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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 The following targets are required and must be implemented
1831 by <file>debian/rules</file>: <tt>clean</tt>, <tt>binary</tt>,
1832 <tt>binary-arch</tt>, <tt>binary-indep</tt>, and <tt>build</tt>.
1833 These are the targets called by <prgn>dpkg-buildpackage</prgn>.
1837 Since an interactive <file>debian/rules</file> script makes it
1838 impossible to auto-compile that package and also makes it hard
1839 for other people to reproduce the same binary package, all
1840 required targets must be non-interactive. It also follows that
1841 any target that these targets depend on must also be
1846 The targets are as follows:
1848 <tag><tt>build</tt> (required)</tag>
1851 The <tt>build</tt> target should perform all the
1852 configuration and compilation of the package.
1853 If a package has an interactive pre-build
1854 configuration routine, the Debian source package
1855 must either be built after this has taken place (so
1856 that the binary package can be built without rerunning
1857 the configuration) or the configuration routine
1858 modified to become non-interactive. (The latter is
1859 preferable if there are architecture-specific features
1860 detected by the configuration routine.)
1864 For some packages, notably ones where the same
1865 source tree is compiled in different ways to produce
1866 two binary packages, the <tt>build</tt> target
1867 does not make much sense. For these packages it is
1868 good enough to provide two (or more) targets
1869 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1870 for each of the ways of building the package, and a
1871 <tt>build</tt> target that does nothing. The
1872 <tt>binary</tt> target will have to build the
1873 package in each of the possible ways and make the
1874 binary package out of each.
1878 The <tt>build</tt> target must not do anything
1879 that might require root privilege.
1883 The <tt>build</tt> target may need to run the
1884 <tt>clean</tt> target first - see below.
1888 When a package has a configuration and build routine
1889 which takes a long time, or when the makefiles are
1890 poorly designed, or when <tt>build</tt> needs to
1891 run <tt>clean</tt> first, it is a good idea to
1892 <tt>touch build</tt> when the build process is
1893 complete. This will ensure that if <tt>debian/rules
1894 build</tt> is run again it will not rebuild the whole
1896 Another common way to do this is for <tt>build</tt>
1897 to depend on <prgn>build-stamp</prgn> and to do
1898 nothing else, and for the <prgn>build-stamp</prgn>
1899 target to do the building and to <tt>touch
1900 build-stamp</tt> on completion. This is
1901 especially useful if the build routine creates a
1902 file or directory called <tt>build</tt>; in such a
1903 case, <tt>build</tt> will need to be listed as
1904 a phony target (i.e., as a dependency of the
1905 <tt>.PHONY</tt> target). See the documentation of
1906 <prgn>make</prgn> for more information on phony
1912 <tag><tt>build-arch</tt> (optional),
1913 <tt>build-indep</tt> (optional)
1917 A package may also provide both of the targets
1918 <tt>build-arch</tt> and <tt>build-indep</tt>.
1919 The <tt>build-arch</tt> target, if provided, should
1920 perform all the configuration and compilation required for
1921 producing all architecture-dependant binary packages
1922 (those packages for which the body of the
1923 <tt>Architecture</tt> field in <tt>debian/control</tt> is
1924 not <tt>all</tt>). Similarly, the <tt>build-indep</tt>
1925 target, if provided, should perform all the configuration
1926 and compilation required for producing all
1927 architecture-independent binary packages (those packages
1928 for which the body of the <tt>Architecture</tt> field
1929 in <tt>debian/control</tt> is <tt>all</tt>).
1930 The <tt>build</tt> target should depend on those of the
1931 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1932 are provided in the rules file.<footnote>
1933 The intent of this split is so that binary-only builds
1934 need not install the dependencies required for
1935 the <tt>build-indep</tt> target. However, this is not
1936 yet used in practice since <tt>dpkg-buildpackage
1937 -B</tt>, and therefore the autobuilders,
1938 invoke <tt>build</tt> rather than <tt>build-arch</tt>
1939 due to the difficulties in determining whether the
1940 optional <tt>build-arch</tt> target exists.
1945 If one or both of the targets <tt>build-arch</tt> and
1946 <tt>build-indep</tt> are not provided, then invoking
1947 <file>debian/rules</file> with one of the not-provided
1948 targets as arguments should produce a exit status code
1949 of 2. Usually this is provided automatically by make
1950 if the target is missing.
1954 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1955 must not do anything that might require root privilege.
1959 <tag><tt>binary</tt> (required), <tt>binary-arch</tt>
1960 (required), <tt>binary-indep</tt> (required)
1964 The <tt>binary</tt> target must be all that is
1965 necessary for the user to build the binary package(s)
1966 produced from this source package. It is
1967 split into two parts: <prgn>binary-arch</prgn> builds
1968 the binary packages which are specific to a particular
1969 architecture, and <tt>binary-indep</tt> builds
1970 those which are not.
1973 <tt>binary</tt> may be (and commonly is) a target with
1974 no commands which simply depends on
1975 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1978 Both <tt>binary-*</tt> targets should depend on the
1979 <tt>build</tt> target, or on the appropriate
1980 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1981 provided, so that the package is built if it has not
1982 been already. It should then create the relevant
1983 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1984 make their control files and <prgn>dpkg-deb</prgn> to
1985 build them and place them in the parent of the top
1990 Both the <tt>binary-arch</tt> and
1991 <tt>binary-indep</tt> targets <em>must</em> exist.
1992 If one of them has nothing to do (which will always be
1993 the case if the source generates only a single binary
1994 package, whether architecture-dependent or not), it
1995 must still exist and must always succeed.
1999 The <tt>binary</tt> targets must be invoked as
2001 The <prgn>fakeroot</prgn> package often allows one
2002 to build a package correctly even without being
2008 <tag><tt>clean</tt> (required)</tag>
2011 This must undo any effects that the <tt>build</tt>
2012 and <tt>binary</tt> targets may have had, except
2013 that it should leave alone any output files created in
2014 the parent directory by a run of a <tt>binary</tt>
2019 If a <tt>build</tt> file is touched at the end of
2020 the <tt>build</tt> target, as suggested above, it
2021 should be removed as the first action that
2022 <tt>clean</tt> performs, so that running
2023 <tt>build</tt> again after an interrupted
2024 <tt>clean</tt> doesn't think that everything is
2029 The <tt>clean</tt> target may need to be
2030 invoked as root if <tt>binary</tt> has been
2031 invoked since the last <tt>clean</tt>, or if
2032 <tt>build</tt> has been invoked as root (since
2033 <tt>build</tt> may create directories, for
2038 <tag><tt>get-orig-source</tt> (optional)</tag>
2041 This target fetches the most recent version of the
2042 original source package from a canonical archive site
2043 (via FTP or WWW, for example), does any necessary
2044 rearrangement to turn it into the original source
2045 tar file format described below, and leaves it in the
2050 This target may be invoked in any directory, and
2051 should take care to clean up any temporary files it
2056 This target is optional, but providing it if
2057 possible is a good idea.
2061 <tag><tt>patch</tt> (optional)</tag>
2064 This target performs whatever additional actions are
2065 required to make the source ready for editing (unpacking
2066 additional upstream archives, applying patches, etc.).
2067 It is recommended to be implemented for any package where
2068 <tt>dpkg-source -x</tt> does not result in source ready
2069 for additional modification. See
2070 <ref id="readmesource">.
2076 The <tt>build</tt>, <tt>binary</tt> and
2077 <tt>clean</tt> targets must be invoked with the current
2078 directory being the package's top-level directory.
2083 Additional targets may exist in <file>debian/rules</file>,
2084 either as published or undocumented interfaces or for the
2085 package's internal use.
2089 The architectures we build on and build for are determined
2090 by <prgn>make</prgn> variables using the
2091 utility <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
2092 You can determine the Debian architecture and the GNU style
2093 architecture specification string for the build architecture as
2094 well as for the host architecture. The build architecture is
2095 the architecture on which <file>debian/rules</file> is run and
2096 the package build is performed. The host architecture is the
2097 architecture on which the resulting package will be installed
2098 and run. These are normally the same, but may be different in
2099 the case of cross-compilation (building packages for one
2100 architecture on machines of a different architecture).
2104 Here is a list of supported <prgn>make</prgn> variables:
2105 <list compact="compact">
2107 <tt>DEB_*_ARCH</tt> (the Debian architecture)
2110 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2113 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2116 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2117 specification string)
2120 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2121 <tt>DEB_*_GNU_TYPE</tt>)
2124 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2125 <tt>DEB_*_GNU_TYPE</tt>)
2127 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2128 the build architecture or <tt>HOST</tt> for specification of the
2133 Backward compatibility can be provided in the rules file
2134 by setting the needed variables to suitable default
2135 values; please refer to the documentation of
2136 <prgn>dpkg-architecture</prgn> for details.
2140 It is important to understand that the <tt>DEB_*_ARCH</tt>
2141 string only determines which Debian architecture we are
2142 building on or for. It should not be used to get the CPU
2143 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2144 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2145 GNU style variables should generally only be used with upstream
2149 <sect1 id="debianrules-options">
2150 <heading><file>debian/rules</file> and
2151 <tt>DEB_BUILD_OPTIONS</tt></heading>
2154 Supporting the standardized environment variable
2155 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2156 contain several flags to change how a package is compiled and
2157 built. Each flag must be in the form <var>flag</var> or
2158 <var>flag</var>=<var>options</var>. If multiple flags are
2159 given, they must be separated by whitespace.<footnote>
2160 Some packages support any delimiter, but whitespace is the
2161 easiest to parse inside a makefile and avoids ambiguity with
2162 flag values that contain commas.
2164 <var>flag</var> must start with a lowercase letter
2165 (<tt>a-z</tt>) and consist only of lowercase letters,
2166 numbers (<tt>0-9</tt>), and the characters
2167 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2168 <var>options</var> must not contain whitespace. The same
2169 tag should not be given multiple times with conflicting
2170 values. Package maintainers may assume that
2171 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2175 The meaning of the following tags has been standardized:
2179 This tag says to not run any build-time test suite
2180 provided by the package.
2184 The presence of this tag means that the package should
2185 be compiled with a minimum of optimization. For C
2186 programs, it is best to add <tt>-O0</tt> to
2187 <tt>CFLAGS</tt> (although this is usually the default).
2188 Some programs might fail to build or run at this level
2189 of optimization; it may be necessary to use
2190 <tt>-O1</tt>, for example.
2194 This tag means that the debugging symbols should not be
2195 stripped from the binary during installation, so that
2196 debugging information may be included in the package.
2198 <tag>parallel=n</tag>
2200 This tag means that the package should be built using up
2201 to <tt>n</tt> parallel processes if the package build
2202 system supports this.<footnote>
2203 Packages built with <tt>make</tt> can often implement
2204 this by passing the <tt>-j</tt><var>n</var> option to
2207 If the package build system does not support parallel
2208 builds, this string must be ignored. If the package
2209 build system only supports a lower level of concurrency
2210 than <var>n</var>, the package should be built using as
2211 many parallel processes as the package build system
2212 supports. It is up to the package maintainer to decide
2213 whether the package build times are long enough and the
2214 package build system is robust enough to make supporting
2215 parallel builds worthwhile.
2221 Unknown flags must be ignored by <file>debian/rules</file>.
2225 The following makefile snippet is an example of how one may
2226 implement the build options; you will probably have to
2227 massage this example in order to make it work for your
2229 <example compact="compact">
2232 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2233 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2234 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2235 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2237 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2242 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2243 INSTALL_PROGRAM += -s
2245 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2246 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2247 MAKEFLAGS += -j$(NUMJOBS)
2252 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2253 # Code to run the package test suite.
2260 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2261 <sect id="substvars">
2262 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2265 When <prgn>dpkg-gencontrol</prgn>
2266 generates <qref id="binarycontrolfiles">binary package control
2267 files</qref> (<file>DEBIAN/control</file>), it performs variable
2268 substitutions on its output just before writing it. Variable
2269 substitutions have the form <tt>${<var>variable</var>}</tt>.
2270 The optional file <file>debian/substvars</file> contains
2271 variable substitutions to be used; variables can also be set
2272 directly from <file>debian/rules</file> using the <tt>-V</tt>
2273 option to the source packaging commands, and certain predefined
2274 variables are also available.
2278 The <file>debian/substvars</file> file is usually generated and
2279 modified dynamically by <file>debian/rules</file> targets, in
2280 which case it must be removed by the <tt>clean</tt> target.
2284 See <manref name="deb-substvars" section="5"> for full
2285 details about source variable substitutions, including the
2286 format of <file>debian/substvars</file>.</p>
2289 <sect id="debianwatch">
2290 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2293 This is an optional, recommended configuration file for the
2294 <tt>uscan</tt> utility which defines how to automatically scan
2295 ftp or http sites for newly available updates of the
2296 package. This is used
2297 by <url id="http://dehs.alioth.debian.org/"> and other Debian QA
2298 tools to help with quality control and maintenance of the
2299 distribution as a whole.
2304 <sect id="debianfiles">
2305 <heading>Generated files list: <file>debian/files</file></heading>
2308 This file is not a permanent part of the source tree; it
2309 is used while building packages to record which files are
2310 being generated. <prgn>dpkg-genchanges</prgn> uses it
2311 when it generates a <file>.changes</file> file.
2315 It should not exist in a shipped source package, and so it
2316 (and any backup files or temporary files such as
2317 <file>files.new</file><footnote>
2318 <file>files.new</file> is used as a temporary file by
2319 <prgn>dpkg-gencontrol</prgn> and
2320 <prgn>dpkg-distaddfile</prgn> - they write a new
2321 version of <tt>files</tt> here before renaming it,
2322 to avoid leaving a corrupted copy if an error
2324 </footnote>) should be removed by the
2325 <tt>clean</tt> target. It may also be wise to
2326 ensure a fresh start by emptying or removing it at the
2327 start of the <tt>binary</tt> target.
2331 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2332 package, it adds an entry to <file>debian/files</file> for the
2333 <file>.deb</file> file that will be created when <tt>dpkg-deb
2334 --build</tt> is run for that binary package. So for most
2335 packages all that needs to be done with this file is to
2336 delete it in the <tt>clean</tt> target.
2340 If a package upload includes files besides the source
2341 package and any binary packages whose control files were
2342 made with <prgn>dpkg-gencontrol</prgn> then they should be
2343 placed in the parent of the package's top-level directory
2344 and <prgn>dpkg-distaddfile</prgn> should be called to add
2345 the file to the list in <file>debian/files</file>.</p>
2348 <sect id="embeddedfiles">
2349 <heading>Convenience copies of code</heading>
2352 Some software packages include in their distribution convenience
2353 copies of code from other software packages, generally so that
2354 users compiling from source don't have to download multiple
2355 packages. Debian packages should not make use of these
2356 convenience copies unless the included package is explicitly
2357 intended to be used in this way.<footnote>
2358 For example, parts of the GNU build system work like this.
2360 If the included code is already in the Debian archive in the
2361 form of a library, the Debian packaging should ensure that
2362 binary packages reference the libraries already in Debian and
2363 the convenience copy is not used. If the included code is not
2364 already in Debian, it should be packaged separately as a
2365 prerequisite if possible.
2367 Having multiple copies of the same code in Debian is
2368 inefficient, often creates either static linking or shared
2369 library conflicts, and, most importantly, increases the
2370 difficulty of handling security vulnerabilities in the
2376 <sect id="readmesource">
2377 <heading>Source package handling:
2378 <file>debian/README.source</file></heading>
2381 If running <prgn>dpkg-source -x</prgn> on a source package
2382 doesn't produce the source of the package, ready for editing,
2383 and allow one to make changes and run
2384 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2385 without taking any additional steps, creating a
2386 <file>debian/README.source</file> documentation file is
2387 recommended. This file should explain how to do all of the
2390 <item>Generate the fully patched source, in a form ready for
2391 editing, that would be built to create Debian
2392 packages. Doing this with a <tt>patch</tt> target in
2393 <file>debian/rules</file> is recommended; see
2394 <ref id="debianrules">.</item>
2395 <item>Modify the source and save those modifications so that
2396 they will be applied when building the package.</item>
2397 <item>Remove source modifications that are currently being
2398 applied when building the package.</item>
2399 <item>Optionally, document what steps are necessary to
2400 upgrade the Debian source package to a new upstream version,
2401 if applicable.</item>
2403 This explanation should include specific commands and mention
2404 any additional required Debian packages. It should not assume
2405 familiarity with any specific Debian packaging system or patch
2410 This explanation may refer to a documentation file installed by
2411 one of the package's build dependencies provided that the
2412 referenced documentation clearly explains these tasks and is not
2413 a general reference manual.
2417 <file>debian/README.source</file> may also include any other
2418 information that would be helpful to someone modifying the
2419 source package. Even if the package doesn't fit the above
2420 description, maintainers are encouraged to document in a
2421 <file>debian/README.source</file> file any source package with a
2422 particularly complex or unintuitive source layout or build
2423 system (for example, a package that builds the same source
2424 multiple times to generate different binary packages).
2430 <chapt id="controlfields">
2431 <heading>Control files and their fields</heading>
2434 The package management system manipulates data represented in
2435 a common format, known as <em>control data</em>, stored in
2436 <em>control files</em>.
2437 Control files are used for source packages, binary packages and
2438 the <file>.changes</file> files which control the installation
2439 of uploaded files<footnote>
2440 <prgn>dpkg</prgn>'s internal databases are in a similar
2445 <sect id="controlsyntax">
2446 <heading>Syntax of control files</heading>
2449 A control file consists of one or more paragraphs of
2451 The paragraphs are also sometimes referred to as stanzas.
2453 The paragraphs are separated by blank lines. Some control
2454 files allow only one paragraph; others allow several, in
2455 which case each paragraph usually refers to a different
2456 package. (For example, in source packages, the first
2457 paragraph refers to the source package, and later paragraphs
2458 refer to binary packages generated from the source.)
2462 Each paragraph consists of a series of data fields; each
2463 field consists of the field name, followed by a colon and
2464 then the data/value associated with that field. It ends at
2465 the end of the (logical) line. Horizontal whitespace
2466 (spaces and tabs) may occur immediately before or after the
2467 value and is ignored there; it is conventional to put a
2468 single space after the colon. For example, a field might
2470 <example compact="compact">
2473 the field name is <tt>Package</tt> and the field value
2478 A paragraph must not contain more than one instance of a
2479 particular field name.
2483 Many fields' values may span several lines; in this case
2484 each continuation line must start with a space or a tab.
2485 Any trailing spaces or tabs at the end of individual
2486 lines of a field value are ignored.
2490 In fields where it is specified that lines may not wrap,
2491 only a single line of data is allowed and whitespace is not
2492 significant in a field body. Whitespace must not appear
2493 inside names (of packages, architectures, files or anything
2494 else) or version numbers, or between the characters of
2495 multi-character version relationships.
2499 Field names are not case-sensitive, but it is usual to
2500 capitalize the field names using mixed case as shown below.
2501 Field values are case-sensitive unless the description of the
2502 field says otherwise.
2506 Blank lines, or lines consisting only of spaces and tabs,
2507 are not allowed within field values or between fields - that
2508 would mean a new paragraph.
2512 All control files must be encoded in UTF-8.
2516 <sect id="sourcecontrolfiles">
2517 <heading>Source package control files -- <file>debian/control</file></heading>
2520 The <file>debian/control</file> file contains the most vital
2521 (and version-independent) information about the source package
2522 and about the binary packages it creates.
2526 The first paragraph of the control file contains information about
2527 the source package in general. The subsequent sets each describe a
2528 binary package that the source tree builds.
2532 The fields in the general paragraph (the first one, for the source
2535 <list compact="compact">
2536 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2537 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2538 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2539 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2540 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2541 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2542 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2543 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2548 The fields in the binary package paragraphs are:
2550 <list compact="compact">
2551 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2552 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2553 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2554 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2555 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2556 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2557 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2558 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2563 The syntax and semantics of the fields are described below.
2567 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2568 generate control files for binary packages (see below), by
2569 <prgn>dpkg-genchanges</prgn> to generate the
2570 <file>.changes</file> file to accompany the upload, and by
2571 <prgn>dpkg-source</prgn> when it creates the
2572 <file>.dsc</file> source control file as part of a source
2573 archive. Many fields are permitted to span multiple lines in
2574 <file>debian/control</file> but not in any other control
2575 file. These tools are responsible for removing the line
2576 breaks from such fields when using fields from
2577 <file>debian/control</file> to generate other control files.
2581 The fields here may contain variable references - their
2582 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2583 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2584 when they generate output control files.
2585 See <ref id="substvars"> for details.
2589 In addition to the control file syntax described <qref
2590 id="controlsyntax">above</qref>, this file may also contain
2591 comment lines starting with <tt>#</tt> without any preceding
2592 whitespace. All such lines are ignored, even in the middle of
2593 continuation lines for a multiline field, and do not end a
2599 <sect id="binarycontrolfiles">
2600 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2603 The <file>DEBIAN/control</file> file contains the most vital
2604 (and version-dependent) information about a binary package. It
2605 consists of a single paragraph.
2609 The fields in this file are:
2611 <list compact="compact">
2612 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2613 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2614 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2615 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2616 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2617 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2618 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2619 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2620 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2621 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2622 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2623 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2628 <sect id="debiansourcecontrolfiles">
2629 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2632 This file consists of a single paragraph, possibly surrounded by
2633 a PGP signature. The fields of that paragraph are listed below.
2634 Their syntax is described above, in <ref id="pkg-controlfields">.
2636 <list compact="compact">
2637 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2638 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2639 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2640 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2641 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2642 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2643 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2644 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2645 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2646 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2647 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2648 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2649 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2654 The source package control file is generated by
2655 <prgn>dpkg-source</prgn> when it builds the source
2656 archive, from other files in the source package,
2657 described above. When unpacking, it is checked against
2658 the files and directories in the other parts of the
2664 <sect id="debianchangesfiles">
2665 <heading>Debian changes files -- <file>.changes</file></heading>
2668 The <file>.changes</file> files are used by the Debian archive
2669 maintenance software to process updates to packages. They
2670 consist of a single paragraph, possibly surrounded by a PGP
2671 signature. That paragraph contains information from the
2672 <file>debian/control</file> file and other data about the
2673 source package gathered via <file>debian/changelog</file>
2674 and <file>debian/rules</file>.
2678 <file>.changes</file> files have a format version that is
2679 incremented whenever the documented fields or their meaning
2680 change. This document describes format &changesversion;.
2684 The fields in this file are:
2686 <list compact="compact">
2687 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2688 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2689 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2690 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2691 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2692 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2693 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2694 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2695 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2696 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2697 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2698 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2699 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2700 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2701 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2702 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2707 <sect id="controlfieldslist">
2708 <heading>List of fields</heading>
2710 <sect1 id="f-Source">
2711 <heading><tt>Source</tt></heading>
2714 This field identifies the source package name.
2718 In <file>debian/control</file> or a <file>.dsc</file> file,
2719 this field must contain only the name of the source package.
2723 In a binary package control file or a <file>.changes</file>
2724 file, the source package name may be followed by a version
2725 number in parentheses<footnote>
2726 It is customary to leave a space after the package name
2727 if a version number is specified.
2729 This version number may be omitted (and is, by
2730 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2731 the <tt>Version</tt> field of the binary package in
2732 question. The field itself may be omitted from a binary
2733 package control file when the source package has the same
2734 name and version as the binary package.
2738 Package names (both source and binary,
2739 see <ref id="f-Package">) must consist only of lower case
2740 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2741 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2742 (<tt>.</tt>). They must be at least two characters long and
2743 must start with an alphanumeric character.
2747 <sect1 id="f-Maintainer">
2748 <heading><tt>Maintainer</tt></heading>
2751 The package maintainer's name and email address. The name
2752 must come first, then the email address inside angle
2753 brackets <tt><></tt> (in RFC822 format).
2757 If the maintainer's name contains a full stop then the
2758 whole field will not work directly as an email address due
2759 to a misfeature in the syntax specified in RFC822; a
2760 program using this field as an address must check for this
2761 and correct the problem if necessary (for example by
2762 putting the name in round brackets and moving it to the
2763 end, and bringing the email address forward).
2767 See <ref id="maintainer"> for additional requirements and
2768 information about package maintainers.
2772 <sect1 id="f-Uploaders">
2773 <heading><tt>Uploaders</tt></heading>
2776 List of the names and email addresses of co-maintainers of the
2777 package, if any. If the package has other maintainers besides
2778 the one named in the <qref id="f-Maintainer">Maintainer
2779 field</qref>, their names and email addresses should be listed
2780 here. The format of each entry is the same as that of the
2781 Maintainer field, and multiple entries must be comma
2786 This is normally an optional field, but if
2787 the <tt>Maintainer</tt> control field names a group of people
2788 and a shared email address, the <tt>Uploaders</tt> field must
2789 be present and must contain at least one human with their
2790 personal email address.
2794 Any parser that interprets the Uploaders field in
2795 <file>debian/control</file> must permit it to span multiple
2796 lines. Line breaks in an Uploaders field that spans multiple
2797 lines are not significant and the semantics of the field are
2798 the same as if the line breaks had not been present.
2802 <sect1 id="f-Changed-By">
2803 <heading><tt>Changed-By</tt></heading>
2806 The name and email address of the person who prepared this
2807 version of the package, usually a maintainer. The syntax is
2808 the same as for the <qref id="f-Maintainer">Maintainer
2813 <sect1 id="f-Section">
2814 <heading><tt>Section</tt></heading>
2817 This field specifies an application area into which the package
2818 has been classified. See <ref id="subsections">.
2822 When it appears in the <file>debian/control</file> file,
2823 it gives the value for the subfield of the same name in
2824 the <tt>Files</tt> field of the <file>.changes</file> file.
2825 It also gives the default for the same field in the binary
2830 <sect1 id="f-Priority">
2831 <heading><tt>Priority</tt></heading>
2834 This field represents how important it is that the user
2835 have the package installed. See <ref id="priorities">.
2839 When it appears in the <file>debian/control</file> file,
2840 it gives the value for the subfield of the same name in
2841 the <tt>Files</tt> field of the <file>.changes</file> file.
2842 It also gives the default for the same field in the binary
2847 <sect1 id="f-Package">
2848 <heading><tt>Package</tt></heading>
2851 The name of the binary package.
2855 Binary package names must follow the same syntax and
2856 restrictions as source package names. See <ref id="f-Source">
2861 <sect1 id="f-Architecture">
2862 <heading><tt>Architecture</tt></heading>
2865 Depending on context and the control file used, the
2866 <tt>Architecture</tt> field can include the following sets of
2870 A unique single word identifying a Debian machine
2871 architecture as described in <ref id="arch-spec">.
2874 An architecture wildcard identifying a set of Debian
2875 machine architectures, see <ref id="arch-wildcard-spec">.
2876 <tt>any</tt> matches all Debian machine architectures
2877 and is the most frequently used.
2880 <tt>all</tt>, which indicates an
2881 architecture-independent package.
2884 <tt>source</tt>, which indicates a source package.
2890 In the main <file>debian/control</file> file in the source
2891 package, this field may contain the special
2892 value <tt>all</tt>, the special architecture
2893 wildcard <tt>any</tt>, or a list of specific and wildcard
2894 architectures separated by spaces. If <tt>all</tt>
2895 or <tt>any</tt> appears, that value must be the entire
2896 contents of the field. Most packages will use
2897 either <tt>all</tt> or <tt>any</tt>.
2901 Specifying a specific list of architectures indicates that the
2902 source will build an architecture-dependent package only on
2903 architectures included in the list. Specifying a list of
2904 architecture wildcards indicates that the source will build an
2905 architecture-dependent package on only those architectures
2906 that match any of the specified architecture wildcards.
2907 Specifying a list of architectures or architecture wildcards
2908 other than <tt>any</tt> is for the minority of cases where a
2909 program is not portable or is not useful on some
2910 architectures. Where possible, the program should be made
2915 In the source package control file <file>.dsc</file>, this
2916 field may contain either the architecture
2917 wildcard <tt>any</tt> or a list of architectures and
2918 architecture wildcards separated by spaces. If a list is
2919 given, it may include (or consist solely of) the special
2920 value <tt>all</tt>. In other words, in <file>.dsc</file>
2921 files unlike the <file>debian/control</file>, <tt>all</tt> may
2922 occur in combination with specific architectures.
2923 The <tt>Architecture</tt> field in the source package control
2924 file <file>.dsc</file> is generally constructed from
2925 the <tt>Architecture</tt> fields in
2926 the <file>debian/control</file> in the source package.
2930 Specifying <tt>any</tt> indicates that the source package
2931 isn't dependent on any particular architecture and should
2932 compile fine on any one. The produced binary package(s)
2933 will either be specific to whatever the current build
2934 architecture is or will be architecture-independent.
2938 Specifying only <tt>all</tt> indicates that the source package
2939 will only build architecture-independent packages. If this is
2940 the case, <tt>all</tt> must be used rather than <tt>any</tt>;
2941 <tt>any</tt> implies that the source package will build at
2942 least one architecture-dependent package.
2946 Specifying a list of architectures or architecture wildcards
2947 indicates that the source will build an architecture-dependent
2948 package, and will only work correctly on the listed or
2949 matching architectures. If the source package also builds at
2950 least one architecture-independent package, <tt>all</tt> will
2951 also be included in the list.
2955 In a <file>.changes</file> file, the <tt>Architecture</tt>
2956 field lists the architecture(s) of the package(s) currently
2957 being uploaded. This will be a list; if the source for the
2958 package is also being uploaded, the special
2959 entry <tt>source</tt> is also present. <tt>all</tt> will be
2960 present if any architecture-independent packages are being
2961 uploaded. Architecture wildcards such as <tt>any</tt> must
2962 never occur in the <tt>Architecture</tt> field in
2963 the <file>.changes</file> file.
2967 See <ref id="debianrules"> for information on how to get
2968 the architecture for the build process.
2972 <sect1 id="f-Essential">
2973 <heading><tt>Essential</tt></heading>
2976 This is a boolean field which may occur only in the
2977 control file of a binary package or in a per-package fields
2978 paragraph of a main source control data file.
2982 If set to <tt>yes</tt> then the package management system
2983 will refuse to remove the package (upgrading and replacing
2984 it is still possible). The other possible value is <tt>no</tt>,
2985 which is the same as not having the field at all.
2990 <heading>Package interrelationship fields:
2991 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2992 <tt>Recommends</tt>, <tt>Suggests</tt>,
2993 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2994 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2998 These fields describe the package's relationships with
2999 other packages. Their syntax and semantics are described
3000 in <ref id="relationships">.</p>
3003 <sect1 id="f-Standards-Version">
3004 <heading><tt>Standards-Version</tt></heading>
3007 The most recent version of the standards (the policy
3008 manual and associated texts) with which the package
3013 The version number has four components: major and minor
3014 version number and major and minor patch level. When the
3015 standards change in a way that requires every package to
3016 change the major number will be changed. Significant
3017 changes that will require work in many packages will be
3018 signaled by a change to the minor number. The major patch
3019 level will be changed for any change to the meaning of the
3020 standards, however small; the minor patch level will be
3021 changed when only cosmetic, typographical or other edits
3022 are made which neither change the meaning of the document
3023 nor affect the contents of packages.
3027 Thus only the first three components of the policy version
3028 are significant in the <em>Standards-Version</em> control
3029 field, and so either these three components or all four
3030 components may be specified.<footnote>
3031 In the past, people specified the full version number
3032 in the Standards-Version field, for example "2.3.0.0".
