1 <!doctype debiandoc system [
2 <!-- include version information so we don't have to hard code it
3 within the document -->
4 <!entity % versiondata SYSTEM "version.ent"> %versiondata;
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 unpacked
1058 <em>and</em> configured before it can be unpacked. 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 .changes files are used by the Debian archive maintenance
2599 software to process updates to packages. They contain one
2600 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 The fields in this file are:
2609 <list compact="compact">
2610 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2611 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2612 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2613 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2614 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2615 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2616 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2617 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2618 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2619 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2620 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2621 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2622 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2623 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2624 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2625 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2630 <sect id="controlfieldslist">
2631 <heading>List of fields</heading>
2633 <sect1 id="f-Source">
2634 <heading><tt>Source</tt></heading>
2637 This field identifies the source package name.
2641 In <file>debian/control</file> or a <file>.dsc</file> file,
2642 this field must contain only the name of the source package.
2646 In a binary package control file or a <file>.changes</file>
2647 file, the source package name may be followed by a version
2648 number in parentheses<footnote>
2649 It is customary to leave a space after the package name
2650 if a version number is specified.
2652 This version number may be omitted (and is, by
2653 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2654 the <tt>Version</tt> field of the binary package in
2655 question. The field itself may be omitted from a binary
2656 package control file when the source package has the same
2657 name and version as the binary package.
2661 Package names (both source and binary,
2662 see <ref id="f-Package">) must consist only of lower case
2663 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2664 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2665 (<tt>.</tt>). They must be at least two characters long and
2666 must start with an alphanumeric character.
2670 <sect1 id="f-Maintainer">
2671 <heading><tt>Maintainer</tt></heading>
2674 The package maintainer's name and email address. The name
2675 must come first, then the email address inside angle
2676 brackets <tt><></tt> (in RFC822 format).
2680 If the maintainer's name contains a full stop then the
2681 whole field will not work directly as an email address due
2682 to a misfeature in the syntax specified in RFC822; a
2683 program using this field as an address must check for this
2684 and correct the problem if necessary (for example by
2685 putting the name in round brackets and moving it to the
2686 end, and bringing the email address forward).
2690 <sect1 id="f-Uploaders">
2691 <heading><tt>Uploaders</tt></heading>
2694 List of the names and email addresses of co-maintainers of
2695 the package, if any. If the package has other maintainers
2696 beside the one named in the
2697 <qref id="f-Maintainer">Maintainer field</qref>, their names
2698 and email addresses should be listed here. The format of each
2699 entry is the same as that of the Maintainer field, and
2700 multiple entries must be comma separated. This is an optional
2705 Any parser that interprets the Uploaders field in
2706 <file>debian/control</file> must permit it to span multiple
2707 lines. Line breaks in an Uploaders field that spans multiple
2708 lines are not significant and the semantics of the field are
2709 the same as if the line breaks had not been present.
2713 <sect1 id="f-Changed-By">
2714 <heading><tt>Changed-By</tt></heading>
2717 The name and email address of the person who prepared this
2718 version of the package, usually a maintainer. The syntax is
2719 the same as for the <qref id="f-Maintainer">Maintainer
2724 <sect1 id="f-Section">
2725 <heading><tt>Section</tt></heading>
2728 This field specifies an application area into which the package
2729 has been classified. See <ref id="subsections">.
2733 When it appears in the <file>debian/control</file> file,
2734 it gives the value for the subfield of the same name in
2735 the <tt>Files</tt> field of the <file>.changes</file> file.
2736 It also gives the default for the same field in the binary
2741 <sect1 id="f-Priority">
2742 <heading><tt>Priority</tt></heading>
2745 This field represents how important it is that the user
2746 have the package installed. See <ref id="priorities">.
2750 When it appears in the <file>debian/control</file> file,
2751 it gives the value for the subfield of the same name in
2752 the <tt>Files</tt> field of the <file>.changes</file> file.
2753 It also gives the default for the same field in the binary
2758 <sect1 id="f-Package">
2759 <heading><tt>Package</tt></heading>
2762 The name of the binary package.
2766 Binary package names must follow the same syntax and
2767 restrictions as source package names. See <ref id="f-Source">
2772 <sect1 id="f-Architecture">
2773 <heading><tt>Architecture</tt></heading>
2776 Depending on context and the control file used, the
2777 <tt>Architecture</tt> field can include the following sets of
2781 A unique single word identifying a Debian machine
2782 architecture as described in <ref id="arch-spec">.
2785 An architecture wildcard identifying a set of Debian
2786 machine architectures, see <ref id="arch-wildcard-spec">.
2787 <tt>any</tt> matches all Debian machine architectures
2788 and is the most frequently used.
2791 <tt>all</tt>, which indicates an
2792 architecture-independent package.
2795 <tt>source</tt>, which indicates a source package.
2801 In the main <file>debian/control</file> file in the source
2802 package, this field may contain the special
2803 value <tt>all</tt>, the special architecture
2804 wildcard <tt>any</tt>, or a list of specific and wildcard
2805 architectures separated by spaces. If <tt>all</tt>
2806 or <tt>any</tt> appears, that value must be the entire
2807 contents of the field. Most packages will use
2808 either <tt>all</tt> or <tt>any</tt>.
2812 Specifying a specific list of architectures indicates that the
2813 source will build an architecture-dependent package only on
2814 architectures included in the list. Specifying a list of
2815 architecture wildcards indicates that the source will build an
2816 architecture-dependent package on only those architectures
2817 that match any of the specified architecture wildcards.
2818 Specifying a list of architectures or architecture wildcards
2819 other than <tt>any</tt> is for the minority of cases where a
2820 program is not portable or is not useful on some
2821 architectures. Where possible, the program should be made
2826 In the source package control file <file>.dsc</file>, this
2827 field may contain either the architecture
2828 wildcard <tt>any</tt> or a list of architectures and
2829 architecture wildcards separated by spaces. If a list is
2830 given, it may include (or consist solely of) the special
2831 value <tt>all</tt>. In other words, in <file>.dsc</file>
2832 files unlike the <file>debian/control</file>, <tt>all</tt> may
2833 occur in combination with specific architectures.
2834 The <tt>Architecture</tt> field in the source package control
2835 file <file>.dsc</file> is generally constructed from
2836 the <tt>Architecture</tt> fields in
2837 the <file>debian/control</file> in the source package.
2841 Specifying <tt>any</tt> indicates that the source package
2842 isn't dependent on any particular architecture and should
2843 compile fine on any one. The produced binary package(s)
2844 will either be specific to whatever the current build
2845 architecture is or will be architecture-independent.
2849 Specifying only <tt>all</tt> indicates that the source package
2850 will only build architecture-independent packages. If this is
2851 the case, <tt>all</tt> must be used rather than <tt>any</tt>;
2852 <tt>any</tt> implies that the source package will build at
2853 least one architecture-dependent package.
2857 Specifying a list of architectures or architecture wildcards
2858 indicates that the source will build an architecture-dependent
2859 package, and will only work correctly on the listed or
2860 matching architectures. If the source package also builds at
2861 least one architecture-independent package, <tt>all</tt> will
2862 also be included in the list.
2866 In a <file>.changes</file> file, the <tt>Architecture</tt>
2867 field lists the architecture(s) of the package(s) currently
2868 being uploaded. This will be a list; if the source for the
2869 package is also being uploaded, the special
2870 entry <tt>source</tt> is also present. <tt>all</tt> will be
2871 present if any architecture-independent packages are being
2872 uploaded. Architecture wildcards such as <tt>any</tt> must
2873 never occur in the <tt>Architecture</tt> field in
2874 the <file>.changes</file> file.
2878 See <ref id="debianrules"> for information on how to get
2879 the architecture for the build process.
2883 <sect1 id="f-Essential">
2884 <heading><tt>Essential</tt></heading>
2887 This is a boolean field which may occur only in the
2888 control file of a binary package or in a per-package fields
2889 paragraph of a main source control data file.
2893 If set to <tt>yes</tt> then the package management system
2894 will refuse to remove the package (upgrading and replacing
2895 it is still possible). The other possible value is <tt>no</tt>,
2896 which is the same as not having the field at all.
2901 <heading>Package interrelationship fields:
2902 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2903 <tt>Recommends</tt>, <tt>Suggests</tt>,
2904 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2905 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2909 These fields describe the package's relationships with
2910 other packages. Their syntax and semantics are described
2911 in <ref id="relationships">.</p>
2914 <sect1 id="f-Standards-Version">
2915 <heading><tt>Standards-Version</tt></heading>
2918 The most recent version of the standards (the policy
2919 manual and associated texts) with which the package
2924 The version number has four components: major and minor
2925 version number and major and minor patch level. When the
2926 standards change in a way that requires every package to
2927 change the major number will be changed. Significant
2928 changes that will require work in many packages will be
2929 signaled by a change to the minor number. The major patch
2930 level will be changed for any change to the meaning of the
2931 standards, however small; the minor patch level will be
2932 changed when only cosmetic, typographical or other edits
2933 are made which neither change the meaning of the document
2934 nor affect the contents of packages.
2938 Thus only the first three components of the policy version
2939 are significant in the <em>Standards-Version</em> control
2940 field, and so either these three components or all four
2941 components may be specified.<footnote>
2942 In the past, people specified the full version number
2943 in the Standards-Version field, for example "2.3.0.0".
2944 Since minor patch-level changes don't introduce new
2945 policy, it was thought it would be better to relax
2946 policy and only require the first 3 components to be
2947 specified, in this example "2.3.0". All four
2948 components may still be used if someone wishes to do so.
2954 <sect1 id="f-Version">
2955 <heading><tt>Version</tt></heading>
2958 The version number of a package. The format is:
2959 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
2963 The three components here are:
2965 <tag><var>epoch</var></tag>
2968 This is a single (generally small) unsigned integer. It
2969 may be omitted, in which case zero is assumed. If it is
2970 omitted then the <var>upstream_version</var> may not
2975 It is provided to allow mistakes in the version numbers
2976 of older versions of a package, and also a package's
2977 previous version numbering schemes, to be left behind.
2981 <tag><var>upstream_version</var></tag>
2984 This is the main part of the version number. It is
2985 usually the version number of the original ("upstream")
2986 package from which the <file>.deb</file> file has been made,
2987 if this is applicable. Usually this will be in the same
2988 format as that specified by the upstream author(s);
2989 however, it may need to be reformatted to fit into the
2990 package management system's format and comparison
2995 The comparison behavior of the package management system
2996 with respect to the <var>upstream_version</var> is
2997 described below. The <var>upstream_version</var>
2998 portion of the version number is mandatory.
3002 The <var>upstream_version</var> may contain only
3003 alphanumerics<footnote>
3004 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3006 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3007 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3008 tilde) and should start with a digit. If there is no
3009 <var>debian_revision</var> then hyphens are not allowed;
3010 if there is no <var>epoch</var> then colons are not
3015 <tag><var>debian_revision</var></tag>
3018 This part of the version number specifies the version of
3019 the Debian package based on the upstream version. It
3020 may contain only alphanumerics and the characters
3021 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3022 tilde) and is compared in the same way as the
3023 <var>upstream_version</var> is.
3027 It is optional; if it isn't present then the
3028 <var>upstream_version</var> may not contain a hyphen.
3029 This format represents the case where a piece of
3030 software was written specifically to be a Debian
3031 package, where the Debian package source must always
3032 be identical to the pristine source and therefore no
3033 revision indication is required.
3037 It is conventional to restart the
3038 <var>debian_revision</var> at <tt>1</tt> each time the
3039 <var>upstream_version</var> is increased.
3043 The package management system will break the version
3044 number apart at the last hyphen in the string (if there
3045 is one) to determine the <var>upstream_version</var> and
3046 <var>debian_revision</var>. The absence of a
3047 <var>debian_revision</var> is equivalent to a
3048 <var>debian_revision</var> of <tt>0</tt>.
3055 When comparing two version numbers, first the <var>epoch</var>
3056 of each are compared, then the <var>upstream_version</var> if
3057 <var>epoch</var> is equal, and then <var>debian_revision</var>
3058 if <var>upstream_version</var> is also equal.
3059 <var>epoch</var> is compared numerically. The
3060 <var>upstream_version</var> and <var>debian_revision</var>
3061 parts are compared by the package management system using the
3062 following algorithm:
3066 The strings are compared from left to right.
3070 First the initial part of each string consisting entirely of
3071 non-digit characters is determined. These two parts (one of
3072 which may be empty) are compared lexically. If a difference
3073 is found it is returned. The lexical comparison is a
3074 comparison of ASCII values modified so that all the letters
3075 sort earlier than all the non-letters and so that a tilde
3076 sorts before anything, even the end of a part. For example,
3077 the following parts are in sorted order from earliest to
3078 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3079 <tt>a</tt>.<footnote>
3080 One common use of <tt>~</tt> is for upstream pre-releases.
3081 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3082 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3087 Then the initial part of the remainder of each string which
3088 consists entirely of digit characters is determined. The
3089 numerical values of these two parts are compared, and any
3090 difference found is returned as the result of the comparison.
3091 For these purposes an empty string (which can only occur at
3092 the end of one or both version strings being compared) counts
3097 These two steps (comparing and removing initial non-digit
3098 strings and initial digit strings) are repeated until a
3099 difference is found or both strings are exhausted.
3103 Note that the purpose of epochs is to allow us to leave behind
3104 mistakes in version numbering, and to cope with situations
3105 where the version numbering scheme changes. It is
3106 <em>not</em> intended to cope with version numbers containing
3107 strings of letters which the package management system cannot
3108 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3109 silly orderings.<footnote>
3110 The author of this manual has heard of a package whose
3111 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3112 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3118 <sect1 id="f-Description">
3119 <heading><tt>Description</tt></heading>
3122 In a source or binary control file, the <tt>Description</tt>
3123 field contains a description of the binary package, consisting
3124 of two parts, the synopsis or the short description, and the
3125 long description. The field's format is as follows:
3130 Description: <single line synopsis>
3131 <extended description over several lines>
3136 The lines in the extended description can have these formats:
3142 Those starting with a single space are part of a paragraph.
3143 Successive lines of this form will be word-wrapped when
3144 displayed. The leading space will usually be stripped off.
3148 Those starting with two or more spaces. These will be
3149 displayed verbatim. If the display cannot be panned
3150 horizontally, the displaying program will line wrap them "hard"
3151 (i.e., without taking account of word breaks). If it can they
3152 will be allowed to trail off to the right. None, one or two
3153 initial spaces may be deleted, but the number of spaces
3154 deleted from each line will be the same (so that you can have
3155 indenting work correctly, for example).
3159 Those containing a single space followed by a single full stop
3160 character. These are rendered as blank lines. This is the
3161 <em>only</em> way to get a blank line<footnote>
3162 Completely empty lines will not be rendered as blank lines.
3163 Instead, they will cause the parser to think you're starting
3164 a whole new record in the control file, and will therefore
3165 likely abort with an error.
3170 Those containing a space, a full stop and some more characters.
3171 These are for future expansion. Do not use them.
3177 Do not use tab characters. Their effect is not predictable.
3181 See <ref id="descriptions"> for further information on this.
3185 In a <file>.changes</file> file, the <tt>Description</tt>
3186 field contains a summary of the descriptions for the packages
3187 being uploaded. For this case, the first line of the field
3188 value (the part on the same line as <tt>Description:</tt>) is
3189 always empty. The content of the field is expressed as
3190 continuation lines, one line per package. Each line is
3191 indented by one space and contains the name of a binary
3192 package, a space, a hyphen (<tt>-</tt>), a space, and the
3193 short description line from that package.
3197 <sect1 id="f-Distribution">
3198 <heading><tt>Distribution</tt></heading>
3201 In a <file>.changes</file> file or parsed changelog output
3202 this contains the (space-separated) name(s) of the
3203 distribution(s) where this version of the package should
3204 be installed. Valid distributions are determined by the
3205 archive maintainers.<footnote>
3206 Example distribution names in the Debian archive used in
3207 <file>.changes</file> files are:
3208 <taglist compact="compact">
3209 <tag><em>unstable</em></tag>
3211 This distribution value refers to the
3212 <em>developmental</em> part of the Debian distribution
3213 tree. Most new packages, new upstream versions of
3214 packages and bug fixes go into the <em>unstable</em>
3218 <tag><em>experimental</em></tag>
3220 The packages with this distribution value are deemed
3221 by their maintainers to be high risk. Oftentimes they
3222 represent early beta or developmental packages from
3223 various sources that the maintainers want people to
3224 try, but are not ready to be a part of the other parts
3225 of the Debian distribution tree.
3230 Others are used for updating stable releases or for
3231 security uploads. More information is available in the
3232 Debian Developer's Reference, section "The Debian
3236 The Debian archive software only supports listing a single
3237 distribution. Migration of packages to other distributions is
3238 handled outside of the upload process.
3243 <heading><tt>Date</tt></heading>
3246 This field includes the date the package was built or last
3247 edited. It must be in the same format as the <var>date</var>
3248 in a <file>debian/changelog</file> entry.
3252 The value of this field is usually extracted from the
3253 <file>debian/changelog</file> file - see
3254 <ref id="dpkgchangelog">).
3258 <sect1 id="f-Format">
3259 <heading><tt>Format</tt></heading>
3262 This field specifies a format revision for the file.
3263 The most current format described in the Policy Manual
3264 is version <strong>1.5</strong>. The syntax of the
3265 format value is the same as that of a package version
3266 number except that no epoch or Debian revision is allowed
3267 - see <ref id="f-Version">.
3271 <sect1 id="f-Urgency">
3272 <heading><tt>Urgency</tt></heading>
3275 This is a description of how important it is to upgrade to
3276 this version from previous ones. It consists of a single
3277 keyword taking one of the values <tt>low</tt>,
3278 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3279 <tt>critical</tt><footnote>
3280 Other urgency values are supported with configuration
3281 changes in the archive software but are not used in Debian.
3282 The urgency affects how quickly a package will be considered
3283 for inclusion into the <tt>testing</tt> distribution and
3284 gives an indication of the importance of any fixes included
3285 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3286 treated as synonymous.
3287 </footnote> (not case-sensitive) followed by an optional
3288 commentary (separated by a space) which is usually in
3289 parentheses. For example:
3292 Urgency: low (HIGH for users of diversions)
3298 The value of this field is usually extracted from the
3299 <file>debian/changelog</file> file - see
3300 <ref id="dpkgchangelog">.
3304 <sect1 id="f-Changes">
3305 <heading><tt>Changes</tt></heading>
3308 This field contains the human-readable changes data, describing
3309 the differences between the last version and the current one.
3313 The first line of the field value (the part on the same line
3314 as <tt>Changes:</tt>) is always empty. The content of the
3315 field is expressed as continuation lines, with each line
3316 indented by at least one space. Blank lines must be
3317 represented by a line consisting only of a space and a full
3322 The value of this field is usually extracted from the
3323 <file>debian/changelog</file> file - see
3324 <ref id="dpkgchangelog">).
3328 Each version's change information should be preceded by a
3329 "title" line giving at least the version, distribution(s)
3330 and urgency, in a human-readable way.
3334 If data from several versions is being returned the entry
3335 for the most recent version should be returned first, and
3336 entries should be separated by the representation of a
3337 blank line (the "title" line may also be followed by the
3338 representation of a blank line).
3342 <sect1 id="f-Binary">
3343 <heading><tt>Binary</tt></heading>
3346 This field is a list of binary packages. Its syntax and
3347 meaning varies depending on the control file in which it
3352 When it appears in the <file>.dsc</file> file, it lists binary
3353 packages which a source package can produce, separated by
3355 A space after each comma is conventional.
3356 </footnote>. It may span multiple lines. The source package
3357 does not necessarily produce all of these binary packages for
3358 every architecture. The source control file doesn't contain
3359 details of which architectures are appropriate for which of
3360 the binary packages.
3364 When it appears in a <file>.changes</file> file, it lists the
3365 names of the binary packages being uploaded, separated by
3366 whitespace (not commas). It may span multiple lines.
3370 <sect1 id="f-Installed-Size">
3371 <heading><tt>Installed-Size</tt></heading>
3374 This field appears in the control files of binary packages,
3375 and in the <file>Packages</file> files. It gives an estimate
3376 of the total amount of disk space required to install the
3377 named package. Actual installed size may vary based on block
3378 size, file system properties, or actions taken by package
3383 The disk space is given as the integer value of the estimated
3384 installed size in bytes, divided by 1024 and rounded up.
3388 <sect1 id="f-Files">
3389 <heading><tt>Files</tt></heading>
3392 This field contains a list of files with information about
3393 each one. The exact information and syntax varies with
3398 In all cases, Files is a multiline field. The first line of
3399 the field value (the part on the same line as <tt>Files:</tt>)
3400 is always empty. The content of the field is expressed as
3401 continuation lines, one line per file. Each line must be
3402 indented by one space and contain a number of sub-fields,
3403 separated by spaces, as described below.
3407 In the <file>.dsc</file> file, each line contains the MD5
3408 checksum, size and filename of the tar file and (if
3409 applicable) diff file which make up the remainder of the
3410 source package<footnote>
3411 That is, the parts which are not the <tt>.dsc</tt>.
3412 </footnote>. For example:
3415 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3416 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3418 The exact forms of the filenames are described
3419 in <ref id="pkg-sourcearchives">.
3423 In the <file>.changes</file> file this contains one line per
3424 file being uploaded. Each line contains the MD5 checksum,
3425 size, section and priority and the filename. For example:
3428 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3429 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3430 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3431 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3433 The <qref id="f-Section">section</qref>
3434 and <qref id="f-Priority">priority</qref> are the values of
3435 the corresponding fields in the main source control file. If
3436 no section or priority is specified then <tt>-</tt> should be
3437 used, though section and priority values must be specified for
3438 new packages to be installed properly.
3442 The special value <tt>byhand</tt> for the section in a
3443 <tt>.changes</tt> file indicates that the file in question
3444 is not an ordinary package file and must by installed by
3445 hand by the distribution maintainers. If the section is
3446 <tt>byhand</tt> the priority should be <tt>-</tt>.
3450 If a new Debian revision of a package is being shipped and
3451 no new original source archive is being distributed the
3452 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3453 entry for the original source archive
3454 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3455 but the <file>.changes</file> file should leave it out. In
3456 this case the original source archive on the distribution
3457 site must match exactly, byte-for-byte, the original
3458 source archive which was used to generate the
3459 <file>.dsc</file> file and diff which are being uploaded.</p>
3462 <sect1 id="f-Closes">
3463 <heading><tt>Closes</tt></heading>
3466 A space-separated list of bug report numbers that the upload
3467 governed by the .changes file closes.
3471 <sect1 id="f-Homepage">
3472 <heading><tt>Homepage</tt></heading>
3475 The URL of the web site for this package, preferably (when
3476 applicable) the site from which the original source can be
3477 obtained and any additional upstream documentation or
3478 information may be found. The content of this field is a
3479 simple URL without any surrounding characters such as
3484 <sect1 id="f-Checksums">
3485 <heading><tt>Checksums-Sha1</tt>
3486 and <tt>Checksums-Sha256</tt></heading>
3489 These fields contain a list of files with a checksum and size
3490 for each one. Both <tt>Checksums-Sha1</tt>
3491 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3492 only in the checksum algorithm used: SHA-1
3493 for <tt>Checksums-Sha1</tt> and SHA-256
3494 for <tt>Checksums-Sha256</tt>.
3498 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3499 multiline fields. The first line of the field value (the part
3500 on the same line as <tt>Checksums-Sha1:</tt>
3501 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3502 of the field is expressed as continuation lines, one line per
3503 file. Each line consists of the checksum, a space, the file
3504 size, a space, and the file name. For example (from
3505 a <file>.changes</file> file):
3508 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3509 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3510 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3511 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3513 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3514 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3515 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3516 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3521 In the <file>.dsc</file> file, these fields should list all
3522 files that make up the source package. In
3523 the <file>.changes</file> file, these fields should list all
3524 files being uploaded. The list of files in these fields
3525 must match the list of files in the <tt>Files</tt> field.
3532 <heading>User-defined fields</heading>
3535 Additional user-defined fields may be added to the
3536 source package control file. Such fields will be
3537 ignored, and not copied to (for example) binary or
3538 source package control files or upload control files.
3542 If you wish to add additional unsupported fields to
3543 these output files you should use the mechanism
3548 Fields in the main source control information file with
3549 names starting <tt>X</tt>, followed by one or more of
3550 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3551 be copied to the output files. Only the part of the
3552 field name after the hyphen will be used in the output
3553 file. Where the letter <tt>B</tt> is used the field
3554 will appear in binary package control files, where the
3555 letter <tt>S</tt> is used in source package control
3556 files and where <tt>C</tt> is used in upload control
3557 (<tt>.changes</tt>) files.
3561 For example, if the main source information control file
3564 XBS-Comment: I stand between the candle and the star.
3566 then the binary and source package control files will contain the
3569 Comment: I stand between the candle and the star.
3578 <chapt id="maintainerscripts">
3579 <heading>Package maintainer scripts and installation procedure</heading>
3582 <heading>Introduction to package maintainer scripts</heading>
3585 It is possible to supply scripts as part of a package which
3586 the package management system will run for you when your
3587 package is installed, upgraded or removed.
3591 These scripts are the files <prgn>preinst</prgn>,
3592 <prgn>postinst</prgn>, <prgn>prerm</prgn> and
3593 <prgn>postrm</prgn> in the control area of the package.
3594 They must be proper executable files; if they are scripts
3595 (which is recommended), they must start with the usual
3596 <tt>#!</tt> convention. They should be readable and
3597 executable by anyone, and must not be world-writable.
3601 The package management system looks at the exit status from
3602 these scripts. It is important that they exit with a
3603 non-zero status if there is an error, so that the package
3604 management system can stop its processing. For shell
3605 scripts this means that you <em>almost always</em> need to
3606 use <tt>set -e</tt> (this is usually true when writing shell
3607 scripts, in fact). It is also important, of course, that
3608 they exit with a zero status if everything went well.
3612 Additionally, packages interacting with users using
3613 <tt>debconf</tt> in the <prgn>postinst</prgn> script should
3614 install a <prgn>config</prgn> script in the control area,
3615 see <ref id="maintscriptprompt"> for details.
3619 When a package is upgraded a combination of the scripts from
3620 the old and new packages is called during the upgrade
3621 procedure. If your scripts are going to be at all
3622 complicated you need to be aware of this, and may need to
3623 check the arguments to your scripts.
3627 Broadly speaking the <prgn>preinst</prgn> is called before
3628 (a particular version of) a package is unpacked, and the
3629 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3630 before (a version of) a package is removed and the
3631 <prgn>postrm</prgn> afterwards.
3635 Programs called from maintainer scripts should not normally
3636 have a path prepended to them. Before installation is
3637 started, the package management system checks to see if the
3638 programs <prgn>ldconfig</prgn>,
3639 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3640 and <prgn>update-rc.d</prgn> can be found via the
3641 <tt>PATH</tt> environment variable. Those programs, and any
3642 other program that one would expect to be in the
3643 <tt>PATH</tt>, should thus be invoked without an absolute
3644 pathname. Maintainer scripts should also not reset the
3645 <tt>PATH</tt>, though they might choose to modify it by
3646 prepending or appending package-specific directories. These
3647 considerations really apply to all shell scripts.</p>
3650 <sect id="idempotency">
3651 <heading>Maintainer scripts idempotency</heading>
3654 It is necessary for the error recovery procedures that the
3655 scripts be idempotent. This means that if it is run
3656 successfully, and then it is called again, it doesn't bomb
3657 out or cause any harm, but just ensures that everything is
3658 the way it ought to be. If the first call failed, or
3659 aborted half way through for some reason, the second call
3660 should merely do the things that were left undone the first
3661 time, if any, and exit with a success status if everything
3663 This is so that if an error occurs, the user interrupts
3664 <prgn>dpkg</prgn> or some other unforeseen circumstance
3665 happens you don't leave the user with a badly-broken
3666 package when <prgn>dpkg</prgn> attempts to repeat the
3672 <sect id="controllingterminal">
3673 <heading>Controlling terminal for maintainer scripts</heading>
3676 Maintainer scripts are not guaranteed to run with a controlling
3677 terminal and may not be able to interact with the user. They
3678 must be able to fall back to noninteractive behavior if no
3679 controlling terminal is available. Maintainer scripts that
3680 prompt via a program conforming to the Debian Configuration
3681 Management Specification (see <ref id="maintscriptprompt">) may
3682 assume that program will handle falling back to noninteractive
3687 For high-priority prompts without a reasonable default answer,
3688 maintainer scripts may abort if there is no controlling
3689 terminal. However, this situation should be avoided if at all
3690 possible, since it prevents automated or unattended installs.
