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10 <title>Debian Policy Manual</title>
11 <author><qref id="authors">The Debian Policy Mailing List</qref></author>
12 <version>version &version;, &date;</version>
15 This manual describes the policy requirements for the Debian
16 GNU/Linux distribution. This includes the structure and
17 contents of the Debian archive and several design issues of
18 the operating system, as well as technical requirements that
19 each package must satisfy to be included in the distribution.
24 Copyright © 1996,1997,1998 Ian Jackson
25 and Christian Schwarz.
28 This manual is free software; you may redistribute it and/or
29 modify it under the terms of the GNU General Public License
30 as published by the Free Software Foundation; either version
31 2, or (at your option) any later version.
35 This is distributed in the hope that it will be useful, but
36 <em>without any warranty</em>; without even the implied
37 warranty of merchantability or fitness for a particular
38 purpose. See the GNU General Public License for more
43 A copy of the GNU General Public License is available as
44 <file>/usr/share/common-licenses/GPL</file> in the Debian GNU/Linux
45 distribution or on the World Wide Web at
46 <url id="http://www.gnu.org/copyleft/gpl.html"
47 name="the GNU General Public Licence">. You can also
48 obtain it by writing to the Free Software Foundation, Inc.,
49 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
57 <heading>About this manual</heading>
59 <heading>Scope</heading>
61 This manual describes the policy requirements for the Debian
62 GNU/Linux distribution. This includes the structure and
63 contents of the Debian archive and several design issues of the
64 operating system, as well as technical requirements that
65 each package must satisfy to be included in the
70 This manual also describes Debian policy as it relates to
71 creating Debian packages. It is not a tutorial on how to build
72 packages, nor is it exhaustive where it comes to describing
73 the behavior of the packaging system. Instead, this manual
74 attempts to define the interface to the package management
75 system that the developers have to be conversant with.<footnote>
76 Informally, the criteria used for inclusion is that the
77 material meet one of the following requirements:
78 <taglist compact="compact">
79 <tag>Standard interfaces</tag>
81 The material presented represents an interface to
82 the packaging system that is mandated for use, and
83 is used by, a significant number of packages, and
84 therefore should not be changed without peer
85 review. Package maintainers can then rely on this
86 interfaces not changing, and the package
87 management software authors need to ensure
88 compatibility with these interface
89 definitions. (Control file and changelog file
90 formats are examples.)
92 <tag>Chosen Convention</tag>
94 If there are a number of technically viable choices
95 that can be made, but one needs to select one of
96 these options for inter-operability. The version
97 number format is one example.
100 Please note that these are not mutually exclusive;
101 selected conventions often become parts of standard
107 The footnotes present in this manual are
108 merely informative, and are not part of Debian policy itself.
112 The appendices to this manual are not necessarily normative,
113 either. Please see <ref id="pkg-scope"> for more information.
117 In the normative part of this manual,
118 the words <em>must</em>, <em>should</em> and
119 <em>may</em>, and the adjectives <em>required</em>,
120 <em>recommended</em> and <em>optional</em>, are used to
121 distinguish the significance of the various guidelines in
122 this policy document. Packages that do not conform to the
123 guidelines denoted by <em>must</em> (or <em>required</em>)
124 will generally not be considered acceptable for the Debian
125 distribution. Non-conformance with guidelines denoted by
126 <em>should</em> (or <em>recommended</em>) will generally be
127 considered a bug, but will not necessarily render a package
128 unsuitable for distribution. Guidelines denoted by
129 <em>may</em> (or <em>optional</em>) are truly optional and
130 adherence is left to the maintainer's discretion.
134 These classifications are roughly equivalent to the bug
135 severities <em>serious</em> (for <em>must</em> or
136 <em>required</em> directive violations), <em>minor</em>,
137 <em>normal</em> or <em>important</em>
138 (for <em>should</em> or <em>recommended</em> directive
139 violations) and <em>wishlist</em> (for <em>optional</em>
142 Compare RFC 2119. Note, however, that these words are
143 used in a different way in this document.
148 Much of the information presented in this manual will be
149 useful even when building a package which is to be
150 distributed in some other way or is intended for local use
156 <heading>New versions of this document</heading>
159 This manual is distributed via the Debian package
160 <package><url name="debian-policy"
161 id="http://packages.debian.org/debian-policy"></package>
162 (<httpsite>packages.debian.org</httpsite>
163 <httppath>/debian-policy</httppath>).
167 The current version of this document is also available from
168 the Debian web mirrors at
169 <tt><url name="/doc/debian-policy/"
170 id="http://www.debian.org/doc/debian-policy/"></tt>.
172 <httpsite>www.debian.org</httpsite>
173 <httppath>/doc/debian-policy/</httppath>)
174 Also available from the same directory are several other
175 formats: <file>policy.html.tar.gz</file>
176 (<httppath>/doc/debian-policy/policy.html.tar.gz</httppath>),
177 <file>policy.pdf.gz</file>
178 (<httppath>/doc/debian-policy/policy.pdf.gz</httppath>)
179 and <file>policy.ps.gz</file>
180 (<httppath>/doc/debian-policy/policy.ps.gz</httppath>).
184 The <package>debian-policy</package> package also includes the file
185 <file>upgrading-checklist.txt.gz</file> which indicates policy
186 changes between versions of this document.
191 <heading>Authors and Maintainers</heading>
194 Originally called "Debian GNU/Linux Policy Manual", this
195 manual was initially written in 1996 by Ian Jackson.
196 It was revised on November 27th, 1996 by David A. Morris.
197 Christian Schwarz added new sections on March 15th, 1997,
198 and reworked/restructured it in April-July 1997.
199 Christoph Lameter contributed the "Web Standard".
200 Julian Gilbey largely restructured it in 2001.
204 Since September 1998, the responsibility for the contents of
205 this document lies on the <url name="debian-policy mailing list"
206 id="mailto:debian-policy@lists.debian.org">. Proposals
207 are discussed there and inserted into policy after a certain
208 consensus is established.
209 <!-- insert shameless policy-process plug here eventually -->
210 The actual editing is done by a group of maintainers that have
211 no editorial powers. These are the current maintainers:
214 <item>Julian Gilbey</item>
215 <item>Branden Robinson</item>
216 <item>Josip Rodin</item>
217 <item>Manoj Srivastava</item>
222 While the authors of this document have tried hard to avoid
223 typos and other errors, these do still occur. If you discover
224 an error in this manual or if you want to give any
225 comments, suggestions, or criticisms please send an email to
226 the Debian Policy List,
227 <email>debian-policy@lists.debian.org</email>, or submit a
228 bug report against the <tt>debian-policy</tt> package.
232 Please do not try to reach the individual authors or maintainers
233 of the Policy Manual regarding changes to the Policy.
238 <heading>Related documents</heading>
241 There are several other documents other than this Policy Manual
242 that are necessary to fully understand some Debian policies and
247 The external "sub-policy" documents are referred to in:
248 <list compact="compact">
249 <item><ref id="fhs"></item>
250 <item><ref id="virtual_pkg"></item>
251 <item><ref id="menus"></item>
252 <item><ref id="mime"></item>
253 <item><ref id="perl"></item>
254 <item><ref id="maintscriptprompt"></item>
255 <item><ref id="emacs"></item>
260 In addition to those, which carry the weight of policy, there
261 is the Debian Developer's Reference. This document describes
262 procedures and resources for Debian developers, but it is
263 <em>not</em> normative; rather, it includes things that don't
264 belong in the Policy, such as best practices for developers.
268 The Developer's Reference is available in the
269 <package>developers-reference</package> package.
270 It's also available from the Debian web mirrors at
271 <tt><url name="/doc/developers-reference/"
272 id="http://www.debian.org/doc/developers-reference/"></tt>.
280 <heading>The Debian Archive</heading>
283 The Debian GNU/Linux system is maintained and distributed as a
284 collection of <em>packages</em>. Since there are so many of
285 them (currently well over 15000), they are split into
286 <em>sections</em> and given <em>priorities</em> to simplify
287 the handling of them.
291 The effort of the Debian project is to build a free operating
292 system, but not every package we want to make accessible is
293 <em>free</em> in our sense (see the Debian Free Software
294 Guidelines, below), or may be imported/exported without
295 restrictions. Thus, the archive is split into the distribution
296 areas or categories based on their licenses and other restrictions.
300 The aims of this are:
302 <list compact="compact">
303 <item>to allow us to make as much software available as we can</item>
304 <item>to allow us to encourage everyone to write free software,
306 <item>to allow us to make it easy for people to produce
307 CD-ROMs of our system without violating any licenses,
308 import/export restrictions, or any other laws.</item>
313 The <em>main</em> category forms the
314 <em>Debian GNU/Linux distribution</em>.
318 Packages in the other distribution areas (<tt>contrib</tt>,
319 <tt>non-free</tt>) are not considered to be part of the Debian
320 distribution, although we support their use and provide
321 infrastructure for them (such as our bug-tracking system and
322 mailing lists). This Debian Policy Manual applies to these
327 <heading>The Debian Free Software Guidelines</heading>
329 The Debian Free Software Guidelines (DFSG) form our
330 definition of "free software". These are:
332 <tag>Free Redistribution
335 The license of a Debian component may not restrict any
336 party from selling or giving away the software as a
337 component of an aggregate software distribution
338 containing programs from several different
339 sources. The license may not require a royalty or
340 other fee for such sale.
345 The program must include source code, and must allow
346 distribution in source code as well as compiled form.
351 The license must allow modifications and derived
352 works, and must allow them to be distributed under the
353 same terms as the license of the original software.
355 <tag>Integrity of The Author's Source Code
358 The license may restrict source-code from being
359 distributed in modified form <em>only</em> if the
360 license allows the distribution of "patch files"
361 with the source code for the purpose of modifying the
362 program at build time. The license must explicitly
363 permit distribution of software built from modified
364 source code. The license may require derived works to
365 carry a different name or version number from the
366 original software. (This is a compromise. The Debian
367 Project encourages all authors to not restrict any
368 files, source or binary, from being modified.)
370 <tag>No Discrimination Against Persons or Groups
373 The license must not discriminate against any person
376 <tag>No Discrimination Against Fields of Endeavor
379 The license must not restrict anyone from making use
380 of the program in a specific field of endeavor. For
381 example, it may not restrict the program from being
382 used in a business, or from being used for genetic
385 <tag>Distribution of License
388 The rights attached to the program must apply to all
389 to whom the program is redistributed without the need
390 for execution of an additional license by those
393 <tag>License Must Not Be Specific to Debian
396 The rights attached to the program must not depend on
397 the program's being part of a Debian system. If the
398 program is extracted from Debian and used or
399 distributed without Debian but otherwise within the
400 terms of the program's license, all parties to whom
401 the program is redistributed must have the same
402 rights as those that are granted in conjunction with
405 <tag>License Must Not Contaminate Other Software
408 The license must not place restrictions on other
409 software that is distributed along with the licensed
410 software. For example, the license must not insist
411 that all other programs distributed on the same medium
412 must be free software.
414 <tag>Example Licenses
417 The "GPL," "BSD," and "Artistic" licenses are examples of
418 licenses that we consider <em>free</em>.
425 <heading>Categories</heading>
428 <heading>The main category</heading>
431 Every package in <em>main</em> must comply with the DFSG
432 (Debian Free Software Guidelines).
436 In addition, the packages in <em>main</em>
437 <list compact="compact">
439 must not require a package outside of <em>main</em>
440 for compilation or execution (thus, the package must
441 not declare a "Depends", "Recommends", or
442 "Build-Depends" relationship on a non-<em>main</em>
446 must not be so buggy that we refuse to support them,
450 must meet all policy requirements presented in this
459 <heading>The contrib category</heading>
462 Every package in <em>contrib</em> must comply with the DFSG.
466 In addition, the packages in <em>contrib</em>
467 <list compact="compact">
469 must not be so buggy that we refuse to support them,
473 must meet all policy requirements presented in this
481 Examples of packages which would be included in
482 <em>contrib</em> are:
483 <list compact="compact">
485 free packages which require <em>contrib</em>,
486 <em>non-free</em> packages or packages which are not
487 in our archive at all for compilation or execution,
491 wrapper packages or other sorts of free accessories for
498 <sect1 id="non-free">
499 <heading>The non-free category</heading>
502 Packages must be placed in <em>non-free</em> if they are
503 not compliant with the DFSG or are encumbered by patents
504 or other legal issues that make their distribution
509 In addition, the packages in <em>non-free</em>
510 <list compact="compact">
512 must not be so buggy that we refuse to support them,
516 must meet all policy requirements presented in this
517 manual that it is possible for them to meet.
519 It is possible that there are policy
520 requirements which the package is unable to
521 meet, for example, if the source is
522 unavailable. These situations will need to be
523 handled on a case-by-case basis.
532 <sect id="pkgcopyright">
533 <heading>Copyright considerations</heading>
536 Every package must be accompanied by a verbatim copy of
537 its copyright and distribution license in the file
538 <file>/usr/share/doc/<var>package</var>/copyright</file>
539 (see <ref id="copyrightfile"> for further details).
543 We reserve the right to restrict files from being included
544 anywhere in our archives if
545 <list compact="compact">
547 their use or distribution would break a law,
550 there is an ethical conflict in their distribution or
554 we would have to sign a license for them, or
557 their distribution would conflict with other project
564 Programs whose authors encourage the user to make
565 donations are fine for the main distribution, provided
566 that the authors do not claim that not donating is
567 immoral, unethical, illegal or something similar; in such
568 a case they must go in <em>non-free</em>.
572 Packages whose copyright permission notices (or patent
573 problems) do not even allow redistribution of binaries
574 only, and where no special permission has been obtained,
575 must not be placed on the Debian FTP site and its mirrors
580 Note that under international copyright law (this applies
581 in the United States, too), <em>no</em> distribution or
582 modification of a work is allowed without an explicit
583 notice saying so. Therefore a program without a copyright
584 notice <em>is</em> copyrighted and you may not do anything
585 to it without risking being sued! Likewise if a program
586 has a copyright notice but no statement saying what is
587 permitted then nothing is permitted.
591 Many authors are unaware of the problems that restrictive
592 copyrights (or lack of copyright notices) can cause for
593 the users of their supposedly-free software. It is often
594 worthwhile contacting such authors diplomatically to ask
595 them to modify their license terms. However, this can be a
596 politically difficult thing to do and you should ask for
597 advice on the <tt>debian-legal</tt> mailing list first, as
602 When in doubt about a copyright, send mail to
603 <email>debian-legal@lists.debian.org</email>. Be prepared
604 to provide us with the copyright statement. Software
605 covered by the GPL, public domain software and BSD-like
606 copyrights are safe; be wary of the phrases "commercial
607 use prohibited" and "distribution restricted".
611 <sect id="subsections">
612 <heading>Sections</heading>
615 The packages in the categories <em>main</em>,
616 <em>contrib</em> and <em>non-free</em> are grouped further
617 into <em>sections</em> to simplify handling.
621 The category and section for each package should be
622 specified in the package's <tt>Section</tt> control record
623 (see <ref id="f-Section">). However, the maintainer of the
624 Debian archive may override this selection to ensure the
625 consistency of the Debian distribution. The
626 <tt>Section</tt> field should be of the form:
627 <list compact="compact">
629 <em>section</em> if the package is in the
630 <em>main</em> category,
633 <em>segment/section</em> if the package is in
634 the <em>contrib</em> or <em>non-free</em>
641 The Debian archive maintainers provide the authoritative
642 list of sections. At present, they are:
643 <em>admin</em>, <em>base</em>, <em>comm</em>,
644 <em>contrib</em>, <em>devel</em>, <em>doc</em>,
645 <em>editors</em>, <em>electronics</em>, <em>embedded</em>,
646 <em>games</em>, <em>gnome</em>, <em>graphics</em>,
647 <em>hamradio</em>, <em>interpreters</em>, <em>kde</em>,
648 <em>libs</em>, <em>libdevel</em>, <em>mail</em>,
649 <em>math</em>, <em>misc</em>, <em>net</em>, <em>news</em>,
650 <em>non-free</em>, <em>oldlibs</em>,
651 <em>otherosfs</em>, <em>perl</em>, <em>python</em>,
652 <em>science</em>, <em>shells</em>,
653 <em>sound</em>, <em>tex</em>, <em>text</em>,
654 <em>utils</em>, <em>web</em>, <em>x11</em>.
658 <sect id="priorities">
659 <heading>Priorities</heading>
662 Each package should have a <em>priority</em> value, which is
663 included in the package's <em>control record</em>
664 (see <ref id="f-Priority">).
665 This information is used by the Debian package management tools to
666 separate high-priority packages from less-important packages.
670 The following <em>priority levels</em> are recognized by the
671 Debian package management tools.
673 <tag><tt>required</tt></tag>
675 Packages which are necessary for the proper
676 functioning of the system (usually, this means that
677 dpkg functionality depends on these packages).
678 Removing a <tt>required</tt> package may cause your
679 system to become totally broken and you may not even
680 be able to use <prgn>dpkg</prgn> to put things back,
681 so only do so if you know what you are doing. Systems
682 with only the <tt>required</tt> packages are probably
683 unusable, but they do have enough functionality to
684 allow the sysadmin to boot and install more software.
686 <tag><tt>important</tt></tag>
688 Important programs, including those which one would
689 expect to find on any Unix-like system. If the
690 expectation is that an experienced Unix person who
691 found it missing would say "What on earth is going on,
692 where is <prgn>foo</prgn>?", it must be an
693 <tt>important</tt> package.<footnote>
694 This is an important criterion because we are
695 trying to produce, amongst other things, a free
698 Other packages without which the system will not run
699 well or be usable must also have priority
700 <tt>important</tt>. This does
701 <em>not</em> include Emacs, the X Window System, TeX
702 or any other large applications. The
703 <tt>important</tt> packages are just a bare minimum of
704 commonly-expected and necessary tools.
706 <tag><tt>standard</tt></tag>
708 These packages provide a reasonably small but not too
709 limited character-mode system. This is what will be
710 installed by default if the user doesn't select anything
711 else. It doesn't include many large applications.
713 <tag><tt>optional</tt></tag>
715 (In a sense everything that isn't required is
716 optional, but that's not what is meant here.) This is
717 all the software that you might reasonably want to
718 install if you didn't know what it was and don't have
719 specialized requirements. This is a much larger system
720 and includes the X Window System, a full TeX
721 distribution, and many applications. Note that
722 optional packages should not conflict with each other.
724 <tag><tt>extra</tt></tag>
726 This contains all packages that conflict with others
727 with required, important, standard or optional
728 priorities, or are only likely to be useful if you
729 already know what they are or have specialized
736 Packages must not depend on packages with lower priority
737 values (excluding build-time dependencies). In order to
738 ensure this, the priorities of one or more packages may need
747 <heading>Binary packages</heading>
750 The Debian GNU/Linux distribution is based on the Debian
751 package management system, called <prgn>dpkg</prgn>. Thus,
752 all packages in the Debian distribution must be provided
753 in the <tt>.deb</tt> file format.
757 <heading>The package name</heading>
760 Every package must have a name that's unique within the Debian
765 The package name is included in the control field
766 <tt>Package</tt>, the format of which is described
767 in <ref id="f-Package">.
768 The package name is also included as a part of the file name
769 of the <tt>.deb</tt> file.
774 <heading>The version of a package</heading>
777 Every package has a version number recorded in its
778 <tt>Version</tt> control file field, described in
779 <ref id="f-Version">.
783 The package management system imposes an ordering on version
784 numbers, so that it can tell whether packages are being up- or
785 downgraded and so that package system front end applications
786 can tell whether a package it finds available is newer than
787 the one installed on the system. The version number format
788 has the most significant parts (as far as comparison is
789 concerned) at the beginning.
793 If an upstream package has problematic version numbers they
794 should be converted to a sane form for use in the
795 <tt>Version</tt> field.
799 <heading>Version numbers based on dates</heading>
802 In general, Debian packages should use the same version
803 numbers as the upstream sources.
807 However, in some cases where the upstream version number is
808 based on a date (e.g., a development "snapshot" release) the
809 package management system cannot handle these version
810 numbers without epochs. For example, dpkg will consider
811 "96May01" to be greater than "96Dec24".
815 To prevent having to use epochs for every new upstream
816 version, the date based portion of the version number
817 should be changed to the following format in such cases:
818 "19960501", "19961224". It is up to the maintainer whether
819 they want to bother the upstream maintainer to change
820 the version numbers upstream, too.
824 Note that other version formats based on dates which are
825 parsed correctly by the package management system should
826 <em>not</em> be changed.
830 Native Debian packages (i.e., packages which have been
831 written especially for Debian) whose version numbers include
832 dates should always use the "YYYYMMDD" format.
839 <heading>The maintainer of a package</heading>
842 Every package must have a Debian maintainer (the
843 maintainer may be one person or a group of people
844 reachable from a common email address, such as a mailing
845 list). The maintainer is responsible for ensuring that
846 the package is placed in the appropriate distributions.
850 The maintainer must be specified in the
851 <tt>Maintainer</tt> control field with their correct name
852 and a working email address. If one person maintains
853 several packages, they should try to avoid having
854 different forms of their name and email address in
855 the <tt>Maintainer</tt> fields of those packages.
859 The format of the <tt>Maintainer</tt> control field is
860 described in <ref id="f-Maintainer">.
864 If the maintainer of a package quits from the Debian
865 project, "Debian QA Group"
866 <email>packages@qa.debian.org</email> takes over the
867 maintainer-ship of the package until someone else
868 volunteers for that task. These packages are called
869 <em>orphaned packages</em>.<footnote>
870 The detailed procedure for doing this gracefully can
871 be found in the Debian Developer's Reference,
872 see <ref id="related">.
877 <sect id="descriptions">
878 <heading>The description of a package</heading>
881 Every Debian package must have an extended description
882 stored in the appropriate field of the control record.
883 The technical information about the format of the
884 <tt>Description</tt> field is in <ref id="f-Description">.
888 The description should describe the package (the program) to a
889 user (system administrator) who has never met it before so that
890 they have enough information to decide whether they want to
891 install it. This description should not just be copied verbatim
892 from the program's documentation.
896 Put important information first, both in the synopsis and
897 extended description. Sometimes only the first part of the
898 synopsis or of the description will be displayed. You can
899 assume that there will usually be a way to see the whole
900 extended description.
904 The description should also give information about the
905 significant dependencies and conflicts between this package
906 and others, so that the user knows why these dependencies and
907 conflicts have been declared.
911 Instructions for configuring or using the package should
912 not be included (that is what installation scripts,
913 manual pages, info files, etc., are for). Copyright
914 statements and other administrivia should not be included
915 either (that is what the copyright file is for).
918 <sect1 id="synopsis"><heading>The single line synopsis</heading>
921 The single line synopsis should be kept brief - certainly
926 Do not include the package name in the synopsis line. The
927 display software knows how to display this already, and you
928 do not need to state it. Remember that in many situations
929 the user may only see the synopsis line - make it as
930 informative as you can.
935 <sect1 id="extendeddesc"><heading>The extended description</heading>
938 Do not try to continue the single line synopsis into the
939 extended description. This will not work correctly when
940 the full description is displayed, and makes no sense
941 where only the summary (the single line synopsis) is
946 The extended description should describe what the package
947 does and how it relates to the rest of the system (in terms
948 of, for example, which subsystem it is which part of).
952 The description field needs to make sense to anyone, even
953 people who have no idea about any of the things the
954 package deals with.<footnote>
955 The blurb that comes with a program in its
956 announcements and/or <prgn>README</prgn> files is
957 rarely suitable for use in a description. It is
958 usually aimed at people who are already in the
959 community where the package is used.
968 <heading>Dependencies</heading>
971 Every package must specify the dependency information
972 about other packages that are required for the first to
977 For example, a dependency entry must be provided for any
978 shared libraries required by a dynamically-linked executable
983 Packages are not required to declare any dependencies they
984 have on other packages which are marked <tt>Essential</tt>
985 (see below), and should not do so unless they depend on a
986 particular version of that package.<footnote>
988 Essential is defined as the minimal set of functionality
989 that must be available and usable on the system even
990 when packages are in an unconfigured (but unpacked)
991 state. This is needed to avoid unresolvable dependency
992 loops on upgrade. If packages add unnecessary
993 dependencies on packages in this set, the chances that
994 there <strong>will</strong> be an unresolvable
995 dependency loop caused by forcing these Essential
996 packages to be configured first before they need to be
997 is greatly increased. It also increases the chances
998 that frontends will be unable to
999 <strong>calculate</strong> an upgrade path, even if one
1003 Also, it's pretty unlikely that functionality from
1004 Essential shall ever be removed (which is one reason why
1005 care must be taken before adding to the Essential
1006 packages set), but <em>packages</em> have been removed
1007 from the Essential set when the functionality moved to a
1008 different package. So depending on these packages
1009 <em>just in case</em> they stop being essential does way
1010 more harm than good.
1016 Sometimes, a package requires another package to be installed
1017 <em>and</em> configured before it can be installed. In this
1018 case, you must specify a <tt>Pre-Depends</tt> entry for
1023 You should not specify a <tt>Pre-Depends</tt> entry for a
1024 package before this has been discussed on the
1025 <tt>debian-devel</tt> mailing list and a consensus about
1026 doing that has been reached.
1030 The format of the package interrelationship control fields is
1031 described in <ref id="relationships">.
1035 <sect id="virtual_pkg">
1036 <heading>Virtual packages</heading>
1039 Sometimes, there are several packages which offer
1040 more-or-less the same functionality. In this case, it's
1041 useful to define a <em>virtual package</em> whose name
1042 describes that common functionality. (The virtual
1043 packages only exist logically, not physically; that's why
1044 they are called <em>virtual</em>.) The packages with this
1045 particular function will then <em>provide</em> the virtual
1046 package. Thus, any other package requiring that function
1047 can simply depend on the virtual package without having to
1048 specify all possible packages individually.
1052 All packages should use virtual package names where
1053 appropriate, and arrange to create new ones if necessary.
1054 They should not use virtual package names (except privately,
1055 amongst a cooperating group of packages) unless they have
1056 been agreed upon and appear in the list of virtual package
1057 names. (See also <ref id="virtual">)
1061 The latest version of the authoritative list of virtual
1062 package names can be found in the <tt>debian-policy</tt> package.
1063 It is also available from the Debian web mirrors at
1064 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1065 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1069 The procedure for updating the list is described in the preface
1076 <heading>Base system</heading>
1079 The <tt>base system</tt> is a minimum subset of the Debian
1080 GNU/Linux system that is installed before everything else
1081 on a new system. Thus, only very few packages are allowed
1082 to go into the <tt>base</tt> section to keep the required
1083 disk usage very small.
1087 Most of these packages will have the priority value
1088 <tt>required</tt> or at least <tt>important</tt>, and many
1089 of them will be tagged <tt>essential</tt> (see below).
1094 <heading>Essential packages</heading>
1097 Some packages are tagged <tt>essential</tt> for a system
1098 using the <tt>Essential</tt> control file field.
1099 The format of the <tt>Essential</tt> control field is
1100 described in <ref id="f-Essential">.
1104 Since these packages cannot be easily removed (one has to
1105 specify an extra <em>force option</em> to
1106 <prgn>dpkg</prgn> to do so), this flag must not be used
1107 unless absolutely necessary. A shared library package
1108 must not be tagged <tt>essential</tt>; dependencies will
1109 prevent its premature removal, and we need to be able to
1110 remove it when it has been superseded.
1114 Since dpkg will not prevent upgrading of other packages
1115 while an <tt>essential</tt> package is in an unconfigured
1116 state, all <tt>essential</tt> packages must supply all of
1117 their core functionality even when unconfigured. If the
1118 package cannot satisfy this requirement it must not be
1119 tagged as essential, and any packages depending on this
1120 package must instead have explicit dependency fields as
1125 You must not tag any packages <tt>essential</tt> before
1126 this has been discussed on the <tt>debian-devel</tt>
1127 mailing list and a consensus about doing that has been
1132 <sect id="maintscripts">
1133 <heading>Maintainer Scripts</heading>
1136 The package installation scripts should avoid producing
1137 output which is unnecessary for the user to see and
1138 should rely on <prgn>dpkg</prgn> to stave off boredom on
1139 the part of a user installing many packages. This means,
1140 amongst other things, using the <tt>--quiet</tt> option on
1141 <prgn>install-info</prgn>.
1145 Errors which occur during the execution of an installation
1146 script must be checked and the installation must not
1147 continue after an error.
1151 Note that in general <ref id="scripts"> applies to package
1152 maintainer scripts, too.
1156 You should not use <prgn>dpkg-divert</prgn> on a file
1157 belonging to another package without consulting the
1158 maintainer of that package first.
1162 All packages which supply an instance of a common command
1163 name (or, in general, filename) should generally use
1164 <prgn>update-alternatives</prgn>, so that they may be
1165 installed together. If <prgn>update-alternatives</prgn>
1166 is not used, then each package must use
1167 <tt>Conflicts</tt> to ensure that other packages are
1168 de-installed. (In this case, it may be appropriate to
1169 specify a conflict against earlier versions of something
1170 that previously did not use
1171 <prgn>update-alternatives</prgn>; this is an exception to
1172 the usual rule that versioned conflicts should be
1176 <sect1 id="maintscriptprompt">
1177 <heading>Prompting in maintainer scripts</heading>
1179 Package maintainer scripts may prompt the user if
1180 necessary. Prompting should be done by communicating
1181 through a program, such as <prgn>debconf</prgn>, which
1182 conforms to the Debian Configuration management
1183 specification, version 2 or higher. Prompting the user by
1184 other means, such as by hand<footnote>
1185 From the Jargon file: by hand 2. By extension,
1186 writing code which does something in an explicit or
1187 low-level way for which a presupplied library
1188 (<em>debconf, in this instance</em>) routine ought
1189 to have been available.
1190 </footnote>, is now deprecated.
1194 The Debian Configuration management specification is included
1195 in the <file>debconf_specification</file> files in the
1196 <package>debian-policy</package> package.
1197 It is also available from the Debian web mirrors at
1198 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1199 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1203 Packages which use the Debian Configuration management
1204 specification may contain an additional
1205 <prgn>config</prgn> script and a <tt>templates</tt>
1206 file in their control archive<footnote>
1207 The control.tar.gz inside the .deb.
1208 See <manref name="deb" section="5">.
1210 The <prgn>config</prgn> script might be run before the
1211 <prgn>preinst</prgn> script, and before the package is unpacked
1212 or any of its dependencies or pre-dependencies are satisfied.
1213 Therefore it must work using only the tools present in
1214 <em>essential</em> packages.<footnote>
1215 <package>Debconf</package> or another tool that
1216 implements the Debian Configuration management
1217 specification will also be installed, and any
1218 versioned dependencies on it will be satisfied
1219 before preconfiguration begins.
1224 Packages should try to minimize the amount of prompting
1225 they need to do, and they should ensure that the user
1226 will only ever be asked each question once. This means
1227 that packages should try to use appropriate shared
1228 configuration files (such as <file>/etc/papersize</file> and
1229 <file>/etc/news/server</file>), and shared
1230 <package>debconf</package> variables rather than each
1231 prompting for their own list of required pieces of
1236 It also means that an upgrade should not ask the same
1237 questions again, unless the user has used
1238 <tt>dpkg --purge</tt> to remove the package's configuration.
1239 The answers to configuration questions should be stored in an
1240 appropriate place in <file>/etc</file> so that the user can
1241 modify them, and how this has been done should be
1246 If a package has a vitally important piece of
1247 information to pass to the user (such as "don't run me
1248 as I am, you must edit the following configuration files
1249 first or you risk your system emitting badly-formatted
1250 messages"), it should display this in the
1251 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1252 prompt the user to hit return to acknowledge the
1253 message. Copyright messages do not count as vitally
1254 important (they belong in
1255 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1256 neither do instructions on how to use a program (these
1257 should be in on-line documentation, where all the users
1262 Any necessary prompting should almost always be confined
1263 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1264 script. If it is done in the <prgn>postinst</prgn>, it
1265 should be protected with a conditional so that
1266 unnecessary prompting doesn't happen if a package's
1267 installation fails and the <prgn>postinst</prgn> is
1268 called with <tt>abort-upgrade</tt>,
1269 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1279 <heading>Source packages</heading>
1281 <sect id="standardsversion">
1282 <heading>Standards conformance</heading>
1285 Source packages should specify the most recent version number
1286 of this policy document with which your package complied
1287 when it was last updated.
1291 This information may be used to file bug reports
1292 automatically if your package becomes too much out of date.
1296 The version is specified in the <tt>Standards-Version</tt>
1298 The format of the <tt>Standards-Version</tt> field is
1299 described in <ref id="f-Standards-Version">.
1303 You should regularly, and especially if your package has
1304 become out of date, check for the newest Policy Manual
1305 available and update your package, if necessary. When your
1306 package complies with the new standards you should update the
1307 <tt>Standards-Version</tt> source package field and
1308 release it.<footnote>
1309 See the file <file>upgrading-checklist</file> for
1310 information about policy which has changed between
1311 different versions of this document.
1317 <sect id="pkg-relations">
1318 <heading>Package relationships</heading>
1321 Source packages should specify which binary packages they
1322 require to be installed or not to be installed in order to
1323 build correctly. For example, if building a package
1324 requires a certain compiler, then the compiler should be
1325 specified as a build-time dependency.
1329 It is not necessary to explicitly specify build-time
1330 relationships on a minimal set of packages that are always
1331 needed to compile, link and put in a Debian package a
1332 standard "Hello World!" program written in C or C++. The
1333 required packages are called <em>build-essential</em>, and
1334 an informational list can be found in
1335 <file>/usr/share/doc/build-essential/list</file> (which is
1336 contained in the <tt>build-essential</tt>
1339 <list compact="compact">
1341 This allows maintaining the list separately
1342 from the policy documents (the list does not
1343 need the kind of control that the policy
1347 Having a separate package allows one to install
1348 the build-essential packages on a machine, as
1349 well as allowing other packages such as tasks to
1350 require installation of the build-essential
1351 packages using the depends relation.
1354 The separate package allows bug reports against
1355 the list to be categorized separately from
1356 the policy management process in the BTS.
