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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
1218 belonging to another package without consulting the
1219 maintainer of that package first.
1223 All packages which supply an instance of a common command
1224 name (or, in general, filename) should generally use
1225 <prgn>update-alternatives</prgn>, so that they may be
1226 installed together. If <prgn>update-alternatives</prgn>
1227 is not used, then each package must use
1228 <tt>Conflicts</tt> to ensure that other packages are
1229 de-installed. (In this case, it may be appropriate to
1230 specify a conflict against earlier versions of something
1231 that previously did not use
1232 <prgn>update-alternatives</prgn>; this is an exception to
1233 the usual rule that versioned conflicts should be
1237 <sect1 id="maintscriptprompt">
1238 <heading>Prompting in maintainer scripts</heading>
1240 Package maintainer scripts may prompt the user if
1241 necessary. Prompting must be done by communicating
1242 through a program, such as <prgn>debconf</prgn>, which
1243 conforms to the Debian Configuration Management
1244 Specification, version 2 or higher.
1248 Packages which are essential, or which are dependencies of
1249 essential packages, may fall back on another prompting method
1250 if no such interface is available when they are executed.
1254 The Debian Configuration Management Specification is included
1255 in the <file>debconf_specification</file> files in the
1256 <package>debian-policy</package> package.
1257 It is also available from the Debian web mirrors at
1258 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1259 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1263 Packages which use the Debian Configuration Management
1264 Specification may contain an additional
1265 <prgn>config</prgn> script and a <tt>templates</tt>
1266 file in their control archive<footnote>
1267 The control.tar.gz inside the .deb.
1268 See <manref name="deb" section="5">.
1270 The <prgn>config</prgn> script might be run before the
1271 <prgn>preinst</prgn> script, and before the package is unpacked
1272 or any of its dependencies or pre-dependencies are satisfied.
1273 Therefore it must work using only the tools present in
1274 <em>essential</em> packages.<footnote>
1275 <package>Debconf</package> or another tool that
1276 implements the Debian Configuration Management
1277 Specification will also be installed, and any
1278 versioned dependencies on it will be satisfied
1279 before preconfiguration begins.
1284 Packages which use the Debian Configuration Management
1285 Specification must allow for translation of their user-visible
1286 messages by using a gettext-based system such as the one
1287 provided by the <package>po-debconf</package> package.
1291 Packages should try to minimize the amount of prompting
1292 they need to do, and they should ensure that the user
1293 will only ever be asked each question once. This means
1294 that packages should try to use appropriate shared
1295 configuration files (such as <file>/etc/papersize</file> and
1296 <file>/etc/news/server</file>), and shared
1297 <package>debconf</package> variables rather than each
1298 prompting for their own list of required pieces of
1303 It also means that an upgrade should not ask the same
1304 questions again, unless the user has used
1305 <tt>dpkg --purge</tt> to remove the package's configuration.
1306 The answers to configuration questions should be stored in an
1307 appropriate place in <file>/etc</file> so that the user can
1308 modify them, and how this has been done should be
1313 If a package has a vitally important piece of
1314 information to pass to the user (such as "don't run me
1315 as I am, you must edit the following configuration files
1316 first or you risk your system emitting badly-formatted
1317 messages"), it should display this in the
1318 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1319 prompt the user to hit return to acknowledge the
1320 message. Copyright messages do not count as vitally
1321 important (they belong in
1322 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1323 neither do instructions on how to use a program (these
1324 should be in on-line documentation, where all the users
1329 Any necessary prompting should almost always be confined
1330 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1331 script. If it is done in the <prgn>postinst</prgn>, it
1332 should be protected with a conditional so that
1333 unnecessary prompting doesn't happen if a package's
1334 installation fails and the <prgn>postinst</prgn> is
1335 called with <tt>abort-upgrade</tt>,
1336 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1346 <heading>Source packages</heading>
1348 <sect id="standardsversion">
1349 <heading>Standards conformance</heading>
1352 Source packages should specify the most recent version number
1353 of this policy document with which your package complied
1354 when it was last updated.
1358 This information may be used to file bug reports
1359 automatically if your package becomes too much out of date.
1363 The version is specified in the <tt>Standards-Version</tt>
1365 The format of the <tt>Standards-Version</tt> field is
1366 described in <ref id="f-Standards-Version">.
1370 You should regularly, and especially if your package has
1371 become out of date, check for the newest Policy Manual
1372 available and update your package, if necessary. When your
1373 package complies with the new standards you should update the
1374 <tt>Standards-Version</tt> source package field and
1375 release it.<footnote>
1376 See the file <file>upgrading-checklist</file> for
1377 information about policy which has changed between
1378 different versions of this document.
1384 <sect id="pkg-relations">
1385 <heading>Package relationships</heading>
1388 Source packages should specify which binary packages they
1389 require to be installed or not to be installed in order to
1390 build correctly. For example, if building a package
1391 requires a certain compiler, then the compiler should be
1392 specified as a build-time dependency.
1396 It is not necessary to explicitly specify build-time
1397 relationships on a minimal set of packages that are always
1398 needed to compile, link and put in a Debian package a
1399 standard "Hello World!" program written in C or C++. The
1400 required packages are called <em>build-essential</em>, and
1401 an informational list can be found in
1402 <file>/usr/share/doc/build-essential/list</file> (which is
1403 contained in the <tt>build-essential</tt>
1406 <list compact="compact">
1408 This allows maintaining the list separately
1409 from the policy documents (the list does not
1410 need the kind of control that the policy
1414 Having a separate package allows one to install
1415 the build-essential packages on a machine, as
1416 well as allowing other packages such as tasks to
1417 require installation of the build-essential
1418 packages using the depends relation.
1421 The separate package allows bug reports against
1422 the list to be categorized separately from
1423 the policy management process in the BTS.
1430 When specifying the set of build-time dependencies, one
1431 should list only those packages explicitly required by the
1432 build. It is not necessary to list packages which are
1433 required merely because some other package in the list of
1434 build-time dependencies depends on them.<footnote>
1435 The reason for this is that dependencies change, and
1436 you should list all those packages, and <em>only</em>
1437 those packages that <em>you</em> need directly. What
1438 others need is their business. For example, if you
1439 only link against <file>libimlib</file>, you will need to
1440 build-depend on <package>libimlib2-dev</package> but
1441 not against any <tt>libjpeg*</tt> packages, even
1442 though <tt>libimlib2-dev</tt> currently depends on
1443 them: installation of <package>libimlib2-dev</package>
1444 will automatically ensure that all of its run-time
1445 dependencies are satisfied.
1450 If build-time dependencies are specified, it must be
1451 possible to build the package and produce working binaries
1452 on a system with only essential and build-essential
1453 packages installed and also those required to satisfy the
1454 build-time relationships (including any implied
1455 relationships). In particular, this means that version
1456 clauses should be used rigorously in build-time
1457 relationships so that one cannot produce bad or
1458 inconsistently configured packages when the relationships
1459 are properly satisfied.
1463 <ref id="relationships"> explains the technical details.
1468 <heading>Changes to the upstream sources</heading>
1471 If changes to the source code are made that are not
1472 specific to the needs of the Debian system, they should be
1473 sent to the upstream authors in whatever form they prefer
1474 so as to be included in the upstream version of the
1479 If you need to configure the package differently for
1480 Debian or for Linux, and the upstream source doesn't
1481 provide a way to do so, you should add such configuration
1482 facilities (for example, a new <prgn>autoconf</prgn> test
1483 or <tt>#define</tt>) and send the patch to the upstream
1484 authors, with the default set to the way they originally
1485 had it. You can then easily override the default in your
1486 <file>debian/rules</file> or wherever is appropriate.
1490 You should make sure that the <prgn>configure</prgn> utility
1491 detects the correct architecture specification string
1492 (refer to <ref id="arch-spec"> for details).
1496 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1497 <prgn>configure</prgn> scripts are used, you should edit the
1498 <file>.in</file> files rather than editing the
1499 <prgn>Makefile</prgn> directly. This allows the user to
1500 reconfigure the package if necessary. You should
1501 <em>not</em> configure the package and edit the generated
1502 <prgn>Makefile</prgn>! This makes it impossible for someone
1503 else to later reconfigure the package without losing the
1509 <sect id="dpkgchangelog">
1510 <heading>Debian changelog: <file>debian/changelog</file></heading>
1513 Changes in the Debian version of the package should be
1514 briefly explained in the Debian changelog file
1515 <file>debian/changelog</file>.<footnote>
1517 Mistakes in changelogs are usually best rectified by
1518 making a new changelog entry rather than "rewriting
1519 history" by editing old changelog entries.
1522 This includes modifications
1523 made in the Debian package compared to the upstream one
1524 as well as other changes and updates to the package.
1526 Although there is nothing stopping an author who is also
1527 the Debian maintainer from using this changelog for all
1528 their changes, it will have to be renamed if the Debian
1529 and upstream maintainers become different people. In such
1530 a case, however, it might be better to maintain the package
1531 as a non-native package.
1536 The format of the <file>debian/changelog</file> allows the
1537 package building tools to discover which version of the package
1538 is being built and find out other release-specific information.
1542 That format is a series of entries like this:
1544 <example compact="compact">
1545 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1547 [optional blank line(s), stripped]
1549 * <var>change details</var>
1550 <var>more change details</var>
1552 [blank line(s), included in output of dpkg-parsechangelog]
1554 * <var>even more change details</var>
1556 [optional blank line(s), stripped]
1558 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1563 <var>package</var> and <var>version</var> are the source
1564 package name and version number.
1568 <var>distribution(s)</var> lists the distributions where
1569 this version should be installed when it is uploaded - it
1570 is copied to the <tt>Distribution</tt> field in the
1571 <file>.changes</file> file. See <ref id="f-Distribution">.
1575 <var>urgency</var> is the value for the <tt>Urgency</tt>
1576 field in the <file>.changes</file> file for the upload
1577 (see <ref id="f-Urgency">). It is not possible to specify
1578 an urgency containing commas; commas are used to separate
1579 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1580 <prgn>dpkg</prgn> changelog format (though there is
1581 currently only one useful <var>keyword</var>,
1586 The change details may in fact be any series of lines
1587 starting with at least two spaces, but conventionally each
1588 change starts with an asterisk and a separating space and
1589 continuation lines are indented so as to bring them in
1590 line with the start of the text above. Blank lines may be
1591 used here to separate groups of changes, if desired.
1595 If this upload resolves bugs recorded in the Bug Tracking
1596 System (BTS), they may be automatically closed on the
1597 inclusion of this package into the Debian archive by
1598 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1599 in the change details.<footnote>
1600 To be precise, the string should match the following
1601 Perl regular expression:
1603 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1605 Then all of the bug numbers listed will be closed by the
1606 archive maintenance script (<prgn>katie</prgn>) using the
1607 <var>version</var> of the changelog entry.
1609 This information is conveyed via the <tt>Closes</tt> field
1610 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1614 The maintainer name and email address used in the changelog
1615 should be the details of the person uploading <em>this</em>
1616 version. They are <em>not</em> necessarily those of the
1617 usual package maintainer. The information here will be
1618 copied to the <tt>Changed-By</tt> field in the
1619 <tt>.changes</tt> file (see <ref id="f-Changed-By">),
1620 and then later used to send an acknowledgement when the
1621 upload has been installed.
1625 The <var>date</var> has the following format<footnote>
1626 This is the same as the format generated by <tt>date
1628 </footnote> (compatible and with the same semantics of
1629 RFC 2822 and RFC 5322):
1630 <example>day-of-week, dd month yyyy hh:mm:ss +zzzz</example>
1632 <list compact="compact">
1634 day-of week is one of: Mon, Tue, Wed, Thu, Fri, Sat, Sun
1637 dd is a one- or two-digit day of the month (01-31)
1640 month is one of: Jan, Feb, Mar, Apr, May, Jun, Jul, Aug,
1643 <item>yyyy is the four-digit year (e.g. 2010)</item>
1644 <item>hh is the two-digit hour (00-23)</item>
1645 <item>mm is the two-digit minutes (00-59)</item>
1646 <item>ss is the two-digit seconds (00-60)</item>
1648 +zzzz or -zzzz is the the time zone offset from Coordinated
1649 Universal Time (UTC). "+" indicates that the time is ahead
1650 of (i.e., east of) UTC and "-" indicates that the time is
1651 behind (i.e., west of) UTC. The first two digits indicate
1652 the hour difference from UTC and the last two digits
1653 indicate the number of additional minutes difference from
1654 UTC. The last two digits must be in the range 00-59.
1660 The first "title" line with the package name must start
1661 at the left hand margin. The "trailer" line with the
1662 maintainer and date details must be preceded by exactly
1663 one space. The maintainer details and the date must be
1664 separated by exactly two spaces.
1668 The entire changelog must be encoded in UTF-8.
1672 For more information on placement of the changelog files
1673 within binary packages, please see <ref id="changelogs">.
1677 <sect id="dpkgcopyright">
1678 <heading>Copyright: <file>debian/copyright</file></heading>
1680 Every package must be accompanied by a verbatim copy of its
1681 copyright information and distribution license in the file
1682 <file>/usr/share/doc/<var>package</var>/copyright</file>
1683 (see <ref id="copyrightfile"> for further details). Also see
1684 <ref id="pkgcopyright"> for further considerations related
1685 to copyrights for packages.
1689 <heading>Error trapping in makefiles</heading>
1692 When <prgn>make</prgn> invokes a command in a makefile
1693 (including your package's upstream makefiles and
1694 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1695 means that <prgn>sh</prgn>'s usual bad error handling
1696 properties apply: if you include a miniature script as one
1697 of the commands in your makefile you'll find that if you
1698 don't do anything about it then errors are not detected
1699 and <prgn>make</prgn> will blithely continue after
1704 Every time you put more than one shell command (this
1705 includes using a loop) in a makefile command you
1706 must make sure that errors are trapped. For
1707 simple compound commands, such as changing directory and
1708 then running a program, using <tt>&&</tt> rather
1709 than semicolon as a command separator is sufficient. For
1710 more complex commands including most loops and
1711 conditionals you should include a separate <tt>set -e</tt>
1712 command at the start of every makefile command that's
1713 actually one of these miniature shell scripts.
1717 <sect id="timestamps">
1718 <heading>Time Stamps</heading>
1720 Maintainers should preserve the modification times of the
1721 upstream source files in a package, as far as is reasonably
1723 The rationale is that there is some information conveyed
1724 by knowing the age of the file, for example, you could
1725 recognize that some documentation is very old by looking
1726 at the modification time, so it would be nice if the
1727 modification time of the upstream source would be
1733 <sect id="restrictions">
1734 <heading>Restrictions on objects in source packages</heading>
1737 The source package may not contain any hard links<footnote>
1739 This is not currently detected when building source
1740 packages, but only when extracting
1744 Hard links may be permitted at some point in the
1745 future, but would require a fair amount of
1748 </footnote>, device special files, sockets or setuid or
1749 setgid files.<footnote>
1750 Setgid directories are allowed.
1755 <sect id="debianrules">
1756 <heading>Main building script: <file>debian/rules</file></heading>
1759 This file must be an executable makefile, and contains the
1760 package-specific recipes for compiling the package and
1761 building binary package(s) from the source.
1765 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1766 so that it can be invoked by saying its name rather than
1767 invoking <prgn>make</prgn> explicitly. That is, invoking
1768 either of <tt>make -f debian/rules <em>args...</em></tt>
1769 or <tt>./debian/rules <em>args...</em></tt> must result in
1774 Since an interactive <file>debian/rules</file> script makes it
1775 impossible to auto-compile that package and also makes it
1776 hard for other people to reproduce the same binary
1777 package, all <em>required targets</em> must be
1778 non-interactive. At a minimum, required targets are the
1779 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1780 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1781 <em>binary-indep</em>, and <em>build</em>. It also follows
1782 that any target that these targets depend on must also be
1787 The targets are as follows (required unless stated otherwise):
1789 <tag><tt>build</tt></tag>
1792 The <tt>build</tt> target should perform all the
1793 configuration and compilation of the package.
1794 If a package has an interactive pre-build
1795 configuration routine, the Debian source package
1796 must either be built after this has taken place (so
1797 that the binary package can be built without rerunning
1798 the configuration) or the configuration routine
1799 modified to become non-interactive. (The latter is
1800 preferable if there are architecture-specific features
1801 detected by the configuration routine.)
1805 For some packages, notably ones where the same
1806 source tree is compiled in different ways to produce
1807 two binary packages, the <tt>build</tt> target
1808 does not make much sense. For these packages it is
1809 good enough to provide two (or more) targets
1810 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1811 for each of the ways of building the package, and a
1812 <tt>build</tt> target that does nothing. The
1813 <tt>binary</tt> target will have to build the
1814 package in each of the possible ways and make the
1815 binary package out of each.
1819 The <tt>build</tt> target must not do anything
1820 that might require root privilege.
1824 The <tt>build</tt> target may need to run the
1825 <tt>clean</tt> target first - see below.
1829 When a package has a configuration and build routine
1830 which takes a long time, or when the makefiles are
1831 poorly designed, or when <tt>build</tt> needs to
1832 run <tt>clean</tt> first, it is a good idea to
1833 <tt>touch build</tt> when the build process is
1834 complete. This will ensure that if <tt>debian/rules
1835 build</tt> is run again it will not rebuild the whole
1837 Another common way to do this is for <tt>build</tt>
1838 to depend on <prgn>build-stamp</prgn> and to do
1839 nothing else, and for the <prgn>build-stamp</prgn>
1840 target to do the building and to <tt>touch
1841 build-stamp</tt> on completion. This is
1842 especially useful if the build routine creates a
1843 file or directory called <tt>build</tt>; in such a
1844 case, <tt>build</tt> will need to be listed as
1845 a phony target (i.e., as a dependency of the
1846 <tt>.PHONY</tt> target). See the documentation of
1847 <prgn>make</prgn> for more information on phony
1853 <tag><tt>build-arch</tt> (optional),
1854 <tt>build-indep</tt> (optional)
1858 A package may also provide both of the targets
1859 <tt>build-arch</tt> and <tt>build-indep</tt>.
1860 The <tt>build-arch</tt> target, if provided, should
1861 perform all the configuration and compilation required for
1862 producing all architecture-dependant binary packages
1863 (those packages for which the body of the
1864 <tt>Architecture</tt> field in <tt>debian/control</tt> is
1865 not <tt>all</tt>). Similarly, the <tt>build-indep</tt>
1866 target, if provided, should perform all the configuration
1867 and compilation required for producing all
1868 architecture-independent binary packages (those packages
1869 for which the body of the <tt>Architecture</tt> field
1870 in <tt>debian/control</tt> is <tt>all</tt>).
1871 The <tt>build</tt> target should depend on those of the
1872 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1873 are provided in the rules file.<footnote>
1874 The intent of this split is so that binary-only builds
1875 need not install the dependencies required for
1876 the <tt>build-indep</tt> target. However, this is not
1877 yet used in practice since <tt>dpkg-buildpackage
1878 -B</tt>, and therefore the autobuilders,
1879 invoke <tt>build</tt> rather than <tt>build-arch</tt>
1880 due to the difficulties in determining whether the
1881 optional <tt>build-arch</tt> target exists.
1886 If one or both of the targets <tt>build-arch</tt> and
1887 <tt>build-indep</tt> are not provided, then invoking
1888 <file>debian/rules</file> with one of the not-provided
1889 targets as arguments should produce a exit status code
1890 of 2. Usually this is provided automatically by make
1891 if the target is missing.
1895 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1896 must not do anything that might require root privilege.
1900 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1901 <tt>binary-indep</tt>
1905 The <tt>binary</tt> target must be all that is
1906 necessary for the user to build the binary package(s)
1907 produced from this source package. It is
1908 split into two parts: <prgn>binary-arch</prgn> builds
1909 the binary packages which are specific to a particular
1910 architecture, and <tt>binary-indep</tt> builds
1911 those which are not.
1914 <tt>binary</tt> may be (and commonly is) a target with
1915 no commands which simply depends on
1916 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1919 Both <tt>binary-*</tt> targets should depend on the
1920 <tt>build</tt> target, or on the appropriate
1921 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1922 provided, so that the package is built if it has not
1923 been already. It should then create the relevant
1924 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1925 make their control files and <prgn>dpkg-deb</prgn> to
1926 build them and place them in the parent of the top
1931 Both the <tt>binary-arch</tt> and
1932 <tt>binary-indep</tt> targets <em>must</em> exist.
1933 If one of them has nothing to do (which will always be
1934 the case if the source generates only a single binary
1935 package, whether architecture-dependent or not), it
1936 must still exist and must always succeed.
1940 The <tt>binary</tt> targets must be invoked as
1942 The <prgn>fakeroot</prgn> package often allows one
1943 to build a package correctly even without being
1949 <tag><tt>clean</tt></tag>
1952 This must undo any effects that the <tt>build</tt>
1953 and <tt>binary</tt> targets may have had, except
1954 that it should leave alone any output files created in
1955 the parent directory by a run of a <tt>binary</tt>
1960 If a <tt>build</tt> file is touched at the end of
1961 the <tt>build</tt> target, as suggested above, it
1962 should be removed as the first action that
1963 <tt>clean</tt> performs, so that running
1964 <tt>build</tt> again after an interrupted
1965 <tt>clean</tt> doesn't think that everything is
1970 The <tt>clean</tt> target may need to be
1971 invoked as root if <tt>binary</tt> has been
1972 invoked since the last <tt>clean</tt>, or if
1973 <tt>build</tt> has been invoked as root (since
1974 <tt>build</tt> may create directories, for
1979 <tag><tt>get-orig-source</tt> (optional)</tag>
1982 This target fetches the most recent version of the
1983 original source package from a canonical archive site
1984 (via FTP or WWW, for example), does any necessary
1985 rearrangement to turn it into the original source
1986 tar file format described below, and leaves it in the
1991 This target may be invoked in any directory, and
1992 should take care to clean up any temporary files it
1997 This target is optional, but providing it if
1998 possible is a good idea.
2002 <tag><tt>patch</tt> (optional)</tag>
2005 This target performs whatever additional actions are
2006 required to make the source ready for editing (unpacking
2007 additional upstream archives, applying patches, etc.).
2008 It is recommended to be implemented for any package where
2009 <tt>dpkg-source -x</tt> does not result in source ready
2010 for additional modification. See
2011 <ref id="readmesource">.
2017 The <tt>build</tt>, <tt>binary</tt> and
2018 <tt>clean</tt> targets must be invoked with the current
2019 directory being the package's top-level directory.
2024 Additional targets may exist in <file>debian/rules</file>,
2025 either as published or undocumented interfaces or for the
2026 package's internal use.
2030 The architectures we build on and build for are determined
2031 by <prgn>make</prgn> variables using the utility
2032 <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
2033 You can determine the
2034 Debian architecture and the GNU style architecture
2035 specification string for the build machine (the machine type
2036 we are building on) as well as for the host machine (the
2037 machine type we are building for). Here is a list of
2038 supported <prgn>make</prgn> variables:
2039 <list compact="compact">
2041 <tt>DEB_*_ARCH</tt> (the Debian architecture)
2044 <tt>DEB_*_ARCH_CPU</tt> (the Debian CPU name)
2047 <tt>DEB_*_ARCH_OS</tt> (the Debian System name)
2050 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
2051 specification string)
2054 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
2055 <tt>DEB_*_GNU_TYPE</tt>)
2058 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
2059 <tt>DEB_*_GNU_TYPE</tt>)
2061 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
2062 the build machine or <tt>HOST</tt> for specification of the
2067 Backward compatibility can be provided in the rules file
2068 by setting the needed variables to suitable default
2069 values; please refer to the documentation of
2070 <prgn>dpkg-architecture</prgn> for details.
2074 It is important to understand that the <tt>DEB_*_ARCH</tt>
2075 string only determines which Debian architecture we are
2076 building on or for. It should not be used to get the CPU
2077 or system information; the <tt>DEB_*_ARCH_CPU</tt> and
2078 <tt>DEB_*_ARCH_OS</tt> variables should be used for that.
2079 GNU style variables should generally only be used with upstream
2083 <sect1 id="debianrules-options">
2084 <heading><file>debian/rules</file> and
2085 <tt>DEB_BUILD_OPTIONS</tt></heading>
2088 Supporting the standardized environment variable
2089 <tt>DEB_BUILD_OPTIONS</tt> is recommended. This variable can
2090 contain several flags to change how a package is compiled and
2091 built. Each flag must be in the form <var>flag</var> or
2092 <var>flag</var>=<var>options</var>. If multiple flags are
2093 given, they must be separated by whitespace.<footnote>
2094 Some packages support any delimiter, but whitespace is the
2095 easiest to parse inside a makefile and avoids ambiguity with
2096 flag values that contain commas.
2098 <var>flag</var> must start with a lowercase letter
2099 (<tt>a-z</tt>) and consist only of lowercase letters,
2100 numbers (<tt>0-9</tt>), and the characters
2101 <tt>-</tt> and <tt>_</tt> (hyphen and underscore).
2102 <var>options</var> must not contain whitespace. The same
2103 tag should not be given multiple times with conflicting
2104 values. Package maintainers may assume that
2105 <tt>DEB_BUILD_OPTIONS</tt> will not contain conflicting tags.
2109 The meaning of the following tags has been standardized:
2113 This tag says to not run any build-time test suite
2114 provided by the package.
2118 The presence of this tag means that the package should
2119 be compiled with a minimum of optimization. For C
2120 programs, it is best to add <tt>-O0</tt> to
2121 <tt>CFLAGS</tt> (although this is usually the default).
2122 Some programs might fail to build or run at this level
2123 of optimization; it may be necessary to use
2124 <tt>-O1</tt>, for example.
2128 This tag means that the debugging symbols should not be
2129 stripped from the binary during installation, so that
2130 debugging information may be included in the package.
2132 <tag>parallel=n</tag>
2134 This tag means that the package should be built using up
2135 to <tt>n</tt> parallel processes if the package build
2136 system supports this.<footnote>
2137 Packages built with <tt>make</tt> can often implement
2138 this by passing the <tt>-j</tt><var>n</var> option to
2141 If the package build system does not support parallel
2142 builds, this string must be ignored. If the package
2143 build system only supports a lower level of concurrency
2144 than <var>n</var>, the package should be built using as
2145 many parallel processes as the package build system
2146 supports. It is up to the package maintainer to decide
2147 whether the package build times are long enough and the
2148 package build system is robust enough to make supporting
2149 parallel builds worthwhile.
2155 Unknown flags must be ignored by <file>debian/rules</file>.
2159 The following makefile snippet is an example of how one may
2160 implement the build options; you will probably have to
2161 massage this example in order to make it work for your
2163 <example compact="compact">
2166 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
2167 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
2168 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
2169 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
2171 ifneq (,$(filter noopt,$(DEB_BUILD_OPTIONS)))
2176 ifeq (,$(filter nostrip,$(DEB_BUILD_OPTIONS)))
2177 INSTALL_PROGRAM += -s
2179 ifneq (,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2180 NUMJOBS = $(patsubst parallel=%,%,$(filter parallel=%,$(DEB_BUILD_OPTIONS)))
2181 MAKEFLAGS += -j$(NUMJOBS)
2186 ifeq (,$(filter nocheck,$(DEB_BUILD_OPTIONS)))
2187 # Code to run the package test suite.
2194 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
2195 <sect id="substvars">
2196 <heading>Variable substitutions: <file>debian/substvars</file></heading>
2199 When <prgn>dpkg-gencontrol</prgn>,
2200 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
2201 generate control files they perform variable substitutions
2202 on their output just before writing it. Variable
2203 substitutions have the form <tt>${<var>variable</var>}</tt>.
2204 The optional file <file>debian/substvars</file> contains
2205 variable substitutions to be used; variables can also be set
2206 directly from <file>debian/rules</file> using the <tt>-V</tt>
2207 option to the source packaging commands, and certain
2208 predefined variables are also available.
2212 The <file>debian/substvars</file> file is usually generated and
2213 modified dynamically by <file>debian/rules</file> targets, in
2214 which case it must be removed by the <tt>clean</tt> target.
2218 See <manref name="deb-substvars" section="5"> for full
2219 details about source variable substitutions, including the
2220 format of <file>debian/substvars</file>.</p>
2223 <sect id="debianwatch">
2224 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2227 This is an optional, recommended control file for the
2228 <tt>uscan</tt> utility which defines how to automatically
2229 scan ftp or http sites for newly available updates of the
2230 package. This is used by <url id="
2231 http://dehs.alioth.debian.org/"> and other Debian QA tools
2232 to help with quality control and maintenance of the
2233 distribution as a whole.
2238 <sect id="debianfiles">
2239 <heading>Generated files list: <file>debian/files</file></heading>
2242 This file is not a permanent part of the source tree; it
2243 is used while building packages to record which files are
2244 being generated. <prgn>dpkg-genchanges</prgn> uses it
2245 when it generates a <file>.changes</file> file.
2249 It should not exist in a shipped source package, and so it
2250 (and any backup files or temporary files such as
2251 <file>files.new</file><footnote>
2252 <file>files.new</file> is used as a temporary file by
2253 <prgn>dpkg-gencontrol</prgn> and
2254 <prgn>dpkg-distaddfile</prgn> - they write a new
2255 version of <tt>files</tt> here before renaming it,
2256 to avoid leaving a corrupted copy if an error
2258 </footnote>) should be removed by the
2259 <tt>clean</tt> target. It may also be wise to
2260 ensure a fresh start by emptying or removing it at the
2261 start of the <tt>binary</tt> target.
2265 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2266 package, it adds an entry to <file>debian/files</file> for the
2267 <file>.deb</file> file that will be created when <tt>dpkg-deb
2268 --build</tt> is run for that binary package. So for most
2269 packages all that needs to be done with this file is to
2270 delete it in the <tt>clean</tt> target.
2274 If a package upload includes files besides the source
2275 package and any binary packages whose control files were
2276 made with <prgn>dpkg-gencontrol</prgn> then they should be
2277 placed in the parent of the package's top-level directory
2278 and <prgn>dpkg-distaddfile</prgn> should be called to add
2279 the file to the list in <file>debian/files</file>.</p>
2282 <sect id="embeddedfiles">
2283 <heading>Convenience copies of code</heading>
2286 Some software packages include in their distribution convenience
2287 copies of code from other software packages, generally so that
2288 users compiling from source don't have to download multiple
2289 packages. Debian packages should not make use of these
2290 convenience copies unless the included package is explicitly
2291 intended to be used in this way.<footnote>
2292 For example, parts of the GNU build system work like this.
2294 If the included code is already in the Debian archive in the
2295 form of a library, the Debian packaging should ensure that
2296 binary packages reference the libraries already in Debian and
2297 the convenience copy is not used. If the included code is not
2298 already in Debian, it should be packaged separately as a
2299 prerequisite if possible.
2301 Having multiple copies of the same code in Debian is
2302 inefficient, often creates either static linking or shared
2303 library conflicts, and, most importantly, increases the
2304 difficulty of handling security vulnerabilities in the
2310 <sect id="readmesource">
2311 <heading>Source package handling:
2312 <file>debian/README.source</file></heading>
2315 If running <prgn>dpkg-source -x</prgn> on a source package
2316 doesn't produce the source of the package, ready for editing,
2317 and allow one to make changes and run
2318 <prgn>dpkg-buildpackage</prgn> to produce a modified package
2319 without taking any additional steps, creating a
2320 <file>debian/README.source</file> documentation file is
2321 recommended. This file should explain how to do all of the
2324 <item>Generate the fully patched source, in a form ready for
2325 editing, that would be built to create Debian
2326 packages. Doing this with a <tt>patch</tt> target in
2327 <file>debian/rules</file> is recommended; see
2328 <ref id="debianrules">.</item>
2329 <item>Modify the source and save those modifications so that
2330 they will be applied when building the package.</item>
2331 <item>Remove source modifications that are currently being
2332 applied when building the package.</item>
2333 <item>Optionally, document what steps are necessary to
2334 upgrade the Debian source package to a new upstream version,
2335 if applicable.</item>
2337 This explanation should include specific commands and mention
2338 any additional required Debian packages. It should not assume
2339 familiarity with any specific Debian packaging system or patch
2344 This explanation may refer to a documentation file installed by
2345 one of the package's build dependencies provided that the
2346 referenced documentation clearly explains these tasks and is not
2347 a general reference manual.
2351 <file>debian/README.source</file> may also include any other
2352 information that would be helpful to someone modifying the
2353 source package. Even if the package doesn't fit the above
2354 description, maintainers are encouraged to document in a
2355 <file>debian/README.source</file> file any source package with a
2356 particularly complex or unintuitive source layout or build
2357 system (for example, a package that builds the same source
2358 multiple times to generate different binary packages).
2364 <chapt id="controlfields">
2365 <heading>Control files and their fields</heading>
2368 The package management system manipulates data represented in
2369 a common format, known as <em>control data</em>, stored in
2370 <em>control files</em>.
2371 Control files are used for source packages, binary packages and
2372 the <file>.changes</file> files which control the installation
2373 of uploaded files<footnote>
2374 <prgn>dpkg</prgn>'s internal databases are in a similar
2379 <sect id="controlsyntax">
2380 <heading>Syntax of control files</heading>
2383 A control file consists of one or more paragraphs of
2385 The paragraphs are also sometimes referred to as stanzas.
2387 The paragraphs are separated by blank lines. Some control
2388 files allow only one paragraph; others allow several, in
2389 which case each paragraph usually refers to a different
2390 package. (For example, in source packages, the first
2391 paragraph refers to the source package, and later paragraphs
2392 refer to binary packages generated from the source.)