3691 In most cases, users will consider this to be a bug in the
3696 <sect id="exitstatus">
3697 <heading>Exit status</heading>
3700 Each script must return a zero exit status for
3701 success, or a nonzero one for failure, since the package
3702 management system looks for the exit status of these scripts
3703 and determines what action to take next based on that datum.
3707 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3712 <list compact="compact">
3714 <var>new-preinst</var> <tt>install</tt>
3717 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3720 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3723 <var>old-preinst</var> <tt>abort-upgrade</tt>
3724 <var>new-version</var>
3729 <list compact="compact">
3731 <var>postinst</var> <tt>configure</tt>
3732 <var>most-recently-configured-version</var>
3735 <var>old-postinst</var> <tt>abort-upgrade</tt>
3736 <var>new-version</var>
3739 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3740 <tt>in-favour</tt> <var>package</var>
3741 <var>new-version</var>
3744 <var>postinst</var> <tt>abort-remove</tt>
3747 <var>deconfigured's-postinst</var>
3748 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3749 <var>failed-install-package</var> <var>version</var>
3750 [<tt>removing</tt> <var>conflicting-package</var>
3756 <list compact="compact">
3758 <var>prerm</var> <tt>remove</tt>
3761 <var>old-prerm</var> <tt>upgrade</tt>
3762 <var>new-version</var>
3765 <var>new-prerm</var> <tt>failed-upgrade</tt>
3766 <var>old-version</var>
3769 <var>conflictor's-prerm</var> <tt>remove</tt>
3770 <tt>in-favour</tt> <var>package</var>
3771 <var>new-version</var>
3774 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3775 <tt>in-favour</tt> <var>package-being-installed</var>
3776 <var>version</var> [<tt>removing</tt>
3777 <var>conflicting-package</var>
3783 <list compact="compact">
3785 <var>postrm</var> <tt>remove</tt>
3788 <var>postrm</var> <tt>purge</tt>
3791 <var>old-postrm</var> <tt>upgrade</tt>
3792 <var>new-version</var>
3795 <var>new-postrm</var> <tt>failed-upgrade</tt>
3796 <var>old-version</var>
3799 <var>new-postrm</var> <tt>abort-install</tt>
3802 <var>new-postrm</var> <tt>abort-install</tt>
3803 <var>old-version</var>
3806 <var>new-postrm</var> <tt>abort-upgrade</tt>
3807 <var>old-version</var>
3810 <var>disappearer's-postrm</var> <tt>disappear</tt>
3811 <var>overwriter</var>
3812 <var>overwriter-version</var>
3818 <sect id="unpackphase">
3819 <heading>Details of unpack phase of installation or upgrade</heading>
3822 The procedure on installation/upgrade/overwrite/disappear
3823 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3824 stage of <tt>dpkg --install</tt>) is as follows. In each
3825 case, if a major error occurs (unless listed below) the
3826 actions are, in general, run backwards - this means that the
3827 maintainer scripts are run with different arguments in
3828 reverse order. These are the "error unwind" calls listed
3835 If a version of the package is already installed, call
3836 <example compact="compact">
3837 <var>old-prerm</var> upgrade <var>new-version</var>
3841 If the script runs but exits with a non-zero
3842 exit status, <prgn>dpkg</prgn> will attempt:
3843 <example compact="compact">
3844 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3846 If this works, the upgrade continues. If this
3847 does not work, the error unwind:
3848 <example compact="compact">
3849 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3851 If this works, then the old-version is
3852 "Installed", if not, the old version is in a
3853 "Half-Configured" state.
3859 If a "conflicting" package is being removed at the same time,
3860 or if any package will be broken (due to <tt>Breaks</tt>):
3863 If <tt>--auto-deconfigure</tt> is
3864 specified, call, for each package to be deconfigured
3865 due to <tt>Breaks</tt>:
3866 <example compact="compact">
3867 <var>deconfigured's-prerm</var> deconfigure \
3868 in-favour <var>package-being-installed</var> <var>version</var>
3871 <example compact="compact">
3872 <var>deconfigured's-postinst</var> abort-deconfigure \
3873 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3875 The deconfigured packages are marked as
3876 requiring configuration, so that if
3877 <tt>--install</tt> is used they will be
3878 configured again if possible.
3881 If any packages depended on a conflicting
3882 package being removed and <tt>--auto-deconfigure</tt> is
3883 specified, call, for each such package:
3884 <example compact="compact">
3885 <var>deconfigured's-prerm</var> deconfigure \
3886 in-favour <var>package-being-installed</var> <var>version</var> \
3887 removing <var>conflicting-package</var> <var>version</var>
3890 <example compact="compact">
3891 <var>deconfigured's-postinst</var> abort-deconfigure \
3892 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3893 removing <var>conflicting-package</var> <var>version</var>
3895 The deconfigured packages are marked as
3896 requiring configuration, so that if
3897 <tt>--install</tt> is used they will be
3898 configured again if possible.
3901 To prepare for removal of each conflicting package, call:
3902 <example compact="compact">
3903 <var>conflictor's-prerm</var> remove \
3904 in-favour <var>package</var> <var>new-version</var>
3907 <example compact="compact">
3908 <var>conflictor's-postinst</var> abort-remove \
3909 in-favour <var>package</var> <var>new-version</var>
3918 If the package is being upgraded, call:
3919 <example compact="compact">
3920 <var>new-preinst</var> upgrade <var>old-version</var>
3922 If this fails, we call:
3924 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3931 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3933 is called. If this works, then the old version
3934 is in an "Installed" state, or else it is left
3935 in an "Unpacked" state.
3940 If it fails, then the old version is left
3941 in an "Half-Installed" state.
3948 Otherwise, if the package had some configuration
3949 files from a previous version installed (i.e., it
3950 is in the "configuration files only" state):
3951 <example compact="compact">
3952 <var>new-preinst</var> install <var>old-version</var>
3956 <var>new-postrm</var> abort-install <var>old-version</var>
3958 If this fails, the package is left in a
3959 "Half-Installed" state, which requires a
3960 reinstall. If it works, the packages is left in
3961 a "Config-Files" state.
3964 Otherwise (i.e., the package was completely purged):
3965 <example compact="compact">
3966 <var>new-preinst</var> install
3969 <example compact="compact">
3970 <var>new-postrm</var> abort-install
3972 If the error-unwind fails, the package is in a
3973 "Half-Installed" phase, and requires a
3974 reinstall. If the error unwind works, the
3975 package is in a not installed state.
3982 The new package's files are unpacked, overwriting any
3983 that may be on the system already, for example any
3984 from the old version of the same package or from
3985 another package. Backups of the old files are kept
3986 temporarily, and if anything goes wrong the package
3987 management system will attempt to put them back as
3988 part of the error unwind.
3992 It is an error for a package to contain files which
3993 are on the system in another package, unless
3994 <tt>Replaces</tt> is used (see <ref id="replaces">).
3996 The following paragraph is not currently the case:
3997 Currently the <tt>- - force-overwrite</tt> flag is
3998 enabled, downgrading it to a warning, but this may not
4004 It is a more serious error for a package to contain a
4005 plain file or other kind of non-directory where another
4006 package has a directory (again, unless
4007 <tt>Replaces</tt> is used). This error can be
4008 overridden if desired using
4009 <tt>--force-overwrite-dir</tt>, but this is not
4014 Packages which overwrite each other's files produce
4015 behavior which, though deterministic, is hard for the
4016 system administrator to understand. It can easily
4017 lead to "missing" programs if, for example, a package
4018 is unpacked which overwrites a file from another
4019 package, and is then removed again.<footnote>
4020 Part of the problem is due to what is arguably a
4021 bug in <prgn>dpkg</prgn>.
4026 A directory will never be replaced by a symbolic link
4027 to a directory or vice versa; instead, the existing
4028 state (symlink or not) will be left alone and
4029 <prgn>dpkg</prgn> will follow the symlink if there is
4038 If the package is being upgraded, call
4039 <example compact="compact">
4040 <var>old-postrm</var> upgrade <var>new-version</var>
4044 If this fails, <prgn>dpkg</prgn> will attempt:
4045 <example compact="compact">
4046 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4048 If this works, installation continues. If not,
4050 <example compact="compact">
4051 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4053 If this fails, the old version is left in a
4054 "Half-Installed" state. If it works, dpkg now
4056 <example compact="compact">
4057 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4059 If this fails, the old version is left in a
4060 "Half-Installed" state. If it works, dpkg now
4062 <example compact="compact">
4063 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4065 If this fails, the old version is in an
4072 This is the point of no return - if
4073 <prgn>dpkg</prgn> gets this far, it won't back off
4074 past this point if an error occurs. This will
4075 leave the package in a fairly bad state, which
4076 will require a successful re-installation to clear
4077 up, but it's when <prgn>dpkg</prgn> starts doing
4078 things that are irreversible.
4083 Any files which were in the old version of the package
4084 but not in the new are removed.
4088 The new file list replaces the old.
4092 The new maintainer scripts replace the old.
4096 Any packages all of whose files have been overwritten
4097 during the installation, and which aren't required for
4098 dependencies, are considered to have been removed.
4099 For each such package
4102 <prgn>dpkg</prgn> calls:
4103 <example compact="compact">
4104 <var>disappearer's-postrm</var> disappear \
4105 <var>overwriter</var> <var>overwriter-version</var>
4109 The package's maintainer scripts are removed.
4112 It is noted in the status database as being in a
4113 sane state, namely not installed (any conffiles
4114 it may have are ignored, rather than being
4115 removed by <prgn>dpkg</prgn>). Note that
4116 disappearing packages do not have their prerm
4117 called, because <prgn>dpkg</prgn> doesn't know
4118 in advance that the package is going to
4125 Any files in the package we're unpacking that are also
4126 listed in the file lists of other packages are removed
4127 from those lists. (This will lobotomize the file list
4128 of the "conflicting" package if there is one.)
4132 The backup files made during installation, above, are
4138 The new package's status is now sane, and recorded as
4143 Here is another point of no return - if the
4144 conflicting package's removal fails we do not unwind
4145 the rest of the installation; the conflicting package
4146 is left in a half-removed limbo.
4151 If there was a conflicting package we go and do the
4152 removal actions (described below), starting with the
4153 removal of the conflicting package's files (any that
4154 are also in the package being unpacked have already
4155 been removed from the conflicting package's file list,
4156 and so do not get removed now).
4162 <sect id="configdetails"><heading>Details of configuration</heading>
4165 When we configure a package (this happens with <tt>dpkg
4166 --install</tt> and <tt>dpkg --configure</tt>), we first
4167 update any <tt>conffile</tt>s and then call:
4168 <example compact="compact">
4169 <var>postinst</var> configure <var>most-recently-configured-version</var>
4174 No attempt is made to unwind after errors during
4175 configuration. If the configuration fails, the package is in
4176 a "Failed Config" state, and an error message is generated.
4180 If there is no most recently configured version
4181 <prgn>dpkg</prgn> will pass a null argument.
4184 Historical note: Truly ancient (pre-1997) versions of
4185 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4186 (including the angle brackets) in this case. Even older
4187 ones did not pass a second argument at all, under any
4188 circumstance. Note that upgrades using such an old dpkg
4189 version are unlikely to work for other reasons, even if
4190 this old argument behavior is handled by your postinst script.
4196 <sect id="removedetails"><heading>Details of removal and/or
4197 configuration purging</heading>
4203 <example compact="compact">
4204 <var>prerm</var> remove
4208 If prerm fails during replacement due to conflict
4210 <var>conflictor's-postinst</var> abort-remove \
4211 in-favour <var>package</var> <var>new-version</var>
4215 <var>postinst</var> abort-remove
4219 If this fails, the package is in a "Half-Configured"
4220 state, or else it remains "Installed".
4224 The package's files are removed (except <tt>conffile</tt>s).
4227 <example compact="compact">
4228 <var>postrm</var> remove
4232 If it fails, there's no error unwind, and the package is in
4233 an "Half-Installed" state.
4238 All the maintainer scripts except the <prgn>postrm</prgn>
4243 If we aren't purging the package we stop here. Note
4244 that packages which have no <prgn>postrm</prgn> and no
4245 <tt>conffile</tt>s are automatically purged when
4246 removed, as there is no difference except for the
4247 <prgn>dpkg</prgn> status.
4251 The <tt>conffile</tt>s and any backup files
4252 (<tt>~</tt>-files, <tt>#*#</tt> files,
4253 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4258 <example compact="compact">
4259 <var>postrm</var> purge
4263 If this fails, the package remains in a "Config-Files"
4268 The package's file list is removed.
4277 <chapt id="relationships">
4278 <heading>Declaring relationships between packages</heading>
4280 <sect id="depsyntax">
4281 <heading>Syntax of relationship fields</heading>
4284 These fields all have a uniform syntax. They are a list of
4285 package names separated by commas.
4289 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4290 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4291 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4292 control file fields of the package, which declare
4293 dependencies on other packages, the package names listed may
4294 also include lists of alternative package names, separated
4295 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4296 if any one of the alternative packages is installed, that
4297 part of the dependency is considered to be satisfied.
4301 All of the fields except for <tt>Provides</tt> may restrict
4302 their applicability to particular versions of each named
4303 package. This is done in parentheses after each individual
4304 package name; the parentheses should contain a relation from
4305 the list below followed by a version number, in the format
4306 described in <ref id="f-Version">.
4310 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4311 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4312 strictly earlier, earlier or equal, exactly equal, later or
4313 equal and strictly later, respectively. The deprecated
4314 forms <tt><</tt> and <tt>></tt> were used to mean
4315 earlier/later or equal, rather than strictly earlier/later,
4316 so they should not appear in new packages (though
4317 <prgn>dpkg</prgn> still supports them).
4321 Whitespace may appear at any point in the version
4322 specification subject to the rules in <ref
4323 id="controlsyntax">, and must appear where it's necessary to
4324 disambiguate; it is not otherwise significant. All of the
4325 relationship fields may span multiple lines. For
4326 consistency and in case of future changes to
4327 <prgn>dpkg</prgn> it is recommended that a single space be
4328 used after a version relationship and before a version
4329 number; it is also conventional to put a single space after
4330 each comma, on either side of each vertical bar, and before
4331 each open parenthesis. When wrapping a relationship field, it
4332 is conventional to do so after a comma and before the space
4333 following that comma.
4337 For example, a list of dependencies might appear as:
4338 <example compact="compact">
4341 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4346 All fields that specify build-time relationships
4347 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4348 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>)
4349 may be restricted to a certain set of architectures. This
4350 is indicated in brackets after each individual package name and
4351 the optional version specification. The brackets enclose a
4352 list of Debian architecture names separated by whitespace.
4353 Exclamation marks may be prepended to each of the names.
4354 (It is not permitted for some names to be prepended with
4355 exclamation marks while others aren't.) If the current Debian
4356 host architecture is not in this list and there are no
4357 exclamation marks in the list, or it is in the list with a
4358 prepended exclamation mark, the package name and the
4359 associated version specification are ignored completely for
4360 the purposes of defining the relationships.
4365 <example compact="compact">
4367 Build-Depends-Indep: texinfo
4368 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4369 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4371 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4372 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4373 <tt>gnumach-dev</tt> only on hurd-i386.
4377 If the architecture-restricted dependency is part of a set of
4378 alternatives using <tt>|</tt>, that alternative is ignored
4379 completely on architectures that do not match the restriction.
4381 <example compact="compact">
4382 Build-Depends: foo [!i386] | bar [!amd64]
4384 is equivalent to <tt>bar</tt> on the i386 architecture, to
4385 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4386 bar</tt> on all other architectures.
4390 All fields that specify build-time relationships may also be
4391 restricted to a certain set of architectures using architecture
4392 wildcards. The syntax for declaring such restrictions is the
4393 same as declaring restrictions using a certain set of
4394 architectures without architecture wildcards. For example:
4395 <example compact="compact">
4396 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4398 is equivalent to <tt>foo</tt> on architectures using the Linux
4399 kernel and any cpu, <tt>bar</tt> on architectures using any
4400 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4401 using a kernel other than Linux.
4405 Note that the binary package relationship fields such as
4406 <tt>Depends</tt> appear in one of the binary package
4407 sections of the control file, whereas the build-time
4408 relationships such as <tt>Build-Depends</tt> appear in the
4409 source package section of the control file (which is the
4414 <sect id="binarydeps">
4415 <heading>Binary Dependencies - <tt>Depends</tt>,
4416 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4417 <tt>Pre-Depends</tt>
4421 Packages can declare in their control file that they have
4422 certain relationships to other packages - for example, that
4423 they may not be installed at the same time as certain other
4424 packages, and/or that they depend on the presence of others.
4428 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4429 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4430 <tt>Breaks</tt> and <tt>Conflicts</tt> control file fields.
4431 <tt>Breaks</tt> is described in <ref id="breaks">, and
4432 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4433 rest are described below.
4437 These seven fields are used to declare a dependency
4438 relationship by one package on another. Except for
4439 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4440 depending (binary) package's control file.
4441 (<tt>Enhances</tt> appears in the recommending package's
4442 control file, and <tt>Breaks</tt> appears in the version of
4443 depended-on package which causes the named package to
4448 A <tt>Depends</tt> field takes effect <em>only</em> when a
4449 package is to be configured. It does not prevent a package
4450 being on the system in an unconfigured state while its
4451 dependencies are unsatisfied, and it is possible to replace
4452 a package whose dependencies are satisfied and which is
4453 properly installed with a different version whose
4454 dependencies are not and cannot be satisfied; when this is
4455 done the depending package will be left unconfigured (since
4456 attempts to configure it will give errors) and will not
4457 function properly. If it is necessary, a
4458 <tt>Pre-Depends</tt> field can be used, which has a partial
4459 effect even when a package is being unpacked, as explained
4460 in detail below. (The other three dependency fields,
4461 <tt>Recommends</tt>, <tt>Suggests</tt> and
4462 <tt>Enhances</tt>, are only used by the various front-ends
4463 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4464 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4468 Since <tt>Depends</tt> only places requirements on the
4469 configuration step, packages in an installation run are usually
4470 all unpacked first and all configured later. This makes it
4471 easier to satisfy all dependencies when multiple packages are
4476 If there is a circular dependency among packages being installed
4477 or removed, installation or removal order honoring the
4478 dependency order is impossible, requiring the dependency loop be
4479 broken at some point and the dependency requirements violated
4480 for at least one package. Packages involved in circular
4481 dependencies may not be able to rely on their dependencies being
4482 configured when being configured or removed depending on which
4483 side of the break of the circular dependency loop they happen to
4484 be on. If one of the packages in the loop has no
4485 <prgn>postinst</prgn> script, then the cycle will be broken at
4486 that package; this ensures that all <prgn>postinst</prgn>
4487 scripts are run with their dependencies properly configured if
4488 this is possible. Otherwise the breaking point is arbitrary.
4489 Packages should therefore avoid circular dependencies where
4490 possible, particularly if they have <prgn>postinst</prgn>
4495 The meaning of the five dependency fields is as follows:
4497 <tag><tt>Depends</tt></tag>
4500 This declares an absolute dependency. A package will
4501 not be configured unless all of the packages listed in
4502 its <tt>Depends</tt> field have been correctly
4503 configured (unless there is a circular dependency as
4508 The <tt>Depends</tt> field should be used if the
4509 depended-on package is required for the depending
4510 package to provide a significant amount of
4515 The <tt>Depends</tt> field should also be used if the
4516 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4517 <prgn>postrm</prgn> scripts require the package to be
4518 present in order to run. (If both packages are involved
4519 in a dependency loop, this might not work as expected; see
4520 the explanation a few paragraphs back.) In the case of
4521 <prgn>postinst</prgn> and <prgn>postrm</prgn>, the
4522 depended-on packages will be unpacked and configured
4523 first. (Note, however, that the <prgn>postrm</prgn>
4524 cannot rely on any non-essential packages to be present
4525 during the <tt>purge</tt> phase.) In the case of
4526 <prgn>prerm</prgn>, the depended-on package will at least
4527 be unpacked (it might be configured too, but you can't
4528 rely on this unless you use <tt>Pre-Depends</tt>).
4531 <tag><tt>Recommends</tt></tag>
4534 This declares a strong, but not absolute, dependency.
4538 The <tt>Recommends</tt> field should list packages
4539 that would be found together with this one in all but
4540 unusual installations.
4544 <tag><tt>Suggests</tt></tag>
4546 This is used to declare that one package may be more
4547 useful with one or more others. Using this field
4548 tells the packaging system and the user that the
4549 listed packages are related to this one and can
4550 perhaps enhance its usefulness, but that installing
4551 this one without them is perfectly reasonable.
4554 <tag><tt>Enhances</tt></tag>
4556 This field is similar to Suggests but works in the
4557 opposite direction. It is used to declare that a
4558 package can enhance the functionality of another
4562 <tag><tt>Pre-Depends</tt></tag>
4565 This field is like <tt>Depends</tt>, except that it
4566 also forces <prgn>dpkg</prgn> to complete installation
4567 of the packages named before even starting the
4568 installation of the package which declares the
4569 pre-dependency, as follows:
4573 When a package declaring a pre-dependency is about to
4574 be <em>unpacked</em> the pre-dependency can be
4575 satisfied if the depended-on package is either fully
4576 configured, <em>or even if</em> the depended-on
4577 package(s) are only unpacked or in the "Half-Configured"
4578 state, provided that they have been configured
4579 correctly at some point in the past (and not removed
4580 or partially removed since). In this case, both the
4581 previously-configured and currently unpacked or
4582 "Half-Configured" versions must satisfy any version
4583 clause in the <tt>Pre-Depends</tt> field.
4587 When the package declaring a pre-dependency is about
4588 to be <em>configured</em>, the pre-dependency will be
4589 treated as a normal <tt>Depends</tt>, that is, it will
4590 be considered satisfied only if the depended-on
4591 package has been correctly configured. However, unlike
4592 with <tt>Depends</tt>, <tt>Pre-Depends</tt> does not
4593 permit circular dependencies to be broken. If a circular
4594 dependency is encountered while attempting to honor
4595 <tt>Pre-Depends</tt>, the installation will be aborted.
4599 <tt>Pre-Depends</tt> are also required if the
4600 <prgn>preinst</prgn> script depends on the named package.
4601 It is best to avoid this situation if possible.
4605 <tt>Pre-Depends</tt> should be used sparingly,
4606 preferably only by packages whose premature upgrade or
4607 installation would hamper the ability of the system to
4608 continue with any upgrade that might be in progress.
4615 When selecting which level of dependency to use you should
4616 consider how important the depended-on package is to the
4617 functionality of the one declaring the dependency. Some
4618 packages are composed of components of varying degrees of
4619 importance. Such a package should list using
4620 <tt>Depends</tt> the package(s) which are required by the
4621 more important components. The other components'
4622 requirements may be mentioned as Suggestions or
4623 Recommendations, as appropriate to the components' relative
4629 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4632 When one binary package declares that it breaks another,
4633 <prgn>dpkg</prgn> will refuse to allow the package which
4634 declares <tt>Breaks</tt> be unpacked unless the broken
4635 package is deconfigured first, and it will refuse to
4636 allow the broken package to be reconfigured.
4640 A package will not be regarded as causing breakage merely
4641 because its configuration files are still installed; it must
4642 be at least "Half-Installed".
4646 A special exception is made for packages which declare that
4647 they break their own package name or a virtual package which
4648 they provide (see below): this does not count as a real
4653 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4654 version clause; such a <tt>Breaks</tt> is introduced in the
4655 version of an (implicit or explicit) dependency which violates
4656 an assumption or reveals a bug in earlier versions of the broken
4657 package, or which takes over a file from earlier versions of the
4658 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
4659 will inform higher-level package management tools that the
4660 broken package must be upgraded before the new one.
4664 If the breaking package also overwrites some files from the
4665 older package, it should use <tt>Replaces</tt> to ensure this
4666 goes smoothly. See <ref id="replaces"> for a full discussion
4667 of taking over files from other packages, including how to
4668 use <tt>Breaks</tt> in those cases.
4672 Many of the cases where <tt>Breaks</tt> should be used were
4673 previously handled with <tt>Conflicts</tt>
4674 because <tt>Breaks</tt> did not yet exist.
4675 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
4676 See <ref id="conflicts"> for more information about the
4681 <sect id="conflicts">
4682 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4685 When one binary package declares a conflict with another
4686 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4687 refuse to allow them to be unpacked on the system at the
4688 same time. This is a stronger restriction than <tt>Breaks</tt>,
4689 which just prevents both packages from being configured at the
4690 same time. Conflicting packages cannot be unpacked on the
4691 system at the same time.
4695 If one package is to be unpacked, the other must be removed
4696 first. If the package being unpacked is marked as replacing
4697 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
4698 normally be used in this case) the one on the system, or the one
4699 on the system is marked as deselected, or both packages are
4700 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
4701 automatically remove the package which is causing the conflict.
4702 Otherwise, it will halt the installation of the new package with
4703 an error. This mechanism is specifically designed to produce an
4704 error when the installed package is <tt>Essential</tt>, but the
4709 A package will not cause a conflict merely because its
4710 configuration files are still installed; it must be at least
4715 A special exception is made for packages which declare a
4716 conflict with their own package name, or with a virtual
4717 package which they provide (see below): this does not
4718 prevent their installation, and allows a package to conflict
4719 with others providing a replacement for it. You use this
4720 feature when you want the package in question to be the only
4721 package providing some feature.
4725 Normally, <tt>Breaks</tt> should be used instead
4726 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
4727 stronger restriction on the ordering of package installation or
4728 upgrade and can make it more difficult for the package manager
4729 to find a correct solution to an upgrade or installation
4730 problem. <tt>Breaks</tt> should be used
4732 <item>when moving a file from one package to another (see
4733 <ref id="replaces">),</item>
4734 <item>when splitting a package (a special case of the previous
4736 <item>when the breaking package exposes a bug in or interacts
4737 badly with particular versions of the broken
4740 <tt>Conflicts</tt> should be used
4742 <item>when two packages provide the same file and will
4743 continue to do so,</item>
4744 <item>in conjunction with <tt>Provides</tt> when only one
4745 package providing a given virtual facility may be installed
4746 at a time (see <ref id="virtual">),</item>
4747 <item>in other cases where one must prevent simultaneous
4748 installation of two packages for reasons that are ongoing
4749 (not fixed in a later version of one of the packages) or
4750 that must prevent both packages from being unpacked at the
4751 same time, not just configured.</item>
4753 Be aware that adding <tt>Conflicts</tt> is normally not the best
4754 solution when two packages provide the same files. Depending on
4755 the reason for that conflict, using alternatives or renaming the
4756 files is often a better approach. See, for
4757 example, <ref id="binaries">.
4761 A <tt>Conflicts</tt> entry may have an "earlier than" version
4762 clause if the reason for the conflict is corrected in a later
4763 version of one of the packages. However, normally the presence
4764 of an "earlier than" version clause is a sign
4765 that <tt>Breaks</tt> should have been used instead. An "earlier
4766 than" version clause in <tt>Conflicts</tt>
4767 prevents <prgn>dpkg</prgn> from upgrading or installing the
4768 package which declares such a conflict until the upgrade or
4769 removal of the conflicted-with package has been completed, which
4770 is a strong restriction.
4774 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4778 As well as the names of actual ("concrete") packages, the
4779 package relationship fields <tt>Depends</tt>,
4780 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4781 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4782 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4783 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4784 may mention "virtual packages".
4788 A <em>virtual package</em> is one which appears in the
4789 <tt>Provides</tt> control file field of another package.
