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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 installed
1062 <em>and</em> configured before it can be installed. 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 installed, 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 installed 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 installed 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 All fields that specify build-time relationships
4377 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4378 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>)
4379 may be restricted to a certain set of architectures. This
4380 is indicated in brackets after each individual package name and
4381 the optional version specification. The brackets enclose a
4382 list of Debian architecture names separated by whitespace.
4383 Exclamation marks may be prepended to each of the names.
4384 (It is not permitted for some names to be prepended with
4385 exclamation marks while others aren't.) If the current Debian
4386 host architecture is not in this list and there are no
4387 exclamation marks in the list, or it is in the list with a
4388 prepended exclamation mark, the package name and the
4389 associated version specification are ignored completely for
4390 the purposes of defining the relationships.
4395 <example compact="compact">
4397 Build-Depends-Indep: texinfo
4398 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4399 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4401 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4402 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4403 <tt>gnumach-dev</tt> only on hurd-i386.
4407 If the architecture-restricted dependency is part of a set of
4408 alternatives using <tt>|</tt>, that alternative is ignored
4409 completely on architectures that do not match the restriction.
4411 <example compact="compact">
4412 Build-Depends: foo [!i386] | bar [!amd64]
4414 is equivalent to <tt>bar</tt> on the i386 architecture, to
4415 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4416 bar</tt> on all other architectures.
4420 All fields that specify build-time relationships may also be
4421 restricted to a certain set of architectures using architecture
4422 wildcards. The syntax for declaring such restrictions is the
4423 same as declaring restrictions using a certain set of
4424 architectures without architecture wildcards. For example:
4425 <example compact="compact">
4426 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4428 is equivalent to <tt>foo</tt> on architectures using the Linux
4429 kernel and any cpu, <tt>bar</tt> on architectures using any
4430 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4431 using a kernel other than Linux.
4435 Note that the binary package relationship fields such as
4436 <tt>Depends</tt> appear in one of the binary package
4437 sections of the control file, whereas the build-time
4438 relationships such as <tt>Build-Depends</tt> appear in the
4439 source package section of the control file (which is the
4444 <sect id="binarydeps">
4445 <heading>Binary Dependencies - <tt>Depends</tt>,
4446 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4447 <tt>Pre-Depends</tt>
4451 Packages can declare in their control file that they have
4452 certain relationships to other packages - for example, that
4453 they may not be installed at the same time as certain other
4454 packages, and/or that they depend on the presence of others.
4458 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4459 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4460 <tt>Breaks</tt> and <tt>Conflicts</tt> control file fields.
4461 <tt>Breaks</tt> is described in <ref id="breaks">, and
4462 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4463 rest are described below.
4467 These seven fields are used to declare a dependency
4468 relationship by one package on another. Except for
4469 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4470 depending (binary) package's control file.
4471 (<tt>Enhances</tt> appears in the recommending package's
4472 control file, and <tt>Breaks</tt> appears in the version of
4473 depended-on package which causes the named package to
4478 A <tt>Depends</tt> field takes effect <em>only</em> when a
4479 package is to be configured. It does not prevent a package
4480 being on the system in an unconfigured state while its
4481 dependencies are unsatisfied, and it is possible to replace
4482 a package whose dependencies are satisfied and which is
4483 properly installed with a different version whose
4484 dependencies are not and cannot be satisfied; when this is
4485 done the depending package will be left unconfigured (since
4486 attempts to configure it will give errors) and will not
4487 function properly. If it is necessary, a
4488 <tt>Pre-Depends</tt> field can be used, which has a partial
4489 effect even when a package is being unpacked, as explained
4490 in detail below. (The other three dependency fields,
4491 <tt>Recommends</tt>, <tt>Suggests</tt> and
4492 <tt>Enhances</tt>, are only used by the various front-ends
4493 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4494 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4498 For this reason packages in an installation run are usually
4499 all unpacked first and all configured later; this gives
4500 later versions of packages with dependencies on later
4501 versions of other packages the opportunity to have their
4502 dependencies satisfied.
4506 In case of circular dependencies, since installation or
4507 removal order honoring the dependency order can't be
4508 established, dependency loops are broken at some point
4509 (based on rules below), and some packages may not be able to
4510 rely on their dependencies being present when being
4511 installed or removed, depending on which side of the break
4512 of the circular dependency loop they happen to be on. If one
4513 of the packages in the loop has no postinst script, then the
4514 cycle will be broken at that package, so as to ensure that
4515 all postinst scripts run with the dependencies properly
4516 configured if this is possible. Otherwise the breaking point
4521 The <tt>Depends</tt> field thus allows package maintainers
4522 to impose an order in which packages should be configured.
4526 The meaning of the five dependency fields is as follows:
4528 <tag><tt>Depends</tt></tag>
4531 This declares an absolute dependency. A package will
4532 not be configured unless all of the packages listed in
4533 its <tt>Depends</tt> field have been correctly
4538 The <tt>Depends</tt> field should be used if the
4539 depended-on package is required for the depending
4540 package to provide a significant amount of
4545 The <tt>Depends</tt> field should also be used if the
4546 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4547 <prgn>postrm</prgn> scripts require the package to be
4548 present in order to run. Note, however, that the
4549 <prgn>postrm</prgn> cannot rely on any non-essential
4550 packages to be present during the <tt>purge</tt>
4554 <tag><tt>Recommends</tt></tag>
4557 This declares a strong, but not absolute, dependency.
4561 The <tt>Recommends</tt> field should list packages
4562 that would be found together with this one in all but
4563 unusual installations.
4567 <tag><tt>Suggests</tt></tag>
4569 This is used to declare that one package may be more
4570 useful with one or more others. Using this field
4571 tells the packaging system and the user that the
4572 listed packages are related to this one and can
4573 perhaps enhance its usefulness, but that installing
4574 this one without them is perfectly reasonable.
4577 <tag><tt>Enhances</tt></tag>
4579 This field is similar to Suggests but works in the
4580 opposite direction. It is used to declare that a
4581 package can enhance the functionality of another
4585 <tag><tt>Pre-Depends</tt></tag>
4588 This field is like <tt>Depends</tt>, except that it
4589 also forces <prgn>dpkg</prgn> to complete installation
4590 of the packages named before even starting the
4591 installation of the package which declares the
4592 pre-dependency, as follows:
4596 When a package declaring a pre-dependency is about to
4597 be <em>unpacked</em> the pre-dependency can be
4598 satisfied if the depended-on package is either fully
4599 configured, <em>or even if</em> the depended-on
4600 package(s) are only unpacked or in the "Half-Configured"
4601 state, provided that they have been configured
4602 correctly at some point in the past (and not removed
4603 or partially removed since). In this case, both the
4604 previously-configured and currently unpacked or
4605 "Half-Configured" versions must satisfy any version
4606 clause in the <tt>Pre-Depends</tt> field.
4610 When the package declaring a pre-dependency is about
4611 to be <em>configured</em>, the pre-dependency will be
4612 treated as a normal <tt>Depends</tt>, that is, it will
4613 be considered satisfied only if the depended-on
4614 package has been correctly configured.
4618 <tt>Pre-Depends</tt> should be used sparingly,
4619 preferably only by packages whose premature upgrade or
4620 installation would hamper the ability of the system to
4621 continue with any upgrade that might be in progress.
4625 <tt>Pre-Depends</tt> are also required if the
4626 <prgn>preinst</prgn> script depends on the named
4627 package. It is best to avoid this situation if
4635 When selecting which level of dependency to use you should
4636 consider how important the depended-on package is to the
4637 functionality of the one declaring the dependency. Some
4638 packages are composed of components of varying degrees of
4639 importance. Such a package should list using
4640 <tt>Depends</tt> the package(s) which are required by the
4641 more important components. The other components'
4642 requirements may be mentioned as Suggestions or
4643 Recommendations, as appropriate to the components' relative
4649 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4652 When one binary package declares that it breaks another,
4653 <prgn>dpkg</prgn> will refuse to allow the package which
4654 declares <tt>Breaks</tt> be installed unless the broken
4655 package is deconfigured first, and it will refuse to
4656 allow the broken package to be reconfigured.
4660 A package will not be regarded as causing breakage merely
4661 because its configuration files are still installed; it must
4662 be at least "Half-Installed".
4666 A special exception is made for packages which declare that
4667 they break their own package name or a virtual package which
4668 they provide (see below): this does not count as a real
4673 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4674 version clause; such a <tt>Breaks</tt> is introduced in the
4675 version of an (implicit or explicit) dependency which violates
4676 an assumption or reveals a bug in earlier versions of the broken
4677 package, or which takes over a file from earlier versions of the
4678 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
4679 will inform higher-level package management tools that the
4680 broken package must be upgraded before the new one.
4684 If the breaking package also overwrites some files from the
4685 older package, it should use <tt>Replaces</tt> to ensure this
4686 goes smoothly. See <ref id="replaces"> for a full discussion
4687 of taking over files from other packages, including how to
4688 use <tt>Breaks</tt> in those cases.
4692 Many of the cases where <tt>Breaks</tt> should be used were
4693 previously handled with <tt>Conflicts</tt>
4694 because <tt>Breaks</tt> did not yet exist.
4695 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
4696 See <ref id="conflicts"> for more information about the
4701 <sect id="conflicts">
4702 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4705 When one binary package declares a conflict with another
4706 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4707 refuse to allow them to be installed on the system at the
4708 same time. This is a stronger restriction than <tt>Breaks</tt>,
4709 which just prevents both packages from being configured at the
4710 same time. Conflicting packages cannot be unpacked on the
4711 system at the same time.
4715 If one package is to be installed, the other must be removed
4716 first. If the package being installed is marked as replacing
4717 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
4718 normally be used in this case) the one on the system, or the one
4719 on the system is marked as deselected, or both packages are
4720 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
4721 automatically remove the package which is causing the conflict.
4722 Otherwise, it will halt the installation of the new package with
4723 an error. This mechanism is specifically designed to produce an
4724 error when the installed package is <tt>Essential</tt>, but the
4729 A package will not cause a conflict merely because its
4730 configuration files are still installed; it must be at least
4735 A special exception is made for packages which declare a
4736 conflict with their own package name, or with a virtual
4737 package which they provide (see below): this does not
4738 prevent their installation, and allows a package to conflict
4739 with others providing a replacement for it. You use this
4740 feature when you want the package in question to be the only
4741 package providing some feature.
4745 Normally, <tt>Breaks</tt> should be used instead
4746 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
4747 stronger restriction on the ordering of package installation or
4748 upgrade and can make it more difficult for the package manager
4749 to find a correct solution to an upgrade or installation
4750 problem. <tt>Breaks</tt> should be used
4752 <item>when moving a file from one package to another (see
4753 <ref id="replaces">),</item>
4754 <item>when splitting a package (a special case of the previous
4756 <item>when the breaking package exposes a bug in or interacts
4757 badly with particular versions of the broken
4760 <tt>Conflicts</tt> should be used
4762 <item>when two packages provide the same file and will
4763 continue to do so,</item>
4764 <item>in conjunction with <tt>Provides</tt> when only one
4765 package providing a given virtual facility may be installed
4766 at a time (see <ref id="virtual">),</item>
4767 <item>in other cases where one must prevent simultaneous
4768 installation of two packages for reasons that are ongoing
4769 (not fixed in a later version of one of the packages) or
4770 that must prevent both packages from being unpacked at the
4771 same time, not just configured.</item>
4773 Be aware that adding <tt>Conflicts</tt> is normally not the best
4774 solution when two packages provide the same files. Depending on
4775 the reason for that conflict, using alternatives or renaming the
4776 files is often a better approach. See, for
4777 example, <ref id="binaries">.
4781 Neither <tt>Breaks</tt> nor <tt>Conflicts</tt> should be used
4782 unless two packages cannot be installed at the same time or
4783 installing them both causes one of them to be broken or
4784 unusable. Having similar functionality or performing the same
4785 tasks as another package is not sufficient reason to
4786 declare <tt>Breaks</tt> or <tt>Conflicts</tt> with that package.
4790 A <tt>Conflicts</tt> entry may have an "earlier than" version
4791 clause if the reason for the conflict is corrected in a later
4792 version of one of the packages. However, normally the presence
4793 of an "earlier than" version clause is a sign
4794 that <tt>Breaks</tt> should have been used instead. An "earlier
4795 than" version clause in <tt>Conflicts</tt>
4796 prevents <prgn>dpkg</prgn> from upgrading or installing the
4797 package which declares such a conflict until the upgrade or
4798 removal of the conflicted-with package has been completed, which
4799 is a strong restriction.
4803 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4807 As well as the names of actual ("concrete") packages, the
4808 package relationship fields <tt>Depends</tt>,
4809 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4810 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4811 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4812 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4813 may mention "virtual packages".
4817 A <em>virtual package</em> is one which appears in the
4818 <tt>Provides</tt> control file field of another package.
4819 The effect is as if the package(s) which provide a
4820 particular virtual package name had been listed by name
4821 everywhere the virtual package name appears. (See also <ref
4826 If there are both concrete and virtual packages of the same
4827 name, then the dependency may be satisfied (or the conflict
4828 caused) by either the concrete package with the name in
4829 question or any other concrete package which provides the
4830 virtual package with the name in question. This is so that,
4831 for example, supposing we have
4832 <example compact="compact">
4835 </example> and someone else releases an enhanced version of
4836 the <tt>bar</tt> package they can say:
4837 <example compact="compact">
4841 and the <tt>bar-plus</tt> package will now also satisfy the
4842 dependency for the <tt>foo</tt> package.
4846 If a relationship field has a version number attached, only real
4847 packages will be considered to see whether the relationship is
4848 satisfied (or the prohibition violated, for a conflict or
4849 breakage). In other words, if a version number is specified,
4850 this is a request to ignore all <tt>Provides</tt> for that
4851 package name and consider only real packages. The package
4852 manager will assume that a package providing that virtual
4853 package is not of the "right" version. A <tt>Provides</tt>
4854 field may not contain version numbers, and the version number of
4855 the concrete package which provides a particular virtual package
4856 will not be considered when considering a dependency on or
4857 conflict with the virtual package name.<footnote>
4858 It is possible that a future release of <prgn>dpkg</prgn> may
4859 add the ability to specify a version number for each virtual
4860 package it provides. This feature is not yet present,
4861 however, and is expected to be used only infrequently.
4866 To specify which of a set of real packages should be the default
4867 to satisfy a particular dependency on a virtual package, list
4868 the real package as an alternative before the virtual one.
4872 If the virtual package represents a facility that can only be
4873 provided by one real package at a time, such as
4874 the <package>mail-transport-agent</package> virtual package that
4875 requires installation of a binary that would conflict with all
4876 other providers of that virtual package (see
4877 <ref id="mail-transport-agents">), all packages providing that
4878 virtual package should also declare a conflict with it
4879 using <tt>Conflicts</tt>. This will ensure that at most one
4880 provider of that virtual package is unpacked or installed at a
4885 <sect id="replaces"><heading>Overwriting files and replacing
4886 packages - <tt>Replaces</tt></heading>
4889 Packages can declare in their control file that they should
4890 overwrite files in certain other packages, or completely
4891 replace other packages. The <tt>Replaces</tt> control file
4892 field has these two distinct purposes.
4895 <sect1><heading>Overwriting files in other packages</heading>
4898 It is usually an error for a package to contain files which
4899 are on the system in another package. However, if the
4900 overwriting package declares that it <tt>Replaces</tt> the one
4901 containing the file being overwritten, then <prgn>dpkg</prgn>
4902 will replace the file from the old package with that from the
4903 new. The file will no longer be listed as "owned" by the old
4904 package and will be taken over by the new package.
4905 Normally, <tt>Breaks</tt> should be used in conjunction
4906 with <tt>Replaces</tt>.<footnote>
4907 To see why <tt>Breaks</tt> is normally needed in addition
4908 to <tt>Replaces</tt>, consider the case of a file in the
4909 package <package>foo</package> being taken over by the
4910 package <package>foo-data</package>.
4911 <tt>Replaces</tt> will allow <package>foo-data</package> to
4912 be installed and take over that file. However,
4913 without <tt>Breaks</tt>, nothing
4914 requires <package>foo</package> to be upgraded to a newer
4915 version that knows it does not include that file and instead
4916 depends on <package>foo-data</package>. Nothing would
4917 prevent the new <package>foo-data</package> package from
4918 being installed and then removed, removing the file that it
4919 took over from <package>foo</package>. After that
4920 operation, the package manager would think the system was in
4921 a consistent state, but the <package>foo</package> package
4922 would be missing one of its files.
4927 For example, if a package <package>foo</package> is split
4928 into <package>foo</package> and <package>foo-data</package>
4929 starting at version 1.2-3, <package>foo-data</package> would
4931 <example compact="compact">
4932 Replaces: foo (<< 1.2-3)
4933 Breaks: foo (<< 1.2-3)
4935 in its control file. The new version of the
4936 package <package>foo</package> would normally have the field
4937 <example compact="compact">
4938 Depends: foo-data (>= 1.2-3)
4940 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
4941 the files moved into <package>foo-data</package> are not
4942 required for normal operation).
4946 If a package is completely replaced in this way, so that
4947 <prgn>dpkg</prgn> does not know of any files it still
4948 contains, it is considered to have "disappeared". It will
4949 be marked as not wanted on the system (selected for
4950 removal) and not installed. Any <tt>conffile</tt>s
4951 details noted for the package will be ignored, as they
4952 will have been taken over by the overwriting package. The
4953 package's <prgn>postrm</prgn> script will be run with a
4954 special argument to allow the package to do any final
4955 cleanup required. See <ref id="mscriptsinstact">.
4957 Replaces is a one way relationship. You have to install
4958 the replacing package after the replaced package.
4963 For this usage of <tt>Replaces</tt>, virtual packages (see
4964 <ref id="virtual">) are not considered when looking at a
4965 <tt>Replaces</tt> field. The packages declared as being
4966 replaced must be mentioned by their real names.
4970 This usage of <tt>Replaces</tt> only takes effect when both
4971 packages are at least partially on the system at once. It is
4972 not relevant if the packages conflict unless the conflict has
4977 <sect1><heading>Replacing whole packages, forcing their
4981 Second, <tt>Replaces</tt> allows the packaging system to
4982 resolve which package should be removed when there is a
4983 conflict (see <ref id="conflicts">). This usage only takes
4984 effect when the two packages <em>do</em> conflict, so that the
4985 two usages of this field do not interfere with each other.
4989 In this situation, the package declared as being replaced
4990 can be a virtual package, so for example, all mail
4991 transport agents (MTAs) would have the following fields in
4992 their control files:
4993 <example compact="compact">
4994 Provides: mail-transport-agent
4995 Conflicts: mail-transport-agent
4996 Replaces: mail-transport-agent
4998 ensuring that only one MTA can be installed at any one
4999 time. See <ref id="virtual"> for more information about this
5004 <sect id="sourcebinarydeps">
5005 <heading>Relationships between source and binary packages -
5006 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5007 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5011 Source packages that require certain binary packages to be
5012 installed or absent at the time of building the package
5013 can declare relationships to those binary packages.
5017 This is done using the <tt>Build-Depends</tt>,
5018 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5019 <tt>Build-Conflicts-Indep</tt> control file fields.
5023 Build-dependencies on "build-essential" binary packages can be
5024 omitted. Please see <ref id="pkg-relations"> for more information.
5028 The dependencies and conflicts they define must be satisfied
5029 (as defined earlier for binary packages) in order to invoke
5030 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5032 There is no Build-Depends-Arch; this role is essentially
5033 met with Build-Depends. Anyone building the
5034 <tt>build-indep</tt> and binary-indep<tt></tt> targets is
5035 assumed to be building the whole package, and therefore
5036 installation of all build dependencies is required.
5039 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5040 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5041 not yet know how to check for its existence, and
5042 <tt>binary-arch</tt>. The purpose of the original split
5043 between <tt>Build-Depends</tt> and
5044 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5045 wouldn't need to install extra packages needed only for the
5046 binary-indep targets. But without a build-arch/build-indep
5047 split, this didn't work, since most of the work is done in
5048 the build target, not in the binary target.
5052 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5053 <tt>binary-arch</tt></tag>
5055 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5056 fields must be satisfied when these targets are invoked.
5058 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5059 and <tt>binary-indep</tt></tag>
5061 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5062 <tt>Build-Depends-Indep</tt>, and
5063 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5064 these targets are invoked.
5072 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5075 Packages containing shared libraries must be constructed with
5076 a little care to make sure that the shared library is always
5077 available. This is especially important for packages whose
5078 shared libraries are vitally important, such as the C library
5079 (currently <tt>libc6</tt>).
5083 Packages involving shared libraries should be split up into
5084 several binary packages. This section mostly deals with how
5085 this separation is to be accomplished; rules for files within
5086 the shared library packages are in <ref id="libraries"> instead.
5089 <sect id="sharedlibs-runtime">
5090 <heading>Run-time shared libraries</heading>
5093 The run-time shared library needs to be placed in a package
5094 whose name changes whenever the shared object version
5097 Since it is common place to install several versions of a
5098 package that just provides shared libraries, it is a
5099 good idea that the library package should not
5100 contain any extraneous non-versioned files, unless they
5101 happen to be in versioned directories.</p>
5103 The most common mechanism is to place it in a package
5105 <package><var>libraryname</var><var>soversion</var></package>,
5106 where <file><var>soversion</var></file> is the version number
5107 in the soname of the shared library<footnote>
5108 The soname is the shared object name: it's the thing
5109 that has to match exactly between building an executable
5110 and running it for the dynamic linker to be able run the
5111 program. For example, if the soname of the library is
5112 <file>libfoo.so.6</file>, the library package would be
5113 called <file>libfoo6</file>.
5115 Alternatively, if it would be confusing to directly append
5116 <var>soversion</var> to <var>libraryname</var> (e.g. because
5117 <var>libraryname</var> itself ends in a number), you may use
5118 <package><var>libraryname</var>-<var>soversion</var></package> and
5119 <package><var>libraryname</var>-<var>soversion</var>-dev</package>
5124 If you have several shared libraries built from the same
5125 source tree you may lump them all together into a single
5126 shared library package, provided that you change all of
5127 their sonames at once (so that you don't get filename
5128 clashes if you try to install different versions of the
5129 combined shared libraries package).
5133 The package should install the shared libraries under
5134 their normal names. For example, the <package>libgdbm3</package>
5135 package should install <file>libgdbm.so.3.0.0</file> as
5136 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5137 renamed or re-linked by any <prgn>prerm</prgn> or
5138 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5139 of renaming things safely without affecting running programs,
5140 and attempts to interfere with this are likely to lead to
5145 Shared libraries should not be installed executable, since
5146 the dynamic linker does not require this and trying to
5147 execute a shared library usually results in a core dump.
