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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.
882 <heading>The maintainer of a package</heading>
885 Every package must have a Debian maintainer (the
886 maintainer may be one person or a group of people
887 reachable from a common email address, such as a mailing
888 list). The maintainer is responsible for ensuring that
889 the package is placed in the appropriate distributions.
893 The maintainer must be specified in the
894 <tt>Maintainer</tt> control field with their correct name
895 and a working email address. If one person maintains
896 several packages, they should try to avoid having
897 different forms of their name and email address in
898 the <tt>Maintainer</tt> fields of those packages.
902 The format of the <tt>Maintainer</tt> control field is
903 described in <ref id="f-Maintainer">.
907 If the maintainer of a package quits from the Debian
908 project, "Debian QA Group"
909 <email>packages@qa.debian.org</email> takes over the
910 maintainer-ship of the package until someone else
911 volunteers for that task. These packages are called
912 <em>orphaned packages</em>.<footnote>
913 The detailed procedure for doing this gracefully can
914 be found in the Debian Developer's Reference,
915 see <ref id="related">.
920 <sect id="descriptions">
921 <heading>The description of a package</heading>
924 Every Debian package must have an extended description
925 stored in the appropriate field of the control record.
926 The technical information about the format of the
927 <tt>Description</tt> field is in <ref id="f-Description">.
931 The description should describe the package (the program) to a
932 user (system administrator) who has never met it before so that
933 they have enough information to decide whether they want to
934 install it. This description should not just be copied verbatim
935 from the program's documentation.
939 Put important information first, both in the synopsis and
940 extended description. Sometimes only the first part of the
941 synopsis or of the description will be displayed. You can
942 assume that there will usually be a way to see the whole
943 extended description.
947 The description should also give information about the
948 significant dependencies and conflicts between this package
949 and others, so that the user knows why these dependencies and
950 conflicts have been declared.
954 Instructions for configuring or using the package should
955 not be included (that is what installation scripts,
956 manual pages, info files, etc., are for). Copyright
957 statements and other administrivia should not be included
958 either (that is what the copyright file is for).
961 <sect1 id="synopsis"><heading>The single line synopsis</heading>
964 The single line synopsis should be kept brief - certainly
969 Do not include the package name in the synopsis line. The
970 display software knows how to display this already, and you
971 do not need to state it. Remember that in many situations
972 the user may only see the synopsis line - make it as
973 informative as you can.
978 <sect1 id="extendeddesc"><heading>The extended description</heading>
981 Do not try to continue the single line synopsis into the
982 extended description. This will not work correctly when
983 the full description is displayed, and makes no sense
984 where only the summary (the single line synopsis) is
989 The extended description should describe what the package
990 does and how it relates to the rest of the system (in terms
991 of, for example, which subsystem it is which part of).
995 The description field needs to make sense to anyone, even
996 people who have no idea about any of the things the
997 package deals with.<footnote>
998 The blurb that comes with a program in its
999 announcements and/or <prgn>README</prgn> files is
1000 rarely suitable for use in a description. It is
1001 usually aimed at people who are already in the
1002 community where the package is used.
1011 <heading>Dependencies</heading>
1014 Every package must specify the dependency information
1015 about other packages that are required for the first to
1020 For example, a dependency entry must be provided for any
1021 shared libraries required by a dynamically-linked executable
1022 binary in a package.
1026 Packages are not required to declare any dependencies they
1027 have on other packages which are marked <tt>Essential</tt>
1028 (see below), and should not do so unless they depend on a
1029 particular version of that package.<footnote>
1031 Essential is needed in part to avoid unresolvable dependency
1032 loops on upgrade. If packages add unnecessary dependencies
1033 on packages in this set, the chances that there
1034 <strong>will</strong> be an unresolvable dependency loop
1035 caused by forcing these Essential packages to be configured
1036 first before they need to be is greatly increased. It also
1037 increases the chances that frontends will be unable to
1038 <strong>calculate</strong> an upgrade path, even if one
1042 Also, functionality is rarely ever removed from the
1043 Essential set, but <em>packages</em> have been removed from
1044 the Essential set when the functionality moved to a
1045 different package. So depending on these packages <em>just
1046 in case</em> they stop being essential does way more harm
1053 Sometimes, a package requires another package to be unpacked
1054 <em>and</em> configured before it can be unpacked. In this
1055 case, you must specify a <tt>Pre-Depends</tt> entry for
1060 You should not specify a <tt>Pre-Depends</tt> entry for a
1061 package before this has been discussed on the
1062 <tt>debian-devel</tt> mailing list and a consensus about
1063 doing that has been reached.
1067 The format of the package interrelationship control fields is
1068 described in <ref id="relationships">.
1072 <sect id="virtual_pkg">
1073 <heading>Virtual packages</heading>
1076 Sometimes, there are several packages which offer
1077 more-or-less the same functionality. In this case, it's
1078 useful to define a <em>virtual package</em> whose name
1079 describes that common functionality. (The virtual
1080 packages only exist logically, not physically; that's why
1081 they are called <em>virtual</em>.) The packages with this
1082 particular function will then <em>provide</em> the virtual
1083 package. Thus, any other package requiring that function
1084 can simply depend on the virtual package without having to
1085 specify all possible packages individually.
1089 All packages should use virtual package names where
1090 appropriate, and arrange to create new ones if necessary.
1091 They should not use virtual package names (except privately,
1092 amongst a cooperating group of packages) unless they have
1093 been agreed upon and appear in the list of virtual package
1094 names. (See also <ref id="virtual">)
1098 The latest version of the authoritative list of virtual
1099 package names can be found in the <tt>debian-policy</tt> package.
1100 It is also available from the Debian web mirrors at
1101 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1102 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1106 The procedure for updating the list is described in the preface
1113 <heading>Base system</heading>
1116 The <tt>base system</tt> is a minimum subset of the Debian
1117 GNU/Linux system that is installed before everything else
1118 on a new system. Only very few packages are allowed to form
1119 part of the base system, in order to keep the required disk
1124 The base system consists of all those packages with priority
1125 <tt>required</tt> or <tt>important</tt>. Many of them will
1126 be tagged <tt>essential</tt> (see below).
1131 <heading>Essential packages</heading>
1134 Essential is defined as the minimal set of functionality that
1135 must be available and usable on the system at all times, even
1136 when packages are in an unconfigured (but unpacked) state.
1137 Packages are tagged <tt>essential</tt> for a system using the
1138 <tt>Essential</tt> control file field. The format of the
1139 <tt>Essential</tt> control field is described in <ref
1144 Since these packages cannot be easily removed (one has to
1145 specify an extra <em>force option</em> to
1146 <prgn>dpkg</prgn> to do so), this flag must not be used
1147 unless absolutely necessary. A shared library package
1148 must not be tagged <tt>essential</tt>; dependencies will
1149 prevent its premature removal, and we need to be able to
1150 remove it when it has been superseded.
1154 Since dpkg will not prevent upgrading of other packages
1155 while an <tt>essential</tt> package is in an unconfigured
1156 state, all <tt>essential</tt> packages must supply all of
1157 their core functionality even when unconfigured. If the
1158 package cannot satisfy this requirement it must not be
1159 tagged as essential, and any packages depending on this
1160 package must instead have explicit dependency fields as
1165 Maintainers should take great care in adding any programs,
1166 interfaces, or functionality to <tt>essential</tt> packages.
1167 Packages may assume that functionality provided by
1168 <tt>essential</tt> packages is always available without
1169 declaring explicit dependencies, which means that removing
1170 functionality from the Essential set is very difficult and is
1171 almost never done. Any capability added to an
1172 <tt>essential</tt> package therefore creates an obligation to
1173 support that capability as part of the Essential set in
1178 You must not tag any packages <tt>essential</tt> before
1179 this has been discussed on the <tt>debian-devel</tt>
1180 mailing list and a consensus about doing that has been
1185 <sect id="maintscripts">
1186 <heading>Maintainer Scripts</heading>
1189 The package installation scripts should avoid producing
1190 output which is unnecessary for the user to see and
1191 should rely on <prgn>dpkg</prgn> to stave off boredom on
1192 the part of a user installing many packages. This means,
1193 amongst other things, using the <tt>--quiet</tt> option on
1194 <prgn>install-info</prgn>.
1198 Errors which occur during the execution of an installation
1199 script must be checked and the installation must not
1200 continue after an error.
1204 Note that in general <ref id="scripts"> applies to package
1205 maintainer scripts, too.
1209 You should not use <prgn>dpkg-divert</prgn> on a file belonging
1210 to another package without consulting the maintainer of that
1211 package first. When adding or removing diversions, package
1212 maintainer scripts must provide the <tt>--package</tt> flag
1213 to <prgn>dpkg-divert</prgn> and must not use <tt>--local</tt>.
1217 All packages which supply an instance of a common command
1218 name (or, in general, filename) should generally use
1219 <prgn>update-alternatives</prgn>, so that they may be
1220 installed together. If <prgn>update-alternatives</prgn>
1221 is not used, then each package must use
1222 <tt>Conflicts</tt> to ensure that other packages are
1223 de-installed. (In this case, it may be appropriate to
1224 specify a conflict against earlier versions of something
1225 that previously did not use
1226 <prgn>update-alternatives</prgn>; this is an exception to
1227 the usual rule that versioned conflicts should be
1231 <sect1 id="maintscriptprompt">
1232 <heading>Prompting in maintainer scripts</heading>
1234 Package maintainer scripts may prompt the user if
1235 necessary. Prompting must be done by communicating
1236 through a program, such as <prgn>debconf</prgn>, which
1237 conforms to the Debian Configuration Management
1238 Specification, version 2 or higher.
1242 Packages which are essential, or which are dependencies of
1243 essential packages, may fall back on another prompting method
1244 if no such interface is available when they are executed.
1248 The Debian Configuration Management Specification is included
1249 in the <file>debconf_specification</file> files in the
1250 <package>debian-policy</package> package.
1251 It is also available from the Debian web mirrors at
1252 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1253 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1257 Packages which use the Debian Configuration Management
1258 Specification may contain an additional
1259 <prgn>config</prgn> script and a <tt>templates</tt>
1260 file in their control archive<footnote>
1261 The control.tar.gz inside the .deb.
1262 See <manref name="deb" section="5">.
1264 The <prgn>config</prgn> script might be run before the
1265 <prgn>preinst</prgn> script, and before the package is unpacked
1266 or any of its dependencies or pre-dependencies are satisfied.
1267 Therefore it must work using only the tools present in
1268 <em>essential</em> packages.<footnote>
1269 <package>Debconf</package> or another tool that
1270 implements the Debian Configuration Management
1271 Specification will also be installed, and any
1272 versioned dependencies on it will be satisfied
1273 before preconfiguration begins.
1278 Packages which use the Debian Configuration Management
1279 Specification must allow for translation of their user-visible
1280 messages by using a gettext-based system such as the one
1281 provided by the <package>po-debconf</package> package.
1285 Packages should try to minimize the amount of prompting
1286 they need to do, and they should ensure that the user
1287 will only ever be asked each question once. This means
1288 that packages should try to use appropriate shared
1289 configuration files (such as <file>/etc/papersize</file> and
1290 <file>/etc/news/server</file>), and shared
1291 <package>debconf</package> variables rather than each
1292 prompting for their own list of required pieces of
1297 It also means that an upgrade should not ask the same
1298 questions again, unless the user has used
1299 <tt>dpkg --purge</tt> to remove the package's configuration.
1300 The answers to configuration questions should be stored in an
1301 appropriate place in <file>/etc</file> so that the user can
1302 modify them, and how this has been done should be
1307 If a package has a vitally important piece of
1308 information to pass to the user (such as "don't run me
1309 as I am, you must edit the following configuration files
1310 first or you risk your system emitting badly-formatted
1311 messages"), it should display this in the
1312 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1313 prompt the user to hit return to acknowledge the
1314 message. Copyright messages do not count as vitally
1315 important (they belong in
1316 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1317 neither do instructions on how to use a program (these
1318 should be in on-line documentation, where all the users
1323 Any necessary prompting should almost always be confined
1324 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1325 script. If it is done in the <prgn>postinst</prgn>, it
1326 should be protected with a conditional so that
1327 unnecessary prompting doesn't happen if a package's
1328 installation fails and the <prgn>postinst</prgn> is
1329 called with <tt>abort-upgrade</tt>,
1330 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1340 <heading>Source packages</heading>
1342 <sect id="standardsversion">
1343 <heading>Standards conformance</heading>
1346 Source packages should specify the most recent version number
1347 of this policy document with which your package complied
1348 when it was last updated.
1352 This information may be used to file bug reports
1353 automatically if your package becomes too much out of date.
1357 The version is specified in the <tt>Standards-Version</tt>
1359 The format of the <tt>Standards-Version</tt> field is
1360 described in <ref id="f-Standards-Version">.
1364 You should regularly, and especially if your package has
1365 become out of date, check for the newest Policy Manual
1366 available and update your package, if necessary. When your
1367 package complies with the new standards you should update the
1368 <tt>Standards-Version</tt> source package field and
1369 release it.<footnote>
1370 See the file <file>upgrading-checklist</file> for
1371 information about policy which has changed between
1372 different versions of this document.
1378 <sect id="pkg-relations">
1379 <heading>Package relationships</heading>
1382 Source packages should specify which binary packages they
1383 require to be installed or not to be installed in order to
1384 build correctly. For example, if building a package
1385 requires a certain compiler, then the compiler should be
1386 specified as a build-time dependency.
1390 It is not necessary to explicitly specify build-time
1391 relationships on a minimal set of packages that are always
1392 needed to compile, link and put in a Debian package a
1393 standard "Hello World!" program written in C or C++. The
1394 required packages are called <em>build-essential</em>, and
1395 an informational list can be found in
1396 <file>/usr/share/doc/build-essential/list</file> (which is
1397 contained in the <tt>build-essential</tt>
1400 <list compact="compact">
1402 This allows maintaining the list separately
1403 from the policy documents (the list does not
1404 need the kind of control that the policy
1408 Having a separate package allows one to install
1409 the build-essential packages on a machine, as
1410 well as allowing other packages such as tasks to
1411 require installation of the build-essential
1412 packages using the depends relation.
1415 The separate package allows bug reports against
1416 the list to be categorized separately from
1417 the policy management process in the BTS.
1424 When specifying the set of build-time dependencies, one
1425 should list only those packages explicitly required by the
1426 build. It is not necessary to list packages which are
1427 required merely because some other package in the list of
1428 build-time dependencies depends on them.<footnote>
1429 The reason for this is that dependencies change, and
1430 you should list all those packages, and <em>only</em>
1431 those packages that <em>you</em> need directly. What
1432 others need is their business. For example, if you
1433 only link against <file>libimlib</file>, you will need to
1434 build-depend on <package>libimlib2-dev</package> but
1435 not against any <tt>libjpeg*</tt> packages, even
1436 though <tt>libimlib2-dev</tt> currently depends on
1437 them: installation of <package>libimlib2-dev</package>
1438 will automatically ensure that all of its run-time
1439 dependencies are satisfied.
1444 If build-time dependencies are specified, it must be
1445 possible to build the package and produce working binaries
1446 on a system with only essential and build-essential
1447 packages installed and also those required to satisfy the
1448 build-time relationships (including any implied
1449 relationships). In particular, this means that version
1450 clauses should be used rigorously in build-time
1451 relationships so that one cannot produce bad or
1452 inconsistently configured packages when the relationships
1453 are properly satisfied.
1457 <ref id="relationships"> explains the technical details.
1462 <heading>Changes to the upstream sources</heading>
1465 If changes to the source code are made that are not
1466 specific to the needs of the Debian system, they should be
1467 sent to the upstream authors in whatever form they prefer
1468 so as to be included in the upstream version of the
1473 If you need to configure the package differently for
1474 Debian or for Linux, and the upstream source doesn't
1475 provide a way to do so, you should add such configuration
1476 facilities (for example, a new <prgn>autoconf</prgn> test
1477 or <tt>#define</tt>) and send the patch to the upstream
1478 authors, with the default set to the way they originally
1479 had it. You can then easily override the default in your
1480 <file>debian/rules</file> or wherever is appropriate.
1484 You should make sure that the <prgn>configure</prgn> utility
1485 detects the correct architecture specification string
1486 (refer to <ref id="arch-spec"> for details).
1490 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1491 <prgn>configure</prgn> scripts are used, you should edit the
1492 <file>.in</file> files rather than editing the
1493 <prgn>Makefile</prgn> directly. This allows the user to
1494 reconfigure the package if necessary. You should
1495 <em>not</em> configure the package and edit the generated
1496 <prgn>Makefile</prgn>! This makes it impossible for someone
1497 else to later reconfigure the package without losing the
1503 <sect id="dpkgchangelog">
1504 <heading>Debian changelog: <file>debian/changelog</file></heading>
1507 Changes in the Debian version of the package should be
1508 briefly explained in the Debian changelog file
1509 <file>debian/changelog</file>.<footnote>
1511 Mistakes in changelogs are usually best rectified by
1512 making a new changelog entry rather than "rewriting
1513 history" by editing old changelog entries.
1516 This includes modifications
1517 made in the Debian package compared to the upstream one
1518 as well as other changes and updates to the package.
1520 Although there is nothing stopping an author who is also
1521 the Debian maintainer from using this changelog for all
1522 their changes, it will have to be renamed if the Debian
1523 and upstream maintainers become different people. In such
1524 a case, however, it might be better to maintain the package
1525 as a non-native package.
1530 The format of the <file>debian/changelog</file> allows the
1531 package building tools to discover which version of the package
1532 is being built and find out other release-specific information.
1536 That format is a series of entries like this:
1538 <example compact="compact">
1539 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1541 [optional blank line(s), stripped]
1543 * <var>change details</var>
1544 <var>more change details</var>
1546 [blank line(s), included in output of dpkg-parsechangelog]
1548 * <var>even more change details</var>
1550 [optional blank line(s), stripped]
1552 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1557 <var>package</var> and <var>version</var> are the source
1558 package name and version number.
1562 <var>distribution(s)</var> lists the distributions where
1563 this version should be installed when it is uploaded - it
1564 is copied to the <tt>Distribution</tt> field in the
1565 <file>.changes</file> file. See <ref id="f-Distribution">.
1569 <var>urgency</var> is the value for the <tt>Urgency</tt>
1570 field in the <file>.changes</file> file for the upload
1571 (see <ref id="f-Urgency">). It is not possible to specify
1572 an urgency containing commas; commas are used to separate
1573 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1574 <prgn>dpkg</prgn> changelog format (though there is
1575 currently only one useful <var>keyword</var>,
1580 The change details may in fact be any series of lines
1581 starting with at least two spaces, but conventionally each
1582 change starts with an asterisk and a separating space and
1583 continuation lines are indented so as to bring them in
1584 line with the start of the text above. Blank lines may be
1585 used here to separate groups of changes, if desired.
1589 If this upload resolves bugs recorded in the Bug Tracking
1590 System (BTS), they may be automatically closed on the
1591 inclusion of this package into the Debian archive by
1592 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1593 in the change details.<footnote>
1594 To be precise, the string should match the following
1595 Perl regular expression:
1597 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1599 Then all of the bug numbers listed will be closed by the
1600 archive maintenance script (<prgn>katie</prgn>) using the
1601 <var>version</var> of the changelog entry.
1603 This information is conveyed via the <tt>Closes</tt> field
1604 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1608 The maintainer name and email address used in the changelog
1609 should be the details of the person uploading <em>this</em>
1610 version. They are <em>not</em> necessarily those of the
1611 usual package maintainer. The information here will be
1612 copied to the <tt>Changed-By</tt> field in the
1613 <tt>.changes</tt> file (see <ref id="f-Changed-By">),
1614 and then later used to send an acknowledgement when the
1615 upload has been installed.
1619 The <var>date</var> has the following format<footnote>
1620 This is the same as the format generated by <tt>date
1622 </footnote> (compatible and with the same semantics of
1623 RFC 2822 and RFC 5322):
1624 <example>day-of-week, dd month yyyy hh:mm:ss +zzzz</example>
1626 <list compact="compact">
1628 day-of week is one of: Mon, Tue, Wed, Thu, Fri, Sat, Sun
1631 dd is a one- or two-digit day of the month (01-31)
1634 month is one of: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug,
1637 <item>yyyy is the four-digit year (e.g. 2010)</item>
1638 <item>hh is the two-digit hour (00-23)</item>
1639 <item>mm is the two-digit minutes (00-59)</item>
1640 <item>ss is the two-digit seconds (00-60)</item>
1642 +zzzz or -zzzz is the the time zone offset from Coordinated
1643 Universal Time (UTC). "+" indicates that the time is ahead
1644 of (i.e., east of) UTC and "-" indicates that the time is
1645 behind (i.e., west of) UTC. The first two digits indicate
1646 the hour difference from UTC and the last two digits
1647 indicate the number of additional minutes difference from
1648 UTC. The last two digits must be in the range 00-59.
1654 The first "title" line with the package name must start
1655 at the left hand margin. The "trailer" line with the
1656 maintainer and date details must be preceded by exactly
1657 one space. The maintainer details and the date must be
1658 separated by exactly two spaces.
1662 The entire changelog must be encoded in UTF-8.
1666 For more information on placement of the changelog files
1667 within binary packages, please see <ref id="changelogs">.
1671 <sect id="dpkgcopyright">
1672 <heading>Copyright: <file>debian/copyright</file></heading>
1674 Every package must be accompanied by a verbatim copy of its
1675 copyright information and distribution license in the file
1676 <file>/usr/share/doc/<var>package</var>/copyright</file>
1677 (see <ref id="copyrightfile"> for further details). Also see
1678 <ref id="pkgcopyright"> for further considerations related
1679 to copyrights for packages.
1683 <heading>Error trapping in makefiles</heading>
1686 When <prgn>make</prgn> invokes a command in a makefile
1687 (including your package's upstream makefiles and
1688 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1689 means that <prgn>sh</prgn>'s usual bad error handling
1690 properties apply: if you include a miniature script as one
1691 of the commands in your makefile you'll find that if you
1692 don't do anything about it then errors are not detected
1693 and <prgn>make</prgn> will blithely continue after
1698 Every time you put more than one shell command (this
1699 includes using a loop) in a makefile command you
1700 must make sure that errors are trapped. For
1701 simple compound commands, such as changing directory and
1702 then running a program, using <tt>&&</tt> rather
1703 than semicolon as a command separator is sufficient. For
1704 more complex commands including most loops and
1705 conditionals you should include a separate <tt>set -e</tt>
1706 command at the start of every makefile command that's
1707 actually one of these miniature shell scripts.
1711 <sect id="timestamps">
1712 <heading>Time Stamps</heading>
1714 Maintainers should preserve the modification times of the
1715 upstream source files in a package, as far as is reasonably
1717 The rationale is that there is some information conveyed
1718 by knowing the age of the file, for example, you could
1719 recognize that some documentation is very old by looking
1720 at the modification time, so it would be nice if the
1721 modification time of the upstream source would be
1727 <sect id="restrictions">
1728 <heading>Restrictions on objects in source packages</heading>
1731 The source package may not contain any hard links<footnote>
1733 This is not currently detected when building source
1734 packages, but only when extracting
1738 Hard links may be permitted at some point in the
1739 future, but would require a fair amount of
1742 </footnote>, device special files, sockets or setuid or
1743 setgid files.<footnote>
1744 Setgid directories are allowed.
1749 <sect id="debianrules">
1750 <heading>Main building script: <file>debian/rules</file></heading>
1753 This file must be an executable makefile, and contains the
1754 package-specific recipes for compiling the package and
1755 building binary package(s) from the source.
1759 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1760 so that it can be invoked by saying its name rather than
1761 invoking <prgn>make</prgn> explicitly. That is, invoking
1762 either of <tt>make -f debian/rules <em>args...</em></tt>
1763 or <tt>./debian/rules <em>args...</em></tt> must result in
1768 Since an interactive <file>debian/rules</file> script makes it
1769 impossible to auto-compile that package and also makes it
1770 hard for other people to reproduce the same binary
1771 package, all <em>required targets</em> must be
1772 non-interactive. At a minimum, required targets are the
1773 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1774 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1775 <em>binary-indep</em>, and <em>build</em>. It also follows
1776 that any target that these targets depend on must also be
1781 The targets are as follows (required unless stated otherwise):
1783 <tag><tt>build</tt></tag>
1786 The <tt>build</tt> target should perform all the
1787 configuration and compilation of the package.
1788 If a package has an interactive pre-build
1789 configuration routine, the Debian source package
1790 must either be built after this has taken place (so
1791 that the binary package can be built without rerunning
1792 the configuration) or the configuration routine
1793 modified to become non-interactive. (The latter is
1794 preferable if there are architecture-specific features
1795 detected by the configuration routine.)
1799 For some packages, notably ones where the same
1800 source tree is compiled in different ways to produce
1801 two binary packages, the <tt>build</tt> target
1802 does not make much sense. For these packages it is
1803 good enough to provide two (or more) targets
1804 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1805 for each of the ways of building the package, and a
1806 <tt>build</tt> target that does nothing. The
1807 <tt>binary</tt> target will have to build the
1808 package in each of the possible ways and make the
1809 binary package out of each.
1813 The <tt>build</tt> target must not do anything
1814 that might require root privilege.
1818 The <tt>build</tt> target may need to run the
1819 <tt>clean</tt> target first - see below.
1823 When a package has a configuration and build routine
1824 which takes a long time, or when the makefiles are
1825 poorly designed, or when <tt>build</tt> needs to
1826 run <tt>clean</tt> first, it is a good idea to
1827 <tt>touch build</tt> when the build process is
1828 complete. This will ensure that if <tt>debian/rules
1829 build</tt> is run again it will not rebuild the whole
1831 Another common way to do this is for <tt>build</tt>
1832 to depend on <prgn>build-stamp</prgn> and to do
1833 nothing else, and for the <prgn>build-stamp</prgn>
1834 target to do the building and to <tt>touch
1835 build-stamp</tt> on completion. This is
1836 especially useful if the build routine creates a
1837 file or directory called <tt>build</tt>; in such a
1838 case, <tt>build</tt> will need to be listed as
1839 a phony target (i.e., as a dependency of the
1840 <tt>.PHONY</tt> target). See the documentation of
1841 <prgn>make</prgn> for more information on phony
1847 <tag><tt>build-arch</tt> (optional),
1848 <tt>build-indep</tt> (optional)
1852 A package may also provide both of the targets
1853 <tt>build-arch</tt> and <tt>build-indep</tt>.
1854 The <tt>build-arch</tt> target, if provided, should
1855 perform all the configuration and compilation required for
1856 producing all architecture-dependant binary packages
1857 (those packages for which the body of the
1858 <tt>Architecture</tt> field in <tt>debian/control</tt> is
1859 not <tt>all</tt>). Similarly, the <tt>build-indep</tt>
1860 target, if provided, should perform all the configuration
1861 and compilation required for producing all
1862 architecture-independent binary packages (those packages
1863 for which the body of the <tt>Architecture</tt> field
1864 in <tt>debian/control</tt> is <tt>all</tt>).
1865 The <tt>build</tt> target should depend on those of the
1866 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1867 are provided in the rules file.<footnote>
1868 The intent of this split is so that binary-only builds
1869 need not install the dependencies required for
1870 the <tt>build-indep</tt> target. However, this is not
1871 yet used in practice since <tt>dpkg-buildpackage
1872 -B</tt>, and therefore the autobuilders,
1873 invoke <tt>build</tt> rather than <tt>build-arch</tt>
1874 due to the difficulties in determining whether the
1875 optional <tt>build-arch</tt> target exists.
1880 If one or both of the targets <tt>build-arch</tt> and
1881 <tt>build-indep</tt> are not provided, then invoking
1882 <file>debian/rules</file> with one of the not-provided
1883 targets as arguments should produce a exit status code
1884 of 2. Usually this is provided automatically by make
1885 if the target is missing.
1889 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1890 must not do anything that might require root privilege.
1894 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1895 <tt>binary-indep</tt>
1899 The <tt>binary</tt> target must be all that is
1900 necessary for the user to build the binary package(s)
1901 produced from this source package. It is
1902 split into two parts: <prgn>binary-arch</prgn> builds
1903 the binary packages which are specific to a particular
1904 architecture, and <tt>binary-indep</tt> builds
1905 those which are not.
1908 <tt>binary</tt> may be (and commonly is) a target with
1909 no commands which simply depends on
1910 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1913 Both <tt>binary-*</tt> targets should depend on the
1914 <tt>build</tt> target, or on the appropriate
1915 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1916 provided, so that the package is built if it has not
1917 been already. It should then create the relevant
1918 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1919 make their control files and <prgn>dpkg-deb</prgn> to
1920 build them and place them in the parent of the top
1925 Both the <tt>binary-arch</tt> and
1926 <tt>binary-indep</tt> targets <em>must</em> exist.
1927 If one of them has nothing to do (which will always be
1928 the case if the source generates only a single binary
1929 package, whether architecture-dependent or not), it
1930 must still exist and must always succeed.
1934 The <tt>binary</tt> targets must be invoked as
1936 The <prgn>fakeroot</prgn> package often allows one
1937 to build a package correctly even without being
1943 <tag><tt>clean</tt></tag>
1946 This must undo any effects that the <tt>build</tt>
1947 and <tt>binary</tt> targets may have had, except
1948 that it should leave alone any output files created in
1949 the parent directory by a run of a <tt>binary</tt>
1954 If a <tt>build</tt> file is touched at the end of
1955 the <tt>build</tt> target, as suggested above, it
1956 should be removed as the first action that
1957 <tt>clean</tt> performs, so that running
1958 <tt>build</tt> again after an interrupted
1959 <tt>clean</tt> doesn't think that everything is
1964 The <tt>clean</tt> target may need to be
1965 invoked as root if <tt>binary</tt> has been
1966 invoked since the last <tt>clean</tt>, or if
1967 <tt>build</tt> has been invoked as root (since
1968 <tt>build</tt> may create directories, for
1973 <tag><tt>get-orig-source</tt> (optional)</tag>
1976 This target fetches the most recent version of the
1977 original source package from a canonical archive site
1978 (via FTP or WWW, for example), does any necessary
1979 rearrangement to turn it into the original source
1980 tar file format described below, and leaves it in the
1985 This target may be invoked in any directory, and
1986 should take care to clean up any temporary files it
1991 This target is optional, but providing it if
1992 possible is a good idea.
1996 <tag><tt>patch</tt> (optional)</tag>
1999 This target performs whatever additional actions are
2000 required to make the source ready for editing (unpacking
2001 additional upstream archives, applying patches, etc.).
2002 It is recommended to be implemented for any package where
2003 <tt>dpkg-source -x</tt> does not result in source ready
2004 for additional modification. See
2005 <ref id="readmesource">.
2011 The <tt>build</tt>, <tt>binary</tt> and
2012 <tt>clean</tt> targets must be invoked with the current
2013 directory being the package's top-level directory.
2018 Additional targets may exist in <file>debian/rules</file>,
2019 either as published or undocumented interfaces or for the
2020 package's internal use.
2024 The architectures we build on and build for are determined
2025 by <prgn>make</prgn> variables using the utility
2026 <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
2027 You can determine the
2028 Debian architecture and the GNU style architecture
2029 specification string for the build machine (the machine type
2030 we are building on) as well as for the host machine (the
2031 machine type we are building for). Here is a list of
2032 supported <prgn>make</prgn> variables:
2033 <list compact="compact">
2035 <tt>DEB_*_ARCH</tt> (the Debian architecture)
2038 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2041 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2044 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2045 specification string)
2048 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2049 <tt>DEB_*_GNU_TYPE</tt>)
2052 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2053 <tt>DEB_*_GNU_TYPE</tt>)
2055 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2056 the build machine or <tt>HOST</tt> for specification of the
2061 Backward compatibility can be provided in the rules file
2062 by setting the needed variables to suitable default
2063 values; please refer to the documentation of
2064 <prgn>dpkg-architecture</prgn> for details.
2068 It is important to understand that the <tt>DEB_*_ARCH</tt>
2069 string only determines which Debian architecture we are
2070 building on or for. It should not be used to get the CPU
2071 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2072 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2073 GNU style variables should generally only be used with upstream
2077 <sect1 id="debianrules-options">
2078 <heading><file>debian/rules</file> and
2079 <tt>DEB_BUILD_OPTIONS</tt></heading>
2082 Supporting the standardized environment variable
2083 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2084 contain several flags to change how a package is compiled and
2085 built. Each flag must be in the form <var>flag</var> or
2086 <var>flag</var>=<var>options</var>. If multiple flags are
2087 given, they must be separated by whitespace.<footnote>
2088 Some packages support any delimiter, but whitespace is the
2089 easiest to parse inside a makefile and avoids ambiguity with
2090 flag values that contain commas.
2092 <var>flag</var> must start with a lowercase letter
2093 (<tt>a-z</tt>) and consist only of lowercase letters,
2094 numbers (<tt>0-9</tt>), and the characters
2095 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2096 <var>options</var> must not contain whitespace. The same
2097 tag should not be given multiple times with conflicting
2098 values. Package maintainers may assume that
2099 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2103 The meaning of the following tags has been standardized:
2107 This tag says to not run any build-time test suite
2108 provided by the package.
2112 The presence of this tag means that the package should
2113 be compiled with a minimum of optimization. For C
2114 programs, it is best to add <tt>-O0</tt> to
2115 <tt>CFLAGS</tt> (although this is usually the default).
2116 Some programs might fail to build or run at this level
2117 of optimization; it may be necessary to use
2118 <tt>-O1</tt>, for example.
2122 This tag means that the debugging symbols should not be
2123 stripped from the binary during installation, so that
2124 debugging information may be included in the package.
