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10 <title>Debian Policy Manual</title>
11 <author><qref id="authors">The Debian Policy Mailing List</qref></author>
12 <version>version &version;, &date;</version>
15 This manual describes the policy requirements for the Debian
16 GNU/Linux distribution. This includes the structure and
17 contents of the Debian archive and several design issues of
18 the operating system, as well as technical requirements that
19 each package must satisfy to be included in the distribution.
24 Copyright © 1996,1997,1998 Ian Jackson
25 and Christian Schwarz.
28 These are the copyright dates of the original Policy manual.
29 Since then, this manual has been updated by many others. No
30 comprehensive collection of copyright notices for subsequent
35 This manual is free software; you may redistribute it and/or
36 modify it under the terms of the GNU General Public License
37 as published by the Free Software Foundation; either version
38 2, or (at your option) any later version.
42 This is distributed in the hope that it will be useful, but
43 <em>without any warranty</em>; without even the implied
44 warranty of merchantability or fitness for a particular
45 purpose. See the GNU General Public License for more
50 A copy of the GNU General Public License is available as
51 <file>/usr/share/common-licenses/GPL</file> in the Debian GNU/Linux
52 distribution or on the World Wide Web at
53 <url id="http://www.gnu.org/copyleft/gpl.html"
54 name="the GNU General Public Licence">. You can also
55 obtain it by writing to the Free Software Foundation, Inc.,
56 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
64 <heading>About this manual</heading>
66 <heading>Scope</heading>
68 This manual describes the policy requirements for the Debian
69 GNU/Linux distribution. This includes the structure and
70 contents of the Debian archive and several design issues of the
71 operating system, as well as technical requirements that
72 each package must satisfy to be included in the
77 This manual also describes Debian policy as it relates to
78 creating Debian packages. It is not a tutorial on how to build
79 packages, nor is it exhaustive where it comes to describing
80 the behavior of the packaging system. Instead, this manual
81 attempts to define the interface to the package management
82 system that the developers have to be conversant with.<footnote>
83 Informally, the criteria used for inclusion is that the
84 material meet one of the following requirements:
85 <taglist compact="compact">
86 <tag>Standard interfaces</tag>
88 The material presented represents an interface to
89 the packaging system that is mandated for use, and
90 is used by, a significant number of packages, and
91 therefore should not be changed without peer
92 review. Package maintainers can then rely on this
93 interface not changing, and the package management
94 software authors need to ensure compatibility with
95 this interface definition. (Control file and
96 changelog file formats are examples.)
98 <tag>Chosen Convention</tag>
100 If there are a number of technically viable choices
101 that can be made, but one needs to select one of
102 these options for inter-operability. The version
103 number format is one example.
106 Please note that these are not mutually exclusive;
107 selected conventions often become parts of standard
113 The footnotes present in this manual are
114 merely informative, and are not part of Debian policy itself.
118 The appendices to this manual are not necessarily normative,
119 either. Please see <ref id="pkg-scope"> for more information.
123 In the normative part of this manual,
124 the words <em>must</em>, <em>should</em> and
125 <em>may</em>, and the adjectives <em>required</em>,
126 <em>recommended</em> and <em>optional</em>, are used to
127 distinguish the significance of the various guidelines in
128 this policy document. Packages that do not conform to the
129 guidelines denoted by <em>must</em> (or <em>required</em>)
130 will generally not be considered acceptable for the Debian
131 distribution. Non-conformance with guidelines denoted by
132 <em>should</em> (or <em>recommended</em>) will generally be
133 considered a bug, but will not necessarily render a package
134 unsuitable for distribution. Guidelines denoted by
135 <em>may</em> (or <em>optional</em>) are truly optional and
136 adherence is left to the maintainer's discretion.
140 These classifications are roughly equivalent to the bug
141 severities <em>serious</em> (for <em>must</em> or
142 <em>required</em> directive violations), <em>minor</em>,
143 <em>normal</em> or <em>important</em>
144 (for <em>should</em> or <em>recommended</em> directive
145 violations) and <em>wishlist</em> (for <em>optional</em>
148 Compare RFC 2119. Note, however, that these words are
149 used in a different way in this document.
154 Much of the information presented in this manual will be
155 useful even when building a package which is to be
156 distributed in some other way or is intended for local use
162 <heading>New versions of this document</heading>
165 This manual is distributed via the Debian package
166 <package><url name="debian-policy"
167 id="http://packages.debian.org/debian-policy"></package>
168 (<httpsite>packages.debian.org</httpsite>
169 <httppath>/debian-policy</httppath>).
173 The current version of this document is also available from
174 the Debian web mirrors at
175 <tt><url name="/doc/debian-policy/"
176 id="http://www.debian.org/doc/debian-policy/"></tt>.
178 <httpsite>www.debian.org</httpsite>
179 <httppath>/doc/debian-policy/</httppath>)
180 Also available from the same directory are several other
181 formats: <file>policy.html.tar.gz</file>
182 (<httppath>/doc/debian-policy/policy.html.tar.gz</httppath>),
183 <file>policy.pdf.gz</file>
184 (<httppath>/doc/debian-policy/policy.pdf.gz</httppath>)
185 and <file>policy.ps.gz</file>
186 (<httppath>/doc/debian-policy/policy.ps.gz</httppath>).
190 The <package>debian-policy</package> package also includes the file
191 <file>upgrading-checklist.txt.gz</file> which indicates policy
192 changes between versions of this document.
197 <heading>Authors and Maintainers</heading>
200 Originally called "Debian GNU/Linux Policy Manual", this
201 manual was initially written in 1996 by Ian Jackson.
202 It was revised on November 27th, 1996 by David A. Morris.
203 Christian Schwarz added new sections on March 15th, 1997,
204 and reworked/restructured it in April-July 1997.
205 Christoph Lameter contributed the "Web Standard".
206 Julian Gilbey largely restructured it in 2001.
210 Since September 1998, the responsibility for the contents of
211 this document lies on the <url name="debian-policy mailing list"
212 id="mailto:debian-policy@lists.debian.org">. Proposals
213 are discussed there and inserted into policy after a certain
214 consensus is established.
215 <!-- insert shameless policy-process plug here eventually -->
216 The actual editing is done by a group of maintainers that have
217 no editorial powers. These are the current maintainers:
220 <item>Julian Gilbey</item>
221 <item>Branden Robinson</item>
222 <item>Josip Rodin</item>
223 <item>Manoj Srivastava</item>
228 While the authors of this document have tried hard to avoid
229 typos and other errors, these do still occur. If you discover
230 an error in this manual or if you want to give any
231 comments, suggestions, or criticisms please send an email to
232 the Debian Policy List,
233 <email>debian-policy@lists.debian.org</email>, or submit a
234 bug report against the <tt>debian-policy</tt> package.
238 Please do not try to reach the individual authors or maintainers
239 of the Policy Manual regarding changes to the Policy.
244 <heading>Related documents</heading>
247 There are several other documents other than this Policy Manual
248 that are necessary to fully understand some Debian policies and
253 The external "sub-policy" documents are referred to in:
254 <list compact="compact">
255 <item><ref id="fhs"></item>
256 <item><ref id="virtual_pkg"></item>
257 <item><ref id="menus"></item>
258 <item><ref id="mime"></item>
259 <item><ref id="perl"></item>
260 <item><ref id="maintscriptprompt"></item>
261 <item><ref id="emacs"></item>
266 In addition to those, which carry the weight of policy, there
267 is the Debian Developer's Reference. This document describes
268 procedures and resources for Debian developers, but it is
269 <em>not</em> normative; rather, it includes things that don't
270 belong in the Policy, such as best practices for developers.
274 The Developer's Reference is available in the
275 <package>developers-reference</package> package.
276 It's also available from the Debian web mirrors at
277 <tt><url name="/doc/developers-reference/"
278 id="http://www.debian.org/doc/developers-reference/"></tt>.
282 <sect id="definitions">
283 <heading>Definitions</heading>
286 The following terms are used in this Policy Manual:
290 The character encoding specified by ANSI X3.4-1986 and its
291 predecessor standards, referred to in MIME as US-ASCII, and
292 corresponding to an encoding in eight bits per character of
293 the first 128 <url id="http://www.unicode.org/"
294 name="Unicode"> characters, with the eighth bit always zero.
298 The transformation format (sometimes called encoding) of
299 <url id="http://www.unicode.org/" name="Unicode"> defined by
300 <url id="http://www.rfc-editor.org/rfc/rfc3629.txt"
301 name="RFC 3629">. UTF-8 has the useful property of having
302 ASCII as a subset, so any text encoded in ASCII is trivially
312 <heading>The Debian Archive</heading>
315 The Debian GNU/Linux system is maintained and distributed as a
316 collection of <em>packages</em>. Since there are so many of
317 them (currently well over 15000), they are split into
318 <em>sections</em> and given <em>priorities</em> to simplify
319 the handling of them.
323 The effort of the Debian project is to build a free operating
324 system, but not every package we want to make accessible is
325 <em>free</em> in our sense (see the Debian Free Software
326 Guidelines, below), or may be imported/exported without
327 restrictions. Thus, the archive is split into areas<footnote>
328 The Debian archive software uses the term "component" internally
329 and in the Release file format to refer to the division of an
330 archive. The Debian Social Contract simply refers to "areas."
331 This document uses terminology similar to the Social Contract.
332 </footnote> based on their licenses and other restrictions.
336 The aims of this are:
338 <list compact="compact">
339 <item>to allow us to make as much software available as we can</item>
340 <item>to allow us to encourage everyone to write free software,
342 <item>to allow us to make it easy for people to produce
343 CD-ROMs of our system without violating any licenses,
344 import/export restrictions, or any other laws.</item>
349 The <em>main</em> archive area forms the <em>Debian GNU/Linux
354 Packages in the other archive areas (<tt>contrib</tt>,
355 <tt>non-free</tt>) are not considered to be part of the Debian
356 distribution, although we support their use and provide
357 infrastructure for them (such as our bug-tracking system and
358 mailing lists). This Debian Policy Manual applies to these
363 <heading>The Debian Free Software Guidelines</heading>
365 The Debian Free Software Guidelines (DFSG) form our
366 definition of "free software". These are:
368 <tag>1. Free Redistribution
371 The license of a Debian component may not restrict any
372 party from selling or giving away the software as a
373 component of an aggregate software distribution
374 containing programs from several different
375 sources. The license may not require a royalty or
376 other fee for such sale.
381 The program must include source code, and must allow
382 distribution in source code as well as compiled form.
384 <tag>3. Derived Works
387 The license must allow modifications and derived
388 works, and must allow them to be distributed under the
389 same terms as the license of the original software.
391 <tag>4. Integrity of The Author's Source Code
394 The license may restrict source-code from being
395 distributed in modified form <em>only</em> if the
396 license allows the distribution of "patch files"
397 with the source code for the purpose of modifying the
398 program at build time. The license must explicitly
399 permit distribution of software built from modified
400 source code. The license may require derived works to
401 carry a different name or version number from the
402 original software. (This is a compromise. The Debian
403 Project encourages all authors to not restrict any
404 files, source or binary, from being modified.)
406 <tag>5. No Discrimination Against Persons or Groups
409 The license must not discriminate against any person
412 <tag>6. No Discrimination Against Fields of Endeavor
415 The license must not restrict anyone from making use
416 of the program in a specific field of endeavor. For
417 example, it may not restrict the program from being
418 used in a business, or from being used for genetic
421 <tag>7. Distribution of License
424 The rights attached to the program must apply to all
425 to whom the program is redistributed without the need
426 for execution of an additional license by those
429 <tag>8. License Must Not Be Specific to Debian
432 The rights attached to the program must not depend on
433 the program's being part of a Debian system. If the
434 program is extracted from Debian and used or
435 distributed without Debian but otherwise within the
436 terms of the program's license, all parties to whom
437 the program is redistributed must have the same
438 rights as those that are granted in conjunction with
441 <tag>9. License Must Not Contaminate Other Software
444 The license must not place restrictions on other
445 software that is distributed along with the licensed
446 software. For example, the license must not insist
447 that all other programs distributed on the same medium
448 must be free software.
450 <tag>10. Example Licenses
453 The "GPL," "BSD," and "Artistic" licenses are examples of
454 licenses that we consider <em>free</em>.
461 <heading>Archive areas</heading>
464 <heading>The main archive area</heading>
467 Every package in <em>main</em> must comply with the DFSG
468 (Debian Free Software Guidelines).
472 In addition, the packages in <em>main</em>
473 <list compact="compact">
475 must not require a package outside of <em>main</em>
476 for compilation or execution (thus, the package must
477 not declare a "Depends", "Recommends", or
478 "Build-Depends" relationship on a non-<em>main</em>
482 must not be so buggy that we refuse to support them,
486 must meet all policy requirements presented in this
495 <heading>The contrib archive area</heading>
498 Every package in <em>contrib</em> must comply with the DFSG.
502 In addition, the packages in <em>contrib</em>
503 <list compact="compact">
505 must not be so buggy that we refuse to support them,
509 must meet all policy requirements presented in this
517 Examples of packages which would be included in
518 <em>contrib</em> are:
519 <list compact="compact">
521 free packages which require <em>contrib</em>,
522 <em>non-free</em> packages or packages which are not
523 in our archive at all for compilation or execution,
527 wrapper packages or other sorts of free accessories for
534 <sect1 id="non-free">
535 <heading>The non-free archive area</heading>
538 Packages must be placed in <em>non-free</em> if they are
539 not compliant with the DFSG or are encumbered by patents
540 or other legal issues that make their distribution
545 In addition, the packages in <em>non-free</em>
546 <list compact="compact">
548 must not be so buggy that we refuse to support them,
552 must meet all policy requirements presented in this
553 manual that it is possible for them to meet.
555 It is possible that there are policy
556 requirements which the package is unable to
557 meet, for example, if the source is
558 unavailable. These situations will need to be
559 handled on a case-by-case basis.
568 <sect id="pkgcopyright">
569 <heading>Copyright considerations</heading>
572 Every package must be accompanied by a verbatim copy of its
573 copyright information and distribution license in the file
574 <file>/usr/share/doc/<var>package</var>/copyright</file>
575 (see <ref id="copyrightfile"> for further details).
579 We reserve the right to restrict files from being included
580 anywhere in our archives if
581 <list compact="compact">
583 their use or distribution would break a law,
586 there is an ethical conflict in their distribution or
590 we would have to sign a license for them, or
593 their distribution would conflict with other project
600 Programs whose authors encourage the user to make
601 donations are fine for the main distribution, provided
602 that the authors do not claim that not donating is
603 immoral, unethical, illegal or something similar; in such
604 a case they must go in <em>non-free</em>.
608 Packages whose copyright permission notices (or patent
609 problems) do not even allow redistribution of binaries
610 only, and where no special permission has been obtained,
611 must not be placed on the Debian FTP site and its mirrors
616 Note that under international copyright law (this applies
617 in the United States, too), <em>no</em> distribution or
618 modification of a work is allowed without an explicit
619 notice saying so. Therefore a program without a copyright
620 notice <em>is</em> copyrighted and you may not do anything
621 to it without risking being sued! Likewise if a program
622 has a copyright notice but no statement saying what is
623 permitted then nothing is permitted.
627 Many authors are unaware of the problems that restrictive
628 copyrights (or lack of copyright notices) can cause for
629 the users of their supposedly-free software. It is often
630 worthwhile contacting such authors diplomatically to ask
631 them to modify their license terms. However, this can be a
632 politically difficult thing to do and you should ask for
633 advice on the <tt>debian-legal</tt> mailing list first, as
638 When in doubt about a copyright, send mail to
639 <email>debian-legal@lists.debian.org</email>. Be prepared
640 to provide us with the copyright statement. Software
641 covered by the GPL, public domain software and BSD-like
642 copyrights are safe; be wary of the phrases "commercial
643 use prohibited" and "distribution restricted".
647 <sect id="subsections">
648 <heading>Sections</heading>
651 The packages in the archive areas <em>main</em>,
652 <em>contrib</em> and <em>non-free</em> are grouped further into
653 <em>sections</em> to simplify handling.
657 The archive area and section for each package should be
658 specified in the package's <tt>Section</tt> control record (see
659 <ref id="f-Section">). However, the maintainer of the Debian
660 archive may override this selection to ensure the consistency of
661 the Debian distribution. The <tt>Section</tt> field should be
663 <list compact="compact">
665 <em>section</em> if the package is in the
666 <em>main</em> archive area,
669 <em>area/section</em> if the package is in
670 the <em>contrib</em> or <em>non-free</em>
677 The Debian archive maintainers provide the authoritative
678 list of sections. At present, they are:
679 <em>admin</em>, <em>cli-mono</em>, <em>comm</em>, <em>database</em>,
680 <em>devel</em>, <em>debug</em>, <em>doc</em>, <em>editors</em>,
681 <em>electronics</em>, <em>embedded</em>, <em>fonts</em>,
682 <em>games</em>, <em>gnome</em>, <em>graphics</em>, <em>gnu-r</em>,
683 <em>gnustep</em>, <em>hamradio</em>, <em>haskell</em>,
684 <em>httpd</em>, <em>interpreters</em>, <em>java</em>, <em>kde</em>,
685 <em>kernel</em>, <em>libs</em>, <em>libdevel</em>, <em>lisp</em>,
686 <em>localization</em>, <em>mail</em>, <em>math</em>, <em>misc</em>,
687 <em>net</em>, <em>news</em>, <em>ocaml</em>, <em>oldlibs</em>,
688 <em>otherosfs</em>, <em>perl</em>, <em>php</em>, <em>python</em>,
689 <em>ruby</em>, <em>science</em>, <em>shells</em>, <em>sound</em>,
690 <em>tex</em>, <em>text</em>, <em>utils</em>, <em>vcs</em>,
691 <em>video</em>, <em>web</em>, <em>x11</em>, <em>xfce</em>,
696 <sect id="priorities">
697 <heading>Priorities</heading>
700 Each package should have a <em>priority</em> value, which is
701 included in the package's <em>control record</em>
702 (see <ref id="f-Priority">).
703 This information is used by the Debian package management tools to
704 separate high-priority packages from less-important packages.
708 The following <em>priority levels</em> are recognized by the
709 Debian package management tools.
711 <tag><tt>required</tt></tag>
713 Packages which are necessary for the proper
714 functioning of the system (usually, this means that
715 dpkg functionality depends on these packages).
716 Removing a <tt>required</tt> package may cause your
717 system to become totally broken and you may not even
718 be able to use <prgn>dpkg</prgn> to put things back,
719 so only do so if you know what you are doing. Systems
720 with only the <tt>required</tt> packages are probably
721 unusable, but they do have enough functionality to
722 allow the sysadmin to boot and install more software.
724 <tag><tt>important</tt></tag>
726 Important programs, including those which one would
727 expect to find on any Unix-like system. If the
728 expectation is that an experienced Unix person who
729 found it missing would say "What on earth is going on,
730 where is <prgn>foo</prgn>?", it must be an
731 <tt>important</tt> package.<footnote>
732 This is an important criterion because we are
733 trying to produce, amongst other things, a free
736 Other packages without which the system will not run
737 well or be usable must also have priority
738 <tt>important</tt>. This does
739 <em>not</em> include Emacs, the X Window System, TeX
740 or any other large applications. The
741 <tt>important</tt> packages are just a bare minimum of
742 commonly-expected and necessary tools.
744 <tag><tt>standard</tt></tag>
746 These packages provide a reasonably small but not too
747 limited character-mode system. This is what will be
748 installed by default if the user doesn't select anything
749 else. It doesn't include many large applications.
751 <tag><tt>optional</tt></tag>
753 (In a sense everything that isn't required is
754 optional, but that's not what is meant here.) This is
755 all the software that you might reasonably want to
756 install if you didn't know what it was and don't have
757 specialized requirements. This is a much larger system
758 and includes the X Window System, a full TeX
759 distribution, and many applications. Note that
760 optional packages should not conflict with each other.
762 <tag><tt>extra</tt></tag>
764 This contains all packages that conflict with others
765 with required, important, standard or optional
766 priorities, or are only likely to be useful if you
767 already know what they are or have specialized
768 requirements (such as packages containing only detached
775 Packages must not depend on packages with lower priority
776 values (excluding build-time dependencies). In order to
777 ensure this, the priorities of one or more packages may need
786 <heading>Binary packages</heading>
789 The Debian GNU/Linux distribution is based on the Debian
790 package management system, called <prgn>dpkg</prgn>. Thus,
791 all packages in the Debian distribution must be provided
792 in the <tt>.deb</tt> file format.
796 <heading>The package name</heading>
799 Every package must have a name that's unique within the Debian
804 The package name is included in the control field
805 <tt>Package</tt>, the format of which is described
806 in <ref id="f-Package">.
807 The package name is also included as a part of the file name
808 of the <tt>.deb</tt> file.
813 <heading>The version of a package</heading>
816 Every package has a version number recorded in its
817 <tt>Version</tt> control file field, described in
818 <ref id="f-Version">.
822 The package management system imposes an ordering on version
823 numbers, so that it can tell whether packages are being up- or
824 downgraded and so that package system front end applications
825 can tell whether a package it finds available is newer than
826 the one installed on the system. The version number format
827 has the most significant parts (as far as comparison is
828 concerned) at the beginning.
832 If an upstream package has problematic version numbers they
833 should be converted to a sane form for use in the
834 <tt>Version</tt> field.
838 <heading>Version numbers based on dates</heading>
841 In general, Debian packages should use the same version
842 numbers as the upstream sources.
846 However, in some cases where the upstream version number is
847 based on a date (e.g., a development "snapshot" release) the
848 package management system cannot handle these version
849 numbers without epochs. For example, dpkg will consider
850 "96May01" to be greater than "96Dec24".
854 To prevent having to use epochs for every new upstream
855 version, the date based portion of the version number
856 should be changed to the following format in such cases:
857 "19960501", "19961224". It is up to the maintainer whether
858 they want to bother the upstream maintainer to change
859 the version numbers upstream, too.
863 Note that other version formats based on dates which are
864 parsed correctly by the package management system should
865 <em>not</em> be changed.
869 Native Debian packages (i.e., packages which have been
870 written especially for Debian) whose version numbers include
871 dates should always use the "YYYYMMDD" format.
878 <heading>The maintainer of a package</heading>
881 Every package must have a Debian maintainer (the
882 maintainer may be one person or a group of people
883 reachable from a common email address, such as a mailing
884 list). The maintainer is responsible for ensuring that
885 the package is placed in the appropriate distributions.
889 The maintainer must be specified in the
890 <tt>Maintainer</tt> control field with their correct name
891 and a working email address. If one person maintains
892 several packages, they should try to avoid having
893 different forms of their name and email address in
894 the <tt>Maintainer</tt> fields of those packages.
898 The format of the <tt>Maintainer</tt> control field is
899 described in <ref id="f-Maintainer">.
903 If the maintainer of a package quits from the Debian
904 project, "Debian QA Group"
905 <email>packages@qa.debian.org</email> takes over the
906 maintainer-ship of the package until someone else
907 volunteers for that task. These packages are called
908 <em>orphaned packages</em>.<footnote>
909 The detailed procedure for doing this gracefully can
910 be found in the Debian Developer's Reference,
911 see <ref id="related">.
916 <sect id="descriptions">
917 <heading>The description of a package</heading>
920 Every Debian package must have an extended description
921 stored in the appropriate field of the control record.
922 The technical information about the format of the
923 <tt>Description</tt> field is in <ref id="f-Description">.
927 The description should describe the package (the program) to a
928 user (system administrator) who has never met it before so that
929 they have enough information to decide whether they want to
930 install it. This description should not just be copied verbatim
931 from the program's documentation.
935 Put important information first, both in the synopsis and
936 extended description. Sometimes only the first part of the
937 synopsis or of the description will be displayed. You can
938 assume that there will usually be a way to see the whole
939 extended description.
943 The description should also give information about the
944 significant dependencies and conflicts between this package
945 and others, so that the user knows why these dependencies and
946 conflicts have been declared.
950 Instructions for configuring or using the package should
951 not be included (that is what installation scripts,
952 manual pages, info files, etc., are for). Copyright
953 statements and other administrivia should not be included
954 either (that is what the copyright file is for).
957 <sect1 id="synopsis"><heading>The single line synopsis</heading>
960 The single line synopsis should be kept brief - certainly
965 Do not include the package name in the synopsis line. The
966 display software knows how to display this already, and you
967 do not need to state it. Remember that in many situations
968 the user may only see the synopsis line - make it as
969 informative as you can.
974 <sect1 id="extendeddesc"><heading>The extended description</heading>
977 Do not try to continue the single line synopsis into the
978 extended description. This will not work correctly when
979 the full description is displayed, and makes no sense
980 where only the summary (the single line synopsis) is
985 The extended description should describe what the package
986 does and how it relates to the rest of the system (in terms
987 of, for example, which subsystem it is which part of).
991 The description field needs to make sense to anyone, even
992 people who have no idea about any of the things the
993 package deals with.<footnote>
994 The blurb that comes with a program in its
995 announcements and/or <prgn>README</prgn> files is
996 rarely suitable for use in a description. It is
997 usually aimed at people who are already in the
998 community where the package is used.
1007 <heading>Dependencies</heading>
1010 Every package must specify the dependency information
1011 about other packages that are required for the first to
1016 For example, a dependency entry must be provided for any
1017 shared libraries required by a dynamically-linked executable
1018 binary in a package.
1022 Packages are not required to declare any dependencies they
1023 have on other packages which are marked <tt>Essential</tt>
1024 (see below), and should not do so unless they depend on a
1025 particular version of that package.<footnote>
1027 Essential is needed in part to avoid unresolvable dependency
1028 loops on upgrade. If packages add unnecessary dependencies
1029 on packages in this set, the chances that there
1030 <strong>will</strong> be an unresolvable dependency loop
1031 caused by forcing these Essential packages to be configured
1032 first before they need to be is greatly increased. It also
1033 increases the chances that frontends will be unable to
1034 <strong>calculate</strong> an upgrade path, even if one
1038 Also, functionality is rarely ever removed from the
1039 Essential set, but <em>packages</em> have been removed from
1040 the Essential set when the functionality moved to a
1041 different package. So depending on these packages <em>just
1042 in case</em> they stop being essential does way more harm
1049 Sometimes, a package requires another package to be installed
1050 <em>and</em> configured before it can be installed. In this
1051 case, you must specify a <tt>Pre-Depends</tt> entry for
1056 You should not specify a <tt>Pre-Depends</tt> entry for a
1057 package before this has been discussed on the
1058 <tt>debian-devel</tt> mailing list and a consensus about
1059 doing that has been reached.
1063 The format of the package interrelationship control fields is
1064 described in <ref id="relationships">.
1068 <sect id="virtual_pkg">
1069 <heading>Virtual packages</heading>
1072 Sometimes, there are several packages which offer
1073 more-or-less the same functionality. In this case, it's
1074 useful to define a <em>virtual package</em> whose name
1075 describes that common functionality. (The virtual
1076 packages only exist logically, not physically; that's why
1077 they are called <em>virtual</em>.) The packages with this
1078 particular function will then <em>provide</em> the virtual
1079 package. Thus, any other package requiring that function
1080 can simply depend on the virtual package without having to
1081 specify all possible packages individually.
1085 All packages should use virtual package names where
1086 appropriate, and arrange to create new ones if necessary.
1087 They should not use virtual package names (except privately,
1088 amongst a cooperating group of packages) unless they have
1089 been agreed upon and appear in the list of virtual package
1090 names. (See also <ref id="virtual">)
1094 The latest version of the authoritative list of virtual
1095 package names can be found in the <tt>debian-policy</tt> package.
1096 It is also available from the Debian web mirrors at
1097 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1098 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1102 The procedure for updating the list is described in the preface
1109 <heading>Base system</heading>
1112 The <tt>base system</tt> is a minimum subset of the Debian
1113 GNU/Linux system that is installed before everything else
1114 on a new system. Only very few packages are allowed to form
1115 part of the base system, in order to keep the required disk
1120 The base system consists of all those packages with priority
1121 <tt>required</tt> or <tt>important</tt>. Many of them will
1122 be tagged <tt>essential</tt> (see below).
1127 <heading>Essential packages</heading>
1130 Essential is defined as the minimal set of functionality that
1131 must be available and usable on the system at all times, even
1132 when packages are in an unconfigured (but unpacked) state.
1133 Packages are tagged <tt>essential</tt> for a system using the
1134 <tt>Essential</tt> control file field. The format of the
1135 <tt>Essential</tt> control field is described in <ref
1140 Since these packages cannot be easily removed (one has to
1141 specify an extra <em>force option</em> to
1142 <prgn>dpkg</prgn> to do so), this flag must not be used
1143 unless absolutely necessary. A shared library package
1144 must not be tagged <tt>essential</tt>; dependencies will
1145 prevent its premature removal, and we need to be able to
1146 remove it when it has been superseded.
1150 Since dpkg will not prevent upgrading of other packages
1151 while an <tt>essential</tt> package is in an unconfigured
1152 state, all <tt>essential</tt> packages must supply all of
1153 their core functionality even when unconfigured. If the
1154 package cannot satisfy this requirement it must not be
1155 tagged as essential, and any packages depending on this
1156 package must instead have explicit dependency fields as
1161 Maintainers should take great care in adding any programs,
1162 interfaces, or functionality to <tt>essential</tt> packages.
1163 Packages may assume that functionality provided by
1164 <tt>essential</tt> packages is always available without
1165 declaring explicit dependencies, which means that removing
1166 functionality from the Essential set is very difficult and is
1167 almost never done. Any capability added to an
1168 <tt>essential</tt> package therefore creates an obligation to
1169 support that capability as part of the Essential set in
1174 You must not tag any packages <tt>essential</tt> before
1175 this has been discussed on the <tt>debian-devel</tt>
1176 mailing list and a consensus about doing that has been
1181 <sect id="maintscripts">
1182 <heading>Maintainer Scripts</heading>
1185 The package installation scripts should avoid producing
1186 output which is unnecessary for the user to see and
1187 should rely on <prgn>dpkg</prgn> to stave off boredom on
1188 the part of a user installing many packages. This means,
1189 amongst other things, using the <tt>--quiet</tt> option on
1190 <prgn>install-info</prgn>.
1194 Errors which occur during the execution of an installation
1195 script must be checked and the installation must not
1196 continue after an error.
1200 Note that in general <ref id="scripts"> applies to package
1201 maintainer scripts, too.
1205 You should not use <prgn>dpkg-divert</prgn> on a file
1206 belonging to another package without consulting the
1207 maintainer of that package first.
1211 All packages which supply an instance of a common command
1212 name (or, in general, filename) should generally use
1213 <prgn>update-alternatives</prgn>, so that they may be
1214 installed together. If <prgn>update-alternatives</prgn>
1215 is not used, then each package must use
1216 <tt>Conflicts</tt> to ensure that other packages are
1217 de-installed. (In this case, it may be appropriate to
1218 specify a conflict against earlier versions of something
1219 that previously did not use
1220 <prgn>update-alternatives</prgn>; this is an exception to
1221 the usual rule that versioned conflicts should be
1225 <sect1 id="maintscriptprompt">
1226 <heading>Prompting in maintainer scripts</heading>
1228 Package maintainer scripts may prompt the user if
1229 necessary. Prompting must be done by communicating
1230 through a program, such as <prgn>debconf</prgn>, which
1231 conforms to the Debian Configuration Management
1232 Specification, version 2 or higher.
1236 Packages which are essential, or which are dependencies of
1237 essential packages, may fall back on another prompting method
1238 if no such interface is available when they are executed.
1242 The Debian Configuration Management Specification is included
1243 in the <file>debconf_specification</file> files in the
1244 <package>debian-policy</package> package.
1245 It is also available from the Debian web mirrors at
1246 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1247 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1251 Packages which use the Debian Configuration Management
1252 Specification may contain an additional
1253 <prgn>config</prgn> script and a <tt>templates</tt>
1254 file in their control archive<footnote>
1255 The control.tar.gz inside the .deb.
1256 See <manref name="deb" section="5">.
1258 The <prgn>config</prgn> script might be run before the
1259 <prgn>preinst</prgn> script, and before the package is unpacked
1260 or any of its dependencies or pre-dependencies are satisfied.
1261 Therefore it must work using only the tools present in
1262 <em>essential</em> packages.<footnote>
1263 <package>Debconf</package> or another tool that
1264 implements the Debian Configuration Management
1265 Specification will also be installed, and any
1266 versioned dependencies on it will be satisfied
1267 before preconfiguration begins.
1272 Packages which use the Debian Configuration Management
1273 Specification must allow for translation of their user-visible
1274 messages by using a gettext-based system such as the one
1275 provided by the <package>po-debconf</package> package.
1279 Packages should try to minimize the amount of prompting
1280 they need to do, and they should ensure that the user
1281 will only ever be asked each question once. This means
1282 that packages should try to use appropriate shared
1283 configuration files (such as <file>/etc/papersize</file> and
1284 <file>/etc/news/server</file>), and shared
1285 <package>debconf</package> variables rather than each
1286 prompting for their own list of required pieces of
1291 It also means that an upgrade should not ask the same
1292 questions again, unless the user has used
1293 <tt>dpkg --purge</tt> to remove the package's configuration.
1294 The answers to configuration questions should be stored in an
1295 appropriate place in <file>/etc</file> so that the user can
1296 modify them, and how this has been done should be
1301 If a package has a vitally important piece of
1302 information to pass to the user (such as "don't run me
1303 as I am, you must edit the following configuration files
1304 first or you risk your system emitting badly-formatted
1305 messages"), it should display this in the
1306 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1307 prompt the user to hit return to acknowledge the
1308 message. Copyright messages do not count as vitally
1309 important (they belong in
1310 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1311 neither do instructions on how to use a program (these
1312 should be in on-line documentation, where all the users
1317 Any necessary prompting should almost always be confined
1318 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1319 script. If it is done in the <prgn>postinst</prgn>, it
1320 should be protected with a conditional so that
1321 unnecessary prompting doesn't happen if a package's
1322 installation fails and the <prgn>postinst</prgn> is
1323 called with <tt>abort-upgrade</tt>,
1324 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1334 <heading>Source packages</heading>
1336 <sect id="standardsversion">
1337 <heading>Standards conformance</heading>
1340 Source packages should specify the most recent version number
1341 of this policy document with which your package complied
1342 when it was last updated.
1346 This information may be used to file bug reports
1347 automatically if your package becomes too much out of date.
1351 The version is specified in the <tt>Standards-Version</tt>
1353 The format of the <tt>Standards-Version</tt> field is
1354 described in <ref id="f-Standards-Version">.
1358 You should regularly, and especially if your package has
1359 become out of date, check for the newest Policy Manual
1360 available and update your package, if necessary. When your
1361 package complies with the new standards you should update the
1362 <tt>Standards-Version</tt> source package field and
1363 release it.<footnote>
1364 See the file <file>upgrading-checklist</file> for
1365 information about policy which has changed between
1366 different versions of this document.
1372 <sect id="pkg-relations">
1373 <heading>Package relationships</heading>
1376 Source packages should specify which binary packages they
1377 require to be installed or not to be installed in order to
1378 build correctly. For example, if building a package
1379 requires a certain compiler, then the compiler should be
1380 specified as a build-time dependency.
1384 It is not necessary to explicitly specify build-time
1385 relationships on a minimal set of packages that are always
1386 needed to compile, link and put in a Debian package a
1387 standard "Hello World!" program written in C or C++. The
1388 required packages are called <em>build-essential</em>, and
1389 an informational list can be found in
1390 <file>/usr/share/doc/build-essential/list</file> (which is
1391 contained in the <tt>build-essential</tt>
1394 <list compact="compact">
1396 This allows maintaining the list separately
1397 from the policy documents (the list does not
1398 need the kind of control that the policy
1402 Having a separate package allows one to install
1403 the build-essential packages on a machine, as
1404 well as allowing other packages such as tasks to
1405 require installation of the build-essential
1406 packages using the depends relation.
1409 The separate package allows bug reports against
1410 the list to be categorized separately from
1411 the policy management process in the BTS.
