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12 <title>Debian Policy Manual</title>
13 <author><qref id="authors">The Debian Policy Mailing List</qref></author>
14 <version>version &version;, &date;</version>
17 This manual describes the policy requirements for the Debian
18 GNU/Linux distribution. This includes the structure and
19 contents of the Debian archive and several design issues of
20 the operating system, as well as technical requirements that
21 each package must satisfy to be included in the distribution.
26 Copyright © 1996,1997,1998 Ian Jackson
27 and Christian Schwarz.
30 These are the copyright dates of the original Policy manual.
31 Since then, this manual has been updated by many others. No
32 comprehensive collection of copyright notices for subsequent
37 This manual is free software; you may redistribute it and/or
38 modify it under the terms of the GNU General Public License
39 as published by the Free Software Foundation; either version
40 2, or (at your option) any later version.
44 This is distributed in the hope that it will be useful, but
45 <em>without any warranty</em>; without even the implied
46 warranty of merchantability or fitness for a particular
47 purpose. See the GNU General Public License for more
52 A copy of the GNU General Public License is available as
53 <file>/usr/share/common-licenses/GPL</file> in the Debian GNU/Linux
54 distribution or on the World Wide Web at
55 <url id="http://www.gnu.org/copyleft/gpl.html"
56 name="the GNU General Public Licence">. You can also
57 obtain it by writing to the Free Software Foundation, Inc.,
58 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
66 <heading>About this manual</heading>
68 <heading>Scope</heading>
70 This manual describes the policy requirements for the Debian
71 GNU/Linux distribution. This includes the structure and
72 contents of the Debian archive and several design issues of the
73 operating system, as well as technical requirements that
74 each package must satisfy to be included in the
79 This manual also describes Debian policy as it relates to
80 creating Debian packages. It is not a tutorial on how to build
81 packages, nor is it exhaustive where it comes to describing
82 the behavior of the packaging system. Instead, this manual
83 attempts to define the interface to the package management
84 system that the developers have to be conversant with.<footnote>
85 Informally, the criteria used for inclusion is that the
86 material meet one of the following requirements:
87 <taglist compact="compact">
88 <tag>Standard interfaces</tag>
90 The material presented represents an interface to
91 the packaging system that is mandated for use, and
92 is used by, a significant number of packages, and
93 therefore should not be changed without peer
94 review. Package maintainers can then rely on this
95 interface not changing, and the package management
96 software authors need to ensure compatibility with
97 this interface definition. (Control file and
98 changelog file formats are examples.)
100 <tag>Chosen Convention</tag>
102 If there are a number of technically viable choices
103 that can be made, but one needs to select one of
104 these options for inter-operability. The version
105 number format is one example.
108 Please note that these are not mutually exclusive;
109 selected conventions often become parts of standard
115 The footnotes present in this manual are
116 merely informative, and are not part of Debian policy itself.
120 The appendices to this manual are not necessarily normative,
121 either. Please see <ref id="pkg-scope"> for more information.
125 In the normative part of this manual,
126 the words <em>must</em>, <em>should</em> and
127 <em>may</em>, and the adjectives <em>required</em>,
128 <em>recommended</em> and <em>optional</em>, are used to
129 distinguish the significance of the various guidelines in
130 this policy document. Packages that do not conform to the
131 guidelines denoted by <em>must</em> (or <em>required</em>)
132 will generally not be considered acceptable for the Debian
133 distribution. Non-conformance with guidelines denoted by
134 <em>should</em> (or <em>recommended</em>) will generally be
135 considered a bug, but will not necessarily render a package
136 unsuitable for distribution. Guidelines denoted by
137 <em>may</em> (or <em>optional</em>) are truly optional and
138 adherence is left to the maintainer's discretion.
142 These classifications are roughly equivalent to the bug
143 severities <em>serious</em> (for <em>must</em> or
144 <em>required</em> directive violations), <em>minor</em>,
145 <em>normal</em> or <em>important</em>
146 (for <em>should</em> or <em>recommended</em> directive
147 violations) and <em>wishlist</em> (for <em>optional</em>
150 Compare RFC 2119. Note, however, that these words are
151 used in a different way in this document.
156 Much of the information presented in this manual will be
157 useful even when building a package which is to be
158 distributed in some other way or is intended for local use
164 <heading>New versions of this document</heading>
167 This manual is distributed via the Debian package
168 <package><url name="debian-policy"
169 id="http://packages.debian.org/debian-policy"></package>
170 (<httpsite>packages.debian.org</httpsite>
171 <httppath>/debian-policy</httppath>).
175 The current version of this document is also available from
176 the Debian web mirrors at
177 <tt><url name="/doc/debian-policy/"
178 id="http://www.debian.org/doc/debian-policy/"></tt>.
180 <httpsite>www.debian.org</httpsite>
181 <httppath>/doc/debian-policy/</httppath>)
182 Also available from the same directory are several other
183 formats: <file>policy.html.tar.gz</file>
184 (<httppath>/doc/debian-policy/policy.html.tar.gz</httppath>),
185 <file>policy.pdf.gz</file>
186 (<httppath>/doc/debian-policy/policy.pdf.gz</httppath>)
187 and <file>policy.ps.gz</file>
188 (<httppath>/doc/debian-policy/policy.ps.gz</httppath>).
192 The <package>debian-policy</package> package also includes the file
193 <file>upgrading-checklist.txt.gz</file> which indicates policy
194 changes between versions of this document.
199 <heading>Authors and Maintainers</heading>
202 Originally called "Debian GNU/Linux Policy Manual", this
203 manual was initially written in 1996 by Ian Jackson.
204 It was revised on November 27th, 1996 by David A. Morris.
205 Christian Schwarz added new sections on March 15th, 1997,
206 and reworked/restructured it in April-July 1997.
207 Christoph Lameter contributed the "Web Standard".
208 Julian Gilbey largely restructured it in 2001.
212 Since September 1998, the responsibility for the contents of
213 this document lies on the <url name="debian-policy mailing list"
214 id="mailto:debian-policy@lists.debian.org">. Proposals
215 are discussed there and inserted into policy after a certain
216 consensus is established.
217 <!-- insert shameless policy-process plug here eventually -->
218 The actual editing is done by a group of maintainers that have
219 no editorial powers. These are the current maintainers:
222 <item>Julian Gilbey</item>
223 <item>Branden Robinson</item>
224 <item>Josip Rodin</item>
225 <item>Manoj Srivastava</item>
230 While the authors of this document have tried hard to avoid
231 typos and other errors, these do still occur. If you discover
232 an error in this manual or if you want to give any
233 comments, suggestions, or criticisms please send an email to
234 the Debian Policy List,
235 <email>debian-policy@lists.debian.org</email>, or submit a
236 bug report against the <tt>debian-policy</tt> package.
240 Please do not try to reach the individual authors or maintainers
241 of the Policy Manual regarding changes to the Policy.
246 <heading>Related documents</heading>
249 There are several other documents other than this Policy Manual
250 that are necessary to fully understand some Debian policies and
255 The external "sub-policy" documents are referred to in:
256 <list compact="compact">
257 <item><ref id="fhs"></item>
258 <item><ref id="virtual_pkg"></item>
259 <item><ref id="menus"></item>
260 <item><ref id="mime"></item>
261 <item><ref id="perl"></item>
262 <item><ref id="maintscriptprompt"></item>
263 <item><ref id="emacs"></item>
268 In addition to those, which carry the weight of policy, there
269 is the Debian Developer's Reference. This document describes
270 procedures and resources for Debian developers, but it is
271 <em>not</em> normative; rather, it includes things that don't
272 belong in the Policy, such as best practices for developers.
276 The Developer's Reference is available in the
277 <package>developers-reference</package> package.
278 It's also available from the Debian web mirrors at
279 <tt><url name="/doc/developers-reference/"
280 id="http://www.debian.org/doc/developers-reference/"></tt>.
284 <sect id="definitions">
285 <heading>Definitions</heading>
288 The following terms are used in this Policy Manual:
292 The character encoding specified by ANSI X3.4-1986 and its
293 predecessor standards, referred to in MIME as US-ASCII, and
294 corresponding to an encoding in eight bits per character of
295 the first 128 <url id="http://www.unicode.org/"
296 name="Unicode"> characters, with the eighth bit always zero.
300 The transformation format (sometimes called encoding) of
301 <url id="http://www.unicode.org/" name="Unicode"> defined by
302 <url id="http://www.rfc-editor.org/rfc/rfc3629.txt"
303 name="RFC 3629">. UTF-8 has the useful property of having
304 ASCII as a subset, so any text encoded in ASCII is trivially
314 <heading>The Debian Archive</heading>
317 The Debian GNU/Linux system is maintained and distributed as a
318 collection of <em>packages</em>. Since there are so many of
319 them (currently well over 15000), they are split into
320 <em>sections</em> and given <em>priorities</em> to simplify
321 the handling of them.
325 The effort of the Debian project is to build a free operating
326 system, but not every package we want to make accessible is
327 <em>free</em> in our sense (see the Debian Free Software
328 Guidelines, below), or may be imported/exported without
329 restrictions. Thus, the archive is split into areas<footnote>
330 The Debian archive software uses the term "component" internally
331 and in the Release file format to refer to the division of an
332 archive. The Debian Social Contract simply refers to "areas."
333 This document uses terminology similar to the Social Contract.
334 </footnote> based on their licenses and other restrictions.
338 The aims of this are:
340 <list compact="compact">
341 <item>to allow us to make as much software available as we can</item>
342 <item>to allow us to encourage everyone to write free software,
344 <item>to allow us to make it easy for people to produce
345 CD-ROMs of our system without violating any licenses,
346 import/export restrictions, or any other laws.</item>
351 The <em>main</em> archive area forms the <em>Debian GNU/Linux
356 Packages in the other archive areas (<tt>contrib</tt>,
357 <tt>non-free</tt>) are not considered to be part of the Debian
358 distribution, although we support their use and provide
359 infrastructure for them (such as our bug-tracking system and
360 mailing lists). This Debian Policy Manual applies to these
365 <heading>The Debian Free Software Guidelines</heading>
367 The Debian Free Software Guidelines (DFSG) form our
368 definition of "free software". These are:
370 <tag>1. Free Redistribution
373 The license of a Debian component may not restrict any
374 party from selling or giving away the software as a
375 component of an aggregate software distribution
376 containing programs from several different
377 sources. The license may not require a royalty or
378 other fee for such sale.
383 The program must include source code, and must allow
384 distribution in source code as well as compiled form.
386 <tag>3. Derived Works
389 The license must allow modifications and derived
390 works, and must allow them to be distributed under the
391 same terms as the license of the original software.
393 <tag>4. Integrity of The Author's Source Code
396 The license may restrict source-code from being
397 distributed in modified form <em>only</em> if the
398 license allows the distribution of "patch files"
399 with the source code for the purpose of modifying the
400 program at build time. The license must explicitly
401 permit distribution of software built from modified
402 source code. The license may require derived works to
403 carry a different name or version number from the
404 original software. (This is a compromise. The Debian
405 Project encourages all authors to not restrict any
406 files, source or binary, from being modified.)
408 <tag>5. No Discrimination Against Persons or Groups
411 The license must not discriminate against any person
414 <tag>6. No Discrimination Against Fields of Endeavor
417 The license must not restrict anyone from making use
418 of the program in a specific field of endeavor. For
419 example, it may not restrict the program from being
420 used in a business, or from being used for genetic
423 <tag>7. Distribution of License
426 The rights attached to the program must apply to all
427 to whom the program is redistributed without the need
428 for execution of an additional license by those
431 <tag>8. License Must Not Be Specific to Debian
434 The rights attached to the program must not depend on
435 the program's being part of a Debian system. If the
436 program is extracted from Debian and used or
437 distributed without Debian but otherwise within the
438 terms of the program's license, all parties to whom
439 the program is redistributed must have the same
440 rights as those that are granted in conjunction with
443 <tag>9. License Must Not Contaminate Other Software
446 The license must not place restrictions on other
447 software that is distributed along with the licensed
448 software. For example, the license must not insist
449 that all other programs distributed on the same medium
450 must be free software.
452 <tag>10. Example Licenses
455 The "GPL," "BSD," and "Artistic" licenses are examples of
456 licenses that we consider <em>free</em>.
463 <heading>Archive areas</heading>
466 <heading>The main archive area</heading>
469 Every package in <em>main</em> must comply with the DFSG
470 (Debian Free Software Guidelines).
474 In addition, the packages in <em>main</em>
475 <list compact="compact">
477 must not require a package outside of <em>main</em>
478 for compilation or execution (thus, the package must
479 not declare a <tt>Pre-Depends</tt>, <tt>Depends</tt>,
480 <tt>Recommends</tt>, <tt>Build-Depends</tt>,
481 or <tt>Build-Depends-Indep</tt> relationship on a
482 non-<em>main</em> package unless a package
483 in <em>main</em> is listed as an alternative),
486 must not be so buggy that we refuse to support them,
490 must meet all policy requirements presented in this
499 <heading>The contrib archive area</heading>
502 Every package in <em>contrib</em> must comply with the DFSG.
506 In addition, the packages in <em>contrib</em>
507 <list compact="compact">
509 must not be so buggy that we refuse to support them,
513 must meet all policy requirements presented in this
521 Examples of packages which would be included in
522 <em>contrib</em> are:
523 <list compact="compact">
525 free packages which require <em>contrib</em>,
526 <em>non-free</em> packages or packages which are not
527 in our archive at all for compilation or execution,
531 wrapper packages or other sorts of free accessories for
538 <sect1 id="non-free">
539 <heading>The non-free archive area</heading>
542 Packages must be placed in <em>non-free</em> if they are
543 not compliant with the DFSG or are encumbered by patents
544 or other legal issues that make their distribution
549 In addition, the packages in <em>non-free</em>
550 <list compact="compact">
552 must not be so buggy that we refuse to support them,
556 must meet all policy requirements presented in this
557 manual that it is possible for them to meet.
559 It is possible that there are policy
560 requirements which the package is unable to
561 meet, for example, if the source is
562 unavailable. These situations will need to be
563 handled on a case-by-case basis.
572 <sect id="pkgcopyright">
573 <heading>Copyright considerations</heading>
576 Every package must be accompanied by a verbatim copy of its
577 copyright information and distribution license in the file
578 <file>/usr/share/doc/<var>package</var>/copyright</file>
579 (see <ref id="copyrightfile"> for further details).
583 We reserve the right to restrict files from being included
584 anywhere in our archives if
585 <list compact="compact">
587 their use or distribution would break a law,
590 there is an ethical conflict in their distribution or
594 we would have to sign a license for them, or
597 their distribution would conflict with other project
604 Programs whose authors encourage the user to make
605 donations are fine for the main distribution, provided
606 that the authors do not claim that not donating is
607 immoral, unethical, illegal or something similar; in such
608 a case they must go in <em>non-free</em>.
612 Packages whose copyright permission notices (or patent
613 problems) do not even allow redistribution of binaries
614 only, and where no special permission has been obtained,
615 must not be placed on the Debian FTP site and its mirrors
620 Note that under international copyright law (this applies
621 in the United States, too), <em>no</em> distribution or
622 modification of a work is allowed without an explicit
623 notice saying so. Therefore a program without a copyright
624 notice <em>is</em> copyrighted and you may not do anything
625 to it without risking being sued! Likewise if a program
626 has a copyright notice but no statement saying what is
627 permitted then nothing is permitted.
631 Many authors are unaware of the problems that restrictive
632 copyrights (or lack of copyright notices) can cause for
633 the users of their supposedly-free software. It is often
634 worthwhile contacting such authors diplomatically to ask
635 them to modify their license terms. However, this can be a
636 politically difficult thing to do and you should ask for
637 advice on the <tt>debian-legal</tt> mailing list first, as
642 When in doubt about a copyright, send mail to
643 <email>debian-legal@lists.debian.org</email>. Be prepared
644 to provide us with the copyright statement. Software
645 covered by the GPL, public domain software and BSD-like
646 copyrights are safe; be wary of the phrases "commercial
647 use prohibited" and "distribution restricted".
651 <sect id="subsections">
652 <heading>Sections</heading>
655 The packages in the archive areas <em>main</em>,
656 <em>contrib</em> and <em>non-free</em> are grouped further into
657 <em>sections</em> to simplify handling.
661 The archive area and section for each package should be
662 specified in the package's <tt>Section</tt> control record (see
663 <ref id="f-Section">). However, the maintainer of the Debian
664 archive may override this selection to ensure the consistency of
665 the Debian distribution. The <tt>Section</tt> field should be
667 <list compact="compact">
669 <em>section</em> if the package is in the
670 <em>main</em> archive area,
673 <em>area/section</em> if the package is in
674 the <em>contrib</em> or <em>non-free</em>
681 The Debian archive maintainers provide the authoritative
682 list of sections. At present, they are:
683 <em>admin</em>, <em>cli-mono</em>, <em>comm</em>, <em>database</em>,
684 <em>devel</em>, <em>debug</em>, <em>doc</em>, <em>editors</em>,
685 <em>electronics</em>, <em>embedded</em>, <em>fonts</em>,
686 <em>games</em>, <em>gnome</em>, <em>graphics</em>, <em>gnu-r</em>,
687 <em>gnustep</em>, <em>hamradio</em>, <em>haskell</em>,
688 <em>httpd</em>, <em>interpreters</em>, <em>java</em>, <em>kde</em>,
689 <em>kernel</em>, <em>libs</em>, <em>libdevel</em>, <em>lisp</em>,
690 <em>localization</em>, <em>mail</em>, <em>math</em>, <em>misc</em>,
691 <em>net</em>, <em>news</em>, <em>ocaml</em>, <em>oldlibs</em>,
692 <em>otherosfs</em>, <em>perl</em>, <em>php</em>, <em>python</em>,
693 <em>ruby</em>, <em>science</em>, <em>shells</em>, <em>sound</em>,
694 <em>tex</em>, <em>text</em>, <em>utils</em>, <em>vcs</em>,
695 <em>video</em>, <em>web</em>, <em>x11</em>, <em>xfce</em>,
696 <em>zope</em>. The additional section <em>debian-installer</em>
697 contains special packages used by the installer and is not used
698 for normal Debian packages.
702 For more information about the sections and their definitions,
703 see the <url id="http://packages.debian.org/unstable/"
704 name="list of sections in unstable">.
708 <sect id="priorities">
709 <heading>Priorities</heading>
712 Each package should have a <em>priority</em> value, which is
713 included in the package's <em>control record</em>
714 (see <ref id="f-Priority">).
715 This information is used by the Debian package management tools to
716 separate high-priority packages from less-important packages.
720 The following <em>priority levels</em> are recognized by the
721 Debian package management tools.
723 <tag><tt>required</tt></tag>
725 Packages which are necessary for the proper
726 functioning of the system (usually, this means that
727 dpkg functionality depends on these packages).
728 Removing a <tt>required</tt> package may cause your
729 system to become totally broken and you may not even
730 be able to use <prgn>dpkg</prgn> to put things back,
731 so only do so if you know what you are doing. Systems
732 with only the <tt>required</tt> packages are probably
733 unusable, but they do have enough functionality to
734 allow the sysadmin to boot and install more software.
736 <tag><tt>important</tt></tag>
738 Important programs, including those which one would
739 expect to find on any Unix-like system. If the
740 expectation is that an experienced Unix person who
741 found it missing would say "What on earth is going on,
742 where is <prgn>foo</prgn>?", it must be an
743 <tt>important</tt> package.<footnote>
744 This is an important criterion because we are
745 trying to produce, amongst other things, a free
748 Other packages without which the system will not run
749 well or be usable must also have priority
750 <tt>important</tt>. This does
751 <em>not</em> include Emacs, the X Window System, TeX
752 or any other large applications. The
753 <tt>important</tt> packages are just a bare minimum of
754 commonly-expected and necessary tools.
756 <tag><tt>standard</tt></tag>
758 These packages provide a reasonably small but not too
759 limited character-mode system. This is what will be
760 installed by default if the user doesn't select anything
761 else. It doesn't include many large applications.
763 <tag><tt>optional</tt></tag>
765 (In a sense everything that isn't required is
766 optional, but that's not what is meant here.) This is
767 all the software that you might reasonably want to
768 install if you didn't know what it was and don't have
769 specialized requirements. This is a much larger system
770 and includes the X Window System, a full TeX
771 distribution, and many applications. Note that
772 optional packages should not conflict with each other.
774 <tag><tt>extra</tt></tag>
776 This contains all packages that conflict with others
777 with required, important, standard or optional
778 priorities, or are only likely to be useful if you
779 already know what they are or have specialized
780 requirements (such as packages containing only detached
787 Packages must not depend on packages with lower priority
788 values (excluding build-time dependencies). In order to
789 ensure this, the priorities of one or more packages may need
798 <heading>Binary packages</heading>
801 The Debian GNU/Linux distribution is based on the Debian
802 package management system, called <prgn>dpkg</prgn>. Thus,
803 all packages in the Debian distribution must be provided
804 in the <tt>.deb</tt> file format.
808 <heading>The package name</heading>
811 Every package must have a name that's unique within the Debian
816 The package name is included in the control field
817 <tt>Package</tt>, the format of which is described
818 in <ref id="f-Package">.
819 The package name is also included as a part of the file name
820 of the <tt>.deb</tt> file.
825 <heading>The version of a package</heading>
828 Every package has a version number recorded in its
829 <tt>Version</tt> control file field, described in
830 <ref id="f-Version">.
834 The package management system imposes an ordering on version
835 numbers, so that it can tell whether packages are being up- or
836 downgraded and so that package system front end applications
837 can tell whether a package it finds available is newer than
838 the one installed on the system. The version number format
839 has the most significant parts (as far as comparison is
840 concerned) at the beginning.
844 If an upstream package has problematic version numbers they
845 should be converted to a sane form for use in the
846 <tt>Version</tt> field.
850 <heading>Version numbers based on dates</heading>
853 In general, Debian packages should use the same version
854 numbers as the upstream sources.
858 However, in some cases where the upstream version number is
859 based on a date (e.g., a development "snapshot" release) the
860 package management system cannot handle these version
861 numbers without epochs. For example, dpkg will consider
862 "96May01" to be greater than "96Dec24".
866 To prevent having to use epochs for every new upstream
867 version, the date based portion of the version number
868 should be changed to the following format in such cases:
869 "19960501", "19961224". It is up to the maintainer whether
870 they want to bother the upstream maintainer to change
871 the version numbers upstream, too.
875 Note that other version formats based on dates which are
876 parsed correctly by the package management system should
877 <em>not</em> be changed.
881 Native Debian packages (i.e., packages which have been
882 written especially for Debian) whose version numbers include
883 dates should always use the "YYYYMMDD" format.
890 <heading>The maintainer of a package</heading>
893 Every package must have a Debian maintainer (the
894 maintainer may be one person or a group of people
895 reachable from a common email address, such as a mailing
896 list). The maintainer is responsible for ensuring that
897 the package is placed in the appropriate distributions.
901 The maintainer must be specified in the
902 <tt>Maintainer</tt> control field with their correct name
903 and a working email address. If one person maintains
904 several packages, they should try to avoid having
905 different forms of their name and email address in
906 the <tt>Maintainer</tt> fields of those packages.
910 The format of the <tt>Maintainer</tt> control field is
911 described in <ref id="f-Maintainer">.
915 If the maintainer of a package quits from the Debian
916 project, "Debian QA Group"
917 <email>packages@qa.debian.org</email> takes over the
918 maintainer-ship of the package until someone else
919 volunteers for that task. These packages are called
920 <em>orphaned packages</em>.<footnote>
921 The detailed procedure for doing this gracefully can
922 be found in the Debian Developer's Reference,
923 see <ref id="related">.
928 <sect id="descriptions">
929 <heading>The description of a package</heading>
932 Every Debian package must have an extended description
933 stored in the appropriate field of the control record.
934 The technical information about the format of the
935 <tt>Description</tt> field is in <ref id="f-Description">.
939 The description should describe the package (the program) to a
940 user (system administrator) who has never met it before so that
941 they have enough information to decide whether they want to
942 install it. This description should not just be copied verbatim
943 from the program's documentation.
947 Put important information first, both in the synopsis and
948 extended description. Sometimes only the first part of the
949 synopsis or of the description will be displayed. You can
950 assume that there will usually be a way to see the whole
951 extended description.
955 The description should also give information about the
956 significant dependencies and conflicts between this package
957 and others, so that the user knows why these dependencies and
958 conflicts have been declared.
962 Instructions for configuring or using the package should
963 not be included (that is what installation scripts,
964 manual pages, info files, etc., are for). Copyright
965 statements and other administrivia should not be included
966 either (that is what the copyright file is for).
969 <sect1 id="synopsis"><heading>The single line synopsis</heading>
972 The single line synopsis should be kept brief - certainly
977 Do not include the package name in the synopsis line. The
978 display software knows how to display this already, and you
979 do not need to state it. Remember that in many situations
980 the user may only see the synopsis line - make it as
981 informative as you can.
986 <sect1 id="extendeddesc"><heading>The extended description</heading>
989 Do not try to continue the single line synopsis into the
990 extended description. This will not work correctly when
991 the full description is displayed, and makes no sense
992 where only the summary (the single line synopsis) is
997 The extended description should describe what the package
998 does and how it relates to the rest of the system (in terms
999 of, for example, which subsystem it is which part of).
1003 The description field needs to make sense to anyone, even
1004 people who have no idea about any of the things the
1005 package deals with.<footnote>
1006 The blurb that comes with a program in its
1007 announcements and/or <prgn>README</prgn> files is
1008 rarely suitable for use in a description. It is
1009 usually aimed at people who are already in the
1010 community where the package is used.
1019 <heading>Dependencies</heading>
1022 Every package must specify the dependency information
1023 about other packages that are required for the first to
1028 For example, a dependency entry must be provided for any
1029 shared libraries required by a dynamically-linked executable
1030 binary in a package.
1034 Packages are not required to declare any dependencies they
1035 have on other packages which are marked <tt>Essential</tt>
1036 (see below), and should not do so unless they depend on a
1037 particular version of that package.<footnote>
1039 Essential is needed in part to avoid unresolvable dependency
1040 loops on upgrade. If packages add unnecessary dependencies
1041 on packages in this set, the chances that there
1042 <strong>will</strong> be an unresolvable dependency loop
1043 caused by forcing these Essential packages to be configured
1044 first before they need to be is greatly increased. It also
1045 increases the chances that frontends will be unable to
1046 <strong>calculate</strong> an upgrade path, even if one
1050 Also, functionality is rarely ever removed from the
1051 Essential set, but <em>packages</em> have been removed from
1052 the Essential set when the functionality moved to a
1053 different package. So depending on these packages <em>just
1054 in case</em> they stop being essential does way more harm
1061 Sometimes, a package requires another package to be unpacked
1062 <em>and</em> configured before it can be unpacked. In this
1063 case, you must specify a <tt>Pre-Depends</tt> entry for
1068 You should not specify a <tt>Pre-Depends</tt> entry for a
1069 package before this has been discussed on the
1070 <tt>debian-devel</tt> mailing list and a consensus about
1071 doing that has been reached.
1075 The format of the package interrelationship control fields is
1076 described in <ref id="relationships">.
1080 <sect id="virtual_pkg">
1081 <heading>Virtual packages</heading>
1084 Sometimes, there are several packages which offer
1085 more-or-less the same functionality. In this case, it's
1086 useful to define a <em>virtual package</em> whose name
1087 describes that common functionality. (The virtual
1088 packages only exist logically, not physically; that's why
1089 they are called <em>virtual</em>.) The packages with this
1090 particular function will then <em>provide</em> the virtual
1091 package. Thus, any other package requiring that function
1092 can simply depend on the virtual package without having to
1093 specify all possible packages individually.
1097 All packages should use virtual package names where
1098 appropriate, and arrange to create new ones if necessary.
1099 They should not use virtual package names (except privately,
1100 amongst a cooperating group of packages) unless they have
1101 been agreed upon and appear in the list of virtual package
1102 names. (See also <ref id="virtual">)
1106 The latest version of the authoritative list of virtual
1107 package names can be found in the <tt>debian-policy</tt> package.
1108 It is also available from the Debian web mirrors at
1109 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1110 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1114 The procedure for updating the list is described in the preface
1121 <heading>Base system</heading>
1124 The <tt>base system</tt> is a minimum subset of the Debian
1125 GNU/Linux system that is installed before everything else
1126 on a new system. Only very few packages are allowed to form
1127 part of the base system, in order to keep the required disk
1132 The base system consists of all those packages with priority
1133 <tt>required</tt> or <tt>important</tt>. Many of them will
1134 be tagged <tt>essential</tt> (see below).
1139 <heading>Essential packages</heading>
1142 Essential is defined as the minimal set of functionality that
1143 must be available and usable on the system at all times, even
1144 when packages are in an unconfigured (but unpacked) state.
1145 Packages are tagged <tt>essential</tt> for a system using the
1146 <tt>Essential</tt> control file field. The format of the
1147 <tt>Essential</tt> control field is described in <ref
1152 Since these packages cannot be easily removed (one has to
1153 specify an extra <em>force option</em> to
1154 <prgn>dpkg</prgn> to do so), this flag must not be used
1155 unless absolutely necessary. A shared library package
1156 must not be tagged <tt>essential</tt>; dependencies will
1157 prevent its premature removal, and we need to be able to
1158 remove it when it has been superseded.
1162 Since dpkg will not prevent upgrading of other packages
1163 while an <tt>essential</tt> package is in an unconfigured
1164 state, all <tt>essential</tt> packages must supply all of
1165 their core functionality even when unconfigured. If the
1166 package cannot satisfy this requirement it must not be
1167 tagged as essential, and any packages depending on this
1168 package must instead have explicit dependency fields as
1173 Maintainers should take great care in adding any programs,
1174 interfaces, or functionality to <tt>essential</tt> packages.
1175 Packages may assume that functionality provided by
1176 <tt>essential</tt> packages is always available without
1177 declaring explicit dependencies, which means that removing
1178 functionality from the Essential set is very difficult and is
1179 almost never done. Any capability added to an
1180 <tt>essential</tt> package therefore creates an obligation to
1181 support that capability as part of the Essential set in
1186 You must not tag any packages <tt>essential</tt> before
1187 this has been discussed on the <tt>debian-devel</tt>
1188 mailing list and a consensus about doing that has been
1193 <sect id="maintscripts">
1194 <heading>Maintainer Scripts</heading>
1197 The package installation scripts should avoid producing
1198 output which is unnecessary for the user to see and
1199 should rely on <prgn>dpkg</prgn> to stave off boredom on
1200 the part of a user installing many packages. This means,
1201 amongst other things, using the <tt>--quiet</tt> option on
1202 <prgn>install-info</prgn>.
1206 Errors which occur during the execution of an installation
1207 script must be checked and the installation must not
1208 continue after an error.
1212 Note that in general <ref id="scripts"> applies to package
1213 maintainer scripts, too.
1217 You should not use <prgn>dpkg-divert</prgn> on a file belonging
1218 to another package without consulting the maintainer of that
1219 package first. When adding or removing diversions, package
1220 maintainer scripts must provide the <tt>--package</tt> flag
1221 to <prgn>dpkg-divert</prgn> and must not use <tt>--local</tt>.
1225 All packages which supply an instance of a common command
1226 name (or, in general, filename) should generally use
1227 <prgn>update-alternatives</prgn>, so that they may be
1228 installed together. If <prgn>update-alternatives</prgn>
1229 is not used, then each package must use
1230 <tt>Conflicts</tt> to ensure that other packages are
1231 de-installed. (In this case, it may be appropriate to
1232 specify a conflict against earlier versions of something
1233 that previously did not use
1234 <prgn>update-alternatives</prgn>; this is an exception to
1235 the usual rule that versioned conflicts should be
1239 <sect1 id="maintscriptprompt">
1240 <heading>Prompting in maintainer scripts</heading>
1242 Package maintainer scripts may prompt the user if
1243 necessary. Prompting must be done by communicating
1244 through a program, such as <prgn>debconf</prgn>, which
1245 conforms to the Debian Configuration Management
1246 Specification, version 2 or higher.
1250 Packages which are essential, or which are dependencies of
1251 essential packages, may fall back on another prompting method
1252 if no such interface is available when they are executed.
1256 The Debian Configuration Management Specification is included
1257 in the <file>debconf_specification</file> files in the
1258 <package>debian-policy</package> package.
1259 It is also available from the Debian web mirrors at
1260 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1261 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1265 Packages which use the Debian Configuration Management
1266 Specification may contain an additional
1267 <prgn>config</prgn> script and a <tt>templates</tt>
1268 file in their control archive<footnote>
1269 The control.tar.gz inside the .deb.
1270 See <manref name="deb" section="5">.
1272 The <prgn>config</prgn> script might be run before the
1273 <prgn>preinst</prgn> script, and before the package is unpacked
1274 or any of its dependencies or pre-dependencies are satisfied.
1275 Therefore it must work using only the tools present in
1276 <em>essential</em> packages.<footnote>
1277 <package>Debconf</package> or another tool that
1278 implements the Debian Configuration Management
1279 Specification will also be installed, and any
1280 versioned dependencies on it will be satisfied
1281 before preconfiguration begins.
1286 Packages which use the Debian Configuration Management
1287 Specification must allow for translation of their user-visible
1288 messages by using a gettext-based system such as the one
1289 provided by the <package>po-debconf</package> package.
1293 Packages should try to minimize the amount of prompting
1294 they need to do, and they should ensure that the user
1295 will only ever be asked each question once. This means
1296 that packages should try to use appropriate shared
1297 configuration files (such as <file>/etc/papersize</file> and
1298 <file>/etc/news/server</file>), and shared
1299 <package>debconf</package> variables rather than each
1300 prompting for their own list of required pieces of
1305 It also means that an upgrade should not ask the same
1306 questions again, unless the user has used
1307 <tt>dpkg --purge</tt> to remove the package's configuration.
1308 The answers to configuration questions should be stored in an
1309 appropriate place in <file>/etc</file> so that the user can
1310 modify them, and how this has been done should be
1315 If a package has a vitally important piece of
1316 information to pass to the user (such as "don't run me
1317 as I am, you must edit the following configuration files
1318 first or you risk your system emitting badly-formatted
1319 messages"), it should display this in the
1320 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1321 prompt the user to hit return to acknowledge the
1322 message. Copyright messages do not count as vitally
1323 important (they belong in
1324 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1325 neither do instructions on how to use a program (these
1326 should be in on-line documentation, where all the users
1331 Any necessary prompting should almost always be confined
1332 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1333 script. If it is done in the <prgn>postinst</prgn>, it
1334 should be protected with a conditional so that
1335 unnecessary prompting doesn't happen if a package's
1336 installation fails and the <prgn>postinst</prgn> is
1337 called with <tt>abort-upgrade</tt>,
1338 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1348 <heading>Source packages</heading>
1350 <sect id="standardsversion">
1351 <heading>Standards conformance</heading>
1354 Source packages should specify the most recent version number
1355 of this policy document with which your package complied
1356 when it was last updated.
1360 This information may be used to file bug reports
1361 automatically if your package becomes too much out of date.
1365 The version is specified in the <tt>Standards-Version</tt>
1367 The format of the <tt>Standards-Version</tt> field is
1368 described in <ref id="f-Standards-Version">.
1372 You should regularly, and especially if your package has
1373 become out of date, check for the newest Policy Manual
1374 available and update your package, if necessary. When your
1375 package complies with the new standards you should update the
1376 <tt>Standards-Version</tt> source package field and
1377 release it.<footnote>
1378 See the file <file>upgrading-checklist</file> for
1379 information about policy which has changed between
1380 different versions of this document.
1386 <sect id="pkg-relations">
1387 <heading>Package relationships</heading>
1390 Source packages should specify which binary packages they
1391 require to be installed or not to be installed in order to
1392 build correctly. For example, if building a package
1393 requires a certain compiler, then the compiler should be
1394 specified as a build-time dependency.
1398 It is not necessary to explicitly specify build-time
1399 relationships on a minimal set of packages that are always
1400 needed to compile, link and put in a Debian package a
1401 standard "Hello World!" program written in C or C++. The
1402 required packages are called <em>build-essential</em>, and
1403 an informational list can be found in
1404 <file>/usr/share/doc/build-essential/list</file> (which is
1405 contained in the <tt>build-essential</tt>
1408 <list compact="compact">
1410 This allows maintaining the list separately
1411 from the policy documents (the list does not
1412 need the kind of control that the policy
1416 Having a separate package allows one to install
1417 the build-essential packages on a machine, as
1418 well as allowing other packages such as tasks to
1419 require installation of the build-essential
1420 packages using the depends relation.