3033 Since minor patch-level changes don't introduce new
3034 policy, it was thought it would be better to relax
3035 policy and only require the first 3 components to be
3036 specified, in this example "2.3.0". All four
3037 components may still be used if someone wishes to do so.
3043 <sect1 id="f-Version">
3044 <heading><tt>Version</tt></heading>
3047 The version number of a package. The format is:
3048 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
3052 The three components here are:
3054 <tag><var>epoch</var></tag>
3057 This is a single (generally small) unsigned integer. It
3058 may be omitted, in which case zero is assumed. If it is
3059 omitted then the <var>upstream_version</var> may not
3064 It is provided to allow mistakes in the version numbers
3065 of older versions of a package, and also a package's
3066 previous version numbering schemes, to be left behind.
3070 <tag><var>upstream_version</var></tag>
3073 This is the main part of the version number. It is
3074 usually the version number of the original ("upstream")
3075 package from which the <file>.deb</file> file has been made,
3076 if this is applicable. Usually this will be in the same
3077 format as that specified by the upstream author(s);
3078 however, it may need to be reformatted to fit into the
3079 package management system's format and comparison
3084 The comparison behavior of the package management system
3085 with respect to the <var>upstream_version</var> is
3086 described below. The <var>upstream_version</var>
3087 portion of the version number is mandatory.
3091 The <var>upstream_version</var> may contain only
3092 alphanumerics<footnote>
3093 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3095 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3096 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3097 tilde) and should start with a digit. If there is no
3098 <var>debian_revision</var> then hyphens are not allowed;
3099 if there is no <var>epoch</var> then colons are not
3104 <tag><var>debian_revision</var></tag>
3107 This part of the version number specifies the version of
3108 the Debian package based on the upstream version. It
3109 may contain only alphanumerics and the characters
3110 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3111 tilde) and is compared in the same way as the
3112 <var>upstream_version</var> is.
3116 It is optional; if it isn't present then the
3117 <var>upstream_version</var> may not contain a hyphen.
3118 This format represents the case where a piece of
3119 software was written specifically to be a Debian
3120 package, where the Debian package source must always
3121 be identical to the pristine source and therefore no
3122 revision indication is required.
3126 It is conventional to restart the
3127 <var>debian_revision</var> at <tt>1</tt> each time the
3128 <var>upstream_version</var> is increased.
3132 The package management system will break the version
3133 number apart at the last hyphen in the string (if there
3134 is one) to determine the <var>upstream_version</var> and
3135 <var>debian_revision</var>. The absence of a
3136 <var>debian_revision</var> is equivalent to a
3137 <var>debian_revision</var> of <tt>0</tt>.
3144 When comparing two version numbers, first the <var>epoch</var>
3145 of each are compared, then the <var>upstream_version</var> if
3146 <var>epoch</var> is equal, and then <var>debian_revision</var>
3147 if <var>upstream_version</var> is also equal.
3148 <var>epoch</var> is compared numerically. The
3149 <var>upstream_version</var> and <var>debian_revision</var>
3150 parts are compared by the package management system using the
3151 following algorithm:
3155 The strings are compared from left to right.
3159 First the initial part of each string consisting entirely of
3160 non-digit characters is determined. These two parts (one of
3161 which may be empty) are compared lexically. If a difference
3162 is found it is returned. The lexical comparison is a
3163 comparison of ASCII values modified so that all the letters
3164 sort earlier than all the non-letters and so that a tilde
3165 sorts before anything, even the end of a part. For example,
3166 the following parts are in sorted order from earliest to
3167 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3168 <tt>a</tt>.<footnote>
3169 One common use of <tt>~</tt> is for upstream pre-releases.
3170 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3171 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3176 Then the initial part of the remainder of each string which
3177 consists entirely of digit characters is determined. The
3178 numerical values of these two parts are compared, and any
3179 difference found is returned as the result of the comparison.
3180 For these purposes an empty string (which can only occur at
3181 the end of one or both version strings being compared) counts
3186 These two steps (comparing and removing initial non-digit
3187 strings and initial digit strings) are repeated until a
3188 difference is found or both strings are exhausted.
3192 Note that the purpose of epochs is to allow us to leave behind
3193 mistakes in version numbering, and to cope with situations
3194 where the version numbering scheme changes. It is
3195 <em>not</em> intended to cope with version numbers containing
3196 strings of letters which the package management system cannot
3197 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3198 silly orderings.<footnote>
3199 The author of this manual has heard of a package whose
3200 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3201 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3207 <sect1 id="f-Description">
3208 <heading><tt>Description</tt></heading>
3211 In a source or binary control file, the <tt>Description</tt>
3212 field contains a description of the binary package, consisting
3213 of two parts, the synopsis or the short description, and the
3214 long description. The field's format is as follows:
3219 Description: <single line synopsis>
3220 <extended description over several lines>
3225 The lines in the extended description can have these formats:
3231 Those starting with a single space are part of a paragraph.
3232 Successive lines of this form will be word-wrapped when
3233 displayed. The leading space will usually be stripped off.
3237 Those starting with two or more spaces. These will be
3238 displayed verbatim. If the display cannot be panned
3239 horizontally, the displaying program will line wrap them "hard"
3240 (i.e., without taking account of word breaks). If it can they
3241 will be allowed to trail off to the right. None, one or two
3242 initial spaces may be deleted, but the number of spaces
3243 deleted from each line will be the same (so that you can have
3244 indenting work correctly, for example).
3248 Those containing a single space followed by a single full stop
3249 character. These are rendered as blank lines. This is the
3250 <em>only</em> way to get a blank line<footnote>
3251 Completely empty lines will not be rendered as blank lines.
3252 Instead, they will cause the parser to think you're starting
3253 a whole new record in the control file, and will therefore
3254 likely abort with an error.
3259 Those containing a space, a full stop and some more characters.
3260 These are for future expansion. Do not use them.
3266 Do not use tab characters. Their effect is not predictable.
3270 See <ref id="descriptions"> for further information on this.
3274 In a <file>.changes</file> file, the <tt>Description</tt>
3275 field contains a summary of the descriptions for the packages
3276 being uploaded. For this case, the first line of the field
3277 value (the part on the same line as <tt>Description:</tt>) is
3278 always empty. The content of the field is expressed as
3279 continuation lines, one line per package. Each line is
3280 indented by one space and contains the name of a binary
3281 package, a space, a hyphen (<tt>-</tt>), a space, and the
3282 short description line from that package.
3286 <sect1 id="f-Distribution">
3287 <heading><tt>Distribution</tt></heading>
3290 In a <file>.changes</file> file or parsed changelog output
3291 this contains the (space-separated) name(s) of the
3292 distribution(s) where this version of the package should
3293 be installed. Valid distributions are determined by the
3294 archive maintainers.<footnote>
3295 Example distribution names in the Debian archive used in
3296 <file>.changes</file> files are:
3297 <taglist compact="compact">
3298 <tag><em>unstable</em></tag>
3300 This distribution value refers to the
3301 <em>developmental</em> part of the Debian distribution
3302 tree. Most new packages, new upstream versions of
3303 packages and bug fixes go into the <em>unstable</em>
3307 <tag><em>experimental</em></tag>
3309 The packages with this distribution value are deemed
3310 by their maintainers to be high risk. Oftentimes they
3311 represent early beta or developmental packages from
3312 various sources that the maintainers want people to
3313 try, but are not ready to be a part of the other parts
3314 of the Debian distribution tree.
3319 Others are used for updating stable releases or for
3320 security uploads. More information is available in the
3321 Debian Developer's Reference, section "The Debian
3325 The Debian archive software only supports listing a single
3326 distribution. Migration of packages to other distributions is
3327 handled outside of the upload process.
3332 <heading><tt>Date</tt></heading>
3335 This field includes the date the package was built or last
3336 edited. It must be in the same format as the <var>date</var>
3337 in a <file>debian/changelog</file> entry.
3341 The value of this field is usually extracted from the
3342 <file>debian/changelog</file> file - see
3343 <ref id="dpkgchangelog">).
3347 <sect1 id="f-Format">
3348 <heading><tt>Format</tt></heading>
3351 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3352 files, this field declares the format version of that file.
3353 The syntax of the field value is the same as that of
3354 a <qref id="f-Version">package version number</qref> except
3355 that no epoch or Debian revision is allowed. The format
3356 described in this document is <tt>&changesversion;</tt>.
3360 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3361 Debian source control</qref> files, this field declares the
3362 format of the source package. The field value is used by
3363 programs acting on a source package to interpret the list of
3364 files in the source package and determine how to unpack it.
3365 The syntax of the field value is a numeric major revision, a
3366 period, a numeric minor revision, and then an optional subtype
3367 after whitespace, which if specified is an alphanumeric word
3368 in parentheses. The subtype is optional in the syntax but may
3369 be mandatory for particular source format revisions.
3371 The source formats currently supported by the Debian archive
3372 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3373 and <tt>3.0 (quilt)</tt>.
3378 <sect1 id="f-Urgency">
3379 <heading><tt>Urgency</tt></heading>
3382 This is a description of how important it is to upgrade to
3383 this version from previous ones. It consists of a single
3384 keyword taking one of the values <tt>low</tt>,
3385 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3386 <tt>critical</tt><footnote>
3387 Other urgency values are supported with configuration
3388 changes in the archive software but are not used in Debian.
3389 The urgency affects how quickly a package will be considered
3390 for inclusion into the <tt>testing</tt> distribution and
3391 gives an indication of the importance of any fixes included
3392 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3393 treated as synonymous.
3394 </footnote> (not case-sensitive) followed by an optional
3395 commentary (separated by a space) which is usually in
3396 parentheses. For example:
3399 Urgency: low (HIGH for users of diversions)
3405 The value of this field is usually extracted from the
3406 <file>debian/changelog</file> file - see
3407 <ref id="dpkgchangelog">.
3411 <sect1 id="f-Changes">
3412 <heading><tt>Changes</tt></heading>
3415 This field contains the human-readable changes data, describing
3416 the differences between the last version and the current one.
3420 The first line of the field value (the part on the same line
3421 as <tt>Changes:</tt>) is always empty. The content of the
3422 field is expressed as continuation lines, with each line
3423 indented by at least one space. Blank lines must be
3424 represented by a line consisting only of a space and a full
3429 The value of this field is usually extracted from the
3430 <file>debian/changelog</file> file - see
3431 <ref id="dpkgchangelog">).
3435 Each version's change information should be preceded by a
3436 "title" line giving at least the version, distribution(s)
3437 and urgency, in a human-readable way.
3441 If data from several versions is being returned the entry
3442 for the most recent version should be returned first, and
3443 entries should be separated by the representation of a
3444 blank line (the "title" line may also be followed by the
3445 representation of a blank line).
3449 <sect1 id="f-Binary">
3450 <heading><tt>Binary</tt></heading>
3453 This field is a list of binary packages. Its syntax and
3454 meaning varies depending on the control file in which it
3459 When it appears in the <file>.dsc</file> file, it lists binary
3460 packages which a source package can produce, separated by
3462 A space after each comma is conventional.
3463 </footnote>. It may span multiple lines. The source package
3464 does not necessarily produce all of these binary packages for
3465 every architecture. The source control file doesn't contain
3466 details of which architectures are appropriate for which of
3467 the binary packages.
3471 When it appears in a <file>.changes</file> file, it lists the
3472 names of the binary packages being uploaded, separated by
3473 whitespace (not commas). It may span multiple lines.
3477 <sect1 id="f-Installed-Size">
3478 <heading><tt>Installed-Size</tt></heading>
3481 This field appears in the control files of binary packages,
3482 and in the <file>Packages</file> files. It gives an estimate
3483 of the total amount of disk space required to install the
3484 named package. Actual installed size may vary based on block
3485 size, file system properties, or actions taken by package
3490 The disk space is given as the integer value of the estimated
3491 installed size in bytes, divided by 1024 and rounded up.
3495 <sect1 id="f-Files">
3496 <heading><tt>Files</tt></heading>
3499 This field contains a list of files with information about
3500 each one. The exact information and syntax varies with
3505 In all cases, Files is a multiline field. The first line of
3506 the field value (the part on the same line as <tt>Files:</tt>)
3507 is always empty. The content of the field is expressed as
3508 continuation lines, one line per file. Each line must be
3509 indented by one space and contain a number of sub-fields,
3510 separated by spaces, as described below.
3514 In the <file>.dsc</file> file, each line contains the MD5
3515 checksum, size and filename of the tar file and (if
3516 applicable) diff file which make up the remainder of the
3517 source package<footnote>
3518 That is, the parts which are not the <tt>.dsc</tt>.
3519 </footnote>. For example:
3522 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3523 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3525 The exact forms of the filenames are described
3526 in <ref id="pkg-sourcearchives">.
3530 In the <file>.changes</file> file this contains one line per
3531 file being uploaded. Each line contains the MD5 checksum,
3532 size, section and priority and the filename. For example:
3535 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3536 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3537 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3538 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3540 The <qref id="f-Section">section</qref>
3541 and <qref id="f-Priority">priority</qref> are the values of
3542 the corresponding fields in the main source control file. If
3543 no section or priority is specified then <tt>-</tt> should be
3544 used, though section and priority values must be specified for
3545 new packages to be installed properly.
3549 The special value <tt>byhand</tt> for the section in a
3550 <tt>.changes</tt> file indicates that the file in question
3551 is not an ordinary package file and must by installed by
3552 hand by the distribution maintainers. If the section is
3553 <tt>byhand</tt> the priority should be <tt>-</tt>.
3557 If a new Debian revision of a package is being shipped and
3558 no new original source archive is being distributed the
3559 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3560 entry for the original source archive
3561 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3562 but the <file>.changes</file> file should leave it out. In
3563 this case the original source archive on the distribution
3564 site must match exactly, byte-for-byte, the original
3565 source archive which was used to generate the
3566 <file>.dsc</file> file and diff which are being uploaded.</p>
3569 <sect1 id="f-Closes">
3570 <heading><tt>Closes</tt></heading>
3573 A space-separated list of bug report numbers that the upload
3574 governed by the .changes file closes.
3578 <sect1 id="f-Homepage">
3579 <heading><tt>Homepage</tt></heading>
3582 The URL of the web site for this package, preferably (when
3583 applicable) the site from which the original source can be
3584 obtained and any additional upstream documentation or
3585 information may be found. The content of this field is a
3586 simple URL without any surrounding characters such as
3591 <sect1 id="f-Checksums">
3592 <heading><tt>Checksums-Sha1</tt>
3593 and <tt>Checksums-Sha256</tt></heading>
3596 These fields contain a list of files with a checksum and size
3597 for each one. Both <tt>Checksums-Sha1</tt>
3598 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3599 only in the checksum algorithm used: SHA-1
3600 for <tt>Checksums-Sha1</tt> and SHA-256
3601 for <tt>Checksums-Sha256</tt>.
3605 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3606 multiline fields. The first line of the field value (the part
3607 on the same line as <tt>Checksums-Sha1:</tt>
3608 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3609 of the field is expressed as continuation lines, one line per
3610 file. Each line consists of the checksum, a space, the file
3611 size, a space, and the file name. For example (from
3612 a <file>.changes</file> file):
3615 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3616 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3617 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3618 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3620 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3621 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3622 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3623 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3628 In the <file>.dsc</file> file, these fields should list all
3629 files that make up the source package. In
3630 the <file>.changes</file> file, these fields should list all
3631 files being uploaded. The list of files in these fields
3632 must match the list of files in the <tt>Files</tt> field.
3638 <heading>User-defined fields</heading>
3641 Additional user-defined fields may be added to the
3642 source package control file. Such fields will be
3643 ignored, and not copied to (for example) binary or
3644 source package control files or upload control files.
3648 If you wish to add additional unsupported fields to
3649 these output files you should use the mechanism
3654 Fields in the main source control information file with
3655 names starting <tt>X</tt>, followed by one or more of
3656 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3657 be copied to the output files. Only the part of the
3658 field name after the hyphen will be used in the output
3659 file. Where the letter <tt>B</tt> is used the field
3660 will appear in binary package control files, where the
3661 letter <tt>S</tt> is used in source package control
3662 files and where <tt>C</tt> is used in upload control
3663 (<tt>.changes</tt>) files.
3667 For example, if the main source information control file
3670 XBS-Comment: I stand between the candle and the star.
3672 then the binary and source package control files will contain the
3675 Comment: I stand between the candle and the star.
3684 <chapt id="maintainerscripts">
3685 <heading>Package maintainer scripts and installation procedure</heading>
3688 <heading>Introduction to package maintainer scripts</heading>
3691 It is possible to supply scripts as part of a package which
3692 the package management system will run for you when your
3693 package is installed, upgraded or removed.
3697 These scripts are the control information
3698 files <prgn>preinst</prgn>, <prgn>postinst</prgn>, <prgn>prerm</prgn>
3699 and <prgn>postrm</prgn>. They must be proper executable files;
3700 if they are scripts (which is recommended), they must start with
3701 the usual <tt>#!</tt> convention. They should be readable and
3702 executable by anyone, and must not be world-writable.
3706 The package management system looks at the exit status from
3707 these scripts. It is important that they exit with a
3708 non-zero status if there is an error, so that the package
3709 management system can stop its processing. For shell
3710 scripts this means that you <em>almost always</em> need to
3711 use <tt>set -e</tt> (this is usually true when writing shell
3712 scripts, in fact). It is also important, of course, that
3713 they exit with a zero status if everything went well.
3717 Additionally, packages interacting with users
3718 using <prgn>debconf</prgn> in the <prgn>postinst</prgn> script
3719 should install a <prgn>config</prgn> script as a control
3720 information file. See <ref id="maintscriptprompt"> for details.
3724 When a package is upgraded a combination of the scripts from
3725 the old and new packages is called during the upgrade
3726 procedure. If your scripts are going to be at all
3727 complicated you need to be aware of this, and may need to
3728 check the arguments to your scripts.
3732 Broadly speaking the <prgn>preinst</prgn> is called before
3733 (a particular version of) a package is installed, and the
3734 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3735 before (a version of) a package is removed and the
3736 <prgn>postrm</prgn> afterwards.
3740 Programs called from maintainer scripts should not normally
3741 have a path prepended to them. Before installation is
3742 started, the package management system checks to see if the
3743 programs <prgn>ldconfig</prgn>,
3744 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3745 and <prgn>update-rc.d</prgn> can be found via the
3746 <tt>PATH</tt> environment variable. Those programs, and any
3747 other program that one would expect to be in the
3748 <tt>PATH</tt>, should thus be invoked without an absolute
3749 pathname. Maintainer scripts should also not reset the
3750 <tt>PATH</tt>, though they might choose to modify it by
3751 prepending or appending package-specific directories. These
3752 considerations really apply to all shell scripts.</p>
3755 <sect id="idempotency">
3756 <heading>Maintainer scripts idempotency</heading>
3759 It is necessary for the error recovery procedures that the
3760 scripts be idempotent. This means that if it is run
3761 successfully, and then it is called again, it doesn't bomb
3762 out or cause any harm, but just ensures that everything is
3763 the way it ought to be. If the first call failed, or
3764 aborted half way through for some reason, the second call
3765 should merely do the things that were left undone the first
3766 time, if any, and exit with a success status if everything
3768 This is so that if an error occurs, the user interrupts
3769 <prgn>dpkg</prgn> or some other unforeseen circumstance
3770 happens you don't leave the user with a badly-broken
3771 package when <prgn>dpkg</prgn> attempts to repeat the
3777 <sect id="controllingterminal">
3778 <heading>Controlling terminal for maintainer scripts</heading>
3781 Maintainer scripts are not guaranteed to run with a controlling
3782 terminal and may not be able to interact with the user. They
3783 must be able to fall back to noninteractive behavior if no
3784 controlling terminal is available. Maintainer scripts that
3785 prompt via a program conforming to the Debian Configuration
3786 Management Specification (see <ref id="maintscriptprompt">) may
3787 assume that program will handle falling back to noninteractive
3792 For high-priority prompts without a reasonable default answer,
3793 maintainer scripts may abort if there is no controlling
3794 terminal. However, this situation should be avoided if at all
3795 possible, since it prevents automated or unattended installs.
3796 In most cases, users will consider this to be a bug in the
3801 <sect id="exitstatus">
3802 <heading>Exit status</heading>
3805 Each script must return a zero exit status for
3806 success, or a nonzero one for failure, since the package
3807 management system looks for the exit status of these scripts
3808 and determines what action to take next based on that datum.
3812 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3817 <list compact="compact">
3819 <var>new-preinst</var> <tt>install</tt>
3822 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3825 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3828 <var>old-preinst</var> <tt>abort-upgrade</tt>
3829 <var>new-version</var>
3834 <list compact="compact">
3836 <var>postinst</var> <tt>configure</tt>
3837 <var>most-recently-configured-version</var>
3840 <var>old-postinst</var> <tt>abort-upgrade</tt>
3841 <var>new-version</var>
3844 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3845 <tt>in-favour</tt> <var>package</var>
3846 <var>new-version</var>
3849 <var>postinst</var> <tt>abort-remove</tt>
3852 <var>deconfigured's-postinst</var>
3853 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3854 <var>failed-install-package</var> <var>version</var>
3855 [<tt>removing</tt> <var>conflicting-package</var>
3861 <list compact="compact">
3863 <var>prerm</var> <tt>remove</tt>
3866 <var>old-prerm</var> <tt>upgrade</tt>
3867 <var>new-version</var>
3870 <var>new-prerm</var> <tt>failed-upgrade</tt>
3871 <var>old-version</var>
3874 <var>conflictor's-prerm</var> <tt>remove</tt>
3875 <tt>in-favour</tt> <var>package</var>
3876 <var>new-version</var>
3879 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3880 <tt>in-favour</tt> <var>package-being-installed</var>
3881 <var>version</var> [<tt>removing</tt>
3882 <var>conflicting-package</var>
3888 <list compact="compact">
3890 <var>postrm</var> <tt>remove</tt>
3893 <var>postrm</var> <tt>purge</tt>
3896 <var>old-postrm</var> <tt>upgrade</tt>
3897 <var>new-version</var>
3900 <var>new-postrm</var> <tt>failed-upgrade</tt>
3901 <var>old-version</var>
3904 <var>new-postrm</var> <tt>abort-install</tt>
3907 <var>new-postrm</var> <tt>abort-install</tt>
3908 <var>old-version</var>
3911 <var>new-postrm</var> <tt>abort-upgrade</tt>
3912 <var>old-version</var>
3915 <var>disappearer's-postrm</var> <tt>disappear</tt>
3916 <var>overwriter</var>
3917 <var>overwriter-version</var>
3923 <sect id="unpackphase">
3924 <heading>Details of unpack phase of installation or upgrade</heading>
3927 The procedure on installation/upgrade/overwrite/disappear
3928 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3929 stage of <tt>dpkg --install</tt>) is as follows. In each
3930 case, if a major error occurs (unless listed below) the
3931 actions are, in general, run backwards - this means that the
3932 maintainer scripts are run with different arguments in
3933 reverse order. These are the "error unwind" calls listed
3940 If a version of the package is already installed, call
3941 <example compact="compact">
3942 <var>old-prerm</var> upgrade <var>new-version</var>
3946 If the script runs but exits with a non-zero
3947 exit status, <prgn>dpkg</prgn> will attempt:
3948 <example compact="compact">
3949 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3951 If this works, the upgrade continues. If this
3952 does not work, the error unwind:
3953 <example compact="compact">
3954 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3956 If this works, then the old-version is
3957 "Installed", if not, the old version is in a
3958 "Half-Configured" state.
3964 If a "conflicting" package is being removed at the same time,
3965 or if any package will be broken (due to <tt>Breaks</tt>):
3968 If <tt>--auto-deconfigure</tt> is
3969 specified, call, for each package to be deconfigured
3970 due to <tt>Breaks</tt>:
3971 <example compact="compact">
3972 <var>deconfigured's-prerm</var> deconfigure \
3973 in-favour <var>package-being-installed</var> <var>version</var>
3976 <example compact="compact">
3977 <var>deconfigured's-postinst</var> abort-deconfigure \
3978 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3980 The deconfigured packages are marked as
3981 requiring configuration, so that if
3982 <tt>--install</tt> is used they will be
3983 configured again if possible.
3986 If any packages depended on a conflicting
3987 package being removed and <tt>--auto-deconfigure</tt> is
3988 specified, call, for each such package:
3989 <example compact="compact">
3990 <var>deconfigured's-prerm</var> deconfigure \
3991 in-favour <var>package-being-installed</var> <var>version</var> \
3992 removing <var>conflicting-package</var> <var>version</var>
3995 <example compact="compact">
3996 <var>deconfigured's-postinst</var> abort-deconfigure \
3997 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3998 removing <var>conflicting-package</var> <var>version</var>
4000 The deconfigured packages are marked as
4001 requiring configuration, so that if
4002 <tt>--install</tt> is used they will be
4003 configured again if possible.
4006 To prepare for removal of each conflicting package, call:
4007 <example compact="compact">
4008 <var>conflictor's-prerm</var> remove \
4009 in-favour <var>package</var> <var>new-version</var>
4012 <example compact="compact">
4013 <var>conflictor's-postinst</var> abort-remove \
4014 in-favour <var>package</var> <var>new-version</var>
4023 If the package is being upgraded, call:
4024 <example compact="compact">
4025 <var>new-preinst</var> upgrade <var>old-version</var>
4027 If this fails, we call:
4029 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4036 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4038 is called. If this works, then the old version
4039 is in an "Installed" state, or else it is left
4040 in an "Unpacked" state.
4045 If it fails, then the old version is left
4046 in an "Half-Installed" state.
4053 Otherwise, if the package had some configuration
4054 files from a previous version installed (i.e., it
4055 is in the "configuration files only" state):
4056 <example compact="compact">
4057 <var>new-preinst</var> install <var>old-version</var>
4061 <var>new-postrm</var> abort-install <var>old-version</var>
4063 If this fails, the package is left in a
4064 "Half-Installed" state, which requires a
4065 reinstall. If it works, the packages is left in
4066 a "Config-Files" state.
4069 Otherwise (i.e., the package was completely purged):
4070 <example compact="compact">
4071 <var>new-preinst</var> install
4074 <example compact="compact">
4075 <var>new-postrm</var> abort-install
4077 If the error-unwind fails, the package is in a
4078 "Half-Installed" phase, and requires a
4079 reinstall. If the error unwind works, the
4080 package is in a not installed state.
4087 The new package's files are unpacked, overwriting any
4088 that may be on the system already, for example any
4089 from the old version of the same package or from
4090 another package. Backups of the old files are kept
4091 temporarily, and if anything goes wrong the package
4092 management system will attempt to put them back as
4093 part of the error unwind.
4097 It is an error for a package to contain files which
4098 are on the system in another package, unless
4099 <tt>Replaces</tt> is used (see <ref id="replaces">).
4101 The following paragraph is not currently the case:
4102 Currently the <tt>- - force-overwrite</tt> flag is
4103 enabled, downgrading it to a warning, but this may not
4109 It is a more serious error for a package to contain a
4110 plain file or other kind of non-directory where another
4111 package has a directory (again, unless
4112 <tt>Replaces</tt> is used). This error can be
4113 overridden if desired using
4114 <tt>--force-overwrite-dir</tt>, but this is not
4119 Packages which overwrite each other's files produce
4120 behavior which, though deterministic, is hard for the
4121 system administrator to understand. It can easily
4122 lead to "missing" programs if, for example, a package
4123 is installed which overwrites a file from another
4124 package, and is then removed again.<footnote>
4125 Part of the problem is due to what is arguably a
4126 bug in <prgn>dpkg</prgn>.
4131 A directory will never be replaced by a symbolic link
4132 to a directory or vice versa; instead, the existing
4133 state (symlink or not) will be left alone and
4134 <prgn>dpkg</prgn> will follow the symlink if there is
4143 If the package is being upgraded, call
4144 <example compact="compact">
4145 <var>old-postrm</var> upgrade <var>new-version</var>
4149 If this fails, <prgn>dpkg</prgn> will attempt:
4150 <example compact="compact">
4151 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4153 If this works, installation continues. If not,
4155 <example compact="compact">
4156 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4158 If this fails, the old version is left in a
4159 "Half-Installed" state. If it works, dpkg now
4161 <example compact="compact">
4162 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4164 If this fails, the old version is left in a
4165 "Half-Installed" state. If it works, dpkg now
4167 <example compact="compact">
4168 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4170 If this fails, the old version is in an
4177 This is the point of no return - if
4178 <prgn>dpkg</prgn> gets this far, it won't back off
4179 past this point if an error occurs. This will
4180 leave the package in a fairly bad state, which
4181 will require a successful re-installation to clear
4182 up, but it's when <prgn>dpkg</prgn> starts doing
4183 things that are irreversible.
4188 Any files which were in the old version of the package
4189 but not in the new are removed.
4193 The new file list replaces the old.
4197 The new maintainer scripts replace the old.
4201 Any packages all of whose files have been overwritten
4202 during the installation, and which aren't required for
4203 dependencies, are considered to have been removed.
4204 For each such package
4207 <prgn>dpkg</prgn> calls:
4208 <example compact="compact">
4209 <var>disappearer's-postrm</var> disappear \
4210 <var>overwriter</var> <var>overwriter-version</var>
4214 The package's maintainer scripts are removed.
4217 It is noted in the status database as being in a
4218 sane state, namely not installed (any conffiles
4219 it may have are ignored, rather than being
4220 removed by <prgn>dpkg</prgn>). Note that
4221 disappearing packages do not have their prerm
4222 called, because <prgn>dpkg</prgn> doesn't know
4223 in advance that the package is going to
4230 Any files in the package we're unpacking that are also
4231 listed in the file lists of other packages are removed
4232 from those lists. (This will lobotomize the file list
4233 of the "conflicting" package if there is one.)
4237 The backup files made during installation, above, are
4243 The new package's status is now sane, and recorded as
4248 Here is another point of no return - if the
4249 conflicting package's removal fails we do not unwind
4250 the rest of the installation; the conflicting package
4251 is left in a half-removed limbo.
4256 If there was a conflicting package we go and do the
4257 removal actions (described below), starting with the
4258 removal of the conflicting package's files (any that
4259 are also in the package being installed have already
4260 been removed from the conflicting package's file list,
4261 and so do not get removed now).
4267 <sect id="configdetails"><heading>Details of configuration</heading>
4270 When we configure a package (this happens with <tt>dpkg
4271 --install</tt> and <tt>dpkg --configure</tt>), we first
4272 update any <tt>conffile</tt>s and then call:
4273 <example compact="compact">
4274 <var>postinst</var> configure <var>most-recently-configured-version</var>
4279 No attempt is made to unwind after errors during
4280 configuration. If the configuration fails, the package is in
4281 a "Failed Config" state, and an error message is generated.
4285 If there is no most recently configured version
4286 <prgn>dpkg</prgn> will pass a null argument.
4289 Historical note: Truly ancient (pre-1997) versions of
4290 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4291 (including the angle brackets) in this case. Even older
4292 ones did not pass a second argument at all, under any
4293 circumstance. Note that upgrades using such an old dpkg
4294 version are unlikely to work for other reasons, even if
4295 this old argument behavior is handled by your postinst script.
4301 <sect id="removedetails"><heading>Details of removal and/or
4302 configuration purging</heading>
4308 <example compact="compact">
4309 <var>prerm</var> remove
4313 If prerm fails during replacement due to conflict
4315 <var>conflictor's-postinst</var> abort-remove \
4316 in-favour <var>package</var> <var>new-version</var>
4320 <var>postinst</var> abort-remove
4324 If this fails, the package is in a "Half-Configured"
4325 state, or else it remains "Installed".