2396 Each paragraph consists of a series of data fields; each
2397 field consists of the field name, followed by a colon and
2398 then the data/value associated with that field. It ends at
2399 the end of the (logical) line. Horizontal whitespace
2400 (spaces and tabs) may occur immediately before or after the
2401 value and is ignored there; it is conventional to put a
2402 single space after the colon. For example, a field might
2404 <example compact="compact">
2407 the field name is <tt>Package</tt> and the field value
2412 A paragraph must not contain more than one instance of a
2413 particular field name.
2417 Many fields' values may span several lines; in this case
2418 each continuation line must start with a space or a tab.
2419 Any trailing spaces or tabs at the end of individual
2420 lines of a field value are ignored.
2424 In fields where it is specified that lines may not wrap,
2425 only a single line of data is allowed and whitespace is not
2426 significant in a field body. Whitespace must not appear
2427 inside names (of packages, architectures, files or anything
2428 else) or version numbers, or between the characters of
2429 multi-character version relationships.
2433 Field names are not case-sensitive, but it is usual to
2434 capitalize the field names using mixed case as shown below.
2435 Field values are case-sensitive unless the description of the
2436 field says otherwise.
2440 Blank lines, or lines consisting only of spaces and tabs,
2441 are not allowed within field values or between fields - that
2442 would mean a new paragraph.
2446 All control files must be encoded in UTF-8.
2450 <sect id="sourcecontrolfiles">
2451 <heading>Source package control files -- <file>debian/control</file></heading>
2454 The <file>debian/control</file> file contains the most vital
2455 (and version-independent) information about the source package
2456 and about the binary packages it creates.
2460 The first paragraph of the control file contains information about
2461 the source package in general. The subsequent sets each describe a
2462 binary package that the source tree builds.
2466 The fields in the general paragraph (the first one, for the source
2469 <list compact="compact">
2470 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2471 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2472 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2473 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2474 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2475 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2476 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2477 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2482 The fields in the binary package paragraphs are:
2484 <list compact="compact">
2485 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2486 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2487 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2488 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2489 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2490 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2491 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2492 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2497 The syntax and semantics of the fields are described below.
2501 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2502 generate control files for binary packages (see below), by
2503 <prgn>dpkg-genchanges</prgn> to generate the
2504 <file>.changes</file> file to accompany the upload, and by
2505 <prgn>dpkg-source</prgn> when it creates the
2506 <file>.dsc</file> source control file as part of a source
2507 archive. Many fields are permitted to span multiple lines in
2508 <file>debian/control</file> but not in any other control
2509 file. These tools are responsible for removing the line
2510 breaks from such fields when using fields from
2511 <file>debian/control</file> to generate other control files.
2515 The fields here may contain variable references - their
2516 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2517 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2518 when they generate output control files.
2519 See <ref id="substvars"> for details.
2523 In addition to the control file syntax described <qref
2524 id="controlsyntax">above</qref>, this file may also contain
2525 comment lines starting with <tt>#</tt> without any preceding
2526 whitespace. All such lines are ignored, even in the middle of
2527 continuation lines for a multiline field, and do not end a
2533 <sect id="binarycontrolfiles">
2534 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2537 The <file>DEBIAN/control</file> file contains the most vital
2538 (and version-dependent) information about a binary package. It
2539 consists of a single paragraph.
2543 The fields in this file are:
2545 <list compact="compact">
2546 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2547 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2548 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2549 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2550 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2551 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2552 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2553 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2554 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2555 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2556 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2557 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2562 <sect id="debiansourcecontrolfiles">
2563 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2566 This file consists of a single paragraph, possibly surrounded by
2567 a PGP signature. The fields of that paragraph are listed below.
2568 Their syntax is described above, in <ref id="pkg-controlfields">.
2570 <list compact="compact">
2571 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2572 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2573 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2574 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2575 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2576 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2577 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2578 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2579 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2580 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2581 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2582 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2583 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2588 The source package control file is generated by
2589 <prgn>dpkg-source</prgn> when it builds the source
2590 archive, from other files in the source package,
2591 described above. When unpacking, it is checked against
2592 the files and directories in the other parts of the
2598 <sect id="debianchangesfiles">
2599 <heading>Debian changes files -- <file>.changes</file></heading>
2602 The <file>.changes</file> files are used by the Debian archive
2603 maintenance software to process updates to packages. They
2604 consist of a single paragraph, possibly surrounded by a PGP
2605 signature. That paragraph contains information from the
2606 <file>debian/control</file> file and other data about the
2607 source package gathered via <file>debian/changelog</file>
2608 and <file>debian/rules</file>.
2612 <file>.changes</file> files have a format version that is
2613 incremented whenever the documented fields or their meaning
2614 change. This document describes format &changesversion;.
2618 The fields in this file are:
2620 <list compact="compact">
2621 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2622 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2623 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2624 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2625 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2626 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2627 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2628 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2629 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2630 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2631 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2632 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2633 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2634 <item><qref id="f-Checksums"><tt>Checksums-Sha1</tt>
2635 and <tt>Checksums-Sha256</tt></qref> (recommended)</item>
2636 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2641 <sect id="controlfieldslist">
2642 <heading>List of fields</heading>
2644 <sect1 id="f-Source">
2645 <heading><tt>Source</tt></heading>
2648 This field identifies the source package name.
2652 In <file>debian/control</file> or a <file>.dsc</file> file,
2653 this field must contain only the name of the source package.
2657 In a binary package control file or a <file>.changes</file>
2658 file, the source package name may be followed by a version
2659 number in parentheses<footnote>
2660 It is customary to leave a space after the package name
2661 if a version number is specified.
2663 This version number may be omitted (and is, by
2664 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2665 the <tt>Version</tt> field of the binary package in
2666 question. The field itself may be omitted from a binary
2667 package control file when the source package has the same
2668 name and version as the binary package.
2672 Package names (both source and binary,
2673 see <ref id="f-Package">) must consist only of lower case
2674 letters (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus
2675 (<tt>+</tt>) and minus (<tt>-</tt>) signs, and periods
2676 (<tt>.</tt>). They must be at least two characters long and
2677 must start with an alphanumeric character.
2681 <sect1 id="f-Maintainer">
2682 <heading><tt>Maintainer</tt></heading>
2685 The package maintainer's name and email address. The name
2686 must come first, then the email address inside angle
2687 brackets <tt><></tt> (in RFC822 format).
2691 If the maintainer's name contains a full stop then the
2692 whole field will not work directly as an email address due
2693 to a misfeature in the syntax specified in RFC822; a
2694 program using this field as an address must check for this
2695 and correct the problem if necessary (for example by
2696 putting the name in round brackets and moving it to the
2697 end, and bringing the email address forward).
2701 <sect1 id="f-Uploaders">
2702 <heading><tt>Uploaders</tt></heading>
2705 List of the names and email addresses of co-maintainers of
2706 the package, if any. If the package has other maintainers
2707 beside the one named in the
2708 <qref id="f-Maintainer">Maintainer field</qref>, their names
2709 and email addresses should be listed here. The format of each
2710 entry is the same as that of the Maintainer field, and
2711 multiple entries must be comma separated. This is an optional
2716 Any parser that interprets the Uploaders field in
2717 <file>debian/control</file> must permit it to span multiple
2718 lines. Line breaks in an Uploaders field that spans multiple
2719 lines are not significant and the semantics of the field are
2720 the same as if the line breaks had not been present.
2724 <sect1 id="f-Changed-By">
2725 <heading><tt>Changed-By</tt></heading>
2728 The name and email address of the person who prepared this
2729 version of the package, usually a maintainer. The syntax is
2730 the same as for the <qref id="f-Maintainer">Maintainer
2735 <sect1 id="f-Section">
2736 <heading><tt>Section</tt></heading>
2739 This field specifies an application area into which the package
2740 has been classified. See <ref id="subsections">.
2744 When it appears in the <file>debian/control</file> file,
2745 it gives the value for the subfield of the same name in
2746 the <tt>Files</tt> field of the <file>.changes</file> file.
2747 It also gives the default for the same field in the binary
2752 <sect1 id="f-Priority">
2753 <heading><tt>Priority</tt></heading>
2756 This field represents how important it is that the user
2757 have the package installed. See <ref id="priorities">.
2761 When it appears in the <file>debian/control</file> file,
2762 it gives the value for the subfield of the same name in
2763 the <tt>Files</tt> field of the <file>.changes</file> file.
2764 It also gives the default for the same field in the binary
2769 <sect1 id="f-Package">
2770 <heading><tt>Package</tt></heading>
2773 The name of the binary package.
2777 Binary package names must follow the same syntax and
2778 restrictions as source package names. See <ref id="f-Source">
2783 <sect1 id="f-Architecture">
2784 <heading><tt>Architecture</tt></heading>
2787 Depending on context and the control file used, the
2788 <tt>Architecture</tt> field can include the following sets of
2792 A unique single word identifying a Debian machine
2793 architecture as described in <ref id="arch-spec">.
2796 An architecture wildcard identifying a set of Debian
2797 machine architectures, see <ref id="arch-wildcard-spec">.
2798 <tt>any</tt> matches all Debian machine architectures
2799 and is the most frequently used.
2802 <tt>all</tt>, which indicates an
2803 architecture-independent package.
2806 <tt>source</tt>, which indicates a source package.
2812 In the main <file>debian/control</file> file in the source
2813 package, this field may contain the special
2814 value <tt>all</tt>, the special architecture
2815 wildcard <tt>any</tt>, or a list of specific and wildcard
2816 architectures separated by spaces. If <tt>all</tt>
2817 or <tt>any</tt> appears, that value must be the entire
2818 contents of the field. Most packages will use
2819 either <tt>all</tt> or <tt>any</tt>.
2823 Specifying a specific list of architectures indicates that the
2824 source will build an architecture-dependent package only on
2825 architectures included in the list. Specifying a list of
2826 architecture wildcards indicates that the source will build an
2827 architecture-dependent package on only those architectures
2828 that match any of the specified architecture wildcards.
2829 Specifying a list of architectures or architecture wildcards
2830 other than <tt>any</tt> is for the minority of cases where a
2831 program is not portable or is not useful on some
2832 architectures. Where possible, the program should be made
2837 In the source package control file <file>.dsc</file>, this
2838 field may contain either the architecture
2839 wildcard <tt>any</tt> or a list of architectures and
2840 architecture wildcards separated by spaces. If a list is
2841 given, it may include (or consist solely of) the special
2842 value <tt>all</tt>. In other words, in <file>.dsc</file>
2843 files unlike the <file>debian/control</file>, <tt>all</tt> may
2844 occur in combination with specific architectures.
2845 The <tt>Architecture</tt> field in the source package control
2846 file <file>.dsc</file> is generally constructed from
2847 the <tt>Architecture</tt> fields in
2848 the <file>debian/control</file> in the source package.
2852 Specifying <tt>any</tt> indicates that the source package
2853 isn't dependent on any particular architecture and should
2854 compile fine on any one. The produced binary package(s)
2855 will either be specific to whatever the current build
2856 architecture is or will be architecture-independent.
2860 Specifying only <tt>all</tt> indicates that the source package
2861 will only build architecture-independent packages. If this is
2862 the case, <tt>all</tt> must be used rather than <tt>any</tt>;
2863 <tt>any</tt> implies that the source package will build at
2864 least one architecture-dependent package.
2868 Specifying a list of architectures or architecture wildcards
2869 indicates that the source will build an architecture-dependent
2870 package, and will only work correctly on the listed or
2871 matching architectures. If the source package also builds at
2872 least one architecture-independent package, <tt>all</tt> will
2873 also be included in the list.
2877 In a <file>.changes</file> file, the <tt>Architecture</tt>
2878 field lists the architecture(s) of the package(s) currently
2879 being uploaded. This will be a list; if the source for the
2880 package is also being uploaded, the special
2881 entry <tt>source</tt> is also present. <tt>all</tt> will be
2882 present if any architecture-independent packages are being
2883 uploaded. Architecture wildcards such as <tt>any</tt> must
2884 never occur in the <tt>Architecture</tt> field in
2885 the <file>.changes</file> file.
2889 See <ref id="debianrules"> for information on how to get
2890 the architecture for the build process.
2894 <sect1 id="f-Essential">
2895 <heading><tt>Essential</tt></heading>
2898 This is a boolean field which may occur only in the
2899 control file of a binary package or in a per-package fields
2900 paragraph of a main source control data file.
2904 If set to <tt>yes</tt> then the package management system
2905 will refuse to remove the package (upgrading and replacing
2906 it is still possible). The other possible value is <tt>no</tt>,
2907 which is the same as not having the field at all.
2912 <heading>Package interrelationship fields:
2913 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2914 <tt>Recommends</tt>, <tt>Suggests</tt>,
2915 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2916 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2920 These fields describe the package's relationships with
2921 other packages. Their syntax and semantics are described
2922 in <ref id="relationships">.</p>
2925 <sect1 id="f-Standards-Version">
2926 <heading><tt>Standards-Version</tt></heading>
2929 The most recent version of the standards (the policy
2930 manual and associated texts) with which the package
2935 The version number has four components: major and minor
2936 version number and major and minor patch level. When the
2937 standards change in a way that requires every package to
2938 change the major number will be changed. Significant
2939 changes that will require work in many packages will be
2940 signaled by a change to the minor number. The major patch
2941 level will be changed for any change to the meaning of the
2942 standards, however small; the minor patch level will be
2943 changed when only cosmetic, typographical or other edits
2944 are made which neither change the meaning of the document
2945 nor affect the contents of packages.
2949 Thus only the first three components of the policy version
2950 are significant in the <em>Standards-Version</em> control
2951 field, and so either these three components or all four
2952 components may be specified.<footnote>
2953 In the past, people specified the full version number
2954 in the Standards-Version field, for example "2.3.0.0".
2955 Since minor patch-level changes don't introduce new
2956 policy, it was thought it would be better to relax
2957 policy and only require the first 3 components to be
2958 specified, in this example "2.3.0". All four
2959 components may still be used if someone wishes to do so.
2965 <sect1 id="f-Version">
2966 <heading><tt>Version</tt></heading>
2969 The version number of a package. The format is:
2970 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
2974 The three components here are:
2976 <tag><var>epoch</var></tag>
2979 This is a single (generally small) unsigned integer. It
2980 may be omitted, in which case zero is assumed. If it is
2981 omitted then the <var>upstream_version</var> may not
2986 It is provided to allow mistakes in the version numbers
2987 of older versions of a package, and also a package's
2988 previous version numbering schemes, to be left behind.
2992 <tag><var>upstream_version</var></tag>
2995 This is the main part of the version number. It is
2996 usually the version number of the original ("upstream")
2997 package from which the <file>.deb</file> file has been made,
2998 if this is applicable. Usually this will be in the same
2999 format as that specified by the upstream author(s);
3000 however, it may need to be reformatted to fit into the
3001 package management system's format and comparison
3006 The comparison behavior of the package management system
3007 with respect to the <var>upstream_version</var> is
3008 described below. The <var>upstream_version</var>
3009 portion of the version number is mandatory.
3013 The <var>upstream_version</var> may contain only
3014 alphanumerics<footnote>
3015 Alphanumerics are <tt>A-Za-z0-9</tt> only.
3017 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
3018 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
3019 tilde) and should start with a digit. If there is no
3020 <var>debian_revision</var> then hyphens are not allowed;
3021 if there is no <var>epoch</var> then colons are not
3026 <tag><var>debian_revision</var></tag>
3029 This part of the version number specifies the version of
3030 the Debian package based on the upstream version. It
3031 may contain only alphanumerics and the characters
3032 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
3033 tilde) and is compared in the same way as the
3034 <var>upstream_version</var> is.
3038 It is optional; if it isn't present then the
3039 <var>upstream_version</var> may not contain a hyphen.
3040 This format represents the case where a piece of
3041 software was written specifically to be a Debian
3042 package, where the Debian package source must always
3043 be identical to the pristine source and therefore no
3044 revision indication is required.
3048 It is conventional to restart the
3049 <var>debian_revision</var> at <tt>1</tt> each time the
3050 <var>upstream_version</var> is increased.
3054 The package management system will break the version
3055 number apart at the last hyphen in the string (if there
3056 is one) to determine the <var>upstream_version</var> and
3057 <var>debian_revision</var>. The absence of a
3058 <var>debian_revision</var> is equivalent to a
3059 <var>debian_revision</var> of <tt>0</tt>.
3066 When comparing two version numbers, first the <var>epoch</var>
3067 of each are compared, then the <var>upstream_version</var> if
3068 <var>epoch</var> is equal, and then <var>debian_revision</var>
3069 if <var>upstream_version</var> is also equal.
3070 <var>epoch</var> is compared numerically. The
3071 <var>upstream_version</var> and <var>debian_revision</var>
3072 parts are compared by the package management system using the
3073 following algorithm:
3077 The strings are compared from left to right.
3081 First the initial part of each string consisting entirely of
3082 non-digit characters is determined. These two parts (one of
3083 which may be empty) are compared lexically. If a difference
3084 is found it is returned. The lexical comparison is a
3085 comparison of ASCII values modified so that all the letters
3086 sort earlier than all the non-letters and so that a tilde
3087 sorts before anything, even the end of a part. For example,
3088 the following parts are in sorted order from earliest to
3089 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
3090 <tt>a</tt>.<footnote>
3091 One common use of <tt>~</tt> is for upstream pre-releases.
3092 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
3093 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
3098 Then the initial part of the remainder of each string which
3099 consists entirely of digit characters is determined. The
3100 numerical values of these two parts are compared, and any
3101 difference found is returned as the result of the comparison.
3102 For these purposes an empty string (which can only occur at
3103 the end of one or both version strings being compared) counts
3108 These two steps (comparing and removing initial non-digit
3109 strings and initial digit strings) are repeated until a
3110 difference is found or both strings are exhausted.
3114 Note that the purpose of epochs is to allow us to leave behind
3115 mistakes in version numbering, and to cope with situations
3116 where the version numbering scheme changes. It is
3117 <em>not</em> intended to cope with version numbers containing
3118 strings of letters which the package management system cannot
3119 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
3120 silly orderings.<footnote>
3121 The author of this manual has heard of a package whose
3122 versions went <tt>1.1</tt>, <tt>1.2</tt>, <tt>1.3</tt>,
3123 <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>, <tt>2</tt> and so
3129 <sect1 id="f-Description">
3130 <heading><tt>Description</tt></heading>
3133 In a source or binary control file, the <tt>Description</tt>
3134 field contains a description of the binary package, consisting
3135 of two parts, the synopsis or the short description, and the
3136 long description. The field's format is as follows:
3141 Description: <single line synopsis>
3142 <extended description over several lines>
3147 The lines in the extended description can have these formats:
3153 Those starting with a single space are part of a paragraph.
3154 Successive lines of this form will be word-wrapped when
3155 displayed. The leading space will usually be stripped off.
3159 Those starting with two or more spaces. These will be
3160 displayed verbatim. If the display cannot be panned
3161 horizontally, the displaying program will line wrap them "hard"
3162 (i.e., without taking account of word breaks). If it can they
3163 will be allowed to trail off to the right. None, one or two
3164 initial spaces may be deleted, but the number of spaces
3165 deleted from each line will be the same (so that you can have
3166 indenting work correctly, for example).
3170 Those containing a single space followed by a single full stop
3171 character. These are rendered as blank lines. This is the
3172 <em>only</em> way to get a blank line<footnote>
3173 Completely empty lines will not be rendered as blank lines.
3174 Instead, they will cause the parser to think you're starting
3175 a whole new record in the control file, and will therefore
3176 likely abort with an error.
3181 Those containing a space, a full stop and some more characters.
3182 These are for future expansion. Do not use them.
3188 Do not use tab characters. Their effect is not predictable.
3192 See <ref id="descriptions"> for further information on this.
3196 In a <file>.changes</file> file, the <tt>Description</tt>
3197 field contains a summary of the descriptions for the packages
3198 being uploaded. For this case, the first line of the field
3199 value (the part on the same line as <tt>Description:</tt>) is
3200 always empty. The content of the field is expressed as
3201 continuation lines, one line per package. Each line is
3202 indented by one space and contains the name of a binary
3203 package, a space, a hyphen (<tt>-</tt>), a space, and the
3204 short description line from that package.
3208 <sect1 id="f-Distribution">
3209 <heading><tt>Distribution</tt></heading>
3212 In a <file>.changes</file> file or parsed changelog output
3213 this contains the (space-separated) name(s) of the
3214 distribution(s) where this version of the package should
3215 be installed. Valid distributions are determined by the
3216 archive maintainers.<footnote>
3217 Example distribution names in the Debian archive used in
3218 <file>.changes</file> files are:
3219 <taglist compact="compact">
3220 <tag><em>unstable</em></tag>
3222 This distribution value refers to the
3223 <em>developmental</em> part of the Debian distribution
3224 tree. Most new packages, new upstream versions of
3225 packages and bug fixes go into the <em>unstable</em>
3229 <tag><em>experimental</em></tag>
3231 The packages with this distribution value are deemed
3232 by their maintainers to be high risk. Oftentimes they
3233 represent early beta or developmental packages from
3234 various sources that the maintainers want people to
3235 try, but are not ready to be a part of the other parts
3236 of the Debian distribution tree.
3241 Others are used for updating stable releases or for
3242 security uploads. More information is available in the
3243 Debian Developer's Reference, section "The Debian
3247 The Debian archive software only supports listing a single
3248 distribution. Migration of packages to other distributions is
3249 handled outside of the upload process.
3254 <heading><tt>Date</tt></heading>
3257 This field includes the date the package was built or last
3258 edited. It must be in the same format as the <var>date</var>
3259 in a <file>debian/changelog</file> entry.
3263 The value of this field is usually extracted from the
3264 <file>debian/changelog</file> file - see
3265 <ref id="dpkgchangelog">).
3269 <sect1 id="f-Format">
3270 <heading><tt>Format</tt></heading>
3273 In <qref id="debianchangesfiles"><file>.changes</file></qref>
3274 files, this field declares the format version of that file.
3275 The syntax of the field value is the same as that of
3276 a <qref id="f-Version">package version number</qref> except
3277 that no epoch or Debian revision is allowed. The format
3278 described in this document is <tt>&changesversion;</tt>.
3282 In <qref id="debiansourcecontrolfiles"><file>.dsc</file>
3283 Debian source control</qref> files, this field declares the
3284 format of the source package. The field value is used by
3285 programs acting on a source package to interpret the list of
3286 files in the source package and determine how to unpack it.
3287 The syntax of the field value is a numeric major revision, a
3288 period, a numeric minor revision, and then an optional subtype
3289 after whitespace, which if specified is an alphanumeric word
3290 in parentheses. The subtype is optional in the syntax but may
3291 be mandatory for particular source format revisions.
3293 The source formats currently supported by the Debian archive
3294 software are <tt>1.0</tt>, <tt>3.0 (native)</tt>,
3295 and <tt>3.0 (quilt)</tt>.
3300 <sect1 id="f-Urgency">
3301 <heading><tt>Urgency</tt></heading>
3304 This is a description of how important it is to upgrade to
3305 this version from previous ones. It consists of a single
3306 keyword taking one of the values <tt>low</tt>,
3307 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
3308 <tt>critical</tt><footnote>
3309 Other urgency values are supported with configuration
3310 changes in the archive software but are not used in Debian.
3311 The urgency affects how quickly a package will be considered
3312 for inclusion into the <tt>testing</tt> distribution and
3313 gives an indication of the importance of any fixes included
3314 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
3315 treated as synonymous.
3316 </footnote> (not case-sensitive) followed by an optional
3317 commentary (separated by a space) which is usually in
3318 parentheses. For example:
3321 Urgency: low (HIGH for users of diversions)
3327 The value of this field is usually extracted from the
3328 <file>debian/changelog</file> file - see
3329 <ref id="dpkgchangelog">.
3333 <sect1 id="f-Changes">
3334 <heading><tt>Changes</tt></heading>
3337 This field contains the human-readable changes data, describing
3338 the differences between the last version and the current one.
3342 The first line of the field value (the part on the same line
3343 as <tt>Changes:</tt>) is always empty. The content of the
3344 field is expressed as continuation lines, with each line
3345 indented by at least one space. Blank lines must be
3346 represented by a line consisting only of a space and a full
3351 The value of this field is usually extracted from the
3352 <file>debian/changelog</file> file - see
3353 <ref id="dpkgchangelog">).
3357 Each version's change information should be preceded by a
3358 "title" line giving at least the version, distribution(s)
3359 and urgency, in a human-readable way.
3363 If data from several versions is being returned the entry
3364 for the most recent version should be returned first, and
3365 entries should be separated by the representation of a
3366 blank line (the "title" line may also be followed by the
3367 representation of a blank line).
3371 <sect1 id="f-Binary">
3372 <heading><tt>Binary</tt></heading>
3375 This field is a list of binary packages. Its syntax and
3376 meaning varies depending on the control file in which it
3381 When it appears in the <file>.dsc</file> file, it lists binary
3382 packages which a source package can produce, separated by
3384 A space after each comma is conventional.
3385 </footnote>. It may span multiple lines. The source package
3386 does not necessarily produce all of these binary packages for
3387 every architecture. The source control file doesn't contain
3388 details of which architectures are appropriate for which of
3389 the binary packages.
3393 When it appears in a <file>.changes</file> file, it lists the
3394 names of the binary packages being uploaded, separated by
3395 whitespace (not commas). It may span multiple lines.
3399 <sect1 id="f-Installed-Size">
3400 <heading><tt>Installed-Size</tt></heading>
3403 This field appears in the control files of binary packages,
3404 and in the <file>Packages</file> files. It gives an estimate
3405 of the total amount of disk space required to install the
3406 named package. Actual installed size may vary based on block
3407 size, file system properties, or actions taken by package
3412 The disk space is given as the integer value of the estimated
3413 installed size in bytes, divided by 1024 and rounded up.
3417 <sect1 id="f-Files">
3418 <heading><tt>Files</tt></heading>
3421 This field contains a list of files with information about
3422 each one. The exact information and syntax varies with
3427 In all cases, Files is a multiline field. The first line of
3428 the field value (the part on the same line as <tt>Files:</tt>)
3429 is always empty. The content of the field is expressed as
3430 continuation lines, one line per file. Each line must be
3431 indented by one space and contain a number of sub-fields,
3432 separated by spaces, as described below.
3436 In the <file>.dsc</file> file, each line contains the MD5
3437 checksum, size and filename of the tar file and (if
3438 applicable) diff file which make up the remainder of the
3439 source package<footnote>
3440 That is, the parts which are not the <tt>.dsc</tt>.
3441 </footnote>. For example:
3444 c6f698f19f2a2aa07dbb9bbda90a2754 571925 example_1.2.orig.tar.gz
3445 938512f08422f3509ff36f125f5873ba 6220 example_1.2-1.diff.gz
3447 The exact forms of the filenames are described
3448 in <ref id="pkg-sourcearchives">.
3452 In the <file>.changes</file> file this contains one line per
3453 file being uploaded. Each line contains the MD5 checksum,
3454 size, section and priority and the filename. For example:
3457 4c31ab7bfc40d3cf49d7811987390357 1428 text extra example_1.2-1.dsc
3458 c6f698f19f2a2aa07dbb9bbda90a2754 571925 text extra example_1.2.orig.tar.gz
3459 938512f08422f3509ff36f125f5873ba 6220 text extra example_1.2-1.diff.gz
3460 7c98fe853b3bbb47a00e5cd129b6cb56 703542 text extra example_1.2-1_i386.deb
3462 The <qref id="f-Section">section</qref>
3463 and <qref id="f-Priority">priority</qref> are the values of
3464 the corresponding fields in the main source control file. If
3465 no section or priority is specified then <tt>-</tt> should be
3466 used, though section and priority values must be specified for
3467 new packages to be installed properly.
3471 The special value <tt>byhand</tt> for the section in a
3472 <tt>.changes</tt> file indicates that the file in question
3473 is not an ordinary package file and must by installed by
3474 hand by the distribution maintainers. If the section is
3475 <tt>byhand</tt> the priority should be <tt>-</tt>.
3479 If a new Debian revision of a package is being shipped and
3480 no new original source archive is being distributed the
3481 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3482 entry for the original source archive
3483 <file><var>package</var>_<var>upstream-version</var>.orig.tar.gz</file>,
3484 but the <file>.changes</file> file should leave it out. In
3485 this case the original source archive on the distribution
3486 site must match exactly, byte-for-byte, the original
3487 source archive which was used to generate the
3488 <file>.dsc</file> file and diff which are being uploaded.</p>
3491 <sect1 id="f-Closes">
3492 <heading><tt>Closes</tt></heading>
3495 A space-separated list of bug report numbers that the upload
3496 governed by the .changes file closes.
3500 <sect1 id="f-Homepage">
3501 <heading><tt>Homepage</tt></heading>
3504 The URL of the web site for this package, preferably (when
3505 applicable) the site from which the original source can be
3506 obtained and any additional upstream documentation or
3507 information may be found. The content of this field is a
3508 simple URL without any surrounding characters such as
3513 <sect1 id="f-Checksums">
3514 <heading><tt>Checksums-Sha1</tt>
3515 and <tt>Checksums-Sha256</tt></heading>
3518 These fields contain a list of files with a checksum and size
3519 for each one. Both <tt>Checksums-Sha1</tt>
3520 and <tt>Checksums-Sha256</tt> have the same syntax and differ
3521 only in the checksum algorithm used: SHA-1
3522 for <tt>Checksums-Sha1</tt> and SHA-256
3523 for <tt>Checksums-Sha256</tt>.
3527 <tt>Checksums-Sha1</tt> and <tt>Checksums-Sha256</tt> are
3528 multiline fields. The first line of the field value (the part
3529 on the same line as <tt>Checksums-Sha1:</tt>
3530 or <tt>Checksums-Sha256:</tt>) is always empty. The content
3531 of the field is expressed as continuation lines, one line per
3532 file. Each line consists of the checksum, a space, the file
3533 size, a space, and the file name. For example (from
3534 a <file>.changes</file> file):
3537 1f418afaa01464e63cc1ee8a66a05f0848bd155c 1276 example_1.0-1.dsc
3538 a0ed1456fad61116f868b1855530dbe948e20f06 171602 example_1.0.orig.tar.gz
3539 5e86ecf0671e113b63388dac81dd8d00e00ef298 6137 example_1.0-1.debian.tar.gz
3540 71a0ff7da0faaf608481195f9cf30974b142c183 548402 example_1.0-1_i386.deb
3542 ac9d57254f7e835bed299926fd51bf6f534597cc3fcc52db01c4bffedae81272 1276 example_1.0-1.dsc
3543 0d123be7f51e61c4bf15e5c492b484054be7e90f3081608a5517007bfb1fd128 171602 example_1.0.orig.tar.gz
3544 f54ae966a5f580571ae7d9ef5e1df0bd42d63e27cb505b27957351a495bc6288 6137 example_1.0-1.debian.tar.gz
3545 3bec05c03974fdecd11d020fc2e8250de8404867a8a2ce865160c250eb723664 548402 example_1.0-1_i386.deb
3550 In the <file>.dsc</file> file, these fields should list all
3551 files that make up the source package. In
3552 the <file>.changes</file> file, these fields should list all
3553 files being uploaded. The list of files in these fields
3554 must match the list of files in the <tt>Files</tt> field.
3560 <heading>User-defined fields</heading>
3563 Additional user-defined fields may be added to the
3564 source package control file. Such fields will be
3565 ignored, and not copied to (for example) binary or
3566 source package control files or upload control files.
3570 If you wish to add additional unsupported fields to
3571 these output files you should use the mechanism
3576 Fields in the main source control information file with
3577 names starting <tt>X</tt>, followed by one or more of
3578 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3579 be copied to the output files. Only the part of the
3580 field name after the hyphen will be used in the output
3581 file. Where the letter <tt>B</tt> is used the field
3582 will appear in binary package control files, where the
3583 letter <tt>S</tt> is used in source package control
3584 files and where <tt>C</tt> is used in upload control
3585 (<tt>.changes</tt>) files.
3589 For example, if the main source information control file
3592 XBS-Comment: I stand between the candle and the star.
3594 then the binary and source package control files will contain the
3597 Comment: I stand between the candle and the star.
3606 <chapt id="maintainerscripts">
3607 <heading>Package maintainer scripts and installation procedure</heading>
3610 <heading>Introduction to package maintainer scripts</heading>
3613 It is possible to supply scripts as part of a package which
3614 the package management system will run for you when your
3615 package is installed, upgraded or removed.
3619 These scripts are the files <prgn>preinst</prgn>,
3620 <prgn>postinst</prgn>, <prgn>prerm</prgn> and
3621 <prgn>postrm</prgn> in the control area of the package.
3622 They must be proper executable files; if they are scripts
3623 (which is recommended), they must start with the usual
3624 <tt>#!</tt> convention. They should be readable and
3625 executable by anyone, and must not be world-writable.
3629 The package management system looks at the exit status from
3630 these scripts. It is important that they exit with a
3631 non-zero status if there is an error, so that the package
3632 management system can stop its processing. For shell
3633 scripts this means that you <em>almost always</em> need to
3634 use <tt>set -e</tt> (this is usually true when writing shell
3635 scripts, in fact). It is also important, of course, that
3636 they exit with a zero status if everything went well.
3640 Additionally, packages interacting with users using
3641 <tt>debconf</tt> in the <prgn>postinst</prgn> script should
3642 install a <prgn>config</prgn> script in the control area,
3643 see <ref id="maintscriptprompt"> for details.
3647 When a package is upgraded a combination of the scripts from
3648 the old and new packages is called during the upgrade
3649 procedure. If your scripts are going to be at all
3650 complicated you need to be aware of this, and may need to
3651 check the arguments to your scripts.
3655 Broadly speaking the <prgn>preinst</prgn> is called before
3656 (a particular version of) a package is installed, and the
3657 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3658 before (a version of) a package is removed and the
3659 <prgn>postrm</prgn> afterwards.
