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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 which use the Debian Configuration management
1225 specification must allow for translation of their messages
1226 by using a gettext-based system such as the one provided by
1227 the <package>po-debconf</package> package.
1231 Packages should try to minimize the amount of prompting
1232 they need to do, and they should ensure that the user
1233 will only ever be asked each question once. This means
1234 that packages should try to use appropriate shared
1235 configuration files (such as <file>/etc/papersize</file> and
1236 <file>/etc/news/server</file>), and shared
1237 <package>debconf</package> variables rather than each
1238 prompting for their own list of required pieces of
1243 It also means that an upgrade should not ask the same
1244 questions again, unless the user has used
1245 <tt>dpkg --purge</tt> to remove the package's configuration.
1246 The answers to configuration questions should be stored in an
1247 appropriate place in <file>/etc</file> so that the user can
1248 modify them, and how this has been done should be
1253 If a package has a vitally important piece of
1254 information to pass to the user (such as "don't run me
1255 as I am, you must edit the following configuration files
1256 first or you risk your system emitting badly-formatted
1257 messages"), it should display this in the
1258 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1259 prompt the user to hit return to acknowledge the
1260 message. Copyright messages do not count as vitally
1261 important (they belong in
1262 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1263 neither do instructions on how to use a program (these
1264 should be in on-line documentation, where all the users
1269 Any necessary prompting should almost always be confined
1270 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1271 script. If it is done in the <prgn>postinst</prgn>, it
1272 should be protected with a conditional so that
1273 unnecessary prompting doesn't happen if a package's
1274 installation fails and the <prgn>postinst</prgn> is
1275 called with <tt>abort-upgrade</tt>,
1276 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1286 <heading>Source packages</heading>
1288 <sect id="standardsversion">
1289 <heading>Standards conformance</heading>
1292 Source packages should specify the most recent version number
1293 of this policy document with which your package complied
1294 when it was last updated.
1298 This information may be used to file bug reports
1299 automatically if your package becomes too much out of date.
1303 The version is specified in the <tt>Standards-Version</tt>
1305 The format of the <tt>Standards-Version</tt> field is
1306 described in <ref id="f-Standards-Version">.
1310 You should regularly, and especially if your package has
1311 become out of date, check for the newest Policy Manual
1312 available and update your package, if necessary. When your
1313 package complies with the new standards you should update the
1314 <tt>Standards-Version</tt> source package field and
1315 release it.<footnote>
1316 See the file <file>upgrading-checklist</file> for
1317 information about policy which has changed between
1318 different versions of this document.
1324 <sect id="pkg-relations">
1325 <heading>Package relationships</heading>
1328 Source packages should specify which binary packages they
1329 require to be installed or not to be installed in order to
1330 build correctly. For example, if building a package
1331 requires a certain compiler, then the compiler should be
1332 specified as a build-time dependency.
1336 It is not necessary to explicitly specify build-time
1337 relationships on a minimal set of packages that are always
1338 needed to compile, link and put in a Debian package a
1339 standard "Hello World!" program written in C or C++. The
1340 required packages are called <em>build-essential</em>, and
1341 an informational list can be found in
1342 <file>/usr/share/doc/build-essential/list</file> (which is
1343 contained in the <tt>build-essential</tt>
1346 <list compact="compact">
1348 This allows maintaining the list separately
1349 from the policy documents (the list does not
1350 need the kind of control that the policy
1354 Having a separate package allows one to install
1355 the build-essential packages on a machine, as
1356 well as allowing other packages such as tasks to
1357 require installation of the build-essential
1358 packages using the depends relation.
1361 The separate package allows bug reports against
1362 the list to be categorized separately from
1363 the policy management process in the BTS.
1370 When specifying the set of build-time dependencies, one
1371 should list only those packages explicitly required by the
1372 build. It is not necessary to list packages which are
1373 required merely because some other package in the list of
1374 build-time dependencies depends on them.<footnote>
1375 The reason for this is that dependencies change, and
1376 you should list all those packages, and <em>only</em>
1377 those packages that <em>you</em> need directly. What
1378 others need is their business. For example, if you
1379 only link against <file>libimlib</file>, you will need to
1380 build-depend on <package>libimlib2-dev</package> but
1381 not against any <tt>libjpeg*</tt> packages, even
1382 though <tt>libimlib2-dev</tt> currently depends on
1383 them: installation of <package>libimlib2-dev</package>
1384 will automatically ensure that all of its run-time
1385 dependencies are satisfied.
1390 If build-time dependencies are specified, it must be
1391 possible to build the package and produce working binaries
1392 on a system with only essential and build-essential
1393 packages installed and also those required to satisfy the
1394 build-time relationships (including any implied
1395 relationships). In particular, this means that version
1396 clauses should be used rigorously in build-time
1397 relationships so that one cannot produce bad or
1398 inconsistently configured packages when the relationships
1399 are properly satisfied.
1403 <ref id="relationships"> explains the technical details.
1408 <heading>Changes to the upstream sources</heading>
1411 If changes to the source code are made that are not
1412 specific to the needs of the Debian system, they should be
1413 sent to the upstream authors in whatever form they prefer
1414 so as to be included in the upstream version of the
1419 If you need to configure the package differently for
1420 Debian or for Linux, and the upstream source doesn't
1421 provide a way to do so, you should add such configuration
1422 facilities (for example, a new <prgn>autoconf</prgn> test
1423 or <tt>#define</tt>) and send the patch to the upstream
1424 authors, with the default set to the way they originally
1425 had it. You can then easily override the default in your
1426 <file>debian/rules</file> or wherever is appropriate.
1430 You should make sure that the <prgn>configure</prgn> utility
1431 detects the correct architecture specification string
1432 (refer to <ref id="arch-spec"> for details).