1423 The separate package allows bug reports against
1424 the list to be categorized separately from
1425 the policy management process in the BTS.
1432 When specifying the set of build-time dependencies, one
1433 should list only those packages explicitly required by the
1434 build. It is not necessary to list packages which are
1435 required merely because some other package in the list of
1436 build-time dependencies depends on them.<footnote>
1437 The reason for this is that dependencies change, and
1438 you should list all those packages, and <em>only</em>
1439 those packages that <em>you</em> need directly. What
1440 others need is their business. For example, if you
1441 only link against <file>libimlib</file>, you will need to
1442 build-depend on <package>libimlib2-dev</package> but
1443 not against any <tt>libjpeg*</tt> packages, even
1444 though <tt>libimlib2-dev</tt> currently depends on
1445 them: installation of <package>libimlib2-dev</package>
1446 will automatically ensure that all of its run-time
1447 dependencies are satisfied.
1452 If build-time dependencies are specified, it must be
1453 possible to build the package and produce working binaries
1454 on a system with only essential and build-essential
1455 packages installed and also those required to satisfy the
1456 build-time relationships (including any implied
1457 relationships). In particular, this means that version
1458 clauses should be used rigorously in build-time
1459 relationships so that one cannot produce bad or
1460 inconsistently configured packages when the relationships
1461 are properly satisfied.
1465 <ref id="relationships"> explains the technical details.
1470 <heading>Changes to the upstream sources</heading>
1473 If changes to the source code are made that are not
1474 specific to the needs of the Debian system, they should be
1475 sent to the upstream authors in whatever form they prefer
1476 so as to be included in the upstream version of the
1481 If you need to configure the package differently for
1482 Debian or for Linux, and the upstream source doesn't
1483 provide a way to do so, you should add such configuration
1484 facilities (for example, a new <prgn>autoconf</prgn> test
1485 or <tt>#define</tt>) and send the patch to the upstream
1486 authors, with the default set to the way they originally
1487 had it. You can then easily override the default in your
1488 <file>debian/rules</file> or wherever is appropriate.
1492 You should make sure that the <prgn>configure</prgn> utility
1493 detects the correct architecture specification string
1494 (refer to <ref id="arch-spec"> for details).
1498 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1499 <prgn>configure</prgn> scripts are used, you should edit the
1500 <file>.in</file> files rather than editing the
1501 <prgn>Makefile</prgn> directly. This allows the user to
1502 reconfigure the package if necessary. You should
1503 <em>not</em> configure the package and edit the generated
1504 <prgn>Makefile</prgn>! This makes it impossible for someone
1505 else to later reconfigure the package without losing the
1511 <sect id="dpkgchangelog">
1512 <heading>Debian changelog: <file>debian/changelog</file></heading>
1515 Changes in the Debian version of the package should be
1516 briefly explained in the Debian changelog file
1517 <file>debian/changelog</file>.<footnote>
1519 Mistakes in changelogs are usually best rectified by
1520 making a new changelog entry rather than "rewriting
1521 history" by editing old changelog entries.
1524 This includes modifications
1525 made in the Debian package compared to the upstream one
1526 as well as other changes and updates to the package.
1528 Although there is nothing stopping an author who is also
1529 the Debian maintainer from using this changelog for all
1530 their changes, it will have to be renamed if the Debian
1531 and upstream maintainers become different people. In such
1532 a case, however, it might be better to maintain the package
1533 as a non-native package.
1538 The format of the <file>debian/changelog</file> allows the
1539 package building tools to discover which version of the package
1540 is being built and find out other release-specific information.
1544 That format is a series of entries like this:
1546 <example compact="compact">
1547 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1549 [optional blank line(s), stripped]
1551 * <var>change details</var>
1552 <var>more change details</var>
1554 [blank line(s), included in output of dpkg-parsechangelog]
1556 * <var>even more change details</var>
1558 [optional blank line(s), stripped]
1560 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1565 <var>package</var> and <var>version</var> are the source
1566 package name and version number.
1570 <var>distribution(s)</var> lists the distributions where
1571 this version should be installed when it is uploaded - it
1572 is copied to the <tt>Distribution</tt> field in the
1573 <file>.changes</file> file. See <ref id="f-Distribution">.
1577 <var>urgency</var> is the value for the <tt>Urgency</tt>
1578 field in the <file>.changes</file> file for the upload
1579 (see <ref id="f-Urgency">). It is not possible to specify
1580 an urgency containing commas; commas are used to separate
1581 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1582 <prgn>dpkg</prgn> changelog format (though there is
1583 currently only one useful <var>keyword</var>,
1588 The change details may in fact be any series of lines
1589 starting with at least two spaces, but conventionally each
1590 change starts with an asterisk and a separating space and
1591 continuation lines are indented so as to bring them in
1592 line with the start of the text above. Blank lines may be
1593 used here to separate groups of changes, if desired.
1597 If this upload resolves bugs recorded in the Bug Tracking
1598 System (BTS), they may be automatically closed on the
1599 inclusion of this package into the Debian archive by
1600 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1601 in the change details.<footnote>
1602 To be precise, the string should match the following
1603 Perl regular expression:
1605 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1607 Then all of the bug numbers listed will be closed by the
1608 archive maintenance script (<prgn>katie</prgn>) using the
1609 <var>version</var> of the changelog entry.
1611 This information is conveyed via the <tt>Closes</tt> field
1612 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1616 The maintainer name and email address used in the changelog
1617 should be the details of the person uploading <em>this</em>
1618 version. They are <em>not</em> necessarily those of the
1619 usual package maintainer. The information here will be
1620 copied to the <tt>Changed-By</tt> field in the
1621 <tt>.changes</tt> file (see <ref id="f-Changed-By">),
1622 and then later used to send an acknowledgement when the
1623 upload has been installed.
1627 The <var>date</var> has the following format<footnote>
1628 This is the same as the format generated by <tt>date
1630 </footnote> (compatible and with the same semantics of
1631 RFC 2822 and RFC 5322):
1632 <example>day-of-week, dd month yyyy hh:mm:ss +zzzz</example>
1634 <list compact="compact">
1636 day-of week is one of: Mon, Tue, Wed, Thu, Fri, Sat, Sun
1639 dd is a one- or two-digit day of the month (01-31)
1642 month is one of: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug,
1645 <item>yyyy is the four-digit year (e.g. 2010)</item>
1646 <item>hh is the two-digit hour (00-23)</item>
1647 <item>mm is the two-digit minutes (00-59)</item>
1648 <item>ss is the two-digit seconds (00-60)</item>
1650 +zzzz or -zzzz is the the time zone offset from Coordinated
1651 Universal Time (UTC). "+" indicates that the time is ahead
1652 of (i.e., east of) UTC and "-" indicates that the time is
1653 behind (i.e., west of) UTC. The first two digits indicate
1654 the hour difference from UTC and the last two digits
1655 indicate the number of additional minutes difference from
1656 UTC. The last two digits must be in the range 00-59.
1662 The first "title" line with the package name must start
1663 at the left hand margin. The "trailer" line with the
1664 maintainer and date details must be preceded by exactly
1665 one space. The maintainer details and the date must be
1666 separated by exactly two spaces.
1670 The entire changelog must be encoded in UTF-8.
1674 For more information on placement of the changelog files
1675 within binary packages, please see <ref id="changelogs">.
1679 <sect id="dpkgcopyright">
1680 <heading>Copyright: <file>debian/copyright</file></heading>
1682 Every package must be accompanied by a verbatim copy of its
1683 copyright information and distribution license in the file
1684 <file>/usr/share/doc/<var>package</var>/copyright</file>
1685 (see <ref id="copyrightfile"> for further details). Also see
1686 <ref id="pkgcopyright"> for further considerations related
1687 to copyrights for packages.
1691 <heading>Error trapping in makefiles</heading>
1694 When <prgn>make</prgn> invokes a command in a makefile
1695 (including your package's upstream makefiles and
1696 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1697 means that <prgn>sh</prgn>'s usual bad error handling
1698 properties apply: if you include a miniature script as one
1699 of the commands in your makefile you'll find that if you
1700 don't do anything about it then errors are not detected
1701 and <prgn>make</prgn> will blithely continue after
1706 Every time you put more than one shell command (this
1707 includes using a loop) in a makefile command you
1708 must make sure that errors are trapped. For
1709 simple compound commands, such as changing directory and
1710 then running a program, using <tt>&&</tt> rather
1711 than semicolon as a command separator is sufficient. For
1712 more complex commands including most loops and
1713 conditionals you should include a separate <tt>set -e</tt>
1714 command at the start of every makefile command that's
1715 actually one of these miniature shell scripts.
1719 <sect id="timestamps">
1720 <heading>Time Stamps</heading>
1722 Maintainers should preserve the modification times of the
1723 upstream source files in a package, as far as is reasonably
1725 The rationale is that there is some information conveyed
1726 by knowing the age of the file, for example, you could
1727 recognize that some documentation is very old by looking
1728 at the modification time, so it would be nice if the
1729 modification time of the upstream source would be
1735 <sect id="restrictions">
1736 <heading>Restrictions on objects in source packages</heading>
1739 The source package may not contain any hard links<footnote>
1741 This is not currently detected when building source
1742 packages, but only when extracting
1746 Hard links may be permitted at some point in the
1747 future, but would require a fair amount of
1750 </footnote>, device special files, sockets or setuid or
1751 setgid files.<footnote>
1752 Setgid directories are allowed.
1757 <sect id="debianrules">
1758 <heading>Main building script: <file>debian/rules</file></heading>
1761 This file must be an executable makefile, and contains the
1762 package-specific recipes for compiling the package and
1763 building binary package(s) from the source.
1767 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1768 so that it can be invoked by saying its name rather than
1769 invoking <prgn>make</prgn> explicitly. That is, invoking
1770 either of <tt>make -f debian/rules <em>args...</em></tt>
1771 or <tt>./debian/rules <em>args...</em></tt> must result in
1776 Since an interactive <file>debian/rules</file> script makes it
1777 impossible to auto-compile that package and also makes it
1778 hard for other people to reproduce the same binary
1779 package, all <em>required targets</em> must be
1780 non-interactive. At a minimum, required targets are the
1781 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1782 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1783 <em>binary-indep</em>, and <em>build</em>. It also follows
1784 that any target that these targets depend on must also be
1789 The targets are as follows (required unless stated otherwise):
1791 <tag><tt>build</tt></tag>
1794 The <tt>build</tt> target should perform all the
1795 configuration and compilation of the package.
1796 If a package has an interactive pre-build
1797 configuration routine, the Debian source package
1798 must either be built after this has taken place (so
1799 that the binary package can be built without rerunning
1800 the configuration) or the configuration routine
1801 modified to become non-interactive. (The latter is
1802 preferable if there are architecture-specific features
1803 detected by the configuration routine.)
1807 For some packages, notably ones where the same
1808 source tree is compiled in different ways to produce
1809 two binary packages, the <tt>build</tt> target
1810 does not make much sense. For these packages it is
1811 good enough to provide two (or more) targets
1812 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1813 for each of the ways of building the package, and a
1814 <tt>build</tt> target that does nothing. The
1815 <tt>binary</tt> target will have to build the
1816 package in each of the possible ways and make the
1817 binary package out of each.
1821 The <tt>build</tt> target must not do anything
1822 that might require root privilege.
1826 The <tt>build</tt> target may need to run the
1827 <tt>clean</tt> target first - see below.
1831 When a package has a configuration and build routine
1832 which takes a long time, or when the makefiles are
1833 poorly designed, or when <tt>build</tt> needs to
1834 run <tt>clean</tt> first, it is a good idea to
1835 <tt>touch build</tt> when the build process is
1836 complete. This will ensure that if <tt>debian/rules
1837 build</tt> is run again it will not rebuild the whole
1839 Another common way to do this is for <tt>build</tt>
1840 to depend on <prgn>build-stamp</prgn> and to do
1841 nothing else, and for the <prgn>build-stamp</prgn>
1842 target to do the building and to <tt>touch
1843 build-stamp</tt> on completion. This is
1844 especially useful if the build routine creates a
1845 file or directory called <tt>build</tt>; in such a
1846 case, <tt>build</tt> will need to be listed as
1847 a phony target (i.e., as a dependency of the
1848 <tt>.PHONY</tt> target). See the documentation of
1849 <prgn>make</prgn> for more information on phony
1855 <tag><tt>build-arch</tt> (optional),
1856 <tt>build-indep</tt> (optional)
1860 A package may also provide both of the targets
1861 <tt>build-arch</tt> and <tt>build-indep</tt>.
1862 The <tt>build-arch</tt> target, if provided, should
1863 perform all the configuration and compilation required for
1864 producing all architecture-dependant binary packages
1865 (those packages for which the body of the
1866 <tt>Architecture</tt> field in <tt>debian/control</tt> is
1867 not <tt>all</tt>). Similarly, the <tt>build-indep</tt>
1868 target, if provided, should perform all the configuration
1869 and compilation required for producing all
1870 architecture-independent binary packages (those packages
1871 for which the body of the <tt>Architecture</tt> field
1872 in <tt>debian/control</tt> is <tt>all</tt>).
1873 The <tt>build</tt> target should depend on those of the
1874 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1875 are provided in the rules file.<footnote>
1876 The intent of this split is so that binary-only builds
1877 need not install the dependencies required for
1878 the <tt>build-indep</tt> target. However, this is not
1879 yet used in practice since <tt>dpkg-buildpackage
1880 -B</tt>, and therefore the autobuilders,
1881 invoke <tt>build</tt> rather than <tt>build-arch</tt>
1882 due to the difficulties in determining whether the
1883 optional <tt>build-arch</tt> target exists.
1888 If one or both of the targets <tt>build-arch</tt> and
1889 <tt>build-indep</tt> are not provided, then invoking
1890 <file>debian/rules</file> with one of the not-provided
1891 targets as arguments should produce a exit status code
1892 of 2. Usually this is provided automatically by make
1893 if the target is missing.
1897 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1898 must not do anything that might require root privilege.
1902 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1903 <tt>binary-indep</tt>
1907 The <tt>binary</tt> target must be all that is
1908 necessary for the user to build the binary package(s)
1909 produced from this source package. It is
1910 split into two parts: <prgn>binary-arch</prgn> builds
1911 the binary packages which are specific to a particular
1912 architecture, and <tt>binary-indep</tt> builds
1913 those which are not.
1916 <tt>binary</tt> may be (and commonly is) a target with
1917 no commands which simply depends on
1918 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1921 Both <tt>binary-*</tt> targets should depend on the
1922 <tt>build</tt> target, or on the appropriate
1923 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1924 provided, so that the package is built if it has not
1925 been already. It should then create the relevant
1926 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1927 make their control files and <prgn>dpkg-deb</prgn> to
1928 build them and place them in the parent of the top
1933 Both the <tt>binary-arch</tt> and
1934 <tt>binary-indep</tt> targets <em>must</em> exist.
1935 If one of them has nothing to do (which will always be
1936 the case if the source generates only a single binary
1937 package, whether architecture-dependent or not), it
1938 must still exist and must always succeed.
1942 The <tt>binary</tt> targets must be invoked as
1944 The <prgn>fakeroot</prgn> package often allows one
1945 to build a package correctly even without being
1951 <tag><tt>clean</tt></tag>
1954 This must undo any effects that the <tt>build</tt>
1955 and <tt>binary</tt> targets may have had, except
1956 that it should leave alone any output files created in
1957 the parent directory by a run of a <tt>binary</tt>
1962 If a <tt>build</tt> file is touched at the end of
1963 the <tt>build</tt> target, as suggested above, it
1964 should be removed as the first action that
1965 <tt>clean</tt> performs, so that running
1966 <tt>build</tt> again after an interrupted
1967 <tt>clean</tt> doesn't think that everything is
1972 The <tt>clean</tt> target may need to be
1973 invoked as root if <tt>binary</tt> has been
1974 invoked since the last <tt>clean</tt>, or if
1975 <tt>build</tt> has been invoked as root (since
1976 <tt>build</tt> may create directories, for
1981 <tag><tt>get-orig-source</tt> (optional)</tag>
1984 This target fetches the most recent version of the
1985 original source package from a canonical archive site
1986 (via FTP or WWW, for example), does any necessary
1987 rearrangement to turn it into the original source
1988 tar file format described below, and leaves it in the
1993 This target may be invoked in any directory, and
1994 should take care to clean up any temporary files it
1999 This target is optional, but providing it if
2000 possible is a good idea.
2004 <tag><tt>patch</tt> (optional)</tag>
2007 This target performs whatever additional actions are
2008 required to make the source ready for editing (unpacking
2009 additional upstream archives, applying patches, etc.).
2010 It is recommended to be implemented for any package where
2011 <tt>dpkg-source -x</tt> does not result in source ready
2012 for additional modification. See
2013 <ref id="readmesource">.
2019 The <tt>build</tt>, <tt>binary</tt> and
2020 <tt>clean</tt> targets must be invoked with the current
2021 directory being the package's top-level directory.
2026 Additional targets may exist in <file>debian/rules</file>,
2027 either as published or undocumented interfaces or for the
2028 package's internal use.
2032 The architectures we build on and build for are determined
2033 by <prgn>make</prgn> variables using the utility
2034 <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
2035 You can determine the
2036 Debian architecture and the GNU style architecture
2037 specification string for the build machine (the machine type
2038 we are building on) as well as for the host machine (the
2039 machine type we are building for). Here is a list of
2040 supported <prgn>make</prgn> variables:
2041 <list compact="compact">
2043 <tt>DEB_*_ARCH</tt> (the Debian architecture)
2046 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2049 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2052 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2053 specification string)
2056 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2057 <tt>DEB_*_GNU_TYPE</tt>)
2060 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2061 <tt>DEB_*_GNU_TYPE</tt>)
2063 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2064 the build machine or <tt>HOST</tt> for specification of the
2069 Backward compatibility can be provided in the rules file
2070 by setting the needed variables to suitable default
2071 values; please refer to the documentation of
2072 <prgn>dpkg-architecture</prgn> for details.
2076 It is important to understand that the <tt>DEB_*_ARCH</tt>
2077 string only determines which Debian architecture we are
2078 building on or for. It should not be used to get the CPU
2079 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2080 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2081 GNU style variables should generally only be used with upstream
2085 <sect1 id="debianrules-options">
2086 <heading><file>debian/rules</file> and
2087 <tt>DEB_BUILD_OPTIONS</tt></heading>
2090 Supporting the standardized environment variable
2091 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2092 contain several flags to change how a package is compiled and
2093 built. Each flag must be in the form <var>flag</var> or
2094 <var>flag</var>=<var>options</var>. If multiple flags are
2095 given, they must be separated by whitespace.<footnote>
2096 Some packages support any delimiter, but whitespace is the
2097 easiest to parse inside a makefile and avoids ambiguity with
2098 flag values that contain commas.
2100 <var>flag</var> must start with a lowercase letter
2101 (<tt>a-z</tt>) and consist only of lowercase letters,
2102 numbers (<tt>0-9</tt>), and the characters
2103 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2104 <var>options</var> must not contain whitespace. The same
2105 tag should not be given multiple times with conflicting
2106 values. Package maintainers may assume that
2107 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2111 The meaning of the following tags has been standardized:
2115 This tag says to not run any build-time test suite
2116 provided by the package.
2120 The presence of this tag means that the package should
2121 be compiled with a minimum of optimization. For C
2122 programs, it is best to add <tt>-O0</tt> to
2123 <tt>CFLAGS</tt> (although this is usually the default).
2124 Some programs might fail to build or run at this level
2125 of optimization; it may be necessary to use
2126 <tt>-O1</tt>, for example.
2130 This tag means that the debugging symbols should not be
2131 stripped from the binary during installation, so that
2132 debugging information may be included in the package.
2134 <tag>parallel=n</tag>
2136 This tag means that the package should be built using up
2137 to <tt>n</tt> parallel processes if the package build
2138 system supports this.<footnote>
2139 Packages built with <tt>make</tt> can often implement
2140 this by passing the <tt>-j</tt><var>n</var> option to
2143 If the package build system does not support parallel
2144 builds, this string must be ignored. If the package
2145 build system only supports a lower level of concurrency
2146 than <var>n</var>, the package should be built using as
2147 many parallel processes as the package build system
2148 supports. It is up to the package maintainer to decide
2149 whether the package build times are long enough and the
2150 package build system is robust enough to make supporting
2151 parallel builds worthwhile.
2157 Unknown flags must be ignored by <file>debian/rules</file>.
2161 The following makefile snippet is an example of how one may
2162 implement the build options; you will probably have to
2163 massage this example in order to make it work for your
2165 <example compact="compact">
2168 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2169 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2170 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2171 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2173 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2178 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2179 INSTALL_PROGRAM += -s
2181 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2182 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2183 MAKEFLAGS += -j$(NUMJOBS)
2188 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2189 # Code to run the package test suite.
2196 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2197 <sect id="substvars">
2198 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2201 When <prgn>dpkg-gencontrol</prgn>,
2202 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
2203 generate control files they perform variable substitutions
2204 on their output just before writing it. Variable
2205 substitutions have the form <tt>${<var>variable</var>}</tt>.
2206 The optional file <file>debian/substvars</file> contains
2207 variable substitutions to be used; variables can also be set
2208 directly from <file>debian/rules</file> using the <tt>-V</tt>
2209 option to the source packaging commands, and certain
2210 predefined variables are also available.
2214 The <file>debian/substvars</file> file is usually generated and
2215 modified dynamically by <file>debian/rules</file> targets, in
2216 which case it must be removed by the <tt>clean</tt> target.
2220 See <manref name="deb-substvars" section="5"> for full
2221 details about source variable substitutions, including the
2222 format of <file>debian/substvars</file>.</p>
2225 <sect id="debianwatch">
2226 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2229 This is an optional, recommended control file for the
2230 <tt>uscan</tt> utility which defines how to automatically
2231 scan ftp or http sites for newly available updates of the
2232 package. This is used by <url id="
2233 http://dehs.alioth.debian.org/"> and other Debian QA tools
2234 to help with quality control and maintenance of the
2235 distribution as a whole.
2240 <sect id="debianfiles">
2241 <heading>Generated files list: <file>debian/files</file></heading>
2244 This file is not a permanent part of the source tree; it
2245 is used while building packages to record which files are
2246 being generated. <prgn>dpkg-genchanges</prgn> uses it
2247 when it generates a <file>.changes</file> file.
2251 It should not exist in a shipped source package, and so it
2252 (and any backup files or temporary files such as
2253 <file>files.new</file><footnote>
2254 <file>files.new</file> is used as a temporary file by
2255 <prgn>dpkg-gencontrol</prgn> and
2256 <prgn>dpkg-distaddfile</prgn> - they write a new
2257 version of <tt>files</tt> here before renaming it,
2258 to avoid leaving a corrupted copy if an error
2260 </footnote>) should be removed by the
2261 <tt>clean</tt> target. It may also be wise to
2262 ensure a fresh start by emptying or removing it at the
2263 start of the <tt>binary</tt> target.
2267 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2268 package, it adds an entry to <file>debian/files</file> for the
2269 <file>.deb</file> file that will be created when <tt>dpkg-deb
2270 --build</tt> is run for that binary package. So for most
2271 packages all that needs to be done with this file is to
2272 delete it in the <tt>clean</tt> target.
2276 If a package upload includes files besides the source
2277 package and any binary packages whose control files were
2278 made with <prgn>dpkg-gencontrol</prgn> then they should be
2279 placed in the parent of the package's top-level directory
2280 and <prgn>dpkg-distaddfile</prgn> should be called to add
2281 the file to the list in <file>debian/files</file>.</p>
2284 <sect id="embeddedfiles">
2285 <heading>Convenience copies of code</heading>
2288 Some software packages include in their distribution convenience
2289 copies of code from other software packages, generally so that
2290 users compiling from source don't have to download multiple
2291 packages. Debian packages should not make use of these
2292 convenience copies unless the included package is explicitly
2293 intended to be used in this way.<footnote>
2294 For example, parts of the GNU build system work like this.
2296 If the included code is already in the Debian archive in the
2297 form of a library, the Debian packaging should ensure that
2298 binary packages reference the libraries already in Debian and
2299 the convenience copy is not used. If the included code is not
2300 already in Debian, it should be packaged separately as a
2301 prerequisite if possible.
2303 Having multiple copies of the same code in Debian is
2304 inefficient, often creates either static linking or shared
2305 library conflicts, and, most importantly, increases the
2306 difficulty of handling security vulnerabilities in the
2312 <sect id="readmesource">
2313 <heading>Source package handling:
2314 <file>debian/README.source</file></heading>
2317 If running <prgn>dpkg-source -x</prgn> on a source package
2318 doesn't produce the source of the package, ready for editing,
2319 and allow one to make changes and run
2320 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2321 without taking any additional steps, creating a
2322 <file>debian/README.source</file> documentation file is
2323 recommended. This file should explain how to do all of the
2326 <item>Generate the fully patched source, in a form ready for
2327 editing, that would be built to create Debian
2328 packages. Doing this with a <tt>patch</tt> target in
2329 <file>debian/rules</file> is recommended; see
2330 <ref id="debianrules">.</item>
2331 <item>Modify the source and save those modifications so that
2332 they will be applied when building the package.</item>
2333 <item>Remove source modifications that are currently being
2334 applied when building the package.</item>
2335 <item>Optionally, document what steps are necessary to
2336 upgrade the Debian source package to a new upstream version,
2337 if applicable.</item>
2339 This explanation should include specific commands and mention
2340 any additional required Debian packages. It should not assume
2341 familiarity with any specific Debian packaging system or patch
2346 This explanation may refer to a documentation file installed by
2347 one of the package's build dependencies provided that the
2348 referenced documentation clearly explains these tasks and is not
2349 a general reference manual.
2353 <file>debian/README.source</file> may also include any other
2354 information that would be helpful to someone modifying the
2355 source package. Even if the package doesn't fit the above
2356 description, maintainers are encouraged to document in a
2357 <file>debian/README.source</file> file any source package with a
2358 particularly complex or unintuitive source layout or build
2359 system (for example, a package that builds the same source
2360 multiple times to generate different binary packages).
2366 <chapt id="controlfields">
2367 <heading>Control files and their fields</heading>
2370 The package management system manipulates data represented in
2371 a common format, known as <em>control data</em>, stored in
2372 <em>control files</em>.
2373 Control files are used for source packages, binary packages and
2374 the <file>.changes</file> files which control the installation
2375 of uploaded files<footnote>
2376 <prgn>dpkg</prgn>'s internal databases are in a similar
2381 <sect id="controlsyntax">
2382 <heading>Syntax of control files</heading>
2385 A control file consists of one or more paragraphs of
2387 The paragraphs are also sometimes referred to as stanzas.
2389 The paragraphs are separated by blank lines. Some control
2390 files allow only one paragraph; others allow several, in
2391 which case each paragraph usually refers to a different
2392 package. (For example, in source packages, the first
2393 paragraph refers to the source package, and later paragraphs
2394 refer to binary packages generated from the source.)
2398 Each paragraph consists of a series of data fields; each
2399 field consists of the field name, followed by a colon and
2400 then the data/value associated with that field. It ends at
2401 the end of the (logical) line. Horizontal whitespace
2402 (spaces and tabs) may occur immediately before or after the
2403 value and is ignored there; it is conventional to put a
2404 single space after the colon. For example, a field might
2406 <example compact="compact">
2409 the field name is <tt>Package</tt> and the field value
2414 A paragraph must not contain more than one instance of a
2415 particular field name.
2419 Many fields' values may span several lines; in this case
2420 each continuation line must start with a space or a tab.
2421 Any trailing spaces or tabs at the end of individual
2422 lines of a field value are ignored.
2426 In fields where it is specified that lines may not wrap,
2427 only a single line of data is allowed and whitespace is not
2428 significant in a field body. Whitespace must not appear
2429 inside names (of packages, architectures, files or anything
2430 else) or version numbers, or between the characters of
2431 multi-character version relationships.
2435 Field names are not case-sensitive, but it is usual to
2436 capitalize the field names using mixed case as shown below.
2437 Field values are case-sensitive unless the description of the
2438 field says otherwise.
2442 Blank lines, or lines consisting only of spaces and tabs,
2443 are not allowed within field values or between fields - that
2444 would mean a new paragraph.
2448 All control files must be encoded in UTF-8.
2452 <sect id="sourcecontrolfiles">
2453 <heading>Source package control files -- <file>debian/control</file></heading>
2456 The <file>debian/control</file> file contains the most vital
2457 (and version-independent) information about the source package
2458 and about the binary packages it creates.
2462 The first paragraph of the control file contains information about
2463 the source package in general. The subsequent sets each describe a
2464 binary package that the source tree builds.
2468 The fields in the general paragraph (the first one, for the source
2471 <list compact="compact">
2472 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2473 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2474 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2475 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2476 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2477 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2478 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2479 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2484 The fields in the binary package paragraphs are:
2486 <list compact="compact">
2487 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2488 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2489 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2490 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2491 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2492 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2493 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2494 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2499 The syntax and semantics of the fields are described below.
2503 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2504 generate control files for binary packages (see below), by
2505 <prgn>dpkg-genchanges</prgn> to generate the
2506 <file>.changes</file> file to accompany the upload, and by
2507 <prgn>dpkg-source</prgn> when it creates the
2508 <file>.dsc</file> source control file as part of a source
2509 archive. Many fields are permitted to span multiple lines in
2510 <file>debian/control</file> but not in any other control
2511 file. These tools are responsible for removing the line
2512 breaks from such fields when using fields from
2513 <file>debian/control</file> to generate other control files.
2517 The fields here may contain variable references - their
2518 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2519 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2520 when they generate output control files.
2521 See <ref id="substvars"> for details.
2525 In addition to the control file syntax described <qref
2526 id="controlsyntax">above</qref>, this file may also contain
2527 comment lines starting with <tt>#</tt> without any preceding
2528 whitespace. All such lines are ignored, even in the middle of
2529 continuation lines for a multiline field, and do not end a
2535 <sect id="binarycontrolfiles">
2536 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2539 The <file>DEBIAN/control</file> file contains the most vital
2540 (and version-dependent) information about a binary package. It
2541 consists of a single paragraph.
2545 The fields in this file are:
2547 <list compact="compact">
2548 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2549 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2550 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2551 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2552 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2553 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2554 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2555 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2556 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2557 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2558 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2559 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2564 <sect id="debiansourcecontrolfiles">
2565 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2568 This file consists of a single paragraph, possibly surrounded by
2569 a PGP signature. The fields of that paragraph are listed below.
2570 Their syntax is described above, in <ref id="pkg-controlfields">.
2572 <list compact="compact">
2573 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2574 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2575 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2576 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2577 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2578 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2579 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2580 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2581 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2582 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2583 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2584 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2585 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2590 The source package control file is generated by
2591 <prgn>dpkg-source</prgn> when it builds the source
2592 archive, from other files in the source package,
2593 described above. When unpacking, it is checked against
2594 the files and directories in the other parts of the
2600 <sect id="debianchangesfiles">
2601 <heading>Debian changes files -- <file>.changes</file></heading>
2604 The <file>.changes</file> files are used by the Debian archive
2605 maintenance software to process updates to packages. They
2606 consist of a single paragraph, possibly surrounded by a PGP
2607 signature. That paragraph contains information from the
2608 <file>debian/control</file> file and other data about the
2609 source package gathered via <file>debian/changelog</file>
2610 and <file>debian/rules</file>.
2614 <file>.changes</file> files have a format version that is
2615 incremented whenever the documented fields or their meaning
2616 change. This document describes format &changesversion;.
2620 The fields in this file are:
2622 <list compact="compact">
2623 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2624 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2625 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2626 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2627 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2628 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2629 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2630 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2631 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2632 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2633 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2634 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2635 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2636 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2637 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2638 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2643 <sect id="controlfieldslist">
2644 <heading>List of fields</heading>
2646 <sect1 id="f-Source">
2647 <heading><tt>Source</tt></heading>
2650 This field identifies the source package name.
2654 In <file>debian/control</file> or a <file>.dsc</file> file,
2655 this field must contain only the name of the source package.
2659 In a binary package control file or a <file>.changes</file>
2660 file, the source package name may be followed by a version
2661 number in parentheses<footnote>
2662 It is customary to leave a space after the package name
2663 if a version number is specified.
2665 This version number may be omitted (and is, by
2666 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2667 the <tt>Version</tt> field of the binary package in
2668 question. The field itself may be omitted from a binary
2669 package control file when the source package has the same
2670 name and version as the binary package.
2674 Package names (both source and binary,
2675 see <ref id="f-Package">) must consist only of lower case
2676 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2677 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2678 (<tt>.</tt>). They must be at least two characters long and
2679 must start with an alphanumeric character.
2683 <sect1 id="f-Maintainer">
2684 <heading><tt>Maintainer</tt></heading>
2687 The package maintainer's name and email address. The name
2688 must come first, then the email address inside angle
2689 brackets <tt><></tt> (in RFC822 format).
2693 If the maintainer's name contains a full stop then the
2694 whole field will not work directly as an email address due
2695 to a misfeature in the syntax specified in RFC822; a
2696 program using this field as an address must check for this
2697 and correct the problem if necessary (for example by
2698 putting the name in round brackets and moving it to the
2699 end, and bringing the email address forward).
2703 <sect1 id="f-Uploaders">
2704 <heading><tt>Uploaders</tt></heading>
2707 List of the names and email addresses of co-maintainers of
2708 the package, if any. If the package has other maintainers
2709 beside the one named in the
2710 <qref id="f-Maintainer">Maintainer field</qref>, their names
2711 and email addresses should be listed here. The format of each
2712 entry is the same as that of the Maintainer field, and
2713 multiple entries must be comma separated. This is an optional
2718 Any parser that interprets the Uploaders field in
2719 <file>debian/control</file> must permit it to span multiple
2720 lines. Line breaks in an Uploaders field that spans multiple
2721 lines are not significant and the semantics of the field are
2722 the same as if the line breaks had not been present.
2726 <sect1 id="f-Changed-By">
2727 <heading><tt>Changed-By</tt></heading>
2730 The name and email address of the person who prepared this
2731 version of the package, usually a maintainer. The syntax is
2732 the same as for the <qref id="f-Maintainer">Maintainer
2737 <sect1 id="f-Section">
2738 <heading><tt>Section</tt></heading>
2741 This field specifies an application area into which the package
2742 has been classified. See <ref id="subsections">.
2746 When it appears in the <file>debian/control</file> file,
2747 it gives the value for the subfield of the same name in
2748 the <tt>Files</tt> field of the <file>.changes</file> file.
2749 It also gives the default for the same field in the binary
2754 <sect1 id="f-Priority">
2755 <heading><tt>Priority</tt></heading>
2758 This field represents how important it is that the user
2759 have the package installed. See <ref id="priorities">.
2763 When it appears in the <file>debian/control</file> file,
2764 it gives the value for the subfield of the same name in
2765 the <tt>Files</tt> field of the <file>.changes</file> file.
2766 It also gives the default for the same field in the binary
2771 <sect1 id="f-Package">
2772 <heading><tt>Package</tt></heading>
2775 The name of the binary package.
2779 Binary package names must follow the same syntax and
2780 restrictions as source package names. See <ref id="f-Source">
2785 <sect1 id="f-Architecture">
2786 <heading><tt>Architecture</tt></heading>
2789 Depending on context and the control file used, the
2790 <tt>Architecture</tt> field can include the following sets of
2794 A unique single word identifying a Debian machine
2795 architecture as described in <ref id="arch-spec">.
2798 An architecture wildcard identifying a set of Debian
2799 machine architectures, see <ref id="arch-wildcard-spec">.
2800 <tt>any</tt> matches all Debian machine architectures
2801 and is the most frequently used.
2804 <tt>all</tt>, which indicates an
2805 architecture-independent package.
2808 <tt>source</tt>, which indicates a source package.
2814 In the main <file>debian/control</file> file in the source
2815 package, this field may contain the special
2816 value <tt>all</tt>, the special architecture
2817 wildcard <tt>any</tt>, or a list of specific and wildcard
2818 architectures separated by spaces. If <tt>all</tt>
2819 or <tt>any</tt> appears, that value must be the entire
2820 contents of the field. Most packages will use
2821 either <tt>all</tt> or <tt>any</tt>.
2825 Specifying a specific list of architectures indicates that the
2826 source will build an architecture-dependent package only on
2827 architectures included in the list. Specifying a list of
2828 architecture wildcards indicates that the source will build an
2829 architecture-dependent package on only those architectures
2830 that match any of the specified architecture wildcards.