5151 The run-time library package should include the symbolic link that
5152 <prgn>ldconfig</prgn> would create for the shared libraries.
5153 For example, the <package>libgdbm3</package> package should include
5154 a symbolic link from <file>/usr/lib/libgdbm.so.3</file> to
5155 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5156 linker (for example <prgn>ld.so</prgn> or
5157 <prgn>ld-linux.so.*</prgn>) can find the library between the
5158 time that <prgn>dpkg</prgn> installs it and the time that
5159 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5161 The package management system requires the library to be
5162 placed before the symbolic link pointing to it in the
5163 <file>.deb</file> file. This is so that when
5164 <prgn>dpkg</prgn> comes to install the symlink
5165 (overwriting the previous symlink pointing at an older
5166 version of the library), the new shared library is already
5167 in place. In the past, this was achieved by creating the
5168 library in the temporary packaging directory before
5169 creating the symlink. Unfortunately, this was not always
5170 effective, since the building of the tar file in the
5171 <file>.deb</file> depended on the behavior of the underlying
5172 file system. Some file systems (such as reiserfs) reorder
5173 the files so that the order of creation is forgotten.
5174 Since version 1.7.0, <prgn>dpkg</prgn>
5175 reorders the files itself as necessary when building a
5176 package. Thus it is no longer important to concern
5177 oneself with the order of file creation.
5181 <sect1 id="ldconfig">
5182 <heading><tt>ldconfig</tt></heading>
5185 Any package installing shared libraries in one of the default
5186 library directories of the dynamic linker (which are currently
5187 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5188 listed in <file>/etc/ld.so.conf</file><footnote>
5190 <list compact="compact">
5191 <item>/usr/local/lib</item>
5192 <item>/usr/lib/libc5-compat</item>
5193 <item>/lib/libc5-compat</item>
5196 must use <prgn>ldconfig</prgn> to update the shared library
5201 The package maintainer scripts must only call
5202 <prgn>ldconfig</prgn> under these circumstances:
5203 <list compact="compact">
5204 <item>When the <prgn>postinst</prgn> script is run with a
5205 first argument of <tt>configure</tt>, the script must call
5206 <prgn>ldconfig</prgn>, and may optionally invoke
5207 <prgn>ldconfig</prgn> at other times.
5209 <item>When the <prgn>postrm</prgn> script is run with a
5210 first argument of <tt>remove</tt>, the script should call
5211 <prgn>ldconfig</prgn>.
5216 During install or upgrade, the preinst is called before
5217 the new files are installed, so calling "ldconfig" is
5218 pointless. The preinst of an existing package can also be
5219 called if an upgrade fails. However, this happens during
5220 the critical time when a shared libs may exist on-disk
5221 under a temporary name. Thus, it is dangerous and
5222 forbidden by current policy to call "ldconfig" at this
5227 When a package is installed or upgraded, "postinst
5228 configure" runs after the new files are safely on-disk.
5229 Since it is perfectly safe to invoke ldconfig
5230 unconditionally in a postinst, it is OK for a package to
5231 simply put ldconfig in its postinst without checking the
5232 argument. The postinst can also be called to recover from
5233 a failed upgrade. This happens before any new files are
5234 unpacked, so there is no reason to call "ldconfig" at this
5239 For a package that is being removed, prerm is
5240 called with all the files intact, so calling ldconfig is
5241 useless. The other calls to "prerm" happen in the case of
5242 upgrade at a time when all the files of the old package
5243 are on-disk, so again calling "ldconfig" is pointless.
5247 postrm, on the other hand, is called with the "remove"
5248 argument just after the files are removed, so this is
5249 the proper time to call "ldconfig" to notify the system
5250 of the fact that the shared libraries from the package
5251 are removed. The postrm can be called at several other
5252 times. At the time of "postrm purge", "postrm
5253 abort-install", or "postrm abort-upgrade", calling
5254 "ldconfig" is useless because the shared lib files are
5255 not on-disk. However, when "postrm" is invoked with
5256 arguments "upgrade", "failed-upgrade", or "disappear", a
5257 shared lib may exist on-disk under a temporary filename.
5265 <sect id="sharedlibs-support-files">
5266 <heading>Shared library support files</heading>
5269 If your package contains files whose names do not change with
5270 each change in the library shared object version, you must not
5271 put them in the shared library package. Otherwise, several
5272 versions of the shared library cannot be installed at the same
5273 time without filename clashes, making upgrades and transitions
5274 unnecessarily difficult.
5278 It is recommended that supporting files and run-time support
5279 programs that do not need to be invoked manually by users, but
5280 are nevertheless required for the package to function, be placed
5281 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5282 preferably under <file>/usr/lib/</file><var>package-name</var>.
5283 If the program or file is architecture independent, the
5284 recommendation is for it to be placed in a subdirectory of
5285 <file>/usr/share</file> instead, preferably under
5286 <file>/usr/share/</file><var>package-name</var>. Following the
5287 <var>package-name</var> naming convention ensures that the file
5288 names change when the shared object version changes.
5292 Run-time support programs that use the shared library but are
5293 not required for the library to function or files used by the
5294 shared library that can be used by any version of the shared
5295 library package should instead be put in a separate package.
5296 This package might typically be named
5297 <package><var>libraryname</var>-tools</package>; note the
5298 absence of the <var>soversion</var> in the package name.
5302 Files and support programs only useful when compiling software
5303 against the library should be included in the development
5304 package for the library.<footnote>
5305 For example, a <file><var>package-name</var>-config</file>
5306 script or <package>pkg-config</package> configuration files.
5311 <sect id="sharedlibs-static">
5312 <heading>Static libraries</heading>
5315 The static library (<file><var>libraryname.a</var></file>)
5316 is usually provided in addition to the shared version.
5317 It is placed into the development package (see below).
5321 In some cases, it is acceptable for a library to be
5322 available in static form only; these cases include:
5324 <item>libraries for languages whose shared library support
5325 is immature or unstable</item>
5326 <item>libraries whose interfaces are in flux or under
5327 development (commonly the case when the library's
5328 major version number is zero, or where the ABI breaks
5329 across patchlevels)</item>
5330 <item>libraries which are explicitly intended to be
5331 available only in static form by their upstream
5336 <sect id="sharedlibs-dev">
5337 <heading>Development files</heading>
5340 If there are development files associated with a shared library,
5341 the source package needs to generate a binary development package
5342 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5343 or if you prefer only to support one development version at a
5344 time, <package><var>libraryname</var>-dev</package>. Installing
5345 the development package must result in installation of all the
5346 development files necessary for compiling programs against that
5347 shared library.<footnote>
5348 This wording allows the development files to be split into
5349 several packages, such as a separate architecture-independent
5350 <package><var>libraryname</var>-headers</package>, provided that
5351 the development package depends on all the required additional
5357 In case several development versions of a library exist, you may
5358 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5359 <ref id="conflicts">) to ensure that the user only installs one
5360 development version at a time (as different development versions are
5361 likely to have the same header files in them, which would cause a
5362 filename clash if both were installed).
5366 The development package should contain a symlink for the associated
5367 shared library without a version number. For example, the
5368 <package>libgdbm-dev</package> package should include a symlink
5369 from <file>/usr/lib/libgdbm.so</file> to
5370 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5371 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5372 <file>libgdbm.so</file> when compiling dynamically.
5376 <sect id="sharedlibs-intradeps">
5377 <heading>Dependencies between the packages of the same library</heading>
5380 Typically the development version should have an exact
5381 version dependency on the runtime library, to make sure that
5382 compilation and linking happens correctly. The
5383 <tt>${binary:Version}</tt> substitution variable can be
5384 useful for this purpose.
5386 Previously, <tt>${Source-Version}</tt> was used, but its name
5387 was confusing and it has been deprecated since dpkg 1.13.19.
5392 <sect id="sharedlibs-shlibdeps">
5393 <heading>Dependencies between the library and other packages -
5394 the <tt>shlibs</tt> system</heading>
5397 If a package contains a binary or library which links to a
5398 shared library, we must ensure that when the package is
5399 installed on the system, all of the libraries needed are
5400 also installed. This requirement led to the creation of the
5401 <tt>shlibs</tt> system, which is very simple in its design:
5402 any package which <em>provides</em> a shared library also
5403 provides information on the package dependencies required to
5404 ensure the presence of this library, and any package which
5405 <em>uses</em> a shared library uses this information to
5406 determine the dependencies it requires. The files which
5407 contain the mapping from shared libraries to the necessary
5408 dependency information are called <file>shlibs</file> files.
5412 When a package is built which contains any shared libraries, it
5413 must provide a <file>shlibs</file> file for other packages to
5414 use. When a package is built which contains any shared
5415 libraries or compiled binaries, it must run
5416 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5417 on these to determine the libraries used and hence the
5418 dependencies needed by this package.<footnote>
5420 <prgn>dpkg-shlibdeps</prgn> will use a program
5421 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
5422 the libraries directly needed by the binaries or shared
5423 libraries in the package.
5427 We say that a binary <tt>foo</tt> <em>directly</em> uses
5428 a library <tt>libbar</tt> if it is explicitly linked
5429 with that library (that is, the library is listed in the ELF
5430 <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
5431 to the link line when the binary is created). Other
5432 libraries that are needed by <tt>libbar</tt> are linked
5433 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5434 linker will load them automatically when it loads
5435 <tt>libbar</tt>. A package should depend on the libraries
5436 it directly uses, but not the libraries it indirectly uses.
5437 The dependencies for those libraries will automatically pull
5438 in the other libraries.
5442 A good example of where this helps is the following. We
5443 could update <tt>libimlib</tt> with a new version that
5444 supports a new graphics format called dgf (but retaining the
5445 same major version number) and depends on <tt>libdgf</tt>.
5446 If we used <prgn>ldd</prgn> to add dependencies for every
5447 library directly or indirectly linked with a binary, every
5448 package that uses <tt>libimlib</tt> would need to be
5449 recompiled so it would also depend on <tt>libdgf</tt> or it
5450 wouldn't run due to missing symbols. Since dependencies are
5451 only added based on ELF <tt>NEEDED</tt> attribute, packages
5452 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
5453 having the dependency on <tt>libdgf</tt> and so they would
5454 not need rebuilding.
5460 In the following sections, we will first describe where the
5461 various <tt>shlibs</tt> files are to be found, then how to
5462 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5463 file format and how to create them if your package contains a
5468 <heading>The <tt>shlibs</tt> files present on the system</heading>
5471 There are several places where <tt>shlibs</tt> files are
5472 found. The following list gives them in the order in which
5474 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5475 (The first one which gives the required information is used.)
5481 <p><file>debian/shlibs.local</file></p>
5484 This lists overrides for this package. This file should
5485 normally not be used, but may be needed temporarily in
5486 unusual situations to work around bugs in other packages,
5487 or in unusual cases where the normally declared dependency
5488 information in the installed <file>shlibs</file> file for
5489 a library cannot be used. This file overrides information
5490 obtained from any other source.
5495 <p><file>/etc/dpkg/shlibs.override</file></p>
5498 This lists global overrides. This list is normally
5499 empty. It is maintained by the local system
5505 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5508 When packages are being built,
5509 any <file>debian/shlibs</file> files are copied into the
5510 control file area of the temporary build directory and
5511 given the name <file>shlibs</file>. These files give
5512 details of any shared libraries included in the same
5514 An example may help here. Let us say that the source
5515 package <tt>foo</tt> generates two binary
5516 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
5517 When building the binary packages, the two packages are
5518 created in the directories <file>debian/libfoo2</file>
5519 and <file>debian/foo-runtime</file> respectively.
5520 (<file>debian/tmp</file> could be used instead of one of
5521 these.) Since <tt>libfoo2</tt> provides the
5522 <tt>libfoo</tt> shared library, it will require a
5523 <tt>shlibs</tt> file, which will be installed in
5524 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually to
5525 become <file>/var/lib/dpkg/info/libfoo2.shlibs</file>.
5526 When <prgn>dpkg-shlibdeps</prgn> is run on the
5527 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
5529 the <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5530 determine whether <tt>foo-prog</tt>'s library
5531 dependencies are satisfied by any of the libraries
5532 provided by <tt>libfoo2</tt>. For this reason,
5533 <prgn>dpkg-shlibdeps</prgn> must only be run once all of
5534 the individual binary packages' <tt>shlibs</tt> files
5535 have been installed into the build directory.
5541 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5544 These are the <file>shlibs</file> files corresponding to
5545 all of the packages installed on the system, and are
5546 maintained by the relevant package maintainers.
5551 <p><file>/etc/dpkg/shlibs.default</file></p>
5554 This file lists any shared libraries whose packages
5555 have failed to provide correct <file>shlibs</file> files.
5556 It was used when the <file>shlibs</file> setup was first
5557 introduced, but it is now normally empty. It is
5558 maintained by the <tt>dpkg</tt> maintainer.
5566 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5567 <file>shlibs</file> files</heading>
5571 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5572 into your <file>debian/rules</file> file. If your package
5573 contains only compiled binaries and libraries (but no scripts),
5574 you can use a command such as:
5575 <example compact="compact">
5576 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5577 debian/tmp/usr/lib/*
5579 Otherwise, you will need to explicitly list the compiled
5580 binaries and libraries.<footnote>
5581 If you are using <tt>debhelper</tt>, the
5582 <prgn>dh_shlibdeps</prgn> program will do this work for you.
5583 It will also correctly handle multi-binary packages.
5588 This command puts the dependency information into the
5589 <file>debian/substvars</file> file, which is then used by
5590 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5591 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5592 field in the control file for this to work.
5596 If you have multiple binary packages, you will need to call
5597 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5598 compiled libraries or binaries. In such a case, you will
5599 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5600 utilities to specify a different <file>substvars</file> file.
5604 If you are creating a udeb for use in the Debian Installer,
5605 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
5606 should use the dependency line of type <tt>udeb</tt> by
5607 adding the <tt>-tudeb</tt> option<footnote>
5608 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5609 will automatically add this option if it knows it is
5611 </footnote>. If there is no dependency line of
5612 type <tt>udeb</tt> in the <file>shlibs</file>
5613 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the regular
5618 For more details on <prgn>dpkg-shlibdeps</prgn>, please see
5619 <ref id="pkg-dpkg-shlibdeps"> and
5620 <manref name="dpkg-shlibdeps" section="1">.
5625 <heading>The <file>shlibs</file> File Format</heading>
5628 Each <file>shlibs</file> file has the same format. Lines
5629 beginning with <tt>#</tt> are considered to be comments and
5630 are ignored. Each line is of the form:
5631 <example compact="compact">
5632 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5637 We will explain this by reference to the example of the
5638 <tt>zlib1g</tt> package, which (at the time of writing)
5639 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5643 <var>type</var> is an optional element that indicates the type
5644 of package for which the line is valid. The only type currently
5645 in use is <tt>udeb</tt>. The colon and space after the type are
5650 <var>library-name</var> is the name of the shared library,
5651 in this case <tt>libz</tt>. (This must match the name part
5652 of the soname, see below.)
5656 <var>soname-version</var> is the version part of the soname of
5657 the library. The soname is the thing that must exactly match
5658 for the library to be recognized by the dynamic linker, and is
5660 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5661 example, <tt>libz.so.1</tt>.<footnote>
5662 This can be determined using the command
5663 <example compact="compact">
5664 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5667 The version part is the part which comes after
5668 <tt>.so.</tt>, so in our case, it is <tt>1</tt>. The soname may
5669 instead be of the form
5670 <tt><var>name</var>-<var>major-version</var>.so</tt>, such
5671 as <tt>libdb-4.8.so</tt>, in which case the name would
5672 be <tt>libdb</tt> and the version would be <tt>4.8</tt>.
5676 <var>dependencies</var> has the same syntax as a dependency
5677 field in a binary package control file. It should give
5678 details of which packages are required to satisfy a binary
5679 built against the version of the library contained in the
5680 package. See <ref id="depsyntax"> for details.
5684 In our example, if the first version of the <tt>zlib1g</tt>
5685 package which contained a minor number of at least
5686 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5687 <tt>shlibs</tt> entry for this library could say:
5688 <example compact="compact">
5689 libz 1 zlib1g (>= 1:1.1.3)
5691 The version-specific dependency is to avoid warnings from
5692 the dynamic linker about using older shared libraries with
5697 As zlib1g also provides a udeb containing the shared library,
5698 there would also be a second line:
5699 <example compact="compact">
5700 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5706 <heading>Providing a <file>shlibs</file> file</heading>
5709 If your package provides a shared library, you need to create
5710 a <file>shlibs</file> file following the format described above.
5711 It is usual to call this file <file>debian/shlibs</file> (but if
5712 you have multiple binary packages, you might want to call it
5713 <file>debian/shlibs.<var>package</var></file> instead). Then
5714 let <file>debian/rules</file> install it in the control area:
5715 <example compact="compact">
5716 install -m644 debian/shlibs debian/tmp/DEBIAN
5718 or, in the case of a multi-binary package:
5719 <example compact="compact">
5720 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5722 An alternative way of doing this is to create the
5723 <file>shlibs</file> file in the control area directly from
5724 <file>debian/rules</file> without using a <file>debian/shlibs</file>
5725 file at all,<footnote>
5726 This is what <prgn>dh_makeshlibs</prgn> in
5727 the <package>debhelper</package> suite does. If your package
5728 also has a udeb that provides a shared
5729 library, <prgn>dh_makeshlibs</prgn> can automatically generate
5730 the <tt>udeb:</tt> lines if you specify the name of the udeb
5731 with the <tt>--add-udeb</tt> option.
5733 since the <file>debian/shlibs</file> file itself is ignored by
5734 <prgn>dpkg-shlibdeps</prgn>.
5738 As <prgn>dpkg-shlibdeps</prgn> reads the
5739 <file>DEBIAN/shlibs</file> files in all of the binary packages
5740 being built from this source package, all of the
5741 <file>DEBIAN/shlibs</file> files should be installed before
5742 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5750 <chapt id="opersys"><heading>The Operating System</heading>
5753 <heading>File system hierarchy</heading>
5757 <heading>File System Structure</heading>
5760 The location of all installed files and directories must
5761 comply with the Filesystem Hierarchy Standard (FHS),
5762 version 2.3, with the exceptions noted below, and except
5763 where doing so would violate other terms of Debian
5764 Policy. The following exceptions to the FHS apply:
5769 The optional rules related to user specific
5770 configuration files for applications are stored in
5771 the user's home directory are relaxed. It is
5772 recommended that such files start with the
5773 '<tt>.</tt>' character (a "dot file"), and if an
5774 application needs to create more than one dot file
5775 then the preferred placement is in a subdirectory
5776 with a name starting with a '.' character, (a "dot
5777 directory"). In this case it is recommended the
5778 configuration files not start with the '.'
5784 The requirement for amd64 to use <file>/lib64</file>
5785 for 64 bit binaries is removed.
5790 The requirement for object files, internal binaries, and
5791 libraries, including <file>libc.so.*</file>, to be located
5792 directly under <file>/lib{,32}</file> and
5793 <file>/usr/lib{,32}</file> is amended, permitting files
5794 to instead be installed to
5795 <file>/lib/<var>triplet</var></file> and
5796 <file>/usr/lib/<var>triplet</var></file>, where
5797 <tt><var>triplet</var></tt> is the value returned by
5798 <tt>dpkg-architecture -qDEB_HOST_GNU_TYPE</tt> for the
5799 architecture of the package. Packages may <em>not</em>
5800 install files to any <var>triplet</var> path other
5801 than the one matching the architecture of that package;
5802 for instance, an <tt>Architecture: amd64</tt> package
5803 containing 32-bit x86 libraries may not install these
5804 libraries to <file>/usr/lib/i486-linux-gnu</file>.
5806 This is necessary in order to reserve the directories for
5807 use in cross-installation of library packages from other
5808 architectures, as part of the planned deployment of
5813 Applications may also use a single subdirectory under
5814 <file>/usr/lib/<var>triplet</var></file>.
5817 The execution time linker/loader, ld*, must still be made
5818 available in the existing location under /lib or /lib64
5819 since this is part of the ELF ABI for the architecture.
5824 The requirement that
5825 <file>/usr/local/share/man</file> be "synonymous"
5826 with <file>/usr/local/man</file> is relaxed to a
5831 The requirement that windowmanagers with a single
5832 configuration file call it <file>system.*wmrc</file>
5833 is removed, as is the restriction that the window
5834 manager subdirectory be named identically to the
5835 window manager name itself.
5840 The requirement that boot manager configuration
5841 files live in <file>/etc</file>, or at least are
5842 symlinked there, is relaxed to a recommendation.
5847 The following directories in the root filesystem are
5848 additionally allowed: <file>/sys</file> and
5849 <file>/selinux</file>. <footnote>These directories
5850 are used as mount points to mount virtual filesystems
5851 to get access to kernel information.</footnote>
5858 The version of this document referred here can be
5859 found in the <tt>debian-policy</tt> package or on <url
5860 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5861 name="FHS (Debian copy)"> alongside this manual (or, if
5862 you have the <package>debian-policy</package> installed,
5864 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5865 (local copy)">). The
5866 latest version, which may be a more recent version, may
5868 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5869 Specific questions about following the standard may be
5870 asked on the <tt>debian-devel</tt> mailing list, or
5871 referred to the FHS mailing list (see the
5872 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
5878 <heading>Site-specific programs</heading>
5881 As mandated by the FHS, packages must not place any
5882 files in <file>/usr/local</file>, either by putting them in
5883 the file system archive to be unpacked by <prgn>dpkg</prgn>
5884 or by manipulating them in their maintainer scripts.
5888 However, the package may create empty directories below
5889 <file>/usr/local</file> so that the system administrator knows
5890 where to place site-specific files. These are not
5891 directories <em>in</em> <file>/usr/local</file>, but are
5892 children of directories in <file>/usr/local</file>. These
5893 directories (<file>/usr/local/*/dir/</file>)
5894 should be removed on package removal if they are
5899 Note that this applies only to
5900 directories <em>below</em> <file>/usr/local</file>,
5901 not <em>in</em> <file>/usr/local</file>. Packages must
5902 not create sub-directories in the
5903 directory <file>/usr/local</file> itself, except those
5904 listed in FHS, section 4.5. However, you may create
5905 directories below them as you wish. You must not remove
5906 any of the directories listed in 4.5, even if you created
5911 Since <file>/usr/local</file> can be mounted read-only from a
5912 remote server, these directories must be created and
5913 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
5914 maintainer scripts and not be included in the
5915 <file>.deb</file> archive. These scripts must not fail if
5916 either of these operations fail.