4329 The package's files are removed (except <tt>conffile</tt>s).
4332 <example compact="compact">
4333 <var>postrm</var> remove
4337 If it fails, there's no error unwind, and the package is in
4338 an "Half-Installed" state.
4343 All the maintainer scripts except the <prgn>postrm</prgn>
4348 If we aren't purging the package we stop here. Note
4349 that packages which have no <prgn>postrm</prgn> and no
4350 <tt>conffile</tt>s are automatically purged when
4351 removed, as there is no difference except for the
4352 <prgn>dpkg</prgn> status.
4356 The <tt>conffile</tt>s and any backup files
4357 (<tt>~</tt>-files, <tt>#*#</tt> files,
4358 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4363 <example compact="compact">
4364 <var>postrm</var> purge
4368 If this fails, the package remains in a "Config-Files"
4373 The package's file list is removed.
4382 <chapt id="relationships">
4383 <heading>Declaring relationships between packages</heading>
4385 <sect id="depsyntax">
4386 <heading>Syntax of relationship fields</heading>
4389 These fields all have a uniform syntax. They are a list of
4390 package names separated by commas.
4394 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4395 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4396 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4397 control fields of the package, which declare
4398 dependencies on other packages, the package names listed may
4399 also include lists of alternative package names, separated
4400 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4401 if any one of the alternative packages is installed, that
4402 part of the dependency is considered to be satisfied.
4406 All of the fields except for <tt>Provides</tt> may restrict
4407 their applicability to particular versions of each named
4408 package. This is done in parentheses after each individual
4409 package name; the parentheses should contain a relation from
4410 the list below followed by a version number, in the format
4411 described in <ref id="f-Version">.
4415 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4416 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4417 strictly earlier, earlier or equal, exactly equal, later or
4418 equal and strictly later, respectively. The deprecated
4419 forms <tt><</tt> and <tt>></tt> were used to mean
4420 earlier/later or equal, rather than strictly earlier/later,
4421 so they should not appear in new packages (though
4422 <prgn>dpkg</prgn> still supports them).
4426 Whitespace may appear at any point in the version
4427 specification subject to the rules in <ref
4428 id="controlsyntax">, and must appear where it's necessary to
4429 disambiguate; it is not otherwise significant. All of the
4430 relationship fields may span multiple lines. For
4431 consistency and in case of future changes to
4432 <prgn>dpkg</prgn> it is recommended that a single space be
4433 used after a version relationship and before a version
4434 number; it is also conventional to put a single space after
4435 each comma, on either side of each vertical bar, and before
4436 each open parenthesis. When wrapping a relationship field, it
4437 is conventional to do so after a comma and before the space
4438 following that comma.
4442 For example, a list of dependencies might appear as:
4443 <example compact="compact">
4446 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4451 Relationships may be restricted to a certain set of
4452 architectures. This is indicated in brackets after each
4453 individual package name and the optional version specification.
4454 The brackets enclose a list of Debian architecture names
4455 separated by whitespace. Exclamation marks may be prepended to
4456 each of the names. (It is not permitted for some names to be
4457 prepended with exclamation marks while others aren't.)
4461 For build relationship fields
4462 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4463 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>), if
4464 the current Debian host architecture is not in this list and
4465 there are no exclamation marks in the list, or it is in the list
4466 with a prepended exclamation mark, the package name and the
4467 associated version specification are ignored completely for the
4468 purposes of defining the relationships.
4473 <example compact="compact">
4475 Build-Depends-Indep: texinfo
4476 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4477 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4479 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4480 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4481 <tt>gnumach-dev</tt> only on hurd-i386.
4485 For binary relationship fields, the architecture restriction
4486 syntax is only supported in the source package control
4487 file <file>debian/control</file>. When the corresponding binary
4488 package control file is generated, the relationship will either
4489 be omitted or included without the architecture restriction
4490 based on the architecture of the binary package. This means
4491 that architecture restrictions must not be used in binary
4492 relationship fields for architecture-independent packages
4493 (<tt>Architecture: all</tt>).
4498 <example compact="compact">
4499 Depends: foo [i386], bar [amd64]
4501 becomes <tt>Depends: foo</tt> when the package is built on
4502 the <tt>i386</tt> architecture, <tt>Depends: bar</tt> when the
4503 package is built on the <tt>amd64</tt> architecture, and omitted
4504 entirely in binary packages built on all other architectures.
4508 If the architecture-restricted dependency is part of a set of
4509 alternatives using <tt>|</tt>, that alternative is ignored
4510 completely on architectures that do not match the restriction.
4512 <example compact="compact">
4513 Build-Depends: foo [!i386] | bar [!amd64]
4515 is equivalent to <tt>bar</tt> on the i386 architecture, to
4516 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4517 bar</tt> on all other architectures.
4521 Relationships may also be restricted to a certain set of
4522 architectures using architecture wildcards. The syntax for
4523 declaring such restrictions is the same as declaring
4524 restrictions using a certain set of architectures without
4525 architecture wildcards. For example:
4526 <example compact="compact">
4527 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4529 is equivalent to <tt>foo</tt> on architectures using the Linux
4530 kernel and any cpu, <tt>bar</tt> on architectures using any
4531 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4532 using a kernel other than Linux.
4536 Note that the binary package relationship fields such as
4537 <tt>Depends</tt> appear in one of the binary package
4538 sections of the control file, whereas the build-time
4539 relationships such as <tt>Build-Depends</tt> appear in the
4540 source package section of the control file (which is the
4545 <sect id="binarydeps">
4546 <heading>Binary Dependencies - <tt>Depends</tt>,
4547 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4548 <tt>Pre-Depends</tt>
4552 Packages can declare in their control file that they have
4553 certain relationships to other packages - for example, that
4554 they may not be installed at the same time as certain other
4555 packages, and/or that they depend on the presence of others.
4559 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4560 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4561 <tt>Breaks</tt> and <tt>Conflicts</tt> control fields.
4562 <tt>Breaks</tt> is described in <ref id="breaks">, and
4563 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4564 rest are described below.
4568 These seven fields are used to declare a dependency
4569 relationship by one package on another. Except for
4570 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4571 depending (binary) package's control file.
4572 (<tt>Enhances</tt> appears in the recommending package's
4573 control file, and <tt>Breaks</tt> appears in the version of
4574 depended-on package which causes the named package to
4579 A <tt>Depends</tt> field takes effect <em>only</em> when a
4580 package is to be configured. It does not prevent a package
4581 being on the system in an unconfigured state while its
4582 dependencies are unsatisfied, and it is possible to replace
4583 a package whose dependencies are satisfied and which is
4584 properly installed with a different version whose
4585 dependencies are not and cannot be satisfied; when this is
4586 done the depending package will be left unconfigured (since
4587 attempts to configure it will give errors) and will not
4588 function properly. If it is necessary, a
4589 <tt>Pre-Depends</tt> field can be used, which has a partial
4590 effect even when a package is being unpacked, as explained
4591 in detail below. (The other three dependency fields,
4592 <tt>Recommends</tt>, <tt>Suggests</tt> and
4593 <tt>Enhances</tt>, are only used by the various front-ends
4594 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4595 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4599 For this reason packages in an installation run are usually
4600 all unpacked first and all configured later; this gives
4601 later versions of packages with dependencies on later
4602 versions of other packages the opportunity to have their
4603 dependencies satisfied.
4607 In case of circular dependencies, since installation or
4608 removal order honoring the dependency order can't be
4609 established, dependency loops are broken at some point
4610 (based on rules below), and some packages may not be able to
4611 rely on their dependencies being present when being
4612 installed or removed, depending on which side of the break
4613 of the circular dependency loop they happen to be on. If one
4614 of the packages in the loop has no postinst script, then the
4615 cycle will be broken at that package, so as to ensure that
4616 all postinst scripts run with the dependencies properly
4617 configured if this is possible. Otherwise the breaking point
4622 The <tt>Depends</tt> field thus allows package maintainers
4623 to impose an order in which packages should be configured.
4627 The meaning of the five dependency fields is as follows:
4629 <tag><tt>Depends</tt></tag>
4632 This declares an absolute dependency. A package will
4633 not be configured unless all of the packages listed in
4634 its <tt>Depends</tt> field have been correctly
4639 The <tt>Depends</tt> field should be used if the
4640 depended-on package is required for the depending
4641 package to provide a significant amount of
4646 The <tt>Depends</tt> field should also be used if the
4647 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4648 <prgn>postrm</prgn> scripts require the package to be
4649 present in order to run. Note, however, that the
4650 <prgn>postrm</prgn> cannot rely on any non-essential
4651 packages to be present during the <tt>purge</tt>
4655 <tag><tt>Recommends</tt></tag>
4658 This declares a strong, but not absolute, dependency.
4662 The <tt>Recommends</tt> field should list packages
4663 that would be found together with this one in all but
4664 unusual installations.
4668 <tag><tt>Suggests</tt></tag>
4670 This is used to declare that one package may be more
4671 useful with one or more others. Using this field
4672 tells the packaging system and the user that the
4673 listed packages are related to this one and can
4674 perhaps enhance its usefulness, but that installing
4675 this one without them is perfectly reasonable.
4678 <tag><tt>Enhances</tt></tag>
4680 This field is similar to Suggests but works in the
4681 opposite direction. It is used to declare that a
4682 package can enhance the functionality of another
4686 <tag><tt>Pre-Depends</tt></tag>
4689 This field is like <tt>Depends</tt>, except that it
4690 also forces <prgn>dpkg</prgn> to complete installation
4691 of the packages named before even starting the
4692 installation of the package which declares the
4693 pre-dependency, as follows:
4697 When a package declaring a pre-dependency is about to
4698 be <em>unpacked</em> the pre-dependency can be
4699 satisfied if the depended-on package is either fully
4700 configured, <em>or even if</em> the depended-on
4701 package(s) are only unpacked or in the "Half-Configured"
4702 state, provided that they have been configured
4703 correctly at some point in the past (and not removed
4704 or partially removed since). In this case, both the
4705 previously-configured and currently unpacked or
4706 "Half-Configured" versions must satisfy any version
4707 clause in the <tt>Pre-Depends</tt> field.
4711 When the package declaring a pre-dependency is about
4712 to be <em>configured</em>, the pre-dependency will be
4713 treated as a normal <tt>Depends</tt>, that is, it will
4714 be considered satisfied only if the depended-on
4715 package has been correctly configured.
4719 <tt>Pre-Depends</tt> should be used sparingly,
4720 preferably only by packages whose premature upgrade or
4721 installation would hamper the ability of the system to
4722 continue with any upgrade that might be in progress.
4726 <tt>Pre-Depends</tt> are also required if the
4727 <prgn>preinst</prgn> script depends on the named
4728 package. It is best to avoid this situation if
4736 When selecting which level of dependency to use you should
4737 consider how important the depended-on package is to the
4738 functionality of the one declaring the dependency. Some
4739 packages are composed of components of varying degrees of
4740 importance. Such a package should list using
4741 <tt>Depends</tt> the package(s) which are required by the
4742 more important components. The other components'
4743 requirements may be mentioned as Suggestions or
4744 Recommendations, as appropriate to the components' relative
4750 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4753 When one binary package declares that it breaks another,
4754 <prgn>dpkg</prgn> will refuse to allow the package which
4755 declares <tt>Breaks</tt> be installed unless the broken
4756 package is deconfigured first, and it will refuse to
4757 allow the broken package to be reconfigured.
4761 A package will not be regarded as causing breakage merely
4762 because its configuration files are still installed; it must
4763 be at least "Half-Installed".
4767 A special exception is made for packages which declare that
4768 they break their own package name or a virtual package which
4769 they provide (see below): this does not count as a real
4774 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4775 version clause; such a <tt>Breaks</tt> is introduced in the
4776 version of an (implicit or explicit) dependency which violates
4777 an assumption or reveals a bug in earlier versions of the broken
4778 package, or which takes over a file from earlier versions of the
4779 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
4780 will inform higher-level package management tools that the
4781 broken package must be upgraded before the new one.
4785 If the breaking package also overwrites some files from the
4786 older package, it should use <tt>Replaces</tt> to ensure this
4787 goes smoothly. See <ref id="replaces"> for a full discussion
4788 of taking over files from other packages, including how to
4789 use <tt>Breaks</tt> in those cases.
4793 Many of the cases where <tt>Breaks</tt> should be used were
4794 previously handled with <tt>Conflicts</tt>
4795 because <tt>Breaks</tt> did not yet exist.
4796 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
4797 See <ref id="conflicts"> for more information about the
4802 <sect id="conflicts">
4803 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4806 When one binary package declares a conflict with another
4807 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4808 refuse to allow them to be installed on the system at the
4809 same time. This is a stronger restriction than <tt>Breaks</tt>,
4810 which just prevents both packages from being configured at the
4811 same time. Conflicting packages cannot be unpacked on the
4812 system at the same time.
4816 If one package is to be installed, the other must be removed
4817 first. If the package being installed is marked as replacing
4818 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
4819 normally be used in this case) the one on the system, or the one
4820 on the system is marked as deselected, or both packages are
4821 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
4822 automatically remove the package which is causing the conflict.
4823 Otherwise, it will halt the installation of the new package with
4824 an error. This mechanism is specifically designed to produce an
4825 error when the installed package is <tt>Essential</tt>, but the
4830 A package will not cause a conflict merely because its
4831 configuration files are still installed; it must be at least
4836 A special exception is made for packages which declare a
4837 conflict with their own package name, or with a virtual
4838 package which they provide (see below): this does not
4839 prevent their installation, and allows a package to conflict
4840 with others providing a replacement for it. You use this
4841 feature when you want the package in question to be the only
4842 package providing some feature.
4846 Normally, <tt>Breaks</tt> should be used instead
4847 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
4848 stronger restriction on the ordering of package installation or
4849 upgrade and can make it more difficult for the package manager
4850 to find a correct solution to an upgrade or installation
4851 problem. <tt>Breaks</tt> should be used
4853 <item>when moving a file from one package to another (see
4854 <ref id="replaces">),</item>
4855 <item>when splitting a package (a special case of the previous
4857 <item>when the breaking package exposes a bug in or interacts
4858 badly with particular versions of the broken
4861 <tt>Conflicts</tt> should be used
4863 <item>when two packages provide the same file and will
4864 continue to do so,</item>
4865 <item>in conjunction with <tt>Provides</tt> when only one
4866 package providing a given virtual facility may be installed
4867 at a time (see <ref id="virtual">),</item>
4868 <item>in other cases where one must prevent simultaneous
4869 installation of two packages for reasons that are ongoing
4870 (not fixed in a later version of one of the packages) or
4871 that must prevent both packages from being unpacked at the
4872 same time, not just configured.</item>
4874 Be aware that adding <tt>Conflicts</tt> is normally not the best
4875 solution when two packages provide the same files. Depending on
4876 the reason for that conflict, using alternatives or renaming the
4877 files is often a better approach. See, for
4878 example, <ref id="binaries">.
4882 Neither <tt>Breaks</tt> nor <tt>Conflicts</tt> should be used
4883 unless two packages cannot be installed at the same time or
4884 installing them both causes one of them to be broken or
4885 unusable. Having similar functionality or performing the same
4886 tasks as another package is not sufficient reason to
4887 declare <tt>Breaks</tt> or <tt>Conflicts</tt> with that package.
4891 A <tt>Conflicts</tt> entry may have an "earlier than" version
4892 clause if the reason for the conflict is corrected in a later
4893 version of one of the packages. However, normally the presence
4894 of an "earlier than" version clause is a sign
4895 that <tt>Breaks</tt> should have been used instead. An "earlier
4896 than" version clause in <tt>Conflicts</tt>
4897 prevents <prgn>dpkg</prgn> from upgrading or installing the
4898 package which declares such a conflict until the upgrade or
4899 removal of the conflicted-with package has been completed, which
4900 is a strong restriction.
4904 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4908 As well as the names of actual ("concrete") packages, the
4909 package relationship fields <tt>Depends</tt>,
4910 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4911 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4912 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4913 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4914 may mention "virtual packages".
4918 A <em>virtual package</em> is one which appears in the
4919 <tt>Provides</tt> control field of another package. The effect
4920 is as if the package(s) which provide a particular virtual
4921 package name had been listed by name everywhere the virtual
4922 package name appears. (See also <ref id="virtual_pkg">)
4926 If there are both concrete and virtual packages of the same
4927 name, then the dependency may be satisfied (or the conflict
4928 caused) by either the concrete package with the name in
4929 question or any other concrete package which provides the
4930 virtual package with the name in question. This is so that,
4931 for example, supposing we have
4932 <example compact="compact">
4935 </example> and someone else releases an enhanced version of
4936 the <tt>bar</tt> package they can say:
4937 <example compact="compact">
4941 and the <tt>bar-plus</tt> package will now also satisfy the
4942 dependency for the <tt>foo</tt> package.
4946 If a relationship field has a version number attached, only real
4947 packages will be considered to see whether the relationship is
4948 satisfied (or the prohibition violated, for a conflict or
4949 breakage). In other words, if a version number is specified,
4950 this is a request to ignore all <tt>Provides</tt> for that
4951 package name and consider only real packages. The package
4952 manager will assume that a package providing that virtual
4953 package is not of the "right" version. A <tt>Provides</tt>
4954 field may not contain version numbers, and the version number of
4955 the concrete package which provides a particular virtual package
4956 will not be considered when considering a dependency on or
4957 conflict with the virtual package name.<footnote>
4958 It is possible that a future release of <prgn>dpkg</prgn> may
4959 add the ability to specify a version number for each virtual
4960 package it provides. This feature is not yet present,
4961 however, and is expected to be used only infrequently.
4966 To specify which of a set of real packages should be the default
4967 to satisfy a particular dependency on a virtual package, list
4968 the real package as an alternative before the virtual one.
4972 If the virtual package represents a facility that can only be
4973 provided by one real package at a time, such as
4974 the <package>mail-transport-agent</package> virtual package that
4975 requires installation of a binary that would conflict with all
4976 other providers of that virtual package (see
4977 <ref id="mail-transport-agents">), all packages providing that
4978 virtual package should also declare a conflict with it
4979 using <tt>Conflicts</tt>. This will ensure that at most one
4980 provider of that virtual package is unpacked or installed at a
4985 <sect id="replaces"><heading>Overwriting files and replacing
4986 packages - <tt>Replaces</tt></heading>
4989 Packages can declare in their control file that they should
4990 overwrite files in certain other packages, or completely replace
4991 other packages. The <tt>Replaces</tt> control field has these
4992 two distinct purposes.
4995 <sect1><heading>Overwriting files in other packages</heading>
4998 It is usually an error for a package to contain files which
4999 are on the system in another package. However, if the
5000 overwriting package declares that it <tt>Replaces</tt> the one
5001 containing the file being overwritten, then <prgn>dpkg</prgn>
5002 will replace the file from the old package with that from the
5003 new. The file will no longer be listed as "owned" by the old
5004 package and will be taken over by the new package.
5005 Normally, <tt>Breaks</tt> should be used in conjunction
5006 with <tt>Replaces</tt>.<footnote>
5007 To see why <tt>Breaks</tt> is normally needed in addition
5008 to <tt>Replaces</tt>, consider the case of a file in the
5009 package <package>foo</package> being taken over by the
5010 package <package>foo-data</package>.
5011 <tt>Replaces</tt> will allow <package>foo-data</package> to
5012 be installed and take over that file. However,
5013 without <tt>Breaks</tt>, nothing
5014 requires <package>foo</package> to be upgraded to a newer
5015 version that knows it does not include that file and instead
5016 depends on <package>foo-data</package>. Nothing would
5017 prevent the new <package>foo-data</package> package from
5018 being installed and then removed, removing the file that it
5019 took over from <package>foo</package>. After that
5020 operation, the package manager would think the system was in
5021 a consistent state, but the <package>foo</package> package
5022 would be missing one of its files.
5027 For example, if a package <package>foo</package> is split
5028 into <package>foo</package> and <package>foo-data</package>
5029 starting at version 1.2-3, <package>foo-data</package> would
5031 <example compact="compact">
5032 Replaces: foo (<< 1.2-3)
5033 Breaks: foo (<< 1.2-3)
5035 in its control file. The new version of the
5036 package <package>foo</package> would normally have the field
5037 <example compact="compact">
5038 Depends: foo-data (>= 1.2-3)
5040 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
5041 the files moved into <package>foo-data</package> are not
5042 required for normal operation).
5046 If a package is completely replaced in this way, so that
5047 <prgn>dpkg</prgn> does not know of any files it still
5048 contains, it is considered to have "disappeared". It will
5049 be marked as not wanted on the system (selected for
5050 removal) and not installed. Any <tt>conffile</tt>s
5051 details noted for the package will be ignored, as they
5052 will have been taken over by the overwriting package. The
5053 package's <prgn>postrm</prgn> script will be run with a
5054 special argument to allow the package to do any final
5055 cleanup required. See <ref id="mscriptsinstact">.
5057 Replaces is a one way relationship. You have to install
5058 the replacing package after the replaced package.
5063 For this usage of <tt>Replaces</tt>, virtual packages (see
5064 <ref id="virtual">) are not considered when looking at a
5065 <tt>Replaces</tt> field. The packages declared as being
5066 replaced must be mentioned by their real names.
5070 This usage of <tt>Replaces</tt> only takes effect when both
5071 packages are at least partially on the system at once. It is
5072 not relevant if the packages conflict unless the conflict has
5077 <sect1><heading>Replacing whole packages, forcing their
5081 Second, <tt>Replaces</tt> allows the packaging system to
5082 resolve which package should be removed when there is a
5083 conflict (see <ref id="conflicts">). This usage only takes
5084 effect when the two packages <em>do</em> conflict, so that the
5085 two usages of this field do not interfere with each other.
5089 In this situation, the package declared as being replaced
5090 can be a virtual package, so for example, all mail
5091 transport agents (MTAs) would have the following fields in
5092 their control files:
5093 <example compact="compact">
5094 Provides: mail-transport-agent
5095 Conflicts: mail-transport-agent
5096 Replaces: mail-transport-agent
5098 ensuring that only one MTA can be installed at any one
5099 time. See <ref id="virtual"> for more information about this
5104 <sect id="sourcebinarydeps">
5105 <heading>Relationships between source and binary packages -
5106 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5107 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5111 Source packages that require certain binary packages to be
5112 installed or absent at the time of building the package
5113 can declare relationships to those binary packages.
5117 This is done using the <tt>Build-Depends</tt>,
5118 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5119 <tt>Build-Conflicts-Indep</tt> control fields.
5123 Build-dependencies on "build-essential" binary packages can be
5124 omitted. Please see <ref id="pkg-relations"> for more information.
5128 The dependencies and conflicts they define must be satisfied
5129 (as defined earlier for binary packages) in order to invoke
5130 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5132 There is no Build-Depends-Arch; this role is essentially
5133 met with Build-Depends. Anyone building the
5134 <tt>build-indep</tt> and <tt>binary-indep</tt> targets is
5135 assumed to be building the whole package, and therefore
5136 installation of all build dependencies is required.
5139 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5140 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5141 not yet know how to check for its existence, and
5142 <tt>binary-arch</tt>. The purpose of the original split
5143 between <tt>Build-Depends</tt> and
5144 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5145 wouldn't need to install extra packages needed only for the
5146 binary-indep targets. But without a build-arch/build-indep
5147 split, this didn't work, since most of the work is done in
5148 the build target, not in the binary target.
5152 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5153 <tt>binary-arch</tt></tag>
5155 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5156 fields must be satisfied when these targets are invoked.
5158 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5159 and <tt>binary-indep</tt></tag>
5161 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5162 <tt>Build-Depends-Indep</tt>, and
5163 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5164 these targets are invoked.
5172 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5175 Packages containing shared libraries must be constructed with
5176 a little care to make sure that the shared library is always
5177 available. This is especially important for packages whose
5178 shared libraries are vitally important, such as the C library
5179 (currently <tt>libc6</tt>).
5183 This section deals only with public shared libraries: shared
5184 libraries that are placed in directories searched by the dynamic
5185 linker by default or which are intended to be linked against
5186 normally and possibly used by other, independent packages. Shared
5187 libraries that are internal to a particular package or that are
5188 only loaded as dynamic modules are not covered by this section and
5189 are not subject to its requirements.
5193 A shared library is identified by the <tt>SONAME</tt> attribute
5194 stored in its dynamic section. When a binary is linked against a
5195 shared library, the <tt>SONAME</tt> of the shared library is
5196 recorded in the binary's <tt>NEEDED</tt> section so that the
5197 dynamic linker knows that library must be loaded at runtime. The
5198 shared library file's full name (which usually contains additional
5199 version information not needed in the <tt>SONAME</tt>) is
5200 therefore normally not referenced directly. Instead, the shared
5201 library is loaded by its <tt>SONAME</tt>, which exists on the file
5202 system as a symlink pointing to the full name of the shared
5203 library. This symlink must be provided by the
5204 package. <ref id="sharedlibs-runtime"> describes how to do this.
5206 This is a convention of shared library versioning, but not a
5207 requirement. Some libraries use the <tt>SONAME</tt> as the full
5208 library file name instead and therefore do not need a symlink.
5209 Most, however, encode additional information about
5210 backwards-compatible revisions as a minor version number in the
5211 file name. The <tt>SONAME</tt> itself only changes when
5212 binaries linked with the earlier version of the shared library
5213 may no longer work, but the filename may change with each
5214 release of the library. See <ref id="sharedlibs-runtime"> for
5220 When linking a binary or another shared library against a shared
5221 library, the <tt>SONAME</tt> for that shared library is not yet
5222 known. Instead, the shared library is found by looking for a file
5223 matching the library name with <tt>.so</tt> appended. This file
5224 exists on the file system as a symlink pointing to the shared
5229 Shared libraries are normally split into several binary packages.
5230 The <tt>SONAME</tt> symlink is installed by the runtime shared
5231 library package, and the bare <tt>.so</tt> symlink is installed in
5232 the development package since it's only used when linking binaries
5233 or shared libraries. However, there are some exceptions for
5234 unusual shared libraries or for shared libraries that are also
5235 loaded as dynamic modules by other programs.
5239 This section is primarily concerned with how the separation of
5240 shared libraries into multiple packages should be done and how
5241 dependencies on and between shared library binary packages are
5242 managed in Debian. <ref id="libraries"> should be read in
5243 conjunction with this section and contains additional rules for
5244 the files contained in the shared library packages.
5247 <sect id="sharedlibs-runtime">
5248 <heading>Run-time shared libraries</heading>
5251 The run-time shared library must be placed in a package
5252 whose name changes whenever the <tt>SONAME</tt> of the shared
5253 library changes. This allows several versions of the shared
5254 library to be installed at the same time, allowing installation
5255 of the new version of the shared library without immediately
5256 breaking binaries that depend on the old version. Normally, the
5257 run-time shared library and its <tt>SONAME</tt> symlink should
5258 be placed in a package named
5259 <package><var>libraryname</var><var>soversion</var></package>,
5260 where <var>soversion</var> is the version number in
5261 the <tt>SONAME</tt> of the shared library.
5262 See <ref id="shlibs"> for detailed information on how to
5263 determine this version. Alternatively, if it would be confusing
5264 to directly append <var>soversion</var>
5265 to <var>libraryname</var> (if, for example, <var>libraryname</var>
5266 itself ends in a number), you should use
5267 <package><var>libraryname</var>-<var>soversion</var></package>
5272 If you have several shared libraries built from the same source
5273 tree, you may lump them all together into a single shared
5274 library package provided that all of their <tt>SONAME</tt>s will
5275 always change together. Be aware that this is not normally the
5276 case, and if the <tt>SONAME</tt>s do not change together,
5277 upgrading such a merged shared library package will be
5278 unnecessarily difficult because of file conflicts with the old
5279 version of the package. When in doubt, always split shared
5280 library packages so that each binary package installs a single
5285 Every time the shared library ABI changes in a way that may
5286 break binaries linked against older versions of the shared
5287 library, the <tt>SONAME</tt> of the library and the
5288 corresponding name for the binary package containing the runtime
5289 shared library should change. Normally, this means
5290 the <tt>SONAME</tt> should change any time an interface is
5291 removed from the shared library or the signature of an interface
5292 (the number of parameters or the types of parameters that it
5293 takes, for example) is changed. This practice is vital to
5294 allowing clean upgrades from older versions of the package and
5295 clean transitions between the old ABI and new ABI without having
5296 to upgrade every affected package simultaneously.
5300 The <tt>SONAME</tt> and binary package name need not, and indeed
5301 normally should not, change if new interfaces are added but none
5302 are removed or changed, since this will not break binaries
5303 linked against the old shared library. Correct versioning of
5304 dependencies on the newer shared library by binaries that use
5305 the new interfaces is handled via
5306 the <qref id="sharedlibs-shlibdeps"><tt>shlibs</tt>
5307 system</qref> or via symbols files (see
5308 <manref name="deb-symbols" section="5">).
5312 The package should install the shared libraries under
5313 their normal names. For example, the <package>libgdbm3</package>
5314 package should install <file>libgdbm.so.3.0.0</file> as
5315 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5316 renamed or re-linked by any <prgn>prerm</prgn> or
5317 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5318 of renaming things safely without affecting running programs,
5319 and attempts to interfere with this are likely to lead to
5324 Shared libraries should not be installed executable, since
5325 the dynamic linker does not require this and trying to
5326 execute a shared library usually results in a core dump.
5330 The run-time library package should include the symbolic link for
5331 the <tt>SONAME</tt> that <prgn>ldconfig</prgn> would create for
5332 the shared libraries. For example,
5333 the <package>libgdbm3</package> package should include a symbolic
5334 link from <file>/usr/lib/libgdbm.so.3</file> to
5335 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5336 linker (for example <prgn>ld.so</prgn> or
5337 <prgn>ld-linux.so.*</prgn>) can find the library between the
5338 time that <prgn>dpkg</prgn> installs it and the time that
5339 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5341 The package management system requires the library to be
5342 placed before the symbolic link pointing to it in the
5343 <file>.deb</file> file. This is so that when
5344 <prgn>dpkg</prgn> comes to install the symlink
5345 (overwriting the previous symlink pointing at an older
5346 version of the library), the new shared library is already
5347 in place. In the past, this was achieved by creating the
5348 library in the temporary packaging directory before
5349 creating the symlink. Unfortunately, this was not always
5350 effective, since the building of the tar file in the
5351 <file>.deb</file> depended on the behavior of the underlying
5352 file system. Some file systems (such as reiserfs) reorder
5353 the files so that the order of creation is forgotten.
5354 Since version 1.7.0, <prgn>dpkg</prgn>
5355 reorders the files itself as necessary when building a
5356 package. Thus it is no longer important to concern
5357 oneself with the order of file creation.
5361 <sect1 id="ldconfig">
5362 <heading><tt>ldconfig</tt></heading>
5365 Any package installing shared libraries in one of the default
5366 library directories of the dynamic linker (which are currently
5367 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5368 listed in <file>/etc/ld.so.conf</file><footnote>
5370 <list compact="compact">
5371 <item>/usr/local/lib</item>
5372 <item>/usr/lib/libc5-compat</item>
5373 <item>/lib/libc5-compat</item>
5376 must use <prgn>ldconfig</prgn> to update the shared library
5381 The package maintainer scripts must only call
5382 <prgn>ldconfig</prgn> under these circumstances:
5383 <list compact="compact">
5384 <item>When the <prgn>postinst</prgn> script is run with a
5385 first argument of <tt>configure</tt>, the script must call
5386 <prgn>ldconfig</prgn>, and may optionally invoke
5387 <prgn>ldconfig</prgn> at other times.
