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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 Relationships may be restricted to a certain set of
4377 architectures. This is indicated in brackets after each
4378 individual package name and the optional version specification.
4379 The brackets enclose a list of Debian architecture names
4380 separated by whitespace. Exclamation marks may be prepended to
4381 each of the names. (It is not permitted for some names to be
4382 prepended with exclamation marks while others aren't.)
4386 For build relationship fields
4387 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4388 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>), if
4389 the current Debian host architecture is not in this list and
4390 there are no exclamation marks in the list, or it is in the list
4391 with a prepended exclamation mark, the package name and the
4392 associated version specification are ignored completely for the
4393 purposes of defining the relationships.
4398 <example compact="compact">
4400 Build-Depends-Indep: texinfo
4401 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4402 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4404 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4405 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4406 <tt>gnumach-dev</tt> only on hurd-i386.
4410 For binary relationship fields, the architecture restriction
4411 syntax is only supported in the source package control
4412 file <file>debian/control</file>. When the corresponding binary
4413 package control file is generated, the relationship will either
4414 be omitted or included without the architecture restriction
4415 based on the architecture of the binary package. This means
4416 that architecture restrictions must not be used in binary
4417 relationship fields for architecture-independent packages
4418 (<tt>Architecture: all</tt>).
4423 <example compact="compact">
4424 Depends: foo [i386], bar [amd64]
4426 becomes <tt>Depends: foo</tt> when the package is built on
4427 the <tt>i386</tt> architecture, <tt>Depends: bar</tt> when the
4428 package is built on the <tt>amd64</tt> architecture, and omitted
4429 entirely in binary packages built on all other architectures.
4433 If the architecture-restricted dependency is part of a set of
4434 alternatives using <tt>|</tt>, that alternative is ignored
4435 completely on architectures that do not match the restriction.
4437 <example compact="compact">
4438 Build-Depends: foo [!i386] | bar [!amd64]
4440 is equivalent to <tt>bar</tt> on the i386 architecture, to
4441 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4442 bar</tt> on all other architectures.
4446 Relationships may also be restricted to a certain set of
4447 architectures using architecture wildcards. The syntax for
4448 declaring such restrictions is the same as declaring
4449 restrictions using a certain set of architectures without
4450 architecture wildcards. For example:
4451 <example compact="compact">
4452 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4454 is equivalent to <tt>foo</tt> on architectures using the Linux
4455 kernel and any cpu, <tt>bar</tt> on architectures using any
4456 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4457 using a kernel other than Linux.
4461 Note that the binary package relationship fields such as
4462 <tt>Depends</tt> appear in one of the binary package
4463 sections of the control file, whereas the build-time
4464 relationships such as <tt>Build-Depends</tt> appear in the
4465 source package section of the control file (which is the
4470 <sect id="binarydeps">
4471 <heading>Binary Dependencies - <tt>Depends</tt>,
4472 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4473 <tt>Pre-Depends</tt>
4477 Packages can declare in their control file that they have
4478 certain relationships to other packages - for example, that
4479 they may not be installed at the same time as certain other
4480 packages, and/or that they depend on the presence of others.
4484 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4485 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4486 <tt>Breaks</tt> and <tt>Conflicts</tt> control file fields.
4487 <tt>Breaks</tt> is described in <ref id="breaks">, and
4488 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4489 rest are described below.
4493 These seven fields are used to declare a dependency
4494 relationship by one package on another. Except for
4495 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4496 depending (binary) package's control file.
4497 (<tt>Enhances</tt> appears in the recommending package's
4498 control file, and <tt>Breaks</tt> appears in the version of
4499 depended-on package which causes the named package to
4504 A <tt>Depends</tt> field takes effect <em>only</em> when a
4505 package is to be configured. It does not prevent a package
4506 being on the system in an unconfigured state while its
4507 dependencies are unsatisfied, and it is possible to replace
4508 a package whose dependencies are satisfied and which is
4509 properly installed with a different version whose
4510 dependencies are not and cannot be satisfied; when this is
4511 done the depending package will be left unconfigured (since
4512 attempts to configure it will give errors) and will not
4513 function properly. If it is necessary, a
4514 <tt>Pre-Depends</tt> field can be used, which has a partial
4515 effect even when a package is being unpacked, as explained
4516 in detail below. (The other three dependency fields,
4517 <tt>Recommends</tt>, <tt>Suggests</tt> and
4518 <tt>Enhances</tt>, are only used by the various front-ends
4519 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4520 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4524 For this reason packages in an installation run are usually
4525 all unpacked first and all configured later; this gives
4526 later versions of packages with dependencies on later
4527 versions of other packages the opportunity to have their
4528 dependencies satisfied.
4532 In case of circular dependencies, since installation or
4533 removal order honoring the dependency order can't be
4534 established, dependency loops are broken at some point
4535 (based on rules below), and some packages may not be able to
4536 rely on their dependencies being present when being
4537 installed or removed, depending on which side of the break
4538 of the circular dependency loop they happen to be on. If one
4539 of the packages in the loop has no postinst script, then the
4540 cycle will be broken at that package, so as to ensure that
4541 all postinst scripts run with the dependencies properly
4542 configured if this is possible. Otherwise the breaking point
4547 The <tt>Depends</tt> field thus allows package maintainers
4548 to impose an order in which packages should be configured.
4552 The meaning of the five dependency fields is as follows:
4554 <tag><tt>Depends</tt></tag>
4557 This declares an absolute dependency. A package will
4558 not be configured unless all of the packages listed in
4559 its <tt>Depends</tt> field have been correctly
4564 The <tt>Depends</tt> field should be used if the
4565 depended-on package is required for the depending
4566 package to provide a significant amount of
4571 The <tt>Depends</tt> field should also be used if the
4572 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4573 <prgn>postrm</prgn> scripts require the package to be
4574 present in order to run. Note, however, that the
4575 <prgn>postrm</prgn> cannot rely on any non-essential
4576 packages to be present during the <tt>purge</tt>
4580 <tag><tt>Recommends</tt></tag>
4583 This declares a strong, but not absolute, dependency.
4587 The <tt>Recommends</tt> field should list packages
4588 that would be found together with this one in all but
4589 unusual installations.
4593 <tag><tt>Suggests</tt></tag>
4595 This is used to declare that one package may be more
4596 useful with one or more others. Using this field
4597 tells the packaging system and the user that the
4598 listed packages are related to this one and can
4599 perhaps enhance its usefulness, but that installing
4600 this one without them is perfectly reasonable.
4603 <tag><tt>Enhances</tt></tag>
4605 This field is similar to Suggests but works in the
4606 opposite direction. It is used to declare that a
4607 package can enhance the functionality of another
4611 <tag><tt>Pre-Depends</tt></tag>
4614 This field is like <tt>Depends</tt>, except that it
4615 also forces <prgn>dpkg</prgn> to complete installation
4616 of the packages named before even starting the
4617 installation of the package which declares the
4618 pre-dependency, as follows:
4622 When a package declaring a pre-dependency is about to
4623 be <em>unpacked</em> the pre-dependency can be
4624 satisfied if the depended-on package is either fully
4625 configured, <em>or even if</em> the depended-on
4626 package(s) are only unpacked or in the "Half-Configured"
4627 state, provided that they have been configured
4628 correctly at some point in the past (and not removed
4629 or partially removed since). In this case, both the
4630 previously-configured and currently unpacked or
4631 "Half-Configured" versions must satisfy any version
4632 clause in the <tt>Pre-Depends</tt> field.
4636 When the package declaring a pre-dependency is about
4637 to be <em>configured</em>, the pre-dependency will be
4638 treated as a normal <tt>Depends</tt>, that is, it will
4639 be considered satisfied only if the depended-on
4640 package has been correctly configured.
4644 <tt>Pre-Depends</tt> should be used sparingly,
4645 preferably only by packages whose premature upgrade or
4646 installation would hamper the ability of the system to
4647 continue with any upgrade that might be in progress.
4651 <tt>Pre-Depends</tt> are also required if the
4652 <prgn>preinst</prgn> script depends on the named
4653 package. It is best to avoid this situation if
4661 When selecting which level of dependency to use you should
4662 consider how important the depended-on package is to the
4663 functionality of the one declaring the dependency. Some
4664 packages are composed of components of varying degrees of
4665 importance. Such a package should list using
4666 <tt>Depends</tt> the package(s) which are required by the
4667 more important components. The other components'
4668 requirements may be mentioned as Suggestions or
4669 Recommendations, as appropriate to the components' relative
4675 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4678 When one binary package declares that it breaks another,
4679 <prgn>dpkg</prgn> will refuse to allow the package which
4680 declares <tt>Breaks</tt> be installed unless the broken
4681 package is deconfigured first, and it will refuse to
4682 allow the broken package to be reconfigured.
4686 A package will not be regarded as causing breakage merely
4687 because its configuration files are still installed; it must
4688 be at least "Half-Installed".
4692 A special exception is made for packages which declare that
4693 they break their own package name or a virtual package which
4694 they provide (see below): this does not count as a real
4699 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4700 version clause; such a <tt>Breaks</tt> is introduced in the
4701 version of an (implicit or explicit) dependency which violates
4702 an assumption or reveals a bug in earlier versions of the broken
4703 package, or which takes over a file from earlier versions of the
4704 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
4705 will inform higher-level package management tools that the
4706 broken package must be upgraded before the new one.
4710 If the breaking package also overwrites some files from the
4711 older package, it should use <tt>Replaces</tt> to ensure this
4712 goes smoothly. See <ref id="replaces"> for a full discussion
4713 of taking over files from other packages, including how to
4714 use <tt>Breaks</tt> in those cases.
4718 Many of the cases where <tt>Breaks</tt> should be used were
4719 previously handled with <tt>Conflicts</tt>
4720 because <tt>Breaks</tt> did not yet exist.
4721 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
4722 See <ref id="conflicts"> for more information about the
4727 <sect id="conflicts">
4728 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4731 When one binary package declares a conflict with another
4732 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4733 refuse to allow them to be installed on the system at the
4734 same time. This is a stronger restriction than <tt>Breaks</tt>,
4735 which just prevents both packages from being configured at the
4736 same time. Conflicting packages cannot be unpacked on the
4737 system at the same time.
4741 If one package is to be installed, the other must be removed
4742 first. If the package being installed is marked as replacing
4743 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
4744 normally be used in this case) the one on the system, or the one
4745 on the system is marked as deselected, or both packages are
4746 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
4747 automatically remove the package which is causing the conflict.
4748 Otherwise, it will halt the installation of the new package with
4749 an error. This mechanism is specifically designed to produce an
4750 error when the installed package is <tt>Essential</tt>, but the
4755 A package will not cause a conflict merely because its
4756 configuration files are still installed; it must be at least
4761 A special exception is made for packages which declare a
4762 conflict with their own package name, or with a virtual
4763 package which they provide (see below): this does not
4764 prevent their installation, and allows a package to conflict
4765 with others providing a replacement for it. You use this
4766 feature when you want the package in question to be the only
4767 package providing some feature.
4771 Normally, <tt>Breaks</tt> should be used instead
4772 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
4773 stronger restriction on the ordering of package installation or
4774 upgrade and can make it more difficult for the package manager
4775 to find a correct solution to an upgrade or installation
4776 problem. <tt>Breaks</tt> should be used
4778 <item>when moving a file from one package to another (see
4779 <ref id="replaces">),</item>
4780 <item>when splitting a package (a special case of the previous
4782 <item>when the breaking package exposes a bug in or interacts
4783 badly with particular versions of the broken
4786 <tt>Conflicts</tt> should be used
4788 <item>when two packages provide the same file and will
4789 continue to do so,</item>
4790 <item>in conjunction with <tt>Provides</tt> when only one
4791 package providing a given virtual facility may be installed
4792 at a time (see <ref id="virtual">),</item>
4793 <item>in other cases where one must prevent simultaneous
4794 installation of two packages for reasons that are ongoing
4795 (not fixed in a later version of one of the packages) or
4796 that must prevent both packages from being unpacked at the
4797 same time, not just configured.</item>
4799 Be aware that adding <tt>Conflicts</tt> is normally not the best
4800 solution when two packages provide the same files. Depending on
4801 the reason for that conflict, using alternatives or renaming the
4802 files is often a better approach. See, for
4803 example, <ref id="binaries">.
4807 Neither <tt>Breaks</tt> nor <tt>Conflicts</tt> should be used
4808 unless two packages cannot be installed at the same time or
4809 installing them both causes one of them to be broken or
4810 unusable. Having similar functionality or performing the same
4811 tasks as another package is not sufficient reason to
4812 declare <tt>Breaks</tt> or <tt>Conflicts</tt> with that package.
4816 A <tt>Conflicts</tt> entry may have an "earlier than" version
4817 clause if the reason for the conflict is corrected in a later
4818 version of one of the packages. However, normally the presence
4819 of an "earlier than" version clause is a sign
4820 that <tt>Breaks</tt> should have been used instead. An "earlier
4821 than" version clause in <tt>Conflicts</tt>
4822 prevents <prgn>dpkg</prgn> from upgrading or installing the
4823 package which declares such a conflict until the upgrade or
4824 removal of the conflicted-with package has been completed, which
4825 is a strong restriction.
4829 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4833 As well as the names of actual ("concrete") packages, the
4834 package relationship fields <tt>Depends</tt>,
4835 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4836 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4837 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4838 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4839 may mention "virtual packages".
4843 A <em>virtual package</em> is one which appears in the
4844 <tt>Provides</tt> control file field of another package.
4845 The effect is as if the package(s) which provide a
4846 particular virtual package name had been listed by name
4847 everywhere the virtual package name appears. (See also <ref
4852 If there are both concrete and virtual packages of the same
4853 name, then the dependency may be satisfied (or the conflict
4854 caused) by either the concrete package with the name in
4855 question or any other concrete package which provides the
4856 virtual package with the name in question. This is so that,
4857 for example, supposing we have
4858 <example compact="compact">
4861 </example> and someone else releases an enhanced version of
4862 the <tt>bar</tt> package they can say:
4863 <example compact="compact">
4867 and the <tt>bar-plus</tt> package will now also satisfy the
4868 dependency for the <tt>foo</tt> package.
4872 If a relationship field has a version number attached, only real
4873 packages will be considered to see whether the relationship is
4874 satisfied (or the prohibition violated, for a conflict or
4875 breakage). In other words, if a version number is specified,
4876 this is a request to ignore all <tt>Provides</tt> for that
4877 package name and consider only real packages. The package
4878 manager will assume that a package providing that virtual
4879 package is not of the "right" version. A <tt>Provides</tt>
4880 field may not contain version numbers, and the version number of
4881 the concrete package which provides a particular virtual package
4882 will not be considered when considering a dependency on or
4883 conflict with the virtual package name.<footnote>
4884 It is possible that a future release of <prgn>dpkg</prgn> may
4885 add the ability to specify a version number for each virtual
4886 package it provides. This feature is not yet present,
4887 however, and is expected to be used only infrequently.
4892 To specify which of a set of real packages should be the default
4893 to satisfy a particular dependency on a virtual package, list
4894 the real package as an alternative before the virtual one.
4898 If the virtual package represents a facility that can only be
4899 provided by one real package at a time, such as
4900 the <package>mail-transport-agent</package> virtual package that
4901 requires installation of a binary that would conflict with all
4902 other providers of that virtual package (see
4903 <ref id="mail-transport-agents">), all packages providing that
4904 virtual package should also declare a conflict with it
4905 using <tt>Conflicts</tt>. This will ensure that at most one
4906 provider of that virtual package is unpacked or installed at a
4911 <sect id="replaces"><heading>Overwriting files and replacing
4912 packages - <tt>Replaces</tt></heading>
4915 Packages can declare in their control file that they should
4916 overwrite files in certain other packages, or completely
4917 replace other packages. The <tt>Replaces</tt> control file
4918 field has these two distinct purposes.
4921 <sect1><heading>Overwriting files in other packages</heading>
4924 It is usually an error for a package to contain files which
4925 are on the system in another package. However, if the
4926 overwriting package declares that it <tt>Replaces</tt> the one
4927 containing the file being overwritten, then <prgn>dpkg</prgn>
4928 will replace the file from the old package with that from the
4929 new. The file will no longer be listed as "owned" by the old
4930 package and will be taken over by the new package.
4931 Normally, <tt>Breaks</tt> should be used in conjunction
4932 with <tt>Replaces</tt>.<footnote>
4933 To see why <tt>Breaks</tt> is normally needed in addition
4934 to <tt>Replaces</tt>, consider the case of a file in the
4935 package <package>foo</package> being taken over by the
4936 package <package>foo-data</package>.
4937 <tt>Replaces</tt> will allow <package>foo-data</package> to
4938 be installed and take over that file. However,
4939 without <tt>Breaks</tt>, nothing
4940 requires <package>foo</package> to be upgraded to a newer
4941 version that knows it does not include that file and instead
4942 depends on <package>foo-data</package>. Nothing would
4943 prevent the new <package>foo-data</package> package from
4944 being installed and then removed, removing the file that it
4945 took over from <package>foo</package>. After that
4946 operation, the package manager would think the system was in
4947 a consistent state, but the <package>foo</package> package
4948 would be missing one of its files.
4953 For example, if a package <package>foo</package> is split
4954 into <package>foo</package> and <package>foo-data</package>
4955 starting at version 1.2-3, <package>foo-data</package> would
4957 <example compact="compact">
4958 Replaces: foo (<< 1.2-3)
4959 Breaks: foo (<< 1.2-3)
4961 in its control file. The new version of the
4962 package <package>foo</package> would normally have the field
4963 <example compact="compact">
4964 Depends: foo-data (>= 1.2-3)
4966 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
4967 the files moved into <package>foo-data</package> are not
4968 required for normal operation).
4972 If a package is completely replaced in this way, so that
4973 <prgn>dpkg</prgn> does not know of any files it still
4974 contains, it is considered to have "disappeared". It will
4975 be marked as not wanted on the system (selected for
4976 removal) and not installed. Any <tt>conffile</tt>s
4977 details noted for the package will be ignored, as they
4978 will have been taken over by the overwriting package. The
4979 package's <prgn>postrm</prgn> script will be run with a
4980 special argument to allow the package to do any final
4981 cleanup required. See <ref id="mscriptsinstact">.
4983 Replaces is a one way relationship. You have to install
4984 the replacing package after the replaced package.
4989 For this usage of <tt>Replaces</tt>, virtual packages (see
4990 <ref id="virtual">) are not considered when looking at a
4991 <tt>Replaces</tt> field. The packages declared as being
4992 replaced must be mentioned by their real names.
4996 This usage of <tt>Replaces</tt> only takes effect when both
4997 packages are at least partially on the system at once. It is
4998 not relevant if the packages conflict unless the conflict has
5003 <sect1><heading>Replacing whole packages, forcing their
5007 Second, <tt>Replaces</tt> allows the packaging system to
5008 resolve which package should be removed when there is a
5009 conflict (see <ref id="conflicts">). This usage only takes
5010 effect when the two packages <em>do</em> conflict, so that the
5011 two usages of this field do not interfere with each other.
5015 In this situation, the package declared as being replaced
5016 can be a virtual package, so for example, all mail
5017 transport agents (MTAs) would have the following fields in
5018 their control files:
5019 <example compact="compact">
5020 Provides: mail-transport-agent
5021 Conflicts: mail-transport-agent
5022 Replaces: mail-transport-agent
5024 ensuring that only one MTA can be installed at any one
5025 time. See <ref id="virtual"> for more information about this
5030 <sect id="sourcebinarydeps">
5031 <heading>Relationships between source and binary packages -
5032 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
5033 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5037 Source packages that require certain binary packages to be
5038 installed or absent at the time of building the package
5039 can declare relationships to those binary packages.
5043 This is done using the <tt>Build-Depends</tt>,
5044 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5045 <tt>Build-Conflicts-Indep</tt> control file fields.
5049 Build-dependencies on "build-essential" binary packages can be
5050 omitted. Please see <ref id="pkg-relations"> for more information.
5054 The dependencies and conflicts they define must be satisfied
5055 (as defined earlier for binary packages) in order to invoke
5056 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5058 There is no Build-Depends-Arch; this role is essentially
5059 met with Build-Depends. Anyone building the
5060 <tt>build-indep</tt> and binary-indep<tt></tt> targets is
5061 assumed to be building the whole package, and therefore
5062 installation of all build dependencies is required.
5065 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5066 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5067 not yet know how to check for its existence, and
5068 <tt>binary-arch</tt>. The purpose of the original split
5069 between <tt>Build-Depends</tt> and
5070 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5071 wouldn't need to install extra packages needed only for the
5072 binary-indep targets. But without a build-arch/build-indep
5073 split, this didn't work, since most of the work is done in
5074 the build target, not in the binary target.
5078 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5079 <tt>binary-arch</tt></tag>
5081 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5082 fields must be satisfied when these targets are invoked.
5084 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5085 and <tt>binary-indep</tt></tag>
5087 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5088 <tt>Build-Depends-Indep</tt>, and
5089 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5090 these targets are invoked.
5098 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5101 Packages containing shared libraries must be constructed with
5102 a little care to make sure that the shared library is always
5103 available. This is especially important for packages whose
5104 shared libraries are vitally important, such as the C library
5105 (currently <tt>libc6</tt>).
5109 Packages involving shared libraries should be split up into
5110 several binary packages. This section mostly deals with how
5111 this separation is to be accomplished; rules for files within
5112 the shared library packages are in <ref id="libraries"> instead.
5115 <sect id="sharedlibs-runtime">
5116 <heading>Run-time shared libraries</heading>
5119 The run-time shared library needs to be placed in a package
5120 whose name changes whenever the shared object version
5123 Since it is common place to install several versions of a
5124 package that just provides shared libraries, it is a
5125 good idea that the library package should not
5126 contain any extraneous non-versioned files, unless they
5127 happen to be in versioned directories.</p>
5129 The most common mechanism is to place it in a package
5131 <package><var>libraryname</var><var>soversion</var></package>,
5132 where <file><var>soversion</var></file> is the version number
5133 in the soname of the shared library<footnote>
5134 The soname is the shared object name: it's the thing
5135 that has to match exactly between building an executable
5136 and running it for the dynamic linker to be able run the
5137 program. For example, if the soname of the library is
5138 <file>libfoo.so.6</file>, the library package would be
5139 called <file>libfoo6</file>.
5141 Alternatively, if it would be confusing to directly append
5142 <var>soversion</var> to <var>libraryname</var> (e.g. because
5143 <var>libraryname</var> itself ends in a number), you may use
5144 <package><var>libraryname</var>-<var>soversion</var></package> and
5145 <package><var>libraryname</var>-<var>soversion</var>-dev</package>
5150 If you have several shared libraries built from the same
5151 source tree you may lump them all together into a single
5152 shared library package, provided that you change all of
5153 their sonames at once (so that you don't get filename
5154 clashes if you try to install different versions of the
5155 combined shared libraries package).