2831 Specifying a list of architectures or architecture wildcards
2832 other than <tt>any</tt> is for the minority of cases where a
2833 program is not portable or is not useful on some
2834 architectures. Where possible, the program should be made
2839 In the source package control file <file>.dsc</file>, this
2840 field may contain either the architecture
2841 wildcard <tt>any</tt> or a list of architectures and
2842 architecture wildcards separated by spaces. If a list is
2843 given, it may include (or consist solely of) the special
2844 value <tt>all</tt>. In other words, in <file>.dsc</file>
2845 files unlike the <file>debian/control</file>, <tt>all</tt> may
2846 occur in combination with specific architectures.
2847 The <tt>Architecture</tt> field in the source package control
2848 file <file>.dsc</file> is generally constructed from
2849 the <tt>Architecture</tt> fields in
2850 the <file>debian/control</file> in the source package.
2854 Specifying <tt>any</tt> indicates that the source package
2855 isn't dependent on any particular architecture and should
2856 compile fine on any one. The produced binary package(s)
2857 will either be specific to whatever the current build
2858 architecture is or will be architecture-independent.
2862 Specifying only <tt>all</tt> indicates that the source package
2863 will only build architecture-independent packages. If this is
2864 the case, <tt>all</tt> must be used rather than <tt>any</tt>;
2865 <tt>any</tt> implies that the source package will build at
2866 least one architecture-dependent package.
2870 Specifying a list of architectures or architecture wildcards
2871 indicates that the source will build an architecture-dependent
2872 package, and will only work correctly on the listed or
2873 matching architectures. If the source package also builds at
2874 least one architecture-independent package, <tt>all</tt> will
2875 also be included in the list.
2879 In a <file>.changes</file> file, the <tt>Architecture</tt>
2880 field lists the architecture(s) of the package(s) currently
2881 being uploaded. This will be a list; if the source for the
2882 package is also being uploaded, the special
2883 entry <tt>source</tt> is also present. <tt>all</tt> will be
2884 present if any architecture-independent packages are being
2885 uploaded. Architecture wildcards such as <tt>any</tt> must
2886 never occur in the <tt>Architecture</tt> field in
2887 the <file>.changes</file> file.
2891 See <ref id="debianrules"> for information on how to get
2892 the architecture for the build process.
2896 <sect1 id="f-Essential">
2897 <heading><tt>Essential</tt></heading>
2900 This is a boolean field which may occur only in the
2901 control file of a binary package or in a per-package fields
2902 paragraph of a main source control data file.
2906 If set to <tt>yes</tt> then the package management system
2907 will refuse to remove the package (upgrading and replacing
2908 it is still possible). The other possible value is <tt>no</tt>,
2909 which is the same as not having the field at all.
2914 <heading>Package interrelationship fields:
2915 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2916 <tt>Recommends</tt>, <tt>Suggests</tt>,
2917 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2918 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2922 These fields describe the package's relationships with
2923 other packages. Their syntax and semantics are described
2924 in <ref id="relationships">.</p>
2927 <sect1 id="f-Standards-Version">
2928 <heading><tt>Standards-Version</tt></heading>
2931 The most recent version of the standards (the policy
2932 manual and associated texts) with which the package
2937 The version number has four components: major and minor
2938 version number and major and minor patch level. When the
2939 standards change in a way that requires every package to
2940 change the major number will be changed. Significant
2941 changes that will require work in many packages will be
2942 signaled by a change to the minor number. The major patch
2943 level will be changed for any change to the meaning of the
2944 standards, however small; the minor patch level will be
2945 changed when only cosmetic, typographical or other edits
2946 are made which neither change the meaning of the document
2947 nor affect the contents of packages.
2951 Thus only the first three components of the policy version
2952 are significant in the <em>Standards-Version</em> control
2953 field, and so either these three components or all four
2954 components may be specified.<footnote>
2955 In the past, people specified the full version number
2956 in the Standards-Version field, for example "2.3.0.0".
2957 Since minor patch-level changes don't introduce new
2958 policy, it was thought it would be better to relax
2959 policy and only require the first 3 components to be
2960 specified, in this example "2.3.0". All four
2961 components may still be used if someone wishes to do so.
2967 <sect1 id="f-Version">
2968 <heading><tt>Version</tt></heading>
2971 The version number of a package. The format is:
2972 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
2976 The three components here are:
2978 <tag><var>epoch</var></tag>
2981 This is a single (generally small) unsigned integer. It
2982 may be omitted, in which case zero is assumed. If it is
2983 omitted then the <var>upstream_version</var> may not
2988 It is provided to allow mistakes in the version numbers
2989 of older versions of a package, and also a package's
2990 previous version numbering schemes, to be left behind.
2994 <tag><var>upstream_version</var></tag>
2997 This is the main part of the version number. It is
2998 usually the version number of the original ("upstream")
2999 package from which the <file>.deb</file> file has been made,
3000 if this is applicable. Usually this will be in the same
3001 format as that specified by the upstream author(s);
3002 however, it may need to be reformatted to fit into the
3003 package management system's format and comparison
3008 The comparison behavior of the package management system
3009 with respect to the <var>upstream_version</var> is
3010 described below. The <var>upstream_version</var>
3011 portion of the version number is mandatory.
3015 The <var>upstream_version</var> may contain only
3016 alphanumerics<footnote>
3017 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3019 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3020 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3021 tilde) and should start with a digit. If there is no
3022 <var>debian_revision</var> then hyphens are not allowed;
3023 if there is no <var>epoch</var> then colons are not
3028 <tag><var>debian_revision</var></tag>
3031 This part of the version number specifies the version of
3032 the Debian package based on the upstream version. It
3033 may contain only alphanumerics and the characters
3034 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3035 tilde) and is compared in the same way as the
3036 <var>upstream_version</var> is.
3040 It is optional; if it isn't present then the
3041 <var>upstream_version</var> may not contain a hyphen.
3042 This format represents the case where a piece of
3043 software was written specifically to be a Debian
3044 package, where the Debian package source must always
3045 be identical to the pristine source and therefore no
3046 revision indication is required.
3050 It is conventional to restart the
3051 <var>debian_revision</var> at <tt>1</tt> each time the
3052 <var>upstream_version</var> is increased.
3056 The package management system will break the version
3057 number apart at the last hyphen in the string (if there
3058 is one) to determine the <var>upstream_version</var> and
3059 <var>debian_revision</var>. The absence of a
3060 <var>debian_revision</var> is equivalent to a
3061 <var>debian_revision</var> of <tt>0</tt>.
3068 When comparing two version numbers, first the <var>epoch</var>
3069 of each are compared, then the <var>upstream_version</var> if
3070 <var>epoch</var> is equal, and then <var>debian_revision</var>
3071 if <var>upstream_version</var> is also equal.
3072 <var>epoch</var> is compared numerically. The
3073 <var>upstream_version</var> and <var>debian_revision</var>
3074 parts are compared by the package management system using the
3075 following algorithm:
3079 The strings are compared from left to right.
3083 First the initial part of each string consisting entirely of
3084 non-digit characters is determined. These two parts (one of
3085 which may be empty) are compared lexically. If a difference
3086 is found it is returned. The lexical comparison is a
3087 comparison of ASCII values modified so that all the letters
3088 sort earlier than all the non-letters and so that a tilde
3089 sorts before anything, even the end of a part. For example,
3090 the following parts are in sorted order from earliest to
3091 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3092 <tt>a</tt>.<footnote>
3093 One common use of <tt>~</tt> is for upstream pre-releases.
3094 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3095 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3100 Then the initial part of the remainder of each string which
3101 consists entirely of digit characters is determined. The
3102 numerical values of these two parts are compared, and any
3103 difference found is returned as the result of the comparison.
3104 For these purposes an empty string (which can only occur at
3105 the end of one or both version strings being compared) counts
3110 These two steps (comparing and removing initial non-digit
3111 strings and initial digit strings) are repeated until a
3112 difference is found or both strings are exhausted.
3116 Note that the purpose of epochs is to allow us to leave behind
3117 mistakes in version numbering, and to cope with situations
3118 where the version numbering scheme changes. It is
3119 <em>not</em> intended to cope with version numbers containing
3120 strings of letters which the package management system cannot
3121 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3122 silly orderings.<footnote>
3123 The author of this manual has heard of a package whose
3124 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3125 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3131 <sect1 id="f-Description">
3132 <heading><tt>Description</tt></heading>
3135 In a source or binary control file, the <tt>Description</tt>
3136 field contains a description of the binary package, consisting
3137 of two parts, the synopsis or the short description, and the
3138 long description. The field's format is as follows:
3143 Description: <single line synopsis>
3144 <extended description over several lines>
3149 The lines in the extended description can have these formats:
3155 Those starting with a single space are part of a paragraph.
3156 Successive lines of this form will be word-wrapped when
3157 displayed. The leading space will usually be stripped off.
3161 Those starting with two or more spaces. These will be
3162 displayed verbatim. If the display cannot be panned
3163 horizontally, the displaying program will line wrap them "hard"
3164 (i.e., without taking account of word breaks). If it can they
3165 will be allowed to trail off to the right. None, one or two
3166 initial spaces may be deleted, but the number of spaces
3167 deleted from each line will be the same (so that you can have
3168 indenting work correctly, for example).
3172 Those containing a single space followed by a single full stop
3173 character. These are rendered as blank lines. This is the
3174 <em>only</em> way to get a blank line<footnote>
3175 Completely empty lines will not be rendered as blank lines.
3176 Instead, they will cause the parser to think you're starting
3177 a whole new record in the control file, and will therefore
3178 likely abort with an error.
3183 Those containing a space, a full stop and some more characters.
3184 These are for future expansion. Do not use them.
3190 Do not use tab characters. Their effect is not predictable.
3194 See <ref id="descriptions"> for further information on this.
3198 In a <file>.changes</file> file, the <tt>Description</tt>
3199 field contains a summary of the descriptions for the packages
3200 being uploaded. For this case, the first line of the field
3201 value (the part on the same line as <tt>Description:</tt>) is
3202 always empty. The content of the field is expressed as
3203 continuation lines, one line per package. Each line is
3204 indented by one space and contains the name of a binary
3205 package, a space, a hyphen (<tt>-</tt>), a space, and the
3206 short description line from that package.
3210 <sect1 id="f-Distribution">
3211 <heading><tt>Distribution</tt></heading>
3214 In a <file>.changes</file> file or parsed changelog output
3215 this contains the (space-separated) name(s) of the
3216 distribution(s) where this version of the package should
3217 be installed. Valid distributions are determined by the
3218 archive maintainers.<footnote>
3219 Example distribution names in the Debian archive used in
3220 <file>.changes</file> files are:
3221 <taglist compact="compact">
3222 <tag><em>unstable</em></tag>
3224 This distribution value refers to the
3225 <em>developmental</em> part of the Debian distribution
3226 tree. Most new packages, new upstream versions of
3227 packages and bug fixes go into the <em>unstable</em>
3231 <tag><em>experimental</em></tag>
3233 The packages with this distribution value are deemed
3234 by their maintainers to be high risk. Oftentimes they
3235 represent early beta or developmental packages from
3236 various sources that the maintainers want people to
3237 try, but are not ready to be a part of the other parts
3238 of the Debian distribution tree.
3243 Others are used for updating stable releases or for
3244 security uploads. More information is available in the
3245 Debian Developer's Reference, section "The Debian
3249 The Debian archive software only supports listing a single
3250 distribution. Migration of packages to other distributions is
3251 handled outside of the upload process.
3256 <heading><tt>Date</tt></heading>
3259 This field includes the date the package was built or last
3260 edited. It must be in the same format as the <var>date</var>
3261 in a <file>debian/changelog</file> entry.
3265 The value of this field is usually extracted from the
3266 <file>debian/changelog</file> file - see
3267 <ref id="dpkgchangelog">).
3271 <sect1 id="f-Format">
3272 <heading><tt>Format</tt></heading>
3275 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3276 files, this field declares the format version of that file.
3277 The syntax of the field value is the same as that of
3278 a <qref id="f-Version">package version number</qref> except
3279 that no epoch or Debian revision is allowed. The format
3280 described in this document is <tt>&changesversion;</tt>.
3284 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3285 Debian source control</qref> files, this field declares the
3286 format of the source package. The field value is used by
3287 programs acting on a source package to interpret the list of
3288 files in the source package and determine how to unpack it.
3289 The syntax of the field value is a numeric major revision, a
3290 period, a numeric minor revision, and then an optional subtype
3291 after whitespace, which if specified is an alphanumeric word
3292 in parentheses. The subtype is optional in the syntax but may
3293 be mandatory for particular source format revisions.
3295 The source formats currently supported by the Debian archive
3296 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3297 and <tt>3.0 (quilt)</tt>.
3302 <sect1 id="f-Urgency">
3303 <heading><tt>Urgency</tt></heading>
3306 This is a description of how important it is to upgrade to
3307 this version from previous ones. It consists of a single
3308 keyword taking one of the values <tt>low</tt>,
3309 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3310 <tt>critical</tt><footnote>
3311 Other urgency values are supported with configuration
3312 changes in the archive software but are not used in Debian.
3313 The urgency affects how quickly a package will be considered
3314 for inclusion into the <tt>testing</tt> distribution and
3315 gives an indication of the importance of any fixes included
3316 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3317 treated as synonymous.
3318 </footnote> (not case-sensitive) followed by an optional
3319 commentary (separated by a space) which is usually in
3320 parentheses. For example:
3323 Urgency: low (HIGH for users of diversions)
3329 The value of this field is usually extracted from the
3330 <file>debian/changelog</file> file - see
3331 <ref id="dpkgchangelog">.
3335 <sect1 id="f-Changes">
3336 <heading><tt>Changes</tt></heading>
3339 This field contains the human-readable changes data, describing
3340 the differences between the last version and the current one.
3344 The first line of the field value (the part on the same line
3345 as <tt>Changes:</tt>) is always empty. The content of the
3346 field is expressed as continuation lines, with each line
3347 indented by at least one space. Blank lines must be
3348 represented by a line consisting only of a space and a full
3353 The value of this field is usually extracted from the
3354 <file>debian/changelog</file> file - see
3355 <ref id="dpkgchangelog">).
3359 Each version's change information should be preceded by a
3360 "title" line giving at least the version, distribution(s)
3361 and urgency, in a human-readable way.
3365 If data from several versions is being returned the entry
3366 for the most recent version should be returned first, and
3367 entries should be separated by the representation of a
3368 blank line (the "title" line may also be followed by the
3369 representation of a blank line).
3373 <sect1 id="f-Binary">
3374 <heading><tt>Binary</tt></heading>
3377 This field is a list of binary packages. Its syntax and
3378 meaning varies depending on the control file in which it
3383 When it appears in the <file>.dsc</file> file, it lists binary
3384 packages which a source package can produce, separated by
3386 A space after each comma is conventional.
3387 </footnote>. It may span multiple lines. The source package
3388 does not necessarily produce all of these binary packages for
3389 every architecture. The source control file doesn't contain
3390 details of which architectures are appropriate for which of
3391 the binary packages.
3395 When it appears in a <file>.changes</file> file, it lists the
3396 names of the binary packages being uploaded, separated by
3397 whitespace (not commas). It may span multiple lines.
3401 <sect1 id="f-Installed-Size">
3402 <heading><tt>Installed-Size</tt></heading>
3405 This field appears in the control files of binary packages,
3406 and in the <file>Packages</file> files. It gives an estimate
3407 of the total amount of disk space required to install the
3408 named package. Actual installed size may vary based on block
3409 size, file system properties, or actions taken by package
3414 The disk space is given as the integer value of the estimated
3415 installed size in bytes, divided by 1024 and rounded up.
3419 <sect1 id="f-Files">
3420 <heading><tt>Files</tt></heading>
3423 This field contains a list of files with information about
3424 each one. The exact information and syntax varies with
3429 In all cases, Files is a multiline field. The first line of
3430 the field value (the part on the same line as <tt>Files:</tt>)
3431 is always empty. The content of the field is expressed as
3432 continuation lines, one line per file. Each line must be
3433 indented by one space and contain a number of sub-fields,
3434 separated by spaces, as described below.
3438 In the <file>.dsc</file> file, each line contains the MD5
3439 checksum, size and filename of the tar file and (if
3440 applicable) diff file which make up the remainder of the
3441 source package<footnote>
3442 That is, the parts which are not the <tt>.dsc</tt>.
3443 </footnote>. For example:
3446 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3447 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3449 The exact forms of the filenames are described
3450 in <ref id="pkg-sourcearchives">.
3454 In the <file>.changes</file> file this contains one line per
3455 file being uploaded. Each line contains the MD5 checksum,
3456 size, section and priority and the filename. For example:
3459 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3460 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3461 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3462 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3464 The <qref id="f-Section">section</qref>
3465 and <qref id="f-Priority">priority</qref> are the values of
3466 the corresponding fields in the main source control file. If
3467 no section or priority is specified then <tt>-</tt> should be
3468 used, though section and priority values must be specified for
3469 new packages to be installed properly.
3473 The special value <tt>byhand</tt> for the section in a
3474 <tt>.changes</tt> file indicates that the file in question
3475 is not an ordinary package file and must by installed by
3476 hand by the distribution maintainers. If the section is
3477 <tt>byhand</tt> the priority should be <tt>-</tt>.
3481 If a new Debian revision of a package is being shipped and
3482 no new original source archive is being distributed the
3483 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3484 entry for the original source archive
3485 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3486 but the <file>.changes</file> file should leave it out. In
3487 this case the original source archive on the distribution
3488 site must match exactly, byte-for-byte, the original
3489 source archive which was used to generate the
3490 <file>.dsc</file> file and diff which are being uploaded.</p>
3493 <sect1 id="f-Closes">
3494 <heading><tt>Closes</tt></heading>
3497 A space-separated list of bug report numbers that the upload
3498 governed by the .changes file closes.
3502 <sect1 id="f-Homepage">
3503 <heading><tt>Homepage</tt></heading>
3506 The URL of the web site for this package, preferably (when
3507 applicable) the site from which the original source can be
3508 obtained and any additional upstream documentation or
3509 information may be found. The content of this field is a
3510 simple URL without any surrounding characters such as
3515 <sect1 id="f-Checksums">
3516 <heading><tt>Checksums-Sha1</tt>
3517 and <tt>Checksums-Sha256</tt></heading>
3520 These fields contain a list of files with a checksum and size
3521 for each one. Both <tt>Checksums-Sha1</tt>
3522 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3523 only in the checksum algorithm used: SHA-1
3524 for <tt>Checksums-Sha1</tt> and SHA-256
3525 for <tt>Checksums-Sha256</tt>.
3529 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3530 multiline fields. The first line of the field value (the part
3531 on the same line as <tt>Checksums-Sha1:</tt>
3532 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3533 of the field is expressed as continuation lines, one line per
3534 file. Each line consists of the checksum, a space, the file
3535 size, a space, and the file name. For example (from
3536 a <file>.changes</file> file):
3539 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3540 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3541 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3542 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3544 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3545 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3546 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3547 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3552 In the <file>.dsc</file> file, these fields should list all
3553 files that make up the source package. In
3554 the <file>.changes</file> file, these fields should list all
3555 files being uploaded. The list of files in these fields
3556 must match the list of files in the <tt>Files</tt> field.
3562 <heading>User-defined fields</heading>
3565 Additional user-defined fields may be added to the
3566 source package control file. Such fields will be
3567 ignored, and not copied to (for example) binary or
3568 source package control files or upload control files.
3572 If you wish to add additional unsupported fields to
3573 these output files you should use the mechanism
3578 Fields in the main source control information file with
3579 names starting <tt>X</tt>, followed by one or more of
3580 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3581 be copied to the output files. Only the part of the
3582 field name after the hyphen will be used in the output
3583 file. Where the letter <tt>B</tt> is used the field
3584 will appear in binary package control files, where the
3585 letter <tt>S</tt> is used in source package control
3586 files and where <tt>C</tt> is used in upload control
3587 (<tt>.changes</tt>) files.
3591 For example, if the main source information control file
3594 XBS-Comment: I stand between the candle and the star.
3596 then the binary and source package control files will contain the
3599 Comment: I stand between the candle and the star.
3608 <chapt id="maintainerscripts">
3609 <heading>Package maintainer scripts and installation procedure</heading>
3612 <heading>Introduction to package maintainer scripts</heading>
3615 It is possible to supply scripts as part of a package which
3616 the package management system will run for you when your
3617 package is installed, upgraded or removed.
3621 These scripts are the files <prgn>preinst</prgn>,
3622 <prgn>postinst</prgn>, <prgn>prerm</prgn> and
3623 <prgn>postrm</prgn> in the control area of the package.
3624 They must be proper executable files; if they are scripts
3625 (which is recommended), they must start with the usual
3626 <tt>#!</tt> convention. They should be readable and
3627 executable by anyone, and must not be world-writable.
3631 The package management system looks at the exit status from
3632 these scripts. It is important that they exit with a
3633 non-zero status if there is an error, so that the package
3634 management system can stop its processing. For shell
3635 scripts this means that you <em>almost always</em> need to
3636 use <tt>set -e</tt> (this is usually true when writing shell
3637 scripts, in fact). It is also important, of course, that
3638 they exit with a zero status if everything went well.
3642 Additionally, packages interacting with users using
3643 <tt>debconf</tt> in the <prgn>postinst</prgn> script should
3644 install a <prgn>config</prgn> script in the control area,
3645 see <ref id="maintscriptprompt"> for details.
3649 When a package is upgraded a combination of the scripts from
3650 the old and new packages is called during the upgrade
3651 procedure. If your scripts are going to be at all
3652 complicated you need to be aware of this, and may need to
3653 check the arguments to your scripts.
3657 Broadly speaking the <prgn>preinst</prgn> is called before
3658 (a particular version of) a package is unpacked, and the
3659 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3660 before (a version of) a package is removed and the
3661 <prgn>postrm</prgn> afterwards.
3665 Programs called from maintainer scripts should not normally
3666 have a path prepended to them. Before installation is
3667 started, the package management system checks to see if the
3668 programs <prgn>ldconfig</prgn>,
3669 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3670 and <prgn>update-rc.d</prgn> can be found via the
3671 <tt>PATH</tt> environment variable. Those programs, and any
3672 other program that one would expect to be in the
3673 <tt>PATH</tt>, should thus be invoked without an absolute
3674 pathname. Maintainer scripts should also not reset the
3675 <tt>PATH</tt>, though they might choose to modify it by
3676 prepending or appending package-specific directories. These
3677 considerations really apply to all shell scripts.</p>
3680 <sect id="idempotency">
3681 <heading>Maintainer scripts idempotency</heading>
3684 It is necessary for the error recovery procedures that the
3685 scripts be idempotent. This means that if it is run
3686 successfully, and then it is called again, it doesn't bomb
3687 out or cause any harm, but just ensures that everything is
3688 the way it ought to be. If the first call failed, or
3689 aborted half way through for some reason, the second call
3690 should merely do the things that were left undone the first
3691 time, if any, and exit with a success status if everything
3693 This is so that if an error occurs, the user interrupts
3694 <prgn>dpkg</prgn> or some other unforeseen circumstance
3695 happens you don't leave the user with a badly-broken
3696 package when <prgn>dpkg</prgn> attempts to repeat the
3702 <sect id="controllingterminal">
3703 <heading>Controlling terminal for maintainer scripts</heading>
3706 Maintainer scripts are not guaranteed to run with a controlling
3707 terminal and may not be able to interact with the user. They
3708 must be able to fall back to noninteractive behavior if no
3709 controlling terminal is available. Maintainer scripts that
3710 prompt via a program conforming to the Debian Configuration
3711 Management Specification (see <ref id="maintscriptprompt">) may
3712 assume that program will handle falling back to noninteractive
3717 For high-priority prompts without a reasonable default answer,
3718 maintainer scripts may abort if there is no controlling
3719 terminal. However, this situation should be avoided if at all
3720 possible, since it prevents automated or unattended installs.
3721 In most cases, users will consider this to be a bug in the
3726 <sect id="exitstatus">
3727 <heading>Exit status</heading>
3730 Each script must return a zero exit status for
3731 success, or a nonzero one for failure, since the package
3732 management system looks for the exit status of these scripts
3733 and determines what action to take next based on that datum.
3737 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3742 <list compact="compact">
3744 <var>new-preinst</var> <tt>install</tt>
3747 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3750 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3753 <var>old-preinst</var> <tt>abort-upgrade</tt>
3754 <var>new-version</var>
3759 <list compact="compact">
3761 <var>postinst</var> <tt>configure</tt>
3762 <var>most-recently-configured-version</var>
3765 <var>old-postinst</var> <tt>abort-upgrade</tt>
3766 <var>new-version</var>
3769 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3770 <tt>in-favour</tt> <var>package</var>
3771 <var>new-version</var>
3774 <var>postinst</var> <tt>abort-remove</tt>
3777 <var>deconfigured's-postinst</var>
3778 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3779 <var>failed-install-package</var> <var>version</var>
3780 [<tt>removing</tt> <var>conflicting-package</var>
3786 <list compact="compact">
3788 <var>prerm</var> <tt>remove</tt>
3791 <var>old-prerm</var> <tt>upgrade</tt>
3792 <var>new-version</var>
3795 <var>new-prerm</var> <tt>failed-upgrade</tt>
3796 <var>old-version</var>
3799 <var>conflictor's-prerm</var> <tt>remove</tt>
3800 <tt>in-favour</tt> <var>package</var>
3801 <var>new-version</var>
3804 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3805 <tt>in-favour</tt> <var>package-being-installed</var>
3806 <var>version</var> [<tt>removing</tt>
3807 <var>conflicting-package</var>
3813 <list compact="compact">
3815 <var>postrm</var> <tt>remove</tt>
3818 <var>postrm</var> <tt>purge</tt>
3821 <var>old-postrm</var> <tt>upgrade</tt>
3822 <var>new-version</var>
3825 <var>new-postrm</var> <tt>failed-upgrade</tt>
3826 <var>old-version</var>
3829 <var>new-postrm</var> <tt>abort-install</tt>
3832 <var>new-postrm</var> <tt>abort-install</tt>
3833 <var>old-version</var>
3836 <var>new-postrm</var> <tt>abort-upgrade</tt>
3837 <var>old-version</var>
3840 <var>disappearer's-postrm</var> <tt>disappear</tt>
3841 <var>overwriter</var>
3842 <var>overwriter-version</var>
3848 <sect id="unpackphase">
3849 <heading>Details of unpack phase of installation or upgrade</heading>
3852 The procedure on installation/upgrade/overwrite/disappear
3853 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3854 stage of <tt>dpkg --install</tt>) is as follows. In each
3855 case, if a major error occurs (unless listed below) the
3856 actions are, in general, run backwards - this means that the
3857 maintainer scripts are run with different arguments in
3858 reverse order. These are the "error unwind" calls listed
3865 If a version of the package is already installed, call
3866 <example compact="compact">
3867 <var>old-prerm</var> upgrade <var>new-version</var>
3871 If the script runs but exits with a non-zero
3872 exit status, <prgn>dpkg</prgn> will attempt:
3873 <example compact="compact">
3874 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3876 If this works, the upgrade continues. If this
3877 does not work, the error unwind:
3878 <example compact="compact">
3879 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3881 If this works, then the old-version is
3882 "Installed", if not, the old version is in a
3883 "Half-Configured" state.
3889 If a "conflicting" package is being removed at the same time,
3890 or if any package will be broken (due to <tt>Breaks</tt>):
3893 If <tt>--auto-deconfigure</tt> is
3894 specified, call, for each package to be deconfigured
3895 due to <tt>Breaks</tt>:
3896 <example compact="compact">
3897 <var>deconfigured's-prerm</var> deconfigure \
3898 in-favour <var>package-being-installed</var> <var>version</var>
3901 <example compact="compact">
3902 <var>deconfigured's-postinst</var> abort-deconfigure \
3903 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3905 The deconfigured packages are marked as
3906 requiring configuration, so that if
3907 <tt>--install</tt> is used they will be
3908 configured again if possible.
3911 If any packages depended on a conflicting
3912 package being removed and <tt>--auto-deconfigure</tt> is
3913 specified, call, for each such package:
3914 <example compact="compact">
3915 <var>deconfigured's-prerm</var> deconfigure \
3916 in-favour <var>package-being-installed</var> <var>version</var> \
3917 removing <var>conflicting-package</var> <var>version</var>
3920 <example compact="compact">
3921 <var>deconfigured's-postinst</var> abort-deconfigure \
3922 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3923 removing <var>conflicting-package</var> <var>version</var>
3925 The deconfigured packages are marked as
3926 requiring configuration, so that if
3927 <tt>--install</tt> is used they will be
3928 configured again if possible.
3931 To prepare for removal of each conflicting package, call:
3932 <example compact="compact">
3933 <var>conflictor's-prerm</var> remove \
3934 in-favour <var>package</var> <var>new-version</var>
3937 <example compact="compact">
3938 <var>conflictor's-postinst</var> abort-remove \
3939 in-favour <var>package</var> <var>new-version</var>
3948 If the package is being upgraded, call:
3949 <example compact="compact">
3950 <var>new-preinst</var> upgrade <var>old-version</var>
3952 If this fails, we call:
3954 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3961 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3963 is called. If this works, then the old version
3964 is in an "Installed" state, or else it is left
3965 in an "Unpacked" state.
3970 If it fails, then the old version is left
3971 in an "Half-Installed" state.
3978 Otherwise, if the package had some configuration
3979 files from a previous version installed (i.e., it
3980 is in the "configuration files only" state):
3981 <example compact="compact">
3982 <var>new-preinst</var> install <var>old-version</var>
3986 <var>new-postrm</var> abort-install <var>old-version</var>
3988 If this fails, the package is left in a
3989 "Half-Installed" state, which requires a
3990 reinstall. If it works, the packages is left in
3991 a "Config-Files" state.
3994 Otherwise (i.e., the package was completely purged):
3995 <example compact="compact">
3996 <var>new-preinst</var> install
3999 <example compact="compact">
4000 <var>new-postrm</var> abort-install
4002 If the error-unwind fails, the package is in a
4003 "Half-Installed" phase, and requires a
4004 reinstall. If the error unwind works, the
4005 package is in a not installed state.
4012 The new package's files are unpacked, overwriting any
4013 that may be on the system already, for example any
4014 from the old version of the same package or from
4015 another package. Backups of the old files are kept
4016 temporarily, and if anything goes wrong the package
4017 management system will attempt to put them back as
4018 part of the error unwind.
4022 It is an error for a package to contain files which
4023 are on the system in another package, unless
4024 <tt>Replaces</tt> is used (see <ref id="replaces">).
4026 The following paragraph is not currently the case:
4027 Currently the <tt>- - force-overwrite</tt> flag is
4028 enabled, downgrading it to a warning, but this may not
4034 It is a more serious error for a package to contain a
4035 plain file or other kind of non-directory where another
4036 package has a directory (again, unless
4037 <tt>Replaces</tt> is used). This error can be
4038 overridden if desired using
4039 <tt>--force-overwrite-dir</tt>, but this is not
4044 Packages which overwrite each other's files produce
4045 behavior which, though deterministic, is hard for the
4046 system administrator to understand. It can easily
4047 lead to "missing" programs if, for example, a package
4048 is unpacked which overwrites a file from another
4049 package, and is then removed again.<footnote>
4050 Part of the problem is due to what is arguably a
4051 bug in <prgn>dpkg</prgn>.
4056 A directory will never be replaced by a symbolic link
4057 to a directory or vice versa; instead, the existing
4058 state (symlink or not) will be left alone and
4059 <prgn>dpkg</prgn> will follow the symlink if there is
4068 If the package is being upgraded, call
4069 <example compact="compact">
4070 <var>old-postrm</var> upgrade <var>new-version</var>
4074 If this fails, <prgn>dpkg</prgn> will attempt:
4075 <example compact="compact">
4076 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4078 If this works, installation continues. If not,
4080 <example compact="compact">
4081 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4083 If this fails, the old version is left in a
4084 "Half-Installed" state. If it works, dpkg now
4086 <example compact="compact">
4087 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4089 If this fails, the old version is left in a
4090 "Half-Installed" state. If it works, dpkg now
4092 <example compact="compact">
4093 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4095 If this fails, the old version is in an
4102 This is the point of no return - if
4103 <prgn>dpkg</prgn> gets this far, it won't back off
4104 past this point if an error occurs. This will
4105 leave the package in a fairly bad state, which
4106 will require a successful re-installation to clear
4107 up, but it's when <prgn>dpkg</prgn> starts doing
4108 things that are irreversible.
4113 Any files which were in the old version of the package
4114 but not in the new are removed.
4118 The new file list replaces the old.
4122 The new maintainer scripts replace the old.
4126 Any packages all of whose files have been overwritten
4127 during the installation, and which aren't required for
4128 dependencies, are considered to have been removed.
4129 For each such package
4132 <prgn>dpkg</prgn> calls:
4133 <example compact="compact">
4134 <var>disappearer's-postrm</var> disappear \
4135 <var>overwriter</var> <var>overwriter-version</var>
4139 The package's maintainer scripts are removed.
4142 It is noted in the status database as being in a
4143 sane state, namely not installed (any conffiles
4144 it may have are ignored, rather than being
4145 removed by <prgn>dpkg</prgn>). Note that
4146 disappearing packages do not have their prerm
4147 called, because <prgn>dpkg</prgn> doesn't know
4148 in advance that the package is going to
4155 Any files in the package we're unpacking that are also
4156 listed in the file lists of other packages are removed
4157 from those lists. (This will lobotomize the file list
4158 of the "conflicting" package if there is one.)
4162 The backup files made during installation, above, are
4168 The new package's status is now sane, and recorded as
4173 Here is another point of no return - if the
4174 conflicting package's removal fails we do not unwind
4175 the rest of the installation; the conflicting package
4176 is left in a half-removed limbo.
4181 If there was a conflicting package we go and do the
4182 removal actions (described below), starting with the
4183 removal of the conflicting package's files (any that
4184 are also in the package being unpacked have already
4185 been removed from the conflicting package's file list,
4186 and so do not get removed now).
4192 <sect id="configdetails"><heading>Details of configuration</heading>
4195 When we configure a package (this happens with <tt>dpkg
4196 --install</tt> and <tt>dpkg --configure</tt>), we first
4197 update any <tt>conffile</tt>s and then call:
4198 <example compact="compact">
4199 <var>postinst</var> configure <var>most-recently-configured-version</var>
4204 No attempt is made to unwind after errors during
4205 configuration. If the configuration fails, the package is in
4206 a "Failed Config" state, and an error message is generated.
4210 If there is no most recently configured version
4211 <prgn>dpkg</prgn> will pass a null argument.
4214 Historical note: Truly ancient (pre-1997) versions of
4215 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4216 (including the angle brackets) in this case. Even older
4217 ones did not pass a second argument at all, under any
4218 circumstance. Note that upgrades using such an old dpkg
4219 version are unlikely to work for other reasons, even if
4220 this old argument behavior is handled by your postinst script.
4226 <sect id="removedetails"><heading>Details of removal and/or
4227 configuration purging</heading>
4233 <example compact="compact">
4234 <var>prerm</var> remove
4238 If prerm fails during replacement due to conflict
4240 <var>conflictor's-postinst</var> abort-remove \
4241 in-favour <var>package</var> <var>new-version</var>
4245 <var>postinst</var> abort-remove
4249 If this fails, the package is in a "Half-Configured"
4250 state, or else it remains "Installed".
4254 The package's files are removed (except <tt>conffile</tt>s).
4257 <example compact="compact">
4258 <var>postrm</var> remove
4262 If it fails, there's no error unwind, and the package is in
4263 an "Half-Installed" state.
4268 All the maintainer scripts except the <prgn>postrm</prgn>
4273 If we aren't purging the package we stop here. Note
4274 that packages which have no <prgn>postrm</prgn> and no
4275 <tt>conffile</tt>s are automatically purged when
4276 removed, as there is no difference except for the
4277 <prgn>dpkg</prgn> status.
4281 The <tt>conffile</tt>s and any backup files
4282 (<tt>~</tt>-files, <tt>#*#</tt> files,
4283 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4288 <example compact="compact">
4289 <var>postrm</var> purge
4293 If this fails, the package remains in a "Config-Files"
4298 The package's file list is removed.
4307 <chapt id="relationships">
4308 <heading>Declaring relationships between packages</heading>
4310 <sect id="depsyntax">
4311 <heading>Syntax of relationship fields</heading>
4314 These fields all have a uniform syntax. They are a list of
4315 package names separated by commas.
