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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>,
692 <em>zope</em>. The additional section <em>debian-installer</em>
693 contains special packages used by the installer and is not used
694 for normal Debian packages.
698 For more information about the sections and their definitions,
699 see the <url id="http://packages.debian.org/unstable/"
700 name="list of sections in unstable">.
704 <sect id="priorities">
705 <heading>Priorities</heading>
708 Each package should have a <em>priority</em> value, which is
709 included in the package's <em>control record</em>
710 (see <ref id="f-Priority">).
711 This information is used by the Debian package management tools to
712 separate high-priority packages from less-important packages.
716 The following <em>priority levels</em> are recognized by the
717 Debian package management tools.
719 <tag><tt>required</tt></tag>
721 Packages which are necessary for the proper
722 functioning of the system (usually, this means that
723 dpkg functionality depends on these packages).
724 Removing a <tt>required</tt> package may cause your
725 system to become totally broken and you may not even
726 be able to use <prgn>dpkg</prgn> to put things back,
727 so only do so if you know what you are doing. Systems
728 with only the <tt>required</tt> packages are probably
729 unusable, but they do have enough functionality to
730 allow the sysadmin to boot and install more software.
732 <tag><tt>important</tt></tag>
734 Important programs, including those which one would
735 expect to find on any Unix-like system. If the
736 expectation is that an experienced Unix person who
737 found it missing would say "What on earth is going on,
738 where is <prgn>foo</prgn>?", it must be an
739 <tt>important</tt> package.<footnote>
740 This is an important criterion because we are
741 trying to produce, amongst other things, a free
744 Other packages without which the system will not run
745 well or be usable must also have priority
746 <tt>important</tt>. This does
747 <em>not</em> include Emacs, the X Window System, TeX
748 or any other large applications. The
749 <tt>important</tt> packages are just a bare minimum of
750 commonly-expected and necessary tools.
752 <tag><tt>standard</tt></tag>
754 These packages provide a reasonably small but not too
755 limited character-mode system. This is what will be
756 installed by default if the user doesn't select anything
757 else. It doesn't include many large applications.
759 <tag><tt>optional</tt></tag>
761 (In a sense everything that isn't required is
762 optional, but that's not what is meant here.) This is
763 all the software that you might reasonably want to
764 install if you didn't know what it was and don't have
765 specialized requirements. This is a much larger system
766 and includes the X Window System, a full TeX
767 distribution, and many applications. Note that
768 optional packages should not conflict with each other.
770 <tag><tt>extra</tt></tag>
772 This contains all packages that conflict with others
773 with required, important, standard or optional
774 priorities, or are only likely to be useful if you
775 already know what they are or have specialized
776 requirements (such as packages containing only detached
783 Packages must not depend on packages with lower priority
784 values (excluding build-time dependencies). In order to
785 ensure this, the priorities of one or more packages may need
794 <heading>Binary packages</heading>
797 The Debian GNU/Linux distribution is based on the Debian
798 package management system, called <prgn>dpkg</prgn>. Thus,
799 all packages in the Debian distribution must be provided
800 in the <tt>.deb</tt> file format.
804 <heading>The package name</heading>
807 Every package must have a name that's unique within the Debian
812 The package name is included in the control field
813 <tt>Package</tt>, the format of which is described
814 in <ref id="f-Package">.
815 The package name is also included as a part of the file name
816 of the <tt>.deb</tt> file.
821 <heading>The version of a package</heading>
824 Every package has a version number recorded in its
825 <tt>Version</tt> control file field, described in
826 <ref id="f-Version">.
830 The package management system imposes an ordering on version
831 numbers, so that it can tell whether packages are being up- or
832 downgraded and so that package system front end applications
833 can tell whether a package it finds available is newer than
834 the one installed on the system. The version number format
835 has the most significant parts (as far as comparison is
836 concerned) at the beginning.
840 If an upstream package has problematic version numbers they
841 should be converted to a sane form for use in the
842 <tt>Version</tt> field.
846 <heading>Version numbers based on dates</heading>
849 In general, Debian packages should use the same version
850 numbers as the upstream sources.
854 However, in some cases where the upstream version number is
855 based on a date (e.g., a development "snapshot" release) the
856 package management system cannot handle these version
857 numbers without epochs. For example, dpkg will consider
858 "96May01" to be greater than "96Dec24".
862 To prevent having to use epochs for every new upstream
863 version, the date based portion of the version number
864 should be changed to the following format in such cases:
865 "19960501", "19961224". It is up to the maintainer whether
866 they want to bother the upstream maintainer to change
867 the version numbers upstream, too.
871 Note that other version formats based on dates which are
872 parsed correctly by the package management system should
873 <em>not</em> be changed.
877 Native Debian packages (i.e., packages which have been
878 written especially for Debian) whose version numbers include
879 dates should always use the "YYYYMMDD" format.
886 <heading>The maintainer of a package</heading>
889 Every package must have a Debian maintainer (the
890 maintainer may be one person or a group of people
891 reachable from a common email address, such as a mailing
892 list). The maintainer is responsible for ensuring that
893 the package is placed in the appropriate distributions.
897 The maintainer must be specified in the
898 <tt>Maintainer</tt> control field with their correct name
899 and a working email address. If one person maintains
900 several packages, they should try to avoid having
901 different forms of their name and email address in
902 the <tt>Maintainer</tt> fields of those packages.
906 The format of the <tt>Maintainer</tt> control field is
907 described in <ref id="f-Maintainer">.
911 If the maintainer of a package quits from the Debian
912 project, "Debian QA Group"
913 <email>packages@qa.debian.org</email> takes over the
914 maintainer-ship of the package until someone else
915 volunteers for that task. These packages are called
916 <em>orphaned packages</em>.<footnote>
917 The detailed procedure for doing this gracefully can
918 be found in the Debian Developer's Reference,
919 see <ref id="related">.
924 <sect id="descriptions">
925 <heading>The description of a package</heading>
928 Every Debian package must have an extended description
929 stored in the appropriate field of the control record.
930 The technical information about the format of the
931 <tt>Description</tt> field is in <ref id="f-Description">.
935 The description should describe the package (the program) to a
936 user (system administrator) who has never met it before so that
937 they have enough information to decide whether they want to
938 install it. This description should not just be copied verbatim
939 from the program's documentation.
943 Put important information first, both in the synopsis and
944 extended description. Sometimes only the first part of the
945 synopsis or of the description will be displayed. You can
946 assume that there will usually be a way to see the whole
947 extended description.
951 The description should also give information about the
952 significant dependencies and conflicts between this package
953 and others, so that the user knows why these dependencies and
954 conflicts have been declared.
958 Instructions for configuring or using the package should
959 not be included (that is what installation scripts,
960 manual pages, info files, etc., are for). Copyright
961 statements and other administrivia should not be included
962 either (that is what the copyright file is for).
965 <sect1 id="synopsis"><heading>The single line synopsis</heading>
968 The single line synopsis should be kept brief - certainly
973 Do not include the package name in the synopsis line. The
974 display software knows how to display this already, and you
975 do not need to state it. Remember that in many situations
976 the user may only see the synopsis line - make it as
977 informative as you can.
982 <sect1 id="extendeddesc"><heading>The extended description</heading>
985 Do not try to continue the single line synopsis into the
986 extended description. This will not work correctly when
987 the full description is displayed, and makes no sense
988 where only the summary (the single line synopsis) is
993 The extended description should describe what the package
994 does and how it relates to the rest of the system (in terms
995 of, for example, which subsystem it is which part of).
999 The description field needs to make sense to anyone, even
1000 people who have no idea about any of the things the
1001 package deals with.<footnote>
1002 The blurb that comes with a program in its
1003 announcements and/or <prgn>README</prgn> files is
1004 rarely suitable for use in a description. It is
1005 usually aimed at people who are already in the
1006 community where the package is used.
1015 <heading>Dependencies</heading>
1018 Every package must specify the dependency information
1019 about other packages that are required for the first to
1024 For example, a dependency entry must be provided for any
1025 shared libraries required by a dynamically-linked executable
1026 binary in a package.
1030 Packages are not required to declare any dependencies they
1031 have on other packages which are marked <tt>Essential</tt>
1032 (see below), and should not do so unless they depend on a
1033 particular version of that package.<footnote>
1035 Essential is needed in part to avoid unresolvable dependency
1036 loops on upgrade. If packages add unnecessary dependencies
1037 on packages in this set, the chances that there
1038 <strong>will</strong> be an unresolvable dependency loop
1039 caused by forcing these Essential packages to be configured
1040 first before they need to be is greatly increased. It also
1041 increases the chances that frontends will be unable to
1042 <strong>calculate</strong> an upgrade path, even if one
1046 Also, functionality is rarely ever removed from the
1047 Essential set, but <em>packages</em> have been removed from
1048 the Essential set when the functionality moved to a
1049 different package. So depending on these packages <em>just
1050 in case</em> they stop being essential does way more harm
1057 Sometimes, a package requires another package to be installed
1058 <em>and</em> configured before it can be installed. In this
1059 case, you must specify a <tt>Pre-Depends</tt> entry for
1064 You should not specify a <tt>Pre-Depends</tt> entry for a
1065 package before this has been discussed on the
1066 <tt>debian-devel</tt> mailing list and a consensus about
1067 doing that has been reached.
1071 The format of the package interrelationship control fields is
1072 described in <ref id="relationships">.
1076 <sect id="virtual_pkg">
1077 <heading>Virtual packages</heading>
1080 Sometimes, there are several packages which offer
1081 more-or-less the same functionality. In this case, it's
1082 useful to define a <em>virtual package</em> whose name
1083 describes that common functionality. (The virtual
1084 packages only exist logically, not physically; that's why
1085 they are called <em>virtual</em>.) The packages with this
1086 particular function will then <em>provide</em> the virtual
1087 package. Thus, any other package requiring that function
1088 can simply depend on the virtual package without having to
1089 specify all possible packages individually.
1093 All packages should use virtual package names where
1094 appropriate, and arrange to create new ones if necessary.
1095 They should not use virtual package names (except privately,
1096 amongst a cooperating group of packages) unless they have
1097 been agreed upon and appear in the list of virtual package
1098 names. (See also <ref id="virtual">)
1102 The latest version of the authoritative list of virtual
1103 package names can be found in the <tt>debian-policy</tt> package.
1104 It is also available from the Debian web mirrors at
1105 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1106 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1110 The procedure for updating the list is described in the preface
1117 <heading>Base system</heading>
1120 The <tt>base system</tt> is a minimum subset of the Debian
1121 GNU/Linux system that is installed before everything else
1122 on a new system. Only very few packages are allowed to form
1123 part of the base system, in order to keep the required disk
1128 The base system consists of all those packages with priority
1129 <tt>required</tt> or <tt>important</tt>. Many of them will
1130 be tagged <tt>essential</tt> (see below).
1135 <heading>Essential packages</heading>
1138 Essential is defined as the minimal set of functionality that
1139 must be available and usable on the system at all times, even
1140 when packages are in an unconfigured (but unpacked) state.
1141 Packages are tagged <tt>essential</tt> for a system using the
1142 <tt>Essential</tt> control file field. The format of the
1143 <tt>Essential</tt> control field is described in <ref
1148 Since these packages cannot be easily removed (one has to
1149 specify an extra <em>force option</em> to
1150 <prgn>dpkg</prgn> to do so), this flag must not be used
1151 unless absolutely necessary. A shared library package
1152 must not be tagged <tt>essential</tt>; dependencies will
1153 prevent its premature removal, and we need to be able to
1154 remove it when it has been superseded.
1158 Since dpkg will not prevent upgrading of other packages
1159 while an <tt>essential</tt> package is in an unconfigured
1160 state, all <tt>essential</tt> packages must supply all of
1161 their core functionality even when unconfigured. If the
1162 package cannot satisfy this requirement it must not be
1163 tagged as essential, and any packages depending on this
1164 package must instead have explicit dependency fields as
1169 Maintainers should take great care in adding any programs,
1170 interfaces, or functionality to <tt>essential</tt> packages.
1171 Packages may assume that functionality provided by
1172 <tt>essential</tt> packages is always available without
1173 declaring explicit dependencies, which means that removing
1174 functionality from the Essential set is very difficult and is
1175 almost never done. Any capability added to an
1176 <tt>essential</tt> package therefore creates an obligation to
1177 support that capability as part of the Essential set in
1182 You must not tag any packages <tt>essential</tt> before
1183 this has been discussed on the <tt>debian-devel</tt>
1184 mailing list and a consensus about doing that has been
1189 <sect id="maintscripts">
1190 <heading>Maintainer Scripts</heading>
1193 The package installation scripts should avoid producing
1194 output which is unnecessary for the user to see and
1195 should rely on <prgn>dpkg</prgn> to stave off boredom on
1196 the part of a user installing many packages. This means,
1197 amongst other things, using the <tt>--quiet</tt> option on
1198 <prgn>install-info</prgn>.
1202 Errors which occur during the execution of an installation
1203 script must be checked and the installation must not
1204 continue after an error.
1208 Note that in general <ref id="scripts"> applies to package
1209 maintainer scripts, too.
1213 You should not use <prgn>dpkg-divert</prgn> on a file
1214 belonging to another package without consulting the
1215 maintainer of that package first.
1219 All packages which supply an instance of a common command
1220 name (or, in general, filename) should generally use
1221 <prgn>update-alternatives</prgn>, so that they may be
1222 installed together. If <prgn>update-alternatives</prgn>
1223 is not used, then each package must use
1224 <tt>Conflicts</tt> to ensure that other packages are
1225 de-installed. (In this case, it may be appropriate to
1226 specify a conflict against earlier versions of something
1227 that previously did not use
1228 <prgn>update-alternatives</prgn>; this is an exception to
1229 the usual rule that versioned conflicts should be
1233 <sect1 id="maintscriptprompt">
1234 <heading>Prompting in maintainer scripts</heading>
1236 Package maintainer scripts may prompt the user if
1237 necessary. Prompting must be done by communicating
1238 through a program, such as <prgn>debconf</prgn>, which
1239 conforms to the Debian Configuration Management
1240 Specification, version 2 or higher.
1244 Packages which are essential, or which are dependencies of
1245 essential packages, may fall back on another prompting method
1246 if no such interface is available when they are executed.
1250 The Debian Configuration Management Specification is included
1251 in the <file>debconf_specification</file> files in the
1252 <package>debian-policy</package> package.
1253 It is also available from the Debian web mirrors at
1254 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1255 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1259 Packages which use the Debian Configuration Management
1260 Specification may contain an additional
1261 <prgn>config</prgn> script and a <tt>templates</tt>
1262 file in their control archive<footnote>
1263 The control.tar.gz inside the .deb.
1264 See <manref name="deb" section="5">.
1266 The <prgn>config</prgn> script might be run before the
1267 <prgn>preinst</prgn> script, and before the package is unpacked
1268 or any of its dependencies or pre-dependencies are satisfied.
1269 Therefore it must work using only the tools present in
1270 <em>essential</em> packages.<footnote>
1271 <package>Debconf</package> or another tool that
1272 implements the Debian Configuration Management
1273 Specification will also be installed, and any
1274 versioned dependencies on it will be satisfied
1275 before preconfiguration begins.
1280 Packages which use the Debian Configuration Management
1281 Specification must allow for translation of their user-visible
1282 messages by using a gettext-based system such as the one
1283 provided by the <package>po-debconf</package> package.
1287 Packages should try to minimize the amount of prompting
1288 they need to do, and they should ensure that the user
1289 will only ever be asked each question once. This means
1290 that packages should try to use appropriate shared
1291 configuration files (such as <file>/etc/papersize</file> and
1292 <file>/etc/news/server</file>), and shared
1293 <package>debconf</package> variables rather than each
1294 prompting for their own list of required pieces of
1299 It also means that an upgrade should not ask the same
1300 questions again, unless the user has used
1301 <tt>dpkg --purge</tt> to remove the package's configuration.
1302 The answers to configuration questions should be stored in an
1303 appropriate place in <file>/etc</file> so that the user can
1304 modify them, and how this has been done should be
1309 If a package has a vitally important piece of
1310 information to pass to the user (such as "don't run me
1311 as I am, you must edit the following configuration files
1312 first or you risk your system emitting badly-formatted
1313 messages"), it should display this in the
1314 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1315 prompt the user to hit return to acknowledge the
1316 message. Copyright messages do not count as vitally
1317 important (they belong in
1318 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1319 neither do instructions on how to use a program (these
1320 should be in on-line documentation, where all the users
1325 Any necessary prompting should almost always be confined
1326 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1327 script. If it is done in the <prgn>postinst</prgn>, it
1328 should be protected with a conditional so that
1329 unnecessary prompting doesn't happen if a package's
1330 installation fails and the <prgn>postinst</prgn> is
1331 called with <tt>abort-upgrade</tt>,
1332 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1342 <heading>Source packages</heading>
1344 <sect id="standardsversion">
1345 <heading>Standards conformance</heading>
1348 Source packages should specify the most recent version number
1349 of this policy document with which your package complied
1350 when it was last updated.
1354 This information may be used to file bug reports
1355 automatically if your package becomes too much out of date.
1359 The version is specified in the <tt>Standards-Version</tt>
1361 The format of the <tt>Standards-Version</tt> field is
1362 described in <ref id="f-Standards-Version">.
1366 You should regularly, and especially if your package has
1367 become out of date, check for the newest Policy Manual
1368 available and update your package, if necessary. When your
1369 package complies with the new standards you should update the
1370 <tt>Standards-Version</tt> source package field and
1371 release it.<footnote>
1372 See the file <file>upgrading-checklist</file> for
1373 information about policy which has changed between
1374 different versions of this document.
1380 <sect id="pkg-relations">
1381 <heading>Package relationships</heading>
1384 Source packages should specify which binary packages they
1385 require to be installed or not to be installed in order to
1386 build correctly. For example, if building a package
1387 requires a certain compiler, then the compiler should be
1388 specified as a build-time dependency.
1392 It is not necessary to explicitly specify build-time
1393 relationships on a minimal set of packages that are always
1394 needed to compile, link and put in a Debian package a
1395 standard "Hello World!" program written in C or C++. The
1396 required packages are called <em>build-essential</em>, and
1397 an informational list can be found in
1398 <file>/usr/share/doc/build-essential/list</file> (which is
1399 contained in the <tt>build-essential</tt>
1402 <list compact="compact">
1404 This allows maintaining the list separately
1405 from the policy documents (the list does not
1406 need the kind of control that the policy
1410 Having a separate package allows one to install
1411 the build-essential packages on a machine, as
1412 well as allowing other packages such as tasks to
1413 require installation of the build-essential
1414 packages using the depends relation.
1417 The separate package allows bug reports against
1418 the list to be categorized separately from
1419 the policy management process in the BTS.
1426 When specifying the set of build-time dependencies, one
1427 should list only those packages explicitly required by the
1428 build. It is not necessary to list packages which are
1429 required merely because some other package in the list of
1430 build-time dependencies depends on them.<footnote>
1431 The reason for this is that dependencies change, and
1432 you should list all those packages, and <em>only</em>
1433 those packages that <em>you</em> need directly. What
1434 others need is their business. For example, if you
1435 only link against <file>libimlib</file>, you will need to
1436 build-depend on <package>libimlib2-dev</package> but
1437 not against any <tt>libjpeg*</tt> packages, even
1438 though <tt>libimlib2-dev</tt> currently depends on
1439 them: installation of <package>libimlib2-dev</package>
1440 will automatically ensure that all of its run-time
1441 dependencies are satisfied.
1446 If build-time dependencies are specified, it must be
1447 possible to build the package and produce working binaries
1448 on a system with only essential and build-essential
1449 packages installed and also those required to satisfy the
1450 build-time relationships (including any implied
1451 relationships). In particular, this means that version
1452 clauses should be used rigorously in build-time
1453 relationships so that one cannot produce bad or
1454 inconsistently configured packages when the relationships
1455 are properly satisfied.
1459 <ref id="relationships"> explains the technical details.
1464 <heading>Changes to the upstream sources</heading>
1467 If changes to the source code are made that are not
1468 specific to the needs of the Debian system, they should be
1469 sent to the upstream authors in whatever form they prefer
1470 so as to be included in the upstream version of the
1475 If you need to configure the package differently for
1476 Debian or for Linux, and the upstream source doesn't
1477 provide a way to do so, you should add such configuration
1478 facilities (for example, a new <prgn>autoconf</prgn> test
1479 or <tt>#define</tt>) and send the patch to the upstream
1480 authors, with the default set to the way they originally
1481 had it. You can then easily override the default in your
1482 <file>debian/rules</file> or wherever is appropriate.
1486 You should make sure that the <prgn>configure</prgn> utility
1487 detects the correct architecture specification string
1488 (refer to <ref id="arch-spec"> for details).
1492 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1493 <prgn>configure</prgn> scripts are used, you should edit the
1494 <file>.in</file> files rather than editing the
1495 <prgn>Makefile</prgn> directly. This allows the user to
1496 reconfigure the package if necessary. You should
1497 <em>not</em> configure the package and edit the generated
1498 <prgn>Makefile</prgn>! This makes it impossible for someone
1499 else to later reconfigure the package without losing the
1505 <sect id="dpkgchangelog">
1506 <heading>Debian changelog: <file>debian/changelog</file></heading>
1509 Changes in the Debian version of the package should be
1510 briefly explained in the Debian changelog file
1511 <file>debian/changelog</file>.<footnote>
1513 Mistakes in changelogs are usually best rectified by
1514 making a new changelog entry rather than "rewriting
1515 history" by editing old changelog entries.
1518 This includes modifications
1519 made in the Debian package compared to the upstream one
1520 as well as other changes and updates to the package.
1522 Although there is nothing stopping an author who is also
1523 the Debian maintainer from using this changelog for all
1524 their changes, it will have to be renamed if the Debian
1525 and upstream maintainers become different people. In such
1526 a case, however, it might be better to maintain the package
1527 as a non-native package.
1532 The format of the <file>debian/changelog</file> allows the
1533 package building tools to discover which version of the package
1534 is being built and find out other release-specific information.
1538 That format is a series of entries like this:
1540 <example compact="compact">
1541 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1543 [optional blank line(s), stripped]
1545 * <var>change details</var>
1546 <var>more change details</var>
1548 [blank line(s), included in output of dpkg-parsechangelog]
1550 * <var>even more change details</var>
1552 [optional blank line(s), stripped]
1554 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1559 <var>package</var> and <var>version</var> are the source
1560 package name and version number.
1564 <var>distribution(s)</var> lists the distributions where
1565 this version should be installed when it is uploaded - it
1566 is copied to the <tt>Distribution</tt> field in the
1567 <file>.changes</file> file. See <ref id="f-Distribution">.
1571 <var>urgency</var> is the value for the <tt>Urgency</tt>
1572 field in the <file>.changes</file> file for the upload
1573 (see <ref id="f-Urgency">). It is not possible to specify
1574 an urgency containing commas; commas are used to separate
1575 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1576 <prgn>dpkg</prgn> changelog format (though there is
1577 currently only one useful <var>keyword</var>,
1582 The change details may in fact be any series of lines
1583 starting with at least two spaces, but conventionally each
1584 change starts with an asterisk and a separating space and
1585 continuation lines are indented so as to bring them in
1586 line with the start of the text above. Blank lines may be
1587 used here to separate groups of changes, if desired.
1591 If this upload resolves bugs recorded in the Bug Tracking
1592 System (BTS), they may be automatically closed on the
1593 inclusion of this package into the Debian archive by
1594 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1595 in the change details.<footnote>
1596 To be precise, the string should match the following
1597 Perl regular expression:
1599 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1601 Then all of the bug numbers listed will be closed by the
1602 archive maintenance script (<prgn>katie</prgn>) using the
1603 <var>version</var> of the changelog entry.
1605 This information is conveyed via the <tt>Closes</tt> field
1606 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1610 The maintainer name and email address used in the changelog
1611 should be the details of the person uploading <em>this</em>
1612 version. They are <em>not</em> necessarily those of the
1613 usual package maintainer. The information here will be
1614 copied to the <tt>Changed-By</tt> field in the
1615 <tt>.changes</tt> file (see <ref id="f-Changed-By">),
1616 and then later used to send an acknowledgement when the
1617 upload has been installed.
1621 The <var>date</var> has the following format<footnote>
1622 This is the same as the format generated by <tt>date
1624 </footnote> (compatible and with the same semantics of
1625 RFC 2822 and RFC 5322):
1626 <example>day-of-week, dd month yyyy hh:mm:ss +zzzz</example>
1628 <list compact="compact">
1630 day-of week is one of: Mon, Tue, Wed, Thu, Fri, Sat, Sun
1633 dd is a one- or two-digit day of the month (01-31)
1636 month is one of: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug,
1639 <item>yyyy is the four-digit year (e.g. 2010)</item>
1640 <item>hh is the two-digit hour (00-23)</item>
1641 <item>mm is the two-digit minutes (00-59)</item>
1642 <item>ss is the two-digit seconds (00-60)</item>
1644 +zzzz or -zzzz is the the time zone offset from Coordinated
1645 Universal Time (UTC). "+" indicates that the time is ahead
1646 of (i.e., east of) UTC and "-" indicates that the time is
1647 behind (i.e., west of) UTC. The first two digits indicate
1648 the hour difference from UTC and the last two digits
1649 indicate the number of additional minutes difference from
1650 UTC. The last two digits must be in the range 00-59.
1656 The first "title" line with the package name must start
1657 at the left hand margin. The "trailer" line with the
1658 maintainer and date details must be preceded by exactly
1659 one space. The maintainer details and the date must be
1660 separated by exactly two spaces.
1664 The entire changelog must be encoded in UTF-8.
1668 For more information on placement of the changelog files
1669 within binary packages, please see <ref id="changelogs">.
1673 <sect id="dpkgcopyright">
1674 <heading>Copyright: <file>debian/copyright</file></heading>
1676 Every package must be accompanied by a verbatim copy of its
1677 copyright information and distribution license in the file
1678 <file>/usr/share/doc/<var>package</var>/copyright</file>
1679 (see <ref id="copyrightfile"> for further details). Also see
1680 <ref id="pkgcopyright"> for further considerations related
1681 to copyrights for packages.
1685 <heading>Error trapping in makefiles</heading>
1688 When <prgn>make</prgn> invokes a command in a makefile
1689 (including your package's upstream makefiles and
1690 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1691 means that <prgn>sh</prgn>'s usual bad error handling
1692 properties apply: if you include a miniature script as one
1693 of the commands in your makefile you'll find that if you
1694 don't do anything about it then errors are not detected
1695 and <prgn>make</prgn> will blithely continue after
1700 Every time you put more than one shell command (this
1701 includes using a loop) in a makefile command you
1702 must make sure that errors are trapped. For
1703 simple compound commands, such as changing directory and
1704 then running a program, using <tt>&&</tt> rather
1705 than semicolon as a command separator is sufficient. For
1706 more complex commands including most loops and
1707 conditionals you should include a separate <tt>set -e</tt>
1708 command at the start of every makefile command that's
1709 actually one of these miniature shell scripts.
1713 <sect id="timestamps">
1714 <heading>Time Stamps</heading>
1716 Maintainers should preserve the modification times of the
1717 upstream source files in a package, as far as is reasonably
1719 The rationale is that there is some information conveyed
1720 by knowing the age of the file, for example, you could
1721 recognize that some documentation is very old by looking
1722 at the modification time, so it would be nice if the
1723 modification time of the upstream source would be
1729 <sect id="restrictions">
1730 <heading>Restrictions on objects in source packages</heading>
1733 The source package may not contain any hard links<footnote>
1735 This is not currently detected when building source
1736 packages, but only when extracting
1740 Hard links may be permitted at some point in the
1741 future, but would require a fair amount of
1744 </footnote>, device special files, sockets or setuid or
1745 setgid files.<footnote>
1746 Setgid directories are allowed.
1751 <sect id="debianrules">
1752 <heading>Main building script: <file>debian/rules</file></heading>
1755 This file must be an executable makefile, and contains the
1756 package-specific recipes for compiling the package and
1757 building binary package(s) from the source.
1761 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1762 so that it can be invoked by saying its name rather than
1763 invoking <prgn>make</prgn> explicitly. That is, invoking
1764 either of <tt>make -f debian/rules <em>args...</em></tt>
1765 or <tt>./debian/rules <em>args...</em></tt> must result in
1770 Since an interactive <file>debian/rules</file> script makes it
1771 impossible to auto-compile that package and also makes it
1772 hard for other people to reproduce the same binary
1773 package, all <em>required targets</em> must be
1774 non-interactive. At a minimum, required targets are the
1775 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1776 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1777 <em>binary-indep</em>, and <em>build</em>. It also follows
1778 that any target that these targets depend on must also be
1783 The targets are as follows (required unless stated otherwise):
1785 <tag><tt>build</tt></tag>
1788 The <tt>build</tt> target should perform all the
1789 configuration and compilation of the package.
1790 If a package has an interactive pre-build
1791 configuration routine, the Debian source package
1792 must either be built after this has taken place (so
1793 that the binary package can be built without rerunning
1794 the configuration) or the configuration routine
1795 modified to become non-interactive. (The latter is
1796 preferable if there are architecture-specific features
1797 detected by the configuration routine.)
1801 For some packages, notably ones where the same
1802 source tree is compiled in different ways to produce
1803 two binary packages, the <tt>build</tt> target
1804 does not make much sense. For these packages it is
1805 good enough to provide two (or more) targets
1806 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1807 for each of the ways of building the package, and a
1808 <tt>build</tt> target that does nothing. The
1809 <tt>binary</tt> target will have to build the
1810 package in each of the possible ways and make the
1811 binary package out of each.
1815 The <tt>build</tt> target must not do anything
1816 that might require root privilege.
1820 The <tt>build</tt> target may need to run the
1821 <tt>clean</tt> target first - see below.
1825 When a package has a configuration and build routine
1826 which takes a long time, or when the makefiles are
1827 poorly designed, or when <tt>build</tt> needs to
1828 run <tt>clean</tt> first, it is a good idea to
1829 <tt>touch build</tt> when the build process is
1830 complete. This will ensure that if <tt>debian/rules
1831 build</tt> is run again it will not rebuild the whole
1833 Another common way to do this is for <tt>build</tt>
1834 to depend on <prgn>build-stamp</prgn> and to do
1835 nothing else, and for the <prgn>build-stamp</prgn>
1836 target to do the building and to <tt>touch
1837 build-stamp</tt> on completion. This is
1838 especially useful if the build routine creates a
1839 file or directory called <tt>build</tt>; in such a
1840 case, <tt>build</tt> will need to be listed as
1841 a phony target (i.e., as a dependency of the
1842 <tt>.PHONY</tt> target). See the documentation of
1843 <prgn>make</prgn> for more information on phony
1849 <tag><tt>build-arch</tt> (optional),
1850 <tt>build-indep</tt> (optional)
1854 A package may also provide both of the targets
1855 <tt>build-arch</tt> and <tt>build-indep</tt>.
1856 The <tt>build-arch</tt> target, if provided, should
1857 perform all the configuration and compilation required for
1858 producing all architecture-dependant binary packages
1859 (those packages for which the body of the
1860 <tt>Architecture</tt> field in <tt>debian/control</tt> is
1861 not <tt>all</tt>). Similarly, the <tt>build-indep</tt>
1862 target, if provided, should perform all the configuration
1863 and compilation required for producing all
1864 architecture-independent binary packages (those packages
1865 for which the body of the <tt>Architecture</tt> field
1866 in <tt>debian/control</tt> is <tt>all</tt>).
1867 The <tt>build</tt> target should depend on those of the
1868 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1869 are provided in the rules file.<footnote>
1870 The intent of this split is so that binary-only builds
1871 need not install the dependencies required for
1872 the <tt>build-indep</tt> target. However, this is not
1873 yet used in practice since <tt>dpkg-buildpackage
1874 -B</tt>, and therefore the autobuilders,
1875 invoke <tt>build</tt> rather than <tt>build-arch</tt>
1876 due to the difficulties in determining whether the
1877 optional <tt>build-arch</tt> target exists.
1882 If one or both of the targets <tt>build-arch</tt> and
1883 <tt>build-indep</tt> are not provided, then invoking
1884 <file>debian/rules</file> with one of the not-provided
1885 targets as arguments should produce a exit status code
1886 of 2. Usually this is provided automatically by make
1887 if the target is missing.
1891 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1892 must not do anything that might require root privilege.
1896 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1897 <tt>binary-indep</tt>
1901 The <tt>binary</tt> target must be all that is
1902 necessary for the user to build the binary package(s)
1903 produced from this source package. It is
1904 split into two parts: <prgn>binary-arch</prgn> builds
1905 the binary packages which are specific to a particular
1906 architecture, and <tt>binary-indep</tt> builds
1907 those which are not.
1910 <tt>binary</tt> may be (and commonly is) a target with
1911 no commands which simply depends on
1912 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1915 Both <tt>binary-*</tt> targets should depend on the
1916 <tt>build</tt> target, or on the appropriate
1917 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1918 provided, so that the package is built if it has not
1919 been already. It should then create the relevant
1920 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1921 make their control files and <prgn>dpkg-deb</prgn> to
1922 build them and place them in the parent of the top
1927 Both the <tt>binary-arch</tt> and
1928 <tt>binary-indep</tt> targets <em>must</em> exist.
1929 If one of them has nothing to do (which will always be
1930 the case if the source generates only a single binary
1931 package, whether architecture-dependent or not), it
1932 must still exist and must always succeed.
1936 The <tt>binary</tt> targets must be invoked as
1938 The <prgn>fakeroot</prgn> package often allows one
1939 to build a package correctly even without being
1945 <tag><tt>clean</tt></tag>
1948 This must undo any effects that the <tt>build</tt>
1949 and <tt>binary</tt> targets may have had, except
1950 that it should leave alone any output files created in
1951 the parent directory by a run of a <tt>binary</tt>
1956 If a <tt>build</tt> file is touched at the end of
1957 the <tt>build</tt> target, as suggested above, it
1958 should be removed as the first action that
1959 <tt>clean</tt> performs, so that running
1960 <tt>build</tt> again after an interrupted
1961 <tt>clean</tt> doesn't think that everything is
1966 The <tt>clean</tt> target may need to be
1967 invoked as root if <tt>binary</tt> has been
1968 invoked since the last <tt>clean</tt>, or if
1969 <tt>build</tt> has been invoked as root (since
1970 <tt>build</tt> may create directories, for
1975 <tag><tt>get-orig-source</tt> (optional)</tag>
1978 This target fetches the most recent version of the
1979 original source package from a canonical archive site
1980 (via FTP or WWW, for example), does any necessary
1981 rearrangement to turn it into the original source
1982 tar file format described below, and leaves it in the
1987 This target may be invoked in any directory, and
1988 should take care to clean up any temporary files it
1993 This target is optional, but providing it if
1994 possible is a good idea.