5920 For example, the <tt>emacsen-common</tt> package could
5921 contain something like
5922 <example compact="compact">
5923 if [ ! -e /usr/local/share/emacs ]
5925 if mkdir /usr/local/share/emacs 2>/dev/null
5927 chown root:staff /usr/local/share/emacs
5928 chmod 2775 /usr/local/share/emacs
5932 in its <prgn>postinst</prgn> script, and
5933 <example compact="compact">
5934 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
5935 rmdir /usr/local/share/emacs 2>/dev/null || true
5937 in the <prgn>prerm</prgn> script. (Note that this form is
5938 used to ensure that if the script is interrupted, the
5939 directory <file>/usr/local/share/emacs</file> will still be
5944 If you do create a directory in <file>/usr/local</file> for
5945 local additions to a package, you should ensure that
5946 settings in <file>/usr/local</file> take precedence over the
5947 equivalents in <file>/usr</file>.
5951 However, because <file>/usr/local</file> and its contents are
5952 for exclusive use of the local administrator, a package
5953 must not rely on the presence or absence of files or
5954 directories in <file>/usr/local</file> for normal operation.
5958 The <file>/usr/local</file> directory itself and all the
5959 subdirectories created by the package should (by default) have
5960 permissions 2775 (group-writable and set-group-id) and be
5961 owned by <tt>root:staff</tt>.
5966 <heading>The system-wide mail directory</heading>
5968 The system-wide mail directory
5969 is <file>/var/mail</file>. This directory is part of the
5970 base system and should not be owned by any particular mail
5971 agents. The use of the old
5972 location <file>/var/spool/mail</file> is deprecated, even
5973 though the spool may still be physically located there.
5979 <heading>Users and groups</heading>
5982 <heading>Introduction</heading>
5984 The Debian system can be configured to use either plain or
5989 Some user ids (UIDs) and group ids (GIDs) are reserved
5990 globally for use by certain packages. Because some
5991 packages need to include files which are owned by these
5992 users or groups, or need the ids compiled into binaries,
5993 these ids must be used on any Debian system only for the
5994 purpose for which they are allocated. This is a serious
5995 restriction, and we should avoid getting in the way of
5996 local administration policies. In particular, many sites
5997 allocate users and/or local system groups starting at 100.
6001 Apart from this we should have dynamically allocated ids,
6002 which should by default be arranged in some sensible
6003 order, but the behavior should be configurable.
6007 Packages other than <tt>base-passwd</tt> must not modify
6008 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
6009 <file>/etc/group</file> or <file>/etc/gshadow</file>.
6014 <heading>UID and GID classes</heading>
6016 The UID and GID numbers are divided into classes as
6022 Globally allocated by the Debian project, the same
6023 on every Debian system. These ids will appear in
6024 the <file>passwd</file> and <file>group</file> files of all
6025 Debian systems, new ids in this range being added
6026 automatically as the <tt>base-passwd</tt> package is
6031 Packages which need a single statically allocated
6032 uid or gid should use one of these; their
6033 maintainers should ask the <tt>base-passwd</tt>
6041 Dynamically allocated system users and groups.
6042 Packages which need a user or group, but can have
6043 this user or group allocated dynamically and
6044 differently on each system, should use <tt>adduser
6045 --system</tt> to create the group and/or user.
6046 <prgn>adduser</prgn> will check for the existence of
6047 the user or group, and if necessary choose an unused
6048 id based on the ranges specified in
6049 <file>adduser.conf</file>.
6053 <tag>1000-59999:</tag>
6056 Dynamically allocated user accounts. By default
6057 <prgn>adduser</prgn> will choose UIDs and GIDs for
6058 user accounts in this range, though
6059 <file>adduser.conf</file> may be used to modify this
6064 <tag>60000-64999:</tag>
6067 Globally allocated by the Debian project, but only
6068 created on demand. The ids are allocated centrally
6069 and statically, but the actual accounts are only
6070 created on users' systems on demand.
6074 These ids are for packages which are obscure or
6075 which require many statically-allocated ids. These
6076 packages should check for and create the accounts in
6077 <file>/etc/passwd</file> or <file>/etc/group</file> (using
6078 <prgn>adduser</prgn> if it has this facility) if
6079 necessary. Packages which are likely to require
6080 further allocations should have a "hole" left after
6081 them in the allocation, to give them room to
6086 <tag>65000-65533:</tag>
6094 User <tt>nobody</tt>. The corresponding gid refers
6095 to the group <tt>nogroup</tt>.
6102 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
6103 not</em> be used, because it is the error return
6112 <sect id="sysvinit">
6113 <heading>System run levels and <file>init.d</file> scripts</heading>
6115 <sect1 id="/etc/init.d">
6116 <heading>Introduction</heading>
6119 The <file>/etc/init.d</file> directory contains the scripts
6120 executed by <prgn>init</prgn> at boot time and when the
6121 init state (or "runlevel") is changed (see <manref
6122 name="init" section="8">).
6126 There are at least two different, yet functionally
6127 equivalent, ways of handling these scripts. For the sake
6128 of simplicity, this document describes only the symbolic
6129 link method. However, it must not be assumed by maintainer
6130 scripts that this method is being used, and any automated
6131 manipulation of the various runlevel behaviors by
6132 maintainer scripts must be performed using
6133 <prgn>update-rc.d</prgn> as described below and not by
6134 manually installing or removing symlinks. For information
6135 on the implementation details of the other method,
6136 implemented in the <tt>file-rc</tt> package, please refer
6137 to the documentation of that package.
6141 These scripts are referenced by symbolic links in the
6142 <file>/etc/rc<var>n</var>.d</file> directories. When changing
6143 runlevels, <prgn>init</prgn> looks in the directory
6144 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
6145 execute, where <tt><var>n</var></tt> is the runlevel that
6146 is being changed to, or <tt>S</tt> for the boot-up
6151 The names of the links all have the form
6152 <file>S<var>mm</var><var>script</var></file> or
6153 <file>K<var>mm</var><var>script</var></file> where
6154 <var>mm</var> is a two-digit number and <var>script</var>
6155 is the name of the script (this should be the same as the
6156 name of the actual script in <file>/etc/init.d</file>).
6160 When <prgn>init</prgn> changes runlevel first the targets
6161 of the links whose names start with a <tt>K</tt> are
6162 executed, each with the single argument <tt>stop</tt>,
6163 followed by the scripts prefixed with an <tt>S</tt>, each
6164 with the single argument <tt>start</tt>. (The links are
6165 those in the <file>/etc/rc<var>n</var>.d</file> directory
6166 corresponding to the new runlevel.) The <tt>K</tt> links
6167 are responsible for killing services and the <tt>S</tt>
6168 link for starting services upon entering the runlevel.
6172 For example, if we are changing from runlevel 2 to
6173 runlevel 3, init will first execute all of the <tt>K</tt>
6174 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
6175 all of the <tt>S</tt> prefixed scripts in that directory.
6176 The links starting with <tt>K</tt> will cause the
6177 referred-to file to be executed with an argument of
6178 <tt>stop</tt>, and the <tt>S</tt> links with an argument
6183 The two-digit number <var>mm</var> is used to determine
6184 the order in which to run the scripts: low-numbered links
6185 have their scripts run first. For example, the
6186 <tt>K20</tt> scripts will be executed before the
6187 <tt>K30</tt> scripts. This is used when a certain service
6188 must be started before another. For example, the name
6189 server <prgn>bind</prgn> might need to be started before
6190 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
6191 can set up its access lists. In this case, the script
6192 that starts <prgn>bind</prgn> would have a lower number
6193 than the script that starts <prgn>inn</prgn> so that it
6195 <example compact="compact">
6202 The two runlevels 0 (halt) and 6 (reboot) are slightly
6203 different. In these runlevels, the links with an
6204 <tt>S</tt> prefix are still called after those with a
6205 <tt>K</tt> prefix, but they too are called with the single
6206 argument <tt>stop</tt>.
6210 <sect1 id="writing-init">
6211 <heading>Writing the scripts</heading>
6214 Packages that include daemons for system services should
6215 place scripts in <file>/etc/init.d</file> to start or stop
6216 services at boot time or during a change of runlevel.
6217 These scripts should be named
6218 <file>/etc/init.d/<var>package</var></file>, and they should
6219 accept one argument, saying what to do:
6222 <tag><tt>start</tt></tag>
6223 <item>start the service,</item>
6225 <tag><tt>stop</tt></tag>
6226 <item>stop the service,</item>
6228 <tag><tt>restart</tt></tag>
6229 <item>stop and restart the service if it's already running,
6230 otherwise start the service</item>
6232 <tag><tt>reload</tt></tag>
6233 <item><p>cause the configuration of the service to be
6234 reloaded without actually stopping and restarting
6237 <tag><tt>force-reload</tt></tag>
6238 <item>cause the configuration to be reloaded if the
6239 service supports this, otherwise restart the
6243 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
6244 <tt>force-reload</tt> options should be supported by all
6245 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
6250 The <file>init.d</file> scripts must ensure that they will
6251 behave sensibly (i.e., returning success and not starting
6252 multiple copies of a service) if invoked with <tt>start</tt>
6253 when the service is already running, or with <tt>stop</tt>
6254 when it isn't, and that they don't kill unfortunately-named
6255 user processes. The best way to achieve this is usually to
6256 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
6261 Be careful of using <tt>set -e</tt> in <file>init.d</file>
6262 scripts. Writing correct <file>init.d</file> scripts requires
6263 accepting various error exit statuses when daemons are already
6264 running or already stopped without aborting
6265 the <file>init.d</file> script, and common <file>init.d</file>
6266 function libraries are not safe to call with <tt>set -e</tt>
6268 <tt>/lib/lsb/init-functions</tt>, which assists in writing
6269 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
6270 in effect and echoing status messages to the console fails,
6272 </footnote>. For <tt>init.d</tt> scripts, it's often easier
6273 to not use <tt>set -e</tt> and instead check the result of
6274 each command separately.
6278 If a service reloads its configuration automatically (as
6279 in the case of <prgn>cron</prgn>, for example), the
6280 <tt>reload</tt> option of the <file>init.d</file> script
6281 should behave as if the configuration has been reloaded
6286 The <file>/etc/init.d</file> scripts must be treated as
6287 configuration files, either (if they are present in the
6288 package, that is, in the .deb file) by marking them as
6289 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6290 by managing them correctly in the maintainer scripts (see
6291 <ref id="config-files">). This is important since we want
6292 to give the local system administrator the chance to adapt
6293 the scripts to the local system, e.g., to disable a
6294 service without de-installing the package, or to specify
6295 some special command line options when starting a service,
6296 while making sure their changes aren't lost during the next
6301 These scripts should not fail obscurely when the
6302 configuration files remain but the package has been
6303 removed, as configuration files remain on the system after
6304 the package has been removed. Only when <prgn>dpkg</prgn>
6305 is executed with the <tt>--purge</tt> option will
6306 configuration files be removed. In particular, as the
6307 <file>/etc/init.d/<var>package</var></file> script itself is
6308 usually a <tt>conffile</tt>, it will remain on the system
6309 if the package is removed but not purged. Therefore, you
6310 should include a <tt>test</tt> statement at the top of the
6312 <example compact="compact">
6313 test -f <var>program-executed-later-in-script</var> || exit 0
6318 Often there are some variables in the <file>init.d</file>
6319 scripts whose values control the behavior of the scripts,
6320 and which a system administrator is likely to want to
6321 change. As the scripts themselves are frequently
6322 <tt>conffile</tt>s, modifying them requires that the
6323 administrator merge in their changes each time the package
6324 is upgraded and the <tt>conffile</tt> changes. To ease
6325 the burden on the system administrator, such configurable
6326 values should not be placed directly in the script.
6327 Instead, they should be placed in a file in
6328 <file>/etc/default</file>, which typically will have the same
6329 base name as the <file>init.d</file> script. This extra file
6330 should be sourced by the script when the script runs. It
6331 must contain only variable settings and comments in SUSv3
6332 <prgn>sh</prgn> format. It may either be a
6333 <tt>conffile</tt> or a configuration file maintained by
6334 the package maintainer scripts. See <ref id="config-files">
6339 To ensure that vital configurable values are always
6340 available, the <file>init.d</file> script should set default
6341 values for each of the shell variables it uses, either
6342 before sourcing the <file>/etc/default/</file> file or
6343 afterwards using something like the <tt>:
6344 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6345 script must behave sensibly and not fail if the
6346 <file>/etc/default</file> file is deleted.
6350 <file>/var/run</file> and <file>/var/lock</file> may be mounted
6351 as temporary filesystems<footnote>
6352 For example, using the <tt>RAMRUN</tt> and <tt>RAMLOCK</tt>
6353 options in <file>/etc/default/rcS</file>.
6354 </footnote>, so the <file>init.d</file> scripts must handle this
6355 correctly. This will typically amount to creating any required
6356 subdirectories dynamically when the <file>init.d</file> script
6357 is run, rather than including them in the package and relying on
6358 <prgn>dpkg</prgn> to create them.
6363 <heading>Interfacing with the initscript system</heading>
6366 Maintainers should use the abstraction layer provided by
6367 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6368 programs to deal with initscripts in their packages'
6369 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6370 and <prgn>postrm</prgn>.
6374 Directly managing the /etc/rc?.d links and directly
6375 invoking the <file>/etc/init.d/</file> initscripts should
6376 be done only by packages providing the initscript
6377 subsystem (such as <prgn>sysv-rc</prgn> and
6378 <prgn>file-rc</prgn>).
6382 <heading>Managing the links</heading>
6385 The program <prgn>update-rc.d</prgn> is provided for
6386 package maintainers to arrange for the proper creation and
6387 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6388 or their functional equivalent if another method is being
6389 used. This may be used by maintainers in their packages'
6390 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6394 You must not include any <file>/etc/rc<var>n</var>.d</file>
6395 symbolic links in the actual archive or manually create or
6396 remove the symbolic links in maintainer scripts; you must
6397 use the <prgn>update-rc.d</prgn> program instead. (The
6398 former will fail if an alternative method of maintaining
6399 runlevel information is being used.) You must not include
6400 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6401 in the archive either. (Only the <tt>sysvinit</tt>
6406 By default <prgn>update-rc.d</prgn> will start services in
6407 each of the multi-user state runlevels (2, 3, 4, and 5)
6408 and stop them in the halt runlevel (0), the single-user
6409 runlevel (1) and the reboot runlevel (6). The system
6410 administrator will have the opportunity to customize
6411 runlevels by simply adding, moving, or removing the
6412 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6413 symbolic links are being used, or by modifying
6414 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6419 To get the default behavior for your package, put in your
6420 <prgn>postinst</prgn> script
6421 <example compact="compact">
6422 update-rc.d <var>package</var> defaults
6424 and in your <prgn>postrm</prgn>
6425 <example compact="compact">
6426 if [ "$1" = purge ]; then
6427 update-rc.d <var>package</var> remove
6429 </example>. Note that if your package changes runlevels
6430 or priority, you may have to remove and recreate the links,
6431 since otherwise the old links may persist. Refer to the
6432 documentation of <prgn>update-rc.d</prgn>.
6436 This will use a default sequence number of 20. If it does
6437 not matter when or in which order the <file>init.d</file>
6438 script is run, use this default. If it does, then you
6439 should talk to the maintainer of the <prgn>sysvinit</prgn>
6440 package or post to <tt>debian-devel</tt>, and they will
6441 help you choose a number.
6445 For more information about using <tt>update-rc.d</tt>,
6446 please consult its man page <manref name="update-rc.d"
6452 <heading>Running initscripts</heading>
6454 The program <prgn>invoke-rc.d</prgn> is provided to make
6455 it easier for package maintainers to properly invoke an
6456 initscript, obeying runlevel and other locally-defined
6457 constraints that might limit a package's right to start,
6458 stop and otherwise manage services. This program may be
6459 used by maintainers in their packages' scripts.
6463 The package maintainer scripts must use
6464 <prgn>invoke-rc.d</prgn> to invoke the
6465 <file>/etc/init.d/*</file> initscripts, instead of
6466 calling them directly.
6470 By default, <prgn>invoke-rc.d</prgn> will pass any
6471 action requests (start, stop, reload, restart...) to the
6472 <file>/etc/init.d</file> script, filtering out requests
6473 to start or restart a service out of its intended
6478 Most packages will simply need to change:
6479 <example compact="compact">/etc/init.d/<package>
6480 <action></example> in their <prgn>postinst</prgn>
6481 and <prgn>prerm</prgn> scripts to:
6482 <example compact="compact">
6483 if which invoke-rc.d >/dev/null 2>&1; then
6484 invoke-rc.d <var>package</var> <action>
6486 /etc/init.d/<var>package</var> <action>
6492 A package should register its initscript services using
6493 <prgn>update-rc.d</prgn> before it tries to invoke them
6494 using <prgn>invoke-rc.d</prgn>. Invocation of
6495 unregistered services may fail.
6499 For more information about using
6500 <prgn>invoke-rc.d</prgn>, please consult its man page
6501 <manref name="invoke-rc.d" section="8">.
6507 <heading>Boot-time initialization</heading>
6510 There used to be another directory, <file>/etc/rc.boot</file>,
6511 which contained scripts which were run once per machine
6512 boot. This has been deprecated in favour of links from
6513 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6514 described in <ref id="/etc/init.d">. Packages must not
6515 place files in <file>/etc/rc.boot</file>.
6520 <heading>Example</heading>
6523 An example on which you can base your
6524 <file>/etc/init.d</file> scripts is found in
6525 <file>/etc/init.d/skeleton</file>.
6532 <heading>Console messages from <file>init.d</file> scripts</heading>
6535 This section describes the formats to be used for messages
6536 written to standard output by the <file>/etc/init.d</file>
6537 scripts. The intent is to improve the consistency of
6538 Debian's startup and shutdown look and feel. For this
6539 reason, please look very carefully at the details. We want
6540 the messages to have the same format in terms of wording,
6541 spaces, punctuation and case of letters.
6545 Here is a list of overall rules that should be used for
6546 messages generated by <file>/etc/init.d</file> scripts.
6552 The message should fit in one line (fewer than 80
6553 characters), start with a capital letter and end with
6554 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6558 If the script is performing some time consuming task in
6559 the background (not merely starting or stopping a
6560 program, for instance), an ellipsis (three dots:
6561 <tt>...</tt>) should be output to the screen, with no
6562 leading or tailing whitespace or line feeds.
6566 The messages should appear as if the computer is telling
6567 the user what it is doing (politely :-), but should not
6568 mention "it" directly. For example, instead of:
6569 <example compact="compact">
6570 I'm starting network daemons: nfsd mountd.
6572 the message should say
6573 <example compact="compact">
6574 Starting network daemons: nfsd mountd.
6581 <tt>init.d</tt> script should use the following standard
6582 message formats for the situations enumerated below.
6588 <p>When daemons are started</p>
6591 If the script starts one or more daemons, the output
6592 should look like this (a single line, no leading
6594 <example compact="compact">
6595 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6597 The <var>description</var> should describe the
6598 subsystem the daemon or set of daemons are part of,
6599 while <var>daemon-1</var> up to <var>daemon-n</var>
6600 denote each daemon's name (typically the file name of
6605 For example, the output of <file>/etc/init.d/lpd</file>
6607 <example compact="compact">
6608 Starting printer spooler: lpd.
6613 This can be achieved by saying
6614 <example compact="compact">
6615 echo -n "Starting printer spooler: lpd"
6616 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6619 in the script. If there are more than one daemon to
6620 start, the output should look like this:
6621 <example compact="compact">
6622 echo -n "Starting remote file system services:"
6623 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6624 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6625 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6628 This makes it possible for the user to see what is
6629 happening and when the final daemon has been started.
6630 Care should be taken in the placement of white spaces:
6631 in the example above the system administrators can
6632 easily comment out a line if they don't want to start
6633 a specific daemon, while the displayed message still
6639 <p>When a system parameter is being set</p>
6642 If you have to set up different system parameters
6643 during the system boot, you should use this format:
6644 <example compact="compact">
6645 Setting <var>parameter</var> to "<var>value</var>".
6650 You can use a statement such as the following to get
6652 <example compact="compact">
6653 echo "Setting DNS domainname to \"$domainname\"."
6658 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
6659 for the left and right quotation marks. A grave accent
6660 (<tt>`</tt>) is not a quote character; neither is an
6661 apostrophe (<tt>'</tt>).
6666 <p>When a daemon is stopped or restarted</p>
6669 When you stop or restart a daemon, you should issue a
6670 message identical to the startup message, except that
6671 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6672 or <tt>Restarting</tt> respectively.
6676 For example, stopping the printer daemon will look like
6678 <example compact="compact">
6679 Stopping printer spooler: lpd.
6685 <p>When something is executed</p>
6688 There are several examples where you have to run a
6689 program at system startup or shutdown to perform a
6690 specific task, for example, setting the system's clock
6691 using <prgn>netdate</prgn> or killing all processes
6692 when the system shuts down. Your message should look
6694 <example compact="compact">
6695 Doing something very useful...done.
6697 You should print the <tt>done.</tt> immediately after
6698 the job has been completed, so that the user is
6699 informed why they have to wait. You can get this
6701 <example compact="compact">
6702 echo -n "Doing something very useful..."
6711 <p>When the configuration is reloaded</p>
6714 When a daemon is forced to reload its configuration
6715 files you should use the following format:
6716 <example compact="compact">
6717 Reloading <var>description</var> configuration...done.
6719 where <var>description</var> is the same as in the
6720 daemon starting message.
6728 <heading>Cron jobs</heading>
6731 Packages must not modify the configuration file
6732 <file>/etc/crontab</file>, and they must not modify the files in
6733 <file>/var/spool/cron/crontabs</file>.</p>
6736 If a package wants to install a job that has to be executed
6737 via cron, it should place a file with the name of the
6738 package in one or more of the following directories:
6739 <example compact="compact">
6745 As these directory names imply, the files within them are
6746 executed on an hourly, daily, weekly, or monthly basis,
6747 respectively. The exact times are listed in
6748 <file>/etc/crontab</file>.</p>
6751 All files installed in any of these directories must be
6752 scripts (e.g., shell scripts or Perl scripts) so that they
6753 can easily be modified by the local system administrator.