4319 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4320 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4321 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4322 control file fields of the package, which declare
4323 dependencies on other packages, the package names listed may
4324 also include lists of alternative package names, separated
4325 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4326 if any one of the alternative packages is installed, that
4327 part of the dependency is considered to be satisfied.
4331 All of the fields except for <tt>Provides</tt> may restrict
4332 their applicability to particular versions of each named
4333 package. This is done in parentheses after each individual
4334 package name; the parentheses should contain a relation from
4335 the list below followed by a version number, in the format
4336 described in <ref id="f-Version">.
4340 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4341 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4342 strictly earlier, earlier or equal, exactly equal, later or
4343 equal and strictly later, respectively. The deprecated
4344 forms <tt><</tt> and <tt>></tt> were used to mean
4345 earlier/later or equal, rather than strictly earlier/later,
4346 so they should not appear in new packages (though
4347 <prgn>dpkg</prgn> still supports them).
4351 Whitespace may appear at any point in the version
4352 specification subject to the rules in <ref
4353 id="controlsyntax">, and must appear where it's necessary to
4354 disambiguate; it is not otherwise significant. All of the
4355 relationship fields may span multiple lines. For
4356 consistency and in case of future changes to
4357 <prgn>dpkg</prgn> it is recommended that a single space be
4358 used after a version relationship and before a version
4359 number; it is also conventional to put a single space after
4360 each comma, on either side of each vertical bar, and before
4361 each open parenthesis. When wrapping a relationship field, it
4362 is conventional to do so after a comma and before the space
4363 following that comma.
4367 For example, a list of dependencies might appear as:
4368 <example compact="compact">
4371 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4376 Relationships may be restricted to a certain set of
4377 architectures. This is indicated in brackets after each
4378 individual package name and the optional version specification.
4379 The brackets enclose a list of Debian architecture names
4380 separated by whitespace. Exclamation marks may be prepended to
4381 each of the names. (It is not permitted for some names to be
4382 prepended with exclamation marks while others aren't.)
4386 For build relationship fields
4387 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4388 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>), if
4389 the current Debian host architecture is not in this list and
4390 there are no exclamation marks in the list, or it is in the list
4391 with a prepended exclamation mark, the package name and the
4392 associated version specification are ignored completely for the
4393 purposes of defining the relationships.
4398 <example compact="compact">
4400 Build-Depends-Indep: texinfo
4401 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4402 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4404 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4405 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4406 <tt>gnumach-dev</tt> only on hurd-i386.
4410 For binary relationship fields, the architecture restriction
4411 syntax is only supported in the source package control
4412 file <file>debian/control</file>. When the corresponding binary
4413 package control file is generated, the relationship will either
4414 be omitted or included without the architecture restriction
4415 based on the architecture of the binary package. This means
4416 that architecture restrictions must not be used in binary
4417 relationship fields for architecture-independent packages
4418 (<tt>Architecture: all</tt>).
4423 <example compact="compact">
4424 Depends: foo [i386], bar [amd64]
4426 becomes <tt>Depends: foo</tt> when the package is built on
4427 the <tt>i386</tt> architecture, <tt>Depends: bar</tt> when the
4428 package is built on the <tt>amd64</tt> architecture, and omitted
4429 entirely in binary packages built on all other architectures.
4433 If the architecture-restricted dependency is part of a set of
4434 alternatives using <tt>|</tt>, that alternative is ignored
4435 completely on architectures that do not match the restriction.
4437 <example compact="compact">
4438 Build-Depends: foo [!i386] | bar [!amd64]
4440 is equivalent to <tt>bar</tt> on the i386 architecture, to
4441 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4442 bar</tt> on all other architectures.
4446 Relationships may also be restricted to a certain set of
4447 architectures using architecture wildcards. The syntax for
4448 declaring such restrictions is the same as declaring
4449 restrictions using a certain set of architectures without
4450 architecture wildcards. For example:
4451 <example compact="compact">
4452 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4454 is equivalent to <tt>foo</tt> on architectures using the Linux
4455 kernel and any cpu, <tt>bar</tt> on architectures using any
4456 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4457 using a kernel other than Linux.
4461 Note that the binary package relationship fields such as
4462 <tt>Depends</tt> appear in one of the binary package
4463 sections of the control file, whereas the build-time
4464 relationships such as <tt>Build-Depends</tt> appear in the
4465 source package section of the control file (which is the
4470 <sect id="binarydeps">
4471 <heading>Binary Dependencies - <tt>Depends</tt>,
4472 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4473 <tt>Pre-Depends</tt>
4477 Packages can declare in their control file that they have
4478 certain relationships to other packages - for example, that
4479 they may not be installed at the same time as certain other
4480 packages, and/or that they depend on the presence of others.
4484 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4485 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4486 <tt>Breaks</tt> and <tt>Conflicts</tt> control file fields.
4487 <tt>Breaks</tt> is described in <ref id="breaks">, and
4488 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4489 rest are described below.
4493 These seven fields are used to declare a dependency
4494 relationship by one package on another. Except for
4495 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4496 depending (binary) package's control file.
4497 (<tt>Enhances</tt> appears in the recommending package's
4498 control file, and <tt>Breaks</tt> appears in the version of
4499 depended-on package which causes the named package to
4504 A <tt>Depends</tt> field takes effect <em>only</em> when a
4505 package is to be configured. It does not prevent a package
4506 being on the system in an unconfigured state while its
4507 dependencies are unsatisfied, and it is possible to replace
4508 a package whose dependencies are satisfied and which is
4509 properly installed with a different version whose
4510 dependencies are not and cannot be satisfied; when this is
4511 done the depending package will be left unconfigured (since
4512 attempts to configure it will give errors) and will not
4513 function properly. If it is necessary, a
4514 <tt>Pre-Depends</tt> field can be used, which has a partial
4515 effect even when a package is being unpacked, as explained
4516 in detail below. (The other three dependency fields,
4517 <tt>Recommends</tt>, <tt>Suggests</tt> and
4518 <tt>Enhances</tt>, are only used by the various front-ends
4519 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4520 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4524 Since <tt>Depends</tt> only places requirements on the
4525 configuration step, packages in an installation run are usually
4526 all unpacked first and all configured later. This makes it
4527 easier to satisfy all dependencies when multiple packages are
4532 If there is a circular dependency among packages being installed
4533 or removed, installation or removal order honoring the
4534 dependency order is impossible, requiring the dependency loop be
4535 broken at some point and the dependency requirements violated
4536 for at least one package. Packages involved in circular
4537 dependencies may not be able to rely on their dependencies being
4538 configured when being configured or removed depending on which
4539 side of the break of the circular dependency loop they happen to
4540 be on. If one of the packages in the loop has no
4541 <prgn>postinst</prgn> script, then the cycle will be broken at
4542 that package; this ensures that all <prgn>postinst</prgn>
4543 scripts are run with their dependencies properly configured if
4544 this is possible. Otherwise the breaking point is arbitrary.
4545 Packages should therefore avoid circular dependencies where
4546 possible, particularly if they have <prgn>postinst</prgn>
4551 The meaning of the five dependency fields is as follows:
4553 <tag><tt>Depends</tt></tag>
4556 This declares an absolute dependency. A package will
4557 not be configured unless all of the packages listed in
4558 its <tt>Depends</tt> field have been correctly
4559 configured (unless there is a circular dependency as
4564 The <tt>Depends</tt> field should be used if the
4565 depended-on package is required for the depending
4566 package to provide a significant amount of
4571 The <tt>Depends</tt> field should also be used if the
4572 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4573 <prgn>postrm</prgn> scripts require the package to be
4574 present in order to run. (If both packages are involved
4575 in a dependency loop, this might not work as expected; see
4576 the explanation a few paragraphs back.) In the case of
4577 <prgn>postinst</prgn> and <prgn>postrm</prgn>, the
4578 depended-on packages will be unpacked and configured
4579 first. (Note, however, that the <prgn>postrm</prgn>
4580 cannot rely on any non-essential packages to be present
4581 during the <tt>purge</tt> phase.) In the case of
4582 <prgn>prerm</prgn>, the depended-on package will at least
4583 be unpacked (it might be configured too, but you can't
4584 rely on this unless you use <tt>Pre-Depends</tt>).
4587 <tag><tt>Recommends</tt></tag>
4590 This declares a strong, but not absolute, dependency.
4594 The <tt>Recommends</tt> field should list packages
4595 that would be found together with this one in all but
4596 unusual installations.
4600 <tag><tt>Suggests</tt></tag>
4602 This is used to declare that one package may be more
4603 useful with one or more others. Using this field
4604 tells the packaging system and the user that the
4605 listed packages are related to this one and can
4606 perhaps enhance its usefulness, but that installing
4607 this one without them is perfectly reasonable.
4610 <tag><tt>Enhances</tt></tag>
4612 This field is similar to Suggests but works in the
4613 opposite direction. It is used to declare that a
4614 package can enhance the functionality of another
4618 <tag><tt>Pre-Depends</tt></tag>
4621 This field is like <tt>Depends</tt>, except that it
4622 also forces <prgn>dpkg</prgn> to complete installation
4623 of the packages named before even starting the
4624 installation of the package which declares the
4625 pre-dependency, as follows:
4629 When a package declaring a pre-dependency is about to
4630 be <em>unpacked</em> the pre-dependency can be
4631 satisfied if the depended-on package is either fully
4632 configured, <em>or even if</em> the depended-on
4633 package(s) are only unpacked or in the "Half-Configured"
4634 state, provided that they have been configured
4635 correctly at some point in the past (and not removed
4636 or partially removed since). In this case, both the
4637 previously-configured and currently unpacked or
4638 "Half-Configured" versions must satisfy any version
4639 clause in the <tt>Pre-Depends</tt> field.
4643 When the package declaring a pre-dependency is about
4644 to be <em>configured</em>, the pre-dependency will be
4645 treated as a normal <tt>Depends</tt>, that is, it will
4646 be considered satisfied only if the depended-on
4647 package has been correctly configured. However, unlike
4648 with <tt>Depends</tt>, <tt>Pre-Depends</tt> does not
4649 permit circular dependencies to be broken. If a circular
4650 dependency is encountered while attempting to honor
4651 <tt>Pre-Depends</tt>, the installation will be aborted.
4655 <tt>Pre-Depends</tt> are also required if the
4656 <prgn>preinst</prgn> script depends on the named package.
4657 It is best to avoid this situation if possible.
4661 <tt>Pre-Depends</tt> should be used sparingly,
4662 preferably only by packages whose premature upgrade or
4663 installation would hamper the ability of the system to
4664 continue with any upgrade that might be in progress.
4671 When selecting which level of dependency to use you should
4672 consider how important the depended-on package is to the
4673 functionality of the one declaring the dependency. Some
4674 packages are composed of components of varying degrees of
4675 importance. Such a package should list using
4676 <tt>Depends</tt> the package(s) which are required by the
4677 more important components. The other components'
4678 requirements may be mentioned as Suggestions or
4679 Recommendations, as appropriate to the components' relative
4685 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4688 When one binary package declares that it breaks another,
4689 <prgn>dpkg</prgn> will refuse to allow the package which
4690 declares <tt>Breaks</tt> be unpacked unless the broken
4691 package is deconfigured first, and it will refuse to
4692 allow the broken package to be reconfigured.
4696 A package will not be regarded as causing breakage merely
4697 because its configuration files are still installed; it must
4698 be at least "Half-Installed".
4702 A special exception is made for packages which declare that
4703 they break their own package name or a virtual package which
4704 they provide (see below): this does not count as a real
4709 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4710 version clause; such a <tt>Breaks</tt> is introduced in the
4711 version of an (implicit or explicit) dependency which violates
4712 an assumption or reveals a bug in earlier versions of the broken
4713 package, or which takes over a file from earlier versions of the
4714 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
4715 will inform higher-level package management tools that the
4716 broken package must be upgraded before the new one.
4720 If the breaking package also overwrites some files from the
4721 older package, it should use <tt>Replaces</tt> to ensure this
4722 goes smoothly. See <ref id="replaces"> for a full discussion
4723 of taking over files from other packages, including how to
4724 use <tt>Breaks</tt> in those cases.
4728 Many of the cases where <tt>Breaks</tt> should be used were
4729 previously handled with <tt>Conflicts</tt>
4730 because <tt>Breaks</tt> did not yet exist.
4731 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
4732 See <ref id="conflicts"> for more information about the
4737 <sect id="conflicts">
4738 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4741 When one binary package declares a conflict with another
4742 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4743 refuse to allow them to be unpacked on the system at the
4744 same time. This is a stronger restriction than <tt>Breaks</tt>,
4745 which just prevents both packages from being configured at the
4746 same time. Conflicting packages cannot be unpacked on the
4747 system at the same time.
4751 If one package is to be unpacked, the other must be removed
4752 first. If the package being unpacked is marked as replacing
4753 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
4754 normally be used in this case) the one on the system, or the one
4755 on the system is marked as deselected, or both packages are
4756 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
4757 automatically remove the package which is causing the conflict.
4758 Otherwise, it will halt the installation of the new package with
4759 an error. This mechanism is specifically designed to produce an
4760 error when the installed package is <tt>Essential</tt>, but the
4765 A package will not cause a conflict merely because its
4766 configuration files are still installed; it must be at least
4771 A special exception is made for packages which declare a
4772 conflict with their own package name, or with a virtual
4773 package which they provide (see below): this does not
4774 prevent their installation, and allows a package to conflict
4775 with others providing a replacement for it. You use this
4776 feature when you want the package in question to be the only
4777 package providing some feature.
4781 Normally, <tt>Breaks</tt> should be used instead
4782 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
4783 stronger restriction on the ordering of package installation or
4784 upgrade and can make it more difficult for the package manager
4785 to find a correct solution to an upgrade or installation
4786 problem. <tt>Breaks</tt> should be used
4788 <item>when moving a file from one package to another (see
4789 <ref id="replaces">),</item>
4790 <item>when splitting a package (a special case of the previous
4792 <item>when the breaking package exposes a bug in or interacts
4793 badly with particular versions of the broken
4796 <tt>Conflicts</tt> should be used
4798 <item>when two packages provide the same file and will
4799 continue to do so,</item>
4800 <item>in conjunction with <tt>Provides</tt> when only one
4801 package providing a given virtual facility may be installed
4802 at a time (see <ref id="virtual">),</item>
4803 <item>in other cases where one must prevent simultaneous
4804 installation of two packages for reasons that are ongoing
4805 (not fixed in a later version of one of the packages) or
4806 that must prevent both packages from being unpacked at the
4807 same time, not just configured.</item>
4809 Be aware that adding <tt>Conflicts</tt> is normally not the best
4810 solution when two packages provide the same files. Depending on
4811 the reason for that conflict, using alternatives or renaming the
4812 files is often a better approach. See, for
4813 example, <ref id="binaries">.
4817 A <tt>Conflicts</tt> entry may have an "earlier than" version
4818 clause if the reason for the conflict is corrected in a later
4819 version of one of the packages. However, normally the presence
4820 of an "earlier than" version clause is a sign
4821 that <tt>Breaks</tt> should have been used instead. An "earlier
4822 than" version clause in <tt>Conflicts</tt>
4823 prevents <prgn>dpkg</prgn> from upgrading or installing the
4824 package which declares such a conflict until the upgrade or
4825 removal of the conflicted-with package has been completed, which
4826 is a strong restriction.
4830 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4834 As well as the names of actual ("concrete") packages, the
4835 package relationship fields <tt>Depends</tt>,
4836 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4837 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4838 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4839 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4840 may mention "virtual packages".
4844 A <em>virtual package</em> is one which appears in the
4845 <tt>Provides</tt> control file field of another package.
4846 The effect is as if the package(s) which provide a
4847 particular virtual package name had been listed by name
4848 everywhere the virtual package name appears. (See also <ref
4853 If there are both concrete and virtual packages of the same
4854 name, then the dependency may be satisfied (or the conflict
4855 caused) by either the concrete package with the name in
4856 question or any other concrete package which provides the
4857 virtual package with the name in question. This is so that,
4858 for example, supposing we have
4859 <example compact="compact">
4862 </example> and someone else releases an enhanced version of
4863 the <tt>bar</tt> package they can say:
4864 <example compact="compact">
4868 and the <tt>bar-plus</tt> package will now also satisfy the
4869 dependency for the <tt>foo</tt> package.
4873 If a relationship field has a version number attached, only real
4874 packages will be considered to see whether the relationship is
4875 satisfied (or the prohibition violated, for a conflict or
4876 breakage). In other words, if a version number is specified,
4877 this is a request to ignore all <tt>Provides</tt> for that
4878 package name and consider only real packages. The package
4879 manager will assume that a package providing that virtual
4880 package is not of the "right" version. A <tt>Provides</tt>
4881 field may not contain version numbers, and the version number of
4882 the concrete package which provides a particular virtual package
4883 will not be considered when considering a dependency on or
4884 conflict with the virtual package name.<footnote>
4885 It is possible that a future release of <prgn>dpkg</prgn> may
4886 add the ability to specify a version number for each virtual
4887 package it provides. This feature is not yet present,
4888 however, and is expected to be used only infrequently.
4893 To specify which of a set of real packages should be the default
4894 to satisfy a particular dependency on a virtual package, list
4895 the real package as an alternative before the virtual one.
4899 If the virtual package represents a facility that can only be
4900 provided by one real package at a time, such as
4901 the <package>mail-transport-agent</package> virtual package that
4902 requires installation of a binary that would conflict with all
4903 other providers of that virtual package (see
4904 <ref id="mail-transport-agents">), all packages providing that
4905 virtual package should also declare a conflict with it
4906 using <tt>Conflicts</tt>. This will ensure that at most one
4907 provider of that virtual package is unpacked or installed at a
4912 <sect id="replaces"><heading>Overwriting files and replacing
4913 packages - <tt>Replaces</tt></heading>
4916 Packages can declare in their control file that they should
4917 overwrite files in certain other packages, or completely
4918 replace other packages. The <tt>Replaces</tt> control file
4919 field has these two distinct purposes.
4922 <sect1><heading>Overwriting files in other packages</heading>
4925 It is usually an error for a package to contain files which
4926 are on the system in another package. However, if the
4927 overwriting package declares that it <tt>Replaces</tt> the one
4928 containing the file being overwritten, then <prgn>dpkg</prgn>
4929 will replace the file from the old package with that from the
4930 new. The file will no longer be listed as "owned" by the old
4931 package and will be taken over by the new package.
4932 Normally, <tt>Breaks</tt> should be used in conjunction
4933 with <tt>Replaces</tt>.<footnote>
4934 To see why <tt>Breaks</tt> is normally needed in addition
4935 to <tt>Replaces</tt>, consider the case of a file in the
4936 package <package>foo</package> being taken over by the
4937 package <package>foo-data</package>.
4938 <tt>Replaces</tt> will allow <package>foo-data</package> to
4939 be installed and take over that file. However,
4940 without <tt>Breaks</tt>, nothing
4941 requires <package>foo</package> to be upgraded to a newer
4942 version that knows it does not include that file and instead
4943 depends on <package>foo-data</package>. Nothing would
4944 prevent the new <package>foo-data</package> package from
4945 being installed and then removed, removing the file that it
4946 took over from <package>foo</package>. After that
4947 operation, the package manager would think the system was in
4948 a consistent state, but the <package>foo</package> package
4949 would be missing one of its files.
4954 For example, if a package <package>foo</package> is split
4955 into <package>foo</package> and <package>foo-data</package>
4956 starting at version 1.2-3, <package>foo-data</package> would
4958 <example compact="compact">
4959 Replaces: foo (<< 1.2-3)
4960 Breaks: foo (<< 1.2-3)
4962 in its control file. The new version of the
4963 package <package>foo</package> would normally have the field
4964 <example compact="compact">
4965 Depends: foo-data (>= 1.2-3)
4967 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
4968 the files moved into <package>foo-data</package> are not
4969 required for normal operation).
4973 If a package is completely replaced in this way, so that
4974 <prgn>dpkg</prgn> does not know of any files it still
4975 contains, it is considered to have "disappeared". It will
4976 be marked as not wanted on the system (selected for
4977 removal) and not installed. Any <tt>conffile</tt>s
4978 details noted for the package will be ignored, as they
4979 will have been taken over by the overwriting package. The
4980 package's <prgn>postrm</prgn> script will be run with a
4981 special argument to allow the package to do any final
4982 cleanup required. See <ref id="mscriptsinstact">.
4984 Replaces is a one way relationship. You have to install
4985 the replacing package after the replaced package.
4990 For this usage of <tt>Replaces</tt>, virtual packages (see
4991 <ref id="virtual">) are not considered when looking at a
4992 <tt>Replaces</tt> field. The packages declared as being
4993 replaced must be mentioned by their real names.
4997 This usage of <tt>Replaces</tt> only takes effect when both
4998 packages are at least partially on the system at once. It is
4999 not relevant if the packages conflict unless the conflict has
5004 <sect1><heading>Replacing whole packages, forcing their
5008 Second, <tt>Replaces</tt> allows the packaging system to
5009 resolve which package should be removed when there is a
5010 conflict (see <ref id="conflicts">). This usage only takes
5011 effect when the two packages <em>do</em> conflict, so that the
5012 two usages of this field do not interfere with each other.
5016 In this situation, the package declared as being replaced
5017 can be a virtual package, so for example, all mail
5018 transport agents (MTAs) would have the following fields in
5019 their control files:
5020 <example compact="compact">
5021 Provides: mail-transport-agent
5022 Conflicts: mail-transport-agent
5023 Replaces: mail-transport-agent
5025 ensuring that only one MTA can be unpacked at any one
5026 time. See <ref id="virtual"> for more information about this
5031 <sect id="sourcebinarydeps">
5032 <heading>Relationships between source and binary packages -
5033 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5034 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5038 Source packages that require certain binary packages to be
5039 installed or absent at the time of building the package
5040 can declare relationships to those binary packages.
5044 This is done using the <tt>Build-Depends</tt>,
5045 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5046 <tt>Build-Conflicts-Indep</tt> control file fields.
5050 Build-dependencies on "build-essential" binary packages can be
5051 omitted. Please see <ref id="pkg-relations"> for more information.
5055 The dependencies and conflicts they define must be satisfied
5056 (as defined earlier for binary packages) in order to invoke
5057 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5059 There is no Build-Depends-Arch; this role is essentially
5060 met with Build-Depends. Anyone building the
5061 <tt>build-indep</tt> and binary-indep<tt></tt> targets is
5062 assumed to be building the whole package, and therefore
5063 installation of all build dependencies is required.
5066 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5067 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5068 not yet know how to check for its existence, and
5069 <tt>binary-arch</tt>. The purpose of the original split
5070 between <tt>Build-Depends</tt> and
5071 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5072 wouldn't need to install extra packages needed only for the
5073 binary-indep targets. But without a build-arch/build-indep
5074 split, this didn't work, since most of the work is done in
5075 the build target, not in the binary target.
5079 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5080 <tt>binary-arch</tt></tag>
5082 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5083 fields must be satisfied when these targets are invoked.
5085 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5086 and <tt>binary-indep</tt></tag>
5088 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5089 <tt>Build-Depends-Indep</tt>, and
5090 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5091 these targets are invoked.
5099 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5102 Packages containing shared libraries must be constructed with
5103 a little care to make sure that the shared library is always
5104 available. This is especially important for packages whose
5105 shared libraries are vitally important, such as the C library
5106 (currently <tt>libc6</tt>).
5110 Packages involving shared libraries should be split up into
5111 several binary packages. This section mostly deals with how
5112 this separation is to be accomplished; rules for files within
5113 the shared library packages are in <ref id="libraries"> instead.
5116 <sect id="sharedlibs-runtime">
5117 <heading>Run-time shared libraries</heading>
5120 The run-time shared library needs to be placed in a package
5121 whose name changes whenever the shared object version
5124 Since it is common place to install several versions of a
5125 package that just provides shared libraries, it is a
5126 good idea that the library package should not
5127 contain any extraneous non-versioned files, unless they
5128 happen to be in versioned directories.</p>
5130 The most common mechanism is to place it in a package
5132 <package><var>libraryname</var><var>soversion</var></package>,
5133 where <file><var>soversion</var></file> is the version number
5134 in the soname of the shared library<footnote>
5135 The soname is the shared object name: it's the thing
5136 that has to match exactly between building an executable
5137 and running it for the dynamic linker to be able run the
5138 program. For example, if the soname of the library is
5139 <file>libfoo.so.6</file>, the library package would be
5140 called <file>libfoo6</file>.
5142 Alternatively, if it would be confusing to directly append
5143 <var>soversion</var> to <var>libraryname</var> (e.g. because
5144 <var>libraryname</var> itself ends in a number), you may use
5145 <package><var>libraryname</var>-<var>soversion</var></package> and
5146 <package><var>libraryname</var>-<var>soversion</var>-dev</package>
5151 If you have several shared libraries built from the same
5152 source tree you may lump them all together into a single
5153 shared library package, provided that you change all of
5154 their sonames at once (so that you don't get filename
5155 clashes if you try to install different versions of the
5156 combined shared libraries package).
5160 The package should install the shared libraries under
5161 their normal names. For example, the <package>libgdbm3</package>
5162 package should install <file>libgdbm.so.3.0.0</file> as
5163 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5164 renamed or re-linked by any <prgn>prerm</prgn> or
5165 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5166 of renaming things safely without affecting running programs,
5167 and attempts to interfere with this are likely to lead to
5172 Shared libraries should not be installed executable, since
5173 the dynamic linker does not require this and trying to
5174 execute a shared library usually results in a core dump.
5178 The run-time library package should include the symbolic link that
5179 <prgn>ldconfig</prgn> would create for the shared libraries.
5180 For example, the <package>libgdbm3</package> package should include
5181 a symbolic link from <file>/usr/lib/libgdbm.so.3</file> to
5182 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5183 linker (for example <prgn>ld.so</prgn> or
5184 <prgn>ld-linux.so.*</prgn>) can find the library between the
5185 time that <prgn>dpkg</prgn> installs it and the time that
5186 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5188 The package management system requires the library to be
5189 placed before the symbolic link pointing to it in the
5190 <file>.deb</file> file. This is so that when
5191 <prgn>dpkg</prgn> comes to install the symlink
5192 (overwriting the previous symlink pointing at an older
5193 version of the library), the new shared library is already
5194 in place. In the past, this was achieved by creating the
5195 library in the temporary packaging directory before
5196 creating the symlink. Unfortunately, this was not always
5197 effective, since the building of the tar file in the
5198 <file>.deb</file> depended on the behavior of the underlying
5199 file system. Some file systems (such as reiserfs) reorder
5200 the files so that the order of creation is forgotten.
5201 Since version 1.7.0, <prgn>dpkg</prgn>
5202 reorders the files itself as necessary when building a
5203 package. Thus it is no longer important to concern
5204 oneself with the order of file creation.
5208 <sect1 id="ldconfig">
5209 <heading><tt>ldconfig</tt></heading>
5212 Any package installing shared libraries in one of the default
5213 library directories of the dynamic linker (which are currently
5214 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5215 listed in <file>/etc/ld.so.conf</file><footnote>
5217 <list compact="compact">
5218 <item>/usr/local/lib</item>
5219 <item>/usr/lib/libc5-compat</item>
5220 <item>/lib/libc5-compat</item>
5223 must use <prgn>ldconfig</prgn> to update the shared library
5228 The package maintainer scripts must only call
5229 <prgn>ldconfig</prgn> under these circumstances:
5230 <list compact="compact">
5231 <item>When the <prgn>postinst</prgn> script is run with a
5232 first argument of <tt>configure</tt>, the script must call
5233 <prgn>ldconfig</prgn>, and may optionally invoke
5234 <prgn>ldconfig</prgn> at other times.
5236 <item>When the <prgn>postrm</prgn> script is run with a
5237 first argument of <tt>remove</tt>, the script should call
5238 <prgn>ldconfig</prgn>.
5243 During install or upgrade, the preinst is called before
5244 the new files are unpacked, so calling "ldconfig" is
5245 pointless. The preinst of an existing package can also be
5246 called if an upgrade fails. However, this happens during
5247 the critical time when a shared libs may exist on-disk
5248 under a temporary name. Thus, it is dangerous and
5249 forbidden by current policy to call "ldconfig" at this
5254 When a package is installed or upgraded, "postinst
5255 configure" runs after the new files are safely on-disk.
5256 Since it is perfectly safe to invoke ldconfig
5257 unconditionally in a postinst, it is OK for a package to
5258 simply put ldconfig in its postinst without checking the
5259 argument. The postinst can also be called to recover from
5260 a failed upgrade. This happens before any new files are
5261 unpacked, so there is no reason to call "ldconfig" at this
5266 For a package that is being removed, prerm is
5267 called with all the files intact, so calling ldconfig is
5268 useless. The other calls to "prerm" happen in the case of
5269 upgrade at a time when all the files of the old package
5270 are on-disk, so again calling "ldconfig" is pointless.
5274 postrm, on the other hand, is called with the "remove"
5275 argument just after the files are removed, so this is
5276 the proper time to call "ldconfig" to notify the system
5277 of the fact that the shared libraries from the package
5278 are removed. The postrm can be called at several other
5279 times. At the time of "postrm purge", "postrm
5280 abort-install", or "postrm abort-upgrade", calling
5281 "ldconfig" is useless because the shared lib files are
5282 not on-disk. However, when "postrm" is invoked with
5283 arguments "upgrade", "failed-upgrade", or "disappear", a
5284 shared lib may exist on-disk under a temporary filename.
5292 <sect id="sharedlibs-support-files">
5293 <heading>Shared library support files</heading>
5296 If your package contains files whose names do not change with
5297 each change in the library shared object version, you must not
5298 put them in the shared library package. Otherwise, several
5299 versions of the shared library cannot be installed at the same
5300 time without filename clashes, making upgrades and transitions
5301 unnecessarily difficult.
5305 It is recommended that supporting files and run-time support
5306 programs that do not need to be invoked manually by users, but
5307 are nevertheless required for the package to function, be placed
5308 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5309 preferably under <file>/usr/lib/</file><var>package-name</var>.
5310 If the program or file is architecture independent, the
5311 recommendation is for it to be placed in a subdirectory of
5312 <file>/usr/share</file> instead, preferably under
5313 <file>/usr/share/</file><var>package-name</var>. Following the
5314 <var>package-name</var> naming convention ensures that the file
5315 names change when the shared object version changes.
5319 Run-time support programs that use the shared library but are
5320 not required for the library to function or files used by the
5321 shared library that can be used by any version of the shared
5322 library package should instead be put in a separate package.
5323 This package might typically be named
5324 <package><var>libraryname</var>-tools</package>; note the
5325 absence of the <var>soversion</var> in the package name.
5329 Files and support programs only useful when compiling software
5330 against the library should be included in the development
5331 package for the library.<footnote>
5332 For example, a <file><var>package-name</var>-config</file>
5333 script or <package>pkg-config</package> configuration files.
5338 <sect id="sharedlibs-static">
5339 <heading>Static libraries</heading>
5342 The static library (<file><var>libraryname.a</var></file>)
5343 is usually provided in addition to the shared version.
5344 It is placed into the development package (see below).
5348 In some cases, it is acceptable for a library to be
5349 available in static form only; these cases include:
5351 <item>libraries for languages whose shared library support
5352 is immature or unstable</item>
5353 <item>libraries whose interfaces are in flux or under
5354 development (commonly the case when the library's
5355 major version number is zero, or where the ABI breaks
5356 across patchlevels)</item>
5357 <item>libraries which are explicitly intended to be
5358 available only in static form by their upstream
5363 <sect id="sharedlibs-dev">
5364 <heading>Development files</heading>
5367 If there are development files associated with a shared library,
5368 the source package needs to generate a binary development package
5369 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5370 or if you prefer only to support one development version at a
5371 time, <package><var>libraryname</var>-dev</package>. Installing
5372 the development package must result in installation of all the
5373 development files necessary for compiling programs against that
5374 shared library.<footnote>
5375 This wording allows the development files to be split into
5376 several packages, such as a separate architecture-independent
5377 <package><var>libraryname</var>-headers</package>, provided that
5378 the development package depends on all the required additional
5384 In case several development versions of a library exist, you may
5385 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5386 <ref id="conflicts">) to ensure that the user only installs one
5387 development version at a time (as different development versions are
5388 likely to have the same header files in them, which would cause a
5389 filename clash if both were unpacked).
5393 The development package should contain a symlink for the associated
5394 shared library without a version number. For example, the
5395 <package>libgdbm-dev</package> package should include a symlink
5396 from <file>/usr/lib/libgdbm.so</file> to
5397 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5398 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5399 <file>libgdbm.so</file> when compiling dynamically.
5403 <sect id="sharedlibs-intradeps">
5404 <heading>Dependencies between the packages of the same library</heading>
5407 Typically the development version should have an exact
5408 version dependency on the runtime library, to make sure that
5409 compilation and linking happens correctly. The
5410 <tt>${binary:Version}</tt> substitution variable can be
5411 useful for this purpose.
5413 Previously, <tt>${Source-Version}</tt> was used, but its name
5414 was confusing and it has been deprecated since dpkg 1.13.19.
5419 <sect id="sharedlibs-shlibdeps">
5420 <heading>Dependencies between the library and other packages -
5421 the <tt>shlibs</tt> system</heading>
5424 If a package contains a binary or library which links to a
5425 shared library, we must ensure that when the package is
5426 installed on the system, all of the libraries needed are
5427 also installed. This requirement led to the creation of the
5428 <tt>shlibs</tt> system, which is very simple in its design:
5429 any package which <em>provides</em> a shared library also
5430 provides information on the package dependencies required to
5431 ensure the presence of this library, and any package which
5432 <em>uses</em> a shared library uses this information to
5433 determine the dependencies it requires. The files which
5434 contain the mapping from shared libraries to the necessary
5435 dependency information are called <file>shlibs</file> files.
5439 When a package is built which contains any shared libraries, it
5440 must provide a <file>shlibs</file> file for other packages to
5441 use. When a package is built which contains any shared
5442 libraries or compiled binaries, it must run
5443 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5444 on these to determine the libraries used and hence the
5445 dependencies needed by this package.<footnote>
5447 <prgn>dpkg-shlibdeps</prgn> will use a program
5448 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
5449 the libraries directly needed by the binaries or shared
5450 libraries in the package.
5454 We say that a binary <tt>foo</tt> <em>directly</em> uses
5455 a library <tt>libbar</tt> if it is explicitly linked
5456 with that library (that is, the library is listed in the ELF
5457 <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
5458 to the link line when the binary is created). Other
5459 libraries that are needed by <tt>libbar</tt> are linked
5460 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5461 linker will load them automatically when it loads
5462 <tt>libbar</tt>. A package should depend on the libraries
5463 it directly uses, but not the libraries it indirectly uses.
5464 The dependencies for those libraries will automatically pull
5465 in the other libraries.
5469 A good example of where this helps is the following. We
5470 could update <tt>libimlib</tt> with a new version that
5471 supports a new graphics format called dgf (but retaining the
5472 same major version number) and depends on <tt>libdgf</tt>.
5473 If we used <prgn>ldd</prgn> to add dependencies for every
5474 library directly or indirectly linked with a binary, every
5475 package that uses <tt>libimlib</tt> would need to be
5476 recompiled so it would also depend on <tt>libdgf</tt> or it
5477 wouldn't run due to missing symbols. Since dependencies are
5478 only added based on ELF <tt>NEEDED</tt> attribute, packages
5479 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
5480 having the dependency on <tt>libdgf</tt> and so they would
5481 not need rebuilding.
5487 In the following sections, we will first describe where the
5488 various <tt>shlibs</tt> files are to be found, then how to
5489 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5490 file format and how to create them if your package contains a
5495 <heading>The <tt>shlibs</tt> files present on the system</heading>
5498 There are several places where <tt>shlibs</tt> files are
5499 found. The following list gives them in the order in which
5501 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5502 (The first one which gives the required information is used.)
5508 <p><file>debian/shlibs.local</file></p>
5511 This lists overrides for this package. This file should
5512 normally not be used, but may be needed temporarily in
5513 unusual situations to work around bugs in other packages,
5514 or in unusual cases where the normally declared dependency
5515 information in the installed <file>shlibs</file> file for
5516 a library cannot be used. This file overrides information
5517 obtained from any other source.
