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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 <heading>The package name</heading>
809 Every package must have a name that's unique within the Debian
814 The package name is included in the control field
815 <tt>Package</tt>, the format of which is described
816 in <ref id="f-Package">.
817 The package name is also included as a part of the file name
818 of the <tt>.deb</tt> file.
823 <heading>The version of a package</heading>
826 Every package has a version number recorded in its
827 <tt>Version</tt> control file field, described in
828 <ref id="f-Version">.
832 The package management system imposes an ordering on version
833 numbers, so that it can tell whether packages are being up- or
834 downgraded and so that package system front end applications
835 can tell whether a package it finds available is newer than
836 the one installed on the system. The version number format
837 has the most significant parts (as far as comparison is
838 concerned) at the beginning.
842 If an upstream package has problematic version numbers they
843 should be converted to a sane form for use in the
844 <tt>Version</tt> field.
848 <heading>Version numbers based on dates</heading>
851 In general, Debian packages should use the same version
852 numbers as the upstream sources. However, upstream version
853 numbers based on some date formats (sometimes used for
854 development or "snapshot" releases) will not be ordered
855 correctly by the package management software. For
856 example, <prgn>dpkg</prgn> will consider "96May01" to be
857 greater than "96Dec24".
861 To prevent having to use epochs for every new upstream
862 version, the date-based portion of any upstream version number
863 should be given in a way that sorts correctly: four-digit year
864 first, followed by a two-digit numeric month, followed by a
865 two-digit numeric date, possibly with punctuation between the
870 Native Debian packages (i.e., packages which have been written
871 especially for Debian) whose version numbers include dates
872 should also follow these rules. If punctuation is desired
873 between the date components, remember that hyphen (<tt>-</tt>)
874 cannot be used in native package versions. Period
875 (<tt>.</tt>) is normally a good choice.
881 <sect id="maintainer">
882 <heading>The maintainer of a package</heading>
885 Every package must have a maintainer. The maintainer may be one
886 person or a group of people reachable from a common email
887 address, such as a mailing list. The maintainer is responsible
888 for maintaining the Debian packaging files, evaluating and
889 responding appropriately to reported bugs, uploading new
890 versions of the package (either directly or through a sponsor),
891 ensuring that the package is placed in the appropriate archive
892 area and included in Debian releases as appropriate for the
893 stability and utility of the package, and requesting removal of
894 the package from the Debian distribution if it is no longer
895 useful or maintainable.
899 The maintainer must be specified in the <tt>Maintainer</tt>
900 control field with their correct name and a working email
901 address. The email address given in the <tt>Maintainer</tt>
902 control field must accept mail from those role accounts in
903 Debian used to send automated mails regarding the package. This
904 includes non-spam mail from the bug-tracking system, all mail
905 from the Debian archive maintenance software, and other role
906 accounts or automated processes that are commonly agreed on by
907 the project.<footnote>
908 A sample implementation of such a whitelist written for the
909 Mailman mailing list management software is used for mailing
910 lists hosted by alioth.debian.org.
912 If one person or team maintains several packages, they should
913 use the same form of their name and email address in
914 the <tt>Maintainer</tt> fields of those packages.
918 The format of the <tt>Maintainer</tt> control field is
919 described in <ref id="f-Maintainer">.
923 If the maintainer of the package is a team of people with a
924 shared email address, the <tt>Uploaders</tt> control field must
925 be present and must contain at least one human with their
926 personal email address. See <ref id="f-Uploaders"> for the
927 syntax of that field.
931 If the maintainer of a package no longer has time or desire to
932 maintain a package, it will be orphaned according to the
933 procedure described in the Debian Developer's Reference
934 (see <ref id="related">). The maintainer then
935 becomes <tt>Debian QA Group <packages@qa.debian.org></tt>.
936 These packages are considered maintained by the Debian project
937 as a whole until someone else volunteers to take over
942 <sect id="descriptions">
943 <heading>The description of a package</heading>
946 Every Debian package must have an extended description
947 stored in the appropriate field of the control record.
948 The technical information about the format of the
949 <tt>Description</tt> field is in <ref id="f-Description">.
953 The description should describe the package (the program) to a
954 user (system administrator) who has never met it before so that
955 they have enough information to decide whether they want to
956 install it. This description should not just be copied verbatim
957 from the program's documentation.
961 Put important information first, both in the synopsis and
962 extended description. Sometimes only the first part of the
963 synopsis or of the description will be displayed. You can
964 assume that there will usually be a way to see the whole
965 extended description.
969 The description should also give information about the
970 significant dependencies and conflicts between this package
971 and others, so that the user knows why these dependencies and
972 conflicts have been declared.
976 Instructions for configuring or using the package should
977 not be included (that is what installation scripts,
978 manual pages, info files, etc., are for). Copyright
979 statements and other administrivia should not be included
980 either (that is what the copyright file is for).
983 <sect1 id="synopsis"><heading>The single line synopsis</heading>
986 The single line synopsis should be kept brief - certainly
991 Do not include the package name in the synopsis line. The
992 display software knows how to display this already, and you
993 do not need to state it. Remember that in many situations
994 the user may only see the synopsis line - make it as
995 informative as you can.
1000 <sect1 id="extendeddesc"><heading>The extended description</heading>
1003 Do not try to continue the single line synopsis into the
1004 extended description. This will not work correctly when
1005 the full description is displayed, and makes no sense
1006 where only the summary (the single line synopsis) is
1011 The extended description should describe what the package
1012 does and how it relates to the rest of the system (in terms
1013 of, for example, which subsystem it is which part of).
1017 The description field needs to make sense to anyone, even
1018 people who have no idea about any of the things the
1019 package deals with.<footnote>
1020 The blurb that comes with a program in its
1021 announcements and/or <prgn>README</prgn> files is
1022 rarely suitable for use in a description. It is
1023 usually aimed at people who are already in the
1024 community where the package is used.
1033 <heading>Dependencies</heading>
1036 Every package must specify the dependency information
1037 about other packages that are required for the first to
1042 For example, a dependency entry must be provided for any
1043 shared libraries required by a dynamically-linked executable
1044 binary in a package.
1048 Packages are not required to declare any dependencies they
1049 have on other packages which are marked <tt>Essential</tt>
1050 (see below), and should not do so unless they depend on a
1051 particular version of that package.<footnote>
1053 Essential is needed in part to avoid unresolvable dependency
1054 loops on upgrade. If packages add unnecessary dependencies
1055 on packages in this set, the chances that there
1056 <strong>will</strong> be an unresolvable dependency loop
1057 caused by forcing these Essential packages to be configured
1058 first before they need to be is greatly increased. It also
1059 increases the chances that frontends will be unable to
1060 <strong>calculate</strong> an upgrade path, even if one
1064 Also, functionality is rarely ever removed from the
1065 Essential set, but <em>packages</em> have been removed from
1066 the Essential set when the functionality moved to a
1067 different package. So depending on these packages <em>just
1068 in case</em> they stop being essential does way more harm
1075 Sometimes, a package requires another package to be installed
1076 <em>and</em> configured before it can be installed. In this
1077 case, you must specify a <tt>Pre-Depends</tt> entry for
1082 You should not specify a <tt>Pre-Depends</tt> entry for a
1083 package before this has been discussed on the
1084 <tt>debian-devel</tt> mailing list and a consensus about
1085 doing that has been reached.
1089 The format of the package interrelationship control fields is
1090 described in <ref id="relationships">.
1094 <sect id="virtual_pkg">
1095 <heading>Virtual packages</heading>
1098 Sometimes, there are several packages which offer
1099 more-or-less the same functionality. In this case, it's
1100 useful to define a <em>virtual package</em> whose name
1101 describes that common functionality. (The virtual
1102 packages only exist logically, not physically; that's why
1103 they are called <em>virtual</em>.) The packages with this
1104 particular function will then <em>provide</em> the virtual
1105 package. Thus, any other package requiring that function
1106 can simply depend on the virtual package without having to
1107 specify all possible packages individually.
1111 All packages should use virtual package names where
1112 appropriate, and arrange to create new ones if necessary.
1113 They should not use virtual package names (except privately,
1114 amongst a cooperating group of packages) unless they have
1115 been agreed upon and appear in the list of virtual package
1116 names. (See also <ref id="virtual">)
1120 The latest version of the authoritative list of virtual
1121 package names can be found in the <tt>debian-policy</tt> package.
1122 It is also available from the Debian web mirrors at
1123 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1124 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1128 The procedure for updating the list is described in the preface
1135 <heading>Base system</heading>
1138 The <tt>base system</tt> is a minimum subset of the Debian
1139 GNU/Linux system that is installed before everything else
1140 on a new system. Only very few packages are allowed to form
1141 part of the base system, in order to keep the required disk
1146 The base system consists of all those packages with priority
1147 <tt>required</tt> or <tt>important</tt>. Many of them will
1148 be tagged <tt>essential</tt> (see below).
1153 <heading>Essential packages</heading>
1156 Essential is defined as the minimal set of functionality that
1157 must be available and usable on the system at all times, even
1158 when packages are in an unconfigured (but unpacked) state.
1159 Packages are tagged <tt>essential</tt> for a system using the
1160 <tt>Essential</tt> control file field. The format of the
1161 <tt>Essential</tt> control field is described in <ref
1166 Since these packages cannot be easily removed (one has to
1167 specify an extra <em>force option</em> to
1168 <prgn>dpkg</prgn> to do so), this flag must not be used
1169 unless absolutely necessary. A shared library package
1170 must not be tagged <tt>essential</tt>; dependencies will
1171 prevent its premature removal, and we need to be able to
1172 remove it when it has been superseded.
1176 Since dpkg will not prevent upgrading of other packages
1177 while an <tt>essential</tt> package is in an unconfigured
1178 state, all <tt>essential</tt> packages must supply all of
1179 their core functionality even when unconfigured. If the
1180 package cannot satisfy this requirement it must not be
1181 tagged as essential, and any packages depending on this
1182 package must instead have explicit dependency fields as
1187 Maintainers should take great care in adding any programs,
1188 interfaces, or functionality to <tt>essential</tt> packages.
1189 Packages may assume that functionality provided by
1190 <tt>essential</tt> packages is always available without
1191 declaring explicit dependencies, which means that removing
1192 functionality from the Essential set is very difficult and is
1193 almost never done. Any capability added to an
1194 <tt>essential</tt> package therefore creates an obligation to
1195 support that capability as part of the Essential set in
1200 You must not tag any packages <tt>essential</tt> before
1201 this has been discussed on the <tt>debian-devel</tt>
1202 mailing list and a consensus about doing that has been
1207 <sect id="maintscripts">
1208 <heading>Maintainer Scripts</heading>
1211 The package installation scripts should avoid producing
1212 output which is unnecessary for the user to see and
1213 should rely on <prgn>dpkg</prgn> to stave off boredom on
1214 the part of a user installing many packages. This means,
1215 amongst other things, using the <tt>--quiet</tt> option on
1216 <prgn>install-info</prgn>.
1220 Errors which occur during the execution of an installation
1221 script must be checked and the installation must not
1222 continue after an error.
1226 Note that in general <ref id="scripts"> applies to package
1227 maintainer scripts, too.
1231 You should not use <prgn>dpkg-divert</prgn> on a file belonging
1232 to another package without consulting the maintainer of that
1233 package first. When adding or removing diversions, package
1234 maintainer scripts must provide the <tt>--package</tt> flag
1235 to <prgn>dpkg-divert</prgn> and must not use <tt>--local</tt>.
1239 All packages which supply an instance of a common command
1240 name (or, in general, filename) should generally use
1241 <prgn>update-alternatives</prgn>, so that they may be
1242 installed together. If <prgn>update-alternatives</prgn>
1243 is not used, then each package must use
1244 <tt>Conflicts</tt> to ensure that other packages are
1245 de-installed. (In this case, it may be appropriate to
1246 specify a conflict against earlier versions of something
1247 that previously did not use
1248 <prgn>update-alternatives</prgn>; this is an exception to
1249 the usual rule that versioned conflicts should be
1253 <sect1 id="maintscriptprompt">
1254 <heading>Prompting in maintainer scripts</heading>
1256 Package maintainer scripts may prompt the user if
1257 necessary. Prompting must be done by communicating
1258 through a program, such as <prgn>debconf</prgn>, which
1259 conforms to the Debian Configuration Management
1260 Specification, version 2 or higher.
1264 Packages which are essential, or which are dependencies of
1265 essential packages, may fall back on another prompting method
1266 if no such interface is available when they are executed.
1270 The Debian Configuration Management Specification is included
1271 in the <file>debconf_specification</file> files in the
1272 <package>debian-policy</package> package.
1273 It is also available from the Debian web mirrors at
1274 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1275 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1279 Packages which use the Debian Configuration Management
1280 Specification may contain an additional
1281 <prgn>config</prgn> script and a <tt>templates</tt>
1282 file in their control archive<footnote>
1283 The control.tar.gz inside the .deb.
1284 See <manref name="deb" section="5">.
1286 The <prgn>config</prgn> script might be run before the
1287 <prgn>preinst</prgn> script, and before the package is unpacked
1288 or any of its dependencies or pre-dependencies are satisfied.
1289 Therefore it must work using only the tools present in
1290 <em>essential</em> packages.<footnote>
1291 <package>Debconf</package> or another tool that
1292 implements the Debian Configuration Management
1293 Specification will also be installed, and any
1294 versioned dependencies on it will be satisfied
1295 before preconfiguration begins.
1300 Packages which use the Debian Configuration Management
1301 Specification must allow for translation of their user-visible
1302 messages by using a gettext-based system such as the one
1303 provided by the <package>po-debconf</package> package.
1307 Packages should try to minimize the amount of prompting
1308 they need to do, and they should ensure that the user
1309 will only ever be asked each question once. This means
1310 that packages should try to use appropriate shared
1311 configuration files (such as <file>/etc/papersize</file> and
1312 <file>/etc/news/server</file>), and shared
1313 <package>debconf</package> variables rather than each
1314 prompting for their own list of required pieces of
1319 It also means that an upgrade should not ask the same
1320 questions again, unless the user has used
1321 <tt>dpkg --purge</tt> to remove the package's configuration.
1322 The answers to configuration questions should be stored in an
1323 appropriate place in <file>/etc</file> so that the user can
1324 modify them, and how this has been done should be
1329 If a package has a vitally important piece of
1330 information to pass to the user (such as "don't run me
1331 as I am, you must edit the following configuration files
1332 first or you risk your system emitting badly-formatted
1333 messages"), it should display this in the
1334 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1335 prompt the user to hit return to acknowledge the
1336 message. Copyright messages do not count as vitally
1337 important (they belong in
1338 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1339 neither do instructions on how to use a program (these
1340 should be in on-line documentation, where all the users
1345 Any necessary prompting should almost always be confined
1346 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1347 script. If it is done in the <prgn>postinst</prgn>, it
1348 should be protected with a conditional so that
1349 unnecessary prompting doesn't happen if a package's
1350 installation fails and the <prgn>postinst</prgn> is
1351 called with <tt>abort-upgrade</tt>,
1352 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1362 <heading>Source packages</heading>
1364 <sect id="standardsversion">
1365 <heading>Standards conformance</heading>
1368 Source packages should specify the most recent version number
1369 of this policy document with which your package complied
1370 when it was last updated.
1374 This information may be used to file bug reports
1375 automatically if your package becomes too much out of date.
1379 The version is specified in the <tt>Standards-Version</tt>
1381 The format of the <tt>Standards-Version</tt> field is
1382 described in <ref id="f-Standards-Version">.
1386 You should regularly, and especially if your package has
1387 become out of date, check for the newest Policy Manual
1388 available and update your package, if necessary. When your
1389 package complies with the new standards you should update the
1390 <tt>Standards-Version</tt> source package field and
1391 release it.<footnote>
1392 See the file <file>upgrading-checklist</file> for
1393 information about policy which has changed between
1394 different versions of this document.
1400 <sect id="pkg-relations">
1401 <heading>Package relationships</heading>
1404 Source packages should specify which binary packages they
1405 require to be installed or not to be installed in order to
1406 build correctly. For example, if building a package
1407 requires a certain compiler, then the compiler should be
1408 specified as a build-time dependency.
1412 It is not necessary to explicitly specify build-time
1413 relationships on a minimal set of packages that are always
1414 needed to compile, link and put in a Debian package a
1415 standard "Hello World!" program written in C or C++. The
1416 required packages are called <em>build-essential</em>, and
1417 an informational list can be found in
1418 <file>/usr/share/doc/build-essential/list</file> (which is
1419 contained in the <tt>build-essential</tt>
1422 <list compact="compact">
1424 This allows maintaining the list separately
1425 from the policy documents (the list does not
1426 need the kind of control that the policy
1430 Having a separate package allows one to install
1431 the build-essential packages on a machine, as
1432 well as allowing other packages such as tasks to
1433 require installation of the build-essential
1434 packages using the depends relation.
1437 The separate package allows bug reports against
1438 the list to be categorized separately from
1439 the policy management process in the BTS.
1446 When specifying the set of build-time dependencies, one
1447 should list only those packages explicitly required by the
1448 build. It is not necessary to list packages which are
1449 required merely because some other package in the list of
1450 build-time dependencies depends on them.<footnote>
1451 The reason for this is that dependencies change, and
1452 you should list all those packages, and <em>only</em>
1453 those packages that <em>you</em> need directly. What
1454 others need is their business. For example, if you
1455 only link against <file>libimlib</file>, you will need to
1456 build-depend on <package>libimlib2-dev</package> but
1457 not against any <tt>libjpeg*</tt> packages, even
1458 though <tt>libimlib2-dev</tt> currently depends on
1459 them: installation of <package>libimlib2-dev</package>
1460 will automatically ensure that all of its run-time
1461 dependencies are satisfied.
1466 If build-time dependencies are specified, it must be
1467 possible to build the package and produce working binaries
1468 on a system with only essential and build-essential
1469 packages installed and also those required to satisfy the
1470 build-time relationships (including any implied
1471 relationships). In particular, this means that version
1472 clauses should be used rigorously in build-time
1473 relationships so that one cannot produce bad or
1474 inconsistently configured packages when the relationships
1475 are properly satisfied.
1479 <ref id="relationships"> explains the technical details.
1484 <heading>Changes to the upstream sources</heading>
1487 If changes to the source code are made that are not
1488 specific to the needs of the Debian system, they should be
1489 sent to the upstream authors in whatever form they prefer
1490 so as to be included in the upstream version of the
1495 If you need to configure the package differently for
1496 Debian or for Linux, and the upstream source doesn't
1497 provide a way to do so, you should add such configuration
1498 facilities (for example, a new <prgn>autoconf</prgn> test
1499 or <tt>#define</tt>) and send the patch to the upstream
1500 authors, with the default set to the way they originally
1501 had it. You can then easily override the default in your
1502 <file>debian/rules</file> or wherever is appropriate.
1506 You should make sure that the <prgn>configure</prgn> utility
1507 detects the correct architecture specification string
1508 (refer to <ref id="arch-spec"> for details).
1512 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1513 <prgn>configure</prgn> scripts are used, you should edit the
1514 <file>.in</file> files rather than editing the
1515 <prgn>Makefile</prgn> directly. This allows the user to
1516 reconfigure the package if necessary. You should
1517 <em>not</em> configure the package and edit the generated
1518 <prgn>Makefile</prgn>! This makes it impossible for someone
1519 else to later reconfigure the package without losing the
1525 <sect id="dpkgchangelog">
1526 <heading>Debian changelog: <file>debian/changelog</file></heading>
1529 Changes in the Debian version of the package should be
1530 briefly explained in the Debian changelog file
1531 <file>debian/changelog</file>.<footnote>
1533 Mistakes in changelogs are usually best rectified by
1534 making a new changelog entry rather than "rewriting
1535 history" by editing old changelog entries.
1538 This includes modifications
1539 made in the Debian package compared to the upstream one
1540 as well as other changes and updates to the package.
1542 Although there is nothing stopping an author who is also
1543 the Debian maintainer from using this changelog for all
1544 their changes, it will have to be renamed if the Debian
1545 and upstream maintainers become different people. In such
1546 a case, however, it might be better to maintain the package
1547 as a non-native package.
1552 The format of the <file>debian/changelog</file> allows the
1553 package building tools to discover which version of the package
1554 is being built and find out other release-specific information.
1558 That format is a series of entries like this:
1560 <example compact="compact">
1561 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1563 [optional blank line(s), stripped]
1565 * <var>change details</var>
1566 <var>more change details</var>
1568 [blank line(s), included in output of dpkg-parsechangelog]
1570 * <var>even more change details</var>
1572 [optional blank line(s), stripped]
1574 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1579 <var>package</var> and <var>version</var> are the source
1580 package name and version number.
1584 <var>distribution(s)</var> lists the distributions where
1585 this version should be installed when it is uploaded - it
1586 is copied to the <tt>Distribution</tt> field in the
1587 <file>.changes</file> file. See <ref id="f-Distribution">.
1591 <var>urgency</var> is the value for the <tt>Urgency</tt>
1592 field in the <file>.changes</file> file for the upload
1593 (see <ref id="f-Urgency">). It is not possible to specify
1594 an urgency containing commas; commas are used to separate
1595 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1596 <prgn>dpkg</prgn> changelog format (though there is
1597 currently only one useful <var>keyword</var>,
1602 The change details may in fact be any series of lines
1603 starting with at least two spaces, but conventionally each
1604 change starts with an asterisk and a separating space and
1605 continuation lines are indented so as to bring them in
1606 line with the start of the text above. Blank lines may be
1607 used here to separate groups of changes, if desired.
1611 If this upload resolves bugs recorded in the Bug Tracking
1612 System (BTS), they may be automatically closed on the
1613 inclusion of this package into the Debian archive by
1614 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1615 in the change details.<footnote>
1616 To be precise, the string should match the following
1617 Perl regular expression:
1619 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1621 Then all of the bug numbers listed will be closed by the
1622 archive maintenance script (<prgn>katie</prgn>) using the
1623 <var>version</var> of the changelog entry.
1625 This information is conveyed via the <tt>Closes</tt> field
1626 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1630 The maintainer name and email address used in the changelog
1631 should be the details of the person uploading <em>this</em>
1632 version. They are <em>not</em> necessarily those of the
1633 usual package maintainer. The information here will be
1634 copied to the <tt>Changed-By</tt> field in the
1635 <tt>.changes</tt> file (see <ref id="f-Changed-By">),
1636 and then later used to send an acknowledgement when the
1637 upload has been installed.
1641 The <var>date</var> has the following format<footnote>
1642 This is the same as the format generated by <tt>date
1644 </footnote> (compatible and with the same semantics of
1645 RFC 2822 and RFC 5322):
1646 <example>day-of-week, dd month yyyy hh:mm:ss +zzzz</example>
1648 <list compact="compact">
1650 day-of week is one of: Mon, Tue, Wed, Thu, Fri, Sat, Sun
1653 dd is a one- or two-digit day of the month (01-31)
1656 month is one of: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug,
1659 <item>yyyy is the four-digit year (e.g. 2010)</item>
1660 <item>hh is the two-digit hour (00-23)</item>
1661 <item>mm is the two-digit minutes (00-59)</item>
1662 <item>ss is the two-digit seconds (00-60)</item>
1664 +zzzz or -zzzz is the the time zone offset from Coordinated
1665 Universal Time (UTC). "+" indicates that the time is ahead
1666 of (i.e., east of) UTC and "-" indicates that the time is
1667 behind (i.e., west of) UTC. The first two digits indicate
1668 the hour difference from UTC and the last two digits
1669 indicate the number of additional minutes difference from
1670 UTC. The last two digits must be in the range 00-59.
1676 The first "title" line with the package name must start
1677 at the left hand margin. The "trailer" line with the
1678 maintainer and date details must be preceded by exactly
1679 one space. The maintainer details and the date must be
1680 separated by exactly two spaces.
1684 The entire changelog must be encoded in UTF-8.
1688 For more information on placement of the changelog files
1689 within binary packages, please see <ref id="changelogs">.
1693 <sect id="dpkgcopyright">
1694 <heading>Copyright: <file>debian/copyright</file></heading>
1696 Every package must be accompanied by a verbatim copy of its
1697 copyright information and distribution license in the file
1698 <file>/usr/share/doc/<var>package</var>/copyright</file>
1699 (see <ref id="copyrightfile"> for further details). Also see
1700 <ref id="pkgcopyright"> for further considerations related
1701 to copyrights for packages.
1705 <heading>Error trapping in makefiles</heading>
1708 When <prgn>make</prgn> invokes a command in a makefile
1709 (including your package's upstream makefiles and
1710 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1711 means that <prgn>sh</prgn>'s usual bad error handling
1712 properties apply: if you include a miniature script as one
1713 of the commands in your makefile you'll find that if you
1714 don't do anything about it then errors are not detected
1715 and <prgn>make</prgn> will blithely continue after
1720 Every time you put more than one shell command (this
1721 includes using a loop) in a makefile command you
1722 must make sure that errors are trapped. For
1723 simple compound commands, such as changing directory and
1724 then running a program, using <tt>&&</tt> rather
1725 than semicolon as a command separator is sufficient. For
1726 more complex commands including most loops and
1727 conditionals you should include a separate <tt>set -e</tt>
1728 command at the start of every makefile command that's
1729 actually one of these miniature shell scripts.
1733 <sect id="timestamps">
1734 <heading>Time Stamps</heading>
1736 Maintainers should preserve the modification times of the
1737 upstream source files in a package, as far as is reasonably
1739 The rationale is that there is some information conveyed
1740 by knowing the age of the file, for example, you could
1741 recognize that some documentation is very old by looking
1742 at the modification time, so it would be nice if the
1743 modification time of the upstream source would be
1749 <sect id="restrictions">
1750 <heading>Restrictions on objects in source packages</heading>
1753 The source package may not contain any hard links<footnote>
1755 This is not currently detected when building source
1756 packages, but only when extracting
1760 Hard links may be permitted at some point in the
1761 future, but would require a fair amount of
1764 </footnote>, device special files, sockets or setuid or
1765 setgid files.<footnote>
1766 Setgid directories are allowed.
1771 <sect id="debianrules">
1772 <heading>Main building script: <file>debian/rules</file></heading>
1775 This file must be an executable makefile, and contains the
1776 package-specific recipes for compiling the package and
1777 building binary package(s) from the source.
1781 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1782 so that it can be invoked by saying its name rather than
1783 invoking <prgn>make</prgn> explicitly. That is, invoking
1784 either of <tt>make -f debian/rules <em>args...</em></tt>
1785 or <tt>./debian/rules <em>args...</em></tt> must result in
1790 Since an interactive <file>debian/rules</file> script makes it
1791 impossible to auto-compile that package and also makes it
1792 hard for other people to reproduce the same binary
1793 package, all <em>required targets</em> must be
1794 non-interactive. At a minimum, required targets are the
1795 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1796 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1797 <em>binary-indep</em>, and <em>build</em>. It also follows
1798 that any target that these targets depend on must also be
1803 The targets are as follows (required unless stated otherwise):
1805 <tag><tt>build</tt></tag>
1808 The <tt>build</tt> target should perform all the
1809 configuration and compilation of the package.
1810 If a package has an interactive pre-build
1811 configuration routine, the Debian source package
1812 must either be built after this has taken place (so
1813 that the binary package can be built without rerunning
1814 the configuration) or the configuration routine
1815 modified to become non-interactive. (The latter is
1816 preferable if there are architecture-specific features
1817 detected by the configuration routine.)
1821 For some packages, notably ones where the same
1822 source tree is compiled in different ways to produce
1823 two binary packages, the <tt>build</tt> target
1824 does not make much sense. For these packages it is
1825 good enough to provide two (or more) targets
1826 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1827 for each of the ways of building the package, and a
1828 <tt>build</tt> target that does nothing. The
1829 <tt>binary</tt> target will have to build the
1830 package in each of the possible ways and make the
1831 binary package out of each.
1835 The <tt>build</tt> target must not do anything
1836 that might require root privilege.
1840 The <tt>build</tt> target may need to run the
1841 <tt>clean</tt> target first - see below.
1845 When a package has a configuration and build routine
1846 which takes a long time, or when the makefiles are
1847 poorly designed, or when <tt>build</tt> needs to
1848 run <tt>clean</tt> first, it is a good idea to
1849 <tt>touch build</tt> when the build process is
1850 complete. This will ensure that if <tt>debian/rules
1851 build</tt> is run again it will not rebuild the whole
1853 Another common way to do this is for <tt>build</tt>
1854 to depend on <prgn>build-stamp</prgn> and to do
1855 nothing else, and for the <prgn>build-stamp</prgn>
1856 target to do the building and to <tt>touch
1857 build-stamp</tt> on completion. This is
1858 especially useful if the build routine creates a
1859 file or directory called <tt>build</tt>; in such a
1860 case, <tt>build</tt> will need to be listed as
1861 a phony target (i.e., as a dependency of the
1862 <tt>.PHONY</tt> target). See the documentation of
1863 <prgn>make</prgn> for more information on phony
1869 <tag><tt>build-arch</tt> (optional),
1870 <tt>build-indep</tt> (optional)
1874 A package may also provide both of the targets
1875 <tt>build-arch</tt> and <tt>build-indep</tt>.
1876 The <tt>build-arch</tt> target, if provided, should
1877 perform all the configuration and compilation required for
1878 producing all architecture-dependant binary packages
1879 (those packages for which the body of the
1880 <tt>Architecture</tt> field in <tt>debian/control</tt> is
1881 not <tt>all</tt>). Similarly, the <tt>build-indep</tt>
1882 target, if provided, should perform all the configuration
1883 and compilation required for producing all
1884 architecture-independent binary packages (those packages
1885 for which the body of the <tt>Architecture</tt> field
1886 in <tt>debian/control</tt> is <tt>all</tt>).
1887 The <tt>build</tt> target should depend on those of the
1888 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1889 are provided in the rules file.<footnote>
1890 The intent of this split is so that binary-only builds
1891 need not install the dependencies required for
1892 the <tt>build-indep</tt> target. However, this is not
1893 yet used in practice since <tt>dpkg-buildpackage
1894 -B</tt>, and therefore the autobuilders,
1895 invoke <tt>build</tt> rather than <tt>build-arch</tt>
1896 due to the difficulties in determining whether the
1897 optional <tt>build-arch</tt> target exists.
1902 If one or both of the targets <tt>build-arch</tt> and
1903 <tt>build-indep</tt> are not provided, then invoking
1904 <file>debian/rules</file> with one of the not-provided
1905 targets as arguments should produce a exit status code
1906 of 2. Usually this is provided automatically by make
1907 if the target is missing.
1911 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1912 must not do anything that might require root privilege.
1916 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1917 <tt>binary-indep</tt>
1921 The <tt>binary</tt> target must be all that is
1922 necessary for the user to build the binary package(s)
1923 produced from this source package. It is
1924 split into two parts: <prgn>binary-arch</prgn> builds
1925 the binary packages which are specific to a particular
1926 architecture, and <tt>binary-indep</tt> builds
1927 those which are not.
1930 <tt>binary</tt> may be (and commonly is) a target with
1931 no commands which simply depends on
1932 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1935 Both <tt>binary-*</tt> targets should depend on the
1936 <tt>build</tt> target, or on the appropriate
1937 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1938 provided, so that the package is built if it has not
1939 been already. It should then create the relevant
1940 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1941 make their control files and <prgn>dpkg-deb</prgn> to
1942 build them and place them in the parent of the top
1947 Both the <tt>binary-arch</tt> and
1948 <tt>binary-indep</tt> targets <em>must</em> exist.
1949 If one of them has nothing to do (which will always be
1950 the case if the source generates only a single binary
1951 package, whether architecture-dependent or not), it
1952 must still exist and must always succeed.
1956 The <tt>binary</tt> targets must be invoked as
1958 The <prgn>fakeroot</prgn> package often allows one
1959 to build a package correctly even without being
1965 <tag><tt>clean</tt></tag>
1968 This must undo any effects that the <tt>build</tt>
1969 and <tt>binary</tt> targets may have had, except
1970 that it should leave alone any output files created in
1971 the parent directory by a run of a <tt>binary</tt>
1976 If a <tt>build</tt> file is touched at the end of
1977 the <tt>build</tt> target, as suggested above, it
1978 should be removed as the first action that
1979 <tt>clean</tt> performs, so that running
1980 <tt>build</tt> again after an interrupted
1981 <tt>clean</tt> doesn't think that everything is
1986 The <tt>clean</tt> target may need to be
1987 invoked as root if <tt>binary</tt> has been
1988 invoked since the last <tt>clean</tt>, or if
1989 <tt>build</tt> has been invoked as root (since
1990 <tt>build</tt> may create directories, for
1995 <tag><tt>get-orig-source</tt> (optional)</tag>
1998 This target fetches the most recent version of the
1999 original source package from a canonical archive site
2000 (via FTP or WWW, for example), does any necessary
2001 rearrangement to turn it into the original source
2002 tar file format described below, and leaves it in the
2007 This target may be invoked in any directory, and
2008 should take care to clean up any temporary files it
2013 This target is optional, but providing it if
2014 possible is a good idea.
2018 <tag><tt>patch</tt> (optional)</tag>
2021 This target performs whatever additional actions are
2022 required to make the source ready for editing (unpacking
2023 additional upstream archives, applying patches, etc.).
2024 It is recommended to be implemented for any package where
2025 <tt>dpkg-source -x</tt> does not result in source ready
2026 for additional modification. See
2027 <ref id="readmesource">.
2033 The <tt>build</tt>, <tt>binary</tt> and
2034 <tt>clean</tt> targets must be invoked with the current
2035 directory being the package's top-level directory.
2040 Additional targets may exist in <file>debian/rules</file>,
2041 either as published or undocumented interfaces or for the
2042 package's internal use.