1418 When specifying the set of build-time dependencies, one
1419 should list only those packages explicitly required by the
1420 build. It is not necessary to list packages which are
1421 required merely because some other package in the list of
1422 build-time dependencies depends on them.<footnote>
1423 The reason for this is that dependencies change, and
1424 you should list all those packages, and <em>only</em>
1425 those packages that <em>you</em> need directly. What
1426 others need is their business. For example, if you
1427 only link against <file>libimlib</file>, you will need to
1428 build-depend on <package>libimlib2-dev</package> but
1429 not against any <tt>libjpeg*</tt> packages, even
1430 though <tt>libimlib2-dev</tt> currently depends on
1431 them: installation of <package>libimlib2-dev</package>
1432 will automatically ensure that all of its run-time
1433 dependencies are satisfied.
1438 If build-time dependencies are specified, it must be
1439 possible to build the package and produce working binaries
1440 on a system with only essential and build-essential
1441 packages installed and also those required to satisfy the
1442 build-time relationships (including any implied
1443 relationships). In particular, this means that version
1444 clauses should be used rigorously in build-time
1445 relationships so that one cannot produce bad or
1446 inconsistently configured packages when the relationships
1447 are properly satisfied.
1451 <ref id="relationships"> explains the technical details.
1456 <heading>Changes to the upstream sources</heading>
1459 If changes to the source code are made that are not
1460 specific to the needs of the Debian system, they should be
1461 sent to the upstream authors in whatever form they prefer
1462 so as to be included in the upstream version of the
1467 If you need to configure the package differently for
1468 Debian or for Linux, and the upstream source doesn't
1469 provide a way to do so, you should add such configuration
1470 facilities (for example, a new <prgn>autoconf</prgn> test
1471 or <tt>#define</tt>) and send the patch to the upstream
1472 authors, with the default set to the way they originally
1473 had it. You can then easily override the default in your
1474 <file>debian/rules</file> or wherever is appropriate.
1478 You should make sure that the <prgn>configure</prgn> utility
1479 detects the correct architecture specification string
1480 (refer to <ref id="arch-spec"> for details).
1484 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1485 <prgn>configure</prgn> scripts are used, you should edit the
1486 <file>.in</file> files rather than editing the
1487 <prgn>Makefile</prgn> directly. This allows the user to
1488 reconfigure the package if necessary. You should
1489 <em>not</em> configure the package and edit the generated
1490 <prgn>Makefile</prgn>! This makes it impossible for someone
1491 else to later reconfigure the package without losing the
1497 <sect id="dpkgchangelog">
1498 <heading>Debian changelog: <file>debian/changelog</file></heading>
1501 Changes in the Debian version of the package should be
1502 briefly explained in the Debian changelog file
1503 <file>debian/changelog</file>.<footnote>
1505 Mistakes in changelogs are usually best rectified by
1506 making a new changelog entry rather than "rewriting
1507 history" by editing old changelog entries.
1510 This includes modifications
1511 made in the Debian package compared to the upstream one
1512 as well as other changes and updates to the package.
1514 Although there is nothing stopping an author who is also
1515 the Debian maintainer from using this changelog for all
1516 their changes, it will have to be renamed if the Debian
1517 and upstream maintainers become different people. In such
1518 a case, however, it might be better to maintain the package
1519 as a non-native package.
1524 The format of the <file>debian/changelog</file> allows the
1525 package building tools to discover which version of the package
1526 is being built and find out other release-specific information.
1530 That format is a series of entries like this:
1532 <example compact="compact">
1533 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1535 [optional blank line(s), stripped]
1537 * <var>change details</var>
1538 <var>more change details</var>
1540 [blank line(s), included in output of dpkg-parsechangelog]
1542 * <var>even more change details</var>
1544 [optional blank line(s), stripped]
1546 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1551 <var>package</var> and <var>version</var> are the source
1552 package name and version number.
1556 <var>distribution(s)</var> lists the distributions where
1557 this version should be installed when it is uploaded - it
1558 is copied to the <tt>Distribution</tt> field in the
1559 <file>.changes</file> file. See <ref id="f-Distribution">.
1563 <var>urgency</var> is the value for the <tt>Urgency</tt>
1564 field in the <file>.changes</file> file for the upload
1565 (see <ref id="f-Urgency">). It is not possible to specify
1566 an urgency containing commas; commas are used to separate
1567 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1568 <prgn>dpkg</prgn> changelog format (though there is
1569 currently only one useful <var>keyword</var>,
1574 The change details may in fact be any series of lines
1575 starting with at least two spaces, but conventionally each
1576 change starts with an asterisk and a separating space and
1577 continuation lines are indented so as to bring them in
1578 line with the start of the text above. Blank lines may be
1579 used here to separate groups of changes, if desired.
1583 If this upload resolves bugs recorded in the Bug Tracking
1584 System (BTS), they may be automatically closed on the
1585 inclusion of this package into the Debian archive by
1586 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1587 in the change details.<footnote>
1588 To be precise, the string should match the following
1589 Perl regular expression:
1591 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1593 Then all of the bug numbers listed will be closed by the
1594 archive maintenance script (<prgn>katie</prgn>) using the
1595 <var>version</var> of the changelog entry.
1597 This information is conveyed via the <tt>Closes</tt> field
1598 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1602 The maintainer name and email address used in the changelog
1603 should be the details of the person uploading <em>this</em>
1604 version. They are <em>not</em> necessarily those of the
1605 usual package maintainer. The information here will be
1606 copied to the <tt>Changed-By</tt> field in the
1607 <tt>.changes</tt> file (see <ref id="f-Changed-By">),
1608 and then later used to send an acknowledgement when the
1609 upload has been installed.
1613 The <var>date</var> must be in RFC822 format<footnote>
1614 This is generated by <tt>date -R</tt>.
1615 </footnote>; it must include the time zone specified
1616 numerically, with the time zone name or abbreviation
1617 optionally present as a comment in parentheses.
1621 The first "title" line with the package name must start
1622 at the left hand margin. The "trailer" line with the
1623 maintainer and date details must be preceded by exactly
1624 one space. The maintainer details and the date must be
1625 separated by exactly two spaces.
1629 The entire changelog must be encoded in UTF-8.
1633 For more information on placement of the changelog files
1634 within binary packages, please see <ref id="changelogs">.
1638 <sect id="dpkgcopyright">
1639 <heading>Copyright: <file>debian/copyright</file></heading>
1641 Every package must be accompanied by a verbatim copy of its
1642 copyright information and distribution license in the file
1643 <file>/usr/share/doc/<var>package</var>/copyright</file>
1644 (see <ref id="copyrightfile"> for further details). Also see
1645 <ref id="pkgcopyright"> for further considerations related
1646 to copyrights for packages.
1650 <heading>Error trapping in makefiles</heading>
1653 When <prgn>make</prgn> invokes a command in a makefile
1654 (including your package's upstream makefiles and
1655 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1656 means that <prgn>sh</prgn>'s usual bad error handling
1657 properties apply: if you include a miniature script as one
1658 of the commands in your makefile you'll find that if you
1659 don't do anything about it then errors are not detected
1660 and <prgn>make</prgn> will blithely continue after
1665 Every time you put more than one shell command (this
1666 includes using a loop) in a makefile command you
1667 must make sure that errors are trapped. For
1668 simple compound commands, such as changing directory and
1669 then running a program, using <tt>&&</tt> rather
1670 than semicolon as a command separator is sufficient. For
1671 more complex commands including most loops and
1672 conditionals you should include a separate <tt>set -e</tt>
1673 command at the start of every makefile command that's
1674 actually one of these miniature shell scripts.
1678 <sect id="timestamps">
1679 <heading>Time Stamps</heading>
1681 Maintainers should preserve the modification times of the
1682 upstream source files in a package, as far as is reasonably
1684 The rationale is that there is some information conveyed
1685 by knowing the age of the file, for example, you could
1686 recognize that some documentation is very old by looking
1687 at the modification time, so it would be nice if the
1688 modification time of the upstream source would be
1694 <sect id="restrictions">
1695 <heading>Restrictions on objects in source packages</heading>
1698 The source package may not contain any hard links<footnote>
1700 This is not currently detected when building source
1701 packages, but only when extracting
1705 Hard links may be permitted at some point in the
1706 future, but would require a fair amount of
1709 </footnote>, device special files, sockets or setuid or
1710 setgid files.<footnote>
1711 Setgid directories are allowed.
1716 <sect id="debianrules">
1717 <heading>Main building script: <file>debian/rules</file></heading>
1720 This file must be an executable makefile, and contains the
1721 package-specific recipes for compiling the package and
1722 building binary package(s) from the source.
1726 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1727 so that it can be invoked by saying its name rather than
1728 invoking <prgn>make</prgn> explicitly. That is, invoking
1729 either of <tt>make -f debian/rules <em>args...</em></tt>
1730 or <tt>./debian/rules <em>args...</em></tt> must result in
1735 Since an interactive <file>debian/rules</file> script makes it
1736 impossible to auto-compile that package and also makes it
1737 hard for other people to reproduce the same binary
1738 package, all <em>required targets</em> must be
1739 non-interactive. At a minimum, required targets are the
1740 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1741 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1742 <em>binary-indep</em>, and <em>build</em>. It also follows
1743 that any target that these targets depend on must also be
1748 The targets are as follows (required unless stated otherwise):
1750 <tag><tt>build</tt></tag>
1753 The <tt>build</tt> target should perform all the
1754 configuration and compilation of the package.
1755 If a package has an interactive pre-build
1756 configuration routine, the Debianized source package
1757 must either be built after this has taken place (so
1758 that the binary package can be built without rerunning
1759 the configuration) or the configuration routine
1760 modified to become non-interactive. (The latter is
1761 preferable if there are architecture-specific features
1762 detected by the configuration routine.)
1766 For some packages, notably ones where the same
1767 source tree is compiled in different ways to produce
1768 two binary packages, the <tt>build</tt> target
1769 does not make much sense. For these packages it is
1770 good enough to provide two (or more) targets
1771 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1772 for each of the ways of building the package, and a
1773 <tt>build</tt> target that does nothing. The
1774 <tt>binary</tt> target will have to build the
1775 package in each of the possible ways and make the
1776 binary package out of each.
1780 The <tt>build</tt> target must not do anything
1781 that might require root privilege.
1785 The <tt>build</tt> target may need to run the
1786 <tt>clean</tt> target first - see below.
1790 When a package has a configuration and build routine
1791 which takes a long time, or when the makefiles are
1792 poorly designed, or when <tt>build</tt> needs to
1793 run <tt>clean</tt> first, it is a good idea to
1794 <tt>touch build</tt> when the build process is
1795 complete. This will ensure that if <tt>debian/rules
1796 build</tt> is run again it will not rebuild the whole
1798 Another common way to do this is for <tt>build</tt>
1799 to depend on <prgn>build-stamp</prgn> and to do
1800 nothing else, and for the <prgn>build-stamp</prgn>
1801 target to do the building and to <tt>touch
1802 build-stamp</tt> on completion. This is
1803 especially useful if the build routine creates a
1804 file or directory called <tt>build</tt>; in such a
1805 case, <tt>build</tt> will need to be listed as
1806 a phony target (i.e., as a dependency of the
1807 <tt>.PHONY</tt> target). See the documentation of
1808 <prgn>make</prgn> for more information on phony
1814 <tag><tt>build-arch</tt> (optional),
1815 <tt>build-indep</tt> (optional)
1819 A package may also provide both of the targets
1820 <tt>build-arch</tt> and <tt>build-indep</tt>.
1821 The <tt>build-arch</tt> target, if provided, should
1822 perform all the configuration and compilation required
1823 for producing all architecture-dependant binary packages
1824 (those packages for which the body of the
1825 <tt>Architecture</tt> field in <tt>debian/control</tt>
1826 is not <tt>all</tt>).
1827 Similarly, the <tt>build-indep</tt> target, if
1828 provided, should perform all the configuration and
1829 compilation required for producing all
1830 architecture-independent binary packages
1831 (those packages for which the body of the
1832 <tt>Architecture</tt> field in <tt>debian/control</tt>
1834 The <tt>build</tt> target should depend on those of the
1835 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1836 are provided in the rules file.
1840 If one or both of the targets <tt>build-arch</tt> and
1841 <tt>build-indep</tt> are not provided, then invoking
1842 <file>debian/rules</file> with one of the not-provided
1843 targets as arguments should produce a exit status code
1844 of 2. Usually this is provided automatically by make
1845 if the target is missing.
1849 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1850 must not do anything that might require root privilege.
1854 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1855 <tt>binary-indep</tt>
1859 The <tt>binary</tt> target must be all that is
1860 necessary for the user to build the binary package(s)
1861 produced from this source package. It is
1862 split into two parts: <prgn>binary-arch</prgn> builds
1863 the binary packages which are specific to a particular
1864 architecture, and <tt>binary-indep</tt> builds
1865 those which are not.
1868 <tt>binary</tt> may be (and commonly is) a target with
1869 no commands which simply depends on
1870 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1873 Both <tt>binary-*</tt> targets should depend on the
1874 <tt>build</tt> target, or on the appropriate
1875 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1876 provided, so that the package is built if it has not
1877 been already. It should then create the relevant
1878 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1879 make their control files and <prgn>dpkg-deb</prgn> to
1880 build them and place them in the parent of the top
1885 Both the <tt>binary-arch</tt> and
1886 <tt>binary-indep</tt> targets <em>must</em> exist.
1887 If one of them has nothing to do (which will always be
1888 the case if the source generates only a single binary
1889 package, whether architecture-dependent or not), it
1890 must still exist and must always succeed.
1894 The <tt>binary</tt> targets must be invoked as
1896 The <prgn>fakeroot</prgn> package often allows one
1897 to build a package correctly even without being
1903 <tag><tt>clean</tt></tag>
1906 This must undo any effects that the <tt>build</tt>
1907 and <tt>binary</tt> targets may have had, except
1908 that it should leave alone any output files created in
1909 the parent directory by a run of a <tt>binary</tt>
1914 If a <tt>build</tt> file is touched at the end of
1915 the <tt>build</tt> target, as suggested above, it
1916 should be removed as the first action that
1917 <tt>clean</tt> performs, so that running
1918 <tt>build</tt> again after an interrupted
1919 <tt>clean</tt> doesn't think that everything is
1924 The <tt>clean</tt> target may need to be
1925 invoked as root if <tt>binary</tt> has been
1926 invoked since the last <tt>clean</tt>, or if
1927 <tt>build</tt> has been invoked as root (since
1928 <tt>build</tt> may create directories, for
1933 <tag><tt>get-orig-source</tt> (optional)</tag>
1936 This target fetches the most recent version of the
1937 original source package from a canonical archive site
1938 (via FTP or WWW, for example), does any necessary
1939 rearrangement to turn it into the original source
1940 tar file format described below, and leaves it in the
1945 This target may be invoked in any directory, and
1946 should take care to clean up any temporary files it
1951 This target is optional, but providing it if
1952 possible is a good idea.
1956 <tag><tt>patch</tt> (optional)</tag>
1959 This target performs whatever additional actions are
1960 required to make the source ready for editing (unpacking
1961 additional upstream archives, applying patches, etc.).
1962 It is recommended to be implemented for any package where
1963 <tt>dpkg-source -x</tt> does not result in source ready
1964 for additional modification. See
1965 <ref id="readmesource">.
1971 The <tt>build</tt>, <tt>binary</tt> and
1972 <tt>clean</tt> targets must be invoked with the current
1973 directory being the package's top-level directory.
1978 Additional targets may exist in <file>debian/rules</file>,
1979 either as published or undocumented interfaces or for the
1980 package's internal use.
1984 The architectures we build on and build for are determined
1985 by <prgn>make</prgn> variables using the utility
1986 <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
1987 You can determine the
1988 Debian architecture and the GNU style architecture
1989 specification string for the build machine (the machine type
1990 we are building on) as well as for the host machine (the
1991 machine type we are building for). Here is a list of
1992 supported <prgn>make</prgn> variables:
1993 <list compact="compact">
1995 <tt>DEB_*_ARCH</tt> (the Debian architecture)
1998 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2001 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2004 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2005 specification string)
2008 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2009 <tt>DEB_*_GNU_TYPE</tt>)
2012 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2013 <tt>DEB_*_GNU_TYPE</tt>)
2015 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2016 the build machine or <tt>HOST</tt> for specification of the
2021 Backward compatibility can be provided in the rules file
2022 by setting the needed variables to suitable default
2023 values; please refer to the documentation of
2024 <prgn>dpkg-architecture</prgn> for details.
2028 It is important to understand that the <tt>DEB_*_ARCH</tt>
2029 string only determines which Debian architecture we are
2030 building on or for. It should not be used to get the CPU
2031 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2032 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2033 GNU style variables should generally only be used with upstream
2037 <sect1 id="debianrules-options">
2038 <heading><file>debian/rules</file> and
2039 <tt>DEB_BUILD_OPTIONS</tt></heading>
2042 Supporting the standardized environment variable
2043 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2044 contain several flags to change how a package is compiled and
2045 built. Each flag must be in the form <var>flag</var> or
2046 <var>flag</var>=<var>options</var>. If multiple flags are
2047 given, they must be separated by whitespace.<footnote>
2048 Some packages support any delimiter, but whitespace is the
2049 easiest to parse inside a makefile and avoids ambiguity with
2050 flag values that contain commas.
2052 <var>flag</var> must start with a lowercase letter
2053 (<tt>a-z</tt>) and consist only of lowercase letters,
2054 numbers (<tt>0-9</tt>), and the characters
2055 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2056 <var>options</var> must not contain whitespace. The same
2057 tag should not be given multiple times with conflicting
2058 values. Package maintainers may assume that
2059 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2063 The meaning of the following tags has been standardized:
2067 This tag says to not run any build-time test suite
2068 provided by the package.
2072 The presence of this tag means that the package should
2073 be compiled with a minimum of optimization. For C
2074 programs, it is best to add <tt>-O0</tt> to
2075 <tt>CFLAGS</tt> (although this is usually the default).
2076 Some programs might fail to build or run at this level
2077 of optimization; it may be necessary to use
2078 <tt>-O1</tt>, for example.
2082 This tag means that the debugging symbols should not be
2083 stripped from the binary during installation, so that
2084 debugging information may be included in the package.
2086 <tag>parallel=n</tag>
2088 This tag means that the package should be built using up
2089 to <tt>n</tt> parallel processes if the package build
2090 system supports this.<footnote>
2091 Packages built with <tt>make</tt> can often implement
2092 this by passing the <tt>-j</tt><var>n</var> option to
2095 If the package build system does not support parallel
2096 builds, this string must be ignored. If the package
2097 build system only supports a lower level of concurrency
2098 than <var>n</var>, the package should be built using as
2099 many parallel processes as the package build system
2100 supports. It is up to the package maintainer to decide
2101 whether the package build times are long enough and the
2102 package build system is robust enough to make supporting
2103 parallel builds worthwhile.
2109 Unknown flags must be ignored by <file>debian/rules</file>.
2113 The following makefile snippet is an example of how one may
2114 implement the build options; you will probably have to
2115 massage this example in order to make it work for your
2117 <example compact="compact">
2120 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2121 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2122 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2123 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2125 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2130 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2131 INSTALL_PROGRAM += -s
2133 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2134 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2135 MAKEFLAGS += -j$(NUMJOBS)
2140 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2141 # Code to run the package test suite.
2148 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2149 <sect id="substvars">
2150 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2153 When <prgn>dpkg-gencontrol</prgn>,
2154 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
2155 generate control files they perform variable substitutions
2156 on their output just before writing it. Variable
2157 substitutions have the form <tt>${<var>variable</var>}</tt>.
2158 The optional file <file>debian/substvars</file> contains
2159 variable substitutions to be used; variables can also be set
2160 directly from <file>debian/rules</file> using the <tt>-V</tt>
2161 option to the source packaging commands, and certain
2162 predefined variables are also available.
2166 The <file>debian/substvars</file> file is usually generated and
2167 modified dynamically by <file>debian/rules</file> targets, in
2168 which case it must be removed by the <tt>clean</tt> target.
2172 See <manref name="deb-substvars" section="5"> for full
2173 details about source variable substitutions, including the
2174 format of <file>debian/substvars</file>.</p>
2177 <sect id="debianwatch">
2178 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2181 This is an optional, recommended control file for the
2182 <tt>uscan</tt> utility which defines how to automatically
2183 scan ftp or http sites for newly available updates of the
2184 package. This is used by <url id="
2185 http://dehs.alioth.debian.org/"> and other Debian QA tools
2186 to help with quality control and maintenance of the
2187 distribution as a whole.
2192 <sect id="debianfiles">
2193 <heading>Generated files list: <file>debian/files</file></heading>
2196 This file is not a permanent part of the source tree; it
2197 is used while building packages to record which files are
2198 being generated. <prgn>dpkg-genchanges</prgn> uses it
2199 when it generates a <file>.changes</file> file.
2203 It should not exist in a shipped source package, and so it
2204 (and any backup files or temporary files such as
2205 <file>files.new</file><footnote>
2206 <file>files.new</file> is used as a temporary file by
2207 <prgn>dpkg-gencontrol</prgn> and
2208 <prgn>dpkg-distaddfile</prgn> - they write a new
2209 version of <tt>files</tt> here before renaming it,
2210 to avoid leaving a corrupted copy if an error
2212 </footnote>) should be removed by the
2213 <tt>clean</tt> target. It may also be wise to
2214 ensure a fresh start by emptying or removing it at the
2215 start of the <tt>binary</tt> target.
2219 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2220 package, it adds an entry to <file>debian/files</file> for the
2221 <file>.deb</file> file that will be created when <tt>dpkg-deb
2222 --build</tt> is run for that binary package. So for most
2223 packages all that needs to be done with this file is to
2224 delete it in the <tt>clean</tt> target.
2228 If a package upload includes files besides the source
2229 package and any binary packages whose control files were
2230 made with <prgn>dpkg-gencontrol</prgn> then they should be
2231 placed in the parent of the package's top-level directory
2232 and <prgn>dpkg-distaddfile</prgn> should be called to add
2233 the file to the list in <file>debian/files</file>.</p>
2236 <sect id="embeddedfiles">
2237 <heading>Convenience copies of code</heading>
2240 Some software packages include in their distribution convenience
2241 copies of code from other software packages, generally so that
2242 users compiling from source don't have to download multiple
2243 packages. Debian packages should not make use of these
2244 convenience copies unless the included package is explicitly
2245 intended to be used in this way.<footnote>
2246 For example, parts of the GNU build system work like this.
2248 If the included code is already in the Debian archive in the
2249 form of a library, the Debian packaging should ensure that
2250 binary packages reference the libraries already in Debian and
2251 the convenience copy is not used. If the included code is not
2252 already in Debian, it should be packaged separately as a
2253 prerequisite if possible.
2255 Having multiple copies of the same code in Debian is
2256 inefficient, often creates either static linking or shared
2257 library conflicts, and, most importantly, increases the
2258 difficulty of handling security vulnerabilities in the
2264 <sect id="readmesource">
2265 <heading>Source package handling:
2266 <file>debian/README.source</file></heading>
2269 If running <prgn>dpkg-source -x</prgn> on a source package
2270 doesn't produce the source of the package, ready for editing,
2271 and allow one to make changes and run
2272 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2273 without taking any additional steps, creating a
2274 <file>debian/README.source</file> documentation file is
2275 recommended. This file should explain how to do all of the
2278 <item>Generate the fully patched source, in a form ready for
2279 editing, that would be built to create Debian
2280 packages. Doing this with a <tt>patch</tt> target in
2281 <file>debian/rules</file> is recommended; see
2282 <ref id="debianrules">.</item>
2283 <item>Modify the source and save those modifications so that
2284 they will be applied when building the package.</item>
2285 <item>Remove source modifications that are currently being
2286 applied when building the package.</item>
2287 <item>Optionally, document what steps are necessary to
2288 upgrade the Debian source package to a new upstream version,
2289 if applicable.</item>
2291 This explanation should include specific commands and mention
2292 any additional required Debian packages. It should not assume
2293 familiarity with any specific Debian packaging system or patch
2298 This explanation may refer to a documentation file installed by
2299 one of the package's build dependencies provided that the
2300 referenced documentation clearly explains these tasks and is not
2301 a general reference manual.
2305 <file>debian/README.source</file> may also include any other
2306 information that would be helpful to someone modifying the
2307 source package. Even if the package doesn't fit the above
2308 description, maintainers are encouraged to document in a
2309 <file>debian/README.source</file> file any source package with a
2310 particularly complex or unintuitive source layout or build
2311 system (for example, a package that builds the same source
2312 multiple times to generate different binary packages).
2318 <chapt id="controlfields">
2319 <heading>Control files and their fields</heading>
2322 The package management system manipulates data represented in
2323 a common format, known as <em>control data</em>, stored in
2324 <em>control files</em>.
2325 Control files are used for source packages, binary packages and
2326 the <file>.changes</file> files which control the installation
2327 of uploaded files<footnote>
2328 <prgn>dpkg</prgn>'s internal databases are in a similar
2333 <sect id="controlsyntax">
2334 <heading>Syntax of control files</heading>
2337 A control file consists of one or more paragraphs of
2339 The paragraphs are also sometimes referred to as stanzas.
2341 The paragraphs are separated by blank lines. Some control
2342 files allow only one paragraph; others allow several, in
2343 which case each paragraph usually refers to a different
2344 package. (For example, in source packages, the first
2345 paragraph refers to the source package, and later paragraphs
2346 refer to binary packages generated from the source.)
2350 Each paragraph consists of a series of data fields; each
2351 field consists of the field name, followed by a colon and
2352 then the data/value associated with that field. It ends at
2353 the end of the (logical) line. Horizontal whitespace
2354 (spaces and tabs) may occur immediately before or after the
2355 value and is ignored there; it is conventional to put a
2356 single space after the colon. For example, a field might
2358 <example compact="compact">
2361 the field name is <tt>Package</tt> and the field value
2366 Many fields' values may span several lines; in this case
2367 each continuation line must start with a space or a tab.
2368 Any trailing spaces or tabs at the end of individual
2369 lines of a field value are ignored.
2373 In fields where it is specified that lines may not wrap,
2374 only a single line of data is allowed and whitespace is not
2375 significant in a field body. Whitespace must not appear
2376 inside names (of packages, architectures, files or anything
2377 else) or version numbers, or between the characters of
2378 multi-character version relationships.
2382 Field names are not case-sensitive, but it is usual to
2383 capitalize the field names using mixed case as shown below.
2384 Field values are case-sensitive unless the description of the
2385 field says otherwise.
2389 Blank lines, or lines consisting only of spaces and tabs,
2390 are not allowed within field values or between fields - that
2391 would mean a new paragraph.
2395 All control files must be encoded in UTF-8.
2399 <sect id="sourcecontrolfiles">
2400 <heading>Source package control files -- <file>debian/control</file></heading>
2403 The <file>debian/control</file> file contains the most vital
2404 (and version-independent) information about the source package
2405 and about the binary packages it creates.
2409 The first paragraph of the control file contains information about
2410 the source package in general. The subsequent sets each describe a
2411 binary package that the source tree builds.
2415 The fields in the general paragraph (the first one, for the source
2418 <list compact="compact">
2419 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2420 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2421 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2422 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2423 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2424 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2425 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2426 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2431 The fields in the binary package paragraphs are:
2433 <list compact="compact">
2434 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2435 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2436 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2437 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2438 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2439 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2440 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2441 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2446 The syntax and semantics of the fields are described below.
2452 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2453 generate control files for binary packages (see below), by
2454 <prgn>dpkg-genchanges</prgn> to generate the
2455 <tt>.changes</tt> file to accompany the upload, and by
2456 <prgn>dpkg-source</prgn> when it creates the
2457 <file>.dsc</file> source control file as part of a source
2458 archive. Many fields are permitted to span multiple lines in
2459 <file>debian/control</file> but not in any other control
2460 file. These tools are responsible for removing the line
2461 breaks from such fields when using fields from
2462 <file>debian/control</file> to generate other control files.
2466 The fields here may contain variable references - their
2467 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2468 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2469 when they generate output control files.
2470 See <ref id="substvars"> for details.
2474 In addition to the control file syntax described <qref
2475 id="controlsyntax">above</qref>, this file may also contain
2476 comment lines starting with <tt>#</tt> without any preceding
2477 whitespace. All such lines are ignored, even in the middle of
2478 continuation lines for a multiline field, and do not end a
2484 <sect id="binarycontrolfiles">
2485 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2488 The <file>DEBIAN/control</file> file contains the most vital
2489 (and version-dependent) information about a binary package.
2493 The fields in this file are:
2495 <list compact="compact">
2496 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2497 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2498 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2499 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2500 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2501 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2502 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2503 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2504 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2505 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2506 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2507 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2512 <sect id="debiansourcecontrolfiles">
2513 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2516 This file contains a series of fields, identified and
2517 separated just like the fields in the control file of
2518 a binary package. The fields are listed below; their
2519 syntax is described above, in <ref id="pkg-controlfields">.
2521 <list compact="compact">
2522 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2523 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2524 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2525 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2526 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2527 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2528 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2529 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2530 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2531 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2532 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2537 The source package control file is generated by
2538 <prgn>dpkg-source</prgn> when it builds the source
2539 archive, from other files in the source package,
2540 described above. When unpacking, it is checked against
2541 the files and directories in the other parts of the
2547 <sect id="debianchangesfiles">
2548 <heading>Debian changes files -- <file>.changes</file></heading>
2551 The .changes files are used by the Debian archive maintenance
2552 software to process updates to packages. They contain one
2553 paragraph which contains information from the
2554 <tt>debian/control</tt> file and other data about the
2555 source package gathered via <tt>debian/changelog</tt>
2556 and <tt>debian/rules</tt>.
2560 The fields in this file are:
2562 <list compact="compact">
2563 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2564 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2565 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2566 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2567 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2568 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2569 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2570 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2571 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2572 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2573 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2574 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2575 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2576 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2581 <sect id="controlfieldslist">
2582 <heading>List of fields</heading>
2584 <sect1 id="f-Source">
2585 <heading><tt>Source</tt></heading>
2588 This field identifies the source package name.
2592 In <file>debian/control</file> or a <file>.dsc</file> file,
2593 this field must contain only the name of the source package.
2597 In a binary package control file or a <file>.changes</file>
2598 file, the source package name may be followed by a version
2599 number in parentheses<footnote>
2600 It is customary to leave a space after the package name
2601 if a version number is specified.
2603 This version number may be omitted (and is, by
2604 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2605 the <tt>Version</tt> field of the binary package in
2606 question. The field itself may be omitted from a binary
2607 package control file when the source package has the same
2608 name and version as the binary package.
2612 Package names (both source and binary,
2613 see <ref id="f-Package">) must consist only of lower case
2614 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2615 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2616 (<tt>.</tt>). They must be at least two characters long and
2617 must start with an alphanumeric character.
2621 <sect1 id="f-Maintainer">
2622 <heading><tt>Maintainer</tt></heading>
2625 The package maintainer's name and email address. The name
2626 should come first, then the email address inside angle
2627 brackets <tt><></tt> (in RFC822 format).
2631 If the maintainer's name contains a full stop then the
2632 whole field will not work directly as an email address due
2633 to a misfeature in the syntax specified in RFC822; a
2634 program using this field as an address must check for this
2635 and correct the problem if necessary (for example by
2636 putting the name in round brackets and moving it to the
2637 end, and bringing the email address forward).
2641 <sect1 id="f-Uploaders">
2642 <heading><tt>Uploaders</tt></heading>
2645 List of the names and email addresses of co-maintainers of
2646 the package, if any. If the package has other maintainers
2647 beside the one named in the
2648 <qref id="f-Maintainer">Maintainer field</qref>, their
2649 names and email addresses should be listed here. The
2650 format is the same as that of the Maintainer tag, and
2651 multiple entries should be comma separated. Currently,
2652 this field is restricted to a single line of data. This
2653 is an optional field.
2656 Any parser that interprets the Uploaders field in
2657 <file>debian/control</file> must permit it to span multiple
2658 lines. Line breaks in an Uploaders field that spans multiple
2659 lines are not significant and the semantics of the field are
2660 the same as if the line breaks had not been present.
2664 <sect1 id="f-Changed-By">
2665 <heading><tt>Changed-By</tt></heading>
2668 The name and email address of the person who changed the
2669 said package. Usually the name of the maintainer.
2670 All the rules for the Maintainer field apply here, too.
2674 <sect1 id="f-Section">
2675 <heading><tt>Section</tt></heading>
2678 This field specifies an application area into which the package
2679 has been classified. See <ref id="subsections">.
2683 When it appears in the <file>debian/control</file> file,
2684 it gives the value for the subfield of the same name in
2685 the <tt>Files</tt> field of the <file>.changes</file> file.
2686 It also gives the default for the same field in the binary
2691 <sect1 id="f-Priority">
2692 <heading><tt>Priority</tt></heading>
2695 This field represents how important it is that the user
2696 have the package installed. See <ref id="priorities">.
2700 When it appears in the <file>debian/control</file> file,
2701 it gives the value for the subfield of the same name in
2702 the <tt>Files</tt> field of the <file>.changes</file> file.
2703 It also gives the default for the same field in the binary
2708 <sect1 id="f-Package">
2709 <heading><tt>Package</tt></heading>
2712 The name of the binary package.
2716 Binary package names must follow the same syntax and
2717 restrictions as source package names. See <ref id="f-Source">
2722 <sect1 id="f-Architecture">
2723 <heading><tt>Architecture</tt></heading>
2726 Depending on context and the control file used, the
2727 <tt>Architecture</tt> field can include the following sets of
2731 A unique single word identifying a Debian machine
2732 architecture as described in <ref id="arch-spec">.
2735 An architecture wildcard identifying a set of Debian
2736 machine architectures, see <ref id="arch-wildcard-spec">.
2739 <tt>all</tt>, which indicates an
2740 architecture-independent package.
2743 <tt>source</tt>, which indicates a source package.
2749 In the main <file>debian/control</file> file in the source
2750 package, this field may contain the special value <tt>all</tt>
2751 or a list of specific and wildcard architectures separated by
2752 spaces. If <tt>all</tt> appears, that value must be the
2753 entire contents of the field. Most packages will use
2754 either <tt>any</tt> or <tt>all</tt>. Specifying a specific
2755 list of architectures is for the minority of cases where a
2756 program is not portable or is not useful on some
2757 architectures, and where possible the program should be made
2762 In the source package control file <file>.dsc</file>, this
2763 field may contain either the special value <tt>any</tt> or a
2764 list of architectures separated by spaces. If a list is given,
2765 it may include (or consist solely of) the special value
2766 <tt>all</tt>. In other words, in <file>.dsc</file> files
2767 unlike the <file>debian/control</file>, <tt>all</tt> may occur
2768 in combination with specific architectures. The
2769 <tt>Architecture</tt> field in the source package control file
2770 <file>.dsc</file> is generally constructed from the
2771 <tt>Architecture</tt> fields in the
2772 <file>debian/control</file> in the source package.
2776 Specifying <tt>any</tt> indicates that the source package
2777 isn't dependent on any particular architecture and should
2778 compile fine on any one. The produced binary package(s)
2779 will either be specific to whatever the current build
2780 architecture is or will be architecture-independent.
2784 Specifying only <tt>all</tt> indicates that the source package
2785 will only build architecture-independent packages. If this is
2786 the case, <tt>all</tt> must be used rather than <tt>any</tt>;
2787 <tt>any</tt> implies that the source package will build at
2788 least one architecture-dependent package.
2792 Specifying a list of architectures indicates that the source
2793 will build an architecture-dependent package, and will only
2794 work correctly on the listed architectures. If the source
2795 package also builds at least one architecture-independent
2796 package, <tt>all</tt> will also be included in the list.
2800 Specifying a list of architecture wildcards indicates that
2801 the source will build an architecture-dependent package on
2802 the union of the lists of architectures from the expansion
2803 of each specified architecture wildcard, and will only
2804 work correctly on the architectures in the union of the
2806 Use of architecture wildcards other than <tt>all</tt> is for
2807 a minority of cases where the program is not portable and
2808 should not be used for most packages. Wildcards are not
2809 expanded into a list of known architectures before comparing
2810 to the build architecutre. Instead, the build architecture
2811 is matched against any wildcards and this package is built
2812 if any wildcard matches.
2814 If the source package also builds at least one
2815 architecture-independent package, <tt>all</tt> will also be
2816 included in the list.