1436 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1437 <prgn>configure</prgn> scripts are used, you should edit the
1438 <file>.in</file> files rather than editing the
1439 <prgn>Makefile</prgn> directly. This allows the user to
1440 reconfigure the package if necessary. You should
1441 <em>not</em> configure the package and edit the generated
1442 <prgn>Makefile</prgn>! This makes it impossible for someone
1443 else to later reconfigure the package without losing the
1449 <sect id="dpkgchangelog">
1450 <heading>Debian changelog: <file>debian/changelog</file></heading>
1453 Changes in the Debian version of the package should be
1454 briefly explained in the Debian changelog file
1455 <file>debian/changelog</file>.<footnote>
1457 Mistakes in changelogs are usually best rectified by
1458 making a new changelog entry rather than "rewriting
1459 history" by editing old changelog entries.
1462 This includes modifications
1463 made in the Debian package compared to the upstream one
1464 as well as other changes and updates to the package.
1466 Although there is nothing stopping an author who is also
1467 the Debian maintainer from using this changelog for all
1468 their changes, it will have to be renamed if the Debian
1469 and upstream maintainers become different people. In such
1470 a case, however, it might be better to maintain the package
1471 as a non-native package.
1480 The format of the <file>debian/changelog</file> allows the
1481 package building tools to discover which version of the package
1482 is being built and find out other release-specific information.
1486 That format is a series of entries like this:
1488 <example compact="compact">
1489 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1491 [optional blank line(s), stripped]
1493 * <var>change details</var>
1494 <var>more change details</var>
1496 [blank line(s), included in output of dpkg-parsechangelog]
1498 * <var>even more change details</var>
1500 [optional blank line(s), stripped]
1502 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1507 <var>package</var> and <var>version</var> are the source
1508 package name and version number.
1512 <var>distribution(s)</var> lists the distributions where
1513 this version should be installed when it is uploaded - it
1514 is copied to the <tt>Distribution</tt> field in the
1515 <file>.changes</file> file. See <ref id="f-Distribution">.
1519 <var>urgency</var> is the value for the <tt>Urgency</tt>
1520 field in the <file>.changes</file> file for the upload
1521 (see <ref id="f-Urgency">). It is not possible to specify
1522 an urgency containing commas; commas are used to separate
1523 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1524 <prgn>dpkg</prgn> changelog format (though there is
1525 currently only one useful <var>keyword</var>,
1530 The change details may in fact be any series of lines
1531 starting with at least two spaces, but conventionally each
1532 change starts with an asterisk and a separating space and
1533 continuation lines are indented so as to bring them in
1534 line with the start of the text above. Blank lines may be
1535 used here to separate groups of changes, if desired.
1539 If this upload resolves bugs recorded in the Bug Tracking
1540 System (BTS), they may be automatically closed on the
1541 inclusion of this package into the Debian archive by
1542 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1543 in the change details.<footnote>
1544 To be precise, the string should match the following
1545 Perl regular expression:
1547 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1549 Then all of the bug numbers listed will be closed by the
1550 archive maintenance script (<prgn>katie</prgn>), or in
1551 the case of an NMU, marked as fixed.
1553 This information is conveyed via the <tt>Closes</tt> field
1554 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1558 The maintainer name and email address used in the changelog
1559 should be the details of the person uploading <em>this</em>
1560 version. They are <em>not</em> necessarily those of the
1561 usual package maintainer. The information here will be
1562 copied to the <tt>Changed-By</tt> field in the
1563 <tt>.changes</tt> file (see <ref id="f-Changed-By">),
1564 and then later used to send an acknowledgement when the
1565 upload has been installed.
1569 The <var>date</var> should be in RFC822 format<footnote>
1570 This is generated by <tt>date -R</tt>.
1571 </footnote>; it should include the time zone specified
1572 numerically, with the time zone name or abbreviation
1573 optionally present as a comment in parentheses.
1577 The first "title" line with the package name should start
1578 at the left hand margin; the "trailer" line with the
1579 maintainer and date details should be preceded by exactly
1580 one space. The maintainer details and the date must be
1581 separated by exactly two spaces.
1585 For more information on placement of the changelog files
1586 within binary packages, please see <ref id="changelogs">.
1589 <sect1><heading>Alternative changelog formats</heading>
1592 In non-experimental packages you must use a format for
1593 <file>debian/changelog</file> which is supported by the most
1594 recent released version of <prgn>dpkg</prgn>.
1598 It is possible to use a format different from the standard
1599 one by providing a changelog parser for the format you wish
1600 to use. The parser must have an API compatible with that
1601 expected by <prgn>dpkg-genchanges</prgn> and
1602 <prgn>dpkg-gencontrol</prgn>, and it must not interact with
1605 If there is general interest in the new format, you should
1606 contact the <package>dpkg</package> maintainer to have the
1607 parser script for it included in the <prgn>dpkg</prgn>
1608 package. (You will need to agree that the parser and its
1609 man page may be distributed under the GNU GPL, just as the rest
1610 of <prgn>dpkg</prgn> is.)
1615 <sect id="dpkgcopyright">
1616 <heading>Copyright: <file>debian/copyright</file></heading>
1618 Every package must be accompanied by a verbatim copy of
1619 its copyright and distribution license in the file
1620 <file>/usr/share/doc/<var>package</var>/copyright</file>
1621 (see <ref id="copyrightfile"> for further details). Also see
1622 <ref id="pkgcopyright"> for further considerations relayed
1623 to copyrights for packages.
1627 <heading>Error trapping in makefiles</heading>
1630 When <prgn>make</prgn> invokes a command in a makefile
1631 (including your package's upstream makefiles and
1632 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1633 means that <prgn>sh</prgn>'s usual bad error handling
1634 properties apply: if you include a miniature script as one
1635 of the commands in your makefile you'll find that if you
1636 don't do anything about it then errors are not detected
1637 and <prgn>make</prgn> will blithely continue after
1642 Every time you put more than one shell command (this
1643 includes using a loop) in a makefile command you
1644 must make sure that errors are trapped. For
1645 simple compound commands, such as changing directory and
1646 then running a program, using <tt>&&</tt> rather
1647 than semicolon as a command separator is sufficient. For
1648 more complex commands including most loops and
1649 conditionals you should include a separate <tt>set -e</tt>
1650 command at the start of every makefile command that's
1651 actually one of these miniature shell scripts.