2046 The architectures we build on and build for are determined
2047 by <prgn>make</prgn> variables using the utility
2048 <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
2049 You can determine the
2050 Debian architecture and the GNU style architecture
2051 specification string for the build machine (the machine type
2052 we are building on) as well as for the host machine (the
2053 machine type we are building for). Here is a list of
2054 supported <prgn>make</prgn> variables:
2055 <list compact="compact">
2057 <tt>DEB_*_ARCH</tt> (the Debian architecture)
2060 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2063 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2066 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2067 specification string)
2070 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2071 <tt>DEB_*_GNU_TYPE</tt>)
2074 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2075 <tt>DEB_*_GNU_TYPE</tt>)
2077 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2078 the build machine or <tt>HOST</tt> for specification of the
2083 Backward compatibility can be provided in the rules file
2084 by setting the needed variables to suitable default
2085 values; please refer to the documentation of
2086 <prgn>dpkg-architecture</prgn> for details.
2090 It is important to understand that the <tt>DEB_*_ARCH</tt>
2091 string only determines which Debian architecture we are
2092 building on or for. It should not be used to get the CPU
2093 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2094 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2095 GNU style variables should generally only be used with upstream
2099 <sect1 id="debianrules-options">
2100 <heading><file>debian/rules</file> and
2101 <tt>DEB_BUILD_OPTIONS</tt></heading>
2104 Supporting the standardized environment variable
2105 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2106 contain several flags to change how a package is compiled and
2107 built. Each flag must be in the form <var>flag</var> or
2108 <var>flag</var>=<var>options</var>. If multiple flags are
2109 given, they must be separated by whitespace.<footnote>
2110 Some packages support any delimiter, but whitespace is the
2111 easiest to parse inside a makefile and avoids ambiguity with
2112 flag values that contain commas.
2114 <var>flag</var> must start with a lowercase letter
2115 (<tt>a-z</tt>) and consist only of lowercase letters,
2116 numbers (<tt>0-9</tt>), and the characters
2117 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2118 <var>options</var> must not contain whitespace. The same
2119 tag should not be given multiple times with conflicting
2120 values. Package maintainers may assume that
2121 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2125 The meaning of the following tags has been standardized:
2129 This tag says to not run any build-time test suite
2130 provided by the package.
2134 The presence of this tag means that the package should
2135 be compiled with a minimum of optimization. For C
2136 programs, it is best to add <tt>-O0</tt> to
2137 <tt>CFLAGS</tt> (although this is usually the default).
2138 Some programs might fail to build or run at this level
2139 of optimization; it may be necessary to use
2140 <tt>-O1</tt>, for example.
2144 This tag means that the debugging symbols should not be
2145 stripped from the binary during installation, so that
2146 debugging information may be included in the package.
2148 <tag>parallel=n</tag>
2150 This tag means that the package should be built using up
2151 to <tt>n</tt> parallel processes if the package build
2152 system supports this.<footnote>
2153 Packages built with <tt>make</tt> can often implement
2154 this by passing the <tt>-j</tt><var>n</var> option to
2157 If the package build system does not support parallel
2158 builds, this string must be ignored. If the package
2159 build system only supports a lower level of concurrency
2160 than <var>n</var>, the package should be built using as
2161 many parallel processes as the package build system
2162 supports. It is up to the package maintainer to decide
2163 whether the package build times are long enough and the
2164 package build system is robust enough to make supporting
2165 parallel builds worthwhile.
2171 Unknown flags must be ignored by <file>debian/rules</file>.
2175 The following makefile snippet is an example of how one may
2176 implement the build options; you will probably have to
2177 massage this example in order to make it work for your
2179 <example compact="compact">
2182 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2183 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2184 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2185 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2187 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2192 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2193 INSTALL_PROGRAM += -s
2195 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2196 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2197 MAKEFLAGS += -j$(NUMJOBS)
2202 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2203 # Code to run the package test suite.
2210 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2211 <sect id="substvars">
2212 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2215 When <prgn>dpkg-gencontrol</prgn>,
2216 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
2217 generate control files they perform variable substitutions
2218 on their output just before writing it. Variable
2219 substitutions have the form <tt>${<var>variable</var>}</tt>.
2220 The optional file <file>debian/substvars</file> contains
2221 variable substitutions to be used; variables can also be set
2222 directly from <file>debian/rules</file> using the <tt>-V</tt>
2223 option to the source packaging commands, and certain
2224 predefined variables are also available.
2228 The <file>debian/substvars</file> file is usually generated and
2229 modified dynamically by <file>debian/rules</file> targets, in
2230 which case it must be removed by the <tt>clean</tt> target.
2234 See <manref name="deb-substvars" section="5"> for full
2235 details about source variable substitutions, including the
2236 format of <file>debian/substvars</file>.</p>
2239 <sect id="debianwatch">
2240 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2243 This is an optional, recommended control file for the
2244 <tt>uscan</tt> utility which defines how to automatically
2245 scan ftp or http sites for newly available updates of the
2246 package. This is used by <url id="
2247 http://dehs.alioth.debian.org/"> and other Debian QA tools
2248 to help with quality control and maintenance of the
2249 distribution as a whole.
2254 <sect id="debianfiles">
2255 <heading>Generated files list: <file>debian/files</file></heading>
2258 This file is not a permanent part of the source tree; it
2259 is used while building packages to record which files are
2260 being generated. <prgn>dpkg-genchanges</prgn> uses it
2261 when it generates a <file>.changes</file> file.
2265 It should not exist in a shipped source package, and so it
2266 (and any backup files or temporary files such as
2267 <file>files.new</file><footnote>
2268 <file>files.new</file> is used as a temporary file by
2269 <prgn>dpkg-gencontrol</prgn> and
2270 <prgn>dpkg-distaddfile</prgn> - they write a new
2271 version of <tt>files</tt> here before renaming it,
2272 to avoid leaving a corrupted copy if an error
2274 </footnote>) should be removed by the
2275 <tt>clean</tt> target. It may also be wise to
2276 ensure a fresh start by emptying or removing it at the
2277 start of the <tt>binary</tt> target.
2281 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2282 package, it adds an entry to <file>debian/files</file> for the
2283 <file>.deb</file> file that will be created when <tt>dpkg-deb
2284 --build</tt> is run for that binary package. So for most
2285 packages all that needs to be done with this file is to
2286 delete it in the <tt>clean</tt> target.
2290 If a package upload includes files besides the source
2291 package and any binary packages whose control files were
2292 made with <prgn>dpkg-gencontrol</prgn> then they should be
2293 placed in the parent of the package's top-level directory
2294 and <prgn>dpkg-distaddfile</prgn> should be called to add
2295 the file to the list in <file>debian/files</file>.</p>
2298 <sect id="embeddedfiles">
2299 <heading>Convenience copies of code</heading>
2302 Some software packages include in their distribution convenience
2303 copies of code from other software packages, generally so that
2304 users compiling from source don't have to download multiple
2305 packages. Debian packages should not make use of these
2306 convenience copies unless the included package is explicitly
2307 intended to be used in this way.<footnote>
2308 For example, parts of the GNU build system work like this.
2310 If the included code is already in the Debian archive in the
2311 form of a library, the Debian packaging should ensure that
2312 binary packages reference the libraries already in Debian and
2313 the convenience copy is not used. If the included code is not
2314 already in Debian, it should be packaged separately as a
2315 prerequisite if possible.
2317 Having multiple copies of the same code in Debian is
2318 inefficient, often creates either static linking or shared
2319 library conflicts, and, most importantly, increases the
2320 difficulty of handling security vulnerabilities in the
2326 <sect id="readmesource">
2327 <heading>Source package handling:
2328 <file>debian/README.source</file></heading>
2331 If running <prgn>dpkg-source -x</prgn> on a source package
2332 doesn't produce the source of the package, ready for editing,
2333 and allow one to make changes and run
2334 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2335 without taking any additional steps, creating a
2336 <file>debian/README.source</file> documentation file is
2337 recommended. This file should explain how to do all of the
2340 <item>Generate the fully patched source, in a form ready for
2341 editing, that would be built to create Debian
2342 packages. Doing this with a <tt>patch</tt> target in
2343 <file>debian/rules</file> is recommended; see
2344 <ref id="debianrules">.</item>
2345 <item>Modify the source and save those modifications so that
2346 they will be applied when building the package.</item>
2347 <item>Remove source modifications that are currently being
2348 applied when building the package.</item>
2349 <item>Optionally, document what steps are necessary to
2350 upgrade the Debian source package to a new upstream version,
2351 if applicable.</item>
2353 This explanation should include specific commands and mention
2354 any additional required Debian packages. It should not assume
2355 familiarity with any specific Debian packaging system or patch
2360 This explanation may refer to a documentation file installed by
2361 one of the package's build dependencies provided that the
2362 referenced documentation clearly explains these tasks and is not
2363 a general reference manual.
2367 <file>debian/README.source</file> may also include any other
2368 information that would be helpful to someone modifying the
2369 source package. Even if the package doesn't fit the above
2370 description, maintainers are encouraged to document in a
2371 <file>debian/README.source</file> file any source package with a
2372 particularly complex or unintuitive source layout or build
2373 system (for example, a package that builds the same source
2374 multiple times to generate different binary packages).
2380 <chapt id="controlfields">
2381 <heading>Control files and their fields</heading>
2384 The package management system manipulates data represented in
2385 a common format, known as <em>control data</em>, stored in
2386 <em>control files</em>.
2387 Control files are used for source packages, binary packages and
2388 the <file>.changes</file> files which control the installation
2389 of uploaded files<footnote>
2390 <prgn>dpkg</prgn>'s internal databases are in a similar
2395 <sect id="controlsyntax">
2396 <heading>Syntax of control files</heading>
2399 A control file consists of one or more paragraphs of
2401 The paragraphs are also sometimes referred to as stanzas.
2403 The paragraphs are separated by blank lines. Some control
2404 files allow only one paragraph; others allow several, in
2405 which case each paragraph usually refers to a different
2406 package. (For example, in source packages, the first
2407 paragraph refers to the source package, and later paragraphs
2408 refer to binary packages generated from the source.)
2412 Each paragraph consists of a series of data fields; each
2413 field consists of the field name, followed by a colon and
2414 then the data/value associated with that field. It ends at
2415 the end of the (logical) line. Horizontal whitespace
2416 (spaces and tabs) may occur immediately before or after the
2417 value and is ignored there; it is conventional to put a
2418 single space after the colon. For example, a field might
2420 <example compact="compact">
2423 the field name is <tt>Package</tt> and the field value
2428 A paragraph must not contain more than one instance of a
2429 particular field name.
2433 Many fields' values may span several lines; in this case
2434 each continuation line must start with a space or a tab.
2435 Any trailing spaces or tabs at the end of individual
2436 lines of a field value are ignored.
2440 In fields where it is specified that lines may not wrap,
2441 only a single line of data is allowed and whitespace is not
2442 significant in a field body. Whitespace must not appear
2443 inside names (of packages, architectures, files or anything
2444 else) or version numbers, or between the characters of
2445 multi-character version relationships.
2449 Field names are not case-sensitive, but it is usual to
2450 capitalize the field names using mixed case as shown below.
2451 Field values are case-sensitive unless the description of the
2452 field says otherwise.
2456 Blank lines, or lines consisting only of spaces and tabs,
2457 are not allowed within field values or between fields - that
2458 would mean a new paragraph.
2462 All control files must be encoded in UTF-8.
2466 <sect id="sourcecontrolfiles">
2467 <heading>Source package control files -- <file>debian/control</file></heading>
2470 The <file>debian/control</file> file contains the most vital
2471 (and version-independent) information about the source package
2472 and about the binary packages it creates.
2476 The first paragraph of the control file contains information about
2477 the source package in general. The subsequent sets each describe a
2478 binary package that the source tree builds.
2482 The fields in the general paragraph (the first one, for the source
2485 <list compact="compact">
2486 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2487 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2488 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2489 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2490 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2491 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2492 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2493 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2498 The fields in the binary package paragraphs are:
2500 <list compact="compact">
2501 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2502 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2503 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2504 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2505 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2506 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2507 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2508 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2513 The syntax and semantics of the fields are described below.
2517 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2518 generate control files for binary packages (see below), by
2519 <prgn>dpkg-genchanges</prgn> to generate the
2520 <file>.changes</file> file to accompany the upload, and by
2521 <prgn>dpkg-source</prgn> when it creates the
2522 <file>.dsc</file> source control file as part of a source
2523 archive. Many fields are permitted to span multiple lines in
2524 <file>debian/control</file> but not in any other control
2525 file. These tools are responsible for removing the line
2526 breaks from such fields when using fields from
2527 <file>debian/control</file> to generate other control files.
2531 The fields here may contain variable references - their
2532 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2533 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2534 when they generate output control files.
2535 See <ref id="substvars"> for details.
2539 In addition to the control file syntax described <qref
2540 id="controlsyntax">above</qref>, this file may also contain
2541 comment lines starting with <tt>#</tt> without any preceding
2542 whitespace. All such lines are ignored, even in the middle of
2543 continuation lines for a multiline field, and do not end a
2549 <sect id="binarycontrolfiles">
2550 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2553 The <file>DEBIAN/control</file> file contains the most vital
2554 (and version-dependent) information about a binary package. It
2555 consists of a single paragraph.
2559 The fields in this file are:
2561 <list compact="compact">
2562 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2563 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2564 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2565 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2566 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2567 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2568 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2569 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2570 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2571 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2572 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2573 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2578 <sect id="debiansourcecontrolfiles">
2579 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2582 This file consists of a single paragraph, possibly surrounded by
2583 a PGP signature. The fields of that paragraph are listed below.
2584 Their syntax is described above, in <ref id="pkg-controlfields">.
2586 <list compact="compact">
2587 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2588 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2589 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2590 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2591 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2592 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2593 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2594 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2595 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2596 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2597 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2598 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2599 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2604 The source package control file is generated by
2605 <prgn>dpkg-source</prgn> when it builds the source
2606 archive, from other files in the source package,
2607 described above. When unpacking, it is checked against
2608 the files and directories in the other parts of the
2614 <sect id="debianchangesfiles">
2615 <heading>Debian changes files -- <file>.changes</file></heading>
2618 The <file>.changes</file> files are used by the Debian archive
2619 maintenance software to process updates to packages. They
2620 consist of a single paragraph, possibly surrounded by a PGP
2621 signature. That paragraph contains information from the
2622 <file>debian/control</file> file and other data about the
2623 source package gathered via <file>debian/changelog</file>
2624 and <file>debian/rules</file>.
2628 <file>.changes</file> files have a format version that is
2629 incremented whenever the documented fields or their meaning
2630 change. This document describes format &changesversion;.
2634 The fields in this file are:
2636 <list compact="compact">
2637 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2638 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2639 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2640 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2641 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2642 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2643 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2644 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2645 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2646 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2647 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2648 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2649 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2650 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2651 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2652 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2657 <sect id="controlfieldslist">
2658 <heading>List of fields</heading>
2660 <sect1 id="f-Source">
2661 <heading><tt>Source</tt></heading>
2664 This field identifies the source package name.
2668 In <file>debian/control</file> or a <file>.dsc</file> file,
2669 this field must contain only the name of the source package.
2673 In a binary package control file or a <file>.changes</file>
2674 file, the source package name may be followed by a version
2675 number in parentheses<footnote>
2676 It is customary to leave a space after the package name
2677 if a version number is specified.
2679 This version number may be omitted (and is, by
2680 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2681 the <tt>Version</tt> field of the binary package in
2682 question. The field itself may be omitted from a binary
2683 package control file when the source package has the same
2684 name and version as the binary package.
2688 Package names (both source and binary,
2689 see <ref id="f-Package">) must consist only of lower case
2690 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2691 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2692 (<tt>.</tt>). They must be at least two characters long and
2693 must start with an alphanumeric character.
2697 <sect1 id="f-Maintainer">
2698 <heading><tt>Maintainer</tt></heading>
2701 The package maintainer's name and email address. The name
2702 must come first, then the email address inside angle
2703 brackets <tt><></tt> (in RFC822 format).
2707 If the maintainer's name contains a full stop then the
2708 whole field will not work directly as an email address due
2709 to a misfeature in the syntax specified in RFC822; a
2710 program using this field as an address must check for this
2711 and correct the problem if necessary (for example by
2712 putting the name in round brackets and moving it to the
2713 end, and bringing the email address forward).
2717 See <ref id="maintainer"> for additional requirements and
2718 information about package maintainers.
2722 <sect1 id="f-Uploaders">
2723 <heading><tt>Uploaders</tt></heading>
2726 List of the names and email addresses of co-maintainers of the
2727 package, if any. If the package has other maintainers besides
2728 the one named in the <qref id="f-Maintainer">Maintainer
2729 field</qref>, their names and email addresses should be listed
2730 here. The format of each entry is the same as that of the
2731 Maintainer field, and multiple entries must be comma
2736 This is normally an optional field, but if
2737 the <tt>Maintainer</tt> control field names a group of people
2738 and a shared email address, the <tt>Uploaders</tt> field must
2739 be present and must contain at least one human with their
2740 personal email address.
2744 Any parser that interprets the Uploaders field in
2745 <file>debian/control</file> must permit it to span multiple
2746 lines. Line breaks in an Uploaders field that spans multiple
2747 lines are not significant and the semantics of the field are
2748 the same as if the line breaks had not been present.
2752 <sect1 id="f-Changed-By">
2753 <heading><tt>Changed-By</tt></heading>
2756 The name and email address of the person who prepared this
2757 version of the package, usually a maintainer. The syntax is
2758 the same as for the <qref id="f-Maintainer">Maintainer
2763 <sect1 id="f-Section">
2764 <heading><tt>Section</tt></heading>
2767 This field specifies an application area into which the package
2768 has been classified. See <ref id="subsections">.
2772 When it appears in the <file>debian/control</file> file,
2773 it gives the value for the subfield of the same name in
2774 the <tt>Files</tt> field of the <file>.changes</file> file.
2775 It also gives the default for the same field in the binary
2780 <sect1 id="f-Priority">
2781 <heading><tt>Priority</tt></heading>
2784 This field represents how important it is that the user
2785 have the package installed. See <ref id="priorities">.
2789 When it appears in the <file>debian/control</file> file,
2790 it gives the value for the subfield of the same name in
2791 the <tt>Files</tt> field of the <file>.changes</file> file.
2792 It also gives the default for the same field in the binary
2797 <sect1 id="f-Package">
2798 <heading><tt>Package</tt></heading>
2801 The name of the binary package.
2805 Binary package names must follow the same syntax and
2806 restrictions as source package names. See <ref id="f-Source">
2811 <sect1 id="f-Architecture">
2812 <heading><tt>Architecture</tt></heading>
2815 Depending on context and the control file used, the
2816 <tt>Architecture</tt> field can include the following sets of
2820 A unique single word identifying a Debian machine
2821 architecture as described in <ref id="arch-spec">.
2824 An architecture wildcard identifying a set of Debian
2825 machine architectures, see <ref id="arch-wildcard-spec">.
2826 <tt>any</tt> matches all Debian machine architectures
2827 and is the most frequently used.
2830 <tt>all</tt>, which indicates an
2831 architecture-independent package.
2834 <tt>source</tt>, which indicates a source package.
2840 In the main <file>debian/control</file> file in the source
2841 package, this field may contain the special
2842 value <tt>all</tt>, the special architecture
2843 wildcard <tt>any</tt>, or a list of specific and wildcard
2844 architectures separated by spaces. If <tt>all</tt>
2845 or <tt>any</tt> appears, that value must be the entire
2846 contents of the field. Most packages will use
2847 either <tt>all</tt> or <tt>any</tt>.
2851 Specifying a specific list of architectures indicates that the
2852 source will build an architecture-dependent package only on
2853 architectures included in the list. Specifying a list of
2854 architecture wildcards indicates that the source will build an
2855 architecture-dependent package on only those architectures
2856 that match any of the specified architecture wildcards.
2857 Specifying a list of architectures or architecture wildcards
2858 other than <tt>any</tt> is for the minority of cases where a
2859 program is not portable or is not useful on some
2860 architectures. Where possible, the program should be made
2865 In the source package control file <file>.dsc</file>, this
2866 field may contain either the architecture
2867 wildcard <tt>any</tt> or a list of architectures and
2868 architecture wildcards separated by spaces. If a list is
2869 given, it may include (or consist solely of) the special
2870 value <tt>all</tt>. In other words, in <file>.dsc</file>
2871 files unlike the <file>debian/control</file>, <tt>all</tt> may
2872 occur in combination with specific architectures.
2873 The <tt>Architecture</tt> field in the source package control
2874 file <file>.dsc</file> is generally constructed from
2875 the <tt>Architecture</tt> fields in
2876 the <file>debian/control</file> in the source package.
2880 Specifying <tt>any</tt> indicates that the source package
2881 isn't dependent on any particular architecture and should
2882 compile fine on any one. The produced binary package(s)
2883 will either be specific to whatever the current build
2884 architecture is or will be architecture-independent.
2888 Specifying only <tt>all</tt> indicates that the source package
2889 will only build architecture-independent packages. If this is
2890 the case, <tt>all</tt> must be used rather than <tt>any</tt>;
2891 <tt>any</tt> implies that the source package will build at
2892 least one architecture-dependent package.
2896 Specifying a list of architectures or architecture wildcards
2897 indicates that the source will build an architecture-dependent
2898 package, and will only work correctly on the listed or
2899 matching architectures. If the source package also builds at
2900 least one architecture-independent package, <tt>all</tt> will
2901 also be included in the list.
2905 In a <file>.changes</file> file, the <tt>Architecture</tt>
2906 field lists the architecture(s) of the package(s) currently
2907 being uploaded. This will be a list; if the source for the
2908 package is also being uploaded, the special
2909 entry <tt>source</tt> is also present. <tt>all</tt> will be
2910 present if any architecture-independent packages are being
2911 uploaded. Architecture wildcards such as <tt>any</tt> must
2912 never occur in the <tt>Architecture</tt> field in
2913 the <file>.changes</file> file.
2917 See <ref id="debianrules"> for information on how to get
2918 the architecture for the build process.
2922 <sect1 id="f-Essential">
2923 <heading><tt>Essential</tt></heading>
2926 This is a boolean field which may occur only in the
2927 control file of a binary package or in a per-package fields
2928 paragraph of a main source control data file.
2932 If set to <tt>yes</tt> then the package management system
2933 will refuse to remove the package (upgrading and replacing
2934 it is still possible). The other possible value is <tt>no</tt>,
2935 which is the same as not having the field at all.
2940 <heading>Package interrelationship fields:
2941 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2942 <tt>Recommends</tt>, <tt>Suggests</tt>,
2943 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2944 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2948 These fields describe the package's relationships with
2949 other packages. Their syntax and semantics are described
2950 in <ref id="relationships">.</p>
2953 <sect1 id="f-Standards-Version">
2954 <heading><tt>Standards-Version</tt></heading>
2957 The most recent version of the standards (the policy
2958 manual and associated texts) with which the package
2963 The version number has four components: major and minor
2964 version number and major and minor patch level. When the
2965 standards change in a way that requires every package to
2966 change the major number will be changed. Significant
2967 changes that will require work in many packages will be
2968 signaled by a change to the minor number. The major patch
2969 level will be changed for any change to the meaning of the
2970 standards, however small; the minor patch level will be
2971 changed when only cosmetic, typographical or other edits
2972 are made which neither change the meaning of the document
2973 nor affect the contents of packages.
2977 Thus only the first three components of the policy version
2978 are significant in the <em>Standards-Version</em> control
2979 field, and so either these three components or all four
2980 components may be specified.<footnote>
2981 In the past, people specified the full version number
2982 in the Standards-Version field, for example "2.3.0.0".
2983 Since minor patch-level changes don't introduce new
2984 policy, it was thought it would be better to relax
2985 policy and only require the first 3 components to be
2986 specified, in this example "2.3.0". All four
2987 components may still be used if someone wishes to do so.
2993 <sect1 id="f-Version">
2994 <heading><tt>Version</tt></heading>
2997 The version number of a package. The format is:
2998 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
3002 The three components here are:
3004 <tag><var>epoch</var></tag>
3007 This is a single (generally small) unsigned integer. It
3008 may be omitted, in which case zero is assumed. If it is
3009 omitted then the <var>upstream_version</var> may not
3014 It is provided to allow mistakes in the version numbers
3015 of older versions of a package, and also a package's
3016 previous version numbering schemes, to be left behind.
3020 <tag><var>upstream_version</var></tag>
3023 This is the main part of the version number. It is
3024 usually the version number of the original ("upstream")
3025 package from which the <file>.deb</file> file has been made,
3026 if this is applicable. Usually this will be in the same
3027 format as that specified by the upstream author(s);
3028 however, it may need to be reformatted to fit into the
3029 package management system's format and comparison
3034 The comparison behavior of the package management system
3035 with respect to the <var>upstream_version</var> is
3036 described below. The <var>upstream_version</var>
3037 portion of the version number is mandatory.
3041 The <var>upstream_version</var> may contain only
3042 alphanumerics<footnote>
3043 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3045 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3046 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3047 tilde) and should start with a digit. If there is no
3048 <var>debian_revision</var> then hyphens are not allowed;
3049 if there is no <var>epoch</var> then colons are not
3054 <tag><var>debian_revision</var></tag>
3057 This part of the version number specifies the version of
3058 the Debian package based on the upstream version. It
3059 may contain only alphanumerics and the characters
3060 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3061 tilde) and is compared in the same way as the
3062 <var>upstream_version</var> is.
3066 It is optional; if it isn't present then the
3067 <var>upstream_version</var> may not contain a hyphen.
3068 This format represents the case where a piece of
3069 software was written specifically to be a Debian
3070 package, where the Debian package source must always
3071 be identical to the pristine source and therefore no
3072 revision indication is required.
3076 It is conventional to restart the
3077 <var>debian_revision</var> at <tt>1</tt> each time the
3078 <var>upstream_version</var> is increased.
3082 The package management system will break the version
3083 number apart at the last hyphen in the string (if there
3084 is one) to determine the <var>upstream_version</var> and
3085 <var>debian_revision</var>. The absence of a
3086 <var>debian_revision</var> is equivalent to a
3087 <var>debian_revision</var> of <tt>0</tt>.
3094 When comparing two version numbers, first the <var>epoch</var>
3095 of each are compared, then the <var>upstream_version</var> if
3096 <var>epoch</var> is equal, and then <var>debian_revision</var>
3097 if <var>upstream_version</var> is also equal.
3098 <var>epoch</var> is compared numerically. The
3099 <var>upstream_version</var> and <var>debian_revision</var>
3100 parts are compared by the package management system using the
3101 following algorithm:
3105 The strings are compared from left to right.
3109 First the initial part of each string consisting entirely of
3110 non-digit characters is determined. These two parts (one of
3111 which may be empty) are compared lexically. If a difference
3112 is found it is returned. The lexical comparison is a
3113 comparison of ASCII values modified so that all the letters
3114 sort earlier than all the non-letters and so that a tilde
3115 sorts before anything, even the end of a part. For example,
3116 the following parts are in sorted order from earliest to
3117 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3118 <tt>a</tt>.<footnote>
3119 One common use of <tt>~</tt> is for upstream pre-releases.
3120 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3121 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3126 Then the initial part of the remainder of each string which
3127 consists entirely of digit characters is determined. The
3128 numerical values of these two parts are compared, and any
3129 difference found is returned as the result of the comparison.
3130 For these purposes an empty string (which can only occur at
3131 the end of one or both version strings being compared) counts
3136 These two steps (comparing and removing initial non-digit
3137 strings and initial digit strings) are repeated until a
3138 difference is found or both strings are exhausted.
3142 Note that the purpose of epochs is to allow us to leave behind
3143 mistakes in version numbering, and to cope with situations
3144 where the version numbering scheme changes. It is
3145 <em>not</em> intended to cope with version numbers containing
3146 strings of letters which the package management system cannot
3147 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3148 silly orderings.<footnote>
3149 The author of this manual has heard of a package whose
3150 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3151 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3157 <sect1 id="f-Description">
3158 <heading><tt>Description</tt></heading>
3161 In a source or binary control file, the <tt>Description</tt>
3162 field contains a description of the binary package, consisting
3163 of two parts, the synopsis or the short description, and the
3164 long description. The field's format is as follows:
3169 Description: <single line synopsis>
3170 <extended description over several lines>
3175 The lines in the extended description can have these formats:
3181 Those starting with a single space are part of a paragraph.
3182 Successive lines of this form will be word-wrapped when
3183 displayed. The leading space will usually be stripped off.
3187 Those starting with two or more spaces. These will be
3188 displayed verbatim. If the display cannot be panned
3189 horizontally, the displaying program will line wrap them "hard"
3190 (i.e., without taking account of word breaks). If it can they
3191 will be allowed to trail off to the right. None, one or two
3192 initial spaces may be deleted, but the number of spaces
3193 deleted from each line will be the same (so that you can have
3194 indenting work correctly, for example).
3198 Those containing a single space followed by a single full stop
3199 character. These are rendered as blank lines. This is the
3200 <em>only</em> way to get a blank line<footnote>
3201 Completely empty lines will not be rendered as blank lines.
3202 Instead, they will cause the parser to think you're starting
3203 a whole new record in the control file, and will therefore
3204 likely abort with an error.
3209 Those containing a space, a full stop and some more characters.
3210 These are for future expansion. Do not use them.
3216 Do not use tab characters. Their effect is not predictable.
3220 See <ref id="descriptions"> for further information on this.
3224 In a <file>.changes</file> file, the <tt>Description</tt>
3225 field contains a summary of the descriptions for the packages
3226 being uploaded. For this case, the first line of the field
3227 value (the part on the same line as <tt>Description:</tt>) is
3228 always empty. The content of the field is expressed as
3229 continuation lines, one line per package. Each line is
3230 indented by one space and contains the name of a binary
3231 package, a space, a hyphen (<tt>-</tt>), a space, and the
3232 short description line from that package.
3236 <sect1 id="f-Distribution">
3237 <heading><tt>Distribution</tt></heading>
3240 In a <file>.changes</file> file or parsed changelog output
3241 this contains the (space-separated) name(s) of the
3242 distribution(s) where this version of the package should
3243 be installed. Valid distributions are determined by the
3244 archive maintainers.<footnote>
3245 Example distribution names in the Debian archive used in
3246 <file>.changes</file> files are:
3247 <taglist compact="compact">
3248 <tag><em>unstable</em></tag>
3250 This distribution value refers to the
3251 <em>developmental</em> part of the Debian distribution
3252 tree. Most new packages, new upstream versions of
3253 packages and bug fixes go into the <em>unstable</em>
3257 <tag><em>experimental</em></tag>
3259 The packages with this distribution value are deemed
3260 by their maintainers to be high risk. Oftentimes they
3261 represent early beta or developmental packages from
3262 various sources that the maintainers want people to
3263 try, but are not ready to be a part of the other parts
3264 of the Debian distribution tree.
3269 Others are used for updating stable releases or for
3270 security uploads. More information is available in the
3271 Debian Developer's Reference, section "The Debian
3275 The Debian archive software only supports listing a single
3276 distribution. Migration of packages to other distributions is
3277 handled outside of the upload process.
3282 <heading><tt>Date</tt></heading>
3285 This field includes the date the package was built or last
3286 edited. It must be in the same format as the <var>date</var>
3287 in a <file>debian/changelog</file> entry.
3291 The value of this field is usually extracted from the
3292 <file>debian/changelog</file> file - see
3293 <ref id="dpkgchangelog">).
3297 <sect1 id="f-Format">
3298 <heading><tt>Format</tt></heading>
3301 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3302 files, this field declares the format version of that file.
3303 The syntax of the field value is the same as that of
3304 a <qref id="f-Version">package version number</qref> except
3305 that no epoch or Debian revision is allowed. The format
3306 described in this document is <tt>&changesversion;</tt>.
3310 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3311 Debian source control</qref> files, this field declares the
3312 format of the source package. The field value is used by
3313 programs acting on a source package to interpret the list of
3314 files in the source package and determine how to unpack it.
3315 The syntax of the field value is a numeric major revision, a
3316 period, a numeric minor revision, and then an optional subtype
3317 after whitespace, which if specified is an alphanumeric word
3318 in parentheses. The subtype is optional in the syntax but may
3319 be mandatory for particular source format revisions.
3321 The source formats currently supported by the Debian archive
3322 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3323 and <tt>3.0 (quilt)</tt>.
3328 <sect1 id="f-Urgency">
3329 <heading><tt>Urgency</tt></heading>
3332 This is a description of how important it is to upgrade to
3333 this version from previous ones. It consists of a single
3334 keyword taking one of the values <tt>low</tt>,
3335 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3336 <tt>critical</tt><footnote>
3337 Other urgency values are supported with configuration
3338 changes in the archive software but are not used in Debian.
3339 The urgency affects how quickly a package will be considered
3340 for inclusion into the <tt>testing</tt> distribution and
3341 gives an indication of the importance of any fixes included
3342 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3343 treated as synonymous.
3344 </footnote> (not case-sensitive) followed by an optional
3345 commentary (separated by a space) which is usually in
3346 parentheses. For example:
3349 Urgency: low (HIGH for users of diversions)
3355 The value of this field is usually extracted from the
3356 <file>debian/changelog</file> file - see
3357 <ref id="dpkgchangelog">.
3361 <sect1 id="f-Changes">
3362 <heading><tt>Changes</tt></heading>
3365 This field contains the human-readable changes data, describing
3366 the differences between the last version and the current one.
3370 The first line of the field value (the part on the same line
3371 as <tt>Changes:</tt>) is always empty. The content of the
3372 field is expressed as continuation lines, with each line
3373 indented by at least one space. Blank lines must be
3374 represented by a line consisting only of a space and a full
3379 The value of this field is usually extracted from the
3380 <file>debian/changelog</file> file - see
3381 <ref id="dpkgchangelog">).
3385 Each version's change information should be preceded by a
3386 "title" line giving at least the version, distribution(s)
3387 and urgency, in a human-readable way.
3391 If data from several versions is being returned the entry
3392 for the most recent version should be returned first, and
3393 entries should be separated by the representation of a
3394 blank line (the "title" line may also be followed by the
3395 representation of a blank line).