1998 <tag><tt>patch</tt> (optional)</tag>
2001 This target performs whatever additional actions are
2002 required to make the source ready for editing (unpacking
2003 additional upstream archives, applying patches, etc.).
2004 It is recommended to be implemented for any package where
2005 <tt>dpkg-source -x</tt> does not result in source ready
2006 for additional modification. See
2007 <ref id="readmesource">.
2013 The <tt>build</tt>, <tt>binary</tt> and
2014 <tt>clean</tt> targets must be invoked with the current
2015 directory being the package's top-level directory.
2020 Additional targets may exist in <file>debian/rules</file>,
2021 either as published or undocumented interfaces or for the
2022 package's internal use.
2026 The architectures we build on and build for are determined
2027 by <prgn>make</prgn> variables using the utility
2028 <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
2029 You can determine the
2030 Debian architecture and the GNU style architecture
2031 specification string for the build machine (the machine type
2032 we are building on) as well as for the host machine (the
2033 machine type we are building for). Here is a list of
2034 supported <prgn>make</prgn> variables:
2035 <list compact="compact">
2037 <tt>DEB_*_ARCH</tt> (the Debian architecture)
2040 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2043 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2046 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2047 specification string)
2050 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2051 <tt>DEB_*_GNU_TYPE</tt>)
2054 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2055 <tt>DEB_*_GNU_TYPE</tt>)
2057 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2058 the build machine or <tt>HOST</tt> for specification of the
2063 Backward compatibility can be provided in the rules file
2064 by setting the needed variables to suitable default
2065 values; please refer to the documentation of
2066 <prgn>dpkg-architecture</prgn> for details.
2070 It is important to understand that the <tt>DEB_*_ARCH</tt>
2071 string only determines which Debian architecture we are
2072 building on or for. It should not be used to get the CPU
2073 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2074 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2075 GNU style variables should generally only be used with upstream
2079 <sect1 id="debianrules-options">
2080 <heading><file>debian/rules</file> and
2081 <tt>DEB_BUILD_OPTIONS</tt></heading>
2084 Supporting the standardized environment variable
2085 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2086 contain several flags to change how a package is compiled and
2087 built. Each flag must be in the form <var>flag</var> or
2088 <var>flag</var>=<var>options</var>. If multiple flags are
2089 given, they must be separated by whitespace.<footnote>
2090 Some packages support any delimiter, but whitespace is the
2091 easiest to parse inside a makefile and avoids ambiguity with
2092 flag values that contain commas.
2094 <var>flag</var> must start with a lowercase letter
2095 (<tt>a-z</tt>) and consist only of lowercase letters,
2096 numbers (<tt>0-9</tt>), and the characters
2097 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2098 <var>options</var> must not contain whitespace. The same
2099 tag should not be given multiple times with conflicting
2100 values. Package maintainers may assume that
2101 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2105 The meaning of the following tags has been standardized:
2109 This tag says to not run any build-time test suite
2110 provided by the package.
2114 The presence of this tag means that the package should
2115 be compiled with a minimum of optimization. For C
2116 programs, it is best to add <tt>-O0</tt> to
2117 <tt>CFLAGS</tt> (although this is usually the default).
2118 Some programs might fail to build or run at this level
2119 of optimization; it may be necessary to use
2120 <tt>-O1</tt>, for example.
2124 This tag means that the debugging symbols should not be
2125 stripped from the binary during installation, so that
2126 debugging information may be included in the package.
2128 <tag>parallel=n</tag>
2130 This tag means that the package should be built using up
2131 to <tt>n</tt> parallel processes if the package build
2132 system supports this.<footnote>
2133 Packages built with <tt>make</tt> can often implement
2134 this by passing the <tt>-j</tt><var>n</var> option to
2137 If the package build system does not support parallel
2138 builds, this string must be ignored. If the package
2139 build system only supports a lower level of concurrency
2140 than <var>n</var>, the package should be built using as
2141 many parallel processes as the package build system
2142 supports. It is up to the package maintainer to decide
2143 whether the package build times are long enough and the
2144 package build system is robust enough to make supporting
2145 parallel builds worthwhile.
2151 Unknown flags must be ignored by <file>debian/rules</file>.
2155 The following makefile snippet is an example of how one may
2156 implement the build options; you will probably have to
2157 massage this example in order to make it work for your
2159 <example compact="compact">
2162 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2163 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2164 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2165 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2167 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2172 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2173 INSTALL_PROGRAM += -s
2175 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2176 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2177 MAKEFLAGS += -j$(NUMJOBS)
2182 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2183 # Code to run the package test suite.
2190 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2191 <sect id="substvars">
2192 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2195 When <prgn>dpkg-gencontrol</prgn>,
2196 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
2197 generate control files they perform variable substitutions
2198 on their output just before writing it. Variable
2199 substitutions have the form <tt>${<var>variable</var>}</tt>.
2200 The optional file <file>debian/substvars</file> contains
2201 variable substitutions to be used; variables can also be set
2202 directly from <file>debian/rules</file> using the <tt>-V</tt>
2203 option to the source packaging commands, and certain
2204 predefined variables are also available.
2208 The <file>debian/substvars</file> file is usually generated and
2209 modified dynamically by <file>debian/rules</file> targets, in
2210 which case it must be removed by the <tt>clean</tt> target.
2214 See <manref name="deb-substvars" section="5"> for full
2215 details about source variable substitutions, including the
2216 format of <file>debian/substvars</file>.</p>
2219 <sect id="debianwatch">
2220 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2223 This is an optional, recommended control file for the
2224 <tt>uscan</tt> utility which defines how to automatically
2225 scan ftp or http sites for newly available updates of the
2226 package. This is used by <url id="
2227 http://dehs.alioth.debian.org/"> and other Debian QA tools
2228 to help with quality control and maintenance of the
2229 distribution as a whole.
2234 <sect id="debianfiles">
2235 <heading>Generated files list: <file>debian/files</file></heading>
2238 This file is not a permanent part of the source tree; it
2239 is used while building packages to record which files are
2240 being generated. <prgn>dpkg-genchanges</prgn> uses it
2241 when it generates a <file>.changes</file> file.
2245 It should not exist in a shipped source package, and so it
2246 (and any backup files or temporary files such as
2247 <file>files.new</file><footnote>
2248 <file>files.new</file> is used as a temporary file by
2249 <prgn>dpkg-gencontrol</prgn> and
2250 <prgn>dpkg-distaddfile</prgn> - they write a new
2251 version of <tt>files</tt> here before renaming it,
2252 to avoid leaving a corrupted copy if an error
2254 </footnote>) should be removed by the
2255 <tt>clean</tt> target. It may also be wise to
2256 ensure a fresh start by emptying or removing it at the
2257 start of the <tt>binary</tt> target.
2261 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2262 package, it adds an entry to <file>debian/files</file> for the
2263 <file>.deb</file> file that will be created when <tt>dpkg-deb
2264 --build</tt> is run for that binary package. So for most
2265 packages all that needs to be done with this file is to
2266 delete it in the <tt>clean</tt> target.
2270 If a package upload includes files besides the source
2271 package and any binary packages whose control files were
2272 made with <prgn>dpkg-gencontrol</prgn> then they should be
2273 placed in the parent of the package's top-level directory
2274 and <prgn>dpkg-distaddfile</prgn> should be called to add
2275 the file to the list in <file>debian/files</file>.</p>
2278 <sect id="embeddedfiles">
2279 <heading>Convenience copies of code</heading>
2282 Some software packages include in their distribution convenience
2283 copies of code from other software packages, generally so that
2284 users compiling from source don't have to download multiple
2285 packages. Debian packages should not make use of these
2286 convenience copies unless the included package is explicitly
2287 intended to be used in this way.<footnote>
2288 For example, parts of the GNU build system work like this.
2290 If the included code is already in the Debian archive in the
2291 form of a library, the Debian packaging should ensure that
2292 binary packages reference the libraries already in Debian and
2293 the convenience copy is not used. If the included code is not
2294 already in Debian, it should be packaged separately as a
2295 prerequisite if possible.
2297 Having multiple copies of the same code in Debian is
2298 inefficient, often creates either static linking or shared
2299 library conflicts, and, most importantly, increases the
2300 difficulty of handling security vulnerabilities in the
2306 <sect id="readmesource">
2307 <heading>Source package handling:
2308 <file>debian/README.source</file></heading>
2311 If running <prgn>dpkg-source -x</prgn> on a source package
2312 doesn't produce the source of the package, ready for editing,
2313 and allow one to make changes and run
2314 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2315 without taking any additional steps, creating a
2316 <file>debian/README.source</file> documentation file is
2317 recommended. This file should explain how to do all of the
2320 <item>Generate the fully patched source, in a form ready for
2321 editing, that would be built to create Debian
2322 packages. Doing this with a <tt>patch</tt> target in
2323 <file>debian/rules</file> is recommended; see
2324 <ref id="debianrules">.</item>
2325 <item>Modify the source and save those modifications so that
2326 they will be applied when building the package.</item>
2327 <item>Remove source modifications that are currently being
2328 applied when building the package.</item>
2329 <item>Optionally, document what steps are necessary to
2330 upgrade the Debian source package to a new upstream version,
2331 if applicable.</item>
2333 This explanation should include specific commands and mention
2334 any additional required Debian packages. It should not assume
2335 familiarity with any specific Debian packaging system or patch
2340 This explanation may refer to a documentation file installed by
2341 one of the package's build dependencies provided that the
2342 referenced documentation clearly explains these tasks and is not
2343 a general reference manual.
2347 <file>debian/README.source</file> may also include any other
2348 information that would be helpful to someone modifying the
2349 source package. Even if the package doesn't fit the above
2350 description, maintainers are encouraged to document in a
2351 <file>debian/README.source</file> file any source package with a
2352 particularly complex or unintuitive source layout or build
2353 system (for example, a package that builds the same source
2354 multiple times to generate different binary packages).
2360 <chapt id="controlfields">
2361 <heading>Control files and their fields</heading>
2364 The package management system manipulates data represented in
2365 a common format, known as <em>control data</em>, stored in
2366 <em>control files</em>.
2367 Control files are used for source packages, binary packages and
2368 the <file>.changes</file> files which control the installation
2369 of uploaded files<footnote>
2370 <prgn>dpkg</prgn>'s internal databases are in a similar
2375 <sect id="controlsyntax">
2376 <heading>Syntax of control files</heading>
2379 A control file consists of one or more paragraphs of
2381 The paragraphs are also sometimes referred to as stanzas.
2383 The paragraphs are separated by blank lines. Some control
2384 files allow only one paragraph; others allow several, in
2385 which case each paragraph usually refers to a different
2386 package. (For example, in source packages, the first
2387 paragraph refers to the source package, and later paragraphs
2388 refer to binary packages generated from the source.)
2392 Each paragraph consists of a series of data fields; each
2393 field consists of the field name, followed by a colon and
2394 then the data/value associated with that field. It ends at
2395 the end of the (logical) line. Horizontal whitespace
2396 (spaces and tabs) may occur immediately before or after the
2397 value and is ignored there; it is conventional to put a
2398 single space after the colon. For example, a field might
2400 <example compact="compact">
2403 the field name is <tt>Package</tt> and the field value
2408 A paragraph must not contain more than one instance of a
2409 particular field name.
2413 Many fields' values may span several lines; in this case
2414 each continuation line must start with a space or a tab.
2415 Any trailing spaces or tabs at the end of individual
2416 lines of a field value are ignored.
2420 In fields where it is specified that lines may not wrap,
2421 only a single line of data is allowed and whitespace is not
2422 significant in a field body. Whitespace must not appear
2423 inside names (of packages, architectures, files or anything
2424 else) or version numbers, or between the characters of
2425 multi-character version relationships.
2429 Field names are not case-sensitive, but it is usual to
2430 capitalize the field names using mixed case as shown below.
2431 Field values are case-sensitive unless the description of the
2432 field says otherwise.
2436 Blank lines, or lines consisting only of spaces and tabs,
2437 are not allowed within field values or between fields - that
2438 would mean a new paragraph.
2442 All control files must be encoded in UTF-8.
2446 <sect id="sourcecontrolfiles">
2447 <heading>Source package control files -- <file>debian/control</file></heading>
2450 The <file>debian/control</file> file contains the most vital
2451 (and version-independent) information about the source package
2452 and about the binary packages it creates.
2456 The first paragraph of the control file contains information about
2457 the source package in general. The subsequent sets each describe a
2458 binary package that the source tree builds.
2462 The fields in the general paragraph (the first one, for the source
2465 <list compact="compact">
2466 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2467 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2468 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2469 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2470 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2471 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2472 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2473 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2478 The fields in the binary package paragraphs are:
2480 <list compact="compact">
2481 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2482 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2483 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2484 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2485 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2486 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2487 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2488 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2493 The syntax and semantics of the fields are described below.
2497 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2498 generate control files for binary packages (see below), by
2499 <prgn>dpkg-genchanges</prgn> to generate the
2500 <tt>.changes</tt> file to accompany the upload, and by
2501 <prgn>dpkg-source</prgn> when it creates the
2502 <file>.dsc</file> source control file as part of a source
2503 archive. Many fields are permitted to span multiple lines in
2504 <file>debian/control</file> but not in any other control
2505 file. These tools are responsible for removing the line
2506 breaks from such fields when using fields from
2507 <file>debian/control</file> to generate other control files.
2511 The fields here may contain variable references - their
2512 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2513 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2514 when they generate output control files.
2515 See <ref id="substvars"> for details.
2519 In addition to the control file syntax described <qref
2520 id="controlsyntax">above</qref>, this file may also contain
2521 comment lines starting with <tt>#</tt> without any preceding
2522 whitespace. All such lines are ignored, even in the middle of
2523 continuation lines for a multiline field, and do not end a
2529 <sect id="binarycontrolfiles">
2530 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2533 The <file>DEBIAN/control</file> file contains the most vital
2534 (and version-dependent) information about a binary package.
2538 The fields in this file are:
2540 <list compact="compact">
2541 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2542 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2543 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2544 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2545 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2546 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2547 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2548 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2549 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2550 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2551 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2552 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2557 <sect id="debiansourcecontrolfiles">
2558 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2561 This file contains a series of fields, identified and
2562 separated just like the fields in the control file of
2563 a binary package. The fields are listed below; their
2564 syntax is described above, in <ref id="pkg-controlfields">.
2566 <list compact="compact">
2567 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2568 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2569 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2570 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2571 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2572 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2573 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2574 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2575 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2576 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2577 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2578 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2579 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2584 The source package control file is generated by
2585 <prgn>dpkg-source</prgn> when it builds the source
2586 archive, from other files in the source package,
2587 described above. When unpacking, it is checked against
2588 the files and directories in the other parts of the
2594 <sect id="debianchangesfiles">
2595 <heading>Debian changes files -- <file>.changes</file></heading>
2598 The <file>.changes</file> files are used by the Debian archive
2599 maintenance software to process updates to packages. They
2600 contain one paragraph which contains information from the
2601 <tt>debian/control</tt> file and other data about the
2602 source package gathered via <tt>debian/changelog</tt>
2603 and <tt>debian/rules</tt>.
2607 <file>.changes</file> files have a format version that is
2608 incremented whenever the documented fields or their meaning
2609 change. This document describes format 1.8.
2613 The fields in this file are:
2615 <list compact="compact">
2616 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2617 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2618 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2619 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2620 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2621 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2622 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2623 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2624 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2625 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2626 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2627 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2628 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2629 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2630 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2631 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2636 <sect id="controlfieldslist">
2637 <heading>List of fields</heading>
2639 <sect1 id="f-Source">
2640 <heading><tt>Source</tt></heading>
2643 This field identifies the source package name.
2647 In <file>debian/control</file> or a <file>.dsc</file> file,
2648 this field must contain only the name of the source package.
2652 In a binary package control file or a <file>.changes</file>
2653 file, the source package name may be followed by a version
2654 number in parentheses<footnote>
2655 It is customary to leave a space after the package name
2656 if a version number is specified.
2658 This version number may be omitted (and is, by
2659 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2660 the <tt>Version</tt> field of the binary package in
2661 question. The field itself may be omitted from a binary
2662 package control file when the source package has the same
2663 name and version as the binary package.
2667 Package names (both source and binary,
2668 see <ref id="f-Package">) must consist only of lower case
2669 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2670 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2671 (<tt>.</tt>). They must be at least two characters long and
2672 must start with an alphanumeric character.
2676 <sect1 id="f-Maintainer">
2677 <heading><tt>Maintainer</tt></heading>
2680 The package maintainer's name and email address. The name
2681 must come first, then the email address inside angle
2682 brackets <tt><></tt> (in RFC822 format).
2686 If the maintainer's name contains a full stop then the
2687 whole field will not work directly as an email address due
2688 to a misfeature in the syntax specified in RFC822; a
2689 program using this field as an address must check for this
2690 and correct the problem if necessary (for example by
2691 putting the name in round brackets and moving it to the
2692 end, and bringing the email address forward).
2696 <sect1 id="f-Uploaders">
2697 <heading><tt>Uploaders</tt></heading>
2700 List of the names and email addresses of co-maintainers of
2701 the package, if any. If the package has other maintainers
2702 beside the one named in the
2703 <qref id="f-Maintainer">Maintainer field</qref>, their names
2704 and email addresses should be listed here. The format of each
2705 entry is the same as that of the Maintainer field, and
2706 multiple entries must be comma separated. This is an optional
2711 Any parser that interprets the Uploaders field in
2712 <file>debian/control</file> must permit it to span multiple
2713 lines. Line breaks in an Uploaders field that spans multiple
2714 lines are not significant and the semantics of the field are
2715 the same as if the line breaks had not been present.
2719 <sect1 id="f-Changed-By">
2720 <heading><tt>Changed-By</tt></heading>
2723 The name and email address of the person who prepared this
2724 version of the package, usually a maintainer. The syntax is
2725 the same as for the <qref id="f-Maintainer">Maintainer
2730 <sect1 id="f-Section">
2731 <heading><tt>Section</tt></heading>
2734 This field specifies an application area into which the package
2735 has been classified. See <ref id="subsections">.
2739 When it appears in the <file>debian/control</file> file,
2740 it gives the value for the subfield of the same name in
2741 the <tt>Files</tt> field of the <file>.changes</file> file.
2742 It also gives the default for the same field in the binary
2747 <sect1 id="f-Priority">
2748 <heading><tt>Priority</tt></heading>
2751 This field represents how important it is that the user
2752 have the package installed. See <ref id="priorities">.
2756 When it appears in the <file>debian/control</file> file,
2757 it gives the value for the subfield of the same name in
2758 the <tt>Files</tt> field of the <file>.changes</file> file.
2759 It also gives the default for the same field in the binary
2764 <sect1 id="f-Package">
2765 <heading><tt>Package</tt></heading>
2768 The name of the binary package.
2772 Binary package names must follow the same syntax and
2773 restrictions as source package names. See <ref id="f-Source">
2778 <sect1 id="f-Architecture">
2779 <heading><tt>Architecture</tt></heading>
2782 Depending on context and the control file used, the
2783 <tt>Architecture</tt> field can include the following sets of
2787 A unique single word identifying a Debian machine
2788 architecture as described in <ref id="arch-spec">.
2791 An architecture wildcard identifying a set of Debian
2792 machine architectures, see <ref id="arch-wildcard-spec">.
2793 <tt>any</tt> matches all Debian machine architectures
2794 and is the most frequently used.
2797 <tt>all</tt>, which indicates an
2798 architecture-independent package.
2801 <tt>source</tt>, which indicates a source package.
2807 In the main <file>debian/control</file> file in the source
2808 package, this field may contain the special
2809 value <tt>all</tt>, the special architecture
2810 wildcard <tt>any</tt>, or a list of specific and wildcard
2811 architectures separated by spaces. If <tt>all</tt>
2812 or <tt>any</tt> appears, that value must be the entire
2813 contents of the field. Most packages will use
2814 either <tt>all</tt> or <tt>any</tt>.
2818 Specifying a specific list of architectures indicates that the
2819 source will build an architecture-dependent package only on
2820 architectures included in the list. Specifying a list of
2821 architecture wildcards indicates that the source will build an
2822 architecture-dependent package on only those architectures
2823 that match any of the specified architecture wildcards.
2824 Specifying a list of architectures or architecture wildcards
2825 other than <tt>any</tt> is for the minority of cases where a
2826 program is not portable or is not useful on some
2827 architectures. Where possible, the program should be made
2832 In the source package control file <file>.dsc</file>, this
2833 field may contain either the architecture
2834 wildcard <tt>any</tt> or a list of architectures and
2835 architecture wildcards separated by spaces. If a list is
2836 given, it may include (or consist solely of) the special
2837 value <tt>all</tt>. In other words, in <file>.dsc</file>
2838 files unlike the <file>debian/control</file>, <tt>all</tt> may
2839 occur in combination with specific architectures.
2840 The <tt>Architecture</tt> field in the source package control
2841 file <file>.dsc</file> is generally constructed from
2842 the <tt>Architecture</tt> fields in
2843 the <file>debian/control</file> in the source package.
2847 Specifying <tt>any</tt> indicates that the source package
2848 isn't dependent on any particular architecture and should
2849 compile fine on any one. The produced binary package(s)
2850 will either be specific to whatever the current build
2851 architecture is or will be architecture-independent.
2855 Specifying only <tt>all</tt> indicates that the source package
2856 will only build architecture-independent packages. If this is
2857 the case, <tt>all</tt> must be used rather than <tt>any</tt>;
2858 <tt>any</tt> implies that the source package will build at
2859 least one architecture-dependent package.
2863 Specifying a list of architectures or architecture wildcards
2864 indicates that the source will build an architecture-dependent
2865 package, and will only work correctly on the listed or
2866 matching architectures. If the source package also builds at
2867 least one architecture-independent package, <tt>all</tt> will
2868 also be included in the list.
2872 In a <file>.changes</file> file, the <tt>Architecture</tt>
2873 field lists the architecture(s) of the package(s) currently
2874 being uploaded. This will be a list; if the source for the
2875 package is also being uploaded, the special
2876 entry <tt>source</tt> is also present. <tt>all</tt> will be
2877 present if any architecture-independent packages are being
2878 uploaded. Architecture wildcards such as <tt>any</tt> must
2879 never occur in the <tt>Architecture</tt> field in
2880 the <file>.changes</file> file.
2884 See <ref id="debianrules"> for information on how to get
2885 the architecture for the build process.
2889 <sect1 id="f-Essential">
2890 <heading><tt>Essential</tt></heading>
2893 This is a boolean field which may occur only in the
2894 control file of a binary package or in a per-package fields
2895 paragraph of a main source control data file.
2899 If set to <tt>yes</tt> then the package management system
2900 will refuse to remove the package (upgrading and replacing
2901 it is still possible). The other possible value is <tt>no</tt>,
2902 which is the same as not having the field at all.
2907 <heading>Package interrelationship fields:
2908 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2909 <tt>Recommends</tt>, <tt>Suggests</tt>,
2910 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2911 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2915 These fields describe the package's relationships with
2916 other packages. Their syntax and semantics are described
2917 in <ref id="relationships">.</p>
2920 <sect1 id="f-Standards-Version">
2921 <heading><tt>Standards-Version</tt></heading>
2924 The most recent version of the standards (the policy
2925 manual and associated texts) with which the package
2930 The version number has four components: major and minor
2931 version number and major and minor patch level. When the
2932 standards change in a way that requires every package to
2933 change the major number will be changed. Significant
2934 changes that will require work in many packages will be
2935 signaled by a change to the minor number. The major patch
2936 level will be changed for any change to the meaning of the
2937 standards, however small; the minor patch level will be
2938 changed when only cosmetic, typographical or other edits
2939 are made which neither change the meaning of the document
2940 nor affect the contents of packages.
2944 Thus only the first three components of the policy version
2945 are significant in the <em>Standards-Version</em> control
2946 field, and so either these three components or all four
2947 components may be specified.<footnote>
2948 In the past, people specified the full version number
2949 in the Standards-Version field, for example "2.3.0.0".
2950 Since minor patch-level changes don't introduce new
2951 policy, it was thought it would be better to relax
2952 policy and only require the first 3 components to be
2953 specified, in this example "2.3.0". All four
2954 components may still be used if someone wishes to do so.
2960 <sect1 id="f-Version">
2961 <heading><tt>Version</tt></heading>
2964 The version number of a package. The format is:
2965 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
2969 The three components here are:
2971 <tag><var>epoch</var></tag>
2974 This is a single (generally small) unsigned integer. It
2975 may be omitted, in which case zero is assumed. If it is
2976 omitted then the <var>upstream_version</var> may not
2981 It is provided to allow mistakes in the version numbers
2982 of older versions of a package, and also a package's
2983 previous version numbering schemes, to be left behind.
2987 <tag><var>upstream_version</var></tag>
2990 This is the main part of the version number. It is
2991 usually the version number of the original ("upstream")
2992 package from which the <file>.deb</file> file has been made,
2993 if this is applicable. Usually this will be in the same
2994 format as that specified by the upstream author(s);
2995 however, it may need to be reformatted to fit into the
2996 package management system's format and comparison
3001 The comparison behavior of the package management system
3002 with respect to the <var>upstream_version</var> is
3003 described below. The <var>upstream_version</var>
3004 portion of the version number is mandatory.
3008 The <var>upstream_version</var> may contain only
3009 alphanumerics<footnote>
3010 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3012 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3013 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3014 tilde) and should start with a digit. If there is no
3015 <var>debian_revision</var> then hyphens are not allowed;
3016 if there is no <var>epoch</var> then colons are not
3021 <tag><var>debian_revision</var></tag>
3024 This part of the version number specifies the version of
3025 the Debian package based on the upstream version. It
3026 may contain only alphanumerics and the characters
3027 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3028 tilde) and is compared in the same way as the
3029 <var>upstream_version</var> is.
3033 It is optional; if it isn't present then the
3034 <var>upstream_version</var> may not contain a hyphen.
3035 This format represents the case where a piece of
3036 software was written specifically to be a Debian
3037 package, where the Debian package source must always
3038 be identical to the pristine source and therefore no
3039 revision indication is required.
3043 It is conventional to restart the
3044 <var>debian_revision</var> at <tt>1</tt> each time the
3045 <var>upstream_version</var> is increased.
3049 The package management system will break the version
3050 number apart at the last hyphen in the string (if there
3051 is one) to determine the <var>upstream_version</var> and
3052 <var>debian_revision</var>. The absence of a
3053 <var>debian_revision</var> is equivalent to a
3054 <var>debian_revision</var> of <tt>0</tt>.
3061 When comparing two version numbers, first the <var>epoch</var>
3062 of each are compared, then the <var>upstream_version</var> if
3063 <var>epoch</var> is equal, and then <var>debian_revision</var>
3064 if <var>upstream_version</var> is also equal.
3065 <var>epoch</var> is compared numerically. The
3066 <var>upstream_version</var> and <var>debian_revision</var>
3067 parts are compared by the package management system using the
3068 following algorithm:
3072 The strings are compared from left to right.
3076 First the initial part of each string consisting entirely of
3077 non-digit characters is determined. These two parts (one of
3078 which may be empty) are compared lexically. If a difference
3079 is found it is returned. The lexical comparison is a
3080 comparison of ASCII values modified so that all the letters
3081 sort earlier than all the non-letters and so that a tilde
3082 sorts before anything, even the end of a part. For example,
3083 the following parts are in sorted order from earliest to
3084 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3085 <tt>a</tt>.<footnote>
3086 One common use of <tt>~</tt> is for upstream pre-releases.
3087 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3088 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3093 Then the initial part of the remainder of each string which
3094 consists entirely of digit characters is determined. The
3095 numerical values of these two parts are compared, and any
3096 difference found is returned as the result of the comparison.
3097 For these purposes an empty string (which can only occur at
3098 the end of one or both version strings being compared) counts
3103 These two steps (comparing and removing initial non-digit
3104 strings and initial digit strings) are repeated until a
3105 difference is found or both strings are exhausted.
3109 Note that the purpose of epochs is to allow us to leave behind
3110 mistakes in version numbering, and to cope with situations
3111 where the version numbering scheme changes. It is
3112 <em>not</em> intended to cope with version numbers containing
3113 strings of letters which the package management system cannot
3114 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3115 silly orderings.<footnote>
3116 The author of this manual has heard of a package whose
3117 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3118 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3124 <sect1 id="f-Description">
3125 <heading><tt>Description</tt></heading>
3128 In a source or binary control file, the <tt>Description</tt>
3129 field contains a description of the binary package, consisting
3130 of two parts, the synopsis or the short description, and the
3131 long description. The field's format is as follows:
3136 Description: <single line synopsis>
3137 <extended description over several lines>
3142 The lines in the extended description can have these formats:
3148 Those starting with a single space are part of a paragraph.
3149 Successive lines of this form will be word-wrapped when
3150 displayed. The leading space will usually be stripped off.
3154 Those starting with two or more spaces. These will be
3155 displayed verbatim. If the display cannot be panned
3156 horizontally, the displaying program will line wrap them "hard"
3157 (i.e., without taking account of word breaks). If it can they
3158 will be allowed to trail off to the right. None, one or two
3159 initial spaces may be deleted, but the number of spaces
3160 deleted from each line will be the same (so that you can have
3161 indenting work correctly, for example).
3165 Those containing a single space followed by a single full stop
3166 character. These are rendered as blank lines. This is the
3167 <em>only</em> way to get a blank line<footnote>
3168 Completely empty lines will not be rendered as blank lines.
3169 Instead, they will cause the parser to think you're starting
3170 a whole new record in the control file, and will therefore
3171 likely abort with an error.
3176 Those containing a space, a full stop and some more characters.
3177 These are for future expansion. Do not use them.
3183 Do not use tab characters. Their effect is not predictable.
3187 See <ref id="descriptions"> for further information on this.
3191 In a <file>.changes</file> file, the <tt>Description</tt>
3192 field contains a summary of the descriptions for the packages
3193 being uploaded. For this case, the first line of the field
3194 value (the part on the same line as <tt>Description:</tt>) is
3195 always empty. The content of the field is expressed as
3196 continuation lines, one line per package. Each line is
3197 indented by one space and contains the name of a binary
3198 package, a space, a hyphen (<tt>-</tt>), a space, and the
3199 short description line from that package.
3203 <sect1 id="f-Distribution">
3204 <heading><tt>Distribution</tt></heading>
3207 In a <file>.changes</file> file or parsed changelog output
3208 this contains the (space-separated) name(s) of the
3209 distribution(s) where this version of the package should
3210 be installed. Valid distributions are determined by the
3211 archive maintainers.<footnote>
3212 Example distribution names in the Debian archive used in
3213 <file>.changes</file> files are:
3214 <taglist compact="compact">
3215 <tag><em>unstable</em></tag>
3217 This distribution value refers to the
3218 <em>developmental</em> part of the Debian distribution
3219 tree. Most new packages, new upstream versions of
3220 packages and bug fixes go into the <em>unstable</em>
3224 <tag><em>experimental</em></tag>
3226 The packages with this distribution value are deemed
3227 by their maintainers to be high risk. Oftentimes they
3228 represent early beta or developmental packages from
3229 various sources that the maintainers want people to
3230 try, but are not ready to be a part of the other parts
3231 of the Debian distribution tree.
3236 Others are used for updating stable releases or for
3237 security uploads. More information is available in the
3238 Debian Developer's Reference, section "The Debian
3242 The Debian archive software only supports listing a single
3243 distribution. Migration of packages to other distributions is
3244 handled outside of the upload process.
3249 <heading><tt>Date</tt></heading>
3252 This field includes the date the package was built or last
3253 edited. It must be in the same format as the <var>date</var>
3254 in a <file>debian/changelog</file> entry.
3258 The value of this field is usually extracted from the
3259 <file>debian/changelog</file> file - see
3260 <ref id="dpkgchangelog">).
3264 <sect1 id="f-Format">
3265 <heading><tt>Format</tt></heading>
3268 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3269 files, this field declares the format version of that file.
3270 The syntax of the field value is the same as that of
3271 a <qref id="f-Version">package version number</qref> except
3272 that no epoch or Debian revision is allowed. The format
3273 described in this document is <tt>1.8</tt>.
3277 In <qref id="debiansourcecontrolfiles"> Debian source
3278 control</qref> files, this field declares the format of the
3279 source package. The field value is used by programs acting on
3280 a source package to interpret the list of files in the source
3281 package and determine how to unpack it. The syntax of the
3282 field value is a numeric major revision, a period, a numeric
3283 minor revision, and then an optional subtype after whitespace,
3284 which if specified is an alphanumeric word in parentheses.
3285 The subtype is optional in the syntax but may be mandatory for
3286 particular source format revisions.<footnote>
3287 The source formats currently supported by the Debian archive
3288 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3289 and <tt>3.0 (quilt)</tt>.
3294 <sect1 id="f-Urgency">
3295 <heading><tt>Urgency</tt></heading>
3298 This is a description of how important it is to upgrade to
3299 this version from previous ones. It consists of a single
3300 keyword taking one of the values <tt>low</tt>,
3301 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3302 <tt>critical</tt><footnote>
3303 Other urgency values are supported with configuration
3304 changes in the archive software but are not used in Debian.
3305 The urgency affects how quickly a package will be considered
3306 for inclusion into the <tt>testing</tt> distribution and
3307 gives an indication of the importance of any fixes included
3308 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3309 treated as synonymous.
3310 </footnote> (not case-sensitive) followed by an optional
3311 commentary (separated by a space) which is usually in
3312 parentheses. For example:
3315 Urgency: low (HIGH for users of diversions)
3321 The value of this field is usually extracted from the
3322 <file>debian/changelog</file> file - see
3323 <ref id="dpkgchangelog">.
3327 <sect1 id="f-Changes">
3328 <heading><tt>Changes</tt></heading>
3331 This field contains the human-readable changes data, describing
3332 the differences between the last version and the current one.
