may be more
4668 useful with one or more others. Using this field
4669 tells the packaging system and the user that the
4670 listed packages are related to this one and can
4671 perhaps enhance its usefulness, but that installing
4672 this one without them is perfectly reasonable.
4675 <tag><tt>Enhances</tt></tag>
4677 This field is similar to Suggests but works in the
4678 opposite direction. It is used to declare that a
4679 package can enhance the functionality of another
4683 <tag><tt>Pre-Depends</tt></tag>
4686 This field is like <tt>Depends</tt>, except that it
4687 also forces <prgn>dpkg</prgn> to complete installation
4688 of the packages named before even starting the
4689 installation of the package which declares the
4690 pre-dependency, as follows:
4694 When a package declaring a pre-dependency is about to
4695 be <em>unpacked</em> the pre-dependency can be
4696 satisfied if the depended-on package is either fully
4697 configured, <em>or even if</em> the depended-on
4698 package(s) are only unpacked or in the "Half-Configured"
4699 state, provided that they have been configured
4700 correctly at some point in the past (and not removed
4701 or partially removed since). In this case, both the
4702 previously-configured and currently unpacked or
4703 "Half-Configured" versions must satisfy any version
4704 clause in the <tt>Pre-Depends</tt> field.
4708 When the package declaring a pre-dependency is about
4709 to be <em>configured</em>, the pre-dependency will be
4710 treated as a normal <tt>Depends</tt>, that is, it will
4711 be considered satisfied only if the depended-on
4712 package has been correctly configured.
4716 <tt>Pre-Depends</tt> should be used sparingly,
4717 preferably only by packages whose premature upgrade or
4718 installation would hamper the ability of the system to
4719 continue with any upgrade that might be in progress.
4723 <tt>Pre-Depends</tt> are also required if the
4724 <prgn>preinst</prgn> script depends on the named
4725 package. It is best to avoid this situation if
4733 When selecting which level of dependency to use you should
4734 consider how important the depended-on package is to the
4735 functionality of the one declaring the dependency. Some
4736 packages are composed of components of varying degrees of
4737 importance. Such a package should list using
4738 <tt>Depends</tt> the package(s) which are required by the
4739 more important components. The other components'
4740 requirements may be mentioned as Suggestions or
4741 Recommendations, as appropriate to the components' relative
4747 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4750 When one binary package declares that it breaks another,
4751 <prgn>dpkg</prgn> will refuse to allow the package which
4752 declares <tt>Breaks</tt> be installed unless the broken
4753 package is deconfigured first, and it will refuse to
4754 allow the broken package to be reconfigured.
4758 A package will not be regarded as causing breakage merely
4759 because its configuration files are still installed; it must
4760 be at least "Half-Installed".
4764 A special exception is made for packages which declare that
4765 they break their own package name or a virtual package which
4766 they provide (see below): this does not count as a real
4771 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4772 version clause; such a <tt>Breaks</tt> is introduced in the
4773 version of an (implicit or explicit) dependency which violates
4774 an assumption or reveals a bug in earlier versions of the broken
4775 package, or which takes over a file from earlier versions of the
4776 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
4777 will inform higher-level package management tools that the
4778 broken package must be upgraded before the new one.
4782 If the breaking package also overwrites some files from the
4783 older package, it should use <tt>Replaces</tt> to ensure this
4784 goes smoothly. See <ref id="replaces"> for a full discussion
4785 of taking over files from other packages, including how to
4786 use <tt>Breaks</tt> in those cases.
4790 Many of the cases where <tt>Breaks</tt> should be used were
4791 previously handled with <tt>Conflicts</tt>
4792 because <tt>Breaks</tt> did not yet exist.
4793 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
4794 See <ref id="conflicts"> for more information about the
4799 <sect id="conflicts">
4800 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4803 When one binary package declares a conflict with another
4804 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4805 refuse to allow them to be installed on the system at the
4806 same time. This is a stronger restriction than <tt>Breaks</tt>,
4807 which just prevents both packages from being configured at the
4808 same time. Conflicting packages cannot be unpacked on the
4809 system at the same time.
4813 If one package is to be installed, the other must be removed
4814 first. If the package being installed is marked as replacing
4815 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
4816 normally be used in this case) the one on the system, or the one
4817 on the system is marked as deselected, or both packages are
4818 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
4819 automatically remove the package which is causing the conflict.
4820 Otherwise, it will halt the installation of the new package with
4821 an error. This mechanism is specifically designed to produce an
4822 error when the installed package is <tt>Essential</tt>, but the
4827 A package will not cause a conflict merely because its
4828 configuration files are still installed; it must be at least
4833 A special exception is made for packages which declare a
4834 conflict with their own package name, or with a virtual
4835 package which they provide (see below): this does not
4836 prevent their installation, and allows a package to conflict
4837 with others providing a replacement for it. You use this
4838 feature when you want the package in question to be the only
4839 package providing some feature.
4843 Normally, <tt>Breaks</tt> should be used instead
4844 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
4845 stronger restriction on the ordering of package installation or
4846 upgrade and can make it more difficult for the package manager
4847 to find a correct solution to an upgrade or installation
4848 problem. <tt>Breaks</tt> should be used
4850 <item>when moving a file from one package to another (see
4851 <ref id="replaces">),</item>
4852 <item>when splitting a package (a special case of the previous
4854 <item>when the breaking package exposes a bug in or interacts
4855 badly with particular versions of the broken
4858 <tt>Conflicts</tt> should be used
4860 <item>when two packages provide the same file and will
4861 continue to do so,</item>
4862 <item>in conjunction with <tt>Provides</tt> when only one
4863 package providing a given virtual facility may be installed
4864 at a time (see <ref id="virtual">),</item>
4865 <item>in other cases where one must prevent simultaneous
4866 installation of two packages for reasons that are ongoing
4867 (not fixed in a later version of one of the packages) or
4868 that must prevent both packages from being unpacked at the
4869 same time, not just configured.</item>
4871 Be aware that adding <tt>Conflicts</tt> is normally not the best
4872 solution when two packages provide the same files. Depending on
4873 the reason for that conflict, using alternatives or renaming the
4874 files is often a better approach. See, for
4875 example, <ref id="binaries">.
4879 Neither <tt>Breaks</tt> nor <tt>Conflicts</tt> should be used
4880 unless two packages cannot be installed at the same time or
4881 installing them both causes one of them to be broken or
4882 unusable. Having similar functionality or performing the same
4883 tasks as another package is not sufficient reason to
4884 declare <tt>Breaks</tt> or <tt>Conflicts</tt> with that package.
4888 A <tt>Conflicts</tt> entry may have an "earlier than" version
4889 clause if the reason for the conflict is corrected in a later
4890 version of one of the packages. However, normally the presence
4891 of an "earlier than" version clause is a sign
4892 that <tt>Breaks</tt> should have been used instead. An "earlier
4893 than" version clause in <tt>Conflicts</tt>
4894 prevents <prgn>dpkg</prgn> from upgrading or installing the
4895 package which declares such a conflict until the upgrade or
4896 removal of the conflicted-with package has been completed, which
4897 is a strong restriction.
4901 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4905 As well as the names of actual ("concrete") packages, the
4906 package relationship fields <tt>Depends</tt>,
4907 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4908 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4909 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4910 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4911 may mention "virtual packages".
4915 A <em>virtual package</em> is one which appears in the
4916 <tt>Provides</tt> control field of another package. The effect
4917 is as if the package(s) which provide a particular virtual
4918 package name had been listed by name everywhere the virtual
4919 package name appears. (See also <ref id="virtual_pkg">)
4923 If there are both concrete and virtual packages of the same
4924 name, then the dependency may be satisfied (or the conflict
4925 caused) by either the concrete package with the name in
4926 question or any other concrete package which provides the
4927 virtual package with the name in question. This is so that,
4928 for example, supposing we have
4929 <example compact="compact">
4932 </example> and someone else releases an enhanced version of
4933 the <tt>bar</tt> package they can say:
4934 <example compact="compact">
4938 and the <tt>bar-plus</tt> package will now also satisfy the
4939 dependency for the <tt>foo</tt> package.
4943 If a relationship field has a version number attached, only real
4944 packages will be considered to see whether the relationship is
4945 satisfied (or the prohibition violated, for a conflict or
4946 breakage). In other words, if a version number is specified,
4947 this is a request to ignore all <tt>Provides</tt> for that
4948 package name and consider only real packages. The package
4949 manager will assume that a package providing that virtual
4950 package is not of the "right" version. A <tt>Provides</tt>
4951 field may not contain version numbers, and the version number of
4952 the concrete package which provides a particular virtual package
4953 will not be considered when considering a dependency on or
4954 conflict with the virtual package name.<footnote>
4955 It is possible that a future release of <prgn>dpkg</prgn> may
4956 add the ability to specify a version number for each virtual
4957 package it provides. This feature is not yet present,
4958 however, and is expected to be used only infrequently.
4963 To specify which of a set of real packages should be the default
4964 to satisfy a particular dependency on a virtual package, list
4965 the real package as an alternative before the virtual one.
4969 If the virtual package represents a facility that can only be
4970 provided by one real package at a time, such as
4971 the <package>mail-transport-agent</package> virtual package that
4972 requires installation of a binary that would conflict with all
4973 other providers of that virtual package (see
4974 <ref id="mail-transport-agents">), all packages providing that
4975 virtual package should also declare a conflict with it
4976 using <tt>Conflicts</tt>. This will ensure that at most one
4977 provider of that virtual package is unpacked or installed at a
4982 <sect id="replaces"><heading>Overwriting files and replacing
4983 packages - <tt>Replaces</tt></heading>
4986 Packages can declare in their control file that they should
4987 overwrite files in certain other packages, or completely replace
4988 other packages. The <tt>Replaces</tt> control field has these
4989 two distinct purposes.
4992 <sect1><heading>Overwriting files in other packages</heading>
4995 It is usually an error for a package to contain files which
4996 are on the system in another package. However, if the
4997 overwriting package declares that it <tt>Replaces</tt> the one
4998 containing the file being overwritten, then <prgn>dpkg</prgn>
4999 will replace the file from the old package with that from the
5000 new. The file will no longer be listed as "owned" by the old
5001 package and will be taken over by the new package.
5002 Normally, <tt>Breaks</tt> should be used in conjunction
5003 with <tt>Replaces</tt>.<footnote>
5004 To see why <tt>Breaks</tt> is normally needed in addition
5005 to <tt>Replaces</tt>, consider the case of a file in the
5006 package <package>foo</package> being taken over by the
5007 package <package>foo-data</package>.
5008 <tt>Replaces</tt> will allow <package>foo-data</package> to
5009 be installed and take over that file. However,
5010 without <tt>Breaks</tt>, nothing
5011 requires <package>foo</package> to be upgraded to a newer
5012 version that knows it does not include that file and instead
5013 depends on <package>foo-data</package>. Nothing would
5014 prevent the new <package>foo-data</package> package from
5015 being installed and then removed, removing the file that it
5016 took over from <package>foo</package>. After that
5017 operation, the package manager would think the system was in
5018 a consistent state, but the <package>foo</package> package
5019 would be missing one of its files.
5024 For example, if a package <package>foo</package> is split
5025 into <package>foo</package> and <package>foo-data</package>
5026 starting at version 1.2-3, <package>foo-data</package> would
5028 <example compact="compact">
5029 Replaces: foo (<< 1.2-3)
5030 Breaks: foo (<< 1.2-3)
5032 in its control file. The new version of the
5033 package <package>foo</package> would normally have the field
5034 <example compact="compact">
5035 Depends: foo-data (>= 1.2-3)
5037 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
5038 the files moved into <package>foo-data</package> are not
5039 required for normal operation).
5043 If a package is completely replaced in this way, so that
5044 <prgn>dpkg</prgn> does not know of any files it still
5045 contains, it is considered to have "disappeared". It will
5046 be marked as not wanted on the system (selected for
5047 removal) and not installed. Any <tt>conffile</tt>s
5048 details noted for the package will be ignored, as they
5049 will have been taken over by the overwriting package. The
5050 package's <prgn>postrm</prgn> script will be run with a
5051 special argument to allow the package to do any final
5052 cleanup required. See <ref id="mscriptsinstact">.
5054 Replaces is a one way relationship. You have to install
5055 the replacing package after the replaced package.
5060 For this usage of <tt>Replaces</tt>, virtual packages (see
5061 <ref id="virtual">) are not considered when looking at a
5062 <tt>Replaces</tt> field. The packages declared as being
5063 replaced must be mentioned by their real names.
5067 This usage of <tt>Replaces</tt> only takes effect when both
5068 packages are at least partially on the system at once. It is
5069 not relevant if the packages conflict unless the conflict has
5074 <sect1><heading>Replacing whole packages, forcing their
5078 Second, <tt>Replaces</tt> allows the packaging system to
5079 resolve which package should be removed when there is a
5080 conflict (see <ref id="conflicts">). This usage only takes
5081 effect when the two packages <em>do</em> conflict, so that the
5082 two usages of this field do not interfere with each other.
5086 In this situation, the package declared as being replaced
5087 can be a virtual package, so for example, all mail
5088 transport agents (MTAs) would have the following fields in
5089 their control files:
5090 <example compact="compact">
5091 Provides: mail-transport-agent
5092 Conflicts: mail-transport-agent
5093 Replaces: mail-transport-agent
5095 ensuring that only one MTA can be installed at any one
5096 time. See <ref id="virtual"> for more information about this
5101 <sect id="sourcebinarydeps">
5102 <heading>Relationships between source and binary packages -
5103 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5104 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5108 Source packages that require certain binary packages to be
5109 installed or absent at the time of building the package
5110 can declare relationships to those binary packages.
5114 This is done using the <tt>Build-Depends</tt>,
5115 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5116 <tt>Build-Conflicts-Indep</tt> control fields.
5120 Build-dependencies on "build-essential" binary packages can be
5121 omitted. Please see <ref id="pkg-relations"> for more information.
5125 The dependencies and conflicts they define must be satisfied
5126 (as defined earlier for binary packages) in order to invoke
5127 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5129 There is no Build-Depends-Arch; this role is essentially
5130 met with Build-Depends. Anyone building the
5131 <tt>build-indep</tt> and <tt>binary-indep</tt> targets is
5132 assumed to be building the whole package, and therefore
5133 installation of all build dependencies is required.
5136 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5137 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5138 not yet know how to check for its existence, and
5139 <tt>binary-arch</tt>. The purpose of the original split
5140 between <tt>Build-Depends</tt> and
5141 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5142 wouldn't need to install extra packages needed only for the
5143 binary-indep targets. But without a build-arch/build-indep
5144 split, this didn't work, since most of the work is done in
5145 the build target, not in the binary target.
5149 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5150 <tt>binary-arch</tt></tag>
5152 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5153 fields must be satisfied when these targets are invoked.
5155 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5156 and <tt>binary-indep</tt></tag>
5158 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5159 <tt>Build-Depends-Indep</tt>, and
5160 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5161 these targets are invoked.
5169 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5172 Packages containing shared libraries must be constructed with
5173 a little care to make sure that the shared library is always
5174 available. This is especially important for packages whose
5175 shared libraries are vitally important, such as the C library
5176 (currently <tt>libc6</tt>).
5180 This section deals only with public shared libraries: shared
5181 libraries that are placed in directories searched by the dynamic
5182 linker by default or which are intended to be linked against
5183 normally and possibly used by other, independent packages. Shared
5184 libraries that are internal to a particular package or that are
5185 only loaded as dynamic modules are not covered by this section and
5186 are not subject to its requirements.
5190 A shared library is identified by the <tt>SONAME</tt> attribute
5191 stored in its dynamic section. When a binary is linked against a
5192 shared library, the <tt>SONAME</tt> of the shared library is
5193 recorded in the binary's <tt>NEEDED</tt> section so that the
5194 dynamic linker knows that library must be loaded at runtime. The
5195 shared library file's full name (which usually contains additional
5196 version information not needed in the <tt>SONAME</tt>) is
5197 therefore normally not referenced directly. Instead, the shared
5198 library is loaded by its <tt>SONAME</tt>, which exists on the file
5199 system as a symlink pointing to the full name of the shared
5200 library. This symlink must be provided by the
5201 package. <ref id="sharedlibs-runtime"> describes how to do this.
5203 This is a convention of shared library versioning, but not a
5204 requirement. Some libraries use the <tt>SONAME</tt> as the full
5205 library file name instead and therefore do not need a symlink.
5206 Most, however, encode additional information about
5207 backwards-compatible revisions as a minor version number in the
5208 file name. The <tt>SONAME</tt> itself only changes when
5209 binaries linked with the earlier version of the shared library
5210 may no longer work, but the filename may change with each
5211 release of the library. See <ref id="sharedlibs-runtime"> for
5217 When linking a binary or another shared library against a shared
5218 library, the <tt>SONAME</tt> for that shared library is not yet
5219 known. Instead, the shared library is found by looking for a file
5220 matching the library name with <tt>.so</tt> appended. This file
5221 exists on the file system as a symlink pointing to the shared
5226 Shared libraries are normally split into several binary packages.
5227 The <tt>SONAME</tt> symlink is installed by the runtime shared
5228 library package, and the bare <tt>.so</tt> symlink is installed in
5229 the development package since it's only used when linking binaries
5230 or shared libraries. However, there are some exceptions for
5231 unusual shared libraries or for shared libraries that are also
5232 loaded as dynamic modules by other programs.
5236 This section is primarily concerned with how the separation of
5237 shared libraries into multiple packages should be done and how
5238 dependencies on and between shared library binary packages are
5239 managed in Debian. <ref id="libraries"> should be read in
5240 conjunction with this section and contains additional rules for
5241 the files contained in the shared library packages.
5244 <sect id="sharedlibs-runtime">
5245 <heading>Run-time shared libraries</heading>
5248 The run-time shared library must be placed in a package
5249 whose name changes whenever the <tt>SONAME</tt> of the shared
5250 library changes. This allows several versions of the shared
5251 library to be installed at the same time, allowing installation
5252 of the new version of the shared library without immediately
5253 breaking binaries that depend on the old version. Normally, the
5254 run-time shared library and its <tt>SONAME</tt> symlink should
5255 be placed in a package named
5256 <package><var>libraryname</var><var>soversion</var></package>,
5257 where <var>soversion</var> is the version number in
5258 the <tt>SONAME</tt> of the shared library.
5259 See <ref id="shlibs"> for detailed information on how to
5260 determine this version. Alternatively, if it would be confusing
5261 to directly append <var>soversion</var>
5262 to <var>libraryname</var> (if, for example, <var>libraryname</var>
5263 itself ends in a number), you should use
5264 <package><var>libraryname</var>-<var>soversion</var></package>
5269 If you have several shared libraries built from the same source
5270 tree, you may lump them all together into a single shared
5271 library package provided that all of their <tt>SONAME</tt>s will
5272 always change together. Be aware that this is not normally the
5273 case, and if the <tt>SONAME</tt>s do not change together,
5274 upgrading such a merged shared library package will be
5275 unnecessarily difficult because of file conflicts with the old
5276 version of the package. When in doubt, always split shared
5277 library packages so that each binary package installs a single
5282 Every time the shared library ABI changes in a way that may
5283 break binaries linked against older versions of the shared
5284 library, the <tt>SONAME</tt> of the library and the
5285 corresponding name for the binary package containing the runtime
5286 shared library should change. Normally, this means
5287 the <tt>SONAME</tt> should change any time an interface is
5288 removed from the shared library or the signature of an interface
5289 (the number of parameters or the types of parameters that it
5290 takes, for example) is changed. This practice is vital to
5291 allowing clean upgrades from older versions of the package and
5292 clean transitions between the old ABI and new ABI without having
5293 to upgrade every affected package simultaneously.
5297 The <tt>SONAME</tt> and binary package name need not, and indeed
5298 normally should not, change if new interfaces are added but none
5299 are removed or changed, since this will not break binaries
5300 linked against the old shared library. Correct versioning of
5301 dependencies on the newer shared library by binaries that use
5302 the new interfaces is handled via
5303 the <qref id="sharedlibs-shlibdeps"><tt>shlibs</tt>
5304 system</qref> or via symbols files (see
5305 <manref name="deb-symbols" section="5">).
5309 The package should install the shared libraries under
5310 their normal names. For example, the <package>libgdbm3</package>
5311 package should install <file>libgdbm.so.3.0.0</file> as
5312 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5313 renamed or re-linked by any <prgn>prerm</prgn> or
5314 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5315 of renaming things safely without affecting running programs,
5316 and attempts to interfere with this are likely to lead to
5321 Shared libraries should not be installed executable, since
5322 the dynamic linker does not require this and trying to
5323 execute a shared library usually results in a core dump.
5327 The run-time library package should include the symbolic link for
5328 the <tt>SONAME</tt> that <prgn>ldconfig</prgn> would create for
5329 the shared libraries. For example,
5330 the <package>libgdbm3</package> package should include a symbolic
5331 link from <file>/usr/lib/libgdbm.so.3</file> to
5332 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5333 linker (for example <prgn>ld.so</prgn> or
5334 <prgn>ld-linux.so.*</prgn>) can find the library between the
5335 time that <prgn>dpkg</prgn> installs it and the time that
5336 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5338 The package management system requires the library to be
5339 placed before the symbolic link pointing to it in the
5340 <file>.deb</file> file. This is so that when
5341 <prgn>dpkg</prgn> comes to install the symlink
5342 (overwriting the previous symlink pointing at an older
5343 version of the library), the new shared library is already
5344 in place. In the past, this was achieved by creating the
5345 library in the temporary packaging directory before
5346 creating the symlink. Unfortunately, this was not always
5347 effective, since the building of the tar file in the
5348 <file>.deb</file> depended on the behavior of the underlying
5349 file system. Some file systems (such as reiserfs) reorder
5350 the files so that the order of creation is forgotten.
5351 Since version 1.7.0, <prgn>dpkg</prgn>
5352 reorders the files itself as necessary when building a
5353 package. Thus it is no longer important to concern
5354 oneself with the order of file creation.
5358 <sect1 id="ldconfig">
5359 <heading><tt>ldconfig</tt></heading>
5362 Any package installing shared libraries in one of the default
5363 library directories of the dynamic linker (which are currently
5364 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5365 listed in <file>/etc/ld.so.conf</file><footnote>
5367 <list compact="compact">
5368 <item>/usr/local/lib</item>
5369 <item>/usr/lib/libc5-compat</item>
5370 <item>/lib/libc5-compat</item>
5373 must use <prgn>ldconfig</prgn> to update the shared library
5378 The package maintainer scripts must only call
5379 <prgn>ldconfig</prgn> under these circumstances:
5380 <list compact="compact">
5381 <item>When the <prgn>postinst</prgn> script is run with a
5382 first argument of <tt>configure</tt>, the script must call
5383 <prgn>ldconfig</prgn>, and may optionally invoke
5384 <prgn>ldconfig</prgn> at other times.