3663 Programs called from maintainer scripts should not normally
3664 have a path prepended to them. Before installation is
3665 started, the package management system checks to see if the
3666 programs <prgn>ldconfig</prgn>,
3667 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3668 and <prgn>update-rc.d</prgn> can be found via the
3669 <tt>PATH</tt> environment variable. Those programs, and any
3670 other program that one would expect to be in the
3671 <tt>PATH</tt>, should thus be invoked without an absolute
3672 pathname. Maintainer scripts should also not reset the
3673 <tt>PATH</tt>, though they might choose to modify it by
3674 prepending or appending package-specific directories. These
3675 considerations really apply to all shell scripts.</p>
3678 <sect id="idempotency">
3679 <heading>Maintainer scripts idempotency</heading>
3682 It is necessary for the error recovery procedures that the
3683 scripts be idempotent. This means that if it is run
3684 successfully, and then it is called again, it doesn't bomb
3685 out or cause any harm, but just ensures that everything is
3686 the way it ought to be. If the first call failed, or
3687 aborted half way through for some reason, the second call
3688 should merely do the things that were left undone the first
3689 time, if any, and exit with a success status if everything
3691 This is so that if an error occurs, the user interrupts
3692 <prgn>dpkg</prgn> or some other unforeseen circumstance
3693 happens you don't leave the user with a badly-broken
3694 package when <prgn>dpkg</prgn> attempts to repeat the
3700 <sect id="controllingterminal">
3701 <heading>Controlling terminal for maintainer scripts</heading>
3704 Maintainer scripts are not guaranteed to run with a controlling
3705 terminal and may not be able to interact with the user. They
3706 must be able to fall back to noninteractive behavior if no
3707 controlling terminal is available. Maintainer scripts that
3708 prompt via a program conforming to the Debian Configuration
3709 Management Specification (see <ref id="maintscriptprompt">) may
3710 assume that program will handle falling back to noninteractive
3715 For high-priority prompts without a reasonable default answer,
3716 maintainer scripts may abort if there is no controlling
3717 terminal. However, this situation should be avoided if at all
3718 possible, since it prevents automated or unattended installs.
3719 In most cases, users will consider this to be a bug in the
3724 <sect id="exitstatus">
3725 <heading>Exit status</heading>
3728 Each script must return a zero exit status for
3729 success, or a nonzero one for failure, since the package
3730 management system looks for the exit status of these scripts
3731 and determines what action to take next based on that datum.
3735 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3740 <list compact="compact">
3742 <var>new-preinst</var> <tt>install</tt>
3745 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3748 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3751 <var>old-preinst</var> <tt>abort-upgrade</tt>
3752 <var>new-version</var>
3757 <list compact="compact">
3759 <var>postinst</var> <tt>configure</tt>
3760 <var>most-recently-configured-version</var>
3763 <var>old-postinst</var> <tt>abort-upgrade</tt>
3764 <var>new-version</var>
3767 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3768 <tt>in-favour</tt> <var>package</var>
3769 <var>new-version</var>
3772 <var>postinst</var> <tt>abort-remove</tt>
3775 <var>deconfigured's-postinst</var>
3776 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3777 <var>failed-install-package</var> <var>version</var>
3778 [<tt>removing</tt> <var>conflicting-package</var>
3784 <list compact="compact">
3786 <var>prerm</var> <tt>remove</tt>
3789 <var>old-prerm</var> <tt>upgrade</tt>
3790 <var>new-version</var>
3793 <var>new-prerm</var> <tt>failed-upgrade</tt>
3794 <var>old-version</var>
3797 <var>conflictor's-prerm</var> <tt>remove</tt>
3798 <tt>in-favour</tt> <var>package</var>
3799 <var>new-version</var>
3802 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3803 <tt>in-favour</tt> <var>package-being-installed</var>
3804 <var>version</var> [<tt>removing</tt>
3805 <var>conflicting-package</var>
3811 <list compact="compact">
3813 <var>postrm</var> <tt>remove</tt>
3816 <var>postrm</var> <tt>purge</tt>
3819 <var>old-postrm</var> <tt>upgrade</tt>
3820 <var>new-version</var>
3823 <var>new-postrm</var> <tt>failed-upgrade</tt>
3824 <var>old-version</var>
3827 <var>new-postrm</var> <tt>abort-install</tt>
3830 <var>new-postrm</var> <tt>abort-install</tt>
3831 <var>old-version</var>
3834 <var>new-postrm</var> <tt>abort-upgrade</tt>
3835 <var>old-version</var>
3838 <var>disappearer's-postrm</var> <tt>disappear</tt>
3839 <var>overwriter</var>
3840 <var>overwriter-version</var>
3846 <sect id="unpackphase">
3847 <heading>Details of unpack phase of installation or upgrade</heading>
3850 The procedure on installation/upgrade/overwrite/disappear
3851 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3852 stage of <tt>dpkg --install</tt>) is as follows. In each
3853 case, if a major error occurs (unless listed below) the
3854 actions are, in general, run backwards - this means that the
3855 maintainer scripts are run with different arguments in
3856 reverse order. These are the "error unwind" calls listed
3863 If a version of the package is already installed, call
3864 <example compact="compact">
3865 <var>old-prerm</var> upgrade <var>new-version</var>
3869 If the script runs but exits with a non-zero
3870 exit status, <prgn>dpkg</prgn> will attempt:
3871 <example compact="compact">
3872 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3874 If this works, the upgrade continues. If this
3875 does not work, the error unwind:
3876 <example compact="compact">
3877 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3879 If this works, then the old-version is
3880 "Installed", if not, the old version is in a
3881 "Half-Configured" state.
3887 If a "conflicting" package is being removed at the same time,
3888 or if any package will be broken (due to <tt>Breaks</tt>):
3891 If <tt>--auto-deconfigure</tt> is
3892 specified, call, for each package to be deconfigured
3893 due to <tt>Breaks</tt>:
3894 <example compact="compact">
3895 <var>deconfigured's-prerm</var> deconfigure \
3896 in-favour <var>package-being-installed</var> <var>version</var>
3899 <example compact="compact">
3900 <var>deconfigured's-postinst</var> abort-deconfigure \
3901 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3903 The deconfigured packages are marked as
3904 requiring configuration, so that if
3905 <tt>--install</tt> is used they will be
3906 configured again if possible.
3909 If any packages depended on a conflicting
3910 package being removed and <tt>--auto-deconfigure</tt> is
3911 specified, call, for each such package:
3912 <example compact="compact">
3913 <var>deconfigured's-prerm</var> deconfigure \
3914 in-favour <var>package-being-installed</var> <var>version</var> \
3915 removing <var>conflicting-package</var> <var>version</var>
3918 <example compact="compact">
3919 <var>deconfigured's-postinst</var> abort-deconfigure \
3920 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3921 removing <var>conflicting-package</var> <var>version</var>
3923 The deconfigured packages are marked as
3924 requiring configuration, so that if
3925 <tt>--install</tt> is used they will be
3926 configured again if possible.
3929 To prepare for removal of each conflicting package, call:
3930 <example compact="compact">
3931 <var>conflictor's-prerm</var> remove \
3932 in-favour <var>package</var> <var>new-version</var>
3935 <example compact="compact">
3936 <var>conflictor's-postinst</var> abort-remove \
3937 in-favour <var>package</var> <var>new-version</var>
3946 If the package is being upgraded, call:
3947 <example compact="compact">
3948 <var>new-preinst</var> upgrade <var>old-version</var>
3950 If this fails, we call:
3952 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3959 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3961 is called. If this works, then the old version
3962 is in an "Installed" state, or else it is left
3963 in an "Unpacked" state.
3968 If it fails, then the old version is left
3969 in an "Half-Installed" state.
3976 Otherwise, if the package had some configuration
3977 files from a previous version installed (i.e., it
3978 is in the "configuration files only" state):
3979 <example compact="compact">
3980 <var>new-preinst</var> install <var>old-version</var>
3984 <var>new-postrm</var> abort-install <var>old-version</var>
3986 If this fails, the package is left in a
3987 "Half-Installed" state, which requires a
3988 reinstall. If it works, the packages is left in
3989 a "Config-Files" state.
3992 Otherwise (i.e., the package was completely purged):
3993 <example compact="compact">
3994 <var>new-preinst</var> install
3997 <example compact="compact">
3998 <var>new-postrm</var> abort-install
4000 If the error-unwind fails, the package is in a
4001 "Half-Installed" phase, and requires a
4002 reinstall. If the error unwind works, the
4003 package is in a not installed state.
4010 The new package's files are unpacked, overwriting any
4011 that may be on the system already, for example any
4012 from the old version of the same package or from
4013 another package. Backups of the old files are kept
4014 temporarily, and if anything goes wrong the package
4015 management system will attempt to put them back as
4016 part of the error unwind.
4020 It is an error for a package to contain files which
4021 are on the system in another package, unless
4022 <tt>Replaces</tt> is used (see <ref id="replaces">).
4024 The following paragraph is not currently the case:
4025 Currently the <tt>- - force-overwrite</tt> flag is
4026 enabled, downgrading it to a warning, but this may not
4032 It is a more serious error for a package to contain a
4033 plain file or other kind of non-directory where another
4034 package has a directory (again, unless
4035 <tt>Replaces</tt> is used). This error can be
4036 overridden if desired using
4037 <tt>--force-overwrite-dir</tt>, but this is not
4042 Packages which overwrite each other's files produce
4043 behavior which, though deterministic, is hard for the
4044 system administrator to understand. It can easily
4045 lead to "missing" programs if, for example, a package
4046 is installed which overwrites a file from another
4047 package, and is then removed again.<footnote>
4048 Part of the problem is due to what is arguably a
4049 bug in <prgn>dpkg</prgn>.
4054 A directory will never be replaced by a symbolic link
4055 to a directory or vice versa; instead, the existing
4056 state (symlink or not) will be left alone and
4057 <prgn>dpkg</prgn> will follow the symlink if there is
4066 If the package is being upgraded, call
4067 <example compact="compact">
4068 <var>old-postrm</var> upgrade <var>new-version</var>
4072 If this fails, <prgn>dpkg</prgn> will attempt:
4073 <example compact="compact">
4074 <var>new-postrm</var> failed-upgrade <var>old-version</var>
4076 If this works, installation continues. If not,
4078 <example compact="compact">
4079 <var>old-preinst</var> abort-upgrade <var>new-version</var>
4081 If this fails, the old version is left in a
4082 "Half-Installed" state. If it works, dpkg now
4084 <example compact="compact">
4085 <var>new-postrm</var> abort-upgrade <var>old-version</var>
4087 If this fails, the old version is left in a
4088 "Half-Installed" state. If it works, dpkg now
4090 <example compact="compact">
4091 <var>old-postinst</var> abort-upgrade <var>new-version</var>
4093 If this fails, the old version is in an
4100 This is the point of no return - if
4101 <prgn>dpkg</prgn> gets this far, it won't back off
4102 past this point if an error occurs. This will
4103 leave the package in a fairly bad state, which
4104 will require a successful re-installation to clear
4105 up, but it's when <prgn>dpkg</prgn> starts doing
4106 things that are irreversible.
4111 Any files which were in the old version of the package
4112 but not in the new are removed.
4116 The new file list replaces the old.
4120 The new maintainer scripts replace the old.
4124 Any packages all of whose files have been overwritten
4125 during the installation, and which aren't required for
4126 dependencies, are considered to have been removed.
4127 For each such package
4130 <prgn>dpkg</prgn> calls:
4131 <example compact="compact">
4132 <var>disappearer's-postrm</var> disappear \
4133 <var>overwriter</var> <var>overwriter-version</var>
4137 The package's maintainer scripts are removed.
4140 It is noted in the status database as being in a
4141 sane state, namely not installed (any conffiles
4142 it may have are ignored, rather than being
4143 removed by <prgn>dpkg</prgn>). Note that
4144 disappearing packages do not have their prerm
4145 called, because <prgn>dpkg</prgn> doesn't know
4146 in advance that the package is going to
4153 Any files in the package we're unpacking that are also
4154 listed in the file lists of other packages are removed
4155 from those lists. (This will lobotomize the file list
4156 of the "conflicting" package if there is one.)
4160 The backup files made during installation, above, are
4166 The new package's status is now sane, and recorded as
4171 Here is another point of no return - if the
4172 conflicting package's removal fails we do not unwind
4173 the rest of the installation; the conflicting package
4174 is left in a half-removed limbo.
4179 If there was a conflicting package we go and do the
4180 removal actions (described below), starting with the
4181 removal of the conflicting package's files (any that
4182 are also in the package being installed have already
4183 been removed from the conflicting package's file list,
4184 and so do not get removed now).
4190 <sect id="configdetails"><heading>Details of configuration</heading>
4193 When we configure a package (this happens with <tt>dpkg
4194 --install</tt> and <tt>dpkg --configure</tt>), we first
4195 update any <tt>conffile</tt>s and then call:
4196 <example compact="compact">
4197 <var>postinst</var> configure <var>most-recently-configured-version</var>
4202 No attempt is made to unwind after errors during
4203 configuration. If the configuration fails, the package is in
4204 a "Failed Config" state, and an error message is generated.
4208 If there is no most recently configured version
4209 <prgn>dpkg</prgn> will pass a null argument.
4212 Historical note: Truly ancient (pre-1997) versions of
4213 <prgn>dpkg</prgn> passed <tt><unknown></tt>
4214 (including the angle brackets) in this case. Even older
4215 ones did not pass a second argument at all, under any
4216 circumstance. Note that upgrades using such an old dpkg
4217 version are unlikely to work for other reasons, even if
4218 this old argument behavior is handled by your postinst script.
4224 <sect id="removedetails"><heading>Details of removal and/or
4225 configuration purging</heading>
4231 <example compact="compact">
4232 <var>prerm</var> remove
4236 If prerm fails during replacement due to conflict
4238 <var>conflictor's-postinst</var> abort-remove \
4239 in-favour <var>package</var> <var>new-version</var>
4243 <var>postinst</var> abort-remove
4247 If this fails, the package is in a "Half-Configured"
4248 state, or else it remains "Installed".
4252 The package's files are removed (except <tt>conffile</tt>s).
4255 <example compact="compact">
4256 <var>postrm</var> remove
4260 If it fails, there's no error unwind, and the package is in
4261 an "Half-Installed" state.
4266 All the maintainer scripts except the <prgn>postrm</prgn>
4271 If we aren't purging the package we stop here. Note
4272 that packages which have no <prgn>postrm</prgn> and no
4273 <tt>conffile</tt>s are automatically purged when
4274 removed, as there is no difference except for the
4275 <prgn>dpkg</prgn> status.
4279 The <tt>conffile</tt>s and any backup files
4280 (<tt>~</tt>-files, <tt>#*#</tt> files,
4281 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
4286 <example compact="compact">
4287 <var>postrm</var> purge
4291 If this fails, the package remains in a "Config-Files"
4296 The package's file list is removed.
4305 <chapt id="relationships">
4306 <heading>Declaring relationships between packages</heading>
4308 <sect id="depsyntax">
4309 <heading>Syntax of relationship fields</heading>
4312 These fields all have a uniform syntax. They are a list of
4313 package names separated by commas.
4317 In the <tt>Depends</tt>, <tt>Recommends</tt>,
4318 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
4319 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
4320 control file fields of the package, which declare
4321 dependencies on other packages, the package names listed may
4322 also include lists of alternative package names, separated
4323 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
4324 if any one of the alternative packages is installed, that
4325 part of the dependency is considered to be satisfied.
4329 All of the fields except for <tt>Provides</tt> may restrict
4330 their applicability to particular versions of each named
4331 package. This is done in parentheses after each individual
4332 package name; the parentheses should contain a relation from
4333 the list below followed by a version number, in the format
4334 described in <ref id="f-Version">.
4338 The relations allowed are <tt><<</tt>, <tt><=</tt>,
4339 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
4340 strictly earlier, earlier or equal, exactly equal, later or
4341 equal and strictly later, respectively. The deprecated
4342 forms <tt><</tt> and <tt>></tt> were used to mean
4343 earlier/later or equal, rather than strictly earlier/later,
4344 so they should not appear in new packages (though
4345 <prgn>dpkg</prgn> still supports them).
4349 Whitespace may appear at any point in the version
4350 specification subject to the rules in <ref
4351 id="controlsyntax">, and must appear where it's necessary to
4352 disambiguate; it is not otherwise significant. All of the
4353 relationship fields may span multiple lines. For
4354 consistency and in case of future changes to
4355 <prgn>dpkg</prgn> it is recommended that a single space be
4356 used after a version relationship and before a version
4357 number; it is also conventional to put a single space after
4358 each comma, on either side of each vertical bar, and before
4359 each open parenthesis. When wrapping a relationship field, it
4360 is conventional to do so after a comma and before the space
4361 following that comma.
4365 For example, a list of dependencies might appear as:
4366 <example compact="compact">
4369 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
4374 All fields that specify build-time relationships
4375 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4376 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>)
4377 may be restricted to a certain set of architectures. This
4378 is indicated in brackets after each individual package name and
4379 the optional version specification. The brackets enclose a
4380 list of Debian architecture names separated by whitespace.
4381 Exclamation marks may be prepended to each of the names.
4382 (It is not permitted for some names to be prepended with
4383 exclamation marks while others aren't.) If the current Debian
4384 host architecture is not in this list and there are no
4385 exclamation marks in the list, or it is in the list with a
4386 prepended exclamation mark, the package name and the
4387 associated version specification are ignored completely for
4388 the purposes of defining the relationships.
4393 <example compact="compact">
4395 Build-Depends-Indep: texinfo
4396 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
4397 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4399 requires <tt>kernel-headers-2.2.10</tt> on all architectures
4400 other than hurd-i386 and requires <tt>hurd-dev</tt> and
4401 <tt>gnumach-dev</tt> only on hurd-i386.
4405 If the architecture-restricted dependency is part of a set of
4406 alternatives using <tt>|</tt>, that alternative is ignored
4407 completely on architectures that do not match the restriction.
4409 <example compact="compact">
4410 Build-Depends: foo [!i386] | bar [!amd64]
4412 is equivalent to <tt>bar</tt> on the i386 architecture, to
4413 <tt>foo</tt> on the amd64 architecture, and to <tt>foo |
4414 bar</tt> on all other architectures.
4418 All fields that specify build-time relationships may also be
4419 restricted to a certain set of architectures using architecture
4420 wildcards. The syntax for declaring such restrictions is the
4421 same as declaring restrictions using a certain set of
4422 architectures without architecture wildcards. For example:
4423 <example compact="compact">
4424 Build-Depends: foo [linux-any], bar [any-i386], baz [!linux-any]
4426 is equivalent to <tt>foo</tt> on architectures using the Linux
4427 kernel and any cpu, <tt>bar</tt> on architectures using any
4428 kernel and an i386 cpu, and <tt>baz</tt> on any architecture
4429 using a kernel other than Linux.
4433 Note that the binary package relationship fields such as
4434 <tt>Depends</tt> appear in one of the binary package
4435 sections of the control file, whereas the build-time
4436 relationships such as <tt>Build-Depends</tt> appear in the
4437 source package section of the control file (which is the
4442 <sect id="binarydeps">
4443 <heading>Binary Dependencies - <tt>Depends</tt>,
4444 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4445 <tt>Pre-Depends</tt>
4449 Packages can declare in their control file that they have
4450 certain relationships to other packages - for example, that
4451 they may not be installed at the same time as certain other
4452 packages, and/or that they depend on the presence of others.
4456 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4457 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4458 <tt>Breaks</tt> and <tt>Conflicts</tt> control file fields.
4459 <tt>Breaks</tt> is described in <ref id="breaks">, and
4460 <tt>Conflicts</tt> is described in <ref id="conflicts">. The
4461 rest are described below.
4465 These seven fields are used to declare a dependency
4466 relationship by one package on another. Except for
4467 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4468 depending (binary) package's control file.
4469 (<tt>Enhances</tt> appears in the recommending package's
4470 control file, and <tt>Breaks</tt> appears in the version of
4471 depended-on package which causes the named package to
4476 A <tt>Depends</tt> field takes effect <em>only</em> when a
4477 package is to be configured. It does not prevent a package
4478 being on the system in an unconfigured state while its
4479 dependencies are unsatisfied, and it is possible to replace
4480 a package whose dependencies are satisfied and which is
4481 properly installed with a different version whose
4482 dependencies are not and cannot be satisfied; when this is
4483 done the depending package will be left unconfigured (since
4484 attempts to configure it will give errors) and will not
4485 function properly. If it is necessary, a
4486 <tt>Pre-Depends</tt> field can be used, which has a partial
4487 effect even when a package is being unpacked, as explained
4488 in detail below. (The other three dependency fields,
4489 <tt>Recommends</tt>, <tt>Suggests</tt> and
4490 <tt>Enhances</tt>, are only used by the various front-ends
4491 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4492 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4496 For this reason packages in an installation run are usually
4497 all unpacked first and all configured later; this gives
4498 later versions of packages with dependencies on later
4499 versions of other packages the opportunity to have their
4500 dependencies satisfied.
4504 In case of circular dependencies, since installation or
4505 removal order honoring the dependency order can't be
4506 established, dependency loops are broken at some point
4507 (based on rules below), and some packages may not be able to
4508 rely on their dependencies being present when being
4509 installed or removed, depending on which side of the break
4510 of the circular dependency loop they happen to be on. If one
4511 of the packages in the loop has no postinst script, then the
4512 cycle will be broken at that package, so as to ensure that
4513 all postinst scripts run with the dependencies properly
4514 configured if this is possible. Otherwise the breaking point
4519 The <tt>Depends</tt> field thus allows package maintainers
4520 to impose an order in which packages should be configured.
4524 The meaning of the five dependency fields is as follows:
4526 <tag><tt>Depends</tt></tag>
4529 This declares an absolute dependency. A package will
4530 not be configured unless all of the packages listed in
4531 its <tt>Depends</tt> field have been correctly
4536 The <tt>Depends</tt> field should be used if the
4537 depended-on package is required for the depending
4538 package to provide a significant amount of
4543 The <tt>Depends</tt> field should also be used if the
4544 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4545 <prgn>postrm</prgn> scripts require the package to be
4546 present in order to run. Note, however, that the
4547 <prgn>postrm</prgn> cannot rely on any non-essential
4548 packages to be present during the <tt>purge</tt>
4552 <tag><tt>Recommends</tt></tag>
4555 This declares a strong, but not absolute, dependency.
4559 The <tt>Recommends</tt> field should list packages
4560 that would be found together with this one in all but
4561 unusual installations.
4565 <tag><tt>Suggests</tt></tag>
4567 This is used to declare that one package may be more
4568 useful with one or more others. Using this field
4569 tells the packaging system and the user that the
4570 listed packages are related to this one and can
4571 perhaps enhance its usefulness, but that installing
4572 this one without them is perfectly reasonable.
4575 <tag><tt>Enhances</tt></tag>
4577 This field is similar to Suggests but works in the
4578 opposite direction. It is used to declare that a
4579 package can enhance the functionality of another
4583 <tag><tt>Pre-Depends</tt></tag>
4586 This field is like <tt>Depends</tt>, except that it
4587 also forces <prgn>dpkg</prgn> to complete installation
4588 of the packages named before even starting the
4589 installation of the package which declares the
4590 pre-dependency, as follows:
4594 When a package declaring a pre-dependency is about to
4595 be <em>unpacked</em> the pre-dependency can be
4596 satisfied if the depended-on package is either fully
4597 configured, <em>or even if</em> the depended-on
4598 package(s) are only unpacked or in the "Half-Configured"
4599 state, provided that they have been configured
4600 correctly at some point in the past (and not removed
4601 or partially removed since). In this case, both the
4602 previously-configured and currently unpacked or
4603 "Half-Configured" versions must satisfy any version
4604 clause in the <tt>Pre-Depends</tt> field.
4608 When the package declaring a pre-dependency is about
4609 to be <em>configured</em>, the pre-dependency will be
4610 treated as a normal <tt>Depends</tt>, that is, it will
4611 be considered satisfied only if the depended-on
4612 package has been correctly configured.
4616 <tt>Pre-Depends</tt> should be used sparingly,
4617 preferably only by packages whose premature upgrade or
4618 installation would hamper the ability of the system to
4619 continue with any upgrade that might be in progress.
4623 <tt>Pre-Depends</tt> are also required if the
4624 <prgn>preinst</prgn> script depends on the named
4625 package. It is best to avoid this situation if
4633 When selecting which level of dependency to use you should
4634 consider how important the depended-on package is to the
4635 functionality of the one declaring the dependency. Some
4636 packages are composed of components of varying degrees of
4637 importance. Such a package should list using
4638 <tt>Depends</tt> the package(s) which are required by the
4639 more important components. The other components'
4640 requirements may be mentioned as Suggestions or
4641 Recommendations, as appropriate to the components' relative
4647 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4650 When one binary package declares that it breaks another,
4651 <prgn>dpkg</prgn> will refuse to allow the package which
4652 declares <tt>Breaks</tt> be installed unless the broken
4653 package is deconfigured first, and it will refuse to
4654 allow the broken package to be reconfigured.
4658 A package will not be regarded as causing breakage merely
4659 because its configuration files are still installed; it must
4660 be at least "Half-Installed".
4664 A special exception is made for packages which declare that
4665 they break their own package name or a virtual package which
4666 they provide (see below): this does not count as a real
4671 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4672 version clause; such a <tt>Breaks</tt> is introduced in the
4673 version of an (implicit or explicit) dependency which violates
4674 an assumption or reveals a bug in earlier versions of the broken
4675 package, or which takes over a file from earlier versions of the
4676 package named in <tt>Breaks</tt>. This use of <tt>Breaks</tt>
4677 will inform higher-level package management tools that the
4678 broken package must be upgraded before the new one.
4682 If the breaking package also overwrites some files from the
4683 older package, it should use <tt>Replaces</tt> to ensure this
4684 goes smoothly. See <ref id="replaces"> for a full discussion
4685 of taking over files from other packages, including how to
4686 use <tt>Breaks</tt> in those cases.
4690 Many of the cases where <tt>Breaks</tt> should be used were
4691 previously handled with <tt>Conflicts</tt>
4692 because <tt>Breaks</tt> did not yet exist.
4693 Many <tt>Conflicts</tt> fields should now be <tt>Breaks</tt>.
4694 See <ref id="conflicts"> for more information about the
4699 <sect id="conflicts">
4700 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4703 When one binary package declares a conflict with another
4704 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4705 refuse to allow them to be installed on the system at the
4706 same time. This is a stronger restriction than <tt>Breaks</tt>,
4707 which just prevents both packages from being configured at the
4708 same time. Conflicting packages cannot be unpacked on the
4709 system at the same time.
4713 If one package is to be installed, the other must be removed
4714 first. If the package being installed is marked as replacing
4715 (see <ref id="replaces">, but note that <tt>Breaks</tt> should
4716 normally be used in this case) the one on the system, or the one
4717 on the system is marked as deselected, or both packages are
4718 marked <tt>Essential</tt>, then <prgn>dpkg</prgn> will
4719 automatically remove the package which is causing the conflict.
4720 Otherwise, it will halt the installation of the new package with
4721 an error. This mechanism is specifically designed to produce an
4722 error when the installed package is <tt>Essential</tt>, but the
4727 A package will not cause a conflict merely because its
4728 configuration files are still installed; it must be at least
4733 A special exception is made for packages which declare a
4734 conflict with their own package name, or with a virtual
4735 package which they provide (see below): this does not
4736 prevent their installation, and allows a package to conflict
4737 with others providing a replacement for it. You use this
4738 feature when you want the package in question to be the only
4739 package providing some feature.
4743 Normally, <tt>Breaks</tt> should be used instead
4744 of <tt>Conflicts</tt> since <tt>Conflicts</tt> imposes a
4745 stronger restriction on the ordering of package installation or
4746 upgrade and can make it more difficult for the package manager
4747 to find a correct solution to an upgrade or installation
4748 problem. <tt>Breaks</tt> should be used
4750 <item>when moving a file from one package to another (see
4751 <ref id="replaces">),</item>
4752 <item>when splitting a package (a special case of the previous
4754 <item>when the breaking package exposes a bug in or interacts
4755 badly with particular versions of the broken
4758 <tt>Conflicts</tt> should be used
4760 <item>when two packages provide the same file and will
4761 continue to do so,</item>
4762 <item>in conjunction with <tt>Provides</tt> when only one
4763 package providing a given virtual facility may be installed
4764 at a time (see <ref id="virtual">),</item>
4765 <item>in other cases where one must prevent simultaneous
4766 installation of two packages for reasons that are ongoing
4767 (not fixed in a later version of one of the packages) or
4768 that must prevent both packages from being unpacked at the
4769 same time, not just configured.</item>
4771 Be aware that adding <tt>Conflicts</tt> is normally not the best
4772 solution when two packages provide the same files. Depending on
4773 the reason for that conflict, using alternatives or renaming the
4774 files is often a better approach. See, for
4775 example, <ref id="binaries">.
4779 A <tt>Conflicts</tt> entry may have an "earlier than" version
4780 clause if the reason for the conflict is corrected in a later
4781 version of one of the packages. However, normally the presence
4782 of an "earlier than" version clause is a sign
4783 that <tt>Breaks</tt> should have been used instead. An "earlier
4784 than" version clause in <tt>Conflicts</tt>
4785 prevents <prgn>dpkg</prgn> from upgrading or installing the
4786 package which declares such a conflict until the upgrade or
4787 removal of the conflicted-with package has been completed, which
4788 is a strong restriction.
4792 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4796 As well as the names of actual ("concrete") packages, the
4797 package relationship fields <tt>Depends</tt>,
4798 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4799 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4800 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4801 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4802 may mention "virtual packages".
4806 A <em>virtual package</em> is one which appears in the
4807 <tt>Provides</tt> control file field of another package.
4808 The effect is as if the package(s) which provide a
4809 particular virtual package name had been listed by name
4810 everywhere the virtual package name appears. (See also <ref
4815 If there are both concrete and virtual packages of the same
4816 name, then the dependency may be satisfied (or the conflict
4817 caused) by either the concrete package with the name in
4818 question or any other concrete package which provides the
4819 virtual package with the name in question. This is so that,
4820 for example, supposing we have
4821 <example compact="compact">
4824 </example> and someone else releases an enhanced version of
4825 the <tt>bar</tt> package they can say:
4826 <example compact="compact">
4830 and the <tt>bar-plus</tt> package will now also satisfy the
4831 dependency for the <tt>foo</tt> package.
4835 If a relationship field has a version number attached, only real
4836 packages will be considered to see whether the relationship is
4837 satisfied (or the prohibition violated, for a conflict or
4838 breakage). In other words, if a version number is specified,
4839 this is a request to ignore all <tt>Provides</tt> for that
4840 package name and consider only real packages. The package
4841 manager will assume that a package providing that virtual
4842 package is not of the "right" version. A <tt>Provides</tt>
4843 field may not contain version numbers, and the version number of
4844 the concrete package which provides a particular virtual package
4845 will not be considered when considering a dependency on or
4846 conflict with the virtual package name.<footnote>
4847 It is possible that a future release of <prgn>dpkg</prgn> may
4848 add the ability to specify a version number for each virtual
4849 package it provides. This feature is not yet present,
4850 however, and is expected to be used only infrequently.
4855 To specify which of a set of real packages should be the default
4856 to satisfy a particular dependency on a virtual package, list
4857 the real package as an alternative before the virtual one.
4861 If the virtual package represents a facility that can only be
4862 provided by one real package at a time, such as
4863 the <package>mail-transport-agent</package> virtual package that
4864 requires installation of a binary that would conflict with all
4865 other providers of that virtual package (see
4866 <ref id="mail-transport-agents">), all packages providing that
4867 virtual package should also declare a conflict with it
4868 using <tt>Conflicts</tt>. This will ensure that at most one
4869 provider of that virtual package is unpacked or installed at a
4874 <sect id="replaces"><heading>Overwriting files and replacing
4875 packages - <tt>Replaces</tt></heading>
4878 Packages can declare in their control file that they should
4879 overwrite files in certain other packages, or completely
4880 replace other packages. The <tt>Replaces</tt> control file
4881 field has these two distinct purposes.
4884 <sect1><heading>Overwriting files in other packages</heading>
4887 It is usually an error for a package to contain files which
4888 are on the system in another package. However, if the
4889 overwriting package declares that it <tt>Replaces</tt> the one
4890 containing the file being overwritten, then <prgn>dpkg</prgn>
4891 will replace the file from the old package with that from the
4892 new. The file will no longer be listed as "owned" by the old
4893 package and will be taken over by the new package.
4894 Normally, <tt>Breaks</tt> should be used in conjunction
4895 with <tt>Replaces</tt>.<footnote>
4896 To see why <tt>Breaks</tt> is normally needed in addition
4897 to <tt>Replaces</tt>, consider the case of a file in the
4898 package <package>foo</package> being taken over by the
4899 package <package>foo-data</package>.
4900 <tt>Replaces</tt> will allow <package>foo-data</package> to
4901 be installed and take over that file. However,
4902 without <tt>Breaks</tt>, nothing
4903 requires <package>foo</package> to be upgraded to a newer
4904 version that knows it does not include that file and instead
4905 depends on <package>foo-data</package>. Nothing would
4906 prevent the new <package>foo-data</package> package from
4907 being installed and then removed, removing the file that it
4908 took over from <package>foo</package>. After that
4909 operation, the package manager would think the system was in
4910 a consistent state, but the <package>foo</package> package
4911 would be missing one of its files.
4916 For example, if a package <package>foo</package> is split
4917 into <package>foo</package> and <package>foo-data</package>
4918 starting at version 1.2-3, <package>foo-data</package> would
4920 <example compact="compact">
4921 Replaces: foo (<< 1.2-3)
4922 Breaks: foo (<< 1.2-3)
4924 in its control file. The new version of the
4925 package <package>foo</package> would normally have the field
4926 <example compact="compact">
4927 Depends: foo-data (>= 1.2-3)
4929 (or possibly <tt>Recommends</tt> or even <tt>Suggests</tt> if
4930 the files moved into <package>foo-data</package> are not
4931 required for normal operation).