5159 The package should install the shared libraries under
5160 their normal names. For example, the <package>libgdbm3</package>
5161 package should install <file>libgdbm.so.3.0.0</file> as
5162 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5163 renamed or re-linked by any <prgn>prerm</prgn> or
5164 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5165 of renaming things safely without affecting running programs,
5166 and attempts to interfere with this are likely to lead to
5171 Shared libraries should not be installed executable, since
5172 the dynamic linker does not require this and trying to
5173 execute a shared library usually results in a core dump.
5177 The run-time library package should include the symbolic link that
5178 <prgn>ldconfig</prgn> would create for the shared libraries.
5179 For example, the <package>libgdbm3</package> package should include
5180 a symbolic link from <file>/usr/lib/libgdbm.so.3</file> to
5181 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5182 linker (for example <prgn>ld.so</prgn> or
5183 <prgn>ld-linux.so.*</prgn>) can find the library between the
5184 time that <prgn>dpkg</prgn> installs it and the time that
5185 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5187 The package management system requires the library to be
5188 placed before the symbolic link pointing to it in the
5189 <file>.deb</file> file. This is so that when
5190 <prgn>dpkg</prgn> comes to install the symlink
5191 (overwriting the previous symlink pointing at an older
5192 version of the library), the new shared library is already
5193 in place. In the past, this was achieved by creating the
5194 library in the temporary packaging directory before
5195 creating the symlink. Unfortunately, this was not always
5196 effective, since the building of the tar file in the
5197 <file>.deb</file> depended on the behavior of the underlying
5198 file system. Some file systems (such as reiserfs) reorder
5199 the files so that the order of creation is forgotten.
5200 Since version 1.7.0, <prgn>dpkg</prgn>
5201 reorders the files itself as necessary when building a
5202 package. Thus it is no longer important to concern
5203 oneself with the order of file creation.
5207 <sect1 id="ldconfig">
5208 <heading><tt>ldconfig</tt></heading>
5211 Any package installing shared libraries in one of the default
5212 library directories of the dynamic linker (which are currently
5213 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5214 listed in <file>/etc/ld.so.conf</file><footnote>
5216 <list compact="compact">
5217 <item>/usr/local/lib</item>
5218 <item>/usr/lib/libc5-compat</item>
5219 <item>/lib/libc5-compat</item>
5222 must use <prgn>ldconfig</prgn> to update the shared library
5227 The package maintainer scripts must only call
5228 <prgn>ldconfig</prgn> under these circumstances:
5229 <list compact="compact">
5230 <item>When the <prgn>postinst</prgn> script is run with a
5231 first argument of <tt>configure</tt>, the script must call
5232 <prgn>ldconfig</prgn>, and may optionally invoke
5233 <prgn>ldconfig</prgn> at other times.
5235 <item>When the <prgn>postrm</prgn> script is run with a
5236 first argument of <tt>remove</tt>, the script should call
5237 <prgn>ldconfig</prgn>.
5242 During install or upgrade, the preinst is called before
5243 the new files are installed, so calling "ldconfig" is
5244 pointless. The preinst of an existing package can also be
5245 called if an upgrade fails. However, this happens during
5246 the critical time when a shared libs may exist on-disk
5247 under a temporary name. Thus, it is dangerous and
5248 forbidden by current policy to call "ldconfig" at this
5253 When a package is installed or upgraded, "postinst
5254 configure" runs after the new files are safely on-disk.
5255 Since it is perfectly safe to invoke ldconfig
5256 unconditionally in a postinst, it is OK for a package to
5257 simply put ldconfig in its postinst without checking the
5258 argument. The postinst can also be called to recover from
5259 a failed upgrade. This happens before any new files are
5260 unpacked, so there is no reason to call "ldconfig" at this
5265 For a package that is being removed, prerm is
5266 called with all the files intact, so calling ldconfig is
5267 useless. The other calls to "prerm" happen in the case of
5268 upgrade at a time when all the files of the old package
5269 are on-disk, so again calling "ldconfig" is pointless.
5273 postrm, on the other hand, is called with the "remove"
5274 argument just after the files are removed, so this is
5275 the proper time to call "ldconfig" to notify the system
5276 of the fact that the shared libraries from the package
5277 are removed. The postrm can be called at several other
5278 times. At the time of "postrm purge", "postrm
5279 abort-install", or "postrm abort-upgrade", calling
5280 "ldconfig" is useless because the shared lib files are
5281 not on-disk. However, when "postrm" is invoked with
5282 arguments "upgrade", "failed-upgrade", or "disappear", a
5283 shared lib may exist on-disk under a temporary filename.
5291 <sect id="sharedlibs-support-files">
5292 <heading>Shared library support files</heading>
5295 If your package contains files whose names do not change with
5296 each change in the library shared object version, you must not
5297 put them in the shared library package. Otherwise, several
5298 versions of the shared library cannot be installed at the same
5299 time without filename clashes, making upgrades and transitions
5300 unnecessarily difficult.
5304 It is recommended that supporting files and run-time support
5305 programs that do not need to be invoked manually by users, but
5306 are nevertheless required for the package to function, be placed
5307 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5308 preferably under <file>/usr/lib/</file><var>package-name</var>.
5309 If the program or file is architecture independent, the
5310 recommendation is for it to be placed in a subdirectory of
5311 <file>/usr/share</file> instead, preferably under
5312 <file>/usr/share/</file><var>package-name</var>. Following the
5313 <var>package-name</var> naming convention ensures that the file
5314 names change when the shared object version changes.
5318 Run-time support programs that use the shared library but are
5319 not required for the library to function or files used by the
5320 shared library that can be used by any version of the shared
5321 library package should instead be put in a separate package.
5322 This package might typically be named
5323 <package><var>libraryname</var>-tools</package>; note the
5324 absence of the <var>soversion</var> in the package name.
5328 Files and support programs only useful when compiling software
5329 against the library should be included in the development
5330 package for the library.<footnote>
5331 For example, a <file><var>package-name</var>-config</file>
5332 script or <package>pkg-config</package> configuration files.
5337 <sect id="sharedlibs-static">
5338 <heading>Static libraries</heading>
5341 The static library (<file><var>libraryname.a</var></file>)
5342 is usually provided in addition to the shared version.
5343 It is placed into the development package (see below).
5347 In some cases, it is acceptable for a library to be
5348 available in static form only; these cases include:
5350 <item>libraries for languages whose shared library support
5351 is immature or unstable</item>
5352 <item>libraries whose interfaces are in flux or under
5353 development (commonly the case when the library's
5354 major version number is zero, or where the ABI breaks
5355 across patchlevels)</item>
5356 <item>libraries which are explicitly intended to be
5357 available only in static form by their upstream
5362 <sect id="sharedlibs-dev">
5363 <heading>Development files</heading>
5366 If there are development files associated with a shared library,
5367 the source package needs to generate a binary development package
5368 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5369 or if you prefer only to support one development version at a
5370 time, <package><var>libraryname</var>-dev</package>. Installing
5371 the development package must result in installation of all the
5372 development files necessary for compiling programs against that
5373 shared library.<footnote>
5374 This wording allows the development files to be split into
5375 several packages, such as a separate architecture-independent
5376 <package><var>libraryname</var>-headers</package>, provided that
5377 the development package depends on all the required additional
5383 In case several development versions of a library exist, you may
5384 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5385 <ref id="conflicts">) to ensure that the user only installs one
5386 development version at a time (as different development versions are
5387 likely to have the same header files in them, which would cause a
5388 filename clash if both were installed).
5392 The development package should contain a symlink for the associated
5393 shared library without a version number. For example, the
5394 <package>libgdbm-dev</package> package should include a symlink
5395 from <file>/usr/lib/libgdbm.so</file> to
5396 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5397 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5398 <file>libgdbm.so</file> when compiling dynamically.
5402 <sect id="sharedlibs-intradeps">
5403 <heading>Dependencies between the packages of the same library</heading>
5406 Typically the development version should have an exact
5407 version dependency on the runtime library, to make sure that
5408 compilation and linking happens correctly. The
5409 <tt>${binary:Version}</tt> substitution variable can be
5410 useful for this purpose.
5412 Previously, <tt>${Source-Version}</tt> was used, but its name
5413 was confusing and it has been deprecated since dpkg 1.13.19.
5418 <sect id="sharedlibs-shlibdeps">
5419 <heading>Dependencies between the library and other packages -
5420 the <tt>shlibs</tt> system</heading>
5423 If a package contains a binary or library which links to a
5424 shared library, we must ensure that when the package is
5425 installed on the system, all of the libraries needed are
5426 also installed. This requirement led to the creation of the
5427 <tt>shlibs</tt> system, which is very simple in its design:
5428 any package which <em>provides</em> a shared library also
5429 provides information on the package dependencies required to
5430 ensure the presence of this library, and any package which
5431 <em>uses</em> a shared library uses this information to
5432 determine the dependencies it requires. The files which
5433 contain the mapping from shared libraries to the necessary
5434 dependency information are called <file>shlibs</file> files.
5438 When a package is built which contains any shared libraries, it
5439 must provide a <file>shlibs</file> file for other packages to
5440 use. When a package is built which contains any shared
5441 libraries or compiled binaries, it must run
5442 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5443 on these to determine the libraries used and hence the
5444 dependencies needed by this package.<footnote>
5446 <prgn>dpkg-shlibdeps</prgn> will use a program
5447 like <prgn>objdump</prgn> or <prgn>readelf</prgn> to find
5448 the libraries directly needed by the binaries or shared
5449 libraries in the package.
5453 We say that a binary <tt>foo</tt> <em>directly</em> uses
5454 a library <tt>libbar</tt> if it is explicitly linked
5455 with that library (that is, the library is listed in the ELF
5456 <tt>NEEDED</tt> attribute, caused by adding <tt>-lbar</tt>
5457 to the link line when the binary is created). Other
5458 libraries that are needed by <tt>libbar</tt> are linked
5459 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5460 linker will load them automatically when it loads
5461 <tt>libbar</tt>. A package should depend on the libraries
5462 it directly uses, but not the libraries it indirectly uses.
5463 The dependencies for those libraries will automatically pull
5464 in the other libraries.
5468 A good example of where this helps is the following. We
5469 could update <tt>libimlib</tt> with a new version that
5470 supports a new graphics format called dgf (but retaining the
5471 same major version number) and depends on <tt>libdgf</tt>.
5472 If we used <prgn>ldd</prgn> to add dependencies for every
5473 library directly or indirectly linked with a binary, every
5474 package that uses <tt>libimlib</tt> would need to be
5475 recompiled so it would also depend on <tt>libdgf</tt> or it
5476 wouldn't run due to missing symbols. Since dependencies are
5477 only added based on ELF <tt>NEEDED</tt> attribute, packages
5478 using <tt>libimlib</tt> can rely on <tt>libimlib</tt> itself
5479 having the dependency on <tt>libdgf</tt> and so they would
5480 not need rebuilding.
5486 In the following sections, we will first describe where the
5487 various <tt>shlibs</tt> files are to be found, then how to
5488 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5489 file format and how to create them if your package contains a
5494 <heading>The <tt>shlibs</tt> files present on the system</heading>
5497 There are several places where <tt>shlibs</tt> files are
5498 found. The following list gives them in the order in which
5500 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5501 (The first one which gives the required information is used.)
5507 <p><file>debian/shlibs.local</file></p>
5510 This lists overrides for this package. This file should
5511 normally not be used, but may be needed temporarily in
5512 unusual situations to work around bugs in other packages,
5513 or in unusual cases where the normally declared dependency
5514 information in the installed <file>shlibs</file> file for
5515 a library cannot be used. This file overrides information
5516 obtained from any other source.
5521 <p><file>/etc/dpkg/shlibs.override</file></p>
5524 This lists global overrides. This list is normally
5525 empty. It is maintained by the local system
5531 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5534 When packages are being built,
5535 any <file>debian/shlibs</file> files are copied into the
5536 control file area of the temporary build directory and
5537 given the name <file>shlibs</file>. These files give
5538 details of any shared libraries included in the same
5540 An example may help here. Let us say that the source
5541 package <tt>foo</tt> generates two binary
5542 packages, <tt>libfoo2</tt> and <tt>foo-runtime</tt>.
5543 When building the binary packages, the two packages are
5544 created in the directories <file>debian/libfoo2</file>
5545 and <file>debian/foo-runtime</file> respectively.
5546 (<file>debian/tmp</file> could be used instead of one of
5547 these.) Since <tt>libfoo2</tt> provides the
5548 <tt>libfoo</tt> shared library, it will require a
5549 <tt>shlibs</tt> file, which will be installed in
5550 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually to
5551 become <file>/var/lib/dpkg/info/libfoo2.shlibs</file>.
5552 When <prgn>dpkg-shlibdeps</prgn> is run on the
5553 executable <file>debian/foo-runtime/usr/bin/foo-prog</file>,
5555 the <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5556 determine whether <tt>foo-prog</tt>'s library
5557 dependencies are satisfied by any of the libraries
5558 provided by <tt>libfoo2</tt>. For this reason,
5559 <prgn>dpkg-shlibdeps</prgn> must only be run once all of
5560 the individual binary packages' <tt>shlibs</tt> files
5561 have been installed into the build directory.
5567 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5570 These are the <file>shlibs</file> files corresponding to
5571 all of the packages installed on the system, and are
5572 maintained by the relevant package maintainers.
5577 <p><file>/etc/dpkg/shlibs.default</file></p>
5580 This file lists any shared libraries whose packages
5581 have failed to provide correct <file>shlibs</file> files.
5582 It was used when the <file>shlibs</file> setup was first
5583 introduced, but it is now normally empty. It is
5584 maintained by the <tt>dpkg</tt> maintainer.
5592 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5593 <file>shlibs</file> files</heading>
5597 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5598 into your <file>debian/rules</file> file. If your package
5599 contains only compiled binaries and libraries (but no scripts),
5600 you can use a command such as:
5601 <example compact="compact">
5602 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5603 debian/tmp/usr/lib/*
5605 Otherwise, you will need to explicitly list the compiled
5606 binaries and libraries.<footnote>
5607 If you are using <tt>debhelper</tt>, the
5608 <prgn>dh_shlibdeps</prgn> program will do this work for you.
5609 It will also correctly handle multi-binary packages.
5614 This command puts the dependency information into the
5615 <file>debian/substvars</file> file, which is then used by
5616 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5617 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5618 field in the control file for this to work.
5622 If you have multiple binary packages, you will need to call
5623 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5624 compiled libraries or binaries. In such a case, you will
5625 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5626 utilities to specify a different <file>substvars</file> file.
5630 If you are creating a udeb for use in the Debian Installer,
5631 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
5632 should use the dependency line of type <tt>udeb</tt> by
5633 adding the <tt>-tudeb</tt> option<footnote>
5634 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5635 will automatically add this option if it knows it is
5637 </footnote>. If there is no dependency line of
5638 type <tt>udeb</tt> in the <file>shlibs</file>
5639 file, <prgn>dpkg-shlibdeps</prgn> will fall back to the regular
5644 For more details on <prgn>dpkg-shlibdeps</prgn>, please see
5645 <ref id="pkg-dpkg-shlibdeps"> and
5646 <manref name="dpkg-shlibdeps" section="1">.
5651 <heading>The <file>shlibs</file> File Format</heading>
5654 Each <file>shlibs</file> file has the same format. Lines
5655 beginning with <tt>#</tt> are considered to be comments and
5656 are ignored. Each line is of the form:
5657 <example compact="compact">
5658 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5663 We will explain this by reference to the example of the
5664 <tt>zlib1g</tt> package, which (at the time of writing)
5665 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5669 <var>type</var> is an optional element that indicates the type
5670 of package for which the line is valid. The only type currently
5671 in use is <tt>udeb</tt>. The colon and space after the type are
5676 <var>library-name</var> is the name of the shared library,
5677 in this case <tt>libz</tt>. (This must match the name part
5678 of the soname, see below.)
5682 <var>soname-version</var> is the version part of the soname of
5683 the library. The soname is the thing that must exactly match
5684 for the library to be recognized by the dynamic linker, and is
5686 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5687 example, <tt>libz.so.1</tt>.<footnote>
5688 This can be determined using the command
5689 <example compact="compact">
5690 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5693 The version part is the part which comes after
5694 <tt>.so.</tt>, so in our case, it is <tt>1</tt>. The soname may
5695 instead be of the form
5696 <tt><var>name</var>-<var>major-version</var>.so</tt>, such
5697 as <tt>libdb-4.8.so</tt>, in which case the name would
5698 be <tt>libdb</tt> and the version would be <tt>4.8</tt>.
5702 <var>dependencies</var> has the same syntax as a dependency
5703 field in a binary package control file. It should give
5704 details of which packages are required to satisfy a binary
5705 built against the version of the library contained in the
5706 package. See <ref id="depsyntax"> for details.
5710 In our example, if the first version of the <tt>zlib1g</tt>
5711 package which contained a minor number of at least
5712 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5713 <tt>shlibs</tt> entry for this library could say:
5714 <example compact="compact">
5715 libz 1 zlib1g (>= 1:1.1.3)
5717 The version-specific dependency is to avoid warnings from
5718 the dynamic linker about using older shared libraries with
5723 As zlib1g also provides a udeb containing the shared library,
5724 there would also be a second line:
5725 <example compact="compact">
5726 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5732 <heading>Providing a <file>shlibs</file> file</heading>
5735 If your package provides a shared library, you need to create
5736 a <file>shlibs</file> file following the format described above.
5737 It is usual to call this file <file>debian/shlibs</file> (but if
5738 you have multiple binary packages, you might want to call it
5739 <file>debian/shlibs.<var>package</var></file> instead). Then
5740 let <file>debian/rules</file> install it in the control area:
5741 <example compact="compact">
5742 install -m644 debian/shlibs debian/tmp/DEBIAN
5744 or, in the case of a multi-binary package:
5745 <example compact="compact">
5746 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5748 An alternative way of doing this is to create the
5749 <file>shlibs</file> file in the control area directly from
5750 <file>debian/rules</file> without using a <file>debian/shlibs</file>
5751 file at all,<footnote>
5752 This is what <prgn>dh_makeshlibs</prgn> in
5753 the <package>debhelper</package> suite does. If your package
5754 also has a udeb that provides a shared
5755 library, <prgn>dh_makeshlibs</prgn> can automatically generate
5756 the <tt>udeb:</tt> lines if you specify the name of the udeb
5757 with the <tt>--add-udeb</tt> option.
5759 since the <file>debian/shlibs</file> file itself is ignored by
5760 <prgn>dpkg-shlibdeps</prgn>.
5764 As <prgn>dpkg-shlibdeps</prgn> reads the
5765 <file>DEBIAN/shlibs</file> files in all of the binary packages
5766 being built from this source package, all of the
5767 <file>DEBIAN/shlibs</file> files should be installed before
5768 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5776 <chapt id="opersys"><heading>The Operating System</heading>
5779 <heading>File system hierarchy</heading>
5783 <heading>File System Structure</heading>
5786 The location of all installed files and directories must
5787 comply with the Filesystem Hierarchy Standard (FHS),
5788 version 2.3, with the exceptions noted below, and except
5789 where doing so would violate other terms of Debian
5790 Policy. The following exceptions to the FHS apply:
5795 The optional rules related to user specific
5796 configuration files for applications are stored in
5797 the user's home directory are relaxed. It is
5798 recommended that such files start with the
5799 '<tt>.</tt>' character (a "dot file"), and if an
5800 application needs to create more than one dot file
5801 then the preferred placement is in a subdirectory
5802 with a name starting with a '.' character, (a "dot
5803 directory"). In this case it is recommended the
5804 configuration files not start with the '.'
5810 The requirement for amd64 to use <file>/lib64</file>
5811 for 64 bit binaries is removed.
5816 The requirement for object files, internal binaries, and
5817 libraries, including <file>libc.so.*</file>, to be located
5818 directly under <file>/lib{,32}</file> and
5819 <file>/usr/lib{,32}</file> is amended, permitting files
5820 to instead be installed to
5821 <file>/lib/<var>triplet</var></file> and
5822 <file>/usr/lib/<var>triplet</var></file>, where
5823 <tt><var>triplet</var></tt> is the value returned by
5824 <tt>dpkg-architecture -qDEB_HOST_GNU_TYPE</tt> for the
5825 architecture of the package. Packages may <em>not</em>
5826 install files to any <var>triplet</var> path other
5827 than the one matching the architecture of that package;
5828 for instance, an <tt>Architecture: amd64</tt> package
5829 containing 32-bit x86 libraries may not install these
5830 libraries to <file>/usr/lib/i486-linux-gnu</file>.
5832 This is necessary in order to reserve the directories for
5833 use in cross-installation of library packages from other
5834 architectures, as part of the planned deployment of
5839 Applications may also use a single subdirectory under
5840 <file>/usr/lib/<var>triplet</var></file>.
5843 The execution time linker/loader, ld*, must still be made
5844 available in the existing location under /lib or /lib64
5845 since this is part of the ELF ABI for the architecture.
5850 The requirement that
5851 <file>/usr/local/share/man</file> be "synonymous"
5852 with <file>/usr/local/man</file> is relaxed to a
5857 The requirement that windowmanagers with a single
5858 configuration file call it <file>system.*wmrc</file>
5859 is removed, as is the restriction that the window
5860 manager subdirectory be named identically to the
5861 window manager name itself.
5866 The requirement that boot manager configuration
5867 files live in <file>/etc</file>, or at least are
5868 symlinked there, is relaxed to a recommendation.
5873 The following directories in the root filesystem are
5874 additionally allowed: <file>/sys</file> and
5875 <file>/selinux</file>. <footnote>These directories
5876 are used as mount points to mount virtual filesystems
5877 to get access to kernel information.</footnote>
5884 The version of this document referred here can be
5885 found in the <tt>debian-policy</tt> package or on <url
5886 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5887 name="FHS (Debian copy)"> alongside this manual (or, if
5888 you have the <package>debian-policy</package> installed,
5890 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5891 (local copy)">). The
5892 latest version, which may be a more recent version, may
5894 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5895 Specific questions about following the standard may be
5896 asked on the <tt>debian-devel</tt> mailing list, or
5897 referred to the FHS mailing list (see the
5898 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
5904 <heading>Site-specific programs</heading>
5907 As mandated by the FHS, packages must not place any
5908 files in <file>/usr/local</file>, either by putting them in
5909 the file system archive to be unpacked by <prgn>dpkg</prgn>
5910 or by manipulating them in their maintainer scripts.