3399 <sect1 id="f-Binary">
3400 <heading><tt>Binary</tt></heading>
3403 This field is a list of binary packages. Its syntax and
3404 meaning varies depending on the control file in which it
3409 When it appears in the <file>.dsc</file> file, it lists binary
3410 packages which a source package can produce, separated by
3412 A space after each comma is conventional.
3413 </footnote>. It may span multiple lines. The source package
3414 does not necessarily produce all of these binary packages for
3415 every architecture. The source control file doesn't contain
3416 details of which architectures are appropriate for which of
3417 the binary packages.
3421 When it appears in a <file>.changes</file> file, it lists the
3422 names of the binary packages being uploaded, separated by
3423 whitespace (not commas). It may span multiple lines.
3427 <sect1 id="f-Installed-Size">
3428 <heading><tt>Installed-Size</tt></heading>
3431 This field appears in the control files of binary packages,
3432 and in the <file>Packages</file> files. It gives an estimate
3433 of the total amount of disk space required to install the
3434 named package. Actual installed size may vary based on block
3435 size, file system properties, or actions taken by package
3440 The disk space is given as the integer value of the estimated
3441 installed size in bytes, divided by 1024 and rounded up.
3445 <sect1 id="f-Files">
3446 <heading><tt>Files</tt></heading>
3449 This field contains a list of files with information about
3450 each one. The exact information and syntax varies with
3455 In all cases, Files is a multiline field. The first line of
3456 the field value (the part on the same line as <tt>Files:</tt>)
3457 is always empty. The content of the field is expressed as
3458 continuation lines, one line per file. Each line must be
3459 indented by one space and contain a number of sub-fields,
3460 separated by spaces, as described below.
3464 In the <file>.dsc</file> file, each line contains the MD5
3465 checksum, size and filename of the tar file and (if
3466 applicable) diff file which make up the remainder of the
3467 source package<footnote>
3468 That is, the parts which are not the <tt>.dsc</tt>.
3469 </footnote>. For example:
3472 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3473 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3475 The exact forms of the filenames are described
3476 in <ref id="pkg-sourcearchives">.
3480 In the <file>.changes</file> file this contains one line per
3481 file being uploaded. Each line contains the MD5 checksum,
3482 size, section and priority and the filename. For example:
3485 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3486 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3487 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3488 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3490 The <qref id="f-Section">section</qref>
3491 and <qref id="f-Priority">priority</qref> are the values of
3492 the corresponding fields in the main source control file. If
3493 no section or priority is specified then <tt>-</tt> should be
3494 used, though section and priority values must be specified for
3495 new packages to be installed properly.
3499 The special value <tt>byhand</tt> for the section in a
3500 <tt>.changes</tt> file indicates that the file in question
3501 is not an ordinary package file and must by installed by
3502 hand by the distribution maintainers. If the section is
3503 <tt>byhand</tt> the priority should be <tt>-</tt>.
3507 If a new Debian revision of a package is being shipped and
3508 no new original source archive is being distributed the
3509 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3510 entry for the original source archive
3511 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3512 but the <file>.changes</file> file should leave it out. In
3513 this case the original source archive on the distribution
3514 site must match exactly, byte-for-byte, the original
3515 source archive which was used to generate the
3516 <file>.dsc</file> file and diff which are being uploaded.</p>
3519 <sect1 id="f-Closes">
3520 <heading><tt>Closes</tt></heading>
3523 A space-separated list of bug report numbers that the upload
3524 governed by the .changes file closes.
3528 <sect1 id="f-Homepage">
3529 <heading><tt>Homepage</tt></heading>
3532 The URL of the web site for this package, preferably (when
3533 applicable) the site from which the original source can be
3534 obtained and any additional upstream documentation or
3535 information may be found. The content of this field is a
3536 simple URL without any surrounding characters such as
3541 <sect1 id="f-Checksums">
3542 <heading><tt>Checksums-Sha1</tt>
3543 and <tt>Checksums-Sha256</tt></heading>
3546 These fields contain a list of files with a checksum and size
3547 for each one. Both <tt>Checksums-Sha1</tt>
3548 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3549 only in the checksum algorithm used: SHA-1
3550 for <tt>Checksums-Sha1</tt> and SHA-256
3551 for <tt>Checksums-Sha256</tt>.
3555 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3556 multiline fields. The first line of the field value (the part
3557 on the same line as <tt>Checksums-Sha1:</tt>
3558 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3559 of the field is expressed as continuation lines, one line per
3560 file. Each line consists of the checksum, a space, the file
3561 size, a space, and the file name. For example (from
3562 a <file>.changes</file> file):
3565 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3566 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3567 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3568 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3570 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3571 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3572 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3573 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3578 In the <file>.dsc</file> file, these fields should list all
3579 files that make up the source package. In
3580 the <file>.changes</file> file, these fields should list all
3581 files being uploaded. The list of files in these fields
3582 must match the list of files in the <tt>Files</tt> field.
3588 <heading>User-defined fields</heading>
3591 Additional user-defined fields may be added to the
3592 source package control file. Such fields will be
3593 ignored, and not copied to (for example) binary or
3594 source package control files or upload control files.
3598 If you wish to add additional unsupported fields to
3599 these output files you should use the mechanism
3604 Fields in the main source control information file with
3605 names starting <tt>X</tt>, followed by one or more of
3606 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3607 be copied to the output files. Only the part of the
3608 field name after the hyphen will be used in the output
3609 file. Where the letter <tt>B</tt> is used the field
3610 will appear in binary package control files, where the
3611 letter <tt>S</tt> is used in source package control
3612 files and where <tt>C</tt> is used in upload control
3613 (<tt>.changes</tt>) files.
3617 For example, if the main source information control file
3620 XBS-Comment: I stand between the candle and the star.
3622 then the binary and source package control files will contain the
3625 Comment: I stand between the candle and the star.
3634 <chapt id="maintainerscripts">
3635 <heading>Package maintainer scripts and installation procedure</heading>
3638 <heading>Introduction to package maintainer scripts</heading>
3641 It is possible to supply scripts as part of a package which
3642 the package management system will run for you when your
3643 package is installed, upgraded or removed.
3647 These scripts are the files <prgn>preinst</prgn>,
3648 <prgn>postinst</prgn>, <prgn>prerm</prgn> and
3649 <prgn>postrm</prgn> in the control area of the package.
3650 They must be proper executable files; if they are scripts
3651 (which is recommended), they must start with the usual
3652 <tt>#!</tt> convention. They should be readable and
3653 executable by anyone, and must not be world-writable.
3657 The package management system looks at the exit status from
3658 these scripts. It is important that they exit with a
3659 non-zero status if there is an error, so that the package
3660 management system can stop its processing. For shell
3661 scripts this means that you <em>almost always</em> need to
3662 use <tt>set -e</tt> (this is usually true when writing shell
3663 scripts, in fact). It is also important, of course, that
3664 they exit with a zero status if everything went well.
3668 Additionally, packages interacting with users using
3669 <tt>debconf</tt> in the <prgn>postinst</prgn> script should
3670 install a <prgn>config</prgn> script in the control area,
3671 see <ref id="maintscriptprompt"> for details.
3675 When a package is upgraded a combination of the scripts from
3676 the old and new packages is called during the upgrade
3677 procedure. If your scripts are going to be at all
3678 complicated you need to be aware of this, and may need to
3679 check the arguments to your scripts.
3683 Broadly speaking the <prgn>preinst</prgn> is called before
3684 (a particular version of) a package is installed, and the
3685 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3686 before (a version of) a package is removed and the
3687 <prgn>postrm</prgn> afterwards.
3691 Programs called from maintainer scripts should not normally
3692 have a path prepended to them. Before installation is
3693 started, the package management system checks to see if the
3694 programs <prgn>ldconfig</prgn>,
3695 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3696 and <prgn>update-rc.d</prgn> can be found via the
3697 <tt>PATH</tt> environment variable. Those programs, and any
3698 other program that one would expect to be in the
3699 <tt>PATH</tt>, should thus be invoked without an absolute
3700 pathname. Maintainer scripts should also not reset the
3701 <tt>PATH</tt>, though they might choose to modify it by
3702 prepending or appending package-specific directories. These
3703 considerations really apply to all shell scripts.</p>
3706 <sect id="idempotency">
3707 <heading>Maintainer scripts idempotency</heading>
3710 It is necessary for the error recovery procedures that the
3711 scripts be idempotent. This means that if it is run
3712 successfully, and then it is called again, it doesn't bomb
3713 out or cause any harm, but just ensures that everything is
3714 the way it ought to be. If the first call failed, or
3715 aborted half way through for some reason, the second call
3716 should merely do the things that were left undone the first
3717 time, if any, and exit with a success status if everything
3719 This is so that if an error occurs, the user interrupts
3720 <prgn>dpkg</prgn> or some other unforeseen circumstance
3721 happens you don't leave the user with a badly-broken
3722 package when <prgn>dpkg</prgn> attempts to repeat the
3728 <sect id="controllingterminal">
3729 <heading>Controlling terminal for maintainer scripts</heading>
3732 Maintainer scripts are not guaranteed to run with a controlling
3733 terminal and may not be able to interact with the user. They
3734 must be able to fall back to noninteractive behavior if no
3735 controlling terminal is available. Maintainer scripts that
3736 prompt via a program conforming to the Debian Configuration
3737 Management Specification (see <ref id="maintscriptprompt">) may
3738 assume that program will handle falling back to noninteractive
3743 For high-priority prompts without a reasonable default answer,
3744 maintainer scripts may abort if there is no controlling
3745 terminal. However, this situation should be avoided if at all
3746 possible, since it prevents automated or unattended installs.
3747 In most cases, users will consider this to be a bug in the
3752 <sect id="exitstatus">
3753 <heading>Exit status</heading>
3756 Each script must return a zero exit status for
3757 success, or a nonzero one for failure, since the package
3758 management system looks for the exit status of these scripts
3759 and determines what action to take next based on that datum.
3763 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3768 <list compact="compact">
3770 <var>new-preinst</var> <tt>install</tt>
3773 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3776 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3779 <var>old-preinst</var> <tt>abort-upgrade</tt>
3780 <var>new-version</var>
3785 <list compact="compact">
3787 <var>postinst</var> <tt>configure</tt>
3788 <var>most-recently-configured-version</var>
3791 <var>old-postinst</var> <tt>abort-upgrade</tt>
3792 <var>new-version</var>
3795 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3796 <tt>in-favour</tt> <var>package</var>
3797 <var>new-version</var>
3800 <var>postinst</var> <tt>abort-remove</tt>
3803 <var>deconfigured's-postinst</var>
3804 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3805 <var>failed-install-package</var> <var>version</var>
3806 [<tt>removing</tt> <var>conflicting-package</var>
3812 <list compact="compact">
3814 <var>prerm</var> <tt>remove</tt>
3817 <var>old-prerm</var> <tt>upgrade</tt>
3818 <var>new-version</var>
3821 <var>new-prerm</var> <tt>failed-upgrade</tt>
3822 <var>old-version</var>
3825 <var>conflictor's-prerm</var> <tt>remove</tt>
3826 <tt>in-favour</tt> <var>package</var>
3827 <var>new-version</var>
3830 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3831 <tt>in-favour</tt> <var>package-being-installed</var>
3832 <var>version</var> [<tt>removing</tt>
3833 <var>conflicting-package</var>
3839 <list compact="compact">
3841 <var>postrm</var> <tt>remove</tt>
3844 <var>postrm</var> <tt>purge</tt>
3847 <var>old-postrm</var> <tt>upgrade</tt>
3848 <var>new-version</var>
3851 <var>new-postrm</var> <tt>failed-upgrade</tt>
3852 <var>old-version</var>
3855 <var>new-postrm</var> <tt>abort-install</tt>
3858 <var>new-postrm</var> <tt>abort-install</tt>
3859 <var>old-version</var>
3862 <var>new-postrm</var> <tt>abort-upgrade</tt>
3863 <var>old-version</var>
3866 <var>disappearer's-postrm</var> <tt>disappear</tt>
3867 <var>overwriter</var>
3868 <var>overwriter-version</var>
3874 <sect id="unpackphase">
3875 <heading>Details of unpack phase of installation or upgrade</heading>
3878 The procedure on installation/upgrade/overwrite/disappear
3879 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3880 stage of <tt>dpkg --install</tt>) is as follows. In each
3881 case, if a major error occurs (unless listed below) the
3882 actions are, in general, run backwards - this means that the
3883 maintainer scripts are run with different arguments in
3884 reverse order. These are the "error unwind" calls listed
3891 If a version of the package is already installed, call
3892 <example compact="compact">
3893 <var>old-prerm</var> upgrade <var>new-version</var>
3897 If the script runs but exits with a non-zero
3898 exit status, <prgn>dpkg</prgn> will attempt:
3899 <example compact="compact">
3900 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3902 If this works, the upgrade continues. If this
3903 does not work, the error unwind:
3904 <example compact="compact">
3905 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3907 If this works, then the old-version is
3908 "Installed", if not, the old version is in a
3909 "Half-Configured" state.
3915 If a "conflicting" package is being removed at the same time,
3916 or if any package will be broken (due to <tt>Breaks</tt>):
3919 If <tt>--auto-deconfigure</tt> is
3920 specified, call, for each package to be deconfigured
3921 due to <tt>Breaks</tt>:
3922 <example compact="compact">
3923 <var>deconfigured's-prerm</var> deconfigure \
3924 in-favour <var>package-being-installed</var> <var>version</var>
3927 <example compact="compact">
3928 <var>deconfigured's-postinst</var> abort-deconfigure \
3929 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3931 The deconfigured packages are marked as
3932 requiring configuration, so that if
3933 <tt>--install</tt> is used they will be
3934 configured again if possible.
3937 If any packages depended on a conflicting
3938 package being removed and <tt>--auto-deconfigure</tt> is
3939 specified, call, for each such package:
3940 <example compact="compact">
3941 <var>deconfigured's-prerm</var> deconfigure \
3942 in-favour <var>package-being-installed</var> <var>version</var> \
3943 removing <var>conflicting-package</var> <var>version</var>
3946 <example compact="compact">
3947 <var>deconfigured's-postinst</var> abort-deconfigure \
3948 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3949 removing <var>conflicting-package</var> <var>version</var>
3951 The deconfigured packages are marked as
3952 requiring configuration, so that if
3953 <tt>--install</tt> is used they will be
3954 configured again if possible.
3957 To prepare for removal of each conflicting package, call:
3958 <example compact="compact">
3959 <var>conflictor's-prerm</var> remove \
3960 in-favour <var>package</var> <var>new-version</var>
3963 <example compact="compact">
3964 <var>conflictor's-postinst</var> abort-remove \
3965 in-favour <var>package</var> <var>new-version</var>
3974 If the package is being upgraded, call:
3975 <example compact="compact">
3976 <var>new-preinst</var> upgrade <var>old-version</var>
3978 If this fails, we call:
3980 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3987 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3989 is called. If this works, then the old version
3990 is in an "Installed" state, or else it is left
3991 in an "Unpacked" state.
3996 If it fails, then the old version is left
3997 in an "Half-Installed" state.
4004 Otherwise, if the package had some configuration
4005 files from a previous version installed (i.e., it
4006 is in the "configuration files only" state):
4007 <example compact="compact">
4008 <var>new-preinst</var> install <var>old-version</var>
4012 <var>new-postrm</var> abort-install <var>old-version</var>
4014 If this fails, the package is left in a
4015 "Half-Installed" state, which requires a
4016 reinstall. If it works, the packages is left in
4017 a "Config-Files" state.
4020 Otherwise (i.e., the package was completely purged):
4021 <example compact="compact">
4022 <var>new-preinst</var> install
4025 <example compact="compact">
4026 <var>new-postrm</var> abort-install
4028 If the error-unwind fails, the package is in a
4029 "Half-Installed" phase, and requires a
4030 reinstall. If the error unwind works, the
4031 package is in a not installed state.
4038 The new package's files are unpacked, overwriting any
4039 that may be on the system already, for example any
4040 from the old version of the same package or from
4041 another package. Backups of the old files are kept
4042 temporarily, and if anything goes wrong the package
4043 management system will attempt to put them back as
4044 part of the error unwind.
4048 It is an error for a package to contain files which
4049 are on the system in another package, unless
4050 <tt>Replaces</tt> is used (see <ref id="replaces">).
4052 The following paragraph is not currently the case:
4053 Currently the <tt>- - force-overwrite</tt> flag is
4054 enabled, downgrading it to a warning, but this may not
4060 It is a more serious error for a package to contain a
4061 plain file or other kind of non-directory where another
4062 package has a directory (again, unless
4063 <tt>Replaces</tt> is used). This error can be
4064 overridden if desired using
4065 <tt>--force-overwrite-dir</tt>, but this is not
4070 Packages which overwrite each other's files produce
4071 behavior which, though deterministic, is hard for the
4072 system administrator to understand. It can easily
4073 lead to "missing" programs if, for example, a package
4074 is installed which overwrites a file from another
4075 package, and is then removed again.<footnote>
4076 Part of the problem is due to what is arguably a
4077 bug in <prgn>dpkg</prgn>.
4082 A directory will never be replaced by a symbolic link
4083 to a directory or vice versa; instead, the existing
4084 state (symlink or not) will be left alone and
4085 <prgn>dpkg</prgn> will follow the symlink if there is
4094 If the package is being upgraded, call
4095 <example compact="compact">
4096 <var>old-postrm</var> upgrade <var>new-version</var>
4100 If this fails, <prgn>dpkg</prgn> will attempt:
4101 <example compact="compact">
4102 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4104 If this works, installation continues. If not,
4106 <example compact="compact">
4107 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4109 If this fails, the old version is left in a
4110 "Half-Installed" state. If it works, dpkg now
4112 <example compact="compact">
4113 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4115 If this fails, the old version is left in a
4116 "Half-Installed" state. If it works, dpkg now
4118 <example compact="compact">
4119 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4121 If this fails, the old version is in an
4128 This is the point of no return - if
4129 <prgn>dpkg</prgn> gets this far, it won't back off
4130 past this point if an error occurs. This will
4131 leave the package in a fairly bad state, which
4132 will require a successful re-installation to clear
4133 up, but it's when <prgn>dpkg</prgn> starts doing
4134 things that are irreversible.
4139 Any files which were in the old version of the package
4140 but not in the new are removed.
4144 The new file list replaces the old.
4148 The new maintainer scripts replace the old.
4152 Any packages all of whose files have been overwritten
4153 during the installation, and which aren't required for
4154 dependencies, are considered to have been removed.
4155 For each such package
4158 <prgn>dpkg</prgn> calls:
4159 <example compact="compact">
4160 <var>disappearer's-postrm</var> disappear \
4161 <var>overwriter</var> <var>overwriter-version</var>
4165 The package's maintainer scripts are removed.
4168 It is noted in the status database as being in a
4169 sane state, namely not installed (any conffiles
4170 it may have are ignored, rather than being
4171 removed by <prgn>dpkg</prgn>). Note that
4172 disappearing packages do not have their prerm
4173 called, because <prgn>dpkg</prgn> doesn't know
4174 in advance that the package is going to
4181 Any files in the package we're unpacking that are also
4182 listed in the file lists of other packages are removed
4183 from those lists. (This will lobotomize the file list
4184 of the "conflicting" package if there is one.)
4188 The backup files made during installation, above, are
4194 The new package's status is now sane, and recorded as
4199 Here is another point of no return - if the
4200 conflicting package's removal fails we do not unwind
4201 the rest of the installation; the conflicting package
4202 is left in a half-removed limbo.
4207 If there was a conflicting package we go and do the
4208 removal actions (described below), starting with the
4209 removal of the conflicting package's files (any that
4210 are also in the package being installed have already
4211 been removed from the conflicting package's file list,
4212 and so do not get removed now).
4218 <sect id="configdetails"><heading>Details of configuration</heading>
4221 When we configure a package (this happens with <tt>dpkg
4222 --install</tt> and <tt>dpkg --configure</tt>), we first
4223 update any <tt>conffile</tt>s and then call:
4224 <example compact="compact">
4225 <var>postinst</var> configure <var>most-recently-configured-version</var>
4230 No attempt is made to unwind after errors during
4231 configuration. If the configuration fails, the package is in
4232 a "Failed Config" state, and an error message is generated.
4236 If there is no most recently configured version
4237 <prgn>dpkg</prgn> will pass a null argument.
4240 Historical note: Truly ancient (pre-1997) versions of
4241 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4242 (including the angle brackets) in this case. Even older
4243 ones did not pass a second argument at all, under any
4244 circumstance. Note that upgrades using such an old dpkg
4245 version are unlikely to work for other reasons, even if
4246 this old argument behavior is handled by your postinst script.
4252 <sect id="removedetails"><heading>Details of removal and/or
4253 configuration purging</heading>
4259 <example compact="compact">
4260 <var>prerm</var> remove
4264 If prerm fails during replacement due to conflict
4266 <var>conflictor's-postinst</var> abort-remove \
4267 in-favour <var>package</var> <var>new-version</var>
4271 <var>postinst</var> abort-remove
4275 If this fails, the package is in a "Half-Configured"
4276 state, or else it remains "Installed".
4280 The package's files are removed (except <tt>conffile</tt>s).
4283 <example compact="compact">
4284 <var>postrm</var> remove
4288 If it fails, there's no error unwind, and the package is in
4289 an "Half-Installed" state.
4294 All the maintainer scripts except the <prgn>postrm</prgn>
4299 If we aren't purging the package we stop here. Note
4300 that packages which have no <prgn>postrm</prgn> and no
4301 <tt>conffile</tt>s are automatically purged when
4302 removed, as there is no difference except for the
4303 <prgn>dpkg</prgn> status.
4307 The <tt>conffile</tt>s and any backup files
4308 (<tt>~</tt>-files, <tt>#*#</tt> files,
4309 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4314 <example compact="compact">
4315 <var>postrm</var> purge
4319 If this fails, the package remains in a "Config-Files"
4324 The package's file list is removed.
4333 <chapt id="relationships">
4334 <heading>Declaring relationships between packages</heading>
4336 <sect id="depsyntax">
4337 <heading>Syntax of relationship fields</heading>
4340 These fields all have a uniform syntax. They are a list of
4341 package names separated by commas.
4345 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4346 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4347 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4348 control file fields of the package, which declare
4349 dependencies on other packages, the package names listed may
4350 also include lists of alternative package names, separated
4351 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4352 if any one of the alternative packages is installed, that
4353 part of the dependency is considered to be satisfied.
4357 All of the fields except for <tt>Provides</tt> may restrict
4358 their applicability to particular versions of each named
4359 package. This is done in parentheses after each individual
4360 package name; the parentheses should contain a relation from
4361 the list below followed by a version number, in the format
4362 described in <ref id="f-Version">.
4366 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4367 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4368 strictly earlier, earlier or equal, exactly equal, later or
4369 equal and strictly later, respectively. The deprecated
4370 forms <tt><</tt> and <tt>></tt> were used to mean
4371 earlier/later or equal, rather than strictly earlier/later,
4372 so they should not appear in new packages (though
4373 <prgn>dpkg</prgn> still supports them).
4377 Whitespace may appear at any point in the version
4378 specification subject to the rules in <ref
4379 id="controlsyntax">, and must appear where it's necessary to
4380 disambiguate; it is not otherwise significant. All of the
4381 relationship fields may span multiple lines. For
4382 consistency and in case of future changes to
4383 <prgn>dpkg</prgn> it is recommended that a single space be
4384 used after a version relationship and before a version
4385 number; it is also conventional to put a single space after
4386 each comma, on either side of each vertical bar, and before
4387 each open parenthesis. When wrapping a relationship field, it
4388 is conventional to do so after a comma and before the space
4389 following that comma.
4393 For example, a list of dependencies might appear as:
4394 <example compact="compact">
4397 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4402 Relationships may be restricted to a certain set of
4403 architectures. This is indicated in brackets after each
4404 individual package name and the optional version specification.
4405 The brackets enclose a list of Debian architecture names
4406 separated by whitespace. Exclamation marks may be prepended to
4407 each of the names. (It is not permitted for some names to be
4408 prepended with exclamation marks while others aren't.)
4412 For build relationship fields
4413 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4414 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>), if
4415 the current Debian host architecture is not in this list and
4416 there are no exclamation marks in the list, or it is in the list
4417 with a prepended exclamation mark, the package name and the
4418 associated version specification are ignored completely for the
4419 purposes of defining the relationships.
4424 <example compact="compact">
4426 Build-Depends-Indep: texinfo
4427 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4428 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4430 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4431 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4432 <tt>gnumach-dev</tt> only on hurd-i386.
4436 For binary relationship fields, the architecture restriction
4437 syntax is only supported in the source package control
4438 file <file>debian/control</file>. When the corresponding binary
4439 package control file is generated, the relationship will either
4440 be omitted or included without the architecture restriction
4441 based on the architecture of the binary package. This means
4442 that architecture restrictions must not be used in binary
4443 relationship fields for architecture-independent packages
4444 (<tt>Architecture: all</tt>).
4449 <example compact="compact">
4450 Depends: foo [i386], bar [amd64]
4452 becomes <tt>Depends: foo</tt> when the package is built on
4453 the <tt>i386</tt> architecture, <tt>Depends: bar</tt> when the
4454 package is built on the <tt>amd64</tt> architecture, and omitted
4455 entirely in binary packages built on all other architectures.
4459 If the architecture-restricted dependency is part of a set of
4460 alternatives using <tt>|</tt>, that alternative is ignored
4461 completely on architectures that do not match the restriction.
4463 <example compact="compact">
4464 Build-Depends: foo [!i386] | bar [!amd64]
4466 is equivalent to <tt>bar</tt> on the i386 architecture, to
4467 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4468 bar</tt> on all other architectures.
4472 Relationships may also be restricted to a certain set of
4473 architectures using architecture wildcards. The syntax for
4474 declaring such restrictions is the same as declaring
4475 restrictions using a certain set of architectures without
4476 architecture wildcards. For example:
4477 <example compact="compact">
4478 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4480 is equivalent to <tt>foo</tt> on architectures using the Linux
4481 kernel and any cpu, <tt>bar</tt> on architectures using any
4482 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4483 using a kernel other than Linux.
4487 Note that the binary package relationship fields such as
4488 <tt>Depends</tt> appear in one of the binary package
4489 sections of the control file, whereas the build-time
4490 relationships such as <tt>Build-Depends</tt> appear in the
4491 source package section of the control file (which is the
4496 <sect id="binarydeps">
4497 <heading>Binary Dependencies - <tt>Depends</tt>,
4498 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4499 <tt>Pre-Depends</tt>
4503 Packages can declare in their control file that they have
4504 certain relationships to other packages - for example, that
4505 they may not be installed at the same time as certain other
4506 packages, and/or that they depend on the presence of others.
4510 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4511 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4512 <tt>Breaks</tt> and <tt>Conflicts</tt> control file fields.
4513 <tt>Breaks</tt> is described in <ref id="breaks">, and
4514 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4515 rest are described below.
4519 These seven fields are used to declare a dependency
4520 relationship by one package on another. Except for
4521 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4522 depending (binary) package's control file.
4523 (<tt>Enhances</tt> appears in the recommending package's
4524 control file, and <tt>Breaks</tt> appears in the version of
4525 depended-on package which causes the named package to
4530 A <tt>Depends</tt> field takes effect <em>only</em> when a
4531 package is to be configured. It does not prevent a package
4532 being on the system in an unconfigured state while its
4533 dependencies are unsatisfied, and it is possible to replace
4534 a package whose dependencies are satisfied and which is
4535 properly installed with a different version whose
4536 dependencies are not and cannot be satisfied; when this is
4537 done the depending package will be left unconfigured (since
4538 attempts to configure it will give errors) and will not
4539 function properly. If it is necessary, a
4540 <tt>Pre-Depends</tt> field can be used, which has a partial
4541 effect even when a package is being unpacked, as explained
4542 in detail below. (The other three dependency fields,
4543 <tt>Recommends</tt>, <tt>Suggests</tt> and
4544 <tt>Enhances</tt>, are only used by the various front-ends
4545 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4546 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4550 For this reason packages in an installation run are usually
4551 all unpacked first and all configured later; this gives
4552 later versions of packages with dependencies on later
4553 versions of other packages the opportunity to have their
4554 dependencies satisfied.
4558 In case of circular dependencies, since installation or
4559 removal order honoring the dependency order can't be
4560 established, dependency loops are broken at some point
4561 (based on rules below), and some packages may not be able to
4562 rely on their dependencies being present when being
4563 installed or removed, depending on which side of the break
4564 of the circular dependency loop they happen to be on. If one
4565 of the packages in the loop has no postinst script, then the
4566 cycle will be broken at that package, so as to ensure that
4567 all postinst scripts run with the dependencies properly
4568 configured if this is possible. Otherwise the breaking point
4573 The <tt>Depends</tt> field thus allows package maintainers
4574 to impose an order in which packages should be configured.
4578 The meaning of the five dependency fields is as follows:
4580 <tag><tt>Depends</tt></tag>
4583 This declares an absolute dependency. A package will
4584 not be configured unless all of the packages listed in
4585 its <tt>Depends</tt> field have been correctly
4590 The <tt>Depends</tt> field should be used if the
4591 depended-on package is required for the depending
4592 package to provide a significant amount of
4597 The <tt>Depends</tt> field should also be used if the
4598 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4599 <prgn>postrm</prgn> scripts require the package to be
4600 present in order to run. Note, however, that the
4601 <prgn>postrm</prgn> cannot rely on any non-essential
4602 packages to be present during the <tt>purge</tt>
4606 <tag><tt>Recommends</tt></tag>
4609 This declares a strong, but not absolute, dependency.
4613 The <tt>Recommends</tt> field should list packages
4614 that would be found together with this one in all but
4615 unusual installations.
4619 <tag><tt>Suggests</tt></tag>
4621 This is used to declare that one package may be more
4622 useful with one or more others. Using this field
4623 tells the packaging system and the user that the
4624 listed packages are related to this one and can
4625 perhaps enhance its usefulness, but that installing
4626 this one without them is perfectly reasonable.
4629 <tag><tt>Enhances</tt></tag>
4631 This field is similar to Suggests but works in the
4632 opposite direction. It is used to declare that a
4633 package can enhance the functionality of another
4637 <tag><tt>Pre-Depends</tt></tag>
4640 This field is like <tt>Depends</tt>, except that it
4641 also forces <prgn>dpkg</prgn> to complete installation
4642 of the packages named before even starting the
4643 installation of the package which declares the
4644 pre-dependency, as follows:
4648 When a package declaring a pre-dependency is about to
4649 be <em>unpacked</em> the pre-dependency can be
4650 satisfied if the depended-on package is either fully
4651 configured, <em>or even if</em> the depended-on
4652 package(s) are only unpacked or in the "Half-Configured"
4653 state, provided that they have been configured
4654 correctly at some point in the past (and not removed
4655 or partially removed since). In this case, both the
4656 previously-configured and currently unpacked or
4657 "Half-Configured" versions must satisfy any version
4658 clause in the <tt>Pre-Depends</tt> field.
4662 When the package declaring a pre-dependency is about
4663 to be <em>configured</em>, the pre-dependency will be
4664 treated as a normal <tt>Depends</tt>, that is, it will
4665 be considered satisfied only if the depended-on
4666 package has been correctly configured.
4670 <tt>Pre-Depends</tt> should be used sparingly,
4671 preferably only by packages whose premature upgrade or
4672 installation would hamper the ability of the system to
4673 continue with any upgrade that might be in progress.
4677 <tt>Pre-Depends</tt> are also required if the
4678 <prgn>preinst</prgn> script depends on the named
4679 package. It is best to avoid this situation if
4687 When selecting which level of dependency to use you should
4688 consider how important the depended-on package is to the
4689 functionality of the one declaring the dependency. Some
4690 packages are composed of components of varying degrees of
4691 importance. Such a package should list using
4692 <tt>Depends</tt> the package(s) which are required by the
4693 more important components. The other components'
4694 requirements may be mentioned as Suggestions or
4695 Recommendations, as appropriate to the components' relative
4701 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4704 When one binary package declares that it breaks another,
4705 <prgn>dpkg</prgn> will refuse to allow the package which
4706 declares <tt>Breaks</tt> be installed unless the broken
4707 package is deconfigured first, and it will refuse to
4708 allow the broken package to be reconfigured.
4712 A package will not be regarded as causing breakage merely
4713 because its configuration files are still installed; it must
4714 be at least "Half-Installed".
4718 A special exception is made for packages which declare that
4719 they break their own package name or a virtual package which
4720 they provide (see below): this does not count as a real
4725 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4726 version clause; such a <tt>Breaks</tt> is introduced in the
4727 version of an (implicit or explicit) dependency which violates
4728 an assumption or reveals a bug in earlier versions of the broken
4729 package, or which takes over a file from earlier versions of the
4730 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
4731 will inform higher-level package management tools that the
4732 broken package must be upgraded before the new one.
4736 If the breaking package also overwrites some files from the
4737 older package, it should use <tt>Replaces</tt> to ensure this
4738 goes smoothly. See <ref id="replaces"> for a full discussion
4739 of taking over files from other packages, including how to
4740 use <tt>Breaks</tt> in those cases.
4744 Many of the cases where <tt>Breaks</tt> should be used were
4745 previously handled with <tt>Conflicts</tt>
4746 because <tt>Breaks</tt> did not yet exist.
4747 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
4748 See <ref id="conflicts"> for more information about the
4753 <sect id="conflicts">
4754 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4757 When one binary package declares a conflict with another
4758 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4759 refuse to allow them to be installed on the system at the
4760 same time. This is a stronger restriction than <tt>Breaks</tt>,
4761 which just prevents both packages from being configured at the
4762 same time. Conflicting packages cannot be unpacked on the
4763 system at the same time.
4767 If one package is to be installed, the other must be removed
4768 first. If the package being installed is marked as replacing
4769 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
4770 normally be used in this case) the one on the system, or the one
4771 on the system is marked as deselected, or both packages are
4772 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
4773 automatically remove the package which is causing the conflict.