6754 In addition, they must be treated as configuration files.
6758 If a certain job has to be executed at some other frequency or
6759 at a specific time, the package should install a file
6760 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6761 same syntax as <file>/etc/crontab</file> and is processed by
6762 <prgn>cron</prgn> automatically. The file must also be
6763 treated as a configuration file. (Note that entries in the
6764 <file>/etc/cron.d</file> directory are not handled by
6765 <prgn>anacron</prgn>. Thus, you should only use this
6766 directory for jobs which may be skipped if the system is not
6769 Unlike <file>crontab</file> files described in the IEEE Std
6770 1003.1-2008 (POSIX.1) available from
6771 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
6772 name="The Open Group">, the files in
6773 <file>/etc/cron.d</file> and the file
6774 <file>/etc/crontab</file> have seven fields; namely:
6776 <item>Minute [0,59]</item>
6777 <item>Hour [0,23]</item>
6778 <item>Day of the month [1,31]</item>
6779 <item>Month of the year [1,12]</item>
6780 <item>Day of the week ([0,6] with 0=Sunday)</item>
6781 <item>Username</item>
6782 <item>Command to be run</item>
6784 Ranges of numbers are allowed. Ranges are two numbers
6785 separated with a hyphen. The specified range is inclusive.
6786 Lists are allowed. A list is a set of numbers (or ranges)
6787 separated by commas. Step values can be used in conjunction
6792 The scripts or <tt>crontab</tt> entries in these directories should
6793 check if all necessary programs are installed before they
6794 try to execute them. Otherwise, problems will arise when a
6795 package was removed but not purged since configuration files
6796 are kept on the system in this situation.
6800 Any <tt>cron</tt> daemon must provide
6801 <file>/usr/bin/crontab</file> and support normal
6802 <tt>crontab</tt> entries as specified in POSIX. The daemon
6803 must also support names for days and months, ranges, and
6804 step values. It has to support <file>/etc/crontab</file>,
6805 and correctly execute the scripts in
6806 <file>/etc/cron.d</file>. The daemon must also correctly
6808 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
6813 <heading>Menus</heading>
6816 The Debian <tt>menu</tt> package provides a standard
6817 interface between packages providing applications and
6818 <em>menu programs</em> (either X window managers or
6819 text-based menu programs such as <prgn>pdmenu</prgn>).
6823 All packages that provide applications that need not be
6824 passed any special command line arguments for normal
6825 operation should register a menu entry for those
6826 applications, so that users of the <tt>menu</tt> package
6827 will automatically get menu entries in their window
6828 managers, as well in shells like <tt>pdmenu</tt>.
6832 Menu entries should follow the current menu policy.
6836 The menu policy can be found in the <tt>menu-policy</tt>
6837 files in the <tt>debian-policy</tt> package.
6838 It is also available from the Debian web mirrors at
6839 <tt><url name="/doc/packaging-manuals/menu-policy/"
6840 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6844 Please also refer to the <em>Debian Menu System</em>
6845 documentation that comes with the <package>menu</package>
6846 package for information about how to register your
6852 <heading>Multimedia handlers</heading>
6855 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6856 is a mechanism for encoding files and data streams and
6857 providing meta-information about them, in particular their
6858 type (e.g. audio or video) and format (e.g. PNG, HTML,
6863 Registration of MIME type handlers allows programs like mail
6864 user agents and web browsers to invoke these handlers to
6865 view, edit or display MIME types they don't support directly.
6869 Packages which provide the ability to view/show/play,
6870 compose, edit or print MIME types should register themselves
6871 as such following the current MIME support policy.
6875 The MIME support policy can be found in the <tt>mime-policy</tt>
6876 files in the <tt>debian-policy</tt> package.
6877 It is also available from the Debian web mirrors at
6878 <tt><url name="/doc/packaging-manuals/mime-policy/"
6879 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
6885 <heading>Keyboard configuration</heading>
6888 To achieve a consistent keyboard configuration so that all
6889 applications interpret a keyboard event the same way, all
6890 programs in the Debian distribution must be configured to
6891 comply with the following guidelines.
6895 The following keys must have the specified interpretations:
6898 <tag><tt><--</tt></tag>
6899 <item>delete the character to the left of the cursor</item>
6901 <tag><tt>Delete</tt></tag>
6902 <item>delete the character to the right of the cursor</item>
6904 <tag><tt>Control+H</tt></tag>
6905 <item>emacs: the help prefix</item>
6908 The interpretation of any keyboard events should be
6909 independent of the terminal that is used, be it a virtual
6910 console, an X terminal emulator, an rlogin/telnet session,
6915 The following list explains how the different programs
6916 should be set up to achieve this:
6922 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
6926 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
6930 X translations are set up to make
6931 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
6932 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
6933 is the vt220 escape code for the "delete character"
6934 key). This must be done by loading the X resources
6935 using <prgn>xrdb</prgn> on all local X displays, not
6936 using the application defaults, so that the
6937 translation resources used correspond to the
6938 <prgn>xmodmap</prgn> settings.
6942 The Linux console is configured to make
6943 <tt><--</tt> generate DEL, and <tt>Delete</tt>
6944 generate <tt>ESC [ 3 ~</tt>.
6948 X applications are configured so that <tt><</tt>
6949 deletes left, and <tt>Delete</tt> deletes right. Motif
6950 applications already work like this.
6954 Terminals should have <tt>stty erase ^?</tt> .
6958 The <tt>xterm</tt> terminfo entry should have <tt>ESC
6959 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
6960 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
6964 Emacs is programmed to map <tt>KB_Backspace</tt> or
6965 the <tt>stty erase</tt> character to
6966 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
6967 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
6968 <tt>^H</tt> to <tt>help</tt> as always.
6972 Other applications use the <tt>stty erase</tt>
6973 character and <tt>kdch1</tt> for the two delete keys,
6974 with ASCII DEL being "delete previous character" and
6975 <tt>kdch1</tt> being "delete character under
6983 This will solve the problem except for the following
6990 Some terminals have a <tt><--</tt> key that cannot
6991 be made to produce anything except <tt>^H</tt>. On
6992 these terminals Emacs help will be unavailable on
6993 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
6994 character takes precedence in Emacs, and has been set
6995 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
6996 available) can be used instead.
7000 Some operating systems use <tt>^H</tt> for <tt>stty
7001 erase</tt>. However, modern telnet versions and all
7002 rlogin versions propagate <tt>stty</tt> settings, and
7003 almost all UNIX versions honour <tt>stty erase</tt>.
7004 Where the <tt>stty</tt> settings are not propagated
7005 correctly, things can be made to work by using
7006 <tt>stty</tt> manually.
7010 Some systems (including previous Debian versions) use
7011 <prgn>xmodmap</prgn> to arrange for both
7012 <tt><--</tt> and <tt>Delete</tt> to generate
7013 <tt>KB_Delete</tt>. We can change the behavior of
7014 their X clients using the same X resources that we use
7015 to do it for our own clients, or configure our clients
7016 using their resources when things are the other way
7017 around. On displays configured like this
7018 <tt>Delete</tt> will not work, but <tt><--</tt>
7023 Some operating systems have different <tt>kdch1</tt>
7024 settings in their <tt>terminfo</tt> database for
7025 <tt>xterm</tt> and others. On these systems the
7026 <tt>Delete</tt> key will not work correctly when you
7027 log in from a system conforming to our policy, but
7028 <tt><--</tt> will.
7035 <heading>Environment variables</heading>
7038 A program must not depend on environment variables to get
7039 reasonable defaults. (That's because these environment
7040 variables would have to be set in a system-wide
7041 configuration file like <file>/etc/profile</file>, which is not
7042 supported by all shells.)
7046 If a program usually depends on environment variables for its
7047 configuration, the program should be changed to fall back to
7048 a reasonable default configuration if these environment
7049 variables are not present. If this cannot be done easily
7050 (e.g., if the source code of a non-free program is not
7051 available), the program must be replaced by a small
7052 "wrapper" shell script which sets the environment variables
7053 if they are not already defined, and calls the original program.
7057 Here is an example of a wrapper script for this purpose:
7059 <example compact="compact">
7061 BAR=${BAR:-/var/lib/fubar}
7063 exec /usr/lib/foo/foo "$@"
7068 Furthermore, as <file>/etc/profile</file> is a configuration
7069 file of the <prgn>base-files</prgn> package, other packages must
7070 not put any environment variables or other commands into that
7075 <sect id="doc-base">
7076 <heading>Registering Documents using doc-base</heading>
7079 The <package>doc-base</package> package implements a
7080 flexible mechanism for handling and presenting
7081 documentation. The recommended practice is for every Debian
7082 package that provides online documentation (other than just
7083 manual pages) to register these documents with
7084 <package>doc-base</package> by installing a
7085 <package>doc-base</package> control file via the
7086 <prgn/install-docs/ script at installation time and
7087 de-register the manuals again when the package is removed.
7090 Please refer to the documentation that comes with the
7091 <package>doc-base</package> package for information and
7100 <heading>Files</heading>
7102 <sect id="binaries">
7103 <heading>Binaries</heading>
7106 Two different packages must not install programs with
7107 different functionality but with the same filenames. (The
7108 case of two programs having the same functionality but
7109 different implementations is handled via "alternatives" or
7110 the "Conflicts" mechanism. See <ref id="maintscripts"> and
7111 <ref id="conflicts"> respectively.) If this case happens,
7112 one of the programs must be renamed. The maintainers should
7113 report this to the <tt>debian-devel</tt> mailing list and
7114 try to find a consensus about which program will have to be
7115 renamed. If a consensus cannot be reached, <em>both</em>
7116 programs must be renamed.
7120 By default, when a package is being built, any binaries
7121 created should include debugging information, as well as
7122 being compiled with optimization. You should also turn on
7123 as many reasonable compilation warnings as possible; this
7124 makes life easier for porters, who can then look at build
7125 logs for possible problems. For the C programming language,
7126 this means the following compilation parameters should be
7128 <example compact="compact">
7130 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
7132 INSTALL = install -s # (or use strip on the files in debian/tmp)
7137 Note that by default all installed binaries should be stripped,
7138 either by using the <tt>-s</tt> flag to
7139 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
7140 the binaries after they have been copied into
7141 <file>debian/tmp</file> but before the tree is made into a
7146 Although binaries in the build tree should be compiled with
7147 debugging information by default, it can often be difficult to
7148 debug programs if they are also subjected to compiler
7149 optimization. For this reason, it is recommended to support the
7150 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
7151 (see <ref id="debianrules-options">). This variable can contain
7152 several flags to change how a package is compiled and built.
7156 It is up to the package maintainer to decide what
7157 compilation options are best for the package. Certain
7158 binaries (such as computationally-intensive programs) will
7159 function better with certain flags (<tt>-O3</tt>, for
7160 example); feel free to use them. Please use good judgment
7161 here. Don't use flags for the sake of it; only use them
7162 if there is good reason to do so. Feel free to override
7163 the upstream author's ideas about which compilation
7164 options are best: they are often inappropriate for our
7170 <sect id="libraries">
7171 <heading>Libraries</heading>
7174 If the package is <strong>architecture: any</strong>, then
7175 the shared library compilation and linking flags must have
7176 <tt>-fPIC</tt>, or the package shall not build on some of
7177 the supported architectures<footnote>
7179 If you are using GCC, <tt>-fPIC</tt> produces code with
7180 relocatable position independent code, which is required for
7181 most architectures to create a shared library, with i386 and
7182 perhaps some others where non position independent code is
7183 permitted in a shared library.
7186 Position independent code may have a performance penalty,
7187 especially on <tt>i386</tt>. However, in most cases the
7188 speed penalty must be measured against the memory wasted on
7189 the few architectures where non position independent code is
7192 </footnote>. Any exception to this rule must be discussed on
7193 the mailing list <em>debian-devel@lists.debian.org</em>, and
7194 a rough consensus obtained. The reasons for not compiling
7195 with <tt>-fPIC</tt> flag must be recorded in the file
7196 <tt>README.Debian</tt>, and care must be taken to either
7197 restrict the architecture or arrange for <tt>-fPIC</tt> to
7198 be used on architectures where it is required.<footnote>
7200 Some of the reasons why this might be required is if the
7201 library contains hand crafted assembly code that is not
7202 relocatable, the speed penalty is excessive for compute
7203 intensive libs, and similar reasons.
7208 As to the static libraries, the common case is not to have
7209 relocatable code, since there is no benefit, unless in specific
7210 cases; therefore the static version must not be compiled
7211 with the <tt>-fPIC</tt> flag. Any exception to this rule
7212 should be discussed on the mailing list
7213 <em>debian-devel@lists.debian.org</em>, and the reasons for
7214 compiling with the <tt>-fPIC</tt> flag must be recorded in
7215 the file <tt>README.Debian</tt>. <footnote>
7217 Some of the reasons for linking static libraries with
7218 the <tt>-fPIC</tt> flag are if, for example, one needs a
7219 Perl API for a library that is under rapid development,
7220 and has an unstable API, so shared libraries are
7221 pointless at this phase of the library's development. In
7222 that case, since Perl needs a library with relocatable
7223 code, it may make sense to create a static library with
7224 relocatable code. Another reason cited is if you are
7225 distilling various libraries into a common shared
7226 library, like <tt>mklibs</tt> does in the Debian
7232 In other words, if both a shared and a static library is
7233 being built, each source unit (<tt>*.c</tt>, for example,
7234 for C files) will need to be compiled twice, for the normal
7238 You must specify the gcc option <tt>-D_REENTRANT</tt>
7239 when building a library (either static or shared) to make
7240 the library compatible with LinuxThreads.
7244 Although not enforced by the build tools, shared libraries
7245 must be linked against all libraries that they use symbols from
7246 in the same way that binaries are. This ensures the correct
7247 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
7248 system and guarantees that all libraries can be safely opened
7249 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
7250 option <tt>-Wl,-z,defs</tt> when building a shared library.
7251 Since this option enforces symbol resolution at build time,
7252 a missing library reference will be caught early as a fatal
7257 All installed shared libraries should be stripped with
7258 <example compact="compact">
7259 strip --strip-unneeded <var>your-lib</var>
7261 (The option <tt>--strip-unneeded</tt> makes
7262 <prgn>strip</prgn> remove only the symbols which aren't
7263 needed for relocation processing.) Shared libraries can
7264 function perfectly well when stripped, since the symbols for
7265 dynamic linking are in a separate part of the ELF object
7267 You might also want to use the options
7268 <tt>--remove-section=.comment</tt> and
7269 <tt>--remove-section=.note</tt> on both shared libraries
7270 and executables, and <tt>--strip-debug</tt> on static
7276 Note that under some circumstances it may be useful to
7277 install a shared library unstripped, for example when
7278 building a separate package to support debugging.
7282 Shared object files (often <file>.so</file> files) that are not
7283 public libraries, that is, they are not meant to be linked
7284 to by third party executables (binaries of other packages),
7285 should be installed in subdirectories of the
7286 <file>/usr/lib</file> directory. Such files are exempt from the
7287 rules that govern ordinary shared libraries, except that
7288 they must not be installed executable and should be
7290 A common example are the so-called "plug-ins",
7291 internal shared objects that are dynamically loaded by
7292 programs using <manref name="dlopen" section="3">.
7297 Packages that use <prgn>libtool</prgn> to create and install
7298 their shared libraries install a file containing additional
7299 metadata (ending in <file>.la</file>) alongside the library.
7300 For public libraries intended for use by other packages, these
7301 files normally should not be included in the Debian package,
7302 since the information they include is not necessary to link with
7303 the shared library on Debian and can add unnecessary additional
7304 dependencies to other programs or libraries.<footnote>
7305 These files store, among other things, all libraries on which
7306 that shared library depends. Unfortunately, if
7307 the <file>.la</file> file is present and contains that
7308 dependency information, using <prgn>libtool</prgn> when
7309 linking against that library will cause the resulting program
7310 or library to be linked against those dependencies as well,
7311 even if this is unnecessary. This can create unneeded
7312 dependencies on shared library packages that would otherwise
7313 be hidden behind the library ABI, and can make library
7314 transitions to new SONAMEs unnecessarily complicated and
7315 difficult to manage.
7317 If the <file>.la</file> file is required for that library (if,
7318 for instance, it's loaded via <tt>libltdl</tt> in a way that
7319 requires that meta-information), the <tt>dependency_libs</tt>
7320 setting in the <file>.la</file> file should normally be set to
7321 the empty string. If the shared library development package has
7322 historically included the <file>.la</file>, it must be retained
7323 in the development package (with <tt>dependency_libs</tt>
7324 emptied) until all libraries that depend on it have removed or
7325 emptied <tt>dependency_libs</tt> in their <file>.la</file>
7326 files to prevent linking with those other libraries
7327 using <prgn>libtool</prgn> from failing.
7331 If the <file>.la</file> must be included, it should be included
7332 in the development (<tt>-dev</tt>) package, unless the library
7333 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
7334 library. If it is intended for use with <tt>libltdl</tt>,
7335 the <file>.la</file> files must go in the run-time library
7340 These requirements for handling of <file>.la</file> files do not
7341 apply to loadable modules or libraries not installed in
7342 directories searched by default by the dynamic linker. Packages
7343 installing loadable modules will frequently need to install
7344 the <file>.la</file> files alongside the modules so that they
7345 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
7346 does not need to be modified for libraries or modules that are
7347 not installed in directories searched by the dynamic linker by
7348 default and not intended for use by other packages.
7352 You must make sure that you use only released versions of
7353 shared libraries to build your packages; otherwise other
7354 users will not be able to run your binaries
7355 properly. Producing source packages that depend on
7356 unreleased compilers is also usually a bad
7363 <heading>Shared libraries</heading>
7365 This section has moved to <ref id="sharedlibs">.
7371 <heading>Scripts</heading>
7374 All command scripts, including the package maintainer
7375 scripts inside the package and used by <prgn>dpkg</prgn>,
7376 should have a <tt>#!</tt> line naming the shell to be used
7381 In the case of Perl scripts this should be
7382 <tt>#!/usr/bin/perl</tt>.
7386 When scripts are installed into a directory in the system
7387 PATH, the script name should not include an extension such
7388 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7389 language currently used to implement it.
7392 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
7393 <file>init.d</file> scripts should almost certainly start
7394 with <tt>set -e</tt> so that errors are detected.
7395 <file>init.d</file> scripts are something of a special case, due
7396 to how frequently they need to call commands that are allowed to
7397 fail, and it may instead be easier to check the exit status of
7398 commands directly. See <ref id="writing-init"> for more
7399 information about writing <file>init.d</file> scripts.
7402 Every script should use <tt>set -e</tt> or check the exit status
7403 of <em>every</em> command.
7406 Scripts may assume that <file>/bin/sh</file> implements the
7407 SUSv3 Shell Command Language<footnote>
7408 Single UNIX Specification, version 3, which is also IEEE
7409 1003.1-2004 (POSIX), and is available on the World Wide Web
7410 from <url id="http://www.unix.org/version3/online.html"
7411 name="The Open Group"> after free
7412 registration.</footnote>
7413 plus the following additional features not mandated by
7415 These features are in widespread use in the Linux community
7416 and are implemented in all of bash, dash, and ksh, the most
7417 common shells users may wish to use as <file>/bin/sh</file>.
7420 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7421 must not generate a newline.</item>
7422 <item><tt>test</tt>, if implemented as a shell built-in, must
7423 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7425 <item><tt>local</tt> to create a scoped variable must be
7426 supported, including listing multiple variables in a single
7427 local command and assigning a value to a variable at the
7428 same time as localizing it. <tt>local</tt> may or
7429 may not preserve the variable value from an outer scope if
7430 no assignment is present. Uses such as:
7434 # ... use a, b, c, d ...
7437 must be supported and must set the value of <tt>c</tt> to
7441 If a shell script requires non-SUSv3 features from the shell
7442 interpreter other than those listed above, the appropriate shell
7443 must be specified in the first line of the script (e.g.,
7444 <tt>#!/bin/bash</tt>) and the package must depend on the package
7445 providing the shell (unless the shell package is marked
7446 "Essential", as in the case of <prgn>bash</prgn>).
7450 You may wish to restrict your script to SUSv3 features plus the
7451 above set when possible so that it may use <file>/bin/sh</file>
7452 as its interpreter. If your script works with <prgn>dash</prgn>
7453 (originally called <prgn>ash</prgn>), it probably complies with
7454 the above requirements, but if you are in doubt, use
7455 <file>/bin/bash</file>.
7459 Perl scripts should check for errors when making any
7460 system calls, including <tt>open</tt>, <tt>print</tt>,
7461 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7465 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7466 scripting languages. See <em>Csh Programming Considered
7467 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7468 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7469 If an upstream package comes with <prgn>csh</prgn> scripts
7470 then you must make sure that they start with
7471 <tt>#!/bin/csh</tt> and make your package depend on the
7472 <prgn>c-shell</prgn> virtual package.
7476 Any scripts which create files in world-writeable
7477 directories (e.g., in <file>/tmp</file>) must use a
7478 mechanism which will fail atomically if a file with the same
7479 name already exists.
7483 The Debian base system provides the <prgn>tempfile</prgn>
7484 and <prgn>mktemp</prgn> utilities for use by scripts for
7491 <heading>Symbolic links</heading>
7494 In general, symbolic links within a top-level directory
7495 should be relative, and symbolic links pointing from one
7496 top-level directory into another should be absolute. (A
7497 top-level directory is a sub-directory of the root
7498 directory <file>/</file>.)
7502 In addition, symbolic links should be specified as short as
7503 possible, i.e., link targets like <file>foo/../bar</file> are
7508 Note that when creating a relative link using
7509 <prgn>ln</prgn> it is not necessary for the target of the
7510 link to exist relative to the working directory you're
7511 running <prgn>ln</prgn> from, nor is it necessary to change
7512 directory to the directory where the link is to be made.
7513 Simply include the string that should appear as the target
7514 of the link (this will be a pathname relative to the
7515 directory in which the link resides) as the first argument
7520 For example, in your <prgn>Makefile</prgn> or
7521 <file>debian/rules</file>, you can do things like:
7522 <example compact="compact">
7523 ln -fs gcc $(prefix)/bin/cc
7524 ln -fs gcc debian/tmp/usr/bin/cc
7525 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7526 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7531 A symbolic link pointing to a compressed file should always
7532 have the same file extension as the referenced file. (For
7533 example, if a file <file>foo.gz</file> is referenced by a
7534 symbolic link, the filename of the link has to end with
7535 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7540 <heading>Device files</heading>
7543 Packages must not include device files or named pipes in the
7548 If a package needs any special device files that are not
7549 included in the base system, it must call
7550 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7551 after notifying the user<footnote>
7552 This notification could be done via a (low-priority)
7553 debconf message, or an echo (printf) statement.