1655 <sect id="timestamps">
1656 <heading>Time Stamps</heading>
1658 Maintainers should preserve the modification times of the
1659 upstream source files in a package, as far as is reasonably
1661 The rationale is that there is some information conveyed
1662 by knowing the age of the file, for example, you could
1663 recognize that some documentation is very old by looking
1664 at the modification time, so it would be nice if the
1665 modification time of the upstream source would be
1671 <sect id="restrictions">
1672 <heading>Restrictions on objects in source packages</heading>
1675 The source package may not contain any hard links<footnote>
1677 This is not currently detected when building source
1678 packages, but only when extracting
1682 Hard links may be permitted at some point in the
1683 future, but would require a fair amount of
1686 </footnote>, device special files, sockets or setuid or
1687 setgid files.<footnote>
1688 Setgid directories are allowed.
1693 <sect id="debianrules">
1694 <heading>Main building script: <file>debian/rules</file></heading>
1697 This file must be an executable makefile, and contains the
1698 package-specific recipes for compiling the package and
1699 building binary package(s) from the source.
1703 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1704 so that it can be invoked by saying its name rather than
1705 invoking <prgn>make</prgn> explicitly.
1709 Since an interactive <file>debian/rules</file> script makes it
1710 impossible to auto-compile that package and also makes it
1711 hard for other people to reproduce the same binary
1712 package, all <em>required targets</em> MUST be
1713 non-interactive. At a minimum, required targets are the
1714 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1715 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1716 <em>binary-indep</em>, and <em>build</em>. It also follows
1717 that any target that these targets depend on must also be
1722 The targets are as follows (required unless stated otherwise):
1724 <tag><tt>build</tt></tag>
1727 The <tt>build</tt> target should perform all the
1728 configuration and compilation of the package.
1729 If a package has an interactive pre-build
1730 configuration routine, the Debianized source package
1731 must either be built after this has taken place (so
1732 that the binary package can be built without rerunning
1733 the configuration) or the configuration routine
1734 modified to become non-interactive. (The latter is
1735 preferable if there are architecture-specific features
1736 detected by the configuration routine.)
1740 For some packages, notably ones where the same
1741 source tree is compiled in different ways to produce
1742 two binary packages, the <tt>build</tt> target
1743 does not make much sense. For these packages it is
1744 good enough to provide two (or more) targets
1745 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1746 for each of the ways of building the package, and a
1747 <tt>build</tt> target that does nothing. The
1748 <tt>binary</tt> target will have to build the
1749 package in each of the possible ways and make the
1750 binary package out of each.
1754 The <tt>build</tt> target must not do anything
1755 that might require root privilege.
1759 The <tt>build</tt> target may need to run the
1760 <tt>clean</tt> target first - see below.
1764 When a package has a configuration and build routine
1765 which takes a long time, or when the makefiles are
1766 poorly designed, or when <tt>build</tt> needs to
1767 run <tt>clean</tt> first, it is a good idea to
1768 <tt>touch build</tt> when the build process is
1769 complete. This will ensure that if <tt>debian/rules
1770 build</tt> is run again it will not rebuild the whole
1772 Another common way to do this is for <tt>build</tt>
1773 to depend on <prgn>build-stamp</prgn> and to do
1774 nothing else, and for the <prgn>build-stamp</prgn>
1775 target to do the building and to <tt>touch
1776 build-stamp</tt> on completion. This is
1777 especially useful if the build routine creates a
1778 file or directory called <tt>build</tt>; in such a
1779 case, <tt>build</tt> will need to be listed as
1780 a phony target (i.e., as a dependency of the
1781 <tt>.PHONY</tt> target). See the documentation of
1782 <prgn>make</prgn> for more information on phony
1788 <tag><tt>build-arch</tt> (optional),
1789 <tt>build-indep</tt> (optional)
1793 A package may also provide both of the targets
1794 <tt>build-arch</tt> and <tt>build-indep</tt>.
1795 The <tt>build-arch</tt> target, if provided, should
1796 perform all the configuration and compilation required
1797 for producing all architecture-dependant binary packages
1798 (those packages for which the body of the
1799 <tt>Architecture</tt> field in <tt>debian/control</tt>
1800 is not <tt>all</tt>).
1801 Similarly, the <tt>build-indep</tt> target, if
1802 provided, should perform all the configuration and
1803 compilation required for producing all
1804 architecture-independent binary packages
1805 (those packages for which the body of the
1806 <tt>Architecture</tt> field in <tt>debian/control</tt>
1808 The <tt>build</tt> target should depend on those of the
1809 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1810 are provided in the rules file.
1814 If one or both of the targets <tt>build-arch</tt> and
1815 <tt>build-indep</tt> are not provided, then invoking
1816 <file>debian/rules</file> with one of the not-provided
1817 targets as arguments should produce a exit status code
1818 of 2. Usually this is provided automatically by make
1819 if the target is missing.
1823 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1824 must not do anything that might require root privilege.
1828 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1829 <tt>binary-indep</tt>
1833 The <tt>binary</tt> target must be all that is
1834 necessary for the user to build the binary package(s)
1835 produced from this source package. It is
1836 split into two parts: <prgn>binary-arch</prgn> builds
1837 the binary packages which are specific to a particular
1838 architecture, and <tt>binary-indep</tt> builds
1839 those which are not.
1842 <tt>binary</tt> may be (and commonly is) a target with
1843 no commands which simply depends on
1844 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1847 Both <tt>binary-*</tt> targets should depend on the
1848 <tt>build</tt> target, or on the appropriate
1849 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1850 provided, so that the package is built if it has not
1851 been already. It should then create the relevant
1852 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1853 make their control files and <prgn>dpkg-deb</prgn> to
1854 build them and place them in the parent of the top
1859 Both the <tt>binary-arch</tt> and
1860 <tt>binary-indep</tt> targets <em>must</em> exist.
1861 If one of them has nothing to do (which will always be
1862 the case if the source generates only a single binary
1863 package, whether architecture-dependent or not), it
1864 must still exist and must always succeed.