4790 The effect is as if the package(s) which provide a
4791 particular virtual package name had been listed by name
4792 everywhere the virtual package name appears. (See also <ref
4797 If there are both concrete and virtual packages of the same
4798 name, then the dependency may be satisfied (or the conflict
4799 caused) by either the concrete package with the name in
4800 question or any other concrete package which provides the
4801 virtual package with the name in question. This is so that,
4802 for example, supposing we have
4803 <example compact="compact">
4806 </example> and someone else releases an enhanced version of
4807 the <tt>bar</tt> package they can say:
4808 <example compact="compact">
4812 and the <tt>bar-plus</tt> package will now also satisfy the
4813 dependency for the <tt>foo</tt> package.
4817 If a relationship field has a version number attached, only real
4818 packages will be considered to see whether the relationship is
4819 satisfied (or the prohibition violated, for a conflict or
4820 breakage). In other words, if a version number is specified,
4821 this is a request to ignore all <tt>Provides</tt> for that
4822 package name and consider only real packages. The package
4823 manager will assume that a package providing that virtual
4824 package is not of the "right" version. A <tt>Provides</tt>
4825 field may not contain version numbers, and the version number of
4826 the concrete package which provides a particular virtual package
4827 will not be considered when considering a dependency on or
4828 conflict with the virtual package name.<footnote>
4829 It is possible that a future release of <prgn>dpkg</prgn> may
4830 add the ability to specify a version number for each virtual
4831 package it provides. This feature is not yet present,
4832 however, and is expected to be used only infrequently.
4837 To specify which of a set of real packages should be the default
4838 to satisfy a particular dependency on a virtual package, list
4839 the real package as an alternative before the virtual one.
4843 If the virtual package represents a facility that can only be
4844 provided by one real package at a time, such as
4845 the <package>mail-transport-agent</package> virtual package that
4846 requires installation of a binary that would conflict with all
4847 other providers of that virtual package (see
4848 <ref id="mail-transport-agents">), all packages providing that
4849 virtual package should also declare a conflict with it
4850 using <tt>Conflicts</tt>. This will ensure that at most one
4851 provider of that virtual package is unpacked or installed at a
4856 <sect id="replaces"><heading>Overwriting files and replacing
4857 packages - <tt>Replaces</tt></heading>
4860 Packages can declare in their control file that they should
4861 overwrite files in certain other packages, or completely
4862 replace other packages. The <tt>Replaces</tt> control file
4863 field has these two distinct purposes.
4866 <sect1><heading>Overwriting files in other packages</heading>
4869 It is usually an error for a package to contain files which
4870 are on the system in another package. However, if the
4871 overwriting package declares that it <tt>Replaces</tt> the one
4872 containing the file being overwritten, then <prgn>dpkg</prgn>
4873 will replace the file from the old package with that from the
4874 new. The file will no longer be listed as "owned" by the old
4875 package and will be taken over by the new package.
4876 Normally, <tt>Breaks</tt> should be used in conjunction
4877 with <tt>Replaces</tt>.<footnote>
4878 To see why <tt>Breaks</tt> is normally needed in addition
4879 to <tt>Replaces</tt>, consider the case of a file in the
4880 package <package>foo</package> being taken over by the
4881 package <package>foo-data</package>.
4882 <tt>Replaces</tt> will allow <package>foo-data</package> to
4883 be installed and take over that file. However,
4884 without <tt>Breaks</tt>, nothing
4885 requires <package>foo</package> to be upgraded to a newer
4886 version that knows it does not include that file and instead
4887 depends on <package>foo-data</package>. Nothing would
4888 prevent the new <package>foo-data</package> package from
4889 being installed and then removed, removing the file that it
4890 took over from <package>foo</package>. After that
4891 operation, the package manager would think the system was in
4892 a consistent state, but the <package>foo</package> package
4893 would be missing one of its files.
4898 For example, if a package <package>foo</package> is split
4899 into <package>foo</package> and <package>foo-data</package>
4900 starting at version 1.2-3, <package>foo-data</package> would
4902 <example compact="compact">
4903 Replaces: foo (<< 1.2-3)
4904 Breaks: foo (<< 1.2-3)
4906 in its control file. The new version of the
4907 package <package>foo</package> would normally have the field
4908 <example compact="compact">
4909 Depends: foo-data (>= 1.2-3)
4911 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
4912 the files moved into <package>foo-data</package> are not
4913 required for normal operation).
4917 If a package is completely replaced in this way, so that
4918 <prgn>dpkg</prgn> does not know of any files it still
4919 contains, it is considered to have "disappeared". It will
4920 be marked as not wanted on the system (selected for
4921 removal) and not installed. Any <tt>conffile</tt>s
4922 details noted for the package will be ignored, as they
4923 will have been taken over by the overwriting package. The
4924 package's <prgn>postrm</prgn> script will be run with a
4925 special argument to allow the package to do any final
4926 cleanup required. See <ref id="mscriptsinstact">.
4928 Replaces is a one way relationship. You have to install
4929 the replacing package after the replaced package.
4934 For this usage of <tt>Replaces</tt>, virtual packages (see
4935 <ref id="virtual">) are not considered when looking at a
4936 <tt>Replaces</tt> field. The packages declared as being
4937 replaced must be mentioned by their real names.
4941 This usage of <tt>Replaces</tt> only takes effect when both
4942 packages are at least partially on the system at once. It is
4943 not relevant if the packages conflict unless the conflict has
4948 <sect1><heading>Replacing whole packages, forcing their
4952 Second, <tt>Replaces</tt> allows the packaging system to
4953 resolve which package should be removed when there is a
4954 conflict (see <ref id="conflicts">). This usage only takes
4955 effect when the two packages <em>do</em> conflict, so that the
4956 two usages of this field do not interfere with each other.
4960 In this situation, the package declared as being replaced
4961 can be a virtual package, so for example, all mail
4962 transport agents (MTAs) would have the following fields in
4963 their control files:
4964 <example compact="compact">
4965 Provides: mail-transport-agent
4966 Conflicts: mail-transport-agent
4967 Replaces: mail-transport-agent
4969 ensuring that only one MTA can be unpacked at any one
4970 time. See <ref id="virtual"> for more information about this
4975 <sect id="sourcebinarydeps">
4976 <heading>Relationships between source and binary packages -
4977 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4978 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
4982 Source packages that require certain binary packages to be
4983 installed or absent at the time of building the package
4984 can declare relationships to those binary packages.
4988 This is done using the <tt>Build-Depends</tt>,
4989 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
4990 <tt>Build-Conflicts-Indep</tt> control file fields.
4994 Build-dependencies on "build-essential" binary packages can be
4995 omitted. Please see <ref id="pkg-relations"> for more information.
4999 The dependencies and conflicts they define must be satisfied
5000 (as defined earlier for binary packages) in order to invoke
5001 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5003 There is no Build-Depends-Arch; this role is essentially
5004 met with Build-Depends. Anyone building the
5005 <tt>build-indep</tt> and binary-indep<tt></tt> targets is
5006 assumed to be building the whole package, and therefore
5007 installation of all build dependencies is required.
5010 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5011 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5012 not yet know how to check for its existence, and
5013 <tt>binary-arch</tt>. The purpose of the original split
5014 between <tt>Build-Depends</tt> and
5015 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5016 wouldn't need to install extra packages needed only for the
5017 binary-indep targets. But without a build-arch/build-indep
5018 split, this didn't work, since most of the work is done in
5019 the build target, not in the binary target.
5023 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5024 <tt>binary-arch</tt></tag>
5026 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5027 fields must be satisfied when these targets are invoked.
5029 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5030 and <tt>binary-indep</tt></tag>
5032 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5033 <tt>Build-Depends-Indep</tt>, and
5034 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5035 these targets are invoked.
5043 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5046 Packages containing shared libraries must be constructed with
5047 a little care to make sure that the shared library is always
5048 available. This is especially important for packages whose
5049 shared libraries are vitally important, such as the C library
5050 (currently <tt>libc6</tt>).
5054 Packages involving shared libraries should be split up into
5055 several binary packages. This section mostly deals with how
5056 this separation is to be accomplished; rules for files within
5057 the shared library packages are in <ref id="libraries"> instead.
5060 <sect id="sharedlibs-runtime">
5061 <heading>Run-time shared libraries</heading>
5064 The run-time shared library needs to be placed in a package
5065 whose name changes whenever the shared object version
5068 Since it is common place to install several versions of a
5069 package that just provides shared libraries, it is a
5070 good idea that the library package should not
5071 contain any extraneous non-versioned files, unless they
5072 happen to be in versioned directories.</p>
5074 The most common mechanism is to place it in a package
5076 <package><var>libraryname</var><var>soversion</var></package>,
5077 where <file><var>soversion</var></file> is the version number
5078 in the soname of the shared library<footnote>
5079 The soname is the shared object name: it's the thing
5080 that has to match exactly between building an executable
5081 and running it for the dynamic linker to be able run the
5082 program. For example, if the soname of the library is
5083 <file>libfoo.so.6</file>, the library package would be
5084 called <file>libfoo6</file>.
5086 Alternatively, if it would be confusing to directly append
5087 <var>soversion</var> to <var>libraryname</var> (e.g. because
5088 <var>libraryname</var> itself ends in a number), you may use
5089 <package><var>libraryname</var>-<var>soversion</var></package> and
5090 <package><var>libraryname</var>-<var>soversion</var>-dev</package>
5095 If you have several shared libraries built from the same
5096 source tree you may lump them all together into a single
5097 shared library package, provided that you change all of
5098 their sonames at once (so that you don't get filename
5099 clashes if you try to install different versions of the
5100 combined shared libraries package).
5104 The package should install the shared libraries under
5105 their normal names. For example, the <package>libgdbm3</package>
5106 package should install <file>libgdbm.so.3.0.0</file> as
5107 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5108 renamed or re-linked by any <prgn>prerm</prgn> or
5109 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5110 of renaming things safely without affecting running programs,
5111 and attempts to interfere with this are likely to lead to
5116 Shared libraries should not be installed executable, since
5117 the dynamic linker does not require this and trying to
5118 execute a shared library usually results in a core dump.
5122 The run-time library package should include the symbolic link that
5123 <prgn>ldconfig</prgn> would create for the shared libraries.
5124 For example, the <package>libgdbm3</package> package should include
5125 a symbolic link from <file>/usr/lib/libgdbm.so.3</file> to
5126 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5127 linker (for example <prgn>ld.so</prgn> or
5128 <prgn>ld-linux.so.*</prgn>) can find the library between the
5129 time that <prgn>dpkg</prgn> installs it and the time that
5130 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5132 The package management system requires the library to be
5133 placed before the symbolic link pointing to it in the
5134 <file>.deb</file> file. This is so that when
5135 <prgn>dpkg</prgn> comes to install the symlink
5136 (overwriting the previous symlink pointing at an older
5137 version of the library), the new shared library is already
5138 in place. In the past, this was achieved by creating the
5139 library in the temporary packaging directory before
5140 creating the symlink. Unfortunately, this was not always
5141 effective, since the building of the tar file in the
5142 <file>.deb</file> depended on the behavior of the underlying
5143 file system. Some file systems (such as reiserfs) reorder
5144 the files so that the order of creation is forgotten.
5145 Since version 1.7.0, <prgn>dpkg</prgn>
5146 reorders the files itself as necessary when building a
5147 package. Thus it is no longer important to concern
5148 oneself with the order of file creation.
5152 <sect1 id="ldconfig">
5153 <heading><tt>ldconfig</tt></heading>
5156 Any package installing shared libraries in one of the default
5157 library directories of the dynamic linker (which are currently
5158 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5159 listed in <file>/etc/ld.so.conf</file><footnote>
5161 <list compact="compact">
5162 <item>/usr/local/lib</item>
5163 <item>/usr/lib/libc5-compat</item>
5164 <item>/lib/libc5-compat</item>
5167 must use <prgn>ldconfig</prgn> to update the shared library
5172 The package maintainer scripts must only call
5173 <prgn>ldconfig</prgn> under these circumstances:
5174 <list compact="compact">
5175 <item>When the <prgn>postinst</prgn> script is run with a
5176 first argument of <tt>configure</tt>, the script must call
5177 <prgn>ldconfig</prgn>, and may optionally invoke
5178 <prgn>ldconfig</prgn> at other times.
5180 <item>When the <prgn>postrm</prgn> script is run with a
5181 first argument of <tt>remove</tt>, the script should call
5182 <prgn>ldconfig</prgn>.
5187 During install or upgrade, the preinst is called before
5188 the new files are unpacked, so calling "ldconfig" is
5189 pointless. The preinst of an existing package can also be
5190 called if an upgrade fails. However, this happens during
5191 the critical time when a shared libs may exist on-disk
5192 under a temporary name. Thus, it is dangerous and
5193 forbidden by current policy to call "ldconfig" at this
5198 When a package is installed or upgraded, "postinst
5199 configure" runs after the new files are safely on-disk.
5200 Since it is perfectly safe to invoke ldconfig
5201 unconditionally in a postinst, it is OK for a package to
5202 simply put ldconfig in its postinst without checking the
5203 argument. The postinst can also be called to recover from
5204 a failed upgrade. This happens before any new files are
5205 unpacked, so there is no reason to call "ldconfig" at this
5210 For a package that is being removed, prerm is
5211 called with all the files intact, so calling ldconfig is
5212 useless. The other calls to "prerm" happen in the case of
5213 upgrade at a time when all the files of the old package
5214 are on-disk, so again calling "ldconfig" is pointless.
5218 postrm, on the other hand, is called with the "remove"
5219 argument just after the files are removed, so this is
5220 the proper time to call "ldconfig" to notify the system
5221 of the fact that the shared libraries from the package
5222 are removed. The postrm can be called at several other
5223 times. At the time of "postrm purge", "postrm
5224 abort-install", or "postrm abort-upgrade", calling
5225 "ldconfig" is useless because the shared lib files are
5226 not on-disk. However, when "postrm" is invoked with
5227 arguments "upgrade", "failed-upgrade", or "disappear", a
5228 shared lib may exist on-disk under a temporary filename.
5236 <sect id="sharedlibs-support-files">
5237 <heading>Shared library support files</heading>
5240 If your package contains files whose names do not change with
5241 each change in the library shared object version, you must not
5242 put them in the shared library package. Otherwise, several
5243 versions of the shared library cannot be installed at the same
5244 time without filename clashes, making upgrades and transitions
5245 unnecessarily difficult.
5249 It is recommended that supporting files and run-time support
5250 programs that do not need to be invoked manually by users, but
5251 are nevertheless required for the package to function, be placed
5252 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5253 preferably under <file>/usr/lib/</file><var>package-name</var>.
5254 If the program or file is architecture independent, the
5255 recommendation is for it to be placed in a subdirectory of
5256 <file>/usr/share</file> instead, preferably under
5257 <file>/usr/share/</file><var>package-name</var>. Following the
5258 <var>package-name</var> naming convention ensures that the file
5259 names change when the shared object version changes.
5263 Run-time support programs that use the shared library but are
5264 not required for the library to function or files used by the
5265 shared library that can be used by any version of the shared
5266 library package should instead be put in a separate package.
5267 This package might typically be named
5268 <package><var>libraryname</var>-tools</package>; note the
5269 absence of the <var>soversion</var> in the package name.
5273 Files and support programs only useful when compiling software
5274 against the library should be included in the development
5275 package for the library.<footnote>
5276 For example, a <file><var>package-name</var>-config</file>
5277 script or <package>pkg-config</package> configuration files.
5282 <sect id="sharedlibs-static">
5283 <heading>Static libraries</heading>
5286 The static library (<file><var>libraryname.a</var></file>)
5287 is usually provided in addition to the shared version.
5288 It is placed into the development package (see below).
5292 In some cases, it is acceptable for a library to be
5293 available in static form only; these cases include:
5295 <item>libraries for languages whose shared library support
5296 is immature or unstable</item>
5297 <item>libraries whose interfaces are in flux or under
5298 development (commonly the case when the library's
5299 major version number is zero, or where the ABI breaks
5300 across patchlevels)</item>
5301 <item>libraries which are explicitly intended to be
5302 available only in static form by their upstream
5307 <sect id="sharedlibs-dev">
5308 <heading>Development files</heading>
5311 If there are development files associated with a shared library,
5312 the source package needs to generate a binary development package
5313 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5314 or if you prefer only to support one development version at a
5315 time, <package><var>libraryname</var>-dev</package>. Installing
5316 the development package must result in installation of all the
5317 development files necessary for compiling programs against that
5318 shared library.<footnote>
5319 This wording allows the development files to be split into
5320 several packages, such as a separate architecture-independent
5321 <package><var>libraryname</var>-headers</package>, provided that
5322 the development package depends on all the required additional
5328 In case several development versions of a library exist, you may
5329 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5330 <ref id="conflicts">) to ensure that the user only installs one
5331 development version at a time (as different development versions are
5332 likely to have the same header files in them, which would cause a
5333 filename clash if both were unpacked).
5337 The development package should contain a symlink for the associated
5338 shared library without a version number. For example, the
5339 <package>libgdbm-dev</package> package should include a symlink
5340 from <file>/usr/lib/libgdbm.so</file> to
5341 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5342 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5343 <file>libgdbm.so</file> when compiling dynamically.
5347 <sect id="sharedlibs-intradeps">
5348 <heading>Dependencies between the packages of the same library</heading>
5351 Typically the development version should have an exact
5352 version dependency on the runtime library, to make sure that
5353 compilation and linking happens correctly. The
5354 <tt>${binary:Version}</tt> substitution variable can be
5355 useful for this purpose.
5357 Previously, <tt>${Source-Version}</tt> was used, but its name
5358 was confusing and it has been deprecated since dpkg 1.13.19.
5363 <sect id="sharedlibs-shlibdeps">
5364 <heading>Dependencies between the library and other packages -
5365 the <tt>shlibs</tt> system</heading>
5368 If a package contains a binary or library which links to a
5369 shared library, we must ensure that when the package is
5370 installed on the system, all of the libraries needed are
5371 also installed. This requirement led to the creation of the
5372 <tt>shlibs</tt> system, which is very simple in its design:
5373 any package which <em>provides</em> a shared library also
5374 provides information on the package dependencies required to
5375 ensure the presence of this library, and any package which
5376 <em>uses</em> a shared library uses this information to
5377 determine the dependencies it requires. The files which
5378 contain the mapping from shared libraries to the necessary
5379 dependency information are called <file>shlibs</file> files.
5383 Thus, when a package is built which contains any shared
5384 libraries, it must provide a <file>shlibs</file> file for other
5385 packages to use, and when a package is built which contains
5386 any shared libraries or compiled binaries, it must run
5387 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5388 on these to determine the libraries used and hence the
5389 dependencies needed by this package.<footnote>
5391 In the past, the shared libraries linked to were
5392 determined by calling <prgn>ldd</prgn>, but now
5393 <prgn>objdump</prgn> is used to do this. The only
5394 change this makes to package building is that
5395 <prgn>dpkg-shlibdeps</prgn> must also be run on shared
5396 libraries, whereas in the past this was unnecessary.
5397 The rest of this footnote explains the advantage that
5402 We say that a binary <tt>foo</tt> <em>directly</em> uses
5403 a library <tt>libbar</tt> if it is explicitly linked
5404 with that library (that is, it uses the flag
5405 <tt>-lbar</tt> during the linking stage). Other
5406 libraries that are needed by <tt>libbar</tt> are linked
5407 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5408 linker will load them automatically when it loads
5409 <tt>libbar</tt>. A package should depend on
5410 the libraries it directly uses, and the dependencies for
5411 those libraries should automatically pull in the other
5416 Unfortunately, the <prgn>ldd</prgn> program shows both
5417 the directly and indirectly used libraries, meaning that
5418 the dependencies determined included both direct and
5419 indirect dependencies. The use of <prgn>objdump</prgn>
5420 avoids this problem by determining only the directly
5425 A good example of where this helps is the following. We
5426 could update <tt>libimlib</tt> with a new version that
5427 supports a new graphics format called dgf (but retaining
5428 the same major version number). If we used the old
5429 <prgn>ldd</prgn> method, every package that uses
5430 <tt>libimlib</tt> would need to be recompiled so it
5431 would also depend on <tt>libdgf</tt> or it wouldn't run
5432 due to missing symbols. However with the new system,
5433 packages using <tt>libimlib</tt> can rely on
5434 <tt>libimlib</tt> itself having the dependency on
5435 <tt>libdgf</tt> and so they would not need rebuilding.
5441 In the following sections, we will first describe where the
5442 various <tt>shlibs</tt> files are to be found, then how to
5443 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5444 file format and how to create them if your package contains a
5449 <heading>The <tt>shlibs</tt> files present on the system</heading>
5452 There are several places where <tt>shlibs</tt> files are
5453 found. The following list gives them in the order in which
5455 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5456 (The first one which gives the required information is used.)
5462 <p><file>debian/shlibs.local</file></p>
5465 This lists overrides for this package. Its use is
5466 described below (see <ref id="shlibslocal">).
5471 <p><file>/etc/dpkg/shlibs.override</file></p>
5474 This lists global overrides. This list is normally
5475 empty. It is maintained by the local system
5481 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5484 When packages are being built, any
5485 <file>debian/shlibs</file> files are copied into the
5486 control file area of the temporary build directory and
5487 given the name <file>shlibs</file>. These files give
5488 details of any shared libraries included in the
5490 An example may help here. Let us say that the
5491 source package <tt>foo</tt> generates two binary
5492 packages, <tt>libfoo2</tt> and
5493 <tt>foo-runtime</tt>. When building the binary
5494 packages, the two packages are created in the
5495 directories <file>debian/libfoo2</file> and
5496 <file>debian/foo-runtime</file> respectively.
5497 (<file>debian/tmp</file> could be used instead of one
5498 of these.) Since <tt>libfoo2</tt> provides the
5499 <tt>libfoo</tt> shared library, it will require a
5500 <tt>shlibs</tt> file, which will be installed in
5501 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually
5503 <file>/var/lib/dpkg/info/libfoo2.shlibs</file>. Then
5504 when <prgn>dpkg-shlibdeps</prgn> is run on the
5506 <file>debian/foo-runtime/usr/bin/foo-prog</file>, it
5508 <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5509 determine whether <tt>foo-prog</tt>'s library
5510 dependencies are satisfied by any of the libraries
5511 provided by <tt>libfoo2</tt>. For this reason,
5512 <prgn>dpkg-shlibdeps</prgn> must only be run once
5513 all of the individual binary packages'
5514 <tt>shlibs</tt> files have been installed into the
5521 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5524 These are the <file>shlibs</file> files corresponding to
5525 all of the packages installed on the system, and are
5526 maintained by the relevant package maintainers.
5531 <p><file>/etc/dpkg/shlibs.default</file></p>
5534 This file lists any shared libraries whose packages
5535 have failed to provide correct <file>shlibs</file> files.
5536 It was used when the <file>shlibs</file> setup was first
5537 introduced, but it is now normally empty. It is
5538 maintained by the <tt>dpkg</tt> maintainer.
5546 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5547 <file>shlibs</file> files</heading>
5551 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5552 into your <file>debian/rules</file> file. If your package
5553 contains only compiled binaries and libraries (but no scripts),
5554 you can use a command such as:
5555 <example compact="compact">
5556 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5557 debian/tmp/usr/lib/*
5559 Otherwise, you will need to explicitly list the compiled
5560 binaries and libraries.<footnote>
5561 If you are using <tt>debhelper</tt>, the
5562 <prgn>dh_shlibdeps</prgn> program will do this work for
5563 you. It will also correctly handle multi-binary
5569 This command puts the dependency information into the
5570 <file>debian/substvars</file> file, which is then used by
5571 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5572 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5573 field in the control file for this to work.
5577 If <prgn>dpkg-shlibdeps</prgn> doesn't complain, you're
5578 done. If it does complain you might need to create your own
5579 <file>debian/shlibs.local</file> file, as explained below (see
5580 <ref id="shlibslocal">).
5584 If you have multiple binary packages, you will need to call
5585 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5586 compiled libraries or binaries. In such a case, you will
5587 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5588 utilities to specify a different <file>substvars</file> file.
5592 If you are creating a udeb for use in the Debian Installer,
5593 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
5594 should use the dependency line of type <tt>udeb</tt> by
5595 adding the <tt>-tudeb</tt> option<footnote>
5596 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5597 will automatically add this option if it knows it is
5599 </footnote>. If there is no dependency line of type <tt>udeb</tt>
5600 in the <file>shlibs</file> file, <prgn>dpkg-shlibdeps</prgn> will
5601 fall back to the regular dependency line.
5605 For more details on dpkg-shlibdeps, please see
5606 <ref id="pkg-dpkg-shlibdeps"> and
5607 <manref name="dpkg-shlibdeps" section="1">.
5612 <heading>The <file>shlibs</file> File Format</heading>
5615 Each <file>shlibs</file> file has the same format. Lines
5616 beginning with <tt>#</tt> are considered to be comments and
5617 are ignored. Each line is of the form:
5618 <example compact="compact">
5619 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5624 We will explain this by reference to the example of the
5625 <tt>zlib1g</tt> package, which (at the time of writing)
5626 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5630 <var>type</var> is an optional element that indicates the type
5631 of package for which the line is valid. The only type currently
5632 in use is <tt>udeb</tt>. The colon and space after the type are
5637 <var>library-name</var> is the name of the shared library,
5638 in this case <tt>libz</tt>. (This must match the name part
5639 of the soname, see below.)
5643 <var>soname-version</var> is the version part of the soname of
5644 the library. The soname is the thing that must exactly match
5645 for the library to be recognized by the dynamic linker, and is
5647 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5648 example, <tt>libz.so.1</tt>.<footnote>
5649 This can be determined using the command
5650 <example compact="compact">
5651 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5654 The version part is the part which comes after
5655 <tt>.so.</tt>, so in our case, it is <tt>1</tt>.
5659 <var>dependencies</var> has the same syntax as a dependency
5660 field in a binary package control file. It should give
5661 details of which packages are required to satisfy a binary
5662 built against the version of the library contained in the
5663 package. See <ref id="depsyntax"> for details.
5667 In our example, if the first version of the <tt>zlib1g</tt>
5668 package which contained a minor number of at least
5669 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5670 <tt>shlibs</tt> entry for this library could say:
5671 <example compact="compact">
5672 libz 1 zlib1g (>= 1:1.1.3)
5674 The version-specific dependency is to avoid warnings from
5675 the dynamic linker about using older shared libraries with
5680 As zlib1g also provides a udeb containing the shared library,
5681 there would also be a second line:
5682 <example compact="compact">
5683 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5689 <heading>Providing a <file>shlibs</file> file</heading>
5692 If your package provides a shared library, you need to create
5693 a <file>shlibs</file> file following the format described above.
5694 It is usual to call this file <file>debian/shlibs</file> (but if
5695 you have multiple binary packages, you might want to call it
5696 <file>debian/shlibs.<var>package</var></file> instead). Then
5697 let <file>debian/rules</file> install it in the control area:
5698 <example compact="compact">
5699 install -m644 debian/shlibs debian/tmp/DEBIAN
5701 or, in the case of a multi-binary package:
5702 <example compact="compact">
5703 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5705 An alternative way of doing this is to create the
5706 <file>shlibs</file> file in the control area directly from
5707 <file>debian/rules</file> without using a <file>debian/shlibs</file>
5708 file at all,<footnote>
5709 This is what <prgn>dh_makeshlibs</prgn> in the
5710 <tt>debhelper</tt> suite does. If your package also has a udeb
5711 that provides a shared library, <prgn>dh_makeshlibs</prgn> can
5712 automatically generate the <tt>udeb:</tt> lines if you specify
5713 the name of the udeb with the <tt>--add-udeb</tt> option.
5715 since the <file>debian/shlibs</file> file itself is ignored by
5716 <prgn>dpkg-shlibdeps</prgn>.
5720 As <prgn>dpkg-shlibdeps</prgn> reads the
5721 <file>DEBIAN/shlibs</file> files in all of the binary packages
5722 being built from this source package, all of the
5723 <file>DEBIAN/shlibs</file> files should be installed before
5724 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5729 <sect1 id="shlibslocal">
5730 <heading>Writing the <file>debian/shlibs.local</file> file</heading>
5733 This file is intended only as a <em>temporary</em> fix if
5734 your binaries or libraries depend on a library whose package
5735 does not yet provide a correct <file>shlibs</file> file.