5386 <item>When the <prgn>postrm</prgn> script is run with a
5387 first argument of <tt>remove</tt>, the script should call
5388 <prgn>ldconfig</prgn>.
5393 During install or upgrade, the preinst is called before
5394 the new files are installed, so calling "ldconfig" is
5395 pointless. The preinst of an existing package can also be
5396 called if an upgrade fails. However, this happens during
5397 the critical time when a shared libs may exist on-disk
5398 under a temporary name. Thus, it is dangerous and
5399 forbidden by current policy to call "ldconfig" at this
5404 When a package is installed or upgraded, "postinst
5405 configure" runs after the new files are safely on-disk.
5406 Since it is perfectly safe to invoke ldconfig
5407 unconditionally in a postinst, it is OK for a package to
5408 simply put ldconfig in its postinst without checking the
5409 argument. The postinst can also be called to recover from
5410 a failed upgrade. This happens before any new files are
5411 unpacked, so there is no reason to call "ldconfig" at this
5416 For a package that is being removed, prerm is
5417 called with all the files intact, so calling ldconfig is
5418 useless. The other calls to "prerm" happen in the case of
5419 upgrade at a time when all the files of the old package
5420 are on-disk, so again calling "ldconfig" is pointless.
5424 postrm, on the other hand, is called with the "remove"
5425 argument just after the files are removed, so this is
5426 the proper time to call "ldconfig" to notify the system
5427 of the fact that the shared libraries from the package
5428 are removed. The postrm can be called at several other
5429 times. At the time of "postrm purge", "postrm
5430 abort-install", or "postrm abort-upgrade", calling
5431 "ldconfig" is useless because the shared lib files are
5432 not on-disk. However, when "postrm" is invoked with
5433 arguments "upgrade", "failed-upgrade", or "disappear", a
5434 shared lib may exist on-disk under a temporary filename.
5442 <sect id="sharedlibs-support-files">
5443 <heading>Shared library support files</heading>
5446 If your package contains files whose names do not change with
5447 each change in the library shared object version, you must not
5448 put them in the shared library package. Otherwise, several
5449 versions of the shared library cannot be installed at the same
5450 time without filename clashes, making upgrades and transitions
5451 unnecessarily difficult.
5455 It is recommended that supporting files and run-time support
5456 programs that do not need to be invoked manually by users, but
5457 are nevertheless required for the package to function, be placed
5458 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5459 preferably under <file>/usr/lib/</file><var>package-name</var>.
5460 If the program or file is architecture independent, the
5461 recommendation is for it to be placed in a subdirectory of
5462 <file>/usr/share</file> instead, preferably under
5463 <file>/usr/share/</file><var>package-name</var>. Following the
5464 <var>package-name</var> naming convention ensures that the file
5465 names change when the shared object version changes.
5469 Run-time support programs that use the shared library but are
5470 not required for the library to function or files used by the
5471 shared library that can be used by any version of the shared
5472 library package should instead be put in a separate package.
5473 This package might typically be named
5474 <package><var>libraryname</var>-tools</package>; note the
5475 absence of the <var>soversion</var> in the package name.
5479 Files and support programs only useful when compiling software
5480 against the library should be included in the development
5481 package for the library.<footnote>
5482 For example, a <file><var>package-name</var>-config</file>
5483 script or <package>pkg-config</package> configuration files.
5488 <sect id="sharedlibs-static">
5489 <heading>Static libraries</heading>
5492 The static library (<file><var>libraryname.a</var></file>)
5493 is usually provided in addition to the shared version.
5494 It is placed into the development package (see below).
5498 In some cases, it is acceptable for a library to be
5499 available in static form only; these cases include:
5501 <item>libraries for languages whose shared library support
5502 is immature or unstable</item>
5503 <item>libraries whose interfaces are in flux or under
5504 development (commonly the case when the library's
5505 major version number is zero, or where the ABI breaks
5506 across patchlevels)</item>
5507 <item>libraries which are explicitly intended to be
5508 available only in static form by their upstream
5513 <sect id="sharedlibs-dev">
5514 <heading>Development files</heading>
5517 If there are development files associated with a shared library,
5518 the source package needs to generate a binary development package
5519 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5520 or if you prefer only to support one development version at a
5521 time, <package><var>libraryname</var>-dev</package>. Installing
5522 the development package must result in installation of all the
5523 development files necessary for compiling programs against that
5524 shared library.<footnote>
5525 This wording allows the development files to be split into
5526 several packages, such as a separate architecture-independent
5527 <package><var>libraryname</var>-headers</package>, provided that
5528 the development package depends on all the required additional
5534 In case several development versions of a library exist, you may
5535 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5536 <ref id="conflicts">) to ensure that the user only installs one
5537 development version at a time (as different development versions are
5538 likely to have the same header files in them, which would cause a
5539 filename clash if both were installed).
5543 The development package should contain a symlink for the associated
5544 shared library without a version number. For example, the
5545 <package>libgdbm-dev</package> package should include a symlink
5546 from <file>/usr/lib/libgdbm.so</file> to
5547 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5548 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5549 <file>libgdbm.so</file> when compiling dynamically.
5553 If the package provides Ada Library Information
5554 (<file>*.ali</file>) files for use with GNAT, these files must be
5555 installed read-only (mode 0444) so that GNAT will not attempt to
5556 recompile them. This overrides the normal file mode requirements
5557 given in <ref id="permissions-owners">.
5561 <sect id="sharedlibs-intradeps">
5562 <heading>Dependencies between the packages of the same library</heading>
5565 Typically the development version should have an exact
5566 version dependency on the runtime library, to make sure that
5567 compilation and linking happens correctly. The
5568 <tt>${binary:Version}</tt> substitution variable can be
5569 useful for this purpose.
5571 Previously, <tt>${Source-Version}</tt> was used, but its name
5572 was confusing and it has been deprecated since dpkg 1.13.19.
5577 <sect id="sharedlibs-shlibdeps">
5578 <heading>Dependencies between the library and other packages -
5579 the <tt>shlibs</tt> system</heading>
5582 If a package contains a binary or library which links to a
5583 shared library, we must ensure that when the package is
5584 installed on the system, all of the libraries needed are
5585 also installed. This requirement led to the creation of the
5586 <tt>shlibs</tt> system, which is very simple in its design:
5587 any package which <em>provides</em> a shared library also
5588 provides information on the package dependencies required to
5589 ensure the presence of this library, and any package which
5590 <em>uses</em> a shared library uses this information to
5591 determine the dependencies it requires. The files which
5592 contain the mapping from shared libraries to the necessary
5593 dependency information are called <file>shlibs</file> files.
5597 When a package is built which contains any shared libraries, it
5598 must provide a <file>shlibs</file> file for other packages to
5599 use. When a package is built which contains any shared
5600 libraries or compiled binaries, it must run
5601 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5602 on these to determine the libraries used and hence the
5603 dependencies needed by this package.<footnote>
5605 <prgn>dpkg-shlibdeps</prgn> will use a program
5606 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
5607 the libraries directly needed by the binaries or shared
5608 libraries in the package.
5612 We say that a binary <tt>foo</tt> <em>directly</em> uses
5613 a library <tt>libbar</tt> if it is explicitly linked
5614 with that library (that is, the library is listed in the ELF
5615 <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
5616 to the link line when the binary is created). Other
5617 libraries that are needed by <tt>libbar</tt> are linked
5618 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5619 linker will load them automatically when it loads
5620 <tt>libbar</tt>. A package should depend on the libraries
5621 it directly uses, but not the libraries it indirectly uses.
5622 The dependencies for those libraries will automatically pull
5623 in the other libraries.
5627 A good example of where this helps is the following. We
5628 could update <tt>libimlib</tt> with a new version that
5629 supports a new graphics format called dgf (but retaining the
5630 same major version number) and depends on <tt>libdgf</tt>.
5631 If we used <prgn>ldd</prgn> to add dependencies for every
5632 library directly or indirectly linked with a binary, every
5633 package that uses <tt>libimlib</tt> would need to be
5634 recompiled so it would also depend on <tt>libdgf</tt> or it
5635 wouldn't run due to missing symbols. Since dependencies are
5636 only added based on ELF <tt>NEEDED</tt> attribute, packages
5637 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
5638 having the dependency on <tt>libdgf</tt> and so they would
5639 not need rebuilding.
5645 In the following sections, we will first describe where the
5646 various <tt>shlibs</tt> files are to be found, then how to
5647 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5648 file format and how to create them if your package contains a
5653 <heading>The <tt>shlibs</tt> files present on the system</heading>
5656 There are several places where <tt>shlibs</tt> files are
5657 found. The following list gives them in the order in which
5659 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5660 (The first one which gives the required information is used.)
5666 <p><file>debian/shlibs.local</file></p>
5669 This lists overrides for this package. This file should
5670 normally not be used, but may be needed temporarily in
5671 unusual situations to work around bugs in other packages,
5672 or in unusual cases where the normally declared dependency
5673 information in the installed <file>shlibs</file> file for
5674 a library cannot be used. This file overrides information
5675 obtained from any other source.
5680 <p><file>/etc/dpkg/shlibs.override</file></p>
5683 This lists global overrides. This list is normally
5684 empty. It is maintained by the local system
5690 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5693 When packages are being built,
5694 any <file>debian/shlibs</file> files are copied into the
5695 control information file area of the temporary build
5696 directory and given the name <file>shlibs</file>. These
5697 files give details of any shared libraries included in the
5698 same package.<footnote>
5699 An example may help here. Let us say that the source
5700 package <tt>foo</tt> generates two binary
5701 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
5702 When building the binary packages, the two packages are
5703 created in the directories <file>debian/libfoo2</file>
5704 and <file>debian/foo-runtime</file> respectively.
5705 (<file>debian/tmp</file> could be used instead of one of
5706 these.) Since <tt>libfoo2</tt> provides the
5707 <tt>libfoo</tt> shared library, it will require a
5708 <tt>shlibs</tt> file, which will be installed in
5709 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually to
5710 become <file>/var/lib/dpkg/info/libfoo2.shlibs</file>.
5711 When <prgn>dpkg-shlibdeps</prgn> is run on the
5712 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
5714 the <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5715 determine whether <tt>foo-prog</tt>'s library
5716 dependencies are satisfied by any of the libraries
5717 provided by <tt>libfoo2</tt>. For this reason,
5718 <prgn>dpkg-shlibdeps</prgn> must only be run once all of
5719 the individual binary packages' <tt>shlibs</tt> files
5720 have been installed into the build directory.
5726 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5729 These are the <file>shlibs</file> files corresponding to
5730 all of the packages installed on the system, and are
5731 maintained by the relevant package maintainers.
5736 <p><file>/etc/dpkg/shlibs.default</file></p>
5739 This file lists any shared libraries whose packages
5740 have failed to provide correct <file>shlibs</file> files.
5741 It was used when the <file>shlibs</file> setup was first
5742 introduced, but it is now normally empty. It is
5743 maintained by the <tt>dpkg</tt> maintainer.
5751 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5752 <file>shlibs</file> files</heading>
5756 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5757 into your <file>debian/rules</file> file. If your package
5758 contains only compiled binaries and libraries (but no scripts),
5759 you can use a command such as:
5760 <example compact="compact">
5761 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5762 debian/tmp/usr/lib/*
5764 Otherwise, you will need to explicitly list the compiled
5765 binaries and libraries.<footnote>
5766 If you are using <tt>debhelper</tt>, the
5767 <prgn>dh_shlibdeps</prgn> program will do this work for you.
5768 It will also correctly handle multi-binary packages.
5773 This command puts the dependency information into the
5774 <file>debian/substvars</file> file, which is then used by
5775 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5776 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5777 field in the control file for this to work.
5781 If you have multiple binary packages, you will need to call
5782 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5783 compiled libraries or binaries. In such a case, you will
5784 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5785 utilities to specify a different <file>substvars</file> file.
5789 If you are creating a udeb for use in the Debian Installer,
5790 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
5791 should use the dependency line of type <tt>udeb</tt> by
5792 adding the <tt>-tudeb</tt> option<footnote>
5793 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5794 will automatically add this option if it knows it is
5796 </footnote>. If there is no dependency line of
5797 type <tt>udeb</tt> in the <file>shlibs</file>
5798 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the regular
5803 For more details on <prgn>dpkg-shlibdeps</prgn>, please see
5804 <ref id="pkg-dpkg-shlibdeps"> and
5805 <manref name="dpkg-shlibdeps" section="1">.
5810 <heading>The <file>shlibs</file> File Format</heading>
5813 Each <file>shlibs</file> file has the same format. Lines
5814 beginning with <tt>#</tt> are considered to be comments and
5815 are ignored. Each line is of the form:
5816 <example compact="compact">
5817 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5822 We will explain this by reference to the example of the
5823 <tt>zlib1g</tt> package, which (at the time of writing)
5824 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5828 <var>type</var> is an optional element that indicates the type
5829 of package for which the line is valid. The only type currently
5830 in use is <tt>udeb</tt>. The colon and space after the type are
5835 <var>library-name</var> is the name of the shared library,
5836 in this case <tt>libz</tt>. (This must match the name part
5837 of the soname, see below.)
5841 <var>soname-version</var> is the version part of the soname of
5842 the library. The soname is the thing that must exactly match
5843 for the library to be recognized by the dynamic linker, and is
5845 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5846 example, <tt>libz.so.1</tt>.<footnote>
5847 This can be determined using the command
5848 <example compact="compact">
5849 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5852 The version part is the part which comes after
5853 <tt>.so.</tt>, so in our case, it is <tt>1</tt>. The soname may
5854 instead be of the form
5855 <tt><var>name</var>-<var>major-version</var>.so</tt>, such
5856 as <tt>libdb-4.8.so</tt>, in which case the name would
5857 be <tt>libdb</tt> and the version would be <tt>4.8</tt>.
5861 <var>dependencies</var> has the same syntax as a dependency
5862 field in a binary package control file. It should give
5863 details of which packages are required to satisfy a binary
5864 built against the version of the library contained in the
5865 package. See <ref id="depsyntax"> for details.
5869 In our example, if the first version of the <tt>zlib1g</tt>
5870 package which contained a minor number of at least
5871 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5872 <tt>shlibs</tt> entry for this library could say:
5873 <example compact="compact">
5874 libz 1 zlib1g (>= 1:1.1.3)
5876 The version-specific dependency is to avoid warnings from
5877 the dynamic linker about using older shared libraries with
5882 As zlib1g also provides a udeb containing the shared library,
5883 there would also be a second line:
5884 <example compact="compact">
5885 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5891 <heading>Providing a <file>shlibs</file> file</heading>
5894 If your package provides a shared library, you need to create
5895 a <file>shlibs</file> file following the format described above.
5896 It is usual to call this file <file>debian/shlibs</file> (but if
5897 you have multiple binary packages, you might want to call it
5898 <file>debian/shlibs.<var>package</var></file> instead). Then
5899 let <file>debian/rules</file> install it in the control
5900 information file area:
5901 <example compact="compact">
5902 install -m644 debian/shlibs debian/tmp/DEBIAN
5904 or, in the case of a multi-binary package:
5905 <example compact="compact">
5906 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5908 An alternative way of doing this is to create the
5909 <file>shlibs</file> file in the control information file area
5910 directly from <file>debian/rules</file> without using
5911 a <file>debian/shlibs</file> file at all,<footnote>
5912 This is what <prgn>dh_makeshlibs</prgn> in
5913 the <package>debhelper</package> suite does. If your package
5914 also has a udeb that provides a shared
5915 library, <prgn>dh_makeshlibs</prgn> can automatically generate
5916 the <tt>udeb:</tt> lines if you specify the name of the udeb
5917 with the <tt>--add-udeb</tt> option.
5919 since the <file>debian/shlibs</file> file itself is ignored by
5920 <prgn>dpkg-shlibdeps</prgn>.
5924 As <prgn>dpkg-shlibdeps</prgn> reads the
5925 <file>DEBIAN/shlibs</file> files in all of the binary packages
5926 being built from this source package, all of the
5927 <file>DEBIAN/shlibs</file> files should be installed before
5928 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5936 <chapt id="opersys"><heading>The Operating System</heading>
5939 <heading>File system hierarchy</heading>
5943 <heading>File System Structure</heading>
5946 The location of all installed files and directories must
5947 comply with the Filesystem Hierarchy Standard (FHS),
5948 version 2.3, with the exceptions noted below, and except
5949 where doing so would violate other terms of Debian
5950 Policy. The following exceptions to the FHS apply:
5955 The optional rules related to user specific
5956 configuration files for applications are stored in
5957 the user's home directory are relaxed. It is
5958 recommended that such files start with the
5959 '<tt>.</tt>' character (a "dot file"), and if an
5960 application needs to create more than one dot file
5961 then the preferred placement is in a subdirectory
5962 with a name starting with a '.' character, (a "dot
5963 directory"). In this case it is recommended the
5964 configuration files not start with the '.'
5970 The requirement for amd64 to use <file>/lib64</file>
5971 for 64 bit binaries is removed.
5976 The requirement for object files, internal binaries, and
5977 libraries, including <file>libc.so.*</file>, to be located
5978 directly under <file>/lib{,32}</file> and
5979 <file>/usr/lib{,32}</file> is amended, permitting files
5980 to instead be installed to
5981 <file>/lib/<var>triplet</var></file> and
5982 <file>/usr/lib/<var>triplet</var></file>, where
5983 <tt><var>triplet</var></tt> is the value returned by
5984 <tt>dpkg-architecture -qDEB_HOST_GNU_TYPE</tt> for the
5985 architecture of the package. Packages may <em>not</em>
5986 install files to any <var>triplet</var> path other
5987 than the one matching the architecture of that package;
5988 for instance, an <tt>Architecture: amd64</tt> package
5989 containing 32-bit x86 libraries may not install these
5990 libraries to <file>/usr/lib/i486-linux-gnu</file>.
5992 This is necessary in order to reserve the directories for
5993 use in cross-installation of library packages from other
5994 architectures, as part of the planned deployment of
5999 Applications may also use a single subdirectory under
6000 <file>/usr/lib/<var>triplet</var></file>.
6003 The execution time linker/loader, ld*, must still be made
6004 available in the existing location under /lib or /lib64
6005 since this is part of the ELF ABI for the architecture.
6010 The requirement that
6011 <file>/usr/local/share/man</file> be "synonymous"
6012 with <file>/usr/local/man</file> is relaxed to a
6017 The requirement that windowmanagers with a single
6018 configuration file call it <file>system.*wmrc</file>
6019 is removed, as is the restriction that the window
6020 manager subdirectory be named identically to the
6021 window manager name itself.
6026 The requirement that boot manager configuration
6027 files live in <file>/etc</file>, or at least are
6028 symlinked there, is relaxed to a recommendation.
6033 The following directories in the root filesystem are
6034 additionally allowed: <file>/sys</file> and
6035 <file>/selinux</file>. <footnote>These directories
6036 are used as mount points to mount virtual filesystems
6037 to get access to kernel information.</footnote>
6044 The version of this document referred here can be
6045 found in the <tt>debian-policy</tt> package or on <url
6046 id="http://www.debian.org/doc/packaging-manuals/fhs/"
6047 name="FHS (Debian copy)"> alongside this manual (or, if
6048 you have the <package>debian-policy</package> installed,
6050 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
6051 (local copy)">). The
6052 latest version, which may be a more recent version, may
6054 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
6055 Specific questions about following the standard may be
6056 asked on the <tt>debian-devel</tt> mailing list, or
6057 referred to the FHS mailing list (see the
6058 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
6064 <heading>Site-specific programs</heading>
6067 As mandated by the FHS, packages must not place any
6068 files in <file>/usr/local</file>, either by putting them in
6069 the file system archive to be unpacked by <prgn>dpkg</prgn>
6070 or by manipulating them in their maintainer scripts.
6074 However, the package may create empty directories below
6075 <file>/usr/local</file> so that the system administrator knows
6076 where to place site-specific files. These are not
6077 directories <em>in</em> <file>/usr/local</file>, but are
6078 children of directories in <file>/usr/local</file>. These
6079 directories (<file>/usr/local/*/dir/</file>)
6080 should be removed on package removal if they are
6085 Note that this applies only to
6086 directories <em>below</em> <file>/usr/local</file>,
6087 not <em>in</em> <file>/usr/local</file>. Packages must
6088 not create sub-directories in the
6089 directory <file>/usr/local</file> itself, except those
6090 listed in FHS, section 4.5. However, you may create
6091 directories below them as you wish. You must not remove
6092 any of the directories listed in 4.5, even if you created
6097 Since <file>/usr/local</file> can be mounted read-only from a
6098 remote server, these directories must be created and
6099 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
6100 maintainer scripts and not be included in the
6101 <file>.deb</file> archive. These scripts must not fail if
6102 either of these operations fail.
6106 For example, the <tt>emacsen-common</tt> package could
6107 contain something like
6108 <example compact="compact">
6109 if [ ! -e /usr/local/share/emacs ]
6111 if mkdir /usr/local/share/emacs 2>/dev/null
6113 chown root:staff /usr/local/share/emacs
6114 chmod 2775 /usr/local/share/emacs
6118 in its <prgn>postinst</prgn> script, and
6119 <example compact="compact">
6120 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
6121 rmdir /usr/local/share/emacs 2>/dev/null || true
6123 in the <prgn>prerm</prgn> script. (Note that this form is
6124 used to ensure that if the script is interrupted, the
6125 directory <file>/usr/local/share/emacs</file> will still be
6130 If you do create a directory in <file>/usr/local</file> for
6131 local additions to a package, you should ensure that
6132 settings in <file>/usr/local</file> take precedence over the
6133 equivalents in <file>/usr</file>.
6137 However, because <file>/usr/local</file> and its contents are
6138 for exclusive use of the local administrator, a package
6139 must not rely on the presence or absence of files or
6140 directories in <file>/usr/local</file> for normal operation.
6144 The <file>/usr/local</file> directory itself and all the
6145 subdirectories created by the package should (by default) have
6146 permissions 2775 (group-writable and set-group-id) and be
6147 owned by <tt>root:staff</tt>.
6152 <heading>The system-wide mail directory</heading>
6154 The system-wide mail directory
6155 is <file>/var/mail</file>. This directory is part of the
6156 base system and should not be owned by any particular mail
6157 agents. The use of the old
6158 location <file>/var/spool/mail</file> is deprecated, even
6159 though the spool may still be physically located there.