5522 <p><file>/etc/dpkg/shlibs.override</file></p>
5525 This lists global overrides. This list is normally
5526 empty. It is maintained by the local system
5532 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5535 When packages are being built,
5536 any <file>debian/shlibs</file> files are copied into the
5537 control file area of the temporary build directory and
5538 given the name <file>shlibs</file>. These files give
5539 details of any shared libraries included in the same
5541 An example may help here. Let us say that the source
5542 package <tt>foo</tt> generates two binary
5543 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
5544 When building the binary packages, the two packages are
5545 created in the directories <file>debian/libfoo2</file>
5546 and <file>debian/foo-runtime</file> respectively.
5547 (<file>debian/tmp</file> could be used instead of one of
5548 these.) Since <tt>libfoo2</tt> provides the
5549 <tt>libfoo</tt> shared library, it will require a
5550 <tt>shlibs</tt> file, which will be installed in
5551 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually to
5552 become <file>/var/lib/dpkg/info/libfoo2.shlibs</file>.
5553 When <prgn>dpkg-shlibdeps</prgn> is run on the
5554 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
5556 the <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5557 determine whether <tt>foo-prog</tt>'s library
5558 dependencies are satisfied by any of the libraries
5559 provided by <tt>libfoo2</tt>. For this reason,
5560 <prgn>dpkg-shlibdeps</prgn> must only be run once all of
5561 the individual binary packages' <tt>shlibs</tt> files
5562 have been installed into the build directory.
5568 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5571 These are the <file>shlibs</file> files corresponding to
5572 all of the packages installed on the system, and are
5573 maintained by the relevant package maintainers.
5578 <p><file>/etc/dpkg/shlibs.default</file></p>
5581 This file lists any shared libraries whose packages
5582 have failed to provide correct <file>shlibs</file> files.
5583 It was used when the <file>shlibs</file> setup was first
5584 introduced, but it is now normally empty. It is
5585 maintained by the <tt>dpkg</tt> maintainer.
5593 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5594 <file>shlibs</file> files</heading>
5598 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5599 into your <file>debian/rules</file> file. If your package
5600 contains only compiled binaries and libraries (but no scripts),
5601 you can use a command such as:
5602 <example compact="compact">
5603 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5604 debian/tmp/usr/lib/*
5606 Otherwise, you will need to explicitly list the compiled
5607 binaries and libraries.<footnote>
5608 If you are using <tt>debhelper</tt>, the
5609 <prgn>dh_shlibdeps</prgn> program will do this work for you.
5610 It will also correctly handle multi-binary packages.
5615 This command puts the dependency information into the
5616 <file>debian/substvars</file> file, which is then used by
5617 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5618 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5619 field in the control file for this to work.
5623 If you have multiple binary packages, you will need to call
5624 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5625 compiled libraries or binaries. In such a case, you will
5626 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5627 utilities to specify a different <file>substvars</file> file.
5631 If you are creating a udeb for use in the Debian Installer,
5632 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
5633 should use the dependency line of type <tt>udeb</tt> by
5634 adding the <tt>-tudeb</tt> option<footnote>
5635 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5636 will automatically add this option if it knows it is
5638 </footnote>. If there is no dependency line of
5639 type <tt>udeb</tt> in the <file>shlibs</file>
5640 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the regular
5645 For more details on <prgn>dpkg-shlibdeps</prgn>, please see
5646 <ref id="pkg-dpkg-shlibdeps"> and
5647 <manref name="dpkg-shlibdeps" section="1">.
5652 <heading>The <file>shlibs</file> File Format</heading>
5655 Each <file>shlibs</file> file has the same format. Lines
5656 beginning with <tt>#</tt> are considered to be comments and
5657 are ignored. Each line is of the form:
5658 <example compact="compact">
5659 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5664 We will explain this by reference to the example of the
5665 <tt>zlib1g</tt> package, which (at the time of writing)
5666 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5670 <var>type</var> is an optional element that indicates the type
5671 of package for which the line is valid. The only type currently
5672 in use is <tt>udeb</tt>. The colon and space after the type are
5677 <var>library-name</var> is the name of the shared library,
5678 in this case <tt>libz</tt>. (This must match the name part
5679 of the soname, see below.)
5683 <var>soname-version</var> is the version part of the soname of
5684 the library. The soname is the thing that must exactly match
5685 for the library to be recognized by the dynamic linker, and is
5687 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5688 example, <tt>libz.so.1</tt>.<footnote>
5689 This can be determined using the command
5690 <example compact="compact">
5691 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5694 The version part is the part which comes after
5695 <tt>.so.</tt>, so in our case, it is <tt>1</tt>. The soname may
5696 instead be of the form
5697 <tt><var>name</var>-<var>major-version</var>.so</tt>, such
5698 as <tt>libdb-4.8.so</tt>, in which case the name would
5699 be <tt>libdb</tt> and the version would be <tt>4.8</tt>.
5703 <var>dependencies</var> has the same syntax as a dependency
5704 field in a binary package control file. It should give
5705 details of which packages are required to satisfy a binary
5706 built against the version of the library contained in the
5707 package. See <ref id="depsyntax"> for details.
5711 In our example, if the first version of the <tt>zlib1g</tt>
5712 package which contained a minor number of at least
5713 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5714 <tt>shlibs</tt> entry for this library could say:
5715 <example compact="compact">
5716 libz 1 zlib1g (>= 1:1.1.3)
5718 The version-specific dependency is to avoid warnings from
5719 the dynamic linker about using older shared libraries with
5724 As zlib1g also provides a udeb containing the shared library,
5725 there would also be a second line:
5726 <example compact="compact">
5727 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5733 <heading>Providing a <file>shlibs</file> file</heading>
5736 If your package provides a shared library, you need to create
5737 a <file>shlibs</file> file following the format described above.
5738 It is usual to call this file <file>debian/shlibs</file> (but if
5739 you have multiple binary packages, you might want to call it
5740 <file>debian/shlibs.<var>package</var></file> instead). Then
5741 let <file>debian/rules</file> install it in the control area:
5742 <example compact="compact">
5743 install -m644 debian/shlibs debian/tmp/DEBIAN
5745 or, in the case of a multi-binary package:
5746 <example compact="compact">
5747 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5749 An alternative way of doing this is to create the
5750 <file>shlibs</file> file in the control area directly from
5751 <file>debian/rules</file> without using a <file>debian/shlibs</file>
5752 file at all,<footnote>
5753 This is what <prgn>dh_makeshlibs</prgn> in
5754 the <package>debhelper</package> suite does. If your package
5755 also has a udeb that provides a shared
5756 library, <prgn>dh_makeshlibs</prgn> can automatically generate
5757 the <tt>udeb:</tt> lines if you specify the name of the udeb
5758 with the <tt>--add-udeb</tt> option.
5760 since the <file>debian/shlibs</file> file itself is ignored by
5761 <prgn>dpkg-shlibdeps</prgn>.
5765 As <prgn>dpkg-shlibdeps</prgn> reads the
5766 <file>DEBIAN/shlibs</file> files in all of the binary packages
5767 being built from this source package, all of the
5768 <file>DEBIAN/shlibs</file> files should be installed before
5769 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5777 <chapt id="opersys"><heading>The Operating System</heading>
5780 <heading>File system hierarchy</heading>
5784 <heading>File System Structure</heading>
5787 The location of all installed files and directories must
5788 comply with the Filesystem Hierarchy Standard (FHS),
5789 version 2.3, with the exceptions noted below, and except
5790 where doing so would violate other terms of Debian
5791 Policy. The following exceptions to the FHS apply:
5796 The optional rules related to user specific
5797 configuration files for applications are stored in
5798 the user's home directory are relaxed. It is
5799 recommended that such files start with the
5800 '<tt>.</tt>' character (a "dot file"), and if an
5801 application needs to create more than one dot file
5802 then the preferred placement is in a subdirectory
5803 with a name starting with a '.' character, (a "dot
5804 directory"). In this case it is recommended the
5805 configuration files not start with the '.'
5811 The requirement for amd64 to use <file>/lib64</file>
5812 for 64 bit binaries is removed.
5817 The requirement for object files, internal binaries, and
5818 libraries, including <file>libc.so.*</file>, to be located
5819 directly under <file>/lib{,32}</file> and
5820 <file>/usr/lib{,32}</file> is amended, permitting files
5821 to instead be installed to
5822 <file>/lib/<var>triplet</var></file> and
5823 <file>/usr/lib/<var>triplet</var></file>, where
5824 <tt><var>triplet</var></tt> is the value returned by
5825 <tt>dpkg-architecture -qDEB_HOST_GNU_TYPE</tt> for the
5826 architecture of the package. Packages may <em>not</em>
5827 install files to any <var>triplet</var> path other
5828 than the one matching the architecture of that package;
5829 for instance, an <tt>Architecture: amd64</tt> package
5830 containing 32-bit x86 libraries may not install these
5831 libraries to <file>/usr/lib/i486-linux-gnu</file>.
5833 This is necessary in order to reserve the directories for
5834 use in cross-installation of library packages from other
5835 architectures, as part of the planned deployment of
5840 Applications may also use a single subdirectory under
5841 <file>/usr/lib/<var>triplet</var></file>.
5844 The execution time linker/loader, ld*, must still be made
5845 available in the existing location under /lib or /lib64
5846 since this is part of the ELF ABI for the architecture.
5851 The requirement that
5852 <file>/usr/local/share/man</file> be "synonymous"
5853 with <file>/usr/local/man</file> is relaxed to a
5858 The requirement that windowmanagers with a single
5859 configuration file call it <file>system.*wmrc</file>
5860 is removed, as is the restriction that the window
5861 manager subdirectory be named identically to the
5862 window manager name itself.
5867 The requirement that boot manager configuration
5868 files live in <file>/etc</file>, or at least are
5869 symlinked there, is relaxed to a recommendation.
5874 The following directories in the root filesystem are
5875 additionally allowed: <file>/sys</file> and
5876 <file>/selinux</file>. <footnote>These directories
5877 are used as mount points to mount virtual filesystems
5878 to get access to kernel information.</footnote>
5885 The version of this document referred here can be
5886 found in the <tt>debian-policy</tt> package or on <url
5887 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5888 name="FHS (Debian copy)"> alongside this manual (or, if
5889 you have the <package>debian-policy</package> installed,
5891 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5892 (local copy)">). The
5893 latest version, which may be a more recent version, may
5895 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5896 Specific questions about following the standard may be
5897 asked on the <tt>debian-devel</tt> mailing list, or
5898 referred to the FHS mailing list (see the
5899 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
5905 <heading>Site-specific programs</heading>
5908 As mandated by the FHS, packages must not place any
5909 files in <file>/usr/local</file>, either by putting them in
5910 the file system archive to be unpacked by <prgn>dpkg</prgn>
5911 or by manipulating them in their maintainer scripts.
5915 However, the package may create empty directories below
5916 <file>/usr/local</file> so that the system administrator knows
5917 where to place site-specific files. These are not
5918 directories <em>in</em> <file>/usr/local</file>, but are
5919 children of directories in <file>/usr/local</file>. These
5920 directories (<file>/usr/local/*/dir/</file>)
5921 should be removed on package removal if they are
5926 Note that this applies only to
5927 directories <em>below</em> <file>/usr/local</file>,
5928 not <em>in</em> <file>/usr/local</file>. Packages must
5929 not create sub-directories in the
5930 directory <file>/usr/local</file> itself, except those
5931 listed in FHS, section 4.5. However, you may create
5932 directories below them as you wish. You must not remove
5933 any of the directories listed in 4.5, even if you created
5938 Since <file>/usr/local</file> can be mounted read-only from a
5939 remote server, these directories must be created and
5940 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
5941 maintainer scripts and not be included in the
5942 <file>.deb</file> archive. These scripts must not fail if
5943 either of these operations fail.
5947 For example, the <tt>emacsen-common</tt> package could
5948 contain something like
5949 <example compact="compact">
5950 if [ ! -e /usr/local/share/emacs ]
5952 if mkdir /usr/local/share/emacs 2>/dev/null
5954 chown root:staff /usr/local/share/emacs
5955 chmod 2775 /usr/local/share/emacs
5959 in its <prgn>postinst</prgn> script, and
5960 <example compact="compact">
5961 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
5962 rmdir /usr/local/share/emacs 2>/dev/null || true
5964 in the <prgn>prerm</prgn> script. (Note that this form is
5965 used to ensure that if the script is interrupted, the
5966 directory <file>/usr/local/share/emacs</file> will still be
5971 If you do create a directory in <file>/usr/local</file> for
5972 local additions to a package, you should ensure that
5973 settings in <file>/usr/local</file> take precedence over the
5974 equivalents in <file>/usr</file>.
5978 However, because <file>/usr/local</file> and its contents are
5979 for exclusive use of the local administrator, a package
5980 must not rely on the presence or absence of files or
5981 directories in <file>/usr/local</file> for normal operation.
5985 The <file>/usr/local</file> directory itself and all the
5986 subdirectories created by the package should (by default) have
5987 permissions 2775 (group-writable and set-group-id) and be
5988 owned by <tt>root:staff</tt>.
5993 <heading>The system-wide mail directory</heading>
5995 The system-wide mail directory
5996 is <file>/var/mail</file>. This directory is part of the
5997 base system and should not be owned by any particular mail
5998 agents. The use of the old
5999 location <file>/var/spool/mail</file> is deprecated, even
6000 though the spool may still be physically located there.
6006 <heading>Users and groups</heading>
6009 <heading>Introduction</heading>
6011 The Debian system can be configured to use either plain or
6016 Some user ids (UIDs) and group ids (GIDs) are reserved
6017 globally for use by certain packages. Because some
6018 packages need to include files which are owned by these
6019 users or groups, or need the ids compiled into binaries,
6020 these ids must be used on any Debian system only for the
6021 purpose for which they are allocated. This is a serious
6022 restriction, and we should avoid getting in the way of
6023 local administration policies. In particular, many sites
6024 allocate users and/or local system groups starting at 100.
6028 Apart from this we should have dynamically allocated ids,
6029 which should by default be arranged in some sensible
6030 order, but the behavior should be configurable.
6034 Packages other than <tt>base-passwd</tt> must not modify
6035 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
6036 <file>/etc/group</file> or <file>/etc/gshadow</file>.
6041 <heading>UID and GID classes</heading>
6043 The UID and GID numbers are divided into classes as
6049 Globally allocated by the Debian project, the same
6050 on every Debian system. These ids will appear in
6051 the <file>passwd</file> and <file>group</file> files of all
6052 Debian systems, new ids in this range being added
6053 automatically as the <tt>base-passwd</tt> package is
6058 Packages which need a single statically allocated
6059 uid or gid should use one of these; their
6060 maintainers should ask the <tt>base-passwd</tt>
6068 Dynamically allocated system users and groups.
6069 Packages which need a user or group, but can have
6070 this user or group allocated dynamically and
6071 differently on each system, should use <tt>adduser
6072 --system</tt> to create the group and/or user.
6073 <prgn>adduser</prgn> will check for the existence of
6074 the user or group, and if necessary choose an unused
6075 id based on the ranges specified in
6076 <file>adduser.conf</file>.
6080 <tag>1000-59999:</tag>
6083 Dynamically allocated user accounts. By default
6084 <prgn>adduser</prgn> will choose UIDs and GIDs for
6085 user accounts in this range, though
6086 <file>adduser.conf</file> may be used to modify this
6091 <tag>60000-64999:</tag>
6094 Globally allocated by the Debian project, but only
6095 created on demand. The ids are allocated centrally
6096 and statically, but the actual accounts are only
6097 created on users' systems on demand.
6101 These ids are for packages which are obscure or
6102 which require many statically-allocated ids. These
6103 packages should check for and create the accounts in
6104 <file>/etc/passwd</file> or <file>/etc/group</file> (using
6105 <prgn>adduser</prgn> if it has this facility) if
6106 necessary. Packages which are likely to require
6107 further allocations should have a "hole" left after
6108 them in the allocation, to give them room to
6113 <tag>65000-65533:</tag>
6121 User <tt>nobody</tt>. The corresponding gid refers
6122 to the group <tt>nogroup</tt>.
6129 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
6130 not</em> be used, because it is the error return
6139 <sect id="sysvinit">
6140 <heading>System run levels and <file>init.d</file> scripts</heading>
6142 <sect1 id="/etc/init.d">
6143 <heading>Introduction</heading>
6146 The <file>/etc/init.d</file> directory contains the scripts
6147 executed by <prgn>init</prgn> at boot time and when the
6148 init state (or "runlevel") is changed (see <manref
6149 name="init" section="8">).
6153 There are at least two different, yet functionally
6154 equivalent, ways of handling these scripts. For the sake
6155 of simplicity, this document describes only the symbolic
6156 link method. However, it must not be assumed by maintainer
6157 scripts that this method is being used, and any automated
6158 manipulation of the various runlevel behaviors by
6159 maintainer scripts must be performed using
6160 <prgn>update-rc.d</prgn> as described below and not by
6161 manually installing or removing symlinks. For information
6162 on the implementation details of the other method,
6163 implemented in the <tt>file-rc</tt> package, please refer
6164 to the documentation of that package.
6168 These scripts are referenced by symbolic links in the
6169 <file>/etc/rc<var>n</var>.d</file> directories. When changing
6170 runlevels, <prgn>init</prgn> looks in the directory
6171 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
6172 execute, where <tt><var>n</var></tt> is the runlevel that
6173 is being changed to, or <tt>S</tt> for the boot-up
6178 The names of the links all have the form
6179 <file>S<var>mm</var><var>script</var></file> or
6180 <file>K<var>mm</var><var>script</var></file> where
6181 <var>mm</var> is a two-digit number and <var>script</var>
6182 is the name of the script (this should be the same as the
6183 name of the actual script in <file>/etc/init.d</file>).
6187 When <prgn>init</prgn> changes runlevel first the targets
6188 of the links whose names start with a <tt>K</tt> are
6189 executed, each with the single argument <tt>stop</tt>,
6190 followed by the scripts prefixed with an <tt>S</tt>, each
6191 with the single argument <tt>start</tt>. (The links are
6192 those in the <file>/etc/rc<var>n</var>.d</file> directory
6193 corresponding to the new runlevel.) The <tt>K</tt> links
6194 are responsible for killing services and the <tt>S</tt>
6195 link for starting services upon entering the runlevel.
6199 For example, if we are changing from runlevel 2 to
6200 runlevel 3, init will first execute all of the <tt>K</tt>
6201 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
6202 all of the <tt>S</tt> prefixed scripts in that directory.
6203 The links starting with <tt>K</tt> will cause the
6204 referred-to file to be executed with an argument of
6205 <tt>stop</tt>, and the <tt>S</tt> links with an argument
6210 The two-digit number <var>mm</var> is used to determine
6211 the order in which to run the scripts: low-numbered links
6212 have their scripts run first. For example, the
6213 <tt>K20</tt> scripts will be executed before the
6214 <tt>K30</tt> scripts. This is used when a certain service
6215 must be started before another. For example, the name
6216 server <prgn>bind</prgn> might need to be started before
6217 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
6218 can set up its access lists. In this case, the script
6219 that starts <prgn>bind</prgn> would have a lower number
6220 than the script that starts <prgn>inn</prgn> so that it
6222 <example compact="compact">
6229 The two runlevels 0 (halt) and 6 (reboot) are slightly
6230 different. In these runlevels, the links with an
6231 <tt>S</tt> prefix are still called after those with a
6232 <tt>K</tt> prefix, but they too are called with the single
6233 argument <tt>stop</tt>.
6237 <sect1 id="writing-init">
6238 <heading>Writing the scripts</heading>
6241 Packages that include daemons for system services should
6242 place scripts in <file>/etc/init.d</file> to start or stop
6243 services at boot time or during a change of runlevel.
6244 These scripts should be named
6245 <file>/etc/init.d/<var>package</var></file>, and they should
6246 accept one argument, saying what to do:
6249 <tag><tt>start</tt></tag>
6250 <item>start the service,</item>
6252 <tag><tt>stop</tt></tag>
6253 <item>stop the service,</item>
6255 <tag><tt>restart</tt></tag>
6256 <item>stop and restart the service if it's already running,
6257 otherwise start the service</item>
6259 <tag><tt>reload</tt></tag>
6260 <item><p>cause the configuration of the service to be
6261 reloaded without actually stopping and restarting
6264 <tag><tt>force-reload</tt></tag>
6265 <item>cause the configuration to be reloaded if the
6266 service supports this, otherwise restart the
6270 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
6271 <tt>force-reload</tt> options should be supported by all
6272 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
6277 The <file>init.d</file> scripts must ensure that they will
6278 behave sensibly (i.e., returning success and not starting
6279 multiple copies of a service) if invoked with <tt>start</tt>
6280 when the service is already running, or with <tt>stop</tt>
6281 when it isn't, and that they don't kill unfortunately-named
6282 user processes. The best way to achieve this is usually to
6283 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
6288 Be careful of using <tt>set -e</tt> in <file>init.d</file>
6289 scripts. Writing correct <file>init.d</file> scripts requires
6290 accepting various error exit statuses when daemons are already
6291 running or already stopped without aborting
6292 the <file>init.d</file> script, and common <file>init.d</file>
6293 function libraries are not safe to call with <tt>set -e</tt>
6295 <tt>/lib/lsb/init-functions</tt>, which assists in writing
6296 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
6297 in effect and echoing status messages to the console fails,
6299 </footnote>. For <tt>init.d</tt> scripts, it's often easier
6300 to not use <tt>set -e</tt> and instead check the result of
6301 each command separately.
6305 If a service reloads its configuration automatically (as
6306 in the case of <prgn>cron</prgn>, for example), the
6307 <tt>reload</tt> option of the <file>init.d</file> script
6308 should behave as if the configuration has been reloaded
6313 The <file>/etc/init.d</file> scripts must be treated as
6314 configuration files, either (if they are present in the
6315 package, that is, in the .deb file) by marking them as
6316 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6317 by managing them correctly in the maintainer scripts (see
6318 <ref id="config-files">). This is important since we want
6319 to give the local system administrator the chance to adapt
6320 the scripts to the local system, e.g., to disable a
6321 service without de-installing the package, or to specify
6322 some special command line options when starting a service,
6323 while making sure their changes aren't lost during the next
6328 These scripts should not fail obscurely when the
6329 configuration files remain but the package has been
6330 removed, as configuration files remain on the system after
6331 the package has been removed. Only when <prgn>dpkg</prgn>
6332 is executed with the <tt>--purge</tt> option will
6333 configuration files be removed. In particular, as the
6334 <file>/etc/init.d/<var>package</var></file> script itself is
6335 usually a <tt>conffile</tt>, it will remain on the system
6336 if the package is removed but not purged. Therefore, you
6337 should include a <tt>test</tt> statement at the top of the
6339 <example compact="compact">
6340 test -f <var>program-executed-later-in-script</var> || exit 0
6345 Often there are some variables in the <file>init.d</file>
6346 scripts whose values control the behavior of the scripts,
6347 and which a system administrator is likely to want to
6348 change. As the scripts themselves are frequently
6349 <tt>conffile</tt>s, modifying them requires that the
6350 administrator merge in their changes each time the package
6351 is upgraded and the <tt>conffile</tt> changes. To ease
6352 the burden on the system administrator, such configurable
6353 values should not be placed directly in the script.
6354 Instead, they should be placed in a file in
6355 <file>/etc/default</file>, which typically will have the same
6356 base name as the <file>init.d</file> script. This extra file
6357 should be sourced by the script when the script runs. It
6358 must contain only variable settings and comments in SUSv3
6359 <prgn>sh</prgn> format. It may either be a
6360 <tt>conffile</tt> or a configuration file maintained by
6361 the package maintainer scripts. See <ref id="config-files">
6366 To ensure that vital configurable values are always
6367 available, the <file>init.d</file> script should set default
6368 values for each of the shell variables it uses, either
6369 before sourcing the <file>/etc/default/</file> file or
6370 afterwards using something like the <tt>:
6371 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6372 script must behave sensibly and not fail if the
6373 <file>/etc/default</file> file is deleted.
6377 <file>/var/run</file> and <file>/var/lock</file> may be mounted
6378 as temporary filesystems<footnote>
6379 For example, using the <tt>RAMRUN</tt> and <tt>RAMLOCK</tt>
6380 options in <file>/etc/default/rcS</file>.
6381 </footnote>, so the <file>init.d</file> scripts must handle this
6382 correctly. This will typically amount to creating any required
6383 subdirectories dynamically when the <file>init.d</file> script
6384 is run, rather than including them in the package and relying on
6385 <prgn>dpkg</prgn> to create them.
6390 <heading>Interfacing with the initscript system</heading>
6393 Maintainers should use the abstraction layer provided by
6394 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6395 programs to deal with initscripts in their packages'
6396 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6397 and <prgn>postrm</prgn>.
6401 Directly managing the /etc/rc?.d links and directly
6402 invoking the <file>/etc/init.d/</file> initscripts should
6403 be done only by packages providing the initscript
6404 subsystem (such as <prgn>sysv-rc</prgn> and
6405 <prgn>file-rc</prgn>).
6409 <heading>Managing the links</heading>
6412 The program <prgn>update-rc.d</prgn> is provided for
6413 package maintainers to arrange for the proper creation and
6414 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6415 or their functional equivalent if another method is being
6416 used. This may be used by maintainers in their packages'
6417 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6421 You must not include any <file>/etc/rc<var>n</var>.d</file>
6422 symbolic links in the actual archive or manually create or
6423 remove the symbolic links in maintainer scripts; you must
6424 use the <prgn>update-rc.d</prgn> program instead. (The
6425 former will fail if an alternative method of maintaining
6426 runlevel information is being used.) You must not include
6427 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6428 in the archive either. (Only the <tt>sysvinit</tt>
6433 By default <prgn>update-rc.d</prgn> will start services in
6434 each of the multi-user state runlevels (2, 3, 4, and 5)
6435 and stop them in the halt runlevel (0), the single-user
6436 runlevel (1) and the reboot runlevel (6). The system
6437 administrator will have the opportunity to customize
6438 runlevels by simply adding, moving, or removing the
6439 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6440 symbolic links are being used, or by modifying
6441 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6446 To get the default behavior for your package, put in your
6447 <prgn>postinst</prgn> script
6448 <example compact="compact">
6449 update-rc.d <var>package</var> defaults
6451 and in your <prgn>postrm</prgn>
6452 <example compact="compact">
6453 if [ "$1" = purge ]; then
6454 update-rc.d <var>package</var> remove
6456 </example>. Note that if your package changes runlevels
6457 or priority, you may have to remove and recreate the links,
6458 since otherwise the old links may persist. Refer to the
6459 documentation of <prgn>update-rc.d</prgn>.
6463 This will use a default sequence number of 20. If it does
6464 not matter when or in which order the <file>init.d</file>
6465 script is run, use this default. If it does, then you
6466 should talk to the maintainer of the <prgn>sysvinit</prgn>
6467 package or post to <tt>debian-devel</tt>, and they will
6468 help you choose a number.
6472 For more information about using <tt>update-rc.d</tt>,
6473 please consult its man page <manref name="update-rc.d"
6479 <heading>Running initscripts</heading>
6481 The program <prgn>invoke-rc.d</prgn> is provided to make
6482 it easier for package maintainers to properly invoke an
6483 initscript, obeying runlevel and other locally-defined
6484 constraints that might limit a package's right to start,
6485 stop and otherwise manage services. This program may be
6486 used by maintainers in their packages' scripts.
6490 The package maintainer scripts must use
6491 <prgn>invoke-rc.d</prgn> to invoke the
6492 <file>/etc/init.d/*</file> initscripts, instead of
6493 calling them directly.
6497 By default, <prgn>invoke-rc.d</prgn> will pass any
6498 action requests (start, stop, reload, restart...) to the
6499 <file>/etc/init.d</file> script, filtering out requests
6500 to start or restart a service out of its intended
6505 Most packages will simply need to change:
6506 <example compact="compact">/etc/init.d/<package>
6507 <action></example> in their <prgn>postinst</prgn>
6508 and <prgn>prerm</prgn> scripts to:
6509 <example compact="compact">
6510 if which invoke-rc.d >/dev/null 2>&1; then
6511 invoke-rc.d <var>package</var> <action>
6513 /etc/init.d/<var>package</var> <action>
6519 A package should register its initscript services using
6520 <prgn>update-rc.d</prgn> before it tries to invoke them
6521 using <prgn>invoke-rc.d</prgn>. Invocation of
6522 unregistered services may fail.
6526 For more information about using
6527 <prgn>invoke-rc.d</prgn>, please consult its man page
6528 <manref name="invoke-rc.d" section="8">.
6534 <heading>Boot-time initialization</heading>
6537 There used to be another directory, <file>/etc/rc.boot</file>,
6538 which contained scripts which were run once per machine
6539 boot. This has been deprecated in favour of links from
6540 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6541 described in <ref id="/etc/init.d">. Packages must not
6542 place files in <file>/etc/rc.boot</file>.
6547 <heading>Example</heading>
6550 An example on which you can base your
6551 <file>/etc/init.d</file> scripts is found in
6552 <file>/etc/init.d/skeleton</file>.
6559 <heading>Console messages from <file>init.d</file> scripts</heading>
6562 This section describes the formats to be used for messages
6563 written to standard output by the <file>/etc/init.d</file>
6564 scripts. The intent is to improve the consistency of
6565 Debian's startup and shutdown look and feel. For this
6566 reason, please look very carefully at the details. We want
6567 the messages to have the same format in terms of wording,
6568 spaces, punctuation and case of letters.
6572 Here is a list of overall rules that should be used for
6573 messages generated by <file>/etc/init.d</file> scripts.
6579 The message should fit in one line (fewer than 80
6580 characters), start with a capital letter and end with
6581 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6585 If the script is performing some time consuming task in
6586 the background (not merely starting or stopping a
6587 program, for instance), an ellipsis (three dots:
6588 <tt>...</tt>) should be output to the screen, with no
6589 leading or tailing whitespace or line feeds.
6593 The messages should appear as if the computer is telling
6594 the user what it is doing (politely :-), but should not
6595 mention "it" directly. For example, instead of:
6596 <example compact="compact">
6597 I'm starting network daemons: nfsd mountd.
6599 the message should say
6600 <example compact="compact">
6601 Starting network daemons: nfsd mountd.
6608 <tt>init.d</tt> script should use the following standard
6609 message formats for the situations enumerated below.
6615 <p>When daemons are started</p>
6618 If the script starts one or more daemons, the output
6619 should look like this (a single line, no leading
6621 <example compact="compact">
6622 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6624 The <var>description</var> should describe the
6625 subsystem the daemon or set of daemons are part of,
6626 while <var>daemon-1</var> up to <var>daemon-n</var>
6627 denote each daemon's name (typically the file name of
6632 For example, the output of <file>/etc/init.d/lpd</file>
6634 <example compact="compact">
6635 Starting printer spooler: lpd.
6640 This can be achieved by saying
6641 <example compact="compact">
6642 echo -n "Starting printer spooler: lpd"
6643 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6646 in the script. If there are more than one daemon to
6647 start, the output should look like this:
6648 <example compact="compact">
6649 echo -n "Starting remote file system services:"
6650 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6651 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6652 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6655 This makes it possible for the user to see what is
6656 happening and when the final daemon has been started.
6657 Care should be taken in the placement of white spaces:
6658 in the example above the system administrators can
6659 easily comment out a line if they don't want to start
6660 a specific daemon, while the displayed message still
6666 <p>When a system parameter is being set</p>
6669 If you have to set up different system parameters
6670 during the system boot, you should use this format:
6671 <example compact="compact">
6672 Setting <var>parameter</var> to "<var>value</var>".
6677 You can use a statement such as the following to get
6679 <example compact="compact">
6680 echo "Setting DNS domainname to \"$domainname\"."
6685 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
6686 for the left and right quotation marks. A grave accent
6687 (<tt>`</tt>) is not a quote character; neither is an
6688 apostrophe (<tt>'</tt>).
6693 <p>When a daemon is stopped or restarted</p>
6696 When you stop or restart a daemon, you should issue a
6697 message identical to the startup message, except that
6698 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6699 or <tt>Restarting</tt> respectively.
6703 For example, stopping the printer daemon will look like
6705 <example compact="compact">
6706 Stopping printer spooler: lpd.
6712 <p>When something is executed</p>
6715 There are several examples where you have to run a
6716 program at system startup or shutdown to perform a
6717 specific task, for example, setting the system's clock
6718 using <prgn>netdate</prgn> or killing all processes
6719 when the system shuts down. Your message should look
6721 <example compact="compact">
6722 Doing something very useful...done.
6724 You should print the <tt>done.</tt> immediately after
6725 the job has been completed, so that the user is
6726 informed why they have to wait. You can get this
6728 <example compact="compact">
6729 echo -n "Doing something very useful..."
6738 <p>When the configuration is reloaded</p>
6741 When a daemon is forced to reload its configuration
6742 files you should use the following format:
6743 <example compact="compact">
6744 Reloading <var>description</var> configuration...done.
6746 where <var>description</var> is the same as in the
6747 daemon starting message.
6755 <heading>Cron jobs</heading>
6758 Packages must not modify the configuration file
6759 <file>/etc/crontab</file>, and they must not modify the files in
6760 <file>/var/spool/cron/crontabs</file>.</p>
6763 If a package wants to install a job that has to be executed
6764 via cron, it should place a file with the name of the
6765 package in one or more of the following directories:
6766 <example compact="compact">
6772 As these directory names imply, the files within them are
6773 executed on an hourly, daily, weekly, or monthly basis,
6774 respectively. The exact times are listed in
6775 <file>/etc/crontab</file>.</p>
6778 All files installed in any of these directories must be
6779 scripts (e.g., shell scripts or Perl scripts) so that they
6780 can easily be modified by the local system administrator.
6781 In addition, they must be treated as configuration files.
6785 If a certain job has to be executed at some other frequency or
6786 at a specific time, the package should install a file
6787 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6788 same syntax as <file>/etc/crontab</file> and is processed by
6789 <prgn>cron</prgn> automatically. The file must also be
6790 treated as a configuration file. (Note that entries in the
6791 <file>/etc/cron.d</file> directory are not handled by
6792 <prgn>anacron</prgn>. Thus, you should only use this
6793 directory for jobs which may be skipped if the system is not
6796 Unlike <file>crontab</file> files described in the IEEE Std
6797 1003.1-2008 (POSIX.1) available from
6798 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
6799 name="The Open Group">, the files in
6800 <file>/etc/cron.d</file> and the file
6801 <file>/etc/crontab</file> have seven fields; namely:
6803 <item>Minute [0,59]</item>
6804 <item>Hour [0,23]</item>
6805 <item>Day of the month [1,31]</item>
6806 <item>Month of the year [1,12]</item>
6807 <item>Day of the week ([0,6] with 0=Sunday)</item>
6808 <item>Username</item>
6809 <item>Command to be run</item>
6811 Ranges of numbers are allowed. Ranges are two numbers
6812 separated with a hyphen. The specified range is inclusive.
6813 Lists are allowed. A list is a set of numbers (or ranges)
6814 separated by commas. Step values can be used in conjunction
6819 The scripts or <tt>crontab</tt> entries in these directories should
6820 check if all necessary programs are installed before they
6821 try to execute them. Otherwise, problems will arise when a
6822 package was removed but not purged since configuration files
6823 are kept on the system in this situation.
6827 Any <tt>cron</tt> daemon must provide
6828 <file>/usr/bin/crontab</file> and support normal
6829 <tt>crontab</tt> entries as specified in POSIX. The daemon
6830 must also support names for days and months, ranges, and
6831 step values. It has to support <file>/etc/crontab</file>,
6832 and correctly execute the scripts in
6833 <file>/etc/cron.d</file>. The daemon must also correctly
6835 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
6840 <heading>Menus</heading>
6843 The Debian <tt>menu</tt> package provides a standard
6844 interface between packages providing applications and
6845 <em>menu programs</em> (either X window managers or
6846 text-based menu programs such as <prgn>pdmenu</prgn>).
6850 All packages that provide applications that need not be
6851 passed any special command line arguments for normal
6852 operation should register a menu entry for those
6853 applications, so that users of the <tt>menu</tt> package
6854 will automatically get menu entries in their window
6855 managers, as well in shells like <tt>pdmenu</tt>.
6859 Menu entries should follow the current menu policy.
6863 The menu policy can be found in the <tt>menu-policy</tt>
6864 files in the <tt>debian-policy</tt> package.
