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10 <title>Debian Policy Manual</title>
11 <author><qref id="authors">The Debian Policy Mailing List</qref></author>
12 <version>version &version;, &date;</version>
15 This manual describes the policy requirements for the Debian
16 GNU/Linux distribution. This includes the structure and
17 contents of the Debian archive and several design issues of
18 the operating system, as well as technical requirements that
19 each package must satisfy to be included in the distribution.
24 Copyright © 1996,1997,1998 Ian Jackson
25 and Christian Schwarz.
28 These are the copyright dates of the original Policy manual.
29 Since then, this manual has been updated by many others. No
30 comprehensive collection of copyright notices for subsequent
35 This manual is free software; you may redistribute it and/or
36 modify it under the terms of the GNU General Public License
37 as published by the Free Software Foundation; either version
38 2, or (at your option) any later version.
42 This is distributed in the hope that it will be useful, but
43 <em>without any warranty</em>; without even the implied
44 warranty of merchantability or fitness for a particular
45 purpose. See the GNU General Public License for more
50 A copy of the GNU General Public License is available as
51 <file>/usr/share/common-licenses/GPL</file> in the Debian GNU/Linux
52 distribution or on the World Wide Web at
53 <url id="http://www.gnu.org/copyleft/gpl.html"
54 name="the GNU General Public Licence">. You can also
55 obtain it by writing to the Free Software Foundation, Inc.,
56 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
64 <heading>About this manual</heading>
66 <heading>Scope</heading>
68 This manual describes the policy requirements for the Debian
69 GNU/Linux distribution. This includes the structure and
70 contents of the Debian archive and several design issues of the
71 operating system, as well as technical requirements that
72 each package must satisfy to be included in the
77 This manual also describes Debian policy as it relates to
78 creating Debian packages. It is not a tutorial on how to build
79 packages, nor is it exhaustive where it comes to describing
80 the behavior of the packaging system. Instead, this manual
81 attempts to define the interface to the package management
82 system that the developers have to be conversant with.<footnote>
83 Informally, the criteria used for inclusion is that the
84 material meet one of the following requirements:
85 <taglist compact="compact">
86 <tag>Standard interfaces</tag>
88 The material presented represents an interface to
89 the packaging system that is mandated for use, and
90 is used by, a significant number of packages, and
91 therefore should not be changed without peer
92 review. Package maintainers can then rely on this
93 interface not changing, and the package management
94 software authors need to ensure compatibility with
95 this interface definition. (Control file and
96 changelog file formats are examples.)
98 <tag>Chosen Convention</tag>
100 If there are a number of technically viable choices
101 that can be made, but one needs to select one of
102 these options for inter-operability. The version
103 number format is one example.
106 Please note that these are not mutually exclusive;
107 selected conventions often become parts of standard
113 The footnotes present in this manual are
114 merely informative, and are not part of Debian policy itself.
118 The appendices to this manual are not necessarily normative,
119 either. Please see <ref id="pkg-scope"> for more information.
123 In the normative part of this manual,
124 the words <em>must</em>, <em>should</em> and
125 <em>may</em>, and the adjectives <em>required</em>,
126 <em>recommended</em> and <em>optional</em>, are used to
127 distinguish the significance of the various guidelines in
128 this policy document. Packages that do not conform to the
129 guidelines denoted by <em>must</em> (or <em>required</em>)
130 will generally not be considered acceptable for the Debian
131 distribution. Non-conformance with guidelines denoted by
132 <em>should</em> (or <em>recommended</em>) will generally be
133 considered a bug, but will not necessarily render a package
134 unsuitable for distribution. Guidelines denoted by
135 <em>may</em> (or <em>optional</em>) are truly optional and
136 adherence is left to the maintainer's discretion.
140 These classifications are roughly equivalent to the bug
141 severities <em>serious</em> (for <em>must</em> or
142 <em>required</em> directive violations), <em>minor</em>,
143 <em>normal</em> or <em>important</em>
144 (for <em>should</em> or <em>recommended</em> directive
145 violations) and <em>wishlist</em> (for <em>optional</em>
148 Compare RFC 2119. Note, however, that these words are
149 used in a different way in this document.
154 Much of the information presented in this manual will be
155 useful even when building a package which is to be
156 distributed in some other way or is intended for local use
162 <heading>New versions of this document</heading>
165 This manual is distributed via the Debian package
166 <package><url name="debian-policy"
167 id="http://packages.debian.org/debian-policy"></package>
168 (<httpsite>packages.debian.org</httpsite>
169 <httppath>/debian-policy</httppath>).
173 The current version of this document is also available from
174 the Debian web mirrors at
175 <tt><url name="/doc/debian-policy/"
176 id="http://www.debian.org/doc/debian-policy/"></tt>.
178 <httpsite>www.debian.org</httpsite>
179 <httppath>/doc/debian-policy/</httppath>)
180 Also available from the same directory are several other
181 formats: <file>policy.html.tar.gz</file>
182 (<httppath>/doc/debian-policy/policy.html.tar.gz</httppath>),
183 <file>policy.pdf.gz</file>
184 (<httppath>/doc/debian-policy/policy.pdf.gz</httppath>)
185 and <file>policy.ps.gz</file>
186 (<httppath>/doc/debian-policy/policy.ps.gz</httppath>).
190 The <package>debian-policy</package> package also includes the file
191 <file>upgrading-checklist.txt.gz</file> which indicates policy
192 changes between versions of this document.
197 <heading>Authors and Maintainers</heading>
200 Originally called "Debian GNU/Linux Policy Manual", this
201 manual was initially written in 1996 by Ian Jackson.
202 It was revised on November 27th, 1996 by David A. Morris.
203 Christian Schwarz added new sections on March 15th, 1997,
204 and reworked/restructured it in April-July 1997.
205 Christoph Lameter contributed the "Web Standard".
206 Julian Gilbey largely restructured it in 2001.
210 Since September 1998, the responsibility for the contents of
211 this document lies on the <url name="debian-policy mailing list"
212 id="mailto:debian-policy@lists.debian.org">. Proposals
213 are discussed there and inserted into policy after a certain
214 consensus is established.
215 <!-- insert shameless policy-process plug here eventually -->
216 The actual editing is done by a group of maintainers that have
217 no editorial powers. These are the current maintainers:
220 <item>Julian Gilbey</item>
221 <item>Branden Robinson</item>
222 <item>Josip Rodin</item>
223 <item>Manoj Srivastava</item>
228 While the authors of this document have tried hard to avoid
229 typos and other errors, these do still occur. If you discover
230 an error in this manual or if you want to give any
231 comments, suggestions, or criticisms please send an email to
232 the Debian Policy List,
233 <email>debian-policy@lists.debian.org</email>, or submit a
234 bug report against the <tt>debian-policy</tt> package.
238 Please do not try to reach the individual authors or maintainers
239 of the Policy Manual regarding changes to the Policy.
244 <heading>Related documents</heading>
247 There are several other documents other than this Policy Manual
248 that are necessary to fully understand some Debian policies and
253 The external "sub-policy" documents are referred to in:
254 <list compact="compact">
255 <item><ref id="fhs"></item>
256 <item><ref id="virtual_pkg"></item>
257 <item><ref id="menus"></item>
258 <item><ref id="mime"></item>
259 <item><ref id="perl"></item>
260 <item><ref id="maintscriptprompt"></item>
261 <item><ref id="emacs"></item>
266 In addition to those, which carry the weight of policy, there
267 is the Debian Developer's Reference. This document describes
268 procedures and resources for Debian developers, but it is
269 <em>not</em> normative; rather, it includes things that don't
270 belong in the Policy, such as best practices for developers.
274 The Developer's Reference is available in the
275 <package>developers-reference</package> package.
276 It's also available from the Debian web mirrors at
277 <tt><url name="/doc/developers-reference/"
278 id="http://www.debian.org/doc/developers-reference/"></tt>.
282 <sect id="definitions">
283 <heading>Definitions</heading>
286 The following terms are used in this Policy Manual:
290 The character encoding specified by ANSI X3.4-1986 and its
291 predecessor standards, referred to in MIME as US-ASCII, and
292 corresponding to an encoding in eight bits per character of
293 the first 128 <url id="http://www.unicode.org/"
294 name="Unicode"> characters, with the eighth bit always zero.
298 The transformation format (sometimes called encoding) of
299 <url id="http://www.unicode.org/" name="Unicode"> defined by
300 <url id="http://www.rfc-editor.org/rfc/rfc3629.txt"
301 name="RFC 3629">. UTF-8 has the useful property of having
302 ASCII as a subset, so any text encoded in ASCII is trivially
312 <heading>The Debian Archive</heading>
315 The Debian GNU/Linux system is maintained and distributed as a
316 collection of <em>packages</em>. Since there are so many of
317 them (currently well over 15000), they are split into
318 <em>sections</em> and given <em>priorities</em> to simplify
319 the handling of them.
323 The effort of the Debian project is to build a free operating
324 system, but not every package we want to make accessible is
325 <em>free</em> in our sense (see the Debian Free Software
326 Guidelines, below), or may be imported/exported without
327 restrictions. Thus, the archive is split into areas<footnote>
328 The Debian archive software uses the term "component" internally
329 and in the Release file format to refer to the division of an
330 archive. The Debian Social Contract simply refers to "areas."
331 This document uses terminology similar to the Social Contract.
332 </footnote> based on their licenses and other restrictions.
336 The aims of this are:
338 <list compact="compact">
339 <item>to allow us to make as much software available as we can</item>
340 <item>to allow us to encourage everyone to write free software,
342 <item>to allow us to make it easy for people to produce
343 CD-ROMs of our system without violating any licenses,
344 import/export restrictions, or any other laws.</item>
349 The <em>main</em> archive area forms the <em>Debian GNU/Linux
354 Packages in the other archive areas (<tt>contrib</tt>,
355 <tt>non-free</tt>) are not considered to be part of the Debian
356 distribution, although we support their use and provide
357 infrastructure for them (such as our bug-tracking system and
358 mailing lists). This Debian Policy Manual applies to these
363 <heading>The Debian Free Software Guidelines</heading>
365 The Debian Free Software Guidelines (DFSG) form our
366 definition of "free software". These are:
368 <tag>1. Free Redistribution
371 The license of a Debian component may not restrict any
372 party from selling or giving away the software as a
373 component of an aggregate software distribution
374 containing programs from several different
375 sources. The license may not require a royalty or
376 other fee for such sale.
381 The program must include source code, and must allow
382 distribution in source code as well as compiled form.
384 <tag>3. Derived Works
387 The license must allow modifications and derived
388 works, and must allow them to be distributed under the
389 same terms as the license of the original software.
391 <tag>4. Integrity of The Author's Source Code
394 The license may restrict source-code from being
395 distributed in modified form <em>only</em> if the
396 license allows the distribution of "patch files"
397 with the source code for the purpose of modifying the
398 program at build time. The license must explicitly
399 permit distribution of software built from modified
400 source code. The license may require derived works to
401 carry a different name or version number from the
402 original software. (This is a compromise. The Debian
403 Project encourages all authors to not restrict any
404 files, source or binary, from being modified.)
406 <tag>5. No Discrimination Against Persons or Groups
409 The license must not discriminate against any person
412 <tag>6. No Discrimination Against Fields of Endeavor
415 The license must not restrict anyone from making use
416 of the program in a specific field of endeavor. For
417 example, it may not restrict the program from being
418 used in a business, or from being used for genetic
421 <tag>7. Distribution of License
424 The rights attached to the program must apply to all
425 to whom the program is redistributed without the need
426 for execution of an additional license by those
429 <tag>8. License Must Not Be Specific to Debian
432 The rights attached to the program must not depend on
433 the program's being part of a Debian system. If the
434 program is extracted from Debian and used or
435 distributed without Debian but otherwise within the
436 terms of the program's license, all parties to whom
437 the program is redistributed must have the same
438 rights as those that are granted in conjunction with
441 <tag>9. License Must Not Contaminate Other Software
444 The license must not place restrictions on other
445 software that is distributed along with the licensed
446 software. For example, the license must not insist
447 that all other programs distributed on the same medium
448 must be free software.
450 <tag>10. Example Licenses
453 The "GPL," "BSD," and "Artistic" licenses are examples of
454 licenses that we consider <em>free</em>.
461 <heading>Archive areas</heading>
464 <heading>The main archive area</heading>
467 Every package in <em>main</em> must comply with the DFSG
468 (Debian Free Software Guidelines).
472 In addition, the packages in <em>main</em>
473 <list compact="compact">
475 must not require a package outside of <em>main</em>
476 for compilation or execution (thus, the package must
477 not declare a "Depends", "Recommends", or
478 "Build-Depends" relationship on a non-<em>main</em>
482 must not be so buggy that we refuse to support them,
486 must meet all policy requirements presented in this
495 <heading>The contrib archive area</heading>
498 Every package in <em>contrib</em> must comply with the DFSG.
502 In addition, the packages in <em>contrib</em>
503 <list compact="compact">
505 must not be so buggy that we refuse to support them,
509 must meet all policy requirements presented in this
517 Examples of packages which would be included in
518 <em>contrib</em> are:
519 <list compact="compact">
521 free packages which require <em>contrib</em>,
522 <em>non-free</em> packages or packages which are not
523 in our archive at all for compilation or execution,
527 wrapper packages or other sorts of free accessories for
534 <sect1 id="non-free">
535 <heading>The non-free archive area</heading>
538 Packages must be placed in <em>non-free</em> if they are
539 not compliant with the DFSG or are encumbered by patents
540 or other legal issues that make their distribution
545 In addition, the packages in <em>non-free</em>
546 <list compact="compact">
548 must not be so buggy that we refuse to support them,
552 must meet all policy requirements presented in this
553 manual that it is possible for them to meet.
555 It is possible that there are policy
556 requirements which the package is unable to
557 meet, for example, if the source is
558 unavailable. These situations will need to be
559 handled on a case-by-case basis.
568 <sect id="pkgcopyright">
569 <heading>Copyright considerations</heading>
572 Every package must be accompanied by a verbatim copy of its
573 copyright information and distribution license in the file
574 <file>/usr/share/doc/<var>package</var>/copyright</file>
575 (see <ref id="copyrightfile"> for further details).
579 We reserve the right to restrict files from being included
580 anywhere in our archives if
581 <list compact="compact">
583 their use or distribution would break a law,
586 there is an ethical conflict in their distribution or
590 we would have to sign a license for them, or
593 their distribution would conflict with other project
600 Programs whose authors encourage the user to make
601 donations are fine for the main distribution, provided
602 that the authors do not claim that not donating is
603 immoral, unethical, illegal or something similar; in such
604 a case they must go in <em>non-free</em>.
608 Packages whose copyright permission notices (or patent
609 problems) do not even allow redistribution of binaries
610 only, and where no special permission has been obtained,
611 must not be placed on the Debian FTP site and its mirrors
616 Note that under international copyright law (this applies
617 in the United States, too), <em>no</em> distribution or
618 modification of a work is allowed without an explicit
619 notice saying so. Therefore a program without a copyright
620 notice <em>is</em> copyrighted and you may not do anything
621 to it without risking being sued! Likewise if a program
622 has a copyright notice but no statement saying what is
623 permitted then nothing is permitted.
627 Many authors are unaware of the problems that restrictive
628 copyrights (or lack of copyright notices) can cause for
629 the users of their supposedly-free software. It is often
630 worthwhile contacting such authors diplomatically to ask
631 them to modify their license terms. However, this can be a
632 politically difficult thing to do and you should ask for
633 advice on the <tt>debian-legal</tt> mailing list first, as
638 When in doubt about a copyright, send mail to
639 <email>debian-legal@lists.debian.org</email>. Be prepared
640 to provide us with the copyright statement. Software
641 covered by the GPL, public domain software and BSD-like
642 copyrights are safe; be wary of the phrases "commercial
643 use prohibited" and "distribution restricted".
647 <sect id="subsections">
648 <heading>Sections</heading>
651 The packages in the archive areas <em>main</em>,
652 <em>contrib</em> and <em>non-free</em> are grouped further into
653 <em>sections</em> to simplify handling.
657 The archive area and section for each package should be
658 specified in the package's <tt>Section</tt> control record (see
659 <ref id="f-Section">). However, the maintainer of the Debian
660 archive may override this selection to ensure the consistency of
661 the Debian distribution. The <tt>Section</tt> field should be
663 <list compact="compact">
665 <em>section</em> if the package is in the
666 <em>main</em> archive area,
669 <em>area/section</em> if the package is in
670 the <em>contrib</em> or <em>non-free</em>
677 The Debian archive maintainers provide the authoritative
678 list of sections. At present, they are:
679 <em>admin</em>, <em>cli-mono</em>, <em>comm</em>, <em>database</em>,
680 <em>devel</em>, <em>debug</em>, <em>doc</em>, <em>editors</em>,
681 <em>electronics</em>, <em>embedded</em>, <em>fonts</em>,
682 <em>games</em>, <em>gnome</em>, <em>graphics</em>, <em>gnu-r</em>,
683 <em>gnustep</em>, <em>hamradio</em>, <em>haskell</em>,
684 <em>httpd</em>, <em>interpreters</em>, <em>java</em>, <em>kde</em>,
685 <em>kernel</em>, <em>libs</em>, <em>libdevel</em>, <em>lisp</em>,
686 <em>localization</em>, <em>mail</em>, <em>math</em>, <em>misc</em>,
687 <em>net</em>, <em>news</em>, <em>ocaml</em>, <em>oldlibs</em>,
688 <em>otherosfs</em>, <em>perl</em>, <em>php</em>, <em>python</em>,
689 <em>ruby</em>, <em>science</em>, <em>shells</em>, <em>sound</em>,
690 <em>tex</em>, <em>text</em>, <em>utils</em>, <em>vcs</em>,
691 <em>video</em>, <em>web</em>, <em>x11</em>, <em>xfce</em>,
692 <em>zope</em>. The additional section <em>debian-installer</em>
693 contains special packages used by the installer and is not used
694 for normal Debian packages.
698 For more information about the sections and their definitions,
699 see the <url id="http://packages.debian.org/unstable/"
700 name="list of sections in unstable">.
704 <sect id="priorities">
705 <heading>Priorities</heading>
708 Each package should have a <em>priority</em> value, which is
709 included in the package's <em>control record</em>
710 (see <ref id="f-Priority">).
711 This information is used by the Debian package management tools to
712 separate high-priority packages from less-important packages.
716 The following <em>priority levels</em> are recognized by the
717 Debian package management tools.
719 <tag><tt>required</tt></tag>
721 Packages which are necessary for the proper
722 functioning of the system (usually, this means that
723 dpkg functionality depends on these packages).
724 Removing a <tt>required</tt> package may cause your
725 system to become totally broken and you may not even
726 be able to use <prgn>dpkg</prgn> to put things back,
727 so only do so if you know what you are doing. Systems
728 with only the <tt>required</tt> packages are probably
729 unusable, but they do have enough functionality to
730 allow the sysadmin to boot and install more software.
732 <tag><tt>important</tt></tag>
734 Important programs, including those which one would
735 expect to find on any Unix-like system. If the
736 expectation is that an experienced Unix person who
737 found it missing would say "What on earth is going on,
738 where is <prgn>foo</prgn>?", it must be an
739 <tt>important</tt> package.<footnote>
740 This is an important criterion because we are
741 trying to produce, amongst other things, a free
744 Other packages without which the system will not run
745 well or be usable must also have priority
746 <tt>important</tt>. This does
747 <em>not</em> include Emacs, the X Window System, TeX
748 or any other large applications. The
749 <tt>important</tt> packages are just a bare minimum of
750 commonly-expected and necessary tools.
752 <tag><tt>standard</tt></tag>
754 These packages provide a reasonably small but not too
755 limited character-mode system. This is what will be
756 installed by default if the user doesn't select anything
757 else. It doesn't include many large applications.
759 <tag><tt>optional</tt></tag>
761 (In a sense everything that isn't required is
762 optional, but that's not what is meant here.) This is
763 all the software that you might reasonably want to
764 install if you didn't know what it was and don't have
765 specialized requirements. This is a much larger system
766 and includes the X Window System, a full TeX
767 distribution, and many applications. Note that
768 optional packages should not conflict with each other.
770 <tag><tt>extra</tt></tag>
772 This contains all packages that conflict with others
773 with required, important, standard or optional
774 priorities, or are only likely to be useful if you
775 already know what they are or have specialized
776 requirements (such as packages containing only detached
783 Packages must not depend on packages with lower priority
784 values (excluding build-time dependencies). In order to
785 ensure this, the priorities of one or more packages may need
794 <heading>Binary packages</heading>
797 The Debian GNU/Linux distribution is based on the Debian
798 package management system, called <prgn>dpkg</prgn>. Thus,
799 all packages in the Debian distribution must be provided
800 in the <tt>.deb</tt> file format.
804 <heading>The package name</heading>
807 Every package must have a name that's unique within the Debian
812 The package name is included in the control field
813 <tt>Package</tt>, the format of which is described
814 in <ref id="f-Package">.
815 The package name is also included as a part of the file name
816 of the <tt>.deb</tt> file.
821 <heading>The version of a package</heading>
824 Every package has a version number recorded in its
825 <tt>Version</tt> control file field, described in
826 <ref id="f-Version">.
830 The package management system imposes an ordering on version
831 numbers, so that it can tell whether packages are being up- or
832 downgraded and so that package system front end applications
833 can tell whether a package it finds available is newer than
834 the one installed on the system. The version number format
835 has the most significant parts (as far as comparison is
836 concerned) at the beginning.
840 If an upstream package has problematic version numbers they
841 should be converted to a sane form for use in the
842 <tt>Version</tt> field.
846 <heading>Version numbers based on dates</heading>
849 In general, Debian packages should use the same version
850 numbers as the upstream sources.
854 However, in some cases where the upstream version number is
855 based on a date (e.g., a development "snapshot" release) the
856 package management system cannot handle these version
857 numbers without epochs. For example, dpkg will consider
858 "96May01" to be greater than "96Dec24".
862 To prevent having to use epochs for every new upstream
863 version, the date based portion of the version number
864 should be changed to the following format in such cases:
865 "19960501", "19961224". It is up to the maintainer whether
866 they want to bother the upstream maintainer to change
867 the version numbers upstream, too.
871 Note that other version formats based on dates which are
872 parsed correctly by the package management system should
873 <em>not</em> be changed.
877 Native Debian packages (i.e., packages which have been
878 written especially for Debian) whose version numbers include
879 dates should always use the "YYYYMMDD" format.
886 <heading>The maintainer of a package</heading>
889 Every package must have a Debian maintainer (the
890 maintainer may be one person or a group of people
891 reachable from a common email address, such as a mailing
892 list). The maintainer is responsible for ensuring that
893 the package is placed in the appropriate distributions.
897 The maintainer must be specified in the
898 <tt>Maintainer</tt> control field with their correct name
899 and a working email address. If one person maintains
900 several packages, they should try to avoid having
901 different forms of their name and email address in
902 the <tt>Maintainer</tt> fields of those packages.
906 The format of the <tt>Maintainer</tt> control field is
907 described in <ref id="f-Maintainer">.
911 If the maintainer of a package quits from the Debian
912 project, "Debian QA Group"
913 <email>packages@qa.debian.org</email> takes over the
914 maintainer-ship of the package until someone else
915 volunteers for that task. These packages are called
916 <em>orphaned packages</em>.<footnote>
917 The detailed procedure for doing this gracefully can
918 be found in the Debian Developer's Reference,
919 see <ref id="related">.
924 <sect id="descriptions">
925 <heading>The description of a package</heading>
928 Every Debian package must have an extended description
929 stored in the appropriate field of the control record.
930 The technical information about the format of the
931 <tt>Description</tt> field is in <ref id="f-Description">.
935 The description should describe the package (the program) to a
936 user (system administrator) who has never met it before so that
937 they have enough information to decide whether they want to
938 install it. This description should not just be copied verbatim
939 from the program's documentation.
943 Put important information first, both in the synopsis and
944 extended description. Sometimes only the first part of the
945 synopsis or of the description will be displayed. You can
946 assume that there will usually be a way to see the whole
947 extended description.
951 The description should also give information about the
952 significant dependencies and conflicts between this package
953 and others, so that the user knows why these dependencies and
954 conflicts have been declared.
958 Instructions for configuring or using the package should
959 not be included (that is what installation scripts,
960 manual pages, info files, etc., are for). Copyright
961 statements and other administrivia should not be included
962 either (that is what the copyright file is for).
965 <sect1 id="synopsis"><heading>The single line synopsis</heading>
968 The single line synopsis should be kept brief - certainly
973 Do not include the package name in the synopsis line. The
974 display software knows how to display this already, and you
975 do not need to state it. Remember that in many situations
976 the user may only see the synopsis line - make it as
977 informative as you can.
982 <sect1 id="extendeddesc"><heading>The extended description</heading>
985 Do not try to continue the single line synopsis into the
986 extended description. This will not work correctly when
987 the full description is displayed, and makes no sense
988 where only the summary (the single line synopsis) is
993 The extended description should describe what the package
994 does and how it relates to the rest of the system (in terms
995 of, for example, which subsystem it is which part of).
999 The description field needs to make sense to anyone, even
1000 people who have no idea about any of the things the
1001 package deals with.<footnote>
1002 The blurb that comes with a program in its
1003 announcements and/or <prgn>README</prgn> files is
1004 rarely suitable for use in a description. It is
1005 usually aimed at people who are already in the
1006 community where the package is used.
1015 <heading>Dependencies</heading>
1018 Every package must specify the dependency information
1019 about other packages that are required for the first to
1024 For example, a dependency entry must be provided for any
1025 shared libraries required by a dynamically-linked executable
1026 binary in a package.
1030 Packages are not required to declare any dependencies they
1031 have on other packages which are marked <tt>Essential</tt>
1032 (see below), and should not do so unless they depend on a
1033 particular version of that package.<footnote>
1035 Essential is needed in part to avoid unresolvable dependency
1036 loops on upgrade. If packages add unnecessary dependencies
1037 on packages in this set, the chances that there
1038 <strong>will</strong> be an unresolvable dependency loop
1039 caused by forcing these Essential packages to be configured
1040 first before they need to be is greatly increased. It also
1041 increases the chances that frontends will be unable to
1042 <strong>calculate</strong> an upgrade path, even if one
1046 Also, functionality is rarely ever removed from the
1047 Essential set, but <em>packages</em> have been removed from
1048 the Essential set when the functionality moved to a
1049 different package. So depending on these packages <em>just
1050 in case</em> they stop being essential does way more harm
1057 Sometimes, a package requires another package to be installed
1058 <em>and</em> configured before it can be installed. In this
1059 case, you must specify a <tt>Pre-Depends</tt> entry for
1064 You should not specify a <tt>Pre-Depends</tt> entry for a
1065 package before this has been discussed on the
1066 <tt>debian-devel</tt> mailing list and a consensus about
1067 doing that has been reached.
1071 The format of the package interrelationship control fields is
1072 described in <ref id="relationships">.
1076 <sect id="virtual_pkg">
1077 <heading>Virtual packages</heading>
1080 Sometimes, there are several packages which offer
1081 more-or-less the same functionality. In this case, it's
1082 useful to define a <em>virtual package</em> whose name
1083 describes that common functionality. (The virtual
1084 packages only exist logically, not physically; that's why
1085 they are called <em>virtual</em>.) The packages with this
1086 particular function will then <em>provide</em> the virtual
1087 package. Thus, any other package requiring that function
1088 can simply depend on the virtual package without having to
1089 specify all possible packages individually.
1093 All packages should use virtual package names where
1094 appropriate, and arrange to create new ones if necessary.
1095 They should not use virtual package names (except privately,
1096 amongst a cooperating group of packages) unless they have
1097 been agreed upon and appear in the list of virtual package
1098 names. (See also <ref id="virtual">)
1102 The latest version of the authoritative list of virtual
1103 package names can be found in the <tt>debian-policy</tt> package.
1104 It is also available from the Debian web mirrors at
1105 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1106 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1110 The procedure for updating the list is described in the preface
1117 <heading>Base system</heading>
1120 The <tt>base system</tt> is a minimum subset of the Debian
1121 GNU/Linux system that is installed before everything else
1122 on a new system. Only very few packages are allowed to form
1123 part of the base system, in order to keep the required disk
1128 The base system consists of all those packages with priority
1129 <tt>required</tt> or <tt>important</tt>. Many of them will
1130 be tagged <tt>essential</tt> (see below).
1135 <heading>Essential packages</heading>
1138 Essential is defined as the minimal set of functionality that
1139 must be available and usable on the system at all times, even
1140 when packages are in an unconfigured (but unpacked) state.
1141 Packages are tagged <tt>essential</tt> for a system using the
1142 <tt>Essential</tt> control file field. The format of the
1143 <tt>Essential</tt> control field is described in <ref
1148 Since these packages cannot be easily removed (one has to
1149 specify an extra <em>force option</em> to
1150 <prgn>dpkg</prgn> to do so), this flag must not be used
1151 unless absolutely necessary. A shared library package
1152 must not be tagged <tt>essential</tt>; dependencies will
1153 prevent its premature removal, and we need to be able to
1154 remove it when it has been superseded.
1158 Since dpkg will not prevent upgrading of other packages
1159 while an <tt>essential</tt> package is in an unconfigured
1160 state, all <tt>essential</tt> packages must supply all of
1161 their core functionality even when unconfigured. If the
1162 package cannot satisfy this requirement it must not be
1163 tagged as essential, and any packages depending on this
1164 package must instead have explicit dependency fields as
1169 Maintainers should take great care in adding any programs,
1170 interfaces, or functionality to <tt>essential</tt> packages.
1171 Packages may assume that functionality provided by
1172 <tt>essential</tt> packages is always available without
1173 declaring explicit dependencies, which means that removing
1174 functionality from the Essential set is very difficult and is
1175 almost never done. Any capability added to an
1176 <tt>essential</tt> package therefore creates an obligation to
1177 support that capability as part of the Essential set in
1182 You must not tag any packages <tt>essential</tt> before
1183 this has been discussed on the <tt>debian-devel</tt>
1184 mailing list and a consensus about doing that has been
1189 <sect id="maintscripts">
1190 <heading>Maintainer Scripts</heading>
1193 The package installation scripts should avoid producing
1194 output which is unnecessary for the user to see and
1195 should rely on <prgn>dpkg</prgn> to stave off boredom on
1196 the part of a user installing many packages. This means,
1197 amongst other things, using the <tt>--quiet</tt> option on
1198 <prgn>install-info</prgn>.
1202 Errors which occur during the execution of an installation
1203 script must be checked and the installation must not
1204 continue after an error.
1208 Note that in general <ref id="scripts"> applies to package
1209 maintainer scripts, too.
1213 You should not use <prgn>dpkg-divert</prgn> on a file
1214 belonging to another package without consulting the
1215 maintainer of that package first.
1219 All packages which supply an instance of a common command
1220 name (or, in general, filename) should generally use
1221 <prgn>update-alternatives</prgn>, so that they may be
1222 installed together. If <prgn>update-alternatives</prgn>
1223 is not used, then each package must use
1224 <tt>Conflicts</tt> to ensure that other packages are
1225 de-installed. (In this case, it may be appropriate to
1226 specify a conflict against earlier versions of something
1227 that previously did not use
1228 <prgn>update-alternatives</prgn>; this is an exception to
1229 the usual rule that versioned conflicts should be
1233 <sect1 id="maintscriptprompt">
1234 <heading>Prompting in maintainer scripts</heading>
1236 Package maintainer scripts may prompt the user if
1237 necessary. Prompting must be done by communicating
1238 through a program, such as <prgn>debconf</prgn>, which
1239 conforms to the Debian Configuration Management
1240 Specification, version 2 or higher.
1244 Packages which are essential, or which are dependencies of
1245 essential packages, may fall back on another prompting method
1246 if no such interface is available when they are executed.
1250 The Debian Configuration Management Specification is included
1251 in the <file>debconf_specification</file> files in the
1252 <package>debian-policy</package> package.
1253 It is also available from the Debian web mirrors at
1254 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1255 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1259 Packages which use the Debian Configuration Management
1260 Specification may contain an additional
1261 <prgn>config</prgn> script and a <tt>templates</tt>
1262 file in their control archive<footnote>
1263 The control.tar.gz inside the .deb.
1264 See <manref name="deb" section="5">.
1266 The <prgn>config</prgn> script might be run before the
1267 <prgn>preinst</prgn> script, and before the package is unpacked
1268 or any of its dependencies or pre-dependencies are satisfied.
1269 Therefore it must work using only the tools present in
1270 <em>essential</em> packages.<footnote>
1271 <package>Debconf</package> or another tool that
1272 implements the Debian Configuration Management
1273 Specification will also be installed, and any
1274 versioned dependencies on it will be satisfied
1275 before preconfiguration begins.
1280 Packages which use the Debian Configuration Management
1281 Specification must allow for translation of their user-visible
1282 messages by using a gettext-based system such as the one
1283 provided by the <package>po-debconf</package> package.
1287 Packages should try to minimize the amount of prompting
1288 they need to do, and they should ensure that the user
1289 will only ever be asked each question once. This means
1290 that packages should try to use appropriate shared
1291 configuration files (such as <file>/etc/papersize</file> and
1292 <file>/etc/news/server</file>), and shared
1293 <package>debconf</package> variables rather than each
1294 prompting for their own list of required pieces of
1299 It also means that an upgrade should not ask the same
1300 questions again, unless the user has used
1301 <tt>dpkg --purge</tt> to remove the package's configuration.
1302 The answers to configuration questions should be stored in an
1303 appropriate place in <file>/etc</file> so that the user can
1304 modify them, and how this has been done should be
1309 If a package has a vitally important piece of
1310 information to pass to the user (such as "don't run me
1311 as I am, you must edit the following configuration files
1312 first or you risk your system emitting badly-formatted
1313 messages"), it should display this in the
1314 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1315 prompt the user to hit return to acknowledge the
1316 message. Copyright messages do not count as vitally
1317 important (they belong in
1318 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1319 neither do instructions on how to use a program (these
1320 should be in on-line documentation, where all the users
1325 Any necessary prompting should almost always be confined
1326 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1327 script. If it is done in the <prgn>postinst</prgn>, it
1328 should be protected with a conditional so that
1329 unnecessary prompting doesn't happen if a package's
1330 installation fails and the <prgn>postinst</prgn> is
1331 called with <tt>abort-upgrade</tt>,
1332 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1342 <heading>Source packages</heading>
1344 <sect id="standardsversion">
1345 <heading>Standards conformance</heading>
1348 Source packages should specify the most recent version number
1349 of this policy document with which your package complied
1350 when it was last updated.
1354 This information may be used to file bug reports
1355 automatically if your package becomes too much out of date.
1359 The version is specified in the <tt>Standards-Version</tt>
1361 The format of the <tt>Standards-Version</tt> field is
1362 described in <ref id="f-Standards-Version">.
1366 You should regularly, and especially if your package has
1367 become out of date, check for the newest Policy Manual
1368 available and update your package, if necessary. When your
1369 package complies with the new standards you should update the
1370 <tt>Standards-Version</tt> source package field and
1371 release it.<footnote>
1372 See the file <file>upgrading-checklist</file> for
1373 information about policy which has changed between
1374 different versions of this document.
1380 <sect id="pkg-relations">
1381 <heading>Package relationships</heading>
1384 Source packages should specify which binary packages they
1385 require to be installed or not to be installed in order to
1386 build correctly. For example, if building a package
1387 requires a certain compiler, then the compiler should be
1388 specified as a build-time dependency.
1392 It is not necessary to explicitly specify build-time
1393 relationships on a minimal set of packages that are always
1394 needed to compile, link and put in a Debian package a
1395 standard "Hello World!" program written in C or C++. The
1396 required packages are called <em>build-essential</em>, and
1397 an informational list can be found in
1398 <file>/usr/share/doc/build-essential/list</file> (which is
1399 contained in the <tt>build-essential</tt>
1402 <list compact="compact">
1404 This allows maintaining the list separately
1405 from the policy documents (the list does not
1406 need the kind of control that the policy
1410 Having a separate package allows one to install
1411 the build-essential packages on a machine, as
1412 well as allowing other packages such as tasks to
1413 require installation of the build-essential
1414 packages using the depends relation.
1417 The separate package allows bug reports against
1418 the list to be categorized separately from
1419 the policy management process in the BTS.