2820 In a <file>.changes</file> file, the <tt>Architecture</tt>
2821 field lists the architecture(s) of the package(s)
2822 currently being uploaded. This will be a list; if the
2823 source for the package is also being uploaded, the special
2824 entry <tt>source</tt> is also present. <tt>all</tt> will be
2825 present if any architecture-independent packages are being
2826 uploaded. <tt>any</tt> may never occur in the
2827 <tt>Architecture</tt> field in the <file>.changes</file>
2832 See <ref id="debianrules"> for information on how to get
2833 the architecture for the build process.
2837 <sect1 id="f-Essential">
2838 <heading><tt>Essential</tt></heading>
2841 This is a boolean field which may occur only in the
2842 control file of a binary package or in a per-package fields
2843 paragraph of a main source control data file.
2847 If set to <tt>yes</tt> then the package management system
2848 will refuse to remove the package (upgrading and replacing
2849 it is still possible). The other possible value is <tt>no</tt>,
2850 which is the same as not having the field at all.
2855 <heading>Package interrelationship fields:
2856 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2857 <tt>Recommends</tt>, <tt>Suggests</tt>,
2858 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2859 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2863 These fields describe the package's relationships with
2864 other packages. Their syntax and semantics are described
2865 in <ref id="relationships">.</p>
2868 <sect1 id="f-Standards-Version">
2869 <heading><tt>Standards-Version</tt></heading>
2872 The most recent version of the standards (the policy
2873 manual and associated texts) with which the package
2878 The version number has four components: major and minor
2879 version number and major and minor patch level. When the
2880 standards change in a way that requires every package to
2881 change the major number will be changed. Significant
2882 changes that will require work in many packages will be
2883 signaled by a change to the minor number. The major patch
2884 level will be changed for any change to the meaning of the
2885 standards, however small; the minor patch level will be
2886 changed when only cosmetic, typographical or other edits
2887 are made which neither change the meaning of the document
2888 nor affect the contents of packages.
2892 Thus only the first three components of the policy version
2893 are significant in the <em>Standards-Version</em> control
2894 field, and so either these three components or all four
2895 components may be specified.<footnote>
2896 In the past, people specified the full version number
2897 in the Standards-Version field, for example "2.3.0.0".
2898 Since minor patch-level changes don't introduce new
2899 policy, it was thought it would be better to relax
2900 policy and only require the first 3 components to be
2901 specified, in this example "2.3.0". All four
2902 components may still be used if someone wishes to do so.
2908 <sect1 id="f-Version">
2909 <heading><tt>Version</tt></heading>
2912 The version number of a package. The format is:
2913 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
2917 The three components here are:
2919 <tag><var>epoch</var></tag>
2922 This is a single (generally small) unsigned integer. It
2923 may be omitted, in which case zero is assumed. If it is
2924 omitted then the <var>upstream_version</var> may not
2929 It is provided to allow mistakes in the version numbers
2930 of older versions of a package, and also a package's
2931 previous version numbering schemes, to be left behind.
2935 <tag><var>upstream_version</var></tag>
2938 This is the main part of the version number. It is
2939 usually the version number of the original ("upstream")
2940 package from which the <file>.deb</file> file has been made,
2941 if this is applicable. Usually this will be in the same
2942 format as that specified by the upstream author(s);
2943 however, it may need to be reformatted to fit into the
2944 package management system's format and comparison
2949 The comparison behavior of the package management system
2950 with respect to the <var>upstream_version</var> is
2951 described below. The <var>upstream_version</var>
2952 portion of the version number is mandatory.
2956 The <var>upstream_version</var> may contain only
2957 alphanumerics<footnote>
2958 Alphanumerics are <tt>A-Za-z0-9</tt> only.
2960 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
2961 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
2962 tilde) and should start with a digit. If there is no
2963 <var>debian_revision</var> then hyphens are not allowed;
2964 if there is no <var>epoch</var> then colons are not
2969 <tag><var>debian_revision</var></tag>
2972 This part of the version number specifies the version of
2973 the Debian package based on the upstream version. It
2974 may contain only alphanumerics and the characters
2975 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
2976 tilde) and is compared in the same way as the
2977 <var>upstream_version</var> is.
2981 It is optional; if it isn't present then the
2982 <var>upstream_version</var> may not contain a hyphen.
2983 This format represents the case where a piece of
2984 software was written specifically to be turned into a
2985 Debian package, and so there is only one "debianisation"
2986 of it and therefore no revision indication is required.
2990 It is conventional to restart the
2991 <var>debian_revision</var> at <tt>1</tt> each time the
2992 <var>upstream_version</var> is increased.
2996 The package management system will break the version
2997 number apart at the last hyphen in the string (if there
2998 is one) to determine the <var>upstream_version</var> and
2999 <var>debian_revision</var>. The absence of a
3000 <var>debian_revision</var> is equivalent to a
3001 <var>debian_revision</var> of <tt>0</tt>.
3008 When comparing two version numbers, first the <var>epoch</var>
3009 of each are compared, then the <var>upstream_version</var> if
3010 <var>epoch</var> is equal, and then <var>debian_revision</var>
3011 if <var>upstream_version</var> is also equal.
3012 <var>epoch</var> is compared numerically. The
3013 <var>upstream_version</var> and <var>debian_revision</var>
3014 parts are compared by the package management system using the
3015 following algorithm:
3019 The strings are compared from left to right.
3023 First the initial part of each string consisting entirely of
3024 non-digit characters is determined. These two parts (one of
3025 which may be empty) are compared lexically. If a difference
3026 is found it is returned. The lexical comparison is a
3027 comparison of ASCII values modified so that all the letters
3028 sort earlier than all the non-letters and so that a tilde
3029 sorts before anything, even the end of a part. For example,
3030 the following parts are in sorted order from earliest to
3031 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3032 <tt>a</tt>.<footnote>
3033 One common use of <tt>~</tt> is for upstream pre-releases.
3034 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3035 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3040 Then the initial part of the remainder of each string which
3041 consists entirely of digit characters is determined. The
3042 numerical values of these two parts are compared, and any
3043 difference found is returned as the result of the comparison.
3044 For these purposes an empty string (which can only occur at
3045 the end of one or both version strings being compared) counts
3050 These two steps (comparing and removing initial non-digit
3051 strings and initial digit strings) are repeated until a
3052 difference is found or both strings are exhausted.
3056 Note that the purpose of epochs is to allow us to leave behind
3057 mistakes in version numbering, and to cope with situations
3058 where the version numbering scheme changes. It is
3059 <em>not</em> intended to cope with version numbers containing
3060 strings of letters which the package management system cannot
3061 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3062 silly orderings (the author of this manual has heard of a
3063 package whose versions went <tt>1.1</tt>, <tt>1.2</tt>,
3064 <tt>1.3</tt>, <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>,
3065 <tt>2</tt> and so forth).
3069 <sect1 id="f-Description">
3070 <heading><tt>Description</tt></heading>
3073 In a source or binary control file, the <tt>Description</tt>
3074 field contains a description of the binary package, consisting
3075 of two parts, the synopsis or the short description, and the
3076 long description. The field's format is as follows:
3081 Description: <single line synopsis>
3082 <extended description over several lines>
3087 The lines in the extended description can have these formats:
3093 Those starting with a single space are part of a paragraph.
3094 Successive lines of this form will be word-wrapped when
3095 displayed. The leading space will usually be stripped off.
3099 Those starting with two or more spaces. These will be
3100 displayed verbatim. If the display cannot be panned
3101 horizontally, the displaying program will line wrap them "hard"
3102 (i.e., without taking account of word breaks). If it can they
3103 will be allowed to trail off to the right. None, one or two
3104 initial spaces may be deleted, but the number of spaces
3105 deleted from each line will be the same (so that you can have
3106 indenting work correctly, for example).
3110 Those containing a single space followed by a single full stop
3111 character. These are rendered as blank lines. This is the
3112 <em>only</em> way to get a blank line<footnote>
3113 Completely empty lines will not be rendered as blank lines.
3114 Instead, they will cause the parser to think you're starting
3115 a whole new record in the control file, and will therefore
3116 likely abort with an error.
3121 Those containing a space, a full stop and some more characters.
3122 These are for future expansion. Do not use them.
3128 Do not use tab characters. Their effect is not predictable.
3132 See <ref id="descriptions"> for further information on this.
3136 In a <file>.changes</file> file, the <tt>Description</tt>
3137 field contains a summary of the descriptions for the packages
3138 being uploaded. For this case, the first line of the field
3139 value (the part on the same line as <tt>Description:</tt>) is
3140 always empty. The content of the field is expressed as
3141 continuation lines, one line per package. Each line is
3142 indented by one space and contains the name of a binary
3143 package, a space, a hyphen (<tt>-</tt>), a space, and the
3144 short description line from that package.
3148 <sect1 id="f-Distribution">
3149 <heading><tt>Distribution</tt></heading>
3152 In a <file>.changes</file> file or parsed changelog output
3153 this contains the (space-separated) name(s) of the
3154 distribution(s) where this version of the package should
3155 be installed. Valid distributions are determined by the
3156 archive maintainers.<footnote>
3157 Example distribution names in the Debian archive used in
3158 <file>.changes</file> files are:
3159 <taglist compact="compact">
3160 <tag><em>unstable</em></tag>
3162 This distribution value refers to the
3163 <em>developmental</em> part of the Debian distribution
3164 tree. Most new packages, new upstream versions of
3165 packages and bug fixes go into the <em>unstable</em>
3169 <tag><em>experimental</em></tag>
3171 The packages with this distribution value are deemed
3172 by their maintainers to be high risk. Oftentimes they
3173 represent early beta or developmental packages from
3174 various sources that the maintainers want people to
3175 try, but are not ready to be a part of the other parts
3176 of the Debian distribution tree.
3181 Others are used for updating stable releases or for
3182 security uploads. More information is available in the
3183 Debian Developer's Reference, section "The Debian
3187 The Debian archive software only supports listing a single
3188 distribution. Migration of packages to other distributions is
3189 handled outside of the upload process.
3194 <heading><tt>Date</tt></heading>
3197 This field includes the date the package was built or last edited.
3201 The value of this field is usually extracted from the
3202 <file>debian/changelog</file> file - see
3203 <ref id="dpkgchangelog">).
3207 <sect1 id="f-Format">
3208 <heading><tt>Format</tt></heading>
3211 This field specifies a format revision for the file.
3212 The most current format described in the Policy Manual
3213 is version <strong>1.5</strong>. The syntax of the
3214 format value is the same as that of a package version
3215 number except that no epoch or Debian revision is allowed
3216 - see <ref id="f-Version">.
3220 <sect1 id="f-Urgency">
3221 <heading><tt>Urgency</tt></heading>
3224 This is a description of how important it is to upgrade to
3225 this version from previous ones. It consists of a single
3226 keyword taking one of the values <tt>low</tt>,
3227 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3228 <tt>critical</tt><footnote>
3229 Other urgency values are supported with configuration
3230 changes in the archive software but are not used in Debian.
3231 The urgency affects how quickly a package will be considered
3232 for inclusion into the <tt>testing</tt> distribution and
3233 gives an indication of the importance of any fixes included
3234 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3235 treated as synonymous.
3236 </footnote> (not case-sensitive) followed by an optional
3237 commentary (separated by a space) which is usually in
3238 parentheses. For example:
3241 Urgency: low (HIGH for users of diversions)
3247 The value of this field is usually extracted from the
3248 <file>debian/changelog</file> file - see
3249 <ref id="dpkgchangelog">.
3253 <sect1 id="f-Changes">
3254 <heading><tt>Changes</tt></heading>
3257 This field contains the human-readable changes data, describing
3258 the differences between the last version and the current one.
3262 The first line of the field value (the part on the same line
3263 as <tt>Changes:</tt>) is always empty. The content of the
3264 field is expressed as continuation lines, with each line
3265 indented by at least one space. Blank lines must be
3266 represented by a line consisting only of a space and a full
3271 The value of this field is usually extracted from the
3272 <file>debian/changelog</file> file - see
3273 <ref id="dpkgchangelog">).
3277 Each version's change information should be preceded by a
3278 "title" line giving at least the version, distribution(s)
3279 and urgency, in a human-readable way.
3283 If data from several versions is being returned the entry
3284 for the most recent version should be returned first, and
3285 entries should be separated by the representation of a
3286 blank line (the "title" line may also be followed by the
3287 representation of a blank line).
3291 <sect1 id="f-Binary">
3292 <heading><tt>Binary</tt></heading>
3295 This field is a list of binary packages. Its syntax and
3296 meaning varies depending on the control file in which it
3301 When it appears in the <file>.dsc</file> file, it lists binary
3302 packages which a source package can produce, separated by
3304 A space after each comma is conventional.
3305 </footnote>. It may span multiple lines. The source package
3306 does not necessarily produce all of these binary packages for
3307 every architecture. The source control file doesn't contain
3308 details of which architectures are appropriate for which of
3309 the binary packages.
3313 When it appears in a <file>.changes</file> file, it lists the
3314 names of the binary packages being uploaded, separated by
3315 whitespace (not commas). It may span multiple lines.
3319 <sect1 id="f-Installed-Size">
3320 <heading><tt>Installed-Size</tt></heading>
3323 This field appears in the control files of binary packages,
3324 and in the <file>Packages</file> files. It gives an estimate
3325 of the total amount of disk space required to install the
3326 named package. Actual installed size may vary based on block
3327 size, file system properties, or actions taken by package
3332 The disk space is given as the integer value of the estimated
3333 installed size in bytes, divided by 1024 and rounded up.
3337 <sect1 id="f-Files">
3338 <heading><tt>Files</tt></heading>
3341 This field contains a list of files with information about
3342 each one. The exact information and syntax varies with
3347 In all cases, Files is a multiline field. The first line of
3348 the field value (the part on the same line as <tt>Files:</tt>)
3349 is always empty. The content of the field is expressed as
3350 continuation lines, one line per file. Each line must be
3351 indented by one space and contain a number of sub-fields,
3352 separated by spaces, as described below.
3356 In the <file>.dsc</file> file, each line contains the MD5
3357 checksum, size and filename of the tar file and (if
3358 applicable) diff file which make up the remainder of the
3359 source package<footnote>
3360 That is, the parts which are not the <tt>.dsc</tt>.
3361 </footnote>. For example:
3364 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3365 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3367 The exact forms of the filenames are described
3368 in <ref id="pkg-sourcearchives">.
3372 In the <file>.changes</file> file this contains one line per
3373 file being uploaded. Each line contains the MD5 checksum,
3374 size, section and priority and the filename. For example:
3377 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3378 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3379 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3380 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3382 The <qref id="f-Section">section</qref>
3383 and <qref id="f-Priority">priority</qref> are the values of
3384 the corresponding fields in the main source control file. If
3385 no section or priority is specified then <tt>-</tt> should be
3386 used, though section and priority values must be specified for
3387 new packages to be installed properly.
3391 The special value <tt>byhand</tt> for the section in a
3392 <tt>.changes</tt> file indicates that the file in question
3393 is not an ordinary package file and must by installed by
3394 hand by the distribution maintainers. If the section is
3395 <tt>byhand</tt> the priority should be <tt>-</tt>.
3399 If a new Debian revision of a package is being shipped and
3400 no new original source archive is being distributed the
3401 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3402 entry for the original source archive
3403 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3404 but the <file>.changes</file> file should leave it out. In
3405 this case the original source archive on the distribution
3406 site must match exactly, byte-for-byte, the original
3407 source archive which was used to generate the
3408 <file>.dsc</file> file and diff which are being uploaded.</p>
3411 <sect1 id="f-Closes">
3412 <heading><tt>Closes</tt></heading>
3415 A space-separated list of bug report numbers that the upload
3416 governed by the .changes file closes.
3420 <sect1 id="f-Homepage">
3421 <heading><tt>Homepage</tt></heading>
3424 The URL of the web site for this package, preferably (when
3425 applicable) the site from which the original source can be
3426 obtained and any additional upstream documentation or
3427 information may be found. The content of this field is a
3428 simple URL without any surrounding characters such as
3436 <heading>User-defined fields</heading>
3439 Additional user-defined fields may be added to the
3440 source package control file. Such fields will be
3441 ignored, and not copied to (for example) binary or
3442 source package control files or upload control files.
3446 If you wish to add additional unsupported fields to
3447 these output files you should use the mechanism
3452 Fields in the main source control information file with
3453 names starting <tt>X</tt>, followed by one or more of
3454 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3455 be copied to the output files. Only the part of the
3456 field name after the hyphen will be used in the output
3457 file. Where the letter <tt>B</tt> is used the field
3458 will appear in binary package control files, where the
3459 letter <tt>S</tt> is used in source package control
3460 files and where <tt>C</tt> is used in upload control
3461 (<tt>.changes</tt>) files.
3465 For example, if the main source information control file
3468 XBS-Comment: I stand between the candle and the star.
3470 then the binary and source package control files will contain the
3473 Comment: I stand between the candle and the star.
3482 <chapt id="maintainerscripts">
3483 <heading>Package maintainer scripts and installation procedure</heading>
3486 <heading>Introduction to package maintainer scripts</heading>
3489 It is possible to supply scripts as part of a package which
3490 the package management system will run for you when your
3491 package is installed, upgraded or removed.
3495 These scripts are the files <prgn>preinst</prgn>,
3496 <prgn>postinst</prgn>, <prgn>prerm</prgn> and
3497 <prgn>postrm</prgn> in the control area of the package.
3498 They must be proper executable files; if they are scripts
3499 (which is recommended), they must start with the usual
3500 <tt>#!</tt> convention. They should be readable and
3501 executable by anyone, and must not be world-writable.
3505 The package management system looks at the exit status from
3506 these scripts. It is important that they exit with a
3507 non-zero status if there is an error, so that the package
3508 management system can stop its processing. For shell
3509 scripts this means that you <em>almost always</em> need to
3510 use <tt>set -e</tt> (this is usually true when writing shell
3511 scripts, in fact). It is also important, of course, that
3512 they exit with a zero status if everything went well.
3516 Additionally, packages interacting with users using
3517 <tt>debconf</tt> in the <prgn>postinst</prgn> script should
3518 install a <prgn>config</prgn> script in the control area,
3519 see <ref id="maintscriptprompt"> for details.
3523 When a package is upgraded a combination of the scripts from
3524 the old and new packages is called during the upgrade
3525 procedure. If your scripts are going to be at all
3526 complicated you need to be aware of this, and may need to
3527 check the arguments to your scripts.
3531 Broadly speaking the <prgn>preinst</prgn> is called before
3532 (a particular version of) a package is installed, and the
3533 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3534 before (a version of) a package is removed and the
3535 <prgn>postrm</prgn> afterwards.
3539 Programs called from maintainer scripts should not normally
3540 have a path prepended to them. Before installation is
3541 started, the package management system checks to see if the
3542 programs <prgn>ldconfig</prgn>,
3543 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3544 and <prgn>update-rc.d</prgn> can be found via the
3545 <tt>PATH</tt> environment variable. Those programs, and any
3546 other program that one would expect to be in the
3547 <tt>PATH</tt>, should thus be invoked without an absolute
3548 pathname. Maintainer scripts should also not reset the
3549 <tt>PATH</tt>, though they might choose to modify it by
3550 prepending or appending package-specific directories. These
3551 considerations really apply to all shell scripts.</p>
3554 <sect id="idempotency">
3555 <heading>Maintainer scripts idempotency</heading>
3558 It is necessary for the error recovery procedures that the
3559 scripts be idempotent. This means that if it is run
3560 successfully, and then it is called again, it doesn't bomb
3561 out or cause any harm, but just ensures that everything is
3562 the way it ought to be. If the first call failed, or
3563 aborted half way through for some reason, the second call
3564 should merely do the things that were left undone the first
3565 time, if any, and exit with a success status if everything
3567 This is so that if an error occurs, the user interrupts
3568 <prgn>dpkg</prgn> or some other unforeseen circumstance
3569 happens you don't leave the user with a badly-broken
3570 package when <prgn>dpkg</prgn> attempts to repeat the
3576 <sect id="controllingterminal">
3577 <heading>Controlling terminal for maintainer scripts</heading>
3580 The maintainer scripts are guaranteed to run with a
3581 controlling terminal and can interact with the user.
3582 Because these scripts may be executed with standard output
3583 redirected into a pipe for logging purposes, Perl scripts
3584 should set unbuffered output by setting <tt>$|=1</tt> so
3585 that the output is printed immediately rather than being
3589 <sect id="exitstatus">
3590 <heading>Exit status</heading>
3593 Each script must return a zero exit status for
3594 success, or a nonzero one for failure, since the package
3595 management system looks for the exit status of these scripts
3596 and determines what action to take next based on that datum.
3600 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3605 <list compact="compact">
3607 <var>new-preinst</var> <tt>install</tt>
3610 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3613 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3616 <var>old-preinst</var> <tt>abort-upgrade</tt>
3617 <var>new-version</var>
3622 <list compact="compact">
3624 <var>postinst</var> <tt>configure</tt>
3625 <var>most-recently-configured-version</var>
3628 <var>old-postinst</var> <tt>abort-upgrade</tt>
3629 <var>new-version</var>
3632 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3633 <tt>in-favour</tt> <var>package</var>
3634 <var>new-version</var>
3637 <var>postinst</var> <tt>abort-remove</tt>
3640 <var>deconfigured's-postinst</var>
3641 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3642 <var>failed-install-package</var> <var>version</var>
3643 [<tt>removing</tt> <var>conflicting-package</var>
3649 <list compact="compact">
3651 <var>prerm</var> <tt>remove</tt>
3654 <var>old-prerm</var> <tt>upgrade</tt>
3655 <var>new-version</var>
3658 <var>new-prerm</var> <tt>failed-upgrade</tt>
3659 <var>old-version</var>
3662 <var>conflictor's-prerm</var> <tt>remove</tt>
3663 <tt>in-favour</tt> <var>package</var>
3664 <var>new-version</var>
3667 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3668 <tt>in-favour</tt> <var>package-being-installed</var>
3669 <var>version</var> [<tt>removing</tt>
3670 <var>conflicting-package</var>
3676 <list compact="compact">
3678 <var>postrm</var> <tt>remove</tt>
3681 <var>postrm</var> <tt>purge</tt>
3684 <var>old-postrm</var> <tt>upgrade</tt>
3685 <var>new-version</var>
3688 <var>new-postrm</var> <tt>failed-upgrade</tt>
3689 <var>old-version</var>
3692 <var>new-postrm</var> <tt>abort-install</tt>
3695 <var>new-postrm</var> <tt>abort-install</tt>
3696 <var>old-version</var>
3699 <var>new-postrm</var> <tt>abort-upgrade</tt>
3700 <var>old-version</var>
3703 <var>disappearer's-postrm</var> <tt>disappear</tt>
3704 <var>overwriter</var>
3705 <var>overwriter-version</var>
3711 <sect id="unpackphase">
3712 <heading>Details of unpack phase of installation or upgrade</heading>
3715 The procedure on installation/upgrade/overwrite/disappear
3716 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3717 stage of <tt>dpkg --install</tt>) is as follows. In each
3718 case, if a major error occurs (unless listed below) the
3719 actions are, in general, run backwards - this means that the
3720 maintainer scripts are run with different arguments in
3721 reverse order. These are the "error unwind" calls listed
3728 If a version of the package is already installed, call
3729 <example compact="compact">
3730 <var>old-prerm</var> upgrade <var>new-version</var>
3734 If the script runs but exits with a non-zero
3735 exit status, <prgn>dpkg</prgn> will attempt:
3736 <example compact="compact">
3737 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3739 If this works, the upgrade continues. If this
3740 does not work, the error unwind:
3741 <example compact="compact">
3742 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3744 If this works, then the old-version is
3745 "Installed", if not, the old version is in a
3746 "Half-Configured" state.
3752 If a "conflicting" package is being removed at the same time,
3753 or if any package will be broken (due to <tt>Breaks</tt>):
3756 If <tt>--auto-deconfigure</tt> is
3757 specified, call, for each package to be deconfigured
3758 due to <tt>Breaks</tt>:
3759 <example compact="compact">
3760 <var>deconfigured's-prerm</var> deconfigure \
3761 in-favour <var>package-being-installed</var> <var>version</var>
3764 <example compact="compact">
3765 <var>deconfigured's-postinst</var> abort-deconfigure \
3766 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3768 The deconfigured packages are marked as
3769 requiring configuration, so that if
3770 <tt>--install</tt> is used they will be
3771 configured again if possible.
3774 If any packages depended on a conflicting
3775 package being removed and <tt>--auto-deconfigure</tt> is
3776 specified, call, for each such package:
3777 <example compact="compact">
3778 <var>deconfigured's-prerm</var> deconfigure \
3779 in-favour <var>package-being-installed</var> <var>version</var> \
3780 removing <var>conflicting-package</var> <var>version</var>
3783 <example compact="compact">
3784 <var>deconfigured's-postinst</var> abort-deconfigure \
3785 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3786 removing <var>conflicting-package</var> <var>version</var>
3788 The deconfigured packages are marked as
3789 requiring configuration, so that if
3790 <tt>--install</tt> is used they will be
3791 configured again if possible.
3794 To prepare for removal of each conflicting package, call:
3795 <example compact="compact">
3796 <var>conflictor's-prerm</var> remove \
3797 in-favour <var>package</var> <var>new-version</var>
3800 <example compact="compact">
3801 <var>conflictor's-postinst</var> abort-remove \
3802 in-favour <var>package</var> <var>new-version</var>
3811 If the package is being upgraded, call:
3812 <example compact="compact">
3813 <var>new-preinst</var> upgrade <var>old-version</var>
3815 If this fails, we call:
3817 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3824 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3826 is called. If this works, then the old version
3827 is in an "Installed" state, or else it is left
3828 in an "Unpacked" state.
3833 If it fails, then the old version is left
3834 in an "Half-Installed" state.
3841 Otherwise, if the package had some configuration
3842 files from a previous version installed (i.e., it
3843 is in the "configuration files only" state):
3844 <example compact="compact">
3845 <var>new-preinst</var> install <var>old-version</var>
3849 <var>new-postrm</var> abort-install <var>old-version</var>
3851 If this fails, the package is left in a
3852 "Half-Installed" state, which requires a
3853 reinstall. If it works, the packages is left in
3854 a "Config-Files" state.
3857 Otherwise (i.e., the package was completely purged):
3858 <example compact="compact">
3859 <var>new-preinst</var> install
3862 <example compact="compact">
3863 <var>new-postrm</var> abort-install
3865 If the error-unwind fails, the package is in a
3866 "Half-Installed" phase, and requires a
3867 reinstall. If the error unwind works, the
3868 package is in a not installed state.
3875 The new package's files are unpacked, overwriting any
3876 that may be on the system already, for example any
3877 from the old version of the same package or from
3878 another package. Backups of the old files are kept
3879 temporarily, and if anything goes wrong the package
3880 management system will attempt to put them back as
3881 part of the error unwind.
3885 It is an error for a package to contain files which
3886 are on the system in another package, unless
3887 <tt>Replaces</tt> is used (see <ref id="replaces">).
3889 The following paragraph is not currently the case:
3890 Currently the <tt>- - force-overwrite</tt> flag is
3891 enabled, downgrading it to a warning, but this may not
3897 It is a more serious error for a package to contain a
3898 plain file or other kind of non-directory where another
3899 package has a directory (again, unless
3900 <tt>Replaces</tt> is used). This error can be
3901 overridden if desired using
3902 <tt>--force-overwrite-dir</tt>, but this is not
3907 Packages which overwrite each other's files produce
3908 behavior which, though deterministic, is hard for the
3909 system administrator to understand. It can easily
3910 lead to "missing" programs if, for example, a package
3911 is installed which overwrites a file from another
3912 package, and is then removed again.<footnote>
3913 Part of the problem is due to what is arguably a
3914 bug in <prgn>dpkg</prgn>.
3919 A directory will never be replaced by a symbolic link
3920 to a directory or vice versa; instead, the existing
3921 state (symlink or not) will be left alone and
3922 <prgn>dpkg</prgn> will follow the symlink if there is
3931 If the package is being upgraded, call
3932 <example compact="compact">
3933 <var>old-postrm</var> upgrade <var>new-version</var>
3937 If this fails, <prgn>dpkg</prgn> will attempt:
3938 <example compact="compact">
3939 <var>new-postrm</var> failed-upgrade <var>old-version</var>
3941 If this works, installation continues. If not,
3943 <example compact="compact">
3944 <var>old-preinst</var> abort-upgrade <var>new-version</var>
3946 If this fails, the old version is left in a
3947 "Half-Installed" state. If it works, dpkg now
3949 <example compact="compact">
3950 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3952 If this fails, the old version is left in a
3953 "Half-Installed" state. If it works, dpkg now
3955 <example compact="compact">
3956 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3958 If this fails, the old version is in an
3965 This is the point of no return - if
3966 <prgn>dpkg</prgn> gets this far, it won't back off
3967 past this point if an error occurs. This will
3968 leave the package in a fairly bad state, which
3969 will require a successful re-installation to clear
3970 up, but it's when <prgn>dpkg</prgn> starts doing
3971 things that are irreversible.
3976 Any files which were in the old version of the package
3977 but not in the new are removed.
3981 The new file list replaces the old.
3985 The new maintainer scripts replace the old.
3989 Any packages all of whose files have been overwritten
3990 during the installation, and which aren't required for
3991 dependencies, are considered to have been removed.
3992 For each such package
3995 <prgn>dpkg</prgn> calls:
3996 <example compact="compact">
3997 <var>disappearer's-postrm</var> disappear \
3998 <var>overwriter</var> <var>overwriter-version</var>
4002 The package's maintainer scripts are removed.
4005 It is noted in the status database as being in a
4006 sane state, namely not installed (any conffiles
4007 it may have are ignored, rather than being
4008 removed by <prgn>dpkg</prgn>). Note that
4009 disappearing packages do not have their prerm
4010 called, because <prgn>dpkg</prgn> doesn't know
4011 in advance that the package is going to
4018 Any files in the package we're unpacking that are also
4019 listed in the file lists of other packages are removed
4020 from those lists. (This will lobotomize the file list
4021 of the "conflicting" package if there is one.)
4025 The backup files made during installation, above, are
4031 The new package's status is now sane, and recorded as
4036 Here is another point of no return - if the
4037 conflicting package's removal fails we do not unwind
4038 the rest of the installation; the conflicting package
4039 is left in a half-removed limbo.
4044 If there was a conflicting package we go and do the
4045 removal actions (described below), starting with the
4046 removal of the conflicting package's files (any that
4047 are also in the package being installed have already
4048 been removed from the conflicting package's file list,
4049 and so do not get removed now).
4055 <sect id="configdetails"><heading>Details of configuration</heading>
4058 When we configure a package (this happens with <tt>dpkg
4059 --install</tt> and <tt>dpkg --configure</tt>), we first
4060 update any <tt>conffile</tt>s and then call:
4061 <example compact="compact">
4062 <var>postinst</var> configure <var>most-recently-configured-version</var>
4067 No attempt is made to unwind after errors during
4068 configuration. If the configuration fails, the package is in
4069 a "Failed Config" state, and an error message is generated.
4073 If there is no most recently configured version
4074 <prgn>dpkg</prgn> will pass a null argument.
4077 Historical note: Truly ancient (pre-1997) versions of
4078 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4079 (including the angle brackets) in this case. Even older
4080 ones did not pass a second argument at all, under any
4081 circumstance. Note that upgrades using such an old dpkg
4082 version are unlikely to work for other reasons, even if
4083 this old argument behavior is handled by your postinst script.
4089 <sect id="removedetails"><heading>Details of removal and/or
4090 configuration purging</heading>
4096 <example compact="compact">
4097 <var>prerm</var> remove
4101 If prerm fails during replacement due to conflict
4103 <var>conflictor's-postinst</var> abort-remove \
4104 in-favour <var>package</var> <var>new-version</var>
4108 <var>postinst</var> abort-remove
4112 If this fails, the package is in a "Half-Configured"
4113 state, or else it remains "Installed".
4117 The package's files are removed (except <tt>conffile</tt>s).
4120 <example compact="compact">
4121 <var>postrm</var> remove
4125 If it fails, there's no error unwind, and the package is in
4126 an "Half-Installed" state.
4131 All the maintainer scripts except the <prgn>postrm</prgn>
4136 If we aren't purging the package we stop here. Note
4137 that packages which have no <prgn>postrm</prgn> and no
4138 <tt>conffile</tt>s are automatically purged when
4139 removed, as there is no difference except for the
4140 <prgn>dpkg</prgn> status.
4144 The <tt>conffile</tt>s and any backup files
4145 (<tt>~</tt>-files, <tt>#*#</tt> files,
4146 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4151 <example compact="compact">
4152 <var>postrm</var> purge
4156 If this fails, the package remains in a "Config-Files"
4161 The package's file list is removed.
4170 <chapt id="relationships">
4171 <heading>Declaring relationships between packages</heading>
4173 <sect id="depsyntax">
4174 <heading>Syntax of relationship fields</heading>
4177 These fields all have a uniform syntax. They are a list of
4178 package names separated by commas.
4182 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4183 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4184 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4185 control file fields of the package, which declare
4186 dependencies on other packages, the package names listed may
4187 also include lists of alternative package names, separated
4188 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4189 if any one of the alternative packages is installed, that
4190 part of the dependency is considered to be satisfied.
4194 All of the fields except for <tt>Provides</tt> may restrict
4195 their applicability to particular versions of each named
4196 package. This is done in parentheses after each individual
4197 package name; the parentheses should contain a relation from
4198 the list below followed by a version number, in the format
4199 described in <ref id="f-Version">.
4203 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4204 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4205 strictly earlier, earlier or equal, exactly equal, later or
4206 equal and strictly later, respectively. The deprecated
4207 forms <tt><</tt> and <tt>></tt> were used to mean
4208 earlier/later or equal, rather than strictly earlier/later,
4209 so they should not appear in new packages (though
4210 <prgn>dpkg</prgn> still supports them).
4214 Whitespace may appear at any point in the version
4215 specification subject to the rules in <ref
4216 id="controlsyntax">, and must appear where it's necessary to
4217 disambiguate; it is not otherwise significant. All of the
4218 relationship fields may span multiple lines. For
4219 consistency and in case of future changes to
4220 <prgn>dpkg</prgn> it is recommended that a single space be
4221 used after a version relationship and before a version
4222 number; it is also conventional to put a single space after
4223 each comma, on either side of each vertical bar, and before
4224 each open parenthesis. When wrapping a relationship field, it
4225 is conventional to do so after a comma and before the space
4226 following that comma.
4230 For example, a list of dependencies might appear as:
4231 <example compact="compact">
4234 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4239 All fields that specify build-time relationships
4240 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4241 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>)
4242 may be restricted to a certain set of architectures. This
4243 is indicated in brackets after each individual package name and
4244 the optional version specification. The brackets enclose a
4245 list of Debian architecture names separated by whitespace.
4246 Exclamation marks may be prepended to each of the names.
4247 (It is not permitted for some names to be prepended with
4248 exclamation marks while others aren't.) If the current Debian
4249 host architecture is not in this list and there are no
4250 exclamation marks in the list, or it is in the list with a
4251 prepended exclamation mark, the package name and the
4252 associated version specification are ignored completely for
4253 the purposes of defining the relationships.
4258 <example compact="compact">
4260 Build-Depends-Indep: texinfo
4261 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4262 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4264 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4265 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4266 <tt>gnumach-dev</tt> only on hurd-i386.
4270 If the architecture-restricted dependency is part of a set of
4271 alternatives using <tt>|</tt>, that alternative is ignored
4272 completely on architectures that do not match the restriction.
4274 <example compact="compact">
4275 Build-Depends: foo [!i386] | bar [!amd64]
4277 is equivalent to <tt>bar</tt> on the i386 architecture, to
4278 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4279 bar</tt> on all other architectures.
4283 Note that the binary package relationship fields such as
4284 <tt>Depends</tt> appear in one of the binary package
4285 sections of the control file, whereas the build-time
4286 relationships such as <tt>Build-Depends</tt> appear in the
4287 source package section of the control file (which is the
4291 All fields that specify build-time relationships
4292 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4293 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>) may also
4294 be restricted to a certain set of architectures using architecture
4295 wildcards. The syntax for declaring such restrictions is the same as
4296 declaring restrictions using a certain set of architectures without
4297 architecture wildcards.
4299 <example compact="compact">
4300 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4302 is equivalent to <tt>foo</tt> on architectures using the Linux
4303 kernel and any cpu, <tt>bar</tt> on architectures using any
4304 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4305 using a kernel other than Linux.