5739 We will assume that you are trying to package a binary
5740 <tt>foo</tt>. When you try running
5741 <prgn>dpkg-shlibdeps</prgn> you get the following error
5742 message (<tt>-O</tt> displays the dependency information on
5743 <tt>stdout</tt> instead of writing it to
5744 <tt>debian/substvars</tt>, and the lines have been wrapped
5745 for ease of reading):
5746 <example compact="compact">
5747 $ dpkg-shlibdeps -O debian/tmp/usr/bin/foo
5748 dpkg-shlibdeps: warning: unable to find dependency
5749 information for shared library libbar (soname 1,
5750 path /usr/lib/libbar.so.1, dependency field Depends)
5751 shlibs:Depends=libc6 (>= 2.2.2-2)
5753 You can then run <prgn>ldd</prgn> on the binary to find the
5754 full location of the library concerned:
5755 <example compact="compact">
5757 libbar.so.1 => /usr/lib/libbar.so.1 (0x4001e000)
5758 libc.so.6 => /lib/libc.so.6 (0x40032000)
5759 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
5761 So the <prgn>foo</prgn> binary depends on the
5762 <prgn>libbar</prgn> shared library, but no package seems to
5763 provide a <file>*.shlibs</file> file handling
5764 <file>libbar.so.1</file> in <file>/var/lib/dpkg/info/</file>. Let's
5765 determine the package responsible:
5766 <example compact="compact">
5767 $ dpkg -S /usr/lib/libbar.so.1
5768 bar1: /usr/lib/libbar.so.1
5769 $ dpkg -s bar1 | grep Version
5772 This tells us that the <tt>bar1</tt> package, version 1.0-1,
5773 is the one we are using. Now we can file a bug against the
5774 <tt>bar1</tt> package and create our own
5775 <file>debian/shlibs.local</file> to locally fix the problem.
5776 Including the following line into your
5777 <file>debian/shlibs.local</file> file:
5778 <example compact="compact">
5779 libbar 1 bar1 (>= 1.0-1)
5781 should allow the package build to work.
5785 As soon as the maintainer of <tt>bar1</tt> provides a
5786 correct <file>shlibs</file> file, you should remove this line
5787 from your <file>debian/shlibs.local</file> file. (You should
5788 probably also then have a versioned <tt>Build-Depends</tt>
5789 on <tt>bar1</tt> to help ensure that others do not have the
5790 same problem building your package.)
5799 <chapt id="opersys"><heading>The Operating System</heading>
5802 <heading>File system hierarchy</heading>
5806 <heading>File System Structure</heading>
5809 The location of all installed files and directories must
5810 comply with the Filesystem Hierarchy Standard (FHS),
5811 version 2.3, with the exceptions noted below, and except
5812 where doing so would violate other terms of Debian
5813 Policy. The following exceptions to the FHS apply:
5818 The optional rules related to user specific
5819 configuration files for applications are stored in
5820 the user's home directory are relaxed. It is
5821 recommended that such files start with the
5822 '<tt>.</tt>' character (a "dot file"), and if an
5823 application needs to create more than one dot file
5824 then the preferred placement is in a subdirectory
5825 with a name starting with a '.' character, (a "dot
5826 directory"). In this case it is recommended the
5827 configuration files not start with the '.'
5833 The requirement for amd64 to use <file>/lib64</file>
5834 for 64 bit binaries is removed.
5839 The requirement for object files, internal binaries, and
5840 libraries, including <file>libc.so.*</file>, to be located
5841 directly under <file>/lib{,32}</file> and
5842 <file>/usr/lib{,32}</file> is amended, permitting files
5843 to instead be installed to
5844 <file>/lib/<var>triplet</var></file> and
5845 <file>/usr/lib/<var>triplet</var></file>, where
5846 <tt><var>triplet</var></tt> is the value returned by
5847 <tt>dpkg-architecture -qDEB_HOST_GNU_TYPE</tt> for the
5848 architecture of the package. Packages may <em>not</em>
5849 install files to any <var>triplet</var> path other
5850 than the one matching the architecture of that package;
5851 for instance, an <tt>Architecture: amd64</tt> package
5852 containing 32-bit x86 libraries may not install these
5853 libraries to <file>/usr/lib/i486-linux-gnu</file>.
5855 This is necessary in order to reserve the directories for
5856 use in cross-installation of library packages from other
5857 architectures, as part of the planned deployment of
5862 Applications may also use a single subdirectory under
5863 <file>/usr/lib/<var>triplet</var></file>.
5866 The execution time linker/loader, ld*, must still be made
5867 available in the existing location under /lib or /lib64
5868 since this is part of the ELF ABI for the architecture.
5873 The requirement that
5874 <file>/usr/local/share/man</file> be "synonymous"
5875 with <file>/usr/local/man</file> is relaxed to a
5880 The requirement that windowmanagers with a single
5881 configuration file call it <file>system.*wmrc</file>
5882 is removed, as is the restriction that the window
5883 manager subdirectory be named identically to the
5884 window manager name itself.
5889 The requirement that boot manager configuration
5890 files live in <file>/etc</file>, or at least are
5891 symlinked there, is relaxed to a recommendation.
5896 The following directories in the root filesystem are
5897 additionally allowed: <file>/sys</file> and
5898 <file>/selinux</file>. <footnote>These directories
5899 are used as mount points to mount virtual filesystems
5900 to get access to kernel information.</footnote>
5907 The version of this document referred here can be
5908 found in the <tt>debian-policy</tt> package or on <url
5909 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5910 name="FHS (Debian copy)"> alongside this manual (or, if
5911 you have the <package>debian-policy</package> installed,
5913 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5914 (local copy)">). The
5915 latest version, which may be a more recent version, may
5917 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5918 Specific questions about following the standard may be
5919 asked on the <tt>debian-devel</tt> mailing list, or
5920 referred to the FHS mailing list (see the
5921 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
5927 <heading>Site-specific programs</heading>
5930 As mandated by the FHS, packages must not place any
5931 files in <file>/usr/local</file>, either by putting them in
5932 the file system archive to be unpacked by <prgn>dpkg</prgn>
5933 or by manipulating them in their maintainer scripts.
5937 However, the package may create empty directories below
5938 <file>/usr/local</file> so that the system administrator knows
5939 where to place site-specific files. These are not
5940 directories <em>in</em> <file>/usr/local</file>, but are
5941 children of directories in <file>/usr/local</file>. These
5942 directories (<file>/usr/local/*/dir/</file>)
5943 should be removed on package removal if they are
5948 Note that this applies only to
5949 directories <em>below</em> <file>/usr/local</file>,
5950 not <em>in</em> <file>/usr/local</file>. Packages must
5951 not create sub-directories in the
5952 directory <file>/usr/local</file> itself, except those
5953 listed in FHS, section 4.5. However, you may create
5954 directories below them as you wish. You must not remove
5955 any of the directories listed in 4.5, even if you created
5960 Since <file>/usr/local</file> can be mounted read-only from a
5961 remote server, these directories must be created and
5962 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
5963 maintainer scripts and not be included in the
5964 <file>.deb</file> archive. These scripts must not fail if
5965 either of these operations fail.
5969 For example, the <tt>emacsen-common</tt> package could
5970 contain something like
5971 <example compact="compact">
5972 if [ ! -e /usr/local/share/emacs ]
5974 if mkdir /usr/local/share/emacs 2>/dev/null
5976 chown root:staff /usr/local/share/emacs
5977 chmod 2775 /usr/local/share/emacs
5981 in its <prgn>postinst</prgn> script, and
5982 <example compact="compact">
5983 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
5984 rmdir /usr/local/share/emacs 2>/dev/null || true
5986 in the <prgn>prerm</prgn> script. (Note that this form is
5987 used to ensure that if the script is interrupted, the
5988 directory <file>/usr/local/share/emacs</file> will still be
5993 If you do create a directory in <file>/usr/local</file> for
5994 local additions to a package, you should ensure that
5995 settings in <file>/usr/local</file> take precedence over the
5996 equivalents in <file>/usr</file>.
6000 However, because <file>/usr/local</file> and its contents are
6001 for exclusive use of the local administrator, a package
6002 must not rely on the presence or absence of files or
6003 directories in <file>/usr/local</file> for normal operation.
6007 The <file>/usr/local</file> directory itself and all the
6008 subdirectories created by the package should (by default) have
6009 permissions 2775 (group-writable and set-group-id) and be
6010 owned by <tt>root:staff</tt>.
6015 <heading>The system-wide mail directory</heading>
6017 The system-wide mail directory
6018 is <file>/var/mail</file>. This directory is part of the
6019 base system and should not be owned by any particular mail
6020 agents. The use of the old
6021 location <file>/var/spool/mail</file> is deprecated, even
6022 though the spool may still be physically located there.
6028 <heading>Users and groups</heading>
6031 <heading>Introduction</heading>
6033 The Debian system can be configured to use either plain or
6038 Some user ids (UIDs) and group ids (GIDs) are reserved
6039 globally for use by certain packages. Because some
6040 packages need to include files which are owned by these
6041 users or groups, or need the ids compiled into binaries,
6042 these ids must be used on any Debian system only for the
6043 purpose for which they are allocated. This is a serious
6044 restriction, and we should avoid getting in the way of
6045 local administration policies. In particular, many sites
6046 allocate users and/or local system groups starting at 100.
6050 Apart from this we should have dynamically allocated ids,
6051 which should by default be arranged in some sensible
6052 order, but the behavior should be configurable.
6056 Packages other than <tt>base-passwd</tt> must not modify
6057 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
6058 <file>/etc/group</file> or <file>/etc/gshadow</file>.
6063 <heading>UID and GID classes</heading>
6065 The UID and GID numbers are divided into classes as
6071 Globally allocated by the Debian project, the same
6072 on every Debian system. These ids will appear in
6073 the <file>passwd</file> and <file>group</file> files of all
6074 Debian systems, new ids in this range being added
6075 automatically as the <tt>base-passwd</tt> package is
6080 Packages which need a single statically allocated
6081 uid or gid should use one of these; their
6082 maintainers should ask the <tt>base-passwd</tt>
6090 Dynamically allocated system users and groups.
6091 Packages which need a user or group, but can have
6092 this user or group allocated dynamically and
6093 differently on each system, should use <tt>adduser
6094 --system</tt> to create the group and/or user.
6095 <prgn>adduser</prgn> will check for the existence of
6096 the user or group, and if necessary choose an unused
6097 id based on the ranges specified in
6098 <file>adduser.conf</file>.
6102 <tag>1000-59999:</tag>
6105 Dynamically allocated user accounts. By default
6106 <prgn>adduser</prgn> will choose UIDs and GIDs for
6107 user accounts in this range, though
6108 <file>adduser.conf</file> may be used to modify this
6113 <tag>60000-64999:</tag>
6116 Globally allocated by the Debian project, but only
6117 created on demand. The ids are allocated centrally
6118 and statically, but the actual accounts are only
6119 created on users' systems on demand.
6123 These ids are for packages which are obscure or
6124 which require many statically-allocated ids. These
6125 packages should check for and create the accounts in
6126 <file>/etc/passwd</file> or <file>/etc/group</file> (using
6127 <prgn>adduser</prgn> if it has this facility) if
6128 necessary. Packages which are likely to require
6129 further allocations should have a "hole" left after
6130 them in the allocation, to give them room to
6135 <tag>65000-65533:</tag>
6143 User <tt>nobody</tt>. The corresponding gid refers
6144 to the group <tt>nogroup</tt>.
6151 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
6152 not</em> be used, because it is the error return
6161 <sect id="sysvinit">
6162 <heading>System run levels and <file>init.d</file> scripts</heading>
6164 <sect1 id="/etc/init.d">
6165 <heading>Introduction</heading>
6168 The <file>/etc/init.d</file> directory contains the scripts
6169 executed by <prgn>init</prgn> at boot time and when the
6170 init state (or "runlevel") is changed (see <manref
6171 name="init" section="8">).
6175 There are at least two different, yet functionally
6176 equivalent, ways of handling these scripts. For the sake
6177 of simplicity, this document describes only the symbolic
6178 link method. However, it must not be assumed by maintainer
6179 scripts that this method is being used, and any automated
6180 manipulation of the various runlevel behaviors by
6181 maintainer scripts must be performed using
6182 <prgn>update-rc.d</prgn> as described below and not by
6183 manually installing or removing symlinks. For information
6184 on the implementation details of the other method,
6185 implemented in the <tt>file-rc</tt> package, please refer
6186 to the documentation of that package.
6190 These scripts are referenced by symbolic links in the
6191 <file>/etc/rc<var>n</var>.d</file> directories. When changing
6192 runlevels, <prgn>init</prgn> looks in the directory
6193 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
6194 execute, where <tt><var>n</var></tt> is the runlevel that
6195 is being changed to, or <tt>S</tt> for the boot-up
6200 The names of the links all have the form
6201 <file>S<var>mm</var><var>script</var></file> or
6202 <file>K<var>mm</var><var>script</var></file> where
6203 <var>mm</var> is a two-digit number and <var>script</var>
6204 is the name of the script (this should be the same as the
6205 name of the actual script in <file>/etc/init.d</file>).
6209 When <prgn>init</prgn> changes runlevel first the targets
6210 of the links whose names start with a <tt>K</tt> are
6211 executed, each with the single argument <tt>stop</tt>,
6212 followed by the scripts prefixed with an <tt>S</tt>, each
6213 with the single argument <tt>start</tt>. (The links are
6214 those in the <file>/etc/rc<var>n</var>.d</file> directory
6215 corresponding to the new runlevel.) The <tt>K</tt> links
6216 are responsible for killing services and the <tt>S</tt>
6217 link for starting services upon entering the runlevel.
6221 For example, if we are changing from runlevel 2 to
6222 runlevel 3, init will first execute all of the <tt>K</tt>
6223 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
6224 all of the <tt>S</tt> prefixed scripts in that directory.
6225 The links starting with <tt>K</tt> will cause the
6226 referred-to file to be executed with an argument of
6227 <tt>stop</tt>, and the <tt>S</tt> links with an argument
6232 The two-digit number <var>mm</var> is used to determine
6233 the order in which to run the scripts: low-numbered links
6234 have their scripts run first. For example, the
6235 <tt>K20</tt> scripts will be executed before the
6236 <tt>K30</tt> scripts. This is used when a certain service
6237 must be started before another. For example, the name
6238 server <prgn>bind</prgn> might need to be started before
6239 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
6240 can set up its access lists. In this case, the script
6241 that starts <prgn>bind</prgn> would have a lower number
6242 than the script that starts <prgn>inn</prgn> so that it
6244 <example compact="compact">
6251 The two runlevels 0 (halt) and 6 (reboot) are slightly
6252 different. In these runlevels, the links with an
6253 <tt>S</tt> prefix are still called after those with a
6254 <tt>K</tt> prefix, but they too are called with the single
6255 argument <tt>stop</tt>.
6259 <sect1 id="writing-init">
6260 <heading>Writing the scripts</heading>
6263 Packages that include daemons for system services should
6264 place scripts in <file>/etc/init.d</file> to start or stop
6265 services at boot time or during a change of runlevel.
6266 These scripts should be named
6267 <file>/etc/init.d/<var>package</var></file>, and they should
6268 accept one argument, saying what to do:
6271 <tag><tt>start</tt></tag>
6272 <item>start the service,</item>
6274 <tag><tt>stop</tt></tag>
6275 <item>stop the service,</item>
6277 <tag><tt>restart</tt></tag>
6278 <item>stop and restart the service if it's already running,
6279 otherwise start the service</item>
6281 <tag><tt>reload</tt></tag>
6282 <item><p>cause the configuration of the service to be
6283 reloaded without actually stopping and restarting
6286 <tag><tt>force-reload</tt></tag>
6287 <item>cause the configuration to be reloaded if the
6288 service supports this, otherwise restart the
6292 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
6293 <tt>force-reload</tt> options should be supported by all
6294 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
6299 The <file>init.d</file> scripts must ensure that they will
6300 behave sensibly (i.e., returning success and not starting
6301 multiple copies of a service) if invoked with <tt>start</tt>
6302 when the service is already running, or with <tt>stop</tt>
6303 when it isn't, and that they don't kill unfortunately-named
6304 user processes. The best way to achieve this is usually to
6305 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
6310 Be careful of using <tt>set -e</tt> in <file>init.d</file>
6311 scripts. Writing correct <file>init.d</file> scripts requires
6312 accepting various error exit statuses when daemons are already
6313 running or already stopped without aborting
6314 the <file>init.d</file> script, and common <file>init.d</file>
6315 function libraries are not safe to call with <tt>set -e</tt>
6317 <tt>/lib/lsb/init-functions</tt>, which assists in writing
6318 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
6319 in effect and echoing status messages to the console fails,
6321 </footnote>. For <tt>init.d</tt> scripts, it's often easier
6322 to not use <tt>set -e</tt> and instead check the result of
6323 each command separately.
6327 If a service reloads its configuration automatically (as
6328 in the case of <prgn>cron</prgn>, for example), the
6329 <tt>reload</tt> option of the <file>init.d</file> script
6330 should behave as if the configuration has been reloaded
6335 The <file>/etc/init.d</file> scripts must be treated as
6336 configuration files, either (if they are present in the
6337 package, that is, in the .deb file) by marking them as
6338 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6339 by managing them correctly in the maintainer scripts (see
6340 <ref id="config-files">). This is important since we want
6341 to give the local system administrator the chance to adapt
6342 the scripts to the local system, e.g., to disable a
6343 service without de-installing the package, or to specify
6344 some special command line options when starting a service,
6345 while making sure their changes aren't lost during the next
6350 These scripts should not fail obscurely when the
6351 configuration files remain but the package has been
6352 removed, as configuration files remain on the system after
6353 the package has been removed. Only when <prgn>dpkg</prgn>
6354 is executed with the <tt>--purge</tt> option will
6355 configuration files be removed. In particular, as the
6356 <file>/etc/init.d/<var>package</var></file> script itself is
6357 usually a <tt>conffile</tt>, it will remain on the system
6358 if the package is removed but not purged. Therefore, you
6359 should include a <tt>test</tt> statement at the top of the
6361 <example compact="compact">
6362 test -f <var>program-executed-later-in-script</var> || exit 0
6367 Often there are some variables in the <file>init.d</file>
6368 scripts whose values control the behavior of the scripts,
6369 and which a system administrator is likely to want to
6370 change. As the scripts themselves are frequently
6371 <tt>conffile</tt>s, modifying them requires that the
6372 administrator merge in their changes each time the package
6373 is upgraded and the <tt>conffile</tt> changes. To ease
6374 the burden on the system administrator, such configurable
6375 values should not be placed directly in the script.
6376 Instead, they should be placed in a file in
6377 <file>/etc/default</file>, which typically will have the same
6378 base name as the <file>init.d</file> script. This extra file
6379 should be sourced by the script when the script runs. It
6380 must contain only variable settings and comments in SUSv3
6381 <prgn>sh</prgn> format. It may either be a
6382 <tt>conffile</tt> or a configuration file maintained by
6383 the package maintainer scripts. See <ref id="config-files">
6388 To ensure that vital configurable values are always
6389 available, the <file>init.d</file> script should set default
6390 values for each of the shell variables it uses, either
6391 before sourcing the <file>/etc/default/</file> file or
6392 afterwards using something like the <tt>:
6393 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6394 script must behave sensibly and not fail if the
6395 <file>/etc/default</file> file is deleted.
6399 <file>/var/run</file> and <file>/var/lock</file> may be mounted
6400 as temporary filesystems<footnote>
6401 For example, using the <tt>RAMRUN</tt> and <tt>RAMLOCK</tt>
6402 options in <file>/etc/default/rcS</file>.
6403 </footnote>, so the <file>init.d</file> scripts must handle this
6404 correctly. This will typically amount to creating any required
6405 subdirectories dynamically when the <file>init.d</file> script
6406 is run, rather than including them in the package and relying on
6407 <prgn>dpkg</prgn> to create them.
6412 <heading>Interfacing with the initscript system</heading>
6415 Maintainers should use the abstraction layer provided by
6416 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6417 programs to deal with initscripts in their packages'
6418 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6419 and <prgn>postrm</prgn>.
6423 Directly managing the /etc/rc?.d links and directly
6424 invoking the <file>/etc/init.d/</file> initscripts should
6425 be done only by packages providing the initscript
6426 subsystem (such as <prgn>sysv-rc</prgn> and
6427 <prgn>file-rc</prgn>).
6431 <heading>Managing the links</heading>
6434 The program <prgn>update-rc.d</prgn> is provided for
6435 package maintainers to arrange for the proper creation and
6436 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6437 or their functional equivalent if another method is being
6438 used. This may be used by maintainers in their packages'
6439 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6443 You must not include any <file>/etc/rc<var>n</var>.d</file>
6444 symbolic links in the actual archive or manually create or
6445 remove the symbolic links in maintainer scripts; you must
6446 use the <prgn>update-rc.d</prgn> program instead. (The
6447 former will fail if an alternative method of maintaining
6448 runlevel information is being used.) You must not include
6449 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6450 in the archive either. (Only the <tt>sysvinit</tt>
6455 By default <prgn>update-rc.d</prgn> will start services in
6456 each of the multi-user state runlevels (2, 3, 4, and 5)
6457 and stop them in the halt runlevel (0), the single-user
6458 runlevel (1) and the reboot runlevel (6). The system
6459 administrator will have the opportunity to customize
6460 runlevels by simply adding, moving, or removing the
6461 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6462 symbolic links are being used, or by modifying
6463 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6468 To get the default behavior for your package, put in your
6469 <prgn>postinst</prgn> script
6470 <example compact="compact">
6471 update-rc.d <var>package</var> defaults
6473 and in your <prgn>postrm</prgn>
6474 <example compact="compact">
6475 if [ "$1" = purge ]; then
6476 update-rc.d <var>package</var> remove
6478 </example>. Note that if your package changes runlevels
6479 or priority, you may have to remove and recreate the links,
6480 since otherwise the old links may persist. Refer to the
6481 documentation of <prgn>update-rc.d</prgn>.
6485 This will use a default sequence number of 20. If it does
6486 not matter when or in which order the <file>init.d</file>
6487 script is run, use this default. If it does, then you
6488 should talk to the maintainer of the <prgn>sysvinit</prgn>
6489 package or post to <tt>debian-devel</tt>, and they will
6490 help you choose a number.
6494 For more information about using <tt>update-rc.d</tt>,
6495 please consult its man page <manref name="update-rc.d"
6501 <heading>Running initscripts</heading>
6503 The program <prgn>invoke-rc.d</prgn> is provided to make
6504 it easier for package maintainers to properly invoke an
6505 initscript, obeying runlevel and other locally-defined
6506 constraints that might limit a package's right to start,
6507 stop and otherwise manage services. This program may be
6508 used by maintainers in their packages' scripts.
6512 The package maintainer scripts must use
6513 <prgn>invoke-rc.d</prgn> to invoke the
6514 <file>/etc/init.d/*</file> initscripts, instead of
6515 calling them directly.
6519 By default, <prgn>invoke-rc.d</prgn> will pass any
6520 action requests (start, stop, reload, restart...) to the
6521 <file>/etc/init.d</file> script, filtering out requests
6522 to start or restart a service out of its intended
6527 Most packages will simply need to change:
6528 <example compact="compact">/etc/init.d/<package>
6529 <action></example> in their <prgn>postinst</prgn>
6530 and <prgn>prerm</prgn> scripts to:
6531 <example compact="compact">
6532 if which invoke-rc.d >/dev/null 2>&1; then
6533 invoke-rc.d <var>package</var> <action>
6535 /etc/init.d/<var>package</var> <action>
6541 A package should register its initscript services using
6542 <prgn>update-rc.d</prgn> before it tries to invoke them
6543 using <prgn>invoke-rc.d</prgn>. Invocation of
6544 unregistered services may fail.
6548 For more information about using
6549 <prgn>invoke-rc.d</prgn>, please consult its man page
6550 <manref name="invoke-rc.d" section="8">.
6556 <heading>Boot-time initialization</heading>
6559 There used to be another directory, <file>/etc/rc.boot</file>,
6560 which contained scripts which were run once per machine
6561 boot. This has been deprecated in favour of links from
6562 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6563 described in <ref id="/etc/init.d">. Packages must not
6564 place files in <file>/etc/rc.boot</file>.
6569 <heading>Example</heading>
6572 An example on which you can base your
6573 <file>/etc/init.d</file> scripts is found in
6574 <file>/etc/init.d/skeleton</file>.
6581 <heading>Console messages from <file>init.d</file> scripts</heading>
6584 This section describes the formats to be used for messages
6585 written to standard output by the <file>/etc/init.d</file>
6586 scripts. The intent is to improve the consistency of
6587 Debian's startup and shutdown look and feel. For this
6588 reason, please look very carefully at the details. We want
6589 the messages to have the same format in terms of wording,
6590 spaces, punctuation and case of letters.
6594 Here is a list of overall rules that should be used for
6595 messages generated by <file>/etc/init.d</file> scripts.
6601 The message should fit in one line (fewer than 80
6602 characters), start with a capital letter and end with
6603 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6607 If the script is performing some time consuming task in
6608 the background (not merely starting or stopping a
6609 program, for instance), an ellipsis (three dots:
6610 <tt>...</tt>) should be output to the screen, with no
6611 leading or tailing whitespace or line feeds.
6615 The messages should appear as if the computer is telling
6616 the user what it is doing (politely :-), but should not
6617 mention "it" directly. For example, instead of:
6618 <example compact="compact">
6619 I'm starting network daemons: nfsd mountd.
6621 the message should say
6622 <example compact="compact">
6623 Starting network daemons: nfsd mountd.
6630 <tt>init.d</tt> script should use the following standard
6631 message formats for the situations enumerated below.
6637 <p>When daemons are started</p>
6640 If the script starts one or more daemons, the output
6641 should look like this (a single line, no leading
6643 <example compact="compact">
6644 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6646 The <var>description</var> should describe the
6647 subsystem the daemon or set of daemons are part of,
6648 while <var>daemon-1</var> up to <var>daemon-n</var>
6649 denote each daemon's name (typically the file name of
6654 For example, the output of <file>/etc/init.d/lpd</file>
6656 <example compact="compact">
6657 Starting printer spooler: lpd.
6662 This can be achieved by saying
6663 <example compact="compact">
6664 echo -n "Starting printer spooler: lpd"
6665 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6668 in the script. If there are more than one daemon to
6669 start, the output should look like this:
6670 <example compact="compact">
6671 echo -n "Starting remote file system services:"
6672 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6673 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6674 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6677 This makes it possible for the user to see what is
6678 happening and when the final daemon has been started.
6679 Care should be taken in the placement of white spaces:
6680 in the example above the system administrators can
6681 easily comment out a line if they don't want to start
6682 a specific daemon, while the displayed message still
6688 <p>When a system parameter is being set</p>
6691 If you have to set up different system parameters
6692 during the system boot, you should use this format:
6693 <example compact="compact">
6694 Setting <var>parameter</var> to "<var>value</var>".
6699 You can use a statement such as the following to get
6701 <example compact="compact">
6702 echo "Setting DNS domainname to \"$domainname\"."
6707 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
6708 for the left and right quotation marks. A grave accent
6709 (<tt>`</tt>) is not a quote character; neither is an
6710 apostrophe (<tt>'</tt>).
6715 <p>When a daemon is stopped or restarted</p>
6718 When you stop or restart a daemon, you should issue a
6719 message identical to the startup message, except that
6720 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6721 or <tt>Restarting</tt> respectively.
6725 For example, stopping the printer daemon will look like
6727 <example compact="compact">
6728 Stopping printer spooler: lpd.
6734 <p>When something is executed</p>
6737 There are several examples where you have to run a
6738 program at system startup or shutdown to perform a
6739 specific task, for example, setting the system's clock
6740 using <prgn>netdate</prgn> or killing all processes
6741 when the system shuts down. Your message should look
6743 <example compact="compact">
6744 Doing something very useful...done.
6746 You should print the <tt>done.</tt> immediately after
6747 the job has been completed, so that the user is
6748 informed why they have to wait. You can get this
6750 <example compact="compact">
6751 echo -n "Doing something very useful..."