6865 It is also available from the Debian web mirrors at
6866 <tt><url name="/doc/packaging-manuals/menu-policy/"
6867 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6871 Please also refer to the <em>Debian Menu System</em>
6872 documentation that comes with the <package>menu</package>
6873 package for information about how to register your
6879 <heading>Multimedia handlers</heading>
6882 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6883 is a mechanism for encoding files and data streams and
6884 providing meta-information about them, in particular their
6885 type (e.g. audio or video) and format (e.g. PNG, HTML,
6890 Registration of MIME type handlers allows programs like mail
6891 user agents and web browsers to invoke these handlers to
6892 view, edit or display MIME types they don't support directly.
6896 Packages which provide the ability to view/show/play,
6897 compose, edit or print MIME types should register themselves
6898 as such following the current MIME support policy.
6902 The MIME support policy can be found in the <tt>mime-policy</tt>
6903 files in the <tt>debian-policy</tt> package.
6904 It is also available from the Debian web mirrors at
6905 <tt><url name="/doc/packaging-manuals/mime-policy/"
6906 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
6912 <heading>Keyboard configuration</heading>
6915 To achieve a consistent keyboard configuration so that all
6916 applications interpret a keyboard event the same way, all
6917 programs in the Debian distribution must be configured to
6918 comply with the following guidelines.
6922 The following keys must have the specified interpretations:
6925 <tag><tt><--</tt></tag>
6926 <item>delete the character to the left of the cursor</item>
6928 <tag><tt>Delete</tt></tag>
6929 <item>delete the character to the right of the cursor</item>
6931 <tag><tt>Control+H</tt></tag>
6932 <item>emacs: the help prefix</item>
6935 The interpretation of any keyboard events should be
6936 independent of the terminal that is used, be it a virtual
6937 console, an X terminal emulator, an rlogin/telnet session,
6942 The following list explains how the different programs
6943 should be set up to achieve this:
6949 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
6953 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
6957 X translations are set up to make
6958 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
6959 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
6960 is the vt220 escape code for the "delete character"
6961 key). This must be done by loading the X resources
6962 using <prgn>xrdb</prgn> on all local X displays, not
6963 using the application defaults, so that the
6964 translation resources used correspond to the
6965 <prgn>xmodmap</prgn> settings.
6969 The Linux console is configured to make
6970 <tt><--</tt> generate DEL, and <tt>Delete</tt>
6971 generate <tt>ESC [ 3 ~</tt>.
6975 X applications are configured so that <tt><</tt>
6976 deletes left, and <tt>Delete</tt> deletes right. Motif
6977 applications already work like this.
6981 Terminals should have <tt>stty erase ^?</tt> .
6985 The <tt>xterm</tt> terminfo entry should have <tt>ESC
6986 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
6987 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
6991 Emacs is programmed to map <tt>KB_Backspace</tt> or
6992 the <tt>stty erase</tt> character to
6993 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
6994 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
6995 <tt>^H</tt> to <tt>help</tt> as always.
6999 Other applications use the <tt>stty erase</tt>
7000 character and <tt>kdch1</tt> for the two delete keys,
7001 with ASCII DEL being "delete previous character" and
7002 <tt>kdch1</tt> being "delete character under
7010 This will solve the problem except for the following
7017 Some terminals have a <tt><--</tt> key that cannot
7018 be made to produce anything except <tt>^H</tt>. On
7019 these terminals Emacs help will be unavailable on
7020 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
7021 character takes precedence in Emacs, and has been set
7022 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
7023 available) can be used instead.
7027 Some operating systems use <tt>^H</tt> for <tt>stty
7028 erase</tt>. However, modern telnet versions and all
7029 rlogin versions propagate <tt>stty</tt> settings, and
7030 almost all UNIX versions honour <tt>stty erase</tt>.
7031 Where the <tt>stty</tt> settings are not propagated
7032 correctly, things can be made to work by using
7033 <tt>stty</tt> manually.
7037 Some systems (including previous Debian versions) use
7038 <prgn>xmodmap</prgn> to arrange for both
7039 <tt><--</tt> and <tt>Delete</tt> to generate
7040 <tt>KB_Delete</tt>. We can change the behavior of
7041 their X clients using the same X resources that we use
7042 to do it for our own clients, or configure our clients
7043 using their resources when things are the other way
7044 around. On displays configured like this
7045 <tt>Delete</tt> will not work, but <tt><--</tt>
7050 Some operating systems have different <tt>kdch1</tt>
7051 settings in their <tt>terminfo</tt> database for
7052 <tt>xterm</tt> and others. On these systems the
7053 <tt>Delete</tt> key will not work correctly when you
7054 log in from a system conforming to our policy, but
7055 <tt><--</tt> will.
7062 <heading>Environment variables</heading>
7065 A program must not depend on environment variables to get
7066 reasonable defaults. (That's because these environment
7067 variables would have to be set in a system-wide
7068 configuration file like <file>/etc/profile</file>, which is not
7069 supported by all shells.)
7073 If a program usually depends on environment variables for its
7074 configuration, the program should be changed to fall back to
7075 a reasonable default configuration if these environment
7076 variables are not present. If this cannot be done easily
7077 (e.g., if the source code of a non-free program is not
7078 available), the program must be replaced by a small
7079 "wrapper" shell script which sets the environment variables
7080 if they are not already defined, and calls the original program.
7084 Here is an example of a wrapper script for this purpose:
7086 <example compact="compact">
7088 BAR=${BAR:-/var/lib/fubar}
7090 exec /usr/lib/foo/foo "$@"
7095 Furthermore, as <file>/etc/profile</file> is a configuration
7096 file of the <prgn>base-files</prgn> package, other packages must
7097 not put any environment variables or other commands into that
7102 <sect id="doc-base">
7103 <heading>Registering Documents using doc-base</heading>
7106 The <package>doc-base</package> package implements a
7107 flexible mechanism for handling and presenting
7108 documentation. The recommended practice is for every Debian
7109 package that provides online documentation (other than just
7110 manual pages) to register these documents with
7111 <package>doc-base</package> by installing a
7112 <package>doc-base</package> control file via the
7113 <prgn/install-docs/ script at installation time and
7114 de-register the manuals again when the package is removed.
7117 Please refer to the documentation that comes with the
7118 <package>doc-base</package> package for information and
7127 <heading>Files</heading>
7129 <sect id="binaries">
7130 <heading>Binaries</heading>
7133 Two different packages must not install programs with
7134 different functionality but with the same filenames. (The
7135 case of two programs having the same functionality but
7136 different implementations is handled via "alternatives" or
7137 the "Conflicts" mechanism. See <ref id="maintscripts"> and
7138 <ref id="conflicts"> respectively.) If this case happens,
7139 one of the programs must be renamed. The maintainers should
7140 report this to the <tt>debian-devel</tt> mailing list and
7141 try to find a consensus about which program will have to be
7142 renamed. If a consensus cannot be reached, <em>both</em>
7143 programs must be renamed.
7147 By default, when a package is being built, any binaries
7148 created should include debugging information, as well as
7149 being compiled with optimization. You should also turn on
7150 as many reasonable compilation warnings as possible; this
7151 makes life easier for porters, who can then look at build
7152 logs for possible problems. For the C programming language,
7153 this means the following compilation parameters should be
7155 <example compact="compact">
7157 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
7159 INSTALL = install -s # (or use strip on the files in debian/tmp)
7164 Note that by default all installed binaries should be stripped,
7165 either by using the <tt>-s</tt> flag to
7166 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
7167 the binaries after they have been copied into
7168 <file>debian/tmp</file> but before the tree is made into a
7173 Although binaries in the build tree should be compiled with
7174 debugging information by default, it can often be difficult to
7175 debug programs if they are also subjected to compiler
7176 optimization. For this reason, it is recommended to support the
7177 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
7178 (see <ref id="debianrules-options">). This variable can contain
7179 several flags to change how a package is compiled and built.
7183 It is up to the package maintainer to decide what
7184 compilation options are best for the package. Certain
7185 binaries (such as computationally-intensive programs) will
7186 function better with certain flags (<tt>-O3</tt>, for
7187 example); feel free to use them. Please use good judgment
7188 here. Don't use flags for the sake of it; only use them
7189 if there is good reason to do so. Feel free to override
7190 the upstream author's ideas about which compilation
7191 options are best: they are often inappropriate for our
7197 <sect id="libraries">
7198 <heading>Libraries</heading>
7201 If the package is <strong>architecture: any</strong>, then
7202 the shared library compilation and linking flags must have
7203 <tt>-fPIC</tt>, or the package shall not build on some of
7204 the supported architectures<footnote>
7206 If you are using GCC, <tt>-fPIC</tt> produces code with
7207 relocatable position independent code, which is required for
7208 most architectures to create a shared library, with i386 and
7209 perhaps some others where non position independent code is
7210 permitted in a shared library.
7213 Position independent code may have a performance penalty,
7214 especially on <tt>i386</tt>. However, in most cases the
7215 speed penalty must be measured against the memory wasted on
7216 the few architectures where non position independent code is
7219 </footnote>. Any exception to this rule must be discussed on
7220 the mailing list <em>debian-devel@lists.debian.org</em>, and
7221 a rough consensus obtained. The reasons for not compiling
7222 with <tt>-fPIC</tt> flag must be recorded in the file
7223 <tt>README.Debian</tt>, and care must be taken to either
7224 restrict the architecture or arrange for <tt>-fPIC</tt> to
7225 be used on architectures where it is required.<footnote>
7227 Some of the reasons why this might be required is if the
7228 library contains hand crafted assembly code that is not
7229 relocatable, the speed penalty is excessive for compute
7230 intensive libs, and similar reasons.
7235 As to the static libraries, the common case is not to have
7236 relocatable code, since there is no benefit, unless in specific
7237 cases; therefore the static version must not be compiled
7238 with the <tt>-fPIC</tt> flag. Any exception to this rule
7239 should be discussed on the mailing list
7240 <em>debian-devel@lists.debian.org</em>, and the reasons for
7241 compiling with the <tt>-fPIC</tt> flag must be recorded in
7242 the file <tt>README.Debian</tt>. <footnote>
7244 Some of the reasons for linking static libraries with
7245 the <tt>-fPIC</tt> flag are if, for example, one needs a
7246 Perl API for a library that is under rapid development,
7247 and has an unstable API, so shared libraries are
7248 pointless at this phase of the library's development. In
7249 that case, since Perl needs a library with relocatable
7250 code, it may make sense to create a static library with
7251 relocatable code. Another reason cited is if you are
7252 distilling various libraries into a common shared
7253 library, like <tt>mklibs</tt> does in the Debian
7259 In other words, if both a shared and a static library is
7260 being built, each source unit (<tt>*.c</tt>, for example,
7261 for C files) will need to be compiled twice, for the normal
7265 You must specify the gcc option <tt>-D_REENTRANT</tt>
7266 when building a library (either static or shared) to make
7267 the library compatible with LinuxThreads.
7271 Although not enforced by the build tools, shared libraries
7272 must be linked against all libraries that they use symbols from
7273 in the same way that binaries are. This ensures the correct
7274 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
7275 system and guarantees that all libraries can be safely opened
7276 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
7277 option <tt>-Wl,-z,defs</tt> when building a shared library.
7278 Since this option enforces symbol resolution at build time,
7279 a missing library reference will be caught early as a fatal
7284 All installed shared libraries should be stripped with
7285 <example compact="compact">
7286 strip --strip-unneeded <var>your-lib</var>
7288 (The option <tt>--strip-unneeded</tt> makes
7289 <prgn>strip</prgn> remove only the symbols which aren't
7290 needed for relocation processing.) Shared libraries can
7291 function perfectly well when stripped, since the symbols for
7292 dynamic linking are in a separate part of the ELF object
7294 You might also want to use the options
7295 <tt>--remove-section=.comment</tt> and
7296 <tt>--remove-section=.note</tt> on both shared libraries
7297 and executables, and <tt>--strip-debug</tt> on static
7303 Note that under some circumstances it may be useful to
7304 install a shared library unstripped, for example when
7305 building a separate package to support debugging.
7309 Shared object files (often <file>.so</file> files) that are not
7310 public libraries, that is, they are not meant to be linked
7311 to by third party executables (binaries of other packages),
7312 should be installed in subdirectories of the
7313 <file>/usr/lib</file> directory. Such files are exempt from the
7314 rules that govern ordinary shared libraries, except that
7315 they must not be installed executable and should be
7317 A common example are the so-called "plug-ins",
7318 internal shared objects that are dynamically loaded by
7319 programs using <manref name="dlopen" section="3">.
7324 Packages that use <prgn>libtool</prgn> to create and install
7325 their shared libraries install a file containing additional
7326 metadata (ending in <file>.la</file>) alongside the library.
7327 For public libraries intended for use by other packages, these
7328 files normally should not be included in the Debian package,
7329 since the information they include is not necessary to link with
7330 the shared library on Debian and can add unnecessary additional
7331 dependencies to other programs or libraries.<footnote>
7332 These files store, among other things, all libraries on which
7333 that shared library depends. Unfortunately, if
7334 the <file>.la</file> file is present and contains that
7335 dependency information, using <prgn>libtool</prgn> when
7336 linking against that library will cause the resulting program
7337 or library to be linked against those dependencies as well,
7338 even if this is unnecessary. This can create unneeded
7339 dependencies on shared library packages that would otherwise
7340 be hidden behind the library ABI, and can make library
7341 transitions to new SONAMEs unnecessarily complicated and
7342 difficult to manage.
7344 If the <file>.la</file> file is required for that library (if,
7345 for instance, it's loaded via <tt>libltdl</tt> in a way that
7346 requires that meta-information), the <tt>dependency_libs</tt>
7347 setting in the <file>.la</file> file should normally be set to
7348 the empty string. If the shared library development package has
7349 historically included the <file>.la</file>, it must be retained
7350 in the development package (with <tt>dependency_libs</tt>
7351 emptied) until all libraries that depend on it have removed or
7352 emptied <tt>dependency_libs</tt> in their <file>.la</file>
7353 files to prevent linking with those other libraries
7354 using <prgn>libtool</prgn> from failing.
7358 If the <file>.la</file> must be included, it should be included
7359 in the development (<tt>-dev</tt>) package, unless the library
7360 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
7361 library. If it is intended for use with <tt>libltdl</tt>,
7362 the <file>.la</file> files must go in the run-time library
7367 These requirements for handling of <file>.la</file> files do not
7368 apply to loadable modules or libraries not installed in
7369 directories searched by default by the dynamic linker. Packages
7370 installing loadable modules will frequently need to install
7371 the <file>.la</file> files alongside the modules so that they
7372 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
7373 does not need to be modified for libraries or modules that are
7374 not installed in directories searched by the dynamic linker by
7375 default and not intended for use by other packages.
7379 You must make sure that you use only released versions of
7380 shared libraries to build your packages; otherwise other
7381 users will not be able to run your binaries
7382 properly. Producing source packages that depend on
7383 unreleased compilers is also usually a bad
7390 <heading>Shared libraries</heading>
7392 This section has moved to <ref id="sharedlibs">.
7398 <heading>Scripts</heading>
7401 All command scripts, including the package maintainer
7402 scripts inside the package and used by <prgn>dpkg</prgn>,
7403 should have a <tt>#!</tt> line naming the shell to be used
7408 In the case of Perl scripts this should be
7409 <tt>#!/usr/bin/perl</tt>.
7413 When scripts are installed into a directory in the system
7414 PATH, the script name should not include an extension such
7415 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7416 language currently used to implement it.
7419 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
7420 <file>init.d</file> scripts should almost certainly start
7421 with <tt>set -e</tt> so that errors are detected.
7422 <file>init.d</file> scripts are something of a special case, due
7423 to how frequently they need to call commands that are allowed to
7424 fail, and it may instead be easier to check the exit status of
7425 commands directly. See <ref id="writing-init"> for more
7426 information about writing <file>init.d</file> scripts.
7429 Every script should use <tt>set -e</tt> or check the exit status
7430 of <em>every</em> command.
7433 Scripts may assume that <file>/bin/sh</file> implements the
7434 SUSv3 Shell Command Language<footnote>
7435 Single UNIX Specification, version 3, which is also IEEE
7436 1003.1-2004 (POSIX), and is available on the World Wide Web
7437 from <url id="http://www.unix.org/version3/online.html"
7438 name="The Open Group"> after free
7439 registration.</footnote>
7440 plus the following additional features not mandated by
7442 These features are in widespread use in the Linux community
7443 and are implemented in all of bash, dash, and ksh, the most
7444 common shells users may wish to use as <file>/bin/sh</file>.
7447 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7448 must not generate a newline.</item>
7449 <item><tt>test</tt>, if implemented as a shell built-in, must
7450 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7452 <item><tt>local</tt> to create a scoped variable must be
7453 supported, including listing multiple variables in a single
7454 local command and assigning a value to a variable at the
7455 same time as localizing it. <tt>local</tt> may or
7456 may not preserve the variable value from an outer scope if
7457 no assignment is present. Uses such as:
7461 # ... use a, b, c, d ...
7464 must be supported and must set the value of <tt>c</tt> to
7468 If a shell script requires non-SUSv3 features from the shell
7469 interpreter other than those listed above, the appropriate shell
7470 must be specified in the first line of the script (e.g.,
7471 <tt>#!/bin/bash</tt>) and the package must depend on the package
7472 providing the shell (unless the shell package is marked
7473 "Essential", as in the case of <prgn>bash</prgn>).
7477 You may wish to restrict your script to SUSv3 features plus the
7478 above set when possible so that it may use <file>/bin/sh</file>
7479 as its interpreter. If your script works with <prgn>dash</prgn>
7480 (originally called <prgn>ash</prgn>), it probably complies with
7481 the above requirements, but if you are in doubt, use
7482 <file>/bin/bash</file>.
7486 Perl scripts should check for errors when making any
7487 system calls, including <tt>open</tt>, <tt>print</tt>,
7488 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7492 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7493 scripting languages. See <em>Csh Programming Considered
7494 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7495 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7496 If an upstream package comes with <prgn>csh</prgn> scripts
7497 then you must make sure that they start with
7498 <tt>#!/bin/csh</tt> and make your package depend on the
7499 <prgn>c-shell</prgn> virtual package.
7503 Any scripts which create files in world-writeable
7504 directories (e.g., in <file>/tmp</file>) must use a
7505 mechanism which will fail atomically if a file with the same
7506 name already exists.
7510 The Debian base system provides the <prgn>tempfile</prgn>
7511 and <prgn>mktemp</prgn> utilities for use by scripts for
7518 <heading>Symbolic links</heading>
7521 In general, symbolic links within a top-level directory
7522 should be relative, and symbolic links pointing from one
7523 top-level directory into another should be absolute. (A
7524 top-level directory is a sub-directory of the root
7525 directory <file>/</file>.)
7529 In addition, symbolic links should be specified as short as
7530 possible, i.e., link targets like <file>foo/../bar</file> are
7535 Note that when creating a relative link using
7536 <prgn>ln</prgn> it is not necessary for the target of the
7537 link to exist relative to the working directory you're
7538 running <prgn>ln</prgn> from, nor is it necessary to change
7539 directory to the directory where the link is to be made.
7540 Simply include the string that should appear as the target
7541 of the link (this will be a pathname relative to the
7542 directory in which the link resides) as the first argument
7547 For example, in your <prgn>Makefile</prgn> or
7548 <file>debian/rules</file>, you can do things like:
7549 <example compact="compact">
7550 ln -fs gcc $(prefix)/bin/cc
7551 ln -fs gcc debian/tmp/usr/bin/cc
7552 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7553 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7558 A symbolic link pointing to a compressed file should always
7559 have the same file extension as the referenced file. (For
7560 example, if a file <file>foo.gz</file> is referenced by a
7561 symbolic link, the filename of the link has to end with
7562 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7567 <heading>Device files</heading>
7570 Packages must not include device files or named pipes in the
7575 If a package needs any special device files that are not
7576 included in the base system, it must call
7577 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7578 after notifying the user<footnote>
7579 This notification could be done via a (low-priority)
7580 debconf message, or an echo (printf) statement.
7585 Packages must not remove any device files in the
7586 <prgn>postrm</prgn> or any other script. This is left to the
7587 system administrator.
7591 Debian uses the serial devices
7592 <file>/dev/ttyS*</file>. Programs using the old
7593 <file>/dev/cu*</file> devices should be changed to use
7594 <file>/dev/ttyS*</file>.
7598 Named pipes needed by the package must be created in
7599 the <prgn>postinst</prgn> script<footnote>
7600 It's better to use <prgn>mkfifo</prgn> rather
7601 than <prgn>mknod</prgn> to create named pipes so that
7602 automated checks for packages incorrectly creating device
7603 files with <prgn>mknod</prgn> won't have false positives.
7604 </footnote> and removed in
7605 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
7610 <sect id="config-files">
7611 <heading>Configuration files</heading>
7614 <heading>Definitions</heading>
7618 <tag>configuration file</tag>
7620 A file that affects the operation of a program, or
7621 provides site- or host-specific information, or
7622 otherwise customizes the behavior of a program.
7623 Typically, configuration files are intended to be
7624 modified by the system administrator (if needed or
7625 desired) to conform to local policy or to provide
7626 more useful site-specific behavior.
7629 <tag><tt>conffile</tt></tag>
7631 A file listed in a package's <tt>conffiles</tt>
7632 file, and is treated specially by <prgn>dpkg</prgn>
7633 (see <ref id="configdetails">).
7639 The distinction between these two is important; they are
7640 not interchangeable concepts. Almost all
7641 <tt>conffile</tt>s are configuration files, but many
7642 configuration files are not <tt>conffiles</tt>.
7646 As noted elsewhere, <file>/etc/init.d</file> scripts,
7647 <file>/etc/default</file> files, scripts installed in
7648 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7649 configuration installed in <file>/etc/cron.d</file> must be
7650 treated as configuration files. In general, any script that
7651 embeds configuration information is de-facto a configuration
7652 file and should be treated as such.
7657 <heading>Location</heading>
7660 Any configuration files created or used by your package
7661 must reside in <file>/etc</file>. If there are several,
7662 consider creating a subdirectory of <file>/etc</file>
7663 named after your package.
7667 If your package creates or uses configuration files
7668 outside of <file>/etc</file>, and it is not feasible to modify
7669 the package to use <file>/etc</file> directly, put the files
7670 in <file>/etc</file> and create symbolic links to those files
7671 from the location that the package requires.
7676 <heading>Behavior</heading>
7679 Configuration file handling must conform to the following
7681 <list compact="compact">
7683 local changes must be preserved during a package
7687 configuration files must be preserved when the
7688 package is removed, and only deleted when the
7692 Obsolete configuration files without local changes may be
7693 removed by the package during upgrade.
7697 The easy way to achieve this behavior is to make the
7698 configuration file a <tt>conffile</tt>. This is
7699 appropriate only if it is possible to distribute a default
7700 version that will work for most installations, although
7701 some system administrators may choose to modify it. This
7702 implies that the default version will be part of the
7703 package distribution, and must not be modified by the
7704 maintainer scripts during installation (or at any other
7709 In order to ensure that local changes are preserved
7710 correctly, no package may contain or make hard links to
7711 conffiles.<footnote>
7712 Rationale: There are two problems with hard links.
7713 The first is that some editors break the link while
7714 editing one of the files, so that the two files may
7715 unwittingly become unlinked and different. The second
7716 is that <prgn>dpkg</prgn> might break the hard link
7717 while upgrading <tt>conffile</tt>s.
7722 The other way to do it is via the maintainer scripts. In
7723 this case, the configuration file must not be listed as a
7724 <tt>conffile</tt> and must not be part of the package
7725 distribution. If the existence of a file is required for
7726 the package to be sensibly configured it is the
7727 responsibility of the package maintainer to provide
7728 maintainer scripts which correctly create, update and
7729 maintain the file and remove it on purge. (See <ref
7730 id="maintainerscripts"> for more information.) These
7731 scripts must be idempotent (i.e., must work correctly if
7732 <prgn>dpkg</prgn> needs to re-run them due to errors
7733 during installation or removal), must cope with all the
7734 variety of ways <prgn>dpkg</prgn> can call maintainer
7735 scripts, must not overwrite or otherwise mangle the user's
7736 configuration without asking, must not ask unnecessary
7737 questions (particularly during upgrades), and must
7738 otherwise be good citizens.
7742 The scripts are not required to configure every possible
7743 option for the package, but only those necessary to get
7744 the package running on a given system. Ideally the
7745 sysadmin should not have to do any configuration other
7746 than that done (semi-)automatically by the
7747 <prgn>postinst</prgn> script.
7751 A common practice is to create a script called
7752 <file><var>package</var>-configure</file> and have the
7753 package's <prgn>postinst</prgn> call it if and only if the
7754 configuration file does not already exist. In certain
7755 cases it is useful for there to be an example or template
7756 file which the maintainer scripts use. Such files should
7757 be in <file>/usr/share/<var>package</var></file> or
7758 <file>/usr/lib/<var>package</var></file> (depending on whether
7759 they are architecture-independent or not). There should
7760 be symbolic links to them from
7761 <file>/usr/share/doc/<var>package</var>/examples</file> if
7762 they are examples, and should be perfectly ordinary
7763 <prgn>dpkg</prgn>-handled files (<em>not</em>
7764 configuration files).
7768 These two styles of configuration file handling must
7769 not be mixed, for that way lies madness:
7770 <prgn>dpkg</prgn> will ask about overwriting the file
7771 every time the package is upgraded.
7776 <heading>Sharing configuration files</heading>
7779 Packages which specify the same file as a
7780 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7781 with each other. (This is an instance of the general rule
7782 about not sharing files. Note that neither alternatives
7783 nor diversions are likely to be appropriate in this case;
7784 in particular, <prgn>dpkg</prgn> does not handle diverted
7785 <tt>conffile</tt>s well.)
7789 The maintainer scripts must not alter a <tt>conffile</tt>
7790 of <em>any</em> package, including the one the scripts
7795 If two or more packages use the same configuration file
7796 and it is reasonable for both to be installed at the same
7797 time, one of these packages must be defined as
7798 <em>owner</em> of the configuration file, i.e., it will be
7799 the package which handles that file as a configuration
7800 file. Other packages that use the configuration file must
7801 depend on the owning package if they require the
7802 configuration file to operate. If the other package will
7803 use the configuration file if present, but is capable of
7804 operating without it, no dependency need be declared.
7808 If it is desirable for two or more related packages to
7809 share a configuration file <em>and</em> for all of the
7810 related packages to be able to modify that configuration
7811 file, then the following should be done:
7812 <enumlist compact="compact">
7814 One of the related packages (the "owning" package)
7815 will manage the configuration file with maintainer
7816 scripts as described in the previous section.
7819 The owning package should also provide a program
7820 that the other packages may use to modify the
7824 The related packages must use the provided program
7825 to make any desired modifications to the
7826 configuration file. They should either depend on
7827 the core package to guarantee that the configuration
7828 modifier program is available or accept gracefully
7829 that they cannot modify the configuration file if it
7830 is not. (This is in addition to the fact that the
7831 configuration file may not even be present in the
7838 Sometimes it's appropriate to create a new package which
7839 provides the basic infrastructure for the other packages
7840 and which manages the shared configuration files. (The
7841 <tt>sgml-base</tt> package is a good example.)
7846 <heading>User configuration files ("dotfiles")</heading>
7849 The files in <file>/etc/skel</file> will automatically be
7850 copied into new user accounts by <prgn>adduser</prgn>.
7851 No other program should reference the files in
7852 <file>/etc/skel</file>.
7856 Therefore, if a program needs a dotfile to exist in
7857 advance in <file>$HOME</file> to work sensibly, that dotfile
7858 should be installed in <file>/etc/skel</file> and treated as a
7863 However, programs that require dotfiles in order to
7864 operate sensibly are a bad thing, unless they do create
7865 the dotfiles themselves automatically.
7869 Furthermore, programs should be configured by the Debian
7870 default installation to behave as closely to the upstream
7871 default behavior as possible.
7875 Therefore, if a program in a Debian package needs to be
7876 configured in some way in order to operate sensibly, that
7877 should be done using a site-wide configuration file placed
7878 in <file>/etc</file>. Only if the program doesn't support a
7879 site-wide default configuration and the package maintainer
7880 doesn't have time to add it may a default per-user file be
7881 placed in <file>/etc/skel</file>.
7885 <file>/etc/skel</file> should be as empty as we can make it.
7886 This is particularly true because there is no easy (or
7887 necessarily desirable) mechanism for ensuring that the
7888 appropriate dotfiles are copied into the accounts of
7889 existing users when a package is installed.
7895 <heading>Log files</heading>
7897 Log files should usually be named
7898 <file>/var/log/<var>package</var>.log</file>. If you have many
7899 log files, or need a separate directory for permission
7900 reasons (<file>/var/log</file> is writable only by
7901 <file>root</file>), you should usually create a directory named
7902 <file>/var/log/<var>package</var></file> and place your log
7907 Log files must be rotated occasionally so that they don't
7908 grow indefinitely; the best way to do this is to drop a log
7909 rotation configuration file into the directory
7910 <file>/etc/logrotate.d</file> and use the facilities provided by
7911 logrotate.<footnote>
7913 The traditional approach to log files has been to set up
7914 <em>ad hoc</em> log rotation schemes using simple shell
7915 scripts and cron. While this approach is highly
7916 customizable, it requires quite a lot of sysadmin work.
7917 Even though the original Debian system helped a little
7918 by automatically installing a system which can be used
7919 as a template, this was deemed not enough.
7923 The use of <prgn>logrotate</prgn>, a program developed
7924 by Red Hat, is better, as it centralizes log management.
7925 It has both a configuration file
7926 (<file>/etc/logrotate.conf</file>) and a directory where
7927 packages can drop their individual log rotation
7928 configurations (<file>/etc/logrotate.d</file>).
7931 Here is a good example for a logrotate config
7932 file (for more information see <manref name="logrotate"
7934 <example compact="compact">
7935 /var/log/foo/*.log {
7940 /etc/init.d/foo force-reload
7944 This rotates all files under <file>/var/log/foo</file>, saves 12
7945 compressed generations, and forces the daemon to reload its
7946 configuration information after the log rotation.
7950 Log files should be removed when the package is
7951 purged (but not when it is only removed). This should be
7952 done by the <prgn>postrm</prgn> script when it is called
7953 with the argument <tt>purge</tt> (see <ref
7954 id="removedetails">).
7959 <heading>Permissions and owners</heading>
7962 The rules in this section are guidelines for general use.
7963 If necessary you may deviate from the details below.
7964 However, if you do so you must make sure that what is done
7965 is secure and you should try to be as consistent as possible
7966 with the rest of the system. You should probably also
7967 discuss it on <prgn>debian-devel</prgn> first.
7971 Files should be owned by <tt>root:root</tt>, and made
7972 writable only by the owner and universally readable (and
7973 executable, if appropriate), that is mode 644 or 755.
7977 Directories should be mode 755 or (for group-writability)
7978 mode 2775. The ownership of the directory should be
7979 consistent with its mode: if a directory is mode 2775, it
7980 should be owned by the group that needs write access to
7983 When a package is upgraded, and the owner or permissions
7984 of a file included in the package has changed, dpkg
7985 arranges for the ownership and permissions to be
7986 correctly set upon installation. However, this does not
7987 extend to directories; the permissions and ownership of
7988 directories already on the system does not change on
7989 install or upgrade of packages. This makes sense, since
7990 otherwise common directories like <tt>/usr</tt> would
7991 always be in flux. To correctly change permissions of a
7992 directory the package owns, explicit action is required,
7993 usually in the <tt>postinst</tt> script. Care must be
7994 taken to handle downgrades as well, in that case.
8001 Setuid and setgid executables should be mode 4755 or 2755
8002 respectively, and owned by the appropriate user or group.
8003 They should not be made unreadable (modes like 4711 or
8004 2711 or even 4111); doing so achieves no extra security,
8005 because anyone can find the binary in the freely available
8006 Debian package; it is merely inconvenient. For the same
8007 reason you should not restrict read or execute permissions
8008 on non-set-id executables.
8012 Some setuid programs need to be restricted to particular
8013 sets of users, using file permissions. In this case they
8014 should be owned by the uid to which they are set-id, and by
8015 the group which should be allowed to execute them. They
8016 should have mode 4754; again there is no point in making
8017 them unreadable to those users who must not be allowed to
8022 It is possible to arrange that the system administrator can
8023 reconfigure the package to correspond to their local
8024 security policy by changing the permissions on a binary:
8025 they can do this by using <prgn>dpkg-statoverride</prgn>, as
8026 described below.<footnote>
8027 Ordinary files installed by <prgn>dpkg</prgn> (as
8028 opposed to <tt>conffile</tt>s and other similar objects)
8029 normally have their permissions reset to the distributed
8030 permissions when the package is reinstalled. However,
8031 the use of <prgn>dpkg-statoverride</prgn> overrides this
8034 Another method you should consider is to create a group for
8035 people allowed to use the program(s) and make any setuid
8036 executables executable only by that group.
8040 If you need to create a new user or group for your package
8041 there are two possibilities. Firstly, you may need to
8042 make some files in the binary package be owned by this
8043 user or group, or you may need to compile the user or
8044 group id (rather than just the name) into the binary
8045 (though this latter should be avoided if possible, as in
8046 this case you need a statically allocated id).</p>
8049 If you need a statically allocated id, you must ask for a
8050 user or group id from the <tt>base-passwd</tt> maintainer,
8051 and must not release the package until you have been
8052 allocated one. Once you have been allocated one you must
8053 either make the package depend on a version of the
8054 <tt>base-passwd</tt> package with the id present in
8055 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
8056 your package to create the user or group itself with the
8057 correct id (using <tt>adduser</tt>) in its
8058 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
8059 the <prgn>postinst</prgn> is to be preferred if it is
8060 possible, otherwise a pre-dependency will be needed on the
8061 <tt>adduser</tt> package.)
8065 On the other hand, the program might be able to determine
8066 the uid or gid from the user or group name at runtime, so
8067 that a dynamically allocated id can be used. In this case
8068 you should choose an appropriate user or group name,
8069 discussing this on <prgn>debian-devel</prgn> and checking
8070 with the <package/base-passwd/ maintainer that it is unique and that
8071 they do not wish you to use a statically allocated id
8072 instead. When this has been checked you must arrange for
8073 your package to create the user or group if necessary using
8074 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
8075 <prgn>postinst</prgn> script (again, the latter is to be
8076 preferred if it is possible).
8080 Note that changing the numeric value of an id associated
8081 with a name is very difficult, and involves searching the
8082 file system for all appropriate files. You need to think
8083 carefully whether a static or dynamic id is required, since
8084 changing your mind later will cause problems.
8087 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
8089 This section is not intended as policy, but as a
8090 description of the use of <prgn>dpkg-statoverride</prgn>.
8094 If a system administrator wishes to have a file (or
8095 directory or other such thing) installed with owner and
8096 permissions different from those in the distributed Debian
8097 package, they can use the <prgn>dpkg-statoverride</prgn>
8098 program to instruct <prgn>dpkg</prgn> to use the different
8099 settings every time the file is installed. Thus the
8100 package maintainer should distribute the files with their
8101 normal permissions, and leave it for the system
8102 administrator to make any desired changes. For example, a
8103 daemon which is normally required to be setuid root, but
8104 in certain situations could be used without being setuid,
8105 should be installed setuid in the <tt>.deb</tt>. Then the
8106 local system administrator can change this if they wish.
8107 If there are two standard ways of doing it, the package
8108 maintainer can use <tt>debconf</tt> to find out the
8109 preference, and call <prgn>dpkg-statoverride</prgn> in the
8110 maintainer script if necessary to accommodate the system
8111 administrator's choice. Care must be taken during
8112 upgrades to not override an existing setting.
8116 Given the above, <prgn>dpkg-statoverride</prgn> is
8117 essentially a tool for system administrators and would not
8118 normally be needed in the maintainer scripts. There is
8119 one type of situation, though, where calls to
8120 <prgn>dpkg-statoverride</prgn> would be needed in the
8121 maintainer scripts, and that involves packages which use
8122 dynamically allocated user or group ids. In such a
8123 situation, something like the following idiom can be very
8124 helpful in the package's <prgn>postinst</prgn>, where
8125 <tt>sysuser</tt> is a dynamically allocated id:
8127 for i in /usr/bin/foo /usr/sbin/bar
8129 # only do something when no setting exists
8130 if ! dpkg-statoverride --list $i >/dev/null 2>&1
8132 #include: debconf processing, question about foo and bar
8133 if [ "$RET" = "true" ] ; then
8134 dpkg-statoverride --update --add sysuser root 4755 $i
8139 The corresponding code to remove the override when the package
8142 for i in /usr/bin/foo /usr/sbin/bar
8144 if dpkg-statoverride --list $i >/dev/null 2>&1
8146 dpkg-statoverride --remove $i
8156 <chapt id="customized-programs">
8157 <heading>Customized programs</heading>
8159 <sect id="arch-spec">
8160 <heading>Architecture specification strings</heading>
8163 If a program needs to specify an <em>architecture specification
8164 string</em> in some place, it should select one of the strings
8165 provided by <tt>dpkg-architecture -L</tt>. The strings are in
8166 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
8167 part is sometimes elided, as when the OS is Linux.