2126 <tag>parallel=n</tag>
2128 This tag means that the package should be built using up
2129 to <tt>n</tt> parallel processes if the package build
2130 system supports this.<footnote>
2131 Packages built with <tt>make</tt> can often implement
2132 this by passing the <tt>-j</tt><var>n</var> option to
2135 If the package build system does not support parallel
2136 builds, this string must be ignored. If the package
2137 build system only supports a lower level of concurrency
2138 than <var>n</var>, the package should be built using as
2139 many parallel processes as the package build system
2140 supports. It is up to the package maintainer to decide
2141 whether the package build times are long enough and the
2142 package build system is robust enough to make supporting
2143 parallel builds worthwhile.
2149 Unknown flags must be ignored by <file>debian/rules</file>.
2153 The following makefile snippet is an example of how one may
2154 implement the build options; you will probably have to
2155 massage this example in order to make it work for your
2157 <example compact="compact">
2160 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2161 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2162 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2163 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2165 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2170 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2171 INSTALL_PROGRAM += -s
2173 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2174 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2175 MAKEFLAGS += -j$(NUMJOBS)
2180 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2181 # Code to run the package test suite.
2188 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2189 <sect id="substvars">
2190 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2193 When <prgn>dpkg-gencontrol</prgn>,
2194 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
2195 generate control files they perform variable substitutions
2196 on their output just before writing it. Variable
2197 substitutions have the form <tt>${<var>variable</var>}</tt>.
2198 The optional file <file>debian/substvars</file> contains
2199 variable substitutions to be used; variables can also be set
2200 directly from <file>debian/rules</file> using the <tt>-V</tt>
2201 option to the source packaging commands, and certain
2202 predefined variables are also available.
2206 The <file>debian/substvars</file> file is usually generated and
2207 modified dynamically by <file>debian/rules</file> targets, in
2208 which case it must be removed by the <tt>clean</tt> target.
2212 See <manref name="deb-substvars" section="5"> for full
2213 details about source variable substitutions, including the
2214 format of <file>debian/substvars</file>.</p>
2217 <sect id="debianwatch">
2218 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2221 This is an optional, recommended control file for the
2222 <tt>uscan</tt> utility which defines how to automatically
2223 scan ftp or http sites for newly available updates of the
2224 package. This is used by <url id="
2225 http://dehs.alioth.debian.org/"> and other Debian QA tools
2226 to help with quality control and maintenance of the
2227 distribution as a whole.
2232 <sect id="debianfiles">
2233 <heading>Generated files list: <file>debian/files</file></heading>
2236 This file is not a permanent part of the source tree; it
2237 is used while building packages to record which files are
2238 being generated. <prgn>dpkg-genchanges</prgn> uses it
2239 when it generates a <file>.changes</file> file.
2243 It should not exist in a shipped source package, and so it
2244 (and any backup files or temporary files such as
2245 <file>files.new</file><footnote>
2246 <file>files.new</file> is used as a temporary file by
2247 <prgn>dpkg-gencontrol</prgn> and
2248 <prgn>dpkg-distaddfile</prgn> - they write a new
2249 version of <tt>files</tt> here before renaming it,
2250 to avoid leaving a corrupted copy if an error
2252 </footnote>) should be removed by the
2253 <tt>clean</tt> target. It may also be wise to
2254 ensure a fresh start by emptying or removing it at the
2255 start of the <tt>binary</tt> target.
2259 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2260 package, it adds an entry to <file>debian/files</file> for the
2261 <file>.deb</file> file that will be created when <tt>dpkg-deb
2262 --build</tt> is run for that binary package. So for most
2263 packages all that needs to be done with this file is to
2264 delete it in the <tt>clean</tt> target.
2268 If a package upload includes files besides the source
2269 package and any binary packages whose control files were
2270 made with <prgn>dpkg-gencontrol</prgn> then they should be
2271 placed in the parent of the package's top-level directory
2272 and <prgn>dpkg-distaddfile</prgn> should be called to add
2273 the file to the list in <file>debian/files</file>.</p>
2276 <sect id="embeddedfiles">
2277 <heading>Convenience copies of code</heading>
2280 Some software packages include in their distribution convenience
2281 copies of code from other software packages, generally so that
2282 users compiling from source don't have to download multiple
2283 packages. Debian packages should not make use of these
2284 convenience copies unless the included package is explicitly
2285 intended to be used in this way.<footnote>
2286 For example, parts of the GNU build system work like this.
2288 If the included code is already in the Debian archive in the
2289 form of a library, the Debian packaging should ensure that
2290 binary packages reference the libraries already in Debian and
2291 the convenience copy is not used. If the included code is not
2292 already in Debian, it should be packaged separately as a
2293 prerequisite if possible.
2295 Having multiple copies of the same code in Debian is
2296 inefficient, often creates either static linking or shared
2297 library conflicts, and, most importantly, increases the
2298 difficulty of handling security vulnerabilities in the
2304 <sect id="readmesource">
2305 <heading>Source package handling:
2306 <file>debian/README.source</file></heading>
2309 If running <prgn>dpkg-source -x</prgn> on a source package
2310 doesn't produce the source of the package, ready for editing,
2311 and allow one to make changes and run
2312 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2313 without taking any additional steps, creating a
2314 <file>debian/README.source</file> documentation file is
2315 recommended. This file should explain how to do all of the
2318 <item>Generate the fully patched source, in a form ready for
2319 editing, that would be built to create Debian
2320 packages. Doing this with a <tt>patch</tt> target in
2321 <file>debian/rules</file> is recommended; see
2322 <ref id="debianrules">.</item>
2323 <item>Modify the source and save those modifications so that
2324 they will be applied when building the package.</item>
2325 <item>Remove source modifications that are currently being
2326 applied when building the package.</item>
2327 <item>Optionally, document what steps are necessary to
2328 upgrade the Debian source package to a new upstream version,
2329 if applicable.</item>
2331 This explanation should include specific commands and mention
2332 any additional required Debian packages. It should not assume
2333 familiarity with any specific Debian packaging system or patch
2338 This explanation may refer to a documentation file installed by
2339 one of the package's build dependencies provided that the
2340 referenced documentation clearly explains these tasks and is not
2341 a general reference manual.
2345 <file>debian/README.source</file> may also include any other
2346 information that would be helpful to someone modifying the
2347 source package. Even if the package doesn't fit the above
2348 description, maintainers are encouraged to document in a
2349 <file>debian/README.source</file> file any source package with a
2350 particularly complex or unintuitive source layout or build
2351 system (for example, a package that builds the same source
2352 multiple times to generate different binary packages).
2358 <chapt id="controlfields">
2359 <heading>Control files and their fields</heading>
2362 The package management system manipulates data represented in
2363 a common format, known as <em>control data</em>, stored in
2364 <em>control files</em>.
2365 Control files are used for source packages, binary packages and
2366 the <file>.changes</file> files which control the installation
2367 of uploaded files<footnote>
2368 <prgn>dpkg</prgn>'s internal databases are in a similar
2373 <sect id="controlsyntax">
2374 <heading>Syntax of control files</heading>
2377 A control file consists of one or more paragraphs of
2379 The paragraphs are also sometimes referred to as stanzas.
2381 The paragraphs are separated by blank lines. Some control
2382 files allow only one paragraph; others allow several, in
2383 which case each paragraph usually refers to a different
2384 package. (For example, in source packages, the first
2385 paragraph refers to the source package, and later paragraphs
2386 refer to binary packages generated from the source.)
2390 Each paragraph consists of a series of data fields; each
2391 field consists of the field name, followed by a colon and
2392 then the data/value associated with that field. It ends at
2393 the end of the (logical) line. Horizontal whitespace
2394 (spaces and tabs) may occur immediately before or after the
2395 value and is ignored there; it is conventional to put a
2396 single space after the colon. For example, a field might
2398 <example compact="compact">
2401 the field name is <tt>Package</tt> and the field value
2406 A paragraph must not contain more than one instance of a
2407 particular field name.
2411 Many fields' values may span several lines; in this case
2412 each continuation line must start with a space or a tab.
2413 Any trailing spaces or tabs at the end of individual
2414 lines of a field value are ignored.
2418 In fields where it is specified that lines may not wrap,
2419 only a single line of data is allowed and whitespace is not
2420 significant in a field body. Whitespace must not appear
2421 inside names (of packages, architectures, files or anything
2422 else) or version numbers, or between the characters of
2423 multi-character version relationships.
2427 Field names are not case-sensitive, but it is usual to
2428 capitalize the field names using mixed case as shown below.
2429 Field values are case-sensitive unless the description of the
2430 field says otherwise.
2434 Blank lines, or lines consisting only of spaces and tabs,
2435 are not allowed within field values or between fields - that
2436 would mean a new paragraph.
2440 All control files must be encoded in UTF-8.
2444 <sect id="sourcecontrolfiles">
2445 <heading>Source package control files -- <file>debian/control</file></heading>
2448 The <file>debian/control</file> file contains the most vital
2449 (and version-independent) information about the source package
2450 and about the binary packages it creates.
2454 The first paragraph of the control file contains information about
2455 the source package in general. The subsequent sets each describe a
2456 binary package that the source tree builds.
2460 The fields in the general paragraph (the first one, for the source
2463 <list compact="compact">
2464 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2465 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2466 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2467 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2468 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2469 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2470 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2471 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2476 The fields in the binary package paragraphs are:
2478 <list compact="compact">
2479 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2480 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2481 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2482 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2483 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2484 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2485 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2486 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2491 The syntax and semantics of the fields are described below.
2495 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2496 generate control files for binary packages (see below), by
2497 <prgn>dpkg-genchanges</prgn> to generate the
2498 <file>.changes</file> file to accompany the upload, and by
2499 <prgn>dpkg-source</prgn> when it creates the
2500 <file>.dsc</file> source control file as part of a source
2501 archive. Many fields are permitted to span multiple lines in
2502 <file>debian/control</file> but not in any other control
2503 file. These tools are responsible for removing the line
2504 breaks from such fields when using fields from
2505 <file>debian/control</file> to generate other control files.
2509 The fields here may contain variable references - their
2510 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2511 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2512 when they generate output control files.
2513 See <ref id="substvars"> for details.
2517 In addition to the control file syntax described <qref
2518 id="controlsyntax">above</qref>, this file may also contain
2519 comment lines starting with <tt>#</tt> without any preceding
2520 whitespace. All such lines are ignored, even in the middle of
2521 continuation lines for a multiline field, and do not end a
2527 <sect id="binarycontrolfiles">
2528 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2531 The <file>DEBIAN/control</file> file contains the most vital
2532 (and version-dependent) information about a binary package. It
2533 consists of a single paragraph.
2537 The fields in this file are:
2539 <list compact="compact">
2540 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2541 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2542 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2543 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2544 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2545 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2546 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2547 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2548 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2549 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2550 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2551 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2556 <sect id="debiansourcecontrolfiles">
2557 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2560 This file consists of a single paragraph, possibly surrounded by
2561 a PGP signature. The fields of that paragraph are listed below.
2562 Their syntax is described above, in <ref id="pkg-controlfields">.
2564 <list compact="compact">
2565 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2566 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2567 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2568 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2569 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2570 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2571 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2572 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2573 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2574 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2575 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2576 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2577 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2582 The source package control file is generated by
2583 <prgn>dpkg-source</prgn> when it builds the source
2584 archive, from other files in the source package,
2585 described above. When unpacking, it is checked against
2586 the files and directories in the other parts of the
2592 <sect id="debianchangesfiles">
2593 <heading>Debian changes files -- <file>.changes</file></heading>
2596 The <file>.changes</file> files are used by the Debian archive
2597 maintenance software to process updates to packages. They
2598 consist of a single paragraph, possibly surrounded by a PGP
2599 signature. That paragraph contains information from the
2600 <file>debian/control</file> file and other data about the
2601 source package gathered via <file>debian/changelog</file>
2602 and <file>debian/rules</file>.
2606 <file>.changes</file> files have a format version that is
2607 incremented whenever the documented fields or their meaning
2608 change. This document describes format &changesversion;.
2612 The fields in this file are:
2614 <list compact="compact">
2615 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2616 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2617 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2618 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2619 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2620 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2621 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2622 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2623 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2624 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2625 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2626 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2627 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2628 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2629 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2630 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2635 <sect id="controlfieldslist">
2636 <heading>List of fields</heading>
2638 <sect1 id="f-Source">
2639 <heading><tt>Source</tt></heading>
2642 This field identifies the source package name.
2646 In <file>debian/control</file> or a <file>.dsc</file> file,
2647 this field must contain only the name of the source package.
2651 In a binary package control file or a <file>.changes</file>
2652 file, the source package name may be followed by a version
2653 number in parentheses<footnote>
2654 It is customary to leave a space after the package name
2655 if a version number is specified.
2657 This version number may be omitted (and is, by
2658 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2659 the <tt>Version</tt> field of the binary package in
2660 question. The field itself may be omitted from a binary
2661 package control file when the source package has the same
2662 name and version as the binary package.
2666 Package names (both source and binary,
2667 see <ref id="f-Package">) must consist only of lower case
2668 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2669 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2670 (<tt>.</tt>). They must be at least two characters long and
2671 must start with an alphanumeric character.
2675 <sect1 id="f-Maintainer">
2676 <heading><tt>Maintainer</tt></heading>
2679 The package maintainer's name and email address. The name
2680 must come first, then the email address inside angle
2681 brackets <tt><></tt> (in RFC822 format).
2685 If the maintainer's name contains a full stop then the
2686 whole field will not work directly as an email address due
2687 to a misfeature in the syntax specified in RFC822; a
2688 program using this field as an address must check for this
2689 and correct the problem if necessary (for example by
2690 putting the name in round brackets and moving it to the
2691 end, and bringing the email address forward).
2695 <sect1 id="f-Uploaders">
2696 <heading><tt>Uploaders</tt></heading>
2699 List of the names and email addresses of co-maintainers of
2700 the package, if any. If the package has other maintainers
2701 beside the one named in the
2702 <qref id="f-Maintainer">Maintainer field</qref>, their names
2703 and email addresses should be listed here. The format of each
2704 entry is the same as that of the Maintainer field, and
2705 multiple entries must be comma separated. This is an optional
2710 Any parser that interprets the Uploaders field in
2711 <file>debian/control</file> must permit it to span multiple
2712 lines. Line breaks in an Uploaders field that spans multiple
2713 lines are not significant and the semantics of the field are
2714 the same as if the line breaks had not been present.
2718 <sect1 id="f-Changed-By">
2719 <heading><tt>Changed-By</tt></heading>
2722 The name and email address of the person who prepared this
2723 version of the package, usually a maintainer. The syntax is
2724 the same as for the <qref id="f-Maintainer">Maintainer
2729 <sect1 id="f-Section">
2730 <heading><tt>Section</tt></heading>
2733 This field specifies an application area into which the package
2734 has been classified. See <ref id="subsections">.
2738 When it appears in the <file>debian/control</file> file,
2739 it gives the value for the subfield of the same name in
2740 the <tt>Files</tt> field of the <file>.changes</file> file.
2741 It also gives the default for the same field in the binary
2746 <sect1 id="f-Priority">
2747 <heading><tt>Priority</tt></heading>
2750 This field represents how important it is that the user
2751 have the package installed. See <ref id="priorities">.
2755 When it appears in the <file>debian/control</file> file,
2756 it gives the value for the subfield of the same name in
2757 the <tt>Files</tt> field of the <file>.changes</file> file.
2758 It also gives the default for the same field in the binary
2763 <sect1 id="f-Package">
2764 <heading><tt>Package</tt></heading>
2767 The name of the binary package.
2771 Binary package names must follow the same syntax and
2772 restrictions as source package names. See <ref id="f-Source">
2777 <sect1 id="f-Architecture">
2778 <heading><tt>Architecture</tt></heading>
2781 Depending on context and the control file used, the
2782 <tt>Architecture</tt> field can include the following sets of
2786 A unique single word identifying a Debian machine
2787 architecture as described in <ref id="arch-spec">.
2790 An architecture wildcard identifying a set of Debian
2791 machine architectures, see <ref id="arch-wildcard-spec">.
2792 <tt>any</tt> matches all Debian machine architectures
2793 and is the most frequently used.
2796 <tt>all</tt>, which indicates an
2797 architecture-independent package.
2800 <tt>source</tt>, which indicates a source package.
2806 In the main <file>debian/control</file> file in the source
2807 package, this field may contain the special
2808 value <tt>all</tt>, the special architecture
2809 wildcard <tt>any</tt>, or a list of specific and wildcard
2810 architectures separated by spaces. If <tt>all</tt>
2811 or <tt>any</tt> appears, that value must be the entire
2812 contents of the field. Most packages will use
2813 either <tt>all</tt> or <tt>any</tt>.
2817 Specifying a specific list of architectures indicates that the
2818 source will build an architecture-dependent package only on
2819 architectures included in the list. Specifying a list of
2820 architecture wildcards indicates that the source will build an
2821 architecture-dependent package on only those architectures
2822 that match any of the specified architecture wildcards.
2823 Specifying a list of architectures or architecture wildcards
2824 other than <tt>any</tt> is for the minority of cases where a
2825 program is not portable or is not useful on some
2826 architectures. Where possible, the program should be made
2831 In the source package control file <file>.dsc</file>, this
2832 field may contain either the architecture
2833 wildcard <tt>any</tt> or a list of architectures and
2834 architecture wildcards separated by spaces. If a list is
2835 given, it may include (or consist solely of) the special
2836 value <tt>all</tt>. In other words, in <file>.dsc</file>
2837 files unlike the <file>debian/control</file>, <tt>all</tt> may
2838 occur in combination with specific architectures.
2839 The <tt>Architecture</tt> field in the source package control
2840 file <file>.dsc</file> is generally constructed from
2841 the <tt>Architecture</tt> fields in
2842 the <file>debian/control</file> in the source package.
2846 Specifying <tt>any</tt> indicates that the source package
2847 isn't dependent on any particular architecture and should
2848 compile fine on any one. The produced binary package(s)
2849 will either be specific to whatever the current build
2850 architecture is or will be architecture-independent.
2854 Specifying only <tt>all</tt> indicates that the source package
2855 will only build architecture-independent packages. If this is
2856 the case, <tt>all</tt> must be used rather than <tt>any</tt>;
2857 <tt>any</tt> implies that the source package will build at
2858 least one architecture-dependent package.
2862 Specifying a list of architectures or architecture wildcards
2863 indicates that the source will build an architecture-dependent
2864 package, and will only work correctly on the listed or
2865 matching architectures. If the source package also builds at
2866 least one architecture-independent package, <tt>all</tt> will
2867 also be included in the list.
2871 In a <file>.changes</file> file, the <tt>Architecture</tt>
2872 field lists the architecture(s) of the package(s) currently
2873 being uploaded. This will be a list; if the source for the
2874 package is also being uploaded, the special
2875 entry <tt>source</tt> is also present. <tt>all</tt> will be
2876 present if any architecture-independent packages are being
2877 uploaded. Architecture wildcards such as <tt>any</tt> must
2878 never occur in the <tt>Architecture</tt> field in
2879 the <file>.changes</file> file.
2883 See <ref id="debianrules"> for information on how to get
2884 the architecture for the build process.
2888 <sect1 id="f-Essential">
2889 <heading><tt>Essential</tt></heading>
2892 This is a boolean field which may occur only in the
2893 control file of a binary package or in a per-package fields
2894 paragraph of a main source control data file.
2898 If set to <tt>yes</tt> then the package management system
2899 will refuse to remove the package (upgrading and replacing
2900 it is still possible). The other possible value is <tt>no</tt>,
2901 which is the same as not having the field at all.
2906 <heading>Package interrelationship fields:
2907 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2908 <tt>Recommends</tt>, <tt>Suggests</tt>,
2909 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2910 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2914 These fields describe the package's relationships with
2915 other packages. Their syntax and semantics are described
2916 in <ref id="relationships">.</p>
2919 <sect1 id="f-Standards-Version">
2920 <heading><tt>Standards-Version</tt></heading>
2923 The most recent version of the standards (the policy
2924 manual and associated texts) with which the package
2929 The version number has four components: major and minor
2930 version number and major and minor patch level. When the
2931 standards change in a way that requires every package to
2932 change the major number will be changed. Significant
2933 changes that will require work in many packages will be
2934 signaled by a change to the minor number. The major patch
2935 level will be changed for any change to the meaning of the
2936 standards, however small; the minor patch level will be
2937 changed when only cosmetic, typographical or other edits
2938 are made which neither change the meaning of the document
2939 nor affect the contents of packages.
2943 Thus only the first three components of the policy version
2944 are significant in the <em>Standards-Version</em> control
2945 field, and so either these three components or all four
2946 components may be specified.<footnote>
2947 In the past, people specified the full version number
2948 in the Standards-Version field, for example "2.3.0.0".
2949 Since minor patch-level changes don't introduce new
2950 policy, it was thought it would be better to relax
2951 policy and only require the first 3 components to be
2952 specified, in this example "2.3.0". All four
2953 components may still be used if someone wishes to do so.
2959 <sect1 id="f-Version">
2960 <heading><tt>Version</tt></heading>
2963 The version number of a package. The format is:
2964 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
2968 The three components here are:
2970 <tag><var>epoch</var></tag>
2973 This is a single (generally small) unsigned integer. It
2974 may be omitted, in which case zero is assumed. If it is
2975 omitted then the <var>upstream_version</var> may not
2980 It is provided to allow mistakes in the version numbers
2981 of older versions of a package, and also a package's
2982 previous version numbering schemes, to be left behind.
2986 <tag><var>upstream_version</var></tag>
2989 This is the main part of the version number. It is
2990 usually the version number of the original ("upstream")
2991 package from which the <file>.deb</file> file has been made,
2992 if this is applicable. Usually this will be in the same
2993 format as that specified by the upstream author(s);
2994 however, it may need to be reformatted to fit into the
2995 package management system's format and comparison
3000 The comparison behavior of the package management system
3001 with respect to the <var>upstream_version</var> is
3002 described below. The <var>upstream_version</var>
3003 portion of the version number is mandatory.
3007 The <var>upstream_version</var> may contain only
3008 alphanumerics<footnote>
3009 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3011 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3012 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3013 tilde) and should start with a digit. If there is no
3014 <var>debian_revision</var> then hyphens are not allowed;
3015 if there is no <var>epoch</var> then colons are not
3020 <tag><var>debian_revision</var></tag>
3023 This part of the version number specifies the version of
3024 the Debian package based on the upstream version. It
3025 may contain only alphanumerics and the characters
3026 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3027 tilde) and is compared in the same way as the
3028 <var>upstream_version</var> is.
3032 It is optional; if it isn't present then the
3033 <var>upstream_version</var> may not contain a hyphen.
3034 This format represents the case where a piece of
3035 software was written specifically to be a Debian
3036 package, where the Debian package source must always
3037 be identical to the pristine source and therefore no
3038 revision indication is required.
3042 It is conventional to restart the
3043 <var>debian_revision</var> at <tt>1</tt> each time the
3044 <var>upstream_version</var> is increased.
3048 The package management system will break the version
3049 number apart at the last hyphen in the string (if there
3050 is one) to determine the <var>upstream_version</var> and
3051 <var>debian_revision</var>. The absence of a
3052 <var>debian_revision</var> is equivalent to a
3053 <var>debian_revision</var> of <tt>0</tt>.
3060 When comparing two version numbers, first the <var>epoch</var>
3061 of each are compared, then the <var>upstream_version</var> if
3062 <var>epoch</var> is equal, and then <var>debian_revision</var>
3063 if <var>upstream_version</var> is also equal.
3064 <var>epoch</var> is compared numerically. The
3065 <var>upstream_version</var> and <var>debian_revision</var>
3066 parts are compared by the package management system using the
3067 following algorithm:
3071 The strings are compared from left to right.
3075 First the initial part of each string consisting entirely of
3076 non-digit characters is determined. These two parts (one of
3077 which may be empty) are compared lexically. If a difference
3078 is found it is returned. The lexical comparison is a
3079 comparison of ASCII values modified so that all the letters
3080 sort earlier than all the non-letters and so that a tilde
3081 sorts before anything, even the end of a part. For example,
3082 the following parts are in sorted order from earliest to
3083 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3084 <tt>a</tt>.<footnote>
3085 One common use of <tt>~</tt> is for upstream pre-releases.
3086 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3087 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3092 Then the initial part of the remainder of each string which
3093 consists entirely of digit characters is determined. The
3094 numerical values of these two parts are compared, and any
3095 difference found is returned as the result of the comparison.
3096 For these purposes an empty string (which can only occur at
3097 the end of one or both version strings being compared) counts
3102 These two steps (comparing and removing initial non-digit
3103 strings and initial digit strings) are repeated until a
3104 difference is found or both strings are exhausted.
3108 Note that the purpose of epochs is to allow us to leave behind
3109 mistakes in version numbering, and to cope with situations
3110 where the version numbering scheme changes. It is
3111 <em>not</em> intended to cope with version numbers containing
3112 strings of letters which the package management system cannot
3113 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3114 silly orderings.<footnote>
3115 The author of this manual has heard of a package whose
3116 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3117 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3123 <sect1 id="f-Description">
3124 <heading><tt>Description</tt></heading>
3127 In a source or binary control file, the <tt>Description</tt>
3128 field contains a description of the binary package, consisting
3129 of two parts, the synopsis or the short description, and the
3130 long description. The field's format is as follows:
3135 Description: <single line synopsis>
3136 <extended description over several lines>
3141 The lines in the extended description can have these formats:
3147 Those starting with a single space are part of a paragraph.
3148 Successive lines of this form will be word-wrapped when
3149 displayed. The leading space will usually be stripped off.
3153 Those starting with two or more spaces. These will be
3154 displayed verbatim. If the display cannot be panned
3155 horizontally, the displaying program will line wrap them "hard"
3156 (i.e., without taking account of word breaks). If it can they
3157 will be allowed to trail off to the right. None, one or two
3158 initial spaces may be deleted, but the number of spaces
3159 deleted from each line will be the same (so that you can have
3160 indenting work correctly, for example).
3164 Those containing a single space followed by a single full stop
3165 character. These are rendered as blank lines. This is the
3166 <em>only</em> way to get a blank line<footnote>
3167 Completely empty lines will not be rendered as blank lines.
3168 Instead, they will cause the parser to think you're starting
3169 a whole new record in the control file, and will therefore
3170 likely abort with an error.
3175 Those containing a space, a full stop and some more characters.
3176 These are for future expansion. Do not use them.
3182 Do not use tab characters. Their effect is not predictable.
3186 See <ref id="descriptions"> for further information on this.
3190 In a <file>.changes</file> file, the <tt>Description</tt>
3191 field contains a summary of the descriptions for the packages
3192 being uploaded. For this case, the first line of the field
3193 value (the part on the same line as <tt>Description:</tt>) is
3194 always empty. The content of the field is expressed as
3195 continuation lines, one line per package. Each line is
3196 indented by one space and contains the name of a binary
3197 package, a space, a hyphen (<tt>-</tt>), a space, and the
3198 short description line from that package.
3202 <sect1 id="f-Distribution">
3203 <heading><tt>Distribution</tt></heading>
3206 In a <file>.changes</file> file or parsed changelog output
3207 this contains the (space-separated) name(s) of the
3208 distribution(s) where this version of the package should
3209 be installed. Valid distributions are determined by the
3210 archive maintainers.<footnote>
3211 Example distribution names in the Debian archive used in
3212 <file>.changes</file> files are:
3213 <taglist compact="compact">
3214 <tag><em>unstable</em></tag>
3216 This distribution value refers to the
3217 <em>developmental</em> part of the Debian distribution
3218 tree. Most new packages, new upstream versions of
3219 packages and bug fixes go into the <em>unstable</em>
3223 <tag><em>experimental</em></tag>
3225 The packages with this distribution value are deemed
3226 by their maintainers to be high risk. Oftentimes they
3227 represent early beta or developmental packages from
3228 various sources that the maintainers want people to
3229 try, but are not ready to be a part of the other parts
3230 of the Debian distribution tree.
3235 Others are used for updating stable releases or for
3236 security uploads. More information is available in the
3237 Debian Developer's Reference, section "The Debian
3241 The Debian archive software only supports listing a single
3242 distribution. Migration of packages to other distributions is
3243 handled outside of the upload process.
3248 <heading><tt>Date</tt></heading>
3251 This field includes the date the package was built or last
3252 edited. It must be in the same format as the <var>date</var>
3253 in a <file>debian/changelog</file> entry.
3257 The value of this field is usually extracted from the
3258 <file>debian/changelog</file> file - see
3259 <ref id="dpkgchangelog">).
3263 <sect1 id="f-Format">
3264 <heading><tt>Format</tt></heading>
3267 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3268 files, this field declares the format version of that file.
3269 The syntax of the field value is the same as that of
3270 a <qref id="f-Version">package version number</qref> except
3271 that no epoch or Debian revision is allowed. The format
3272 described in this document is <tt>&changesversion;</tt>.
3276 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3277 Debian source control</qref> files, this field declares the
3278 format of the source package. The field value is used by
3279 programs acting on a source package to interpret the list of
3280 files in the source package and determine how to unpack it.
3281 The syntax of the field value is a numeric major revision, a
3282 period, a numeric minor revision, and then an optional subtype
3283 after whitespace, which if specified is an alphanumeric word
3284 in parentheses. The subtype is optional in the syntax but may
3285 be mandatory for particular source format revisions.
3287 The source formats currently supported by the Debian archive
3288 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3289 and <tt>3.0 (quilt)</tt>.
3294 <sect1 id="f-Urgency">
3295 <heading><tt>Urgency</tt></heading>
3298 This is a description of how important it is to upgrade to
3299 this version from previous ones. It consists of a single
3300 keyword taking one of the values <tt>low</tt>,
3301 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3302 <tt>critical</tt><footnote>
3303 Other urgency values are supported with configuration
3304 changes in the archive software but are not used in Debian.
3305 The urgency affects how quickly a package will be considered
3306 for inclusion into the <tt>testing</tt> distribution and
3307 gives an indication of the importance of any fixes included
3308 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3309 treated as synonymous.
3310 </footnote> (not case-sensitive) followed by an optional
3311 commentary (separated by a space) which is usually in
3312 parentheses. For example:
3315 Urgency: low (HIGH for users of diversions)
3321 The value of this field is usually extracted from the
3322 <file>debian/changelog</file> file - see
3323 <ref id="dpkgchangelog">.
3327 <sect1 id="f-Changes">
3328 <heading><tt>Changes</tt></heading>
3331 This field contains the human-readable changes data, describing
3332 the differences between the last version and the current one.
3336 The first line of the field value (the part on the same line
3337 as <tt>Changes:</tt>) is always empty. The content of the
3338 field is expressed as continuation lines, with each line
3339 indented by at least one space. Blank lines must be
3340 represented by a line consisting only of a space and a full
3345 The value of this field is usually extracted from the
3346 <file>debian/changelog</file> file - see
3347 <ref id="dpkgchangelog">).
3351 Each version's change information should be preceded by a
3352 "title" line giving at least the version, distribution(s)
3353 and urgency, in a human-readable way.
3357 If data from several versions is being returned the entry
3358 for the most recent version should be returned first, and
3359 entries should be separated by the representation of a
3360 blank line (the "title" line may also be followed by the
3361 representation of a blank line).
3365 <sect1 id="f-Binary">
3366 <heading><tt>Binary</tt></heading>
3369 This field is a list of binary packages. Its syntax and
3370 meaning varies depending on the control file in which it
3375 When it appears in the <file>.dsc</file> file, it lists binary
3376 packages which a source package can produce, separated by
3378 A space after each comma is conventional.
3379 </footnote>. It may span multiple lines. The source package
3380 does not necessarily produce all of these binary packages for
3381 every architecture. The source control file doesn't contain
3382 details of which architectures are appropriate for which of
3383 the binary packages.
3387 When it appears in a <file>.changes</file> file, it lists the
3388 names of the binary packages being uploaded, separated by
3389 whitespace (not commas). It may span multiple lines.
3393 <sect1 id="f-Installed-Size">
3394 <heading><tt>Installed-Size</tt></heading>
3397 This field appears in the control files of binary packages,
3398 and in the <file>Packages</file> files. It gives an estimate
3399 of the total amount of disk space required to install the
3400 named package. Actual installed size may vary based on block
3401 size, file system properties, or actions taken by package
3406 The disk space is given as the integer value of the estimated
3407 installed size in bytes, divided by 1024 and rounded up.
3411 <sect1 id="f-Files">
3412 <heading><tt>Files</tt></heading>
3415 This field contains a list of files with information about
3416 each one. The exact information and syntax varies with
3421 In all cases, Files is a multiline field. The first line of
3422 the field value (the part on the same line as <tt>Files:</tt>)
3423 is always empty. The content of the field is expressed as
3424 continuation lines, one line per file. Each line must be
3425 indented by one space and contain a number of sub-fields,
3426 separated by spaces, as described below.
3430 In the <file>.dsc</file> file, each line contains the MD5
3431 checksum, size and filename of the tar file and (if
3432 applicable) diff file which make up the remainder of the
3433 source package<footnote>
3434 That is, the parts which are not the <tt>.dsc</tt>.
3435 </footnote>. For example:
3438 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3439 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3441 The exact forms of the filenames are described
3442 in <ref id="pkg-sourcearchives">.
3446 In the <file>.changes</file> file this contains one line per
3447 file being uploaded. Each line contains the MD5 checksum,
3448 size, section and priority and the filename. For example:
3451 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3452 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3453 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3454 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3456 The <qref id="f-Section">section</qref>
3457 and <qref id="f-Priority">priority</qref> are the values of
3458 the corresponding fields in the main source control file. If
3459 no section or priority is specified then <tt>-</tt> should be
3460 used, though section and priority values must be specified for
3461 new packages to be installed properly.
3465 The special value <tt>byhand</tt> for the section in a
3466 <tt>.changes</tt> file indicates that the file in question
3467 is not an ordinary package file and must by installed by
3468 hand by the distribution maintainers. If the section is
3469 <tt>byhand</tt> the priority should be <tt>-</tt>.