3336 The first line of the field value (the part on the same line
3337 as <tt>Changes:</tt>) is always empty. The content of the
3338 field is expressed as continuation lines, with each line
3339 indented by at least one space. Blank lines must be
3340 represented by a line consisting only of a space and a full
3345 The value of this field is usually extracted from the
3346 <file>debian/changelog</file> file - see
3347 <ref id="dpkgchangelog">).
3351 Each version's change information should be preceded by a
3352 "title" line giving at least the version, distribution(s)
3353 and urgency, in a human-readable way.
3357 If data from several versions is being returned the entry
3358 for the most recent version should be returned first, and
3359 entries should be separated by the representation of a
3360 blank line (the "title" line may also be followed by the
3361 representation of a blank line).
3365 <sect1 id="f-Binary">
3366 <heading><tt>Binary</tt></heading>
3369 This field is a list of binary packages. Its syntax and
3370 meaning varies depending on the control file in which it
3375 When it appears in the <file>.dsc</file> file, it lists binary
3376 packages which a source package can produce, separated by
3378 A space after each comma is conventional.
3379 </footnote>. It may span multiple lines. The source package
3380 does not necessarily produce all of these binary packages for
3381 every architecture. The source control file doesn't contain
3382 details of which architectures are appropriate for which of
3383 the binary packages.
3387 When it appears in a <file>.changes</file> file, it lists the
3388 names of the binary packages being uploaded, separated by
3389 whitespace (not commas). It may span multiple lines.
3393 <sect1 id="f-Installed-Size">
3394 <heading><tt>Installed-Size</tt></heading>
3397 This field appears in the control files of binary packages,
3398 and in the <file>Packages</file> files. It gives an estimate
3399 of the total amount of disk space required to install the
3400 named package. Actual installed size may vary based on block
3401 size, file system properties, or actions taken by package
3406 The disk space is given as the integer value of the estimated
3407 installed size in bytes, divided by 1024 and rounded up.
3411 <sect1 id="f-Files">
3412 <heading><tt>Files</tt></heading>
3415 This field contains a list of files with information about
3416 each one. The exact information and syntax varies with
3421 In all cases, Files is a multiline field. The first line of
3422 the field value (the part on the same line as <tt>Files:</tt>)
3423 is always empty. The content of the field is expressed as
3424 continuation lines, one line per file. Each line must be
3425 indented by one space and contain a number of sub-fields,
3426 separated by spaces, as described below.
3430 In the <file>.dsc</file> file, each line contains the MD5
3431 checksum, size and filename of the tar file and (if
3432 applicable) diff file which make up the remainder of the
3433 source package<footnote>
3434 That is, the parts which are not the <tt>.dsc</tt>.
3435 </footnote>. For example:
3438 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3439 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3441 The exact forms of the filenames are described
3442 in <ref id="pkg-sourcearchives">.
3446 In the <file>.changes</file> file this contains one line per
3447 file being uploaded. Each line contains the MD5 checksum,
3448 size, section and priority and the filename. For example:
3451 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3452 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3453 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3454 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3456 The <qref id="f-Section">section</qref>
3457 and <qref id="f-Priority">priority</qref> are the values of
3458 the corresponding fields in the main source control file. If
3459 no section or priority is specified then <tt>-</tt> should be
3460 used, though section and priority values must be specified for
3461 new packages to be installed properly.
3465 The special value <tt>byhand</tt> for the section in a
3466 <tt>.changes</tt> file indicates that the file in question
3467 is not an ordinary package file and must by installed by
3468 hand by the distribution maintainers. If the section is
3469 <tt>byhand</tt> the priority should be <tt>-</tt>.
3473 If a new Debian revision of a package is being shipped and
3474 no new original source archive is being distributed the
3475 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3476 entry for the original source archive
3477 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3478 but the <file>.changes</file> file should leave it out. In
3479 this case the original source archive on the distribution
3480 site must match exactly, byte-for-byte, the original
3481 source archive which was used to generate the
3482 <file>.dsc</file> file and diff which are being uploaded.</p>
3485 <sect1 id="f-Closes">
3486 <heading><tt>Closes</tt></heading>
3489 A space-separated list of bug report numbers that the upload
3490 governed by the .changes file closes.
3494 <sect1 id="f-Homepage">
3495 <heading><tt>Homepage</tt></heading>
3498 The URL of the web site for this package, preferably (when
3499 applicable) the site from which the original source can be
3500 obtained and any additional upstream documentation or
3501 information may be found. The content of this field is a
3502 simple URL without any surrounding characters such as
3507 <sect1 id="f-Checksums">
3508 <heading><tt>Checksums-Sha1</tt>
3509 and <tt>Checksums-Sha256</tt></heading>
3512 These fields contain a list of files with a checksum and size
3513 for each one. Both <tt>Checksums-Sha1</tt>
3514 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3515 only in the checksum algorithm used: SHA-1
3516 for <tt>Checksums-Sha1</tt> and SHA-256
3517 for <tt>Checksums-Sha256</tt>.
3521 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3522 multiline fields. The first line of the field value (the part
3523 on the same line as <tt>Checksums-Sha1:</tt>
3524 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3525 of the field is expressed as continuation lines, one line per
3526 file. Each line consists of the checksum, a space, the file
3527 size, a space, and the file name. For example (from
3528 a <file>.changes</file> file):
3531 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3532 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3533 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3534 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3536 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3537 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3538 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3539 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3544 In the <file>.dsc</file> file, these fields should list all
3545 files that make up the source package. In
3546 the <file>.changes</file> file, these fields should list all
3547 files being uploaded. The list of files in these fields
3548 must match the list of files in the <tt>Files</tt> field.
3554 <heading>User-defined fields</heading>
3557 Additional user-defined fields may be added to the
3558 source package control file. Such fields will be
3559 ignored, and not copied to (for example) binary or
3560 source package control files or upload control files.
3564 If you wish to add additional unsupported fields to
3565 these output files you should use the mechanism
3570 Fields in the main source control information file with
3571 names starting <tt>X</tt>, followed by one or more of
3572 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3573 be copied to the output files. Only the part of the
3574 field name after the hyphen will be used in the output
3575 file. Where the letter <tt>B</tt> is used the field
3576 will appear in binary package control files, where the
3577 letter <tt>S</tt> is used in source package control
3578 files and where <tt>C</tt> is used in upload control
3579 (<tt>.changes</tt>) files.
3583 For example, if the main source information control file
3586 XBS-Comment: I stand between the candle and the star.
3588 then the binary and source package control files will contain the
3591 Comment: I stand between the candle and the star.
3600 <chapt id="maintainerscripts">
3601 <heading>Package maintainer scripts and installation procedure</heading>
3604 <heading>Introduction to package maintainer scripts</heading>
3607 It is possible to supply scripts as part of a package which
3608 the package management system will run for you when your
3609 package is installed, upgraded or removed.
3613 These scripts are the files <prgn>preinst</prgn>,
3614 <prgn>postinst</prgn>, <prgn>prerm</prgn> and
3615 <prgn>postrm</prgn> in the control area of the package.
3616 They must be proper executable files; if they are scripts
3617 (which is recommended), they must start with the usual
3618 <tt>#!</tt> convention. They should be readable and
3619 executable by anyone, and must not be world-writable.
3623 The package management system looks at the exit status from
3624 these scripts. It is important that they exit with a
3625 non-zero status if there is an error, so that the package
3626 management system can stop its processing. For shell
3627 scripts this means that you <em>almost always</em> need to
3628 use <tt>set -e</tt> (this is usually true when writing shell
3629 scripts, in fact). It is also important, of course, that
3630 they exit with a zero status if everything went well.
3634 Additionally, packages interacting with users using
3635 <tt>debconf</tt> in the <prgn>postinst</prgn> script should
3636 install a <prgn>config</prgn> script in the control area,
3637 see <ref id="maintscriptprompt"> for details.
3641 When a package is upgraded a combination of the scripts from
3642 the old and new packages is called during the upgrade
3643 procedure. If your scripts are going to be at all
3644 complicated you need to be aware of this, and may need to
3645 check the arguments to your scripts.
3649 Broadly speaking the <prgn>preinst</prgn> is called before
3650 (a particular version of) a package is installed, and the
3651 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3652 before (a version of) a package is removed and the
3653 <prgn>postrm</prgn> afterwards.
3657 Programs called from maintainer scripts should not normally
3658 have a path prepended to them. Before installation is
3659 started, the package management system checks to see if the
3660 programs <prgn>ldconfig</prgn>,
3661 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3662 and <prgn>update-rc.d</prgn> can be found via the
3663 <tt>PATH</tt> environment variable. Those programs, and any
3664 other program that one would expect to be in the
3665 <tt>PATH</tt>, should thus be invoked without an absolute
3666 pathname. Maintainer scripts should also not reset the
3667 <tt>PATH</tt>, though they might choose to modify it by
3668 prepending or appending package-specific directories. These
3669 considerations really apply to all shell scripts.</p>
3672 <sect id="idempotency">
3673 <heading>Maintainer scripts idempotency</heading>
3676 It is necessary for the error recovery procedures that the
3677 scripts be idempotent. This means that if it is run
3678 successfully, and then it is called again, it doesn't bomb
3679 out or cause any harm, but just ensures that everything is
3680 the way it ought to be. If the first call failed, or
3681 aborted half way through for some reason, the second call
3682 should merely do the things that were left undone the first
3683 time, if any, and exit with a success status if everything
3685 This is so that if an error occurs, the user interrupts
3686 <prgn>dpkg</prgn> or some other unforeseen circumstance
3687 happens you don't leave the user with a badly-broken
3688 package when <prgn>dpkg</prgn> attempts to repeat the
3694 <sect id="controllingterminal">
3695 <heading>Controlling terminal for maintainer scripts</heading>
3698 Maintainer scripts are not guaranteed to run with a controlling
3699 terminal and may not be able to interact with the user. They
3700 must be able to fall back to noninteractive behavior if no
3701 controlling terminal is available. Maintainer scripts that
3702 prompt via a program conforming to the Debian Configuration
3703 Management Specification (see <ref id="maintscriptprompt">) may
3704 assume that program will handle falling back to noninteractive
3709 For high-priority prompts without a reasonable default answer,
3710 maintainer scripts may abort if there is no controlling
3711 terminal. However, this situation should be avoided if at all
3712 possible, since it prevents automated or unattended installs.
3713 In most cases, users will consider this to be a bug in the
3718 <sect id="exitstatus">
3719 <heading>Exit status</heading>
3722 Each script must return a zero exit status for
3723 success, or a nonzero one for failure, since the package
3724 management system looks for the exit status of these scripts
3725 and determines what action to take next based on that datum.
3729 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3734 <list compact="compact">
3736 <var>new-preinst</var> <tt>install</tt>
3739 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3742 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3745 <var>old-preinst</var> <tt>abort-upgrade</tt>
3746 <var>new-version</var>
3751 <list compact="compact">
3753 <var>postinst</var> <tt>configure</tt>
3754 <var>most-recently-configured-version</var>
3757 <var>old-postinst</var> <tt>abort-upgrade</tt>
3758 <var>new-version</var>
3761 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3762 <tt>in-favour</tt> <var>package</var>
3763 <var>new-version</var>
3766 <var>postinst</var> <tt>abort-remove</tt>
3769 <var>deconfigured's-postinst</var>
3770 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3771 <var>failed-install-package</var> <var>version</var>
3772 [<tt>removing</tt> <var>conflicting-package</var>
3778 <list compact="compact">
3780 <var>prerm</var> <tt>remove</tt>
3783 <var>old-prerm</var> <tt>upgrade</tt>
3784 <var>new-version</var>
3787 <var>new-prerm</var> <tt>failed-upgrade</tt>
3788 <var>old-version</var>
3791 <var>conflictor's-prerm</var> <tt>remove</tt>
3792 <tt>in-favour</tt> <var>package</var>
3793 <var>new-version</var>
3796 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3797 <tt>in-favour</tt> <var>package-being-installed</var>
3798 <var>version</var> [<tt>removing</tt>
3799 <var>conflicting-package</var>
3805 <list compact="compact">
3807 <var>postrm</var> <tt>remove</tt>
3810 <var>postrm</var> <tt>purge</tt>
3813 <var>old-postrm</var> <tt>upgrade</tt>
3814 <var>new-version</var>
3817 <var>new-postrm</var> <tt>failed-upgrade</tt>
3818 <var>old-version</var>
3821 <var>new-postrm</var> <tt>abort-install</tt>
3824 <var>new-postrm</var> <tt>abort-install</tt>
3825 <var>old-version</var>
3828 <var>new-postrm</var> <tt>abort-upgrade</tt>
3829 <var>old-version</var>
3832 <var>disappearer's-postrm</var> <tt>disappear</tt>
3833 <var>overwriter</var>
3834 <var>overwriter-version</var>
3840 <sect id="unpackphase">
3841 <heading>Details of unpack phase of installation or upgrade</heading>
3844 The procedure on installation/upgrade/overwrite/disappear
3845 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3846 stage of <tt>dpkg --install</tt>) is as follows. In each
3847 case, if a major error occurs (unless listed below) the
3848 actions are, in general, run backwards - this means that the
3849 maintainer scripts are run with different arguments in
3850 reverse order. These are the "error unwind" calls listed
3857 If a version of the package is already installed, call
3858 <example compact="compact">
3859 <var>old-prerm</var> upgrade <var>new-version</var>
3863 If the script runs but exits with a non-zero
3864 exit status, <prgn>dpkg</prgn> will attempt:
3865 <example compact="compact">
3866 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3868 If this works, the upgrade continues. If this
3869 does not work, the error unwind:
3870 <example compact="compact">
3871 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3873 If this works, then the old-version is
3874 "Installed", if not, the old version is in a
3875 "Half-Configured" state.
3881 If a "conflicting" package is being removed at the same time,
3882 or if any package will be broken (due to <tt>Breaks</tt>):
3885 If <tt>--auto-deconfigure</tt> is
3886 specified, call, for each package to be deconfigured
3887 due to <tt>Breaks</tt>:
3888 <example compact="compact">
3889 <var>deconfigured's-prerm</var> deconfigure \
3890 in-favour <var>package-being-installed</var> <var>version</var>
3893 <example compact="compact">
3894 <var>deconfigured's-postinst</var> abort-deconfigure \
3895 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3897 The deconfigured packages are marked as
3898 requiring configuration, so that if
3899 <tt>--install</tt> is used they will be
3900 configured again if possible.
3903 If any packages depended on a conflicting
3904 package being removed and <tt>--auto-deconfigure</tt> is
3905 specified, call, for each such package:
3906 <example compact="compact">
3907 <var>deconfigured's-prerm</var> deconfigure \
3908 in-favour <var>package-being-installed</var> <var>version</var> \
3909 removing <var>conflicting-package</var> <var>version</var>
3912 <example compact="compact">
3913 <var>deconfigured's-postinst</var> abort-deconfigure \
3914 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3915 removing <var>conflicting-package</var> <var>version</var>
3917 The deconfigured packages are marked as
3918 requiring configuration, so that if
3919 <tt>--install</tt> is used they will be
3920 configured again if possible.
3923 To prepare for removal of each conflicting package, call:
3924 <example compact="compact">
3925 <var>conflictor's-prerm</var> remove \
3926 in-favour <var>package</var> <var>new-version</var>
3929 <example compact="compact">
3930 <var>conflictor's-postinst</var> abort-remove \
3931 in-favour <var>package</var> <var>new-version</var>
3940 If the package is being upgraded, call:
3941 <example compact="compact">
3942 <var>new-preinst</var> upgrade <var>old-version</var>
3944 If this fails, we call:
3946 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3953 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3955 is called. If this works, then the old version
3956 is in an "Installed" state, or else it is left
3957 in an "Unpacked" state.
3962 If it fails, then the old version is left
3963 in an "Half-Installed" state.
3970 Otherwise, if the package had some configuration
3971 files from a previous version installed (i.e., it
3972 is in the "configuration files only" state):
3973 <example compact="compact">
3974 <var>new-preinst</var> install <var>old-version</var>
3978 <var>new-postrm</var> abort-install <var>old-version</var>
3980 If this fails, the package is left in a
3981 "Half-Installed" state, which requires a
3982 reinstall. If it works, the packages is left in
3983 a "Config-Files" state.
3986 Otherwise (i.e., the package was completely purged):
3987 <example compact="compact">
3988 <var>new-preinst</var> install
3991 <example compact="compact">
3992 <var>new-postrm</var> abort-install
3994 If the error-unwind fails, the package is in a
3995 "Half-Installed" phase, and requires a
3996 reinstall. If the error unwind works, the
3997 package is in a not installed state.
4004 The new package's files are unpacked, overwriting any
4005 that may be on the system already, for example any
4006 from the old version of the same package or from
4007 another package. Backups of the old files are kept
4008 temporarily, and if anything goes wrong the package
4009 management system will attempt to put them back as
4010 part of the error unwind.
4014 It is an error for a package to contain files which
4015 are on the system in another package, unless
4016 <tt>Replaces</tt> is used (see <ref id="replaces">).
4018 The following paragraph is not currently the case:
4019 Currently the <tt>- - force-overwrite</tt> flag is
4020 enabled, downgrading it to a warning, but this may not
4026 It is a more serious error for a package to contain a
4027 plain file or other kind of non-directory where another
4028 package has a directory (again, unless
4029 <tt>Replaces</tt> is used). This error can be
4030 overridden if desired using
4031 <tt>--force-overwrite-dir</tt>, but this is not
4036 Packages which overwrite each other's files produce
4037 behavior which, though deterministic, is hard for the
4038 system administrator to understand. It can easily
4039 lead to "missing" programs if, for example, a package
4040 is installed which overwrites a file from another
4041 package, and is then removed again.<footnote>
4042 Part of the problem is due to what is arguably a
4043 bug in <prgn>dpkg</prgn>.
4048 A directory will never be replaced by a symbolic link
4049 to a directory or vice versa; instead, the existing
4050 state (symlink or not) will be left alone and
4051 <prgn>dpkg</prgn> will follow the symlink if there is
4060 If the package is being upgraded, call
4061 <example compact="compact">
4062 <var>old-postrm</var> upgrade <var>new-version</var>
4066 If this fails, <prgn>dpkg</prgn> will attempt:
4067 <example compact="compact">
4068 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4070 If this works, installation continues. If not,
4072 <example compact="compact">
4073 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4075 If this fails, the old version is left in a
4076 "Half-Installed" state. If it works, dpkg now
4078 <example compact="compact">
4079 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4081 If this fails, the old version is left in a
4082 "Half-Installed" state. If it works, dpkg now
4084 <example compact="compact">
4085 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4087 If this fails, the old version is in an
4094 This is the point of no return - if
4095 <prgn>dpkg</prgn> gets this far, it won't back off
4096 past this point if an error occurs. This will
4097 leave the package in a fairly bad state, which
4098 will require a successful re-installation to clear
4099 up, but it's when <prgn>dpkg</prgn> starts doing
4100 things that are irreversible.
4105 Any files which were in the old version of the package
4106 but not in the new are removed.
4110 The new file list replaces the old.
4114 The new maintainer scripts replace the old.
4118 Any packages all of whose files have been overwritten
4119 during the installation, and which aren't required for
4120 dependencies, are considered to have been removed.
4121 For each such package
4124 <prgn>dpkg</prgn> calls:
4125 <example compact="compact">
4126 <var>disappearer's-postrm</var> disappear \
4127 <var>overwriter</var> <var>overwriter-version</var>
4131 The package's maintainer scripts are removed.
4134 It is noted in the status database as being in a
4135 sane state, namely not installed (any conffiles
4136 it may have are ignored, rather than being
4137 removed by <prgn>dpkg</prgn>). Note that
4138 disappearing packages do not have their prerm
4139 called, because <prgn>dpkg</prgn> doesn't know
4140 in advance that the package is going to
4147 Any files in the package we're unpacking that are also
4148 listed in the file lists of other packages are removed
4149 from those lists. (This will lobotomize the file list
4150 of the "conflicting" package if there is one.)
4154 The backup files made during installation, above, are
4160 The new package's status is now sane, and recorded as
4165 Here is another point of no return - if the
4166 conflicting package's removal fails we do not unwind
4167 the rest of the installation; the conflicting package
4168 is left in a half-removed limbo.
4173 If there was a conflicting package we go and do the
4174 removal actions (described below), starting with the
4175 removal of the conflicting package's files (any that
4176 are also in the package being installed have already
4177 been removed from the conflicting package's file list,
4178 and so do not get removed now).
4184 <sect id="configdetails"><heading>Details of configuration</heading>
4187 When we configure a package (this happens with <tt>dpkg
4188 --install</tt> and <tt>dpkg --configure</tt>), we first
4189 update any <tt>conffile</tt>s and then call:
4190 <example compact="compact">
4191 <var>postinst</var> configure <var>most-recently-configured-version</var>
4196 No attempt is made to unwind after errors during
4197 configuration. If the configuration fails, the package is in
4198 a "Failed Config" state, and an error message is generated.
4202 If there is no most recently configured version
4203 <prgn>dpkg</prgn> will pass a null argument.
4206 Historical note: Truly ancient (pre-1997) versions of
4207 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4208 (including the angle brackets) in this case. Even older
4209 ones did not pass a second argument at all, under any
4210 circumstance. Note that upgrades using such an old dpkg
4211 version are unlikely to work for other reasons, even if
4212 this old argument behavior is handled by your postinst script.
4218 <sect id="removedetails"><heading>Details of removal and/or
4219 configuration purging</heading>
4225 <example compact="compact">
4226 <var>prerm</var> remove
4230 If prerm fails during replacement due to conflict
4232 <var>conflictor's-postinst</var> abort-remove \
4233 in-favour <var>package</var> <var>new-version</var>
4237 <var>postinst</var> abort-remove
4241 If this fails, the package is in a "Half-Configured"
4242 state, or else it remains "Installed".
4246 The package's files are removed (except <tt>conffile</tt>s).
4249 <example compact="compact">
4250 <var>postrm</var> remove
4254 If it fails, there's no error unwind, and the package is in
4255 an "Half-Installed" state.
4260 All the maintainer scripts except the <prgn>postrm</prgn>
4265 If we aren't purging the package we stop here. Note
4266 that packages which have no <prgn>postrm</prgn> and no
4267 <tt>conffile</tt>s are automatically purged when
4268 removed, as there is no difference except for the
4269 <prgn>dpkg</prgn> status.
4273 The <tt>conffile</tt>s and any backup files
4274 (<tt>~</tt>-files, <tt>#*#</tt> files,
4275 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4280 <example compact="compact">
4281 <var>postrm</var> purge
4285 If this fails, the package remains in a "Config-Files"
4290 The package's file list is removed.
4299 <chapt id="relationships">
4300 <heading>Declaring relationships between packages</heading>
4302 <sect id="depsyntax">
4303 <heading>Syntax of relationship fields</heading>
4306 These fields all have a uniform syntax. They are a list of
4307 package names separated by commas.
4311 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4312 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4313 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4314 control file fields of the package, which declare
4315 dependencies on other packages, the package names listed may
4316 also include lists of alternative package names, separated
4317 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4318 if any one of the alternative packages is installed, that
4319 part of the dependency is considered to be satisfied.
4323 All of the fields except for <tt>Provides</tt> may restrict
4324 their applicability to particular versions of each named
4325 package. This is done in parentheses after each individual
4326 package name; the parentheses should contain a relation from
4327 the list below followed by a version number, in the format
4328 described in <ref id="f-Version">.
4332 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4333 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4334 strictly earlier, earlier or equal, exactly equal, later or
4335 equal and strictly later, respectively. The deprecated
4336 forms <tt><</tt> and <tt>></tt> were used to mean
4337 earlier/later or equal, rather than strictly earlier/later,
4338 so they should not appear in new packages (though
4339 <prgn>dpkg</prgn> still supports them).
4343 Whitespace may appear at any point in the version
4344 specification subject to the rules in <ref
4345 id="controlsyntax">, and must appear where it's necessary to
4346 disambiguate; it is not otherwise significant. All of the
4347 relationship fields may span multiple lines. For
4348 consistency and in case of future changes to
4349 <prgn>dpkg</prgn> it is recommended that a single space be
4350 used after a version relationship and before a version
4351 number; it is also conventional to put a single space after
4352 each comma, on either side of each vertical bar, and before
4353 each open parenthesis. When wrapping a relationship field, it
4354 is conventional to do so after a comma and before the space
4355 following that comma.
4359 For example, a list of dependencies might appear as:
4360 <example compact="compact">
4363 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4368 All fields that specify build-time relationships
4369 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4370 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>)
4371 may be restricted to a certain set of architectures. This
4372 is indicated in brackets after each individual package name and
4373 the optional version specification. The brackets enclose a
4374 list of Debian architecture names separated by whitespace.
4375 Exclamation marks may be prepended to each of the names.
4376 (It is not permitted for some names to be prepended with
4377 exclamation marks while others aren't.) If the current Debian
4378 host architecture is not in this list and there are no
4379 exclamation marks in the list, or it is in the list with a
4380 prepended exclamation mark, the package name and the
4381 associated version specification are ignored completely for
4382 the purposes of defining the relationships.
4387 <example compact="compact">
4389 Build-Depends-Indep: texinfo
4390 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4391 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4393 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4394 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4395 <tt>gnumach-dev</tt> only on hurd-i386.
4399 If the architecture-restricted dependency is part of a set of
4400 alternatives using <tt>|</tt>, that alternative is ignored
4401 completely on architectures that do not match the restriction.
4403 <example compact="compact">
4404 Build-Depends: foo [!i386] | bar [!amd64]
4406 is equivalent to <tt>bar</tt> on the i386 architecture, to
4407 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4408 bar</tt> on all other architectures.
4412 All fields that specify build-time relationships may also be
4413 restricted to a certain set of architectures using architecture
4414 wildcards. The syntax for declaring such restrictions is the
4415 same as declaring restrictions using a certain set of
4416 architectures without architecture wildcards. For example:
4417 <example compact="compact">
4418 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4420 is equivalent to <tt>foo</tt> on architectures using the Linux
4421 kernel and any cpu, <tt>bar</tt> on architectures using any
4422 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4423 using a kernel other than Linux.
4427 Note that the binary package relationship fields such as
4428 <tt>Depends</tt> appear in one of the binary package
4429 sections of the control file, whereas the build-time
4430 relationships such as <tt>Build-Depends</tt> appear in the
4431 source package section of the control file (which is the
4436 <sect id="binarydeps">
4437 <heading>Binary Dependencies - <tt>Depends</tt>,
4438 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4439 <tt>Pre-Depends</tt>
4443 Packages can declare in their control file that they have
4444 certain relationships to other packages - for example, that
4445 they may not be installed at the same time as certain other
4446 packages, and/or that they depend on the presence of others.
4450 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4451 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4452 <tt>Breaks</tt> and <tt>Conflicts</tt> control file fields.
4453 <tt>Breaks</tt> is described in <ref id="breaks">, and
4454 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4455 rest are described below.
4459 These seven fields are used to declare a dependency
4460 relationship by one package on another. Except for
4461 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4462 depending (binary) package's control file.
4463 (<tt>Enhances</tt> appears in the recommending package's
4464 control file, and <tt>Breaks</tt> appears in the version of
4465 depended-on package which causes the named package to
4470 A <tt>Depends</tt> field takes effect <em>only</em> when a
4471 package is to be configured. It does not prevent a package
4472 being on the system in an unconfigured state while its
4473 dependencies are unsatisfied, and it is possible to replace
4474 a package whose dependencies are satisfied and which is
4475 properly installed with a different version whose
4476 dependencies are not and cannot be satisfied; when this is
4477 done the depending package will be left unconfigured (since
4478 attempts to configure it will give errors) and will not
4479 function properly. If it is necessary, a
4480 <tt>Pre-Depends</tt> field can be used, which has a partial
4481 effect even when a package is being unpacked, as explained
4482 in detail below. (The other three dependency fields,
4483 <tt>Recommends</tt>, <tt>Suggests</tt> and
4484 <tt>Enhances</tt>, are only used by the various front-ends
4485 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4486 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4490 For this reason packages in an installation run are usually
4491 all unpacked first and all configured later; this gives
4492 later versions of packages with dependencies on later
4493 versions of other packages the opportunity to have their
4494 dependencies satisfied.
4498 In case of circular dependencies, since installation or
4499 removal order honoring the dependency order can't be
4500 established, dependency loops are broken at some point
4501 (based on rules below), and some packages may not be able to
4502 rely on their dependencies being present when being
4503 installed or removed, depending on which side of the break
4504 of the circular dependency loop they happen to be on. If one
4505 of the packages in the loop has no postinst script, then the
4506 cycle will be broken at that package, so as to ensure that
4507 all postinst scripts run with the dependencies properly
4508 configured if this is possible. Otherwise the breaking point
4513 The <tt>Depends</tt> field thus allows package maintainers
4514 to impose an order in which packages should be configured.
4518 The meaning of the five dependency fields is as follows:
4520 <tag><tt>Depends</tt></tag>
4523 This declares an absolute dependency. A package will
4524 not be configured unless all of the packages listed in
4525 its <tt>Depends</tt> field have been correctly
4530 The <tt>Depends</tt> field should be used if the
4531 depended-on package is required for the depending
4532 package to provide a significant amount of
4537 The <tt>Depends</tt> field should also be used if the
4538 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4539 <prgn>postrm</prgn> scripts require the package to be
4540 present in order to run. Note, however, that the
4541 <prgn>postrm</prgn> cannot rely on any non-essential
4542 packages to be present during the <tt>purge</tt>
4546 <tag><tt>Recommends</tt></tag>
4549 This declares a strong, but not absolute, dependency.
4553 The <tt>Recommends</tt> field should list packages
4554 that would be found together with this one in all but
4555 unusual installations.
4559 <tag><tt>Suggests</tt></tag>
4561 This is used to declare that one package may be more
4562 useful with one or more others. Using this field
4563 tells the packaging system and the user that the
4564 listed packages are related to this one and can
4565 perhaps enhance its usefulness, but that installing
4566 this one without them is perfectly reasonable.
4569 <tag><tt>Enhances</tt></tag>
4571 This field is similar to Suggests but works in the
4572 opposite direction. It is used to declare that a
4573 package can enhance the functionality of another
4577 <tag><tt>Pre-Depends</tt></tag>
4580 This field is like <tt>Depends</tt>, except that it
4581 also forces <prgn>dpkg</prgn> to complete installation
4582 of the packages named before even starting the
4583 installation of the package which declares the
4584 pre-dependency, as follows:
4588 When a package declaring a pre-dependency is about to
4589 be <em>unpacked</em> the pre-dependency can be
4590 satisfied if the depended-on package is either fully
4591 configured, <em>or even if</em> the depended-on
4592 package(s) are only unpacked or in the "Half-Configured"
4593 state, provided that they have been configured
4594 correctly at some point in the past (and not removed
4595 or partially removed since). In this case, both the
4596 previously-configured and currently unpacked or
4597 "Half-Configured" versions must satisfy any version
4598 clause in the <tt>Pre-Depends</tt> field.
4602 When the package declaring a pre-dependency is about
4603 to be <em>configured</em>, the pre-dependency will be
4604 treated as a normal <tt>Depends</tt>, that is, it will
4605 be considered satisfied only if the depended-on
4606 package has been correctly configured.
4610 <tt>Pre-Depends</tt> should be used sparingly,
4611 preferably only by packages whose premature upgrade or
4612 installation would hamper the ability of the system to
4613 continue with any upgrade that might be in progress.
4617 <tt>Pre-Depends</tt> are also required if the
4618 <prgn>preinst</prgn> script depends on the named
4619 package. It is best to avoid this situation if
4627 When selecting which level of dependency to use you should
4628 consider how important the depended-on package is to the
4629 functionality of the one declaring the dependency. Some
4630 packages are composed of components of varying degrees of
4631 importance. Such a package should list using
4632 <tt>Depends</tt> the package(s) which are required by the
4633 more important components. The other components'
4634 requirements may be mentioned as Suggestions or
4635 Recommendations, as appropriate to the components' relative
4641 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4644 When one binary package declares that it breaks another,
4645 <prgn>dpkg</prgn> will refuse to allow the package which
4646 declares <tt>Breaks</tt> be installed unless the broken
4647 package is deconfigured first, and it will refuse to
4648 allow the broken package to be reconfigured.
4652 A package will not be regarded as causing breakage merely
4653 because its configuration files are still installed; it must
4654 be at least "Half-Installed".
4658 A special exception is made for packages which declare that
4659 they break their own package name or a virtual package which
4660 they provide (see below): this does not count as a real
4665 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4666 version clause; such a <tt>Breaks</tt> is introduced in the
4667 version of an (implicit or explicit) dependency which violates
4668 an assumption or reveals a bug in earlier versions of the broken
4669 package, or which takes over a file from earlier versions of the
4670 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
4671 will inform higher-level package management tools that the
4672 broken package must be upgraded before the new one.
4676 If the breaking package also overwrites some files from the
4677 older package, it should use <tt>Replaces</tt> to ensure this
4678 goes smoothly. See <ref id="replaces"> for a full discussion
4679 of taking over files from other packages, including how to
4680 use <tt>Breaks</tt> in those cases.
4684 Many of the cases where <tt>Breaks</tt> should be used were
4685 previously handled with <tt>Conflicts</tt>
4686 because <tt>Breaks</tt> did not yet exist.
4687 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
4688 See <ref id="conflicts"> for more information about the
4693 <sect id="conflicts">
4694 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4697 When one binary package declares a conflict with another
4698 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4699 refuse to allow them to be installed on the system at the
4700 same time. This is a stronger restriction than <tt>Breaks</tt>,
4701 which just prevents both packages from being configured at the
4702 same time. Conflicting packages cannot be unpacked on the
4703 system at the same time.
4707 If one package is to be installed, the other must be removed
4708 first. If the package being installed is marked as replacing
4709 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
4710 normally be used in this case) the one on the system, or the one
4711 on the system is marked as deselected, or both packages are
4712 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
4713 automatically remove the package which is causing the conflict.
4714 Otherwise, it will halt the installation of the new package with
4715 an error. This mechanism is specifically designed to produce an
4716 error when the installed package is <tt>Essential</tt>, but the
4721 A package will not cause a conflict merely because its
4722 configuration files are still installed; it must be at least
4727 A special exception is made for packages which declare a
4728 conflict with their own package name, or with a virtual
4729 package which they provide (see below): this does not
4730 prevent their installation, and allows a package to conflict
4731 with others providing a replacement for it. You use this
4732 feature when you want the package in question to be the only
4733 package providing some feature.