5914 However, the package may create empty directories below
5915 <file>/usr/local</file> so that the system administrator knows
5916 where to place site-specific files. These are not
5917 directories <em>in</em> <file>/usr/local</file>, but are
5918 children of directories in <file>/usr/local</file>. These
5919 directories (<file>/usr/local/*/dir/</file>)
5920 should be removed on package removal if they are
5925 Note that this applies only to
5926 directories <em>below</em> <file>/usr/local</file>,
5927 not <em>in</em> <file>/usr/local</file>. Packages must
5928 not create sub-directories in the
5929 directory <file>/usr/local</file> itself, except those
5930 listed in FHS, section 4.5. However, you may create
5931 directories below them as you wish. You must not remove
5932 any of the directories listed in 4.5, even if you created
5937 Since <file>/usr/local</file> can be mounted read-only from a
5938 remote server, these directories must be created and
5939 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
5940 maintainer scripts and not be included in the
5941 <file>.deb</file> archive. These scripts must not fail if
5942 either of these operations fail.
5946 For example, the <tt>emacsen-common</tt> package could
5947 contain something like
5948 <example compact="compact">
5949 if [ ! -e /usr/local/share/emacs ]
5951 if mkdir /usr/local/share/emacs 2>/dev/null
5953 chown root:staff /usr/local/share/emacs
5954 chmod 2775 /usr/local/share/emacs
5958 in its <prgn>postinst</prgn> script, and
5959 <example compact="compact">
5960 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
5961 rmdir /usr/local/share/emacs 2>/dev/null || true
5963 in the <prgn>prerm</prgn> script. (Note that this form is
5964 used to ensure that if the script is interrupted, the
5965 directory <file>/usr/local/share/emacs</file> will still be
5970 If you do create a directory in <file>/usr/local</file> for
5971 local additions to a package, you should ensure that
5972 settings in <file>/usr/local</file> take precedence over the
5973 equivalents in <file>/usr</file>.
5977 However, because <file>/usr/local</file> and its contents are
5978 for exclusive use of the local administrator, a package
5979 must not rely on the presence or absence of files or
5980 directories in <file>/usr/local</file> for normal operation.
5984 The <file>/usr/local</file> directory itself and all the
5985 subdirectories created by the package should (by default) have
5986 permissions 2775 (group-writable and set-group-id) and be
5987 owned by <tt>root:staff</tt>.
5992 <heading>The system-wide mail directory</heading>
5994 The system-wide mail directory
5995 is <file>/var/mail</file>. This directory is part of the
5996 base system and should not be owned by any particular mail
5997 agents. The use of the old
5998 location <file>/var/spool/mail</file> is deprecated, even
5999 though the spool may still be physically located there.
6005 <heading>Users and groups</heading>
6008 <heading>Introduction</heading>
6010 The Debian system can be configured to use either plain or
6015 Some user ids (UIDs) and group ids (GIDs) are reserved
6016 globally for use by certain packages. Because some
6017 packages need to include files which are owned by these
6018 users or groups, or need the ids compiled into binaries,
6019 these ids must be used on any Debian system only for the
6020 purpose for which they are allocated. This is a serious
6021 restriction, and we should avoid getting in the way of
6022 local administration policies. In particular, many sites
6023 allocate users and/or local system groups starting at 100.
6027 Apart from this we should have dynamically allocated ids,
6028 which should by default be arranged in some sensible
6029 order, but the behavior should be configurable.
6033 Packages other than <tt>base-passwd</tt> must not modify
6034 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
6035 <file>/etc/group</file> or <file>/etc/gshadow</file>.
6040 <heading>UID and GID classes</heading>
6042 The UID and GID numbers are divided into classes as
6048 Globally allocated by the Debian project, the same
6049 on every Debian system. These ids will appear in
6050 the <file>passwd</file> and <file>group</file> files of all
6051 Debian systems, new ids in this range being added
6052 automatically as the <tt>base-passwd</tt> package is
6057 Packages which need a single statically allocated
6058 uid or gid should use one of these; their
6059 maintainers should ask the <tt>base-passwd</tt>
6067 Dynamically allocated system users and groups.
6068 Packages which need a user or group, but can have
6069 this user or group allocated dynamically and
6070 differently on each system, should use <tt>adduser
6071 --system</tt> to create the group and/or user.
6072 <prgn>adduser</prgn> will check for the existence of
6073 the user or group, and if necessary choose an unused
6074 id based on the ranges specified in
6075 <file>adduser.conf</file>.
6079 <tag>1000-59999:</tag>
6082 Dynamically allocated user accounts. By default
6083 <prgn>adduser</prgn> will choose UIDs and GIDs for
6084 user accounts in this range, though
6085 <file>adduser.conf</file> may be used to modify this
6090 <tag>60000-64999:</tag>
6093 Globally allocated by the Debian project, but only
6094 created on demand. The ids are allocated centrally
6095 and statically, but the actual accounts are only
6096 created on users' systems on demand.
6100 These ids are for packages which are obscure or
6101 which require many statically-allocated ids. These
6102 packages should check for and create the accounts in
6103 <file>/etc/passwd</file> or <file>/etc/group</file> (using
6104 <prgn>adduser</prgn> if it has this facility) if
6105 necessary. Packages which are likely to require
6106 further allocations should have a "hole" left after
6107 them in the allocation, to give them room to
6112 <tag>65000-65533:</tag>
6120 User <tt>nobody</tt>. The corresponding gid refers
6121 to the group <tt>nogroup</tt>.
6128 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
6129 not</em> be used, because it is the error return
6138 <sect id="sysvinit">
6139 <heading>System run levels and <file>init.d</file> scripts</heading>
6141 <sect1 id="/etc/init.d">
6142 <heading>Introduction</heading>
6145 The <file>/etc/init.d</file> directory contains the scripts
6146 executed by <prgn>init</prgn> at boot time and when the
6147 init state (or "runlevel") is changed (see <manref
6148 name="init" section="8">).
6152 There are at least two different, yet functionally
6153 equivalent, ways of handling these scripts. For the sake
6154 of simplicity, this document describes only the symbolic
6155 link method. However, it must not be assumed by maintainer
6156 scripts that this method is being used, and any automated
6157 manipulation of the various runlevel behaviors by
6158 maintainer scripts must be performed using
6159 <prgn>update-rc.d</prgn> as described below and not by
6160 manually installing or removing symlinks. For information
6161 on the implementation details of the other method,
6162 implemented in the <tt>file-rc</tt> package, please refer
6163 to the documentation of that package.
6167 These scripts are referenced by symbolic links in the
6168 <file>/etc/rc<var>n</var>.d</file> directories. When changing
6169 runlevels, <prgn>init</prgn> looks in the directory
6170 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
6171 execute, where <tt><var>n</var></tt> is the runlevel that
6172 is being changed to, or <tt>S</tt> for the boot-up
6177 The names of the links all have the form
6178 <file>S<var>mm</var><var>script</var></file> or
6179 <file>K<var>mm</var><var>script</var></file> where
6180 <var>mm</var> is a two-digit number and <var>script</var>
6181 is the name of the script (this should be the same as the
6182 name of the actual script in <file>/etc/init.d</file>).
6186 When <prgn>init</prgn> changes runlevel first the targets
6187 of the links whose names start with a <tt>K</tt> are
6188 executed, each with the single argument <tt>stop</tt>,
6189 followed by the scripts prefixed with an <tt>S</tt>, each
6190 with the single argument <tt>start</tt>. (The links are
6191 those in the <file>/etc/rc<var>n</var>.d</file> directory
6192 corresponding to the new runlevel.) The <tt>K</tt> links
6193 are responsible for killing services and the <tt>S</tt>
6194 link for starting services upon entering the runlevel.
6198 For example, if we are changing from runlevel 2 to
6199 runlevel 3, init will first execute all of the <tt>K</tt>
6200 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
6201 all of the <tt>S</tt> prefixed scripts in that directory.
6202 The links starting with <tt>K</tt> will cause the
6203 referred-to file to be executed with an argument of
6204 <tt>stop</tt>, and the <tt>S</tt> links with an argument
6209 The two-digit number <var>mm</var> is used to determine
6210 the order in which to run the scripts: low-numbered links
6211 have their scripts run first. For example, the
6212 <tt>K20</tt> scripts will be executed before the
6213 <tt>K30</tt> scripts. This is used when a certain service
6214 must be started before another. For example, the name
6215 server <prgn>bind</prgn> might need to be started before
6216 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
6217 can set up its access lists. In this case, the script
6218 that starts <prgn>bind</prgn> would have a lower number
6219 than the script that starts <prgn>inn</prgn> so that it
6221 <example compact="compact">
6228 The two runlevels 0 (halt) and 6 (reboot) are slightly
6229 different. In these runlevels, the links with an
6230 <tt>S</tt> prefix are still called after those with a
6231 <tt>K</tt> prefix, but they too are called with the single
6232 argument <tt>stop</tt>.
6236 <sect1 id="writing-init">
6237 <heading>Writing the scripts</heading>
6240 Packages that include daemons for system services should
6241 place scripts in <file>/etc/init.d</file> to start or stop
6242 services at boot time or during a change of runlevel.
6243 These scripts should be named
6244 <file>/etc/init.d/<var>package</var></file>, and they should
6245 accept one argument, saying what to do:
6248 <tag><tt>start</tt></tag>
6249 <item>start the service,</item>
6251 <tag><tt>stop</tt></tag>
6252 <item>stop the service,</item>
6254 <tag><tt>restart</tt></tag>
6255 <item>stop and restart the service if it's already running,
6256 otherwise start the service</item>
6258 <tag><tt>reload</tt></tag>
6259 <item><p>cause the configuration of the service to be
6260 reloaded without actually stopping and restarting
6263 <tag><tt>force-reload</tt></tag>
6264 <item>cause the configuration to be reloaded if the
6265 service supports this, otherwise restart the
6269 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
6270 <tt>force-reload</tt> options should be supported by all
6271 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
6276 The <file>init.d</file> scripts must ensure that they will
6277 behave sensibly (i.e., returning success and not starting
6278 multiple copies of a service) if invoked with <tt>start</tt>
6279 when the service is already running, or with <tt>stop</tt>
6280 when it isn't, and that they don't kill unfortunately-named
6281 user processes. The best way to achieve this is usually to
6282 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
6287 Be careful of using <tt>set -e</tt> in <file>init.d</file>
6288 scripts. Writing correct <file>init.d</file> scripts requires
6289 accepting various error exit statuses when daemons are already
6290 running or already stopped without aborting
6291 the <file>init.d</file> script, and common <file>init.d</file>
6292 function libraries are not safe to call with <tt>set -e</tt>
6294 <tt>/lib/lsb/init-functions</tt>, which assists in writing
6295 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
6296 in effect and echoing status messages to the console fails,
6298 </footnote>. For <tt>init.d</tt> scripts, it's often easier
6299 to not use <tt>set -e</tt> and instead check the result of
6300 each command separately.
6304 If a service reloads its configuration automatically (as
6305 in the case of <prgn>cron</prgn>, for example), the
6306 <tt>reload</tt> option of the <file>init.d</file> script
6307 should behave as if the configuration has been reloaded
6312 The <file>/etc/init.d</file> scripts must be treated as
6313 configuration files, either (if they are present in the
6314 package, that is, in the .deb file) by marking them as
6315 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6316 by managing them correctly in the maintainer scripts (see
6317 <ref id="config-files">). This is important since we want
6318 to give the local system administrator the chance to adapt
6319 the scripts to the local system, e.g., to disable a
6320 service without de-installing the package, or to specify
6321 some special command line options when starting a service,
6322 while making sure their changes aren't lost during the next
6327 These scripts should not fail obscurely when the
6328 configuration files remain but the package has been
6329 removed, as configuration files remain on the system after
6330 the package has been removed. Only when <prgn>dpkg</prgn>
6331 is executed with the <tt>--purge</tt> option will
6332 configuration files be removed. In particular, as the
6333 <file>/etc/init.d/<var>package</var></file> script itself is
6334 usually a <tt>conffile</tt>, it will remain on the system
6335 if the package is removed but not purged. Therefore, you
6336 should include a <tt>test</tt> statement at the top of the
6338 <example compact="compact">
6339 test -f <var>program-executed-later-in-script</var> || exit 0
6344 Often there are some variables in the <file>init.d</file>
6345 scripts whose values control the behavior of the scripts,
6346 and which a system administrator is likely to want to
6347 change. As the scripts themselves are frequently
6348 <tt>conffile</tt>s, modifying them requires that the
6349 administrator merge in their changes each time the package
6350 is upgraded and the <tt>conffile</tt> changes. To ease
6351 the burden on the system administrator, such configurable
6352 values should not be placed directly in the script.
6353 Instead, they should be placed in a file in
6354 <file>/etc/default</file>, which typically will have the same
6355 base name as the <file>init.d</file> script. This extra file
6356 should be sourced by the script when the script runs. It
6357 must contain only variable settings and comments in SUSv3
6358 <prgn>sh</prgn> format. It may either be a
6359 <tt>conffile</tt> or a configuration file maintained by
6360 the package maintainer scripts. See <ref id="config-files">
6365 To ensure that vital configurable values are always
6366 available, the <file>init.d</file> script should set default
6367 values for each of the shell variables it uses, either
6368 before sourcing the <file>/etc/default/</file> file or
6369 afterwards using something like the <tt>:
6370 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6371 script must behave sensibly and not fail if the
6372 <file>/etc/default</file> file is deleted.
6376 <file>/var/run</file> and <file>/var/lock</file> may be mounted
6377 as temporary filesystems<footnote>
6378 For example, using the <tt>RAMRUN</tt> and <tt>RAMLOCK</tt>
6379 options in <file>/etc/default/rcS</file>.
6380 </footnote>, so the <file>init.d</file> scripts must handle this
6381 correctly. This will typically amount to creating any required
6382 subdirectories dynamically when the <file>init.d</file> script
6383 is run, rather than including them in the package and relying on
6384 <prgn>dpkg</prgn> to create them.
6389 <heading>Interfacing with the initscript system</heading>
6392 Maintainers should use the abstraction layer provided by
6393 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6394 programs to deal with initscripts in their packages'
6395 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6396 and <prgn>postrm</prgn>.
6400 Directly managing the /etc/rc?.d links and directly
6401 invoking the <file>/etc/init.d/</file> initscripts should
6402 be done only by packages providing the initscript
6403 subsystem (such as <prgn>sysv-rc</prgn> and
6404 <prgn>file-rc</prgn>).
6408 <heading>Managing the links</heading>
6411 The program <prgn>update-rc.d</prgn> is provided for
6412 package maintainers to arrange for the proper creation and
6413 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6414 or their functional equivalent if another method is being
6415 used. This may be used by maintainers in their packages'
6416 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6420 You must not include any <file>/etc/rc<var>n</var>.d</file>
6421 symbolic links in the actual archive or manually create or
6422 remove the symbolic links in maintainer scripts; you must
6423 use the <prgn>update-rc.d</prgn> program instead. (The
6424 former will fail if an alternative method of maintaining
6425 runlevel information is being used.) You must not include
6426 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6427 in the archive either. (Only the <tt>sysvinit</tt>
6432 By default <prgn>update-rc.d</prgn> will start services in
6433 each of the multi-user state runlevels (2, 3, 4, and 5)
6434 and stop them in the halt runlevel (0), the single-user
6435 runlevel (1) and the reboot runlevel (6). The system
6436 administrator will have the opportunity to customize
6437 runlevels by simply adding, moving, or removing the
6438 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6439 symbolic links are being used, or by modifying
6440 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6445 To get the default behavior for your package, put in your
6446 <prgn>postinst</prgn> script
6447 <example compact="compact">
6448 update-rc.d <var>package</var> defaults
6450 and in your <prgn>postrm</prgn>
6451 <example compact="compact">
6452 if [ "$1" = purge ]; then
6453 update-rc.d <var>package</var> remove
6455 </example>. Note that if your package changes runlevels
6456 or priority, you may have to remove and recreate the links,
6457 since otherwise the old links may persist. Refer to the
6458 documentation of <prgn>update-rc.d</prgn>.
6462 This will use a default sequence number of 20. If it does
6463 not matter when or in which order the <file>init.d</file>
6464 script is run, use this default. If it does, then you
6465 should talk to the maintainer of the <prgn>sysvinit</prgn>
6466 package or post to <tt>debian-devel</tt>, and they will
6467 help you choose a number.
6471 For more information about using <tt>update-rc.d</tt>,
6472 please consult its man page <manref name="update-rc.d"
6478 <heading>Running initscripts</heading>
6480 The program <prgn>invoke-rc.d</prgn> is provided to make
6481 it easier for package maintainers to properly invoke an
6482 initscript, obeying runlevel and other locally-defined
6483 constraints that might limit a package's right to start,
6484 stop and otherwise manage services. This program may be
6485 used by maintainers in their packages' scripts.
6489 The package maintainer scripts must use
6490 <prgn>invoke-rc.d</prgn> to invoke the
6491 <file>/etc/init.d/*</file> initscripts, instead of
6492 calling them directly.
6496 By default, <prgn>invoke-rc.d</prgn> will pass any
6497 action requests (start, stop, reload, restart...) to the
6498 <file>/etc/init.d</file> script, filtering out requests
6499 to start or restart a service out of its intended
6504 Most packages will simply need to change:
6505 <example compact="compact">/etc/init.d/<package>
6506 <action></example> in their <prgn>postinst</prgn>
6507 and <prgn>prerm</prgn> scripts to:
6508 <example compact="compact">
6509 if which invoke-rc.d >/dev/null 2>&1; then
6510 invoke-rc.d <var>package</var> <action>
6512 /etc/init.d/<var>package</var> <action>
6518 A package should register its initscript services using
6519 <prgn>update-rc.d</prgn> before it tries to invoke them
6520 using <prgn>invoke-rc.d</prgn>. Invocation of
6521 unregistered services may fail.
6525 For more information about using
6526 <prgn>invoke-rc.d</prgn>, please consult its man page
6527 <manref name="invoke-rc.d" section="8">.
6533 <heading>Boot-time initialization</heading>
6536 There used to be another directory, <file>/etc/rc.boot</file>,
6537 which contained scripts which were run once per machine
6538 boot. This has been deprecated in favour of links from
6539 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6540 described in <ref id="/etc/init.d">. Packages must not
6541 place files in <file>/etc/rc.boot</file>.
6546 <heading>Example</heading>
6549 An example on which you can base your
6550 <file>/etc/init.d</file> scripts is found in
6551 <file>/etc/init.d/skeleton</file>.
6558 <heading>Console messages from <file>init.d</file> scripts</heading>
6561 This section describes the formats to be used for messages
6562 written to standard output by the <file>/etc/init.d</file>
6563 scripts. The intent is to improve the consistency of
6564 Debian's startup and shutdown look and feel. For this
6565 reason, please look very carefully at the details. We want
6566 the messages to have the same format in terms of wording,
6567 spaces, punctuation and case of letters.
6571 Here is a list of overall rules that should be used for
6572 messages generated by <file>/etc/init.d</file> scripts.
6578 The message should fit in one line (fewer than 80
6579 characters), start with a capital letter and end with
6580 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6584 If the script is performing some time consuming task in
6585 the background (not merely starting or stopping a
6586 program, for instance), an ellipsis (three dots:
6587 <tt>...</tt>) should be output to the screen, with no
6588 leading or tailing whitespace or line feeds.
6592 The messages should appear as if the computer is telling
6593 the user what it is doing (politely :-), but should not
6594 mention "it" directly. For example, instead of:
6595 <example compact="compact">
6596 I'm starting network daemons: nfsd mountd.
6598 the message should say
6599 <example compact="compact">
6600 Starting network daemons: nfsd mountd.
6607 <tt>init.d</tt> script should use the following standard
6608 message formats for the situations enumerated below.
6614 <p>When daemons are started</p>
6617 If the script starts one or more daemons, the output
6618 should look like this (a single line, no leading
6620 <example compact="compact">
6621 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6623 The <var>description</var> should describe the
6624 subsystem the daemon or set of daemons are part of,
6625 while <var>daemon-1</var> up to <var>daemon-n</var>
6626 denote each daemon's name (typically the file name of
6631 For example, the output of <file>/etc/init.d/lpd</file>
6633 <example compact="compact">
6634 Starting printer spooler: lpd.
6639 This can be achieved by saying
6640 <example compact="compact">
6641 echo -n "Starting printer spooler: lpd"
6642 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6645 in the script. If there are more than one daemon to
6646 start, the output should look like this:
6647 <example compact="compact">
6648 echo -n "Starting remote file system services:"
6649 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6650 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6651 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6654 This makes it possible for the user to see what is
6655 happening and when the final daemon has been started.
6656 Care should be taken in the placement of white spaces:
6657 in the example above the system administrators can
6658 easily comment out a line if they don't want to start
6659 a specific daemon, while the displayed message still
6665 <p>When a system parameter is being set</p>
6668 If you have to set up different system parameters
6669 during the system boot, you should use this format:
6670 <example compact="compact">
6671 Setting <var>parameter</var> to "<var>value</var>".
6676 You can use a statement such as the following to get
6678 <example compact="compact">
6679 echo "Setting DNS domainname to \"$domainname\"."
6684 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
6685 for the left and right quotation marks. A grave accent
6686 (<tt>`</tt>) is not a quote character; neither is an
6687 apostrophe (<tt>'</tt>).
6692 <p>When a daemon is stopped or restarted</p>
6695 When you stop or restart a daemon, you should issue a
6696 message identical to the startup message, except that
6697 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6698 or <tt>Restarting</tt> respectively.
6702 For example, stopping the printer daemon will look like
6704 <example compact="compact">
6705 Stopping printer spooler: lpd.
6711 <p>When something is executed</p>
6714 There are several examples where you have to run a
6715 program at system startup or shutdown to perform a
6716 specific task, for example, setting the system's clock
6717 using <prgn>netdate</prgn> or killing all processes
6718 when the system shuts down. Your message should look
6720 <example compact="compact">
6721 Doing something very useful...done.
6723 You should print the <tt>done.</tt> immediately after
6724 the job has been completed, so that the user is
6725 informed why they have to wait. You can get this
6727 <example compact="compact">
6728 echo -n "Doing something very useful..."
6737 <p>When the configuration is reloaded</p>
6740 When a daemon is forced to reload its configuration
6741 files you should use the following format:
6742 <example compact="compact">
6743 Reloading <var>description</var> configuration...done.
6745 where <var>description</var> is the same as in the
6746 daemon starting message.