4774 Otherwise, it will halt the installation of the new package with
4775 an error. This mechanism is specifically designed to produce an
4776 error when the installed package is <tt>Essential</tt>, but the
4781 A package will not cause a conflict merely because its
4782 configuration files are still installed; it must be at least
4787 A special exception is made for packages which declare a
4788 conflict with their own package name, or with a virtual
4789 package which they provide (see below): this does not
4790 prevent their installation, and allows a package to conflict
4791 with others providing a replacement for it. You use this
4792 feature when you want the package in question to be the only
4793 package providing some feature.
4797 Normally, <tt>Breaks</tt> should be used instead
4798 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
4799 stronger restriction on the ordering of package installation or
4800 upgrade and can make it more difficult for the package manager
4801 to find a correct solution to an upgrade or installation
4802 problem. <tt>Breaks</tt> should be used
4804 <item>when moving a file from one package to another (see
4805 <ref id="replaces">),</item>
4806 <item>when splitting a package (a special case of the previous
4808 <item>when the breaking package exposes a bug in or interacts
4809 badly with particular versions of the broken
4812 <tt>Conflicts</tt> should be used
4814 <item>when two packages provide the same file and will
4815 continue to do so,</item>
4816 <item>in conjunction with <tt>Provides</tt> when only one
4817 package providing a given virtual facility may be installed
4818 at a time (see <ref id="virtual">),</item>
4819 <item>in other cases where one must prevent simultaneous
4820 installation of two packages for reasons that are ongoing
4821 (not fixed in a later version of one of the packages) or
4822 that must prevent both packages from being unpacked at the
4823 same time, not just configured.</item>
4825 Be aware that adding <tt>Conflicts</tt> is normally not the best
4826 solution when two packages provide the same files. Depending on
4827 the reason for that conflict, using alternatives or renaming the
4828 files is often a better approach. See, for
4829 example, <ref id="binaries">.
4833 Neither <tt>Breaks</tt> nor <tt>Conflicts</tt> should be used
4834 unless two packages cannot be installed at the same time or
4835 installing them both causes one of them to be broken or
4836 unusable. Having similar functionality or performing the same
4837 tasks as another package is not sufficient reason to
4838 declare <tt>Breaks</tt> or <tt>Conflicts</tt> with that package.
4842 A <tt>Conflicts</tt> entry may have an "earlier than" version
4843 clause if the reason for the conflict is corrected in a later
4844 version of one of the packages. However, normally the presence
4845 of an "earlier than" version clause is a sign
4846 that <tt>Breaks</tt> should have been used instead. An "earlier
4847 than" version clause in <tt>Conflicts</tt>
4848 prevents <prgn>dpkg</prgn> from upgrading or installing the
4849 package which declares such a conflict until the upgrade or
4850 removal of the conflicted-with package has been completed, which
4851 is a strong restriction.
4855 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4859 As well as the names of actual ("concrete") packages, the
4860 package relationship fields <tt>Depends</tt>,
4861 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4862 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4863 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4864 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4865 may mention "virtual packages".
4869 A <em>virtual package</em> is one which appears in the
4870 <tt>Provides</tt> control file field of another package.
4871 The effect is as if the package(s) which provide a
4872 particular virtual package name had been listed by name
4873 everywhere the virtual package name appears. (See also <ref
4878 If there are both concrete and virtual packages of the same
4879 name, then the dependency may be satisfied (or the conflict
4880 caused) by either the concrete package with the name in
4881 question or any other concrete package which provides the
4882 virtual package with the name in question. This is so that,
4883 for example, supposing we have
4884 <example compact="compact">
4887 </example> and someone else releases an enhanced version of
4888 the <tt>bar</tt> package they can say:
4889 <example compact="compact">
4893 and the <tt>bar-plus</tt> package will now also satisfy the
4894 dependency for the <tt>foo</tt> package.
4898 If a relationship field has a version number attached, only real
4899 packages will be considered to see whether the relationship is
4900 satisfied (or the prohibition violated, for a conflict or
4901 breakage). In other words, if a version number is specified,
4902 this is a request to ignore all <tt>Provides</tt> for that
4903 package name and consider only real packages. The package
4904 manager will assume that a package providing that virtual
4905 package is not of the "right" version. A <tt>Provides</tt>
4906 field may not contain version numbers, and the version number of
4907 the concrete package which provides a particular virtual package
4908 will not be considered when considering a dependency on or
4909 conflict with the virtual package name.<footnote>
4910 It is possible that a future release of <prgn>dpkg</prgn> may
4911 add the ability to specify a version number for each virtual
4912 package it provides. This feature is not yet present,
4913 however, and is expected to be used only infrequently.
4918 To specify which of a set of real packages should be the default
4919 to satisfy a particular dependency on a virtual package, list
4920 the real package as an alternative before the virtual one.
4924 If the virtual package represents a facility that can only be
4925 provided by one real package at a time, such as
4926 the <package>mail-transport-agent</package> virtual package that
4927 requires installation of a binary that would conflict with all
4928 other providers of that virtual package (see
4929 <ref id="mail-transport-agents">), all packages providing that
4930 virtual package should also declare a conflict with it
4931 using <tt>Conflicts</tt>. This will ensure that at most one
4932 provider of that virtual package is unpacked or installed at a
4937 <sect id="replaces"><heading>Overwriting files and replacing
4938 packages - <tt>Replaces</tt></heading>
4941 Packages can declare in their control file that they should
4942 overwrite files in certain other packages, or completely
4943 replace other packages. The <tt>Replaces</tt> control file
4944 field has these two distinct purposes.
4947 <sect1><heading>Overwriting files in other packages</heading>
4950 It is usually an error for a package to contain files which
4951 are on the system in another package. However, if the
4952 overwriting package declares that it <tt>Replaces</tt> the one
4953 containing the file being overwritten, then <prgn>dpkg</prgn>
4954 will replace the file from the old package with that from the
4955 new. The file will no longer be listed as "owned" by the old
4956 package and will be taken over by the new package.
4957 Normally, <tt>Breaks</tt> should be used in conjunction
4958 with <tt>Replaces</tt>.<footnote>
4959 To see why <tt>Breaks</tt> is normally needed in addition
4960 to <tt>Replaces</tt>, consider the case of a file in the
4961 package <package>foo</package> being taken over by the
4962 package <package>foo-data</package>.
4963 <tt>Replaces</tt> will allow <package>foo-data</package> to
4964 be installed and take over that file. However,
4965 without <tt>Breaks</tt>, nothing
4966 requires <package>foo</package> to be upgraded to a newer
4967 version that knows it does not include that file and instead
4968 depends on <package>foo-data</package>. Nothing would
4969 prevent the new <package>foo-data</package> package from
4970 being installed and then removed, removing the file that it
4971 took over from <package>foo</package>. After that
4972 operation, the package manager would think the system was in
4973 a consistent state, but the <package>foo</package> package
4974 would be missing one of its files.
4979 For example, if a package <package>foo</package> is split
4980 into <package>foo</package> and <package>foo-data</package>
4981 starting at version 1.2-3, <package>foo-data</package> would
4983 <example compact="compact">
4984 Replaces: foo (<< 1.2-3)
4985 Breaks: foo (<< 1.2-3)
4987 in its control file. The new version of the
4988 package <package>foo</package> would normally have the field
4989 <example compact="compact">
4990 Depends: foo-data (>= 1.2-3)
4992 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
4993 the files moved into <package>foo-data</package> are not
4994 required for normal operation).
4998 If a package is completely replaced in this way, so that
4999 <prgn>dpkg</prgn> does not know of any files it still
5000 contains, it is considered to have "disappeared". It will
5001 be marked as not wanted on the system (selected for
5002 removal) and not installed. Any <tt>conffile</tt>s
5003 details noted for the package will be ignored, as they
5004 will have been taken over by the overwriting package. The
5005 package's <prgn>postrm</prgn> script will be run with a
5006 special argument to allow the package to do any final
5007 cleanup required. See <ref id="mscriptsinstact">.
5009 Replaces is a one way relationship. You have to install
5010 the replacing package after the replaced package.
5015 For this usage of <tt>Replaces</tt>, virtual packages (see
5016 <ref id="virtual">) are not considered when looking at a
5017 <tt>Replaces</tt> field. The packages declared as being
5018 replaced must be mentioned by their real names.
5022 This usage of <tt>Replaces</tt> only takes effect when both
5023 packages are at least partially on the system at once. It is
5024 not relevant if the packages conflict unless the conflict has
5029 <sect1><heading>Replacing whole packages, forcing their
5033 Second, <tt>Replaces</tt> allows the packaging system to
5034 resolve which package should be removed when there is a
5035 conflict (see <ref id="conflicts">). This usage only takes
5036 effect when the two packages <em>do</em> conflict, so that the
5037 two usages of this field do not interfere with each other.
5041 In this situation, the package declared as being replaced
5042 can be a virtual package, so for example, all mail
5043 transport agents (MTAs) would have the following fields in
5044 their control files:
5045 <example compact="compact">
5046 Provides: mail-transport-agent
5047 Conflicts: mail-transport-agent
5048 Replaces: mail-transport-agent
5050 ensuring that only one MTA can be installed at any one
5051 time. See <ref id="virtual"> for more information about this
5056 <sect id="sourcebinarydeps">
5057 <heading>Relationships between source and binary packages -
5058 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5059 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5063 Source packages that require certain binary packages to be
5064 installed or absent at the time of building the package
5065 can declare relationships to those binary packages.
5069 This is done using the <tt>Build-Depends</tt>,
5070 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5071 <tt>Build-Conflicts-Indep</tt> control file fields.
5075 Build-dependencies on "build-essential" binary packages can be
5076 omitted. Please see <ref id="pkg-relations"> for more information.
5080 The dependencies and conflicts they define must be satisfied
5081 (as defined earlier for binary packages) in order to invoke
5082 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5084 There is no Build-Depends-Arch; this role is essentially
5085 met with Build-Depends. Anyone building the
5086 <tt>build-indep</tt> and <tt>binary-indep</tt> targets is
5087 assumed to be building the whole package, and therefore
5088 installation of all build dependencies is required.
5091 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5092 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5093 not yet know how to check for its existence, and
5094 <tt>binary-arch</tt>. The purpose of the original split
5095 between <tt>Build-Depends</tt> and
5096 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5097 wouldn't need to install extra packages needed only for the
5098 binary-indep targets. But without a build-arch/build-indep
5099 split, this didn't work, since most of the work is done in
5100 the build target, not in the binary target.
5104 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5105 <tt>binary-arch</tt></tag>
5107 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5108 fields must be satisfied when these targets are invoked.
5110 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5111 and <tt>binary-indep</tt></tag>
5113 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5114 <tt>Build-Depends-Indep</tt>, and
5115 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5116 these targets are invoked.
5124 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5127 Packages containing shared libraries must be constructed with
5128 a little care to make sure that the shared library is always
5129 available. This is especially important for packages whose
5130 shared libraries are vitally important, such as the C library
5131 (currently <tt>libc6</tt>).
5135 Packages involving shared libraries should be split up into
5136 several binary packages. This section mostly deals with how
5137 this separation is to be accomplished; rules for files within
5138 the shared library packages are in <ref id="libraries"> instead.
5141 <sect id="sharedlibs-runtime">
5142 <heading>Run-time shared libraries</heading>
5145 The run-time shared library needs to be placed in a package
5146 whose name changes whenever the shared object version
5149 Since it is common place to install several versions of a
5150 package that just provides shared libraries, it is a
5151 good idea that the library package should not
5152 contain any extraneous non-versioned files, unless they
5153 happen to be in versioned directories.</p>
5155 The most common mechanism is to place it in a package
5157 <package><var>libraryname</var><var>soversion</var></package>,
5158 where <file><var>soversion</var></file> is the version number
5159 in the soname of the shared library<footnote>
5160 The soname is the shared object name: it's the thing
5161 that has to match exactly between building an executable
5162 and running it for the dynamic linker to be able run the
5163 program. For example, if the soname of the library is
5164 <file>libfoo.so.6</file>, the library package would be
5165 called <file>libfoo6</file>.
5167 Alternatively, if it would be confusing to directly append
5168 <var>soversion</var> to <var>libraryname</var> (e.g. because
5169 <var>libraryname</var> itself ends in a number), you may use
5170 <package><var>libraryname</var>-<var>soversion</var></package> and
5171 <package><var>libraryname</var>-<var>soversion</var>-dev</package>
5176 If you have several shared libraries built from the same
5177 source tree you may lump them all together into a single
5178 shared library package, provided that you change all of
5179 their sonames at once (so that you don't get filename
5180 clashes if you try to install different versions of the
5181 combined shared libraries package).
5185 The package should install the shared libraries under
5186 their normal names. For example, the <package>libgdbm3</package>
5187 package should install <file>libgdbm.so.3.0.0</file> as
5188 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5189 renamed or re-linked by any <prgn>prerm</prgn> or
5190 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5191 of renaming things safely without affecting running programs,
5192 and attempts to interfere with this are likely to lead to
5197 Shared libraries should not be installed executable, since
5198 the dynamic linker does not require this and trying to
5199 execute a shared library usually results in a core dump.
5203 The run-time library package should include the symbolic link that
5204 <prgn>ldconfig</prgn> would create for the shared libraries.
5205 For example, the <package>libgdbm3</package> package should include
5206 a symbolic link from <file>/usr/lib/libgdbm.so.3</file> to
5207 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5208 linker (for example <prgn>ld.so</prgn> or
5209 <prgn>ld-linux.so.*</prgn>) can find the library between the
5210 time that <prgn>dpkg</prgn> installs it and the time that
5211 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5213 The package management system requires the library to be
5214 placed before the symbolic link pointing to it in the
5215 <file>.deb</file> file. This is so that when
5216 <prgn>dpkg</prgn> comes to install the symlink
5217 (overwriting the previous symlink pointing at an older
5218 version of the library), the new shared library is already
5219 in place. In the past, this was achieved by creating the
5220 library in the temporary packaging directory before
5221 creating the symlink. Unfortunately, this was not always
5222 effective, since the building of the tar file in the
5223 <file>.deb</file> depended on the behavior of the underlying
5224 file system. Some file systems (such as reiserfs) reorder
5225 the files so that the order of creation is forgotten.
5226 Since version 1.7.0, <prgn>dpkg</prgn>
5227 reorders the files itself as necessary when building a
5228 package. Thus it is no longer important to concern
5229 oneself with the order of file creation.
5233 <sect1 id="ldconfig">
5234 <heading><tt>ldconfig</tt></heading>
5237 Any package installing shared libraries in one of the default
5238 library directories of the dynamic linker (which are currently
5239 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5240 listed in <file>/etc/ld.so.conf</file><footnote>
5242 <list compact="compact">
5243 <item>/usr/local/lib</item>
5244 <item>/usr/lib/libc5-compat</item>
5245 <item>/lib/libc5-compat</item>
5248 must use <prgn>ldconfig</prgn> to update the shared library
5253 The package maintainer scripts must only call
5254 <prgn>ldconfig</prgn> under these circumstances:
5255 <list compact="compact">
5256 <item>When the <prgn>postinst</prgn> script is run with a
5257 first argument of <tt>configure</tt>, the script must call
5258 <prgn>ldconfig</prgn>, and may optionally invoke
5259 <prgn>ldconfig</prgn> at other times.
5261 <item>When the <prgn>postrm</prgn> script is run with a
5262 first argument of <tt>remove</tt>, the script should call
5263 <prgn>ldconfig</prgn>.
5268 During install or upgrade, the preinst is called before
5269 the new files are installed, so calling "ldconfig" is
5270 pointless. The preinst of an existing package can also be
5271 called if an upgrade fails. However, this happens during
5272 the critical time when a shared libs may exist on-disk
5273 under a temporary name. Thus, it is dangerous and
5274 forbidden by current policy to call "ldconfig" at this
5279 When a package is installed or upgraded, "postinst
5280 configure" runs after the new files are safely on-disk.
5281 Since it is perfectly safe to invoke ldconfig
5282 unconditionally in a postinst, it is OK for a package to
5283 simply put ldconfig in its postinst without checking the
5284 argument. The postinst can also be called to recover from
5285 a failed upgrade. This happens before any new files are
5286 unpacked, so there is no reason to call "ldconfig" at this
5291 For a package that is being removed, prerm is
5292 called with all the files intact, so calling ldconfig is
5293 useless. The other calls to "prerm" happen in the case of
5294 upgrade at a time when all the files of the old package
5295 are on-disk, so again calling "ldconfig" is pointless.
5299 postrm, on the other hand, is called with the "remove"
5300 argument just after the files are removed, so this is
5301 the proper time to call "ldconfig" to notify the system
5302 of the fact that the shared libraries from the package
5303 are removed. The postrm can be called at several other
5304 times. At the time of "postrm purge", "postrm
5305 abort-install", or "postrm abort-upgrade", calling
5306 "ldconfig" is useless because the shared lib files are
5307 not on-disk. However, when "postrm" is invoked with
5308 arguments "upgrade", "failed-upgrade", or "disappear", a
5309 shared lib may exist on-disk under a temporary filename.
5317 <sect id="sharedlibs-support-files">
5318 <heading>Shared library support files</heading>
5321 If your package contains files whose names do not change with
5322 each change in the library shared object version, you must not
5323 put them in the shared library package. Otherwise, several
5324 versions of the shared library cannot be installed at the same
5325 time without filename clashes, making upgrades and transitions
5326 unnecessarily difficult.
5330 It is recommended that supporting files and run-time support
5331 programs that do not need to be invoked manually by users, but
5332 are nevertheless required for the package to function, be placed
5333 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5334 preferably under <file>/usr/lib/</file><var>package-name</var>.
5335 If the program or file is architecture independent, the
5336 recommendation is for it to be placed in a subdirectory of
5337 <file>/usr/share</file> instead, preferably under
5338 <file>/usr/share/</file><var>package-name</var>. Following the
5339 <var>package-name</var> naming convention ensures that the file
5340 names change when the shared object version changes.
5344 Run-time support programs that use the shared library but are
5345 not required for the library to function or files used by the
5346 shared library that can be used by any version of the shared
5347 library package should instead be put in a separate package.
5348 This package might typically be named
5349 <package><var>libraryname</var>-tools</package>; note the
5350 absence of the <var>soversion</var> in the package name.
5354 Files and support programs only useful when compiling software
5355 against the library should be included in the development
5356 package for the library.<footnote>
5357 For example, a <file><var>package-name</var>-config</file>
5358 script or <package>pkg-config</package> configuration files.
5363 <sect id="sharedlibs-static">
5364 <heading>Static libraries</heading>
5367 The static library (<file><var>libraryname.a</var></file>)
5368 is usually provided in addition to the shared version.
5369 It is placed into the development package (see below).
5373 In some cases, it is acceptable for a library to be
5374 available in static form only; these cases include:
5376 <item>libraries for languages whose shared library support
5377 is immature or unstable</item>
5378 <item>libraries whose interfaces are in flux or under
5379 development (commonly the case when the library's
5380 major version number is zero, or where the ABI breaks
5381 across patchlevels)</item>
5382 <item>libraries which are explicitly intended to be
5383 available only in static form by their upstream
5388 <sect id="sharedlibs-dev">
5389 <heading>Development files</heading>
5392 If there are development files associated with a shared library,
5393 the source package needs to generate a binary development package
5394 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5395 or if you prefer only to support one development version at a
5396 time, <package><var>libraryname</var>-dev</package>. Installing
5397 the development package must result in installation of all the
5398 development files necessary for compiling programs against that
5399 shared library.<footnote>
5400 This wording allows the development files to be split into
5401 several packages, such as a separate architecture-independent
5402 <package><var>libraryname</var>-headers</package>, provided that
5403 the development package depends on all the required additional
5409 In case several development versions of a library exist, you may
5410 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5411 <ref id="conflicts">) to ensure that the user only installs one
5412 development version at a time (as different development versions are
5413 likely to have the same header files in them, which would cause a
5414 filename clash if both were installed).
5418 The development package should contain a symlink for the associated
5419 shared library without a version number. For example, the
5420 <package>libgdbm-dev</package> package should include a symlink
5421 from <file>/usr/lib/libgdbm.so</file> to
5422 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5423 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5424 <file>libgdbm.so</file> when compiling dynamically.
5428 <sect id="sharedlibs-intradeps">
5429 <heading>Dependencies between the packages of the same library</heading>
5432 Typically the development version should have an exact
5433 version dependency on the runtime library, to make sure that
5434 compilation and linking happens correctly. The
5435 <tt>${binary:Version}</tt> substitution variable can be
5436 useful for this purpose.
5438 Previously, <tt>${Source-Version}</tt> was used, but its name
5439 was confusing and it has been deprecated since dpkg 1.13.19.
5444 <sect id="sharedlibs-shlibdeps">
5445 <heading>Dependencies between the library and other packages -
5446 the <tt>shlibs</tt> system</heading>
5449 If a package contains a binary or library which links to a
5450 shared library, we must ensure that when the package is
5451 installed on the system, all of the libraries needed are
5452 also installed. This requirement led to the creation of the
5453 <tt>shlibs</tt> system, which is very simple in its design:
5454 any package which <em>provides</em> a shared library also
5455 provides information on the package dependencies required to
5456 ensure the presence of this library, and any package which
5457 <em>uses</em> a shared library uses this information to
5458 determine the dependencies it requires. The files which
5459 contain the mapping from shared libraries to the necessary
5460 dependency information are called <file>shlibs</file> files.
5464 When a package is built which contains any shared libraries, it
5465 must provide a <file>shlibs</file> file for other packages to
5466 use. When a package is built which contains any shared
5467 libraries or compiled binaries, it must run
5468 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5469 on these to determine the libraries used and hence the
5470 dependencies needed by this package.<footnote>
5472 <prgn>dpkg-shlibdeps</prgn> will use a program
5473 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
5474 the libraries directly needed by the binaries or shared
5475 libraries in the package.
5479 We say that a binary <tt>foo</tt> <em>directly</em> uses
5480 a library <tt>libbar</tt> if it is explicitly linked
5481 with that library (that is, the library is listed in the ELF
5482 <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
5483 to the link line when the binary is created). Other
5484 libraries that are needed by <tt>libbar</tt> are linked
5485 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5486 linker will load them automatically when it loads
5487 <tt>libbar</tt>. A package should depend on the libraries
5488 it directly uses, but not the libraries it indirectly uses.
5489 The dependencies for those libraries will automatically pull
5490 in the other libraries.
5494 A good example of where this helps is the following. We
5495 could update <tt>libimlib</tt> with a new version that
5496 supports a new graphics format called dgf (but retaining the
5497 same major version number) and depends on <tt>libdgf</tt>.
5498 If we used <prgn>ldd</prgn> to add dependencies for every
5499 library directly or indirectly linked with a binary, every
5500 package that uses <tt>libimlib</tt> would need to be
5501 recompiled so it would also depend on <tt>libdgf</tt> or it
5502 wouldn't run due to missing symbols. Since dependencies are
5503 only added based on ELF <tt>NEEDED</tt> attribute, packages
5504 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
5505 having the dependency on <tt>libdgf</tt> and so they would
5506 not need rebuilding.
5512 In the following sections, we will first describe where the
5513 various <tt>shlibs</tt> files are to be found, then how to
5514 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5515 file format and how to create them if your package contains a
5520 <heading>The <tt>shlibs</tt> files present on the system</heading>
5523 There are several places where <tt>shlibs</tt> files are
5524 found. The following list gives them in the order in which
5526 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5527 (The first one which gives the required information is used.)
5533 <p><file>debian/shlibs.local</file></p>
5536 This lists overrides for this package. This file should
5537 normally not be used, but may be needed temporarily in
5538 unusual situations to work around bugs in other packages,
5539 or in unusual cases where the normally declared dependency
5540 information in the installed <file>shlibs</file> file for
5541 a library cannot be used. This file overrides information
5542 obtained from any other source.
5547 <p><file>/etc/dpkg/shlibs.override</file></p>
5550 This lists global overrides. This list is normally
5551 empty. It is maintained by the local system
5557 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5560 When packages are being built,
5561 any <file>debian/shlibs</file> files are copied into the
5562 control file area of the temporary build directory and
5563 given the name <file>shlibs</file>. These files give
5564 details of any shared libraries included in the same
5566 An example may help here. Let us say that the source
5567 package <tt>foo</tt> generates two binary
5568 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
5569 When building the binary packages, the two packages are
5570 created in the directories <file>debian/libfoo2</file>
5571 and <file>debian/foo-runtime</file> respectively.
5572 (<file>debian/tmp</file> could be used instead of one of
5573 these.) Since <tt>libfoo2</tt> provides the
5574 <tt>libfoo</tt> shared library, it will require a
5575 <tt>shlibs</tt> file, which will be installed in
5576 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually to
5577 become <file>/var/lib/dpkg/info/libfoo2.shlibs</file>.
5578 When <prgn>dpkg-shlibdeps</prgn> is run on the
5579 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
5581 the <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5582 determine whether <tt>foo-prog</tt>'s library
5583 dependencies are satisfied by any of the libraries
5584 provided by <tt>libfoo2</tt>. For this reason,
5585 <prgn>dpkg-shlibdeps</prgn> must only be run once all of
5586 the individual binary packages' <tt>shlibs</tt> files
5587 have been installed into the build directory.
5593 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5596 These are the <file>shlibs</file> files corresponding to
5597 all of the packages installed on the system, and are
5598 maintained by the relevant package maintainers.
5603 <p><file>/etc/dpkg/shlibs.default</file></p>
5606 This file lists any shared libraries whose packages
5607 have failed to provide correct <file>shlibs</file> files.
5608 It was used when the <file>shlibs</file> setup was first
5609 introduced, but it is now normally empty. It is
5610 maintained by the <tt>dpkg</tt> maintainer.
5618 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5619 <file>shlibs</file> files</heading>
5623 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5624 into your <file>debian/rules</file> file. If your package
5625 contains only compiled binaries and libraries (but no scripts),
5626 you can use a command such as:
5627 <example compact="compact">
5628 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5629 debian/tmp/usr/lib/*
5631 Otherwise, you will need to explicitly list the compiled
5632 binaries and libraries.<footnote>
5633 If you are using <tt>debhelper</tt>, the
5634 <prgn>dh_shlibdeps</prgn> program will do this work for you.
5635 It will also correctly handle multi-binary packages.
5640 This command puts the dependency information into the
5641 <file>debian/substvars</file> file, which is then used by
5642 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5643 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5644 field in the control file for this to work.
5648 If you have multiple binary packages, you will need to call
5649 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5650 compiled libraries or binaries. In such a case, you will
5651 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5652 utilities to specify a different <file>substvars</file> file.
5656 If you are creating a udeb for use in the Debian Installer,
5657 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
5658 should use the dependency line of type <tt>udeb</tt> by
5659 adding the <tt>-tudeb</tt> option<footnote>
5660 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5661 will automatically add this option if it knows it is
5663 </footnote>. If there is no dependency line of
5664 type <tt>udeb</tt> in the <file>shlibs</file>
5665 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the regular
5670 For more details on <prgn>dpkg-shlibdeps</prgn>, please see
5671 <ref id="pkg-dpkg-shlibdeps"> and
5672 <manref name="dpkg-shlibdeps" section="1">.
5677 <heading>The <file>shlibs</file> File Format</heading>
5680 Each <file>shlibs</file> file has the same format. Lines
5681 beginning with <tt>#</tt> are considered to be comments and
5682 are ignored. Each line is of the form:
5683 <example compact="compact">
5684 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5689 We will explain this by reference to the example of the
5690 <tt>zlib1g</tt> package, which (at the time of writing)
5691 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5695 <var>type</var> is an optional element that indicates the type
5696 of package for which the line is valid. The only type currently
5697 in use is <tt>udeb</tt>. The colon and space after the type are
5702 <var>library-name</var> is the name of the shared library,
5703 in this case <tt>libz</tt>. (This must match the name part
5704 of the soname, see below.)
5708 <var>soname-version</var> is the version part of the soname of
5709 the library. The soname is the thing that must exactly match
5710 for the library to be recognized by the dynamic linker, and is
5712 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5713 example, <tt>libz.so.1</tt>.<footnote>
5714 This can be determined using the command
5715 <example compact="compact">
5716 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5719 The version part is the part which comes after
5720 <tt>.so.</tt>, so in our case, it is <tt>1</tt>. The soname may
5721 instead be of the form
5722 <tt><var>name</var>-<var>major-version</var>.so</tt>, such
5723 as <tt>libdb-4.8.so</tt>, in which case the name would
5724 be <tt>libdb</tt> and the version would be <tt>4.8</tt>.
5728 <var>dependencies</var> has the same syntax as a dependency
5729 field in a binary package control file. It should give
5730 details of which packages are required to satisfy a binary
5731 built against the version of the library contained in the
5732 package. See <ref id="depsyntax"> for details.
5736 In our example, if the first version of the <tt>zlib1g</tt>
5737 package which contained a minor number of at least
5738 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5739 <tt>shlibs</tt> entry for this library could say:
5740 <example compact="compact">
5741 libz 1 zlib1g (>= 1:1.1.3)
5743 The version-specific dependency is to avoid warnings from
5744 the dynamic linker about using older shared libraries with
5749 As zlib1g also provides a udeb containing the shared library,
5750 there would also be a second line:
5751 <example compact="compact">
5752 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5758 <heading>Providing a <file>shlibs</file> file</heading>
5761 If your package provides a shared library, you need to create
5762 a <file>shlibs</file> file following the format described above.
5763 It is usual to call this file <file>debian/shlibs</file> (but if
5764 you have multiple binary packages, you might want to call it
5765 <file>debian/shlibs.<var>package</var></file> instead). Then
5766 let <file>debian/rules</file> install it in the control area:
5767 <example compact="compact">
5768 install -m644 debian/shlibs debian/tmp/DEBIAN
5770 or, in the case of a multi-binary package:
5771 <example compact="compact">
5772 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5774 An alternative way of doing this is to create the
5775 <file>shlibs</file> file in the control area directly from
5776 <file>debian/rules</file> without using a <file>debian/shlibs</file>
5777 file at all,<footnote>
5778 This is what <prgn>dh_makeshlibs</prgn> in
5779 the <package>debhelper</package> suite does. If your package
5780 also has a udeb that provides a shared
5781 library, <prgn>dh_makeshlibs</prgn> can automatically generate
5782 the <tt>udeb:</tt> lines if you specify the name of the udeb
5783 with the <tt>--add-udeb</tt> option.
5785 since the <file>debian/shlibs</file> file itself is ignored by
5786 <prgn>dpkg-shlibdeps</prgn>.
5790 As <prgn>dpkg-shlibdeps</prgn> reads the
5791 <file>DEBIAN/shlibs</file> files in all of the binary packages
5792 being built from this source package, all of the
5793 <file>DEBIAN/shlibs</file> files should be installed before
5794 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5802 <chapt id="opersys"><heading>The Operating System</heading>
5805 <heading>File system hierarchy</heading>
5809 <heading>File System Structure</heading>
5812 The location of all installed files and directories must
5813 comply with the Filesystem Hierarchy Standard (FHS),
5814 version 2.3, with the exceptions noted below, and except
5815 where doing so would violate other terms of Debian
5816 Policy. The following exceptions to the FHS apply:
5821 The optional rules related to user specific
5822 configuration files for applications are stored in
5823 the user's home directory are relaxed. It is
5824 recommended that such files start with the
5825 '<tt>.</tt>' character (a "dot file"), and if an
5826 application needs to create more than one dot file
5827 then the preferred placement is in a subdirectory
5828 with a name starting with a '.' character, (a "dot
5829 directory"). In this case it is recommended the
5830 configuration files not start with the '.'
5836 The requirement for amd64 to use <file>/lib64</file>
5837 for 64 bit binaries is removed.
5842 The requirement for object files, internal binaries, and
5843 libraries, including <file>libc.so.*</file>, to be located
5844 directly under <file>/lib{,32}</file> and
5845 <file>/usr/lib{,32}</file> is amended, permitting files
5846 to instead be installed to
5847 <file>/lib/<var>triplet</var></file> and
5848 <file>/usr/lib/<var>triplet</var></file>, where
5849 <tt><var>triplet</var></tt> is the value returned by
5850 <tt>dpkg-architecture -qDEB_HOST_GNU_TYPE</tt> for the
5851 architecture of the package. Packages may <em>not</em>
5852 install files to any <var>triplet</var> path other
5853 than the one matching the architecture of that package;
5854 for instance, an <tt>Architecture: amd64</tt> package
5855 containing 32-bit x86 libraries may not install these
5856 libraries to <file>/usr/lib/i486-linux-gnu</file>.
5858 This is necessary in order to reserve the directories for
5859 use in cross-installation of library packages from other
5860 architectures, as part of the planned deployment of
5865 Applications may also use a single subdirectory under
5866 <file>/usr/lib/<var>triplet</var></file>.
5869 The execution time linker/loader, ld*, must still be made
5870 available in the existing location under /lib or /lib64
5871 since this is part of the ELF ABI for the architecture.
5876 The requirement that
5877 <file>/usr/local/share/man</file> be "synonymous"
5878 with <file>/usr/local/man</file> is relaxed to a
5883 The requirement that windowmanagers with a single
5884 configuration file call it <file>system.*wmrc</file>
5885 is removed, as is the restriction that the window
5886 manager subdirectory be named identically to the
5887 window manager name itself.
5892 The requirement that boot manager configuration
5893 files live in <file>/etc</file>, or at least are
5894 symlinked there, is relaxed to a recommendation.
5899 The following directories in the root filesystem are
5900 additionally allowed: <file>/sys</file> and
5901 <file>/selinux</file>. <footnote>These directories
5902 are used as mount points to mount virtual filesystems
5903 to get access to kernel information.</footnote>
5910 The version of this document referred here can be
5911 found in the <tt>debian-policy</tt> package or on <url
5912 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5913 name="FHS (Debian copy)"> alongside this manual (or, if
5914 you have the <package>debian-policy</package> installed,
5916 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5917 (local copy)">). The
5918 latest version, which may be a more recent version, may
5920 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5921 Specific questions about following the standard may be
5922 asked on the <tt>debian-devel</tt> mailing list, or
5923 referred to the FHS mailing list (see the
5924 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
5930 <heading>Site-specific programs</heading>
5933 As mandated by the FHS, packages must not place any
5934 files in <file>/usr/local</file>, either by putting them in
5935 the file system archive to be unpacked by <prgn>dpkg</prgn>
5936 or by manipulating them in their maintainer scripts.