4737 Normally, <tt>Breaks</tt> should be used instead
4738 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
4739 stronger restriction on the ordering of package installation or
4740 upgrade and can make it more difficult for the package manager
4741 to find a correct solution to an upgrade or installation
4742 problem. <tt>Breaks</tt> should be used
4744 <item>when moving a file from one package to another (see
4745 <ref id="replaces">),</item>
4746 <item>when splitting a package (a special case of the previous
4748 <item>when the breaking package exposes a bug in or interacts
4749 badly with particular versions of the broken
4752 <tt>Conflicts</tt> should be used
4754 <item>when two packages provide the same file and will
4755 continue to do so,</item>
4756 <item>in conjunction with <tt>Provides</tt> when only one
4757 package providing a given virtual facility may be installed
4758 at a time (see <ref id="virtual">),</item>
4759 <item>in other cases where one must prevent simultaneous
4760 installation of two packages for reasons that are ongoing
4761 (not fixed in a later version of one of the packages) or
4762 that must prevent both packages from being unpacked at the
4763 same time, not just configured.</item>
4765 Be aware that adding <tt>Conflicts</tt> is normally not the best
4766 solution when two packages provide the same files. Depending on
4767 the reason for that conflict, using alternatives or renaming the
4768 files is often a better approach. See, for
4769 example, <ref id="binaries">.
4773 A <tt>Conflicts</tt> entry may have an "earlier than" version
4774 clause if the reason for the conflict is corrected in a later
4775 version of one of the packages. However, normally the presence
4776 of an "earlier than" version clause is a sign
4777 that <tt>Breaks</tt> should have been used instead. An "earlier
4778 than" version clause in <tt>Conflicts</tt>
4779 prevents <prgn>dpkg</prgn> from upgrading or installing the
4780 package which declares such a conflict until the upgrade or
4781 removal of the conflicted-with package has been completed, which
4782 is a strong restriction.
4786 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4790 As well as the names of actual ("concrete") packages, the
4791 package relationship fields <tt>Depends</tt>,
4792 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4793 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4794 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4795 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4796 may mention "virtual packages".
4800 A <em>virtual package</em> is one which appears in the
4801 <tt>Provides</tt> control file field of another package.
4802 The effect is as if the package(s) which provide a
4803 particular virtual package name had been listed by name
4804 everywhere the virtual package name appears. (See also <ref
4809 If there are both concrete and virtual packages of the same
4810 name, then the dependency may be satisfied (or the conflict
4811 caused) by either the concrete package with the name in
4812 question or any other concrete package which provides the
4813 virtual package with the name in question. This is so that,
4814 for example, supposing we have
4815 <example compact="compact">
4818 </example> and someone else releases an enhanced version of
4819 the <tt>bar</tt> package they can say:
4820 <example compact="compact">
4824 and the <tt>bar-plus</tt> package will now also satisfy the
4825 dependency for the <tt>foo</tt> package.
4829 If a relationship field has a version number attached, only real
4830 packages will be considered to see whether the relationship is
4831 satisfied (or the prohibition violated, for a conflict or
4832 breakage). In other words, if a version number is specified,
4833 this is a request to ignore all <tt>Provides</tt> for that
4834 package name and consider only real packages. The package
4835 manager will assume that a package providing that virtual
4836 package is not of the "right" version. A <tt>Provides</tt>
4837 field may not contain version numbers, and the version number of
4838 the concrete package which provides a particular virtual package
4839 will not be considered when considering a dependency on or
4840 conflict with the virtual package name.<footnote>
4841 It is possible that a future release of <prgn>dpkg</prgn> may
4842 add the ability to specify a version number for each virtual
4843 package it provides. This feature is not yet present,
4844 however, and is expected to be used only infrequently.
4849 To specify which of a set of real packages should be the default
4850 to satisfy a particular dependency on a virtual package, list
4851 the real package as an alternative before the virtual one.
4855 If the virtual package represents a facility that can only be
4856 provided by one real package at a time, such as
4857 the <package>mail-transport-agent</package> virtual package that
4858 requires installation of a binary that would conflict with all
4859 other providers of that virtual package (see
4860 <ref id="mail-transport-agents">), all packages providing that
4861 virtual package should also declare a conflict with it
4862 using <tt>Conflicts</tt>. This will ensure that at most one
4863 provider of that virtual package is unpacked or installed at a
4868 <sect id="replaces"><heading>Overwriting files and replacing
4869 packages - <tt>Replaces</tt></heading>
4872 Packages can declare in their control file that they should
4873 overwrite files in certain other packages, or completely
4874 replace other packages. The <tt>Replaces</tt> control file
4875 field has these two distinct purposes.
4878 <sect1><heading>Overwriting files in other packages</heading>
4881 It is usually an error for a package to contain files which
4882 are on the system in another package. However, if the
4883 overwriting package declares that it <tt>Replaces</tt> the one
4884 containing the file being overwritten, then <prgn>dpkg</prgn>
4885 will replace the file from the old package with that from the
4886 new. The file will no longer be listed as "owned" by the old
4887 package and will be taken over by the new package.
4888 Normally, <tt>Breaks</tt> should be used in conjunction
4889 with <tt>Replaces</tt>.<footnote>
4890 To see why <tt>Breaks</tt> is normally needed in addition
4891 to <tt>Replaces</tt>, consider the case of a file in the
4892 package <package>foo</package> being taken over by the
4893 package <package>foo-data</package>.
4894 <tt>Replaces</tt> will allow <package>foo-data</package> to
4895 be installed and take over that file. However,
4896 without <tt>Breaks</tt>, nothing
4897 requires <package>foo</package> to be upgraded to a newer
4898 version that knows it does not include that file and instead
4899 depends on <package>foo-data</package>. Nothing would
4900 prevent the new <package>foo-data</package> package from
4901 being installed and then removed, removing the file that it
4902 took over from <package>foo</package>. After that
4903 operation, the package manager would think the system was in
4904 a consistent state, but the <package>foo</package> package
4905 would be missing one of its files.
4910 For example, if a package <package>foo</package> is split
4911 into <package>foo</package> and <package>foo-data</package>
4912 starting at version 1.2-3, <package>foo-data</package> would
4914 <example compact="compact">
4915 Replaces: foo (<< 1.2-3)
4916 Breaks: foo (<< 1.2-3)
4918 in its control file. The new version of the
4919 package <package>foo</package> would normally have the field
4920 <example compact="compact">
4921 Depends: foo-data (>= 1.2-3)
4923 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
4924 the files moved into <package>foo-data</package> are not
4925 required for normal operation).
4929 If a package is completely replaced in this way, so that
4930 <prgn>dpkg</prgn> does not know of any files it still
4931 contains, it is considered to have "disappeared". It will
4932 be marked as not wanted on the system (selected for
4933 removal) and not installed. Any <tt>conffile</tt>s
4934 details noted for the package will be ignored, as they
4935 will have been taken over by the overwriting package. The
4936 package's <prgn>postrm</prgn> script will be run with a
4937 special argument to allow the package to do any final
4938 cleanup required. See <ref id="mscriptsinstact">.
4940 Replaces is a one way relationship. You have to install
4941 the replacing package after the replaced package.
4946 For this usage of <tt>Replaces</tt>, virtual packages (see
4947 <ref id="virtual">) are not considered when looking at a
4948 <tt>Replaces</tt> field. The packages declared as being
4949 replaced must be mentioned by their real names.
4953 This usage of <tt>Replaces</tt> only takes effect when both
4954 packages are at least partially on the system at once. It is
4955 not relevant if the packages conflict unless the conflict has
4960 <sect1><heading>Replacing whole packages, forcing their
4964 Second, <tt>Replaces</tt> allows the packaging system to
4965 resolve which package should be removed when there is a
4966 conflict (see <ref id="conflicts">). This usage only takes
4967 effect when the two packages <em>do</em> conflict, so that the
4968 two usages of this field do not interfere with each other.
4972 In this situation, the package declared as being replaced
4973 can be a virtual package, so for example, all mail
4974 transport agents (MTAs) would have the following fields in
4975 their control files:
4976 <example compact="compact">
4977 Provides: mail-transport-agent
4978 Conflicts: mail-transport-agent
4979 Replaces: mail-transport-agent
4981 ensuring that only one MTA can be installed at any one
4982 time. See <ref id="virtual"> for more information about this
4987 <sect id="sourcebinarydeps">
4988 <heading>Relationships between source and binary packages -
4989 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4990 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
4994 Source packages that require certain binary packages to be
4995 installed or absent at the time of building the package
4996 can declare relationships to those binary packages.
5000 This is done using the <tt>Build-Depends</tt>,
5001 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5002 <tt>Build-Conflicts-Indep</tt> control file fields.
5006 Build-dependencies on "build-essential" binary packages can be
5007 omitted. Please see <ref id="pkg-relations"> for more information.
5011 The dependencies and conflicts they define must be satisfied
5012 (as defined earlier for binary packages) in order to invoke
5013 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5015 There is no Build-Depends-Arch; this role is essentially
5016 met with Build-Depends. Anyone building the
5017 <tt>build-indep</tt> and binary-indep<tt></tt> targets is
5018 assumed to be building the whole package, and therefore
5019 installation of all build dependencies is required.
5022 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5023 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5024 not yet know how to check for its existence, and
5025 <tt>binary-arch</tt>. The purpose of the original split
5026 between <tt>Build-Depends</tt> and
5027 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5028 wouldn't need to install extra packages needed only for the
5029 binary-indep targets. But without a build-arch/build-indep
5030 split, this didn't work, since most of the work is done in
5031 the build target, not in the binary target.
5035 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5036 <tt>binary-arch</tt></tag>
5038 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5039 fields must be satisfied when these targets are invoked.
5041 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5042 and <tt>binary-indep</tt></tag>
5044 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5045 <tt>Build-Depends-Indep</tt>, and
5046 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5047 these targets are invoked.
5055 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5058 Packages containing shared libraries must be constructed with
5059 a little care to make sure that the shared library is always
5060 available. This is especially important for packages whose
5061 shared libraries are vitally important, such as the C library
5062 (currently <tt>libc6</tt>).
5066 Packages involving shared libraries should be split up into
5067 several binary packages. This section mostly deals with how
5068 this separation is to be accomplished; rules for files within
5069 the shared library packages are in <ref id="libraries"> instead.
5072 <sect id="sharedlibs-runtime">
5073 <heading>Run-time shared libraries</heading>
5076 The run-time shared library needs to be placed in a package
5077 whose name changes whenever the shared object version
5080 Since it is common place to install several versions of a
5081 package that just provides shared libraries, it is a
5082 good idea that the library package should not
5083 contain any extraneous non-versioned files, unless they
5084 happen to be in versioned directories.</p>
5086 The most common mechanism is to place it in a package
5088 <package><var>libraryname</var><var>soversion</var></package>,
5089 where <file><var>soversion</var></file> is the version number
5090 in the soname of the shared library<footnote>
5091 The soname is the shared object name: it's the thing
5092 that has to match exactly between building an executable
5093 and running it for the dynamic linker to be able run the
5094 program. For example, if the soname of the library is
5095 <file>libfoo.so.6</file>, the library package would be
5096 called <file>libfoo6</file>.
5098 Alternatively, if it would be confusing to directly append
5099 <var>soversion</var> to <var>libraryname</var> (e.g. because
5100 <var>libraryname</var> itself ends in a number), you may use
5101 <package><var>libraryname</var>-<var>soversion</var></package> and
5102 <package><var>libraryname</var>-<var>soversion</var>-dev</package>
5107 If you have several shared libraries built from the same
5108 source tree you may lump them all together into a single
5109 shared library package, provided that you change all of
5110 their sonames at once (so that you don't get filename
5111 clashes if you try to install different versions of the
5112 combined shared libraries package).
5116 The package should install the shared libraries under
5117 their normal names. For example, the <package>libgdbm3</package>
5118 package should install <file>libgdbm.so.3.0.0</file> as
5119 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5120 renamed or re-linked by any <prgn>prerm</prgn> or
5121 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5122 of renaming things safely without affecting running programs,
5123 and attempts to interfere with this are likely to lead to
5128 Shared libraries should not be installed executable, since
5129 the dynamic linker does not require this and trying to
5130 execute a shared library usually results in a core dump.
5134 The run-time library package should include the symbolic link that
5135 <prgn>ldconfig</prgn> would create for the shared libraries.
5136 For example, the <package>libgdbm3</package> package should include
5137 a symbolic link from <file>/usr/lib/libgdbm.so.3</file> to
5138 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5139 linker (for example <prgn>ld.so</prgn> or
5140 <prgn>ld-linux.so.*</prgn>) can find the library between the
5141 time that <prgn>dpkg</prgn> installs it and the time that
5142 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5144 The package management system requires the library to be
5145 placed before the symbolic link pointing to it in the
5146 <file>.deb</file> file. This is so that when
5147 <prgn>dpkg</prgn> comes to install the symlink
5148 (overwriting the previous symlink pointing at an older
5149 version of the library), the new shared library is already
5150 in place. In the past, this was achieved by creating the
5151 library in the temporary packaging directory before
5152 creating the symlink. Unfortunately, this was not always
5153 effective, since the building of the tar file in the
5154 <file>.deb</file> depended on the behavior of the underlying
5155 file system. Some file systems (such as reiserfs) reorder
5156 the files so that the order of creation is forgotten.
5157 Since version 1.7.0, <prgn>dpkg</prgn>
5158 reorders the files itself as necessary when building a
5159 package. Thus it is no longer important to concern
5160 oneself with the order of file creation.
5164 <sect1 id="ldconfig">
5165 <heading><tt>ldconfig</tt></heading>
5168 Any package installing shared libraries in one of the default
5169 library directories of the dynamic linker (which are currently
5170 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5171 listed in <file>/etc/ld.so.conf</file><footnote>
5173 <list compact="compact">
5174 <item>/usr/local/lib</item>
5175 <item>/usr/lib/libc5-compat</item>
5176 <item>/lib/libc5-compat</item>
5179 must use <prgn>ldconfig</prgn> to update the shared library
5184 The package maintainer scripts must only call
5185 <prgn>ldconfig</prgn> under these circumstances:
5186 <list compact="compact">
5187 <item>When the <prgn>postinst</prgn> script is run with a
5188 first argument of <tt>configure</tt>, the script must call
5189 <prgn>ldconfig</prgn>, and may optionally invoke
5190 <prgn>ldconfig</prgn> at other times.
5192 <item>When the <prgn>postrm</prgn> script is run with a
5193 first argument of <tt>remove</tt>, the script should call
5194 <prgn>ldconfig</prgn>.
5199 During install or upgrade, the preinst is called before
5200 the new files are installed, so calling "ldconfig" is
5201 pointless. The preinst of an existing package can also be
5202 called if an upgrade fails. However, this happens during
5203 the critical time when a shared libs may exist on-disk
5204 under a temporary name. Thus, it is dangerous and
5205 forbidden by current policy to call "ldconfig" at this
5210 When a package is installed or upgraded, "postinst
5211 configure" runs after the new files are safely on-disk.
5212 Since it is perfectly safe to invoke ldconfig
5213 unconditionally in a postinst, it is OK for a package to
5214 simply put ldconfig in its postinst without checking the
5215 argument. The postinst can also be called to recover from
5216 a failed upgrade. This happens before any new files are
5217 unpacked, so there is no reason to call "ldconfig" at this
5222 For a package that is being removed, prerm is
5223 called with all the files intact, so calling ldconfig is
5224 useless. The other calls to "prerm" happen in the case of
5225 upgrade at a time when all the files of the old package
5226 are on-disk, so again calling "ldconfig" is pointless.
5230 postrm, on the other hand, is called with the "remove"
5231 argument just after the files are removed, so this is
5232 the proper time to call "ldconfig" to notify the system
5233 of the fact that the shared libraries from the package
5234 are removed. The postrm can be called at several other
5235 times. At the time of "postrm purge", "postrm
5236 abort-install", or "postrm abort-upgrade", calling
5237 "ldconfig" is useless because the shared lib files are
5238 not on-disk. However, when "postrm" is invoked with
5239 arguments "upgrade", "failed-upgrade", or "disappear", a
5240 shared lib may exist on-disk under a temporary filename.
5248 <sect id="sharedlibs-support-files">
5249 <heading>Shared library support files</heading>
5252 If your package contains files whose names do not change with
5253 each change in the library shared object version, you must not
5254 put them in the shared library package. Otherwise, several
5255 versions of the shared library cannot be installed at the same
5256 time without filename clashes, making upgrades and transitions
5257 unnecessarily difficult.
5261 It is recommended that supporting files and run-time support
5262 programs that do not need to be invoked manually by users, but
5263 are nevertheless required for the package to function, be placed
5264 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5265 preferably under <file>/usr/lib/</file><var>package-name</var>.
5266 If the program or file is architecture independent, the
5267 recommendation is for it to be placed in a subdirectory of
5268 <file>/usr/share</file> instead, preferably under
5269 <file>/usr/share/</file><var>package-name</var>. Following the
5270 <var>package-name</var> naming convention ensures that the file
5271 names change when the shared object version changes.
5275 Run-time support programs that use the shared library but are
5276 not required for the library to function or files used by the
5277 shared library that can be used by any version of the shared
5278 library package should instead be put in a separate package.
5279 This package might typically be named
5280 <package><var>libraryname</var>-tools</package>; note the
5281 absence of the <var>soversion</var> in the package name.
5285 Files and support programs only useful when compiling software
5286 against the library should be included in the development
5287 package for the library.<footnote>
5288 For example, a <file><var>package-name</var>-config</file>
5289 script or <package>pkg-config</package> configuration files.
5294 <sect id="sharedlibs-static">
5295 <heading>Static libraries</heading>
5298 The static library (<file><var>libraryname.a</var></file>)
5299 is usually provided in addition to the shared version.
5300 It is placed into the development package (see below).
5304 In some cases, it is acceptable for a library to be
5305 available in static form only; these cases include:
5307 <item>libraries for languages whose shared library support
5308 is immature or unstable</item>
5309 <item>libraries whose interfaces are in flux or under
5310 development (commonly the case when the library's
5311 major version number is zero, or where the ABI breaks
5312 across patchlevels)</item>
5313 <item>libraries which are explicitly intended to be
5314 available only in static form by their upstream
5319 <sect id="sharedlibs-dev">
5320 <heading>Development files</heading>
5323 If there are development files associated with a shared library,
5324 the source package needs to generate a binary development package
5325 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5326 or if you prefer only to support one development version at a
5327 time, <package><var>libraryname</var>-dev</package>. Installing
5328 the development package must result in installation of all the
5329 development files necessary for compiling programs against that
5330 shared library.<footnote>
5331 This wording allows the development files to be split into
5332 several packages, such as a separate architecture-independent
5333 <package><var>libraryname</var>-headers</package>, provided that
5334 the development package depends on all the required additional
5340 In case several development versions of a library exist, you may
5341 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5342 <ref id="conflicts">) to ensure that the user only installs one
5343 development version at a time (as different development versions are
5344 likely to have the same header files in them, which would cause a
5345 filename clash if both were installed).
5349 The development package should contain a symlink for the associated
5350 shared library without a version number. For example, the
5351 <package>libgdbm-dev</package> package should include a symlink
5352 from <file>/usr/lib/libgdbm.so</file> to
5353 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5354 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5355 <file>libgdbm.so</file> when compiling dynamically.
5359 <sect id="sharedlibs-intradeps">
5360 <heading>Dependencies between the packages of the same library</heading>
5363 Typically the development version should have an exact
5364 version dependency on the runtime library, to make sure that
5365 compilation and linking happens correctly. The
5366 <tt>${binary:Version}</tt> substitution variable can be
5367 useful for this purpose.
5369 Previously, <tt>${Source-Version}</tt> was used, but its name
5370 was confusing and it has been deprecated since dpkg 1.13.19.
5375 <sect id="sharedlibs-shlibdeps">
5376 <heading>Dependencies between the library and other packages -
5377 the <tt>shlibs</tt> system</heading>
5380 If a package contains a binary or library which links to a
5381 shared library, we must ensure that when the package is
5382 installed on the system, all of the libraries needed are
5383 also installed. This requirement led to the creation of the
5384 <tt>shlibs</tt> system, which is very simple in its design:
5385 any package which <em>provides</em> a shared library also
5386 provides information on the package dependencies required to
5387 ensure the presence of this library, and any package which
5388 <em>uses</em> a shared library uses this information to
5389 determine the dependencies it requires. The files which
5390 contain the mapping from shared libraries to the necessary
5391 dependency information are called <file>shlibs</file> files.
5395 Thus, when a package is built which contains any shared
5396 libraries, it must provide a <file>shlibs</file> file for other
5397 packages to use, and when a package is built which contains
5398 any shared libraries or compiled binaries, it must run
5399 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5400 on these to determine the libraries used and hence the
5401 dependencies needed by this package.<footnote>
5403 In the past, the shared libraries linked to were
5404 determined by calling <prgn>ldd</prgn>, but now
5405 <prgn>objdump</prgn> is used to do this. The only
5406 change this makes to package building is that
5407 <prgn>dpkg-shlibdeps</prgn> must also be run on shared
5408 libraries, whereas in the past this was unnecessary.
5409 The rest of this footnote explains the advantage that
5414 We say that a binary <tt>foo</tt> <em>directly</em> uses
5415 a library <tt>libbar</tt> if it is explicitly linked
5416 with that library (that is, it uses the flag
5417 <tt>-lbar</tt> during the linking stage). Other
5418 libraries that are needed by <tt>libbar</tt> are linked
5419 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5420 linker will load them automatically when it loads
5421 <tt>libbar</tt>. A package should depend on
5422 the libraries it directly uses, and the dependencies for
5423 those libraries should automatically pull in the other
5428 Unfortunately, the <prgn>ldd</prgn> program shows both
5429 the directly and indirectly used libraries, meaning that
5430 the dependencies determined included both direct and
5431 indirect dependencies. The use of <prgn>objdump</prgn>
5432 avoids this problem by determining only the directly
5437 A good example of where this helps is the following. We
5438 could update <tt>libimlib</tt> with a new version that
5439 supports a new graphics format called dgf (but retaining
5440 the same major version number). If we used the old
5441 <prgn>ldd</prgn> method, every package that uses
5442 <tt>libimlib</tt> would need to be recompiled so it
5443 would also depend on <tt>libdgf</tt> or it wouldn't run
5444 due to missing symbols. However with the new system,
5445 packages using <tt>libimlib</tt> can rely on
5446 <tt>libimlib</tt> itself having the dependency on
5447 <tt>libdgf</tt> and so they would not need rebuilding.
5453 In the following sections, we will first describe where the
5454 various <tt>shlibs</tt> files are to be found, then how to
5455 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5456 file format and how to create them if your package contains a
5461 <heading>The <tt>shlibs</tt> files present on the system</heading>
5464 There are several places where <tt>shlibs</tt> files are
5465 found. The following list gives them in the order in which
5467 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5468 (The first one which gives the required information is used.)
5474 <p><file>debian/shlibs.local</file></p>
5477 This lists overrides for this package. Its use is
5478 described below (see <ref id="shlibslocal">).
5483 <p><file>/etc/dpkg/shlibs.override</file></p>
5486 This lists global overrides. This list is normally
5487 empty. It is maintained by the local system
5493 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5496 When packages are being built, any
5497 <file>debian/shlibs</file> files are copied into the
5498 control file area of the temporary build directory and
5499 given the name <file>shlibs</file>. These files give
5500 details of any shared libraries included in the
5502 An example may help here. Let us say that the
5503 source package <tt>foo</tt> generates two binary
5504 packages, <tt>libfoo2</tt> and
5505 <tt>foo-runtime</tt>. When building the binary
5506 packages, the two packages are created in the
5507 directories <file>debian/libfoo2</file> and
5508 <file>debian/foo-runtime</file> respectively.
5509 (<file>debian/tmp</file> could be used instead of one
5510 of these.) Since <tt>libfoo2</tt> provides the
5511 <tt>libfoo</tt> shared library, it will require a
5512 <tt>shlibs</tt> file, which will be installed in
5513 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually
5515 <file>/var/lib/dpkg/info/libfoo2.shlibs</file>. Then
5516 when <prgn>dpkg-shlibdeps</prgn> is run on the
5518 <file>debian/foo-runtime/usr/bin/foo-prog</file>, it
5520 <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5521 determine whether <tt>foo-prog</tt>'s library
5522 dependencies are satisfied by any of the libraries
5523 provided by <tt>libfoo2</tt>. For this reason,
5524 <prgn>dpkg-shlibdeps</prgn> must only be run once
5525 all of the individual binary packages'
5526 <tt>shlibs</tt> files have been installed into the
5533 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5536 These are the <file>shlibs</file> files corresponding to
5537 all of the packages installed on the system, and are
5538 maintained by the relevant package maintainers.
5543 <p><file>/etc/dpkg/shlibs.default</file></p>
5546 This file lists any shared libraries whose packages
5547 have failed to provide correct <file>shlibs</file> files.
5548 It was used when the <file>shlibs</file> setup was first
5549 introduced, but it is now normally empty. It is
5550 maintained by the <tt>dpkg</tt> maintainer.
5558 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5559 <file>shlibs</file> files</heading>
5563 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5564 into your <file>debian/rules</file> file. If your package
5565 contains only compiled binaries and libraries (but no scripts),
5566 you can use a command such as:
5567 <example compact="compact">
5568 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5569 debian/tmp/usr/lib/*
5571 Otherwise, you will need to explicitly list the compiled
5572 binaries and libraries.<footnote>
5573 If you are using <tt>debhelper</tt>, the
5574 <prgn>dh_shlibdeps</prgn> program will do this work for
5575 you. It will also correctly handle multi-binary
5581 This command puts the dependency information into the
5582 <file>debian/substvars</file> file, which is then used by
5583 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5584 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5585 field in the control file for this to work.
5589 If <prgn>dpkg-shlibdeps</prgn> doesn't complain, you're
5590 done. If it does complain you might need to create your own
5591 <file>debian/shlibs.local</file> file, as explained below (see
5592 <ref id="shlibslocal">).
5596 If you have multiple binary packages, you will need to call
5597 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5598 compiled libraries or binaries. In such a case, you will
5599 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5600 utilities to specify a different <file>substvars</file> file.
5604 If you are creating a udeb for use in the Debian Installer,
5605 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
5606 should use the dependency line of type <tt>udeb</tt> by
5607 adding the <tt>-tudeb</tt> option<footnote>
5608 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5609 will automatically add this option if it knows it is
5611 </footnote>. If there is no dependency line of type <tt>udeb</tt>
5612 in the <file>shlibs</file> file, <prgn>dpkg-shlibdeps</prgn> will
5613 fall back to the regular dependency line.
5617 For more details on dpkg-shlibdeps, please see
5618 <ref id="pkg-dpkg-shlibdeps"> and
5619 <manref name="dpkg-shlibdeps" section="1">.
5624 <heading>The <file>shlibs</file> File Format</heading>
5627 Each <file>shlibs</file> file has the same format. Lines
5628 beginning with <tt>#</tt> are considered to be comments and
5629 are ignored. Each line is of the form:
5630 <example compact="compact">
5631 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5636 We will explain this by reference to the example of the
5637 <tt>zlib1g</tt> package, which (at the time of writing)
5638 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5642 <var>type</var> is an optional element that indicates the type
5643 of package for which the line is valid. The only type currently
5644 in use is <tt>udeb</tt>. The colon and space after the type are
5649 <var>library-name</var> is the name of the shared library,
5650 in this case <tt>libz</tt>. (This must match the name part
5651 of the soname, see below.)
5655 <var>soname-version</var> is the version part of the soname of
5656 the library. The soname is the thing that must exactly match
5657 for the library to be recognized by the dynamic linker, and is
5659 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5660 example, <tt>libz.so.1</tt>.<footnote>
5661 This can be determined using the command
5662 <example compact="compact">
5663 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5666 The version part is the part which comes after
5667 <tt>.so.</tt>, so in our case, it is <tt>1</tt>.
5671 <var>dependencies</var> has the same syntax as a dependency
5672 field in a binary package control file. It should give
5673 details of which packages are required to satisfy a binary
5674 built against the version of the library contained in the
5675 package. See <ref id="depsyntax"> for details.
5679 In our example, if the first version of the <tt>zlib1g</tt>
5680 package which contained a minor number of at least
5681 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5682 <tt>shlibs</tt> entry for this library could say:
5683 <example compact="compact">
5684 libz 1 zlib1g (>= 1:1.1.3)
5686 The version-specific dependency is to avoid warnings from
5687 the dynamic linker about using older shared libraries with
5692 As zlib1g also provides a udeb containing the shared library,
5693 there would also be a second line:
5694 <example compact="compact">
5695 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5701 <heading>Providing a <file>shlibs</file> file</heading>
5704 If your package provides a shared library, you need to create
5705 a <file>shlibs</file> file following the format described above.
5706 It is usual to call this file <file>debian/shlibs</file> (but if
5707 you have multiple binary packages, you might want to call it
5708 <file>debian/shlibs.<var>package</var></file> instead). Then
5709 let <file>debian/rules</file> install it in the control area:
5710 <example compact="compact">
5711 install -m644 debian/shlibs debian/tmp/DEBIAN
5713 or, in the case of a multi-binary package:
5714 <example compact="compact">
5715 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5717 An alternative way of doing this is to create the
5718 <file>shlibs</file> file in the control area directly from
5719 <file>debian/rules</file> without using a <file>debian/shlibs</file>
5720 file at all,<footnote>
5721 This is what <prgn>dh_makeshlibs</prgn> in the
5722 <tt>debhelper</tt> suite does. If your package also has a udeb
5723 that provides a shared library, <prgn>dh_makeshlibs</prgn> can
5724 automatically generate the <tt>udeb:</tt> lines if you specify
5725 the name of the udeb with the <tt>--add-udeb</tt> option.
5727 since the <file>debian/shlibs</file> file itself is ignored by
5728 <prgn>dpkg-shlibdeps</prgn>.
5732 As <prgn>dpkg-shlibdeps</prgn> reads the
5733 <file>DEBIAN/shlibs</file> files in all of the binary packages
5734 being built from this source package, all of the
5735 <file>DEBIAN/shlibs</file> files should be installed before
5736 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5741 <sect1 id="shlibslocal">
5742 <heading>Writing the <file>debian/shlibs.local</file> file</heading>
5745 This file is intended only as a <em>temporary</em> fix if
5746 your binaries or libraries depend on a library whose package
5747 does not yet provide a correct <file>shlibs</file> file.
5751 We will assume that you are trying to package a binary
5752 <tt>foo</tt>. When you try running
5753 <prgn>dpkg-shlibdeps</prgn> you get the following error
5754 message (<tt>-O</tt> displays the dependency information on
5755 <tt>stdout</tt> instead of writing it to
5756 <tt>debian/substvars</tt>, and the lines have been wrapped
5757 for ease of reading):
5758 <example compact="compact">
5759 $ dpkg-shlibdeps -O debian/tmp/usr/bin/foo
5760 dpkg-shlibdeps: warning: unable to find dependency
5761 information for shared library libbar (soname 1,
5762 path /usr/lib/libbar.so.1, dependency field Depends)
5763 shlibs:Depends=libc6 (>= 2.2.2-2)
5765 You can then run <prgn>ldd</prgn> on the binary to find the
5766 full location of the library concerned:
5767 <example compact="compact">
5769 libbar.so.1 => /usr/lib/libbar.so.1 (0x4001e000)
5770 libc.so.6 => /lib/libc.so.6 (0x40032000)
5771 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
5773 So the <prgn>foo</prgn> binary depends on the
5774 <prgn>libbar</prgn> shared library, but no package seems to
5775 provide a <file>*.shlibs</file> file handling
5776 <file>libbar.so.1</file> in <file>/var/lib/dpkg/info/</file>. Let's
5777 determine the package responsible:
5778 <example compact="compact">
5779 $ dpkg -S /usr/lib/libbar.so.1
5780 bar1: /usr/lib/libbar.so.1
5781 $ dpkg -s bar1 | grep Version
5784 This tells us that the <tt>bar1</tt> package, version 1.0-1,
5785 is the one we are using. Now we can file a bug against the
5786 <tt>bar1</tt> package and create our own
5787 <file>debian/shlibs.local</file> to locally fix the problem.
5788 Including the following line into your
5789 <file>debian/shlibs.local</file> file:
5790 <example compact="compact">
5791 libbar 1 bar1 (>= 1.0-1)
5793 should allow the package build to work.
5797 As soon as the maintainer of <tt>bar1</tt> provides a
5798 correct <file>shlibs</file> file, you should remove this line
5799 from your <file>debian/shlibs.local</file> file. (You should
5800 probably also then have a versioned <tt>Build-Depends</tt>
5801 on <tt>bar1</tt> to help ensure that others do not have the
5802 same problem building your package.)
5811 <chapt id="opersys"><heading>The Operating System</heading>
5814 <heading>File system hierarchy</heading>
5818 <heading>File System Structure</heading>
5821 The location of all installed files and directories must
5822 comply with the Filesystem Hierarchy Standard (FHS),
5823 version 2.3, with the exceptions noted below, and except
5824 where doing so would violate other terms of Debian
5825 Policy. The following exceptions to the FHS apply:
5830 The optional rules related to user specific
5831 configuration files for applications are stored in
5832 the user's home directory are relaxed. It is
5833 recommended that such files start with the
5834 '<tt>.</tt>' character (a "dot file"), and if an
5835 application needs to create more than one dot file
5836 then the preferred placement is in a subdirectory
5837 with a name starting with a '.' character, (a "dot
5838 directory"). In this case it is recommended the
5839 configuration files not start with the '.'
5845 The requirement for amd64 to use <file>/lib64</file>
5846 for 64 bit binaries is removed.