6760 <p>When the configuration is reloaded</p>
6763 When a daemon is forced to reload its configuration
6764 files you should use the following format:
6765 <example compact="compact">
6766 Reloading <var>description</var> configuration...done.
6768 where <var>description</var> is the same as in the
6769 daemon starting message.
6777 <heading>Cron jobs</heading>
6780 Packages must not modify the configuration file
6781 <file>/etc/crontab</file>, and they must not modify the files in
6782 <file>/var/spool/cron/crontabs</file>.</p>
6785 If a package wants to install a job that has to be executed
6786 via cron, it should place a file with the name of the
6787 package in one or more of the following directories:
6788 <example compact="compact">
6794 As these directory names imply, the files within them are
6795 executed on an hourly, daily, weekly, or monthly basis,
6796 respectively. The exact times are listed in
6797 <file>/etc/crontab</file>.</p>
6800 All files installed in any of these directories must be
6801 scripts (e.g., shell scripts or Perl scripts) so that they
6802 can easily be modified by the local system administrator.
6803 In addition, they must be treated as configuration files.
6807 If a certain job has to be executed at some other frequency or
6808 at a specific time, the package should install a file
6809 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6810 same syntax as <file>/etc/crontab</file> and is processed by
6811 <prgn>cron</prgn> automatically. The file must also be
6812 treated as a configuration file. (Note that entries in the
6813 <file>/etc/cron.d</file> directory are not handled by
6814 <prgn>anacron</prgn>. Thus, you should only use this
6815 directory for jobs which may be skipped if the system is not
6818 Unlike <file>crontab</file> files described in the IEEE Std
6819 1003.1-2008 (POSIX.1) available from
6820 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
6821 name="The Open Group">, the files in
6822 <file>/etc/cron.d</file> and the file
6823 <file>/etc/crontab</file> have seven fields; namely:
6825 <item>Minute [0,59]</item>
6826 <item>Hour [0,23]</item>
6827 <item>Day of the month [1,31]</item>
6828 <item>Month of the year [1,12]</item>
6829 <item>Day of the week ([0,6] with 0=Sunday)</item>
6830 <item>Username</item>
6831 <item>Command to be run</item>
6833 Ranges of numbers are allowed. Ranges are two numbers
6834 separated with a hyphen. The specified range is inclusive.
6835 Lists are allowed. A list is a set of numbers (or ranges)
6836 separated by commas. Step values can be used in conjunction
6841 The scripts or <tt>crontab</tt> entries in these directories should
6842 check if all necessary programs are installed before they
6843 try to execute them. Otherwise, problems will arise when a
6844 package was removed but not purged since configuration files
6845 are kept on the system in this situation.
6849 Any <tt>cron</tt> daemon must provide
6850 <file>/usr/bin/crontab</file> and support normal
6851 <tt>crontab</tt> entries as specified in POSIX. The daemon
6852 must also support names for days and months, ranges, and
6853 step values. It has to support <file>/etc/crontab</file>,
6854 and correctly execute the scripts in
6855 <file>/etc/cron.d</file>. The daemon must also correctly
6857 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
6862 <heading>Menus</heading>
6865 The Debian <tt>menu</tt> package provides a standard
6866 interface between packages providing applications and
6867 <em>menu programs</em> (either X window managers or
6868 text-based menu programs such as <prgn>pdmenu</prgn>).
6872 All packages that provide applications that need not be
6873 passed any special command line arguments for normal
6874 operation should register a menu entry for those
6875 applications, so that users of the <tt>menu</tt> package
6876 will automatically get menu entries in their window
6877 managers, as well in shells like <tt>pdmenu</tt>.
6881 Menu entries should follow the current menu policy.
6885 The menu policy can be found in the <tt>menu-policy</tt>
6886 files in the <tt>debian-policy</tt> package.
6887 It is also available from the Debian web mirrors at
6888 <tt><url name="/doc/packaging-manuals/menu-policy/"
6889 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6893 Please also refer to the <em>Debian Menu System</em>
6894 documentation that comes with the <package>menu</package>
6895 package for information about how to register your
6901 <heading>Multimedia handlers</heading>
6904 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6905 is a mechanism for encoding files and data streams and
6906 providing meta-information about them, in particular their
6907 type (e.g. audio or video) and format (e.g. PNG, HTML,
6912 Registration of MIME type handlers allows programs like mail
6913 user agents and web browsers to invoke these handlers to
6914 view, edit or display MIME types they don't support directly.
6918 Packages which provide the ability to view/show/play,
6919 compose, edit or print MIME types should register themselves
6920 as such following the current MIME support policy.
6924 The MIME support policy can be found in the <tt>mime-policy</tt>
6925 files in the <tt>debian-policy</tt> package.
6926 It is also available from the Debian web mirrors at
6927 <tt><url name="/doc/packaging-manuals/mime-policy/"
6928 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
6934 <heading>Keyboard configuration</heading>
6937 To achieve a consistent keyboard configuration so that all
6938 applications interpret a keyboard event the same way, all
6939 programs in the Debian distribution must be configured to
6940 comply with the following guidelines.
6944 The following keys must have the specified interpretations:
6947 <tag><tt><--</tt></tag>
6948 <item>delete the character to the left of the cursor</item>
6950 <tag><tt>Delete</tt></tag>
6951 <item>delete the character to the right of the cursor</item>
6953 <tag><tt>Control+H</tt></tag>
6954 <item>emacs: the help prefix</item>
6957 The interpretation of any keyboard events should be
6958 independent of the terminal that is used, be it a virtual
6959 console, an X terminal emulator, an rlogin/telnet session,
6964 The following list explains how the different programs
6965 should be set up to achieve this:
6971 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
6975 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
6979 X translations are set up to make
6980 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
6981 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
6982 is the vt220 escape code for the "delete character"
6983 key). This must be done by loading the X resources
6984 using <prgn>xrdb</prgn> on all local X displays, not
6985 using the application defaults, so that the
6986 translation resources used correspond to the
6987 <prgn>xmodmap</prgn> settings.
6991 The Linux console is configured to make
6992 <tt><--</tt> generate DEL, and <tt>Delete</tt>
6993 generate <tt>ESC [ 3 ~</tt>.
6997 X applications are configured so that <tt><</tt>
6998 deletes left, and <tt>Delete</tt> deletes right. Motif
6999 applications already work like this.
7003 Terminals should have <tt>stty erase ^?</tt> .
7007 The <tt>xterm</tt> terminfo entry should have <tt>ESC
7008 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
7009 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
7013 Emacs is programmed to map <tt>KB_Backspace</tt> or
7014 the <tt>stty erase</tt> character to
7015 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
7016 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
7017 <tt>^H</tt> to <tt>help</tt> as always.
7021 Other applications use the <tt>stty erase</tt>
7022 character and <tt>kdch1</tt> for the two delete keys,
7023 with ASCII DEL being "delete previous character" and
7024 <tt>kdch1</tt> being "delete character under
7032 This will solve the problem except for the following
7039 Some terminals have a <tt><--</tt> key that cannot
7040 be made to produce anything except <tt>^H</tt>. On
7041 these terminals Emacs help will be unavailable on
7042 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
7043 character takes precedence in Emacs, and has been set
7044 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
7045 available) can be used instead.
7049 Some operating systems use <tt>^H</tt> for <tt>stty
7050 erase</tt>. However, modern telnet versions and all
7051 rlogin versions propagate <tt>stty</tt> settings, and
7052 almost all UNIX versions honour <tt>stty erase</tt>.
7053 Where the <tt>stty</tt> settings are not propagated
7054 correctly, things can be made to work by using
7055 <tt>stty</tt> manually.
7059 Some systems (including previous Debian versions) use
7060 <prgn>xmodmap</prgn> to arrange for both
7061 <tt><--</tt> and <tt>Delete</tt> to generate
7062 <tt>KB_Delete</tt>. We can change the behavior of
7063 their X clients using the same X resources that we use
7064 to do it for our own clients, or configure our clients
7065 using their resources when things are the other way
7066 around. On displays configured like this
7067 <tt>Delete</tt> will not work, but <tt><--</tt>
7072 Some operating systems have different <tt>kdch1</tt>
7073 settings in their <tt>terminfo</tt> database for
7074 <tt>xterm</tt> and others. On these systems the
7075 <tt>Delete</tt> key will not work correctly when you
7076 log in from a system conforming to our policy, but
7077 <tt><--</tt> will.
7084 <heading>Environment variables</heading>
7087 A program must not depend on environment variables to get
7088 reasonable defaults. (That's because these environment
7089 variables would have to be set in a system-wide
7090 configuration file like <file>/etc/profile</file>, which is not
7091 supported by all shells.)
7095 If a program usually depends on environment variables for its
7096 configuration, the program should be changed to fall back to
7097 a reasonable default configuration if these environment
7098 variables are not present. If this cannot be done easily
7099 (e.g., if the source code of a non-free program is not
7100 available), the program must be replaced by a small
7101 "wrapper" shell script which sets the environment variables
7102 if they are not already defined, and calls the original program.
7106 Here is an example of a wrapper script for this purpose:
7108 <example compact="compact">
7110 BAR=${BAR:-/var/lib/fubar}
7112 exec /usr/lib/foo/foo "$@"
7117 Furthermore, as <file>/etc/profile</file> is a configuration
7118 file of the <prgn>base-files</prgn> package, other packages must
7119 not put any environment variables or other commands into that
7124 <sect id="doc-base">
7125 <heading>Registering Documents using doc-base</heading>
7128 The <package>doc-base</package> package implements a
7129 flexible mechanism for handling and presenting
7130 documentation. The recommended practice is for every Debian
7131 package that provides online documentation (other than just
7132 manual pages) to register these documents with
7133 <package>doc-base</package> by installing a
7134 <package>doc-base</package> control file via the
7135 <prgn/install-docs/ script at installation time and
7136 de-register the manuals again when the package is removed.
7139 Please refer to the documentation that comes with the
7140 <package>doc-base</package> package for information and
7149 <heading>Files</heading>
7151 <sect id="binaries">
7152 <heading>Binaries</heading>
7155 Two different packages must not install programs with
7156 different functionality but with the same filenames. (The
7157 case of two programs having the same functionality but
7158 different implementations is handled via "alternatives" or
7159 the "Conflicts" mechanism. See <ref id="maintscripts"> and
7160 <ref id="conflicts"> respectively.) If this case happens,
7161 one of the programs must be renamed. The maintainers should
7162 report this to the <tt>debian-devel</tt> mailing list and
7163 try to find a consensus about which program will have to be
7164 renamed. If a consensus cannot be reached, <em>both</em>
7165 programs must be renamed.
7169 By default, when a package is being built, any binaries
7170 created should include debugging information, as well as
7171 being compiled with optimization. You should also turn on
7172 as many reasonable compilation warnings as possible; this
7173 makes life easier for porters, who can then look at build
7174 logs for possible problems. For the C programming language,
7175 this means the following compilation parameters should be
7177 <example compact="compact">
7179 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
7181 INSTALL = install -s # (or use strip on the files in debian/tmp)
7186 Note that by default all installed binaries should be stripped,
7187 either by using the <tt>-s</tt> flag to
7188 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
7189 the binaries after they have been copied into
7190 <file>debian/tmp</file> but before the tree is made into a
7195 Although binaries in the build tree should be compiled with
7196 debugging information by default, it can often be difficult to
7197 debug programs if they are also subjected to compiler
7198 optimization. For this reason, it is recommended to support the
7199 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
7200 (see <ref id="debianrules-options">). This variable can contain
7201 several flags to change how a package is compiled and built.
7205 It is up to the package maintainer to decide what
7206 compilation options are best for the package. Certain
7207 binaries (such as computationally-intensive programs) will
7208 function better with certain flags (<tt>-O3</tt>, for
7209 example); feel free to use them. Please use good judgment
7210 here. Don't use flags for the sake of it; only use them
7211 if there is good reason to do so. Feel free to override
7212 the upstream author's ideas about which compilation
7213 options are best: they are often inappropriate for our
7219 <sect id="libraries">
7220 <heading>Libraries</heading>
7223 If the package is <strong>architecture: any</strong>, then
7224 the shared library compilation and linking flags must have
7225 <tt>-fPIC</tt>, or the package shall not build on some of
7226 the supported architectures<footnote>
7228 If you are using GCC, <tt>-fPIC</tt> produces code with
7229 relocatable position independent code, which is required for
7230 most architectures to create a shared library, with i386 and
7231 perhaps some others where non position independent code is
7232 permitted in a shared library.
7235 Position independent code may have a performance penalty,
7236 especially on <tt>i386</tt>. However, in most cases the
7237 speed penalty must be measured against the memory wasted on
7238 the few architectures where non position independent code is
7241 </footnote>. Any exception to this rule must be discussed on
7242 the mailing list <em>debian-devel@lists.debian.org</em>, and
7243 a rough consensus obtained. The reasons for not compiling
7244 with <tt>-fPIC</tt> flag must be recorded in the file
7245 <tt>README.Debian</tt>, and care must be taken to either
7246 restrict the architecture or arrange for <tt>-fPIC</tt> to
7247 be used on architectures where it is required.<footnote>
7249 Some of the reasons why this might be required is if the
7250 library contains hand crafted assembly code that is not
7251 relocatable, the speed penalty is excessive for compute
7252 intensive libs, and similar reasons.
7257 As to the static libraries, the common case is not to have
7258 relocatable code, since there is no benefit, unless in specific
7259 cases; therefore the static version must not be compiled
7260 with the <tt>-fPIC</tt> flag. Any exception to this rule
7261 should be discussed on the mailing list
7262 <em>debian-devel@lists.debian.org</em>, and the reasons for
7263 compiling with the <tt>-fPIC</tt> flag must be recorded in
7264 the file <tt>README.Debian</tt>. <footnote>
7266 Some of the reasons for linking static libraries with
7267 the <tt>-fPIC</tt> flag are if, for example, one needs a
7268 Perl API for a library that is under rapid development,
7269 and has an unstable API, so shared libraries are
7270 pointless at this phase of the library's development. In
7271 that case, since Perl needs a library with relocatable
7272 code, it may make sense to create a static library with
7273 relocatable code. Another reason cited is if you are
7274 distilling various libraries into a common shared
7275 library, like <tt>mklibs</tt> does in the Debian
7281 In other words, if both a shared and a static library is
7282 being built, each source unit (<tt>*.c</tt>, for example,
7283 for C files) will need to be compiled twice, for the normal
7287 You must specify the gcc option <tt>-D_REENTRANT</tt>
7288 when building a library (either static or shared) to make
7289 the library compatible with LinuxThreads.
7293 Although not enforced by the build tools, shared libraries
7294 must be linked against all libraries that they use symbols from
7295 in the same way that binaries are. This ensures the correct
7296 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
7297 system and guarantees that all libraries can be safely opened
7298 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
7299 option <tt>-Wl,-z,defs</tt> when building a shared library.
7300 Since this option enforces symbol resolution at build time,
7301 a missing library reference will be caught early as a fatal
7306 All installed shared libraries should be stripped with
7307 <example compact="compact">
7308 strip --strip-unneeded <var>your-lib</var>
7310 (The option <tt>--strip-unneeded</tt> makes
7311 <prgn>strip</prgn> remove only the symbols which aren't
7312 needed for relocation processing.) Shared libraries can
7313 function perfectly well when stripped, since the symbols for
7314 dynamic linking are in a separate part of the ELF object
7316 You might also want to use the options
7317 <tt>--remove-section=.comment</tt> and
7318 <tt>--remove-section=.note</tt> on both shared libraries
7319 and executables, and <tt>--strip-debug</tt> on static
7325 Note that under some circumstances it may be useful to
7326 install a shared library unstripped, for example when
7327 building a separate package to support debugging.
7331 Shared object files (often <file>.so</file> files) that are not
7332 public libraries, that is, they are not meant to be linked
7333 to by third party executables (binaries of other packages),
7334 should be installed in subdirectories of the
7335 <file>/usr/lib</file> directory. Such files are exempt from the
7336 rules that govern ordinary shared libraries, except that
7337 they must not be installed executable and should be
7339 A common example are the so-called "plug-ins",
7340 internal shared objects that are dynamically loaded by
7341 programs using <manref name="dlopen" section="3">.
7346 An ever increasing number of packages are using
7347 <prgn>libtool</prgn> to do their linking. The latest GNU
7348 libtools (>= 1.3a) can take advantage of the metadata in the
7349 installed <prgn>libtool</prgn> archive files (<file>*.la</file>
7350 files). The main advantage of <prgn>libtool</prgn>'s
7351 <file>.la</file> files is that it allows <prgn>libtool</prgn> to
7352 store and subsequently access metadata with respect to the
7353 libraries it builds. <prgn>libtool</prgn> will search for
7354 those files, which contain a lot of useful information about
7355 a library (such as library dependency information for static
7356 linking). Also, they're <em>essential</em> for programs
7357 using <tt>libltdl</tt>.<footnote>
7358 Although <prgn>libtool</prgn> is fully capable of
7359 linking against shared libraries which don't have
7360 <tt>.la</tt> files, as it is a mere shell script it can
7361 add considerably to the build time of a
7362 <prgn>libtool</prgn>-using package if that shell script
7363 has to derive all this information from first principles
7364 for each library every time it is linked. With the
7365 advent of <prgn>libtool</prgn> version 1.4 (and to a
7366 lesser extent <prgn>libtool</prgn> version 1.3), the
7367 <file>.la</file> files also store information about
7368 inter-library dependencies which cannot necessarily be
7369 derived after the <file>.la</file> file is deleted.
7374 Packages that use <prgn>libtool</prgn> to create shared
7375 libraries should include the <file>.la</file> files in the
7376 <tt>-dev</tt> package, unless the package relies on
7377 <tt>libtool</tt>'s <tt>libltdl</tt> library, in which case
7378 the <tt>.la</tt> files must go in the run-time library
7383 You must make sure that you use only released versions of
7384 shared libraries to build your packages; otherwise other
7385 users will not be able to run your binaries
7386 properly. Producing source packages that depend on
7387 unreleased compilers is also usually a bad
7394 <heading>Shared libraries</heading>
7396 This section has moved to <ref id="sharedlibs">.
7402 <heading>Scripts</heading>
7405 All command scripts, including the package maintainer
7406 scripts inside the package and used by <prgn>dpkg</prgn>,
7407 should have a <tt>#!</tt> line naming the shell to be used
7412 In the case of Perl scripts this should be
7413 <tt>#!/usr/bin/perl</tt>.
7417 When scripts are installed into a directory in the system
7418 PATH, the script name should not include an extension such
7419 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7420 language currently used to implement it.
7423 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
7424 <file>init.d</file> scripts should almost certainly start
7425 with <tt>set -e</tt> so that errors are detected.
7426 <file>init.d</file> scripts are something of a special case, due
7427 to how frequently they need to call commands that are allowed to
7428 fail, and it may instead be easier to check the exit status of
7429 commands directly. See <ref id="writing-init"> for more
7430 information about writing <file>init.d</file> scripts.
7433 Every script should use <tt>set -e</tt> or check the exit status
7434 of <em>every</em> command.
7437 Scripts may assume that <file>/bin/sh</file> implements the
7438 SUSv3 Shell Command Language<footnote>
7439 Single UNIX Specification, version 3, which is also IEEE
7440 1003.1-2004 (POSIX), and is available on the World Wide Web
7441 from <url id="http://www.unix.org/version3/online.html"
7442 name="The Open Group"> after free
7443 registration.</footnote>
7444 plus the following additional features not mandated by
7446 These features are in widespread use in the Linux community
7447 and are implemented in all of bash, dash, and ksh, the most
7448 common shells users may wish to use as <file>/bin/sh</file>.
7451 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7452 must not generate a newline.</item>
7453 <item><tt>test</tt>, if implemented as a shell built-in, must
7454 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7456 <item><tt>local</tt> to create a scoped variable must be
7457 supported, including listing multiple variables in a single
7458 local command and assigning a value to a variable at the
7459 same time as localizing it. <tt>local</tt> may or
7460 may not preserve the variable value from an outer scope if
7461 no assignment is present. Uses such as:
7465 # ... use a, b, c, d ...
7468 must be supported and must set the value of <tt>c</tt> to
7472 If a shell script requires non-SUSv3 features from the shell
7473 interpreter other than those listed above, the appropriate shell
7474 must be specified in the first line of the script (e.g.,
7475 <tt>#!/bin/bash</tt>) and the package must depend on the package
7476 providing the shell (unless the shell package is marked
7477 "Essential", as in the case of <prgn>bash</prgn>).
7481 You may wish to restrict your script to SUSv3 features plus the
7482 above set when possible so that it may use <file>/bin/sh</file>
7483 as its interpreter. If your script works with <prgn>dash</prgn>
7484 (originally called <prgn>ash</prgn>), it probably complies with
7485 the above requirements, but if you are in doubt, use
7486 <file>/bin/bash</file>.
7490 Perl scripts should check for errors when making any
7491 system calls, including <tt>open</tt>, <tt>print</tt>,
7492 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7496 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7497 scripting languages. See <em>Csh Programming Considered
7498 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7499 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7500 If an upstream package comes with <prgn>csh</prgn> scripts
7501 then you must make sure that they start with
7502 <tt>#!/bin/csh</tt> and make your package depend on the
7503 <prgn>c-shell</prgn> virtual package.
7507 Any scripts which create files in world-writeable
7508 directories (e.g., in <file>/tmp</file>) must use a
7509 mechanism which will fail atomically if a file with the same
7510 name already exists.
7514 The Debian base system provides the <prgn>tempfile</prgn>
7515 and <prgn>mktemp</prgn> utilities for use by scripts for
7522 <heading>Symbolic links</heading>
7525 In general, symbolic links within a top-level directory
7526 should be relative, and symbolic links pointing from one
7527 top-level directory into another should be absolute. (A
7528 top-level directory is a sub-directory of the root
7529 directory <file>/</file>.)
7533 In addition, symbolic links should be specified as short as
7534 possible, i.e., link targets like <file>foo/../bar</file> are
7539 Note that when creating a relative link using
7540 <prgn>ln</prgn> it is not necessary for the target of the
7541 link to exist relative to the working directory you're
7542 running <prgn>ln</prgn> from, nor is it necessary to change
7543 directory to the directory where the link is to be made.
7544 Simply include the string that should appear as the target
7545 of the link (this will be a pathname relative to the
7546 directory in which the link resides) as the first argument
7551 For example, in your <prgn>Makefile</prgn> or
7552 <file>debian/rules</file>, you can do things like:
7553 <example compact="compact">
7554 ln -fs gcc $(prefix)/bin/cc
7555 ln -fs gcc debian/tmp/usr/bin/cc
7556 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7557 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7562 A symbolic link pointing to a compressed file should always
7563 have the same file extension as the referenced file. (For
7564 example, if a file <file>foo.gz</file> is referenced by a
7565 symbolic link, the filename of the link has to end with
7566 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7571 <heading>Device files</heading>
7574 Packages must not include device files or named pipes in the
7579 If a package needs any special device files that are not
7580 included in the base system, it must call
7581 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7582 after notifying the user<footnote>
7583 This notification could be done via a (low-priority)
7584 debconf message, or an echo (printf) statement.
7589 Packages must not remove any device files in the
7590 <prgn>postrm</prgn> or any other script. This is left to the
7591 system administrator.
7595 Debian uses the serial devices
7596 <file>/dev/ttyS*</file>. Programs using the old
7597 <file>/dev/cu*</file> devices should be changed to use
7598 <file>/dev/ttyS*</file>.
7602 Named pipes needed by the package must be created in
7603 the <prgn>postinst</prgn> script<footnote>
7604 It's better to use <prgn>mkfifo</prgn> rather
7605 than <prgn>mknod</prgn> to create named pipes so that
7606 automated checks for packages incorrectly creating device
7607 files with <prgn>mknod</prgn> won't have false positives.
7608 </footnote> and removed in
7609 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
7614 <sect id="config-files">
7615 <heading>Configuration files</heading>
7618 <heading>Definitions</heading>
7622 <tag>configuration file</tag>
7624 A file that affects the operation of a program, or
7625 provides site- or host-specific information, or
7626 otherwise customizes the behavior of a program.
7627 Typically, configuration files are intended to be
7628 modified by the system administrator (if needed or
7629 desired) to conform to local policy or to provide
7630 more useful site-specific behavior.
7633 <tag><tt>conffile</tt></tag>
7635 A file listed in a package's <tt>conffiles</tt>
7636 file, and is treated specially by <prgn>dpkg</prgn>
7637 (see <ref id="configdetails">).
7643 The distinction between these two is important; they are
7644 not interchangeable concepts. Almost all
7645 <tt>conffile</tt>s are configuration files, but many
7646 configuration files are not <tt>conffiles</tt>.
7650 As noted elsewhere, <file>/etc/init.d</file> scripts,
7651 <file>/etc/default</file> files, scripts installed in
7652 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7653 configuration installed in <file>/etc/cron.d</file> must be
7654 treated as configuration files. In general, any script that
7655 embeds configuration information is de-facto a configuration
7656 file and should be treated as such.
7661 <heading>Location</heading>
7664 Any configuration files created or used by your package
7665 must reside in <file>/etc</file>. If there are several,
7666 consider creating a subdirectory of <file>/etc</file>
7667 named after your package.
7671 If your package creates or uses configuration files
7672 outside of <file>/etc</file>, and it is not feasible to modify
7673 the package to use <file>/etc</file> directly, put the files
7674 in <file>/etc</file> and create symbolic links to those files
7675 from the location that the package requires.
7680 <heading>Behavior</heading>
7683 Configuration file handling must conform to the following
7685 <list compact="compact">
7687 local changes must be preserved during a package
7691 configuration files must be preserved when the
7692 package is removed, and only deleted when the
7696 Obsolete configuration files without local changes may be
7697 removed by the package during upgrade.
7701 The easy way to achieve this behavior is to make the
7702 configuration file a <tt>conffile</tt>. This is
7703 appropriate only if it is possible to distribute a default
7704 version that will work for most installations, although
7705 some system administrators may choose to modify it. This
7706 implies that the default version will be part of the
7707 package distribution, and must not be modified by the
7708 maintainer scripts during installation (or at any other
7713 In order to ensure that local changes are preserved
7714 correctly, no package may contain or make hard links to
7715 conffiles.<footnote>
7716 Rationale: There are two problems with hard links.
7717 The first is that some editors break the link while
7718 editing one of the files, so that the two files may
7719 unwittingly become unlinked and different. The second
7720 is that <prgn>dpkg</prgn> might break the hard link
7721 while upgrading <tt>conffile</tt>s.
7726 The other way to do it is via the maintainer scripts. In
7727 this case, the configuration file must not be listed as a
7728 <tt>conffile</tt> and must not be part of the package
7729 distribution. If the existence of a file is required for
7730 the package to be sensibly configured it is the
7731 responsibility of the package maintainer to provide
7732 maintainer scripts which correctly create, update and
7733 maintain the file and remove it on purge. (See <ref
7734 id="maintainerscripts"> for more information.) These
7735 scripts must be idempotent (i.e., must work correctly if
7736 <prgn>dpkg</prgn> needs to re-run them due to errors
7737 during installation or removal), must cope with all the
7738 variety of ways <prgn>dpkg</prgn> can call maintainer
7739 scripts, must not overwrite or otherwise mangle the user's
7740 configuration without asking, must not ask unnecessary
7741 questions (particularly during upgrades), and must
7742 otherwise be good citizens.
7746 The scripts are not required to configure every possible
7747 option for the package, but only those necessary to get
7748 the package running on a given system. Ideally the
7749 sysadmin should not have to do any configuration other
7750 than that done (semi-)automatically by the
7751 <prgn>postinst</prgn> script.
7755 A common practice is to create a script called
7756 <file><var>package</var>-configure</file> and have the
7757 package's <prgn>postinst</prgn> call it if and only if the
7758 configuration file does not already exist. In certain
7759 cases it is useful for there to be an example or template
7760 file which the maintainer scripts use. Such files should
7761 be in <file>/usr/share/<var>package</var></file> or
7762 <file>/usr/lib/<var>package</var></file> (depending on whether
7763 they are architecture-independent or not). There should
7764 be symbolic links to them from
7765 <file>/usr/share/doc/<var>package</var>/examples</file> if
7766 they are examples, and should be perfectly ordinary
7767 <prgn>dpkg</prgn>-handled files (<em>not</em>
7768 configuration files).