7558 Packages must not remove any device files in the
7559 <prgn>postrm</prgn> or any other script. This is left to the
7560 system administrator.
7564 Debian uses the serial devices
7565 <file>/dev/ttyS*</file>. Programs using the old
7566 <file>/dev/cu*</file> devices should be changed to use
7567 <file>/dev/ttyS*</file>.
7571 Named pipes needed by the package must be created in
7572 the <prgn>postinst</prgn> script<footnote>
7573 It's better to use <prgn>mkfifo</prgn> rather
7574 than <prgn>mknod</prgn> to create named pipes so that
7575 automated checks for packages incorrectly creating device
7576 files with <prgn>mknod</prgn> won't have false positives.
7577 </footnote> and removed in
7578 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
7583 <sect id="config-files">
7584 <heading>Configuration files</heading>
7587 <heading>Definitions</heading>
7591 <tag>configuration file</tag>
7593 A file that affects the operation of a program, or
7594 provides site- or host-specific information, or
7595 otherwise customizes the behavior of a program.
7596 Typically, configuration files are intended to be
7597 modified by the system administrator (if needed or
7598 desired) to conform to local policy or to provide
7599 more useful site-specific behavior.
7602 <tag><tt>conffile</tt></tag>
7604 A file listed in a package's <tt>conffiles</tt>
7605 file, and is treated specially by <prgn>dpkg</prgn>
7606 (see <ref id="configdetails">).
7612 The distinction between these two is important; they are
7613 not interchangeable concepts. Almost all
7614 <tt>conffile</tt>s are configuration files, but many
7615 configuration files are not <tt>conffiles</tt>.
7619 As noted elsewhere, <file>/etc/init.d</file> scripts,
7620 <file>/etc/default</file> files, scripts installed in
7621 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7622 configuration installed in <file>/etc/cron.d</file> must be
7623 treated as configuration files. In general, any script that
7624 embeds configuration information is de-facto a configuration
7625 file and should be treated as such.
7630 <heading>Location</heading>
7633 Any configuration files created or used by your package
7634 must reside in <file>/etc</file>. If there are several,
7635 consider creating a subdirectory of <file>/etc</file>
7636 named after your package.
7640 If your package creates or uses configuration files
7641 outside of <file>/etc</file>, and it is not feasible to modify
7642 the package to use <file>/etc</file> directly, put the files
7643 in <file>/etc</file> and create symbolic links to those files
7644 from the location that the package requires.
7649 <heading>Behavior</heading>
7652 Configuration file handling must conform to the following
7654 <list compact="compact">
7656 local changes must be preserved during a package
7660 configuration files must be preserved when the
7661 package is removed, and only deleted when the
7665 Obsolete configuration files without local changes may be
7666 removed by the package during upgrade.
7670 The easy way to achieve this behavior is to make the
7671 configuration file a <tt>conffile</tt>. This is
7672 appropriate only if it is possible to distribute a default
7673 version that will work for most installations, although
7674 some system administrators may choose to modify it. This
7675 implies that the default version will be part of the
7676 package distribution, and must not be modified by the
7677 maintainer scripts during installation (or at any other
7682 In order to ensure that local changes are preserved
7683 correctly, no package may contain or make hard links to
7684 conffiles.<footnote>
7685 Rationale: There are two problems with hard links.
7686 The first is that some editors break the link while
7687 editing one of the files, so that the two files may
7688 unwittingly become unlinked and different. The second
7689 is that <prgn>dpkg</prgn> might break the hard link
7690 while upgrading <tt>conffile</tt>s.
7695 The other way to do it is via the maintainer scripts. In
7696 this case, the configuration file must not be listed as a
7697 <tt>conffile</tt> and must not be part of the package
7698 distribution. If the existence of a file is required for
7699 the package to be sensibly configured it is the
7700 responsibility of the package maintainer to provide
7701 maintainer scripts which correctly create, update and
7702 maintain the file and remove it on purge. (See <ref
7703 id="maintainerscripts"> for more information.) These
7704 scripts must be idempotent (i.e., must work correctly if
7705 <prgn>dpkg</prgn> needs to re-run them due to errors
7706 during installation or removal), must cope with all the
7707 variety of ways <prgn>dpkg</prgn> can call maintainer
7708 scripts, must not overwrite or otherwise mangle the user's
7709 configuration without asking, must not ask unnecessary
7710 questions (particularly during upgrades), and must
7711 otherwise be good citizens.
7715 The scripts are not required to configure every possible
7716 option for the package, but only those necessary to get
7717 the package running on a given system. Ideally the
7718 sysadmin should not have to do any configuration other
7719 than that done (semi-)automatically by the
7720 <prgn>postinst</prgn> script.
7724 A common practice is to create a script called
7725 <file><var>package</var>-configure</file> and have the
7726 package's <prgn>postinst</prgn> call it if and only if the
7727 configuration file does not already exist. In certain
7728 cases it is useful for there to be an example or template
7729 file which the maintainer scripts use. Such files should
7730 be in <file>/usr/share/<var>package</var></file> or
7731 <file>/usr/lib/<var>package</var></file> (depending on whether
7732 they are architecture-independent or not). There should
7733 be symbolic links to them from
7734 <file>/usr/share/doc/<var>package</var>/examples</file> if
7735 they are examples, and should be perfectly ordinary
7736 <prgn>dpkg</prgn>-handled files (<em>not</em>
7737 configuration files).
7741 These two styles of configuration file handling must
7742 not be mixed, for that way lies madness:
7743 <prgn>dpkg</prgn> will ask about overwriting the file
7744 every time the package is upgraded.
7749 <heading>Sharing configuration files</heading>
7752 Packages which specify the same file as a
7753 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7754 with each other. (This is an instance of the general rule
7755 about not sharing files. Note that neither alternatives
7756 nor diversions are likely to be appropriate in this case;
7757 in particular, <prgn>dpkg</prgn> does not handle diverted
7758 <tt>conffile</tt>s well.)
7762 The maintainer scripts must not alter a <tt>conffile</tt>
7763 of <em>any</em> package, including the one the scripts
7768 If two or more packages use the same configuration file
7769 and it is reasonable for both to be installed at the same
7770 time, one of these packages must be defined as
7771 <em>owner</em> of the configuration file, i.e., it will be
7772 the package which handles that file as a configuration
7773 file. Other packages that use the configuration file must
7774 depend on the owning package if they require the
7775 configuration file to operate. If the other package will
7776 use the configuration file if present, but is capable of
7777 operating without it, no dependency need be declared.
7781 If it is desirable for two or more related packages to
7782 share a configuration file <em>and</em> for all of the
7783 related packages to be able to modify that configuration
7784 file, then the following should be done:
7785 <enumlist compact="compact">
7787 One of the related packages (the "owning" package)
7788 will manage the configuration file with maintainer
7789 scripts as described in the previous section.
7792 The owning package should also provide a program
7793 that the other packages may use to modify the
7797 The related packages must use the provided program
7798 to make any desired modifications to the
7799 configuration file. They should either depend on
7800 the core package to guarantee that the configuration
7801 modifier program is available or accept gracefully
7802 that they cannot modify the configuration file if it
7803 is not. (This is in addition to the fact that the
7804 configuration file may not even be present in the
7811 Sometimes it's appropriate to create a new package which
7812 provides the basic infrastructure for the other packages
7813 and which manages the shared configuration files. (The
7814 <tt>sgml-base</tt> package is a good example.)
7819 <heading>User configuration files ("dotfiles")</heading>
7822 The files in <file>/etc/skel</file> will automatically be
7823 copied into new user accounts by <prgn>adduser</prgn>.
7824 No other program should reference the files in
7825 <file>/etc/skel</file>.
7829 Therefore, if a program needs a dotfile to exist in
7830 advance in <file>$HOME</file> to work sensibly, that dotfile
7831 should be installed in <file>/etc/skel</file> and treated as a
7836 However, programs that require dotfiles in order to
7837 operate sensibly are a bad thing, unless they do create
7838 the dotfiles themselves automatically.
7842 Furthermore, programs should be configured by the Debian
7843 default installation to behave as closely to the upstream
7844 default behavior as possible.
7848 Therefore, if a program in a Debian package needs to be
7849 configured in some way in order to operate sensibly, that
7850 should be done using a site-wide configuration file placed
7851 in <file>/etc</file>. Only if the program doesn't support a
7852 site-wide default configuration and the package maintainer
7853 doesn't have time to add it may a default per-user file be
7854 placed in <file>/etc/skel</file>.
7858 <file>/etc/skel</file> should be as empty as we can make it.
7859 This is particularly true because there is no easy (or
7860 necessarily desirable) mechanism for ensuring that the
7861 appropriate dotfiles are copied into the accounts of
7862 existing users when a package is installed.
7868 <heading>Log files</heading>
7870 Log files should usually be named
7871 <file>/var/log/<var>package</var>.log</file>. If you have many
7872 log files, or need a separate directory for permission
7873 reasons (<file>/var/log</file> is writable only by
7874 <file>root</file>), you should usually create a directory named
7875 <file>/var/log/<var>package</var></file> and place your log
7880 Log files must be rotated occasionally so that they don't
7881 grow indefinitely; the best way to do this is to drop a log
7882 rotation configuration file into the directory
7883 <file>/etc/logrotate.d</file> and use the facilities provided by
7884 logrotate.<footnote>
7886 The traditional approach to log files has been to set up
7887 <em>ad hoc</em> log rotation schemes using simple shell
7888 scripts and cron. While this approach is highly
7889 customizable, it requires quite a lot of sysadmin work.
7890 Even though the original Debian system helped a little
7891 by automatically installing a system which can be used
7892 as a template, this was deemed not enough.
7896 The use of <prgn>logrotate</prgn>, a program developed
7897 by Red Hat, is better, as it centralizes log management.
7898 It has both a configuration file
7899 (<file>/etc/logrotate.conf</file>) and a directory where
7900 packages can drop their individual log rotation
7901 configurations (<file>/etc/logrotate.d</file>).
7904 Here is a good example for a logrotate config
7905 file (for more information see <manref name="logrotate"
7907 <example compact="compact">
7908 /var/log/foo/*.log {
7913 /etc/init.d/foo force-reload
7917 This rotates all files under <file>/var/log/foo</file>, saves 12
7918 compressed generations, and forces the daemon to reload its
7919 configuration information after the log rotation.
7923 Log files should be removed when the package is
7924 purged (but not when it is only removed). This should be
7925 done by the <prgn>postrm</prgn> script when it is called
7926 with the argument <tt>purge</tt> (see <ref
7927 id="removedetails">).
7932 <heading>Permissions and owners</heading>
7935 The rules in this section are guidelines for general use.
7936 If necessary you may deviate from the details below.
7937 However, if you do so you must make sure that what is done
7938 is secure and you should try to be as consistent as possible
7939 with the rest of the system. You should probably also
7940 discuss it on <prgn>debian-devel</prgn> first.
7944 Files should be owned by <tt>root:root</tt>, and made
7945 writable only by the owner and universally readable (and
7946 executable, if appropriate), that is mode 644 or 755.
7950 Directories should be mode 755 or (for group-writability)
7951 mode 2775. The ownership of the directory should be
7952 consistent with its mode: if a directory is mode 2775, it
7953 should be owned by the group that needs write access to
7956 When a package is upgraded, and the owner or permissions
7957 of a file included in the package has changed, dpkg
7958 arranges for the ownership and permissions to be
7959 correctly set upon installation. However, this does not
7960 extend to directories; the permissions and ownership of
7961 directories already on the system does not change on
7962 install or upgrade of packages. This makes sense, since
7963 otherwise common directories like <tt>/usr</tt> would
7964 always be in flux. To correctly change permissions of a
7965 directory the package owns, explicit action is required,
7966 usually in the <tt>postinst</tt> script. Care must be
7967 taken to handle downgrades as well, in that case.
7974 Setuid and setgid executables should be mode 4755 or 2755
7975 respectively, and owned by the appropriate user or group.
7976 They should not be made unreadable (modes like 4711 or
7977 2711 or even 4111); doing so achieves no extra security,
7978 because anyone can find the binary in the freely available
7979 Debian package; it is merely inconvenient. For the same
7980 reason you should not restrict read or execute permissions
7981 on non-set-id executables.
7985 Some setuid programs need to be restricted to particular
7986 sets of users, using file permissions. In this case they
7987 should be owned by the uid to which they are set-id, and by
7988 the group which should be allowed to execute them. They
7989 should have mode 4754; again there is no point in making
7990 them unreadable to those users who must not be allowed to
7995 It is possible to arrange that the system administrator can
7996 reconfigure the package to correspond to their local
7997 security policy by changing the permissions on a binary:
7998 they can do this by using <prgn>dpkg-statoverride</prgn>, as
7999 described below.<footnote>
8000 Ordinary files installed by <prgn>dpkg</prgn> (as
8001 opposed to <tt>conffile</tt>s and other similar objects)
8002 normally have their permissions reset to the distributed
8003 permissions when the package is reinstalled. However,
8004 the use of <prgn>dpkg-statoverride</prgn> overrides this
8007 Another method you should consider is to create a group for
8008 people allowed to use the program(s) and make any setuid
8009 executables executable only by that group.
8013 If you need to create a new user or group for your package
8014 there are two possibilities. Firstly, you may need to
8015 make some files in the binary package be owned by this
8016 user or group, or you may need to compile the user or
8017 group id (rather than just the name) into the binary
8018 (though this latter should be avoided if possible, as in
8019 this case you need a statically allocated id).</p>
8022 If you need a statically allocated id, you must ask for a
8023 user or group id from the <tt>base-passwd</tt> maintainer,
8024 and must not release the package until you have been
8025 allocated one. Once you have been allocated one you must
8026 either make the package depend on a version of the
8027 <tt>base-passwd</tt> package with the id present in
8028 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
8029 your package to create the user or group itself with the
8030 correct id (using <tt>adduser</tt>) in its
8031 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
8032 the <prgn>postinst</prgn> is to be preferred if it is
8033 possible, otherwise a pre-dependency will be needed on the
8034 <tt>adduser</tt> package.)
8038 On the other hand, the program might be able to determine
8039 the uid or gid from the user or group name at runtime, so
8040 that a dynamically allocated id can be used. In this case
8041 you should choose an appropriate user or group name,
8042 discussing this on <prgn>debian-devel</prgn> and checking
8043 with the <package/base-passwd/ maintainer that it is unique and that
8044 they do not wish you to use a statically allocated id
8045 instead. When this has been checked you must arrange for
8046 your package to create the user or group if necessary using
8047 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
8048 <prgn>postinst</prgn> script (again, the latter is to be
8049 preferred if it is possible).
8053 Note that changing the numeric value of an id associated
8054 with a name is very difficult, and involves searching the
8055 file system for all appropriate files. You need to think
8056 carefully whether a static or dynamic id is required, since
8057 changing your mind later will cause problems.
8060 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
8062 This section is not intended as policy, but as a
8063 description of the use of <prgn>dpkg-statoverride</prgn>.
8067 If a system administrator wishes to have a file (or
8068 directory or other such thing) installed with owner and
8069 permissions different from those in the distributed Debian
8070 package, they can use the <prgn>dpkg-statoverride</prgn>
8071 program to instruct <prgn>dpkg</prgn> to use the different
8072 settings every time the file is installed. Thus the
8073 package maintainer should distribute the files with their
8074 normal permissions, and leave it for the system
8075 administrator to make any desired changes. For example, a
8076 daemon which is normally required to be setuid root, but
8077 in certain situations could be used without being setuid,
8078 should be installed setuid in the <tt>.deb</tt>. Then the
8079 local system administrator can change this if they wish.
8080 If there are two standard ways of doing it, the package
8081 maintainer can use <tt>debconf</tt> to find out the
8082 preference, and call <prgn>dpkg-statoverride</prgn> in the
8083 maintainer script if necessary to accommodate the system
8084 administrator's choice. Care must be taken during
8085 upgrades to not override an existing setting.
8089 Given the above, <prgn>dpkg-statoverride</prgn> is
8090 essentially a tool for system administrators and would not
8091 normally be needed in the maintainer scripts. There is
8092 one type of situation, though, where calls to
8093 <prgn>dpkg-statoverride</prgn> would be needed in the
8094 maintainer scripts, and that involves packages which use
8095 dynamically allocated user or group ids. In such a
8096 situation, something like the following idiom can be very
8097 helpful in the package's <prgn>postinst</prgn>, where
8098 <tt>sysuser</tt> is a dynamically allocated id:
8100 for i in /usr/bin/foo /usr/sbin/bar
8102 # only do something when no setting exists
8103 if ! dpkg-statoverride --list $i >/dev/null 2>&1
8105 #include: debconf processing, question about foo and bar
8106 if [ "$RET" = "true" ] ; then
8107 dpkg-statoverride --update --add sysuser root 4755 $i
8112 The corresponding code to remove the override when the package
8115 for i in /usr/bin/foo /usr/sbin/bar
8117 if dpkg-statoverride --list $i >/dev/null 2>&1
8119 dpkg-statoverride --remove $i
8129 <chapt id="customized-programs">
8130 <heading>Customized programs</heading>
8132 <sect id="arch-spec">
8133 <heading>Architecture specification strings</heading>
8136 If a program needs to specify an <em>architecture specification
8137 string</em> in some place, it should select one of the strings
8138 provided by <tt>dpkg-architecture -L</tt>. The strings are in
8139 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
8140 part is sometimes elided, as when the OS is Linux.
8144 Note that we don't want to use
8145 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
8146 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
8147 since this would make our programs incompatible with other
8148 Linux distributions. We also don't use something like
8149 <tt><var>arch</var>-unknown-linux</tt>, since the
8150 <tt>unknown</tt> does not look very good.
8153 <sect1 id="arch-wildcard-spec">
8154 <heading>Architecture wildcards</heading>
8157 A package may specify an architecture wildcard. Architecture
8158 wildcards are in the format <tt>any</tt> (which matches every
8159 architecture), <tt><var>os</var></tt>-any, or
8160 any-<tt><var>cpu</var></tt>. <footnote>
8161 Internally, the package system normalizes the GNU triplets
8162 and the Debian arches into Debian arch triplets (which are
8163 kind of inverted GNU triplets), with the first component of
8164 the triplet representing the libc and ABI in use, and then
8165 does matching against those triplets. However, such
8166 triplets are an internal implementation detail that should
8167 not be used by packages directly. The libc and ABI portion
8168 is handled internally by the package system based on
8169 the <var>os</var> and <var>cpu</var>.
8176 <heading>Daemons</heading>
8179 The configuration files <file>/etc/services</file>,
8180 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
8181 by the <prgn>netbase</prgn> package and must not be modified
8186 If a package requires a new entry in one of these files, the
8187 maintainer should get in contact with the
8188 <prgn>netbase</prgn> maintainer, who will add the entries
8189 and release a new version of the <prgn>netbase</prgn>
8194 The configuration file <file>/etc/inetd.conf</file> must not be
8195 modified by the package's scripts except via the
8196 <prgn>update-inetd</prgn> script or the
8197 <file>DebianNet.pm</file> Perl module. See their documentation
8198 for details on how to add entries.
8202 If a package wants to install an example entry into
8203 <file>/etc/inetd.conf</file>, the entry must be preceded with
8204 exactly one hash character (<tt>#</tt>). Such lines are
8205 treated as "commented out by user" by the
8206 <prgn>update-inetd</prgn> script and are not changed or
8207 activated during package updates.
8212 <heading>Using pseudo-ttys and modifying wtmp, utmp and
8216 Some programs need to create pseudo-ttys. This should be done
8217 using Unix98 ptys if the C library supports it. The resulting
8218 program must not be installed setuid root, unless that
8219 is required for other functionality.
8223 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
8224 <file>/var/log/lastlog</file> must be installed writable by
8225 group <tt>utmp</tt>. Programs which need to modify those
8226 files must be installed setgid <tt>utmp</tt>.
8231 <heading>Editors and pagers</heading>
8234 Some programs have the ability to launch an editor or pager
8235 program to edit or display a text document. Since there are
8236 lots of different editors and pagers available in the Debian
8237 distribution, the system administrator and each user should
8238 have the possibility to choose their preferred editor and
8243 In addition, every program should choose a good default
8244 editor/pager if none is selected by the user or system
8249 Thus, every program that launches an editor or pager must
8250 use the EDITOR or PAGER environment variable to determine
8251 the editor or pager the user wishes to use. If these
8252 variables are not set, the programs <file>/usr/bin/editor</file>
8253 and <file>/usr/bin/pager</file> should be used, respectively.
8257 These two files are managed through the <prgn>dpkg</prgn>
8258 "alternatives" mechanism. Thus every package providing an
8259 editor or pager must call the
8260 <prgn>update-alternatives</prgn> script to register these
8265 If it is very hard to adapt a program to make use of the
8266 EDITOR or PAGER variables, that program may be configured to
8267 use <file>/usr/bin/sensible-editor</file> and
8268 <file>/usr/bin/sensible-pager</file> as the editor or pager
8269 program respectively. These are two scripts provided in the
8270 <package>sensible-utils</package> package that check the EDITOR
8271 and PAGER variables and launch the appropriate program, and fall
8272 back to <file>/usr/bin/editor</file>
8273 and <file>/usr/bin/pager</file> if the variable is not set.
8277 A program may also use the VISUAL environment variable to
8278 determine the user's choice of editor. If it exists, it
8279 should take precedence over EDITOR. This is in fact what
8280 <file>/usr/bin/sensible-editor</file> does.
8284 It is not required for a package to depend on
8285 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
8286 package to provide such virtual packages.<footnote>
8287 The Debian base system already provides an editor and a
8293 <sect id="web-appl">
8294 <heading>Web servers and applications</heading>
8297 This section describes the locations and URLs that should
8298 be used by all web servers and web applications in the
8305 Cgi-bin executable files are installed in the
8307 <example compact="compact">
8308 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
8310 and should be referred to as
8311 <example compact="compact">
8312 http://localhost/cgi-bin/<var>cgi-bin-name</var>
8318 <p>Access to HTML documents</p>
8321 HTML documents for a package are stored in
8322 <file>/usr/share/doc/<var>package</var></file>
8323 and can be referred to as
8324 <example compact="compact">
8325 http://localhost/doc/<var>package</var>/<var>filename</var>
8330 The web server should restrict access to the document
8331 tree so that only clients on the same host can read
8332 the documents. If the web server does not support such
8333 access controls, then it should not provide access at
8334 all, or ask about providing access during installation.