1426 When specifying the set of build-time dependencies, one
1427 should list only those packages explicitly required by the
1428 build. It is not necessary to list packages which are
1429 required merely because some other package in the list of
1430 build-time dependencies depends on them.<footnote>
1431 The reason for this is that dependencies change, and
1432 you should list all those packages, and <em>only</em>
1433 those packages that <em>you</em> need directly. What
1434 others need is their business. For example, if you
1435 only link against <file>libimlib</file>, you will need to
1436 build-depend on <package>libimlib2-dev</package> but
1437 not against any <tt>libjpeg*</tt> packages, even
1438 though <tt>libimlib2-dev</tt> currently depends on
1439 them: installation of <package>libimlib2-dev</package>
1440 will automatically ensure that all of its run-time
1441 dependencies are satisfied.
1446 If build-time dependencies are specified, it must be
1447 possible to build the package and produce working binaries
1448 on a system with only essential and build-essential
1449 packages installed and also those required to satisfy the
1450 build-time relationships (including any implied
1451 relationships). In particular, this means that version
1452 clauses should be used rigorously in build-time
1453 relationships so that one cannot produce bad or
1454 inconsistently configured packages when the relationships
1455 are properly satisfied.
1459 <ref id="relationships"> explains the technical details.
1464 <heading>Changes to the upstream sources</heading>
1467 If changes to the source code are made that are not
1468 specific to the needs of the Debian system, they should be
1469 sent to the upstream authors in whatever form they prefer
1470 so as to be included in the upstream version of the
1475 If you need to configure the package differently for
1476 Debian or for Linux, and the upstream source doesn't
1477 provide a way to do so, you should add such configuration
1478 facilities (for example, a new <prgn>autoconf</prgn> test
1479 or <tt>#define</tt>) and send the patch to the upstream
1480 authors, with the default set to the way they originally
1481 had it. You can then easily override the default in your
1482 <file>debian/rules</file> or wherever is appropriate.
1486 You should make sure that the <prgn>configure</prgn> utility
1487 detects the correct architecture specification string
1488 (refer to <ref id="arch-spec"> for details).
1492 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1493 <prgn>configure</prgn> scripts are used, you should edit the
1494 <file>.in</file> files rather than editing the
1495 <prgn>Makefile</prgn> directly. This allows the user to
1496 reconfigure the package if necessary. You should
1497 <em>not</em> configure the package and edit the generated
1498 <prgn>Makefile</prgn>! This makes it impossible for someone
1499 else to later reconfigure the package without losing the
1505 <sect id="dpkgchangelog">
1506 <heading>Debian changelog: <file>debian/changelog</file></heading>
1509 Changes in the Debian version of the package should be
1510 briefly explained in the Debian changelog file
1511 <file>debian/changelog</file>.<footnote>
1513 Mistakes in changelogs are usually best rectified by
1514 making a new changelog entry rather than "rewriting
1515 history" by editing old changelog entries.
1518 This includes modifications
1519 made in the Debian package compared to the upstream one
1520 as well as other changes and updates to the package.
1522 Although there is nothing stopping an author who is also
1523 the Debian maintainer from using this changelog for all
1524 their changes, it will have to be renamed if the Debian
1525 and upstream maintainers become different people. In such
1526 a case, however, it might be better to maintain the package
1527 as a non-native package.
1532 The format of the <file>debian/changelog</file> allows the
1533 package building tools to discover which version of the package
1534 is being built and find out other release-specific information.
1538 That format is a series of entries like this:
1540 <example compact="compact">
1541 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1543 [optional blank line(s), stripped]
1545 * <var>change details</var>
1546 <var>more change details</var>
1548 [blank line(s), included in output of dpkg-parsechangelog]
1550 * <var>even more change details</var>
1552 [optional blank line(s), stripped]
1554 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1559 <var>package</var> and <var>version</var> are the source
1560 package name and version number.
1564 <var>distribution(s)</var> lists the distributions where
1565 this version should be installed when it is uploaded - it
1566 is copied to the <tt>Distribution</tt> field in the
1567 <file>.changes</file> file. See <ref id="f-Distribution">.
1571 <var>urgency</var> is the value for the <tt>Urgency</tt>
1572 field in the <file>.changes</file> file for the upload
1573 (see <ref id="f-Urgency">). It is not possible to specify
1574 an urgency containing commas; commas are used to separate
1575 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1576 <prgn>dpkg</prgn> changelog format (though there is
1577 currently only one useful <var>keyword</var>,
1582 The change details may in fact be any series of lines
1583 starting with at least two spaces, but conventionally each
1584 change starts with an asterisk and a separating space and
1585 continuation lines are indented so as to bring them in
1586 line with the start of the text above. Blank lines may be
1587 used here to separate groups of changes, if desired.
1591 If this upload resolves bugs recorded in the Bug Tracking
1592 System (BTS), they may be automatically closed on the
1593 inclusion of this package into the Debian archive by
1594 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1595 in the change details.<footnote>
1596 To be precise, the string should match the following
1597 Perl regular expression:
1599 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1601 Then all of the bug numbers listed will be closed by the
1602 archive maintenance script (<prgn>katie</prgn>) using the
1603 <var>version</var> of the changelog entry.
1605 This information is conveyed via the <tt>Closes</tt> field
1606 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1610 The maintainer name and email address used in the changelog
1611 should be the details of the person uploading <em>this</em>
1612 version. They are <em>not</em> necessarily those of the
1613 usual package maintainer. The information here will be
1614 copied to the <tt>Changed-By</tt> field in the
1615 <tt>.changes</tt> file (see <ref id="f-Changed-By">),
1616 and then later used to send an acknowledgement when the
1617 upload has been installed.
1621 The <var>date</var> has the following format<footnote>
1622 This is the same as the format generated by <tt>date
1624 </footnote> (compatible and with the same semantics of
1625 RFC 2822 and RFC 5322):
1626 <example>day-of-week, dd month yyyy hh:mm:ss +zzzz</example>
1628 <list compact="compact">
1630 day-of week is one of: Mon, Tue, Wed, Thu, Fri, Sat, Sun
1633 dd is a one- or two-digit day of the month (01-31)
1636 month is one of: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug,
1639 <item>yyyy is the four-digit year (e.g. 2010)</item>
1640 <item>hh is the two-digit hour (00-23)</item>
1641 <item>mm is the two-digit minutes (00-59)</item>
1642 <item>ss is the two-digit seconds (00-60)</item>
1644 +zzzz or -zzzz is the the time zone offset from Coordinated
1645 Universal Time (UTC). "+" indicates that the time is ahead
1646 of (i.e., east of) UTC and "-" indicates that the time is
1647 behind (i.e., west of) UTC. The first two digits indicate
1648 the hour difference from UTC and the last two digits
1649 indicate the number of additional minutes difference from
1650 UTC. The last two digits must be in the range 00-59.
1656 The first "title" line with the package name must start
1657 at the left hand margin. The "trailer" line with the
1658 maintainer and date details must be preceded by exactly
1659 one space. The maintainer details and the date must be
1660 separated by exactly two spaces.
1664 The entire changelog must be encoded in UTF-8.
1668 For more information on placement of the changelog files
1669 within binary packages, please see <ref id="changelogs">.
1673 <sect id="dpkgcopyright">
1674 <heading>Copyright: <file>debian/copyright</file></heading>
1676 Every package must be accompanied by a verbatim copy of its
1677 copyright information and distribution license in the file
1678 <file>/usr/share/doc/<var>package</var>/copyright</file>
1679 (see <ref id="copyrightfile"> for further details). Also see
1680 <ref id="pkgcopyright"> for further considerations related
1681 to copyrights for packages.
1685 <heading>Error trapping in makefiles</heading>
1688 When <prgn>make</prgn> invokes a command in a makefile
1689 (including your package's upstream makefiles and
1690 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1691 means that <prgn>sh</prgn>'s usual bad error handling
1692 properties apply: if you include a miniature script as one
1693 of the commands in your makefile you'll find that if you
1694 don't do anything about it then errors are not detected
1695 and <prgn>make</prgn> will blithely continue after
1700 Every time you put more than one shell command (this
1701 includes using a loop) in a makefile command you
1702 must make sure that errors are trapped. For
1703 simple compound commands, such as changing directory and
1704 then running a program, using <tt>&&</tt> rather
1705 than semicolon as a command separator is sufficient. For
1706 more complex commands including most loops and
1707 conditionals you should include a separate <tt>set -e</tt>
1708 command at the start of every makefile command that's
1709 actually one of these miniature shell scripts.
1713 <sect id="timestamps">
1714 <heading>Time Stamps</heading>
1716 Maintainers should preserve the modification times of the
1717 upstream source files in a package, as far as is reasonably
1719 The rationale is that there is some information conveyed
1720 by knowing the age of the file, for example, you could
1721 recognize that some documentation is very old by looking
1722 at the modification time, so it would be nice if the
1723 modification time of the upstream source would be
1729 <sect id="restrictions">
1730 <heading>Restrictions on objects in source packages</heading>
1733 The source package may not contain any hard links<footnote>
1735 This is not currently detected when building source
1736 packages, but only when extracting
1740 Hard links may be permitted at some point in the
1741 future, but would require a fair amount of
1744 </footnote>, device special files, sockets or setuid or
1745 setgid files.<footnote>
1746 Setgid directories are allowed.
1751 <sect id="debianrules">
1752 <heading>Main building script: <file>debian/rules</file></heading>
1755 This file must be an executable makefile, and contains the
1756 package-specific recipes for compiling the package and
1757 building binary package(s) from the source.
1761 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1762 so that it can be invoked by saying its name rather than
1763 invoking <prgn>make</prgn> explicitly. That is, invoking
1764 either of <tt>make -f debian/rules <em>args...</em></tt>
1765 or <tt>./debian/rules <em>args...</em></tt> must result in
1770 Since an interactive <file>debian/rules</file> script makes it
1771 impossible to auto-compile that package and also makes it
1772 hard for other people to reproduce the same binary
1773 package, all <em>required targets</em> must be
1774 non-interactive. At a minimum, required targets are the
1775 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1776 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1777 <em>binary-indep</em>, and <em>build</em>. It also follows
1778 that any target that these targets depend on must also be
1783 The targets are as follows (required unless stated otherwise):
1785 <tag><tt>build</tt></tag>
1788 The <tt>build</tt> target should perform all the
1789 configuration and compilation of the package.
1790 If a package has an interactive pre-build
1791 configuration routine, the Debian source package
1792 must either be built after this has taken place (so
1793 that the binary package can be built without rerunning
1794 the configuration) or the configuration routine
1795 modified to become non-interactive. (The latter is
1796 preferable if there are architecture-specific features
1797 detected by the configuration routine.)
1801 For some packages, notably ones where the same
1802 source tree is compiled in different ways to produce
1803 two binary packages, the <tt>build</tt> target
1804 does not make much sense. For these packages it is
1805 good enough to provide two (or more) targets
1806 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1807 for each of the ways of building the package, and a
1808 <tt>build</tt> target that does nothing. The
1809 <tt>binary</tt> target will have to build the
1810 package in each of the possible ways and make the
1811 binary package out of each.
1815 The <tt>build</tt> target must not do anything
1816 that might require root privilege.
1820 The <tt>build</tt> target may need to run the
1821 <tt>clean</tt> target first - see below.
1825 When a package has a configuration and build routine
1826 which takes a long time, or when the makefiles are
1827 poorly designed, or when <tt>build</tt> needs to
1828 run <tt>clean</tt> first, it is a good idea to
1829 <tt>touch build</tt> when the build process is
1830 complete. This will ensure that if <tt>debian/rules
1831 build</tt> is run again it will not rebuild the whole
1833 Another common way to do this is for <tt>build</tt>
1834 to depend on <prgn>build-stamp</prgn> and to do
1835 nothing else, and for the <prgn>build-stamp</prgn>
1836 target to do the building and to <tt>touch
1837 build-stamp</tt> on completion. This is
1838 especially useful if the build routine creates a
1839 file or directory called <tt>build</tt>; in such a
1840 case, <tt>build</tt> will need to be listed as
1841 a phony target (i.e., as a dependency of the
1842 <tt>.PHONY</tt> target). See the documentation of
1843 <prgn>make</prgn> for more information on phony
1849 <tag><tt>build-arch</tt> (optional),
1850 <tt>build-indep</tt> (optional)
1854 A package may also provide both of the targets
1855 <tt>build-arch</tt> and <tt>build-indep</tt>.
1856 The <tt>build-arch</tt> target, if provided, should
1857 perform all the configuration and compilation required for
1858 producing all architecture-dependant binary packages
1859 (those packages for which the body of the
1860 <tt>Architecture</tt> field in <tt>debian/control</tt> is
1861 not <tt>all</tt>). Similarly, the <tt>build-indep</tt>
1862 target, if provided, should perform all the configuration
1863 and compilation required for producing all
1864 architecture-independent binary packages (those packages
1865 for which the body of the <tt>Architecture</tt> field
1866 in <tt>debian/control</tt> is <tt>all</tt>).
1867 The <tt>build</tt> target should depend on those of the
1868 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1869 are provided in the rules file.<footnote>
1870 The intent of this split is so that binary-only builds
1871 need not install the dependencies required for
1872 the <tt>build-indep</tt> target. However, this is not
1873 yet used in practice since <tt>dpkg-buildpackage
1874 -B</tt>, and therefore the autobuilders,
1875 invoke <tt>build</tt> rather than <tt>build-arch</tt>
1876 due to the difficulties in determining whether the
1877 optional <tt>build-arch</tt> target exists.
1882 If one or both of the targets <tt>build-arch</tt> and
1883 <tt>build-indep</tt> are not provided, then invoking
1884 <file>debian/rules</file> with one of the not-provided
1885 targets as arguments should produce a exit status code
1886 of 2. Usually this is provided automatically by make
1887 if the target is missing.
1891 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1892 must not do anything that might require root privilege.
1896 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1897 <tt>binary-indep</tt>
1901 The <tt>binary</tt> target must be all that is
1902 necessary for the user to build the binary package(s)
1903 produced from this source package. It is
1904 split into two parts: <prgn>binary-arch</prgn> builds
1905 the binary packages which are specific to a particular
1906 architecture, and <tt>binary-indep</tt> builds
1907 those which are not.
1910 <tt>binary</tt> may be (and commonly is) a target with
1911 no commands which simply depends on
1912 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1915 Both <tt>binary-*</tt> targets should depend on the
1916 <tt>build</tt> target, or on the appropriate
1917 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1918 provided, so that the package is built if it has not
1919 been already. It should then create the relevant
1920 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1921 make their control files and <prgn>dpkg-deb</prgn> to
1922 build them and place them in the parent of the top
1927 Both the <tt>binary-arch</tt> and
1928 <tt>binary-indep</tt> targets <em>must</em> exist.
1929 If one of them has nothing to do (which will always be
1930 the case if the source generates only a single binary
1931 package, whether architecture-dependent or not), it
1932 must still exist and must always succeed.
1936 The <tt>binary</tt> targets must be invoked as
1938 The <prgn>fakeroot</prgn> package often allows one
1939 to build a package correctly even without being
1945 <tag><tt>clean</tt></tag>
1948 This must undo any effects that the <tt>build</tt>
1949 and <tt>binary</tt> targets may have had, except
1950 that it should leave alone any output files created in
1951 the parent directory by a run of a <tt>binary</tt>
1956 If a <tt>build</tt> file is touched at the end of
1957 the <tt>build</tt> target, as suggested above, it
1958 should be removed as the first action that
1959 <tt>clean</tt> performs, so that running
1960 <tt>build</tt> again after an interrupted
1961 <tt>clean</tt> doesn't think that everything is
1966 The <tt>clean</tt> target may need to be
1967 invoked as root if <tt>binary</tt> has been
1968 invoked since the last <tt>clean</tt>, or if
1969 <tt>build</tt> has been invoked as root (since
1970 <tt>build</tt> may create directories, for
1975 <tag><tt>get-orig-source</tt> (optional)</tag>
1978 This target fetches the most recent version of the
1979 original source package from a canonical archive site
1980 (via FTP or WWW, for example), does any necessary
1981 rearrangement to turn it into the original source
1982 tar file format described below, and leaves it in the
1987 This target may be invoked in any directory, and
1988 should take care to clean up any temporary files it
1993 This target is optional, but providing it if
1994 possible is a good idea.
1998 <tag><tt>patch</tt> (optional)</tag>
2001 This target performs whatever additional actions are
2002 required to make the source ready for editing (unpacking
2003 additional upstream archives, applying patches, etc.).
2004 It is recommended to be implemented for any package where
2005 <tt>dpkg-source -x</tt> does not result in source ready
2006 for additional modification. See
2007 <ref id="readmesource">.
2013 The <tt>build</tt>, <tt>binary</tt> and
2014 <tt>clean</tt> targets must be invoked with the current
2015 directory being the package's top-level directory.
2020 Additional targets may exist in <file>debian/rules</file>,
2021 either as published or undocumented interfaces or for the
2022 package's internal use.
2026 The architectures we build on and build for are determined
2027 by <prgn>make</prgn> variables using the utility
2028 <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
2029 You can determine the
2030 Debian architecture and the GNU style architecture
2031 specification string for the build machine (the machine type
2032 we are building on) as well as for the host machine (the
2033 machine type we are building for). Here is a list of
2034 supported <prgn>make</prgn> variables:
2035 <list compact="compact">
2037 <tt>DEB_*_ARCH</tt> (the Debian architecture)
2040 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2043 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2046 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2047 specification string)
2050 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2051 <tt>DEB_*_GNU_TYPE</tt>)
2054 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2055 <tt>DEB_*_GNU_TYPE</tt>)
2057 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2058 the build machine or <tt>HOST</tt> for specification of the
2063 Backward compatibility can be provided in the rules file
2064 by setting the needed variables to suitable default
2065 values; please refer to the documentation of
2066 <prgn>dpkg-architecture</prgn> for details.
2070 It is important to understand that the <tt>DEB_*_ARCH</tt>
2071 string only determines which Debian architecture we are
2072 building on or for. It should not be used to get the CPU
2073 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2074 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2075 GNU style variables should generally only be used with upstream
2079 <sect1 id="debianrules-options">
2080 <heading><file>debian/rules</file> and
2081 <tt>DEB_BUILD_OPTIONS</tt></heading>
2084 Supporting the standardized environment variable
2085 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2086 contain several flags to change how a package is compiled and
2087 built. Each flag must be in the form <var>flag</var> or
2088 <var>flag</var>=<var>options</var>. If multiple flags are
2089 given, they must be separated by whitespace.<footnote>
2090 Some packages support any delimiter, but whitespace is the
2091 easiest to parse inside a makefile and avoids ambiguity with
2092 flag values that contain commas.
2094 <var>flag</var> must start with a lowercase letter
2095 (<tt>a-z</tt>) and consist only of lowercase letters,
2096 numbers (<tt>0-9</tt>), and the characters
2097 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2098 <var>options</var> must not contain whitespace. The same
2099 tag should not be given multiple times with conflicting
2100 values. Package maintainers may assume that
2101 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2105 The meaning of the following tags has been standardized:
2109 This tag says to not run any build-time test suite
2110 provided by the package.
2114 The presence of this tag means that the package should
2115 be compiled with a minimum of optimization. For C
2116 programs, it is best to add <tt>-O0</tt> to
2117 <tt>CFLAGS</tt> (although this is usually the default).
2118 Some programs might fail to build or run at this level
2119 of optimization; it may be necessary to use
2120 <tt>-O1</tt>, for example.
2124 This tag means that the debugging symbols should not be
2125 stripped from the binary during installation, so that
2126 debugging information may be included in the package.
2128 <tag>parallel=n</tag>
2130 This tag means that the package should be built using up
2131 to <tt>n</tt> parallel processes if the package build
2132 system supports this.<footnote>
2133 Packages built with <tt>make</tt> can often implement
2134 this by passing the <tt>-j</tt><var>n</var> option to
2137 If the package build system does not support parallel
2138 builds, this string must be ignored. If the package
2139 build system only supports a lower level of concurrency
2140 than <var>n</var>, the package should be built using as
2141 many parallel processes as the package build system
2142 supports. It is up to the package maintainer to decide
2143 whether the package build times are long enough and the
2144 package build system is robust enough to make supporting
2145 parallel builds worthwhile.
2151 Unknown flags must be ignored by <file>debian/rules</file>.
2155 The following makefile snippet is an example of how one may
2156 implement the build options; you will probably have to
2157 massage this example in order to make it work for your
2159 <example compact="compact">
2162 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2163 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2164 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2165 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2167 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2172 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2173 INSTALL_PROGRAM += -s
2175 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2176 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2177 MAKEFLAGS += -j$(NUMJOBS)
2182 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2183 # Code to run the package test suite.
2190 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2191 <sect id="substvars">
2192 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2195 When <prgn>dpkg-gencontrol</prgn>,
2196 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
2197 generate control files they perform variable substitutions
2198 on their output just before writing it. Variable
2199 substitutions have the form <tt>${<var>variable</var>}</tt>.
2200 The optional file <file>debian/substvars</file> contains
2201 variable substitutions to be used; variables can also be set
2202 directly from <file>debian/rules</file> using the <tt>-V</tt>
2203 option to the source packaging commands, and certain
2204 predefined variables are also available.
2208 The <file>debian/substvars</file> file is usually generated and
2209 modified dynamically by <file>debian/rules</file> targets, in
2210 which case it must be removed by the <tt>clean</tt> target.
2214 See <manref name="deb-substvars" section="5"> for full
2215 details about source variable substitutions, including the
2216 format of <file>debian/substvars</file>.</p>
2219 <sect id="debianwatch">
2220 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2223 This is an optional, recommended control file for the
2224 <tt>uscan</tt> utility which defines how to automatically
2225 scan ftp or http sites for newly available updates of the
2226 package. This is used by <url id="
2227 http://dehs.alioth.debian.org/"> and other Debian QA tools
2228 to help with quality control and maintenance of the
2229 distribution as a whole.
2234 <sect id="debianfiles">
2235 <heading>Generated files list: <file>debian/files</file></heading>
2238 This file is not a permanent part of the source tree; it
2239 is used while building packages to record which files are
2240 being generated. <prgn>dpkg-genchanges</prgn> uses it
2241 when it generates a <file>.changes</file> file.
2245 It should not exist in a shipped source package, and so it
2246 (and any backup files or temporary files such as
2247 <file>files.new</file><footnote>
2248 <file>files.new</file> is used as a temporary file by
2249 <prgn>dpkg-gencontrol</prgn> and
2250 <prgn>dpkg-distaddfile</prgn> - they write a new
2251 version of <tt>files</tt> here before renaming it,
2252 to avoid leaving a corrupted copy if an error
2254 </footnote>) should be removed by the
2255 <tt>clean</tt> target. It may also be wise to
2256 ensure a fresh start by emptying or removing it at the
2257 start of the <tt>binary</tt> target.
2261 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2262 package, it adds an entry to <file>debian/files</file> for the
2263 <file>.deb</file> file that will be created when <tt>dpkg-deb
2264 --build</tt> is run for that binary package. So for most
2265 packages all that needs to be done with this file is to
2266 delete it in the <tt>clean</tt> target.
2270 If a package upload includes files besides the source
2271 package and any binary packages whose control files were
2272 made with <prgn>dpkg-gencontrol</prgn> then they should be
2273 placed in the parent of the package's top-level directory
2274 and <prgn>dpkg-distaddfile</prgn> should be called to add
2275 the file to the list in <file>debian/files</file>.</p>
2278 <sect id="embeddedfiles">
2279 <heading>Convenience copies of code</heading>
2282 Some software packages include in their distribution convenience
2283 copies of code from other software packages, generally so that
2284 users compiling from source don't have to download multiple
2285 packages. Debian packages should not make use of these
2286 convenience copies unless the included package is explicitly
2287 intended to be used in this way.<footnote>
2288 For example, parts of the GNU build system work like this.
2290 If the included code is already in the Debian archive in the
2291 form of a library, the Debian packaging should ensure that
2292 binary packages reference the libraries already in Debian and
2293 the convenience copy is not used. If the included code is not
2294 already in Debian, it should be packaged separately as a
2295 prerequisite if possible.
2297 Having multiple copies of the same code in Debian is
2298 inefficient, often creates either static linking or shared
2299 library conflicts, and, most importantly, increases the
2300 difficulty of handling security vulnerabilities in the
2306 <sect id="readmesource">
2307 <heading>Source package handling:
2308 <file>debian/README.source</file></heading>
2311 If running <prgn>dpkg-source -x</prgn> on a source package
2312 doesn't produce the source of the package, ready for editing,
2313 and allow one to make changes and run
2314 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2315 without taking any additional steps, creating a
2316 <file>debian/README.source</file> documentation file is
2317 recommended. This file should explain how to do all of the
2320 <item>Generate the fully patched source, in a form ready for
2321 editing, that would be built to create Debian
2322 packages. Doing this with a <tt>patch</tt> target in
2323 <file>debian/rules</file> is recommended; see
2324 <ref id="debianrules">.</item>
2325 <item>Modify the source and save those modifications so that
2326 they will be applied when building the package.</item>
2327 <item>Remove source modifications that are currently being
2328 applied when building the package.</item>
2329 <item>Optionally, document what steps are necessary to
2330 upgrade the Debian source package to a new upstream version,
2331 if applicable.</item>
2333 This explanation should include specific commands and mention
2334 any additional required Debian packages. It should not assume
2335 familiarity with any specific Debian packaging system or patch
2340 This explanation may refer to a documentation file installed by
2341 one of the package's build dependencies provided that the
2342 referenced documentation clearly explains these tasks and is not
2343 a general reference manual.
2347 <file>debian/README.source</file> may also include any other
2348 information that would be helpful to someone modifying the
2349 source package. Even if the package doesn't fit the above
2350 description, maintainers are encouraged to document in a
2351 <file>debian/README.source</file> file any source package with a
2352 particularly complex or unintuitive source layout or build
2353 system (for example, a package that builds the same source
2354 multiple times to generate different binary packages).
2360 <chapt id="controlfields">
2361 <heading>Control files and their fields</heading>
2364 The package management system manipulates data represented in
2365 a common format, known as <em>control data</em>, stored in
2366 <em>control files</em>.
2367 Control files are used for source packages, binary packages and
2368 the <file>.changes</file> files which control the installation
2369 of uploaded files<footnote>
2370 <prgn>dpkg</prgn>'s internal databases are in a similar
2375 <sect id="controlsyntax">
2376 <heading>Syntax of control files</heading>
2379 A control file consists of one or more paragraphs of
2381 The paragraphs are also sometimes referred to as stanzas.
2383 The paragraphs are separated by blank lines. Some control
2384 files allow only one paragraph; others allow several, in
2385 which case each paragraph usually refers to a different
2386 package. (For example, in source packages, the first
2387 paragraph refers to the source package, and later paragraphs
2388 refer to binary packages generated from the source.)
2392 Each paragraph consists of a series of data fields; each
2393 field consists of the field name, followed by a colon and
2394 then the data/value associated with that field. It ends at
2395 the end of the (logical) line. Horizontal whitespace
2396 (spaces and tabs) may occur immediately before or after the
2397 value and is ignored there; it is conventional to put a
2398 single space after the colon. For example, a field might
2400 <example compact="compact">
2403 the field name is <tt>Package</tt> and the field value
2408 A paragraph must not contain more than one instance of a
2409 particular field name.
2413 Many fields' values may span several lines; in this case
2414 each continuation line must start with a space or a tab.
2415 Any trailing spaces or tabs at the end of individual
2416 lines of a field value are ignored.
2420 In fields where it is specified that lines may not wrap,
2421 only a single line of data is allowed and whitespace is not
2422 significant in a field body. Whitespace must not appear
2423 inside names (of packages, architectures, files or anything
2424 else) or version numbers, or between the characters of
2425 multi-character version relationships.
2429 Field names are not case-sensitive, but it is usual to
2430 capitalize the field names using mixed case as shown below.
2431 Field values are case-sensitive unless the description of the
2432 field says otherwise.
2436 Blank lines, or lines consisting only of spaces and tabs,
2437 are not allowed within field values or between fields - that
2438 would mean a new paragraph.
2442 All control files must be encoded in UTF-8.
2446 <sect id="sourcecontrolfiles">
2447 <heading>Source package control files -- <file>debian/control</file></heading>
2450 The <file>debian/control</file> file contains the most vital
2451 (and version-independent) information about the source package
2452 and about the binary packages it creates.
2456 The first paragraph of the control file contains information about
2457 the source package in general. The subsequent sets each describe a
2458 binary package that the source tree builds.
2462 The fields in the general paragraph (the first one, for the source
2465 <list compact="compact">
2466 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2467 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2468 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2469 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2470 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2471 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2472 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2473 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2478 The fields in the binary package paragraphs are:
2480 <list compact="compact">
2481 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2482 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2483 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2484 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2485 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2486 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2487 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2488 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2493 The syntax and semantics of the fields are described below.
2497 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2498 generate control files for binary packages (see below), by
2499 <prgn>dpkg-genchanges</prgn> to generate the
2500 <tt>.changes</tt> file to accompany the upload, and by
2501 <prgn>dpkg-source</prgn> when it creates the
2502 <file>.dsc</file> source control file as part of a source
2503 archive. Many fields are permitted to span multiple lines in
2504 <file>debian/control</file> but not in any other control
2505 file. These tools are responsible for removing the line
2506 breaks from such fields when using fields from
2507 <file>debian/control</file> to generate other control files.
2511 The fields here may contain variable references - their
2512 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2513 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2514 when they generate output control files.
2515 See <ref id="substvars"> for details.
2519 In addition to the control file syntax described <qref
2520 id="controlsyntax">above</qref>, this file may also contain
2521 comment lines starting with <tt>#</tt> without any preceding
2522 whitespace. All such lines are ignored, even in the middle of
2523 continuation lines for a multiline field, and do not end a
2529 <sect id="binarycontrolfiles">
2530 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2533 The <file>DEBIAN/control</file> file contains the most vital
2534 (and version-dependent) information about a binary package.
2538 The structure of the Debian changes files is versionned, and
2539 this document describes the format 1.8.
2543 The fields in this file are:
2545 <list compact="compact">
2546 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2547 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2548 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2549 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2550 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2551 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2552 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2553 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2554 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2555 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2556 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2557 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2562 <sect id="debiansourcecontrolfiles">
2563 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2566 This file contains a series of fields, identified and
2567 separated just like the fields in the control file of
2568 a binary package. The fields are listed below; their
2569 syntax is described above, in <ref id="pkg-controlfields">.
2571 <list compact="compact">
2572 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2573 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2574 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2575 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2576 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2577 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2578 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2579 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2580 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2581 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2582 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2583 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2584 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2589 The source package control file is generated by
2590 <prgn>dpkg-source</prgn> when it builds the source
2591 archive, from other files in the source package,
2592 described above. When unpacking, it is checked against
2593 the files and directories in the other parts of the
2599 <sect id="debianchangesfiles">
2600 <heading>Debian changes files -- <file>.changes</file></heading>
2603 The .changes files are used by the Debian archive maintenance
2604 software to process updates to packages. They contain one
2605 paragraph which contains information from the
2606 <tt>debian/control</tt> file and other data about the
2607 source package gathered via <tt>debian/changelog</tt>
2608 and <tt>debian/rules</tt>.
2612 The fields in this file are:
2614 <list compact="compact">
2615 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2616 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2617 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2618 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2619 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2620 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2621 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2622 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2623 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory) <footnote>The meaning of that field changed in version 1.7.</footnote></item>
2624 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref> <footnote>Introduced in format 1.7.</footnote></item>
2625 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2626 <item><qref id="f-Closes"><tt>Closes</tt></qref> <footnote>Introduced in format 1.6.</footnote></item>
2627 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2628 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2629 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2630 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2635 <sect id="controlfieldslist">
2636 <heading>List of fields</heading>
2638 <sect1 id="f-Source">
2639 <heading><tt>Source</tt></heading>
2642 This field identifies the source package name.
2646 In <file>debian/control</file> or a <file>.dsc</file> file,
2647 this field must contain only the name of the source package.
2651 In a binary package control file or a <file>.changes</file>
2652 file, the source package name may be followed by a version
2653 number in parentheses<footnote>
2654 It is customary to leave a space after the package name
2655 if a version number is specified.
2657 This version number may be omitted (and is, by
2658 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2659 the <tt>Version</tt> field of the binary package in
2660 question. The field itself may be omitted from a binary
2661 package control file when the source package has the same
2662 name and version as the binary package.
2666 Package names (both source and binary,
2667 see <ref id="f-Package">) must consist only of lower case
2668 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2669 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2670 (<tt>.</tt>). They must be at least two characters long and
2671 must start with an alphanumeric character.
2675 <sect1 id="f-Maintainer">
2676 <heading><tt>Maintainer</tt></heading>
2679 The package maintainer's name and email address. The name
2680 must come first, then the email address inside angle
2681 brackets <tt><></tt> (in RFC822 format).
2685 If the maintainer's name contains a full stop then the
2686 whole field will not work directly as an email address due
2687 to a misfeature in the syntax specified in RFC822; a
2688 program using this field as an address must check for this
2689 and correct the problem if necessary (for example by
2690 putting the name in round brackets and moving it to the
2691 end, and bringing the email address forward).
2695 <sect1 id="f-Uploaders">
2696 <heading><tt>Uploaders</tt></heading>
2699 List of the names and email addresses of co-maintainers of
2700 the package, if any. If the package has other maintainers
2701 beside the one named in the
2702 <qref id="f-Maintainer">Maintainer field</qref>, their names
2703 and email addresses should be listed here. The format of each
2704 entry is the same as that of the Maintainer field, and
2705 multiple entries must be comma separated. This is an optional
2710 Any parser that interprets the Uploaders field in
2711 <file>debian/control</file> must permit it to span multiple
2712 lines. Line breaks in an Uploaders field that spans multiple
2713 lines are not significant and the semantics of the field are
2714 the same as if the line breaks had not been present.
2718 <sect1 id="f-Changed-By">
2719 <heading><tt>Changed-By</tt></heading>
2722 The name and email address of the person who prepared this
2723 version of the package, usually a maintainer. The syntax is
2724 the same as for the <qref id="f-Maintainer">Maintainer
2729 <sect1 id="f-Section">
2730 <heading><tt>Section</tt></heading>
2733 This field specifies an application area into which the package
2734 has been classified. See <ref id="subsections">.
2738 When it appears in the <file>debian/control</file> file,
2739 it gives the value for the subfield of the same name in
2740 the <tt>Files</tt> field of the <file>.changes</file> file.
2741 It also gives the default for the same field in the binary
2746 <sect1 id="f-Priority">
2747 <heading><tt>Priority</tt></heading>
2750 This field represents how important it is that the user
2751 have the package installed. See <ref id="priorities">.
2755 When it appears in the <file>debian/control</file> file,
2756 it gives the value for the subfield of the same name in
2757 the <tt>Files</tt> field of the <file>.changes</file> file.
2758 It also gives the default for the same field in the binary
2763 <sect1 id="f-Package">
2764 <heading><tt>Package</tt></heading>
2767 The name of the binary package.
2771 Binary package names must follow the same syntax and
2772 restrictions as source package names. See <ref id="f-Source">
2777 <sect1 id="f-Architecture">
2778 <heading><tt>Architecture</tt></heading>
2781 Depending on context and the control file used, the
2782 <tt>Architecture</tt> field can include the following sets of
2786 A unique single word identifying a Debian machine
2787 architecture as described in <ref id="arch-spec">.
2790 An architecture wildcard identifying a set of Debian
2791 machine architectures, see <ref id="arch-wildcard-spec">.
2792 <tt>any</tt> matches all Debian machine architectures
2793 and is the most frequently used.
2796 <tt>all</tt>, which indicates an
2797 architecture-independent package.
2800 <tt>source</tt>, which indicates a source package.
2806 In the main <file>debian/control</file> file in the source
2807 package, this field may contain the special
2808 value <tt>all</tt>, the special architecture
2809 wildcard <tt>any</tt>, or a list of specific and wildcard
2810 architectures separated by spaces. If <tt>all</tt>
2811 or <tt>any</tt> appears, that value must be the entire
2812 contents of the field. Most packages will use
2813 either <tt>all</tt> or <tt>any</tt>.
2817 Specifying a specific list of architectures indicates that the
2818 source will build an architecture-dependent package only on
2819 architectures included in the list. Specifying a list of
2820 architecture wildcards indicates that the source will build an
2821 architecture-dependent package on only those architectures
2822 that match any of the specified architecture wildcards.
2823 Specifying a list of architectures or architecture wildcards
2824 other than <tt>any</tt> is for the minority of cases where a
2825 program is not portable or is not useful on some
2826 architectures. Where possible, the program should be made
2831 In the source package control file <file>.dsc</file>, this
2832 field may contain either the architecture
2833 wildcard <tt>any</tt> or a list of architectures and
2834 architecture wildcards separated by spaces. If a list is
2835 given, it may include (or consist solely of) the special
2836 value <tt>all</tt>. In other words, in <file>.dsc</file>
2837 files unlike the <file>debian/control</file>, <tt>all</tt> may
2838 occur in combination with specific architectures.