1363 When specifying the set of build-time dependencies, one
1364 should list only those packages explicitly required by the
1365 build. It is not necessary to list packages which are
1366 required merely because some other package in the list of
1367 build-time dependencies depends on them.<footnote>
1368 The reason for this is that dependencies change, and
1369 you should list all those packages, and <em>only</em>
1370 those packages that <em>you</em> need directly. What
1371 others need is their business. For example, if you
1372 only link against <file>libimlib</file>, you will need to
1373 build-depend on <package>libimlib2-dev</package> but
1374 not against any <tt>libjpeg*</tt> packages, even
1375 though <tt>libimlib2-dev</tt> currently depends on
1376 them: installation of <package>libimlib2-dev</package>
1377 will automatically ensure that all of its run-time
1378 dependencies are satisfied.
1383 If build-time dependencies are specified, it must be
1384 possible to build the package and produce working binaries
1385 on a system with only essential and build-essential
1386 packages installed and also those required to satisfy the
1387 build-time relationships (including any implied
1388 relationships). In particular, this means that version
1389 clauses should be used rigorously in build-time
1390 relationships so that one cannot produce bad or
1391 inconsistently configured packages when the relationships
1392 are properly satisfied.
1396 <ref id="relationships"> explains the technical details.
1401 <heading>Changes to the upstream sources</heading>
1404 If changes to the source code are made that are not
1405 specific to the needs of the Debian system, they should be
1406 sent to the upstream authors in whatever form they prefer
1407 so as to be included in the upstream version of the
1412 If you need to configure the package differently for
1413 Debian or for Linux, and the upstream source doesn't
1414 provide a way to do so, you should add such configuration
1415 facilities (for example, a new <prgn>autoconf</prgn> test
1416 or <tt>#define</tt>) and send the patch to the upstream
1417 authors, with the default set to the way they originally
1418 had it. You can then easily override the default in your
1419 <file>debian/rules</file> or wherever is appropriate.
1423 You should make sure that the <prgn>configure</prgn> utility
1424 detects the correct architecture specification string
1425 (refer to <ref id="arch-spec"> for details).
1429 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1430 <prgn>configure</prgn> scripts are used, you should edit the
1431 <file>.in</file> files rather than editing the
1432 <prgn>Makefile</prgn> directly. This allows the user to
1433 reconfigure the package if necessary. You should
1434 <em>not</em> configure the package and edit the generated
1435 <prgn>Makefile</prgn>! This makes it impossible for someone
1436 else to later reconfigure the package without losing the
1442 <sect id="dpkgchangelog">
1443 <heading>Debian changelog: <file>debian/changelog</file></heading>
1446 Changes in the Debian version of the package should be
1447 briefly explained in the Debian changelog file
1448 <file>debian/changelog</file>.<footnote>
1450 Mistakes in changelogs are usually best rectified by
1451 making a new changelog entry rather than "rewriting
1452 history" by editing old changelog entries.
1455 This includes modifications
1456 made in the Debian package compared to the upstream one
1457 as well as other changes and updates to the package.
1459 Although there is nothing stopping an author who is also
1460 the Debian maintainer from using this changelog for all
1461 their changes, it will have to be renamed if the Debian
1462 and upstream maintainers become different people. In such
1463 a case, however, it might be better to maintain the package
1464 as a non-native package.
1473 The format of the <file>debian/changelog</file> allows the
1474 package building tools to discover which version of the package
1475 is being built and find out other release-specific information.
1479 That format is a series of entries like this:
1481 <example compact="compact">
1482 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1484 [optional blank line(s), stripped]
1486 * <var>change details</var>
1487 <var>more change details</var>
1489 [blank line(s), included in output of dpkg-parsechangelog]
1491 * <var>even more change details</var>
1493 [optional blank line(s), stripped]
1495 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1500 <var>package</var> and <var>version</var> are the source
1501 package name and version number.
1505 <var>distribution(s)</var> lists the distributions where
1506 this version should be installed when it is uploaded - it
1507 is copied to the <tt>Distribution</tt> field in the
1508 <file>.changes</file> file. See <ref id="f-Distribution">.
1512 <var>urgency</var> is the value for the <tt>Urgency</tt>
1513 field in the <file>.changes</file> file for the upload
1514 (see <ref id="f-Urgency">). It is not possible to specify
1515 an urgency containing commas; commas are used to separate
1516 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1517 <prgn>dpkg</prgn> changelog format (though there is
1518 currently only one useful <var>keyword</var>,
1523 The change details may in fact be any series of lines
1524 starting with at least two spaces, but conventionally each
1525 change starts with an asterisk and a separating space and
1526 continuation lines are indented so as to bring them in
1527 line with the start of the text above. Blank lines may be
1528 used here to separate groups of changes, if desired.
1532 If this upload resolves bugs recorded in the Bug Tracking
1533 System (BTS), they may be automatically closed on the
1534 inclusion of this package into the Debian archive by
1535 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1536 in the change details.<footnote>
1537 To be precise, the string should match the following
1538 Perl regular expression:
1540 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1542 Then all of the bug numbers listed will be closed by the
1543 archive maintenance script (<prgn>katie</prgn>), or in
1544 the case of an NMU, marked as fixed.
1546 This information is conveyed via the <tt>Closes</tt> field
1547 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1551 The maintainer name and email address used in the changelog
1552 should be the details of the person uploading <em>this</em>
1553 version. They are <em>not</em> necessarily those of the
1554 usual package maintainer. The information here will be
1555 copied to the <tt>Changed-By</tt> field in the
1556 <tt>.changes</tt> file (see <ref id="f-Changed-By">),
1557 and then later used to send an acknowledgement when the
1558 upload has been installed.
1562 The <var>date</var> should be in RFC822 format<footnote>
1563 This is generated by <tt>date -R</tt>.
1564 </footnote>; it should include the time zone specified
1565 numerically, with the time zone name or abbreviation
1566 optionally present as a comment in parentheses.
1570 The first "title" line with the package name should start
1571 at the left hand margin; the "trailer" line with the
1572 maintainer and date details should be preceded by exactly
1573 one space. The maintainer details and the date must be
1574 separated by exactly two spaces.
1578 For more information on placement of the changelog files
1579 within binary packages, please see <ref id="changelogs">.
1582 <sect1><heading>Alternative changelog formats</heading>
1585 In non-experimental packages you must use a format for
1586 <file>debian/changelog</file> which is supported by the most
1587 recent released version of <prgn>dpkg</prgn>.
1591 It is possible to use a format different from the standard
1592 one by providing a changelog parser for the format you wish
1593 to use. The parser must have an API compatible with that
1594 expected by <prgn>dpkg-genchanges</prgn> and
1595 <prgn>dpkg-gencontrol</prgn>, and it must not interact with
1598 If there is general interest in the new format, you should
1599 contact the <package>dpkg</package> maintainer to have the
1600 parser script for it included in the <prgn>dpkg</prgn>
1601 package. (You will need to agree that the parser and its
1602 man page may be distributed under the GNU GPL, just as the rest
1603 of <prgn>dpkg</prgn> is.)
1608 <sect id="dpkgcopyright">
1609 <heading>Copyright: <file>debian/copyright</file></heading>
1611 Every package must be accompanied by a verbatim copy of
1612 its copyright and distribution license in the file
1613 <file>/usr/share/doc/<var>package</var>/copyright</file>
1614 (see <ref id="copyrightfile"> for further details). Also see
1615 <ref id="pkgcopyright"> for further considerations relayed
1616 to copyrights for packages.
1620 <heading>Error trapping in makefiles</heading>
1623 When <prgn>make</prgn> invokes a command in a makefile
1624 (including your package's upstream makefiles and
1625 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1626 means that <prgn>sh</prgn>'s usual bad error handling
1627 properties apply: if you include a miniature script as one
1628 of the commands in your makefile you'll find that if you
1629 don't do anything about it then errors are not detected
1630 and <prgn>make</prgn> will blithely continue after
1635 Every time you put more than one shell command (this
1636 includes using a loop) in a makefile command you
1637 must make sure that errors are trapped. For
1638 simple compound commands, such as changing directory and
1639 then running a program, using <tt>&&</tt> rather
1640 than semicolon as a command separator is sufficient. For
1641 more complex commands including most loops and
1642 conditionals you should include a separate <tt>set -e</tt>
1643 command at the start of every makefile command that's
1644 actually one of these miniature shell scripts.
1648 <sect id="timestamps">
1649 <heading>Time Stamps</heading>
1651 Maintainers should preserve the modification times of the
1652 upstream source files in a package, as far as is reasonably
1654 The rationale is that there is some information conveyed
1655 by knowing the age of the file, for example, you could
1656 recognize that some documentation is very old by looking
1657 at the modification time, so it would be nice if the
1658 modification time of the upstream source would be
1664 <sect id="restrictions">
1665 <heading>Restrictions on objects in source packages</heading>
1668 The source package may not contain any hard links<footnote>
1670 This is not currently detected when building source
1671 packages, but only when extracting
1675 Hard links may be permitted at some point in the
1676 future, but would require a fair amount of
1679 </footnote>, device special files, sockets or setuid or
1680 setgid files.<footnote>
1681 Setgid directories are allowed.
1686 <sect id="debianrules">
1687 <heading>Main building script: <file>debian/rules</file></heading>
1690 This file must be an executable makefile, and contains the
1691 package-specific recipes for compiling the package and
1692 building binary package(s) from the source.
1696 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1697 so that it can be invoked by saying its name rather than
1698 invoking <prgn>make</prgn> explicitly.
1702 Since an interactive <file>debian/rules</file> script makes it
1703 impossible to auto-compile that package and also makes it
1704 hard for other people to reproduce the same binary
1705 package, all <em>required targets</em> MUST be
1706 non-interactive. At a minimum, required targets are the
1707 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1708 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1709 <em>binary-indep</em>, and <em>build</em>. It also follows
1710 that any target that these targets depend on must also be
1715 The targets are as follows (required unless stated otherwise):
1717 <tag><tt>build</tt></tag>
1720 The <tt>build</tt> target should perform all the
1721 configuration and compilation of the package.
1722 If a package has an interactive pre-build
1723 configuration routine, the Debianized source package
1724 must either be built after this has taken place (so
1725 that the binary package can be built without rerunning
1726 the configuration) or the configuration routine
1727 modified to become non-interactive. (The latter is
1728 preferable if there are architecture-specific features
1729 detected by the configuration routine.)
1733 For some packages, notably ones where the same
1734 source tree is compiled in different ways to produce
1735 two binary packages, the <tt>build</tt> target
1736 does not make much sense. For these packages it is
1737 good enough to provide two (or more) targets
1738 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1739 for each of the ways of building the package, and a
1740 <tt>build</tt> target that does nothing. The
1741 <tt>binary</tt> target will have to build the
1742 package in each of the possible ways and make the
1743 binary package out of each.
1747 The <tt>build</tt> target must not do anything
1748 that might require root privilege.
1752 The <tt>build</tt> target may need to run the
1753 <tt>clean</tt> target first - see below.
1757 When a package has a configuration and build routine
1758 which takes a long time, or when the makefiles are
1759 poorly designed, or when <tt>build</tt> needs to
1760 run <tt>clean</tt> first, it is a good idea to
1761 <tt>touch build</tt> when the build process is
1762 complete. This will ensure that if <tt>debian/rules
1763 build</tt> is run again it will not rebuild the whole
1765 Another common way to do this is for <tt>build</tt>
1766 to depend on <prgn>build-stamp</prgn> and to do
1767 nothing else, and for the <prgn>build-stamp</prgn>
1768 target to do the building and to <tt>touch
1769 build-stamp</tt> on completion. This is
1770 especially useful if the build routine creates a
1771 file or directory called <tt>build</tt>; in such a
1772 case, <tt>build</tt> will need to be listed as
1773 a phony target (i.e., as a dependency of the
1774 <tt>.PHONY</tt> target). See the documentation of
1775 <prgn>make</prgn> for more information on phony
1781 <tag><tt>build-arch</tt> (optional),
1782 <tt>build-indep</tt> (optional)
1786 A package may also provide both of the targets
1787 <tt>build-arch</tt> and <tt>build-indep</tt>.
1788 The <tt>build-arch</tt> target, if provided, should
1789 perform all the configuration and compilation required
1790 for producing all architecture-dependant binary packages
1791 (those packages for which the body of the
1792 <tt>Architecture</tt> field in <tt>debian/control</tt>
1793 is not <tt>all</tt>).
1794 Similarly, the <tt>build-indep</tt> target, if
1795 provided, should perform all the configuration and
1796 compilation required for producing all
1797 architecture-independent binary packages
1798 (those packages for which the body of the
1799 <tt>Architecture</tt> field in <tt>debian/control</tt>
1801 The <tt>build</tt> target should depend on those of the
1802 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1803 are provided in the rules file.
1807 If one or both of the targets <tt>build-arch</tt> and
1808 <tt>build-indep</tt> are not provided, then invoking
1809 <file>debian/rules</file> with one of the not-provided
1810 targets as arguments should produce a exit status code
1811 of 2. Usually this is provided automatically by make
1812 if the target is missing.
1816 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1817 must not do anything that might require root privilege.
1821 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1822 <tt>binary-indep</tt>
1826 The <tt>binary</tt> target must be all that is
1827 necessary for the user to build the binary package(s)
1828 produced from this source package. It is
1829 split into two parts: <prgn>binary-arch</prgn> builds
1830 the binary packages which are specific to a particular
1831 architecture, and <tt>binary-indep</tt> builds
1832 those which are not.
1835 <tt>binary</tt> may be (and commonly is) a target with
1836 no commands which simply depends on
1837 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1840 Both <tt>binary-*</tt> targets should depend on the
1841 <tt>build</tt> target, or on the appropriate
1842 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1843 provided, so that the package is built if it has not
1844 been already. It should then create the relevant
1845 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1846 make their control files and <prgn>dpkg-deb</prgn> to
1847 build them and place them in the parent of the top
1852 Both the <tt>binary-arch</tt> and
1853 <tt>binary-indep</tt> targets <em>must</em> exist.
1854 If one of them has nothing to do (which will always be
1855 the case if the source generates only a single binary
1856 package, whether architecture-dependent or not), it
1857 must still exist and must always succeed.
1861 The <tt>binary</tt> targets must be invoked as
1863 The <prgn>fakeroot</prgn> package often allows one
1864 to build a package correctly even without being
1870 <tag><tt>clean</tt></tag>
1873 This must undo any effects that the <tt>build</tt>
1874 and <tt>binary</tt> targets may have had, except
1875 that it should leave alone any output files created in
1876 the parent directory by a run of a <tt>binary</tt>
1881 If a <tt>build</tt> file is touched at the end of
1882 the <tt>build</tt> target, as suggested above, it
1883 should be removed as the first action that
1884 <tt>clean</tt> performs, so that running
1885 <tt>build</tt> again after an interrupted
1886 <tt>clean</tt> doesn't think that everything is
1891 The <tt>clean</tt> target may need to be
1892 invoked as root if <tt>binary</tt> has been
1893 invoked since the last <tt>clean</tt>, or if
1894 <tt>build</tt> has been invoked as root (since
1895 <tt>build</tt> may create directories, for
1900 <tag><tt>get-orig-source</tt> (optional)</tag>
1903 This target fetches the most recent version of the
1904 original source package from a canonical archive site
1905 (via FTP or WWW, for example), does any necessary
1906 rearrangement to turn it into the original source
1907 tar file format described below, and leaves it in the
1912 This target may be invoked in any directory, and
1913 should take care to clean up any temporary files it
1918 This target is optional, but providing it if
1919 possible is a good idea.
1925 The <tt>build</tt>, <tt>binary</tt> and
1926 <tt>clean</tt> targets must be invoked with the current
1927 directory being the package's top-level directory.
1932 Additional targets may exist in <file>debian/rules</file>,
1933 either as published or undocumented interfaces or for the
1934 package's internal use.
1938 The architectures we build on and build for are determined
1939 by <prgn>make</prgn> variables using the utility
1940 <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
1941 You can determine the
1942 Debian architecture and the GNU style architecture
1943 specification string for the build machine (the machine type
1944 we are building on) as well as for the host machine (the
1945 machine type we are building for). Here is a list of
1946 supported <prgn>make</prgn> variables:
1947 <list compact="compact">
1949 <tt>DEB_*_ARCH</tt> (the Debian architecture)
1952 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
1953 specification string)
1956 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
1957 <tt>DEB_*_GNU_TYPE</tt>)
1960 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
1961 <tt>DEB_*_GNU_TYPE</tt>)
1963 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
1964 the build machine or <tt>HOST</tt> for specification of the
1969 Backward compatibility can be provided in the rules file
1970 by setting the needed variables to suitable default
1971 values; please refer to the documentation of
1972 <prgn>dpkg-architecture</prgn> for details.
1976 It is important to understand that the <tt>DEB_*_ARCH</tt>
1977 string only determines which Debian architecture we are
1978 building on or for. It should not be used to get the CPU
1979 or system information; the GNU style variables should be
1984 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
1985 <sect id="substvars">
1986 <heading>Variable substitutions: <file>debian/substvars</file></heading>
1989 When <prgn>dpkg-gencontrol</prgn>,
1990 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
1991 generate control files they perform variable substitutions
1992 on their output just before writing it. Variable
1993 substitutions have the form <tt>${<var>variable</var>}</tt>.
1994 The optional file <file>debian/substvars</file> contains
1995 variable substitutions to be used; variables can also be set
1996 directly from <file>debian/rules</file> using the <tt>-V</tt>
1997 option to the source packaging commands, and certain
1998 predefined variables are also available.
2002 The <file>debian/substvars</file> file is usually generated and
2003 modified dynamically by <file>debian/rules</file> targets, in
2004 which case it must be removed by the <tt>clean</tt> target.
2008 See <manref name="dpkg-source" section="1"> for full
2009 details about source variable substitutions, including the
2010 format of <file>debian/substvars</file>.</p>
2013 <sect id="debianwatch">
2014 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2017 This is an optional, recommended control file for the
2018 <tt>uscan</tt> utility which defines how to automatically
2019 scan ftp or http sites for newly available updates of the
2020 package. This is used by <url id="
2021 http://dehs.alioth.debian.org/"> and other Debian QA tools
2022 to help with quality control and maintenance of the
2023 distribution as a whole.
2028 <sect id="debianfiles">
2029 <heading>Generated files list: <file>debian/files</file></heading>
2032 This file is not a permanent part of the source tree; it
2033 is used while building packages to record which files are
2034 being generated. <prgn>dpkg-genchanges</prgn> uses it
2035 when it generates a <file>.changes</file> file.
2039 It should not exist in a shipped source package, and so it
2040 (and any backup files or temporary files such as
2041 <file>files.new</file><footnote>
2042 <file>files.new</file> is used as a temporary file by
2043 <prgn>dpkg-gencontrol</prgn> and
2044 <prgn>dpkg-distaddfile</prgn> - they write a new
2045 version of <tt>files</tt> here before renaming it,
2046 to avoid leaving a corrupted copy if an error
2048 </footnote>) should be removed by the
2049 <tt>clean</tt> target. It may also be wise to
2050 ensure a fresh start by emptying or removing it at the
2051 start of the <tt>binary</tt> target.
2055 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2056 package, it adds an entry to <file>debian/files</file> for the
2057 <file>.deb</file> file that will be created when <tt>dpkg-deb
2058 --build</tt> is run for that binary package. So for most
2059 packages all that needs to be done with this file is to
2060 delete it in the <tt>clean</tt> target.
2064 If a package upload includes files besides the source
2065 package and any binary packages whose control files were
2066 made with <prgn>dpkg-gencontrol</prgn> then they should be
2067 placed in the parent of the package's top-level directory
2068 and <prgn>dpkg-distaddfile</prgn> should be called to add
2069 the file to the list in <file>debian/files</file>.</p>
2075 <chapt id="controlfields">
2076 <heading>Control files and their fields</heading>
2079 The package management system manipulates data represented in
2080 a common format, known as <em>control data</em>, stored in
2081 <em>control files</em>.
2082 Control files are used for source packages, binary packages and
2083 the <file>.changes</file> files which control the installation
2084 of uploaded files<footnote>
2085 <prgn>dpkg</prgn>'s internal databases are in a similar
2090 <sect id="controlsyntax">
2091 <heading>Syntax of control files</heading>
2094 A control file consists of one or more paragraphs of
2096 The paragraphs are also sometimes referred to as stanzas.
2098 The paragraphs are separated by blank lines. Some control
2099 files allow only one paragraph; others allow several, in
2100 which case each paragraph usually refers to a different
2101 package. (For example, in source packages, the first
2102 paragraph refers to the source package, and later paragraphs
2103 refer to binary packages generated from the source.)
2107 Each paragraph consists of a series of data fields; each
2108 field consists of the field name, followed by a colon and
2109 then the data/value associated with that field. It ends at
2110 the end of the (logical) line. Horizontal whitespace
2111 (spaces and tabs) may occur immediately before or after the
2112 value and is ignored there; it is conventional to put a
2113 single space after the colon. For example, a field might
2115 <example compact="compact">
2118 the field name is <tt>Package</tt> and the field value
2123 Many fields' values may span several lines; in this case
2124 each continuation line must start with a space or a tab.
2125 Any trailing spaces or tabs at the end of individual
2126 lines of a field value are ignored.
2130 In fields where it is specified that lines may not wrap,
2131 only a single line of data is allowed and whitespace is not
2132 significant in a field body. Whitespace must not appear
2133 inside names (of packages, architectures, files or anything
2134 else) or version numbers, or between the characters of
2135 multi-character version relationships.
2139 Field names are not case-sensitive, but it is usual to
2140 capitalize the field names using mixed case as shown below.
2144 Blank lines, or lines consisting only of spaces and tabs,
2145 are not allowed within field values or between fields - that
2146 would mean a new paragraph.
2151 <sect id="sourcecontrolfiles">
2152 <heading>Source package control files -- <file>debian/control</file></heading>
2155 The <file>debian/control</file> file contains the most vital
2156 (and version-independent) information about the source package
2157 and about the binary packages it creates.
2161 The first paragraph of the control file contains information about
2162 the source package in general. The subsequent sets each describe a
2163 binary package that the source tree builds.
2167 The fields in the general paragraph (the first one, for the source
2170 <list compact="compact">
2171 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2172 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2173 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2174 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2175 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2176 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2177 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2182 The fields in the binary package paragraphs are:
2184 <list compact="compact">
2185 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2186 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2187 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2188 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2189 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2190 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2191 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2196 The syntax and semantics of the fields are described below.
2202 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2203 generate control files for binary packages (see below), by
2204 <prgn>dpkg-genchanges</prgn> to generate the
2205 <tt>.changes</tt> file to accompany the upload, and by
2206 <prgn>dpkg-source</prgn> when it creates the
2207 <file>.dsc</file> source control file as part of a source
2208 archive. Many fields are permitted to span multiple lines in
2209 <file>debian/control</file> but not in any other control
2210 file. These tools are responsible for removing the line
2211 breaks from such fields when using fields from
2212 <file>debian/control</file> to generate other control files.
2216 The fields here may contain variable references - their
2217 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2218 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2219 when they generate output control files.
2220 See <ref id="substvars"> for details.
2225 <sect id="binarycontrolfiles">
2226 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2229 The <file>DEBIAN/control</file> file contains the most vital
2230 (and version-dependent) information about a binary package.
2234 The fields in this file are:
2236 <list compact="compact">
2237 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2238 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2239 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2240 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2241 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2242 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2243 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2244 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2245 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2246 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2247 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2252 <sect id="debiansourcecontrolfiles">
2253 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2256 This file contains a series of fields, identified and
2257 separated just like the fields in the control file of
2258 a binary package. The fields are listed below; their
2259 syntax is described above, in <ref id="pkg-controlfields">.
2261 <list compact="compact">
2262 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2263 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2264 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2265 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2266 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2267 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2268 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2269 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2270 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2271 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2276 The source package control file is generated by
2277 <prgn>dpkg-source</prgn> when it builds the source
2278 archive, from other files in the source package,
2279 described above. When unpacking, it is checked against
2280 the files and directories in the other parts of the
2286 <sect id="debianchangesfiles">
2287 <heading>Debian changes files -- <file>.changes</file></heading>
2290 The .changes files are used by the Debian archive maintenance
2291 software to process updates to packages. They contain one
2292 paragraph which contains information from the
2293 <tt>debian/control</tt> file and other data about the
2294 source package gathered via <tt>debian/changelog</tt>
2295 and <tt>debian/rules</tt>.
2299 The fields in this file are:
2301 <list compact="compact">
2302 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2303 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2304 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2305 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2306 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2307 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2308 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2309 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2310 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2311 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2312 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2313 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2314 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2315 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2320 <sect id="controlfieldslist">
2321 <heading>List of fields</heading>
2323 <sect1 id="f-Source">
2324 <heading><tt>Source</tt></heading>
2327 This field identifies the source package name.
2331 In <file>debian/control</file> or a <file>.dsc</file> file,
2332 this field must contain only the name of the source package.
2336 In a binary package control file or a <file>.changes</file>
2337 file, the source package name may be followed by a version
2338 number in parentheses<footnote>
2339 It is customary to leave a space after the package name
2340 if a version number is specified.
2342 This version number may be omitted (and is, by
2343 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2344 the <tt>Version</tt> field of the binary package in
2345 question. The field itself may be omitted from a binary
2346 package control file when the source package has the same
2347 name and version as the binary package.
2351 <sect1 id="f-Maintainer">
2352 <heading><tt>Maintainer</tt></heading>
2355 The package maintainer's name and email address. The name
2356 should come first, then the email address inside angle
2357 brackets <tt><></tt> (in RFC822 format).
2361 If the maintainer's name contains a full stop then the
2362 whole field will not work directly as an email address due
2363 to a misfeature in the syntax specified in RFC822; a
2364 program using this field as an address must check for this
2365 and correct the problem if necessary (for example by
2366 putting the name in round brackets and moving it to the
2367 end, and bringing the email address forward).
2371 <sect1 id="f-Uploaders">
2372 <heading><tt>Uploaders</tt></heading>
2375 List of the names and email addresses of co-maintainers of
2376 the package, if any. If the package has other maintainers
2377 beside the one named in the
2378 <qref id="f-Maintainer">Maintainer field</qref>, their
2379 names and email addresses should be listed here. The
2380 format is the same as that of the Maintainer tag, and
2381 multiple entries should be comma separated. Currently,
2382 this field is restricted to a single line of data. This
2383 is an optional field.
2386 Any parser that interprets the Uploaders field in
2387 <file>debian/control</file> should permit it to span multiple
2389 In the future, the Uploaders field in
2390 <file>debian/control</file> (but not other control files)
2391 will be permitted to span multiple lines and interpreting
2392 a multi-line Uploaders field shall be mandatory.
2393 </footnote>. Line breaks in an Uploaders field that spans
2394 multiple lines are not significant and the semantics of
2395 the field are the same as if the line breaks had not been
2400 <sect1 id="f-Changed-By">
2401 <heading><tt>Changed-By</tt></heading>
2404 The name and email address of the person who changed the
2405 said package. Usually the name of the maintainer.
2406 All the rules for the Maintainer field apply here, too.
2410 <sect1 id="f-Section">
2411 <heading><tt>Section</tt></heading>
2414 This field specifies an application area into which the package
2415 has been classified. See <ref id="subsections">.
2419 When it appears in the <file>debian/control</file> file,
2420 it gives the value for the subfield of the same name in
2421 the <tt>Files</tt> field of the <file>.changes</file> file.
2422 It also gives the default for the same field in the binary
2427 <sect1 id="f-Priority">
2428 <heading><tt>Priority</tt></heading>
2431 This field represents how important that it is that the user
2432 have the package installed. See <ref id="priorities">.
2436 When it appears in the <file>debian/control</file> file,
2437 it gives the value for the subfield of the same name in
2438 the <tt>Files</tt> field of the <file>.changes</file> file.
2439 It also gives the default for the same field in the binary
2444 <sect1 id="f-Package">
2445 <heading><tt>Package</tt></heading>
2448 The name of the binary package.
2452 Package names must consist only of lower case letters
2453 (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus (<tt>+</tt>)
2454 and minus (<tt>-</tt>) signs, and periods (<tt>.</tt>).
2455 They must be at least two characters long and must start
2456 with an alphanumeric character.
2460 <sect1 id="f-Architecture">
2461 <heading><tt>Architecture</tt></heading>
2464 Depending on context and the control file used, the
2465 <tt>Architecture</tt> field can include the following sets of
2468 <item>A unique single word identifying a Debian machine
2469 architecture, see <ref id="arch-spec">.
2470 <item><tt>all</tt>, which indicates an
2471 architecture-independent package.
2472 <item><tt>any</tt>, which indicates a package available
2473 for building on any architecture.
2474 <item><tt>source</tt>, which indicates a source package.
2479 In the main <file>debian/control</file> file in the source
2480 package, or in the source package control file
2481 <file>.dsc</file>, one may specify a list of architectures
2482 separated by spaces, or the special values <tt>any</tt> or
2487 Specifying <tt>any</tt> indicates that the source package
2488 isn't dependent on any particular architecture and should
2489 compile fine on any one. The produced binary package(s)
2490 will be specific to whatever the current build architecture
2492 This is the most often used setting, and is recommended
2493 for new packages that aren't <tt>Architecture: all</tt>.
2498 Specifying a list of architectures indicates that the source
2499 will build an architecture-dependent package, and will only
2500 work correctly on the listed architectures.<footnote>
2501 This is a setting used for a minority of cases where the
2502 program is not portable. Generally, it should not be used
2508 In a <file>.changes</file> file, the <tt>Architecture</tt>
2509 field lists the architecture(s) of the package(s)
2510 currently being uploaded. This will be a list; if the
2511 source for the package is also being uploaded, the special
2512 entry <tt>source</tt> is also present.
2516 See <ref id="debianrules"> for information how to get the
2517 architecture for the build process.
2521 <sect1 id="f-Essential">
2522 <heading><tt>Essential</tt></heading>
2525 This is a boolean field which may occur only in the
2526 control file of a binary package or in a per-package fields
2527 paragraph of a main source control data file.
2531 If set to <tt>yes</tt> then the package management system
2532 will refuse to remove the package (upgrading and replacing
2533 it is still possible). The other possible value is <tt>no</tt>,
2534 which is the same as not having the field at all.
2539 <heading>Package interrelationship fields:
2540 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2541 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Conflicts</tt>,
2542 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2546 These fields describe the package's relationships with
2547 other packages. Their syntax and semantics are described
2548 in <ref id="relationships">.</p>
2551 <sect1 id="f-Standards-Version">
2552 <heading><tt>Standards-Version</tt></heading>
2555 The most recent version of the standards (the policy
2556 manual and associated texts) with which the package
2561 The version number has four components: major and minor
2562 version number and major and minor patch level. When the
2563 standards change in a way that requires every package to
2564 change the major number will be changed. Significant
2565 changes that will require work in many packages will be
2566 signaled by a change to the minor number. The major patch
2567 level will be changed for any change to the meaning of the
2568 standards, however small; the minor patch level will be
2569 changed when only cosmetic, typographical or other edits
2570 are made which neither change the meaning of the document
2571 nor affect the contents of packages.
2575 Thus only the first three components of the policy version
2576 are significant in the <em>Standards-Version</em> control
2577 field, and so either these three components or the all
2578 four components may be specified.<footnote>
2579 In the past, people specified the full version number
2580 in the Standards-Version field, for example "2.3.0.0".
2581 Since minor patch-level changes don't introduce new
2582 policy, it was thought it would be better to relax
2583 policy and only require the first 3 components to be
2584 specified, in this example "2.3.0". All four
2585 components may still be used if someone wishes to do so.
2591 <sect1 id="f-Version">
2592 <heading><tt>Version</tt></heading>
2595 The version number of a package. The format is:
2596 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
2600 The three components here are:
2602 <tag><var>epoch</var></tag>
2605 This is a single (generally small) unsigned integer. It
2606 may be omitted, in which case zero is assumed. If it is
2607 omitted then the <var>upstream_version</var> may not
2612 It is provided to allow mistakes in the version numbers
2613 of older versions of a package, and also a package's
2614 previous version numbering schemes, to be left behind.
2618 <tag><var>upstream_version</var></tag>
2621 This is the main part of the version number. It is
2622 usually the version number of the original ("upstream")
2623 package from which the <file>.deb</file> file has been made,
2624 if this is applicable. Usually this will be in the same
2625 format as that specified by the upstream author(s);
2626 however, it may need to be reformatted to fit into the
2627 package management system's format and comparison
2632 The comparison behavior of the package management system
2633 with respect to the <var>upstream_version</var> is
2634 described below. The <var>upstream_version</var>
2635 portion of the version number is mandatory.
2639 The <var>upstream_version</var> may contain only
2640 alphanumerics<footnote>
2641 Alphanumerics are <tt>A-Za-z0-9</tt> only.
2643 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
2644 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
2645 tilde) and should start with a digit. If there is no
2646 <var>debian_revision</var> then hyphens are not allowed;
2647 if there is no <var>epoch</var> then colons are not
2652 <tag><var>debian_revision</var></tag>
2655 This part of the version number specifies the version of
2656 the Debian package based on the upstream version. It
2657 may contain only alphanumerics and the characters
2658 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
2659 tilde) and is compared in the same way as the
2660 <var>upstream_version</var> is.
2664 It is optional; if it isn't present then the
2665 <var>upstream_version</var> may not contain a hyphen.
2666 This format represents the case where a piece of
2667 software was written specifically to be turned into a
2668 Debian package, and so there is only one "debianisation"
2669 of it and therefore no revision indication is required.
2673 It is conventional to restart the
2674 <var>debian_revision</var> at <tt>1</tt> each time the
2675 <var>upstream_version</var> is increased.
2679 The package management system will break the version
2680 number apart at the last hyphen in the string (if there
2681 is one) to determine the <var>upstream_version</var> and
2682 <var>debian_revision</var>. The absence of a
2683 <var>debian_revision</var> compares earlier than the
2684 presence of one (but note that the
2685 <var>debian_revision</var> is the least significant part
2686 of the version number).
2693 The <var>upstream_version</var> and <var>debian_revision</var>
2694 parts are compared by the package management system using the
2699 The strings are compared from left to right.
2703 First the initial part of each string consisting entirely of
2704 non-digit characters is determined. These two parts (one of
2705 which may be empty) are compared lexically. If a difference
2706 is found it is returned. The lexical comparison is a
2707 comparison of ASCII values modified so that all the letters
2708 sort earlier than all the non-letters and so that a tilde
2709 sorts before anything, even the end of a part. For example,
2710 the following parts are in sorted order from earliest to
2711 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
2712 <tt>a</tt>.<footnote>
2713 One common use of <tt>~</tt> is for upstream pre-releases.
2714 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
2715 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
2720 Then the initial part of the remainder of each string which
2721 consists entirely of digit characters is determined. The
2722 numerical values of these two parts are compared, and any
2723 difference found is returned as the result of the comparison.