5389 <item>When the <prgn>postrm</prgn> script is run with a
5390 first argument of <tt>remove</tt>, the script should call
5391 <prgn>ldconfig</prgn>.
5396 During install or upgrade, the preinst is called before
5397 the new files are installed, so calling "ldconfig" is
5398 pointless. The preinst of an existing package can also be
5399 called if an upgrade fails. However, this happens during
5400 the critical time when a shared libs may exist on-disk
5401 under a temporary name. Thus, it is dangerous and
5402 forbidden by current policy to call "ldconfig" at this
5407 When a package is installed or upgraded, "postinst
5408 configure" runs after the new files are safely on-disk.
5409 Since it is perfectly safe to invoke ldconfig
5410 unconditionally in a postinst, it is OK for a package to
5411 simply put ldconfig in its postinst without checking the
5412 argument. The postinst can also be called to recover from
5413 a failed upgrade. This happens before any new files are
5414 unpacked, so there is no reason to call "ldconfig" at this
5419 For a package that is being removed, prerm is
5420 called with all the files intact, so calling ldconfig is
5421 useless. The other calls to "prerm" happen in the case of
5422 upgrade at a time when all the files of the old package
5423 are on-disk, so again calling "ldconfig" is pointless.
5427 postrm, on the other hand, is called with the "remove"
5428 argument just after the files are removed, so this is
5429 the proper time to call "ldconfig" to notify the system
5430 of the fact that the shared libraries from the package
5431 are removed. The postrm can be called at several other
5432 times. At the time of "postrm purge", "postrm
5433 abort-install", or "postrm abort-upgrade", calling
5434 "ldconfig" is useless because the shared lib files are
5435 not on-disk. However, when "postrm" is invoked with
5436 arguments "upgrade", "failed-upgrade", or "disappear", a
5437 shared lib may exist on-disk under a temporary filename.
5445 <sect id="sharedlibs-support-files">
5446 <heading>Shared library support files</heading>
5449 If your package contains files whose names do not change with
5450 each change in the library shared object version, you must not
5451 put them in the shared library package. Otherwise, several
5452 versions of the shared library cannot be installed at the same
5453 time without filename clashes, making upgrades and transitions
5454 unnecessarily difficult.
5458 It is recommended that supporting files and run-time support
5459 programs that do not need to be invoked manually by users, but
5460 are nevertheless required for the package to function, be placed
5461 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5462 preferably under <file>/usr/lib/</file><var>package-name</var>.
5463 If the program or file is architecture independent, the
5464 recommendation is for it to be placed in a subdirectory of
5465 <file>/usr/share</file> instead, preferably under
5466 <file>/usr/share/</file><var>package-name</var>. Following the
5467 <var>package-name</var> naming convention ensures that the file
5468 names change when the shared object version changes.
5472 Run-time support programs that use the shared library but are
5473 not required for the library to function or files used by the
5474 shared library that can be used by any version of the shared
5475 library package should instead be put in a separate package.
5476 This package might typically be named
5477 <package><var>libraryname</var>-tools</package>; note the
5478 absence of the <var>soversion</var> in the package name.
5482 Files and support programs only useful when compiling software
5483 against the library should be included in the development
5484 package for the library.<footnote>
5485 For example, a <file><var>package-name</var>-config</file>
5486 script or <package>pkg-config</package> configuration files.
5491 <sect id="sharedlibs-static">
5492 <heading>Static libraries</heading>
5495 The static library (<file><var>libraryname.a</var></file>)
5496 is usually provided in addition to the shared version.
5497 It is placed into the development package (see below).
5501 In some cases, it is acceptable for a library to be
5502 available in static form only; these cases include:
5504 <item>libraries for languages whose shared library support
5505 is immature or unstable</item>
5506 <item>libraries whose interfaces are in flux or under
5507 development (commonly the case when the library's
5508 major version number is zero, or where the ABI breaks
5509 across patchlevels)</item>
5510 <item>libraries which are explicitly intended to be
5511 available only in static form by their upstream
5516 <sect id="sharedlibs-dev">
5517 <heading>Development files</heading>
5520 If there are development files associated with a shared library,
5521 the source package needs to generate a binary development package
5522 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5523 or if you prefer only to support one development version at a
5524 time, <package><var>libraryname</var>-dev</package>. Installing
5525 the development package must result in installation of all the
5526 development files necessary for compiling programs against that
5527 shared library.<footnote>
5528 This wording allows the development files to be split into
5529 several packages, such as a separate architecture-independent
5530 <package><var>libraryname</var>-headers</package>, provided that
5531 the development package depends on all the required additional
5537 In case several development versions of a library exist, you may
5538 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5539 <ref id="conflicts">) to ensure that the user only installs one
5540 development version at a time (as different development versions are
5541 likely to have the same header files in them, which would cause a
5542 filename clash if both were installed).
5546 The development package should contain a symlink for the associated
5547 shared library without a version number. For example, the
5548 <package>libgdbm-dev</package> package should include a symlink
5549 from <file>/usr/lib/libgdbm.so</file> to
5550 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5551 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5552 <file>libgdbm.so</file> when compiling dynamically.
5556 If the package provides Ada Library Information
5557 (<file>*.ali</file>) files for use with GNAT, these files must be
5558 installed read-only (mode 0444) so that GNAT will not attempt to
5559 recompile them. This overrides the normal file mode requirements
5560 given in <ref id="permissions-owners">.
5564 <sect id="sharedlibs-intradeps">
5565 <heading>Dependencies between the packages of the same library</heading>
5568 Typically the development version should have an exact
5569 version dependency on the runtime library, to make sure that
5570 compilation and linking happens correctly. The
5571 <tt>${binary:Version}</tt> substitution variable can be
5572 useful for this purpose.
5574 Previously, <tt>${Source-Version}</tt> was used, but its name
5575 was confusing and it has been deprecated since dpkg 1.13.19.
5580 <sect id="sharedlibs-shlibdeps">
5581 <heading>Dependencies between the library and other packages -
5582 the <tt>shlibs</tt> system</heading>
5585 If a package contains a binary or library which links to a
5586 shared library, we must ensure that when the package is
5587 installed on the system, all of the libraries needed are
5588 also installed. This requirement led to the creation of the
5589 <tt>shlibs</tt> system, which is very simple in its design:
5590 any package which <em>provides</em> a shared library also
5591 provides information on the package dependencies required to
5592 ensure the presence of this library, and any package which
5593 <em>uses</em> a shared library uses this information to
5594 determine the dependencies it requires. The files which
5595 contain the mapping from shared libraries to the necessary
5596 dependency information are called <file>shlibs</file> files.
5600 When a package is built which contains any shared libraries, it
5601 must provide a <file>shlibs</file> file for other packages to
5602 use. When a package is built which contains any shared
5603 libraries or compiled binaries, it must run
5604 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5605 on these to determine the libraries used and hence the
5606 dependencies needed by this package.<footnote>
5608 <prgn>dpkg-shlibdeps</prgn> will use a program
5609 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
5610 the libraries directly needed by the binaries or shared
5611 libraries in the package.
5615 We say that a binary <tt>foo</tt> <em>directly</em> uses
5616 a library <tt>libbar</tt> if it is explicitly linked
5617 with that library (that is, the library is listed in the ELF
5618 <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
5619 to the link line when the binary is created). Other
5620 libraries that are needed by <tt>libbar</tt> are linked
5621 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5622 linker will load them automatically when it loads
5623 <tt>libbar</tt>. A package should depend on the libraries
5624 it directly uses, but not the libraries it indirectly uses.
5625 The dependencies for those libraries will automatically pull
5626 in the other libraries.
5630 A good example of where this helps is the following. We
5631 could update <tt>libimlib</tt> with a new version that
5632 supports a new graphics format called dgf (but retaining the
5633 same major version number) and depends on <tt>libdgf</tt>.
5634 If we used <prgn>ldd</prgn> to add dependencies for every
5635 library directly or indirectly linked with a binary, every
5636 package that uses <tt>libimlib</tt> would need to be
5637 recompiled so it would also depend on <tt>libdgf</tt> or it
5638 wouldn't run due to missing symbols. Since dependencies are
5639 only added based on ELF <tt>NEEDED</tt> attribute, packages
5640 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
5641 having the dependency on <tt>libdgf</tt> and so they would
5642 not need rebuilding.
5648 In the following sections, we will first describe where the
5649 various <tt>shlibs</tt> files are to be found, then how to
5650 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5651 file format and how to create them if your package contains a
5656 <heading>The <tt>shlibs</tt> files present on the system</heading>
5659 There are several places where <tt>shlibs</tt> files are
5660 found. The following list gives them in the order in which
5662 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5663 (The first one which gives the required information is used.)
5669 <p><file>debian/shlibs.local</file></p>
5672 This lists overrides for this package. This file should
5673 normally not be used, but may be needed temporarily in
5674 unusual situations to work around bugs in other packages,
5675 or in unusual cases where the normally declared dependency
5676 information in the installed <file>shlibs</file> file for
5677 a library cannot be used. This file overrides information
5678 obtained from any other source.
5683 <p><file>/etc/dpkg/shlibs.override</file></p>
5686 This lists global overrides. This list is normally
5687 empty. It is maintained by the local system
5693 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5696 When packages are being built,
5697 any <file>debian/shlibs</file> files are copied into the
5698 control information file area of the temporary build
5699 directory and given the name <file>shlibs</file>. These
5700 files give details of any shared libraries included in the
5701 same package.<footnote>
5702 An example may help here. Let us say that the source
5703 package <tt>foo</tt> generates two binary
5704 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
5705 When building the binary packages, the two packages are
5706 created in the directories <file>debian/libfoo2</file>
5707 and <file>debian/foo-runtime</file> respectively.
5708 (<file>debian/tmp</file> could be used instead of one of
5709 these.) Since <tt>libfoo2</tt> provides the
5710 <tt>libfoo</tt> shared library, it will require a
5711 <tt>shlibs</tt> file, which will be installed in
5712 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually to
5713 become <file>/var/lib/dpkg/info/libfoo2.shlibs</file>.
5714 When <prgn>dpkg-shlibdeps</prgn> is run on the
5715 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
5717 the <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5718 determine whether <tt>foo-prog</tt>'s library
5719 dependencies are satisfied by any of the libraries
5720 provided by <tt>libfoo2</tt>. For this reason,
5721 <prgn>dpkg-shlibdeps</prgn> must only be run once all of
5722 the individual binary packages' <tt>shlibs</tt> files
5723 have been installed into the build directory.
5729 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5732 These are the <file>shlibs</file> files corresponding to
5733 all of the packages installed on the system, and are
5734 maintained by the relevant package maintainers.
5739 <p><file>/etc/dpkg/shlibs.default</file></p>
5742 This file lists any shared libraries whose packages
5743 have failed to provide correct <file>shlibs</file> files.
5744 It was used when the <file>shlibs</file> setup was first
5745 introduced, but it is now normally empty. It is
5746 maintained by the <tt>dpkg</tt> maintainer.
5754 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5755 <file>shlibs</file> files</heading>
5759 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5760 into your <file>debian/rules</file> file. If your package
5761 contains only compiled binaries and libraries (but no scripts),
5762 you can use a command such as:
5763 <example compact="compact">
5764 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5765 debian/tmp/usr/lib/*
5767 Otherwise, you will need to explicitly list the compiled
5768 binaries and libraries.<footnote>
5769 If you are using <tt>debhelper</tt>, the
5770 <prgn>dh_shlibdeps</prgn> program will do this work for you.
5771 It will also correctly handle multi-binary packages.
5776 This command puts the dependency information into the
5777 <file>debian/substvars</file> file, which is then used by
5778 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5779 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5780 field in the control file for this to work.
5784 If you have multiple binary packages, you will need to call
5785 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5786 compiled libraries or binaries. In such a case, you will
5787 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5788 utilities to specify a different <file>substvars</file> file.
5792 If you are creating a udeb for use in the Debian Installer,
5793 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
5794 should use the dependency line of type <tt>udeb</tt> by
5795 adding the <tt>-tudeb</tt> option<footnote>
5796 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5797 will automatically add this option if it knows it is
5799 </footnote>. If there is no dependency line of
5800 type <tt>udeb</tt> in the <file>shlibs</file>
5801 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the regular
5806 For more details on <prgn>dpkg-shlibdeps</prgn>, please see
5807 <ref id="pkg-dpkg-shlibdeps"> and
5808 <manref name="dpkg-shlibdeps" section="1">.
5813 <heading>The <file>shlibs</file> File Format</heading>
5816 Each <file>shlibs</file> file has the same format. Lines
5817 beginning with <tt>#</tt> are considered to be comments and
5818 are ignored. Each line is of the form:
5819 <example compact="compact">
5820 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5825 We will explain this by reference to the example of the
5826 <tt>zlib1g</tt> package, which (at the time of writing)
5827 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5831 <var>type</var> is an optional element that indicates the type
5832 of package for which the line is valid. The only type currently
5833 in use is <tt>udeb</tt>. The colon and space after the type are
5838 <var>library-name</var> is the name of the shared library,
5839 in this case <tt>libz</tt>. (This must match the name part
5840 of the soname, see below.)
5844 <var>soname-version</var> is the version part of the soname of
5845 the library. The soname is the thing that must exactly match
5846 for the library to be recognized by the dynamic linker, and is
5848 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5849 example, <tt>libz.so.1</tt>.<footnote>
5850 This can be determined using the command
5851 <example compact="compact">
5852 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5855 The version part is the part which comes after
5856 <tt>.so.</tt>, so in our case, it is <tt>1</tt>. The soname may
5857 instead be of the form
5858 <tt><var>name</var>-<var>major-version</var>.so</tt>, such
5859 as <tt>libdb-4.8.so</tt>, in which case the name would
5860 be <tt>libdb</tt> and the version would be <tt>4.8</tt>.
5864 <var>dependencies</var> has the same syntax as a dependency
5865 field in a binary package control file. It should give
5866 details of which packages are required to satisfy a binary
5867 built against the version of the library contained in the
5868 package. See <ref id="depsyntax"> for details.
5872 In our example, if the first version of the <tt>zlib1g</tt>
5873 package which contained a minor number of at least
5874 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5875 <tt>shlibs</tt> entry for this library could say:
5876 <example compact="compact">
5877 libz 1 zlib1g (>= 1:1.1.3)
5879 The version-specific dependency is to avoid warnings from
5880 the dynamic linker about using older shared libraries with
5885 As zlib1g also provides a udeb containing the shared library,
5886 there would also be a second line:
5887 <example compact="compact">
5888 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5894 <heading>Providing a <file>shlibs</file> file</heading>
5897 If your package provides a shared library, you need to create
5898 a <file>shlibs</file> file following the format described above.
5899 It is usual to call this file <file>debian/shlibs</file> (but if
5900 you have multiple binary packages, you might want to call it
5901 <file>debian/shlibs.<var>package</var></file> instead). Then
5902 let <file>debian/rules</file> install it in the control
5903 information file area:
5904 <example compact="compact">
5905 install -m644 debian/shlibs debian/tmp/DEBIAN
5907 or, in the case of a multi-binary package:
5908 <example compact="compact">
5909 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5911 An alternative way of doing this is to create the
5912 <file>shlibs</file> file in the control information file area
5913 directly from <file>debian/rules</file> without using
5914 a <file>debian/shlibs</file> file at all,<footnote>
5915 This is what <prgn>dh_makeshlibs</prgn> in
5916 the <package>debhelper</package> suite does. If your package
5917 also has a udeb that provides a shared
5918 library, <prgn>dh_makeshlibs</prgn> can automatically generate
5919 the <tt>udeb:</tt> lines if you specify the name of the udeb
5920 with the <tt>--add-udeb</tt> option.
5922 since the <file>debian/shlibs</file> file itself is ignored by
5923 <prgn>dpkg-shlibdeps</prgn>.
5927 As <prgn>dpkg-shlibdeps</prgn> reads the
5928 <file>DEBIAN/shlibs</file> files in all of the binary packages
5929 being built from this source package, all of the
5930 <file>DEBIAN/shlibs</file> files should be installed before
5931 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5939 <chapt id="opersys"><heading>The Operating System</heading>
5942 <heading>File system hierarchy</heading>
5946 <heading>File System Structure</heading>
5949 The location of all installed files and directories must
5950 comply with the Filesystem Hierarchy Standard (FHS),
5951 version 2.3, with the exceptions noted below, and except
5952 where doing so would violate other terms of Debian
5953 Policy. The following exceptions to the FHS apply:
5958 The optional rules related to user specific
5959 configuration files for applications are stored in
5960 the user's home directory are relaxed. It is
5961 recommended that such files start with the
5962 '<tt>.</tt>' character (a "dot file"), and if an
5963 application needs to create more than one dot file
5964 then the preferred placement is in a subdirectory
5965 with a name starting with a '.' character, (a "dot
5966 directory"). In this case it is recommended the
5967 configuration files not start with the '.'
5973 The requirement for amd64 to use <file>/lib64</file>
5974 for 64 bit binaries is removed.
5979 The requirement for object files, internal binaries, and
5980 libraries, including <file>libc.so.*</file>, to be located
5981 directly under <file>/lib{,32}</file> and
5982 <file>/usr/lib{,32}</file> is amended, permitting files
5983 to instead be installed to
5984 <file>/lib/<var>triplet</var></file> and
5985 <file>/usr/lib/<var>triplet</var></file>, where
5986 <tt><var>triplet</var></tt> is the value returned by
5987 <tt>dpkg-architecture -qDEB_HOST_GNU_TYPE</tt> for the
5988 architecture of the package. Packages may <em>not</em>
5989 install files to any <var>triplet</var> path other
5990 than the one matching the architecture of that package;
5991 for instance, an <tt>Architecture: amd64</tt> package
5992 containing 32-bit x86 libraries may not install these
5993 libraries to <file>/usr/lib/i486-linux-gnu</file>.
5995 This is necessary in order to reserve the directories for
5996 use in cross-installation of library packages from other
5997 architectures, as part of the planned deployment of
6002 Applications may also use a single subdirectory under
6003 <file>/usr/lib/<var>triplet</var></file>.
6006 The execution time linker/loader, ld*, must still be made
6007 available in the existing location under /lib or /lib64
6008 since this is part of the ELF ABI for the architecture.
6013 The requirement that
6014 <file>/usr/local/share/man</file> be "synonymous"
6015 with <file>/usr/local/man</file> is relaxed to a
6020 The requirement that windowmanagers with a single
6021 configuration file call it <file>system.*wmrc</file>
6022 is removed, as is the restriction that the window
6023 manager subdirectory be named identically to the
6024 window manager name itself.
6029 The requirement that boot manager configuration
6030 files live in <file>/etc</file>, or at least are
6031 symlinked there, is relaxed to a recommendation.
6036 The following directories in the root filesystem are
6037 additionally allowed: <file>/sys</file> and
6038 <file>/selinux</file>. <footnote>These directories
6039 are used as mount points to mount virtual filesystems
6040 to get access to kernel information.</footnote>
6047 The version of this document referred here can be
6048 found in the <tt>debian-policy</tt> package or on <url
6049 id="http://www.debian.org/doc/packaging-manuals/fhs/"
6050 name="FHS (Debian copy)"> alongside this manual (or, if
6051 you have the <package>debian-policy</package> installed,
6053 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
6054 (local copy)">). The
6055 latest version, which may be a more recent version, may
6057 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
6058 Specific questions about following the standard may be
6059 asked on the <tt>debian-devel</tt> mailing list, or
6060 referred to the FHS mailing list (see the
6061 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
6067 <heading>Site-specific programs</heading>
6070 As mandated by the FHS, packages must not place any
6071 files in <file>/usr/local</file>, either by putting them in
6072 the file system archive to be unpacked by <prgn>dpkg</prgn>
6073 or by manipulating them in their maintainer scripts.
6077 However, the package may create empty directories below
6078 <file>/usr/local</file> so that the system administrator knows
6079 where to place site-specific files. These are not
6080 directories <em>in</em> <file>/usr/local</file>, but are
6081 children of directories in <file>/usr/local</file>. These
6082 directories (<file>/usr/local/*/dir/</file>)
6083 should be removed on package removal if they are
6088 Note that this applies only to
6089 directories <em>below</em> <file>/usr/local</file>,
6090 not <em>in</em> <file>/usr/local</file>. Packages must
6091 not create sub-directories in the
6092 directory <file>/usr/local</file> itself, except those
6093 listed in FHS, section 4.5. However, you may create
6094 directories below them as you wish. You must not remove
6095 any of the directories listed in 4.5, even if you created
6100 Since <file>/usr/local</file> can be mounted read-only from a
6101 remote server, these directories must be created and
6102 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
6103 maintainer scripts and not be included in the
6104 <file>.deb</file> archive. These scripts must not fail if
6105 either of these operations fail.
6109 For example, the <tt>emacsen-common</tt> package could
6110 contain something like
6111 <example compact="compact">
6112 if [ ! -e /usr/local/share/emacs ]
6114 if mkdir /usr/local/share/emacs 2>/dev/null
6116 chown root:staff /usr/local/share/emacs
6117 chmod 2775 /usr/local/share/emacs
6121 in its <prgn>postinst</prgn> script, and
6122 <example compact="compact">
6123 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
6124 rmdir /usr/local/share/emacs 2>/dev/null || true
6126 in the <prgn>prerm</prgn> script. (Note that this form is
6127 used to ensure that if the script is interrupted, the
6128 directory <file>/usr/local/share/emacs</file> will still be
6133 If you do create a directory in <file>/usr/local</file> for
6134 local additions to a package, you should ensure that
6135 settings in <file>/usr/local</file> take precedence over the
6136 equivalents in <file>/usr</file>.
6140 However, because <file>/usr/local</file> and its contents are
6141 for exclusive use of the local administrator, a package
6142 must not rely on the presence or absence of files or
6143 directories in <file>/usr/local</file> for normal operation.
6147 The <file>/usr/local</file> directory itself and all the
6148 subdirectories created by the package should (by default) have
6149 permissions 2775 (group-writable and set-group-id) and be
6150 owned by <tt>root:staff</tt>.
6155 <heading>The system-wide mail directory</heading>
6157 The system-wide mail directory
6158 is <file>/var/mail</file>. This directory is part of the
6159 base system and should not be owned by any particular mail
6160 agents. The use of the old
6161 location <file>/var/spool/mail</file> is deprecated, even
6162 though the spool may still be physically located there.
6168 <heading>Users and groups</heading>
6171 <heading>Introduction</heading>
6173 The Debian system can be configured to use either plain or
6178 Some user ids (UIDs) and group ids (GIDs) are reserved
6179 globally for use by certain packages. Because some
6180 packages need to include files which are owned by these
6181 users or groups, or need the ids compiled into binaries,
6182 these ids must be used on any Debian system only for the
6183 purpose for which they are allocated. This is a serious
6184 restriction, and we should avoid getting in the way of
6185 local administration policies. In particular, many sites
6186 allocate users and/or local system groups starting at 100.
6190 Apart from this we should have dynamically allocated ids,
6191 which should by default be arranged in some sensible
6192 order, but the behavior should be configurable.
6196 Packages other than <tt>base-passwd</tt> must not modify
6197 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
6198 <file>/etc/group</file> or <file>/etc/gshadow</file>.
6203 <heading>UID and GID classes</heading>
6205 The UID and GID numbers are divided into classes as
6211 Globally allocated by the Debian project, the same
6212 on every Debian system. These ids will appear in
6213 the <file>passwd</file> and <file>group</file> files of all
6214 Debian systems, new ids in this range being added
6215 automatically as the <tt>base-passwd</tt> package is
6220 Packages which need a single statically allocated
6221 uid or gid should use one of these; their
6222 maintainers should ask the <tt>base-passwd</tt>
6230 Dynamically allocated system users and groups.
6231 Packages which need a user or group, but can have
6232 this user or group allocated dynamically and
6233 differently on each system, should use <tt>adduser
6234 --system</tt> to create the group and/or user.
6235 <prgn>adduser</prgn> will check for the existence of
6236 the user or group, and if necessary choose an unused
6237 id based on the ranges specified in
6238 <file>adduser.conf</file>.
6242 <tag>1000-59999:</tag>
6245 Dynamically allocated user accounts. By default
6246 <prgn>adduser</prgn> will choose UIDs and GIDs for
6247 user accounts in this range, though
6248 <file>adduser.conf</file> may be used to modify this
6253 <tag>60000-64999:</tag>
6256 Globally allocated by the Debian project, but only
6257 created on demand. The ids are allocated centrally
6258 and statically, but the actual accounts are only
6259 created on users' systems on demand.
6263 These ids are for packages which are obscure or
6264 which require many statically-allocated ids. These
6265 packages should check for and create the accounts in
6266 <file>/etc/passwd</file> or <file>/etc/group</file> (using
6267 <prgn>adduser</prgn> if it has this facility) if
6268 necessary. Packages which are likely to require
6269 further allocations should have a "hole" left after
6270 them in the allocation, to give them room to
6275 <tag>65000-65533:</tag>
6283 User <tt>nobody</tt>. The corresponding gid refers
6284 to the group <tt>nogroup</tt>.
6291 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
6292 not</em> be used, because it is the error return
6301 <sect id="sysvinit">
6302 <heading>System run levels and <file>init.d</file> scripts</heading>
6304 <sect1 id="/etc/init.d">
6305 <heading>Introduction</heading>
6308 The <file>/etc/init.d</file> directory contains the scripts
6309 executed by <prgn>init</prgn> at boot time and when the
6310 init state (or "runlevel") is changed (see <manref
6311 name="init" section="8">).
6315 There are at least two different, yet functionally
6316 equivalent, ways of handling these scripts. For the sake
6317 of simplicity, this document describes only the symbolic
6318 link method. However, it must not be assumed by maintainer
6319 scripts that this method is being used, and any automated
6320 manipulation of the various runlevel behaviors by
6321 maintainer scripts must be performed using
6322 <prgn>update-rc.d</prgn> as described below and not by
6323 manually installing or removing symlinks. For information
6324 on the implementation details of the other method,
6325 implemented in the <tt>file-rc</tt> package, please refer
6326 to the documentation of that package.
6330 These scripts are referenced by symbolic links in the
6331 <file>/etc/rc<var>n</var>.d</file> directories. When changing
6332 runlevels, <prgn>init</prgn> looks in the directory
6333 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
6334 execute, where <tt><var>n</var></tt> is the runlevel that
6335 is being changed to, or <tt>S</tt> for the boot-up
6340 The names of the links all have the form
6341 <file>S<var>mm</var><var>script</var></file> or
6342 <file>K<var>mm</var><var>script</var></file> where
6343 <var>mm</var> is a two-digit number and <var>script</var>
6344 is the name of the script (this should be the same as the
6345 name of the actual script in <file>/etc/init.d</file>).
6349 When <prgn>init</prgn> changes runlevel first the targets
6350 of the links whose names start with a <tt>K</tt> are
6351 executed, each with the single argument <tt>stop</tt>,
6352 followed by the scripts prefixed with an <tt>S</tt>, each
6353 with the single argument <tt>start</tt>. (The links are
6354 those in the <file>/etc/rc<var>n</var>.d</file> directory
6355 corresponding to the new runlevel.) The <tt>K</tt> links
6356 are responsible for killing services and the <tt>S</tt>
6357 link for starting services upon entering the runlevel.
6361 For example, if we are changing from runlevel 2 to
6362 runlevel 3, init will first execute all of the <tt>K</tt>
6363 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
6364 all of the <tt>S</tt> prefixed scripts in that directory.
6365 The links starting with <tt>K</tt> will cause the
6366 referred-to file to be executed with an argument of
6367 <tt>stop</tt>, and the <tt>S</tt> links with an argument
6372 The two-digit number <var>mm</var> is used to determine
6373 the order in which to run the scripts: low-numbered links
6374 have their scripts run first. For example, the
6375 <tt>K20</tt> scripts will be executed before the
6376 <tt>K30</tt> scripts. This is used when a certain service
6377 must be started before another. For example, the name
6378 server <prgn>bind</prgn> might need to be started before
6379 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
6380 can set up its access lists. In this case, the script
6381 that starts <prgn>bind</prgn> would have a lower number
6382 than the script that starts <prgn>inn</prgn> so that it
6384 <example compact="compact">
6391 The two runlevels 0 (halt) and 6 (reboot) are slightly
6392 different. In these runlevels, the links with an
6393 <tt>S</tt> prefix are still called after those with a
6394 <tt>K</tt> prefix, but they too are called with the single
6395 argument <tt>stop</tt>.
6399 <sect1 id="writing-init">
6400 <heading>Writing the scripts</heading>
6403 Packages that include daemons for system services should
6404 place scripts in <file>/etc/init.d</file> to start or stop
6405 services at boot time or during a change of runlevel.
6406 These scripts should be named
6407 <file>/etc/init.d/<var>package</var></file>, and they should
6408 accept one argument, saying what to do:
6411 <tag><tt>start</tt></tag>
6412 <item>start the service,</item>
6414 <tag><tt>stop</tt></tag>
6415 <item>stop the service,</item>
6417 <tag><tt>restart</tt></tag>
6418 <item>stop and restart the service if it's already running,
6419 otherwise start the service</item>
6421 <tag><tt>reload</tt></tag>
6422 <item><p>cause the configuration of the service to be
6423 reloaded without actually stopping and restarting
6426 <tag><tt>force-reload</tt></tag>
6427 <item>cause the configuration to be reloaded if the
6428 service supports this, otherwise restart the
6432 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
6433 <tt>force-reload</tt> options should be supported by all
6434 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
6439 The <file>init.d</file> scripts must ensure that they will
6440 behave sensibly (i.e., returning success and not starting
6441 multiple copies of a service) if invoked with <tt>start</tt>
6442 when the service is already running, or with <tt>stop</tt>
6443 when it isn't, and that they don't kill unfortunately-named
6444 user processes. The best way to achieve this is usually to
6445 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
6450 Be careful of using <tt>set -e</tt> in <file>init.d</file>
6451 scripts. Writing correct <file>init.d</file> scripts requires
6452 accepting various error exit statuses when daemons are already
6453 running or already stopped without aborting
6454 the <file>init.d</file> script, and common <file>init.d</file>
6455 function libraries are not safe to call with <tt>set -e</tt>
6457 <tt>/lib/lsb/init-functions</tt>, which assists in writing
6458 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
6459 in effect and echoing status messages to the console fails,
6461 </footnote>. For <tt>init.d</tt> scripts, it's often easier
6462 to not use <tt>set -e</tt> and instead check the result of
6463 each command separately.