2839 The <tt>Architecture</tt> field in the source package control
2840 file <file>.dsc</file> is generally constructed from
2841 the <tt>Architecture</tt> fields in
2842 the <file>debian/control</file> in the source package.
2846 Specifying <tt>any</tt> indicates that the source package
2847 isn't dependent on any particular architecture and should
2848 compile fine on any one. The produced binary package(s)
2849 will either be specific to whatever the current build
2850 architecture is or will be architecture-independent.
2854 Specifying only <tt>all</tt> indicates that the source package
2855 will only build architecture-independent packages. If this is
2856 the case, <tt>all</tt> must be used rather than <tt>any</tt>;
2857 <tt>any</tt> implies that the source package will build at
2858 least one architecture-dependent package.
2862 Specifying a list of architectures or architecture wildcards
2863 indicates that the source will build an architecture-dependent
2864 package, and will only work correctly on the listed or
2865 matching architectures. If the source package also builds at
2866 least one architecture-independent package, <tt>all</tt> will
2867 also be included in the list.
2871 In a <file>.changes</file> file, the <tt>Architecture</tt>
2872 field lists the architecture(s) of the package(s) currently
2873 being uploaded. This will be a list; if the source for the
2874 package is also being uploaded, the special
2875 entry <tt>source</tt> is also present. <tt>all</tt> will be
2876 present if any architecture-independent packages are being
2877 uploaded. Architecture wildcards such as <tt>any</tt> must
2878 never occur in the <tt>Architecture</tt> field in
2879 the <file>.changes</file> file.
2883 See <ref id="debianrules"> for information on how to get
2884 the architecture for the build process.
2888 <sect1 id="f-Essential">
2889 <heading><tt>Essential</tt></heading>
2892 This is a boolean field which may occur only in the
2893 control file of a binary package or in a per-package fields
2894 paragraph of a main source control data file.
2898 If set to <tt>yes</tt> then the package management system
2899 will refuse to remove the package (upgrading and replacing
2900 it is still possible). The other possible value is <tt>no</tt>,
2901 which is the same as not having the field at all.
2906 <heading>Package interrelationship fields:
2907 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2908 <tt>Recommends</tt>, <tt>Suggests</tt>,
2909 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2910 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2914 These fields describe the package's relationships with
2915 other packages. Their syntax and semantics are described
2916 in <ref id="relationships">.</p>
2919 <sect1 id="f-Standards-Version">
2920 <heading><tt>Standards-Version</tt></heading>
2923 The most recent version of the standards (the policy
2924 manual and associated texts) with which the package
2929 The version number has four components: major and minor
2930 version number and major and minor patch level. When the
2931 standards change in a way that requires every package to
2932 change the major number will be changed. Significant
2933 changes that will require work in many packages will be
2934 signaled by a change to the minor number. The major patch
2935 level will be changed for any change to the meaning of the
2936 standards, however small; the minor patch level will be
2937 changed when only cosmetic, typographical or other edits
2938 are made which neither change the meaning of the document
2939 nor affect the contents of packages.
2943 Thus only the first three components of the policy version
2944 are significant in the <em>Standards-Version</em> control
2945 field, and so either these three components or all four
2946 components may be specified.<footnote>
2947 In the past, people specified the full version number
2948 in the Standards-Version field, for example "2.3.0.0".
2949 Since minor patch-level changes don't introduce new
2950 policy, it was thought it would be better to relax
2951 policy and only require the first 3 components to be
2952 specified, in this example "2.3.0". All four
2953 components may still be used if someone wishes to do so.
2959 <sect1 id="f-Version">
2960 <heading><tt>Version</tt></heading>
2963 The version number of a package. The format is:
2964 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
2968 The three components here are:
2970 <tag><var>epoch</var></tag>
2973 This is a single (generally small) unsigned integer. It
2974 may be omitted, in which case zero is assumed. If it is
2975 omitted then the <var>upstream_version</var> may not
2980 It is provided to allow mistakes in the version numbers
2981 of older versions of a package, and also a package's
2982 previous version numbering schemes, to be left behind.
2986 <tag><var>upstream_version</var></tag>
2989 This is the main part of the version number. It is
2990 usually the version number of the original ("upstream")
2991 package from which the <file>.deb</file> file has been made,
2992 if this is applicable. Usually this will be in the same
2993 format as that specified by the upstream author(s);
2994 however, it may need to be reformatted to fit into the
2995 package management system's format and comparison
3000 The comparison behavior of the package management system
3001 with respect to the <var>upstream_version</var> is
3002 described below. The <var>upstream_version</var>
3003 portion of the version number is mandatory.
3007 The <var>upstream_version</var> may contain only
3008 alphanumerics<footnote>
3009 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3011 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3012 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3013 tilde) and should start with a digit. If there is no
3014 <var>debian_revision</var> then hyphens are not allowed;
3015 if there is no <var>epoch</var> then colons are not
3020 <tag><var>debian_revision</var></tag>
3023 This part of the version number specifies the version of
3024 the Debian package based on the upstream version. It
3025 may contain only alphanumerics and the characters
3026 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3027 tilde) and is compared in the same way as the
3028 <var>upstream_version</var> is.
3032 It is optional; if it isn't present then the
3033 <var>upstream_version</var> may not contain a hyphen.
3034 This format represents the case where a piece of
3035 software was written specifically to be a Debian
3036 package, where the Debian package source must always
3037 be identical to the pristine source and therefore no
3038 revision indication is required.
3042 It is conventional to restart the
3043 <var>debian_revision</var> at <tt>1</tt> each time the
3044 <var>upstream_version</var> is increased.
3048 The package management system will break the version
3049 number apart at the last hyphen in the string (if there
3050 is one) to determine the <var>upstream_version</var> and
3051 <var>debian_revision</var>. The absence of a
3052 <var>debian_revision</var> is equivalent to a
3053 <var>debian_revision</var> of <tt>0</tt>.
3060 When comparing two version numbers, first the <var>epoch</var>
3061 of each are compared, then the <var>upstream_version</var> if
3062 <var>epoch</var> is equal, and then <var>debian_revision</var>
3063 if <var>upstream_version</var> is also equal.
3064 <var>epoch</var> is compared numerically. The
3065 <var>upstream_version</var> and <var>debian_revision</var>
3066 parts are compared by the package management system using the
3067 following algorithm:
3071 The strings are compared from left to right.
3075 First the initial part of each string consisting entirely of
3076 non-digit characters is determined. These two parts (one of
3077 which may be empty) are compared lexically. If a difference
3078 is found it is returned. The lexical comparison is a
3079 comparison of ASCII values modified so that all the letters
3080 sort earlier than all the non-letters and so that a tilde
3081 sorts before anything, even the end of a part. For example,
3082 the following parts are in sorted order from earliest to
3083 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3084 <tt>a</tt>.<footnote>
3085 One common use of <tt>~</tt> is for upstream pre-releases.
3086 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3087 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3092 Then the initial part of the remainder of each string which
3093 consists entirely of digit characters is determined. The
3094 numerical values of these two parts are compared, and any
3095 difference found is returned as the result of the comparison.
3096 For these purposes an empty string (which can only occur at
3097 the end of one or both version strings being compared) counts
3102 These two steps (comparing and removing initial non-digit
3103 strings and initial digit strings) are repeated until a
3104 difference is found or both strings are exhausted.
3108 Note that the purpose of epochs is to allow us to leave behind
3109 mistakes in version numbering, and to cope with situations
3110 where the version numbering scheme changes. It is
3111 <em>not</em> intended to cope with version numbers containing
3112 strings of letters which the package management system cannot
3113 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3114 silly orderings.<footnote>
3115 The author of this manual has heard of a package whose
3116 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3117 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3123 <sect1 id="f-Description">
3124 <heading><tt>Description</tt></heading>
3127 In a source or binary control file, the <tt>Description</tt>
3128 field contains a description of the binary package, consisting
3129 of two parts, the synopsis or the short description, and the
3130 long description. The field's format is as follows:
3135 Description: <single line synopsis>
3136 <extended description over several lines>
3141 The lines in the extended description can have these formats:
3147 Those starting with a single space are part of a paragraph.
3148 Successive lines of this form will be word-wrapped when
3149 displayed. The leading space will usually be stripped off.
3153 Those starting with two or more spaces. These will be
3154 displayed verbatim. If the display cannot be panned
3155 horizontally, the displaying program will line wrap them "hard"
3156 (i.e., without taking account of word breaks). If it can they
3157 will be allowed to trail off to the right. None, one or two
3158 initial spaces may be deleted, but the number of spaces
3159 deleted from each line will be the same (so that you can have
3160 indenting work correctly, for example).
3164 Those containing a single space followed by a single full stop
3165 character. These are rendered as blank lines. This is the
3166 <em>only</em> way to get a blank line<footnote>
3167 Completely empty lines will not be rendered as blank lines.
3168 Instead, they will cause the parser to think you're starting
3169 a whole new record in the control file, and will therefore
3170 likely abort with an error.
3175 Those containing a space, a full stop and some more characters.
3176 These are for future expansion. Do not use them.
3182 Do not use tab characters. Their effect is not predictable.
3186 See <ref id="descriptions"> for further information on this.
3190 In a <file>.changes</file> file, the <tt>Description</tt>
3191 field contains a summary of the descriptions for the packages
3192 being uploaded. For this case, the first line of the field
3193 value (the part on the same line as <tt>Description:</tt>) is
3194 always empty. The content of the field is expressed as
3195 continuation lines, one line per package. Each line is
3196 indented by one space and contains the name of a binary
3197 package, a space, a hyphen (<tt>-</tt>), a space, and the
3198 short description line from that package.
3202 <sect1 id="f-Distribution">
3203 <heading><tt>Distribution</tt></heading>
3206 In a <file>.changes</file> file or parsed changelog output
3207 this contains the (space-separated) name(s) of the
3208 distribution(s) where this version of the package should
3209 be installed. Valid distributions are determined by the
3210 archive maintainers.<footnote>
3211 Example distribution names in the Debian archive used in
3212 <file>.changes</file> files are:
3213 <taglist compact="compact">
3214 <tag><em>unstable</em></tag>
3216 This distribution value refers to the
3217 <em>developmental</em> part of the Debian distribution
3218 tree. Most new packages, new upstream versions of
3219 packages and bug fixes go into the <em>unstable</em>
3223 <tag><em>experimental</em></tag>
3225 The packages with this distribution value are deemed
3226 by their maintainers to be high risk. Oftentimes they
3227 represent early beta or developmental packages from
3228 various sources that the maintainers want people to
3229 try, but are not ready to be a part of the other parts
3230 of the Debian distribution tree.
3235 Others are used for updating stable releases or for
3236 security uploads. More information is available in the
3237 Debian Developer's Reference, section "The Debian
3241 The Debian archive software only supports listing a single
3242 distribution. Migration of packages to other distributions is
3243 handled outside of the upload process.
3248 <heading><tt>Date</tt></heading>
3251 This field includes the date the package was built or last
3252 edited. It must be in the same format as the <var>date</var>
3253 in a <file>debian/changelog</file> entry.
3257 The value of this field is usually extracted from the
3258 <file>debian/changelog</file> file - see
3259 <ref id="dpkgchangelog">).
3263 <sect1 id="f-Format">
3264 <heading><tt>Format</tt></heading>
3267 In <qref id="debianchangesfiles">changes</qref> files, this field
3268 specifies a format revision for the file. The syntax of the
3269 format value is the same as that of a package version
3270 number except that no epoch or Debian revision is allowed
3271 - see <ref id="f-Version">.
3275 In <qref id="debiansourcecontrolfiles"> Debian source control</qref>
3276 files, this field specifies a format revision for the source package.
3277 The syntax of the format value is the same as that of a package version
3278 number, except that no epoch or Debian revision is allowed
3279 and that it can optionally be followed by a parenthesis with a name
3280 <footnote>dpkg-source uses the major number and the content of the
3281 parenthesis to decide which perl module to use to build or unpack
3282 the source package. For instance, Dpkg::Source::Package::V1 for format
3283 1.0 and Dpkg::Source::Package::V3::quilt for format 3.0 (quilt)
3288 <sect1 id="f-Urgency">
3289 <heading><tt>Urgency</tt></heading>
3292 This is a description of how important it is to upgrade to
3293 this version from previous ones. It consists of a single
3294 keyword taking one of the values <tt>low</tt>,
3295 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3296 <tt>critical</tt><footnote>
3297 Other urgency values are supported with configuration
3298 changes in the archive software but are not used in Debian.
3299 The urgency affects how quickly a package will be considered
3300 for inclusion into the <tt>testing</tt> distribution and
3301 gives an indication of the importance of any fixes included
3302 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3303 treated as synonymous.
3304 </footnote> (not case-sensitive) followed by an optional
3305 commentary (separated by a space) which is usually in
3306 parentheses. For example:
3309 Urgency: low (HIGH for users of diversions)
3315 The value of this field is usually extracted from the
3316 <file>debian/changelog</file> file - see
3317 <ref id="dpkgchangelog">.
3321 <sect1 id="f-Changes">
3322 <heading><tt>Changes</tt></heading>
3325 This field contains the human-readable changes data, describing
3326 the differences between the last version and the current one.
3330 The first line of the field value (the part on the same line
3331 as <tt>Changes:</tt>) is always empty. The content of the
3332 field is expressed as continuation lines, with each line
3333 indented by at least one space. Blank lines must be
3334 represented by a line consisting only of a space and a full
3339 The value of this field is usually extracted from the
3340 <file>debian/changelog</file> file - see
3341 <ref id="dpkgchangelog">).
3345 Each version's change information should be preceded by a
3346 "title" line giving at least the version, distribution(s)
3347 and urgency, in a human-readable way.
3351 If data from several versions is being returned the entry
3352 for the most recent version should be returned first, and
3353 entries should be separated by the representation of a
3354 blank line (the "title" line may also be followed by the
3355 representation of a blank line).
3359 <sect1 id="f-Binary">
3360 <heading><tt>Binary</tt></heading>
3363 This field is a list of binary packages. Its syntax and
3364 meaning varies depending on the control file in which it
3369 When it appears in the <file>.dsc</file> file, it lists binary
3370 packages which a source package can produce, separated by
3372 A space after each comma is conventional.
3373 </footnote>. It may span multiple lines. The source package
3374 does not necessarily produce all of these binary packages for
3375 every architecture. The source control file doesn't contain
3376 details of which architectures are appropriate for which of
3377 the binary packages.
3381 When it appears in a <file>.changes</file> file, it lists the
3382 names of the binary packages being uploaded, separated by
3383 whitespace (not commas). It may span multiple lines.
3387 <sect1 id="f-Installed-Size">
3388 <heading><tt>Installed-Size</tt></heading>
3391 This field appears in the control files of binary packages,
3392 and in the <file>Packages</file> files. It gives an estimate
3393 of the total amount of disk space required to install the
3394 named package. Actual installed size may vary based on block
3395 size, file system properties, or actions taken by package
3400 The disk space is given as the integer value of the estimated
3401 installed size in bytes, divided by 1024 and rounded up.
3405 <sect1 id="f-Files">
3406 <heading><tt>Files</tt></heading>
3409 This field contains a list of files with information about
3410 each one. The exact information and syntax varies with
3415 In all cases, Files is a multiline field. The first line of
3416 the field value (the part on the same line as <tt>Files:</tt>)
3417 is always empty. The content of the field is expressed as
3418 continuation lines, one line per file. Each line must be
3419 indented by one space and contain a number of sub-fields,
3420 separated by spaces, as described below.
3424 In the <file>.dsc</file> file, each line contains the MD5
3425 checksum, size and filename of the tar file and (if
3426 applicable) diff file which make up the remainder of the
3427 source package<footnote>
3428 That is, the parts which are not the <tt>.dsc</tt>.
3429 </footnote>. For example:
3432 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3433 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3435 The exact forms of the filenames are described
3436 in <ref id="pkg-sourcearchives">.
3440 In the <file>.changes</file> file this contains one line per
3441 file being uploaded. Each line contains the MD5 checksum,
3442 size, section and priority and the filename. For example:
3445 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3446 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3447 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3448 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3450 The <qref id="f-Section">section</qref>
3451 and <qref id="f-Priority">priority</qref> are the values of
3452 the corresponding fields in the main source control file. If
3453 no section or priority is specified then <tt>-</tt> should be
3454 used, though section and priority values must be specified for
3455 new packages to be installed properly.
3459 The special value <tt>byhand</tt> for the section in a
3460 <tt>.changes</tt> file indicates that the file in question
3461 is not an ordinary package file and must by installed by
3462 hand by the distribution maintainers. If the section is
3463 <tt>byhand</tt> the priority should be <tt>-</tt>.
3467 If a new Debian revision of a package is being shipped and
3468 no new original source archive is being distributed the
3469 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3470 entry for the original source archive
3471 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3472 but the <file>.changes</file> file should leave it out. In
3473 this case the original source archive on the distribution
3474 site must match exactly, byte-for-byte, the original
3475 source archive which was used to generate the
3476 <file>.dsc</file> file and diff which are being uploaded.</p>
3479 <sect1 id="f-Closes">
3480 <heading><tt>Closes</tt></heading>
3483 A space-separated list of bug report numbers that the upload
3484 governed by the .changes file closes.
3488 <sect1 id="f-Homepage">
3489 <heading><tt>Homepage</tt></heading>
3492 The URL of the web site for this package, preferably (when
3493 applicable) the site from which the original source can be
3494 obtained and any additional upstream documentation or
3495 information may be found. The content of this field is a
3496 simple URL without any surrounding characters such as
3501 <sect1 id="f-Checksums">
3502 <heading><tt>Checksums-Sha1</tt>
3503 and <tt>Checksums-Sha256</tt></heading>
3506 These fields contain a list of files with a checksum and size
3507 for each one. Both <tt>Checksums-Sha1</tt>
3508 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3509 only in the checksum algorithm used: SHA-1
3510 for <tt>Checksums-Sha1</tt> and SHA-256
3511 for <tt>Checksums-Sha256</tt>.
3515 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3516 multiline fields. The first line of the field value (the part
3517 on the same line as <tt>Checksums-Sha1:</tt>
3518 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3519 of the field is expressed as continuation lines, one line per
3520 file. Each line consists of the checksum, a space, the file
3521 size, a space, and the file name. For example (from
3522 a <file>.changes</file> file):
3525 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3526 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3527 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3528 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3530 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3531 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3532 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3533 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3538 In the <file>.dsc</file> file, these fields should list all
3539 files that make up the source package. In
3540 the <file>.changes</file> file, these fields should list all
3541 files being uploaded. The list of files in these fields
3542 must match the list of files in the <tt>Files</tt> field.
3546 <sect1 id="f-Checksums-Sha1">
3547 <heading><tt>Checksums-Sha1</tt></heading>
3550 This field is similar to the <qref id="f-Files">Files</qref>
3551 field, except that it uses the Sha1 algorithm instead of MD5
3556 <sect1 id="f-Checksums-Sha256">
3557 <heading><tt>Checksums-Sha256</tt></heading>
3560 This field is similar to the <qref id="f-Files">Files</qref>
3561 field, except that it uses the Sha1 algorithm instead of MD5
3569 <heading>User-defined fields</heading>
3572 Additional user-defined fields may be added to the
3573 source package control file. Such fields will be
3574 ignored, and not copied to (for example) binary or
3575 source package control files or upload control files.
3579 If you wish to add additional unsupported fields to
3580 these output files you should use the mechanism
3585 Fields in the main source control information file with
3586 names starting <tt>X</tt>, followed by one or more of
3587 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3588 be copied to the output files. Only the part of the
3589 field name after the hyphen will be used in the output
3590 file. Where the letter <tt>B</tt> is used the field
3591 will appear in binary package control files, where the
3592 letter <tt>S</tt> is used in source package control
3593 files and where <tt>C</tt> is used in upload control
3594 (<tt>.changes</tt>) files.
3598 For example, if the main source information control file
3601 XBS-Comment: I stand between the candle and the star.
3603 then the binary and source package control files will contain the
3606 Comment: I stand between the candle and the star.
3615 <chapt id="maintainerscripts">
3616 <heading>Package maintainer scripts and installation procedure</heading>
3619 <heading>Introduction to package maintainer scripts</heading>
3622 It is possible to supply scripts as part of a package which
3623 the package management system will run for you when your
3624 package is installed, upgraded or removed.
3628 These scripts are the files <prgn>preinst</prgn>,
3629 <prgn>postinst</prgn>, <prgn>prerm</prgn> and
3630 <prgn>postrm</prgn> in the control area of the package.
3631 They must be proper executable files; if they are scripts
3632 (which is recommended), they must start with the usual
3633 <tt>#!</tt> convention. They should be readable and
3634 executable by anyone, and must not be world-writable.
3638 The package management system looks at the exit status from
3639 these scripts. It is important that they exit with a
3640 non-zero status if there is an error, so that the package
3641 management system can stop its processing. For shell
3642 scripts this means that you <em>almost always</em> need to
3643 use <tt>set -e</tt> (this is usually true when writing shell
3644 scripts, in fact). It is also important, of course, that
3645 they exit with a zero status if everything went well.
3649 Additionally, packages interacting with users using
3650 <tt>debconf</tt> in the <prgn>postinst</prgn> script should
3651 install a <prgn>config</prgn> script in the control area,
3652 see <ref id="maintscriptprompt"> for details.
3656 When a package is upgraded a combination of the scripts from
3657 the old and new packages is called during the upgrade
3658 procedure. If your scripts are going to be at all
3659 complicated you need to be aware of this, and may need to
3660 check the arguments to your scripts.
3664 Broadly speaking the <prgn>preinst</prgn> is called before
3665 (a particular version of) a package is installed, and the
3666 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3667 before (a version of) a package is removed and the
3668 <prgn>postrm</prgn> afterwards.
3672 Programs called from maintainer scripts should not normally
3673 have a path prepended to them. Before installation is
3674 started, the package management system checks to see if the
3675 programs <prgn>ldconfig</prgn>,
3676 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3677 and <prgn>update-rc.d</prgn> can be found via the
3678 <tt>PATH</tt> environment variable. Those programs, and any
3679 other program that one would expect to be in the
3680 <tt>PATH</tt>, should thus be invoked without an absolute
3681 pathname. Maintainer scripts should also not reset the
3682 <tt>PATH</tt>, though they might choose to modify it by
3683 prepending or appending package-specific directories. These
3684 considerations really apply to all shell scripts.</p>
3687 <sect id="idempotency">
3688 <heading>Maintainer scripts idempotency</heading>
3691 It is necessary for the error recovery procedures that the
3692 scripts be idempotent. This means that if it is run
3693 successfully, and then it is called again, it doesn't bomb
3694 out or cause any harm, but just ensures that everything is
3695 the way it ought to be. If the first call failed, or
3696 aborted half way through for some reason, the second call
3697 should merely do the things that were left undone the first
3698 time, if any, and exit with a success status if everything
3700 This is so that if an error occurs, the user interrupts
3701 <prgn>dpkg</prgn> or some other unforeseen circumstance
3702 happens you don't leave the user with a badly-broken
3703 package when <prgn>dpkg</prgn> attempts to repeat the
3709 <sect id="controllingterminal">
3710 <heading>Controlling terminal for maintainer scripts</heading>
3713 Maintainer scripts are not guaranteed to run with a controlling
3714 terminal and may not be able to interact with the user. They
3715 must be able to fall back to noninteractive behavior if no
3716 controlling terminal is available. Maintainer scripts that
3717 prompt via a program conforming to the Debian Configuration
3718 Management Specification (see <ref id="maintscriptprompt">) may
3719 assume that program will handle falling back to noninteractive
3724 For high-priority prompts without a reasonable default answer,
3725 maintainer scripts may abort if there is no controlling
3726 terminal. However, this situation should be avoided if at all
3727 possible, since it prevents automated or unattended installs.
3728 In most cases, users will consider this to be a bug in the
3733 <sect id="exitstatus">
3734 <heading>Exit status</heading>
3737 Each script must return a zero exit status for
3738 success, or a nonzero one for failure, since the package
3739 management system looks for the exit status of these scripts
3740 and determines what action to take next based on that datum.
3744 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3749 <list compact="compact">
3751 <var>new-preinst</var> <tt>install</tt>
3754 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3757 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3760 <var>old-preinst</var> <tt>abort-upgrade</tt>
3761 <var>new-version</var>
3766 <list compact="compact">
3768 <var>postinst</var> <tt>configure</tt>
3769 <var>most-recently-configured-version</var>
3772 <var>old-postinst</var> <tt>abort-upgrade</tt>
3773 <var>new-version</var>
3776 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3777 <tt>in-favour</tt> <var>package</var>
3778 <var>new-version</var>
3781 <var>postinst</var> <tt>abort-remove</tt>
3784 <var>deconfigured's-postinst</var>
3785 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3786 <var>failed-install-package</var> <var>version</var>
3787 [<tt>removing</tt> <var>conflicting-package</var>
3793 <list compact="compact">
3795 <var>prerm</var> <tt>remove</tt>
3798 <var>old-prerm</var> <tt>upgrade</tt>
3799 <var>new-version</var>
3802 <var>new-prerm</var> <tt>failed-upgrade</tt>
3803 <var>old-version</var>
3806 <var>conflictor's-prerm</var> <tt>remove</tt>
3807 <tt>in-favour</tt> <var>package</var>
3808 <var>new-version</var>
3811 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3812 <tt>in-favour</tt> <var>package-being-installed</var>
3813 <var>version</var> [<tt>removing</tt>
3814 <var>conflicting-package</var>
3820 <list compact="compact">
3822 <var>postrm</var> <tt>remove</tt>
3825 <var>postrm</var> <tt>purge</tt>
3828 <var>old-postrm</var> <tt>upgrade</tt>
3829 <var>new-version</var>
3832 <var>new-postrm</var> <tt>failed-upgrade</tt>
3833 <var>old-version</var>
3836 <var>new-postrm</var> <tt>abort-install</tt>
3839 <var>new-postrm</var> <tt>abort-install</tt>
3840 <var>old-version</var>
3843 <var>new-postrm</var> <tt>abort-upgrade</tt>
3844 <var>old-version</var>
3847 <var>disappearer's-postrm</var> <tt>disappear</tt>
3848 <var>overwriter</var>
3849 <var>overwriter-version</var>
3855 <sect id="unpackphase">
3856 <heading>Details of unpack phase of installation or upgrade</heading>
3859 The procedure on installation/upgrade/overwrite/disappear
3860 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3861 stage of <tt>dpkg --install</tt>) is as follows. In each
3862 case, if a major error occurs (unless listed below) the
3863 actions are, in general, run backwards - this means that the
3864 maintainer scripts are run with different arguments in
3865 reverse order. These are the "error unwind" calls listed
3872 If a version of the package is already installed, call
3873 <example compact="compact">
3874 <var>old-prerm</var> upgrade <var>new-version</var>
3878 If the script runs but exits with a non-zero
3879 exit status, <prgn>dpkg</prgn> will attempt:
3880 <example compact="compact">
3881 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3883 If this works, the upgrade continues. If this
3884 does not work, the error unwind:
3885 <example compact="compact">
3886 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3888 If this works, then the old-version is
3889 "Installed", if not, the old version is in a
3890 "Half-Configured" state.
3896 If a "conflicting" package is being removed at the same time,
3897 or if any package will be broken (due to <tt>Breaks</tt>):
3900 If <tt>--auto-deconfigure</tt> is
3901 specified, call, for each package to be deconfigured
3902 due to <tt>Breaks</tt>:
3903 <example compact="compact">
3904 <var>deconfigured's-prerm</var> deconfigure \
3905 in-favour <var>package-being-installed</var> <var>version</var>
3908 <example compact="compact">
3909 <var>deconfigured's-postinst</var> abort-deconfigure \
3910 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3912 The deconfigured packages are marked as
3913 requiring configuration, so that if
3914 <tt>--install</tt> is used they will be
3915 configured again if possible.
3918 If any packages depended on a conflicting
3919 package being removed and <tt>--auto-deconfigure</tt> is
3920 specified, call, for each such package:
3921 <example compact="compact">
3922 <var>deconfigured's-prerm</var> deconfigure \
3923 in-favour <var>package-being-installed</var> <var>version</var> \
3924 removing <var>conflicting-package</var> <var>version</var>
3927 <example compact="compact">
3928 <var>deconfigured's-postinst</var> abort-deconfigure \
3929 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3930 removing <var>conflicting-package</var> <var>version</var>
3932 The deconfigured packages are marked as
3933 requiring configuration, so that if
3934 <tt>--install</tt> is used they will be
3935 configured again if possible.
3938 To prepare for removal of each conflicting package, call:
3939 <example compact="compact">
3940 <var>conflictor's-prerm</var> remove \
3941 in-favour <var>package</var> <var>new-version</var>
3944 <example compact="compact">
3945 <var>conflictor's-postinst</var> abort-remove \
3946 in-favour <var>package</var> <var>new-version</var>
3955 If the package is being upgraded, call:
3956 <example compact="compact">
3957 <var>new-preinst</var> upgrade <var>old-version</var>
3959 If this fails, we call:
3961 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3968 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3970 is called. If this works, then the old version
3971 is in an "Installed" state, or else it is left
3972 in an "Unpacked" state.
3977 If it fails, then the old version is left
3978 in an "Half-Installed" state.
3985 Otherwise, if the package had some configuration
3986 files from a previous version installed (i.e., it
3987 is in the "configuration files only" state):
3988 <example compact="compact">
3989 <var>new-preinst</var> install <var>old-version</var>
3993 <var>new-postrm</var> abort-install <var>old-version</var>
3995 If this fails, the package is left in a
3996 "Half-Installed" state, which requires a
3997 reinstall. If it works, the packages is left in
3998 a "Config-Files" state.
4001 Otherwise (i.e., the package was completely purged):
4002 <example compact="compact">
4003 <var>new-preinst</var> install
4006 <example compact="compact">
4007 <var>new-postrm</var> abort-install
4009 If the error-unwind fails, the package is in a
4010 "Half-Installed" phase, and requires a
4011 reinstall. If the error unwind works, the
4012 package is in a not installed state.
4019 The new package's files are unpacked, overwriting any
4020 that may be on the system already, for example any
4021 from the old version of the same package or from
4022 another package. Backups of the old files are kept
4023 temporarily, and if anything goes wrong the package
4024 management system will attempt to put them back as
4025 part of the error unwind.
4029 It is an error for a package to contain files which
4030 are on the system in another package, unless
4031 <tt>Replaces</tt> is used (see <ref id="replaces">).
4033 The following paragraph is not currently the case:
4034 Currently the <tt>- - force-overwrite</tt> flag is
4035 enabled, downgrading it to a warning, but this may not
4041 It is a more serious error for a package to contain a
4042 plain file or other kind of non-directory where another
4043 package has a directory (again, unless
4044 <tt>Replaces</tt> is used). This error can be
4045 overridden if desired using
4046 <tt>--force-overwrite-dir</tt>, but this is not
4051 Packages which overwrite each other's files produce
4052 behavior which, though deterministic, is hard for the
4053 system administrator to understand. It can easily
4054 lead to "missing" programs if, for example, a package
4055 is installed which overwrites a file from another
4056 package, and is then removed again.<footnote>
4057 Part of the problem is due to what is arguably a
4058 bug in <prgn>dpkg</prgn>.
4063 A directory will never be replaced by a symbolic link
4064 to a directory or vice versa; instead, the existing
4065 state (symlink or not) will be left alone and
4066 <prgn>dpkg</prgn> will follow the symlink if there is
4075 If the package is being upgraded, call
4076 <example compact="compact">
4077 <var>old-postrm</var> upgrade <var>new-version</var>
4081 If this fails, <prgn>dpkg</prgn> will attempt:
4082 <example compact="compact">
4083 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4085 If this works, installation continues. If not,
4087 <example compact="compact">
4088 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4090 If this fails, the old version is left in a
4091 "Half-Installed" state. If it works, dpkg now
4093 <example compact="compact">
4094 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4096 If this fails, the old version is left in a
4097 "Half-Installed" state. If it works, dpkg now
4099 <example compact="compact">
4100 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4102 If this fails, the old version is in an
4109 This is the point of no return - if
4110 <prgn>dpkg</prgn> gets this far, it won't back off
4111 past this point if an error occurs. This will
4112 leave the package in a fairly bad state, which
4113 will require a successful re-installation to clear
4114 up, but it's when <prgn>dpkg</prgn> starts doing
4115 things that are irreversible.
4120 Any files which were in the old version of the package
4121 but not in the new are removed.
4125 The new file list replaces the old.
4129 The new maintainer scripts replace the old.
4133 Any packages all of whose files have been overwritten
4134 during the installation, and which aren't required for
4135 dependencies, are considered to have been removed.
4136 For each such package
4139 <prgn>dpkg</prgn> calls:
4140 <example compact="compact">
4141 <var>disappearer's-postrm</var> disappear \
4142 <var>overwriter</var> <var>overwriter-version</var>
4146 The package's maintainer scripts are removed.
4149 It is noted in the status database as being in a
4150 sane state, namely not installed (any conffiles
4151 it may have are ignored, rather than being
4152 removed by <prgn>dpkg</prgn>). Note that
4153 disappearing packages do not have their prerm
4154 called, because <prgn>dpkg</prgn> doesn't know
4155 in advance that the package is going to
4162 Any files in the package we're unpacking that are also
4163 listed in the file lists of other packages are removed
4164 from those lists. (This will lobotomize the file list
4165 of the "conflicting" package if there is one.)
4169 The backup files made during installation, above, are
4175 The new package's status is now sane, and recorded as
4180 Here is another point of no return - if the
4181 conflicting package's removal fails we do not unwind
4182 the rest of the installation; the conflicting package
4183 is left in a half-removed limbo.
4188 If there was a conflicting package we go and do the
4189 removal actions (described below), starting with the
4190 removal of the conflicting package's files (any that
4191 are also in the package being installed have already
4192 been removed from the conflicting package's file list,
4193 and so do not get removed now).
4199 <sect id="configdetails"><heading>Details of configuration</heading>
4202 When we configure a package (this happens with <tt>dpkg
4203 --install</tt> and <tt>dpkg --configure</tt>), we first
4204 update any <tt>conffile</tt>s and then call:
4205 <example compact="compact">
4206 <var>postinst</var> configure <var>most-recently-configured-version</var>
4211 No attempt is made to unwind after errors during
4212 configuration. If the configuration fails, the package is in
4213 a "Failed Config" state, and an error message is generated.
4217 If there is no most recently configured version
4218 <prgn>dpkg</prgn> will pass a null argument.
4221 Historical note: Truly ancient (pre-1997) versions of
4222 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4223 (including the angle brackets) in this case. Even older
4224 ones did not pass a second argument at all, under any
4225 circumstance. Note that upgrades using such an old dpkg
4226 version are unlikely to work for other reasons, even if
4227 this old argument behavior is handled by your postinst script.
4233 <sect id="removedetails"><heading>Details of removal and/or
4234 configuration purging</heading>
4240 <example compact="compact">
4241 <var>prerm</var> remove
4245 If prerm fails during replacement due to conflict
4247 <var>conflictor's-postinst</var> abort-remove \
4248 in-favour <var>package</var> <var>new-version</var>
4252 <var>postinst</var> abort-remove
4256 If this fails, the package is in a "Half-Configured"
4257 state, or else it remains "Installed".
4261 The package's files are removed (except <tt>conffile</tt>s).
4264 <example compact="compact">
4265 <var>postrm</var> remove
4269 If it fails, there's no error unwind, and the package is in
4270 an "Half-Installed" state.
4275 All the maintainer scripts except the <prgn>postrm</prgn>
4280 If we aren't purging the package we stop here. Note
4281 that packages which have no <prgn>postrm</prgn> and no
4282 <tt>conffile</tt>s are automatically purged when
4283 removed, as there is no difference except for the
4284 <prgn>dpkg</prgn> status.
4288 The <tt>conffile</tt>s and any backup files
4289 (<tt>~</tt>-files, <tt>#*#</tt> files,
4290 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4295 <example compact="compact">
4296 <var>postrm</var> purge
4300 If this fails, the package remains in a "Config-Files"
4305 The package's file list is removed.
4314 <chapt id="relationships">
4315 <heading>Declaring relationships between packages</heading>
4317 <sect id="depsyntax">
4318 <heading>Syntax of relationship fields</heading>
4321 These fields all have a uniform syntax. They are a list of
4322 package names separated by commas.