1868 The <tt>binary</tt> targets must be invoked as
1870 The <prgn>fakeroot</prgn> package often allows one
1871 to build a package correctly even without being
1877 <tag><tt>clean</tt></tag>
1880 This must undo any effects that the <tt>build</tt>
1881 and <tt>binary</tt> targets may have had, except
1882 that it should leave alone any output files created in
1883 the parent directory by a run of a <tt>binary</tt>
1888 If a <tt>build</tt> file is touched at the end of
1889 the <tt>build</tt> target, as suggested above, it
1890 should be removed as the first action that
1891 <tt>clean</tt> performs, so that running
1892 <tt>build</tt> again after an interrupted
1893 <tt>clean</tt> doesn't think that everything is
1898 The <tt>clean</tt> target may need to be
1899 invoked as root if <tt>binary</tt> has been
1900 invoked since the last <tt>clean</tt>, or if
1901 <tt>build</tt> has been invoked as root (since
1902 <tt>build</tt> may create directories, for
1907 <tag><tt>get-orig-source</tt> (optional)</tag>
1910 This target fetches the most recent version of the
1911 original source package from a canonical archive site
1912 (via FTP or WWW, for example), does any necessary
1913 rearrangement to turn it into the original source
1914 tar file format described below, and leaves it in the
1919 This target may be invoked in any directory, and
1920 should take care to clean up any temporary files it
1925 This target is optional, but providing it if
1926 possible is a good idea.
1932 The <tt>build</tt>, <tt>binary</tt> and
1933 <tt>clean</tt> targets must be invoked with the current
1934 directory being the package's top-level directory.
1939 Additional targets may exist in <file>debian/rules</file>,
1940 either as published or undocumented interfaces or for the
1941 package's internal use.
1945 The architectures we build on and build for are determined
1946 by <prgn>make</prgn> variables using the utility
1947 <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
1948 You can determine the
1949 Debian architecture and the GNU style architecture
1950 specification string for the build machine (the machine type
1951 we are building on) as well as for the host machine (the
1952 machine type we are building for). Here is a list of
1953 supported <prgn>make</prgn> variables:
1954 <list compact="compact">
1956 <tt>DEB_*_ARCH</tt> (the Debian architecture)
1959 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
1960 specification string)
1963 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
1964 <tt>DEB_*_GNU_TYPE</tt>)
1967 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
1968 <tt>DEB_*_GNU_TYPE</tt>)
1970 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
1971 the build machine or <tt>HOST</tt> for specification of the
1976 Backward compatibility can be provided in the rules file
1977 by setting the needed variables to suitable default
1978 values; please refer to the documentation of
1979 <prgn>dpkg-architecture</prgn> for details.
1983 It is important to understand that the <tt>DEB_*_ARCH</tt>
1984 string only determines which Debian architecture we are
1985 building on or for. It should not be used to get the CPU
1986 or system information; the GNU style variables should be
1991 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
1992 <sect id="substvars">
1993 <heading>Variable substitutions: <file>debian/substvars</file></heading>
1996 When <prgn>dpkg-gencontrol</prgn>,
1997 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
1998 generate control files they perform variable substitutions
1999 on their output just before writing it. Variable
2000 substitutions have the form <tt>${<var>variable</var>}</tt>.
2001 The optional file <file>debian/substvars</file> contains
2002 variable substitutions to be used; variables can also be set
2003 directly from <file>debian/rules</file> using the <tt>-V</tt>
2004 option to the source packaging commands, and certain
2005 predefined variables are also available.
2009 The <file>debian/substvars</file> file is usually generated and
2010 modified dynamically by <file>debian/rules</file> targets, in
2011 which case it must be removed by the <tt>clean</tt> target.
2015 See <manref name="dpkg-source" section="1"> for full
2016 details about source variable substitutions, including the
2017 format of <file>debian/substvars</file>.</p>
2020 <sect id="debianwatch">
2021 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2024 This is an optional, recommended control file for the
2025 <tt>uscan</tt> utility which defines how to automatically
2026 scan ftp or http sites for newly available updates of the
2027 package. This is used by <url id="
2028 http://dehs.alioth.debian.org/"> and other Debian QA tools
2029 to help with quality control and maintenance of the
2030 distribution as a whole.
2035 <sect id="debianfiles">
2036 <heading>Generated files list: <file>debian/files</file></heading>
2039 This file is not a permanent part of the source tree; it
2040 is used while building packages to record which files are
2041 being generated. <prgn>dpkg-genchanges</prgn> uses it
2042 when it generates a <file>.changes</file> file.
2046 It should not exist in a shipped source package, and so it
2047 (and any backup files or temporary files such as
2048 <file>files.new</file><footnote>
2049 <file>files.new</file> is used as a temporary file by
2050 <prgn>dpkg-gencontrol</prgn> and
2051 <prgn>dpkg-distaddfile</prgn> - they write a new
2052 version of <tt>files</tt> here before renaming it,
2053 to avoid leaving a corrupted copy if an error
2055 </footnote>) should be removed by the
2056 <tt>clean</tt> target. It may also be wise to
2057 ensure a fresh start by emptying or removing it at the
2058 start of the <tt>binary</tt> target.
2062 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2063 package, it adds an entry to <file>debian/files</file> for the
2064 <file>.deb</file> file that will be created when <tt>dpkg-deb
2065 --build</tt> is run for that binary package. So for most
2066 packages all that needs to be done with this file is to
2067 delete it in the <tt>clean</tt> target.
2071 If a package upload includes files besides the source
2072 package and any binary packages whose control files were
2073 made with <prgn>dpkg-gencontrol</prgn> then they should be
2074 placed in the parent of the package's top-level directory
2075 and <prgn>dpkg-distaddfile</prgn> should be called to add
2076 the file to the list in <file>debian/files</file>.</p>
2082 <chapt id="controlfields">
2083 <heading>Control files and their fields</heading>
2086 The package management system manipulates data represented in
2087 a common format, known as <em>control data</em>, stored in
2088 <em>control files</em>.
2089 Control files are used for source packages, binary packages and
2090 the <file>.changes</file> files which control the installation
2091 of uploaded files<footnote>
2092 <prgn>dpkg</prgn>'s internal databases are in a similar
2097 <sect id="controlsyntax">
2098 <heading>Syntax of control files</heading>
2101 A control file consists of one or more paragraphs of
2103 The paragraphs are also sometimes referred to as stanzas.
2105 The paragraphs are separated by blank lines. Some control
2106 files allow only one paragraph; others allow several, in
2107 which case each paragraph usually refers to a different
2108 package. (For example, in source packages, the first
2109 paragraph refers to the source package, and later paragraphs
2110 refer to binary packages generated from the source.)