8339 <p>Access to images</p>
8341 It is recommended that images for a package be stored
8342 in <tt>/usr/share/images/<var>package</var></tt> and
8343 may be referred to through an alias <tt>/images/</tt>
8346 http://localhost/images/<package>/<filename>
8353 <p>Web Document Root</p>
8356 Web Applications should try to avoid storing files in
8357 the Web Document Root. Instead they should use the
8358 /usr/share/doc/<var>package</var> directory for
8359 documents and register the Web Application via the
8360 <package>doc-base</package> package. If access to the
8361 web document root is unavoidable then use
8362 <example compact="compact">
8365 as the Document Root. This might be just a symbolic
8366 link to the location where the system administrator
8367 has put the real document root.
8370 <item><p>Providing httpd and/or httpd-cgi</p>
8372 All web servers should provide the virtual package
8373 <tt>httpd</tt>. If a web server has CGI support it should
8374 provide <tt>httpd-cgi</tt> additionally.
8377 All web applications which do not contain CGI scripts should
8378 depend on <tt>httpd</tt>, all those web applications which
8379 <tt>do</tt> contain CGI scripts, should depend on
8387 <sect id="mail-transport-agents">
8388 <heading>Mail transport, delivery and user agents</heading>
8391 Debian packages which process electronic mail, whether mail
8392 user agents (MUAs) or mail transport agents (MTAs), must
8393 ensure that they are compatible with the configuration
8394 decisions below. Failure to do this may result in lost
8395 mail, broken <tt>From:</tt> lines, and other serious brain
8400 The mail spool is <file>/var/mail</file> and the interface to
8401 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8402 the FHS). On older systems, the mail spool may be
8403 physically located in <file>/var/spool/mail</file>, but all
8404 access to the mail spool should be via the
8405 <file>/var/mail</file> symlink. The mail spool is part of the
8406 base system and not part of the MTA package.
8410 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8411 programs (such as IMAP daemons) must lock the mailbox in an
8412 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8413 be combined with dot locking. To avoid deadlocks, a program
8414 should use <tt>fcntl()</tt> first and dot locking after
8415 this, or alternatively implement the two locking methods in
8416 a non blocking way<footnote>
8417 If it is not possible to establish both locks, the
8418 system shouldn't wait for the second lock to be
8419 established, but remove the first lock, wait a (random)
8420 time, and start over locking again.
8421 </footnote>. Using the functions <tt>maillock</tt> and
8422 <tt>mailunlock</tt> provided by the
8423 <tt>liblockfile*</tt><footnote>
8424 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8425 to use these functions.
8426 </footnote> packages is the recommended way to realize this.
8430 Mailboxes are generally either mode 600 and owned by
8431 <var>user</var> or mode 660 and owned by
8432 <tt><var>user</var>:mail</tt><footnote>
8433 There are two traditional permission schemes for mail spools:
8434 mode 600 with all mail delivery done by processes running as
8435 the destination user, or mode 660 and owned by group mail with
8436 mail delivery done by a process running as a system user in
8437 group mail. Historically, Debian required mode 660 mail
8438 spools to enable the latter model, but that model has become
8439 increasingly uncommon and the principle of least privilege
8440 indicates that mail systems that use the first model should
8441 use permissions of 600. If delivery to programs is permitted,
8442 it's easier to keep the mail system secure if the delivery
8443 agent runs as the destination user. Debian Policy therefore
8444 permits either scheme.
8445 </footnote>. The local system administrator may choose a
8446 different permission scheme; packages should not make
8447 assumptions about the permission and ownership of mailboxes
8448 unless required (such as when creating a new mailbox). A MUA
8449 may remove a mailbox (unless it has nonstandard permissions) in
8450 which case the MTA or another MUA must recreate it if needed.
8454 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8455 be setgid mail to do the locking mentioned above (and
8456 must obviously avoid accessing other users' mailboxes
8457 using this privilege).</p>
8460 <file>/etc/aliases</file> is the source file for the system mail
8461 aliases (e.g., postmaster, usenet, etc.), it is the one
8462 which the sysadmin and <prgn>postinst</prgn> scripts may
8463 edit. After <file>/etc/aliases</file> is edited the program or
8464 human editing it must call <prgn>newaliases</prgn>. All MTA
8465 packages must come with a <prgn>newaliases</prgn> program,
8466 even if it does nothing, but older MTA packages did not do
8467 this so programs should not fail if <prgn>newaliases</prgn>
8468 cannot be found. Note that because of this, all MTA
8469 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8470 <tt>Replaces: mail-transport-agent</tt> control file
8475 The convention of writing <tt>forward to
8476 <var>address</var></tt> in the mailbox itself is not
8477 supported. Use a <tt>.forward</tt> file instead.</p>
8480 The <prgn>rmail</prgn> program used by UUCP
8481 for incoming mail should be <file>/usr/sbin/rmail</file>.
8482 Likewise, <prgn>rsmtp</prgn>, for receiving
8483 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8487 If your package needs to know what hostname to use on (for
8488 example) outgoing news and mail messages which are generated
8489 locally, you should use the file <file>/etc/mailname</file>. It
8490 will contain the portion after the username and <tt>@</tt>
8491 (at) sign for email addresses of users on the machine
8492 (followed by a newline).
8496 Such a package should check for the existence of this file
8497 when it is being configured. If it exists, it should be
8498 used without comment, although an MTA's configuration script
8499 may wish to prompt the user even if it finds that this file
8500 exists. If the file does not exist, the package should
8501 prompt the user for the value (preferably using
8502 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8503 as well as using it in the package's configuration. The
8504 prompt should make it clear that the name will not just be
8505 used by that package. For example, in this situation the
8506 <tt>inn</tt> package could say something like:
8507 <example compact="compact">
8508 Please enter the "mail name" of your system. This is the
8509 hostname portion of the address to be shown on outgoing
8510 news and mail messages. The default is
8511 <var>syshostname</var>, your system's host name. Mail
8512 name ["<var>syshostname</var>"]:
8514 where <var>syshostname</var> is the output of <tt>hostname
8520 <heading>News system configuration</heading>
8523 All the configuration files related to the NNTP (news)
8524 servers and clients should be located under
8525 <file>/etc/news</file>.</p>
8528 There are some configuration issues that apply to a number
8529 of news clients and server packages on the machine. These
8533 <tag><file>/etc/news/organization</file></tag>
8535 A string which should appear as the
8536 organization header for all messages posted
8537 by NNTP clients on the machine
8540 <tag><file>/etc/news/server</file></tag>
8542 Contains the FQDN of the upstream NNTP
8543 server, or localhost if the local machine is
8548 Other global files may be added as required for cross-package news
8555 <heading>Programs for the X Window System</heading>
8558 <heading>Providing X support and package priorities</heading>
8561 Programs that can be configured with support for the X
8562 Window System must be configured to do so and must declare
8563 any package dependencies necessary to satisfy their
8564 runtime requirements when using the X Window System. If
8565 such a package is of higher priority than the X packages
8566 on which it depends, it is required that either the
8567 X-specific components be split into a separate package, or
8568 that an alternative version of the package, which includes
8569 X support, be provided, or that the package's priority be
8575 <heading>Packages providing an X server</heading>
8578 Packages that provide an X server that, directly or
8579 indirectly, communicates with real input and display
8580 hardware should declare in their control data that they
8581 provide the virtual package <tt>xserver</tt>.<footnote>
8582 This implements current practice, and provides an
8583 actual policy for usage of the <tt>xserver</tt>
8584 virtual package which appears in the virtual packages
8585 list. In a nutshell, X servers that interface
8586 directly with the display and input hardware or via
8587 another subsystem (e.g., GGI) should provide
8588 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8589 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8595 <heading>Packages providing a terminal emulator</heading>
8598 Packages that provide a terminal emulator for the X Window
8599 System which meet the criteria listed below should declare
8600 in their control data that they provide the virtual
8601 package <tt>x-terminal-emulator</tt>. They should also
8602 register themselves as an alternative for
8603 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8608 To be an <tt>x-terminal-emulator</tt>, a program must:
8609 <list compact="compact">
8611 Be able to emulate a DEC VT100 terminal, or a
8612 compatible terminal.
8616 Support the command-line option <tt>-e
8617 <var>command</var></tt>, which creates a new
8618 terminal window<footnote>
8619 "New terminal window" does not necessarily mean
8620 a new top-level X window directly parented by
8621 the window manager; it could, if the terminal
8622 emulator application were so coded, be a new
8623 "view" in a multiple-document interface (MDI).
8625 and runs the specified <var>command</var>,
8626 interpreting the entirety of the rest of the command
8627 line as a command to pass straight to exec, in the
8628 manner that <tt>xterm</tt> does.
8632 Support the command-line option <tt>-T
8633 <var>title</var></tt>, which creates a new terminal
8634 window with the window title <var>title</var>.
8641 <heading>Packages providing a window manager</heading>
8644 Packages that provide a window manager should declare in
8645 their control data that they provide the virtual package
8646 <tt>x-window-manager</tt>. They should also register
8647 themselves as an alternative for
8648 <file>/usr/bin/x-window-manager</file>, with a priority
8649 calculated as follows:
8650 <list compact="compact">
8652 Start with a priority of 20.
8656 If the window manager supports the Debian menu
8657 system, add 20 points if this support is available
8658 in the package's default configuration (i.e., no
8659 configuration files belonging to the system or user
8660 have to be edited to activate the feature); if
8661 configuration files must be modified, add only 10
8667 If the window manager complies with <url
8668 id="http://www.freedesktop.org/Standards/wm-spec"
8669 name="The Window Manager Specification Project">,
8670 written by the <url id="http://www.freedesktop.org/"
8671 name="Free Desktop Group">, add 40 points.
8675 If the window manager permits the X session to be
8676 restarted using a <em>different</em> window manager
8677 (without killing the X server) in its default
8678 configuration, add 10 points; otherwise add none.
8685 <heading>Packages providing fonts</heading>
8688 Packages that provide fonts for the X Window
8690 For the purposes of Debian Policy, a "font for the X
8691 Window System" is one which is accessed via X protocol
8692 requests. Fonts for the Linux console, for PostScript
8693 renderer, or any other purpose, do not fit this
8694 definition. Any tool which makes such fonts available
8695 to the X Window System, however, must abide by this
8698 must do a number of things to ensure that they are both
8699 available without modification of the X or font server
8700 configuration, and that they do not corrupt files used by
8701 other font packages to register information about
8705 Fonts of any type supported by the X Window System
8706 must be in a separate binary package from any
8707 executables, libraries, or documentation (except
8708 that specific to the fonts shipped, such as their
8709 license information). If one or more of the fonts
8710 so packaged are necessary for proper operation of
8711 the package with which they are associated the font
8712 package may be Recommended; if the fonts merely
8713 provide an enhancement, a Suggests relationship may
8714 be used. Packages must not Depend on font
8716 This is because the X server may retrieve fonts
8717 from the local file system or over the network
8718 from an X font server; the Debian package system
8719 is empowered to deal only with the local
8725 BDF fonts must be converted to PCF fonts with the
8726 <prgn>bdftopcf</prgn> utility (available in the
8727 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8728 placed in a directory that corresponds to their
8730 <list compact="compact">
8732 100 dpi fonts must be placed in
8733 <file>/usr/share/fonts/X11/100dpi/</file>.
8737 75 dpi fonts must be placed in
8738 <file>/usr/share/fonts/X11/75dpi/</file>.
8742 Character-cell fonts, cursor fonts, and other
8743 low-resolution fonts must be placed in
8744 <file>/usr/share/fonts/X11/misc/</file>.
8750 Type 1 fonts must be placed in
8751 <file>/usr/share/fonts/X11/Type1/</file>. If font
8752 metric files are available, they must be placed here
8757 Subdirectories of <file>/usr/share/fonts/X11/</file>
8758 other than those listed above must be neither
8759 created nor used. (The <file>PEX</file>, <file>CID</file>,
8760 <file>Speedo</file>, and <file>cyrillic</file> directories
8761 are excepted for historical reasons, but installation of
8762 files into these directories remains discouraged.)
8766 Font packages may, instead of placing files directly
8767 in the X font directories listed above, provide
8768 symbolic links in that font directory pointing to
8769 the files' actual location in the filesystem. Such
8770 a location must comply with the FHS.
8774 Font packages should not contain both 75dpi and
8775 100dpi versions of a font. If both are available,
8776 they should be provided in separate binary packages
8777 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8778 the names of the packages containing the
8779 corresponding fonts.
8783 Fonts destined for the <file>misc</file> subdirectory
8784 should not be included in the same package as 75dpi
8785 or 100dpi fonts; instead, they should be provided in
8786 a separate package with <tt>-misc</tt> appended to
8791 Font packages must not provide the files
8792 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8793 <file>fonts.scale</file> in a font directory:
8796 <file>fonts.dir</file> files must not be provided at all.
8800 <file>fonts.alias</file> and <file>fonts.scale</file>
8801 files, if needed, should be provided in the
8803 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8804 where <var>fontdir</var> is the name of the
8806 <file>/usr/share/fonts/X11/</file> where the
8807 package's corresponding fonts are stored
8808 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8809 <var>package</var> is the name of the package
8810 that provides these fonts, and
8811 <var>extension</var> is either <tt>scale</tt>
8812 or <tt>alias</tt>, whichever corresponds to
8819 Font packages must declare a dependency on
8820 <tt>xfonts-utils</tt> in their control
8825 Font packages that provide one or more
8826 <file>fonts.scale</file> files as described above must
8827 invoke <prgn>update-fonts-scale</prgn> on each
8828 directory into which they installed fonts
8829 <em>before</em> invoking
8830 <prgn>update-fonts-dir</prgn> on that directory.
8831 This invocation must occur in both the
8832 <prgn>postinst</prgn> (for all arguments) and
8833 <prgn>postrm</prgn> (for all arguments except
8834 <tt>upgrade</tt>) scripts.
8838 Font packages that provide one or more
8839 <file>fonts.alias</file> files as described above must
8840 invoke <prgn>update-fonts-alias</prgn> on each
8841 directory into which they installed fonts. This
8842 invocation must occur in both the
8843 <prgn>postinst</prgn> (for all arguments) and
8844 <prgn>postrm</prgn> (for all arguments except
8845 <tt>upgrade</tt>) scripts.
8849 Font packages must invoke
8850 <prgn>update-fonts-dir</prgn> on each directory into
8851 which they installed fonts. This invocation must
8852 occur in both the <prgn>postinst</prgn> (for all
8853 arguments) and <prgn>postrm</prgn> (for all
8854 arguments except <tt>upgrade</tt>) scripts.
8858 Font packages must not provide alias names for the
8859 fonts they include which collide with alias names
8860 already in use by fonts already packaged.
8864 Font packages must not provide fonts with the same
8865 XLFD registry name as another font already packaged.
8871 <sect1 id="appdefaults">
8872 <heading>Application defaults files</heading>
8875 Application defaults files must be installed in the
8876 directory <file>/etc/X11/app-defaults/</file> (use of a
8877 localized subdirectory of <file>/etc/X11/</file> as described
8878 in the <em>X Toolkit Intrinsics - C Language
8879 Interface</em> manual is also permitted). They must be
8880 registered as <tt>conffile</tt>s or handled as
8881 configuration files.
8885 Customization of programs' X resources may also be
8886 supported with the provision of a file with the same name
8887 as that of the package placed in
8888 the <file>/etc/X11/Xresources/</file> directory, which
8889 must be registered as a <tt>conffile</tt> or handled as a
8890 configuration file.<footnote>
8891 Note that this mechanism is not the same as using
8892 app-defaults; app-defaults are tied to the client
8893 binary on the local file system, whereas X resources
8894 are stored in the X server and affect all connecting
8901 <heading>Installation directory issues</heading>
8904 Historically, packages using the X Window System used a
8905 separate set of installation directories from other packages.
8906 This practice has been discontinued and packages using the X
8907 Window System should now generally be installed in the same
8908 directories as any other package. Specifically, packages must
8909 not install files under the <file>/usr/X11R6/</file> directory
8910 and the <file>/usr/X11R6/</file> directory hierarchy should be
8911 regarded as obsolete.
8915 Include files previously installed under
8916 <file>/usr/X11R6/include/X11/</file> should be installed into
8917 <file>/usr/include/X11/</file>. For files previously
8918 installed into subdirectories of
8919 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
8920 determine if subdirectories of <file>/usr/lib/</file> and
8921 <file>/usr/share/</file> can be used. If not, a subdirectory
8922 of <file>/usr/lib/X11/</file> should be used.
8926 Configuration files for window, display, or session managers
8927 or other applications that are tightly integrated with the X
8928 Window System may be placed in a subdirectory
8929 of <file>/etc/X11/</file> corresponding to the package name.
8930 Other X Window System applications should use
8931 the <file>/etc/</file> directory unless otherwise mandated by
8932 policy (such as for <ref id="appdefaults">).
8937 <heading>The OSF/Motif and OpenMotif libraries</heading>
8940 <em>Programs that require the non-DFSG-compliant OSF/Motif or
8941 OpenMotif libraries</em><footnote>
8942 OSF/Motif and OpenMotif are collectively referred to as
8943 "Motif" in this policy document.
8945 should be compiled against and tested with LessTif (a free
8946 re-implementation of Motif) instead. If the maintainer
8947 judges that the program or programs do not work
8948 sufficiently well with LessTif to be distributed and
8949 supported, but do so when compiled against Motif, then two
8950 versions of the package should be created; one linked
8951 statically against Motif and with <tt>-smotif</tt>
8952 appended to the package name, and one linked dynamically
8953 against Motif and with <tt>-dmotif</tt> appended to the
8958 Both Motif-linked versions are dependent
8959 upon non-DFSG-compliant software and thus cannot be
8960 uploaded to the <em>main</em> distribution; if the
8961 software is itself DFSG-compliant it may be uploaded to
8962 the <em>contrib</em> distribution. While known existing
8963 versions of Motif permit unlimited redistribution of
8964 binaries linked against the library (whether statically or
8965 dynamically), it is the package maintainer's
8966 responsibility to determine whether this is permitted by
8967 the license of the copy of Motif in their possession.
8973 <heading>Perl programs and modules</heading>
8976 Perl programs and modules should follow the current Perl policy.
8980 The Perl policy can be found in the <tt>perl-policy</tt>
8981 files in the <tt>debian-policy</tt> package.
8982 It is also available from the Debian web mirrors at
8983 <tt><url name="/doc/packaging-manuals/perl-policy/"
8984 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
8989 <heading>Emacs lisp programs</heading>
8992 Please refer to the "Debian Emacs Policy" for details of how to
8993 package emacs lisp programs.
8997 The Emacs policy is available in
8998 <file>debian-emacs-policy.gz</file> of the
8999 <package>emacsen-common</package> package.
9000 It is also available from the Debian web mirrors at
9001 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
9002 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
9007 <heading>Games</heading>
9010 The permissions on <file>/var/games</file> are mode 755, owner
9011 <tt>root</tt> and group <tt>root</tt>.
9015 Each game decides on its own security policy.</p>
9018 Games which require protected, privileged access to
9019 high-score files, saved games, etc., may be made
9020 set-<em>group</em>-id (mode 2755) and owned by
9021 <tt>root:games</tt>, and use files and directories with
9022 appropriate permissions (770 <tt>root:games</tt>, for
9023 example). They must not be made
9024 set-<em>user</em>-id, as this causes security problems. (If
9025 an attacker can subvert any set-user-id game they can
9026 overwrite the executable of any other, causing other players
9027 of these games to run a Trojan horse program. With a
9028 set-group-id game the attacker only gets access to less
9029 important game data, and if they can get at the other
9030 players' accounts at all it will take considerably more
9034 Some packages, for example some fortune cookie programs, are
9035 configured by the upstream authors to install with their
9036 data files or other static information made unreadable so
9037 that they can only be accessed through set-id programs
9038 provided. You should not do this in a Debian package: anyone can
9039 download the <file>.deb</file> file and read the data from it,
9040 so there is no point making the files unreadable. Not
9041 making the files unreadable also means that you don't have
9042 to make so many programs set-id, which reduces the risk of a
9046 As described in the FHS, binaries of games should be
9047 installed in the directory <file>/usr/games</file>. This also
9048 applies to games that use the X Window System. Manual pages
9049 for games (X and non-X games) should be installed in
9050 <file>/usr/share/man/man6</file>.</p>
9056 <heading>Documentation</heading>
9059 <heading>Manual pages</heading>
9062 You should install manual pages in <prgn>nroff</prgn> source
9063 form, in appropriate places under <file>/usr/share/man</file>.
9064 You should only use sections 1 to 9 (see the FHS for more
9065 details). You must not install a pre-formatted "cat page".
9069 Each program, utility, and function should have an
9070 associated manual page included in the same package. It is
9071 suggested that all configuration files also have a manual
9072 page included as well. Manual pages for protocols and other
9073 auxiliary things are optional.
9077 If no manual page is available, this is considered as a bug
9078 and should be reported to the Debian Bug Tracking System (the
9079 maintainer of the package is allowed to write this bug report
9080 themselves, if they so desire). Do not close the bug report
9081 until a proper man page is available.<footnote>
9082 It is not very hard to write a man page. See the
9083 <url id="http://www.schweikhardt.net/man_page_howto.html"
9084 name="Man-Page-HOWTO">,
9085 <manref name="man" section="7">, the examples
9086 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
9087 the helper program <prgn>help2man</prgn>, or the
9088 directory <file>/usr/share/doc/man-db/examples</file>.
9093 You may forward a complaint about a missing man page to the
9094 upstream authors, and mark the bug as forwarded in the
9095 Debian bug tracking system. Even though the GNU Project do
9096 not in general consider the lack of a man page to be a bug,
9097 we do; if they tell you that they don't consider it a bug
9098 you should leave the bug in our bug tracking system open
9103 Manual pages should be installed compressed using <tt>gzip -9</tt>.
9107 If one man page needs to be accessible via several names it
9108 is better to use a symbolic link than the <file>.so</file>
9109 feature, but there is no need to fiddle with the relevant
9110 parts of the upstream source to change from <file>.so</file> to
9111 symlinks: don't do it unless it's easy. You should not
9112 create hard links in the manual page directories, nor put
9113 absolute filenames in <file>.so</file> directives. The filename
9114 in a <file>.so</file> in a man page should be relative to the
9115 base of the man page tree (usually
9116 <file>/usr/share/man</file>). If you do not create any links
9117 (whether symlinks, hard links, or <tt>.so</tt> directives)
9118 in the file system to the alternate names of the man page,
9119 then you should not rely on <prgn>man</prgn> finding your
9120 man page under those names based solely on the information in
9121 the man page's header.<footnote>
9122 Supporting this in <prgn>man</prgn> often requires
9123 unreasonable processing time to find a manual page or to
9124 report that none exists, and moves knowledge into man's
9125 database that would be better left in the file system.