4309 <sect id="binarydeps">
4310 <heading>Binary Dependencies - <tt>Depends</tt>,
4311 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4312 <tt>Pre-Depends</tt>
4316 Packages can declare in their control file that they have
4317 certain relationships to other packages - for example, that
4318 they may not be installed at the same time as certain other
4319 packages, and/or that they depend on the presence of others.
4323 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4324 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4325 <tt>Breaks</tt> and <tt>Conflicts</tt> control file fields.
4326 <tt>Breaks</tt> is described in <ref id="breaks">, and
4327 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4328 rest are described below.
4332 These seven fields are used to declare a dependency
4333 relationship by one package on another. Except for
4334 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4335 depending (binary) package's control file.
4336 (<tt>Enhances</tt> appears in the recommending package's
4337 control file, and <tt>Breaks</tt> appears in the version of
4338 depended-on package which causes the named package to
4343 A <tt>Depends</tt> field takes effect <em>only</em> when a
4344 package is to be configured. It does not prevent a package
4345 being on the system in an unconfigured state while its
4346 dependencies are unsatisfied, and it is possible to replace
4347 a package whose dependencies are satisfied and which is
4348 properly installed with a different version whose
4349 dependencies are not and cannot be satisfied; when this is
4350 done the depending package will be left unconfigured (since
4351 attempts to configure it will give errors) and will not
4352 function properly. If it is necessary, a
4353 <tt>Pre-Depends</tt> field can be used, which has a partial
4354 effect even when a package is being unpacked, as explained
4355 in detail below. (The other three dependency fields,
4356 <tt>Recommends</tt>, <tt>Suggests</tt> and
4357 <tt>Enhances</tt>, are only used by the various front-ends
4358 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4359 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4363 For this reason packages in an installation run are usually
4364 all unpacked first and all configured later; this gives
4365 later versions of packages with dependencies on later
4366 versions of other packages the opportunity to have their
4367 dependencies satisfied.
4371 In case of circular dependencies, since installation or
4372 removal order honoring the dependency order can't be
4373 established, dependency loops are broken at some point
4374 (based on rules below), and some packages may not be able to
4375 rely on their dependencies being present when being
4376 installed or removed, depending on which side of the break
4377 of the circular dependency loop they happen to be on. If one
4378 of the packages in the loop has no postinst script, then the
4379 cycle will be broken at that package, so as to ensure that
4380 all postinst scripts run with the dependencies properly
4381 configured if this is possible. Otherwise the breaking point
4386 The <tt>Depends</tt> field thus allows package maintainers
4387 to impose an order in which packages should be configured.
4391 The meaning of the five dependency fields is as follows:
4393 <tag><tt>Depends</tt></tag>
4396 This declares an absolute dependency. A package will
4397 not be configured unless all of the packages listed in
4398 its <tt>Depends</tt> field have been correctly
4403 The <tt>Depends</tt> field should be used if the
4404 depended-on package is required for the depending
4405 package to provide a significant amount of
4410 The <tt>Depends</tt> field should also be used if the
4411 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4412 <prgn>postrm</prgn> scripts require the package to be
4413 present in order to run. Note, however, that the
4414 <prgn>postrm</prgn> cannot rely on any non-essential
4415 packages to be present during the <tt>purge</tt>
4419 <tag><tt>Recommends</tt></tag>
4422 This declares a strong, but not absolute, dependency.
4426 The <tt>Recommends</tt> field should list packages
4427 that would be found together with this one in all but
4428 unusual installations.
4432 <tag><tt>Suggests</tt></tag>
4434 This is used to declare that one package may be more
4435 useful with one or more others. Using this field
4436 tells the packaging system and the user that the
4437 listed packages are related to this one and can
4438 perhaps enhance its usefulness, but that installing
4439 this one without them is perfectly reasonable.
4442 <tag><tt>Enhances</tt></tag>
4444 This field is similar to Suggests but works in the
4445 opposite direction. It is used to declare that a
4446 package can enhance the functionality of another
4450 <tag><tt>Pre-Depends</tt></tag>
4453 This field is like <tt>Depends</tt>, except that it
4454 also forces <prgn>dpkg</prgn> to complete installation
4455 of the packages named before even starting the
4456 installation of the package which declares the
4457 pre-dependency, as follows:
4461 When a package declaring a pre-dependency is about to
4462 be <em>unpacked</em> the pre-dependency can be
4463 satisfied if the depended-on package is either fully
4464 configured, <em>or even if</em> the depended-on
4465 package(s) are only unpacked or in the "Half-Configured"
4466 state, provided that they have been configured
4467 correctly at some point in the past (and not removed
4468 or partially removed since). In this case, both the
4469 previously-configured and currently unpacked or
4470 "Half-Configured" versions must satisfy any version
4471 clause in the <tt>Pre-Depends</tt> field.
4475 When the package declaring a pre-dependency is about
4476 to be <em>configured</em>, the pre-dependency will be
4477 treated as a normal <tt>Depends</tt>, that is, it will
4478 be considered satisfied only if the depended-on
4479 package has been correctly configured.
4483 <tt>Pre-Depends</tt> should be used sparingly,
4484 preferably only by packages whose premature upgrade or
4485 installation would hamper the ability of the system to
4486 continue with any upgrade that might be in progress.
4490 <tt>Pre-Depends</tt> are also required if the
4491 <prgn>preinst</prgn> script depends on the named
4492 package. It is best to avoid this situation if
4500 When selecting which level of dependency to use you should
4501 consider how important the depended-on package is to the
4502 functionality of the one declaring the dependency. Some
4503 packages are composed of components of varying degrees of
4504 importance. Such a package should list using
4505 <tt>Depends</tt> the package(s) which are required by the
4506 more important components. The other components'
4507 requirements may be mentioned as Suggestions or
4508 Recommendations, as appropriate to the components' relative
4514 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4517 When one binary package declares that it breaks another,
4518 <prgn>dpkg</prgn> will refuse to allow the package which
4519 declares <tt>Breaks</tt> be installed unless the broken
4520 package is deconfigured first, and it will refuse to
4521 allow the broken package to be reconfigured.
4525 A package will not be regarded as causing breakage merely
4526 because its configuration files are still installed; it must
4527 be at least "Half-Installed".
4531 A special exception is made for packages which declare that
4532 they break their own package name or a virtual package which
4533 they provide (see below): this does not count as a real
4538 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4539 version clause; such a <tt>Breaks</tt> is introduced in the
4540 version of an (implicit or explicit) dependency which
4541 violates an assumption or reveals a bug in earlier versions
4542 of the broken package. This use of <tt>Breaks</tt> will
4543 inform higher-level package management tools that broken
4544 package must be upgraded before the new one.
4548 If the breaking package also overwrites some files from the
4549 older package, it should use <tt>Replaces</tt> (not
4550 <tt>Conflicts</tt>) to ensure this goes smoothly.
4554 <sect id="conflicts">
4555 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4558 When one binary package declares a conflict with another
4559 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4560 refuse to allow them to be installed on the system at the
4565 If one package is to be installed, the other must be removed
4566 first - if the package being installed is marked as
4567 replacing (see <ref id="replaces">) the one on the system,
4568 or the one on the system is marked as deselected, or both
4569 packages are marked <tt>Essential</tt>, then
4570 <prgn>dpkg</prgn> will automatically remove the package
4571 which is causing the conflict, otherwise it will halt the
4572 installation of the new package with an error. This
4573 mechanism is specifically designed to produce an error when
4574 the installed package is <tt>Essential</tt>, but the new
4579 A package will not cause a conflict merely because its
4580 configuration files are still installed; it must be at least
4585 A special exception is made for packages which declare a
4586 conflict with their own package name, or with a virtual
4587 package which they provide (see below): this does not
4588 prevent their installation, and allows a package to conflict
4589 with others providing a replacement for it. You use this
4590 feature when you want the package in question to be the only
4591 package providing some feature.
4595 A <tt>Conflicts</tt> entry should almost never have an
4596 "earlier than" version clause. This would prevent
4597 <prgn>dpkg</prgn> from upgrading or installing the package
4598 which declared such a conflict until the upgrade or removal
4599 of the conflicted-with package had been completed. Instead,
4600 <tt>Breaks</tt> may be used.
4604 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4608 As well as the names of actual ("concrete") packages, the
4609 package relationship fields <tt>Depends</tt>,
4610 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4611 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4612 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4613 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4614 may mention "virtual packages".
4618 A <em>virtual package</em> is one which appears in the
4619 <tt>Provides</tt> control file field of another package.
4620 The effect is as if the package(s) which provide a
4621 particular virtual package name had been listed by name
4622 everywhere the virtual package name appears. (See also <ref
4627 If there are both concrete and virtual packages of the same
4628 name, then the dependency may be satisfied (or the conflict
4629 caused) by either the concrete package with the name in
4630 question or any other concrete package which provides the
4631 virtual package with the name in question. This is so that,
4632 for example, supposing we have
4633 <example compact="compact">
4636 </example> and someone else releases an enhanced version of
4637 the <tt>bar</tt> package they can say:
4638 <example compact="compact">
4642 and the <tt>bar-plus</tt> package will now also satisfy the
4643 dependency for the <tt>foo</tt> package.
4647 If a relationship field has a version number attached
4648 then only real packages will be considered to see whether
4649 the relationship is satisfied (or the prohibition violated,
4650 for a conflict or breakage) - it is assumed that a real
4651 package which provides the virtual package is not of the
4652 "right" version. So, a <tt>Provides</tt> field may not
4653 contain version numbers, and the version number of the
4654 concrete package which provides a particular virtual package
4655 will not be looked at when considering a dependency on or
4656 conflict with the virtual package name.
4660 It is likely that the ability will be added in a future
4661 release of <prgn>dpkg</prgn> to specify a version number for
4662 each virtual package it provides. This feature is not yet
4663 present, however, and is expected to be used only
4668 If you want to specify which of a set of real packages
4669 should be the default to satisfy a particular dependency on
4670 a virtual package, you should list the real package as an
4671 alternative before the virtual one.
4676 <sect id="replaces"><heading>Overwriting files and replacing
4677 packages - <tt>Replaces</tt></heading>
4680 Packages can declare in their control file that they should
4681 overwrite files in certain other packages, or completely
4682 replace other packages. The <tt>Replaces</tt> control file
4683 field has these two distinct purposes.
4686 <sect1><heading>Overwriting files in other packages</heading>
4689 Firstly, as mentioned before, it is usually an error for a
4690 package to contain files which are on the system in
4695 However, if the overwriting package declares that it
4696 <tt>Replaces</tt> the one containing the file being
4697 overwritten, then <prgn>dpkg</prgn> will replace the file
4698 from the old package with that from the new. The file
4699 will no longer be listed as "owned" by the old package.
4703 If a package is completely replaced in this way, so that
4704 <prgn>dpkg</prgn> does not know of any files it still
4705 contains, it is considered to have "disappeared". It will
4706 be marked as not wanted on the system (selected for
4707 removal) and not installed. Any <tt>conffile</tt>s
4708 details noted for the package will be ignored, as they
4709 will have been taken over by the overwriting package. The
4710 package's <prgn>postrm</prgn> script will be run with a
4711 special argument to allow the package to do any final
4712 cleanup required. See <ref id="mscriptsinstact">.
4715 Replaces is a one way relationship -- you have to
4716 install the replacing package after the replaced
4723 For this usage of <tt>Replaces</tt>, virtual packages (see
4724 <ref id="virtual">) are not considered when looking at a
4725 <tt>Replaces</tt> field - the packages declared as being
4726 replaced must be mentioned by their real names.
4730 Furthermore, this usage of <tt>Replaces</tt> only takes
4731 effect when both packages are at least partially on the
4732 system at once, so that it can only happen if they do not
4733 conflict or if the conflict has been overridden.
4738 <sect1><heading>Replacing whole packages, forcing their
4742 Secondly, <tt>Replaces</tt> allows the packaging system to
4743 resolve which package should be removed when there is a
4744 conflict - see <ref id="conflicts">. This usage only
4745 takes effect when the two packages <em>do</em> conflict,
4746 so that the two usages of this field do not interfere with
4751 In this situation, the package declared as being replaced
4752 can be a virtual package, so for example, all mail
4753 transport agents (MTAs) would have the following fields in
4754 their control files:
4755 <example compact="compact">
4756 Provides: mail-transport-agent
4757 Conflicts: mail-transport-agent
4758 Replaces: mail-transport-agent
4760 ensuring that only one MTA can be installed at any one
4765 <sect id="sourcebinarydeps">
4766 <heading>Relationships between source and binary packages -
4767 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4768 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
4772 Source packages that require certain binary packages to be
4773 installed or absent at the time of building the package
4774 can declare relationships to those binary packages.
4778 This is done using the <tt>Build-Depends</tt>,
4779 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
4780 <tt>Build-Conflicts-Indep</tt> control file fields.
4784 Build-dependencies on "build-essential" binary packages can be
4785 omitted. Please see <ref id="pkg-relations"> for more information.
4789 The dependencies and conflicts they define must be satisfied
4790 (as defined earlier for binary packages) in order to invoke
4791 the targets in <tt>debian/rules</tt>, as follows:<footnote>
4793 If you make "build-arch" or "binary-arch", you need
4794 Build-Depends. If you make "build-indep" or
4795 "binary-indep", you need Build-Depends and
4796 Build-Depends-Indep. If you make "build" or "binary",
4800 There is no Build-Depends-Arch; this role is essentially
4801 met with Build-Depends. Anyone building the
4802 <tt>build-indep</tt> and binary-indep<tt></tt> targets
4803 is basically assumed to be building the whole package
4804 anyway and so installs all build dependencies. The
4805 autobuilders use <tt>dpkg-buildpackage -B</tt>, which
4806 calls <tt>build</tt> (not <tt>build-arch</tt>, since it
4807 does not yet know how to check for its existence) and
4808 <tt>binary-arch</tt>.
4811 The purpose of the original split, I recall, was so that
4812 the autobuilders wouldn't need to install extra packages
4813 needed only for the binary-indep targets. But without a
4814 build-arch/build-indep split, this didn't work, since
4815 most of the work is done in the build target, not in the
4821 <tag><tt>Build-Depends</tt>, <tt>Build-Conflicts</tt></tag>
4823 The <tt>Build-Depends</tt> and
4824 <tt>Build-Conflicts</tt> fields must be satisfied when
4825 any of the following targets is invoked:
4826 <tt>build</tt>, <tt>clean</tt>, <tt>binary</tt>,
4827 <tt>binary-arch</tt>, <tt>build-arch</tt>,
4828 <tt>build-indep</tt> and <tt>binary-indep</tt>.
4830 <tag><tt>Build-Depends-Indep</tt>,
4831 <tt>Build-Conflicts-Indep</tt></tag>
4833 The <tt>Build-Depends-Indep</tt> and
4834 <tt>Build-Conflicts-Indep</tt> fields must be
4835 satisfied when any of the following targets is
4836 invoked: <tt>build</tt>, <tt>build-indep</tt>,
4837 <tt>binary</tt> and <tt>binary-indep</tt>.
4847 <chapt id="sharedlibs"><heading>Shared libraries</heading>
4850 Packages containing shared libraries must be constructed with
4851 a little care to make sure that the shared library is always
4852 available. This is especially important for packages whose
4853 shared libraries are vitally important, such as the C library
4854 (currently <tt>libc6</tt>).
4858 Packages involving shared libraries should be split up into
4859 several binary packages. This section mostly deals with how
4860 this separation is to be accomplished; rules for files within
4861 the shared library packages are in <ref id="libraries"> instead.
4864 <sect id="sharedlibs-runtime">
4865 <heading>Run-time shared libraries</heading>
4868 The run-time shared library needs to be placed in a package
4869 whose name changes whenever the shared object version
4872 Since it is common place to install several versions of a
4873 package that just provides shared libraries, it is a
4874 good idea that the library package should not
4875 contain any extraneous non-versioned files, unless they
4876 happen to be in versioned directories.</p>
4878 The most common mechanism is to place it in a package
4880 <package><var>libraryname</var><var>soversion</var></package>,
4881 where <file><var>soversion</var></file> is the version number
4882 in the soname of the shared library<footnote>
4883 The soname is the shared object name: it's the thing
4884 that has to match exactly between building an executable
4885 and running it for the dynamic linker to be able run the
4886 program. For example, if the soname of the library is
4887 <file>libfoo.so.6</file>, the library package would be
4888 called <file>libfoo6</file>.
4890 Alternatively, if it would be confusing to directly append
4891 <var>soversion</var> to <var>libraryname</var> (e.g. because
4892 <var>libraryname</var> itself ends in a number), you may use
4893 <package><var>libraryname</var>-<var>soversion</var></package> and
4894 <package><var>libraryname</var>-<var>soversion</var>-dev</package>
4899 If you have several shared libraries built from the same
4900 source tree you may lump them all together into a single
4901 shared library package, provided that you change all of
4902 their sonames at once (so that you don't get filename
4903 clashes if you try to install different versions of the
4904 combined shared libraries package).
4908 The package should install the shared libraries under
4909 their normal names. For example, the <package>libgdbm3</package>
4910 package should install <file>libgdbm.so.3.0.0</file> as
4911 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
4912 renamed or re-linked by any <prgn>prerm</prgn> or
4913 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
4914 of renaming things safely without affecting running programs,
4915 and attempts to interfere with this are likely to lead to
4920 Shared libraries should not be installed executable, since
4921 the dynamic linker does not require this and trying to
4922 execute a shared library usually results in a core dump.
4926 The run-time library package should include the symbolic link that
4927 <prgn>ldconfig</prgn> would create for the shared libraries.
4928 For example, the <package>libgdbm3</package> package should include
4929 a symbolic link from <file>/usr/lib/libgdbm.so.3</file> to
4930 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
4931 linker (for example <prgn>ld.so</prgn> or
4932 <prgn>ld-linux.so.*</prgn>) can find the library between the
4933 time that <prgn>dpkg</prgn> installs it and the time that
4934 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
4936 The package management system requires the library to be
4937 placed before the symbolic link pointing to it in the
4938 <file>.deb</file> file. This is so that when
4939 <prgn>dpkg</prgn> comes to install the symlink
4940 (overwriting the previous symlink pointing at an older
4941 version of the library), the new shared library is already
4942 in place. In the past, this was achieved by creating the
4943 library in the temporary packaging directory before
4944 creating the symlink. Unfortunately, this was not always
4945 effective, since the building of the tar file in the
4946 <file>.deb</file> depended on the behavior of the underlying
4947 file system. Some file systems (such as reiserfs) reorder
4948 the files so that the order of creation is forgotten.
4949 Since version 1.7.0, <prgn>dpkg</prgn>
4950 reorders the files itself as necessary when building a
4951 package. Thus it is no longer important to concern
4952 oneself with the order of file creation.
4956 <sect1 id="ldconfig">
4957 <heading><tt>ldconfig</tt></heading>
4960 Any package installing shared libraries in one of the default
4961 library directories of the dynamic linker (which are currently
4962 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
4963 listed in <file>/etc/ld.so.conf</file><footnote>
4965 <list compact="compact">
4966 <item>/usr/local/lib</item>
4967 <item>/usr/lib/libc5-compat</item>
4968 <item>/lib/libc5-compat</item>
4971 must use <prgn>ldconfig</prgn> to update the shared library
4976 The package maintainer scripts must only call
4977 <prgn>ldconfig</prgn> under these circumstances:
4978 <list compact="compact">
4979 <item>When the <prgn>postinst</prgn> script is run with a
4980 first argument of <tt>configure</tt>, the script must call
4981 <prgn>ldconfig</prgn>, and may optionally invoke
4982 <prgn>ldconfig</prgn> at other times.
4984 <item>When the <prgn>postrm</prgn> script is run with a
4985 first argument of <tt>remove</tt>, the script should call
4986 <prgn>ldconfig</prgn>.
4991 During install or upgrade, the preinst is called before
4992 the new files are installed, so calling "ldconfig" is
4993 pointless. The preinst of an existing package can also be
4994 called if an upgrade fails. However, this happens during
4995 the critical time when a shared libs may exist on-disk
4996 under a temporary name. Thus, it is dangerous and
4997 forbidden by current policy to call "ldconfig" at this
5002 When a package is installed or upgraded, "postinst
5003 configure" runs after the new files are safely on-disk.
5004 Since it is perfectly safe to invoke ldconfig
5005 unconditionally in a postinst, it is OK for a package to
5006 simply put ldconfig in its postinst without checking the
5007 argument. The postinst can also be called to recover from
5008 a failed upgrade. This happens before any new files are
5009 unpacked, so there is no reason to call "ldconfig" at this
5014 For a package that is being removed, prerm is
5015 called with all the files intact, so calling ldconfig is
5016 useless. The other calls to "prerm" happen in the case of
5017 upgrade at a time when all the files of the old package
5018 are on-disk, so again calling "ldconfig" is pointless.
5022 postrm, on the other hand, is called with the "remove"
5023 argument just after the files are removed, so this is
5024 the proper time to call "ldconfig" to notify the system
5025 of the fact that the shared libraries from the package
5026 are removed. The postrm can be called at several other
5027 times. At the time of "postrm purge", "postrm
5028 abort-install", or "postrm abort-upgrade", calling
5029 "ldconfig" is useless because the shared lib files are
5030 not on-disk. However, when "postrm" is invoked with
5031 arguments "upgrade", "failed-upgrade", or "disappear", a
5032 shared lib may exist on-disk under a temporary filename.
5040 <sect id="sharedlibs-support-files">
5041 <heading>Shared library support files</heading>
5044 If your package contains files whose names do not change with
5045 each change in the library shared object version, you must not
5046 put them in the shared library package. Otherwise, several
5047 versions of the shared library cannot be installed at the same
5048 time without filename clashes, making upgrades and transitions
5049 unnecessarily difficult.
5053 It is recommended that supporting files and run-time support
5054 programs that do not need to be invoked manually by users, but
5055 are nevertheless required for the package to function, be placed
5056 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5057 preferably under <file>/usr/lib/</file><var>package-name</var>.
5058 If the program or file is architecture independent, the
5059 recommendation is for it to be placed in a subdirectory of
5060 <file>/usr/share</file> instead, preferably under
5061 <file>/usr/share/</file><var>package-name</var>. Following the
5062 <var>package-name</var> naming convention ensures that the file
5063 names change when the shared object version changes.
5067 Run-time support programs that use the shared library but are
5068 not required for the library to function or files used by the
5069 shared library that can be used by any version of the shared
5070 library package should instead be put in a separate package.
5071 This package might typically be named
5072 <package><var>libraryname</var>-tools</package>; note the
5073 absence of the <var>soversion</var> in the package name.
5077 Files and support programs only useful when compiling software
5078 against the library should be included in the development
5079 package for the library.<footnote>
5080 For example, a <file><var>package-name</var>-config</file>
5081 script or <package>pkg-config</package> configuration files.
5086 <sect id="sharedlibs-static">
5087 <heading>Static libraries</heading>
5090 The static library (<file><var>libraryname.a</var></file>)
5091 is usually provided in addition to the shared version.
5092 It is placed into the development package (see below).
5096 In some cases, it is acceptable for a library to be
5097 available in static form only; these cases include:
5099 <item>libraries for languages whose shared library support
5100 is immature or unstable</item>
5101 <item>libraries whose interfaces are in flux or under
5102 development (commonly the case when the library's
5103 major version number is zero, or where the ABI breaks
5104 across patchlevels)</item>
5105 <item>libraries which are explicitly intended to be
5106 available only in static form by their upstream
5111 <sect id="sharedlibs-dev">
5112 <heading>Development files</heading>
5115 The development files associated to a shared library need to be
5116 placed in a package called
5117 <package><var>libraryname</var><var>soversion</var>-dev</package>,
5118 or if you prefer only to support one development version at a
5119 time, <package><var>libraryname</var>-dev</package>.
5123 In case several development versions of a library exist, you may
5124 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5125 <ref id="conflicts">) to ensure that the user only installs one
5126 development version at a time (as different development versions are
5127 likely to have the same header files in them, which would cause a
5128 filename clash if both were installed).
5132 The development package should contain a symlink for the associated
5133 shared library without a version number. For example, the
5134 <package>libgdbm-dev</package> package should include a symlink
5135 from <file>/usr/lib/libgdbm.so</file> to
5136 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5137 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5138 <file>libgdbm.so</file> when compiling dynamically.
5142 <sect id="sharedlibs-intradeps">
5143 <heading>Dependencies between the packages of the same library</heading>
5146 Typically the development version should have an exact
5147 version dependency on the runtime library, to make sure that
5148 compilation and linking happens correctly. The
5149 <tt>${binary:Version}</tt> substitution variable can be
5150 useful for this purpose.
5152 Previously, <tt>${Source-Version}</tt> was used, but its name
5153 was confusing and it has been deprecated since dpkg 1.13.19.
5158 <sect id="sharedlibs-shlibdeps">
5159 <heading>Dependencies between the library and other packages -
5160 the <tt>shlibs</tt> system</heading>
5163 If a package contains a binary or library which links to a
5164 shared library, we must ensure that when the package is
5165 installed on the system, all of the libraries needed are
5166 also installed. This requirement led to the creation of the
5167 <tt>shlibs</tt> system, which is very simple in its design:
5168 any package which <em>provides</em> a shared library also
5169 provides information on the package dependencies required to
5170 ensure the presence of this library, and any package which
5171 <em>uses</em> a shared library uses this information to
5172 determine the dependencies it requires. The files which
5173 contain the mapping from shared libraries to the necessary
5174 dependency information are called <file>shlibs</file> files.
5178 Thus, when a package is built which contains any shared
5179 libraries, it must provide a <file>shlibs</file> file for other
5180 packages to use, and when a package is built which contains
5181 any shared libraries or compiled binaries, it must run
5182 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5183 on these to determine the libraries used and hence the
5184 dependencies needed by this package.<footnote>
5186 In the past, the shared libraries linked to were
5187 determined by calling <prgn>ldd</prgn>, but now
5188 <prgn>objdump</prgn> is used to do this. The only
5189 change this makes to package building is that
5190 <prgn>dpkg-shlibdeps</prgn> must also be run on shared
5191 libraries, whereas in the past this was unnecessary.
5192 The rest of this footnote explains the advantage that
5197 We say that a binary <tt>foo</tt> <em>directly</em> uses
5198 a library <tt>libbar</tt> if it is explicitly linked
5199 with that library (that is, it uses the flag
5200 <tt>-lbar</tt> during the linking stage). Other
5201 libraries that are needed by <tt>libbar</tt> are linked
5202 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5203 linker will load them automatically when it loads
5204 <tt>libbar</tt>. A package should depend on
5205 the libraries it directly uses, and the dependencies for
5206 those libraries should automatically pull in the other
5211 Unfortunately, the <prgn>ldd</prgn> program shows both
5212 the directly and indirectly used libraries, meaning that
5213 the dependencies determined included both direct and
5214 indirect dependencies. The use of <prgn>objdump</prgn>
5215 avoids this problem by determining only the directly
5220 A good example of where this helps is the following. We
5221 could update <tt>libimlib</tt> with a new version that
5222 supports a new graphics format called dgf (but retaining
5223 the same major version number). If we used the old
5224 <prgn>ldd</prgn> method, every package that uses
5225 <tt>libimlib</tt> would need to be recompiled so it
5226 would also depend on <tt>libdgf</tt> or it wouldn't run
5227 due to missing symbols. However with the new system,
5228 packages using <tt>libimlib</tt> can rely on
5229 <tt>libimlib</tt> itself having the dependency on
5230 <tt>libdgf</tt> and so they would not need rebuilding.
5236 In the following sections, we will first describe where the
5237 various <tt>shlibs</tt> files are to be found, then how to
5238 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5239 file format and how to create them if your package contains a
5244 <heading>The <tt>shlibs</tt> files present on the system</heading>
5247 There are several places where <tt>shlibs</tt> files are
5248 found. The following list gives them in the order in which
5250 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5251 (The first one which gives the required information is used.)
5257 <p><file>debian/shlibs.local</file></p>
5260 This lists overrides for this package. Its use is
5261 described below (see <ref id="shlibslocal">).
5266 <p><file>/etc/dpkg/shlibs.override</file></p>
5269 This lists global overrides. This list is normally
5270 empty. It is maintained by the local system
5276 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5279 When packages are being built, any
5280 <file>debian/shlibs</file> files are copied into the
5281 control file area of the temporary build directory and
5282 given the name <file>shlibs</file>. These files give
5283 details of any shared libraries included in the
5285 An example may help here. Let us say that the
5286 source package <tt>foo</tt> generates two binary
5287 packages, <tt>libfoo2</tt> and
5288 <tt>foo-runtime</tt>. When building the binary
5289 packages, the two packages are created in the
5290 directories <file>debian/libfoo2</file> and
5291 <file>debian/foo-runtime</file> respectively.
5292 (<file>debian/tmp</file> could be used instead of one
5293 of these.) Since <tt>libfoo2</tt> provides the
5294 <tt>libfoo</tt> shared library, it will require a
5295 <tt>shlibs</tt> file, which will be installed in
5296 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually
5298 <file>/var/lib/dpkg/info/libfoo2.shlibs</file>. Then
5299 when <prgn>dpkg-shlibdeps</prgn> is run on the
5301 <file>debian/foo-runtime/usr/bin/foo-prog</file>, it
5303 <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5304 determine whether <tt>foo-prog</tt>'s library
5305 dependencies are satisfied by any of the libraries
5306 provided by <tt>libfoo2</tt>. For this reason,
5307 <prgn>dpkg-shlibdeps</prgn> must only be run once
5308 all of the individual binary packages'
5309 <tt>shlibs</tt> files have been installed into the
5316 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5319 These are the <file>shlibs</file> files corresponding to
5320 all of the packages installed on the system, and are
5321 maintained by the relevant package maintainers.
5326 <p><file>/etc/dpkg/shlibs.default</file></p>
5329 This file lists any shared libraries whose packages
5330 have failed to provide correct <file>shlibs</file> files.
5331 It was used when the <file>shlibs</file> setup was first
5332 introduced, but it is now normally empty. It is
5333 maintained by the <tt>dpkg</tt> maintainer.
5341 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5342 <file>shlibs</file> files</heading>
5346 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5347 into your <file>debian/rules</file> file. If your package
5348 contains only compiled binaries and libraries (but no scripts),
5349 you can use a command such as:
5350 <example compact="compact">
5351 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5352 debian/tmp/usr/lib/*
5354 Otherwise, you will need to explicitly list the compiled
5355 binaries and libraries.<footnote>
5356 If you are using <tt>debhelper</tt>, the
5357 <prgn>dh_shlibdeps</prgn> program will do this work for
5358 you. It will also correctly handle multi-binary
5364 This command puts the dependency information into the
5365 <file>debian/substvars</file> file, which is then used by
5366 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5367 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5368 field in the control file for this to work.
5372 If <prgn>dpkg-shlibdeps</prgn> doesn't complain, you're
5373 done. If it does complain you might need to create your own
5374 <file>debian/shlibs.local</file> file, as explained below (see
5375 <ref id="shlibslocal">).
5379 If you have multiple binary packages, you will need to call
5380 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5381 compiled libraries or binaries. In such a case, you will
5382 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5383 utilities to specify a different <file>substvars</file> file.
5387 If you are creating a udeb for use in the Debian Installer,
5388 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
5389 should use the dependency line of type <tt>udeb</tt> by
5390 adding the <tt>-tudeb</tt> option<footnote>
5391 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5392 will automatically add this option if it knows it is
5394 </footnote>. If there is no dependency line of type <tt>udeb</tt>
5395 in the <file>shlibs</file> file, <prgn>dpkg-shlibdeps</prgn> will
5396 fall back to the regular dependency line.
5400 For more details on dpkg-shlibdeps, please see
5401 <ref id="pkg-dpkg-shlibdeps"> and
5402 <manref name="dpkg-shlibdeps" section="1">.
5407 <heading>The <file>shlibs</file> File Format</heading>
5410 Each <file>shlibs</file> file has the same format. Lines
5411 beginning with <tt>#</tt> are considered to be comments and
5412 are ignored. Each line is of the form:
5413 <example compact="compact">
5414 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5419 We will explain this by reference to the example of the
5420 <tt>zlib1g</tt> package, which (at the time of writing)
5421 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5425 <var>type</var> is an optional element that indicates the type
5426 of package for which the line is valid. The only type currently
5427 in use is <tt>udeb</tt>. The colon and space after the type are
5432 <var>library-name</var> is the name of the shared library,
5433 in this case <tt>libz</tt>. (This must match the name part
5434 of the soname, see below.)
5438 <var>soname-version</var> is the version part of the soname of
5439 the library. The soname is the thing that must exactly match
5440 for the library to be recognized by the dynamic linker, and is
5442 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5443 example, <tt>libz.so.1</tt>.<footnote>
5444 This can be determined using the command
5445 <example compact="compact">
5446 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5449 The version part is the part which comes after
5450 <tt>.so.</tt>, so in our case, it is <tt>1</tt>.
5454 <var>dependencies</var> has the same syntax as a dependency
5455 field in a binary package control file. It should give
5456 details of which packages are required to satisfy a binary
5457 built against the version of the library contained in the
5458 package. See <ref id="depsyntax"> for details.
5462 In our example, if the first version of the <tt>zlib1g</tt>
5463 package which contained a minor number of at least
5464 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5465 <tt>shlibs</tt> entry for this library could say:
5466 <example compact="compact">
5467 libz 1 zlib1g (>= 1:1.1.3)
5469 The version-specific dependency is to avoid warnings from
5470 the dynamic linker about using older shared libraries with
5475 As zlib1g also provides a udeb containing the shared library,
5476 there would also be a second line:
5477 <example compact="compact">
5478 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5484 <heading>Providing a <file>shlibs</file> file</heading>
5487 If your package provides a shared library, you need to create
5488 a <file>shlibs</file> file following the format described above.
5489 It is usual to call this file <file>debian/shlibs</file> (but if
5490 you have multiple binary packages, you might want to call it
5491 <file>debian/shlibs.<var>package</var></file> instead). Then
5492 let <file>debian/rules</file> install it in the control area:
5493 <example compact="compact">
5494 install -m644 debian/shlibs debian/tmp/DEBIAN
5496 or, in the case of a multi-binary package:
5497 <example compact="compact">
5498 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5500 An alternative way of doing this is to create the
5501 <file>shlibs</file> file in the control area directly from
5502 <file>debian/rules</file> without using a <file>debian/shlibs</file>
5503 file at all,<footnote>
5504 This is what <prgn>dh_makeshlibs</prgn> in the
5505 <tt>debhelper</tt> suite does. If your package also has a udeb
5506 that provides a shared library, <prgn>dh_makeshlibs</prgn> can
5507 automatically generate the <tt>udeb:</tt> lines if you specify
5508 the name of the udeb with the <tt>--add-udeb</tt> option.
5510 since the <file>debian/shlibs</file> file itself is ignored by
5511 <prgn>dpkg-shlibdeps</prgn>.
5515 As <prgn>dpkg-shlibdeps</prgn> reads the
5516 <file>DEBIAN/shlibs</file> files in all of the binary packages
5517 being built from this source package, all of the
5518 <file>DEBIAN/shlibs</file> files should be installed before
5519 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5524 <sect1 id="shlibslocal">
5525 <heading>Writing the <file>debian/shlibs.local</file> file</heading>
5528 This file is intended only as a <em>temporary</em> fix if
5529 your binaries or libraries depend on a library whose package
5530 does not yet provide a correct <file>shlibs</file> file.