2724 For these purposes an empty string (which can only occur at
2725 the end of one or both version strings being compared) counts
2730 These two steps (comparing and removing initial non-digit
2731 strings and initial digit strings) are repeated until a
2732 difference is found or both strings are exhausted.
2736 Note that the purpose of epochs is to allow us to leave behind
2737 mistakes in version numbering, and to cope with situations
2738 where the version numbering scheme changes. It is
2739 <em>not</em> intended to cope with version numbers containing
2740 strings of letters which the package management system cannot
2741 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
2742 silly orderings (the author of this manual has heard of a
2743 package whose versions went <tt>1.1</tt>, <tt>1.2</tt>,
2744 <tt>1.3</tt>, <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>,
2745 <tt>2</tt> and so forth).
2749 <sect1 id="f-Description">
2750 <heading><tt>Description</tt></heading>
2753 In a source or binary control file, the <tt>Description</tt>
2754 field contains a description of the binary package, consisting
2755 of two parts, the synopsis or the short description, and the
2756 long description. The field's format is as follows:
2761 Description: <single line synopsis>
2762 <extended description over several lines>
2767 The lines in the extended description can have these formats:
2773 Those starting with a single space are part of a paragraph.
2774 Successive lines of this form will be word-wrapped when
2775 displayed. The leading space will usually be stripped off.
2779 Those starting with two or more spaces. These will be
2780 displayed verbatim. If the display cannot be panned
2781 horizontally, the displaying program will line wrap them "hard"
2782 (i.e., without taking account of word breaks). If it can they
2783 will be allowed to trail off to the right. None, one or two
2784 initial spaces may be deleted, but the number of spaces
2785 deleted from each line will be the same (so that you can have
2786 indenting work correctly, for example).
2790 Those containing a single space followed by a single full stop
2791 character. These are rendered as blank lines. This is the
2792 <em>only</em> way to get a blank line<footnote>
2793 Completely empty lines will not be rendered as blank lines.
2794 Instead, they will cause the parser to think you're starting
2795 a whole new record in the control file, and will therefore
2796 likely abort with an error.
2801 Those containing a space, a full stop and some more characters.
2802 These are for future expansion. Do not use them.
2808 Do not use tab characters. Their effect is not predictable.
2812 See <ref id="descriptions"> for further information on this.
2816 In a <file>.changes</file> file, the <tt>Description</tt> field
2817 contains a summary of the descriptions for the packages being
2822 The part of the field before the first newline is empty;
2823 thereafter each line has the name of a binary package and
2824 the summary description line from that binary package.
2825 Each line is indented by one space.
2830 <sect1 id="f-Distribution">
2831 <heading><tt>Distribution</tt></heading>
2834 In a <file>.changes</file> file or parsed changelog output
2835 this contains the (space-separated) name(s) of the
2836 distribution(s) where this version of the package should
2837 be installed. Valid distributions are determined by the
2838 archive maintainers.<footnote>
2839 Current distribution names are:
2840 <taglist compact="compact">
2841 <tag><em>stable</em></tag>
2843 This is the current "released" version of Debian
2844 GNU/Linux. Once the distribution is
2845 <em>stable</em> only security fixes and other
2846 major bug fixes are allowed. When changes are
2847 made to this distribution, the release number is
2848 increased (for example: 2.2r1 becomes 2.2r2 then
2852 <tag><em>unstable</em></tag>
2854 This distribution value refers to the
2855 <em>developmental</em> part of the Debian
2856 distribution tree. New packages, new upstream
2857 versions of packages and bug fixes go into the
2858 <em>unstable</em> directory tree. Download from
2859 this distribution at your own risk.
2862 <tag><em>testing</em></tag>
2864 This distribution value refers to the
2865 <em>testing</em> part of the Debian distribution
2866 tree. It receives its packages from the
2867 unstable distribution after a short time lag to
2868 ensure that there are no major issues with the
2869 unstable packages. It is less prone to breakage
2870 than unstable, but still risky. It is not
2871 possible to upload packages directly to
2875 <tag><em>frozen</em></tag>
2877 From time to time, the <em>testing</em>
2878 distribution enters a state of "code-freeze" in
2879 anticipation of release as a <em>stable</em>
2880 version. During this period of testing only
2881 fixes for existing or newly-discovered bugs will
2882 be allowed. The exact details of this stage are
2883 determined by the Release Manager.
2886 <tag><em>experimental</em></tag>
2888 The packages with this distribution value are
2889 deemed by their maintainers to be high
2890 risk. Oftentimes they represent early beta or
2891 developmental packages from various sources that
2892 the maintainers want people to try, but are not
2893 ready to be a part of the other parts of the
2894 Debian distribution tree. Download at your own
2900 You should list <em>all</em> distributions that the
2901 package should be installed into.
2905 More information is available in the Debian Developer's
2906 Reference, section "The Debian archive".
2913 <heading><tt>Date</tt></heading>
2916 This field includes the date the package was built or last edited.
2920 The value of this field is usually extracted from the
2921 <file>debian/changelog</file> file - see
2922 <ref id="dpkgchangelog">).
2926 <sect1 id="f-Format">
2927 <heading><tt>Format</tt></heading>
2930 This field specifies a format revision for the file.
2931 The most current format described in the Policy Manual
2932 is version <strong>1.5</strong>. The syntax of the
2933 format value is the same as that of a package version
2934 number except that no epoch or Debian revision is allowed
2935 - see <ref id="f-Version">.
2939 <sect1 id="f-Urgency">
2940 <heading><tt>Urgency</tt></heading>
2943 This is a description of how important it is to upgrade to
2944 this version from previous ones. It consists of a single
2945 keyword taking one of the values <tt>low</tt>,
2946 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
2947 <tt>critical</tt><footnote>
2948 Other urgency values are supported with configuration
2949 changes in the archive software but are not used in Debian.
2950 The urgency affects how quickly a package will be considered
2951 for inclusion into the <tt>testing</tt> distribution and
2952 gives an indication of the importance of any fixes included
2953 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
2954 treated as synonymous.
2955 </footnote> (not case-sensitive) followed by an optional
2956 commentary (separated by a space) which is usually in
2957 parentheses. For example:
2960 Urgency: low (HIGH for users of diversions)
2966 The value of this field is usually extracted from the
2967 <file>debian/changelog</file> file - see
2968 <ref id="dpkgchangelog">.
2972 <sect1 id="f-Changes">
2973 <heading><tt>Changes</tt></heading>
2976 This field contains the human-readable changes data, describing
2977 the differences between the last version and the current one.
2981 There should be nothing in this field before the first
2982 newline; all the subsequent lines must be indented by at
2983 least one space; blank lines must be represented by a line
2984 consisting only of a space and a full stop.
2988 The value of this field is usually extracted from the
2989 <file>debian/changelog</file> file - see
2990 <ref id="dpkgchangelog">).
2994 Each version's change information should be preceded by a
2995 "title" line giving at least the version, distribution(s)
2996 and urgency, in a human-readable way.
3000 If data from several versions is being returned the entry
3001 for the most recent version should be returned first, and
3002 entries should be separated by the representation of a
3003 blank line (the "title" line may also be followed by the
3004 representation of blank line).
3008 <sect1 id="f-Binary">
3009 <heading><tt>Binary</tt></heading>
3012 This field is a list of binary packages.
3016 When it appears in the <file>.dsc</file> file it is the list
3017 of binary packages which a source package can produce. It
3018 does not necessarily produce all of these binary packages
3019 for every architecture. The source control file doesn't
3020 contain details of which architectures are appropriate for
3021 which of the binary packages.
3025 When it appears in a <file>.changes</file> file it lists the
3026 names of the binary packages actually being uploaded.
3030 The syntax is a list of binary packages separated by
3032 A space after each comma is conventional.
3033 </footnote>. Currently the packages must be separated using
3034 only spaces in the <file>.changes</file> file.
3038 <sect1 id="f-Installed-Size">
3039 <heading><tt>Installed-Size</tt></heading>
3042 This field appears in the control files of binary
3043 packages, and in the <file>Packages</file> files. It gives
3044 the total amount of disk space required to install the
3049 The disk space is represented in kilobytes as a simple
3054 <sect1 id="f-Files">
3055 <heading><tt>Files</tt></heading>
3058 This field contains a list of files with information about
3059 each one. The exact information and syntax varies with
3060 the context. In all cases the part of the field
3061 contents on the same line as the field name is empty. The
3062 remainder of the field is one line per file, each line
3063 being indented by one space and containing a number of
3064 sub-fields separated by spaces.
3068 In the <file>.dsc</file> file, each line contains the MD5
3069 checksum, size and filename of the tar file and (if applicable)
3070 diff file which make up the remainder of the source
3072 That is, the parts which are not the <tt>.dsc</tt>.
3074 The exact forms of the filenames are described
3075 in <ref id="pkg-sourcearchives">.
3079 In the <file>.changes</file> file this contains one line per
3080 file being uploaded. Each line contains the MD5 checksum,
3081 size, section and priority and the filename.
3082 The <qref id="f-Section">section</qref>
3083 and <qref id="f-Priority">priority</qref>
3084 are the values of the corresponding fields in
3085 the main source control file. If no section or priority is
3086 specified then <tt>-</tt> should be used, though section
3087 and priority values must be specified for new packages to
3088 be installed properly.
3092 The special value <tt>byhand</tt> for the section in a
3093 <tt>.changes</tt> file indicates that the file in question
3094 is not an ordinary package file and must by installed by
3095 hand by the distribution maintainers. If the section is
3096 <tt>byhand</tt> the priority should be <tt>-</tt>.
3100 If a new Debian revision of a package is being shipped and
3101 no new original source archive is being distributed the
3102 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3103 entry for the original source archive
3104 <file><var>package</var>-<var>upstream-version</var>.orig.tar.gz</file>,
3105 but the <file>.changes</file> file should leave it out. In
3106 this case the original source archive on the distribution
3107 site must match exactly, byte-for-byte, the original
3108 source archive which was used to generate the
3109 <file>.dsc</file> file and diff which are being uploaded.</p>
3112 <sect1 id="f-Closes">
3113 <heading><tt>Closes</tt></heading>
3116 A space-separated list of bug report numbers that the upload
3117 governed by the .changes file closes.
3124 <heading>User-defined fields</heading>
3127 Additional user-defined fields may be added to the
3128 source package control file. Such fields will be
3129 ignored, and not copied to (for example) binary or
3130 source package control files or upload control files.
3134 If you wish to add additional unsupported fields to
3135 these output files you should use the mechanism
3140 Fields in the main source control information file with
3141 names starting <tt>X</tt>, followed by one or more of
3142 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3143 be copied to the output files. Only the part of the
3144 field name after the hyphen will be used in the output
3145 file. Where the letter <tt>B</tt> is used the field
3146 will appear in binary package control files, where the
3147 letter <tt>S</tt> is used in source package control
3148 files and where <tt>C</tt> is used in upload control
3149 (<tt>.changes</tt>) files.
3153 For example, if the main source information control file
3156 XBS-Comment: I stand between the candle and the star.
3158 then the binary and source package control files will contain the
3161 Comment: I stand between the candle and the star.
3170 <chapt id="maintainerscripts">
3171 <heading>Package maintainer scripts and installation procedure</heading>
3174 <heading>Introduction to package maintainer scripts</heading>
3177 It is possible to supply scripts as part of a package which
3178 the package management system will run for you when your
3179 package is installed, upgraded or removed.
3183 These scripts are the files <prgn>preinst</prgn>,
3184 <prgn>postinst</prgn>, <prgn>prerm</prgn> and
3185 <prgn>postrm</prgn> in the control area of the package.
3186 They must be proper executable files; if they are scripts
3187 (which is recommended), they must start with the usual
3188 <tt>#!</tt> convention. They should be readable and
3189 executable by anyone, and must not be world-writable.
3193 The package management system looks at the exit status from
3194 these scripts. It is important that they exit with a
3195 non-zero status if there is an error, so that the package
3196 management system can stop its processing. For shell
3197 scripts this means that you <em>almost always</em> need to
3198 use <tt>set -e</tt> (this is usually true when writing shell
3199 scripts, in fact). It is also important, of course, that
3200 they don't exit with a non-zero status if everything went
3205 Additionally, packages interacting with users using
3206 <tt>debconf</tt> in the <prgn>postinst</prgn> script should
3207 install a <prgn>config</prgn> script in the control area,
3208 see <ref id="maintscriptprompt"> for details.
3212 When a package is upgraded a combination of the scripts from
3213 the old and new packages is called during the upgrade
3214 procedure. If your scripts are going to be at all
3215 complicated you need to be aware of this, and may need to
3216 check the arguments to your scripts.
3220 Broadly speaking the <prgn>preinst</prgn> is called before
3221 (a particular version of) a package is installed, and the
3222 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3223 before (a version of) a package is removed and the
3224 <prgn>postrm</prgn> afterwards.
3228 Programs called from maintainer scripts should not normally
3229 have a path prepended to them. Before installation is
3230 started, the package management system checks to see if the
3231 programs <prgn>ldconfig</prgn>,
3232 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3233 and <prgn>update-rc.d</prgn> can be found via the
3234 <tt>PATH</tt> environment variable. Those programs, and any
3235 other program that one would expect to be in the
3236 <tt>PATH</tt>, should thus be invoked without an absolute
3237 pathname. Maintainer scripts should also not reset the
3238 <tt>PATH</tt>, though they might choose to modify it by
3239 prepending or appending package-specific directories. These
3240 considerations really apply to all shell scripts.</p>
3243 <sect id="idempotency">
3244 <heading>Maintainer scripts Idempotency</heading>
3247 It is necessary for the error recovery procedures that the
3248 scripts be idempotent. This means that if it is run
3249 successfully, and then it is called again, it doesn't bomb
3250 out or cause any harm, but just ensures that everything is
3251 the way it ought to be. If the first call failed, or
3252 aborted half way through for some reason, the second call
3253 should merely do the things that were left undone the first
3254 time, if any, and exit with a success status if everything
3256 This is so that if an error occurs, the user interrupts
3257 <prgn>dpkg</prgn> or some other unforeseen circumstance
3258 happens you don't leave the user with a badly-broken
3259 package when <prgn>dpkg</prgn> attempts to repeat the
3265 <sect id="controllingterminal">
3266 <heading>Controlling terminal for maintainer scripts</heading>
3269 The maintainer scripts are guaranteed to run with a
3270 controlling terminal and can interact with the user.
3271 Because these scripts may be executed with standard output
3272 redirected into a pipe for logging purposes, Perl scripts
3273 should set unbuffered output by setting <tt>$|=1</tt> so
3274 that the output is printed immediately rather than being
3278 <sect id="exitstatus">
3279 <heading>Exit status</heading>
3282 Each script must return a zero exit status for
3283 success, or a nonzero one for failure, since the package
3284 management system looks for the exit status of these scripts
3285 and determines what action to take next based on that datum.
3289 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3294 <list compact="compact">
3296 <var>new-preinst</var> <tt>install</tt>
3299 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3302 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3305 <var>old-preinst</var> <tt>abort-upgrade</tt>
3306 <var>new-version</var>
3311 <list compact="compact">
3313 <var>postinst</var> <tt>configure</tt>
3314 <var>most-recently-configured-version</var>
3317 <var>old-postinst</var> <tt>abort-upgrade</tt>
3318 <var>new-version</var>
3321 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3322 <tt>in-favour</tt> <var>package</var>
3323 <var>new-version</var>
3326 <var>postinst</var> <tt>abort-remove</tt>
3329 <var>deconfigured's-postinst</var>
3330 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3331 <var>failed-install-package</var> <var>version</var>
3332 <tt>removing</tt> <var>conflicting-package</var>
3338 <list compact="compact">
3340 <var>prerm</var> <tt>remove</tt>
3343 <var>old-prerm</var> <tt>upgrade</tt>
3344 <var>new-version</var>
3347 <var>new-prerm</var> <tt>failed-upgrade</tt>
3348 <var>old-version</var>
3351 <var>conflictor's-prerm</var> <tt>remove</tt>
3352 <tt>in-favour</tt> <var>package</var>
3353 <var>new-version</var>
3356 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3357 <tt>in-favour</tt> <var>package-being-installed</var>
3358 <var>version</var> <tt>removing</tt>
3359 <var>conflicting-package</var>
3365 <list compact="compact">
3367 <var>postrm</var> <tt>remove</tt>
3370 <var>postrm</var> <tt>purge</tt>
3373 <var>old-postrm</var> <tt>upgrade</tt>
3374 <var>new-version</var>
3377 <var>new-postrm</var> <tt>failed-upgrade</tt>
3378 <var>old-version</var>
3381 <var>new-postrm</var> <tt>abort-install</tt>
3384 <var>new-postrm</var> <tt>abort-install</tt>
3385 <var>old-version</var>
3388 <var>new-postrm</var> <tt>abort-upgrade</tt>
3389 <var>old-version</var>
3392 <var>disappearer's-postrm</var> <tt>disappear</tt>
3393 <var>overwriter</var>
3394 <var>overwriter-version</var>
3400 <sect id="unpackphase">
3401 <heading>Details of unpack phase of installation or upgrade</heading>
3404 The procedure on installation/upgrade/overwrite/disappear
3405 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3406 stage of <tt>dpkg --install</tt>) is as follows. In each
3407 case, if a major error occurs (unless listed below) the
3408 actions are, in general, run backwards - this means that the
3409 maintainer scripts are run with different arguments in
3410 reverse order. These are the "error unwind" calls listed
3417 If a version of the package is already installed, call
3418 <example compact="compact">
3419 <var>old-prerm</var> upgrade <var>new-version</var>
3423 If the script runs but exits with a non-zero
3424 exit status, <prgn>dpkg</prgn> will attempt:
3425 <example compact="compact">
3426 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3428 If this works, the upgrade continues. If this
3429 does not work, the error unwind:
3430 <example compact="compact">
3431 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3433 If this works, then the old-version is
3434 "Installed", if not, the old version is in a
3435 "Failed-Config" state.
3441 If a "conflicting" package is being removed at the same time:
3444 If any packages depended on that conflicting
3445 package and <tt>--auto-deconfigure</tt> is
3446 specified, call, for each such package:
3447 <example compact="compact">
3448 <var>deconfigured's-prerm</var> deconfigure \
3449 in-favour <var>package-being-installed</var> <var>version</var> \
3450 removing <var>conflicting-package</var> <var>version</var>
3453 <example compact="compact">
3454 <var>deconfigured's-postinst</var> abort-deconfigure \
3455 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3456 removing <var>conflicting-package</var> <var>version</var>
3458 The deconfigured packages are marked as
3459 requiring configuration, so that if
3460 <tt>--install</tt> is used they will be
3461 configured again if possible.
3464 To prepare for removal of the conflicting package, call:
3465 <example compact="compact">
3466 <var>conflictor's-prerm</var> remove \
3467 in-favour <var>package</var> <var>new-version</var>
3470 <example compact="compact">
3471 <var>conflictor's-postinst</var> abort-remove \
3472 in-favour <var>package</var> <var>new-version</var>
3481 If the package is being upgraded, call:
3482 <example compact="compact">
3483 <var>new-preinst</var> upgrade <var>old-version</var>
3485 If this fails, we call:
3487 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3494 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3496 is called. If this works, then the old version
3497 is in an "Installed" state, or else it is left
3498 in an "Unpacked" state.
3503 If it fails, then the old version is left
3504 in an "Half-Installed" state.
3511 Otherwise, if the package had some configuration
3512 files from a previous version installed (i.e., it
3513 is in the "configuration files only" state):
3514 <example compact="compact">
3515 <var>new-preinst</var> install <var>old-version</var>
3519 <var>new-postrm</var> abort-install <var>old-version</var>
3521 If this fails, the package is left in a
3522 "Half-Installed" state, which requires a
3523 reinstall. If it works, the packages is left in
3524 a "Config Files" state.
3527 Otherwise (i.e., the package was completely purged):
3528 <example compact="compact">
3529 <var>new-preinst</var> install
3532 <example compact="compact">
3533 <var>new-postrm</var> abort-install
3535 If the error-unwind fails, the package is in a
3536 "Half Installed" phase, and requires a
3537 reinstall. If the error unwind works, the
3538 package is in a not installed state.
3545 The new package's files are unpacked, overwriting any
3546 that may be on the system already, for example any
3547 from the old version of the same package or from
3548 another package. Backups of the old files are kept
3549 temporarily, and if anything goes wrong the package
3550 management system will attempt to put them back as
3551 part of the error unwind.
3555 It is an error for a package to contain files which
3556 are on the system in another package, unless
3557 <tt>Replaces</tt> is used (see <ref id="replaces">).
3559 The following paragraph is not currently the case:
3560 Currently the <tt>- - force-overwrite</tt> flag is
3561 enabled, downgrading it to a warning, but this may not
3567 It is a more serious error for a package to contain a
3568 plain file or other kind of non-directory where another
3569 package has a directory (again, unless
3570 <tt>Replaces</tt> is used). This error can be
3571 overridden if desired using
3572 <tt>--force-overwrite-dir</tt>, but this is not
3577 Packages which overwrite each other's files produce
3578 behavior which, though deterministic, is hard for the
3579 system administrator to understand. It can easily
3580 lead to "missing" programs if, for example, a package
3581 is installed which overwrites a file from another
3582 package, and is then removed again.<footnote>
3583 Part of the problem is due to what is arguably a
3584 bug in <prgn>dpkg</prgn>.
3589 A directory will never be replaced by a symbolic link
3590 to a directory or vice versa; instead, the existing
3591 state (symlink or not) will be left alone and
3592 <prgn>dpkg</prgn> will follow the symlink if there is
3601 If the package is being upgraded, call
3602 <example compact="compact">
3603 <var>old-postrm</var> upgrade <var>new-version</var>
3607 If this fails, <prgn>dpkg</prgn> will attempt:
3608 <example compact="compact">
3609 <var>new-postrm</var> failed-upgrade <var>old-version</var>
3611 If this works, installation continues. If not,
3613 <example compact="compact">
3614 <var>old-preinst</var> abort-upgrade <var>new-version</var>
3616 If this fails, the old version is left in an
3617 "Half Installed" state. If it works, dpkg now
3619 <example compact="compact">
3620 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3622 If this fails, the old version is left in an
3623 "Half Installed" state. If it works, dpkg now
3625 <example compact="compact">
3626 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3628 If this fails, the old version is in an
3635 This is the point of no return - if
3636 <prgn>dpkg</prgn> gets this far, it won't back off
3637 past this point if an error occurs. This will
3638 leave the package in a fairly bad state, which
3639 will require a successful re-installation to clear
3640 up, but it's when <prgn>dpkg</prgn> starts doing
3641 things that are irreversible.
3646 Any files which were in the old version of the package
3647 but not in the new are removed.
3651 The new file list replaces the old.
3655 The new maintainer scripts replace the old.
3659 Any packages all of whose files have been overwritten
3660 during the installation, and which aren't required for
3661 dependencies, are considered to have been removed.
3662 For each such package
3665 <prgn>dpkg</prgn> calls:
3666 <example compact="compact">
3667 <var>disappearer's-postrm</var> disappear \
3668 <var>overwriter</var> <var>overwriter-version</var>
3672 The package's maintainer scripts are removed.
3675 It is noted in the status database as being in a
3676 sane state, namely not installed (any conffiles
3677 it may have are ignored, rather than being
3678 removed by <prgn>dpkg</prgn>). Note that
3679 disappearing packages do not have their prerm
3680 called, because <prgn>dpkg</prgn> doesn't know
3681 in advance that the package is going to
3688 Any files in the package we're unpacking that are also
3689 listed in the file lists of other packages are removed
3690 from those lists. (This will lobotomize the file list
3691 of the "conflicting" package if there is one.)
3695 The backup files made during installation, above, are
3701 The new package's status is now sane, and recorded as
3706 Here is another point of no return - if the
3707 conflicting package's removal fails we do not unwind
3708 the rest of the installation; the conflicting package
3709 is left in a half-removed limbo.
3714 If there was a conflicting package we go and do the
3715 removal actions (described below), starting with the
3716 removal of the conflicting package's files (any that
3717 are also in the package being installed have already
3718 been removed from the conflicting package's file list,
3719 and so do not get removed now).
3725 <sect id="configdetails"><heading>Details of configuration</heading>
3728 When we configure a package (this happens with <tt>dpkg
3729 --install</tt> and <tt>dpkg --configure</tt>), we first
3730 update any <tt>conffile</tt>s and then call:
3731 <example compact="compact">
3732 <var>postinst</var> configure <var>most-recently-configured-version</var>
3737 No attempt is made to unwind after errors during
3738 configuration. If the configuration fails, the package is in
3739 a "Failed Config" state, and an error message is generated.
3743 If there is no most recently configured version
3744 <prgn>dpkg</prgn> will pass a null argument.
3747 Historical note: Truly ancient (pre-1997) versions of
3748 <prgn>dpkg</prgn> passed <tt><unknown></tt>
3749 (including the angle brackets) in this case. Even older
3750 ones did not pass a second argument at all, under any
3751 circumstance. Note that upgrades using such an old dpkg
3752 version are unlikely to work for other reasons, even if
3753 this old argument behavior is handled by your postinst script.
3759 <sect id="removedetails"><heading>Details of removal and/or
3760 configuration purging</heading>
3766 <example compact="compact">
3767 <var>prerm</var> remove
3771 If prerm fails during replacement due to conflict
3773 <var>conflictor's-postinst</var> abort-remove \
3774 in-favour <var>package</var> <var>new-version</var>
3778 <var>postinst</var> abort-remove
3782 If this fails, the package is in a "Failed-Config"
3783 state, or else it remains "Installed".
3787 The package's files are removed (except <tt>conffile</tt>s).
3790 <example compact="compact">
3791 <var>postrm</var> remove
3795 If it fails, there's no error unwind, and the package is in
3796 an "Half-Installed" state.
3801 All the maintainer scripts except the <prgn>postrm</prgn>
3806 If we aren't purging the package we stop here. Note
3807 that packages which have no <prgn>postrm</prgn> and no
3808 <tt>conffile</tt>s are automatically purged when
3809 removed, as there is no difference except for the
3810 <prgn>dpkg</prgn> status.
3814 The <tt>conffile</tt>s and any backup files
3815 (<tt>~</tt>-files, <tt>#*#</tt> files,
3816 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
3821 <example compact="compact">
3822 <var>postrm</var> purge
3826 If this fails, the package remains in a "Config-Files"
3831 The package's file list is removed.
3840 <chapt id="relationships">
3841 <heading>Declaring relationships between packages</heading>
3843 <sect id="depsyntax">
3844 <heading>Syntax of relationship fields</heading>
3847 These fields all have a uniform syntax. They are a list of
3848 package names separated by commas.
3852 In the <tt>Depends</tt>, <tt>Recommends</tt>,
3853 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
3854 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
3855 control file fields of the package, which declare
3856 dependencies on other packages, the package names listed may
3857 also include lists of alternative package names, separated
3858 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
3859 if any one of the alternative packages is installed, that
3860 part of the dependency is considered to be satisfied.
3864 All of the fields except for <tt>Provides</tt> may restrict
3865 their applicability to particular versions of each named
3866 package. This is done in parentheses after each individual
3867 package name; the parentheses should contain a relation from
3868 the list below followed by a version number, in the format
3869 described in <ref id="f-Version">.
3873 The relations allowed are <tt><<</tt>, <tt><=</tt>,
3874 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
3875 strictly earlier, earlier or equal, exactly equal, later or
3876 equal and strictly later, respectively. The deprecated
3877 forms <tt><</tt> and <tt>></tt> were used to mean
3878 earlier/later or equal, rather than strictly earlier/later,
3879 so they should not appear in new packages (though
3880 <prgn>dpkg</prgn> still supports them).
3884 Whitespace may appear at any point in the version
3885 specification subject to the rules in <ref
3886 id="controlsyntax">, and must appear where it's necessary to
3887 disambiguate; it is not otherwise significant. For
3888 consistency and in case of future changes to
3889 <prgn>dpkg</prgn> it is recommended that a single space be
3890 used after a version relationship and before a version
3891 number; it is also conventional to put a single space after
3892 each comma, on either side of each vertical bar, and before
3893 each open parenthesis.
3897 For example, a list of dependencies might appear as:
3898 <example compact="compact">
3901 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
3906 All fields that specify build-time relationships
3907 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
3908 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>)
3909 may be restricted to a certain set of architectures. This
3910 is indicated in brackets after each individual package name and
3911 the optional version specification. The brackets enclose a
3912 list of Debian architecture names separated by whitespace.
3913 Exclamation marks may be prepended to each of the names.
3914 (It is not permitted for some names to be prepended with
3915 exclamation marks while others aren't.) If the current Debian
3916 host architecture is not in this list and there are no
3917 exclamation marks in the list, or it is in the list with a
3918 prepended exclamation mark, the package name and the
3919 associated version specification are ignored completely for
3920 the purposes of defining the relationships.
3925 <example compact="compact">
3927 Build-Depends-Indep: texinfo
3928 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
3929 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
3934 Note that the binary package relationship fields such as
3935 <tt>Depends</tt> appear in one of the binary package
3936 sections of the control file, whereas the build-time
3937 relationships such as <tt>Build-Depends</tt> appear in the
3938 source package section of the control file (which is the
3943 <sect id="binarydeps">
3944 <heading>Binary Dependencies - <tt>Depends</tt>,
3945 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
3946 <tt>Pre-Depends</tt>
3950 Packages can declare in their control file that they have
3951 certain relationships to other packages - for example, that
3952 they may not be installed at the same time as certain other
3953 packages, and/or that they depend on the presence of others.
3957 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
3958 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt> and
3959 <tt>Conflicts</tt> control file fields.
3963 These six fields are used to declare a dependency
3964 relationship by one package on another. Except for
3965 <tt>Enhances</tt>, they appear in the depending (binary)
3966 package's control file. (<tt>Enhances</tt> appears in the
3967 recommending package's control file.)
3971 A <tt>Depends</tt> field takes effect <em>only</em> when a
3972 package is to be configured. It does not prevent a package
3973 being on the system in an unconfigured state while its
3974 dependencies are unsatisfied, and it is possible to replace
3975 a package whose dependencies are satisfied and which is
3976 properly installed with a different version whose
3977 dependencies are not and cannot be satisfied; when this is
3978 done the depending package will be left unconfigured (since
3979 attempts to configure it will give errors) and will not
3980 function properly. If it is necessary, a
3981 <tt>Pre-Depends</tt> field can be used, which has a partial
3982 effect even when a package is being unpacked, as explained
3983 in detail below. (The other three dependency fields,
3984 <tt>Recommends</tt>, <tt>Suggests</tt> and
3985 <tt>Enhances</tt>, are only used by the various front-ends
3986 to <prgn>dpkg</prgn> such as <prgn>dselect</prgn>.)
3990 For this reason packages in an installation run are usually
3991 all unpacked first and all configured later; this gives
3992 later versions of packages with dependencies on later
3993 versions of other packages the opportunity to have their
3994 dependencies satisfied.
3998 In case of circular dependencies, since installation or
3999 removal order honoring the dependency order can't be
4000 established, dependency loops are broken at some point
4001 (based on rules below), and some packages may not be able to
4002 rely on their dependencies being present when being
4003 installed or removed, depending on which side of the break
4004 of the circular dependcy loop they happen to be on. If one
4005 of the packages in the loop has no postinst script, then the
4006 cycle will be broken at that package, so as to ensure that
4007 all postinst scripts run with the dependencies properly
4008 configured if this is possible. Otherwise the breaking point
4013 The <tt>Depends</tt> field thus allows package maintainers
4014 to impose an order in which packages should be configured.
4018 The meaning of the five dependency fields is as follows:
4020 <tag><tt>Depends</tt></tag>
4023 This declares an absolute dependency. A package will
4024 not be configured unless all of the packages listed in
4025 its <tt>Depends</tt> field have been correctly
4030 The <tt>Depends</tt> field should be used if the
4031 depended-on package is required for the depending
4032 package to provide a significant amount of
4037 The <tt>Depends</tt> field should also be used if the
4038 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4039 <prgn>postrm</prgn> scripts require the package to be
4040 present in order to run. Note, however, that the
4041 <prgn>postrm</prgn> cannot rely on any non-essential
4042 packages to be present during the <tt>purge</tt>
4046 <tag><tt>Recommends</tt></tag>
4049 This declares a strong, but not absolute, dependency.
4053 The <tt>Recommends</tt> field should list packages
4054 that would be found together with this one in all but
4055 unusual installations.
4059 <tag><tt>Suggests</tt></tag>
4061 This is used to declare that one package may be more
4062 useful with one or more others. Using this field
4063 tells the packaging system and the user that the
4064 listed packages are related to this one and can
4065 perhaps enhance its usefulness, but that installing
4066 this one without them is perfectly reasonable.
4069 <tag><tt>Enhances</tt></tag>
4071 This field is similar to Suggests but works in the
4072 opposite direction. It is used to declare that a
4073 package can enhance the functionality of another
4077 <tag><tt>Pre-Depends</tt></tag>
4080 This field is like <tt>Depends</tt>, except that it
4081 also forces <prgn>dpkg</prgn> to complete installation
4082 of the packages named before even starting the
4083 installation of the package which declares the
4084 pre-dependency, as follows:
4088 When a package declaring a pre-dependency is about to
4089 be <em>unpacked</em> the pre-dependency can be
4090 satisfied if the depended-on package is either fully
4091 configured, <em>or even if</em> the depended-on
4092 package(s) are only unpacked or half-configured,
4093 provided that they have been configured correctly at
4094 some point in the past (and not removed or partially
4095 removed since). In this case, both the
4096 previously-configured and currently unpacked or
4097 half-configured versions must satisfy any version
4098 clause in the <tt>Pre-Depends</tt> field.
4102 When the package declaring a pre-dependency is about
4103 to be <em>configured</em>, the pre-dependency will be
4104 treated as a normal <tt>Depends</tt>, that is, it will
4105 be considered satisfied only if the depended-on
4106 package has been correctly configured.
4110 <tt>Pre-Depends</tt> should be used sparingly,
4111 preferably only by packages whose premature upgrade or
4112 installation would hamper the ability of the system to
4113 continue with any upgrade that might be in progress.