6467 If a service reloads its configuration automatically (as
6468 in the case of <prgn>cron</prgn>, for example), the
6469 <tt>reload</tt> option of the <file>init.d</file> script
6470 should behave as if the configuration has been reloaded
6475 The <file>/etc/init.d</file> scripts must be treated as
6476 configuration files, either (if they are present in the
6477 package, that is, in the .deb file) by marking them as
6478 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6479 by managing them correctly in the maintainer scripts (see
6480 <ref id="config-files">). This is important since we want
6481 to give the local system administrator the chance to adapt
6482 the scripts to the local system, e.g., to disable a
6483 service without de-installing the package, or to specify
6484 some special command line options when starting a service,
6485 while making sure their changes aren't lost during the next
6490 These scripts should not fail obscurely when the
6491 configuration files remain but the package has been
6492 removed, as configuration files remain on the system after
6493 the package has been removed. Only when <prgn>dpkg</prgn>
6494 is executed with the <tt>--purge</tt> option will
6495 configuration files be removed. In particular, as the
6496 <file>/etc/init.d/<var>package</var></file> script itself is
6497 usually a <tt>conffile</tt>, it will remain on the system
6498 if the package is removed but not purged. Therefore, you
6499 should include a <tt>test</tt> statement at the top of the
6501 <example compact="compact">
6502 test -f <var>program-executed-later-in-script</var> || exit 0
6507 Often there are some variables in the <file>init.d</file>
6508 scripts whose values control the behavior of the scripts,
6509 and which a system administrator is likely to want to
6510 change. As the scripts themselves are frequently
6511 <tt>conffile</tt>s, modifying them requires that the
6512 administrator merge in their changes each time the package
6513 is upgraded and the <tt>conffile</tt> changes. To ease
6514 the burden on the system administrator, such configurable
6515 values should not be placed directly in the script.
6516 Instead, they should be placed in a file in
6517 <file>/etc/default</file>, which typically will have the same
6518 base name as the <file>init.d</file> script. This extra file
6519 should be sourced by the script when the script runs. It
6520 must contain only variable settings and comments in SUSv3
6521 <prgn>sh</prgn> format. It may either be a
6522 <tt>conffile</tt> or a configuration file maintained by
6523 the package maintainer scripts. See <ref id="config-files">
6528 To ensure that vital configurable values are always
6529 available, the <file>init.d</file> script should set default
6530 values for each of the shell variables it uses, either
6531 before sourcing the <file>/etc/default/</file> file or
6532 afterwards using something like the <tt>:
6533 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6534 script must behave sensibly and not fail if the
6535 <file>/etc/default</file> file is deleted.
6539 <file>/var/run</file> and <file>/var/lock</file> may be mounted
6540 as temporary filesystems<footnote>
6541 For example, using the <tt>RAMRUN</tt> and <tt>RAMLOCK</tt>
6542 options in <file>/etc/default/rcS</file>.
6543 </footnote>, so the <file>init.d</file> scripts must handle this
6544 correctly. This will typically amount to creating any required
6545 subdirectories dynamically when the <file>init.d</file> script
6546 is run, rather than including them in the package and relying on
6547 <prgn>dpkg</prgn> to create them.
6552 <heading>Interfacing with the initscript system</heading>
6555 Maintainers should use the abstraction layer provided by
6556 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6557 programs to deal with initscripts in their packages'
6558 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6559 and <prgn>postrm</prgn>.
6563 Directly managing the /etc/rc?.d links and directly
6564 invoking the <file>/etc/init.d/</file> initscripts should
6565 be done only by packages providing the initscript
6566 subsystem (such as <prgn>sysv-rc</prgn> and
6567 <prgn>file-rc</prgn>).
6571 <heading>Managing the links</heading>
6574 The program <prgn>update-rc.d</prgn> is provided for
6575 package maintainers to arrange for the proper creation and
6576 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6577 or their functional equivalent if another method is being
6578 used. This may be used by maintainers in their packages'
6579 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6583 You must not include any <file>/etc/rc<var>n</var>.d</file>
6584 symbolic links in the actual archive or manually create or
6585 remove the symbolic links in maintainer scripts; you must
6586 use the <prgn>update-rc.d</prgn> program instead. (The
6587 former will fail if an alternative method of maintaining
6588 runlevel information is being used.) You must not include
6589 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6590 in the archive either. (Only the <tt>sysvinit</tt>
6595 By default <prgn>update-rc.d</prgn> will start services in
6596 each of the multi-user state runlevels (2, 3, 4, and 5)
6597 and stop them in the halt runlevel (0), the single-user
6598 runlevel (1) and the reboot runlevel (6). The system
6599 administrator will have the opportunity to customize
6600 runlevels by simply adding, moving, or removing the
6601 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6602 symbolic links are being used, or by modifying
6603 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6608 To get the default behavior for your package, put in your
6609 <prgn>postinst</prgn> script
6610 <example compact="compact">
6611 update-rc.d <var>package</var> defaults
6613 and in your <prgn>postrm</prgn>
6614 <example compact="compact">
6615 if [ "$1" = purge ]; then
6616 update-rc.d <var>package</var> remove
6618 </example>. Note that if your package changes runlevels
6619 or priority, you may have to remove and recreate the links,
6620 since otherwise the old links may persist. Refer to the
6621 documentation of <prgn>update-rc.d</prgn>.
6625 This will use a default sequence number of 20. If it does
6626 not matter when or in which order the <file>init.d</file>
6627 script is run, use this default. If it does, then you
6628 should talk to the maintainer of the <prgn>sysvinit</prgn>
6629 package or post to <tt>debian-devel</tt>, and they will
6630 help you choose a number.
6634 For more information about using <tt>update-rc.d</tt>,
6635 please consult its man page <manref name="update-rc.d"
6641 <heading>Running initscripts</heading>
6643 The program <prgn>invoke-rc.d</prgn> is provided to make
6644 it easier for package maintainers to properly invoke an
6645 initscript, obeying runlevel and other locally-defined
6646 constraints that might limit a package's right to start,
6647 stop and otherwise manage services. This program may be
6648 used by maintainers in their packages' scripts.
6652 The package maintainer scripts must use
6653 <prgn>invoke-rc.d</prgn> to invoke the
6654 <file>/etc/init.d/*</file> initscripts, instead of
6655 calling them directly.
6659 By default, <prgn>invoke-rc.d</prgn> will pass any
6660 action requests (start, stop, reload, restart...) to the
6661 <file>/etc/init.d</file> script, filtering out requests
6662 to start or restart a service out of its intended
6667 Most packages will simply need to change:
6668 <example compact="compact">/etc/init.d/<package>
6669 <action></example> in their <prgn>postinst</prgn>
6670 and <prgn>prerm</prgn> scripts to:
6671 <example compact="compact">
6672 if which invoke-rc.d >/dev/null 2>&1; then
6673 invoke-rc.d <var>package</var> <action>
6675 /etc/init.d/<var>package</var> <action>
6681 A package should register its initscript services using
6682 <prgn>update-rc.d</prgn> before it tries to invoke them
6683 using <prgn>invoke-rc.d</prgn>. Invocation of
6684 unregistered services may fail.
6688 For more information about using
6689 <prgn>invoke-rc.d</prgn>, please consult its man page
6690 <manref name="invoke-rc.d" section="8">.
6696 <heading>Boot-time initialization</heading>
6699 There used to be another directory, <file>/etc/rc.boot</file>,
6700 which contained scripts which were run once per machine
6701 boot. This has been deprecated in favour of links from
6702 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6703 described in <ref id="/etc/init.d">. Packages must not
6704 place files in <file>/etc/rc.boot</file>.
6709 <heading>Example</heading>
6712 An example on which you can base your
6713 <file>/etc/init.d</file> scripts is found in
6714 <file>/etc/init.d/skeleton</file>.
6721 <heading>Console messages from <file>init.d</file> scripts</heading>
6724 This section describes the formats to be used for messages
6725 written to standard output by the <file>/etc/init.d</file>
6726 scripts. The intent is to improve the consistency of
6727 Debian's startup and shutdown look and feel. For this
6728 reason, please look very carefully at the details. We want
6729 the messages to have the same format in terms of wording,
6730 spaces, punctuation and case of letters.
6734 Here is a list of overall rules that should be used for
6735 messages generated by <file>/etc/init.d</file> scripts.
6741 The message should fit in one line (fewer than 80
6742 characters), start with a capital letter and end with
6743 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6747 If the script is performing some time consuming task in
6748 the background (not merely starting or stopping a
6749 program, for instance), an ellipsis (three dots:
6750 <tt>...</tt>) should be output to the screen, with no
6751 leading or tailing whitespace or line feeds.
6755 The messages should appear as if the computer is telling
6756 the user what it is doing (politely :-), but should not
6757 mention "it" directly. For example, instead of:
6758 <example compact="compact">
6759 I'm starting network daemons: nfsd mountd.
6761 the message should say
6762 <example compact="compact">
6763 Starting network daemons: nfsd mountd.
6770 <tt>init.d</tt> script should use the following standard
6771 message formats for the situations enumerated below.
6777 <p>When daemons are started</p>
6780 If the script starts one or more daemons, the output
6781 should look like this (a single line, no leading
6783 <example compact="compact">
6784 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6786 The <var>description</var> should describe the
6787 subsystem the daemon or set of daemons are part of,
6788 while <var>daemon-1</var> up to <var>daemon-n</var>
6789 denote each daemon's name (typically the file name of
6794 For example, the output of <file>/etc/init.d/lpd</file>
6796 <example compact="compact">
6797 Starting printer spooler: lpd.
6802 This can be achieved by saying
6803 <example compact="compact">
6804 echo -n "Starting printer spooler: lpd"
6805 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6808 in the script. If there are more than one daemon to
6809 start, the output should look like this:
6810 <example compact="compact">
6811 echo -n "Starting remote file system services:"
6812 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6813 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6814 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6817 This makes it possible for the user to see what is
6818 happening and when the final daemon has been started.
6819 Care should be taken in the placement of white spaces:
6820 in the example above the system administrators can
6821 easily comment out a line if they don't want to start
6822 a specific daemon, while the displayed message still
6828 <p>When a system parameter is being set</p>
6831 If you have to set up different system parameters
6832 during the system boot, you should use this format:
6833 <example compact="compact">
6834 Setting <var>parameter</var> to "<var>value</var>".
6839 You can use a statement such as the following to get
6841 <example compact="compact">
6842 echo "Setting DNS domainname to \"$domainname\"."
6847 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
6848 for the left and right quotation marks. A grave accent
6849 (<tt>`</tt>) is not a quote character; neither is an
6850 apostrophe (<tt>'</tt>).
6855 <p>When a daemon is stopped or restarted</p>
6858 When you stop or restart a daemon, you should issue a
6859 message identical to the startup message, except that
6860 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6861 or <tt>Restarting</tt> respectively.
6865 For example, stopping the printer daemon will look like
6867 <example compact="compact">
6868 Stopping printer spooler: lpd.
6874 <p>When something is executed</p>
6877 There are several examples where you have to run a
6878 program at system startup or shutdown to perform a
6879 specific task, for example, setting the system's clock
6880 using <prgn>netdate</prgn> or killing all processes
6881 when the system shuts down. Your message should look
6883 <example compact="compact">
6884 Doing something very useful...done.
6886 You should print the <tt>done.</tt> immediately after
6887 the job has been completed, so that the user is
6888 informed why they have to wait. You can get this
6890 <example compact="compact">
6891 echo -n "Doing something very useful..."
6900 <p>When the configuration is reloaded</p>
6903 When a daemon is forced to reload its configuration
6904 files you should use the following format:
6905 <example compact="compact">
6906 Reloading <var>description</var> configuration...done.
6908 where <var>description</var> is the same as in the
6909 daemon starting message.
6917 <heading>Cron jobs</heading>
6920 Packages must not modify the configuration file
6921 <file>/etc/crontab</file>, and they must not modify the files in
6922 <file>/var/spool/cron/crontabs</file>.</p>
6925 If a package wants to install a job that has to be executed
6926 via cron, it should place a file with the name of the
6927 package in one or more of the following directories:
6928 <example compact="compact">
6934 As these directory names imply, the files within them are
6935 executed on an hourly, daily, weekly, or monthly basis,
6936 respectively. The exact times are listed in
6937 <file>/etc/crontab</file>.</p>
6940 All files installed in any of these directories must be
6941 scripts (e.g., shell scripts or Perl scripts) so that they
6942 can easily be modified by the local system administrator.
6943 In addition, they must be treated as configuration files.
6947 If a certain job has to be executed at some other frequency or
6948 at a specific time, the package should install a file
6949 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6950 same syntax as <file>/etc/crontab</file> and is processed by
6951 <prgn>cron</prgn> automatically. The file must also be
6952 treated as a configuration file. (Note that entries in the
6953 <file>/etc/cron.d</file> directory are not handled by
6954 <prgn>anacron</prgn>. Thus, you should only use this
6955 directory for jobs which may be skipped if the system is not
6958 Unlike <file>crontab</file> files described in the IEEE Std
6959 1003.1-2008 (POSIX.1) available from
6960 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
6961 name="The Open Group">, the files in
6962 <file>/etc/cron.d</file> and the file
6963 <file>/etc/crontab</file> have seven fields; namely:
6965 <item>Minute [0,59]</item>
6966 <item>Hour [0,23]</item>
6967 <item>Day of the month [1,31]</item>
6968 <item>Month of the year [1,12]</item>
6969 <item>Day of the week ([0,6] with 0=Sunday)</item>
6970 <item>Username</item>
6971 <item>Command to be run</item>
6973 Ranges of numbers are allowed. Ranges are two numbers
6974 separated with a hyphen. The specified range is inclusive.
6975 Lists are allowed. A list is a set of numbers (or ranges)
6976 separated by commas. Step values can be used in conjunction
6981 The scripts or <tt>crontab</tt> entries in these directories should
6982 check if all necessary programs are installed before they
6983 try to execute them. Otherwise, problems will arise when a
6984 package was removed but not purged since configuration files
6985 are kept on the system in this situation.
6989 Any <tt>cron</tt> daemon must provide
6990 <file>/usr/bin/crontab</file> and support normal
6991 <tt>crontab</tt> entries as specified in POSIX. The daemon
6992 must also support names for days and months, ranges, and
6993 step values. It has to support <file>/etc/crontab</file>,
6994 and correctly execute the scripts in
6995 <file>/etc/cron.d</file>. The daemon must also correctly
6997 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
7002 <heading>Menus</heading>
7005 The Debian <tt>menu</tt> package provides a standard
7006 interface between packages providing applications and
7007 <em>menu programs</em> (either X window managers or
7008 text-based menu programs such as <prgn>pdmenu</prgn>).
7012 All packages that provide applications that need not be
7013 passed any special command line arguments for normal
7014 operation should register a menu entry for those
7015 applications, so that users of the <tt>menu</tt> package
7016 will automatically get menu entries in their window
7017 managers, as well in shells like <tt>pdmenu</tt>.
7021 Menu entries should follow the current menu policy.
7025 The menu policy can be found in the <tt>menu-policy</tt>
7026 files in the <tt>debian-policy</tt> package.
7027 It is also available from the Debian web mirrors at
7028 <tt><url name="/doc/packaging-manuals/menu-policy/"
7029 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
7033 Please also refer to the <em>Debian Menu System</em>
7034 documentation that comes with the <package>menu</package>
7035 package for information about how to register your
7041 <heading>Multimedia handlers</heading>
7044 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
7045 is a mechanism for encoding files and data streams and
7046 providing meta-information about them, in particular their
7047 type (e.g. audio or video) and format (e.g. PNG, HTML,
7052 Registration of MIME type handlers allows programs like mail
7053 user agents and web browsers to invoke these handlers to
7054 view, edit or display MIME types they don't support directly.
7058 Packages which provide the ability to view/show/play,
7059 compose, edit or print MIME types should register themselves
7060 as such following the current MIME support policy.
7064 The MIME support policy can be found in the <tt>mime-policy</tt>
7065 files in the <tt>debian-policy</tt> package.
7066 It is also available from the Debian web mirrors at
7067 <tt><url name="/doc/packaging-manuals/mime-policy/"
7068 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
7074 <heading>Keyboard configuration</heading>
7077 To achieve a consistent keyboard configuration so that all
7078 applications interpret a keyboard event the same way, all
7079 programs in the Debian distribution must be configured to
7080 comply with the following guidelines.
7084 The following keys must have the specified interpretations:
7087 <tag><tt><--</tt></tag>
7088 <item>delete the character to the left of the cursor</item>
7090 <tag><tt>Delete</tt></tag>
7091 <item>delete the character to the right of the cursor</item>
7093 <tag><tt>Control+H</tt></tag>
7094 <item>emacs: the help prefix</item>
7097 The interpretation of any keyboard events should be
7098 independent of the terminal that is used, be it a virtual
7099 console, an X terminal emulator, an rlogin/telnet session,
7104 The following list explains how the different programs
7105 should be set up to achieve this:
7111 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
7115 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
7119 X translations are set up to make
7120 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
7121 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
7122 is the vt220 escape code for the "delete character"
7123 key). This must be done by loading the X resources
7124 using <prgn>xrdb</prgn> on all local X displays, not
7125 using the application defaults, so that the
7126 translation resources used correspond to the
7127 <prgn>xmodmap</prgn> settings.
7131 The Linux console is configured to make
7132 <tt><--</tt> generate DEL, and <tt>Delete</tt>
7133 generate <tt>ESC [ 3 ~</tt>.
7137 X applications are configured so that <tt><</tt>
7138 deletes left, and <tt>Delete</tt> deletes right. Motif
7139 applications already work like this.
7143 Terminals should have <tt>stty erase ^?</tt> .
7147 The <tt>xterm</tt> terminfo entry should have <tt>ESC
7148 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
7149 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
7153 Emacs is programmed to map <tt>KB_Backspace</tt> or
7154 the <tt>stty erase</tt> character to
7155 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
7156 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
7157 <tt>^H</tt> to <tt>help</tt> as always.
7161 Other applications use the <tt>stty erase</tt>
7162 character and <tt>kdch1</tt> for the two delete keys,
7163 with ASCII DEL being "delete previous character" and
7164 <tt>kdch1</tt> being "delete character under
7172 This will solve the problem except for the following
7179 Some terminals have a <tt><--</tt> key that cannot
7180 be made to produce anything except <tt>^H</tt>. On
7181 these terminals Emacs help will be unavailable on
7182 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
7183 character takes precedence in Emacs, and has been set
7184 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
7185 available) can be used instead.
7189 Some operating systems use <tt>^H</tt> for <tt>stty
7190 erase</tt>. However, modern telnet versions and all
7191 rlogin versions propagate <tt>stty</tt> settings, and
7192 almost all UNIX versions honour <tt>stty erase</tt>.
7193 Where the <tt>stty</tt> settings are not propagated
7194 correctly, things can be made to work by using
7195 <tt>stty</tt> manually.
7199 Some systems (including previous Debian versions) use
7200 <prgn>xmodmap</prgn> to arrange for both
7201 <tt><--</tt> and <tt>Delete</tt> to generate
7202 <tt>KB_Delete</tt>. We can change the behavior of
7203 their X clients using the same X resources that we use
7204 to do it for our own clients, or configure our clients
7205 using their resources when things are the other way
7206 around. On displays configured like this
7207 <tt>Delete</tt> will not work, but <tt><--</tt>
7212 Some operating systems have different <tt>kdch1</tt>
7213 settings in their <tt>terminfo</tt> database for
7214 <tt>xterm</tt> and others. On these systems the
7215 <tt>Delete</tt> key will not work correctly when you
7216 log in from a system conforming to our policy, but
7217 <tt><--</tt> will.
7224 <heading>Environment variables</heading>
7227 A program must not depend on environment variables to get
7228 reasonable defaults. (That's because these environment
7229 variables would have to be set in a system-wide
7230 configuration file like <file>/etc/profile</file>, which is not
7231 supported by all shells.)
7235 If a program usually depends on environment variables for its
7236 configuration, the program should be changed to fall back to
7237 a reasonable default configuration if these environment
7238 variables are not present. If this cannot be done easily
7239 (e.g., if the source code of a non-free program is not
7240 available), the program must be replaced by a small
7241 "wrapper" shell script which sets the environment variables
7242 if they are not already defined, and calls the original program.
7246 Here is an example of a wrapper script for this purpose:
7248 <example compact="compact">
7250 BAR=${BAR:-/var/lib/fubar}
7252 exec /usr/lib/foo/foo "$@"
7257 Furthermore, as <file>/etc/profile</file> is a configuration
7258 file of the <prgn>base-files</prgn> package, other packages must
7259 not put any environment variables or other commands into that
7264 <sect id="doc-base">
7265 <heading>Registering Documents using doc-base</heading>
7268 The <package>doc-base</package> package implements a
7269 flexible mechanism for handling and presenting
7270 documentation. The recommended practice is for every Debian
7271 package that provides online documentation (other than just
7272 manual pages) to register these documents with
7273 <package>doc-base</package> by installing a
7274 <package>doc-base</package> control file via the
7275 <prgn/install-docs/ script at installation time and
7276 de-register the manuals again when the package is removed.
7279 Please refer to the documentation that comes with the
7280 <package>doc-base</package> package for information and
7289 <heading>Files</heading>
7291 <sect id="binaries">
7292 <heading>Binaries</heading>
7295 Two different packages must not install programs with
7296 different functionality but with the same filenames. (The
7297 case of two programs having the same functionality but
7298 different implementations is handled via "alternatives" or
7299 the "Conflicts" mechanism. See <ref id="maintscripts"> and
7300 <ref id="conflicts"> respectively.) If this case happens,
7301 one of the programs must be renamed. The maintainers should
7302 report this to the <tt>debian-devel</tt> mailing list and
7303 try to find a consensus about which program will have to be
7304 renamed. If a consensus cannot be reached, <em>both</em>
7305 programs must be renamed.
7309 By default, when a package is being built, any binaries
7310 created should include debugging information, as well as
7311 being compiled with optimization. You should also turn on
7312 as many reasonable compilation warnings as possible; this
7313 makes life easier for porters, who can then look at build
7314 logs for possible problems. For the C programming language,
7315 this means the following compilation parameters should be
7317 <example compact="compact">
7319 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
7321 INSTALL = install -s # (or use strip on the files in debian/tmp)
7326 Note that by default all installed binaries should be stripped,
7327 either by using the <tt>-s</tt> flag to
7328 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
7329 the binaries after they have been copied into
7330 <file>debian/tmp</file> but before the tree is made into a
7335 Although binaries in the build tree should be compiled with
7336 debugging information by default, it can often be difficult to
7337 debug programs if they are also subjected to compiler
7338 optimization. For this reason, it is recommended to support the
7339 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
7340 (see <ref id="debianrules-options">). This variable can contain
7341 several flags to change how a package is compiled and built.
7345 It is up to the package maintainer to decide what
7346 compilation options are best for the package. Certain
7347 binaries (such as computationally-intensive programs) will
7348 function better with certain flags (<tt>-O3</tt>, for
7349 example); feel free to use them. Please use good judgment
7350 here. Don't use flags for the sake of it; only use them
7351 if there is good reason to do so. Feel free to override
7352 the upstream author's ideas about which compilation
7353 options are best: they are often inappropriate for our
7359 <sect id="libraries">
7360 <heading>Libraries</heading>
7363 If the package is <strong>architecture: any</strong>, then
7364 the shared library compilation and linking flags must have
7365 <tt>-fPIC</tt>, or the package shall not build on some of
7366 the supported architectures<footnote>
7368 If you are using GCC, <tt>-fPIC</tt> produces code with
7369 relocatable position independent code, which is required for
7370 most architectures to create a shared library, with i386 and
7371 perhaps some others where non position independent code is
7372 permitted in a shared library.
7375 Position independent code may have a performance penalty,
7376 especially on <tt>i386</tt>. However, in most cases the
7377 speed penalty must be measured against the memory wasted on
7378 the few architectures where non position independent code is
7381 </footnote>. Any exception to this rule must be discussed on
7382 the mailing list <em>debian-devel@lists.debian.org</em>, and
7383 a rough consensus obtained. The reasons for not compiling
7384 with <tt>-fPIC</tt> flag must be recorded in the file
7385 <tt>README.Debian</tt>, and care must be taken to either
7386 restrict the architecture or arrange for <tt>-fPIC</tt> to
7387 be used on architectures where it is required.<footnote>
7389 Some of the reasons why this might be required is if the
7390 library contains hand crafted assembly code that is not
7391 relocatable, the speed penalty is excessive for compute
7392 intensive libs, and similar reasons.
7397 As to the static libraries, the common case is not to have
7398 relocatable code, since there is no benefit, unless in specific
7399 cases; therefore the static version must not be compiled
7400 with the <tt>-fPIC</tt> flag. Any exception to this rule
7401 should be discussed on the mailing list
7402 <em>debian-devel@lists.debian.org</em>, and the reasons for
7403 compiling with the <tt>-fPIC</tt> flag must be recorded in
7404 the file <tt>README.Debian</tt>. <footnote>
7406 Some of the reasons for linking static libraries with
7407 the <tt>-fPIC</tt> flag are if, for example, one needs a
7408 Perl API for a library that is under rapid development,
7409 and has an unstable API, so shared libraries are
7410 pointless at this phase of the library's development. In
7411 that case, since Perl needs a library with relocatable
7412 code, it may make sense to create a static library with
7413 relocatable code. Another reason cited is if you are
7414 distilling various libraries into a common shared
7415 library, like <tt>mklibs</tt> does in the Debian
7421 In other words, if both a shared and a static library is
7422 being built, each source unit (<tt>*.c</tt>, for example,
7423 for C files) will need to be compiled twice, for the normal
7428 Libraries should be built with threading support and to be
7429 thread-safe if the library supports this.
7433 Although not enforced by the build tools, shared libraries
7434 must be linked against all libraries that they use symbols from
7435 in the same way that binaries are. This ensures the correct
7436 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
7437 system and guarantees that all libraries can be safely opened
7438 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
7439 option <tt>-Wl,-z,defs</tt> when building a shared library.
7440 Since this option enforces symbol resolution at build time,
7441 a missing library reference will be caught early as a fatal
7446 All installed shared libraries should be stripped with
7447 <example compact="compact">
7448 strip --strip-unneeded <var>your-lib</var>
7450 (The option <tt>--strip-unneeded</tt> makes
7451 <prgn>strip</prgn> remove only the symbols which aren't
7452 needed for relocation processing.) Shared libraries can
7453 function perfectly well when stripped, since the symbols for
7454 dynamic linking are in a separate part of the ELF object
7456 You might also want to use the options
7457 <tt>--remove-section=.comment</tt> and
7458 <tt>--remove-section=.note</tt> on both shared libraries
7459 and executables, and <tt>--strip-debug</tt> on static
7465 Note that under some circumstances it may be useful to
7466 install a shared library unstripped, for example when
7467 building a separate package to support debugging.
7471 Shared object files (often <file>.so</file> files) that are not
7472 public libraries, that is, they are not meant to be linked
7473 to by third party executables (binaries of other packages),
7474 should be installed in subdirectories of the
7475 <file>/usr/lib</file> directory. Such files are exempt from the
7476 rules that govern ordinary shared libraries, except that
7477 they must not be installed executable and should be
7479 A common example are the so-called "plug-ins",
7480 internal shared objects that are dynamically loaded by
7481 programs using <manref name="dlopen" section="3">.
7486 Packages that use <prgn>libtool</prgn> to create and install
7487 their shared libraries install a file containing additional
7488 metadata (ending in <file>.la</file>) alongside the library.
7489 For public libraries intended for use by other packages, these
7490 files normally should not be included in the Debian package,
7491 since the information they include is not necessary to link with
7492 the shared library on Debian and can add unnecessary additional
7493 dependencies to other programs or libraries.<footnote>
7494 These files store, among other things, all libraries on which
7495 that shared library depends. Unfortunately, if
7496 the <file>.la</file> file is present and contains that
7497 dependency information, using <prgn>libtool</prgn> when
7498 linking against that library will cause the resulting program
7499 or library to be linked against those dependencies as well,
7500 even if this is unnecessary. This can create unneeded
7501 dependencies on shared library packages that would otherwise
7502 be hidden behind the library ABI, and can make library
7503 transitions to new SONAMEs unnecessarily complicated and
7504 difficult to manage.
7506 If the <file>.la</file> file is required for that library (if,
7507 for instance, it's loaded via <tt>libltdl</tt> in a way that
7508 requires that meta-information), the <tt>dependency_libs</tt>
7509 setting in the <file>.la</file> file should normally be set to
7510 the empty string. If the shared library development package has
7511 historically included the <file>.la</file>, it must be retained
7512 in the development package (with <tt>dependency_libs</tt>
7513 emptied) until all libraries that depend on it have removed or
7514 emptied <tt>dependency_libs</tt> in their <file>.la</file>
7515 files to prevent linking with those other libraries
7516 using <prgn>libtool</prgn> from failing.
7520 If the <file>.la</file> must be included, it should be included
7521 in the development (<tt>-dev</tt>) package, unless the library
7522 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
7523 library. If it is intended for use with <tt>libltdl</tt>,
7524 the <file>.la</file> files must go in the run-time library
7529 These requirements for handling of <file>.la</file> files do not
7530 apply to loadable modules or libraries not installed in
7531 directories searched by default by the dynamic linker. Packages
7532 installing loadable modules will frequently need to install
7533 the <file>.la</file> files alongside the modules so that they
7534 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
7535 does not need to be modified for libraries or modules that are
7536 not installed in directories searched by the dynamic linker by
7537 default and not intended for use by other packages.
7541 You must make sure that you use only released versions of
7542 shared libraries to build your packages; otherwise other
7543 users will not be able to run your binaries
7544 properly. Producing source packages that depend on
7545 unreleased compilers is also usually a bad
7552 <heading>Shared libraries</heading>
7554 This section has moved to <ref id="sharedlibs">.
7560 <heading>Scripts</heading>
7563 All command scripts, including the package maintainer
7564 scripts inside the package and used by <prgn>dpkg</prgn>,
7565 should have a <tt>#!</tt> line naming the shell to be used
7570 In the case of Perl scripts this should be
7571 <tt>#!/usr/bin/perl</tt>.
7575 When scripts are installed into a directory in the system
7576 PATH, the script name should not include an extension such
7577 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7578 language currently used to implement it.
7581 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
7582 <file>init.d</file> scripts should almost certainly start
7583 with <tt>set -e</tt> so that errors are detected.
7584 <file>init.d</file> scripts are something of a special case, due
7585 to how frequently they need to call commands that are allowed to
7586 fail, and it may instead be easier to check the exit status of
7587 commands directly. See <ref id="writing-init"> for more
7588 information about writing <file>init.d</file> scripts.
7591 Every script should use <tt>set -e</tt> or check the exit status
7592 of <em>every</em> command.
7595 Scripts may assume that <file>/bin/sh</file> implements the
7596 SUSv3 Shell Command Language<footnote>
7597 Single UNIX Specification, version 3, which is also IEEE
7598 1003.1-2004 (POSIX), and is available on the World Wide Web
7599 from <url id="http://www.unix.org/version3/online.html"
7600 name="The Open Group"> after free
7601 registration.</footnote>
7602 plus the following additional features not mandated by
7604 These features are in widespread use in the Linux community
7605 and are implemented in all of bash, dash, and ksh, the most
7606 common shells users may wish to use as <file>/bin/sh</file>.
7609 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7610 must not generate a newline.</item>
7611 <item><tt>test</tt>, if implemented as a shell built-in, must
7612 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7614 <item><tt>local</tt> to create a scoped variable must be
7615 supported, including listing multiple variables in a single
7616 local command and assigning a value to a variable at the
7617 same time as localizing it. <tt>local</tt> may or
7618 may not preserve the variable value from an outer scope if
7619 no assignment is present. Uses such as:
7623 # ... use a, b, c, d ...
7626 must be supported and must set the value of <tt>c</tt> to
7629 <item>The XSI extension to <prgn>kill</prgn> allowing <tt>kill
7630 -<var>signal</var></tt>, where <var>signal</var> is either
7631 the name of a signal or one of the numeric signals listed in
7632 the XSI extension (0, 1, 2, 3, 6, 9, 14, and 15), must be
7633 supported if <prgn>kill</prgn> is implemented as a shell
7636 <item>The XSI extension to <prgn>trap</prgn> allowing numeric
7637 signals must be supported. In addition to the signal
7638 numbers listed in the extension, which are the same as for
7639 <prgn>kill</prgn> above, 13 (SIGPIPE) must be allowed.