5534 We will assume that you are trying to package a binary
5535 <tt>foo</tt>. When you try running
5536 <prgn>dpkg-shlibdeps</prgn> you get the following error
5537 message (<tt>-O</tt> displays the dependency information on
5538 <tt>stdout</tt> instead of writing it to
5539 <tt>debian/substvars</tt>, and the lines have been wrapped
5540 for ease of reading):
5541 <example compact="compact">
5542 $ dpkg-shlibdeps -O debian/tmp/usr/bin/foo
5543 dpkg-shlibdeps: warning: unable to find dependency
5544 information for shared library libbar (soname 1,
5545 path /usr/lib/libbar.so.1, dependency field Depends)
5546 shlibs:Depends=libc6 (>= 2.2.2-2)
5548 You can then run <prgn>ldd</prgn> on the binary to find the
5549 full location of the library concerned:
5550 <example compact="compact">
5552 libbar.so.1 => /usr/lib/libbar.so.1 (0x4001e000)
5553 libc.so.6 => /lib/libc.so.6 (0x40032000)
5554 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
5556 So the <prgn>foo</prgn> binary depends on the
5557 <prgn>libbar</prgn> shared library, but no package seems to
5558 provide a <file>*.shlibs</file> file handling
5559 <file>libbar.so.1</file> in <file>/var/lib/dpkg/info/</file>. Let's
5560 determine the package responsible:
5561 <example compact="compact">
5562 $ dpkg -S /usr/lib/libbar.so.1
5563 bar1: /usr/lib/libbar.so.1
5564 $ dpkg -s bar1 | grep Version
5567 This tells us that the <tt>bar1</tt> package, version 1.0-1,
5568 is the one we are using. Now we can file a bug against the
5569 <tt>bar1</tt> package and create our own
5570 <file>debian/shlibs.local</file> to locally fix the problem.
5571 Including the following line into your
5572 <file>debian/shlibs.local</file> file:
5573 <example compact="compact">
5574 libbar 1 bar1 (>= 1.0-1)
5576 should allow the package build to work.
5580 As soon as the maintainer of <tt>bar1</tt> provides a
5581 correct <file>shlibs</file> file, you should remove this line
5582 from your <file>debian/shlibs.local</file> file. (You should
5583 probably also then have a versioned <tt>Build-Depends</tt>
5584 on <tt>bar1</tt> to help ensure that others do not have the
5585 same problem building your package.)
5594 <chapt id="opersys"><heading>The Operating System</heading>
5597 <heading>File system hierarchy</heading>
5601 <heading>File System Structure</heading>
5604 The location of all installed files and directories must
5605 comply with the Filesystem Hierarchy Standard (FHS),
5606 version 2.3, with the exceptions noted below, and except
5607 where doing so would violate other terms of Debian
5608 Policy. The following exceptions to the FHS apply:
5613 The optional rules related to user specific
5614 configuration files for applications are stored in
5615 the user's home directory are relaxed. It is
5616 recommended that such files start with the
5617 '<tt>.</tt>' character (a "dot file"), and if an
5618 application needs to create more than one dot file
5619 then the preferred placement is in a subdirectory
5620 with a name starting with a '.' character, (a "dot
5621 directory"). In this case it is recommended the
5622 configuration files not start with the '.'
5628 The requirement for amd64 to use <file>/lib64</file>
5629 for 64 bit binaries is removed.
5634 The requirement for object files, internal binaries, and
5635 libraries, including <file>libc.so.*</file>, to be located
5636 directly under <file>/lib{,32}</file> and
5637 <file>/usr/lib{,32}</file> is amended, permitting files
5638 to instead be installed to
5639 <file>/lib/<var>triplet</var></file> and
5640 <file>/usr/lib/<var>triplet</var></file>, where
5641 <tt><var>triplet</var></tt> is the value returned by
5642 <tt>dpkg-architecture -qDEB_HOST_GNU_TYPE</tt> for the
5643 architecture of the package. Packages may <em>not</em>
5644 install files to any <var>triplet</var> path other
5645 than the one matching the architecture of that package;
5646 for instance, an <tt>Architecture: amd64</tt> package
5647 containing 32-bit x86 libraries may not install these
5648 libraries to <file>/usr/lib/i486-linux-gnu</file>.
5650 This is necessary in order to reserve the directories for
5651 use in cross-installation of library packages from other
5652 architectures, as part of the planned deployment of
5657 Applications may also use a single subdirectory under
5658 <file>/usr/lib/<var>triplet</var></file>.
5661 The execution time linker/loader, ld*, must still be made
5662 available in the existing location under /lib or /lib64
5663 since this is part of the ELF ABI for the architecture.
5668 The requirement that
5669 <file>/usr/local/share/man</file> be "synonymous"
5670 with <file>/usr/local/man</file> is relaxed to a
5675 The requirement that windowmanagers with a single
5676 configuration file call it <file>system.*wmrc</file>
5677 is removed, as is the restriction that the window
5678 manager subdirectory be named identically to the
5679 window manager name itself.
5684 The requirement that boot manager configuration
5685 files live in <file>/etc</file>, or at least are
5686 symlinked there, is relaxed to a recommendation.
5691 The following directories in the root filesystem are
5692 additionally allowed: <file>/sys</file> and
5693 <file>/selinux</file>. <footnote>These directories
5694 are used as mount points to mount virtual filesystems
5695 to get access to kernel information.</footnote>
5702 The version of this document referred here can be
5703 found in the <tt>debian-policy</tt> package or on <url
5704 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5705 name="FHS (Debian copy)"> alongside this manual (or, if
5706 you have the <package>debian-policy</package> installed,
5708 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5709 (local copy)">). The
5710 latest version, which may be a more recent version, may
5712 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5713 Specific questions about following the standard may be
5714 asked on the <tt>debian-devel</tt> mailing list, or
5715 referred to the FHS mailing list (see the
5716 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
5722 <heading>Site-specific programs</heading>
5725 As mandated by the FHS, packages must not place any
5726 files in <file>/usr/local</file>, either by putting them in
5727 the file system archive to be unpacked by <prgn>dpkg</prgn>
5728 or by manipulating them in their maintainer scripts.
5732 However, the package may create empty directories below
5733 <file>/usr/local</file> so that the system administrator knows
5734 where to place site-specific files. These are not
5735 directories <em>in</em> <file>/usr/local</file>, but are
5736 children of directories in <file>/usr/local</file>. These
5737 directories (<file>/usr/local/*/dir/</file>)
5738 should be removed on package removal if they are
5743 Note that this applies only to
5744 directories <em>below</em> <file>/usr/local</file>,
5745 not <em>in</em> <file>/usr/local</file>. Packages must
5746 not create sub-directories in the
5747 directory <file>/usr/local</file> itself, except those
5748 listed in FHS, section 4.5. However, you may create
5749 directories below them as you wish. You must not remove
5750 any of the directories listed in 4.5, even if you created
5755 Since <file>/usr/local</file> can be mounted read-only from a
5756 remote server, these directories must be created and
5757 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
5758 maintainer scripts and not be included in the
5759 <file>.deb</file> archive. These scripts must not fail if
5760 either of these operations fail.
5764 For example, the <tt>emacsen-common</tt> package could
5765 contain something like
5766 <example compact="compact">
5767 if [ ! -e /usr/local/share/emacs ]
5769 if mkdir /usr/local/share/emacs 2>/dev/null
5771 chown root:staff /usr/local/share/emacs
5772 chmod 2775 /usr/local/share/emacs
5776 in its <prgn>postinst</prgn> script, and
5777 <example compact="compact">
5778 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
5779 rmdir /usr/local/share/emacs 2>/dev/null || true
5781 in the <prgn>prerm</prgn> script. (Note that this form is
5782 used to ensure that if the script is interrupted, the
5783 directory <file>/usr/local/share/emacs</file> will still be
5788 If you do create a directory in <file>/usr/local</file> for
5789 local additions to a package, you should ensure that
5790 settings in <file>/usr/local</file> take precedence over the
5791 equivalents in <file>/usr</file>.
5795 However, because <file>/usr/local</file> and its contents are
5796 for exclusive use of the local administrator, a package
5797 must not rely on the presence or absence of files or
5798 directories in <file>/usr/local</file> for normal operation.
5802 The <file>/usr/local</file> directory itself and all the
5803 subdirectories created by the package should (by default) have
5804 permissions 2775 (group-writable and set-group-id) and be
5805 owned by <tt>root:staff</tt>.
5810 <heading>The system-wide mail directory</heading>
5812 The system-wide mail directory
5813 is <file>/var/mail</file>. This directory is part of the
5814 base system and should not be owned by any particular mail
5815 agents. The use of the old
5816 location <file>/var/spool/mail</file> is deprecated, even
5817 though the spool may still be physically located there.
5823 <heading>Users and groups</heading>
5826 <heading>Introduction</heading>
5828 The Debian system can be configured to use either plain or
5833 Some user ids (UIDs) and group ids (GIDs) are reserved
5834 globally for use by certain packages. Because some
5835 packages need to include files which are owned by these
5836 users or groups, or need the ids compiled into binaries,
5837 these ids must be used on any Debian system only for the
5838 purpose for which they are allocated. This is a serious
5839 restriction, and we should avoid getting in the way of
5840 local administration policies. In particular, many sites
5841 allocate users and/or local system groups starting at 100.
5845 Apart from this we should have dynamically allocated ids,
5846 which should by default be arranged in some sensible
5847 order, but the behavior should be configurable.
5851 Packages other than <tt>base-passwd</tt> must not modify
5852 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
5853 <file>/etc/group</file> or <file>/etc/gshadow</file>.
5858 <heading>UID and GID classes</heading>
5860 The UID and GID numbers are divided into classes as
5866 Globally allocated by the Debian project, the same
5867 on every Debian system. These ids will appear in
5868 the <file>passwd</file> and <file>group</file> files of all
5869 Debian systems, new ids in this range being added
5870 automatically as the <tt>base-passwd</tt> package is
5875 Packages which need a single statically allocated
5876 uid or gid should use one of these; their
5877 maintainers should ask the <tt>base-passwd</tt>
5885 Dynamically allocated system users and groups.
5886 Packages which need a user or group, but can have
5887 this user or group allocated dynamically and
5888 differently on each system, should use <tt>adduser
5889 --system</tt> to create the group and/or user.
5890 <prgn>adduser</prgn> will check for the existence of
5891 the user or group, and if necessary choose an unused
5892 id based on the ranges specified in
5893 <file>adduser.conf</file>.
5897 <tag>1000-29999:</tag>
5900 Dynamically allocated user accounts. By default
5901 <prgn>adduser</prgn> will choose UIDs and GIDs for
5902 user accounts in this range, though
5903 <file>adduser.conf</file> may be used to modify this
5908 <tag>30000-59999:</tag>
5913 <tag>60000-64999:</tag>
5916 Globally allocated by the Debian project, but only
5917 created on demand. The ids are allocated centrally
5918 and statically, but the actual accounts are only
5919 created on users' systems on demand.
5923 These ids are for packages which are obscure or
5924 which require many statically-allocated ids. These
5925 packages should check for and create the accounts in
5926 <file>/etc/passwd</file> or <file>/etc/group</file> (using
5927 <prgn>adduser</prgn> if it has this facility) if
5928 necessary. Packages which are likely to require
5929 further allocations should have a "hole" left after
5930 them in the allocation, to give them room to
5935 <tag>65000-65533:</tag>
5943 User <tt>nobody</tt>. The corresponding gid refers
5944 to the group <tt>nogroup</tt>.
5951 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
5952 not</em> be used, because it is the error return
5961 <sect id="sysvinit">
5962 <heading>System run levels and <file>init.d</file> scripts</heading>
5964 <sect1 id="/etc/init.d">
5965 <heading>Introduction</heading>
5968 The <file>/etc/init.d</file> directory contains the scripts
5969 executed by <prgn>init</prgn> at boot time and when the
5970 init state (or "runlevel") is changed (see <manref
5971 name="init" section="8">).
5975 There are at least two different, yet functionally
5976 equivalent, ways of handling these scripts. For the sake
5977 of simplicity, this document describes only the symbolic
5978 link method. However, it must not be assumed by maintainer
5979 scripts that this method is being used, and any automated
5980 manipulation of the various runlevel behaviors by
5981 maintainer scripts must be performed using
5982 <prgn>update-rc.d</prgn> as described below and not by
5983 manually installing or removing symlinks. For information
5984 on the implementation details of the other method,
5985 implemented in the <tt>file-rc</tt> package, please refer
5986 to the documentation of that package.
5990 These scripts are referenced by symbolic links in the
5991 <file>/etc/rc<var>n</var>.d</file> directories. When changing
5992 runlevels, <prgn>init</prgn> looks in the directory
5993 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
5994 execute, where <tt><var>n</var></tt> is the runlevel that
5995 is being changed to, or <tt>S</tt> for the boot-up
6000 The names of the links all have the form
6001 <file>S<var>mm</var><var>script</var></file> or
6002 <file>K<var>mm</var><var>script</var></file> where
6003 <var>mm</var> is a two-digit number and <var>script</var>
6004 is the name of the script (this should be the same as the
6005 name of the actual script in <file>/etc/init.d</file>).
6009 When <prgn>init</prgn> changes runlevel first the targets
6010 of the links whose names start with a <tt>K</tt> are
6011 executed, each with the single argument <tt>stop</tt>,
6012 followed by the scripts prefixed with an <tt>S</tt>, each
6013 with the single argument <tt>start</tt>. (The links are
6014 those in the <file>/etc/rc<var>n</var>.d</file> directory
6015 corresponding to the new runlevel.) The <tt>K</tt> links
6016 are responsible for killing services and the <tt>S</tt>
6017 link for starting services upon entering the runlevel.
6021 For example, if we are changing from runlevel 2 to
6022 runlevel 3, init will first execute all of the <tt>K</tt>
6023 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
6024 all of the <tt>S</tt> prefixed scripts in that directory.
6025 The links starting with <tt>K</tt> will cause the
6026 referred-to file to be executed with an argument of
6027 <tt>stop</tt>, and the <tt>S</tt> links with an argument
6032 The two-digit number <var>mm</var> is used to determine
6033 the order in which to run the scripts: low-numbered links
6034 have their scripts run first. For example, the
6035 <tt>K20</tt> scripts will be executed before the
6036 <tt>K30</tt> scripts. This is used when a certain service
6037 must be started before another. For example, the name
6038 server <prgn>bind</prgn> might need to be started before
6039 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
6040 can set up its access lists. In this case, the script
6041 that starts <prgn>bind</prgn> would have a lower number
6042 than the script that starts <prgn>inn</prgn> so that it
6044 <example compact="compact">
6051 The two runlevels 0 (halt) and 6 (reboot) are slightly
6052 different. In these runlevels, the links with an
6053 <tt>S</tt> prefix are still called after those with a
6054 <tt>K</tt> prefix, but they too are called with the single
6055 argument <tt>stop</tt>.
6060 <heading>Writing the scripts</heading>
6063 Packages that include daemons for system services should
6064 place scripts in <file>/etc/init.d</file> to start or stop
6065 services at boot time or during a change of runlevel.
6066 These scripts should be named
6067 <file>/etc/init.d/<var>package</var></file>, and they should
6068 accept one argument, saying what to do:
6071 <tag><tt>start</tt></tag>
6072 <item>start the service,</item>
6074 <tag><tt>stop</tt></tag>
6075 <item>stop the service,</item>
6077 <tag><tt>restart</tt></tag>
6078 <item>stop and restart the service if it's already running,
6079 otherwise start the service</item>
6081 <tag><tt>reload</tt></tag>
6082 <item><p>cause the configuration of the service to be
6083 reloaded without actually stopping and restarting
6086 <tag><tt>force-reload</tt></tag>
6087 <item>cause the configuration to be reloaded if the
6088 service supports this, otherwise restart the
6092 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
6093 <tt>force-reload</tt> options should be supported by all
6094 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
6099 The <file>init.d</file> scripts must ensure that they will
6100 behave sensibly (i.e., returning success and not starting
6101 multiple copies of a service) if invoked with <tt>start</tt>
6102 when the service is already running, or with <tt>stop</tt>
6103 when it isn't, and that they don't kill unfortunately-named
6104 user processes. The best way to achieve this is usually to
6105 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
6110 If a service reloads its configuration automatically (as
6111 in the case of <prgn>cron</prgn>, for example), the
6112 <tt>reload</tt> option of the <file>init.d</file> script
6113 should behave as if the configuration has been reloaded
6118 The <file>/etc/init.d</file> scripts must be treated as
6119 configuration files, either (if they are present in the
6120 package, that is, in the .deb file) by marking them as
6121 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6122 by managing them correctly in the maintainer scripts (see
6123 <ref id="config-files">). This is important since we want
6124 to give the local system administrator the chance to adapt
6125 the scripts to the local system, e.g., to disable a
6126 service without de-installing the package, or to specify
6127 some special command line options when starting a service,
6128 while making sure their changes aren't lost during the next
6133 These scripts should not fail obscurely when the
6134 configuration files remain but the package has been
6135 removed, as configuration files remain on the system after
6136 the package has been removed. Only when <prgn>dpkg</prgn>
6137 is executed with the <tt>--purge</tt> option will
6138 configuration files be removed. In particular, as the
6139 <file>/etc/init.d/<var>package</var></file> script itself is
6140 usually a <tt>conffile</tt>, it will remain on the system
6141 if the package is removed but not purged. Therefore, you
6142 should include a <tt>test</tt> statement at the top of the
6144 <example compact="compact">
6145 test -f <var>program-executed-later-in-script</var> || exit 0
6150 Often there are some variables in the <file>init.d</file>
6151 scripts whose values control the behavior of the scripts,
6152 and which a system administrator is likely to want to
6153 change. As the scripts themselves are frequently
6154 <tt>conffile</tt>s, modifying them requires that the
6155 administrator merge in their changes each time the package
6156 is upgraded and the <tt>conffile</tt> changes. To ease
6157 the burden on the system administrator, such configurable
6158 values should not be placed directly in the script.
6159 Instead, they should be placed in a file in
6160 <file>/etc/default</file>, which typically will have the same
6161 base name as the <file>init.d</file> script. This extra file
6162 should be sourced by the script when the script runs. It
6163 must contain only variable settings and comments in SUSv3
6164 <prgn>sh</prgn> format. It may either be a
6165 <tt>conffile</tt> or a configuration file maintained by
6166 the package maintainer scripts. See <ref id="config-files">
6171 To ensure that vital configurable values are always
6172 available, the <file>init.d</file> script should set default
6173 values for each of the shell variables it uses, either
6174 before sourcing the <file>/etc/default/</file> file or
6175 afterwards using something like the <tt>:
6176 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6177 script must behave sensibly and not fail if the
6178 <file>/etc/default</file> file is deleted.
6182 <file>/var/run</file> and <file>/var/lock</file> may be mounted
6183 as temporary filesystems<footnote>
6184 For example, using the <tt>RAMRUN</tt> and <tt>RAMLOCK</tt>
6185 options in <file>/etc/default/rcS</file>.
6186 </footnote>, so the <file>init.d</file> scripts must handle this
6187 correctly. This will typically amount to creating any required
6188 subdirectories dynamically when the <file>init.d</file> script
6189 is run, rather than including them in the package and relying on
6190 <prgn>dpkg</prgn> to create them.
6195 <heading>Interfacing with the initscript system</heading>
6198 Maintainers should use the abstraction layer provided by
6199 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6200 programs to deal with initscripts in their packages'
6201 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6202 and <prgn>postrm</prgn>.
6206 Directly managing the /etc/rc?.d links and directly
6207 invoking the <file>/etc/init.d/</file> initscripts should
6208 be done only by packages providing the initscript
6209 subsystem (such as <prgn>sysv-rc</prgn> and
6210 <prgn>file-rc</prgn>).
6214 <heading>Managing the links</heading>
6217 The program <prgn>update-rc.d</prgn> is provided for
6218 package maintainers to arrange for the proper creation and
6219 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6220 or their functional equivalent if another method is being
6221 used. This may be used by maintainers in their packages'
6222 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6226 You must not include any <file>/etc/rc<var>n</var>.d</file>
6227 symbolic links in the actual archive or manually create or
6228 remove the symbolic links in maintainer scripts; you must
6229 use the <prgn>update-rc.d</prgn> program instead. (The
6230 former will fail if an alternative method of maintaining
6231 runlevel information is being used.) You must not include
6232 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6233 in the archive either. (Only the <tt>sysvinit</tt>
6238 By default <prgn>update-rc.d</prgn> will start services in
6239 each of the multi-user state runlevels (2, 3, 4, and 5)
6240 and stop them in the halt runlevel (0), the single-user
6241 runlevel (1) and the reboot runlevel (6). The system
6242 administrator will have the opportunity to customize
6243 runlevels by simply adding, moving, or removing the
6244 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6245 symbolic links are being used, or by modifying
6246 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6251 To get the default behavior for your package, put in your
6252 <prgn>postinst</prgn> script
6253 <example compact="compact">
6254 update-rc.d <var>package</var> defaults
6256 and in your <prgn>postrm</prgn>
6257 <example compact="compact">
6258 if [ "$1" = purge ]; then
6259 update-rc.d <var>package</var> remove
6261 </example>. Note that if your package changes runlevels
6262 or priority, you may have to remove and recreate the links,
6263 since otherwise the old links may persist. Refer to the
6264 documentation of <prgn>update-rc.d</prgn>.
6268 This will use a default sequence number of 20. If it does
6269 not matter when or in which order the <file>init.d</file>
6270 script is run, use this default. If it does, then you
6271 should talk to the maintainer of the <prgn>sysvinit</prgn>
6272 package or post to <tt>debian-devel</tt>, and they will
6273 help you choose a number.
6277 For more information about using <tt>update-rc.d</tt>,
6278 please consult its man page <manref name="update-rc.d"
6284 <heading>Running initscripts</heading>
6286 The program <prgn>invoke-rc.d</prgn> is provided to make
6287 it easier for package maintainers to properly invoke an
6288 initscript, obeying runlevel and other locally-defined
6289 constraints that might limit a package's right to start,
6290 stop and otherwise manage services. This program may be
6291 used by maintainers in their packages' scripts.
6295 The package maintainer scripts must use
6296 <prgn>invoke-rc.d</prgn> to invoke the
6297 <file>/etc/init.d/*</file> initscripts, instead of
6298 calling them directly.
6302 By default, <prgn>invoke-rc.d</prgn> will pass any
6303 action requests (start, stop, reload, restart...) to the
6304 <file>/etc/init.d</file> script, filtering out requests
6305 to start or restart a service out of its intended
6310 Most packages will simply need to change:
6311 <example compact="compact">/etc/init.d/<package>
6312 <action></example> in their <prgn>postinst</prgn>
6313 and <prgn>prerm</prgn> scripts to:
6314 <example compact="compact">
6315 if which invoke-rc.d >/dev/null 2>&1; then
6316 invoke-rc.d <var>package</var> <action>
6318 /etc/init.d/<var>package</var> <action>
6324 A package should register its initscript services using
6325 <prgn>update-rc.d</prgn> before it tries to invoke them
6326 using <prgn>invoke-rc.d</prgn>. Invocation of
6327 unregistered services may fail.
6331 For more information about using
6332 <prgn>invoke-rc.d</prgn>, please consult its man page
6333 <manref name="invoke-rc.d" section="8">.
6339 <heading>Boot-time initialization</heading>
6342 There used to be another directory, <file>/etc/rc.boot</file>,
6343 which contained scripts which were run once per machine
6344 boot. This has been deprecated in favour of links from
6345 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6346 described in <ref id="/etc/init.d">. Packages must not
6347 place files in <file>/etc/rc.boot</file>.
6352 <heading>Example</heading>
6355 An example on which you can base your
6356 <file>/etc/init.d</file> scripts is found in
6357 <file>/etc/init.d/skeleton</file>.
6364 <heading>Console messages from <file>init.d</file> scripts</heading>
6367 This section describes the formats to be used for messages
6368 written to standard output by the <file>/etc/init.d</file>
6369 scripts. The intent is to improve the consistency of
6370 Debian's startup and shutdown look and feel. For this
6371 reason, please look very carefully at the details. We want
6372 the messages to have the same format in terms of wording,
6373 spaces, punctuation and case of letters.
6377 Here is a list of overall rules that should be used for
6378 messages generated by <file>/etc/init.d</file> scripts.
6384 The message should fit in one line (fewer than 80
6385 characters), start with a capital letter and end with
6386 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6390 If the script is performing some time consuming task in
6391 the background (not merely starting or stopping a
6392 program, for instance), an ellipsis (three dots:
6393 <tt>...</tt>) should be output to the screen, with no
6394 leading or tailing whitespace or line feeds.
6398 The messages should appear as if the computer is telling
6399 the user what it is doing (politely :-), but should not
6400 mention "it" directly. For example, instead of:
6401 <example compact="compact">
6402 I'm starting network daemons: nfsd mountd.
6404 the message should say
6405 <example compact="compact">
6406 Starting network daemons: nfsd mountd.
6413 <tt>init.d</tt> script should use the following standard
6414 message formats for the situations enumerated below.
6420 <p>When daemons are started</p>
6423 If the script starts one or more daemons, the output
6424 should look like this (a single line, no leading
6426 <example compact="compact">
6427 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6429 The <var>description</var> should describe the
6430 subsystem the daemon or set of daemons are part of,
6431 while <var>daemon-1</var> up to <var>daemon-n</var>
6432 denote each daemon's name (typically the file name of
6437 For example, the output of <file>/etc/init.d/lpd</file>
6439 <example compact="compact">
6440 Starting printer spooler: lpd.
6445 This can be achieved by saying
6446 <example compact="compact">
6447 echo -n "Starting printer spooler: lpd"
6448 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6451 in the script. If there are more than one daemon to
6452 start, the output should look like this:
6453 <example compact="compact">
6454 echo -n "Starting remote file system services:"
6455 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6456 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6457 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6460 This makes it possible for the user to see what is
6461 happening and when the final daemon has been started.
6462 Care should be taken in the placement of white spaces:
6463 in the example above the system administrators can
6464 easily comment out a line if they don't want to start
6465 a specific daemon, while the displayed message still
6471 <p>When a system parameter is being set</p>
6474 If you have to set up different system parameters
6475 during the system boot, you should use this format:
6476 <example compact="compact">
6477 Setting <var>parameter</var> to "<var>value</var>".
6482 You can use a statement such as the following to get
6484 <example compact="compact">
6485 echo "Setting DNS domainname to \"$domainname\"."
6490 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
6491 for the left and right quotation marks. A grave accent
6492 (<tt>`</tt>) is not a quote character; neither is an
6493 apostrophe (<tt>'</tt>).
6498 <p>When a daemon is stopped or restarted</p>
6501 When you stop or restart a daemon, you should issue a
6502 message identical to the startup message, except that
6503 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6504 or <tt>Restarting</tt> respectively.
6508 For example, stopping the printer daemon will look like
6510 <example compact="compact">
6511 Stopping printer spooler: lpd.
6517 <p>When something is executed</p>
6520 There are several examples where you have to run a
6521 program at system startup or shutdown to perform a
6522 specific task, for example, setting the system's clock
6523 using <prgn>netdate</prgn> or killing all processes
6524 when the system shuts down. Your message should look
6526 <example compact="compact">
6527 Doing something very useful...done.
6529 You should print the <tt>done.</tt> immediately after
6530 the job has been completed, so that the user is
6531 informed why they have to wait. You can get this
6533 <example compact="compact">
6534 echo -n "Doing something very useful..."
6543 <p>When the configuration is reloaded</p>
6546 When a daemon is forced to reload its configuration
6547 files you should use the following format:
6548 <example compact="compact">
6549 Reloading <var>description</var> configuration...done.
6551 where <var>description</var> is the same as in the
6552 daemon starting message.
6560 <heading>Cron jobs</heading>
6563 Packages must not modify the configuration file
6564 <file>/etc/crontab</file>, and they must not modify the files in
6565 <file>/var/spool/cron/crontabs</file>.</p>
6568 If a package wants to install a job that has to be executed
6569 via cron, it should place a file with the name of the
6570 package in one or more of the following directories:
6571 <example compact="compact">
6577 As these directory names imply, the files within them are
6578 executed on an hourly, daily, weekly, or monthly basis,
6579 respectively. The exact times are listed in
6580 <file>/etc/crontab</file>.</p>
6583 All files installed in any of these directories must be
6584 scripts (e.g., shell scripts or Perl scripts) so that they
6585 can easily be modified by the local system administrator.
6586 In addition, they must be treated as configuration files.
6590 If a certain job has to be executed at some other frequency or
6591 at a specific time, the package should install a file
6592 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6593 same syntax as <file>/etc/crontab</file> and is processed by
6594 <prgn>cron</prgn> automatically. The file must also be
6595 treated as a configuration file. (Note that entries in the
6596 <file>/etc/cron.d</file> directory are not handled by
6597 <prgn>anacron</prgn>. Thus, you should only use this
6598 directory for jobs which may be skipped if the system is not
6601 Unlike <file>crontab</file> files described in the IEEE Std
6602 1003.1-2008 (POSIX.1) available from
6603 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
6604 name="The Open Group">, the files in
6605 <file>/etc/cron.d</file> and the file
6606 <file>/etc/crontab</file> have seven fields; namely:
6608 <item>Minute [0,59]</item>
6609 <item>Hour [0,23]</item>
6610 <item>Day of the month [1,31]</item>
6611 <item>Month of the year [1,12]</item>
6612 <item>Day of the week ([0,6] with 0=Sunday)</item>
6613 <item>Username</item>
6614 <item>Command to be run</item>
6616 Ranges of numbers are allowed. Ranges are two numbers
6617 separated with a hyphen. The specified range is inclusive.
6618 Lists are allowed. A list is a set of numbers (or ranges)
6619 separated by commas. Step values can be used in conjunction
6624 The scripts or <tt>crontab</tt> entries in these directories should
6625 check if all necessary programs are installed before they
6626 try to execute them. Otherwise, problems will arise when a
6627 package was removed but not purged since configuration files
6628 are kept on the system in this situation.
6632 Any <tt>cron</tt> daemon must provide
6633 <file>/usr/bin/crontab</file> and support normal
6634 <tt>crontab</tt> entries as specified in POSIX. The daemon
6635 must also support names for days and months, ranges, and
6636 step values. It has to support <file>/etc/crontab</file>,
6637 and correctly execute the scripts in
6638 <file>/etc/cron.d</file>. The daemon must also correctly
6640 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
6645 <heading>Menus</heading>
6648 The Debian <tt>menu</tt> package provides a standard
6649 interface between packages providing applications and
6650 <em>menu programs</em> (either X window managers or
6651 text-based menu programs such as <prgn>pdmenu</prgn>).
6655 All packages that provide applications that need not be
6656 passed any special command line arguments for normal
6657 operation should register a menu entry for those
6658 applications, so that users of the <tt>menu</tt> package
6659 will automatically get menu entries in their window
6660 managers, as well in shells like <tt>pdmenu</tt>.
6664 Menu entries should follow the current menu policy.
6668 The menu policy can be found in the <tt>menu-policy</tt>
6669 files in the <tt>debian-policy</tt> package.
6670 It is also available from the Debian web mirrors at
6671 <tt><url name="/doc/packaging-manuals/menu-policy/"
6672 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6676 Please also refer to the <em>Debian Menu System</em>
6677 documentation that comes with the <package>menu</package>
6678 package for information about how to register your
6684 <heading>Multimedia handlers</heading>
6687 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6688 is a mechanism for encoding files and data streams and
6689 providing meta-information about them, in particular their
6690 type (e.g. audio or video) and format (e.g. PNG, HTML,
6695 Registration of MIME type handlers allows programs like mail
6696 user agents and web browsers to invoke these handlers to
6697 view, edit or display MIME types they don't support directly.
6701 Packages which provide the ability to view/show/play,
6702 compose, edit or print MIME types should register themselves
6703 as such following the current MIME support policy.
6707 The MIME support policy can be found in the <tt>mime-policy</tt>
6708 files in the <tt>debian-policy</tt> package.
6709 It is also available from the Debian web mirrors at
6710 <tt><url name="/doc/packaging-manuals/mime-policy/"
6711 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
6717 <heading>Keyboard configuration</heading>
6720 To achieve a consistent keyboard configuration so that all
6721 applications interpret a keyboard event the same way, all
6722 programs in the Debian distribution must be configured to
6723 comply with the following guidelines.
6727 The following keys must have the specified interpretations:
6730 <tag><tt><--</tt></tag>
6731 <item>delete the character to the left of the cursor</item>
6733 <tag><tt>Delete</tt></tag>
6734 <item>delete the character to the right of the cursor</item>
6736 <tag><tt>Control+H</tt></tag>
6737 <item>emacs: the help prefix</item>
6740 The interpretation of any keyboard events should be
6741 independent of the terminal that is used, be it a virtual
6742 console, an X terminal emulator, an rlogin/telnet session,
6747 The following list explains how the different programs
6748 should be set up to achieve this:
6754 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
6758 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
6762 X translations are set up to make
6763 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
6764 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
6765 is the vt220 escape code for the "delete character"
6766 key). This must be done by loading the X resources
6767 using <prgn>xrdb</prgn> on all local X displays, not
6768 using the application defaults, so that the
6769 translation resources used correspond to the
6770 <prgn>xmodmap</prgn> settings.
6774 The Linux console is configured to make
6775 <tt><--</tt> generate DEL, and <tt>Delete</tt>
6776 generate <tt>ESC [ 3 ~</tt>.
6780 X applications are configured so that <tt><</tt>
6781 deletes left, and <tt>Delete</tt> deletes right. Motif
6782 applications already work like this.
6786 Terminals should have <tt>stty erase ^?</tt> .
6790 The <tt>xterm</tt> terminfo entry should have <tt>ESC
6791 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
6792 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
6796 Emacs is programmed to map <tt>KB_Backspace</tt> or
6797 the <tt>stty erase</tt> character to
6798 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
6799 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
6800 <tt>^H</tt> to <tt>help</tt> as always.
6804 Other applications use the <tt>stty erase</tt>
6805 character and <tt>kdch1</tt> for the two delete keys,
6806 with ASCII DEL being "delete previous character" and
6807 <tt>kdch1</tt> being "delete character under
6815 This will solve the problem except for the following
6822 Some terminals have a <tt><--</tt> key that cannot
6823 be made to produce anything except <tt>^H</tt>. On
6824 these terminals Emacs help will be unavailable on
6825 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
6826 character takes precedence in Emacs, and has been set
6827 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
6828 available) can be used instead.
6832 Some operating systems use <tt>^H</tt> for <tt>stty
6833 erase</tt>. However, modern telnet versions and all
6834 rlogin versions propagate <tt>stty</tt> settings, and
6835 almost all UNIX versions honour <tt>stty erase</tt>.
6836 Where the <tt>stty</tt> settings are not propagated
6837 correctly, things can be made to work by using
6838 <tt>stty</tt> manually.
6842 Some systems (including previous Debian versions) use
6843 <prgn>xmodmap</prgn> to arrange for both
6844 <tt><--</tt> and <tt>Delete</tt> to generate
6845 <tt>KB_Delete</tt>. We can change the behavior of
6846 their X clients using the same X resources that we use
6847 to do it for our own clients, or configure our clients
6848 using their resources when things are the other way
6849 around. On displays configured like this
6850 <tt>Delete</tt> will not work, but <tt><--</tt>
6855 Some operating systems have different <tt>kdch1</tt>
6856 settings in their <tt>terminfo</tt> database for
6857 <tt>xterm</tt> and others. On these systems the
6858 <tt>Delete</tt> key will not work correctly when you
6859 log in from a system conforming to our policy, but
6860 <tt><--</tt> will.
6867 <heading>Environment variables</heading>
6870 A program must not depend on environment variables to get
6871 reasonable defaults. (That's because these environment
6872 variables would have to be set in a system-wide
6873 configuration file like <file>/etc/profile</file>, which is not
6874 supported by all shells.)
6878 If a program usually depends on environment variables for its
6879 configuration, the program should be changed to fall back to
6880 a reasonable default configuration if these environment
6881 variables are not present. If this cannot be done easily
6882 (e.g., if the source code of a non-free program is not
6883 available), the program must be replaced by a small
6884 "wrapper" shell script which sets the environment variables
6885 if they are not already defined, and calls the original program.
6889 Here is an example of a wrapper script for this purpose:
6891 <example compact="compact">
6893 BAR=${BAR:-/var/lib/fubar}
6895 exec /usr/lib/foo/foo "$@"
6900 Furthermore, as <file>/etc/profile</file> is a configuration
6901 file of the <prgn>base-files</prgn> package, other packages must
6902 not put any environment variables or other commands into that
6907 <sect id="doc-base">
6908 <heading>Registering Documents using doc-base</heading>
6911 The <package>doc-base</package> package implements a
6912 flexible mechanism for handling and presenting
6913 documentation. The recommended practice is for every Debian
6914 package that provides online documentation (other than just
6915 manual pages) to register these documents with
6916 <package>doc-base</package> by installing a
6917 <package>doc-base</package> control file via the
6918 <prgn/install-docs/ script at installation time and
6919 de-register the manuals again when the package is removed.