4117 <tt>Pre-Depends</tt> are also required if the
4118 <prgn>preinst</prgn> script depends on the named
4119 package. It is best to avoid this situation if
4127 When selecting which level of dependency to use you should
4128 consider how important the depended-on package is to the
4129 functionality of the one declaring the dependency. Some
4130 packages are composed of components of varying degrees of
4131 importance. Such a package should list using
4132 <tt>Depends</tt> the package(s) which are required by the
4133 more important components. The other components'
4134 requirements may be mentioned as Suggestions or
4135 Recommendations, as appropriate to the components' relative
4140 <sect id="conflicts">
4141 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4144 When one binary package declares a conflict with another
4145 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4146 refuse to allow them to be installed on the system at the
4151 If one package is to be installed, the other must be removed
4152 first - if the package being installed is marked as
4153 replacing (see <ref id="replaces">) the one on the system,
4154 or the one on the system is marked as deselected, or both
4155 packages are marked <tt>Essential</tt>, then
4156 <prgn>dpkg</prgn> will automatically remove the package
4157 which is causing the conflict, otherwise it will halt the
4158 installation of the new package with an error. This
4159 mechanism is specifically designed to produce an error when
4160 the installed package is <tt>Essential</tt>, but the new
4165 A package will not cause a conflict merely because its
4166 configuration files are still installed; it must be at least
4171 A special exception is made for packages which declare a
4172 conflict with their own package name, or with a virtual
4173 package which they provide (see below): this does not
4174 prevent their installation, and allows a package to conflict
4175 with others providing a replacement for it. You use this
4176 feature when you want the package in question to be the only
4177 package providing some feature.
4181 A <tt>Conflicts</tt> entry should almost never have an
4182 "earlier than" version clause. This would prevent
4183 <prgn>dpkg</prgn> from upgrading or installing the package
4184 which declared such a conflict until the upgrade or removal
4185 of the conflicted-with package had been completed.
4189 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4193 As well as the names of actual ("concrete") packages, the
4194 package relationship fields <tt>Depends</tt>,
4195 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4196 <tt>Pre-Depends</tt>, <tt>Conflicts</tt>,
4197 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4198 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4199 may mention "virtual packages".
4203 A <em>virtual package</em> is one which appears in the
4204 <tt>Provides</tt> control file field of another package.
4205 The effect is as if the package(s) which provide a
4206 particular virtual package name had been listed by name
4207 everywhere the virtual package name appears. (See also <ref
4212 If there are both concrete and virtual packages of the same
4213 name, then the dependency may be satisfied (or the conflict
4214 caused) by either the concrete package with the name in
4215 question or any other concrete package which provides the
4216 virtual package with the name in question. This is so that,
4217 for example, supposing we have
4218 <example compact="compact">
4221 </example> and someone else releases an enhanced version of
4222 the <tt>bar</tt> package they can say:
4223 <example compact="compact">
4227 and the <tt>bar-plus</tt> package will now also satisfy the
4228 dependency for the <tt>foo</tt> package.
4232 If a dependency or a conflict has a version number attached
4233 then only real packages will be considered to see whether
4234 the relationship is satisfied (or the prohibition violated,
4235 for a conflict) - it is assumed that a real package which
4236 provides the virtual package is not of the "right" version.
4237 So, a <tt>Provides</tt> field may not contain version
4238 numbers, and the version number of the concrete package
4239 which provides a particular virtual package will not be
4240 looked at when considering a dependency on or conflict with
4241 the virtual package name.
4245 It is likely that the ability will be added in a future
4246 release of <prgn>dpkg</prgn> to specify a version number for
4247 each virtual package it provides. This feature is not yet
4248 present, however, and is expected to be used only
4253 If you want to specify which of a set of real packages
4254 should be the default to satisfy a particular dependency on
4255 a virtual package, you should list the real package as an
4256 alternative before the virtual one.
4261 <sect id="replaces"><heading>Overwriting files and replacing
4262 packages - <tt>Replaces</tt></heading>
4265 Packages can declare in their control file that they should
4266 overwrite files in certain other packages, or completely
4267 replace other packages. The <tt>Replaces</tt> control file
4268 field has these two distinct purposes.
4271 <sect1><heading>Overwriting files in other packages</heading>
4274 Firstly, as mentioned before, it is usually an error for a
4275 package to contain files which are on the system in
4280 However, if the overwriting package declares that it
4281 <tt>Replaces</tt> the one containing the file being
4282 overwritten, then <prgn>dpkg</prgn> will replace the file
4283 from the old package with that from the new. The file
4284 will no longer be listed as "owned" by the old package.
4288 If a package is completely replaced in this way, so that
4289 <prgn>dpkg</prgn> does not know of any files it still
4290 contains, it is considered to have "disappeared". It will
4291 be marked as not wanted on the system (selected for
4292 removal) and not installed. Any <tt>conffile</tt>s
4293 details noted for the package will be ignored, as they
4294 will have been taken over by the overwriting package. The
4295 package's <prgn>postrm</prgn> script will be run with a
4296 special argument to allow the package to do any final
4297 cleanup required. See <ref id="mscriptsinstact">.
4300 Replaces is a one way relationship -- you have to
4301 install the replacing package after the replaced
4308 For this usage of <tt>Replaces</tt>, virtual packages (see
4309 <ref id="virtual">) are not considered when looking at a
4310 <tt>Replaces</tt> field - the packages declared as being
4311 replaced must be mentioned by their real names.
4315 Furthermore, this usage of <tt>Replaces</tt> only takes
4316 effect when both packages are at least partially on the
4317 system at once, so that it can only happen if they do not
4318 conflict or if the conflict has been overridden.
4323 <sect1><heading>Replacing whole packages, forcing their
4327 Secondly, <tt>Replaces</tt> allows the packaging system to
4328 resolve which package should be removed when there is a
4329 conflict - see <ref id="conflicts">. This usage only
4330 takes effect when the two packages <em>do</em> conflict,
4331 so that the two usages of this field do not interfere with
4336 In this situation, the package declared as being replaced
4337 can be a virtual package, so for example, all mail
4338 transport agents (MTAs) would have the following fields in
4339 their control files:
4340 <example compact="compact">
4341 Provides: mail-transport-agent
4342 Conflicts: mail-transport-agent
4343 Replaces: mail-transport-agent
4345 ensuring that only one MTA can be installed at any one
4350 <sect id="sourcebinarydeps">
4351 <heading>Relationships between source and binary packages -
4352 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4353 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
4357 Source packages that require certain binary packages to be
4358 installed or absent at the time of building the package
4359 can declare relationships to those binary packages.
4363 This is done using the <tt>Build-Depends</tt>,
4364 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
4365 <tt>Build-Conflicts-Indep</tt> control file fields.
4369 Build-dependencies on "build-essential" binary packages can be
4370 omitted. Please see <ref id="pkg-relations"> for more information.
4374 The dependencies and conflicts they define must be satisfied
4375 (as defined earlier for binary packages) in order to invoke
4376 the targets in <tt>debian/rules</tt>, as follows:<footnote>
4378 If you make "build-arch" or "binary-arch", you need
4379 Build-Depends. If you make "build-indep" or
4380 "binary-indep", you need Build-Depends and
4381 Build-Depends-Indep. If you make "build" or "binary",
4385 There is no Build-Depends-Arch; this role is essentially
4386 met with Build-Depends. Anyone building the
4387 <tt>build-indep</tt> and binary-indep<tt></tt> targets
4388 is basically assumed to be building the whole package
4389 anyway and so installs all build dependencies. The
4390 autobuilders use <tt>dpkg-buildpackage -B</tt>, which
4391 calls <tt>build</tt> (not <tt>build-arch</tt>, since it
4392 does not yet know how to check for its existence) and
4393 <tt>binary-arch</tt>.
4396 The purpose of the original split, I recall, was so that
4397 the autobuilders wouldn't need to install extra packages
4398 needed only for the binary-indep targets. But without a
4399 build-arch/build-indep split, this didn't work, since
4400 most of the work is done in the build target, not in the
4406 <tag><tt>Build-Depends</tt>, <tt>Build-Conflicts</tt></tag>
4408 The <tt>Build-Depends</tt> and
4409 <tt>Build-Conflicts</tt> fields must be satisfied when
4410 any of the following targets is invoked:
4411 <tt>build</tt>, <tt>clean</tt>, <tt>binary</tt>,
4412 <tt>binary-arch</tt>, <tt>build-arch</tt>,
4413 <tt>build-indep</tt> and <tt>binary-indep</tt>.
4415 <tag><tt>Build-Depends-Indep</tt>,
4416 <tt>Build-Conflicts-Indep</tt></tag>
4418 The <tt>Build-Depends-Indep</tt> and
4419 <tt>Build-Conflicts-Indep</tt> fields must be
4420 satisfied when any of the following targets is
4421 invoked: <tt>build</tt>, <tt>build-indep</tt>,
4422 <tt>binary</tt> and <tt>binary-indep</tt>.
4432 <chapt id="sharedlibs"><heading>Shared libraries</heading>
4435 Packages containing shared libraries must be constructed with
4436 a little care to make sure that the shared library is always
4437 available. This is especially important for packages whose
4438 shared libraries are vitally important, such as the C library
4439 (currently <tt>libc6</tt>).
4443 Packages involving shared libraries should be split up into
4444 several binary packages. This section mostly deals with how
4445 this separation is to be accomplished; rules for files within
4446 the shared library packages are in <ref id="libraries"> instead.
4449 <sect id="sharedlibs-runtime">
4450 <heading>Run-time shared libraries</heading>
4453 The run-time shared library needs to be placed in a package
4454 whose name changes whenever the shared object version
4457 Since it is common place to install several versions of a
4458 package that just provides shared libraries, it is a
4459 good idea that the library package should not
4460 contain any extraneous non-versioned files, unless they
4461 happen to be in versioned directories.</p>
4463 The most common mechanism is to place it in a package
4465 <package><var>libraryname</var><var>soversion</var></package>,
4466 where <file><var>soversion</var></file> is the version number
4467 in the soname of the shared library<footnote>
4468 The soname is the shared object name: it's the thing
4469 that has to match exactly between building an executable
4470 and running it for the dynamic linker to be able run the
4471 program. For example, if the soname of the library is
4472 <file>libfoo.so.6</file>, the library package would be
4473 called <file>libfoo6</file>.
4475 Alternatively, if it would be confusing to directly append
4476 <var>soversion</var> to <var>libraryname</var> (e.g. because
4477 <var>libraryname</var> itself ends in a number), you may use
4478 <package><var>libraryname</var>-<var>soversion</var></package> and
4479 <package><var>libraryname</var>-<var>soversion</var>-dev</package>
4484 If your package includes run-time support programs that
4485 do not need to be invoked manually by users, but are
4486 nevertheless required for the package to function, then it
4487 is recommended that these programs are placed
4488 (if they are binary) in a subdirectory of
4489 <file>/usr/lib</file>, preferably under
4490 <file>/usr/lib/</file><var>package-name</var>.
4491 If the program is architecture independent, the
4492 recommendation is for it to be placed in a subdirectory of
4493 <file>/usr/share</file> instead, preferably under
4494 <file>/usr/share/</file><var>package-name</var>.
4499 If you have several shared libraries built from the same
4500 source tree you may lump them all together into a single
4501 shared library package, provided that you change all of
4502 their sonames at once (so that you don't get filename
4503 clashes if you try to install different versions of the
4504 combined shared libraries package).
4508 The package should install the shared libraries under
4509 their normal names. For example, the <package>libgdbm3</package>
4510 package should install <file>libgdbm.so.3.0.0</file> as
4511 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
4512 renamed or re-linked by any <prgn>prerm</prgn> or
4513 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
4514 of renaming things safely without affecting running programs,
4515 and attempts to interfere with this are likely to lead to
4520 Shared libraries should not be installed executable, since
4521 the dynamic linker does not require this and trying to
4522 execute a shared library usually results in a core dump.
4526 The run-time library package should include the symbolic link that
4527 <prgn>ldconfig</prgn> would create for the shared libraries.
4528 For example, the <package>libgdbm3</package> package should include
4529 a symbolic link from <file>/usr/lib/libgdbm.so.3</file> to
4530 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
4531 linker (for example <prgn>ld.so</prgn> or
4532 <prgn>ld-linux.so.*</prgn>) can find the library between the
4533 time that <prgn>dpkg</prgn> installs it and the time that
4534 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
4536 The package management system requires the library to be
4537 placed before the symbolic link pointing to it in the
4538 <file>.deb</file> file. This is so that when
4539 <prgn>dpkg</prgn> comes to install the symlink
4540 (overwriting the previous symlink pointing at an older
4541 version of the library), the new shared library is already
4542 in place. In the past, this was achieved by creating the
4543 library in the temporary packaging directory before
4544 creating the symlink. Unfortunately, this was not always
4545 effective, since the building of the tar file in the
4546 <file>.deb</file> depended on the behavior of the underlying
4547 file system. Some file systems (such as reiserfs) reorder
4548 the files so that the order of creation is forgotten.
4549 Since version 1.7.0, <prgn>dpkg</prgn>
4550 reorders the files itself as necessary when building a
4551 package. Thus it is no longer important to concern
4552 oneself with the order of file creation.
4556 <sect1 id="ldconfig">
4557 <heading><tt>ldconfig</tt></heading>
4560 Any package installing shared libraries in one of the default
4561 library directories of the dynamic linker (which are currently
4562 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
4563 listed in <file>/etc/ld.so.conf</file><footnote>
4565 <list compact="compact">
4566 <item>/usr/local/lib</item>
4567 <item>/usr/lib/libc5-compat</item>
4568 <item>/lib/libc5-compat</item>
4571 must use <prgn>ldconfig</prgn> to update the shared library
4576 The package maintainer scripts must only call
4577 <prgn>ldconfig</prgn> under these circumstances:
4578 <list compact="compact">
4579 <item>When the <prgn>postinst</prgn> script is run with a
4580 first argument of <tt>configure</tt>, the script must call
4581 <prgn>ldconfig</prgn>, and may optionally invoke
4582 <prgn>ldconfig</prgn> at other times.
4584 <item>When the <prgn>postrm</prgn> script is run with a
4585 first argument of <tt>remove</tt>, the script should call
4586 <prgn>ldconfig</prgn>.
4591 During install or upgrade, the preinst is called before
4592 the new files are installed, so calling "ldconfig" is
4593 pointless. The preinst of an existing package can also be
4594 called if an upgrade fails. However, this happens during
4595 the critical time when a shared libs may exist on-disk
4596 under a temporary name. Thus, it is dangerous and
4597 forbidden by current policy to call "ldconfig" at this
4602 When a package is installed or upgraded, "postinst
4603 configure" runs after the new files are safely on-disk.
4604 Since it is perfectly safe to invoke ldconfig
4605 unconditionally in a postinst, it is OK for a package to
4606 simply put ldconfig in its postinst without checking the
4607 argument. The postinst can also be called to recover from
4608 a failed upgrade. This happens before any new files are
4609 unpacked, so there is no reason to call "ldconfig" at this
4614 For a package that is being removed, prerm is
4615 called with all the files intact, so calling ldconfig is
4616 useless. The other calls to "prerm" happen in the case of
4617 upgrade at a time when all the files of the old package
4618 are on-disk, so again calling "ldconfig" is pointless.
4622 postrm, on the other hand, is called with the "remove"
4623 argument just after the files are removed, so this is
4624 the proper time to call "ldconfig" to notify the system
4625 of the fact that the shared libraries from the package
4626 are removed. The postrm can be called at several other
4627 times. At the time of "postrm purge", "postrm
4628 abort-install", or "postrm abort-upgrade", calling
4629 "ldconfig" is useless because the shared lib files are
4630 not on-disk. However, when "postrm" is invoked with
4631 arguments "upgrade", "failed-upgrade", or "disappear", a
4632 shared lib may exist on-disk under a temporary filename.
4640 <sect id="sharedlibs-runtime-progs">
4641 <heading>Run-time support programs</heading>
4644 If your package has some run-time support programs which use
4645 the shared library you must not put them in the shared
4646 library package. If you do that then you won't be able to
4647 install several versions of the shared library without
4648 getting filename clashes.
4652 Instead, either create another package for the runtime binaries
4653 (this package might typically be named
4654 <package><var>libraryname</var>-runtime</package>; note the absence
4655 of the <var>soversion</var> in the package name), or if the
4656 development package is small, include them in there.
4660 <sect id="sharedlibs-static">
4661 <heading>Static libraries</heading>
4664 The static library (<file><var>libraryname.a</var></file>)
4665 is usually provided in addition to the shared version.
4666 It is placed into the development package (see below).
4670 In some cases, it is acceptable for a library to be
4671 available in static form only; these cases include:
4673 <item>libraries for languages whose shared library support
4674 is immature or unstable</item>
4675 <item>libraries whose interfaces are in flux or under
4676 development (commonly the case when the library's
4677 major version number is zero, or where the ABI breaks
4678 across patchlevels)</item>
4679 <item>libraries which are explicitly intended to be
4680 available only in static form by their upstream
4685 <sect id="sharedlibs-dev">
4686 <heading>Development files</heading>
4689 The development files associated to a shared library need to be
4690 placed in a package called
4691 <package><var>libraryname</var><var>soversion</var>-dev</package>,
4692 or if you prefer only to support one development version at a
4693 time, <package><var>libraryname</var>-dev</package>.
4697 In case several development versions of a library exist, you may
4698 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
4699 <ref id="conflicts">) to ensure that the user only installs one
4700 development version at a time (as different development versions are
4701 likely to have the same header files in them, which would cause a
4702 filename clash if both were installed).
4706 The development package should contain a symlink for the associated
4707 shared library without a version number. For example, the
4708 <package>libgdbm-dev</package> package should include a symlink
4709 from <file>/usr/lib/libgdbm.so</file> to
4710 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
4711 (<prgn>ld</prgn>) when compiling packages, as it will only look for
4712 <file>libgdbm.so</file> when compiling dynamically.
4716 <sect id="sharedlibs-intradeps">
4717 <heading>Dependencies between the packages of the same library</heading>
4720 Typically the development version should have an exact
4721 version dependency on the runtime library, to make sure that
4722 compilation and linking happens correctly. The
4723 <tt>${binary:Version}</tt> substitution variable can be
4724 useful for this purpose.
4726 Previously, <tt>${Source-Version}</tt> was used, but its name
4727 was confusing and it has been deprecated since dpkg 1.13.19.
4732 <sect id="sharedlibs-shlibdeps">
4733 <heading>Dependencies between the library and other packages -
4734 the <tt>shlibs</tt> system</heading>
4737 If a package contains a binary or library which links to a
4738 shared library, we must ensure that when the package is
4739 installed on the system, all of the libraries needed are
4740 also installed. This requirement led to the creation of the
4741 <tt>shlibs</tt> system, which is very simple in its design:
4742 any package which <em>provides</em> a shared library also
4743 provides information on the package dependencies required to
4744 ensure the presence of this library, and any package which
4745 <em>uses</em> a shared library uses this information to
4746 determine the dependencies it requires. The files which
4747 contain the mapping from shared libraries to the necessary
4748 dependency information are called <file>shlibs</file> files.
4752 Thus, when a package is built which contains any shared
4753 libraries, it must provide a <file>shlibs</file> file for other
4754 packages to use, and when a package is built which contains
4755 any shared libraries or compiled binaries, it must run
4756 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
4757 on these to determine the libraries used and hence the
4758 dependencies needed by this package.<footnote>
4760 In the past, the shared libraries linked to were
4761 determined by calling <prgn>ldd</prgn>, but now
4762 <prgn>objdump</prgn> is used to do this. The only
4763 change this makes to package building is that
4764 <prgn>dpkg-shlibdeps</prgn> must also be run on shared
4765 libraries, whereas in the past this was unnecessary.
4766 The rest of this footnote explains the advantage that
4771 We say that a binary <tt>foo</tt> <em>directly</em> uses
4772 a library <tt>libbar</tt> if it is explicitly linked
4773 with that library (that is, it uses the flag
4774 <tt>-lbar</tt> during the linking stage). Other
4775 libraries that are needed by <tt>libbar</tt> are linked
4776 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
4777 linker will load them automatically when it loads
4778 <tt>libbar</tt>. A package should depend on
4779 the libraries it directly uses, and the dependencies for
4780 those libraries should automatically pull in the other
4785 Unfortunately, the <prgn>ldd</prgn> program shows both
4786 the directly and indirectly used libraries, meaning that
4787 the dependencies determined included both direct and
4788 indirect dependencies. The use of <prgn>objdump</prgn>
4789 avoids this problem by determining only the directly
4794 A good example of where this helps is the following. We
4795 could update <tt>libimlib</tt> with a new version that
4796 supports a new graphics format called dgf (but retaining
4797 the same major version number). If we used the old
4798 <prgn>ldd</prgn> method, every package that uses
4799 <tt>libimlib</tt> would need to be recompiled so it
4800 would also depend on <tt>libdgf</tt> or it wouldn't run
4801 due to missing symbols. However with the new system,
4802 packages using <tt>libimlib</tt> can rely on
4803 <tt>libimlib</tt> itself having the dependency on
4804 <tt>libdgf</tt> and so they would not need rebuilding.
4810 In the following sections, we will first describe where the
4811 various <tt>shlibs</tt> files are to be found, then how to
4812 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
4813 file format and how to create them if your package contains a
4818 <heading>The <tt>shlibs</tt> files present on the system</heading>
4821 There are several places where <tt>shlibs</tt> files are
4822 found. The following list gives them in the order in which
4824 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
4825 (The first one which gives the required information is used.)
4831 <p><file>debian/shlibs.local</file></p>
4834 This lists overrides for this package. Its use is
4835 described below (see <ref id="shlibslocal">).
4840 <p><file>/etc/dpkg/shlibs.override</file></p>
4843 This lists global overrides. This list is normally
4844 empty. It is maintained by the local system
4850 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
4853 When packages are being built, any
4854 <file>debian/shlibs</file> files are copied into the
4855 control file area of the temporary build directory and
4856 given the name <file>shlibs</file>. These files give
4857 details of any shared libraries included in the
4859 An example may help here. Let us say that the
4860 source package <tt>foo</tt> generates two binary
4861 packages, <tt>libfoo2</tt> and
4862 <tt>foo-runtime</tt>. When building the binary
4863 packages, the two packages are created in the
4864 directories <file>debian/libfoo2</file> and
4865 <file>debian/foo-runtime</file> respectively.
4866 (<file>debian/tmp</file> could be used instead of one
4867 of these.) Since <tt>libfoo2</tt> provides the
4868 <tt>libfoo</tt> shared library, it will require a
4869 <tt>shlibs</tt> file, which will be installed in
4870 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually
4872 <file>/var/lib/dpkg/info/libfoo2.shlibs</file>. Then
4873 when <prgn>dpkg-shlibdeps</prgn> is run on the
4875 <file>debian/foo-runtime/usr/bin/foo-prog</file>, it
4877 <file>debian/libfoo2/DEBIAN/shlibs</file> file to
4878 determine whether <tt>foo-prog</tt>'s library
4879 dependencies are satisfied by any of the libraries
4880 provided by <tt>libfoo2</tt>. For this reason,
4881 <prgn>dpkg-shlibdeps</prgn> must only be run once
4882 all of the individual binary packages'
4883 <tt>shlibs</tt> files have been installed into the
4890 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
4893 These are the <file>shlibs</file> files corresponding to
4894 all of the packages installed on the system, and are
4895 maintained by the relevant package maintainers.
4900 <p><file>/etc/dpkg/shlibs.default</file></p>
4903 This file lists any shared libraries whose packages
4904 have failed to provide correct <file>shlibs</file> files.
4905 It was used when the <file>shlibs</file> setup was first
4906 introduced, but it is now normally empty. It is
4907 maintained by the <tt>dpkg</tt> maintainer.
4915 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
4916 <file>shlibs</file> files</heading>
4920 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
4921 into your <file>debian/rules</file> file. If your package
4922 contains only compiled binaries and libraries (but no scripts),
4923 you can use a command such as:
4924 <example compact="compact">
4925 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
4926 debian/tmp/usr/lib/*
4928 Otherwise, you will need to explicitly list the compiled
4929 binaries and libraries.<footnote>
4930 If you are using <tt>debhelper</tt>, the
4931 <prgn>dh_shlibdeps</prgn> program will do this work for
4932 you. It will also correctly handle multi-binary
4938 This command puts the dependency information into the
4939 <file>debian/substvars</file> file, which is then used by
4940 <prgn>dpkg-gencontrol</prgn>. You will need to place a
4941 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
4942 field in the control file for this to work.
4946 If <prgn>dpkg-shlibdeps</prgn> doesn't complain, you're
4947 done. If it does complain you might need to create your own
4948 <file>debian/shlibs.local</file> file, as explained below (see
4949 <ref id="shlibslocal">).
4953 If you have multiple binary packages, you will need to call
4954 <prgn>dpkg-shlibdeps</prgn> on each one which contains
4955 compiled libraries or binaries. In such a case, you will
4956 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
4957 utilities to specify a different <file>substvars</file> file.
4961 For more details on dpkg-shlibdeps, please see
4962 <ref id="pkg-dpkg-shlibdeps"> and
4963 <manref name="dpkg-shlibdeps" section="1">.
4968 <heading>The <file>shlibs</file> File Format</heading>
4971 Each <file>shlibs</file> file has the same format. Lines
4972 beginning with <tt>#</tt> are considered to be comments and
4973 are ignored. Each line is of the form:
4974 <example compact="compact">
4975 <var>library-name</var> <var>soname-version-number</var> <var>dependencies ...</var>
4980 We will explain this by reference to the example of the
4981 <tt>zlib1g</tt> package, which (at the time of writing)
4982 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
4986 <var>library-name</var> is the name of the shared library,
4987 in this case <tt>libz</tt>. (This must match the name part
4988 of the soname, see below.)
4992 <var>soname-version-number</var> is the version part of the
4993 soname of the library. The soname is the thing that must
4994 exactly match for the library to be recognized by the
4995 dynamic linker, and is usually of the form
4996 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
4997 example, <tt>libz.so.1</tt>.<footnote>
4998 This can be determined using the command
4999 <example compact="compact">
5000 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5003 The version part is the part which comes after
5004 <tt>.so.</tt>, so in our case, it is <tt>1</tt>.
5008 <var>dependencies</var> has the same syntax as a dependency
5009 field in a binary package control file. It should give
5010 details of which packages are required to satisfy a binary
5011 built against the version of the library contained in the
5012 package. See <ref id="depsyntax"> for details.
5016 In our example, if the first version of the <tt>zlib1g</tt>
5017 package which contained a minor number of at least
5018 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5019 <tt>shlibs</tt> entry for this library could say:
5020 <example compact="compact">
5021 libz 1 zlib1g (>= 1:1.1.3)
5023 The version-specific dependency is to avoid warnings from
5024 the dynamic linker about using older shared libraries with
5030 <heading>Providing a <file>shlibs</file> file</heading>
5033 If your package provides a shared library, you need to create
5034 a <file>shlibs</file> file following the format described above.
5035 It is usual to call this file <file>debian/shlibs</file> (but if
5036 you have multiple binary packages, you might want to call it
5037 <file>debian/shlibs.<var>package</var></file> instead). Then
5038 let <file>debian/rules</file> install it in the control area:
5039 <example compact="compact">
5040 install -m644 debian/shlibs debian/tmp/DEBIAN
5042 or, in the case of a multi-binary package:
5043 <example compact="compact">
5044 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5046 An alternative way of doing this is to create the
5047 <file>shlibs</file> file in the control area directly from
5048 <file>debian/rules</file> without using a <file>debian/shlibs</file>
5049 file at all,<footnote>
5050 This is what <prgn>dh_makeshlibs</prgn> in the
5051 <tt>debhelper</tt> suite does.
5053 since the <file>debian/shlibs</file> file itself is ignored by
5054 <prgn>dpkg-shlibdeps</prgn>.
5058 As <prgn>dpkg-shlibdeps</prgn> reads the
5059 <file>DEBIAN/shlibs</file> files in all of the binary packages
5060 being built from this source package, all of the
5061 <file>DEBIAN/shlibs</file> files should be installed before
5062 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5067 <sect1 id="shlibslocal">
5068 <heading>Writing the <file>debian/shlibs.local</file> file</heading>
5071 This file is intended only as a <em>temporary</em> fix if
5072 your binaries or libraries depend on a library whose package
5073 does not yet provide a correct <file>shlibs</file> file.
5077 We will assume that you are trying to package a binary
5078 <tt>foo</tt>. When you try running
5079 <prgn>dpkg-shlibdeps</prgn> you get the following error
5080 message (<tt>-O</tt> displays the dependency information on
5081 <tt>stdout</tt> instead of writing it to
5082 <tt>debian/substvars</tt>, and the lines have been wrapped
5083 for ease of reading):
5084 <example compact="compact">
5085 $ dpkg-shlibdeps -O debian/tmp/usr/bin/foo
5086 dpkg-shlibdeps: warning: unable to find dependency
5087 information for shared library libbar (soname 1,
5088 path /usr/lib/libbar.so.1, dependency field Depends)
5089 shlibs:Depends=libc6 (>= 2.2.2-2)
5091 You can then run <prgn>ldd</prgn> on the binary to find the
5092 full location of the library concerned:
5093 <example compact="compact">
5095 libbar.so.1 => /usr/lib/libbar.so.1 (0x4001e000)
5096 libc.so.6 => /lib/libc.so.6 (0x40032000)
5097 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
5099 So the <prgn>foo</prgn> binary depends on the
5100 <prgn>libbar</prgn> shared library, but no package seems to
5101 provide a <file>*.shlibs</file> file handling
5102 <file>libbar.so.1</file> in <file>/var/lib/dpkg/info/</file>. Let's
5103 determine the package responsible:
5104 <example compact="compact">
5105 $ dpkg -S /usr/lib/libbar.so.1
5106 bar1: /usr/lib/libbar.so.1
5107 $ dpkg -s bar1 | grep Version
5110 This tells us that the <tt>bar1</tt> package, version 1.0-1,
5111 is the one we are using. Now we can file a bug against the
5112 <tt>bar1</tt> package and create our own
5113 <file>debian/shlibs.local</file> to locally fix the problem.
5114 Including the following line into your
5115 <file>debian/shlibs.local</file> file:
5116 <example compact="compact">
5117 libbar 1 bar1 (>= 1.0-1)
5119 should allow the package build to work.
5123 As soon as the maintainer of <tt>bar1</tt> provides a
5124 correct <file>shlibs</file> file, you should remove this line
5125 from your <file>debian/shlibs.local</file> file. (You should
5126 probably also then have a versioned <tt>Build-Depends</tt>
5127 on <tt>bar1</tt> to help ensure that others do not have the
5128 same problem building your package.)
5137 <chapt id="opersys"><heading>The Operating System</heading>
5140 <heading>File system hierarchy</heading>
5144 <heading>File system Structure</heading>
5147 The location of all installed files and directories must
5148 comply with the File system Hierarchy Standard (FHS),
5149 version 2.3, with the exceptions noted below, and except
5150 where doing so would violate other terms of Debian
5151 Policy. The following exceptions to the FHS apply:
5156 Legacy XFree86 servers are permitted to retain the
5157 configuration file location
5158 <file>/etc/X11/XF86Config-4</file>.
5163 The optional rules related to user specific
5164 configuration files for applications are stored in
5165 the user's home directory are relaxed. It is
5166 recommended that such files start with the
5167 '<tt>.</tt>' character (a "dot file"), and if an
5168 application needs to create more than one dot file
5169 then the preferred placement is in a subdirectory
5170 with a name starting with a '.' character, (a "dot
5171 directory"). In this case it is recommended the
5172 configuration files not start with the '.'
5178 The requirement for amd64 to use <file>/lib64</file>
5179 for 64 bit binaries is removed.
5184 The requirement that
5185 <file>/usr/local/share/man</file> be "synonymous"
5186 with <file>/usr/local/man</file> is relaxed to a
5191 The requirement that windowmanagers with a single
5192 configuration file call it <file>system.*wmrc</file>
5193 is removed, as is the restriction that the window
5194 manager subdirectory be named identically to the
5195 window manager name itself.
5200 The requirement that boot manager configuration
5201 files live in <file>/etc</file>, or at least are
5202 symlinked there, is relaxed to a recommendation.
5209 The version of this document referred here can be
5210 found in the <tt>debian-policy</tt> package or on <url
5211 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5212 name="FHS (Debian copy)"> alongside this manual (or, if
5213 you have the <package>debian-policy</package> installed,
5215 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5216 (local copy)">). The
5217 latest version, which may be a more recent version, may
5219 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5220 Specific questions about following the standard may be
5221 asked on the <tt>debian-devel</tt> mailing list, or
5222 referred to the FHS mailing list (see the
5223 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
5229 <heading>Site-specific programs</heading>
5232 As mandated by the FHS, packages must not place any
5233 files in <file>/usr/local</file>, either by putting them in
5234 the file system archive to be unpacked by <prgn>dpkg</prgn>
5235 or by manipulating them in their maintainer scripts.
5239 However, the package may create empty directories below
5240 <file>/usr/local</file> so that the system administrator knows
5241 where to place site-specific files. These are not
5242 directories <em>in</em> <file>/usr/local</file>, but are
5243 children of directories in <file>/usr/local</file>. These
5244 directories (<file>/usr/local/*/dir/</file>)
5245 should be removed on package removal if they are
5250 Note, that this applies only to directories <em>below</em>
5251 <file>/usr/local</file>, not <em>in</em> <file>/usr/local</file>.
5252 Packages must not create sub-directories in the directory
5253 <file>/usr/local</file> itself, except those listed in FHS,
5254 section 4.5. However, you may create directories below
5255 them as you wish. You must not remove any of the
5256 directories listed in 4.5, even if you created them.
5260 Since <file>/usr/local</file> can be mounted read-only from a
5261 remote server, these directories must be created and
5262 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
5263 maintainer scripts and not be included in the
5264 <file>.deb</file> archive. These scripts must not fail if
5265 either of these operations fail.
5269 For example, the <tt>emacsen-common</tt> package could
5270 contain something like
5271 <example compact="compact">
5272 if [ ! -e /usr/local/share/emacs ]
5274 if mkdir /usr/local/share/emacs 2>/dev/null
5276 chown root:staff /usr/local/share/emacs
5277 chmod 2775 /usr/local/share/emacs
5281 in its <prgn>postinst</prgn> script, and
5282 <example compact="compact">
5283 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
5284 rmdir /usr/local/share/emacs 2>/dev/null || true
5286 in the <prgn>prerm</prgn> script. (Note that this form is
5287 used to ensure that if the script is interrupted, the
5288 directory <file>/usr/local/share/emacs</file> will still be
5293 If you do create a directory in <file>/usr/local</file> for
5294 local additions to a package, you should ensure that
5295 settings in <file>/usr/local</file> take precedence over the
5296 equivalents in <file>/usr</file>.