5940 However, the package may create empty directories below
5941 <file>/usr/local</file> so that the system administrator knows
5942 where to place site-specific files. These are not
5943 directories <em>in</em> <file>/usr/local</file>, but are
5944 children of directories in <file>/usr/local</file>. These
5945 directories (<file>/usr/local/*/dir/</file>)
5946 should be removed on package removal if they are
5951 Note that this applies only to
5952 directories <em>below</em> <file>/usr/local</file>,
5953 not <em>in</em> <file>/usr/local</file>. Packages must
5954 not create sub-directories in the
5955 directory <file>/usr/local</file> itself, except those
5956 listed in FHS, section 4.5. However, you may create
5957 directories below them as you wish. You must not remove
5958 any of the directories listed in 4.5, even if you created
5963 Since <file>/usr/local</file> can be mounted read-only from a
5964 remote server, these directories must be created and
5965 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
5966 maintainer scripts and not be included in the
5967 <file>.deb</file> archive. These scripts must not fail if
5968 either of these operations fail.
5972 For example, the <tt>emacsen-common</tt> package could
5973 contain something like
5974 <example compact="compact">
5975 if [ ! -e /usr/local/share/emacs ]
5977 if mkdir /usr/local/share/emacs 2>/dev/null
5979 chown root:staff /usr/local/share/emacs
5980 chmod 2775 /usr/local/share/emacs
5984 in its <prgn>postinst</prgn> script, and
5985 <example compact="compact">
5986 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
5987 rmdir /usr/local/share/emacs 2>/dev/null || true
5989 in the <prgn>prerm</prgn> script. (Note that this form is
5990 used to ensure that if the script is interrupted, the
5991 directory <file>/usr/local/share/emacs</file> will still be
5996 If you do create a directory in <file>/usr/local</file> for
5997 local additions to a package, you should ensure that
5998 settings in <file>/usr/local</file> take precedence over the
5999 equivalents in <file>/usr</file>.
6003 However, because <file>/usr/local</file> and its contents are
6004 for exclusive use of the local administrator, a package
6005 must not rely on the presence or absence of files or
6006 directories in <file>/usr/local</file> for normal operation.
6010 The <file>/usr/local</file> directory itself and all the
6011 subdirectories created by the package should (by default) have
6012 permissions 2775 (group-writable and set-group-id) and be
6013 owned by <tt>root:staff</tt>.
6018 <heading>The system-wide mail directory</heading>
6020 The system-wide mail directory
6021 is <file>/var/mail</file>. This directory is part of the
6022 base system and should not be owned by any particular mail
6023 agents. The use of the old
6024 location <file>/var/spool/mail</file> is deprecated, even
6025 though the spool may still be physically located there.
6031 <heading>Users and groups</heading>
6034 <heading>Introduction</heading>
6036 The Debian system can be configured to use either plain or
6041 Some user ids (UIDs) and group ids (GIDs) are reserved
6042 globally for use by certain packages. Because some
6043 packages need to include files which are owned by these
6044 users or groups, or need the ids compiled into binaries,
6045 these ids must be used on any Debian system only for the
6046 purpose for which they are allocated. This is a serious
6047 restriction, and we should avoid getting in the way of
6048 local administration policies. In particular, many sites
6049 allocate users and/or local system groups starting at 100.
6053 Apart from this we should have dynamically allocated ids,
6054 which should by default be arranged in some sensible
6055 order, but the behavior should be configurable.
6059 Packages other than <tt>base-passwd</tt> must not modify
6060 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
6061 <file>/etc/group</file> or <file>/etc/gshadow</file>.
6066 <heading>UID and GID classes</heading>
6068 The UID and GID numbers are divided into classes as
6074 Globally allocated by the Debian project, the same
6075 on every Debian system. These ids will appear in
6076 the <file>passwd</file> and <file>group</file> files of all
6077 Debian systems, new ids in this range being added
6078 automatically as the <tt>base-passwd</tt> package is
6083 Packages which need a single statically allocated
6084 uid or gid should use one of these; their
6085 maintainers should ask the <tt>base-passwd</tt>
6093 Dynamically allocated system users and groups.
6094 Packages which need a user or group, but can have
6095 this user or group allocated dynamically and
6096 differently on each system, should use <tt>adduser
6097 --system</tt> to create the group and/or user.
6098 <prgn>adduser</prgn> will check for the existence of
6099 the user or group, and if necessary choose an unused
6100 id based on the ranges specified in
6101 <file>adduser.conf</file>.
6105 <tag>1000-59999:</tag>
6108 Dynamically allocated user accounts. By default
6109 <prgn>adduser</prgn> will choose UIDs and GIDs for
6110 user accounts in this range, though
6111 <file>adduser.conf</file> may be used to modify this
6116 <tag>60000-64999:</tag>
6119 Globally allocated by the Debian project, but only
6120 created on demand. The ids are allocated centrally
6121 and statically, but the actual accounts are only
6122 created on users' systems on demand.
6126 These ids are for packages which are obscure or
6127 which require many statically-allocated ids. These
6128 packages should check for and create the accounts in
6129 <file>/etc/passwd</file> or <file>/etc/group</file> (using
6130 <prgn>adduser</prgn> if it has this facility) if
6131 necessary. Packages which are likely to require
6132 further allocations should have a "hole" left after
6133 them in the allocation, to give them room to
6138 <tag>65000-65533:</tag>
6146 User <tt>nobody</tt>. The corresponding gid refers
6147 to the group <tt>nogroup</tt>.
6154 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
6155 not</em> be used, because it is the error return
6164 <sect id="sysvinit">
6165 <heading>System run levels and <file>init.d</file> scripts</heading>
6167 <sect1 id="/etc/init.d">
6168 <heading>Introduction</heading>
6171 The <file>/etc/init.d</file> directory contains the scripts
6172 executed by <prgn>init</prgn> at boot time and when the
6173 init state (or "runlevel") is changed (see <manref
6174 name="init" section="8">).
6178 There are at least two different, yet functionally
6179 equivalent, ways of handling these scripts. For the sake
6180 of simplicity, this document describes only the symbolic
6181 link method. However, it must not be assumed by maintainer
6182 scripts that this method is being used, and any automated
6183 manipulation of the various runlevel behaviors by
6184 maintainer scripts must be performed using
6185 <prgn>update-rc.d</prgn> as described below and not by
6186 manually installing or removing symlinks. For information
6187 on the implementation details of the other method,
6188 implemented in the <tt>file-rc</tt> package, please refer
6189 to the documentation of that package.
6193 These scripts are referenced by symbolic links in the
6194 <file>/etc/rc<var>n</var>.d</file> directories. When changing
6195 runlevels, <prgn>init</prgn> looks in the directory
6196 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
6197 execute, where <tt><var>n</var></tt> is the runlevel that
6198 is being changed to, or <tt>S</tt> for the boot-up
6203 The names of the links all have the form
6204 <file>S<var>mm</var><var>script</var></file> or
6205 <file>K<var>mm</var><var>script</var></file> where
6206 <var>mm</var> is a two-digit number and <var>script</var>
6207 is the name of the script (this should be the same as the
6208 name of the actual script in <file>/etc/init.d</file>).
6212 When <prgn>init</prgn> changes runlevel first the targets
6213 of the links whose names start with a <tt>K</tt> are
6214 executed, each with the single argument <tt>stop</tt>,
6215 followed by the scripts prefixed with an <tt>S</tt>, each
6216 with the single argument <tt>start</tt>. (The links are
6217 those in the <file>/etc/rc<var>n</var>.d</file> directory
6218 corresponding to the new runlevel.) The <tt>K</tt> links
6219 are responsible for killing services and the <tt>S</tt>
6220 link for starting services upon entering the runlevel.
6224 For example, if we are changing from runlevel 2 to
6225 runlevel 3, init will first execute all of the <tt>K</tt>
6226 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
6227 all of the <tt>S</tt> prefixed scripts in that directory.
6228 The links starting with <tt>K</tt> will cause the
6229 referred-to file to be executed with an argument of
6230 <tt>stop</tt>, and the <tt>S</tt> links with an argument
6235 The two-digit number <var>mm</var> is used to determine
6236 the order in which to run the scripts: low-numbered links
6237 have their scripts run first. For example, the
6238 <tt>K20</tt> scripts will be executed before the
6239 <tt>K30</tt> scripts. This is used when a certain service
6240 must be started before another. For example, the name
6241 server <prgn>bind</prgn> might need to be started before
6242 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
6243 can set up its access lists. In this case, the script
6244 that starts <prgn>bind</prgn> would have a lower number
6245 than the script that starts <prgn>inn</prgn> so that it
6247 <example compact="compact">
6254 The two runlevels 0 (halt) and 6 (reboot) are slightly
6255 different. In these runlevels, the links with an
6256 <tt>S</tt> prefix are still called after those with a
6257 <tt>K</tt> prefix, but they too are called with the single
6258 argument <tt>stop</tt>.
6262 <sect1 id="writing-init">
6263 <heading>Writing the scripts</heading>
6266 Packages that include daemons for system services should
6267 place scripts in <file>/etc/init.d</file> to start or stop
6268 services at boot time or during a change of runlevel.
6269 These scripts should be named
6270 <file>/etc/init.d/<var>package</var></file>, and they should
6271 accept one argument, saying what to do:
6274 <tag><tt>start</tt></tag>
6275 <item>start the service,</item>
6277 <tag><tt>stop</tt></tag>
6278 <item>stop the service,</item>
6280 <tag><tt>restart</tt></tag>
6281 <item>stop and restart the service if it's already running,
6282 otherwise start the service</item>
6284 <tag><tt>reload</tt></tag>
6285 <item><p>cause the configuration of the service to be
6286 reloaded without actually stopping and restarting
6289 <tag><tt>force-reload</tt></tag>
6290 <item>cause the configuration to be reloaded if the
6291 service supports this, otherwise restart the
6295 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
6296 <tt>force-reload</tt> options should be supported by all
6297 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
6302 The <file>init.d</file> scripts must ensure that they will
6303 behave sensibly (i.e., returning success and not starting
6304 multiple copies of a service) if invoked with <tt>start</tt>
6305 when the service is already running, or with <tt>stop</tt>
6306 when it isn't, and that they don't kill unfortunately-named
6307 user processes. The best way to achieve this is usually to
6308 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
6313 Be careful of using <tt>set -e</tt> in <file>init.d</file>
6314 scripts. Writing correct <file>init.d</file> scripts requires
6315 accepting various error exit statuses when daemons are already
6316 running or already stopped without aborting
6317 the <file>init.d</file> script, and common <file>init.d</file>
6318 function libraries are not safe to call with <tt>set -e</tt>
6320 <tt>/lib/lsb/init-functions</tt>, which assists in writing
6321 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
6322 in effect and echoing status messages to the console fails,
6324 </footnote>. For <tt>init.d</tt> scripts, it's often easier
6325 to not use <tt>set -e</tt> and instead check the result of
6326 each command separately.
6330 If a service reloads its configuration automatically (as
6331 in the case of <prgn>cron</prgn>, for example), the
6332 <tt>reload</tt> option of the <file>init.d</file> script
6333 should behave as if the configuration has been reloaded
6338 The <file>/etc/init.d</file> scripts must be treated as
6339 configuration files, either (if they are present in the
6340 package, that is, in the .deb file) by marking them as
6341 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6342 by managing them correctly in the maintainer scripts (see
6343 <ref id="config-files">). This is important since we want
6344 to give the local system administrator the chance to adapt
6345 the scripts to the local system, e.g., to disable a
6346 service without de-installing the package, or to specify
6347 some special command line options when starting a service,
6348 while making sure their changes aren't lost during the next
6353 These scripts should not fail obscurely when the
6354 configuration files remain but the package has been
6355 removed, as configuration files remain on the system after
6356 the package has been removed. Only when <prgn>dpkg</prgn>
6357 is executed with the <tt>--purge</tt> option will
6358 configuration files be removed. In particular, as the
6359 <file>/etc/init.d/<var>package</var></file> script itself is
6360 usually a <tt>conffile</tt>, it will remain on the system
6361 if the package is removed but not purged. Therefore, you
6362 should include a <tt>test</tt> statement at the top of the
6364 <example compact="compact">
6365 test -f <var>program-executed-later-in-script</var> || exit 0
6370 Often there are some variables in the <file>init.d</file>
6371 scripts whose values control the behavior of the scripts,
6372 and which a system administrator is likely to want to
6373 change. As the scripts themselves are frequently
6374 <tt>conffile</tt>s, modifying them requires that the
6375 administrator merge in their changes each time the package
6376 is upgraded and the <tt>conffile</tt> changes. To ease
6377 the burden on the system administrator, such configurable
6378 values should not be placed directly in the script.
6379 Instead, they should be placed in a file in
6380 <file>/etc/default</file>, which typically will have the same
6381 base name as the <file>init.d</file> script. This extra file
6382 should be sourced by the script when the script runs. It
6383 must contain only variable settings and comments in SUSv3
6384 <prgn>sh</prgn> format. It may either be a
6385 <tt>conffile</tt> or a configuration file maintained by
6386 the package maintainer scripts. See <ref id="config-files">
6391 To ensure that vital configurable values are always
6392 available, the <file>init.d</file> script should set default
6393 values for each of the shell variables it uses, either
6394 before sourcing the <file>/etc/default/</file> file or
6395 afterwards using something like the <tt>:
6396 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6397 script must behave sensibly and not fail if the
6398 <file>/etc/default</file> file is deleted.
6402 <file>/var/run</file> and <file>/var/lock</file> may be mounted
6403 as temporary filesystems<footnote>
6404 For example, using the <tt>RAMRUN</tt> and <tt>RAMLOCK</tt>
6405 options in <file>/etc/default/rcS</file>.
6406 </footnote>, so the <file>init.d</file> scripts must handle this
6407 correctly. This will typically amount to creating any required
6408 subdirectories dynamically when the <file>init.d</file> script
6409 is run, rather than including them in the package and relying on
6410 <prgn>dpkg</prgn> to create them.
6415 <heading>Interfacing with the initscript system</heading>
6418 Maintainers should use the abstraction layer provided by
6419 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6420 programs to deal with initscripts in their packages'
6421 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6422 and <prgn>postrm</prgn>.
6426 Directly managing the /etc/rc?.d links and directly
6427 invoking the <file>/etc/init.d/</file> initscripts should
6428 be done only by packages providing the initscript
6429 subsystem (such as <prgn>sysv-rc</prgn> and
6430 <prgn>file-rc</prgn>).
6434 <heading>Managing the links</heading>
6437 The program <prgn>update-rc.d</prgn> is provided for
6438 package maintainers to arrange for the proper creation and
6439 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6440 or their functional equivalent if another method is being
6441 used. This may be used by maintainers in their packages'
6442 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6446 You must not include any <file>/etc/rc<var>n</var>.d</file>
6447 symbolic links in the actual archive or manually create or
6448 remove the symbolic links in maintainer scripts; you must
6449 use the <prgn>update-rc.d</prgn> program instead. (The
6450 former will fail if an alternative method of maintaining
6451 runlevel information is being used.) You must not include
6452 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6453 in the archive either. (Only the <tt>sysvinit</tt>
6458 By default <prgn>update-rc.d</prgn> will start services in
6459 each of the multi-user state runlevels (2, 3, 4, and 5)
6460 and stop them in the halt runlevel (0), the single-user
6461 runlevel (1) and the reboot runlevel (6). The system
6462 administrator will have the opportunity to customize
6463 runlevels by simply adding, moving, or removing the
6464 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6465 symbolic links are being used, or by modifying
6466 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6471 To get the default behavior for your package, put in your
6472 <prgn>postinst</prgn> script
6473 <example compact="compact">
6474 update-rc.d <var>package</var> defaults
6476 and in your <prgn>postrm</prgn>
6477 <example compact="compact">
6478 if [ "$1" = purge ]; then
6479 update-rc.d <var>package</var> remove
6481 </example>. Note that if your package changes runlevels
6482 or priority, you may have to remove and recreate the links,
6483 since otherwise the old links may persist. Refer to the
6484 documentation of <prgn>update-rc.d</prgn>.
6488 This will use a default sequence number of 20. If it does
6489 not matter when or in which order the <file>init.d</file>
6490 script is run, use this default. If it does, then you
6491 should talk to the maintainer of the <prgn>sysvinit</prgn>
6492 package or post to <tt>debian-devel</tt>, and they will
6493 help you choose a number.
6497 For more information about using <tt>update-rc.d</tt>,
6498 please consult its man page <manref name="update-rc.d"
6504 <heading>Running initscripts</heading>
6506 The program <prgn>invoke-rc.d</prgn> is provided to make
6507 it easier for package maintainers to properly invoke an
6508 initscript, obeying runlevel and other locally-defined
6509 constraints that might limit a package's right to start,
6510 stop and otherwise manage services. This program may be
6511 used by maintainers in their packages' scripts.
6515 The package maintainer scripts must use
6516 <prgn>invoke-rc.d</prgn> to invoke the
6517 <file>/etc/init.d/*</file> initscripts, instead of
6518 calling them directly.
6522 By default, <prgn>invoke-rc.d</prgn> will pass any
6523 action requests (start, stop, reload, restart...) to the
6524 <file>/etc/init.d</file> script, filtering out requests
6525 to start or restart a service out of its intended
6530 Most packages will simply need to change:
6531 <example compact="compact">/etc/init.d/<package>
6532 <action></example> in their <prgn>postinst</prgn>
6533 and <prgn>prerm</prgn> scripts to:
6534 <example compact="compact">
6535 if which invoke-rc.d >/dev/null 2>&1; then
6536 invoke-rc.d <var>package</var> <action>
6538 /etc/init.d/<var>package</var> <action>
6544 A package should register its initscript services using
6545 <prgn>update-rc.d</prgn> before it tries to invoke them
6546 using <prgn>invoke-rc.d</prgn>. Invocation of
6547 unregistered services may fail.
6551 For more information about using
6552 <prgn>invoke-rc.d</prgn>, please consult its man page
6553 <manref name="invoke-rc.d" section="8">.
6559 <heading>Boot-time initialization</heading>
6562 There used to be another directory, <file>/etc/rc.boot</file>,
6563 which contained scripts which were run once per machine
6564 boot. This has been deprecated in favour of links from
6565 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6566 described in <ref id="/etc/init.d">. Packages must not
6567 place files in <file>/etc/rc.boot</file>.
6572 <heading>Example</heading>
6575 An example on which you can base your
6576 <file>/etc/init.d</file> scripts is found in
6577 <file>/etc/init.d/skeleton</file>.
6584 <heading>Console messages from <file>init.d</file> scripts</heading>
6587 This section describes the formats to be used for messages
6588 written to standard output by the <file>/etc/init.d</file>
6589 scripts. The intent is to improve the consistency of
6590 Debian's startup and shutdown look and feel. For this
6591 reason, please look very carefully at the details. We want
6592 the messages to have the same format in terms of wording,
6593 spaces, punctuation and case of letters.
6597 Here is a list of overall rules that should be used for
6598 messages generated by <file>/etc/init.d</file> scripts.
6604 The message should fit in one line (fewer than 80
6605 characters), start with a capital letter and end with
6606 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6610 If the script is performing some time consuming task in
6611 the background (not merely starting or stopping a
6612 program, for instance), an ellipsis (three dots:
6613 <tt>...</tt>) should be output to the screen, with no
6614 leading or tailing whitespace or line feeds.
6618 The messages should appear as if the computer is telling
6619 the user what it is doing (politely :-), but should not
6620 mention "it" directly. For example, instead of:
6621 <example compact="compact">
6622 I'm starting network daemons: nfsd mountd.
6624 the message should say
6625 <example compact="compact">
6626 Starting network daemons: nfsd mountd.
6633 <tt>init.d</tt> script should use the following standard
6634 message formats for the situations enumerated below.
6640 <p>When daemons are started</p>
6643 If the script starts one or more daemons, the output
6644 should look like this (a single line, no leading
6646 <example compact="compact">
6647 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6649 The <var>description</var> should describe the
6650 subsystem the daemon or set of daemons are part of,
6651 while <var>daemon-1</var> up to <var>daemon-n</var>
6652 denote each daemon's name (typically the file name of
6657 For example, the output of <file>/etc/init.d/lpd</file>
6659 <example compact="compact">
6660 Starting printer spooler: lpd.
6665 This can be achieved by saying
6666 <example compact="compact">
6667 echo -n "Starting printer spooler: lpd"
6668 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6671 in the script. If there are more than one daemon to
6672 start, the output should look like this:
6673 <example compact="compact">
6674 echo -n "Starting remote file system services:"
6675 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6676 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6677 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6680 This makes it possible for the user to see what is
6681 happening and when the final daemon has been started.
6682 Care should be taken in the placement of white spaces:
6683 in the example above the system administrators can
6684 easily comment out a line if they don't want to start
6685 a specific daemon, while the displayed message still
6691 <p>When a system parameter is being set</p>
6694 If you have to set up different system parameters
6695 during the system boot, you should use this format:
6696 <example compact="compact">
6697 Setting <var>parameter</var> to "<var>value</var>".
6702 You can use a statement such as the following to get
6704 <example compact="compact">
6705 echo "Setting DNS domainname to \"$domainname\"."
6710 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
6711 for the left and right quotation marks. A grave accent
6712 (<tt>`</tt>) is not a quote character; neither is an
6713 apostrophe (<tt>'</tt>).
6718 <p>When a daemon is stopped or restarted</p>
6721 When you stop or restart a daemon, you should issue a
6722 message identical to the startup message, except that
6723 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6724 or <tt>Restarting</tt> respectively.
6728 For example, stopping the printer daemon will look like
6730 <example compact="compact">
6731 Stopping printer spooler: lpd.
6737 <p>When something is executed</p>
6740 There are several examples where you have to run a
6741 program at system startup or shutdown to perform a
6742 specific task, for example, setting the system's clock
6743 using <prgn>netdate</prgn> or killing all processes
6744 when the system shuts down. Your message should look
6746 <example compact="compact">
6747 Doing something very useful...done.
6749 You should print the <tt>done.</tt> immediately after
6750 the job has been completed, so that the user is
6751 informed why they have to wait. You can get this
6753 <example compact="compact">
6754 echo -n "Doing something very useful..."
6763 <p>When the configuration is reloaded</p>
6766 When a daemon is forced to reload its configuration
6767 files you should use the following format:
6768 <example compact="compact">
6769 Reloading <var>description</var> configuration...done.
6771 where <var>description</var> is the same as in the
6772 daemon starting message.
6780 <heading>Cron jobs</heading>
6783 Packages must not modify the configuration file
6784 <file>/etc/crontab</file>, and they must not modify the files in
6785 <file>/var/spool/cron/crontabs</file>.</p>
6788 If a package wants to install a job that has to be executed
6789 via cron, it should place a file with the name of the
6790 package in one or more of the following directories:
6791 <example compact="compact">
6797 As these directory names imply, the files within them are
6798 executed on an hourly, daily, weekly, or monthly basis,
6799 respectively. The exact times are listed in
6800 <file>/etc/crontab</file>.</p>
6803 All files installed in any of these directories must be
6804 scripts (e.g., shell scripts or Perl scripts) so that they
6805 can easily be modified by the local system administrator.
6806 In addition, they must be treated as configuration files.
6810 If a certain job has to be executed at some other frequency or
6811 at a specific time, the package should install a file
6812 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6813 same syntax as <file>/etc/crontab</file> and is processed by
6814 <prgn>cron</prgn> automatically. The file must also be
6815 treated as a configuration file. (Note that entries in the
6816 <file>/etc/cron.d</file> directory are not handled by
6817 <prgn>anacron</prgn>. Thus, you should only use this
6818 directory for jobs which may be skipped if the system is not
6821 Unlike <file>crontab</file> files described in the IEEE Std
6822 1003.1-2008 (POSIX.1) available from
6823 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
6824 name="The Open Group">, the files in
6825 <file>/etc/cron.d</file> and the file
6826 <file>/etc/crontab</file> have seven fields; namely:
6828 <item>Minute [0,59]</item>
6829 <item>Hour [0,23]</item>
6830 <item>Day of the month [1,31]</item>
6831 <item>Month of the year [1,12]</item>
6832 <item>Day of the week ([0,6] with 0=Sunday)</item>
6833 <item>Username</item>
6834 <item>Command to be run</item>
6836 Ranges of numbers are allowed. Ranges are two numbers
6837 separated with a hyphen. The specified range is inclusive.
6838 Lists are allowed. A list is a set of numbers (or ranges)
6839 separated by commas. Step values can be used in conjunction
6844 The scripts or <tt>crontab</tt> entries in these directories should
6845 check if all necessary programs are installed before they
6846 try to execute them. Otherwise, problems will arise when a
6847 package was removed but not purged since configuration files
6848 are kept on the system in this situation.
6852 Any <tt>cron</tt> daemon must provide
6853 <file>/usr/bin/crontab</file> and support normal
6854 <tt>crontab</tt> entries as specified in POSIX. The daemon
6855 must also support names for days and months, ranges, and
6856 step values. It has to support <file>/etc/crontab</file>,
6857 and correctly execute the scripts in
6858 <file>/etc/cron.d</file>. The daemon must also correctly
6860 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
6865 <heading>Menus</heading>
6868 The Debian <tt>menu</tt> package provides a standard
6869 interface between packages providing applications and
6870 <em>menu programs</em> (either X window managers or
6871 text-based menu programs such as <prgn>pdmenu</prgn>).
6875 All packages that provide applications that need not be
6876 passed any special command line arguments for normal
6877 operation should register a menu entry for those
6878 applications, so that users of the <tt>menu</tt> package
6879 will automatically get menu entries in their window
6880 managers, as well in shells like <tt>pdmenu</tt>.
6884 Menu entries should follow the current menu policy.
6888 The menu policy can be found in the <tt>menu-policy</tt>
6889 files in the <tt>debian-policy</tt> package.
6890 It is also available from the Debian web mirrors at
6891 <tt><url name="/doc/packaging-manuals/menu-policy/"
6892 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6896 Please also refer to the <em>Debian Menu System</em>
6897 documentation that comes with the <package>menu</package>
6898 package for information about how to register your
6904 <heading>Multimedia handlers</heading>
6907 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6908 is a mechanism for encoding files and data streams and
6909 providing meta-information about them, in particular their
6910 type (e.g. audio or video) and format (e.g. PNG, HTML,
6915 Registration of MIME type handlers allows programs like mail
6916 user agents and web browsers to invoke these handlers to
6917 view, edit or display MIME types they don't support directly.
6921 Packages which provide the ability to view/show/play,
6922 compose, edit or print MIME types should register themselves
6923 as such following the current MIME support policy.
6927 The MIME support policy can be found in the <tt>mime-policy</tt>
6928 files in the <tt>debian-policy</tt> package.
6929 It is also available from the Debian web mirrors at
6930 <tt><url name="/doc/packaging-manuals/mime-policy/"
6931 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
6937 <heading>Keyboard configuration</heading>
6940 To achieve a consistent keyboard configuration so that all
6941 applications interpret a keyboard event the same way, all
6942 programs in the Debian distribution must be configured to
6943 comply with the following guidelines.
6947 The following keys must have the specified interpretations:
6950 <tag><tt><--</tt></tag>
6951 <item>delete the character to the left of the cursor</item>
6953 <tag><tt>Delete</tt></tag>
6954 <item>delete the character to the right of the cursor</item>
6956 <tag><tt>Control+H</tt></tag>
6957 <item>emacs: the help prefix</item>
6960 The interpretation of any keyboard events should be
6961 independent of the terminal that is used, be it a virtual
6962 console, an X terminal emulator, an rlogin/telnet session,
6967 The following list explains how the different programs
6968 should be set up to achieve this:
6974 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
6978 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
6982 X translations are set up to make
6983 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
6984 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
6985 is the vt220 escape code for the "delete character"
6986 key). This must be done by loading the X resources
6987 using <prgn>xrdb</prgn> on all local X displays, not
6988 using the application defaults, so that the
6989 translation resources used correspond to the
6990 <prgn>xmodmap</prgn> settings.
6994 The Linux console is configured to make
6995 <tt><--</tt> generate DEL, and <tt>Delete</tt>
6996 generate <tt>ESC [ 3 ~</tt>.
7000 X applications are configured so that <tt><</tt>
7001 deletes left, and <tt>Delete</tt> deletes right. Motif
7002 applications already work like this.
7006 Terminals should have <tt>stty erase ^?</tt> .
7010 The <tt>xterm</tt> terminfo entry should have <tt>ESC
7011 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
7012 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
7016 Emacs is programmed to map <tt>KB_Backspace</tt> or
7017 the <tt>stty erase</tt> character to
7018 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
7019 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
7020 <tt>^H</tt> to <tt>help</tt> as always.
7024 Other applications use the <tt>stty erase</tt>
7025 character and <tt>kdch1</tt> for the two delete keys,
7026 with ASCII DEL being "delete previous character" and
7027 <tt>kdch1</tt> being "delete character under
7035 This will solve the problem except for the following
7042 Some terminals have a <tt><--</tt> key that cannot
7043 be made to produce anything except <tt>^H</tt>. On
7044 these terminals Emacs help will be unavailable on
7045 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
7046 character takes precedence in Emacs, and has been set
7047 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
7048 available) can be used instead.
7052 Some operating systems use <tt>^H</tt> for <tt>stty
7053 erase</tt>. However, modern telnet versions and all
7054 rlogin versions propagate <tt>stty</tt> settings, and
7055 almost all UNIX versions honour <tt>stty erase</tt>.
7056 Where the <tt>stty</tt> settings are not propagated
7057 correctly, things can be made to work by using
7058 <tt>stty</tt> manually.
7062 Some systems (including previous Debian versions) use
7063 <prgn>xmodmap</prgn> to arrange for both
7064 <tt><--</tt> and <tt>Delete</tt> to generate
7065 <tt>KB_Delete</tt>. We can change the behavior of
7066 their X clients using the same X resources that we use
7067 to do it for our own clients, or configure our clients
7068 using their resources when things are the other way
7069 around. On displays configured like this
7070 <tt>Delete</tt> will not work, but <tt><--</tt>
7075 Some operating systems have different <tt>kdch1</tt>
7076 settings in their <tt>terminfo</tt> database for
7077 <tt>xterm</tt> and others. On these systems the
7078 <tt>Delete</tt> key will not work correctly when you
7079 log in from a system conforming to our policy, but
7080 <tt><--</tt> will.
7087 <heading>Environment variables</heading>
7090 A program must not depend on environment variables to get
7091 reasonable defaults. (That's because these environment
7092 variables would have to be set in a system-wide
7093 configuration file like <file>/etc/profile</file>, which is not
7094 supported by all shells.)
7098 If a program usually depends on environment variables for its
7099 configuration, the program should be changed to fall back to
7100 a reasonable default configuration if these environment
7101 variables are not present. If this cannot be done easily
7102 (e.g., if the source code of a non-free program is not
7103 available), the program must be replaced by a small
7104 "wrapper" shell script which sets the environment variables
7105 if they are not already defined, and calls the original program.
7109 Here is an example of a wrapper script for this purpose:
7111 <example compact="compact">
7113 BAR=${BAR:-/var/lib/fubar}
7115 exec /usr/lib/foo/foo "$@"
7120 Furthermore, as <file>/etc/profile</file> is a configuration
7121 file of the <prgn>base-files</prgn> package, other packages must
7122 not put any environment variables or other commands into that
7127 <sect id="doc-base">
7128 <heading>Registering Documents using doc-base</heading>
7131 The <package>doc-base</package> package implements a
7132 flexible mechanism for handling and presenting
7133 documentation. The recommended practice is for every Debian
7134 package that provides online documentation (other than just
7135 manual pages) to register these documents with
7136 <package>doc-base</package> by installing a
7137 <package>doc-base</package> control file via the
7138 <prgn/install-docs/ script at installation time and
7139 de-register the manuals again when the package is removed.
7142 Please refer to the documentation that comes with the
7143 <package>doc-base</package> package for information and
7152 <heading>Files</heading>
7154 <sect id="binaries">
7155 <heading>Binaries</heading>
7158 Two different packages must not install programs with
7159 different functionality but with the same filenames. (The
7160 case of two programs having the same functionality but
7161 different implementations is handled via "alternatives" or
7162 the "Conflicts" mechanism. See <ref id="maintscripts"> and
7163 <ref id="conflicts"> respectively.) If this case happens,
7164 one of the programs must be renamed. The maintainers should
7165 report this to the <tt>debian-devel</tt> mailing list and
7166 try to find a consensus about which program will have to be
7167 renamed. If a consensus cannot be reached, <em>both</em>
7168 programs must be renamed.
7172 By default, when a package is being built, any binaries
7173 created should include debugging information, as well as
7174 being compiled with optimization. You should also turn on
7175 as many reasonable compilation warnings as possible; this
7176 makes life easier for porters, who can then look at build
7177 logs for possible problems. For the C programming language,
7178 this means the following compilation parameters should be
7180 <example compact="compact">
7182 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
7184 INSTALL = install -s # (or use strip on the files in debian/tmp)
7189 Note that by default all installed binaries should be stripped,
7190 either by using the <tt>-s</tt> flag to
7191 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
7192 the binaries after they have been copied into
7193 <file>debian/tmp</file> but before the tree is made into a
7198 Although binaries in the build tree should be compiled with
7199 debugging information by default, it can often be difficult to
7200 debug programs if they are also subjected to compiler
7201 optimization. For this reason, it is recommended to support the
7202 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
7203 (see <ref id="debianrules-options">). This variable can contain
7204 several flags to change how a package is compiled and built.