2114 Each paragraph consists of a series of data fields; each
2115 field consists of the field name, followed by a colon and
2116 then the data/value associated with that field. It ends at
2117 the end of the (logical) line. Horizontal whitespace
2118 (spaces and tabs) may occur immediately before or after the
2119 value and is ignored there; it is conventional to put a
2120 single space after the colon. For example, a field might
2122 <example compact="compact">
2125 the field name is <tt>Package</tt> and the field value
2130 Many fields' values may span several lines; in this case
2131 each continuation line must start with a space or a tab.
2132 Any trailing spaces or tabs at the end of individual
2133 lines of a field value are ignored.
2137 In fields where it is specified that lines may not wrap,
2138 only a single line of data is allowed and whitespace is not
2139 significant in a field body. Whitespace must not appear
2140 inside names (of packages, architectures, files or anything
2141 else) or version numbers, or between the characters of
2142 multi-character version relationships.
2146 Field names are not case-sensitive, but it is usual to
2147 capitalize the field names using mixed case as shown below.
2151 Blank lines, or lines consisting only of spaces and tabs,
2152 are not allowed within field values or between fields - that
2153 would mean a new paragraph.
2158 <sect id="sourcecontrolfiles">
2159 <heading>Source package control files -- <file>debian/control</file></heading>
2162 The <file>debian/control</file> file contains the most vital
2163 (and version-independent) information about the source package
2164 and about the binary packages it creates.
2168 The first paragraph of the control file contains information about
2169 the source package in general. The subsequent sets each describe a
2170 binary package that the source tree builds.
2174 The fields in the general paragraph (the first one, for the source
2177 <list compact="compact">
2178 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2179 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2180 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2181 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2182 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2183 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2184 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2189 The fields in the binary package paragraphs are:
2191 <list compact="compact">
2192 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2193 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2194 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2195 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2196 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2197 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2198 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2203 The syntax and semantics of the fields are described below.
2209 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2210 generate control files for binary packages (see below), by
2211 <prgn>dpkg-genchanges</prgn> to generate the
2212 <tt>.changes</tt> file to accompany the upload, and by
2213 <prgn>dpkg-source</prgn> when it creates the
2214 <file>.dsc</file> source control file as part of a source
2215 archive. Many fields are permitted to span multiple lines in
2216 <file>debian/control</file> but not in any other control
2217 file. These tools are responsible for removing the line
2218 breaks from such fields when using fields from
2219 <file>debian/control</file> to generate other control files.
2223 The fields here may contain variable references - their
2224 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2225 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2226 when they generate output control files.
2227 See <ref id="substvars"> for details.
2232 <sect id="binarycontrolfiles">
2233 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2236 The <file>DEBIAN/control</file> file contains the most vital
2237 (and version-dependent) information about a binary package.
2241 The fields in this file are:
2243 <list compact="compact">
2244 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2245 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2246 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2247 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2248 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2249 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2250 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2251 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2252 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2253 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2254 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2259 <sect id="debiansourcecontrolfiles">
2260 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2263 This file contains a series of fields, identified and
2264 separated just like the fields in the control file of
2265 a binary package. The fields are listed below; their
2266 syntax is described above, in <ref id="pkg-controlfields">.
2268 <list compact="compact">
2269 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2270 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2271 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2272 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2273 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2274 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2275 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2276 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2277 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2278 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2283 The source package control file is generated by
2284 <prgn>dpkg-source</prgn> when it builds the source
2285 archive, from other files in the source package,
2286 described above. When unpacking, it is checked against
2287 the files and directories in the other parts of the
2293 <sect id="debianchangesfiles">
2294 <heading>Debian changes files -- <file>.changes</file></heading>
2297 The .changes files are used by the Debian archive maintenance
2298 software to process updates to packages. They contain one
2299 paragraph which contains information from the
2300 <tt>debian/control</tt> file and other data about the
2301 source package gathered via <tt>debian/changelog</tt>
2302 and <tt>debian/rules</tt>.
2306 The fields in this file are:
2308 <list compact="compact">
2309 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2310 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2311 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2312 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2313 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2314 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2315 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2316 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2317 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2318 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2319 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2320 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2321 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2322 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2327 <sect id="controlfieldslist">
2328 <heading>List of fields</heading>
2330 <sect1 id="f-Source">
2331 <heading><tt>Source</tt></heading>
2334 This field identifies the source package name.
2338 In <file>debian/control</file> or a <file>.dsc</file> file,
2339 this field must contain only the name of the source package.
2343 In a binary package control file or a <file>.changes</file>
2344 file, the source package name may be followed by a version
2345 number in parentheses<footnote>
2346 It is customary to leave a space after the package name
2347 if a version number is specified.
2349 This version number may be omitted (and is, by
2350 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2351 the <tt>Version</tt> field of the binary package in
2352 question. The field itself may be omitted from a binary
2353 package control file when the source package has the same
2354 name and version as the binary package.
2358 <sect1 id="f-Maintainer">
2359 <heading><tt>Maintainer</tt></heading>
2362 The package maintainer's name and email address. The name
2363 should come first, then the email address inside angle
2364 brackets <tt><></tt> (in RFC822 format).
2368 If the maintainer's name contains a full stop then the
2369 whole field will not work directly as an email address due
2370 to a misfeature in the syntax specified in RFC822; a
2371 program using this field as an address must check for this
2372 and correct the problem if necessary (for example by
2373 putting the name in round brackets and moving it to the
2374 end, and bringing the email address forward).
2378 <sect1 id="f-Uploaders">
2379 <heading><tt>Uploaders</tt></heading>
2382 List of the names and email addresses of co-maintainers of
2383 the package, if any. If the package has other maintainers
2384 beside the one named in the
2385 <qref id="f-Maintainer">Maintainer field</qref>, their
2386 names and email addresses should be listed here. The
2387 format is the same as that of the Maintainer tag, and
2388 multiple entries should be comma separated. Currently,
2389 this field is restricted to a single line of data. This
2390 is an optional field.