5300 However, because <file>/usr/local</file> and its contents are
5301 for exclusive use of the local administrator, a package
5302 must not rely on the presence or absence of files or
5303 directories in <file>/usr/local</file> for normal operation.
5307 The <file>/usr/local</file> directory itself and all the
5308 subdirectories created by the package should (by default) have
5309 permissions 2775 (group-writable and set-group-id) and be
5310 owned by <tt>root.staff</tt>.
5315 <heading>The system-wide mail directory</heading>
5317 The system-wide mail directory is <file>/var/mail</file>. This
5318 directory is part of the base system and should not owned
5319 by any particular mail agents. The use of the old
5320 location <file>/var/spool/mail</file> is deprecated, even
5321 though the spool may still be physically located there.
5322 To maintain partial upgrade compatibility for systems
5323 which have <file>/var/spool/mail</file> as their physical mail
5324 spool, packages using <file>/var/mail</file> must depend on
5325 either <package>libc6</package> (>= 2.1.3-13), or on
5326 <package>base-files</package> (>= 2.2.0), or on later
5327 versions of either one of these packages.
5333 <heading>Users and groups</heading>
5336 <heading>Introduction</heading>
5338 The Debian system can be configured to use either plain or
5343 Some user ids (UIDs) and group ids (GIDs) are reserved
5344 globally for use by certain packages. Because some
5345 packages need to include files which are owned by these
5346 users or groups, or need the ids compiled into binaries,
5347 these ids must be used on any Debian system only for the
5348 purpose for which they are allocated. This is a serious
5349 restriction, and we should avoid getting in the way of
5350 local administration policies. In particular, many sites
5351 allocate users and/or local system groups starting at 100.
5355 Apart from this we should have dynamically allocated ids,
5356 which should by default be arranged in some sensible
5357 order, but the behavior should be configurable.
5361 Packages other than <tt>base-passwd</tt> must not modify
5362 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
5363 <file>/etc/group</file> or <file>/etc/gshadow</file>.
5368 <heading>UID and GID classes</heading>
5370 The UID and GID numbers are divided into classes as
5376 Globally allocated by the Debian project, the same
5377 on every Debian system. These ids will appear in
5378 the <file>passwd</file> and <file>group</file> files of all
5379 Debian systems, new ids in this range being added
5380 automatically as the <tt>base-passwd</tt> package is
5385 Packages which need a single statically allocated
5386 uid or gid should use one of these; their
5387 maintainers should ask the <tt>base-passwd</tt>
5395 Dynamically allocated system users and groups.
5396 Packages which need a user or group, but can have
5397 this user or group allocated dynamically and
5398 differently on each system, should use <tt>adduser
5399 --system</tt> to create the group and/or user.
5400 <prgn>adduser</prgn> will check for the existence of
5401 the user or group, and if necessary choose an unused
5402 id based on the ranges specified in
5403 <file>adduser.conf</file>.
5407 <tag>1000-29999:</tag>
5410 Dynamically allocated user accounts. By default
5411 <prgn>adduser</prgn> will choose UIDs and GIDs for
5412 user accounts in this range, though
5413 <file>adduser.conf</file> may be used to modify this
5418 <tag>30000-59999:</tag>
5423 <tag>60000-64999:</tag>
5426 Globally allocated by the Debian project, but only
5427 created on demand. The ids are allocated centrally
5428 and statically, but the actual accounts are only
5429 created on users' systems on demand.
5433 These ids are for packages which are obscure or
5434 which require many statically-allocated ids. These
5435 packages should check for and create the accounts in
5436 <file>/etc/passwd</file> or <file>/etc/group</file> (using
5437 <prgn>adduser</prgn> if it has this facility) if
5438 necessary. Packages which are likely to require
5439 further allocations should have a "hole" left after
5440 them in the allocation, to give them room to
5445 <tag>65000-65533:</tag>
5453 User <tt>nobody</tt>. The corresponding gid refers
5454 to the group <tt>nogroup</tt>.
5461 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
5462 not</em> be used, because it is the error return
5471 <sect id="sysvinit">
5472 <heading>System run levels and <file>init.d</file> scripts</heading>
5474 <sect1 id="/etc/init.d">
5475 <heading>Introduction</heading>
5478 The <file>/etc/init.d</file> directory contains the scripts
5479 executed by <prgn>init</prgn> at boot time and when the
5480 init state (or "runlevel") is changed (see <manref
5481 name="init" section="8">).
5485 There are at least two different, yet functionally
5486 equivalent, ways of handling these scripts. For the sake
5487 of simplicity, this document describes only the symbolic
5488 link method. However, it must not be assumed by maintainer
5489 scripts that this method is being used, and any automated
5490 manipulation of the various runlevel behaviors by
5491 maintainer scripts must be performed using
5492 <prgn>update-rc.d</prgn> as described below and not by
5493 manually installing or removing symlinks. For information
5494 on the implementation details of the other method,
5495 implemented in the <tt>file-rc</tt> package, please refer
5496 to the documentation of that package.
5500 These scripts are referenced by symbolic links in the
5501 <file>/etc/rc<var>n</var>.d</file> directories. When changing
5502 runlevels, <prgn>init</prgn> looks in the directory
5503 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
5504 execute, where <tt><var>n</var></tt> is the runlevel that
5505 is being changed to, or <tt>S</tt> for the boot-up
5510 The names of the links all have the form
5511 <file>S<var>mm</var><var>script</var></file> or
5512 <file>K<var>mm</var><var>script</var></file> where
5513 <var>mm</var> is a two-digit number and <var>script</var>
5514 is the name of the script (this should be the same as the
5515 name of the actual script in <file>/etc/init.d</file>).
5519 When <prgn>init</prgn> changes runlevel first the targets
5520 of the links whose names start with a <tt>K</tt> are
5521 executed, each with the single argument <tt>stop</tt>,
5522 followed by the scripts prefixed with an <tt>S</tt>, each
5523 with the single argument <tt>start</tt>. (The links are
5524 those in the <file>/etc/rc<var>n</var>.d</file> directory
5525 corresponding to the new runlevel.) The <tt>K</tt> links
5526 are responsible for killing services and the <tt>S</tt>
5527 link for starting services upon entering the runlevel.
5531 For example, if we are changing from runlevel 2 to
5532 runlevel 3, init will first execute all of the <tt>K</tt>
5533 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
5534 all of the <tt>S</tt> prefixed scripts in that directory.
5535 The links starting with <tt>K</tt> will cause the
5536 referred-to file to be executed with an argument of
5537 <tt>stop</tt>, and the <tt>S</tt> links with an argument
5542 The two-digit number <var>mm</var> is used to determine
5543 the order in which to run the scripts: low-numbered links
5544 have their scripts run first. For example, the
5545 <tt>K20</tt> scripts will be executed before the
5546 <tt>K30</tt> scripts. This is used when a certain service
5547 must be started before another. For example, the name
5548 server <prgn>bind</prgn> might need to be started before
5549 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
5550 can set up its access lists. In this case, the script
5551 that starts <prgn>bind</prgn> would have a lower number
5552 than the script that starts <prgn>inn</prgn> so that it
5554 <example compact="compact">
5561 The two runlevels 0 (halt) and 6 (reboot) are slightly
5562 different. In these runlevels, the links with an
5563 <tt>S</tt> prefix are still called after those with a
5564 <tt>K</tt> prefix, but they too are called with the single
5565 argument <tt>stop</tt>.
5569 Also, if the script name ends in <tt>.sh</tt>, the script
5570 will be sourced in runlevel <tt>S</tt> rather than being
5571 run in a forked subprocess, but will be explicitly run by
5572 <prgn>sh</prgn> in all other runlevels.
5577 <heading>Writing the scripts</heading>
5580 Packages that include daemons for system services should
5581 place scripts in <file>/etc/init.d</file> to start or stop
5582 services at boot time or during a change of runlevel.
5583 These scripts should be named
5584 <file>/etc/init.d/<var>package</var></file>, and they should
5585 accept one argument, saying what to do:
5588 <tag><tt>start</tt></tag>
5589 <item>start the service,</item>
5591 <tag><tt>stop</tt></tag>
5592 <item>stop the service,</item>
5594 <tag><tt>restart</tt></tag>
5595 <item>stop and restart the service if it's already running,
5596 otherwise start the service</item>
5598 <tag><tt>reload</tt></tag>
5599 <item><p>cause the configuration of the service to be
5600 reloaded without actually stopping and restarting
5603 <tag><tt>force-reload</tt></tag>
5604 <item>cause the configuration to be reloaded if the
5605 service supports this, otherwise restart the
5609 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
5610 <tt>force-reload</tt> options should be supported by all
5611 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
5616 The <file>init.d</file> scripts must ensure that they will
5617 behave sensibly if invoked with <tt>start</tt> when the
5618 service is already running, or with <tt>stop</tt> when it
5619 isn't, and that they don't kill unfortunately-named user
5620 processes. The best way to achieve this is usually to use
5621 <prgn>start-stop-daemon</prgn>.
5625 If a service reloads its configuration automatically (as
5626 in the case of <prgn>cron</prgn>, for example), the
5627 <tt>reload</tt> option of the <file>init.d</file> script
5628 should behave as if the configuration has been reloaded
5633 The <file>/etc/init.d</file> scripts must be treated as
5634 configuration files, either (if they are present in the
5635 package, that is, in the .deb file) by marking them as
5636 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
5637 by managing them correctly in the maintainer scripts (see
5638 <ref id="config-files">). This is important since we want
5639 to give the local system administrator the chance to adapt
5640 the scripts to the local system, e.g., to disable a
5641 service without de-installing the package, or to specify
5642 some special command line options when starting a service,
5643 while making sure their changes aren't lost during the next
5648 These scripts should not fail obscurely when the
5649 configuration files remain but the package has been
5650 removed, as configuration files remain on the system after
5651 the package has been removed. Only when <prgn>dpkg</prgn>
5652 is executed with the <tt>--purge</tt> option will
5653 configuration files be removed. In particular, as the
5654 <file>/etc/init.d/<var>package</var></file> script itself is
5655 usually a <tt>conffile</tt>, it will remain on the system
5656 if the package is removed but not purged. Therefore, you
5657 should include a <tt>test</tt> statement at the top of the
5659 <example compact="compact">
5660 test -f <var>program-executed-later-in-script</var> || exit 0
5665 Often there are some variables in the <file>init.d</file>
5666 scripts whose values control the behavior of the scripts,
5667 and which a system administrator is likely to want to
5668 change. As the scripts themselves are frequently
5669 <tt>conffile</tt>s, modifying them requires that the
5670 administrator merge in their changes each time the package
5671 is upgraded and the <tt>conffile</tt> changes. To ease
5672 the burden on the system administrator, such configurable
5673 values should not be placed directly in the script.
5674 Instead, they should be placed in a file in
5675 <file>/etc/default</file>, which typically will have the same
5676 base name as the <file>init.d</file> script. This extra file
5677 should be sourced by the script when the script runs. It
5678 must contain only variable settings and comments in SUSv3
5679 <prgn>sh</prgn> format. It may either be a
5680 <tt>conffile</tt> or a configuration file maintained by
5681 the package maintainer scripts. See <ref id="config-files">
5686 To ensure that vital configurable values are always
5687 available, the <file>init.d</file> script should set default
5688 values for each of the shell variables it uses, either
5689 before sourcing the <file>/etc/default/</file> file or
5690 afterwards using something like the <tt>:
5691 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
5692 script must behave sensibly and not fail if the
5693 <file>/etc/default</file> file is deleted.
5698 <heading>Interfacing with the initscript system</heading>
5701 Maintainers should use the abstraction layer provided by
5702 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
5703 programs to deal with initscripts in their packages'
5704 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
5705 and <prgn>postrm</prgn>.
5709 Directly managing the /etc/rc?.d links and directly
5710 invoking the <file>/etc/init.d/</file> initscripts should
5711 be done only by packages providing the initscript
5712 subsystem (such as <prgn>sysv-rc</prgn> and
5713 <prgn>file-rc</prgn>).
5717 <heading>Managing the links</heading>
5720 The program <prgn>update-rc.d</prgn> is provided for
5721 package maintainers to arrange for the proper creation and
5722 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
5723 or their functional equivalent if another method is being
5724 used. This may be used by maintainers in their packages'
5725 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
5729 You must not include any <file>/etc/rc<var>n</var>.d</file>
5730 symbolic links in the actual archive or manually create or
5731 remove the symbolic links in maintainer scripts; you must
5732 use the <prgn>update-rc.d</prgn> program instead. (The
5733 former will fail if an alternative method of maintaining
5734 runlevel information is being used.) You must not include
5735 the <file>/etc/rc<var>n</var>.d</file> directories themselves
5736 in the archive either. (Only the <tt>sysvinit</tt>
5741 By default <prgn>update-rc.d</prgn> will start services in
5742 each of the multi-user state runlevels (2, 3, 4, and 5)
5743 and stop them in the halt runlevel (0), the single-user
5744 runlevel (1) and the reboot runlevel (6). The system
5745 administrator will have the opportunity to customize
5746 runlevels by simply adding, moving, or removing the
5747 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
5748 symbolic links are being used, or by modifying
5749 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
5754 To get the default behavior for your package, put in your
5755 <prgn>postinst</prgn> script
5756 <example compact="compact">
5757 update-rc.d <var>package</var> defaults
5759 and in your <prgn>postrm</prgn>
5760 <example compact="compact">
5761 if [ "$1" = purge ]; then
5762 update-rc.d <var>package</var> remove
5764 </example>. Note that if your package changes runlevels
5765 or priority, you may have to remove and recreate the links,
5766 since otherwise the old links may persist. Refer to the
5767 documentation of <prgn>update-rc.d</prgn>.
5771 This will use a default sequence number of 20. If it does
5772 not matter when or in which order the <file>init.d</file>
5773 script is run, use this default. If it does, then you
5774 should talk to the maintainer of the <prgn>sysvinit</prgn>
5775 package or post to <tt>debian-devel</tt>, and they will
5776 help you choose a number.
5780 For more information about using <tt>update-rc.d</tt>,
5781 please consult its man page <manref name="update-rc.d"
5787 <heading>Running initscripts</heading>
5789 The program <prgn>invoke-rc.d</prgn> is provided to make
5790 it easier for package maintainers to properly invoke an
5791 initscript, obeying runlevel and other locally-defined
5792 constraints that might limit a package's right to start,
5793 stop and otherwise manage services. This program may be
5794 used by maintainers in their packages' scripts.
5798 The package maintainer scripts must use
5799 <prgn>invoke-rc.d</prgn> to invoke the
5800 <file>/etc/init.d/*</file> initscripts, instead of
5801 calling them directly.
5805 By default, <prgn>invoke-rc.d</prgn> will pass any
5806 action requests (start, stop, reload, restart...) to the
5807 <file>/etc/init.d</file> script, filtering out requests
5808 to start or restart a service out of its intended
5813 Most packages will simply need to change:
5814 <example compact="compact">/etc/init.d/<package>
5815 <action></example> in their <prgn>postinst</prgn>
5816 and <prgn>prerm</prgn> scripts to:
5817 <example compact="compact">
5818 if which invoke-rc.d >/dev/null 2>&1; then
5819 invoke-rc.d <var>package</var> <action>
5821 /etc/init.d/<var>package</var> <action>
5827 A package should register its initscript services using
5828 <prgn>update-rc.d</prgn> before it tries to invoke them
5829 using <prgn>invoke-rc.d</prgn>. Invocation of
5830 unregistered services may fail.
5834 For more information about using
5835 <prgn>invoke-rc.d</prgn>, please consult its man page
5836 <manref name="invoke-rc.d" section="8">.
5842 <heading>Boot-time initialization</heading>
5845 There used to be another directory, <file>/etc/rc.boot</file>,
5846 which contained scripts which were run once per machine
5847 boot. This has been deprecated in favour of links from
5848 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
5849 described in <ref id="/etc/init.d">. Packages must not
5850 place files in <file>/etc/rc.boot</file>.
5855 <heading>Example</heading>
5858 An example on which you can base your
5859 <file>/etc/init.d</file> scripts is found in
5860 <file>/etc/init.d/skeleton</file>.
5867 <heading>Console messages from <file>init.d</file> scripts</heading>
5870 This section describes the formats to be used for messages
5871 written to standard output by the <file>/etc/init.d</file>
5872 scripts. The intent is to improve the consistency of
5873 Debian's startup and shutdown look and feel. For this
5874 reason, please look very carefully at the details. We want
5875 the messages to have the same format in terms of wording,
5876 spaces, punctuation and case of letters.
5880 Here is a list of overall rules that should be used for
5881 messages generated by <file>/etc/init.d</file> scripts.
5887 The message should fit in one line (fewer than 80
5888 characters), start with a capital letter and end with
5889 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
5893 If the script is performing some time consuming task in
5894 the background (not merely starting or stopping a
5895 program, for instance), an ellipsis (three dots:
5896 <tt>...</tt>) should be output to the screen, with no
5897 leading or tailing whitespace or line feeds.
5901 The messages should appear as if the computer is telling
5902 the user what it is doing (politely :-), but should not
5903 mention "it" directly. For example, instead of:
5904 <example compact="compact">
5905 I'm starting network daemons: nfsd mountd.
5907 the message should say
5908 <example compact="compact">
5909 Starting network daemons: nfsd mountd.
5916 <tt>init.d</tt> script should use the following standard
5917 message formats for the situations enumerated below.
5923 <p>When daemons are started</p>
5926 If the script starts one or more daemons, the output
5927 should look like this (a single line, no leading
5929 <example compact="compact">
5930 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
5932 The <var>description</var> should describe the
5933 subsystem the daemon or set of daemons are part of,
5934 while <var>daemon-1</var> up to <var>daemon-n</var>
5935 denote each daemon's name (typically the file name of
5940 For example, the output of <file>/etc/init.d/lpd</file>
5942 <example compact="compact">
5943 Starting printer spooler: lpd.
5948 This can be achieved by saying
5949 <example compact="compact">
5950 echo -n "Starting printer spooler: lpd"
5951 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
5954 in the script. If there are more than one daemon to
5955 start, the output should look like this:
5956 <example compact="compact">
5957 echo -n "Starting remote file system services:"
5958 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
5959 echo -n " mountd"; start-stop-daemon --start --quiet mountd
5960 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
5963 This makes it possible for the user to see what is
5964 happening and when the final daemon has been started.
5965 Care should be taken in the placement of white spaces:
5966 in the example above the system administrators can
5967 easily comment out a line if they don't want to start
5968 a specific daemon, while the displayed message still
5974 <p>When a system parameter is being set</p>
5977 If you have to set up different system parameters
5978 during the system boot, you should use this format:
5979 <example compact="compact">
5980 Setting <var>parameter</var> to "<var>value</var>".
5985 You can use a statement such as the following to get
5987 <example compact="compact">
5988 echo "Setting DNS domainname to \"$domainname\"."
5993 Note that the same symbol (<tt>"</tt>) is used for the left
5994 and right quotation marks. A grave accent (<tt>`</tt>) is
5995 not a quote character; neither is an apostrophe
6001 <p>When a daemon is stopped or restarted</p>
6004 When you stop or restart a daemon, you should issue a
6005 message identical to the startup message, except that
6006 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6007 or <tt>Restarting</tt> respectively.
6011 For example, stopping the printer daemon will look like
6013 <example compact="compact">
6014 Stopping printer spooler: lpd.
6020 <p>When something is executed</p>
6023 There are several examples where you have to run a
6024 program at system startup or shutdown to perform a
6025 specific task, for example, setting the system's clock
6026 using <prgn>netdate</prgn> or killing all processes
6027 when the system shuts down. Your message should look
6029 <example compact="compact">
6030 Doing something very useful...done.
6032 You should print the <tt>done.</tt> immediately after
6033 the job has been completed, so that the user is
6034 informed why they have to wait. You can get this
6036 <example compact="compact">
6037 echo -n "Doing something very useful..."
6046 <p>When the configuration is reloaded</p>
6049 When a daemon is forced to reload its configuration
6050 files you should use the following format:
6051 <example compact="compact">
6052 Reloading <var>description</var> configuration...done.
6054 where <var>description</var> is the same as in the
6055 daemon starting message.
6063 <heading>Cron jobs</heading>
6066 Packages must not modify the configuration file
6067 <file>/etc/crontab</file>, and they must not modify the files in
6068 <file>/var/spool/cron/crontabs</file>.</p>
6071 If a package wants to install a job that has to be executed
6072 via cron, it should place a file with the name of the
6073 package in one or more of the following directories:
6074 <example compact="compact">
6079 As these directory names imply, the files within them are
6080 executed on a daily, weekly, or monthly basis,
6081 respectively. The exact times are listed in
6082 <file>/etc/crontab</file>.</p>
6085 All files installed in any of these directories must be
6086 scripts (e.g., shell scripts or Perl scripts) so that they
6087 can easily be modified by the local system administrator.
6088 In addition, they should be treated as configuration
6093 If a certain job has to be executed more frequently than
6094 daily, the package should install a file
6095 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6096 same syntax as <file>/etc/crontab</file> and is processed by
6097 <prgn>cron</prgn> automatically. The file must also be
6098 treated as a configuration file. (Note that entries in the
6099 <file>/etc/cron.d</file> directory are not handled by
6100 <prgn>anacron</prgn>. Thus, you should only use this
6101 directory for jobs which may be skipped if the system is not
6105 The scripts or crontab entries in these directories should
6106 check if all necessary programs are installed before they
6107 try to execute them. Otherwise, problems will arise when a
6108 package was removed but not purged since configuration files
6109 are kept on the system in this situation.</p>
6113 <heading>Menus</heading>
6116 The Debian <tt>menu</tt> package provides a standard
6117 interface between packages providing applications and
6118 <em>menu programs</em> (either X window managers or
6119 text-based menu programs such as <prgn>pdmenu</prgn>).
6123 All packages that provide applications that need not be
6124 passed any special command line arguments for normal
6125 operation should register a menu entry for those
6126 applications, so that users of the <tt>menu</tt> package
6127 will automatically get menu entries in their window
6128 managers, as well in shells like <tt>pdmenu</tt>.
6132 Menu entries should follow the current menu policy.
6136 The menu policy can be found in the <tt>menu-policy</tt>
6137 files in the <tt>debian-policy</tt> package.
6138 It is also available from the Debian web mirrors at
6139 <tt><url name="/doc/packaging-manuals/menu-policy/"
6140 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6144 Please also refer to the <em>Debian Menu System</em>
6145 documentation that comes with the <package>menu</package>
6146 package for information about how to register your
6152 <heading>Multimedia handlers</heading>
6155 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6156 is a mechanism for encoding files and data streams and
6157 providing meta-information about them, in particular their
6158 type (e.g. audio or video) and format (e.g. PNG, HTML,
6163 Registration of MIME type handlers allows programs like mail
6164 user agents and web browsers to invoke these handlers to
6165 view, edit or display MIME types they don't support directly.
6169 Packages which provide the ability to view/show/play,
6170 compose, edit or print MIME types should register themselves
6171 as such following the current MIME support policy.
6175 The MIME support policy can be found in the <tt>mime-policy</tt>
6176 files in the <tt>debian-policy</tt> package.
6177 It is also available from the Debian web mirrors at
6178 <tt><url name="/doc/packaging-manuals/mime-policy/"
6179 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
6185 <heading>Keyboard configuration</heading>
6188 To achieve a consistent keyboard configuration so that all
6189 applications interpret a keyboard event the same way, all
6190 programs in the Debian distribution must be configured to
6191 comply with the following guidelines.
6195 The following keys must have the specified interpretations:
6198 <tag><tt><--</tt></tag>
6199 <item>delete the character to the left of the cursor</item>
6201 <tag><tt>Delete</tt></tag>
6202 <item>delete the character to the right of the cursor</item>
6204 <tag><tt>Control+H</tt></tag>
6205 <item>emacs: the help prefix</item>
6208 The interpretation of any keyboard events should be
6209 independent of the terminal that is used, be it a virtual
6210 console, an X terminal emulator, an rlogin/telnet session,
6215 The following list explains how the different programs
6216 should be set up to achieve this:
6222 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
6226 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
6230 X translations are set up to make
6231 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
6232 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
6233 is the vt220 escape code for the "delete character"
6234 key). This must be done by loading the X resources
6235 using <prgn>xrdb</prgn> on all local X displays, not
6236 using the application defaults, so that the
6237 translation resources used correspond to the
6238 <prgn>xmodmap</prgn> settings.
6242 The Linux console is configured to make
6243 <tt><--</tt> generate DEL, and <tt>Delete</tt>
6244 generate <tt>ESC [ 3 ~</tt>.
6248 X applications are configured so that <tt><</tt>
6249 deletes left, and <tt>Delete</tt> deletes right. Motif
6250 applications already work like this.
6254 Terminals should have <tt>stty erase ^?</tt> .
6258 The <tt>xterm</tt> terminfo entry should have <tt>ESC
6259 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
6260 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
6264 Emacs is programmed to map <tt>KB_Backspace</tt> or
6265 the <tt>stty erase</tt> character to
6266 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
6267 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
6268 <tt>^H</tt> to <tt>help</tt> as always.
6272 Other applications use the <tt>stty erase</tt>
6273 character and <tt>kdch1</tt> for the two delete keys,
6274 with ASCII DEL being "delete previous character" and
6275 <tt>kdch1</tt> being "delete character under
6283 This will solve the problem except for the following
6290 Some terminals have a <tt><--</tt> key that cannot
6291 be made to produce anything except <tt>^H</tt>. On
6292 these terminals Emacs help will be unavailable on
6293 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
6294 character takes precedence in Emacs, and has been set
6295 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
6296 available) can be used instead.
6300 Some operating systems use <tt>^H</tt> for <tt>stty
6301 erase</tt>. However, modern telnet versions and all
6302 rlogin versions propagate <tt>stty</tt> settings, and
6303 almost all UNIX versions honour <tt>stty erase</tt>.
6304 Where the <tt>stty</tt> settings are not propagated
6305 correctly, things can be made to work by using
6306 <tt>stty</tt> manually.
6310 Some systems (including previous Debian versions) use
6311 <prgn>xmodmap</prgn> to arrange for both
6312 <tt><--</tt> and <tt>Delete</tt> to generate
6313 <tt>KB_Delete</tt>. We can change the behavior of
6314 their X clients using the same X resources that we use
6315 to do it for our own clients, or configure our clients
6316 using their resources when things are the other way
6317 around. On displays configured like this
6318 <tt>Delete</tt> will not work, but <tt><--</tt>
6323 Some operating systems have different <tt>kdch1</tt>
6324 settings in their <tt>terminfo</tt> database for
6325 <tt>xterm</tt> and others. On these systems the
6326 <tt>Delete</tt> key will not work correctly when you
6327 log in from a system conforming to our policy, but
6328 <tt><--</tt> will.
6335 <heading>Environment variables</heading>
6338 A program must not depend on environment variables to get
6339 reasonable defaults. (That's because these environment
6340 variables would have to be set in a system-wide
6341 configuration file like <file>/etc/profile</file>, which is not
6342 supported by all shells.)
6346 If a program usually depends on environment variables for its
6347 configuration, the program should be changed to fall back to
6348 a reasonable default configuration if these environment
6349 variables are not present. If this cannot be done easily
6350 (e.g., if the source code of a non-free program is not
6351 available), the program must be replaced by a small
6352 "wrapper" shell script which sets the environment variables
6353 if they are not already defined, and calls the original program.
6357 Here is an example of a wrapper script for this purpose:
6359 <example compact="compact">
6361 BAR=${BAR:-/var/lib/fubar}
6363 exec /usr/lib/foo/foo "$@"
6368 Furthermore, as <file>/etc/profile</file> is a configuration
6369 file of the <prgn>base-files</prgn> package, other packages must
6370 not put any environment variables or other commands into that
6375 <sect id="doc-base">
6376 <heading>Registering Documents using doc-base</heading>
6379 The <package>doc-base</package> package implements a
6380 flexible mechanism for handling and presenting
6381 documentation. The recommended practice is for every Debian
6382 package that provides online documentation (other than just
6383 manual pages) to register these documents with
6384 <package>doc-base</package> by installing a
6385 <package>doc-base</package> control file via the
6386 <prgn/install-docs/ script at installation time and
6387 de-register the manuals again when the package is removed.
6390 Please refer to the documentation that comes with the
6391 <package>doc-base</package> package for information and
6400 <heading>Files</heading>
6403 <heading>Binaries</heading>
6406 Two different packages must not install programs with
6407 different functionality but with the same filenames. (The
6408 case of two programs having the same functionality but
6409 different implementations is handled via "alternatives" or
6410 the "Conflicts" mechanism. See <ref id="maintscripts"> and
6411 <ref id="conflicts"> respectively.) If this case happens,
6412 one of the programs must be renamed. The maintainers should
6413 report this to the <tt>debian-devel</tt> mailing list and
6414 try to find a consensus about which program will have to be
6415 renamed. If a consensus cannot be reached, <em>both</em>
6416 programs must be renamed.
6420 By default, when a package is being built, any binaries
6421 created should include debugging information, as well as
6422 being compiled with optimization. You should also turn on
6423 as many reasonable compilation warnings as possible; this
6424 makes life easier for porters, who can then look at build
6425 logs for possible problems. For the C programming language,
6426 this means the following compilation parameters should be
6428 <example compact="compact">
6430 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
6432 INSTALL = install -s # (or use strip on the files in debian/tmp)
6437 Note that by default all installed binaries should be stripped,
6438 either by using the <tt>-s</tt> flag to
6439 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
6440 the binaries after they have been copied into
6441 <file>debian/tmp</file> but before the tree is made into a
6446 Although binaries in the build tree should be compiled with
6447 debugging information by default, it can often be difficult
6448 to debug programs if they are also subjected to compiler
6449 optimization. For this reason, it is recommended to support
6450 the standardized environment
6451 variable <tt>DEB_BUILD_OPTIONS</tt>. This variable can
6452 contain several flags to change how a package is compiled
6460 The presence of this string means that the package
6461 should be compiled with a minimum of optimization.
6462 For C programs, it is best to add <tt>-O0</tt>
6463 to <tt>CFLAGS</tt> (although this is usually the
6464 default). Some programs might fail to build or run at
6465 this level of optimization; it may be necessary to
6466 use <tt>-O1</tt>, for example.
6470 This string means that the debugging symbols should
6471 not be stripped from the binary during installation,
6472 so that debugging information may be included in the package.
6478 The following makefile snippet is an example of how one may
6479 implement the build options; you will probably have to
6480 massage this example in order to make it work for your
6482 <example compact="compact">
6485 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
6486 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
6487 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
6488 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
6490 ifneq (,$(findstring noopt,$(DEB_BUILD_OPTIONS)))
6495 ifeq (,$(findstring nostrip,$(DEB_BUILD_OPTIONS)))
6496 INSTALL_PROGRAM += -s
6502 It is up to the package maintainer to decide what
6503 compilation options are best for the package. Certain
6504 binaries (such as computationally-intensive programs) will
6505 function better with certain flags (<tt>-O3</tt>, for
6506 example); feel free to use them. Please use good judgment
6507 here. Don't use flags for the sake of it; only use them
6508 if there is good reason to do so. Feel free to override
6509 the upstream author's ideas about which compilation
6510 options are best: they are often inappropriate for our
6516 <sect id="libraries">
6517 <heading>Libraries</heading>
6520 If the package is <strong>architecture: any</strong>, then
6521 the shared library compilation and linking flags must have
6522 <tt>-fPIC</tt>, or the package shall not build on some of
6523 the supported architectures<footnote>
6525 If you are using GCC, <tt>-fPIC</tt> produces code with
6526 relocatable position independent code, which is required for
6527 most architectures to create a shared library, with i386 and
6528 perhaps some others where non position independent code is
6529 permitted in a shared library.
6532 Position independent code may have a performance penalty,
6533 especially on <tt>i386</tt>. However, in most cases the
6534 speed penalty must be measured against the memory wasted on
6535 the few architectures where non position independent code is
6538 </footnote>. Any exception to this rule must be discussed on
6539 the mailing list <em>debian-devel@lists.debian.org</em>, and
6540 a rough consensus obtained. The reasons for not compiling
6541 with <tt>-fPIC</tt> flag must be recorded in the file
6542 <tt>README.Debian</tt>, and care must be taken to either
6543 restrict the architecture or arrange for <tt>-fPIC</tt> to
6544 be used on architectures where it is required.<footnote>
6546 Some of the reasons why this might be required is if the
6547 library contains hand crafted assembly code that is not
6548 relocatable, the speed penalty is excessive for compute
6549 intensive libs, and similar reasons.
6554 As to the static libraries, the common case is not to have
6555 relocatable code, since there is no benefit, unless in specific
6556 cases; therefore the static version must not be compiled
6557 with the <tt>-fPIC</tt> flag. Any exception to this rule
6558 should be discussed on the mailing list
6559 <em>debian-devel@lists.debian.org</em>, and the reasons for
6560 compiling with the <tt>-fPIC</tt> flag must be recorded in
6561 the file <tt>README.Debian</tt>. <footnote>
6563 Some of the reasons for linking static libraries with
6564 the <tt>-fPIC</tt> flag are if, for example, one needs a
6565 Perl API for a library that is under rapid development,
6566 and has an unstable API, so shared libraries are
6567 pointless at this phase of the library's development. In
6568 that case, since Perl needs a library with relocatable
6569 code, it may make sense to create a static library with
6570 relocatable code. Another reason cited is if you are
6571 distilling various libraries into a common shared
6572 library, like <tt>mklibs</tt> does in the Debian
6578 In other words, if both a shared and a static library is
6579 being built, each source unit (<tt>*.c</tt>, for example,
6580 for C files) will need to be compiled twice, for the normal
6584 You must specify the gcc option <tt>-D_REENTRANT</tt>
6585 when building a library (either static or shared) to make
6586 the library compatible with LinuxThreads.
6590 Although not enforced by the build tools, shared libraries
6591 must be linked against all libraries that they use symbols from
6592 in the same way that binaries are. This ensures the correct
6593 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
6594 system and guarantees that all libraries can be safely opened
6595 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
6596 option <tt>-Wl,-z,defs</tt> when building a shared library.