5851 The requirement for object files, internal binaries, and
5852 libraries, including <file>libc.so.*</file>, to be located
5853 directly under <file>/lib{,32}</file> and
5854 <file>/usr/lib{,32}</file> is amended, permitting files
5855 to instead be installed to
5856 <file>/lib/<var>triplet</var></file> and
5857 <file>/usr/lib/<var>triplet</var></file>, where
5858 <tt><var>triplet</var></tt> is the value returned by
5859 <tt>dpkg-architecture -qDEB_HOST_GNU_TYPE</tt> for the
5860 architecture of the package. Packages may <em>not</em>
5861 install files to any <var>triplet</var> path other
5862 than the one matching the architecture of that package;
5863 for instance, an <tt>Architecture: amd64</tt> package
5864 containing 32-bit x86 libraries may not install these
5865 libraries to <file>/usr/lib/i486-linux-gnu</file>.
5867 This is necessary in order to reserve the directories for
5868 use in cross-installation of library packages from other
5869 architectures, as part of the planned deployment of
5874 Applications may also use a single subdirectory under
5875 <file>/usr/lib/<var>triplet</var></file>.
5878 The execution time linker/loader, ld*, must still be made
5879 available in the existing location under /lib or /lib64
5880 since this is part of the ELF ABI for the architecture.
5885 The requirement that
5886 <file>/usr/local/share/man</file> be "synonymous"
5887 with <file>/usr/local/man</file> is relaxed to a
5892 The requirement that windowmanagers with a single
5893 configuration file call it <file>system.*wmrc</file>
5894 is removed, as is the restriction that the window
5895 manager subdirectory be named identically to the
5896 window manager name itself.
5901 The requirement that boot manager configuration
5902 files live in <file>/etc</file>, or at least are
5903 symlinked there, is relaxed to a recommendation.
5908 The following directories in the root filesystem are
5909 additionally allowed: <file>/sys</file> and
5910 <file>/selinux</file>. <footnote>These directories
5911 are used as mount points to mount virtual filesystems
5912 to get access to kernel information.</footnote>
5919 The version of this document referred here can be
5920 found in the <tt>debian-policy</tt> package or on <url
5921 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5922 name="FHS (Debian copy)"> alongside this manual (or, if
5923 you have the <package>debian-policy</package> installed,
5925 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5926 (local copy)">). The
5927 latest version, which may be a more recent version, may
5929 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5930 Specific questions about following the standard may be
5931 asked on the <tt>debian-devel</tt> mailing list, or
5932 referred to the FHS mailing list (see the
5933 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
5939 <heading>Site-specific programs</heading>
5942 As mandated by the FHS, packages must not place any
5943 files in <file>/usr/local</file>, either by putting them in
5944 the file system archive to be unpacked by <prgn>dpkg</prgn>
5945 or by manipulating them in their maintainer scripts.
5949 However, the package may create empty directories below
5950 <file>/usr/local</file> so that the system administrator knows
5951 where to place site-specific files. These are not
5952 directories <em>in</em> <file>/usr/local</file>, but are
5953 children of directories in <file>/usr/local</file>. These
5954 directories (<file>/usr/local/*/dir/</file>)
5955 should be removed on package removal if they are
5960 Note that this applies only to
5961 directories <em>below</em> <file>/usr/local</file>,
5962 not <em>in</em> <file>/usr/local</file>. Packages must
5963 not create sub-directories in the
5964 directory <file>/usr/local</file> itself, except those
5965 listed in FHS, section 4.5. However, you may create
5966 directories below them as you wish. You must not remove
5967 any of the directories listed in 4.5, even if you created
5972 Since <file>/usr/local</file> can be mounted read-only from a
5973 remote server, these directories must be created and
5974 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
5975 maintainer scripts and not be included in the
5976 <file>.deb</file> archive. These scripts must not fail if
5977 either of these operations fail.
5981 For example, the <tt>emacsen-common</tt> package could
5982 contain something like
5983 <example compact="compact">
5984 if [ ! -e /usr/local/share/emacs ]
5986 if mkdir /usr/local/share/emacs 2>/dev/null
5988 chown root:staff /usr/local/share/emacs
5989 chmod 2775 /usr/local/share/emacs
5993 in its <prgn>postinst</prgn> script, and
5994 <example compact="compact">
5995 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
5996 rmdir /usr/local/share/emacs 2>/dev/null || true
5998 in the <prgn>prerm</prgn> script. (Note that this form is
5999 used to ensure that if the script is interrupted, the
6000 directory <file>/usr/local/share/emacs</file> will still be
6005 If you do create a directory in <file>/usr/local</file> for
6006 local additions to a package, you should ensure that
6007 settings in <file>/usr/local</file> take precedence over the
6008 equivalents in <file>/usr</file>.
6012 However, because <file>/usr/local</file> and its contents are
6013 for exclusive use of the local administrator, a package
6014 must not rely on the presence or absence of files or
6015 directories in <file>/usr/local</file> for normal operation.
6019 The <file>/usr/local</file> directory itself and all the
6020 subdirectories created by the package should (by default) have
6021 permissions 2775 (group-writable and set-group-id) and be
6022 owned by <tt>root:staff</tt>.
6027 <heading>The system-wide mail directory</heading>
6029 The system-wide mail directory
6030 is <file>/var/mail</file>. This directory is part of the
6031 base system and should not be owned by any particular mail
6032 agents. The use of the old
6033 location <file>/var/spool/mail</file> is deprecated, even
6034 though the spool may still be physically located there.
6040 <heading>Users and groups</heading>
6043 <heading>Introduction</heading>
6045 The Debian system can be configured to use either plain or
6050 Some user ids (UIDs) and group ids (GIDs) are reserved
6051 globally for use by certain packages. Because some
6052 packages need to include files which are owned by these
6053 users or groups, or need the ids compiled into binaries,
6054 these ids must be used on any Debian system only for the
6055 purpose for which they are allocated. This is a serious
6056 restriction, and we should avoid getting in the way of
6057 local administration policies. In particular, many sites
6058 allocate users and/or local system groups starting at 100.
6062 Apart from this we should have dynamically allocated ids,
6063 which should by default be arranged in some sensible
6064 order, but the behavior should be configurable.
6068 Packages other than <tt>base-passwd</tt> must not modify
6069 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
6070 <file>/etc/group</file> or <file>/etc/gshadow</file>.
6075 <heading>UID and GID classes</heading>
6077 The UID and GID numbers are divided into classes as
6083 Globally allocated by the Debian project, the same
6084 on every Debian system. These ids will appear in
6085 the <file>passwd</file> and <file>group</file> files of all
6086 Debian systems, new ids in this range being added
6087 automatically as the <tt>base-passwd</tt> package is
6092 Packages which need a single statically allocated
6093 uid or gid should use one of these; their
6094 maintainers should ask the <tt>base-passwd</tt>
6102 Dynamically allocated system users and groups.
6103 Packages which need a user or group, but can have
6104 this user or group allocated dynamically and
6105 differently on each system, should use <tt>adduser
6106 --system</tt> to create the group and/or user.
6107 <prgn>adduser</prgn> will check for the existence of
6108 the user or group, and if necessary choose an unused
6109 id based on the ranges specified in
6110 <file>adduser.conf</file>.
6114 <tag>1000-59999:</tag>
6117 Dynamically allocated user accounts. By default
6118 <prgn>adduser</prgn> will choose UIDs and GIDs for
6119 user accounts in this range, though
6120 <file>adduser.conf</file> may be used to modify this
6125 <tag>60000-64999:</tag>
6128 Globally allocated by the Debian project, but only
6129 created on demand. The ids are allocated centrally
6130 and statically, but the actual accounts are only
6131 created on users' systems on demand.
6135 These ids are for packages which are obscure or
6136 which require many statically-allocated ids. These
6137 packages should check for and create the accounts in
6138 <file>/etc/passwd</file> or <file>/etc/group</file> (using
6139 <prgn>adduser</prgn> if it has this facility) if
6140 necessary. Packages which are likely to require
6141 further allocations should have a "hole" left after
6142 them in the allocation, to give them room to
6147 <tag>65000-65533:</tag>
6155 User <tt>nobody</tt>. The corresponding gid refers
6156 to the group <tt>nogroup</tt>.
6163 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
6164 not</em> be used, because it is the error return
6173 <sect id="sysvinit">
6174 <heading>System run levels and <file>init.d</file> scripts</heading>
6176 <sect1 id="/etc/init.d">
6177 <heading>Introduction</heading>
6180 The <file>/etc/init.d</file> directory contains the scripts
6181 executed by <prgn>init</prgn> at boot time and when the
6182 init state (or "runlevel") is changed (see <manref
6183 name="init" section="8">).
6187 There are at least two different, yet functionally
6188 equivalent, ways of handling these scripts. For the sake
6189 of simplicity, this document describes only the symbolic
6190 link method. However, it must not be assumed by maintainer
6191 scripts that this method is being used, and any automated
6192 manipulation of the various runlevel behaviors by
6193 maintainer scripts must be performed using
6194 <prgn>update-rc.d</prgn> as described below and not by
6195 manually installing or removing symlinks. For information
6196 on the implementation details of the other method,
6197 implemented in the <tt>file-rc</tt> package, please refer
6198 to the documentation of that package.
6202 These scripts are referenced by symbolic links in the
6203 <file>/etc/rc<var>n</var>.d</file> directories. When changing
6204 runlevels, <prgn>init</prgn> looks in the directory
6205 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
6206 execute, where <tt><var>n</var></tt> is the runlevel that
6207 is being changed to, or <tt>S</tt> for the boot-up
6212 The names of the links all have the form
6213 <file>S<var>mm</var><var>script</var></file> or
6214 <file>K<var>mm</var><var>script</var></file> where
6215 <var>mm</var> is a two-digit number and <var>script</var>
6216 is the name of the script (this should be the same as the
6217 name of the actual script in <file>/etc/init.d</file>).
6221 When <prgn>init</prgn> changes runlevel first the targets
6222 of the links whose names start with a <tt>K</tt> are
6223 executed, each with the single argument <tt>stop</tt>,
6224 followed by the scripts prefixed with an <tt>S</tt>, each
6225 with the single argument <tt>start</tt>. (The links are
6226 those in the <file>/etc/rc<var>n</var>.d</file> directory
6227 corresponding to the new runlevel.) The <tt>K</tt> links
6228 are responsible for killing services and the <tt>S</tt>
6229 link for starting services upon entering the runlevel.
6233 For example, if we are changing from runlevel 2 to
6234 runlevel 3, init will first execute all of the <tt>K</tt>
6235 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
6236 all of the <tt>S</tt> prefixed scripts in that directory.
6237 The links starting with <tt>K</tt> will cause the
6238 referred-to file to be executed with an argument of
6239 <tt>stop</tt>, and the <tt>S</tt> links with an argument
6244 The two-digit number <var>mm</var> is used to determine
6245 the order in which to run the scripts: low-numbered links
6246 have their scripts run first. For example, the
6247 <tt>K20</tt> scripts will be executed before the
6248 <tt>K30</tt> scripts. This is used when a certain service
6249 must be started before another. For example, the name
6250 server <prgn>bind</prgn> might need to be started before
6251 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
6252 can set up its access lists. In this case, the script
6253 that starts <prgn>bind</prgn> would have a lower number
6254 than the script that starts <prgn>inn</prgn> so that it
6256 <example compact="compact">
6263 The two runlevels 0 (halt) and 6 (reboot) are slightly
6264 different. In these runlevels, the links with an
6265 <tt>S</tt> prefix are still called after those with a
6266 <tt>K</tt> prefix, but they too are called with the single
6267 argument <tt>stop</tt>.
6271 <sect1 id="writing-init">
6272 <heading>Writing the scripts</heading>
6275 Packages that include daemons for system services should
6276 place scripts in <file>/etc/init.d</file> to start or stop
6277 services at boot time or during a change of runlevel.
6278 These scripts should be named
6279 <file>/etc/init.d/<var>package</var></file>, and they should
6280 accept one argument, saying what to do:
6283 <tag><tt>start</tt></tag>
6284 <item>start the service,</item>
6286 <tag><tt>stop</tt></tag>
6287 <item>stop the service,</item>
6289 <tag><tt>restart</tt></tag>
6290 <item>stop and restart the service if it's already running,
6291 otherwise start the service</item>
6293 <tag><tt>reload</tt></tag>
6294 <item><p>cause the configuration of the service to be
6295 reloaded without actually stopping and restarting
6298 <tag><tt>force-reload</tt></tag>
6299 <item>cause the configuration to be reloaded if the
6300 service supports this, otherwise restart the
6304 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
6305 <tt>force-reload</tt> options should be supported by all
6306 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
6311 The <file>init.d</file> scripts must ensure that they will
6312 behave sensibly (i.e., returning success and not starting
6313 multiple copies of a service) if invoked with <tt>start</tt>
6314 when the service is already running, or with <tt>stop</tt>
6315 when it isn't, and that they don't kill unfortunately-named
6316 user processes. The best way to achieve this is usually to
6317 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
6322 Be careful of using <tt>set -e</tt> in <file>init.d</file>
6323 scripts. Writing correct <file>init.d</file> scripts requires
6324 accepting various error exit statuses when daemons are already
6325 running or already stopped without aborting
6326 the <file>init.d</file> script, and common <file>init.d</file>
6327 function libraries are not safe to call with <tt>set -e</tt>
6329 <tt>/lib/lsb/init-functions</tt>, which assists in writing
6330 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
6331 in effect and echoing status messages to the console fails,
6333 </footnote>. For <tt>init.d</tt> scripts, it's often easier
6334 to not use <tt>set -e</tt> and instead check the result of
6335 each command separately.
6339 If a service reloads its configuration automatically (as
6340 in the case of <prgn>cron</prgn>, for example), the
6341 <tt>reload</tt> option of the <file>init.d</file> script
6342 should behave as if the configuration has been reloaded
6347 The <file>/etc/init.d</file> scripts must be treated as
6348 configuration files, either (if they are present in the
6349 package, that is, in the .deb file) by marking them as
6350 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6351 by managing them correctly in the maintainer scripts (see
6352 <ref id="config-files">). This is important since we want
6353 to give the local system administrator the chance to adapt
6354 the scripts to the local system, e.g., to disable a
6355 service without de-installing the package, or to specify
6356 some special command line options when starting a service,
6357 while making sure their changes aren't lost during the next
6362 These scripts should not fail obscurely when the
6363 configuration files remain but the package has been
6364 removed, as configuration files remain on the system after
6365 the package has been removed. Only when <prgn>dpkg</prgn>
6366 is executed with the <tt>--purge</tt> option will
6367 configuration files be removed. In particular, as the
6368 <file>/etc/init.d/<var>package</var></file> script itself is
6369 usually a <tt>conffile</tt>, it will remain on the system
6370 if the package is removed but not purged. Therefore, you
6371 should include a <tt>test</tt> statement at the top of the
6373 <example compact="compact">
6374 test -f <var>program-executed-later-in-script</var> || exit 0
6379 Often there are some variables in the <file>init.d</file>
6380 scripts whose values control the behavior of the scripts,
6381 and which a system administrator is likely to want to
6382 change. As the scripts themselves are frequently
6383 <tt>conffile</tt>s, modifying them requires that the
6384 administrator merge in their changes each time the package
6385 is upgraded and the <tt>conffile</tt> changes. To ease
6386 the burden on the system administrator, such configurable
6387 values should not be placed directly in the script.
6388 Instead, they should be placed in a file in
6389 <file>/etc/default</file>, which typically will have the same
6390 base name as the <file>init.d</file> script. This extra file
6391 should be sourced by the script when the script runs. It
6392 must contain only variable settings and comments in SUSv3
6393 <prgn>sh</prgn> format. It may either be a
6394 <tt>conffile</tt> or a configuration file maintained by
6395 the package maintainer scripts. See <ref id="config-files">
6400 To ensure that vital configurable values are always
6401 available, the <file>init.d</file> script should set default
6402 values for each of the shell variables it uses, either
6403 before sourcing the <file>/etc/default/</file> file or
6404 afterwards using something like the <tt>:
6405 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6406 script must behave sensibly and not fail if the
6407 <file>/etc/default</file> file is deleted.
6411 <file>/var/run</file> and <file>/var/lock</file> may be mounted
6412 as temporary filesystems<footnote>
6413 For example, using the <tt>RAMRUN</tt> and <tt>RAMLOCK</tt>
6414 options in <file>/etc/default/rcS</file>.
6415 </footnote>, so the <file>init.d</file> scripts must handle this
6416 correctly. This will typically amount to creating any required
6417 subdirectories dynamically when the <file>init.d</file> script
6418 is run, rather than including them in the package and relying on
6419 <prgn>dpkg</prgn> to create them.
6424 <heading>Interfacing with the initscript system</heading>
6427 Maintainers should use the abstraction layer provided by
6428 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6429 programs to deal with initscripts in their packages'
6430 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6431 and <prgn>postrm</prgn>.
6435 Directly managing the /etc/rc?.d links and directly
6436 invoking the <file>/etc/init.d/</file> initscripts should
6437 be done only by packages providing the initscript
6438 subsystem (such as <prgn>sysv-rc</prgn> and
6439 <prgn>file-rc</prgn>).
6443 <heading>Managing the links</heading>
6446 The program <prgn>update-rc.d</prgn> is provided for
6447 package maintainers to arrange for the proper creation and
6448 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6449 or their functional equivalent if another method is being
6450 used. This may be used by maintainers in their packages'
6451 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6455 You must not include any <file>/etc/rc<var>n</var>.d</file>
6456 symbolic links in the actual archive or manually create or
6457 remove the symbolic links in maintainer scripts; you must
6458 use the <prgn>update-rc.d</prgn> program instead. (The
6459 former will fail if an alternative method of maintaining
6460 runlevel information is being used.) You must not include
6461 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6462 in the archive either. (Only the <tt>sysvinit</tt>
6467 By default <prgn>update-rc.d</prgn> will start services in
6468 each of the multi-user state runlevels (2, 3, 4, and 5)
6469 and stop them in the halt runlevel (0), the single-user
6470 runlevel (1) and the reboot runlevel (6). The system
6471 administrator will have the opportunity to customize
6472 runlevels by simply adding, moving, or removing the
6473 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6474 symbolic links are being used, or by modifying
6475 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6480 To get the default behavior for your package, put in your
6481 <prgn>postinst</prgn> script
6482 <example compact="compact">
6483 update-rc.d <var>package</var> defaults
6485 and in your <prgn>postrm</prgn>
6486 <example compact="compact">
6487 if [ "$1" = purge ]; then
6488 update-rc.d <var>package</var> remove
6490 </example>. Note that if your package changes runlevels
6491 or priority, you may have to remove and recreate the links,
6492 since otherwise the old links may persist. Refer to the
6493 documentation of <prgn>update-rc.d</prgn>.
6497 This will use a default sequence number of 20. If it does
6498 not matter when or in which order the <file>init.d</file>
6499 script is run, use this default. If it does, then you
6500 should talk to the maintainer of the <prgn>sysvinit</prgn>
6501 package or post to <tt>debian-devel</tt>, and they will
6502 help you choose a number.
6506 For more information about using <tt>update-rc.d</tt>,
6507 please consult its man page <manref name="update-rc.d"
6513 <heading>Running initscripts</heading>
6515 The program <prgn>invoke-rc.d</prgn> is provided to make
6516 it easier for package maintainers to properly invoke an
6517 initscript, obeying runlevel and other locally-defined
6518 constraints that might limit a package's right to start,
6519 stop and otherwise manage services. This program may be
6520 used by maintainers in their packages' scripts.
6524 The package maintainer scripts must use
6525 <prgn>invoke-rc.d</prgn> to invoke the
6526 <file>/etc/init.d/*</file> initscripts, instead of
6527 calling them directly.
6531 By default, <prgn>invoke-rc.d</prgn> will pass any
6532 action requests (start, stop, reload, restart...) to the
6533 <file>/etc/init.d</file> script, filtering out requests
6534 to start or restart a service out of its intended
6539 Most packages will simply need to change:
6540 <example compact="compact">/etc/init.d/<package>
6541 <action></example> in their <prgn>postinst</prgn>
6542 and <prgn>prerm</prgn> scripts to:
6543 <example compact="compact">
6544 if which invoke-rc.d >/dev/null 2>&1; then
6545 invoke-rc.d <var>package</var> <action>
6547 /etc/init.d/<var>package</var> <action>
6553 A package should register its initscript services using
6554 <prgn>update-rc.d</prgn> before it tries to invoke them
6555 using <prgn>invoke-rc.d</prgn>. Invocation of
6556 unregistered services may fail.
6560 For more information about using
6561 <prgn>invoke-rc.d</prgn>, please consult its man page
6562 <manref name="invoke-rc.d" section="8">.
6568 <heading>Boot-time initialization</heading>
6571 There used to be another directory, <file>/etc/rc.boot</file>,
6572 which contained scripts which were run once per machine
6573 boot. This has been deprecated in favour of links from
6574 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6575 described in <ref id="/etc/init.d">. Packages must not
6576 place files in <file>/etc/rc.boot</file>.
6581 <heading>Example</heading>
6584 An example on which you can base your
6585 <file>/etc/init.d</file> scripts is found in
6586 <file>/etc/init.d/skeleton</file>.
6593 <heading>Console messages from <file>init.d</file> scripts</heading>
6596 This section describes the formats to be used for messages
6597 written to standard output by the <file>/etc/init.d</file>
6598 scripts. The intent is to improve the consistency of
6599 Debian's startup and shutdown look and feel. For this
6600 reason, please look very carefully at the details. We want
6601 the messages to have the same format in terms of wording,
6602 spaces, punctuation and case of letters.
6606 Here is a list of overall rules that should be used for
6607 messages generated by <file>/etc/init.d</file> scripts.
6613 The message should fit in one line (fewer than 80
6614 characters), start with a capital letter and end with
6615 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6619 If the script is performing some time consuming task in
6620 the background (not merely starting or stopping a
6621 program, for instance), an ellipsis (three dots:
6622 <tt>...</tt>) should be output to the screen, with no
6623 leading or tailing whitespace or line feeds.
6627 The messages should appear as if the computer is telling
6628 the user what it is doing (politely :-), but should not
6629 mention "it" directly. For example, instead of:
6630 <example compact="compact">
6631 I'm starting network daemons: nfsd mountd.
6633 the message should say
6634 <example compact="compact">
6635 Starting network daemons: nfsd mountd.
6642 <tt>init.d</tt> script should use the following standard
6643 message formats for the situations enumerated below.
6649 <p>When daemons are started</p>
6652 If the script starts one or more daemons, the output
6653 should look like this (a single line, no leading
6655 <example compact="compact">
6656 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6658 The <var>description</var> should describe the
6659 subsystem the daemon or set of daemons are part of,
6660 while <var>daemon-1</var> up to <var>daemon-n</var>
6661 denote each daemon's name (typically the file name of
6666 For example, the output of <file>/etc/init.d/lpd</file>
6668 <example compact="compact">
6669 Starting printer spooler: lpd.
6674 This can be achieved by saying
6675 <example compact="compact">
6676 echo -n "Starting printer spooler: lpd"
6677 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6680 in the script. If there are more than one daemon to
6681 start, the output should look like this:
6682 <example compact="compact">
6683 echo -n "Starting remote file system services:"
6684 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6685 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6686 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6689 This makes it possible for the user to see what is
6690 happening and when the final daemon has been started.
6691 Care should be taken in the placement of white spaces:
6692 in the example above the system administrators can
6693 easily comment out a line if they don't want to start
6694 a specific daemon, while the displayed message still
6700 <p>When a system parameter is being set</p>
6703 If you have to set up different system parameters
6704 during the system boot, you should use this format:
6705 <example compact="compact">
6706 Setting <var>parameter</var> to "<var>value</var>".
6711 You can use a statement such as the following to get
6713 <example compact="compact">
6714 echo "Setting DNS domainname to \"$domainname\"."
6719 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
6720 for the left and right quotation marks. A grave accent
6721 (<tt>`</tt>) is not a quote character; neither is an
6722 apostrophe (<tt>'</tt>).
6727 <p>When a daemon is stopped or restarted</p>
6730 When you stop or restart a daemon, you should issue a
6731 message identical to the startup message, except that
6732 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6733 or <tt>Restarting</tt> respectively.
6737 For example, stopping the printer daemon will look like
6739 <example compact="compact">
6740 Stopping printer spooler: lpd.
6746 <p>When something is executed</p>
6749 There are several examples where you have to run a
6750 program at system startup or shutdown to perform a
6751 specific task, for example, setting the system's clock
6752 using <prgn>netdate</prgn> or killing all processes
6753 when the system shuts down. Your message should look
6755 <example compact="compact">
6756 Doing something very useful...done.
6758 You should print the <tt>done.</tt> immediately after
6759 the job has been completed, so that the user is
6760 informed why they have to wait. You can get this
6762 <example compact="compact">
6763 echo -n "Doing something very useful..."
6772 <p>When the configuration is reloaded</p>
6775 When a daemon is forced to reload its configuration
6776 files you should use the following format:
6777 <example compact="compact">
6778 Reloading <var>description</var> configuration...done.
6780 where <var>description</var> is the same as in the
6781 daemon starting message.
6789 <heading>Cron jobs</heading>
6792 Packages must not modify the configuration file
6793 <file>/etc/crontab</file>, and they must not modify the files in
6794 <file>/var/spool/cron/crontabs</file>.</p>
6797 If a package wants to install a job that has to be executed
6798 via cron, it should place a file with the name of the
6799 package in one or more of the following directories:
6800 <example compact="compact">
6806 As these directory names imply, the files within them are
6807 executed on an hourly, daily, weekly, or monthly basis,
6808 respectively. The exact times are listed in
6809 <file>/etc/crontab</file>.</p>
6812 All files installed in any of these directories must be
6813 scripts (e.g., shell scripts or Perl scripts) so that they
6814 can easily be modified by the local system administrator.
6815 In addition, they must be treated as configuration files.
6819 If a certain job has to be executed at some other frequency or
6820 at a specific time, the package should install a file
6821 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6822 same syntax as <file>/etc/crontab</file> and is processed by
6823 <prgn>cron</prgn> automatically. The file must also be
6824 treated as a configuration file. (Note that entries in the
6825 <file>/etc/cron.d</file> directory are not handled by
6826 <prgn>anacron</prgn>. Thus, you should only use this
6827 directory for jobs which may be skipped if the system is not
6830 Unlike <file>crontab</file> files described in the IEEE Std
6831 1003.1-2008 (POSIX.1) available from
6832 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
6833 name="The Open Group">, the files in
6834 <file>/etc/cron.d</file> and the file
6835 <file>/etc/crontab</file> have seven fields; namely:
6837 <item>Minute [0,59]</item>
6838 <item>Hour [0,23]</item>
6839 <item>Day of the month [1,31]</item>
6840 <item>Month of the year [1,12]</item>
6841 <item>Day of the week ([0,6] with 0=Sunday)</item>
6842 <item>Username</item>
6843 <item>Command to be run</item>
6845 Ranges of numbers are allowed. Ranges are two numbers
6846 separated with a hyphen. The specified range is inclusive.
6847 Lists are allowed. A list is a set of numbers (or ranges)
6848 separated by commas. Step values can be used in conjunction
6853 The scripts or <tt>crontab</tt> entries in these directories should
6854 check if all necessary programs are installed before they
6855 try to execute them. Otherwise, problems will arise when a
6856 package was removed but not purged since configuration files
6857 are kept on the system in this situation.
6861 Any <tt>cron</tt> daemon must provide
6862 <file>/usr/bin/crontab</file> and support normal
6863 <tt>crontab</tt> entries as specified in POSIX. The daemon
6864 must also support names for days and months, ranges, and
6865 step values. It has to support <file>/etc/crontab</file>,
6866 and correctly execute the scripts in
6867 <file>/etc/cron.d</file>. The daemon must also correctly
6869 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
6874 <heading>Menus</heading>
6877 The Debian <tt>menu</tt> package provides a standard
6878 interface between packages providing applications and
6879 <em>menu programs</em> (either X window managers or
6880 text-based menu programs such as <prgn>pdmenu</prgn>).
6884 All packages that provide applications that need not be
6885 passed any special command line arguments for normal
6886 operation should register a menu entry for those
6887 applications, so that users of the <tt>menu</tt> package
6888 will automatically get menu entries in their window
6889 managers, as well in shells like <tt>pdmenu</tt>.
6893 Menu entries should follow the current menu policy.
6897 The menu policy can be found in the <tt>menu-policy</tt>
6898 files in the <tt>debian-policy</tt> package.
6899 It is also available from the Debian web mirrors at
6900 <tt><url name="/doc/packaging-manuals/menu-policy/"
6901 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6905 Please also refer to the <em>Debian Menu System</em>
6906 documentation that comes with the <package>menu</package>
6907 package for information about how to register your
6913 <heading>Multimedia handlers</heading>
6916 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6917 is a mechanism for encoding files and data streams and
6918 providing meta-information about them, in particular their
6919 type (e.g. audio or video) and format (e.g. PNG, HTML,
6924 Registration of MIME type handlers allows programs like mail
6925 user agents and web browsers to invoke these handlers to
6926 view, edit or display MIME types they don't support directly.
6930 Packages which provide the ability to view/show/play,
6931 compose, edit or print MIME types should register themselves
6932 as such following the current MIME support policy.
6936 The MIME support policy can be found in the <tt>mime-policy</tt>
6937 files in the <tt>debian-policy</tt> package.
6938 It is also available from the Debian web mirrors at
6939 <tt><url name="/doc/packaging-manuals/mime-policy/"
6940 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
6946 <heading>Keyboard configuration</heading>
6949 To achieve a consistent keyboard configuration so that all
6950 applications interpret a keyboard event the same way, all
6951 programs in the Debian distribution must be configured to
6952 comply with the following guidelines.
6956 The following keys must have the specified interpretations:
6959 <tag><tt><--</tt></tag>
6960 <item>delete the character to the left of the cursor</item>
6962 <tag><tt>Delete</tt></tag>
6963 <item>delete the character to the right of the cursor</item>
6965 <tag><tt>Control+H</tt></tag>
6966 <item>emacs: the help prefix</item>
6969 The interpretation of any keyboard events should be
6970 independent of the terminal that is used, be it a virtual
6971 console, an X terminal emulator, an rlogin/telnet session,
6976 The following list explains how the different programs
6977 should be set up to achieve this:
6983 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
6987 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
6991 X translations are set up to make
6992 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
6993 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
6994 is the vt220 escape code for the "delete character"
6995 key). This must be done by loading the X resources
6996 using <prgn>xrdb</prgn> on all local X displays, not
6997 using the application defaults, so that the
6998 translation resources used correspond to the
6999 <prgn>xmodmap</prgn> settings.
7003 The Linux console is configured to make
7004 <tt><--</tt> generate DEL, and <tt>Delete</tt>
7005 generate <tt>ESC [ 3 ~</tt>.
7009 X applications are configured so that <tt><</tt>
7010 deletes left, and <tt>Delete</tt> deletes right. Motif
7011 applications already work like this.
7015 Terminals should have <tt>stty erase ^?</tt> .
7019 The <tt>xterm</tt> terminfo entry should have <tt>ESC
7020 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
7021 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
7025 Emacs is programmed to map <tt>KB_Backspace</tt> or
7026 the <tt>stty erase</tt> character to
7027 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
7028 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
7029 <tt>^H</tt> to <tt>help</tt> as always.
7033 Other applications use the <tt>stty erase</tt>
7034 character and <tt>kdch1</tt> for the two delete keys,
7035 with ASCII DEL being "delete previous character" and
7036 <tt>kdch1</tt> being "delete character under
7044 This will solve the problem except for the following
7051 Some terminals have a <tt><--</tt> key that cannot
7052 be made to produce anything except <tt>^H</tt>. On
7053 these terminals Emacs help will be unavailable on
7054 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
7055 character takes precedence in Emacs, and has been set
7056 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
7057 available) can be used instead.
7061 Some operating systems use <tt>^H</tt> for <tt>stty
7062 erase</tt>. However, modern telnet versions and all
7063 rlogin versions propagate <tt>stty</tt> settings, and
7064 almost all UNIX versions honour <tt>stty erase</tt>.
7065 Where the <tt>stty</tt> settings are not propagated
7066 correctly, things can be made to work by using
7067 <tt>stty</tt> manually.
7071 Some systems (including previous Debian versions) use
7072 <prgn>xmodmap</prgn> to arrange for both
7073 <tt><--</tt> and <tt>Delete</tt> to generate
7074 <tt>KB_Delete</tt>. We can change the behavior of
7075 their X clients using the same X resources that we use
7076 to do it for our own clients, or configure our clients
7077 using their resources when things are the other way
7078 around. On displays configured like this
7079 <tt>Delete</tt> will not work, but <tt><--</tt>
7084 Some operating systems have different <tt>kdch1</tt>
7085 settings in their <tt>terminfo</tt> database for
7086 <tt>xterm</tt> and others. On these systems the
7087 <tt>Delete</tt> key will not work correctly when you
7088 log in from a system conforming to our policy, but
7089 <tt><--</tt> will.
7096 <heading>Environment variables</heading>
7099 A program must not depend on environment variables to get
7100 reasonable defaults. (That's because these environment
7101 variables would have to be set in a system-wide
7102 configuration file like <file>/etc/profile</file>, which is not
7103 supported by all shells.)
7107 If a program usually depends on environment variables for its
7108 configuration, the program should be changed to fall back to
7109 a reasonable default configuration if these environment
7110 variables are not present. If this cannot be done easily
7111 (e.g., if the source code of a non-free program is not
7112 available), the program must be replaced by a small
7113 "wrapper" shell script which sets the environment variables
7114 if they are not already defined, and calls the original program.
7118 Here is an example of a wrapper script for this purpose:
7120 <example compact="compact">
7122 BAR=${BAR:-/var/lib/fubar}
7124 exec /usr/lib/foo/foo "$@"
7129 Furthermore, as <file>/etc/profile</file> is a configuration
7130 file of the <prgn>base-files</prgn> package, other packages must
7131 not put any environment variables or other commands into that
7136 <sect id="doc-base">
7137 <heading>Registering Documents using doc-base</heading>
7140 The <package>doc-base</package> package implements a
7141 flexible mechanism for handling and presenting
7142 documentation. The recommended practice is for every Debian
7143 package that provides online documentation (other than just
7144 manual pages) to register these documents with
7145 <package>doc-base</package> by installing a
7146 <package>doc-base</package> control file via the
7147 <prgn/install-docs/ script at installation time and
7148 de-register the manuals again when the package is removed.