7208 It is up to the package maintainer to decide what
7209 compilation options are best for the package. Certain
7210 binaries (such as computationally-intensive programs) will
7211 function better with certain flags (<tt>-O3</tt>, for
7212 example); feel free to use them. Please use good judgment
7213 here. Don't use flags for the sake of it; only use them
7214 if there is good reason to do so. Feel free to override
7215 the upstream author's ideas about which compilation
7216 options are best: they are often inappropriate for our
7222 <sect id="libraries">
7223 <heading>Libraries</heading>
7226 If the package is <strong>architecture: any</strong>, then
7227 the shared library compilation and linking flags must have
7228 <tt>-fPIC</tt>, or the package shall not build on some of
7229 the supported architectures<footnote>
7231 If you are using GCC, <tt>-fPIC</tt> produces code with
7232 relocatable position independent code, which is required for
7233 most architectures to create a shared library, with i386 and
7234 perhaps some others where non position independent code is
7235 permitted in a shared library.
7238 Position independent code may have a performance penalty,
7239 especially on <tt>i386</tt>. However, in most cases the
7240 speed penalty must be measured against the memory wasted on
7241 the few architectures where non position independent code is
7244 </footnote>. Any exception to this rule must be discussed on
7245 the mailing list <em>debian-devel@lists.debian.org</em>, and
7246 a rough consensus obtained. The reasons for not compiling
7247 with <tt>-fPIC</tt> flag must be recorded in the file
7248 <tt>README.Debian</tt>, and care must be taken to either
7249 restrict the architecture or arrange for <tt>-fPIC</tt> to
7250 be used on architectures where it is required.<footnote>
7252 Some of the reasons why this might be required is if the
7253 library contains hand crafted assembly code that is not
7254 relocatable, the speed penalty is excessive for compute
7255 intensive libs, and similar reasons.
7260 As to the static libraries, the common case is not to have
7261 relocatable code, since there is no benefit, unless in specific
7262 cases; therefore the static version must not be compiled
7263 with the <tt>-fPIC</tt> flag. Any exception to this rule
7264 should be discussed on the mailing list
7265 <em>debian-devel@lists.debian.org</em>, and the reasons for
7266 compiling with the <tt>-fPIC</tt> flag must be recorded in
7267 the file <tt>README.Debian</tt>. <footnote>
7269 Some of the reasons for linking static libraries with
7270 the <tt>-fPIC</tt> flag are if, for example, one needs a
7271 Perl API for a library that is under rapid development,
7272 and has an unstable API, so shared libraries are
7273 pointless at this phase of the library's development. In
7274 that case, since Perl needs a library with relocatable
7275 code, it may make sense to create a static library with
7276 relocatable code. Another reason cited is if you are
7277 distilling various libraries into a common shared
7278 library, like <tt>mklibs</tt> does in the Debian
7284 In other words, if both a shared and a static library is
7285 being built, each source unit (<tt>*.c</tt>, for example,
7286 for C files) will need to be compiled twice, for the normal
7291 Libraries should be built with threading support and to be
7292 thread-safe if the library supports this.
7296 Although not enforced by the build tools, shared libraries
7297 must be linked against all libraries that they use symbols from
7298 in the same way that binaries are. This ensures the correct
7299 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
7300 system and guarantees that all libraries can be safely opened
7301 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
7302 option <tt>-Wl,-z,defs</tt> when building a shared library.
7303 Since this option enforces symbol resolution at build time,
7304 a missing library reference will be caught early as a fatal
7309 All installed shared libraries should be stripped with
7310 <example compact="compact">
7311 strip --strip-unneeded <var>your-lib</var>
7313 (The option <tt>--strip-unneeded</tt> makes
7314 <prgn>strip</prgn> remove only the symbols which aren't
7315 needed for relocation processing.) Shared libraries can
7316 function perfectly well when stripped, since the symbols for
7317 dynamic linking are in a separate part of the ELF object
7319 You might also want to use the options
7320 <tt>--remove-section=.comment</tt> and
7321 <tt>--remove-section=.note</tt> on both shared libraries
7322 and executables, and <tt>--strip-debug</tt> on static
7328 Note that under some circumstances it may be useful to
7329 install a shared library unstripped, for example when
7330 building a separate package to support debugging.
7334 Shared object files (often <file>.so</file> files) that are not
7335 public libraries, that is, they are not meant to be linked
7336 to by third party executables (binaries of other packages),
7337 should be installed in subdirectories of the
7338 <file>/usr/lib</file> directory. Such files are exempt from the
7339 rules that govern ordinary shared libraries, except that
7340 they must not be installed executable and should be
7342 A common example are the so-called "plug-ins",
7343 internal shared objects that are dynamically loaded by
7344 programs using <manref name="dlopen" section="3">.
7349 Packages that use <prgn>libtool</prgn> to create and install
7350 their shared libraries install a file containing additional
7351 metadata (ending in <file>.la</file>) alongside the library.
7352 For public libraries intended for use by other packages, these
7353 files normally should not be included in the Debian package,
7354 since the information they include is not necessary to link with
7355 the shared library on Debian and can add unnecessary additional
7356 dependencies to other programs or libraries.<footnote>
7357 These files store, among other things, all libraries on which
7358 that shared library depends. Unfortunately, if
7359 the <file>.la</file> file is present and contains that
7360 dependency information, using <prgn>libtool</prgn> when
7361 linking against that library will cause the resulting program
7362 or library to be linked against those dependencies as well,
7363 even if this is unnecessary. This can create unneeded
7364 dependencies on shared library packages that would otherwise
7365 be hidden behind the library ABI, and can make library
7366 transitions to new SONAMEs unnecessarily complicated and
7367 difficult to manage.
7369 If the <file>.la</file> file is required for that library (if,
7370 for instance, it's loaded via <tt>libltdl</tt> in a way that
7371 requires that meta-information), the <tt>dependency_libs</tt>
7372 setting in the <file>.la</file> file should normally be set to
7373 the empty string. If the shared library development package has
7374 historically included the <file>.la</file>, it must be retained
7375 in the development package (with <tt>dependency_libs</tt>
7376 emptied) until all libraries that depend on it have removed or
7377 emptied <tt>dependency_libs</tt> in their <file>.la</file>
7378 files to prevent linking with those other libraries
7379 using <prgn>libtool</prgn> from failing.
7383 If the <file>.la</file> must be included, it should be included
7384 in the development (<tt>-dev</tt>) package, unless the library
7385 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
7386 library. If it is intended for use with <tt>libltdl</tt>,
7387 the <file>.la</file> files must go in the run-time library
7392 These requirements for handling of <file>.la</file> files do not
7393 apply to loadable modules or libraries not installed in
7394 directories searched by default by the dynamic linker. Packages
7395 installing loadable modules will frequently need to install
7396 the <file>.la</file> files alongside the modules so that they
7397 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
7398 does not need to be modified for libraries or modules that are
7399 not installed in directories searched by the dynamic linker by
7400 default and not intended for use by other packages.
7404 You must make sure that you use only released versions of
7405 shared libraries to build your packages; otherwise other
7406 users will not be able to run your binaries
7407 properly. Producing source packages that depend on
7408 unreleased compilers is also usually a bad
7415 <heading>Shared libraries</heading>
7417 This section has moved to <ref id="sharedlibs">.
7423 <heading>Scripts</heading>
7426 All command scripts, including the package maintainer
7427 scripts inside the package and used by <prgn>dpkg</prgn>,
7428 should have a <tt>#!</tt> line naming the shell to be used
7433 In the case of Perl scripts this should be
7434 <tt>#!/usr/bin/perl</tt>.
7438 When scripts are installed into a directory in the system
7439 PATH, the script name should not include an extension such
7440 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7441 language currently used to implement it.
7444 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
7445 <file>init.d</file> scripts should almost certainly start
7446 with <tt>set -e</tt> so that errors are detected.
7447 <file>init.d</file> scripts are something of a special case, due
7448 to how frequently they need to call commands that are allowed to
7449 fail, and it may instead be easier to check the exit status of
7450 commands directly. See <ref id="writing-init"> for more
7451 information about writing <file>init.d</file> scripts.
7454 Every script should use <tt>set -e</tt> or check the exit status
7455 of <em>every</em> command.
7458 Scripts may assume that <file>/bin/sh</file> implements the
7459 SUSv3 Shell Command Language<footnote>
7460 Single UNIX Specification, version 3, which is also IEEE
7461 1003.1-2004 (POSIX), and is available on the World Wide Web
7462 from <url id="http://www.unix.org/version3/online.html"
7463 name="The Open Group"> after free
7464 registration.</footnote>
7465 plus the following additional features not mandated by
7467 These features are in widespread use in the Linux community
7468 and are implemented in all of bash, dash, and ksh, the most
7469 common shells users may wish to use as <file>/bin/sh</file>.
7472 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7473 must not generate a newline.</item>
7474 <item><tt>test</tt>, if implemented as a shell built-in, must
7475 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7477 <item><tt>local</tt> to create a scoped variable must be
7478 supported, including listing multiple variables in a single
7479 local command and assigning a value to a variable at the
7480 same time as localizing it. <tt>local</tt> may or
7481 may not preserve the variable value from an outer scope if
7482 no assignment is present. Uses such as:
7486 # ... use a, b, c, d ...
7489 must be supported and must set the value of <tt>c</tt> to
7493 If a shell script requires non-SUSv3 features from the shell
7494 interpreter other than those listed above, the appropriate shell
7495 must be specified in the first line of the script (e.g.,
7496 <tt>#!/bin/bash</tt>) and the package must depend on the package
7497 providing the shell (unless the shell package is marked
7498 "Essential", as in the case of <prgn>bash</prgn>).
7502 You may wish to restrict your script to SUSv3 features plus the
7503 above set when possible so that it may use <file>/bin/sh</file>
7504 as its interpreter. If your script works with <prgn>dash</prgn>
7505 (originally called <prgn>ash</prgn>), it probably complies with
7506 the above requirements, but if you are in doubt, use
7507 <file>/bin/bash</file>.
7511 Perl scripts should check for errors when making any
7512 system calls, including <tt>open</tt>, <tt>print</tt>,
7513 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7517 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7518 scripting languages. See <em>Csh Programming Considered
7519 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7520 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7521 If an upstream package comes with <prgn>csh</prgn> scripts
7522 then you must make sure that they start with
7523 <tt>#!/bin/csh</tt> and make your package depend on the
7524 <prgn>c-shell</prgn> virtual package.
7528 Any scripts which create files in world-writeable
7529 directories (e.g., in <file>/tmp</file>) must use a
7530 mechanism which will fail atomically if a file with the same
7531 name already exists.
7535 The Debian base system provides the <prgn>tempfile</prgn>
7536 and <prgn>mktemp</prgn> utilities for use by scripts for
7543 <heading>Symbolic links</heading>
7546 In general, symbolic links within a top-level directory
7547 should be relative, and symbolic links pointing from one
7548 top-level directory into another should be absolute. (A
7549 top-level directory is a sub-directory of the root
7550 directory <file>/</file>.)
7554 In addition, symbolic links should be specified as short as
7555 possible, i.e., link targets like <file>foo/../bar</file> are
7560 Note that when creating a relative link using
7561 <prgn>ln</prgn> it is not necessary for the target of the
7562 link to exist relative to the working directory you're
7563 running <prgn>ln</prgn> from, nor is it necessary to change
7564 directory to the directory where the link is to be made.
7565 Simply include the string that should appear as the target
7566 of the link (this will be a pathname relative to the
7567 directory in which the link resides) as the first argument
7572 For example, in your <prgn>Makefile</prgn> or
7573 <file>debian/rules</file>, you can do things like:
7574 <example compact="compact">
7575 ln -fs gcc $(prefix)/bin/cc
7576 ln -fs gcc debian/tmp/usr/bin/cc
7577 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7578 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7583 A symbolic link pointing to a compressed file should always
7584 have the same file extension as the referenced file. (For
7585 example, if a file <file>foo.gz</file> is referenced by a
7586 symbolic link, the filename of the link has to end with
7587 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7592 <heading>Device files</heading>
7595 Packages must not include device files or named pipes in the
7600 If a package needs any special device files that are not
7601 included in the base system, it must call
7602 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7603 after notifying the user<footnote>
7604 This notification could be done via a (low-priority)
7605 debconf message, or an echo (printf) statement.
7610 Packages must not remove any device files in the
7611 <prgn>postrm</prgn> or any other script. This is left to the
7612 system administrator.
7616 Debian uses the serial devices
7617 <file>/dev/ttyS*</file>. Programs using the old
7618 <file>/dev/cu*</file> devices should be changed to use
7619 <file>/dev/ttyS*</file>.
7623 Named pipes needed by the package must be created in
7624 the <prgn>postinst</prgn> script<footnote>
7625 It's better to use <prgn>mkfifo</prgn> rather
7626 than <prgn>mknod</prgn> to create named pipes so that
7627 automated checks for packages incorrectly creating device
7628 files with <prgn>mknod</prgn> won't have false positives.
7629 </footnote> and removed in
7630 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
7635 <sect id="config-files">
7636 <heading>Configuration files</heading>
7639 <heading>Definitions</heading>
7643 <tag>configuration file</tag>
7645 A file that affects the operation of a program, or
7646 provides site- or host-specific information, or
7647 otherwise customizes the behavior of a program.
7648 Typically, configuration files are intended to be
7649 modified by the system administrator (if needed or
7650 desired) to conform to local policy or to provide
7651 more useful site-specific behavior.
7654 <tag><tt>conffile</tt></tag>
7656 A file listed in a package's <tt>conffiles</tt>
7657 file, and is treated specially by <prgn>dpkg</prgn>
7658 (see <ref id="configdetails">).
7664 The distinction between these two is important; they are
7665 not interchangeable concepts. Almost all
7666 <tt>conffile</tt>s are configuration files, but many
7667 configuration files are not <tt>conffiles</tt>.
7671 As noted elsewhere, <file>/etc/init.d</file> scripts,
7672 <file>/etc/default</file> files, scripts installed in
7673 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7674 configuration installed in <file>/etc/cron.d</file> must be
7675 treated as configuration files. In general, any script that
7676 embeds configuration information is de-facto a configuration
7677 file and should be treated as such.
7682 <heading>Location</heading>
7685 Any configuration files created or used by your package
7686 must reside in <file>/etc</file>. If there are several,
7687 consider creating a subdirectory of <file>/etc</file>
7688 named after your package.
7692 If your package creates or uses configuration files
7693 outside of <file>/etc</file>, and it is not feasible to modify
7694 the package to use <file>/etc</file> directly, put the files
7695 in <file>/etc</file> and create symbolic links to those files
7696 from the location that the package requires.
7701 <heading>Behavior</heading>
7704 Configuration file handling must conform to the following
7706 <list compact="compact">
7708 local changes must be preserved during a package
7712 configuration files must be preserved when the
7713 package is removed, and only deleted when the
7717 Obsolete configuration files without local changes may be
7718 removed by the package during upgrade.
7722 The easy way to achieve this behavior is to make the
7723 configuration file a <tt>conffile</tt>. This is
7724 appropriate only if it is possible to distribute a default
7725 version that will work for most installations, although
7726 some system administrators may choose to modify it. This
7727 implies that the default version will be part of the
7728 package distribution, and must not be modified by the
7729 maintainer scripts during installation (or at any other
7734 In order to ensure that local changes are preserved
7735 correctly, no package may contain or make hard links to
7736 conffiles.<footnote>
7737 Rationale: There are two problems with hard links.
7738 The first is that some editors break the link while
7739 editing one of the files, so that the two files may
7740 unwittingly become unlinked and different. The second
7741 is that <prgn>dpkg</prgn> might break the hard link
7742 while upgrading <tt>conffile</tt>s.
7747 The other way to do it is via the maintainer scripts. In
7748 this case, the configuration file must not be listed as a
7749 <tt>conffile</tt> and must not be part of the package
7750 distribution. If the existence of a file is required for
7751 the package to be sensibly configured it is the
7752 responsibility of the package maintainer to provide
7753 maintainer scripts which correctly create, update and
7754 maintain the file and remove it on purge. (See <ref
7755 id="maintainerscripts"> for more information.) These
7756 scripts must be idempotent (i.e., must work correctly if
7757 <prgn>dpkg</prgn> needs to re-run them due to errors
7758 during installation or removal), must cope with all the
7759 variety of ways <prgn>dpkg</prgn> can call maintainer
7760 scripts, must not overwrite or otherwise mangle the user's
7761 configuration without asking, must not ask unnecessary
7762 questions (particularly during upgrades), and must
7763 otherwise be good citizens.
7767 The scripts are not required to configure every possible
7768 option for the package, but only those necessary to get
7769 the package running on a given system. Ideally the
7770 sysadmin should not have to do any configuration other
7771 than that done (semi-)automatically by the
7772 <prgn>postinst</prgn> script.
7776 A common practice is to create a script called
7777 <file><var>package</var>-configure</file> and have the
7778 package's <prgn>postinst</prgn> call it if and only if the
7779 configuration file does not already exist. In certain
7780 cases it is useful for there to be an example or template
7781 file which the maintainer scripts use. Such files should
7782 be in <file>/usr/share/<var>package</var></file> or
7783 <file>/usr/lib/<var>package</var></file> (depending on whether
7784 they are architecture-independent or not). There should
7785 be symbolic links to them from
7786 <file>/usr/share/doc/<var>package</var>/examples</file> if
7787 they are examples, and should be perfectly ordinary
7788 <prgn>dpkg</prgn>-handled files (<em>not</em>
7789 configuration files).
7793 These two styles of configuration file handling must
7794 not be mixed, for that way lies madness:
7795 <prgn>dpkg</prgn> will ask about overwriting the file
7796 every time the package is upgraded.
7801 <heading>Sharing configuration files</heading>
7804 Packages which specify the same file as a
7805 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7806 with each other. (This is an instance of the general rule
7807 about not sharing files. Note that neither alternatives
7808 nor diversions are likely to be appropriate in this case;
7809 in particular, <prgn>dpkg</prgn> does not handle diverted
7810 <tt>conffile</tt>s well.)
7814 The maintainer scripts must not alter a <tt>conffile</tt>
7815 of <em>any</em> package, including the one the scripts
7820 If two or more packages use the same configuration file
7821 and it is reasonable for both to be installed at the same
7822 time, one of these packages must be defined as
7823 <em>owner</em> of the configuration file, i.e., it will be
7824 the package which handles that file as a configuration
7825 file. Other packages that use the configuration file must
7826 depend on the owning package if they require the
7827 configuration file to operate. If the other package will
7828 use the configuration file if present, but is capable of
7829 operating without it, no dependency need be declared.
7833 If it is desirable for two or more related packages to
7834 share a configuration file <em>and</em> for all of the
7835 related packages to be able to modify that configuration
7836 file, then the following should be done:
7837 <enumlist compact="compact">
7839 One of the related packages (the "owning" package)
7840 will manage the configuration file with maintainer
7841 scripts as described in the previous section.
7844 The owning package should also provide a program
7845 that the other packages may use to modify the
7849 The related packages must use the provided program
7850 to make any desired modifications to the
7851 configuration file. They should either depend on
7852 the core package to guarantee that the configuration
7853 modifier program is available or accept gracefully
7854 that they cannot modify the configuration file if it
7855 is not. (This is in addition to the fact that the
7856 configuration file may not even be present in the
7863 Sometimes it's appropriate to create a new package which
7864 provides the basic infrastructure for the other packages
7865 and which manages the shared configuration files. (The
7866 <tt>sgml-base</tt> package is a good example.)
7871 <heading>User configuration files ("dotfiles")</heading>
7874 The files in <file>/etc/skel</file> will automatically be
7875 copied into new user accounts by <prgn>adduser</prgn>.
7876 No other program should reference the files in
7877 <file>/etc/skel</file>.
7881 Therefore, if a program needs a dotfile to exist in
7882 advance in <file>$HOME</file> to work sensibly, that dotfile
7883 should be installed in <file>/etc/skel</file> and treated as a
7888 However, programs that require dotfiles in order to
7889 operate sensibly are a bad thing, unless they do create
7890 the dotfiles themselves automatically.
7894 Furthermore, programs should be configured by the Debian
7895 default installation to behave as closely to the upstream
7896 default behavior as possible.
7900 Therefore, if a program in a Debian package needs to be
7901 configured in some way in order to operate sensibly, that
7902 should be done using a site-wide configuration file placed
7903 in <file>/etc</file>. Only if the program doesn't support a
7904 site-wide default configuration and the package maintainer
7905 doesn't have time to add it may a default per-user file be
7906 placed in <file>/etc/skel</file>.
7910 <file>/etc/skel</file> should be as empty as we can make it.
7911 This is particularly true because there is no easy (or
7912 necessarily desirable) mechanism for ensuring that the
7913 appropriate dotfiles are copied into the accounts of
7914 existing users when a package is installed.
7920 <heading>Log files</heading>
7922 Log files should usually be named
7923 <file>/var/log/<var>package</var>.log</file>. If you have many
7924 log files, or need a separate directory for permission
7925 reasons (<file>/var/log</file> is writable only by
7926 <file>root</file>), you should usually create a directory named
7927 <file>/var/log/<var>package</var></file> and place your log
7932 Log files must be rotated occasionally so that they don't
7933 grow indefinitely; the best way to do this is to drop a log
7934 rotation configuration file into the directory
7935 <file>/etc/logrotate.d</file> and use the facilities provided by
7936 logrotate.<footnote>
7938 The traditional approach to log files has been to set up
7939 <em>ad hoc</em> log rotation schemes using simple shell
7940 scripts and cron. While this approach is highly
7941 customizable, it requires quite a lot of sysadmin work.
7942 Even though the original Debian system helped a little
7943 by automatically installing a system which can be used
7944 as a template, this was deemed not enough.
7948 The use of <prgn>logrotate</prgn>, a program developed
7949 by Red Hat, is better, as it centralizes log management.
7950 It has both a configuration file
7951 (<file>/etc/logrotate.conf</file>) and a directory where
7952 packages can drop their individual log rotation
7953 configurations (<file>/etc/logrotate.d</file>).
7956 Here is a good example for a logrotate config
7957 file (for more information see <manref name="logrotate"
7959 <example compact="compact">
7960 /var/log/foo/*.log {
7965 /etc/init.d/foo force-reload
7969 This rotates all files under <file>/var/log/foo</file>, saves 12
7970 compressed generations, and forces the daemon to reload its
7971 configuration information after the log rotation.
7975 Log files should be removed when the package is
7976 purged (but not when it is only removed). This should be
7977 done by the <prgn>postrm</prgn> script when it is called
7978 with the argument <tt>purge</tt> (see <ref
7979 id="removedetails">).
7984 <heading>Permissions and owners</heading>
7987 The rules in this section are guidelines for general use.
7988 If necessary you may deviate from the details below.
7989 However, if you do so you must make sure that what is done
7990 is secure and you should try to be as consistent as possible
7991 with the rest of the system. You should probably also
7992 discuss it on <prgn>debian-devel</prgn> first.
7996 Files should be owned by <tt>root:root</tt>, and made
7997 writable only by the owner and universally readable (and
7998 executable, if appropriate), that is mode 644 or 755.
8002 Directories should be mode 755 or (for group-writability)
8003 mode 2775. The ownership of the directory should be
8004 consistent with its mode: if a directory is mode 2775, it
8005 should be owned by the group that needs write access to
8008 When a package is upgraded, and the owner or permissions
8009 of a file included in the package has changed, dpkg
8010 arranges for the ownership and permissions to be
8011 correctly set upon installation. However, this does not
8012 extend to directories; the permissions and ownership of
8013 directories already on the system does not change on
8014 install or upgrade of packages. This makes sense, since
8015 otherwise common directories like <tt>/usr</tt> would
8016 always be in flux. To correctly change permissions of a
8017 directory the package owns, explicit action is required,
8018 usually in the <tt>postinst</tt> script. Care must be
8019 taken to handle downgrades as well, in that case.
8026 Setuid and setgid executables should be mode 4755 or 2755
8027 respectively, and owned by the appropriate user or group.
8028 They should not be made unreadable (modes like 4711 or
8029 2711 or even 4111); doing so achieves no extra security,
8030 because anyone can find the binary in the freely available
8031 Debian package; it is merely inconvenient. For the same
8032 reason you should not restrict read or execute permissions
8033 on non-set-id executables.
8037 Some setuid programs need to be restricted to particular
8038 sets of users, using file permissions. In this case they
8039 should be owned by the uid to which they are set-id, and by
8040 the group which should be allowed to execute them. They
8041 should have mode 4754; again there is no point in making
8042 them unreadable to those users who must not be allowed to
8047 It is possible to arrange that the system administrator can
8048 reconfigure the package to correspond to their local
8049 security policy by changing the permissions on a binary:
8050 they can do this by using <prgn>dpkg-statoverride</prgn>, as
8051 described below.<footnote>
8052 Ordinary files installed by <prgn>dpkg</prgn> (as
8053 opposed to <tt>conffile</tt>s and other similar objects)
8054 normally have their permissions reset to the distributed
8055 permissions when the package is reinstalled. However,
8056 the use of <prgn>dpkg-statoverride</prgn> overrides this
8059 Another method you should consider is to create a group for
8060 people allowed to use the program(s) and make any setuid
8061 executables executable only by that group.
8065 If you need to create a new user or group for your package
8066 there are two possibilities. Firstly, you may need to
8067 make some files in the binary package be owned by this
8068 user or group, or you may need to compile the user or
8069 group id (rather than just the name) into the binary
8070 (though this latter should be avoided if possible, as in
8071 this case you need a statically allocated id).</p>
8074 If you need a statically allocated id, you must ask for a
8075 user or group id from the <tt>base-passwd</tt> maintainer,
8076 and must not release the package until you have been
8077 allocated one. Once you have been allocated one you must
8078 either make the package depend on a version of the
8079 <tt>base-passwd</tt> package with the id present in
8080 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
8081 your package to create the user or group itself with the
8082 correct id (using <tt>adduser</tt>) in its
8083 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
8084 the <prgn>postinst</prgn> is to be preferred if it is
8085 possible, otherwise a pre-dependency will be needed on the
8086 <tt>adduser</tt> package.)
8090 On the other hand, the program might be able to determine
8091 the uid or gid from the user or group name at runtime, so
8092 that a dynamically allocated id can be used. In this case
8093 you should choose an appropriate user or group name,
8094 discussing this on <prgn>debian-devel</prgn> and checking
8095 with the <package/base-passwd/ maintainer that it is unique and that
8096 they do not wish you to use a statically allocated id
8097 instead. When this has been checked you must arrange for
8098 your package to create the user or group if necessary using
8099 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
8100 <prgn>postinst</prgn> script (again, the latter is to be
8101 preferred if it is possible).
8105 Note that changing the numeric value of an id associated
8106 with a name is very difficult, and involves searching the
8107 file system for all appropriate files. You need to think
8108 carefully whether a static or dynamic id is required, since
8109 changing your mind later will cause problems.
8112 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
8114 This section is not intended as policy, but as a
8115 description of the use of <prgn>dpkg-statoverride</prgn>.
8119 If a system administrator wishes to have a file (or
8120 directory or other such thing) installed with owner and
8121 permissions different from those in the distributed Debian
8122 package, they can use the <prgn>dpkg-statoverride</prgn>
8123 program to instruct <prgn>dpkg</prgn> to use the different
8124 settings every time the file is installed. Thus the
8125 package maintainer should distribute the files with their
8126 normal permissions, and leave it for the system
8127 administrator to make any desired changes. For example, a
8128 daemon which is normally required to be setuid root, but
8129 in certain situations could be used without being setuid,
8130 should be installed setuid in the <tt>.deb</tt>. Then the
8131 local system administrator can change this if they wish.
8132 If there are two standard ways of doing it, the package
8133 maintainer can use <tt>debconf</tt> to find out the
8134 preference, and call <prgn>dpkg-statoverride</prgn> in the
8135 maintainer script if necessary to accommodate the system
8136 administrator's choice. Care must be taken during
8137 upgrades to not override an existing setting.
8141 Given the above, <prgn>dpkg-statoverride</prgn> is
8142 essentially a tool for system administrators and would not
8143 normally be needed in the maintainer scripts. There is
8144 one type of situation, though, where calls to
8145 <prgn>dpkg-statoverride</prgn> would be needed in the
8146 maintainer scripts, and that involves packages which use
8147 dynamically allocated user or group ids. In such a
8148 situation, something like the following idiom can be very
8149 helpful in the package's <prgn>postinst</prgn>, where
8150 <tt>sysuser</tt> is a dynamically allocated id:
8152 for i in /usr/bin/foo /usr/sbin/bar
8154 # only do something when no setting exists
8155 if ! dpkg-statoverride --list $i >/dev/null 2>&1
8157 #include: debconf processing, question about foo and bar
8158 if [ "$RET" = "true" ] ; then
8159 dpkg-statoverride --update --add sysuser root 4755 $i
8164 The corresponding code to remove the override when the package
8167 for i in /usr/bin/foo /usr/sbin/bar
8169 if dpkg-statoverride --list $i >/dev/null 2>&1
8171 dpkg-statoverride --remove $i
8181 <chapt id="customized-programs">
8182 <heading>Customized programs</heading>
8184 <sect id="arch-spec">
8185 <heading>Architecture specification strings</heading>
8188 If a program needs to specify an <em>architecture specification
8189 string</em> in some place, it should select one of the strings
8190 provided by <tt>dpkg-architecture -L</tt>. The strings are in
8191 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
8192 part is sometimes elided, as when the OS is Linux.
8196 Note that we don't want to use
8197 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
8198 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
8199 since this would make our programs incompatible with other
8200 Linux distributions. We also don't use something like
8201 <tt><var>arch</var>-unknown-linux</tt>, since the
8202 <tt>unknown</tt> does not look very good.
8205 <sect1 id="arch-wildcard-spec">
8206 <heading>Architecture wildcards</heading>
8209 A package may specify an architecture wildcard. Architecture
8210 wildcards are in the format <tt>any</tt> (which matches every
8211 architecture), <tt><var>os</var></tt>-any, or
8212 any-<tt><var>cpu</var></tt>. <footnote>
8213 Internally, the package system normalizes the GNU triplets
8214 and the Debian arches into Debian arch triplets (which are
8215 kind of inverted GNU triplets), with the first component of
8216 the triplet representing the libc and ABI in use, and then
8217 does matching against those triplets. However, such
8218 triplets are an internal implementation detail that should
8219 not be used by packages directly. The libc and ABI portion
8220 is handled internally by the package system based on
8221 the <var>os</var> and <var>cpu</var>.
8228 <heading>Daemons</heading>
8231 The configuration files <file>/etc/services</file>,
8232 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
8233 by the <prgn>netbase</prgn> package and must not be modified
8238 If a package requires a new entry in one of these files, the
8239 maintainer should get in contact with the
8240 <prgn>netbase</prgn> maintainer, who will add the entries
8241 and release a new version of the <prgn>netbase</prgn>
8246 The configuration file <file>/etc/inetd.conf</file> must not be
8247 modified by the package's scripts except via the
8248 <prgn>update-inetd</prgn> script or the
8249 <file>DebianNet.pm</file> Perl module. See their documentation
8250 for details on how to add entries.
8254 If a package wants to install an example entry into
8255 <file>/etc/inetd.conf</file>, the entry must be preceded with
8256 exactly one hash character (<tt>#</tt>). Such lines are
8257 treated as "commented out by user" by the
8258 <prgn>update-inetd</prgn> script and are not changed or
8259 activated during package updates.
8264 <heading>Using pseudo-ttys and modifying wtmp, utmp and
8268 Some programs need to create pseudo-ttys. This should be done
8269 using Unix98 ptys if the C library supports it. The resulting
8270 program must not be installed setuid root, unless that
8271 is required for other functionality.
8275 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
8276 <file>/var/log/lastlog</file> must be installed writable by
8277 group <tt>utmp</tt>. Programs which need to modify those
8278 files must be installed setgid <tt>utmp</tt>.
8283 <heading>Editors and pagers</heading>
8286 Some programs have the ability to launch an editor or pager
8287 program to edit or display a text document. Since there are
8288 lots of different editors and pagers available in the Debian
8289 distribution, the system administrator and each user should
8290 have the possibility to choose their preferred editor and
8295 In addition, every program should choose a good default
8296 editor/pager if none is selected by the user or system
8301 Thus, every program that launches an editor or pager must
8302 use the EDITOR or PAGER environment variable to determine
8303 the editor or pager the user wishes to use. If these
8304 variables are not set, the programs <file>/usr/bin/editor</file>
8305 and <file>/usr/bin/pager</file> should be used, respectively.
8309 These two files are managed through the <prgn>dpkg</prgn>
8310 "alternatives" mechanism. Every package providing an editor or
8311 pager must call the <prgn>update-alternatives</prgn> script to
8312 register as an alternative for <file>/usr/bin/editor</file>
8313 or <file>/usr/bin/pager</file> as appropriate. The alternative
8314 should have a slave alternative
8315 for <file>/usr/share/man/man1/editor.1.gz</file>
8316 or <file>/usr/share/man/man1/pager.1.gz</file> pointing to the
8317 corresponding manual page.
8321 If it is very hard to adapt a program to make use of the
8322 EDITOR or PAGER variables, that program may be configured to
8323 use <file>/usr/bin/sensible-editor</file> and
8324 <file>/usr/bin/sensible-pager</file> as the editor or pager
8325 program respectively. These are two scripts provided in the
8326 <package>sensible-utils</package> package that check the EDITOR
8327 and PAGER variables and launch the appropriate program, and fall
8328 back to <file>/usr/bin/editor</file>
8329 and <file>/usr/bin/pager</file> if the variable is not set.
8333 A program may also use the VISUAL environment variable to
8334 determine the user's choice of editor. If it exists, it
8335 should take precedence over EDITOR. This is in fact what
8336 <file>/usr/bin/sensible-editor</file> does.
8340 It is not required for a package to depend on
8341 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
8342 package to provide such virtual packages.<footnote>
8343 The Debian base system already provides an editor and a
8349 <sect id="web-appl">
8350 <heading>Web servers and applications</heading>
8353 This section describes the locations and URLs that should
8354 be used by all web servers and web applications in the
8361 Cgi-bin executable files are installed in the
8363 <example compact="compact">
8364 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
8366 or a subdirectory of that directory, and should be
8368 <example compact="compact">
8369 http://localhost/cgi-bin/<var>cgi-bin-name</var>
8371 (possibly with a subdirectory name
8372 before <var>cgi-bin-name</var>).