7642 If a shell script requires non-SUSv3 features from the shell
7643 interpreter other than those listed above, the appropriate shell
7644 must be specified in the first line of the script (e.g.,
7645 <tt>#!/bin/bash</tt>) and the package must depend on the package
7646 providing the shell (unless the shell package is marked
7647 "Essential", as in the case of <prgn>bash</prgn>).
7651 You may wish to restrict your script to SUSv3 features plus the
7652 above set when possible so that it may use <file>/bin/sh</file>
7653 as its interpreter. If your script works with <prgn>dash</prgn>
7654 (originally called <prgn>ash</prgn>), it probably complies with
7655 the above requirements, but if you are in doubt, use
7656 <file>/bin/bash</file>.
7660 Perl scripts should check for errors when making any
7661 system calls, including <tt>open</tt>, <tt>print</tt>,
7662 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7666 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7667 scripting languages. See <em>Csh Programming Considered
7668 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7669 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7670 If an upstream package comes with <prgn>csh</prgn> scripts
7671 then you must make sure that they start with
7672 <tt>#!/bin/csh</tt> and make your package depend on the
7673 <prgn>c-shell</prgn> virtual package.
7677 Any scripts which create files in world-writeable
7678 directories (e.g., in <file>/tmp</file>) must use a
7679 mechanism which will fail atomically if a file with the same
7680 name already exists.
7684 The Debian base system provides the <prgn>tempfile</prgn>
7685 and <prgn>mktemp</prgn> utilities for use by scripts for
7692 <heading>Symbolic links</heading>
7695 In general, symbolic links within a top-level directory
7696 should be relative, and symbolic links pointing from one
7697 top-level directory into another should be absolute. (A
7698 top-level directory is a sub-directory of the root
7699 directory <file>/</file>.)
7703 In addition, symbolic links should be specified as short as
7704 possible, i.e., link targets like <file>foo/../bar</file> are
7709 Note that when creating a relative link using
7710 <prgn>ln</prgn> it is not necessary for the target of the
7711 link to exist relative to the working directory you're
7712 running <prgn>ln</prgn> from, nor is it necessary to change
7713 directory to the directory where the link is to be made.
7714 Simply include the string that should appear as the target
7715 of the link (this will be a pathname relative to the
7716 directory in which the link resides) as the first argument
7721 For example, in your <prgn>Makefile</prgn> or
7722 <file>debian/rules</file>, you can do things like:
7723 <example compact="compact">
7724 ln -fs gcc $(prefix)/bin/cc
7725 ln -fs gcc debian/tmp/usr/bin/cc
7726 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7727 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7732 A symbolic link pointing to a compressed file should always
7733 have the same file extension as the referenced file. (For
7734 example, if a file <file>foo.gz</file> is referenced by a
7735 symbolic link, the filename of the link has to end with
7736 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7741 <heading>Device files</heading>
7744 Packages must not include device files or named pipes in the
7749 If a package needs any special device files that are not
7750 included in the base system, it must call
7751 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7752 after notifying the user<footnote>
7753 This notification could be done via a (low-priority)
7754 debconf message, or an echo (printf) statement.
7759 Packages must not remove any device files in the
7760 <prgn>postrm</prgn> or any other script. This is left to the
7761 system administrator.
7765 Debian uses the serial devices
7766 <file>/dev/ttyS*</file>. Programs using the old
7767 <file>/dev/cu*</file> devices should be changed to use
7768 <file>/dev/ttyS*</file>.
7772 Named pipes needed by the package must be created in
7773 the <prgn>postinst</prgn> script<footnote>
7774 It's better to use <prgn>mkfifo</prgn> rather
7775 than <prgn>mknod</prgn> to create named pipes so that
7776 automated checks for packages incorrectly creating device
7777 files with <prgn>mknod</prgn> won't have false positives.
7778 </footnote> and removed in
7779 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
7784 <sect id="config-files">
7785 <heading>Configuration files</heading>
7788 <heading>Definitions</heading>
7792 <tag>configuration file</tag>
7794 A file that affects the operation of a program, or
7795 provides site- or host-specific information, or
7796 otherwise customizes the behavior of a program.
7797 Typically, configuration files are intended to be
7798 modified by the system administrator (if needed or
7799 desired) to conform to local policy or to provide
7800 more useful site-specific behavior.
7803 <tag><tt>conffile</tt></tag>
7805 A file listed in a package's <tt>conffiles</tt>
7806 file, and is treated specially by <prgn>dpkg</prgn>
7807 (see <ref id="configdetails">).
7813 The distinction between these two is important; they are
7814 not interchangeable concepts. Almost all
7815 <tt>conffile</tt>s are configuration files, but many
7816 configuration files are not <tt>conffiles</tt>.
7820 As noted elsewhere, <file>/etc/init.d</file> scripts,
7821 <file>/etc/default</file> files, scripts installed in
7822 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7823 configuration installed in <file>/etc/cron.d</file> must be
7824 treated as configuration files. In general, any script that
7825 embeds configuration information is de-facto a configuration
7826 file and should be treated as such.
7831 <heading>Location</heading>
7834 Any configuration files created or used by your package
7835 must reside in <file>/etc</file>. If there are several,
7836 consider creating a subdirectory of <file>/etc</file>
7837 named after your package.
7841 If your package creates or uses configuration files
7842 outside of <file>/etc</file>, and it is not feasible to modify
7843 the package to use <file>/etc</file> directly, put the files
7844 in <file>/etc</file> and create symbolic links to those files
7845 from the location that the package requires.
7850 <heading>Behavior</heading>
7853 Configuration file handling must conform to the following
7855 <list compact="compact">
7857 local changes must be preserved during a package
7861 configuration files must be preserved when the
7862 package is removed, and only deleted when the
7866 Obsolete configuration files without local changes may be
7867 removed by the package during upgrade.
7871 The easy way to achieve this behavior is to make the
7872 configuration file a <tt>conffile</tt>. This is
7873 appropriate only if it is possible to distribute a default
7874 version that will work for most installations, although
7875 some system administrators may choose to modify it. This
7876 implies that the default version will be part of the
7877 package distribution, and must not be modified by the
7878 maintainer scripts during installation (or at any other
7883 In order to ensure that local changes are preserved
7884 correctly, no package may contain or make hard links to
7885 conffiles.<footnote>
7886 Rationale: There are two problems with hard links.
7887 The first is that some editors break the link while
7888 editing one of the files, so that the two files may
7889 unwittingly become unlinked and different. The second
7890 is that <prgn>dpkg</prgn> might break the hard link
7891 while upgrading <tt>conffile</tt>s.
7896 The other way to do it is via the maintainer scripts. In
7897 this case, the configuration file must not be listed as a
7898 <tt>conffile</tt> and must not be part of the package
7899 distribution. If the existence of a file is required for
7900 the package to be sensibly configured it is the
7901 responsibility of the package maintainer to provide
7902 maintainer scripts which correctly create, update and
7903 maintain the file and remove it on purge. (See <ref
7904 id="maintainerscripts"> for more information.) These
7905 scripts must be idempotent (i.e., must work correctly if
7906 <prgn>dpkg</prgn> needs to re-run them due to errors
7907 during installation or removal), must cope with all the
7908 variety of ways <prgn>dpkg</prgn> can call maintainer
7909 scripts, must not overwrite or otherwise mangle the user's
7910 configuration without asking, must not ask unnecessary
7911 questions (particularly during upgrades), and must
7912 otherwise be good citizens.
7916 The scripts are not required to configure every possible
7917 option for the package, but only those necessary to get
7918 the package running on a given system. Ideally the
7919 sysadmin should not have to do any configuration other
7920 than that done (semi-)automatically by the
7921 <prgn>postinst</prgn> script.
7925 A common practice is to create a script called
7926 <file><var>package</var>-configure</file> and have the
7927 package's <prgn>postinst</prgn> call it if and only if the
7928 configuration file does not already exist. In certain
7929 cases it is useful for there to be an example or template
7930 file which the maintainer scripts use. Such files should
7931 be in <file>/usr/share/<var>package</var></file> or
7932 <file>/usr/lib/<var>package</var></file> (depending on whether
7933 they are architecture-independent or not). There should
7934 be symbolic links to them from
7935 <file>/usr/share/doc/<var>package</var>/examples</file> if
7936 they are examples, and should be perfectly ordinary
7937 <prgn>dpkg</prgn>-handled files (<em>not</em>
7938 configuration files).
7942 These two styles of configuration file handling must
7943 not be mixed, for that way lies madness:
7944 <prgn>dpkg</prgn> will ask about overwriting the file
7945 every time the package is upgraded.
7950 <heading>Sharing configuration files</heading>
7953 Packages which specify the same file as a
7954 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7955 with each other. (This is an instance of the general rule
7956 about not sharing files. Note that neither alternatives
7957 nor diversions are likely to be appropriate in this case;
7958 in particular, <prgn>dpkg</prgn> does not handle diverted
7959 <tt>conffile</tt>s well.)
7963 The maintainer scripts must not alter a <tt>conffile</tt>
7964 of <em>any</em> package, including the one the scripts
7969 If two or more packages use the same configuration file
7970 and it is reasonable for both to be installed at the same
7971 time, one of these packages must be defined as
7972 <em>owner</em> of the configuration file, i.e., it will be
7973 the package which handles that file as a configuration
7974 file. Other packages that use the configuration file must
7975 depend on the owning package if they require the
7976 configuration file to operate. If the other package will
7977 use the configuration file if present, but is capable of
7978 operating without it, no dependency need be declared.
7982 If it is desirable for two or more related packages to
7983 share a configuration file <em>and</em> for all of the
7984 related packages to be able to modify that configuration
7985 file, then the following should be done:
7986 <enumlist compact="compact">
7988 One of the related packages (the "owning" package)
7989 will manage the configuration file with maintainer
7990 scripts as described in the previous section.
7993 The owning package should also provide a program
7994 that the other packages may use to modify the
7998 The related packages must use the provided program
7999 to make any desired modifications to the
8000 configuration file. They should either depend on
8001 the core package to guarantee that the configuration
8002 modifier program is available or accept gracefully
8003 that they cannot modify the configuration file if it
8004 is not. (This is in addition to the fact that the
8005 configuration file may not even be present in the
8012 Sometimes it's appropriate to create a new package which
8013 provides the basic infrastructure for the other packages
8014 and which manages the shared configuration files. (The
8015 <tt>sgml-base</tt> package is a good example.)
8020 <heading>User configuration files ("dotfiles")</heading>
8023 The files in <file>/etc/skel</file> will automatically be
8024 copied into new user accounts by <prgn>adduser</prgn>.
8025 No other program should reference the files in
8026 <file>/etc/skel</file>.
8030 Therefore, if a program needs a dotfile to exist in
8031 advance in <file>$HOME</file> to work sensibly, that dotfile
8032 should be installed in <file>/etc/skel</file> and treated as a
8037 However, programs that require dotfiles in order to
8038 operate sensibly are a bad thing, unless they do create
8039 the dotfiles themselves automatically.
8043 Furthermore, programs should be configured by the Debian
8044 default installation to behave as closely to the upstream
8045 default behavior as possible.
8049 Therefore, if a program in a Debian package needs to be
8050 configured in some way in order to operate sensibly, that
8051 should be done using a site-wide configuration file placed
8052 in <file>/etc</file>. Only if the program doesn't support a
8053 site-wide default configuration and the package maintainer
8054 doesn't have time to add it may a default per-user file be
8055 placed in <file>/etc/skel</file>.
8059 <file>/etc/skel</file> should be as empty as we can make it.
8060 This is particularly true because there is no easy (or
8061 necessarily desirable) mechanism for ensuring that the
8062 appropriate dotfiles are copied into the accounts of
8063 existing users when a package is installed.
8069 <heading>Log files</heading>
8071 Log files should usually be named
8072 <file>/var/log/<var>package</var>.log</file>. If you have many
8073 log files, or need a separate directory for permission
8074 reasons (<file>/var/log</file> is writable only by
8075 <file>root</file>), you should usually create a directory named
8076 <file>/var/log/<var>package</var></file> and place your log
8081 Log files must be rotated occasionally so that they don't grow
8082 indefinitely. The best way to do this is to install a log
8083 rotation configuration file in the
8084 directory <file>/etc/logrotate.d</file>, normally
8085 named <file>/etc/logrotate.d/<var>package</var></file>, and use
8086 the facilities provided by <prgn>logrotate</prgn>.
8089 The traditional approach to log files has been to set up
8090 <em>ad hoc</em> log rotation schemes using simple shell
8091 scripts and cron. While this approach is highly
8092 customizable, it requires quite a lot of sysadmin work.
8093 Even though the original Debian system helped a little
8094 by automatically installing a system which can be used
8095 as a template, this was deemed not enough.
8099 The use of <prgn>logrotate</prgn>, a program developed
8100 by Red Hat, is better, as it centralizes log management.
8101 It has both a configuration file
8102 (<file>/etc/logrotate.conf</file>) and a directory where
8103 packages can drop their individual log rotation
8104 configurations (<file>/etc/logrotate.d</file>).
8107 Here is a good example for a logrotate config
8108 file (for more information see <manref name="logrotate"
8110 <example compact="compact">
8111 /var/log/foo/*.log {
8117 start-stop-daemon -K -p /var/run/foo.pid -s HUP -x /usr/sbin/foo -q
8121 This rotates all files under <file>/var/log/foo</file>, saves 12
8122 compressed generations, and tells the daemon to reopen its log
8123 files after the log rotation. It skips this log rotation
8124 (via <tt>missingok</tt>) if no such log file is present, which
8125 avoids errors if the package is removed but not purged.
8129 Log files should be removed when the package is
8130 purged (but not when it is only removed). This should be
8131 done by the <prgn>postrm</prgn> script when it is called
8132 with the argument <tt>purge</tt> (see <ref
8133 id="removedetails">).
8137 <sect id="permissions-owners">
8138 <heading>Permissions and owners</heading>
8141 The rules in this section are guidelines for general use.
8142 If necessary you may deviate from the details below.
8143 However, if you do so you must make sure that what is done
8144 is secure and you should try to be as consistent as possible
8145 with the rest of the system. You should probably also
8146 discuss it on <prgn>debian-devel</prgn> first.
8150 Files should be owned by <tt>root:root</tt>, and made
8151 writable only by the owner and universally readable (and
8152 executable, if appropriate), that is mode 644 or 755.
8156 Directories should be mode 755 or (for group-writability)
8157 mode 2775. The ownership of the directory should be
8158 consistent with its mode: if a directory is mode 2775, it
8159 should be owned by the group that needs write access to
8162 When a package is upgraded, and the owner or permissions
8163 of a file included in the package has changed, dpkg
8164 arranges for the ownership and permissions to be
8165 correctly set upon installation. However, this does not
8166 extend to directories; the permissions and ownership of
8167 directories already on the system does not change on
8168 install or upgrade of packages. This makes sense, since
8169 otherwise common directories like <tt>/usr</tt> would
8170 always be in flux. To correctly change permissions of a
8171 directory the package owns, explicit action is required,
8172 usually in the <tt>postinst</tt> script. Care must be
8173 taken to handle downgrades as well, in that case.
8179 Control information files should be owned by <tt>root:root</tt>
8180 and either mode 644 (for most files) or mode 755 (for
8181 executables such as <qref id="maintscripts">maintainer
8186 Setuid and setgid executables should be mode 4755 or 2755
8187 respectively, and owned by the appropriate user or group.
8188 They should not be made unreadable (modes like 4711 or
8189 2711 or even 4111); doing so achieves no extra security,
8190 because anyone can find the binary in the freely available
8191 Debian package; it is merely inconvenient. For the same
8192 reason you should not restrict read or execute permissions
8193 on non-set-id executables.
8197 Some setuid programs need to be restricted to particular
8198 sets of users, using file permissions. In this case they
8199 should be owned by the uid to which they are set-id, and by
8200 the group which should be allowed to execute them. They
8201 should have mode 4754; again there is no point in making
8202 them unreadable to those users who must not be allowed to
8207 It is possible to arrange that the system administrator can
8208 reconfigure the package to correspond to their local
8209 security policy by changing the permissions on a binary:
8210 they can do this by using <prgn>dpkg-statoverride</prgn>, as
8211 described below.<footnote>
8212 Ordinary files installed by <prgn>dpkg</prgn> (as
8213 opposed to <tt>conffile</tt>s and other similar objects)
8214 normally have their permissions reset to the distributed
8215 permissions when the package is reinstalled. However,
8216 the use of <prgn>dpkg-statoverride</prgn> overrides this
8219 Another method you should consider is to create a group for
8220 people allowed to use the program(s) and make any setuid
8221 executables executable only by that group.
8225 If you need to create a new user or group for your package
8226 there are two possibilities. Firstly, you may need to
8227 make some files in the binary package be owned by this
8228 user or group, or you may need to compile the user or
8229 group id (rather than just the name) into the binary
8230 (though this latter should be avoided if possible, as in
8231 this case you need a statically allocated id).</p>
8234 If you need a statically allocated id, you must ask for a
8235 user or group id from the <tt>base-passwd</tt> maintainer,
8236 and must not release the package until you have been
8237 allocated one. Once you have been allocated one you must
8238 either make the package depend on a version of the
8239 <tt>base-passwd</tt> package with the id present in
8240 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
8241 your package to create the user or group itself with the
8242 correct id (using <tt>adduser</tt>) in its
8243 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
8244 the <prgn>postinst</prgn> is to be preferred if it is
8245 possible, otherwise a pre-dependency will be needed on the
8246 <tt>adduser</tt> package.)
8250 On the other hand, the program might be able to determine
8251 the uid or gid from the user or group name at runtime, so
8252 that a dynamically allocated id can be used. In this case
8253 you should choose an appropriate user or group name,
8254 discussing this on <prgn>debian-devel</prgn> and checking
8255 with the <package/base-passwd/ maintainer that it is unique and that
8256 they do not wish you to use a statically allocated id
8257 instead. When this has been checked you must arrange for
8258 your package to create the user or group if necessary using
8259 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
8260 <prgn>postinst</prgn> script (again, the latter is to be
8261 preferred if it is possible).
8265 Note that changing the numeric value of an id associated
8266 with a name is very difficult, and involves searching the
8267 file system for all appropriate files. You need to think
8268 carefully whether a static or dynamic id is required, since
8269 changing your mind later will cause problems.
8272 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
8274 This section is not intended as policy, but as a
8275 description of the use of <prgn>dpkg-statoverride</prgn>.
8279 If a system administrator wishes to have a file (or
8280 directory or other such thing) installed with owner and
8281 permissions different from those in the distributed Debian
8282 package, they can use the <prgn>dpkg-statoverride</prgn>
8283 program to instruct <prgn>dpkg</prgn> to use the different
8284 settings every time the file is installed. Thus the
8285 package maintainer should distribute the files with their
8286 normal permissions, and leave it for the system
8287 administrator to make any desired changes. For example, a
8288 daemon which is normally required to be setuid root, but
8289 in certain situations could be used without being setuid,
8290 should be installed setuid in the <tt>.deb</tt>. Then the
8291 local system administrator can change this if they wish.
8292 If there are two standard ways of doing it, the package
8293 maintainer can use <tt>debconf</tt> to find out the
8294 preference, and call <prgn>dpkg-statoverride</prgn> in the
8295 maintainer script if necessary to accommodate the system
8296 administrator's choice. Care must be taken during
8297 upgrades to not override an existing setting.
8301 Given the above, <prgn>dpkg-statoverride</prgn> is
8302 essentially a tool for system administrators and would not
8303 normally be needed in the maintainer scripts. There is
8304 one type of situation, though, where calls to
8305 <prgn>dpkg-statoverride</prgn> would be needed in the
8306 maintainer scripts, and that involves packages which use
8307 dynamically allocated user or group ids. In such a
8308 situation, something like the following idiom can be very
8309 helpful in the package's <prgn>postinst</prgn>, where
8310 <tt>sysuser</tt> is a dynamically allocated id:
8312 for i in /usr/bin/foo /usr/sbin/bar
8314 # only do something when no setting exists
8315 if ! dpkg-statoverride --list $i >/dev/null 2>&1
8317 #include: debconf processing, question about foo and bar
8318 if [ "$RET" = "true" ] ; then
8319 dpkg-statoverride --update --add sysuser root 4755 $i
8324 The corresponding code to remove the override when the package
8327 for i in /usr/bin/foo /usr/sbin/bar
8329 if dpkg-statoverride --list $i >/dev/null 2>&1
8331 dpkg-statoverride --remove $i
8341 <chapt id="customized-programs">
8342 <heading>Customized programs</heading>
8344 <sect id="arch-spec">
8345 <heading>Architecture specification strings</heading>
8348 If a program needs to specify an <em>architecture specification
8349 string</em> in some place, it should select one of the strings
8350 provided by <tt>dpkg-architecture -L</tt>. The strings are in
8351 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
8352 part is sometimes elided, as when the OS is Linux.
8356 Note that we don't want to use
8357 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
8358 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
8359 since this would make our programs incompatible with other
8360 Linux distributions. We also don't use something like
8361 <tt><var>arch</var>-unknown-linux</tt>, since the
8362 <tt>unknown</tt> does not look very good.
8365 <sect1 id="arch-wildcard-spec">
8366 <heading>Architecture wildcards</heading>
8369 A package may specify an architecture wildcard. Architecture
8370 wildcards are in the format <tt>any</tt> (which matches every
8371 architecture), <tt><var>os</var></tt>-any, or
8372 any-<tt><var>cpu</var></tt>. <footnote>
8373 Internally, the package system normalizes the GNU triplets
8374 and the Debian arches into Debian arch triplets (which are
8375 kind of inverted GNU triplets), with the first component of
8376 the triplet representing the libc and ABI in use, and then
8377 does matching against those triplets. However, such
8378 triplets are an internal implementation detail that should
8379 not be used by packages directly. The libc and ABI portion
8380 is handled internally by the package system based on
8381 the <var>os</var> and <var>cpu</var>.
8388 <heading>Daemons</heading>
8391 The configuration files <file>/etc/services</file>,
8392 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
8393 by the <prgn>netbase</prgn> package and must not be modified
8398 If a package requires a new entry in one of these files, the
8399 maintainer should get in contact with the
8400 <prgn>netbase</prgn> maintainer, who will add the entries
8401 and release a new version of the <prgn>netbase</prgn>
8406 The configuration file <file>/etc/inetd.conf</file> must not be
8407 modified by the package's scripts except via the
8408 <prgn>update-inetd</prgn> script or the
8409 <file>DebianNet.pm</file> Perl module. See their documentation
8410 for details on how to add entries.
8414 If a package wants to install an example entry into
8415 <file>/etc/inetd.conf</file>, the entry must be preceded with
8416 exactly one hash character (<tt>#</tt>). Such lines are
8417 treated as "commented out by user" by the
8418 <prgn>update-inetd</prgn> script and are not changed or
8419 activated during package updates.
8424 <heading>Using pseudo-ttys and modifying wtmp, utmp and
8428 Some programs need to create pseudo-ttys. This should be done
8429 using Unix98 ptys if the C library supports it. The resulting
8430 program must not be installed setuid root, unless that
8431 is required for other functionality.
8435 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
8436 <file>/var/log/lastlog</file> must be installed writable by
8437 group <tt>utmp</tt>. Programs which need to modify those
8438 files must be installed setgid <tt>utmp</tt>.
8443 <heading>Editors and pagers</heading>
8446 Some programs have the ability to launch an editor or pager
8447 program to edit or display a text document. Since there are
8448 lots of different editors and pagers available in the Debian
8449 distribution, the system administrator and each user should
8450 have the possibility to choose their preferred editor and
8455 In addition, every program should choose a good default
8456 editor/pager if none is selected by the user or system
8461 Thus, every program that launches an editor or pager must
8462 use the EDITOR or PAGER environment variable to determine
8463 the editor or pager the user wishes to use. If these
8464 variables are not set, the programs <file>/usr/bin/editor</file>
8465 and <file>/usr/bin/pager</file> should be used, respectively.
8469 These two files are managed through the <prgn>dpkg</prgn>
8470 "alternatives" mechanism. Every package providing an editor or
8471 pager must call the <prgn>update-alternatives</prgn> script to
8472 register as an alternative for <file>/usr/bin/editor</file>
8473 or <file>/usr/bin/pager</file> as appropriate. The alternative
8474 should have a slave alternative
8475 for <file>/usr/share/man/man1/editor.1.gz</file>
8476 or <file>/usr/share/man/man1/pager.1.gz</file> pointing to the
8477 corresponding manual page.
8481 If it is very hard to adapt a program to make use of the
8482 EDITOR or PAGER variables, that program may be configured to
8483 use <file>/usr/bin/sensible-editor</file> and
8484 <file>/usr/bin/sensible-pager</file> as the editor or pager
8485 program respectively. These are two scripts provided in the
8486 <package>sensible-utils</package> package that check the EDITOR
8487 and PAGER variables and launch the appropriate program, and fall
8488 back to <file>/usr/bin/editor</file>
8489 and <file>/usr/bin/pager</file> if the variable is not set.
8493 A program may also use the VISUAL environment variable to
8494 determine the user's choice of editor. If it exists, it
8495 should take precedence over EDITOR. This is in fact what
8496 <file>/usr/bin/sensible-editor</file> does.
8500 It is not required for a package to depend on
8501 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
8502 package to provide such virtual packages.<footnote>
8503 The Debian base system already provides an editor and a
8509 <sect id="web-appl">
8510 <heading>Web servers and applications</heading>
8513 This section describes the locations and URLs that should
8514 be used by all web servers and web applications in the
8521 Cgi-bin executable files are installed in the
8523 <example compact="compact">
8524 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
8526 or a subdirectory of that directory, and should be
8528 <example compact="compact">
8529 http://localhost/cgi-bin/<var>cgi-bin-name</var>
8531 (possibly with a subdirectory name
8532 before <var>cgi-bin-name</var>).
8536 <p>Access to HTML documents</p>
8539 HTML documents for a package are stored in
8540 <file>/usr/share/doc/<var>package</var></file>
8541 and can be referred to as
8542 <example compact="compact">
8543 http://localhost/doc/<var>package</var>/<var>filename</var>
8548 The web server should restrict access to the document
8549 tree so that only clients on the same host can read
8550 the documents. If the web server does not support such
8551 access controls, then it should not provide access at
8552 all, or ask about providing access during installation.
8557 <p>Access to images</p>
8559 It is recommended that images for a package be stored
8560 in <tt>/usr/share/images/<var>package</var></tt> and
8561 may be referred to through an alias <tt>/images/</tt>
8564 http://localhost/images/<package>/<filename>
8571 <p>Web Document Root</p>
8574 Web Applications should try to avoid storing files in
8575 the Web Document Root. Instead they should use the
8576 /usr/share/doc/<var>package</var> directory for
8577 documents and register the Web Application via the
8578 <package>doc-base</package> package. If access to the
8579 web document root is unavoidable then use
8580 <example compact="compact">
8583 as the Document Root. This might be just a symbolic
8584 link to the location where the system administrator
8585 has put the real document root.
8588 <item><p>Providing httpd and/or httpd-cgi</p>
8590 All web servers should provide the virtual package
8591 <tt>httpd</tt>. If a web server has CGI support it should
8592 provide <tt>httpd-cgi</tt> additionally.
8595 All web applications which do not contain CGI scripts should
8596 depend on <tt>httpd</tt>, all those web applications which
8597 <tt>do</tt> contain CGI scripts, should depend on
8605 <sect id="mail-transport-agents">
8606 <heading>Mail transport, delivery and user agents</heading>
8609 Debian packages which process electronic mail, whether mail
8610 user agents (MUAs) or mail transport agents (MTAs), must
8611 ensure that they are compatible with the configuration
8612 decisions below. Failure to do this may result in lost
8613 mail, broken <tt>From:</tt> lines, and other serious brain
8618 The mail spool is <file>/var/mail</file> and the interface to
8619 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8620 the FHS). On older systems, the mail spool may be
8621 physically located in <file>/var/spool/mail</file>, but all
8622 access to the mail spool should be via the
8623 <file>/var/mail</file> symlink. The mail spool is part of the
8624 base system and not part of the MTA package.
8628 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8629 programs (such as IMAP daemons) must lock the mailbox in an
8630 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8631 be combined with dot locking. To avoid deadlocks, a program
8632 should use <tt>fcntl()</tt> first and dot locking after
8633 this, or alternatively implement the two locking methods in
8634 a non blocking way<footnote>
8635 If it is not possible to establish both locks, the
8636 system shouldn't wait for the second lock to be
8637 established, but remove the first lock, wait a (random)
8638 time, and start over locking again.
8639 </footnote>. Using the functions <tt>maillock</tt> and
8640 <tt>mailunlock</tt> provided by the
8641 <tt>liblockfile*</tt><footnote>
8642 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8643 to use these functions.
8644 </footnote> packages is the recommended way to realize this.
8648 Mailboxes are generally either mode 600 and owned by
8649 <var>user</var> or mode 660 and owned by
8650 <tt><var>user</var>:mail</tt><footnote>
8651 There are two traditional permission schemes for mail spools:
8652 mode 600 with all mail delivery done by processes running as
8653 the destination user, or mode 660 and owned by group mail with
8654 mail delivery done by a process running as a system user in
8655 group mail. Historically, Debian required mode 660 mail
8656 spools to enable the latter model, but that model has become
8657 increasingly uncommon and the principle of least privilege
8658 indicates that mail systems that use the first model should
8659 use permissions of 600. If delivery to programs is permitted,
8660 it's easier to keep the mail system secure if the delivery
8661 agent runs as the destination user. Debian Policy therefore
8662 permits either scheme.
8663 </footnote>. The local system administrator may choose a
8664 different permission scheme; packages should not make
8665 assumptions about the permission and ownership of mailboxes
8666 unless required (such as when creating a new mailbox). A MUA
8667 may remove a mailbox (unless it has nonstandard permissions) in
8668 which case the MTA or another MUA must recreate it if needed.
8672 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8673 be setgid mail to do the locking mentioned above (and
8674 must obviously avoid accessing other users' mailboxes
8675 using this privilege).</p>
8678 <file>/etc/aliases</file> is the source file for the system mail
8679 aliases (e.g., postmaster, usenet, etc.), it is the one
8680 which the sysadmin and <prgn>postinst</prgn> scripts may
8681 edit. After <file>/etc/aliases</file> is edited the program or
8682 human editing it must call <prgn>newaliases</prgn>. All MTA
8683 packages must come with a <prgn>newaliases</prgn> program,
8684 even if it does nothing, but older MTA packages did not do
8685 this so programs should not fail if <prgn>newaliases</prgn>
8686 cannot be found. Note that because of this, all MTA
8687 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8688 <tt>Replaces: mail-transport-agent</tt> control fields.
8692 The convention of writing <tt>forward to
8693 <var>address</var></tt> in the mailbox itself is not
8694 supported. Use a <tt>.forward</tt> file instead.</p>
8697 The <prgn>rmail</prgn> program used by UUCP
8698 for incoming mail should be <file>/usr/sbin/rmail</file>.
8699 Likewise, <prgn>rsmtp</prgn>, for receiving
8700 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8704 If your package needs to know what hostname to use on (for
8705 example) outgoing news and mail messages which are generated
8706 locally, you should use the file <file>/etc/mailname</file>. It
8707 will contain the portion after the username and <tt>@</tt>
8708 (at) sign for email addresses of users on the machine
8709 (followed by a newline).