9126 This support is therefore deprecated and will cease to
9127 be present in the future.
9132 Manual pages in locale-specific subdirectories of
9133 <file>/usr/share/man</file> should use either UTF-8 or the usual
9134 legacy encoding for that language (normally the one corresponding
9135 to the shortest relevant locale name in
9136 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
9137 <file>/usr/share/man/fr</file> should use either UTF-8 or
9138 ISO-8859-1.<footnote>
9139 <prgn>man</prgn> will automatically detect whether UTF-8 is in
9140 use. In future, all manual pages will be required to use
9146 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
9147 included in the subdirectory name unless it indicates a
9148 significant difference in the language, as this excludes
9149 speakers of the language in other countries.<footnote>
9150 At the time of writing, Chinese and Portuguese are the main
9151 languages with such differences, so <file>pt_BR</file>,
9152 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
9157 If a localized version of a manual page is provided, it should
9158 either be up-to-date or it should be obvious to the reader that
9159 it is outdated and the original manual page should be used
9160 instead. This can be done either by a note at the beginning of
9161 the manual page or by showing the missing or changed portions in
9162 the original language instead of the target language.
9167 <heading>Info documents</heading>
9170 Info documents should be installed in <file>/usr/share/info</file>.
9171 They should be compressed with <tt>gzip -9</tt>.
9175 The <prgn>install-info</prgn> program maintains a directory of
9176 installed info documents in <file>/usr/share/info/dir</file> for
9177 the use of info readers.<footnote>
9178 It was previously necessary for packages installing info
9179 documents to run <prgn>install-info</prgn> from maintainer
9180 scripts. This is no longer necessary. The installation
9181 system now uses dpkg triggers.
9183 This file must not be included in packages. Packages containing
9184 info documents should depend on <tt>dpkg (>= 1.15.4) |
9185 install-info</tt> to ensure that the directory file is properly
9186 rebuilt during partial upgrades from Debian 5.0 (lenny) and
9191 Info documents should contain section and directory entry
9192 information in the document for the use
9193 of <prgn>install-info</prgn>. The section should be specified
9194 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
9195 space and the section of this info page. The directory entry or
9196 entries should be included between
9197 a <tt>START-INFO-DIR-ENTRY</tt> line and
9198 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
9200 INFO-DIR-SECTION Individual utilities
9201 START-INFO-DIR-ENTRY
9202 * example: (example). An example info directory entry.
9205 To determine which section to use, you should look
9206 at <file>/usr/share/info/dir</file> on your system and choose
9207 the most relevant (or create a new section if none of the
9208 current sections are relevant).<footnote>
9209 Normally, info documents are generated from Texinfo source.
9210 To include this information in the generated info document, if
9211 it is absent, add commands like:
9213 @dircategory Individual utilities
9215 * example: (example). An example info directory entry.
9218 to the Texinfo source of the document and ensure that the info
9219 documents are rebuilt from source during the package build.
9225 <heading>Additional documentation</heading>
9228 Any additional documentation that comes with the package may
9229 be installed at the discretion of the package maintainer.
9230 Plain text documentation should be installed in the directory
9231 <file>/usr/share/doc/<var>package</var></file>, where
9232 <var>package</var> is the name of the package, and
9233 compressed with <tt>gzip -9</tt> unless it is small.
9237 If a package comes with large amounts of documentation which
9238 many users of the package will not require you should create
9239 a separate binary package to contain it, so that it does not
9240 take up disk space on the machines of users who do not need
9241 or want it installed.</p>
9244 It is often a good idea to put text information files
9245 (<file>README</file>s, changelogs, and so forth) that come with
9246 the source package in <file>/usr/share/doc/<var>package</var></file>
9247 in the binary package. However, you don't need to install
9248 the instructions for building and installing the package, of
9252 Packages must not require the existence of any files in
9253 <file>/usr/share/doc/</file> in order to function
9255 The system administrator should be able to
9256 delete files in <file>/usr/share/doc/</file> without causing
9257 any programs to break.
9259 Any files that are referenced by programs but are also
9260 useful as stand alone documentation should be installed under
9261 <file>/usr/share/<var>package</var>/</file> with symbolic links from
9262 <file>/usr/share/doc/<var>package</var></file>.
9266 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9267 link to another directory in <file>/usr/share/doc</file> only if
9268 the two packages both come from the same source and the
9269 first package Depends on the second.<footnote>
9271 Please note that this does not override the section on
9272 changelog files below, so the file
9273 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
9274 must refer to the changelog for the current version of
9275 <var>package</var> in question. In practice, this means
9276 that the sources of the target and the destination of the
9277 symlink must be the same (same source package and
9284 Former Debian releases placed all additional documentation
9285 in <file>/usr/doc/<var>package</var></file>. This has been
9286 changed to <file>/usr/share/doc/<var>package</var></file>,
9287 and packages must not put documentation in the directory
9288 <file>/usr/doc/<var>package</var></file>. <footnote>
9289 At this phase of the transition, we no longer require a
9290 symbolic link in <file>/usr/doc/</file>. At a later point,
9291 policy shall change to make the symbolic links a bug.
9297 <heading>Preferred documentation formats</heading>
9300 The unification of Debian documentation is being carried out
9304 If your package comes with extensive documentation in a
9305 markup format that can be converted to various other formats
9306 you should if possible ship HTML versions in a binary
9307 package, in the directory
9308 <file>/usr/share/doc/<var>appropriate-package</var></file> or
9309 its subdirectories.<footnote>
9310 The rationale: The important thing here is that HTML
9311 docs should be available in <em>some</em> package, not
9312 necessarily in the main binary package.
9317 Other formats such as PostScript may be provided at the
9318 package maintainer's discretion.
9322 <sect id="copyrightfile">
9323 <heading>Copyright information</heading>
9326 Every package must be accompanied by a verbatim copy of its
9327 copyright information and distribution license in the file
9328 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
9329 file must neither be compressed nor be a symbolic link.
9333 In addition, the copyright file must say where the upstream
9334 sources (if any) were obtained. It should name the original
9335 authors of the package and the Debian maintainer(s) who were
9336 involved with its creation.
9340 Packages in the <em>contrib</em> or <em>non-free</em> archive
9341 areas should state in the copyright file that the package is not
9342 part of the Debian GNU/Linux distribution and briefly explain
9347 A copy of the file which will be installed in
9348 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9349 be in <file>debian/copyright</file> in the source package.
9353 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9354 link to another directory in <file>/usr/share/doc</file> only if
9355 the two packages both come from the same source and the
9356 first package Depends on the second. These rules are
9357 important because copyrights must be extractable by
9362 Packages distributed under the Apache license (version 2.0), the
9363 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
9364 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
9365 1.3) should refer to the corresponding files
9366 under <file>/usr/share/common-licenses</file>,<footnote>
9369 <file>/usr/share/common-licenses/Apache-2.0</file>,
9370 <file>/usr/share/common-licenses/Artistic</file>,
9371 <file>/usr/share/common-licenses/GPL-1</file>,
9372 <file>/usr/share/common-licenses/GPL-2</file>,
9373 <file>/usr/share/common-licenses/GPL-3</file>,
9374 <file>/usr/share/common-licenses/LGPL-2</file>,
9375 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9376 <file>/usr/share/common-licenses/LGPL-3</file>,
9377 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
9378 <file>/usr/share/common-licenses/GFDL-1.3</file>
9379 respectively. The University of California BSD license is
9380 also included in <package>base-files</package> as
9381 <file>/usr/share/common-licenses/BSD</file>, but given the
9382 brevity of this license, its specificity to code whose
9383 copyright is held by the Regents of the University of
9384 California, and the frequency of minor wording changes, its
9385 text should be included in the copyright file rather than
9386 referencing this file.
9388 </footnote> rather than quoting them in the copyright
9393 You should not use the copyright file as a general <file>README</file>
9394 file. If your package has such a file it should be
9395 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9396 <file>README.Debian</file> or some other appropriate place.</p>
9400 <heading>Examples</heading>
9403 Any examples (configurations, source files, whatever),
9404 should be installed in a directory
9405 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9406 files should not be referenced by any program: they're there
9407 for the benefit of the system administrator and users as
9408 documentation only. Architecture-specific example files
9409 should be installed in a directory
9410 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9412 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9413 latter directory itself may be a symbolic link to the
9418 If the purpose of a package is to provide examples, then the
9419 example files may be installed into
9420 <file>/usr/share/doc/<var>package</var></file>.
9424 <sect id="changelogs">
9425 <heading>Changelog files</heading>
9428 Packages that are not Debian-native must contain a
9429 compressed copy of the <file>debian/changelog</file> file from
9430 the Debian source tree in
9431 <file>/usr/share/doc/<var>package</var></file> with the name
9432 <file>changelog.Debian.gz</file>.
9436 If an upstream changelog is available, it should be accessible as
9437 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9438 plain text. If the upstream changelog is distributed in
9439 HTML, it should be made available in that form as
9440 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9441 and a plain text <file>changelog.gz</file> should be generated
9442 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9443 the upstream changelog files do not already conform to this
9444 naming convention, then this may be achieved either by
9445 renaming the files, or by adding a symbolic link, at the
9446 maintainer's discretion.<footnote>
9447 Rationale: People should not have to look in places for
9448 upstream changelogs merely because they are given
9449 different names or are distributed in HTML format.
9454 All of these files should be installed compressed using
9455 <tt>gzip -9</tt>, as they will become large with time even
9456 if they start out small.
9460 If the package has only one changelog which is used both as
9461 the Debian changelog and the upstream one because there is
9462 no separate upstream maintainer then that changelog should
9463 usually be installed as
9464 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9465 there is a separate upstream maintainer, but no upstream
9466 changelog, then the Debian changelog should still be called
9467 <file>changelog.Debian.gz</file>.
9471 For details about the format and contents of the Debian
9472 changelog file, please see <ref id="dpkgchangelog">.
9477 <appendix id="pkg-scope">
9478 <heading>Introduction and scope of these appendices</heading>
9481 These appendices are taken essentially verbatim from the
9482 now-deprecated Packaging Manual, version 3.2.1.0. They are
9483 the chapters which are likely to be of use to package
9484 maintainers and which have not already been included in the
9485 policy document itself. Most of these sections are very likely
9486 not relevant to policy; they should be treated as
9487 documentation for the packaging system. Please note that these
9488 appendices are included for convenience, and for historical
9489 reasons: they used to be part of policy package, and they have
9490 not yet been incorporated into dpkg documentation. However,
9491 they still have value, and hence they are presented here.
9495 They have not yet been checked to ensure that they are
9496 compatible with the contents of policy, and if there are any
9497 contradictions, the version in the main policy document takes
9498 precedence. The remaining chapters of the old Packaging
9499 Manual have also not been read in detail to ensure that there
9500 are not parts which have been left out. Both of these will be
9505 Certain parts of the Packaging manual were integrated into the
9506 Policy Manual proper, and removed from the appendices. Links
9507 have been placed from the old locations to the new ones.
9511 <prgn>dpkg</prgn> is a suite of programs for creating binary
9512 package files and installing and removing them on Unix
9514 <prgn>dpkg</prgn> is targeted primarily at Debian
9515 GNU/Linux, but may work on or be ported to other
9521 The binary packages are designed for the management of
9522 installed executable programs (usually compiled binaries) and
9523 their associated data, though source code examples and
9524 documentation are provided as part of some packages.</p>
9527 This manual describes the technical aspects of creating Debian
9528 binary packages (<file>.deb</file> files). It documents the
9529 behavior of the package management programs
9530 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9531 they interact with packages.</p>
9534 It also documents the interaction between
9535 <prgn>dselect</prgn>'s core and the access method scripts it
9536 uses to actually install the selected packages, and describes
9537 how to create a new access method.</p>
9540 This manual does not go into detail about the options and
9541 usage of the package building and installation tools. It
9542 should therefore be read in conjunction with those programs'
9547 The utility programs which are provided with <prgn>dpkg</prgn>
9548 for managing various system configuration and similar issues,
9549 such as <prgn>update-rc.d</prgn> and
9550 <prgn>install-info</prgn>, are not described in detail here -
9551 please see their man pages.
9555 It is assumed that the reader is reasonably familiar with the
9556 <prgn>dpkg</prgn> System Administrators' manual.
9557 Unfortunately this manual does not yet exist.
9561 The Debian version of the FSF's GNU hello program is provided
9562 as an example for people wishing to create Debian
9563 packages. The Debian <prgn>debmake</prgn> package is
9564 recommended as a very helpful tool in creating and maintaining
9565 Debian packages. However, while the tools and examples are
9566 helpful, they do not replace the need to read and follow the
9567 Policy and Programmer's Manual.</p>
9570 <appendix id="pkg-binarypkg">
9571 <heading>Binary packages (from old Packaging Manual)</heading>
9574 The binary package has two main sections. The first part
9575 consists of various control information files and scripts used
9576 by <prgn>dpkg</prgn> when installing and removing. See <ref
9577 id="pkg-controlarea">.
9581 The second part is an archive containing the files and
9582 directories to be installed.
9586 In the future binary packages may also contain other
9587 components, such as checksums and digital signatures. The
9588 format for the archive is described in full in the
9589 <file>deb(5)</file> man page.
9593 <sect id="pkg-bincreating"><heading>Creating package files -
9594 <prgn>dpkg-deb</prgn>
9598 All manipulation of binary package files is done by
9599 <prgn>dpkg-deb</prgn>; it's the only program that has
9600 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9601 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9602 will spot that the options requested are appropriate to
9603 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9608 In order to create a binary package you must make a
9609 directory tree which contains all the files and directories
9610 you want to have in the file system data part of the package.
9611 In Debian-format source packages this directory is usually
9612 <file>debian/tmp</file>, relative to the top of the package's
9617 They should have the locations (relative to the root of the
9618 directory tree you're constructing) ownerships and
9619 permissions which you want them to have on the system when
9624 With current versions of <prgn>dpkg</prgn> the uid/username
9625 and gid/groupname mappings for the users and groups being
9626 used should be the same on the system where the package is
9627 built and the one where it is installed.
9631 You need to add one special directory to the root of the
9632 miniature file system tree you're creating:
9633 <prgn>DEBIAN</prgn>. It should contain the control
9634 information files, notably the binary package control file
9635 (see <ref id="pkg-controlfile">).
9639 The <prgn>DEBIAN</prgn> directory will not appear in the
9640 file system archive of the package, and so won't be installed
9641 by <prgn>dpkg</prgn> when the package is installed.
9645 When you've prepared the package, you should invoke:
9647 dpkg --build <var>directory</var>
9652 This will build the package in
9653 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9654 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9655 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9660 See the man page <manref name="dpkg-deb" section="8"> for details of how
9661 to examine the contents of this newly-created file. You may find the
9662 output of following commands enlightening:
9664 dpkg-deb --info <var>filename</var>.deb
9665 dpkg-deb --contents <var>filename</var>.deb
9666 dpkg --contents <var>filename</var>.deb
9668 To view the copyright file for a package you could use this command:
9670 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
9675 <sect id="pkg-controlarea">
9676 <heading>Package control information files</heading>
9679 The control information portion of a binary package is a
9680 collection of files with names known to <prgn>dpkg</prgn>.
9681 It will treat the contents of these files specially - some
9682 of them contain information used by <prgn>dpkg</prgn> when
9683 installing or removing the package; others are scripts which
9684 the package maintainer wants <prgn>dpkg</prgn> to run.
9688 It is possible to put other files in the package control
9689 area, but this is not generally a good idea (though they
9690 will largely be ignored).
9694 Here is a brief list of the control info files supported by
9695 <prgn>dpkg</prgn> and a summary of what they're used for.
9700 <tag><tt>control</tt>
9703 This is the key description file used by
9704 <prgn>dpkg</prgn>. It specifies the package's name
9705 and version, gives its description for the user,
9706 states its relationships with other packages, and so
9707 forth. See <ref id="sourcecontrolfiles"> and
9708 <ref id="binarycontrolfiles">.
9712 It is usually generated automatically from information
9713 in the source package by the
9714 <prgn>dpkg-gencontrol</prgn> program, and with
9715 assistance from <prgn>dpkg-shlibdeps</prgn>.
9716 See <ref id="pkg-sourcetools">.
9720 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9725 These are executable files (usually scripts) which
9726 <prgn>dpkg</prgn> runs during installation, upgrade
9727 and removal of packages. They allow the package to
9728 deal with matters which are particular to that package
9729 or require more complicated processing than that
9730 provided by <prgn>dpkg</prgn>. Details of when and
9731 how they are called are in <ref id="maintainerscripts">.
9735 It is very important to make these scripts idempotent.
9736 See <ref id="idempotency">.
9740 The maintainer scripts are not guaranteed to run with a
9741 controlling terminal and may not be able to interact with
9742 the user. See <ref id="controllingterminal">.
9746 <tag><tt>conffiles</tt>
9749 This file contains a list of configuration files which
9750 are to be handled automatically by <prgn>dpkg</prgn>
9751 (see <ref id="pkg-conffiles">). Note that not necessarily
9752 every configuration file should be listed here.
9755 <tag><tt>shlibs</tt>
9758 This file contains a list of the shared libraries
9759 supplied by the package, with dependency details for
9760 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9761 when it determines what dependencies are required in a
9762 package control file. The <tt>shlibs</tt> file format
9763 is described on <ref id="shlibs">.
9768 <sect id="pkg-controlfile">
9769 <heading>The main control information file: <tt>control</tt></heading>
9772 The most important control information file used by
9773 <prgn>dpkg</prgn> when it installs a package is
9774 <tt>control</tt>. It contains all the package's "vital
9779 The binary package control files of packages built from
9780 Debian sources are made by a special tool,
9781 <prgn>dpkg-gencontrol</prgn>, which reads
9782 <file>debian/control</file> and <file>debian/changelog</file> to
9783 find the information it needs. See <ref id="pkg-sourcepkg"> for
9788 The fields in binary package control files are listed in
9789 <ref id="binarycontrolfiles">.
9793 A description of the syntax of control files and the purpose
9794 of the fields is available in <ref id="controlfields">.
9799 <heading>Time Stamps</heading>
9802 See <ref id="timestamps">.
9807 <appendix id="pkg-sourcepkg">
9808 <heading>Source packages (from old Packaging Manual) </heading>
9811 The Debian binary packages in the distribution are generated
9812 from Debian sources, which are in a special format to assist
9813 the easy and automatic building of binaries.
9816 <sect id="pkg-sourcetools">
9817 <heading>Tools for processing source packages</heading>
9820 Various tools are provided for manipulating source packages;
9821 they pack and unpack sources and help build of binary
9822 packages and help manage the distribution of new versions.
9826 They are introduced and typical uses described here; see
9827 <manref name="dpkg-source" section="1"> for full
9828 documentation about their arguments and operation.
9832 For examples of how to construct a Debian source package,
9833 and how to use those utilities that are used by Debian
9834 source packages, please see the <prgn>hello</prgn> example
9838 <sect1 id="pkg-dpkg-source">
9840 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9845 This program is frequently used by hand, and is also
9846 called from package-independent automated building scripts
9847 such as <prgn>dpkg-buildpackage</prgn>.
9851 To unpack a package it is typically invoked with
9853 dpkg-source -x <var>.../path/to/filename</var>.dsc
9858 with the <file><var>filename</var>.tar.gz</file> and
9859 <file><var>filename</var>.diff.gz</file> (if applicable) in
9860 the same directory. It unpacks into
9861 <file><var>package</var>-<var>version</var></file>, and if
9863 <file><var>package</var>-<var>version</var>.orig</file>, in
9864 the current directory.
9868 To create a packed source archive it is typically invoked:
9870 dpkg-source -b <var>package</var>-<var>version</var>
9875 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
9876 <file>.diff.gz</file> (if appropriate) in the current
9877 directory. <prgn>dpkg-source</prgn> does not clean the
9878 source tree first - this must be done separately if it is
9883 See also <ref id="pkg-sourcearchives">.</p>
9887 <sect1 id="pkg-dpkg-buildpackage">
9889 <prgn>dpkg-buildpackage</prgn> - overall package-building
9894 <prgn>dpkg-buildpackage</prgn> is a script which invokes
9895 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
9896 targets <tt>clean</tt>, <tt>build</tt> and
9897 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
9898 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
9899 source and binary package upload.
9903 It is usually invoked by hand from the top level of the
9904 built or unbuilt source directory. It may be invoked with
9905 no arguments; useful arguments include:
9906 <taglist compact="compact">
9907 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
9910 Do not sign the <tt>.changes</tt> file or the
9911 source package <tt>.dsc</tt> file, respectively.</p>
9913 <tag><tt>-p<var>sign-command</var></tt></tag>
9916 Invoke <var>sign-command</var> instead of finding
9917 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
9918 <var>sign-command</var> must behave just like
9919 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
9921 <tag><tt>-r<var>root-command</var></tt></tag>
9924 When root privilege is required, invoke the command
9925 <var>root-command</var>. <var>root-command</var>
9926 should invoke its first argument as a command, from
9927 the <prgn>PATH</prgn> if necessary, and pass its
9928 second and subsequent arguments to the command it
9929 calls. If no <var>root-command</var> is supplied
9930 then <var>dpkg-buildpackage</var> will take no
9931 special action to gain root privilege, so that for
9932 most packages it will have to be invoked as root to
9935 <tag><tt>-b</tt>, <tt>-B</tt></tag>
9938 Two types of binary-only build and upload - see
9939 <manref name="dpkg-source" section="1">.
9946 <sect1 id="pkg-dpkg-gencontrol">
9948 <prgn>dpkg-gencontrol</prgn> - generates binary package
9953 This program is usually called from <file>debian/rules</file>
9954 (see <ref id="pkg-sourcetree">) in the top level of the source
9959 This is usually done just before the files and directories in the
9960 temporary directory tree where the package is being built have their
9961 permissions and ownerships set and the package is constructed using
9962 <prgn>dpkg-deb/</prgn>
9964 This is so that the control file which is produced has
9965 the right permissions
9970 <prgn>dpkg-gencontrol</prgn> must be called after all the
9971 files which are to go into the package have been placed in
9972 the temporary build directory, so that its calculation of
9973 the installed size of a package is correct.