6754 <heading>Cron jobs</heading>
6757 Packages must not modify the configuration file
6758 <file>/etc/crontab</file>, and they must not modify the files in
6759 <file>/var/spool/cron/crontabs</file>.</p>
6762 If a package wants to install a job that has to be executed
6763 via cron, it should place a file with the name of the
6764 package in one or more of the following directories:
6765 <example compact="compact">
6771 As these directory names imply, the files within them are
6772 executed on an hourly, daily, weekly, or monthly basis,
6773 respectively. The exact times are listed in
6774 <file>/etc/crontab</file>.</p>
6777 All files installed in any of these directories must be
6778 scripts (e.g., shell scripts or Perl scripts) so that they
6779 can easily be modified by the local system administrator.
6780 In addition, they must be treated as configuration files.
6784 If a certain job has to be executed at some other frequency or
6785 at a specific time, the package should install a file
6786 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6787 same syntax as <file>/etc/crontab</file> and is processed by
6788 <prgn>cron</prgn> automatically. The file must also be
6789 treated as a configuration file. (Note that entries in the
6790 <file>/etc/cron.d</file> directory are not handled by
6791 <prgn>anacron</prgn>. Thus, you should only use this
6792 directory for jobs which may be skipped if the system is not
6795 Unlike <file>crontab</file> files described in the IEEE Std
6796 1003.1-2008 (POSIX.1) available from
6797 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
6798 name="The Open Group">, the files in
6799 <file>/etc/cron.d</file> and the file
6800 <file>/etc/crontab</file> have seven fields; namely:
6802 <item>Minute [0,59]</item>
6803 <item>Hour [0,23]</item>
6804 <item>Day of the month [1,31]</item>
6805 <item>Month of the year [1,12]</item>
6806 <item>Day of the week ([0,6] with 0=Sunday)</item>
6807 <item>Username</item>
6808 <item>Command to be run</item>
6810 Ranges of numbers are allowed. Ranges are two numbers
6811 separated with a hyphen. The specified range is inclusive.
6812 Lists are allowed. A list is a set of numbers (or ranges)
6813 separated by commas. Step values can be used in conjunction
6818 The scripts or <tt>crontab</tt> entries in these directories should
6819 check if all necessary programs are installed before they
6820 try to execute them. Otherwise, problems will arise when a
6821 package was removed but not purged since configuration files
6822 are kept on the system in this situation.
6826 Any <tt>cron</tt> daemon must provide
6827 <file>/usr/bin/crontab</file> and support normal
6828 <tt>crontab</tt> entries as specified in POSIX. The daemon
6829 must also support names for days and months, ranges, and
6830 step values. It has to support <file>/etc/crontab</file>,
6831 and correctly execute the scripts in
6832 <file>/etc/cron.d</file>. The daemon must also correctly
6834 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
6839 <heading>Menus</heading>
6842 The Debian <tt>menu</tt> package provides a standard
6843 interface between packages providing applications and
6844 <em>menu programs</em> (either X window managers or
6845 text-based menu programs such as <prgn>pdmenu</prgn>).
6849 All packages that provide applications that need not be
6850 passed any special command line arguments for normal
6851 operation should register a menu entry for those
6852 applications, so that users of the <tt>menu</tt> package
6853 will automatically get menu entries in their window
6854 managers, as well in shells like <tt>pdmenu</tt>.
6858 Menu entries should follow the current menu policy.
6862 The menu policy can be found in the <tt>menu-policy</tt>
6863 files in the <tt>debian-policy</tt> package.
6864 It is also available from the Debian web mirrors at
6865 <tt><url name="/doc/packaging-manuals/menu-policy/"
6866 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6870 Please also refer to the <em>Debian Menu System</em>
6871 documentation that comes with the <package>menu</package>
6872 package for information about how to register your
6878 <heading>Multimedia handlers</heading>
6881 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6882 is a mechanism for encoding files and data streams and
6883 providing meta-information about them, in particular their
6884 type (e.g. audio or video) and format (e.g. PNG, HTML,
6889 Registration of MIME type handlers allows programs like mail
6890 user agents and web browsers to invoke these handlers to
6891 view, edit or display MIME types they don't support directly.
6895 Packages which provide the ability to view/show/play,
6896 compose, edit or print MIME types should register themselves
6897 as such following the current MIME support policy.
6901 The MIME support policy can be found in the <tt>mime-policy</tt>
6902 files in the <tt>debian-policy</tt> package.
6903 It is also available from the Debian web mirrors at
6904 <tt><url name="/doc/packaging-manuals/mime-policy/"
6905 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
6911 <heading>Keyboard configuration</heading>
6914 To achieve a consistent keyboard configuration so that all
6915 applications interpret a keyboard event the same way, all
6916 programs in the Debian distribution must be configured to
6917 comply with the following guidelines.
6921 The following keys must have the specified interpretations:
6924 <tag><tt><--</tt></tag>
6925 <item>delete the character to the left of the cursor</item>
6927 <tag><tt>Delete</tt></tag>
6928 <item>delete the character to the right of the cursor</item>
6930 <tag><tt>Control+H</tt></tag>
6931 <item>emacs: the help prefix</item>
6934 The interpretation of any keyboard events should be
6935 independent of the terminal that is used, be it a virtual
6936 console, an X terminal emulator, an rlogin/telnet session,
6941 The following list explains how the different programs
6942 should be set up to achieve this:
6948 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
6952 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
6956 X translations are set up to make
6957 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
6958 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
6959 is the vt220 escape code for the "delete character"
6960 key). This must be done by loading the X resources
6961 using <prgn>xrdb</prgn> on all local X displays, not
6962 using the application defaults, so that the
6963 translation resources used correspond to the
6964 <prgn>xmodmap</prgn> settings.
6968 The Linux console is configured to make
6969 <tt><--</tt> generate DEL, and <tt>Delete</tt>
6970 generate <tt>ESC [ 3 ~</tt>.
6974 X applications are configured so that <tt><</tt>
6975 deletes left, and <tt>Delete</tt> deletes right. Motif
6976 applications already work like this.
6980 Terminals should have <tt>stty erase ^?</tt> .
6984 The <tt>xterm</tt> terminfo entry should have <tt>ESC
6985 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
6986 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
6990 Emacs is programmed to map <tt>KB_Backspace</tt> or
6991 the <tt>stty erase</tt> character to
6992 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
6993 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
6994 <tt>^H</tt> to <tt>help</tt> as always.
6998 Other applications use the <tt>stty erase</tt>
6999 character and <tt>kdch1</tt> for the two delete keys,
7000 with ASCII DEL being "delete previous character" and
7001 <tt>kdch1</tt> being "delete character under
7009 This will solve the problem except for the following
7016 Some terminals have a <tt><--</tt> key that cannot
7017 be made to produce anything except <tt>^H</tt>. On
7018 these terminals Emacs help will be unavailable on
7019 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
7020 character takes precedence in Emacs, and has been set
7021 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
7022 available) can be used instead.
7026 Some operating systems use <tt>^H</tt> for <tt>stty
7027 erase</tt>. However, modern telnet versions and all
7028 rlogin versions propagate <tt>stty</tt> settings, and
7029 almost all UNIX versions honour <tt>stty erase</tt>.
7030 Where the <tt>stty</tt> settings are not propagated
7031 correctly, things can be made to work by using
7032 <tt>stty</tt> manually.
7036 Some systems (including previous Debian versions) use
7037 <prgn>xmodmap</prgn> to arrange for both
7038 <tt><--</tt> and <tt>Delete</tt> to generate
7039 <tt>KB_Delete</tt>. We can change the behavior of
7040 their X clients using the same X resources that we use
7041 to do it for our own clients, or configure our clients
7042 using their resources when things are the other way
7043 around. On displays configured like this
7044 <tt>Delete</tt> will not work, but <tt><--</tt>
7049 Some operating systems have different <tt>kdch1</tt>
7050 settings in their <tt>terminfo</tt> database for
7051 <tt>xterm</tt> and others. On these systems the
7052 <tt>Delete</tt> key will not work correctly when you
7053 log in from a system conforming to our policy, but
7054 <tt><--</tt> will.
7061 <heading>Environment variables</heading>
7064 A program must not depend on environment variables to get
7065 reasonable defaults. (That's because these environment
7066 variables would have to be set in a system-wide
7067 configuration file like <file>/etc/profile</file>, which is not
7068 supported by all shells.)
7072 If a program usually depends on environment variables for its
7073 configuration, the program should be changed to fall back to
7074 a reasonable default configuration if these environment
7075 variables are not present. If this cannot be done easily
7076 (e.g., if the source code of a non-free program is not
7077 available), the program must be replaced by a small
7078 "wrapper" shell script which sets the environment variables
7079 if they are not already defined, and calls the original program.
7083 Here is an example of a wrapper script for this purpose:
7085 <example compact="compact">
7087 BAR=${BAR:-/var/lib/fubar}
7089 exec /usr/lib/foo/foo "$@"
7094 Furthermore, as <file>/etc/profile</file> is a configuration
7095 file of the <prgn>base-files</prgn> package, other packages must
7096 not put any environment variables or other commands into that
7101 <sect id="doc-base">
7102 <heading>Registering Documents using doc-base</heading>
7105 The <package>doc-base</package> package implements a
7106 flexible mechanism for handling and presenting
7107 documentation. The recommended practice is for every Debian
7108 package that provides online documentation (other than just
7109 manual pages) to register these documents with
7110 <package>doc-base</package> by installing a
7111 <package>doc-base</package> control file via the
7112 <prgn/install-docs/ script at installation time and
7113 de-register the manuals again when the package is removed.
7116 Please refer to the documentation that comes with the
7117 <package>doc-base</package> package for information and
7126 <heading>Files</heading>
7128 <sect id="binaries">
7129 <heading>Binaries</heading>
7132 Two different packages must not install programs with
7133 different functionality but with the same filenames. (The
7134 case of two programs having the same functionality but
7135 different implementations is handled via "alternatives" or
7136 the "Conflicts" mechanism. See <ref id="maintscripts"> and
7137 <ref id="conflicts"> respectively.) If this case happens,
7138 one of the programs must be renamed. The maintainers should
7139 report this to the <tt>debian-devel</tt> mailing list and
7140 try to find a consensus about which program will have to be
7141 renamed. If a consensus cannot be reached, <em>both</em>
7142 programs must be renamed.
7146 By default, when a package is being built, any binaries
7147 created should include debugging information, as well as
7148 being compiled with optimization. You should also turn on
7149 as many reasonable compilation warnings as possible; this
7150 makes life easier for porters, who can then look at build
7151 logs for possible problems. For the C programming language,
7152 this means the following compilation parameters should be
7154 <example compact="compact">
7156 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
7158 INSTALL = install -s # (or use strip on the files in debian/tmp)
7163 Note that by default all installed binaries should be stripped,
7164 either by using the <tt>-s</tt> flag to
7165 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
7166 the binaries after they have been copied into
7167 <file>debian/tmp</file> but before the tree is made into a
7172 Although binaries in the build tree should be compiled with
7173 debugging information by default, it can often be difficult to
7174 debug programs if they are also subjected to compiler
7175 optimization. For this reason, it is recommended to support the
7176 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
7177 (see <ref id="debianrules-options">). This variable can contain
7178 several flags to change how a package is compiled and built.
7182 It is up to the package maintainer to decide what
7183 compilation options are best for the package. Certain
7184 binaries (such as computationally-intensive programs) will
7185 function better with certain flags (<tt>-O3</tt>, for
7186 example); feel free to use them. Please use good judgment
7187 here. Don't use flags for the sake of it; only use them
7188 if there is good reason to do so. Feel free to override
7189 the upstream author's ideas about which compilation
7190 options are best: they are often inappropriate for our
7196 <sect id="libraries">
7197 <heading>Libraries</heading>
7200 If the package is <strong>architecture: any</strong>, then
7201 the shared library compilation and linking flags must have
7202 <tt>-fPIC</tt>, or the package shall not build on some of
7203 the supported architectures<footnote>
7205 If you are using GCC, <tt>-fPIC</tt> produces code with
7206 relocatable position independent code, which is required for
7207 most architectures to create a shared library, with i386 and
7208 perhaps some others where non position independent code is
7209 permitted in a shared library.
7212 Position independent code may have a performance penalty,
7213 especially on <tt>i386</tt>. However, in most cases the
7214 speed penalty must be measured against the memory wasted on
7215 the few architectures where non position independent code is
7218 </footnote>. Any exception to this rule must be discussed on
7219 the mailing list <em>debian-devel@lists.debian.org</em>, and
7220 a rough consensus obtained. The reasons for not compiling
7221 with <tt>-fPIC</tt> flag must be recorded in the file
7222 <tt>README.Debian</tt>, and care must be taken to either
7223 restrict the architecture or arrange for <tt>-fPIC</tt> to
7224 be used on architectures where it is required.<footnote>
7226 Some of the reasons why this might be required is if the
7227 library contains hand crafted assembly code that is not
7228 relocatable, the speed penalty is excessive for compute
7229 intensive libs, and similar reasons.
7234 As to the static libraries, the common case is not to have
7235 relocatable code, since there is no benefit, unless in specific
7236 cases; therefore the static version must not be compiled
7237 with the <tt>-fPIC</tt> flag. Any exception to this rule
7238 should be discussed on the mailing list
7239 <em>debian-devel@lists.debian.org</em>, and the reasons for
7240 compiling with the <tt>-fPIC</tt> flag must be recorded in
7241 the file <tt>README.Debian</tt>. <footnote>
7243 Some of the reasons for linking static libraries with
7244 the <tt>-fPIC</tt> flag are if, for example, one needs a
7245 Perl API for a library that is under rapid development,
7246 and has an unstable API, so shared libraries are
7247 pointless at this phase of the library's development. In
7248 that case, since Perl needs a library with relocatable
7249 code, it may make sense to create a static library with
7250 relocatable code. Another reason cited is if you are
7251 distilling various libraries into a common shared
7252 library, like <tt>mklibs</tt> does in the Debian
7258 In other words, if both a shared and a static library is
7259 being built, each source unit (<tt>*.c</tt>, for example,
7260 for C files) will need to be compiled twice, for the normal
7265 Libraries should be built with threading support and to be
7266 thread-safe if the library supports this.
7270 Although not enforced by the build tools, shared libraries
7271 must be linked against all libraries that they use symbols from
7272 in the same way that binaries are. This ensures the correct
7273 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
7274 system and guarantees that all libraries can be safely opened
7275 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
7276 option <tt>-Wl,-z,defs</tt> when building a shared library.
7277 Since this option enforces symbol resolution at build time,
7278 a missing library reference will be caught early as a fatal
7283 All installed shared libraries should be stripped with
7284 <example compact="compact">
7285 strip --strip-unneeded <var>your-lib</var>
7287 (The option <tt>--strip-unneeded</tt> makes
7288 <prgn>strip</prgn> remove only the symbols which aren't
7289 needed for relocation processing.) Shared libraries can
7290 function perfectly well when stripped, since the symbols for
7291 dynamic linking are in a separate part of the ELF object
7293 You might also want to use the options
7294 <tt>--remove-section=.comment</tt> and
7295 <tt>--remove-section=.note</tt> on both shared libraries
7296 and executables, and <tt>--strip-debug</tt> on static
7302 Note that under some circumstances it may be useful to
7303 install a shared library unstripped, for example when
7304 building a separate package to support debugging.
7308 Shared object files (often <file>.so</file> files) that are not
7309 public libraries, that is, they are not meant to be linked
7310 to by third party executables (binaries of other packages),
7311 should be installed in subdirectories of the
7312 <file>/usr/lib</file> directory. Such files are exempt from the
7313 rules that govern ordinary shared libraries, except that
7314 they must not be installed executable and should be
7316 A common example are the so-called "plug-ins",
7317 internal shared objects that are dynamically loaded by
7318 programs using <manref name="dlopen" section="3">.
7323 Packages that use <prgn>libtool</prgn> to create and install
7324 their shared libraries install a file containing additional
7325 metadata (ending in <file>.la</file>) alongside the library.
7326 For public libraries intended for use by other packages, these
7327 files normally should not be included in the Debian package,
7328 since the information they include is not necessary to link with
7329 the shared library on Debian and can add unnecessary additional
7330 dependencies to other programs or libraries.<footnote>
7331 These files store, among other things, all libraries on which
7332 that shared library depends. Unfortunately, if
7333 the <file>.la</file> file is present and contains that
7334 dependency information, using <prgn>libtool</prgn> when
7335 linking against that library will cause the resulting program
7336 or library to be linked against those dependencies as well,
7337 even if this is unnecessary. This can create unneeded
7338 dependencies on shared library packages that would otherwise
7339 be hidden behind the library ABI, and can make library
7340 transitions to new SONAMEs unnecessarily complicated and
7341 difficult to manage.
7343 If the <file>.la</file> file is required for that library (if,
7344 for instance, it's loaded via <tt>libltdl</tt> in a way that
7345 requires that meta-information), the <tt>dependency_libs</tt>
7346 setting in the <file>.la</file> file should normally be set to
7347 the empty string. If the shared library development package has
7348 historically included the <file>.la</file>, it must be retained
7349 in the development package (with <tt>dependency_libs</tt>
7350 emptied) until all libraries that depend on it have removed or
7351 emptied <tt>dependency_libs</tt> in their <file>.la</file>
7352 files to prevent linking with those other libraries
7353 using <prgn>libtool</prgn> from failing.
7357 If the <file>.la</file> must be included, it should be included
7358 in the development (<tt>-dev</tt>) package, unless the library
7359 will be loaded by <prgn>libtool</prgn>'s <tt>libltdl</tt>
7360 library. If it is intended for use with <tt>libltdl</tt>,
7361 the <file>.la</file> files must go in the run-time library
7366 These requirements for handling of <file>.la</file> files do not
7367 apply to loadable modules or libraries not installed in
7368 directories searched by default by the dynamic linker. Packages
7369 installing loadable modules will frequently need to install
7370 the <file>.la</file> files alongside the modules so that they
7371 can be loaded by <tt>libltdl</tt>. <tt>dependency_libs</tt>
7372 does not need to be modified for libraries or modules that are
7373 not installed in directories searched by the dynamic linker by
7374 default and not intended for use by other packages.
7378 You must make sure that you use only released versions of
7379 shared libraries to build your packages; otherwise other
7380 users will not be able to run your binaries
7381 properly. Producing source packages that depend on
7382 unreleased compilers is also usually a bad
7389 <heading>Shared libraries</heading>
7391 This section has moved to <ref id="sharedlibs">.
7397 <heading>Scripts</heading>
7400 All command scripts, including the package maintainer
7401 scripts inside the package and used by <prgn>dpkg</prgn>,
7402 should have a <tt>#!</tt> line naming the shell to be used
7407 In the case of Perl scripts this should be
7408 <tt>#!/usr/bin/perl</tt>.
7412 When scripts are installed into a directory in the system
7413 PATH, the script name should not include an extension such
7414 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7415 language currently used to implement it.
7418 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
7419 <file>init.d</file> scripts should almost certainly start
7420 with <tt>set -e</tt> so that errors are detected.
7421 <file>init.d</file> scripts are something of a special case, due
7422 to how frequently they need to call commands that are allowed to
7423 fail, and it may instead be easier to check the exit status of
7424 commands directly. See <ref id="writing-init"> for more
7425 information about writing <file>init.d</file> scripts.
7428 Every script should use <tt>set -e</tt> or check the exit status
7429 of <em>every</em> command.
7432 Scripts may assume that <file>/bin/sh</file> implements the
7433 SUSv3 Shell Command Language<footnote>
7434 Single UNIX Specification, version 3, which is also IEEE
7435 1003.1-2004 (POSIX), and is available on the World Wide Web
7436 from <url id="http://www.unix.org/version3/online.html"
7437 name="The Open Group"> after free
7438 registration.</footnote>
7439 plus the following additional features not mandated by
7441 These features are in widespread use in the Linux community
7442 and are implemented in all of bash, dash, and ksh, the most
7443 common shells users may wish to use as <file>/bin/sh</file>.
7446 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7447 must not generate a newline.</item>
7448 <item><tt>test</tt>, if implemented as a shell built-in, must
7449 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7451 <item><tt>local</tt> to create a scoped variable must be
7452 supported, including listing multiple variables in a single
7453 local command and assigning a value to a variable at the
7454 same time as localizing it. <tt>local</tt> may or
7455 may not preserve the variable value from an outer scope if
7456 no assignment is present. Uses such as:
7460 # ... use a, b, c, d ...
7463 must be supported and must set the value of <tt>c</tt> to
7467 If a shell script requires non-SUSv3 features from the shell
7468 interpreter other than those listed above, the appropriate shell
7469 must be specified in the first line of the script (e.g.,
7470 <tt>#!/bin/bash</tt>) and the package must depend on the package
7471 providing the shell (unless the shell package is marked
7472 "Essential", as in the case of <prgn>bash</prgn>).
7476 You may wish to restrict your script to SUSv3 features plus the
7477 above set when possible so that it may use <file>/bin/sh</file>
7478 as its interpreter. If your script works with <prgn>dash</prgn>
7479 (originally called <prgn>ash</prgn>), it probably complies with
7480 the above requirements, but if you are in doubt, use
7481 <file>/bin/bash</file>.
7485 Perl scripts should check for errors when making any
7486 system calls, including <tt>open</tt>, <tt>print</tt>,
7487 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7491 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7492 scripting languages. See <em>Csh Programming Considered
7493 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7494 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7495 If an upstream package comes with <prgn>csh</prgn> scripts
7496 then you must make sure that they start with
7497 <tt>#!/bin/csh</tt> and make your package depend on the
7498 <prgn>c-shell</prgn> virtual package.
7502 Any scripts which create files in world-writeable
7503 directories (e.g., in <file>/tmp</file>) must use a
7504 mechanism which will fail atomically if a file with the same
7505 name already exists.
7509 The Debian base system provides the <prgn>tempfile</prgn>
7510 and <prgn>mktemp</prgn> utilities for use by scripts for
7517 <heading>Symbolic links</heading>
7520 In general, symbolic links within a top-level directory
7521 should be relative, and symbolic links pointing from one
7522 top-level directory into another should be absolute. (A
7523 top-level directory is a sub-directory of the root
7524 directory <file>/</file>.)
7528 In addition, symbolic links should be specified as short as
7529 possible, i.e., link targets like <file>foo/../bar</file> are
7534 Note that when creating a relative link using
7535 <prgn>ln</prgn> it is not necessary for the target of the
7536 link to exist relative to the working directory you're
7537 running <prgn>ln</prgn> from, nor is it necessary to change
7538 directory to the directory where the link is to be made.