4326 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4327 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4328 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4329 control file fields of the package, which declare
4330 dependencies on other packages, the package names listed may
4331 also include lists of alternative package names, separated
4332 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4333 if any one of the alternative packages is installed, that
4334 part of the dependency is considered to be satisfied.
4338 All of the fields except for <tt>Provides</tt> may restrict
4339 their applicability to particular versions of each named
4340 package. This is done in parentheses after each individual
4341 package name; the parentheses should contain a relation from
4342 the list below followed by a version number, in the format
4343 described in <ref id="f-Version">.
4347 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4348 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4349 strictly earlier, earlier or equal, exactly equal, later or
4350 equal and strictly later, respectively. The deprecated
4351 forms <tt><</tt> and <tt>></tt> were used to mean
4352 earlier/later or equal, rather than strictly earlier/later,
4353 so they should not appear in new packages (though
4354 <prgn>dpkg</prgn> still supports them).
4358 Whitespace may appear at any point in the version
4359 specification subject to the rules in <ref
4360 id="controlsyntax">, and must appear where it's necessary to
4361 disambiguate; it is not otherwise significant. All of the
4362 relationship fields may span multiple lines. For
4363 consistency and in case of future changes to
4364 <prgn>dpkg</prgn> it is recommended that a single space be
4365 used after a version relationship and before a version
4366 number; it is also conventional to put a single space after
4367 each comma, on either side of each vertical bar, and before
4368 each open parenthesis. When wrapping a relationship field, it
4369 is conventional to do so after a comma and before the space
4370 following that comma.
4374 For example, a list of dependencies might appear as:
4375 <example compact="compact">
4378 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4383 All fields that specify build-time relationships
4384 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4385 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>)
4386 may be restricted to a certain set of architectures. This
4387 is indicated in brackets after each individual package name and
4388 the optional version specification. The brackets enclose a
4389 list of Debian architecture names separated by whitespace.
4390 Exclamation marks may be prepended to each of the names.
4391 (It is not permitted for some names to be prepended with
4392 exclamation marks while others aren't.) If the current Debian
4393 host architecture is not in this list and there are no
4394 exclamation marks in the list, or it is in the list with a
4395 prepended exclamation mark, the package name and the
4396 associated version specification are ignored completely for
4397 the purposes of defining the relationships.
4402 <example compact="compact">
4404 Build-Depends-Indep: texinfo
4405 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4406 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4408 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4409 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4410 <tt>gnumach-dev</tt> only on hurd-i386.
4414 If the architecture-restricted dependency is part of a set of
4415 alternatives using <tt>|</tt>, that alternative is ignored
4416 completely on architectures that do not match the restriction.
4418 <example compact="compact">
4419 Build-Depends: foo [!i386] | bar [!amd64]
4421 is equivalent to <tt>bar</tt> on the i386 architecture, to
4422 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4423 bar</tt> on all other architectures.
4427 All fields that specify build-time relationships may also be
4428 restricted to a certain set of architectures using architecture
4429 wildcards. The syntax for declaring such restrictions is the
4430 same as declaring restrictions using a certain set of
4431 architectures without architecture wildcards. For example:
4432 <example compact="compact">
4433 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4435 is equivalent to <tt>foo</tt> on architectures using the Linux
4436 kernel and any cpu, <tt>bar</tt> on architectures using any
4437 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4438 using a kernel other than Linux.
4442 Note that the binary package relationship fields such as
4443 <tt>Depends</tt> appear in one of the binary package
4444 sections of the control file, whereas the build-time
4445 relationships such as <tt>Build-Depends</tt> appear in the
4446 source package section of the control file (which is the
4451 <sect id="binarydeps">
4452 <heading>Binary Dependencies - <tt>Depends</tt>,
4453 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4454 <tt>Pre-Depends</tt>
4458 Packages can declare in their control file that they have
4459 certain relationships to other packages - for example, that
4460 they may not be installed at the same time as certain other
4461 packages, and/or that they depend on the presence of others.
4465 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4466 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4467 <tt>Breaks</tt> and <tt>Conflicts</tt> control file fields.
4468 <tt>Breaks</tt> is described in <ref id="breaks">, and
4469 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4470 rest are described below.
4474 These seven fields are used to declare a dependency
4475 relationship by one package on another. Except for
4476 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4477 depending (binary) package's control file.
4478 (<tt>Enhances</tt> appears in the recommending package's
4479 control file, and <tt>Breaks</tt> appears in the version of
4480 depended-on package which causes the named package to
4485 A <tt>Depends</tt> field takes effect <em>only</em> when a
4486 package is to be configured. It does not prevent a package
4487 being on the system in an unconfigured state while its
4488 dependencies are unsatisfied, and it is possible to replace
4489 a package whose dependencies are satisfied and which is
4490 properly installed with a different version whose
4491 dependencies are not and cannot be satisfied; when this is
4492 done the depending package will be left unconfigured (since
4493 attempts to configure it will give errors) and will not
4494 function properly. If it is necessary, a
4495 <tt>Pre-Depends</tt> field can be used, which has a partial
4496 effect even when a package is being unpacked, as explained
4497 in detail below. (The other three dependency fields,
4498 <tt>Recommends</tt>, <tt>Suggests</tt> and
4499 <tt>Enhances</tt>, are only used by the various front-ends
4500 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4501 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4505 For this reason packages in an installation run are usually
4506 all unpacked first and all configured later; this gives
4507 later versions of packages with dependencies on later
4508 versions of other packages the opportunity to have their
4509 dependencies satisfied.
4513 In case of circular dependencies, since installation or
4514 removal order honoring the dependency order can't be
4515 established, dependency loops are broken at some point
4516 (based on rules below), and some packages may not be able to
4517 rely on their dependencies being present when being
4518 installed or removed, depending on which side of the break
4519 of the circular dependency loop they happen to be on. If one
4520 of the packages in the loop has no postinst script, then the
4521 cycle will be broken at that package, so as to ensure that
4522 all postinst scripts run with the dependencies properly
4523 configured if this is possible. Otherwise the breaking point
4528 The <tt>Depends</tt> field thus allows package maintainers
4529 to impose an order in which packages should be configured.
4533 The meaning of the five dependency fields is as follows:
4535 <tag><tt>Depends</tt></tag>
4538 This declares an absolute dependency. A package will
4539 not be configured unless all of the packages listed in
4540 its <tt>Depends</tt> field have been correctly
4545 The <tt>Depends</tt> field should be used if the
4546 depended-on package is required for the depending
4547 package to provide a significant amount of
4552 The <tt>Depends</tt> field should also be used if the
4553 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4554 <prgn>postrm</prgn> scripts require the package to be
4555 present in order to run. Note, however, that the
4556 <prgn>postrm</prgn> cannot rely on any non-essential
4557 packages to be present during the <tt>purge</tt>
4561 <tag><tt>Recommends</tt></tag>
4564 This declares a strong, but not absolute, dependency.
4568 The <tt>Recommends</tt> field should list packages
4569 that would be found together with this one in all but
4570 unusual installations.
4574 <tag><tt>Suggests</tt></tag>
4576 This is used to declare that one package may be more
4577 useful with one or more others. Using this field
4578 tells the packaging system and the user that the
4579 listed packages are related to this one and can
4580 perhaps enhance its usefulness, but that installing
4581 this one without them is perfectly reasonable.
4584 <tag><tt>Enhances</tt></tag>
4586 This field is similar to Suggests but works in the
4587 opposite direction. It is used to declare that a
4588 package can enhance the functionality of another
4592 <tag><tt>Pre-Depends</tt></tag>
4595 This field is like <tt>Depends</tt>, except that it
4596 also forces <prgn>dpkg</prgn> to complete installation
4597 of the packages named before even starting the
4598 installation of the package which declares the
4599 pre-dependency, as follows:
4603 When a package declaring a pre-dependency is about to
4604 be <em>unpacked</em> the pre-dependency can be
4605 satisfied if the depended-on package is either fully
4606 configured, <em>or even if</em> the depended-on
4607 package(s) are only unpacked or in the "Half-Configured"
4608 state, provided that they have been configured
4609 correctly at some point in the past (and not removed
4610 or partially removed since). In this case, both the
4611 previously-configured and currently unpacked or
4612 "Half-Configured" versions must satisfy any version
4613 clause in the <tt>Pre-Depends</tt> field.
4617 When the package declaring a pre-dependency is about
4618 to be <em>configured</em>, the pre-dependency will be
4619 treated as a normal <tt>Depends</tt>, that is, it will
4620 be considered satisfied only if the depended-on
4621 package has been correctly configured.
4625 <tt>Pre-Depends</tt> should be used sparingly,
4626 preferably only by packages whose premature upgrade or
4627 installation would hamper the ability of the system to
4628 continue with any upgrade that might be in progress.
4632 <tt>Pre-Depends</tt> are also required if the
4633 <prgn>preinst</prgn> script depends on the named
4634 package. It is best to avoid this situation if
4642 When selecting which level of dependency to use you should
4643 consider how important the depended-on package is to the
4644 functionality of the one declaring the dependency. Some
4645 packages are composed of components of varying degrees of
4646 importance. Such a package should list using
4647 <tt>Depends</tt> the package(s) which are required by the
4648 more important components. The other components'
4649 requirements may be mentioned as Suggestions or
4650 Recommendations, as appropriate to the components' relative
4656 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4659 When one binary package declares that it breaks another,
4660 <prgn>dpkg</prgn> will refuse to allow the package which
4661 declares <tt>Breaks</tt> be installed unless the broken
4662 package is deconfigured first, and it will refuse to
4663 allow the broken package to be reconfigured.
4667 A package will not be regarded as causing breakage merely
4668 because its configuration files are still installed; it must
4669 be at least "Half-Installed".
4673 A special exception is made for packages which declare that
4674 they break their own package name or a virtual package which
4675 they provide (see below): this does not count as a real
4680 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4681 version clause; such a <tt>Breaks</tt> is introduced in the
4682 version of an (implicit or explicit) dependency which violates
4683 an assumption or reveals a bug in earlier versions of the broken
4684 package, or which takes over a file from earlier versions of the
4685 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
4686 will inform higher-level package management tools that the
4687 broken package must be upgraded before the new one.
4691 If the breaking package also overwrites some files from the
4692 older package, it should use <tt>Replaces</tt> to ensure this
4693 goes smoothly. See <ref id="replaces"> for a full discussion
4694 of taking over files from other packages, including how to
4695 use <tt>Breaks</tt> in those cases.
4699 Many of the cases where <tt>Breaks</tt> should be used were
4700 previously handled with <tt>Conflicts</tt>
4701 because <tt>Breaks</tt> did not yet exist.
4702 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
4703 See <ref id="conflicts"> for more information about the
4708 <sect id="conflicts">
4709 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4712 When one binary package declares a conflict with another
4713 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4714 refuse to allow them to be installed on the system at the
4715 same time. This is a stronger restriction than <tt>Breaks</tt>,
4716 which just prevents both packages from being configured at the
4717 same time. Conflicting packages cannot be unpacked on the
4718 system at the same time.
4722 If one package is to be installed, the other must be removed
4723 first. If the package being installed is marked as replacing
4724 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
4725 normally be used in this case) the one on the system, or the one
4726 on the system is marked as deselected, or both packages are
4727 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
4728 automatically remove the package which is causing the conflict.
4729 Otherwise, it will halt the installation of the new package with
4730 an error. This mechanism is specifically designed to produce an
4731 error when the installed package is <tt>Essential</tt>, but the
4736 A package will not cause a conflict merely because its
4737 configuration files are still installed; it must be at least
4742 A special exception is made for packages which declare a
4743 conflict with their own package name, or with a virtual
4744 package which they provide (see below): this does not
4745 prevent their installation, and allows a package to conflict
4746 with others providing a replacement for it. You use this
4747 feature when you want the package in question to be the only
4748 package providing some feature.
4752 Normally, <tt>Breaks</tt> should be used instead
4753 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
4754 stronger restriction on the ordering of package installation or
4755 upgrade and can make it more difficult for the package manager
4756 to find a correct solution to an upgrade or installation
4757 problem. <tt>Breaks</tt> should be used
4759 <item>when moving a file from one package to another (see
4760 <ref id="replaces">),</item>
4761 <item>when splitting a package (a special case of the previous
4763 <item>when the breaking package exposes a bug in or interacts
4764 badly with particular versions of the broken
4767 <tt>Conflicts</tt> should be used
4769 <item>when two packages provide the same file and will
4770 continue to do so,</item>
4771 <item>in conjunction with <tt>Provides</tt> when only one
4772 package providing a given virtual facility may be installed
4773 at a time (see <ref id="virtual">),</item>
4774 <item>in other cases where one must prevent simultaneous
4775 installation of two packages for reasons that are ongoing
4776 (not fixed in a later version of one of the packages) or
4777 that must prevent both packages from being unpacked at the
4778 same time, not just configured.</item>
4780 Be aware that adding <tt>Conflicts</tt> is normally not the best
4781 solution when two packages provide the same files. Depending on
4782 the reason for that conflict, using alternatives or renaming the
4783 files is often a better approach. See, for
4784 example, <ref id="binaries">.
4788 A <tt>Conflicts</tt> entry may have an "earlier than" version
4789 clause if the reason for the conflict is corrected in a later
4790 version of one of the packages. However, normally the presence
4791 of an "earlier than" version clause is a sign
4792 that <tt>Breaks</tt> should have been used instead. An "earlier
4793 than" version clause in <tt>Conflicts</tt>
4794 prevents <prgn>dpkg</prgn> from upgrading or installing the
4795 package which declares such a conflict until the upgrade or
4796 removal of the conflicted-with package has been completed, which
4797 is a strong restriction.
4801 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4805 As well as the names of actual ("concrete") packages, the
4806 package relationship fields <tt>Depends</tt>,
4807 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4808 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4809 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4810 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4811 may mention "virtual packages".
4815 A <em>virtual package</em> is one which appears in the
4816 <tt>Provides</tt> control file field of another package.
4817 The effect is as if the package(s) which provide a
4818 particular virtual package name had been listed by name
4819 everywhere the virtual package name appears. (See also <ref
4824 If there are both concrete and virtual packages of the same
4825 name, then the dependency may be satisfied (or the conflict
4826 caused) by either the concrete package with the name in
4827 question or any other concrete package which provides the
4828 virtual package with the name in question. This is so that,
4829 for example, supposing we have
4830 <example compact="compact">
4833 </example> and someone else releases an enhanced version of
4834 the <tt>bar</tt> package they can say:
4835 <example compact="compact">
4839 and the <tt>bar-plus</tt> package will now also satisfy the
4840 dependency for the <tt>foo</tt> package.
4844 If a relationship field has a version number attached, only real
4845 packages will be considered to see whether the relationship is
4846 satisfied (or the prohibition violated, for a conflict or
4847 breakage). In other words, if a version number is specified,
4848 this is a request to ignore all <tt>Provides</tt> for that
4849 package name and consider only real packages. The package
4850 manager will assume that a package providing that virtual
4851 package is not of the "right" version. A <tt>Provides</tt>
4852 field may not contain version numbers, and the version number of
4853 the concrete package which provides a particular virtual package
4854 will not be considered when considering a dependency on or
4855 conflict with the virtual package name.<footnote>
4856 It is possible that a future release of <prgn>dpkg</prgn> may
4857 add the ability to specify a version number for each virtual
4858 package it provides. This feature is not yet present,
4859 however, and is expected to be used only infrequently.
4864 To specify which of a set of real packages should be the default
4865 to satisfy a particular dependency on a virtual package, list
4866 the real package as an alternative before the virtual one.
4870 If the virtual package represents a facility that can only be
4871 provided by one real package at a time, such as
4872 the <package>mail-transport-agent</package> virtual package that
4873 requires installation of a binary that would conflict with all
4874 other providers of that virtual package (see
4875 <ref id="mail-transport-agents">), all packages providing that
4876 virtual package should also declare a conflict with it
4877 using <tt>Conflicts</tt>. This will ensure that at most one
4878 provider of that virtual package is unpacked or installed at a
4883 <sect id="replaces"><heading>Overwriting files and replacing
4884 packages - <tt>Replaces</tt></heading>
4887 Packages can declare in their control file that they should
4888 overwrite files in certain other packages, or completely
4889 replace other packages. The <tt>Replaces</tt> control file
4890 field has these two distinct purposes.
4893 <sect1><heading>Overwriting files in other packages</heading>
4896 It is usually an error for a package to contain files which
4897 are on the system in another package. However, if the
4898 overwriting package declares that it <tt>Replaces</tt> the one
4899 containing the file being overwritten, then <prgn>dpkg</prgn>
4900 will replace the file from the old package with that from the
4901 new. The file will no longer be listed as "owned" by the old
4902 package and will be taken over by the new package.
4903 Normally, <tt>Breaks</tt> should be used in conjunction
4904 with <tt>Replaces</tt>.<footnote>
4905 To see why <tt>Breaks</tt> is normally needed in addition
4906 to <tt>Replaces</tt>, consider the case of a file in the
4907 package <package>foo</package> being taken over by the
4908 package <package>foo-data</package>.
4909 <tt>Replaces</tt> will allow <package>foo-data</package> to
4910 be installed and take over that file. However,
4911 without <tt>Breaks</tt>, nothing
4912 requires <package>foo</package> to be upgraded to a newer
4913 version that knows it does not include that file and instead
4914 depends on <package>foo-data</package>. Nothing would
4915 prevent the new <package>foo-data</package> package from
4916 being installed and then removed, removing the file that it
4917 took over from <package>foo</package>. After that
4918 operation, the package manager would think the system was in
4919 a consistent state, but the <package>foo</package> package
4920 would be missing one of its files.
4925 For example, if a package <package>foo</package> is split
4926 into <package>foo</package> and <package>foo-data</package>
4927 starting at version 1.2-3, <package>foo-data</package> would
4929 <example compact="compact">
4930 Replaces: foo (<< 1.2-3)
4931 Breaks: foo (<< 1.2-3)
4933 in its control file. The new version of the
4934 package <package>foo</package> would normally have the field
4935 <example compact="compact">
4936 Depends: foo-data (>= 1.2-3)
4938 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
4939 the files moved into <package>foo-data</package> are not
4940 required for normal operation).
4944 If a package is completely replaced in this way, so that
4945 <prgn>dpkg</prgn> does not know of any files it still
4946 contains, it is considered to have "disappeared". It will
4947 be marked as not wanted on the system (selected for
4948 removal) and not installed. Any <tt>conffile</tt>s
4949 details noted for the package will be ignored, as they
4950 will have been taken over by the overwriting package. The
4951 package's <prgn>postrm</prgn> script will be run with a
4952 special argument to allow the package to do any final
4953 cleanup required. See <ref id="mscriptsinstact">.
4955 Replaces is a one way relationship. You have to install
4956 the replacing package after the replaced package.
4961 For this usage of <tt>Replaces</tt>, virtual packages (see
4962 <ref id="virtual">) are not considered when looking at a
4963 <tt>Replaces</tt> field. The packages declared as being
4964 replaced must be mentioned by their real names.
4968 This usage of <tt>Replaces</tt> only takes effect when both
4969 packages are at least partially on the system at once. It is
4970 not relevant if the packages conflict unless the conflict has
4975 <sect1><heading>Replacing whole packages, forcing their
4979 Second, <tt>Replaces</tt> allows the packaging system to
4980 resolve which package should be removed when there is a
4981 conflict (see <ref id="conflicts">). This usage only takes
4982 effect when the two packages <em>do</em> conflict, so that the
4983 two usages of this field do not interfere with each other.
4987 In this situation, the package declared as being replaced
4988 can be a virtual package, so for example, all mail
4989 transport agents (MTAs) would have the following fields in
4990 their control files:
4991 <example compact="compact">
4992 Provides: mail-transport-agent
4993 Conflicts: mail-transport-agent
4994 Replaces: mail-transport-agent
4996 ensuring that only one MTA can be installed at any one
4997 time. See <ref id="virtual"> for more information about this
5002 <sect id="sourcebinarydeps">
5003 <heading>Relationships between source and binary packages -
5004 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5005 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5009 Source packages that require certain binary packages to be
5010 installed or absent at the time of building the package
5011 can declare relationships to those binary packages.
5015 This is done using the <tt>Build-Depends</tt>,
5016 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5017 <tt>Build-Conflicts-Indep</tt> control file fields.
5021 Build-dependencies on "build-essential" binary packages can be
5022 omitted. Please see <ref id="pkg-relations"> for more information.
5026 The dependencies and conflicts they define must be satisfied
5027 (as defined earlier for binary packages) in order to invoke
5028 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5030 There is no Build-Depends-Arch; this role is essentially
5031 met with Build-Depends. Anyone building the
5032 <tt>build-indep</tt> and binary-indep<tt></tt> targets is
5033 assumed to be building the whole package, and therefore
5034 installation of all build dependencies is required.
5037 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5038 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5039 not yet know how to check for its existence, and
5040 <tt>binary-arch</tt>. The purpose of the original split
5041 between <tt>Build-Depends</tt> and
5042 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5043 wouldn't need to install extra packages needed only for the
5044 binary-indep targets. But without a build-arch/build-indep
5045 split, this didn't work, since most of the work is done in
5046 the build target, not in the binary target.
5050 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5051 <tt>binary-arch</tt></tag>
5053 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5054 fields must be satisfied when these targets are invoked.
5056 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5057 and <tt>binary-indep</tt></tag>
5059 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5060 <tt>Build-Depends-Indep</tt>, and
5061 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5062 these targets are invoked.
5070 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5073 Packages containing shared libraries must be constructed with
5074 a little care to make sure that the shared library is always
5075 available. This is especially important for packages whose
5076 shared libraries are vitally important, such as the C library
5077 (currently <tt>libc6</tt>).
5081 Packages involving shared libraries should be split up into
5082 several binary packages. This section mostly deals with how
5083 this separation is to be accomplished; rules for files within
5084 the shared library packages are in <ref id="libraries"> instead.
5087 <sect id="sharedlibs-runtime">
5088 <heading>Run-time shared libraries</heading>
5091 The run-time shared library needs to be placed in a package
5092 whose name changes whenever the shared object version
5095 Since it is common place to install several versions of a
5096 package that just provides shared libraries, it is a
5097 good idea that the library package should not
5098 contain any extraneous non-versioned files, unless they
5099 happen to be in versioned directories.</p>
5101 The most common mechanism is to place it in a package
5103 <package><var>libraryname</var><var>soversion</var></package>,
5104 where <file><var>soversion</var></file> is the version number
5105 in the soname of the shared library<footnote>
5106 The soname is the shared object name: it's the thing
5107 that has to match exactly between building an executable
5108 and running it for the dynamic linker to be able run the
5109 program. For example, if the soname of the library is
5110 <file>libfoo.so.6</file>, the library package would be
5111 called <file>libfoo6</file>.
5113 Alternatively, if it would be confusing to directly append
5114 <var>soversion</var> to <var>libraryname</var> (e.g. because
5115 <var>libraryname</var> itself ends in a number), you may use
5116 <package><var>libraryname</var>-<var>soversion</var></package> and
5117 <package><var>libraryname</var>-<var>soversion</var>-dev</package>
5122 If you have several shared libraries built from the same
5123 source tree you may lump them all together into a single
5124 shared library package, provided that you change all of
5125 their sonames at once (so that you don't get filename
5126 clashes if you try to install different versions of the
5127 combined shared libraries package).
5131 The package should install the shared libraries under
5132 their normal names. For example, the <package>libgdbm3</package>
5133 package should install <file>libgdbm.so.3.0.0</file> as
5134 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5135 renamed or re-linked by any <prgn>prerm</prgn> or
5136 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5137 of renaming things safely without affecting running programs,
5138 and attempts to interfere with this are likely to lead to
5143 Shared libraries should not be installed executable, since
5144 the dynamic linker does not require this and trying to
5145 execute a shared library usually results in a core dump.
5149 The run-time library package should include the symbolic link that
5150 <prgn>ldconfig</prgn> would create for the shared libraries.
5151 For example, the <package>libgdbm3</package> package should include
5152 a symbolic link from <file>/usr/lib/libgdbm.so.3</file> to
5153 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5154 linker (for example <prgn>ld.so</prgn> or
5155 <prgn>ld-linux.so.*</prgn>) can find the library between the
5156 time that <prgn>dpkg</prgn> installs it and the time that
5157 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5159 The package management system requires the library to be
5160 placed before the symbolic link pointing to it in the
5161 <file>.deb</file> file. This is so that when
5162 <prgn>dpkg</prgn> comes to install the symlink
5163 (overwriting the previous symlink pointing at an older
5164 version of the library), the new shared library is already
5165 in place. In the past, this was achieved by creating the
5166 library in the temporary packaging directory before
5167 creating the symlink. Unfortunately, this was not always
5168 effective, since the building of the tar file in the
5169 <file>.deb</file> depended on the behavior of the underlying
5170 file system. Some file systems (such as reiserfs) reorder
5171 the files so that the order of creation is forgotten.
5172 Since version 1.7.0, <prgn>dpkg</prgn>
5173 reorders the files itself as necessary when building a
5174 package. Thus it is no longer important to concern
5175 oneself with the order of file creation.
5179 <sect1 id="ldconfig">
5180 <heading><tt>ldconfig</tt></heading>
5183 Any package installing shared libraries in one of the default
5184 library directories of the dynamic linker (which are currently
5185 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5186 listed in <file>/etc/ld.so.conf</file><footnote>
5188 <list compact="compact">
5189 <item>/usr/local/lib</item>
5190 <item>/usr/lib/libc5-compat</item>
5191 <item>/lib/libc5-compat</item>
5194 must use <prgn>ldconfig</prgn> to update the shared library
5199 The package maintainer scripts must only call
5200 <prgn>ldconfig</prgn> under these circumstances:
5201 <list compact="compact">
5202 <item>When the <prgn>postinst</prgn> script is run with a
5203 first argument of <tt>configure</tt>, the script must call
5204 <prgn>ldconfig</prgn>, and may optionally invoke
5205 <prgn>ldconfig</prgn> at other times.
5207 <item>When the <prgn>postrm</prgn> script is run with a
5208 first argument of <tt>remove</tt>, the script should call
5209 <prgn>ldconfig</prgn>.
5214 During install or upgrade, the preinst is called before
5215 the new files are installed, so calling "ldconfig" is
5216 pointless. The preinst of an existing package can also be
5217 called if an upgrade fails. However, this happens during
5218 the critical time when a shared libs may exist on-disk
5219 under a temporary name. Thus, it is dangerous and
5220 forbidden by current policy to call "ldconfig" at this
5225 When a package is installed or upgraded, "postinst
5226 configure" runs after the new files are safely on-disk.
5227 Since it is perfectly safe to invoke ldconfig
5228 unconditionally in a postinst, it is OK for a package to
5229 simply put ldconfig in its postinst without checking the
5230 argument. The postinst can also be called to recover from
5231 a failed upgrade. This happens before any new files are
5232 unpacked, so there is no reason to call "ldconfig" at this
5237 For a package that is being removed, prerm is
5238 called with all the files intact, so calling ldconfig is
5239 useless. The other calls to "prerm" happen in the case of
5240 upgrade at a time when all the files of the old package
5241 are on-disk, so again calling "ldconfig" is pointless.
5245 postrm, on the other hand, is called with the "remove"
5246 argument just after the files are removed, so this is
5247 the proper time to call "ldconfig" to notify the system
5248 of the fact that the shared libraries from the package
5249 are removed. The postrm can be called at several other
5250 times. At the time of "postrm purge", "postrm
5251 abort-install", or "postrm abort-upgrade", calling
5252 "ldconfig" is useless because the shared lib files are
5253 not on-disk. However, when "postrm" is invoked with
5254 arguments "upgrade", "failed-upgrade", or "disappear", a
5255 shared lib may exist on-disk under a temporary filename.
5263 <sect id="sharedlibs-support-files">
5264 <heading>Shared library support files</heading>
5267 If your package contains files whose names do not change with
5268 each change in the library shared object version, you must not
5269 put them in the shared library package. Otherwise, several
5270 versions of the shared library cannot be installed at the same
5271 time without filename clashes, making upgrades and transitions
5272 unnecessarily difficult.
5276 It is recommended that supporting files and run-time support
5277 programs that do not need to be invoked manually by users, but
5278 are nevertheless required for the package to function, be placed
5279 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5280 preferably under <file>/usr/lib/</file><var>package-name</var>.
5281 If the program or file is architecture independent, the
5282 recommendation is for it to be placed in a subdirectory of
5283 <file>/usr/share</file> instead, preferably under
5284 <file>/usr/share/</file><var>package-name</var>. Following the
5285 <var>package-name</var> naming convention ensures that the file
5286 names change when the shared object version changes.
5290 Run-time support programs that use the shared library but are
5291 not required for the library to function or files used by the
5292 shared library that can be used by any version of the shared
5293 library package should instead be put in a separate package.
5294 This package might typically be named
5295 <package><var>libraryname</var>-tools</package>; note the
5296 absence of the <var>soversion</var> in the package name.
5300 Files and support programs only useful when compiling software
5301 against the library should be included in the development
5302 package for the library.<footnote>
5303 For example, a <file><var>package-name</var>-config</file>
5304 script or <package>pkg-config</package> configuration files.
5309 <sect id="sharedlibs-static">
5310 <heading>Static libraries</heading>
5313 The static library (<file><var>libraryname.a</var></file>)
5314 is usually provided in addition to the shared version.
5315 It is placed into the development package (see below).
5319 In some cases, it is acceptable for a library to be
5320 available in static form only; these cases include:
5322 <item>libraries for languages whose shared library support
5323 is immature or unstable</item>
5324 <item>libraries whose interfaces are in flux or under
5325 development (commonly the case when the library's
5326 major version number is zero, or where the ABI breaks
5327 across patchlevels)</item>
5328 <item>libraries which are explicitly intended to be
5329 available only in static form by their upstream
5334 <sect id="sharedlibs-dev">
5335 <heading>Development files</heading>
5338 If there are development files associated with a shared library,
5339 the source package needs to generate a binary development package
5340 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5341 or if you prefer only to support one development version at a
5342 time, <package><var>libraryname</var>-dev</package>. Installing
5343 the development package must result in installation of all the
5344 development files necessary for compiling programs against that
5345 shared library.<footnote>
5346 This wording allows the development files to be split into
5347 several packages, such as a separate architecture-independent
5348 <package><var>libraryname</var>-headers</package>, provided that
5349 the development package depends on all the required additional
5355 In case several development versions of a library exist, you may
5356 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5357 <ref id="conflicts">) to ensure that the user only installs one
5358 development version at a time (as different development versions are
5359 likely to have the same header files in them, which would cause a
5360 filename clash if both were installed).
5364 The development package should contain a symlink for the associated
5365 shared library without a version number. For example, the
5366 <package>libgdbm-dev</package> package should include a symlink
5367 from <file>/usr/lib/libgdbm.so</file> to
5368 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5369 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5370 <file>libgdbm.so</file> when compiling dynamically.
5374 <sect id="sharedlibs-intradeps">
5375 <heading>Dependencies between the packages of the same library</heading>
5378 Typically the development version should have an exact
5379 version dependency on the runtime library, to make sure that
5380 compilation and linking happens correctly. The
5381 <tt>${binary:Version}</tt> substitution variable can be
5382 useful for this purpose.
5384 Previously, <tt>${Source-Version}</tt> was used, but its name
5385 was confusing and it has been deprecated since dpkg 1.13.19.
5390 <sect id="sharedlibs-shlibdeps">
5391 <heading>Dependencies between the library and other packages -
5392 the <tt>shlibs</tt> system</heading>
5395 If a package contains a binary or library which links to a
5396 shared library, we must ensure that when the package is
5397 installed on the system, all of the libraries needed are
5398 also installed. This requirement led to the creation of the
5399 <tt>shlibs</tt> system, which is very simple in its design:
5400 any package which <em>provides</em> a shared library also
5401 provides information on the package dependencies required to
5402 ensure the presence of this library, and any package which
5403 <em>uses</em> a shared library uses this information to
5404 determine the dependencies it requires. The files which
5405 contain the mapping from shared libraries to the necessary
5406 dependency information are called <file>shlibs</file> files.
5410 Thus, when a package is built which contains any shared
5411 libraries, it must provide a <file>shlibs</file> file for other
5412 packages to use, and when a package is built which contains
5413 any shared libraries or compiled binaries, it must run
5414 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5415 on these to determine the libraries used and hence the
5416 dependencies needed by this package.<footnote>
5418 In the past, the shared libraries linked to were
5419 determined by calling <prgn>ldd</prgn>, but now
5420 <prgn>objdump</prgn> is used to do this. The only
5421 change this makes to package building is that
5422 <prgn>dpkg-shlibdeps</prgn> must also be run on shared
5423 libraries, whereas in the past this was unnecessary.
5424 The rest of this footnote explains the advantage that
5429 We say that a binary <tt>foo</tt> <em>directly</em> uses
5430 a library <tt>libbar</tt> if it is explicitly linked
5431 with that library (that is, it uses the flag
5432 <tt>-lbar</tt> during the linking stage). Other
5433 libraries that are needed by <tt>libbar</tt> are linked
5434 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5435 linker will load them automatically when it loads
5436 <tt>libbar</tt>. A package should depend on
5437 the libraries it directly uses, and the dependencies for
5438 those libraries should automatically pull in the other
5443 Unfortunately, the <prgn>ldd</prgn> program shows both
5444 the directly and indirectly used libraries, meaning that
5445 the dependencies determined included both direct and
5446 indirect dependencies. The use of <prgn>objdump</prgn>
5447 avoids this problem by determining only the directly
5452 A good example of where this helps is the following. We
5453 could update <tt>libimlib</tt> with a new version that
5454 supports a new graphics format called dgf (but retaining
5455 the same major version number). If we used the old
5456 <prgn>ldd</prgn> method, every package that uses
5457 <tt>libimlib</tt> would need to be recompiled so it
5458 would also depend on <tt>libdgf</tt> or it wouldn't run
5459 due to missing symbols. However with the new system,
5460 packages using <tt>libimlib</tt> can rely on
5461 <tt>libimlib</tt> itself having the dependency on
5462 <tt>libdgf</tt> and so they would not need rebuilding.
5468 In the following sections, we will first describe where the
5469 various <tt>shlibs</tt> files are to be found, then how to
5470 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5471 file format and how to create them if your package contains a
5476 <heading>The <tt>shlibs</tt> files present on the system</heading>
5479 There are several places where <tt>shlibs</tt> files are
5480 found. The following list gives them in the order in which
5482 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5483 (The first one which gives the required information is used.)
5489 <p><file>debian/shlibs.local</file></p>
5492 This lists overrides for this package. Its use is
5493 described below (see <ref id="shlibslocal">).
5498 <p><file>/etc/dpkg/shlibs.override</file></p>
5501 This lists global overrides. This list is normally
5502 empty. It is maintained by the local system
5508 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5511 When packages are being built, any
5512 <file>debian/shlibs</file> files are copied into the
5513 control file area of the temporary build directory and
5514 given the name <file>shlibs</file>. These files give
5515 details of any shared libraries included in the
5517 An example may help here. Let us say that the
5518 source package <tt>foo</tt> generates two binary
5519 packages, <tt>libfoo2</tt> and
5520 <tt>foo-runtime</tt>. When building the binary
5521 packages, the two packages are created in the
5522 directories <file>debian/libfoo2</file> and
5523 <file>debian/foo-runtime</file> respectively.
5524 (<file>debian/tmp</file> could be used instead of one
5525 of these.) Since <tt>libfoo2</tt> provides the
5526 <tt>libfoo</tt> shared library, it will require a
5527 <tt>shlibs</tt> file, which will be installed in
5528 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually
5530 <file>/var/lib/dpkg/info/libfoo2.shlibs</file>. Then
5531 when <prgn>dpkg-shlibdeps</prgn> is run on the
5533 <file>debian/foo-runtime/usr/bin/foo-prog</file>, it
5535 <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5536 determine whether <tt>foo-prog</tt>'s library
5537 dependencies are satisfied by any of the libraries
5538 provided by <tt>libfoo2</tt>. For this reason,
5539 <prgn>dpkg-shlibdeps</prgn> must only be run once
5540 all of the individual binary packages'
5541 <tt>shlibs</tt> files have been installed into the
5548 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5551 These are the <file>shlibs</file> files corresponding to
5552 all of the packages installed on the system, and are
5553 maintained by the relevant package maintainers.
5558 <p><file>/etc/dpkg/shlibs.default</file></p>
5561 This file lists any shared libraries whose packages
5562 have failed to provide correct <file>shlibs</file> files.