4935 If a package is completely replaced in this way, so that
4936 <prgn>dpkg</prgn> does not know of any files it still
4937 contains, it is considered to have "disappeared". It will
4938 be marked as not wanted on the system (selected for
4939 removal) and not installed. Any <tt>conffile</tt>s
4940 details noted for the package will be ignored, as they
4941 will have been taken over by the overwriting package. The
4942 package's <prgn>postrm</prgn> script will be run with a
4943 special argument to allow the package to do any final
4944 cleanup required. See <ref id="mscriptsinstact">.
4946 Replaces is a one way relationship. You have to install
4947 the replacing package after the replaced package.
4952 For this usage of <tt>Replaces</tt>, virtual packages (see
4953 <ref id="virtual">) are not considered when looking at a
4954 <tt>Replaces</tt> field. The packages declared as being
4955 replaced must be mentioned by their real names.
4959 This usage of <tt>Replaces</tt> only takes effect when both
4960 packages are at least partially on the system at once. It is
4961 not relevant if the packages conflict unless the conflict has
4966 <sect1><heading>Replacing whole packages, forcing their
4970 Second, <tt>Replaces</tt> allows the packaging system to
4971 resolve which package should be removed when there is a
4972 conflict (see <ref id="conflicts">). This usage only takes
4973 effect when the two packages <em>do</em> conflict, so that the
4974 two usages of this field do not interfere with each other.
4978 In this situation, the package declared as being replaced
4979 can be a virtual package, so for example, all mail
4980 transport agents (MTAs) would have the following fields in
4981 their control files:
4982 <example compact="compact">
4983 Provides: mail-transport-agent
4984 Conflicts: mail-transport-agent
4985 Replaces: mail-transport-agent
4987 ensuring that only one MTA can be installed at any one
4988 time. See <ref id="virtual"> for more information about this
4993 <sect id="sourcebinarydeps">
4994 <heading>Relationships between source and binary packages -
4995 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4996 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
5000 Source packages that require certain binary packages to be
5001 installed or absent at the time of building the package
5002 can declare relationships to those binary packages.
5006 This is done using the <tt>Build-Depends</tt>,
5007 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
5008 <tt>Build-Conflicts-Indep</tt> control file fields.
5012 Build-dependencies on "build-essential" binary packages can be
5013 omitted. Please see <ref id="pkg-relations"> for more information.
5017 The dependencies and conflicts they define must be satisfied
5018 (as defined earlier for binary packages) in order to invoke
5019 the targets in <tt>debian/rules</tt>, as follows:<footnote>
5021 There is no Build-Depends-Arch; this role is essentially
5022 met with Build-Depends. Anyone building the
5023 <tt>build-indep</tt> and binary-indep<tt></tt> targets is
5024 assumed to be building the whole package, and therefore
5025 installation of all build dependencies is required.
5028 The autobuilders use <tt>dpkg-buildpackage -B</tt>, which
5029 calls <tt>build</tt>, not <tt>build-arch</tt> since it does
5030 not yet know how to check for its existence, and
5031 <tt>binary-arch</tt>. The purpose of the original split
5032 between <tt>Build-Depends</tt> and
5033 <tt>Build-Depends-Indep</tt> was so that the autobuilders
5034 wouldn't need to install extra packages needed only for the
5035 binary-indep targets. But without a build-arch/build-indep
5036 split, this didn't work, since most of the work is done in
5037 the build target, not in the binary target.
5041 <tag><tt>clean</tt>, <tt>build-arch</tt>, and
5042 <tt>binary-arch</tt></tag>
5044 Only the <tt>Build-Depends</tt> and <tt>Build-Conflicts</tt>
5045 fields must be satisfied when these targets are invoked.
5047 <tag><tt>build</tt>, <tt>build-indep</tt>, <tt>binary</tt>,
5048 and <tt>binary-indep</tt></tag>
5050 The <tt>Build-Depends</tt>, <tt>Build-Conflicts</tt>,
5051 <tt>Build-Depends-Indep</tt>, and
5052 <tt>Build-Conflicts-Indep</tt> fields must be satisfied when
5053 these targets are invoked.
5061 <chapt id="sharedlibs"><heading>Shared libraries</heading>
5064 Packages containing shared libraries must be constructed with
5065 a little care to make sure that the shared library is always
5066 available. This is especially important for packages whose
5067 shared libraries are vitally important, such as the C library
5068 (currently <tt>libc6</tt>).
5072 Packages involving shared libraries should be split up into
5073 several binary packages. This section mostly deals with how
5074 this separation is to be accomplished; rules for files within
5075 the shared library packages are in <ref id="libraries"> instead.
5078 <sect id="sharedlibs-runtime">
5079 <heading>Run-time shared libraries</heading>
5082 The run-time shared library needs to be placed in a package
5083 whose name changes whenever the shared object version
5086 Since it is common place to install several versions of a
5087 package that just provides shared libraries, it is a
5088 good idea that the library package should not
5089 contain any extraneous non-versioned files, unless they
5090 happen to be in versioned directories.</p>
5092 The most common mechanism is to place it in a package
5094 <package><var>libraryname</var><var>soversion</var></package>,
5095 where <file><var>soversion</var></file> is the version number
5096 in the soname of the shared library<footnote>
5097 The soname is the shared object name: it's the thing
5098 that has to match exactly between building an executable
5099 and running it for the dynamic linker to be able run the
5100 program. For example, if the soname of the library is
5101 <file>libfoo.so.6</file>, the library package would be
5102 called <file>libfoo6</file>.
5104 Alternatively, if it would be confusing to directly append
5105 <var>soversion</var> to <var>libraryname</var> (e.g. because
5106 <var>libraryname</var> itself ends in a number), you may use
5107 <package><var>libraryname</var>-<var>soversion</var></package> and
5108 <package><var>libraryname</var>-<var>soversion</var>-dev</package>
5113 If you have several shared libraries built from the same
5114 source tree you may lump them all together into a single
5115 shared library package, provided that you change all of
5116 their sonames at once (so that you don't get filename
5117 clashes if you try to install different versions of the
5118 combined shared libraries package).
5122 The package should install the shared libraries under
5123 their normal names. For example, the <package>libgdbm3</package>
5124 package should install <file>libgdbm.so.3.0.0</file> as
5125 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
5126 renamed or re-linked by any <prgn>prerm</prgn> or
5127 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
5128 of renaming things safely without affecting running programs,
5129 and attempts to interfere with this are likely to lead to
5134 Shared libraries should not be installed executable, since
5135 the dynamic linker does not require this and trying to
5136 execute a shared library usually results in a core dump.
5140 The run-time library package should include the symbolic link that
5141 <prgn>ldconfig</prgn> would create for the shared libraries.
5142 For example, the <package>libgdbm3</package> package should include
5143 a symbolic link from <file>/usr/lib/libgdbm.so.3</file> to
5144 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
5145 linker (for example <prgn>ld.so</prgn> or
5146 <prgn>ld-linux.so.*</prgn>) can find the library between the
5147 time that <prgn>dpkg</prgn> installs it and the time that
5148 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
5150 The package management system requires the library to be
5151 placed before the symbolic link pointing to it in the
5152 <file>.deb</file> file. This is so that when
5153 <prgn>dpkg</prgn> comes to install the symlink
5154 (overwriting the previous symlink pointing at an older
5155 version of the library), the new shared library is already
5156 in place. In the past, this was achieved by creating the
5157 library in the temporary packaging directory before
5158 creating the symlink. Unfortunately, this was not always
5159 effective, since the building of the tar file in the
5160 <file>.deb</file> depended on the behavior of the underlying
5161 file system. Some file systems (such as reiserfs) reorder
5162 the files so that the order of creation is forgotten.
5163 Since version 1.7.0, <prgn>dpkg</prgn>
5164 reorders the files itself as necessary when building a
5165 package. Thus it is no longer important to concern
5166 oneself with the order of file creation.
5170 <sect1 id="ldconfig">
5171 <heading><tt>ldconfig</tt></heading>
5174 Any package installing shared libraries in one of the default
5175 library directories of the dynamic linker (which are currently
5176 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
5177 listed in <file>/etc/ld.so.conf</file><footnote>
5179 <list compact="compact">
5180 <item>/usr/local/lib</item>
5181 <item>/usr/lib/libc5-compat</item>
5182 <item>/lib/libc5-compat</item>
5185 must use <prgn>ldconfig</prgn> to update the shared library
5190 The package maintainer scripts must only call
5191 <prgn>ldconfig</prgn> under these circumstances:
5192 <list compact="compact">
5193 <item>When the <prgn>postinst</prgn> script is run with a
5194 first argument of <tt>configure</tt>, the script must call
5195 <prgn>ldconfig</prgn>, and may optionally invoke
5196 <prgn>ldconfig</prgn> at other times.
5198 <item>When the <prgn>postrm</prgn> script is run with a
5199 first argument of <tt>remove</tt>, the script should call
5200 <prgn>ldconfig</prgn>.
5205 During install or upgrade, the preinst is called before
5206 the new files are installed, so calling "ldconfig" is
5207 pointless. The preinst of an existing package can also be
5208 called if an upgrade fails. However, this happens during
5209 the critical time when a shared libs may exist on-disk
5210 under a temporary name. Thus, it is dangerous and
5211 forbidden by current policy to call "ldconfig" at this
5216 When a package is installed or upgraded, "postinst
5217 configure" runs after the new files are safely on-disk.
5218 Since it is perfectly safe to invoke ldconfig
5219 unconditionally in a postinst, it is OK for a package to
5220 simply put ldconfig in its postinst without checking the
5221 argument. The postinst can also be called to recover from
5222 a failed upgrade. This happens before any new files are
5223 unpacked, so there is no reason to call "ldconfig" at this
5228 For a package that is being removed, prerm is
5229 called with all the files intact, so calling ldconfig is
5230 useless. The other calls to "prerm" happen in the case of
5231 upgrade at a time when all the files of the old package
5232 are on-disk, so again calling "ldconfig" is pointless.
5236 postrm, on the other hand, is called with the "remove"
5237 argument just after the files are removed, so this is
5238 the proper time to call "ldconfig" to notify the system
5239 of the fact that the shared libraries from the package
5240 are removed. The postrm can be called at several other
5241 times. At the time of "postrm purge", "postrm
5242 abort-install", or "postrm abort-upgrade", calling
5243 "ldconfig" is useless because the shared lib files are
5244 not on-disk. However, when "postrm" is invoked with
5245 arguments "upgrade", "failed-upgrade", or "disappear", a
5246 shared lib may exist on-disk under a temporary filename.
5254 <sect id="sharedlibs-support-files">
5255 <heading>Shared library support files</heading>
5258 If your package contains files whose names do not change with
5259 each change in the library shared object version, you must not
5260 put them in the shared library package. Otherwise, several
5261 versions of the shared library cannot be installed at the same
5262 time without filename clashes, making upgrades and transitions
5263 unnecessarily difficult.
5267 It is recommended that supporting files and run-time support
5268 programs that do not need to be invoked manually by users, but
5269 are nevertheless required for the package to function, be placed
5270 (if they are binary) in a subdirectory of <file>/usr/lib</file>,
5271 preferably under <file>/usr/lib/</file><var>package-name</var>.
5272 If the program or file is architecture independent, the
5273 recommendation is for it to be placed in a subdirectory of
5274 <file>/usr/share</file> instead, preferably under
5275 <file>/usr/share/</file><var>package-name</var>. Following the
5276 <var>package-name</var> naming convention ensures that the file
5277 names change when the shared object version changes.
5281 Run-time support programs that use the shared library but are
5282 not required for the library to function or files used by the
5283 shared library that can be used by any version of the shared
5284 library package should instead be put in a separate package.
5285 This package might typically be named
5286 <package><var>libraryname</var>-tools</package>; note the
5287 absence of the <var>soversion</var> in the package name.
5291 Files and support programs only useful when compiling software
5292 against the library should be included in the development
5293 package for the library.<footnote>
5294 For example, a <file><var>package-name</var>-config</file>
5295 script or <package>pkg-config</package> configuration files.
5300 <sect id="sharedlibs-static">
5301 <heading>Static libraries</heading>
5304 The static library (<file><var>libraryname.a</var></file>)
5305 is usually provided in addition to the shared version.
5306 It is placed into the development package (see below).
5310 In some cases, it is acceptable for a library to be
5311 available in static form only; these cases include:
5313 <item>libraries for languages whose shared library support
5314 is immature or unstable</item>
5315 <item>libraries whose interfaces are in flux or under
5316 development (commonly the case when the library's
5317 major version number is zero, or where the ABI breaks
5318 across patchlevels)</item>
5319 <item>libraries which are explicitly intended to be
5320 available only in static form by their upstream
5325 <sect id="sharedlibs-dev">
5326 <heading>Development files</heading>
5329 If there are development files associated with a shared library,
5330 the source package needs to generate a binary development package
5331 named <package><var>libraryname</var><var>soversion</var>-dev</package>,
5332 or if you prefer only to support one development version at a
5333 time, <package><var>libraryname</var>-dev</package>. Installing
5334 the development package must result in installation of all the
5335 development files necessary for compiling programs against that
5336 shared library.<footnote>
5337 This wording allows the development files to be split into
5338 several packages, such as a separate architecture-independent
5339 <package><var>libraryname</var>-headers</package>, provided that
5340 the development package depends on all the required additional
5346 In case several development versions of a library exist, you may
5347 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
5348 <ref id="conflicts">) to ensure that the user only installs one
5349 development version at a time (as different development versions are
5350 likely to have the same header files in them, which would cause a
5351 filename clash if both were installed).
5355 The development package should contain a symlink for the associated
5356 shared library without a version number. For example, the
5357 <package>libgdbm-dev</package> package should include a symlink
5358 from <file>/usr/lib/libgdbm.so</file> to
5359 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
5360 (<prgn>ld</prgn>) when compiling packages, as it will only look for
5361 <file>libgdbm.so</file> when compiling dynamically.
5365 <sect id="sharedlibs-intradeps">
5366 <heading>Dependencies between the packages of the same library</heading>
5369 Typically the development version should have an exact
5370 version dependency on the runtime library, to make sure that
5371 compilation and linking happens correctly. The
5372 <tt>${binary:Version}</tt> substitution variable can be
5373 useful for this purpose.
5375 Previously, <tt>${Source-Version}</tt> was used, but its name
5376 was confusing and it has been deprecated since dpkg 1.13.19.
5381 <sect id="sharedlibs-shlibdeps">
5382 <heading>Dependencies between the library and other packages -
5383 the <tt>shlibs</tt> system</heading>
5386 If a package contains a binary or library which links to a
5387 shared library, we must ensure that when the package is
5388 installed on the system, all of the libraries needed are
5389 also installed. This requirement led to the creation of the
5390 <tt>shlibs</tt> system, which is very simple in its design:
5391 any package which <em>provides</em> a shared library also
5392 provides information on the package dependencies required to
5393 ensure the presence of this library, and any package which
5394 <em>uses</em> a shared library uses this information to
5395 determine the dependencies it requires. The files which
5396 contain the mapping from shared libraries to the necessary
5397 dependency information are called <file>shlibs</file> files.
5401 Thus, when a package is built which contains any shared
5402 libraries, it must provide a <file>shlibs</file> file for other
5403 packages to use, and when a package is built which contains
5404 any shared libraries or compiled binaries, it must run
5405 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5406 on these to determine the libraries used and hence the
5407 dependencies needed by this package.<footnote>
5409 In the past, the shared libraries linked to were
5410 determined by calling <prgn>ldd</prgn>, but now
5411 <prgn>objdump</prgn> is used to do this. The only
5412 change this makes to package building is that
5413 <prgn>dpkg-shlibdeps</prgn> must also be run on shared
5414 libraries, whereas in the past this was unnecessary.
5415 The rest of this footnote explains the advantage that
5420 We say that a binary <tt>foo</tt> <em>directly</em> uses
5421 a library <tt>libbar</tt> if it is explicitly linked
5422 with that library (that is, it uses the flag
5423 <tt>-lbar</tt> during the linking stage). Other
5424 libraries that are needed by <tt>libbar</tt> are linked
5425 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
5426 linker will load them automatically when it loads
5427 <tt>libbar</tt>. A package should depend on
5428 the libraries it directly uses, and the dependencies for
5429 those libraries should automatically pull in the other
5434 Unfortunately, the <prgn>ldd</prgn> program shows both
5435 the directly and indirectly used libraries, meaning that
5436 the dependencies determined included both direct and
5437 indirect dependencies. The use of <prgn>objdump</prgn>
5438 avoids this problem by determining only the directly
5443 A good example of where this helps is the following. We
5444 could update <tt>libimlib</tt> with a new version that
5445 supports a new graphics format called dgf (but retaining
5446 the same major version number). If we used the old
5447 <prgn>ldd</prgn> method, every package that uses
5448 <tt>libimlib</tt> would need to be recompiled so it
5449 would also depend on <tt>libdgf</tt> or it wouldn't run
5450 due to missing symbols. However with the new system,
5451 packages using <tt>libimlib</tt> can rely on
5452 <tt>libimlib</tt> itself having the dependency on
5453 <tt>libdgf</tt> and so they would not need rebuilding.
5459 In the following sections, we will first describe where the
5460 various <tt>shlibs</tt> files are to be found, then how to
5461 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
5462 file format and how to create them if your package contains a
5467 <heading>The <tt>shlibs</tt> files present on the system</heading>
5470 There are several places where <tt>shlibs</tt> files are
5471 found. The following list gives them in the order in which
5473 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
5474 (The first one which gives the required information is used.)
5480 <p><file>debian/shlibs.local</file></p>
5483 This lists overrides for this package. Its use is
5484 described below (see <ref id="shlibslocal">).
5489 <p><file>/etc/dpkg/shlibs.override</file></p>
5492 This lists global overrides. This list is normally
5493 empty. It is maintained by the local system
5499 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
5502 When packages are being built, any
5503 <file>debian/shlibs</file> files are copied into the
5504 control file area of the temporary build directory and
5505 given the name <file>shlibs</file>. These files give
5506 details of any shared libraries included in the
5508 An example may help here. Let us say that the
5509 source package <tt>foo</tt> generates two binary
5510 packages, <tt>libfoo2</tt> and
5511 <tt>foo-runtime</tt>. When building the binary
5512 packages, the two packages are created in the
5513 directories <file>debian/libfoo2</file> and
5514 <file>debian/foo-runtime</file> respectively.
5515 (<file>debian/tmp</file> could be used instead of one
5516 of these.) Since <tt>libfoo2</tt> provides the
5517 <tt>libfoo</tt> shared library, it will require a
5518 <tt>shlibs</tt> file, which will be installed in
5519 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually
5521 <file>/var/lib/dpkg/info/libfoo2.shlibs</file>. Then
5522 when <prgn>dpkg-shlibdeps</prgn> is run on the
5524 <file>debian/foo-runtime/usr/bin/foo-prog</file>, it
5526 <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5527 determine whether <tt>foo-prog</tt>'s library
5528 dependencies are satisfied by any of the libraries
5529 provided by <tt>libfoo2</tt>. For this reason,
5530 <prgn>dpkg-shlibdeps</prgn> must only be run once
5531 all of the individual binary packages'
5532 <tt>shlibs</tt> files have been installed into the
5539 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5542 These are the <file>shlibs</file> files corresponding to
5543 all of the packages installed on the system, and are
5544 maintained by the relevant package maintainers.
5549 <p><file>/etc/dpkg/shlibs.default</file></p>
5552 This file lists any shared libraries whose packages
5553 have failed to provide correct <file>shlibs</file> files.
5554 It was used when the <file>shlibs</file> setup was first
5555 introduced, but it is now normally empty. It is
5556 maintained by the <tt>dpkg</tt> maintainer.
5564 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5565 <file>shlibs</file> files</heading>
5569 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5570 into your <file>debian/rules</file> file. If your package
5571 contains only compiled binaries and libraries (but no scripts),
5572 you can use a command such as:
5573 <example compact="compact">
5574 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5575 debian/tmp/usr/lib/*
5577 Otherwise, you will need to explicitly list the compiled
5578 binaries and libraries.<footnote>
5579 If you are using <tt>debhelper</tt>, the
5580 <prgn>dh_shlibdeps</prgn> program will do this work for
5581 you. It will also correctly handle multi-binary
5587 This command puts the dependency information into the
5588 <file>debian/substvars</file> file, which is then used by
5589 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5590 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5591 field in the control file for this to work.
5595 If <prgn>dpkg-shlibdeps</prgn> doesn't complain, you're
5596 done. If it does complain you might need to create your own
5597 <file>debian/shlibs.local</file> file, as explained below (see
5598 <ref id="shlibslocal">).
5602 If you have multiple binary packages, you will need to call
5603 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5604 compiled libraries or binaries. In such a case, you will
5605 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5606 utilities to specify a different <file>substvars</file> file.
5610 If you are creating a udeb for use in the Debian Installer,
5611 you will need to specify that <prgn>dpkg-shlibdeps</prgn>
5612 should use the dependency line of type <tt>udeb</tt> by
5613 adding the <tt>-tudeb</tt> option<footnote>
5614 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5615 will automatically add this option if it knows it is
5617 </footnote>. If there is no dependency line of type <tt>udeb</tt>
5618 in the <file>shlibs</file> file, <prgn>dpkg-shlibdeps</prgn> will
5619 fall back to the regular dependency line.
5623 For more details on dpkg-shlibdeps, please see
5624 <ref id="pkg-dpkg-shlibdeps"> and
5625 <manref name="dpkg-shlibdeps" section="1">.
5630 <heading>The <file>shlibs</file> File Format</heading>
5633 Each <file>shlibs</file> file has the same format. Lines
5634 beginning with <tt>#</tt> are considered to be comments and
5635 are ignored. Each line is of the form:
5636 <example compact="compact">
5637 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5642 We will explain this by reference to the example of the
5643 <tt>zlib1g</tt> package, which (at the time of writing)
5644 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5648 <var>type</var> is an optional element that indicates the type
5649 of package for which the line is valid. The only type currently
5650 in use is <tt>udeb</tt>. The colon and space after the type are
5655 <var>library-name</var> is the name of the shared library,
5656 in this case <tt>libz</tt>. (This must match the name part
5657 of the soname, see below.)
5661 <var>soname-version</var> is the version part of the soname of
5662 the library. The soname is the thing that must exactly match
5663 for the library to be recognized by the dynamic linker, and is
5665 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5666 example, <tt>libz.so.1</tt>.<footnote>
5667 This can be determined using the command
5668 <example compact="compact">
5669 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5672 The version part is the part which comes after
5673 <tt>.so.</tt>, so in our case, it is <tt>1</tt>.
5677 <var>dependencies</var> has the same syntax as a dependency
5678 field in a binary package control file. It should give
5679 details of which packages are required to satisfy a binary
5680 built against the version of the library contained in the
5681 package. See <ref id="depsyntax"> for details.
5685 In our example, if the first version of the <tt>zlib1g</tt>
5686 package which contained a minor number of at least
5687 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5688 <tt>shlibs</tt> entry for this library could say:
5689 <example compact="compact">
5690 libz 1 zlib1g (>= 1:1.1.3)
5692 The version-specific dependency is to avoid warnings from
5693 the dynamic linker about using older shared libraries with
5698 As zlib1g also provides a udeb containing the shared library,
5699 there would also be a second line:
5700 <example compact="compact">
5701 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5707 <heading>Providing a <file>shlibs</file> file</heading>
5710 If your package provides a shared library, you need to create
5711 a <file>shlibs</file> file following the format described above.
5712 It is usual to call this file <file>debian/shlibs</file> (but if
5713 you have multiple binary packages, you might want to call it
5714 <file>debian/shlibs.<var>package</var></file> instead). Then
5715 let <file>debian/rules</file> install it in the control area:
5716 <example compact="compact">
5717 install -m644 debian/shlibs debian/tmp/DEBIAN
5719 or, in the case of a multi-binary package:
5720 <example compact="compact">
5721 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5723 An alternative way of doing this is to create the
5724 <file>shlibs</file> file in the control area directly from
5725 <file>debian/rules</file> without using a <file>debian/shlibs</file>
5726 file at all,<footnote>
5727 This is what <prgn>dh_makeshlibs</prgn> in the
5728 <tt>debhelper</tt> suite does. If your package also has a udeb
5729 that provides a shared library, <prgn>dh_makeshlibs</prgn> can
5730 automatically generate the <tt>udeb:</tt> lines if you specify
5731 the name of the udeb with the <tt>--add-udeb</tt> option.
5733 since the <file>debian/shlibs</file> file itself is ignored by
5734 <prgn>dpkg-shlibdeps</prgn>.
5738 As <prgn>dpkg-shlibdeps</prgn> reads the
5739 <file>DEBIAN/shlibs</file> files in all of the binary packages
5740 being built from this source package, all of the
5741 <file>DEBIAN/shlibs</file> files should be installed before
5742 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5747 <sect1 id="shlibslocal">
5748 <heading>Writing the <file>debian/shlibs.local</file> file</heading>
5751 This file is intended only as a <em>temporary</em> fix if
5752 your binaries or libraries depend on a library whose package
5753 does not yet provide a correct <file>shlibs</file> file.
5757 We will assume that you are trying to package a binary
5758 <tt>foo</tt>. When you try running
5759 <prgn>dpkg-shlibdeps</prgn> you get the following error
5760 message (<tt>-O</tt> displays the dependency information on
5761 <tt>stdout</tt> instead of writing it to
5762 <tt>debian/substvars</tt>, and the lines have been wrapped
5763 for ease of reading):
5764 <example compact="compact">
5765 $ dpkg-shlibdeps -O debian/tmp/usr/bin/foo
5766 dpkg-shlibdeps: warning: unable to find dependency
5767 information for shared library libbar (soname 1,
5768 path /usr/lib/libbar.so.1, dependency field Depends)
5769 shlibs:Depends=libc6 (>= 2.2.2-2)
5771 You can then run <prgn>ldd</prgn> on the binary to find the
5772 full location of the library concerned:
5773 <example compact="compact">
5775 libbar.so.1 => /usr/lib/libbar.so.1 (0x4001e000)
5776 libc.so.6 => /lib/libc.so.6 (0x40032000)
5777 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
5779 So the <prgn>foo</prgn> binary depends on the
5780 <prgn>libbar</prgn> shared library, but no package seems to
5781 provide a <file>*.shlibs</file> file handling
5782 <file>libbar.so.1</file> in <file>/var/lib/dpkg/info/</file>. Let's
5783 determine the package responsible:
5784 <example compact="compact">
5785 $ dpkg -S /usr/lib/libbar.so.1
5786 bar1: /usr/lib/libbar.so.1
5787 $ dpkg -s bar1 | grep Version
5790 This tells us that the <tt>bar1</tt> package, version 1.0-1,
5791 is the one we are using. Now we can file a bug against the
5792 <tt>bar1</tt> package and create our own
5793 <file>debian/shlibs.local</file> to locally fix the problem.
5794 Including the following line into your
5795 <file>debian/shlibs.local</file> file:
5796 <example compact="compact">
5797 libbar 1 bar1 (>= 1.0-1)
5799 should allow the package build to work.
5803 As soon as the maintainer of <tt>bar1</tt> provides a
5804 correct <file>shlibs</file> file, you should remove this line
5805 from your <file>debian/shlibs.local</file> file. (You should
5806 probably also then have a versioned <tt>Build-Depends</tt>
5807 on <tt>bar1</tt> to help ensure that others do not have the
5808 same problem building your package.)
5817 <chapt id="opersys"><heading>The Operating System</heading>
5820 <heading>File system hierarchy</heading>
5824 <heading>File System Structure</heading>
5827 The location of all installed files and directories must
5828 comply with the Filesystem Hierarchy Standard (FHS),
5829 version 2.3, with the exceptions noted below, and except
5830 where doing so would violate other terms of Debian
5831 Policy. The following exceptions to the FHS apply:
5836 The optional rules related to user specific
5837 configuration files for applications are stored in
5838 the user's home directory are relaxed. It is
5839 recommended that such files start with the
5840 '<tt>.</tt>' character (a "dot file"), and if an
5841 application needs to create more than one dot file
5842 then the preferred placement is in a subdirectory
5843 with a name starting with a '.' character, (a "dot
5844 directory"). In this case it is recommended the
5845 configuration files not start with the '.'
5851 The requirement for amd64 to use <file>/lib64</file>
5852 for 64 bit binaries is removed.
5857 The requirement for object files, internal binaries, and
5858 libraries, including <file>libc.so.*</file>, to be located
5859 directly under <file>/lib{,32}</file> and
5860 <file>/usr/lib{,32}</file> is amended, permitting files
5861 to instead be installed to
5862 <file>/lib/<var>triplet</var></file> and
5863 <file>/usr/lib/<var>triplet</var></file>, where
5864 <tt><var>triplet</var></tt> is the value returned by
5865 <tt>dpkg-architecture -qDEB_HOST_GNU_TYPE</tt> for the
5866 architecture of the package. Packages may <em>not</em>
5867 install files to any <var>triplet</var> path other
5868 than the one matching the architecture of that package;
5869 for instance, an <tt>Architecture: amd64</tt> package
5870 containing 32-bit x86 libraries may not install these
5871 libraries to <file>/usr/lib/i486-linux-gnu</file>.
5873 This is necessary in order to reserve the directories for
5874 use in cross-installation of library packages from other
5875 architectures, as part of the planned deployment of
5880 Applications may also use a single subdirectory under
5881 <file>/usr/lib/<var>triplet</var></file>.
5884 The execution time linker/loader, ld*, must still be made
5885 available in the existing location under /lib or /lib64
5886 since this is part of the ELF ABI for the architecture.
5891 The requirement that
5892 <file>/usr/local/share/man</file> be "synonymous"
5893 with <file>/usr/local/man</file> is relaxed to a
5898 The requirement that windowmanagers with a single
5899 configuration file call it <file>system.*wmrc</file>
5900 is removed, as is the restriction that the window
5901 manager subdirectory be named identically to the
5902 window manager name itself.
5907 The requirement that boot manager configuration
5908 files live in <file>/etc</file>, or at least are
5909 symlinked there, is relaxed to a recommendation.
5914 The following directories in the root filesystem are
5915 additionally allowed: <file>/sys</file> and
5916 <file>/selinux</file>. <footnote>These directories
5917 are used as mount points to mount virtual filesystems
5918 to get access to kernel information.</footnote>
5925 The version of this document referred here can be
5926 found in the <tt>debian-policy</tt> package or on <url
5927 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5928 name="FHS (Debian copy)"> alongside this manual (or, if
5929 you have the <package>debian-policy</package> installed,
5931 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5932 (local copy)">). The
5933 latest version, which may be a more recent version, may
5935 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5936 Specific questions about following the standard may be
5937 asked on the <tt>debian-devel</tt> mailing list, or
5938 referred to the FHS mailing list (see the
5939 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
5945 <heading>Site-specific programs</heading>
5948 As mandated by the FHS, packages must not place any
5949 files in <file>/usr/local</file>, either by putting them in
5950 the file system archive to be unpacked by <prgn>dpkg</prgn>
5951 or by manipulating them in their maintainer scripts.
5955 However, the package may create empty directories below
5956 <file>/usr/local</file> so that the system administrator knows
5957 where to place site-specific files. These are not
5958 directories <em>in</em> <file>/usr/local</file>, but are
5959 children of directories in <file>/usr/local</file>. These
5960 directories (<file>/usr/local/*/dir/</file>)
5961 should be removed on package removal if they are
5966 Note that this applies only to
5967 directories <em>below</em> <file>/usr/local</file>,
5968 not <em>in</em> <file>/usr/local</file>. Packages must
5969 not create sub-directories in the
5970 directory <file>/usr/local</file> itself, except those
5971 listed in FHS, section 4.5. However, you may create
5972 directories below them as you wish. You must not remove
5973 any of the directories listed in 4.5, even if you created
5978 Since <file>/usr/local</file> can be mounted read-only from a
5979 remote server, these directories must be created and
5980 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
5981 maintainer scripts and not be included in the
5982 <file>.deb</file> archive. These scripts must not fail if
5983 either of these operations fail.
5987 For example, the <tt>emacsen-common</tt> package could
5988 contain something like
5989 <example compact="compact">
5990 if [ ! -e /usr/local/share/emacs ]
5992 if mkdir /usr/local/share/emacs 2>/dev/null
5994 chown root:staff /usr/local/share/emacs
5995 chmod 2775 /usr/local/share/emacs
5999 in its <prgn>postinst</prgn> script, and
6000 <example compact="compact">
6001 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
6002 rmdir /usr/local/share/emacs 2>/dev/null || true
6004 in the <prgn>prerm</prgn> script. (Note that this form is
6005 used to ensure that if the script is interrupted, the
6006 directory <file>/usr/local/share/emacs</file> will still be
6011 If you do create a directory in <file>/usr/local</file> for
6012 local additions to a package, you should ensure that
6013 settings in <file>/usr/local</file> take precedence over the
6014 equivalents in <file>/usr</file>.
6018 However, because <file>/usr/local</file> and its contents are
6019 for exclusive use of the local administrator, a package
6020 must not rely on the presence or absence of files or
6021 directories in <file>/usr/local</file> for normal operation.
6025 The <file>/usr/local</file> directory itself and all the
6026 subdirectories created by the package should (by default) have
6027 permissions 2775 (group-writable and set-group-id) and be
6028 owned by <tt>root:staff</tt>.