8171 Note that we don't want to use
8172 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
8173 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
8174 since this would make our programs incompatible with other
8175 Linux distributions. We also don't use something like
8176 <tt><var>arch</var>-unknown-linux</tt>, since the
8177 <tt>unknown</tt> does not look very good.
8180 <sect1 id="arch-wildcard-spec">
8181 <heading>Architecture wildcards</heading>
8184 A package may specify an architecture wildcard. Architecture
8185 wildcards are in the format <tt>any</tt> (which matches every
8186 architecture), <tt><var>os</var></tt>-any, or
8187 any-<tt><var>cpu</var></tt>. <footnote>
8188 Internally, the package system normalizes the GNU triplets
8189 and the Debian arches into Debian arch triplets (which are
8190 kind of inverted GNU triplets), with the first component of
8191 the triplet representing the libc and ABI in use, and then
8192 does matching against those triplets. However, such
8193 triplets are an internal implementation detail that should
8194 not be used by packages directly. The libc and ABI portion
8195 is handled internally by the package system based on
8196 the <var>os</var> and <var>cpu</var>.
8203 <heading>Daemons</heading>
8206 The configuration files <file>/etc/services</file>,
8207 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
8208 by the <prgn>netbase</prgn> package and must not be modified
8213 If a package requires a new entry in one of these files, the
8214 maintainer should get in contact with the
8215 <prgn>netbase</prgn> maintainer, who will add the entries
8216 and release a new version of the <prgn>netbase</prgn>
8221 The configuration file <file>/etc/inetd.conf</file> must not be
8222 modified by the package's scripts except via the
8223 <prgn>update-inetd</prgn> script or the
8224 <file>DebianNet.pm</file> Perl module. See their documentation
8225 for details on how to add entries.
8229 If a package wants to install an example entry into
8230 <file>/etc/inetd.conf</file>, the entry must be preceded with
8231 exactly one hash character (<tt>#</tt>). Such lines are
8232 treated as "commented out by user" by the
8233 <prgn>update-inetd</prgn> script and are not changed or
8234 activated during package updates.
8239 <heading>Using pseudo-ttys and modifying wtmp, utmp and
8243 Some programs need to create pseudo-ttys. This should be done
8244 using Unix98 ptys if the C library supports it. The resulting
8245 program must not be installed setuid root, unless that
8246 is required for other functionality.
8250 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
8251 <file>/var/log/lastlog</file> must be installed writable by
8252 group <tt>utmp</tt>. Programs which need to modify those
8253 files must be installed setgid <tt>utmp</tt>.
8258 <heading>Editors and pagers</heading>
8261 Some programs have the ability to launch an editor or pager
8262 program to edit or display a text document. Since there are
8263 lots of different editors and pagers available in the Debian
8264 distribution, the system administrator and each user should
8265 have the possibility to choose their preferred editor and
8270 In addition, every program should choose a good default
8271 editor/pager if none is selected by the user or system
8276 Thus, every program that launches an editor or pager must
8277 use the EDITOR or PAGER environment variable to determine
8278 the editor or pager the user wishes to use. If these
8279 variables are not set, the programs <file>/usr/bin/editor</file>
8280 and <file>/usr/bin/pager</file> should be used, respectively.
8284 These two files are managed through the <prgn>dpkg</prgn>
8285 "alternatives" mechanism. Thus every package providing an
8286 editor or pager must call the
8287 <prgn>update-alternatives</prgn> script to register these
8292 If it is very hard to adapt a program to make use of the
8293 EDITOR or PAGER variables, that program may be configured to
8294 use <file>/usr/bin/sensible-editor</file> and
8295 <file>/usr/bin/sensible-pager</file> as the editor or pager
8296 program respectively. These are two scripts provided in the
8297 <package>sensible-utils</package> package that check the EDITOR
8298 and PAGER variables and launch the appropriate program, and fall
8299 back to <file>/usr/bin/editor</file>
8300 and <file>/usr/bin/pager</file> if the variable is not set.
8304 A program may also use the VISUAL environment variable to
8305 determine the user's choice of editor. If it exists, it
8306 should take precedence over EDITOR. This is in fact what
8307 <file>/usr/bin/sensible-editor</file> does.
8311 It is not required for a package to depend on
8312 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
8313 package to provide such virtual packages.<footnote>
8314 The Debian base system already provides an editor and a
8320 <sect id="web-appl">
8321 <heading>Web servers and applications</heading>
8324 This section describes the locations and URLs that should
8325 be used by all web servers and web applications in the
8332 Cgi-bin executable files are installed in the
8334 <example compact="compact">
8335 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
8337 and should be referred to as
8338 <example compact="compact">
8339 http://localhost/cgi-bin/<var>cgi-bin-name</var>
8345 <p>Access to HTML documents</p>
8348 HTML documents for a package are stored in
8349 <file>/usr/share/doc/<var>package</var></file>
8350 and can be referred to as
8351 <example compact="compact">
8352 http://localhost/doc/<var>package</var>/<var>filename</var>
8357 The web server should restrict access to the document
8358 tree so that only clients on the same host can read
8359 the documents. If the web server does not support such
8360 access controls, then it should not provide access at
8361 all, or ask about providing access during installation.
8366 <p>Access to images</p>
8368 It is recommended that images for a package be stored
8369 in <tt>/usr/share/images/<var>package</var></tt> and
8370 may be referred to through an alias <tt>/images/</tt>
8373 http://localhost/images/<package>/<filename>
8380 <p>Web Document Root</p>
8383 Web Applications should try to avoid storing files in
8384 the Web Document Root. Instead they should use the
8385 /usr/share/doc/<var>package</var> directory for
8386 documents and register the Web Application via the
8387 <package>doc-base</package> package. If access to the
8388 web document root is unavoidable then use
8389 <example compact="compact">
8392 as the Document Root. This might be just a symbolic
8393 link to the location where the system administrator
8394 has put the real document root.
8397 <item><p>Providing httpd and/or httpd-cgi</p>
8399 All web servers should provide the virtual package
8400 <tt>httpd</tt>. If a web server has CGI support it should
8401 provide <tt>httpd-cgi</tt> additionally.
8404 All web applications which do not contain CGI scripts should
8405 depend on <tt>httpd</tt>, all those web applications which
8406 <tt>do</tt> contain CGI scripts, should depend on
8414 <sect id="mail-transport-agents">
8415 <heading>Mail transport, delivery and user agents</heading>
8418 Debian packages which process electronic mail, whether mail
8419 user agents (MUAs) or mail transport agents (MTAs), must
8420 ensure that they are compatible with the configuration
8421 decisions below. Failure to do this may result in lost
8422 mail, broken <tt>From:</tt> lines, and other serious brain
8427 The mail spool is <file>/var/mail</file> and the interface to
8428 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8429 the FHS). On older systems, the mail spool may be
8430 physically located in <file>/var/spool/mail</file>, but all
8431 access to the mail spool should be via the
8432 <file>/var/mail</file> symlink. The mail spool is part of the
8433 base system and not part of the MTA package.
8437 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8438 programs (such as IMAP daemons) must lock the mailbox in an
8439 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8440 be combined with dot locking. To avoid deadlocks, a program
8441 should use <tt>fcntl()</tt> first and dot locking after
8442 this, or alternatively implement the two locking methods in
8443 a non blocking way<footnote>
8444 If it is not possible to establish both locks, the
8445 system shouldn't wait for the second lock to be
8446 established, but remove the first lock, wait a (random)
8447 time, and start over locking again.
8448 </footnote>. Using the functions <tt>maillock</tt> and
8449 <tt>mailunlock</tt> provided by the
8450 <tt>liblockfile*</tt><footnote>
8451 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8452 to use these functions.
8453 </footnote> packages is the recommended way to realize this.
8457 Mailboxes are generally either mode 600 and owned by
8458 <var>user</var> or mode 660 and owned by
8459 <tt><var>user</var>:mail</tt><footnote>
8460 There are two traditional permission schemes for mail spools:
8461 mode 600 with all mail delivery done by processes running as
8462 the destination user, or mode 660 and owned by group mail with
8463 mail delivery done by a process running as a system user in
8464 group mail. Historically, Debian required mode 660 mail
8465 spools to enable the latter model, but that model has become
8466 increasingly uncommon and the principle of least privilege
8467 indicates that mail systems that use the first model should
8468 use permissions of 600. If delivery to programs is permitted,
8469 it's easier to keep the mail system secure if the delivery
8470 agent runs as the destination user. Debian Policy therefore
8471 permits either scheme.
8472 </footnote>. The local system administrator may choose a
8473 different permission scheme; packages should not make
8474 assumptions about the permission and ownership of mailboxes
8475 unless required (such as when creating a new mailbox). A MUA
8476 may remove a mailbox (unless it has nonstandard permissions) in
8477 which case the MTA or another MUA must recreate it if needed.
8481 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8482 be setgid mail to do the locking mentioned above (and
8483 must obviously avoid accessing other users' mailboxes
8484 using this privilege).</p>
8487 <file>/etc/aliases</file> is the source file for the system mail
8488 aliases (e.g., postmaster, usenet, etc.), it is the one
8489 which the sysadmin and <prgn>postinst</prgn> scripts may
8490 edit. After <file>/etc/aliases</file> is edited the program or
8491 human editing it must call <prgn>newaliases</prgn>. All MTA
8492 packages must come with a <prgn>newaliases</prgn> program,
8493 even if it does nothing, but older MTA packages did not do
8494 this so programs should not fail if <prgn>newaliases</prgn>
8495 cannot be found. Note that because of this, all MTA
8496 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8497 <tt>Replaces: mail-transport-agent</tt> control file
8502 The convention of writing <tt>forward to
8503 <var>address</var></tt> in the mailbox itself is not
8504 supported. Use a <tt>.forward</tt> file instead.</p>
8507 The <prgn>rmail</prgn> program used by UUCP
8508 for incoming mail should be <file>/usr/sbin/rmail</file>.
8509 Likewise, <prgn>rsmtp</prgn>, for receiving
8510 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8514 If your package needs to know what hostname to use on (for
8515 example) outgoing news and mail messages which are generated
8516 locally, you should use the file <file>/etc/mailname</file>. It
8517 will contain the portion after the username and <tt>@</tt>
8518 (at) sign for email addresses of users on the machine
8519 (followed by a newline).
8523 Such a package should check for the existence of this file
8524 when it is being configured. If it exists, it should be
8525 used without comment, although an MTA's configuration script
8526 may wish to prompt the user even if it finds that this file
8527 exists. If the file does not exist, the package should
8528 prompt the user for the value (preferably using
8529 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8530 as well as using it in the package's configuration. The
8531 prompt should make it clear that the name will not just be
8532 used by that package. For example, in this situation the
8533 <tt>inn</tt> package could say something like:
8534 <example compact="compact">
8535 Please enter the "mail name" of your system. This is the
8536 hostname portion of the address to be shown on outgoing
8537 news and mail messages. The default is
8538 <var>syshostname</var>, your system's host name. Mail
8539 name ["<var>syshostname</var>"]:
8541 where <var>syshostname</var> is the output of <tt>hostname
8547 <heading>News system configuration</heading>
8550 All the configuration files related to the NNTP (news)
8551 servers and clients should be located under
8552 <file>/etc/news</file>.</p>
8555 There are some configuration issues that apply to a number
8556 of news clients and server packages on the machine. These
8560 <tag><file>/etc/news/organization</file></tag>
8562 A string which should appear as the
8563 organization header for all messages posted
8564 by NNTP clients on the machine
8567 <tag><file>/etc/news/server</file></tag>
8569 Contains the FQDN of the upstream NNTP
8570 server, or localhost if the local machine is
8575 Other global files may be added as required for cross-package news
8582 <heading>Programs for the X Window System</heading>
8585 <heading>Providing X support and package priorities</heading>
8588 Programs that can be configured with support for the X
8589 Window System must be configured to do so and must declare
8590 any package dependencies necessary to satisfy their
8591 runtime requirements when using the X Window System. If
8592 such a package is of higher priority than the X packages
8593 on which it depends, it is required that either the
8594 X-specific components be split into a separate package, or
8595 that an alternative version of the package, which includes
8596 X support, be provided, or that the package's priority be
8602 <heading>Packages providing an X server</heading>
8605 Packages that provide an X server that, directly or
8606 indirectly, communicates with real input and display
8607 hardware should declare in their control data that they
8608 provide the virtual package <tt>xserver</tt>.<footnote>
8609 This implements current practice, and provides an
8610 actual policy for usage of the <tt>xserver</tt>
8611 virtual package which appears in the virtual packages
8612 list. In a nutshell, X servers that interface
8613 directly with the display and input hardware or via
8614 another subsystem (e.g., GGI) should provide
8615 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8616 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8622 <heading>Packages providing a terminal emulator</heading>
8625 Packages that provide a terminal emulator for the X Window
8626 System which meet the criteria listed below should declare
8627 in their control data that they provide the virtual
8628 package <tt>x-terminal-emulator</tt>. They should also
8629 register themselves as an alternative for
8630 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8635 To be an <tt>x-terminal-emulator</tt>, a program must:
8636 <list compact="compact">
8638 Be able to emulate a DEC VT100 terminal, or a
8639 compatible terminal.
8643 Support the command-line option <tt>-e
8644 <var>command</var></tt>, which creates a new
8645 terminal window<footnote>
8646 "New terminal window" does not necessarily mean
8647 a new top-level X window directly parented by
8648 the window manager; it could, if the terminal
8649 emulator application were so coded, be a new
8650 "view" in a multiple-document interface (MDI).
8652 and runs the specified <var>command</var>,
8653 interpreting the entirety of the rest of the command
8654 line as a command to pass straight to exec, in the
8655 manner that <tt>xterm</tt> does.
8659 Support the command-line option <tt>-T
8660 <var>title</var></tt>, which creates a new terminal
8661 window with the window title <var>title</var>.
8668 <heading>Packages providing a window manager</heading>
8671 Packages that provide a window manager should declare in
8672 their control data that they provide the virtual package
8673 <tt>x-window-manager</tt>. They should also register
8674 themselves as an alternative for
8675 <file>/usr/bin/x-window-manager</file>, with a priority
8676 calculated as follows:
8677 <list compact="compact">
8679 Start with a priority of 20.
8683 If the window manager supports the Debian menu
8684 system, add 20 points if this support is available
8685 in the package's default configuration (i.e., no
8686 configuration files belonging to the system or user
8687 have to be edited to activate the feature); if
8688 configuration files must be modified, add only 10
8694 If the window manager complies with <url
8695 id="http://www.freedesktop.org/Standards/wm-spec"
8696 name="The Window Manager Specification Project">,
8697 written by the <url id="http://www.freedesktop.org/"
8698 name="Free Desktop Group">, add 40 points.
8702 If the window manager permits the X session to be
8703 restarted using a <em>different</em> window manager
8704 (without killing the X server) in its default
8705 configuration, add 10 points; otherwise add none.
8712 <heading>Packages providing fonts</heading>
8715 Packages that provide fonts for the X Window
8717 For the purposes of Debian Policy, a "font for the X
8718 Window System" is one which is accessed via X protocol
8719 requests. Fonts for the Linux console, for PostScript
8720 renderer, or any other purpose, do not fit this
8721 definition. Any tool which makes such fonts available
8722 to the X Window System, however, must abide by this
8725 must do a number of things to ensure that they are both
8726 available without modification of the X or font server
8727 configuration, and that they do not corrupt files used by
8728 other font packages to register information about
8732 Fonts of any type supported by the X Window System
8733 must be in a separate binary package from any
8734 executables, libraries, or documentation (except
8735 that specific to the fonts shipped, such as their
8736 license information). If one or more of the fonts
8737 so packaged are necessary for proper operation of
8738 the package with which they are associated the font
8739 package may be Recommended; if the fonts merely
8740 provide an enhancement, a Suggests relationship may
8741 be used. Packages must not Depend on font
8743 This is because the X server may retrieve fonts
8744 from the local file system or over the network
8745 from an X font server; the Debian package system
8746 is empowered to deal only with the local
8752 BDF fonts must be converted to PCF fonts with the
8753 <prgn>bdftopcf</prgn> utility (available in the
8754 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8755 placed in a directory that corresponds to their
8757 <list compact="compact">
8759 100 dpi fonts must be placed in
8760 <file>/usr/share/fonts/X11/100dpi/</file>.
8764 75 dpi fonts must be placed in
8765 <file>/usr/share/fonts/X11/75dpi/</file>.
8769 Character-cell fonts, cursor fonts, and other
8770 low-resolution fonts must be placed in
8771 <file>/usr/share/fonts/X11/misc/</file>.
8777 Type 1 fonts must be placed in
8778 <file>/usr/share/fonts/X11/Type1/</file>. If font
8779 metric files are available, they must be placed here
8784 Subdirectories of <file>/usr/share/fonts/X11/</file>
8785 other than those listed above must be neither
8786 created nor used. (The <file>PEX</file>, <file>CID</file>,
8787 <file>Speedo</file>, and <file>cyrillic</file> directories
8788 are excepted for historical reasons, but installation of
8789 files into these directories remains discouraged.)
8793 Font packages may, instead of placing files directly
8794 in the X font directories listed above, provide
8795 symbolic links in that font directory pointing to
8796 the files' actual location in the filesystem. Such
8797 a location must comply with the FHS.
8801 Font packages should not contain both 75dpi and
8802 100dpi versions of a font. If both are available,
8803 they should be provided in separate binary packages
8804 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8805 the names of the packages containing the
8806 corresponding fonts.
8810 Fonts destined for the <file>misc</file> subdirectory
8811 should not be included in the same package as 75dpi
8812 or 100dpi fonts; instead, they should be provided in
8813 a separate package with <tt>-misc</tt> appended to
8818 Font packages must not provide the files
8819 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8820 <file>fonts.scale</file> in a font directory:
8823 <file>fonts.dir</file> files must not be provided at all.
8827 <file>fonts.alias</file> and <file>fonts.scale</file>
8828 files, if needed, should be provided in the
8830 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8831 where <var>fontdir</var> is the name of the
8833 <file>/usr/share/fonts/X11/</file> where the
8834 package's corresponding fonts are stored
8835 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8836 <var>package</var> is the name of the package
8837 that provides these fonts, and
8838 <var>extension</var> is either <tt>scale</tt>
8839 or <tt>alias</tt>, whichever corresponds to
8846 Font packages must declare a dependency on
8847 <tt>xfonts-utils</tt> in their control
8852 Font packages that provide one or more
8853 <file>fonts.scale</file> files as described above must
8854 invoke <prgn>update-fonts-scale</prgn> on each
8855 directory into which they installed fonts
8856 <em>before</em> invoking
8857 <prgn>update-fonts-dir</prgn> on that directory.
8858 This invocation must occur in both the
8859 <prgn>postinst</prgn> (for all arguments) and
8860 <prgn>postrm</prgn> (for all arguments except
8861 <tt>upgrade</tt>) scripts.
8865 Font packages that provide one or more
8866 <file>fonts.alias</file> files as described above must
8867 invoke <prgn>update-fonts-alias</prgn> on each
8868 directory into which they installed fonts. This
8869 invocation must occur in both the
8870 <prgn>postinst</prgn> (for all arguments) and
8871 <prgn>postrm</prgn> (for all arguments except
8872 <tt>upgrade</tt>) scripts.
8876 Font packages must invoke
8877 <prgn>update-fonts-dir</prgn> on each directory into
8878 which they installed fonts. This invocation must
8879 occur in both the <prgn>postinst</prgn> (for all
8880 arguments) and <prgn>postrm</prgn> (for all
8881 arguments except <tt>upgrade</tt>) scripts.
8885 Font packages must not provide alias names for the
8886 fonts they include which collide with alias names
8887 already in use by fonts already packaged.
8891 Font packages must not provide fonts with the same
8892 XLFD registry name as another font already packaged.
8898 <sect1 id="appdefaults">
8899 <heading>Application defaults files</heading>
8902 Application defaults files must be installed in the
8903 directory <file>/etc/X11/app-defaults/</file> (use of a
8904 localized subdirectory of <file>/etc/X11/</file> as described
8905 in the <em>X Toolkit Intrinsics - C Language
8906 Interface</em> manual is also permitted). They must be
8907 registered as <tt>conffile</tt>s or handled as
8908 configuration files.
8912 Customization of programs' X resources may also be
8913 supported with the provision of a file with the same name
8914 as that of the package placed in
8915 the <file>/etc/X11/Xresources/</file> directory, which
8916 must be registered as a <tt>conffile</tt> or handled as a
8917 configuration file.<footnote>
8918 Note that this mechanism is not the same as using
8919 app-defaults; app-defaults are tied to the client
8920 binary on the local file system, whereas X resources
8921 are stored in the X server and affect all connecting
8928 <heading>Installation directory issues</heading>
8931 Historically, packages using the X Window System used a
8932 separate set of installation directories from other packages.
8933 This practice has been discontinued and packages using the X
8934 Window System should now generally be installed in the same
8935 directories as any other package. Specifically, packages must
8936 not install files under the <file>/usr/X11R6/</file> directory
8937 and the <file>/usr/X11R6/</file> directory hierarchy should be
8938 regarded as obsolete.
8942 Include files previously installed under
8943 <file>/usr/X11R6/include/X11/</file> should be installed into
8944 <file>/usr/include/X11/</file>. For files previously
8945 installed into subdirectories of
8946 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
8947 determine if subdirectories of <file>/usr/lib/</file> and
8948 <file>/usr/share/</file> can be used. If not, a subdirectory
8949 of <file>/usr/lib/X11/</file> should be used.
8953 Configuration files for window, display, or session managers
8954 or other applications that are tightly integrated with the X
8955 Window System may be placed in a subdirectory
8956 of <file>/etc/X11/</file> corresponding to the package name.
8957 Other X Window System applications should use
8958 the <file>/etc/</file> directory unless otherwise mandated by
8959 policy (such as for <ref id="appdefaults">).
8964 <heading>The OSF/Motif and OpenMotif libraries</heading>
8967 <em>Programs that require the non-DFSG-compliant OSF/Motif or
8968 OpenMotif libraries</em><footnote>
8969 OSF/Motif and OpenMotif are collectively referred to as
8970 "Motif" in this policy document.
8972 should be compiled against and tested with LessTif (a free
8973 re-implementation of Motif) instead. If the maintainer
8974 judges that the program or programs do not work
8975 sufficiently well with LessTif to be distributed and
8976 supported, but do so when compiled against Motif, then two
8977 versions of the package should be created; one linked
8978 statically against Motif and with <tt>-smotif</tt>
8979 appended to the package name, and one linked dynamically
8980 against Motif and with <tt>-dmotif</tt> appended to the
8985 Both Motif-linked versions are dependent
8986 upon non-DFSG-compliant software and thus cannot be
8987 uploaded to the <em>main</em> distribution; if the
8988 software is itself DFSG-compliant it may be uploaded to
8989 the <em>contrib</em> distribution. While known existing
8990 versions of Motif permit unlimited redistribution of
8991 binaries linked against the library (whether statically or
8992 dynamically), it is the package maintainer's
8993 responsibility to determine whether this is permitted by
8994 the license of the copy of Motif in their possession.
9000 <heading>Perl programs and modules</heading>
9003 Perl programs and modules should follow the current Perl policy.
9007 The Perl policy can be found in the <tt>perl-policy</tt>
9008 files in the <tt>debian-policy</tt> package.
9009 It is also available from the Debian web mirrors at
9010 <tt><url name="/doc/packaging-manuals/perl-policy/"
9011 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
9016 <heading>Emacs lisp programs</heading>
9019 Please refer to the "Debian Emacs Policy" for details of how to
9020 package emacs lisp programs.
9024 The Emacs policy is available in
9025 <file>debian-emacs-policy.gz</file> of the
9026 <package>emacsen-common</package> package.
9027 It is also available from the Debian web mirrors at
9028 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
9029 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
9034 <heading>Games</heading>
9037 The permissions on <file>/var/games</file> are mode 755, owner
9038 <tt>root</tt> and group <tt>root</tt>.
9042 Each game decides on its own security policy.</p>
9045 Games which require protected, privileged access to
9046 high-score files, saved games, etc., may be made
9047 set-<em>group</em>-id (mode 2755) and owned by
9048 <tt>root:games</tt>, and use files and directories with
9049 appropriate permissions (770 <tt>root:games</tt>, for
9050 example). They must not be made
9051 set-<em>user</em>-id, as this causes security problems. (If
9052 an attacker can subvert any set-user-id game they can
9053 overwrite the executable of any other, causing other players
9054 of these games to run a Trojan horse program. With a
9055 set-group-id game the attacker only gets access to less
9056 important game data, and if they can get at the other
9057 players' accounts at all it will take considerably more
9061 Some packages, for example some fortune cookie programs, are
9062 configured by the upstream authors to install with their
9063 data files or other static information made unreadable so
9064 that they can only be accessed through set-id programs
9065 provided. You should not do this in a Debian package: anyone can
9066 download the <file>.deb</file> file and read the data from it,
9067 so there is no point making the files unreadable. Not
9068 making the files unreadable also means that you don't have
9069 to make so many programs set-id, which reduces the risk of a
9073 As described in the FHS, binaries of games should be
9074 installed in the directory <file>/usr/games</file>. This also
9075 applies to games that use the X Window System. Manual pages
9076 for games (X and non-X games) should be installed in
9077 <file>/usr/share/man/man6</file>.</p>
9083 <heading>Documentation</heading>
9086 <heading>Manual pages</heading>
9089 You should install manual pages in <prgn>nroff</prgn> source
9090 form, in appropriate places under <file>/usr/share/man</file>.
9091 You should only use sections 1 to 9 (see the FHS for more
9092 details). You must not install a pre-formatted "cat page".
9096 Each program, utility, and function should have an
9097 associated manual page included in the same package. It is
9098 suggested that all configuration files also have a manual
9099 page included as well. Manual pages for protocols and other
9100 auxiliary things are optional.
9104 If no manual page is available, this is considered as a bug
9105 and should be reported to the Debian Bug Tracking System (the
9106 maintainer of the package is allowed to write this bug report
9107 themselves, if they so desire). Do not close the bug report
9108 until a proper man page is available.<footnote>
9109 It is not very hard to write a man page. See the
9110 <url id="http://www.schweikhardt.net/man_page_howto.html"
9111 name="Man-Page-HOWTO">,
9112 <manref name="man" section="7">, the examples
9113 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
9114 the helper program <prgn>help2man</prgn>, or the
9115 directory <file>/usr/share/doc/man-db/examples</file>.
9120 You may forward a complaint about a missing man page to the
9121 upstream authors, and mark the bug as forwarded in the
9122 Debian bug tracking system. Even though the GNU Project do
9123 not in general consider the lack of a man page to be a bug,
9124 we do; if they tell you that they don't consider it a bug
9125 you should leave the bug in our bug tracking system open
9130 Manual pages should be installed compressed using <tt>gzip -9</tt>.
9134 If one man page needs to be accessible via several names it
9135 is better to use a symbolic link than the <file>.so</file>
9136 feature, but there is no need to fiddle with the relevant
9137 parts of the upstream source to change from <file>.so</file> to
9138 symlinks: don't do it unless it's easy. You should not
9139 create hard links in the manual page directories, nor put
9140 absolute filenames in <file>.so</file> directives. The filename
9141 in a <file>.so</file> in a man page should be relative to the
9142 base of the man page tree (usually
9143 <file>/usr/share/man</file>). If you do not create any links
9144 (whether symlinks, hard links, or <tt>.so</tt> directives)
9145 in the file system to the alternate names of the man page,
9146 then you should not rely on <prgn>man</prgn> finding your
9147 man page under those names based solely on the information in
9148 the man page's header.<footnote>
9149 Supporting this in <prgn>man</prgn> often requires
9150 unreasonable processing time to find a manual page or to
9151 report that none exists, and moves knowledge into man's
9152 database that would be better left in the file system.
9153 This support is therefore deprecated and will cease to
9154 be present in the future.
9159 Manual pages in locale-specific subdirectories of
9160 <file>/usr/share/man</file> should use either UTF-8 or the usual
9161 legacy encoding for that language (normally the one corresponding
9162 to the shortest relevant locale name in
9163 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
9164 <file>/usr/share/man/fr</file> should use either UTF-8 or
9165 ISO-8859-1.<footnote>
9166 <prgn>man</prgn> will automatically detect whether UTF-8 is in
9167 use. In future, all manual pages will be required to use
9173 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
9174 included in the subdirectory name unless it indicates a
9175 significant difference in the language, as this excludes
9176 speakers of the language in other countries.<footnote>
9177 At the time of writing, Chinese and Portuguese are the main
9178 languages with such differences, so <file>pt_BR</file>,
9179 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
9184 If a localized version of a manual page is provided, it should
9185 either be up-to-date or it should be obvious to the reader that
9186 it is outdated and the original manual page should be used
9187 instead. This can be done either by a note at the beginning of
9188 the manual page or by showing the missing or changed portions in
9189 the original language instead of the target language.
9194 <heading>Info documents</heading>
9197 Info documents should be installed in <file>/usr/share/info</file>.
9198 They should be compressed with <tt>gzip -9</tt>.
9202 The <prgn>install-info</prgn> program maintains a directory of
9203 installed info documents in <file>/usr/share/info/dir</file> for
9204 the use of info readers.<footnote>
9205 It was previously necessary for packages installing info
9206 documents to run <prgn>install-info</prgn> from maintainer
9207 scripts. This is no longer necessary. The installation
9208 system now uses dpkg triggers.
9210 This file must not be included in packages. Packages containing
9211 info documents should depend on <tt>dpkg (>= 1.15.4) |
9212 install-info</tt> to ensure that the directory file is properly
9213 rebuilt during partial upgrades from Debian 5.0 (lenny) and
9218 Info documents should contain section and directory entry
9219 information in the document for the use
9220 of <prgn>install-info</prgn>. The section should be specified
9221 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
9222 space and the section of this info page. The directory entry or
9223 entries should be included between
9224 a <tt>START-INFO-DIR-ENTRY</tt> line and
9225 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
9227 INFO-DIR-SECTION Individual utilities
9228 START-INFO-DIR-ENTRY
9229 * example: (example). An example info directory entry.
9232 To determine which section to use, you should look
9233 at <file>/usr/share/info/dir</file> on your system and choose
9234 the most relevant (or create a new section if none of the
9235 current sections are relevant).<footnote>
9236 Normally, info documents are generated from Texinfo source.
9237 To include this information in the generated info document, if
9238 it is absent, add commands like:
9240 @dircategory Individual utilities
9242 * example: (example). An example info directory entry.
9245 to the Texinfo source of the document and ensure that the info
9246 documents are rebuilt from source during the package build.
9252 <heading>Additional documentation</heading>
9255 Any additional documentation that comes with the package may
9256 be installed at the discretion of the package maintainer.
9257 Plain text documentation should be installed in the directory
9258 <file>/usr/share/doc/<var>package</var></file>, where
9259 <var>package</var> is the name of the package, and
9260 compressed with <tt>gzip -9</tt> unless it is small.
9264 If a package comes with large amounts of documentation which
9265 many users of the package will not require you should create
9266 a separate binary package to contain it, so that it does not
9267 take up disk space on the machines of users who do not need
9268 or want it installed.</p>
9271 It is often a good idea to put text information files
9272 (<file>README</file>s, changelogs, and so forth) that come with
9273 the source package in <file>/usr/share/doc/<var>package</var></file>
9274 in the binary package. However, you don't need to install
9275 the instructions for building and installing the package, of
9279 Packages must not require the existence of any files in
9280 <file>/usr/share/doc/</file> in order to function
9282 The system administrator should be able to
9283 delete files in <file>/usr/share/doc/</file> without causing
9284 any programs to break.
9286 Any files that are referenced by programs but are also
9287 useful as stand alone documentation should be installed under
9288 <file>/usr/share/<var>package</var>/</file> with symbolic links from
9289 <file>/usr/share/doc/<var>package</var></file>.
9293 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9294 link to another directory in <file>/usr/share/doc</file> only if
9295 the two packages both come from the same source and the
9296 first package Depends on the second.<footnote>
9298 Please note that this does not override the section on
9299 changelog files below, so the file
9300 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
9301 must refer to the changelog for the current version of
9302 <var>package</var> in question. In practice, this means
9303 that the sources of the target and the destination of the
9304 symlink must be the same (same source package and
9311 Former Debian releases placed all additional documentation
9312 in <file>/usr/doc/<var>package</var></file>. This has been
9313 changed to <file>/usr/share/doc/<var>package</var></file>,
9314 and packages must not put documentation in the directory
9315 <file>/usr/doc/<var>package</var></file>. <footnote>
9316 At this phase of the transition, we no longer require a
9317 symbolic link in <file>/usr/doc/</file>. At a later point,
9318 policy shall change to make the symbolic links a bug.
9324 <heading>Preferred documentation formats</heading>
9327 The unification of Debian documentation is being carried out
9331 If your package comes with extensive documentation in a
9332 markup format that can be converted to various other formats
9333 you should if possible ship HTML versions in a binary
9334 package, in the directory
9335 <file>/usr/share/doc/<var>appropriate-package</var></file> or
9336 its subdirectories.<footnote>
9337 The rationale: The important thing here is that HTML
9338 docs should be available in <em>some</em> package, not
9339 necessarily in the main binary package.
9344 Other formats such as PostScript may be provided at the
9345 package maintainer's discretion.
9349 <sect id="copyrightfile">
9350 <heading>Copyright information</heading>
9353 Every package must be accompanied by a verbatim copy of its
9354 copyright information and distribution license in the file
9355 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
9356 file must neither be compressed nor be a symbolic link.
9360 In addition, the copyright file must say where the upstream
9361 sources (if any) were obtained. It should name the original
9362 authors of the package and the Debian maintainer(s) who were
9363 involved with its creation.
9367 Packages in the <em>contrib</em> or <em>non-free</em> archive
9368 areas should state in the copyright file that the package is not
9369 part of the Debian GNU/Linux distribution and briefly explain
9374 A copy of the file which will be installed in
9375 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9376 be in <file>debian/copyright</file> in the source package.
9380 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9381 link to another directory in <file>/usr/share/doc</file> only if
9382 the two packages both come from the same source and the
9383 first package Depends on the second. These rules are
9384 important because copyrights must be extractable by
9389 Packages distributed under the Apache license (version 2.0), the
9390 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
9391 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
9392 1.3) should refer to the corresponding files
9393 under <file>/usr/share/common-licenses</file>,<footnote>
9396 <file>/usr/share/common-licenses/Apache-2.0</file>,
9397 <file>/usr/share/common-licenses/Artistic</file>,
9398 <file>/usr/share/common-licenses/GPL-1</file>,
9399 <file>/usr/share/common-licenses/GPL-2</file>,
9400 <file>/usr/share/common-licenses/GPL-3</file>,
9401 <file>/usr/share/common-licenses/LGPL-2</file>,
9402 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9403 <file>/usr/share/common-licenses/LGPL-3</file>,
9404 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
9405 <file>/usr/share/common-licenses/GFDL-1.3</file>
9406 respectively. The University of California BSD license is
9407 also included in <package>base-files</package> as
9408 <file>/usr/share/common-licenses/BSD</file>, but given the
9409 brevity of this license, its specificity to code whose
9410 copyright is held by the Regents of the University of
9411 California, and the frequency of minor wording changes, its
9412 text should be included in the copyright file rather than
9413 referencing this file.
9415 </footnote> rather than quoting them in the copyright
9420 You should not use the copyright file as a general <file>README</file>
9421 file. If your package has such a file it should be
9422 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9423 <file>README.Debian</file> or some other appropriate place.</p>
9427 <heading>Examples</heading>
9430 Any examples (configurations, source files, whatever),
9431 should be installed in a directory
9432 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9433 files should not be referenced by any program: they're there
9434 for the benefit of the system administrator and users as
9435 documentation only. Architecture-specific example files
9436 should be installed in a directory
9437 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9439 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9440 latter directory itself may be a symbolic link to the
9445 If the purpose of a package is to provide examples, then the
9446 example files may be installed into
9447 <file>/usr/share/doc/<var>package</var></file>.