2393 Any parser that interprets the Uploaders field in
2394 <file>debian/control</file> should permit it to span multiple
2396 In the future, the Uploaders field in
2397 <file>debian/control</file> (but not other control files)
2398 will be permitted to span multiple lines and interpreting
2399 a multi-line Uploaders field shall be mandatory.
2400 </footnote>. Line breaks in an Uploaders field that spans
2401 multiple lines are not significant and the semantics of
2402 the field are the same as if the line breaks had not been
2407 <sect1 id="f-Changed-By">
2408 <heading><tt>Changed-By</tt></heading>
2411 The name and email address of the person who changed the
2412 said package. Usually the name of the maintainer.
2413 All the rules for the Maintainer field apply here, too.
2417 <sect1 id="f-Section">
2418 <heading><tt>Section</tt></heading>
2421 This field specifies an application area into which the package
2422 has been classified. See <ref id="subsections">.
2426 When it appears in the <file>debian/control</file> file,
2427 it gives the value for the subfield of the same name in
2428 the <tt>Files</tt> field of the <file>.changes</file> file.
2429 It also gives the default for the same field in the binary
2434 <sect1 id="f-Priority">
2435 <heading><tt>Priority</tt></heading>
2438 This field represents how important that it is that the user
2439 have the package installed. See <ref id="priorities">.
2443 When it appears in the <file>debian/control</file> file,
2444 it gives the value for the subfield of the same name in
2445 the <tt>Files</tt> field of the <file>.changes</file> file.
2446 It also gives the default for the same field in the binary
2451 <sect1 id="f-Package">
2452 <heading><tt>Package</tt></heading>
2455 The name of the binary package.
2459 Package names must consist only of lower case letters
2460 (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus (<tt>+</tt>)
2461 and minus (<tt>-</tt>) signs, and periods (<tt>.</tt>).
2462 They must be at least two characters long and must start
2463 with an alphanumeric character.
2467 <sect1 id="f-Architecture">
2468 <heading><tt>Architecture</tt></heading>
2471 Depending on context and the control file used, the
2472 <tt>Architecture</tt> field can include the following sets of
2475 <item>A unique single word identifying a Debian machine
2476 architecture, see <ref id="arch-spec">.
2477 <item><tt>all</tt>, which indicates an
2478 architecture-independent package.
2479 <item><tt>any</tt>, which indicates a package available
2480 for building on any architecture.
2481 <item><tt>source</tt>, which indicates a source package.
2486 In the main <file>debian/control</file> file in the source
2487 package, or in the source package control file
2488 <file>.dsc</file>, one may specify a list of architectures
2489 separated by spaces, or the special values <tt>any</tt> or
2494 Specifying <tt>any</tt> indicates that the source package
2495 isn't dependent on any particular architecture and should
2496 compile fine on any one. The produced binary package(s)
2497 will be specific to whatever the current build architecture
2499 This is the most often used setting, and is recommended
2500 for new packages that aren't <tt>Architecture: all</tt>.
2505 Specifying a list of architectures indicates that the source
2506 will build an architecture-dependent package, and will only
2507 work correctly on the listed architectures.<footnote>
2508 This is a setting used for a minority of cases where the
2509 program is not portable. Generally, it should not be used
2515 In a <file>.changes</file> file, the <tt>Architecture</tt>
2516 field lists the architecture(s) of the package(s)
2517 currently being uploaded. This will be a list; if the
2518 source for the package is also being uploaded, the special
2519 entry <tt>source</tt> is also present.
2523 See <ref id="debianrules"> for information how to get the
2524 architecture for the build process.
2528 <sect1 id="f-Essential">
2529 <heading><tt>Essential</tt></heading>
2532 This is a boolean field which may occur only in the
2533 control file of a binary package or in a per-package fields
2534 paragraph of a main source control data file.
2538 If set to <tt>yes</tt> then the package management system
2539 will refuse to remove the package (upgrading and replacing
2540 it is still possible). The other possible value is <tt>no</tt>,
2541 which is the same as not having the field at all.
2546 <heading>Package interrelationship fields:
2547 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2548 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Conflicts</tt>,
2549 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2553 These fields describe the package's relationships with
2554 other packages. Their syntax and semantics are described
2555 in <ref id="relationships">.</p>
2558 <sect1 id="f-Standards-Version">
2559 <heading><tt>Standards-Version</tt></heading>
2562 The most recent version of the standards (the policy
2563 manual and associated texts) with which the package
2568 The version number has four components: major and minor
2569 version number and major and minor patch level. When the
2570 standards change in a way that requires every package to
2571 change the major number will be changed. Significant
2572 changes that will require work in many packages will be
2573 signaled by a change to the minor number. The major patch
2574 level will be changed for any change to the meaning of the
2575 standards, however small; the minor patch level will be
2576 changed when only cosmetic, typographical or other edits
2577 are made which neither change the meaning of the document
2578 nor affect the contents of packages.
2582 Thus only the first three components of the policy version
2583 are significant in the <em>Standards-Version</em> control
2584 field, and so either these three components or the all
2585 four components may be specified.<footnote>
2586 In the past, people specified the full version number
2587 in the Standards-Version field, for example "2.3.0.0".
2588 Since minor patch-level changes don't introduce new
2589 policy, it was thought it would be better to relax
2590 policy and only require the first 3 components to be
2591 specified, in this example "2.3.0". All four
2592 components may still be used if someone wishes to do so.
2598 <sect1 id="f-Version">
2599 <heading><tt>Version</tt></heading>
2602 The version number of a package. The format is:
2603 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
2607 The three components here are:
2609 <tag><var>epoch</var></tag>
2612 This is a single (generally small) unsigned integer. It
2613 may be omitted, in which case zero is assumed. If it is
2614 omitted then the <var>upstream_version</var> may not
2619 It is provided to allow mistakes in the version numbers
2620 of older versions of a package, and also a package's
2621 previous version numbering schemes, to be left behind.