3473 If a new Debian revision of a package is being shipped and
3474 no new original source archive is being distributed the
3475 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3476 entry for the original source archive
3477 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3478 but the <file>.changes</file> file should leave it out. In
3479 this case the original source archive on the distribution
3480 site must match exactly, byte-for-byte, the original
3481 source archive which was used to generate the
3482 <file>.dsc</file> file and diff which are being uploaded.</p>
3485 <sect1 id="f-Closes">
3486 <heading><tt>Closes</tt></heading>
3489 A space-separated list of bug report numbers that the upload
3490 governed by the .changes file closes.
3494 <sect1 id="f-Homepage">
3495 <heading><tt>Homepage</tt></heading>
3498 The URL of the web site for this package, preferably (when
3499 applicable) the site from which the original source can be
3500 obtained and any additional upstream documentation or
3501 information may be found. The content of this field is a
3502 simple URL without any surrounding characters such as
3507 <sect1 id="f-Checksums">
3508 <heading><tt>Checksums-Sha1</tt>
3509 and <tt>Checksums-Sha256</tt></heading>
3512 These fields contain a list of files with a checksum and size
3513 for each one. Both <tt>Checksums-Sha1</tt>
3514 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3515 only in the checksum algorithm used: SHA-1
3516 for <tt>Checksums-Sha1</tt> and SHA-256
3517 for <tt>Checksums-Sha256</tt>.
3521 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3522 multiline fields. The first line of the field value (the part
3523 on the same line as <tt>Checksums-Sha1:</tt>
3524 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3525 of the field is expressed as continuation lines, one line per
3526 file. Each line consists of the checksum, a space, the file
3527 size, a space, and the file name. For example (from
3528 a <file>.changes</file> file):
3531 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3532 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3533 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3534 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3536 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3537 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3538 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3539 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3544 In the <file>.dsc</file> file, these fields should list all
3545 files that make up the source package. In
3546 the <file>.changes</file> file, these fields should list all
3547 files being uploaded. The list of files in these fields
3548 must match the list of files in the <tt>Files</tt> field.
3554 <heading>User-defined fields</heading>
3557 Additional user-defined fields may be added to the
3558 source package control file. Such fields will be
3559 ignored, and not copied to (for example) binary or
3560 source package control files or upload control files.
3564 If you wish to add additional unsupported fields to
3565 these output files you should use the mechanism
3570 Fields in the main source control information file with
3571 names starting <tt>X</tt>, followed by one or more of
3572 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3573 be copied to the output files. Only the part of the
3574 field name after the hyphen will be used in the output
3575 file. Where the letter <tt>B</tt> is used the field
3576 will appear in binary package control files, where the
3577 letter <tt>S</tt> is used in source package control
3578 files and where <tt>C</tt> is used in upload control
3579 (<tt>.changes</tt>) files.
3583 For example, if the main source information control file
3586 XBS-Comment: I stand between the candle and the star.
3588 then the binary and source package control files will contain the
3591 Comment: I stand between the candle and the star.
3600 <chapt id="maintainerscripts">
3601 <heading>Package maintainer scripts and installation procedure</heading>
3604 <heading>Introduction to package maintainer scripts</heading>
3607 It is possible to supply scripts as part of a package which
3608 the package management system will run for you when your
3609 package is installed, upgraded or removed.
3613 These scripts are the files <prgn>preinst</prgn>,
3614 <prgn>postinst</prgn>, <prgn>prerm</prgn> and
3615 <prgn>postrm</prgn> in the control area of the package.
3616 They must be proper executable files; if they are scripts
3617 (which is recommended), they must start with the usual
3618 <tt>#!</tt> convention. They should be readable and
3619 executable by anyone, and must not be world-writable.
3623 The package management system looks at the exit status from
3624 these scripts. It is important that they exit with a
3625 non-zero status if there is an error, so that the package
3626 management system can stop its processing. For shell
3627 scripts this means that you <em>almost always</em> need to
3628 use <tt>set -e</tt> (this is usually true when writing shell
3629 scripts, in fact). It is also important, of course, that
3630 they exit with a zero status if everything went well.
3634 Additionally, packages interacting with users using
3635 <tt>debconf</tt> in the <prgn>postinst</prgn> script should
3636 install a <prgn>config</prgn> script in the control area,
3637 see <ref id="maintscriptprompt"> for details.
3641 When a package is upgraded a combination of the scripts from
3642 the old and new packages is called during the upgrade
3643 procedure. If your scripts are going to be at all
3644 complicated you need to be aware of this, and may need to
3645 check the arguments to your scripts.
3649 Broadly speaking the <prgn>preinst</prgn> is called before
3650 (a particular version of) a package is unpacked, and the
3651 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3652 before (a version of) a package is removed and the
3653 <prgn>postrm</prgn> afterwards.
3657 Programs called from maintainer scripts should not normally
3658 have a path prepended to them. Before installation is
3659 started, the package management system checks to see if the
3660 programs <prgn>ldconfig</prgn>,
3661 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3662 and <prgn>update-rc.d</prgn> can be found via the
3663 <tt>PATH</tt> environment variable. Those programs, and any
3664 other program that one would expect to be in the
3665 <tt>PATH</tt>, should thus be invoked without an absolute
3666 pathname. Maintainer scripts should also not reset the
3667 <tt>PATH</tt>, though they might choose to modify it by
3668 prepending or appending package-specific directories. These
3669 considerations really apply to all shell scripts.</p>
3672 <sect id="idempotency">
3673 <heading>Maintainer scripts idempotency</heading>
3676 It is necessary for the error recovery procedures that the
3677 scripts be idempotent. This means that if it is run
3678 successfully, and then it is called again, it doesn't bomb
3679 out or cause any harm, but just ensures that everything is
3680 the way it ought to be. If the first call failed, or
3681 aborted half way through for some reason, the second call
3682 should merely do the things that were left undone the first
3683 time, if any, and exit with a success status if everything
3685 This is so that if an error occurs, the user interrupts
3686 <prgn>dpkg</prgn> or some other unforeseen circumstance
3687 happens you don't leave the user with a badly-broken
3688 package when <prgn>dpkg</prgn> attempts to repeat the
3694 <sect id="controllingterminal">
3695 <heading>Controlling terminal for maintainer scripts</heading>
3698 Maintainer scripts are not guaranteed to run with a controlling
3699 terminal and may not be able to interact with the user. They
3700 must be able to fall back to noninteractive behavior if no
3701 controlling terminal is available. Maintainer scripts that
3702 prompt via a program conforming to the Debian Configuration
3703 Management Specification (see <ref id="maintscriptprompt">) may
3704 assume that program will handle falling back to noninteractive
3709 For high-priority prompts without a reasonable default answer,
3710 maintainer scripts may abort if there is no controlling
3711 terminal. However, this situation should be avoided if at all
3712 possible, since it prevents automated or unattended installs.
3713 In most cases, users will consider this to be a bug in the
3718 <sect id="exitstatus">
3719 <heading>Exit status</heading>
3722 Each script must return a zero exit status for
3723 success, or a nonzero one for failure, since the package
3724 management system looks for the exit status of these scripts
3725 and determines what action to take next based on that datum.
3729 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3734 <list compact="compact">
3736 <var>new-preinst</var> <tt>install</tt>
3739 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3742 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3745 <var>old-preinst</var> <tt>abort-upgrade</tt>
3746 <var>new-version</var>
3751 <list compact="compact">
3753 <var>postinst</var> <tt>configure</tt>
3754 <var>most-recently-configured-version</var>
3757 <var>old-postinst</var> <tt>abort-upgrade</tt>
3758 <var>new-version</var>
3761 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3762 <tt>in-favour</tt> <var>package</var>
3763 <var>new-version</var>
3766 <var>postinst</var> <tt>abort-remove</tt>
3769 <var>deconfigured's-postinst</var>
3770 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3771 <var>failed-install-package</var> <var>version</var>
3772 [<tt>removing</tt> <var>conflicting-package</var>
3778 <list compact="compact">
3780 <var>prerm</var> <tt>remove</tt>
3783 <var>old-prerm</var> <tt>upgrade</tt>
3784 <var>new-version</var>
3787 <var>new-prerm</var> <tt>failed-upgrade</tt>
3788 <var>old-version</var>
3791 <var>conflictor's-prerm</var> <tt>remove</tt>
3792 <tt>in-favour</tt> <var>package</var>
3793 <var>new-version</var>
3796 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3797 <tt>in-favour</tt> <var>package-being-installed</var>
3798 <var>version</var> [<tt>removing</tt>
3799 <var>conflicting-package</var>
3805 <list compact="compact">
3807 <var>postrm</var> <tt>remove</tt>
3810 <var>postrm</var> <tt>purge</tt>
3813 <var>old-postrm</var> <tt>upgrade</tt>
3814 <var>new-version</var>
3817 <var>new-postrm</var> <tt>failed-upgrade</tt>
3818 <var>old-version</var>
3821 <var>new-postrm</var> <tt>abort-install</tt>
3824 <var>new-postrm</var> <tt>abort-install</tt>
3825 <var>old-version</var>
3828 <var>new-postrm</var> <tt>abort-upgrade</tt>
3829 <var>old-version</var>
3832 <var>disappearer's-postrm</var> <tt>disappear</tt>
3833 <var>overwriter</var>
3834 <var>overwriter-version</var>
3840 <sect id="unpackphase">
3841 <heading>Details of unpack phase of installation or upgrade</heading>
3844 The procedure on installation/upgrade/overwrite/disappear
3845 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3846 stage of <tt>dpkg --install</tt>) is as follows. In each
3847 case, if a major error occurs (unless listed below) the
3848 actions are, in general, run backwards - this means that the
3849 maintainer scripts are run with different arguments in
3850 reverse order. These are the "error unwind" calls listed
3857 If a version of the package is already installed, call
3858 <example compact="compact">
3859 <var>old-prerm</var> upgrade <var>new-version</var>
3863 If the script runs but exits with a non-zero
3864 exit status, <prgn>dpkg</prgn> will attempt:
3865 <example compact="compact">
3866 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3868 If this works, the upgrade continues. If this
3869 does not work, the error unwind:
3870 <example compact="compact">
3871 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3873 If this works, then the old-version is
3874 "Installed", if not, the old version is in a
3875 "Half-Configured" state.
3881 If a "conflicting" package is being removed at the same time,
3882 or if any package will be broken (due to <tt>Breaks</tt>):
3885 If <tt>--auto-deconfigure</tt> is
3886 specified, call, for each package to be deconfigured
3887 due to <tt>Breaks</tt>:
3888 <example compact="compact">
3889 <var>deconfigured's-prerm</var> deconfigure \
3890 in-favour <var>package-being-installed</var> <var>version</var>
3893 <example compact="compact">
3894 <var>deconfigured's-postinst</var> abort-deconfigure \
3895 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3897 The deconfigured packages are marked as
3898 requiring configuration, so that if
3899 <tt>--install</tt> is used they will be
3900 configured again if possible.
3903 If any packages depended on a conflicting
3904 package being removed and <tt>--auto-deconfigure</tt> is
3905 specified, call, for each such package:
3906 <example compact="compact">
3907 <var>deconfigured's-prerm</var> deconfigure \
3908 in-favour <var>package-being-installed</var> <var>version</var> \
3909 removing <var>conflicting-package</var> <var>version</var>
3912 <example compact="compact">
3913 <var>deconfigured's-postinst</var> abort-deconfigure \
3914 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3915 removing <var>conflicting-package</var> <var>version</var>
3917 The deconfigured packages are marked as
3918 requiring configuration, so that if
3919 <tt>--install</tt> is used they will be
3920 configured again if possible.
3923 To prepare for removal of each conflicting package, call:
3924 <example compact="compact">
3925 <var>conflictor's-prerm</var> remove \
3926 in-favour <var>package</var> <var>new-version</var>
3929 <example compact="compact">
3930 <var>conflictor's-postinst</var> abort-remove \
3931 in-favour <var>package</var> <var>new-version</var>
3940 If the package is being upgraded, call:
3941 <example compact="compact">
3942 <var>new-preinst</var> upgrade <var>old-version</var>
3944 If this fails, we call:
3946 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3953 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3955 is called. If this works, then the old version
3956 is in an "Installed" state, or else it is left
3957 in an "Unpacked" state.
3962 If it fails, then the old version is left
3963 in an "Half-Installed" state.
3970 Otherwise, if the package had some configuration
3971 files from a previous version installed (i.e., it
3972 is in the "configuration files only" state):
3973 <example compact="compact">
3974 <var>new-preinst</var> install <var>old-version</var>
3978 <var>new-postrm</var> abort-install <var>old-version</var>
3980 If this fails, the package is left in a
3981 "Half-Installed" state, which requires a
3982 reinstall. If it works, the packages is left in
3983 a "Config-Files" state.
3986 Otherwise (i.e., the package was completely purged):
3987 <example compact="compact">
3988 <var>new-preinst</var> install
3991 <example compact="compact">
3992 <var>new-postrm</var> abort-install
3994 If the error-unwind fails, the package is in a
3995 "Half-Installed" phase, and requires a
3996 reinstall. If the error unwind works, the
3997 package is in a not installed state.
4004 The new package's files are unpacked, overwriting any
4005 that may be on the system already, for example any
4006 from the old version of the same package or from
4007 another package. Backups of the old files are kept
4008 temporarily, and if anything goes wrong the package
4009 management system will attempt to put them back as
4010 part of the error unwind.
4014 It is an error for a package to contain files which
4015 are on the system in another package, unless
4016 <tt>Replaces</tt> is used (see <ref id="replaces">).
4018 The following paragraph is not currently the case:
4019 Currently the <tt>- - force-overwrite</tt> flag is
4020 enabled, downgrading it to a warning, but this may not
4026 It is a more serious error for a package to contain a
4027 plain file or other kind of non-directory where another
4028 package has a directory (again, unless
4029 <tt>Replaces</tt> is used). This error can be
4030 overridden if desired using
4031 <tt>--force-overwrite-dir</tt>, but this is not
4036 Packages which overwrite each other's files produce
4037 behavior which, though deterministic, is hard for the
4038 system administrator to understand. It can easily
4039 lead to "missing" programs if, for example, a package
4040 is unpacked which overwrites a file from another
4041 package, and is then removed again.<footnote>
4042 Part of the problem is due to what is arguably a
4043 bug in <prgn>dpkg</prgn>.
4048 A directory will never be replaced by a symbolic link
4049 to a directory or vice versa; instead, the existing
4050 state (symlink or not) will be left alone and
4051 <prgn>dpkg</prgn> will follow the symlink if there is
4060 If the package is being upgraded, call
4061 <example compact="compact">
4062 <var>old-postrm</var> upgrade <var>new-version</var>
4066 If this fails, <prgn>dpkg</prgn> will attempt:
4067 <example compact="compact">
4068 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4070 If this works, installation continues. If not,
4072 <example compact="compact">
4073 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4075 If this fails, the old version is left in a
4076 "Half-Installed" state. If it works, dpkg now
4078 <example compact="compact">
4079 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4081 If this fails, the old version is left in a
4082 "Half-Installed" state. If it works, dpkg now
4084 <example compact="compact">
4085 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4087 If this fails, the old version is in an
4094 This is the point of no return - if
4095 <prgn>dpkg</prgn> gets this far, it won't back off
4096 past this point if an error occurs. This will
4097 leave the package in a fairly bad state, which
4098 will require a successful re-installation to clear
4099 up, but it's when <prgn>dpkg</prgn> starts doing
4100 things that are irreversible.
4105 Any files which were in the old version of the package
4106 but not in the new are removed.
4110 The new file list replaces the old.
4114 The new maintainer scripts replace the old.
4118 Any packages all of whose files have been overwritten
4119 during the installation, and which aren't required for
4120 dependencies, are considered to have been removed.
4121 For each such package
4124 <prgn>dpkg</prgn> calls:
4125 <example compact="compact">
4126 <var>disappearer's-postrm</var> disappear \
4127 <var>overwriter</var> <var>overwriter-version</var>
4131 The package's maintainer scripts are removed.
4134 It is noted in the status database as being in a
4135 sane state, namely not installed (any conffiles
4136 it may have are ignored, rather than being
4137 removed by <prgn>dpkg</prgn>). Note that
4138 disappearing packages do not have their prerm
4139 called, because <prgn>dpkg</prgn> doesn't know
4140 in advance that the package is going to
4147 Any files in the package we're unpacking that are also
4148 listed in the file lists of other packages are removed
4149 from those lists. (This will lobotomize the file list
4150 of the "conflicting" package if there is one.)
4154 The backup files made during installation, above, are
4160 The new package's status is now sane, and recorded as
4165 Here is another point of no return - if the
4166 conflicting package's removal fails we do not unwind
4167 the rest of the installation; the conflicting package
4168 is left in a half-removed limbo.
4173 If there was a conflicting package we go and do the
4174 removal actions (described below), starting with the
4175 removal of the conflicting package's files (any that
4176 are also in the package being unpacked have already
4177 been removed from the conflicting package's file list,
4178 and so do not get removed now).
4184 <sect id="configdetails"><heading>Details of configuration</heading>
4187 When we configure a package (this happens with <tt>dpkg
4188 --install</tt> and <tt>dpkg --configure</tt>), we first
4189 update any <tt>conffile</tt>s and then call:
4190 <example compact="compact">
4191 <var>postinst</var> configure <var>most-recently-configured-version</var>
4196 No attempt is made to unwind after errors during
4197 configuration. If the configuration fails, the package is in
4198 a "Failed Config" state, and an error message is generated.
4202 If there is no most recently configured version
4203 <prgn>dpkg</prgn> will pass a null argument.
4206 Historical note: Truly ancient (pre-1997) versions of
4207 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4208 (including the angle brackets) in this case. Even older
4209 ones did not pass a second argument at all, under any
4210 circumstance. Note that upgrades using such an old dpkg
4211 version are unlikely to work for other reasons, even if
4212 this old argument behavior is handled by your postinst script.
4218 <sect id="removedetails"><heading>Details of removal and/or
4219 configuration purging</heading>
4225 <example compact="compact">
4226 <var>prerm</var> remove
4230 If prerm fails during replacement due to conflict
4232 <var>conflictor's-postinst</var> abort-remove \
4233 in-favour <var>package</var> <var>new-version</var>
4237 <var>postinst</var> abort-remove
4241 If this fails, the package is in a "Half-Configured"
4242 state, or else it remains "Installed".
4246 The package's files are removed (except <tt>conffile</tt>s).
4249 <example compact="compact">
4250 <var>postrm</var> remove
4254 If it fails, there's no error unwind, and the package is in
4255 an "Half-Installed" state.
4260 All the maintainer scripts except the <prgn>postrm</prgn>
4265 If we aren't purging the package we stop here. Note
4266 that packages which have no <prgn>postrm</prgn> and no
4267 <tt>conffile</tt>s are automatically purged when
4268 removed, as there is no difference except for the
4269 <prgn>dpkg</prgn> status.
4273 The <tt>conffile</tt>s and any backup files
4274 (<tt>~</tt>-files, <tt>#*#</tt> files,
4275 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4280 <example compact="compact">
4281 <var>postrm</var> purge
4285 If this fails, the package remains in a "Config-Files"
4290 The package's file list is removed.
4299 <chapt id="relationships">
4300 <heading>Declaring relationships between packages</heading>
4302 <sect id="depsyntax">
4303 <heading>Syntax of relationship fields</heading>
4306 These fields all have a uniform syntax. They are a list of
4307 package names separated by commas.
4311 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4312 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4313 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4314 control file fields of the package, which declare
4315 dependencies on other packages, the package names listed may
4316 also include lists of alternative package names, separated
4317 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4318 if any one of the alternative packages is installed, that
4319 part of the dependency is considered to be satisfied.
4323 All of the fields except for <tt>Provides</tt> may restrict
4324 their applicability to particular versions of each named
4325 package. This is done in parentheses after each individual
4326 package name; the parentheses should contain a relation from
4327 the list below followed by a version number, in the format
4328 described in <ref id="f-Version">.
4332 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4333 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4334 strictly earlier, earlier or equal, exactly equal, later or
4335 equal and strictly later, respectively. The deprecated
4336 forms <tt><</tt> and <tt>></tt> were used to mean
4337 earlier/later or equal, rather than strictly earlier/later,
4338 so they should not appear in new packages (though
4339 <prgn>dpkg</prgn> still supports them).
4343 Whitespace may appear at any point in the version
4344 specification subject to the rules in <ref
4345 id="controlsyntax">, and must appear where it's necessary to
4346 disambiguate; it is not otherwise significant. All of the
4347 relationship fields may span multiple lines. For
4348 consistency and in case of future changes to
4349 <prgn>dpkg</prgn> it is recommended that a single space be
4350 used after a version relationship and before a version
4351 number; it is also conventional to put a single space after
4352 each comma, on either side of each vertical bar, and before
4353 each open parenthesis. When wrapping a relationship field, it
4354 is conventional to do so after a comma and before the space
4355 following that comma.
4359 For example, a list of dependencies might appear as:
4360 <example compact="compact">
4363 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4368 Relationships may be restricted to a certain set of
4369 architectures. This is indicated in brackets after each
4370 individual package name and the optional version specification.
4371 The brackets enclose a list of Debian architecture names
4372 separated by whitespace. Exclamation marks may be prepended to
4373 each of the names. (It is not permitted for some names to be
4374 prepended with exclamation marks while others aren't.)
4378 For build relationship fields
4379 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4380 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>), if
4381 the current Debian host architecture is not in this list and
4382 there are no exclamation marks in the list, or it is in the list
4383 with a prepended exclamation mark, the package name and the
4384 associated version specification are ignored completely for the
4385 purposes of defining the relationships.
4390 <example compact="compact">
4392 Build-Depends-Indep: texinfo
4393 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4394 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4396 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4397 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4398 <tt>gnumach-dev</tt> only on hurd-i386.
4402 For binary relationship fields, the architecture restriction
4403 syntax is only supported in the source package control
4404 file <file>debian/control</file>. When the corresponding binary
4405 package control file is generated, the relationship will either
4406 be omitted or included without the architecture restriction
4407 based on the architecture of the binary package. This means
4408 that architecture restrictions must not be used in binary
4409 relationship fields for architecture-independent packages
4410 (<tt>Architecture: all</tt>).
4415 <example compact="compact">
4416 Depends: foo [i386], bar [amd64]
4418 becomes <tt>Depends: foo</tt> when the package is built on
4419 the <tt>i386</tt> architecture, <tt>Depends: bar</tt> when the
4420 package is built on the <tt>amd64</tt> architecture, and omitted
4421 entirely in binary packages built on all other architectures.
4425 If the architecture-restricted dependency is part of a set of
4426 alternatives using <tt>|</tt>, that alternative is ignored
4427 completely on architectures that do not match the restriction.
4429 <example compact="compact">
4430 Build-Depends: foo [!i386] | bar [!amd64]
4432 is equivalent to <tt>bar</tt> on the i386 architecture, to
4433 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4434 bar</tt> on all other architectures.
4438 Relationships may also be restricted to a certain set of
4439 architectures using architecture wildcards. The syntax for
4440 declaring such restrictions is the same as declaring
4441 restrictions using a certain set of architectures without
4442 architecture wildcards. For example:
4443 <example compact="compact">
4444 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4446 is equivalent to <tt>foo</tt> on architectures using the Linux
4447 kernel and any cpu, <tt>bar</tt> on architectures using any
4448 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4449 using a kernel other than Linux.
4453 Note that the binary package relationship fields such as
4454 <tt>Depends</tt> appear in one of the binary package
4455 sections of the control file, whereas the build-time
4456 relationships such as <tt>Build-Depends</tt> appear in the
4457 source package section of the control file (which is the
4462 <sect id="binarydeps">
4463 <heading>Binary Dependencies - <tt>Depends</tt>,
4464 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4465 <tt>Pre-Depends</tt>
4469 Packages can declare in their control file that they have
4470 certain relationships to other packages - for example, that
4471 they may not be installed at the same time as certain other
4472 packages, and/or that they depend on the presence of others.
4476 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4477 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4478 <tt>Breaks</tt> and <tt>Conflicts</tt> control file fields.
4479 <tt>Breaks</tt> is described in <ref id="breaks">, and
4480 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4481 rest are described below.
4485 These seven fields are used to declare a dependency
4486 relationship by one package on another. Except for
4487 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4488 depending (binary) package's control file.
4489 (<tt>Enhances</tt> appears in the recommending package's
4490 control file, and <tt>Breaks</tt> appears in the version of
4491 depended-on package which causes the named package to
4496 A <tt>Depends</tt> field takes effect <em>only</em> when a
4497 package is to be configured. It does not prevent a package
4498 being on the system in an unconfigured state while its
4499 dependencies are unsatisfied, and it is possible to replace
4500 a package whose dependencies are satisfied and which is
4501 properly installed with a different version whose
4502 dependencies are not and cannot be satisfied; when this is
4503 done the depending package will be left unconfigured (since
4504 attempts to configure it will give errors) and will not
4505 function properly. If it is necessary, a
4506 <tt>Pre-Depends</tt> field can be used, which has a partial
4507 effect even when a package is being unpacked, as explained
4508 in detail below. (The other three dependency fields,
4509 <tt>Recommends</tt>, <tt>Suggests</tt> and
4510 <tt>Enhances</tt>, are only used by the various front-ends
4511 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4512 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4516 Since <tt>Depends</tt> only places requirements on the
4517 configuration step, packages in an installation run are usually
4518 all unpacked first and all configured later. This makes it
4519 easier to satisfy all dependencies when multiple packages are
4524 If there is a circular dependency among packages being installed
4525 or removed, installation or removal order honoring the
4526 dependency order is impossible, requiring the dependency loop be
4527 broken at some point and the dependency requirements violated
4528 for at least one package. Packages involved in circular
4529 dependencies may not be able to rely on their dependencies being
4530 configured when being configured or removed depending on which
4531 side of the break of the circular dependency loop they happen to
4532 be on. If one of the packages in the loop has no
4533 <prgn>postinst</prgn> script, then the cycle will be broken at
4534 that package; this ensures that all <prgn>postinst</prgn>
4535 scripts are run with their dependencies properly configured if
4536 this is possible. Otherwise the breaking point is arbitrary.
4537 Packages should therefore avoid circular dependencies where
4538 possible, particularly if they have <prgn>postinst</prgn>
4543 The meaning of the five dependency fields is as follows:
4545 <tag><tt>Depends</tt></tag>
4548 This declares an absolute dependency. A package will
4549 not be configured unless all of the packages listed in
4550 its <tt>Depends</tt> field have been correctly
4551 configured (unless there is a circular dependency as
4556 The <tt>Depends</tt> field should be used if the
4557 depended-on package is required for the depending
4558 package to provide a significant amount of
4563 The <tt>Depends</tt> field should also be used if the
4564 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4565 <prgn>postrm</prgn> scripts require the package to be
4566 present in order to run. (If both packages are involved
4567 in a dependency loop, this might not work as expected; see
4568 the explanation a few paragraphs back.) In the case of
4569 <prgn>postinst</prgn> and <prgn>postrm</prgn>, the
4570 depended-on packages will be unpacked and configured
4571 first. (Note, however, that the <prgn>postrm</prgn>
4572 cannot rely on any non-essential packages to be present
4573 during the <tt>purge</tt> phase.) In the case of
4574 <prgn>prerm</prgn>, the depended-on package will at least
4575 be unpacked (it might be configured too, but you can't
4576 rely on this unless you use <tt>Pre-Depends</tt>).
4579 <tag><tt>Recommends</tt></tag>
4582 This declares a strong, but not absolute, dependency.
4586 The <tt>Recommends</tt> field should list packages
4587 that would be found together with this one in all but
4588 unusual installations.
4592 <tag><tt>Suggests</tt></tag>
4594 This is used to declare that one package may be more
4595 useful with one or more others. Using this field
4596 tells the packaging system and the user that the
4597 listed packages are related to this one and can
4598 perhaps enhance its usefulness, but that installing
4599 this one without them is perfectly reasonable.
4602 <tag><tt>Enhances</tt></tag>
4604 This field is similar to Suggests but works in the
4605 opposite direction. It is used to declare that a
4606 package can enhance the functionality of another
4610 <tag><tt>Pre-Depends</tt></tag>
4613 This field is like <tt>Depends</tt>, except that it
4614 also forces <prgn>dpkg</prgn> to complete installation
4615 of the packages named before even starting the
4616 installation of the package which declares the
4617 pre-dependency, as follows:
4621 When a package declaring a pre-dependency is about to
4622 be <em>unpacked</em> the pre-dependency can be
4623 satisfied if the depended-on package is either fully
4624 configured, <em>or even if</em> the depended-on
4625 package(s) are only unpacked or in the "Half-Configured"
4626 state, provided that they have been configured
4627 correctly at some point in the past (and not removed
4628 or partially removed since). In this case, both the
4629 previously-configured and currently unpacked or
4630 "Half-Configured" versions must satisfy any version
4631 clause in the <tt>Pre-Depends</tt> field.
4635 When the package declaring a pre-dependency is about
4636 to be <em>configured</em>, the pre-dependency will be
4637 treated as a normal <tt>Depends</tt>, that is, it will
4638 be considered satisfied only if the depended-on
4639 package has been correctly configured. However, unlike
4640 with <tt>Depends</tt>, <tt>Pre-Depends</tt> does not
4641 permit circular dependencies to be broken. If a circular
4642 dependency is encountered while attempting to honor
4643 <tt>Pre-Depends</tt>, the installation will be aborted.
4647 <tt>Pre-Depends</tt> are also required if the
4648 <prgn>preinst</prgn> script depends on the named package.
4649 It is best to avoid this situation if possible.
4653 <tt>Pre-Depends</tt> should be used sparingly,
4654 preferably only by packages whose premature upgrade or
4655 installation would hamper the ability of the system to
4656 continue with any upgrade that might be in progress.
4663 When selecting which level of dependency to use you should
4664 consider how important the depended-on package is to the
4665 functionality of the one declaring the dependency. Some
4666 packages are composed of components of varying degrees of
4667 importance. Such a package should list using
4668 <tt>Depends</tt> the package(s) which are required by the
4669 more important components. The other components'
4670 requirements may be mentioned as Suggestions or
4671 Recommendations, as appropriate to the components' relative
4677 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4680 When one binary package declares that it breaks another,
4681 <prgn>dpkg</prgn> will refuse to allow the package which
4682 declares <tt>Breaks</tt> be unpacked unless the broken
4683 package is deconfigured first, and it will refuse to
4684 allow the broken package to be reconfigured.
4688 A package will not be regarded as causing breakage merely
4689 because its configuration files are still installed; it must
4690 be at least "Half-Installed".
4694 A special exception is made for packages which declare that
4695 they break their own package name or a virtual package which
4696 they provide (see below): this does not count as a real
4701 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4702 version clause; such a <tt>Breaks</tt> is introduced in the
4703 version of an (implicit or explicit) dependency which violates
4704 an assumption or reveals a bug in earlier versions of the broken
4705 package, or which takes over a file from earlier versions of the
4706 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
4707 will inform higher-level package management tools that the
4708 broken package must be upgraded before the new one.
4712 If the breaking package also overwrites some files from the
4713 older package, it should use <tt>Replaces</tt> to ensure this
4714 goes smoothly. See <ref id="replaces"> for a full discussion
4715 of taking over files from other packages, including how to
4716 use <tt>Breaks</tt> in those cases.
4720 Many of the cases where <tt>Breaks</tt> should be used were
4721 previously handled with <tt>Conflicts</tt>
4722 because <tt>Breaks</tt> did not yet exist.
4723 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
4724 See <ref id="conflicts"> for more information about the
4729 <sect id="conflicts">
4730 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4733 When one binary package declares a conflict with another
4734 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4735 refuse to allow them to be unpacked on the system at the
4736 same time. This is a stronger restriction than <tt>Breaks</tt>,
4737 which just prevents both packages from being configured at the
4738 same time. Conflicting packages cannot be unpacked on the
4739 system at the same time.
4743 If one package is to be unpacked, the other must be removed
4744 first. If the package being unpacked is marked as replacing
4745 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
4746 normally be used in this case) the one on the system, or the one
4747 on the system is marked as deselected, or both packages are
4748 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
4749 automatically remove the package which is causing the conflict.
4750 Otherwise, it will halt the installation of the new package with
4751 an error. This mechanism is specifically designed to produce an
4752 error when the installed package is <tt>Essential</tt>, but the
4757 A package will not cause a conflict merely because its
4758 configuration files are still installed; it must be at least
4763 A special exception is made for packages which declare a
4764 conflict with their own package name, or with a virtual
4765 package which they provide (see below): this does not
4766 prevent their installation, and allows a package to conflict
4767 with others providing a replacement for it. You use this
4768 feature when you want the package in question to be the only
4769 package providing some feature.
4773 Normally, <tt>Breaks</tt> should be used instead
4774 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
4775 stronger restriction on the ordering of package installation or
4776 upgrade and can make it more difficult for the package manager
4777 to find a correct solution to an upgrade or installation
4778 problem. <tt>Breaks</tt> should be used
4780 <item>when moving a file from one package to another (see
4781 <ref id="replaces">),</item>
4782 <item>when splitting a package (a special case of the previous
4784 <item>when the breaking package exposes a bug in or interacts
4785 badly with particular versions of the broken
4788 <tt>Conflicts</tt> should be used
4790 <item>when two packages provide the same file and will
4791 continue to do so,</item>
4792 <item>in conjunction with <tt>Provides</tt> when only one
4793 package providing a given virtual facility may be installed
4794 at a time (see <ref id="virtual">),</item>
4795 <item>in other cases where one must prevent simultaneous
4796 installation of two packages for reasons that are ongoing
4797 (not fixed in a later version of one of the packages) or
4798 that must prevent both packages from being unpacked at the
4799 same time, not just configured.</item>
4801 Be aware that adding <tt>Conflicts</tt> is normally not the best
4802 solution when two packages provide the same files. Depending on
4803 the reason for that conflict, using alternatives or renaming the
4804 files is often a better approach. See, for
4805 example, <ref id="binaries">.