6597 Since this option enforces symbol resolution at build time,
6598 a missing library reference will be caught early as a fatal
6603 All installed shared libraries should be stripped with
6604 <example compact="compact">
6605 strip --strip-unneeded <var>your-lib</var>
6607 (The option <tt>--strip-unneeded</tt> makes
6608 <prgn>strip</prgn> remove only the symbols which aren't
6609 needed for relocation processing.) Shared libraries can
6610 function perfectly well when stripped, since the symbols for
6611 dynamic linking are in a separate part of the ELF object
6613 You might also want to use the options
6614 <tt>--remove-section=.comment</tt> and
6615 <tt>--remove-section=.note</tt> on both shared libraries
6616 and executables, and <tt>--strip-debug</tt> on static
6622 Note that under some circumstances it may be useful to
6623 install a shared library unstripped, for example when
6624 building a separate package to support debugging.
6628 Shared object files (often <file>.so</file> files) that are not
6629 public libraries, that is, they are not meant to be linked
6630 to by third party executables (binaries of other packages),
6631 should be installed in subdirectories of the
6632 <file>/usr/lib</file> directory. Such files are exempt from the
6633 rules that govern ordinary shared libraries, except that
6634 they must not be installed executable and should be
6636 A common example are the so-called "plug-ins",
6637 internal shared objects that are dynamically loaded by
6638 programs using <manref name="dlopen" section="3">.
6643 Packages containing shared libraries that may be linked to
6644 by other packages' binaries, but which for some
6645 <em>compelling</em> reason can not be installed in
6646 <file>/usr/lib</file> directory, may install the shared library
6647 files in subdirectories of the <file>/usr/lib</file> directory,
6648 in which case they should arrange to add that directory in
6649 <file>/etc/ld.so.conf</file> in the package's post-installation
6650 script, and remove it in the package's post-removal script.
6654 An ever increasing number of packages are using
6655 <prgn>libtool</prgn> to do their linking. The latest GNU
6656 libtools (>= 1.3a) can take advantage of the metadata in the
6657 installed <prgn>libtool</prgn> archive files (<file>*.la</file>
6658 files). The main advantage of <prgn>libtool</prgn>'s
6659 <file>.la</file> files is that it allows <prgn>libtool</prgn> to
6660 store and subsequently access metadata with respect to the
6661 libraries it builds. <prgn>libtool</prgn> will search for
6662 those files, which contain a lot of useful information about
6663 a library (such as library dependency information for static
6664 linking). Also, they're <em>essential</em> for programs
6665 using <tt>libltdl</tt>.<footnote>
6666 Although <prgn>libtool</prgn> is fully capable of
6667 linking against shared libraries which don't have
6668 <tt>.la</tt> files, as it is a mere shell script it can
6669 add considerably to the build time of a
6670 <prgn>libtool</prgn>-using package if that shell script
6671 has to derive all this information from first principles
6672 for each library every time it is linked. With the
6673 advent of <prgn>libtool</prgn> version 1.4 (and to a
6674 lesser extent <prgn>libtool</prgn> version 1.3), the
6675 <file>.la</file> files also store information about
6676 inter-library dependencies which cannot necessarily be
6677 derived after the <file>.la</file> file is deleted.
6682 Packages that use <prgn>libtool</prgn> to create shared
6683 libraries should include the <file>.la</file> files in the
6684 <tt>-dev</tt> package, unless the package relies on
6685 <tt>libtool</tt>'s <tt>libltdl</tt> library, in which case
6686 the <tt>.la</tt> files must go in the run-time library
6691 You must make sure that you use only released versions of
6692 shared libraries to build your packages; otherwise other
6693 users will not be able to run your binaries
6694 properly. Producing source packages that depend on
6695 unreleased compilers is also usually a bad
6702 <heading>Shared libraries</heading>
6704 This section has moved to <ref id="sharedlibs">.
6710 <heading>Scripts</heading>
6713 All command scripts, including the package maintainer
6714 scripts inside the package and used by <prgn>dpkg</prgn>,
6715 should have a <tt>#!</tt> line naming the shell to be used
6720 In the case of Perl scripts this should be
6721 <tt>#!/usr/bin/perl</tt>.
6725 When scripts are installed into a directory in the system
6726 PATH, the script name should not include an extension such
6727 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
6728 language currently used to implement it.
6731 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>)
6732 should almost certainly start with <tt>set -e</tt> so that
6733 errors are detected. Every script should use
6734 <tt>set -e</tt> or check the exit status of <em>every</em>
6739 Scripts may assume that <file>/bin/sh</file> implements the
6740 SUSv3 Shell Command Language<footnote>
6741 Single UNIX Specification, version 3, which is also IEEE
6742 1003.1-2004 (POSIX), and is available on the World Wide Web
6743 from <url id="http://www.unix.org/version3/online.html"
6744 name="The Open Group"> after free
6745 registration.</footnote>
6746 plus the following additional features not mandated by
6748 These features are in widespread use in the Linux community
6749 and are implemented in all of bash, dash, and ksh, the most
6750 common shells users may wish to use as <file>/bin/sh</file>.
6753 <item><tt>echo -n</tt>, if implemented as a shell built-in,
6754 must not generate a newline.</item>
6755 <item><tt>test</tt>, if implemented as a shell built-in, must
6756 support <tt>-a</tt> and <tt>-o</tt> as binary logical
6758 <item><tt>local</tt> to create a scoped variable must be
6759 supported; however, <tt>local</tt> may or may not preserve
6760 the variable value from an outer scope and may or may not
6761 support arguments more complex than simple variables. Only
6773 If a shell script requires non-SUSv3 features from the shell
6774 interpreter other than those listed above, the appropriate shell
6775 must be specified in the first line of the script (e.g.,
6776 <tt>#!/bin/bash</tt>) and the package must depend on the package
6777 providing the shell (unless the shell package is marked
6778 "Essential", as in the case of <prgn>bash</prgn>).
6782 You may wish to restrict your script to SUSv3 features plus the
6783 above set when possible so that it may use <file>/bin/sh</file>
6784 as its interpreter. If your script works with <prgn>dash</prgn>
6785 (originally called <prgn>ash</prgn>), it probably complies with
6786 the above requirements, but if you are in doubt, use
6787 <file>/bin/bash</file>.
6791 Perl scripts should check for errors when making any
6792 system calls, including <tt>open</tt>, <tt>print</tt>,
6793 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
6797 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
6798 scripting languages. See <em>Csh Programming Considered
6799 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
6800 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
6801 If an upstream package comes with <prgn>csh</prgn> scripts
6802 then you must make sure that they start with
6803 <tt>#!/bin/csh</tt> and make your package depend on the
6804 <prgn>c-shell</prgn> virtual package.
6808 Any scripts which create files in world-writeable
6809 directories (e.g., in <file>/tmp</file>) must use a
6810 mechanism which will fail atomically if a file with the same
6811 name already exists.
6815 The Debian base system provides the <prgn>tempfile</prgn>
6816 and <prgn>mktemp</prgn> utilities for use by scripts for
6823 <heading>Symbolic links</heading>
6826 In general, symbolic links within a top-level directory
6827 should be relative, and symbolic links pointing from one
6828 top-level directory into another should be absolute. (A
6829 top-level directory is a sub-directory of the root
6830 directory <file>/</file>.)
6834 In addition, symbolic links should be specified as short as
6835 possible, i.e., link targets like <file>foo/../bar</file> are
6840 Note that when creating a relative link using
6841 <prgn>ln</prgn> it is not necessary for the target of the
6842 link to exist relative to the working directory you're
6843 running <prgn>ln</prgn> from, nor is it necessary to change
6844 directory to the directory where the link is to be made.
6845 Simply include the string that should appear as the target
6846 of the link (this will be a pathname relative to the
6847 directory in which the link resides) as the first argument
6852 For example, in your <prgn>Makefile</prgn> or
6853 <file>debian/rules</file>, you can do things like:
6854 <example compact="compact">
6855 ln -fs gcc $(prefix)/bin/cc
6856 ln -fs gcc debian/tmp/usr/bin/cc
6857 ln -fs ../sbin/sendmail $(prefix)/bin/runq
6858 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
6863 A symbolic link pointing to a compressed file should always
6864 have the same file extension as the referenced file. (For
6865 example, if a file <file>foo.gz</file> is referenced by a
6866 symbolic link, the filename of the link has to end with
6867 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
6872 <heading>Device files</heading>
6875 Packages must not include device files in the package file
6880 If a package needs any special device files that are not
6881 included in the base system, it must call
6882 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
6883 after notifying the user<footnote>
6884 This notification could be done via a (low-priority)
6885 debconf message, or an echo (printf) statement.
6890 Packages must not remove any device files in the
6891 <prgn>postrm</prgn> or any other script. This is left to the
6892 system administrator.
6896 Debian uses the serial devices
6897 <file>/dev/ttyS*</file>. Programs using the old
6898 <file>/dev/cu*</file> devices should be changed to use
6899 <file>/dev/ttyS*</file>.
6903 <sect id="config-files">
6904 <heading>Configuration files</heading>
6907 <heading>Definitions</heading>
6911 <tag>configuration file</tag>
6913 A file that affects the operation of a program, or
6914 provides site- or host-specific information, or
6915 otherwise customizes the behavior of a program.
6916 Typically, configuration files are intended to be
6917 modified by the system administrator (if needed or
6918 desired) to conform to local policy or to provide
6919 more useful site-specific behavior.
6922 <tag><tt>conffile</tt></tag>
6924 A file listed in a package's <tt>conffiles</tt>
6925 file, and is treated specially by <prgn>dpkg</prgn>
6926 (see <ref id="configdetails">).
6932 The distinction between these two is important; they are
6933 not interchangeable concepts. Almost all
6934 <tt>conffile</tt>s are configuration files, but many
6935 configuration files are not <tt>conffiles</tt>.
6939 Note that a script that embeds configuration information
6940 (such as most of the files in <file>/etc/default</file> and
6941 <file>/etc/cron.{daily,weekly,monthly}</file>) is de-facto a
6942 configuration file and should be treated as such.
6947 <heading>Location</heading>
6950 Any configuration files created or used by your package
6951 must reside in <file>/etc</file>. If there are several,
6952 consider creating a subdirectory of <file>/etc</file>
6953 named after your package.
6957 If your package creates or uses configuration files
6958 outside of <file>/etc</file>, and it is not feasible to modify
6959 the package to use <file>/etc</file> directly, put the files
6960 in <file>/etc</file> and create symbolic links to those files
6961 from the location that the package requires.
6966 <heading>Behavior</heading>
6969 Configuration file handling must conform to the following
6971 <list compact="compact">
6973 local changes must be preserved during a package
6977 configuration files must be preserved when the
6978 package is removed, and only deleted when the
6985 The easy way to achieve this behavior is to make the
6986 configuration file a <tt>conffile</tt>. This is
6987 appropriate only if it is possible to distribute a default
6988 version that will work for most installations, although
6989 some system administrators may choose to modify it. This
6990 implies that the default version will be part of the
6991 package distribution, and must not be modified by the
6992 maintainer scripts during installation (or at any other
6997 In order to ensure that local changes are preserved
6998 correctly, no package may contain or make hard links to
6999 conffiles.<footnote>
7000 Rationale: There are two problems with hard links.
7001 The first is that some editors break the link while
7002 editing one of the files, so that the two files may
7003 unwittingly become unlinked and different. The second
7004 is that <prgn>dpkg</prgn> might break the hard link
7005 while upgrading <tt>conffile</tt>s.
7010 The other way to do it is via the maintainer scripts. In
7011 this case, the configuration file must not be listed as a
7012 <tt>conffile</tt> and must not be part of the package
7013 distribution. If the existence of a file is required for
7014 the package to be sensibly configured it is the
7015 responsibility of the package maintainer to provide
7016 maintainer scripts which correctly create, update and
7017 maintain the file and remove it on purge. (See <ref
7018 id="maintainerscripts"> for more information.) These
7019 scripts must be idempotent (i.e., must work correctly if
7020 <prgn>dpkg</prgn> needs to re-run them due to errors
7021 during installation or removal), must cope with all the
7022 variety of ways <prgn>dpkg</prgn> can call maintainer
7023 scripts, must not overwrite or otherwise mangle the user's
7024 configuration without asking, must not ask unnecessary
7025 questions (particularly during upgrades), and must
7026 otherwise be good citizens.
7030 The scripts are not required to configure every possible
7031 option for the package, but only those necessary to get
7032 the package running on a given system. Ideally the
7033 sysadmin should not have to do any configuration other
7034 than that done (semi-)automatically by the
7035 <prgn>postinst</prgn> script.
7039 A common practice is to create a script called
7040 <file><var>package</var>-configure</file> and have the
7041 package's <prgn>postinst</prgn> call it if and only if the
7042 configuration file does not already exist. In certain
7043 cases it is useful for there to be an example or template
7044 file which the maintainer scripts use. Such files should
7045 be in <file>/usr/share/<var>package</var></file> or
7046 <file>/usr/lib/<var>package</var></file> (depending on whether
7047 they are architecture-independent or not). There should
7048 be symbolic links to them from
7049 <file>/usr/share/doc/<var>package</var>/examples</file> if
7050 they are examples, and should be perfectly ordinary
7051 <prgn>dpkg</prgn>-handled files (<em>not</em>
7052 configuration files).
7056 These two styles of configuration file handling must
7057 not be mixed, for that way lies madness:
7058 <prgn>dpkg</prgn> will ask about overwriting the file
7059 every time the package is upgraded.
7064 <heading>Sharing configuration files</heading>
7067 Packages which specify the same file as a
7068 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7069 with each other. (This is an instance of the general rule
7070 about not sharing files. Note that neither alternatives
7071 nor diversions are likely to be appropriate in this case;
7072 in particular, <prgn>dpkg</prgn> does not handle diverted
7073 <tt>conffile</tt>s well.)
7077 The maintainer scripts must not alter a <tt>conffile</tt>
7078 of <em>any</em> package, including the one the scripts
7083 If two or more packages use the same configuration file
7084 and it is reasonable for both to be installed at the same
7085 time, one of these packages must be defined as
7086 <em>owner</em> of the configuration file, i.e., it will be
7087 the package which handles that file as a configuration
7088 file. Other packages that use the configuration file must
7089 depend on the owning package if they require the
7090 configuration file to operate. If the other package will
7091 use the configuration file if present, but is capable of
7092 operating without it, no dependency need be declared.
7096 If it is desirable for two or more related packages to
7097 share a configuration file <em>and</em> for all of the
7098 related packages to be able to modify that configuration
7099 file, then the following should be done:
7100 <enumlist compact="compact">
7102 One of the related packages (the "owning" package)
7103 will manage the configuration file with maintainer
7104 scripts as described in the previous section.
7107 The owning package should also provide a program
7108 that the other packages may use to modify the
7112 The related packages must use the provided program
7113 to make any desired modifications to the
7114 configuration file. They should either depend on
7115 the core package to guarantee that the configuration
7116 modifier program is available or accept gracefully
7117 that they cannot modify the configuration file if it
7118 is not. (This is in addition to the fact that the
7119 configuration file may not even be present in the
7126 Sometimes it's appropriate to create a new package which
7127 provides the basic infrastructure for the other packages
7128 and which manages the shared configuration files. (The
7129 <tt>sgml-base</tt> package is a good example.)
7134 <heading>User configuration files ("dotfiles")</heading>
7137 The files in <file>/etc/skel</file> will automatically be
7138 copied into new user accounts by <prgn>adduser</prgn>.
7139 No other program should reference the files in
7140 <file>/etc/skel</file>.
7144 Therefore, if a program needs a dotfile to exist in
7145 advance in <file>$HOME</file> to work sensibly, that dotfile
7146 should be installed in <file>/etc/skel</file> and treated as a
7151 However, programs that require dotfiles in order to
7152 operate sensibly are a bad thing, unless they do create
7153 the dotfiles themselves automatically.
7157 Furthermore, programs should be configured by the Debian
7158 default installation to behave as closely to the upstream
7159 default behavior as possible.
7163 Therefore, if a program in a Debian package needs to be
7164 configured in some way in order to operate sensibly, that
7165 should be done using a site-wide configuration file placed
7166 in <file>/etc</file>. Only if the program doesn't support a
7167 site-wide default configuration and the package maintainer
7168 doesn't have time to add it may a default per-user file be
7169 placed in <file>/etc/skel</file>.
7173 <file>/etc/skel</file> should be as empty as we can make it.
7174 This is particularly true because there is no easy (or
7175 necessarily desirable) mechanism for ensuring that the
7176 appropriate dotfiles are copied into the accounts of
7177 existing users when a package is installed.
7183 <heading>Log files</heading>
7185 Log files should usually be named
7186 <file>/var/log/<var>package</var>.log</file>. If you have many
7187 log files, or need a separate directory for permission
7188 reasons (<file>/var/log</file> is writable only by
7189 <file>root</file>), you should usually create a directory named
7190 <file>/var/log/<var>package</var></file> and place your log
7195 Log files must be rotated occasionally so that they don't
7196 grow indefinitely; the best way to do this is to drop a log
7197 rotation configuration file into the directory
7198 <file>/etc/logrotate.d</file> and use the facilities provided by
7199 logrotate.<footnote>
7201 The traditional approach to log files has been to set up
7202 <em>ad hoc</em> log rotation schemes using simple shell
7203 scripts and cron. While this approach is highly
7204 customizable, it requires quite a lot of sysadmin work.
7205 Even though the original Debian system helped a little
7206 by automatically installing a system which can be used
7207 as a template, this was deemed not enough.
7211 The use of <prgn>logrotate</prgn>, a program developed
7212 by Red Hat, is better, as it centralizes log management.
7213 It has both a configuration file
7214 (<file>/etc/logrotate.conf</file>) and a directory where
7215 packages can drop their individual log rotation
7216 configurations (<file>/etc/logrotate.d</file>).
7219 Here is a good example for a logrotate config
7220 file (for more information see <manref name="logrotate"
7222 <example compact="compact">
7223 /var/log/foo/*.log {
7228 /etc/init.d/foo force-reload
7232 This rotates all files under <file>/var/log/foo</file>, saves 12
7233 compressed generations, and forces the daemon to reload its
7234 configuration information after the log rotation.
7238 Log files should be removed when the package is
7239 purged (but not when it is only removed). This should be
7240 done by the <prgn>postrm</prgn> script when it is called
7241 with the argument <tt>purge</tt> (see <ref
7242 id="removedetails">).
7247 <heading>Permissions and owners</heading>
7250 The rules in this section are guidelines for general use.
7251 If necessary you may deviate from the details below.
7252 However, if you do so you must make sure that what is done
7253 is secure and you should try to be as consistent as possible
7254 with the rest of the system. You should probably also
7255 discuss it on <prgn>debian-devel</prgn> first.
7259 Files should be owned by <tt>root.root</tt>, and made
7260 writable only by the owner and universally readable (and
7261 executable, if appropriate), that is mode 644 or 755.
7265 Directories should be mode 755 or (for group-writability)
7266 mode 2775. The ownership of the directory should be
7267 consistent with its mode: if a directory is mode 2775, it
7268 should be owned by the group that needs write access to
7271 When a package is upgraded, and the owner or permissions
7272 of a file included in the package has changed, dpkg
7273 arranges for the ownership and permissions to be
7274 correctly set upon installation. However, this does not
7275 extend to directories; the permissions and ownership of
7276 directories already on the system does not change on
7277 install or upgrade of packages. This makes sense, since
7278 otherwise common directories like <tt>/usr</tt> would
7279 always be in flux. To correctly change permissions of a
7280 directory the package owns, explicit action is required,
7281 usually in the <tt>postinst</tt> script. Care must be
7282 taken to handle downgrades as well, in that case.
7289 Setuid and setgid executables should be mode 4755 or 2755
7290 respectively, and owned by the appropriate user or group.
7291 They should not be made unreadable (modes like 4711 or
7292 2711 or even 4111); doing so achieves no extra security,
7293 because anyone can find the binary in the freely available
7294 Debian package; it is merely inconvenient. For the same
7295 reason you should not restrict read or execute permissions
7296 on non-set-id executables.
7300 Some setuid programs need to be restricted to particular
7301 sets of users, using file permissions. In this case they
7302 should be owned by the uid to which they are set-id, and by
7303 the group which should be allowed to execute them. They
7304 should have mode 4754; again there is no point in making
7305 them unreadable to those users who must not be allowed to
7310 It is possible to arrange that the system administrator can
7311 reconfigure the package to correspond to their local
7312 security policy by changing the permissions on a binary:
7313 they can do this by using <prgn>dpkg-statoverride</prgn>, as
7314 described below.<footnote>
7315 Ordinary files installed by <prgn>dpkg</prgn> (as
7316 opposed to <tt>conffile</tt>s and other similar objects)
7317 normally have their permissions reset to the distributed
7318 permissions when the package is reinstalled. However,
7319 the use of <prgn>dpkg-statoverride</prgn> overrides this
7320 default behavior. If you use this method, you should
7321 remember to describe <prgn>dpkg-statoverride</prgn> in
7322 the package documentation; being a relatively new
7323 addition to Debian, it is probably not yet well-known.
7325 Another method you should consider is to create a group for
7326 people allowed to use the program(s) and make any setuid
7327 executables executable only by that group.
7331 If you need to create a new user or group for your package
7332 there are two possibilities. Firstly, you may need to
7333 make some files in the binary package be owned by this
7334 user or group, or you may need to compile the user or
7335 group id (rather than just the name) into the binary
7336 (though this latter should be avoided if possible, as in
7337 this case you need a statically allocated id).</p>
7340 If you need a statically allocated id, you must ask for a
7341 user or group id from the <tt>base-passwd</tt> maintainer,
7342 and must not release the package until you have been
7343 allocated one. Once you have been allocated one you must
7344 either make the package depend on a version of the
7345 <tt>base-passwd</tt> package with the id present in
7346 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
7347 your package to create the user or group itself with the
7348 correct id (using <tt>adduser</tt>) in its
7349 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
7350 the <prgn>postinst</prgn> is to be preferred if it is
7351 possible, otherwise a pre-dependency will be needed on the
7352 <tt>adduser</tt> package.)
7356 On the other hand, the program might be able to determine
7357 the uid or gid from the user or group name at runtime, so
7358 that a dynamically allocated id can be used. In this case
7359 you should choose an appropriate user or group name,
7360 discussing this on <prgn>debian-devel</prgn> and checking
7361 with the <package/base-passwd/ maintainer that it is unique and that
7362 they do not wish you to use a statically allocated id
7363 instead. When this has been checked you must arrange for
7364 your package to create the user or group if necessary using
7365 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
7366 <prgn>postinst</prgn> script (again, the latter is to be
7367 preferred if it is possible).
7371 Note that changing the numeric value of an id associated
7372 with a name is very difficult, and involves searching the
7373 file system for all appropriate files. You need to think
7374 carefully whether a static or dynamic id is required, since
7375 changing your mind later will cause problems.
7378 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
7380 This section is not intended as policy, but as a
7381 description of the use of <prgn>dpkg-statoverride</prgn>.
7385 <prgn>dpkg-statoverride</prgn> is a replacement for the
7386 deprecated <tt>suidmanager</tt> package. Packages which
7387 previously used <tt>suidmanager</tt> should have a
7388 <tt>Conflicts: suidmanager (<< 0.50)</tt> entry (or even
7389 <tt>(<< 0.52)</tt>), and calls to <tt>suidregister</tt>
7390 and <tt>suidunregister</tt> should now be simply removed
7391 from the maintainer scripts.
7395 If a system administrator wishes to have a file (or
7396 directory or other such thing) installed with owner and
7397 permissions different from those in the distributed Debian
7398 package, they can use the <prgn>dpkg-statoverride</prgn>
7399 program to instruct <prgn>dpkg</prgn> to use the different
7400 settings every time the file is installed. Thus the
7401 package maintainer should distribute the files with their
7402 normal permissions, and leave it for the system
7403 administrator to make any desired changes. For example, a
7404 daemon which is normally required to be setuid root, but
7405 in certain situations could be used without being setuid,
7406 should be installed setuid in the <tt>.deb</tt>. Then the
7407 local system administrator can change this if they wish.
7408 If there are two standard ways of doing it, the package
7409 maintainer can use <tt>debconf</tt> to find out the
7410 preference, and call <prgn>dpkg-statoverride</prgn> in the
7411 maintainer script if necessary to accommodate the system
7412 administrator's choice. Care must be taken during
7413 upgrades to not override an existing setting.
7417 Given the above, <prgn>dpkg-statoverride</prgn> is
7418 essentially a tool for system administrators and would not
7419 normally be needed in the maintainer scripts. There is
7420 one type of situation, though, where calls to
7421 <prgn>dpkg-statoverride</prgn> would be needed in the
7422 maintainer scripts, and that involves packages which use
7423 dynamically allocated user or group ids. In such a
7424 situation, something like the following idiom can be very
7425 helpful in the package's <prgn>postinst</prgn>, where
7426 <tt>sysuser</tt> is a dynamically allocated id:
7428 for i in /usr/bin/foo /usr/sbin/bar
7430 # only do something when no setting exists
7431 if ! dpkg-statoverride --list $i >/dev/null 2>&1
7433 #include: debconf processing, question about foo and bar
7434 if [ "$RET" = "true" ] ; then
7435 dpkg-statoverride --update --add sysuser root 4755 $i
7440 The corresponding <tt>dpkg-statoverride --remove</tt>
7441 calls can then be made unconditionally when the package is
7449 <chapt id="customized-programs">
7450 <heading>Customized programs</heading>
7452 <sect id="arch-spec">
7453 <heading>Architecture specification strings</heading>
7456 If a program needs to specify an <em>architecture specification
7457 string</em> in some place, it should select one of the
7458 strings provided by <tt>dpkg-architecture -L</tt>. The
7459 strings are in the format
7460 <tt><var>os</var>-<var>arch</var></tt>, though the OS part
7461 is sometimes elided, as when the OS is Linux.<footnote>
7462 <p>Currently, the strings are:
7463 i386 ia64 alpha amd64 armeb arm hppa m32r m68k mips
7464 mipsel powerpc ppc64 s390 s390x sh3 sh3eb sh4 sh4eb
7465 sparc darwin-i386 darwin-ia64 darwin-alpha darwin-amd64
7466 darwin-armeb darwin-arm darwin-hppa darwin-m32r
7467 darwin-m68k darwin-mips darwin-mipsel darwin-powerpc
7468 darwin-ppc64 darwin-s390 darwin-s390x darwin-sh3
7469 darwin-sh3eb darwin-sh4 darwin-sh4eb darwin-sparc
7470 freebsd-i386 freebsd-ia64 freebsd-alpha freebsd-amd64
7471 freebsd-armeb freebsd-arm freebsd-hppa freebsd-m32r
7472 freebsd-m68k freebsd-mips freebsd-mipsel freebsd-powerpc
7473 freebsd-ppc64 freebsd-s390 freebsd-s390x freebsd-sh3
7474 freebsd-sh3eb freebsd-sh4 freebsd-sh4eb freebsd-sparc
7475 kfreebsd-i386 kfreebsd-ia64 kfreebsd-alpha
7476 kfreebsd-amd64 kfreebsd-armeb kfreebsd-arm kfreebsd-hppa
7477 kfreebsd-m32r kfreebsd-m68k kfreebsd-mips
7478 kfreebsd-mipsel kfreebsd-powerpc kfreebsd-ppc64
7479 kfreebsd-s390 kfreebsd-s390x kfreebsd-sh3 kfreebsd-sh3eb
7480 kfreebsd-sh4 kfreebsd-sh4eb kfreebsd-sparc knetbsd-i386
7481 knetbsd-ia64 knetbsd-alpha knetbsd-amd64 knetbsd-armeb
7482 knetbsd-arm knetbsd-hppa knetbsd-m32r knetbsd-m68k
7483 knetbsd-mips knetbsd-mipsel knetbsd-powerpc
7484 knetbsd-ppc64 knetbsd-s390 knetbsd-s390x knetbsd-sh3
7485 knetbsd-sh3eb knetbsd-sh4 knetbsd-sh4eb knetbsd-sparc
7486 netbsd-i386 netbsd-ia64 netbsd-alpha netbsd-amd64
7487 netbsd-armeb netbsd-arm netbsd-hppa netbsd-m32r
7488 netbsd-m68k netbsd-mips netbsd-mipsel netbsd-powerpc
7489 netbsd-ppc64 netbsd-s390 netbsd-s390x netbsd-sh3
7490 netbsd-sh3eb netbsd-sh4 netbsd-sh4eb netbsd-sparc
7491 openbsd-i386 openbsd-ia64 openbsd-alpha openbsd-amd64
7492 openbsd-armeb openbsd-arm openbsd-hppa openbsd-m32r
7493 openbsd-m68k openbsd-mips openbsd-mipsel openbsd-powerpc
7494 openbsd-ppc64 openbsd-s390 openbsd-s390x openbsd-sh3
7495 openbsd-sh3eb openbsd-sh4 openbsd-sh4eb openbsd-sparc
7496 hurd-i386 hurd-ia64 hurd-alpha hurd-amd64 hurd-armeb
7497 hurd-arm hurd-hppa hurd-m32r hurd-m68k hurd-mips
7498 hurd-mipsel hurd-powerpc hurd-ppc64 hurd-s390 hurd-s390x
7499 hurd-sh3 hurd-sh3eb hurd-sh4 hurd-sh4eb hurd-sparc
7505 Note that we don't want to use
7506 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
7507 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
7508 since this would make our programs incompatible with other
7509 Linux distributions. We also don't use something like
7510 <tt><var>arch</var>-unknown-linux</tt>, since the
7511 <tt>unknown</tt> does not look very good.
7516 <heading>Daemons</heading>
7519 The configuration files <file>/etc/services</file>,
7520 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
7521 by the <prgn>netbase</prgn> package and must not be modified
7526 If a package requires a new entry in one of these files, the
7527 maintainer should get in contact with the
7528 <prgn>netbase</prgn> maintainer, who will add the entries
7529 and release a new version of the <prgn>netbase</prgn>
7534 The configuration file <file>/etc/inetd.conf</file> must not be
7535 modified by the package's scripts except via the
7536 <prgn>update-inetd</prgn> script or the
7537 <file>DebianNet.pm</file> Perl module. See their documentation
7538 for details on how to add entries.
7542 If a package wants to install an example entry into
7543 <file>/etc/inetd.conf</file>, the entry must be preceded with
7544 exactly one hash character (<tt>#</tt>). Such lines are
7545 treated as "commented out by user" by the
7546 <prgn>update-inetd</prgn> script and are not changed or
7547 activated during package updates.
7552 <heading>Using pseudo-ttys and modifying wtmp, utmp and
7556 Some programs need to create pseudo-ttys. This should be done
7557 using Unix98 ptys if the C library supports it. The resulting
7558 program must not be installed setuid root, unless that
7559 is required for other functionality.
7563 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
7564 <file>/var/log/lastlog</file> must be installed writable by
7565 group <tt>utmp</tt>. Programs which need to modify those
7566 files must be installed setgid <tt>utmp</tt>.
7571 <heading>Editors and pagers</heading>
7574 Some programs have the ability to launch an editor or pager
7575 program to edit or display a text document. Since there are
7576 lots of different editors and pagers available in the Debian
7577 distribution, the system administrator and each user should
7578 have the possibility to choose their preferred editor and
7583 In addition, every program should choose a good default
7584 editor/pager if none is selected by the user or system
7589 Thus, every program that launches an editor or pager must
7590 use the EDITOR or PAGER environment variable to determine
7591 the editor or pager the user wishes to use. If these
7592 variables are not set, the programs <file>/usr/bin/editor</file>
7593 and <file>/usr/bin/pager</file> should be used, respectively.
7597 These two files are managed through the <prgn>dpkg</prgn>
7598 "alternatives" mechanism. Thus every package providing an
7599 editor or pager must call the
7600 <prgn>update-alternatives</prgn> script to register these
7605 If it is very hard to adapt a program to make use of the
7606 EDITOR or PAGER variables, that program may be configured to
7607 use <file>/usr/bin/sensible-editor</file> and
7608 <file>/usr/bin/sensible-pager</file> as the editor or pager
7609 program respectively. These are two scripts provided in the
7610 Debian base system that check the EDITOR and PAGER variables
7611 and launch the appropriate program, and fall back to
7612 <file>/usr/bin/editor</file> and <file>/usr/bin/pager</file> if the
7613 variable is not set.
7617 A program may also use the VISUAL environment variable to
7618 determine the user's choice of editor. If it exists, it
7619 should take precedence over EDITOR. This is in fact what
7620 <file>/usr/bin/sensible-editor</file> does.
7624 It is not required for a package to depend on
7625 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
7626 package to provide such virtual packages.<footnote>
7627 The Debian base system already provides an editor and a
7633 <sect id="web-appl">
7634 <heading>Web servers and applications</heading>
7637 This section describes the locations and URLs that should
7638 be used by all web servers and web applications in the
7645 Cgi-bin executable files are installed in the
7647 <example compact="compact">
7648 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
7650 and should be referred to as
7651 <example compact="compact">
7652 http://localhost/cgi-bin/<var>cgi-bin-name</var>
7658 <p>Access to HTML documents</p>
7661 HTML documents for a package are stored in
7662 <file>/usr/share/doc/<var>package</var></file>
7663 and can be referred to as
7664 <example compact="compact">
7665 http://localhost/doc/<var>package</var>/<var>filename</var>
7670 The web server should restrict access to the document
7671 tree so that only clients on the same host can read
7672 the documents. If the web server does not support such
7673 access controls, then it should not provide access at
7674 all, or ask about providing access during installation.
7679 <p>Access to images</p>
7681 It is recommended that images for a package be stored
7682 in <tt>/usr/share/images/<var>package</var></tt> and
7683 may be referred to through an alias <tt>/images/</tt>
7686 http://localhost/images/<package>/<filename>
7693 <p>Web Document Root</p>
7696 Web Applications should try to avoid storing files in
7697 the Web Document Root. Instead they should use the
7698 /usr/share/doc/<var>package</var> directory for
7699 documents and register the Web Application via the
7700 <package>doc-base</package> package. If access to the
7701 web document root is unavoidable then use
7702 <example compact="compact">
7705 as the Document Root. This might be just a symbolic
7706 link to the location where the system administrator
7707 has put the real document root.
7710 <item><p>Providing httpd and/or httpd-cgi</p>
7712 All web servers should provide the virtual package
7713 <tt>httpd</tt>. If a web server has CGI support it should
7714 provide <tt>httpd-cgi</tt> additionally.