6165 <heading>Users and groups</heading>
6168 <heading>Introduction</heading>
6170 The Debian system can be configured to use either plain or
6175 Some user ids (UIDs) and group ids (GIDs) are reserved
6176 globally for use by certain packages. Because some
6177 packages need to include files which are owned by these
6178 users or groups, or need the ids compiled into binaries,
6179 these ids must be used on any Debian system only for the
6180 purpose for which they are allocated. This is a serious
6181 restriction, and we should avoid getting in the way of
6182 local administration policies. In particular, many sites
6183 allocate users and/or local system groups starting at 100.
6187 Apart from this we should have dynamically allocated ids,
6188 which should by default be arranged in some sensible
6189 order, but the behavior should be configurable.
6193 Packages other than <tt>base-passwd</tt> must not modify
6194 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
6195 <file>/etc/group</file> or <file>/etc/gshadow</file>.
6200 <heading>UID and GID classes</heading>
6202 The UID and GID numbers are divided into classes as
6208 Globally allocated by the Debian project, the same
6209 on every Debian system. These ids will appear in
6210 the <file>passwd</file> and <file>group</file> files of all
6211 Debian systems, new ids in this range being added
6212 automatically as the <tt>base-passwd</tt> package is
6217 Packages which need a single statically allocated
6218 uid or gid should use one of these; their
6219 maintainers should ask the <tt>base-passwd</tt>
6227 Dynamically allocated system users and groups.
6228 Packages which need a user or group, but can have
6229 this user or group allocated dynamically and
6230 differently on each system, should use <tt>adduser
6231 --system</tt> to create the group and/or user.
6232 <prgn>adduser</prgn> will check for the existence of
6233 the user or group, and if necessary choose an unused
6234 id based on the ranges specified in
6235 <file>adduser.conf</file>.
6239 <tag>1000-59999:</tag>
6242 Dynamically allocated user accounts. By default
6243 <prgn>adduser</prgn> will choose UIDs and GIDs for
6244 user accounts in this range, though
6245 <file>adduser.conf</file> may be used to modify this
6250 <tag>60000-64999:</tag>
6253 Globally allocated by the Debian project, but only
6254 created on demand. The ids are allocated centrally
6255 and statically, but the actual accounts are only
6256 created on users' systems on demand.
6260 These ids are for packages which are obscure or
6261 which require many statically-allocated ids. These
6262 packages should check for and create the accounts in
6263 <file>/etc/passwd</file> or <file>/etc/group</file> (using
6264 <prgn>adduser</prgn> if it has this facility) if
6265 necessary. Packages which are likely to require
6266 further allocations should have a "hole" left after
6267 them in the allocation, to give them room to
6272 <tag>65000-65533:</tag>
6280 User <tt>nobody</tt>. The corresponding gid refers
6281 to the group <tt>nogroup</tt>.
6288 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
6289 not</em> be used, because it is the error return
6298 <sect id="sysvinit">
6299 <heading>System run levels and <file>init.d</file> scripts</heading>
6301 <sect1 id="/etc/init.d">
6302 <heading>Introduction</heading>
6305 The <file>/etc/init.d</file> directory contains the scripts
6306 executed by <prgn>init</prgn> at boot time and when the
6307 init state (or "runlevel") is changed (see <manref
6308 name="init" section="8">).
6312 There are at least two different, yet functionally
6313 equivalent, ways of handling these scripts. For the sake
6314 of simplicity, this document describes only the symbolic
6315 link method. However, it must not be assumed by maintainer
6316 scripts that this method is being used, and any automated
6317 manipulation of the various runlevel behaviors by
6318 maintainer scripts must be performed using
6319 <prgn>update-rc.d</prgn> as described below and not by
6320 manually installing or removing symlinks. For information
6321 on the implementation details of the other method,
6322 implemented in the <tt>file-rc</tt> package, please refer
6323 to the documentation of that package.
6327 These scripts are referenced by symbolic links in the
6328 <file>/etc/rc<var>n</var>.d</file> directories. When changing
6329 runlevels, <prgn>init</prgn> looks in the directory
6330 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
6331 execute, where <tt><var>n</var></tt> is the runlevel that
6332 is being changed to, or <tt>S</tt> for the boot-up
6337 The names of the links all have the form
6338 <file>S<var>mm</var><var>script</var></file> or
6339 <file>K<var>mm</var><var>script</var></file> where
6340 <var>mm</var> is a two-digit number and <var>script</var>
6341 is the name of the script (this should be the same as the
6342 name of the actual script in <file>/etc/init.d</file>).
6346 When <prgn>init</prgn> changes runlevel first the targets
6347 of the links whose names start with a <tt>K</tt> are
6348 executed, each with the single argument <tt>stop</tt>,
6349 followed by the scripts prefixed with an <tt>S</tt>, each
6350 with the single argument <tt>start</tt>. (The links are
6351 those in the <file>/etc/rc<var>n</var>.d</file> directory
6352 corresponding to the new runlevel.) The <tt>K</tt> links
6353 are responsible for killing services and the <tt>S</tt>
6354 link for starting services upon entering the runlevel.
6358 For example, if we are changing from runlevel 2 to
6359 runlevel 3, init will first execute all of the <tt>K</tt>
6360 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
6361 all of the <tt>S</tt> prefixed scripts in that directory.
6362 The links starting with <tt>K</tt> will cause the
6363 referred-to file to be executed with an argument of
6364 <tt>stop</tt>, and the <tt>S</tt> links with an argument
6369 The two-digit number <var>mm</var> is used to determine
6370 the order in which to run the scripts: low-numbered links
6371 have their scripts run first. For example, the
6372 <tt>K20</tt> scripts will be executed before the
6373 <tt>K30</tt> scripts. This is used when a certain service
6374 must be started before another. For example, the name
6375 server <prgn>bind</prgn> might need to be started before
6376 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
6377 can set up its access lists. In this case, the script
6378 that starts <prgn>bind</prgn> would have a lower number
6379 than the script that starts <prgn>inn</prgn> so that it
6381 <example compact="compact">
6388 The two runlevels 0 (halt) and 6 (reboot) are slightly
6389 different. In these runlevels, the links with an
6390 <tt>S</tt> prefix are still called after those with a
6391 <tt>K</tt> prefix, but they too are called with the single
6392 argument <tt>stop</tt>.
6396 <sect1 id="writing-init">
6397 <heading>Writing the scripts</heading>
6400 Packages that include daemons for system services should
6401 place scripts in <file>/etc/init.d</file> to start or stop
6402 services at boot time or during a change of runlevel.
6403 These scripts should be named
6404 <file>/etc/init.d/<var>package</var></file>, and they should
6405 accept one argument, saying what to do:
6408 <tag><tt>start</tt></tag>
6409 <item>start the service,</item>
6411 <tag><tt>stop</tt></tag>
6412 <item>stop the service,</item>
6414 <tag><tt>restart</tt></tag>
6415 <item>stop and restart the service if it's already running,
6416 otherwise start the service</item>
6418 <tag><tt>reload</tt></tag>
6419 <item><p>cause the configuration of the service to be
6420 reloaded without actually stopping and restarting
6423 <tag><tt>force-reload</tt></tag>
6424 <item>cause the configuration to be reloaded if the
6425 service supports this, otherwise restart the
6429 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
6430 <tt>force-reload</tt> options should be supported by all
6431 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
6436 The <file>init.d</file> scripts must ensure that they will
6437 behave sensibly (i.e., returning success and not starting
6438 multiple copies of a service) if invoked with <tt>start</tt>
6439 when the service is already running, or with <tt>stop</tt>
6440 when it isn't, and that they don't kill unfortunately-named
6441 user processes. The best way to achieve this is usually to
6442 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
6447 Be careful of using <tt>set -e</tt> in <file>init.d</file>
6448 scripts. Writing correct <file>init.d</file> scripts requires
6449 accepting various error exit statuses when daemons are already
6450 running or already stopped without aborting
6451 the <file>init.d</file> script, and common <file>init.d</file>
6452 function libraries are not safe to call with <tt>set -e</tt>
6454 <tt>/lib/lsb/init-functions</tt>, which assists in writing
6455 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
6456 in effect and echoing status messages to the console fails,
6458 </footnote>. For <tt>init.d</tt> scripts, it's often easier
6459 to not use <tt>set -e</tt> and instead check the result of
6460 each command separately.
6464 If a service reloads its configuration automatically (as
6465 in the case of <prgn>cron</prgn>, for example), the
6466 <tt>reload</tt> option of the <file>init.d</file> script
6467 should behave as if the configuration has been reloaded
6472 The <file>/etc/init.d</file> scripts must be treated as
6473 configuration files, either (if they are present in the
6474 package, that is, in the .deb file) by marking them as
6475 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6476 by managing them correctly in the maintainer scripts (see
6477 <ref id="config-files">). This is important since we want
6478 to give the local system administrator the chance to adapt
6479 the scripts to the local system, e.g., to disable a
6480 service without de-installing the package, or to specify
6481 some special command line options when starting a service,
6482 while making sure their changes aren't lost during the next
6487 These scripts should not fail obscurely when the
6488 configuration files remain but the package has been
6489 removed, as configuration files remain on the system after
6490 the package has been removed. Only when <prgn>dpkg</prgn>
6491 is executed with the <tt>--purge</tt> option will
6492 configuration files be removed. In particular, as the
6493 <file>/etc/init.d/<var>package</var></file> script itself is
6494 usually a <tt>conffile</tt>, it will remain on the system
6495 if the package is removed but not purged. Therefore, you
6496 should include a <tt>test</tt> statement at the top of the
6498 <example compact="compact">
6499 test -f <var>program-executed-later-in-script</var> || exit 0
6504 Often there are some variables in the <file>init.d</file>
6505 scripts whose values control the behavior of the scripts,
6506 and which a system administrator is likely to want to
6507 change. As the scripts themselves are frequently
6508 <tt>conffile</tt>s, modifying them requires that the
6509 administrator merge in their changes each time the package
6510 is upgraded and the <tt>conffile</tt> changes. To ease
6511 the burden on the system administrator, such configurable
6512 values should not be placed directly in the script.
6513 Instead, they should be placed in a file in
6514 <file>/etc/default</file>, which typically will have the same
6515 base name as the <file>init.d</file> script. This extra file
6516 should be sourced by the script when the script runs. It
6517 must contain only variable settings and comments in SUSv3
6518 <prgn>sh</prgn> format. It may either be a
6519 <tt>conffile</tt> or a configuration file maintained by
6520 the package maintainer scripts. See <ref id="config-files">
6525 To ensure that vital configurable values are always
6526 available, the <file>init.d</file> script should set default
6527 values for each of the shell variables it uses, either
6528 before sourcing the <file>/etc/default/</file> file or
6529 afterwards using something like the <tt>:
6530 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6531 script must behave sensibly and not fail if the
6532 <file>/etc/default</file> file is deleted.
6536 <file>/var/run</file> and <file>/var/lock</file> may be mounted
6537 as temporary filesystems<footnote>
6538 For example, using the <tt>RAMRUN</tt> and <tt>RAMLOCK</tt>
6539 options in <file>/etc/default/rcS</file>.
6540 </footnote>, so the <file>init.d</file> scripts must handle this
6541 correctly. This will typically amount to creating any required
6542 subdirectories dynamically when the <file>init.d</file> script
6543 is run, rather than including them in the package and relying on
6544 <prgn>dpkg</prgn> to create them.
6549 <heading>Interfacing with the initscript system</heading>
6552 Maintainers should use the abstraction layer provided by
6553 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6554 programs to deal with initscripts in their packages'
6555 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6556 and <prgn>postrm</prgn>.
6560 Directly managing the /etc/rc?.d links and directly
6561 invoking the <file>/etc/init.d/</file> initscripts should
6562 be done only by packages providing the initscript
6563 subsystem (such as <prgn>sysv-rc</prgn> and
6564 <prgn>file-rc</prgn>).
6568 <heading>Managing the links</heading>
6571 The program <prgn>update-rc.d</prgn> is provided for
6572 package maintainers to arrange for the proper creation and
6573 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6574 or their functional equivalent if another method is being
6575 used. This may be used by maintainers in their packages'
6576 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6580 You must not include any <file>/etc/rc<var>n</var>.d</file>
6581 symbolic links in the actual archive or manually create or
6582 remove the symbolic links in maintainer scripts; you must
6583 use the <prgn>update-rc.d</prgn> program instead. (The
6584 former will fail if an alternative method of maintaining
6585 runlevel information is being used.) You must not include
6586 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6587 in the archive either. (Only the <tt>sysvinit</tt>
6592 By default <prgn>update-rc.d</prgn> will start services in
6593 each of the multi-user state runlevels (2, 3, 4, and 5)
6594 and stop them in the halt runlevel (0), the single-user
6595 runlevel (1) and the reboot runlevel (6). The system
6596 administrator will have the opportunity to customize
6597 runlevels by simply adding, moving, or removing the
6598 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6599 symbolic links are being used, or by modifying
6600 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6605 To get the default behavior for your package, put in your
6606 <prgn>postinst</prgn> script
6607 <example compact="compact">
6608 update-rc.d <var>package</var> defaults
6610 and in your <prgn>postrm</prgn>
6611 <example compact="compact">
6612 if [ "$1" = purge ]; then
6613 update-rc.d <var>package</var> remove
6615 </example>. Note that if your package changes runlevels
6616 or priority, you may have to remove and recreate the links,
6617 since otherwise the old links may persist. Refer to the
6618 documentation of <prgn>update-rc.d</prgn>.
6622 This will use a default sequence number of 20. If it does
6623 not matter when or in which order the <file>init.d</file>
6624 script is run, use this default. If it does, then you
6625 should talk to the maintainer of the <prgn>sysvinit</prgn>
6626 package or post to <tt>debian-devel</tt>, and they will
6627 help you choose a number.
6631 For more information about using <tt>update-rc.d</tt>,
6632 please consult its man page <manref name="update-rc.d"
6638 <heading>Running initscripts</heading>
6640 The program <prgn>invoke-rc.d</prgn> is provided to make
6641 it easier for package maintainers to properly invoke an
6642 initscript, obeying runlevel and other locally-defined
6643 constraints that might limit a package's right to start,
6644 stop and otherwise manage services. This program may be
6645 used by maintainers in their packages' scripts.
6649 The package maintainer scripts must use
6650 <prgn>invoke-rc.d</prgn> to invoke the
6651 <file>/etc/init.d/*</file> initscripts, instead of
6652 calling them directly.
6656 By default, <prgn>invoke-rc.d</prgn> will pass any
6657 action requests (start, stop, reload, restart...) to the
6658 <file>/etc/init.d</file> script, filtering out requests
6659 to start or restart a service out of its intended
6664 Most packages will simply need to change:
6665 <example compact="compact">/etc/init.d/<package>
6666 <action></example> in their <prgn>postinst</prgn>
6667 and <prgn>prerm</prgn> scripts to:
6668 <example compact="compact">
6669 if which invoke-rc.d >/dev/null 2>&1; then
6670 invoke-rc.d <var>package</var> <action>
6672 /etc/init.d/<var>package</var> <action>
6678 A package should register its initscript services using
6679 <prgn>update-rc.d</prgn> before it tries to invoke them
6680 using <prgn>invoke-rc.d</prgn>. Invocation of
6681 unregistered services may fail.
6685 For more information about using
6686 <prgn>invoke-rc.d</prgn>, please consult its man page
6687 <manref name="invoke-rc.d" section="8">.
6693 <heading>Boot-time initialization</heading>
6696 There used to be another directory, <file>/etc/rc.boot</file>,
6697 which contained scripts which were run once per machine
6698 boot. This has been deprecated in favour of links from
6699 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6700 described in <ref id="/etc/init.d">. Packages must not
6701 place files in <file>/etc/rc.boot</file>.
6706 <heading>Example</heading>
6709 An example on which you can base your
6710 <file>/etc/init.d</file> scripts is found in
6711 <file>/etc/init.d/skeleton</file>.
6718 <heading>Console messages from <file>init.d</file> scripts</heading>
6721 This section describes the formats to be used for messages
6722 written to standard output by the <file>/etc/init.d</file>
6723 scripts. The intent is to improve the consistency of
6724 Debian's startup and shutdown look and feel. For this
6725 reason, please look very carefully at the details. We want
6726 the messages to have the same format in terms of wording,
6727 spaces, punctuation and case of letters.
6731 Here is a list of overall rules that should be used for
6732 messages generated by <file>/etc/init.d</file> scripts.
6738 The message should fit in one line (fewer than 80
6739 characters), start with a capital letter and end with
6740 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6744 If the script is performing some time consuming task in
6745 the background (not merely starting or stopping a
6746 program, for instance), an ellipsis (three dots:
6747 <tt>...</tt>) should be output to the screen, with no
6748 leading or tailing whitespace or line feeds.
6752 The messages should appear as if the computer is telling
6753 the user what it is doing (politely :-), but should not
6754 mention "it" directly. For example, instead of:
6755 <example compact="compact">
6756 I'm starting network daemons: nfsd mountd.
6758 the message should say
6759 <example compact="compact">
6760 Starting network daemons: nfsd mountd.
6767 <tt>init.d</tt> script should use the following standard
6768 message formats for the situations enumerated below.
6774 <p>When daemons are started</p>
6777 If the script starts one or more daemons, the output
6778 should look like this (a single line, no leading
6780 <example compact="compact">
6781 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6783 The <var>description</var> should describe the
6784 subsystem the daemon or set of daemons are part of,
6785 while <var>daemon-1</var> up to <var>daemon-n</var>
6786 denote each daemon's name (typically the file name of
6791 For example, the output of <file>/etc/init.d/lpd</file>
6793 <example compact="compact">
6794 Starting printer spooler: lpd.
6799 This can be achieved by saying
6800 <example compact="compact">
6801 echo -n "Starting printer spooler: lpd"
6802 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6805 in the script. If there are more than one daemon to
6806 start, the output should look like this:
6807 <example compact="compact">
6808 echo -n "Starting remote file system services:"
6809 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6810 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6811 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6814 This makes it possible for the user to see what is
6815 happening and when the final daemon has been started.
6816 Care should be taken in the placement of white spaces:
6817 in the example above the system administrators can
6818 easily comment out a line if they don't want to start
6819 a specific daemon, while the displayed message still
6825 <p>When a system parameter is being set</p>
6828 If you have to set up different system parameters
6829 during the system boot, you should use this format:
6830 <example compact="compact">
6831 Setting <var>parameter</var> to "<var>value</var>".
6836 You can use a statement such as the following to get
6838 <example compact="compact">
6839 echo "Setting DNS domainname to \"$domainname\"."
6844 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
6845 for the left and right quotation marks. A grave accent
6846 (<tt>`</tt>) is not a quote character; neither is an
6847 apostrophe (<tt>'</tt>).
6852 <p>When a daemon is stopped or restarted</p>
6855 When you stop or restart a daemon, you should issue a
6856 message identical to the startup message, except that
6857 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6858 or <tt>Restarting</tt> respectively.
6862 For example, stopping the printer daemon will look like
6864 <example compact="compact">
6865 Stopping printer spooler: lpd.
6871 <p>When something is executed</p>
6874 There are several examples where you have to run a
6875 program at system startup or shutdown to perform a
6876 specific task, for example, setting the system's clock
6877 using <prgn>netdate</prgn> or killing all processes
6878 when the system shuts down. Your message should look
6880 <example compact="compact">
6881 Doing something very useful...done.
6883 You should print the <tt>done.</tt> immediately after
6884 the job has been completed, so that the user is
6885 informed why they have to wait. You can get this
6887 <example compact="compact">
6888 echo -n "Doing something very useful..."
6897 <p>When the configuration is reloaded</p>
6900 When a daemon is forced to reload its configuration
6901 files you should use the following format:
6902 <example compact="compact">
6903 Reloading <var>description</var> configuration...done.
6905 where <var>description</var> is the same as in the
6906 daemon starting message.
6914 <heading>Cron jobs</heading>
6917 Packages must not modify the configuration file
6918 <file>/etc/crontab</file>, and they must not modify the files in
6919 <file>/var/spool/cron/crontabs</file>.</p>
6922 If a package wants to install a job that has to be executed
6923 via cron, it should place a file with the name of the
6924 package in one or more of the following directories:
6925 <example compact="compact">
6931 As these directory names imply, the files within them are
6932 executed on an hourly, daily, weekly, or monthly basis,
6933 respectively. The exact times are listed in
6934 <file>/etc/crontab</file>.</p>
6937 All files installed in any of these directories must be
6938 scripts (e.g., shell scripts or Perl scripts) so that they
6939 can easily be modified by the local system administrator.
6940 In addition, they must be treated as configuration files.
6944 If a certain job has to be executed at some other frequency or
6945 at a specific time, the package should install a file
6946 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6947 same syntax as <file>/etc/crontab</file> and is processed by
6948 <prgn>cron</prgn> automatically. The file must also be
6949 treated as a configuration file. (Note that entries in the
6950 <file>/etc/cron.d</file> directory are not handled by
6951 <prgn>anacron</prgn>. Thus, you should only use this
6952 directory for jobs which may be skipped if the system is not
6955 Unlike <file>crontab</file> files described in the IEEE Std
6956 1003.1-2008 (POSIX.1) available from
6957 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
6958 name="The Open Group">, the files in
6959 <file>/etc/cron.d</file> and the file
6960 <file>/etc/crontab</file> have seven fields; namely:
6962 <item>Minute [0,59]</item>
6963 <item>Hour [0,23]</item>
6964 <item>Day of the month [1,31]</item>
6965 <item>Month of the year [1,12]</item>
6966 <item>Day of the week ([0,6] with 0=Sunday)</item>
6967 <item>Username</item>
6968 <item>Command to be run</item>
6970 Ranges of numbers are allowed. Ranges are two numbers
6971 separated with a hyphen. The specified range is inclusive.
6972 Lists are allowed. A list is a set of numbers (or ranges)
6973 separated by commas. Step values can be used in conjunction
6978 The scripts or <tt>crontab</tt> entries in these directories should
6979 check if all necessary programs are installed before they
6980 try to execute them. Otherwise, problems will arise when a
6981 package was removed but not purged since configuration files
6982 are kept on the system in this situation.
6986 Any <tt>cron</tt> daemon must provide
6987 <file>/usr/bin/crontab</file> and support normal
6988 <tt>crontab</tt> entries as specified in POSIX. The daemon
6989 must also support names for days and months, ranges, and
6990 step values. It has to support <file>/etc/crontab</file>,
6991 and correctly execute the scripts in
6992 <file>/etc/cron.d</file>. The daemon must also correctly
6994 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
6999 <heading>Menus</heading>
7002 The Debian <tt>menu</tt> package provides a standard
7003 interface between packages providing applications and
7004 <em>menu programs</em> (either X window managers or
7005 text-based menu programs such as <prgn>pdmenu</prgn>).