8713 Such a package should check for the existence of this file
8714 when it is being configured. If it exists, it should be
8715 used without comment, although an MTA's configuration script
8716 may wish to prompt the user even if it finds that this file
8717 exists. If the file does not exist, the package should
8718 prompt the user for the value (preferably using
8719 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8720 as well as using it in the package's configuration. The
8721 prompt should make it clear that the name will not just be
8722 used by that package. For example, in this situation the
8723 <tt>inn</tt> package could say something like:
8724 <example compact="compact">
8725 Please enter the "mail name" of your system. This is the
8726 hostname portion of the address to be shown on outgoing
8727 news and mail messages. The default is
8728 <var>syshostname</var>, your system's host name. Mail
8729 name ["<var>syshostname</var>"]:
8731 where <var>syshostname</var> is the output of <tt>hostname
8737 <heading>News system configuration</heading>
8740 All the configuration files related to the NNTP (news)
8741 servers and clients should be located under
8742 <file>/etc/news</file>.</p>
8745 There are some configuration issues that apply to a number
8746 of news clients and server packages on the machine. These
8750 <tag><file>/etc/news/organization</file></tag>
8752 A string which should appear as the
8753 organization header for all messages posted
8754 by NNTP clients on the machine
8757 <tag><file>/etc/news/server</file></tag>
8759 Contains the FQDN of the upstream NNTP
8760 server, or localhost if the local machine is
8765 Other global files may be added as required for cross-package news
8772 <heading>Programs for the X Window System</heading>
8775 <heading>Providing X support and package priorities</heading>
8778 Programs that can be configured with support for the X
8779 Window System must be configured to do so and must declare
8780 any package dependencies necessary to satisfy their
8781 runtime requirements when using the X Window System. If
8782 such a package is of higher priority than the X packages
8783 on which it depends, it is required that either the
8784 X-specific components be split into a separate package, or
8785 that an alternative version of the package, which includes
8786 X support, be provided, or that the package's priority be
8792 <heading>Packages providing an X server</heading>
8795 Packages that provide an X server that, directly or
8796 indirectly, communicates with real input and display
8797 hardware should declare in their <tt>Provides</tt> control
8798 field that they provide the virtual
8799 package <tt>xserver</tt>.<footnote>
8800 This implements current practice, and provides an
8801 actual policy for usage of the <tt>xserver</tt>
8802 virtual package which appears in the virtual packages
8803 list. In a nutshell, X servers that interface
8804 directly with the display and input hardware or via
8805 another subsystem (e.g., GGI) should provide
8806 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8807 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8813 <heading>Packages providing a terminal emulator</heading>
8816 Packages that provide a terminal emulator for the X Window
8817 System which meet the criteria listed below should declare in
8818 their <tt>Provides</tt> control field that they provide the
8819 virtual package <tt>x-terminal-emulator</tt>. They should
8820 also register themselves as an alternative for
8821 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8822 20. That alternative should have a slave alternative
8823 for <file>/usr/share/man/man1/x-terminal-emulator.1.gz</file>
8824 pointing to the corresponding manual page.
8828 To be an <tt>x-terminal-emulator</tt>, a program must:
8829 <list compact="compact">
8831 Be able to emulate a DEC VT100 terminal, or a
8832 compatible terminal.
8836 Support the command-line option <tt>-e
8837 <var>command</var></tt>, which creates a new
8838 terminal window<footnote>
8839 "New terminal window" does not necessarily mean
8840 a new top-level X window directly parented by
8841 the window manager; it could, if the terminal
8842 emulator application were so coded, be a new
8843 "view" in a multiple-document interface (MDI).
8845 and runs the specified <var>command</var>,
8846 interpreting the entirety of the rest of the command
8847 line as a command to pass straight to exec, in the
8848 manner that <tt>xterm</tt> does.
8852 Support the command-line option <tt>-T
8853 <var>title</var></tt>, which creates a new terminal
8854 window with the window title <var>title</var>.
8861 <heading>Packages providing a window manager</heading>
8864 Packages that provide a window manager should declare in
8865 their <tt>Provides</tt> control field that they provide the
8866 virtual package <tt>x-window-manager</tt>. They should also
8867 register themselves as an alternative for
8868 <file>/usr/bin/x-window-manager</file>, with a priority
8869 calculated as follows:
8870 <list compact="compact">
8872 Start with a priority of 20.
8876 If the window manager supports the Debian menu
8877 system, add 20 points if this support is available
8878 in the package's default configuration (i.e., no
8879 configuration files belonging to the system or user
8880 have to be edited to activate the feature); if
8881 configuration files must be modified, add only 10
8887 If the window manager complies with <url
8888 id="http://www.freedesktop.org/Standards/wm-spec"
8889 name="The Window Manager Specification Project">,
8890 written by the <url id="http://www.freedesktop.org/"
8891 name="Free Desktop Group">, add 40 points.
8895 If the window manager permits the X session to be
8896 restarted using a <em>different</em> window manager
8897 (without killing the X server) in its default
8898 configuration, add 10 points; otherwise add none.
8901 That alternative should have a slave alternative
8902 for <file>/usr/share/man/man1/x-window-manager.1.gz</file>
8903 pointing to the corresponding manual page.
8908 <heading>Packages providing fonts</heading>
8911 Packages that provide fonts for the X Window
8913 For the purposes of Debian Policy, a "font for the X
8914 Window System" is one which is accessed via X protocol
8915 requests. Fonts for the Linux console, for PostScript
8916 renderer, or any other purpose, do not fit this
8917 definition. Any tool which makes such fonts available
8918 to the X Window System, however, must abide by this
8921 must do a number of things to ensure that they are both
8922 available without modification of the X or font server
8923 configuration, and that they do not corrupt files used by
8924 other font packages to register information about
8928 Fonts of any type supported by the X Window System
8929 must be in a separate binary package from any
8930 executables, libraries, or documentation (except
8931 that specific to the fonts shipped, such as their
8932 license information). If one or more of the fonts
8933 so packaged are necessary for proper operation of
8934 the package with which they are associated the font
8935 package may be Recommended; if the fonts merely
8936 provide an enhancement, a Suggests relationship may
8937 be used. Packages must not Depend on font
8939 This is because the X server may retrieve fonts
8940 from the local file system or over the network
8941 from an X font server; the Debian package system
8942 is empowered to deal only with the local
8948 BDF fonts must be converted to PCF fonts with the
8949 <prgn>bdftopcf</prgn> utility (available in the
8950 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8951 placed in a directory that corresponds to their
8953 <list compact="compact">
8955 100 dpi fonts must be placed in
8956 <file>/usr/share/fonts/X11/100dpi/</file>.
8960 75 dpi fonts must be placed in
8961 <file>/usr/share/fonts/X11/75dpi/</file>.
8965 Character-cell fonts, cursor fonts, and other
8966 low-resolution fonts must be placed in
8967 <file>/usr/share/fonts/X11/misc/</file>.
8973 Type 1 fonts must be placed in
8974 <file>/usr/share/fonts/X11/Type1/</file>. If font
8975 metric files are available, they must be placed here
8980 Subdirectories of <file>/usr/share/fonts/X11/</file>
8981 other than those listed above must be neither
8982 created nor used. (The <file>PEX</file>, <file>CID</file>,
8983 <file>Speedo</file>, and <file>cyrillic</file> directories
8984 are excepted for historical reasons, but installation of
8985 files into these directories remains discouraged.)
8989 Font packages may, instead of placing files directly
8990 in the X font directories listed above, provide
8991 symbolic links in that font directory pointing to
8992 the files' actual location in the filesystem. Such
8993 a location must comply with the FHS.
8997 Font packages should not contain both 75dpi and
8998 100dpi versions of a font. If both are available,
8999 they should be provided in separate binary packages
9000 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
9001 the names of the packages containing the
9002 corresponding fonts.
9006 Fonts destined for the <file>misc</file> subdirectory
9007 should not be included in the same package as 75dpi
9008 or 100dpi fonts; instead, they should be provided in
9009 a separate package with <tt>-misc</tt> appended to
9014 Font packages must not provide the files
9015 <file>fonts.dir</file>, <file>fonts.alias</file>, or
9016 <file>fonts.scale</file> in a font directory:
9019 <file>fonts.dir</file> files must not be provided at all.
9023 <file>fonts.alias</file> and <file>fonts.scale</file>
9024 files, if needed, should be provided in the
9026 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
9027 where <var>fontdir</var> is the name of the
9029 <file>/usr/share/fonts/X11/</file> where the
9030 package's corresponding fonts are stored
9031 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
9032 <var>package</var> is the name of the package
9033 that provides these fonts, and
9034 <var>extension</var> is either <tt>scale</tt>
9035 or <tt>alias</tt>, whichever corresponds to
9042 Font packages must declare a dependency on
9043 <tt>xfonts-utils</tt> in their <tt>Depends</tt>
9044 or <tt>Pre-Depends</tt> control field.
9048 Font packages that provide one or more
9049 <file>fonts.scale</file> files as described above must
9050 invoke <prgn>update-fonts-scale</prgn> on each
9051 directory into which they installed fonts
9052 <em>before</em> invoking
9053 <prgn>update-fonts-dir</prgn> on that directory.
9054 This invocation must occur in both the
9055 <prgn>postinst</prgn> (for all arguments) and
9056 <prgn>postrm</prgn> (for all arguments except
9057 <tt>upgrade</tt>) scripts.
9061 Font packages that provide one or more
9062 <file>fonts.alias</file> files as described above must
9063 invoke <prgn>update-fonts-alias</prgn> on each
9064 directory into which they installed fonts. This
9065 invocation must occur in both the
9066 <prgn>postinst</prgn> (for all arguments) and
9067 <prgn>postrm</prgn> (for all arguments except
9068 <tt>upgrade</tt>) scripts.
9072 Font packages must invoke
9073 <prgn>update-fonts-dir</prgn> on each directory into
9074 which they installed fonts. This invocation must
9075 occur in both the <prgn>postinst</prgn> (for all
9076 arguments) and <prgn>postrm</prgn> (for all
9077 arguments except <tt>upgrade</tt>) scripts.
9081 Font packages must not provide alias names for the
9082 fonts they include which collide with alias names
9083 already in use by fonts already packaged.
9087 Font packages must not provide fonts with the same
9088 XLFD registry name as another font already packaged.
9094 <sect1 id="appdefaults">
9095 <heading>Application defaults files</heading>
9098 Application defaults files must be installed in the
9099 directory <file>/etc/X11/app-defaults/</file> (use of a
9100 localized subdirectory of <file>/etc/X11/</file> as described
9101 in the <em>X Toolkit Intrinsics - C Language
9102 Interface</em> manual is also permitted). They must be
9103 registered as <tt>conffile</tt>s or handled as
9104 configuration files.
9108 Customization of programs' X resources may also be
9109 supported with the provision of a file with the same name
9110 as that of the package placed in
9111 the <file>/etc/X11/Xresources/</file> directory, which
9112 must be registered as a <tt>conffile</tt> or handled as a
9113 configuration file.<footnote>
9114 Note that this mechanism is not the same as using
9115 app-defaults; app-defaults are tied to the client
9116 binary on the local file system, whereas X resources
9117 are stored in the X server and affect all connecting
9124 <heading>Installation directory issues</heading>
9127 Historically, packages using the X Window System used a
9128 separate set of installation directories from other packages.
9129 This practice has been discontinued and packages using the X
9130 Window System should now generally be installed in the same
9131 directories as any other package. Specifically, packages must
9132 not install files under the <file>/usr/X11R6/</file> directory
9133 and the <file>/usr/X11R6/</file> directory hierarchy should be
9134 regarded as obsolete.
9138 Include files previously installed under
9139 <file>/usr/X11R6/include/X11/</file> should be installed into
9140 <file>/usr/include/X11/</file>. For files previously
9141 installed into subdirectories of
9142 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
9143 determine if subdirectories of <file>/usr/lib/</file> and
9144 <file>/usr/share/</file> can be used. If not, a subdirectory
9145 of <file>/usr/lib/X11/</file> should be used.
9149 Configuration files for window, display, or session managers
9150 or other applications that are tightly integrated with the X
9151 Window System may be placed in a subdirectory
9152 of <file>/etc/X11/</file> corresponding to the package name.
9153 Other X Window System applications should use
9154 the <file>/etc/</file> directory unless otherwise mandated by
9155 policy (such as for <ref id="appdefaults">).
9160 <heading>The OSF/Motif and OpenMotif libraries</heading>
9163 <em>Programs that require the non-DFSG-compliant OSF/Motif or
9164 OpenMotif libraries</em><footnote>
9165 OSF/Motif and OpenMotif are collectively referred to as
9166 "Motif" in this policy document.
9168 should be compiled against and tested with LessTif (a free
9169 re-implementation of Motif) instead. If the maintainer
9170 judges that the program or programs do not work
9171 sufficiently well with LessTif to be distributed and
9172 supported, but do so when compiled against Motif, then two
9173 versions of the package should be created; one linked
9174 statically against Motif and with <tt>-smotif</tt>
9175 appended to the package name, and one linked dynamically
9176 against Motif and with <tt>-dmotif</tt> appended to the
9181 Both Motif-linked versions are dependent
9182 upon non-DFSG-compliant software and thus cannot be
9183 uploaded to the <em>main</em> distribution; if the
9184 software is itself DFSG-compliant it may be uploaded to
9185 the <em>contrib</em> distribution. While known existing
9186 versions of Motif permit unlimited redistribution of
9187 binaries linked against the library (whether statically or
9188 dynamically), it is the package maintainer's
9189 responsibility to determine whether this is permitted by
9190 the license of the copy of Motif in their possession.
9196 <heading>Perl programs and modules</heading>
9199 Perl programs and modules should follow the current Perl policy.
9203 The Perl policy can be found in the <tt>perl-policy</tt>
9204 files in the <tt>debian-policy</tt> package.
9205 It is also available from the Debian web mirrors at
9206 <tt><url name="/doc/packaging-manuals/perl-policy/"
9207 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
9212 <heading>Emacs lisp programs</heading>
9215 Please refer to the "Debian Emacs Policy" for details of how to
9216 package emacs lisp programs.
9220 The Emacs policy is available in
9221 <file>debian-emacs-policy.gz</file> of the
9222 <package>emacsen-common</package> package.
9223 It is also available from the Debian web mirrors at
9224 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
9225 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
9230 <heading>Games</heading>
9233 The permissions on <file>/var/games</file> are mode 755, owner
9234 <tt>root</tt> and group <tt>root</tt>.
9238 Each game decides on its own security policy.</p>
9241 Games which require protected, privileged access to
9242 high-score files, saved games, etc., may be made
9243 set-<em>group</em>-id (mode 2755) and owned by
9244 <tt>root:games</tt>, and use files and directories with
9245 appropriate permissions (770 <tt>root:games</tt>, for
9246 example). They must not be made
9247 set-<em>user</em>-id, as this causes security problems. (If
9248 an attacker can subvert any set-user-id game they can
9249 overwrite the executable of any other, causing other players
9250 of these games to run a Trojan horse program. With a
9251 set-group-id game the attacker only gets access to less
9252 important game data, and if they can get at the other
9253 players' accounts at all it will take considerably more
9257 Some packages, for example some fortune cookie programs, are
9258 configured by the upstream authors to install with their
9259 data files or other static information made unreadable so
9260 that they can only be accessed through set-id programs
9261 provided. You should not do this in a Debian package: anyone can
9262 download the <file>.deb</file> file and read the data from it,
9263 so there is no point making the files unreadable. Not
9264 making the files unreadable also means that you don't have
9265 to make so many programs set-id, which reduces the risk of a
9269 As described in the FHS, binaries of games should be
9270 installed in the directory <file>/usr/games</file>. This also
9271 applies to games that use the X Window System. Manual pages
9272 for games (X and non-X games) should be installed in
9273 <file>/usr/share/man/man6</file>.</p>
9279 <heading>Documentation</heading>
9282 <heading>Manual pages</heading>
9285 You should install manual pages in <prgn>nroff</prgn> source
9286 form, in appropriate places under <file>/usr/share/man</file>.
9287 You should only use sections 1 to 9 (see the FHS for more
9288 details). You must not install a pre-formatted "cat page".
9292 Each program, utility, and function should have an
9293 associated manual page included in the same package. It is
9294 suggested that all configuration files also have a manual
9295 page included as well. Manual pages for protocols and other
9296 auxiliary things are optional.
9300 If no manual page is available, this is considered as a bug
9301 and should be reported to the Debian Bug Tracking System (the
9302 maintainer of the package is allowed to write this bug report
9303 themselves, if they so desire). Do not close the bug report
9304 until a proper man page is available.<footnote>
9305 It is not very hard to write a man page. See the
9306 <url id="http://www.schweikhardt.net/man_page_howto.html"
9307 name="Man-Page-HOWTO">,
9308 <manref name="man" section="7">, the examples
9309 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
9310 the helper program <prgn>help2man</prgn>, or the
9311 directory <file>/usr/share/doc/man-db/examples</file>.
9316 You may forward a complaint about a missing man page to the
9317 upstream authors, and mark the bug as forwarded in the
9318 Debian bug tracking system. Even though the GNU Project do
9319 not in general consider the lack of a man page to be a bug,
9320 we do; if they tell you that they don't consider it a bug
9321 you should leave the bug in our bug tracking system open
9326 Manual pages should be installed compressed using <tt>gzip -9</tt>.
9330 If one man page needs to be accessible via several names it
9331 is better to use a symbolic link than the <file>.so</file>
9332 feature, but there is no need to fiddle with the relevant
9333 parts of the upstream source to change from <file>.so</file> to
9334 symlinks: don't do it unless it's easy. You should not
9335 create hard links in the manual page directories, nor put
9336 absolute filenames in <file>.so</file> directives. The filename
9337 in a <file>.so</file> in a man page should be relative to the
9338 base of the man page tree (usually
9339 <file>/usr/share/man</file>). If you do not create any links
9340 (whether symlinks, hard links, or <tt>.so</tt> directives)
9341 in the file system to the alternate names of the man page,
9342 then you should not rely on <prgn>man</prgn> finding your
9343 man page under those names based solely on the information in
9344 the man page's header.<footnote>
9345 Supporting this in <prgn>man</prgn> often requires
9346 unreasonable processing time to find a manual page or to
9347 report that none exists, and moves knowledge into man's
9348 database that would be better left in the file system.
9349 This support is therefore deprecated and will cease to
9350 be present in the future.
9355 Manual pages in locale-specific subdirectories of
9356 <file>/usr/share/man</file> should use either UTF-8 or the usual
9357 legacy encoding for that language (normally the one corresponding
9358 to the shortest relevant locale name in
9359 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
9360 <file>/usr/share/man/fr</file> should use either UTF-8 or
9361 ISO-8859-1.<footnote>
9362 <prgn>man</prgn> will automatically detect whether UTF-8 is in
9363 use. In future, all manual pages will be required to use
9369 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
9370 included in the subdirectory name unless it indicates a
9371 significant difference in the language, as this excludes
9372 speakers of the language in other countries.<footnote>
9373 At the time of writing, Chinese and Portuguese are the main
9374 languages with such differences, so <file>pt_BR</file>,
9375 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
9380 If a localized version of a manual page is provided, it should
9381 either be up-to-date or it should be obvious to the reader that
9382 it is outdated and the original manual page should be used
9383 instead. This can be done either by a note at the beginning of
9384 the manual page or by showing the missing or changed portions in
9385 the original language instead of the target language.
9390 <heading>Info documents</heading>
9393 Info documents should be installed in <file>/usr/share/info</file>.
9394 They should be compressed with <tt>gzip -9</tt>.
9398 The <prgn>install-info</prgn> program maintains a directory of
9399 installed info documents in <file>/usr/share/info/dir</file> for
9400 the use of info readers.<footnote>
9401 It was previously necessary for packages installing info
9402 documents to run <prgn>install-info</prgn> from maintainer
9403 scripts. This is no longer necessary. The installation
9404 system now uses dpkg triggers.
9406 This file must not be included in packages. Packages containing
9407 info documents should depend on <tt>dpkg (>= 1.15.4) |
9408 install-info</tt> to ensure that the directory file is properly
9409 rebuilt during partial upgrades from Debian 5.0 (lenny) and
9414 Info documents should contain section and directory entry
9415 information in the document for the use
9416 of <prgn>install-info</prgn>. The section should be specified
9417 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
9418 space and the section of this info page. The directory entry or
9419 entries should be included between
9420 a <tt>START-INFO-DIR-ENTRY</tt> line and
9421 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
9423 INFO-DIR-SECTION Individual utilities
9424 START-INFO-DIR-ENTRY
9425 * example: (example). An example info directory entry.
9428 To determine which section to use, you should look
9429 at <file>/usr/share/info/dir</file> on your system and choose
9430 the most relevant (or create a new section if none of the
9431 current sections are relevant).<footnote>
9432 Normally, info documents are generated from Texinfo source.
9433 To include this information in the generated info document, if
9434 it is absent, add commands like:
9436 @dircategory Individual utilities
9438 * example: (example). An example info directory entry.
9441 to the Texinfo source of the document and ensure that the info
9442 documents are rebuilt from source during the package build.
9448 <heading>Additional documentation</heading>
9451 Any additional documentation that comes with the package may
9452 be installed at the discretion of the package maintainer.
9453 Plain text documentation should be installed in the directory
9454 <file>/usr/share/doc/<var>package</var></file>, where
9455 <var>package</var> is the name of the package, and
9456 compressed with <tt>gzip -9</tt> unless it is small.
9460 If a package comes with large amounts of documentation which
9461 many users of the package will not require you should create
9462 a separate binary package to contain it, so that it does not
9463 take up disk space on the machines of users who do not need
9464 or want it installed.</p>
9467 It is often a good idea to put text information files
9468 (<file>README</file>s, changelogs, and so forth) that come with
9469 the source package in <file>/usr/share/doc/<var>package</var></file>
9470 in the binary package. However, you don't need to install
9471 the instructions for building and installing the package, of
9475 Packages must not require the existence of any files in
9476 <file>/usr/share/doc/</file> in order to function
9478 The system administrator should be able to
9479 delete files in <file>/usr/share/doc/</file> without causing
9480 any programs to break.
9482 Any files that are referenced by programs but are also
9483 useful as stand alone documentation should be installed under
9484 <file>/usr/share/<var>package</var>/</file> with symbolic links from
9485 <file>/usr/share/doc/<var>package</var></file>.
9489 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9490 link to another directory in <file>/usr/share/doc</file> only if
9491 the two packages both come from the same source and the
9492 first package Depends on the second.<footnote>
9494 Please note that this does not override the section on
9495 changelog files below, so the file
9496 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
9497 must refer to the changelog for the current version of
9498 <var>package</var> in question. In practice, this means
9499 that the sources of the target and the destination of the
9500 symlink must be the same (same source package and
9507 Former Debian releases placed all additional documentation
9508 in <file>/usr/doc/<var>package</var></file>. This has been
9509 changed to <file>/usr/share/doc/<var>package</var></file>,
9510 and packages must not put documentation in the directory
9511 <file>/usr/doc/<var>package</var></file>. <footnote>
9512 At this phase of the transition, we no longer require a
9513 symbolic link in <file>/usr/doc/</file>. At a later point,
9514 policy shall change to make the symbolic links a bug.
9520 <heading>Preferred documentation formats</heading>
9523 The unification of Debian documentation is being carried out
9527 If your package comes with extensive documentation in a
9528 markup format that can be converted to various other formats
9529 you should if possible ship HTML versions in a binary
9530 package, in the directory
9531 <file>/usr/share/doc/<var>appropriate-package</var></file> or
9532 its subdirectories.<footnote>
9533 The rationale: The important thing here is that HTML
9534 docs should be available in <em>some</em> package, not
9535 necessarily in the main binary package.
9540 Other formats such as PostScript may be provided at the
9541 package maintainer's discretion.
9545 <sect id="copyrightfile">
9546 <heading>Copyright information</heading>
9549 Every package must be accompanied by a verbatim copy of its
9550 copyright information and distribution license in the file
9551 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
9552 file must neither be compressed nor be a symbolic link.
9556 In addition, the copyright file must say where the upstream
9557 sources (if any) were obtained. It should name the original
9558 authors of the package and the Debian maintainer(s) who were
9559 involved with its creation.
9563 Packages in the <em>contrib</em> or <em>non-free</em> archive
9564 areas should state in the copyright file that the package is not
9565 part of the Debian GNU/Linux distribution and briefly explain
9570 A copy of the file which will be installed in
9571 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9572 be in <file>debian/copyright</file> in the source package.
9576 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9577 link to another directory in <file>/usr/share/doc</file> only if
9578 the two packages both come from the same source and the
9579 first package Depends on the second. These rules are
9580 important because copyrights must be extractable by
9585 Packages distributed under the Apache license (version 2.0), the
9586 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
9587 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
9588 1.3) should refer to the corresponding files
9589 under <file>/usr/share/common-licenses</file>,<footnote>
9592 <file>/usr/share/common-licenses/Apache-2.0</file>,
9593 <file>/usr/share/common-licenses/Artistic</file>,
9594 <file>/usr/share/common-licenses/GPL-1</file>,
9595 <file>/usr/share/common-licenses/GPL-2</file>,
9596 <file>/usr/share/common-licenses/GPL-3</file>,
9597 <file>/usr/share/common-licenses/LGPL-2</file>,
9598 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9599 <file>/usr/share/common-licenses/LGPL-3</file>,
9600 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
9601 <file>/usr/share/common-licenses/GFDL-1.3</file>
9602 respectively. The University of California BSD license is
9603 also included in <package>base-files</package> as
9604 <file>/usr/share/common-licenses/BSD</file>, but given the
9605 brevity of this license, its specificity to code whose
9606 copyright is held by the Regents of the University of
9607 California, and the frequency of minor wording changes, its
9608 text should be included in the copyright file rather than
9609 referencing this file.
9611 </footnote> rather than quoting them in the copyright
9616 You should not use the copyright file as a general <file>README</file>
9617 file. If your package has such a file it should be
9618 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9619 <file>README.Debian</file> or some other appropriate place.</p>
9623 <heading>Examples</heading>
9626 Any examples (configurations, source files, whatever),
9627 should be installed in a directory
9628 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9629 files should not be referenced by any program: they're there
9630 for the benefit of the system administrator and users as
9631 documentation only. Architecture-specific example files
9632 should be installed in a directory
9633 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9635 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9636 latter directory itself may be a symbolic link to the
9641 If the purpose of a package is to provide examples, then the
9642 example files may be installed into
9643 <file>/usr/share/doc/<var>package</var></file>.
9647 <sect id="changelogs">
9648 <heading>Changelog files</heading>
9651 Packages that are not Debian-native must contain a
9652 compressed copy of the <file>debian/changelog</file> file from
9653 the Debian source tree in
9654 <file>/usr/share/doc/<var>package</var></file> with the name
9655 <file>changelog.Debian.gz</file>.
9659 If an upstream changelog is available, it should be accessible as
9660 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9661 plain text. If the upstream changelog is distributed in
9662 HTML, it should be made available in that form as
9663 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9664 and a plain text <file>changelog.gz</file> should be generated
9665 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9666 the upstream changelog files do not already conform to this
9667 naming convention, then this may be achieved either by
9668 renaming the files, or by adding a symbolic link, at the
9669 maintainer's discretion.<footnote>
9670 Rationale: People should not have to look in places for
9671 upstream changelogs merely because they are given
9672 different names or are distributed in HTML format.
9677 All of these files should be installed compressed using
9678 <tt>gzip -9</tt>, as they will become large with time even
9679 if they start out small.
9683 If the package has only one changelog which is used both as
9684 the Debian changelog and the upstream one because there is
9685 no separate upstream maintainer then that changelog should
9686 usually be installed as
9687 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9688 there is a separate upstream maintainer, but no upstream
9689 changelog, then the Debian changelog should still be called
9690 <file>changelog.Debian.gz</file>.
9694 For details about the format and contents of the Debian
9695 changelog file, please see <ref id="dpkgchangelog">.
9700 <appendix id="pkg-scope">
9701 <heading>Introduction and scope of these appendices</heading>
9704 These appendices are taken essentially verbatim from the
9705 now-deprecated Packaging Manual, version 3.2.1.0. They are
9706 the chapters which are likely to be of use to package
9707 maintainers and which have not already been included in the
9708 policy document itself. Most of these sections are very likely
9709 not relevant to policy; they should be treated as
9710 documentation for the packaging system. Please note that these
9711 appendices are included for convenience, and for historical
9712 reasons: they used to be part of policy package, and they have
9713 not yet been incorporated into dpkg documentation. However,
9714 they still have value, and hence they are presented here.
9718 They have not yet been checked to ensure that they are
9719 compatible with the contents of policy, and if there are any
9720 contradictions, the version in the main policy document takes
9721 precedence. The remaining chapters of the old Packaging
9722 Manual have also not been read in detail to ensure that there
9723 are not parts which have been left out. Both of these will be
9728 Certain parts of the Packaging manual were integrated into the
9729 Policy Manual proper, and removed from the appendices. Links
9730 have been placed from the old locations to the new ones.
9734 <prgn>dpkg</prgn> is a suite of programs for creating binary
9735 package files and installing and removing them on Unix
9737 <prgn>dpkg</prgn> is targeted primarily at Debian
9738 GNU/Linux, but may work on or be ported to other
9744 The binary packages are designed for the management of
9745 installed executable programs (usually compiled binaries) and
9746 their associated data, though source code examples and
9747 documentation are provided as part of some packages.</p>
9750 This manual describes the technical aspects of creating Debian
9751 binary packages (<file>.deb</file> files). It documents the
9752 behavior of the package management programs
9753 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9754 they interact with packages.</p>
9757 It also documents the interaction between
9758 <prgn>dselect</prgn>'s core and the access method scripts it
9759 uses to actually install the selected packages, and describes
9760 how to create a new access method.</p>
9763 This manual does not go into detail about the options and
9764 usage of the package building and installation tools. It
9765 should therefore be read in conjunction with those programs'
9770 The utility programs which are provided with <prgn>dpkg</prgn>
9771 for managing various system configuration and similar issues,
9772 such as <prgn>update-rc.d</prgn> and
9773 <prgn>install-info</prgn>, are not described in detail here -
9774 please see their man pages.
9778 It is assumed that the reader is reasonably familiar with the
9779 <prgn>dpkg</prgn> System Administrators' manual.
9780 Unfortunately this manual does not yet exist.
9784 The Debian version of the FSF's GNU hello program is provided
9785 as an example for people wishing to create Debian
9786 packages. The Debian <prgn>debmake</prgn> package is
9787 recommended as a very helpful tool in creating and maintaining
9788 Debian packages. However, while the tools and examples are
9789 helpful, they do not replace the need to read and follow the
9790 Policy and Programmer's Manual.</p>
9793 <appendix id="pkg-binarypkg">
9794 <heading>Binary packages (from old Packaging Manual)</heading>
9797 The binary package has two main sections. The first part
9798 consists of various control information files and scripts used
9799 by <prgn>dpkg</prgn> when installing and removing. See <ref
9800 id="pkg-controlarea">.
9804 The second part is an archive containing the files and
9805 directories to be installed.
9809 In the future binary packages may also contain other
9810 components, such as checksums and digital signatures. The
9811 format for the archive is described in full in the
9812 <file>deb(5)</file> man page.