6922 Please refer to the documentation that comes with the
6923 <package>doc-base</package> package for information and
6932 <heading>Files</heading>
6935 <heading>Binaries</heading>
6938 Two different packages must not install programs with
6939 different functionality but with the same filenames. (The
6940 case of two programs having the same functionality but
6941 different implementations is handled via "alternatives" or
6942 the "Conflicts" mechanism. See <ref id="maintscripts"> and
6943 <ref id="conflicts"> respectively.) If this case happens,
6944 one of the programs must be renamed. The maintainers should
6945 report this to the <tt>debian-devel</tt> mailing list and
6946 try to find a consensus about which program will have to be
6947 renamed. If a consensus cannot be reached, <em>both</em>
6948 programs must be renamed.
6952 By default, when a package is being built, any binaries
6953 created should include debugging information, as well as
6954 being compiled with optimization. You should also turn on
6955 as many reasonable compilation warnings as possible; this
6956 makes life easier for porters, who can then look at build
6957 logs for possible problems. For the C programming language,
6958 this means the following compilation parameters should be
6960 <example compact="compact">
6962 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
6964 INSTALL = install -s # (or use strip on the files in debian/tmp)
6969 Note that by default all installed binaries should be stripped,
6970 either by using the <tt>-s</tt> flag to
6971 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
6972 the binaries after they have been copied into
6973 <file>debian/tmp</file> but before the tree is made into a
6978 Although binaries in the build tree should be compiled with
6979 debugging information by default, it can often be difficult to
6980 debug programs if they are also subjected to compiler
6981 optimization. For this reason, it is recommended to support the
6982 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
6983 (see <ref id="debianrules-options">). This variable can contain
6984 several flags to change how a package is compiled and built.
6988 It is up to the package maintainer to decide what
6989 compilation options are best for the package. Certain
6990 binaries (such as computationally-intensive programs) will
6991 function better with certain flags (<tt>-O3</tt>, for
6992 example); feel free to use them. Please use good judgment
6993 here. Don't use flags for the sake of it; only use them
6994 if there is good reason to do so. Feel free to override
6995 the upstream author's ideas about which compilation
6996 options are best: they are often inappropriate for our
7002 <sect id="libraries">
7003 <heading>Libraries</heading>
7006 If the package is <strong>architecture: any</strong>, then
7007 the shared library compilation and linking flags must have
7008 <tt>-fPIC</tt>, or the package shall not build on some of
7009 the supported architectures<footnote>
7011 If you are using GCC, <tt>-fPIC</tt> produces code with
7012 relocatable position independent code, which is required for
7013 most architectures to create a shared library, with i386 and
7014 perhaps some others where non position independent code is
7015 permitted in a shared library.
7018 Position independent code may have a performance penalty,
7019 especially on <tt>i386</tt>. However, in most cases the
7020 speed penalty must be measured against the memory wasted on
7021 the few architectures where non position independent code is
7024 </footnote>. Any exception to this rule must be discussed on
7025 the mailing list <em>debian-devel@lists.debian.org</em>, and
7026 a rough consensus obtained. The reasons for not compiling
7027 with <tt>-fPIC</tt> flag must be recorded in the file
7028 <tt>README.Debian</tt>, and care must be taken to either
7029 restrict the architecture or arrange for <tt>-fPIC</tt> to
7030 be used on architectures where it is required.<footnote>
7032 Some of the reasons why this might be required is if the
7033 library contains hand crafted assembly code that is not
7034 relocatable, the speed penalty is excessive for compute
7035 intensive libs, and similar reasons.
7040 As to the static libraries, the common case is not to have
7041 relocatable code, since there is no benefit, unless in specific
7042 cases; therefore the static version must not be compiled
7043 with the <tt>-fPIC</tt> flag. Any exception to this rule
7044 should be discussed on the mailing list
7045 <em>debian-devel@lists.debian.org</em>, and the reasons for
7046 compiling with the <tt>-fPIC</tt> flag must be recorded in
7047 the file <tt>README.Debian</tt>. <footnote>
7049 Some of the reasons for linking static libraries with
7050 the <tt>-fPIC</tt> flag are if, for example, one needs a
7051 Perl API for a library that is under rapid development,
7052 and has an unstable API, so shared libraries are
7053 pointless at this phase of the library's development. In
7054 that case, since Perl needs a library with relocatable
7055 code, it may make sense to create a static library with
7056 relocatable code. Another reason cited is if you are
7057 distilling various libraries into a common shared
7058 library, like <tt>mklibs</tt> does in the Debian
7064 In other words, if both a shared and a static library is
7065 being built, each source unit (<tt>*.c</tt>, for example,
7066 for C files) will need to be compiled twice, for the normal
7070 You must specify the gcc option <tt>-D_REENTRANT</tt>
7071 when building a library (either static or shared) to make
7072 the library compatible with LinuxThreads.
7076 Although not enforced by the build tools, shared libraries
7077 must be linked against all libraries that they use symbols from
7078 in the same way that binaries are. This ensures the correct
7079 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
7080 system and guarantees that all libraries can be safely opened
7081 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
7082 option <tt>-Wl,-z,defs</tt> when building a shared library.
7083 Since this option enforces symbol resolution at build time,
7084 a missing library reference will be caught early as a fatal
7089 All installed shared libraries should be stripped with
7090 <example compact="compact">
7091 strip --strip-unneeded <var>your-lib</var>
7093 (The option <tt>--strip-unneeded</tt> makes
7094 <prgn>strip</prgn> remove only the symbols which aren't
7095 needed for relocation processing.) Shared libraries can
7096 function perfectly well when stripped, since the symbols for
7097 dynamic linking are in a separate part of the ELF object
7099 You might also want to use the options
7100 <tt>--remove-section=.comment</tt> and
7101 <tt>--remove-section=.note</tt> on both shared libraries
7102 and executables, and <tt>--strip-debug</tt> on static
7108 Note that under some circumstances it may be useful to
7109 install a shared library unstripped, for example when
7110 building a separate package to support debugging.
7114 Shared object files (often <file>.so</file> files) that are not
7115 public libraries, that is, they are not meant to be linked
7116 to by third party executables (binaries of other packages),
7117 should be installed in subdirectories of the
7118 <file>/usr/lib</file> directory. Such files are exempt from the
7119 rules that govern ordinary shared libraries, except that
7120 they must not be installed executable and should be
7122 A common example are the so-called "plug-ins",
7123 internal shared objects that are dynamically loaded by
7124 programs using <manref name="dlopen" section="3">.
7129 An ever increasing number of packages are using
7130 <prgn>libtool</prgn> to do their linking. The latest GNU
7131 libtools (>= 1.3a) can take advantage of the metadata in the
7132 installed <prgn>libtool</prgn> archive files (<file>*.la</file>
7133 files). The main advantage of <prgn>libtool</prgn>'s
7134 <file>.la</file> files is that it allows <prgn>libtool</prgn> to
7135 store and subsequently access metadata with respect to the
7136 libraries it builds. <prgn>libtool</prgn> will search for
7137 those files, which contain a lot of useful information about
7138 a library (such as library dependency information for static
7139 linking). Also, they're <em>essential</em> for programs
7140 using <tt>libltdl</tt>.<footnote>
7141 Although <prgn>libtool</prgn> is fully capable of
7142 linking against shared libraries which don't have
7143 <tt>.la</tt> files, as it is a mere shell script it can
7144 add considerably to the build time of a
7145 <prgn>libtool</prgn>-using package if that shell script
7146 has to derive all this information from first principles
7147 for each library every time it is linked. With the
7148 advent of <prgn>libtool</prgn> version 1.4 (and to a
7149 lesser extent <prgn>libtool</prgn> version 1.3), the
7150 <file>.la</file> files also store information about
7151 inter-library dependencies which cannot necessarily be
7152 derived after the <file>.la</file> file is deleted.
7157 Packages that use <prgn>libtool</prgn> to create shared
7158 libraries should include the <file>.la</file> files in the
7159 <tt>-dev</tt> package, unless the package relies on
7160 <tt>libtool</tt>'s <tt>libltdl</tt> library, in which case
7161 the <tt>.la</tt> files must go in the run-time library
7166 You must make sure that you use only released versions of
7167 shared libraries to build your packages; otherwise other
7168 users will not be able to run your binaries
7169 properly. Producing source packages that depend on
7170 unreleased compilers is also usually a bad
7177 <heading>Shared libraries</heading>
7179 This section has moved to <ref id="sharedlibs">.
7185 <heading>Scripts</heading>
7188 All command scripts, including the package maintainer
7189 scripts inside the package and used by <prgn>dpkg</prgn>,
7190 should have a <tt>#!</tt> line naming the shell to be used
7195 In the case of Perl scripts this should be
7196 <tt>#!/usr/bin/perl</tt>.
7200 When scripts are installed into a directory in the system
7201 PATH, the script name should not include an extension such
7202 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7203 language currently used to implement it.
7206 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>)
7207 should almost certainly start with <tt>set -e</tt> so that
7208 errors are detected. Every script should use
7209 <tt>set -e</tt> or check the exit status of <em>every</em>
7214 Scripts may assume that <file>/bin/sh</file> implements the
7215 SUSv3 Shell Command Language<footnote>
7216 Single UNIX Specification, version 3, which is also IEEE
7217 1003.1-2004 (POSIX), and is available on the World Wide Web
7218 from <url id="http://www.unix.org/version3/online.html"
7219 name="The Open Group"> after free
7220 registration.</footnote>
7221 plus the following additional features not mandated by
7223 These features are in widespread use in the Linux community
7224 and are implemented in all of bash, dash, and ksh, the most
7225 common shells users may wish to use as <file>/bin/sh</file>.
7228 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7229 must not generate a newline.</item>
7230 <item><tt>test</tt>, if implemented as a shell built-in, must
7231 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7233 <item><tt>local</tt> to create a scoped variable must be
7234 supported, including listing multiple variables in a single
7235 local command and assigning a value to a variable at the
7236 same time as localizing it. <tt>local</tt> may or
7237 may not preserve the variable value from an outer scope if
7238 no assignment is present. Uses such as:
7242 # ... use a, b, c, d ...
7245 must be supported and must set the value of <tt>c</tt> to
7249 If a shell script requires non-SUSv3 features from the shell
7250 interpreter other than those listed above, the appropriate shell
7251 must be specified in the first line of the script (e.g.,
7252 <tt>#!/bin/bash</tt>) and the package must depend on the package
7253 providing the shell (unless the shell package is marked
7254 "Essential", as in the case of <prgn>bash</prgn>).
7258 You may wish to restrict your script to SUSv3 features plus the
7259 above set when possible so that it may use <file>/bin/sh</file>
7260 as its interpreter. If your script works with <prgn>dash</prgn>
7261 (originally called <prgn>ash</prgn>), it probably complies with
7262 the above requirements, but if you are in doubt, use
7263 <file>/bin/bash</file>.
7267 Perl scripts should check for errors when making any
7268 system calls, including <tt>open</tt>, <tt>print</tt>,
7269 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7273 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7274 scripting languages. See <em>Csh Programming Considered
7275 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7276 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7277 If an upstream package comes with <prgn>csh</prgn> scripts
7278 then you must make sure that they start with
7279 <tt>#!/bin/csh</tt> and make your package depend on the
7280 <prgn>c-shell</prgn> virtual package.
7284 Any scripts which create files in world-writeable
7285 directories (e.g., in <file>/tmp</file>) must use a
7286 mechanism which will fail atomically if a file with the same
7287 name already exists.
7291 The Debian base system provides the <prgn>tempfile</prgn>
7292 and <prgn>mktemp</prgn> utilities for use by scripts for
7299 <heading>Symbolic links</heading>
7302 In general, symbolic links within a top-level directory
7303 should be relative, and symbolic links pointing from one
7304 top-level directory into another should be absolute. (A
7305 top-level directory is a sub-directory of the root
7306 directory <file>/</file>.)
7310 In addition, symbolic links should be specified as short as
7311 possible, i.e., link targets like <file>foo/../bar</file> are
7316 Note that when creating a relative link using
7317 <prgn>ln</prgn> it is not necessary for the target of the
7318 link to exist relative to the working directory you're
7319 running <prgn>ln</prgn> from, nor is it necessary to change
7320 directory to the directory where the link is to be made.
7321 Simply include the string that should appear as the target
7322 of the link (this will be a pathname relative to the
7323 directory in which the link resides) as the first argument
7328 For example, in your <prgn>Makefile</prgn> or
7329 <file>debian/rules</file>, you can do things like:
7330 <example compact="compact">
7331 ln -fs gcc $(prefix)/bin/cc
7332 ln -fs gcc debian/tmp/usr/bin/cc
7333 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7334 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7339 A symbolic link pointing to a compressed file should always
7340 have the same file extension as the referenced file. (For
7341 example, if a file <file>foo.gz</file> is referenced by a
7342 symbolic link, the filename of the link has to end with
7343 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7348 <heading>Device files</heading>
7351 Packages must not include device files or named pipes in the
7356 If a package needs any special device files that are not
7357 included in the base system, it must call
7358 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7359 after notifying the user<footnote>
7360 This notification could be done via a (low-priority)
7361 debconf message, or an echo (printf) statement.
7366 Packages must not remove any device files in the
7367 <prgn>postrm</prgn> or any other script. This is left to the
7368 system administrator.
7372 Debian uses the serial devices
7373 <file>/dev/ttyS*</file>. Programs using the old
7374 <file>/dev/cu*</file> devices should be changed to use
7375 <file>/dev/ttyS*</file>.
7379 Named pipes needed by the package must be created in
7380 the <prgn>postinst</prgn> script<footnote>
7381 It's better to use <prgn>mkfifo</prgn> rather
7382 than <prgn>mknod</prgn> to create named pipes so that
7383 automated checks for packages incorrectly creating device
7384 files with <prgn>mknod</prgn> won't have false positives.
7385 </footnote> and removed in
7386 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
7391 <sect id="config-files">
7392 <heading>Configuration files</heading>
7395 <heading>Definitions</heading>
7399 <tag>configuration file</tag>
7401 A file that affects the operation of a program, or
7402 provides site- or host-specific information, or
7403 otherwise customizes the behavior of a program.
7404 Typically, configuration files are intended to be
7405 modified by the system administrator (if needed or
7406 desired) to conform to local policy or to provide
7407 more useful site-specific behavior.
7410 <tag><tt>conffile</tt></tag>
7412 A file listed in a package's <tt>conffiles</tt>
7413 file, and is treated specially by <prgn>dpkg</prgn>
7414 (see <ref id="configdetails">).
7420 The distinction between these two is important; they are
7421 not interchangeable concepts. Almost all
7422 <tt>conffile</tt>s are configuration files, but many
7423 configuration files are not <tt>conffiles</tt>.
7427 As noted elsewhere, <file>/etc/init.d</file> scripts,
7428 <file>/etc/default</file> files, scripts installed in
7429 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7430 configuration installed in <file>/etc/cron.d</file> must be
7431 treated as configuration files. In general, any script that
7432 embeds configuration information is de-facto a configuration
7433 file and should be treated as such.
7438 <heading>Location</heading>
7441 Any configuration files created or used by your package
7442 must reside in <file>/etc</file>. If there are several,
7443 consider creating a subdirectory of <file>/etc</file>
7444 named after your package.
7448 If your package creates or uses configuration files
7449 outside of <file>/etc</file>, and it is not feasible to modify
7450 the package to use <file>/etc</file> directly, put the files
7451 in <file>/etc</file> and create symbolic links to those files
7452 from the location that the package requires.
7457 <heading>Behavior</heading>
7460 Configuration file handling must conform to the following
7462 <list compact="compact">
7464 local changes must be preserved during a package
7468 configuration files must be preserved when the
7469 package is removed, and only deleted when the
7476 The easy way to achieve this behavior is to make the
7477 configuration file a <tt>conffile</tt>. This is
7478 appropriate only if it is possible to distribute a default
7479 version that will work for most installations, although
7480 some system administrators may choose to modify it. This
7481 implies that the default version will be part of the
7482 package distribution, and must not be modified by the
7483 maintainer scripts during installation (or at any other
7488 In order to ensure that local changes are preserved
7489 correctly, no package may contain or make hard links to
7490 conffiles.<footnote>
7491 Rationale: There are two problems with hard links.
7492 The first is that some editors break the link while
7493 editing one of the files, so that the two files may
7494 unwittingly become unlinked and different. The second
7495 is that <prgn>dpkg</prgn> might break the hard link
7496 while upgrading <tt>conffile</tt>s.
7501 The other way to do it is via the maintainer scripts. In
7502 this case, the configuration file must not be listed as a
7503 <tt>conffile</tt> and must not be part of the package
7504 distribution. If the existence of a file is required for
7505 the package to be sensibly configured it is the
7506 responsibility of the package maintainer to provide
7507 maintainer scripts which correctly create, update and
7508 maintain the file and remove it on purge. (See <ref
7509 id="maintainerscripts"> for more information.) These
7510 scripts must be idempotent (i.e., must work correctly if
7511 <prgn>dpkg</prgn> needs to re-run them due to errors
7512 during installation or removal), must cope with all the
7513 variety of ways <prgn>dpkg</prgn> can call maintainer
7514 scripts, must not overwrite or otherwise mangle the user's
7515 configuration without asking, must not ask unnecessary
7516 questions (particularly during upgrades), and must
7517 otherwise be good citizens.
7521 The scripts are not required to configure every possible
7522 option for the package, but only those necessary to get
7523 the package running on a given system. Ideally the
7524 sysadmin should not have to do any configuration other
7525 than that done (semi-)automatically by the
7526 <prgn>postinst</prgn> script.
7530 A common practice is to create a script called
7531 <file><var>package</var>-configure</file> and have the
7532 package's <prgn>postinst</prgn> call it if and only if the
7533 configuration file does not already exist. In certain
7534 cases it is useful for there to be an example or template
7535 file which the maintainer scripts use. Such files should
7536 be in <file>/usr/share/<var>package</var></file> or
7537 <file>/usr/lib/<var>package</var></file> (depending on whether
7538 they are architecture-independent or not). There should
7539 be symbolic links to them from
7540 <file>/usr/share/doc/<var>package</var>/examples</file> if
7541 they are examples, and should be perfectly ordinary
7542 <prgn>dpkg</prgn>-handled files (<em>not</em>
7543 configuration files).
7547 These two styles of configuration file handling must
7548 not be mixed, for that way lies madness:
7549 <prgn>dpkg</prgn> will ask about overwriting the file
7550 every time the package is upgraded.
7555 <heading>Sharing configuration files</heading>
7558 Packages which specify the same file as a
7559 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7560 with each other. (This is an instance of the general rule
7561 about not sharing files. Note that neither alternatives
7562 nor diversions are likely to be appropriate in this case;
7563 in particular, <prgn>dpkg</prgn> does not handle diverted
7564 <tt>conffile</tt>s well.)
7568 The maintainer scripts must not alter a <tt>conffile</tt>
7569 of <em>any</em> package, including the one the scripts
7574 If two or more packages use the same configuration file
7575 and it is reasonable for both to be installed at the same
7576 time, one of these packages must be defined as
7577 <em>owner</em> of the configuration file, i.e., it will be
7578 the package which handles that file as a configuration
7579 file. Other packages that use the configuration file must
7580 depend on the owning package if they require the
7581 configuration file to operate. If the other package will
7582 use the configuration file if present, but is capable of
7583 operating without it, no dependency need be declared.
7587 If it is desirable for two or more related packages to
7588 share a configuration file <em>and</em> for all of the
7589 related packages to be able to modify that configuration
7590 file, then the following should be done:
7591 <enumlist compact="compact">
7593 One of the related packages (the "owning" package)
7594 will manage the configuration file with maintainer
7595 scripts as described in the previous section.
7598 The owning package should also provide a program
7599 that the other packages may use to modify the
7603 The related packages must use the provided program
7604 to make any desired modifications to the
7605 configuration file. They should either depend on
7606 the core package to guarantee that the configuration
7607 modifier program is available or accept gracefully
7608 that they cannot modify the configuration file if it
7609 is not. (This is in addition to the fact that the
7610 configuration file may not even be present in the
7617 Sometimes it's appropriate to create a new package which
7618 provides the basic infrastructure for the other packages
7619 and which manages the shared configuration files. (The
7620 <tt>sgml-base</tt> package is a good example.)
7625 <heading>User configuration files ("dotfiles")</heading>
7628 The files in <file>/etc/skel</file> will automatically be
7629 copied into new user accounts by <prgn>adduser</prgn>.
7630 No other program should reference the files in
7631 <file>/etc/skel</file>.
7635 Therefore, if a program needs a dotfile to exist in
7636 advance in <file>$HOME</file> to work sensibly, that dotfile
7637 should be installed in <file>/etc/skel</file> and treated as a
7642 However, programs that require dotfiles in order to
7643 operate sensibly are a bad thing, unless they do create
7644 the dotfiles themselves automatically.
7648 Furthermore, programs should be configured by the Debian
7649 default installation to behave as closely to the upstream
7650 default behavior as possible.
7654 Therefore, if a program in a Debian package needs to be
7655 configured in some way in order to operate sensibly, that
7656 should be done using a site-wide configuration file placed
7657 in <file>/etc</file>. Only if the program doesn't support a
7658 site-wide default configuration and the package maintainer
7659 doesn't have time to add it may a default per-user file be
7660 placed in <file>/etc/skel</file>.
7664 <file>/etc/skel</file> should be as empty as we can make it.
7665 This is particularly true because there is no easy (or
7666 necessarily desirable) mechanism for ensuring that the
7667 appropriate dotfiles are copied into the accounts of
7668 existing users when a package is installed.
7674 <heading>Log files</heading>
7676 Log files should usually be named
7677 <file>/var/log/<var>package</var>.log</file>. If you have many
7678 log files, or need a separate directory for permission
7679 reasons (<file>/var/log</file> is writable only by
7680 <file>root</file>), you should usually create a directory named
7681 <file>/var/log/<var>package</var></file> and place your log
7686 Log files must be rotated occasionally so that they don't
7687 grow indefinitely; the best way to do this is to drop a log
7688 rotation configuration file into the directory
7689 <file>/etc/logrotate.d</file> and use the facilities provided by
7690 logrotate.<footnote>
7692 The traditional approach to log files has been to set up
7693 <em>ad hoc</em> log rotation schemes using simple shell
7694 scripts and cron. While this approach is highly
7695 customizable, it requires quite a lot of sysadmin work.
7696 Even though the original Debian system helped a little
7697 by automatically installing a system which can be used
7698 as a template, this was deemed not enough.
7702 The use of <prgn>logrotate</prgn>, a program developed
7703 by Red Hat, is better, as it centralizes log management.
7704 It has both a configuration file
7705 (<file>/etc/logrotate.conf</file>) and a directory where
7706 packages can drop their individual log rotation
7707 configurations (<file>/etc/logrotate.d</file>).
7710 Here is a good example for a logrotate config
7711 file (for more information see <manref name="logrotate"
7713 <example compact="compact">
7714 /var/log/foo/*.log {
7719 /etc/init.d/foo force-reload
7723 This rotates all files under <file>/var/log/foo</file>, saves 12
7724 compressed generations, and forces the daemon to reload its
7725 configuration information after the log rotation.
7729 Log files should be removed when the package is
7730 purged (but not when it is only removed). This should be
7731 done by the <prgn>postrm</prgn> script when it is called
7732 with the argument <tt>purge</tt> (see <ref
7733 id="removedetails">).
7738 <heading>Permissions and owners</heading>
7741 The rules in this section are guidelines for general use.
7742 If necessary you may deviate from the details below.
7743 However, if you do so you must make sure that what is done
7744 is secure and you should try to be as consistent as possible
7745 with the rest of the system. You should probably also
7746 discuss it on <prgn>debian-devel</prgn> first.
7750 Files should be owned by <tt>root:root</tt>, and made
7751 writable only by the owner and universally readable (and
7752 executable, if appropriate), that is mode 644 or 755.
7756 Directories should be mode 755 or (for group-writability)
7757 mode 2775. The ownership of the directory should be
7758 consistent with its mode: if a directory is mode 2775, it
7759 should be owned by the group that needs write access to
7762 When a package is upgraded, and the owner or permissions
7763 of a file included in the package has changed, dpkg
7764 arranges for the ownership and permissions to be
7765 correctly set upon installation. However, this does not
7766 extend to directories; the permissions and ownership of
7767 directories already on the system does not change on
7768 install or upgrade of packages. This makes sense, since
7769 otherwise common directories like <tt>/usr</tt> would
7770 always be in flux. To correctly change permissions of a
7771 directory the package owns, explicit action is required,
7772 usually in the <tt>postinst</tt> script. Care must be
7773 taken to handle downgrades as well, in that case.
7780 Setuid and setgid executables should be mode 4755 or 2755
7781 respectively, and owned by the appropriate user or group.
7782 They should not be made unreadable (modes like 4711 or
7783 2711 or even 4111); doing so achieves no extra security,
7784 because anyone can find the binary in the freely available
7785 Debian package; it is merely inconvenient. For the same
7786 reason you should not restrict read or execute permissions
7787 on non-set-id executables.
7791 Some setuid programs need to be restricted to particular
7792 sets of users, using file permissions. In this case they
7793 should be owned by the uid to which they are set-id, and by
7794 the group which should be allowed to execute them. They
7795 should have mode 4754; again there is no point in making
7796 them unreadable to those users who must not be allowed to
7801 It is possible to arrange that the system administrator can
7802 reconfigure the package to correspond to their local
7803 security policy by changing the permissions on a binary:
7804 they can do this by using <prgn>dpkg-statoverride</prgn>, as
7805 described below.<footnote>
7806 Ordinary files installed by <prgn>dpkg</prgn> (as
7807 opposed to <tt>conffile</tt>s and other similar objects)
7808 normally have their permissions reset to the distributed
7809 permissions when the package is reinstalled. However,
7810 the use of <prgn>dpkg-statoverride</prgn> overrides this
7811 default behavior. If you use this method, you should
7812 remember to describe <prgn>dpkg-statoverride</prgn> in
7813 the package documentation; being a relatively new
7814 addition to Debian, it is probably not yet well-known.
7816 Another method you should consider is to create a group for
7817 people allowed to use the program(s) and make any setuid
7818 executables executable only by that group.
7822 If you need to create a new user or group for your package
7823 there are two possibilities. Firstly, you may need to
7824 make some files in the binary package be owned by this
7825 user or group, or you may need to compile the user or
7826 group id (rather than just the name) into the binary
7827 (though this latter should be avoided if possible, as in
7828 this case you need a statically allocated id).</p>
7831 If you need a statically allocated id, you must ask for a
7832 user or group id from the <tt>base-passwd</tt> maintainer,
7833 and must not release the package until you have been
7834 allocated one. Once you have been allocated one you must
7835 either make the package depend on a version of the
7836 <tt>base-passwd</tt> package with the id present in
7837 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
7838 your package to create the user or group itself with the
7839 correct id (using <tt>adduser</tt>) in its
7840 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
7841 the <prgn>postinst</prgn> is to be preferred if it is
7842 possible, otherwise a pre-dependency will be needed on the
7843 <tt>adduser</tt> package.)
7847 On the other hand, the program might be able to determine
7848 the uid or gid from the user or group name at runtime, so
7849 that a dynamically allocated id can be used. In this case
7850 you should choose an appropriate user or group name,
7851 discussing this on <prgn>debian-devel</prgn> and checking
7852 with the <package/base-passwd/ maintainer that it is unique and that
7853 they do not wish you to use a statically allocated id
7854 instead. When this has been checked you must arrange for
7855 your package to create the user or group if necessary using
7856 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
7857 <prgn>postinst</prgn> script (again, the latter is to be
7858 preferred if it is possible).
7862 Note that changing the numeric value of an id associated
7863 with a name is very difficult, and involves searching the
7864 file system for all appropriate files. You need to think
7865 carefully whether a static or dynamic id is required, since
7866 changing your mind later will cause problems.
7869 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
7871 This section is not intended as policy, but as a
7872 description of the use of <prgn>dpkg-statoverride</prgn>.
7876 If a system administrator wishes to have a file (or
7877 directory or other such thing) installed with owner and
7878 permissions different from those in the distributed Debian
7879 package, they can use the <prgn>dpkg-statoverride</prgn>
7880 program to instruct <prgn>dpkg</prgn> to use the different
7881 settings every time the file is installed. Thus the
7882 package maintainer should distribute the files with their
7883 normal permissions, and leave it for the system
7884 administrator to make any desired changes. For example, a
7885 daemon which is normally required to be setuid root, but
7886 in certain situations could be used without being setuid,
7887 should be installed setuid in the <tt>.deb</tt>. Then the
7888 local system administrator can change this if they wish.
7889 If there are two standard ways of doing it, the package
7890 maintainer can use <tt>debconf</tt> to find out the
7891 preference, and call <prgn>dpkg-statoverride</prgn> in the
7892 maintainer script if necessary to accommodate the system
7893 administrator's choice. Care must be taken during
7894 upgrades to not override an existing setting.
7898 Given the above, <prgn>dpkg-statoverride</prgn> is
7899 essentially a tool for system administrators and would not
7900 normally be needed in the maintainer scripts. There is
7901 one type of situation, though, where calls to
7902 <prgn>dpkg-statoverride</prgn> would be needed in the
7903 maintainer scripts, and that involves packages which use
7904 dynamically allocated user or group ids. In such a
7905 situation, something like the following idiom can be very
7906 helpful in the package's <prgn>postinst</prgn>, where
7907 <tt>sysuser</tt> is a dynamically allocated id:
7909 for i in /usr/bin/foo /usr/sbin/bar
7911 # only do something when no setting exists
7912 if ! dpkg-statoverride --list $i >/dev/null 2>&1
7914 #include: debconf processing, question about foo and bar
7915 if [ "$RET" = "true" ] ; then
7916 dpkg-statoverride --update --add sysuser root 4755 $i
7921 The corresponding code to remove the override when the package
7924 for i in /usr/bin/foo /usr/sbin/bar
7926 if dpkg-statoverride --list $i >/dev/null 2>&1
7928 dpkg-statoverride --remove $i
7938 <chapt id="customized-programs">
7939 <heading>Customized programs</heading>
7941 <sect id="arch-spec">
7942 <heading>Architecture specification strings</heading>
7945 If a program needs to specify an <em>architecture specification
7946 string</em> in some place, it should select one of the
7947 strings provided by <tt>dpkg-architecture -L</tt>. The
7948 strings are in the format
7949 <tt><var>os</var>-<var>arch</var></tt>, though the OS part
7950 is sometimes elided, as when the OS is Linux.<footnote>
7951 <p>Currently, the strings are:
7952 i386 ia64 alpha amd64 armeb arm hppa m32r m68k mips
7953 mipsel powerpc ppc64 s390 s390x sh3 sh3eb sh4 sh4eb
7954 sparc darwin-i386 darwin-ia64 darwin-alpha darwin-amd64
7955 darwin-armeb darwin-arm darwin-hppa darwin-m32r
7956 darwin-m68k darwin-mips darwin-mipsel darwin-powerpc
7957 darwin-ppc64 darwin-s390 darwin-s390x darwin-sh3
7958 darwin-sh3eb darwin-sh4 darwin-sh4eb darwin-sparc
7959 freebsd-i386 freebsd-ia64 freebsd-alpha freebsd-amd64
7960 freebsd-armeb freebsd-arm freebsd-hppa freebsd-m32r
7961 freebsd-m68k freebsd-mips freebsd-mipsel freebsd-powerpc
7962 freebsd-ppc64 freebsd-s390 freebsd-s390x freebsd-sh3
7963 freebsd-sh3eb freebsd-sh4 freebsd-sh4eb freebsd-sparc
7964 kfreebsd-i386 kfreebsd-ia64 kfreebsd-alpha
7965 kfreebsd-amd64 kfreebsd-armeb kfreebsd-arm kfreebsd-hppa
7966 kfreebsd-m32r kfreebsd-m68k kfreebsd-mips
7967 kfreebsd-mipsel kfreebsd-powerpc kfreebsd-ppc64
7968 kfreebsd-s390 kfreebsd-s390x kfreebsd-sh3 kfreebsd-sh3eb
7969 kfreebsd-sh4 kfreebsd-sh4eb kfreebsd-sparc knetbsd-i386
7970 knetbsd-ia64 knetbsd-alpha knetbsd-amd64 knetbsd-armeb
7971 knetbsd-arm knetbsd-hppa knetbsd-m32r knetbsd-m68k
7972 knetbsd-mips knetbsd-mipsel knetbsd-powerpc
7973 knetbsd-ppc64 knetbsd-s390 knetbsd-s390x knetbsd-sh3
7974 knetbsd-sh3eb knetbsd-sh4 knetbsd-sh4eb knetbsd-sparc
7975 netbsd-i386 netbsd-ia64 netbsd-alpha netbsd-amd64
7976 netbsd-armeb netbsd-arm netbsd-hppa netbsd-m32r
7977 netbsd-m68k netbsd-mips netbsd-mipsel netbsd-powerpc
7978 netbsd-ppc64 netbsd-s390 netbsd-s390x netbsd-sh3
7979 netbsd-sh3eb netbsd-sh4 netbsd-sh4eb netbsd-sparc
7980 openbsd-i386 openbsd-ia64 openbsd-alpha openbsd-amd64
7981 openbsd-armeb openbsd-arm openbsd-hppa openbsd-m32r
7982 openbsd-m68k openbsd-mips openbsd-mipsel openbsd-powerpc
7983 openbsd-ppc64 openbsd-s390 openbsd-s390x openbsd-sh3
7984 openbsd-sh3eb openbsd-sh4 openbsd-sh4eb openbsd-sparc
7985 hurd-i386 hurd-ia64 hurd-alpha hurd-amd64 hurd-armeb
7986 hurd-arm hurd-hppa hurd-m32r hurd-m68k hurd-mips
7987 hurd-mipsel hurd-powerpc hurd-ppc64 hurd-s390 hurd-s390x
7988 hurd-sh3 hurd-sh3eb hurd-sh4 hurd-sh4eb hurd-sparc
7994 Note that we don't want to use
7995 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
7996 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
7997 since this would make our programs incompatible with other
7998 Linux distributions. We also don't use something like
7999 <tt><var>arch</var>-unknown-linux</tt>, since the
8000 <tt>unknown</tt> does not look very good.
8004 <sect id="arch-wildcard-spec">
8005 <heading>Architecture Wildcards</heading>
8008 A package may specify an architecture wildcard. Architecture
8009 wildcards are in the format <tt>any</tt> (which matches every
8010 architecture), <tt><var>os</var></tt>-any, or
8011 any-<tt><var>cpu</var></tt>. <footnote>
8012 Internally, the package system normalizes the GNU triplets and
8013 the Debian arches into Debian arch triplets (which are kind of
8014 inverted GNU triplets), with the first component of the
8015 triplet representing the libc and ABI in use. When matching
8016 two Debian arch triplets, whenever an <var>any</var> is found
8017 it matches with anything on the other side, like in:
8019 gnu-linux-i386 is matched by gnu-linux-any
8020 gnu-kfreebsd-amd64 is matched by any-any-amd64
8022 And, for example, <var>any</var> is normalized to
8023 <var>any-any-any</var>.
8029 <heading>Daemons</heading>
8032 The configuration files <file>/etc/services</file>,
8033 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
8034 by the <prgn>netbase</prgn> package and must not be modified
8039 If a package requires a new entry in one of these files, the
8040 maintainer should get in contact with the
8041 <prgn>netbase</prgn> maintainer, who will add the entries
8042 and release a new version of the <prgn>netbase</prgn>
8047 The configuration file <file>/etc/inetd.conf</file> must not be
8048 modified by the package's scripts except via the
8049 <prgn>update-inetd</prgn> script or the
8050 <file>DebianNet.pm</file> Perl module. See their documentation
8051 for details on how to add entries.
8055 If a package wants to install an example entry into
8056 <file>/etc/inetd.conf</file>, the entry must be preceded with
8057 exactly one hash character (<tt>#</tt>). Such lines are
8058 treated as "commented out by user" by the
8059 <prgn>update-inetd</prgn> script and are not changed or
8060 activated during package updates.
8065 <heading>Using pseudo-ttys and modifying wtmp, utmp and
8069 Some programs need to create pseudo-ttys. This should be done
8070 using Unix98 ptys if the C library supports it. The resulting
8071 program must not be installed setuid root, unless that
8072 is required for other functionality.