5563 It was used when the <file>shlibs</file> setup was first
5564 introduced, but it is now normally empty. It is
5565 maintained by the <tt>dpkg</tt> maintainer.
5573 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5574 <file>shlibs</file> files</heading>
5578 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5579 into your <file>debian/rules</file> file. If your package
5580 contains only compiled binaries and libraries (but no scripts),
5581 you can use a command such as:
5582 <example compact="compact">
5583 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5584 debian/tmp/usr/lib/*
5586 Otherwise, you will need to explicitly list the compiled
5587 binaries and libraries.<footnote>
5588 If you are using <tt>debhelper</tt>, the
5589 <prgn>dh_shlibdeps</prgn> program will do this work for
5590 you. It will also correctly handle multi-binary
5596 This command puts the dependency information into the
5597 <file>debian/substvars</file> file, which is then used by
5598 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5599 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5600 field in the control file for this to work.
5604 If <prgn>dpkg-shlibdeps</prgn> doesn't complain, you're
5605 done. If it does complain you might need to create your own
5606 <file>debian/shlibs.local</file> file, as explained below (see
5607 <ref id="shlibslocal">).
5611 If you have multiple binary packages, you will need to call
5612 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5613 compiled libraries or binaries. In such a case, you will
5614 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5615 utilities to specify a different <file>substvars</file> file.
5619 If you are creating a udeb for use in the Debian Installer,
5620 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
5621 should use the dependency line of type <tt>udeb</tt> by
5622 adding the <tt>-tudeb</tt> option<footnote>
5623 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5624 will automatically add this option if it knows it is
5626 </footnote>. If there is no dependency line of type <tt>udeb</tt>
5627 in the <file>shlibs</file> file, <prgn>dpkg-shlibdeps</prgn> will
5628 fall back to the regular dependency line.
5632 For more details on dpkg-shlibdeps, please see
5633 <ref id="pkg-dpkg-shlibdeps"> and
5634 <manref name="dpkg-shlibdeps" section="1">.
5639 <heading>The <file>shlibs</file> File Format</heading>
5642 Each <file>shlibs</file> file has the same format. Lines
5643 beginning with <tt>#</tt> are considered to be comments and
5644 are ignored. Each line is of the form:
5645 <example compact="compact">
5646 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5651 We will explain this by reference to the example of the
5652 <tt>zlib1g</tt> package, which (at the time of writing)
5653 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5657 <var>type</var> is an optional element that indicates the type
5658 of package for which the line is valid. The only type currently
5659 in use is <tt>udeb</tt>. The colon and space after the type are
5664 <var>library-name</var> is the name of the shared library,
5665 in this case <tt>libz</tt>. (This must match the name part
5666 of the soname, see below.)
5670 <var>soname-version</var> is the version part of the soname of
5671 the library. The soname is the thing that must exactly match
5672 for the library to be recognized by the dynamic linker, and is
5674 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5675 example, <tt>libz.so.1</tt>.<footnote>
5676 This can be determined using the command
5677 <example compact="compact">
5678 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5681 The version part is the part which comes after
5682 <tt>.so.</tt>, so in our case, it is <tt>1</tt>.
5686 <var>dependencies</var> has the same syntax as a dependency
5687 field in a binary package control file. It should give
5688 details of which packages are required to satisfy a binary
5689 built against the version of the library contained in the
5690 package. See <ref id="depsyntax"> for details.
5694 In our example, if the first version of the <tt>zlib1g</tt>
5695 package which contained a minor number of at least
5696 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5697 <tt>shlibs</tt> entry for this library could say:
5698 <example compact="compact">
5699 libz 1 zlib1g (>= 1:1.1.3)
5701 The version-specific dependency is to avoid warnings from
5702 the dynamic linker about using older shared libraries with
5707 As zlib1g also provides a udeb containing the shared library,
5708 there would also be a second line:
5709 <example compact="compact">
5710 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5716 <heading>Providing a <file>shlibs</file> file</heading>
5719 If your package provides a shared library, you need to create
5720 a <file>shlibs</file> file following the format described above.
5721 It is usual to call this file <file>debian/shlibs</file> (but if
5722 you have multiple binary packages, you might want to call it
5723 <file>debian/shlibs.<var>package</var></file> instead). Then
5724 let <file>debian/rules</file> install it in the control area:
5725 <example compact="compact">
5726 install -m644 debian/shlibs debian/tmp/DEBIAN
5728 or, in the case of a multi-binary package:
5729 <example compact="compact">
5730 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5732 An alternative way of doing this is to create the
5733 <file>shlibs</file> file in the control area directly from
5734 <file>debian/rules</file> without using a <file>debian/shlibs</file>
5735 file at all,<footnote>
5736 This is what <prgn>dh_makeshlibs</prgn> in the
5737 <tt>debhelper</tt> suite does. If your package also has a udeb
5738 that provides a shared library, <prgn>dh_makeshlibs</prgn> can
5739 automatically generate the <tt>udeb:</tt> lines if you specify
5740 the name of the udeb with the <tt>--add-udeb</tt> option.
5742 since the <file>debian/shlibs</file> file itself is ignored by
5743 <prgn>dpkg-shlibdeps</prgn>.
5747 As <prgn>dpkg-shlibdeps</prgn> reads the
5748 <file>DEBIAN/shlibs</file> files in all of the binary packages
5749 being built from this source package, all of the
5750 <file>DEBIAN/shlibs</file> files should be installed before
5751 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5756 <sect1 id="shlibslocal">
5757 <heading>Writing the <file>debian/shlibs.local</file> file</heading>
5760 This file is intended only as a <em>temporary</em> fix if
5761 your binaries or libraries depend on a library whose package
5762 does not yet provide a correct <file>shlibs</file> file.
5766 We will assume that you are trying to package a binary
5767 <tt>foo</tt>. When you try running
5768 <prgn>dpkg-shlibdeps</prgn> you get the following error
5769 message (<tt>-O</tt> displays the dependency information on
5770 <tt>stdout</tt> instead of writing it to
5771 <tt>debian/substvars</tt>, and the lines have been wrapped
5772 for ease of reading):
5773 <example compact="compact">
5774 $ dpkg-shlibdeps -O debian/tmp/usr/bin/foo
5775 dpkg-shlibdeps: warning: unable to find dependency
5776 information for shared library libbar (soname 1,
5777 path /usr/lib/libbar.so.1, dependency field Depends)
5778 shlibs:Depends=libc6 (>= 2.2.2-2)
5780 You can then run <prgn>ldd</prgn> on the binary to find the
5781 full location of the library concerned:
5782 <example compact="compact">
5784 libbar.so.1 => /usr/lib/libbar.so.1 (0x4001e000)
5785 libc.so.6 => /lib/libc.so.6 (0x40032000)
5786 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
5788 So the <prgn>foo</prgn> binary depends on the
5789 <prgn>libbar</prgn> shared library, but no package seems to
5790 provide a <file>*.shlibs</file> file handling
5791 <file>libbar.so.1</file> in <file>/var/lib/dpkg/info/</file>. Let's
5792 determine the package responsible:
5793 <example compact="compact">
5794 $ dpkg -S /usr/lib/libbar.so.1
5795 bar1: /usr/lib/libbar.so.1
5796 $ dpkg -s bar1 | grep Version
5799 This tells us that the <tt>bar1</tt> package, version 1.0-1,
5800 is the one we are using. Now we can file a bug against the
5801 <tt>bar1</tt> package and create our own
5802 <file>debian/shlibs.local</file> to locally fix the problem.
5803 Including the following line into your
5804 <file>debian/shlibs.local</file> file:
5805 <example compact="compact">
5806 libbar 1 bar1 (>= 1.0-1)
5808 should allow the package build to work.
5812 As soon as the maintainer of <tt>bar1</tt> provides a
5813 correct <file>shlibs</file> file, you should remove this line
5814 from your <file>debian/shlibs.local</file> file. (You should
5815 probably also then have a versioned <tt>Build-Depends</tt>
5816 on <tt>bar1</tt> to help ensure that others do not have the
5817 same problem building your package.)
5826 <chapt id="opersys"><heading>The Operating System</heading>
5829 <heading>File system hierarchy</heading>
5833 <heading>File System Structure</heading>
5836 The location of all installed files and directories must
5837 comply with the Filesystem Hierarchy Standard (FHS),
5838 version 2.3, with the exceptions noted below, and except
5839 where doing so would violate other terms of Debian
5840 Policy. The following exceptions to the FHS apply:
5845 The optional rules related to user specific
5846 configuration files for applications are stored in
5847 the user's home directory are relaxed. It is
5848 recommended that such files start with the
5849 '<tt>.</tt>' character (a "dot file"), and if an
5850 application needs to create more than one dot file
5851 then the preferred placement is in a subdirectory
5852 with a name starting with a '.' character, (a "dot
5853 directory"). In this case it is recommended the
5854 configuration files not start with the '.'
5860 The requirement for amd64 to use <file>/lib64</file>
5861 for 64 bit binaries is removed.
5866 The requirement for object files, internal binaries, and
5867 libraries, including <file>libc.so.*</file>, to be located
5868 directly under <file>/lib{,32}</file> and
5869 <file>/usr/lib{,32}</file> is amended, permitting files
5870 to instead be installed to
5871 <file>/lib/<var>triplet</var></file> and
5872 <file>/usr/lib/<var>triplet</var></file>, where
5873 <tt><var>triplet</var></tt> is the value returned by
5874 <tt>dpkg-architecture -qDEB_HOST_GNU_TYPE</tt> for the
5875 architecture of the package. Packages may <em>not</em>
5876 install files to any <var>triplet</var> path other
5877 than the one matching the architecture of that package;
5878 for instance, an <tt>Architecture: amd64</tt> package
5879 containing 32-bit x86 libraries may not install these
5880 libraries to <file>/usr/lib/i486-linux-gnu</file>.
5882 This is necessary in order to reserve the directories for
5883 use in cross-installation of library packages from other
5884 architectures, as part of the planned deployment of
5889 Applications may also use a single subdirectory under
5890 <file>/usr/lib/<var>triplet</var></file>.
5893 The execution time linker/loader, ld*, must still be made
5894 available in the existing location under /lib or /lib64
5895 since this is part of the ELF ABI for the architecture.
5900 The requirement that
5901 <file>/usr/local/share/man</file> be "synonymous"
5902 with <file>/usr/local/man</file> is relaxed to a
5907 The requirement that windowmanagers with a single
5908 configuration file call it <file>system.*wmrc</file>
5909 is removed, as is the restriction that the window
5910 manager subdirectory be named identically to the
5911 window manager name itself.
5916 The requirement that boot manager configuration
5917 files live in <file>/etc</file>, or at least are
5918 symlinked there, is relaxed to a recommendation.
5923 The following directories in the root filesystem are
5924 additionally allowed: <file>/sys</file> and
5925 <file>/selinux</file>. <footnote>These directories
5926 are used as mount points to mount virtual filesystems
5927 to get access to kernel information.</footnote>
5934 The version of this document referred here can be
5935 found in the <tt>debian-policy</tt> package or on <url
5936 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5937 name="FHS (Debian copy)"> alongside this manual (or, if
5938 you have the <package>debian-policy</package> installed,
5940 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5941 (local copy)">). The
5942 latest version, which may be a more recent version, may
5944 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5945 Specific questions about following the standard may be
5946 asked on the <tt>debian-devel</tt> mailing list, or
5947 referred to the FHS mailing list (see the
5948 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
5954 <heading>Site-specific programs</heading>
5957 As mandated by the FHS, packages must not place any
5958 files in <file>/usr/local</file>, either by putting them in
5959 the file system archive to be unpacked by <prgn>dpkg</prgn>
5960 or by manipulating them in their maintainer scripts.
5964 However, the package may create empty directories below
5965 <file>/usr/local</file> so that the system administrator knows
5966 where to place site-specific files. These are not
5967 directories <em>in</em> <file>/usr/local</file>, but are
5968 children of directories in <file>/usr/local</file>. These
5969 directories (<file>/usr/local/*/dir/</file>)
5970 should be removed on package removal if they are
5975 Note that this applies only to
5976 directories <em>below</em> <file>/usr/local</file>,
5977 not <em>in</em> <file>/usr/local</file>. Packages must
5978 not create sub-directories in the
5979 directory <file>/usr/local</file> itself, except those
5980 listed in FHS, section 4.5. However, you may create
5981 directories below them as you wish. You must not remove
5982 any of the directories listed in 4.5, even if you created
5987 Since <file>/usr/local</file> can be mounted read-only from a
5988 remote server, these directories must be created and
5989 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
5990 maintainer scripts and not be included in the
5991 <file>.deb</file> archive. These scripts must not fail if
5992 either of these operations fail.
5996 For example, the <tt>emacsen-common</tt> package could
5997 contain something like
5998 <example compact="compact">
5999 if [ ! -e /usr/local/share/emacs ]
6001 if mkdir /usr/local/share/emacs 2>/dev/null
6003 chown root:staff /usr/local/share/emacs
6004 chmod 2775 /usr/local/share/emacs
6008 in its <prgn>postinst</prgn> script, and
6009 <example compact="compact">
6010 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
6011 rmdir /usr/local/share/emacs 2>/dev/null || true
6013 in the <prgn>prerm</prgn> script. (Note that this form is
6014 used to ensure that if the script is interrupted, the
6015 directory <file>/usr/local/share/emacs</file> will still be
6020 If you do create a directory in <file>/usr/local</file> for
6021 local additions to a package, you should ensure that
6022 settings in <file>/usr/local</file> take precedence over the
6023 equivalents in <file>/usr</file>.
6027 However, because <file>/usr/local</file> and its contents are
6028 for exclusive use of the local administrator, a package
6029 must not rely on the presence or absence of files or
6030 directories in <file>/usr/local</file> for normal operation.
6034 The <file>/usr/local</file> directory itself and all the
6035 subdirectories created by the package should (by default) have
6036 permissions 2775 (group-writable and set-group-id) and be
6037 owned by <tt>root:staff</tt>.
6042 <heading>The system-wide mail directory</heading>
6044 The system-wide mail directory
6045 is <file>/var/mail</file>. This directory is part of the
6046 base system and should not be owned by any particular mail
6047 agents. The use of the old
6048 location <file>/var/spool/mail</file> is deprecated, even
6049 though the spool may still be physically located there.
6055 <heading>Users and groups</heading>
6058 <heading>Introduction</heading>
6060 The Debian system can be configured to use either plain or
6065 Some user ids (UIDs) and group ids (GIDs) are reserved
6066 globally for use by certain packages. Because some
6067 packages need to include files which are owned by these
6068 users or groups, or need the ids compiled into binaries,
6069 these ids must be used on any Debian system only for the
6070 purpose for which they are allocated. This is a serious
6071 restriction, and we should avoid getting in the way of
6072 local administration policies. In particular, many sites
6073 allocate users and/or local system groups starting at 100.
6077 Apart from this we should have dynamically allocated ids,
6078 which should by default be arranged in some sensible
6079 order, but the behavior should be configurable.
6083 Packages other than <tt>base-passwd</tt> must not modify
6084 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
6085 <file>/etc/group</file> or <file>/etc/gshadow</file>.
6090 <heading>UID and GID classes</heading>
6092 The UID and GID numbers are divided into classes as
6098 Globally allocated by the Debian project, the same
6099 on every Debian system. These ids will appear in
6100 the <file>passwd</file> and <file>group</file> files of all
6101 Debian systems, new ids in this range being added
6102 automatically as the <tt>base-passwd</tt> package is
6107 Packages which need a single statically allocated
6108 uid or gid should use one of these; their
6109 maintainers should ask the <tt>base-passwd</tt>
6117 Dynamically allocated system users and groups.
6118 Packages which need a user or group, but can have
6119 this user or group allocated dynamically and
6120 differently on each system, should use <tt>adduser
6121 --system</tt> to create the group and/or user.
6122 <prgn>adduser</prgn> will check for the existence of
6123 the user or group, and if necessary choose an unused
6124 id based on the ranges specified in
6125 <file>adduser.conf</file>.
6129 <tag>1000-59999:</tag>
6132 Dynamically allocated user accounts. By default
6133 <prgn>adduser</prgn> will choose UIDs and GIDs for
6134 user accounts in this range, though
6135 <file>adduser.conf</file> may be used to modify this
6140 <tag>60000-64999:</tag>
6143 Globally allocated by the Debian project, but only
6144 created on demand. The ids are allocated centrally
6145 and statically, but the actual accounts are only
6146 created on users' systems on demand.
6150 These ids are for packages which are obscure or
6151 which require many statically-allocated ids. These
6152 packages should check for and create the accounts in
6153 <file>/etc/passwd</file> or <file>/etc/group</file> (using
6154 <prgn>adduser</prgn> if it has this facility) if
6155 necessary. Packages which are likely to require
6156 further allocations should have a "hole" left after
6157 them in the allocation, to give them room to
6162 <tag>65000-65533:</tag>
6170 User <tt>nobody</tt>. The corresponding gid refers
6171 to the group <tt>nogroup</tt>.
6178 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
6179 not</em> be used, because it is the error return
6188 <sect id="sysvinit">
6189 <heading>System run levels and <file>init.d</file> scripts</heading>
6191 <sect1 id="/etc/init.d">
6192 <heading>Introduction</heading>
6195 The <file>/etc/init.d</file> directory contains the scripts
6196 executed by <prgn>init</prgn> at boot time and when the
6197 init state (or "runlevel") is changed (see <manref
6198 name="init" section="8">).
6202 There are at least two different, yet functionally
6203 equivalent, ways of handling these scripts. For the sake
6204 of simplicity, this document describes only the symbolic
6205 link method. However, it must not be assumed by maintainer
6206 scripts that this method is being used, and any automated
6207 manipulation of the various runlevel behaviors by
6208 maintainer scripts must be performed using
6209 <prgn>update-rc.d</prgn> as described below and not by
6210 manually installing or removing symlinks. For information
6211 on the implementation details of the other method,
6212 implemented in the <tt>file-rc</tt> package, please refer
6213 to the documentation of that package.
6217 These scripts are referenced by symbolic links in the
6218 <file>/etc/rc<var>n</var>.d</file> directories. When changing
6219 runlevels, <prgn>init</prgn> looks in the directory
6220 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
6221 execute, where <tt><var>n</var></tt> is the runlevel that
6222 is being changed to, or <tt>S</tt> for the boot-up
6227 The names of the links all have the form
6228 <file>S<var>mm</var><var>script</var></file> or
6229 <file>K<var>mm</var><var>script</var></file> where
6230 <var>mm</var> is a two-digit number and <var>script</var>
6231 is the name of the script (this should be the same as the
6232 name of the actual script in <file>/etc/init.d</file>).
6236 When <prgn>init</prgn> changes runlevel first the targets
6237 of the links whose names start with a <tt>K</tt> are
6238 executed, each with the single argument <tt>stop</tt>,
6239 followed by the scripts prefixed with an <tt>S</tt>, each
6240 with the single argument <tt>start</tt>. (The links are
6241 those in the <file>/etc/rc<var>n</var>.d</file> directory
6242 corresponding to the new runlevel.) The <tt>K</tt> links
6243 are responsible for killing services and the <tt>S</tt>
6244 link for starting services upon entering the runlevel.
6248 For example, if we are changing from runlevel 2 to
6249 runlevel 3, init will first execute all of the <tt>K</tt>
6250 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
6251 all of the <tt>S</tt> prefixed scripts in that directory.
6252 The links starting with <tt>K</tt> will cause the
6253 referred-to file to be executed with an argument of
6254 <tt>stop</tt>, and the <tt>S</tt> links with an argument
6259 The two-digit number <var>mm</var> is used to determine
6260 the order in which to run the scripts: low-numbered links
6261 have their scripts run first. For example, the
6262 <tt>K20</tt> scripts will be executed before the
6263 <tt>K30</tt> scripts. This is used when a certain service
6264 must be started before another. For example, the name
6265 server <prgn>bind</prgn> might need to be started before
6266 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
6267 can set up its access lists. In this case, the script
6268 that starts <prgn>bind</prgn> would have a lower number
6269 than the script that starts <prgn>inn</prgn> so that it
6271 <example compact="compact">
6278 The two runlevels 0 (halt) and 6 (reboot) are slightly
6279 different. In these runlevels, the links with an
6280 <tt>S</tt> prefix are still called after those with a
6281 <tt>K</tt> prefix, but they too are called with the single
6282 argument <tt>stop</tt>.
6286 <sect1 id="writing-init">
6287 <heading>Writing the scripts</heading>
6290 Packages that include daemons for system services should
6291 place scripts in <file>/etc/init.d</file> to start or stop
6292 services at boot time or during a change of runlevel.
6293 These scripts should be named
6294 <file>/etc/init.d/<var>package</var></file>, and they should
6295 accept one argument, saying what to do:
6298 <tag><tt>start</tt></tag>
6299 <item>start the service,</item>
6301 <tag><tt>stop</tt></tag>
6302 <item>stop the service,</item>
6304 <tag><tt>restart</tt></tag>
6305 <item>stop and restart the service if it's already running,
6306 otherwise start the service</item>
6308 <tag><tt>reload</tt></tag>
6309 <item><p>cause the configuration of the service to be
6310 reloaded without actually stopping and restarting
6313 <tag><tt>force-reload</tt></tag>
6314 <item>cause the configuration to be reloaded if the
6315 service supports this, otherwise restart the
6319 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
6320 <tt>force-reload</tt> options should be supported by all
6321 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
6326 The <file>init.d</file> scripts must ensure that they will
6327 behave sensibly (i.e., returning success and not starting
6328 multiple copies of a service) if invoked with <tt>start</tt>
6329 when the service is already running, or with <tt>stop</tt>
6330 when it isn't, and that they don't kill unfortunately-named
6331 user processes. The best way to achieve this is usually to
6332 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
6337 Be careful of using <tt>set -e</tt> in <file>init.d</file>
6338 scripts. Writing correct <file>init.d</file> scripts requires
6339 accepting various error exit statuses when daemons are already
6340 running or already stopped without aborting
6341 the <file>init.d</file> script, and common <file>init.d</file>
6342 function libraries are not safe to call with <tt>set -e</tt>
6344 <tt>/lib/lsb/init-functions</tt>, which assists in writing
6345 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
6346 in effect and echoing status messages to the console fails,
6348 </footnote>. For <tt>init.d</tt> scripts, it's often easier
6349 to not use <tt>set -e</tt> and instead check the result of
6350 each command separately.
6354 If a service reloads its configuration automatically (as
6355 in the case of <prgn>cron</prgn>, for example), the
6356 <tt>reload</tt> option of the <file>init.d</file> script
6357 should behave as if the configuration has been reloaded
6362 The <file>/etc/init.d</file> scripts must be treated as
6363 configuration files, either (if they are present in the
6364 package, that is, in the .deb file) by marking them as
6365 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6366 by managing them correctly in the maintainer scripts (see
6367 <ref id="config-files">). This is important since we want
6368 to give the local system administrator the chance to adapt
6369 the scripts to the local system, e.g., to disable a
6370 service without de-installing the package, or to specify
6371 some special command line options when starting a service,
6372 while making sure their changes aren't lost during the next
6377 These scripts should not fail obscurely when the
6378 configuration files remain but the package has been
6379 removed, as configuration files remain on the system after
6380 the package has been removed. Only when <prgn>dpkg</prgn>
6381 is executed with the <tt>--purge</tt> option will
6382 configuration files be removed. In particular, as the
6383 <file>/etc/init.d/<var>package</var></file> script itself is
6384 usually a <tt>conffile</tt>, it will remain on the system
6385 if the package is removed but not purged. Therefore, you
6386 should include a <tt>test</tt> statement at the top of the
6388 <example compact="compact">
6389 test -f <var>program-executed-later-in-script</var> || exit 0
6394 Often there are some variables in the <file>init.d</file>
6395 scripts whose values control the behavior of the scripts,
6396 and which a system administrator is likely to want to
6397 change. As the scripts themselves are frequently
6398 <tt>conffile</tt>s, modifying them requires that the
6399 administrator merge in their changes each time the package
6400 is upgraded and the <tt>conffile</tt> changes. To ease
6401 the burden on the system administrator, such configurable
6402 values should not be placed directly in the script.
6403 Instead, they should be placed in a file in
6404 <file>/etc/default</file>, which typically will have the same
6405 base name as the <file>init.d</file> script. This extra file
6406 should be sourced by the script when the script runs. It
6407 must contain only variable settings and comments in SUSv3
6408 <prgn>sh</prgn> format. It may either be a
6409 <tt>conffile</tt> or a configuration file maintained by
6410 the package maintainer scripts. See <ref id="config-files">
6415 To ensure that vital configurable values are always
6416 available, the <file>init.d</file> script should set default
6417 values for each of the shell variables it uses, either
6418 before sourcing the <file>/etc/default/</file> file or
6419 afterwards using something like the <tt>:
6420 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6421 script must behave sensibly and not fail if the
6422 <file>/etc/default</file> file is deleted.
6426 <file>/var/run</file> and <file>/var/lock</file> may be mounted
6427 as temporary filesystems<footnote>
6428 For example, using the <tt>RAMRUN</tt> and <tt>RAMLOCK</tt>
6429 options in <file>/etc/default/rcS</file>.
6430 </footnote>, so the <file>init.d</file> scripts must handle this
6431 correctly. This will typically amount to creating any required
6432 subdirectories dynamically when the <file>init.d</file> script
6433 is run, rather than including them in the package and relying on
6434 <prgn>dpkg</prgn> to create them.
6439 <heading>Interfacing with the initscript system</heading>
6442 Maintainers should use the abstraction layer provided by
6443 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6444 programs to deal with initscripts in their packages'
6445 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6446 and <prgn>postrm</prgn>.
6450 Directly managing the /etc/rc?.d links and directly
6451 invoking the <file>/etc/init.d/</file> initscripts should
6452 be done only by packages providing the initscript
6453 subsystem (such as <prgn>sysv-rc</prgn> and
6454 <prgn>file-rc</prgn>).
6458 <heading>Managing the links</heading>
6461 The program <prgn>update-rc.d</prgn> is provided for
6462 package maintainers to arrange for the proper creation and
6463 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6464 or their functional equivalent if another method is being
6465 used. This may be used by maintainers in their packages'
6466 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6470 You must not include any <file>/etc/rc<var>n</var>.d</file>
6471 symbolic links in the actual archive or manually create or
6472 remove the symbolic links in maintainer scripts; you must
6473 use the <prgn>update-rc.d</prgn> program instead. (The
6474 former will fail if an alternative method of maintaining
6475 runlevel information is being used.) You must not include
6476 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6477 in the archive either. (Only the <tt>sysvinit</tt>
6482 By default <prgn>update-rc.d</prgn> will start services in
6483 each of the multi-user state runlevels (2, 3, 4, and 5)
6484 and stop them in the halt runlevel (0), the single-user
6485 runlevel (1) and the reboot runlevel (6). The system
6486 administrator will have the opportunity to customize
6487 runlevels by simply adding, moving, or removing the
6488 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6489 symbolic links are being used, or by modifying
6490 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6495 To get the default behavior for your package, put in your
6496 <prgn>postinst</prgn> script
6497 <example compact="compact">
6498 update-rc.d <var>package</var> defaults
6500 and in your <prgn>postrm</prgn>
6501 <example compact="compact">
6502 if [ "$1" = purge ]; then
6503 update-rc.d <var>package</var> remove
6505 </example>. Note that if your package changes runlevels
6506 or priority, you may have to remove and recreate the links,
6507 since otherwise the old links may persist. Refer to the
6508 documentation of <prgn>update-rc.d</prgn>.
6512 This will use a default sequence number of 20. If it does
6513 not matter when or in which order the <file>init.d</file>
6514 script is run, use this default. If it does, then you
6515 should talk to the maintainer of the <prgn>sysvinit</prgn>
6516 package or post to <tt>debian-devel</tt>, and they will
6517 help you choose a number.
6521 For more information about using <tt>update-rc.d</tt>,
6522 please consult its man page <manref name="update-rc.d"
6528 <heading>Running initscripts</heading>
6530 The program <prgn>invoke-rc.d</prgn> is provided to make
6531 it easier for package maintainers to properly invoke an
6532 initscript, obeying runlevel and other locally-defined
6533 constraints that might limit a package's right to start,
6534 stop and otherwise manage services. This program may be
6535 used by maintainers in their packages' scripts.
6539 The package maintainer scripts must use
6540 <prgn>invoke-rc.d</prgn> to invoke the
6541 <file>/etc/init.d/*</file> initscripts, instead of
6542 calling them directly.
6546 By default, <prgn>invoke-rc.d</prgn> will pass any
6547 action requests (start, stop, reload, restart...) to the
6548 <file>/etc/init.d</file> script, filtering out requests
6549 to start or restart a service out of its intended
6554 Most packages will simply need to change:
6555 <example compact="compact">/etc/init.d/<package>
6556 <action></example> in their <prgn>postinst</prgn>
6557 and <prgn>prerm</prgn> scripts to:
6558 <example compact="compact">
6559 if which invoke-rc.d >/dev/null 2>&1; then
6560 invoke-rc.d <var>package</var> <action>
6562 /etc/init.d/<var>package</var> <action>
6568 A package should register its initscript services using
6569 <prgn>update-rc.d</prgn> before it tries to invoke them
6570 using <prgn>invoke-rc.d</prgn>. Invocation of
6571 unregistered services may fail.
6575 For more information about using
6576 <prgn>invoke-rc.d</prgn>, please consult its man page
6577 <manref name="invoke-rc.d" section="8">.
6583 <heading>Boot-time initialization</heading>
6586 There used to be another directory, <file>/etc/rc.boot</file>,
6587 which contained scripts which were run once per machine
6588 boot. This has been deprecated in favour of links from
6589 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6590 described in <ref id="/etc/init.d">. Packages must not
6591 place files in <file>/etc/rc.boot</file>.
6596 <heading>Example</heading>
6599 An example on which you can base your
6600 <file>/etc/init.d</file> scripts is found in
6601 <file>/etc/init.d/skeleton</file>.
6608 <heading>Console messages from <file>init.d</file> scripts</heading>
6611 This section describes the formats to be used for messages
6612 written to standard output by the <file>/etc/init.d</file>
6613 scripts. The intent is to improve the consistency of
6614 Debian's startup and shutdown look and feel. For this
6615 reason, please look very carefully at the details. We want
6616 the messages to have the same format in terms of wording,
6617 spaces, punctuation and case of letters.
6621 Here is a list of overall rules that should be used for
6622 messages generated by <file>/etc/init.d</file> scripts.
6628 The message should fit in one line (fewer than 80
6629 characters), start with a capital letter and end with
6630 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6634 If the script is performing some time consuming task in
6635 the background (not merely starting or stopping a
6636 program, for instance), an ellipsis (three dots:
6637 <tt>...</tt>) should be output to the screen, with no
6638 leading or tailing whitespace or line feeds.
6642 The messages should appear as if the computer is telling
6643 the user what it is doing (politely :-), but should not
6644 mention "it" directly. For example, instead of:
6645 <example compact="compact">
6646 I'm starting network daemons: nfsd mountd.
6648 the message should say
6649 <example compact="compact">
6650 Starting network daemons: nfsd mountd.
6657 <tt>init.d</tt> script should use the following standard
6658 message formats for the situations enumerated below.
6664 <p>When daemons are started</p>
6667 If the script starts one or more daemons, the output
6668 should look like this (a single line, no leading
6670 <example compact="compact">
6671 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6673 The <var>description</var> should describe the
6674 subsystem the daemon or set of daemons are part of,
6675 while <var>daemon-1</var> up to <var>daemon-n</var>
6676 denote each daemon's name (typically the file name of
6681 For example, the output of <file>/etc/init.d/lpd</file>
6683 <example compact="compact">
6684 Starting printer spooler: lpd.
6689 This can be achieved by saying
6690 <example compact="compact">
6691 echo -n "Starting printer spooler: lpd"
6692 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6695 in the script. If there are more than one daemon to
6696 start, the output should look like this:
6697 <example compact="compact">
6698 echo -n "Starting remote file system services:"
6699 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6700 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6701 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6704 This makes it possible for the user to see what is
6705 happening and when the final daemon has been started.
6706 Care should be taken in the placement of white spaces:
6707 in the example above the system administrators can
6708 easily comment out a line if they don't want to start
6709 a specific daemon, while the displayed message still
6715 <p>When a system parameter is being set</p>
6718 If you have to set up different system parameters
6719 during the system boot, you should use this format:
6720 <example compact="compact">
6721 Setting <var>parameter</var> to "<var>value</var>".
6726 You can use a statement such as the following to get
6728 <example compact="compact">
6729 echo "Setting DNS domainname to \"$domainname\"."
6734 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
6735 for the left and right quotation marks. A grave accent
6736 (<tt>`</tt>) is not a quote character; neither is an
6737 apostrophe (<tt>'</tt>).
6742 <p>When a daemon is stopped or restarted</p>
6745 When you stop or restart a daemon, you should issue a
6746 message identical to the startup message, except that
6747 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6748 or <tt>Restarting</tt> respectively.
6752 For example, stopping the printer daemon will look like
6754 <example compact="compact">
6755 Stopping printer spooler: lpd.
6761 <p>When something is executed</p>
6764 There are several examples where you have to run a
6765 program at system startup or shutdown to perform a
6766 specific task, for example, setting the system's clock
6767 using <prgn>netdate</prgn> or killing all processes
6768 when the system shuts down. Your message should look
6770 <example compact="compact">
6771 Doing something very useful...done.
6773 You should print the <tt>done.</tt> immediately after
6774 the job has been completed, so that the user is
6775 informed why they have to wait. You can get this
6777 <example compact="compact">
6778 echo -n "Doing something very useful..."
6787 <p>When the configuration is reloaded</p>
6790 When a daemon is forced to reload its configuration
6791 files you should use the following format:
6792 <example compact="compact">
6793 Reloading <var>description</var> configuration...done.
6795 where <var>description</var> is the same as in the
6796 daemon starting message.
6804 <heading>Cron jobs</heading>
6807 Packages must not modify the configuration file
6808 <file>/etc/crontab</file>, and they must not modify the files in
6809 <file>/var/spool/cron/crontabs</file>.</p>
6812 If a package wants to install a job that has to be executed
6813 via cron, it should place a file with the name of the
6814 package in one or more of the following directories:
6815 <example compact="compact">
6821 As these directory names imply, the files within them are
6822 executed on an hourly, daily, weekly, or monthly basis,
6823 respectively. The exact times are listed in
6824 <file>/etc/crontab</file>.</p>
6827 All files installed in any of these directories must be
6828 scripts (e.g., shell scripts or Perl scripts) so that they
6829 can easily be modified by the local system administrator.
6830 In addition, they must be treated as configuration files.
6834 If a certain job has to be executed at some other frequency or
6835 at a specific time, the package should install a file
6836 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6837 same syntax as <file>/etc/crontab</file> and is processed by
6838 <prgn>cron</prgn> automatically. The file must also be
6839 treated as a configuration file. (Note that entries in the
6840 <file>/etc/cron.d</file> directory are not handled by
6841 <prgn>anacron</prgn>. Thus, you should only use this
6842 directory for jobs which may be skipped if the system is not
6845 Unlike <file>crontab</file> files described in the IEEE Std
6846 1003.1-2008 (POSIX.1) available from
6847 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
6848 name="The Open Group">, the files in
6849 <file>/etc/cron.d</file> and the file
6850 <file>/etc/crontab</file> have seven fields; namely:
6852 <item>Minute [0,59]</item>
6853 <item>Hour [0,23]</item>
6854 <item>Day of the month [1,31]</item>
6855 <item>Month of the year [1,12]</item>
6856 <item>Day of the week ([0,6] with 0=Sunday)</item>
6857 <item>Username</item>
6858 <item>Command to be run</item>
6860 Ranges of numbers are allowed. Ranges are two numbers
6861 separated with a hyphen. The specified range is inclusive.
6862 Lists are allowed. A list is a set of numbers (or ranges)
6863 separated by commas. Step values can be used in conjunction
6868 The scripts or <tt>crontab</tt> entries in these directories should
6869 check if all necessary programs are installed before they
6870 try to execute them. Otherwise, problems will arise when a
6871 package was removed but not purged since configuration files
6872 are kept on the system in this situation.
6876 Any <tt>cron</tt> daemon must provide
6877 <file>/usr/bin/crontab</file> and support normal
6878 <tt>crontab</tt> entries as specified in POSIX. The daemon
6879 must also support names for days and months, ranges, and
6880 step values. It has to support <file>/etc/crontab</file>,
6881 and correctly execute the scripts in
6882 <file>/etc/cron.d</file>. The daemon must also correctly
6884 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
6889 <heading>Menus</heading>
6892 The Debian <tt>menu</tt> package provides a standard
6893 interface between packages providing applications and
6894 <em>menu programs</em> (either X window managers or
6895 text-based menu programs such as <prgn>pdmenu</prgn>).