7717 All web applications which do not contain CGI scripts should
7718 depend on <tt>httpd</tt>, all those web applications which
7719 <tt>do</tt> contain CGI scripts, should depend on
7727 <sect id="mail-transport-agents">
7728 <heading>Mail transport, delivery and user agents</heading>
7731 Debian packages which process electronic mail, whether mail
7732 user agents (MUAs) or mail transport agents (MTAs), must
7733 ensure that they are compatible with the configuration
7734 decisions below. Failure to do this may result in lost
7735 mail, broken <tt>From:</tt> lines, and other serious brain
7740 The mail spool is <file>/var/mail</file> and the interface to
7741 send a mail message is <file>/usr/sbin/sendmail</file> (as per
7742 the FHS). On older systems, the mail spool may be
7743 physically located in <file>/var/spool/mail</file>, but all
7744 access to the mail spool should be via the
7745 <file>/var/mail</file> symlink. The mail spool is part of the
7746 base system and not part of the MTA package.
7750 All Debian MUAs, MTAs, MDAs and other mailbox accessing
7751 programs (such as IMAP daemons) must lock the mailbox in an
7752 NFS-safe way. This means that <tt>fcntl()</tt> locking must
7753 be combined with dot locking. To avoid deadlocks, a program
7754 should use <tt>fcntl()</tt> first and dot locking after
7755 this, or alternatively implement the two locking methods in
7756 a non blocking way<footnote>
7757 If it is not possible to establish both locks, the
7758 system shouldn't wait for the second lock to be
7759 established, but remove the first lock, wait a (random)
7760 time, and start over locking again.
7761 </footnote>. Using the functions <tt>maillock</tt> and
7762 <tt>mailunlock</tt> provided by the
7763 <tt>liblockfile*</tt><footnote>
7764 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
7765 to use these functions.
7766 </footnote> packages is the recommended way to realize this.
7770 Mailboxes are generally mode 660
7771 <tt><var>user</var>.mail</tt> unless the system
7772 administrator has chosen otherwise. A MUA may remove a
7773 mailbox (unless it has nonstandard permissions) in which
7774 case the MTA or another MUA must recreate it if needed.
7775 Mailboxes must be writable by group mail.
7779 The mail spool is 2775 <tt>root.mail</tt>, and MUAs should
7780 be setgid mail to do the locking mentioned above (and
7781 must obviously avoid accessing other users' mailboxes
7782 using this privilege).</p>
7785 <file>/etc/aliases</file> is the source file for the system mail
7786 aliases (e.g., postmaster, usenet, etc.), it is the one
7787 which the sysadmin and <prgn>postinst</prgn> scripts may
7788 edit. After <file>/etc/aliases</file> is edited the program or
7789 human editing it must call <prgn>newaliases</prgn>. All MTA
7790 packages must come with a <prgn>newaliases</prgn> program,
7791 even if it does nothing, but older MTA packages did not do
7792 this so programs should not fail if <prgn>newaliases</prgn>
7793 cannot be found. Note that because of this, all MTA
7794 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
7795 <tt>Replaces: mail-transport-agent</tt> control file
7800 The convention of writing <tt>forward to
7801 <var>address</var></tt> in the mailbox itself is not
7802 supported. Use a <tt>.forward</tt> file instead.</p>
7805 The <prgn>rmail</prgn> program used by UUCP
7806 for incoming mail should be <file>/usr/sbin/rmail</file>.
7807 Likewise, <prgn>rsmtp</prgn>, for receiving
7808 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
7812 If your package needs to know what hostname to use on (for
7813 example) outgoing news and mail messages which are generated
7814 locally, you should use the file <file>/etc/mailname</file>. It
7815 will contain the portion after the username and <tt>@</tt>
7816 (at) sign for email addresses of users on the machine
7817 (followed by a newline).
7821 Such a package should check for the existence of this file
7822 when it is being configured. If it exists, it should be
7823 used without comment, although an MTA's configuration script
7824 may wish to prompt the user even if it finds that this file
7825 exists. If the file does not exist, the package should
7826 prompt the user for the value (preferably using
7827 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
7828 as well as using it in the package's configuration. The
7829 prompt should make it clear that the name will not just be
7830 used by that package. For example, in this situation the
7831 <tt>inn</tt> package could say something like:
7832 <example compact="compact">
7833 Please enter the "mail name" of your system. This is the
7834 hostname portion of the address to be shown on outgoing
7835 news and mail messages. The default is
7836 <var>syshostname</var>, your system's host name. Mail
7837 name ["<var>syshostname</var>"]:
7839 where <var>syshostname</var> is the output of <tt>hostname
7845 <heading>News system configuration</heading>
7848 All the configuration files related to the NNTP (news)
7849 servers and clients should be located under
7850 <file>/etc/news</file>.</p>
7853 There are some configuration issues that apply to a number
7854 of news clients and server packages on the machine. These
7858 <tag><file>/etc/news/organization</file></tag>
7860 A string which should appear as the
7861 organization header for all messages posted
7862 by NNTP clients on the machine
7865 <tag><file>/etc/news/server</file></tag>
7867 Contains the FQDN of the upstream NNTP
7868 server, or localhost if the local machine is
7873 Other global files may be added as required for cross-package news
7880 <heading>Programs for the X Window System</heading>
7883 <heading>Providing X support and package priorities</heading>
7886 Programs that can be configured with support for the X
7887 Window System must be configured to do so and must declare
7888 any package dependencies necessary to satisfy their
7889 runtime requirements when using the X Window System. If
7890 such a package is of higher priority than the X packages
7891 on which it depends, it is required that either the
7892 X-specific components be split into a separate package, or
7893 that an alternative version of the package, which includes
7894 X support, be provided, or that the package's priority be
7900 <heading>Packages providing an X server</heading>
7903 Packages that provide an X server that, directly or
7904 indirectly, communicates with real input and display
7905 hardware should declare in their control data that they
7906 provide the virtual package <tt>xserver</tt>.<footnote>
7907 This implements current practice, and provides an
7908 actual policy for usage of the <tt>xserver</tt>
7909 virtual package which appears in the virtual packages
7910 list. In a nutshell, X servers that interface
7911 directly with the display and input hardware or via
7912 another subsystem (e.g., GGI) should provide
7913 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
7914 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
7920 <heading>Packages providing a terminal emulator</heading>
7923 Packages that provide a terminal emulator for the X Window
7924 System which meet the criteria listed below should declare
7925 in their control data that they provide the virtual
7926 package <tt>x-terminal-emulator</tt>. They should also
7927 register themselves as an alternative for
7928 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
7933 To be an <tt>x-terminal-emulator</tt>, a program must:
7934 <list compact="compact">
7936 Be able to emulate a DEC VT100 terminal, or a
7937 compatible terminal.
7941 Support the command-line option <tt>-e
7942 <var>command</var></tt>, which creates a new
7943 terminal window<footnote>
7944 "New terminal window" does not necessarily mean
7945 a new top-level X window directly parented by
7946 the window manager; it could, if the terminal
7947 emulator application were so coded, be a new
7948 "view" in a multiple-document interface (MDI).
7950 and runs the specified <var>command</var>,
7951 interpreting the entirety of the rest of the command
7952 line as a command to pass straight to exec, in the
7953 manner that <tt>xterm</tt> does.
7957 Support the command-line option <tt>-T
7958 <var>title</var></tt>, which creates a new terminal
7959 window with the window title <var>title</var>.
7966 <heading>Packages providing a window manager</heading>
7969 Packages that provide a window manager should declare in
7970 their control data that they provide the virtual package
7971 <tt>x-window-manager</tt>. They should also register
7972 themselves as an alternative for
7973 <file>/usr/bin/x-window-manager</file>, with a priority
7974 calculated as follows:
7975 <list compact="compact">
7977 Start with a priority of 20.
7981 If the window manager supports the Debian menu
7982 system, add 20 points if this support is available
7983 in the package's default configuration (i.e., no
7984 configuration files belonging to the system or user
7985 have to be edited to activate the feature); if
7986 configuration files must be modified, add only 10
7992 If the window manager complies with <url
7993 id="http://www.freedesktop.org/Standards/wm-spec"
7994 name="The Window Manager Specification Project">,
7995 written by the <url id="http://www.freedesktop.org/"
7996 name="Free Desktop Group">, add 40 points.
8000 If the window manager permits the X session to be
8001 restarted using a <em>different</em> window manager
8002 (without killing the X server) in its default
8003 configuration, add 10 points; otherwise add none.
8010 <heading>Packages providing fonts</heading>
8013 Packages that provide fonts for the X Window
8015 For the purposes of Debian Policy, a "font for the X
8016 Window System" is one which is accessed via X protocol
8017 requests. Fonts for the Linux console, for PostScript
8018 renderer, or any other purpose, do not fit this
8019 definition. Any tool which makes such fonts available
8020 to the X Window System, however, must abide by this
8023 must do a number of things to ensure that they are both
8024 available without modification of the X or font server
8025 configuration, and that they do not corrupt files used by
8026 other font packages to register information about
8030 Fonts of any type supported by the X Window System
8031 must be in a separate binary package from any
8032 executables, libraries, or documentation (except
8033 that specific to the fonts shipped, such as their
8034 license information). If one or more of the fonts
8035 so packaged are necessary for proper operation of
8036 the package with which they are associated the font
8037 package may be Recommended; if the fonts merely
8038 provide an enhancement, a Suggests relationship may
8039 be used. Packages must not Depend on font
8041 This is because the X server may retrieve fonts
8042 from the local file system or over the network
8043 from an X font server; the Debian package system
8044 is empowered to deal only with the local
8050 BDF fonts must be converted to PCF fonts with the
8051 <prgn>bdftopcf</prgn> utility (available in the
8052 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8053 placed in a directory that corresponds to their
8055 <list compact="compact">
8057 100 dpi fonts must be placed in
8058 <file>/usr/share/fonts/X11/100dpi/</file>.
8062 75 dpi fonts must be placed in
8063 <file>/usr/share/fonts/X11/75dpi/</file>.
8067 Character-cell fonts, cursor fonts, and other
8068 low-resolution fonts must be placed in
8069 <file>/usr/share/fonts/X11/misc/</file>.
8075 Speedo fonts must be placed in
8076 <file>/usr/share/fonts/X11/Speedo/</file>.
8080 Type 1 fonts must be placed in
8081 <file>/usr/share/fonts/X11/Type1/</file>. If font
8082 metric files are available, they must be placed here
8087 Subdirectories of <file>/usr/share/fonts/X11/</file>
8088 other than those listed above must be neither
8089 created nor used. (The <file>PEX</file>, <file>CID</file>,
8090 and <file>cyrillic</file> directories are excepted for
8091 historical reasons, but installation of files into
8092 these directories remains discouraged.)
8096 Font packages may, instead of placing files directly
8097 in the X font directories listed above, provide
8098 symbolic links in that font directory pointing to
8099 the files' actual location in the filesystem. Such
8100 a location must comply with the FHS.
8104 Font packages should not contain both 75dpi and
8105 100dpi versions of a font. If both are available,
8106 they should be provided in separate binary packages
8107 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8108 the names of the packages containing the
8109 corresponding fonts.
8113 Fonts destined for the <file>misc</file> subdirectory
8114 should not be included in the same package as 75dpi
8115 or 100dpi fonts; instead, they should be provided in
8116 a separate package with <tt>-misc</tt> appended to
8121 Font packages must not provide the files
8122 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8123 <file>fonts.scale</file> in a font directory:
8126 <file>fonts.dir</file> files must not be provided at all.
8130 <file>fonts.alias</file> and <file>fonts.scale</file>
8131 files, if needed, should be provided in the
8133 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8134 where <var>fontdir</var> is the name of the
8136 <file>/usr/share/fonts/X11/</file> where the
8137 package's corresponding fonts are stored
8138 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8139 <var>package</var> is the name of the package
8140 that provides these fonts, and
8141 <var>extension</var> is either <tt>scale</tt>
8142 or <tt>alias</tt>, whichever corresponds to
8149 Font packages must declare a dependency on
8150 <tt>xfonts-utils</tt> in their control
8155 Font packages that provide one or more
8156 <file>fonts.scale</file> files as described above must
8157 invoke <prgn>update-fonts-scale</prgn> on each
8158 directory into which they installed fonts
8159 <em>before</em> invoking
8160 <prgn>update-fonts-dir</prgn> on that directory.
8161 This invocation must occur in both the
8162 <prgn>postinst</prgn> (for all arguments) and
8163 <prgn>postrm</prgn> (for all arguments except
8164 <tt>upgrade</tt>) scripts.
8168 Font packages that provide one or more
8169 <file>fonts.alias</file> files as described above must
8170 invoke <prgn>update-fonts-alias</prgn> on each
8171 directory into which they installed fonts. This
8172 invocation must occur in both the
8173 <prgn>postinst</prgn> (for all arguments) and
8174 <prgn>postrm</prgn> (for all arguments except
8175 <tt>upgrade</tt>) scripts.
8179 Font packages must invoke
8180 <prgn>update-fonts-dir</prgn> on each directory into
8181 which they installed fonts. This invocation must
8182 occur in both the <prgn>postinst</prgn> (for all
8183 arguments) and <prgn>postrm</prgn> (for all
8184 arguments except <tt>upgrade</tt>) scripts.
8188 Font packages must not provide alias names for the
8189 fonts they include which collide with alias names
8190 already in use by fonts already packaged.
8194 Font packages must not provide fonts with the same
8195 XLFD registry name as another font already packaged.
8202 <heading>Application defaults files</heading>
8205 Application defaults files must be installed in the
8206 directory <file>/etc/X11/app-defaults/</file> (use of a
8207 localized subdirectory of <file>/etc/X11/</file> as described
8208 in the <em>X Toolkit Intrinsics - C Language
8209 Interface</em> manual is also permitted). They must be
8210 registered as <tt>conffile</tt>s or handled as
8211 configuration files. Packages must not provide the
8212 directory <file>/usr/X11R6/lib/X11/app-defaults/</file>.
8216 Customization of programs' X resources may also be
8217 supported with the provision of a file with the same name
8218 as that of the package placed in the
8219 <file>/etc/X11/Xresources/</file> directory, which must
8220 registered as a <tt>conffile</tt> or handled as a
8221 configuration file.<footnote>
8222 Note that this mechanism is not the same as using
8223 app-defaults; app-defaults are tied to the client
8224 binary on the local file system, whereas X resources
8225 are stored in the X server and affect all connecting
8228 <em>Important:</em> packages that install files into the
8229 <file>/etc/X11/Xresources/</file> directory must conflict with
8230 <tt>xbase (<< 3.3.2.3a-2)</tt>; if this is not done
8231 it is possible for the installing package to destroy a
8232 previously-existing <file>/etc/X11/Xresources</file> file
8233 which had been customized by the system administrator.
8238 <heading>Installation directory issues</heading>
8241 Packages using the X Window System should not be
8242 configured to install files under the
8243 <file>/usr/X11R6/</file> directory. The
8244 <file>/usr/X11R6/</file> directory hierarchy should be
8245 regarded as obsolete.
8249 Programs that use GNU <prgn>autoconf</prgn> and
8250 <prgn>automake</prgn> are usually easily configured at
8251 compile time to use <file>/usr/</file> instead of
8252 <file>/usr/X11R6/</file>, and this should be done whenever
8253 possible. Configuration files for window managers and
8254 display managers should be placed in a subdirectory of
8255 <file>/etc/X11/</file> corresponding to the package name due
8256 to these programs' tight integration with the mechanisms
8257 of the X Window System. Application-level programs should
8258 use the <file>/etc/</file> directory unless otherwise mandated
8263 The installation of files into subdirectories
8264 of <file>/usr/X11R6/include/X11/</file> and
8265 <file>/usr/X11R6/lib/X11/</file> is now prohibited;
8266 package maintainers should determine if subdirectories of
8267 <file>/usr/lib/</file> and <file>/usr/share/</file> can be used
8272 Packages should install any relevant files into the
8273 directories <file>/usr/include/X11/</file> and
8274 <file>/usr/lib/X11/</file>, but if they do so, they must
8275 pre-depend on <tt>x11-common (>=
8276 1:7.0.0)</tt><footnote>
8278 These libraries used to be all symbolic
8279 links. However, with <tt>X11R7</tt>,
8280 <tt>/usr/include/X11</tt> and <tt>/usr/lib/X11</tt>
8281 are now real directories, and packages
8282 <strong>should</strong> ship their files here instead
8283 of in <tt>/usr/X11R6/{include,lib}/X11</tt>.
8284 <tt>x11-common (>= 1:7.0.0) </tt> is the package
8285 responsible for converting these symlinks into
8293 <heading>The OSF/Motif and OpenMotif libraries</heading>
8296 <em>Programs that require the non-DFSG-compliant OSF/Motif or
8297 OpenMotif libraries</em><footnote>
8298 OSF/Motif and OpenMotif are collectively referred to as
8299 "Motif" in this policy document.
8301 should be compiled against and tested with LessTif (a free
8302 re-implementation of Motif) instead. If the maintainer
8303 judges that the program or programs do not work
8304 sufficiently well with LessTif to be distributed and
8305 supported, but do so when compiled against Motif, then two
8306 versions of the package should be created; one linked
8307 statically against Motif and with <tt>-smotif</tt>
8308 appended to the package name, and one linked dynamically
8309 against Motif and with <tt>-dmotif</tt> appended to the
8314 Both Motif-linked versions are dependent
8315 upon non-DFSG-compliant software and thus cannot be
8316 uploaded to the <em>main</em> distribution; if the
8317 software is itself DFSG-compliant it may be uploaded to
8318 the <em>contrib</em> distribution. While known existing
8319 versions of Motif permit unlimited redistribution of
8320 binaries linked against the library (whether statically or
8321 dynamically), it is the package maintainer's
8322 responsibility to determine whether this is permitted by
8323 the license of the copy of Motif in their possession.
8329 <heading>Perl programs and modules</heading>
8332 Perl programs and modules should follow the current Perl policy.
8336 The Perl policy can be found in the <tt>perl-policy</tt>
8337 files in the <tt>debian-policy</tt> package.
8338 It is also available from the Debian web mirrors at
8339 <tt><url name="/doc/packaging-manuals/perl-policy/"
8340 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
8345 <heading>Emacs lisp programs</heading>
8348 Please refer to the "Debian Emacs Policy" for details of how to
8349 package emacs lisp programs.
8353 The Emacs policy is available in
8354 <file>debian-emacs-policy.gz</file> of the
8355 <package>emacsen-common</package> package.
8356 It is also available from the Debian web mirrors at
8357 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
8358 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
8363 <heading>Games</heading>
8366 The permissions on <file>/var/games</file> are mode 755, owner
8367 <tt>root</tt> and group <tt>root</tt>.
8371 Each game decides on its own security policy.</p>
8374 Games which require protected, privileged access to
8375 high-score files, saved games, etc., may be made
8376 set-<em>group</em>-id (mode 2755) and owned by
8377 <tt>root.games</tt>, and use files and directories with
8378 appropriate permissions (770 <tt>root.games</tt>, for
8379 example). They must not be made
8380 set-<em>user</em>-id, as this causes security problems. (If
8381 an attacker can subvert any set-user-id game they can
8382 overwrite the executable of any other, causing other players
8383 of these games to run a Trojan horse program. With a
8384 set-group-id game the attacker only gets access to less
8385 important game data, and if they can get at the other
8386 players' accounts at all it will take considerably more
8390 Some packages, for example some fortune cookie programs, are
8391 configured by the upstream authors to install with their
8392 data files or other static information made unreadable so
8393 that they can only be accessed through set-id programs
8394 provided. You should not do this in a Debian package: anyone can
8395 download the <file>.deb</file> file and read the data from it,
8396 so there is no point making the files unreadable. Not
8397 making the files unreadable also means that you don't have
8398 to make so many programs set-id, which reduces the risk of a
8402 As described in the FHS, binaries of games should be
8403 installed in the directory <file>/usr/games</file>. This also
8404 applies to games that use the X Window System. Manual pages
8405 for games (X and non-X games) should be installed in
8406 <file>/usr/share/man/man6</file>.</p>
8412 <heading>Documentation</heading>
8415 <heading>Manual pages</heading>
8418 You should install manual pages in <prgn>nroff</prgn> source
8419 form, in appropriate places under <file>/usr/share/man</file>.
8420 You should only use sections 1 to 9 (see the FHS for more
8421 details). You must not install a pre-formatted "cat page".
8425 Each program, utility, and function should have an
8426 associated manual page included in the same package. It is
8427 suggested that all configuration files also have a manual
8428 page included as well. Manual pages for protocols and other
8429 auxiliary things are optional.
8433 If no manual page is available, this is considered as a bug
8434 and should be reported to the Debian Bug Tracking System (the
8435 maintainer of the package is allowed to write this bug report
8436 themselves, if they so desire). Do not close the bug report
8437 until a proper man page is available.<footnote>
8438 It is not very hard to write a man page. See the
8439 <url id="http://www.schweikhardt.net/man_page_howto.html"
8440 name="Man-Page-HOWTO">,
8441 <manref name="man" section="7">, the examples
8442 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
8443 the helper programs <prgn>help2man</prgn>, or the
8444 directory <file>/usr/share/doc/man-db/examples</file>.
8449 You may forward a complaint about a missing man page to the
8450 upstream authors, and mark the bug as forwarded in the
8451 Debian bug tracking system. Even though the GNU Project do
8452 not in general consider the lack of a man page to be a bug,
8453 we do; if they tell you that they don't consider it a bug
8454 you should leave the bug in our bug tracking system open
8459 Manual pages should be installed compressed using <tt>gzip -9</tt>.
8463 If one man page needs to be accessible via several names it
8464 is better to use a symbolic link than the <file>.so</file>
8465 feature, but there is no need to fiddle with the relevant
8466 parts of the upstream source to change from <file>.so</file> to
8467 symlinks: don't do it unless it's easy. You should not
8468 create hard links in the manual page directories, nor put
8469 absolute filenames in <file>.so</file> directives. The filename
8470 in a <file>.so</file> in a man page should be relative to the
8471 base of the man page tree (usually
8472 <file>/usr/share/man</file>). If you do not create any links
8473 (whether symlinks, hard links, or <tt>.so</tt> directives)
8474 in the file system to the alternate names of the man page,
8475 then you should not rely on <prgn>man</prgn> finding your
8476 man page under those names based solely on the information in
8477 the man page's header.<footnote>
8478 Supporting this in <prgn>man</prgn> often requires
8479 unreasonable processing time to find a manual page or to
8480 report that none exists, and moves knowledge into man's
8481 database that would be better left in the file system.
8482 This support is therefore deprecated and will cease to
8483 be present in the future.
8489 <heading>Info documents</heading>
8492 Info documents should be installed in <file>/usr/share/info</file>.
8493 They should be compressed with <tt>gzip -9</tt>.
8497 Your package should call <prgn>install-info</prgn> to update
8498 the Info <file>dir</file> file in its <prgn>postinst</prgn>
8499 script when called with a <tt>configure</tt> argument, for
8501 <example compact="compact">
8502 install-info --quiet --section Development Development \
8503 /usr/share/info/foobar.info
8507 It is a good idea to specify a section for the location of
8508 your program; this is done with the <tt>--section</tt>
8509 switch. To determine which section to use, you should look
8510 at <file>/usr/share/info/dir</file> on your system and choose the most
8511 relevant (or create a new section if none of the current
8512 sections are relevant). Note that the <tt>--section</tt>
8513 flag takes two arguments; the first is a regular expression
8514 to match (case-insensitively) against an existing section,
8515 the second is used when creating a new one.</p>
8518 You should remove the entries in the <prgn>prerm</prgn>
8519 script when called with a <tt>remove</tt> argument:
8520 <example compact="compact">
8521 install-info --quiet --remove /usr/share/info/foobar.info
8525 If <prgn>install-info</prgn> cannot find a description entry
8526 in the Info file you must supply one. See <manref
8527 name="install-info" section="8"> for details.</p>
8531 <heading>Additional documentation</heading>
8534 Any additional documentation that comes with the package may
8535 be installed at the discretion of the package maintainer.
8536 Plain text documentation should be installed in the directory
8537 <file>/usr/share/doc/<var>package</var></file>, where
8538 <var>package</var> is the name of the package, and
8539 compressed with <tt>gzip -9</tt> unless it is small.
8543 If a package comes with large amounts of documentation which
8544 many users of the package will not require you should create
8545 a separate binary package to contain it, so that it does not
8546 take up disk space on the machines of users who do not need
8547 or want it installed.</p>
8550 It is often a good idea to put text information files
8551 (<file>README</file>s, changelogs, and so forth) that come with
8552 the source package in <file>/usr/share/doc/<var>package</var></file>
8553 in the binary package. However, you don't need to install
8554 the instructions for building and installing the package, of
8558 Packages must not require the existence of any files in
8559 <file>/usr/share/doc/</file> in order to function
8561 The system administrator should be able to
8562 delete files in <file>/usr/share/doc/</file> without causing
8563 any programs to break.
8565 Any files that are referenced by programs but are also
8566 useful as stand alone documentation should be installed under
8567 <file>/usr/share/<var>package</var>/</file> with symbolic links from
8568 <file>/usr/share/doc/<var>package</var></file>.
8572 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8573 link to another directory in <file>/usr/share/doc</file> only if
8574 the two packages both come from the same source and the
8575 first package Depends on the second.<footnote>
8577 Please note that this does not override the section on
8578 changelog files below, so the file
8579 <file>/usr/share/<var>package</var>/changelog.Debian.gz</file>
8580 must refer to the changelog for the current version of
8581 <var>package</var> in question. In practice, this means
8582 that the sources of the target and the destination of the
8583 symlink must be the same (same source package and
8590 Former Debian releases placed all additional documentation
8591 in <file>/usr/doc/<var>package</var></file>. This has been
8592 changed to <file>/usr/share/doc/<var>package</var></file>,
8593 and packages must not put documentation in the directory
8594 <file>/usr/doc/<var>package</var></file>. <footnote>
8595 At this phase of the transition, we no longer require a
8596 symbolic link in <file>/usr/doc/</file>. At a later point,
8597 policy shall change to make the symbolic links a bug.
8603 <heading>Preferred documentation formats</heading>
8606 The unification of Debian documentation is being carried out
8610 If your package comes with extensive documentation in a
8611 markup format that can be converted to various other formats
8612 you should if possible ship HTML versions in a binary
8613 package, in the directory
8614 <file>/usr/share/doc/<var>appropriate-package</var></file> or
8615 its subdirectories.<footnote>
8616 The rationale: The important thing here is that HTML
8617 docs should be available in <em>some</em> package, not
8618 necessarily in the main binary package.
8623 Other formats such as PostScript may be provided at the
8624 package maintainer's discretion.
8628 <sect id="copyrightfile">
8629 <heading>Copyright information</heading>
8632 Every package must be accompanied by a verbatim copy of its
8633 copyright and distribution license in the file
8634 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
8635 file must neither be compressed nor be a symbolic link.
8639 In addition, the copyright file must say where the upstream
8640 sources (if any) were obtained. It should name the original
8641 authors of the package and the Debian maintainer(s) who were
8642 involved with its creation.</p>
8645 A copy of the file which will be installed in
8646 <file>/usr/share/doc/<var>package</var>/copyright</file> should
8647 be in <file>debian/copyright</file> in the source package.
8651 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8652 link to another directory in <file>/usr/share/doc</file> only if
8653 the two packages both come from the same source and the
8654 first package Depends on the second. These rules are
8655 important because copyrights must be extractable by
8660 Packages distributed under the UCB BSD license, the Artistic
8661 license, the GNU GPL, and the GNU LGPL, should refer to the
8662 corresponding files under
8663 <file>/usr/share/common-licenses</file>,<footnote>
8666 <file>/usr/share/common-licenses/Artistic</file>,
8667 <file>/usr/share/common-licenses/BSD</file>,
8668 <file>/usr/share/common-licenses/GPL</file>,
8669 <file>/usr/share/common-licenses/LGPL</file>,
8670 <file>/usr/share/common-licenses/GFDL</file>,
8671 <file>/usr/share/common-licenses/GPL-2</file>, and
8672 <file>/usr/share/common-licenses/LGPL-2.1</file>, and so
8673 on. Note that the GFDL is new here, and the license file
8674 may not yet be in place in
8675 <file>/usr/share/common-licenses/GFDL</file>.
8677 </footnote> rather than quoting them in the copyright
8682 You should not use the copyright file as a general <file>README</file>
8683 file. If your package has such a file it should be
8684 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
8685 <file>README.Debian</file> or some other appropriate place.</p>
8689 <heading>Examples</heading>
8692 Any examples (configurations, source files, whatever),
8693 should be installed in a directory
8694 <file>/usr/share/doc/<var>package</var>/examples</file>. These
8695 files should not be referenced by any program: they're there
8696 for the benefit of the system administrator and users as
8697 documentation only. Architecture-specific example files
8698 should be installed in a directory
8699 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
8701 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
8702 latter directory itself may be a symbolic link to the
8707 If the purpose of a package is to provide examples, then the
8708 example files may be installed into
8709 <file>/usr/share/doc/<var>package</var></file>.
8713 <sect id="changelogs">
8714 <heading>Changelog files</heading>
8717 Packages that are not Debian-native must contain a
8718 compressed copy of the <file>debian/changelog</file> file from
8719 the Debian source tree in
8720 <file>/usr/share/doc/<var>package</var></file> with the name
8721 <file>changelog.Debian.gz</file>.
8725 If an upstream changelog is available, it should be accessible as
8726 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
8727 plain text. If the upstream changelog is distributed in
8728 HTML, it should be made available in that form as
8729 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
8730 and a plain text <file>changelog.gz</file> should be generated
8731 from it using, for example, <tt>lynx -dump -nolist</tt>. If
8732 the upstream changelog files do not already conform to this
8733 naming convention, then this may be achieved either by
8734 renaming the files, or by adding a symbolic link, at the
8735 maintainer's discretion.<footnote>
8736 Rationale: People should not have to look in places for
8737 upstream changelogs merely because they are given
8738 different names or are distributed in HTML format.
8743 All of these files should be installed compressed using
8744 <tt>gzip -9</tt>, as they will become large with time even
8745 if they start out small.
8749 If the package has only one changelog which is used both as
8750 the Debian changelog and the upstream one because there is
8751 no separate upstream maintainer then that changelog should
8752 usually be installed as
8753 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
8754 there is a separate upstream maintainer, but no upstream
8755 changelog, then the Debian changelog should still be called
8756 <file>changelog.Debian.gz</file>.
8760 For details about the format and contents of the Debian
8761 changelog file, please see <ref id="dpkgchangelog">.
8766 <appendix id="pkg-scope">
8767 <heading>Introduction and scope of these appendices</heading>
8770 These appendices are taken essentially verbatim from the
8771 now-deprecated Packaging Manual, version 3.2.1.0. They are
8772 the chapters which are likely to be of use to package
8773 maintainers and which have not already been included in the
8774 policy document itself. Most of these sections are very likely
8775 not relevant to policy; they should be treated as
8776 documentation for the packaging system. Please note that these
8777 appendices are included for convenience, and for historical
8778 reasons: they used to be part of policy package, and they have
8779 not yet been incorporated into dpkg documentation. However,
8780 they still have value, and hence they are presented here.
8784 They have not yet been checked to ensure that they are
8785 compatible with the contents of policy, and if there are any
8786 contradictions, the version in the main policy document takes
8787 precedence. The remaining chapters of the old Packaging
8788 Manual have also not been read in detail to ensure that there
8789 are not parts which have been left out. Both of these will be
8794 Certain parts of the Packaging manual were integrated into the
8795 Policy Manual proper, and removed from the appendices. Links
8796 have been placed from the old locations to the new ones.
8800 <prgn>dpkg</prgn> is a suite of programs for creating binary
8801 package files and installing and removing them on Unix
8803 <prgn>dpkg</prgn> is targeted primarily at Debian
8804 GNU/Linux, but may work on or be ported to other
8810 The binary packages are designed for the management of
8811 installed executable programs (usually compiled binaries) and
8812 their associated data, though source code examples and
8813 documentation are provided as part of some packages.</p>
8816 This manual describes the technical aspects of creating Debian
8817 binary packages (<file>.deb</file> files). It documents the
8818 behavior of the package management programs
8819 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
8820 they interact with packages.</p>
8823 It also documents the interaction between
8824 <prgn>dselect</prgn>'s core and the access method scripts it
8825 uses to actually install the selected packages, and describes
8826 how to create a new access method.</p>
8829 This manual does not go into detail about the options and
8830 usage of the package building and installation tools. It
8831 should therefore be read in conjunction with those programs'
8836 The utility programs which are provided with <prgn>dpkg</prgn>
8837 for managing various system configuration and similar issues,
8838 such as <prgn>update-rc.d</prgn> and
8839 <prgn>install-info</prgn>, are not described in detail here -
8840 please see their man pages.
8844 It is assumed that the reader is reasonably familiar with the
8845 <prgn>dpkg</prgn> System Administrators' manual.
8846 Unfortunately this manual does not yet exist.
8850 The Debian version of the FSF's GNU hello program is provided
8851 as an example for people wishing to create Debian
8852 packages. The Debian <prgn>debmake</prgn> package is
8853 recommended as a very helpful tool in creating and maintaining
8854 Debian packages. However, while the tools and examples are
8855 helpful, they do not replace the need to read and follow the
8856 Policy and Programmer's Manual.</p>
8859 <appendix id="pkg-binarypkg">
8860 <heading>Binary packages (from old Packaging Manual)</heading>
8863 The binary package has two main sections. The first part
8864 consists of various control information files and scripts used
8865 by <prgn>dpkg</prgn> when installing and removing. See <ref
8866 id="pkg-controlarea">.
8870 The second part is an archive containing the files and
8871 directories to be installed.
8875 In the future binary packages may also contain other
8876 components, such as checksums and digital signatures. The
8877 format for the archive is described in full in the
8878 <file>deb(5)</file> man page.
8882 <sect id="pkg-bincreating"><heading>Creating package files -
8883 <prgn>dpkg-deb</prgn>
8887 All manipulation of binary package files is done by
8888 <prgn>dpkg-deb</prgn>; it's the only program that has
8889 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
8890 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
8891 will spot that the options requested are appropriate to
8892 <prgn>dpkg-deb</prgn> and invoke that instead with the same
8897 In order to create a binary package you must make a
8898 directory tree which contains all the files and directories
8899 you want to have in the file system data part of the package.