8076 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
8077 <file>/var/log/lastlog</file> must be installed writable by
8078 group <tt>utmp</tt>. Programs which need to modify those
8079 files must be installed setgid <tt>utmp</tt>.
8084 <heading>Editors and pagers</heading>
8087 Some programs have the ability to launch an editor or pager
8088 program to edit or display a text document. Since there are
8089 lots of different editors and pagers available in the Debian
8090 distribution, the system administrator and each user should
8091 have the possibility to choose their preferred editor and
8096 In addition, every program should choose a good default
8097 editor/pager if none is selected by the user or system
8102 Thus, every program that launches an editor or pager must
8103 use the EDITOR or PAGER environment variable to determine
8104 the editor or pager the user wishes to use. If these
8105 variables are not set, the programs <file>/usr/bin/editor</file>
8106 and <file>/usr/bin/pager</file> should be used, respectively.
8110 These two files are managed through the <prgn>dpkg</prgn>
8111 "alternatives" mechanism. Thus every package providing an
8112 editor or pager must call the
8113 <prgn>update-alternatives</prgn> script to register these
8118 If it is very hard to adapt a program to make use of the
8119 EDITOR or PAGER variables, that program may be configured to
8120 use <file>/usr/bin/sensible-editor</file> and
8121 <file>/usr/bin/sensible-pager</file> as the editor or pager
8122 program respectively. These are two scripts provided in the
8123 <package>sensible-utils</package> package that check the EDITOR
8124 and PAGER variables and launch the appropriate program, and fall
8125 back to <file>/usr/bin/editor</file>
8126 and <file>/usr/bin/pager</file> if the variable is not set.
8130 A program may also use the VISUAL environment variable to
8131 determine the user's choice of editor. If it exists, it
8132 should take precedence over EDITOR. This is in fact what
8133 <file>/usr/bin/sensible-editor</file> does.
8137 It is not required for a package to depend on
8138 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
8139 package to provide such virtual packages.<footnote>
8140 The Debian base system already provides an editor and a
8146 <sect id="web-appl">
8147 <heading>Web servers and applications</heading>
8150 This section describes the locations and URLs that should
8151 be used by all web servers and web applications in the
8158 Cgi-bin executable files are installed in the
8160 <example compact="compact">
8161 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
8163 and should be referred to as
8164 <example compact="compact">
8165 http://localhost/cgi-bin/<var>cgi-bin-name</var>
8171 <p>Access to HTML documents</p>
8174 HTML documents for a package are stored in
8175 <file>/usr/share/doc/<var>package</var></file>
8176 and can be referred to as
8177 <example compact="compact">
8178 http://localhost/doc/<var>package</var>/<var>filename</var>
8183 The web server should restrict access to the document
8184 tree so that only clients on the same host can read
8185 the documents. If the web server does not support such
8186 access controls, then it should not provide access at
8187 all, or ask about providing access during installation.
8192 <p>Access to images</p>
8194 It is recommended that images for a package be stored
8195 in <tt>/usr/share/images/<var>package</var></tt> and
8196 may be referred to through an alias <tt>/images/</tt>
8199 http://localhost/images/<package>/<filename>
8206 <p>Web Document Root</p>
8209 Web Applications should try to avoid storing files in
8210 the Web Document Root. Instead they should use the
8211 /usr/share/doc/<var>package</var> directory for
8212 documents and register the Web Application via the
8213 <package>doc-base</package> package. If access to the
8214 web document root is unavoidable then use
8215 <example compact="compact">
8218 as the Document Root. This might be just a symbolic
8219 link to the location where the system administrator
8220 has put the real document root.
8223 <item><p>Providing httpd and/or httpd-cgi</p>
8225 All web servers should provide the virtual package
8226 <tt>httpd</tt>. If a web server has CGI support it should
8227 provide <tt>httpd-cgi</tt> additionally.
8230 All web applications which do not contain CGI scripts should
8231 depend on <tt>httpd</tt>, all those web applications which
8232 <tt>do</tt> contain CGI scripts, should depend on
8240 <sect id="mail-transport-agents">
8241 <heading>Mail transport, delivery and user agents</heading>
8244 Debian packages which process electronic mail, whether mail
8245 user agents (MUAs) or mail transport agents (MTAs), must
8246 ensure that they are compatible with the configuration
8247 decisions below. Failure to do this may result in lost
8248 mail, broken <tt>From:</tt> lines, and other serious brain
8253 The mail spool is <file>/var/mail</file> and the interface to
8254 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8255 the FHS). On older systems, the mail spool may be
8256 physically located in <file>/var/spool/mail</file>, but all
8257 access to the mail spool should be via the
8258 <file>/var/mail</file> symlink. The mail spool is part of the
8259 base system and not part of the MTA package.
8263 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8264 programs (such as IMAP daemons) must lock the mailbox in an
8265 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8266 be combined with dot locking. To avoid deadlocks, a program
8267 should use <tt>fcntl()</tt> first and dot locking after
8268 this, or alternatively implement the two locking methods in
8269 a non blocking way<footnote>
8270 If it is not possible to establish both locks, the
8271 system shouldn't wait for the second lock to be
8272 established, but remove the first lock, wait a (random)
8273 time, and start over locking again.
8274 </footnote>. Using the functions <tt>maillock</tt> and
8275 <tt>mailunlock</tt> provided by the
8276 <tt>liblockfile*</tt><footnote>
8277 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8278 to use these functions.
8279 </footnote> packages is the recommended way to realize this.
8283 Mailboxes are generally either mode 600 and owned by
8284 <var>user</var> or mode 660 and owned by
8285 <tt><var>user</var>:mail</tt><footnote>
8286 There are two traditional permission schemes for mail spools:
8287 mode 600 with all mail delivery done by processes running as
8288 the destination user, or mode 660 and owned by group mail with
8289 mail delivery done by a process running as a system user in
8290 group mail. Historically, Debian required mode 660 mail
8291 spools to enable the latter model, but that model has become
8292 increasingly uncommon and the principle of least privilege
8293 indicates that mail systems that use the first model should
8294 use permissions of 600. If delivery to programs is permitted,
8295 it's easier to keep the mail system secure if the delivery
8296 agent runs as the destination user. Debian Policy therefore
8297 permits either scheme.
8298 </footnote>. The local system administrator may choose a
8299 different permission scheme; packages should not make
8300 assumptions about the permission and ownership of mailboxes
8301 unless required (such as when creating a new mailbox). A MUA
8302 may remove a mailbox (unless it has nonstandard permissions) in
8303 which case the MTA or another MUA must recreate it if needed.
8307 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8308 be setgid mail to do the locking mentioned above (and
8309 must obviously avoid accessing other users' mailboxes
8310 using this privilege).</p>
8313 <file>/etc/aliases</file> is the source file for the system mail
8314 aliases (e.g., postmaster, usenet, etc.), it is the one
8315 which the sysadmin and <prgn>postinst</prgn> scripts may
8316 edit. After <file>/etc/aliases</file> is edited the program or
8317 human editing it must call <prgn>newaliases</prgn>. All MTA
8318 packages must come with a <prgn>newaliases</prgn> program,
8319 even if it does nothing, but older MTA packages did not do
8320 this so programs should not fail if <prgn>newaliases</prgn>
8321 cannot be found. Note that because of this, all MTA
8322 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8323 <tt>Replaces: mail-transport-agent</tt> control file
8328 The convention of writing <tt>forward to
8329 <var>address</var></tt> in the mailbox itself is not
8330 supported. Use a <tt>.forward</tt> file instead.</p>
8333 The <prgn>rmail</prgn> program used by UUCP
8334 for incoming mail should be <file>/usr/sbin/rmail</file>.
8335 Likewise, <prgn>rsmtp</prgn>, for receiving
8336 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8340 If your package needs to know what hostname to use on (for
8341 example) outgoing news and mail messages which are generated
8342 locally, you should use the file <file>/etc/mailname</file>. It
8343 will contain the portion after the username and <tt>@</tt>
8344 (at) sign for email addresses of users on the machine
8345 (followed by a newline).
8349 Such a package should check for the existence of this file
8350 when it is being configured. If it exists, it should be
8351 used without comment, although an MTA's configuration script
8352 may wish to prompt the user even if it finds that this file
8353 exists. If the file does not exist, the package should
8354 prompt the user for the value (preferably using
8355 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8356 as well as using it in the package's configuration. The
8357 prompt should make it clear that the name will not just be
8358 used by that package. For example, in this situation the
8359 <tt>inn</tt> package could say something like:
8360 <example compact="compact">
8361 Please enter the "mail name" of your system. This is the
8362 hostname portion of the address to be shown on outgoing
8363 news and mail messages. The default is
8364 <var>syshostname</var>, your system's host name. Mail
8365 name ["<var>syshostname</var>"]:
8367 where <var>syshostname</var> is the output of <tt>hostname
8373 <heading>News system configuration</heading>
8376 All the configuration files related to the NNTP (news)
8377 servers and clients should be located under
8378 <file>/etc/news</file>.</p>
8381 There are some configuration issues that apply to a number
8382 of news clients and server packages on the machine. These
8386 <tag><file>/etc/news/organization</file></tag>
8388 A string which should appear as the
8389 organization header for all messages posted
8390 by NNTP clients on the machine
8393 <tag><file>/etc/news/server</file></tag>
8395 Contains the FQDN of the upstream NNTP
8396 server, or localhost if the local machine is
8401 Other global files may be added as required for cross-package news
8408 <heading>Programs for the X Window System</heading>
8411 <heading>Providing X support and package priorities</heading>
8414 Programs that can be configured with support for the X
8415 Window System must be configured to do so and must declare
8416 any package dependencies necessary to satisfy their
8417 runtime requirements when using the X Window System. If
8418 such a package is of higher priority than the X packages
8419 on which it depends, it is required that either the
8420 X-specific components be split into a separate package, or
8421 that an alternative version of the package, which includes
8422 X support, be provided, or that the package's priority be
8428 <heading>Packages providing an X server</heading>
8431 Packages that provide an X server that, directly or
8432 indirectly, communicates with real input and display
8433 hardware should declare in their control data that they
8434 provide the virtual package <tt>xserver</tt>.<footnote>
8435 This implements current practice, and provides an
8436 actual policy for usage of the <tt>xserver</tt>
8437 virtual package which appears in the virtual packages
8438 list. In a nutshell, X servers that interface
8439 directly with the display and input hardware or via
8440 another subsystem (e.g., GGI) should provide
8441 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8442 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8448 <heading>Packages providing a terminal emulator</heading>
8451 Packages that provide a terminal emulator for the X Window
8452 System which meet the criteria listed below should declare
8453 in their control data that they provide the virtual
8454 package <tt>x-terminal-emulator</tt>. They should also
8455 register themselves as an alternative for
8456 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8461 To be an <tt>x-terminal-emulator</tt>, a program must:
8462 <list compact="compact">
8464 Be able to emulate a DEC VT100 terminal, or a
8465 compatible terminal.
8469 Support the command-line option <tt>-e
8470 <var>command</var></tt>, which creates a new
8471 terminal window<footnote>
8472 "New terminal window" does not necessarily mean
8473 a new top-level X window directly parented by
8474 the window manager; it could, if the terminal
8475 emulator application were so coded, be a new
8476 "view" in a multiple-document interface (MDI).
8478 and runs the specified <var>command</var>,
8479 interpreting the entirety of the rest of the command
8480 line as a command to pass straight to exec, in the
8481 manner that <tt>xterm</tt> does.
8485 Support the command-line option <tt>-T
8486 <var>title</var></tt>, which creates a new terminal
8487 window with the window title <var>title</var>.
8494 <heading>Packages providing a window manager</heading>
8497 Packages that provide a window manager should declare in
8498 their control data that they provide the virtual package
8499 <tt>x-window-manager</tt>. They should also register
8500 themselves as an alternative for
8501 <file>/usr/bin/x-window-manager</file>, with a priority
8502 calculated as follows:
8503 <list compact="compact">
8505 Start with a priority of 20.
8509 If the window manager supports the Debian menu
8510 system, add 20 points if this support is available
8511 in the package's default configuration (i.e., no
8512 configuration files belonging to the system or user
8513 have to be edited to activate the feature); if
8514 configuration files must be modified, add only 10
8520 If the window manager complies with <url
8521 id="http://www.freedesktop.org/Standards/wm-spec"
8522 name="The Window Manager Specification Project">,
8523 written by the <url id="http://www.freedesktop.org/"
8524 name="Free Desktop Group">, add 40 points.
8528 If the window manager permits the X session to be
8529 restarted using a <em>different</em> window manager
8530 (without killing the X server) in its default
8531 configuration, add 10 points; otherwise add none.
8538 <heading>Packages providing fonts</heading>
8541 Packages that provide fonts for the X Window
8543 For the purposes of Debian Policy, a "font for the X
8544 Window System" is one which is accessed via X protocol
8545 requests. Fonts for the Linux console, for PostScript
8546 renderer, or any other purpose, do not fit this
8547 definition. Any tool which makes such fonts available
8548 to the X Window System, however, must abide by this
8551 must do a number of things to ensure that they are both
8552 available without modification of the X or font server
8553 configuration, and that they do not corrupt files used by
8554 other font packages to register information about
8558 Fonts of any type supported by the X Window System
8559 must be in a separate binary package from any
8560 executables, libraries, or documentation (except
8561 that specific to the fonts shipped, such as their
8562 license information). If one or more of the fonts
8563 so packaged are necessary for proper operation of
8564 the package with which they are associated the font
8565 package may be Recommended; if the fonts merely
8566 provide an enhancement, a Suggests relationship may
8567 be used. Packages must not Depend on font
8569 This is because the X server may retrieve fonts
8570 from the local file system or over the network
8571 from an X font server; the Debian package system
8572 is empowered to deal only with the local
8578 BDF fonts must be converted to PCF fonts with the
8579 <prgn>bdftopcf</prgn> utility (available in the
8580 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8581 placed in a directory that corresponds to their
8583 <list compact="compact">
8585 100 dpi fonts must be placed in
8586 <file>/usr/share/fonts/X11/100dpi/</file>.
8590 75 dpi fonts must be placed in
8591 <file>/usr/share/fonts/X11/75dpi/</file>.
8595 Character-cell fonts, cursor fonts, and other
8596 low-resolution fonts must be placed in
8597 <file>/usr/share/fonts/X11/misc/</file>.
8603 Type 1 fonts must be placed in
8604 <file>/usr/share/fonts/X11/Type1/</file>. If font
8605 metric files are available, they must be placed here
8610 Subdirectories of <file>/usr/share/fonts/X11/</file>
8611 other than those listed above must be neither
8612 created nor used. (The <file>PEX</file>, <file>CID</file>,
8613 <file>Speedo</file>, and <file>cyrillic</file> directories
8614 are excepted for historical reasons, but installation of
8615 files into these directories remains discouraged.)
8619 Font packages may, instead of placing files directly
8620 in the X font directories listed above, provide
8621 symbolic links in that font directory pointing to
8622 the files' actual location in the filesystem. Such
8623 a location must comply with the FHS.
8627 Font packages should not contain both 75dpi and
8628 100dpi versions of a font. If both are available,
8629 they should be provided in separate binary packages
8630 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8631 the names of the packages containing the
8632 corresponding fonts.
8636 Fonts destined for the <file>misc</file> subdirectory
8637 should not be included in the same package as 75dpi
8638 or 100dpi fonts; instead, they should be provided in
8639 a separate package with <tt>-misc</tt> appended to
8644 Font packages must not provide the files
8645 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8646 <file>fonts.scale</file> in a font directory:
8649 <file>fonts.dir</file> files must not be provided at all.
8653 <file>fonts.alias</file> and <file>fonts.scale</file>
8654 files, if needed, should be provided in the
8656 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8657 where <var>fontdir</var> is the name of the
8659 <file>/usr/share/fonts/X11/</file> where the
8660 package's corresponding fonts are stored
8661 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8662 <var>package</var> is the name of the package
8663 that provides these fonts, and
8664 <var>extension</var> is either <tt>scale</tt>
8665 or <tt>alias</tt>, whichever corresponds to
8672 Font packages must declare a dependency on
8673 <tt>xfonts-utils</tt> in their control
8678 Font packages that provide one or more
8679 <file>fonts.scale</file> files as described above must
8680 invoke <prgn>update-fonts-scale</prgn> on each
8681 directory into which they installed fonts
8682 <em>before</em> invoking
8683 <prgn>update-fonts-dir</prgn> on that directory.
8684 This invocation must occur in both the
8685 <prgn>postinst</prgn> (for all arguments) and
8686 <prgn>postrm</prgn> (for all arguments except
8687 <tt>upgrade</tt>) scripts.
8691 Font packages that provide one or more
8692 <file>fonts.alias</file> files as described above must
8693 invoke <prgn>update-fonts-alias</prgn> on each
8694 directory into which they installed fonts. This
8695 invocation must occur in both the
8696 <prgn>postinst</prgn> (for all arguments) and
8697 <prgn>postrm</prgn> (for all arguments except
8698 <tt>upgrade</tt>) scripts.
8702 Font packages must invoke
8703 <prgn>update-fonts-dir</prgn> on each directory into
8704 which they installed fonts. This invocation must
8705 occur in both the <prgn>postinst</prgn> (for all
8706 arguments) and <prgn>postrm</prgn> (for all
8707 arguments except <tt>upgrade</tt>) scripts.
8711 Font packages must not provide alias names for the
8712 fonts they include which collide with alias names
8713 already in use by fonts already packaged.
8717 Font packages must not provide fonts with the same
8718 XLFD registry name as another font already packaged.
8724 <sect1 id="appdefaults">
8725 <heading>Application defaults files</heading>
8728 Application defaults files must be installed in the
8729 directory <file>/etc/X11/app-defaults/</file> (use of a
8730 localized subdirectory of <file>/etc/X11/</file> as described
8731 in the <em>X Toolkit Intrinsics - C Language
8732 Interface</em> manual is also permitted). They must be
8733 registered as <tt>conffile</tt>s or handled as
8734 configuration files.
8738 Customization of programs' X resources may also be
8739 supported with the provision of a file with the same name
8740 as that of the package placed in
8741 the <file>/etc/X11/Xresources/</file> directory, which
8742 must be registered as a <tt>conffile</tt> or handled as a
8743 configuration file.<footnote>
8744 Note that this mechanism is not the same as using
8745 app-defaults; app-defaults are tied to the client
8746 binary on the local file system, whereas X resources
8747 are stored in the X server and affect all connecting
8754 <heading>Installation directory issues</heading>
8757 Historically, packages using the X Window System used a
8758 separate set of installation directories from other packages.
8759 This practice has been discontinued and packages using the X
8760 Window System should now generally be installed in the same
8761 directories as any other package. Specifically, packages must
8762 not install files under the <file>/usr/X11R6/</file> directory
8763 and the <file>/usr/X11R6/</file> directory hierarchy should be
8764 regarded as obsolete.
8768 Include files previously installed under
8769 <file>/usr/X11R6/include/X11/</file> should be installed into
8770 <file>/usr/include/X11/</file>. For files previously
8771 installed into subdirectories of
8772 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
8773 determine if subdirectories of <file>/usr/lib/</file> and
8774 <file>/usr/share/</file> can be used. If not, a subdirectory
8775 of <file>/usr/lib/X11/</file> should be used.
8779 Configuration files for window, display, or session managers
8780 or other applications that are tightly integrated with the X
8781 Window System may be placed in a subdirectory
8782 of <file>/etc/X11/</file> corresponding to the package name.
8783 Other X Window System applications should use
8784 the <file>/etc/</file> directory unless otherwise mandated by
8785 policy (such as for <ref id="appdefaults">).
8790 <heading>The OSF/Motif and OpenMotif libraries</heading>
8793 <em>Programs that require the non-DFSG-compliant OSF/Motif or
8794 OpenMotif libraries</em><footnote>
8795 OSF/Motif and OpenMotif are collectively referred to as
8796 "Motif" in this policy document.
8798 should be compiled against and tested with LessTif (a free
8799 re-implementation of Motif) instead. If the maintainer
8800 judges that the program or programs do not work
8801 sufficiently well with LessTif to be distributed and
8802 supported, but do so when compiled against Motif, then two
8803 versions of the package should be created; one linked
8804 statically against Motif and with <tt>-smotif</tt>
8805 appended to the package name, and one linked dynamically
8806 against Motif and with <tt>-dmotif</tt> appended to the
8811 Both Motif-linked versions are dependent
8812 upon non-DFSG-compliant software and thus cannot be
8813 uploaded to the <em>main</em> distribution; if the
8814 software is itself DFSG-compliant it may be uploaded to
8815 the <em>contrib</em> distribution. While known existing
8816 versions of Motif permit unlimited redistribution of
8817 binaries linked against the library (whether statically or
8818 dynamically), it is the package maintainer's
8819 responsibility to determine whether this is permitted by
8820 the license of the copy of Motif in their possession.
8826 <heading>Perl programs and modules</heading>
8829 Perl programs and modules should follow the current Perl policy.
8833 The Perl policy can be found in the <tt>perl-policy</tt>
8834 files in the <tt>debian-policy</tt> package.
8835 It is also available from the Debian web mirrors at
8836 <tt><url name="/doc/packaging-manuals/perl-policy/"
8837 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
8842 <heading>Emacs lisp programs</heading>
8845 Please refer to the "Debian Emacs Policy" for details of how to
8846 package emacs lisp programs.
8850 The Emacs policy is available in
8851 <file>debian-emacs-policy.gz</file> of the
8852 <package>emacsen-common</package> package.
8853 It is also available from the Debian web mirrors at
8854 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
8855 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
8860 <heading>Games</heading>
8863 The permissions on <file>/var/games</file> are mode 755, owner
8864 <tt>root</tt> and group <tt>root</tt>.
8868 Each game decides on its own security policy.</p>
8871 Games which require protected, privileged access to
8872 high-score files, saved games, etc., may be made
8873 set-<em>group</em>-id (mode 2755) and owned by
8874 <tt>root:games</tt>, and use files and directories with
8875 appropriate permissions (770 <tt>root:games</tt>, for
8876 example). They must not be made
8877 set-<em>user</em>-id, as this causes security problems. (If
8878 an attacker can subvert any set-user-id game they can
8879 overwrite the executable of any other, causing other players
8880 of these games to run a Trojan horse program. With a
8881 set-group-id game the attacker only gets access to less
8882 important game data, and if they can get at the other
8883 players' accounts at all it will take considerably more
8887 Some packages, for example some fortune cookie programs, are
8888 configured by the upstream authors to install with their
8889 data files or other static information made unreadable so
8890 that they can only be accessed through set-id programs
8891 provided. You should not do this in a Debian package: anyone can
8892 download the <file>.deb</file> file and read the data from it,
8893 so there is no point making the files unreadable. Not
8894 making the files unreadable also means that you don't have
8895 to make so many programs set-id, which reduces the risk of a
8899 As described in the FHS, binaries of games should be
8900 installed in the directory <file>/usr/games</file>. This also
8901 applies to games that use the X Window System. Manual pages
8902 for games (X and non-X games) should be installed in
8903 <file>/usr/share/man/man6</file>.</p>
8909 <heading>Documentation</heading>
8912 <heading>Manual pages</heading>
8915 You should install manual pages in <prgn>nroff</prgn> source
8916 form, in appropriate places under <file>/usr/share/man</file>.
8917 You should only use sections 1 to 9 (see the FHS for more
8918 details). You must not install a pre-formatted "cat page".
8922 Each program, utility, and function should have an
8923 associated manual page included in the same package. It is
8924 suggested that all configuration files also have a manual
8925 page included as well. Manual pages for protocols and other
8926 auxiliary things are optional.
8930 If no manual page is available, this is considered as a bug
8931 and should be reported to the Debian Bug Tracking System (the
8932 maintainer of the package is allowed to write this bug report
8933 themselves, if they so desire). Do not close the bug report
8934 until a proper man page is available.<footnote>
8935 It is not very hard to write a man page. See the
8936 <url id="http://www.schweikhardt.net/man_page_howto.html"
8937 name="Man-Page-HOWTO">,
8938 <manref name="man" section="7">, the examples
8939 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
8940 the helper programs <prgn>help2man</prgn>, or the
8941 directory <file>/usr/share/doc/man-db/examples</file>.
8946 You may forward a complaint about a missing man page to the
8947 upstream authors, and mark the bug as forwarded in the
8948 Debian bug tracking system. Even though the GNU Project do
8949 not in general consider the lack of a man page to be a bug,
8950 we do; if they tell you that they don't consider it a bug
8951 you should leave the bug in our bug tracking system open
8956 Manual pages should be installed compressed using <tt>gzip -9</tt>.
8960 If one man page needs to be accessible via several names it
8961 is better to use a symbolic link than the <file>.so</file>
8962 feature, but there is no need to fiddle with the relevant
8963 parts of the upstream source to change from <file>.so</file> to
8964 symlinks: don't do it unless it's easy. You should not
8965 create hard links in the manual page directories, nor put
8966 absolute filenames in <file>.so</file> directives. The filename
8967 in a <file>.so</file> in a man page should be relative to the
8968 base of the man page tree (usually
8969 <file>/usr/share/man</file>). If you do not create any links
8970 (whether symlinks, hard links, or <tt>.so</tt> directives)
8971 in the file system to the alternate names of the man page,
8972 then you should not rely on <prgn>man</prgn> finding your
8973 man page under those names based solely on the information in
8974 the man page's header.<footnote>
8975 Supporting this in <prgn>man</prgn> often requires
8976 unreasonable processing time to find a manual page or to
8977 report that none exists, and moves knowledge into man's
8978 database that would be better left in the file system.
8979 This support is therefore deprecated and will cease to
8980 be present in the future.
8985 Manual pages in locale-specific subdirectories of
8986 <file>/usr/share/man</file> should use either UTF-8 or the usual
8987 legacy encoding for that language (normally the one corresponding
8988 to the shortest relevant locale name in
8989 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
8990 <file>/usr/share/man/fr</file> should use either UTF-8 or
8991 ISO-8859-1.<footnote>
8992 <prgn>man</prgn> will automatically detect whether UTF-8 is in
8993 use. In future, all manual pages will be required to use
8999 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
9000 included in the subdirectory name unless it indicates a
9001 significant difference in the language, as this excludes
9002 speakers of the language in other countries.<footnote>
9003 At the time of writing, Chinese and Portuguese are the main
9004 languages with such differences, so <file>pt_BR</file>,
9005 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
9010 If a localized version of a manual page is provided, it should
9011 either be up-to-date or it should be obvious to the reader that
9012 it is outdated and the original manual page should be used
9013 instead. This can be done either by a note at the beginning of
9014 the manual page or by showing the missing or changed portions in
9015 the original language instead of the target language.
9020 <heading>Info documents</heading>
9023 Info documents should be installed in <file>/usr/share/info</file>.
9024 They should be compressed with <tt>gzip -9</tt>.
9028 The <prgn>install-info</prgn> program maintains a directory of
9029 installed info documents in <file>/usr/share/info/dir</file> for
9030 the use of info readers.<footnote>
9031 It was previously necessary for packages installing info
9032 documents to run <prgn>install-info</prgn> from maintainer
9033 scripts. This is no longer necessary. The installation
9034 system now uses dpkg triggers.
9036 This file must not be included in packages. Packages containing
9037 info documents should depend on <tt>dpkg (>= 1.15.4) |
9038 install-info</tt> to ensure that the directory file is properly
9039 rebuilt during partial upgrades from Debian 5.0 (lenny) and
9044 Info documents should contain section and directory entry
9045 information in the document for the use
9046 of <prgn>install-info</prgn>. The section should be specified
9047 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
9048 space and the section of this info page. The directory entry or
9049 entries should be included between
9050 a <tt>START-INFO-DIR-ENTRY</tt> line and
9051 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
9053 INFO-DIR-SECTION Individual utilities
9054 START-INFO-DIR-ENTRY
9055 * example: (example). An example info directory entry.
9058 To determine which section to use, you should look
9059 at <file>/usr/share/info/dir</file> on your system and choose
9060 the most relevant (or create a new section if none of the
9061 current sections are relevant).<footnote>
9062 Normally, info documents are generated from Texinfo source.
9063 To include this information in the generated info document, if
9064 it is absent, add commands like:
9066 @dircategory Individual utilities
9068 * example: (example). An example info directory entry.
9071 to the Texinfo source of the document and ensure that the info
9072 documents are rebuilt from source during the package build.
9078 <heading>Additional documentation</heading>
9081 Any additional documentation that comes with the package may
9082 be installed at the discretion of the package maintainer.
9083 Plain text documentation should be installed in the directory
9084 <file>/usr/share/doc/<var>package</var></file>, where
9085 <var>package</var> is the name of the package, and
9086 compressed with <tt>gzip -9</tt> unless it is small.
9090 If a package comes with large amounts of documentation which
9091 many users of the package will not require you should create
9092 a separate binary package to contain it, so that it does not
9093 take up disk space on the machines of users who do not need
9094 or want it installed.</p>
9097 It is often a good idea to put text information files
9098 (<file>README</file>s, changelogs, and so forth) that come with
9099 the source package in <file>/usr/share/doc/<var>package</var></file>
9100 in the binary package. However, you don't need to install
9101 the instructions for building and installing the package, of
9105 Packages must not require the existence of any files in
9106 <file>/usr/share/doc/</file> in order to function
9108 The system administrator should be able to
9109 delete files in <file>/usr/share/doc/</file> without causing
9110 any programs to break.
9112 Any files that are referenced by programs but are also
9113 useful as stand alone documentation should be installed under
9114 <file>/usr/share/<var>package</var>/</file> with symbolic links from
9115 <file>/usr/share/doc/<var>package</var></file>.
9119 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9120 link to another directory in <file>/usr/share/doc</file> only if
9121 the two packages both come from the same source and the
9122 first package Depends on the second.<footnote>
9124 Please note that this does not override the section on
9125 changelog files below, so the file
9126 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
9127 must refer to the changelog for the current version of
9128 <var>package</var> in question. In practice, this means
9129 that the sources of the target and the destination of the
9130 symlink must be the same (same source package and
9137 Former Debian releases placed all additional documentation
9138 in <file>/usr/doc/<var>package</var></file>. This has been
9139 changed to <file>/usr/share/doc/<var>package</var></file>,
9140 and packages must not put documentation in the directory
9141 <file>/usr/doc/<var>package</var></file>. <footnote>
9142 At this phase of the transition, we no longer require a
9143 symbolic link in <file>/usr/doc/</file>. At a later point,
9144 policy shall change to make the symbolic links a bug.
9150 <heading>Preferred documentation formats</heading>
9153 The unification of Debian documentation is being carried out
9157 If your package comes with extensive documentation in a
9158 markup format that can be converted to various other formats
9159 you should if possible ship HTML versions in a binary
9160 package, in the directory
9161 <file>/usr/share/doc/<var>appropriate-package</var></file> or
9162 its subdirectories.<footnote>
9163 The rationale: The important thing here is that HTML
9164 docs should be available in <em>some</em> package, not
9165 necessarily in the main binary package.
9170 Other formats such as PostScript may be provided at the
9171 package maintainer's discretion.
9175 <sect id="copyrightfile">
9176 <heading>Copyright information</heading>
9179 Every package must be accompanied by a verbatim copy of its
9180 copyright information and distribution license in the file
9181 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
9182 file must neither be compressed nor be a symbolic link.
9186 In addition, the copyright file must say where the upstream
9187 sources (if any) were obtained. It should name the original
9188 authors of the package and the Debian maintainer(s) who were
9189 involved with its creation.
9193 Packages in the <em>contrib</em> or <em>non-free</em> archive
9194 areas should state in the copyright file that the package is not
9195 part of the Debian GNU/Linux distribution and briefly explain
9200 A copy of the file which will be installed in
9201 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9202 be in <file>debian/copyright</file> in the source package.
9206 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9207 link to another directory in <file>/usr/share/doc</file> only if
9208 the two packages both come from the same source and the
9209 first package Depends on the second. These rules are
9210 important because copyrights must be extractable by
9215 Packages distributed under the UCB BSD license, the Apache
9216 license (version 2.0), the Artistic license, the GNU GPL
9217 (version 2 or 3), the GNU LGPL (versions 2, 2.1, or 3), and the
9218 GNU FDL (versions 1.2 or 1.3) should refer to the corresponding
9219 files under <file>/usr/share/common-licenses</file>,<footnote>
9222 <file>/usr/share/common-licenses/BSD</file>,
9223 <file>/usr/share/common-licenses/Apache-2.0</file>,
9224 <file>/usr/share/common-licenses/Artistic</file>,
9225 <file>/usr/share/common-licenses/GPL-2</file>,
9226 <file>/usr/share/common-licenses/GPL-3</file>,
9227 <file>/usr/share/common-licenses/LGPL-2</file>,
9228 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9229 <file>/usr/share/common-licenses/LGPL-3</file>,
9230 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
9231 <file>/usr/share/common-licenses/GFDL-1.3</file>
9234 </footnote> rather than quoting them in the copyright
9239 You should not use the copyright file as a general <file>README</file>
9240 file. If your package has such a file it should be
9241 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9242 <file>README.Debian</file> or some other appropriate place.</p>
9246 <heading>Examples</heading>
9249 Any examples (configurations, source files, whatever),
9250 should be installed in a directory
9251 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9252 files should not be referenced by any program: they're there
9253 for the benefit of the system administrator and users as
9254 documentation only. Architecture-specific example files
9255 should be installed in a directory
9256 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9258 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9259 latter directory itself may be a symbolic link to the
9264 If the purpose of a package is to provide examples, then the
9265 example files may be installed into
9266 <file>/usr/share/doc/<var>package</var></file>.
9270 <sect id="changelogs">
9271 <heading>Changelog files</heading>
9274 Packages that are not Debian-native must contain a
9275 compressed copy of the <file>debian/changelog</file> file from
9276 the Debian source tree in
9277 <file>/usr/share/doc/<var>package</var></file> with the name
9278 <file>changelog.Debian.gz</file>.
9282 If an upstream changelog is available, it should be accessible as
9283 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9284 plain text. If the upstream changelog is distributed in
9285 HTML, it should be made available in that form as
9286 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9287 and a plain text <file>changelog.gz</file> should be generated
9288 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9289 the upstream changelog files do not already conform to this
9290 naming convention, then this may be achieved either by
9291 renaming the files, or by adding a symbolic link, at the
9292 maintainer's discretion.<footnote>
9293 Rationale: People should not have to look in places for
9294 upstream changelogs merely because they are given
9295 different names or are distributed in HTML format.
9300 All of these files should be installed compressed using
9301 <tt>gzip -9</tt>, as they will become large with time even
9302 if they start out small.
9306 If the package has only one changelog which is used both as
9307 the Debian changelog and the upstream one because there is
9308 no separate upstream maintainer then that changelog should
9309 usually be installed as
9310 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9311 there is a separate upstream maintainer, but no upstream
9312 changelog, then the Debian changelog should still be called
9313 <file>changelog.Debian.gz</file>.
9317 For details about the format and contents of the Debian
9318 changelog file, please see <ref id="dpkgchangelog">.
9323 <appendix id="pkg-scope">
9324 <heading>Introduction and scope of these appendices</heading>
9327 These appendices are taken essentially verbatim from the
9328 now-deprecated Packaging Manual, version 3.2.1.0. They are
9329 the chapters which are likely to be of use to package
9330 maintainers and which have not already been included in the
9331 policy document itself. Most of these sections are very likely
9332 not relevant to policy; they should be treated as
9333 documentation for the packaging system. Please note that these
9334 appendices are included for convenience, and for historical
9335 reasons: they used to be part of policy package, and they have
9336 not yet been incorporated into dpkg documentation. However,
9337 they still have value, and hence they are presented here.
9341 They have not yet been checked to ensure that they are
9342 compatible with the contents of policy, and if there are any
9343 contradictions, the version in the main policy document takes
9344 precedence. The remaining chapters of the old Packaging
9345 Manual have also not been read in detail to ensure that there
9346 are not parts which have been left out. Both of these will be
9351 Certain parts of the Packaging manual were integrated into the
9352 Policy Manual proper, and removed from the appendices. Links
9353 have been placed from the old locations to the new ones.