7151 Please refer to the documentation that comes with the
7152 <package>doc-base</package> package for information and
7161 <heading>Files</heading>
7163 <sect id="binaries">
7164 <heading>Binaries</heading>
7167 Two different packages must not install programs with
7168 different functionality but with the same filenames. (The
7169 case of two programs having the same functionality but
7170 different implementations is handled via "alternatives" or
7171 the "Conflicts" mechanism. See <ref id="maintscripts"> and
7172 <ref id="conflicts"> respectively.) If this case happens,
7173 one of the programs must be renamed. The maintainers should
7174 report this to the <tt>debian-devel</tt> mailing list and
7175 try to find a consensus about which program will have to be
7176 renamed. If a consensus cannot be reached, <em>both</em>
7177 programs must be renamed.
7181 By default, when a package is being built, any binaries
7182 created should include debugging information, as well as
7183 being compiled with optimization. You should also turn on
7184 as many reasonable compilation warnings as possible; this
7185 makes life easier for porters, who can then look at build
7186 logs for possible problems. For the C programming language,
7187 this means the following compilation parameters should be
7189 <example compact="compact">
7191 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
7193 INSTALL = install -s # (or use strip on the files in debian/tmp)
7198 Note that by default all installed binaries should be stripped,
7199 either by using the <tt>-s</tt> flag to
7200 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
7201 the binaries after they have been copied into
7202 <file>debian/tmp</file> but before the tree is made into a
7207 Although binaries in the build tree should be compiled with
7208 debugging information by default, it can often be difficult to
7209 debug programs if they are also subjected to compiler
7210 optimization. For this reason, it is recommended to support the
7211 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
7212 (see <ref id="debianrules-options">). This variable can contain
7213 several flags to change how a package is compiled and built.
7217 It is up to the package maintainer to decide what
7218 compilation options are best for the package. Certain
7219 binaries (such as computationally-intensive programs) will
7220 function better with certain flags (<tt>-O3</tt>, for
7221 example); feel free to use them. Please use good judgment
7222 here. Don't use flags for the sake of it; only use them
7223 if there is good reason to do so. Feel free to override
7224 the upstream author's ideas about which compilation
7225 options are best: they are often inappropriate for our
7231 <sect id="libraries">
7232 <heading>Libraries</heading>
7235 If the package is <strong>architecture: any</strong>, then
7236 the shared library compilation and linking flags must have
7237 <tt>-fPIC</tt>, or the package shall not build on some of
7238 the supported architectures<footnote>
7240 If you are using GCC, <tt>-fPIC</tt> produces code with
7241 relocatable position independent code, which is required for
7242 most architectures to create a shared library, with i386 and
7243 perhaps some others where non position independent code is
7244 permitted in a shared library.
7247 Position independent code may have a performance penalty,
7248 especially on <tt>i386</tt>. However, in most cases the
7249 speed penalty must be measured against the memory wasted on
7250 the few architectures where non position independent code is
7253 </footnote>. Any exception to this rule must be discussed on
7254 the mailing list <em>debian-devel@lists.debian.org</em>, and
7255 a rough consensus obtained. The reasons for not compiling
7256 with <tt>-fPIC</tt> flag must be recorded in the file
7257 <tt>README.Debian</tt>, and care must be taken to either
7258 restrict the architecture or arrange for <tt>-fPIC</tt> to
7259 be used on architectures where it is required.<footnote>
7261 Some of the reasons why this might be required is if the
7262 library contains hand crafted assembly code that is not
7263 relocatable, the speed penalty is excessive for compute
7264 intensive libs, and similar reasons.
7269 As to the static libraries, the common case is not to have
7270 relocatable code, since there is no benefit, unless in specific
7271 cases; therefore the static version must not be compiled
7272 with the <tt>-fPIC</tt> flag. Any exception to this rule
7273 should be discussed on the mailing list
7274 <em>debian-devel@lists.debian.org</em>, and the reasons for
7275 compiling with the <tt>-fPIC</tt> flag must be recorded in
7276 the file <tt>README.Debian</tt>. <footnote>
7278 Some of the reasons for linking static libraries with
7279 the <tt>-fPIC</tt> flag are if, for example, one needs a
7280 Perl API for a library that is under rapid development,
7281 and has an unstable API, so shared libraries are
7282 pointless at this phase of the library's development. In
7283 that case, since Perl needs a library with relocatable
7284 code, it may make sense to create a static library with
7285 relocatable code. Another reason cited is if you are
7286 distilling various libraries into a common shared
7287 library, like <tt>mklibs</tt> does in the Debian
7293 In other words, if both a shared and a static library is
7294 being built, each source unit (<tt>*.c</tt>, for example,
7295 for C files) will need to be compiled twice, for the normal
7299 You must specify the gcc option <tt>-D_REENTRANT</tt>
7300 when building a library (either static or shared) to make
7301 the library compatible with LinuxThreads.
7305 Although not enforced by the build tools, shared libraries
7306 must be linked against all libraries that they use symbols from
7307 in the same way that binaries are. This ensures the correct
7308 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
7309 system and guarantees that all libraries can be safely opened
7310 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
7311 option <tt>-Wl,-z,defs</tt> when building a shared library.
7312 Since this option enforces symbol resolution at build time,
7313 a missing library reference will be caught early as a fatal
7318 All installed shared libraries should be stripped with
7319 <example compact="compact">
7320 strip --strip-unneeded <var>your-lib</var>
7322 (The option <tt>--strip-unneeded</tt> makes
7323 <prgn>strip</prgn> remove only the symbols which aren't
7324 needed for relocation processing.) Shared libraries can
7325 function perfectly well when stripped, since the symbols for
7326 dynamic linking are in a separate part of the ELF object
7328 You might also want to use the options
7329 <tt>--remove-section=.comment</tt> and
7330 <tt>--remove-section=.note</tt> on both shared libraries
7331 and executables, and <tt>--strip-debug</tt> on static
7337 Note that under some circumstances it may be useful to
7338 install a shared library unstripped, for example when
7339 building a separate package to support debugging.
7343 Shared object files (often <file>.so</file> files) that are not
7344 public libraries, that is, they are not meant to be linked
7345 to by third party executables (binaries of other packages),
7346 should be installed in subdirectories of the
7347 <file>/usr/lib</file> directory. Such files are exempt from the
7348 rules that govern ordinary shared libraries, except that
7349 they must not be installed executable and should be
7351 A common example are the so-called "plug-ins",
7352 internal shared objects that are dynamically loaded by
7353 programs using <manref name="dlopen" section="3">.
7358 An ever increasing number of packages are using
7359 <prgn>libtool</prgn> to do their linking. The latest GNU
7360 libtools (>= 1.3a) can take advantage of the metadata in the
7361 installed <prgn>libtool</prgn> archive files (<file>*.la</file>
7362 files). The main advantage of <prgn>libtool</prgn>'s
7363 <file>.la</file> files is that it allows <prgn>libtool</prgn> to
7364 store and subsequently access metadata with respect to the
7365 libraries it builds. <prgn>libtool</prgn> will search for
7366 those files, which contain a lot of useful information about
7367 a library (such as library dependency information for static
7368 linking). Also, they're <em>essential</em> for programs
7369 using <tt>libltdl</tt>.<footnote>
7370 Although <prgn>libtool</prgn> is fully capable of
7371 linking against shared libraries which don't have
7372 <tt>.la</tt> files, as it is a mere shell script it can
7373 add considerably to the build time of a
7374 <prgn>libtool</prgn>-using package if that shell script
7375 has to derive all this information from first principles
7376 for each library every time it is linked. With the
7377 advent of <prgn>libtool</prgn> version 1.4 (and to a
7378 lesser extent <prgn>libtool</prgn> version 1.3), the
7379 <file>.la</file> files also store information about
7380 inter-library dependencies which cannot necessarily be
7381 derived after the <file>.la</file> file is deleted.
7386 Packages that use <prgn>libtool</prgn> to create shared
7387 libraries should include the <file>.la</file> files in the
7388 <tt>-dev</tt> package, unless the package relies on
7389 <tt>libtool</tt>'s <tt>libltdl</tt> library, in which case
7390 the <tt>.la</tt> files must go in the run-time library
7395 You must make sure that you use only released versions of
7396 shared libraries to build your packages; otherwise other
7397 users will not be able to run your binaries
7398 properly. Producing source packages that depend on
7399 unreleased compilers is also usually a bad
7406 <heading>Shared libraries</heading>
7408 This section has moved to <ref id="sharedlibs">.
7414 <heading>Scripts</heading>
7417 All command scripts, including the package maintainer
7418 scripts inside the package and used by <prgn>dpkg</prgn>,
7419 should have a <tt>#!</tt> line naming the shell to be used
7424 In the case of Perl scripts this should be
7425 <tt>#!/usr/bin/perl</tt>.
7429 When scripts are installed into a directory in the system
7430 PATH, the script name should not include an extension such
7431 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7432 language currently used to implement it.
7435 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
7436 <file>init.d</file> scripts should almost certainly start
7437 with <tt>set -e</tt> so that errors are detected.
7438 <file>init.d</file> scripts are something of a special case, due
7439 to how frequently they need to call commands that are allowed to
7440 fail, and it may instead be easier to check the exit status of
7441 commands directly. See <ref id="writing-init"> for more
7442 information about writing <file>init.d</file> scripts.
7445 Every script should use <tt>set -e</tt> or check the exit status
7446 of <em>every</em> command.
7449 Scripts may assume that <file>/bin/sh</file> implements the
7450 SUSv3 Shell Command Language<footnote>
7451 Single UNIX Specification, version 3, which is also IEEE
7452 1003.1-2004 (POSIX), and is available on the World Wide Web
7453 from <url id="http://www.unix.org/version3/online.html"
7454 name="The Open Group"> after free
7455 registration.</footnote>
7456 plus the following additional features not mandated by
7458 These features are in widespread use in the Linux community
7459 and are implemented in all of bash, dash, and ksh, the most
7460 common shells users may wish to use as <file>/bin/sh</file>.
7463 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7464 must not generate a newline.</item>
7465 <item><tt>test</tt>, if implemented as a shell built-in, must
7466 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7468 <item><tt>local</tt> to create a scoped variable must be
7469 supported, including listing multiple variables in a single
7470 local command and assigning a value to a variable at the
7471 same time as localizing it. <tt>local</tt> may or
7472 may not preserve the variable value from an outer scope if
7473 no assignment is present. Uses such as:
7477 # ... use a, b, c, d ...
7480 must be supported and must set the value of <tt>c</tt> to
7484 If a shell script requires non-SUSv3 features from the shell
7485 interpreter other than those listed above, the appropriate shell
7486 must be specified in the first line of the script (e.g.,
7487 <tt>#!/bin/bash</tt>) and the package must depend on the package
7488 providing the shell (unless the shell package is marked
7489 "Essential", as in the case of <prgn>bash</prgn>).
7493 You may wish to restrict your script to SUSv3 features plus the
7494 above set when possible so that it may use <file>/bin/sh</file>
7495 as its interpreter. If your script works with <prgn>dash</prgn>
7496 (originally called <prgn>ash</prgn>), it probably complies with
7497 the above requirements, but if you are in doubt, use
7498 <file>/bin/bash</file>.
7502 Perl scripts should check for errors when making any
7503 system calls, including <tt>open</tt>, <tt>print</tt>,
7504 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7508 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7509 scripting languages. See <em>Csh Programming Considered
7510 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7511 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7512 If an upstream package comes with <prgn>csh</prgn> scripts
7513 then you must make sure that they start with
7514 <tt>#!/bin/csh</tt> and make your package depend on the
7515 <prgn>c-shell</prgn> virtual package.
7519 Any scripts which create files in world-writeable
7520 directories (e.g., in <file>/tmp</file>) must use a
7521 mechanism which will fail atomically if a file with the same
7522 name already exists.
7526 The Debian base system provides the <prgn>tempfile</prgn>
7527 and <prgn>mktemp</prgn> utilities for use by scripts for
7534 <heading>Symbolic links</heading>
7537 In general, symbolic links within a top-level directory
7538 should be relative, and symbolic links pointing from one
7539 top-level directory into another should be absolute. (A
7540 top-level directory is a sub-directory of the root
7541 directory <file>/</file>.)
7545 In addition, symbolic links should be specified as short as
7546 possible, i.e., link targets like <file>foo/../bar</file> are
7551 Note that when creating a relative link using
7552 <prgn>ln</prgn> it is not necessary for the target of the
7553 link to exist relative to the working directory you're
7554 running <prgn>ln</prgn> from, nor is it necessary to change
7555 directory to the directory where the link is to be made.
7556 Simply include the string that should appear as the target
7557 of the link (this will be a pathname relative to the
7558 directory in which the link resides) as the first argument
7563 For example, in your <prgn>Makefile</prgn> or
7564 <file>debian/rules</file>, you can do things like:
7565 <example compact="compact">
7566 ln -fs gcc $(prefix)/bin/cc
7567 ln -fs gcc debian/tmp/usr/bin/cc
7568 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7569 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7574 A symbolic link pointing to a compressed file should always
7575 have the same file extension as the referenced file. (For
7576 example, if a file <file>foo.gz</file> is referenced by a
7577 symbolic link, the filename of the link has to end with
7578 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7583 <heading>Device files</heading>
7586 Packages must not include device files or named pipes in the
7591 If a package needs any special device files that are not
7592 included in the base system, it must call
7593 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7594 after notifying the user<footnote>
7595 This notification could be done via a (low-priority)
7596 debconf message, or an echo (printf) statement.
7601 Packages must not remove any device files in the
7602 <prgn>postrm</prgn> or any other script. This is left to the
7603 system administrator.
7607 Debian uses the serial devices
7608 <file>/dev/ttyS*</file>. Programs using the old
7609 <file>/dev/cu*</file> devices should be changed to use
7610 <file>/dev/ttyS*</file>.
7614 Named pipes needed by the package must be created in
7615 the <prgn>postinst</prgn> script<footnote>
7616 It's better to use <prgn>mkfifo</prgn> rather
7617 than <prgn>mknod</prgn> to create named pipes so that
7618 automated checks for packages incorrectly creating device
7619 files with <prgn>mknod</prgn> won't have false positives.
7620 </footnote> and removed in
7621 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
7626 <sect id="config-files">
7627 <heading>Configuration files</heading>
7630 <heading>Definitions</heading>
7634 <tag>configuration file</tag>
7636 A file that affects the operation of a program, or
7637 provides site- or host-specific information, or
7638 otherwise customizes the behavior of a program.
7639 Typically, configuration files are intended to be
7640 modified by the system administrator (if needed or
7641 desired) to conform to local policy or to provide
7642 more useful site-specific behavior.
7645 <tag><tt>conffile</tt></tag>
7647 A file listed in a package's <tt>conffiles</tt>
7648 file, and is treated specially by <prgn>dpkg</prgn>
7649 (see <ref id="configdetails">).
7655 The distinction between these two is important; they are
7656 not interchangeable concepts. Almost all
7657 <tt>conffile</tt>s are configuration files, but many
7658 configuration files are not <tt>conffiles</tt>.
7662 As noted elsewhere, <file>/etc/init.d</file> scripts,
7663 <file>/etc/default</file> files, scripts installed in
7664 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7665 configuration installed in <file>/etc/cron.d</file> must be
7666 treated as configuration files. In general, any script that
7667 embeds configuration information is de-facto a configuration
7668 file and should be treated as such.
7673 <heading>Location</heading>
7676 Any configuration files created or used by your package
7677 must reside in <file>/etc</file>. If there are several,
7678 consider creating a subdirectory of <file>/etc</file>
7679 named after your package.
7683 If your package creates or uses configuration files
7684 outside of <file>/etc</file>, and it is not feasible to modify
7685 the package to use <file>/etc</file> directly, put the files
7686 in <file>/etc</file> and create symbolic links to those files
7687 from the location that the package requires.
7692 <heading>Behavior</heading>
7695 Configuration file handling must conform to the following
7697 <list compact="compact">
7699 local changes must be preserved during a package
7703 configuration files must be preserved when the
7704 package is removed, and only deleted when the
7708 Obsolete configuration files without local changes may be
7709 removed by the package during upgrade.
7713 The easy way to achieve this behavior is to make the
7714 configuration file a <tt>conffile</tt>. This is
7715 appropriate only if it is possible to distribute a default
7716 version that will work for most installations, although
7717 some system administrators may choose to modify it. This
7718 implies that the default version will be part of the
7719 package distribution, and must not be modified by the
7720 maintainer scripts during installation (or at any other
7725 In order to ensure that local changes are preserved
7726 correctly, no package may contain or make hard links to
7727 conffiles.<footnote>
7728 Rationale: There are two problems with hard links.
7729 The first is that some editors break the link while
7730 editing one of the files, so that the two files may
7731 unwittingly become unlinked and different. The second
7732 is that <prgn>dpkg</prgn> might break the hard link
7733 while upgrading <tt>conffile</tt>s.
7738 The other way to do it is via the maintainer scripts. In
7739 this case, the configuration file must not be listed as a
7740 <tt>conffile</tt> and must not be part of the package
7741 distribution. If the existence of a file is required for
7742 the package to be sensibly configured it is the
7743 responsibility of the package maintainer to provide
7744 maintainer scripts which correctly create, update and
7745 maintain the file and remove it on purge. (See <ref
7746 id="maintainerscripts"> for more information.) These
7747 scripts must be idempotent (i.e., must work correctly if
7748 <prgn>dpkg</prgn> needs to re-run them due to errors
7749 during installation or removal), must cope with all the
7750 variety of ways <prgn>dpkg</prgn> can call maintainer
7751 scripts, must not overwrite or otherwise mangle the user's
7752 configuration without asking, must not ask unnecessary
7753 questions (particularly during upgrades), and must
7754 otherwise be good citizens.
7758 The scripts are not required to configure every possible
7759 option for the package, but only those necessary to get
7760 the package running on a given system. Ideally the
7761 sysadmin should not have to do any configuration other
7762 than that done (semi-)automatically by the
7763 <prgn>postinst</prgn> script.
7767 A common practice is to create a script called
7768 <file><var>package</var>-configure</file> and have the
7769 package's <prgn>postinst</prgn> call it if and only if the
7770 configuration file does not already exist. In certain
7771 cases it is useful for there to be an example or template
7772 file which the maintainer scripts use. Such files should
7773 be in <file>/usr/share/<var>package</var></file> or
7774 <file>/usr/lib/<var>package</var></file> (depending on whether
7775 they are architecture-independent or not). There should
7776 be symbolic links to them from
7777 <file>/usr/share/doc/<var>package</var>/examples</file> if
7778 they are examples, and should be perfectly ordinary
7779 <prgn>dpkg</prgn>-handled files (<em>not</em>
7780 configuration files).
7784 These two styles of configuration file handling must
7785 not be mixed, for that way lies madness:
7786 <prgn>dpkg</prgn> will ask about overwriting the file
7787 every time the package is upgraded.
7792 <heading>Sharing configuration files</heading>
7795 Packages which specify the same file as a
7796 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7797 with each other. (This is an instance of the general rule
7798 about not sharing files. Note that neither alternatives
7799 nor diversions are likely to be appropriate in this case;
7800 in particular, <prgn>dpkg</prgn> does not handle diverted
7801 <tt>conffile</tt>s well.)
7805 The maintainer scripts must not alter a <tt>conffile</tt>
7806 of <em>any</em> package, including the one the scripts
7811 If two or more packages use the same configuration file
7812 and it is reasonable for both to be installed at the same
7813 time, one of these packages must be defined as
7814 <em>owner</em> of the configuration file, i.e., it will be
7815 the package which handles that file as a configuration
7816 file. Other packages that use the configuration file must
7817 depend on the owning package if they require the
7818 configuration file to operate. If the other package will
7819 use the configuration file if present, but is capable of
7820 operating without it, no dependency need be declared.
7824 If it is desirable for two or more related packages to
7825 share a configuration file <em>and</em> for all of the
7826 related packages to be able to modify that configuration
7827 file, then the following should be done:
7828 <enumlist compact="compact">
7830 One of the related packages (the "owning" package)
7831 will manage the configuration file with maintainer
7832 scripts as described in the previous section.
7835 The owning package should also provide a program
7836 that the other packages may use to modify the
7840 The related packages must use the provided program
7841 to make any desired modifications to the
7842 configuration file. They should either depend on
7843 the core package to guarantee that the configuration
7844 modifier program is available or accept gracefully
7845 that they cannot modify the configuration file if it
7846 is not. (This is in addition to the fact that the
7847 configuration file may not even be present in the
7854 Sometimes it's appropriate to create a new package which
7855 provides the basic infrastructure for the other packages
7856 and which manages the shared configuration files. (The
7857 <tt>sgml-base</tt> package is a good example.)
7862 <heading>User configuration files ("dotfiles")</heading>
7865 The files in <file>/etc/skel</file> will automatically be
7866 copied into new user accounts by <prgn>adduser</prgn>.
7867 No other program should reference the files in
7868 <file>/etc/skel</file>.
7872 Therefore, if a program needs a dotfile to exist in
7873 advance in <file>$HOME</file> to work sensibly, that dotfile
7874 should be installed in <file>/etc/skel</file> and treated as a
7879 However, programs that require dotfiles in order to
7880 operate sensibly are a bad thing, unless they do create
7881 the dotfiles themselves automatically.
7885 Furthermore, programs should be configured by the Debian
7886 default installation to behave as closely to the upstream
7887 default behavior as possible.
7891 Therefore, if a program in a Debian package needs to be
7892 configured in some way in order to operate sensibly, that
7893 should be done using a site-wide configuration file placed
7894 in <file>/etc</file>. Only if the program doesn't support a
7895 site-wide default configuration and the package maintainer
7896 doesn't have time to add it may a default per-user file be
7897 placed in <file>/etc/skel</file>.
7901 <file>/etc/skel</file> should be as empty as we can make it.
7902 This is particularly true because there is no easy (or
7903 necessarily desirable) mechanism for ensuring that the
7904 appropriate dotfiles are copied into the accounts of
7905 existing users when a package is installed.
7911 <heading>Log files</heading>
7913 Log files should usually be named
7914 <file>/var/log/<var>package</var>.log</file>. If you have many
7915 log files, or need a separate directory for permission
7916 reasons (<file>/var/log</file> is writable only by
7917 <file>root</file>), you should usually create a directory named
7918 <file>/var/log/<var>package</var></file> and place your log
7923 Log files must be rotated occasionally so that they don't
7924 grow indefinitely; the best way to do this is to drop a log
7925 rotation configuration file into the directory
7926 <file>/etc/logrotate.d</file> and use the facilities provided by
7927 logrotate.<footnote>
7929 The traditional approach to log files has been to set up
7930 <em>ad hoc</em> log rotation schemes using simple shell
7931 scripts and cron. While this approach is highly
7932 customizable, it requires quite a lot of sysadmin work.
7933 Even though the original Debian system helped a little
7934 by automatically installing a system which can be used
7935 as a template, this was deemed not enough.
7939 The use of <prgn>logrotate</prgn>, a program developed
7940 by Red Hat, is better, as it centralizes log management.
7941 It has both a configuration file
7942 (<file>/etc/logrotate.conf</file>) and a directory where
7943 packages can drop their individual log rotation
7944 configurations (<file>/etc/logrotate.d</file>).
7947 Here is a good example for a logrotate config
7948 file (for more information see <manref name="logrotate"
7950 <example compact="compact">
7951 /var/log/foo/*.log {
7956 /etc/init.d/foo force-reload
7960 This rotates all files under <file>/var/log/foo</file>, saves 12
7961 compressed generations, and forces the daemon to reload its
7962 configuration information after the log rotation.
7966 Log files should be removed when the package is
7967 purged (but not when it is only removed). This should be
7968 done by the <prgn>postrm</prgn> script when it is called
7969 with the argument <tt>purge</tt> (see <ref
7970 id="removedetails">).
7975 <heading>Permissions and owners</heading>
7978 The rules in this section are guidelines for general use.
7979 If necessary you may deviate from the details below.
7980 However, if you do so you must make sure that what is done
7981 is secure and you should try to be as consistent as possible
7982 with the rest of the system. You should probably also
7983 discuss it on <prgn>debian-devel</prgn> first.
7987 Files should be owned by <tt>root:root</tt>, and made
7988 writable only by the owner and universally readable (and
7989 executable, if appropriate), that is mode 644 or 755.
7993 Directories should be mode 755 or (for group-writability)
7994 mode 2775. The ownership of the directory should be
7995 consistent with its mode: if a directory is mode 2775, it
7996 should be owned by the group that needs write access to
7999 When a package is upgraded, and the owner or permissions
8000 of a file included in the package has changed, dpkg
8001 arranges for the ownership and permissions to be
8002 correctly set upon installation. However, this does not
8003 extend to directories; the permissions and ownership of
8004 directories already on the system does not change on
8005 install or upgrade of packages. This makes sense, since
8006 otherwise common directories like <tt>/usr</tt> would
8007 always be in flux. To correctly change permissions of a
8008 directory the package owns, explicit action is required,
8009 usually in the <tt>postinst</tt> script. Care must be
8010 taken to handle downgrades as well, in that case.
8017 Setuid and setgid executables should be mode 4755 or 2755
8018 respectively, and owned by the appropriate user or group.
8019 They should not be made unreadable (modes like 4711 or
8020 2711 or even 4111); doing so achieves no extra security,
8021 because anyone can find the binary in the freely available
8022 Debian package; it is merely inconvenient. For the same
8023 reason you should not restrict read or execute permissions
8024 on non-set-id executables.
8028 Some setuid programs need to be restricted to particular
8029 sets of users, using file permissions. In this case they
8030 should be owned by the uid to which they are set-id, and by
8031 the group which should be allowed to execute them. They
8032 should have mode 4754; again there is no point in making
8033 them unreadable to those users who must not be allowed to
8038 It is possible to arrange that the system administrator can
8039 reconfigure the package to correspond to their local
8040 security policy by changing the permissions on a binary:
8041 they can do this by using <prgn>dpkg-statoverride</prgn>, as
8042 described below.<footnote>
8043 Ordinary files installed by <prgn>dpkg</prgn> (as
8044 opposed to <tt>conffile</tt>s and other similar objects)
8045 normally have their permissions reset to the distributed
8046 permissions when the package is reinstalled. However,
8047 the use of <prgn>dpkg-statoverride</prgn> overrides this
8050 Another method you should consider is to create a group for
8051 people allowed to use the program(s) and make any setuid
8052 executables executable only by that group.
8056 If you need to create a new user or group for your package
8057 there are two possibilities. Firstly, you may need to
8058 make some files in the binary package be owned by this
8059 user or group, or you may need to compile the user or
8060 group id (rather than just the name) into the binary
8061 (though this latter should be avoided if possible, as in
8062 this case you need a statically allocated id).</p>
8065 If you need a statically allocated id, you must ask for a
8066 user or group id from the <tt>base-passwd</tt> maintainer,
8067 and must not release the package until you have been
8068 allocated one. Once you have been allocated one you must
8069 either make the package depend on a version of the
8070 <tt>base-passwd</tt> package with the id present in
8071 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
8072 your package to create the user or group itself with the
8073 correct id (using <tt>adduser</tt>) in its
8074 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
8075 the <prgn>postinst</prgn> is to be preferred if it is
8076 possible, otherwise a pre-dependency will be needed on the
8077 <tt>adduser</tt> package.)
8081 On the other hand, the program might be able to determine
8082 the uid or gid from the user or group name at runtime, so
8083 that a dynamically allocated id can be used. In this case
8084 you should choose an appropriate user or group name,
8085 discussing this on <prgn>debian-devel</prgn> and checking
8086 with the <package/base-passwd/ maintainer that it is unique and that
8087 they do not wish you to use a statically allocated id
8088 instead. When this has been checked you must arrange for
8089 your package to create the user or group if necessary using
8090 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
8091 <prgn>postinst</prgn> script (again, the latter is to be
8092 preferred if it is possible).
8096 Note that changing the numeric value of an id associated
8097 with a name is very difficult, and involves searching the
8098 file system for all appropriate files. You need to think
8099 carefully whether a static or dynamic id is required, since
8100 changing your mind later will cause problems.
8103 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
8105 This section is not intended as policy, but as a
8106 description of the use of <prgn>dpkg-statoverride</prgn>.
8110 If a system administrator wishes to have a file (or
8111 directory or other such thing) installed with owner and
8112 permissions different from those in the distributed Debian
8113 package, they can use the <prgn>dpkg-statoverride</prgn>
8114 program to instruct <prgn>dpkg</prgn> to use the different
8115 settings every time the file is installed. Thus the
8116 package maintainer should distribute the files with their
8117 normal permissions, and leave it for the system
8118 administrator to make any desired changes. For example, a
8119 daemon which is normally required to be setuid root, but
8120 in certain situations could be used without being setuid,
8121 should be installed setuid in the <tt>.deb</tt>. Then the
8122 local system administrator can change this if they wish.
8123 If there are two standard ways of doing it, the package
8124 maintainer can use <tt>debconf</tt> to find out the
8125 preference, and call <prgn>dpkg-statoverride</prgn> in the
8126 maintainer script if necessary to accommodate the system
8127 administrator's choice. Care must be taken during
8128 upgrades to not override an existing setting.
8132 Given the above, <prgn>dpkg-statoverride</prgn> is
8133 essentially a tool for system administrators and would not
8134 normally be needed in the maintainer scripts. There is
8135 one type of situation, though, where calls to
8136 <prgn>dpkg-statoverride</prgn> would be needed in the
8137 maintainer scripts, and that involves packages which use
8138 dynamically allocated user or group ids. In such a
8139 situation, something like the following idiom can be very
8140 helpful in the package's <prgn>postinst</prgn>, where
8141 <tt>sysuser</tt> is a dynamically allocated id:
8143 for i in /usr/bin/foo /usr/sbin/bar
8145 # only do something when no setting exists
8146 if ! dpkg-statoverride --list $i >/dev/null 2>&1
8148 #include: debconf processing, question about foo and bar
8149 if [ "$RET" = "true" ] ; then
8150 dpkg-statoverride --update --add sysuser root 4755 $i
8155 The corresponding code to remove the override when the package
8158 for i in /usr/bin/foo /usr/sbin/bar
8160 if dpkg-statoverride --list $i >/dev/null 2>&1
8162 dpkg-statoverride --remove $i
8172 <chapt id="customized-programs">
8173 <heading>Customized programs</heading>
8175 <sect id="arch-spec">
8176 <heading>Architecture specification strings</heading>
8179 If a program needs to specify an <em>architecture specification
8180 string</em> in some place, it should select one of the strings
8181 provided by <tt>dpkg-architecture -L</tt>. The strings are in
8182 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
8183 part is sometimes elided, as when the OS is Linux.
8187 Note that we don't want to use
8188 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
8189 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
8190 since this would make our programs incompatible with other
8191 Linux distributions. We also don't use something like
8192 <tt><var>arch</var>-unknown-linux</tt>, since the
8193 <tt>unknown</tt> does not look very good.
8196 <sect1 id="arch-wildcard-spec">
8197 <heading>Architecture wildcards</heading>
8200 A package may specify an architecture wildcard. Architecture
8201 wildcards are in the format <tt>any</tt> (which matches every
8202 architecture), <tt><var>os</var></tt>-any, or
8203 any-<tt><var>cpu</var></tt>. <footnote>
8204 Internally, the package system normalizes the GNU triplets
8205 and the Debian arches into Debian arch triplets (which are
8206 kind of inverted GNU triplets), with the first component of
8207 the triplet representing the libc and ABI in use, and then
8208 does matching against those triplets. However, such
8209 triplets are an internal implementation detail that should
8210 not be used by packages directly. The libc and ABI portion
8211 is handled internally by the package system based on
8212 the <var>os</var> and <var>cpu</var>.
8219 <heading>Daemons</heading>
8222 The configuration files <file>/etc/services</file>,
8223 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
8224 by the <prgn>netbase</prgn> package and must not be modified
8229 If a package requires a new entry in one of these files, the
8230 maintainer should get in contact with the
8231 <prgn>netbase</prgn> maintainer, who will add the entries
8232 and release a new version of the <prgn>netbase</prgn>
8237 The configuration file <file>/etc/inetd.conf</file> must not be
8238 modified by the package's scripts except via the
8239 <prgn>update-inetd</prgn> script or the
8240 <file>DebianNet.pm</file> Perl module. See their documentation
8241 for details on how to add entries.
8245 If a package wants to install an example entry into
8246 <file>/etc/inetd.conf</file>, the entry must be preceded with
8247 exactly one hash character (<tt>#</tt>). Such lines are
8248 treated as "commented out by user" by the
8249 <prgn>update-inetd</prgn> script and are not changed or
8250 activated during package updates.
8255 <heading>Using pseudo-ttys and modifying wtmp, utmp and
8259 Some programs need to create pseudo-ttys. This should be done
8260 using Unix98 ptys if the C library supports it. The resulting
8261 program must not be installed setuid root, unless that
8262 is required for other functionality.
8266 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
8267 <file>/var/log/lastlog</file> must be installed writable by
8268 group <tt>utmp</tt>. Programs which need to modify those
8269 files must be installed setgid <tt>utmp</tt>.
8274 <heading>Editors and pagers</heading>
8277 Some programs have the ability to launch an editor or pager
8278 program to edit or display a text document. Since there are
8279 lots of different editors and pagers available in the Debian
8280 distribution, the system administrator and each user should
8281 have the possibility to choose their preferred editor and
8286 In addition, every program should choose a good default
8287 editor/pager if none is selected by the user or system
8292 Thus, every program that launches an editor or pager must
8293 use the EDITOR or PAGER environment variable to determine
8294 the editor or pager the user wishes to use. If these
8295 variables are not set, the programs <file>/usr/bin/editor</file>
8296 and <file>/usr/bin/pager</file> should be used, respectively.
8300 These two files are managed through the <prgn>dpkg</prgn>
8301 "alternatives" mechanism. Thus every package providing an
8302 editor or pager must call the
8303 <prgn>update-alternatives</prgn> script to register these
8308 If it is very hard to adapt a program to make use of the
8309 EDITOR or PAGER variables, that program may be configured to
8310 use <file>/usr/bin/sensible-editor</file> and
8311 <file>/usr/bin/sensible-pager</file> as the editor or pager
8312 program respectively. These are two scripts provided in the
8313 <package>sensible-utils</package> package that check the EDITOR
8314 and PAGER variables and launch the appropriate program, and fall
8315 back to <file>/usr/bin/editor</file>
8316 and <file>/usr/bin/pager</file> if the variable is not set.