7009 All packages that provide applications that need not be
7010 passed any special command line arguments for normal
7011 operation should register a menu entry for those
7012 applications, so that users of the <tt>menu</tt> package
7013 will automatically get menu entries in their window
7014 managers, as well in shells like <tt>pdmenu</tt>.
7018 Menu entries should follow the current menu policy.
7022 The menu policy can be found in the <tt>menu-policy</tt>
7023 files in the <tt>debian-policy</tt> package.
7024 It is also available from the Debian web mirrors at
7025 <tt><url name="/doc/packaging-manuals/menu-policy/"
7026 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
7030 Please also refer to the <em>Debian Menu System</em>
7031 documentation that comes with the <package>menu</package>
7032 package for information about how to register your
7038 <heading>Multimedia handlers</heading>
7041 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
7042 is a mechanism for encoding files and data streams and
7043 providing meta-information about them, in particular their
7044 type (e.g. audio or video) and format (e.g. PNG, HTML,
7049 Registration of MIME type handlers allows programs like mail
7050 user agents and web browsers to invoke these handlers to
7051 view, edit or display MIME types they don't support directly.
7055 Packages which provide the ability to view/show/play,
7056 compose, edit or print MIME types should register themselves
7057 as such following the current MIME support policy.
7061 The MIME support policy can be found in the <tt>mime-policy</tt>
7062 files in the <tt>debian-policy</tt> package.
7063 It is also available from the Debian web mirrors at
7064 <tt><url name="/doc/packaging-manuals/mime-policy/"
7065 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
7071 <heading>Keyboard configuration</heading>
7074 To achieve a consistent keyboard configuration so that all
7075 applications interpret a keyboard event the same way, all
7076 programs in the Debian distribution must be configured to
7077 comply with the following guidelines.
7081 The following keys must have the specified interpretations:
7084 <tag><tt><--</tt></tag>
7085 <item>delete the character to the left of the cursor</item>
7087 <tag><tt>Delete</tt></tag>
7088 <item>delete the character to the right of the cursor</item>
7090 <tag><tt>Control+H</tt></tag>
7091 <item>emacs: the help prefix</item>
7094 The interpretation of any keyboard events should be
7095 independent of the terminal that is used, be it a virtual
7096 console, an X terminal emulator, an rlogin/telnet session,
7101 The following list explains how the different programs
7102 should be set up to achieve this:
7108 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
7112 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
7116 X translations are set up to make
7117 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
7118 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
7119 is the vt220 escape code for the "delete character"
7120 key). This must be done by loading the X resources
7121 using <prgn>xrdb</prgn> on all local X displays, not
7122 using the application defaults, so that the
7123 translation resources used correspond to the
7124 <prgn>xmodmap</prgn> settings.
7128 The Linux console is configured to make
7129 <tt><--</tt> generate DEL, and <tt>Delete</tt>
7130 generate <tt>ESC [ 3 ~</tt>.
7134 X applications are configured so that <tt><</tt>
7135 deletes left, and <tt>Delete</tt> deletes right. Motif
7136 applications already work like this.
7140 Terminals should have <tt>stty erase ^?</tt> .
7144 The <tt>xterm</tt> terminfo entry should have <tt>ESC
7145 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
7146 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
7150 Emacs is programmed to map <tt>KB_Backspace</tt> or
7151 the <tt>stty erase</tt> character to
7152 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
7153 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
7154 <tt>^H</tt> to <tt>help</tt> as always.
7158 Other applications use the <tt>stty erase</tt>
7159 character and <tt>kdch1</tt> for the two delete keys,
7160 with ASCII DEL being "delete previous character" and
7161 <tt>kdch1</tt> being "delete character under
7169 This will solve the problem except for the following
7176 Some terminals have a <tt><--</tt> key that cannot
7177 be made to produce anything except <tt>^H</tt>. On
7178 these terminals Emacs help will be unavailable on
7179 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
7180 character takes precedence in Emacs, and has been set
7181 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
7182 available) can be used instead.
7186 Some operating systems use <tt>^H</tt> for <tt>stty
7187 erase</tt>. However, modern telnet versions and all
7188 rlogin versions propagate <tt>stty</tt> settings, and
7189 almost all UNIX versions honour <tt>stty erase</tt>.
7190 Where the <tt>stty</tt> settings are not propagated
7191 correctly, things can be made to work by using
7192 <tt>stty</tt> manually.
7196 Some systems (including previous Debian versions) use
7197 <prgn>xmodmap</prgn> to arrange for both
7198 <tt><--</tt> and <tt>Delete</tt> to generate
7199 <tt>KB_Delete</tt>. We can change the behavior of
7200 their X clients using the same X resources that we use
7201 to do it for our own clients, or configure our clients
7202 using their resources when things are the other way
7203 around. On displays configured like this
7204 <tt>Delete</tt> will not work, but <tt><--</tt>
7209 Some operating systems have different <tt>kdch1</tt>
7210 settings in their <tt>terminfo</tt> database for
7211 <tt>xterm</tt> and others. On these systems the
7212 <tt>Delete</tt> key will not work correctly when you
7213 log in from a system conforming to our policy, but
7214 <tt><--</tt> will.
7221 <heading>Environment variables</heading>
7224 A program must not depend on environment variables to get
7225 reasonable defaults. (That's because these environment
7226 variables would have to be set in a system-wide
7227 configuration file like <file>/etc/profile</file>, which is not
7228 supported by all shells.)
7232 If a program usually depends on environment variables for its
7233 configuration, the program should be changed to fall back to
7234 a reasonable default configuration if these environment
7235 variables are not present. If this cannot be done easily
7236 (e.g., if the source code of a non-free program is not
7237 available), the program must be replaced by a small
7238 "wrapper" shell script which sets the environment variables
7239 if they are not already defined, and calls the original program.
7243 Here is an example of a wrapper script for this purpose:
7245 <example compact="compact">
7247 BAR=${BAR:-/var/lib/fubar}
7249 exec /usr/lib/foo/foo "$@"
7254 Furthermore, as <file>/etc/profile</file> is a configuration
7255 file of the <prgn>base-files</prgn> package, other packages must
7256 not put any environment variables or other commands into that
7261 <sect id="doc-base">
7262 <heading>Registering Documents using doc-base</heading>
7265 The <package>doc-base</package> package implements a
7266 flexible mechanism for handling and presenting
7267 documentation. The recommended practice is for every Debian
7268 package that provides online documentation (other than just
7269 manual pages) to register these documents with
7270 <package>doc-base</package> by installing a
7271 <package>doc-base</package> control file via the
7272 <prgn/install-docs/ script at installation time and
7273 de-register the manuals again when the package is removed.
7276 Please refer to the documentation that comes with the
7277 <package>doc-base</package> package for information and
7286 <heading>Files</heading>
7288 <sect id="binaries">
7289 <heading>Binaries</heading>
7292 Two different packages must not install programs with
7293 different functionality but with the same filenames. (The
7294 case of two programs having the same functionality but
7295 different implementations is handled via "alternatives" or
7296 the "Conflicts" mechanism. See <ref id="maintscripts"> and
7297 <ref id="conflicts"> respectively.) If this case happens,
7298 one of the programs must be renamed. The maintainers should
7299 report this to the <tt>debian-devel</tt> mailing list and
7300 try to find a consensus about which program will have to be
7301 renamed. If a consensus cannot be reached, <em>both</em>
7302 programs must be renamed.
7306 By default, when a package is being built, any binaries
7307 created should include debugging information, as well as
7308 being compiled with optimization. You should also turn on
7309 as many reasonable compilation warnings as possible; this
7310 makes life easier for porters, who can then look at build
7311 logs for possible problems. For the C programming language,
7312 this means the following compilation parameters should be
7314 <example compact="compact">
7316 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
7318 INSTALL = install -s # (or use strip on the files in debian/tmp)
7323 Note that by default all installed binaries should be stripped,
7324 either by using the <tt>-s</tt> flag to
7325 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
7326 the binaries after they have been copied into
7327 <file>debian/tmp</file> but before the tree is made into a
7332 Although binaries in the build tree should be compiled with
7333 debugging information by default, it can often be difficult to
7334 debug programs if they are also subjected to compiler
7335 optimization. For this reason, it is recommended to support the
7336 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
7337 (see <ref id="debianrules-options">). This variable can contain
7338 several flags to change how a package is compiled and built.
7342 It is up to the package maintainer to decide what
7343 compilation options are best for the package. Certain
7344 binaries (such as computationally-intensive programs) will
7345 function better with certain flags (<tt>-O3</tt>, for
7346 example); feel free to use them. Please use good judgment
7347 here. Don't use flags for the sake of it; only use them
7348 if there is good reason to do so. Feel free to override
7349 the upstream author's ideas about which compilation
7350 options are best: they are often inappropriate for our
7356 <sect id="libraries">
7357 <heading>Libraries</heading>
7360 If the package is <strong>architecture: any</strong>, then
7361 the shared library compilation and linking flags must have
7362 <tt>-fPIC</tt>, or the package shall not build on some of
7363 the supported architectures<footnote>
7365 If you are using GCC, <tt>-fPIC</tt> produces code with
7366 relocatable position independent code, which is required for
7367 most architectures to create a shared library, with i386 and
7368 perhaps some others where non position independent code is
7369 permitted in a shared library.
7372 Position independent code may have a performance penalty,
7373 especially on <tt>i386</tt>. However, in most cases the
7374 speed penalty must be measured against the memory wasted on
7375 the few architectures where non position independent code is
7378 </footnote>. Any exception to this rule must be discussed on
7379 the mailing list <em>debian-devel@lists.debian.org</em>, and
7380 a rough consensus obtained. The reasons for not compiling
7381 with <tt>-fPIC</tt> flag must be recorded in the file
7382 <tt>README.Debian</tt>, and care must be taken to either
7383 restrict the architecture or arrange for <tt>-fPIC</tt> to
7384 be used on architectures where it is required.<footnote>
7386 Some of the reasons why this might be required is if the
7387 library contains hand crafted assembly code that is not
7388 relocatable, the speed penalty is excessive for compute
7389 intensive libs, and similar reasons.
7394 As to the static libraries, the common case is not to have
7395 relocatable code, since there is no benefit, unless in specific
7396 cases; therefore the static version must not be compiled
7397 with the <tt>-fPIC</tt> flag. Any exception to this rule
7398 should be discussed on the mailing list
7399 <em>debian-devel@lists.debian.org</em>, and the reasons for
7400 compiling with the <tt>-fPIC</tt> flag must be recorded in
7401 the file <tt>README.Debian</tt>. <footnote>
7403 Some of the reasons for linking static libraries with
7404 the <tt>-fPIC</tt> flag are if, for example, one needs a
7405 Perl API for a library that is under rapid development,
7406 and has an unstable API, so shared libraries are
7407 pointless at this phase of the library's development. In
7408 that case, since Perl needs a library with relocatable
7409 code, it may make sense to create a static library with
7410 relocatable code. Another reason cited is if you are
7411 distilling various libraries into a common shared
7412 library, like <tt>mklibs</tt> does in the Debian
7418 In other words, if both a shared and a static library is
7419 being built, each source unit (<tt>*.c</tt>, for example,
7420 for C files) will need to be compiled twice, for the normal
7425 Libraries should be built with threading support and to be
7426 thread-safe if the library supports this.
7430 Although not enforced by the build tools, shared libraries
7431 must be linked against all libraries that they use symbols from
7432 in the same way that binaries are. This ensures the correct
7433 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
7434 system and guarantees that all libraries can be safely opened
7435 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
7436 option <tt>-Wl,-z,defs</tt> when building a shared library.
7437 Since this option enforces symbol resolution at build time,
7438 a missing library reference will be caught early as a fatal
7443 All installed shared libraries should be stripped with
7444 <example compact="compact">
7445 strip --strip-unneeded <var>your-lib</var>
7447 (The option <tt>--strip-unneeded</tt> makes
7448 <prgn>strip</prgn> remove only the symbols which aren't
7449 needed for relocation processing.) Shared libraries can
7450 function perfectly well when stripped, since the symbols for
7451 dynamic linking are in a separate part of the ELF object
7453 You might also want to use the options
7454 <tt>--remove-section=.comment</tt> and
7455 <tt>--remove-section=.note</tt> on both shared libraries
7456 and executables, and <tt>--strip-debug</tt> on static
7462 Note that under some circumstances it may be useful to
7463 install a shared library unstripped, for example when
7464 building a separate package to support debugging.
7468 Shared object files (often <file>.so</file> files) that are not
7469 public libraries, that is, they are not meant to be linked
7470 to by third party executables (binaries of other packages),
7471 should be installed in subdirectories of the
7472 <file>/usr/lib</file> directory. Such files are exempt from the
7473 rules that govern ordinary shared libraries, except that
7474 they must not be installed executable and should be
7476 A common example are the so-called "plug-ins",
7477 internal shared objects that are dynamically loaded by
7478 programs using <manref name="dlopen" section="3">.
7483 Packages that use <prgn>libtool</prgn> to create and install
7484 their shared libraries install a file containing additional
7485 metadata (ending in <file>.la</file>) alongside the library.
7486 For public libraries intended for use by other packages, these
7487 files normally should not be included in the Debian package,
7488 since the information they include is not necessary to link with
7489 the shared library on Debian and can add unnecessary additional
7490 dependencies to other programs or libraries.<footnote>
7491 These files store, among other things, all libraries on which
7492 that shared library depends. Unfortunately, if
7493 the <file>.la</file> file is present and contains that
7494 dependency information, using <prgn>libtool</prgn> when
7495 linking against that library will cause the resulting program
7496 or library to be linked against those dependencies as well,
7497 even if this is unnecessary. This can create unneeded
7498 dependencies on shared library packages that would otherwise
7499 be hidden behind the library ABI, and can make library
7500 transitions to new SONAMEs unnecessarily complicated and
7501 difficult to manage.
7503 If the <file>.la</file> file is required for that library (if,
7504 for instance, it's loaded via <tt>libltdl</tt> in a way that
7505 requires that meta-information), the <tt>dependency_libs</tt>
7506 setting in the <file>.la</file> file should normally be set to
7507 the empty string. If the shared library development package has
7508 historically included the <file>.la</file>, it must be retained
7509 in the development package (with <tt>dependency_libs</tt>
7510 emptied) until all libraries that depend on it have removed or
7511 emptied <tt>dependency_libs</tt> in their <file>.la</file>
7512 files to prevent linking with those other libraries
7513 using <prgn>libtool</prgn> from failing.
7517 If the <file>.la</file> must be included, it should be included
7518 in the development (<tt>-dev</tt>) package, unless the library
7519 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
7520 library. If it is intended for use with <tt>libltdl</tt>,
7521 the <file>.la</file> files must go in the run-time library
7526 These requirements for handling of <file>.la</file> files do not
7527 apply to loadable modules or libraries not installed in
7528 directories searched by default by the dynamic linker. Packages
7529 installing loadable modules will frequently need to install
7530 the <file>.la</file> files alongside the modules so that they
7531 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
7532 does not need to be modified for libraries or modules that are
7533 not installed in directories searched by the dynamic linker by
7534 default and not intended for use by other packages.
7538 You must make sure that you use only released versions of
7539 shared libraries to build your packages; otherwise other
7540 users will not be able to run your binaries
7541 properly. Producing source packages that depend on
7542 unreleased compilers is also usually a bad
7549 <heading>Shared libraries</heading>
7551 This section has moved to <ref id="sharedlibs">.
7557 <heading>Scripts</heading>
7560 All command scripts, including the package maintainer
7561 scripts inside the package and used by <prgn>dpkg</prgn>,
7562 should have a <tt>#!</tt> line naming the shell to be used
7567 In the case of Perl scripts this should be
7568 <tt>#!/usr/bin/perl</tt>.
7572 When scripts are installed into a directory in the system
7573 PATH, the script name should not include an extension such
7574 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7575 language currently used to implement it.
7578 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
7579 <file>init.d</file> scripts should almost certainly start
7580 with <tt>set -e</tt> so that errors are detected.
7581 <file>init.d</file> scripts are something of a special case, due
7582 to how frequently they need to call commands that are allowed to
7583 fail, and it may instead be easier to check the exit status of
7584 commands directly. See <ref id="writing-init"> for more
7585 information about writing <file>init.d</file> scripts.
7588 Every script should use <tt>set -e</tt> or check the exit status
7589 of <em>every</em> command.
7592 Scripts may assume that <file>/bin/sh</file> implements the
7593 SUSv3 Shell Command Language<footnote>
7594 Single UNIX Specification, version 3, which is also IEEE
7595 1003.1-2004 (POSIX), and is available on the World Wide Web
7596 from <url id="http://www.unix.org/version3/online.html"
7597 name="The Open Group"> after free
7598 registration.</footnote>
7599 plus the following additional features not mandated by
7601 These features are in widespread use in the Linux community
7602 and are implemented in all of bash, dash, and ksh, the most
7603 common shells users may wish to use as <file>/bin/sh</file>.
7606 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7607 must not generate a newline.</item>
7608 <item><tt>test</tt>, if implemented as a shell built-in, must
7609 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7611 <item><tt>local</tt> to create a scoped variable must be
7612 supported, including listing multiple variables in a single
7613 local command and assigning a value to a variable at the
7614 same time as localizing it. <tt>local</tt> may or
7615 may not preserve the variable value from an outer scope if
7616 no assignment is present. Uses such as:
7620 # ... use a, b, c, d ...
7623 must be supported and must set the value of <tt>c</tt> to
7626 <item>The XSI extension to <prgn>kill</prgn> allowing <tt>kill
7627 -<var>signal</var></tt>, where <var>signal</var> is either
7628 the name of a signal or one of the numeric signals listed in
7629 the XSI extension (0, 1, 2, 3, 6, 9, 14, and 15), must be
7630 supported if <prgn>kill</prgn> is implemented as a shell
7633 <item>The XSI extension to <prgn>trap</prgn> allowing numeric
7634 signals must be supported. In addition to the signal
7635 numbers listed in the extension, which are the same as for
7636 <prgn>kill</prgn> above, 13 (SIGPIPE) must be allowed.
7639 If a shell script requires non-SUSv3 features from the shell
7640 interpreter other than those listed above, the appropriate shell
7641 must be specified in the first line of the script (e.g.,
7642 <tt>#!/bin/bash</tt>) and the package must depend on the package
7643 providing the shell (unless the shell package is marked
7644 "Essential", as in the case of <prgn>bash</prgn>).
7648 You may wish to restrict your script to SUSv3 features plus the
7649 above set when possible so that it may use <file>/bin/sh</file>
7650 as its interpreter. If your script works with <prgn>dash</prgn>
7651 (originally called <prgn>ash</prgn>), it probably complies with
7652 the above requirements, but if you are in doubt, use
7653 <file>/bin/bash</file>.
7657 Perl scripts should check for errors when making any
7658 system calls, including <tt>open</tt>, <tt>print</tt>,
7659 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7663 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7664 scripting languages. See <em>Csh Programming Considered
7665 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7666 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7667 If an upstream package comes with <prgn>csh</prgn> scripts
7668 then you must make sure that they start with
7669 <tt>#!/bin/csh</tt> and make your package depend on the
7670 <prgn>c-shell</prgn> virtual package.
7674 Any scripts which create files in world-writeable
7675 directories (e.g., in <file>/tmp</file>) must use a
7676 mechanism which will fail atomically if a file with the same
7677 name already exists.
7681 The Debian base system provides the <prgn>tempfile</prgn>
7682 and <prgn>mktemp</prgn> utilities for use by scripts for
7689 <heading>Symbolic links</heading>
7692 In general, symbolic links within a top-level directory
7693 should be relative, and symbolic links pointing from one
7694 top-level directory into another should be absolute. (A
7695 top-level directory is a sub-directory of the root
7696 directory <file>/</file>.)
7700 In addition, symbolic links should be specified as short as
7701 possible, i.e., link targets like <file>foo/../bar</file> are
7706 Note that when creating a relative link using
7707 <prgn>ln</prgn> it is not necessary for the target of the
7708 link to exist relative to the working directory you're
7709 running <prgn>ln</prgn> from, nor is it necessary to change
7710 directory to the directory where the link is to be made.
7711 Simply include the string that should appear as the target
7712 of the link (this will be a pathname relative to the
7713 directory in which the link resides) as the first argument
7718 For example, in your <prgn>Makefile</prgn> or
7719 <file>debian/rules</file>, you can do things like:
7720 <example compact="compact">
7721 ln -fs gcc $(prefix)/bin/cc
7722 ln -fs gcc debian/tmp/usr/bin/cc
7723 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7724 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7729 A symbolic link pointing to a compressed file should always
7730 have the same file extension as the referenced file. (For
7731 example, if a file <file>foo.gz</file> is referenced by a
7732 symbolic link, the filename of the link has to end with
7733 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7738 <heading>Device files</heading>
7741 Packages must not include device files or named pipes in the
7746 If a package needs any special device files that are not
7747 included in the base system, it must call
7748 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7749 after notifying the user<footnote>
7750 This notification could be done via a (low-priority)
7751 debconf message, or an echo (printf) statement.
7756 Packages must not remove any device files in the
7757 <prgn>postrm</prgn> or any other script. This is left to the
7758 system administrator.
7762 Debian uses the serial devices
7763 <file>/dev/ttyS*</file>. Programs using the old
7764 <file>/dev/cu*</file> devices should be changed to use
7765 <file>/dev/ttyS*</file>.
7769 Named pipes needed by the package must be created in
7770 the <prgn>postinst</prgn> script<footnote>
7771 It's better to use <prgn>mkfifo</prgn> rather
7772 than <prgn>mknod</prgn> to create named pipes so that
7773 automated checks for packages incorrectly creating device
7774 files with <prgn>mknod</prgn> won't have false positives.
7775 </footnote> and removed in
7776 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
7781 <sect id="config-files">
7782 <heading>Configuration files</heading>
7785 <heading>Definitions</heading>
7789 <tag>configuration file</tag>
7791 A file that affects the operation of a program, or
7792 provides site- or host-specific information, or
7793 otherwise customizes the behavior of a program.
7794 Typically, configuration files are intended to be
7795 modified by the system administrator (if needed or
7796 desired) to conform to local policy or to provide
7797 more useful site-specific behavior.