9451 <sect id="changelogs">
9452 <heading>Changelog files</heading>
9455 Packages that are not Debian-native must contain a
9456 compressed copy of the <file>debian/changelog</file> file from
9457 the Debian source tree in
9458 <file>/usr/share/doc/<var>package</var></file> with the name
9459 <file>changelog.Debian.gz</file>.
9463 If an upstream changelog is available, it should be accessible as
9464 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9465 plain text. If the upstream changelog is distributed in
9466 HTML, it should be made available in that form as
9467 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9468 and a plain text <file>changelog.gz</file> should be generated
9469 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9470 the upstream changelog files do not already conform to this
9471 naming convention, then this may be achieved either by
9472 renaming the files, or by adding a symbolic link, at the
9473 maintainer's discretion.<footnote>
9474 Rationale: People should not have to look in places for
9475 upstream changelogs merely because they are given
9476 different names or are distributed in HTML format.
9481 All of these files should be installed compressed using
9482 <tt>gzip -9</tt>, as they will become large with time even
9483 if they start out small.
9487 If the package has only one changelog which is used both as
9488 the Debian changelog and the upstream one because there is
9489 no separate upstream maintainer then that changelog should
9490 usually be installed as
9491 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9492 there is a separate upstream maintainer, but no upstream
9493 changelog, then the Debian changelog should still be called
9494 <file>changelog.Debian.gz</file>.
9498 For details about the format and contents of the Debian
9499 changelog file, please see <ref id="dpkgchangelog">.
9504 <appendix id="pkg-scope">
9505 <heading>Introduction and scope of these appendices</heading>
9508 These appendices are taken essentially verbatim from the
9509 now-deprecated Packaging Manual, version 3.2.1.0. They are
9510 the chapters which are likely to be of use to package
9511 maintainers and which have not already been included in the
9512 policy document itself. Most of these sections are very likely
9513 not relevant to policy; they should be treated as
9514 documentation for the packaging system. Please note that these
9515 appendices are included for convenience, and for historical
9516 reasons: they used to be part of policy package, and they have
9517 not yet been incorporated into dpkg documentation. However,
9518 they still have value, and hence they are presented here.
9522 They have not yet been checked to ensure that they are
9523 compatible with the contents of policy, and if there are any
9524 contradictions, the version in the main policy document takes
9525 precedence. The remaining chapters of the old Packaging
9526 Manual have also not been read in detail to ensure that there
9527 are not parts which have been left out. Both of these will be
9532 Certain parts of the Packaging manual were integrated into the
9533 Policy Manual proper, and removed from the appendices. Links
9534 have been placed from the old locations to the new ones.
9538 <prgn>dpkg</prgn> is a suite of programs for creating binary
9539 package files and installing and removing them on Unix
9541 <prgn>dpkg</prgn> is targeted primarily at Debian
9542 GNU/Linux, but may work on or be ported to other
9548 The binary packages are designed for the management of
9549 installed executable programs (usually compiled binaries) and
9550 their associated data, though source code examples and
9551 documentation are provided as part of some packages.</p>
9554 This manual describes the technical aspects of creating Debian
9555 binary packages (<file>.deb</file> files). It documents the
9556 behavior of the package management programs
9557 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9558 they interact with packages.</p>
9561 It also documents the interaction between
9562 <prgn>dselect</prgn>'s core and the access method scripts it
9563 uses to actually install the selected packages, and describes
9564 how to create a new access method.</p>
9567 This manual does not go into detail about the options and
9568 usage of the package building and installation tools. It
9569 should therefore be read in conjunction with those programs'
9574 The utility programs which are provided with <prgn>dpkg</prgn>
9575 for managing various system configuration and similar issues,
9576 such as <prgn>update-rc.d</prgn> and
9577 <prgn>install-info</prgn>, are not described in detail here -
9578 please see their man pages.
9582 It is assumed that the reader is reasonably familiar with the
9583 <prgn>dpkg</prgn> System Administrators' manual.
9584 Unfortunately this manual does not yet exist.
9588 The Debian version of the FSF's GNU hello program is provided
9589 as an example for people wishing to create Debian
9590 packages. The Debian <prgn>debmake</prgn> package is
9591 recommended as a very helpful tool in creating and maintaining
9592 Debian packages. However, while the tools and examples are
9593 helpful, they do not replace the need to read and follow the
9594 Policy and Programmer's Manual.</p>
9597 <appendix id="pkg-binarypkg">
9598 <heading>Binary packages (from old Packaging Manual)</heading>
9601 The binary package has two main sections. The first part
9602 consists of various control information files and scripts used
9603 by <prgn>dpkg</prgn> when installing and removing. See <ref
9604 id="pkg-controlarea">.
9608 The second part is an archive containing the files and
9609 directories to be installed.
9613 In the future binary packages may also contain other
9614 components, such as checksums and digital signatures. The
9615 format for the archive is described in full in the
9616 <file>deb(5)</file> man page.
9620 <sect id="pkg-bincreating"><heading>Creating package files -
9621 <prgn>dpkg-deb</prgn>
9625 All manipulation of binary package files is done by
9626 <prgn>dpkg-deb</prgn>; it's the only program that has
9627 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9628 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9629 will spot that the options requested are appropriate to
9630 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9635 In order to create a binary package you must make a
9636 directory tree which contains all the files and directories
9637 you want to have in the file system data part of the package.
9638 In Debian-format source packages this directory is usually
9639 <file>debian/tmp</file>, relative to the top of the package's
9644 They should have the locations (relative to the root of the
9645 directory tree you're constructing) ownerships and
9646 permissions which you want them to have on the system when
9651 With current versions of <prgn>dpkg</prgn> the uid/username
9652 and gid/groupname mappings for the users and groups being
9653 used should be the same on the system where the package is
9654 built and the one where it is installed.
9658 You need to add one special directory to the root of the
9659 miniature file system tree you're creating:
9660 <prgn>DEBIAN</prgn>. It should contain the control
9661 information files, notably the binary package control file
9662 (see <ref id="pkg-controlfile">).
9666 The <prgn>DEBIAN</prgn> directory will not appear in the
9667 file system archive of the package, and so won't be installed
9668 by <prgn>dpkg</prgn> when the package is unpacked.
9672 When you've prepared the package, you should invoke:
9674 dpkg --build <var>directory</var>
9679 This will build the package in
9680 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9681 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9682 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9687 See the man page <manref name="dpkg-deb" section="8"> for details of how
9688 to examine the contents of this newly-created file. You may find the
9689 output of following commands enlightening:
9691 dpkg-deb --info <var>filename</var>.deb
9692 dpkg-deb --contents <var>filename</var>.deb
9693 dpkg --contents <var>filename</var>.deb
9695 To view the copyright file for a package you could use this command:
9697 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
9702 <sect id="pkg-controlarea">
9703 <heading>Package control information files</heading>
9706 The control information portion of a binary package is a
9707 collection of files with names known to <prgn>dpkg</prgn>.
9708 It will treat the contents of these files specially - some
9709 of them contain information used by <prgn>dpkg</prgn> when
9710 installing or removing the package; others are scripts which
9711 the package maintainer wants <prgn>dpkg</prgn> to run.
9715 It is possible to put other files in the package control
9716 area, but this is not generally a good idea (though they
9717 will largely be ignored).
9721 Here is a brief list of the control info files supported by
9722 <prgn>dpkg</prgn> and a summary of what they're used for.
9727 <tag><tt>control</tt>
9730 This is the key description file used by
9731 <prgn>dpkg</prgn>. It specifies the package's name
9732 and version, gives its description for the user,
9733 states its relationships with other packages, and so
9734 forth. See <ref id="sourcecontrolfiles"> and
9735 <ref id="binarycontrolfiles">.
9739 It is usually generated automatically from information
9740 in the source package by the
9741 <prgn>dpkg-gencontrol</prgn> program, and with
9742 assistance from <prgn>dpkg-shlibdeps</prgn>.
9743 See <ref id="pkg-sourcetools">.
9747 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9752 These are executable files (usually scripts) which
9753 <prgn>dpkg</prgn> runs during installation, upgrade
9754 and removal of packages. They allow the package to
9755 deal with matters which are particular to that package
9756 or require more complicated processing than that
9757 provided by <prgn>dpkg</prgn>. Details of when and
9758 how they are called are in <ref id="maintainerscripts">.
9762 It is very important to make these scripts idempotent.
9763 See <ref id="idempotency">.
9767 The maintainer scripts are not guaranteed to run with a
9768 controlling terminal and may not be able to interact with
9769 the user. See <ref id="controllingterminal">.
9773 <tag><tt>conffiles</tt>
9776 This file contains a list of configuration files which
9777 are to be handled automatically by <prgn>dpkg</prgn>
9778 (see <ref id="pkg-conffiles">). Note that not necessarily
9779 every configuration file should be listed here.
9782 <tag><tt>shlibs</tt>
9785 This file contains a list of the shared libraries
9786 supplied by the package, with dependency details for
9787 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9788 when it determines what dependencies are required in a
9789 package control file. The <tt>shlibs</tt> file format
9790 is described on <ref id="shlibs">.
9795 <sect id="pkg-controlfile">
9796 <heading>The main control information file: <tt>control</tt></heading>
9799 The most important control information file used by
9800 <prgn>dpkg</prgn> when it installs a package is
9801 <tt>control</tt>. It contains all the package's "vital
9806 The binary package control files of packages built from
9807 Debian sources are made by a special tool,
9808 <prgn>dpkg-gencontrol</prgn>, which reads
9809 <file>debian/control</file> and <file>debian/changelog</file> to
9810 find the information it needs. See <ref id="pkg-sourcepkg"> for
9815 The fields in binary package control files are listed in
9816 <ref id="binarycontrolfiles">.
9820 A description of the syntax of control files and the purpose
9821 of the fields is available in <ref id="controlfields">.
9826 <heading>Time Stamps</heading>
9829 See <ref id="timestamps">.
9834 <appendix id="pkg-sourcepkg">
9835 <heading>Source packages (from old Packaging Manual) </heading>
9838 The Debian binary packages in the distribution are generated
9839 from Debian sources, which are in a special format to assist
9840 the easy and automatic building of binaries.
9843 <sect id="pkg-sourcetools">
9844 <heading>Tools for processing source packages</heading>
9847 Various tools are provided for manipulating source packages;
9848 they pack and unpack sources and help build of binary
9849 packages and help manage the distribution of new versions.
9853 They are introduced and typical uses described here; see
9854 <manref name="dpkg-source" section="1"> for full
9855 documentation about their arguments and operation.
9859 For examples of how to construct a Debian source package,
9860 and how to use those utilities that are used by Debian
9861 source packages, please see the <prgn>hello</prgn> example
9865 <sect1 id="pkg-dpkg-source">
9867 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9872 This program is frequently used by hand, and is also
9873 called from package-independent automated building scripts
9874 such as <prgn>dpkg-buildpackage</prgn>.
9878 To unpack a package it is typically invoked with
9880 dpkg-source -x <var>.../path/to/filename</var>.dsc
9885 with the <file><var>filename</var>.tar.gz</file> and
9886 <file><var>filename</var>.diff.gz</file> (if applicable) in
9887 the same directory. It unpacks into
9888 <file><var>package</var>-<var>version</var></file>, and if
9890 <file><var>package</var>-<var>version</var>.orig</file>, in
9891 the current directory.
9895 To create a packed source archive it is typically invoked:
9897 dpkg-source -b <var>package</var>-<var>version</var>
9902 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
9903 <file>.diff.gz</file> (if appropriate) in the current
9904 directory. <prgn>dpkg-source</prgn> does not clean the
9905 source tree first - this must be done separately if it is
9910 See also <ref id="pkg-sourcearchives">.</p>
9914 <sect1 id="pkg-dpkg-buildpackage">
9916 <prgn>dpkg-buildpackage</prgn> - overall package-building
9921 <prgn>dpkg-buildpackage</prgn> is a script which invokes
9922 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
9923 targets <tt>clean</tt>, <tt>build</tt> and
9924 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
9925 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
9926 source and binary package upload.
9930 It is usually invoked by hand from the top level of the
9931 built or unbuilt source directory. It may be invoked with
9932 no arguments; useful arguments include:
9933 <taglist compact="compact">
9934 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
9937 Do not sign the <tt>.changes</tt> file or the
9938 source package <tt>.dsc</tt> file, respectively.</p>
9940 <tag><tt>-p<var>sign-command</var></tt></tag>
9943 Invoke <var>sign-command</var> instead of finding
9944 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
9945 <var>sign-command</var> must behave just like
9946 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
9948 <tag><tt>-r<var>root-command</var></tt></tag>
9951 When root privilege is required, invoke the command
9952 <var>root-command</var>. <var>root-command</var>
9953 should invoke its first argument as a command, from
9954 the <prgn>PATH</prgn> if necessary, and pass its
9955 second and subsequent arguments to the command it
9956 calls. If no <var>root-command</var> is supplied
9957 then <var>dpkg-buildpackage</var> will take no
9958 special action to gain root privilege, so that for
9959 most packages it will have to be invoked as root to
9962 <tag><tt>-b</tt>, <tt>-B</tt></tag>
9965 Two types of binary-only build and upload - see
9966 <manref name="dpkg-source" section="1">.
9973 <sect1 id="pkg-dpkg-gencontrol">
9975 <prgn>dpkg-gencontrol</prgn> - generates binary package
9980 This program is usually called from <file>debian/rules</file>
9981 (see <ref id="pkg-sourcetree">) in the top level of the source
9986 This is usually done just before the files and directories in the
9987 temporary directory tree where the package is being built have their
9988 permissions and ownerships set and the package is constructed using
9989 <prgn>dpkg-deb/</prgn>
9991 This is so that the control file which is produced has
9992 the right permissions
9997 <prgn>dpkg-gencontrol</prgn> must be called after all the
9998 files which are to go into the package have been placed in
9999 the temporary build directory, so that its calculation of
10000 the installed size of a package is correct.
10004 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
10005 be run after <prgn>dpkg-shlibdeps</prgn> so that the
10006 variable substitutions created by
10007 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
10012 For a package which generates only one binary package, and
10013 which builds it in <file>debian/tmp</file> relative to the top
10014 of the source package, it is usually sufficient to call
10015 <prgn>dpkg-gencontrol</prgn>.
10019 Sources which build several binaries will typically need
10022 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
10023 </example> The <tt>-P</tt> tells
10024 <prgn>dpkg-gencontrol</prgn> that the package is being
10025 built in a non-default directory, and the <tt>-p</tt>
10026 tells it which package's control file should be generated.
10030 <prgn>dpkg-gencontrol</prgn> also adds information to the
10031 list of files in <file>debian/files</file>, for the benefit of
10032 (for example) a future invocation of
10033 <prgn>dpkg-genchanges</prgn>.</p>
10036 <sect1 id="pkg-dpkg-shlibdeps">
10038 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
10043 This program is usually called from <file>debian/rules</file>
10044 just before <prgn>dpkg-gencontrol</prgn> (see <ref
10045 id="pkg-sourcetree">), in the top level of the source tree.
10049 Its arguments are executables and shared libraries
10052 They may be specified either in the locations in the
10053 source tree where they are created or in the locations
10054 in the temporary build tree where they are installed
10055 prior to binary package creation.
10057 </footnote> for which shared library dependencies should
10058 be included in the binary package's control file.
10062 If some of the found shared libraries should only
10063 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
10064 some warrant a <tt>Pre-Depends</tt>, this can be achieved
10065 by using the <tt>-d<var>dependency-field</var></tt> option
10066 before those executable(s). (Each <tt>-d</tt> option
10067 takes effect until the next <tt>-d</tt>.)
10071 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
10072 output control file to be modified. Instead by default it
10073 adds to the <file>debian/substvars</file> file variable
10074 settings like <tt>shlibs:Depends</tt>. These variable
10075 settings must be referenced in dependency fields in the
10076 appropriate per-binary-package sections of the source
10081 For example, a package that generates an essential part
10082 which requires dependencies, and optional parts that
10083 which only require a recommendation, would separate those
10084 two sets of dependencies into two different fields.<footnote>
10085 At the time of writing, an example for this was the
10086 <package/xmms/ package, with Depends used for the xmms
10087 executable, Recommends for the plug-ins and Suggests for
10088 even more optional features provided by unzip.
10090 It can say in its <file>debian/rules</file>:
10092 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
10093 -dRecommends <var>optionalpart anotheroptionalpart</var>
10095 and then in its main control file <file>debian/control</file>:
10098 Depends: ${shlibs:Depends}
10099 Recommends: ${shlibs:Recommends}
10105 Sources which produce several binary packages with
10106 different shared library dependency requirements can use
10107 the <tt>-p<var>varnameprefix</var></tt> option to override
10108 the default <tt>shlibs:</tt> prefix (one invocation of
10109 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
10110 They can thus produce several sets of dependency
10111 variables, each of the form
10112 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
10113 which can be referred to in the appropriate parts of the
10114 binary package control files.
10119 <sect1 id="pkg-dpkg-distaddfile">
10121 <prgn>dpkg-distaddfile</prgn> - adds a file to
10122 <file>debian/files</file>
10126 Some packages' uploads need to include files other than
10127 the source and binary package files.
10131 <prgn>dpkg-distaddfile</prgn> adds a file to the
10132 <file>debian/files</file> file so that it will be included in
10133 the <file>.changes</file> file when
10134 <prgn>dpkg-genchanges</prgn> is run.
10138 It is usually invoked from the <tt>binary</tt> target of
10139 <file>debian/rules</file>:
10141 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
10143 The <var>filename</var> is relative to the directory where
10144 <prgn>dpkg-genchanges</prgn> will expect to find it - this
10145 is usually the directory above the top level of the source
10146 tree. The <file>debian/rules</file> target should put the
10147 file there just before or just after calling
10148 <prgn>dpkg-distaddfile</prgn>.
10152 The <var>section</var> and <var>priority</var> are passed
10153 unchanged into the resulting <file>.changes</file> file.
10158 <sect1 id="pkg-dpkg-genchanges">
10160 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
10161 upload control file
10165 This program is usually called by package-independent
10166 automatic building scripts such as
10167 <prgn>dpkg-buildpackage</prgn>, but it may also be called
10172 It is usually called in the top level of a built source
10173 tree, and when invoked with no arguments will print out a
10174 straightforward <file>.changes</file> file based on the
10175 information in the source package's changelog and control
10176 file and the binary and source packages which should have
10182 <sect1 id="pkg-dpkg-parsechangelog">
10184 <prgn>dpkg-parsechangelog</prgn> - produces parsed
10185 representation of a changelog
10189 This program is used internally by
10190 <prgn>dpkg-source</prgn> et al. It may also occasionally
10191 be useful in <file>debian/rules</file> and elsewhere. It
10192 parses a changelog, <file>debian/changelog</file> by default,
10193 and prints a control-file format representation of the
10194 information in it to standard output.
10198 <sect1 id="pkg-dpkg-architecture">
10200 <prgn>dpkg-architecture</prgn> - information about the build and
10205 This program can be used manually, but is also invoked by
10206 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
10207 environment or make variables which specify the build and host
10208 architecture for the package building process.
10213 <sect id="pkg-sourcetree">
10214 <heading>The Debian package source tree</heading>
10217 The source archive scheme described later is intended to
10218 allow a Debian package source tree with some associated
10219 control information to be reproduced and transported easily.
10220 The Debian package source tree is a version of the original
10221 program with certain files added for the benefit of the
10222 packaging process, and with any other changes required
10223 made to the rest of the source code and installation
10228 The extra files created for Debian are in the subdirectory
10229 <file>debian</file> of the top level of the Debian package
10230 source tree. They are described below.
10233 <sect1 id="pkg-debianrules">
10234 <heading><file>debian/rules</file> - the main building script</heading>
10237 See <ref id="debianrules">.
10241 <sect1 id="pkg-srcsubstvars">
10242 <heading><file>debian/substvars</file> and variable substitutions</heading>
10245 See <ref id="substvars">.
10251 <heading><file>debian/files</file></heading>
10254 See <ref id="debianfiles">.
10258 <sect1><heading><file>debian/tmp</file>
10262 This is the canonical temporary location for the
10263 construction of binary packages by the <tt>binary</tt>
10264 target. The directory <file>tmp</file> serves as the root of
10265 the file system tree as it is being constructed (for
10266 example, by using the package's upstream makefiles install
10267 targets and redirecting the output there), and it also
10268 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10269 id="pkg-bincreating">.
10273 If several binary packages are generated from the same
10274 source tree it is usual to use several
10275 <file>debian/tmp<var>something</var></file> directories, for
10276 example <file>tmp-a</file> or <file>tmp-doc</file>.
10280 Whatever <file>tmp</file> directories are created and used by
10281 <tt>binary</tt> must of course be removed by the
10282 <tt>clean</tt> target.</p></sect1>
10286 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10290 As it exists on the FTP site, a Debian source package
10291 consists of three related files. You must have the right
10292 versions of all three to be able to use them.
10297 <tag>Debian source control file - <tt>.dsc</tt></tag>
10299 This file is a control file used by <prgn>dpkg-source</prgn>
10300 to extract a source package.
10301 See <ref id="debiansourcecontrolfiles">.
10305 Original source archive -
10307 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10313 This is a compressed (with <tt>gzip -9</tt>)
10314 <prgn>tar</prgn> file containing the source code from
10315 the upstream authors of the program.
10320 Debian package diff -
10322 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10328 This is a unified context diff (<tt>diff -u</tt>)
10329 giving the changes which are required to turn the
10330 original source into the Debian source. These changes
10331 may only include editing and creating plain files.
10332 The permissions of files, the targets of symbolic
10333 links and the characteristics of special files or
10334 pipes may not be changed and no files may be removed
10339 All the directories in the diff must exist, except the
10340 <file>debian</file> subdirectory of the top of the source
10341 tree, which will be created by
10342 <prgn>dpkg-source</prgn> if necessary when unpacking.
10346 The <prgn>dpkg-source</prgn> program will
10347 automatically make the <file>debian/rules</file> file
10348 executable (see below).</p></item>
10353 If there is no original source code - for example, if the
10354 package is specially prepared for Debian or the Debian
10355 maintainer is the same as the upstream maintainer - the
10356 format is slightly different: then there is no diff, and the
10358 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10359 and preferably contains a directory named
10360 <file><var>package</var>-<var>version</var></file>.
10365 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10368 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10369 Debian source package. However, if it is not available it
10370 is possible to unpack a Debian source archive as follows:
10371 <enumlist compact="compact">
10374 Untar the tarfile, which will create a <file>.orig</file>
10378 <p>Rename the <file>.orig</file> directory to
10379 <file><var>package</var>-<var>version</var></file>.</p>
10383 Create the subdirectory <file>debian</file> at the top of
10384 the source tree.</p>
10386 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10388 <item><p>Untar the tarfile again if you want a copy of the original
10389 source code alongside the Debian version.</p>
10394 It is not possible to generate a valid Debian source archive
10395 without using <prgn>dpkg-source</prgn>. In particular,
10396 attempting to use <prgn>diff</prgn> directly to generate the
10397 <file>.diff.gz</file> file will not work.
10401 <heading>Restrictions on objects in source packages</heading>
10404 The source package may not contain any hard links
10406 This is not currently detected when building source
10407 packages, but only when extracting
10411 Hard links may be permitted at some point in the
10412 future, but would require a fair amount of
10414 </footnote>, device special files, sockets or setuid or
10417 Setgid directories are allowed.
10422 The source packaging tools manage the changes between the
10423 original and Debian source using <prgn>diff</prgn> and
10424 <prgn>patch</prgn>. Turning the original source tree as
10425 included in the <file>.orig.tar.gz</file> into the Debian
10426 package source must not involve any changes which cannot be
10427 handled by these tools. Problematic changes which cause
10428 <prgn>dpkg-source</prgn> to halt with an error when
10429 building the source package are:
10430 <list compact="compact">
10431 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10433 <item><p>Changing the targets of symbolic links.</p>
10435 <item><p>Creating directories, other than <file>debian</file>.</p>
10437 <item><p>Changes to the contents of binary files.</p></item>
10438 </list> Changes which cause <prgn>dpkg-source</prgn> to
10439 print a warning but continue anyway are:
10440 <list compact="compact">
10443 Removing files, directories or symlinks.
10445 Renaming a file is not treated specially - it is
10446 seen as the removal of the old file (which
10447 generates a warning, but is otherwise ignored),
10448 and the creation of the new one.
10454 Changed text files which are missing the usual final
10455 newline (either in the original or the modified
10460 Changes which are not represented, but which are not detected by
10461 <prgn>dpkg-source</prgn>, are:
10462 <list compact="compact">
10463 <item><p>Changing the permissions of files (other than
10464 <file>debian/rules</file>) and directories.</p></item>
10469 The <file>debian</file> directory and <file>debian/rules</file>
10470 are handled specially by <prgn>dpkg-source</prgn> - before
10471 applying the changes it will create the <file>debian</file>
10472 directory, and afterwards it will make
10473 <file>debian/rules</file> world-executable.
10479 <appendix id="pkg-controlfields">
10480 <heading>Control files and their fields (from old Packaging Manual)</heading>
10483 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10484 data in a common format, known as control files. Binary and
10485 source packages have control data as do the <file>.changes</file>
10486 files which control the installation of uploaded files, and
10487 <prgn>dpkg</prgn>'s internal databases are in a similar
10492 <heading>Syntax of control files</heading>
10495 See <ref id="controlsyntax">.
10499 It is important to note that there are several fields which
10500 are optional as far as <prgn>dpkg</prgn> and the related
10501 tools are concerned, but which must appear in every Debian
10502 package, or whose omission may cause problems.
10507 <heading>List of fields</heading>
10510 See <ref id="controlfieldslist">.
10514 This section now contains only the fields that didn't belong
10515 to the Policy manual.
10518 <sect1 id="pkg-f-Filename">
10519 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10522 These fields in <tt>Packages</tt> files give the
10523 filename(s) of (the parts of) a package in the
10524 distribution directories, relative to the root of the
10525 Debian hierarchy. If the package has been split into
10526 several parts the parts are all listed in order, separated
10531 <sect1 id="pkg-f-Size">
10532 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10535 These fields in <file>Packages</file> files give the size (in
10536 bytes, expressed in decimal) and MD5 checksum of the
10537 file(s) which make(s) up a binary package in the
10538 distribution. If the package is split into several parts
10539 the values for the parts are listed in order, separated by
10544 <sect1 id="pkg-f-Status">
10545 <heading><tt>Status</tt></heading>
10548 This field in <prgn>dpkg</prgn>'s status file records
10549 whether the user wants a package installed, removed or
10550 left alone, whether it is broken (requiring
10551 re-installation) or not and what its current state on the
10552 system is. Each of these pieces of information is a
10557 <sect1 id="pkg-f-Config-Version">
10558 <heading><tt>Config-Version</tt></heading>
10561 If a package is not installed or not configured, this
10562 field in <prgn>dpkg</prgn>'s status file records the last
10563 version of the package which was successfully
10568 <sect1 id="pkg-f-Conffiles">
10569 <heading><tt>Conffiles</tt></heading>
10572 This field in <prgn>dpkg</prgn>'s status file contains
10573 information about the automatically-managed configuration
10574 files held by a package. This field should <em>not</em>
10575 appear anywhere in a package!
10580 <heading>Obsolete fields</heading>
10583 These are still recognized by <prgn>dpkg</prgn> but should
10584 not appear anywhere any more.
10586 <taglist compact="compact">
10588 <tag><tt>Revision</tt></tag>
10589 <tag><tt>Package-Revision</tt></tag>
10590 <tag><tt>Package_Revision</tt></tag>
10592 The Debian revision part of the package version was
10593 at one point in a separate control file field. This
10594 field went through several names.
10597 <tag><tt>Recommended</tt></tag>
10598 <item>Old name for <tt>Recommends</tt>.</item>
10600 <tag><tt>Optional</tt></tag>
10601 <item>Old name for <tt>Suggests</tt>.</item>
10603 <tag><tt>Class</tt></tag>
10604 <item>Old name for <tt>Priority</tt>.</item>
10613 <appendix id="pkg-conffiles">
10614 <heading>Configuration file handling (from old Packaging Manual)</heading>
10617 <prgn>dpkg</prgn> can do a certain amount of automatic
10618 handling of package configuration files.
10622 Whether this mechanism is appropriate depends on a number of
10623 factors, but basically there are two approaches to any
10624 particular configuration file.
10628 The easy method is to ship a best-effort configuration in the
10629 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10630 handle updates. If the user is unlikely to want to edit the
10631 file, but you need them to be able to without losing their
10632 changes, and a new package with a changed version of the file
10633 is only released infrequently, this is a good approach.
10637 The hard method is to build the configuration file from
10638 scratch in the <prgn>postinst</prgn> script, and to take the
10639 responsibility for fixing any mistakes made in earlier
10640 versions of the package automatically. This will be
10641 appropriate if the file is likely to need to be different on
10645 <sect><heading>Automatic handling of configuration files by
10650 A package may contain a control area file called
10651 <tt>conffiles</tt>. This file should be a list of filenames
10652 of configuration files needing automatic handling, separated
10653 by newlines. The filenames should be absolute pathnames,
10654 and the files referred to should actually exist in the
10659 When a package is upgraded <prgn>dpkg</prgn> will process
10660 the configuration files during the configuration stage,
10661 shortly before it runs the package's <prgn>postinst</prgn>
10666 For each file it checks to see whether the version of the
10667 file included in the package is the same as the one that was
10668 included in the last version of the package (the one that is
10669 being upgraded from); it also compares the version currently
10670 installed on the system with the one shipped with the last
10675 If neither the user nor the package maintainer has changed
10676 the file, it is left alone. If one or the other has changed
10677 their version, then the changed version is preferred - i.e.,
10678 if the user edits their file, but the package maintainer
10679 doesn't ship a different version, the user's changes will
10680 stay, silently, but if the maintainer ships a new version
10681 and the user hasn't edited it the new version will be
10682 installed (with an informative message). If both have
10683 changed their version the user is prompted about the problem
10684 and must resolve the differences themselves.
10688 The comparisons are done by calculating the MD5 message
10689 digests of the files, and storing the MD5 of the file as it
10690 was included in the most recent version of the package.
10694 When a package is installed for the first time
10695 <prgn>dpkg</prgn> will install the file that comes with it,
10696 unless that would mean overwriting a file already on the
10701 However, note that <prgn>dpkg</prgn> will <em>not</em>
10702 replace a conffile that was removed by the user (or by a
10703 script). This is necessary because with some programs a
10704 missing file produces an effect hard or impossible to
10705 achieve in another way, so that a missing file needs to be
10706 kept that way if the user did it.
10710 Note that a package should <em>not</em> modify a
10711 <prgn>dpkg</prgn>-handled conffile in its maintainer
10712 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10713 the user confusing and possibly dangerous options for
10714 conffile update when the package is upgraded.</p>
10717 <sect><heading>Fully-featured maintainer script configuration
10722 For files which contain site-specific information such as
10723 the hostname and networking details and so forth, it is
10724 better to create the file in the package's
10725 <prgn>postinst</prgn> script.
10729 This will typically involve examining the state of the rest
10730 of the system to determine values and other information, and
10731 may involve prompting the user for some information which
10732 can't be obtained some other way.
10736 When using this method there are a couple of important
10737 issues which should be considered:
10741 If you discover a bug in the program which generates the
10742 configuration file, or if the format of the file changes
10743 from one version to the next, you will have to arrange for
10744 the postinst script to do something sensible - usually this
10745 will mean editing the installed configuration file to remove
10746 the problem or change the syntax. You will have to do this
10747 very carefully, since the user may have changed the file,
10748 perhaps to fix the very problem that your script is trying
10749 to deal with - you will have to detect these situations and
10750 deal with them correctly.
10754 If you do go down this route it's probably a good idea to
10755 make the program that generates the configuration file(s) a
10756 separate program in <file>/usr/sbin</file>, by convention called
10757 <file><var>package</var>config</file> and then run that if
10758 appropriate from the post-installation script. The
10759 <tt><var>package</var>config</tt> program should not
10760 unquestioningly overwrite an existing configuration - if its
10761 mode of operation is geared towards setting up a package for
10762 the first time (rather than any arbitrary reconfiguration
10763 later) you should have it check whether the configuration
10764 already exists, and require a <tt>--force</tt> flag to
10765 overwrite it.</p></sect>
10768 <appendix id="pkg-alternatives"><heading>Alternative versions of
10769 an interface - <prgn>update-alternatives</prgn> (from old
10774 When several packages all provide different versions of the
10775 same program or file it is useful to have the system select a
10776 default, but to allow the system administrator to change it
10777 and have their decisions respected.
10781 For example, there are several versions of the <prgn>vi</prgn>
10782 editor, and there is no reason to prevent all of them from
10783 being installed at once, each under their own name
10784 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10785 Nevertheless it is desirable to have the name <tt>vi</tt>
10786 refer to something, at least by default.
10790 If all the packages involved cooperate, this can be done with
10791 <prgn>update-alternatives</prgn>.
10795 Each package provides its own version under its own name, and
10796 calls <prgn>update-alternatives</prgn> in its postinst to
10797 register its version (and again in its prerm to deregister
10802 See the man page <manref name="update-alternatives"
10803 section="8"> for details.
10807 If <prgn>update-alternatives</prgn> does not seem appropriate
10808 you may wish to consider using diversions instead.</p>
10811 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10812 package's version of a file (from old Packaging Manual)
10816 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10817 when it reinstalls the package it belongs to, and to have it
10818 put the file from the package somewhere else instead.
10822 This can be used locally to override a package's version of a
10823 file, or by one package to override another's version (or
10824 provide a wrapper for it).
10828 Before deciding to use a diversion, read <ref
10829 id="pkg-alternatives"> to see if you really want a diversion
10830 rather than several alternative versions of a program.
10834 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10835 and updated by a special program <prgn>dpkg-divert</prgn>.
10836 Please see <manref name="dpkg-divert" section="8"> for full
10837 details of its operation.
10841 When a package wishes to divert a file from another, it should
10842 call <prgn>dpkg-divert</prgn> in its preinst to add the
10843 diversion and rename the existing file. For example,
10844 supposing that a <prgn>smailwrapper</prgn> package wishes to
10845 install a wrapper around <file>/usr/sbin/smail</file>:
10847 dpkg-divert --package smailwrapper --add --rename \
10848 --divert /usr/sbin/smail.real /usr/sbin/smail
10849 </example> The <tt>--package smailwrapper</tt> ensures that
10850 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
10851 can bypass the diversion and get installed as the true version.
10852 It's safe to add the diversion unconditionally on upgrades since
10853 it will be left unchanged if it already exists, but
10854 <prgn>dpkg-divert</prgn> will display a message. To suppress that
10855 message, make the command conditional on the version from which
10856 the package is being upgraded:
10858 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
10859 dpkg-divert --package smailwrapper --add --rename \
10860 --divert /usr/sbin/smail.real /usr/sbin/smail
10862 </example> where <tt>1.0-2</tt> is the version at which the
10863 diversion was first added to the package. Running the command
10864 during abort-upgrade is pointless but harmless.
10868 The postrm has to do the reverse:
10870 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
10871 dpkg-divert --package smailwrapper --remove --rename \
10872 --divert /usr/sbin/smail.real /usr/sbin/smail
10874 </example> If the diversion was added at a particular version, the
10875 postrm should also handle the failure case of upgrading from an
10876 older version (unless the older version is so old that direct
10877 upgrades are no longer supported):
10879 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
10880 dpkg-divert --package smailwrapper --remove --rename \
10881 --divert /usr/sbin/smail.real /usr/sbin/smail
10883 </example> where <tt>1.02-2</tt> is the version at which the
10884 diversion was first added to the package. The postrm should not
10885 remove the diversion on upgrades both because there's no reason to
10886 remove the diversion only to immediately re-add it and since the
10887 postrm of the old package is run after unpacking so the removal of
10888 the diversion will fail.
10892 Do not attempt to divert a file which is vitally important for
10893 the system's operation - when using <prgn>dpkg-divert</prgn>
10894 there is a time, after it has been diverted but before
10895 <prgn>dpkg</prgn> has installed the new version, when the file
10896 does not exist.</p>
10901 <!-- Local variables: -->
10902 <!-- indent-tabs-mode: t -->
10904 <!-- vim:set ai et sts=2 sw=2 tw=76: -->