6033 <heading>The system-wide mail directory</heading>
6035 The system-wide mail directory
6036 is <file>/var/mail</file>. This directory is part of the
6037 base system and should not be owned by any particular mail
6038 agents. The use of the old
6039 location <file>/var/spool/mail</file> is deprecated, even
6040 though the spool may still be physically located there.
6046 <heading>Users and groups</heading>
6049 <heading>Introduction</heading>
6051 The Debian system can be configured to use either plain or
6056 Some user ids (UIDs) and group ids (GIDs) are reserved
6057 globally for use by certain packages. Because some
6058 packages need to include files which are owned by these
6059 users or groups, or need the ids compiled into binaries,
6060 these ids must be used on any Debian system only for the
6061 purpose for which they are allocated. This is a serious
6062 restriction, and we should avoid getting in the way of
6063 local administration policies. In particular, many sites
6064 allocate users and/or local system groups starting at 100.
6068 Apart from this we should have dynamically allocated ids,
6069 which should by default be arranged in some sensible
6070 order, but the behavior should be configurable.
6074 Packages other than <tt>base-passwd</tt> must not modify
6075 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
6076 <file>/etc/group</file> or <file>/etc/gshadow</file>.
6081 <heading>UID and GID classes</heading>
6083 The UID and GID numbers are divided into classes as
6089 Globally allocated by the Debian project, the same
6090 on every Debian system. These ids will appear in
6091 the <file>passwd</file> and <file>group</file> files of all
6092 Debian systems, new ids in this range being added
6093 automatically as the <tt>base-passwd</tt> package is
6098 Packages which need a single statically allocated
6099 uid or gid should use one of these; their
6100 maintainers should ask the <tt>base-passwd</tt>
6108 Dynamically allocated system users and groups.
6109 Packages which need a user or group, but can have
6110 this user or group allocated dynamically and
6111 differently on each system, should use <tt>adduser
6112 --system</tt> to create the group and/or user.
6113 <prgn>adduser</prgn> will check for the existence of
6114 the user or group, and if necessary choose an unused
6115 id based on the ranges specified in
6116 <file>adduser.conf</file>.
6120 <tag>1000-59999:</tag>
6123 Dynamically allocated user accounts. By default
6124 <prgn>adduser</prgn> will choose UIDs and GIDs for
6125 user accounts in this range, though
6126 <file>adduser.conf</file> may be used to modify this
6131 <tag>60000-64999:</tag>
6134 Globally allocated by the Debian project, but only
6135 created on demand. The ids are allocated centrally
6136 and statically, but the actual accounts are only
6137 created on users' systems on demand.
6141 These ids are for packages which are obscure or
6142 which require many statically-allocated ids. These
6143 packages should check for and create the accounts in
6144 <file>/etc/passwd</file> or <file>/etc/group</file> (using
6145 <prgn>adduser</prgn> if it has this facility) if
6146 necessary. Packages which are likely to require
6147 further allocations should have a "hole" left after
6148 them in the allocation, to give them room to
6153 <tag>65000-65533:</tag>
6161 User <tt>nobody</tt>. The corresponding gid refers
6162 to the group <tt>nogroup</tt>.
6169 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
6170 not</em> be used, because it is the error return
6179 <sect id="sysvinit">
6180 <heading>System run levels and <file>init.d</file> scripts</heading>
6182 <sect1 id="/etc/init.d">
6183 <heading>Introduction</heading>
6186 The <file>/etc/init.d</file> directory contains the scripts
6187 executed by <prgn>init</prgn> at boot time and when the
6188 init state (or "runlevel") is changed (see <manref
6189 name="init" section="8">).
6193 There are at least two different, yet functionally
6194 equivalent, ways of handling these scripts. For the sake
6195 of simplicity, this document describes only the symbolic
6196 link method. However, it must not be assumed by maintainer
6197 scripts that this method is being used, and any automated
6198 manipulation of the various runlevel behaviors by
6199 maintainer scripts must be performed using
6200 <prgn>update-rc.d</prgn> as described below and not by
6201 manually installing or removing symlinks. For information
6202 on the implementation details of the other method,
6203 implemented in the <tt>file-rc</tt> package, please refer
6204 to the documentation of that package.
6208 These scripts are referenced by symbolic links in the
6209 <file>/etc/rc<var>n</var>.d</file> directories. When changing
6210 runlevels, <prgn>init</prgn> looks in the directory
6211 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
6212 execute, where <tt><var>n</var></tt> is the runlevel that
6213 is being changed to, or <tt>S</tt> for the boot-up
6218 The names of the links all have the form
6219 <file>S<var>mm</var><var>script</var></file> or
6220 <file>K<var>mm</var><var>script</var></file> where
6221 <var>mm</var> is a two-digit number and <var>script</var>
6222 is the name of the script (this should be the same as the
6223 name of the actual script in <file>/etc/init.d</file>).
6227 When <prgn>init</prgn> changes runlevel first the targets
6228 of the links whose names start with a <tt>K</tt> are
6229 executed, each with the single argument <tt>stop</tt>,
6230 followed by the scripts prefixed with an <tt>S</tt>, each
6231 with the single argument <tt>start</tt>. (The links are
6232 those in the <file>/etc/rc<var>n</var>.d</file> directory
6233 corresponding to the new runlevel.) The <tt>K</tt> links
6234 are responsible for killing services and the <tt>S</tt>
6235 link for starting services upon entering the runlevel.
6239 For example, if we are changing from runlevel 2 to
6240 runlevel 3, init will first execute all of the <tt>K</tt>
6241 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
6242 all of the <tt>S</tt> prefixed scripts in that directory.
6243 The links starting with <tt>K</tt> will cause the
6244 referred-to file to be executed with an argument of
6245 <tt>stop</tt>, and the <tt>S</tt> links with an argument
6250 The two-digit number <var>mm</var> is used to determine
6251 the order in which to run the scripts: low-numbered links
6252 have their scripts run first. For example, the
6253 <tt>K20</tt> scripts will be executed before the
6254 <tt>K30</tt> scripts. This is used when a certain service
6255 must be started before another. For example, the name
6256 server <prgn>bind</prgn> might need to be started before
6257 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
6258 can set up its access lists. In this case, the script
6259 that starts <prgn>bind</prgn> would have a lower number
6260 than the script that starts <prgn>inn</prgn> so that it
6262 <example compact="compact">
6269 The two runlevels 0 (halt) and 6 (reboot) are slightly
6270 different. In these runlevels, the links with an
6271 <tt>S</tt> prefix are still called after those with a
6272 <tt>K</tt> prefix, but they too are called with the single
6273 argument <tt>stop</tt>.
6277 <sect1 id="writing-init">
6278 <heading>Writing the scripts</heading>
6281 Packages that include daemons for system services should
6282 place scripts in <file>/etc/init.d</file> to start or stop
6283 services at boot time or during a change of runlevel.
6284 These scripts should be named
6285 <file>/etc/init.d/<var>package</var></file>, and they should
6286 accept one argument, saying what to do:
6289 <tag><tt>start</tt></tag>
6290 <item>start the service,</item>
6292 <tag><tt>stop</tt></tag>
6293 <item>stop the service,</item>
6295 <tag><tt>restart</tt></tag>
6296 <item>stop and restart the service if it's already running,
6297 otherwise start the service</item>
6299 <tag><tt>reload</tt></tag>
6300 <item><p>cause the configuration of the service to be
6301 reloaded without actually stopping and restarting
6304 <tag><tt>force-reload</tt></tag>
6305 <item>cause the configuration to be reloaded if the
6306 service supports this, otherwise restart the
6310 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
6311 <tt>force-reload</tt> options should be supported by all
6312 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
6317 The <file>init.d</file> scripts must ensure that they will
6318 behave sensibly (i.e., returning success and not starting
6319 multiple copies of a service) if invoked with <tt>start</tt>
6320 when the service is already running, or with <tt>stop</tt>
6321 when it isn't, and that they don't kill unfortunately-named
6322 user processes. The best way to achieve this is usually to
6323 use <prgn>start-stop-daemon</prgn> with the <tt>--oknodo</tt>
6328 Be careful of using <tt>set -e</tt> in <file>init.d</file>
6329 scripts. Writing correct <file>init.d</file> scripts requires
6330 accepting various error exit statuses when daemons are already
6331 running or already stopped without aborting
6332 the <file>init.d</file> script, and common <file>init.d</file>
6333 function libraries are not safe to call with <tt>set -e</tt>
6335 <tt>/lib/lsb/init-functions</tt>, which assists in writing
6336 LSB-compliant init scripts, may fail if <tt>set -e</tt> is
6337 in effect and echoing status messages to the console fails,
6339 </footnote>. For <tt>init.d</tt> scripts, it's often easier
6340 to not use <tt>set -e</tt> and instead check the result of
6341 each command separately.
6345 If a service reloads its configuration automatically (as
6346 in the case of <prgn>cron</prgn>, for example), the
6347 <tt>reload</tt> option of the <file>init.d</file> script
6348 should behave as if the configuration has been reloaded
6353 The <file>/etc/init.d</file> scripts must be treated as
6354 configuration files, either (if they are present in the
6355 package, that is, in the .deb file) by marking them as
6356 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
6357 by managing them correctly in the maintainer scripts (see
6358 <ref id="config-files">). This is important since we want
6359 to give the local system administrator the chance to adapt
6360 the scripts to the local system, e.g., to disable a
6361 service without de-installing the package, or to specify
6362 some special command line options when starting a service,
6363 while making sure their changes aren't lost during the next
6368 These scripts should not fail obscurely when the
6369 configuration files remain but the package has been
6370 removed, as configuration files remain on the system after
6371 the package has been removed. Only when <prgn>dpkg</prgn>
6372 is executed with the <tt>--purge</tt> option will
6373 configuration files be removed. In particular, as the
6374 <file>/etc/init.d/<var>package</var></file> script itself is
6375 usually a <tt>conffile</tt>, it will remain on the system
6376 if the package is removed but not purged. Therefore, you
6377 should include a <tt>test</tt> statement at the top of the
6379 <example compact="compact">
6380 test -f <var>program-executed-later-in-script</var> || exit 0
6385 Often there are some variables in the <file>init.d</file>
6386 scripts whose values control the behavior of the scripts,
6387 and which a system administrator is likely to want to
6388 change. As the scripts themselves are frequently
6389 <tt>conffile</tt>s, modifying them requires that the
6390 administrator merge in their changes each time the package
6391 is upgraded and the <tt>conffile</tt> changes. To ease
6392 the burden on the system administrator, such configurable
6393 values should not be placed directly in the script.
6394 Instead, they should be placed in a file in
6395 <file>/etc/default</file>, which typically will have the same
6396 base name as the <file>init.d</file> script. This extra file
6397 should be sourced by the script when the script runs. It
6398 must contain only variable settings and comments in SUSv3
6399 <prgn>sh</prgn> format. It may either be a
6400 <tt>conffile</tt> or a configuration file maintained by
6401 the package maintainer scripts. See <ref id="config-files">
6406 To ensure that vital configurable values are always
6407 available, the <file>init.d</file> script should set default
6408 values for each of the shell variables it uses, either
6409 before sourcing the <file>/etc/default/</file> file or
6410 afterwards using something like the <tt>:
6411 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
6412 script must behave sensibly and not fail if the
6413 <file>/etc/default</file> file is deleted.
6417 <file>/var/run</file> and <file>/var/lock</file> may be mounted
6418 as temporary filesystems<footnote>
6419 For example, using the <tt>RAMRUN</tt> and <tt>RAMLOCK</tt>
6420 options in <file>/etc/default/rcS</file>.
6421 </footnote>, so the <file>init.d</file> scripts must handle this
6422 correctly. This will typically amount to creating any required
6423 subdirectories dynamically when the <file>init.d</file> script
6424 is run, rather than including them in the package and relying on
6425 <prgn>dpkg</prgn> to create them.
6430 <heading>Interfacing with the initscript system</heading>
6433 Maintainers should use the abstraction layer provided by
6434 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
6435 programs to deal with initscripts in their packages'
6436 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
6437 and <prgn>postrm</prgn>.
6441 Directly managing the /etc/rc?.d links and directly
6442 invoking the <file>/etc/init.d/</file> initscripts should
6443 be done only by packages providing the initscript
6444 subsystem (such as <prgn>sysv-rc</prgn> and
6445 <prgn>file-rc</prgn>).
6449 <heading>Managing the links</heading>
6452 The program <prgn>update-rc.d</prgn> is provided for
6453 package maintainers to arrange for the proper creation and
6454 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
6455 or their functional equivalent if another method is being
6456 used. This may be used by maintainers in their packages'
6457 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
6461 You must not include any <file>/etc/rc<var>n</var>.d</file>
6462 symbolic links in the actual archive or manually create or
6463 remove the symbolic links in maintainer scripts; you must
6464 use the <prgn>update-rc.d</prgn> program instead. (The
6465 former will fail if an alternative method of maintaining
6466 runlevel information is being used.) You must not include
6467 the <file>/etc/rc<var>n</var>.d</file> directories themselves
6468 in the archive either. (Only the <tt>sysvinit</tt>
6473 By default <prgn>update-rc.d</prgn> will start services in
6474 each of the multi-user state runlevels (2, 3, 4, and 5)
6475 and stop them in the halt runlevel (0), the single-user
6476 runlevel (1) and the reboot runlevel (6). The system
6477 administrator will have the opportunity to customize
6478 runlevels by simply adding, moving, or removing the
6479 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
6480 symbolic links are being used, or by modifying
6481 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
6486 To get the default behavior for your package, put in your
6487 <prgn>postinst</prgn> script
6488 <example compact="compact">
6489 update-rc.d <var>package</var> defaults
6491 and in your <prgn>postrm</prgn>
6492 <example compact="compact">
6493 if [ "$1" = purge ]; then
6494 update-rc.d <var>package</var> remove
6496 </example>. Note that if your package changes runlevels
6497 or priority, you may have to remove and recreate the links,
6498 since otherwise the old links may persist. Refer to the
6499 documentation of <prgn>update-rc.d</prgn>.
6503 This will use a default sequence number of 20. If it does
6504 not matter when or in which order the <file>init.d</file>
6505 script is run, use this default. If it does, then you
6506 should talk to the maintainer of the <prgn>sysvinit</prgn>
6507 package or post to <tt>debian-devel</tt>, and they will
6508 help you choose a number.
6512 For more information about using <tt>update-rc.d</tt>,
6513 please consult its man page <manref name="update-rc.d"
6519 <heading>Running initscripts</heading>
6521 The program <prgn>invoke-rc.d</prgn> is provided to make
6522 it easier for package maintainers to properly invoke an
6523 initscript, obeying runlevel and other locally-defined
6524 constraints that might limit a package's right to start,
6525 stop and otherwise manage services. This program may be
6526 used by maintainers in their packages' scripts.
6530 The package maintainer scripts must use
6531 <prgn>invoke-rc.d</prgn> to invoke the
6532 <file>/etc/init.d/*</file> initscripts, instead of
6533 calling them directly.
6537 By default, <prgn>invoke-rc.d</prgn> will pass any
6538 action requests (start, stop, reload, restart...) to the
6539 <file>/etc/init.d</file> script, filtering out requests
6540 to start or restart a service out of its intended
6545 Most packages will simply need to change:
6546 <example compact="compact">/etc/init.d/<package>
6547 <action></example> in their <prgn>postinst</prgn>
6548 and <prgn>prerm</prgn> scripts to:
6549 <example compact="compact">
6550 if which invoke-rc.d >/dev/null 2>&1; then
6551 invoke-rc.d <var>package</var> <action>
6553 /etc/init.d/<var>package</var> <action>
6559 A package should register its initscript services using
6560 <prgn>update-rc.d</prgn> before it tries to invoke them
6561 using <prgn>invoke-rc.d</prgn>. Invocation of
6562 unregistered services may fail.
6566 For more information about using
6567 <prgn>invoke-rc.d</prgn>, please consult its man page
6568 <manref name="invoke-rc.d" section="8">.
6574 <heading>Boot-time initialization</heading>
6577 There used to be another directory, <file>/etc/rc.boot</file>,
6578 which contained scripts which were run once per machine
6579 boot. This has been deprecated in favour of links from
6580 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6581 described in <ref id="/etc/init.d">. Packages must not
6582 place files in <file>/etc/rc.boot</file>.
6587 <heading>Example</heading>
6590 An example on which you can base your
6591 <file>/etc/init.d</file> scripts is found in
6592 <file>/etc/init.d/skeleton</file>.
6599 <heading>Console messages from <file>init.d</file> scripts</heading>
6602 This section describes the formats to be used for messages
6603 written to standard output by the <file>/etc/init.d</file>
6604 scripts. The intent is to improve the consistency of
6605 Debian's startup and shutdown look and feel. For this
6606 reason, please look very carefully at the details. We want
6607 the messages to have the same format in terms of wording,
6608 spaces, punctuation and case of letters.
6612 Here is a list of overall rules that should be used for
6613 messages generated by <file>/etc/init.d</file> scripts.
6619 The message should fit in one line (fewer than 80
6620 characters), start with a capital letter and end with
6621 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6625 If the script is performing some time consuming task in
6626 the background (not merely starting or stopping a
6627 program, for instance), an ellipsis (three dots:
6628 <tt>...</tt>) should be output to the screen, with no
6629 leading or tailing whitespace or line feeds.
6633 The messages should appear as if the computer is telling
6634 the user what it is doing (politely :-), but should not
6635 mention "it" directly. For example, instead of:
6636 <example compact="compact">
6637 I'm starting network daemons: nfsd mountd.
6639 the message should say
6640 <example compact="compact">
6641 Starting network daemons: nfsd mountd.
6648 <tt>init.d</tt> script should use the following standard
6649 message formats for the situations enumerated below.
6655 <p>When daemons are started</p>
6658 If the script starts one or more daemons, the output
6659 should look like this (a single line, no leading
6661 <example compact="compact">
6662 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6664 The <var>description</var> should describe the
6665 subsystem the daemon or set of daemons are part of,
6666 while <var>daemon-1</var> up to <var>daemon-n</var>
6667 denote each daemon's name (typically the file name of
6672 For example, the output of <file>/etc/init.d/lpd</file>
6674 <example compact="compact">
6675 Starting printer spooler: lpd.
6680 This can be achieved by saying
6681 <example compact="compact">
6682 echo -n "Starting printer spooler: lpd"
6683 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6686 in the script. If there are more than one daemon to
6687 start, the output should look like this:
6688 <example compact="compact">
6689 echo -n "Starting remote file system services:"
6690 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6691 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6692 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6695 This makes it possible for the user to see what is
6696 happening and when the final daemon has been started.
6697 Care should be taken in the placement of white spaces:
6698 in the example above the system administrators can
6699 easily comment out a line if they don't want to start
6700 a specific daemon, while the displayed message still
6706 <p>When a system parameter is being set</p>
6709 If you have to set up different system parameters
6710 during the system boot, you should use this format:
6711 <example compact="compact">
6712 Setting <var>parameter</var> to "<var>value</var>".
6717 You can use a statement such as the following to get
6719 <example compact="compact">
6720 echo "Setting DNS domainname to \"$domainname\"."
6725 Note that the same symbol (<tt>"</tt>) <!-- " --> is used
6726 for the left and right quotation marks. A grave accent
6727 (<tt>`</tt>) is not a quote character; neither is an
6728 apostrophe (<tt>'</tt>).
6733 <p>When a daemon is stopped or restarted</p>
6736 When you stop or restart a daemon, you should issue a
6737 message identical to the startup message, except that
6738 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6739 or <tt>Restarting</tt> respectively.
6743 For example, stopping the printer daemon will look like
6745 <example compact="compact">
6746 Stopping printer spooler: lpd.
6752 <p>When something is executed</p>
6755 There are several examples where you have to run a
6756 program at system startup or shutdown to perform a
6757 specific task, for example, setting the system's clock
6758 using <prgn>netdate</prgn> or killing all processes
6759 when the system shuts down. Your message should look
6761 <example compact="compact">
6762 Doing something very useful...done.
6764 You should print the <tt>done.</tt> immediately after
6765 the job has been completed, so that the user is
6766 informed why they have to wait. You can get this
6768 <example compact="compact">
6769 echo -n "Doing something very useful..."
6778 <p>When the configuration is reloaded</p>
6781 When a daemon is forced to reload its configuration
6782 files you should use the following format:
6783 <example compact="compact">
6784 Reloading <var>description</var> configuration...done.
6786 where <var>description</var> is the same as in the
6787 daemon starting message.
6795 <heading>Cron jobs</heading>
6798 Packages must not modify the configuration file
6799 <file>/etc/crontab</file>, and they must not modify the files in
6800 <file>/var/spool/cron/crontabs</file>.</p>
6803 If a package wants to install a job that has to be executed
6804 via cron, it should place a file with the name of the
6805 package in one or more of the following directories:
6806 <example compact="compact">
6812 As these directory names imply, the files within them are
6813 executed on an hourly, daily, weekly, or monthly basis,
6814 respectively. The exact times are listed in
6815 <file>/etc/crontab</file>.</p>
6818 All files installed in any of these directories must be
6819 scripts (e.g., shell scripts or Perl scripts) so that they
6820 can easily be modified by the local system administrator.
6821 In addition, they must be treated as configuration files.
6825 If a certain job has to be executed at some other frequency or
6826 at a specific time, the package should install a file
6827 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6828 same syntax as <file>/etc/crontab</file> and is processed by
6829 <prgn>cron</prgn> automatically. The file must also be
6830 treated as a configuration file. (Note that entries in the
6831 <file>/etc/cron.d</file> directory are not handled by
6832 <prgn>anacron</prgn>. Thus, you should only use this
6833 directory for jobs which may be skipped if the system is not
6836 Unlike <file>crontab</file> files described in the IEEE Std
6837 1003.1-2008 (POSIX.1) available from
6838 <url id="http://www.opengroup.org/onlinepubs/9699919799/"
6839 name="The Open Group">, the files in
6840 <file>/etc/cron.d</file> and the file
6841 <file>/etc/crontab</file> have seven fields; namely:
6843 <item>Minute [0,59]</item>
6844 <item>Hour [0,23]</item>
6845 <item>Day of the month [1,31]</item>
6846 <item>Month of the year [1,12]</item>
6847 <item>Day of the week ([0,6] with 0=Sunday)</item>
6848 <item>Username</item>
6849 <item>Command to be run</item>
6851 Ranges of numbers are allowed. Ranges are two numbers
6852 separated with a hyphen. The specified range is inclusive.
6853 Lists are allowed. A list is a set of numbers (or ranges)
6854 separated by commas. Step values can be used in conjunction
6859 The scripts or <tt>crontab</tt> entries in these directories should
6860 check if all necessary programs are installed before they
6861 try to execute them. Otherwise, problems will arise when a
6862 package was removed but not purged since configuration files
6863 are kept on the system in this situation.
6867 Any <tt>cron</tt> daemon must provide
6868 <file>/usr/bin/crontab</file> and support normal
6869 <tt>crontab</tt> entries as specified in POSIX. The daemon
6870 must also support names for days and months, ranges, and
6871 step values. It has to support <file>/etc/crontab</file>,
6872 and correctly execute the scripts in
6873 <file>/etc/cron.d</file>. The daemon must also correctly
6875 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>.
6880 <heading>Menus</heading>
6883 The Debian <tt>menu</tt> package provides a standard
6884 interface between packages providing applications and
6885 <em>menu programs</em> (either X window managers or
6886 text-based menu programs such as <prgn>pdmenu</prgn>).
6890 All packages that provide applications that need not be
6891 passed any special command line arguments for normal
6892 operation should register a menu entry for those
6893 applications, so that users of the <tt>menu</tt> package
6894 will automatically get menu entries in their window
6895 managers, as well in shells like <tt>pdmenu</tt>.
6899 Menu entries should follow the current menu policy.
6903 The menu policy can be found in the <tt>menu-policy</tt>
6904 files in the <tt>debian-policy</tt> package.
6905 It is also available from the Debian web mirrors at
6906 <tt><url name="/doc/packaging-manuals/menu-policy/"
6907 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6911 Please also refer to the <em>Debian Menu System</em>
6912 documentation that comes with the <package>menu</package>
6913 package for information about how to register your
6919 <heading>Multimedia handlers</heading>
6922 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6923 is a mechanism for encoding files and data streams and
6924 providing meta-information about them, in particular their
6925 type (e.g. audio or video) and format (e.g. PNG, HTML,
6930 Registration of MIME type handlers allows programs like mail
6931 user agents and web browsers to invoke these handlers to
6932 view, edit or display MIME types they don't support directly.
6936 Packages which provide the ability to view/show/play,
6937 compose, edit or print MIME types should register themselves
6938 as such following the current MIME support policy.
6942 The MIME support policy can be found in the <tt>mime-policy</tt>
6943 files in the <tt>debian-policy</tt> package.
6944 It is also available from the Debian web mirrors at
6945 <tt><url name="/doc/packaging-manuals/mime-policy/"
6946 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
6952 <heading>Keyboard configuration</heading>
6955 To achieve a consistent keyboard configuration so that all
6956 applications interpret a keyboard event the same way, all
6957 programs in the Debian distribution must be configured to
6958 comply with the following guidelines.
6962 The following keys must have the specified interpretations:
6965 <tag><tt><--</tt></tag>
6966 <item>delete the character to the left of the cursor</item>
6968 <tag><tt>Delete</tt></tag>
6969 <item>delete the character to the right of the cursor</item>
6971 <tag><tt>Control+H</tt></tag>
6972 <item>emacs: the help prefix</item>
6975 The interpretation of any keyboard events should be
6976 independent of the terminal that is used, be it a virtual
6977 console, an X terminal emulator, an rlogin/telnet session,
6982 The following list explains how the different programs
6983 should be set up to achieve this:
6989 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
6993 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
6997 X translations are set up to make
6998 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
6999 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
7000 is the vt220 escape code for the "delete character"
7001 key). This must be done by loading the X resources
7002 using <prgn>xrdb</prgn> on all local X displays, not
7003 using the application defaults, so that the
7004 translation resources used correspond to the
7005 <prgn>xmodmap</prgn> settings.
7009 The Linux console is configured to make
7010 <tt><--</tt> generate DEL, and <tt>Delete</tt>
7011 generate <tt>ESC [ 3 ~</tt>.
7015 X applications are configured so that <tt><</tt>
7016 deletes left, and <tt>Delete</tt> deletes right. Motif
7017 applications already work like this.
7021 Terminals should have <tt>stty erase ^?</tt> .
7025 The <tt>xterm</tt> terminfo entry should have <tt>ESC
7026 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
7027 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
7031 Emacs is programmed to map <tt>KB_Backspace</tt> or
7032 the <tt>stty erase</tt> character to
7033 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
7034 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
7035 <tt>^H</tt> to <tt>help</tt> as always.
7039 Other applications use the <tt>stty erase</tt>
7040 character and <tt>kdch1</tt> for the two delete keys,
7041 with ASCII DEL being "delete previous character" and
7042 <tt>kdch1</tt> being "delete character under
7050 This will solve the problem except for the following
7057 Some terminals have a <tt><--</tt> key that cannot
7058 be made to produce anything except <tt>^H</tt>. On
7059 these terminals Emacs help will be unavailable on
7060 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
7061 character takes precedence in Emacs, and has been set
7062 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
7063 available) can be used instead.
7067 Some operating systems use <tt>^H</tt> for <tt>stty
7068 erase</tt>. However, modern telnet versions and all
7069 rlogin versions propagate <tt>stty</tt> settings, and
7070 almost all UNIX versions honour <tt>stty erase</tt>.
7071 Where the <tt>stty</tt> settings are not propagated
7072 correctly, things can be made to work by using
7073 <tt>stty</tt> manually.
7077 Some systems (including previous Debian versions) use
7078 <prgn>xmodmap</prgn> to arrange for both
7079 <tt><--</tt> and <tt>Delete</tt> to generate
7080 <tt>KB_Delete</tt>. We can change the behavior of
7081 their X clients using the same X resources that we use
7082 to do it for our own clients, or configure our clients
7083 using their resources when things are the other way
7084 around. On displays configured like this
7085 <tt>Delete</tt> will not work, but <tt><--</tt>
7090 Some operating systems have different <tt>kdch1</tt>
7091 settings in their <tt>terminfo</tt> database for
7092 <tt>xterm</tt> and others. On these systems the
7093 <tt>Delete</tt> key will not work correctly when you
7094 log in from a system conforming to our policy, but
7095 <tt><--</tt> will.
7102 <heading>Environment variables</heading>
7105 A program must not depend on environment variables to get
7106 reasonable defaults. (That's because these environment
7107 variables would have to be set in a system-wide
7108 configuration file like <file>/etc/profile</file>, which is not
7109 supported by all shells.)
7113 If a program usually depends on environment variables for its
7114 configuration, the program should be changed to fall back to
7115 a reasonable default configuration if these environment
7116 variables are not present. If this cannot be done easily
7117 (e.g., if the source code of a non-free program is not
7118 available), the program must be replaced by a small
7119 "wrapper" shell script which sets the environment variables
7120 if they are not already defined, and calls the original program.
7124 Here is an example of a wrapper script for this purpose:
7126 <example compact="compact">
7128 BAR=${BAR:-/var/lib/fubar}
7130 exec /usr/lib/foo/foo "$@"
7135 Furthermore, as <file>/etc/profile</file> is a configuration
7136 file of the <prgn>base-files</prgn> package, other packages must
7137 not put any environment variables or other commands into that
7142 <sect id="doc-base">
7143 <heading>Registering Documents using doc-base</heading>
7146 The <package>doc-base</package> package implements a
7147 flexible mechanism for handling and presenting
7148 documentation. The recommended practice is for every Debian
7149 package that provides online documentation (other than just
7150 manual pages) to register these documents with
7151 <package>doc-base</package> by installing a
7152 <package>doc-base</package> control file via the
7153 <prgn/install-docs/ script at installation time and
7154 de-register the manuals again when the package is removed.
7157 Please refer to the documentation that comes with the
7158 <package>doc-base</package> package for information and
7167 <heading>Files</heading>
7169 <sect id="binaries">
7170 <heading>Binaries</heading>
7173 Two different packages must not install programs with
7174 different functionality but with the same filenames. (The
7175 case of two programs having the same functionality but
7176 different implementations is handled via "alternatives" or
7177 the "Conflicts" mechanism. See <ref id="maintscripts"> and
7178 <ref id="conflicts"> respectively.) If this case happens,
7179 one of the programs must be renamed. The maintainers should
7180 report this to the <tt>debian-devel</tt> mailing list and
7181 try to find a consensus about which program will have to be
7182 renamed. If a consensus cannot be reached, <em>both</em>
7183 programs must be renamed.
7187 By default, when a package is being built, any binaries
7188 created should include debugging information, as well as
7189 being compiled with optimization. You should also turn on
7190 as many reasonable compilation warnings as possible; this
7191 makes life easier for porters, who can then look at build
7192 logs for possible problems. For the C programming language,
7193 this means the following compilation parameters should be
7195 <example compact="compact">
7197 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
7199 INSTALL = install -s # (or use strip on the files in debian/tmp)
7204 Note that by default all installed binaries should be stripped,
7205 either by using the <tt>-s</tt> flag to
7206 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
7207 the binaries after they have been copied into
7208 <file>debian/tmp</file> but before the tree is made into a
7213 Although binaries in the build tree should be compiled with
7214 debugging information by default, it can often be difficult to
7215 debug programs if they are also subjected to compiler
7216 optimization. For this reason, it is recommended to support the
7217 standardized environment variable <tt>DEB_BUILD_OPTIONS</tt>
7218 (see <ref id="debianrules-options">). This variable can contain
7219 several flags to change how a package is compiled and built.
7223 It is up to the package maintainer to decide what
7224 compilation options are best for the package. Certain
7225 binaries (such as computationally-intensive programs) will
7226 function better with certain flags (<tt>-O3</tt>, for
7227 example); feel free to use them. Please use good judgment
7228 here. Don't use flags for the sake of it; only use them
7229 if there is good reason to do so. Feel free to override
7230 the upstream author's ideas about which compilation
7231 options are best: they are often inappropriate for our
7237 <sect id="libraries">
7238 <heading>Libraries</heading>
7241 If the package is <strong>architecture: any</strong>, then
7242 the shared library compilation and linking flags must have
7243 <tt>-fPIC</tt>, or the package shall not build on some of
7244 the supported architectures<footnote>
7246 If you are using GCC, <tt>-fPIC</tt> produces code with
7247 relocatable position independent code, which is required for
7248 most architectures to create a shared library, with i386 and
7249 perhaps some others where non position independent code is
7250 permitted in a shared library.
7253 Position independent code may have a performance penalty,
7254 especially on <tt>i386</tt>. However, in most cases the
7255 speed penalty must be measured against the memory wasted on
7256 the few architectures where non position independent code is
7259 </footnote>. Any exception to this rule must be discussed on
7260 the mailing list <em>debian-devel@lists.debian.org</em>, and
7261 a rough consensus obtained. The reasons for not compiling
7262 with <tt>-fPIC</tt> flag must be recorded in the file
7263 <tt>README.Debian</tt>, and care must be taken to either
7264 restrict the architecture or arrange for <tt>-fPIC</tt> to
7265 be used on architectures where it is required.<footnote>
7267 Some of the reasons why this might be required is if the
7268 library contains hand crafted assembly code that is not
7269 relocatable, the speed penalty is excessive for compute
7270 intensive libs, and similar reasons.