4809 Neither <tt>Breaks</tt> nor <tt>Conflicts</tt> should be used
4810 unless two packages cannot be installed at the same time or
4811 installing them both causes one of them to be broken or
4812 unusable. Having similar functionality or performing the same
4813 tasks as another package is not sufficient reason to
4814 declare <tt>Breaks</tt> or <tt>Conflicts</tt> with that package.
4818 A <tt>Conflicts</tt> entry may have an "earlier than" version
4819 clause if the reason for the conflict is corrected in a later
4820 version of one of the packages. However, normally the presence
4821 of an "earlier than" version clause is a sign
4822 that <tt>Breaks</tt> should have been used instead. An "earlier
4823 than" version clause in <tt>Conflicts</tt>
4824 prevents <prgn>dpkg</prgn> from upgrading or installing the
4825 package which declares such a conflict until the upgrade or
4826 removal of the conflicted-with package has been completed, which
4827 is a strong restriction.
4831 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4835 As well as the names of actual ("concrete") packages, the
4836 package relationship fields <tt>Depends</tt>,
4837 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4838 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4839 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4840 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4841 may mention "virtual packages".
4845 A <em>virtual package</em> is one which appears in the
4846 <tt>Provides</tt> control file field of another package.
4847 The effect is as if the package(s) which provide a
4848 particular virtual package name had been listed by name
4849 everywhere the virtual package name appears. (See also <ref
4854 If there are both concrete and virtual packages of the same
4855 name, then the dependency may be satisfied (or the conflict
4856 caused) by either the concrete package with the name in
4857 question or any other concrete package which provides the
4858 virtual package with the name in question. This is so that,
4859 for example, supposing we have
4860 <example compact="compact">
4863 </example> and someone else releases an enhanced version of
4864 the <tt>bar</tt> package they can say:
4865 <example compact="compact">
4869 and the <tt>bar-plus</tt> package will now also satisfy the
4870 dependency for the <tt>foo</tt> package.
4874 If a relationship field has a version number attached, only real
4875 packages will be considered to see whether the relationship is
4876 satisfied (or the prohibition violated, for a conflict or
4877 breakage). In other words, if a version number is specified,
4878 this is a request to ignore all <tt>Provides</tt> for that
4879 package name and consider only real packages. The package
4880 manager will assume that a package providing that virtual
4881 package is not of the "right" version. A <tt>Provides</tt>
4882 field may not contain version numbers, and the version number of
4883 the concrete package which provides a particular virtual package
4884 will not be considered when considering a dependency on or
4885 conflict with the virtual package name.<footnote>
4886 It is possible that a future release of <prgn>dpkg</prgn> may
4887 add the ability to specify a version number for each virtual
4888 package it provides. This feature is not yet present,
4889 however, and is expected to be used only infrequently.
4894 To specify which of a set of real packages should be the default
4895 to satisfy a particular dependency on a virtual package, list
4896 the real package as an alternative before the virtual one.
4900 If the virtual package represents a facility that can only be
4901 provided by one real package at a time, such as
4902 the <package>mail-transport-agent</package> virtual package that
4903 requires installation of a binary that would conflict with all
4904 other providers of that virtual package (see
4905 <ref id="mail-transport-agents">), all packages providing that
4906 virtual package should also declare a conflict with it
4907 using <tt>Conflicts</tt>. This will ensure that at most one
4908 provider of that virtual package is unpacked or installed at a
4913 <sect id="replaces"><heading>Overwriting files and replacing
4914 packages - <tt>Replaces</tt></heading>
4917 Packages can declare in their control file that they should
4918 overwrite files in certain other packages, or completely
4919 replace other packages. The <tt>Replaces</tt> control file
4920 field has these two distinct purposes.
4923 <sect1><heading>Overwriting files in other packages</heading>
4926 It is usually an error for a package to contain files which
4927 are on the system in another package. However, if the
4928 overwriting package declares that it <tt>Replaces</tt> the one
4929 containing the file being overwritten, then <prgn>dpkg</prgn>
4930 will replace the file from the old package with that from the
4931 new. The file will no longer be listed as "owned" by the old
4932 package and will be taken over by the new package.
4933 Normally, <tt>Breaks</tt> should be used in conjunction
4934 with <tt>Replaces</tt>.<footnote>
4935 To see why <tt>Breaks</tt> is normally needed in addition
4936 to <tt>Replaces</tt>, consider the case of a file in the
4937 package <package>foo</package> being taken over by the
4938 package <package>foo-data</package>.
4939 <tt>Replaces</tt> will allow <package>foo-data</package> to
4940 be installed and take over that file. However,
4941 without <tt>Breaks</tt>, nothing
4942 requires <package>foo</package> to be upgraded to a newer
4943 version that knows it does not include that file and instead
4944 depends on <package>foo-data</package>. Nothing would
4945 prevent the new <package>foo-data</package> package from
4946 being installed and then removed, removing the file that it
4947 took over from <package>foo</package>. After that
4948 operation, the package manager would think the system was in
4949 a consistent state, but the <package>foo</package> package
4950 would be missing one of its files.
4955 For example, if a package <package>foo</package> is split
4956 into <package>foo</package> and <package>foo-data</package>
4957 starting at version 1.2-3, <package>foo-data</package> would
4959 <example compact="compact">
4960 Replaces: foo (<< 1.2-3)
4961 Breaks: foo (<< 1.2-3)
4963 in its control file. The new version of the
4964 package <package>foo</package> would normally have the field
4965 <example compact="compact">
4966 Depends: foo-data (>= 1.2-3)
4968 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
4969 the files moved into <package>foo-data</package> are not
4970 required for normal operation).
4974 If a package is completely replaced in this way, so that
4975 <prgn>dpkg</prgn> does not know of any files it still
4976 contains, it is considered to have "disappeared". It will
4977 be marked as not wanted on the system (selected for
4978 removal) and not installed. Any <tt>conffile</tt>s
4979 details noted for the package will be ignored, as they
4980 will have been taken over by the overwriting package. The
4981 package's <prgn>postrm</prgn> script will be run with a
4982 special argument to allow the package to do any final
4983 cleanup required. See <ref id="mscriptsinstact">.
4985 Replaces is a one way relationship. You have to install
4986 the replacing package after the replaced package.
4991 For this usage of <tt>Replaces</tt>, virtual packages (see
4992 <ref id="virtual">) are not considered when looking at a
4993 <tt>Replaces</tt> field. The packages declared as being
4994 replaced must be mentioned by their real names.
4998 This usage of <tt>Replaces</tt> only takes effect when both
4999 packages are at least partially on the system at once. It is
5000 not relevant if the packages conflict unless the conflict has
5005 <sect1><heading>Replacing whole packages, forcing their
5009 Second, <tt>Replaces</tt> allows the packaging system to
5010 resolve which package should be removed when there is a
5011 conflict (see <ref id="conflicts">). This usage only takes
5012 effect when the two packages <em>do</em> conflict, so that the
5013 two usages of this field do not interfere with each other.
5017 In this situation, the package declared as being replaced
5018 can be a virtual package, so for example, all mail
5019 transport agents (MTAs) would have the following fields in
5020 their control files:
5021 <example compact="compact">
5022 Provides: mail-transport-agent
5023 Conflicts: mail-transport-agent
5024 Replaces: mail-transport-agent
5026 ensuring that only one MTA can be unpacked at any one
5027 time. See <ref id="virtual"> for more information about this
5032 <sect id="sourcebinarydeps">
5033 <heading>Relationships between source and binary packages -
5034 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5035 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5039 Source packages that require certain binary packages to be
5040 installed or absent at the time of building the package
5041 can declare relationships to those binary packages.
5045 This is done using the <tt>Build-Depends</tt>,
5046 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5047 <tt>Build-Conflicts-Indep</tt> control file fields.
5051 Build-dependencies on "build-essential" binary packages can be
5052 omitted. Please see <ref id="pkg-relations"> for more information.
5056 The dependencies and conflicts they define must be satisfied
5057 (as defined earlier for binary packages) in order to invoke
5058 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5060 There is no Build-Depends-Arch; this role is essentially
5061 met with Build-Depends. Anyone building the
5062 <tt>build-indep</tt> and <tt>binary-indep</tt> targets is
5063 assumed to be building the whole package, and therefore
5064 installation of all build dependencies is required.
5067 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5068 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5069 not yet know how to check for its existence, and
5070 <tt>binary-arch</tt>. The purpose of the original split
5071 between <tt>Build-Depends</tt> and
5072 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5073 wouldn't need to install extra packages needed only for the
5074 binary-indep targets. But without a build-arch/build-indep
5075 split, this didn't work, since most of the work is done in
5076 the build target, not in the binary target.
5080 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5081 <tt>binary-arch</tt></tag>
5083 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5084 fields must be satisfied when these targets are invoked.
5086 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5087 and <tt>binary-indep</tt></tag>
5089 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5090 <tt>Build-Depends-Indep</tt>, and
5091 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5092 these targets are invoked.
5100 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5103 Packages containing shared libraries must be constructed with
5104 a little care to make sure that the shared library is always
5105 available. This is especially important for packages whose
5106 shared libraries are vitally important, such as the C library
5107 (currently <tt>libc6</tt>).
5111 Packages involving shared libraries should be split up into
5112 several binary packages. This section mostly deals with how
5113 this separation is to be accomplished; rules for files within
5114 the shared library packages are in <ref id="libraries"> instead.
5117 <sect id="sharedlibs-runtime">
5118 <heading>Run-time shared libraries</heading>
5121 The run-time shared library needs to be placed in a package
5122 whose name changes whenever the shared object version
5125 Since it is common place to install several versions of a
5126 package that just provides shared libraries, it is a
5127 good idea that the library package should not
5128 contain any extraneous non-versioned files, unless they
5129 happen to be in versioned directories.</p>
5131 The most common mechanism is to place it in a package
5133 <package><var>libraryname</var><var>soversion</var></package>,
5134 where <file><var>soversion</var></file> is the version number
5135 in the soname of the shared library<footnote>
5136 The soname is the shared object name: it's the thing
5137 that has to match exactly between building an executable
5138 and running it for the dynamic linker to be able run the
5139 program. For example, if the soname of the library is
5140 <file>libfoo.so.6</file>, the library package would be
5141 called <file>libfoo6</file>.
5143 Alternatively, if it would be confusing to directly append
5144 <var>soversion</var> to <var>libraryname</var> (e.g. because
5145 <var>libraryname</var> itself ends in a number), you may use
5146 <package><var>libraryname</var>-<var>soversion</var></package> and
5147 <package><var>libraryname</var>-<var>soversion</var>-dev</package>
5152 If you have several shared libraries built from the same
5153 source tree you may lump them all together into a single
5154 shared library package, provided that you change all of
5155 their sonames at once (so that you don't get filename
5156 clashes if you try to install different versions of the
5157 combined shared libraries package).
5161 The package should install the shared libraries under
5162 their normal names. For example, the <package>libgdbm3</package>
5163 package should install <file>libgdbm.so.3.0.0</file> as
5164 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5165 renamed or re-linked by any <prgn>prerm</prgn> or
5166 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5167 of renaming things safely without affecting running programs,
5168 and attempts to interfere with this are likely to lead to
5173 Shared libraries should not be installed executable, since
5174 the dynamic linker does not require this and trying to
5175 execute a shared library usually results in a core dump.
5179 The run-time library package should include the symbolic link that
5180 <prgn>ldconfig</prgn> would create for the shared libraries.
5181 For example, the <package>libgdbm3</package> package should include
5182 a symbolic link from <file>/usr/lib/libgdbm.so.3</file> to
5183 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5184 linker (for example <prgn>ld.so</prgn> or
5185 <prgn>ld-linux.so.*</prgn>) can find the library between the
5186 time that <prgn>dpkg</prgn> installs it and the time that
5187 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5189 The package management system requires the library to be
5190 placed before the symbolic link pointing to it in the
5191 <file>.deb</file> file. This is so that when
5192 <prgn>dpkg</prgn> comes to install the symlink
5193 (overwriting the previous symlink pointing at an older
5194 version of the library), the new shared library is already
5195 in place. In the past, this was achieved by creating the
5196 library in the temporary packaging directory before
5197 creating the symlink. Unfortunately, this was not always
5198 effective, since the building of the tar file in the
5199 <file>.deb</file> depended on the behavior of the underlying
5200 file system. Some file systems (such as reiserfs) reorder
5201 the files so that the order of creation is forgotten.
5202 Since version 1.7.0, <prgn>dpkg</prgn>
5203 reorders the files itself as necessary when building a
5204 package. Thus it is no longer important to concern
5205 oneself with the order of file creation.
5209 <sect1 id="ldconfig">
5210 <heading><tt>ldconfig</tt></heading>
5213 Any package installing shared libraries in one of the default
5214 library directories of the dynamic linker (which are currently
5215 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5216 listed in <file>/etc/ld.so.conf</file><footnote>
5218 <list compact="compact">
5219 <item>/usr/local/lib</item>
5220 <item>/usr/lib/libc5-compat</item>
5221 <item>/lib/libc5-compat</item>
5224 must use <prgn>ldconfig</prgn> to update the shared library
5229 The package maintainer scripts must only call
5230 <prgn>ldconfig</prgn> under these circumstances:
5231 <list compact="compact">
5232 <item>When the <prgn>postinst</prgn> script is run with a
5233 first argument of <tt>configure</tt>, the script must call
5234 <prgn>ldconfig</prgn>, and may optionally invoke
5235 <prgn>ldconfig</prgn> at other times.
5237 <item>When the <prgn>postrm</prgn> script is run with a
5238 first argument of <tt>remove</tt>, the script should call
5239 <prgn>ldconfig</prgn>.
5244 During install or upgrade, the preinst is called before
5245 the new files are unpacked, so calling "ldconfig" is
5246 pointless. The preinst of an existing package can also be
5247 called if an upgrade fails. However, this happens during
5248 the critical time when a shared libs may exist on-disk
5249 under a temporary name. Thus, it is dangerous and
5250 forbidden by current policy to call "ldconfig" at this
5255 When a package is installed or upgraded, "postinst
5256 configure" runs after the new files are safely on-disk.
5257 Since it is perfectly safe to invoke ldconfig
5258 unconditionally in a postinst, it is OK for a package to
5259 simply put ldconfig in its postinst without checking the
5260 argument. The postinst can also be called to recover from
5261 a failed upgrade. This happens before any new files are
5262 unpacked, so there is no reason to call "ldconfig" at this
5267 For a package that is being removed, prerm is
5268 called with all the files intact, so calling ldconfig is
5269 useless. The other calls to "prerm" happen in the case of
5270 upgrade at a time when all the files of the old package
5271 are on-disk, so again calling "ldconfig" is pointless.
5275 postrm, on the other hand, is called with the "remove"
5276 argument just after the files are removed, so this is
5277 the proper time to call "ldconfig" to notify the system
5278 of the fact that the shared libraries from the package
5279 are removed. The postrm can be called at several other
5280 times. At the time of "postrm purge", "postrm
5281 abort-install", or "postrm abort-upgrade", calling
5282 "ldconfig" is useless because the shared lib files are
5283 not on-disk. However, when "postrm" is invoked with
5284 arguments "upgrade", "failed-upgrade", or "disappear", a
5285 shared lib may exist on-disk under a temporary filename.
5293 <sect id="sharedlibs-support-files">
5294 <heading>Shared library support files</heading>
5297 If your package contains files whose names do not change with
5298 each change in the library shared object version, you must not
5299 put them in the shared library package. Otherwise, several
5300 versions of the shared library cannot be installed at the same
5301 time without filename clashes, making upgrades and transitions
5302 unnecessarily difficult.
5306 It is recommended that supporting files and run-time support
5307 programs that do not need to be invoked manually by users, but
5308 are nevertheless required for the package to function, be placed
5309 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5310 preferably under <file>/usr/lib/</file><var>package-name</var>.
5311 If the program or file is architecture independent, the
5312 recommendation is for it to be placed in a subdirectory of
5313 <file>/usr/share</file> instead, preferably under
5314 <file>/usr/share/</file><var>package-name</var>. Following the
5315 <var>package-name</var> naming convention ensures that the file
5316 names change when the shared object version changes.
5320 Run-time support programs that use the shared library but are
5321 not required for the library to function or files used by the
5322 shared library that can be used by any version of the shared
5323 library package should instead be put in a separate package.
5324 This package might typically be named
5325 <package><var>libraryname</var>-tools</package>; note the
5326 absence of the <var>soversion</var> in the package name.
5330 Files and support programs only useful when compiling software
5331 against the library should be included in the development
5332 package for the library.<footnote>
5333 For example, a <file><var>package-name</var>-config</file>
5334 script or <package>pkg-config</package> configuration files.
5339 <sect id="sharedlibs-static">
5340 <heading>Static libraries</heading>
5343 The static library (<file><var>libraryname.a</var></file>)
5344 is usually provided in addition to the shared version.
5345 It is placed into the development package (see below).
5349 In some cases, it is acceptable for a library to be
5350 available in static form only; these cases include:
5352 <item>libraries for languages whose shared library support
5353 is immature or unstable</item>
5354 <item>libraries whose interfaces are in flux or under
5355 development (commonly the case when the library's
5356 major version number is zero, or where the ABI breaks
5357 across patchlevels)</item>
5358 <item>libraries which are explicitly intended to be
5359 available only in static form by their upstream
5364 <sect id="sharedlibs-dev">
5365 <heading>Development files</heading>
5368 If there are development files associated with a shared library,
5369 the source package needs to generate a binary development package
5370 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5371 or if you prefer only to support one development version at a
5372 time, <package><var>libraryname</var>-dev</package>. Installing
5373 the development package must result in installation of all the
5374 development files necessary for compiling programs against that
5375 shared library.<footnote>
5376 This wording allows the development files to be split into
5377 several packages, such as a separate architecture-independent
5378 <package><var>libraryname</var>-headers</package>, provided that
5379 the development package depends on all the required additional
5385 In case several development versions of a library exist, you may
5386 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5387 <ref id="conflicts">) to ensure that the user only installs one
5388 development version at a time (as different development versions are
5389 likely to have the same header files in them, which would cause a
5390 filename clash if both were unpacked).
5394 The development package should contain a symlink for the associated
5395 shared library without a version number. For example, the
5396 <package>libgdbm-dev</package> package should include a symlink
5397 from <file>/usr/lib/libgdbm.so</file> to
5398 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5399 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5400 <file>libgdbm.so</file> when compiling dynamically.
5404 <sect id="sharedlibs-intradeps">
5405 <heading>Dependencies between the packages of the same library</heading>
5408 Typically the development version should have an exact
5409 version dependency on the runtime library, to make sure that
5410 compilation and linking happens correctly. The
5411 <tt>${binary:Version}</tt> substitution variable can be
5412 useful for this purpose.
5414 Previously, <tt>${Source-Version}</tt> was used, but its name
5415 was confusing and it has been deprecated since dpkg 1.13.19.
5420 <sect id="sharedlibs-shlibdeps">
5421 <heading>Dependencies between the library and other packages -
5422 the <tt>shlibs</tt> system</heading>
5425 If a package contains a binary or library which links to a
5426 shared library, we must ensure that when the package is
5427 installed on the system, all of the libraries needed are
5428 also installed. This requirement led to the creation of the
5429 <tt>shlibs</tt> system, which is very simple in its design:
5430 any package which <em>provides</em> a shared library also
5431 provides information on the package dependencies required to
5432 ensure the presence of this library, and any package which
5433 <em>uses</em> a shared library uses this information to
5434 determine the dependencies it requires. The files which
5435 contain the mapping from shared libraries to the necessary
5436 dependency information are called <file>shlibs</file> files.
5440 When a package is built which contains any shared libraries, it
5441 must provide a <file>shlibs</file> file for other packages to
5442 use. When a package is built which contains any shared
5443 libraries or compiled binaries, it must run
5444 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5445 on these to determine the libraries used and hence the
5446 dependencies needed by this package.<footnote>
5448 <prgn>dpkg-shlibdeps</prgn> will use a program
5449 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
5450 the libraries directly needed by the binaries or shared
5451 libraries in the package.
5455 We say that a binary <tt>foo</tt> <em>directly</em> uses
5456 a library <tt>libbar</tt> if it is explicitly linked
5457 with that library (that is, the library is listed in the ELF
5458 <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
5459 to the link line when the binary is created). Other
5460 libraries that are needed by <tt>libbar</tt> are linked
5461 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5462 linker will load them automatically when it loads
5463 <tt>libbar</tt>. A package should depend on the libraries
5464 it directly uses, but not the libraries it indirectly uses.
5465 The dependencies for those libraries will automatically pull
5466 in the other libraries.
5470 A good example of where this helps is the following. We
5471 could update <tt>libimlib</tt> with a new version that
5472 supports a new graphics format called dgf (but retaining the
5473 same major version number) and depends on <tt>libdgf</tt>.
5474 If we used <prgn>ldd</prgn> to add dependencies for every
5475 library directly or indirectly linked with a binary, every
5476 package that uses <tt>libimlib</tt> would need to be
5477 recompiled so it would also depend on <tt>libdgf</tt> or it
5478 wouldn't run due to missing symbols. Since dependencies are
5479 only added based on ELF <tt>NEEDED</tt> attribute, packages
5480 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
5481 having the dependency on <tt>libdgf</tt> and so they would
5482 not need rebuilding.
5488 In the following sections, we will first describe where the
5489 various <tt>shlibs</tt> files are to be found, then how to
5490 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5491 file format and how to create them if your package contains a
5496 <heading>The <tt>shlibs</tt> files present on the system</heading>
5499 There are several places where <tt>shlibs</tt> files are
5500 found. The following list gives them in the order in which
5502 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5503 (The first one which gives the required information is used.)
5509 <p><file>debian/shlibs.local</file></p>
5512 This lists overrides for this package. This file should
5513 normally not be used, but may be needed temporarily in
5514 unusual situations to work around bugs in other packages,
5515 or in unusual cases where the normally declared dependency
5516 information in the installed <file>shlibs</file> file for
5517 a library cannot be used. This file overrides information
5518 obtained from any other source.
5523 <p><file>/etc/dpkg/shlibs.override</file></p>
5526 This lists global overrides. This list is normally
5527 empty. It is maintained by the local system
5533 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5536 When packages are being built,
5537 any <file>debian/shlibs</file> files are copied into the
5538 control file area of the temporary build directory and
5539 given the name <file>shlibs</file>. These files give
5540 details of any shared libraries included in the same
5542 An example may help here. Let us say that the source
5543 package <tt>foo</tt> generates two binary
5544 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
5545 When building the binary packages, the two packages are
5546 created in the directories <file>debian/libfoo2</file>
5547 and <file>debian/foo-runtime</file> respectively.
5548 (<file>debian/tmp</file> could be used instead of one of
5549 these.) Since <tt>libfoo2</tt> provides the
5550 <tt>libfoo</tt> shared library, it will require a
5551 <tt>shlibs</tt> file, which will be installed in
5552 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually to
5553 become <file>/var/lib/dpkg/info/libfoo2.shlibs</file>.
5554 When <prgn>dpkg-shlibdeps</prgn> is run on the
5555 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
5557 the <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5558 determine whether <tt>foo-prog</tt>'s library
5559 dependencies are satisfied by any of the libraries
5560 provided by <tt>libfoo2</tt>. For this reason,
5561 <prgn>dpkg-shlibdeps</prgn> must only be run once all of
5562 the individual binary packages' <tt>shlibs</tt> files
5563 have been installed into the build directory.
5569 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5572 These are the <file>shlibs</file> files corresponding to
5573 all of the packages installed on the system, and are
5574 maintained by the relevant package maintainers.
5579 <p><file>/etc/dpkg/shlibs.default</file></p>
5582 This file lists any shared libraries whose packages
5583 have failed to provide correct <file>shlibs</file> files.
5584 It was used when the <file>shlibs</file> setup was first
5585 introduced, but it is now normally empty. It is
5586 maintained by the <tt>dpkg</tt> maintainer.
5594 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5595 <file>shlibs</file> files</heading>
5599 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5600 into your <file>debian/rules</file> file. If your package
5601 contains only compiled binaries and libraries (but no scripts),
5602 you can use a command such as:
5603 <example compact="compact">
5604 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5605 debian/tmp/usr/lib/*
5607 Otherwise, you will need to explicitly list the compiled
5608 binaries and libraries.<footnote>
5609 If you are using <tt>debhelper</tt>, the
5610 <prgn>dh_shlibdeps</prgn> program will do this work for you.
5611 It will also correctly handle multi-binary packages.
5616 This command puts the dependency information into the
5617 <file>debian/substvars</file> file, which is then used by
5618 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5619 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5620 field in the control file for this to work.
5624 If you have multiple binary packages, you will need to call
5625 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5626 compiled libraries or binaries. In such a case, you will
5627 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5628 utilities to specify a different <file>substvars</file> file.
5632 If you are creating a udeb for use in the Debian Installer,
5633 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
5634 should use the dependency line of type <tt>udeb</tt> by
5635 adding the <tt>-tudeb</tt> option<footnote>
5636 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5637 will automatically add this option if it knows it is
5639 </footnote>. If there is no dependency line of
5640 type <tt>udeb</tt> in the <file>shlibs</file>
5641 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the regular
5646 For more details on <prgn>dpkg-shlibdeps</prgn>, please see
5647 <ref id="pkg-dpkg-shlibdeps"> and
5648 <manref name="dpkg-shlibdeps" section="1">.
5653 <heading>The <file>shlibs</file> File Format</heading>
5656 Each <file>shlibs</file> file has the same format. Lines
5657 beginning with <tt>#</tt> are considered to be comments and
5658 are ignored. Each line is of the form:
5659 <example compact="compact">
5660 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5665 We will explain this by reference to the example of the
5666 <tt>zlib1g</tt> package, which (at the time of writing)
5667 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5671 <var>type</var> is an optional element that indicates the type
5672 of package for which the line is valid. The only type currently
5673 in use is <tt>udeb</tt>. The colon and space after the type are
5678 <var>library-name</var> is the name of the shared library,
5679 in this case <tt>libz</tt>. (This must match the name part
5680 of the soname, see below.)
5684 <var>soname-version</var> is the version part of the soname of
5685 the library. The soname is the thing that must exactly match
5686 for the library to be recognized by the dynamic linker, and is
5688 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5689 example, <tt>libz.so.1</tt>.<footnote>
5690 This can be determined using the command
5691 <example compact="compact">
5692 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5695 The version part is the part which comes after
5696 <tt>.so.</tt>, so in our case, it is <tt>1</tt>. The soname may
5697 instead be of the form
5698 <tt><var>name</var>-<var>major-version</var>.so</tt>, such
5699 as <tt>libdb-4.8.so</tt>, in which case the name would
5700 be <tt>libdb</tt> and the version would be <tt>4.8</tt>.
5704 <var>dependencies</var> has the same syntax as a dependency
5705 field in a binary package control file. It should give
5706 details of which packages are required to satisfy a binary
5707 built against the version of the library contained in the
5708 package. See <ref id="depsyntax"> for details.
5712 In our example, if the first version of the <tt>zlib1g</tt>
5713 package which contained a minor number of at least
5714 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5715 <tt>shlibs</tt> entry for this library could say:
5716 <example compact="compact">
5717 libz 1 zlib1g (>= 1:1.1.3)
5719 The version-specific dependency is to avoid warnings from
5720 the dynamic linker about using older shared libraries with
5725 As zlib1g also provides a udeb containing the shared library,
5726 there would also be a second line:
5727 <example compact="compact">
5728 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5734 <heading>Providing a <file>shlibs</file> file</heading>
5737 If your package provides a shared library, you need to create
5738 a <file>shlibs</file> file following the format described above.
5739 It is usual to call this file <file>debian/shlibs</file> (but if
5740 you have multiple binary packages, you might want to call it
5741 <file>debian/shlibs.<var>package</var></file> instead). Then
5742 let <file>debian/rules</file> install it in the control area:
5743 <example compact="compact">
5744 install -m644 debian/shlibs debian/tmp/DEBIAN
5746 or, in the case of a multi-binary package:
5747 <example compact="compact">
5748 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5750 An alternative way of doing this is to create the
5751 <file>shlibs</file> file in the control area directly from
5752 <file>debian/rules</file> without using a <file>debian/shlibs</file>
5753 file at all,<footnote>
5754 This is what <prgn>dh_makeshlibs</prgn> in
5755 the <package>debhelper</package> suite does. If your package
5756 also has a udeb that provides a shared
5757 library, <prgn>dh_makeshlibs</prgn> can automatically generate
5758 the <tt>udeb:</tt> lines if you specify the name of the udeb
5759 with the <tt>--add-udeb</tt> option.
5761 since the <file>debian/shlibs</file> file itself is ignored by
5762 <prgn>dpkg-shlibdeps</prgn>.
5766 As <prgn>dpkg-shlibdeps</prgn> reads the
5767 <file>DEBIAN/shlibs</file> files in all of the binary packages
5768 being built from this source package, all of the
5769 <file>DEBIAN/shlibs</file> files should be installed before
5770 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5778 <chapt id="opersys"><heading>The Operating System</heading>
5781 <heading>File system hierarchy</heading>
5785 <heading>File System Structure</heading>
5788 The location of all installed files and directories must
5789 comply with the Filesystem Hierarchy Standard (FHS),
5790 version 2.3, with the exceptions noted below, and except
5791 where doing so would violate other terms of Debian
5792 Policy. The following exceptions to the FHS apply:
5797 The optional rules related to user specific
5798 configuration files for applications are stored in
5799 the user's home directory are relaxed. It is
5800 recommended that such files start with the
5801 '<tt>.</tt>' character (a "dot file"), and if an
5802 application needs to create more than one dot file
5803 then the preferred placement is in a subdirectory
5804 with a name starting with a '.' character, (a "dot
5805 directory"). In this case it is recommended the
5806 configuration files not start with the '.'
5812 The requirement for amd64 to use <file>/lib64</file>
5813 for 64 bit binaries is removed.
5818 The requirement for object files, internal binaries, and
5819 libraries, including <file>libc.so.*</file>, to be located
5820 directly under <file>/lib{,32}</file> and
5821 <file>/usr/lib{,32}</file> is amended, permitting files
5822 to instead be installed to
5823 <file>/lib/<var>triplet</var></file> and
5824 <file>/usr/lib/<var>triplet</var></file>, where
5825 <tt><var>triplet</var></tt> is the value returned by
5826 <tt>dpkg-architecture -qDEB_HOST_GNU_TYPE</tt> for the
5827 architecture of the package. Packages may <em>not</em>
5828 install files to any <var>triplet</var> path other
5829 than the one matching the architecture of that package;
5830 for instance, an <tt>Architecture: amd64</tt> package
5831 containing 32-bit x86 libraries may not install these
5832 libraries to <file>/usr/lib/i486-linux-gnu</file>.
5834 This is necessary in order to reserve the directories for
5835 use in cross-installation of library packages from other
5836 architectures, as part of the planned deployment of
5841 Applications may also use a single subdirectory under
5842 <file>/usr/lib/<var>triplet</var></file>.
5845 The execution time linker/loader, ld*, must still be made
5846 available in the existing location under /lib or /lib64
5847 since this is part of the ELF ABI for the architecture.
5852 The requirement that
5853 <file>/usr/local/share/man</file> be "synonymous"
5854 with <file>/usr/local/man</file> is relaxed to a
5859 The requirement that windowmanagers with a single
5860 configuration file call it <file>system.*wmrc</file>
5861 is removed, as is the restriction that the window
5862 manager subdirectory be named identically to the
5863 window manager name itself.
5868 The requirement that boot manager configuration
5869 files live in <file>/etc</file>, or at least are
5870 symlinked there, is relaxed to a recommendation.
5875 The following directories in the root filesystem are
5876 additionally allowed: <file>/sys</file> and
5877 <file>/selinux</file>. <footnote>These directories
5878 are used as mount points to mount virtual filesystems
5879 to get access to kernel information.</footnote>
5886 The version of this document referred here can be
5887 found in the <tt>debian-policy</tt> package or on <url
5888 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5889 name="FHS (Debian copy)"> alongside this manual (or, if
5890 you have the <package>debian-policy</package> installed,
5892 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5893 (local copy)">). The
5894 latest version, which may be a more recent version, may
5896 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5897 Specific questions about following the standard may be
5898 asked on the <tt>debian-devel</tt> mailing list, or
5899 referred to the FHS mailing list (see the
5900 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
5906 <heading>Site-specific programs</heading>
5909 As mandated by the FHS, packages must not place any
5910 files in <file>/usr/local</file>, either by putting them in
5911 the file system archive to be unpacked by <prgn>dpkg</prgn>
5912 or by manipulating them in their maintainer scripts.
5916 However, the package may create empty directories below
5917 <file>/usr/local</file> so that the system administrator knows
5918 where to place site-specific files. These are not
5919 directories <em>in</em> <file>/usr/local</file>, but are
5920 children of directories in <file>/usr/local</file>. These
5921 directories (<file>/usr/local/*/dir/</file>)
5922 should be removed on package removal if they are
5927 Note that this applies only to
5928 directories <em>below</em> <file>/usr/local</file>,
5929 not <em>in</em> <file>/usr/local</file>. Packages must
5930 not create sub-directories in the
5931 directory <file>/usr/local</file> itself, except those
5932 listed in FHS, section 4.5. However, you may create
5933 directories below them as you wish. You must not remove
5934 any of the directories listed in 4.5, even if you created
5939 Since <file>/usr/local</file> can be mounted read-only from a
5940 remote server, these directories must be created and
5941 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
5942 maintainer scripts and not be included in the
5943 <file>.deb</file> archive. These scripts must not fail if
5944 either of these operations fail.