7772 These two styles of configuration file handling must
7773 not be mixed, for that way lies madness:
7774 <prgn>dpkg</prgn> will ask about overwriting the file
7775 every time the package is upgraded.
7780 <heading>Sharing configuration files</heading>
7783 Packages which specify the same file as a
7784 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7785 with each other. (This is an instance of the general rule
7786 about not sharing files. Note that neither alternatives
7787 nor diversions are likely to be appropriate in this case;
7788 in particular, <prgn>dpkg</prgn> does not handle diverted
7789 <tt>conffile</tt>s well.)
7793 The maintainer scripts must not alter a <tt>conffile</tt>
7794 of <em>any</em> package, including the one the scripts
7799 If two or more packages use the same configuration file
7800 and it is reasonable for both to be installed at the same
7801 time, one of these packages must be defined as
7802 <em>owner</em> of the configuration file, i.e., it will be
7803 the package which handles that file as a configuration
7804 file. Other packages that use the configuration file must
7805 depend on the owning package if they require the
7806 configuration file to operate. If the other package will
7807 use the configuration file if present, but is capable of
7808 operating without it, no dependency need be declared.
7812 If it is desirable for two or more related packages to
7813 share a configuration file <em>and</em> for all of the
7814 related packages to be able to modify that configuration
7815 file, then the following should be done:
7816 <enumlist compact="compact">
7818 One of the related packages (the "owning" package)
7819 will manage the configuration file with maintainer
7820 scripts as described in the previous section.
7823 The owning package should also provide a program
7824 that the other packages may use to modify the
7828 The related packages must use the provided program
7829 to make any desired modifications to the
7830 configuration file. They should either depend on
7831 the core package to guarantee that the configuration
7832 modifier program is available or accept gracefully
7833 that they cannot modify the configuration file if it
7834 is not. (This is in addition to the fact that the
7835 configuration file may not even be present in the
7842 Sometimes it's appropriate to create a new package which
7843 provides the basic infrastructure for the other packages
7844 and which manages the shared configuration files. (The
7845 <tt>sgml-base</tt> package is a good example.)
7850 <heading>User configuration files ("dotfiles")</heading>
7853 The files in <file>/etc/skel</file> will automatically be
7854 copied into new user accounts by <prgn>adduser</prgn>.
7855 No other program should reference the files in
7856 <file>/etc/skel</file>.
7860 Therefore, if a program needs a dotfile to exist in
7861 advance in <file>$HOME</file> to work sensibly, that dotfile
7862 should be installed in <file>/etc/skel</file> and treated as a
7867 However, programs that require dotfiles in order to
7868 operate sensibly are a bad thing, unless they do create
7869 the dotfiles themselves automatically.
7873 Furthermore, programs should be configured by the Debian
7874 default installation to behave as closely to the upstream
7875 default behavior as possible.
7879 Therefore, if a program in a Debian package needs to be
7880 configured in some way in order to operate sensibly, that
7881 should be done using a site-wide configuration file placed
7882 in <file>/etc</file>. Only if the program doesn't support a
7883 site-wide default configuration and the package maintainer
7884 doesn't have time to add it may a default per-user file be
7885 placed in <file>/etc/skel</file>.
7889 <file>/etc/skel</file> should be as empty as we can make it.
7890 This is particularly true because there is no easy (or
7891 necessarily desirable) mechanism for ensuring that the
7892 appropriate dotfiles are copied into the accounts of
7893 existing users when a package is installed.
7899 <heading>Log files</heading>
7901 Log files should usually be named
7902 <file>/var/log/<var>package</var>.log</file>. If you have many
7903 log files, or need a separate directory for permission
7904 reasons (<file>/var/log</file> is writable only by
7905 <file>root</file>), you should usually create a directory named
7906 <file>/var/log/<var>package</var></file> and place your log
7911 Log files must be rotated occasionally so that they don't
7912 grow indefinitely; the best way to do this is to drop a log
7913 rotation configuration file into the directory
7914 <file>/etc/logrotate.d</file> and use the facilities provided by
7915 logrotate.<footnote>
7917 The traditional approach to log files has been to set up
7918 <em>ad hoc</em> log rotation schemes using simple shell
7919 scripts and cron. While this approach is highly
7920 customizable, it requires quite a lot of sysadmin work.
7921 Even though the original Debian system helped a little
7922 by automatically installing a system which can be used
7923 as a template, this was deemed not enough.
7927 The use of <prgn>logrotate</prgn>, a program developed
7928 by Red Hat, is better, as it centralizes log management.
7929 It has both a configuration file
7930 (<file>/etc/logrotate.conf</file>) and a directory where
7931 packages can drop their individual log rotation
7932 configurations (<file>/etc/logrotate.d</file>).
7935 Here is a good example for a logrotate config
7936 file (for more information see <manref name="logrotate"
7938 <example compact="compact">
7939 /var/log/foo/*.log {
7944 /etc/init.d/foo force-reload
7948 This rotates all files under <file>/var/log/foo</file>, saves 12
7949 compressed generations, and forces the daemon to reload its
7950 configuration information after the log rotation.
7954 Log files should be removed when the package is
7955 purged (but not when it is only removed). This should be
7956 done by the <prgn>postrm</prgn> script when it is called
7957 with the argument <tt>purge</tt> (see <ref
7958 id="removedetails">).
7963 <heading>Permissions and owners</heading>
7966 The rules in this section are guidelines for general use.
7967 If necessary you may deviate from the details below.
7968 However, if you do so you must make sure that what is done
7969 is secure and you should try to be as consistent as possible
7970 with the rest of the system. You should probably also
7971 discuss it on <prgn>debian-devel</prgn> first.
7975 Files should be owned by <tt>root:root</tt>, and made
7976 writable only by the owner and universally readable (and
7977 executable, if appropriate), that is mode 644 or 755.
7981 Directories should be mode 755 or (for group-writability)
7982 mode 2775. The ownership of the directory should be
7983 consistent with its mode: if a directory is mode 2775, it
7984 should be owned by the group that needs write access to
7987 When a package is upgraded, and the owner or permissions
7988 of a file included in the package has changed, dpkg
7989 arranges for the ownership and permissions to be
7990 correctly set upon installation. However, this does not
7991 extend to directories; the permissions and ownership of
7992 directories already on the system does not change on
7993 install or upgrade of packages. This makes sense, since
7994 otherwise common directories like <tt>/usr</tt> would
7995 always be in flux. To correctly change permissions of a
7996 directory the package owns, explicit action is required,
7997 usually in the <tt>postinst</tt> script. Care must be
7998 taken to handle downgrades as well, in that case.
8005 Setuid and setgid executables should be mode 4755 or 2755
8006 respectively, and owned by the appropriate user or group.
8007 They should not be made unreadable (modes like 4711 or
8008 2711 or even 4111); doing so achieves no extra security,
8009 because anyone can find the binary in the freely available
8010 Debian package; it is merely inconvenient. For the same
8011 reason you should not restrict read or execute permissions
8012 on non-set-id executables.
8016 Some setuid programs need to be restricted to particular
8017 sets of users, using file permissions. In this case they
8018 should be owned by the uid to which they are set-id, and by
8019 the group which should be allowed to execute them. They
8020 should have mode 4754; again there is no point in making
8021 them unreadable to those users who must not be allowed to
8026 It is possible to arrange that the system administrator can
8027 reconfigure the package to correspond to their local
8028 security policy by changing the permissions on a binary:
8029 they can do this by using <prgn>dpkg-statoverride</prgn>, as
8030 described below.<footnote>
8031 Ordinary files installed by <prgn>dpkg</prgn> (as
8032 opposed to <tt>conffile</tt>s and other similar objects)
8033 normally have their permissions reset to the distributed
8034 permissions when the package is reinstalled. However,
8035 the use of <prgn>dpkg-statoverride</prgn> overrides this
8038 Another method you should consider is to create a group for
8039 people allowed to use the program(s) and make any setuid
8040 executables executable only by that group.
8044 If you need to create a new user or group for your package
8045 there are two possibilities. Firstly, you may need to
8046 make some files in the binary package be owned by this
8047 user or group, or you may need to compile the user or
8048 group id (rather than just the name) into the binary
8049 (though this latter should be avoided if possible, as in
8050 this case you need a statically allocated id).</p>
8053 If you need a statically allocated id, you must ask for a
8054 user or group id from the <tt>base-passwd</tt> maintainer,
8055 and must not release the package until you have been
8056 allocated one. Once you have been allocated one you must
8057 either make the package depend on a version of the
8058 <tt>base-passwd</tt> package with the id present in
8059 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
8060 your package to create the user or group itself with the
8061 correct id (using <tt>adduser</tt>) in its
8062 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
8063 the <prgn>postinst</prgn> is to be preferred if it is
8064 possible, otherwise a pre-dependency will be needed on the
8065 <tt>adduser</tt> package.)
8069 On the other hand, the program might be able to determine
8070 the uid or gid from the user or group name at runtime, so
8071 that a dynamically allocated id can be used. In this case
8072 you should choose an appropriate user or group name,
8073 discussing this on <prgn>debian-devel</prgn> and checking
8074 with the <package/base-passwd/ maintainer that it is unique and that
8075 they do not wish you to use a statically allocated id
8076 instead. When this has been checked you must arrange for
8077 your package to create the user or group if necessary using
8078 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
8079 <prgn>postinst</prgn> script (again, the latter is to be
8080 preferred if it is possible).
8084 Note that changing the numeric value of an id associated
8085 with a name is very difficult, and involves searching the
8086 file system for all appropriate files. You need to think
8087 carefully whether a static or dynamic id is required, since
8088 changing your mind later will cause problems.
8091 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
8093 This section is not intended as policy, but as a
8094 description of the use of <prgn>dpkg-statoverride</prgn>.
8098 If a system administrator wishes to have a file (or
8099 directory or other such thing) installed with owner and
8100 permissions different from those in the distributed Debian
8101 package, they can use the <prgn>dpkg-statoverride</prgn>
8102 program to instruct <prgn>dpkg</prgn> to use the different
8103 settings every time the file is installed. Thus the
8104 package maintainer should distribute the files with their
8105 normal permissions, and leave it for the system
8106 administrator to make any desired changes. For example, a
8107 daemon which is normally required to be setuid root, but
8108 in certain situations could be used without being setuid,
8109 should be installed setuid in the <tt>.deb</tt>. Then the
8110 local system administrator can change this if they wish.
8111 If there are two standard ways of doing it, the package
8112 maintainer can use <tt>debconf</tt> to find out the
8113 preference, and call <prgn>dpkg-statoverride</prgn> in the
8114 maintainer script if necessary to accommodate the system
8115 administrator's choice. Care must be taken during
8116 upgrades to not override an existing setting.
8120 Given the above, <prgn>dpkg-statoverride</prgn> is
8121 essentially a tool for system administrators and would not
8122 normally be needed in the maintainer scripts. There is
8123 one type of situation, though, where calls to
8124 <prgn>dpkg-statoverride</prgn> would be needed in the
8125 maintainer scripts, and that involves packages which use
8126 dynamically allocated user or group ids. In such a
8127 situation, something like the following idiom can be very
8128 helpful in the package's <prgn>postinst</prgn>, where
8129 <tt>sysuser</tt> is a dynamically allocated id:
8131 for i in /usr/bin/foo /usr/sbin/bar
8133 # only do something when no setting exists
8134 if ! dpkg-statoverride --list $i >/dev/null 2>&1
8136 #include: debconf processing, question about foo and bar
8137 if [ "$RET" = "true" ] ; then
8138 dpkg-statoverride --update --add sysuser root 4755 $i
8143 The corresponding code to remove the override when the package
8146 for i in /usr/bin/foo /usr/sbin/bar
8148 if dpkg-statoverride --list $i >/dev/null 2>&1
8150 dpkg-statoverride --remove $i
8160 <chapt id="customized-programs">
8161 <heading>Customized programs</heading>
8163 <sect id="arch-spec">
8164 <heading>Architecture specification strings</heading>
8167 If a program needs to specify an <em>architecture specification
8168 string</em> in some place, it should select one of the strings
8169 provided by <tt>dpkg-architecture -L</tt>. The strings are in
8170 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
8171 part is sometimes elided, as when the OS is Linux.
8175 Note that we don't want to use
8176 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
8177 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
8178 since this would make our programs incompatible with other
8179 Linux distributions. We also don't use something like
8180 <tt><var>arch</var>-unknown-linux</tt>, since the
8181 <tt>unknown</tt> does not look very good.
8184 <sect1 id="arch-wildcard-spec">
8185 <heading>Architecture wildcards</heading>
8188 A package may specify an architecture wildcard. Architecture
8189 wildcards are in the format <tt>any</tt> (which matches every
8190 architecture), <tt><var>os</var></tt>-any, or
8191 any-<tt><var>cpu</var></tt>. <footnote>
8192 Internally, the package system normalizes the GNU triplets
8193 and the Debian arches into Debian arch triplets (which are
8194 kind of inverted GNU triplets), with the first component of
8195 the triplet representing the libc and ABI in use, and then
8196 does matching against those triplets. However, such
8197 triplets are an internal implementation detail that should
8198 not be used by packages directly. The libc and ABI portion
8199 is handled internally by the package system based on
8200 the <var>os</var> and <var>cpu</var>.
8207 <heading>Daemons</heading>
8210 The configuration files <file>/etc/services</file>,
8211 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
8212 by the <prgn>netbase</prgn> package and must not be modified
8217 If a package requires a new entry in one of these files, the
8218 maintainer should get in contact with the
8219 <prgn>netbase</prgn> maintainer, who will add the entries
8220 and release a new version of the <prgn>netbase</prgn>
8225 The configuration file <file>/etc/inetd.conf</file> must not be
8226 modified by the package's scripts except via the
8227 <prgn>update-inetd</prgn> script or the
8228 <file>DebianNet.pm</file> Perl module. See their documentation
8229 for details on how to add entries.
8233 If a package wants to install an example entry into
8234 <file>/etc/inetd.conf</file>, the entry must be preceded with
8235 exactly one hash character (<tt>#</tt>). Such lines are
8236 treated as "commented out by user" by the
8237 <prgn>update-inetd</prgn> script and are not changed or
8238 activated during package updates.
8243 <heading>Using pseudo-ttys and modifying wtmp, utmp and
8247 Some programs need to create pseudo-ttys. This should be done
8248 using Unix98 ptys if the C library supports it. The resulting
8249 program must not be installed setuid root, unless that
8250 is required for other functionality.
8254 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
8255 <file>/var/log/lastlog</file> must be installed writable by
8256 group <tt>utmp</tt>. Programs which need to modify those
8257 files must be installed setgid <tt>utmp</tt>.
8262 <heading>Editors and pagers</heading>
8265 Some programs have the ability to launch an editor or pager
8266 program to edit or display a text document. Since there are
8267 lots of different editors and pagers available in the Debian
8268 distribution, the system administrator and each user should
8269 have the possibility to choose their preferred editor and
8274 In addition, every program should choose a good default
8275 editor/pager if none is selected by the user or system
8280 Thus, every program that launches an editor or pager must
8281 use the EDITOR or PAGER environment variable to determine
8282 the editor or pager the user wishes to use. If these
8283 variables are not set, the programs <file>/usr/bin/editor</file>
8284 and <file>/usr/bin/pager</file> should be used, respectively.
8288 These two files are managed through the <prgn>dpkg</prgn>
8289 "alternatives" mechanism. Thus every package providing an
8290 editor or pager must call the
8291 <prgn>update-alternatives</prgn> script to register these
8296 If it is very hard to adapt a program to make use of the
8297 EDITOR or PAGER variables, that program may be configured to
8298 use <file>/usr/bin/sensible-editor</file> and
8299 <file>/usr/bin/sensible-pager</file> as the editor or pager
8300 program respectively. These are two scripts provided in the
8301 <package>sensible-utils</package> package that check the EDITOR
8302 and PAGER variables and launch the appropriate program, and fall
8303 back to <file>/usr/bin/editor</file>
8304 and <file>/usr/bin/pager</file> if the variable is not set.
8308 A program may also use the VISUAL environment variable to
8309 determine the user's choice of editor. If it exists, it
8310 should take precedence over EDITOR. This is in fact what
8311 <file>/usr/bin/sensible-editor</file> does.
8315 It is not required for a package to depend on
8316 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
8317 package to provide such virtual packages.<footnote>
8318 The Debian base system already provides an editor and a
8324 <sect id="web-appl">
8325 <heading>Web servers and applications</heading>
8328 This section describes the locations and URLs that should
8329 be used by all web servers and web applications in the
8336 Cgi-bin executable files are installed in the
8338 <example compact="compact">
8339 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
8341 and should be referred to as
8342 <example compact="compact">
8343 http://localhost/cgi-bin/<var>cgi-bin-name</var>
8349 <p>Access to HTML documents</p>
8352 HTML documents for a package are stored in
8353 <file>/usr/share/doc/<var>package</var></file>
8354 and can be referred to as
8355 <example compact="compact">
8356 http://localhost/doc/<var>package</var>/<var>filename</var>
8361 The web server should restrict access to the document
8362 tree so that only clients on the same host can read
8363 the documents. If the web server does not support such
8364 access controls, then it should not provide access at
8365 all, or ask about providing access during installation.
8370 <p>Access to images</p>
8372 It is recommended that images for a package be stored
8373 in <tt>/usr/share/images/<var>package</var></tt> and
8374 may be referred to through an alias <tt>/images/</tt>
8377 http://localhost/images/<package>/<filename>
8384 <p>Web Document Root</p>
8387 Web Applications should try to avoid storing files in
8388 the Web Document Root. Instead they should use the
8389 /usr/share/doc/<var>package</var> directory for
8390 documents and register the Web Application via the
8391 <package>doc-base</package> package. If access to the
8392 web document root is unavoidable then use
8393 <example compact="compact">
8396 as the Document Root. This might be just a symbolic
8397 link to the location where the system administrator
8398 has put the real document root.
8401 <item><p>Providing httpd and/or httpd-cgi</p>
8403 All web servers should provide the virtual package
8404 <tt>httpd</tt>. If a web server has CGI support it should
8405 provide <tt>httpd-cgi</tt> additionally.
8408 All web applications which do not contain CGI scripts should
8409 depend on <tt>httpd</tt>, all those web applications which
8410 <tt>do</tt> contain CGI scripts, should depend on
8418 <sect id="mail-transport-agents">
8419 <heading>Mail transport, delivery and user agents</heading>
8422 Debian packages which process electronic mail, whether mail
8423 user agents (MUAs) or mail transport agents (MTAs), must
8424 ensure that they are compatible with the configuration
8425 decisions below. Failure to do this may result in lost
8426 mail, broken <tt>From:</tt> lines, and other serious brain
8431 The mail spool is <file>/var/mail</file> and the interface to
8432 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8433 the FHS). On older systems, the mail spool may be
8434 physically located in <file>/var/spool/mail</file>, but all
8435 access to the mail spool should be via the
8436 <file>/var/mail</file> symlink. The mail spool is part of the
8437 base system and not part of the MTA package.
8441 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8442 programs (such as IMAP daemons) must lock the mailbox in an
8443 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8444 be combined with dot locking. To avoid deadlocks, a program
8445 should use <tt>fcntl()</tt> first and dot locking after
8446 this, or alternatively implement the two locking methods in
8447 a non blocking way<footnote>
8448 If it is not possible to establish both locks, the
8449 system shouldn't wait for the second lock to be
8450 established, but remove the first lock, wait a (random)
8451 time, and start over locking again.
8452 </footnote>. Using the functions <tt>maillock</tt> and
8453 <tt>mailunlock</tt> provided by the
8454 <tt>liblockfile*</tt><footnote>
8455 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8456 to use these functions.
8457 </footnote> packages is the recommended way to realize this.
8461 Mailboxes are generally either mode 600 and owned by
8462 <var>user</var> or mode 660 and owned by
8463 <tt><var>user</var>:mail</tt><footnote>
8464 There are two traditional permission schemes for mail spools:
8465 mode 600 with all mail delivery done by processes running as
8466 the destination user, or mode 660 and owned by group mail with
8467 mail delivery done by a process running as a system user in
8468 group mail. Historically, Debian required mode 660 mail
8469 spools to enable the latter model, but that model has become
8470 increasingly uncommon and the principle of least privilege
8471 indicates that mail systems that use the first model should
8472 use permissions of 600. If delivery to programs is permitted,
8473 it's easier to keep the mail system secure if the delivery
8474 agent runs as the destination user. Debian Policy therefore
8475 permits either scheme.
8476 </footnote>. The local system administrator may choose a
8477 different permission scheme; packages should not make
8478 assumptions about the permission and ownership of mailboxes
8479 unless required (such as when creating a new mailbox). A MUA
8480 may remove a mailbox (unless it has nonstandard permissions) in
8481 which case the MTA or another MUA must recreate it if needed.
8485 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8486 be setgid mail to do the locking mentioned above (and
8487 must obviously avoid accessing other users' mailboxes
8488 using this privilege).</p>
8491 <file>/etc/aliases</file> is the source file for the system mail
8492 aliases (e.g., postmaster, usenet, etc.), it is the one
8493 which the sysadmin and <prgn>postinst</prgn> scripts may
8494 edit. After <file>/etc/aliases</file> is edited the program or
8495 human editing it must call <prgn>newaliases</prgn>. All MTA
8496 packages must come with a <prgn>newaliases</prgn> program,
8497 even if it does nothing, but older MTA packages did not do
8498 this so programs should not fail if <prgn>newaliases</prgn>
8499 cannot be found. Note that because of this, all MTA
8500 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8501 <tt>Replaces: mail-transport-agent</tt> control file
8506 The convention of writing <tt>forward to
8507 <var>address</var></tt> in the mailbox itself is not
8508 supported. Use a <tt>.forward</tt> file instead.</p>
8511 The <prgn>rmail</prgn> program used by UUCP
8512 for incoming mail should be <file>/usr/sbin/rmail</file>.
8513 Likewise, <prgn>rsmtp</prgn>, for receiving
8514 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8518 If your package needs to know what hostname to use on (for
8519 example) outgoing news and mail messages which are generated
8520 locally, you should use the file <file>/etc/mailname</file>. It
8521 will contain the portion after the username and <tt>@</tt>
8522 (at) sign for email addresses of users on the machine
8523 (followed by a newline).
8527 Such a package should check for the existence of this file
8528 when it is being configured. If it exists, it should be
8529 used without comment, although an MTA's configuration script
8530 may wish to prompt the user even if it finds that this file
8531 exists. If the file does not exist, the package should
8532 prompt the user for the value (preferably using
8533 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8534 as well as using it in the package's configuration. The
8535 prompt should make it clear that the name will not just be
8536 used by that package. For example, in this situation the
8537 <tt>inn</tt> package could say something like:
8538 <example compact="compact">
8539 Please enter the "mail name" of your system. This is the
8540 hostname portion of the address to be shown on outgoing
8541 news and mail messages. The default is
8542 <var>syshostname</var>, your system's host name. Mail
8543 name ["<var>syshostname</var>"]:
8545 where <var>syshostname</var> is the output of <tt>hostname
8551 <heading>News system configuration</heading>
8554 All the configuration files related to the NNTP (news)
8555 servers and clients should be located under
8556 <file>/etc/news</file>.</p>
8559 There are some configuration issues that apply to a number
8560 of news clients and server packages on the machine. These
8564 <tag><file>/etc/news/organization</file></tag>
8566 A string which should appear as the
8567 organization header for all messages posted
8568 by NNTP clients on the machine
8571 <tag><file>/etc/news/server</file></tag>
8573 Contains the FQDN of the upstream NNTP
8574 server, or localhost if the local machine is
8579 Other global files may be added as required for cross-package news
8586 <heading>Programs for the X Window System</heading>
8589 <heading>Providing X support and package priorities</heading>
8592 Programs that can be configured with support for the X
8593 Window System must be configured to do so and must declare
8594 any package dependencies necessary to satisfy their
8595 runtime requirements when using the X Window System. If
8596 such a package is of higher priority than the X packages
8597 on which it depends, it is required that either the
8598 X-specific components be split into a separate package, or
8599 that an alternative version of the package, which includes
8600 X support, be provided, or that the package's priority be
8606 <heading>Packages providing an X server</heading>
8609 Packages that provide an X server that, directly or
8610 indirectly, communicates with real input and display
8611 hardware should declare in their control data that they
8612 provide the virtual package <tt>xserver</tt>.<footnote>
8613 This implements current practice, and provides an
8614 actual policy for usage of the <tt>xserver</tt>
8615 virtual package which appears in the virtual packages
8616 list. In a nutshell, X servers that interface
8617 directly with the display and input hardware or via
8618 another subsystem (e.g., GGI) should provide
8619 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8620 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8626 <heading>Packages providing a terminal emulator</heading>
8629 Packages that provide a terminal emulator for the X Window
8630 System which meet the criteria listed below should declare
8631 in their control data that they provide the virtual
8632 package <tt>x-terminal-emulator</tt>. They should also
8633 register themselves as an alternative for
8634 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8639 To be an <tt>x-terminal-emulator</tt>, a program must:
8640 <list compact="compact">
8642 Be able to emulate a DEC VT100 terminal, or a
8643 compatible terminal.
8647 Support the command-line option <tt>-e
8648 <var>command</var></tt>, which creates a new
8649 terminal window<footnote>
8650 "New terminal window" does not necessarily mean
8651 a new top-level X window directly parented by
8652 the window manager; it could, if the terminal
8653 emulator application were so coded, be a new
8654 "view" in a multiple-document interface (MDI).
8656 and runs the specified <var>command</var>,
8657 interpreting the entirety of the rest of the command
8658 line as a command to pass straight to exec, in the
8659 manner that <tt>xterm</tt> does.
8663 Support the command-line option <tt>-T
8664 <var>title</var></tt>, which creates a new terminal
8665 window with the window title <var>title</var>.
8672 <heading>Packages providing a window manager</heading>
8675 Packages that provide a window manager should declare in
8676 their control data that they provide the virtual package
8677 <tt>x-window-manager</tt>. They should also register
8678 themselves as an alternative for
8679 <file>/usr/bin/x-window-manager</file>, with a priority
8680 calculated as follows:
8681 <list compact="compact">
8683 Start with a priority of 20.
8687 If the window manager supports the Debian menu
8688 system, add 20 points if this support is available
8689 in the package's default configuration (i.e., no
8690 configuration files belonging to the system or user
8691 have to be edited to activate the feature); if
8692 configuration files must be modified, add only 10
8698 If the window manager complies with <url
8699 id="http://www.freedesktop.org/Standards/wm-spec"
8700 name="The Window Manager Specification Project">,
8701 written by the <url id="http://www.freedesktop.org/"
8702 name="Free Desktop Group">, add 40 points.
8706 If the window manager permits the X session to be
8707 restarted using a <em>different</em> window manager
8708 (without killing the X server) in its default
8709 configuration, add 10 points; otherwise add none.
8716 <heading>Packages providing fonts</heading>
8719 Packages that provide fonts for the X Window
8721 For the purposes of Debian Policy, a "font for the X
8722 Window System" is one which is accessed via X protocol
8723 requests. Fonts for the Linux console, for PostScript
8724 renderer, or any other purpose, do not fit this
8725 definition. Any tool which makes such fonts available
8726 to the X Window System, however, must abide by this
8729 must do a number of things to ensure that they are both
8730 available without modification of the X or font server
8731 configuration, and that they do not corrupt files used by
8732 other font packages to register information about
8736 Fonts of any type supported by the X Window System
8737 must be in a separate binary package from any
8738 executables, libraries, or documentation (except
8739 that specific to the fonts shipped, such as their
8740 license information). If one or more of the fonts
8741 so packaged are necessary for proper operation of
8742 the package with which they are associated the font
8743 package may be Recommended; if the fonts merely
8744 provide an enhancement, a Suggests relationship may
8745 be used. Packages must not Depend on font
8747 This is because the X server may retrieve fonts
8748 from the local file system or over the network
8749 from an X font server; the Debian package system
8750 is empowered to deal only with the local
8756 BDF fonts must be converted to PCF fonts with the
8757 <prgn>bdftopcf</prgn> utility (available in the
8758 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8759 placed in a directory that corresponds to their
8761 <list compact="compact">
8763 100 dpi fonts must be placed in
8764 <file>/usr/share/fonts/X11/100dpi/</file>.