6899 All packages that provide applications that need not be
6900 passed any special command line arguments for normal
6901 operation should register a menu entry for those
6902 applications, so that users of the <tt>menu</tt> package
6903 will automatically get menu entries in their window
6904 managers, as well in shells like <tt>pdmenu</tt>.
6908 Menu entries should follow the current menu policy.
6912 The menu policy can be found in the <tt>menu-policy</tt>
6913 files in the <tt>debian-policy</tt> package.
6914 It is also available from the Debian web mirrors at
6915 <tt><url name="/doc/packaging-manuals/menu-policy/"
6916 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6920 Please also refer to the <em>Debian Menu System</em>
6921 documentation that comes with the <package>menu</package>
6922 package for information about how to register your
6928 <heading>Multimedia handlers</heading>
6931 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6932 is a mechanism for encoding files and data streams and
6933 providing meta-information about them, in particular their
6934 type (e.g. audio or video) and format (e.g. PNG, HTML,
6939 Registration of MIME type handlers allows programs like mail
6940 user agents and web browsers to invoke these handlers to
6941 view, edit or display MIME types they don't support directly.
6945 Packages which provide the ability to view/show/play,
6946 compose, edit or print MIME types should register themselves
6947 as such following the current MIME support policy.
6951 The MIME support policy can be found in the <tt>mime-policy</tt>
6952 files in the <tt>debian-policy</tt> package.
6953 It is also available from the Debian web mirrors at
6954 <tt><url name="/doc/packaging-manuals/mime-policy/"
6955 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
6961 <heading>Keyboard configuration</heading>
6964 To achieve a consistent keyboard configuration so that all
6965 applications interpret a keyboard event the same way, all
6966 programs in the Debian distribution must be configured to
6967 comply with the following guidelines.
6971 The following keys must have the specified interpretations:
6974 <tag><tt><--</tt></tag>
6975 <item>delete the character to the left of the cursor</item>
6977 <tag><tt>Delete</tt></tag>
6978 <item>delete the character to the right of the cursor</item>
6980 <tag><tt>Control+H</tt></tag>
6981 <item>emacs: the help prefix</item>
6984 The interpretation of any keyboard events should be
6985 independent of the terminal that is used, be it a virtual
6986 console, an X terminal emulator, an rlogin/telnet session,
6991 The following list explains how the different programs
6992 should be set up to achieve this:
6998 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
7002 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
7006 X translations are set up to make
7007 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
7008 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
7009 is the vt220 escape code for the "delete character"
7010 key). This must be done by loading the X resources
7011 using <prgn>xrdb</prgn> on all local X displays, not
7012 using the application defaults, so that the
7013 translation resources used correspond to the
7014 <prgn>xmodmap</prgn> settings.
7018 The Linux console is configured to make
7019 <tt><--</tt> generate DEL, and <tt>Delete</tt>
7020 generate <tt>ESC [ 3 ~</tt>.
7024 X applications are configured so that <tt><</tt>
7025 deletes left, and <tt>Delete</tt> deletes right. Motif
7026 applications already work like this.
7030 Terminals should have <tt>stty erase ^?</tt> .
7034 The <tt>xterm</tt> terminfo entry should have <tt>ESC
7035 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
7036 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
7040 Emacs is programmed to map <tt>KB_Backspace</tt> or
7041 the <tt>stty erase</tt> character to
7042 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
7043 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
7044 <tt>^H</tt> to <tt>help</tt> as always.
7048 Other applications use the <tt>stty erase</tt>
7049 character and <tt>kdch1</tt> for the two delete keys,
7050 with ASCII DEL being "delete previous character" and
7051 <tt>kdch1</tt> being "delete character under
7059 This will solve the problem except for the following
7066 Some terminals have a <tt><--</tt> key that cannot
7067 be made to produce anything except <tt>^H</tt>. On
7068 these terminals Emacs help will be unavailable on
7069 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
7070 character takes precedence in Emacs, and has been set
7071 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
7072 available) can be used instead.
7076 Some operating systems use <tt>^H</tt> for <tt>stty
7077 erase</tt>. However, modern telnet versions and all
7078 rlogin versions propagate <tt>stty</tt> settings, and
7079 almost all UNIX versions honour <tt>stty erase</tt>.
7080 Where the <tt>stty</tt> settings are not propagated
7081 correctly, things can be made to work by using
7082 <tt>stty</tt> manually.
7086 Some systems (including previous Debian versions) use
7087 <prgn>xmodmap</prgn> to arrange for both
7088 <tt><--</tt> and <tt>Delete</tt> to generate
7089 <tt>KB_Delete</tt>. We can change the behavior of
7090 their X clients using the same X resources that we use
7091 to do it for our own clients, or configure our clients
7092 using their resources when things are the other way
7093 around. On displays configured like this
7094 <tt>Delete</tt> will not work, but <tt><--</tt>
7099 Some operating systems have different <tt>kdch1</tt>
7100 settings in their <tt>terminfo</tt> database for
7101 <tt>xterm</tt> and others. On these systems the
7102 <tt>Delete</tt> key will not work correctly when you
7103 log in from a system conforming to our policy, but
7104 <tt><--</tt> will.
7111 <heading>Environment variables</heading>
7114 A program must not depend on environment variables to get
7115 reasonable defaults. (That's because these environment
7116 variables would have to be set in a system-wide
7117 configuration file like <file>/etc/profile</file>, which is not
7118 supported by all shells.)
7122 If a program usually depends on environment variables for its
7123 configuration, the program should be changed to fall back to
7124 a reasonable default configuration if these environment
7125 variables are not present. If this cannot be done easily
7126 (e.g., if the source code of a non-free program is not
7127 available), the program must be replaced by a small
7128 "wrapper" shell script which sets the environment variables
7129 if they are not already defined, and calls the original program.
7133 Here is an example of a wrapper script for this purpose:
7135 <example compact="compact">
7137 BAR=${BAR:-/var/lib/fubar}
7139 exec /usr/lib/foo/foo "$@"
7144 Furthermore, as <file>/etc/profile</file> is a configuration
7145 file of the <prgn>base-files</prgn> package, other packages must
7146 not put any environment variables or other commands into that
7151 <sect id="doc-base">
7152 <heading>Registering Documents using doc-base</heading>
7155 The <package>doc-base</package> package implements a
7156 flexible mechanism for handling and presenting
7157 documentation. The recommended practice is for every Debian
7158 package that provides online documentation (other than just
7159 manual pages) to register these documents with
7160 <package>doc-base</package> by installing a
7161 <package>doc-base</package> control file via the
7162 <prgn/install-docs/ script at installation time and
7163 de-register the manuals again when the package is removed.
7166 Please refer to the documentation that comes with the
7167 <package>doc-base</package> package for information and
7176 <heading>Files</heading>
7178 <sect id="binaries">
7179 <heading>Binaries</heading>
7182 Two different packages must not install programs with
7183 different functionality but with the same filenames. (The
7184 case of two programs having the same functionality but
7185 different implementations is handled via "alternatives" or
7186 the "Conflicts" mechanism. See <ref id="maintscripts"> and
7187 <ref id="conflicts"> respectively.) If this case happens,
7188 one of the programs must be renamed. The maintainers should
7189 report this to the <tt>debian-devel</tt> mailing list and
7190 try to find a consensus about which program will have to be
7191 renamed. If a consensus cannot be reached, <em>both</em>
7192 programs must be renamed.
7196 By default, when a package is being built, any binaries
7197 created should include debugging information, as well as
7198 being compiled with optimization. You should also turn on
7199 as many reasonable compilation warnings as possible; this
7200 makes life easier for porters, who can then look at build
7201 logs for possible problems. For the C programming language,
7202 this means the following compilation parameters should be
7204 <example compact="compact">
7206 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
7208 INSTALL = install -s # (or use strip on the files in debian/tmp)
7213 Note that by default all installed binaries should be stripped,
7214 either by using the <tt>-s</tt> flag to
7215 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
7216 the binaries after they have been copied into
7217 <file>debian/tmp</file> but before the tree is made into a
7222 Although binaries in the build tree should be compiled with
7223 debugging information by default, it can often be difficult to
7224 debug programs if they are also subjected to compiler
7225 optimization. For this reason, it is recommended to support the
7226 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
7227 (see <ref id="debianrules-options">). This variable can contain
7228 several flags to change how a package is compiled and built.
7232 It is up to the package maintainer to decide what
7233 compilation options are best for the package. Certain
7234 binaries (such as computationally-intensive programs) will
7235 function better with certain flags (<tt>-O3</tt>, for
7236 example); feel free to use them. Please use good judgment
7237 here. Don't use flags for the sake of it; only use them
7238 if there is good reason to do so. Feel free to override
7239 the upstream author's ideas about which compilation
7240 options are best: they are often inappropriate for our
7246 <sect id="libraries">
7247 <heading>Libraries</heading>
7250 If the package is <strong>architecture: any</strong>, then
7251 the shared library compilation and linking flags must have
7252 <tt>-fPIC</tt>, or the package shall not build on some of
7253 the supported architectures<footnote>
7255 If you are using GCC, <tt>-fPIC</tt> produces code with
7256 relocatable position independent code, which is required for
7257 most architectures to create a shared library, with i386 and
7258 perhaps some others where non position independent code is
7259 permitted in a shared library.
7262 Position independent code may have a performance penalty,
7263 especially on <tt>i386</tt>. However, in most cases the
7264 speed penalty must be measured against the memory wasted on
7265 the few architectures where non position independent code is
7268 </footnote>. Any exception to this rule must be discussed on
7269 the mailing list <em>debian-devel@lists.debian.org</em>, and
7270 a rough consensus obtained. The reasons for not compiling
7271 with <tt>-fPIC</tt> flag must be recorded in the file
7272 <tt>README.Debian</tt>, and care must be taken to either
7273 restrict the architecture or arrange for <tt>-fPIC</tt> to
7274 be used on architectures where it is required.<footnote>
7276 Some of the reasons why this might be required is if the
7277 library contains hand crafted assembly code that is not
7278 relocatable, the speed penalty is excessive for compute
7279 intensive libs, and similar reasons.
7284 As to the static libraries, the common case is not to have
7285 relocatable code, since there is no benefit, unless in specific
7286 cases; therefore the static version must not be compiled
7287 with the <tt>-fPIC</tt> flag. Any exception to this rule
7288 should be discussed on the mailing list
7289 <em>debian-devel@lists.debian.org</em>, and the reasons for
7290 compiling with the <tt>-fPIC</tt> flag must be recorded in
7291 the file <tt>README.Debian</tt>. <footnote>
7293 Some of the reasons for linking static libraries with
7294 the <tt>-fPIC</tt> flag are if, for example, one needs a
7295 Perl API for a library that is under rapid development,
7296 and has an unstable API, so shared libraries are
7297 pointless at this phase of the library's development. In
7298 that case, since Perl needs a library with relocatable
7299 code, it may make sense to create a static library with
7300 relocatable code. Another reason cited is if you are
7301 distilling various libraries into a common shared
7302 library, like <tt>mklibs</tt> does in the Debian
7308 In other words, if both a shared and a static library is
7309 being built, each source unit (<tt>*.c</tt>, for example,
7310 for C files) will need to be compiled twice, for the normal
7314 You must specify the gcc option <tt>-D_REENTRANT</tt>
7315 when building a library (either static or shared) to make
7316 the library compatible with LinuxThreads.
7320 Although not enforced by the build tools, shared libraries
7321 must be linked against all libraries that they use symbols from
7322 in the same way that binaries are. This ensures the correct
7323 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
7324 system and guarantees that all libraries can be safely opened
7325 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
7326 option <tt>-Wl,-z,defs</tt> when building a shared library.
7327 Since this option enforces symbol resolution at build time,
7328 a missing library reference will be caught early as a fatal
7333 All installed shared libraries should be stripped with
7334 <example compact="compact">
7335 strip --strip-unneeded <var>your-lib</var>
7337 (The option <tt>--strip-unneeded</tt> makes
7338 <prgn>strip</prgn> remove only the symbols which aren't
7339 needed for relocation processing.) Shared libraries can
7340 function perfectly well when stripped, since the symbols for
7341 dynamic linking are in a separate part of the ELF object
7343 You might also want to use the options
7344 <tt>--remove-section=.comment</tt> and
7345 <tt>--remove-section=.note</tt> on both shared libraries
7346 and executables, and <tt>--strip-debug</tt> on static
7352 Note that under some circumstances it may be useful to
7353 install a shared library unstripped, for example when
7354 building a separate package to support debugging.
7358 Shared object files (often <file>.so</file> files) that are not
7359 public libraries, that is, they are not meant to be linked
7360 to by third party executables (binaries of other packages),
7361 should be installed in subdirectories of the
7362 <file>/usr/lib</file> directory. Such files are exempt from the
7363 rules that govern ordinary shared libraries, except that
7364 they must not be installed executable and should be
7366 A common example are the so-called "plug-ins",
7367 internal shared objects that are dynamically loaded by
7368 programs using <manref name="dlopen" section="3">.
7373 An ever increasing number of packages are using
7374 <prgn>libtool</prgn> to do their linking. The latest GNU
7375 libtools (>= 1.3a) can take advantage of the metadata in the
7376 installed <prgn>libtool</prgn> archive files (<file>*.la</file>
7377 files). The main advantage of <prgn>libtool</prgn>'s
7378 <file>.la</file> files is that it allows <prgn>libtool</prgn> to
7379 store and subsequently access metadata with respect to the
7380 libraries it builds. <prgn>libtool</prgn> will search for
7381 those files, which contain a lot of useful information about
7382 a library (such as library dependency information for static
7383 linking). Also, they're <em>essential</em> for programs
7384 using <tt>libltdl</tt>.<footnote>
7385 Although <prgn>libtool</prgn> is fully capable of
7386 linking against shared libraries which don't have
7387 <tt>.la</tt> files, as it is a mere shell script it can
7388 add considerably to the build time of a
7389 <prgn>libtool</prgn>-using package if that shell script
7390 has to derive all this information from first principles
7391 for each library every time it is linked. With the
7392 advent of <prgn>libtool</prgn> version 1.4 (and to a
7393 lesser extent <prgn>libtool</prgn> version 1.3), the
7394 <file>.la</file> files also store information about
7395 inter-library dependencies which cannot necessarily be
7396 derived after the <file>.la</file> file is deleted.
7401 Packages that use <prgn>libtool</prgn> to create shared
7402 libraries should include the <file>.la</file> files in the
7403 <tt>-dev</tt> package, unless the package relies on
7404 <tt>libtool</tt>'s <tt>libltdl</tt> library, in which case
7405 the <tt>.la</tt> files must go in the run-time library
7410 You must make sure that you use only released versions of
7411 shared libraries to build your packages; otherwise other
7412 users will not be able to run your binaries
7413 properly. Producing source packages that depend on
7414 unreleased compilers is also usually a bad
7421 <heading>Shared libraries</heading>
7423 This section has moved to <ref id="sharedlibs">.
7429 <heading>Scripts</heading>
7432 All command scripts, including the package maintainer
7433 scripts inside the package and used by <prgn>dpkg</prgn>,
7434 should have a <tt>#!</tt> line naming the shell to be used
7439 In the case of Perl scripts this should be
7440 <tt>#!/usr/bin/perl</tt>.
7444 When scripts are installed into a directory in the system
7445 PATH, the script name should not include an extension such
7446 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7447 language currently used to implement it.
7450 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
7451 <file>init.d</file> scripts should almost certainly start
7452 with <tt>set -e</tt> so that errors are detected.
7453 <file>init.d</file> scripts are something of a special case, due
7454 to how frequently they need to call commands that are allowed to
7455 fail, and it may instead be easier to check the exit status of
7456 commands directly. See <ref id="writing-init"> for more
7457 information about writing <file>init.d</file> scripts.
7460 Every script should use <tt>set -e</tt> or check the exit status
7461 of <em>every</em> command.
7464 Scripts may assume that <file>/bin/sh</file> implements the
7465 SUSv3 Shell Command Language<footnote>
7466 Single UNIX Specification, version 3, which is also IEEE
7467 1003.1-2004 (POSIX), and is available on the World Wide Web
7468 from <url id="http://www.unix.org/version3/online.html"
7469 name="The Open Group"> after free
7470 registration.</footnote>
7471 plus the following additional features not mandated by
7473 These features are in widespread use in the Linux community
7474 and are implemented in all of bash, dash, and ksh, the most
7475 common shells users may wish to use as <file>/bin/sh</file>.
7478 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7479 must not generate a newline.</item>
7480 <item><tt>test</tt>, if implemented as a shell built-in, must
7481 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7483 <item><tt>local</tt> to create a scoped variable must be
7484 supported, including listing multiple variables in a single
7485 local command and assigning a value to a variable at the
7486 same time as localizing it. <tt>local</tt> may or
7487 may not preserve the variable value from an outer scope if
7488 no assignment is present. Uses such as:
7492 # ... use a, b, c, d ...
7495 must be supported and must set the value of <tt>c</tt> to
7499 If a shell script requires non-SUSv3 features from the shell
7500 interpreter other than those listed above, the appropriate shell
7501 must be specified in the first line of the script (e.g.,
7502 <tt>#!/bin/bash</tt>) and the package must depend on the package
7503 providing the shell (unless the shell package is marked
7504 "Essential", as in the case of <prgn>bash</prgn>).
7508 You may wish to restrict your script to SUSv3 features plus the
7509 above set when possible so that it may use <file>/bin/sh</file>
7510 as its interpreter. If your script works with <prgn>dash</prgn>
7511 (originally called <prgn>ash</prgn>), it probably complies with
7512 the above requirements, but if you are in doubt, use
7513 <file>/bin/bash</file>.
7517 Perl scripts should check for errors when making any
7518 system calls, including <tt>open</tt>, <tt>print</tt>,
7519 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7523 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7524 scripting languages. See <em>Csh Programming Considered
7525 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7526 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7527 If an upstream package comes with <prgn>csh</prgn> scripts
7528 then you must make sure that they start with
7529 <tt>#!/bin/csh</tt> and make your package depend on the
7530 <prgn>c-shell</prgn> virtual package.
7534 Any scripts which create files in world-writeable
7535 directories (e.g., in <file>/tmp</file>) must use a
7536 mechanism which will fail atomically if a file with the same
7537 name already exists.
7541 The Debian base system provides the <prgn>tempfile</prgn>
7542 and <prgn>mktemp</prgn> utilities for use by scripts for
7549 <heading>Symbolic links</heading>
7552 In general, symbolic links within a top-level directory
7553 should be relative, and symbolic links pointing from one
7554 top-level directory into another should be absolute. (A
7555 top-level directory is a sub-directory of the root
7556 directory <file>/</file>.)
7560 In addition, symbolic links should be specified as short as
7561 possible, i.e., link targets like <file>foo/../bar</file> are
7566 Note that when creating a relative link using
7567 <prgn>ln</prgn> it is not necessary for the target of the
7568 link to exist relative to the working directory you're
7569 running <prgn>ln</prgn> from, nor is it necessary to change
7570 directory to the directory where the link is to be made.
7571 Simply include the string that should appear as the target
7572 of the link (this will be a pathname relative to the
7573 directory in which the link resides) as the first argument
7578 For example, in your <prgn>Makefile</prgn> or
7579 <file>debian/rules</file>, you can do things like:
7580 <example compact="compact">
7581 ln -fs gcc $(prefix)/bin/cc
7582 ln -fs gcc debian/tmp/usr/bin/cc
7583 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7584 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7589 A symbolic link pointing to a compressed file should always
7590 have the same file extension as the referenced file. (For
7591 example, if a file <file>foo.gz</file> is referenced by a
7592 symbolic link, the filename of the link has to end with
7593 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7598 <heading>Device files</heading>
7601 Packages must not include device files or named pipes in the
7606 If a package needs any special device files that are not
7607 included in the base system, it must call
7608 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7609 after notifying the user<footnote>
7610 This notification could be done via a (low-priority)
7611 debconf message, or an echo (printf) statement.
7616 Packages must not remove any device files in the
7617 <prgn>postrm</prgn> or any other script. This is left to the
7618 system administrator.
7622 Debian uses the serial devices
7623 <file>/dev/ttyS*</file>. Programs using the old
7624 <file>/dev/cu*</file> devices should be changed to use
7625 <file>/dev/ttyS*</file>.
7629 Named pipes needed by the package must be created in
7630 the <prgn>postinst</prgn> script<footnote>
7631 It's better to use <prgn>mkfifo</prgn> rather
7632 than <prgn>mknod</prgn> to create named pipes so that
7633 automated checks for packages incorrectly creating device
7634 files with <prgn>mknod</prgn> won't have false positives.
7635 </footnote> and removed in
7636 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
7641 <sect id="config-files">
7642 <heading>Configuration files</heading>
7645 <heading>Definitions</heading>
7649 <tag>configuration file</tag>
7651 A file that affects the operation of a program, or
7652 provides site- or host-specific information, or
7653 otherwise customizes the behavior of a program.
7654 Typically, configuration files are intended to be
7655 modified by the system administrator (if needed or
7656 desired) to conform to local policy or to provide
7657 more useful site-specific behavior.
7660 <tag><tt>conffile</tt></tag>
7662 A file listed in a package's <tt>conffiles</tt>
7663 file, and is treated specially by <prgn>dpkg</prgn>
7664 (see <ref id="configdetails">).
7670 The distinction between these two is important; they are
7671 not interchangeable concepts. Almost all
7672 <tt>conffile</tt>s are configuration files, but many
7673 configuration files are not <tt>conffiles</tt>.
7677 As noted elsewhere, <file>/etc/init.d</file> scripts,
7678 <file>/etc/default</file> files, scripts installed in
7679 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7680 configuration installed in <file>/etc/cron.d</file> must be
7681 treated as configuration files. In general, any script that
7682 embeds configuration information is de-facto a configuration
7683 file and should be treated as such.
7688 <heading>Location</heading>
7691 Any configuration files created or used by your package
7692 must reside in <file>/etc</file>. If there are several,
7693 consider creating a subdirectory of <file>/etc</file>
7694 named after your package.
7698 If your package creates or uses configuration files
7699 outside of <file>/etc</file>, and it is not feasible to modify
7700 the package to use <file>/etc</file> directly, put the files
7701 in <file>/etc</file> and create symbolic links to those files
7702 from the location that the package requires.
7707 <heading>Behavior</heading>
7710 Configuration file handling must conform to the following
7712 <list compact="compact">
7714 local changes must be preserved during a package
7718 configuration files must be preserved when the
7719 package is removed, and only deleted when the
7723 Obsolete configuration files without local changes may be
7724 removed by the package during upgrade.
7728 The easy way to achieve this behavior is to make the
7729 configuration file a <tt>conffile</tt>. This is
7730 appropriate only if it is possible to distribute a default
7731 version that will work for most installations, although
7732 some system administrators may choose to modify it. This
7733 implies that the default version will be part of the
7734 package distribution, and must not be modified by the
7735 maintainer scripts during installation (or at any other
7740 In order to ensure that local changes are preserved
7741 correctly, no package may contain or make hard links to
7742 conffiles.<footnote>
7743 Rationale: There are two problems with hard links.
7744 The first is that some editors break the link while
7745 editing one of the files, so that the two files may
7746 unwittingly become unlinked and different. The second
7747 is that <prgn>dpkg</prgn> might break the hard link
7748 while upgrading <tt>conffile</tt>s.
7753 The other way to do it is via the maintainer scripts. In
7754 this case, the configuration file must not be listed as a
7755 <tt>conffile</tt> and must not be part of the package
7756 distribution. If the existence of a file is required for
7757 the package to be sensibly configured it is the
7758 responsibility of the package maintainer to provide
7759 maintainer scripts which correctly create, update and
7760 maintain the file and remove it on purge. (See <ref
7761 id="maintainerscripts"> for more information.) These
7762 scripts must be idempotent (i.e., must work correctly if
7763 <prgn>dpkg</prgn> needs to re-run them due to errors
7764 during installation or removal), must cope with all the
7765 variety of ways <prgn>dpkg</prgn> can call maintainer
7766 scripts, must not overwrite or otherwise mangle the user's
7767 configuration without asking, must not ask unnecessary
7768 questions (particularly during upgrades), and must
7769 otherwise be good citizens.
7773 The scripts are not required to configure every possible
7774 option for the package, but only those necessary to get
7775 the package running on a given system. Ideally the
7776 sysadmin should not have to do any configuration other
7777 than that done (semi-)automatically by the
7778 <prgn>postinst</prgn> script.
7782 A common practice is to create a script called
7783 <file><var>package</var>-configure</file> and have the
7784 package's <prgn>postinst</prgn> call it if and only if the
7785 configuration file does not already exist. In certain
7786 cases it is useful for there to be an example or template
7787 file which the maintainer scripts use. Such files should
7788 be in <file>/usr/share/<var>package</var></file> or
7789 <file>/usr/lib/<var>package</var></file> (depending on whether
7790 they are architecture-independent or not). There should
7791 be symbolic links to them from
7792 <file>/usr/share/doc/<var>package</var>/examples</file> if
7793 they are examples, and should be perfectly ordinary
7794 <prgn>dpkg</prgn>-handled files (<em>not</em>
7795 configuration files).
7799 These two styles of configuration file handling must
7800 not be mixed, for that way lies madness:
7801 <prgn>dpkg</prgn> will ask about overwriting the file
7802 every time the package is upgraded.
7807 <heading>Sharing configuration files</heading>
7810 Packages which specify the same file as a
7811 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7812 with each other. (This is an instance of the general rule
7813 about not sharing files. Note that neither alternatives
7814 nor diversions are likely to be appropriate in this case;
7815 in particular, <prgn>dpkg</prgn> does not handle diverted
7816 <tt>conffile</tt>s well.)
7820 The maintainer scripts must not alter a <tt>conffile</tt>
7821 of <em>any</em> package, including the one the scripts
7826 If two or more packages use the same configuration file
7827 and it is reasonable for both to be installed at the same
7828 time, one of these packages must be defined as
7829 <em>owner</em> of the configuration file, i.e., it will be
7830 the package which handles that file as a configuration
7831 file. Other packages that use the configuration file must
7832 depend on the owning package if they require the
7833 configuration file to operate. If the other package will
7834 use the configuration file if present, but is capable of
7835 operating without it, no dependency need be declared.
7839 If it is desirable for two or more related packages to
7840 share a configuration file <em>and</em> for all of the
7841 related packages to be able to modify that configuration
7842 file, then the following should be done:
7843 <enumlist compact="compact">
7845 One of the related packages (the "owning" package)
7846 will manage the configuration file with maintainer
7847 scripts as described in the previous section.
7850 The owning package should also provide a program
7851 that the other packages may use to modify the
7855 The related packages must use the provided program
7856 to make any desired modifications to the
7857 configuration file. They should either depend on
7858 the core package to guarantee that the configuration
7859 modifier program is available or accept gracefully
7860 that they cannot modify the configuration file if it
7861 is not. (This is in addition to the fact that the
7862 configuration file may not even be present in the
7869 Sometimes it's appropriate to create a new package which
7870 provides the basic infrastructure for the other packages
7871 and which manages the shared configuration files. (The
7872 <tt>sgml-base</tt> package is a good example.)
7877 <heading>User configuration files ("dotfiles")</heading>
7880 The files in <file>/etc/skel</file> will automatically be
7881 copied into new user accounts by <prgn>adduser</prgn>.
7882 No other program should reference the files in
7883 <file>/etc/skel</file>.
7887 Therefore, if a program needs a dotfile to exist in
7888 advance in <file>$HOME</file> to work sensibly, that dotfile
7889 should be installed in <file>/etc/skel</file> and treated as a
7894 However, programs that require dotfiles in order to
7895 operate sensibly are a bad thing, unless they do create
7896 the dotfiles themselves automatically.
7900 Furthermore, programs should be configured by the Debian
7901 default installation to behave as closely to the upstream
7902 default behavior as possible.
7906 Therefore, if a program in a Debian package needs to be
7907 configured in some way in order to operate sensibly, that
7908 should be done using a site-wide configuration file placed
7909 in <file>/etc</file>. Only if the program doesn't support a
7910 site-wide default configuration and the package maintainer
7911 doesn't have time to add it may a default per-user file be
7912 placed in <file>/etc/skel</file>.
7916 <file>/etc/skel</file> should be as empty as we can make it.
7917 This is particularly true because there is no easy (or
7918 necessarily desirable) mechanism for ensuring that the
7919 appropriate dotfiles are copied into the accounts of
7920 existing users when a package is installed.
7926 <heading>Log files</heading>
7928 Log files should usually be named
7929 <file>/var/log/<var>package</var>.log</file>. If you have many
7930 log files, or need a separate directory for permission
7931 reasons (<file>/var/log</file> is writable only by
7932 <file>root</file>), you should usually create a directory named
7933 <file>/var/log/<var>package</var></file> and place your log
7938 Log files must be rotated occasionally so that they don't
7939 grow indefinitely; the best way to do this is to drop a log
7940 rotation configuration file into the directory
7941 <file>/etc/logrotate.d</file> and use the facilities provided by
7942 logrotate.<footnote>
7944 The traditional approach to log files has been to set up
7945 <em>ad hoc</em> log rotation schemes using simple shell
7946 scripts and cron. While this approach is highly
7947 customizable, it requires quite a lot of sysadmin work.
7948 Even though the original Debian system helped a little
7949 by automatically installing a system which can be used
7950 as a template, this was deemed not enough.
7954 The use of <prgn>logrotate</prgn>, a program developed
7955 by Red Hat, is better, as it centralizes log management.
7956 It has both a configuration file
7957 (<file>/etc/logrotate.conf</file>) and a directory where
7958 packages can drop their individual log rotation
7959 configurations (<file>/etc/logrotate.d</file>).
7962 Here is a good example for a logrotate config
7963 file (for more information see <manref name="logrotate"
7965 <example compact="compact">
7966 /var/log/foo/*.log {
7971 /etc/init.d/foo force-reload
7975 This rotates all files under <file>/var/log/foo</file>, saves 12
7976 compressed generations, and forces the daemon to reload its
7977 configuration information after the log rotation.
7981 Log files should be removed when the package is
7982 purged (but not when it is only removed). This should be
7983 done by the <prgn>postrm</prgn> script when it is called
7984 with the argument <tt>purge</tt> (see <ref
7985 id="removedetails">).
7990 <heading>Permissions and owners</heading>
7993 The rules in this section are guidelines for general use.
7994 If necessary you may deviate from the details below.
7995 However, if you do so you must make sure that what is done
7996 is secure and you should try to be as consistent as possible
7997 with the rest of the system. You should probably also
7998 discuss it on <prgn>debian-devel</prgn> first.
8002 Files should be owned by <tt>root:root</tt>, and made
8003 writable only by the owner and universally readable (and
8004 executable, if appropriate), that is mode 644 or 755.
8008 Directories should be mode 755 or (for group-writability)
8009 mode 2775. The ownership of the directory should be
8010 consistent with its mode: if a directory is mode 2775, it
8011 should be owned by the group that needs write access to
8014 When a package is upgraded, and the owner or permissions
8015 of a file included in the package has changed, dpkg
8016 arranges for the ownership and permissions to be
8017 correctly set upon installation. However, this does not
8018 extend to directories; the permissions and ownership of
8019 directories already on the system does not change on
8020 install or upgrade of packages. This makes sense, since
8021 otherwise common directories like <tt>/usr</tt> would
8022 always be in flux. To correctly change permissions of a
8023 directory the package owns, explicit action is required,
8024 usually in the <tt>postinst</tt> script. Care must be
8025 taken to handle downgrades as well, in that case.
8032 Setuid and setgid executables should be mode 4755 or 2755
8033 respectively, and owned by the appropriate user or group.
8034 They should not be made unreadable (modes like 4711 or
8035 2711 or even 4111); doing so achieves no extra security,
8036 because anyone can find the binary in the freely available
8037 Debian package; it is merely inconvenient. For the same
8038 reason you should not restrict read or execute permissions
8039 on non-set-id executables.
8043 Some setuid programs need to be restricted to particular
8044 sets of users, using file permissions. In this case they
8045 should be owned by the uid to which they are set-id, and by
8046 the group which should be allowed to execute them. They
8047 should have mode 4754; again there is no point in making
8048 them unreadable to those users who must not be allowed to
8053 It is possible to arrange that the system administrator can
8054 reconfigure the package to correspond to their local
8055 security policy by changing the permissions on a binary:
8056 they can do this by using <prgn>dpkg-statoverride</prgn>, as
8057 described below.<footnote>
8058 Ordinary files installed by <prgn>dpkg</prgn> (as
8059 opposed to <tt>conffile</tt>s and other similar objects)
8060 normally have their permissions reset to the distributed
8061 permissions when the package is reinstalled. However,
8062 the use of <prgn>dpkg-statoverride</prgn> overrides this
8065 Another method you should consider is to create a group for
8066 people allowed to use the program(s) and make any setuid
8067 executables executable only by that group.
8071 If you need to create a new user or group for your package
8072 there are two possibilities. Firstly, you may need to
8073 make some files in the binary package be owned by this
8074 user or group, or you may need to compile the user or
8075 group id (rather than just the name) into the binary
8076 (though this latter should be avoided if possible, as in
8077 this case you need a statically allocated id).</p>
8080 If you need a statically allocated id, you must ask for a
8081 user or group id from the <tt>base-passwd</tt> maintainer,
8082 and must not release the package until you have been
8083 allocated one. Once you have been allocated one you must
8084 either make the package depend on a version of the
8085 <tt>base-passwd</tt> package with the id present in
8086 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
8087 your package to create the user or group itself with the
8088 correct id (using <tt>adduser</tt>) in its
8089 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
8090 the <prgn>postinst</prgn> is to be preferred if it is
8091 possible, otherwise a pre-dependency will be needed on the
8092 <tt>adduser</tt> package.)
8096 On the other hand, the program might be able to determine
8097 the uid or gid from the user or group name at runtime, so
8098 that a dynamically allocated id can be used. In this case
8099 you should choose an appropriate user or group name,
8100 discussing this on <prgn>debian-devel</prgn> and checking
8101 with the <package/base-passwd/ maintainer that it is unique and that
8102 they do not wish you to use a statically allocated id
8103 instead. When this has been checked you must arrange for
8104 your package to create the user or group if necessary using
8105 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
8106 <prgn>postinst</prgn> script (again, the latter is to be
8107 preferred if it is possible).
8111 Note that changing the numeric value of an id associated
8112 with a name is very difficult, and involves searching the
8113 file system for all appropriate files. You need to think
8114 carefully whether a static or dynamic id is required, since
8115 changing your mind later will cause problems.
8118 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
8120 This section is not intended as policy, but as a
8121 description of the use of <prgn>dpkg-statoverride</prgn>.
8125 If a system administrator wishes to have a file (or
8126 directory or other such thing) installed with owner and
8127 permissions different from those in the distributed Debian
8128 package, they can use the <prgn>dpkg-statoverride</prgn>
8129 program to instruct <prgn>dpkg</prgn> to use the different
8130 settings every time the file is installed. Thus the
8131 package maintainer should distribute the files with their
8132 normal permissions, and leave it for the system
8133 administrator to make any desired changes. For example, a
8134 daemon which is normally required to be setuid root, but
8135 in certain situations could be used without being setuid,
8136 should be installed setuid in the <tt>.deb</tt>. Then the
8137 local system administrator can change this if they wish.
8138 If there are two standard ways of doing it, the package
8139 maintainer can use <tt>debconf</tt> to find out the
8140 preference, and call <prgn>dpkg-statoverride</prgn> in the
8141 maintainer script if necessary to accommodate the system
8142 administrator's choice. Care must be taken during
8143 upgrades to not override an existing setting.