9357 <prgn>dpkg</prgn> is a suite of programs for creating binary
9358 package files and installing and removing them on Unix
9360 <prgn>dpkg</prgn> is targeted primarily at Debian
9361 GNU/Linux, but may work on or be ported to other
9367 The binary packages are designed for the management of
9368 installed executable programs (usually compiled binaries) and
9369 their associated data, though source code examples and
9370 documentation are provided as part of some packages.</p>
9373 This manual describes the technical aspects of creating Debian
9374 binary packages (<file>.deb</file> files). It documents the
9375 behavior of the package management programs
9376 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9377 they interact with packages.</p>
9380 It also documents the interaction between
9381 <prgn>dselect</prgn>'s core and the access method scripts it
9382 uses to actually install the selected packages, and describes
9383 how to create a new access method.</p>
9386 This manual does not go into detail about the options and
9387 usage of the package building and installation tools. It
9388 should therefore be read in conjunction with those programs'
9393 The utility programs which are provided with <prgn>dpkg</prgn>
9394 for managing various system configuration and similar issues,
9395 such as <prgn>update-rc.d</prgn> and
9396 <prgn>install-info</prgn>, are not described in detail here -
9397 please see their man pages.
9401 It is assumed that the reader is reasonably familiar with the
9402 <prgn>dpkg</prgn> System Administrators' manual.
9403 Unfortunately this manual does not yet exist.
9407 The Debian version of the FSF's GNU hello program is provided
9408 as an example for people wishing to create Debian
9409 packages. The Debian <prgn>debmake</prgn> package is
9410 recommended as a very helpful tool in creating and maintaining
9411 Debian packages. However, while the tools and examples are
9412 helpful, they do not replace the need to read and follow the
9413 Policy and Programmer's Manual.</p>
9416 <appendix id="pkg-binarypkg">
9417 <heading>Binary packages (from old Packaging Manual)</heading>
9420 The binary package has two main sections. The first part
9421 consists of various control information files and scripts used
9422 by <prgn>dpkg</prgn> when installing and removing. See <ref
9423 id="pkg-controlarea">.
9427 The second part is an archive containing the files and
9428 directories to be installed.
9432 In the future binary packages may also contain other
9433 components, such as checksums and digital signatures. The
9434 format for the archive is described in full in the
9435 <file>deb(5)</file> man page.
9439 <sect id="pkg-bincreating"><heading>Creating package files -
9440 <prgn>dpkg-deb</prgn>
9444 All manipulation of binary package files is done by
9445 <prgn>dpkg-deb</prgn>; it's the only program that has
9446 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9447 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9448 will spot that the options requested are appropriate to
9449 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9454 In order to create a binary package you must make a
9455 directory tree which contains all the files and directories
9456 you want to have in the file system data part of the package.
9457 In Debian-format source packages this directory is usually
9458 <file>debian/tmp</file>, relative to the top of the package's
9463 They should have the locations (relative to the root of the
9464 directory tree you're constructing) ownerships and
9465 permissions which you want them to have on the system when
9470 With current versions of <prgn>dpkg</prgn> the uid/username
9471 and gid/groupname mappings for the users and groups being
9472 used should be the same on the system where the package is
9473 built and the one where it is installed.
9477 You need to add one special directory to the root of the
9478 miniature file system tree you're creating:
9479 <prgn>DEBIAN</prgn>. It should contain the control
9480 information files, notably the binary package control file
9481 (see <ref id="pkg-controlfile">).
9485 The <prgn>DEBIAN</prgn> directory will not appear in the
9486 file system archive of the package, and so won't be installed
9487 by <prgn>dpkg</prgn> when the package is installed.
9491 When you've prepared the package, you should invoke:
9493 dpkg --build <var>directory</var>
9498 This will build the package in
9499 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9500 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9501 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9506 See the man page <manref name="dpkg-deb" section="8"> for details of how
9507 to examine the contents of this newly-created file. You may find the
9508 output of following commands enlightening:
9510 dpkg-deb --info <var>filename</var>.deb
9511 dpkg-deb --contents <var>filename</var>.deb
9512 dpkg --contents <var>filename</var>.deb
9514 To view the copyright file for a package you could use this command:
9516 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
9521 <sect id="pkg-controlarea">
9522 <heading>Package control information files</heading>
9525 The control information portion of a binary package is a
9526 collection of files with names known to <prgn>dpkg</prgn>.
9527 It will treat the contents of these files specially - some
9528 of them contain information used by <prgn>dpkg</prgn> when
9529 installing or removing the package; others are scripts which
9530 the package maintainer wants <prgn>dpkg</prgn> to run.
9534 It is possible to put other files in the package control
9535 area, but this is not generally a good idea (though they
9536 will largely be ignored).
9540 Here is a brief list of the control info files supported by
9541 <prgn>dpkg</prgn> and a summary of what they're used for.
9546 <tag><tt>control</tt>
9549 This is the key description file used by
9550 <prgn>dpkg</prgn>. It specifies the package's name
9551 and version, gives its description for the user,
9552 states its relationships with other packages, and so
9553 forth. See <ref id="sourcecontrolfiles"> and
9554 <ref id="binarycontrolfiles">.
9558 It is usually generated automatically from information
9559 in the source package by the
9560 <prgn>dpkg-gencontrol</prgn> program, and with
9561 assistance from <prgn>dpkg-shlibdeps</prgn>.
9562 See <ref id="pkg-sourcetools">.
9566 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9571 These are executable files (usually scripts) which
9572 <prgn>dpkg</prgn> runs during installation, upgrade
9573 and removal of packages. They allow the package to
9574 deal with matters which are particular to that package
9575 or require more complicated processing than that
9576 provided by <prgn>dpkg</prgn>. Details of when and
9577 how they are called are in <ref id="maintainerscripts">.
9581 It is very important to make these scripts idempotent.
9582 See <ref id="idempotency">.
9586 The maintainer scripts are guaranteed to run with a
9587 controlling terminal and can interact with the user.
9588 See <ref id="controllingterminal">.
9592 <tag><tt>conffiles</tt>
9595 This file contains a list of configuration files which
9596 are to be handled automatically by <prgn>dpkg</prgn>
9597 (see <ref id="pkg-conffiles">). Note that not necessarily
9598 every configuration file should be listed here.
9601 <tag><tt>shlibs</tt>
9604 This file contains a list of the shared libraries
9605 supplied by the package, with dependency details for
9606 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9607 when it determines what dependencies are required in a
9608 package control file. The <tt>shlibs</tt> file format
9609 is described on <ref id="shlibs">.
9614 <sect id="pkg-controlfile">
9615 <heading>The main control information file: <tt>control</tt></heading>
9618 The most important control information file used by
9619 <prgn>dpkg</prgn> when it installs a package is
9620 <tt>control</tt>. It contains all the package's "vital
9625 The binary package control files of packages built from
9626 Debian sources are made by a special tool,
9627 <prgn>dpkg-gencontrol</prgn>, which reads
9628 <file>debian/control</file> and <file>debian/changelog</file> to
9629 find the information it needs. See <ref id="pkg-sourcepkg"> for
9634 The fields in binary package control files are listed in
9635 <ref id="binarycontrolfiles">.
9639 A description of the syntax of control files and the purpose
9640 of the fields is available in <ref id="controlfields">.
9645 <heading>Time Stamps</heading>
9648 See <ref id="timestamps">.
9653 <appendix id="pkg-sourcepkg">
9654 <heading>Source packages (from old Packaging Manual) </heading>
9657 The Debian binary packages in the distribution are generated
9658 from Debian sources, which are in a special format to assist
9659 the easy and automatic building of binaries.
9662 <sect id="pkg-sourcetools">
9663 <heading>Tools for processing source packages</heading>
9666 Various tools are provided for manipulating source packages;
9667 they pack and unpack sources and help build of binary
9668 packages and help manage the distribution of new versions.
9672 They are introduced and typical uses described here; see
9673 <manref name="dpkg-source" section="1"> for full
9674 documentation about their arguments and operation.
9678 For examples of how to construct a Debian source package,
9679 and how to use those utilities that are used by Debian
9680 source packages, please see the <prgn>hello</prgn> example
9684 <sect1 id="pkg-dpkg-source">
9686 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9691 This program is frequently used by hand, and is also
9692 called from package-independent automated building scripts
9693 such as <prgn>dpkg-buildpackage</prgn>.
9697 To unpack a package it is typically invoked with
9699 dpkg-source -x <var>.../path/to/filename</var>.dsc
9704 with the <file><var>filename</var>.tar.gz</file> and
9705 <file><var>filename</var>.diff.gz</file> (if applicable) in
9706 the same directory. It unpacks into
9707 <file><var>package</var>-<var>version</var></file>, and if
9709 <file><var>package</var>-<var>version</var>.orig</file>, in
9710 the current directory.
9714 To create a packed source archive it is typically invoked:
9716 dpkg-source -b <var>package</var>-<var>version</var>
9721 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
9722 <file>.diff.gz</file> (if appropriate) in the current
9723 directory. <prgn>dpkg-source</prgn> does not clean the
9724 source tree first - this must be done separately if it is
9729 See also <ref id="pkg-sourcearchives">.</p>
9733 <sect1 id="pkg-dpkg-buildpackage">
9735 <prgn>dpkg-buildpackage</prgn> - overall package-building
9740 <prgn>dpkg-buildpackage</prgn> is a script which invokes
9741 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
9742 targets <tt>clean</tt>, <tt>build</tt> and
9743 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
9744 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
9745 source and binary package upload.
9749 It is usually invoked by hand from the top level of the
9750 built or unbuilt source directory. It may be invoked with
9751 no arguments; useful arguments include:
9752 <taglist compact="compact">
9753 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
9756 Do not sign the <tt>.changes</tt> file or the
9757 source package <tt>.dsc</tt> file, respectively.</p>
9759 <tag><tt>-p<var>sign-command</var></tt></tag>
9762 Invoke <var>sign-command</var> instead of finding
9763 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
9764 <var>sign-command</var> must behave just like
9765 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
9767 <tag><tt>-r<var>root-command</var></tt></tag>
9770 When root privilege is required, invoke the command
9771 <var>root-command</var>. <var>root-command</var>
9772 should invoke its first argument as a command, from
9773 the <prgn>PATH</prgn> if necessary, and pass its
9774 second and subsequent arguments to the command it
9775 calls. If no <var>root-command</var> is supplied
9776 then <var>dpkg-buildpackage</var> will take no
9777 special action to gain root privilege, so that for
9778 most packages it will have to be invoked as root to
9781 <tag><tt>-b</tt>, <tt>-B</tt></tag>
9784 Two types of binary-only build and upload - see
9785 <manref name="dpkg-source" section="1">.
9792 <sect1 id="pkg-dpkg-gencontrol">
9794 <prgn>dpkg-gencontrol</prgn> - generates binary package
9799 This program is usually called from <file>debian/rules</file>
9800 (see <ref id="pkg-sourcetree">) in the top level of the source
9805 This is usually done just before the files and directories in the
9806 temporary directory tree where the package is being built have their
9807 permissions and ownerships set and the package is constructed using
9808 <prgn>dpkg-deb/</prgn>
9810 This is so that the control file which is produced has
9811 the right permissions
9816 <prgn>dpkg-gencontrol</prgn> must be called after all the
9817 files which are to go into the package have been placed in
9818 the temporary build directory, so that its calculation of
9819 the installed size of a package is correct.
9823 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
9824 be run after <prgn>dpkg-shlibdeps</prgn> so that the
9825 variable substitutions created by
9826 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
9831 For a package which generates only one binary package, and
9832 which builds it in <file>debian/tmp</file> relative to the top
9833 of the source package, it is usually sufficient to call
9834 <prgn>dpkg-gencontrol</prgn>.
9838 Sources which build several binaries will typically need
9841 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
9842 </example> The <tt>-P</tt> tells
9843 <prgn>dpkg-gencontrol</prgn> that the package is being
9844 built in a non-default directory, and the <tt>-p</tt>
9845 tells it which package's control file should be generated.
9849 <prgn>dpkg-gencontrol</prgn> also adds information to the
9850 list of files in <file>debian/files</file>, for the benefit of
9851 (for example) a future invocation of
9852 <prgn>dpkg-genchanges</prgn>.</p>
9855 <sect1 id="pkg-dpkg-shlibdeps">
9857 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
9862 This program is usually called from <file>debian/rules</file>
9863 just before <prgn>dpkg-gencontrol</prgn> (see <ref
9864 id="pkg-sourcetree">), in the top level of the source tree.
9868 Its arguments are executables and shared libraries
9871 They may be specified either in the locations in the
9872 source tree where they are created or in the locations
9873 in the temporary build tree where they are installed
9874 prior to binary package creation.
9876 </footnote> for which shared library dependencies should
9877 be included in the binary package's control file.
9881 If some of the found shared libraries should only
9882 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
9883 some warrant a <tt>Pre-Depends</tt>, this can be achieved
9884 by using the <tt>-d<var>dependency-field</var></tt> option
9885 before those executable(s). (Each <tt>-d</tt> option
9886 takes effect until the next <tt>-d</tt>.)
9890 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
9891 output control file to be modified. Instead by default it
9892 adds to the <file>debian/substvars</file> file variable
9893 settings like <tt>shlibs:Depends</tt>. These variable
9894 settings must be referenced in dependency fields in the
9895 appropriate per-binary-package sections of the source
9900 For example, a package that generates an essential part
9901 which requires dependencies, and optional parts that
9902 which only require a recommendation, would separate those
9903 two sets of dependencies into two different fields.<footnote>
9904 At the time of writing, an example for this was the
9905 <package/xmms/ package, with Depends used for the xmms
9906 executable, Recommends for the plug-ins and Suggests for
9907 even more optional features provided by unzip.
9909 It can say in its <file>debian/rules</file>:
9911 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
9912 -dRecommends <var>optionalpart anotheroptionalpart</var>
9914 and then in its main control file <file>debian/control</file>:
9917 Depends: ${shlibs:Depends}
9918 Recommends: ${shlibs:Recommends}
9924 Sources which produce several binary packages with
9925 different shared library dependency requirements can use
9926 the <tt>-p<var>varnameprefix</var></tt> option to override
9927 the default <tt>shlibs:</tt> prefix (one invocation of
9928 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
9929 They can thus produce several sets of dependency
9930 variables, each of the form
9931 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
9932 which can be referred to in the appropriate parts of the
9933 binary package control files.
9938 <sect1 id="pkg-dpkg-distaddfile">
9940 <prgn>dpkg-distaddfile</prgn> - adds a file to
9941 <file>debian/files</file>
9945 Some packages' uploads need to include files other than
9946 the source and binary package files.
9950 <prgn>dpkg-distaddfile</prgn> adds a file to the
9951 <file>debian/files</file> file so that it will be included in
9952 the <file>.changes</file> file when
9953 <prgn>dpkg-genchanges</prgn> is run.
9957 It is usually invoked from the <tt>binary</tt> target of
9958 <file>debian/rules</file>:
9960 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
9962 The <var>filename</var> is relative to the directory where
9963 <prgn>dpkg-genchanges</prgn> will expect to find it - this
9964 is usually the directory above the top level of the source
9965 tree. The <file>debian/rules</file> target should put the
9966 file there just before or just after calling
9967 <prgn>dpkg-distaddfile</prgn>.
9971 The <var>section</var> and <var>priority</var> are passed
9972 unchanged into the resulting <file>.changes</file> file.
9977 <sect1 id="pkg-dpkg-genchanges">
9979 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
9984 This program is usually called by package-independent
9985 automatic building scripts such as
9986 <prgn>dpkg-buildpackage</prgn>, but it may also be called
9991 It is usually called in the top level of a built source
9992 tree, and when invoked with no arguments will print out a
9993 straightforward <file>.changes</file> file based on the
9994 information in the source package's changelog and control
9995 file and the binary and source packages which should have
10001 <sect1 id="pkg-dpkg-parsechangelog">
10003 <prgn>dpkg-parsechangelog</prgn> - produces parsed
10004 representation of a changelog
10008 This program is used internally by
10009 <prgn>dpkg-source</prgn> et al. It may also occasionally
10010 be useful in <file>debian/rules</file> and elsewhere. It
10011 parses a changelog, <file>debian/changelog</file> by default,
10012 and prints a control-file format representation of the
10013 information in it to standard output.
10017 <sect1 id="pkg-dpkg-architecture">
10019 <prgn>dpkg-architecture</prgn> - information about the build and
10024 This program can be used manually, but is also invoked by
10025 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
10026 environment or make variables which specify the build and host
10027 architecture for the package building process.
10032 <sect id="pkg-sourcetree">
10033 <heading>The Debianised source tree</heading>
10036 The source archive scheme described later is intended to
10037 allow a Debianised source tree with some associated control
10038 information to be reproduced and transported easily. The
10039 Debianised source tree is a version of the original program
10040 with certain files added for the benefit of the
10041 Debianisation process, and with any other changes required
10042 made to the rest of the source code and installation
10047 The extra files created for Debian are in the subdirectory
10048 <file>debian</file> of the top level of the Debianised source
10049 tree. They are described below.
10052 <sect1 id="pkg-debianrules">
10053 <heading><file>debian/rules</file> - the main building script</heading>
10056 See <ref id="debianrules">.
10061 <sect1 id="pkg-dpkgchangelog">
10062 <heading><file>debian/changelog</file></heading>
10065 See <ref id="dpkgchangelog">.
10068 <sect2><heading>Defining alternative changelog formats
10072 It is possible to use a different format to the standard
10073 one, by providing a parser for the format you wish to
10078 In order to have <tt>dpkg-parsechangelog</tt> run your
10079 parser, you must include a line within the last 40 lines
10080 of your file matching the Perl regular expression:
10081 <tt>\schangelog-format:\s+([0-9a-z]+)\W</tt> The part in
10082 parentheses should be the name of the format. For
10083 example, you might say:
10085 @@@ changelog-format: joebloggs @@@
10087 Changelog format names are non-empty strings of alphanumerics.
10091 If such a line exists then <tt>dpkg-parsechangelog</tt>
10092 will look for the parser as
10093 <file>/usr/lib/dpkg/parsechangelog/<var>format-name</var></file>
10095 <file>/usr/local/lib/dpkg/parsechangelog/<var>format-name</var></file>;
10096 it is an error for it not to find it, or for it not to
10097 be an executable program. The default changelog format
10098 is <tt>dpkg</tt>, and a parser for it is provided with
10099 the <tt>dpkg</tt> package.
10103 The parser will be invoked with the changelog open on
10104 standard input at the start of the file. It should read
10105 the file (it may seek if it wishes) to determine the
10106 information required and return the parsed information
10107 to standard output in the form of a series of control
10108 fields in the standard format. By default it should
10109 return information about only the most recent version in
10110 the changelog; it should accept a
10111 <tt>-v<var>version</var></tt> option to return changes
10112 information from all versions present <em>strictly
10113 after</em> <var>version</var>, and it should then be an
10114 error for <var>version</var> not to be present in the
10120 <list compact="compact">
10121 <item><qref id="f-Source"><tt>Source</tt></qref></item>
10122 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
10123 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
10124 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (mandatory)</item>
10125 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
10126 <item><qref id="f-Date"><tt>Date</tt></qref></item>
10127 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
10132 If several versions are being returned (due to the use
10133 of <tt>-v</tt>), the urgency value should be of the
10134 highest urgency code listed at the start of any of the
10135 versions requested followed by the concatenated
10136 (space-separated) comments from all the versions
10137 requested; the maintainer, version, distribution and
10138 date should always be from the most recent version.
10142 For the format of the <tt>Changes</tt> field see
10143 <ref id="f-Changes">.
10147 If the changelog format which is being parsed always or
10148 almost always leaves a blank line between individual
10149 change notes these blank lines should be stripped out,
10150 so as to make the resulting output compact.
10154 If the changelog format does not contain date or package
10155 name information this information should be omitted from
10156 the output. The parser should not attempt to synthesize
10157 it or find it from other sources.
10161 If the changelog does not have the expected format the
10162 parser should exit with a nonzero exit status, rather
10163 than trying to muddle through and possibly generating
10168 A changelog parser may not interact with the user at
10174 <sect1 id="pkg-srcsubstvars">
10175 <heading><file>debian/substvars</file> and variable substitutions</heading>
10178 See <ref id="substvars">.
10184 <heading><file>debian/files</file></heading>
10187 See <ref id="debianfiles">.
10191 <sect1><heading><file>debian/tmp</file>
10195 This is the canonical temporary location for the
10196 construction of binary packages by the <tt>binary</tt>
10197 target. The directory <file>tmp</file> serves as the root of
10198 the file system tree as it is being constructed (for
10199 example, by using the package's upstream makefiles install
10200 targets and redirecting the output there), and it also
10201 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10202 id="pkg-bincreating">.
10206 If several binary packages are generated from the same
10207 source tree it is usual to use several
10208 <file>debian/tmp<var>something</var></file> directories, for
10209 example <file>tmp-a</file> or <file>tmp-doc</file>.
10213 Whatever <file>tmp</file> directories are created and used by
10214 <tt>binary</tt> must of course be removed by the
10215 <tt>clean</tt> target.</p></sect1>
10219 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10223 As it exists on the FTP site, a Debian source package
10224 consists of three related files. You must have the right
10225 versions of all three to be able to use them.
10230 <tag>Debian source control file - <tt>.dsc</tt></tag>
10232 This file is a control file used by <prgn>dpkg-source</prgn>
10233 to extract a source package.
10234 See <ref id="debiansourcecontrolfiles">.
10238 Original source archive -
10240 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10246 This is a compressed (with <tt>gzip -9</tt>)
10247 <prgn>tar</prgn> file containing the source code from
10248 the upstream authors of the program.
10253 Debianisation diff -
10255 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10261 This is a unified context diff (<tt>diff -u</tt>)
10262 giving the changes which are required to turn the
10263 original source into the Debian source. These changes
10264 may only include editing and creating plain files.
10265 The permissions of files, the targets of symbolic
10266 links and the characteristics of special files or
10267 pipes may not be changed and no files may be removed
10272 All the directories in the diff must exist, except the
10273 <file>debian</file> subdirectory of the top of the source
10274 tree, which will be created by
10275 <prgn>dpkg-source</prgn> if necessary when unpacking.
10279 The <prgn>dpkg-source</prgn> program will
10280 automatically make the <file>debian/rules</file> file
10281 executable (see below).</p></item>
10286 If there is no original source code - for example, if the
10287 package is specially prepared for Debian or the Debian
10288 maintainer is the same as the upstream maintainer - the
10289 format is slightly different: then there is no diff, and the
10291 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10292 and preferably contains a directory named
10293 <file><var>package</var>-<var>version</var></file>.
10298 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10301 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10302 Debian source package. However, if it is not available it
10303 is possible to unpack a Debian source archive as follows:
10304 <enumlist compact="compact">
10307 Untar the tarfile, which will create a <file>.orig</file>
10311 <p>Rename the <file>.orig</file> directory to
10312 <file><var>package</var>-<var>version</var></file>.</p>
10316 Create the subdirectory <file>debian</file> at the top of
10317 the source tree.</p>
10319 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10321 <item><p>Untar the tarfile again if you want a copy of the original
10322 source code alongside the Debianised version.</p>
10327 It is not possible to generate a valid Debian source archive
10328 without using <prgn>dpkg-source</prgn>. In particular,
10329 attempting to use <prgn>diff</prgn> directly to generate the
10330 <file>.diff.gz</file> file will not work.
10334 <heading>Restrictions on objects in source packages</heading>
10337 The source package may not contain any hard links
10339 This is not currently detected when building source
10340 packages, but only when extracting
10344 Hard links may be permitted at some point in the
10345 future, but would require a fair amount of
10347 </footnote>, device special files, sockets or setuid or
10350 Setgid directories are allowed.
10355 The source packaging tools manage the changes between the
10356 original and Debianised source using <prgn>diff</prgn> and
10357 <prgn>patch</prgn>. Turning the original source tree as
10358 included in the <file>.orig.tar.gz</file> into the debianised
10359 source must not involve any changes which cannot be
10360 handled by these tools. Problematic changes which cause
10361 <prgn>dpkg-source</prgn> to halt with an error when
10362 building the source package are:
10363 <list compact="compact">
10364 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10366 <item><p>Changing the targets of symbolic links.</p>
10368 <item><p>Creating directories, other than <file>debian</file>.</p>
10370 <item><p>Changes to the contents of binary files.</p></item>
10371 </list> Changes which cause <prgn>dpkg-source</prgn> to
10372 print a warning but continue anyway are:
10373 <list compact="compact">
10376 Removing files, directories or symlinks.
10378 Renaming a file is not treated specially - it is
10379 seen as the removal of the old file (which
10380 generates a warning, but is otherwise ignored),
10381 and the creation of the new one.
10387 Changed text files which are missing the usual final
10388 newline (either in the original or the modified
10393 Changes which are not represented, but which are not detected by
10394 <prgn>dpkg-source</prgn>, are:
10395 <list compact="compact">
10396 <item><p>Changing the permissions of files (other than
10397 <file>debian/rules</file>) and directories.</p></item>
10402 The <file>debian</file> directory and <file>debian/rules</file>
10403 are handled specially by <prgn>dpkg-source</prgn> - before
10404 applying the changes it will create the <file>debian</file>
10405 directory, and afterwards it will make
10406 <file>debian/rules</file> world-executable.
10412 <appendix id="pkg-controlfields">
10413 <heading>Control files and their fields (from old Packaging Manual)</heading>
10416 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10417 data in a common format, known as control files. Binary and
10418 source packages have control data as do the <file>.changes</file>
10419 files which control the installation of uploaded files, and
10420 <prgn>dpkg</prgn>'s internal databases are in a similar
10425 <heading>Syntax of control files</heading>
10428 See <ref id="controlsyntax">.
10432 It is important to note that there are several fields which
10433 are optional as far as <prgn>dpkg</prgn> and the related
10434 tools are concerned, but which must appear in every Debian
10435 package, or whose omission may cause problems.
10440 <heading>List of fields</heading>
10443 See <ref id="controlfieldslist">.
10447 This section now contains only the fields that didn't belong
10448 to the Policy manual.
10451 <sect1 id="pkg-f-Filename">
10452 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10455 These fields in <tt>Packages</tt> files give the
10456 filename(s) of (the parts of) a package in the
10457 distribution directories, relative to the root of the
10458 Debian hierarchy. If the package has been split into
10459 several parts the parts are all listed in order, separated
10464 <sect1 id="pkg-f-Size">
10465 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10468 These fields in <file>Packages</file> files give the size (in
10469 bytes, expressed in decimal) and MD5 checksum of the
10470 file(s) which make(s) up a binary package in the
10471 distribution. If the package is split into several parts
10472 the values for the parts are listed in order, separated by
10477 <sect1 id="pkg-f-Status">
10478 <heading><tt>Status</tt></heading>
10481 This field in <prgn>dpkg</prgn>'s status file records
10482 whether the user wants a package installed, removed or
10483 left alone, whether it is broken (requiring
10484 re-installation) or not and what its current state on the
10485 system is. Each of these pieces of information is a
10490 <sect1 id="pkg-f-Config-Version">
10491 <heading><tt>Config-Version</tt></heading>
10494 If a package is not installed or not configured, this
10495 field in <prgn>dpkg</prgn>'s status file records the last
10496 version of the package which was successfully
10501 <sect1 id="pkg-f-Conffiles">
10502 <heading><tt>Conffiles</tt></heading>
10505 This field in <prgn>dpkg</prgn>'s status file contains
10506 information about the automatically-managed configuration
10507 files held by a package. This field should <em>not</em>
10508 appear anywhere in a package!
10513 <heading>Obsolete fields</heading>
10516 These are still recognized by <prgn>dpkg</prgn> but should
10517 not appear anywhere any more.
10519 <taglist compact="compact">
10521 <tag><tt>Revision</tt></tag>
10522 <tag><tt>Package-Revision</tt></tag>
10523 <tag><tt>Package_Revision</tt></tag>
10525 The Debian revision part of the package version was
10526 at one point in a separate control file field. This
10527 field went through several names.
10530 <tag><tt>Recommended</tt></tag>
10531 <item>Old name for <tt>Recommends</tt>.</item>
10533 <tag><tt>Optional</tt></tag>
10534 <item>Old name for <tt>Suggests</tt>.</item>
10536 <tag><tt>Class</tt></tag>
10537 <item>Old name for <tt>Priority</tt>.</item>
10546 <appendix id="pkg-conffiles">
10547 <heading>Configuration file handling (from old Packaging Manual)</heading>
10550 <prgn>dpkg</prgn> can do a certain amount of automatic
10551 handling of package configuration files.
10555 Whether this mechanism is appropriate depends on a number of
10556 factors, but basically there are two approaches to any
10557 particular configuration file.
10561 The easy method is to ship a best-effort configuration in the
10562 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10563 handle updates. If the user is unlikely to want to edit the
10564 file, but you need them to be able to without losing their
10565 changes, and a new package with a changed version of the file
10566 is only released infrequently, this is a good approach.
10570 The hard method is to build the configuration file from
10571 scratch in the <prgn>postinst</prgn> script, and to take the
10572 responsibility for fixing any mistakes made in earlier
10573 versions of the package automatically. This will be
10574 appropriate if the file is likely to need to be different on
10578 <sect><heading>Automatic handling of configuration files by
10583 A package may contain a control area file called
10584 <tt>conffiles</tt>. This file should be a list of filenames
10585 of configuration files needing automatic handling, separated
10586 by newlines. The filenames should be absolute pathnames,
10587 and the files referred to should actually exist in the
10592 When a package is upgraded <prgn>dpkg</prgn> will process
10593 the configuration files during the configuration stage,
10594 shortly before it runs the package's <prgn>postinst</prgn>
10599 For each file it checks to see whether the version of the
10600 file included in the package is the same as the one that was
10601 included in the last version of the package (the one that is
10602 being upgraded from); it also compares the version currently
10603 installed on the system with the one shipped with the last
10608 If neither the user nor the package maintainer has changed
10609 the file, it is left alone. If one or the other has changed
10610 their version, then the changed version is preferred - i.e.,
10611 if the user edits their file, but the package maintainer
10612 doesn't ship a different version, the user's changes will
10613 stay, silently, but if the maintainer ships a new version
10614 and the user hasn't edited it the new version will be
10615 installed (with an informative message). If both have
10616 changed their version the user is prompted about the problem
10617 and must resolve the differences themselves.
10621 The comparisons are done by calculating the MD5 message
10622 digests of the files, and storing the MD5 of the file as it
10623 was included in the most recent version of the package.
10627 When a package is installed for the first time
10628 <prgn>dpkg</prgn> will install the file that comes with it,
10629 unless that would mean overwriting a file already on the
10634 However, note that <prgn>dpkg</prgn> will <em>not</em>
10635 replace a conffile that was removed by the user (or by a
10636 script). This is necessary because with some programs a
10637 missing file produces an effect hard or impossible to
10638 achieve in another way, so that a missing file needs to be
10639 kept that way if the user did it.
10643 Note that a package should <em>not</em> modify a
10644 <prgn>dpkg</prgn>-handled conffile in its maintainer
10645 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10646 the user confusing and possibly dangerous options for
10647 conffile update when the package is upgraded.</p>
10650 <sect><heading>Fully-featured maintainer script configuration
10655 For files which contain site-specific information such as
10656 the hostname and networking details and so forth, it is
10657 better to create the file in the package's
10658 <prgn>postinst</prgn> script.
10662 This will typically involve examining the state of the rest
10663 of the system to determine values and other information, and
10664 may involve prompting the user for some information which
10665 can't be obtained some other way.
10669 When using this method there are a couple of important
10670 issues which should be considered:
10674 If you discover a bug in the program which generates the
10675 configuration file, or if the format of the file changes
10676 from one version to the next, you will have to arrange for
10677 the postinst script to do something sensible - usually this
10678 will mean editing the installed configuration file to remove
10679 the problem or change the syntax. You will have to do this
10680 very carefully, since the user may have changed the file,
10681 perhaps to fix the very problem that your script is trying
10682 to deal with - you will have to detect these situations and
10683 deal with them correctly.
10687 If you do go down this route it's probably a good idea to
10688 make the program that generates the configuration file(s) a
10689 separate program in <file>/usr/sbin</file>, by convention called
10690 <file><var>package</var>config</file> and then run that if
10691 appropriate from the post-installation script. The
10692 <tt><var>package</var>config</tt> program should not
10693 unquestioningly overwrite an existing configuration - if its
10694 mode of operation is geared towards setting up a package for
10695 the first time (rather than any arbitrary reconfiguration
10696 later) you should have it check whether the configuration
10697 already exists, and require a <tt>--force</tt> flag to
10698 overwrite it.</p></sect>
10701 <appendix id="pkg-alternatives"><heading>Alternative versions of
10702 an interface - <prgn>update-alternatives</prgn> (from old
10707 When several packages all provide different versions of the
10708 same program or file it is useful to have the system select a
10709 default, but to allow the system administrator to change it
10710 and have their decisions respected.
10714 For example, there are several versions of the <prgn>vi</prgn>
10715 editor, and there is no reason to prevent all of them from
10716 being installed at once, each under their own name
10717 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10718 Nevertheless it is desirable to have the name <tt>vi</tt>
10719 refer to something, at least by default.
10723 If all the packages involved cooperate, this can be done with
10724 <prgn>update-alternatives</prgn>.
10728 Each package provides its own version under its own name, and
10729 calls <prgn>update-alternatives</prgn> in its postinst to
10730 register its version (and again in its prerm to deregister
10735 See the man page <manref name="update-alternatives"
10736 section="8"> for details.
10740 If <prgn>update-alternatives</prgn> does not seem appropriate
10741 you may wish to consider using diversions instead.</p>
10744 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10745 package's version of a file (from old Packaging Manual)
10749 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10750 when it reinstalls the package it belongs to, and to have it
10751 put the file from the package somewhere else instead.
10755 This can be used locally to override a package's version of a
10756 file, or by one package to override another's version (or
10757 provide a wrapper for it).
10761 Before deciding to use a diversion, read <ref
10762 id="pkg-alternatives"> to see if you really want a diversion
10763 rather than several alternative versions of a program.
10767 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10768 and updated by a special program <prgn>dpkg-divert</prgn>.
10769 Please see <manref name="dpkg-divert" section="8"> for full
10770 details of its operation.
10774 When a package wishes to divert a file from another, it should
10775 call <prgn>dpkg-divert</prgn> in its preinst to add the
10776 diversion and rename the existing file. For example,
10777 supposing that a <prgn>smailwrapper</prgn> package wishes to
10778 install a wrapper around <file>/usr/sbin/smail</file>:
10780 dpkg-divert --package smailwrapper --add --rename \
10781 --divert /usr/sbin/smail.real /usr/sbin/smail
10782 </example> The <tt>--package smailwrapper</tt> ensures that
10783 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
10784 can bypass the diversion and get installed as the true version.
10785 It's safe to add the diversion unconditionally on upgrades since
10786 it will be left unchanged if it already exists, but
10787 <prgn>dpkg-divert</prgn> will display a message. To suppress that
10788 message, make the command conditional on the version from which
10789 the package is being upgraded:
10791 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
10792 dpkg-divert --package smailwrapper --add --rename \
10793 --divert /usr/sbin/smail.real /usr/sbin/smail
10795 </example> where <tt>1.0-2</tt> is the version at which the
10796 diversion was first added to the package. Running the command
10797 during abort-upgrade is pointless but harmless.
10801 The postrm has to do the reverse:
10803 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
10804 dpkg-divert --package smailwrapper --remove --rename \
10805 --divert /usr/sbin/smail.real /usr/sbin/smail
10807 </example> If the diversion was added at a particular version, the
10808 postrm should also handle the failure case of upgrading from an
10809 older version (unless the older version is so old that direct
10810 upgrades are no longer supported):
10812 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
10813 dpkg-divert --package smailwrapper --remove --rename \
10814 --divert /usr/sbin/smail.real /usr/sbin/smail
10816 </example> where <tt>1.02-2</tt> is the version at which the
10817 diversion was first added to the package. The postrm should not
10818 remove the diversion on upgrades both because there's no reason to
10819 remove the diversion only to immediately re-add it and since the
10820 postrm of the old package is run after unpacking so the removal of
10821 the diversion will fail.
10825 Do not attempt to divert a file which is vitally important for
10826 the system's operation - when using <prgn>dpkg-divert</prgn>
10827 there is a time, after it has been diverted but before
10828 <prgn>dpkg</prgn> has installed the new version, when the file
10829 does not exist.</p>
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