8768 75 dpi fonts must be placed in
8769 <file>/usr/share/fonts/X11/75dpi/</file>.
8773 Character-cell fonts, cursor fonts, and other
8774 low-resolution fonts must be placed in
8775 <file>/usr/share/fonts/X11/misc/</file>.
8781 Type 1 fonts must be placed in
8782 <file>/usr/share/fonts/X11/Type1/</file>. If font
8783 metric files are available, they must be placed here
8788 Subdirectories of <file>/usr/share/fonts/X11/</file>
8789 other than those listed above must be neither
8790 created nor used. (The <file>PEX</file>, <file>CID</file>,
8791 <file>Speedo</file>, and <file>cyrillic</file> directories
8792 are excepted for historical reasons, but installation of
8793 files into these directories remains discouraged.)
8797 Font packages may, instead of placing files directly
8798 in the X font directories listed above, provide
8799 symbolic links in that font directory pointing to
8800 the files' actual location in the filesystem. Such
8801 a location must comply with the FHS.
8805 Font packages should not contain both 75dpi and
8806 100dpi versions of a font. If both are available,
8807 they should be provided in separate binary packages
8808 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8809 the names of the packages containing the
8810 corresponding fonts.
8814 Fonts destined for the <file>misc</file> subdirectory
8815 should not be included in the same package as 75dpi
8816 or 100dpi fonts; instead, they should be provided in
8817 a separate package with <tt>-misc</tt> appended to
8822 Font packages must not provide the files
8823 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8824 <file>fonts.scale</file> in a font directory:
8827 <file>fonts.dir</file> files must not be provided at all.
8831 <file>fonts.alias</file> and <file>fonts.scale</file>
8832 files, if needed, should be provided in the
8834 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8835 where <var>fontdir</var> is the name of the
8837 <file>/usr/share/fonts/X11/</file> where the
8838 package's corresponding fonts are stored
8839 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8840 <var>package</var> is the name of the package
8841 that provides these fonts, and
8842 <var>extension</var> is either <tt>scale</tt>
8843 or <tt>alias</tt>, whichever corresponds to
8850 Font packages must declare a dependency on
8851 <tt>xfonts-utils</tt> in their control
8856 Font packages that provide one or more
8857 <file>fonts.scale</file> files as described above must
8858 invoke <prgn>update-fonts-scale</prgn> on each
8859 directory into which they installed fonts
8860 <em>before</em> invoking
8861 <prgn>update-fonts-dir</prgn> on that directory.
8862 This invocation must occur in both the
8863 <prgn>postinst</prgn> (for all arguments) and
8864 <prgn>postrm</prgn> (for all arguments except
8865 <tt>upgrade</tt>) scripts.
8869 Font packages that provide one or more
8870 <file>fonts.alias</file> files as described above must
8871 invoke <prgn>update-fonts-alias</prgn> on each
8872 directory into which they installed fonts. This
8873 invocation must occur in both the
8874 <prgn>postinst</prgn> (for all arguments) and
8875 <prgn>postrm</prgn> (for all arguments except
8876 <tt>upgrade</tt>) scripts.
8880 Font packages must invoke
8881 <prgn>update-fonts-dir</prgn> on each directory into
8882 which they installed fonts. This invocation must
8883 occur in both the <prgn>postinst</prgn> (for all
8884 arguments) and <prgn>postrm</prgn> (for all
8885 arguments except <tt>upgrade</tt>) scripts.
8889 Font packages must not provide alias names for the
8890 fonts they include which collide with alias names
8891 already in use by fonts already packaged.
8895 Font packages must not provide fonts with the same
8896 XLFD registry name as another font already packaged.
8902 <sect1 id="appdefaults">
8903 <heading>Application defaults files</heading>
8906 Application defaults files must be installed in the
8907 directory <file>/etc/X11/app-defaults/</file> (use of a
8908 localized subdirectory of <file>/etc/X11/</file> as described
8909 in the <em>X Toolkit Intrinsics - C Language
8910 Interface</em> manual is also permitted). They must be
8911 registered as <tt>conffile</tt>s or handled as
8912 configuration files.
8916 Customization of programs' X resources may also be
8917 supported with the provision of a file with the same name
8918 as that of the package placed in
8919 the <file>/etc/X11/Xresources/</file> directory, which
8920 must be registered as a <tt>conffile</tt> or handled as a
8921 configuration file.<footnote>
8922 Note that this mechanism is not the same as using
8923 app-defaults; app-defaults are tied to the client
8924 binary on the local file system, whereas X resources
8925 are stored in the X server and affect all connecting
8932 <heading>Installation directory issues</heading>
8935 Historically, packages using the X Window System used a
8936 separate set of installation directories from other packages.
8937 This practice has been discontinued and packages using the X
8938 Window System should now generally be installed in the same
8939 directories as any other package. Specifically, packages must
8940 not install files under the <file>/usr/X11R6/</file> directory
8941 and the <file>/usr/X11R6/</file> directory hierarchy should be
8942 regarded as obsolete.
8946 Include files previously installed under
8947 <file>/usr/X11R6/include/X11/</file> should be installed into
8948 <file>/usr/include/X11/</file>. For files previously
8949 installed into subdirectories of
8950 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
8951 determine if subdirectories of <file>/usr/lib/</file> and
8952 <file>/usr/share/</file> can be used. If not, a subdirectory
8953 of <file>/usr/lib/X11/</file> should be used.
8957 Configuration files for window, display, or session managers
8958 or other applications that are tightly integrated with the X
8959 Window System may be placed in a subdirectory
8960 of <file>/etc/X11/</file> corresponding to the package name.
8961 Other X Window System applications should use
8962 the <file>/etc/</file> directory unless otherwise mandated by
8963 policy (such as for <ref id="appdefaults">).
8968 <heading>The OSF/Motif and OpenMotif libraries</heading>
8971 <em>Programs that require the non-DFSG-compliant OSF/Motif or
8972 OpenMotif libraries</em><footnote>
8973 OSF/Motif and OpenMotif are collectively referred to as
8974 "Motif" in this policy document.
8976 should be compiled against and tested with LessTif (a free
8977 re-implementation of Motif) instead. If the maintainer
8978 judges that the program or programs do not work
8979 sufficiently well with LessTif to be distributed and
8980 supported, but do so when compiled against Motif, then two
8981 versions of the package should be created; one linked
8982 statically against Motif and with <tt>-smotif</tt>
8983 appended to the package name, and one linked dynamically
8984 against Motif and with <tt>-dmotif</tt> appended to the
8989 Both Motif-linked versions are dependent
8990 upon non-DFSG-compliant software and thus cannot be
8991 uploaded to the <em>main</em> distribution; if the
8992 software is itself DFSG-compliant it may be uploaded to
8993 the <em>contrib</em> distribution. While known existing
8994 versions of Motif permit unlimited redistribution of
8995 binaries linked against the library (whether statically or
8996 dynamically), it is the package maintainer's
8997 responsibility to determine whether this is permitted by
8998 the license of the copy of Motif in their possession.
9004 <heading>Perl programs and modules</heading>
9007 Perl programs and modules should follow the current Perl policy.
9011 The Perl policy can be found in the <tt>perl-policy</tt>
9012 files in the <tt>debian-policy</tt> package.
9013 It is also available from the Debian web mirrors at
9014 <tt><url name="/doc/packaging-manuals/perl-policy/"
9015 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
9020 <heading>Emacs lisp programs</heading>
9023 Please refer to the "Debian Emacs Policy" for details of how to
9024 package emacs lisp programs.
9028 The Emacs policy is available in
9029 <file>debian-emacs-policy.gz</file> of the
9030 <package>emacsen-common</package> package.
9031 It is also available from the Debian web mirrors at
9032 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
9033 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
9038 <heading>Games</heading>
9041 The permissions on <file>/var/games</file> are mode 755, owner
9042 <tt>root</tt> and group <tt>root</tt>.
9046 Each game decides on its own security policy.</p>
9049 Games which require protected, privileged access to
9050 high-score files, saved games, etc., may be made
9051 set-<em>group</em>-id (mode 2755) and owned by
9052 <tt>root:games</tt>, and use files and directories with
9053 appropriate permissions (770 <tt>root:games</tt>, for
9054 example). They must not be made
9055 set-<em>user</em>-id, as this causes security problems. (If
9056 an attacker can subvert any set-user-id game they can
9057 overwrite the executable of any other, causing other players
9058 of these games to run a Trojan horse program. With a
9059 set-group-id game the attacker only gets access to less
9060 important game data, and if they can get at the other
9061 players' accounts at all it will take considerably more
9065 Some packages, for example some fortune cookie programs, are
9066 configured by the upstream authors to install with their
9067 data files or other static information made unreadable so
9068 that they can only be accessed through set-id programs
9069 provided. You should not do this in a Debian package: anyone can
9070 download the <file>.deb</file> file and read the data from it,
9071 so there is no point making the files unreadable. Not
9072 making the files unreadable also means that you don't have
9073 to make so many programs set-id, which reduces the risk of a
9077 As described in the FHS, binaries of games should be
9078 installed in the directory <file>/usr/games</file>. This also
9079 applies to games that use the X Window System. Manual pages
9080 for games (X and non-X games) should be installed in
9081 <file>/usr/share/man/man6</file>.</p>
9087 <heading>Documentation</heading>
9090 <heading>Manual pages</heading>
9093 You should install manual pages in <prgn>nroff</prgn> source
9094 form, in appropriate places under <file>/usr/share/man</file>.
9095 You should only use sections 1 to 9 (see the FHS for more
9096 details). You must not install a pre-formatted "cat page".
9100 Each program, utility, and function should have an
9101 associated manual page included in the same package. It is
9102 suggested that all configuration files also have a manual
9103 page included as well. Manual pages for protocols and other
9104 auxiliary things are optional.
9108 If no manual page is available, this is considered as a bug
9109 and should be reported to the Debian Bug Tracking System (the
9110 maintainer of the package is allowed to write this bug report
9111 themselves, if they so desire). Do not close the bug report
9112 until a proper man page is available.<footnote>
9113 It is not very hard to write a man page. See the
9114 <url id="http://www.schweikhardt.net/man_page_howto.html"
9115 name="Man-Page-HOWTO">,
9116 <manref name="man" section="7">, the examples
9117 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
9118 the helper program <prgn>help2man</prgn>, or the
9119 directory <file>/usr/share/doc/man-db/examples</file>.
9124 You may forward a complaint about a missing man page to the
9125 upstream authors, and mark the bug as forwarded in the
9126 Debian bug tracking system. Even though the GNU Project do
9127 not in general consider the lack of a man page to be a bug,
9128 we do; if they tell you that they don't consider it a bug
9129 you should leave the bug in our bug tracking system open
9134 Manual pages should be installed compressed using <tt>gzip -9</tt>.
9138 If one man page needs to be accessible via several names it
9139 is better to use a symbolic link than the <file>.so</file>
9140 feature, but there is no need to fiddle with the relevant
9141 parts of the upstream source to change from <file>.so</file> to
9142 symlinks: don't do it unless it's easy. You should not
9143 create hard links in the manual page directories, nor put
9144 absolute filenames in <file>.so</file> directives. The filename
9145 in a <file>.so</file> in a man page should be relative to the
9146 base of the man page tree (usually
9147 <file>/usr/share/man</file>). If you do not create any links
9148 (whether symlinks, hard links, or <tt>.so</tt> directives)
9149 in the file system to the alternate names of the man page,
9150 then you should not rely on <prgn>man</prgn> finding your
9151 man page under those names based solely on the information in
9152 the man page's header.<footnote>
9153 Supporting this in <prgn>man</prgn> often requires
9154 unreasonable processing time to find a manual page or to
9155 report that none exists, and moves knowledge into man's
9156 database that would be better left in the file system.
9157 This support is therefore deprecated and will cease to
9158 be present in the future.
9163 Manual pages in locale-specific subdirectories of
9164 <file>/usr/share/man</file> should use either UTF-8 or the usual
9165 legacy encoding for that language (normally the one corresponding
9166 to the shortest relevant locale name in
9167 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
9168 <file>/usr/share/man/fr</file> should use either UTF-8 or
9169 ISO-8859-1.<footnote>
9170 <prgn>man</prgn> will automatically detect whether UTF-8 is in
9171 use. In future, all manual pages will be required to use
9177 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
9178 included in the subdirectory name unless it indicates a
9179 significant difference in the language, as this excludes
9180 speakers of the language in other countries.<footnote>
9181 At the time of writing, Chinese and Portuguese are the main
9182 languages with such differences, so <file>pt_BR</file>,
9183 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
9188 If a localized version of a manual page is provided, it should
9189 either be up-to-date or it should be obvious to the reader that
9190 it is outdated and the original manual page should be used
9191 instead. This can be done either by a note at the beginning of
9192 the manual page or by showing the missing or changed portions in
9193 the original language instead of the target language.
9198 <heading>Info documents</heading>
9201 Info documents should be installed in <file>/usr/share/info</file>.
9202 They should be compressed with <tt>gzip -9</tt>.
9206 The <prgn>install-info</prgn> program maintains a directory of
9207 installed info documents in <file>/usr/share/info/dir</file> for
9208 the use of info readers.<footnote>
9209 It was previously necessary for packages installing info
9210 documents to run <prgn>install-info</prgn> from maintainer
9211 scripts. This is no longer necessary. The installation
9212 system now uses dpkg triggers.
9214 This file must not be included in packages. Packages containing
9215 info documents should depend on <tt>dpkg (>= 1.15.4) |
9216 install-info</tt> to ensure that the directory file is properly
9217 rebuilt during partial upgrades from Debian 5.0 (lenny) and
9222 Info documents should contain section and directory entry
9223 information in the document for the use
9224 of <prgn>install-info</prgn>. The section should be specified
9225 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
9226 space and the section of this info page. The directory entry or
9227 entries should be included between
9228 a <tt>START-INFO-DIR-ENTRY</tt> line and
9229 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
9231 INFO-DIR-SECTION Individual utilities
9232 START-INFO-DIR-ENTRY
9233 * example: (example). An example info directory entry.
9236 To determine which section to use, you should look
9237 at <file>/usr/share/info/dir</file> on your system and choose
9238 the most relevant (or create a new section if none of the
9239 current sections are relevant).<footnote>
9240 Normally, info documents are generated from Texinfo source.
9241 To include this information in the generated info document, if
9242 it is absent, add commands like:
9244 @dircategory Individual utilities
9246 * example: (example). An example info directory entry.
9249 to the Texinfo source of the document and ensure that the info
9250 documents are rebuilt from source during the package build.
9256 <heading>Additional documentation</heading>
9259 Any additional documentation that comes with the package may
9260 be installed at the discretion of the package maintainer.
9261 Plain text documentation should be installed in the directory
9262 <file>/usr/share/doc/<var>package</var></file>, where
9263 <var>package</var> is the name of the package, and
9264 compressed with <tt>gzip -9</tt> unless it is small.
9268 If a package comes with large amounts of documentation which
9269 many users of the package will not require you should create
9270 a separate binary package to contain it, so that it does not
9271 take up disk space on the machines of users who do not need
9272 or want it installed.</p>
9275 It is often a good idea to put text information files
9276 (<file>README</file>s, changelogs, and so forth) that come with
9277 the source package in <file>/usr/share/doc/<var>package</var></file>
9278 in the binary package. However, you don't need to install
9279 the instructions for building and installing the package, of
9283 Packages must not require the existence of any files in
9284 <file>/usr/share/doc/</file> in order to function
9286 The system administrator should be able to
9287 delete files in <file>/usr/share/doc/</file> without causing
9288 any programs to break.
9290 Any files that are referenced by programs but are also
9291 useful as stand alone documentation should be installed under
9292 <file>/usr/share/<var>package</var>/</file> with symbolic links from
9293 <file>/usr/share/doc/<var>package</var></file>.
9297 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9298 link to another directory in <file>/usr/share/doc</file> only if
9299 the two packages both come from the same source and the
9300 first package Depends on the second.<footnote>
9302 Please note that this does not override the section on
9303 changelog files below, so the file
9304 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
9305 must refer to the changelog for the current version of
9306 <var>package</var> in question. In practice, this means
9307 that the sources of the target and the destination of the
9308 symlink must be the same (same source package and
9315 Former Debian releases placed all additional documentation
9316 in <file>/usr/doc/<var>package</var></file>. This has been
9317 changed to <file>/usr/share/doc/<var>package</var></file>,
9318 and packages must not put documentation in the directory
9319 <file>/usr/doc/<var>package</var></file>. <footnote>
9320 At this phase of the transition, we no longer require a
9321 symbolic link in <file>/usr/doc/</file>. At a later point,
9322 policy shall change to make the symbolic links a bug.
9328 <heading>Preferred documentation formats</heading>
9331 The unification of Debian documentation is being carried out
9335 If your package comes with extensive documentation in a
9336 markup format that can be converted to various other formats
9337 you should if possible ship HTML versions in a binary
9338 package, in the directory
9339 <file>/usr/share/doc/<var>appropriate-package</var></file> or
9340 its subdirectories.<footnote>
9341 The rationale: The important thing here is that HTML
9342 docs should be available in <em>some</em> package, not
9343 necessarily in the main binary package.
9348 Other formats such as PostScript may be provided at the
9349 package maintainer's discretion.
9353 <sect id="copyrightfile">
9354 <heading>Copyright information</heading>
9357 Every package must be accompanied by a verbatim copy of its
9358 copyright information and distribution license in the file
9359 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
9360 file must neither be compressed nor be a symbolic link.
9364 In addition, the copyright file must say where the upstream
9365 sources (if any) were obtained. It should name the original
9366 authors of the package and the Debian maintainer(s) who were
9367 involved with its creation.
9371 Packages in the <em>contrib</em> or <em>non-free</em> archive
9372 areas should state in the copyright file that the package is not
9373 part of the Debian GNU/Linux distribution and briefly explain
9378 A copy of the file which will be installed in
9379 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9380 be in <file>debian/copyright</file> in the source package.
9384 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9385 link to another directory in <file>/usr/share/doc</file> only if
9386 the two packages both come from the same source and the
9387 first package Depends on the second. These rules are
9388 important because copyrights must be extractable by
9393 Packages distributed under the Apache license (version 2.0), the
9394 Artistic license, the GNU GPL (version 2 or 3), the GNU LGPL
9395 (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or 1.3)
9396 should refer to the corresponding files
9397 under <file>/usr/share/common-licenses</file>,<footnote>
9400 <file>/usr/share/common-licenses/Apache-2.0</file>,
9401 <file>/usr/share/common-licenses/Artistic</file>,
9402 <file>/usr/share/common-licenses/GPL-2</file>,
9403 <file>/usr/share/common-licenses/GPL-3</file>,
9404 <file>/usr/share/common-licenses/LGPL-2</file>,
9405 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9406 <file>/usr/share/common-licenses/LGPL-3</file>,
9407 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
9408 <file>/usr/share/common-licenses/GFDL-1.3</file>
9409 respectively. The University of California BSD license is
9410 also included in <package>base-files</package> as
9411 <file>/usr/share/common-licenses/BSD</file>, but given the
9412 brevity of this license, its specificity to code whose
9413 copyright is held by the Regents of the University of
9414 California, and the frequency of minor wording changes, its
9415 text should be included in the copyright file rather than
9416 referencing this file.
9418 </footnote> rather than quoting them in the copyright
9423 You should not use the copyright file as a general <file>README</file>
9424 file. If your package has such a file it should be
9425 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9426 <file>README.Debian</file> or some other appropriate place.</p>
9430 <heading>Examples</heading>
9433 Any examples (configurations, source files, whatever),
9434 should be installed in a directory
9435 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9436 files should not be referenced by any program: they're there
9437 for the benefit of the system administrator and users as
9438 documentation only. Architecture-specific example files
9439 should be installed in a directory
9440 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9442 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9443 latter directory itself may be a symbolic link to the
9448 If the purpose of a package is to provide examples, then the
9449 example files may be installed into
9450 <file>/usr/share/doc/<var>package</var></file>.
9454 <sect id="changelogs">
9455 <heading>Changelog files</heading>
9458 Packages that are not Debian-native must contain a
9459 compressed copy of the <file>debian/changelog</file> file from
9460 the Debian source tree in
9461 <file>/usr/share/doc/<var>package</var></file> with the name
9462 <file>changelog.Debian.gz</file>.
9466 If an upstream changelog is available, it should be accessible as
9467 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9468 plain text. If the upstream changelog is distributed in
9469 HTML, it should be made available in that form as
9470 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9471 and a plain text <file>changelog.gz</file> should be generated
9472 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9473 the upstream changelog files do not already conform to this
9474 naming convention, then this may be achieved either by
9475 renaming the files, or by adding a symbolic link, at the
9476 maintainer's discretion.<footnote>
9477 Rationale: People should not have to look in places for
9478 upstream changelogs merely because they are given
9479 different names or are distributed in HTML format.
9484 All of these files should be installed compressed using
9485 <tt>gzip -9</tt>, as they will become large with time even
9486 if they start out small.
9490 If the package has only one changelog which is used both as
9491 the Debian changelog and the upstream one because there is
9492 no separate upstream maintainer then that changelog should
9493 usually be installed as
9494 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9495 there is a separate upstream maintainer, but no upstream
9496 changelog, then the Debian changelog should still be called
9497 <file>changelog.Debian.gz</file>.
9501 For details about the format and contents of the Debian
9502 changelog file, please see <ref id="dpkgchangelog">.
9507 <appendix id="pkg-scope">
9508 <heading>Introduction and scope of these appendices</heading>
9511 These appendices are taken essentially verbatim from the
9512 now-deprecated Packaging Manual, version 3.2.1.0. They are
9513 the chapters which are likely to be of use to package
9514 maintainers and which have not already been included in the
9515 policy document itself. Most of these sections are very likely
9516 not relevant to policy; they should be treated as
9517 documentation for the packaging system. Please note that these
9518 appendices are included for convenience, and for historical
9519 reasons: they used to be part of policy package, and they have
9520 not yet been incorporated into dpkg documentation. However,
9521 they still have value, and hence they are presented here.
9525 They have not yet been checked to ensure that they are
9526 compatible with the contents of policy, and if there are any
9527 contradictions, the version in the main policy document takes
9528 precedence. The remaining chapters of the old Packaging
9529 Manual have also not been read in detail to ensure that there
9530 are not parts which have been left out. Both of these will be
9535 Certain parts of the Packaging manual were integrated into the
9536 Policy Manual proper, and removed from the appendices. Links
9537 have been placed from the old locations to the new ones.
9541 <prgn>dpkg</prgn> is a suite of programs for creating binary
9542 package files and installing and removing them on Unix
9544 <prgn>dpkg</prgn> is targeted primarily at Debian
9545 GNU/Linux, but may work on or be ported to other
9551 The binary packages are designed for the management of
9552 installed executable programs (usually compiled binaries) and
9553 their associated data, though source code examples and
9554 documentation are provided as part of some packages.</p>
9557 This manual describes the technical aspects of creating Debian
9558 binary packages (<file>.deb</file> files). It documents the
9559 behavior of the package management programs
9560 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9561 they interact with packages.</p>
9564 It also documents the interaction between
9565 <prgn>dselect</prgn>'s core and the access method scripts it
9566 uses to actually install the selected packages, and describes
9567 how to create a new access method.</p>
9570 This manual does not go into detail about the options and
9571 usage of the package building and installation tools. It
9572 should therefore be read in conjunction with those programs'
9577 The utility programs which are provided with <prgn>dpkg</prgn>
9578 for managing various system configuration and similar issues,
9579 such as <prgn>update-rc.d</prgn> and
9580 <prgn>install-info</prgn>, are not described in detail here -
9581 please see their man pages.
9585 It is assumed that the reader is reasonably familiar with the
9586 <prgn>dpkg</prgn> System Administrators' manual.
9587 Unfortunately this manual does not yet exist.
9591 The Debian version of the FSF's GNU hello program is provided
9592 as an example for people wishing to create Debian
9593 packages. The Debian <prgn>debmake</prgn> package is
9594 recommended as a very helpful tool in creating and maintaining
9595 Debian packages. However, while the tools and examples are
9596 helpful, they do not replace the need to read and follow the
9597 Policy and Programmer's Manual.</p>
9600 <appendix id="pkg-binarypkg">
9601 <heading>Binary packages (from old Packaging Manual)</heading>
9604 The binary package has two main sections. The first part
9605 consists of various control information files and scripts used
9606 by <prgn>dpkg</prgn> when installing and removing. See <ref
9607 id="pkg-controlarea">.
9611 The second part is an archive containing the files and
9612 directories to be installed.
9616 In the future binary packages may also contain other
9617 components, such as checksums and digital signatures. The
9618 format for the archive is described in full in the
9619 <file>deb(5)</file> man page.
9623 <sect id="pkg-bincreating"><heading>Creating package files -
9624 <prgn>dpkg-deb</prgn>
9628 All manipulation of binary package files is done by
9629 <prgn>dpkg-deb</prgn>; it's the only program that has
9630 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9631 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9632 will spot that the options requested are appropriate to
9633 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9638 In order to create a binary package you must make a
9639 directory tree which contains all the files and directories
9640 you want to have in the file system data part of the package.
9641 In Debian-format source packages this directory is usually
9642 <file>debian/tmp</file>, relative to the top of the package's
9647 They should have the locations (relative to the root of the
9648 directory tree you're constructing) ownerships and
9649 permissions which you want them to have on the system when
9654 With current versions of <prgn>dpkg</prgn> the uid/username
9655 and gid/groupname mappings for the users and groups being
9656 used should be the same on the system where the package is
9657 built and the one where it is installed.
9661 You need to add one special directory to the root of the
9662 miniature file system tree you're creating:
9663 <prgn>DEBIAN</prgn>. It should contain the control
9664 information files, notably the binary package control file
9665 (see <ref id="pkg-controlfile">).
9669 The <prgn>DEBIAN</prgn> directory will not appear in the
9670 file system archive of the package, and so won't be installed
9671 by <prgn>dpkg</prgn> when the package is unpacked.
9675 When you've prepared the package, you should invoke:
9677 dpkg --build <var>directory</var>
9682 This will build the package in
9683 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9684 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9685 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9690 See the man page <manref name="dpkg-deb" section="8"> for details of how
9691 to examine the contents of this newly-created file. You may find the
9692 output of following commands enlightening:
9694 dpkg-deb --info <var>filename</var>.deb
9695 dpkg-deb --contents <var>filename</var>.deb
9696 dpkg --contents <var>filename</var>.deb
9698 To view the copyright file for a package you could use this command:
9700 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
9705 <sect id="pkg-controlarea">
9706 <heading>Package control information files</heading>
9709 The control information portion of a binary package is a
9710 collection of files with names known to <prgn>dpkg</prgn>.
9711 It will treat the contents of these files specially - some
9712 of them contain information used by <prgn>dpkg</prgn> when
9713 installing or removing the package; others are scripts which
9714 the package maintainer wants <prgn>dpkg</prgn> to run.
9718 It is possible to put other files in the package control
9719 area, but this is not generally a good idea (though they
9720 will largely be ignored).
9724 Here is a brief list of the control info files supported by
9725 <prgn>dpkg</prgn> and a summary of what they're used for.
9730 <tag><tt>control</tt>
9733 This is the key description file used by
9734 <prgn>dpkg</prgn>. It specifies the package's name
9735 and version, gives its description for the user,
9736 states its relationships with other packages, and so
9737 forth. See <ref id="sourcecontrolfiles"> and
9738 <ref id="binarycontrolfiles">.
9742 It is usually generated automatically from information
9743 in the source package by the
9744 <prgn>dpkg-gencontrol</prgn> program, and with
9745 assistance from <prgn>dpkg-shlibdeps</prgn>.
9746 See <ref id="pkg-sourcetools">.
9750 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9755 These are executable files (usually scripts) which
9756 <prgn>dpkg</prgn> runs during installation, upgrade
9757 and removal of packages. They allow the package to
9758 deal with matters which are particular to that package
9759 or require more complicated processing than that
9760 provided by <prgn>dpkg</prgn>. Details of when and
9761 how they are called are in <ref id="maintainerscripts">.