5948 For example, the <tt>emacsen-common</tt> package could
5949 contain something like
5950 <example compact="compact">
5951 if [ ! -e /usr/local/share/emacs ]
5953 if mkdir /usr/local/share/emacs 2>/dev/null
5955 chown root:staff /usr/local/share/emacs
5956 chmod 2775 /usr/local/share/emacs
5960 in its <prgn>postinst</prgn> script, and
5961 <example compact="compact">
5962 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
5963 rmdir /usr/local/share/emacs 2>/dev/null || true
5965 in the <prgn>prerm</prgn> script. (Note that this form is
5966 used to ensure that if the script is interrupted, the
5967 directory <file>/usr/local/share/emacs</file> will still be
5972 If you do create a directory in <file>/usr/local</file> for
5973 local additions to a package, you should ensure that
5974 settings in <file>/usr/local</file> take precedence over the
5975 equivalents in <file>/usr</file>.
5979 However, because <file>/usr/local</file> and its contents are
5980 for exclusive use of the local administrator, a package
5981 must not rely on the presence or absence of files or
5982 directories in <file>/usr/local</file> for normal operation.
5986 The <file>/usr/local</file> directory itself and all the
5987 subdirectories created by the package should (by default) have
5988 permissions 2775 (group-writable and set-group-id) and be
5989 owned by <tt>root:staff</tt>.
5994 <heading>The system-wide mail directory</heading>
5996 The system-wide mail directory
5997 is <file>/var/mail</file>. This directory is part of the
5998 base system and should not be owned by any particular mail
5999 agents. The use of the old
6000 location <file>/var/spool/mail</file> is deprecated, even
6001 though the spool may still be physically located there.
6007 <heading>Users and groups</heading>
6010 <heading>Introduction</heading>
6012 The Debian system can be configured to use either plain or
6017 Some user ids (UIDs) and group ids (GIDs) are reserved
6018 globally for use by certain packages. Because some
6019 packages need to include files which are owned by these
6020 users or groups, or need the ids compiled into binaries,
6021 these ids must be used on any Debian system only for the
6022 purpose for which they are allocated. This is a serious
6023 restriction, and we should avoid getting in the way of
6024 local administration policies. In particular, many sites
6025 allocate users and/or local system groups starting at 100.
6029 Apart from this we should have dynamically allocated ids,
6030 which should by default be arranged in some sensible
6031 order, but the behavior should be configurable.
6035 Packages other than <tt>base-passwd</tt> must not modify
6036 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
6037 <file>/etc/group</file> or <file>/etc/gshadow</file>.
6042 <heading>UID and GID classes</heading>
6044 The UID and GID numbers are divided into classes as
6050 Globally allocated by the Debian project, the same
6051 on every Debian system. These ids will appear in
6052 the <file>passwd</file> and <file>group</file> files of all
6053 Debian systems, new ids in this range being added
6054 automatically as the <tt>base-passwd</tt> package is
6059 Packages which need a single statically allocated
6060 uid or gid should use one of these; their
6061 maintainers should ask the <tt>base-passwd</tt>
6069 Dynamically allocated system users and groups.
6070 Packages which need a user or group, but can have
6071 this user or group allocated dynamically and
6072 differently on each system, should use <tt>adduser
6073 --system</tt> to create the group and/or user.
6074 <prgn>adduser</prgn> will check for the existence of
6075 the user or group, and if necessary choose an unused
6076 id based on the ranges specified in
6077 <file>adduser.conf</file>.
6081 <tag>1000-59999:</tag>
6084 Dynamically allocated user accounts. By default
6085 <prgn>adduser</prgn> will choose UIDs and GIDs for
6086 user accounts in this range, though
6087 <file>adduser.conf</file> may be used to modify this
6092 <tag>60000-64999:</tag>
6095 Globally allocated by the Debian project, but only
6096 created on demand. The ids are allocated centrally
6097 and statically, but the actual accounts are only
6098 created on users' systems on demand.
6102 These ids are for packages which are obscure or
6103 which require many statically-allocated ids. These
6104 packages should check for and create the accounts in
6105 <file>/etc/passwd</file> or <file>/etc/group</file> (using
6106 <prgn>adduser</prgn> if it has this facility) if
6107 necessary. Packages which are likely to require
6108 further allocations should have a "hole" left after
6109 them in the allocation, to give them room to
6114 <tag>65000-65533:</tag>
6122 User <tt>nobody</tt>. The corresponding gid refers
6123 to the group <tt>nogroup</tt>.
6130 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
6131 not</em> be used, because it is the error return
6140 <sect id="sysvinit">
6141 <heading>System run levels and <file>init.d</file> scripts</heading>
6143 <sect1 id="/etc/init.d">
6144 <heading>Introduction</heading>
6147 The <file>/etc/init.d</file> directory contains the scripts
6148 executed by <prgn>init</prgn> at boot time and when the
6149 init state (or "runlevel") is changed (see <manref
6150 name="init" section="8">).
6154 There are at least two different, yet functionally
6155 equivalent, ways of handling these scripts. For the sake
6156 of simplicity, this document describes only the symbolic
6157 link method. However, it must not be assumed by maintainer
6158 scripts that this method is being used, and any automated
6159 manipulation of the various runlevel behaviors by
6160 maintainer scripts must be performed using
6161 <prgn>update-rc.d</prgn> as described below and not by
6162 manually installing or removing symlinks. For information
6163 on the implementation details of the other method,
6164 implemented in the <tt>file-rc</tt> package, please refer
6165 to the documentation of that package.
6169 These scripts are referenced by symbolic links in the
6170 <file>/etc/rc<var>n</var>.d</file> directories. When changing
6171 runlevels, <prgn>init</prgn> looks in the directory
6172 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
6173 execute, where <tt><var>n</var></tt> is the runlevel that
6174 is being changed to, or <tt>S</tt> for the boot-up
6179 The names of the links all have the form
6180 <file>S<var>mm</var><var>script</var></file> or
6181 <file>K<var>mm</var><var>script</var></file> where
6182 <var>mm</var> is a two-digit number and <var>script</var>
6183 is the name of the script (this should be the same as the
6184 name of the actual script in <file>/etc/init.d</file>).
6188 When <prgn>init</prgn> changes runlevel first the targets
6189 of the links whose names start with a <tt>K</tt> are
6190 executed, each with the single argument <tt>stop</tt>,
6191 followed by the scripts prefixed with an <tt>S</tt>, each
6192 with the single argument <tt>start</tt>. (The links are
6193 those in the <file>/etc/rc<var>n</var>.d</file> directory
6194 corresponding to the new runlevel.) The <tt>K</tt> links
6195 are responsible for killing services and the <tt>S</tt>
6196 link for starting services upon entering the runlevel.
6200 For example, if we are changing from runlevel 2 to
6201 runlevel 3, init will first execute all of the <tt>K</tt>
6202 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
6203 all of the <tt>S</tt> prefixed scripts in that directory.
6204 The links starting with <tt>K</tt> will cause the
6205 referred-to file to be executed with an argument of
6206 <tt>stop</tt>, and the <tt>S</tt> links with an argument
6211 The two-digit number <var>mm</var> is used to determine
6212 the order in which to run the scripts: low-numbered links
6213 have their scripts run first. For example, the
6214 <tt>K20</tt> scripts will be executed before the
6215 <tt>K30</tt> scripts. This is used when a certain service
6216 must be started before another. For example, the name
6217 server <prgn>bind</prgn> might need to be started before
6218 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
6219 can set up its access lists. In this case, the script
6220 that starts <prgn>bind</prgn> would have a lower number
6221 than the script that starts <prgn>inn</prgn> so that it
6223 <example compact="compact">
6230 The two runlevels 0 (halt) and 6 (reboot) are slightly
6231 different. In these runlevels, the links with an
6232 <tt>S</tt> prefix are still called after those with a
6233 <tt>K</tt> prefix, but they too are called with the single
6234 argument <tt>stop</tt>.
6238 <sect1 id="writing-init">
6239 <heading>Writing the scripts</heading>
6242 Packages that include daemons for system services should
6243 place scripts in <file>/etc/init.d</file> to start or stop
6244 services at boot time or during a change of runlevel.
6245 These scripts should be named
6246 <file>/etc/init.d/<var>package</var></file>, and they should
6247 accept one argument, saying what to do:
6250 <tag><tt>start</tt></tag>
6251 <item>start the service,</item>
6253 <tag><tt>stop</tt></tag>
6254 <item>stop the service,</item>
6256 <tag><tt>restart</tt></tag>
6257 <item>stop and restart the service if it's already running,
6258 otherwise start the service</item>
6260 <tag><tt>reload</tt></tag>
6261 <item><p>cause the configuration of the service to be
6262 reloaded without actually stopping and restarting
6265 <tag><tt>force-reload</tt></tag>
6266 <item>cause the configuration to be reloaded if the
6267 service supports this, otherwise restart the
6271 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
6272 <tt>force-reload</tt> options should be supported by all
6273 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
6278 The <file>init.d</file> scripts must ensure that they will
6279 behave sensibly (i.e., returning success and not starting
6280 multiple copies of a service) if invoked with <tt>start</tt>
6281 when the service is already running, or with <tt>stop</tt>
6282 when it isn't, and that they don't kill unfortunately-named
6283 user processes. The best way to achieve this is usually to
6284 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
6289 Be careful of using <tt>set -e</tt> in <file>init.d</file>
6290 scripts. Writing correct <file>init.d</file> scripts requires
6291 accepting various error exit statuses when daemons are already
6292 running or already stopped without aborting
6293 the <file>init.d</file> script, and common <file>init.d</file>
6294 function libraries are not safe to call with <tt>set -e</tt>
6296 <tt>/lib/lsb/init-functions</tt>, which assists in writing
6297 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
6298 in effect and echoing status messages to the console fails,
6300 </footnote>. For <tt>init.d</tt> scripts, it's often easier
6301 to not use <tt>set -e</tt> and instead check the result of
6302 each command separately.
6306 If a service reloads its configuration automatically (as
6307 in the case of <prgn>cron</prgn>, for example), the
6308 <tt>reload</tt> option of the <file>init.d</file> script
6309 should behave as if the configuration has been reloaded
6314 The <file>/etc/init.d</file> scripts must be treated as
6315 configuration files, either (if they are present in the
6316 package, that is, in the .deb file) by marking them as
6317 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6318 by managing them correctly in the maintainer scripts (see
6319 <ref id="config-files">). This is important since we want
6320 to give the local system administrator the chance to adapt
6321 the scripts to the local system, e.g., to disable a
6322 service without de-installing the package, or to specify
6323 some special command line options when starting a service,
6324 while making sure their changes aren't lost during the next
6329 These scripts should not fail obscurely when the
6330 configuration files remain but the package has been
6331 removed, as configuration files remain on the system after
6332 the package has been removed. Only when <prgn>dpkg</prgn>
6333 is executed with the <tt>--purge</tt> option will
6334 configuration files be removed. In particular, as the
6335 <file>/etc/init.d/<var>package</var></file> script itself is
6336 usually a <tt>conffile</tt>, it will remain on the system
6337 if the package is removed but not purged. Therefore, you
6338 should include a <tt>test</tt> statement at the top of the
6340 <example compact="compact">
6341 test -f <var>program-executed-later-in-script</var> || exit 0
6346 Often there are some variables in the <file>init.d</file>
6347 scripts whose values control the behavior of the scripts,
6348 and which a system administrator is likely to want to
6349 change. As the scripts themselves are frequently
6350 <tt>conffile</tt>s, modifying them requires that the
6351 administrator merge in their changes each time the package
6352 is upgraded and the <tt>conffile</tt> changes. To ease
6353 the burden on the system administrator, such configurable
6354 values should not be placed directly in the script.
6355 Instead, they should be placed in a file in
6356 <file>/etc/default</file>, which typically will have the same
6357 base name as the <file>init.d</file> script. This extra file
6358 should be sourced by the script when the script runs. It
6359 must contain only variable settings and comments in SUSv3
6360 <prgn>sh</prgn> format. It may either be a
6361 <tt>conffile</tt> or a configuration file maintained by
6362 the package maintainer scripts. See <ref id="config-files">
6367 To ensure that vital configurable values are always
6368 available, the <file>init.d</file> script should set default
6369 values for each of the shell variables it uses, either
6370 before sourcing the <file>/etc/default/</file> file or
6371 afterwards using something like the <tt>:
6372 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6373 script must behave sensibly and not fail if the
6374 <file>/etc/default</file> file is deleted.
6378 <file>/var/run</file> and <file>/var/lock</file> may be mounted
6379 as temporary filesystems<footnote>
6380 For example, using the <tt>RAMRUN</tt> and <tt>RAMLOCK</tt>
6381 options in <file>/etc/default/rcS</file>.
6382 </footnote>, so the <file>init.d</file> scripts must handle this
6383 correctly. This will typically amount to creating any required
6384 subdirectories dynamically when the <file>init.d</file> script
6385 is run, rather than including them in the package and relying on
6386 <prgn>dpkg</prgn> to create them.
6391 <heading>Interfacing with the initscript system</heading>
6394 Maintainers should use the abstraction layer provided by
6395 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6396 programs to deal with initscripts in their packages'
6397 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6398 and <prgn>postrm</prgn>.
6402 Directly managing the /etc/rc?.d links and directly
6403 invoking the <file>/etc/init.d/</file> initscripts should
6404 be done only by packages providing the initscript
6405 subsystem (such as <prgn>sysv-rc</prgn> and
6406 <prgn>file-rc</prgn>).
6410 <heading>Managing the links</heading>
6413 The program <prgn>update-rc.d</prgn> is provided for
6414 package maintainers to arrange for the proper creation and
6415 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6416 or their functional equivalent if another method is being
6417 used. This may be used by maintainers in their packages'
6418 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6422 You must not include any <file>/etc/rc<var>n</var>.d</file>
6423 symbolic links in the actual archive or manually create or
6424 remove the symbolic links in maintainer scripts; you must
6425 use the <prgn>update-rc.d</prgn> program instead. (The
6426 former will fail if an alternative method of maintaining
6427 runlevel information is being used.) You must not include
6428 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6429 in the archive either. (Only the <tt>sysvinit</tt>
6434 By default <prgn>update-rc.d</prgn> will start services in
6435 each of the multi-user state runlevels (2, 3, 4, and 5)
6436 and stop them in the halt runlevel (0), the single-user
6437 runlevel (1) and the reboot runlevel (6). The system
6438 administrator will have the opportunity to customize
6439 runlevels by simply adding, moving, or removing the
6440 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6441 symbolic links are being used, or by modifying
6442 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6447 To get the default behavior for your package, put in your
6448 <prgn>postinst</prgn> script
6449 <example compact="compact">
6450 update-rc.d <var>package</var> defaults
6452 and in your <prgn>postrm</prgn>
6453 <example compact="compact">
6454 if [ "$1" = purge ]; then
6455 update-rc.d <var>package</var> remove
6457 </example>. Note that if your package changes runlevels
6458 or priority, you may have to remove and recreate the links,
6459 since otherwise the old links may persist. Refer to the
6460 documentation of <prgn>update-rc.d</prgn>.
6464 This will use a default sequence number of 20. If it does
6465 not matter when or in which order the <file>init.d</file>
6466 script is run, use this default. If it does, then you
6467 should talk to the maintainer of the <prgn>sysvinit</prgn>
6468 package or post to <tt>debian-devel</tt>, and they will
6469 help you choose a number.
6473 For more information about using <tt>update-rc.d</tt>,
6474 please consult its man page <manref name="update-rc.d"
6480 <heading>Running initscripts</heading>
6482 The program <prgn>invoke-rc.d</prgn> is provided to make
6483 it easier for package maintainers to properly invoke an
6484 initscript, obeying runlevel and other locally-defined
6485 constraints that might limit a package's right to start,
6486 stop and otherwise manage services. This program may be
6487 used by maintainers in their packages' scripts.
6491 The package maintainer scripts must use
6492 <prgn>invoke-rc.d</prgn> to invoke the
6493 <file>/etc/init.d/*</file> initscripts, instead of
6494 calling them directly.
6498 By default, <prgn>invoke-rc.d</prgn> will pass any
6499 action requests (start, stop, reload, restart...) to the
6500 <file>/etc/init.d</file> script, filtering out requests
6501 to start or restart a service out of its intended
6506 Most packages will simply need to change:
6507 <example compact="compact">/etc/init.d/<package>
6508 <action></example> in their <prgn>postinst</prgn>
6509 and <prgn>prerm</prgn> scripts to:
6510 <example compact="compact">
6511 if which invoke-rc.d >/dev/null 2>&1; then
6512 invoke-rc.d <var>package</var> <action>
6514 /etc/init.d/<var>package</var> <action>
6520 A package should register its initscript services using
6521 <prgn>update-rc.d</prgn> before it tries to invoke them
6522 using <prgn>invoke-rc.d</prgn>. Invocation of
6523 unregistered services may fail.
6527 For more information about using
6528 <prgn>invoke-rc.d</prgn>, please consult its man page
6529 <manref name="invoke-rc.d" section="8">.
6535 <heading>Boot-time initialization</heading>
6538 There used to be another directory, <file>/etc/rc.boot</file>,
6539 which contained scripts which were run once per machine
6540 boot. This has been deprecated in favour of links from
6541 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6542 described in <ref id="/etc/init.d">. Packages must not
6543 place files in <file>/etc/rc.boot</file>.
6548 <heading>Example</heading>
6551 An example on which you can base your
6552 <file>/etc/init.d</file> scripts is found in
6553 <file>/etc/init.d/skeleton</file>.
6560 <heading>Console messages from <file>init.d</file> scripts</heading>
6563 This section describes the formats to be used for messages
6564 written to standard output by the <file>/etc/init.d</file>
6565 scripts. The intent is to improve the consistency of
6566 Debian's startup and shutdown look and feel. For this
6567 reason, please look very carefully at the details. We want
6568 the messages to have the same format in terms of wording,
6569 spaces, punctuation and case of letters.
6573 Here is a list of overall rules that should be used for
6574 messages generated by <file>/etc/init.d</file> scripts.
6580 The message should fit in one line (fewer than 80
6581 characters), start with a capital letter and end with
6582 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6586 If the script is performing some time consuming task in
6587 the background (not merely starting or stopping a
6588 program, for instance), an ellipsis (three dots:
6589 <tt>...</tt>) should be output to the screen, with no
6590 leading or tailing whitespace or line feeds.
6594 The messages should appear as if the computer is telling
6595 the user what it is doing (politely :-), but should not
6596 mention "it" directly. For example, instead of:
6597 <example compact="compact">
6598 I'm starting network daemons: nfsd mountd.
6600 the message should say
6601 <example compact="compact">
6602 Starting network daemons: nfsd mountd.
6609 <tt>init.d</tt> script should use the following standard
6610 message formats for the situations enumerated below.
6616 <p>When daemons are started</p>
6619 If the script starts one or more daemons, the output
6620 should look like this (a single line, no leading
6622 <example compact="compact">
6623 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6625 The <var>description</var> should describe the
6626 subsystem the daemon or set of daemons are part of,
6627 while <var>daemon-1</var> up to <var>daemon-n</var>
6628 denote each daemon's name (typically the file name of
6633 For example, the output of <file>/etc/init.d/lpd</file>
6635 <example compact="compact">
6636 Starting printer spooler: lpd.
6641 This can be achieved by saying
6642 <example compact="compact">
6643 echo -n "Starting printer spooler: lpd"
6644 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6647 in the script. If there are more than one daemon to
6648 start, the output should look like this:
6649 <example compact="compact">
6650 echo -n "Starting remote file system services:"
6651 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6652 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6653 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6656 This makes it possible for the user to see what is
6657 happening and when the final daemon has been started.
6658 Care should be taken in the placement of white spaces:
6659 in the example above the system administrators can
6660 easily comment out a line if they don't want to start
6661 a specific daemon, while the displayed message still
6667 <p>When a system parameter is being set</p>
6670 If you have to set up different system parameters
6671 during the system boot, you should use this format:
6672 <example compact="compact">
6673 Setting <var>parameter</var> to "<var>value</var>".
6678 You can use a statement such as the following to get
6680 <example compact="compact">
6681 echo "Setting DNS domainname to \"$domainname\"."
6686 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
6687 for the left and right quotation marks. A grave accent
6688 (<tt>`</tt>) is not a quote character; neither is an
6689 apostrophe (<tt>'</tt>).
6694 <p>When a daemon is stopped or restarted</p>
6697 When you stop or restart a daemon, you should issue a
6698 message identical to the startup message, except that
6699 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6700 or <tt>Restarting</tt> respectively.
6704 For example, stopping the printer daemon will look like
6706 <example compact="compact">
6707 Stopping printer spooler: lpd.
6713 <p>When something is executed</p>
6716 There are several examples where you have to run a
6717 program at system startup or shutdown to perform a
6718 specific task, for example, setting the system's clock
6719 using <prgn>netdate</prgn> or killing all processes
6720 when the system shuts down. Your message should look
6722 <example compact="compact">
6723 Doing something very useful...done.
6725 You should print the <tt>done.</tt> immediately after
6726 the job has been completed, so that the user is
6727 informed why they have to wait. You can get this
6729 <example compact="compact">
6730 echo -n "Doing something very useful..."
6739 <p>When the configuration is reloaded</p>
6742 When a daemon is forced to reload its configuration
6743 files you should use the following format:
6744 <example compact="compact">
6745 Reloading <var>description</var> configuration...done.
6747 where <var>description</var> is the same as in the
6748 daemon starting message.
6756 <heading>Cron jobs</heading>
6759 Packages must not modify the configuration file
6760 <file>/etc/crontab</file>, and they must not modify the files in
6761 <file>/var/spool/cron/crontabs</file>.</p>
6764 If a package wants to install a job that has to be executed
6765 via cron, it should place a file with the name of the
6766 package in one or more of the following directories:
6767 <example compact="compact">
6773 As these directory names imply, the files within them are
6774 executed on an hourly, daily, weekly, or monthly basis,
6775 respectively. The exact times are listed in
6776 <file>/etc/crontab</file>.</p>
6779 All files installed in any of these directories must be
6780 scripts (e.g., shell scripts or Perl scripts) so that they
6781 can easily be modified by the local system administrator.
6782 In addition, they must be treated as configuration files.
6786 If a certain job has to be executed at some other frequency or
6787 at a specific time, the package should install a file
6788 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6789 same syntax as <file>/etc/crontab</file> and is processed by
6790 <prgn>cron</prgn> automatically. The file must also be
6791 treated as a configuration file. (Note that entries in the
6792 <file>/etc/cron.d</file> directory are not handled by
6793 <prgn>anacron</prgn>. Thus, you should only use this
6794 directory for jobs which may be skipped if the system is not
6797 Unlike <file>crontab</file> files described in the IEEE Std
6798 1003.1-2008 (POSIX.1) available from
6799 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
6800 name="The Open Group">, the files in
6801 <file>/etc/cron.d</file> and the file
6802 <file>/etc/crontab</file> have seven fields; namely:
6804 <item>Minute [0,59]</item>
6805 <item>Hour [0,23]</item>
6806 <item>Day of the month [1,31]</item>
6807 <item>Month of the year [1,12]</item>
6808 <item>Day of the week ([0,6] with 0=Sunday)</item>
6809 <item>Username</item>
6810 <item>Command to be run</item>
6812 Ranges of numbers are allowed. Ranges are two numbers
6813 separated with a hyphen. The specified range is inclusive.
6814 Lists are allowed. A list is a set of numbers (or ranges)
6815 separated by commas. Step values can be used in conjunction
6820 The scripts or <tt>crontab</tt> entries in these directories should
6821 check if all necessary programs are installed before they
6822 try to execute them. Otherwise, problems will arise when a
6823 package was removed but not purged since configuration files
6824 are kept on the system in this situation.
6828 Any <tt>cron</tt> daemon must provide
6829 <file>/usr/bin/crontab</file> and support normal
6830 <tt>crontab</tt> entries as specified in POSIX. The daemon
6831 must also support names for days and months, ranges, and
6832 step values. It has to support <file>/etc/crontab</file>,
6833 and correctly execute the scripts in
6834 <file>/etc/cron.d</file>. The daemon must also correctly
6836 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
6841 <heading>Menus</heading>
6844 The Debian <tt>menu</tt> package provides a standard
6845 interface between packages providing applications and
6846 <em>menu programs</em> (either X window managers or
6847 text-based menu programs such as <prgn>pdmenu</prgn>).
6851 All packages that provide applications that need not be
6852 passed any special command line arguments for normal
6853 operation should register a menu entry for those
6854 applications, so that users of the <tt>menu</tt> package
6855 will automatically get menu entries in their window
6856 managers, as well in shells like <tt>pdmenu</tt>.
6860 Menu entries should follow the current menu policy.
6864 The menu policy can be found in the <tt>menu-policy</tt>
6865 files in the <tt>debian-policy</tt> package.
6866 It is also available from the Debian web mirrors at
6867 <tt><url name="/doc/packaging-manuals/menu-policy/"
6868 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6872 Please also refer to the <em>Debian Menu System</em>
6873 documentation that comes with the <package>menu</package>
6874 package for information about how to register your
6880 <heading>Multimedia handlers</heading>
6883 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6884 is a mechanism for encoding files and data streams and
6885 providing meta-information about them, in particular their
6886 type (e.g. audio or video) and format (e.g. PNG, HTML,
6891 Registration of MIME type handlers allows programs like mail
6892 user agents and web browsers to invoke these handlers to
6893 view, edit or display MIME types they don't support directly.
6897 Packages which provide the ability to view/show/play,
6898 compose, edit or print MIME types should register themselves
6899 as such following the current MIME support policy.
6903 The MIME support policy can be found in the <tt>mime-policy</tt>
6904 files in the <tt>debian-policy</tt> package.
6905 It is also available from the Debian web mirrors at
6906 <tt><url name="/doc/packaging-manuals/mime-policy/"
6907 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
6913 <heading>Keyboard configuration</heading>
6916 To achieve a consistent keyboard configuration so that all
6917 applications interpret a keyboard event the same way, all
6918 programs in the Debian distribution must be configured to
6919 comply with the following guidelines.
6923 The following keys must have the specified interpretations:
6926 <tag><tt><--</tt></tag>
6927 <item>delete the character to the left of the cursor</item>
6929 <tag><tt>Delete</tt></tag>
6930 <item>delete the character to the right of the cursor</item>
6932 <tag><tt>Control+H</tt></tag>
6933 <item>emacs: the help prefix</item>
6936 The interpretation of any keyboard events should be
6937 independent of the terminal that is used, be it a virtual
6938 console, an X terminal emulator, an rlogin/telnet session,
6943 The following list explains how the different programs
6944 should be set up to achieve this:
6950 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
6954 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
6958 X translations are set up to make
6959 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
6960 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
6961 is the vt220 escape code for the "delete character"
6962 key). This must be done by loading the X resources
6963 using <prgn>xrdb</prgn> on all local X displays, not
6964 using the application defaults, so that the
6965 translation resources used correspond to the
6966 <prgn>xmodmap</prgn> settings.
6970 The Linux console is configured to make
6971 <tt><--</tt> generate DEL, and <tt>Delete</tt>
6972 generate <tt>ESC [ 3 ~</tt>.
6976 X applications are configured so that <tt><</tt>
6977 deletes left, and <tt>Delete</tt> deletes right. Motif
6978 applications already work like this.
6982 Terminals should have <tt>stty erase ^?</tt> .
6986 The <tt>xterm</tt> terminfo entry should have <tt>ESC
6987 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
6988 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
6992 Emacs is programmed to map <tt>KB_Backspace</tt> or
6993 the <tt>stty erase</tt> character to
6994 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
6995 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
6996 <tt>^H</tt> to <tt>help</tt> as always.
7000 Other applications use the <tt>stty erase</tt>
7001 character and <tt>kdch1</tt> for the two delete keys,
7002 with ASCII DEL being "delete previous character" and
7003 <tt>kdch1</tt> being "delete character under
7011 This will solve the problem except for the following
7018 Some terminals have a <tt><--</tt> key that cannot
7019 be made to produce anything except <tt>^H</tt>. On
7020 these terminals Emacs help will be unavailable on
7021 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
7022 character takes precedence in Emacs, and has been set
7023 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
7024 available) can be used instead.
7028 Some operating systems use <tt>^H</tt> for <tt>stty
7029 erase</tt>. However, modern telnet versions and all
7030 rlogin versions propagate <tt>stty</tt> settings, and
7031 almost all UNIX versions honour <tt>stty erase</tt>.
7032 Where the <tt>stty</tt> settings are not propagated
7033 correctly, things can be made to work by using
7034 <tt>stty</tt> manually.
7038 Some systems (including previous Debian versions) use
7039 <prgn>xmodmap</prgn> to arrange for both
7040 <tt><--</tt> and <tt>Delete</tt> to generate
7041 <tt>KB_Delete</tt>. We can change the behavior of
7042 their X clients using the same X resources that we use
7043 to do it for our own clients, or configure our clients
7044 using their resources when things are the other way
7045 around. On displays configured like this
7046 <tt>Delete</tt> will not work, but <tt><--</tt>
7051 Some operating systems have different <tt>kdch1</tt>
7052 settings in their <tt>terminfo</tt> database for
7053 <tt>xterm</tt> and others. On these systems the
7054 <tt>Delete</tt> key will not work correctly when you
7055 log in from a system conforming to our policy, but
7056 <tt><--</tt> will.
7063 <heading>Environment variables</heading>
7066 A program must not depend on environment variables to get
7067 reasonable defaults. (That's because these environment
7068 variables would have to be set in a system-wide
7069 configuration file like <file>/etc/profile</file>, which is not
7070 supported by all shells.)
7074 If a program usually depends on environment variables for its
7075 configuration, the program should be changed to fall back to
7076 a reasonable default configuration if these environment
7077 variables are not present. If this cannot be done easily
7078 (e.g., if the source code of a non-free program is not
7079 available), the program must be replaced by a small
7080 "wrapper" shell script which sets the environment variables
7081 if they are not already defined, and calls the original program.
7085 Here is an example of a wrapper script for this purpose:
7087 <example compact="compact">
7089 BAR=${BAR:-/var/lib/fubar}
7091 exec /usr/lib/foo/foo "$@"
7096 Furthermore, as <file>/etc/profile</file> is a configuration
7097 file of the <prgn>base-files</prgn> package, other packages must
7098 not put any environment variables or other commands into that
7103 <sect id="doc-base">
7104 <heading>Registering Documents using doc-base</heading>
7107 The <package>doc-base</package> package implements a
7108 flexible mechanism for handling and presenting
7109 documentation. The recommended practice is for every Debian
7110 package that provides online documentation (other than just
7111 manual pages) to register these documents with
7112 <package>doc-base</package> by installing a
7113 <package>doc-base</package> control file via the
7114 <prgn/install-docs/ script at installation time and
7115 de-register the manuals again when the package is removed.
7118 Please refer to the documentation that comes with the
7119 <package>doc-base</package> package for information and
7128 <heading>Files</heading>
7130 <sect id="binaries">
7131 <heading>Binaries</heading>
7134 Two different packages must not install programs with
7135 different functionality but with the same filenames. (The
7136 case of two programs having the same functionality but
7137 different implementations is handled via "alternatives" or
7138 the "Conflicts" mechanism. See <ref id="maintscripts"> and
7139 <ref id="conflicts"> respectively.) If this case happens,
7140 one of the programs must be renamed. The maintainers should
7141 report this to the <tt>debian-devel</tt> mailing list and
7142 try to find a consensus about which program will have to be
7143 renamed. If a consensus cannot be reached, <em>both</em>
7144 programs must be renamed.
7148 By default, when a package is being built, any binaries
7149 created should include debugging information, as well as
7150 being compiled with optimization. You should also turn on
7151 as many reasonable compilation warnings as possible; this
7152 makes life easier for porters, who can then look at build
7153 logs for possible problems. For the C programming language,
7154 this means the following compilation parameters should be
7156 <example compact="compact">
7158 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
7160 INSTALL = install -s # (or use strip on the files in debian/tmp)
7165 Note that by default all installed binaries should be stripped,
7166 either by using the <tt>-s</tt> flag to
7167 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
7168 the binaries after they have been copied into
7169 <file>debian/tmp</file> but before the tree is made into a
7174 Although binaries in the build tree should be compiled with
7175 debugging information by default, it can often be difficult to
7176 debug programs if they are also subjected to compiler
7177 optimization. For this reason, it is recommended to support the
7178 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
7179 (see <ref id="debianrules-options">). This variable can contain
7180 several flags to change how a package is compiled and built.
7184 It is up to the package maintainer to decide what
7185 compilation options are best for the package. Certain
7186 binaries (such as computationally-intensive programs) will
7187 function better with certain flags (<tt>-O3</tt>, for
7188 example); feel free to use them. Please use good judgment
7189 here. Don't use flags for the sake of it; only use them
7190 if there is good reason to do so. Feel free to override
7191 the upstream author's ideas about which compilation
7192 options are best: they are often inappropriate for our
7198 <sect id="libraries">
7199 <heading>Libraries</heading>
7202 If the package is <strong>architecture: any</strong>, then
7203 the shared library compilation and linking flags must have
7204 <tt>-fPIC</tt>, or the package shall not build on some of
7205 the supported architectures<footnote>
7207 If you are using GCC, <tt>-fPIC</tt> produces code with
7208 relocatable position independent code, which is required for
7209 most architectures to create a shared library, with i386 and
7210 perhaps some others where non position independent code is
7211 permitted in a shared library.