7539 Simply include the string that should appear as the target
7540 of the link (this will be a pathname relative to the
7541 directory in which the link resides) as the first argument
7546 For example, in your <prgn>Makefile</prgn> or
7547 <file>debian/rules</file>, you can do things like:
7548 <example compact="compact">
7549 ln -fs gcc $(prefix)/bin/cc
7550 ln -fs gcc debian/tmp/usr/bin/cc
7551 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7552 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7557 A symbolic link pointing to a compressed file should always
7558 have the same file extension as the referenced file. (For
7559 example, if a file <file>foo.gz</file> is referenced by a
7560 symbolic link, the filename of the link has to end with
7561 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7566 <heading>Device files</heading>
7569 Packages must not include device files or named pipes in the
7574 If a package needs any special device files that are not
7575 included in the base system, it must call
7576 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7577 after notifying the user<footnote>
7578 This notification could be done via a (low-priority)
7579 debconf message, or an echo (printf) statement.
7584 Packages must not remove any device files in the
7585 <prgn>postrm</prgn> or any other script. This is left to the
7586 system administrator.
7590 Debian uses the serial devices
7591 <file>/dev/ttyS*</file>. Programs using the old
7592 <file>/dev/cu*</file> devices should be changed to use
7593 <file>/dev/ttyS*</file>.
7597 Named pipes needed by the package must be created in
7598 the <prgn>postinst</prgn> script<footnote>
7599 It's better to use <prgn>mkfifo</prgn> rather
7600 than <prgn>mknod</prgn> to create named pipes so that
7601 automated checks for packages incorrectly creating device
7602 files with <prgn>mknod</prgn> won't have false positives.
7603 </footnote> and removed in
7604 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
7609 <sect id="config-files">
7610 <heading>Configuration files</heading>
7613 <heading>Definitions</heading>
7617 <tag>configuration file</tag>
7619 A file that affects the operation of a program, or
7620 provides site- or host-specific information, or
7621 otherwise customizes the behavior of a program.
7622 Typically, configuration files are intended to be
7623 modified by the system administrator (if needed or
7624 desired) to conform to local policy or to provide
7625 more useful site-specific behavior.
7628 <tag><tt>conffile</tt></tag>
7630 A file listed in a package's <tt>conffiles</tt>
7631 file, and is treated specially by <prgn>dpkg</prgn>
7632 (see <ref id="configdetails">).
7638 The distinction between these two is important; they are
7639 not interchangeable concepts. Almost all
7640 <tt>conffile</tt>s are configuration files, but many
7641 configuration files are not <tt>conffiles</tt>.
7645 As noted elsewhere, <file>/etc/init.d</file> scripts,
7646 <file>/etc/default</file> files, scripts installed in
7647 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7648 configuration installed in <file>/etc/cron.d</file> must be
7649 treated as configuration files. In general, any script that
7650 embeds configuration information is de-facto a configuration
7651 file and should be treated as such.
7656 <heading>Location</heading>
7659 Any configuration files created or used by your package
7660 must reside in <file>/etc</file>. If there are several,
7661 consider creating a subdirectory of <file>/etc</file>
7662 named after your package.
7666 If your package creates or uses configuration files
7667 outside of <file>/etc</file>, and it is not feasible to modify
7668 the package to use <file>/etc</file> directly, put the files
7669 in <file>/etc</file> and create symbolic links to those files
7670 from the location that the package requires.
7675 <heading>Behavior</heading>
7678 Configuration file handling must conform to the following
7680 <list compact="compact">
7682 local changes must be preserved during a package
7686 configuration files must be preserved when the
7687 package is removed, and only deleted when the
7691 Obsolete configuration files without local changes may be
7692 removed by the package during upgrade.
7696 The easy way to achieve this behavior is to make the
7697 configuration file a <tt>conffile</tt>. This is
7698 appropriate only if it is possible to distribute a default
7699 version that will work for most installations, although
7700 some system administrators may choose to modify it. This
7701 implies that the default version will be part of the
7702 package distribution, and must not be modified by the
7703 maintainer scripts during installation (or at any other
7708 In order to ensure that local changes are preserved
7709 correctly, no package may contain or make hard links to
7710 conffiles.<footnote>
7711 Rationale: There are two problems with hard links.
7712 The first is that some editors break the link while
7713 editing one of the files, so that the two files may
7714 unwittingly become unlinked and different. The second
7715 is that <prgn>dpkg</prgn> might break the hard link
7716 while upgrading <tt>conffile</tt>s.
7721 The other way to do it is via the maintainer scripts. In
7722 this case, the configuration file must not be listed as a
7723 <tt>conffile</tt> and must not be part of the package
7724 distribution. If the existence of a file is required for
7725 the package to be sensibly configured it is the
7726 responsibility of the package maintainer to provide
7727 maintainer scripts which correctly create, update and
7728 maintain the file and remove it on purge. (See <ref
7729 id="maintainerscripts"> for more information.) These
7730 scripts must be idempotent (i.e., must work correctly if
7731 <prgn>dpkg</prgn> needs to re-run them due to errors
7732 during installation or removal), must cope with all the
7733 variety of ways <prgn>dpkg</prgn> can call maintainer
7734 scripts, must not overwrite or otherwise mangle the user's
7735 configuration without asking, must not ask unnecessary
7736 questions (particularly during upgrades), and must
7737 otherwise be good citizens.
7741 The scripts are not required to configure every possible
7742 option for the package, but only those necessary to get
7743 the package running on a given system. Ideally the
7744 sysadmin should not have to do any configuration other
7745 than that done (semi-)automatically by the
7746 <prgn>postinst</prgn> script.
7750 A common practice is to create a script called
7751 <file><var>package</var>-configure</file> and have the
7752 package's <prgn>postinst</prgn> call it if and only if the
7753 configuration file does not already exist. In certain
7754 cases it is useful for there to be an example or template
7755 file which the maintainer scripts use. Such files should
7756 be in <file>/usr/share/<var>package</var></file> or
7757 <file>/usr/lib/<var>package</var></file> (depending on whether
7758 they are architecture-independent or not). There should
7759 be symbolic links to them from
7760 <file>/usr/share/doc/<var>package</var>/examples</file> if
7761 they are examples, and should be perfectly ordinary
7762 <prgn>dpkg</prgn>-handled files (<em>not</em>
7763 configuration files).
7767 These two styles of configuration file handling must
7768 not be mixed, for that way lies madness:
7769 <prgn>dpkg</prgn> will ask about overwriting the file
7770 every time the package is upgraded.
7775 <heading>Sharing configuration files</heading>
7778 Packages which specify the same file as a
7779 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7780 with each other. (This is an instance of the general rule
7781 about not sharing files. Note that neither alternatives
7782 nor diversions are likely to be appropriate in this case;
7783 in particular, <prgn>dpkg</prgn> does not handle diverted
7784 <tt>conffile</tt>s well.)
7788 The maintainer scripts must not alter a <tt>conffile</tt>
7789 of <em>any</em> package, including the one the scripts
7794 If two or more packages use the same configuration file
7795 and it is reasonable for both to be installed at the same
7796 time, one of these packages must be defined as
7797 <em>owner</em> of the configuration file, i.e., it will be
7798 the package which handles that file as a configuration
7799 file. Other packages that use the configuration file must
7800 depend on the owning package if they require the
7801 configuration file to operate. If the other package will
7802 use the configuration file if present, but is capable of
7803 operating without it, no dependency need be declared.
7807 If it is desirable for two or more related packages to
7808 share a configuration file <em>and</em> for all of the
7809 related packages to be able to modify that configuration
7810 file, then the following should be done:
7811 <enumlist compact="compact">
7813 One of the related packages (the "owning" package)
7814 will manage the configuration file with maintainer
7815 scripts as described in the previous section.
7818 The owning package should also provide a program
7819 that the other packages may use to modify the
7823 The related packages must use the provided program
7824 to make any desired modifications to the
7825 configuration file. They should either depend on
7826 the core package to guarantee that the configuration
7827 modifier program is available or accept gracefully
7828 that they cannot modify the configuration file if it
7829 is not. (This is in addition to the fact that the
7830 configuration file may not even be present in the
7837 Sometimes it's appropriate to create a new package which
7838 provides the basic infrastructure for the other packages
7839 and which manages the shared configuration files. (The
7840 <tt>sgml-base</tt> package is a good example.)
7845 <heading>User configuration files ("dotfiles")</heading>
7848 The files in <file>/etc/skel</file> will automatically be
7849 copied into new user accounts by <prgn>adduser</prgn>.
7850 No other program should reference the files in
7851 <file>/etc/skel</file>.
7855 Therefore, if a program needs a dotfile to exist in
7856 advance in <file>$HOME</file> to work sensibly, that dotfile
7857 should be installed in <file>/etc/skel</file> and treated as a
7862 However, programs that require dotfiles in order to
7863 operate sensibly are a bad thing, unless they do create
7864 the dotfiles themselves automatically.
7868 Furthermore, programs should be configured by the Debian
7869 default installation to behave as closely to the upstream
7870 default behavior as possible.
7874 Therefore, if a program in a Debian package needs to be
7875 configured in some way in order to operate sensibly, that
7876 should be done using a site-wide configuration file placed
7877 in <file>/etc</file>. Only if the program doesn't support a
7878 site-wide default configuration and the package maintainer
7879 doesn't have time to add it may a default per-user file be
7880 placed in <file>/etc/skel</file>.
7884 <file>/etc/skel</file> should be as empty as we can make it.
7885 This is particularly true because there is no easy (or
7886 necessarily desirable) mechanism for ensuring that the
7887 appropriate dotfiles are copied into the accounts of
7888 existing users when a package is installed.
7894 <heading>Log files</heading>
7896 Log files should usually be named
7897 <file>/var/log/<var>package</var>.log</file>. If you have many
7898 log files, or need a separate directory for permission
7899 reasons (<file>/var/log</file> is writable only by
7900 <file>root</file>), you should usually create a directory named
7901 <file>/var/log/<var>package</var></file> and place your log
7906 Log files must be rotated occasionally so that they don't
7907 grow indefinitely; the best way to do this is to drop a log
7908 rotation configuration file into the directory
7909 <file>/etc/logrotate.d</file> and use the facilities provided by
7910 logrotate.<footnote>
7912 The traditional approach to log files has been to set up
7913 <em>ad hoc</em> log rotation schemes using simple shell
7914 scripts and cron. While this approach is highly
7915 customizable, it requires quite a lot of sysadmin work.
7916 Even though the original Debian system helped a little
7917 by automatically installing a system which can be used
7918 as a template, this was deemed not enough.
7922 The use of <prgn>logrotate</prgn>, a program developed
7923 by Red Hat, is better, as it centralizes log management.
7924 It has both a configuration file
7925 (<file>/etc/logrotate.conf</file>) and a directory where
7926 packages can drop their individual log rotation
7927 configurations (<file>/etc/logrotate.d</file>).
7930 Here is a good example for a logrotate config
7931 file (for more information see <manref name="logrotate"
7933 <example compact="compact">
7934 /var/log/foo/*.log {
7939 /etc/init.d/foo force-reload
7943 This rotates all files under <file>/var/log/foo</file>, saves 12
7944 compressed generations, and forces the daemon to reload its
7945 configuration information after the log rotation.
7949 Log files should be removed when the package is
7950 purged (but not when it is only removed). This should be
7951 done by the <prgn>postrm</prgn> script when it is called
7952 with the argument <tt>purge</tt> (see <ref
7953 id="removedetails">).
7958 <heading>Permissions and owners</heading>
7961 The rules in this section are guidelines for general use.
7962 If necessary you may deviate from the details below.
7963 However, if you do so you must make sure that what is done
7964 is secure and you should try to be as consistent as possible
7965 with the rest of the system. You should probably also
7966 discuss it on <prgn>debian-devel</prgn> first.
7970 Files should be owned by <tt>root:root</tt>, and made
7971 writable only by the owner and universally readable (and
7972 executable, if appropriate), that is mode 644 or 755.
7976 Directories should be mode 755 or (for group-writability)
7977 mode 2775. The ownership of the directory should be
7978 consistent with its mode: if a directory is mode 2775, it
7979 should be owned by the group that needs write access to
7982 When a package is upgraded, and the owner or permissions
7983 of a file included in the package has changed, dpkg
7984 arranges for the ownership and permissions to be
7985 correctly set upon installation. However, this does not
7986 extend to directories; the permissions and ownership of
7987 directories already on the system does not change on
7988 install or upgrade of packages. This makes sense, since
7989 otherwise common directories like <tt>/usr</tt> would
7990 always be in flux. To correctly change permissions of a
7991 directory the package owns, explicit action is required,
7992 usually in the <tt>postinst</tt> script. Care must be
7993 taken to handle downgrades as well, in that case.
8000 Setuid and setgid executables should be mode 4755 or 2755
8001 respectively, and owned by the appropriate user or group.
8002 They should not be made unreadable (modes like 4711 or
8003 2711 or even 4111); doing so achieves no extra security,
8004 because anyone can find the binary in the freely available
8005 Debian package; it is merely inconvenient. For the same
8006 reason you should not restrict read or execute permissions
8007 on non-set-id executables.
8011 Some setuid programs need to be restricted to particular
8012 sets of users, using file permissions. In this case they
8013 should be owned by the uid to which they are set-id, and by
8014 the group which should be allowed to execute them. They
8015 should have mode 4754; again there is no point in making
8016 them unreadable to those users who must not be allowed to
8021 It is possible to arrange that the system administrator can
8022 reconfigure the package to correspond to their local
8023 security policy by changing the permissions on a binary:
8024 they can do this by using <prgn>dpkg-statoverride</prgn>, as
8025 described below.<footnote>
8026 Ordinary files installed by <prgn>dpkg</prgn> (as
8027 opposed to <tt>conffile</tt>s and other similar objects)
8028 normally have their permissions reset to the distributed
8029 permissions when the package is reinstalled. However,
8030 the use of <prgn>dpkg-statoverride</prgn> overrides this
8033 Another method you should consider is to create a group for
8034 people allowed to use the program(s) and make any setuid
8035 executables executable only by that group.
8039 If you need to create a new user or group for your package
8040 there are two possibilities. Firstly, you may need to
8041 make some files in the binary package be owned by this
8042 user or group, or you may need to compile the user or
8043 group id (rather than just the name) into the binary
8044 (though this latter should be avoided if possible, as in
8045 this case you need a statically allocated id).</p>
8048 If you need a statically allocated id, you must ask for a
8049 user or group id from the <tt>base-passwd</tt> maintainer,
8050 and must not release the package until you have been
8051 allocated one. Once you have been allocated one you must
8052 either make the package depend on a version of the
8053 <tt>base-passwd</tt> package with the id present in
8054 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
8055 your package to create the user or group itself with the
8056 correct id (using <tt>adduser</tt>) in its
8057 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
8058 the <prgn>postinst</prgn> is to be preferred if it is
8059 possible, otherwise a pre-dependency will be needed on the
8060 <tt>adduser</tt> package.)
8064 On the other hand, the program might be able to determine
8065 the uid or gid from the user or group name at runtime, so
8066 that a dynamically allocated id can be used. In this case
8067 you should choose an appropriate user or group name,
8068 discussing this on <prgn>debian-devel</prgn> and checking
8069 with the <package/base-passwd/ maintainer that it is unique and that
8070 they do not wish you to use a statically allocated id
8071 instead. When this has been checked you must arrange for
8072 your package to create the user or group if necessary using
8073 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
8074 <prgn>postinst</prgn> script (again, the latter is to be
8075 preferred if it is possible).
8079 Note that changing the numeric value of an id associated
8080 with a name is very difficult, and involves searching the
8081 file system for all appropriate files. You need to think
8082 carefully whether a static or dynamic id is required, since
8083 changing your mind later will cause problems.
8086 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
8088 This section is not intended as policy, but as a
8089 description of the use of <prgn>dpkg-statoverride</prgn>.
8093 If a system administrator wishes to have a file (or
8094 directory or other such thing) installed with owner and
8095 permissions different from those in the distributed Debian
8096 package, they can use the <prgn>dpkg-statoverride</prgn>
8097 program to instruct <prgn>dpkg</prgn> to use the different
8098 settings every time the file is installed. Thus the
8099 package maintainer should distribute the files with their
8100 normal permissions, and leave it for the system
8101 administrator to make any desired changes. For example, a
8102 daemon which is normally required to be setuid root, but
8103 in certain situations could be used without being setuid,
8104 should be installed setuid in the <tt>.deb</tt>. Then the
8105 local system administrator can change this if they wish.
8106 If there are two standard ways of doing it, the package
8107 maintainer can use <tt>debconf</tt> to find out the
8108 preference, and call <prgn>dpkg-statoverride</prgn> in the
8109 maintainer script if necessary to accommodate the system
8110 administrator's choice. Care must be taken during
8111 upgrades to not override an existing setting.
8115 Given the above, <prgn>dpkg-statoverride</prgn> is
8116 essentially a tool for system administrators and would not
8117 normally be needed in the maintainer scripts. There is
8118 one type of situation, though, where calls to
8119 <prgn>dpkg-statoverride</prgn> would be needed in the
8120 maintainer scripts, and that involves packages which use
8121 dynamically allocated user or group ids. In such a
8122 situation, something like the following idiom can be very
8123 helpful in the package's <prgn>postinst</prgn>, where
8124 <tt>sysuser</tt> is a dynamically allocated id:
8126 for i in /usr/bin/foo /usr/sbin/bar
8128 # only do something when no setting exists
8129 if ! dpkg-statoverride --list $i >/dev/null 2>&1
8131 #include: debconf processing, question about foo and bar
8132 if [ "$RET" = "true" ] ; then
8133 dpkg-statoverride --update --add sysuser root 4755 $i
8138 The corresponding code to remove the override when the package
8141 for i in /usr/bin/foo /usr/sbin/bar
8143 if dpkg-statoverride --list $i >/dev/null 2>&1
8145 dpkg-statoverride --remove $i
8155 <chapt id="customized-programs">
8156 <heading>Customized programs</heading>
8158 <sect id="arch-spec">
8159 <heading>Architecture specification strings</heading>
8162 If a program needs to specify an <em>architecture specification
8163 string</em> in some place, it should select one of the strings
8164 provided by <tt>dpkg-architecture -L</tt>. The strings are in
8165 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
8166 part is sometimes elided, as when the OS is Linux.
8170 Note that we don't want to use
8171 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
8172 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
8173 since this would make our programs incompatible with other
8174 Linux distributions. We also don't use something like
8175 <tt><var>arch</var>-unknown-linux</tt>, since the
8176 <tt>unknown</tt> does not look very good.
8179 <sect1 id="arch-wildcard-spec">
8180 <heading>Architecture wildcards</heading>
8183 A package may specify an architecture wildcard. Architecture
8184 wildcards are in the format <tt>any</tt> (which matches every
8185 architecture), <tt><var>os</var></tt>-any, or
8186 any-<tt><var>cpu</var></tt>. <footnote>
8187 Internally, the package system normalizes the GNU triplets
8188 and the Debian arches into Debian arch triplets (which are
8189 kind of inverted GNU triplets), with the first component of
8190 the triplet representing the libc and ABI in use, and then
8191 does matching against those triplets. However, such
8192 triplets are an internal implementation detail that should
8193 not be used by packages directly. The libc and ABI portion
8194 is handled internally by the package system based on
8195 the <var>os</var> and <var>cpu</var>.
8202 <heading>Daemons</heading>
8205 The configuration files <file>/etc/services</file>,
8206 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
8207 by the <prgn>netbase</prgn> package and must not be modified
8212 If a package requires a new entry in one of these files, the
8213 maintainer should get in contact with the
8214 <prgn>netbase</prgn> maintainer, who will add the entries
8215 and release a new version of the <prgn>netbase</prgn>
8220 The configuration file <file>/etc/inetd.conf</file> must not be
8221 modified by the package's scripts except via the
8222 <prgn>update-inetd</prgn> script or the
8223 <file>DebianNet.pm</file> Perl module. See their documentation
8224 for details on how to add entries.
8228 If a package wants to install an example entry into
8229 <file>/etc/inetd.conf</file>, the entry must be preceded with
8230 exactly one hash character (<tt>#</tt>). Such lines are
8231 treated as "commented out by user" by the
8232 <prgn>update-inetd</prgn> script and are not changed or
8233 activated during package updates.
8238 <heading>Using pseudo-ttys and modifying wtmp, utmp and
8242 Some programs need to create pseudo-ttys. This should be done
8243 using Unix98 ptys if the C library supports it. The resulting
8244 program must not be installed setuid root, unless that
8245 is required for other functionality.
8249 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
8250 <file>/var/log/lastlog</file> must be installed writable by
8251 group <tt>utmp</tt>. Programs which need to modify those
8252 files must be installed setgid <tt>utmp</tt>.
8257 <heading>Editors and pagers</heading>
8260 Some programs have the ability to launch an editor or pager
8261 program to edit or display a text document. Since there are
8262 lots of different editors and pagers available in the Debian
8263 distribution, the system administrator and each user should
8264 have the possibility to choose their preferred editor and
8269 In addition, every program should choose a good default
8270 editor/pager if none is selected by the user or system
8275 Thus, every program that launches an editor or pager must
8276 use the EDITOR or PAGER environment variable to determine
8277 the editor or pager the user wishes to use. If these
8278 variables are not set, the programs <file>/usr/bin/editor</file>
8279 and <file>/usr/bin/pager</file> should be used, respectively.
8283 These two files are managed through the <prgn>dpkg</prgn>
8284 "alternatives" mechanism. Thus every package providing an
8285 editor or pager must call the
8286 <prgn>update-alternatives</prgn> script to register these
8291 If it is very hard to adapt a program to make use of the
8292 EDITOR or PAGER variables, that program may be configured to
8293 use <file>/usr/bin/sensible-editor</file> and
8294 <file>/usr/bin/sensible-pager</file> as the editor or pager
8295 program respectively. These are two scripts provided in the
8296 <package>sensible-utils</package> package that check the EDITOR
8297 and PAGER variables and launch the appropriate program, and fall
8298 back to <file>/usr/bin/editor</file>
8299 and <file>/usr/bin/pager</file> if the variable is not set.
8303 A program may also use the VISUAL environment variable to
8304 determine the user's choice of editor. If it exists, it
8305 should take precedence over EDITOR. This is in fact what
8306 <file>/usr/bin/sensible-editor</file> does.
8310 It is not required for a package to depend on
8311 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
8312 package to provide such virtual packages.<footnote>
8313 The Debian base system already provides an editor and a
8319 <sect id="web-appl">
8320 <heading>Web servers and applications</heading>
8323 This section describes the locations and URLs that should
8324 be used by all web servers and web applications in the
8331 Cgi-bin executable files are installed in the
8333 <example compact="compact">
8334 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
8336 and should be referred to as
8337 <example compact="compact">
8338 http://localhost/cgi-bin/<var>cgi-bin-name</var>
8344 <p>Access to HTML documents</p>
8347 HTML documents for a package are stored in
8348 <file>/usr/share/doc/<var>package</var></file>
8349 and can be referred to as
8350 <example compact="compact">
8351 http://localhost/doc/<var>package</var>/<var>filename</var>
8356 The web server should restrict access to the document
8357 tree so that only clients on the same host can read
8358 the documents. If the web server does not support such
8359 access controls, then it should not provide access at
8360 all, or ask about providing access during installation.