8147 Given the above, <prgn>dpkg-statoverride</prgn> is
8148 essentially a tool for system administrators and would not
8149 normally be needed in the maintainer scripts. There is
8150 one type of situation, though, where calls to
8151 <prgn>dpkg-statoverride</prgn> would be needed in the
8152 maintainer scripts, and that involves packages which use
8153 dynamically allocated user or group ids. In such a
8154 situation, something like the following idiom can be very
8155 helpful in the package's <prgn>postinst</prgn>, where
8156 <tt>sysuser</tt> is a dynamically allocated id:
8158 for i in /usr/bin/foo /usr/sbin/bar
8160 # only do something when no setting exists
8161 if ! dpkg-statoverride --list $i >/dev/null 2>&1
8163 #include: debconf processing, question about foo and bar
8164 if [ "$RET" = "true" ] ; then
8165 dpkg-statoverride --update --add sysuser root 4755 $i
8170 The corresponding code to remove the override when the package
8173 for i in /usr/bin/foo /usr/sbin/bar
8175 if dpkg-statoverride --list $i >/dev/null 2>&1
8177 dpkg-statoverride --remove $i
8187 <chapt id="customized-programs">
8188 <heading>Customized programs</heading>
8190 <sect id="arch-spec">
8191 <heading>Architecture specification strings</heading>
8194 If a program needs to specify an <em>architecture specification
8195 string</em> in some place, it should select one of the strings
8196 provided by <tt>dpkg-architecture -L</tt>. The strings are in
8197 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
8198 part is sometimes elided, as when the OS is Linux.
8202 Note that we don't want to use
8203 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
8204 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
8205 since this would make our programs incompatible with other
8206 Linux distributions. We also don't use something like
8207 <tt><var>arch</var>-unknown-linux</tt>, since the
8208 <tt>unknown</tt> does not look very good.
8211 <sect1 id="arch-wildcard-spec">
8212 <heading>Architecture wildcards</heading>
8215 A package may specify an architecture wildcard. Architecture
8216 wildcards are in the format <tt>any</tt> (which matches every
8217 architecture), <tt><var>os</var></tt>-any, or
8218 any-<tt><var>cpu</var></tt>. <footnote>
8219 Internally, the package system normalizes the GNU triplets
8220 and the Debian arches into Debian arch triplets (which are
8221 kind of inverted GNU triplets), with the first component of
8222 the triplet representing the libc and ABI in use, and then
8223 does matching against those triplets. However, such
8224 triplets are an internal implementation detail that should
8225 not be used by packages directly. The libc and ABI portion
8226 is handled internally by the package system based on
8227 the <var>os</var> and <var>cpu</var>.
8234 <heading>Daemons</heading>
8237 The configuration files <file>/etc/services</file>,
8238 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
8239 by the <prgn>netbase</prgn> package and must not be modified
8244 If a package requires a new entry in one of these files, the
8245 maintainer should get in contact with the
8246 <prgn>netbase</prgn> maintainer, who will add the entries
8247 and release a new version of the <prgn>netbase</prgn>
8252 The configuration file <file>/etc/inetd.conf</file> must not be
8253 modified by the package's scripts except via the
8254 <prgn>update-inetd</prgn> script or the
8255 <file>DebianNet.pm</file> Perl module. See their documentation
8256 for details on how to add entries.
8260 If a package wants to install an example entry into
8261 <file>/etc/inetd.conf</file>, the entry must be preceded with
8262 exactly one hash character (<tt>#</tt>). Such lines are
8263 treated as "commented out by user" by the
8264 <prgn>update-inetd</prgn> script and are not changed or
8265 activated during package updates.
8270 <heading>Using pseudo-ttys and modifying wtmp, utmp and
8274 Some programs need to create pseudo-ttys. This should be done
8275 using Unix98 ptys if the C library supports it. The resulting
8276 program must not be installed setuid root, unless that
8277 is required for other functionality.
8281 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
8282 <file>/var/log/lastlog</file> must be installed writable by
8283 group <tt>utmp</tt>. Programs which need to modify those
8284 files must be installed setgid <tt>utmp</tt>.
8289 <heading>Editors and pagers</heading>
8292 Some programs have the ability to launch an editor or pager
8293 program to edit or display a text document. Since there are
8294 lots of different editors and pagers available in the Debian
8295 distribution, the system administrator and each user should
8296 have the possibility to choose their preferred editor and
8301 In addition, every program should choose a good default
8302 editor/pager if none is selected by the user or system
8307 Thus, every program that launches an editor or pager must
8308 use the EDITOR or PAGER environment variable to determine
8309 the editor or pager the user wishes to use. If these
8310 variables are not set, the programs <file>/usr/bin/editor</file>
8311 and <file>/usr/bin/pager</file> should be used, respectively.
8315 These two files are managed through the <prgn>dpkg</prgn>
8316 "alternatives" mechanism. Thus every package providing an
8317 editor or pager must call the
8318 <prgn>update-alternatives</prgn> script to register these
8323 If it is very hard to adapt a program to make use of the
8324 EDITOR or PAGER variables, that program may be configured to
8325 use <file>/usr/bin/sensible-editor</file> and
8326 <file>/usr/bin/sensible-pager</file> as the editor or pager
8327 program respectively. These are two scripts provided in the
8328 <package>sensible-utils</package> package that check the EDITOR
8329 and PAGER variables and launch the appropriate program, and fall
8330 back to <file>/usr/bin/editor</file>
8331 and <file>/usr/bin/pager</file> if the variable is not set.
8335 A program may also use the VISUAL environment variable to
8336 determine the user's choice of editor. If it exists, it
8337 should take precedence over EDITOR. This is in fact what
8338 <file>/usr/bin/sensible-editor</file> does.
8342 It is not required for a package to depend on
8343 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
8344 package to provide such virtual packages.<footnote>
8345 The Debian base system already provides an editor and a
8351 <sect id="web-appl">
8352 <heading>Web servers and applications</heading>
8355 This section describes the locations and URLs that should
8356 be used by all web servers and web applications in the
8363 Cgi-bin executable files are installed in the
8365 <example compact="compact">
8366 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
8368 and should be referred to as
8369 <example compact="compact">
8370 http://localhost/cgi-bin/<var>cgi-bin-name</var>
8376 <p>Access to HTML documents</p>
8379 HTML documents for a package are stored in
8380 <file>/usr/share/doc/<var>package</var></file>
8381 and can be referred to as
8382 <example compact="compact">
8383 http://localhost/doc/<var>package</var>/<var>filename</var>
8388 The web server should restrict access to the document
8389 tree so that only clients on the same host can read
8390 the documents. If the web server does not support such
8391 access controls, then it should not provide access at
8392 all, or ask about providing access during installation.
8397 <p>Access to images</p>
8399 It is recommended that images for a package be stored
8400 in <tt>/usr/share/images/<var>package</var></tt> and
8401 may be referred to through an alias <tt>/images/</tt>
8404 http://localhost/images/<package>/<filename>
8411 <p>Web Document Root</p>
8414 Web Applications should try to avoid storing files in
8415 the Web Document Root. Instead they should use the
8416 /usr/share/doc/<var>package</var> directory for
8417 documents and register the Web Application via the
8418 <package>doc-base</package> package. If access to the
8419 web document root is unavoidable then use
8420 <example compact="compact">
8423 as the Document Root. This might be just a symbolic
8424 link to the location where the system administrator
8425 has put the real document root.
8428 <item><p>Providing httpd and/or httpd-cgi</p>
8430 All web servers should provide the virtual package
8431 <tt>httpd</tt>. If a web server has CGI support it should
8432 provide <tt>httpd-cgi</tt> additionally.
8435 All web applications which do not contain CGI scripts should
8436 depend on <tt>httpd</tt>, all those web applications which
8437 <tt>do</tt> contain CGI scripts, should depend on
8445 <sect id="mail-transport-agents">
8446 <heading>Mail transport, delivery and user agents</heading>
8449 Debian packages which process electronic mail, whether mail
8450 user agents (MUAs) or mail transport agents (MTAs), must
8451 ensure that they are compatible with the configuration
8452 decisions below. Failure to do this may result in lost
8453 mail, broken <tt>From:</tt> lines, and other serious brain
8458 The mail spool is <file>/var/mail</file> and the interface to
8459 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8460 the FHS). On older systems, the mail spool may be
8461 physically located in <file>/var/spool/mail</file>, but all
8462 access to the mail spool should be via the
8463 <file>/var/mail</file> symlink. The mail spool is part of the
8464 base system and not part of the MTA package.
8468 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8469 programs (such as IMAP daemons) must lock the mailbox in an
8470 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8471 be combined with dot locking. To avoid deadlocks, a program
8472 should use <tt>fcntl()</tt> first and dot locking after
8473 this, or alternatively implement the two locking methods in
8474 a non blocking way<footnote>
8475 If it is not possible to establish both locks, the
8476 system shouldn't wait for the second lock to be
8477 established, but remove the first lock, wait a (random)
8478 time, and start over locking again.
8479 </footnote>. Using the functions <tt>maillock</tt> and
8480 <tt>mailunlock</tt> provided by the
8481 <tt>liblockfile*</tt><footnote>
8482 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8483 to use these functions.
8484 </footnote> packages is the recommended way to realize this.
8488 Mailboxes are generally either mode 600 and owned by
8489 <var>user</var> or mode 660 and owned by
8490 <tt><var>user</var>:mail</tt><footnote>
8491 There are two traditional permission schemes for mail spools:
8492 mode 600 with all mail delivery done by processes running as
8493 the destination user, or mode 660 and owned by group mail with
8494 mail delivery done by a process running as a system user in
8495 group mail. Historically, Debian required mode 660 mail
8496 spools to enable the latter model, but that model has become
8497 increasingly uncommon and the principle of least privilege
8498 indicates that mail systems that use the first model should
8499 use permissions of 600. If delivery to programs is permitted,
8500 it's easier to keep the mail system secure if the delivery
8501 agent runs as the destination user. Debian Policy therefore
8502 permits either scheme.
8503 </footnote>. The local system administrator may choose a
8504 different permission scheme; packages should not make
8505 assumptions about the permission and ownership of mailboxes
8506 unless required (such as when creating a new mailbox). A MUA
8507 may remove a mailbox (unless it has nonstandard permissions) in
8508 which case the MTA or another MUA must recreate it if needed.
8512 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8513 be setgid mail to do the locking mentioned above (and
8514 must obviously avoid accessing other users' mailboxes
8515 using this privilege).</p>
8518 <file>/etc/aliases</file> is the source file for the system mail
8519 aliases (e.g., postmaster, usenet, etc.), it is the one
8520 which the sysadmin and <prgn>postinst</prgn> scripts may
8521 edit. After <file>/etc/aliases</file> is edited the program or
8522 human editing it must call <prgn>newaliases</prgn>. All MTA
8523 packages must come with a <prgn>newaliases</prgn> program,
8524 even if it does nothing, but older MTA packages did not do
8525 this so programs should not fail if <prgn>newaliases</prgn>
8526 cannot be found. Note that because of this, all MTA
8527 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8528 <tt>Replaces: mail-transport-agent</tt> control file
8533 The convention of writing <tt>forward to
8534 <var>address</var></tt> in the mailbox itself is not
8535 supported. Use a <tt>.forward</tt> file instead.</p>
8538 The <prgn>rmail</prgn> program used by UUCP
8539 for incoming mail should be <file>/usr/sbin/rmail</file>.
8540 Likewise, <prgn>rsmtp</prgn>, for receiving
8541 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8545 If your package needs to know what hostname to use on (for
8546 example) outgoing news and mail messages which are generated
8547 locally, you should use the file <file>/etc/mailname</file>. It
8548 will contain the portion after the username and <tt>@</tt>
8549 (at) sign for email addresses of users on the machine
8550 (followed by a newline).
8554 Such a package should check for the existence of this file
8555 when it is being configured. If it exists, it should be
8556 used without comment, although an MTA's configuration script
8557 may wish to prompt the user even if it finds that this file
8558 exists. If the file does not exist, the package should
8559 prompt the user for the value (preferably using
8560 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8561 as well as using it in the package's configuration. The
8562 prompt should make it clear that the name will not just be
8563 used by that package. For example, in this situation the
8564 <tt>inn</tt> package could say something like:
8565 <example compact="compact">
8566 Please enter the "mail name" of your system. This is the
8567 hostname portion of the address to be shown on outgoing
8568 news and mail messages. The default is
8569 <var>syshostname</var>, your system's host name. Mail
8570 name ["<var>syshostname</var>"]:
8572 where <var>syshostname</var> is the output of <tt>hostname
8578 <heading>News system configuration</heading>
8581 All the configuration files related to the NNTP (news)
8582 servers and clients should be located under
8583 <file>/etc/news</file>.</p>
8586 There are some configuration issues that apply to a number
8587 of news clients and server packages on the machine. These
8591 <tag><file>/etc/news/organization</file></tag>
8593 A string which should appear as the
8594 organization header for all messages posted
8595 by NNTP clients on the machine
8598 <tag><file>/etc/news/server</file></tag>
8600 Contains the FQDN of the upstream NNTP
8601 server, or localhost if the local machine is
8606 Other global files may be added as required for cross-package news
8613 <heading>Programs for the X Window System</heading>
8616 <heading>Providing X support and package priorities</heading>
8619 Programs that can be configured with support for the X
8620 Window System must be configured to do so and must declare
8621 any package dependencies necessary to satisfy their
8622 runtime requirements when using the X Window System. If
8623 such a package is of higher priority than the X packages
8624 on which it depends, it is required that either the
8625 X-specific components be split into a separate package, or
8626 that an alternative version of the package, which includes
8627 X support, be provided, or that the package's priority be
8633 <heading>Packages providing an X server</heading>
8636 Packages that provide an X server that, directly or
8637 indirectly, communicates with real input and display
8638 hardware should declare in their control data that they
8639 provide the virtual package <tt>xserver</tt>.<footnote>
8640 This implements current practice, and provides an
8641 actual policy for usage of the <tt>xserver</tt>
8642 virtual package which appears in the virtual packages
8643 list. In a nutshell, X servers that interface
8644 directly with the display and input hardware or via
8645 another subsystem (e.g., GGI) should provide
8646 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8647 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8653 <heading>Packages providing a terminal emulator</heading>
8656 Packages that provide a terminal emulator for the X Window
8657 System which meet the criteria listed below should declare
8658 in their control data that they provide the virtual
8659 package <tt>x-terminal-emulator</tt>. They should also
8660 register themselves as an alternative for
8661 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8666 To be an <tt>x-terminal-emulator</tt>, a program must:
8667 <list compact="compact">
8669 Be able to emulate a DEC VT100 terminal, or a
8670 compatible terminal.
8674 Support the command-line option <tt>-e
8675 <var>command</var></tt>, which creates a new
8676 terminal window<footnote>
8677 "New terminal window" does not necessarily mean
8678 a new top-level X window directly parented by
8679 the window manager; it could, if the terminal
8680 emulator application were so coded, be a new
8681 "view" in a multiple-document interface (MDI).
8683 and runs the specified <var>command</var>,
8684 interpreting the entirety of the rest of the command
8685 line as a command to pass straight to exec, in the
8686 manner that <tt>xterm</tt> does.
8690 Support the command-line option <tt>-T
8691 <var>title</var></tt>, which creates a new terminal
8692 window with the window title <var>title</var>.
8699 <heading>Packages providing a window manager</heading>
8702 Packages that provide a window manager should declare in
8703 their control data that they provide the virtual package
8704 <tt>x-window-manager</tt>. They should also register
8705 themselves as an alternative for
8706 <file>/usr/bin/x-window-manager</file>, with a priority
8707 calculated as follows:
8708 <list compact="compact">
8710 Start with a priority of 20.
8714 If the window manager supports the Debian menu
8715 system, add 20 points if this support is available
8716 in the package's default configuration (i.e., no
8717 configuration files belonging to the system or user
8718 have to be edited to activate the feature); if
8719 configuration files must be modified, add only 10
8725 If the window manager complies with <url
8726 id="http://www.freedesktop.org/Standards/wm-spec"
8727 name="The Window Manager Specification Project">,
8728 written by the <url id="http://www.freedesktop.org/"
8729 name="Free Desktop Group">, add 40 points.
8733 If the window manager permits the X session to be
8734 restarted using a <em>different</em> window manager
8735 (without killing the X server) in its default
8736 configuration, add 10 points; otherwise add none.
8743 <heading>Packages providing fonts</heading>
8746 Packages that provide fonts for the X Window
8748 For the purposes of Debian Policy, a "font for the X
8749 Window System" is one which is accessed via X protocol
8750 requests. Fonts for the Linux console, for PostScript
8751 renderer, or any other purpose, do not fit this
8752 definition. Any tool which makes such fonts available
8753 to the X Window System, however, must abide by this
8756 must do a number of things to ensure that they are both
8757 available without modification of the X or font server
8758 configuration, and that they do not corrupt files used by
8759 other font packages to register information about
8763 Fonts of any type supported by the X Window System
8764 must be in a separate binary package from any
8765 executables, libraries, or documentation (except
8766 that specific to the fonts shipped, such as their
8767 license information). If one or more of the fonts
8768 so packaged are necessary for proper operation of
8769 the package with which they are associated the font
8770 package may be Recommended; if the fonts merely
8771 provide an enhancement, a Suggests relationship may
8772 be used. Packages must not Depend on font
8774 This is because the X server may retrieve fonts
8775 from the local file system or over the network
8776 from an X font server; the Debian package system
8777 is empowered to deal only with the local
8783 BDF fonts must be converted to PCF fonts with the
8784 <prgn>bdftopcf</prgn> utility (available in the
8785 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8786 placed in a directory that corresponds to their
8788 <list compact="compact">
8790 100 dpi fonts must be placed in
8791 <file>/usr/share/fonts/X11/100dpi/</file>.
8795 75 dpi fonts must be placed in
8796 <file>/usr/share/fonts/X11/75dpi/</file>.
8800 Character-cell fonts, cursor fonts, and other
8801 low-resolution fonts must be placed in
8802 <file>/usr/share/fonts/X11/misc/</file>.
8808 Type 1 fonts must be placed in
8809 <file>/usr/share/fonts/X11/Type1/</file>. If font
8810 metric files are available, they must be placed here
8815 Subdirectories of <file>/usr/share/fonts/X11/</file>
8816 other than those listed above must be neither
8817 created nor used. (The <file>PEX</file>, <file>CID</file>,
8818 <file>Speedo</file>, and <file>cyrillic</file> directories
8819 are excepted for historical reasons, but installation of
8820 files into these directories remains discouraged.)
8824 Font packages may, instead of placing files directly
8825 in the X font directories listed above, provide
8826 symbolic links in that font directory pointing to
8827 the files' actual location in the filesystem. Such
8828 a location must comply with the FHS.
8832 Font packages should not contain both 75dpi and
8833 100dpi versions of a font. If both are available,
8834 they should be provided in separate binary packages
8835 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8836 the names of the packages containing the
8837 corresponding fonts.
8841 Fonts destined for the <file>misc</file> subdirectory
8842 should not be included in the same package as 75dpi
8843 or 100dpi fonts; instead, they should be provided in
8844 a separate package with <tt>-misc</tt> appended to
8849 Font packages must not provide the files
8850 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8851 <file>fonts.scale</file> in a font directory:
8854 <file>fonts.dir</file> files must not be provided at all.
8858 <file>fonts.alias</file> and <file>fonts.scale</file>
8859 files, if needed, should be provided in the
8861 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8862 where <var>fontdir</var> is the name of the
8864 <file>/usr/share/fonts/X11/</file> where the
8865 package's corresponding fonts are stored
8866 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8867 <var>package</var> is the name of the package
8868 that provides these fonts, and
8869 <var>extension</var> is either <tt>scale</tt>
8870 or <tt>alias</tt>, whichever corresponds to
8877 Font packages must declare a dependency on
8878 <tt>xfonts-utils</tt> in their control
8883 Font packages that provide one or more
8884 <file>fonts.scale</file> files as described above must
8885 invoke <prgn>update-fonts-scale</prgn> on each
8886 directory into which they installed fonts
8887 <em>before</em> invoking
8888 <prgn>update-fonts-dir</prgn> on that directory.
8889 This invocation must occur in both the
8890 <prgn>postinst</prgn> (for all arguments) and
8891 <prgn>postrm</prgn> (for all arguments except
8892 <tt>upgrade</tt>) scripts.
8896 Font packages that provide one or more
8897 <file>fonts.alias</file> files as described above must
8898 invoke <prgn>update-fonts-alias</prgn> on each
8899 directory into which they installed fonts. This
8900 invocation must occur in both the
8901 <prgn>postinst</prgn> (for all arguments) and
8902 <prgn>postrm</prgn> (for all arguments except
8903 <tt>upgrade</tt>) scripts.
8907 Font packages must invoke
8908 <prgn>update-fonts-dir</prgn> on each directory into
8909 which they installed fonts. This invocation must
8910 occur in both the <prgn>postinst</prgn> (for all
8911 arguments) and <prgn>postrm</prgn> (for all
8912 arguments except <tt>upgrade</tt>) scripts.
8916 Font packages must not provide alias names for the
8917 fonts they include which collide with alias names
8918 already in use by fonts already packaged.
8922 Font packages must not provide fonts with the same
8923 XLFD registry name as another font already packaged.
8929 <sect1 id="appdefaults">
8930 <heading>Application defaults files</heading>
8933 Application defaults files must be installed in the
8934 directory <file>/etc/X11/app-defaults/</file> (use of a
8935 localized subdirectory of <file>/etc/X11/</file> as described
8936 in the <em>X Toolkit Intrinsics - C Language
8937 Interface</em> manual is also permitted). They must be
8938 registered as <tt>conffile</tt>s or handled as
8939 configuration files.
8943 Customization of programs' X resources may also be
8944 supported with the provision of a file with the same name
8945 as that of the package placed in
8946 the <file>/etc/X11/Xresources/</file> directory, which
8947 must be registered as a <tt>conffile</tt> or handled as a
8948 configuration file.<footnote>
8949 Note that this mechanism is not the same as using
8950 app-defaults; app-defaults are tied to the client
8951 binary on the local file system, whereas X resources
8952 are stored in the X server and affect all connecting
8959 <heading>Installation directory issues</heading>
8962 Historically, packages using the X Window System used a
8963 separate set of installation directories from other packages.
8964 This practice has been discontinued and packages using the X
8965 Window System should now generally be installed in the same
8966 directories as any other package. Specifically, packages must
8967 not install files under the <file>/usr/X11R6/</file> directory
8968 and the <file>/usr/X11R6/</file> directory hierarchy should be
8969 regarded as obsolete.
8973 Include files previously installed under
8974 <file>/usr/X11R6/include/X11/</file> should be installed into
8975 <file>/usr/include/X11/</file>. For files previously
8976 installed into subdirectories of
8977 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
8978 determine if subdirectories of <file>/usr/lib/</file> and
8979 <file>/usr/share/</file> can be used. If not, a subdirectory
8980 of <file>/usr/lib/X11/</file> should be used.
8984 Configuration files for window, display, or session managers
8985 or other applications that are tightly integrated with the X
8986 Window System may be placed in a subdirectory
8987 of <file>/etc/X11/</file> corresponding to the package name.
8988 Other X Window System applications should use
8989 the <file>/etc/</file> directory unless otherwise mandated by
8990 policy (such as for <ref id="appdefaults">).
8995 <heading>The OSF/Motif and OpenMotif libraries</heading>
8998 <em>Programs that require the non-DFSG-compliant OSF/Motif or
8999 OpenMotif libraries</em><footnote>
9000 OSF/Motif and OpenMotif are collectively referred to as
9001 "Motif" in this policy document.
9003 should be compiled against and tested with LessTif (a free
9004 re-implementation of Motif) instead. If the maintainer
9005 judges that the program or programs do not work
9006 sufficiently well with LessTif to be distributed and
9007 supported, but do so when compiled against Motif, then two
9008 versions of the package should be created; one linked
9009 statically against Motif and with <tt>-smotif</tt>
9010 appended to the package name, and one linked dynamically
9011 against Motif and with <tt>-dmotif</tt> appended to the
9016 Both Motif-linked versions are dependent
9017 upon non-DFSG-compliant software and thus cannot be
9018 uploaded to the <em>main</em> distribution; if the
9019 software is itself DFSG-compliant it may be uploaded to
9020 the <em>contrib</em> distribution. While known existing
9021 versions of Motif permit unlimited redistribution of
9022 binaries linked against the library (whether statically or
9023 dynamically), it is the package maintainer's
9024 responsibility to determine whether this is permitted by
9025 the license of the copy of Motif in their possession.
9031 <heading>Perl programs and modules</heading>
9034 Perl programs and modules should follow the current Perl policy.
9038 The Perl policy can be found in the <tt>perl-policy</tt>
9039 files in the <tt>debian-policy</tt> package.
9040 It is also available from the Debian web mirrors at
9041 <tt><url name="/doc/packaging-manuals/perl-policy/"
9042 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
9047 <heading>Emacs lisp programs</heading>
9050 Please refer to the "Debian Emacs Policy" for details of how to
9051 package emacs lisp programs.
9055 The Emacs policy is available in
9056 <file>debian-emacs-policy.gz</file> of the
9057 <package>emacsen-common</package> package.
9058 It is also available from the Debian web mirrors at
9059 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
9060 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
9065 <heading>Games</heading>
9068 The permissions on <file>/var/games</file> are mode 755, owner
9069 <tt>root</tt> and group <tt>root</tt>.
9073 Each game decides on its own security policy.</p>
9076 Games which require protected, privileged access to
9077 high-score files, saved games, etc., may be made
9078 set-<em>group</em>-id (mode 2755) and owned by
9079 <tt>root:games</tt>, and use files and directories with
9080 appropriate permissions (770 <tt>root:games</tt>, for
9081 example). They must not be made
9082 set-<em>user</em>-id, as this causes security problems. (If
9083 an attacker can subvert any set-user-id game they can
9084 overwrite the executable of any other, causing other players
9085 of these games to run a Trojan horse program. With a
9086 set-group-id game the attacker only gets access to less
9087 important game data, and if they can get at the other
9088 players' accounts at all it will take considerably more
9092 Some packages, for example some fortune cookie programs, are
9093 configured by the upstream authors to install with their
9094 data files or other static information made unreadable so
9095 that they can only be accessed through set-id programs
9096 provided. You should not do this in a Debian package: anyone can
9097 download the <file>.deb</file> file and read the data from it,
9098 so there is no point making the files unreadable. Not
9099 making the files unreadable also means that you don't have
9100 to make so many programs set-id, which reduces the risk of a
9104 As described in the FHS, binaries of games should be
9105 installed in the directory <file>/usr/games</file>. This also
9106 applies to games that use the X Window System. Manual pages
9107 for games (X and non-X games) should be installed in
9108 <file>/usr/share/man/man6</file>.</p>
9114 <heading>Documentation</heading>
9117 <heading>Manual pages</heading>
9120 You should install manual pages in <prgn>nroff</prgn> source
9121 form, in appropriate places under <file>/usr/share/man</file>.
9122 You should only use sections 1 to 9 (see the FHS for more
9123 details). You must not install a pre-formatted "cat page".
9127 Each program, utility, and function should have an
9128 associated manual page included in the same package. It is
9129 suggested that all configuration files also have a manual
9130 page included as well. Manual pages for protocols and other
9131 auxiliary things are optional.
9135 If no manual page is available, this is considered as a bug
9136 and should be reported to the Debian Bug Tracking System (the
9137 maintainer of the package is allowed to write this bug report
9138 themselves, if they so desire). Do not close the bug report
9139 until a proper man page is available.<footnote>
9140 It is not very hard to write a man page. See the
9141 <url id="http://www.schweikhardt.net/man_page_howto.html"
9142 name="Man-Page-HOWTO">,
9143 <manref name="man" section="7">, the examples
9144 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
9145 the helper program <prgn>help2man</prgn>, or the
9146 directory <file>/usr/share/doc/man-db/examples</file>.
9151 You may forward a complaint about a missing man page to the
9152 upstream authors, and mark the bug as forwarded in the
9153 Debian bug tracking system. Even though the GNU Project do
9154 not in general consider the lack of a man page to be a bug,
9155 we do; if they tell you that they don't consider it a bug
9156 you should leave the bug in our bug tracking system open
9161 Manual pages should be installed compressed using <tt>gzip -9</tt>.
9165 If one man page needs to be accessible via several names it
9166 is better to use a symbolic link than the <file>.so</file>
9167 feature, but there is no need to fiddle with the relevant
9168 parts of the upstream source to change from <file>.so</file> to
9169 symlinks: don't do it unless it's easy. You should not
9170 create hard links in the manual page directories, nor put
9171 absolute filenames in <file>.so</file> directives. The filename
9172 in a <file>.so</file> in a man page should be relative to the
9173 base of the man page tree (usually
9174 <file>/usr/share/man</file>). If you do not create any links
9175 (whether symlinks, hard links, or <tt>.so</tt> directives)
9176 in the file system to the alternate names of the man page,
9177 then you should not rely on <prgn>man</prgn> finding your
9178 man page under those names based solely on the information in
9179 the man page's header.<footnote>
9180 Supporting this in <prgn>man</prgn> often requires
9181 unreasonable processing time to find a manual page or to
9182 report that none exists, and moves knowledge into man's
9183 database that would be better left in the file system.
9184 This support is therefore deprecated and will cease to
9185 be present in the future.
9190 Manual pages in locale-specific subdirectories of
9191 <file>/usr/share/man</file> should use either UTF-8 or the usual
9192 legacy encoding for that language (normally the one corresponding
9193 to the shortest relevant locale name in
9194 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
9195 <file>/usr/share/man/fr</file> should use either UTF-8 or
9196 ISO-8859-1.<footnote>
9197 <prgn>man</prgn> will automatically detect whether UTF-8 is in
9198 use. In future, all manual pages will be required to use
9204 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
9205 included in the subdirectory name unless it indicates a
9206 significant difference in the language, as this excludes
9207 speakers of the language in other countries.<footnote>
9208 At the time of writing, Chinese and Portuguese are the main
9209 languages with such differences, so <file>pt_BR</file>,
9210 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
9215 If a localized version of a manual page is provided, it should
9216 either be up-to-date or it should be obvious to the reader that
9217 it is outdated and the original manual page should be used
9218 instead. This can be done either by a note at the beginning of
9219 the manual page or by showing the missing or changed portions in
9220 the original language instead of the target language.
9225 <heading>Info documents</heading>
9228 Info documents should be installed in <file>/usr/share/info</file>.
9229 They should be compressed with <tt>gzip -9</tt>.
9233 The <prgn>install-info</prgn> program maintains a directory of
9234 installed info documents in <file>/usr/share/info/dir</file> for
9235 the use of info readers.<footnote>
9236 It was previously necessary for packages installing info
9237 documents to run <prgn>install-info</prgn> from maintainer
9238 scripts. This is no longer necessary. The installation
9239 system now uses dpkg triggers.
9241 This file must not be included in packages. Packages containing
9242 info documents should depend on <tt>dpkg (>= 1.15.4) |
9243 install-info</tt> to ensure that the directory file is properly
9244 rebuilt during partial upgrades from Debian 5.0 (lenny) and
9249 Info documents should contain section and directory entry
9250 information in the document for the use
9251 of <prgn>install-info</prgn>. The section should be specified
9252 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
9253 space and the section of this info page. The directory entry or
9254 entries should be included between
9255 a <tt>START-INFO-DIR-ENTRY</tt> line and
9256 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
9258 INFO-DIR-SECTION Individual utilities
9259 START-INFO-DIR-ENTRY
9260 * example: (example). An example info directory entry.
9263 To determine which section to use, you should look
9264 at <file>/usr/share/info/dir</file> on your system and choose
9265 the most relevant (or create a new section if none of the
9266 current sections are relevant).<footnote>
9267 Normally, info documents are generated from Texinfo source.
9268 To include this information in the generated info document, if
9269 it is absent, add commands like:
9271 @dircategory Individual utilities
9273 * example: (example). An example info directory entry.
9276 to the Texinfo source of the document and ensure that the info
9277 documents are rebuilt from source during the package build.
9283 <heading>Additional documentation</heading>
9286 Any additional documentation that comes with the package may
9287 be installed at the discretion of the package maintainer.
9288 Plain text documentation should be installed in the directory
9289 <file>/usr/share/doc/<var>package</var></file>, where
9290 <var>package</var> is the name of the package, and
9291 compressed with <tt>gzip -9</tt> unless it is small.
9295 If a package comes with large amounts of documentation which
9296 many users of the package will not require you should create
9297 a separate binary package to contain it, so that it does not
9298 take up disk space on the machines of users who do not need
9299 or want it installed.</p>
9302 It is often a good idea to put text information files
9303 (<file>README</file>s, changelogs, and so forth) that come with
9304 the source package in <file>/usr/share/doc/<var>package</var></file>
9305 in the binary package. However, you don't need to install
9306 the instructions for building and installing the package, of
9310 Packages must not require the existence of any files in
9311 <file>/usr/share/doc/</file> in order to function
9313 The system administrator should be able to
9314 delete files in <file>/usr/share/doc/</file> without causing
9315 any programs to break.
9317 Any files that are referenced by programs but are also
9318 useful as stand alone documentation should be installed under
9319 <file>/usr/share/<var>package</var>/</file> with symbolic links from
9320 <file>/usr/share/doc/<var>package</var></file>.
9324 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9325 link to another directory in <file>/usr/share/doc</file> only if
9326 the two packages both come from the same source and the
9327 first package Depends on the second.<footnote>
9329 Please note that this does not override the section on
9330 changelog files below, so the file
9331 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
9332 must refer to the changelog for the current version of
9333 <var>package</var> in question. In practice, this means
9334 that the sources of the target and the destination of the
9335 symlink must be the same (same source package and
9342 Former Debian releases placed all additional documentation
9343 in <file>/usr/doc/<var>package</var></file>. This has been
9344 changed to <file>/usr/share/doc/<var>package</var></file>,
9345 and packages must not put documentation in the directory
9346 <file>/usr/doc/<var>package</var></file>. <footnote>
9347 At this phase of the transition, we no longer require a
9348 symbolic link in <file>/usr/doc/</file>. At a later point,
9349 policy shall change to make the symbolic links a bug.
9355 <heading>Preferred documentation formats</heading>
9358 The unification of Debian documentation is being carried out
9362 If your package comes with extensive documentation in a
9363 markup format that can be converted to various other formats
9364 you should if possible ship HTML versions in a binary
9365 package, in the directory
9366 <file>/usr/share/doc/<var>appropriate-package</var></file> or
9367 its subdirectories.<footnote>
9368 The rationale: The important thing here is that HTML
9369 docs should be available in <em>some</em> package, not
9370 necessarily in the main binary package.
9375 Other formats such as PostScript may be provided at the
9376 package maintainer's discretion.
9380 <sect id="copyrightfile">
9381 <heading>Copyright information</heading>
9384 Every package must be accompanied by a verbatim copy of its
9385 copyright information and distribution license in the file
9386 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
9387 file must neither be compressed nor be a symbolic link.
9391 In addition, the copyright file must say where the upstream
9392 sources (if any) were obtained. It should name the original
9393 authors of the package and the Debian maintainer(s) who were
9394 involved with its creation.
9398 Packages in the <em>contrib</em> or <em>non-free</em> archive
9399 areas should state in the copyright file that the package is not
9400 part of the Debian GNU/Linux distribution and briefly explain
9405 A copy of the file which will be installed in
9406 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9407 be in <file>debian/copyright</file> in the source package.
9411 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9412 link to another directory in <file>/usr/share/doc</file> only if
9413 the two packages both come from the same source and the
9414 first package Depends on the second. These rules are
9415 important because copyrights must be extractable by
9420 Packages distributed under the Apache license (version 2.0), the
9421 Artistic license, the GNU GPL (version 2 or 3), the GNU LGPL
9422 (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or 1.3)
9423 should refer to the corresponding files
9424 under <file>/usr/share/common-licenses</file>,<footnote>
9427 <file>/usr/share/common-licenses/Apache-2.0</file>,
9428 <file>/usr/share/common-licenses/Artistic</file>,
9429 <file>/usr/share/common-licenses/GPL-2</file>,
9430 <file>/usr/share/common-licenses/GPL-3</file>,
9431 <file>/usr/share/common-licenses/LGPL-2</file>,
9432 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9433 <file>/usr/share/common-licenses/LGPL-3</file>,
9434 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
9435 <file>/usr/share/common-licenses/GFDL-1.3</file>
9436 respectively. The University of California BSD license is
9437 also included in <package>base-files</package> as
9438 <file>/usr/share/common-licenses/BSD</file>, but given the
9439 brevity of this license, its specificity to code whose
9440 copyright is held by the Regents of the University of
9441 California, and the frequency of minor wording changes, its
9442 text should be included in the copyright file rather than
9443 referencing this file.
9445 </footnote> rather than quoting them in the copyright
9450 You should not use the copyright file as a general <file>README</file>
9451 file. If your package has such a file it should be
9452 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9453 <file>README.Debian</file> or some other appropriate place.</p>
9457 <heading>Examples</heading>
9460 Any examples (configurations, source files, whatever),
9461 should be installed in a directory
9462 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9463 files should not be referenced by any program: they're there
9464 for the benefit of the system administrator and users as
9465 documentation only. Architecture-specific example files
9466 should be installed in a directory
9467 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9469 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9470 latter directory itself may be a symbolic link to the
9475 If the purpose of a package is to provide examples, then the
9476 example files may be installed into
9477 <file>/usr/share/doc/<var>package</var></file>.