7214 Position independent code may have a performance penalty,
7215 especially on <tt>i386</tt>. However, in most cases the
7216 speed penalty must be measured against the memory wasted on
7217 the few architectures where non position independent code is
7220 </footnote>. Any exception to this rule must be discussed on
7221 the mailing list <em>debian-devel@lists.debian.org</em>, and
7222 a rough consensus obtained. The reasons for not compiling
7223 with <tt>-fPIC</tt> flag must be recorded in the file
7224 <tt>README.Debian</tt>, and care must be taken to either
7225 restrict the architecture or arrange for <tt>-fPIC</tt> to
7226 be used on architectures where it is required.<footnote>
7228 Some of the reasons why this might be required is if the
7229 library contains hand crafted assembly code that is not
7230 relocatable, the speed penalty is excessive for compute
7231 intensive libs, and similar reasons.
7236 As to the static libraries, the common case is not to have
7237 relocatable code, since there is no benefit, unless in specific
7238 cases; therefore the static version must not be compiled
7239 with the <tt>-fPIC</tt> flag. Any exception to this rule
7240 should be discussed on the mailing list
7241 <em>debian-devel@lists.debian.org</em>, and the reasons for
7242 compiling with the <tt>-fPIC</tt> flag must be recorded in
7243 the file <tt>README.Debian</tt>. <footnote>
7245 Some of the reasons for linking static libraries with
7246 the <tt>-fPIC</tt> flag are if, for example, one needs a
7247 Perl API for a library that is under rapid development,
7248 and has an unstable API, so shared libraries are
7249 pointless at this phase of the library's development. In
7250 that case, since Perl needs a library with relocatable
7251 code, it may make sense to create a static library with
7252 relocatable code. Another reason cited is if you are
7253 distilling various libraries into a common shared
7254 library, like <tt>mklibs</tt> does in the Debian
7260 In other words, if both a shared and a static library is
7261 being built, each source unit (<tt>*.c</tt>, for example,
7262 for C files) will need to be compiled twice, for the normal
7267 Libraries should be built with threading support and to be
7268 thread-safe if the library supports this.
7272 Although not enforced by the build tools, shared libraries
7273 must be linked against all libraries that they use symbols from
7274 in the same way that binaries are. This ensures the correct
7275 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
7276 system and guarantees that all libraries can be safely opened
7277 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
7278 option <tt>-Wl,-z,defs</tt> when building a shared library.
7279 Since this option enforces symbol resolution at build time,
7280 a missing library reference will be caught early as a fatal
7285 All installed shared libraries should be stripped with
7286 <example compact="compact">
7287 strip --strip-unneeded <var>your-lib</var>
7289 (The option <tt>--strip-unneeded</tt> makes
7290 <prgn>strip</prgn> remove only the symbols which aren't
7291 needed for relocation processing.) Shared libraries can
7292 function perfectly well when stripped, since the symbols for
7293 dynamic linking are in a separate part of the ELF object
7295 You might also want to use the options
7296 <tt>--remove-section=.comment</tt> and
7297 <tt>--remove-section=.note</tt> on both shared libraries
7298 and executables, and <tt>--strip-debug</tt> on static
7304 Note that under some circumstances it may be useful to
7305 install a shared library unstripped, for example when
7306 building a separate package to support debugging.
7310 Shared object files (often <file>.so</file> files) that are not
7311 public libraries, that is, they are not meant to be linked
7312 to by third party executables (binaries of other packages),
7313 should be installed in subdirectories of the
7314 <file>/usr/lib</file> directory. Such files are exempt from the
7315 rules that govern ordinary shared libraries, except that
7316 they must not be installed executable and should be
7318 A common example are the so-called "plug-ins",
7319 internal shared objects that are dynamically loaded by
7320 programs using <manref name="dlopen" section="3">.
7325 Packages that use <prgn>libtool</prgn> to create and install
7326 their shared libraries install a file containing additional
7327 metadata (ending in <file>.la</file>) alongside the library.
7328 For public libraries intended for use by other packages, these
7329 files normally should not be included in the Debian package,
7330 since the information they include is not necessary to link with
7331 the shared library on Debian and can add unnecessary additional
7332 dependencies to other programs or libraries.<footnote>
7333 These files store, among other things, all libraries on which
7334 that shared library depends. Unfortunately, if
7335 the <file>.la</file> file is present and contains that
7336 dependency information, using <prgn>libtool</prgn> when
7337 linking against that library will cause the resulting program
7338 or library to be linked against those dependencies as well,
7339 even if this is unnecessary. This can create unneeded
7340 dependencies on shared library packages that would otherwise
7341 be hidden behind the library ABI, and can make library
7342 transitions to new SONAMEs unnecessarily complicated and
7343 difficult to manage.
7345 If the <file>.la</file> file is required for that library (if,
7346 for instance, it's loaded via <tt>libltdl</tt> in a way that
7347 requires that meta-information), the <tt>dependency_libs</tt>
7348 setting in the <file>.la</file> file should normally be set to
7349 the empty string. If the shared library development package has
7350 historically included the <file>.la</file>, it must be retained
7351 in the development package (with <tt>dependency_libs</tt>
7352 emptied) until all libraries that depend on it have removed or
7353 emptied <tt>dependency_libs</tt> in their <file>.la</file>
7354 files to prevent linking with those other libraries
7355 using <prgn>libtool</prgn> from failing.
7359 If the <file>.la</file> must be included, it should be included
7360 in the development (<tt>-dev</tt>) package, unless the library
7361 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
7362 library. If it is intended for use with <tt>libltdl</tt>,
7363 the <file>.la</file> files must go in the run-time library
7368 These requirements for handling of <file>.la</file> files do not
7369 apply to loadable modules or libraries not installed in
7370 directories searched by default by the dynamic linker. Packages
7371 installing loadable modules will frequently need to install
7372 the <file>.la</file> files alongside the modules so that they
7373 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
7374 does not need to be modified for libraries or modules that are
7375 not installed in directories searched by the dynamic linker by
7376 default and not intended for use by other packages.
7380 You must make sure that you use only released versions of
7381 shared libraries to build your packages; otherwise other
7382 users will not be able to run your binaries
7383 properly. Producing source packages that depend on
7384 unreleased compilers is also usually a bad
7391 <heading>Shared libraries</heading>
7393 This section has moved to <ref id="sharedlibs">.
7399 <heading>Scripts</heading>
7402 All command scripts, including the package maintainer
7403 scripts inside the package and used by <prgn>dpkg</prgn>,
7404 should have a <tt>#!</tt> line naming the shell to be used
7409 In the case of Perl scripts this should be
7410 <tt>#!/usr/bin/perl</tt>.
7414 When scripts are installed into a directory in the system
7415 PATH, the script name should not include an extension such
7416 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7417 language currently used to implement it.
7420 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
7421 <file>init.d</file> scripts should almost certainly start
7422 with <tt>set -e</tt> so that errors are detected.
7423 <file>init.d</file> scripts are something of a special case, due
7424 to how frequently they need to call commands that are allowed to
7425 fail, and it may instead be easier to check the exit status of
7426 commands directly. See <ref id="writing-init"> for more
7427 information about writing <file>init.d</file> scripts.
7430 Every script should use <tt>set -e</tt> or check the exit status
7431 of <em>every</em> command.
7434 Scripts may assume that <file>/bin/sh</file> implements the
7435 SUSv3 Shell Command Language<footnote>
7436 Single UNIX Specification, version 3, which is also IEEE
7437 1003.1-2004 (POSIX), and is available on the World Wide Web
7438 from <url id="http://www.unix.org/version3/online.html"
7439 name="The Open Group"> after free
7440 registration.</footnote>
7441 plus the following additional features not mandated by
7443 These features are in widespread use in the Linux community
7444 and are implemented in all of bash, dash, and ksh, the most
7445 common shells users may wish to use as <file>/bin/sh</file>.
7448 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7449 must not generate a newline.</item>
7450 <item><tt>test</tt>, if implemented as a shell built-in, must
7451 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7453 <item><tt>local</tt> to create a scoped variable must be
7454 supported, including listing multiple variables in a single
7455 local command and assigning a value to a variable at the
7456 same time as localizing it. <tt>local</tt> may or
7457 may not preserve the variable value from an outer scope if
7458 no assignment is present. Uses such as:
7462 # ... use a, b, c, d ...
7465 must be supported and must set the value of <tt>c</tt> to
7469 If a shell script requires non-SUSv3 features from the shell
7470 interpreter other than those listed above, the appropriate shell
7471 must be specified in the first line of the script (e.g.,
7472 <tt>#!/bin/bash</tt>) and the package must depend on the package
7473 providing the shell (unless the shell package is marked
7474 "Essential", as in the case of <prgn>bash</prgn>).
7478 You may wish to restrict your script to SUSv3 features plus the
7479 above set when possible so that it may use <file>/bin/sh</file>
7480 as its interpreter. If your script works with <prgn>dash</prgn>
7481 (originally called <prgn>ash</prgn>), it probably complies with
7482 the above requirements, but if you are in doubt, use
7483 <file>/bin/bash</file>.
7487 Perl scripts should check for errors when making any
7488 system calls, including <tt>open</tt>, <tt>print</tt>,
7489 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7493 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7494 scripting languages. See <em>Csh Programming Considered
7495 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7496 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7497 If an upstream package comes with <prgn>csh</prgn> scripts
7498 then you must make sure that they start with
7499 <tt>#!/bin/csh</tt> and make your package depend on the
7500 <prgn>c-shell</prgn> virtual package.
7504 Any scripts which create files in world-writeable
7505 directories (e.g., in <file>/tmp</file>) must use a
7506 mechanism which will fail atomically if a file with the same
7507 name already exists.
7511 The Debian base system provides the <prgn>tempfile</prgn>
7512 and <prgn>mktemp</prgn> utilities for use by scripts for
7519 <heading>Symbolic links</heading>
7522 In general, symbolic links within a top-level directory
7523 should be relative, and symbolic links pointing from one
7524 top-level directory into another should be absolute. (A
7525 top-level directory is a sub-directory of the root
7526 directory <file>/</file>.)
7530 In addition, symbolic links should be specified as short as
7531 possible, i.e., link targets like <file>foo/../bar</file> are
7536 Note that when creating a relative link using
7537 <prgn>ln</prgn> it is not necessary for the target of the
7538 link to exist relative to the working directory you're
7539 running <prgn>ln</prgn> from, nor is it necessary to change
7540 directory to the directory where the link is to be made.
7541 Simply include the string that should appear as the target
7542 of the link (this will be a pathname relative to the
7543 directory in which the link resides) as the first argument
7548 For example, in your <prgn>Makefile</prgn> or
7549 <file>debian/rules</file>, you can do things like:
7550 <example compact="compact">
7551 ln -fs gcc $(prefix)/bin/cc
7552 ln -fs gcc debian/tmp/usr/bin/cc
7553 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7554 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7559 A symbolic link pointing to a compressed file should always
7560 have the same file extension as the referenced file. (For
7561 example, if a file <file>foo.gz</file> is referenced by a
7562 symbolic link, the filename of the link has to end with
7563 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7568 <heading>Device files</heading>
7571 Packages must not include device files or named pipes in the
7576 If a package needs any special device files that are not
7577 included in the base system, it must call
7578 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7579 after notifying the user<footnote>
7580 This notification could be done via a (low-priority)
7581 debconf message, or an echo (printf) statement.
7586 Packages must not remove any device files in the
7587 <prgn>postrm</prgn> or any other script. This is left to the
7588 system administrator.
7592 Debian uses the serial devices
7593 <file>/dev/ttyS*</file>. Programs using the old
7594 <file>/dev/cu*</file> devices should be changed to use
7595 <file>/dev/ttyS*</file>.
7599 Named pipes needed by the package must be created in
7600 the <prgn>postinst</prgn> script<footnote>
7601 It's better to use <prgn>mkfifo</prgn> rather
7602 than <prgn>mknod</prgn> to create named pipes so that
7603 automated checks for packages incorrectly creating device
7604 files with <prgn>mknod</prgn> won't have false positives.
7605 </footnote> and removed in
7606 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
7611 <sect id="config-files">
7612 <heading>Configuration files</heading>
7615 <heading>Definitions</heading>
7619 <tag>configuration file</tag>
7621 A file that affects the operation of a program, or
7622 provides site- or host-specific information, or
7623 otherwise customizes the behavior of a program.
7624 Typically, configuration files are intended to be
7625 modified by the system administrator (if needed or
7626 desired) to conform to local policy or to provide
7627 more useful site-specific behavior.
7630 <tag><tt>conffile</tt></tag>
7632 A file listed in a package's <tt>conffiles</tt>
7633 file, and is treated specially by <prgn>dpkg</prgn>
7634 (see <ref id="configdetails">).
7640 The distinction between these two is important; they are
7641 not interchangeable concepts. Almost all
7642 <tt>conffile</tt>s are configuration files, but many
7643 configuration files are not <tt>conffiles</tt>.
7647 As noted elsewhere, <file>/etc/init.d</file> scripts,
7648 <file>/etc/default</file> files, scripts installed in
7649 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7650 configuration installed in <file>/etc/cron.d</file> must be
7651 treated as configuration files. In general, any script that
7652 embeds configuration information is de-facto a configuration
7653 file and should be treated as such.
7658 <heading>Location</heading>
7661 Any configuration files created or used by your package
7662 must reside in <file>/etc</file>. If there are several,
7663 consider creating a subdirectory of <file>/etc</file>
7664 named after your package.
7668 If your package creates or uses configuration files
7669 outside of <file>/etc</file>, and it is not feasible to modify
7670 the package to use <file>/etc</file> directly, put the files
7671 in <file>/etc</file> and create symbolic links to those files
7672 from the location that the package requires.
7677 <heading>Behavior</heading>
7680 Configuration file handling must conform to the following
7682 <list compact="compact">
7684 local changes must be preserved during a package
7688 configuration files must be preserved when the
7689 package is removed, and only deleted when the
7693 Obsolete configuration files without local changes may be
7694 removed by the package during upgrade.
7698 The easy way to achieve this behavior is to make the
7699 configuration file a <tt>conffile</tt>. This is
7700 appropriate only if it is possible to distribute a default
7701 version that will work for most installations, although
7702 some system administrators may choose to modify it. This
7703 implies that the default version will be part of the
7704 package distribution, and must not be modified by the
7705 maintainer scripts during installation (or at any other
7710 In order to ensure that local changes are preserved
7711 correctly, no package may contain or make hard links to
7712 conffiles.<footnote>
7713 Rationale: There are two problems with hard links.
7714 The first is that some editors break the link while
7715 editing one of the files, so that the two files may
7716 unwittingly become unlinked and different. The second
7717 is that <prgn>dpkg</prgn> might break the hard link
7718 while upgrading <tt>conffile</tt>s.
7723 The other way to do it is via the maintainer scripts. In
7724 this case, the configuration file must not be listed as a
7725 <tt>conffile</tt> and must not be part of the package
7726 distribution. If the existence of a file is required for
7727 the package to be sensibly configured it is the
7728 responsibility of the package maintainer to provide
7729 maintainer scripts which correctly create, update and
7730 maintain the file and remove it on purge. (See <ref
7731 id="maintainerscripts"> for more information.) These
7732 scripts must be idempotent (i.e., must work correctly if
7733 <prgn>dpkg</prgn> needs to re-run them due to errors
7734 during installation or removal), must cope with all the
7735 variety of ways <prgn>dpkg</prgn> can call maintainer
7736 scripts, must not overwrite or otherwise mangle the user's
7737 configuration without asking, must not ask unnecessary
7738 questions (particularly during upgrades), and must
7739 otherwise be good citizens.
7743 The scripts are not required to configure every possible
7744 option for the package, but only those necessary to get
7745 the package running on a given system. Ideally the
7746 sysadmin should not have to do any configuration other
7747 than that done (semi-)automatically by the
7748 <prgn>postinst</prgn> script.
7752 A common practice is to create a script called
7753 <file><var>package</var>-configure</file> and have the
7754 package's <prgn>postinst</prgn> call it if and only if the
7755 configuration file does not already exist. In certain
7756 cases it is useful for there to be an example or template
7757 file which the maintainer scripts use. Such files should
7758 be in <file>/usr/share/<var>package</var></file> or
7759 <file>/usr/lib/<var>package</var></file> (depending on whether
7760 they are architecture-independent or not). There should
7761 be symbolic links to them from
7762 <file>/usr/share/doc/<var>package</var>/examples</file> if
7763 they are examples, and should be perfectly ordinary
7764 <prgn>dpkg</prgn>-handled files (<em>not</em>
7765 configuration files).
7769 These two styles of configuration file handling must
7770 not be mixed, for that way lies madness:
7771 <prgn>dpkg</prgn> will ask about overwriting the file
7772 every time the package is upgraded.
7777 <heading>Sharing configuration files</heading>
7780 Packages which specify the same file as a
7781 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7782 with each other. (This is an instance of the general rule
7783 about not sharing files. Note that neither alternatives
7784 nor diversions are likely to be appropriate in this case;
7785 in particular, <prgn>dpkg</prgn> does not handle diverted
7786 <tt>conffile</tt>s well.)
7790 The maintainer scripts must not alter a <tt>conffile</tt>
7791 of <em>any</em> package, including the one the scripts
7796 If two or more packages use the same configuration file
7797 and it is reasonable for both to be installed at the same
7798 time, one of these packages must be defined as
7799 <em>owner</em> of the configuration file, i.e., it will be
7800 the package which handles that file as a configuration
7801 file. Other packages that use the configuration file must
7802 depend on the owning package if they require the
7803 configuration file to operate. If the other package will
7804 use the configuration file if present, but is capable of
7805 operating without it, no dependency need be declared.
7809 If it is desirable for two or more related packages to
7810 share a configuration file <em>and</em> for all of the
7811 related packages to be able to modify that configuration
7812 file, then the following should be done:
7813 <enumlist compact="compact">
7815 One of the related packages (the "owning" package)
7816 will manage the configuration file with maintainer
7817 scripts as described in the previous section.
7820 The owning package should also provide a program
7821 that the other packages may use to modify the
7825 The related packages must use the provided program
7826 to make any desired modifications to the
7827 configuration file. They should either depend on
7828 the core package to guarantee that the configuration
7829 modifier program is available or accept gracefully
7830 that they cannot modify the configuration file if it
7831 is not. (This is in addition to the fact that the
7832 configuration file may not even be present in the
7839 Sometimes it's appropriate to create a new package which
7840 provides the basic infrastructure for the other packages
7841 and which manages the shared configuration files. (The
7842 <tt>sgml-base</tt> package is a good example.)
7847 <heading>User configuration files ("dotfiles")</heading>
7850 The files in <file>/etc/skel</file> will automatically be
7851 copied into new user accounts by <prgn>adduser</prgn>.
7852 No other program should reference the files in
7853 <file>/etc/skel</file>.
7857 Therefore, if a program needs a dotfile to exist in
7858 advance in <file>$HOME</file> to work sensibly, that dotfile
7859 should be installed in <file>/etc/skel</file> and treated as a
7864 However, programs that require dotfiles in order to
7865 operate sensibly are a bad thing, unless they do create
7866 the dotfiles themselves automatically.
7870 Furthermore, programs should be configured by the Debian
7871 default installation to behave as closely to the upstream
7872 default behavior as possible.
7876 Therefore, if a program in a Debian package needs to be
7877 configured in some way in order to operate sensibly, that
7878 should be done using a site-wide configuration file placed
7879 in <file>/etc</file>. Only if the program doesn't support a
7880 site-wide default configuration and the package maintainer
7881 doesn't have time to add it may a default per-user file be
7882 placed in <file>/etc/skel</file>.
7886 <file>/etc/skel</file> should be as empty as we can make it.
7887 This is particularly true because there is no easy (or
7888 necessarily desirable) mechanism for ensuring that the
7889 appropriate dotfiles are copied into the accounts of
7890 existing users when a package is installed.
7896 <heading>Log files</heading>
7898 Log files should usually be named
7899 <file>/var/log/<var>package</var>.log</file>. If you have many
7900 log files, or need a separate directory for permission
7901 reasons (<file>/var/log</file> is writable only by
7902 <file>root</file>), you should usually create a directory named
7903 <file>/var/log/<var>package</var></file> and place your log
7908 Log files must be rotated occasionally so that they don't
7909 grow indefinitely; the best way to do this is to drop a log
7910 rotation configuration file into the directory
7911 <file>/etc/logrotate.d</file> and use the facilities provided by
7912 logrotate.<footnote>
7914 The traditional approach to log files has been to set up
7915 <em>ad hoc</em> log rotation schemes using simple shell
7916 scripts and cron. While this approach is highly
7917 customizable, it requires quite a lot of sysadmin work.
7918 Even though the original Debian system helped a little
7919 by automatically installing a system which can be used
7920 as a template, this was deemed not enough.
7924 The use of <prgn>logrotate</prgn>, a program developed
7925 by Red Hat, is better, as it centralizes log management.
7926 It has both a configuration file
7927 (<file>/etc/logrotate.conf</file>) and a directory where
7928 packages can drop their individual log rotation
7929 configurations (<file>/etc/logrotate.d</file>).
7932 Here is a good example for a logrotate config
7933 file (for more information see <manref name="logrotate"
7935 <example compact="compact">
7936 /var/log/foo/*.log {
7941 /etc/init.d/foo force-reload
7945 This rotates all files under <file>/var/log/foo</file>, saves 12
7946 compressed generations, and forces the daemon to reload its
7947 configuration information after the log rotation.
7951 Log files should be removed when the package is
7952 purged (but not when it is only removed). This should be
7953 done by the <prgn>postrm</prgn> script when it is called
7954 with the argument <tt>purge</tt> (see <ref
7955 id="removedetails">).
7960 <heading>Permissions and owners</heading>
7963 The rules in this section are guidelines for general use.
7964 If necessary you may deviate from the details below.
7965 However, if you do so you must make sure that what is done
7966 is secure and you should try to be as consistent as possible
7967 with the rest of the system. You should probably also
7968 discuss it on <prgn>debian-devel</prgn> first.
7972 Files should be owned by <tt>root:root</tt>, and made
7973 writable only by the owner and universally readable (and
7974 executable, if appropriate), that is mode 644 or 755.
7978 Directories should be mode 755 or (for group-writability)
7979 mode 2775. The ownership of the directory should be
7980 consistent with its mode: if a directory is mode 2775, it
7981 should be owned by the group that needs write access to
7984 When a package is upgraded, and the owner or permissions
7985 of a file included in the package has changed, dpkg
7986 arranges for the ownership and permissions to be
7987 correctly set upon installation. However, this does not
7988 extend to directories; the permissions and ownership of
7989 directories already on the system does not change on
7990 install or upgrade of packages. This makes sense, since
7991 otherwise common directories like <tt>/usr</tt> would
7992 always be in flux. To correctly change permissions of a
7993 directory the package owns, explicit action is required,
7994 usually in the <tt>postinst</tt> script. Care must be
7995 taken to handle downgrades as well, in that case.
8002 Setuid and setgid executables should be mode 4755 or 2755
8003 respectively, and owned by the appropriate user or group.
8004 They should not be made unreadable (modes like 4711 or
8005 2711 or even 4111); doing so achieves no extra security,
8006 because anyone can find the binary in the freely available
8007 Debian package; it is merely inconvenient. For the same
8008 reason you should not restrict read or execute permissions
8009 on non-set-id executables.
8013 Some setuid programs need to be restricted to particular
8014 sets of users, using file permissions. In this case they
8015 should be owned by the uid to which they are set-id, and by
8016 the group which should be allowed to execute them. They
8017 should have mode 4754; again there is no point in making
8018 them unreadable to those users who must not be allowed to
8023 It is possible to arrange that the system administrator can
8024 reconfigure the package to correspond to their local
8025 security policy by changing the permissions on a binary:
8026 they can do this by using <prgn>dpkg-statoverride</prgn>, as
8027 described below.<footnote>
8028 Ordinary files installed by <prgn>dpkg</prgn> (as
8029 opposed to <tt>conffile</tt>s and other similar objects)
8030 normally have their permissions reset to the distributed
8031 permissions when the package is reinstalled. However,
8032 the use of <prgn>dpkg-statoverride</prgn> overrides this
8035 Another method you should consider is to create a group for
8036 people allowed to use the program(s) and make any setuid
8037 executables executable only by that group.
8041 If you need to create a new user or group for your package
8042 there are two possibilities. Firstly, you may need to
8043 make some files in the binary package be owned by this
8044 user or group, or you may need to compile the user or
8045 group id (rather than just the name) into the binary
8046 (though this latter should be avoided if possible, as in
8047 this case you need a statically allocated id).</p>
8050 If you need a statically allocated id, you must ask for a
8051 user or group id from the <tt>base-passwd</tt> maintainer,
8052 and must not release the package until you have been
8053 allocated one. Once you have been allocated one you must
8054 either make the package depend on a version of the
8055 <tt>base-passwd</tt> package with the id present in
8056 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
8057 your package to create the user or group itself with the
8058 correct id (using <tt>adduser</tt>) in its
8059 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
8060 the <prgn>postinst</prgn> is to be preferred if it is
8061 possible, otherwise a pre-dependency will be needed on the
8062 <tt>adduser</tt> package.)
8066 On the other hand, the program might be able to determine
8067 the uid or gid from the user or group name at runtime, so
8068 that a dynamically allocated id can be used. In this case
8069 you should choose an appropriate user or group name,
8070 discussing this on <prgn>debian-devel</prgn> and checking
8071 with the <package/base-passwd/ maintainer that it is unique and that
8072 they do not wish you to use a statically allocated id
8073 instead. When this has been checked you must arrange for
8074 your package to create the user or group if necessary using
8075 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
8076 <prgn>postinst</prgn> script (again, the latter is to be
8077 preferred if it is possible).
8081 Note that changing the numeric value of an id associated
8082 with a name is very difficult, and involves searching the
8083 file system for all appropriate files. You need to think
8084 carefully whether a static or dynamic id is required, since
8085 changing your mind later will cause problems.
8088 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
8090 This section is not intended as policy, but as a
8091 description of the use of <prgn>dpkg-statoverride</prgn>.
8095 If a system administrator wishes to have a file (or
8096 directory or other such thing) installed with owner and
8097 permissions different from those in the distributed Debian
8098 package, they can use the <prgn>dpkg-statoverride</prgn>
8099 program to instruct <prgn>dpkg</prgn> to use the different
8100 settings every time the file is installed. Thus the
8101 package maintainer should distribute the files with their
8102 normal permissions, and leave it for the system
8103 administrator to make any desired changes. For example, a
8104 daemon which is normally required to be setuid root, but
8105 in certain situations could be used without being setuid,
8106 should be installed setuid in the <tt>.deb</tt>. Then the
8107 local system administrator can change this if they wish.
8108 If there are two standard ways of doing it, the package
8109 maintainer can use <tt>debconf</tt> to find out the
8110 preference, and call <prgn>dpkg-statoverride</prgn> in the
8111 maintainer script if necessary to accommodate the system
8112 administrator's choice. Care must be taken during
8113 upgrades to not override an existing setting.
8117 Given the above, <prgn>dpkg-statoverride</prgn> is
8118 essentially a tool for system administrators and would not
8119 normally be needed in the maintainer scripts. There is
8120 one type of situation, though, where calls to
8121 <prgn>dpkg-statoverride</prgn> would be needed in the
8122 maintainer scripts, and that involves packages which use
8123 dynamically allocated user or group ids. In such a
8124 situation, something like the following idiom can be very
8125 helpful in the package's <prgn>postinst</prgn>, where
8126 <tt>sysuser</tt> is a dynamically allocated id:
8128 for i in /usr/bin/foo /usr/sbin/bar
8130 # only do something when no setting exists
8131 if ! dpkg-statoverride --list $i >/dev/null 2>&1
8133 #include: debconf processing, question about foo and bar
8134 if [ "$RET" = "true" ] ; then
8135 dpkg-statoverride --update --add sysuser root 4755 $i
8140 The corresponding code to remove the override when the package
8143 for i in /usr/bin/foo /usr/sbin/bar
8145 if dpkg-statoverride --list $i >/dev/null 2>&1
8147 dpkg-statoverride --remove $i
8157 <chapt id="customized-programs">
8158 <heading>Customized programs</heading>
8160 <sect id="arch-spec">
8161 <heading>Architecture specification strings</heading>
8164 If a program needs to specify an <em>architecture specification
8165 string</em> in some place, it should select one of the strings
8166 provided by <tt>dpkg-architecture -L</tt>. The strings are in
8167 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
8168 part is sometimes elided, as when the OS is Linux.
8172 Note that we don't want to use
8173 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
8174 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
8175 since this would make our programs incompatible with other
8176 Linux distributions. We also don't use something like
8177 <tt><var>arch</var>-unknown-linux</tt>, since the
8178 <tt>unknown</tt> does not look very good.
8181 <sect1 id="arch-wildcard-spec">
8182 <heading>Architecture wildcards</heading>
8185 A package may specify an architecture wildcard. Architecture
8186 wildcards are in the format <tt>any</tt> (which matches every
8187 architecture), <tt><var>os</var></tt>-any, or
8188 any-<tt><var>cpu</var></tt>. <footnote>
8189 Internally, the package system normalizes the GNU triplets
8190 and the Debian arches into Debian arch triplets (which are
8191 kind of inverted GNU triplets), with the first component of
8192 the triplet representing the libc and ABI in use, and then
8193 does matching against those triplets. However, such
8194 triplets are an internal implementation detail that should
8195 not be used by packages directly. The libc and ABI portion
8196 is handled internally by the package system based on
8197 the <var>os</var> and <var>cpu</var>.
8204 <heading>Daemons</heading>
8207 The configuration files <file>/etc/services</file>,
8208 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
8209 by the <prgn>netbase</prgn> package and must not be modified
8214 If a package requires a new entry in one of these files, the
8215 maintainer should get in contact with the
8216 <prgn>netbase</prgn> maintainer, who will add the entries
8217 and release a new version of the <prgn>netbase</prgn>
8222 The configuration file <file>/etc/inetd.conf</file> must not be
8223 modified by the package's scripts except via the
8224 <prgn>update-inetd</prgn> script or the
8225 <file>DebianNet.pm</file> Perl module. See their documentation
8226 for details on how to add entries.
8230 If a package wants to install an example entry into
8231 <file>/etc/inetd.conf</file>, the entry must be preceded with
8232 exactly one hash character (<tt>#</tt>). Such lines are
8233 treated as "commented out by user" by the
8234 <prgn>update-inetd</prgn> script and are not changed or
8235 activated during package updates.
8240 <heading>Using pseudo-ttys and modifying wtmp, utmp and
8244 Some programs need to create pseudo-ttys. This should be done
8245 using Unix98 ptys if the C library supports it. The resulting
8246 program must not be installed setuid root, unless that
8247 is required for other functionality.
8251 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
8252 <file>/var/log/lastlog</file> must be installed writable by
8253 group <tt>utmp</tt>. Programs which need to modify those
8254 files must be installed setgid <tt>utmp</tt>.
8259 <heading>Editors and pagers</heading>
8262 Some programs have the ability to launch an editor or pager
8263 program to edit or display a text document. Since there are
8264 lots of different editors and pagers available in the Debian
8265 distribution, the system administrator and each user should
8266 have the possibility to choose their preferred editor and
8271 In addition, every program should choose a good default
8272 editor/pager if none is selected by the user or system
8277 Thus, every program that launches an editor or pager must
8278 use the EDITOR or PAGER environment variable to determine
8279 the editor or pager the user wishes to use. If these
8280 variables are not set, the programs <file>/usr/bin/editor</file>
8281 and <file>/usr/bin/pager</file> should be used, respectively.
8285 These two files are managed through the <prgn>dpkg</prgn>
8286 "alternatives" mechanism. Every package providing an editor or
8287 pager must call the <prgn>update-alternatives</prgn> script to
8288 register as an alternative for <file>/usr/bin/editor</file>
8289 or <file>/usr/bin/pager</file> as appropriate. The alternative
8290 should have a slave alternative
8291 for <file>/usr/share/man/man1/editor.1.gz</file>
8292 or <file>/usr/share/man/man1/pager.1.gz</file> pointing to the
8293 corresponding manual page.
8297 If it is very hard to adapt a program to make use of the
8298 EDITOR or PAGER variables, that program may be configured to
8299 use <file>/usr/bin/sensible-editor</file> and
8300 <file>/usr/bin/sensible-pager</file> as the editor or pager
8301 program respectively. These are two scripts provided in the
8302 <package>sensible-utils</package> package that check the EDITOR
8303 and PAGER variables and launch the appropriate program, and fall
8304 back to <file>/usr/bin/editor</file>
8305 and <file>/usr/bin/pager</file> if the variable is not set.
8309 A program may also use the VISUAL environment variable to
8310 determine the user's choice of editor. If it exists, it
8311 should take precedence over EDITOR. This is in fact what
8312 <file>/usr/bin/sensible-editor</file> does.
8316 It is not required for a package to depend on
8317 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
8318 package to provide such virtual packages.<footnote>
8319 The Debian base system already provides an editor and a
8325 <sect id="web-appl">
8326 <heading>Web servers and applications</heading>
8329 This section describes the locations and URLs that should
8330 be used by all web servers and web applications in the
8337 Cgi-bin executable files are installed in the
8339 <example compact="compact">
8340 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
8342 or a subdirectory of that directory, and should be
8344 <example compact="compact">
8345 http://localhost/cgi-bin/<var>cgi-bin-name</var>
8347 (possibly with a subdirectory name
8348 before <var>cgi-bin-name</var>).
8352 <p>Access to HTML documents</p>
8355 HTML documents for a package are stored in
8356 <file>/usr/share/doc/<var>package</var></file>
8357 and can be referred to as
8358 <example compact="compact">
8359 http://localhost/doc/<var>package</var>/<var>filename</var>
8364 The web server should restrict access to the document
8365 tree so that only clients on the same host can read
8366 the documents. If the web server does not support such
8367 access controls, then it should not provide access at
8368 all, or ask about providing access during installation.