9816 <sect id="pkg-bincreating"><heading>Creating package files -
9817 <prgn>dpkg-deb</prgn>
9821 All manipulation of binary package files is done by
9822 <prgn>dpkg-deb</prgn>; it's the only program that has
9823 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9824 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9825 will spot that the options requested are appropriate to
9826 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9831 In order to create a binary package you must make a
9832 directory tree which contains all the files and directories
9833 you want to have in the file system data part of the package.
9834 In Debian-format source packages this directory is usually
9835 <file>debian/tmp</file>, relative to the top of the package's
9840 They should have the locations (relative to the root of the
9841 directory tree you're constructing) ownerships and
9842 permissions which you want them to have on the system when
9847 With current versions of <prgn>dpkg</prgn> the uid/username
9848 and gid/groupname mappings for the users and groups being
9849 used should be the same on the system where the package is
9850 built and the one where it is installed.
9854 You need to add one special directory to the root of the
9855 miniature file system tree you're creating:
9856 <prgn>DEBIAN</prgn>. It should contain the control
9857 information files, notably the binary package control file
9858 (see <ref id="pkg-controlfile">).
9862 The <prgn>DEBIAN</prgn> directory will not appear in the
9863 file system archive of the package, and so won't be installed
9864 by <prgn>dpkg</prgn> when the package is installed.
9868 When you've prepared the package, you should invoke:
9870 dpkg --build <var>directory</var>
9875 This will build the package in
9876 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9877 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9878 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9883 See the man page <manref name="dpkg-deb" section="8"> for details of how
9884 to examine the contents of this newly-created file. You may find the
9885 output of following commands enlightening:
9887 dpkg-deb --info <var>filename</var>.deb
9888 dpkg-deb --contents <var>filename</var>.deb
9889 dpkg --contents <var>filename</var>.deb
9891 To view the copyright file for a package you could use this command:
9893 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
9898 <sect id="pkg-controlarea">
9899 <heading>Package control information files</heading>
9902 The control information portion of a binary package is a
9903 collection of files with names known to <prgn>dpkg</prgn>.
9904 It will treat the contents of these files specially - some
9905 of them contain information used by <prgn>dpkg</prgn> when
9906 installing or removing the package; others are scripts which
9907 the package maintainer wants <prgn>dpkg</prgn> to run.
9911 It is possible to put other files in the package control
9912 information file area, but this is not generally a good idea
9913 (though they will largely be ignored).
9917 Here is a brief list of the control information files supported
9918 by <prgn>dpkg</prgn> and a summary of what they're used for.
9923 <tag><tt>control</tt>
9926 This is the key description file used by
9927 <prgn>dpkg</prgn>. It specifies the package's name
9928 and version, gives its description for the user,
9929 states its relationships with other packages, and so
9930 forth. See <ref id="sourcecontrolfiles"> and
9931 <ref id="binarycontrolfiles">.
9935 It is usually generated automatically from information
9936 in the source package by the
9937 <prgn>dpkg-gencontrol</prgn> program, and with
9938 assistance from <prgn>dpkg-shlibdeps</prgn>.
9939 See <ref id="pkg-sourcetools">.
9943 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9948 These are executable files (usually scripts) which
9949 <prgn>dpkg</prgn> runs during installation, upgrade
9950 and removal of packages. They allow the package to
9951 deal with matters which are particular to that package
9952 or require more complicated processing than that
9953 provided by <prgn>dpkg</prgn>. Details of when and
9954 how they are called are in <ref id="maintainerscripts">.
9958 It is very important to make these scripts idempotent.
9959 See <ref id="idempotency">.
9963 The maintainer scripts are not guaranteed to run with a
9964 controlling terminal and may not be able to interact with
9965 the user. See <ref id="controllingterminal">.
9969 <tag><tt>conffiles</tt>
9972 This file contains a list of configuration files which
9973 are to be handled automatically by <prgn>dpkg</prgn>
9974 (see <ref id="pkg-conffiles">). Note that not necessarily
9975 every configuration file should be listed here.
9978 <tag><tt>shlibs</tt>
9981 This file contains a list of the shared libraries
9982 supplied by the package, with dependency details for
9983 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9984 when it determines what dependencies are required in a
9985 package control file. The <tt>shlibs</tt> file format
9986 is described on <ref id="shlibs">.
9991 <sect id="pkg-controlfile">
9992 <heading>The main control information file: <tt>control</tt></heading>
9995 The most important control information file used by
9996 <prgn>dpkg</prgn> when it installs a package is
9997 <tt>control</tt>. It contains all the package's "vital
10002 The binary package control files of packages built from
10003 Debian sources are made by a special tool,
10004 <prgn>dpkg-gencontrol</prgn>, which reads
10005 <file>debian/control</file> and <file>debian/changelog</file> to
10006 find the information it needs. See <ref id="pkg-sourcepkg"> for
10011 The fields in binary package control files are listed in
10012 <ref id="binarycontrolfiles">.
10016 A description of the syntax of control files and the purpose
10017 of the fields is available in <ref id="controlfields">.
10022 <heading>Time Stamps</heading>
10025 See <ref id="timestamps">.
10030 <appendix id="pkg-sourcepkg">
10031 <heading>Source packages (from old Packaging Manual) </heading>
10034 The Debian binary packages in the distribution are generated
10035 from Debian sources, which are in a special format to assist
10036 the easy and automatic building of binaries.
10039 <sect id="pkg-sourcetools">
10040 <heading>Tools for processing source packages</heading>
10043 Various tools are provided for manipulating source packages;
10044 they pack and unpack sources and help build of binary
10045 packages and help manage the distribution of new versions.
10049 They are introduced and typical uses described here; see
10050 <manref name="dpkg-source" section="1"> for full
10051 documentation about their arguments and operation.
10055 For examples of how to construct a Debian source package,
10056 and how to use those utilities that are used by Debian
10057 source packages, please see the <prgn>hello</prgn> example
10061 <sect1 id="pkg-dpkg-source">
10063 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
10068 This program is frequently used by hand, and is also
10069 called from package-independent automated building scripts
10070 such as <prgn>dpkg-buildpackage</prgn>.
10074 To unpack a package it is typically invoked with
10076 dpkg-source -x <var>.../path/to/filename</var>.dsc
10081 with the <file><var>filename</var>.tar.gz</file> and
10082 <file><var>filename</var>.diff.gz</file> (if applicable) in
10083 the same directory. It unpacks into
10084 <file><var>package</var>-<var>version</var></file>, and if
10086 <file><var>package</var>-<var>version</var>.orig</file>, in
10087 the current directory.
10091 To create a packed source archive it is typically invoked:
10093 dpkg-source -b <var>package</var>-<var>version</var>
10098 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
10099 <file>.diff.gz</file> (if appropriate) in the current
10100 directory. <prgn>dpkg-source</prgn> does not clean the
10101 source tree first - this must be done separately if it is
10106 See also <ref id="pkg-sourcearchives">.</p>
10110 <sect1 id="pkg-dpkg-buildpackage">
10112 <prgn>dpkg-buildpackage</prgn> - overall package-building
10117 <prgn>dpkg-buildpackage</prgn> is a script which invokes
10118 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
10119 targets <tt>clean</tt>, <tt>build</tt> and
10120 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
10121 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
10122 source and binary package upload.
10126 It is usually invoked by hand from the top level of the
10127 built or unbuilt source directory. It may be invoked with
10128 no arguments; useful arguments include:
10129 <taglist compact="compact">
10130 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
10133 Do not sign the <tt>.changes</tt> file or the
10134 source package <tt>.dsc</tt> file, respectively.</p>
10136 <tag><tt>-p<var>sign-command</var></tt></tag>
10139 Invoke <var>sign-command</var> instead of finding
10140 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
10141 <var>sign-command</var> must behave just like
10142 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
10144 <tag><tt>-r<var>root-command</var></tt></tag>
10147 When root privilege is required, invoke the command
10148 <var>root-command</var>. <var>root-command</var>
10149 should invoke its first argument as a command, from
10150 the <prgn>PATH</prgn> if necessary, and pass its
10151 second and subsequent arguments to the command it
10152 calls. If no <var>root-command</var> is supplied
10153 then <var>dpkg-buildpackage</var> will take no
10154 special action to gain root privilege, so that for
10155 most packages it will have to be invoked as root to
10158 <tag><tt>-b</tt>, <tt>-B</tt></tag>
10161 Two types of binary-only build and upload - see
10162 <manref name="dpkg-source" section="1">.
10169 <sect1 id="pkg-dpkg-gencontrol">
10171 <prgn>dpkg-gencontrol</prgn> - generates binary package
10176 This program is usually called from <file>debian/rules</file>
10177 (see <ref id="pkg-sourcetree">) in the top level of the source
10182 This is usually done just before the files and directories in the
10183 temporary directory tree where the package is being built have their
10184 permissions and ownerships set and the package is constructed using
10185 <prgn>dpkg-deb/</prgn>
10187 This is so that the control file which is produced has
10188 the right permissions
10193 <prgn>dpkg-gencontrol</prgn> must be called after all the
10194 files which are to go into the package have been placed in
10195 the temporary build directory, so that its calculation of
10196 the installed size of a package is correct.
10200 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
10201 be run after <prgn>dpkg-shlibdeps</prgn> so that the
10202 variable substitutions created by
10203 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
10208 For a package which generates only one binary package, and
10209 which builds it in <file>debian/tmp</file> relative to the top
10210 of the source package, it is usually sufficient to call
10211 <prgn>dpkg-gencontrol</prgn>.
10215 Sources which build several binaries will typically need
10218 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
10219 </example> The <tt>-P</tt> tells
10220 <prgn>dpkg-gencontrol</prgn> that the package is being
10221 built in a non-default directory, and the <tt>-p</tt>
10222 tells it which package's control file should be generated.
10226 <prgn>dpkg-gencontrol</prgn> also adds information to the
10227 list of files in <file>debian/files</file>, for the benefit of
10228 (for example) a future invocation of
10229 <prgn>dpkg-genchanges</prgn>.</p>
10232 <sect1 id="pkg-dpkg-shlibdeps">
10234 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
10239 This program is usually called from <file>debian/rules</file>
10240 just before <prgn>dpkg-gencontrol</prgn> (see <ref
10241 id="pkg-sourcetree">), in the top level of the source tree.
10245 Its arguments are executables and shared libraries
10248 They may be specified either in the locations in the
10249 source tree where they are created or in the locations
10250 in the temporary build tree where they are installed
10251 prior to binary package creation.
10253 </footnote> for which shared library dependencies should
10254 be included in the binary package's control file.
10258 If some of the found shared libraries should only
10259 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
10260 some warrant a <tt>Pre-Depends</tt>, this can be achieved
10261 by using the <tt>-d<var>dependency-field</var></tt> option
10262 before those executable(s). (Each <tt>-d</tt> option
10263 takes effect until the next <tt>-d</tt>.)
10267 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
10268 output control file to be modified. Instead by default it
10269 adds to the <file>debian/substvars</file> file variable
10270 settings like <tt>shlibs:Depends</tt>. These variable
10271 settings must be referenced in dependency fields in the
10272 appropriate per-binary-package sections of the source
10277 For example, a package that generates an essential part
10278 which requires dependencies, and optional parts that
10279 which only require a recommendation, would separate those
10280 two sets of dependencies into two different fields.<footnote>
10281 At the time of writing, an example for this was the
10282 <package/xmms/ package, with Depends used for the xmms
10283 executable, Recommends for the plug-ins and Suggests for
10284 even more optional features provided by unzip.
10286 It can say in its <file>debian/rules</file>:
10288 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
10289 -dRecommends <var>optionalpart anotheroptionalpart</var>
10291 and then in its main control file <file>debian/control</file>:
10294 Depends: ${shlibs:Depends}
10295 Recommends: ${shlibs:Recommends}
10301 Sources which produce several binary packages with
10302 different shared library dependency requirements can use
10303 the <tt>-p<var>varnameprefix</var></tt> option to override
10304 the default <tt>shlibs:</tt> prefix (one invocation of
10305 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
10306 They can thus produce several sets of dependency
10307 variables, each of the form
10308 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
10309 which can be referred to in the appropriate parts of the
10310 binary package control files.
10315 <sect1 id="pkg-dpkg-distaddfile">
10317 <prgn>dpkg-distaddfile</prgn> - adds a file to
10318 <file>debian/files</file>
10322 Some packages' uploads need to include files other than
10323 the source and binary package files.
10327 <prgn>dpkg-distaddfile</prgn> adds a file to the
10328 <file>debian/files</file> file so that it will be included in
10329 the <file>.changes</file> file when
10330 <prgn>dpkg-genchanges</prgn> is run.
10334 It is usually invoked from the <tt>binary</tt> target of
10335 <file>debian/rules</file>:
10337 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
10339 The <var>filename</var> is relative to the directory where
10340 <prgn>dpkg-genchanges</prgn> will expect to find it - this
10341 is usually the directory above the top level of the source
10342 tree. The <file>debian/rules</file> target should put the
10343 file there just before or just after calling
10344 <prgn>dpkg-distaddfile</prgn>.
10348 The <var>section</var> and <var>priority</var> are passed
10349 unchanged into the resulting <file>.changes</file> file.
10354 <sect1 id="pkg-dpkg-genchanges">
10356 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
10357 upload control file
10361 This program is usually called by package-independent
10362 automatic building scripts such as
10363 <prgn>dpkg-buildpackage</prgn>, but it may also be called
10368 It is usually called in the top level of a built source
10369 tree, and when invoked with no arguments will print out a
10370 straightforward <file>.changes</file> file based on the
10371 information in the source package's changelog and control
10372 file and the binary and source packages which should have
10378 <sect1 id="pkg-dpkg-parsechangelog">
10380 <prgn>dpkg-parsechangelog</prgn> - produces parsed
10381 representation of a changelog
10385 This program is used internally by
10386 <prgn>dpkg-source</prgn> et al. It may also occasionally
10387 be useful in <file>debian/rules</file> and elsewhere. It
10388 parses a changelog, <file>debian/changelog</file> by default,
10389 and prints a control-file format representation of the
10390 information in it to standard output.
10394 <sect1 id="pkg-dpkg-architecture">
10396 <prgn>dpkg-architecture</prgn> - information about the build and
10401 This program can be used manually, but is also invoked by
10402 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
10403 environment or make variables which specify the build and host
10404 architecture for the package building process.
10409 <sect id="pkg-sourcetree">
10410 <heading>The Debian package source tree</heading>
10413 The source archive scheme described later is intended to
10414 allow a Debian package source tree with some associated
10415 control information to be reproduced and transported easily.
10416 The Debian package source tree is a version of the original
10417 program with certain files added for the benefit of the
10418 packaging process, and with any other changes required
10419 made to the rest of the source code and installation
10424 The extra files created for Debian are in the subdirectory
10425 <file>debian</file> of the top level of the Debian package
10426 source tree. They are described below.
10429 <sect1 id="pkg-debianrules">
10430 <heading><file>debian/rules</file> - the main building script</heading>
10433 See <ref id="debianrules">.
10437 <sect1 id="pkg-srcsubstvars">
10438 <heading><file>debian/substvars</file> and variable substitutions</heading>
10441 See <ref id="substvars">.
10447 <heading><file>debian/files</file></heading>
10450 See <ref id="debianfiles">.
10454 <sect1><heading><file>debian/tmp</file>
10458 This is the canonical temporary location for the
10459 construction of binary packages by the <tt>binary</tt>
10460 target. The directory <file>tmp</file> serves as the root of
10461 the file system tree as it is being constructed (for
10462 example, by using the package's upstream makefiles install
10463 targets and redirecting the output there), and it also
10464 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10465 id="pkg-bincreating">.
10469 If several binary packages are generated from the same
10470 source tree it is usual to use several
10471 <file>debian/tmp<var>something</var></file> directories, for
10472 example <file>tmp-a</file> or <file>tmp-doc</file>.
10476 Whatever <file>tmp</file> directories are created and used by
10477 <tt>binary</tt> must of course be removed by the
10478 <tt>clean</tt> target.</p></sect1>
10482 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10486 As it exists on the FTP site, a Debian source package
10487 consists of three related files. You must have the right
10488 versions of all three to be able to use them.
10493 <tag>Debian source control file - <tt>.dsc</tt></tag>
10495 This file is a control file used by <prgn>dpkg-source</prgn>
10496 to extract a source package.
10497 See <ref id="debiansourcecontrolfiles">.
10501 Original source archive -
10503 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10509 This is a compressed (with <tt>gzip -9</tt>)
10510 <prgn>tar</prgn> file containing the source code from
10511 the upstream authors of the program.
10516 Debian package diff -
10518 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10524 This is a unified context diff (<tt>diff -u</tt>)
10525 giving the changes which are required to turn the
10526 original source into the Debian source. These changes
10527 may only include editing and creating plain files.
10528 The permissions of files, the targets of symbolic
10529 links and the characteristics of special files or
10530 pipes may not be changed and no files may be removed
10535 All the directories in the diff must exist, except the
10536 <file>debian</file> subdirectory of the top of the source
10537 tree, which will be created by
10538 <prgn>dpkg-source</prgn> if necessary when unpacking.
10542 The <prgn>dpkg-source</prgn> program will
10543 automatically make the <file>debian/rules</file> file
10544 executable (see below).</p></item>
10549 If there is no original source code - for example, if the
10550 package is specially prepared for Debian or the Debian
10551 maintainer is the same as the upstream maintainer - the
10552 format is slightly different: then there is no diff, and the
10554 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10555 and preferably contains a directory named
10556 <file><var>package</var>-<var>version</var></file>.
10561 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10564 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10565 Debian source package. However, if it is not available it
10566 is possible to unpack a Debian source archive as follows:
10567 <enumlist compact="compact">
10570 Untar the tarfile, which will create a <file>.orig</file>
10574 <p>Rename the <file>.orig</file> directory to
10575 <file><var>package</var>-<var>version</var></file>.</p>
10579 Create the subdirectory <file>debian</file> at the top of
10580 the source tree.</p>
10582 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10584 <item><p>Untar the tarfile again if you want a copy of the original
10585 source code alongside the Debian version.</p>
10590 It is not possible to generate a valid Debian source archive
10591 without using <prgn>dpkg-source</prgn>. In particular,
10592 attempting to use <prgn>diff</prgn> directly to generate the
10593 <file>.diff.gz</file> file will not work.
10597 <heading>Restrictions on objects in source packages</heading>
10600 The source package may not contain any hard links
10602 This is not currently detected when building source
10603 packages, but only when extracting
10607 Hard links may be permitted at some point in the
10608 future, but would require a fair amount of
10610 </footnote>, device special files, sockets or setuid or
10613 Setgid directories are allowed.
10618 The source packaging tools manage the changes between the
10619 original and Debian source using <prgn>diff</prgn> and
10620 <prgn>patch</prgn>. Turning the original source tree as
10621 included in the <file>.orig.tar.gz</file> into the Debian
10622 package source must not involve any changes which cannot be
10623 handled by these tools. Problematic changes which cause
10624 <prgn>dpkg-source</prgn> to halt with an error when
10625 building the source package are:
10626 <list compact="compact">
10627 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10629 <item><p>Changing the targets of symbolic links.</p>
10631 <item><p>Creating directories, other than <file>debian</file>.</p>
10633 <item><p>Changes to the contents of binary files.</p></item>
10634 </list> Changes which cause <prgn>dpkg-source</prgn> to
10635 print a warning but continue anyway are:
10636 <list compact="compact">
10639 Removing files, directories or symlinks.
10641 Renaming a file is not treated specially - it is
10642 seen as the removal of the old file (which
10643 generates a warning, but is otherwise ignored),
10644 and the creation of the new one.
10650 Changed text files which are missing the usual final
10651 newline (either in the original or the modified
10656 Changes which are not represented, but which are not detected by
10657 <prgn>dpkg-source</prgn>, are:
10658 <list compact="compact">
10659 <item><p>Changing the permissions of files (other than
10660 <file>debian/rules</file>) and directories.</p></item>
10665 The <file>debian</file> directory and <file>debian/rules</file>
10666 are handled specially by <prgn>dpkg-source</prgn> - before
10667 applying the changes it will create the <file>debian</file>
10668 directory, and afterwards it will make
10669 <file>debian/rules</file> world-executable.
10675 <appendix id="pkg-controlfields">
10676 <heading>Control files and their fields (from old Packaging Manual)</heading>
10679 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10680 data in a common format, known as control files. Binary and
10681 source packages have control data as do the <file>.changes</file>
10682 files which control the installation of uploaded files, and
10683 <prgn>dpkg</prgn>'s internal databases are in a similar
10688 <heading>Syntax of control files</heading>
10691 See <ref id="controlsyntax">.
10695 It is important to note that there are several fields which
10696 are optional as far as <prgn>dpkg</prgn> and the related
10697 tools are concerned, but which must appear in every Debian
10698 package, or whose omission may cause problems.
10703 <heading>List of fields</heading>
10706 See <ref id="controlfieldslist">.
10710 This section now contains only the fields that didn't belong
10711 to the Policy manual.
10714 <sect1 id="pkg-f-Filename">
10715 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10718 These fields in <tt>Packages</tt> files give the
10719 filename(s) of (the parts of) a package in the
10720 distribution directories, relative to the root of the
10721 Debian hierarchy. If the package has been split into
10722 several parts the parts are all listed in order, separated
10727 <sect1 id="pkg-f-Size">
10728 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10731 These fields in <file>Packages</file> files give the size (in
10732 bytes, expressed in decimal) and MD5 checksum of the
10733 file(s) which make(s) up a binary package in the
10734 distribution. If the package is split into several parts
10735 the values for the parts are listed in order, separated by
10740 <sect1 id="pkg-f-Status">
10741 <heading><tt>Status</tt></heading>
10744 This field in <prgn>dpkg</prgn>'s status file records
10745 whether the user wants a package installed, removed or
10746 left alone, whether it is broken (requiring
10747 re-installation) or not and what its current state on the
10748 system is. Each of these pieces of information is a
10753 <sect1 id="pkg-f-Config-Version">
10754 <heading><tt>Config-Version</tt></heading>
10757 If a package is not installed or not configured, this
10758 field in <prgn>dpkg</prgn>'s status file records the last
10759 version of the package which was successfully
10764 <sect1 id="pkg-f-Conffiles">
10765 <heading><tt>Conffiles</tt></heading>
10768 This field in <prgn>dpkg</prgn>'s status file contains
10769 information about the automatically-managed configuration
10770 files held by a package. This field should <em>not</em>
10771 appear anywhere in a package!
10776 <heading>Obsolete fields</heading>
10779 These are still recognized by <prgn>dpkg</prgn> but should
10780 not appear anywhere any more.
10782 <taglist compact="compact">
10784 <tag><tt>Revision</tt></tag>
10785 <tag><tt>Package-Revision</tt></tag>
10786 <tag><tt>Package_Revision</tt></tag>
10788 The Debian revision part of the package version was
10789 at one point in a separate control field. This
10790 field went through several names.
10793 <tag><tt>Recommended</tt></tag>
10794 <item>Old name for <tt>Recommends</tt>.</item>
10796 <tag><tt>Optional</tt></tag>
10797 <item>Old name for <tt>Suggests</tt>.</item>
10799 <tag><tt>Class</tt></tag>
10800 <item>Old name for <tt>Priority</tt>.</item>
10809 <appendix id="pkg-conffiles">
10810 <heading>Configuration file handling (from old Packaging Manual)</heading>
10813 <prgn>dpkg</prgn> can do a certain amount of automatic
10814 handling of package configuration files.
10818 Whether this mechanism is appropriate depends on a number of
10819 factors, but basically there are two approaches to any
10820 particular configuration file.
10824 The easy method is to ship a best-effort configuration in the
10825 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10826 handle updates. If the user is unlikely to want to edit the
10827 file, but you need them to be able to without losing their
10828 changes, and a new package with a changed version of the file
10829 is only released infrequently, this is a good approach.
10833 The hard method is to build the configuration file from
10834 scratch in the <prgn>postinst</prgn> script, and to take the
10835 responsibility for fixing any mistakes made in earlier
10836 versions of the package automatically. This will be
10837 appropriate if the file is likely to need to be different on
10841 <sect><heading>Automatic handling of configuration files by
10846 A package may contain a control information file called
10847 <tt>conffiles</tt>. This file should be a list of filenames
10848 of configuration files needing automatic handling, separated
10849 by newlines. The filenames should be absolute pathnames,
10850 and the files referred to should actually exist in the
10855 When a package is upgraded <prgn>dpkg</prgn> will process
10856 the configuration files during the configuration stage,
10857 shortly before it runs the package's <prgn>postinst</prgn>
10862 For each file it checks to see whether the version of the
10863 file included in the package is the same as the one that was
10864 included in the last version of the package (the one that is
10865 being upgraded from); it also compares the version currently
10866 installed on the system with the one shipped with the last
10871 If neither the user nor the package maintainer has changed
10872 the file, it is left alone. If one or the other has changed
10873 their version, then the changed version is preferred - i.e.,
10874 if the user edits their file, but the package maintainer
10875 doesn't ship a different version, the user's changes will
10876 stay, silently, but if the maintainer ships a new version
10877 and the user hasn't edited it the new version will be
10878 installed (with an informative message). If both have
10879 changed their version the user is prompted about the problem
10880 and must resolve the differences themselves.
10884 The comparisons are done by calculating the MD5 message
10885 digests of the files, and storing the MD5 of the file as it
10886 was included in the most recent version of the package.
10890 When a package is installed for the first time
10891 <prgn>dpkg</prgn> will install the file that comes with it,
10892 unless that would mean overwriting a file already on the
10897 However, note that <prgn>dpkg</prgn> will <em>not</em>
10898 replace a conffile that was removed by the user (or by a
10899 script). This is necessary because with some programs a
10900 missing file produces an effect hard or impossible to
10901 achieve in another way, so that a missing file needs to be
10902 kept that way if the user did it.
10906 Note that a package should <em>not</em> modify a
10907 <prgn>dpkg</prgn>-handled conffile in its maintainer
10908 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10909 the user confusing and possibly dangerous options for
10910 conffile update when the package is upgraded.</p>
10913 <sect><heading>Fully-featured maintainer script configuration
10918 For files which contain site-specific information such as
10919 the hostname and networking details and so forth, it is
10920 better to create the file in the package's
10921 <prgn>postinst</prgn> script.
10925 This will typically involve examining the state of the rest
10926 of the system to determine values and other information, and
10927 may involve prompting the user for some information which
10928 can't be obtained some other way.
10932 When using this method there are a couple of important
10933 issues which should be considered:
10937 If you discover a bug in the program which generates the
10938 configuration file, or if the format of the file changes
10939 from one version to the next, you will have to arrange for
10940 the postinst script to do something sensible - usually this
10941 will mean editing the installed configuration file to remove
10942 the problem or change the syntax. You will have to do this
10943 very carefully, since the user may have changed the file,
10944 perhaps to fix the very problem that your script is trying
10945 to deal with - you will have to detect these situations and
10946 deal with them correctly.
10950 If you do go down this route it's probably a good idea to
10951 make the program that generates the configuration file(s) a
10952 separate program in <file>/usr/sbin</file>, by convention called
10953 <file><var>package</var>config</file> and then run that if
10954 appropriate from the post-installation script. The
10955 <tt><var>package</var>config</tt> program should not
10956 unquestioningly overwrite an existing configuration - if its
10957 mode of operation is geared towards setting up a package for
10958 the first time (rather than any arbitrary reconfiguration
10959 later) you should have it check whether the configuration
10960 already exists, and require a <tt>--force</tt> flag to
10961 overwrite it.</p></sect>
10964 <appendix id="pkg-alternatives"><heading>Alternative versions of
10965 an interface - <prgn>update-alternatives</prgn> (from old
10970 When several packages all provide different versions of the
10971 same program or file it is useful to have the system select a
10972 default, but to allow the system administrator to change it
10973 and have their decisions respected.
10977 For example, there are several versions of the <prgn>vi</prgn>
10978 editor, and there is no reason to prevent all of them from
10979 being installed at once, each under their own name
10980 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10981 Nevertheless it is desirable to have the name <tt>vi</tt>
10982 refer to something, at least by default.
10986 If all the packages involved cooperate, this can be done with
10987 <prgn>update-alternatives</prgn>.
10991 Each package provides its own version under its own name, and
10992 calls <prgn>update-alternatives</prgn> in its postinst to
10993 register its version (and again in its prerm to deregister
10998 See the man page <manref name="update-alternatives"
10999 section="8"> for details.
11003 If <prgn>update-alternatives</prgn> does not seem appropriate
11004 you may wish to consider using diversions instead.</p>
11007 <appendix id="pkg-diversions"><heading>Diversions - overriding a
11008 package's version of a file (from old Packaging Manual)
11012 It is possible to have <prgn>dpkg</prgn> not overwrite a file
11013 when it reinstalls the package it belongs to, and to have it
11014 put the file from the package somewhere else instead.
11018 This can be used locally to override a package's version of a
11019 file, or by one package to override another's version (or
11020 provide a wrapper for it).
11024 Before deciding to use a diversion, read <ref
11025 id="pkg-alternatives"> to see if you really want a diversion
11026 rather than several alternative versions of a program.
11030 There is a diversion list, which is read by <prgn>dpkg</prgn>,
11031 and updated by a special program <prgn>dpkg-divert</prgn>.
11032 Please see <manref name="dpkg-divert" section="8"> for full
11033 details of its operation.
11037 When a package wishes to divert a file from another, it should
11038 call <prgn>dpkg-divert</prgn> in its preinst to add the
11039 diversion and rename the existing file. For example,
11040 supposing that a <prgn>smailwrapper</prgn> package wishes to
11041 install a wrapper around <file>/usr/sbin/smail</file>:
11043 dpkg-divert --package smailwrapper --add --rename \
11044 --divert /usr/sbin/smail.real /usr/sbin/smail
11045 </example> The <tt>--package smailwrapper</tt> ensures that
11046 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
11047 can bypass the diversion and get installed as the true version.
11048 It's safe to add the diversion unconditionally on upgrades since
11049 it will be left unchanged if it already exists, but
11050 <prgn>dpkg-divert</prgn> will display a message. To suppress that
11051 message, make the command conditional on the version from which
11052 the package is being upgraded:
11054 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
11055 dpkg-divert --package smailwrapper --add --rename \
11056 --divert /usr/sbin/smail.real /usr/sbin/smail
11058 </example> where <tt>1.0-2</tt> is the version at which the
11059 diversion was first added to the package. Running the command
11060 during abort-upgrade is pointless but harmless.
11064 The postrm has to do the reverse:
11066 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
11067 dpkg-divert --package smailwrapper --remove --rename \
11068 --divert /usr/sbin/smail.real /usr/sbin/smail
11070 </example> If the diversion was added at a particular version, the
11071 postrm should also handle the failure case of upgrading from an
11072 older version (unless the older version is so old that direct
11073 upgrades are no longer supported):
11075 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
11076 dpkg-divert --package smailwrapper --remove --rename \
11077 --divert /usr/sbin/smail.real /usr/sbin/smail
11079 </example> where <tt>1.02-2</tt> is the version at which the
11080 diversion was first added to the package. The postrm should not
11081 remove the diversion on upgrades both because there's no reason to
11082 remove the diversion only to immediately re-add it and since the
11083 postrm of the old package is run after unpacking so the removal of
11084 the diversion will fail.
11088 Do not attempt to divert a file which is vitally important for
11089 the system's operation - when using <prgn>dpkg-divert</prgn>
11090 there is a time, after it has been diverted but before
11091 <prgn>dpkg</prgn> has installed the new version, when the file
11092 does not exist.</p>
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