8365 <p>Access to images</p>
8367 It is recommended that images for a package be stored
8368 in <tt>/usr/share/images/<var>package</var></tt> and
8369 may be referred to through an alias <tt>/images/</tt>
8372 http://localhost/images/<package>/<filename>
8379 <p>Web Document Root</p>
8382 Web Applications should try to avoid storing files in
8383 the Web Document Root. Instead they should use the
8384 /usr/share/doc/<var>package</var> directory for
8385 documents and register the Web Application via the
8386 <package>doc-base</package> package. If access to the
8387 web document root is unavoidable then use
8388 <example compact="compact">
8391 as the Document Root. This might be just a symbolic
8392 link to the location where the system administrator
8393 has put the real document root.
8396 <item><p>Providing httpd and/or httpd-cgi</p>
8398 All web servers should provide the virtual package
8399 <tt>httpd</tt>. If a web server has CGI support it should
8400 provide <tt>httpd-cgi</tt> additionally.
8403 All web applications which do not contain CGI scripts should
8404 depend on <tt>httpd</tt>, all those web applications which
8405 <tt>do</tt> contain CGI scripts, should depend on
8413 <sect id="mail-transport-agents">
8414 <heading>Mail transport, delivery and user agents</heading>
8417 Debian packages which process electronic mail, whether mail
8418 user agents (MUAs) or mail transport agents (MTAs), must
8419 ensure that they are compatible with the configuration
8420 decisions below. Failure to do this may result in lost
8421 mail, broken <tt>From:</tt> lines, and other serious brain
8426 The mail spool is <file>/var/mail</file> and the interface to
8427 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8428 the FHS). On older systems, the mail spool may be
8429 physically located in <file>/var/spool/mail</file>, but all
8430 access to the mail spool should be via the
8431 <file>/var/mail</file> symlink. The mail spool is part of the
8432 base system and not part of the MTA package.
8436 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8437 programs (such as IMAP daemons) must lock the mailbox in an
8438 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8439 be combined with dot locking. To avoid deadlocks, a program
8440 should use <tt>fcntl()</tt> first and dot locking after
8441 this, or alternatively implement the two locking methods in
8442 a non blocking way<footnote>
8443 If it is not possible to establish both locks, the
8444 system shouldn't wait for the second lock to be
8445 established, but remove the first lock, wait a (random)
8446 time, and start over locking again.
8447 </footnote>. Using the functions <tt>maillock</tt> and
8448 <tt>mailunlock</tt> provided by the
8449 <tt>liblockfile*</tt><footnote>
8450 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8451 to use these functions.
8452 </footnote> packages is the recommended way to realize this.
8456 Mailboxes are generally either mode 600 and owned by
8457 <var>user</var> or mode 660 and owned by
8458 <tt><var>user</var>:mail</tt><footnote>
8459 There are two traditional permission schemes for mail spools:
8460 mode 600 with all mail delivery done by processes running as
8461 the destination user, or mode 660 and owned by group mail with
8462 mail delivery done by a process running as a system user in
8463 group mail. Historically, Debian required mode 660 mail
8464 spools to enable the latter model, but that model has become
8465 increasingly uncommon and the principle of least privilege
8466 indicates that mail systems that use the first model should
8467 use permissions of 600. If delivery to programs is permitted,
8468 it's easier to keep the mail system secure if the delivery
8469 agent runs as the destination user. Debian Policy therefore
8470 permits either scheme.
8471 </footnote>. The local system administrator may choose a
8472 different permission scheme; packages should not make
8473 assumptions about the permission and ownership of mailboxes
8474 unless required (such as when creating a new mailbox). A MUA
8475 may remove a mailbox (unless it has nonstandard permissions) in
8476 which case the MTA or another MUA must recreate it if needed.
8480 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8481 be setgid mail to do the locking mentioned above (and
8482 must obviously avoid accessing other users' mailboxes
8483 using this privilege).</p>
8486 <file>/etc/aliases</file> is the source file for the system mail
8487 aliases (e.g., postmaster, usenet, etc.), it is the one
8488 which the sysadmin and <prgn>postinst</prgn> scripts may
8489 edit. After <file>/etc/aliases</file> is edited the program or
8490 human editing it must call <prgn>newaliases</prgn>. All MTA
8491 packages must come with a <prgn>newaliases</prgn> program,
8492 even if it does nothing, but older MTA packages did not do
8493 this so programs should not fail if <prgn>newaliases</prgn>
8494 cannot be found. Note that because of this, all MTA
8495 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8496 <tt>Replaces: mail-transport-agent</tt> control file
8501 The convention of writing <tt>forward to
8502 <var>address</var></tt> in the mailbox itself is not
8503 supported. Use a <tt>.forward</tt> file instead.</p>
8506 The <prgn>rmail</prgn> program used by UUCP
8507 for incoming mail should be <file>/usr/sbin/rmail</file>.
8508 Likewise, <prgn>rsmtp</prgn>, for receiving
8509 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8513 If your package needs to know what hostname to use on (for
8514 example) outgoing news and mail messages which are generated
8515 locally, you should use the file <file>/etc/mailname</file>. It
8516 will contain the portion after the username and <tt>@</tt>
8517 (at) sign for email addresses of users on the machine
8518 (followed by a newline).
8522 Such a package should check for the existence of this file
8523 when it is being configured. If it exists, it should be
8524 used without comment, although an MTA's configuration script
8525 may wish to prompt the user even if it finds that this file
8526 exists. If the file does not exist, the package should
8527 prompt the user for the value (preferably using
8528 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8529 as well as using it in the package's configuration. The
8530 prompt should make it clear that the name will not just be
8531 used by that package. For example, in this situation the
8532 <tt>inn</tt> package could say something like:
8533 <example compact="compact">
8534 Please enter the "mail name" of your system. This is the
8535 hostname portion of the address to be shown on outgoing
8536 news and mail messages. The default is
8537 <var>syshostname</var>, your system's host name. Mail
8538 name ["<var>syshostname</var>"]:
8540 where <var>syshostname</var> is the output of <tt>hostname
8546 <heading>News system configuration</heading>
8549 All the configuration files related to the NNTP (news)
8550 servers and clients should be located under
8551 <file>/etc/news</file>.</p>
8554 There are some configuration issues that apply to a number
8555 of news clients and server packages on the machine. These
8559 <tag><file>/etc/news/organization</file></tag>
8561 A string which should appear as the
8562 organization header for all messages posted
8563 by NNTP clients on the machine
8566 <tag><file>/etc/news/server</file></tag>
8568 Contains the FQDN of the upstream NNTP
8569 server, or localhost if the local machine is
8574 Other global files may be added as required for cross-package news
8581 <heading>Programs for the X Window System</heading>
8584 <heading>Providing X support and package priorities</heading>
8587 Programs that can be configured with support for the X
8588 Window System must be configured to do so and must declare
8589 any package dependencies necessary to satisfy their
8590 runtime requirements when using the X Window System. If
8591 such a package is of higher priority than the X packages
8592 on which it depends, it is required that either the
8593 X-specific components be split into a separate package, or
8594 that an alternative version of the package, which includes
8595 X support, be provided, or that the package's priority be
8601 <heading>Packages providing an X server</heading>
8604 Packages that provide an X server that, directly or
8605 indirectly, communicates with real input and display
8606 hardware should declare in their control data that they
8607 provide the virtual package <tt>xserver</tt>.<footnote>
8608 This implements current practice, and provides an
8609 actual policy for usage of the <tt>xserver</tt>
8610 virtual package which appears in the virtual packages
8611 list. In a nutshell, X servers that interface
8612 directly with the display and input hardware or via
8613 another subsystem (e.g., GGI) should provide
8614 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8615 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8621 <heading>Packages providing a terminal emulator</heading>
8624 Packages that provide a terminal emulator for the X Window
8625 System which meet the criteria listed below should declare
8626 in their control data that they provide the virtual
8627 package <tt>x-terminal-emulator</tt>. They should also
8628 register themselves as an alternative for
8629 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8634 To be an <tt>x-terminal-emulator</tt>, a program must:
8635 <list compact="compact">
8637 Be able to emulate a DEC VT100 terminal, or a
8638 compatible terminal.
8642 Support the command-line option <tt>-e
8643 <var>command</var></tt>, which creates a new
8644 terminal window<footnote>
8645 "New terminal window" does not necessarily mean
8646 a new top-level X window directly parented by
8647 the window manager; it could, if the terminal
8648 emulator application were so coded, be a new
8649 "view" in a multiple-document interface (MDI).
8651 and runs the specified <var>command</var>,
8652 interpreting the entirety of the rest of the command
8653 line as a command to pass straight to exec, in the
8654 manner that <tt>xterm</tt> does.
8658 Support the command-line option <tt>-T
8659 <var>title</var></tt>, which creates a new terminal
8660 window with the window title <var>title</var>.
8667 <heading>Packages providing a window manager</heading>
8670 Packages that provide a window manager should declare in
8671 their control data that they provide the virtual package
8672 <tt>x-window-manager</tt>. They should also register
8673 themselves as an alternative for
8674 <file>/usr/bin/x-window-manager</file>, with a priority
8675 calculated as follows:
8676 <list compact="compact">
8678 Start with a priority of 20.
8682 If the window manager supports the Debian menu
8683 system, add 20 points if this support is available
8684 in the package's default configuration (i.e., no
8685 configuration files belonging to the system or user
8686 have to be edited to activate the feature); if
8687 configuration files must be modified, add only 10
8693 If the window manager complies with <url
8694 id="http://www.freedesktop.org/Standards/wm-spec"
8695 name="The Window Manager Specification Project">,
8696 written by the <url id="http://www.freedesktop.org/"
8697 name="Free Desktop Group">, add 40 points.
8701 If the window manager permits the X session to be
8702 restarted using a <em>different</em> window manager
8703 (without killing the X server) in its default
8704 configuration, add 10 points; otherwise add none.
8711 <heading>Packages providing fonts</heading>
8714 Packages that provide fonts for the X Window
8716 For the purposes of Debian Policy, a "font for the X
8717 Window System" is one which is accessed via X protocol
8718 requests. Fonts for the Linux console, for PostScript
8719 renderer, or any other purpose, do not fit this
8720 definition. Any tool which makes such fonts available
8721 to the X Window System, however, must abide by this
8724 must do a number of things to ensure that they are both
8725 available without modification of the X or font server
8726 configuration, and that they do not corrupt files used by
8727 other font packages to register information about
8731 Fonts of any type supported by the X Window System
8732 must be in a separate binary package from any
8733 executables, libraries, or documentation (except
8734 that specific to the fonts shipped, such as their
8735 license information). If one or more of the fonts
8736 so packaged are necessary for proper operation of
8737 the package with which they are associated the font
8738 package may be Recommended; if the fonts merely
8739 provide an enhancement, a Suggests relationship may
8740 be used. Packages must not Depend on font
8742 This is because the X server may retrieve fonts
8743 from the local file system or over the network
8744 from an X font server; the Debian package system
8745 is empowered to deal only with the local
8751 BDF fonts must be converted to PCF fonts with the
8752 <prgn>bdftopcf</prgn> utility (available in the
8753 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8754 placed in a directory that corresponds to their
8756 <list compact="compact">
8758 100 dpi fonts must be placed in
8759 <file>/usr/share/fonts/X11/100dpi/</file>.
8763 75 dpi fonts must be placed in
8764 <file>/usr/share/fonts/X11/75dpi/</file>.
8768 Character-cell fonts, cursor fonts, and other
8769 low-resolution fonts must be placed in
8770 <file>/usr/share/fonts/X11/misc/</file>.
8776 Type 1 fonts must be placed in
8777 <file>/usr/share/fonts/X11/Type1/</file>. If font
8778 metric files are available, they must be placed here
8783 Subdirectories of <file>/usr/share/fonts/X11/</file>
8784 other than those listed above must be neither
8785 created nor used. (The <file>PEX</file>, <file>CID</file>,
8786 <file>Speedo</file>, and <file>cyrillic</file> directories
8787 are excepted for historical reasons, but installation of
8788 files into these directories remains discouraged.)
8792 Font packages may, instead of placing files directly
8793 in the X font directories listed above, provide
8794 symbolic links in that font directory pointing to
8795 the files' actual location in the filesystem. Such
8796 a location must comply with the FHS.
8800 Font packages should not contain both 75dpi and
8801 100dpi versions of a font. If both are available,
8802 they should be provided in separate binary packages
8803 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8804 the names of the packages containing the
8805 corresponding fonts.
8809 Fonts destined for the <file>misc</file> subdirectory
8810 should not be included in the same package as 75dpi
8811 or 100dpi fonts; instead, they should be provided in
8812 a separate package with <tt>-misc</tt> appended to
8817 Font packages must not provide the files
8818 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8819 <file>fonts.scale</file> in a font directory:
8822 <file>fonts.dir</file> files must not be provided at all.
8826 <file>fonts.alias</file> and <file>fonts.scale</file>
8827 files, if needed, should be provided in the
8829 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8830 where <var>fontdir</var> is the name of the
8832 <file>/usr/share/fonts/X11/</file> where the
8833 package's corresponding fonts are stored
8834 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8835 <var>package</var> is the name of the package
8836 that provides these fonts, and
8837 <var>extension</var> is either <tt>scale</tt>
8838 or <tt>alias</tt>, whichever corresponds to
8845 Font packages must declare a dependency on
8846 <tt>xfonts-utils</tt> in their control
8851 Font packages that provide one or more
8852 <file>fonts.scale</file> files as described above must
8853 invoke <prgn>update-fonts-scale</prgn> on each
8854 directory into which they installed fonts
8855 <em>before</em> invoking
8856 <prgn>update-fonts-dir</prgn> on that directory.
8857 This invocation must occur in both the
8858 <prgn>postinst</prgn> (for all arguments) and
8859 <prgn>postrm</prgn> (for all arguments except
8860 <tt>upgrade</tt>) scripts.
8864 Font packages that provide one or more
8865 <file>fonts.alias</file> files as described above must
8866 invoke <prgn>update-fonts-alias</prgn> on each
8867 directory into which they installed fonts. This
8868 invocation must occur in both the
8869 <prgn>postinst</prgn> (for all arguments) and
8870 <prgn>postrm</prgn> (for all arguments except
8871 <tt>upgrade</tt>) scripts.
8875 Font packages must invoke
8876 <prgn>update-fonts-dir</prgn> on each directory into
8877 which they installed fonts. This invocation must
8878 occur in both the <prgn>postinst</prgn> (for all
8879 arguments) and <prgn>postrm</prgn> (for all
8880 arguments except <tt>upgrade</tt>) scripts.
8884 Font packages must not provide alias names for the
8885 fonts they include which collide with alias names
8886 already in use by fonts already packaged.
8890 Font packages must not provide fonts with the same
8891 XLFD registry name as another font already packaged.
8897 <sect1 id="appdefaults">
8898 <heading>Application defaults files</heading>
8901 Application defaults files must be installed in the
8902 directory <file>/etc/X11/app-defaults/</file> (use of a
8903 localized subdirectory of <file>/etc/X11/</file> as described
8904 in the <em>X Toolkit Intrinsics - C Language
8905 Interface</em> manual is also permitted). They must be
8906 registered as <tt>conffile</tt>s or handled as
8907 configuration files.
8911 Customization of programs' X resources may also be
8912 supported with the provision of a file with the same name
8913 as that of the package placed in
8914 the <file>/etc/X11/Xresources/</file> directory, which
8915 must be registered as a <tt>conffile</tt> or handled as a
8916 configuration file.<footnote>
8917 Note that this mechanism is not the same as using
8918 app-defaults; app-defaults are tied to the client
8919 binary on the local file system, whereas X resources
8920 are stored in the X server and affect all connecting
8927 <heading>Installation directory issues</heading>
8930 Historically, packages using the X Window System used a
8931 separate set of installation directories from other packages.
8932 This practice has been discontinued and packages using the X
8933 Window System should now generally be installed in the same
8934 directories as any other package. Specifically, packages must
8935 not install files under the <file>/usr/X11R6/</file> directory
8936 and the <file>/usr/X11R6/</file> directory hierarchy should be
8937 regarded as obsolete.
8941 Include files previously installed under
8942 <file>/usr/X11R6/include/X11/</file> should be installed into
8943 <file>/usr/include/X11/</file>. For files previously
8944 installed into subdirectories of
8945 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
8946 determine if subdirectories of <file>/usr/lib/</file> and
8947 <file>/usr/share/</file> can be used. If not, a subdirectory
8948 of <file>/usr/lib/X11/</file> should be used.
8952 Configuration files for window, display, or session managers
8953 or other applications that are tightly integrated with the X
8954 Window System may be placed in a subdirectory
8955 of <file>/etc/X11/</file> corresponding to the package name.
8956 Other X Window System applications should use
8957 the <file>/etc/</file> directory unless otherwise mandated by
8958 policy (such as for <ref id="appdefaults">).
8963 <heading>The OSF/Motif and OpenMotif libraries</heading>
8966 <em>Programs that require the non-DFSG-compliant OSF/Motif or
8967 OpenMotif libraries</em><footnote>
8968 OSF/Motif and OpenMotif are collectively referred to as
8969 "Motif" in this policy document.
8971 should be compiled against and tested with LessTif (a free
8972 re-implementation of Motif) instead. If the maintainer
8973 judges that the program or programs do not work
8974 sufficiently well with LessTif to be distributed and
8975 supported, but do so when compiled against Motif, then two
8976 versions of the package should be created; one linked
8977 statically against Motif and with <tt>-smotif</tt>
8978 appended to the package name, and one linked dynamically
8979 against Motif and with <tt>-dmotif</tt> appended to the
8984 Both Motif-linked versions are dependent
8985 upon non-DFSG-compliant software and thus cannot be
8986 uploaded to the <em>main</em> distribution; if the
8987 software is itself DFSG-compliant it may be uploaded to
8988 the <em>contrib</em> distribution. While known existing
8989 versions of Motif permit unlimited redistribution of
8990 binaries linked against the library (whether statically or
8991 dynamically), it is the package maintainer's
8992 responsibility to determine whether this is permitted by
8993 the license of the copy of Motif in their possession.
8999 <heading>Perl programs and modules</heading>
9002 Perl programs and modules should follow the current Perl policy.
9006 The Perl policy can be found in the <tt>perl-policy</tt>
9007 files in the <tt>debian-policy</tt> package.
9008 It is also available from the Debian web mirrors at
9009 <tt><url name="/doc/packaging-manuals/perl-policy/"
9010 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
9015 <heading>Emacs lisp programs</heading>
9018 Please refer to the "Debian Emacs Policy" for details of how to
9019 package emacs lisp programs.
9023 The Emacs policy is available in
9024 <file>debian-emacs-policy.gz</file> of the
9025 <package>emacsen-common</package> package.
9026 It is also available from the Debian web mirrors at
9027 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
9028 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
9033 <heading>Games</heading>
9036 The permissions on <file>/var/games</file> are mode 755, owner
9037 <tt>root</tt> and group <tt>root</tt>.
9041 Each game decides on its own security policy.</p>
9044 Games which require protected, privileged access to
9045 high-score files, saved games, etc., may be made
9046 set-<em>group</em>-id (mode 2755) and owned by
9047 <tt>root:games</tt>, and use files and directories with
9048 appropriate permissions (770 <tt>root:games</tt>, for
9049 example). They must not be made
9050 set-<em>user</em>-id, as this causes security problems. (If
9051 an attacker can subvert any set-user-id game they can
9052 overwrite the executable of any other, causing other players
9053 of these games to run a Trojan horse program. With a
9054 set-group-id game the attacker only gets access to less
9055 important game data, and if they can get at the other
9056 players' accounts at all it will take considerably more
9060 Some packages, for example some fortune cookie programs, are
9061 configured by the upstream authors to install with their
9062 data files or other static information made unreadable so
9063 that they can only be accessed through set-id programs
9064 provided. You should not do this in a Debian package: anyone can
9065 download the <file>.deb</file> file and read the data from it,
9066 so there is no point making the files unreadable. Not
9067 making the files unreadable also means that you don't have
9068 to make so many programs set-id, which reduces the risk of a
9072 As described in the FHS, binaries of games should be
9073 installed in the directory <file>/usr/games</file>. This also
9074 applies to games that use the X Window System. Manual pages
9075 for games (X and non-X games) should be installed in
9076 <file>/usr/share/man/man6</file>.</p>
9082 <heading>Documentation</heading>
9085 <heading>Manual pages</heading>
9088 You should install manual pages in <prgn>nroff</prgn> source
9089 form, in appropriate places under <file>/usr/share/man</file>.
9090 You should only use sections 1 to 9 (see the FHS for more
9091 details). You must not install a pre-formatted "cat page".
9095 Each program, utility, and function should have an
9096 associated manual page included in the same package. It is
9097 suggested that all configuration files also have a manual
9098 page included as well. Manual pages for protocols and other
9099 auxiliary things are optional.
9103 If no manual page is available, this is considered as a bug
9104 and should be reported to the Debian Bug Tracking System (the
9105 maintainer of the package is allowed to write this bug report
9106 themselves, if they so desire). Do not close the bug report
9107 until a proper man page is available.<footnote>
9108 It is not very hard to write a man page. See the
9109 <url id="http://www.schweikhardt.net/man_page_howto.html"
9110 name="Man-Page-HOWTO">,
9111 <manref name="man" section="7">, the examples
9112 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
9113 the helper program <prgn>help2man</prgn>, or the
9114 directory <file>/usr/share/doc/man-db/examples</file>.
9119 You may forward a complaint about a missing man page to the
9120 upstream authors, and mark the bug as forwarded in the
9121 Debian bug tracking system. Even though the GNU Project do
9122 not in general consider the lack of a man page to be a bug,
9123 we do; if they tell you that they don't consider it a bug
9124 you should leave the bug in our bug tracking system open
9129 Manual pages should be installed compressed using <tt>gzip -9</tt>.
9133 If one man page needs to be accessible via several names it
9134 is better to use a symbolic link than the <file>.so</file>
9135 feature, but there is no need to fiddle with the relevant
9136 parts of the upstream source to change from <file>.so</file> to
9137 symlinks: don't do it unless it's easy. You should not
9138 create hard links in the manual page directories, nor put
9139 absolute filenames in <file>.so</file> directives. The filename
9140 in a <file>.so</file> in a man page should be relative to the
9141 base of the man page tree (usually
9142 <file>/usr/share/man</file>). If you do not create any links
9143 (whether symlinks, hard links, or <tt>.so</tt> directives)
9144 in the file system to the alternate names of the man page,
9145 then you should not rely on <prgn>man</prgn> finding your
9146 man page under those names based solely on the information in
9147 the man page's header.<footnote>
9148 Supporting this in <prgn>man</prgn> often requires
9149 unreasonable processing time to find a manual page or to
9150 report that none exists, and moves knowledge into man's
9151 database that would be better left in the file system.