9977 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
9978 be run after <prgn>dpkg-shlibdeps</prgn> so that the
9979 variable substitutions created by
9980 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
9985 For a package which generates only one binary package, and
9986 which builds it in <file>debian/tmp</file> relative to the top
9987 of the source package, it is usually sufficient to call
9988 <prgn>dpkg-gencontrol</prgn>.
9992 Sources which build several binaries will typically need
9995 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
9996 </example> The <tt>-P</tt> tells
9997 <prgn>dpkg-gencontrol</prgn> that the package is being
9998 built in a non-default directory, and the <tt>-p</tt>
9999 tells it which package's control file should be generated.
10003 <prgn>dpkg-gencontrol</prgn> also adds information to the
10004 list of files in <file>debian/files</file>, for the benefit of
10005 (for example) a future invocation of
10006 <prgn>dpkg-genchanges</prgn>.</p>
10009 <sect1 id="pkg-dpkg-shlibdeps">
10011 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
10016 This program is usually called from <file>debian/rules</file>
10017 just before <prgn>dpkg-gencontrol</prgn> (see <ref
10018 id="pkg-sourcetree">), in the top level of the source tree.
10022 Its arguments are executables and shared libraries
10025 They may be specified either in the locations in the
10026 source tree where they are created or in the locations
10027 in the temporary build tree where they are installed
10028 prior to binary package creation.
10030 </footnote> for which shared library dependencies should
10031 be included in the binary package's control file.
10035 If some of the found shared libraries should only
10036 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
10037 some warrant a <tt>Pre-Depends</tt>, this can be achieved
10038 by using the <tt>-d<var>dependency-field</var></tt> option
10039 before those executable(s). (Each <tt>-d</tt> option
10040 takes effect until the next <tt>-d</tt>.)
10044 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
10045 output control file to be modified. Instead by default it
10046 adds to the <file>debian/substvars</file> file variable
10047 settings like <tt>shlibs:Depends</tt>. These variable
10048 settings must be referenced in dependency fields in the
10049 appropriate per-binary-package sections of the source
10054 For example, a package that generates an essential part
10055 which requires dependencies, and optional parts that
10056 which only require a recommendation, would separate those
10057 two sets of dependencies into two different fields.<footnote>
10058 At the time of writing, an example for this was the
10059 <package/xmms/ package, with Depends used for the xmms
10060 executable, Recommends for the plug-ins and Suggests for
10061 even more optional features provided by unzip.
10063 It can say in its <file>debian/rules</file>:
10065 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
10066 -dRecommends <var>optionalpart anotheroptionalpart</var>
10068 and then in its main control file <file>debian/control</file>:
10071 Depends: ${shlibs:Depends}
10072 Recommends: ${shlibs:Recommends}
10078 Sources which produce several binary packages with
10079 different shared library dependency requirements can use
10080 the <tt>-p<var>varnameprefix</var></tt> option to override
10081 the default <tt>shlibs:</tt> prefix (one invocation of
10082 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
10083 They can thus produce several sets of dependency
10084 variables, each of the form
10085 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
10086 which can be referred to in the appropriate parts of the
10087 binary package control files.
10092 <sect1 id="pkg-dpkg-distaddfile">
10094 <prgn>dpkg-distaddfile</prgn> - adds a file to
10095 <file>debian/files</file>
10099 Some packages' uploads need to include files other than
10100 the source and binary package files.
10104 <prgn>dpkg-distaddfile</prgn> adds a file to the
10105 <file>debian/files</file> file so that it will be included in
10106 the <file>.changes</file> file when
10107 <prgn>dpkg-genchanges</prgn> is run.
10111 It is usually invoked from the <tt>binary</tt> target of
10112 <file>debian/rules</file>:
10114 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
10116 The <var>filename</var> is relative to the directory where
10117 <prgn>dpkg-genchanges</prgn> will expect to find it - this
10118 is usually the directory above the top level of the source
10119 tree. The <file>debian/rules</file> target should put the
10120 file there just before or just after calling
10121 <prgn>dpkg-distaddfile</prgn>.
10125 The <var>section</var> and <var>priority</var> are passed
10126 unchanged into the resulting <file>.changes</file> file.
10131 <sect1 id="pkg-dpkg-genchanges">
10133 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
10134 upload control file
10138 This program is usually called by package-independent
10139 automatic building scripts such as
10140 <prgn>dpkg-buildpackage</prgn>, but it may also be called
10145 It is usually called in the top level of a built source
10146 tree, and when invoked with no arguments will print out a
10147 straightforward <file>.changes</file> file based on the
10148 information in the source package's changelog and control
10149 file and the binary and source packages which should have
10155 <sect1 id="pkg-dpkg-parsechangelog">
10157 <prgn>dpkg-parsechangelog</prgn> - produces parsed
10158 representation of a changelog
10162 This program is used internally by
10163 <prgn>dpkg-source</prgn> et al. It may also occasionally
10164 be useful in <file>debian/rules</file> and elsewhere. It
10165 parses a changelog, <file>debian/changelog</file> by default,
10166 and prints a control-file format representation of the
10167 information in it to standard output.
10171 <sect1 id="pkg-dpkg-architecture">
10173 <prgn>dpkg-architecture</prgn> - information about the build and
10178 This program can be used manually, but is also invoked by
10179 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
10180 environment or make variables which specify the build and host
10181 architecture for the package building process.
10186 <sect id="pkg-sourcetree">
10187 <heading>The Debian package source tree</heading>
10190 The source archive scheme described later is intended to
10191 allow a Debian package source tree with some associated
10192 control information to be reproduced and transported easily.
10193 The Debian package source tree is a version of the original
10194 program with certain files added for the benefit of the
10195 packaging process, and with any other changes required
10196 made to the rest of the source code and installation
10201 The extra files created for Debian are in the subdirectory
10202 <file>debian</file> of the top level of the Debian package
10203 source tree. They are described below.
10206 <sect1 id="pkg-debianrules">
10207 <heading><file>debian/rules</file> - the main building script</heading>
10210 See <ref id="debianrules">.
10214 <sect1 id="pkg-srcsubstvars">
10215 <heading><file>debian/substvars</file> and variable substitutions</heading>
10218 See <ref id="substvars">.
10224 <heading><file>debian/files</file></heading>
10227 See <ref id="debianfiles">.
10231 <sect1><heading><file>debian/tmp</file>
10235 This is the canonical temporary location for the
10236 construction of binary packages by the <tt>binary</tt>
10237 target. The directory <file>tmp</file> serves as the root of
10238 the file system tree as it is being constructed (for
10239 example, by using the package's upstream makefiles install
10240 targets and redirecting the output there), and it also
10241 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10242 id="pkg-bincreating">.
10246 If several binary packages are generated from the same
10247 source tree it is usual to use several
10248 <file>debian/tmp<var>something</var></file> directories, for
10249 example <file>tmp-a</file> or <file>tmp-doc</file>.
10253 Whatever <file>tmp</file> directories are created and used by
10254 <tt>binary</tt> must of course be removed by the
10255 <tt>clean</tt> target.</p></sect1>
10259 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10263 As it exists on the FTP site, a Debian source package
10264 consists of three related files. You must have the right
10265 versions of all three to be able to use them.
10270 <tag>Debian source control file - <tt>.dsc</tt></tag>
10272 This file is a control file used by <prgn>dpkg-source</prgn>
10273 to extract a source package.
10274 See <ref id="debiansourcecontrolfiles">.
10278 Original source archive -
10280 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10286 This is a compressed (with <tt>gzip -9</tt>)
10287 <prgn>tar</prgn> file containing the source code from
10288 the upstream authors of the program.
10293 Debian package diff -
10295 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10301 This is a unified context diff (<tt>diff -u</tt>)
10302 giving the changes which are required to turn the
10303 original source into the Debian source. These changes
10304 may only include editing and creating plain files.
10305 The permissions of files, the targets of symbolic
10306 links and the characteristics of special files or
10307 pipes may not be changed and no files may be removed
10312 All the directories in the diff must exist, except the
10313 <file>debian</file> subdirectory of the top of the source
10314 tree, which will be created by
10315 <prgn>dpkg-source</prgn> if necessary when unpacking.
10319 The <prgn>dpkg-source</prgn> program will
10320 automatically make the <file>debian/rules</file> file
10321 executable (see below).</p></item>
10326 If there is no original source code - for example, if the
10327 package is specially prepared for Debian or the Debian
10328 maintainer is the same as the upstream maintainer - the
10329 format is slightly different: then there is no diff, and the
10331 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10332 and preferably contains a directory named
10333 <file><var>package</var>-<var>version</var></file>.
10338 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10341 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10342 Debian source package. However, if it is not available it
10343 is possible to unpack a Debian source archive as follows:
10344 <enumlist compact="compact">
10347 Untar the tarfile, which will create a <file>.orig</file>
10351 <p>Rename the <file>.orig</file> directory to
10352 <file><var>package</var>-<var>version</var></file>.</p>
10356 Create the subdirectory <file>debian</file> at the top of
10357 the source tree.</p>
10359 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10361 <item><p>Untar the tarfile again if you want a copy of the original
10362 source code alongside the Debian version.</p>
10367 It is not possible to generate a valid Debian source archive
10368 without using <prgn>dpkg-source</prgn>. In particular,
10369 attempting to use <prgn>diff</prgn> directly to generate the
10370 <file>.diff.gz</file> file will not work.
10374 <heading>Restrictions on objects in source packages</heading>
10377 The source package may not contain any hard links
10379 This is not currently detected when building source
10380 packages, but only when extracting
10384 Hard links may be permitted at some point in the
10385 future, but would require a fair amount of
10387 </footnote>, device special files, sockets or setuid or
10390 Setgid directories are allowed.
10395 The source packaging tools manage the changes between the
10396 original and Debian source using <prgn>diff</prgn> and
10397 <prgn>patch</prgn>. Turning the original source tree as
10398 included in the <file>.orig.tar.gz</file> into the Debian
10399 package source must not involve any changes which cannot be
10400 handled by these tools. Problematic changes which cause
10401 <prgn>dpkg-source</prgn> to halt with an error when
10402 building the source package are:
10403 <list compact="compact">
10404 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10406 <item><p>Changing the targets of symbolic links.</p>
10408 <item><p>Creating directories, other than <file>debian</file>.</p>
10410 <item><p>Changes to the contents of binary files.</p></item>
10411 </list> Changes which cause <prgn>dpkg-source</prgn> to
10412 print a warning but continue anyway are:
10413 <list compact="compact">
10416 Removing files, directories or symlinks.
10418 Renaming a file is not treated specially - it is
10419 seen as the removal of the old file (which
10420 generates a warning, but is otherwise ignored),
10421 and the creation of the new one.
10427 Changed text files which are missing the usual final
10428 newline (either in the original or the modified
10433 Changes which are not represented, but which are not detected by
10434 <prgn>dpkg-source</prgn>, are:
10435 <list compact="compact">
10436 <item><p>Changing the permissions of files (other than
10437 <file>debian/rules</file>) and directories.</p></item>
10442 The <file>debian</file> directory and <file>debian/rules</file>
10443 are handled specially by <prgn>dpkg-source</prgn> - before
10444 applying the changes it will create the <file>debian</file>
10445 directory, and afterwards it will make
10446 <file>debian/rules</file> world-executable.
10452 <appendix id="pkg-controlfields">
10453 <heading>Control files and their fields (from old Packaging Manual)</heading>
10456 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10457 data in a common format, known as control files. Binary and
10458 source packages have control data as do the <file>.changes</file>
10459 files which control the installation of uploaded files, and
10460 <prgn>dpkg</prgn>'s internal databases are in a similar
10465 <heading>Syntax of control files</heading>
10468 See <ref id="controlsyntax">.
10472 It is important to note that there are several fields which
10473 are optional as far as <prgn>dpkg</prgn> and the related
10474 tools are concerned, but which must appear in every Debian
10475 package, or whose omission may cause problems.
10480 <heading>List of fields</heading>
10483 See <ref id="controlfieldslist">.
10487 This section now contains only the fields that didn't belong
10488 to the Policy manual.
10491 <sect1 id="pkg-f-Filename">
10492 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10495 These fields in <tt>Packages</tt> files give the
10496 filename(s) of (the parts of) a package in the
10497 distribution directories, relative to the root of the
10498 Debian hierarchy. If the package has been split into
10499 several parts the parts are all listed in order, separated
10504 <sect1 id="pkg-f-Size">
10505 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10508 These fields in <file>Packages</file> files give the size (in
10509 bytes, expressed in decimal) and MD5 checksum of the
10510 file(s) which make(s) up a binary package in the
10511 distribution. If the package is split into several parts
10512 the values for the parts are listed in order, separated by
10517 <sect1 id="pkg-f-Status">
10518 <heading><tt>Status</tt></heading>
10521 This field in <prgn>dpkg</prgn>'s status file records
10522 whether the user wants a package installed, removed or
10523 left alone, whether it is broken (requiring
10524 re-installation) or not and what its current state on the
10525 system is. Each of these pieces of information is a
10530 <sect1 id="pkg-f-Config-Version">
10531 <heading><tt>Config-Version</tt></heading>
10534 If a package is not installed or not configured, this
10535 field in <prgn>dpkg</prgn>'s status file records the last
10536 version of the package which was successfully
10541 <sect1 id="pkg-f-Conffiles">
10542 <heading><tt>Conffiles</tt></heading>
10545 This field in <prgn>dpkg</prgn>'s status file contains
10546 information about the automatically-managed configuration
10547 files held by a package. This field should <em>not</em>
10548 appear anywhere in a package!
10553 <heading>Obsolete fields</heading>
10556 These are still recognized by <prgn>dpkg</prgn> but should
10557 not appear anywhere any more.
10559 <taglist compact="compact">
10561 <tag><tt>Revision</tt></tag>
10562 <tag><tt>Package-Revision</tt></tag>
10563 <tag><tt>Package_Revision</tt></tag>
10565 The Debian revision part of the package version was
10566 at one point in a separate control file field. This
10567 field went through several names.
10570 <tag><tt>Recommended</tt></tag>
10571 <item>Old name for <tt>Recommends</tt>.</item>
10573 <tag><tt>Optional</tt></tag>
10574 <item>Old name for <tt>Suggests</tt>.</item>
10576 <tag><tt>Class</tt></tag>
10577 <item>Old name for <tt>Priority</tt>.</item>
10586 <appendix id="pkg-conffiles">
10587 <heading>Configuration file handling (from old Packaging Manual)</heading>
10590 <prgn>dpkg</prgn> can do a certain amount of automatic
10591 handling of package configuration files.
10595 Whether this mechanism is appropriate depends on a number of
10596 factors, but basically there are two approaches to any
10597 particular configuration file.
10601 The easy method is to ship a best-effort configuration in the
10602 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10603 handle updates. If the user is unlikely to want to edit the
10604 file, but you need them to be able to without losing their
10605 changes, and a new package with a changed version of the file
10606 is only released infrequently, this is a good approach.
10610 The hard method is to build the configuration file from
10611 scratch in the <prgn>postinst</prgn> script, and to take the
10612 responsibility for fixing any mistakes made in earlier
10613 versions of the package automatically. This will be
10614 appropriate if the file is likely to need to be different on
10618 <sect><heading>Automatic handling of configuration files by
10623 A package may contain a control area file called
10624 <tt>conffiles</tt>. This file should be a list of filenames
10625 of configuration files needing automatic handling, separated
10626 by newlines. The filenames should be absolute pathnames,
10627 and the files referred to should actually exist in the
10632 When a package is upgraded <prgn>dpkg</prgn> will process
10633 the configuration files during the configuration stage,
10634 shortly before it runs the package's <prgn>postinst</prgn>
10639 For each file it checks to see whether the version of the
10640 file included in the package is the same as the one that was
10641 included in the last version of the package (the one that is
10642 being upgraded from); it also compares the version currently
10643 installed on the system with the one shipped with the last
10648 If neither the user nor the package maintainer has changed
10649 the file, it is left alone. If one or the other has changed
10650 their version, then the changed version is preferred - i.e.,
10651 if the user edits their file, but the package maintainer
10652 doesn't ship a different version, the user's changes will
10653 stay, silently, but if the maintainer ships a new version
10654 and the user hasn't edited it the new version will be
10655 installed (with an informative message). If both have
10656 changed their version the user is prompted about the problem
10657 and must resolve the differences themselves.
10661 The comparisons are done by calculating the MD5 message
10662 digests of the files, and storing the MD5 of the file as it
10663 was included in the most recent version of the package.
10667 When a package is installed for the first time
10668 <prgn>dpkg</prgn> will install the file that comes with it,
10669 unless that would mean overwriting a file already on the
10674 However, note that <prgn>dpkg</prgn> will <em>not</em>
10675 replace a conffile that was removed by the user (or by a
10676 script). This is necessary because with some programs a
10677 missing file produces an effect hard or impossible to
10678 achieve in another way, so that a missing file needs to be
10679 kept that way if the user did it.
10683 Note that a package should <em>not</em> modify a
10684 <prgn>dpkg</prgn>-handled conffile in its maintainer
10685 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10686 the user confusing and possibly dangerous options for
10687 conffile update when the package is upgraded.</p>
10690 <sect><heading>Fully-featured maintainer script configuration
10695 For files which contain site-specific information such as
10696 the hostname and networking details and so forth, it is
10697 better to create the file in the package's
10698 <prgn>postinst</prgn> script.
10702 This will typically involve examining the state of the rest
10703 of the system to determine values and other information, and
10704 may involve prompting the user for some information which
10705 can't be obtained some other way.
10709 When using this method there are a couple of important
10710 issues which should be considered:
10714 If you discover a bug in the program which generates the
10715 configuration file, or if the format of the file changes
10716 from one version to the next, you will have to arrange for
10717 the postinst script to do something sensible - usually this
10718 will mean editing the installed configuration file to remove
10719 the problem or change the syntax. You will have to do this
10720 very carefully, since the user may have changed the file,
10721 perhaps to fix the very problem that your script is trying
10722 to deal with - you will have to detect these situations and
10723 deal with them correctly.
10727 If you do go down this route it's probably a good idea to
10728 make the program that generates the configuration file(s) a
10729 separate program in <file>/usr/sbin</file>, by convention called
10730 <file><var>package</var>config</file> and then run that if
10731 appropriate from the post-installation script. The
10732 <tt><var>package</var>config</tt> program should not
10733 unquestioningly overwrite an existing configuration - if its
10734 mode of operation is geared towards setting up a package for
10735 the first time (rather than any arbitrary reconfiguration
10736 later) you should have it check whether the configuration
10737 already exists, and require a <tt>--force</tt> flag to
10738 overwrite it.</p></sect>
10741 <appendix id="pkg-alternatives"><heading>Alternative versions of
10742 an interface - <prgn>update-alternatives</prgn> (from old
10747 When several packages all provide different versions of the
10748 same program or file it is useful to have the system select a
10749 default, but to allow the system administrator to change it
10750 and have their decisions respected.
10754 For example, there are several versions of the <prgn>vi</prgn>
10755 editor, and there is no reason to prevent all of them from
10756 being installed at once, each under their own name
10757 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10758 Nevertheless it is desirable to have the name <tt>vi</tt>
10759 refer to something, at least by default.
10763 If all the packages involved cooperate, this can be done with
10764 <prgn>update-alternatives</prgn>.
10768 Each package provides its own version under its own name, and
10769 calls <prgn>update-alternatives</prgn> in its postinst to
10770 register its version (and again in its prerm to deregister
10775 See the man page <manref name="update-alternatives"
10776 section="8"> for details.
10780 If <prgn>update-alternatives</prgn> does not seem appropriate
10781 you may wish to consider using diversions instead.</p>
10784 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10785 package's version of a file (from old Packaging Manual)
10789 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10790 when it reinstalls the package it belongs to, and to have it
10791 put the file from the package somewhere else instead.
10795 This can be used locally to override a package's version of a
10796 file, or by one package to override another's version (or
10797 provide a wrapper for it).
10801 Before deciding to use a diversion, read <ref
10802 id="pkg-alternatives"> to see if you really want a diversion
10803 rather than several alternative versions of a program.
10807 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10808 and updated by a special program <prgn>dpkg-divert</prgn>.
10809 Please see <manref name="dpkg-divert" section="8"> for full
10810 details of its operation.
10814 When a package wishes to divert a file from another, it should
10815 call <prgn>dpkg-divert</prgn> in its preinst to add the
10816 diversion and rename the existing file. For example,
10817 supposing that a <prgn>smailwrapper</prgn> package wishes to
10818 install a wrapper around <file>/usr/sbin/smail</file>:
10820 dpkg-divert --package smailwrapper --add --rename \
10821 --divert /usr/sbin/smail.real /usr/sbin/smail
10822 </example> The <tt>--package smailwrapper</tt> ensures that
10823 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
10824 can bypass the diversion and get installed as the true version.
10825 It's safe to add the diversion unconditionally on upgrades since
10826 it will be left unchanged if it already exists, but
10827 <prgn>dpkg-divert</prgn> will display a message. To suppress that
10828 message, make the command conditional on the version from which
10829 the package is being upgraded:
10831 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
10832 dpkg-divert --package smailwrapper --add --rename \
10833 --divert /usr/sbin/smail.real /usr/sbin/smail
10835 </example> where <tt>1.0-2</tt> is the version at which the
10836 diversion was first added to the package. Running the command
10837 during abort-upgrade is pointless but harmless.
10841 The postrm has to do the reverse:
10843 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
10844 dpkg-divert --package smailwrapper --remove --rename \
10845 --divert /usr/sbin/smail.real /usr/sbin/smail
10847 </example> If the diversion was added at a particular version, the
10848 postrm should also handle the failure case of upgrading from an
10849 older version (unless the older version is so old that direct
10850 upgrades are no longer supported):
10852 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
10853 dpkg-divert --package smailwrapper --remove --rename \
10854 --divert /usr/sbin/smail.real /usr/sbin/smail
10856 </example> where <tt>1.02-2</tt> is the version at which the
10857 diversion was first added to the package. The postrm should not
10858 remove the diversion on upgrades both because there's no reason to
10859 remove the diversion only to immediately re-add it and since the
10860 postrm of the old package is run after unpacking so the removal of
10861 the diversion will fail.
10865 Do not attempt to divert a file which is vitally important for
10866 the system's operation - when using <prgn>dpkg-divert</prgn>
10867 there is a time, after it has been diverted but before
10868 <prgn>dpkg</prgn> has installed the new version, when the file
10869 does not exist.</p>
10874 <!-- Local variables: -->
10875 <!-- indent-tabs-mode: t -->
10877 <!-- vim:set ai et sts=2 sw=2 tw=76: -->