7800 <tag><tt>conffile</tt></tag>
7802 A file listed in a package's <tt>conffiles</tt>
7803 file, and is treated specially by <prgn>dpkg</prgn>
7804 (see <ref id="configdetails">).
7810 The distinction between these two is important; they are
7811 not interchangeable concepts. Almost all
7812 <tt>conffile</tt>s are configuration files, but many
7813 configuration files are not <tt>conffiles</tt>.
7817 As noted elsewhere, <file>/etc/init.d</file> scripts,
7818 <file>/etc/default</file> files, scripts installed in
7819 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7820 configuration installed in <file>/etc/cron.d</file> must be
7821 treated as configuration files. In general, any script that
7822 embeds configuration information is de-facto a configuration
7823 file and should be treated as such.
7828 <heading>Location</heading>
7831 Any configuration files created or used by your package
7832 must reside in <file>/etc</file>. If there are several,
7833 consider creating a subdirectory of <file>/etc</file>
7834 named after your package.
7838 If your package creates or uses configuration files
7839 outside of <file>/etc</file>, and it is not feasible to modify
7840 the package to use <file>/etc</file> directly, put the files
7841 in <file>/etc</file> and create symbolic links to those files
7842 from the location that the package requires.
7847 <heading>Behavior</heading>
7850 Configuration file handling must conform to the following
7852 <list compact="compact">
7854 local changes must be preserved during a package
7858 configuration files must be preserved when the
7859 package is removed, and only deleted when the
7863 Obsolete configuration files without local changes may be
7864 removed by the package during upgrade.
7868 The easy way to achieve this behavior is to make the
7869 configuration file a <tt>conffile</tt>. This is
7870 appropriate only if it is possible to distribute a default
7871 version that will work for most installations, although
7872 some system administrators may choose to modify it. This
7873 implies that the default version will be part of the
7874 package distribution, and must not be modified by the
7875 maintainer scripts during installation (or at any other
7880 In order to ensure that local changes are preserved
7881 correctly, no package may contain or make hard links to
7882 conffiles.<footnote>
7883 Rationale: There are two problems with hard links.
7884 The first is that some editors break the link while
7885 editing one of the files, so that the two files may
7886 unwittingly become unlinked and different. The second
7887 is that <prgn>dpkg</prgn> might break the hard link
7888 while upgrading <tt>conffile</tt>s.
7893 The other way to do it is via the maintainer scripts. In
7894 this case, the configuration file must not be listed as a
7895 <tt>conffile</tt> and must not be part of the package
7896 distribution. If the existence of a file is required for
7897 the package to be sensibly configured it is the
7898 responsibility of the package maintainer to provide
7899 maintainer scripts which correctly create, update and
7900 maintain the file and remove it on purge. (See <ref
7901 id="maintainerscripts"> for more information.) These
7902 scripts must be idempotent (i.e., must work correctly if
7903 <prgn>dpkg</prgn> needs to re-run them due to errors
7904 during installation or removal), must cope with all the
7905 variety of ways <prgn>dpkg</prgn> can call maintainer
7906 scripts, must not overwrite or otherwise mangle the user's
7907 configuration without asking, must not ask unnecessary
7908 questions (particularly during upgrades), and must
7909 otherwise be good citizens.
7913 The scripts are not required to configure every possible
7914 option for the package, but only those necessary to get
7915 the package running on a given system. Ideally the
7916 sysadmin should not have to do any configuration other
7917 than that done (semi-)automatically by the
7918 <prgn>postinst</prgn> script.
7922 A common practice is to create a script called
7923 <file><var>package</var>-configure</file> and have the
7924 package's <prgn>postinst</prgn> call it if and only if the
7925 configuration file does not already exist. In certain
7926 cases it is useful for there to be an example or template
7927 file which the maintainer scripts use. Such files should
7928 be in <file>/usr/share/<var>package</var></file> or
7929 <file>/usr/lib/<var>package</var></file> (depending on whether
7930 they are architecture-independent or not). There should
7931 be symbolic links to them from
7932 <file>/usr/share/doc/<var>package</var>/examples</file> if
7933 they are examples, and should be perfectly ordinary
7934 <prgn>dpkg</prgn>-handled files (<em>not</em>
7935 configuration files).
7939 These two styles of configuration file handling must
7940 not be mixed, for that way lies madness:
7941 <prgn>dpkg</prgn> will ask about overwriting the file
7942 every time the package is upgraded.
7947 <heading>Sharing configuration files</heading>
7950 Packages which specify the same file as a
7951 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7952 with each other. (This is an instance of the general rule
7953 about not sharing files. Note that neither alternatives
7954 nor diversions are likely to be appropriate in this case;
7955 in particular, <prgn>dpkg</prgn> does not handle diverted
7956 <tt>conffile</tt>s well.)
7960 The maintainer scripts must not alter a <tt>conffile</tt>
7961 of <em>any</em> package, including the one the scripts
7966 If two or more packages use the same configuration file
7967 and it is reasonable for both to be installed at the same
7968 time, one of these packages must be defined as
7969 <em>owner</em> of the configuration file, i.e., it will be
7970 the package which handles that file as a configuration
7971 file. Other packages that use the configuration file must
7972 depend on the owning package if they require the
7973 configuration file to operate. If the other package will
7974 use the configuration file if present, but is capable of
7975 operating without it, no dependency need be declared.
7979 If it is desirable for two or more related packages to
7980 share a configuration file <em>and</em> for all of the
7981 related packages to be able to modify that configuration
7982 file, then the following should be done:
7983 <enumlist compact="compact">
7985 One of the related packages (the "owning" package)
7986 will manage the configuration file with maintainer
7987 scripts as described in the previous section.
7990 The owning package should also provide a program
7991 that the other packages may use to modify the
7995 The related packages must use the provided program
7996 to make any desired modifications to the
7997 configuration file. They should either depend on
7998 the core package to guarantee that the configuration
7999 modifier program is available or accept gracefully
8000 that they cannot modify the configuration file if it
8001 is not. (This is in addition to the fact that the
8002 configuration file may not even be present in the
8009 Sometimes it's appropriate to create a new package which
8010 provides the basic infrastructure for the other packages
8011 and which manages the shared configuration files. (The
8012 <tt>sgml-base</tt> package is a good example.)
8017 <heading>User configuration files ("dotfiles")</heading>
8020 The files in <file>/etc/skel</file> will automatically be
8021 copied into new user accounts by <prgn>adduser</prgn>.
8022 No other program should reference the files in
8023 <file>/etc/skel</file>.
8027 Therefore, if a program needs a dotfile to exist in
8028 advance in <file>$HOME</file> to work sensibly, that dotfile
8029 should be installed in <file>/etc/skel</file> and treated as a
8034 However, programs that require dotfiles in order to
8035 operate sensibly are a bad thing, unless they do create
8036 the dotfiles themselves automatically.
8040 Furthermore, programs should be configured by the Debian
8041 default installation to behave as closely to the upstream
8042 default behavior as possible.
8046 Therefore, if a program in a Debian package needs to be
8047 configured in some way in order to operate sensibly, that
8048 should be done using a site-wide configuration file placed
8049 in <file>/etc</file>. Only if the program doesn't support a
8050 site-wide default configuration and the package maintainer
8051 doesn't have time to add it may a default per-user file be
8052 placed in <file>/etc/skel</file>.
8056 <file>/etc/skel</file> should be as empty as we can make it.
8057 This is particularly true because there is no easy (or
8058 necessarily desirable) mechanism for ensuring that the
8059 appropriate dotfiles are copied into the accounts of
8060 existing users when a package is installed.
8066 <heading>Log files</heading>
8068 Log files should usually be named
8069 <file>/var/log/<var>package</var>.log</file>. If you have many
8070 log files, or need a separate directory for permission
8071 reasons (<file>/var/log</file> is writable only by
8072 <file>root</file>), you should usually create a directory named
8073 <file>/var/log/<var>package</var></file> and place your log
8078 Log files must be rotated occasionally so that they don't grow
8079 indefinitely. The best way to do this is to install a log
8080 rotation configuration file in the
8081 directory <file>/etc/logrotate.d</file>, normally
8082 named <file>/etc/logrotate.d/<var>package</var></file>, and use
8083 the facilities provided by <prgn>logrotate</prgn>.
8086 The traditional approach to log files has been to set up
8087 <em>ad hoc</em> log rotation schemes using simple shell
8088 scripts and cron. While this approach is highly
8089 customizable, it requires quite a lot of sysadmin work.
8090 Even though the original Debian system helped a little
8091 by automatically installing a system which can be used
8092 as a template, this was deemed not enough.
8096 The use of <prgn>logrotate</prgn>, a program developed
8097 by Red Hat, is better, as it centralizes log management.
8098 It has both a configuration file
8099 (<file>/etc/logrotate.conf</file>) and a directory where
8100 packages can drop their individual log rotation
8101 configurations (<file>/etc/logrotate.d</file>).
8104 Here is a good example for a logrotate config
8105 file (for more information see <manref name="logrotate"
8107 <example compact="compact">
8108 /var/log/foo/*.log {
8114 start-stop-daemon -K -p /var/run/foo.pid -s HUP -x /usr/sbin/foo -q
8118 This rotates all files under <file>/var/log/foo</file>, saves 12
8119 compressed generations, and tells the daemon to reopen its log
8120 files after the log rotation. It skips this log rotation
8121 (via <tt>missingok</tt>) if no such log file is present, which
8122 avoids errors if the package is removed but not purged.
8126 Log files should be removed when the package is
8127 purged (but not when it is only removed). This should be
8128 done by the <prgn>postrm</prgn> script when it is called
8129 with the argument <tt>purge</tt> (see <ref
8130 id="removedetails">).
8134 <sect id="permissions-owners">
8135 <heading>Permissions and owners</heading>
8138 The rules in this section are guidelines for general use.
8139 If necessary you may deviate from the details below.
8140 However, if you do so you must make sure that what is done
8141 is secure and you should try to be as consistent as possible
8142 with the rest of the system. You should probably also
8143 discuss it on <prgn>debian-devel</prgn> first.
8147 Files should be owned by <tt>root:root</tt>, and made
8148 writable only by the owner and universally readable (and
8149 executable, if appropriate), that is mode 644 or 755.
8153 Directories should be mode 755 or (for group-writability)
8154 mode 2775. The ownership of the directory should be
8155 consistent with its mode: if a directory is mode 2775, it
8156 should be owned by the group that needs write access to
8159 When a package is upgraded, and the owner or permissions
8160 of a file included in the package has changed, dpkg
8161 arranges for the ownership and permissions to be
8162 correctly set upon installation. However, this does not
8163 extend to directories; the permissions and ownership of
8164 directories already on the system does not change on
8165 install or upgrade of packages. This makes sense, since
8166 otherwise common directories like <tt>/usr</tt> would
8167 always be in flux. To correctly change permissions of a
8168 directory the package owns, explicit action is required,
8169 usually in the <tt>postinst</tt> script. Care must be
8170 taken to handle downgrades as well, in that case.
8176 Control information files should be owned by <tt>root:root</tt>
8177 and either mode 644 (for most files) or mode 755 (for
8178 executables such as <qref id="maintscripts">maintainer
8183 Setuid and setgid executables should be mode 4755 or 2755
8184 respectively, and owned by the appropriate user or group.
8185 They should not be made unreadable (modes like 4711 or
8186 2711 or even 4111); doing so achieves no extra security,
8187 because anyone can find the binary in the freely available
8188 Debian package; it is merely inconvenient. For the same
8189 reason you should not restrict read or execute permissions
8190 on non-set-id executables.
8194 Some setuid programs need to be restricted to particular
8195 sets of users, using file permissions. In this case they
8196 should be owned by the uid to which they are set-id, and by
8197 the group which should be allowed to execute them. They
8198 should have mode 4754; again there is no point in making
8199 them unreadable to those users who must not be allowed to
8204 It is possible to arrange that the system administrator can
8205 reconfigure the package to correspond to their local
8206 security policy by changing the permissions on a binary:
8207 they can do this by using <prgn>dpkg-statoverride</prgn>, as
8208 described below.<footnote>
8209 Ordinary files installed by <prgn>dpkg</prgn> (as
8210 opposed to <tt>conffile</tt>s and other similar objects)
8211 normally have their permissions reset to the distributed
8212 permissions when the package is reinstalled. However,
8213 the use of <prgn>dpkg-statoverride</prgn> overrides this
8216 Another method you should consider is to create a group for
8217 people allowed to use the program(s) and make any setuid
8218 executables executable only by that group.
8222 If you need to create a new user or group for your package
8223 there are two possibilities. Firstly, you may need to
8224 make some files in the binary package be owned by this
8225 user or group, or you may need to compile the user or
8226 group id (rather than just the name) into the binary
8227 (though this latter should be avoided if possible, as in
8228 this case you need a statically allocated id).</p>
8231 If you need a statically allocated id, you must ask for a
8232 user or group id from the <tt>base-passwd</tt> maintainer,
8233 and must not release the package until you have been
8234 allocated one. Once you have been allocated one you must
8235 either make the package depend on a version of the
8236 <tt>base-passwd</tt> package with the id present in
8237 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
8238 your package to create the user or group itself with the
8239 correct id (using <tt>adduser</tt>) in its
8240 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
8241 the <prgn>postinst</prgn> is to be preferred if it is
8242 possible, otherwise a pre-dependency will be needed on the
8243 <tt>adduser</tt> package.)
8247 On the other hand, the program might be able to determine
8248 the uid or gid from the user or group name at runtime, so
8249 that a dynamically allocated id can be used. In this case
8250 you should choose an appropriate user or group name,
8251 discussing this on <prgn>debian-devel</prgn> and checking
8252 with the <package/base-passwd/ maintainer that it is unique and that
8253 they do not wish you to use a statically allocated id
8254 instead. When this has been checked you must arrange for
8255 your package to create the user or group if necessary using
8256 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
8257 <prgn>postinst</prgn> script (again, the latter is to be
8258 preferred if it is possible).
8262 Note that changing the numeric value of an id associated
8263 with a name is very difficult, and involves searching the
8264 file system for all appropriate files. You need to think
8265 carefully whether a static or dynamic id is required, since
8266 changing your mind later will cause problems.
8269 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
8271 This section is not intended as policy, but as a
8272 description of the use of <prgn>dpkg-statoverride</prgn>.
8276 If a system administrator wishes to have a file (or
8277 directory or other such thing) installed with owner and
8278 permissions different from those in the distributed Debian
8279 package, they can use the <prgn>dpkg-statoverride</prgn>
8280 program to instruct <prgn>dpkg</prgn> to use the different
8281 settings every time the file is installed. Thus the
8282 package maintainer should distribute the files with their
8283 normal permissions, and leave it for the system
8284 administrator to make any desired changes. For example, a
8285 daemon which is normally required to be setuid root, but
8286 in certain situations could be used without being setuid,
8287 should be installed setuid in the <tt>.deb</tt>. Then the
8288 local system administrator can change this if they wish.
8289 If there are two standard ways of doing it, the package
8290 maintainer can use <tt>debconf</tt> to find out the
8291 preference, and call <prgn>dpkg-statoverride</prgn> in the
8292 maintainer script if necessary to accommodate the system
8293 administrator's choice. Care must be taken during
8294 upgrades to not override an existing setting.
8298 Given the above, <prgn>dpkg-statoverride</prgn> is
8299 essentially a tool for system administrators and would not
8300 normally be needed in the maintainer scripts. There is
8301 one type of situation, though, where calls to
8302 <prgn>dpkg-statoverride</prgn> would be needed in the
8303 maintainer scripts, and that involves packages which use
8304 dynamically allocated user or group ids. In such a
8305 situation, something like the following idiom can be very
8306 helpful in the package's <prgn>postinst</prgn>, where
8307 <tt>sysuser</tt> is a dynamically allocated id:
8309 for i in /usr/bin/foo /usr/sbin/bar
8311 # only do something when no setting exists
8312 if ! dpkg-statoverride --list $i >/dev/null 2>&1
8314 #include: debconf processing, question about foo and bar
8315 if [ "$RET" = "true" ] ; then
8316 dpkg-statoverride --update --add sysuser root 4755 $i
8321 The corresponding code to remove the override when the package
8324 for i in /usr/bin/foo /usr/sbin/bar
8326 if dpkg-statoverride --list $i >/dev/null 2>&1
8328 dpkg-statoverride --remove $i
8338 <chapt id="customized-programs">
8339 <heading>Customized programs</heading>
8341 <sect id="arch-spec">
8342 <heading>Architecture specification strings</heading>
8345 If a program needs to specify an <em>architecture specification
8346 string</em> in some place, it should select one of the strings
8347 provided by <tt>dpkg-architecture -L</tt>. The strings are in
8348 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
8349 part is sometimes elided, as when the OS is Linux.
8353 Note that we don't want to use
8354 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
8355 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
8356 since this would make our programs incompatible with other
8357 Linux distributions. We also don't use something like
8358 <tt><var>arch</var>-unknown-linux</tt>, since the
8359 <tt>unknown</tt> does not look very good.
8362 <sect1 id="arch-wildcard-spec">
8363 <heading>Architecture wildcards</heading>
8366 A package may specify an architecture wildcard. Architecture
8367 wildcards are in the format <tt>any</tt> (which matches every
8368 architecture), <tt><var>os</var></tt>-any, or
8369 any-<tt><var>cpu</var></tt>. <footnote>
8370 Internally, the package system normalizes the GNU triplets
8371 and the Debian arches into Debian arch triplets (which are
8372 kind of inverted GNU triplets), with the first component of
8373 the triplet representing the libc and ABI in use, and then
8374 does matching against those triplets. However, such
8375 triplets are an internal implementation detail that should
8376 not be used by packages directly. The libc and ABI portion
8377 is handled internally by the package system based on
8378 the <var>os</var> and <var>cpu</var>.
8385 <heading>Daemons</heading>
8388 The configuration files <file>/etc/services</file>,
8389 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
8390 by the <prgn>netbase</prgn> package and must not be modified
8395 If a package requires a new entry in one of these files, the
8396 maintainer should get in contact with the
8397 <prgn>netbase</prgn> maintainer, who will add the entries
8398 and release a new version of the <prgn>netbase</prgn>
8403 The configuration file <file>/etc/inetd.conf</file> must not be
8404 modified by the package's scripts except via the
8405 <prgn>update-inetd</prgn> script or the
8406 <file>DebianNet.pm</file> Perl module. See their documentation
8407 for details on how to add entries.
8411 If a package wants to install an example entry into
8412 <file>/etc/inetd.conf</file>, the entry must be preceded with
8413 exactly one hash character (<tt>#</tt>). Such lines are
8414 treated as "commented out by user" by the
8415 <prgn>update-inetd</prgn> script and are not changed or
8416 activated during package updates.
8421 <heading>Using pseudo-ttys and modifying wtmp, utmp and
8425 Some programs need to create pseudo-ttys. This should be done
8426 using Unix98 ptys if the C library supports it. The resulting
8427 program must not be installed setuid root, unless that
8428 is required for other functionality.
8432 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
8433 <file>/var/log/lastlog</file> must be installed writable by
8434 group <tt>utmp</tt>. Programs which need to modify those
8435 files must be installed setgid <tt>utmp</tt>.
8440 <heading>Editors and pagers</heading>
8443 Some programs have the ability to launch an editor or pager
8444 program to edit or display a text document. Since there are
8445 lots of different editors and pagers available in the Debian
8446 distribution, the system administrator and each user should
8447 have the possibility to choose their preferred editor and
8452 In addition, every program should choose a good default
8453 editor/pager if none is selected by the user or system
8458 Thus, every program that launches an editor or pager must
8459 use the EDITOR or PAGER environment variable to determine
8460 the editor or pager the user wishes to use. If these
8461 variables are not set, the programs <file>/usr/bin/editor</file>
8462 and <file>/usr/bin/pager</file> should be used, respectively.
8466 These two files are managed through the <prgn>dpkg</prgn>
8467 "alternatives" mechanism. Every package providing an editor or
8468 pager must call the <prgn>update-alternatives</prgn> script to
8469 register as an alternative for <file>/usr/bin/editor</file>
8470 or <file>/usr/bin/pager</file> as appropriate. The alternative
8471 should have a slave alternative
8472 for <file>/usr/share/man/man1/editor.1.gz</file>
8473 or <file>/usr/share/man/man1/pager.1.gz</file> pointing to the
8474 corresponding manual page.
8478 If it is very hard to adapt a program to make use of the
8479 EDITOR or PAGER variables, that program may be configured to
8480 use <file>/usr/bin/sensible-editor</file> and
8481 <file>/usr/bin/sensible-pager</file> as the editor or pager
8482 program respectively. These are two scripts provided in the
8483 <package>sensible-utils</package> package that check the EDITOR
8484 and PAGER variables and launch the appropriate program, and fall
8485 back to <file>/usr/bin/editor</file>
8486 and <file>/usr/bin/pager</file> if the variable is not set.
8490 A program may also use the VISUAL environment variable to
8491 determine the user's choice of editor. If it exists, it
8492 should take precedence over EDITOR. This is in fact what
8493 <file>/usr/bin/sensible-editor</file> does.
8497 It is not required for a package to depend on
8498 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
8499 package to provide such virtual packages.<footnote>
8500 The Debian base system already provides an editor and a
8506 <sect id="web-appl">
8507 <heading>Web servers and applications</heading>
8510 This section describes the locations and URLs that should
8511 be used by all web servers and web applications in the
8518 Cgi-bin executable files are installed in the
8520 <example compact="compact">
8521 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
8523 or a subdirectory of that directory, and should be
8525 <example compact="compact">
8526 http://localhost/cgi-bin/<var>cgi-bin-name</var>
8528 (possibly with a subdirectory name
8529 before <var>cgi-bin-name</var>).
8533 <p>Access to HTML documents</p>
8536 HTML documents for a package are stored in
8537 <file>/usr/share/doc/<var>package</var></file>
8538 and can be referred to as
8539 <example compact="compact">
8540 http://localhost/doc/<var>package</var>/<var>filename</var>
8545 The web server should restrict access to the document
8546 tree so that only clients on the same host can read
8547 the documents. If the web server does not support such
8548 access controls, then it should not provide access at
8549 all, or ask about providing access during installation.
8554 <p>Access to images</p>
8556 It is recommended that images for a package be stored
8557 in <tt>/usr/share/images/<var>package</var></tt> and
8558 may be referred to through an alias <tt>/images/</tt>
8561 http://localhost/images/<package>/<filename>
8568 <p>Web Document Root</p>
8571 Web Applications should try to avoid storing files in
8572 the Web Document Root. Instead they should use the
8573 /usr/share/doc/<var>package</var> directory for
8574 documents and register the Web Application via the
8575 <package>doc-base</package> package. If access to the
8576 web document root is unavoidable then use
8577 <example compact="compact">
8580 as the Document Root. This might be just a symbolic
8581 link to the location where the system administrator
8582 has put the real document root.