8320 A program may also use the VISUAL environment variable to
8321 determine the user's choice of editor. If it exists, it
8322 should take precedence over EDITOR. This is in fact what
8323 <file>/usr/bin/sensible-editor</file> does.
8327 It is not required for a package to depend on
8328 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
8329 package to provide such virtual packages.<footnote>
8330 The Debian base system already provides an editor and a
8336 <sect id="web-appl">
8337 <heading>Web servers and applications</heading>
8340 This section describes the locations and URLs that should
8341 be used by all web servers and web applications in the
8348 Cgi-bin executable files are installed in the
8350 <example compact="compact">
8351 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
8353 and should be referred to as
8354 <example compact="compact">
8355 http://localhost/cgi-bin/<var>cgi-bin-name</var>
8361 <p>Access to HTML documents</p>
8364 HTML documents for a package are stored in
8365 <file>/usr/share/doc/<var>package</var></file>
8366 and can be referred to as
8367 <example compact="compact">
8368 http://localhost/doc/<var>package</var>/<var>filename</var>
8373 The web server should restrict access to the document
8374 tree so that only clients on the same host can read
8375 the documents. If the web server does not support such
8376 access controls, then it should not provide access at
8377 all, or ask about providing access during installation.
8382 <p>Access to images</p>
8384 It is recommended that images for a package be stored
8385 in <tt>/usr/share/images/<var>package</var></tt> and
8386 may be referred to through an alias <tt>/images/</tt>
8389 http://localhost/images/<package>/<filename>
8396 <p>Web Document Root</p>
8399 Web Applications should try to avoid storing files in
8400 the Web Document Root. Instead they should use the
8401 /usr/share/doc/<var>package</var> directory for
8402 documents and register the Web Application via the
8403 <package>doc-base</package> package. If access to the
8404 web document root is unavoidable then use
8405 <example compact="compact">
8408 as the Document Root. This might be just a symbolic
8409 link to the location where the system administrator
8410 has put the real document root.
8413 <item><p>Providing httpd and/or httpd-cgi</p>
8415 All web servers should provide the virtual package
8416 <tt>httpd</tt>. If a web server has CGI support it should
8417 provide <tt>httpd-cgi</tt> additionally.
8420 All web applications which do not contain CGI scripts should
8421 depend on <tt>httpd</tt>, all those web applications which
8422 <tt>do</tt> contain CGI scripts, should depend on
8430 <sect id="mail-transport-agents">
8431 <heading>Mail transport, delivery and user agents</heading>
8434 Debian packages which process electronic mail, whether mail
8435 user agents (MUAs) or mail transport agents (MTAs), must
8436 ensure that they are compatible with the configuration
8437 decisions below. Failure to do this may result in lost
8438 mail, broken <tt>From:</tt> lines, and other serious brain
8443 The mail spool is <file>/var/mail</file> and the interface to
8444 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8445 the FHS). On older systems, the mail spool may be
8446 physically located in <file>/var/spool/mail</file>, but all
8447 access to the mail spool should be via the
8448 <file>/var/mail</file> symlink. The mail spool is part of the
8449 base system and not part of the MTA package.
8453 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8454 programs (such as IMAP daemons) must lock the mailbox in an
8455 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8456 be combined with dot locking. To avoid deadlocks, a program
8457 should use <tt>fcntl()</tt> first and dot locking after
8458 this, or alternatively implement the two locking methods in
8459 a non blocking way<footnote>
8460 If it is not possible to establish both locks, the
8461 system shouldn't wait for the second lock to be
8462 established, but remove the first lock, wait a (random)
8463 time, and start over locking again.
8464 </footnote>. Using the functions <tt>maillock</tt> and
8465 <tt>mailunlock</tt> provided by the
8466 <tt>liblockfile*</tt><footnote>
8467 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8468 to use these functions.
8469 </footnote> packages is the recommended way to realize this.
8473 Mailboxes are generally either mode 600 and owned by
8474 <var>user</var> or mode 660 and owned by
8475 <tt><var>user</var>:mail</tt><footnote>
8476 There are two traditional permission schemes for mail spools:
8477 mode 600 with all mail delivery done by processes running as
8478 the destination user, or mode 660 and owned by group mail with
8479 mail delivery done by a process running as a system user in
8480 group mail. Historically, Debian required mode 660 mail
8481 spools to enable the latter model, but that model has become
8482 increasingly uncommon and the principle of least privilege
8483 indicates that mail systems that use the first model should
8484 use permissions of 600. If delivery to programs is permitted,
8485 it's easier to keep the mail system secure if the delivery
8486 agent runs as the destination user. Debian Policy therefore
8487 permits either scheme.
8488 </footnote>. The local system administrator may choose a
8489 different permission scheme; packages should not make
8490 assumptions about the permission and ownership of mailboxes
8491 unless required (such as when creating a new mailbox). A MUA
8492 may remove a mailbox (unless it has nonstandard permissions) in
8493 which case the MTA or another MUA must recreate it if needed.
8497 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8498 be setgid mail to do the locking mentioned above (and
8499 must obviously avoid accessing other users' mailboxes
8500 using this privilege).</p>
8503 <file>/etc/aliases</file> is the source file for the system mail
8504 aliases (e.g., postmaster, usenet, etc.), it is the one
8505 which the sysadmin and <prgn>postinst</prgn> scripts may
8506 edit. After <file>/etc/aliases</file> is edited the program or
8507 human editing it must call <prgn>newaliases</prgn>. All MTA
8508 packages must come with a <prgn>newaliases</prgn> program,
8509 even if it does nothing, but older MTA packages did not do
8510 this so programs should not fail if <prgn>newaliases</prgn>
8511 cannot be found. Note that because of this, all MTA
8512 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8513 <tt>Replaces: mail-transport-agent</tt> control file
8518 The convention of writing <tt>forward to
8519 <var>address</var></tt> in the mailbox itself is not
8520 supported. Use a <tt>.forward</tt> file instead.</p>
8523 The <prgn>rmail</prgn> program used by UUCP
8524 for incoming mail should be <file>/usr/sbin/rmail</file>.
8525 Likewise, <prgn>rsmtp</prgn>, for receiving
8526 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8530 If your package needs to know what hostname to use on (for
8531 example) outgoing news and mail messages which are generated
8532 locally, you should use the file <file>/etc/mailname</file>. It
8533 will contain the portion after the username and <tt>@</tt>
8534 (at) sign for email addresses of users on the machine
8535 (followed by a newline).
8539 Such a package should check for the existence of this file
8540 when it is being configured. If it exists, it should be
8541 used without comment, although an MTA's configuration script
8542 may wish to prompt the user even if it finds that this file
8543 exists. If the file does not exist, the package should
8544 prompt the user for the value (preferably using
8545 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8546 as well as using it in the package's configuration. The
8547 prompt should make it clear that the name will not just be
8548 used by that package. For example, in this situation the
8549 <tt>inn</tt> package could say something like:
8550 <example compact="compact">
8551 Please enter the "mail name" of your system. This is the
8552 hostname portion of the address to be shown on outgoing
8553 news and mail messages. The default is
8554 <var>syshostname</var>, your system's host name. Mail
8555 name ["<var>syshostname</var>"]:
8557 where <var>syshostname</var> is the output of <tt>hostname
8563 <heading>News system configuration</heading>
8566 All the configuration files related to the NNTP (news)
8567 servers and clients should be located under
8568 <file>/etc/news</file>.</p>
8571 There are some configuration issues that apply to a number
8572 of news clients and server packages on the machine. These
8576 <tag><file>/etc/news/organization</file></tag>
8578 A string which should appear as the
8579 organization header for all messages posted
8580 by NNTP clients on the machine
8583 <tag><file>/etc/news/server</file></tag>
8585 Contains the FQDN of the upstream NNTP
8586 server, or localhost if the local machine is
8591 Other global files may be added as required for cross-package news
8598 <heading>Programs for the X Window System</heading>
8601 <heading>Providing X support and package priorities</heading>
8604 Programs that can be configured with support for the X
8605 Window System must be configured to do so and must declare
8606 any package dependencies necessary to satisfy their
8607 runtime requirements when using the X Window System. If
8608 such a package is of higher priority than the X packages
8609 on which it depends, it is required that either the
8610 X-specific components be split into a separate package, or
8611 that an alternative version of the package, which includes
8612 X support, be provided, or that the package's priority be
8618 <heading>Packages providing an X server</heading>
8621 Packages that provide an X server that, directly or
8622 indirectly, communicates with real input and display
8623 hardware should declare in their control data that they
8624 provide the virtual package <tt>xserver</tt>.<footnote>
8625 This implements current practice, and provides an
8626 actual policy for usage of the <tt>xserver</tt>
8627 virtual package which appears in the virtual packages
8628 list. In a nutshell, X servers that interface
8629 directly with the display and input hardware or via
8630 another subsystem (e.g., GGI) should provide
8631 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8632 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8638 <heading>Packages providing a terminal emulator</heading>
8641 Packages that provide a terminal emulator for the X Window
8642 System which meet the criteria listed below should declare
8643 in their control data that they provide the virtual
8644 package <tt>x-terminal-emulator</tt>. They should also
8645 register themselves as an alternative for
8646 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8651 To be an <tt>x-terminal-emulator</tt>, a program must:
8652 <list compact="compact">
8654 Be able to emulate a DEC VT100 terminal, or a
8655 compatible terminal.
8659 Support the command-line option <tt>-e
8660 <var>command</var></tt>, which creates a new
8661 terminal window<footnote>
8662 "New terminal window" does not necessarily mean
8663 a new top-level X window directly parented by
8664 the window manager; it could, if the terminal
8665 emulator application were so coded, be a new
8666 "view" in a multiple-document interface (MDI).
8668 and runs the specified <var>command</var>,
8669 interpreting the entirety of the rest of the command
8670 line as a command to pass straight to exec, in the
8671 manner that <tt>xterm</tt> does.
8675 Support the command-line option <tt>-T
8676 <var>title</var></tt>, which creates a new terminal
8677 window with the window title <var>title</var>.
8684 <heading>Packages providing a window manager</heading>
8687 Packages that provide a window manager should declare in
8688 their control data that they provide the virtual package
8689 <tt>x-window-manager</tt>. They should also register
8690 themselves as an alternative for
8691 <file>/usr/bin/x-window-manager</file>, with a priority
8692 calculated as follows:
8693 <list compact="compact">
8695 Start with a priority of 20.
8699 If the window manager supports the Debian menu
8700 system, add 20 points if this support is available
8701 in the package's default configuration (i.e., no
8702 configuration files belonging to the system or user
8703 have to be edited to activate the feature); if
8704 configuration files must be modified, add only 10
8710 If the window manager complies with <url
8711 id="http://www.freedesktop.org/Standards/wm-spec"
8712 name="The Window Manager Specification Project">,
8713 written by the <url id="http://www.freedesktop.org/"
8714 name="Free Desktop Group">, add 40 points.
8718 If the window manager permits the X session to be
8719 restarted using a <em>different</em> window manager
8720 (without killing the X server) in its default
8721 configuration, add 10 points; otherwise add none.
8728 <heading>Packages providing fonts</heading>
8731 Packages that provide fonts for the X Window
8733 For the purposes of Debian Policy, a "font for the X
8734 Window System" is one which is accessed via X protocol
8735 requests. Fonts for the Linux console, for PostScript
8736 renderer, or any other purpose, do not fit this
8737 definition. Any tool which makes such fonts available
8738 to the X Window System, however, must abide by this
8741 must do a number of things to ensure that they are both
8742 available without modification of the X or font server
8743 configuration, and that they do not corrupt files used by
8744 other font packages to register information about
8748 Fonts of any type supported by the X Window System
8749 must be in a separate binary package from any
8750 executables, libraries, or documentation (except
8751 that specific to the fonts shipped, such as their
8752 license information). If one or more of the fonts
8753 so packaged are necessary for proper operation of
8754 the package with which they are associated the font
8755 package may be Recommended; if the fonts merely
8756 provide an enhancement, a Suggests relationship may
8757 be used. Packages must not Depend on font
8759 This is because the X server may retrieve fonts
8760 from the local file system or over the network
8761 from an X font server; the Debian package system
8762 is empowered to deal only with the local
8768 BDF fonts must be converted to PCF fonts with the
8769 <prgn>bdftopcf</prgn> utility (available in the
8770 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8771 placed in a directory that corresponds to their
8773 <list compact="compact">
8775 100 dpi fonts must be placed in
8776 <file>/usr/share/fonts/X11/100dpi/</file>.
8780 75 dpi fonts must be placed in
8781 <file>/usr/share/fonts/X11/75dpi/</file>.
8785 Character-cell fonts, cursor fonts, and other
8786 low-resolution fonts must be placed in
8787 <file>/usr/share/fonts/X11/misc/</file>.
8793 Type 1 fonts must be placed in
8794 <file>/usr/share/fonts/X11/Type1/</file>. If font
8795 metric files are available, they must be placed here
8800 Subdirectories of <file>/usr/share/fonts/X11/</file>
8801 other than those listed above must be neither
8802 created nor used. (The <file>PEX</file>, <file>CID</file>,
8803 <file>Speedo</file>, and <file>cyrillic</file> directories
8804 are excepted for historical reasons, but installation of
8805 files into these directories remains discouraged.)
8809 Font packages may, instead of placing files directly
8810 in the X font directories listed above, provide
8811 symbolic links in that font directory pointing to
8812 the files' actual location in the filesystem. Such
8813 a location must comply with the FHS.
8817 Font packages should not contain both 75dpi and
8818 100dpi versions of a font. If both are available,
8819 they should be provided in separate binary packages
8820 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8821 the names of the packages containing the
8822 corresponding fonts.
8826 Fonts destined for the <file>misc</file> subdirectory
8827 should not be included in the same package as 75dpi
8828 or 100dpi fonts; instead, they should be provided in
8829 a separate package with <tt>-misc</tt> appended to
8834 Font packages must not provide the files
8835 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8836 <file>fonts.scale</file> in a font directory:
8839 <file>fonts.dir</file> files must not be provided at all.
8843 <file>fonts.alias</file> and <file>fonts.scale</file>
8844 files, if needed, should be provided in the
8846 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8847 where <var>fontdir</var> is the name of the
8849 <file>/usr/share/fonts/X11/</file> where the
8850 package's corresponding fonts are stored
8851 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8852 <var>package</var> is the name of the package
8853 that provides these fonts, and
8854 <var>extension</var> is either <tt>scale</tt>
8855 or <tt>alias</tt>, whichever corresponds to
8862 Font packages must declare a dependency on
8863 <tt>xfonts-utils</tt> in their control
8868 Font packages that provide one or more
8869 <file>fonts.scale</file> files as described above must
8870 invoke <prgn>update-fonts-scale</prgn> on each
8871 directory into which they installed fonts
8872 <em>before</em> invoking
8873 <prgn>update-fonts-dir</prgn> on that directory.
8874 This invocation must occur in both the
8875 <prgn>postinst</prgn> (for all arguments) and
8876 <prgn>postrm</prgn> (for all arguments except
8877 <tt>upgrade</tt>) scripts.
8881 Font packages that provide one or more
8882 <file>fonts.alias</file> files as described above must
8883 invoke <prgn>update-fonts-alias</prgn> on each
8884 directory into which they installed fonts. This
8885 invocation must occur in both the
8886 <prgn>postinst</prgn> (for all arguments) and
8887 <prgn>postrm</prgn> (for all arguments except
8888 <tt>upgrade</tt>) scripts.
8892 Font packages must invoke
8893 <prgn>update-fonts-dir</prgn> on each directory into
8894 which they installed fonts. This invocation must
8895 occur in both the <prgn>postinst</prgn> (for all
8896 arguments) and <prgn>postrm</prgn> (for all
8897 arguments except <tt>upgrade</tt>) scripts.
8901 Font packages must not provide alias names for the
8902 fonts they include which collide with alias names
8903 already in use by fonts already packaged.
8907 Font packages must not provide fonts with the same
8908 XLFD registry name as another font already packaged.
8914 <sect1 id="appdefaults">
8915 <heading>Application defaults files</heading>
8918 Application defaults files must be installed in the
8919 directory <file>/etc/X11/app-defaults/</file> (use of a
8920 localized subdirectory of <file>/etc/X11/</file> as described
8921 in the <em>X Toolkit Intrinsics - C Language
8922 Interface</em> manual is also permitted). They must be
8923 registered as <tt>conffile</tt>s or handled as
8924 configuration files.
8928 Customization of programs' X resources may also be
8929 supported with the provision of a file with the same name
8930 as that of the package placed in
8931 the <file>/etc/X11/Xresources/</file> directory, which
8932 must be registered as a <tt>conffile</tt> or handled as a
8933 configuration file.<footnote>
8934 Note that this mechanism is not the same as using
8935 app-defaults; app-defaults are tied to the client
8936 binary on the local file system, whereas X resources
8937 are stored in the X server and affect all connecting
8944 <heading>Installation directory issues</heading>
8947 Historically, packages using the X Window System used a
8948 separate set of installation directories from other packages.
8949 This practice has been discontinued and packages using the X
8950 Window System should now generally be installed in the same
8951 directories as any other package. Specifically, packages must
8952 not install files under the <file>/usr/X11R6/</file> directory
8953 and the <file>/usr/X11R6/</file> directory hierarchy should be
8954 regarded as obsolete.
8958 Include files previously installed under
8959 <file>/usr/X11R6/include/X11/</file> should be installed into
8960 <file>/usr/include/X11/</file>. For files previously
8961 installed into subdirectories of
8962 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
8963 determine if subdirectories of <file>/usr/lib/</file> and
8964 <file>/usr/share/</file> can be used. If not, a subdirectory
8965 of <file>/usr/lib/X11/</file> should be used.
8969 Configuration files for window, display, or session managers
8970 or other applications that are tightly integrated with the X
8971 Window System may be placed in a subdirectory
8972 of <file>/etc/X11/</file> corresponding to the package name.
8973 Other X Window System applications should use
8974 the <file>/etc/</file> directory unless otherwise mandated by
8975 policy (such as for <ref id="appdefaults">).
8980 <heading>The OSF/Motif and OpenMotif libraries</heading>
8983 <em>Programs that require the non-DFSG-compliant OSF/Motif or
8984 OpenMotif libraries</em><footnote>
8985 OSF/Motif and OpenMotif are collectively referred to as
8986 "Motif" in this policy document.
8988 should be compiled against and tested with LessTif (a free
8989 re-implementation of Motif) instead. If the maintainer
8990 judges that the program or programs do not work
8991 sufficiently well with LessTif to be distributed and
8992 supported, but do so when compiled against Motif, then two
8993 versions of the package should be created; one linked
8994 statically against Motif and with <tt>-smotif</tt>
8995 appended to the package name, and one linked dynamically
8996 against Motif and with <tt>-dmotif</tt> appended to the
9001 Both Motif-linked versions are dependent
9002 upon non-DFSG-compliant software and thus cannot be
9003 uploaded to the <em>main</em> distribution; if the
9004 software is itself DFSG-compliant it may be uploaded to
9005 the <em>contrib</em> distribution. While known existing
9006 versions of Motif permit unlimited redistribution of
9007 binaries linked against the library (whether statically or
9008 dynamically), it is the package maintainer's
9009 responsibility to determine whether this is permitted by
9010 the license of the copy of Motif in their possession.
9016 <heading>Perl programs and modules</heading>
9019 Perl programs and modules should follow the current Perl policy.
9023 The Perl policy can be found in the <tt>perl-policy</tt>
9024 files in the <tt>debian-policy</tt> package.
9025 It is also available from the Debian web mirrors at
9026 <tt><url name="/doc/packaging-manuals/perl-policy/"
9027 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
9032 <heading>Emacs lisp programs</heading>
9035 Please refer to the "Debian Emacs Policy" for details of how to
9036 package emacs lisp programs.
9040 The Emacs policy is available in
9041 <file>debian-emacs-policy.gz</file> of the
9042 <package>emacsen-common</package> package.
9043 It is also available from the Debian web mirrors at
9044 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
9045 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
9050 <heading>Games</heading>
9053 The permissions on <file>/var/games</file> are mode 755, owner
9054 <tt>root</tt> and group <tt>root</tt>.
9058 Each game decides on its own security policy.</p>
9061 Games which require protected, privileged access to
9062 high-score files, saved games, etc., may be made
9063 set-<em>group</em>-id (mode 2755) and owned by
9064 <tt>root:games</tt>, and use files and directories with
9065 appropriate permissions (770 <tt>root:games</tt>, for
9066 example). They must not be made
9067 set-<em>user</em>-id, as this causes security problems. (If
9068 an attacker can subvert any set-user-id game they can
9069 overwrite the executable of any other, causing other players
9070 of these games to run a Trojan horse program. With a
9071 set-group-id game the attacker only gets access to less
9072 important game data, and if they can get at the other
9073 players' accounts at all it will take considerably more
9077 Some packages, for example some fortune cookie programs, are
9078 configured by the upstream authors to install with their
9079 data files or other static information made unreadable so
9080 that they can only be accessed through set-id programs
9081 provided. You should not do this in a Debian package: anyone can
9082 download the <file>.deb</file> file and read the data from it,
9083 so there is no point making the files unreadable. Not
9084 making the files unreadable also means that you don't have
9085 to make so many programs set-id, which reduces the risk of a
9089 As described in the FHS, binaries of games should be
9090 installed in the directory <file>/usr/games</file>. This also
9091 applies to games that use the X Window System. Manual pages
9092 for games (X and non-X games) should be installed in
9093 <file>/usr/share/man/man6</file>.</p>
9099 <heading>Documentation</heading>
9102 <heading>Manual pages</heading>
9105 You should install manual pages in <prgn>nroff</prgn> source
9106 form, in appropriate places under <file>/usr/share/man</file>.
9107 You should only use sections 1 to 9 (see the FHS for more
9108 details). You must not install a pre-formatted "cat page".
9112 Each program, utility, and function should have an
9113 associated manual page included in the same package. It is
9114 suggested that all configuration files also have a manual
9115 page included as well. Manual pages for protocols and other
9116 auxiliary things are optional.
9120 If no manual page is available, this is considered as a bug
9121 and should be reported to the Debian Bug Tracking System (the
9122 maintainer of the package is allowed to write this bug report
9123 themselves, if they so desire). Do not close the bug report
9124 until a proper man page is available.<footnote>
9125 It is not very hard to write a man page. See the
9126 <url id="http://www.schweikhardt.net/man_page_howto.html"
9127 name="Man-Page-HOWTO">,
9128 <manref name="man" section="7">, the examples
9129 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
9130 the helper program <prgn>help2man</prgn>, or the
9131 directory <file>/usr/share/doc/man-db/examples</file>.
9136 You may forward a complaint about a missing man page to the
9137 upstream authors, and mark the bug as forwarded in the
9138 Debian bug tracking system. Even though the GNU Project do
9139 not in general consider the lack of a man page to be a bug,
9140 we do; if they tell you that they don't consider it a bug
9141 you should leave the bug in our bug tracking system open
9146 Manual pages should be installed compressed using <tt>gzip -9</tt>.
9150 If one man page needs to be accessible via several names it
9151 is better to use a symbolic link than the <file>.so</file>
9152 feature, but there is no need to fiddle with the relevant
9153 parts of the upstream source to change from <file>.so</file> to
9154 symlinks: don't do it unless it's easy. You should not
9155 create hard links in the manual page directories, nor put
9156 absolute filenames in <file>.so</file> directives. The filename
9157 in a <file>.so</file> in a man page should be relative to the
9158 base of the man page tree (usually
9159 <file>/usr/share/man</file>). If you do not create any links
9160 (whether symlinks, hard links, or <tt>.so</tt> directives)
9161 in the file system to the alternate names of the man page,
9162 then you should not rely on <prgn>man</prgn> finding your
9163 man page under those names based solely on the information in
9164 the man page's header.<footnote>
9165 Supporting this in <prgn>man</prgn> often requires
9166 unreasonable processing time to find a manual page or to
9167 report that none exists, and moves knowledge into man's
9168 database that would be better left in the file system.
9169 This support is therefore deprecated and will cease to
9170 be present in the future.
9175 Manual pages in locale-specific subdirectories of
9176 <file>/usr/share/man</file> should use either UTF-8 or the usual
9177 legacy encoding for that language (normally the one corresponding
9178 to the shortest relevant locale name in
9179 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
9180 <file>/usr/share/man/fr</file> should use either UTF-8 or
9181 ISO-8859-1.<footnote>
9182 <prgn>man</prgn> will automatically detect whether UTF-8 is in
9183 use. In future, all manual pages will be required to use
9189 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
9190 included in the subdirectory name unless it indicates a
9191 significant difference in the language, as this excludes
9192 speakers of the language in other countries.<footnote>
9193 At the time of writing, Chinese and Portuguese are the main
9194 languages with such differences, so <file>pt_BR</file>,
9195 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
9200 If a localized version of a manual page is provided, it should
9201 either be up-to-date or it should be obvious to the reader that
9202 it is outdated and the original manual page should be used
9203 instead. This can be done either by a note at the beginning of
9204 the manual page or by showing the missing or changed portions in
9205 the original language instead of the target language.
9210 <heading>Info documents</heading>
9213 Info documents should be installed in <file>/usr/share/info</file>.
9214 They should be compressed with <tt>gzip -9</tt>.
9218 The <prgn>install-info</prgn> program maintains a directory of
9219 installed info documents in <file>/usr/share/info/dir</file> for
9220 the use of info readers.<footnote>
9221 It was previously necessary for packages installing info
9222 documents to run <prgn>install-info</prgn> from maintainer
9223 scripts. This is no longer necessary. The installation
9224 system now uses dpkg triggers.
9226 This file must not be included in packages. Packages containing
9227 info documents should depend on <tt>dpkg (>= 1.15.4) |
9228 install-info</tt> to ensure that the directory file is properly
9229 rebuilt during partial upgrades from Debian 5.0 (lenny) and
9234 Info documents should contain section and directory entry
9235 information in the document for the use
9236 of <prgn>install-info</prgn>. The section should be specified
9237 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
9238 space and the section of this info page. The directory entry or
9239 entries should be included between
9240 a <tt>START-INFO-DIR-ENTRY</tt> line and
9241 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
9243 INFO-DIR-SECTION Individual utilities
9244 START-INFO-DIR-ENTRY
9245 * example: (example). An example info directory entry.
9248 To determine which section to use, you should look
9249 at <file>/usr/share/info/dir</file> on your system and choose
9250 the most relevant (or create a new section if none of the
9251 current sections are relevant).<footnote>
9252 Normally, info documents are generated from Texinfo source.
9253 To include this information in the generated info document, if
9254 it is absent, add commands like:
9256 @dircategory Individual utilities
9258 * example: (example). An example info directory entry.
9261 to the Texinfo source of the document and ensure that the info
9262 documents are rebuilt from source during the package build.
9268 <heading>Additional documentation</heading>
9271 Any additional documentation that comes with the package may
9272 be installed at the discretion of the package maintainer.
9273 Plain text documentation should be installed in the directory
9274 <file>/usr/share/doc/<var>package</var></file>, where
9275 <var>package</var> is the name of the package, and
9276 compressed with <tt>gzip -9</tt> unless it is small.
9280 If a package comes with large amounts of documentation which
9281 many users of the package will not require you should create
9282 a separate binary package to contain it, so that it does not
9283 take up disk space on the machines of users who do not need
9284 or want it installed.</p>
9287 It is often a good idea to put text information files
9288 (<file>README</file>s, changelogs, and so forth) that come with
9289 the source package in <file>/usr/share/doc/<var>package</var></file>
9290 in the binary package. However, you don't need to install
9291 the instructions for building and installing the package, of
9295 Packages must not require the existence of any files in
9296 <file>/usr/share/doc/</file> in order to function
9298 The system administrator should be able to
9299 delete files in <file>/usr/share/doc/</file> without causing
9300 any programs to break.
9302 Any files that are referenced by programs but are also
9303 useful as stand alone documentation should be installed under
9304 <file>/usr/share/<var>package</var>/</file> with symbolic links from
9305 <file>/usr/share/doc/<var>package</var></file>.
9309 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9310 link to another directory in <file>/usr/share/doc</file> only if
9311 the two packages both come from the same source and the
9312 first package Depends on the second.<footnote>
9314 Please note that this does not override the section on
9315 changelog files below, so the file
9316 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
9317 must refer to the changelog for the current version of
9318 <var>package</var> in question. In practice, this means
9319 that the sources of the target and the destination of the
9320 symlink must be the same (same source package and
9327 Former Debian releases placed all additional documentation
9328 in <file>/usr/doc/<var>package</var></file>. This has been
9329 changed to <file>/usr/share/doc/<var>package</var></file>,
9330 and packages must not put documentation in the directory
9331 <file>/usr/doc/<var>package</var></file>. <footnote>
9332 At this phase of the transition, we no longer require a
9333 symbolic link in <file>/usr/doc/</file>. At a later point,
9334 policy shall change to make the symbolic links a bug.
9340 <heading>Preferred documentation formats</heading>
9343 The unification of Debian documentation is being carried out
9347 If your package comes with extensive documentation in a
9348 markup format that can be converted to various other formats
9349 you should if possible ship HTML versions in a binary
9350 package, in the directory
9351 <file>/usr/share/doc/<var>appropriate-package</var></file> or
9352 its subdirectories.<footnote>
9353 The rationale: The important thing here is that HTML
9354 docs should be available in <em>some</em> package, not
9355 necessarily in the main binary package.
9360 Other formats such as PostScript may be provided at the
9361 package maintainer's discretion.
9365 <sect id="copyrightfile">
9366 <heading>Copyright information</heading>
9369 Every package must be accompanied by a verbatim copy of its
9370 copyright information and distribution license in the file
9371 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
9372 file must neither be compressed nor be a symbolic link.
9376 In addition, the copyright file must say where the upstream
9377 sources (if any) were obtained. It should name the original
9378 authors of the package and the Debian maintainer(s) who were
9379 involved with its creation.
9383 Packages in the <em>contrib</em> or <em>non-free</em> archive
9384 areas should state in the copyright file that the package is not
9385 part of the Debian GNU/Linux distribution and briefly explain
9390 A copy of the file which will be installed in
9391 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9392 be in <file>debian/copyright</file> in the source package.
9396 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9397 link to another directory in <file>/usr/share/doc</file> only if
9398 the two packages both come from the same source and the
9399 first package Depends on the second. These rules are
9400 important because copyrights must be extractable by
9405 Packages distributed under the Apache license (version 2.0), the
9406 Artistic license, the GNU GPL (version 2 or 3), the GNU LGPL
9407 (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or 1.3)
9408 should refer to the corresponding files
9409 under <file>/usr/share/common-licenses</file>,<footnote>
9412 <file>/usr/share/common-licenses/Apache-2.0</file>,
9413 <file>/usr/share/common-licenses/Artistic</file>,
9414 <file>/usr/share/common-licenses/GPL-2</file>,
9415 <file>/usr/share/common-licenses/GPL-3</file>,
9416 <file>/usr/share/common-licenses/LGPL-2</file>,
9417 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9418 <file>/usr/share/common-licenses/LGPL-3</file>,
9419 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
9420 <file>/usr/share/common-licenses/GFDL-1.3</file>
9421 respectively. The University of California BSD license is
9422 also included in <package>base-files</package> as
9423 <file>/usr/share/common-licenses/BSD</file>, but given the
9424 brevity of this license, its specificity to code whose
9425 copyright is held by the Regents of the University of
9426 California, and the frequency of minor wording changes, its
9427 text should be included in the copyright file rather than
9428 referencing this file.
9430 </footnote> rather than quoting them in the copyright
9435 You should not use the copyright file as a general <file>README</file>
9436 file. If your package has such a file it should be
9437 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9438 <file>README.Debian</file> or some other appropriate place.</p>
9442 <heading>Examples</heading>
9445 Any examples (configurations, source files, whatever),
9446 should be installed in a directory
9447 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9448 files should not be referenced by any program: they're there
9449 for the benefit of the system administrator and users as
9450 documentation only. Architecture-specific example files
9451 should be installed in a directory
9452 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9454 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9455 latter directory itself may be a symbolic link to the
9460 If the purpose of a package is to provide examples, then the
9461 example files may be installed into
9462 <file>/usr/share/doc/<var>package</var></file>.
9466 <sect id="changelogs">
9467 <heading>Changelog files</heading>
9470 Packages that are not Debian-native must contain a
9471 compressed copy of the <file>debian/changelog</file> file from
9472 the Debian source tree in
9473 <file>/usr/share/doc/<var>package</var></file> with the name
9474 <file>changelog.Debian.gz</file>.
9478 If an upstream changelog is available, it should be accessible as
9479 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9480 plain text. If the upstream changelog is distributed in
9481 HTML, it should be made available in that form as
9482 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9483 and a plain text <file>changelog.gz</file> should be generated
9484 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9485 the upstream changelog files do not already conform to this
9486 naming convention, then this may be achieved either by
9487 renaming the files, or by adding a symbolic link, at the
9488 maintainer's discretion.<footnote>
9489 Rationale: People should not have to look in places for
9490 upstream changelogs merely because they are given
9491 different names or are distributed in HTML format.
9496 All of these files should be installed compressed using
9497 <tt>gzip -9</tt>, as they will become large with time even
9498 if they start out small.
9502 If the package has only one changelog which is used both as
9503 the Debian changelog and the upstream one because there is
9504 no separate upstream maintainer then that changelog should
9505 usually be installed as
9506 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9507 there is a separate upstream maintainer, but no upstream
9508 changelog, then the Debian changelog should still be called
9509 <file>changelog.Debian.gz</file>.
9513 For details about the format and contents of the Debian
9514 changelog file, please see <ref id="dpkgchangelog">.
9519 <appendix id="pkg-scope">
9520 <heading>Introduction and scope of these appendices</heading>
9523 These appendices are taken essentially verbatim from the
9524 now-deprecated Packaging Manual, version 3.2.1.0. They are
9525 the chapters which are likely to be of use to package
9526 maintainers and which have not already been included in the
9527 policy document itself. Most of these sections are very likely
9528 not relevant to policy; they should be treated as
9529 documentation for the packaging system. Please note that these
9530 appendices are included for convenience, and for historical
9531 reasons: they used to be part of policy package, and they have
9532 not yet been incorporated into dpkg documentation. However,
9533 they still have value, and hence they are presented here.