8373 <p>Access to images</p>
8375 It is recommended that images for a package be stored
8376 in <tt>/usr/share/images/<var>package</var></tt> and
8377 may be referred to through an alias <tt>/images/</tt>
8380 http://localhost/images/<package>/<filename>
8387 <p>Web Document Root</p>
8390 Web Applications should try to avoid storing files in
8391 the Web Document Root. Instead they should use the
8392 /usr/share/doc/<var>package</var> directory for
8393 documents and register the Web Application via the
8394 <package>doc-base</package> package. If access to the
8395 web document root is unavoidable then use
8396 <example compact="compact">
8399 as the Document Root. This might be just a symbolic
8400 link to the location where the system administrator
8401 has put the real document root.
8404 <item><p>Providing httpd and/or httpd-cgi</p>
8406 All web servers should provide the virtual package
8407 <tt>httpd</tt>. If a web server has CGI support it should
8408 provide <tt>httpd-cgi</tt> additionally.
8411 All web applications which do not contain CGI scripts should
8412 depend on <tt>httpd</tt>, all those web applications which
8413 <tt>do</tt> contain CGI scripts, should depend on
8421 <sect id="mail-transport-agents">
8422 <heading>Mail transport, delivery and user agents</heading>
8425 Debian packages which process electronic mail, whether mail
8426 user agents (MUAs) or mail transport agents (MTAs), must
8427 ensure that they are compatible with the configuration
8428 decisions below. Failure to do this may result in lost
8429 mail, broken <tt>From:</tt> lines, and other serious brain
8434 The mail spool is <file>/var/mail</file> and the interface to
8435 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8436 the FHS). On older systems, the mail spool may be
8437 physically located in <file>/var/spool/mail</file>, but all
8438 access to the mail spool should be via the
8439 <file>/var/mail</file> symlink. The mail spool is part of the
8440 base system and not part of the MTA package.
8444 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8445 programs (such as IMAP daemons) must lock the mailbox in an
8446 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8447 be combined with dot locking. To avoid deadlocks, a program
8448 should use <tt>fcntl()</tt> first and dot locking after
8449 this, or alternatively implement the two locking methods in
8450 a non blocking way<footnote>
8451 If it is not possible to establish both locks, the
8452 system shouldn't wait for the second lock to be
8453 established, but remove the first lock, wait a (random)
8454 time, and start over locking again.
8455 </footnote>. Using the functions <tt>maillock</tt> and
8456 <tt>mailunlock</tt> provided by the
8457 <tt>liblockfile*</tt><footnote>
8458 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8459 to use these functions.
8460 </footnote> packages is the recommended way to realize this.
8464 Mailboxes are generally either mode 600 and owned by
8465 <var>user</var> or mode 660 and owned by
8466 <tt><var>user</var>:mail</tt><footnote>
8467 There are two traditional permission schemes for mail spools:
8468 mode 600 with all mail delivery done by processes running as
8469 the destination user, or mode 660 and owned by group mail with
8470 mail delivery done by a process running as a system user in
8471 group mail. Historically, Debian required mode 660 mail
8472 spools to enable the latter model, but that model has become
8473 increasingly uncommon and the principle of least privilege
8474 indicates that mail systems that use the first model should
8475 use permissions of 600. If delivery to programs is permitted,
8476 it's easier to keep the mail system secure if the delivery
8477 agent runs as the destination user. Debian Policy therefore
8478 permits either scheme.
8479 </footnote>. The local system administrator may choose a
8480 different permission scheme; packages should not make
8481 assumptions about the permission and ownership of mailboxes
8482 unless required (such as when creating a new mailbox). A MUA
8483 may remove a mailbox (unless it has nonstandard permissions) in
8484 which case the MTA or another MUA must recreate it if needed.
8488 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8489 be setgid mail to do the locking mentioned above (and
8490 must obviously avoid accessing other users' mailboxes
8491 using this privilege).</p>
8494 <file>/etc/aliases</file> is the source file for the system mail
8495 aliases (e.g., postmaster, usenet, etc.), it is the one
8496 which the sysadmin and <prgn>postinst</prgn> scripts may
8497 edit. After <file>/etc/aliases</file> is edited the program or
8498 human editing it must call <prgn>newaliases</prgn>. All MTA
8499 packages must come with a <prgn>newaliases</prgn> program,
8500 even if it does nothing, but older MTA packages did not do
8501 this so programs should not fail if <prgn>newaliases</prgn>
8502 cannot be found. Note that because of this, all MTA
8503 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8504 <tt>Replaces: mail-transport-agent</tt> control file
8509 The convention of writing <tt>forward to
8510 <var>address</var></tt> in the mailbox itself is not
8511 supported. Use a <tt>.forward</tt> file instead.</p>
8514 The <prgn>rmail</prgn> program used by UUCP
8515 for incoming mail should be <file>/usr/sbin/rmail</file>.
8516 Likewise, <prgn>rsmtp</prgn>, for receiving
8517 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8521 If your package needs to know what hostname to use on (for
8522 example) outgoing news and mail messages which are generated
8523 locally, you should use the file <file>/etc/mailname</file>. It
8524 will contain the portion after the username and <tt>@</tt>
8525 (at) sign for email addresses of users on the machine
8526 (followed by a newline).
8530 Such a package should check for the existence of this file
8531 when it is being configured. If it exists, it should be
8532 used without comment, although an MTA's configuration script
8533 may wish to prompt the user even if it finds that this file
8534 exists. If the file does not exist, the package should
8535 prompt the user for the value (preferably using
8536 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8537 as well as using it in the package's configuration. The
8538 prompt should make it clear that the name will not just be
8539 used by that package. For example, in this situation the
8540 <tt>inn</tt> package could say something like:
8541 <example compact="compact">
8542 Please enter the "mail name" of your system. This is the
8543 hostname portion of the address to be shown on outgoing
8544 news and mail messages. The default is
8545 <var>syshostname</var>, your system's host name. Mail
8546 name ["<var>syshostname</var>"]:
8548 where <var>syshostname</var> is the output of <tt>hostname
8554 <heading>News system configuration</heading>
8557 All the configuration files related to the NNTP (news)
8558 servers and clients should be located under
8559 <file>/etc/news</file>.</p>
8562 There are some configuration issues that apply to a number
8563 of news clients and server packages on the machine. These
8567 <tag><file>/etc/news/organization</file></tag>
8569 A string which should appear as the
8570 organization header for all messages posted
8571 by NNTP clients on the machine
8574 <tag><file>/etc/news/server</file></tag>
8576 Contains the FQDN of the upstream NNTP
8577 server, or localhost if the local machine is
8582 Other global files may be added as required for cross-package news
8589 <heading>Programs for the X Window System</heading>
8592 <heading>Providing X support and package priorities</heading>
8595 Programs that can be configured with support for the X
8596 Window System must be configured to do so and must declare
8597 any package dependencies necessary to satisfy their
8598 runtime requirements when using the X Window System. If
8599 such a package is of higher priority than the X packages
8600 on which it depends, it is required that either the
8601 X-specific components be split into a separate package, or
8602 that an alternative version of the package, which includes
8603 X support, be provided, or that the package's priority be
8609 <heading>Packages providing an X server</heading>
8612 Packages that provide an X server that, directly or
8613 indirectly, communicates with real input and display
8614 hardware should declare in their control data that they
8615 provide the virtual package <tt>xserver</tt>.<footnote>
8616 This implements current practice, and provides an
8617 actual policy for usage of the <tt>xserver</tt>
8618 virtual package which appears in the virtual packages
8619 list. In a nutshell, X servers that interface
8620 directly with the display and input hardware or via
8621 another subsystem (e.g., GGI) should provide
8622 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8623 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8629 <heading>Packages providing a terminal emulator</heading>
8632 Packages that provide a terminal emulator for the X Window
8633 System which meet the criteria listed below should declare
8634 in their control data that they provide the virtual
8635 package <tt>x-terminal-emulator</tt>. They should also
8636 register themselves as an alternative for
8637 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8638 20. That alternative should have a slave alternative
8639 for <file>/usr/share/man/man1/x-terminal-emulator.1.gz</file>
8640 pointing to the corresponding manual page.
8644 To be an <tt>x-terminal-emulator</tt>, a program must:
8645 <list compact="compact">
8647 Be able to emulate a DEC VT100 terminal, or a
8648 compatible terminal.
8652 Support the command-line option <tt>-e
8653 <var>command</var></tt>, which creates a new
8654 terminal window<footnote>
8655 "New terminal window" does not necessarily mean
8656 a new top-level X window directly parented by
8657 the window manager; it could, if the terminal
8658 emulator application were so coded, be a new
8659 "view" in a multiple-document interface (MDI).
8661 and runs the specified <var>command</var>,
8662 interpreting the entirety of the rest of the command
8663 line as a command to pass straight to exec, in the
8664 manner that <tt>xterm</tt> does.
8668 Support the command-line option <tt>-T
8669 <var>title</var></tt>, which creates a new terminal
8670 window with the window title <var>title</var>.
8677 <heading>Packages providing a window manager</heading>
8680 Packages that provide a window manager should declare in
8681 their control data that they provide the virtual package
8682 <tt>x-window-manager</tt>. They should also register
8683 themselves as an alternative for
8684 <file>/usr/bin/x-window-manager</file>, with a priority
8685 calculated as follows:
8686 <list compact="compact">
8688 Start with a priority of 20.
8692 If the window manager supports the Debian menu
8693 system, add 20 points if this support is available
8694 in the package's default configuration (i.e., no
8695 configuration files belonging to the system or user
8696 have to be edited to activate the feature); if
8697 configuration files must be modified, add only 10
8703 If the window manager complies with <url
8704 id="http://www.freedesktop.org/Standards/wm-spec"
8705 name="The Window Manager Specification Project">,
8706 written by the <url id="http://www.freedesktop.org/"
8707 name="Free Desktop Group">, add 40 points.
8711 If the window manager permits the X session to be
8712 restarted using a <em>different</em> window manager
8713 (without killing the X server) in its default
8714 configuration, add 10 points; otherwise add none.
8717 That alternative should have a slave alternative
8718 for <file>/usr/share/man/man1/x-window-manager.1.gz</file>
8719 pointing to the corresponding manual page.
8724 <heading>Packages providing fonts</heading>
8727 Packages that provide fonts for the X Window
8729 For the purposes of Debian Policy, a "font for the X
8730 Window System" is one which is accessed via X protocol
8731 requests. Fonts for the Linux console, for PostScript
8732 renderer, or any other purpose, do not fit this
8733 definition. Any tool which makes such fonts available
8734 to the X Window System, however, must abide by this
8737 must do a number of things to ensure that they are both
8738 available without modification of the X or font server
8739 configuration, and that they do not corrupt files used by
8740 other font packages to register information about
8744 Fonts of any type supported by the X Window System
8745 must be in a separate binary package from any
8746 executables, libraries, or documentation (except
8747 that specific to the fonts shipped, such as their
8748 license information). If one or more of the fonts
8749 so packaged are necessary for proper operation of
8750 the package with which they are associated the font
8751 package may be Recommended; if the fonts merely
8752 provide an enhancement, a Suggests relationship may
8753 be used. Packages must not Depend on font
8755 This is because the X server may retrieve fonts
8756 from the local file system or over the network
8757 from an X font server; the Debian package system
8758 is empowered to deal only with the local
8764 BDF fonts must be converted to PCF fonts with the
8765 <prgn>bdftopcf</prgn> utility (available in the
8766 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8767 placed in a directory that corresponds to their
8769 <list compact="compact">
8771 100 dpi fonts must be placed in
8772 <file>/usr/share/fonts/X11/100dpi/</file>.
8776 75 dpi fonts must be placed in
8777 <file>/usr/share/fonts/X11/75dpi/</file>.
8781 Character-cell fonts, cursor fonts, and other
8782 low-resolution fonts must be placed in
8783 <file>/usr/share/fonts/X11/misc/</file>.
8789 Type 1 fonts must be placed in
8790 <file>/usr/share/fonts/X11/Type1/</file>. If font
8791 metric files are available, they must be placed here
8796 Subdirectories of <file>/usr/share/fonts/X11/</file>
8797 other than those listed above must be neither
8798 created nor used. (The <file>PEX</file>, <file>CID</file>,
8799 <file>Speedo</file>, and <file>cyrillic</file> directories
8800 are excepted for historical reasons, but installation of
8801 files into these directories remains discouraged.)
8805 Font packages may, instead of placing files directly
8806 in the X font directories listed above, provide
8807 symbolic links in that font directory pointing to
8808 the files' actual location in the filesystem. Such
8809 a location must comply with the FHS.
8813 Font packages should not contain both 75dpi and
8814 100dpi versions of a font. If both are available,
8815 they should be provided in separate binary packages
8816 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8817 the names of the packages containing the
8818 corresponding fonts.
8822 Fonts destined for the <file>misc</file> subdirectory
8823 should not be included in the same package as 75dpi
8824 or 100dpi fonts; instead, they should be provided in
8825 a separate package with <tt>-misc</tt> appended to
8830 Font packages must not provide the files
8831 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8832 <file>fonts.scale</file> in a font directory:
8835 <file>fonts.dir</file> files must not be provided at all.
8839 <file>fonts.alias</file> and <file>fonts.scale</file>
8840 files, if needed, should be provided in the
8842 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8843 where <var>fontdir</var> is the name of the
8845 <file>/usr/share/fonts/X11/</file> where the
8846 package's corresponding fonts are stored
8847 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8848 <var>package</var> is the name of the package
8849 that provides these fonts, and
8850 <var>extension</var> is either <tt>scale</tt>
8851 or <tt>alias</tt>, whichever corresponds to
8858 Font packages must declare a dependency on
8859 <tt>xfonts-utils</tt> in their control
8864 Font packages that provide one or more
8865 <file>fonts.scale</file> files as described above must
8866 invoke <prgn>update-fonts-scale</prgn> on each
8867 directory into which they installed fonts
8868 <em>before</em> invoking
8869 <prgn>update-fonts-dir</prgn> on that directory.
8870 This invocation must occur in both the
8871 <prgn>postinst</prgn> (for all arguments) and
8872 <prgn>postrm</prgn> (for all arguments except
8873 <tt>upgrade</tt>) scripts.
8877 Font packages that provide one or more
8878 <file>fonts.alias</file> files as described above must
8879 invoke <prgn>update-fonts-alias</prgn> on each
8880 directory into which they installed fonts. This
8881 invocation must occur in both the
8882 <prgn>postinst</prgn> (for all arguments) and
8883 <prgn>postrm</prgn> (for all arguments except
8884 <tt>upgrade</tt>) scripts.
8888 Font packages must invoke
8889 <prgn>update-fonts-dir</prgn> on each directory into
8890 which they installed fonts. This invocation must
8891 occur in both the <prgn>postinst</prgn> (for all
8892 arguments) and <prgn>postrm</prgn> (for all
8893 arguments except <tt>upgrade</tt>) scripts.
8897 Font packages must not provide alias names for the
8898 fonts they include which collide with alias names
8899 already in use by fonts already packaged.
8903 Font packages must not provide fonts with the same
8904 XLFD registry name as another font already packaged.
8910 <sect1 id="appdefaults">
8911 <heading>Application defaults files</heading>
8914 Application defaults files must be installed in the
8915 directory <file>/etc/X11/app-defaults/</file> (use of a
8916 localized subdirectory of <file>/etc/X11/</file> as described
8917 in the <em>X Toolkit Intrinsics - C Language
8918 Interface</em> manual is also permitted). They must be
8919 registered as <tt>conffile</tt>s or handled as
8920 configuration files.
8924 Customization of programs' X resources may also be
8925 supported with the provision of a file with the same name
8926 as that of the package placed in
8927 the <file>/etc/X11/Xresources/</file> directory, which
8928 must be registered as a <tt>conffile</tt> or handled as a
8929 configuration file.<footnote>
8930 Note that this mechanism is not the same as using
8931 app-defaults; app-defaults are tied to the client
8932 binary on the local file system, whereas X resources
8933 are stored in the X server and affect all connecting
8940 <heading>Installation directory issues</heading>
8943 Historically, packages using the X Window System used a
8944 separate set of installation directories from other packages.
8945 This practice has been discontinued and packages using the X
8946 Window System should now generally be installed in the same
8947 directories as any other package. Specifically, packages must
8948 not install files under the <file>/usr/X11R6/</file> directory
8949 and the <file>/usr/X11R6/</file> directory hierarchy should be
8950 regarded as obsolete.
8954 Include files previously installed under
8955 <file>/usr/X11R6/include/X11/</file> should be installed into
8956 <file>/usr/include/X11/</file>. For files previously
8957 installed into subdirectories of
8958 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
8959 determine if subdirectories of <file>/usr/lib/</file> and
8960 <file>/usr/share/</file> can be used. If not, a subdirectory
8961 of <file>/usr/lib/X11/</file> should be used.
8965 Configuration files for window, display, or session managers
8966 or other applications that are tightly integrated with the X
8967 Window System may be placed in a subdirectory
8968 of <file>/etc/X11/</file> corresponding to the package name.
8969 Other X Window System applications should use
8970 the <file>/etc/</file> directory unless otherwise mandated by
8971 policy (such as for <ref id="appdefaults">).
8976 <heading>The OSF/Motif and OpenMotif libraries</heading>
8979 <em>Programs that require the non-DFSG-compliant OSF/Motif or
8980 OpenMotif libraries</em><footnote>
8981 OSF/Motif and OpenMotif are collectively referred to as
8982 "Motif" in this policy document.
8984 should be compiled against and tested with LessTif (a free
8985 re-implementation of Motif) instead. If the maintainer
8986 judges that the program or programs do not work
8987 sufficiently well with LessTif to be distributed and
8988 supported, but do so when compiled against Motif, then two
8989 versions of the package should be created; one linked
8990 statically against Motif and with <tt>-smotif</tt>
8991 appended to the package name, and one linked dynamically
8992 against Motif and with <tt>-dmotif</tt> appended to the
8997 Both Motif-linked versions are dependent
8998 upon non-DFSG-compliant software and thus cannot be
8999 uploaded to the <em>main</em> distribution; if the
9000 software is itself DFSG-compliant it may be uploaded to
9001 the <em>contrib</em> distribution. While known existing
9002 versions of Motif permit unlimited redistribution of
9003 binaries linked against the library (whether statically or
9004 dynamically), it is the package maintainer's
9005 responsibility to determine whether this is permitted by
9006 the license of the copy of Motif in their possession.
9012 <heading>Perl programs and modules</heading>
9015 Perl programs and modules should follow the current Perl policy.
9019 The Perl policy can be found in the <tt>perl-policy</tt>
9020 files in the <tt>debian-policy</tt> package.
9021 It is also available from the Debian web mirrors at
9022 <tt><url name="/doc/packaging-manuals/perl-policy/"
9023 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
9028 <heading>Emacs lisp programs</heading>
9031 Please refer to the "Debian Emacs Policy" for details of how to
9032 package emacs lisp programs.
9036 The Emacs policy is available in
9037 <file>debian-emacs-policy.gz</file> of the
9038 <package>emacsen-common</package> package.
9039 It is also available from the Debian web mirrors at
9040 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
9041 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
9046 <heading>Games</heading>
9049 The permissions on <file>/var/games</file> are mode 755, owner
9050 <tt>root</tt> and group <tt>root</tt>.
9054 Each game decides on its own security policy.</p>
9057 Games which require protected, privileged access to
9058 high-score files, saved games, etc., may be made
9059 set-<em>group</em>-id (mode 2755) and owned by
9060 <tt>root:games</tt>, and use files and directories with
9061 appropriate permissions (770 <tt>root:games</tt>, for
9062 example). They must not be made
9063 set-<em>user</em>-id, as this causes security problems. (If
9064 an attacker can subvert any set-user-id game they can
9065 overwrite the executable of any other, causing other players
9066 of these games to run a Trojan horse program. With a
9067 set-group-id game the attacker only gets access to less
9068 important game data, and if they can get at the other
9069 players' accounts at all it will take considerably more
9073 Some packages, for example some fortune cookie programs, are
9074 configured by the upstream authors to install with their
9075 data files or other static information made unreadable so
9076 that they can only be accessed through set-id programs
9077 provided. You should not do this in a Debian package: anyone can
9078 download the <file>.deb</file> file and read the data from it,
9079 so there is no point making the files unreadable. Not
9080 making the files unreadable also means that you don't have
9081 to make so many programs set-id, which reduces the risk of a
9085 As described in the FHS, binaries of games should be
9086 installed in the directory <file>/usr/games</file>. This also
9087 applies to games that use the X Window System. Manual pages
9088 for games (X and non-X games) should be installed in
9089 <file>/usr/share/man/man6</file>.</p>
9095 <heading>Documentation</heading>
9098 <heading>Manual pages</heading>
9101 You should install manual pages in <prgn>nroff</prgn> source
9102 form, in appropriate places under <file>/usr/share/man</file>.
9103 You should only use sections 1 to 9 (see the FHS for more
9104 details). You must not install a pre-formatted "cat page".
9108 Each program, utility, and function should have an
9109 associated manual page included in the same package. It is
9110 suggested that all configuration files also have a manual
9111 page included as well. Manual pages for protocols and other
9112 auxiliary things are optional.
9116 If no manual page is available, this is considered as a bug
9117 and should be reported to the Debian Bug Tracking System (the
9118 maintainer of the package is allowed to write this bug report
9119 themselves, if they so desire). Do not close the bug report
9120 until a proper man page is available.<footnote>
9121 It is not very hard to write a man page. See the
9122 <url id="http://www.schweikhardt.net/man_page_howto.html"
9123 name="Man-Page-HOWTO">,
9124 <manref name="man" section="7">, the examples
9125 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
9126 the helper program <prgn>help2man</prgn>, or the
9127 directory <file>/usr/share/doc/man-db/examples</file>.
9132 You may forward a complaint about a missing man page to the
9133 upstream authors, and mark the bug as forwarded in the
9134 Debian bug tracking system. Even though the GNU Project do
9135 not in general consider the lack of a man page to be a bug,
9136 we do; if they tell you that they don't consider it a bug
9137 you should leave the bug in our bug tracking system open
9142 Manual pages should be installed compressed using <tt>gzip -9</tt>.
9146 If one man page needs to be accessible via several names it
9147 is better to use a symbolic link than the <file>.so</file>
9148 feature, but there is no need to fiddle with the relevant
9149 parts of the upstream source to change from <file>.so</file> to
9150 symlinks: don't do it unless it's easy. You should not
9151 create hard links in the manual page directories, nor put
9152 absolute filenames in <file>.so</file> directives. The filename
9153 in a <file>.so</file> in a man page should be relative to the
9154 base of the man page tree (usually
9155 <file>/usr/share/man</file>). If you do not create any links
9156 (whether symlinks, hard links, or <tt>.so</tt> directives)
9157 in the file system to the alternate names of the man page,
9158 then you should not rely on <prgn>man</prgn> finding your
9159 man page under those names based solely on the information in
9160 the man page's header.<footnote>
9161 Supporting this in <prgn>man</prgn> often requires
9162 unreasonable processing time to find a manual page or to
9163 report that none exists, and moves knowledge into man's
9164 database that would be better left in the file system.
9165 This support is therefore deprecated and will cease to
9166 be present in the future.
9171 Manual pages in locale-specific subdirectories of
9172 <file>/usr/share/man</file> should use either UTF-8 or the usual
9173 legacy encoding for that language (normally the one corresponding
9174 to the shortest relevant locale name in
9175 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
9176 <file>/usr/share/man/fr</file> should use either UTF-8 or
9177 ISO-8859-1.<footnote>
9178 <prgn>man</prgn> will automatically detect whether UTF-8 is in
9179 use. In future, all manual pages will be required to use
9185 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
9186 included in the subdirectory name unless it indicates a
9187 significant difference in the language, as this excludes
9188 speakers of the language in other countries.<footnote>
9189 At the time of writing, Chinese and Portuguese are the main
9190 languages with such differences, so <file>pt_BR</file>,
9191 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
9196 If a localized version of a manual page is provided, it should
9197 either be up-to-date or it should be obvious to the reader that
9198 it is outdated and the original manual page should be used
9199 instead. This can be done either by a note at the beginning of
9200 the manual page or by showing the missing or changed portions in
9201 the original language instead of the target language.
9206 <heading>Info documents</heading>
9209 Info documents should be installed in <file>/usr/share/info</file>.
9210 They should be compressed with <tt>gzip -9</tt>.
9214 The <prgn>install-info</prgn> program maintains a directory of
9215 installed info documents in <file>/usr/share/info/dir</file> for
9216 the use of info readers.<footnote>
9217 It was previously necessary for packages installing info
9218 documents to run <prgn>install-info</prgn> from maintainer
9219 scripts. This is no longer necessary. The installation
9220 system now uses dpkg triggers.
9222 This file must not be included in packages. Packages containing
9223 info documents should depend on <tt>dpkg (>= 1.15.4) |
9224 install-info</tt> to ensure that the directory file is properly
9225 rebuilt during partial upgrades from Debian 5.0 (lenny) and
9230 Info documents should contain section and directory entry
9231 information in the document for the use
9232 of <prgn>install-info</prgn>. The section should be specified
9233 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
9234 space and the section of this info page. The directory entry or
9235 entries should be included between
9236 a <tt>START-INFO-DIR-ENTRY</tt> line and
9237 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
9239 INFO-DIR-SECTION Individual utilities
9240 START-INFO-DIR-ENTRY
9241 * example: (example). An example info directory entry.
9244 To determine which section to use, you should look
9245 at <file>/usr/share/info/dir</file> on your system and choose
9246 the most relevant (or create a new section if none of the
9247 current sections are relevant).<footnote>
9248 Normally, info documents are generated from Texinfo source.
9249 To include this information in the generated info document, if
9250 it is absent, add commands like:
9252 @dircategory Individual utilities
9254 * example: (example). An example info directory entry.
9257 to the Texinfo source of the document and ensure that the info
9258 documents are rebuilt from source during the package build.
9264 <heading>Additional documentation</heading>
9267 Any additional documentation that comes with the package may
9268 be installed at the discretion of the package maintainer.
9269 Plain text documentation should be installed in the directory
9270 <file>/usr/share/doc/<var>package</var></file>, where
9271 <var>package</var> is the name of the package, and
9272 compressed with <tt>gzip -9</tt> unless it is small.
9276 If a package comes with large amounts of documentation which
9277 many users of the package will not require you should create
9278 a separate binary package to contain it, so that it does not
9279 take up disk space on the machines of users who do not need
9280 or want it installed.</p>
9283 It is often a good idea to put text information files
9284 (<file>README</file>s, changelogs, and so forth) that come with
9285 the source package in <file>/usr/share/doc/<var>package</var></file>
9286 in the binary package. However, you don't need to install
9287 the instructions for building and installing the package, of
9291 Packages must not require the existence of any files in
9292 <file>/usr/share/doc/</file> in order to function
9294 The system administrator should be able to
9295 delete files in <file>/usr/share/doc/</file> without causing
9296 any programs to break.
9298 Any files that are referenced by programs but are also
9299 useful as stand alone documentation should be installed under
9300 <file>/usr/share/<var>package</var>/</file> with symbolic links from
9301 <file>/usr/share/doc/<var>package</var></file>.
9305 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9306 link to another directory in <file>/usr/share/doc</file> only if
9307 the two packages both come from the same source and the
9308 first package Depends on the second.<footnote>
9310 Please note that this does not override the section on
9311 changelog files below, so the file
9312 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
9313 must refer to the changelog for the current version of
9314 <var>package</var> in question. In practice, this means
9315 that the sources of the target and the destination of the
9316 symlink must be the same (same source package and
9323 Former Debian releases placed all additional documentation
9324 in <file>/usr/doc/<var>package</var></file>. This has been
9325 changed to <file>/usr/share/doc/<var>package</var></file>,
9326 and packages must not put documentation in the directory
9327 <file>/usr/doc/<var>package</var></file>. <footnote>
9328 At this phase of the transition, we no longer require a
9329 symbolic link in <file>/usr/doc/</file>. At a later point,
9330 policy shall change to make the symbolic links a bug.
9336 <heading>Preferred documentation formats</heading>
9339 The unification of Debian documentation is being carried out
9343 If your package comes with extensive documentation in a
9344 markup format that can be converted to various other formats
9345 you should if possible ship HTML versions in a binary
9346 package, in the directory
9347 <file>/usr/share/doc/<var>appropriate-package</var></file> or
9348 its subdirectories.<footnote>
9349 The rationale: The important thing here is that HTML
9350 docs should be available in <em>some</em> package, not
9351 necessarily in the main binary package.
9356 Other formats such as PostScript may be provided at the
9357 package maintainer's discretion.
9361 <sect id="copyrightfile">
9362 <heading>Copyright information</heading>
9365 Every package must be accompanied by a verbatim copy of its
9366 copyright information and distribution license in the file
9367 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
9368 file must neither be compressed nor be a symbolic link.
9372 In addition, the copyright file must say where the upstream
9373 sources (if any) were obtained. It should name the original
9374 authors of the package and the Debian maintainer(s) who were
9375 involved with its creation.
9379 Packages in the <em>contrib</em> or <em>non-free</em> archive
9380 areas should state in the copyright file that the package is not
9381 part of the Debian GNU/Linux distribution and briefly explain
9386 A copy of the file which will be installed in
9387 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9388 be in <file>debian/copyright</file> in the source package.
9392 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9393 link to another directory in <file>/usr/share/doc</file> only if
9394 the two packages both come from the same source and the
9395 first package Depends on the second. These rules are
9396 important because copyrights must be extractable by
9401 Packages distributed under the Apache license (version 2.0), the
9402 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
9403 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
9404 1.3) should refer to the corresponding files
9405 under <file>/usr/share/common-licenses</file>,<footnote>
9408 <file>/usr/share/common-licenses/Apache-2.0</file>,
9409 <file>/usr/share/common-licenses/Artistic</file>,
9410 <file>/usr/share/common-licenses/GPL-1</file>,
9411 <file>/usr/share/common-licenses/GPL-2</file>,
9412 <file>/usr/share/common-licenses/GPL-3</file>,
9413 <file>/usr/share/common-licenses/LGPL-2</file>,
9414 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9415 <file>/usr/share/common-licenses/LGPL-3</file>,
9416 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
9417 <file>/usr/share/common-licenses/GFDL-1.3</file>
9418 respectively. The University of California BSD license is
9419 also included in <package>base-files</package> as
9420 <file>/usr/share/common-licenses/BSD</file>, but given the
9421 brevity of this license, its specificity to code whose
9422 copyright is held by the Regents of the University of
9423 California, and the frequency of minor wording changes, its
9424 text should be included in the copyright file rather than
9425 referencing this file.
9427 </footnote> rather than quoting them in the copyright
9432 You should not use the copyright file as a general <file>README</file>
9433 file. If your package has such a file it should be
9434 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9435 <file>README.Debian</file> or some other appropriate place.</p>
9439 <heading>Examples</heading>
9442 Any examples (configurations, source files, whatever),
9443 should be installed in a directory
9444 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9445 files should not be referenced by any program: they're there
9446 for the benefit of the system administrator and users as
9447 documentation only. Architecture-specific example files
9448 should be installed in a directory
9449 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9451 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9452 latter directory itself may be a symbolic link to the
9457 If the purpose of a package is to provide examples, then the
9458 example files may be installed into
9459 <file>/usr/share/doc/<var>package</var></file>.
9463 <sect id="changelogs">
9464 <heading>Changelog files</heading>
9467 Packages that are not Debian-native must contain a
9468 compressed copy of the <file>debian/changelog</file> file from
9469 the Debian source tree in
9470 <file>/usr/share/doc/<var>package</var></file> with the name
9471 <file>changelog.Debian.gz</file>.
9475 If an upstream changelog is available, it should be accessible as
9476 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9477 plain text. If the upstream changelog is distributed in
9478 HTML, it should be made available in that form as
9479 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9480 and a plain text <file>changelog.gz</file> should be generated
9481 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9482 the upstream changelog files do not already conform to this
9483 naming convention, then this may be achieved either by
9484 renaming the files, or by adding a symbolic link, at the
9485 maintainer's discretion.<footnote>
9486 Rationale: People should not have to look in places for
9487 upstream changelogs merely because they are given
9488 different names or are distributed in HTML format.
9493 All of these files should be installed compressed using
9494 <tt>gzip -9</tt>, as they will become large with time even
9495 if they start out small.
9499 If the package has only one changelog which is used both as
9500 the Debian changelog and the upstream one because there is
9501 no separate upstream maintainer then that changelog should
9502 usually be installed as
9503 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9504 there is a separate upstream maintainer, but no upstream
9505 changelog, then the Debian changelog should still be called
9506 <file>changelog.Debian.gz</file>.
9510 For details about the format and contents of the Debian
9511 changelog file, please see <ref id="dpkgchangelog">.
9516 <appendix id="pkg-scope">
9517 <heading>Introduction and scope of these appendices</heading>
9520 These appendices are taken essentially verbatim from the
9521 now-deprecated Packaging Manual, version 3.2.1.0. They are
9522 the chapters which are likely to be of use to package
9523 maintainers and which have not already been included in the
9524 policy document itself. Most of these sections are very likely
9525 not relevant to policy; they should be treated as
9526 documentation for the packaging system. Please note that these
9527 appendices are included for convenience, and for historical
9528 reasons: they used to be part of policy package, and they have
9529 not yet been incorporated into dpkg documentation. However,
9530 they still have value, and hence they are presented here.
9534 They have not yet been checked to ensure that they are
9535 compatible with the contents of policy, and if there are any
9536 contradictions, the version in the main policy document takes
9537 precedence. The remaining chapters of the old Packaging
9538 Manual have also not been read in detail to ensure that there
9539 are not parts which have been left out. Both of these will be
9544 Certain parts of the Packaging manual were integrated into the
9545 Policy Manual proper, and removed from the appendices. Links
9546 have been placed from the old locations to the new ones.