8585 <item><p>Providing httpd and/or httpd-cgi</p>
8587 All web servers should provide the virtual package
8588 <tt>httpd</tt>. If a web server has CGI support it should
8589 provide <tt>httpd-cgi</tt> additionally.
8592 All web applications which do not contain CGI scripts should
8593 depend on <tt>httpd</tt>, all those web applications which
8594 <tt>do</tt> contain CGI scripts, should depend on
8602 <sect id="mail-transport-agents">
8603 <heading>Mail transport, delivery and user agents</heading>
8606 Debian packages which process electronic mail, whether mail
8607 user agents (MUAs) or mail transport agents (MTAs), must
8608 ensure that they are compatible with the configuration
8609 decisions below. Failure to do this may result in lost
8610 mail, broken <tt>From:</tt> lines, and other serious brain
8615 The mail spool is <file>/var/mail</file> and the interface to
8616 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8617 the FHS). On older systems, the mail spool may be
8618 physically located in <file>/var/spool/mail</file>, but all
8619 access to the mail spool should be via the
8620 <file>/var/mail</file> symlink. The mail spool is part of the
8621 base system and not part of the MTA package.
8625 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8626 programs (such as IMAP daemons) must lock the mailbox in an
8627 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8628 be combined with dot locking. To avoid deadlocks, a program
8629 should use <tt>fcntl()</tt> first and dot locking after
8630 this, or alternatively implement the two locking methods in
8631 a non blocking way<footnote>
8632 If it is not possible to establish both locks, the
8633 system shouldn't wait for the second lock to be
8634 established, but remove the first lock, wait a (random)
8635 time, and start over locking again.
8636 </footnote>. Using the functions <tt>maillock</tt> and
8637 <tt>mailunlock</tt> provided by the
8638 <tt>liblockfile*</tt><footnote>
8639 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8640 to use these functions.
8641 </footnote> packages is the recommended way to realize this.
8645 Mailboxes are generally either mode 600 and owned by
8646 <var>user</var> or mode 660 and owned by
8647 <tt><var>user</var>:mail</tt><footnote>
8648 There are two traditional permission schemes for mail spools:
8649 mode 600 with all mail delivery done by processes running as
8650 the destination user, or mode 660 and owned by group mail with
8651 mail delivery done by a process running as a system user in
8652 group mail. Historically, Debian required mode 660 mail
8653 spools to enable the latter model, but that model has become
8654 increasingly uncommon and the principle of least privilege
8655 indicates that mail systems that use the first model should
8656 use permissions of 600. If delivery to programs is permitted,
8657 it's easier to keep the mail system secure if the delivery
8658 agent runs as the destination user. Debian Policy therefore
8659 permits either scheme.
8660 </footnote>. The local system administrator may choose a
8661 different permission scheme; packages should not make
8662 assumptions about the permission and ownership of mailboxes
8663 unless required (such as when creating a new mailbox). A MUA
8664 may remove a mailbox (unless it has nonstandard permissions) in
8665 which case the MTA or another MUA must recreate it if needed.
8669 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8670 be setgid mail to do the locking mentioned above (and
8671 must obviously avoid accessing other users' mailboxes
8672 using this privilege).</p>
8675 <file>/etc/aliases</file> is the source file for the system mail
8676 aliases (e.g., postmaster, usenet, etc.), it is the one
8677 which the sysadmin and <prgn>postinst</prgn> scripts may
8678 edit. After <file>/etc/aliases</file> is edited the program or
8679 human editing it must call <prgn>newaliases</prgn>. All MTA
8680 packages must come with a <prgn>newaliases</prgn> program,
8681 even if it does nothing, but older MTA packages did not do
8682 this so programs should not fail if <prgn>newaliases</prgn>
8683 cannot be found. Note that because of this, all MTA
8684 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8685 <tt>Replaces: mail-transport-agent</tt> control fields.
8689 The convention of writing <tt>forward to
8690 <var>address</var></tt> in the mailbox itself is not
8691 supported. Use a <tt>.forward</tt> file instead.</p>
8694 The <prgn>rmail</prgn> program used by UUCP
8695 for incoming mail should be <file>/usr/sbin/rmail</file>.
8696 Likewise, <prgn>rsmtp</prgn>, for receiving
8697 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8701 If your package needs to know what hostname to use on (for
8702 example) outgoing news and mail messages which are generated
8703 locally, you should use the file <file>/etc/mailname</file>. It
8704 will contain the portion after the username and <tt>@</tt>
8705 (at) sign for email addresses of users on the machine
8706 (followed by a newline).
8710 Such a package should check for the existence of this file
8711 when it is being configured. If it exists, it should be
8712 used without comment, although an MTA's configuration script
8713 may wish to prompt the user even if it finds that this file
8714 exists. If the file does not exist, the package should
8715 prompt the user for the value (preferably using
8716 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8717 as well as using it in the package's configuration. The
8718 prompt should make it clear that the name will not just be
8719 used by that package. For example, in this situation the
8720 <tt>inn</tt> package could say something like:
8721 <example compact="compact">
8722 Please enter the "mail name" of your system. This is the
8723 hostname portion of the address to be shown on outgoing
8724 news and mail messages. The default is
8725 <var>syshostname</var>, your system's host name. Mail
8726 name ["<var>syshostname</var>"]:
8728 where <var>syshostname</var> is the output of <tt>hostname
8734 <heading>News system configuration</heading>
8737 All the configuration files related to the NNTP (news)
8738 servers and clients should be located under
8739 <file>/etc/news</file>.</p>
8742 There are some configuration issues that apply to a number
8743 of news clients and server packages on the machine. These
8747 <tag><file>/etc/news/organization</file></tag>
8749 A string which should appear as the
8750 organization header for all messages posted
8751 by NNTP clients on the machine
8754 <tag><file>/etc/news/server</file></tag>
8756 Contains the FQDN of the upstream NNTP
8757 server, or localhost if the local machine is
8762 Other global files may be added as required for cross-package news
8769 <heading>Programs for the X Window System</heading>
8772 <heading>Providing X support and package priorities</heading>
8775 Programs that can be configured with support for the X
8776 Window System must be configured to do so and must declare
8777 any package dependencies necessary to satisfy their
8778 runtime requirements when using the X Window System. If
8779 such a package is of higher priority than the X packages
8780 on which it depends, it is required that either the
8781 X-specific components be split into a separate package, or
8782 that an alternative version of the package, which includes
8783 X support, be provided, or that the package's priority be
8789 <heading>Packages providing an X server</heading>
8792 Packages that provide an X server that, directly or
8793 indirectly, communicates with real input and display
8794 hardware should declare in their <tt>Provides</tt> control
8795 field that they provide the virtual
8796 package <tt>xserver</tt>.<footnote>
8797 This implements current practice, and provides an
8798 actual policy for usage of the <tt>xserver</tt>
8799 virtual package which appears in the virtual packages
8800 list. In a nutshell, X servers that interface
8801 directly with the display and input hardware or via
8802 another subsystem (e.g., GGI) should provide
8803 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8804 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8810 <heading>Packages providing a terminal emulator</heading>
8813 Packages that provide a terminal emulator for the X Window
8814 System which meet the criteria listed below should declare in
8815 their <tt>Provides</tt> control field that they provide the
8816 virtual package <tt>x-terminal-emulator</tt>. They should
8817 also register themselves as an alternative for
8818 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8819 20. That alternative should have a slave alternative
8820 for <file>/usr/share/man/man1/x-terminal-emulator.1.gz</file>
8821 pointing to the corresponding manual page.
8825 To be an <tt>x-terminal-emulator</tt>, a program must:
8826 <list compact="compact">
8828 Be able to emulate a DEC VT100 terminal, or a
8829 compatible terminal.
8833 Support the command-line option <tt>-e
8834 <var>command</var></tt>, which creates a new
8835 terminal window<footnote>
8836 "New terminal window" does not necessarily mean
8837 a new top-level X window directly parented by
8838 the window manager; it could, if the terminal
8839 emulator application were so coded, be a new
8840 "view" in a multiple-document interface (MDI).
8842 and runs the specified <var>command</var>,
8843 interpreting the entirety of the rest of the command
8844 line as a command to pass straight to exec, in the
8845 manner that <tt>xterm</tt> does.
8849 Support the command-line option <tt>-T
8850 <var>title</var></tt>, which creates a new terminal
8851 window with the window title <var>title</var>.
8858 <heading>Packages providing a window manager</heading>
8861 Packages that provide a window manager should declare in
8862 their <tt>Provides</tt> control field that they provide the
8863 virtual package <tt>x-window-manager</tt>. They should also
8864 register themselves as an alternative for
8865 <file>/usr/bin/x-window-manager</file>, with a priority
8866 calculated as follows:
8867 <list compact="compact">
8869 Start with a priority of 20.
8873 If the window manager supports the Debian menu
8874 system, add 20 points if this support is available
8875 in the package's default configuration (i.e., no
8876 configuration files belonging to the system or user
8877 have to be edited to activate the feature); if
8878 configuration files must be modified, add only 10
8884 If the window manager complies with <url
8885 id="http://www.freedesktop.org/Standards/wm-spec"
8886 name="The Window Manager Specification Project">,
8887 written by the <url id="http://www.freedesktop.org/"
8888 name="Free Desktop Group">, add 40 points.
8892 If the window manager permits the X session to be
8893 restarted using a <em>different</em> window manager
8894 (without killing the X server) in its default
8895 configuration, add 10 points; otherwise add none.
8898 That alternative should have a slave alternative
8899 for <file>/usr/share/man/man1/x-window-manager.1.gz</file>
8900 pointing to the corresponding manual page.
8905 <heading>Packages providing fonts</heading>
8908 Packages that provide fonts for the X Window
8910 For the purposes of Debian Policy, a "font for the X
8911 Window System" is one which is accessed via X protocol
8912 requests. Fonts for the Linux console, for PostScript
8913 renderer, or any other purpose, do not fit this
8914 definition. Any tool which makes such fonts available
8915 to the X Window System, however, must abide by this
8918 must do a number of things to ensure that they are both
8919 available without modification of the X or font server
8920 configuration, and that they do not corrupt files used by
8921 other font packages to register information about
8925 Fonts of any type supported by the X Window System
8926 must be in a separate binary package from any
8927 executables, libraries, or documentation (except
8928 that specific to the fonts shipped, such as their
8929 license information). If one or more of the fonts
8930 so packaged are necessary for proper operation of
8931 the package with which they are associated the font
8932 package may be Recommended; if the fonts merely
8933 provide an enhancement, a Suggests relationship may
8934 be used. Packages must not Depend on font
8936 This is because the X server may retrieve fonts
8937 from the local file system or over the network
8938 from an X font server; the Debian package system
8939 is empowered to deal only with the local
8945 BDF fonts must be converted to PCF fonts with the
8946 <prgn>bdftopcf</prgn> utility (available in the
8947 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8948 placed in a directory that corresponds to their
8950 <list compact="compact">
8952 100 dpi fonts must be placed in
8953 <file>/usr/share/fonts/X11/100dpi/</file>.
8957 75 dpi fonts must be placed in
8958 <file>/usr/share/fonts/X11/75dpi/</file>.
8962 Character-cell fonts, cursor fonts, and other
8963 low-resolution fonts must be placed in
8964 <file>/usr/share/fonts/X11/misc/</file>.
8970 Type 1 fonts must be placed in
8971 <file>/usr/share/fonts/X11/Type1/</file>. If font
8972 metric files are available, they must be placed here
8977 Subdirectories of <file>/usr/share/fonts/X11/</file>
8978 other than those listed above must be neither
8979 created nor used. (The <file>PEX</file>, <file>CID</file>,
8980 <file>Speedo</file>, and <file>cyrillic</file> directories
8981 are excepted for historical reasons, but installation of
8982 files into these directories remains discouraged.)
8986 Font packages may, instead of placing files directly
8987 in the X font directories listed above, provide
8988 symbolic links in that font directory pointing to
8989 the files' actual location in the filesystem. Such
8990 a location must comply with the FHS.
8994 Font packages should not contain both 75dpi and
8995 100dpi versions of a font. If both are available,
8996 they should be provided in separate binary packages
8997 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8998 the names of the packages containing the
8999 corresponding fonts.
9003 Fonts destined for the <file>misc</file> subdirectory
9004 should not be included in the same package as 75dpi
9005 or 100dpi fonts; instead, they should be provided in
9006 a separate package with <tt>-misc</tt> appended to
9011 Font packages must not provide the files
9012 <file>fonts.dir</file>, <file>fonts.alias</file>, or
9013 <file>fonts.scale</file> in a font directory:
9016 <file>fonts.dir</file> files must not be provided at all.
9020 <file>fonts.alias</file> and <file>fonts.scale</file>
9021 files, if needed, should be provided in the
9023 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
9024 where <var>fontdir</var> is the name of the
9026 <file>/usr/share/fonts/X11/</file> where the
9027 package's corresponding fonts are stored
9028 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
9029 <var>package</var> is the name of the package
9030 that provides these fonts, and
9031 <var>extension</var> is either <tt>scale</tt>
9032 or <tt>alias</tt>, whichever corresponds to
9039 Font packages must declare a dependency on
9040 <tt>xfonts-utils</tt> in their <tt>Depends</tt>
9041 or <tt>Pre-Depends</tt> control field.
9045 Font packages that provide one or more
9046 <file>fonts.scale</file> files as described above must
9047 invoke <prgn>update-fonts-scale</prgn> on each
9048 directory into which they installed fonts
9049 <em>before</em> invoking
9050 <prgn>update-fonts-dir</prgn> on that directory.
9051 This invocation must occur in both the
9052 <prgn>postinst</prgn> (for all arguments) and
9053 <prgn>postrm</prgn> (for all arguments except
9054 <tt>upgrade</tt>) scripts.
9058 Font packages that provide one or more
9059 <file>fonts.alias</file> files as described above must
9060 invoke <prgn>update-fonts-alias</prgn> on each
9061 directory into which they installed fonts. This
9062 invocation must occur in both the
9063 <prgn>postinst</prgn> (for all arguments) and
9064 <prgn>postrm</prgn> (for all arguments except
9065 <tt>upgrade</tt>) scripts.
9069 Font packages must invoke
9070 <prgn>update-fonts-dir</prgn> on each directory into
9071 which they installed fonts. This invocation must
9072 occur in both the <prgn>postinst</prgn> (for all
9073 arguments) and <prgn>postrm</prgn> (for all
9074 arguments except <tt>upgrade</tt>) scripts.
9078 Font packages must not provide alias names for the
9079 fonts they include which collide with alias names
9080 already in use by fonts already packaged.
9084 Font packages must not provide fonts with the same
9085 XLFD registry name as another font already packaged.
9091 <sect1 id="appdefaults">
9092 <heading>Application defaults files</heading>
9095 Application defaults files must be installed in the
9096 directory <file>/etc/X11/app-defaults/</file> (use of a
9097 localized subdirectory of <file>/etc/X11/</file> as described
9098 in the <em>X Toolkit Intrinsics - C Language
9099 Interface</em> manual is also permitted). They must be
9100 registered as <tt>conffile</tt>s or handled as
9101 configuration files.
9105 Customization of programs' X resources may also be
9106 supported with the provision of a file with the same name
9107 as that of the package placed in
9108 the <file>/etc/X11/Xresources/</file> directory, which
9109 must be registered as a <tt>conffile</tt> or handled as a
9110 configuration file.<footnote>
9111 Note that this mechanism is not the same as using
9112 app-defaults; app-defaults are tied to the client
9113 binary on the local file system, whereas X resources
9114 are stored in the X server and affect all connecting
9121 <heading>Installation directory issues</heading>
9124 Historically, packages using the X Window System used a
9125 separate set of installation directories from other packages.
9126 This practice has been discontinued and packages using the X
9127 Window System should now generally be installed in the same
9128 directories as any other package. Specifically, packages must
9129 not install files under the <file>/usr/X11R6/</file> directory
9130 and the <file>/usr/X11R6/</file> directory hierarchy should be
9131 regarded as obsolete.
9135 Include files previously installed under
9136 <file>/usr/X11R6/include/X11/</file> should be installed into
9137 <file>/usr/include/X11/</file>. For files previously
9138 installed into subdirectories of
9139 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
9140 determine if subdirectories of <file>/usr/lib/</file> and
9141 <file>/usr/share/</file> can be used. If not, a subdirectory
9142 of <file>/usr/lib/X11/</file> should be used.
9146 Configuration files for window, display, or session managers
9147 or other applications that are tightly integrated with the X
9148 Window System may be placed in a subdirectory
9149 of <file>/etc/X11/</file> corresponding to the package name.
9150 Other X Window System applications should use
9151 the <file>/etc/</file> directory unless otherwise mandated by
9152 policy (such as for <ref id="appdefaults">).
9157 <heading>The OSF/Motif and OpenMotif libraries</heading>
9160 <em>Programs that require the non-DFSG-compliant OSF/Motif or
9161 OpenMotif libraries</em><footnote>
9162 OSF/Motif and OpenMotif are collectively referred to as
9163 "Motif" in this policy document.
9165 should be compiled against and tested with LessTif (a free
9166 re-implementation of Motif) instead. If the maintainer
9167 judges that the program or programs do not work
9168 sufficiently well with LessTif to be distributed and
9169 supported, but do so when compiled against Motif, then two
9170 versions of the package should be created; one linked
9171 statically against Motif and with <tt>-smotif</tt>
9172 appended to the package name, and one linked dynamically
9173 against Motif and with <tt>-dmotif</tt> appended to the
9178 Both Motif-linked versions are dependent
9179 upon non-DFSG-compliant software and thus cannot be
9180 uploaded to the <em>main</em> distribution; if the
9181 software is itself DFSG-compliant it may be uploaded to
9182 the <em>contrib</em> distribution. While known existing
9183 versions of Motif permit unlimited redistribution of
9184 binaries linked against the library (whether statically or
9185 dynamically), it is the package maintainer's
9186 responsibility to determine whether this is permitted by
9187 the license of the copy of Motif in their possession.
9193 <heading>Perl programs and modules</heading>
9196 Perl programs and modules should follow the current Perl policy.
9200 The Perl policy can be found in the <tt>perl-policy</tt>
9201 files in the <tt>debian-policy</tt> package.
9202 It is also available from the Debian web mirrors at
9203 <tt><url name="/doc/packaging-manuals/perl-policy/"
9204 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
9209 <heading>Emacs lisp programs</heading>
9212 Please refer to the "Debian Emacs Policy" for details of how to
9213 package emacs lisp programs.
9217 The Emacs policy is available in
9218 <file>debian-emacs-policy.gz</file> of the
9219 <package>emacsen-common</package> package.
9220 It is also available from the Debian web mirrors at
9221 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
9222 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
9227 <heading>Games</heading>
9230 The permissions on <file>/var/games</file> are mode 755, owner
9231 <tt>root</tt> and group <tt>root</tt>.
9235 Each game decides on its own security policy.</p>
9238 Games which require protected, privileged access to
9239 high-score files, saved games, etc., may be made
9240 set-<em>group</em>-id (mode 2755) and owned by
9241 <tt>root:games</tt>, and use files and directories with
9242 appropriate permissions (770 <tt>root:games</tt>, for
9243 example). They must not be made
9244 set-<em>user</em>-id, as this causes security problems. (If
9245 an attacker can subvert any set-user-id game they can
9246 overwrite the executable of any other, causing other players
9247 of these games to run a Trojan horse program. With a
9248 set-group-id game the attacker only gets access to less
9249 important game data, and if they can get at the other
9250 players' accounts at all it will take considerably more
9254 Some packages, for example some fortune cookie programs, are
9255 configured by the upstream authors to install with their
9256 data files or other static information made unreadable so
9257 that they can only be accessed through set-id programs
9258 provided. You should not do this in a Debian package: anyone can
9259 download the <file>.deb</file> file and read the data from it,
9260 so there is no point making the files unreadable. Not
9261 making the files unreadable also means that you don't have
9262 to make so many programs set-id, which reduces the risk of a
9266 As described in the FHS, binaries of games should be
9267 installed in the directory <file>/usr/games</file>. This also
9268 applies to games that use the X Window System. Manual pages
9269 for games (X and non-X games) should be installed in
9270 <file>/usr/share/man/man6</file>.</p>
9276 <heading>Documentation</heading>
9279 <heading>Manual pages</heading>
9282 You should install manual pages in <prgn>nroff</prgn> source
9283 form, in appropriate places under <file>/usr/share/man</file>.
9284 You should only use sections 1 to 9 (see the FHS for more
9285 details). You must not install a pre-formatted "cat page".
9289 Each program, utility, and function should have an
9290 associated manual page included in the same package. It is
9291 suggested that all configuration files also have a manual
9292 page included as well. Manual pages for protocols and other
9293 auxiliary things are optional.
9297 If no manual page is available, this is considered as a bug
9298 and should be reported to the Debian Bug Tracking System (the
9299 maintainer of the package is allowed to write this bug report
9300 themselves, if they so desire). Do not close the bug report
9301 until a proper man page is available.<footnote>
9302 It is not very hard to write a man page. See the
9303 <url id="http://www.schweikhardt.net/man_page_howto.html"
9304 name="Man-Page-HOWTO">,
9305 <manref name="man" section="7">, the examples
9306 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
9307 the helper program <prgn>help2man</prgn>, or the
9308 directory <file>/usr/share/doc/man-db/examples</file>.
9313 You may forward a complaint about a missing man page to the
9314 upstream authors, and mark the bug as forwarded in the
9315 Debian bug tracking system. Even though the GNU Project do
9316 not in general consider the lack of a man page to be a bug,
9317 we do; if they tell you that they don't consider it a bug
9318 you should leave the bug in our bug tracking system open
9323 Manual pages should be installed compressed using <tt>gzip -9</tt>.
9327 If one man page needs to be accessible via several names it
9328 is better to use a symbolic link than the <file>.so</file>
9329 feature, but there is no need to fiddle with the relevant
9330 parts of the upstream source to change from <file>.so</file> to
9331 symlinks: don't do it unless it's easy. You should not
9332 create hard links in the manual page directories, nor put
9333 absolute filenames in <file>.so</file> directives. The filename
9334 in a <file>.so</file> in a man page should be relative to the
9335 base of the man page tree (usually
9336 <file>/usr/share/man</file>). If you do not create any links
9337 (whether symlinks, hard links, or <tt>.so</tt> directives)
9338 in the file system to the alternate names of the man page,
9339 then you should not rely on <prgn>man</prgn> finding your
9340 man page under those names based solely on the information in
9341 the man page's header.<footnote>
9342 Supporting this in <prgn>man</prgn> often requires
9343 unreasonable processing time to find a manual page or to
9344 report that none exists, and moves knowledge into man's
9345 database that would be better left in the file system.