9152 This support is therefore deprecated and will cease to
9153 be present in the future.
9158 Manual pages in locale-specific subdirectories of
9159 <file>/usr/share/man</file> should use either UTF-8 or the usual
9160 legacy encoding for that language (normally the one corresponding
9161 to the shortest relevant locale name in
9162 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
9163 <file>/usr/share/man/fr</file> should use either UTF-8 or
9164 ISO-8859-1.<footnote>
9165 <prgn>man</prgn> will automatically detect whether UTF-8 is in
9166 use. In future, all manual pages will be required to use
9172 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
9173 included in the subdirectory name unless it indicates a
9174 significant difference in the language, as this excludes
9175 speakers of the language in other countries.<footnote>
9176 At the time of writing, Chinese and Portuguese are the main
9177 languages with such differences, so <file>pt_BR</file>,
9178 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
9183 If a localized version of a manual page is provided, it should
9184 either be up-to-date or it should be obvious to the reader that
9185 it is outdated and the original manual page should be used
9186 instead. This can be done either by a note at the beginning of
9187 the manual page or by showing the missing or changed portions in
9188 the original language instead of the target language.
9193 <heading>Info documents</heading>
9196 Info documents should be installed in <file>/usr/share/info</file>.
9197 They should be compressed with <tt>gzip -9</tt>.
9201 The <prgn>install-info</prgn> program maintains a directory of
9202 installed info documents in <file>/usr/share/info/dir</file> for
9203 the use of info readers.<footnote>
9204 It was previously necessary for packages installing info
9205 documents to run <prgn>install-info</prgn> from maintainer
9206 scripts. This is no longer necessary. The installation
9207 system now uses dpkg triggers.
9209 This file must not be included in packages. Packages containing
9210 info documents should depend on <tt>dpkg (>= 1.15.4) |
9211 install-info</tt> to ensure that the directory file is properly
9212 rebuilt during partial upgrades from Debian 5.0 (lenny) and
9217 Info documents should contain section and directory entry
9218 information in the document for the use
9219 of <prgn>install-info</prgn>. The section should be specified
9220 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
9221 space and the section of this info page. The directory entry or
9222 entries should be included between
9223 a <tt>START-INFO-DIR-ENTRY</tt> line and
9224 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
9226 INFO-DIR-SECTION Individual utilities
9227 START-INFO-DIR-ENTRY
9228 * example: (example). An example info directory entry.
9231 To determine which section to use, you should look
9232 at <file>/usr/share/info/dir</file> on your system and choose
9233 the most relevant (or create a new section if none of the
9234 current sections are relevant).<footnote>
9235 Normally, info documents are generated from Texinfo source.
9236 To include this information in the generated info document, if
9237 it is absent, add commands like:
9239 @dircategory Individual utilities
9241 * example: (example). An example info directory entry.
9244 to the Texinfo source of the document and ensure that the info
9245 documents are rebuilt from source during the package build.
9251 <heading>Additional documentation</heading>
9254 Any additional documentation that comes with the package may
9255 be installed at the discretion of the package maintainer.
9256 Plain text documentation should be installed in the directory
9257 <file>/usr/share/doc/<var>package</var></file>, where
9258 <var>package</var> is the name of the package, and
9259 compressed with <tt>gzip -9</tt> unless it is small.
9263 If a package comes with large amounts of documentation which
9264 many users of the package will not require you should create
9265 a separate binary package to contain it, so that it does not
9266 take up disk space on the machines of users who do not need
9267 or want it installed.</p>
9270 It is often a good idea to put text information files
9271 (<file>README</file>s, changelogs, and so forth) that come with
9272 the source package in <file>/usr/share/doc/<var>package</var></file>
9273 in the binary package. However, you don't need to install
9274 the instructions for building and installing the package, of
9278 Packages must not require the existence of any files in
9279 <file>/usr/share/doc/</file> in order to function
9281 The system administrator should be able to
9282 delete files in <file>/usr/share/doc/</file> without causing
9283 any programs to break.
9285 Any files that are referenced by programs but are also
9286 useful as stand alone documentation should be installed under
9287 <file>/usr/share/<var>package</var>/</file> with symbolic links from
9288 <file>/usr/share/doc/<var>package</var></file>.
9292 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9293 link to another directory in <file>/usr/share/doc</file> only if
9294 the two packages both come from the same source and the
9295 first package Depends on the second.<footnote>
9297 Please note that this does not override the section on
9298 changelog files below, so the file
9299 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
9300 must refer to the changelog for the current version of
9301 <var>package</var> in question. In practice, this means
9302 that the sources of the target and the destination of the
9303 symlink must be the same (same source package and
9310 Former Debian releases placed all additional documentation
9311 in <file>/usr/doc/<var>package</var></file>. This has been
9312 changed to <file>/usr/share/doc/<var>package</var></file>,
9313 and packages must not put documentation in the directory
9314 <file>/usr/doc/<var>package</var></file>. <footnote>
9315 At this phase of the transition, we no longer require a
9316 symbolic link in <file>/usr/doc/</file>. At a later point,
9317 policy shall change to make the symbolic links a bug.
9323 <heading>Preferred documentation formats</heading>
9326 The unification of Debian documentation is being carried out
9330 If your package comes with extensive documentation in a
9331 markup format that can be converted to various other formats
9332 you should if possible ship HTML versions in a binary
9333 package, in the directory
9334 <file>/usr/share/doc/<var>appropriate-package</var></file> or
9335 its subdirectories.<footnote>
9336 The rationale: The important thing here is that HTML
9337 docs should be available in <em>some</em> package, not
9338 necessarily in the main binary package.
9343 Other formats such as PostScript may be provided at the
9344 package maintainer's discretion.
9348 <sect id="copyrightfile">
9349 <heading>Copyright information</heading>
9352 Every package must be accompanied by a verbatim copy of its
9353 copyright information and distribution license in the file
9354 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
9355 file must neither be compressed nor be a symbolic link.
9359 In addition, the copyright file must say where the upstream
9360 sources (if any) were obtained. It should name the original
9361 authors of the package and the Debian maintainer(s) who were
9362 involved with its creation.
9366 Packages in the <em>contrib</em> or <em>non-free</em> archive
9367 areas should state in the copyright file that the package is not
9368 part of the Debian GNU/Linux distribution and briefly explain
9373 A copy of the file which will be installed in
9374 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9375 be in <file>debian/copyright</file> in the source package.
9379 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9380 link to another directory in <file>/usr/share/doc</file> only if
9381 the two packages both come from the same source and the
9382 first package Depends on the second. These rules are
9383 important because copyrights must be extractable by
9388 Packages distributed under the Apache license (version 2.0), the
9389 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
9390 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
9391 1.3) should refer to the corresponding files
9392 under <file>/usr/share/common-licenses</file>,<footnote>
9395 <file>/usr/share/common-licenses/Apache-2.0</file>,
9396 <file>/usr/share/common-licenses/Artistic</file>,
9397 <file>/usr/share/common-licenses/GPL-1</file>,
9398 <file>/usr/share/common-licenses/GPL-2</file>,
9399 <file>/usr/share/common-licenses/GPL-3</file>,
9400 <file>/usr/share/common-licenses/LGPL-2</file>,
9401 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9402 <file>/usr/share/common-licenses/LGPL-3</file>,
9403 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
9404 <file>/usr/share/common-licenses/GFDL-1.3</file>
9405 respectively. The University of California BSD license is
9406 also included in <package>base-files</package> as
9407 <file>/usr/share/common-licenses/BSD</file>, but given the
9408 brevity of this license, its specificity to code whose
9409 copyright is held by the Regents of the University of
9410 California, and the frequency of minor wording changes, its
9411 text should be included in the copyright file rather than
9412 referencing this file.
9414 </footnote> rather than quoting them in the copyright
9419 You should not use the copyright file as a general <file>README</file>
9420 file. If your package has such a file it should be
9421 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9422 <file>README.Debian</file> or some other appropriate place.</p>
9426 <heading>Examples</heading>
9429 Any examples (configurations, source files, whatever),
9430 should be installed in a directory
9431 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9432 files should not be referenced by any program: they're there
9433 for the benefit of the system administrator and users as
9434 documentation only. Architecture-specific example files
9435 should be installed in a directory
9436 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9438 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9439 latter directory itself may be a symbolic link to the
9444 If the purpose of a package is to provide examples, then the
9445 example files may be installed into
9446 <file>/usr/share/doc/<var>package</var></file>.
9450 <sect id="changelogs">
9451 <heading>Changelog files</heading>
9454 Packages that are not Debian-native must contain a
9455 compressed copy of the <file>debian/changelog</file> file from
9456 the Debian source tree in
9457 <file>/usr/share/doc/<var>package</var></file> with the name
9458 <file>changelog.Debian.gz</file>.
9462 If an upstream changelog is available, it should be accessible as
9463 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9464 plain text. If the upstream changelog is distributed in
9465 HTML, it should be made available in that form as
9466 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9467 and a plain text <file>changelog.gz</file> should be generated
9468 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9469 the upstream changelog files do not already conform to this
9470 naming convention, then this may be achieved either by
9471 renaming the files, or by adding a symbolic link, at the
9472 maintainer's discretion.<footnote>
9473 Rationale: People should not have to look in places for
9474 upstream changelogs merely because they are given
9475 different names or are distributed in HTML format.
9480 All of these files should be installed compressed using
9481 <tt>gzip -9</tt>, as they will become large with time even
9482 if they start out small.
9486 If the package has only one changelog which is used both as
9487 the Debian changelog and the upstream one because there is
9488 no separate upstream maintainer then that changelog should
9489 usually be installed as
9490 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9491 there is a separate upstream maintainer, but no upstream
9492 changelog, then the Debian changelog should still be called
9493 <file>changelog.Debian.gz</file>.
9497 For details about the format and contents of the Debian
9498 changelog file, please see <ref id="dpkgchangelog">.
9503 <appendix id="pkg-scope">
9504 <heading>Introduction and scope of these appendices</heading>
9507 These appendices are taken essentially verbatim from the
9508 now-deprecated Packaging Manual, version 3.2.1.0. They are
9509 the chapters which are likely to be of use to package
9510 maintainers and which have not already been included in the
9511 policy document itself. Most of these sections are very likely
9512 not relevant to policy; they should be treated as
9513 documentation for the packaging system. Please note that these
9514 appendices are included for convenience, and for historical
9515 reasons: they used to be part of policy package, and they have
9516 not yet been incorporated into dpkg documentation. However,
9517 they still have value, and hence they are presented here.
9521 They have not yet been checked to ensure that they are
9522 compatible with the contents of policy, and if there are any
9523 contradictions, the version in the main policy document takes
9524 precedence. The remaining chapters of the old Packaging
9525 Manual have also not been read in detail to ensure that there
9526 are not parts which have been left out. Both of these will be
9531 Certain parts of the Packaging manual were integrated into the
9532 Policy Manual proper, and removed from the appendices. Links
9533 have been placed from the old locations to the new ones.
9537 <prgn>dpkg</prgn> is a suite of programs for creating binary
9538 package files and installing and removing them on Unix
9540 <prgn>dpkg</prgn> is targeted primarily at Debian
9541 GNU/Linux, but may work on or be ported to other
9547 The binary packages are designed for the management of
9548 installed executable programs (usually compiled binaries) and
9549 their associated data, though source code examples and
9550 documentation are provided as part of some packages.</p>
9553 This manual describes the technical aspects of creating Debian
9554 binary packages (<file>.deb</file> files). It documents the
9555 behavior of the package management programs
9556 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9557 they interact with packages.</p>
9560 It also documents the interaction between
9561 <prgn>dselect</prgn>'s core and the access method scripts it
9562 uses to actually install the selected packages, and describes
9563 how to create a new access method.</p>
9566 This manual does not go into detail about the options and
9567 usage of the package building and installation tools. It
9568 should therefore be read in conjunction with those programs'
9573 The utility programs which are provided with <prgn>dpkg</prgn>
9574 for managing various system configuration and similar issues,
9575 such as <prgn>update-rc.d</prgn> and
9576 <prgn>install-info</prgn>, are not described in detail here -
9577 please see their man pages.
9581 It is assumed that the reader is reasonably familiar with the
9582 <prgn>dpkg</prgn> System Administrators' manual.
9583 Unfortunately this manual does not yet exist.
9587 The Debian version of the FSF's GNU hello program is provided
9588 as an example for people wishing to create Debian
9589 packages. The Debian <prgn>debmake</prgn> package is
9590 recommended as a very helpful tool in creating and maintaining
9591 Debian packages. However, while the tools and examples are
9592 helpful, they do not replace the need to read and follow the
9593 Policy and Programmer's Manual.</p>
9596 <appendix id="pkg-binarypkg">
9597 <heading>Binary packages (from old Packaging Manual)</heading>
9600 The binary package has two main sections. The first part
9601 consists of various control information files and scripts used
9602 by <prgn>dpkg</prgn> when installing and removing. See <ref
9603 id="pkg-controlarea">.
9607 The second part is an archive containing the files and
9608 directories to be installed.
9612 In the future binary packages may also contain other
9613 components, such as checksums and digital signatures. The
9614 format for the archive is described in full in the
9615 <file>deb(5)</file> man page.
9619 <sect id="pkg-bincreating"><heading>Creating package files -
9620 <prgn>dpkg-deb</prgn>
9624 All manipulation of binary package files is done by
9625 <prgn>dpkg-deb</prgn>; it's the only program that has
9626 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9627 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9628 will spot that the options requested are appropriate to
9629 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9634 In order to create a binary package you must make a
9635 directory tree which contains all the files and directories
9636 you want to have in the file system data part of the package.
9637 In Debian-format source packages this directory is usually
9638 <file>debian/tmp</file>, relative to the top of the package's
9643 They should have the locations (relative to the root of the
9644 directory tree you're constructing) ownerships and
9645 permissions which you want them to have on the system when
9650 With current versions of <prgn>dpkg</prgn> the uid/username
9651 and gid/groupname mappings for the users and groups being
9652 used should be the same on the system where the package is
9653 built and the one where it is installed.
9657 You need to add one special directory to the root of the
9658 miniature file system tree you're creating:
9659 <prgn>DEBIAN</prgn>. It should contain the control
9660 information files, notably the binary package control file
9661 (see <ref id="pkg-controlfile">).
9665 The <prgn>DEBIAN</prgn> directory will not appear in the
9666 file system archive of the package, and so won't be installed
9667 by <prgn>dpkg</prgn> when the package is installed.
9671 When you've prepared the package, you should invoke:
9673 dpkg --build <var>directory</var>
9678 This will build the package in
9679 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9680 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9681 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9686 See the man page <manref name="dpkg-deb" section="8"> for details of how
9687 to examine the contents of this newly-created file. You may find the
9688 output of following commands enlightening:
9690 dpkg-deb --info <var>filename</var>.deb
9691 dpkg-deb --contents <var>filename</var>.deb
9692 dpkg --contents <var>filename</var>.deb
9694 To view the copyright file for a package you could use this command:
9696 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
9701 <sect id="pkg-controlarea">
9702 <heading>Package control information files</heading>
9705 The control information portion of a binary package is a
9706 collection of files with names known to <prgn>dpkg</prgn>.
9707 It will treat the contents of these files specially - some
9708 of them contain information used by <prgn>dpkg</prgn> when
9709 installing or removing the package; others are scripts which
9710 the package maintainer wants <prgn>dpkg</prgn> to run.
9714 It is possible to put other files in the package control
9715 area, but this is not generally a good idea (though they
9716 will largely be ignored).
9720 Here is a brief list of the control info files supported by
9721 <prgn>dpkg</prgn> and a summary of what they're used for.
9726 <tag><tt>control</tt>
9729 This is the key description file used by
9730 <prgn>dpkg</prgn>. It specifies the package's name
9731 and version, gives its description for the user,
9732 states its relationships with other packages, and so
9733 forth. See <ref id="sourcecontrolfiles"> and
9734 <ref id="binarycontrolfiles">.
9738 It is usually generated automatically from information
9739 in the source package by the
9740 <prgn>dpkg-gencontrol</prgn> program, and with
9741 assistance from <prgn>dpkg-shlibdeps</prgn>.
9742 See <ref id="pkg-sourcetools">.
9746 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9751 These are executable files (usually scripts) which
9752 <prgn>dpkg</prgn> runs during installation, upgrade
9753 and removal of packages. They allow the package to
9754 deal with matters which are particular to that package
9755 or require more complicated processing than that
9756 provided by <prgn>dpkg</prgn>. Details of when and
9757 how they are called are in <ref id="maintainerscripts">.
9761 It is very important to make these scripts idempotent.
9762 See <ref id="idempotency">.
9766 The maintainer scripts are not guaranteed to run with a
9767 controlling terminal and may not be able to interact with
9768 the user. See <ref id="controllingterminal">.
9772 <tag><tt>conffiles</tt>
9775 This file contains a list of configuration files which
9776 are to be handled automatically by <prgn>dpkg</prgn>
9777 (see <ref id="pkg-conffiles">). Note that not necessarily
9778 every configuration file should be listed here.
9781 <tag><tt>shlibs</tt>
9784 This file contains a list of the shared libraries
9785 supplied by the package, with dependency details for
9786 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9787 when it determines what dependencies are required in a
9788 package control file. The <tt>shlibs</tt> file format
9789 is described on <ref id="shlibs">.
9794 <sect id="pkg-controlfile">
9795 <heading>The main control information file: <tt>control</tt></heading>
9798 The most important control information file used by
9799 <prgn>dpkg</prgn> when it installs a package is
9800 <tt>control</tt>. It contains all the package's "vital
9805 The binary package control files of packages built from
9806 Debian sources are made by a special tool,
9807 <prgn>dpkg-gencontrol</prgn>, which reads
9808 <file>debian/control</file> and <file>debian/changelog</file> to
9809 find the information it needs. See <ref id="pkg-sourcepkg"> for
9814 The fields in binary package control files are listed in
9815 <ref id="binarycontrolfiles">.
9819 A description of the syntax of control files and the purpose
9820 of the fields is available in <ref id="controlfields">.
9825 <heading>Time Stamps</heading>
9828 See <ref id="timestamps">.
9833 <appendix id="pkg-sourcepkg">
9834 <heading>Source packages (from old Packaging Manual) </heading>
9837 The Debian binary packages in the distribution are generated
9838 from Debian sources, which are in a special format to assist
9839 the easy and automatic building of binaries.
9842 <sect id="pkg-sourcetools">
9843 <heading>Tools for processing source packages</heading>
9846 Various tools are provided for manipulating source packages;
9847 they pack and unpack sources and help build of binary
9848 packages and help manage the distribution of new versions.
9852 They are introduced and typical uses described here; see
9853 <manref name="dpkg-source" section="1"> for full
9854 documentation about their arguments and operation.
9858 For examples of how to construct a Debian source package,
9859 and how to use those utilities that are used by Debian
9860 source packages, please see the <prgn>hello</prgn> example
9864 <sect1 id="pkg-dpkg-source">
9866 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9871 This program is frequently used by hand, and is also
9872 called from package-independent automated building scripts
9873 such as <prgn>dpkg-buildpackage</prgn>.
9877 To unpack a package it is typically invoked with
9879 dpkg-source -x <var>.../path/to/filename</var>.dsc
9884 with the <file><var>filename</var>.tar.gz</file> and
9885 <file><var>filename</var>.diff.gz</file> (if applicable) in
9886 the same directory. It unpacks into
9887 <file><var>package</var>-<var>version</var></file>, and if
9889 <file><var>package</var>-<var>version</var>.orig</file>, in
9890 the current directory.
9894 To create a packed source archive it is typically invoked:
9896 dpkg-source -b <var>package</var>-<var>version</var>
9901 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
9902 <file>.diff.gz</file> (if appropriate) in the current
9903 directory. <prgn>dpkg-source</prgn> does not clean the
9904 source tree first - this must be done separately if it is
9909 See also <ref id="pkg-sourcearchives">.</p>
9913 <sect1 id="pkg-dpkg-buildpackage">
9915 <prgn>dpkg-buildpackage</prgn> - overall package-building
9920 <prgn>dpkg-buildpackage</prgn> is a script which invokes
9921 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
9922 targets <tt>clean</tt>, <tt>build</tt> and
9923 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
9924 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
9925 source and binary package upload.
9929 It is usually invoked by hand from the top level of the
9930 built or unbuilt source directory. It may be invoked with
9931 no arguments; useful arguments include:
9932 <taglist compact="compact">
9933 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
9936 Do not sign the <tt>.changes</tt> file or the
9937 source package <tt>.dsc</tt> file, respectively.</p>
9939 <tag><tt>-p<var>sign-command</var></tt></tag>
9942 Invoke <var>sign-command</var> instead of finding
9943 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
9944 <var>sign-command</var> must behave just like
9945 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
9947 <tag><tt>-r<var>root-command</var></tt></tag>
9950 When root privilege is required, invoke the command
9951 <var>root-command</var>. <var>root-command</var>
9952 should invoke its first argument as a command, from
9953 the <prgn>PATH</prgn> if necessary, and pass its
9954 second and subsequent arguments to the command it
9955 calls. If no <var>root-command</var> is supplied
9956 then <var>dpkg-buildpackage</var> will take no
9957 special action to gain root privilege, so that for
9958 most packages it will have to be invoked as root to
9961 <tag><tt>-b</tt>, <tt>-B</tt></tag>
9964 Two types of binary-only build and upload - see
9965 <manref name="dpkg-source" section="1">.
9972 <sect1 id="pkg-dpkg-gencontrol">
9974 <prgn>dpkg-gencontrol</prgn> - generates binary package
9979 This program is usually called from <file>debian/rules</file>
9980 (see <ref id="pkg-sourcetree">) in the top level of the source
9985 This is usually done just before the files and directories in the
9986 temporary directory tree where the package is being built have their
9987 permissions and ownerships set and the package is constructed using
9988 <prgn>dpkg-deb/</prgn>
9990 This is so that the control file which is produced has
9991 the right permissions
9996 <prgn>dpkg-gencontrol</prgn> must be called after all the
9997 files which are to go into the package have been placed in
9998 the temporary build directory, so that its calculation of
9999 the installed size of a package is correct.