8376 <p>Access to HTML documents</p>
8379 HTML documents for a package are stored in
8380 <file>/usr/share/doc/<var>package</var></file>
8381 and can be referred to as
8382 <example compact="compact">
8383 http://localhost/doc/<var>package</var>/<var>filename</var>
8388 The web server should restrict access to the document
8389 tree so that only clients on the same host can read
8390 the documents. If the web server does not support such
8391 access controls, then it should not provide access at
8392 all, or ask about providing access during installation.
8397 <p>Access to images</p>
8399 It is recommended that images for a package be stored
8400 in <tt>/usr/share/images/<var>package</var></tt> and
8401 may be referred to through an alias <tt>/images/</tt>
8404 http://localhost/images/<package>/<filename>
8411 <p>Web Document Root</p>
8414 Web Applications should try to avoid storing files in
8415 the Web Document Root. Instead they should use the
8416 /usr/share/doc/<var>package</var> directory for
8417 documents and register the Web Application via the
8418 <package>doc-base</package> package. If access to the
8419 web document root is unavoidable then use
8420 <example compact="compact">
8423 as the Document Root. This might be just a symbolic
8424 link to the location where the system administrator
8425 has put the real document root.
8428 <item><p>Providing httpd and/or httpd-cgi</p>
8430 All web servers should provide the virtual package
8431 <tt>httpd</tt>. If a web server has CGI support it should
8432 provide <tt>httpd-cgi</tt> additionally.
8435 All web applications which do not contain CGI scripts should
8436 depend on <tt>httpd</tt>, all those web applications which
8437 <tt>do</tt> contain CGI scripts, should depend on
8445 <sect id="mail-transport-agents">
8446 <heading>Mail transport, delivery and user agents</heading>
8449 Debian packages which process electronic mail, whether mail
8450 user agents (MUAs) or mail transport agents (MTAs), must
8451 ensure that they are compatible with the configuration
8452 decisions below. Failure to do this may result in lost
8453 mail, broken <tt>From:</tt> lines, and other serious brain
8458 The mail spool is <file>/var/mail</file> and the interface to
8459 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8460 the FHS). On older systems, the mail spool may be
8461 physically located in <file>/var/spool/mail</file>, but all
8462 access to the mail spool should be via the
8463 <file>/var/mail</file> symlink. The mail spool is part of the
8464 base system and not part of the MTA package.
8468 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8469 programs (such as IMAP daemons) must lock the mailbox in an
8470 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8471 be combined with dot locking. To avoid deadlocks, a program
8472 should use <tt>fcntl()</tt> first and dot locking after
8473 this, or alternatively implement the two locking methods in
8474 a non blocking way<footnote>
8475 If it is not possible to establish both locks, the
8476 system shouldn't wait for the second lock to be
8477 established, but remove the first lock, wait a (random)
8478 time, and start over locking again.
8479 </footnote>. Using the functions <tt>maillock</tt> and
8480 <tt>mailunlock</tt> provided by the
8481 <tt>liblockfile*</tt><footnote>
8482 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8483 to use these functions.
8484 </footnote> packages is the recommended way to realize this.
8488 Mailboxes are generally either mode 600 and owned by
8489 <var>user</var> or mode 660 and owned by
8490 <tt><var>user</var>:mail</tt><footnote>
8491 There are two traditional permission schemes for mail spools:
8492 mode 600 with all mail delivery done by processes running as
8493 the destination user, or mode 660 and owned by group mail with
8494 mail delivery done by a process running as a system user in
8495 group mail. Historically, Debian required mode 660 mail
8496 spools to enable the latter model, but that model has become
8497 increasingly uncommon and the principle of least privilege
8498 indicates that mail systems that use the first model should
8499 use permissions of 600. If delivery to programs is permitted,
8500 it's easier to keep the mail system secure if the delivery
8501 agent runs as the destination user. Debian Policy therefore
8502 permits either scheme.
8503 </footnote>. The local system administrator may choose a
8504 different permission scheme; packages should not make
8505 assumptions about the permission and ownership of mailboxes
8506 unless required (such as when creating a new mailbox). A MUA
8507 may remove a mailbox (unless it has nonstandard permissions) in
8508 which case the MTA or another MUA must recreate it if needed.
8512 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8513 be setgid mail to do the locking mentioned above (and
8514 must obviously avoid accessing other users' mailboxes
8515 using this privilege).</p>
8518 <file>/etc/aliases</file> is the source file for the system mail
8519 aliases (e.g., postmaster, usenet, etc.), it is the one
8520 which the sysadmin and <prgn>postinst</prgn> scripts may
8521 edit. After <file>/etc/aliases</file> is edited the program or
8522 human editing it must call <prgn>newaliases</prgn>. All MTA
8523 packages must come with a <prgn>newaliases</prgn> program,
8524 even if it does nothing, but older MTA packages did not do
8525 this so programs should not fail if <prgn>newaliases</prgn>
8526 cannot be found. Note that because of this, all MTA
8527 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8528 <tt>Replaces: mail-transport-agent</tt> control file
8533 The convention of writing <tt>forward to
8534 <var>address</var></tt> in the mailbox itself is not
8535 supported. Use a <tt>.forward</tt> file instead.</p>
8538 The <prgn>rmail</prgn> program used by UUCP
8539 for incoming mail should be <file>/usr/sbin/rmail</file>.
8540 Likewise, <prgn>rsmtp</prgn>, for receiving
8541 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8545 If your package needs to know what hostname to use on (for
8546 example) outgoing news and mail messages which are generated
8547 locally, you should use the file <file>/etc/mailname</file>. It
8548 will contain the portion after the username and <tt>@</tt>
8549 (at) sign for email addresses of users on the machine
8550 (followed by a newline).
8554 Such a package should check for the existence of this file
8555 when it is being configured. If it exists, it should be
8556 used without comment, although an MTA's configuration script
8557 may wish to prompt the user even if it finds that this file
8558 exists. If the file does not exist, the package should
8559 prompt the user for the value (preferably using
8560 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8561 as well as using it in the package's configuration. The
8562 prompt should make it clear that the name will not just be
8563 used by that package. For example, in this situation the
8564 <tt>inn</tt> package could say something like:
8565 <example compact="compact">
8566 Please enter the "mail name" of your system. This is the
8567 hostname portion of the address to be shown on outgoing
8568 news and mail messages. The default is
8569 <var>syshostname</var>, your system's host name. Mail
8570 name ["<var>syshostname</var>"]:
8572 where <var>syshostname</var> is the output of <tt>hostname
8578 <heading>News system configuration</heading>
8581 All the configuration files related to the NNTP (news)
8582 servers and clients should be located under
8583 <file>/etc/news</file>.</p>
8586 There are some configuration issues that apply to a number
8587 of news clients and server packages on the machine. These
8591 <tag><file>/etc/news/organization</file></tag>
8593 A string which should appear as the
8594 organization header for all messages posted
8595 by NNTP clients on the machine
8598 <tag><file>/etc/news/server</file></tag>
8600 Contains the FQDN of the upstream NNTP
8601 server, or localhost if the local machine is
8606 Other global files may be added as required for cross-package news
8613 <heading>Programs for the X Window System</heading>
8616 <heading>Providing X support and package priorities</heading>
8619 Programs that can be configured with support for the X
8620 Window System must be configured to do so and must declare
8621 any package dependencies necessary to satisfy their
8622 runtime requirements when using the X Window System. If
8623 such a package is of higher priority than the X packages
8624 on which it depends, it is required that either the
8625 X-specific components be split into a separate package, or
8626 that an alternative version of the package, which includes
8627 X support, be provided, or that the package's priority be
8633 <heading>Packages providing an X server</heading>
8636 Packages that provide an X server that, directly or
8637 indirectly, communicates with real input and display
8638 hardware should declare in their control data that they
8639 provide the virtual package <tt>xserver</tt>.<footnote>
8640 This implements current practice, and provides an
8641 actual policy for usage of the <tt>xserver</tt>
8642 virtual package which appears in the virtual packages
8643 list. In a nutshell, X servers that interface
8644 directly with the display and input hardware or via
8645 another subsystem (e.g., GGI) should provide
8646 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8647 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8653 <heading>Packages providing a terminal emulator</heading>
8656 Packages that provide a terminal emulator for the X Window
8657 System which meet the criteria listed below should declare
8658 in their control data that they provide the virtual
8659 package <tt>x-terminal-emulator</tt>. They should also
8660 register themselves as an alternative for
8661 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8662 20. That alternative should have a slave alternative
8663 for <file>/usr/share/man/man1/x-terminal-emulator.1.gz</file>
8664 pointing to the corresponding manual page.
8668 To be an <tt>x-terminal-emulator</tt>, a program must:
8669 <list compact="compact">
8671 Be able to emulate a DEC VT100 terminal, or a
8672 compatible terminal.
8676 Support the command-line option <tt>-e
8677 <var>command</var></tt>, which creates a new
8678 terminal window<footnote>
8679 "New terminal window" does not necessarily mean
8680 a new top-level X window directly parented by
8681 the window manager; it could, if the terminal
8682 emulator application were so coded, be a new
8683 "view" in a multiple-document interface (MDI).
8685 and runs the specified <var>command</var>,
8686 interpreting the entirety of the rest of the command
8687 line as a command to pass straight to exec, in the
8688 manner that <tt>xterm</tt> does.
8692 Support the command-line option <tt>-T
8693 <var>title</var></tt>, which creates a new terminal
8694 window with the window title <var>title</var>.
8701 <heading>Packages providing a window manager</heading>
8704 Packages that provide a window manager should declare in
8705 their control data that they provide the virtual package
8706 <tt>x-window-manager</tt>. They should also register
8707 themselves as an alternative for
8708 <file>/usr/bin/x-window-manager</file>, with a priority
8709 calculated as follows:
8710 <list compact="compact">
8712 Start with a priority of 20.
8716 If the window manager supports the Debian menu
8717 system, add 20 points if this support is available
8718 in the package's default configuration (i.e., no
8719 configuration files belonging to the system or user
8720 have to be edited to activate the feature); if
8721 configuration files must be modified, add only 10
8727 If the window manager complies with <url
8728 id="http://www.freedesktop.org/Standards/wm-spec"
8729 name="The Window Manager Specification Project">,
8730 written by the <url id="http://www.freedesktop.org/"
8731 name="Free Desktop Group">, add 40 points.
8735 If the window manager permits the X session to be
8736 restarted using a <em>different</em> window manager
8737 (without killing the X server) in its default
8738 configuration, add 10 points; otherwise add none.
8741 That alternative should have a slave alternative
8742 for <file>/usr/share/man/man1/x-window-manager.1.gz</file>
8743 pointing to the corresponding manual page.
8748 <heading>Packages providing fonts</heading>
8751 Packages that provide fonts for the X Window
8753 For the purposes of Debian Policy, a "font for the X
8754 Window System" is one which is accessed via X protocol
8755 requests. Fonts for the Linux console, for PostScript
8756 renderer, or any other purpose, do not fit this
8757 definition. Any tool which makes such fonts available
8758 to the X Window System, however, must abide by this
8761 must do a number of things to ensure that they are both
8762 available without modification of the X or font server
8763 configuration, and that they do not corrupt files used by
8764 other font packages to register information about
8768 Fonts of any type supported by the X Window System
8769 must be in a separate binary package from any
8770 executables, libraries, or documentation (except
8771 that specific to the fonts shipped, such as their
8772 license information). If one or more of the fonts
8773 so packaged are necessary for proper operation of
8774 the package with which they are associated the font
8775 package may be Recommended; if the fonts merely
8776 provide an enhancement, a Suggests relationship may
8777 be used. Packages must not Depend on font
8779 This is because the X server may retrieve fonts
8780 from the local file system or over the network
8781 from an X font server; the Debian package system
8782 is empowered to deal only with the local
8788 BDF fonts must be converted to PCF fonts with the
8789 <prgn>bdftopcf</prgn> utility (available in the
8790 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8791 placed in a directory that corresponds to their
8793 <list compact="compact">
8795 100 dpi fonts must be placed in
8796 <file>/usr/share/fonts/X11/100dpi/</file>.
8800 75 dpi fonts must be placed in
8801 <file>/usr/share/fonts/X11/75dpi/</file>.
8805 Character-cell fonts, cursor fonts, and other
8806 low-resolution fonts must be placed in
8807 <file>/usr/share/fonts/X11/misc/</file>.
8813 Type 1 fonts must be placed in
8814 <file>/usr/share/fonts/X11/Type1/</file>. If font
8815 metric files are available, they must be placed here
8820 Subdirectories of <file>/usr/share/fonts/X11/</file>
8821 other than those listed above must be neither
8822 created nor used. (The <file>PEX</file>, <file>CID</file>,
8823 <file>Speedo</file>, and <file>cyrillic</file> directories
8824 are excepted for historical reasons, but installation of
8825 files into these directories remains discouraged.)
8829 Font packages may, instead of placing files directly
8830 in the X font directories listed above, provide
8831 symbolic links in that font directory pointing to
8832 the files' actual location in the filesystem. Such
8833 a location must comply with the FHS.
8837 Font packages should not contain both 75dpi and
8838 100dpi versions of a font. If both are available,
8839 they should be provided in separate binary packages
8840 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8841 the names of the packages containing the
8842 corresponding fonts.
8846 Fonts destined for the <file>misc</file> subdirectory
8847 should not be included in the same package as 75dpi
8848 or 100dpi fonts; instead, they should be provided in
8849 a separate package with <tt>-misc</tt> appended to
8854 Font packages must not provide the files
8855 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8856 <file>fonts.scale</file> in a font directory:
8859 <file>fonts.dir</file> files must not be provided at all.
8863 <file>fonts.alias</file> and <file>fonts.scale</file>
8864 files, if needed, should be provided in the
8866 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8867 where <var>fontdir</var> is the name of the
8869 <file>/usr/share/fonts/X11/</file> where the
8870 package's corresponding fonts are stored
8871 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8872 <var>package</var> is the name of the package
8873 that provides these fonts, and
8874 <var>extension</var> is either <tt>scale</tt>
8875 or <tt>alias</tt>, whichever corresponds to
8882 Font packages must declare a dependency on
8883 <tt>xfonts-utils</tt> in their control
8888 Font packages that provide one or more
8889 <file>fonts.scale</file> files as described above must
8890 invoke <prgn>update-fonts-scale</prgn> on each
8891 directory into which they installed fonts
8892 <em>before</em> invoking
8893 <prgn>update-fonts-dir</prgn> on that directory.
8894 This invocation must occur in both the
8895 <prgn>postinst</prgn> (for all arguments) and
8896 <prgn>postrm</prgn> (for all arguments except
8897 <tt>upgrade</tt>) scripts.
8901 Font packages that provide one or more
8902 <file>fonts.alias</file> files as described above must
8903 invoke <prgn>update-fonts-alias</prgn> on each
8904 directory into which they installed fonts. This
8905 invocation must occur in both the
8906 <prgn>postinst</prgn> (for all arguments) and
8907 <prgn>postrm</prgn> (for all arguments except
8908 <tt>upgrade</tt>) scripts.
8912 Font packages must invoke
8913 <prgn>update-fonts-dir</prgn> on each directory into
8914 which they installed fonts. This invocation must
8915 occur in both the <prgn>postinst</prgn> (for all
8916 arguments) and <prgn>postrm</prgn> (for all
8917 arguments except <tt>upgrade</tt>) scripts.
8921 Font packages must not provide alias names for the
8922 fonts they include which collide with alias names
8923 already in use by fonts already packaged.
8927 Font packages must not provide fonts with the same
8928 XLFD registry name as another font already packaged.
8934 <sect1 id="appdefaults">
8935 <heading>Application defaults files</heading>
8938 Application defaults files must be installed in the
8939 directory <file>/etc/X11/app-defaults/</file> (use of a
8940 localized subdirectory of <file>/etc/X11/</file> as described
8941 in the <em>X Toolkit Intrinsics - C Language
8942 Interface</em> manual is also permitted). They must be
8943 registered as <tt>conffile</tt>s or handled as
8944 configuration files.
8948 Customization of programs' X resources may also be
8949 supported with the provision of a file with the same name
8950 as that of the package placed in
8951 the <file>/etc/X11/Xresources/</file> directory, which
8952 must be registered as a <tt>conffile</tt> or handled as a
8953 configuration file.<footnote>
8954 Note that this mechanism is not the same as using
8955 app-defaults; app-defaults are tied to the client
8956 binary on the local file system, whereas X resources
8957 are stored in the X server and affect all connecting
8964 <heading>Installation directory issues</heading>
8967 Historically, packages using the X Window System used a
8968 separate set of installation directories from other packages.
8969 This practice has been discontinued and packages using the X
8970 Window System should now generally be installed in the same
8971 directories as any other package. Specifically, packages must
8972 not install files under the <file>/usr/X11R6/</file> directory
8973 and the <file>/usr/X11R6/</file> directory hierarchy should be
8974 regarded as obsolete.
8978 Include files previously installed under
8979 <file>/usr/X11R6/include/X11/</file> should be installed into
8980 <file>/usr/include/X11/</file>. For files previously
8981 installed into subdirectories of
8982 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
8983 determine if subdirectories of <file>/usr/lib/</file> and
8984 <file>/usr/share/</file> can be used. If not, a subdirectory
8985 of <file>/usr/lib/X11/</file> should be used.
8989 Configuration files for window, display, or session managers
8990 or other applications that are tightly integrated with the X
8991 Window System may be placed in a subdirectory
8992 of <file>/etc/X11/</file> corresponding to the package name.
8993 Other X Window System applications should use
8994 the <file>/etc/</file> directory unless otherwise mandated by
8995 policy (such as for <ref id="appdefaults">).
9000 <heading>The OSF/Motif and OpenMotif libraries</heading>
9003 <em>Programs that require the non-DFSG-compliant OSF/Motif or
9004 OpenMotif libraries</em><footnote>
9005 OSF/Motif and OpenMotif are collectively referred to as
9006 "Motif" in this policy document.
9008 should be compiled against and tested with LessTif (a free
9009 re-implementation of Motif) instead. If the maintainer
9010 judges that the program or programs do not work
9011 sufficiently well with LessTif to be distributed and
9012 supported, but do so when compiled against Motif, then two
9013 versions of the package should be created; one linked
9014 statically against Motif and with <tt>-smotif</tt>
9015 appended to the package name, and one linked dynamically
9016 against Motif and with <tt>-dmotif</tt> appended to the
9021 Both Motif-linked versions are dependent
9022 upon non-DFSG-compliant software and thus cannot be
9023 uploaded to the <em>main</em> distribution; if the
9024 software is itself DFSG-compliant it may be uploaded to
9025 the <em>contrib</em> distribution. While known existing
9026 versions of Motif permit unlimited redistribution of
9027 binaries linked against the library (whether statically or
9028 dynamically), it is the package maintainer's
9029 responsibility to determine whether this is permitted by
9030 the license of the copy of Motif in their possession.
9036 <heading>Perl programs and modules</heading>
9039 Perl programs and modules should follow the current Perl policy.
9043 The Perl policy can be found in the <tt>perl-policy</tt>
9044 files in the <tt>debian-policy</tt> package.
9045 It is also available from the Debian web mirrors at
9046 <tt><url name="/doc/packaging-manuals/perl-policy/"
9047 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
9052 <heading>Emacs lisp programs</heading>
9055 Please refer to the "Debian Emacs Policy" for details of how to
9056 package emacs lisp programs.
9060 The Emacs policy is available in
9061 <file>debian-emacs-policy.gz</file> of the
9062 <package>emacsen-common</package> package.
9063 It is also available from the Debian web mirrors at
9064 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
9065 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
9070 <heading>Games</heading>
9073 The permissions on <file>/var/games</file> are mode 755, owner
9074 <tt>root</tt> and group <tt>root</tt>.
9078 Each game decides on its own security policy.</p>
9081 Games which require protected, privileged access to
9082 high-score files, saved games, etc., may be made
9083 set-<em>group</em>-id (mode 2755) and owned by
9084 <tt>root:games</tt>, and use files and directories with
9085 appropriate permissions (770 <tt>root:games</tt>, for
9086 example). They must not be made
9087 set-<em>user</em>-id, as this causes security problems. (If
9088 an attacker can subvert any set-user-id game they can
9089 overwrite the executable of any other, causing other players
9090 of these games to run a Trojan horse program. With a
9091 set-group-id game the attacker only gets access to less
9092 important game data, and if they can get at the other
9093 players' accounts at all it will take considerably more
9097 Some packages, for example some fortune cookie programs, are
9098 configured by the upstream authors to install with their
9099 data files or other static information made unreadable so
9100 that they can only be accessed through set-id programs
9101 provided. You should not do this in a Debian package: anyone can
9102 download the <file>.deb</file> file and read the data from it,
9103 so there is no point making the files unreadable. Not
9104 making the files unreadable also means that you don't have
9105 to make so many programs set-id, which reduces the risk of a
9109 As described in the FHS, binaries of games should be
9110 installed in the directory <file>/usr/games</file>. This also
9111 applies to games that use the X Window System. Manual pages
9112 for games (X and non-X games) should be installed in
9113 <file>/usr/share/man/man6</file>.</p>
9119 <heading>Documentation</heading>
9122 <heading>Manual pages</heading>
9125 You should install manual pages in <prgn>nroff</prgn> source
9126 form, in appropriate places under <file>/usr/share/man</file>.
9127 You should only use sections 1 to 9 (see the FHS for more
9128 details). You must not install a pre-formatted "cat page".
9132 Each program, utility, and function should have an
9133 associated manual page included in the same package. It is
9134 suggested that all configuration files also have a manual
9135 page included as well. Manual pages for protocols and other
9136 auxiliary things are optional.
9140 If no manual page is available, this is considered as a bug
9141 and should be reported to the Debian Bug Tracking System (the
9142 maintainer of the package is allowed to write this bug report
9143 themselves, if they so desire). Do not close the bug report
9144 until a proper man page is available.<footnote>
9145 It is not very hard to write a man page. See the
9146 <url id="http://www.schweikhardt.net/man_page_howto.html"
9147 name="Man-Page-HOWTO">,
9148 <manref name="man" section="7">, the examples
9149 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
9150 the helper program <prgn>help2man</prgn>, or the
9151 directory <file>/usr/share/doc/man-db/examples</file>.
9156 You may forward a complaint about a missing man page to the
9157 upstream authors, and mark the bug as forwarded in the
9158 Debian bug tracking system. Even though the GNU Project do
9159 not in general consider the lack of a man page to be a bug,
9160 we do; if they tell you that they don't consider it a bug
9161 you should leave the bug in our bug tracking system open
9166 Manual pages should be installed compressed using <tt>gzip -9</tt>.
9170 If one man page needs to be accessible via several names it
9171 is better to use a symbolic link than the <file>.so</file>
9172 feature, but there is no need to fiddle with the relevant
9173 parts of the upstream source to change from <file>.so</file> to
9174 symlinks: don't do it unless it's easy. You should not
9175 create hard links in the manual page directories, nor put
9176 absolute filenames in <file>.so</file> directives. The filename
9177 in a <file>.so</file> in a man page should be relative to the
9178 base of the man page tree (usually
9179 <file>/usr/share/man</file>). If you do not create any links
9180 (whether symlinks, hard links, or <tt>.so</tt> directives)
9181 in the file system to the alternate names of the man page,
9182 then you should not rely on <prgn>man</prgn> finding your
9183 man page under those names based solely on the information in
9184 the man page's header.<footnote>
9185 Supporting this in <prgn>man</prgn> often requires
9186 unreasonable processing time to find a manual page or to
9187 report that none exists, and moves knowledge into man's
9188 database that would be better left in the file system.
9189 This support is therefore deprecated and will cease to
9190 be present in the future.
9195 Manual pages in locale-specific subdirectories of
9196 <file>/usr/share/man</file> should use either UTF-8 or the usual
9197 legacy encoding for that language (normally the one corresponding
9198 to the shortest relevant locale name in
9199 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
9200 <file>/usr/share/man/fr</file> should use either UTF-8 or
9201 ISO-8859-1.<footnote>
9202 <prgn>man</prgn> will automatically detect whether UTF-8 is in
9203 use. In future, all manual pages will be required to use
9209 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
9210 included in the subdirectory name unless it indicates a
9211 significant difference in the language, as this excludes
9212 speakers of the language in other countries.<footnote>
9213 At the time of writing, Chinese and Portuguese are the main
9214 languages with such differences, so <file>pt_BR</file>,
9215 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
9220 If a localized version of a manual page is provided, it should
9221 either be up-to-date or it should be obvious to the reader that
9222 it is outdated and the original manual page should be used
9223 instead. This can be done either by a note at the beginning of
9224 the manual page or by showing the missing or changed portions in
9225 the original language instead of the target language.
9230 <heading>Info documents</heading>
9233 Info documents should be installed in <file>/usr/share/info</file>.
9234 They should be compressed with <tt>gzip -9</tt>.
9238 The <prgn>install-info</prgn> program maintains a directory of
9239 installed info documents in <file>/usr/share/info/dir</file> for
9240 the use of info readers.<footnote>
9241 It was previously necessary for packages installing info
9242 documents to run <prgn>install-info</prgn> from maintainer
9243 scripts. This is no longer necessary. The installation
9244 system now uses dpkg triggers.
9246 This file must not be included in packages. Packages containing
9247 info documents should depend on <tt>dpkg (>= 1.15.4) |
9248 install-info</tt> to ensure that the directory file is properly
9249 rebuilt during partial upgrades from Debian 5.0 (lenny) and
9254 Info documents should contain section and directory entry
9255 information in the document for the use
9256 of <prgn>install-info</prgn>. The section should be specified
9257 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
9258 space and the section of this info page. The directory entry or
9259 entries should be included between
9260 a <tt>START-INFO-DIR-ENTRY</tt> line and
9261 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
9263 INFO-DIR-SECTION Individual utilities
9264 START-INFO-DIR-ENTRY
9265 * example: (example). An example info directory entry.
9268 To determine which section to use, you should look
9269 at <file>/usr/share/info/dir</file> on your system and choose
9270 the most relevant (or create a new section if none of the
9271 current sections are relevant).<footnote>
9272 Normally, info documents are generated from Texinfo source.
9273 To include this information in the generated info document, if
9274 it is absent, add commands like:
9276 @dircategory Individual utilities
9278 * example: (example). An example info directory entry.
9281 to the Texinfo source of the document and ensure that the info
9282 documents are rebuilt from source during the package build.
9288 <heading>Additional documentation</heading>
9291 Any additional documentation that comes with the package may
9292 be installed at the discretion of the package maintainer.
9293 Plain text documentation should be installed in the directory
9294 <file>/usr/share/doc/<var>package</var></file>, where
9295 <var>package</var> is the name of the package, and
9296 compressed with <tt>gzip -9</tt> unless it is small.
9300 If a package comes with large amounts of documentation which
9301 many users of the package will not require you should create
9302 a separate binary package to contain it, so that it does not
9303 take up disk space on the machines of users who do not need
9304 or want it installed.</p>
9307 It is often a good idea to put text information files
9308 (<file>README</file>s, changelogs, and so forth) that come with
9309 the source package in <file>/usr/share/doc/<var>package</var></file>
9310 in the binary package. However, you don't need to install
9311 the instructions for building and installing the package, of
9315 Packages must not require the existence of any files in
9316 <file>/usr/share/doc/</file> in order to function
9318 The system administrator should be able to
9319 delete files in <file>/usr/share/doc/</file> without causing
9320 any programs to break.
9322 Any files that are referenced by programs but are also
9323 useful as stand alone documentation should be installed under
9324 <file>/usr/share/<var>package</var>/</file> with symbolic links from
9325 <file>/usr/share/doc/<var>package</var></file>.
9329 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9330 link to another directory in <file>/usr/share/doc</file> only if
9331 the two packages both come from the same source and the
9332 first package Depends on the second.<footnote>
9334 Please note that this does not override the section on
9335 changelog files below, so the file
9336 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
9337 must refer to the changelog for the current version of
9338 <var>package</var> in question. In practice, this means
9339 that the sources of the target and the destination of the
9340 symlink must be the same (same source package and
9347 Former Debian releases placed all additional documentation
9348 in <file>/usr/doc/<var>package</var></file>. This has been
9349 changed to <file>/usr/share/doc/<var>package</var></file>,
9350 and packages must not put documentation in the directory
9351 <file>/usr/doc/<var>package</var></file>. <footnote>
9352 At this phase of the transition, we no longer require a
9353 symbolic link in <file>/usr/doc/</file>. At a later point,
9354 policy shall change to make the symbolic links a bug.
9360 <heading>Preferred documentation formats</heading>
9363 The unification of Debian documentation is being carried out
9367 If your package comes with extensive documentation in a
9368 markup format that can be converted to various other formats
9369 you should if possible ship HTML versions in a binary
9370 package, in the directory
9371 <file>/usr/share/doc/<var>appropriate-package</var></file> or
9372 its subdirectories.<footnote>
9373 The rationale: The important thing here is that HTML
9374 docs should be available in <em>some</em> package, not
9375 necessarily in the main binary package.
9380 Other formats such as PostScript may be provided at the
9381 package maintainer's discretion.
9385 <sect id="copyrightfile">
9386 <heading>Copyright information</heading>
9389 Every package must be accompanied by a verbatim copy of its
9390 copyright information and distribution license in the file
9391 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
9392 file must neither be compressed nor be a symbolic link.
9396 In addition, the copyright file must say where the upstream
9397 sources (if any) were obtained. It should name the original
9398 authors of the package and the Debian maintainer(s) who were
9399 involved with its creation.
9403 Packages in the <em>contrib</em> or <em>non-free</em> archive
9404 areas should state in the copyright file that the package is not
9405 part of the Debian GNU/Linux distribution and briefly explain
9410 A copy of the file which will be installed in
9411 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9412 be in <file>debian/copyright</file> in the source package.
9416 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9417 link to another directory in <file>/usr/share/doc</file> only if
9418 the two packages both come from the same source and the
9419 first package Depends on the second. These rules are
9420 important because copyrights must be extractable by
9425 Packages distributed under the Apache license (version 2.0), the
9426 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
9427 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
9428 1.3) should refer to the corresponding files
9429 under <file>/usr/share/common-licenses</file>,<footnote>
9432 <file>/usr/share/common-licenses/Apache-2.0</file>,
9433 <file>/usr/share/common-licenses/Artistic</file>,
9434 <file>/usr/share/common-licenses/GPL-1</file>,
9435 <file>/usr/share/common-licenses/GPL-2</file>,
9436 <file>/usr/share/common-licenses/GPL-3</file>,
9437 <file>/usr/share/common-licenses/LGPL-2</file>,
9438 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9439 <file>/usr/share/common-licenses/LGPL-3</file>,
9440 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
9441 <file>/usr/share/common-licenses/GFDL-1.3</file>
9442 respectively. The University of California BSD license is
9443 also included in <package>base-files</package> as
9444 <file>/usr/share/common-licenses/BSD</file>, but given the
9445 brevity of this license, its specificity to code whose
9446 copyright is held by the Regents of the University of
9447 California, and the frequency of minor wording changes, its
9448 text should be included in the copyright file rather than
9449 referencing this file.
9451 </footnote> rather than quoting them in the copyright
9456 You should not use the copyright file as a general <file>README</file>
9457 file. If your package has such a file it should be
9458 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9459 <file>README.Debian</file> or some other appropriate place.</p>
9463 <heading>Examples</heading>
9466 Any examples (configurations, source files, whatever),
9467 should be installed in a directory
9468 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9469 files should not be referenced by any program: they're there
9470 for the benefit of the system administrator and users as
9471 documentation only. Architecture-specific example files
9472 should be installed in a directory
9473 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9475 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9476 latter directory itself may be a symbolic link to the
9481 If the purpose of a package is to provide examples, then the
9482 example files may be installed into
9483 <file>/usr/share/doc/<var>package</var></file>.
9487 <sect id="changelogs">
9488 <heading>Changelog files</heading>
9491 Packages that are not Debian-native must contain a
9492 compressed copy of the <file>debian/changelog</file> file from
9493 the Debian source tree in
9494 <file>/usr/share/doc/<var>package</var></file> with the name
9495 <file>changelog.Debian.gz</file>.
9499 If an upstream changelog is available, it should be accessible as
9500 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9501 plain text. If the upstream changelog is distributed in
9502 HTML, it should be made available in that form as
9503 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9504 and a plain text <file>changelog.gz</file> should be generated
9505 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9506 the upstream changelog files do not already conform to this
9507 naming convention, then this may be achieved either by
9508 renaming the files, or by adding a symbolic link, at the
9509 maintainer's discretion.<footnote>
9510 Rationale: People should not have to look in places for
9511 upstream changelogs merely because they are given
9512 different names or are distributed in HTML format.
9517 All of these files should be installed compressed using
9518 <tt>gzip -9</tt>, as they will become large with time even
9519 if they start out small.
9523 If the package has only one changelog which is used both as
9524 the Debian changelog and the upstream one because there is
9525 no separate upstream maintainer then that changelog should
9526 usually be installed as
9527 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9528 there is a separate upstream maintainer, but no upstream
9529 changelog, then the Debian changelog should still be called
9530 <file>changelog.Debian.gz</file>.
9534 For details about the format and contents of the Debian
9535 changelog file, please see <ref id="dpkgchangelog">.
9540 <appendix id="pkg-scope">
9541 <heading>Introduction and scope of these appendices</heading>
9544 These appendices are taken essentially verbatim from the
9545 now-deprecated Packaging Manual, version 3.2.1.0. They are
9546 the chapters which are likely to be of use to package
9547 maintainers and which have not already been included in the
9548 policy document itself. Most of these sections are very likely
9549 not relevant to policy; they should be treated as
9550 documentation for the packaging system. Please note that these
9551 appendices are included for convenience, and for historical
9552 reasons: they used to be part of policy package, and they have
9553 not yet been incorporated into dpkg documentation. However,
9554 they still have value, and hence they are presented here.