9481 <sect id="changelogs">
9482 <heading>Changelog files</heading>
9485 Packages that are not Debian-native must contain a
9486 compressed copy of the <file>debian/changelog</file> file from
9487 the Debian source tree in
9488 <file>/usr/share/doc/<var>package</var></file> with the name
9489 <file>changelog.Debian.gz</file>.
9493 If an upstream changelog is available, it should be accessible as
9494 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9495 plain text. If the upstream changelog is distributed in
9496 HTML, it should be made available in that form as
9497 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9498 and a plain text <file>changelog.gz</file> should be generated
9499 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9500 the upstream changelog files do not already conform to this
9501 naming convention, then this may be achieved either by
9502 renaming the files, or by adding a symbolic link, at the
9503 maintainer's discretion.<footnote>
9504 Rationale: People should not have to look in places for
9505 upstream changelogs merely because they are given
9506 different names or are distributed in HTML format.
9511 All of these files should be installed compressed using
9512 <tt>gzip -9</tt>, as they will become large with time even
9513 if they start out small.
9517 If the package has only one changelog which is used both as
9518 the Debian changelog and the upstream one because there is
9519 no separate upstream maintainer then that changelog should
9520 usually be installed as
9521 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9522 there is a separate upstream maintainer, but no upstream
9523 changelog, then the Debian changelog should still be called
9524 <file>changelog.Debian.gz</file>.
9528 For details about the format and contents of the Debian
9529 changelog file, please see <ref id="dpkgchangelog">.
9534 <appendix id="pkg-scope">
9535 <heading>Introduction and scope of these appendices</heading>
9538 These appendices are taken essentially verbatim from the
9539 now-deprecated Packaging Manual, version 3.2.1.0. They are
9540 the chapters which are likely to be of use to package
9541 maintainers and which have not already been included in the
9542 policy document itself. Most of these sections are very likely
9543 not relevant to policy; they should be treated as
9544 documentation for the packaging system. Please note that these
9545 appendices are included for convenience, and for historical
9546 reasons: they used to be part of policy package, and they have
9547 not yet been incorporated into dpkg documentation. However,
9548 they still have value, and hence they are presented here.
9552 They have not yet been checked to ensure that they are
9553 compatible with the contents of policy, and if there are any
9554 contradictions, the version in the main policy document takes
9555 precedence. The remaining chapters of the old Packaging
9556 Manual have also not been read in detail to ensure that there
9557 are not parts which have been left out. Both of these will be
9562 Certain parts of the Packaging manual were integrated into the
9563 Policy Manual proper, and removed from the appendices. Links
9564 have been placed from the old locations to the new ones.
9568 <prgn>dpkg</prgn> is a suite of programs for creating binary
9569 package files and installing and removing them on Unix
9571 <prgn>dpkg</prgn> is targeted primarily at Debian
9572 GNU/Linux, but may work on or be ported to other
9578 The binary packages are designed for the management of
9579 installed executable programs (usually compiled binaries) and
9580 their associated data, though source code examples and
9581 documentation are provided as part of some packages.</p>
9584 This manual describes the technical aspects of creating Debian
9585 binary packages (<file>.deb</file> files). It documents the
9586 behavior of the package management programs
9587 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9588 they interact with packages.</p>
9591 It also documents the interaction between
9592 <prgn>dselect</prgn>'s core and the access method scripts it
9593 uses to actually install the selected packages, and describes
9594 how to create a new access method.</p>
9597 This manual does not go into detail about the options and
9598 usage of the package building and installation tools. It
9599 should therefore be read in conjunction with those programs'
9604 The utility programs which are provided with <prgn>dpkg</prgn>
9605 for managing various system configuration and similar issues,
9606 such as <prgn>update-rc.d</prgn> and
9607 <prgn>install-info</prgn>, are not described in detail here -
9608 please see their man pages.
9612 It is assumed that the reader is reasonably familiar with the
9613 <prgn>dpkg</prgn> System Administrators' manual.
9614 Unfortunately this manual does not yet exist.
9618 The Debian version of the FSF's GNU hello program is provided
9619 as an example for people wishing to create Debian
9620 packages. The Debian <prgn>debmake</prgn> package is
9621 recommended as a very helpful tool in creating and maintaining
9622 Debian packages. However, while the tools and examples are
9623 helpful, they do not replace the need to read and follow the
9624 Policy and Programmer's Manual.</p>
9627 <appendix id="pkg-binarypkg">
9628 <heading>Binary packages (from old Packaging Manual)</heading>
9631 The binary package has two main sections. The first part
9632 consists of various control information files and scripts used
9633 by <prgn>dpkg</prgn> when installing and removing. See <ref
9634 id="pkg-controlarea">.
9638 The second part is an archive containing the files and
9639 directories to be installed.
9643 In the future binary packages may also contain other
9644 components, such as checksums and digital signatures. The
9645 format for the archive is described in full in the
9646 <file>deb(5)</file> man page.
9650 <sect id="pkg-bincreating"><heading>Creating package files -
9651 <prgn>dpkg-deb</prgn>
9655 All manipulation of binary package files is done by
9656 <prgn>dpkg-deb</prgn>; it's the only program that has
9657 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9658 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9659 will spot that the options requested are appropriate to
9660 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9665 In order to create a binary package you must make a
9666 directory tree which contains all the files and directories
9667 you want to have in the file system data part of the package.
9668 In Debian-format source packages this directory is usually
9669 <file>debian/tmp</file>, relative to the top of the package's
9674 They should have the locations (relative to the root of the
9675 directory tree you're constructing) ownerships and
9676 permissions which you want them to have on the system when
9681 With current versions of <prgn>dpkg</prgn> the uid/username
9682 and gid/groupname mappings for the users and groups being
9683 used should be the same on the system where the package is
9684 built and the one where it is installed.
9688 You need to add one special directory to the root of the
9689 miniature file system tree you're creating:
9690 <prgn>DEBIAN</prgn>. It should contain the control
9691 information files, notably the binary package control file
9692 (see <ref id="pkg-controlfile">).
9696 The <prgn>DEBIAN</prgn> directory will not appear in the
9697 file system archive of the package, and so won't be installed
9698 by <prgn>dpkg</prgn> when the package is installed.
9702 When you've prepared the package, you should invoke:
9704 dpkg --build <var>directory</var>
9709 This will build the package in
9710 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9711 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9712 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9717 See the man page <manref name="dpkg-deb" section="8"> for details of how
9718 to examine the contents of this newly-created file. You may find the
9719 output of following commands enlightening:
9721 dpkg-deb --info <var>filename</var>.deb
9722 dpkg-deb --contents <var>filename</var>.deb
9723 dpkg --contents <var>filename</var>.deb
9725 To view the copyright file for a package you could use this command:
9727 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
9732 <sect id="pkg-controlarea">
9733 <heading>Package control information files</heading>
9736 The control information portion of a binary package is a
9737 collection of files with names known to <prgn>dpkg</prgn>.
9738 It will treat the contents of these files specially - some
9739 of them contain information used by <prgn>dpkg</prgn> when
9740 installing or removing the package; others are scripts which
9741 the package maintainer wants <prgn>dpkg</prgn> to run.
9745 It is possible to put other files in the package control
9746 area, but this is not generally a good idea (though they
9747 will largely be ignored).
9751 Here is a brief list of the control info files supported by
9752 <prgn>dpkg</prgn> and a summary of what they're used for.
9757 <tag><tt>control</tt>
9760 This is the key description file used by
9761 <prgn>dpkg</prgn>. It specifies the package's name
9762 and version, gives its description for the user,
9763 states its relationships with other packages, and so
9764 forth. See <ref id="sourcecontrolfiles"> and
9765 <ref id="binarycontrolfiles">.
9769 It is usually generated automatically from information
9770 in the source package by the
9771 <prgn>dpkg-gencontrol</prgn> program, and with
9772 assistance from <prgn>dpkg-shlibdeps</prgn>.
9773 See <ref id="pkg-sourcetools">.
9777 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9782 These are executable files (usually scripts) which
9783 <prgn>dpkg</prgn> runs during installation, upgrade
9784 and removal of packages. They allow the package to
9785 deal with matters which are particular to that package
9786 or require more complicated processing than that
9787 provided by <prgn>dpkg</prgn>. Details of when and
9788 how they are called are in <ref id="maintainerscripts">.
9792 It is very important to make these scripts idempotent.
9793 See <ref id="idempotency">.
9797 The maintainer scripts are not guaranteed to run with a
9798 controlling terminal and may not be able to interact with
9799 the user. See <ref id="controllingterminal">.
9803 <tag><tt>conffiles</tt>
9806 This file contains a list of configuration files which
9807 are to be handled automatically by <prgn>dpkg</prgn>
9808 (see <ref id="pkg-conffiles">). Note that not necessarily
9809 every configuration file should be listed here.
9812 <tag><tt>shlibs</tt>
9815 This file contains a list of the shared libraries
9816 supplied by the package, with dependency details for
9817 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9818 when it determines what dependencies are required in a
9819 package control file. The <tt>shlibs</tt> file format
9820 is described on <ref id="shlibs">.
9825 <sect id="pkg-controlfile">
9826 <heading>The main control information file: <tt>control</tt></heading>
9829 The most important control information file used by
9830 <prgn>dpkg</prgn> when it installs a package is
9831 <tt>control</tt>. It contains all the package's "vital
9836 The binary package control files of packages built from
9837 Debian sources are made by a special tool,
9838 <prgn>dpkg-gencontrol</prgn>, which reads
9839 <file>debian/control</file> and <file>debian/changelog</file> to
9840 find the information it needs. See <ref id="pkg-sourcepkg"> for
9845 The fields in binary package control files are listed in
9846 <ref id="binarycontrolfiles">.
9850 A description of the syntax of control files and the purpose
9851 of the fields is available in <ref id="controlfields">.
9856 <heading>Time Stamps</heading>
9859 See <ref id="timestamps">.
9864 <appendix id="pkg-sourcepkg">
9865 <heading>Source packages (from old Packaging Manual) </heading>
9868 The Debian binary packages in the distribution are generated
9869 from Debian sources, which are in a special format to assist
9870 the easy and automatic building of binaries.
9873 <sect id="pkg-sourcetools">
9874 <heading>Tools for processing source packages</heading>
9877 Various tools are provided for manipulating source packages;
9878 they pack and unpack sources and help build of binary
9879 packages and help manage the distribution of new versions.
9883 They are introduced and typical uses described here; see
9884 <manref name="dpkg-source" section="1"> for full
9885 documentation about their arguments and operation.
9889 For examples of how to construct a Debian source package,
9890 and how to use those utilities that are used by Debian
9891 source packages, please see the <prgn>hello</prgn> example
9895 <sect1 id="pkg-dpkg-source">
9897 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9902 This program is frequently used by hand, and is also
9903 called from package-independent automated building scripts
9904 such as <prgn>dpkg-buildpackage</prgn>.
9908 To unpack a package it is typically invoked with
9910 dpkg-source -x <var>.../path/to/filename</var>.dsc
9915 with the <file><var>filename</var>.tar.gz</file> and
9916 <file><var>filename</var>.diff.gz</file> (if applicable) in
9917 the same directory. It unpacks into
9918 <file><var>package</var>-<var>version</var></file>, and if
9920 <file><var>package</var>-<var>version</var>.orig</file>, in
9921 the current directory.
9925 To create a packed source archive it is typically invoked:
9927 dpkg-source -b <var>package</var>-<var>version</var>
9932 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
9933 <file>.diff.gz</file> (if appropriate) in the current
9934 directory. <prgn>dpkg-source</prgn> does not clean the
9935 source tree first - this must be done separately if it is
9940 See also <ref id="pkg-sourcearchives">.</p>
9944 <sect1 id="pkg-dpkg-buildpackage">
9946 <prgn>dpkg-buildpackage</prgn> - overall package-building
9951 <prgn>dpkg-buildpackage</prgn> is a script which invokes
9952 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
9953 targets <tt>clean</tt>, <tt>build</tt> and
9954 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
9955 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
9956 source and binary package upload.
9960 It is usually invoked by hand from the top level of the
9961 built or unbuilt source directory. It may be invoked with
9962 no arguments; useful arguments include:
9963 <taglist compact="compact">
9964 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
9967 Do not sign the <tt>.changes</tt> file or the
9968 source package <tt>.dsc</tt> file, respectively.</p>
9970 <tag><tt>-p<var>sign-command</var></tt></tag>
9973 Invoke <var>sign-command</var> instead of finding
9974 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
9975 <var>sign-command</var> must behave just like
9976 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
9978 <tag><tt>-r<var>root-command</var></tt></tag>
9981 When root privilege is required, invoke the command
9982 <var>root-command</var>. <var>root-command</var>
9983 should invoke its first argument as a command, from
9984 the <prgn>PATH</prgn> if necessary, and pass its
9985 second and subsequent arguments to the command it
9986 calls. If no <var>root-command</var> is supplied
9987 then <var>dpkg-buildpackage</var> will take no
9988 special action to gain root privilege, so that for
9989 most packages it will have to be invoked as root to
9992 <tag><tt>-b</tt>, <tt>-B</tt></tag>
9995 Two types of binary-only build and upload - see
9996 <manref name="dpkg-source" section="1">.
10003 <sect1 id="pkg-dpkg-gencontrol">
10005 <prgn>dpkg-gencontrol</prgn> - generates binary package
10010 This program is usually called from <file>debian/rules</file>
10011 (see <ref id="pkg-sourcetree">) in the top level of the source
10016 This is usually done just before the files and directories in the
10017 temporary directory tree where the package is being built have their
10018 permissions and ownerships set and the package is constructed using
10019 <prgn>dpkg-deb/</prgn>
10021 This is so that the control file which is produced has
10022 the right permissions
10027 <prgn>dpkg-gencontrol</prgn> must be called after all the
10028 files which are to go into the package have been placed in
10029 the temporary build directory, so that its calculation of
10030 the installed size of a package is correct.
10034 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
10035 be run after <prgn>dpkg-shlibdeps</prgn> so that the
10036 variable substitutions created by
10037 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
10042 For a package which generates only one binary package, and
10043 which builds it in <file>debian/tmp</file> relative to the top
10044 of the source package, it is usually sufficient to call
10045 <prgn>dpkg-gencontrol</prgn>.
10049 Sources which build several binaries will typically need
10052 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
10053 </example> The <tt>-P</tt> tells
10054 <prgn>dpkg-gencontrol</prgn> that the package is being
10055 built in a non-default directory, and the <tt>-p</tt>
10056 tells it which package's control file should be generated.
10060 <prgn>dpkg-gencontrol</prgn> also adds information to the
10061 list of files in <file>debian/files</file>, for the benefit of
10062 (for example) a future invocation of
10063 <prgn>dpkg-genchanges</prgn>.</p>
10066 <sect1 id="pkg-dpkg-shlibdeps">
10068 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
10073 This program is usually called from <file>debian/rules</file>
10074 just before <prgn>dpkg-gencontrol</prgn> (see <ref
10075 id="pkg-sourcetree">), in the top level of the source tree.
10079 Its arguments are executables and shared libraries
10082 They may be specified either in the locations in the
10083 source tree where they are created or in the locations
10084 in the temporary build tree where they are installed
10085 prior to binary package creation.
10087 </footnote> for which shared library dependencies should
10088 be included in the binary package's control file.
10092 If some of the found shared libraries should only
10093 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
10094 some warrant a <tt>Pre-Depends</tt>, this can be achieved
10095 by using the <tt>-d<var>dependency-field</var></tt> option
10096 before those executable(s). (Each <tt>-d</tt> option
10097 takes effect until the next <tt>-d</tt>.)
10101 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
10102 output control file to be modified. Instead by default it
10103 adds to the <file>debian/substvars</file> file variable
10104 settings like <tt>shlibs:Depends</tt>. These variable
10105 settings must be referenced in dependency fields in the
10106 appropriate per-binary-package sections of the source
10111 For example, a package that generates an essential part
10112 which requires dependencies, and optional parts that
10113 which only require a recommendation, would separate those
10114 two sets of dependencies into two different fields.<footnote>
10115 At the time of writing, an example for this was the
10116 <package/xmms/ package, with Depends used for the xmms
10117 executable, Recommends for the plug-ins and Suggests for
10118 even more optional features provided by unzip.
10120 It can say in its <file>debian/rules</file>:
10122 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
10123 -dRecommends <var>optionalpart anotheroptionalpart</var>
10125 and then in its main control file <file>debian/control</file>:
10128 Depends: ${shlibs:Depends}
10129 Recommends: ${shlibs:Recommends}
10135 Sources which produce several binary packages with
10136 different shared library dependency requirements can use
10137 the <tt>-p<var>varnameprefix</var></tt> option to override
10138 the default <tt>shlibs:</tt> prefix (one invocation of
10139 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
10140 They can thus produce several sets of dependency
10141 variables, each of the form
10142 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
10143 which can be referred to in the appropriate parts of the
10144 binary package control files.
10149 <sect1 id="pkg-dpkg-distaddfile">
10151 <prgn>dpkg-distaddfile</prgn> - adds a file to
10152 <file>debian/files</file>
10156 Some packages' uploads need to include files other than
10157 the source and binary package files.
10161 <prgn>dpkg-distaddfile</prgn> adds a file to the
10162 <file>debian/files</file> file so that it will be included in
10163 the <file>.changes</file> file when
10164 <prgn>dpkg-genchanges</prgn> is run.
10168 It is usually invoked from the <tt>binary</tt> target of
10169 <file>debian/rules</file>:
10171 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
10173 The <var>filename</var> is relative to the directory where
10174 <prgn>dpkg-genchanges</prgn> will expect to find it - this
10175 is usually the directory above the top level of the source
10176 tree. The <file>debian/rules</file> target should put the
10177 file there just before or just after calling
10178 <prgn>dpkg-distaddfile</prgn>.
10182 The <var>section</var> and <var>priority</var> are passed
10183 unchanged into the resulting <file>.changes</file> file.
10188 <sect1 id="pkg-dpkg-genchanges">
10190 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
10191 upload control file
10195 This program is usually called by package-independent
10196 automatic building scripts such as
10197 <prgn>dpkg-buildpackage</prgn>, but it may also be called
10202 It is usually called in the top level of a built source
10203 tree, and when invoked with no arguments will print out a
10204 straightforward <file>.changes</file> file based on the
10205 information in the source package's changelog and control
10206 file and the binary and source packages which should have
10212 <sect1 id="pkg-dpkg-parsechangelog">
10214 <prgn>dpkg-parsechangelog</prgn> - produces parsed
10215 representation of a changelog
10219 This program is used internally by
10220 <prgn>dpkg-source</prgn> et al. It may also occasionally
10221 be useful in <file>debian/rules</file> and elsewhere. It
10222 parses a changelog, <file>debian/changelog</file> by default,
10223 and prints a control-file format representation of the
10224 information in it to standard output.
10228 <sect1 id="pkg-dpkg-architecture">
10230 <prgn>dpkg-architecture</prgn> - information about the build and
10235 This program can be used manually, but is also invoked by
10236 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
10237 environment or make variables which specify the build and host
10238 architecture for the package building process.
10243 <sect id="pkg-sourcetree">
10244 <heading>The Debian package source tree</heading>
10247 The source archive scheme described later is intended to
10248 allow a Debian package source tree with some associated
10249 control information to be reproduced and transported easily.
10250 The Debian package source tree is a version of the original
10251 program with certain files added for the benefit of the
10252 packaging process, and with any other changes required
10253 made to the rest of the source code and installation
10258 The extra files created for Debian are in the subdirectory
10259 <file>debian</file> of the top level of the Debian package
10260 source tree. They are described below.
10263 <sect1 id="pkg-debianrules">
10264 <heading><file>debian/rules</file> - the main building script</heading>
10267 See <ref id="debianrules">.
10271 <sect1 id="pkg-srcsubstvars">
10272 <heading><file>debian/substvars</file> and variable substitutions</heading>
10275 See <ref id="substvars">.
10281 <heading><file>debian/files</file></heading>
10284 See <ref id="debianfiles">.
10288 <sect1><heading><file>debian/tmp</file>
10292 This is the canonical temporary location for the
10293 construction of binary packages by the <tt>binary</tt>
10294 target. The directory <file>tmp</file> serves as the root of
10295 the file system tree as it is being constructed (for
10296 example, by using the package's upstream makefiles install
10297 targets and redirecting the output there), and it also
10298 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10299 id="pkg-bincreating">.
10303 If several binary packages are generated from the same
10304 source tree it is usual to use several
10305 <file>debian/tmp<var>something</var></file> directories, for
10306 example <file>tmp-a</file> or <file>tmp-doc</file>.
10310 Whatever <file>tmp</file> directories are created and used by
10311 <tt>binary</tt> must of course be removed by the
10312 <tt>clean</tt> target.</p></sect1>
10316 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10320 As it exists on the FTP site, a Debian source package
10321 consists of three related files. You must have the right
10322 versions of all three to be able to use them.
10327 <tag>Debian source control file - <tt>.dsc</tt></tag>
10329 This file is a control file used by <prgn>dpkg-source</prgn>
10330 to extract a source package.
10331 See <ref id="debiansourcecontrolfiles">.
10335 Original source archive -
10337 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10343 This is a compressed (with <tt>gzip -9</tt>)
10344 <prgn>tar</prgn> file containing the source code from
10345 the upstream authors of the program.
10350 Debian package diff -
10352 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10358 This is a unified context diff (<tt>diff -u</tt>)
10359 giving the changes which are required to turn the
10360 original source into the Debian source. These changes
10361 may only include editing and creating plain files.
10362 The permissions of files, the targets of symbolic
10363 links and the characteristics of special files or
10364 pipes may not be changed and no files may be removed
10369 All the directories in the diff must exist, except the
10370 <file>debian</file> subdirectory of the top of the source
10371 tree, which will be created by
10372 <prgn>dpkg-source</prgn> if necessary when unpacking.
10376 The <prgn>dpkg-source</prgn> program will
10377 automatically make the <file>debian/rules</file> file
10378 executable (see below).</p></item>
10383 If there is no original source code - for example, if the
10384 package is specially prepared for Debian or the Debian
10385 maintainer is the same as the upstream maintainer - the
10386 format is slightly different: then there is no diff, and the
10388 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10389 and preferably contains a directory named
10390 <file><var>package</var>-<var>version</var></file>.
10395 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10398 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10399 Debian source package. However, if it is not available it
10400 is possible to unpack a Debian source archive as follows:
10401 <enumlist compact="compact">
10404 Untar the tarfile, which will create a <file>.orig</file>
10408 <p>Rename the <file>.orig</file> directory to
10409 <file><var>package</var>-<var>version</var></file>.</p>
10413 Create the subdirectory <file>debian</file> at the top of
10414 the source tree.</p>
10416 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10418 <item><p>Untar the tarfile again if you want a copy of the original
10419 source code alongside the Debian version.</p>
10424 It is not possible to generate a valid Debian source archive
10425 without using <prgn>dpkg-source</prgn>. In particular,
10426 attempting to use <prgn>diff</prgn> directly to generate the
10427 <file>.diff.gz</file> file will not work.
10431 <heading>Restrictions on objects in source packages</heading>
10434 The source package may not contain any hard links
10436 This is not currently detected when building source
10437 packages, but only when extracting
10441 Hard links may be permitted at some point in the
10442 future, but would require a fair amount of
10444 </footnote>, device special files, sockets or setuid or
10447 Setgid directories are allowed.
10452 The source packaging tools manage the changes between the
10453 original and Debian source using <prgn>diff</prgn> and
10454 <prgn>patch</prgn>. Turning the original source tree as
10455 included in the <file>.orig.tar.gz</file> into the Debian
10456 package source must not involve any changes which cannot be
10457 handled by these tools. Problematic changes which cause
10458 <prgn>dpkg-source</prgn> to halt with an error when
10459 building the source package are:
10460 <list compact="compact">
10461 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10463 <item><p>Changing the targets of symbolic links.</p>
10465 <item><p>Creating directories, other than <file>debian</file>.</p>
10467 <item><p>Changes to the contents of binary files.</p></item>
10468 </list> Changes which cause <prgn>dpkg-source</prgn> to
10469 print a warning but continue anyway are:
10470 <list compact="compact">
10473 Removing files, directories or symlinks.
10475 Renaming a file is not treated specially - it is
10476 seen as the removal of the old file (which
10477 generates a warning, but is otherwise ignored),
10478 and the creation of the new one.
10484 Changed text files which are missing the usual final
10485 newline (either in the original or the modified
10490 Changes which are not represented, but which are not detected by
10491 <prgn>dpkg-source</prgn>, are:
10492 <list compact="compact">
10493 <item><p>Changing the permissions of files (other than
10494 <file>debian/rules</file>) and directories.</p></item>
10499 The <file>debian</file> directory and <file>debian/rules</file>
10500 are handled specially by <prgn>dpkg-source</prgn> - before
10501 applying the changes it will create the <file>debian</file>
10502 directory, and afterwards it will make
10503 <file>debian/rules</file> world-executable.
10509 <appendix id="pkg-controlfields">
10510 <heading>Control files and their fields (from old Packaging Manual)</heading>
10513 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10514 data in a common format, known as control files. Binary and
10515 source packages have control data as do the <file>.changes</file>
10516 files which control the installation of uploaded files, and
10517 <prgn>dpkg</prgn>'s internal databases are in a similar
10522 <heading>Syntax of control files</heading>
10525 See <ref id="controlsyntax">.
10529 It is important to note that there are several fields which
10530 are optional as far as <prgn>dpkg</prgn> and the related
10531 tools are concerned, but which must appear in every Debian
10532 package, or whose omission may cause problems.
10537 <heading>List of fields</heading>
10540 See <ref id="controlfieldslist">.
10544 This section now contains only the fields that didn't belong
10545 to the Policy manual.
10548 <sect1 id="pkg-f-Filename">
10549 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10552 These fields in <tt>Packages</tt> files give the
10553 filename(s) of (the parts of) a package in the
10554 distribution directories, relative to the root of the
10555 Debian hierarchy. If the package has been split into
10556 several parts the parts are all listed in order, separated
10561 <sect1 id="pkg-f-Size">
10562 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10565 These fields in <file>Packages</file> files give the size (in
10566 bytes, expressed in decimal) and MD5 checksum of the
10567 file(s) which make(s) up a binary package in the
10568 distribution. If the package is split into several parts
10569 the values for the parts are listed in order, separated by
10574 <sect1 id="pkg-f-Status">
10575 <heading><tt>Status</tt></heading>
10578 This field in <prgn>dpkg</prgn>'s status file records
10579 whether the user wants a package installed, removed or
10580 left alone, whether it is broken (requiring
10581 re-installation) or not and what its current state on the
10582 system is. Each of these pieces of information is a
10587 <sect1 id="pkg-f-Config-Version">
10588 <heading><tt>Config-Version</tt></heading>
10591 If a package is not installed or not configured, this
10592 field in <prgn>dpkg</prgn>'s status file records the last
10593 version of the package which was successfully
10598 <sect1 id="pkg-f-Conffiles">
10599 <heading><tt>Conffiles</tt></heading>
10602 This field in <prgn>dpkg</prgn>'s status file contains
10603 information about the automatically-managed configuration
10604 files held by a package. This field should <em>not</em>
10605 appear anywhere in a package!
10610 <heading>Obsolete fields</heading>
10613 These are still recognized by <prgn>dpkg</prgn> but should
10614 not appear anywhere any more.
10616 <taglist compact="compact">
10618 <tag><tt>Revision</tt></tag>
10619 <tag><tt>Package-Revision</tt></tag>
10620 <tag><tt>Package_Revision</tt></tag>
10622 The Debian revision part of the package version was
10623 at one point in a separate control file field. This
10624 field went through several names.
10627 <tag><tt>Recommended</tt></tag>
10628 <item>Old name for <tt>Recommends</tt>.</item>
10630 <tag><tt>Optional</tt></tag>
10631 <item>Old name for <tt>Suggests</tt>.</item>
10633 <tag><tt>Class</tt></tag>
10634 <item>Old name for <tt>Priority</tt>.</item>
10643 <appendix id="pkg-conffiles">
10644 <heading>Configuration file handling (from old Packaging Manual)</heading>
10647 <prgn>dpkg</prgn> can do a certain amount of automatic
10648 handling of package configuration files.
10652 Whether this mechanism is appropriate depends on a number of
10653 factors, but basically there are two approaches to any
10654 particular configuration file.
10658 The easy method is to ship a best-effort configuration in the
10659 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10660 handle updates. If the user is unlikely to want to edit the
10661 file, but you need them to be able to without losing their
10662 changes, and a new package with a changed version of the file
10663 is only released infrequently, this is a good approach.
10667 The hard method is to build the configuration file from
10668 scratch in the <prgn>postinst</prgn> script, and to take the
10669 responsibility for fixing any mistakes made in earlier
10670 versions of the package automatically. This will be
10671 appropriate if the file is likely to need to be different on
10675 <sect><heading>Automatic handling of configuration files by
10680 A package may contain a control area file called
10681 <tt>conffiles</tt>. This file should be a list of filenames
10682 of configuration files needing automatic handling, separated
10683 by newlines. The filenames should be absolute pathnames,
10684 and the files referred to should actually exist in the
10689 When a package is upgraded <prgn>dpkg</prgn> will process
10690 the configuration files during the configuration stage,
10691 shortly before it runs the package's <prgn>postinst</prgn>
10696 For each file it checks to see whether the version of the
10697 file included in the package is the same as the one that was
10698 included in the last version of the package (the one that is
10699 being upgraded from); it also compares the version currently
10700 installed on the system with the one shipped with the last
10705 If neither the user nor the package maintainer has changed
10706 the file, it is left alone. If one or the other has changed
10707 their version, then the changed version is preferred - i.e.,
10708 if the user edits their file, but the package maintainer
10709 doesn't ship a different version, the user's changes will
10710 stay, silently, but if the maintainer ships a new version
10711 and the user hasn't edited it the new version will be
10712 installed (with an informative message). If both have
10713 changed their version the user is prompted about the problem
10714 and must resolve the differences themselves.
10718 The comparisons are done by calculating the MD5 message
10719 digests of the files, and storing the MD5 of the file as it
10720 was included in the most recent version of the package.
10724 When a package is installed for the first time
10725 <prgn>dpkg</prgn> will install the file that comes with it,
10726 unless that would mean overwriting a file already on the
10731 However, note that <prgn>dpkg</prgn> will <em>not</em>
10732 replace a conffile that was removed by the user (or by a
10733 script). This is necessary because with some programs a
10734 missing file produces an effect hard or impossible to
10735 achieve in another way, so that a missing file needs to be
10736 kept that way if the user did it.
10740 Note that a package should <em>not</em> modify a
10741 <prgn>dpkg</prgn>-handled conffile in its maintainer
10742 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10743 the user confusing and possibly dangerous options for
10744 conffile update when the package is upgraded.</p>
10747 <sect><heading>Fully-featured maintainer script configuration
10752 For files which contain site-specific information such as
10753 the hostname and networking details and so forth, it is
10754 better to create the file in the package's
10755 <prgn>postinst</prgn> script.
10759 This will typically involve examining the state of the rest
10760 of the system to determine values and other information, and
10761 may involve prompting the user for some information which
10762 can't be obtained some other way.
10766 When using this method there are a couple of important
10767 issues which should be considered:
10771 If you discover a bug in the program which generates the
10772 configuration file, or if the format of the file changes
10773 from one version to the next, you will have to arrange for
10774 the postinst script to do something sensible - usually this
10775 will mean editing the installed configuration file to remove
10776 the problem or change the syntax. You will have to do this
10777 very carefully, since the user may have changed the file,
10778 perhaps to fix the very problem that your script is trying
10779 to deal with - you will have to detect these situations and
10780 deal with them correctly.
10784 If you do go down this route it's probably a good idea to
10785 make the program that generates the configuration file(s) a
10786 separate program in <file>/usr/sbin</file>, by convention called
10787 <file><var>package</var>config</file> and then run that if
10788 appropriate from the post-installation script. The
10789 <tt><var>package</var>config</tt> program should not
10790 unquestioningly overwrite an existing configuration - if its
10791 mode of operation is geared towards setting up a package for
10792 the first time (rather than any arbitrary reconfiguration
10793 later) you should have it check whether the configuration
10794 already exists, and require a <tt>--force</tt> flag to
10795 overwrite it.</p></sect>
10798 <appendix id="pkg-alternatives"><heading>Alternative versions of
10799 an interface - <prgn>update-alternatives</prgn> (from old
10804 When several packages all provide different versions of the
10805 same program or file it is useful to have the system select a
10806 default, but to allow the system administrator to change it
10807 and have their decisions respected.
10811 For example, there are several versions of the <prgn>vi</prgn>
10812 editor, and there is no reason to prevent all of them from
10813 being installed at once, each under their own name
10814 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10815 Nevertheless it is desirable to have the name <tt>vi</tt>
10816 refer to something, at least by default.
10820 If all the packages involved cooperate, this can be done with
10821 <prgn>update-alternatives</prgn>.
10825 Each package provides its own version under its own name, and
10826 calls <prgn>update-alternatives</prgn> in its postinst to
10827 register its version (and again in its prerm to deregister
10832 See the man page <manref name="update-alternatives"
10833 section="8"> for details.
10837 If <prgn>update-alternatives</prgn> does not seem appropriate
10838 you may wish to consider using diversions instead.</p>
10841 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10842 package's version of a file (from old Packaging Manual)
10846 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10847 when it reinstalls the package it belongs to, and to have it
10848 put the file from the package somewhere else instead.
10852 This can be used locally to override a package's version of a
10853 file, or by one package to override another's version (or
10854 provide a wrapper for it).
10858 Before deciding to use a diversion, read <ref
10859 id="pkg-alternatives"> to see if you really want a diversion
10860 rather than several alternative versions of a program.
10864 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10865 and updated by a special program <prgn>dpkg-divert</prgn>.
10866 Please see <manref name="dpkg-divert" section="8"> for full
10867 details of its operation.
10871 When a package wishes to divert a file from another, it should
10872 call <prgn>dpkg-divert</prgn> in its preinst to add the
10873 diversion and rename the existing file. For example,
10874 supposing that a <prgn>smailwrapper</prgn> package wishes to
10875 install a wrapper around <file>/usr/sbin/smail</file>:
10877 dpkg-divert --package smailwrapper --add --rename \
10878 --divert /usr/sbin/smail.real /usr/sbin/smail
10879 </example> The <tt>--package smailwrapper</tt> ensures that
10880 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
10881 can bypass the diversion and get installed as the true version.
10882 It's safe to add the diversion unconditionally on upgrades since
10883 it will be left unchanged if it already exists, but
10884 <prgn>dpkg-divert</prgn> will display a message. To suppress that
10885 message, make the command conditional on the version from which
10886 the package is being upgraded:
10888 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
10889 dpkg-divert --package smailwrapper --add --rename \
10890 --divert /usr/sbin/smail.real /usr/sbin/smail
10892 </example> where <tt>1.0-2</tt> is the version at which the
10893 diversion was first added to the package. Running the command
10894 during abort-upgrade is pointless but harmless.
10898 The postrm has to do the reverse:
10900 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
10901 dpkg-divert --package smailwrapper --remove --rename \
10902 --divert /usr/sbin/smail.real /usr/sbin/smail
10904 </example> If the diversion was added at a particular version, the
10905 postrm should also handle the failure case of upgrading from an
10906 older version (unless the older version is so old that direct
10907 upgrades are no longer supported):
10909 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
10910 dpkg-divert --package smailwrapper --remove --rename \
10911 --divert /usr/sbin/smail.real /usr/sbin/smail
10913 </example> where <tt>1.02-2</tt> is the version at which the
10914 diversion was first added to the package. The postrm should not
10915 remove the diversion on upgrades both because there's no reason to
10916 remove the diversion only to immediately re-add it and since the
10917 postrm of the old package is run after unpacking so the removal of
10918 the diversion will fail.
10922 Do not attempt to divert a file which is vitally important for
10923 the system's operation - when using <prgn>dpkg-divert</prgn>
10924 there is a time, after it has been diverted but before
10925 <prgn>dpkg</prgn> has installed the new version, when the file
10926 does not exist.</p>
10931 <!-- Local variables: -->
10932 <!-- indent-tabs-mode: t -->
10934 <!-- vim:set ai et sts=2 sw=2 tw=76: -->