7275 As to the static libraries, the common case is not to have
7276 relocatable code, since there is no benefit, unless in specific
7277 cases; therefore the static version must not be compiled
7278 with the <tt>-fPIC</tt> flag. Any exception to this rule
7279 should be discussed on the mailing list
7280 <em>debian-devel@lists.debian.org</em>, and the reasons for
7281 compiling with the <tt>-fPIC</tt> flag must be recorded in
7282 the file <tt>README.Debian</tt>. <footnote>
7284 Some of the reasons for linking static libraries with
7285 the <tt>-fPIC</tt> flag are if, for example, one needs a
7286 Perl API for a library that is under rapid development,
7287 and has an unstable API, so shared libraries are
7288 pointless at this phase of the library's development. In
7289 that case, since Perl needs a library with relocatable
7290 code, it may make sense to create a static library with
7291 relocatable code. Another reason cited is if you are
7292 distilling various libraries into a common shared
7293 library, like <tt>mklibs</tt> does in the Debian
7299 In other words, if both a shared and a static library is
7300 being built, each source unit (<tt>*.c</tt>, for example,
7301 for C files) will need to be compiled twice, for the normal
7305 You must specify the gcc option <tt>-D_REENTRANT</tt>
7306 when building a library (either static or shared) to make
7307 the library compatible with LinuxThreads.
7311 Although not enforced by the build tools, shared libraries
7312 must be linked against all libraries that they use symbols from
7313 in the same way that binaries are. This ensures the correct
7314 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
7315 system and guarantees that all libraries can be safely opened
7316 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
7317 option <tt>-Wl,-z,defs</tt> when building a shared library.
7318 Since this option enforces symbol resolution at build time,
7319 a missing library reference will be caught early as a fatal
7324 All installed shared libraries should be stripped with
7325 <example compact="compact">
7326 strip --strip-unneeded <var>your-lib</var>
7328 (The option <tt>--strip-unneeded</tt> makes
7329 <prgn>strip</prgn> remove only the symbols which aren't
7330 needed for relocation processing.) Shared libraries can
7331 function perfectly well when stripped, since the symbols for
7332 dynamic linking are in a separate part of the ELF object
7334 You might also want to use the options
7335 <tt>--remove-section=.comment</tt> and
7336 <tt>--remove-section=.note</tt> on both shared libraries
7337 and executables, and <tt>--strip-debug</tt> on static
7343 Note that under some circumstances it may be useful to
7344 install a shared library unstripped, for example when
7345 building a separate package to support debugging.
7349 Shared object files (often <file>.so</file> files) that are not
7350 public libraries, that is, they are not meant to be linked
7351 to by third party executables (binaries of other packages),
7352 should be installed in subdirectories of the
7353 <file>/usr/lib</file> directory. Such files are exempt from the
7354 rules that govern ordinary shared libraries, except that
7355 they must not be installed executable and should be
7357 A common example are the so-called "plug-ins",
7358 internal shared objects that are dynamically loaded by
7359 programs using <manref name="dlopen" section="3">.
7364 An ever increasing number of packages are using
7365 <prgn>libtool</prgn> to do their linking. The latest GNU
7366 libtools (>= 1.3a) can take advantage of the metadata in the
7367 installed <prgn>libtool</prgn> archive files (<file>*.la</file>
7368 files). The main advantage of <prgn>libtool</prgn>'s
7369 <file>.la</file> files is that it allows <prgn>libtool</prgn> to
7370 store and subsequently access metadata with respect to the
7371 libraries it builds. <prgn>libtool</prgn> will search for
7372 those files, which contain a lot of useful information about
7373 a library (such as library dependency information for static
7374 linking). Also, they're <em>essential</em> for programs
7375 using <tt>libltdl</tt>.<footnote>
7376 Although <prgn>libtool</prgn> is fully capable of
7377 linking against shared libraries which don't have
7378 <tt>.la</tt> files, as it is a mere shell script it can
7379 add considerably to the build time of a
7380 <prgn>libtool</prgn>-using package if that shell script
7381 has to derive all this information from first principles
7382 for each library every time it is linked. With the
7383 advent of <prgn>libtool</prgn> version 1.4 (and to a
7384 lesser extent <prgn>libtool</prgn> version 1.3), the
7385 <file>.la</file> files also store information about
7386 inter-library dependencies which cannot necessarily be
7387 derived after the <file>.la</file> file is deleted.
7392 Packages that use <prgn>libtool</prgn> to create shared
7393 libraries should include the <file>.la</file> files in the
7394 <tt>-dev</tt> package, unless the package relies on
7395 <tt>libtool</tt>'s <tt>libltdl</tt> library, in which case
7396 the <tt>.la</tt> files must go in the run-time library
7401 You must make sure that you use only released versions of
7402 shared libraries to build your packages; otherwise other
7403 users will not be able to run your binaries
7404 properly. Producing source packages that depend on
7405 unreleased compilers is also usually a bad
7412 <heading>Shared libraries</heading>
7414 This section has moved to <ref id="sharedlibs">.
7420 <heading>Scripts</heading>
7423 All command scripts, including the package maintainer
7424 scripts inside the package and used by <prgn>dpkg</prgn>,
7425 should have a <tt>#!</tt> line naming the shell to be used
7430 In the case of Perl scripts this should be
7431 <tt>#!/usr/bin/perl</tt>.
7435 When scripts are installed into a directory in the system
7436 PATH, the script name should not include an extension such
7437 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
7438 language currently used to implement it.
7441 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>) other than
7442 <file>init.d</file> scripts should almost certainly start
7443 with <tt>set -e</tt> so that errors are detected.
7444 <file>init.d</file> scripts are something of a special case, due
7445 to how frequently they need to call commands that are allowed to
7446 fail, and it may instead be easier to check the exit status of
7447 commands directly. See <ref id="writing-init"> for more
7448 information about writing <file>init.d</file> scripts.
7451 Every script should use <tt>set -e</tt> or check the exit status
7452 of <em>every</em> command.
7455 Scripts may assume that <file>/bin/sh</file> implements the
7456 SUSv3 Shell Command Language<footnote>
7457 Single UNIX Specification, version 3, which is also IEEE
7458 1003.1-2004 (POSIX), and is available on the World Wide Web
7459 from <url id="http://www.unix.org/version3/online.html"
7460 name="The Open Group"> after free
7461 registration.</footnote>
7462 plus the following additional features not mandated by
7464 These features are in widespread use in the Linux community
7465 and are implemented in all of bash, dash, and ksh, the most
7466 common shells users may wish to use as <file>/bin/sh</file>.
7469 <item><tt>echo -n</tt>, if implemented as a shell built-in,
7470 must not generate a newline.</item>
7471 <item><tt>test</tt>, if implemented as a shell built-in, must
7472 support <tt>-a</tt> and <tt>-o</tt> as binary logical
7474 <item><tt>local</tt> to create a scoped variable must be
7475 supported, including listing multiple variables in a single
7476 local command and assigning a value to a variable at the
7477 same time as localizing it. <tt>local</tt> may or
7478 may not preserve the variable value from an outer scope if
7479 no assignment is present. Uses such as:
7483 # ... use a, b, c, d ...
7486 must be supported and must set the value of <tt>c</tt> to
7490 If a shell script requires non-SUSv3 features from the shell
7491 interpreter other than those listed above, the appropriate shell
7492 must be specified in the first line of the script (e.g.,
7493 <tt>#!/bin/bash</tt>) and the package must depend on the package
7494 providing the shell (unless the shell package is marked
7495 "Essential", as in the case of <prgn>bash</prgn>).
7499 You may wish to restrict your script to SUSv3 features plus the
7500 above set when possible so that it may use <file>/bin/sh</file>
7501 as its interpreter. If your script works with <prgn>dash</prgn>
7502 (originally called <prgn>ash</prgn>), it probably complies with
7503 the above requirements, but if you are in doubt, use
7504 <file>/bin/bash</file>.
7508 Perl scripts should check for errors when making any
7509 system calls, including <tt>open</tt>, <tt>print</tt>,
7510 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
7514 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
7515 scripting languages. See <em>Csh Programming Considered
7516 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
7517 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
7518 If an upstream package comes with <prgn>csh</prgn> scripts
7519 then you must make sure that they start with
7520 <tt>#!/bin/csh</tt> and make your package depend on the
7521 <prgn>c-shell</prgn> virtual package.
7525 Any scripts which create files in world-writeable
7526 directories (e.g., in <file>/tmp</file>) must use a
7527 mechanism which will fail atomically if a file with the same
7528 name already exists.
7532 The Debian base system provides the <prgn>tempfile</prgn>
7533 and <prgn>mktemp</prgn> utilities for use by scripts for
7540 <heading>Symbolic links</heading>
7543 In general, symbolic links within a top-level directory
7544 should be relative, and symbolic links pointing from one
7545 top-level directory into another should be absolute. (A
7546 top-level directory is a sub-directory of the root
7547 directory <file>/</file>.)
7551 In addition, symbolic links should be specified as short as
7552 possible, i.e., link targets like <file>foo/../bar</file> are
7557 Note that when creating a relative link using
7558 <prgn>ln</prgn> it is not necessary for the target of the
7559 link to exist relative to the working directory you're
7560 running <prgn>ln</prgn> from, nor is it necessary to change
7561 directory to the directory where the link is to be made.
7562 Simply include the string that should appear as the target
7563 of the link (this will be a pathname relative to the
7564 directory in which the link resides) as the first argument
7569 For example, in your <prgn>Makefile</prgn> or
7570 <file>debian/rules</file>, you can do things like:
7571 <example compact="compact">
7572 ln -fs gcc $(prefix)/bin/cc
7573 ln -fs gcc debian/tmp/usr/bin/cc
7574 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7575 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7580 A symbolic link pointing to a compressed file should always
7581 have the same file extension as the referenced file. (For
7582 example, if a file <file>foo.gz</file> is referenced by a
7583 symbolic link, the filename of the link has to end with
7584 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7589 <heading>Device files</heading>
7592 Packages must not include device files or named pipes in the
7597 If a package needs any special device files that are not
7598 included in the base system, it must call
7599 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7600 after notifying the user<footnote>
7601 This notification could be done via a (low-priority)
7602 debconf message, or an echo (printf) statement.
7607 Packages must not remove any device files in the
7608 <prgn>postrm</prgn> or any other script. This is left to the
7609 system administrator.
7613 Debian uses the serial devices
7614 <file>/dev/ttyS*</file>. Programs using the old
7615 <file>/dev/cu*</file> devices should be changed to use
7616 <file>/dev/ttyS*</file>.
7620 Named pipes needed by the package must be created in
7621 the <prgn>postinst</prgn> script<footnote>
7622 It's better to use <prgn>mkfifo</prgn> rather
7623 than <prgn>mknod</prgn> to create named pipes so that
7624 automated checks for packages incorrectly creating device
7625 files with <prgn>mknod</prgn> won't have false positives.
7626 </footnote> and removed in
7627 the <prgn>prerm</prgn> or <prgn>postrm</prgn> script as
7632 <sect id="config-files">
7633 <heading>Configuration files</heading>
7636 <heading>Definitions</heading>
7640 <tag>configuration file</tag>
7642 A file that affects the operation of a program, or
7643 provides site- or host-specific information, or
7644 otherwise customizes the behavior of a program.
7645 Typically, configuration files are intended to be
7646 modified by the system administrator (if needed or
7647 desired) to conform to local policy or to provide
7648 more useful site-specific behavior.
7651 <tag><tt>conffile</tt></tag>
7653 A file listed in a package's <tt>conffiles</tt>
7654 file, and is treated specially by <prgn>dpkg</prgn>
7655 (see <ref id="configdetails">).
7661 The distinction between these two is important; they are
7662 not interchangeable concepts. Almost all
7663 <tt>conffile</tt>s are configuration files, but many
7664 configuration files are not <tt>conffiles</tt>.
7668 As noted elsewhere, <file>/etc/init.d</file> scripts,
7669 <file>/etc/default</file> files, scripts installed in
7670 <file>/etc/cron.{hourly,daily,weekly,monthly}</file>, and cron
7671 configuration installed in <file>/etc/cron.d</file> must be
7672 treated as configuration files. In general, any script that
7673 embeds configuration information is de-facto a configuration
7674 file and should be treated as such.
7679 <heading>Location</heading>
7682 Any configuration files created or used by your package
7683 must reside in <file>/etc</file>. If there are several,
7684 consider creating a subdirectory of <file>/etc</file>
7685 named after your package.
7689 If your package creates or uses configuration files
7690 outside of <file>/etc</file>, and it is not feasible to modify
7691 the package to use <file>/etc</file> directly, put the files
7692 in <file>/etc</file> and create symbolic links to those files
7693 from the location that the package requires.
7698 <heading>Behavior</heading>
7701 Configuration file handling must conform to the following
7703 <list compact="compact">
7705 local changes must be preserved during a package
7709 configuration files must be preserved when the
7710 package is removed, and only deleted when the
7714 Obsolete configuration files without local changes may be
7715 removed by the package during upgrade.
7719 The easy way to achieve this behavior is to make the
7720 configuration file a <tt>conffile</tt>. This is
7721 appropriate only if it is possible to distribute a default
7722 version that will work for most installations, although
7723 some system administrators may choose to modify it. This
7724 implies that the default version will be part of the
7725 package distribution, and must not be modified by the
7726 maintainer scripts during installation (or at any other
7731 In order to ensure that local changes are preserved
7732 correctly, no package may contain or make hard links to
7733 conffiles.<footnote>
7734 Rationale: There are two problems with hard links.
7735 The first is that some editors break the link while
7736 editing one of the files, so that the two files may
7737 unwittingly become unlinked and different. The second
7738 is that <prgn>dpkg</prgn> might break the hard link
7739 while upgrading <tt>conffile</tt>s.
7744 The other way to do it is via the maintainer scripts. In
7745 this case, the configuration file must not be listed as a
7746 <tt>conffile</tt> and must not be part of the package
7747 distribution. If the existence of a file is required for
7748 the package to be sensibly configured it is the
7749 responsibility of the package maintainer to provide
7750 maintainer scripts which correctly create, update and
7751 maintain the file and remove it on purge. (See <ref
7752 id="maintainerscripts"> for more information.) These
7753 scripts must be idempotent (i.e., must work correctly if
7754 <prgn>dpkg</prgn> needs to re-run them due to errors
7755 during installation or removal), must cope with all the
7756 variety of ways <prgn>dpkg</prgn> can call maintainer
7757 scripts, must not overwrite or otherwise mangle the user's
7758 configuration without asking, must not ask unnecessary
7759 questions (particularly during upgrades), and must
7760 otherwise be good citizens.
7764 The scripts are not required to configure every possible
7765 option for the package, but only those necessary to get
7766 the package running on a given system. Ideally the
7767 sysadmin should not have to do any configuration other
7768 than that done (semi-)automatically by the
7769 <prgn>postinst</prgn> script.
7773 A common practice is to create a script called
7774 <file><var>package</var>-configure</file> and have the
7775 package's <prgn>postinst</prgn> call it if and only if the
7776 configuration file does not already exist. In certain
7777 cases it is useful for there to be an example or template
7778 file which the maintainer scripts use. Such files should
7779 be in <file>/usr/share/<var>package</var></file> or
7780 <file>/usr/lib/<var>package</var></file> (depending on whether
7781 they are architecture-independent or not). There should
7782 be symbolic links to them from
7783 <file>/usr/share/doc/<var>package</var>/examples</file> if
7784 they are examples, and should be perfectly ordinary
7785 <prgn>dpkg</prgn>-handled files (<em>not</em>
7786 configuration files).
7790 These two styles of configuration file handling must
7791 not be mixed, for that way lies madness:
7792 <prgn>dpkg</prgn> will ask about overwriting the file
7793 every time the package is upgraded.
7798 <heading>Sharing configuration files</heading>
7801 Packages which specify the same file as a
7802 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7803 with each other. (This is an instance of the general rule
7804 about not sharing files. Note that neither alternatives
7805 nor diversions are likely to be appropriate in this case;
7806 in particular, <prgn>dpkg</prgn> does not handle diverted
7807 <tt>conffile</tt>s well.)
7811 The maintainer scripts must not alter a <tt>conffile</tt>
7812 of <em>any</em> package, including the one the scripts
7817 If two or more packages use the same configuration file
7818 and it is reasonable for both to be installed at the same
7819 time, one of these packages must be defined as
7820 <em>owner</em> of the configuration file, i.e., it will be
7821 the package which handles that file as a configuration
7822 file. Other packages that use the configuration file must
7823 depend on the owning package if they require the
7824 configuration file to operate. If the other package will
7825 use the configuration file if present, but is capable of
7826 operating without it, no dependency need be declared.
7830 If it is desirable for two or more related packages to
7831 share a configuration file <em>and</em> for all of the
7832 related packages to be able to modify that configuration
7833 file, then the following should be done:
7834 <enumlist compact="compact">
7836 One of the related packages (the "owning" package)
7837 will manage the configuration file with maintainer
7838 scripts as described in the previous section.
7841 The owning package should also provide a program
7842 that the other packages may use to modify the
7846 The related packages must use the provided program
7847 to make any desired modifications to the
7848 configuration file. They should either depend on
7849 the core package to guarantee that the configuration
7850 modifier program is available or accept gracefully
7851 that they cannot modify the configuration file if it
7852 is not. (This is in addition to the fact that the
7853 configuration file may not even be present in the
7860 Sometimes it's appropriate to create a new package which
7861 provides the basic infrastructure for the other packages
7862 and which manages the shared configuration files. (The
7863 <tt>sgml-base</tt> package is a good example.)
7868 <heading>User configuration files ("dotfiles")</heading>
7871 The files in <file>/etc/skel</file> will automatically be
7872 copied into new user accounts by <prgn>adduser</prgn>.
7873 No other program should reference the files in
7874 <file>/etc/skel</file>.
7878 Therefore, if a program needs a dotfile to exist in
7879 advance in <file>$HOME</file> to work sensibly, that dotfile
7880 should be installed in <file>/etc/skel</file> and treated as a
7885 However, programs that require dotfiles in order to
7886 operate sensibly are a bad thing, unless they do create
7887 the dotfiles themselves automatically.
7891 Furthermore, programs should be configured by the Debian
7892 default installation to behave as closely to the upstream
7893 default behavior as possible.
7897 Therefore, if a program in a Debian package needs to be
7898 configured in some way in order to operate sensibly, that
7899 should be done using a site-wide configuration file placed
7900 in <file>/etc</file>. Only if the program doesn't support a
7901 site-wide default configuration and the package maintainer
7902 doesn't have time to add it may a default per-user file be
7903 placed in <file>/etc/skel</file>.
7907 <file>/etc/skel</file> should be as empty as we can make it.
7908 This is particularly true because there is no easy (or
7909 necessarily desirable) mechanism for ensuring that the
7910 appropriate dotfiles are copied into the accounts of
7911 existing users when a package is installed.
7917 <heading>Log files</heading>
7919 Log files should usually be named
7920 <file>/var/log/<var>package</var>.log</file>. If you have many
7921 log files, or need a separate directory for permission
7922 reasons (<file>/var/log</file> is writable only by
7923 <file>root</file>), you should usually create a directory named
7924 <file>/var/log/<var>package</var></file> and place your log
7929 Log files must be rotated occasionally so that they don't
7930 grow indefinitely; the best way to do this is to drop a log
7931 rotation configuration file into the directory
7932 <file>/etc/logrotate.d</file> and use the facilities provided by
7933 logrotate.<footnote>
7935 The traditional approach to log files has been to set up
7936 <em>ad hoc</em> log rotation schemes using simple shell
7937 scripts and cron. While this approach is highly
7938 customizable, it requires quite a lot of sysadmin work.
7939 Even though the original Debian system helped a little
7940 by automatically installing a system which can be used
7941 as a template, this was deemed not enough.
7945 The use of <prgn>logrotate</prgn>, a program developed
7946 by Red Hat, is better, as it centralizes log management.
7947 It has both a configuration file
7948 (<file>/etc/logrotate.conf</file>) and a directory where
7949 packages can drop their individual log rotation
7950 configurations (<file>/etc/logrotate.d</file>).
7953 Here is a good example for a logrotate config
7954 file (for more information see <manref name="logrotate"
7956 <example compact="compact">
7957 /var/log/foo/*.log {
7962 /etc/init.d/foo force-reload
7966 This rotates all files under <file>/var/log/foo</file>, saves 12
7967 compressed generations, and forces the daemon to reload its
7968 configuration information after the log rotation.
7972 Log files should be removed when the package is
7973 purged (but not when it is only removed). This should be
7974 done by the <prgn>postrm</prgn> script when it is called
7975 with the argument <tt>purge</tt> (see <ref
7976 id="removedetails">).
7981 <heading>Permissions and owners</heading>
7984 The rules in this section are guidelines for general use.
7985 If necessary you may deviate from the details below.
7986 However, if you do so you must make sure that what is done
7987 is secure and you should try to be as consistent as possible
7988 with the rest of the system. You should probably also
7989 discuss it on <prgn>debian-devel</prgn> first.
7993 Files should be owned by <tt>root:root</tt>, and made
7994 writable only by the owner and universally readable (and
7995 executable, if appropriate), that is mode 644 or 755.
7999 Directories should be mode 755 or (for group-writability)
8000 mode 2775. The ownership of the directory should be
8001 consistent with its mode: if a directory is mode 2775, it
8002 should be owned by the group that needs write access to
8005 When a package is upgraded, and the owner or permissions
8006 of a file included in the package has changed, dpkg
8007 arranges for the ownership and permissions to be
8008 correctly set upon installation. However, this does not
8009 extend to directories; the permissions and ownership of
8010 directories already on the system does not change on
8011 install or upgrade of packages. This makes sense, since
8012 otherwise common directories like <tt>/usr</tt> would
8013 always be in flux. To correctly change permissions of a
8014 directory the package owns, explicit action is required,
8015 usually in the <tt>postinst</tt> script. Care must be
8016 taken to handle downgrades as well, in that case.
8023 Setuid and setgid executables should be mode 4755 or 2755
8024 respectively, and owned by the appropriate user or group.
8025 They should not be made unreadable (modes like 4711 or
8026 2711 or even 4111); doing so achieves no extra security,
8027 because anyone can find the binary in the freely available
8028 Debian package; it is merely inconvenient. For the same
8029 reason you should not restrict read or execute permissions
8030 on non-set-id executables.
8034 Some setuid programs need to be restricted to particular
8035 sets of users, using file permissions. In this case they
8036 should be owned by the uid to which they are set-id, and by
8037 the group which should be allowed to execute them. They
8038 should have mode 4754; again there is no point in making
8039 them unreadable to those users who must not be allowed to
8044 It is possible to arrange that the system administrator can
8045 reconfigure the package to correspond to their local
8046 security policy by changing the permissions on a binary:
8047 they can do this by using <prgn>dpkg-statoverride</prgn>, as
8048 described below.<footnote>
8049 Ordinary files installed by <prgn>dpkg</prgn> (as
8050 opposed to <tt>conffile</tt>s and other similar objects)
8051 normally have their permissions reset to the distributed
8052 permissions when the package is reinstalled. However,
8053 the use of <prgn>dpkg-statoverride</prgn> overrides this
8056 Another method you should consider is to create a group for
8057 people allowed to use the program(s) and make any setuid
8058 executables executable only by that group.
8062 If you need to create a new user or group for your package
8063 there are two possibilities. Firstly, you may need to
8064 make some files in the binary package be owned by this
8065 user or group, or you may need to compile the user or
8066 group id (rather than just the name) into the binary
8067 (though this latter should be avoided if possible, as in
8068 this case you need a statically allocated id).</p>
8071 If you need a statically allocated id, you must ask for a
8072 user or group id from the <tt>base-passwd</tt> maintainer,
8073 and must not release the package until you have been
8074 allocated one. Once you have been allocated one you must
8075 either make the package depend on a version of the
8076 <tt>base-passwd</tt> package with the id present in
8077 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
8078 your package to create the user or group itself with the
8079 correct id (using <tt>adduser</tt>) in its
8080 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
8081 the <prgn>postinst</prgn> is to be preferred if it is
8082 possible, otherwise a pre-dependency will be needed on the
8083 <tt>adduser</tt> package.)
8087 On the other hand, the program might be able to determine
8088 the uid or gid from the user or group name at runtime, so
8089 that a dynamically allocated id can be used. In this case
8090 you should choose an appropriate user or group name,
8091 discussing this on <prgn>debian-devel</prgn> and checking
8092 with the <package/base-passwd/ maintainer that it is unique and that
8093 they do not wish you to use a statically allocated id
8094 instead. When this has been checked you must arrange for
8095 your package to create the user or group if necessary using
8096 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
8097 <prgn>postinst</prgn> script (again, the latter is to be
8098 preferred if it is possible).
8102 Note that changing the numeric value of an id associated
8103 with a name is very difficult, and involves searching the
8104 file system for all appropriate files. You need to think
8105 carefully whether a static or dynamic id is required, since
8106 changing your mind later will cause problems.
8109 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
8111 This section is not intended as policy, but as a
8112 description of the use of <prgn>dpkg-statoverride</prgn>.
8116 If a system administrator wishes to have a file (or
8117 directory or other such thing) installed with owner and
8118 permissions different from those in the distributed Debian
8119 package, they can use the <prgn>dpkg-statoverride</prgn>
8120 program to instruct <prgn>dpkg</prgn> to use the different
8121 settings every time the file is installed. Thus the
8122 package maintainer should distribute the files with their
8123 normal permissions, and leave it for the system
8124 administrator to make any desired changes. For example, a
8125 daemon which is normally required to be setuid root, but
8126 in certain situations could be used without being setuid,
8127 should be installed setuid in the <tt>.deb</tt>. Then the
8128 local system administrator can change this if they wish.
8129 If there are two standard ways of doing it, the package
8130 maintainer can use <tt>debconf</tt> to find out the
8131 preference, and call <prgn>dpkg-statoverride</prgn> in the
8132 maintainer script if necessary to accommodate the system
8133 administrator's choice. Care must be taken during
8134 upgrades to not override an existing setting.
8138 Given the above, <prgn>dpkg-statoverride</prgn> is
8139 essentially a tool for system administrators and would not
8140 normally be needed in the maintainer scripts. There is
8141 one type of situation, though, where calls to
8142 <prgn>dpkg-statoverride</prgn> would be needed in the
8143 maintainer scripts, and that involves packages which use
8144 dynamically allocated user or group ids. In such a
8145 situation, something like the following idiom can be very
8146 helpful in the package's <prgn>postinst</prgn>, where
8147 <tt>sysuser</tt> is a dynamically allocated id:
8149 for i in /usr/bin/foo /usr/sbin/bar
8151 # only do something when no setting exists
8152 if ! dpkg-statoverride --list $i >/dev/null 2>&1
8154 #include: debconf processing, question about foo and bar
8155 if [ "$RET" = "true" ] ; then
8156 dpkg-statoverride --update --add sysuser root 4755 $i
8161 The corresponding code to remove the override when the package
8164 for i in /usr/bin/foo /usr/sbin/bar
8166 if dpkg-statoverride --list $i >/dev/null 2>&1
8168 dpkg-statoverride --remove $i
8178 <chapt id="customized-programs">
8179 <heading>Customized programs</heading>
8181 <sect id="arch-spec">
8182 <heading>Architecture specification strings</heading>
8185 If a program needs to specify an <em>architecture specification
8186 string</em> in some place, it should select one of the strings
8187 provided by <tt>dpkg-architecture -L</tt>. The strings are in
8188 the format <tt><var>os</var>-<var>arch</var></tt>, though the OS
8189 part is sometimes elided, as when the OS is Linux.
8193 Note that we don't want to use
8194 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
8195 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
8196 since this would make our programs incompatible with other
8197 Linux distributions. We also don't use something like
8198 <tt><var>arch</var>-unknown-linux</tt>, since the
8199 <tt>unknown</tt> does not look very good.
8202 <sect1 id="arch-wildcard-spec">
8203 <heading>Architecture wildcards</heading>
8206 A package may specify an architecture wildcard. Architecture
8207 wildcards are in the format <tt>any</tt> (which matches every
8208 architecture), <tt><var>os</var></tt>-any, or
8209 any-<tt><var>cpu</var></tt>. <footnote>
8210 Internally, the package system normalizes the GNU triplets
8211 and the Debian arches into Debian arch triplets (which are
8212 kind of inverted GNU triplets), with the first component of
8213 the triplet representing the libc and ABI in use, and then
8214 does matching against those triplets. However, such
8215 triplets are an internal implementation detail that should
8216 not be used by packages directly. The libc and ABI portion
8217 is handled internally by the package system based on
8218 the <var>os</var> and <var>cpu</var>.
8225 <heading>Daemons</heading>
8228 The configuration files <file>/etc/services</file>,
8229 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
8230 by the <prgn>netbase</prgn> package and must not be modified
8235 If a package requires a new entry in one of these files, the
8236 maintainer should get in contact with the
8237 <prgn>netbase</prgn> maintainer, who will add the entries
8238 and release a new version of the <prgn>netbase</prgn>
8243 The configuration file <file>/etc/inetd.conf</file> must not be
8244 modified by the package's scripts except via the
8245 <prgn>update-inetd</prgn> script or the
8246 <file>DebianNet.pm</file> Perl module. See their documentation
8247 for details on how to add entries.
8251 If a package wants to install an example entry into
8252 <file>/etc/inetd.conf</file>, the entry must be preceded with
8253 exactly one hash character (<tt>#</tt>). Such lines are
8254 treated as "commented out by user" by the
8255 <prgn>update-inetd</prgn> script and are not changed or
8256 activated during package updates.
8261 <heading>Using pseudo-ttys and modifying wtmp, utmp and
8265 Some programs need to create pseudo-ttys. This should be done
8266 using Unix98 ptys if the C library supports it. The resulting
8267 program must not be installed setuid root, unless that
8268 is required for other functionality.
8272 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
8273 <file>/var/log/lastlog</file> must be installed writable by
8274 group <tt>utmp</tt>. Programs which need to modify those
8275 files must be installed setgid <tt>utmp</tt>.
8280 <heading>Editors and pagers</heading>
8283 Some programs have the ability to launch an editor or pager
8284 program to edit or display a text document. Since there are
8285 lots of different editors and pagers available in the Debian
8286 distribution, the system administrator and each user should
8287 have the possibility to choose their preferred editor and
8292 In addition, every program should choose a good default
8293 editor/pager if none is selected by the user or system
8298 Thus, every program that launches an editor or pager must
8299 use the EDITOR or PAGER environment variable to determine
8300 the editor or pager the user wishes to use. If these
8301 variables are not set, the programs <file>/usr/bin/editor</file>
8302 and <file>/usr/bin/pager</file> should be used, respectively.
8306 These two files are managed through the <prgn>dpkg</prgn>
8307 "alternatives" mechanism. Thus every package providing an
8308 editor or pager must call the
8309 <prgn>update-alternatives</prgn> script to register these
8314 If it is very hard to adapt a program to make use of the
8315 EDITOR or PAGER variables, that program may be configured to
8316 use <file>/usr/bin/sensible-editor</file> and
8317 <file>/usr/bin/sensible-pager</file> as the editor or pager
8318 program respectively. These are two scripts provided in the
8319 <package>sensible-utils</package> package that check the EDITOR
8320 and PAGER variables and launch the appropriate program, and fall
8321 back to <file>/usr/bin/editor</file>
8322 and <file>/usr/bin/pager</file> if the variable is not set.
8326 A program may also use the VISUAL environment variable to
8327 determine the user's choice of editor. If it exists, it
8328 should take precedence over EDITOR. This is in fact what
8329 <file>/usr/bin/sensible-editor</file> does.
8333 It is not required for a package to depend on
8334 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
8335 package to provide such virtual packages.<footnote>
8336 The Debian base system already provides an editor and a
8342 <sect id="web-appl">
8343 <heading>Web servers and applications</heading>
8346 This section describes the locations and URLs that should
8347 be used by all web servers and web applications in the
8354 Cgi-bin executable files are installed in the
8356 <example compact="compact">
8357 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
8359 or a subdirectory of that directory, and should be
8361 <example compact="compact">
8362 http://localhost/cgi-bin/<var>cgi-bin-name</var>
8364 (possibly with a subdirectory name
8365 before <var>cgi-bin-name</var>).
8369 <p>Access to HTML documents</p>
8372 HTML documents for a package are stored in
8373 <file>/usr/share/doc/<var>package</var></file>
8374 and can be referred to as
8375 <example compact="compact">
8376 http://localhost/doc/<var>package</var>/<var>filename</var>
8381 The web server should restrict access to the document
8382 tree so that only clients on the same host can read
8383 the documents. If the web server does not support such
8384 access controls, then it should not provide access at
8385 all, or ask about providing access during installation.
8390 <p>Access to images</p>
8392 It is recommended that images for a package be stored
8393 in <tt>/usr/share/images/<var>package</var></tt> and
8394 may be referred to through an alias <tt>/images/</tt>
8397 http://localhost/images/<package>/<filename>
8404 <p>Web Document Root</p>
8407 Web Applications should try to avoid storing files in
8408 the Web Document Root. Instead they should use the
8409 /usr/share/doc/<var>package</var> directory for
8410 documents and register the Web Application via the
8411 <package>doc-base</package> package. If access to the
8412 web document root is unavoidable then use
8413 <example compact="compact">
8416 as the Document Root. This might be just a symbolic
8417 link to the location where the system administrator
8418 has put the real document root.
8421 <item><p>Providing httpd and/or httpd-cgi</p>
8423 All web servers should provide the virtual package
8424 <tt>httpd</tt>. If a web server has CGI support it should
8425 provide <tt>httpd-cgi</tt> additionally.
8428 All web applications which do not contain CGI scripts should
8429 depend on <tt>httpd</tt>, all those web applications which
8430 <tt>do</tt> contain CGI scripts, should depend on
8438 <sect id="mail-transport-agents">
8439 <heading>Mail transport, delivery and user agents</heading>
8442 Debian packages which process electronic mail, whether mail
8443 user agents (MUAs) or mail transport agents (MTAs), must
8444 ensure that they are compatible with the configuration
8445 decisions below. Failure to do this may result in lost
8446 mail, broken <tt>From:</tt> lines, and other serious brain
8451 The mail spool is <file>/var/mail</file> and the interface to
8452 send a mail message is <file>/usr/sbin/sendmail</file> (as per
8453 the FHS). On older systems, the mail spool may be
8454 physically located in <file>/var/spool/mail</file>, but all
8455 access to the mail spool should be via the
8456 <file>/var/mail</file> symlink. The mail spool is part of the
8457 base system and not part of the MTA package.