9346 This support is therefore deprecated and will cease to
9347 be present in the future.
9352 Manual pages in locale-specific subdirectories of
9353 <file>/usr/share/man</file> should use either UTF-8 or the usual
9354 legacy encoding for that language (normally the one corresponding
9355 to the shortest relevant locale name in
9356 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
9357 <file>/usr/share/man/fr</file> should use either UTF-8 or
9358 ISO-8859-1.<footnote>
9359 <prgn>man</prgn> will automatically detect whether UTF-8 is in
9360 use. In future, all manual pages will be required to use
9366 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
9367 included in the subdirectory name unless it indicates a
9368 significant difference in the language, as this excludes
9369 speakers of the language in other countries.<footnote>
9370 At the time of writing, Chinese and Portuguese are the main
9371 languages with such differences, so <file>pt_BR</file>,
9372 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
9377 If a localized version of a manual page is provided, it should
9378 either be up-to-date or it should be obvious to the reader that
9379 it is outdated and the original manual page should be used
9380 instead. This can be done either by a note at the beginning of
9381 the manual page or by showing the missing or changed portions in
9382 the original language instead of the target language.
9387 <heading>Info documents</heading>
9390 Info documents should be installed in <file>/usr/share/info</file>.
9391 They should be compressed with <tt>gzip -9</tt>.
9395 The <prgn>install-info</prgn> program maintains a directory of
9396 installed info documents in <file>/usr/share/info/dir</file> for
9397 the use of info readers.<footnote>
9398 It was previously necessary for packages installing info
9399 documents to run <prgn>install-info</prgn> from maintainer
9400 scripts. This is no longer necessary. The installation
9401 system now uses dpkg triggers.
9403 This file must not be included in packages. Packages containing
9404 info documents should depend on <tt>dpkg (>= 1.15.4) |
9405 install-info</tt> to ensure that the directory file is properly
9406 rebuilt during partial upgrades from Debian 5.0 (lenny) and
9411 Info documents should contain section and directory entry
9412 information in the document for the use
9413 of <prgn>install-info</prgn>. The section should be specified
9414 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
9415 space and the section of this info page. The directory entry or
9416 entries should be included between
9417 a <tt>START-INFO-DIR-ENTRY</tt> line and
9418 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
9420 INFO-DIR-SECTION Individual utilities
9421 START-INFO-DIR-ENTRY
9422 * example: (example). An example info directory entry.
9425 To determine which section to use, you should look
9426 at <file>/usr/share/info/dir</file> on your system and choose
9427 the most relevant (or create a new section if none of the
9428 current sections are relevant).<footnote>
9429 Normally, info documents are generated from Texinfo source.
9430 To include this information in the generated info document, if
9431 it is absent, add commands like:
9433 @dircategory Individual utilities
9435 * example: (example). An example info directory entry.
9438 to the Texinfo source of the document and ensure that the info
9439 documents are rebuilt from source during the package build.
9445 <heading>Additional documentation</heading>
9448 Any additional documentation that comes with the package may
9449 be installed at the discretion of the package maintainer.
9450 Plain text documentation should be installed in the directory
9451 <file>/usr/share/doc/<var>package</var></file>, where
9452 <var>package</var> is the name of the package, and
9453 compressed with <tt>gzip -9</tt> unless it is small.
9457 If a package comes with large amounts of documentation which
9458 many users of the package will not require you should create
9459 a separate binary package to contain it, so that it does not
9460 take up disk space on the machines of users who do not need
9461 or want it installed.</p>
9464 It is often a good idea to put text information files
9465 (<file>README</file>s, changelogs, and so forth) that come with
9466 the source package in <file>/usr/share/doc/<var>package</var></file>
9467 in the binary package. However, you don't need to install
9468 the instructions for building and installing the package, of
9472 Packages must not require the existence of any files in
9473 <file>/usr/share/doc/</file> in order to function
9475 The system administrator should be able to
9476 delete files in <file>/usr/share/doc/</file> without causing
9477 any programs to break.
9479 Any files that are referenced by programs but are also
9480 useful as stand alone documentation should be installed under
9481 <file>/usr/share/<var>package</var>/</file> with symbolic links from
9482 <file>/usr/share/doc/<var>package</var></file>.
9486 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9487 link to another directory in <file>/usr/share/doc</file> only if
9488 the two packages both come from the same source and the
9489 first package Depends on the second.<footnote>
9491 Please note that this does not override the section on
9492 changelog files below, so the file
9493 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
9494 must refer to the changelog for the current version of
9495 <var>package</var> in question. In practice, this means
9496 that the sources of the target and the destination of the
9497 symlink must be the same (same source package and
9504 Former Debian releases placed all additional documentation
9505 in <file>/usr/doc/<var>package</var></file>. This has been
9506 changed to <file>/usr/share/doc/<var>package</var></file>,
9507 and packages must not put documentation in the directory
9508 <file>/usr/doc/<var>package</var></file>. <footnote>
9509 At this phase of the transition, we no longer require a
9510 symbolic link in <file>/usr/doc/</file>. At a later point,
9511 policy shall change to make the symbolic links a bug.
9517 <heading>Preferred documentation formats</heading>
9520 The unification of Debian documentation is being carried out
9524 If your package comes with extensive documentation in a
9525 markup format that can be converted to various other formats
9526 you should if possible ship HTML versions in a binary
9527 package, in the directory
9528 <file>/usr/share/doc/<var>appropriate-package</var></file> or
9529 its subdirectories.<footnote>
9530 The rationale: The important thing here is that HTML
9531 docs should be available in <em>some</em> package, not
9532 necessarily in the main binary package.
9537 Other formats such as PostScript may be provided at the
9538 package maintainer's discretion.
9542 <sect id="copyrightfile">
9543 <heading>Copyright information</heading>
9546 Every package must be accompanied by a verbatim copy of its
9547 copyright information and distribution license in the file
9548 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
9549 file must neither be compressed nor be a symbolic link.
9553 In addition, the copyright file must say where the upstream
9554 sources (if any) were obtained. It should name the original
9555 authors of the package and the Debian maintainer(s) who were
9556 involved with its creation.
9560 Packages in the <em>contrib</em> or <em>non-free</em> archive
9561 areas should state in the copyright file that the package is not
9562 part of the Debian GNU/Linux distribution and briefly explain
9567 A copy of the file which will be installed in
9568 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9569 be in <file>debian/copyright</file> in the source package.
9573 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9574 link to another directory in <file>/usr/share/doc</file> only if
9575 the two packages both come from the same source and the
9576 first package Depends on the second. These rules are
9577 important because copyrights must be extractable by
9582 Packages distributed under the Apache license (version 2.0), the
9583 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
9584 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
9585 1.3) should refer to the corresponding files
9586 under <file>/usr/share/common-licenses</file>,<footnote>
9589 <file>/usr/share/common-licenses/Apache-2.0</file>,
9590 <file>/usr/share/common-licenses/Artistic</file>,
9591 <file>/usr/share/common-licenses/GPL-1</file>,
9592 <file>/usr/share/common-licenses/GPL-2</file>,
9593 <file>/usr/share/common-licenses/GPL-3</file>,
9594 <file>/usr/share/common-licenses/LGPL-2</file>,
9595 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9596 <file>/usr/share/common-licenses/LGPL-3</file>,
9597 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
9598 <file>/usr/share/common-licenses/GFDL-1.3</file>
9599 respectively. The University of California BSD license is
9600 also included in <package>base-files</package> as
9601 <file>/usr/share/common-licenses/BSD</file>, but given the
9602 brevity of this license, its specificity to code whose
9603 copyright is held by the Regents of the University of
9604 California, and the frequency of minor wording changes, its
9605 text should be included in the copyright file rather than
9606 referencing this file.
9608 </footnote> rather than quoting them in the copyright
9613 You should not use the copyright file as a general <file>README</file>
9614 file. If your package has such a file it should be
9615 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9616 <file>README.Debian</file> or some other appropriate place.</p>
9620 <heading>Examples</heading>
9623 Any examples (configurations, source files, whatever),
9624 should be installed in a directory
9625 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9626 files should not be referenced by any program: they're there
9627 for the benefit of the system administrator and users as
9628 documentation only. Architecture-specific example files
9629 should be installed in a directory
9630 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9632 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9633 latter directory itself may be a symbolic link to the
9638 If the purpose of a package is to provide examples, then the
9639 example files may be installed into
9640 <file>/usr/share/doc/<var>package</var></file>.
9644 <sect id="changelogs">
9645 <heading>Changelog files</heading>
9648 Packages that are not Debian-native must contain a
9649 compressed copy of the <file>debian/changelog</file> file from
9650 the Debian source tree in
9651 <file>/usr/share/doc/<var>package</var></file> with the name
9652 <file>changelog.Debian.gz</file>.
9656 If an upstream changelog is available, it should be accessible as
9657 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9658 plain text. If the upstream changelog is distributed in
9659 HTML, it should be made available in that form as
9660 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9661 and a plain text <file>changelog.gz</file> should be generated
9662 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9663 the upstream changelog files do not already conform to this
9664 naming convention, then this may be achieved either by
9665 renaming the files, or by adding a symbolic link, at the
9666 maintainer's discretion.<footnote>
9667 Rationale: People should not have to look in places for
9668 upstream changelogs merely because they are given
9669 different names or are distributed in HTML format.
9674 All of these files should be installed compressed using
9675 <tt>gzip -9</tt>, as they will become large with time even
9676 if they start out small.
9680 If the package has only one changelog which is used both as
9681 the Debian changelog and the upstream one because there is
9682 no separate upstream maintainer then that changelog should
9683 usually be installed as
9684 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9685 there is a separate upstream maintainer, but no upstream
9686 changelog, then the Debian changelog should still be called
9687 <file>changelog.Debian.gz</file>.
9691 For details about the format and contents of the Debian
9692 changelog file, please see <ref id="dpkgchangelog">.
9697 <appendix id="pkg-scope">
9698 <heading>Introduction and scope of these appendices</heading>
9701 These appendices are taken essentially verbatim from the
9702 now-deprecated Packaging Manual, version 3.2.1.0. They are
9703 the chapters which are likely to be of use to package
9704 maintainers and which have not already been included in the
9705 policy document itself. Most of these sections are very likely
9706 not relevant to policy; they should be treated as
9707 documentation for the packaging system. Please note that these
9708 appendices are included for convenience, and for historical
9709 reasons: they used to be part of policy package, and they have
9710 not yet been incorporated into dpkg documentation. However,
9711 they still have value, and hence they are presented here.
9715 They have not yet been checked to ensure that they are
9716 compatible with the contents of policy, and if there are any
9717 contradictions, the version in the main policy document takes
9718 precedence. The remaining chapters of the old Packaging
9719 Manual have also not been read in detail to ensure that there
9720 are not parts which have been left out. Both of these will be
9725 Certain parts of the Packaging manual were integrated into the
9726 Policy Manual proper, and removed from the appendices. Links
9727 have been placed from the old locations to the new ones.
9731 <prgn>dpkg</prgn> is a suite of programs for creating binary
9732 package files and installing and removing them on Unix
9734 <prgn>dpkg</prgn> is targeted primarily at Debian
9735 GNU/Linux, but may work on or be ported to other
9741 The binary packages are designed for the management of
9742 installed executable programs (usually compiled binaries) and
9743 their associated data, though source code examples and
9744 documentation are provided as part of some packages.</p>
9747 This manual describes the technical aspects of creating Debian
9748 binary packages (<file>.deb</file> files). It documents the
9749 behavior of the package management programs
9750 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9751 they interact with packages.</p>
9754 It also documents the interaction between
9755 <prgn>dselect</prgn>'s core and the access method scripts it
9756 uses to actually install the selected packages, and describes
9757 how to create a new access method.</p>
9760 This manual does not go into detail about the options and
9761 usage of the package building and installation tools. It
9762 should therefore be read in conjunction with those programs'
9767 The utility programs which are provided with <prgn>dpkg</prgn>
9768 for managing various system configuration and similar issues,
9769 such as <prgn>update-rc.d</prgn> and
9770 <prgn>install-info</prgn>, are not described in detail here -
9771 please see their man pages.
9775 It is assumed that the reader is reasonably familiar with the
9776 <prgn>dpkg</prgn> System Administrators' manual.
9777 Unfortunately this manual does not yet exist.
9781 The Debian version of the FSF's GNU hello program is provided
9782 as an example for people wishing to create Debian
9783 packages. The Debian <prgn>debmake</prgn> package is
9784 recommended as a very helpful tool in creating and maintaining
9785 Debian packages. However, while the tools and examples are
9786 helpful, they do not replace the need to read and follow the
9787 Policy and Programmer's Manual.</p>
9790 <appendix id="pkg-binarypkg">
9791 <heading>Binary packages (from old Packaging Manual)</heading>
9794 The binary package has two main sections. The first part
9795 consists of various control information files and scripts used
9796 by <prgn>dpkg</prgn> when installing and removing. See <ref
9797 id="pkg-controlarea">.
9801 The second part is an archive containing the files and
9802 directories to be installed.
9806 In the future binary packages may also contain other
9807 components, such as checksums and digital signatures. The
9808 format for the archive is described in full in the
9809 <file>deb(5)</file> man page.
9813 <sect id="pkg-bincreating"><heading>Creating package files -
9814 <prgn>dpkg-deb</prgn>
9818 All manipulation of binary package files is done by
9819 <prgn>dpkg-deb</prgn>; it's the only program that has
9820 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9821 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9822 will spot that the options requested are appropriate to
9823 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9828 In order to create a binary package you must make a
9829 directory tree which contains all the files and directories
9830 you want to have in the file system data part of the package.
9831 In Debian-format source packages this directory is usually
9832 <file>debian/tmp</file>, relative to the top of the package's
9837 They should have the locations (relative to the root of the
9838 directory tree you're constructing) ownerships and
9839 permissions which you want them to have on the system when
9844 With current versions of <prgn>dpkg</prgn> the uid/username
9845 and gid/groupname mappings for the users and groups being
9846 used should be the same on the system where the package is
9847 built and the one where it is installed.
9851 You need to add one special directory to the root of the
9852 miniature file system tree you're creating:
9853 <prgn>DEBIAN</prgn>. It should contain the control
9854 information files, notably the binary package control file
9855 (see <ref id="pkg-controlfile">).
9859 The <prgn>DEBIAN</prgn> directory will not appear in the
9860 file system archive of the package, and so won't be installed
9861 by <prgn>dpkg</prgn> when the package is installed.
9865 When you've prepared the package, you should invoke:
9867 dpkg --build <var>directory</var>
9872 This will build the package in
9873 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9874 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9875 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9880 See the man page <manref name="dpkg-deb" section="8"> for details of how
9881 to examine the contents of this newly-created file. You may find the
9882 output of following commands enlightening:
9884 dpkg-deb --info <var>filename</var>.deb
9885 dpkg-deb --contents <var>filename</var>.deb
9886 dpkg --contents <var>filename</var>.deb
9888 To view the copyright file for a package you could use this command:
9890 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
9895 <sect id="pkg-controlarea">
9896 <heading>Package control information files</heading>
9899 The control information portion of a binary package is a
9900 collection of files with names known to <prgn>dpkg</prgn>.
9901 It will treat the contents of these files specially - some
9902 of them contain information used by <prgn>dpkg</prgn> when
9903 installing or removing the package; others are scripts which
9904 the package maintainer wants <prgn>dpkg</prgn> to run.
9908 It is possible to put other files in the package control
9909 information file area, but this is not generally a good idea
9910 (though they will largely be ignored).
9914 Here is a brief list of the control information files supported
9915 by <prgn>dpkg</prgn> and a summary of what they're used for.
9920 <tag><tt>control</tt>
9923 This is the key description file used by
9924 <prgn>dpkg</prgn>. It specifies the package's name
9925 and version, gives its description for the user,
9926 states its relationships with other packages, and so
9927 forth. See <ref id="sourcecontrolfiles"> and
9928 <ref id="binarycontrolfiles">.
9932 It is usually generated automatically from information
9933 in the source package by the
9934 <prgn>dpkg-gencontrol</prgn> program, and with
9935 assistance from <prgn>dpkg-shlibdeps</prgn>.
9936 See <ref id="pkg-sourcetools">.
9940 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9945 These are executable files (usually scripts) which
9946 <prgn>dpkg</prgn> runs during installation, upgrade
9947 and removal of packages. They allow the package to
9948 deal with matters which are particular to that package
9949 or require more complicated processing than that
9950 provided by <prgn>dpkg</prgn>. Details of when and
9951 how they are called are in <ref id="maintainerscripts">.
9955 It is very important to make these scripts idempotent.
9956 See <ref id="idempotency">.
9960 The maintainer scripts are not guaranteed to run with a
9961 controlling terminal and may not be able to interact with
9962 the user. See <ref id="controllingterminal">.
9966 <tag><tt>conffiles</tt>
9969 This file contains a list of configuration files which
9970 are to be handled automatically by <prgn>dpkg</prgn>
9971 (see <ref id="pkg-conffiles">). Note that not necessarily
9972 every configuration file should be listed here.
9975 <tag><tt>shlibs</tt>
9978 This file contains a list of the shared libraries
9979 supplied by the package, with dependency details for
9980 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9981 when it determines what dependencies are required in a
9982 package control file. The <tt>shlibs</tt> file format
9983 is described on <ref id="shlibs">.
9988 <sect id="pkg-controlfile">
9989 <heading>The main control information file: <tt>control</tt></heading>
9992 The most important control information file used by
9993 <prgn>dpkg</prgn> when it installs a package is
9994 <tt>control</tt>. It contains all the package's "vital
9999 The binary package control files of packages built from
10000 Debian sources are made by a special tool,
10001 <prgn>dpkg-gencontrol</prgn>, which reads
10002 <file>debian/control</file> and <file>debian/changelog</file> to
10003 find the information it needs. See <ref id="pkg-sourcepkg"> for
10008 The fields in binary package control files are listed in
10009 <ref id="binarycontrolfiles">.
10013 A description of the syntax of control files and the purpose
10014 of the fields is available in <ref id="controlfields">.
10019 <heading>Time Stamps</heading>
10022 See <ref id="timestamps">.
10027 <appendix id="pkg-sourcepkg">
10028 <heading>Source packages (from old Packaging Manual) </heading>
10031 The Debian binary packages in the distribution are generated
10032 from Debian sources, which are in a special format to assist
10033 the easy and automatic building of binaries.
10036 <sect id="pkg-sourcetools">
10037 <heading>Tools for processing source packages</heading>
10040 Various tools are provided for manipulating source packages;
10041 they pack and unpack sources and help build of binary
10042 packages and help manage the distribution of new versions.
10046 They are introduced and typical uses described here; see
10047 <manref name="dpkg-source" section="1"> for full
10048 documentation about their arguments and operation.
10052 For examples of how to construct a Debian source package,
10053 and how to use those utilities that are used by Debian
10054 source packages, please see the <prgn>hello</prgn> example
10058 <sect1 id="pkg-dpkg-source">
10060 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
10065 This program is frequently used by hand, and is also
10066 called from package-independent automated building scripts
10067 such as <prgn>dpkg-buildpackage</prgn>.
10071 To unpack a package it is typically invoked with
10073 dpkg-source -x <var>.../path/to/filename</var>.dsc
10078 with the <file><var>filename</var>.tar.gz</file> and
10079 <file><var>filename</var>.diff.gz</file> (if applicable) in
10080 the same directory. It unpacks into
10081 <file><var>package</var>-<var>version</var></file>, and if
10083 <file><var>package</var>-<var>version</var>.orig</file>, in
10084 the current directory.
10088 To create a packed source archive it is typically invoked:
10090 dpkg-source -b <var>package</var>-<var>version</var>
10095 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
10096 <file>.diff.gz</file> (if appropriate) in the current
10097 directory. <prgn>dpkg-source</prgn> does not clean the
10098 source tree first - this must be done separately if it is
10103 See also <ref id="pkg-sourcearchives">.</p>
10107 <sect1 id="pkg-dpkg-buildpackage">
10109 <prgn>dpkg-buildpackage</prgn> - overall package-building
10114 <prgn>dpkg-buildpackage</prgn> is a script which invokes
10115 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
10116 targets <tt>clean</tt>, <tt>build</tt> and
10117 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
10118 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
10119 source and binary package upload.
10123 It is usually invoked by hand from the top level of the
10124 built or unbuilt source directory. It may be invoked with
10125 no arguments; useful arguments include:
10126 <taglist compact="compact">
10127 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
10130 Do not sign the <tt>.changes</tt> file or the
10131 source package <tt>.dsc</tt> file, respectively.</p>
10133 <tag><tt>-p<var>sign-command</var></tt></tag>
10136 Invoke <var>sign-command</var> instead of finding
10137 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
10138 <var>sign-command</var> must behave just like
10139 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
10141 <tag><tt>-r<var>root-command</var></tt></tag>
10144 When root privilege is required, invoke the command
10145 <var>root-command</var>. <var>root-command</var>
10146 should invoke its first argument as a command, from
10147 the <prgn>PATH</prgn> if necessary, and pass its
10148 second and subsequent arguments to the command it
10149 calls. If no <var>root-command</var> is supplied
10150 then <var>dpkg-buildpackage</var> will take no
10151 special action to gain root privilege, so that for
10152 most packages it will have to be invoked as root to
10155 <tag><tt>-b</tt>, <tt>-B</tt></tag>
10158 Two types of binary-only build and upload - see
10159 <manref name="dpkg-source" section="1">.
10166 <sect1 id="pkg-dpkg-gencontrol">
10168 <prgn>dpkg-gencontrol</prgn> - generates binary package
10173 This program is usually called from <file>debian/rules</file>
10174 (see <ref id="pkg-sourcetree">) in the top level of the source
10179 This is usually done just before the files and directories in the
10180 temporary directory tree where the package is being built have their
10181 permissions and ownerships set and the package is constructed using
10182 <prgn>dpkg-deb/</prgn>
10184 This is so that the control file which is produced has
10185 the right permissions
10190 <prgn>dpkg-gencontrol</prgn> must be called after all the
10191 files which are to go into the package have been placed in
10192 the temporary build directory, so that its calculation of
10193 the installed size of a package is correct.