8900 In Debian-format source packages this directory is usually
8901 <file>debian/tmp</file>, relative to the top of the package's
8906 They should have the locations (relative to the root of the
8907 directory tree you're constructing) ownerships and
8908 permissions which you want them to have on the system when
8913 With current versions of <prgn>dpkg</prgn> the uid/username
8914 and gid/groupname mappings for the users and groups being
8915 used should be the same on the system where the package is
8916 built and the one where it is installed.
8920 You need to add one special directory to the root of the
8921 miniature file system tree you're creating:
8922 <prgn>DEBIAN</prgn>. It should contain the control
8923 information files, notably the binary package control file
8924 (see <ref id="pkg-controlfile">).
8928 The <prgn>DEBIAN</prgn> directory will not appear in the
8929 file system archive of the package, and so won't be installed
8930 by <prgn>dpkg</prgn> when the package is installed.
8934 When you've prepared the package, you should invoke:
8936 dpkg --build <var>directory</var>
8941 This will build the package in
8942 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
8943 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
8944 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
8949 See the man page <manref name="dpkg-deb" section="8"> for details of how
8950 to examine the contents of this newly-created file. You may find the
8951 output of following commands enlightening:
8953 dpkg-deb --info <var>filename</var>.deb
8954 dpkg-deb --contents <var>filename</var>.deb
8955 dpkg --contents <var>filename</var>.deb
8957 To view the copyright file for a package you could use this command:
8959 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - \*/copyright | pager
8964 <sect id="pkg-controlarea">
8965 <heading>Package control information files</heading>
8968 The control information portion of a binary package is a
8969 collection of files with names known to <prgn>dpkg</prgn>.
8970 It will treat the contents of these files specially - some
8971 of them contain information used by <prgn>dpkg</prgn> when
8972 installing or removing the package; others are scripts which
8973 the package maintainer wants <prgn>dpkg</prgn> to run.
8977 It is possible to put other files in the package control
8978 area, but this is not generally a good idea (though they
8979 will largely be ignored).
8983 Here is a brief list of the control info files supported by
8984 <prgn>dpkg</prgn> and a summary of what they're used for.
8989 <tag><tt>control</tt>
8992 This is the key description file used by
8993 <prgn>dpkg</prgn>. It specifies the package's name
8994 and version, gives its description for the user,
8995 states its relationships with other packages, and so
8996 forth. See <ref id="sourcecontrolfiles"> and
8997 <ref id="binarycontrolfiles">.
9001 It is usually generated automatically from information
9002 in the source package by the
9003 <prgn>dpkg-gencontrol</prgn> program, and with
9004 assistance from <prgn>dpkg-shlibdeps</prgn>.
9005 See <ref id="pkg-sourcetools">.
9009 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9014 These are executable files (usually scripts) which
9015 <prgn>dpkg</prgn> runs during installation, upgrade
9016 and removal of packages. They allow the package to
9017 deal with matters which are particular to that package
9018 or require more complicated processing than that
9019 provided by <prgn>dpkg</prgn>. Details of when and
9020 how they are called are in <ref id="maintainerscripts">.
9024 It is very important to make these scripts idempotent.
9025 See <ref id="idempotency">.
9029 The maintainer scripts are guaranteed to run with a
9030 controlling terminal and can interact with the user.
9031 See <ref id="controllingterminal">.
9035 <tag><tt>conffiles</tt>
9038 This file contains a list of configuration files which
9039 are to be handled automatically by <prgn>dpkg</prgn>
9040 (see <ref id="pkg-conffiles">). Note that not necessarily
9041 every configuration file should be listed here.
9044 <tag><tt>shlibs</tt>
9047 This file contains a list of the shared libraries
9048 supplied by the package, with dependency details for
9049 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9050 when it determines what dependencies are required in a
9051 package control file. The <tt>shlibs</tt> file format
9052 is described on <ref id="shlibs">.
9057 <sect id="pkg-controlfile">
9058 <heading>The main control information file: <tt>control</tt></heading>
9061 The most important control information file used by
9062 <prgn>dpkg</prgn> when it installs a package is
9063 <tt>control</tt>. It contains all the package's "vital
9068 The binary package control files of packages built from
9069 Debian sources are made by a special tool,
9070 <prgn>dpkg-gencontrol</prgn>, which reads
9071 <file>debian/control</file> and <file>debian/changelog</file> to
9072 find the information it needs. See <ref id="pkg-sourcepkg"> for
9077 The fields in binary package control files are listed in
9078 <ref id="binarycontrolfiles">.
9082 A description of the syntax of control files and the purpose
9083 of the fields is available in <ref id="controlfields">.
9088 <heading>Time Stamps</heading>
9091 See <ref id="timestamps">.
9096 <appendix id="pkg-sourcepkg">
9097 <heading>Source packages (from old Packaging Manual) </heading>
9100 The Debian binary packages in the distribution are generated
9101 from Debian sources, which are in a special format to assist
9102 the easy and automatic building of binaries.
9105 <sect id="pkg-sourcetools">
9106 <heading>Tools for processing source packages</heading>
9109 Various tools are provided for manipulating source packages;
9110 they pack and unpack sources and help build of binary
9111 packages and help manage the distribution of new versions.
9115 They are introduced and typical uses described here; see
9116 <manref name="dpkg-source" section="1"> for full
9117 documentation about their arguments and operation.
9121 For examples of how to construct a Debian source package,
9122 and how to use those utilities that are used by Debian
9123 source packages, please see the <prgn>hello</prgn> example
9127 <sect1 id="pkg-dpkg-source">
9129 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9134 This program is frequently used by hand, and is also
9135 called from package-independent automated building scripts
9136 such as <prgn>dpkg-buildpackage</prgn>.
9140 To unpack a package it is typically invoked with
9142 dpkg-source -x <var>.../path/to/filename</var>.dsc
9147 with the <file><var>filename</var>.tar.gz</file> and
9148 <file><var>filename</var>.diff.gz</file> (if applicable) in
9149 the same directory. It unpacks into
9150 <file><var>package</var>-<var>version</var></file>, and if
9152 <file><var>package</var>-<var>version</var>.orig</file>, in
9153 the current directory.
9157 To create a packed source archive it is typically invoked:
9159 dpkg-source -b <var>package</var>-<var>version</var>
9164 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
9165 <file>.diff.gz</file> (if appropriate) in the current
9166 directory. <prgn>dpkg-source</prgn> does not clean the
9167 source tree first - this must be done separately if it is
9172 See also <ref id="pkg-sourcearchives">.</p>
9176 <sect1 id="pkg-dpkg-buildpackage">
9178 <prgn>dpkg-buildpackage</prgn> - overall package-building
9183 <prgn>dpkg-buildpackage</prgn> is a script which invokes
9184 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
9185 targets <tt>clean</tt>, <tt>build</tt> and
9186 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
9187 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
9188 source and binary package upload.
9192 It is usually invoked by hand from the top level of the
9193 built or unbuilt source directory. It may be invoked with
9194 no arguments; useful arguments include:
9195 <taglist compact="compact">
9196 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
9199 Do not sign the <tt>.changes</tt> file or the
9200 source package <tt>.dsc</tt> file, respectively.</p>
9202 <tag><tt>-p<var>sign-command</var></tt></tag>
9205 Invoke <var>sign-command</var> instead of finding
9206 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
9207 <var>sign-command</var> must behave just like
9208 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
9210 <tag><tt>-r<var>root-command</var></tt></tag>
9213 When root privilege is required, invoke the command
9214 <var>root-command</var>. <var>root-command</var>
9215 should invoke its first argument as a command, from
9216 the <prgn>PATH</prgn> if necessary, and pass its
9217 second and subsequent arguments to the command it
9218 calls. If no <var>root-command</var> is supplied
9219 then <var>dpkg-buildpackage</var> will take no
9220 special action to gain root privilege, so that for
9221 most packages it will have to be invoked as root to
9224 <tag><tt>-b</tt>, <tt>-B</tt></tag>
9227 Two types of binary-only build and upload - see
9228 <manref name="dpkg-source" section="1">.
9235 <sect1 id="pkg-dpkg-gencontrol">
9237 <prgn>dpkg-gencontrol</prgn> - generates binary package
9242 This program is usually called from <file>debian/rules</file>
9243 (see <ref id="pkg-sourcetree">) in the top level of the source
9248 This is usually done just before the files and directories in the
9249 temporary directory tree where the package is being built have their
9250 permissions and ownerships set and the package is constructed using
9251 <prgn>dpkg-deb/</prgn>
9253 This is so that the control file which is produced has
9254 the right permissions
9259 <prgn>dpkg-gencontrol</prgn> must be called after all the
9260 files which are to go into the package have been placed in
9261 the temporary build directory, so that its calculation of
9262 the installed size of a package is correct.
9266 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
9267 be run after <prgn>dpkg-shlibdeps</prgn> so that the
9268 variable substitutions created by
9269 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
9274 For a package which generates only one binary package, and
9275 which builds it in <file>debian/tmp</file> relative to the top
9276 of the source package, it is usually sufficient to call
9277 <prgn>dpkg-gencontrol</prgn>.
9281 Sources which build several binaries will typically need
9284 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
9285 </example> The <tt>-P</tt> tells
9286 <prgn>dpkg-gencontrol</prgn> that the package is being
9287 built in a non-default directory, and the <tt>-p</tt>
9288 tells it which package's control file should be generated.
9292 <prgn>dpkg-gencontrol</prgn> also adds information to the
9293 list of files in <file>debian/files</file>, for the benefit of
9294 (for example) a future invocation of
9295 <prgn>dpkg-genchanges</prgn>.</p>
9298 <sect1 id="pkg-dpkg-shlibdeps">
9300 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
9305 This program is usually called from <file>debian/rules</file>
9306 just before <prgn>dpkg-gencontrol</prgn> (see <ref
9307 id="pkg-sourcetree">), in the top level of the source tree.
9311 Its arguments are executables.
9314 In a forthcoming dpkg version,
9315 <prgn>dpkg-shlibdeps</prgn> would be required to be
9316 called on shared libraries as well.
9319 They may be specified either in the locations in the
9320 source tree where they are created or in the locations
9321 in the temporary build tree where they are installed
9322 prior to binary package creation.
9324 </footnote> for which shared library dependencies should
9325 be included in the binary package's control file.
9329 If some of the found shared libraries should only
9330 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
9331 some warrant a <tt>Pre-Depends</tt>, this can be achieved
9332 by using the <tt>-d<var>dependency-field</var></tt> option
9333 before those executable(s). (Each <tt>-d</tt> option
9334 takes effect until the next <tt>-d</tt>.)
9338 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
9339 output control file to be modified. Instead by default it
9340 adds to the <file>debian/substvars</file> file variable
9341 settings like <tt>shlibs:Depends</tt>. These variable
9342 settings must be referenced in dependency fields in the
9343 appropriate per-binary-package sections of the source
9348 For example, a package that generates an essential part
9349 which requires dependencies, and optional parts that
9350 which only require a recommendation, would separate those
9351 two sets of dependencies into two different fields.<footnote>
9352 At the time of writing, an example for this was the
9353 <package/xmms/ package, with Depends used for the xmms
9354 executable, Recommends for the plug-ins and Suggests for
9355 even more optional features provided by unzip.
9357 It can say in its <file>debian/rules</file>:
9359 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
9360 -dRecommends <var>optionalpart anotheroptionalpart</var>
9362 and then in its main control file <file>debian/control</file>:
9365 Depends: ${shlibs:Pre-Depends}
9366 Recommends: ${shlibs:Recommends}
9372 Sources which produce several binary packages with
9373 different shared library dependency requirements can use
9374 the <tt>-p<var>varnameprefix</var></tt> option to override
9375 the default <tt>shlibs:</tt> prefix (one invocation of
9376 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
9377 They can thus produce several sets of dependency
9378 variables, each of the form
9379 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
9380 which can be referred to in the appropriate parts of the
9381 binary package control files.
9386 <sect1 id="pkg-dpkg-distaddfile">
9388 <prgn>dpkg-distaddfile</prgn> - adds a file to
9389 <file>debian/files</file>
9393 Some packages' uploads need to include files other than
9394 the source and binary package files.
9398 <prgn>dpkg-distaddfile</prgn> adds a file to the
9399 <file>debian/files</file> file so that it will be included in
9400 the <file>.changes</file> file when
9401 <prgn>dpkg-genchanges</prgn> is run.
9405 It is usually invoked from the <tt>binary</tt> target of
9406 <file>debian/rules</file>:
9408 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
9410 The <var>filename</var> is relative to the directory where
9411 <prgn>dpkg-genchanges</prgn> will expect to find it - this
9412 is usually the directory above the top level of the source
9413 tree. The <file>debian/rules</file> target should put the
9414 file there just before or just after calling
9415 <prgn>dpkg-distaddfile</prgn>.
9419 The <var>section</var> and <var>priority</var> are passed
9420 unchanged into the resulting <file>.changes</file> file.
9425 <sect1 id="pkg-dpkg-genchanges">
9427 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
9432 This program is usually called by package-independent
9433 automatic building scripts such as
9434 <prgn>dpkg-buildpackage</prgn>, but it may also be called
9439 It is usually called in the top level of a built source
9440 tree, and when invoked with no arguments will print out a
9441 straightforward <file>.changes</file> file based on the
9442 information in the source package's changelog and control
9443 file and the binary and source packages which should have
9449 <sect1 id="pkg-dpkg-parsechangelog">
9451 <prgn>dpkg-parsechangelog</prgn> - produces parsed
9452 representation of a changelog
9456 This program is used internally by
9457 <prgn>dpkg-source</prgn> et al. It may also occasionally
9458 be useful in <file>debian/rules</file> and elsewhere. It
9459 parses a changelog, <file>debian/changelog</file> by default,
9460 and prints a control-file format representation of the
9461 information in it to standard output.
9465 <sect1 id="pkg-dpkg-architecture">
9467 <prgn>dpkg-architecture</prgn> - information about the build and
9472 This program can be used manually, but is also invoked by
9473 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
9474 to set environment or make variables which specify the build and
9475 host architecture for the package building process.
9480 <sect id="pkg-sourcetree">
9481 <heading>The Debianised source tree</heading>
9484 The source archive scheme described later is intended to
9485 allow a Debianised source tree with some associated control
9486 information to be reproduced and transported easily. The
9487 Debianised source tree is a version of the original program
9488 with certain files added for the benefit of the
9489 Debianisation process, and with any other changes required
9490 made to the rest of the source code and installation
9495 The extra files created for Debian are in the subdirectory
9496 <file>debian</file> of the top level of the Debianised source
9497 tree. They are described below.
9500 <sect1 id="pkg-debianrules">
9501 <heading><file>debian/rules</file> - the main building script</heading>
9504 See <ref id="debianrules">.
9509 <sect1 id="pkg-dpkgchangelog">
9510 <heading><file>debian/changelog</file></heading>
9513 See <ref id="dpkgchangelog">.
9517 It is recommended that the entire changelog be encoded in the
9518 <url id="http://www.cis.ohio-state.edu/cgi-bin/rfc/rfc2279.html" name="UTF-8">
9520 <url id="http://www.unicode.org/"
9521 name="Unicode">.<footnote>
9523 I think it is fairly obvious that we need to
9524 eventually transition to UTF-8 for our package
9525 infrastructure; it is really the only sane char-set in
9526 an international environment. Now, we can't switch to
9527 using UTF-8 for package control fields and the like
9528 until dpkg has better support, but one thing we can
9529 start doing today is requesting that Debian changelogs
9530 are UTF-8 encoded. At some point in time, we can start
9531 requiring them to do so.
9534 Checking for non-UTF8 characters in a changelog is
9535 trivial. Dump the file through
9536 <example>iconv -f utf-8 -t ucs-4</example>
9537 discard the output, and check the return
9538 value. If there are any characters in the stream
9539 which are invalid UTF-8 sequences, iconv will exit
9540 with an error code; and this will be the case for the
9541 vast majority of other character sets.
9546 <sect2><heading>Defining alternative changelog formats
9550 It is possible to use a different format to the standard
9551 one, by providing a parser for the format you wish to
9556 In order to have <tt>dpkg-parsechangelog</tt> run your
9557 parser, you must include a line within the last 40 lines
9558 of your file matching the Perl regular expression:
9559 <tt>\schangelog-format:\s+([0-9a-z]+)\W</tt> The part in
9560 parentheses should be the name of the format. For
9561 example, you might say:
9563 @@@ changelog-format: joebloggs @@@
9565 Changelog format names are non-empty strings of alphanumerics.
9569 If such a line exists then <tt>dpkg-parsechangelog</tt>
9570 will look for the parser as
9571 <file>/usr/lib/dpkg/parsechangelog/<var>format-name</var></file>
9573 <file>/usr/local/lib/dpkg/parsechangelog/<var>format-name</var></file>;
9574 it is an error for it not to find it, or for it not to
9575 be an executable program. The default changelog format
9576 is <tt>dpkg</tt>, and a parser for it is provided with
9577 the <tt>dpkg</tt> package.
9581 The parser will be invoked with the changelog open on
9582 standard input at the start of the file. It should read
9583 the file (it may seek if it wishes) to determine the
9584 information required and return the parsed information
9585 to standard output in the form of a series of control
9586 fields in the standard format. By default it should
9587 return information about only the most recent version in
9588 the changelog; it should accept a
9589 <tt>-v<var>version</var></tt> option to return changes
9590 information from all versions present <em>strictly
9591 after</em> <var>version</var>, and it should then be an
9592 error for <var>version</var> not to be present in the
9598 <list compact="compact">
9599 <item><qref id="f-Source"><tt>Source</tt></qref></item>
9600 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
9601 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
9602 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (mandatory)</item>
9603 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
9604 <item><qref id="f-Date"><tt>Date</tt></qref></item>
9605 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
9610 If several versions are being returned (due to the use
9611 of <tt>-v</tt>), the urgency value should be of the
9612 highest urgency code listed at the start of any of the
9613 versions requested followed by the concatenated
9614 (space-separated) comments from all the versions
9615 requested; the maintainer, version, distribution and
9616 date should always be from the most recent version.
9620 For the format of the <tt>Changes</tt> field see
9621 <ref id="f-Changes">.
9625 If the changelog format which is being parsed always or
9626 almost always leaves a blank line between individual
9627 change notes these blank lines should be stripped out,
9628 so as to make the resulting output compact.
9632 If the changelog format does not contain date or package
9633 name information this information should be omitted from
9634 the output. The parser should not attempt to synthesize
9635 it or find it from other sources.
9639 If the changelog does not have the expected format the
9640 parser should exit with a nonzero exit status, rather
9641 than trying to muddle through and possibly generating
9646 A changelog parser may not interact with the user at
9652 <sect1 id="pkg-srcsubstvars">
9653 <heading><file>debian/substvars</file> and variable substitutions</heading>
9656 See <ref id="substvars">.
9662 <heading><file>debian/files</file></heading>
9665 See <ref id="debianfiles">.
9669 <sect1><heading><file>debian/tmp</file>
9673 This is the canonical temporary location for the
9674 construction of binary packages by the <tt>binary</tt>
9675 target. The directory <file>tmp</file> serves as the root of
9676 the file system tree as it is being constructed (for
9677 example, by using the package's upstream makefiles install
9678 targets and redirecting the output there), and it also
9679 contains the <tt>DEBIAN</tt> subdirectory. See <ref
9680 id="pkg-bincreating">.
9684 If several binary packages are generated from the same
9685 source tree it is usual to use several
9686 <file>debian/tmp<var>something</var></file> directories, for
9687 example <file>tmp-a</file> or <file>tmp-doc</file>.
9691 Whatever <file>tmp</file> directories are created and used by
9692 <tt>binary</tt> must of course be removed by the
9693 <tt>clean</tt> target.</p></sect1>
9697 <sect id="pkg-sourcearchives"><heading>Source packages as archives
9701 As it exists on the FTP site, a Debian source package
9702 consists of three related files. You must have the right
9703 versions of all three to be able to use them.
9708 <tag>Debian source control file - <tt>.dsc</tt></tag>
9710 This file is a control file used by <prgn>dpkg-source</prgn>
9711 to extract a source package.
9712 See <ref id="debiansourcecontrolfiles">.
9716 Original source archive -
9718 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
9724 This is a compressed (with <tt>gzip -9</tt>)
9725 <prgn>tar</prgn> file containing the source code from
9726 the upstream authors of the program.
9731 Debianisation diff -
9733 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
9739 This is a unified context diff (<tt>diff -u</tt>)
9740 giving the changes which are required to turn the
9741 original source into the Debian source. These changes
9742 may only include editing and creating plain files.
9743 The permissions of files, the targets of symbolic
9744 links and the characteristics of special files or
9745 pipes may not be changed and no files may be removed
9750 All the directories in the diff must exist, except the
9751 <file>debian</file> subdirectory of the top of the source
9752 tree, which will be created by
9753 <prgn>dpkg-source</prgn> if necessary when unpacking.
9757 The <prgn>dpkg-source</prgn> program will
9758 automatically make the <file>debian/rules</file> file
9759 executable (see below).</p></item>
9764 If there is no original source code - for example, if the
9765 package is specially prepared for Debian or the Debian
9766 maintainer is the same as the upstream maintainer - the
9767 format is slightly different: then there is no diff, and the
9769 <file><var>package</var>_<var>version</var>.tar.gz</file>,
9770 and preferably contains a directory named
9771 <file><var>package</var>-<var>version</var></file>.
9776 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
9779 <tt>dpkg-source -x</tt> is the recommended way to unpack a
9780 Debian source package. However, if it is not available it
9781 is possible to unpack a Debian source archive as follows:
9782 <enumlist compact="compact">
9785 Untar the tarfile, which will create a <file>.orig</file>
9789 <p>Rename the <file>.orig</file> directory to
9790 <file><var>package</var>-<var>version</var></file>.</p>
9794 Create the subdirectory <file>debian</file> at the top of
9795 the source tree.</p>
9797 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
9799 <item><p>Untar the tarfile again if you want a copy of the original
9800 source code alongside the Debianised version.</p>
9805 It is not possible to generate a valid Debian source archive
9806 without using <prgn>dpkg-source</prgn>. In particular,
9807 attempting to use <prgn>diff</prgn> directly to generate the
9808 <file>.diff.gz</file> file will not work.
9812 <heading>Restrictions on objects in source packages</heading>
9815 The source package may not contain any hard links
9817 This is not currently detected when building source
9818 packages, but only when extracting
9822 Hard links may be permitted at some point in the
9823 future, but would require a fair amount of
9825 </footnote>, device special files, sockets or setuid or
9828 Setgid directories are allowed.
9833 The source packaging tools manage the changes between the
9834 original and Debianised source using <prgn>diff</prgn> and
9835 <prgn>patch</prgn>. Turning the original source tree as
9836 included in the <file>.orig.tar.gz</file> into the debianised
9837 source must not involve any changes which cannot be
9838 handled by these tools. Problematic changes which cause
9839 <prgn>dpkg-source</prgn> to halt with an error when
9840 building the source package are:
9841 <list compact="compact">
9842 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
9844 <item><p>Changing the targets of symbolic links.</p>
9846 <item><p>Creating directories, other than <file>debian</file>.</p>
9848 <item><p>Changes to the contents of binary files.</p></item>
9849 </list> Changes which cause <prgn>dpkg-source</prgn> to
9850 print a warning but continue anyway are:
9851 <list compact="compact">
9854 Removing files, directories or symlinks.
9856 Renaming a file is not treated specially - it is
9857 seen as the removal of the old file (which
9858 generates a warning, but is otherwise ignored),
9859 and the creation of the new one.
9865 Changed text files which are missing the usual final
9866 newline (either in the original or the modified
9871 Changes which are not represented, but which are not detected by
9872 <prgn>dpkg-source</prgn>, are:
9873 <list compact="compact">
9874 <item><p>Changing the permissions of files (other than
9875 <file>debian/rules</file>) and directories.</p></item>
9880 The <file>debian</file> directory and <file>debian/rules</file>
9881 are handled specially by <prgn>dpkg-source</prgn> - before
9882 applying the changes it will create the <file>debian</file>
9883 directory, and afterwards it will make
9884 <file>debian/rules</file> world-executable.
9890 <appendix id="pkg-controlfields">
9891 <heading>Control files and their fields (from old Packaging Manual)</heading>
9894 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
9895 data in a common format, known as control files. Binary and
9896 source packages have control data as do the <file>.changes</file>
9897 files which control the installation of uploaded files, and
9898 <prgn>dpkg</prgn>'s internal databases are in a similar
9903 <heading>Syntax of control files</heading>
9906 See <ref id="controlsyntax">.
9910 It is important to note that there are several fields which
9911 are optional as far as <prgn>dpkg</prgn> and the related
9912 tools are concerned, but which must appear in every Debian
9913 package, or whose omission may cause problems.
9918 <heading>List of fields</heading>
9921 See <ref id="controlfieldslist">.
9925 This section now contains only the fields that didn't belong
9926 to the Policy manual.
9929 <sect1 id="pkg-f-Filename">
9930 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
9933 These fields in <tt>Packages</tt> files give the
9934 filename(s) of (the parts of) a package in the
9935 distribution directories, relative to the root of the
9936 Debian hierarchy. If the package has been split into
9937 several parts the parts are all listed in order, separated
9942 <sect1 id="pkg-f-Size">
9943 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
9946 These fields in <file>Packages</file> files give the size (in
9947 bytes, expressed in decimal) and MD5 checksum of the
9948 file(s) which make(s) up a binary package in the
9949 distribution. If the package is split into several parts
9950 the values for the parts are listed in order, separated by
9955 <sect1 id="pkg-f-Status">
9956 <heading><tt>Status</tt></heading>
9959 This field in <prgn>dpkg</prgn>'s status file records
9960 whether the user wants a package installed, removed or
9961 left alone, whether it is broken (requiring
9962 re-installation) or not and what its current state on the
9963 system is. Each of these pieces of information is a
9968 <sect1 id="pkg-f-Config-Version">
9969 <heading><tt>Config-Version</tt></heading>
9972 If a package is not installed or not configured, this
9973 field in <prgn>dpkg</prgn>'s status file records the last
9974 version of the package which was successfully
9979 <sect1 id="pkg-f-Conffiles">
9980 <heading><tt>Conffiles</tt></heading>
9983 This field in <prgn>dpkg</prgn>'s status file contains
9984 information about the automatically-managed configuration
9985 files held by a package. This field should <em>not</em>
9986 appear anywhere in a package!
9991 <heading>Obsolete fields</heading>
9994 These are still recognized by <prgn>dpkg</prgn> but should
9995 not appear anywhere any more.
9997 <taglist compact="compact">
9999 <tag><tt>Revision</tt></tag>
10000 <tag><tt>Package-Revision</tt></tag>
10001 <tag><tt>Package_Revision</tt></tag>
10003 The Debian revision part of the package version was
10004 at one point in a separate control file field. This
10005 field went through several names.
10008 <tag><tt>Recommended</tt></tag>
10009 <item>Old name for <tt>Recommends</tt>.</item>
10011 <tag><tt>Optional</tt></tag>
10012 <item>Old name for <tt>Suggests</tt>.</item>
10014 <tag><tt>Class</tt></tag>
10015 <item>Old name for <tt>Priority</tt>.</item>
10024 <appendix id="pkg-conffiles">
10025 <heading>Configuration file handling (from old Packaging Manual)</heading>
10028 <prgn>dpkg</prgn> can do a certain amount of automatic
10029 handling of package configuration files.
10033 Whether this mechanism is appropriate depends on a number of
10034 factors, but basically there are two approaches to any
10035 particular configuration file.
10039 The easy method is to ship a best-effort configuration in the
10040 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10041 handle updates. If the user is unlikely to want to edit the
10042 file, but you need them to be able to without losing their
10043 changes, and a new package with a changed version of the file
10044 is only released infrequently, this is a good approach.
10048 The hard method is to build the configuration file from
10049 scratch in the <prgn>postinst</prgn> script, and to take the
10050 responsibility for fixing any mistakes made in earlier
10051 versions of the package automatically. This will be
10052 appropriate if the file is likely to need to be different on
10056 <sect><heading>Automatic handling of configuration files by
10061 A package may contain a control area file called
10062 <tt>conffiles</tt>. This file should be a list of filenames
10063 of configuration files needing automatic handling, separated
10064 by newlines. The filenames should be absolute pathnames,
10065 and the files referred to should actually exist in the
10070 When a package is upgraded <prgn>dpkg</prgn> will process
10071 the configuration files during the configuration stage,
10072 shortly before it runs the package's <prgn>postinst</prgn>
10077 For each file it checks to see whether the version of the
10078 file included in the package is the same as the one that was
10079 included in the last version of the package (the one that is
10080 being upgraded from); it also compares the version currently
10081 installed on the system with the one shipped with the last
10086 If neither the user nor the package maintainer has changed
10087 the file, it is left alone. If one or the other has changed
10088 their version, then the changed version is preferred - i.e.,
10089 if the user edits their file, but the package maintainer
10090 doesn't ship a different version, the user's changes will
10091 stay, silently, but if the maintainer ships a new version
10092 and the user hasn't edited it the new version will be
10093 installed (with an informative message). If both have
10094 changed their version the user is prompted about the problem
10095 and must resolve the differences themselves.
10099 The comparisons are done by calculating the MD5 message
10100 digests of the files, and storing the MD5 of the file as it
10101 was included in the most recent version of the package.
10105 When a package is installed for the first time
10106 <prgn>dpkg</prgn> will install the file that comes with it,
10107 unless that would mean overwriting a file already on the
10112 However, note that <prgn>dpkg</prgn> will <em>not</em>
10113 replace a conffile that was removed by the user (or by a
10114 script). This is necessary because with some programs a
10115 missing file produces an effect hard or impossible to
10116 achieve in another way, so that a missing file needs to be
10117 kept that way if the user did it.
10121 Note that a package should <em>not</em> modify a
10122 <prgn>dpkg</prgn>-handled conffile in its maintainer
10123 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10124 the user confusing and possibly dangerous options for
10125 conffile update when the package is upgraded.</p>
10128 <sect><heading>Fully-featured maintainer script configuration
10133 For files which contain site-specific information such as
10134 the hostname and networking details and so forth, it is
10135 better to create the file in the package's
10136 <prgn>postinst</prgn> script.
10140 This will typically involve examining the state of the rest
10141 of the system to determine values and other information, and
10142 may involve prompting the user for some information which
10143 can't be obtained some other way.
10147 When using this method there are a couple of important
10148 issues which should be considered:
10152 If you discover a bug in the program which generates the
10153 configuration file, or if the format of the file changes
10154 from one version to the next, you will have to arrange for
10155 the postinst script to do something sensible - usually this
10156 will mean editing the installed configuration file to remove
10157 the problem or change the syntax. You will have to do this
10158 very carefully, since the user may have changed the file,
10159 perhaps to fix the very problem that your script is trying
10160 to deal with - you will have to detect these situations and
10161 deal with them correctly.
10165 If you do go down this route it's probably a good idea to
10166 make the program that generates the configuration file(s) a
10167 separate program in <file>/usr/sbin</file>, by convention called
10168 <file><var>package</var>config</file> and then run that if
10169 appropriate from the post-installation script. The
10170 <tt><var>package</var>config</tt> program should not
10171 unquestioningly overwrite an existing configuration - if its
10172 mode of operation is geared towards setting up a package for
10173 the first time (rather than any arbitrary reconfiguration
10174 later) you should have it check whether the configuration
10175 already exists, and require a <tt>--force</tt> flag to
10176 overwrite it.</p></sect>
10179 <appendix id="pkg-alternatives"><heading>Alternative versions of
10180 an interface - <prgn>update-alternatives</prgn> (from old
10185 When several packages all provide different versions of the
10186 same program or file it is useful to have the system select a
10187 default, but to allow the system administrator to change it
10188 and have their decisions respected.
10192 For example, there are several versions of the <prgn>vi</prgn>
10193 editor, and there is no reason to prevent all of them from
10194 being installed at once, each under their own name
10195 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10196 Nevertheless it is desirable to have the name <tt>vi</tt>
10197 refer to something, at least by default.
10201 If all the packages involved cooperate, this can be done with
10202 <prgn>update-alternatives</prgn>.
10206 Each package provides its own version under its own name, and
10207 calls <prgn>update-alternatives</prgn> in its postinst to
10208 register its version (and again in its prerm to deregister
10213 See the man page <manref name="update-alternatives"
10214 section="8"> for details.
10218 If <prgn>update-alternatives</prgn> does not seem appropriate
10219 you may wish to consider using diversions instead.</p>
10222 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10223 package's version of a file (from old Packaging Manual)
10227 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10228 when it reinstalls the package it belongs to, and to have it
10229 put the file from the package somewhere else instead.
10233 This can be used locally to override a package's version of a
10234 file, or by one package to override another's version (or
10235 provide a wrapper for it).
10239 Before deciding to use a diversion, read <ref
10240 id="pkg-alternatives"> to see if you really want a diversion
10241 rather than several alternative versions of a program.
10245 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10246 and updated by a special program <prgn>dpkg-divert</prgn>.
10247 Please see <manref name="dpkg-divert" section="8"> for full
10248 details of its operation.
10252 When a package wishes to divert a file from another, it should
10253 call <prgn>dpkg-divert</prgn> in its preinst to add the
10254 diversion and rename the existing file. For example,
10255 supposing that a <prgn>smailwrapper</prgn> package wishes to
10256 install a wrapper around <file>/usr/sbin/smail</file>:
10258 if [ install = "$1" ]; then
10259 dpkg-divert --package smailwrapper --add --rename \
10260 --divert /usr/sbin/smail.real /usr/sbin/smail
10262 </example> Testing <tt>$1</tt> is necessary so that the script
10263 doesn't try to add the diversion again when
10264 <prgn>smailwrapper</prgn> is upgraded. The <tt>--package
10265 smailwrapper</tt> ensures that <prgn>smailwrapper</prgn>'s
10266 copy of <file>/usr/sbin/smail</file> can bypass the diversion and
10267 get installed as the true version.
10271 The postrm has to do the reverse:
10273 if [ remove = "$1" ]; then
10274 dpkg-divert --package smailwrapper --remove --rename \
10275 --divert /usr/sbin/smail.real /usr/sbin/smail
10281 Do not attempt to divert a file which is vitally important for
10282 the system's operation - when using <prgn>dpkg-divert</prgn>
10283 there is a time, after it has been diverted but before
10284 <prgn>dpkg</prgn> has installed the new version, when the file
10285 does not exist.</p>
10290 <!-- vim:set ai et sts=2 sw=2 tw=76: -->