8461 All Debian MUAs, MTAs, MDAs and other mailbox accessing
8462 programs (such as IMAP daemons) must lock the mailbox in an
8463 NFS-safe way. This means that <tt>fcntl()</tt> locking must
8464 be combined with dot locking. To avoid deadlocks, a program
8465 should use <tt>fcntl()</tt> first and dot locking after
8466 this, or alternatively implement the two locking methods in
8467 a non blocking way<footnote>
8468 If it is not possible to establish both locks, the
8469 system shouldn't wait for the second lock to be
8470 established, but remove the first lock, wait a (random)
8471 time, and start over locking again.
8472 </footnote>. Using the functions <tt>maillock</tt> and
8473 <tt>mailunlock</tt> provided by the
8474 <tt>liblockfile*</tt><footnote>
8475 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
8476 to use these functions.
8477 </footnote> packages is the recommended way to realize this.
8481 Mailboxes are generally either mode 600 and owned by
8482 <var>user</var> or mode 660 and owned by
8483 <tt><var>user</var>:mail</tt><footnote>
8484 There are two traditional permission schemes for mail spools:
8485 mode 600 with all mail delivery done by processes running as
8486 the destination user, or mode 660 and owned by group mail with
8487 mail delivery done by a process running as a system user in
8488 group mail. Historically, Debian required mode 660 mail
8489 spools to enable the latter model, but that model has become
8490 increasingly uncommon and the principle of least privilege
8491 indicates that mail systems that use the first model should
8492 use permissions of 600. If delivery to programs is permitted,
8493 it's easier to keep the mail system secure if the delivery
8494 agent runs as the destination user. Debian Policy therefore
8495 permits either scheme.
8496 </footnote>. The local system administrator may choose a
8497 different permission scheme; packages should not make
8498 assumptions about the permission and ownership of mailboxes
8499 unless required (such as when creating a new mailbox). A MUA
8500 may remove a mailbox (unless it has nonstandard permissions) in
8501 which case the MTA or another MUA must recreate it if needed.
8505 The mail spool is 2775 <tt>root:mail</tt>, and MUAs should
8506 be setgid mail to do the locking mentioned above (and
8507 must obviously avoid accessing other users' mailboxes
8508 using this privilege).</p>
8511 <file>/etc/aliases</file> is the source file for the system mail
8512 aliases (e.g., postmaster, usenet, etc.), it is the one
8513 which the sysadmin and <prgn>postinst</prgn> scripts may
8514 edit. After <file>/etc/aliases</file> is edited the program or
8515 human editing it must call <prgn>newaliases</prgn>. All MTA
8516 packages must come with a <prgn>newaliases</prgn> program,
8517 even if it does nothing, but older MTA packages did not do
8518 this so programs should not fail if <prgn>newaliases</prgn>
8519 cannot be found. Note that because of this, all MTA
8520 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
8521 <tt>Replaces: mail-transport-agent</tt> control file
8526 The convention of writing <tt>forward to
8527 <var>address</var></tt> in the mailbox itself is not
8528 supported. Use a <tt>.forward</tt> file instead.</p>
8531 The <prgn>rmail</prgn> program used by UUCP
8532 for incoming mail should be <file>/usr/sbin/rmail</file>.
8533 Likewise, <prgn>rsmtp</prgn>, for receiving
8534 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
8538 If your package needs to know what hostname to use on (for
8539 example) outgoing news and mail messages which are generated
8540 locally, you should use the file <file>/etc/mailname</file>. It
8541 will contain the portion after the username and <tt>@</tt>
8542 (at) sign for email addresses of users on the machine
8543 (followed by a newline).
8547 Such a package should check for the existence of this file
8548 when it is being configured. If it exists, it should be
8549 used without comment, although an MTA's configuration script
8550 may wish to prompt the user even if it finds that this file
8551 exists. If the file does not exist, the package should
8552 prompt the user for the value (preferably using
8553 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
8554 as well as using it in the package's configuration. The
8555 prompt should make it clear that the name will not just be
8556 used by that package. For example, in this situation the
8557 <tt>inn</tt> package could say something like:
8558 <example compact="compact">
8559 Please enter the "mail name" of your system. This is the
8560 hostname portion of the address to be shown on outgoing
8561 news and mail messages. The default is
8562 <var>syshostname</var>, your system's host name. Mail
8563 name ["<var>syshostname</var>"]:
8565 where <var>syshostname</var> is the output of <tt>hostname
8571 <heading>News system configuration</heading>
8574 All the configuration files related to the NNTP (news)
8575 servers and clients should be located under
8576 <file>/etc/news</file>.</p>
8579 There are some configuration issues that apply to a number
8580 of news clients and server packages on the machine. These
8584 <tag><file>/etc/news/organization</file></tag>
8586 A string which should appear as the
8587 organization header for all messages posted
8588 by NNTP clients on the machine
8591 <tag><file>/etc/news/server</file></tag>
8593 Contains the FQDN of the upstream NNTP
8594 server, or localhost if the local machine is
8599 Other global files may be added as required for cross-package news
8606 <heading>Programs for the X Window System</heading>
8609 <heading>Providing X support and package priorities</heading>
8612 Programs that can be configured with support for the X
8613 Window System must be configured to do so and must declare
8614 any package dependencies necessary to satisfy their
8615 runtime requirements when using the X Window System. If
8616 such a package is of higher priority than the X packages
8617 on which it depends, it is required that either the
8618 X-specific components be split into a separate package, or
8619 that an alternative version of the package, which includes
8620 X support, be provided, or that the package's priority be
8626 <heading>Packages providing an X server</heading>
8629 Packages that provide an X server that, directly or
8630 indirectly, communicates with real input and display
8631 hardware should declare in their control data that they
8632 provide the virtual package <tt>xserver</tt>.<footnote>
8633 This implements current practice, and provides an
8634 actual policy for usage of the <tt>xserver</tt>
8635 virtual package which appears in the virtual packages
8636 list. In a nutshell, X servers that interface
8637 directly with the display and input hardware or via
8638 another subsystem (e.g., GGI) should provide
8639 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8640 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8646 <heading>Packages providing a terminal emulator</heading>
8649 Packages that provide a terminal emulator for the X Window
8650 System which meet the criteria listed below should declare
8651 in their control data that they provide the virtual
8652 package <tt>x-terminal-emulator</tt>. They should also
8653 register themselves as an alternative for
8654 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8659 To be an <tt>x-terminal-emulator</tt>, a program must:
8660 <list compact="compact">
8662 Be able to emulate a DEC VT100 terminal, or a
8663 compatible terminal.
8667 Support the command-line option <tt>-e
8668 <var>command</var></tt>, which creates a new
8669 terminal window<footnote>
8670 "New terminal window" does not necessarily mean
8671 a new top-level X window directly parented by
8672 the window manager; it could, if the terminal
8673 emulator application were so coded, be a new
8674 "view" in a multiple-document interface (MDI).
8676 and runs the specified <var>command</var>,
8677 interpreting the entirety of the rest of the command
8678 line as a command to pass straight to exec, in the
8679 manner that <tt>xterm</tt> does.
8683 Support the command-line option <tt>-T
8684 <var>title</var></tt>, which creates a new terminal
8685 window with the window title <var>title</var>.
8692 <heading>Packages providing a window manager</heading>
8695 Packages that provide a window manager should declare in
8696 their control data that they provide the virtual package
8697 <tt>x-window-manager</tt>. They should also register
8698 themselves as an alternative for
8699 <file>/usr/bin/x-window-manager</file>, with a priority
8700 calculated as follows:
8701 <list compact="compact">
8703 Start with a priority of 20.
8707 If the window manager supports the Debian menu
8708 system, add 20 points if this support is available
8709 in the package's default configuration (i.e., no
8710 configuration files belonging to the system or user
8711 have to be edited to activate the feature); if
8712 configuration files must be modified, add only 10
8718 If the window manager complies with <url
8719 id="http://www.freedesktop.org/Standards/wm-spec"
8720 name="The Window Manager Specification Project">,
8721 written by the <url id="http://www.freedesktop.org/"
8722 name="Free Desktop Group">, add 40 points.
8726 If the window manager permits the X session to be
8727 restarted using a <em>different</em> window manager
8728 (without killing the X server) in its default
8729 configuration, add 10 points; otherwise add none.
8736 <heading>Packages providing fonts</heading>
8739 Packages that provide fonts for the X Window
8741 For the purposes of Debian Policy, a "font for the X
8742 Window System" is one which is accessed via X protocol
8743 requests. Fonts for the Linux console, for PostScript
8744 renderer, or any other purpose, do not fit this
8745 definition. Any tool which makes such fonts available
8746 to the X Window System, however, must abide by this
8749 must do a number of things to ensure that they are both
8750 available without modification of the X or font server
8751 configuration, and that they do not corrupt files used by
8752 other font packages to register information about
8756 Fonts of any type supported by the X Window System
8757 must be in a separate binary package from any
8758 executables, libraries, or documentation (except
8759 that specific to the fonts shipped, such as their
8760 license information). If one or more of the fonts
8761 so packaged are necessary for proper operation of
8762 the package with which they are associated the font
8763 package may be Recommended; if the fonts merely
8764 provide an enhancement, a Suggests relationship may
8765 be used. Packages must not Depend on font
8767 This is because the X server may retrieve fonts
8768 from the local file system or over the network
8769 from an X font server; the Debian package system
8770 is empowered to deal only with the local
8776 BDF fonts must be converted to PCF fonts with the
8777 <prgn>bdftopcf</prgn> utility (available in the
8778 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8779 placed in a directory that corresponds to their
8781 <list compact="compact">
8783 100 dpi fonts must be placed in
8784 <file>/usr/share/fonts/X11/100dpi/</file>.
8788 75 dpi fonts must be placed in
8789 <file>/usr/share/fonts/X11/75dpi/</file>.
8793 Character-cell fonts, cursor fonts, and other
8794 low-resolution fonts must be placed in
8795 <file>/usr/share/fonts/X11/misc/</file>.
8801 Type 1 fonts must be placed in
8802 <file>/usr/share/fonts/X11/Type1/</file>. If font
8803 metric files are available, they must be placed here
8808 Subdirectories of <file>/usr/share/fonts/X11/</file>
8809 other than those listed above must be neither
8810 created nor used. (The <file>PEX</file>, <file>CID</file>,
8811 <file>Speedo</file>, and <file>cyrillic</file> directories
8812 are excepted for historical reasons, but installation of
8813 files into these directories remains discouraged.)
8817 Font packages may, instead of placing files directly
8818 in the X font directories listed above, provide
8819 symbolic links in that font directory pointing to
8820 the files' actual location in the filesystem. Such
8821 a location must comply with the FHS.
8825 Font packages should not contain both 75dpi and
8826 100dpi versions of a font. If both are available,
8827 they should be provided in separate binary packages
8828 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8829 the names of the packages containing the
8830 corresponding fonts.
8834 Fonts destined for the <file>misc</file> subdirectory
8835 should not be included in the same package as 75dpi
8836 or 100dpi fonts; instead, they should be provided in
8837 a separate package with <tt>-misc</tt> appended to
8842 Font packages must not provide the files
8843 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8844 <file>fonts.scale</file> in a font directory:
8847 <file>fonts.dir</file> files must not be provided at all.
8851 <file>fonts.alias</file> and <file>fonts.scale</file>
8852 files, if needed, should be provided in the
8854 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8855 where <var>fontdir</var> is the name of the
8857 <file>/usr/share/fonts/X11/</file> where the
8858 package's corresponding fonts are stored
8859 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8860 <var>package</var> is the name of the package
8861 that provides these fonts, and
8862 <var>extension</var> is either <tt>scale</tt>
8863 or <tt>alias</tt>, whichever corresponds to
8870 Font packages must declare a dependency on
8871 <tt>xfonts-utils</tt> in their control
8876 Font packages that provide one or more
8877 <file>fonts.scale</file> files as described above must
8878 invoke <prgn>update-fonts-scale</prgn> on each
8879 directory into which they installed fonts
8880 <em>before</em> invoking
8881 <prgn>update-fonts-dir</prgn> on that directory.
8882 This invocation must occur in both the
8883 <prgn>postinst</prgn> (for all arguments) and
8884 <prgn>postrm</prgn> (for all arguments except
8885 <tt>upgrade</tt>) scripts.
8889 Font packages that provide one or more
8890 <file>fonts.alias</file> files as described above must
8891 invoke <prgn>update-fonts-alias</prgn> on each
8892 directory into which they installed fonts. This
8893 invocation must occur in both the
8894 <prgn>postinst</prgn> (for all arguments) and
8895 <prgn>postrm</prgn> (for all arguments except
8896 <tt>upgrade</tt>) scripts.
8900 Font packages must invoke
8901 <prgn>update-fonts-dir</prgn> on each directory into
8902 which they installed fonts. This invocation must
8903 occur in both the <prgn>postinst</prgn> (for all
8904 arguments) and <prgn>postrm</prgn> (for all
8905 arguments except <tt>upgrade</tt>) scripts.
8909 Font packages must not provide alias names for the
8910 fonts they include which collide with alias names
8911 already in use by fonts already packaged.
8915 Font packages must not provide fonts with the same
8916 XLFD registry name as another font already packaged.
8922 <sect1 id="appdefaults">
8923 <heading>Application defaults files</heading>
8926 Application defaults files must be installed in the
8927 directory <file>/etc/X11/app-defaults/</file> (use of a
8928 localized subdirectory of <file>/etc/X11/</file> as described
8929 in the <em>X Toolkit Intrinsics - C Language
8930 Interface</em> manual is also permitted). They must be
8931 registered as <tt>conffile</tt>s or handled as
8932 configuration files.
8936 Customization of programs' X resources may also be
8937 supported with the provision of a file with the same name
8938 as that of the package placed in
8939 the <file>/etc/X11/Xresources/</file> directory, which
8940 must be registered as a <tt>conffile</tt> or handled as a
8941 configuration file.<footnote>
8942 Note that this mechanism is not the same as using
8943 app-defaults; app-defaults are tied to the client
8944 binary on the local file system, whereas X resources
8945 are stored in the X server and affect all connecting
8952 <heading>Installation directory issues</heading>
8955 Historically, packages using the X Window System used a
8956 separate set of installation directories from other packages.
8957 This practice has been discontinued and packages using the X
8958 Window System should now generally be installed in the same
8959 directories as any other package. Specifically, packages must
8960 not install files under the <file>/usr/X11R6/</file> directory
8961 and the <file>/usr/X11R6/</file> directory hierarchy should be
8962 regarded as obsolete.
8966 Include files previously installed under
8967 <file>/usr/X11R6/include/X11/</file> should be installed into
8968 <file>/usr/include/X11/</file>. For files previously
8969 installed into subdirectories of
8970 <file>/usr/X11R6/lib/X11/</file>, package maintainers should
8971 determine if subdirectories of <file>/usr/lib/</file> and
8972 <file>/usr/share/</file> can be used. If not, a subdirectory
8973 of <file>/usr/lib/X11/</file> should be used.
8977 Configuration files for window, display, or session managers
8978 or other applications that are tightly integrated with the X
8979 Window System may be placed in a subdirectory
8980 of <file>/etc/X11/</file> corresponding to the package name.
8981 Other X Window System applications should use
8982 the <file>/etc/</file> directory unless otherwise mandated by
8983 policy (such as for <ref id="appdefaults">).
8988 <heading>The OSF/Motif and OpenMotif libraries</heading>
8991 <em>Programs that require the non-DFSG-compliant OSF/Motif or
8992 OpenMotif libraries</em><footnote>
8993 OSF/Motif and OpenMotif are collectively referred to as
8994 "Motif" in this policy document.
8996 should be compiled against and tested with LessTif (a free
8997 re-implementation of Motif) instead. If the maintainer
8998 judges that the program or programs do not work
8999 sufficiently well with LessTif to be distributed and
9000 supported, but do so when compiled against Motif, then two
9001 versions of the package should be created; one linked
9002 statically against Motif and with <tt>-smotif</tt>
9003 appended to the package name, and one linked dynamically
9004 against Motif and with <tt>-dmotif</tt> appended to the
9009 Both Motif-linked versions are dependent
9010 upon non-DFSG-compliant software and thus cannot be
9011 uploaded to the <em>main</em> distribution; if the
9012 software is itself DFSG-compliant it may be uploaded to
9013 the <em>contrib</em> distribution. While known existing
9014 versions of Motif permit unlimited redistribution of
9015 binaries linked against the library (whether statically or
9016 dynamically), it is the package maintainer's
9017 responsibility to determine whether this is permitted by
9018 the license of the copy of Motif in their possession.
9024 <heading>Perl programs and modules</heading>
9027 Perl programs and modules should follow the current Perl policy.
9031 The Perl policy can be found in the <tt>perl-policy</tt>
9032 files in the <tt>debian-policy</tt> package.
9033 It is also available from the Debian web mirrors at
9034 <tt><url name="/doc/packaging-manuals/perl-policy/"
9035 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
9040 <heading>Emacs lisp programs</heading>
9043 Please refer to the "Debian Emacs Policy" for details of how to
9044 package emacs lisp programs.
9048 The Emacs policy is available in
9049 <file>debian-emacs-policy.gz</file> of the
9050 <package>emacsen-common</package> package.
9051 It is also available from the Debian web mirrors at
9052 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
9053 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
9058 <heading>Games</heading>
9061 The permissions on <file>/var/games</file> are mode 755, owner
9062 <tt>root</tt> and group <tt>root</tt>.
9066 Each game decides on its own security policy.</p>
9069 Games which require protected, privileged access to
9070 high-score files, saved games, etc., may be made
9071 set-<em>group</em>-id (mode 2755) and owned by
9072 <tt>root:games</tt>, and use files and directories with
9073 appropriate permissions (770 <tt>root:games</tt>, for
9074 example). They must not be made
9075 set-<em>user</em>-id, as this causes security problems. (If
9076 an attacker can subvert any set-user-id game they can
9077 overwrite the executable of any other, causing other players
9078 of these games to run a Trojan horse program. With a
9079 set-group-id game the attacker only gets access to less
9080 important game data, and if they can get at the other
9081 players' accounts at all it will take considerably more
9085 Some packages, for example some fortune cookie programs, are
9086 configured by the upstream authors to install with their
9087 data files or other static information made unreadable so
9088 that they can only be accessed through set-id programs
9089 provided. You should not do this in a Debian package: anyone can
9090 download the <file>.deb</file> file and read the data from it,
9091 so there is no point making the files unreadable. Not
9092 making the files unreadable also means that you don't have
9093 to make so many programs set-id, which reduces the risk of a
9097 As described in the FHS, binaries of games should be
9098 installed in the directory <file>/usr/games</file>. This also
9099 applies to games that use the X Window System. Manual pages
9100 for games (X and non-X games) should be installed in
9101 <file>/usr/share/man/man6</file>.</p>
9107 <heading>Documentation</heading>
9110 <heading>Manual pages</heading>
9113 You should install manual pages in <prgn>nroff</prgn> source
9114 form, in appropriate places under <file>/usr/share/man</file>.
9115 You should only use sections 1 to 9 (see the FHS for more
9116 details). You must not install a pre-formatted "cat page".
9120 Each program, utility, and function should have an
9121 associated manual page included in the same package. It is
9122 suggested that all configuration files also have a manual
9123 page included as well. Manual pages for protocols and other
9124 auxiliary things are optional.
9128 If no manual page is available, this is considered as a bug
9129 and should be reported to the Debian Bug Tracking System (the
9130 maintainer of the package is allowed to write this bug report
9131 themselves, if they so desire). Do not close the bug report
9132 until a proper man page is available.<footnote>
9133 It is not very hard to write a man page. See the
9134 <url id="http://www.schweikhardt.net/man_page_howto.html"
9135 name="Man-Page-HOWTO">,
9136 <manref name="man" section="7">, the examples
9137 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
9138 the helper program <prgn>help2man</prgn>, or the
9139 directory <file>/usr/share/doc/man-db/examples</file>.
9144 You may forward a complaint about a missing man page to the
9145 upstream authors, and mark the bug as forwarded in the
9146 Debian bug tracking system. Even though the GNU Project do
9147 not in general consider the lack of a man page to be a bug,
9148 we do; if they tell you that they don't consider it a bug
9149 you should leave the bug in our bug tracking system open
9154 Manual pages should be installed compressed using <tt>gzip -9</tt>.
9158 If one man page needs to be accessible via several names it
9159 is better to use a symbolic link than the <file>.so</file>
9160 feature, but there is no need to fiddle with the relevant
9161 parts of the upstream source to change from <file>.so</file> to
9162 symlinks: don't do it unless it's easy. You should not
9163 create hard links in the manual page directories, nor put
9164 absolute filenames in <file>.so</file> directives. The filename
9165 in a <file>.so</file> in a man page should be relative to the
9166 base of the man page tree (usually
9167 <file>/usr/share/man</file>). If you do not create any links
9168 (whether symlinks, hard links, or <tt>.so</tt> directives)
9169 in the file system to the alternate names of the man page,
9170 then you should not rely on <prgn>man</prgn> finding your
9171 man page under those names based solely on the information in
9172 the man page's header.<footnote>
9173 Supporting this in <prgn>man</prgn> often requires
9174 unreasonable processing time to find a manual page or to
9175 report that none exists, and moves knowledge into man's
9176 database that would be better left in the file system.
9177 This support is therefore deprecated and will cease to
9178 be present in the future.
9183 Manual pages in locale-specific subdirectories of
9184 <file>/usr/share/man</file> should use either UTF-8 or the usual
9185 legacy encoding for that language (normally the one corresponding
9186 to the shortest relevant locale name in
9187 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
9188 <file>/usr/share/man/fr</file> should use either UTF-8 or
9189 ISO-8859-1.<footnote>
9190 <prgn>man</prgn> will automatically detect whether UTF-8 is in
9191 use. In future, all manual pages will be required to use
9197 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
9198 included in the subdirectory name unless it indicates a
9199 significant difference in the language, as this excludes
9200 speakers of the language in other countries.<footnote>
9201 At the time of writing, Chinese and Portuguese are the main
9202 languages with such differences, so <file>pt_BR</file>,
9203 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
9208 If a localized version of a manual page is provided, it should
9209 either be up-to-date or it should be obvious to the reader that
9210 it is outdated and the original manual page should be used
9211 instead. This can be done either by a note at the beginning of
9212 the manual page or by showing the missing or changed portions in
9213 the original language instead of the target language.
9218 <heading>Info documents</heading>
9221 Info documents should be installed in <file>/usr/share/info</file>.
9222 They should be compressed with <tt>gzip -9</tt>.
9226 The <prgn>install-info</prgn> program maintains a directory of
9227 installed info documents in <file>/usr/share/info/dir</file> for
9228 the use of info readers.<footnote>
9229 It was previously necessary for packages installing info
9230 documents to run <prgn>install-info</prgn> from maintainer
9231 scripts. This is no longer necessary. The installation
9232 system now uses dpkg triggers.
9234 This file must not be included in packages. Packages containing
9235 info documents should depend on <tt>dpkg (>= 1.15.4) |
9236 install-info</tt> to ensure that the directory file is properly
9237 rebuilt during partial upgrades from Debian 5.0 (lenny) and
9242 Info documents should contain section and directory entry
9243 information in the document for the use
9244 of <prgn>install-info</prgn>. The section should be specified
9245 via a line starting with <tt>INFO-DIR-SECTION</tt> followed by a
9246 space and the section of this info page. The directory entry or
9247 entries should be included between
9248 a <tt>START-INFO-DIR-ENTRY</tt> line and
9249 an <tt>END-INFO-DIR-ENTRY</tt> line. For example:
9251 INFO-DIR-SECTION Individual utilities
9252 START-INFO-DIR-ENTRY
9253 * example: (example). An example info directory entry.
9256 To determine which section to use, you should look
9257 at <file>/usr/share/info/dir</file> on your system and choose
9258 the most relevant (or create a new section if none of the
9259 current sections are relevant).<footnote>
9260 Normally, info documents are generated from Texinfo source.
9261 To include this information in the generated info document, if
9262 it is absent, add commands like:
9264 @dircategory Individual utilities
9266 * example: (example). An example info directory entry.
9269 to the Texinfo source of the document and ensure that the info
9270 documents are rebuilt from source during the package build.
9276 <heading>Additional documentation</heading>
9279 Any additional documentation that comes with the package may
9280 be installed at the discretion of the package maintainer.
9281 Plain text documentation should be installed in the directory
9282 <file>/usr/share/doc/<var>package</var></file>, where
9283 <var>package</var> is the name of the package, and
9284 compressed with <tt>gzip -9</tt> unless it is small.
9288 If a package comes with large amounts of documentation which
9289 many users of the package will not require you should create
9290 a separate binary package to contain it, so that it does not
9291 take up disk space on the machines of users who do not need
9292 or want it installed.</p>
9295 It is often a good idea to put text information files
9296 (<file>README</file>s, changelogs, and so forth) that come with
9297 the source package in <file>/usr/share/doc/<var>package</var></file>
9298 in the binary package. However, you don't need to install
9299 the instructions for building and installing the package, of
9303 Packages must not require the existence of any files in
9304 <file>/usr/share/doc/</file> in order to function
9306 The system administrator should be able to
9307 delete files in <file>/usr/share/doc/</file> without causing
9308 any programs to break.
9310 Any files that are referenced by programs but are also
9311 useful as stand alone documentation should be installed under
9312 <file>/usr/share/<var>package</var>/</file> with symbolic links from
9313 <file>/usr/share/doc/<var>package</var></file>.
9317 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9318 link to another directory in <file>/usr/share/doc</file> only if
9319 the two packages both come from the same source and the
9320 first package Depends on the second.<footnote>
9322 Please note that this does not override the section on
9323 changelog files below, so the file
9324 <file>/usr/share/doc/<var>package</var>/changelog.Debian.gz</file>
9325 must refer to the changelog for the current version of
9326 <var>package</var> in question. In practice, this means
9327 that the sources of the target and the destination of the
9328 symlink must be the same (same source package and
9335 Former Debian releases placed all additional documentation
9336 in <file>/usr/doc/<var>package</var></file>. This has been
9337 changed to <file>/usr/share/doc/<var>package</var></file>,
9338 and packages must not put documentation in the directory
9339 <file>/usr/doc/<var>package</var></file>. <footnote>
9340 At this phase of the transition, we no longer require a
9341 symbolic link in <file>/usr/doc/</file>. At a later point,
9342 policy shall change to make the symbolic links a bug.
9348 <heading>Preferred documentation formats</heading>
9351 The unification of Debian documentation is being carried out
9355 If your package comes with extensive documentation in a
9356 markup format that can be converted to various other formats
9357 you should if possible ship HTML versions in a binary
9358 package, in the directory
9359 <file>/usr/share/doc/<var>appropriate-package</var></file> or
9360 its subdirectories.<footnote>
9361 The rationale: The important thing here is that HTML
9362 docs should be available in <em>some</em> package, not
9363 necessarily in the main binary package.
9368 Other formats such as PostScript may be provided at the
9369 package maintainer's discretion.
9373 <sect id="copyrightfile">
9374 <heading>Copyright information</heading>
9377 Every package must be accompanied by a verbatim copy of its
9378 copyright information and distribution license in the file
9379 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
9380 file must neither be compressed nor be a symbolic link.
9384 In addition, the copyright file must say where the upstream
9385 sources (if any) were obtained. It should name the original
9386 authors of the package and the Debian maintainer(s) who were
9387 involved with its creation.
9391 Packages in the <em>contrib</em> or <em>non-free</em> archive
9392 areas should state in the copyright file that the package is not
9393 part of the Debian GNU/Linux distribution and briefly explain
9398 A copy of the file which will be installed in
9399 <file>/usr/share/doc/<var>package</var>/copyright</file> should
9400 be in <file>debian/copyright</file> in the source package.
9404 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
9405 link to another directory in <file>/usr/share/doc</file> only if
9406 the two packages both come from the same source and the
9407 first package Depends on the second. These rules are
9408 important because copyrights must be extractable by
9413 Packages distributed under the Apache license (version 2.0), the
9414 Artistic license, the GNU GPL (versions 1, 2, or 3), the GNU
9415 LGPL (versions 2, 2.1, or 3), and the GNU FDL (versions 1.2 or
9416 1.3) should refer to the corresponding files
9417 under <file>/usr/share/common-licenses</file>,<footnote>
9420 <file>/usr/share/common-licenses/Apache-2.0</file>,
9421 <file>/usr/share/common-licenses/Artistic</file>,
9422 <file>/usr/share/common-licenses/GPL-1</file>,
9423 <file>/usr/share/common-licenses/GPL-2</file>,
9424 <file>/usr/share/common-licenses/GPL-3</file>,
9425 <file>/usr/share/common-licenses/LGPL-2</file>,
9426 <file>/usr/share/common-licenses/LGPL-2.1</file>,
9427 <file>/usr/share/common-licenses/LGPL-3</file>,
9428 <file>/usr/share/common-licenses/GFDL-1.2</file>, and
9429 <file>/usr/share/common-licenses/GFDL-1.3</file>
9430 respectively. The University of California BSD license is
9431 also included in <package>base-files</package> as
9432 <file>/usr/share/common-licenses/BSD</file>, but given the
9433 brevity of this license, its specificity to code whose
9434 copyright is held by the Regents of the University of
9435 California, and the frequency of minor wording changes, its
9436 text should be included in the copyright file rather than
9437 referencing this file.
9439 </footnote> rather than quoting them in the copyright
9444 You should not use the copyright file as a general <file>README</file>
9445 file. If your package has such a file it should be
9446 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
9447 <file>README.Debian</file> or some other appropriate place.</p>
9451 <heading>Examples</heading>
9454 Any examples (configurations, source files, whatever),
9455 should be installed in a directory
9456 <file>/usr/share/doc/<var>package</var>/examples</file>. These
9457 files should not be referenced by any program: they're there
9458 for the benefit of the system administrator and users as
9459 documentation only. Architecture-specific example files
9460 should be installed in a directory
9461 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
9463 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
9464 latter directory itself may be a symbolic link to the
9469 If the purpose of a package is to provide examples, then the
9470 example files may be installed into
9471 <file>/usr/share/doc/<var>package</var></file>.
9475 <sect id="changelogs">
9476 <heading>Changelog files</heading>
9479 Packages that are not Debian-native must contain a
9480 compressed copy of the <file>debian/changelog</file> file from
9481 the Debian source tree in
9482 <file>/usr/share/doc/<var>package</var></file> with the name
9483 <file>changelog.Debian.gz</file>.
9487 If an upstream changelog is available, it should be accessible as
9488 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
9489 plain text. If the upstream changelog is distributed in
9490 HTML, it should be made available in that form as
9491 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
9492 and a plain text <file>changelog.gz</file> should be generated
9493 from it using, for example, <tt>lynx -dump -nolist</tt>. If
9494 the upstream changelog files do not already conform to this
9495 naming convention, then this may be achieved either by
9496 renaming the files, or by adding a symbolic link, at the
9497 maintainer's discretion.<footnote>
9498 Rationale: People should not have to look in places for
9499 upstream changelogs merely because they are given
9500 different names or are distributed in HTML format.
9505 All of these files should be installed compressed using
9506 <tt>gzip -9</tt>, as they will become large with time even
9507 if they start out small.
9511 If the package has only one changelog which is used both as
9512 the Debian changelog and the upstream one because there is
9513 no separate upstream maintainer then that changelog should
9514 usually be installed as
9515 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
9516 there is a separate upstream maintainer, but no upstream
9517 changelog, then the Debian changelog should still be called
9518 <file>changelog.Debian.gz</file>.
9522 For details about the format and contents of the Debian
9523 changelog file, please see <ref id="dpkgchangelog">.
9528 <appendix id="pkg-scope">
9529 <heading>Introduction and scope of these appendices</heading>
9532 These appendices are taken essentially verbatim from the
9533 now-deprecated Packaging Manual, version 3.2.1.0. They are
9534 the chapters which are likely to be of use to package
9535 maintainers and which have not already been included in the
9536 policy document itself. Most of these sections are very likely
9537 not relevant to policy; they should be treated as
9538 documentation for the packaging system. Please note that these
9539 appendices are included for convenience, and for historical
9540 reasons: they used to be part of policy package, and they have
9541 not yet been incorporated into dpkg documentation. However,
9542 they still have value, and hence they are presented here.
9546 They have not yet been checked to ensure that they are
9547 compatible with the contents of policy, and if there are any
9548 contradictions, the version in the main policy document takes
9549 precedence. The remaining chapters of the old Packaging
9550 Manual have also not been read in detail to ensure that there
9551 are not parts which have been left out. Both of these will be
9556 Certain parts of the Packaging manual were integrated into the
9557 Policy Manual proper, and removed from the appendices. Links
9558 have been placed from the old locations to the new ones.
9562 <prgn>dpkg</prgn> is a suite of programs for creating binary
9563 package files and installing and removing them on Unix
9565 <prgn>dpkg</prgn> is targeted primarily at Debian
9566 GNU/Linux, but may work on or be ported to other
9572 The binary packages are designed for the management of
9573 installed executable programs (usually compiled binaries) and
9574 their associated data, though source code examples and
9575 documentation are provided as part of some packages.</p>
9578 This manual describes the technical aspects of creating Debian
9579 binary packages (<file>.deb</file> files). It documents the
9580 behavior of the package management programs
9581 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
9582 they interact with packages.</p>
9585 It also documents the interaction between
9586 <prgn>dselect</prgn>'s core and the access method scripts it
9587 uses to actually install the selected packages, and describes
9588 how to create a new access method.</p>
9591 This manual does not go into detail about the options and
9592 usage of the package building and installation tools. It
9593 should therefore be read in conjunction with those programs'
9598 The utility programs which are provided with <prgn>dpkg</prgn>
9599 for managing various system configuration and similar issues,
9600 such as <prgn>update-rc.d</prgn> and
9601 <prgn>install-info</prgn>, are not described in detail here -
9602 please see their man pages.