10197 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
10198 be run after <prgn>dpkg-shlibdeps</prgn> so that the
10199 variable substitutions created by
10200 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
10205 For a package which generates only one binary package, and
10206 which builds it in <file>debian/tmp</file> relative to the top
10207 of the source package, it is usually sufficient to call
10208 <prgn>dpkg-gencontrol</prgn>.
10212 Sources which build several binaries will typically need
10215 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
10216 </example> The <tt>-P</tt> tells
10217 <prgn>dpkg-gencontrol</prgn> that the package is being
10218 built in a non-default directory, and the <tt>-p</tt>
10219 tells it which package's control file should be generated.
10223 <prgn>dpkg-gencontrol</prgn> also adds information to the
10224 list of files in <file>debian/files</file>, for the benefit of
10225 (for example) a future invocation of
10226 <prgn>dpkg-genchanges</prgn>.</p>
10229 <sect1 id="pkg-dpkg-shlibdeps">
10231 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
10236 This program is usually called from <file>debian/rules</file>
10237 just before <prgn>dpkg-gencontrol</prgn> (see <ref
10238 id="pkg-sourcetree">), in the top level of the source tree.
10242 Its arguments are executables and shared libraries
10245 They may be specified either in the locations in the
10246 source tree where they are created or in the locations
10247 in the temporary build tree where they are installed
10248 prior to binary package creation.
10250 </footnote> for which shared library dependencies should
10251 be included in the binary package's control file.
10255 If some of the found shared libraries should only
10256 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
10257 some warrant a <tt>Pre-Depends</tt>, this can be achieved
10258 by using the <tt>-d<var>dependency-field</var></tt> option
10259 before those executable(s). (Each <tt>-d</tt> option
10260 takes effect until the next <tt>-d</tt>.)
10264 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
10265 output control file to be modified. Instead by default it
10266 adds to the <file>debian/substvars</file> file variable
10267 settings like <tt>shlibs:Depends</tt>. These variable
10268 settings must be referenced in dependency fields in the
10269 appropriate per-binary-package sections of the source
10274 For example, a package that generates an essential part
10275 which requires dependencies, and optional parts that
10276 which only require a recommendation, would separate those
10277 two sets of dependencies into two different fields.<footnote>
10278 At the time of writing, an example for this was the
10279 <package/xmms/ package, with Depends used for the xmms
10280 executable, Recommends for the plug-ins and Suggests for
10281 even more optional features provided by unzip.
10283 It can say in its <file>debian/rules</file>:
10285 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
10286 -dRecommends <var>optionalpart anotheroptionalpart</var>
10288 and then in its main control file <file>debian/control</file>:
10291 Depends: ${shlibs:Depends}
10292 Recommends: ${shlibs:Recommends}
10298 Sources which produce several binary packages with
10299 different shared library dependency requirements can use
10300 the <tt>-p<var>varnameprefix</var></tt> option to override
10301 the default <tt>shlibs:</tt> prefix (one invocation of
10302 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
10303 They can thus produce several sets of dependency
10304 variables, each of the form
10305 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
10306 which can be referred to in the appropriate parts of the
10307 binary package control files.
10312 <sect1 id="pkg-dpkg-distaddfile">
10314 <prgn>dpkg-distaddfile</prgn> - adds a file to
10315 <file>debian/files</file>
10319 Some packages' uploads need to include files other than
10320 the source and binary package files.
10324 <prgn>dpkg-distaddfile</prgn> adds a file to the
10325 <file>debian/files</file> file so that it will be included in
10326 the <file>.changes</file> file when
10327 <prgn>dpkg-genchanges</prgn> is run.
10331 It is usually invoked from the <tt>binary</tt> target of
10332 <file>debian/rules</file>:
10334 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
10336 The <var>filename</var> is relative to the directory where
10337 <prgn>dpkg-genchanges</prgn> will expect to find it - this
10338 is usually the directory above the top level of the source
10339 tree. The <file>debian/rules</file> target should put the
10340 file there just before or just after calling
10341 <prgn>dpkg-distaddfile</prgn>.
10345 The <var>section</var> and <var>priority</var> are passed
10346 unchanged into the resulting <file>.changes</file> file.
10351 <sect1 id="pkg-dpkg-genchanges">
10353 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
10354 upload control file
10358 This program is usually called by package-independent
10359 automatic building scripts such as
10360 <prgn>dpkg-buildpackage</prgn>, but it may also be called
10365 It is usually called in the top level of a built source
10366 tree, and when invoked with no arguments will print out a
10367 straightforward <file>.changes</file> file based on the
10368 information in the source package's changelog and control
10369 file and the binary and source packages which should have
10375 <sect1 id="pkg-dpkg-parsechangelog">
10377 <prgn>dpkg-parsechangelog</prgn> - produces parsed
10378 representation of a changelog
10382 This program is used internally by
10383 <prgn>dpkg-source</prgn> et al. It may also occasionally
10384 be useful in <file>debian/rules</file> and elsewhere. It
10385 parses a changelog, <file>debian/changelog</file> by default,
10386 and prints a control-file format representation of the
10387 information in it to standard output.
10391 <sect1 id="pkg-dpkg-architecture">
10393 <prgn>dpkg-architecture</prgn> - information about the build and
10398 This program can be used manually, but is also invoked by
10399 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
10400 environment or make variables which specify the build and host
10401 architecture for the package building process.
10406 <sect id="pkg-sourcetree">
10407 <heading>The Debian package source tree</heading>
10410 The source archive scheme described later is intended to
10411 allow a Debian package source tree with some associated
10412 control information to be reproduced and transported easily.
10413 The Debian package source tree is a version of the original
10414 program with certain files added for the benefit of the
10415 packaging process, and with any other changes required
10416 made to the rest of the source code and installation
10421 The extra files created for Debian are in the subdirectory
10422 <file>debian</file> of the top level of the Debian package
10423 source tree. They are described below.
10426 <sect1 id="pkg-debianrules">
10427 <heading><file>debian/rules</file> - the main building script</heading>
10430 See <ref id="debianrules">.
10434 <sect1 id="pkg-srcsubstvars">
10435 <heading><file>debian/substvars</file> and variable substitutions</heading>
10438 See <ref id="substvars">.
10444 <heading><file>debian/files</file></heading>
10447 See <ref id="debianfiles">.
10451 <sect1><heading><file>debian/tmp</file>
10455 This is the canonical temporary location for the
10456 construction of binary packages by the <tt>binary</tt>
10457 target. The directory <file>tmp</file> serves as the root of
10458 the file system tree as it is being constructed (for
10459 example, by using the package's upstream makefiles install
10460 targets and redirecting the output there), and it also
10461 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10462 id="pkg-bincreating">.
10466 If several binary packages are generated from the same
10467 source tree it is usual to use several
10468 <file>debian/tmp<var>something</var></file> directories, for
10469 example <file>tmp-a</file> or <file>tmp-doc</file>.
10473 Whatever <file>tmp</file> directories are created and used by
10474 <tt>binary</tt> must of course be removed by the
10475 <tt>clean</tt> target.</p></sect1>
10479 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10483 As it exists on the FTP site, a Debian source package
10484 consists of three related files. You must have the right
10485 versions of all three to be able to use them.
10490 <tag>Debian source control file - <tt>.dsc</tt></tag>
10492 This file is a control file used by <prgn>dpkg-source</prgn>
10493 to extract a source package.
10494 See <ref id="debiansourcecontrolfiles">.
10498 Original source archive -
10500 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10506 This is a compressed (with <tt>gzip -9</tt>)
10507 <prgn>tar</prgn> file containing the source code from
10508 the upstream authors of the program.
10513 Debian package diff -
10515 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10521 This is a unified context diff (<tt>diff -u</tt>)
10522 giving the changes which are required to turn the
10523 original source into the Debian source. These changes
10524 may only include editing and creating plain files.
10525 The permissions of files, the targets of symbolic
10526 links and the characteristics of special files or
10527 pipes may not be changed and no files may be removed
10532 All the directories in the diff must exist, except the
10533 <file>debian</file> subdirectory of the top of the source
10534 tree, which will be created by
10535 <prgn>dpkg-source</prgn> if necessary when unpacking.
10539 The <prgn>dpkg-source</prgn> program will
10540 automatically make the <file>debian/rules</file> file
10541 executable (see below).</p></item>
10546 If there is no original source code - for example, if the
10547 package is specially prepared for Debian or the Debian
10548 maintainer is the same as the upstream maintainer - the
10549 format is slightly different: then there is no diff, and the
10551 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10552 and preferably contains a directory named
10553 <file><var>package</var>-<var>version</var></file>.
10558 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10561 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10562 Debian source package. However, if it is not available it
10563 is possible to unpack a Debian source archive as follows:
10564 <enumlist compact="compact">
10567 Untar the tarfile, which will create a <file>.orig</file>
10571 <p>Rename the <file>.orig</file> directory to
10572 <file><var>package</var>-<var>version</var></file>.</p>
10576 Create the subdirectory <file>debian</file> at the top of
10577 the source tree.</p>
10579 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10581 <item><p>Untar the tarfile again if you want a copy of the original
10582 source code alongside the Debian version.</p>
10587 It is not possible to generate a valid Debian source archive
10588 without using <prgn>dpkg-source</prgn>. In particular,
10589 attempting to use <prgn>diff</prgn> directly to generate the
10590 <file>.diff.gz</file> file will not work.
10594 <heading>Restrictions on objects in source packages</heading>
10597 The source package may not contain any hard links
10599 This is not currently detected when building source
10600 packages, but only when extracting
10604 Hard links may be permitted at some point in the
10605 future, but would require a fair amount of
10607 </footnote>, device special files, sockets or setuid or
10610 Setgid directories are allowed.
10615 The source packaging tools manage the changes between the
10616 original and Debian source using <prgn>diff</prgn> and
10617 <prgn>patch</prgn>. Turning the original source tree as
10618 included in the <file>.orig.tar.gz</file> into the Debian
10619 package source must not involve any changes which cannot be
10620 handled by these tools. Problematic changes which cause
10621 <prgn>dpkg-source</prgn> to halt with an error when
10622 building the source package are:
10623 <list compact="compact">
10624 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10626 <item><p>Changing the targets of symbolic links.</p>
10628 <item><p>Creating directories, other than <file>debian</file>.</p>
10630 <item><p>Changes to the contents of binary files.</p></item>
10631 </list> Changes which cause <prgn>dpkg-source</prgn> to
10632 print a warning but continue anyway are:
10633 <list compact="compact">
10636 Removing files, directories or symlinks.
10638 Renaming a file is not treated specially - it is
10639 seen as the removal of the old file (which
10640 generates a warning, but is otherwise ignored),
10641 and the creation of the new one.
10647 Changed text files which are missing the usual final
10648 newline (either in the original or the modified
10653 Changes which are not represented, but which are not detected by
10654 <prgn>dpkg-source</prgn>, are:
10655 <list compact="compact">
10656 <item><p>Changing the permissions of files (other than
10657 <file>debian/rules</file>) and directories.</p></item>
10662 The <file>debian</file> directory and <file>debian/rules</file>
10663 are handled specially by <prgn>dpkg-source</prgn> - before
10664 applying the changes it will create the <file>debian</file>
10665 directory, and afterwards it will make
10666 <file>debian/rules</file> world-executable.
10672 <appendix id="pkg-controlfields">
10673 <heading>Control files and their fields (from old Packaging Manual)</heading>
10676 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10677 data in a common format, known as control files. Binary and
10678 source packages have control data as do the <file>.changes</file>
10679 files which control the installation of uploaded files, and
10680 <prgn>dpkg</prgn>'s internal databases are in a similar
10685 <heading>Syntax of control files</heading>
10688 See <ref id="controlsyntax">.
10692 It is important to note that there are several fields which
10693 are optional as far as <prgn>dpkg</prgn> and the related
10694 tools are concerned, but which must appear in every Debian
10695 package, or whose omission may cause problems.
10700 <heading>List of fields</heading>
10703 See <ref id="controlfieldslist">.
10707 This section now contains only the fields that didn't belong
10708 to the Policy manual.
10711 <sect1 id="pkg-f-Filename">
10712 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10715 These fields in <tt>Packages</tt> files give the
10716 filename(s) of (the parts of) a package in the
10717 distribution directories, relative to the root of the
10718 Debian hierarchy. If the package has been split into
10719 several parts the parts are all listed in order, separated
10724 <sect1 id="pkg-f-Size">
10725 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10728 These fields in <file>Packages</file> files give the size (in
10729 bytes, expressed in decimal) and MD5 checksum of the
10730 file(s) which make(s) up a binary package in the
10731 distribution. If the package is split into several parts
10732 the values for the parts are listed in order, separated by
10737 <sect1 id="pkg-f-Status">
10738 <heading><tt>Status</tt></heading>
10741 This field in <prgn>dpkg</prgn>'s status file records
10742 whether the user wants a package installed, removed or
10743 left alone, whether it is broken (requiring
10744 re-installation) or not and what its current state on the
10745 system is. Each of these pieces of information is a
10750 <sect1 id="pkg-f-Config-Version">
10751 <heading><tt>Config-Version</tt></heading>
10754 If a package is not installed or not configured, this
10755 field in <prgn>dpkg</prgn>'s status file records the last
10756 version of the package which was successfully
10761 <sect1 id="pkg-f-Conffiles">
10762 <heading><tt>Conffiles</tt></heading>
10765 This field in <prgn>dpkg</prgn>'s status file contains
10766 information about the automatically-managed configuration
10767 files held by a package. This field should <em>not</em>
10768 appear anywhere in a package!
10773 <heading>Obsolete fields</heading>
10776 These are still recognized by <prgn>dpkg</prgn> but should
10777 not appear anywhere any more.
10779 <taglist compact="compact">
10781 <tag><tt>Revision</tt></tag>
10782 <tag><tt>Package-Revision</tt></tag>
10783 <tag><tt>Package_Revision</tt></tag>
10785 The Debian revision part of the package version was
10786 at one point in a separate control field. This
10787 field went through several names.
10790 <tag><tt>Recommended</tt></tag>
10791 <item>Old name for <tt>Recommends</tt>.</item>
10793 <tag><tt>Optional</tt></tag>
10794 <item>Old name for <tt>Suggests</tt>.</item>
10796 <tag><tt>Class</tt></tag>
10797 <item>Old name for <tt>Priority</tt>.</item>
10806 <appendix id="pkg-conffiles">
10807 <heading>Configuration file handling (from old Packaging Manual)</heading>
10810 <prgn>dpkg</prgn> can do a certain amount of automatic
10811 handling of package configuration files.
10815 Whether this mechanism is appropriate depends on a number of
10816 factors, but basically there are two approaches to any
10817 particular configuration file.
10821 The easy method is to ship a best-effort configuration in the
10822 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10823 handle updates. If the user is unlikely to want to edit the
10824 file, but you need them to be able to without losing their
10825 changes, and a new package with a changed version of the file
10826 is only released infrequently, this is a good approach.
10830 The hard method is to build the configuration file from
10831 scratch in the <prgn>postinst</prgn> script, and to take the
10832 responsibility for fixing any mistakes made in earlier
10833 versions of the package automatically. This will be
10834 appropriate if the file is likely to need to be different on
10838 <sect><heading>Automatic handling of configuration files by
10843 A package may contain a control information file called
10844 <tt>conffiles</tt>. This file should be a list of filenames
10845 of configuration files needing automatic handling, separated
10846 by newlines. The filenames should be absolute pathnames,
10847 and the files referred to should actually exist in the
10852 When a package is upgraded <prgn>dpkg</prgn> will process
10853 the configuration files during the configuration stage,
10854 shortly before it runs the package's <prgn>postinst</prgn>
10859 For each file it checks to see whether the version of the
10860 file included in the package is the same as the one that was
10861 included in the last version of the package (the one that is
10862 being upgraded from); it also compares the version currently
10863 installed on the system with the one shipped with the last
10868 If neither the user nor the package maintainer has changed
10869 the file, it is left alone. If one or the other has changed
10870 their version, then the changed version is preferred - i.e.,
10871 if the user edits their file, but the package maintainer
10872 doesn't ship a different version, the user's changes will
10873 stay, silently, but if the maintainer ships a new version
10874 and the user hasn't edited it the new version will be
10875 installed (with an informative message). If both have
10876 changed their version the user is prompted about the problem
10877 and must resolve the differences themselves.
10881 The comparisons are done by calculating the MD5 message
10882 digests of the files, and storing the MD5 of the file as it
10883 was included in the most recent version of the package.
10887 When a package is installed for the first time
10888 <prgn>dpkg</prgn> will install the file that comes with it,
10889 unless that would mean overwriting a file already on the
10894 However, note that <prgn>dpkg</prgn> will <em>not</em>
10895 replace a conffile that was removed by the user (or by a
10896 script). This is necessary because with some programs a
10897 missing file produces an effect hard or impossible to
10898 achieve in another way, so that a missing file needs to be
10899 kept that way if the user did it.
10903 Note that a package should <em>not</em> modify a
10904 <prgn>dpkg</prgn>-handled conffile in its maintainer
10905 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10906 the user confusing and possibly dangerous options for
10907 conffile update when the package is upgraded.</p>
10910 <sect><heading>Fully-featured maintainer script configuration
10915 For files which contain site-specific information such as
10916 the hostname and networking details and so forth, it is
10917 better to create the file in the package's
10918 <prgn>postinst</prgn> script.
10922 This will typically involve examining the state of the rest
10923 of the system to determine values and other information, and
10924 may involve prompting the user for some information which
10925 can't be obtained some other way.
10929 When using this method there are a couple of important
10930 issues which should be considered:
10934 If you discover a bug in the program which generates the
10935 configuration file, or if the format of the file changes
10936 from one version to the next, you will have to arrange for
10937 the postinst script to do something sensible - usually this
10938 will mean editing the installed configuration file to remove
10939 the problem or change the syntax. You will have to do this
10940 very carefully, since the user may have changed the file,
10941 perhaps to fix the very problem that your script is trying
10942 to deal with - you will have to detect these situations and
10943 deal with them correctly.
10947 If you do go down this route it's probably a good idea to
10948 make the program that generates the configuration file(s) a
10949 separate program in <file>/usr/sbin</file>, by convention called
10950 <file><var>package</var>config</file> and then run that if
10951 appropriate from the post-installation script. The
10952 <tt><var>package</var>config</tt> program should not
10953 unquestioningly overwrite an existing configuration - if its
10954 mode of operation is geared towards setting up a package for
10955 the first time (rather than any arbitrary reconfiguration
10956 later) you should have it check whether the configuration
10957 already exists, and require a <tt>--force</tt> flag to
10958 overwrite it.</p></sect>
10961 <appendix id="pkg-alternatives"><heading>Alternative versions of
10962 an interface - <prgn>update-alternatives</prgn> (from old
10967 When several packages all provide different versions of the
10968 same program or file it is useful to have the system select a
10969 default, but to allow the system administrator to change it
10970 and have their decisions respected.
10974 For example, there are several versions of the <prgn>vi</prgn>
10975 editor, and there is no reason to prevent all of them from
10976 being installed at once, each under their own name
10977 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10978 Nevertheless it is desirable to have the name <tt>vi</tt>
10979 refer to something, at least by default.
10983 If all the packages involved cooperate, this can be done with
10984 <prgn>update-alternatives</prgn>.
10988 Each package provides its own version under its own name, and
10989 calls <prgn>update-alternatives</prgn> in its postinst to
10990 register its version (and again in its prerm to deregister
10995 See the man page <manref name="update-alternatives"
10996 section="8"> for details.
11000 If <prgn>update-alternatives</prgn> does not seem appropriate
11001 you may wish to consider using diversions instead.</p>
11004 <appendix id="pkg-diversions"><heading>Diversions - overriding a
11005 package's version of a file (from old Packaging Manual)
11009 It is possible to have <prgn>dpkg</prgn> not overwrite a file
11010 when it reinstalls the package it belongs to, and to have it
11011 put the file from the package somewhere else instead.
11015 This can be used locally to override a package's version of a
11016 file, or by one package to override another's version (or
11017 provide a wrapper for it).
11021 Before deciding to use a diversion, read <ref
11022 id="pkg-alternatives"> to see if you really want a diversion
11023 rather than several alternative versions of a program.
11027 There is a diversion list, which is read by <prgn>dpkg</prgn>,
11028 and updated by a special program <prgn>dpkg-divert</prgn>.
11029 Please see <manref name="dpkg-divert" section="8"> for full
11030 details of its operation.
11034 When a package wishes to divert a file from another, it should
11035 call <prgn>dpkg-divert</prgn> in its preinst to add the
11036 diversion and rename the existing file. For example,
11037 supposing that a <prgn>smailwrapper</prgn> package wishes to
11038 install a wrapper around <file>/usr/sbin/smail</file>:
11040 dpkg-divert --package smailwrapper --add --rename \
11041 --divert /usr/sbin/smail.real /usr/sbin/smail
11042 </example> The <tt>--package smailwrapper</tt> ensures that
11043 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
11044 can bypass the diversion and get installed as the true version.
11045 It's safe to add the diversion unconditionally on upgrades since
11046 it will be left unchanged if it already exists, but
11047 <prgn>dpkg-divert</prgn> will display a message. To suppress that
11048 message, make the command conditional on the version from which
11049 the package is being upgraded:
11051 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
11052 dpkg-divert --package smailwrapper --add --rename \
11053 --divert /usr/sbin/smail.real /usr/sbin/smail
11055 </example> where <tt>1.0-2</tt> is the version at which the
11056 diversion was first added to the package. Running the command
11057 during abort-upgrade is pointless but harmless.
11061 The postrm has to do the reverse:
11063 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
11064 dpkg-divert --package smailwrapper --remove --rename \
11065 --divert /usr/sbin/smail.real /usr/sbin/smail
11067 </example> If the diversion was added at a particular version, the
11068 postrm should also handle the failure case of upgrading from an
11069 older version (unless the older version is so old that direct
11070 upgrades are no longer supported):
11072 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
11073 dpkg-divert --package smailwrapper --remove --rename \
11074 --divert /usr/sbin/smail.real /usr/sbin/smail
11076 </example> where <tt>1.02-2</tt> is the version at which the
11077 diversion was first added to the package. The postrm should not
11078 remove the diversion on upgrades both because there's no reason to
11079 remove the diversion only to immediately re-add it and since the
11080 postrm of the old package is run after unpacking so the removal of
11081 the diversion will fail.
11085 Do not attempt to divert a file which is vitally important for
11086 the system's operation - when using <prgn>dpkg-divert</prgn>
11087 there is a time, after it has been diverted but before
11088 <prgn>dpkg</prgn> has installed the new version, when the file
11089 does not exist.</p>
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