9550 <prgn>dpkg</prgn> is a suite of programs for creating binary
9551 package files and installing and removing them on Unix
9553 <prgn>dpkg</prgn> is targeted primarily at Debian
9554 GNU/Linux, but may work on or be ported to other
9560 The binary packages are designed for the management of
9561 installed executable programs (usually compiled binaries) and
9562 their associated data, though source code examples and
9563 documentation are provided as part of some packages.</p>
9566 This manual describes the technical aspects of creating Debian
9567 binary packages (<file>.deb</file> files). It documents the
9568 behavior of the package management programs
9569 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9570 they interact with packages.</p>
9573 It also documents the interaction between
9574 <prgn>dselect</prgn>'s core and the access method scripts it
9575 uses to actually install the selected packages, and describes
9576 how to create a new access method.</p>
9579 This manual does not go into detail about the options and
9580 usage of the package building and installation tools. It
9581 should therefore be read in conjunction with those programs'
9586 The utility programs which are provided with <prgn>dpkg</prgn>
9587 for managing various system configuration and similar issues,
9588 such as <prgn>update-rc.d</prgn> and
9589 <prgn>install-info</prgn>, are not described in detail here -
9590 please see their man pages.
9594 It is assumed that the reader is reasonably familiar with the
9595 <prgn>dpkg</prgn> System Administrators' manual.
9596 Unfortunately this manual does not yet exist.
9600 The Debian version of the FSF's GNU hello program is provided
9601 as an example for people wishing to create Debian
9602 packages. The Debian <prgn>debmake</prgn> package is
9603 recommended as a very helpful tool in creating and maintaining
9604 Debian packages. However, while the tools and examples are
9605 helpful, they do not replace the need to read and follow the
9606 Policy and Programmer's Manual.</p>
9609 <appendix id="pkg-binarypkg">
9610 <heading>Binary packages (from old Packaging Manual)</heading>
9613 The binary package has two main sections. The first part
9614 consists of various control information files and scripts used
9615 by <prgn>dpkg</prgn> when installing and removing. See <ref
9616 id="pkg-controlarea">.
9620 The second part is an archive containing the files and
9621 directories to be installed.
9625 In the future binary packages may also contain other
9626 components, such as checksums and digital signatures. The
9627 format for the archive is described in full in the
9628 <file>deb(5)</file> man page.
9632 <sect id="pkg-bincreating"><heading>Creating package files -
9633 <prgn>dpkg-deb</prgn>
9637 All manipulation of binary package files is done by
9638 <prgn>dpkg-deb</prgn>; it's the only program that has
9639 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9640 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9641 will spot that the options requested are appropriate to
9642 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9647 In order to create a binary package you must make a
9648 directory tree which contains all the files and directories
9649 you want to have in the file system data part of the package.
9650 In Debian-format source packages this directory is usually
9651 <file>debian/tmp</file>, relative to the top of the package's
9656 They should have the locations (relative to the root of the
9657 directory tree you're constructing) ownerships and
9658 permissions which you want them to have on the system when
9663 With current versions of <prgn>dpkg</prgn> the uid/username
9664 and gid/groupname mappings for the users and groups being
9665 used should be the same on the system where the package is
9666 built and the one where it is installed.
9670 You need to add one special directory to the root of the
9671 miniature file system tree you're creating:
9672 <prgn>DEBIAN</prgn>. It should contain the control
9673 information files, notably the binary package control file
9674 (see <ref id="pkg-controlfile">).
9678 The <prgn>DEBIAN</prgn> directory will not appear in the
9679 file system archive of the package, and so won't be installed
9680 by <prgn>dpkg</prgn> when the package is unpacked.
9684 When you've prepared the package, you should invoke:
9686 dpkg --build <var>directory</var>
9691 This will build the package in
9692 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9693 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9694 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9699 See the man page <manref name="dpkg-deb" section="8"> for details of how
9700 to examine the contents of this newly-created file. You may find the
9701 output of following commands enlightening:
9703 dpkg-deb --info <var>filename</var>.deb
9704 dpkg-deb --contents <var>filename</var>.deb
9705 dpkg --contents <var>filename</var>.deb
9707 To view the copyright file for a package you could use this command:
9709 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
9714 <sect id="pkg-controlarea">
9715 <heading>Package control information files</heading>
9718 The control information portion of a binary package is a
9719 collection of files with names known to <prgn>dpkg</prgn>.
9720 It will treat the contents of these files specially - some
9721 of them contain information used by <prgn>dpkg</prgn> when
9722 installing or removing the package; others are scripts which
9723 the package maintainer wants <prgn>dpkg</prgn> to run.
9727 It is possible to put other files in the package control
9728 area, but this is not generally a good idea (though they
9729 will largely be ignored).
9733 Here is a brief list of the control info files supported by
9734 <prgn>dpkg</prgn> and a summary of what they're used for.
9739 <tag><tt>control</tt>
9742 This is the key description file used by
9743 <prgn>dpkg</prgn>. It specifies the package's name
9744 and version, gives its description for the user,
9745 states its relationships with other packages, and so
9746 forth. See <ref id="sourcecontrolfiles"> and
9747 <ref id="binarycontrolfiles">.
9751 It is usually generated automatically from information
9752 in the source package by the
9753 <prgn>dpkg-gencontrol</prgn> program, and with
9754 assistance from <prgn>dpkg-shlibdeps</prgn>.
9755 See <ref id="pkg-sourcetools">.
9759 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9764 These are executable files (usually scripts) which
9765 <prgn>dpkg</prgn> runs during installation, upgrade
9766 and removal of packages. They allow the package to
9767 deal with matters which are particular to that package
9768 or require more complicated processing than that
9769 provided by <prgn>dpkg</prgn>. Details of when and
9770 how they are called are in <ref id="maintainerscripts">.
9774 It is very important to make these scripts idempotent.
9775 See <ref id="idempotency">.
9779 The maintainer scripts are not guaranteed to run with a
9780 controlling terminal and may not be able to interact with
9781 the user. See <ref id="controllingterminal">.
9785 <tag><tt>conffiles</tt>
9788 This file contains a list of configuration files which
9789 are to be handled automatically by <prgn>dpkg</prgn>
9790 (see <ref id="pkg-conffiles">). Note that not necessarily
9791 every configuration file should be listed here.
9794 <tag><tt>shlibs</tt>
9797 This file contains a list of the shared libraries
9798 supplied by the package, with dependency details for
9799 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9800 when it determines what dependencies are required in a
9801 package control file. The <tt>shlibs</tt> file format
9802 is described on <ref id="shlibs">.
9807 <sect id="pkg-controlfile">
9808 <heading>The main control information file: <tt>control</tt></heading>
9811 The most important control information file used by
9812 <prgn>dpkg</prgn> when it installs a package is
9813 <tt>control</tt>. It contains all the package's "vital
9818 The binary package control files of packages built from
9819 Debian sources are made by a special tool,
9820 <prgn>dpkg-gencontrol</prgn>, which reads
9821 <file>debian/control</file> and <file>debian/changelog</file> to
9822 find the information it needs. See <ref id="pkg-sourcepkg"> for
9827 The fields in binary package control files are listed in
9828 <ref id="binarycontrolfiles">.
9832 A description of the syntax of control files and the purpose
9833 of the fields is available in <ref id="controlfields">.
9838 <heading>Time Stamps</heading>
9841 See <ref id="timestamps">.
9846 <appendix id="pkg-sourcepkg">
9847 <heading>Source packages (from old Packaging Manual) </heading>
9850 The Debian binary packages in the distribution are generated
9851 from Debian sources, which are in a special format to assist
9852 the easy and automatic building of binaries.
9855 <sect id="pkg-sourcetools">
9856 <heading>Tools for processing source packages</heading>
9859 Various tools are provided for manipulating source packages;
9860 they pack and unpack sources and help build of binary
9861 packages and help manage the distribution of new versions.
9865 They are introduced and typical uses described here; see
9866 <manref name="dpkg-source" section="1"> for full
9867 documentation about their arguments and operation.
9871 For examples of how to construct a Debian source package,
9872 and how to use those utilities that are used by Debian
9873 source packages, please see the <prgn>hello</prgn> example
9877 <sect1 id="pkg-dpkg-source">
9879 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9884 This program is frequently used by hand, and is also
9885 called from package-independent automated building scripts
9886 such as <prgn>dpkg-buildpackage</prgn>.
9890 To unpack a package it is typically invoked with
9892 dpkg-source -x <var>.../path/to/filename</var>.dsc
9897 with the <file><var>filename</var>.tar.gz</file> and
9898 <file><var>filename</var>.diff.gz</file> (if applicable) in
9899 the same directory. It unpacks into
9900 <file><var>package</var>-<var>version</var></file>, and if
9902 <file><var>package</var>-<var>version</var>.orig</file>, in
9903 the current directory.
9907 To create a packed source archive it is typically invoked:
9909 dpkg-source -b <var>package</var>-<var>version</var>
9914 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
9915 <file>.diff.gz</file> (if appropriate) in the current
9916 directory. <prgn>dpkg-source</prgn> does not clean the
9917 source tree first - this must be done separately if it is
9922 See also <ref id="pkg-sourcearchives">.</p>
9926 <sect1 id="pkg-dpkg-buildpackage">
9928 <prgn>dpkg-buildpackage</prgn> - overall package-building
9933 <prgn>dpkg-buildpackage</prgn> is a script which invokes
9934 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
9935 targets <tt>clean</tt>, <tt>build</tt> and
9936 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
9937 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
9938 source and binary package upload.
9942 It is usually invoked by hand from the top level of the
9943 built or unbuilt source directory. It may be invoked with
9944 no arguments; useful arguments include:
9945 <taglist compact="compact">
9946 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
9949 Do not sign the <tt>.changes</tt> file or the
9950 source package <tt>.dsc</tt> file, respectively.</p>
9952 <tag><tt>-p<var>sign-command</var></tt></tag>
9955 Invoke <var>sign-command</var> instead of finding
9956 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
9957 <var>sign-command</var> must behave just like
9958 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
9960 <tag><tt>-r<var>root-command</var></tt></tag>
9963 When root privilege is required, invoke the command
9964 <var>root-command</var>. <var>root-command</var>
9965 should invoke its first argument as a command, from
9966 the <prgn>PATH</prgn> if necessary, and pass its
9967 second and subsequent arguments to the command it
9968 calls. If no <var>root-command</var> is supplied
9969 then <var>dpkg-buildpackage</var> will take no
9970 special action to gain root privilege, so that for
9971 most packages it will have to be invoked as root to
9974 <tag><tt>-b</tt>, <tt>-B</tt></tag>
9977 Two types of binary-only build and upload - see
9978 <manref name="dpkg-source" section="1">.
9985 <sect1 id="pkg-dpkg-gencontrol">
9987 <prgn>dpkg-gencontrol</prgn> - generates binary package
9992 This program is usually called from <file>debian/rules</file>
9993 (see <ref id="pkg-sourcetree">) in the top level of the source
9998 This is usually done just before the files and directories in the
9999 temporary directory tree where the package is being built have their
10000 permissions and ownerships set and the package is constructed using
10001 <prgn>dpkg-deb/</prgn>
10003 This is so that the control file which is produced has
10004 the right permissions
10009 <prgn>dpkg-gencontrol</prgn> must be called after all the
10010 files which are to go into the package have been placed in
10011 the temporary build directory, so that its calculation of
10012 the installed size of a package is correct.
10016 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
10017 be run after <prgn>dpkg-shlibdeps</prgn> so that the
10018 variable substitutions created by
10019 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
10024 For a package which generates only one binary package, and
10025 which builds it in <file>debian/tmp</file> relative to the top
10026 of the source package, it is usually sufficient to call
10027 <prgn>dpkg-gencontrol</prgn>.
10031 Sources which build several binaries will typically need
10034 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
10035 </example> The <tt>-P</tt> tells
10036 <prgn>dpkg-gencontrol</prgn> that the package is being
10037 built in a non-default directory, and the <tt>-p</tt>
10038 tells it which package's control file should be generated.
10042 <prgn>dpkg-gencontrol</prgn> also adds information to the
10043 list of files in <file>debian/files</file>, for the benefit of
10044 (for example) a future invocation of
10045 <prgn>dpkg-genchanges</prgn>.</p>
10048 <sect1 id="pkg-dpkg-shlibdeps">
10050 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
10055 This program is usually called from <file>debian/rules</file>
10056 just before <prgn>dpkg-gencontrol</prgn> (see <ref
10057 id="pkg-sourcetree">), in the top level of the source tree.
10061 Its arguments are executables and shared libraries
10064 They may be specified either in the locations in the
10065 source tree where they are created or in the locations
10066 in the temporary build tree where they are installed
10067 prior to binary package creation.
10069 </footnote> for which shared library dependencies should
10070 be included in the binary package's control file.
10074 If some of the found shared libraries should only
10075 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
10076 some warrant a <tt>Pre-Depends</tt>, this can be achieved
10077 by using the <tt>-d<var>dependency-field</var></tt> option
10078 before those executable(s). (Each <tt>-d</tt> option
10079 takes effect until the next <tt>-d</tt>.)
10083 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
10084 output control file to be modified. Instead by default it
10085 adds to the <file>debian/substvars</file> file variable
10086 settings like <tt>shlibs:Depends</tt>. These variable
10087 settings must be referenced in dependency fields in the
10088 appropriate per-binary-package sections of the source
10093 For example, a package that generates an essential part
10094 which requires dependencies, and optional parts that
10095 which only require a recommendation, would separate those
10096 two sets of dependencies into two different fields.<footnote>
10097 At the time of writing, an example for this was the
10098 <package/xmms/ package, with Depends used for the xmms
10099 executable, Recommends for the plug-ins and Suggests for
10100 even more optional features provided by unzip.
10102 It can say in its <file>debian/rules</file>:
10104 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
10105 -dRecommends <var>optionalpart anotheroptionalpart</var>
10107 and then in its main control file <file>debian/control</file>:
10110 Depends: ${shlibs:Depends}
10111 Recommends: ${shlibs:Recommends}
10117 Sources which produce several binary packages with
10118 different shared library dependency requirements can use
10119 the <tt>-p<var>varnameprefix</var></tt> option to override
10120 the default <tt>shlibs:</tt> prefix (one invocation of
10121 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
10122 They can thus produce several sets of dependency
10123 variables, each of the form
10124 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
10125 which can be referred to in the appropriate parts of the
10126 binary package control files.
10131 <sect1 id="pkg-dpkg-distaddfile">
10133 <prgn>dpkg-distaddfile</prgn> - adds a file to
10134 <file>debian/files</file>
10138 Some packages' uploads need to include files other than
10139 the source and binary package files.
10143 <prgn>dpkg-distaddfile</prgn> adds a file to the
10144 <file>debian/files</file> file so that it will be included in
10145 the <file>.changes</file> file when
10146 <prgn>dpkg-genchanges</prgn> is run.
10150 It is usually invoked from the <tt>binary</tt> target of
10151 <file>debian/rules</file>:
10153 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
10155 The <var>filename</var> is relative to the directory where
10156 <prgn>dpkg-genchanges</prgn> will expect to find it - this
10157 is usually the directory above the top level of the source
10158 tree. The <file>debian/rules</file> target should put the
10159 file there just before or just after calling
10160 <prgn>dpkg-distaddfile</prgn>.
10164 The <var>section</var> and <var>priority</var> are passed
10165 unchanged into the resulting <file>.changes</file> file.
10170 <sect1 id="pkg-dpkg-genchanges">
10172 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
10173 upload control file
10177 This program is usually called by package-independent
10178 automatic building scripts such as
10179 <prgn>dpkg-buildpackage</prgn>, but it may also be called
10184 It is usually called in the top level of a built source
10185 tree, and when invoked with no arguments will print out a
10186 straightforward <file>.changes</file> file based on the
10187 information in the source package's changelog and control
10188 file and the binary and source packages which should have
10194 <sect1 id="pkg-dpkg-parsechangelog">
10196 <prgn>dpkg-parsechangelog</prgn> - produces parsed
10197 representation of a changelog
10201 This program is used internally by
10202 <prgn>dpkg-source</prgn> et al. It may also occasionally
10203 be useful in <file>debian/rules</file> and elsewhere. It
10204 parses a changelog, <file>debian/changelog</file> by default,
10205 and prints a control-file format representation of the
10206 information in it to standard output.
10210 <sect1 id="pkg-dpkg-architecture">
10212 <prgn>dpkg-architecture</prgn> - information about the build and
10217 This program can be used manually, but is also invoked by
10218 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
10219 environment or make variables which specify the build and host
10220 architecture for the package building process.
10225 <sect id="pkg-sourcetree">
10226 <heading>The Debian package source tree</heading>
10229 The source archive scheme described later is intended to
10230 allow a Debian package source tree with some associated
10231 control information to be reproduced and transported easily.
10232 The Debian package source tree is a version of the original
10233 program with certain files added for the benefit of the
10234 packaging process, and with any other changes required
10235 made to the rest of the source code and installation
10240 The extra files created for Debian are in the subdirectory
10241 <file>debian</file> of the top level of the Debian package
10242 source tree. They are described below.
10245 <sect1 id="pkg-debianrules">
10246 <heading><file>debian/rules</file> - the main building script</heading>
10249 See <ref id="debianrules">.
10253 <sect1 id="pkg-srcsubstvars">
10254 <heading><file>debian/substvars</file> and variable substitutions</heading>
10257 See <ref id="substvars">.
10263 <heading><file>debian/files</file></heading>
10266 See <ref id="debianfiles">.
10270 <sect1><heading><file>debian/tmp</file>
10274 This is the canonical temporary location for the
10275 construction of binary packages by the <tt>binary</tt>
10276 target. The directory <file>tmp</file> serves as the root of
10277 the file system tree as it is being constructed (for
10278 example, by using the package's upstream makefiles install
10279 targets and redirecting the output there), and it also
10280 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10281 id="pkg-bincreating">.
10285 If several binary packages are generated from the same
10286 source tree it is usual to use several
10287 <file>debian/tmp<var>something</var></file> directories, for
10288 example <file>tmp-a</file> or <file>tmp-doc</file>.
10292 Whatever <file>tmp</file> directories are created and used by
10293 <tt>binary</tt> must of course be removed by the
10294 <tt>clean</tt> target.</p></sect1>
10298 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10302 As it exists on the FTP site, a Debian source package
10303 consists of three related files. You must have the right
10304 versions of all three to be able to use them.
10309 <tag>Debian source control file - <tt>.dsc</tt></tag>
10311 This file is a control file used by <prgn>dpkg-source</prgn>
10312 to extract a source package.
10313 See <ref id="debiansourcecontrolfiles">.
10317 Original source archive -
10319 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10325 This is a compressed (with <tt>gzip -9</tt>)
10326 <prgn>tar</prgn> file containing the source code from
10327 the upstream authors of the program.
10332 Debian package diff -
10334 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10340 This is a unified context diff (<tt>diff -u</tt>)
10341 giving the changes which are required to turn the
10342 original source into the Debian source. These changes
10343 may only include editing and creating plain files.
10344 The permissions of files, the targets of symbolic
10345 links and the characteristics of special files or
10346 pipes may not be changed and no files may be removed
10351 All the directories in the diff must exist, except the
10352 <file>debian</file> subdirectory of the top of the source
10353 tree, which will be created by
10354 <prgn>dpkg-source</prgn> if necessary when unpacking.
10358 The <prgn>dpkg-source</prgn> program will
10359 automatically make the <file>debian/rules</file> file
10360 executable (see below).</p></item>
10365 If there is no original source code - for example, if the
10366 package is specially prepared for Debian or the Debian
10367 maintainer is the same as the upstream maintainer - the
10368 format is slightly different: then there is no diff, and the
10370 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10371 and preferably contains a directory named
10372 <file><var>package</var>-<var>version</var></file>.
10377 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10380 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10381 Debian source package. However, if it is not available it
10382 is possible to unpack a Debian source archive as follows:
10383 <enumlist compact="compact">
10386 Untar the tarfile, which will create a <file>.orig</file>
10390 <p>Rename the <file>.orig</file> directory to
10391 <file><var>package</var>-<var>version</var></file>.</p>
10395 Create the subdirectory <file>debian</file> at the top of
10396 the source tree.</p>
10398 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10400 <item><p>Untar the tarfile again if you want a copy of the original
10401 source code alongside the Debian version.</p>
10406 It is not possible to generate a valid Debian source archive
10407 without using <prgn>dpkg-source</prgn>. In particular,
10408 attempting to use <prgn>diff</prgn> directly to generate the
10409 <file>.diff.gz</file> file will not work.
10413 <heading>Restrictions on objects in source packages</heading>
10416 The source package may not contain any hard links
10418 This is not currently detected when building source
10419 packages, but only when extracting
10423 Hard links may be permitted at some point in the
10424 future, but would require a fair amount of
10426 </footnote>, device special files, sockets or setuid or
10429 Setgid directories are allowed.
10434 The source packaging tools manage the changes between the
10435 original and Debian source using <prgn>diff</prgn> and
10436 <prgn>patch</prgn>. Turning the original source tree as
10437 included in the <file>.orig.tar.gz</file> into the Debian
10438 package source must not involve any changes which cannot be
10439 handled by these tools. Problematic changes which cause
10440 <prgn>dpkg-source</prgn> to halt with an error when
10441 building the source package are:
10442 <list compact="compact">
10443 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10445 <item><p>Changing the targets of symbolic links.</p>
10447 <item><p>Creating directories, other than <file>debian</file>.</p>
10449 <item><p>Changes to the contents of binary files.</p></item>
10450 </list> Changes which cause <prgn>dpkg-source</prgn> to
10451 print a warning but continue anyway are:
10452 <list compact="compact">
10455 Removing files, directories or symlinks.
10457 Renaming a file is not treated specially - it is
10458 seen as the removal of the old file (which
10459 generates a warning, but is otherwise ignored),
10460 and the creation of the new one.
10466 Changed text files which are missing the usual final
10467 newline (either in the original or the modified
10472 Changes which are not represented, but which are not detected by
10473 <prgn>dpkg-source</prgn>, are:
10474 <list compact="compact">
10475 <item><p>Changing the permissions of files (other than
10476 <file>debian/rules</file>) and directories.</p></item>
10481 The <file>debian</file> directory and <file>debian/rules</file>
10482 are handled specially by <prgn>dpkg-source</prgn> - before
10483 applying the changes it will create the <file>debian</file>
10484 directory, and afterwards it will make
10485 <file>debian/rules</file> world-executable.
10491 <appendix id="pkg-controlfields">
10492 <heading>Control files and their fields (from old Packaging Manual)</heading>
10495 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10496 data in a common format, known as control files. Binary and
10497 source packages have control data as do the <file>.changes</file>
10498 files which control the installation of uploaded files, and
10499 <prgn>dpkg</prgn>'s internal databases are in a similar
10504 <heading>Syntax of control files</heading>
10507 See <ref id="controlsyntax">.
10511 It is important to note that there are several fields which
10512 are optional as far as <prgn>dpkg</prgn> and the related
10513 tools are concerned, but which must appear in every Debian
10514 package, or whose omission may cause problems.
10519 <heading>List of fields</heading>
10522 See <ref id="controlfieldslist">.
10526 This section now contains only the fields that didn't belong
10527 to the Policy manual.
10530 <sect1 id="pkg-f-Filename">
10531 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10534 These fields in <tt>Packages</tt> files give the
10535 filename(s) of (the parts of) a package in the
10536 distribution directories, relative to the root of the
10537 Debian hierarchy. If the package has been split into
10538 several parts the parts are all listed in order, separated
10543 <sect1 id="pkg-f-Size">
10544 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10547 These fields in <file>Packages</file> files give the size (in
10548 bytes, expressed in decimal) and MD5 checksum of the
10549 file(s) which make(s) up a binary package in the
10550 distribution. If the package is split into several parts
10551 the values for the parts are listed in order, separated by
10556 <sect1 id="pkg-f-Status">
10557 <heading><tt>Status</tt></heading>
10560 This field in <prgn>dpkg</prgn>'s status file records
10561 whether the user wants a package installed, removed or
10562 left alone, whether it is broken (requiring
10563 re-installation) or not and what its current state on the
10564 system is. Each of these pieces of information is a
10569 <sect1 id="pkg-f-Config-Version">
10570 <heading><tt>Config-Version</tt></heading>
10573 If a package is not installed or not configured, this
10574 field in <prgn>dpkg</prgn>'s status file records the last
10575 version of the package which was successfully
10580 <sect1 id="pkg-f-Conffiles">
10581 <heading><tt>Conffiles</tt></heading>
10584 This field in <prgn>dpkg</prgn>'s status file contains
10585 information about the automatically-managed configuration
10586 files held by a package. This field should <em>not</em>
10587 appear anywhere in a package!
10592 <heading>Obsolete fields</heading>
10595 These are still recognized by <prgn>dpkg</prgn> but should
10596 not appear anywhere any more.
10598 <taglist compact="compact">
10600 <tag><tt>Revision</tt></tag>
10601 <tag><tt>Package-Revision</tt></tag>
10602 <tag><tt>Package_Revision</tt></tag>
10604 The Debian revision part of the package version was
10605 at one point in a separate control file field. This
10606 field went through several names.
10609 <tag><tt>Recommended</tt></tag>
10610 <item>Old name for <tt>Recommends</tt>.</item>
10612 <tag><tt>Optional</tt></tag>
10613 <item>Old name for <tt>Suggests</tt>.</item>
10615 <tag><tt>Class</tt></tag>
10616 <item>Old name for <tt>Priority</tt>.</item>
10625 <appendix id="pkg-conffiles">
10626 <heading>Configuration file handling (from old Packaging Manual)</heading>
10629 <prgn>dpkg</prgn> can do a certain amount of automatic
10630 handling of package configuration files.
10634 Whether this mechanism is appropriate depends on a number of
10635 factors, but basically there are two approaches to any
10636 particular configuration file.
10640 The easy method is to ship a best-effort configuration in the
10641 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10642 handle updates. If the user is unlikely to want to edit the
10643 file, but you need them to be able to without losing their
10644 changes, and a new package with a changed version of the file
10645 is only released infrequently, this is a good approach.
10649 The hard method is to build the configuration file from
10650 scratch in the <prgn>postinst</prgn> script, and to take the
10651 responsibility for fixing any mistakes made in earlier
10652 versions of the package automatically. This will be
10653 appropriate if the file is likely to need to be different on
10657 <sect><heading>Automatic handling of configuration files by
10662 A package may contain a control area file called
10663 <tt>conffiles</tt>. This file should be a list of filenames
10664 of configuration files needing automatic handling, separated
10665 by newlines. The filenames should be absolute pathnames,
10666 and the files referred to should actually exist in the
10671 When a package is upgraded <prgn>dpkg</prgn> will process
10672 the configuration files during the configuration stage,
10673 shortly before it runs the package's <prgn>postinst</prgn>
10678 For each file it checks to see whether the version of the
10679 file included in the package is the same as the one that was
10680 included in the last version of the package (the one that is
10681 being upgraded from); it also compares the version currently
10682 installed on the system with the one shipped with the last
10687 If neither the user nor the package maintainer has changed
10688 the file, it is left alone. If one or the other has changed
10689 their version, then the changed version is preferred - i.e.,
10690 if the user edits their file, but the package maintainer
10691 doesn't ship a different version, the user's changes will
10692 stay, silently, but if the maintainer ships a new version
10693 and the user hasn't edited it the new version will be
10694 installed (with an informative message). If both have
10695 changed their version the user is prompted about the problem
10696 and must resolve the differences themselves.
10700 The comparisons are done by calculating the MD5 message
10701 digests of the files, and storing the MD5 of the file as it
10702 was included in the most recent version of the package.
10706 When a package is installed for the first time
10707 <prgn>dpkg</prgn> will install the file that comes with it,
10708 unless that would mean overwriting a file already on the
10713 However, note that <prgn>dpkg</prgn> will <em>not</em>
10714 replace a conffile that was removed by the user (or by a
10715 script). This is necessary because with some programs a
10716 missing file produces an effect hard or impossible to
10717 achieve in another way, so that a missing file needs to be
10718 kept that way if the user did it.
10722 Note that a package should <em>not</em> modify a
10723 <prgn>dpkg</prgn>-handled conffile in its maintainer
10724 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10725 the user confusing and possibly dangerous options for
10726 conffile update when the package is upgraded.</p>
10729 <sect><heading>Fully-featured maintainer script configuration
10734 For files which contain site-specific information such as
10735 the hostname and networking details and so forth, it is
10736 better to create the file in the package's
10737 <prgn>postinst</prgn> script.
10741 This will typically involve examining the state of the rest
10742 of the system to determine values and other information, and
10743 may involve prompting the user for some information which
10744 can't be obtained some other way.
10748 When using this method there are a couple of important
10749 issues which should be considered:
10753 If you discover a bug in the program which generates the
10754 configuration file, or if the format of the file changes
10755 from one version to the next, you will have to arrange for
10756 the postinst script to do something sensible - usually this
10757 will mean editing the installed configuration file to remove
10758 the problem or change the syntax. You will have to do this
10759 very carefully, since the user may have changed the file,
10760 perhaps to fix the very problem that your script is trying
10761 to deal with - you will have to detect these situations and
10762 deal with them correctly.
10766 If you do go down this route it's probably a good idea to
10767 make the program that generates the configuration file(s) a
10768 separate program in <file>/usr/sbin</file>, by convention called
10769 <file><var>package</var>config</file> and then run that if
10770 appropriate from the post-installation script. The
10771 <tt><var>package</var>config</tt> program should not
10772 unquestioningly overwrite an existing configuration - if its
10773 mode of operation is geared towards setting up a package for
10774 the first time (rather than any arbitrary reconfiguration
10775 later) you should have it check whether the configuration
10776 already exists, and require a <tt>--force</tt> flag to
10777 overwrite it.</p></sect>
10780 <appendix id="pkg-alternatives"><heading>Alternative versions of
10781 an interface - <prgn>update-alternatives</prgn> (from old
10786 When several packages all provide different versions of the
10787 same program or file it is useful to have the system select a
10788 default, but to allow the system administrator to change it
10789 and have their decisions respected.
10793 For example, there are several versions of the <prgn>vi</prgn>
10794 editor, and there is no reason to prevent all of them from
10795 being installed at once, each under their own name
10796 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10797 Nevertheless it is desirable to have the name <tt>vi</tt>
10798 refer to something, at least by default.
10802 If all the packages involved cooperate, this can be done with
10803 <prgn>update-alternatives</prgn>.
10807 Each package provides its own version under its own name, and
10808 calls <prgn>update-alternatives</prgn> in its postinst to
10809 register its version (and again in its prerm to deregister
10814 See the man page <manref name="update-alternatives"
10815 section="8"> for details.
10819 If <prgn>update-alternatives</prgn> does not seem appropriate
10820 you may wish to consider using diversions instead.</p>
10823 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10824 package's version of a file (from old Packaging Manual)
10828 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10829 when it reinstalls the package it belongs to, and to have it
10830 put the file from the package somewhere else instead.
10834 This can be used locally to override a package's version of a
10835 file, or by one package to override another's version (or
10836 provide a wrapper for it).
10840 Before deciding to use a diversion, read <ref
10841 id="pkg-alternatives"> to see if you really want a diversion
10842 rather than several alternative versions of a program.
10846 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10847 and updated by a special program <prgn>dpkg-divert</prgn>.
10848 Please see <manref name="dpkg-divert" section="8"> for full
10849 details of its operation.
10853 When a package wishes to divert a file from another, it should
10854 call <prgn>dpkg-divert</prgn> in its preinst to add the
10855 diversion and rename the existing file. For example,
10856 supposing that a <prgn>smailwrapper</prgn> package wishes to
10857 install a wrapper around <file>/usr/sbin/smail</file>:
10859 dpkg-divert --package smailwrapper --add --rename \
10860 --divert /usr/sbin/smail.real /usr/sbin/smail
10861 </example> The <tt>--package smailwrapper</tt> ensures that
10862 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
10863 can bypass the diversion and get installed as the true version.
10864 It's safe to add the diversion unconditionally on upgrades since
10865 it will be left unchanged if it already exists, but
10866 <prgn>dpkg-divert</prgn> will display a message. To suppress that
10867 message, make the command conditional on the version from which
10868 the package is being upgraded:
10870 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
10871 dpkg-divert --package smailwrapper --add --rename \
10872 --divert /usr/sbin/smail.real /usr/sbin/smail
10874 </example> where <tt>1.0-2</tt> is the version at which the
10875 diversion was first added to the package. Running the command
10876 during abort-upgrade is pointless but harmless.
10880 The postrm has to do the reverse:
10882 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
10883 dpkg-divert --package smailwrapper --remove --rename \
10884 --divert /usr/sbin/smail.real /usr/sbin/smail
10886 </example> If the diversion was added at a particular version, the
10887 postrm should also handle the failure case of upgrading from an
10888 older version (unless the older version is so old that direct
10889 upgrades are no longer supported):
10891 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
10892 dpkg-divert --package smailwrapper --remove --rename \
10893 --divert /usr/sbin/smail.real /usr/sbin/smail
10895 </example> where <tt>1.02-2</tt> is the version at which the
10896 diversion was first added to the package. The postrm should not
10897 remove the diversion on upgrades both because there's no reason to
10898 remove the diversion only to immediately re-add it and since the
10899 postrm of the old package is run after unpacking so the removal of
10900 the diversion will fail.
10904 Do not attempt to divert a file which is vitally important for
10905 the system's operation - when using <prgn>dpkg-divert</prgn>
10906 there is a time, after it has been diverted but before
10907 <prgn>dpkg</prgn> has installed the new version, when the file
10908 does not exist.</p>
10913 <!-- Local variables: -->
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