9558 They have not yet been checked to ensure that they are
9559 compatible with the contents of policy, and if there are any
9560 contradictions, the version in the main policy document takes
9561 precedence. The remaining chapters of the old Packaging
9562 Manual have also not been read in detail to ensure that there
9563 are not parts which have been left out. Both of these will be
9568 Certain parts of the Packaging manual were integrated into the
9569 Policy Manual proper, and removed from the appendices. Links
9570 have been placed from the old locations to the new ones.
9574 <prgn>dpkg</prgn> is a suite of programs for creating binary
9575 package files and installing and removing them on Unix
9577 <prgn>dpkg</prgn> is targeted primarily at Debian
9578 GNU/Linux, but may work on or be ported to other
9584 The binary packages are designed for the management of
9585 installed executable programs (usually compiled binaries) and
9586 their associated data, though source code examples and
9587 documentation are provided as part of some packages.</p>
9590 This manual describes the technical aspects of creating Debian
9591 binary packages (<file>.deb</file> files). It documents the
9592 behavior of the package management programs
9593 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9594 they interact with packages.</p>
9597 It also documents the interaction between
9598 <prgn>dselect</prgn>'s core and the access method scripts it
9599 uses to actually install the selected packages, and describes
9600 how to create a new access method.</p>
9603 This manual does not go into detail about the options and
9604 usage of the package building and installation tools. It
9605 should therefore be read in conjunction with those programs'
9610 The utility programs which are provided with <prgn>dpkg</prgn>
9611 for managing various system configuration and similar issues,
9612 such as <prgn>update-rc.d</prgn> and
9613 <prgn>install-info</prgn>, are not described in detail here -
9614 please see their man pages.
9618 It is assumed that the reader is reasonably familiar with the
9619 <prgn>dpkg</prgn> System Administrators' manual.
9620 Unfortunately this manual does not yet exist.
9624 The Debian version of the FSF's GNU hello program is provided
9625 as an example for people wishing to create Debian
9626 packages. The Debian <prgn>debmake</prgn> package is
9627 recommended as a very helpful tool in creating and maintaining
9628 Debian packages. However, while the tools and examples are
9629 helpful, they do not replace the need to read and follow the
9630 Policy and Programmer's Manual.</p>
9633 <appendix id="pkg-binarypkg">
9634 <heading>Binary packages (from old Packaging Manual)</heading>
9637 The binary package has two main sections. The first part
9638 consists of various control information files and scripts used
9639 by <prgn>dpkg</prgn> when installing and removing. See <ref
9640 id="pkg-controlarea">.
9644 The second part is an archive containing the files and
9645 directories to be installed.
9649 In the future binary packages may also contain other
9650 components, such as checksums and digital signatures. The
9651 format for the archive is described in full in the
9652 <file>deb(5)</file> man page.
9656 <sect id="pkg-bincreating"><heading>Creating package files -
9657 <prgn>dpkg-deb</prgn>
9661 All manipulation of binary package files is done by
9662 <prgn>dpkg-deb</prgn>; it's the only program that has
9663 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9664 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9665 will spot that the options requested are appropriate to
9666 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9671 In order to create a binary package you must make a
9672 directory tree which contains all the files and directories
9673 you want to have in the file system data part of the package.
9674 In Debian-format source packages this directory is usually
9675 <file>debian/tmp</file>, relative to the top of the package's
9680 They should have the locations (relative to the root of the
9681 directory tree you're constructing) ownerships and
9682 permissions which you want them to have on the system when
9687 With current versions of <prgn>dpkg</prgn> the uid/username
9688 and gid/groupname mappings for the users and groups being
9689 used should be the same on the system where the package is
9690 built and the one where it is installed.
9694 You need to add one special directory to the root of the
9695 miniature file system tree you're creating:
9696 <prgn>DEBIAN</prgn>. It should contain the control
9697 information files, notably the binary package control file
9698 (see <ref id="pkg-controlfile">).
9702 The <prgn>DEBIAN</prgn> directory will not appear in the
9703 file system archive of the package, and so won't be installed
9704 by <prgn>dpkg</prgn> when the package is installed.
9708 When you've prepared the package, you should invoke:
9710 dpkg --build <var>directory</var>
9715 This will build the package in
9716 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9717 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9718 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9723 See the man page <manref name="dpkg-deb" section="8"> for details of how
9724 to examine the contents of this newly-created file. You may find the
9725 output of following commands enlightening:
9727 dpkg-deb --info <var>filename</var>.deb
9728 dpkg-deb --contents <var>filename</var>.deb
9729 dpkg --contents <var>filename</var>.deb
9731 To view the copyright file for a package you could use this command:
9733 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
9738 <sect id="pkg-controlarea">
9739 <heading>Package control information files</heading>
9742 The control information portion of a binary package is a
9743 collection of files with names known to <prgn>dpkg</prgn>.
9744 It will treat the contents of these files specially - some
9745 of them contain information used by <prgn>dpkg</prgn> when
9746 installing or removing the package; others are scripts which
9747 the package maintainer wants <prgn>dpkg</prgn> to run.
9751 It is possible to put other files in the package control
9752 area, but this is not generally a good idea (though they
9753 will largely be ignored).
9757 Here is a brief list of the control info files supported by
9758 <prgn>dpkg</prgn> and a summary of what they're used for.
9763 <tag><tt>control</tt>
9766 This is the key description file used by
9767 <prgn>dpkg</prgn>. It specifies the package's name
9768 and version, gives its description for the user,
9769 states its relationships with other packages, and so
9770 forth. See <ref id="sourcecontrolfiles"> and
9771 <ref id="binarycontrolfiles">.
9775 It is usually generated automatically from information
9776 in the source package by the
9777 <prgn>dpkg-gencontrol</prgn> program, and with
9778 assistance from <prgn>dpkg-shlibdeps</prgn>.
9779 See <ref id="pkg-sourcetools">.
9783 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9788 These are executable files (usually scripts) which
9789 <prgn>dpkg</prgn> runs during installation, upgrade
9790 and removal of packages. They allow the package to
9791 deal with matters which are particular to that package
9792 or require more complicated processing than that
9793 provided by <prgn>dpkg</prgn>. Details of when and
9794 how they are called are in <ref id="maintainerscripts">.
9798 It is very important to make these scripts idempotent.
9799 See <ref id="idempotency">.
9803 The maintainer scripts are not guaranteed to run with a
9804 controlling terminal and may not be able to interact with
9805 the user. See <ref id="controllingterminal">.
9809 <tag><tt>conffiles</tt>
9812 This file contains a list of configuration files which
9813 are to be handled automatically by <prgn>dpkg</prgn>
9814 (see <ref id="pkg-conffiles">). Note that not necessarily
9815 every configuration file should be listed here.
9818 <tag><tt>shlibs</tt>
9821 This file contains a list of the shared libraries
9822 supplied by the package, with dependency details for
9823 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9824 when it determines what dependencies are required in a
9825 package control file. The <tt>shlibs</tt> file format
9826 is described on <ref id="shlibs">.
9831 <sect id="pkg-controlfile">
9832 <heading>The main control information file: <tt>control</tt></heading>
9835 The most important control information file used by
9836 <prgn>dpkg</prgn> when it installs a package is
9837 <tt>control</tt>. It contains all the package's "vital
9842 The binary package control files of packages built from
9843 Debian sources are made by a special tool,
9844 <prgn>dpkg-gencontrol</prgn>, which reads
9845 <file>debian/control</file> and <file>debian/changelog</file> to
9846 find the information it needs. See <ref id="pkg-sourcepkg"> for
9851 The fields in binary package control files are listed in
9852 <ref id="binarycontrolfiles">.
9856 A description of the syntax of control files and the purpose
9857 of the fields is available in <ref id="controlfields">.
9862 <heading>Time Stamps</heading>
9865 See <ref id="timestamps">.
9870 <appendix id="pkg-sourcepkg">
9871 <heading>Source packages (from old Packaging Manual) </heading>
9874 The Debian binary packages in the distribution are generated
9875 from Debian sources, which are in a special format to assist
9876 the easy and automatic building of binaries.
9879 <sect id="pkg-sourcetools">
9880 <heading>Tools for processing source packages</heading>
9883 Various tools are provided for manipulating source packages;
9884 they pack and unpack sources and help build of binary
9885 packages and help manage the distribution of new versions.
9889 They are introduced and typical uses described here; see
9890 <manref name="dpkg-source" section="1"> for full
9891 documentation about their arguments and operation.
9895 For examples of how to construct a Debian source package,
9896 and how to use those utilities that are used by Debian
9897 source packages, please see the <prgn>hello</prgn> example
9901 <sect1 id="pkg-dpkg-source">
9903 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9908 This program is frequently used by hand, and is also
9909 called from package-independent automated building scripts
9910 such as <prgn>dpkg-buildpackage</prgn>.
9914 To unpack a package it is typically invoked with
9916 dpkg-source -x <var>.../path/to/filename</var>.dsc
9921 with the <file><var>filename</var>.tar.gz</file> and
9922 <file><var>filename</var>.diff.gz</file> (if applicable) in
9923 the same directory. It unpacks into
9924 <file><var>package</var>-<var>version</var></file>, and if
9926 <file><var>package</var>-<var>version</var>.orig</file>, in
9927 the current directory.
9931 To create a packed source archive it is typically invoked:
9933 dpkg-source -b <var>package</var>-<var>version</var>
9938 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
9939 <file>.diff.gz</file> (if appropriate) in the current
9940 directory. <prgn>dpkg-source</prgn> does not clean the
9941 source tree first - this must be done separately if it is
9946 See also <ref id="pkg-sourcearchives">.</p>
9950 <sect1 id="pkg-dpkg-buildpackage">
9952 <prgn>dpkg-buildpackage</prgn> - overall package-building
9957 <prgn>dpkg-buildpackage</prgn> is a script which invokes
9958 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
9959 targets <tt>clean</tt>, <tt>build</tt> and
9960 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
9961 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
9962 source and binary package upload.
9966 It is usually invoked by hand from the top level of the
9967 built or unbuilt source directory. It may be invoked with
9968 no arguments; useful arguments include:
9969 <taglist compact="compact">
9970 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
9973 Do not sign the <tt>.changes</tt> file or the
9974 source package <tt>.dsc</tt> file, respectively.</p>
9976 <tag><tt>-p<var>sign-command</var></tt></tag>
9979 Invoke <var>sign-command</var> instead of finding
9980 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
9981 <var>sign-command</var> must behave just like
9982 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
9984 <tag><tt>-r<var>root-command</var></tt></tag>
9987 When root privilege is required, invoke the command
9988 <var>root-command</var>. <var>root-command</var>
9989 should invoke its first argument as a command, from
9990 the <prgn>PATH</prgn> if necessary, and pass its
9991 second and subsequent arguments to the command it
9992 calls. If no <var>root-command</var> is supplied
9993 then <var>dpkg-buildpackage</var> will take no
9994 special action to gain root privilege, so that for
9995 most packages it will have to be invoked as root to
9998 <tag><tt>-b</tt>, <tt>-B</tt></tag>
10001 Two types of binary-only build and upload - see
10002 <manref name="dpkg-source" section="1">.
10009 <sect1 id="pkg-dpkg-gencontrol">
10011 <prgn>dpkg-gencontrol</prgn> - generates binary package
10016 This program is usually called from <file>debian/rules</file>
10017 (see <ref id="pkg-sourcetree">) in the top level of the source
10022 This is usually done just before the files and directories in the
10023 temporary directory tree where the package is being built have their
10024 permissions and ownerships set and the package is constructed using
10025 <prgn>dpkg-deb/</prgn>
10027 This is so that the control file which is produced has
10028 the right permissions
10033 <prgn>dpkg-gencontrol</prgn> must be called after all the
10034 files which are to go into the package have been placed in
10035 the temporary build directory, so that its calculation of
10036 the installed size of a package is correct.
10040 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
10041 be run after <prgn>dpkg-shlibdeps</prgn> so that the
10042 variable substitutions created by
10043 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
10048 For a package which generates only one binary package, and
10049 which builds it in <file>debian/tmp</file> relative to the top
10050 of the source package, it is usually sufficient to call
10051 <prgn>dpkg-gencontrol</prgn>.
10055 Sources which build several binaries will typically need
10058 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
10059 </example> The <tt>-P</tt> tells
10060 <prgn>dpkg-gencontrol</prgn> that the package is being
10061 built in a non-default directory, and the <tt>-p</tt>
10062 tells it which package's control file should be generated.
10066 <prgn>dpkg-gencontrol</prgn> also adds information to the
10067 list of files in <file>debian/files</file>, for the benefit of
10068 (for example) a future invocation of
10069 <prgn>dpkg-genchanges</prgn>.</p>
10072 <sect1 id="pkg-dpkg-shlibdeps">
10074 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
10079 This program is usually called from <file>debian/rules</file>
10080 just before <prgn>dpkg-gencontrol</prgn> (see <ref
10081 id="pkg-sourcetree">), in the top level of the source tree.
10085 Its arguments are executables and shared libraries
10088 They may be specified either in the locations in the
10089 source tree where they are created or in the locations
10090 in the temporary build tree where they are installed
10091 prior to binary package creation.
10093 </footnote> for which shared library dependencies should
10094 be included in the binary package's control file.
10098 If some of the found shared libraries should only
10099 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
10100 some warrant a <tt>Pre-Depends</tt>, this can be achieved
10101 by using the <tt>-d<var>dependency-field</var></tt> option
10102 before those executable(s). (Each <tt>-d</tt> option
10103 takes effect until the next <tt>-d</tt>.)
10107 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
10108 output control file to be modified. Instead by default it
10109 adds to the <file>debian/substvars</file> file variable
10110 settings like <tt>shlibs:Depends</tt>. These variable
10111 settings must be referenced in dependency fields in the
10112 appropriate per-binary-package sections of the source
10117 For example, a package that generates an essential part
10118 which requires dependencies, and optional parts that
10119 which only require a recommendation, would separate those
10120 two sets of dependencies into two different fields.<footnote>
10121 At the time of writing, an example for this was the
10122 <package/xmms/ package, with Depends used for the xmms
10123 executable, Recommends for the plug-ins and Suggests for
10124 even more optional features provided by unzip.
10126 It can say in its <file>debian/rules</file>:
10128 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
10129 -dRecommends <var>optionalpart anotheroptionalpart</var>
10131 and then in its main control file <file>debian/control</file>:
10134 Depends: ${shlibs:Depends}
10135 Recommends: ${shlibs:Recommends}
10141 Sources which produce several binary packages with
10142 different shared library dependency requirements can use
10143 the <tt>-p<var>varnameprefix</var></tt> option to override
10144 the default <tt>shlibs:</tt> prefix (one invocation of
10145 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
10146 They can thus produce several sets of dependency
10147 variables, each of the form
10148 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
10149 which can be referred to in the appropriate parts of the
10150 binary package control files.
10155 <sect1 id="pkg-dpkg-distaddfile">
10157 <prgn>dpkg-distaddfile</prgn> - adds a file to
10158 <file>debian/files</file>
10162 Some packages' uploads need to include files other than
10163 the source and binary package files.
10167 <prgn>dpkg-distaddfile</prgn> adds a file to the
10168 <file>debian/files</file> file so that it will be included in
10169 the <file>.changes</file> file when
10170 <prgn>dpkg-genchanges</prgn> is run.
10174 It is usually invoked from the <tt>binary</tt> target of
10175 <file>debian/rules</file>:
10177 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
10179 The <var>filename</var> is relative to the directory where
10180 <prgn>dpkg-genchanges</prgn> will expect to find it - this
10181 is usually the directory above the top level of the source
10182 tree. The <file>debian/rules</file> target should put the
10183 file there just before or just after calling
10184 <prgn>dpkg-distaddfile</prgn>.
10188 The <var>section</var> and <var>priority</var> are passed
10189 unchanged into the resulting <file>.changes</file> file.
10194 <sect1 id="pkg-dpkg-genchanges">
10196 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
10197 upload control file
10201 This program is usually called by package-independent
10202 automatic building scripts such as
10203 <prgn>dpkg-buildpackage</prgn>, but it may also be called
10208 It is usually called in the top level of a built source
10209 tree, and when invoked with no arguments will print out a
10210 straightforward <file>.changes</file> file based on the
10211 information in the source package's changelog and control
10212 file and the binary and source packages which should have
10218 <sect1 id="pkg-dpkg-parsechangelog">
10220 <prgn>dpkg-parsechangelog</prgn> - produces parsed
10221 representation of a changelog
10225 This program is used internally by
10226 <prgn>dpkg-source</prgn> et al. It may also occasionally
10227 be useful in <file>debian/rules</file> and elsewhere. It
10228 parses a changelog, <file>debian/changelog</file> by default,
10229 and prints a control-file format representation of the
10230 information in it to standard output.
10234 <sect1 id="pkg-dpkg-architecture">
10236 <prgn>dpkg-architecture</prgn> - information about the build and
10241 This program can be used manually, but is also invoked by
10242 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
10243 environment or make variables which specify the build and host
10244 architecture for the package building process.
10249 <sect id="pkg-sourcetree">
10250 <heading>The Debian package source tree</heading>
10253 The source archive scheme described later is intended to
10254 allow a Debian package source tree with some associated
10255 control information to be reproduced and transported easily.
10256 The Debian package source tree is a version of the original
10257 program with certain files added for the benefit of the
10258 packaging process, and with any other changes required
10259 made to the rest of the source code and installation
10264 The extra files created for Debian are in the subdirectory
10265 <file>debian</file> of the top level of the Debian package
10266 source tree. They are described below.
10269 <sect1 id="pkg-debianrules">
10270 <heading><file>debian/rules</file> - the main building script</heading>
10273 See <ref id="debianrules">.
10277 <sect1 id="pkg-srcsubstvars">
10278 <heading><file>debian/substvars</file> and variable substitutions</heading>
10281 See <ref id="substvars">.
10287 <heading><file>debian/files</file></heading>
10290 See <ref id="debianfiles">.
10294 <sect1><heading><file>debian/tmp</file>
10298 This is the canonical temporary location for the
10299 construction of binary packages by the <tt>binary</tt>
10300 target. The directory <file>tmp</file> serves as the root of
10301 the file system tree as it is being constructed (for
10302 example, by using the package's upstream makefiles install
10303 targets and redirecting the output there), and it also
10304 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10305 id="pkg-bincreating">.
10309 If several binary packages are generated from the same
10310 source tree it is usual to use several
10311 <file>debian/tmp<var>something</var></file> directories, for
10312 example <file>tmp-a</file> or <file>tmp-doc</file>.
10316 Whatever <file>tmp</file> directories are created and used by
10317 <tt>binary</tt> must of course be removed by the
10318 <tt>clean</tt> target.</p></sect1>
10322 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10326 As it exists on the FTP site, a Debian source package
10327 consists of three related files. You must have the right
10328 versions of all three to be able to use them.
10333 <tag>Debian source control file - <tt>.dsc</tt></tag>
10335 This file is a control file used by <prgn>dpkg-source</prgn>
10336 to extract a source package.
10337 See <ref id="debiansourcecontrolfiles">.
10341 Original source archive -
10343 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10349 This is a compressed (with <tt>gzip -9</tt>)
10350 <prgn>tar</prgn> file containing the source code from
10351 the upstream authors of the program.
10356 Debian package diff -
10358 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10364 This is a unified context diff (<tt>diff -u</tt>)
10365 giving the changes which are required to turn the
10366 original source into the Debian source. These changes
10367 may only include editing and creating plain files.
10368 The permissions of files, the targets of symbolic
10369 links and the characteristics of special files or
10370 pipes may not be changed and no files may be removed
10375 All the directories in the diff must exist, except the
10376 <file>debian</file> subdirectory of the top of the source
10377 tree, which will be created by
10378 <prgn>dpkg-source</prgn> if necessary when unpacking.
10382 The <prgn>dpkg-source</prgn> program will
10383 automatically make the <file>debian/rules</file> file
10384 executable (see below).</p></item>
10389 If there is no original source code - for example, if the
10390 package is specially prepared for Debian or the Debian
10391 maintainer is the same as the upstream maintainer - the
10392 format is slightly different: then there is no diff, and the
10394 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10395 and preferably contains a directory named
10396 <file><var>package</var>-<var>version</var></file>.
10401 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10404 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10405 Debian source package. However, if it is not available it
10406 is possible to unpack a Debian source archive as follows:
10407 <enumlist compact="compact">
10410 Untar the tarfile, which will create a <file>.orig</file>
10414 <p>Rename the <file>.orig</file> directory to
10415 <file><var>package</var>-<var>version</var></file>.</p>
10419 Create the subdirectory <file>debian</file> at the top of
10420 the source tree.</p>
10422 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10424 <item><p>Untar the tarfile again if you want a copy of the original
10425 source code alongside the Debian version.</p>
10430 It is not possible to generate a valid Debian source archive
10431 without using <prgn>dpkg-source</prgn>. In particular,
10432 attempting to use <prgn>diff</prgn> directly to generate the
10433 <file>.diff.gz</file> file will not work.
10437 <heading>Restrictions on objects in source packages</heading>
10440 The source package may not contain any hard links
10442 This is not currently detected when building source
10443 packages, but only when extracting
10447 Hard links may be permitted at some point in the
10448 future, but would require a fair amount of
10450 </footnote>, device special files, sockets or setuid or
10453 Setgid directories are allowed.
10458 The source packaging tools manage the changes between the
10459 original and Debian source using <prgn>diff</prgn> and
10460 <prgn>patch</prgn>. Turning the original source tree as
10461 included in the <file>.orig.tar.gz</file> into the Debian
10462 package source must not involve any changes which cannot be
10463 handled by these tools. Problematic changes which cause
10464 <prgn>dpkg-source</prgn> to halt with an error when
10465 building the source package are:
10466 <list compact="compact">
10467 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10469 <item><p>Changing the targets of symbolic links.</p>
10471 <item><p>Creating directories, other than <file>debian</file>.</p>
10473 <item><p>Changes to the contents of binary files.</p></item>
10474 </list> Changes which cause <prgn>dpkg-source</prgn> to
10475 print a warning but continue anyway are:
10476 <list compact="compact">
10479 Removing files, directories or symlinks.
10481 Renaming a file is not treated specially - it is
10482 seen as the removal of the old file (which
10483 generates a warning, but is otherwise ignored),
10484 and the creation of the new one.
10490 Changed text files which are missing the usual final
10491 newline (either in the original or the modified
10496 Changes which are not represented, but which are not detected by
10497 <prgn>dpkg-source</prgn>, are:
10498 <list compact="compact">
10499 <item><p>Changing the permissions of files (other than
10500 <file>debian/rules</file>) and directories.</p></item>
10505 The <file>debian</file> directory and <file>debian/rules</file>
10506 are handled specially by <prgn>dpkg-source</prgn> - before
10507 applying the changes it will create the <file>debian</file>
10508 directory, and afterwards it will make
10509 <file>debian/rules</file> world-executable.
10515 <appendix id="pkg-controlfields">
10516 <heading>Control files and their fields (from old Packaging Manual)</heading>
10519 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10520 data in a common format, known as control files. Binary and
10521 source packages have control data as do the <file>.changes</file>
10522 files which control the installation of uploaded files, and
10523 <prgn>dpkg</prgn>'s internal databases are in a similar
10528 <heading>Syntax of control files</heading>
10531 See <ref id="controlsyntax">.
10535 It is important to note that there are several fields which
10536 are optional as far as <prgn>dpkg</prgn> and the related
10537 tools are concerned, but which must appear in every Debian
10538 package, or whose omission may cause problems.
10543 <heading>List of fields</heading>
10546 See <ref id="controlfieldslist">.
10550 This section now contains only the fields that didn't belong
10551 to the Policy manual.
10554 <sect1 id="pkg-f-Filename">
10555 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10558 These fields in <tt>Packages</tt> files give the
10559 filename(s) of (the parts of) a package in the
10560 distribution directories, relative to the root of the
10561 Debian hierarchy. If the package has been split into
10562 several parts the parts are all listed in order, separated
10567 <sect1 id="pkg-f-Size">
10568 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10571 These fields in <file>Packages</file> files give the size (in
10572 bytes, expressed in decimal) and MD5 checksum of the
10573 file(s) which make(s) up a binary package in the
10574 distribution. If the package is split into several parts
10575 the values for the parts are listed in order, separated by
10580 <sect1 id="pkg-f-Status">
10581 <heading><tt>Status</tt></heading>
10584 This field in <prgn>dpkg</prgn>'s status file records
10585 whether the user wants a package installed, removed or
10586 left alone, whether it is broken (requiring
10587 re-installation) or not and what its current state on the
10588 system is. Each of these pieces of information is a
10593 <sect1 id="pkg-f-Config-Version">
10594 <heading><tt>Config-Version</tt></heading>
10597 If a package is not installed or not configured, this
10598 field in <prgn>dpkg</prgn>'s status file records the last
10599 version of the package which was successfully
10604 <sect1 id="pkg-f-Conffiles">
10605 <heading><tt>Conffiles</tt></heading>
10608 This field in <prgn>dpkg</prgn>'s status file contains
10609 information about the automatically-managed configuration
10610 files held by a package. This field should <em>not</em>
10611 appear anywhere in a package!
10616 <heading>Obsolete fields</heading>
10619 These are still recognized by <prgn>dpkg</prgn> but should
10620 not appear anywhere any more.
10622 <taglist compact="compact">
10624 <tag><tt>Revision</tt></tag>
10625 <tag><tt>Package-Revision</tt></tag>
10626 <tag><tt>Package_Revision</tt></tag>
10628 The Debian revision part of the package version was
10629 at one point in a separate control file field. This
10630 field went through several names.
10633 <tag><tt>Recommended</tt></tag>
10634 <item>Old name for <tt>Recommends</tt>.</item>
10636 <tag><tt>Optional</tt></tag>
10637 <item>Old name for <tt>Suggests</tt>.</item>
10639 <tag><tt>Class</tt></tag>
10640 <item>Old name for <tt>Priority</tt>.</item>
10649 <appendix id="pkg-conffiles">
10650 <heading>Configuration file handling (from old Packaging Manual)</heading>
10653 <prgn>dpkg</prgn> can do a certain amount of automatic
10654 handling of package configuration files.
10658 Whether this mechanism is appropriate depends on a number of
10659 factors, but basically there are two approaches to any
10660 particular configuration file.
10664 The easy method is to ship a best-effort configuration in the
10665 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10666 handle updates. If the user is unlikely to want to edit the
10667 file, but you need them to be able to without losing their
10668 changes, and a new package with a changed version of the file
10669 is only released infrequently, this is a good approach.
10673 The hard method is to build the configuration file from
10674 scratch in the <prgn>postinst</prgn> script, and to take the
10675 responsibility for fixing any mistakes made in earlier
10676 versions of the package automatically. This will be
10677 appropriate if the file is likely to need to be different on
10681 <sect><heading>Automatic handling of configuration files by
10686 A package may contain a control area file called
10687 <tt>conffiles</tt>. This file should be a list of filenames
10688 of configuration files needing automatic handling, separated
10689 by newlines. The filenames should be absolute pathnames,
10690 and the files referred to should actually exist in the
10695 When a package is upgraded <prgn>dpkg</prgn> will process
10696 the configuration files during the configuration stage,
10697 shortly before it runs the package's <prgn>postinst</prgn>
10702 For each file it checks to see whether the version of the
10703 file included in the package is the same as the one that was
10704 included in the last version of the package (the one that is
10705 being upgraded from); it also compares the version currently
10706 installed on the system with the one shipped with the last
10711 If neither the user nor the package maintainer has changed
10712 the file, it is left alone. If one or the other has changed
10713 their version, then the changed version is preferred - i.e.,
10714 if the user edits their file, but the package maintainer
10715 doesn't ship a different version, the user's changes will
10716 stay, silently, but if the maintainer ships a new version
10717 and the user hasn't edited it the new version will be
10718 installed (with an informative message). If both have
10719 changed their version the user is prompted about the problem
10720 and must resolve the differences themselves.
10724 The comparisons are done by calculating the MD5 message
10725 digests of the files, and storing the MD5 of the file as it
10726 was included in the most recent version of the package.
10730 When a package is installed for the first time
10731 <prgn>dpkg</prgn> will install the file that comes with it,
10732 unless that would mean overwriting a file already on the
10737 However, note that <prgn>dpkg</prgn> will <em>not</em>
10738 replace a conffile that was removed by the user (or by a
10739 script). This is necessary because with some programs a
10740 missing file produces an effect hard or impossible to
10741 achieve in another way, so that a missing file needs to be
10742 kept that way if the user did it.
10746 Note that a package should <em>not</em> modify a
10747 <prgn>dpkg</prgn>-handled conffile in its maintainer
10748 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10749 the user confusing and possibly dangerous options for
10750 conffile update when the package is upgraded.</p>
10753 <sect><heading>Fully-featured maintainer script configuration
10758 For files which contain site-specific information such as
10759 the hostname and networking details and so forth, it is
10760 better to create the file in the package's
10761 <prgn>postinst</prgn> script.
10765 This will typically involve examining the state of the rest
10766 of the system to determine values and other information, and
10767 may involve prompting the user for some information which
10768 can't be obtained some other way.
10772 When using this method there are a couple of important
10773 issues which should be considered:
10777 If you discover a bug in the program which generates the
10778 configuration file, or if the format of the file changes
10779 from one version to the next, you will have to arrange for
10780 the postinst script to do something sensible - usually this
10781 will mean editing the installed configuration file to remove
10782 the problem or change the syntax. You will have to do this
10783 very carefully, since the user may have changed the file,
10784 perhaps to fix the very problem that your script is trying
10785 to deal with - you will have to detect these situations and
10786 deal with them correctly.
10790 If you do go down this route it's probably a good idea to
10791 make the program that generates the configuration file(s) a
10792 separate program in <file>/usr/sbin</file>, by convention called
10793 <file><var>package</var>config</file> and then run that if
10794 appropriate from the post-installation script. The
10795 <tt><var>package</var>config</tt> program should not
10796 unquestioningly overwrite an existing configuration - if its
10797 mode of operation is geared towards setting up a package for
10798 the first time (rather than any arbitrary reconfiguration
10799 later) you should have it check whether the configuration
10800 already exists, and require a <tt>--force</tt> flag to
10801 overwrite it.</p></sect>
10804 <appendix id="pkg-alternatives"><heading>Alternative versions of
10805 an interface - <prgn>update-alternatives</prgn> (from old
10810 When several packages all provide different versions of the
10811 same program or file it is useful to have the system select a
10812 default, but to allow the system administrator to change it
10813 and have their decisions respected.
10817 For example, there are several versions of the <prgn>vi</prgn>
10818 editor, and there is no reason to prevent all of them from
10819 being installed at once, each under their own name
10820 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10821 Nevertheless it is desirable to have the name <tt>vi</tt>
10822 refer to something, at least by default.
10826 If all the packages involved cooperate, this can be done with
10827 <prgn>update-alternatives</prgn>.
10831 Each package provides its own version under its own name, and
10832 calls <prgn>update-alternatives</prgn> in its postinst to
10833 register its version (and again in its prerm to deregister
10838 See the man page <manref name="update-alternatives"
10839 section="8"> for details.
10843 If <prgn>update-alternatives</prgn> does not seem appropriate
10844 you may wish to consider using diversions instead.</p>
10847 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10848 package's version of a file (from old Packaging Manual)
10852 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10853 when it reinstalls the package it belongs to, and to have it
10854 put the file from the package somewhere else instead.
10858 This can be used locally to override a package's version of a
10859 file, or by one package to override another's version (or
10860 provide a wrapper for it).
10864 Before deciding to use a diversion, read <ref
10865 id="pkg-alternatives"> to see if you really want a diversion
10866 rather than several alternative versions of a program.
10870 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10871 and updated by a special program <prgn>dpkg-divert</prgn>.
10872 Please see <manref name="dpkg-divert" section="8"> for full
10873 details of its operation.
10877 When a package wishes to divert a file from another, it should
10878 call <prgn>dpkg-divert</prgn> in its preinst to add the
10879 diversion and rename the existing file. For example,
10880 supposing that a <prgn>smailwrapper</prgn> package wishes to
10881 install a wrapper around <file>/usr/sbin/smail</file>:
10883 dpkg-divert --package smailwrapper --add --rename \
10884 --divert /usr/sbin/smail.real /usr/sbin/smail
10885 </example> The <tt>--package smailwrapper</tt> ensures that
10886 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
10887 can bypass the diversion and get installed as the true version.
10888 It's safe to add the diversion unconditionally on upgrades since
10889 it will be left unchanged if it already exists, but
10890 <prgn>dpkg-divert</prgn> will display a message. To suppress that
10891 message, make the command conditional on the version from which
10892 the package is being upgraded:
10894 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
10895 dpkg-divert --package smailwrapper --add --rename \
10896 --divert /usr/sbin/smail.real /usr/sbin/smail
10898 </example> where <tt>1.0-2</tt> is the version at which the
10899 diversion was first added to the package. Running the command
10900 during abort-upgrade is pointless but harmless.
10904 The postrm has to do the reverse:
10906 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
10907 dpkg-divert --package smailwrapper --remove --rename \
10908 --divert /usr/sbin/smail.real /usr/sbin/smail
10910 </example> If the diversion was added at a particular version, the
10911 postrm should also handle the failure case of upgrading from an
10912 older version (unless the older version is so old that direct
10913 upgrades are no longer supported):
10915 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
10916 dpkg-divert --package smailwrapper --remove --rename \
10917 --divert /usr/sbin/smail.real /usr/sbin/smail
10919 </example> where <tt>1.02-2</tt> is the version at which the
10920 diversion was first added to the package. The postrm should not
10921 remove the diversion on upgrades both because there's no reason to
10922 remove the diversion only to immediately re-add it and since the
10923 postrm of the old package is run after unpacking so the removal of
10924 the diversion will fail.
10928 Do not attempt to divert a file which is vitally important for
10929 the system's operation - when using <prgn>dpkg-divert</prgn>
10930 there is a time, after it has been diverted but before
10931 <prgn>dpkg</prgn> has installed the new version, when the file
10932 does not exist.</p>
10937 <!-- Local variables: -->
10938 <!-- indent-tabs-mode: t -->
10940 <!-- vim:set ai et sts=2 sw=2 tw=76: -->