2625 <tag><var>upstream_version</var></tag>
2628 This is the main part of the version number. It is
2629 usually the version number of the original ("upstream")
2630 package from which the <file>.deb</file> file has been made,
2631 if this is applicable. Usually this will be in the same
2632 format as that specified by the upstream author(s);
2633 however, it may need to be reformatted to fit into the
2634 package management system's format and comparison
2639 The comparison behavior of the package management system
2640 with respect to the <var>upstream_version</var> is
2641 described below. The <var>upstream_version</var>
2642 portion of the version number is mandatory.
2646 The <var>upstream_version</var> may contain only
2647 alphanumerics<footnote>
2648 Alphanumerics are <tt>A-Za-z0-9</tt> only.
2650 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
2651 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
2652 tilde) and should start with a digit. If there is no
2653 <var>debian_revision</var> then hyphens are not allowed;
2654 if there is no <var>epoch</var> then colons are not
2659 <tag><var>debian_revision</var></tag>
2662 This part of the version number specifies the version of
2663 the Debian package based on the upstream version. It
2664 may contain only alphanumerics and the characters
2665 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
2666 tilde) and is compared in the same way as the
2667 <var>upstream_version</var> is.
2671 It is optional; if it isn't present then the
2672 <var>upstream_version</var> may not contain a hyphen.
2673 This format represents the case where a piece of
2674 software was written specifically to be turned into a
2675 Debian package, and so there is only one "debianisation"
2676 of it and therefore no revision indication is required.
2680 It is conventional to restart the
2681 <var>debian_revision</var> at <tt>1</tt> each time the
2682 <var>upstream_version</var> is increased.
2686 The package management system will break the version
2687 number apart at the last hyphen in the string (if there
2688 is one) to determine the <var>upstream_version</var> and
2689 <var>debian_revision</var>. The absence of a
2690 <var>debian_revision</var> compares earlier than the
2691 presence of one (but note that the
2692 <var>debian_revision</var> is the least significant part
2693 of the version number).
2700 The <var>upstream_version</var> and <var>debian_revision</var>
2701 parts are compared by the package management system using the
2706 The strings are compared from left to right.
2710 First the initial part of each string consisting entirely of
2711 non-digit characters is determined. These two parts (one of
2712 which may be empty) are compared lexically. If a difference
2713 is found it is returned. The lexical comparison is a
2714 comparison of ASCII values modified so that all the letters
2715 sort earlier than all the non-letters and so that a tilde
2716 sorts before anything, even the end of a part. For example,
2717 the following parts are in sorted order from earliest to
2718 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
2719 <tt>a</tt>.<footnote>
2720 One common use of <tt>~</tt> is for upstream pre-releases.
2721 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
2722 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
2727 Then the initial part of the remainder of each string which
2728 consists entirely of digit characters is determined. The
2729 numerical values of these two parts are compared, and any
2730 difference found is returned as the result of the comparison.
2731 For these purposes an empty string (which can only occur at
2732 the end of one or both version strings being compared) counts
2737 These two steps (comparing and removing initial non-digit
2738 strings and initial digit strings) are repeated until a
2739 difference is found or both strings are exhausted.
2743 Note that the purpose of epochs is to allow us to leave behind
2744 mistakes in version numbering, and to cope with situations
2745 where the version numbering scheme changes. It is
2746 <em>not</em> intended to cope with version numbers containing
2747 strings of letters which the package management system cannot
2748 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
2749 silly orderings (the author of this manual has heard of a
2750 package whose versions went <tt>1.1</tt>, <tt>1.2</tt>,
2751 <tt>1.3</tt>, <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>,
2752 <tt>2</tt> and so forth).
2756 <sect1 id="f-Description">
2757 <heading><tt>Description</tt></heading>
2760 In a source or binary control file, the <tt>Description</tt>
2761 field contains a description of the binary package, consisting
2762 of two parts, the synopsis or the short description, and the
2763 long description. The field's format is as follows:
2768 Description: <single line synopsis>
2769 <extended description over several lines>
2774 The lines in the extended description can have these formats:
2780 Those starting with a single space are part of a paragraph.
2781 Successive lines of this form will be word-wrapped when
2782 displayed. The leading space will usually be stripped off.
2786 Those starting with two or more spaces. These will be
2787 displayed verbatim. If the display cannot be panned
2788 horizontally, the displaying program will line wrap them "hard"
2789 (i.e., without taking account of word breaks). If it can they
2790 will be allowed to trail off to the right. None, one or two
2791 initial spaces may be deleted, but the number of spaces
2792 deleted from each line will be the same (so that you can have
2793 indenting work correctly, for example).
2797 Those containing a single space followed by a single full stop
2798 character. These are rendered as blank lines. This is the
2799 <em>only</em> way to get a blank line<footnote>
2800 Completely empty lines will not be rendered as blank lines.
2801 Instead, they will cause the parser to think you're starting
2802 a whole new record in the control file, and will therefore
2803 likely abort with an error.
2808 Those containing a space, a full stop and some more characters.
2809 These are for future expansion. Do not use them.
2815 Do not use tab characters. Their effect is not predictable.
2819 See <ref id="descriptions"> for further information on this.
2823 In a <file>.changes</file> file, the <tt>Description</tt> field
2824 contains a summary of the descriptions for the packages being
2829 The part of the field before the first newline is empty;
2830 thereafter each line has the name of a binary package and
2831 the summary description line from that binary package.
2832 Each line is indented by one space.
2837 <sect1 id="f-Distribution">
2838 <heading><tt>Distribution</tt></heading>
2841 In a <file>.changes</file> file or parsed changelog output
2842 this contains the (space-separated) name(s) of the
2843 distribution(s) where this version of the package should
2844 be installed. Valid distributions are determined by the
2845 archive maintainers.<footnote>
2846 Current distribution names are:
2847 <taglist compact="compact">
2848 <tag><em>stable</em></tag>
2850 This is the current "released" version of Debian
2851 GNU/Linux. Once the distribution is
2852 <em>stable</em> only security fixes and other
2853 major bug fixes are allowed. When changes are
2854 made to this distribution, the release number is
2855 increased (for example: 2.2r1 becomes 2.2r2 then
2859 <tag><em>unstable</em></tag>
2861 This distribution value refers to the
2862 <em>developmental</em> part of the Debian
2863 distribution tree. New packages, new upstream
2864 versions of packages and bug fixes go into the
2865 <em>unstable</em> directory tree. Download from
2866 this distribution at your own risk.