10003 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
10004 be run after <prgn>dpkg-shlibdeps</prgn> so that the
10005 variable substitutions created by
10006 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
10011 For a package which generates only one binary package, and
10012 which builds it in <file>debian/tmp</file> relative to the top
10013 of the source package, it is usually sufficient to call
10014 <prgn>dpkg-gencontrol</prgn>.
10018 Sources which build several binaries will typically need
10021 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
10022 </example> The <tt>-P</tt> tells
10023 <prgn>dpkg-gencontrol</prgn> that the package is being
10024 built in a non-default directory, and the <tt>-p</tt>
10025 tells it which package's control file should be generated.
10029 <prgn>dpkg-gencontrol</prgn> also adds information to the
10030 list of files in <file>debian/files</file>, for the benefit of
10031 (for example) a future invocation of
10032 <prgn>dpkg-genchanges</prgn>.</p>
10035 <sect1 id="pkg-dpkg-shlibdeps">
10037 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
10042 This program is usually called from <file>debian/rules</file>
10043 just before <prgn>dpkg-gencontrol</prgn> (see <ref
10044 id="pkg-sourcetree">), in the top level of the source tree.
10048 Its arguments are executables and shared libraries
10051 They may be specified either in the locations in the
10052 source tree where they are created or in the locations
10053 in the temporary build tree where they are installed
10054 prior to binary package creation.
10056 </footnote> for which shared library dependencies should
10057 be included in the binary package's control file.
10061 If some of the found shared libraries should only
10062 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
10063 some warrant a <tt>Pre-Depends</tt>, this can be achieved
10064 by using the <tt>-d<var>dependency-field</var></tt> option
10065 before those executable(s). (Each <tt>-d</tt> option
10066 takes effect until the next <tt>-d</tt>.)
10070 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
10071 output control file to be modified. Instead by default it
10072 adds to the <file>debian/substvars</file> file variable
10073 settings like <tt>shlibs:Depends</tt>. These variable
10074 settings must be referenced in dependency fields in the
10075 appropriate per-binary-package sections of the source
10080 For example, a package that generates an essential part
10081 which requires dependencies, and optional parts that
10082 which only require a recommendation, would separate those
10083 two sets of dependencies into two different fields.<footnote>
10084 At the time of writing, an example for this was the
10085 <package/xmms/ package, with Depends used for the xmms
10086 executable, Recommends for the plug-ins and Suggests for
10087 even more optional features provided by unzip.
10089 It can say in its <file>debian/rules</file>:
10091 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
10092 -dRecommends <var>optionalpart anotheroptionalpart</var>
10094 and then in its main control file <file>debian/control</file>:
10097 Depends: ${shlibs:Depends}
10098 Recommends: ${shlibs:Recommends}
10104 Sources which produce several binary packages with
10105 different shared library dependency requirements can use
10106 the <tt>-p<var>varnameprefix</var></tt> option to override
10107 the default <tt>shlibs:</tt> prefix (one invocation of
10108 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
10109 They can thus produce several sets of dependency
10110 variables, each of the form
10111 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
10112 which can be referred to in the appropriate parts of the
10113 binary package control files.
10118 <sect1 id="pkg-dpkg-distaddfile">
10120 <prgn>dpkg-distaddfile</prgn> - adds a file to
10121 <file>debian/files</file>
10125 Some packages' uploads need to include files other than
10126 the source and binary package files.
10130 <prgn>dpkg-distaddfile</prgn> adds a file to the
10131 <file>debian/files</file> file so that it will be included in
10132 the <file>.changes</file> file when
10133 <prgn>dpkg-genchanges</prgn> is run.
10137 It is usually invoked from the <tt>binary</tt> target of
10138 <file>debian/rules</file>:
10140 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
10142 The <var>filename</var> is relative to the directory where
10143 <prgn>dpkg-genchanges</prgn> will expect to find it - this
10144 is usually the directory above the top level of the source
10145 tree. The <file>debian/rules</file> target should put the
10146 file there just before or just after calling
10147 <prgn>dpkg-distaddfile</prgn>.
10151 The <var>section</var> and <var>priority</var> are passed
10152 unchanged into the resulting <file>.changes</file> file.
10157 <sect1 id="pkg-dpkg-genchanges">
10159 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
10160 upload control file
10164 This program is usually called by package-independent
10165 automatic building scripts such as
10166 <prgn>dpkg-buildpackage</prgn>, but it may also be called
10171 It is usually called in the top level of a built source
10172 tree, and when invoked with no arguments will print out a
10173 straightforward <file>.changes</file> file based on the
10174 information in the source package's changelog and control
10175 file and the binary and source packages which should have
10181 <sect1 id="pkg-dpkg-parsechangelog">
10183 <prgn>dpkg-parsechangelog</prgn> - produces parsed
10184 representation of a changelog
10188 This program is used internally by
10189 <prgn>dpkg-source</prgn> et al. It may also occasionally
10190 be useful in <file>debian/rules</file> and elsewhere. It
10191 parses a changelog, <file>debian/changelog</file> by default,
10192 and prints a control-file format representation of the
10193 information in it to standard output.
10197 <sect1 id="pkg-dpkg-architecture">
10199 <prgn>dpkg-architecture</prgn> - information about the build and
10204 This program can be used manually, but is also invoked by
10205 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
10206 environment or make variables which specify the build and host
10207 architecture for the package building process.
10212 <sect id="pkg-sourcetree">
10213 <heading>The Debian package source tree</heading>
10216 The source archive scheme described later is intended to
10217 allow a Debian package source tree with some associated
10218 control information to be reproduced and transported easily.
10219 The Debian package source tree is a version of the original
10220 program with certain files added for the benefit of the
10221 packaging process, and with any other changes required
10222 made to the rest of the source code and installation
10227 The extra files created for Debian are in the subdirectory
10228 <file>debian</file> of the top level of the Debian package
10229 source tree. They are described below.
10232 <sect1 id="pkg-debianrules">
10233 <heading><file>debian/rules</file> - the main building script</heading>
10236 See <ref id="debianrules">.
10240 <sect1 id="pkg-srcsubstvars">
10241 <heading><file>debian/substvars</file> and variable substitutions</heading>
10244 See <ref id="substvars">.
10250 <heading><file>debian/files</file></heading>
10253 See <ref id="debianfiles">.
10257 <sect1><heading><file>debian/tmp</file>
10261 This is the canonical temporary location for the
10262 construction of binary packages by the <tt>binary</tt>
10263 target. The directory <file>tmp</file> serves as the root of
10264 the file system tree as it is being constructed (for
10265 example, by using the package's upstream makefiles install
10266 targets and redirecting the output there), and it also
10267 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10268 id="pkg-bincreating">.
10272 If several binary packages are generated from the same
10273 source tree it is usual to use several
10274 <file>debian/tmp<var>something</var></file> directories, for
10275 example <file>tmp-a</file> or <file>tmp-doc</file>.
10279 Whatever <file>tmp</file> directories are created and used by
10280 <tt>binary</tt> must of course be removed by the
10281 <tt>clean</tt> target.</p></sect1>
10285 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10289 As it exists on the FTP site, a Debian source package
10290 consists of three related files. You must have the right
10291 versions of all three to be able to use them.
10296 <tag>Debian source control file - <tt>.dsc</tt></tag>
10298 This file is a control file used by <prgn>dpkg-source</prgn>
10299 to extract a source package.
10300 See <ref id="debiansourcecontrolfiles">.
10304 Original source archive -
10306 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10312 This is a compressed (with <tt>gzip -9</tt>)
10313 <prgn>tar</prgn> file containing the source code from
10314 the upstream authors of the program.
10319 Debian package diff -
10321 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10327 This is a unified context diff (<tt>diff -u</tt>)
10328 giving the changes which are required to turn the
10329 original source into the Debian source. These changes
10330 may only include editing and creating plain files.
10331 The permissions of files, the targets of symbolic
10332 links and the characteristics of special files or
10333 pipes may not be changed and no files may be removed
10338 All the directories in the diff must exist, except the
10339 <file>debian</file> subdirectory of the top of the source
10340 tree, which will be created by
10341 <prgn>dpkg-source</prgn> if necessary when unpacking.
10345 The <prgn>dpkg-source</prgn> program will
10346 automatically make the <file>debian/rules</file> file
10347 executable (see below).</p></item>
10352 If there is no original source code - for example, if the
10353 package is specially prepared for Debian or the Debian
10354 maintainer is the same as the upstream maintainer - the
10355 format is slightly different: then there is no diff, and the
10357 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10358 and preferably contains a directory named
10359 <file><var>package</var>-<var>version</var></file>.
10364 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10367 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10368 Debian source package. However, if it is not available it
10369 is possible to unpack a Debian source archive as follows:
10370 <enumlist compact="compact">
10373 Untar the tarfile, which will create a <file>.orig</file>
10377 <p>Rename the <file>.orig</file> directory to
10378 <file><var>package</var>-<var>version</var></file>.</p>
10382 Create the subdirectory <file>debian</file> at the top of
10383 the source tree.</p>
10385 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10387 <item><p>Untar the tarfile again if you want a copy of the original
10388 source code alongside the Debian version.</p>
10393 It is not possible to generate a valid Debian source archive
10394 without using <prgn>dpkg-source</prgn>. In particular,
10395 attempting to use <prgn>diff</prgn> directly to generate the
10396 <file>.diff.gz</file> file will not work.
10400 <heading>Restrictions on objects in source packages</heading>
10403 The source package may not contain any hard links
10405 This is not currently detected when building source
10406 packages, but only when extracting
10410 Hard links may be permitted at some point in the
10411 future, but would require a fair amount of
10413 </footnote>, device special files, sockets or setuid or
10416 Setgid directories are allowed.
10421 The source packaging tools manage the changes between the
10422 original and Debian source using <prgn>diff</prgn> and
10423 <prgn>patch</prgn>. Turning the original source tree as
10424 included in the <file>.orig.tar.gz</file> into the Debian
10425 package source must not involve any changes which cannot be
10426 handled by these tools. Problematic changes which cause
10427 <prgn>dpkg-source</prgn> to halt with an error when
10428 building the source package are:
10429 <list compact="compact">
10430 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10432 <item><p>Changing the targets of symbolic links.</p>
10434 <item><p>Creating directories, other than <file>debian</file>.</p>
10436 <item><p>Changes to the contents of binary files.</p></item>
10437 </list> Changes which cause <prgn>dpkg-source</prgn> to
10438 print a warning but continue anyway are:
10439 <list compact="compact">
10442 Removing files, directories or symlinks.
10444 Renaming a file is not treated specially - it is
10445 seen as the removal of the old file (which
10446 generates a warning, but is otherwise ignored),
10447 and the creation of the new one.
10453 Changed text files which are missing the usual final
10454 newline (either in the original or the modified
10459 Changes which are not represented, but which are not detected by
10460 <prgn>dpkg-source</prgn>, are:
10461 <list compact="compact">
10462 <item><p>Changing the permissions of files (other than
10463 <file>debian/rules</file>) and directories.</p></item>
10468 The <file>debian</file> directory and <file>debian/rules</file>
10469 are handled specially by <prgn>dpkg-source</prgn> - before
10470 applying the changes it will create the <file>debian</file>
10471 directory, and afterwards it will make
10472 <file>debian/rules</file> world-executable.
10478 <appendix id="pkg-controlfields">
10479 <heading>Control files and their fields (from old Packaging Manual)</heading>
10482 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10483 data in a common format, known as control files. Binary and
10484 source packages have control data as do the <file>.changes</file>
10485 files which control the installation of uploaded files, and
10486 <prgn>dpkg</prgn>'s internal databases are in a similar
10491 <heading>Syntax of control files</heading>
10494 See <ref id="controlsyntax">.
10498 It is important to note that there are several fields which
10499 are optional as far as <prgn>dpkg</prgn> and the related
10500 tools are concerned, but which must appear in every Debian
10501 package, or whose omission may cause problems.
10506 <heading>List of fields</heading>
10509 See <ref id="controlfieldslist">.
10513 This section now contains only the fields that didn't belong
10514 to the Policy manual.
10517 <sect1 id="pkg-f-Filename">
10518 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10521 These fields in <tt>Packages</tt> files give the
10522 filename(s) of (the parts of) a package in the
10523 distribution directories, relative to the root of the
10524 Debian hierarchy. If the package has been split into
10525 several parts the parts are all listed in order, separated
10530 <sect1 id="pkg-f-Size">
10531 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10534 These fields in <file>Packages</file> files give the size (in
10535 bytes, expressed in decimal) and MD5 checksum of the
10536 file(s) which make(s) up a binary package in the
10537 distribution. If the package is split into several parts
10538 the values for the parts are listed in order, separated by
10543 <sect1 id="pkg-f-Status">
10544 <heading><tt>Status</tt></heading>
10547 This field in <prgn>dpkg</prgn>'s status file records
10548 whether the user wants a package installed, removed or
10549 left alone, whether it is broken (requiring
10550 re-installation) or not and what its current state on the
10551 system is. Each of these pieces of information is a
10556 <sect1 id="pkg-f-Config-Version">
10557 <heading><tt>Config-Version</tt></heading>
10560 If a package is not installed or not configured, this
10561 field in <prgn>dpkg</prgn>'s status file records the last
10562 version of the package which was successfully
10567 <sect1 id="pkg-f-Conffiles">
10568 <heading><tt>Conffiles</tt></heading>
10571 This field in <prgn>dpkg</prgn>'s status file contains
10572 information about the automatically-managed configuration
10573 files held by a package. This field should <em>not</em>
10574 appear anywhere in a package!
10579 <heading>Obsolete fields</heading>
10582 These are still recognized by <prgn>dpkg</prgn> but should
10583 not appear anywhere any more.
10585 <taglist compact="compact">
10587 <tag><tt>Revision</tt></tag>
10588 <tag><tt>Package-Revision</tt></tag>
10589 <tag><tt>Package_Revision</tt></tag>
10591 The Debian revision part of the package version was
10592 at one point in a separate control file field. This
10593 field went through several names.
10596 <tag><tt>Recommended</tt></tag>
10597 <item>Old name for <tt>Recommends</tt>.</item>
10599 <tag><tt>Optional</tt></tag>
10600 <item>Old name for <tt>Suggests</tt>.</item>
10602 <tag><tt>Class</tt></tag>
10603 <item>Old name for <tt>Priority</tt>.</item>
10612 <appendix id="pkg-conffiles">
10613 <heading>Configuration file handling (from old Packaging Manual)</heading>
10616 <prgn>dpkg</prgn> can do a certain amount of automatic
10617 handling of package configuration files.
10621 Whether this mechanism is appropriate depends on a number of
10622 factors, but basically there are two approaches to any
10623 particular configuration file.
10627 The easy method is to ship a best-effort configuration in the
10628 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10629 handle updates. If the user is unlikely to want to edit the
10630 file, but you need them to be able to without losing their
10631 changes, and a new package with a changed version of the file
10632 is only released infrequently, this is a good approach.
10636 The hard method is to build the configuration file from
10637 scratch in the <prgn>postinst</prgn> script, and to take the
10638 responsibility for fixing any mistakes made in earlier
10639 versions of the package automatically. This will be
10640 appropriate if the file is likely to need to be different on
10644 <sect><heading>Automatic handling of configuration files by
10649 A package may contain a control area file called
10650 <tt>conffiles</tt>. This file should be a list of filenames
10651 of configuration files needing automatic handling, separated
10652 by newlines. The filenames should be absolute pathnames,
10653 and the files referred to should actually exist in the
10658 When a package is upgraded <prgn>dpkg</prgn> will process
10659 the configuration files during the configuration stage,
10660 shortly before it runs the package's <prgn>postinst</prgn>
10665 For each file it checks to see whether the version of the
10666 file included in the package is the same as the one that was
10667 included in the last version of the package (the one that is
10668 being upgraded from); it also compares the version currently
10669 installed on the system with the one shipped with the last
10674 If neither the user nor the package maintainer has changed
10675 the file, it is left alone. If one or the other has changed
10676 their version, then the changed version is preferred - i.e.,
10677 if the user edits their file, but the package maintainer
10678 doesn't ship a different version, the user's changes will
10679 stay, silently, but if the maintainer ships a new version
10680 and the user hasn't edited it the new version will be
10681 installed (with an informative message). If both have
10682 changed their version the user is prompted about the problem
10683 and must resolve the differences themselves.
10687 The comparisons are done by calculating the MD5 message
10688 digests of the files, and storing the MD5 of the file as it
10689 was included in the most recent version of the package.
10693 When a package is installed for the first time
10694 <prgn>dpkg</prgn> will install the file that comes with it,
10695 unless that would mean overwriting a file already on the
10700 However, note that <prgn>dpkg</prgn> will <em>not</em>
10701 replace a conffile that was removed by the user (or by a
10702 script). This is necessary because with some programs a
10703 missing file produces an effect hard or impossible to
10704 achieve in another way, so that a missing file needs to be
10705 kept that way if the user did it.
10709 Note that a package should <em>not</em> modify a
10710 <prgn>dpkg</prgn>-handled conffile in its maintainer
10711 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10712 the user confusing and possibly dangerous options for
10713 conffile update when the package is upgraded.</p>
10716 <sect><heading>Fully-featured maintainer script configuration
10721 For files which contain site-specific information such as
10722 the hostname and networking details and so forth, it is
10723 better to create the file in the package's
10724 <prgn>postinst</prgn> script.
10728 This will typically involve examining the state of the rest
10729 of the system to determine values and other information, and
10730 may involve prompting the user for some information which
10731 can't be obtained some other way.
10735 When using this method there are a couple of important
10736 issues which should be considered:
10740 If you discover a bug in the program which generates the
10741 configuration file, or if the format of the file changes
10742 from one version to the next, you will have to arrange for
10743 the postinst script to do something sensible - usually this
10744 will mean editing the installed configuration file to remove
10745 the problem or change the syntax. You will have to do this
10746 very carefully, since the user may have changed the file,
10747 perhaps to fix the very problem that your script is trying
10748 to deal with - you will have to detect these situations and
10749 deal with them correctly.
10753 If you do go down this route it's probably a good idea to
10754 make the program that generates the configuration file(s) a
10755 separate program in <file>/usr/sbin</file>, by convention called
10756 <file><var>package</var>config</file> and then run that if
10757 appropriate from the post-installation script. The
10758 <tt><var>package</var>config</tt> program should not
10759 unquestioningly overwrite an existing configuration - if its
10760 mode of operation is geared towards setting up a package for
10761 the first time (rather than any arbitrary reconfiguration
10762 later) you should have it check whether the configuration
10763 already exists, and require a <tt>--force</tt> flag to
10764 overwrite it.</p></sect>
10767 <appendix id="pkg-alternatives"><heading>Alternative versions of
10768 an interface - <prgn>update-alternatives</prgn> (from old
10773 When several packages all provide different versions of the
10774 same program or file it is useful to have the system select a
10775 default, but to allow the system administrator to change it
10776 and have their decisions respected.
10780 For example, there are several versions of the <prgn>vi</prgn>
10781 editor, and there is no reason to prevent all of them from
10782 being installed at once, each under their own name
10783 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10784 Nevertheless it is desirable to have the name <tt>vi</tt>
10785 refer to something, at least by default.
10789 If all the packages involved cooperate, this can be done with
10790 <prgn>update-alternatives</prgn>.
10794 Each package provides its own version under its own name, and
10795 calls <prgn>update-alternatives</prgn> in its postinst to
10796 register its version (and again in its prerm to deregister
10801 See the man page <manref name="update-alternatives"
10802 section="8"> for details.
10806 If <prgn>update-alternatives</prgn> does not seem appropriate
10807 you may wish to consider using diversions instead.</p>
10810 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10811 package's version of a file (from old Packaging Manual)
10815 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10816 when it reinstalls the package it belongs to, and to have it
10817 put the file from the package somewhere else instead.
10821 This can be used locally to override a package's version of a
10822 file, or by one package to override another's version (or
10823 provide a wrapper for it).
10827 Before deciding to use a diversion, read <ref
10828 id="pkg-alternatives"> to see if you really want a diversion
10829 rather than several alternative versions of a program.
10833 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10834 and updated by a special program <prgn>dpkg-divert</prgn>.
10835 Please see <manref name="dpkg-divert" section="8"> for full
10836 details of its operation.
10840 When a package wishes to divert a file from another, it should
10841 call <prgn>dpkg-divert</prgn> in its preinst to add the
10842 diversion and rename the existing file. For example,
10843 supposing that a <prgn>smailwrapper</prgn> package wishes to
10844 install a wrapper around <file>/usr/sbin/smail</file>:
10846 dpkg-divert --package smailwrapper --add --rename \
10847 --divert /usr/sbin/smail.real /usr/sbin/smail
10848 </example> The <tt>--package smailwrapper</tt> ensures that
10849 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
10850 can bypass the diversion and get installed as the true version.
10851 It's safe to add the diversion unconditionally on upgrades since
10852 it will be left unchanged if it already exists, but
10853 <prgn>dpkg-divert</prgn> will display a message. To suppress that
10854 message, make the command conditional on the version from which
10855 the package is being upgraded:
10857 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
10858 dpkg-divert --package smailwrapper --add --rename \
10859 --divert /usr/sbin/smail.real /usr/sbin/smail
10861 </example> where <tt>1.0-2</tt> is the version at which the
10862 diversion was first added to the package. Running the command
10863 during abort-upgrade is pointless but harmless.
10867 The postrm has to do the reverse:
10869 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
10870 dpkg-divert --package smailwrapper --remove --rename \
10871 --divert /usr/sbin/smail.real /usr/sbin/smail
10873 </example> If the diversion was added at a particular version, the
10874 postrm should also handle the failure case of upgrading from an
10875 older version (unless the older version is so old that direct
10876 upgrades are no longer supported):
10878 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
10879 dpkg-divert --package smailwrapper --remove --rename \
10880 --divert /usr/sbin/smail.real /usr/sbin/smail
10882 </example> where <tt>1.02-2</tt> is the version at which the
10883 diversion was first added to the package. The postrm should not
10884 remove the diversion on upgrades both because there's no reason to
10885 remove the diversion only to immediately re-add it and since the
10886 postrm of the old package is run after unpacking so the removal of
10887 the diversion will fail.
10891 Do not attempt to divert a file which is vitally important for
10892 the system's operation - when using <prgn>dpkg-divert</prgn>
10893 there is a time, after it has been diverted but before
10894 <prgn>dpkg</prgn> has installed the new version, when the file
10895 does not exist.</p>
10900 <!-- Local variables: -->
10901 <!-- indent-tabs-mode: t -->
10903 <!-- vim:set ai et sts=2 sw=2 tw=76: -->