9537 They have not yet been checked to ensure that they are
9538 compatible with the contents of policy, and if there are any
9539 contradictions, the version in the main policy document takes
9540 precedence. The remaining chapters of the old Packaging
9541 Manual have also not been read in detail to ensure that there
9542 are not parts which have been left out. Both of these will be
9547 Certain parts of the Packaging manual were integrated into the
9548 Policy Manual proper, and removed from the appendices. Links
9549 have been placed from the old locations to the new ones.
9553 <prgn>dpkg</prgn> is a suite of programs for creating binary
9554 package files and installing and removing them on Unix
9556 <prgn>dpkg</prgn> is targeted primarily at Debian
9557 GNU/Linux, but may work on or be ported to other
9563 The binary packages are designed for the management of
9564 installed executable programs (usually compiled binaries) and
9565 their associated data, though source code examples and
9566 documentation are provided as part of some packages.</p>
9569 This manual describes the technical aspects of creating Debian
9570 binary packages (<file>.deb</file> files). It documents the
9571 behavior of the package management programs
9572 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9573 they interact with packages.</p>
9576 It also documents the interaction between
9577 <prgn>dselect</prgn>'s core and the access method scripts it
9578 uses to actually install the selected packages, and describes
9579 how to create a new access method.</p>
9582 This manual does not go into detail about the options and
9583 usage of the package building and installation tools. It
9584 should therefore be read in conjunction with those programs'
9589 The utility programs which are provided with <prgn>dpkg</prgn>
9590 for managing various system configuration and similar issues,
9591 such as <prgn>update-rc.d</prgn> and
9592 <prgn>install-info</prgn>, are not described in detail here -
9593 please see their man pages.
9597 It is assumed that the reader is reasonably familiar with the
9598 <prgn>dpkg</prgn> System Administrators' manual.
9599 Unfortunately this manual does not yet exist.
9603 The Debian version of the FSF's GNU hello program is provided
9604 as an example for people wishing to create Debian
9605 packages. The Debian <prgn>debmake</prgn> package is
9606 recommended as a very helpful tool in creating and maintaining
9607 Debian packages. However, while the tools and examples are
9608 helpful, they do not replace the need to read and follow the
9609 Policy and Programmer's Manual.</p>
9612 <appendix id="pkg-binarypkg">
9613 <heading>Binary packages (from old Packaging Manual)</heading>
9616 The binary package has two main sections. The first part
9617 consists of various control information files and scripts used
9618 by <prgn>dpkg</prgn> when installing and removing. See <ref
9619 id="pkg-controlarea">.
9623 The second part is an archive containing the files and
9624 directories to be installed.
9628 In the future binary packages may also contain other
9629 components, such as checksums and digital signatures. The
9630 format for the archive is described in full in the
9631 <file>deb(5)</file> man page.
9635 <sect id="pkg-bincreating"><heading>Creating package files -
9636 <prgn>dpkg-deb</prgn>
9640 All manipulation of binary package files is done by
9641 <prgn>dpkg-deb</prgn>; it's the only program that has
9642 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9643 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9644 will spot that the options requested are appropriate to
9645 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9650 In order to create a binary package you must make a
9651 directory tree which contains all the files and directories
9652 you want to have in the file system data part of the package.
9653 In Debian-format source packages this directory is usually
9654 <file>debian/tmp</file>, relative to the top of the package's
9659 They should have the locations (relative to the root of the
9660 directory tree you're constructing) ownerships and
9661 permissions which you want them to have on the system when
9666 With current versions of <prgn>dpkg</prgn> the uid/username
9667 and gid/groupname mappings for the users and groups being
9668 used should be the same on the system where the package is
9669 built and the one where it is installed.
9673 You need to add one special directory to the root of the
9674 miniature file system tree you're creating:
9675 <prgn>DEBIAN</prgn>. It should contain the control
9676 information files, notably the binary package control file
9677 (see <ref id="pkg-controlfile">).
9681 The <prgn>DEBIAN</prgn> directory will not appear in the
9682 file system archive of the package, and so won't be installed
9683 by <prgn>dpkg</prgn> when the package is installed.
9687 When you've prepared the package, you should invoke:
9689 dpkg --build <var>directory</var>
9694 This will build the package in
9695 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9696 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9697 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9702 See the man page <manref name="dpkg-deb" section="8"> for details of how
9703 to examine the contents of this newly-created file. You may find the
9704 output of following commands enlightening:
9706 dpkg-deb --info <var>filename</var>.deb
9707 dpkg-deb --contents <var>filename</var>.deb
9708 dpkg --contents <var>filename</var>.deb
9710 To view the copyright file for a package you could use this command:
9712 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
9717 <sect id="pkg-controlarea">
9718 <heading>Package control information files</heading>
9721 The control information portion of a binary package is a
9722 collection of files with names known to <prgn>dpkg</prgn>.
9723 It will treat the contents of these files specially - some
9724 of them contain information used by <prgn>dpkg</prgn> when
9725 installing or removing the package; others are scripts which
9726 the package maintainer wants <prgn>dpkg</prgn> to run.
9730 It is possible to put other files in the package control
9731 area, but this is not generally a good idea (though they
9732 will largely be ignored).
9736 Here is a brief list of the control info files supported by
9737 <prgn>dpkg</prgn> and a summary of what they're used for.
9742 <tag><tt>control</tt>
9745 This is the key description file used by
9746 <prgn>dpkg</prgn>. It specifies the package's name
9747 and version, gives its description for the user,
9748 states its relationships with other packages, and so
9749 forth. See <ref id="sourcecontrolfiles"> and
9750 <ref id="binarycontrolfiles">.
9754 It is usually generated automatically from information
9755 in the source package by the
9756 <prgn>dpkg-gencontrol</prgn> program, and with
9757 assistance from <prgn>dpkg-shlibdeps</prgn>.
9758 See <ref id="pkg-sourcetools">.
9762 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9767 These are executable files (usually scripts) which
9768 <prgn>dpkg</prgn> runs during installation, upgrade
9769 and removal of packages. They allow the package to
9770 deal with matters which are particular to that package
9771 or require more complicated processing than that
9772 provided by <prgn>dpkg</prgn>. Details of when and
9773 how they are called are in <ref id="maintainerscripts">.
9777 It is very important to make these scripts idempotent.
9778 See <ref id="idempotency">.
9782 The maintainer scripts are not guaranteed to run with a
9783 controlling terminal and may not be able to interact with
9784 the user. See <ref id="controllingterminal">.
9788 <tag><tt>conffiles</tt>
9791 This file contains a list of configuration files which
9792 are to be handled automatically by <prgn>dpkg</prgn>
9793 (see <ref id="pkg-conffiles">). Note that not necessarily
9794 every configuration file should be listed here.
9797 <tag><tt>shlibs</tt>
9800 This file contains a list of the shared libraries
9801 supplied by the package, with dependency details for
9802 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9803 when it determines what dependencies are required in a
9804 package control file. The <tt>shlibs</tt> file format
9805 is described on <ref id="shlibs">.
9810 <sect id="pkg-controlfile">
9811 <heading>The main control information file: <tt>control</tt></heading>
9814 The most important control information file used by
9815 <prgn>dpkg</prgn> when it installs a package is
9816 <tt>control</tt>. It contains all the package's "vital
9821 The binary package control files of packages built from
9822 Debian sources are made by a special tool,
9823 <prgn>dpkg-gencontrol</prgn>, which reads
9824 <file>debian/control</file> and <file>debian/changelog</file> to
9825 find the information it needs. See <ref id="pkg-sourcepkg"> for
9830 The fields in binary package control files are listed in
9831 <ref id="binarycontrolfiles">.
9835 A description of the syntax of control files and the purpose
9836 of the fields is available in <ref id="controlfields">.
9841 <heading>Time Stamps</heading>
9844 See <ref id="timestamps">.
9849 <appendix id="pkg-sourcepkg">
9850 <heading>Source packages (from old Packaging Manual) </heading>
9853 The Debian binary packages in the distribution are generated
9854 from Debian sources, which are in a special format to assist
9855 the easy and automatic building of binaries.
9858 <sect id="pkg-sourcetools">
9859 <heading>Tools for processing source packages</heading>
9862 Various tools are provided for manipulating source packages;
9863 they pack and unpack sources and help build of binary
9864 packages and help manage the distribution of new versions.
9868 They are introduced and typical uses described here; see
9869 <manref name="dpkg-source" section="1"> for full
9870 documentation about their arguments and operation.
9874 For examples of how to construct a Debian source package,
9875 and how to use those utilities that are used by Debian
9876 source packages, please see the <prgn>hello</prgn> example
9880 <sect1 id="pkg-dpkg-source">
9882 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9887 This program is frequently used by hand, and is also
9888 called from package-independent automated building scripts
9889 such as <prgn>dpkg-buildpackage</prgn>.
9893 To unpack a package it is typically invoked with
9895 dpkg-source -x <var>.../path/to/filename</var>.dsc
9900 with the <file><var>filename</var>.tar.gz</file> and
9901 <file><var>filename</var>.diff.gz</file> (if applicable) in
9902 the same directory. It unpacks into
9903 <file><var>package</var>-<var>version</var></file>, and if
9905 <file><var>package</var>-<var>version</var>.orig</file>, in
9906 the current directory.
9910 To create a packed source archive it is typically invoked:
9912 dpkg-source -b <var>package</var>-<var>version</var>
9917 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
9918 <file>.diff.gz</file> (if appropriate) in the current
9919 directory. <prgn>dpkg-source</prgn> does not clean the
9920 source tree first - this must be done separately if it is
9925 See also <ref id="pkg-sourcearchives">.</p>
9929 <sect1 id="pkg-dpkg-buildpackage">
9931 <prgn>dpkg-buildpackage</prgn> - overall package-building
9936 <prgn>dpkg-buildpackage</prgn> is a script which invokes
9937 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
9938 targets <tt>clean</tt>, <tt>build</tt> and
9939 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
9940 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
9941 source and binary package upload.
9945 It is usually invoked by hand from the top level of the
9946 built or unbuilt source directory. It may be invoked with
9947 no arguments; useful arguments include:
9948 <taglist compact="compact">
9949 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
9952 Do not sign the <tt>.changes</tt> file or the
9953 source package <tt>.dsc</tt> file, respectively.</p>
9955 <tag><tt>-p<var>sign-command</var></tt></tag>
9958 Invoke <var>sign-command</var> instead of finding
9959 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
9960 <var>sign-command</var> must behave just like
9961 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
9963 <tag><tt>-r<var>root-command</var></tt></tag>
9966 When root privilege is required, invoke the command
9967 <var>root-command</var>. <var>root-command</var>
9968 should invoke its first argument as a command, from
9969 the <prgn>PATH</prgn> if necessary, and pass its
9970 second and subsequent arguments to the command it
9971 calls. If no <var>root-command</var> is supplied
9972 then <var>dpkg-buildpackage</var> will take no
9973 special action to gain root privilege, so that for
9974 most packages it will have to be invoked as root to
9977 <tag><tt>-b</tt>, <tt>-B</tt></tag>
9980 Two types of binary-only build and upload - see
9981 <manref name="dpkg-source" section="1">.
9988 <sect1 id="pkg-dpkg-gencontrol">
9990 <prgn>dpkg-gencontrol</prgn> - generates binary package
9995 This program is usually called from <file>debian/rules</file>
9996 (see <ref id="pkg-sourcetree">) in the top level of the source
10001 This is usually done just before the files and directories in the
10002 temporary directory tree where the package is being built have their
10003 permissions and ownerships set and the package is constructed using
10004 <prgn>dpkg-deb/</prgn>
10006 This is so that the control file which is produced has
10007 the right permissions
10012 <prgn>dpkg-gencontrol</prgn> must be called after all the
10013 files which are to go into the package have been placed in
10014 the temporary build directory, so that its calculation of
10015 the installed size of a package is correct.
10019 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
10020 be run after <prgn>dpkg-shlibdeps</prgn> so that the
10021 variable substitutions created by
10022 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
10027 For a package which generates only one binary package, and
10028 which builds it in <file>debian/tmp</file> relative to the top
10029 of the source package, it is usually sufficient to call
10030 <prgn>dpkg-gencontrol</prgn>.
10034 Sources which build several binaries will typically need
10037 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
10038 </example> The <tt>-P</tt> tells
10039 <prgn>dpkg-gencontrol</prgn> that the package is being
10040 built in a non-default directory, and the <tt>-p</tt>
10041 tells it which package's control file should be generated.
10045 <prgn>dpkg-gencontrol</prgn> also adds information to the
10046 list of files in <file>debian/files</file>, for the benefit of
10047 (for example) a future invocation of
10048 <prgn>dpkg-genchanges</prgn>.</p>
10051 <sect1 id="pkg-dpkg-shlibdeps">
10053 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
10058 This program is usually called from <file>debian/rules</file>
10059 just before <prgn>dpkg-gencontrol</prgn> (see <ref
10060 id="pkg-sourcetree">), in the top level of the source tree.
10064 Its arguments are executables and shared libraries
10067 They may be specified either in the locations in the
10068 source tree where they are created or in the locations
10069 in the temporary build tree where they are installed
10070 prior to binary package creation.
10072 </footnote> for which shared library dependencies should
10073 be included in the binary package's control file.
10077 If some of the found shared libraries should only
10078 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
10079 some warrant a <tt>Pre-Depends</tt>, this can be achieved
10080 by using the <tt>-d<var>dependency-field</var></tt> option
10081 before those executable(s). (Each <tt>-d</tt> option
10082 takes effect until the next <tt>-d</tt>.)
10086 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
10087 output control file to be modified. Instead by default it
10088 adds to the <file>debian/substvars</file> file variable
10089 settings like <tt>shlibs:Depends</tt>. These variable
10090 settings must be referenced in dependency fields in the
10091 appropriate per-binary-package sections of the source
10096 For example, a package that generates an essential part
10097 which requires dependencies, and optional parts that
10098 which only require a recommendation, would separate those
10099 two sets of dependencies into two different fields.<footnote>
10100 At the time of writing, an example for this was the
10101 <package/xmms/ package, with Depends used for the xmms
10102 executable, Recommends for the plug-ins and Suggests for
10103 even more optional features provided by unzip.
10105 It can say in its <file>debian/rules</file>:
10107 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
10108 -dRecommends <var>optionalpart anotheroptionalpart</var>
10110 and then in its main control file <file>debian/control</file>:
10113 Depends: ${shlibs:Depends}
10114 Recommends: ${shlibs:Recommends}
10120 Sources which produce several binary packages with
10121 different shared library dependency requirements can use
10122 the <tt>-p<var>varnameprefix</var></tt> option to override
10123 the default <tt>shlibs:</tt> prefix (one invocation of
10124 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
10125 They can thus produce several sets of dependency
10126 variables, each of the form
10127 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
10128 which can be referred to in the appropriate parts of the
10129 binary package control files.
10134 <sect1 id="pkg-dpkg-distaddfile">
10136 <prgn>dpkg-distaddfile</prgn> - adds a file to
10137 <file>debian/files</file>
10141 Some packages' uploads need to include files other than
10142 the source and binary package files.
10146 <prgn>dpkg-distaddfile</prgn> adds a file to the
10147 <file>debian/files</file> file so that it will be included in
10148 the <file>.changes</file> file when
10149 <prgn>dpkg-genchanges</prgn> is run.
10153 It is usually invoked from the <tt>binary</tt> target of
10154 <file>debian/rules</file>:
10156 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
10158 The <var>filename</var> is relative to the directory where
10159 <prgn>dpkg-genchanges</prgn> will expect to find it - this
10160 is usually the directory above the top level of the source
10161 tree. The <file>debian/rules</file> target should put the
10162 file there just before or just after calling
10163 <prgn>dpkg-distaddfile</prgn>.
10167 The <var>section</var> and <var>priority</var> are passed
10168 unchanged into the resulting <file>.changes</file> file.
10173 <sect1 id="pkg-dpkg-genchanges">
10175 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
10176 upload control file
10180 This program is usually called by package-independent
10181 automatic building scripts such as
10182 <prgn>dpkg-buildpackage</prgn>, but it may also be called
10187 It is usually called in the top level of a built source
10188 tree, and when invoked with no arguments will print out a
10189 straightforward <file>.changes</file> file based on the
10190 information in the source package's changelog and control
10191 file and the binary and source packages which should have
10197 <sect1 id="pkg-dpkg-parsechangelog">
10199 <prgn>dpkg-parsechangelog</prgn> - produces parsed
10200 representation of a changelog
10204 This program is used internally by
10205 <prgn>dpkg-source</prgn> et al. It may also occasionally
10206 be useful in <file>debian/rules</file> and elsewhere. It
10207 parses a changelog, <file>debian/changelog</file> by default,
10208 and prints a control-file format representation of the
10209 information in it to standard output.
10213 <sect1 id="pkg-dpkg-architecture">
10215 <prgn>dpkg-architecture</prgn> - information about the build and
10220 This program can be used manually, but is also invoked by
10221 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
10222 environment or make variables which specify the build and host
10223 architecture for the package building process.
10228 <sect id="pkg-sourcetree">
10229 <heading>The Debian package source tree</heading>
10232 The source archive scheme described later is intended to
10233 allow a Debian package source tree with some associated
10234 control information to be reproduced and transported easily.
10235 The Debian package source tree is a version of the original
10236 program with certain files added for the benefit of the
10237 packaging process, and with any other changes required
10238 made to the rest of the source code and installation
10243 The extra files created for Debian are in the subdirectory
10244 <file>debian</file> of the top level of the Debian package
10245 source tree. They are described below.
10248 <sect1 id="pkg-debianrules">
10249 <heading><file>debian/rules</file> - the main building script</heading>
10252 See <ref id="debianrules">.
10256 <sect1 id="pkg-srcsubstvars">
10257 <heading><file>debian/substvars</file> and variable substitutions</heading>
10260 See <ref id="substvars">.
10266 <heading><file>debian/files</file></heading>
10269 See <ref id="debianfiles">.
10273 <sect1><heading><file>debian/tmp</file>
10277 This is the canonical temporary location for the
10278 construction of binary packages by the <tt>binary</tt>
10279 target. The directory <file>tmp</file> serves as the root of
10280 the file system tree as it is being constructed (for
10281 example, by using the package's upstream makefiles install
10282 targets and redirecting the output there), and it also
10283 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10284 id="pkg-bincreating">.
10288 If several binary packages are generated from the same
10289 source tree it is usual to use several
10290 <file>debian/tmp<var>something</var></file> directories, for
10291 example <file>tmp-a</file> or <file>tmp-doc</file>.
10295 Whatever <file>tmp</file> directories are created and used by
10296 <tt>binary</tt> must of course be removed by the
10297 <tt>clean</tt> target.</p></sect1>
10301 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10305 As it exists on the FTP site, a Debian source package
10306 consists of three related files. You must have the right
10307 versions of all three to be able to use them.
10312 <tag>Debian source control file - <tt>.dsc</tt></tag>
10314 This file is a control file used by <prgn>dpkg-source</prgn>
10315 to extract a source package.
10316 See <ref id="debiansourcecontrolfiles">.
10320 Original source archive -
10322 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10328 This is a compressed (with <tt>gzip -9</tt>)
10329 <prgn>tar</prgn> file containing the source code from
10330 the upstream authors of the program.
10335 Debian package diff -
10337 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10343 This is a unified context diff (<tt>diff -u</tt>)
10344 giving the changes which are required to turn the
10345 original source into the Debian source. These changes
10346 may only include editing and creating plain files.
10347 The permissions of files, the targets of symbolic
10348 links and the characteristics of special files or
10349 pipes may not be changed and no files may be removed
10354 All the directories in the diff must exist, except the
10355 <file>debian</file> subdirectory of the top of the source
10356 tree, which will be created by
10357 <prgn>dpkg-source</prgn> if necessary when unpacking.
10361 The <prgn>dpkg-source</prgn> program will
10362 automatically make the <file>debian/rules</file> file
10363 executable (see below).</p></item>
10368 If there is no original source code - for example, if the
10369 package is specially prepared for Debian or the Debian
10370 maintainer is the same as the upstream maintainer - the
10371 format is slightly different: then there is no diff, and the
10373 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10374 and preferably contains a directory named
10375 <file><var>package</var>-<var>version</var></file>.
10380 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10383 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10384 Debian source package. However, if it is not available it
10385 is possible to unpack a Debian source archive as follows:
10386 <enumlist compact="compact">
10389 Untar the tarfile, which will create a <file>.orig</file>
10393 <p>Rename the <file>.orig</file> directory to
10394 <file><var>package</var>-<var>version</var></file>.</p>
10398 Create the subdirectory <file>debian</file> at the top of
10399 the source tree.</p>
10401 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10403 <item><p>Untar the tarfile again if you want a copy of the original
10404 source code alongside the Debian version.</p>
10409 It is not possible to generate a valid Debian source archive
10410 without using <prgn>dpkg-source</prgn>. In particular,
10411 attempting to use <prgn>diff</prgn> directly to generate the
10412 <file>.diff.gz</file> file will not work.
10416 <heading>Restrictions on objects in source packages</heading>
10419 The source package may not contain any hard links
10421 This is not currently detected when building source
10422 packages, but only when extracting
10426 Hard links may be permitted at some point in the
10427 future, but would require a fair amount of
10429 </footnote>, device special files, sockets or setuid or
10432 Setgid directories are allowed.
10437 The source packaging tools manage the changes between the
10438 original and Debian source using <prgn>diff</prgn> and
10439 <prgn>patch</prgn>. Turning the original source tree as
10440 included in the <file>.orig.tar.gz</file> into the Debian
10441 package source must not involve any changes which cannot be
10442 handled by these tools. Problematic changes which cause
10443 <prgn>dpkg-source</prgn> to halt with an error when
10444 building the source package are:
10445 <list compact="compact">
10446 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10448 <item><p>Changing the targets of symbolic links.</p>
10450 <item><p>Creating directories, other than <file>debian</file>.</p>
10452 <item><p>Changes to the contents of binary files.</p></item>
10453 </list> Changes which cause <prgn>dpkg-source</prgn> to
10454 print a warning but continue anyway are:
10455 <list compact="compact">
10458 Removing files, directories or symlinks.
10460 Renaming a file is not treated specially - it is
10461 seen as the removal of the old file (which
10462 generates a warning, but is otherwise ignored),
10463 and the creation of the new one.
10469 Changed text files which are missing the usual final
10470 newline (either in the original or the modified
10475 Changes which are not represented, but which are not detected by
10476 <prgn>dpkg-source</prgn>, are:
10477 <list compact="compact">
10478 <item><p>Changing the permissions of files (other than
10479 <file>debian/rules</file>) and directories.</p></item>
10484 The <file>debian</file> directory and <file>debian/rules</file>
10485 are handled specially by <prgn>dpkg-source</prgn> - before
10486 applying the changes it will create the <file>debian</file>
10487 directory, and afterwards it will make
10488 <file>debian/rules</file> world-executable.
10494 <appendix id="pkg-controlfields">
10495 <heading>Control files and their fields (from old Packaging Manual)</heading>
10498 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10499 data in a common format, known as control files. Binary and
10500 source packages have control data as do the <file>.changes</file>
10501 files which control the installation of uploaded files, and
10502 <prgn>dpkg</prgn>'s internal databases are in a similar
10507 <heading>Syntax of control files</heading>
10510 See <ref id="controlsyntax">.
10514 It is important to note that there are several fields which
10515 are optional as far as <prgn>dpkg</prgn> and the related
10516 tools are concerned, but which must appear in every Debian
10517 package, or whose omission may cause problems.
10522 <heading>List of fields</heading>
10525 See <ref id="controlfieldslist">.
10529 This section now contains only the fields that didn't belong
10530 to the Policy manual.
10533 <sect1 id="pkg-f-Filename">
10534 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10537 These fields in <tt>Packages</tt> files give the
10538 filename(s) of (the parts of) a package in the
10539 distribution directories, relative to the root of the
10540 Debian hierarchy. If the package has been split into
10541 several parts the parts are all listed in order, separated
10546 <sect1 id="pkg-f-Size">
10547 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10550 These fields in <file>Packages</file> files give the size (in
10551 bytes, expressed in decimal) and MD5 checksum of the
10552 file(s) which make(s) up a binary package in the
10553 distribution. If the package is split into several parts
10554 the values for the parts are listed in order, separated by
10559 <sect1 id="pkg-f-Status">
10560 <heading><tt>Status</tt></heading>
10563 This field in <prgn>dpkg</prgn>'s status file records
10564 whether the user wants a package installed, removed or
10565 left alone, whether it is broken (requiring
10566 re-installation) or not and what its current state on the
10567 system is. Each of these pieces of information is a
10572 <sect1 id="pkg-f-Config-Version">
10573 <heading><tt>Config-Version</tt></heading>
10576 If a package is not installed or not configured, this
10577 field in <prgn>dpkg</prgn>'s status file records the last
10578 version of the package which was successfully
10583 <sect1 id="pkg-f-Conffiles">
10584 <heading><tt>Conffiles</tt></heading>
10587 This field in <prgn>dpkg</prgn>'s status file contains
10588 information about the automatically-managed configuration
10589 files held by a package. This field should <em>not</em>
10590 appear anywhere in a package!
10595 <heading>Obsolete fields</heading>
10598 These are still recognized by <prgn>dpkg</prgn> but should
10599 not appear anywhere any more.
10601 <taglist compact="compact">
10603 <tag><tt>Revision</tt></tag>
10604 <tag><tt>Package-Revision</tt></tag>
10605 <tag><tt>Package_Revision</tt></tag>
10607 The Debian revision part of the package version was
10608 at one point in a separate control file field. This
10609 field went through several names.
10612 <tag><tt>Recommended</tt></tag>
10613 <item>Old name for <tt>Recommends</tt>.</item>
10615 <tag><tt>Optional</tt></tag>
10616 <item>Old name for <tt>Suggests</tt>.</item>
10618 <tag><tt>Class</tt></tag>
10619 <item>Old name for <tt>Priority</tt>.</item>
10628 <appendix id="pkg-conffiles">
10629 <heading>Configuration file handling (from old Packaging Manual)</heading>
10632 <prgn>dpkg</prgn> can do a certain amount of automatic
10633 handling of package configuration files.
10637 Whether this mechanism is appropriate depends on a number of
10638 factors, but basically there are two approaches to any
10639 particular configuration file.
10643 The easy method is to ship a best-effort configuration in the
10644 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10645 handle updates. If the user is unlikely to want to edit the
10646 file, but you need them to be able to without losing their
10647 changes, and a new package with a changed version of the file
10648 is only released infrequently, this is a good approach.
10652 The hard method is to build the configuration file from
10653 scratch in the <prgn>postinst</prgn> script, and to take the
10654 responsibility for fixing any mistakes made in earlier
10655 versions of the package automatically. This will be
10656 appropriate if the file is likely to need to be different on
10660 <sect><heading>Automatic handling of configuration files by
10665 A package may contain a control area file called
10666 <tt>conffiles</tt>. This file should be a list of filenames
10667 of configuration files needing automatic handling, separated
10668 by newlines. The filenames should be absolute pathnames,
10669 and the files referred to should actually exist in the
10674 When a package is upgraded <prgn>dpkg</prgn> will process
10675 the configuration files during the configuration stage,
10676 shortly before it runs the package's <prgn>postinst</prgn>
10681 For each file it checks to see whether the version of the
10682 file included in the package is the same as the one that was
10683 included in the last version of the package (the one that is
10684 being upgraded from); it also compares the version currently
10685 installed on the system with the one shipped with the last
10690 If neither the user nor the package maintainer has changed
10691 the file, it is left alone. If one or the other has changed
10692 their version, then the changed version is preferred - i.e.,
10693 if the user edits their file, but the package maintainer
10694 doesn't ship a different version, the user's changes will
10695 stay, silently, but if the maintainer ships a new version
10696 and the user hasn't edited it the new version will be
10697 installed (with an informative message). If both have
10698 changed their version the user is prompted about the problem
10699 and must resolve the differences themselves.
10703 The comparisons are done by calculating the MD5 message
10704 digests of the files, and storing the MD5 of the file as it
10705 was included in the most recent version of the package.
10709 When a package is installed for the first time
10710 <prgn>dpkg</prgn> will install the file that comes with it,
10711 unless that would mean overwriting a file already on the
10716 However, note that <prgn>dpkg</prgn> will <em>not</em>
10717 replace a conffile that was removed by the user (or by a
10718 script). This is necessary because with some programs a
10719 missing file produces an effect hard or impossible to
10720 achieve in another way, so that a missing file needs to be
10721 kept that way if the user did it.
10725 Note that a package should <em>not</em> modify a
10726 <prgn>dpkg</prgn>-handled conffile in its maintainer
10727 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10728 the user confusing and possibly dangerous options for
10729 conffile update when the package is upgraded.</p>
10732 <sect><heading>Fully-featured maintainer script configuration
10737 For files which contain site-specific information such as
10738 the hostname and networking details and so forth, it is
10739 better to create the file in the package's
10740 <prgn>postinst</prgn> script.
10744 This will typically involve examining the state of the rest
10745 of the system to determine values and other information, and
10746 may involve prompting the user for some information which
10747 can't be obtained some other way.
10751 When using this method there are a couple of important
10752 issues which should be considered:
10756 If you discover a bug in the program which generates the
10757 configuration file, or if the format of the file changes
10758 from one version to the next, you will have to arrange for
10759 the postinst script to do something sensible - usually this
10760 will mean editing the installed configuration file to remove
10761 the problem or change the syntax. You will have to do this
10762 very carefully, since the user may have changed the file,
10763 perhaps to fix the very problem that your script is trying
10764 to deal with - you will have to detect these situations and
10765 deal with them correctly.
10769 If you do go down this route it's probably a good idea to
10770 make the program that generates the configuration file(s) a
10771 separate program in <file>/usr/sbin</file>, by convention called
10772 <file><var>package</var>config</file> and then run that if
10773 appropriate from the post-installation script. The
10774 <tt><var>package</var>config</tt> program should not
10775 unquestioningly overwrite an existing configuration - if its
10776 mode of operation is geared towards setting up a package for
10777 the first time (rather than any arbitrary reconfiguration
10778 later) you should have it check whether the configuration
10779 already exists, and require a <tt>--force</tt> flag to
10780 overwrite it.</p></sect>
10783 <appendix id="pkg-alternatives"><heading>Alternative versions of
10784 an interface - <prgn>update-alternatives</prgn> (from old
10789 When several packages all provide different versions of the
10790 same program or file it is useful to have the system select a
10791 default, but to allow the system administrator to change it
10792 and have their decisions respected.
10796 For example, there are several versions of the <prgn>vi</prgn>
10797 editor, and there is no reason to prevent all of them from
10798 being installed at once, each under their own name
10799 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10800 Nevertheless it is desirable to have the name <tt>vi</tt>
10801 refer to something, at least by default.
10805 If all the packages involved cooperate, this can be done with
10806 <prgn>update-alternatives</prgn>.
10810 Each package provides its own version under its own name, and
10811 calls <prgn>update-alternatives</prgn> in its postinst to
10812 register its version (and again in its prerm to deregister
10817 See the man page <manref name="update-alternatives"
10818 section="8"> for details.
10822 If <prgn>update-alternatives</prgn> does not seem appropriate
10823 you may wish to consider using diversions instead.</p>
10826 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10827 package's version of a file (from old Packaging Manual)
10831 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10832 when it reinstalls the package it belongs to, and to have it
10833 put the file from the package somewhere else instead.
10837 This can be used locally to override a package's version of a
10838 file, or by one package to override another's version (or
10839 provide a wrapper for it).
10843 Before deciding to use a diversion, read <ref
10844 id="pkg-alternatives"> to see if you really want a diversion
10845 rather than several alternative versions of a program.
10849 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10850 and updated by a special program <prgn>dpkg-divert</prgn>.
10851 Please see <manref name="dpkg-divert" section="8"> for full
10852 details of its operation.
10856 When a package wishes to divert a file from another, it should
10857 call <prgn>dpkg-divert</prgn> in its preinst to add the
10858 diversion and rename the existing file. For example,
10859 supposing that a <prgn>smailwrapper</prgn> package wishes to
10860 install a wrapper around <file>/usr/sbin/smail</file>:
10862 dpkg-divert --package smailwrapper --add --rename \
10863 --divert /usr/sbin/smail.real /usr/sbin/smail
10864 </example> The <tt>--package smailwrapper</tt> ensures that
10865 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
10866 can bypass the diversion and get installed as the true version.
10867 It's safe to add the diversion unconditionally on upgrades since
10868 it will be left unchanged if it already exists, but
10869 <prgn>dpkg-divert</prgn> will display a message. To suppress that
10870 message, make the command conditional on the version from which
10871 the package is being upgraded:
10873 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
10874 dpkg-divert --package smailwrapper --add --rename \
10875 --divert /usr/sbin/smail.real /usr/sbin/smail
10877 </example> where <tt>1.0-2</tt> is the version at which the
10878 diversion was first added to the package. Running the command
10879 during abort-upgrade is pointless but harmless.
10883 The postrm has to do the reverse:
10885 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
10886 dpkg-divert --package smailwrapper --remove --rename \
10887 --divert /usr/sbin/smail.real /usr/sbin/smail
10889 </example> If the diversion was added at a particular version, the
10890 postrm should also handle the failure case of upgrading from an
10891 older version (unless the older version is so old that direct
10892 upgrades are no longer supported):
10894 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
10895 dpkg-divert --package smailwrapper --remove --rename \
10896 --divert /usr/sbin/smail.real /usr/sbin/smail
10898 </example> where <tt>1.02-2</tt> is the version at which the
10899 diversion was first added to the package. The postrm should not
10900 remove the diversion on upgrades both because there's no reason to
10901 remove the diversion only to immediately re-add it and since the
10902 postrm of the old package is run after unpacking so the removal of
10903 the diversion will fail.
10907 Do not attempt to divert a file which is vitally important for
10908 the system's operation - when using <prgn>dpkg-divert</prgn>
10909 there is a time, after it has been diverted but before
10910 <prgn>dpkg</prgn> has installed the new version, when the file
10911 does not exist.</p>
10916 <!-- Local variables: -->
10917 <!-- indent-tabs-mode: t -->
10919 <!-- vim:set ai et sts=2 sw=2 tw=76: -->