9765 It is very important to make these scripts idempotent.
9766 See <ref id="idempotency">.
9770 The maintainer scripts are not guaranteed to run with a
9771 controlling terminal and may not be able to interact with
9772 the user. See <ref id="controllingterminal">.
9776 <tag><tt>conffiles</tt>
9779 This file contains a list of configuration files which
9780 are to be handled automatically by <prgn>dpkg</prgn>
9781 (see <ref id="pkg-conffiles">). Note that not necessarily
9782 every configuration file should be listed here.
9785 <tag><tt>shlibs</tt>
9788 This file contains a list of the shared libraries
9789 supplied by the package, with dependency details for
9790 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9791 when it determines what dependencies are required in a
9792 package control file. The <tt>shlibs</tt> file format
9793 is described on <ref id="shlibs">.
9798 <sect id="pkg-controlfile">
9799 <heading>The main control information file: <tt>control</tt></heading>
9802 The most important control information file used by
9803 <prgn>dpkg</prgn> when it installs a package is
9804 <tt>control</tt>. It contains all the package's "vital
9809 The binary package control files of packages built from
9810 Debian sources are made by a special tool,
9811 <prgn>dpkg-gencontrol</prgn>, which reads
9812 <file>debian/control</file> and <file>debian/changelog</file> to
9813 find the information it needs. See <ref id="pkg-sourcepkg"> for
9818 The fields in binary package control files are listed in
9819 <ref id="binarycontrolfiles">.
9823 A description of the syntax of control files and the purpose
9824 of the fields is available in <ref id="controlfields">.
9829 <heading>Time Stamps</heading>
9832 See <ref id="timestamps">.
9837 <appendix id="pkg-sourcepkg">
9838 <heading>Source packages (from old Packaging Manual) </heading>
9841 The Debian binary packages in the distribution are generated
9842 from Debian sources, which are in a special format to assist
9843 the easy and automatic building of binaries.
9846 <sect id="pkg-sourcetools">
9847 <heading>Tools for processing source packages</heading>
9850 Various tools are provided for manipulating source packages;
9851 they pack and unpack sources and help build of binary
9852 packages and help manage the distribution of new versions.
9856 They are introduced and typical uses described here; see
9857 <manref name="dpkg-source" section="1"> for full
9858 documentation about their arguments and operation.
9862 For examples of how to construct a Debian source package,
9863 and how to use those utilities that are used by Debian
9864 source packages, please see the <prgn>hello</prgn> example
9868 <sect1 id="pkg-dpkg-source">
9870 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9875 This program is frequently used by hand, and is also
9876 called from package-independent automated building scripts
9877 such as <prgn>dpkg-buildpackage</prgn>.
9881 To unpack a package it is typically invoked with
9883 dpkg-source -x <var>.../path/to/filename</var>.dsc
9888 with the <file><var>filename</var>.tar.gz</file> and
9889 <file><var>filename</var>.diff.gz</file> (if applicable) in
9890 the same directory. It unpacks into
9891 <file><var>package</var>-<var>version</var></file>, and if
9893 <file><var>package</var>-<var>version</var>.orig</file>, in
9894 the current directory.
9898 To create a packed source archive it is typically invoked:
9900 dpkg-source -b <var>package</var>-<var>version</var>
9905 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
9906 <file>.diff.gz</file> (if appropriate) in the current
9907 directory. <prgn>dpkg-source</prgn> does not clean the
9908 source tree first - this must be done separately if it is
9913 See also <ref id="pkg-sourcearchives">.</p>
9917 <sect1 id="pkg-dpkg-buildpackage">
9919 <prgn>dpkg-buildpackage</prgn> - overall package-building
9924 <prgn>dpkg-buildpackage</prgn> is a script which invokes
9925 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
9926 targets <tt>clean</tt>, <tt>build</tt> and
9927 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
9928 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
9929 source and binary package upload.
9933 It is usually invoked by hand from the top level of the
9934 built or unbuilt source directory. It may be invoked with
9935 no arguments; useful arguments include:
9936 <taglist compact="compact">
9937 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
9940 Do not sign the <tt>.changes</tt> file or the
9941 source package <tt>.dsc</tt> file, respectively.</p>
9943 <tag><tt>-p<var>sign-command</var></tt></tag>
9946 Invoke <var>sign-command</var> instead of finding
9947 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
9948 <var>sign-command</var> must behave just like
9949 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
9951 <tag><tt>-r<var>root-command</var></tt></tag>
9954 When root privilege is required, invoke the command
9955 <var>root-command</var>. <var>root-command</var>
9956 should invoke its first argument as a command, from
9957 the <prgn>PATH</prgn> if necessary, and pass its
9958 second and subsequent arguments to the command it
9959 calls. If no <var>root-command</var> is supplied
9960 then <var>dpkg-buildpackage</var> will take no
9961 special action to gain root privilege, so that for
9962 most packages it will have to be invoked as root to
9965 <tag><tt>-b</tt>, <tt>-B</tt></tag>
9968 Two types of binary-only build and upload - see
9969 <manref name="dpkg-source" section="1">.
9976 <sect1 id="pkg-dpkg-gencontrol">
9978 <prgn>dpkg-gencontrol</prgn> - generates binary package
9983 This program is usually called from <file>debian/rules</file>
9984 (see <ref id="pkg-sourcetree">) in the top level of the source
9989 This is usually done just before the files and directories in the
9990 temporary directory tree where the package is being built have their
9991 permissions and ownerships set and the package is constructed using
9992 <prgn>dpkg-deb/</prgn>
9994 This is so that the control file which is produced has
9995 the right permissions
10000 <prgn>dpkg-gencontrol</prgn> must be called after all the
10001 files which are to go into the package have been placed in
10002 the temporary build directory, so that its calculation of
10003 the installed size of a package is correct.
10007 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
10008 be run after <prgn>dpkg-shlibdeps</prgn> so that the
10009 variable substitutions created by
10010 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
10015 For a package which generates only one binary package, and
10016 which builds it in <file>debian/tmp</file> relative to the top
10017 of the source package, it is usually sufficient to call
10018 <prgn>dpkg-gencontrol</prgn>.
10022 Sources which build several binaries will typically need
10025 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
10026 </example> The <tt>-P</tt> tells
10027 <prgn>dpkg-gencontrol</prgn> that the package is being
10028 built in a non-default directory, and the <tt>-p</tt>
10029 tells it which package's control file should be generated.
10033 <prgn>dpkg-gencontrol</prgn> also adds information to the
10034 list of files in <file>debian/files</file>, for the benefit of
10035 (for example) a future invocation of
10036 <prgn>dpkg-genchanges</prgn>.</p>
10039 <sect1 id="pkg-dpkg-shlibdeps">
10041 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
10046 This program is usually called from <file>debian/rules</file>
10047 just before <prgn>dpkg-gencontrol</prgn> (see <ref
10048 id="pkg-sourcetree">), in the top level of the source tree.
10052 Its arguments are executables and shared libraries
10055 They may be specified either in the locations in the
10056 source tree where they are created or in the locations
10057 in the temporary build tree where they are installed
10058 prior to binary package creation.
10060 </footnote> for which shared library dependencies should
10061 be included in the binary package's control file.
10065 If some of the found shared libraries should only
10066 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
10067 some warrant a <tt>Pre-Depends</tt>, this can be achieved
10068 by using the <tt>-d<var>dependency-field</var></tt> option
10069 before those executable(s). (Each <tt>-d</tt> option
10070 takes effect until the next <tt>-d</tt>.)
10074 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
10075 output control file to be modified. Instead by default it
10076 adds to the <file>debian/substvars</file> file variable
10077 settings like <tt>shlibs:Depends</tt>. These variable
10078 settings must be referenced in dependency fields in the
10079 appropriate per-binary-package sections of the source
10084 For example, a package that generates an essential part
10085 which requires dependencies, and optional parts that
10086 which only require a recommendation, would separate those
10087 two sets of dependencies into two different fields.<footnote>
10088 At the time of writing, an example for this was the
10089 <package/xmms/ package, with Depends used for the xmms
10090 executable, Recommends for the plug-ins and Suggests for
10091 even more optional features provided by unzip.
10093 It can say in its <file>debian/rules</file>:
10095 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
10096 -dRecommends <var>optionalpart anotheroptionalpart</var>
10098 and then in its main control file <file>debian/control</file>:
10101 Depends: ${shlibs:Depends}
10102 Recommends: ${shlibs:Recommends}
10108 Sources which produce several binary packages with
10109 different shared library dependency requirements can use
10110 the <tt>-p<var>varnameprefix</var></tt> option to override
10111 the default <tt>shlibs:</tt> prefix (one invocation of
10112 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
10113 They can thus produce several sets of dependency
10114 variables, each of the form
10115 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
10116 which can be referred to in the appropriate parts of the
10117 binary package control files.
10122 <sect1 id="pkg-dpkg-distaddfile">
10124 <prgn>dpkg-distaddfile</prgn> - adds a file to
10125 <file>debian/files</file>
10129 Some packages' uploads need to include files other than
10130 the source and binary package files.
10134 <prgn>dpkg-distaddfile</prgn> adds a file to the
10135 <file>debian/files</file> file so that it will be included in
10136 the <file>.changes</file> file when
10137 <prgn>dpkg-genchanges</prgn> is run.
10141 It is usually invoked from the <tt>binary</tt> target of
10142 <file>debian/rules</file>:
10144 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
10146 The <var>filename</var> is relative to the directory where
10147 <prgn>dpkg-genchanges</prgn> will expect to find it - this
10148 is usually the directory above the top level of the source
10149 tree. The <file>debian/rules</file> target should put the
10150 file there just before or just after calling
10151 <prgn>dpkg-distaddfile</prgn>.
10155 The <var>section</var> and <var>priority</var> are passed
10156 unchanged into the resulting <file>.changes</file> file.
10161 <sect1 id="pkg-dpkg-genchanges">
10163 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
10164 upload control file
10168 This program is usually called by package-independent
10169 automatic building scripts such as
10170 <prgn>dpkg-buildpackage</prgn>, but it may also be called
10175 It is usually called in the top level of a built source
10176 tree, and when invoked with no arguments will print out a
10177 straightforward <file>.changes</file> file based on the
10178 information in the source package's changelog and control
10179 file and the binary and source packages which should have
10185 <sect1 id="pkg-dpkg-parsechangelog">
10187 <prgn>dpkg-parsechangelog</prgn> - produces parsed
10188 representation of a changelog
10192 This program is used internally by
10193 <prgn>dpkg-source</prgn> et al. It may also occasionally
10194 be useful in <file>debian/rules</file> and elsewhere. It
10195 parses a changelog, <file>debian/changelog</file> by default,
10196 and prints a control-file format representation of the
10197 information in it to standard output.
10201 <sect1 id="pkg-dpkg-architecture">
10203 <prgn>dpkg-architecture</prgn> - information about the build and
10208 This program can be used manually, but is also invoked by
10209 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
10210 environment or make variables which specify the build and host
10211 architecture for the package building process.
10216 <sect id="pkg-sourcetree">
10217 <heading>The Debian package source tree</heading>
10220 The source archive scheme described later is intended to
10221 allow a Debian package source tree with some associated
10222 control information to be reproduced and transported easily.
10223 The Debian package source tree is a version of the original
10224 program with certain files added for the benefit of the
10225 packaging process, and with any other changes required
10226 made to the rest of the source code and installation
10231 The extra files created for Debian are in the subdirectory
10232 <file>debian</file> of the top level of the Debian package
10233 source tree. They are described below.
10236 <sect1 id="pkg-debianrules">
10237 <heading><file>debian/rules</file> - the main building script</heading>
10240 See <ref id="debianrules">.
10244 <sect1 id="pkg-srcsubstvars">
10245 <heading><file>debian/substvars</file> and variable substitutions</heading>
10248 See <ref id="substvars">.
10254 <heading><file>debian/files</file></heading>
10257 See <ref id="debianfiles">.
10261 <sect1><heading><file>debian/tmp</file>
10265 This is the canonical temporary location for the
10266 construction of binary packages by the <tt>binary</tt>
10267 target. The directory <file>tmp</file> serves as the root of
10268 the file system tree as it is being constructed (for
10269 example, by using the package's upstream makefiles install
10270 targets and redirecting the output there), and it also
10271 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10272 id="pkg-bincreating">.
10276 If several binary packages are generated from the same
10277 source tree it is usual to use several
10278 <file>debian/tmp<var>something</var></file> directories, for
10279 example <file>tmp-a</file> or <file>tmp-doc</file>.
10283 Whatever <file>tmp</file> directories are created and used by
10284 <tt>binary</tt> must of course be removed by the
10285 <tt>clean</tt> target.</p></sect1>
10289 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10293 As it exists on the FTP site, a Debian source package
10294 consists of three related files. You must have the right
10295 versions of all three to be able to use them.
10300 <tag>Debian source control file - <tt>.dsc</tt></tag>
10302 This file is a control file used by <prgn>dpkg-source</prgn>
10303 to extract a source package.
10304 See <ref id="debiansourcecontrolfiles">.
10308 Original source archive -
10310 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10316 This is a compressed (with <tt>gzip -9</tt>)
10317 <prgn>tar</prgn> file containing the source code from
10318 the upstream authors of the program.
10323 Debian package diff -
10325 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10331 This is a unified context diff (<tt>diff -u</tt>)
10332 giving the changes which are required to turn the
10333 original source into the Debian source. These changes
10334 may only include editing and creating plain files.
10335 The permissions of files, the targets of symbolic
10336 links and the characteristics of special files or
10337 pipes may not be changed and no files may be removed
10342 All the directories in the diff must exist, except the
10343 <file>debian</file> subdirectory of the top of the source
10344 tree, which will be created by
10345 <prgn>dpkg-source</prgn> if necessary when unpacking.
10349 The <prgn>dpkg-source</prgn> program will
10350 automatically make the <file>debian/rules</file> file
10351 executable (see below).</p></item>
10356 If there is no original source code - for example, if the
10357 package is specially prepared for Debian or the Debian
10358 maintainer is the same as the upstream maintainer - the
10359 format is slightly different: then there is no diff, and the
10361 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10362 and preferably contains a directory named
10363 <file><var>package</var>-<var>version</var></file>.
10368 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10371 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10372 Debian source package. However, if it is not available it
10373 is possible to unpack a Debian source archive as follows:
10374 <enumlist compact="compact">
10377 Untar the tarfile, which will create a <file>.orig</file>
10381 <p>Rename the <file>.orig</file> directory to
10382 <file><var>package</var>-<var>version</var></file>.</p>
10386 Create the subdirectory <file>debian</file> at the top of
10387 the source tree.</p>
10389 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10391 <item><p>Untar the tarfile again if you want a copy of the original
10392 source code alongside the Debian version.</p>
10397 It is not possible to generate a valid Debian source archive
10398 without using <prgn>dpkg-source</prgn>. In particular,
10399 attempting to use <prgn>diff</prgn> directly to generate the
10400 <file>.diff.gz</file> file will not work.
10404 <heading>Restrictions on objects in source packages</heading>
10407 The source package may not contain any hard links
10409 This is not currently detected when building source
10410 packages, but only when extracting
10414 Hard links may be permitted at some point in the
10415 future, but would require a fair amount of
10417 </footnote>, device special files, sockets or setuid or
10420 Setgid directories are allowed.
10425 The source packaging tools manage the changes between the
10426 original and Debian source using <prgn>diff</prgn> and
10427 <prgn>patch</prgn>. Turning the original source tree as
10428 included in the <file>.orig.tar.gz</file> into the Debian
10429 package source must not involve any changes which cannot be
10430 handled by these tools. Problematic changes which cause
10431 <prgn>dpkg-source</prgn> to halt with an error when
10432 building the source package are:
10433 <list compact="compact">
10434 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10436 <item><p>Changing the targets of symbolic links.</p>
10438 <item><p>Creating directories, other than <file>debian</file>.</p>
10440 <item><p>Changes to the contents of binary files.</p></item>
10441 </list> Changes which cause <prgn>dpkg-source</prgn> to
10442 print a warning but continue anyway are:
10443 <list compact="compact">
10446 Removing files, directories or symlinks.
10448 Renaming a file is not treated specially - it is
10449 seen as the removal of the old file (which
10450 generates a warning, but is otherwise ignored),
10451 and the creation of the new one.
10457 Changed text files which are missing the usual final
10458 newline (either in the original or the modified
10463 Changes which are not represented, but which are not detected by
10464 <prgn>dpkg-source</prgn>, are:
10465 <list compact="compact">
10466 <item><p>Changing the permissions of files (other than
10467 <file>debian/rules</file>) and directories.</p></item>
10472 The <file>debian</file> directory and <file>debian/rules</file>
10473 are handled specially by <prgn>dpkg-source</prgn> - before
10474 applying the changes it will create the <file>debian</file>
10475 directory, and afterwards it will make
10476 <file>debian/rules</file> world-executable.
10482 <appendix id="pkg-controlfields">
10483 <heading>Control files and their fields (from old Packaging Manual)</heading>
10486 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10487 data in a common format, known as control files. Binary and
10488 source packages have control data as do the <file>.changes</file>
10489 files which control the installation of uploaded files, and
10490 <prgn>dpkg</prgn>'s internal databases are in a similar
10495 <heading>Syntax of control files</heading>
10498 See <ref id="controlsyntax">.
10502 It is important to note that there are several fields which
10503 are optional as far as <prgn>dpkg</prgn> and the related
10504 tools are concerned, but which must appear in every Debian
10505 package, or whose omission may cause problems.
10510 <heading>List of fields</heading>
10513 See <ref id="controlfieldslist">.
10517 This section now contains only the fields that didn't belong
10518 to the Policy manual.
10521 <sect1 id="pkg-f-Filename">
10522 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10525 These fields in <tt>Packages</tt> files give the
10526 filename(s) of (the parts of) a package in the
10527 distribution directories, relative to the root of the
10528 Debian hierarchy. If the package has been split into
10529 several parts the parts are all listed in order, separated
10534 <sect1 id="pkg-f-Size">
10535 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10538 These fields in <file>Packages</file> files give the size (in
10539 bytes, expressed in decimal) and MD5 checksum of the
10540 file(s) which make(s) up a binary package in the
10541 distribution. If the package is split into several parts
10542 the values for the parts are listed in order, separated by
10547 <sect1 id="pkg-f-Status">
10548 <heading><tt>Status</tt></heading>
10551 This field in <prgn>dpkg</prgn>'s status file records
10552 whether the user wants a package installed, removed or
10553 left alone, whether it is broken (requiring
10554 re-installation) or not and what its current state on the
10555 system is. Each of these pieces of information is a
10560 <sect1 id="pkg-f-Config-Version">
10561 <heading><tt>Config-Version</tt></heading>
10564 If a package is not installed or not configured, this
10565 field in <prgn>dpkg</prgn>'s status file records the last
10566 version of the package which was successfully
10571 <sect1 id="pkg-f-Conffiles">
10572 <heading><tt>Conffiles</tt></heading>
10575 This field in <prgn>dpkg</prgn>'s status file contains
10576 information about the automatically-managed configuration
10577 files held by a package. This field should <em>not</em>
10578 appear anywhere in a package!
10583 <heading>Obsolete fields</heading>
10586 These are still recognized by <prgn>dpkg</prgn> but should
10587 not appear anywhere any more.
10589 <taglist compact="compact">
10591 <tag><tt>Revision</tt></tag>
10592 <tag><tt>Package-Revision</tt></tag>
10593 <tag><tt>Package_Revision</tt></tag>
10595 The Debian revision part of the package version was
10596 at one point in a separate control file field. This
10597 field went through several names.
10600 <tag><tt>Recommended</tt></tag>
10601 <item>Old name for <tt>Recommends</tt>.</item>
10603 <tag><tt>Optional</tt></tag>
10604 <item>Old name for <tt>Suggests</tt>.</item>
10606 <tag><tt>Class</tt></tag>
10607 <item>Old name for <tt>Priority</tt>.</item>
10616 <appendix id="pkg-conffiles">
10617 <heading>Configuration file handling (from old Packaging Manual)</heading>
10620 <prgn>dpkg</prgn> can do a certain amount of automatic
10621 handling of package configuration files.
10625 Whether this mechanism is appropriate depends on a number of
10626 factors, but basically there are two approaches to any
10627 particular configuration file.
10631 The easy method is to ship a best-effort configuration in the
10632 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10633 handle updates. If the user is unlikely to want to edit the
10634 file, but you need them to be able to without losing their
10635 changes, and a new package with a changed version of the file
10636 is only released infrequently, this is a good approach.
10640 The hard method is to build the configuration file from
10641 scratch in the <prgn>postinst</prgn> script, and to take the
10642 responsibility for fixing any mistakes made in earlier
10643 versions of the package automatically. This will be
10644 appropriate if the file is likely to need to be different on
10648 <sect><heading>Automatic handling of configuration files by
10653 A package may contain a control area file called
10654 <tt>conffiles</tt>. This file should be a list of filenames
10655 of configuration files needing automatic handling, separated
10656 by newlines. The filenames should be absolute pathnames,
10657 and the files referred to should actually exist in the
10662 When a package is upgraded <prgn>dpkg</prgn> will process
10663 the configuration files during the configuration stage,
10664 shortly before it runs the package's <prgn>postinst</prgn>
10669 For each file it checks to see whether the version of the
10670 file included in the package is the same as the one that was
10671 included in the last version of the package (the one that is
10672 being upgraded from); it also compares the version currently
10673 installed on the system with the one shipped with the last
10678 If neither the user nor the package maintainer has changed
10679 the file, it is left alone. If one or the other has changed
10680 their version, then the changed version is preferred - i.e.,
10681 if the user edits their file, but the package maintainer
10682 doesn't ship a different version, the user's changes will
10683 stay, silently, but if the maintainer ships a new version
10684 and the user hasn't edited it the new version will be
10685 installed (with an informative message). If both have
10686 changed their version the user is prompted about the problem
10687 and must resolve the differences themselves.
10691 The comparisons are done by calculating the MD5 message
10692 digests of the files, and storing the MD5 of the file as it
10693 was included in the most recent version of the package.
10697 When a package is installed for the first time
10698 <prgn>dpkg</prgn> will install the file that comes with it,
10699 unless that would mean overwriting a file already on the
10704 However, note that <prgn>dpkg</prgn> will <em>not</em>
10705 replace a conffile that was removed by the user (or by a
10706 script). This is necessary because with some programs a
10707 missing file produces an effect hard or impossible to
10708 achieve in another way, so that a missing file needs to be
10709 kept that way if the user did it.
10713 Note that a package should <em>not</em> modify a
10714 <prgn>dpkg</prgn>-handled conffile in its maintainer
10715 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10716 the user confusing and possibly dangerous options for
10717 conffile update when the package is upgraded.</p>
10720 <sect><heading>Fully-featured maintainer script configuration
10725 For files which contain site-specific information such as
10726 the hostname and networking details and so forth, it is
10727 better to create the file in the package's
10728 <prgn>postinst</prgn> script.
10732 This will typically involve examining the state of the rest
10733 of the system to determine values and other information, and
10734 may involve prompting the user for some information which
10735 can't be obtained some other way.
10739 When using this method there are a couple of important
10740 issues which should be considered:
10744 If you discover a bug in the program which generates the
10745 configuration file, or if the format of the file changes
10746 from one version to the next, you will have to arrange for
10747 the postinst script to do something sensible - usually this
10748 will mean editing the installed configuration file to remove
10749 the problem or change the syntax. You will have to do this
10750 very carefully, since the user may have changed the file,
10751 perhaps to fix the very problem that your script is trying
10752 to deal with - you will have to detect these situations and
10753 deal with them correctly.
10757 If you do go down this route it's probably a good idea to
10758 make the program that generates the configuration file(s) a
10759 separate program in <file>/usr/sbin</file>, by convention called
10760 <file><var>package</var>config</file> and then run that if
10761 appropriate from the post-installation script. The
10762 <tt><var>package</var>config</tt> program should not
10763 unquestioningly overwrite an existing configuration - if its
10764 mode of operation is geared towards setting up a package for
10765 the first time (rather than any arbitrary reconfiguration
10766 later) you should have it check whether the configuration
10767 already exists, and require a <tt>--force</tt> flag to
10768 overwrite it.</p></sect>
10771 <appendix id="pkg-alternatives"><heading>Alternative versions of
10772 an interface - <prgn>update-alternatives</prgn> (from old
10777 When several packages all provide different versions of the
10778 same program or file it is useful to have the system select a
10779 default, but to allow the system administrator to change it
10780 and have their decisions respected.
10784 For example, there are several versions of the <prgn>vi</prgn>
10785 editor, and there is no reason to prevent all of them from
10786 being installed at once, each under their own name
10787 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10788 Nevertheless it is desirable to have the name <tt>vi</tt>
10789 refer to something, at least by default.
10793 If all the packages involved cooperate, this can be done with
10794 <prgn>update-alternatives</prgn>.
10798 Each package provides its own version under its own name, and
10799 calls <prgn>update-alternatives</prgn> in its postinst to
10800 register its version (and again in its prerm to deregister
10805 See the man page <manref name="update-alternatives"
10806 section="8"> for details.
10810 If <prgn>update-alternatives</prgn> does not seem appropriate
10811 you may wish to consider using diversions instead.</p>
10814 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10815 package's version of a file (from old Packaging Manual)
10819 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10820 when it reinstalls the package it belongs to, and to have it
10821 put the file from the package somewhere else instead.
10825 This can be used locally to override a package's version of a
10826 file, or by one package to override another's version (or
10827 provide a wrapper for it).
10831 Before deciding to use a diversion, read <ref
10832 id="pkg-alternatives"> to see if you really want a diversion
10833 rather than several alternative versions of a program.
10837 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10838 and updated by a special program <prgn>dpkg-divert</prgn>.
10839 Please see <manref name="dpkg-divert" section="8"> for full
10840 details of its operation.
10844 When a package wishes to divert a file from another, it should
10845 call <prgn>dpkg-divert</prgn> in its preinst to add the
10846 diversion and rename the existing file. For example,
10847 supposing that a <prgn>smailwrapper</prgn> package wishes to
10848 install a wrapper around <file>/usr/sbin/smail</file>:
10850 dpkg-divert --package smailwrapper --add --rename \
10851 --divert /usr/sbin/smail.real /usr/sbin/smail
10852 </example> The <tt>--package smailwrapper</tt> ensures that
10853 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
10854 can bypass the diversion and get installed as the true version.
10855 It's safe to add the diversion unconditionally on upgrades since
10856 it will be left unchanged if it already exists, but
10857 <prgn>dpkg-divert</prgn> will display a message. To suppress that
10858 message, make the command conditional on the version from which
10859 the package is being upgraded:
10861 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
10862 dpkg-divert --package smailwrapper --add --rename \
10863 --divert /usr/sbin/smail.real /usr/sbin/smail
10865 </example> where <tt>1.0-2</tt> is the version at which the
10866 diversion was first added to the package. Running the command
10867 during abort-upgrade is pointless but harmless.
10871 The postrm has to do the reverse:
10873 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
10874 dpkg-divert --package smailwrapper --remove --rename \
10875 --divert /usr/sbin/smail.real /usr/sbin/smail
10877 </example> If the diversion was added at a particular version, the
10878 postrm should also handle the failure case of upgrading from an
10879 older version (unless the older version is so old that direct
10880 upgrades are no longer supported):
10882 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
10883 dpkg-divert --package smailwrapper --remove --rename \
10884 --divert /usr/sbin/smail.real /usr/sbin/smail
10886 </example> where <tt>1.02-2</tt> is the version at which the
10887 diversion was first added to the package. The postrm should not
10888 remove the diversion on upgrades both because there's no reason to
10889 remove the diversion only to immediately re-add it and since the
10890 postrm of the old package is run after unpacking so the removal of
10891 the diversion will fail.
10895 Do not attempt to divert a file which is vitally important for
10896 the system's operation - when using <prgn>dpkg-divert</prgn>
10897 there is a time, after it has been diverted but before
10898 <prgn>dpkg</prgn> has installed the new version, when the file
10899 does not exist.</p>
10904 <!-- Local variables: -->
10905 <!-- indent-tabs-mode: t -->
10907 <!-- vim:set ai et sts=2 sw=2 tw=76: -->