9606 It is assumed that the reader is reasonably familiar with the
9607 <prgn>dpkg</prgn> System Administrators' manual.
9608 Unfortunately this manual does not yet exist.
9612 The Debian version of the FSF's GNU hello program is provided
9613 as an example for people wishing to create Debian
9614 packages. The Debian <prgn>debmake</prgn> package is
9615 recommended as a very helpful tool in creating and maintaining
9616 Debian packages. However, while the tools and examples are
9617 helpful, they do not replace the need to read and follow the
9618 Policy and Programmer's Manual.</p>
9621 <appendix id="pkg-binarypkg">
9622 <heading>Binary packages (from old Packaging Manual)</heading>
9625 The binary package has two main sections. The first part
9626 consists of various control information files and scripts used
9627 by <prgn>dpkg</prgn> when installing and removing. See <ref
9628 id="pkg-controlarea">.
9632 The second part is an archive containing the files and
9633 directories to be installed.
9637 In the future binary packages may also contain other
9638 components, such as checksums and digital signatures. The
9639 format for the archive is described in full in the
9640 <file>deb(5)</file> man page.
9644 <sect id="pkg-bincreating"><heading>Creating package files -
9645 <prgn>dpkg-deb</prgn>
9649 All manipulation of binary package files is done by
9650 <prgn>dpkg-deb</prgn>; it's the only program that has
9651 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9652 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9653 will spot that the options requested are appropriate to
9654 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9659 In order to create a binary package you must make a
9660 directory tree which contains all the files and directories
9661 you want to have in the file system data part of the package.
9662 In Debian-format source packages this directory is usually
9663 <file>debian/tmp</file>, relative to the top of the package's
9668 They should have the locations (relative to the root of the
9669 directory tree you're constructing) ownerships and
9670 permissions which you want them to have on the system when
9675 With current versions of <prgn>dpkg</prgn> the uid/username
9676 and gid/groupname mappings for the users and groups being
9677 used should be the same on the system where the package is
9678 built and the one where it is installed.
9682 You need to add one special directory to the root of the
9683 miniature file system tree you're creating:
9684 <prgn>DEBIAN</prgn>. It should contain the control
9685 information files, notably the binary package control file
9686 (see <ref id="pkg-controlfile">).
9690 The <prgn>DEBIAN</prgn> directory will not appear in the
9691 file system archive of the package, and so won't be installed
9692 by <prgn>dpkg</prgn> when the package is installed.
9696 When you've prepared the package, you should invoke:
9698 dpkg --build <var>directory</var>
9703 This will build the package in
9704 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9705 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9706 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9711 See the man page <manref name="dpkg-deb" section="8"> for details of how
9712 to examine the contents of this newly-created file. You may find the
9713 output of following commands enlightening:
9715 dpkg-deb --info <var>filename</var>.deb
9716 dpkg-deb --contents <var>filename</var>.deb
9717 dpkg --contents <var>filename</var>.deb
9719 To view the copyright file for a package you could use this command:
9721 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - --wildcards \*/copyright | pager
9726 <sect id="pkg-controlarea">
9727 <heading>Package control information files</heading>
9730 The control information portion of a binary package is a
9731 collection of files with names known to <prgn>dpkg</prgn>.
9732 It will treat the contents of these files specially - some
9733 of them contain information used by <prgn>dpkg</prgn> when
9734 installing or removing the package; others are scripts which
9735 the package maintainer wants <prgn>dpkg</prgn> to run.
9739 It is possible to put other files in the package control
9740 area, but this is not generally a good idea (though they
9741 will largely be ignored).
9745 Here is a brief list of the control info files supported by
9746 <prgn>dpkg</prgn> and a summary of what they're used for.
9751 <tag><tt>control</tt>
9754 This is the key description file used by
9755 <prgn>dpkg</prgn>. It specifies the package's name
9756 and version, gives its description for the user,
9757 states its relationships with other packages, and so
9758 forth. See <ref id="sourcecontrolfiles"> and
9759 <ref id="binarycontrolfiles">.
9763 It is usually generated automatically from information
9764 in the source package by the
9765 <prgn>dpkg-gencontrol</prgn> program, and with
9766 assistance from <prgn>dpkg-shlibdeps</prgn>.
9767 See <ref id="pkg-sourcetools">.
9771 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9776 These are executable files (usually scripts) which
9777 <prgn>dpkg</prgn> runs during installation, upgrade
9778 and removal of packages. They allow the package to
9779 deal with matters which are particular to that package
9780 or require more complicated processing than that
9781 provided by <prgn>dpkg</prgn>. Details of when and
9782 how they are called are in <ref id="maintainerscripts">.
9786 It is very important to make these scripts idempotent.
9787 See <ref id="idempotency">.
9791 The maintainer scripts are not guaranteed to run with a
9792 controlling terminal and may not be able to interact with
9793 the user. See <ref id="controllingterminal">.
9797 <tag><tt>conffiles</tt>
9800 This file contains a list of configuration files which
9801 are to be handled automatically by <prgn>dpkg</prgn>
9802 (see <ref id="pkg-conffiles">). Note that not necessarily
9803 every configuration file should be listed here.
9806 <tag><tt>shlibs</tt>
9809 This file contains a list of the shared libraries
9810 supplied by the package, with dependency details for
9811 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9812 when it determines what dependencies are required in a
9813 package control file. The <tt>shlibs</tt> file format
9814 is described on <ref id="shlibs">.
9819 <sect id="pkg-controlfile">
9820 <heading>The main control information file: <tt>control</tt></heading>
9823 The most important control information file used by
9824 <prgn>dpkg</prgn> when it installs a package is
9825 <tt>control</tt>. It contains all the package's "vital
9830 The binary package control files of packages built from
9831 Debian sources are made by a special tool,
9832 <prgn>dpkg-gencontrol</prgn>, which reads
9833 <file>debian/control</file> and <file>debian/changelog</file> to
9834 find the information it needs. See <ref id="pkg-sourcepkg"> for
9839 The fields in binary package control files are listed in
9840 <ref id="binarycontrolfiles">.
9844 A description of the syntax of control files and the purpose
9845 of the fields is available in <ref id="controlfields">.
9850 <heading>Time Stamps</heading>
9853 See <ref id="timestamps">.
9858 <appendix id="pkg-sourcepkg">
9859 <heading>Source packages (from old Packaging Manual) </heading>
9862 The Debian binary packages in the distribution are generated
9863 from Debian sources, which are in a special format to assist
9864 the easy and automatic building of binaries.
9867 <sect id="pkg-sourcetools">
9868 <heading>Tools for processing source packages</heading>
9871 Various tools are provided for manipulating source packages;
9872 they pack and unpack sources and help build of binary
9873 packages and help manage the distribution of new versions.
9877 They are introduced and typical uses described here; see
9878 <manref name="dpkg-source" section="1"> for full
9879 documentation about their arguments and operation.
9883 For examples of how to construct a Debian source package,
9884 and how to use those utilities that are used by Debian
9885 source packages, please see the <prgn>hello</prgn> example
9889 <sect1 id="pkg-dpkg-source">
9891 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9896 This program is frequently used by hand, and is also
9897 called from package-independent automated building scripts
9898 such as <prgn>dpkg-buildpackage</prgn>.
9902 To unpack a package it is typically invoked with
9904 dpkg-source -x <var>.../path/to/filename</var>.dsc
9909 with the <file><var>filename</var>.tar.gz</file> and
9910 <file><var>filename</var>.diff.gz</file> (if applicable) in
9911 the same directory. It unpacks into
9912 <file><var>package</var>-<var>version</var></file>, and if
9914 <file><var>package</var>-<var>version</var>.orig</file>, in
9915 the current directory.
9919 To create a packed source archive it is typically invoked:
9921 dpkg-source -b <var>package</var>-<var>version</var>
9926 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
9927 <file>.diff.gz</file> (if appropriate) in the current
9928 directory. <prgn>dpkg-source</prgn> does not clean the
9929 source tree first - this must be done separately if it is
9934 See also <ref id="pkg-sourcearchives">.</p>
9938 <sect1 id="pkg-dpkg-buildpackage">
9940 <prgn>dpkg-buildpackage</prgn> - overall package-building
9945 <prgn>dpkg-buildpackage</prgn> is a script which invokes
9946 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
9947 targets <tt>clean</tt>, <tt>build</tt> and
9948 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
9949 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
9950 source and binary package upload.
9954 It is usually invoked by hand from the top level of the
9955 built or unbuilt source directory. It may be invoked with
9956 no arguments; useful arguments include:
9957 <taglist compact="compact">
9958 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
9961 Do not sign the <tt>.changes</tt> file or the
9962 source package <tt>.dsc</tt> file, respectively.</p>
9964 <tag><tt>-p<var>sign-command</var></tt></tag>
9967 Invoke <var>sign-command</var> instead of finding
9968 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
9969 <var>sign-command</var> must behave just like
9970 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
9972 <tag><tt>-r<var>root-command</var></tt></tag>
9975 When root privilege is required, invoke the command
9976 <var>root-command</var>. <var>root-command</var>
9977 should invoke its first argument as a command, from
9978 the <prgn>PATH</prgn> if necessary, and pass its
9979 second and subsequent arguments to the command it
9980 calls. If no <var>root-command</var> is supplied
9981 then <var>dpkg-buildpackage</var> will take no
9982 special action to gain root privilege, so that for
9983 most packages it will have to be invoked as root to
9986 <tag><tt>-b</tt>, <tt>-B</tt></tag>
9989 Two types of binary-only build and upload - see
9990 <manref name="dpkg-source" section="1">.
9997 <sect1 id="pkg-dpkg-gencontrol">
9999 <prgn>dpkg-gencontrol</prgn> - generates binary package
10004 This program is usually called from <file>debian/rules</file>
10005 (see <ref id="pkg-sourcetree">) in the top level of the source
10010 This is usually done just before the files and directories in the
10011 temporary directory tree where the package is being built have their
10012 permissions and ownerships set and the package is constructed using
10013 <prgn>dpkg-deb/</prgn>
10015 This is so that the control file which is produced has
10016 the right permissions
10021 <prgn>dpkg-gencontrol</prgn> must be called after all the
10022 files which are to go into the package have been placed in
10023 the temporary build directory, so that its calculation of
10024 the installed size of a package is correct.
10028 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
10029 be run after <prgn>dpkg-shlibdeps</prgn> so that the
10030 variable substitutions created by
10031 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
10036 For a package which generates only one binary package, and
10037 which builds it in <file>debian/tmp</file> relative to the top
10038 of the source package, it is usually sufficient to call
10039 <prgn>dpkg-gencontrol</prgn>.
10043 Sources which build several binaries will typically need
10046 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
10047 </example> The <tt>-P</tt> tells
10048 <prgn>dpkg-gencontrol</prgn> that the package is being
10049 built in a non-default directory, and the <tt>-p</tt>
10050 tells it which package's control file should be generated.
10054 <prgn>dpkg-gencontrol</prgn> also adds information to the
10055 list of files in <file>debian/files</file>, for the benefit of
10056 (for example) a future invocation of
10057 <prgn>dpkg-genchanges</prgn>.</p>
10060 <sect1 id="pkg-dpkg-shlibdeps">
10062 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
10067 This program is usually called from <file>debian/rules</file>
10068 just before <prgn>dpkg-gencontrol</prgn> (see <ref
10069 id="pkg-sourcetree">), in the top level of the source tree.
10073 Its arguments are executables and shared libraries
10076 They may be specified either in the locations in the
10077 source tree where they are created or in the locations
10078 in the temporary build tree where they are installed
10079 prior to binary package creation.
10081 </footnote> for which shared library dependencies should
10082 be included in the binary package's control file.
10086 If some of the found shared libraries should only
10087 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
10088 some warrant a <tt>Pre-Depends</tt>, this can be achieved
10089 by using the <tt>-d<var>dependency-field</var></tt> option
10090 before those executable(s). (Each <tt>-d</tt> option
10091 takes effect until the next <tt>-d</tt>.)
10095 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
10096 output control file to be modified. Instead by default it
10097 adds to the <file>debian/substvars</file> file variable
10098 settings like <tt>shlibs:Depends</tt>. These variable
10099 settings must be referenced in dependency fields in the
10100 appropriate per-binary-package sections of the source
10105 For example, a package that generates an essential part
10106 which requires dependencies, and optional parts that
10107 which only require a recommendation, would separate those
10108 two sets of dependencies into two different fields.<footnote>
10109 At the time of writing, an example for this was the
10110 <package/xmms/ package, with Depends used for the xmms
10111 executable, Recommends for the plug-ins and Suggests for
10112 even more optional features provided by unzip.
10114 It can say in its <file>debian/rules</file>:
10116 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
10117 -dRecommends <var>optionalpart anotheroptionalpart</var>
10119 and then in its main control file <file>debian/control</file>:
10122 Depends: ${shlibs:Depends}
10123 Recommends: ${shlibs:Recommends}
10129 Sources which produce several binary packages with
10130 different shared library dependency requirements can use
10131 the <tt>-p<var>varnameprefix</var></tt> option to override
10132 the default <tt>shlibs:</tt> prefix (one invocation of
10133 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
10134 They can thus produce several sets of dependency
10135 variables, each of the form
10136 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
10137 which can be referred to in the appropriate parts of the
10138 binary package control files.
10143 <sect1 id="pkg-dpkg-distaddfile">
10145 <prgn>dpkg-distaddfile</prgn> - adds a file to
10146 <file>debian/files</file>
10150 Some packages' uploads need to include files other than
10151 the source and binary package files.
10155 <prgn>dpkg-distaddfile</prgn> adds a file to the
10156 <file>debian/files</file> file so that it will be included in
10157 the <file>.changes</file> file when
10158 <prgn>dpkg-genchanges</prgn> is run.
10162 It is usually invoked from the <tt>binary</tt> target of
10163 <file>debian/rules</file>:
10165 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
10167 The <var>filename</var> is relative to the directory where
10168 <prgn>dpkg-genchanges</prgn> will expect to find it - this
10169 is usually the directory above the top level of the source
10170 tree. The <file>debian/rules</file> target should put the
10171 file there just before or just after calling
10172 <prgn>dpkg-distaddfile</prgn>.
10176 The <var>section</var> and <var>priority</var> are passed
10177 unchanged into the resulting <file>.changes</file> file.
10182 <sect1 id="pkg-dpkg-genchanges">
10184 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
10185 upload control file
10189 This program is usually called by package-independent
10190 automatic building scripts such as
10191 <prgn>dpkg-buildpackage</prgn>, but it may also be called
10196 It is usually called in the top level of a built source
10197 tree, and when invoked with no arguments will print out a
10198 straightforward <file>.changes</file> file based on the
10199 information in the source package's changelog and control
10200 file and the binary and source packages which should have
10206 <sect1 id="pkg-dpkg-parsechangelog">
10208 <prgn>dpkg-parsechangelog</prgn> - produces parsed
10209 representation of a changelog
10213 This program is used internally by
10214 <prgn>dpkg-source</prgn> et al. It may also occasionally
10215 be useful in <file>debian/rules</file> and elsewhere. It
10216 parses a changelog, <file>debian/changelog</file> by default,
10217 and prints a control-file format representation of the
10218 information in it to standard output.
10222 <sect1 id="pkg-dpkg-architecture">
10224 <prgn>dpkg-architecture</prgn> - information about the build and
10229 This program can be used manually, but is also invoked by
10230 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
10231 environment or make variables which specify the build and host
10232 architecture for the package building process.
10237 <sect id="pkg-sourcetree">
10238 <heading>The Debian package source tree</heading>
10241 The source archive scheme described later is intended to
10242 allow a Debian package source tree with some associated
10243 control information to be reproduced and transported easily.
10244 The Debian package source tree is a version of the original
10245 program with certain files added for the benefit of the
10246 packaging process, and with any other changes required
10247 made to the rest of the source code and installation
10252 The extra files created for Debian are in the subdirectory
10253 <file>debian</file> of the top level of the Debian package
10254 source tree. They are described below.
10257 <sect1 id="pkg-debianrules">
10258 <heading><file>debian/rules</file> - the main building script</heading>
10261 See <ref id="debianrules">.
10265 <sect1 id="pkg-srcsubstvars">
10266 <heading><file>debian/substvars</file> and variable substitutions</heading>
10269 See <ref id="substvars">.
10275 <heading><file>debian/files</file></heading>
10278 See <ref id="debianfiles">.
10282 <sect1><heading><file>debian/tmp</file>
10286 This is the canonical temporary location for the
10287 construction of binary packages by the <tt>binary</tt>
10288 target. The directory <file>tmp</file> serves as the root of
10289 the file system tree as it is being constructed (for
10290 example, by using the package's upstream makefiles install
10291 targets and redirecting the output there), and it also
10292 contains the <tt>DEBIAN</tt> subdirectory. See <ref
10293 id="pkg-bincreating">.
10297 If several binary packages are generated from the same
10298 source tree it is usual to use several
10299 <file>debian/tmp<var>something</var></file> directories, for
10300 example <file>tmp-a</file> or <file>tmp-doc</file>.
10304 Whatever <file>tmp</file> directories are created and used by
10305 <tt>binary</tt> must of course be removed by the
10306 <tt>clean</tt> target.</p></sect1>
10310 <sect id="pkg-sourcearchives"><heading>Source packages as archives
10314 As it exists on the FTP site, a Debian source package
10315 consists of three related files. You must have the right
10316 versions of all three to be able to use them.
10321 <tag>Debian source control file - <tt>.dsc</tt></tag>
10323 This file is a control file used by <prgn>dpkg-source</prgn>
10324 to extract a source package.
10325 See <ref id="debiansourcecontrolfiles">.
10329 Original source archive -
10331 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
10337 This is a compressed (with <tt>gzip -9</tt>)
10338 <prgn>tar</prgn> file containing the source code from
10339 the upstream authors of the program.
10344 Debian package diff -
10346 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
10352 This is a unified context diff (<tt>diff -u</tt>)
10353 giving the changes which are required to turn the
10354 original source into the Debian source. These changes
10355 may only include editing and creating plain files.
10356 The permissions of files, the targets of symbolic
10357 links and the characteristics of special files or
10358 pipes may not be changed and no files may be removed
10363 All the directories in the diff must exist, except the
10364 <file>debian</file> subdirectory of the top of the source
10365 tree, which will be created by
10366 <prgn>dpkg-source</prgn> if necessary when unpacking.
10370 The <prgn>dpkg-source</prgn> program will
10371 automatically make the <file>debian/rules</file> file
10372 executable (see below).</p></item>
10377 If there is no original source code - for example, if the
10378 package is specially prepared for Debian or the Debian
10379 maintainer is the same as the upstream maintainer - the
10380 format is slightly different: then there is no diff, and the
10382 <file><var>package</var>_<var>version</var>.tar.gz</file>,
10383 and preferably contains a directory named
10384 <file><var>package</var>-<var>version</var></file>.
10389 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
10392 <tt>dpkg-source -x</tt> is the recommended way to unpack a
10393 Debian source package. However, if it is not available it
10394 is possible to unpack a Debian source archive as follows:
10395 <enumlist compact="compact">
10398 Untar the tarfile, which will create a <file>.orig</file>
10402 <p>Rename the <file>.orig</file> directory to
10403 <file><var>package</var>-<var>version</var></file>.</p>
10407 Create the subdirectory <file>debian</file> at the top of
10408 the source tree.</p>
10410 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
10412 <item><p>Untar the tarfile again if you want a copy of the original
10413 source code alongside the Debian version.</p>
10418 It is not possible to generate a valid Debian source archive
10419 without using <prgn>dpkg-source</prgn>. In particular,
10420 attempting to use <prgn>diff</prgn> directly to generate the
10421 <file>.diff.gz</file> file will not work.
10425 <heading>Restrictions on objects in source packages</heading>
10428 The source package may not contain any hard links
10430 This is not currently detected when building source
10431 packages, but only when extracting
10435 Hard links may be permitted at some point in the
10436 future, but would require a fair amount of
10438 </footnote>, device special files, sockets or setuid or
10441 Setgid directories are allowed.
10446 The source packaging tools manage the changes between the
10447 original and Debian source using <prgn>diff</prgn> and
10448 <prgn>patch</prgn>. Turning the original source tree as
10449 included in the <file>.orig.tar.gz</file> into the Debian
10450 package source must not involve any changes which cannot be
10451 handled by these tools. Problematic changes which cause
10452 <prgn>dpkg-source</prgn> to halt with an error when
10453 building the source package are:
10454 <list compact="compact">
10455 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10457 <item><p>Changing the targets of symbolic links.</p>
10459 <item><p>Creating directories, other than <file>debian</file>.</p>
10461 <item><p>Changes to the contents of binary files.</p></item>
10462 </list> Changes which cause <prgn>dpkg-source</prgn> to
10463 print a warning but continue anyway are:
10464 <list compact="compact">
10467 Removing files, directories or symlinks.
10469 Renaming a file is not treated specially - it is
10470 seen as the removal of the old file (which
10471 generates a warning, but is otherwise ignored),
10472 and the creation of the new one.
10478 Changed text files which are missing the usual final
10479 newline (either in the original or the modified
10484 Changes which are not represented, but which are not detected by
10485 <prgn>dpkg-source</prgn>, are:
10486 <list compact="compact">
10487 <item><p>Changing the permissions of files (other than
10488 <file>debian/rules</file>) and directories.</p></item>
10493 The <file>debian</file> directory and <file>debian/rules</file>
10494 are handled specially by <prgn>dpkg-source</prgn> - before
10495 applying the changes it will create the <file>debian</file>
10496 directory, and afterwards it will make
10497 <file>debian/rules</file> world-executable.
10503 <appendix id="pkg-controlfields">
10504 <heading>Control files and their fields (from old Packaging Manual)</heading>
10507 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10508 data in a common format, known as control files. Binary and
10509 source packages have control data as do the <file>.changes</file>
10510 files which control the installation of uploaded files, and
10511 <prgn>dpkg</prgn>'s internal databases are in a similar
10516 <heading>Syntax of control files</heading>
10519 See <ref id="controlsyntax">.
10523 It is important to note that there are several fields which
10524 are optional as far as <prgn>dpkg</prgn> and the related
10525 tools are concerned, but which must appear in every Debian
10526 package, or whose omission may cause problems.
10531 <heading>List of fields</heading>
10534 See <ref id="controlfieldslist">.
10538 This section now contains only the fields that didn't belong
10539 to the Policy manual.
10542 <sect1 id="pkg-f-Filename">
10543 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10546 These fields in <tt>Packages</tt> files give the
10547 filename(s) of (the parts of) a package in the
10548 distribution directories, relative to the root of the
10549 Debian hierarchy. If the package has been split into
10550 several parts the parts are all listed in order, separated
10555 <sect1 id="pkg-f-Size">
10556 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10559 These fields in <file>Packages</file> files give the size (in
10560 bytes, expressed in decimal) and MD5 checksum of the
10561 file(s) which make(s) up a binary package in the
10562 distribution. If the package is split into several parts
10563 the values for the parts are listed in order, separated by
10568 <sect1 id="pkg-f-Status">
10569 <heading><tt>Status</tt></heading>
10572 This field in <prgn>dpkg</prgn>'s status file records
10573 whether the user wants a package installed, removed or
10574 left alone, whether it is broken (requiring
10575 re-installation) or not and what its current state on the
10576 system is. Each of these pieces of information is a
10581 <sect1 id="pkg-f-Config-Version">
10582 <heading><tt>Config-Version</tt></heading>
10585 If a package is not installed or not configured, this
10586 field in <prgn>dpkg</prgn>'s status file records the last
10587 version of the package which was successfully
10592 <sect1 id="pkg-f-Conffiles">
10593 <heading><tt>Conffiles</tt></heading>
10596 This field in <prgn>dpkg</prgn>'s status file contains
10597 information about the automatically-managed configuration
10598 files held by a package. This field should <em>not</em>
10599 appear anywhere in a package!
10604 <heading>Obsolete fields</heading>
10607 These are still recognized by <prgn>dpkg</prgn> but should
10608 not appear anywhere any more.
10610 <taglist compact="compact">
10612 <tag><tt>Revision</tt></tag>
10613 <tag><tt>Package-Revision</tt></tag>
10614 <tag><tt>Package_Revision</tt></tag>
10616 The Debian revision part of the package version was
10617 at one point in a separate control file field. This
10618 field went through several names.
10621 <tag><tt>Recommended</tt></tag>
10622 <item>Old name for <tt>Recommends</tt>.</item>
10624 <tag><tt>Optional</tt></tag>
10625 <item>Old name for <tt>Suggests</tt>.</item>
10627 <tag><tt>Class</tt></tag>
10628 <item>Old name for <tt>Priority</tt>.</item>
10637 <appendix id="pkg-conffiles">
10638 <heading>Configuration file handling (from old Packaging Manual)</heading>
10641 <prgn>dpkg</prgn> can do a certain amount of automatic
10642 handling of package configuration files.
10646 Whether this mechanism is appropriate depends on a number of
10647 factors, but basically there are two approaches to any
10648 particular configuration file.
10652 The easy method is to ship a best-effort configuration in the
10653 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10654 handle updates. If the user is unlikely to want to edit the
10655 file, but you need them to be able to without losing their
10656 changes, and a new package with a changed version of the file
10657 is only released infrequently, this is a good approach.
10661 The hard method is to build the configuration file from
10662 scratch in the <prgn>postinst</prgn> script, and to take the
10663 responsibility for fixing any mistakes made in earlier
10664 versions of the package automatically. This will be
10665 appropriate if the file is likely to need to be different on
10669 <sect><heading>Automatic handling of configuration files by
10674 A package may contain a control area file called
10675 <tt>conffiles</tt>. This file should be a list of filenames
10676 of configuration files needing automatic handling, separated
10677 by newlines. The filenames should be absolute pathnames,
10678 and the files referred to should actually exist in the
10683 When a package is upgraded <prgn>dpkg</prgn> will process
10684 the configuration files during the configuration stage,
10685 shortly before it runs the package's <prgn>postinst</prgn>
10690 For each file it checks to see whether the version of the
10691 file included in the package is the same as the one that was
10692 included in the last version of the package (the one that is
10693 being upgraded from); it also compares the version currently
10694 installed on the system with the one shipped with the last
10699 If neither the user nor the package maintainer has changed
10700 the file, it is left alone. If one or the other has changed
10701 their version, then the changed version is preferred - i.e.,
10702 if the user edits their file, but the package maintainer
10703 doesn't ship a different version, the user's changes will
10704 stay, silently, but if the maintainer ships a new version
10705 and the user hasn't edited it the new version will be
10706 installed (with an informative message). If both have
10707 changed their version the user is prompted about the problem
10708 and must resolve the differences themselves.
10712 The comparisons are done by calculating the MD5 message
10713 digests of the files, and storing the MD5 of the file as it
10714 was included in the most recent version of the package.
10718 When a package is installed for the first time
10719 <prgn>dpkg</prgn> will install the file that comes with it,
10720 unless that would mean overwriting a file already on the
10725 However, note that <prgn>dpkg</prgn> will <em>not</em>
10726 replace a conffile that was removed by the user (or by a
10727 script). This is necessary because with some programs a
10728 missing file produces an effect hard or impossible to
10729 achieve in another way, so that a missing file needs to be
10730 kept that way if the user did it.
10734 Note that a package should <em>not</em> modify a
10735 <prgn>dpkg</prgn>-handled conffile in its maintainer
10736 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10737 the user confusing and possibly dangerous options for
10738 conffile update when the package is upgraded.</p>
10741 <sect><heading>Fully-featured maintainer script configuration
10746 For files which contain site-specific information such as
10747 the hostname and networking details and so forth, it is
10748 better to create the file in the package's
10749 <prgn>postinst</prgn> script.
10753 This will typically involve examining the state of the rest
10754 of the system to determine values and other information, and
10755 may involve prompting the user for some information which
10756 can't be obtained some other way.
10760 When using this method there are a couple of important
10761 issues which should be considered:
10765 If you discover a bug in the program which generates the
10766 configuration file, or if the format of the file changes
10767 from one version to the next, you will have to arrange for
10768 the postinst script to do something sensible - usually this
10769 will mean editing the installed configuration file to remove
10770 the problem or change the syntax. You will have to do this
10771 very carefully, since the user may have changed the file,
10772 perhaps to fix the very problem that your script is trying
10773 to deal with - you will have to detect these situations and
10774 deal with them correctly.
10778 If you do go down this route it's probably a good idea to
10779 make the program that generates the configuration file(s) a
10780 separate program in <file>/usr/sbin</file>, by convention called
10781 <file><var>package</var>config</file> and then run that if
10782 appropriate from the post-installation script. The
10783 <tt><var>package</var>config</tt> program should not
10784 unquestioningly overwrite an existing configuration - if its
10785 mode of operation is geared towards setting up a package for
10786 the first time (rather than any arbitrary reconfiguration
10787 later) you should have it check whether the configuration
10788 already exists, and require a <tt>--force</tt> flag to
10789 overwrite it.</p></sect>
10792 <appendix id="pkg-alternatives"><heading>Alternative versions of
10793 an interface - <prgn>update-alternatives</prgn> (from old
10798 When several packages all provide different versions of the
10799 same program or file it is useful to have the system select a
10800 default, but to allow the system administrator to change it
10801 and have their decisions respected.
10805 For example, there are several versions of the <prgn>vi</prgn>
10806 editor, and there is no reason to prevent all of them from
10807 being installed at once, each under their own name
10808 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10809 Nevertheless it is desirable to have the name <tt>vi</tt>
10810 refer to something, at least by default.
10814 If all the packages involved cooperate, this can be done with
10815 <prgn>update-alternatives</prgn>.
10819 Each package provides its own version under its own name, and
10820 calls <prgn>update-alternatives</prgn> in its postinst to
10821 register its version (and again in its prerm to deregister
10826 See the man page <manref name="update-alternatives"
10827 section="8"> for details.
10831 If <prgn>update-alternatives</prgn> does not seem appropriate
10832 you may wish to consider using diversions instead.</p>
10835 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10836 package's version of a file (from old Packaging Manual)
10840 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10841 when it reinstalls the package it belongs to, and to have it
10842 put the file from the package somewhere else instead.
10846 This can be used locally to override a package's version of a
10847 file, or by one package to override another's version (or
10848 provide a wrapper for it).
10852 Before deciding to use a diversion, read <ref
10853 id="pkg-alternatives"> to see if you really want a diversion
10854 rather than several alternative versions of a program.
10858 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10859 and updated by a special program <prgn>dpkg-divert</prgn>.
10860 Please see <manref name="dpkg-divert" section="8"> for full
10861 details of its operation.
10865 When a package wishes to divert a file from another, it should
10866 call <prgn>dpkg-divert</prgn> in its preinst to add the
10867 diversion and rename the existing file. For example,
10868 supposing that a <prgn>smailwrapper</prgn> package wishes to
10869 install a wrapper around <file>/usr/sbin/smail</file>:
10871 dpkg-divert --package smailwrapper --add --rename \
10872 --divert /usr/sbin/smail.real /usr/sbin/smail
10873 </example> The <tt>--package smailwrapper</tt> ensures that
10874 <prgn>smailwrapper</prgn>'s copy of <file>/usr/sbin/smail</file>
10875 can bypass the diversion and get installed as the true version.
10876 It's safe to add the diversion unconditionally on upgrades since
10877 it will be left unchanged if it already exists, but
10878 <prgn>dpkg-divert</prgn> will display a message. To suppress that
10879 message, make the command conditional on the version from which
10880 the package is being upgraded:
10882 if [ upgrade != "$1" ] || dpkg --compare-versions "$2" lt 1.0-2; then
10883 dpkg-divert --package smailwrapper --add --rename \
10884 --divert /usr/sbin/smail.real /usr/sbin/smail
10886 </example> where <tt>1.0-2</tt> is the version at which the
10887 diversion was first added to the package. Running the command
10888 during abort-upgrade is pointless but harmless.
10892 The postrm has to do the reverse:
10894 if [ remove = "$1" -o abort-install = "$1" -o disappear = "$1" ]; then
10895 dpkg-divert --package smailwrapper --remove --rename \
10896 --divert /usr/sbin/smail.real /usr/sbin/smail
10898 </example> If the diversion was added at a particular version, the
10899 postrm should also handle the failure case of upgrading from an
10900 older version (unless the older version is so old that direct
10901 upgrades are no longer supported):
10903 if [ abort-upgrade = "$1" ] && dpkg --compare-versions "$2" lt 1.0-2; then
10904 dpkg-divert --package smailwrapper --remove --rename \
10905 --divert /usr/sbin/smail.real /usr/sbin/smail
10907 </example> where <tt>1.02-2</tt> is the version at which the
10908 diversion was first added to the package. The postrm should not
10909 remove the diversion on upgrades both because there's no reason to
10910 remove the diversion only to immediately re-add it and since the
10911 postrm of the old package is run after unpacking so the removal of
10912 the diversion will fail.
10916 Do not attempt to divert a file which is vitally important for
10917 the system's operation - when using <prgn>dpkg-divert</prgn>
10918 there is a time, after it has been diverted but before
10919 <prgn>dpkg</prgn> has installed the new version, when the file
10920 does not exist.</p>
10925 <!-- Local variables: -->
10926 <!-- indent-tabs-mode: t -->
10928 <!-- vim:set ai et sts=2 sw=2 tw=76: -->