2869 <tag><em>testing</em></tag>
2871 This distribution value refers to the
2872 <em>testing</em> part of the Debian distribution
2873 tree. It receives its packages from the
2874 unstable distribution after a short time lag to
2875 ensure that there are no major issues with the
2876 unstable packages. It is less prone to breakage
2877 than unstable, but still risky. It is not
2878 possible to upload packages directly to
2882 <tag><em>frozen</em></tag>
2884 From time to time, the <em>testing</em>
2885 distribution enters a state of "code-freeze" in
2886 anticipation of release as a <em>stable</em>
2887 version. During this period of testing only
2888 fixes for existing or newly-discovered bugs will
2889 be allowed. The exact details of this stage are
2890 determined by the Release Manager.
2893 <tag><em>experimental</em></tag>
2895 The packages with this distribution value are
2896 deemed by their maintainers to be high
2897 risk. Oftentimes they represent early beta or
2898 developmental packages from various sources that
2899 the maintainers want people to try, but are not
2900 ready to be a part of the other parts of the
2901 Debian distribution tree. Download at your own
2907 You should list <em>all</em> distributions that the
2908 package should be installed into.
2912 More information is available in the Debian Developer's
2913 Reference, section "The Debian archive".
2920 <heading><tt>Date</tt></heading>
2923 This field includes the date the package was built or last edited.
2927 The value of this field is usually extracted from the
2928 <file>debian/changelog</file> file - see
2929 <ref id="dpkgchangelog">).
2933 <sect1 id="f-Format">
2934 <heading><tt>Format</tt></heading>
2937 This field specifies a format revision for the file.
2938 The most current format described in the Policy Manual
2939 is version <strong>1.5</strong>. The syntax of the
2940 format value is the same as that of a package version
2941 number except that no epoch or Debian revision is allowed
2942 - see <ref id="f-Version">.
2946 <sect1 id="f-Urgency">
2947 <heading><tt>Urgency</tt></heading>
2950 This is a description of how important it is to upgrade to
2951 this version from previous ones. It consists of a single
2952 keyword taking one of the values <tt>low</tt>,
2953 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
2954 <tt>critical</tt><footnote>
2955 Other urgency values are supported with configuration
2956 changes in the archive software but are not used in Debian.
2957 The urgency affects how quickly a package will be considered
2958 for inclusion into the <tt>testing</tt> distribution and
2959 gives an indication of the importance of any fixes included
2960 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
2961 treated as synonymous.
2962 </footnote> (not case-sensitive) followed by an optional
2963 commentary (separated by a space) which is usually in
2964 parentheses. For example:
2967 Urgency: low (HIGH for users of diversions)
2973 The value of this field is usually extracted from the
2974 <file>debian/changelog</file> file - see
2975 <ref id="dpkgchangelog">.
2979 <sect1 id="f-Changes">
2980 <heading><tt>Changes</tt></heading>
2983 This field contains the human-readable changes data, describing
2984 the differences between the last version and the current one.
2988 There should be nothing in this field before the first
2989 newline; all the subsequent lines must be indented by at
2990 least one space; blank lines must be represented by a line
2991 consisting only of a space and a full stop.
2995 The value of this field is usually extracted from the
2996 <file>debian/changelog</file> file - see
2997 <ref id="dpkgchangelog">).
3001 Each version's change information should be preceded by a
3002 "title" line giving at least the version, distribution(s)
3003 and urgency, in a human-readable way.
3007 If data from several versions is being returned the entry
3008 for the most recent version should be returned first, and
3009 entries should be separated by the representation of a
3010 blank line (the "title" line may also be followed by the
3011 representation of blank line).
3015 <sect1 id="f-Binary">
3016 <heading><tt>Binary</tt></heading>
3019 This field is a list of binary packages.
3023 When it appears in the <file>.dsc</file> file it is the list
3024 of binary packages which a source package can produce. It
3025 does not necessarily produce all of these binary packages
3026 for every architecture. The source control file doesn't
3027 contain details of which architectures are appropriate for
3028 which of the binary packages.
3032 When it appears in a <file>.changes</file> file it lists the
3033 names of the binary packages actually being uploaded.
3037 The syntax is a list of binary packages separated by
3039 A space after each comma is conventional.
3040 </footnote>. Currently the packages must be separated using
3041 only spaces in the <file>.changes</file> file.
3045 <sect1 id="f-Installed-Size">
3046 <heading><tt>Installed-Size</tt></heading>
3049 This field appears in the control files of binary
3050 packages, and in the <file>Packages</file> files. It gives
3051 the total amount of disk space required to install the
3056 The disk space is represented in kilobytes as a simple
3061 <sect1 id="f-Files">
3062 <heading><tt>Files</tt></heading>
3065 This field contains a list of files with information about
3066 each one. The exact information and syntax varies with
3067 the context. In all cases the part of the field
3068 contents on the same line as the field name is empty. The
3069 remainder of the field is one line per file, each line
3070 being indented by one space and containing a number of
3071 sub-fields separated by spaces.
3075 In the <file>.dsc</file> file, each line contains the MD5
3076 checksum, size and filename of the tar file and (if applicable)
3077 diff file which make up the remainder of the source
3079 That is, the parts which are not the <tt>.dsc</tt>.
3081 The exact forms of the filenames are described
3082 in <ref id="pkg-sourcearchives">.
3086 In the <file>.changes</file> file this contains one line per
3087 file being uploaded. Each line contains the MD5 checksum,
3088 size, section and priority and the filename.
3089 The <qref id="f-Section">section</qref>
3090 and <qref id="f-Priority">priority</qref>
3091 are the values of the corresponding fields in
3092 the main source control file. If no section or priority is
3093 specified then <tt>-</tt> should be used, though section
3094 and priority values must be specified for new packages to
3095 be installed properly.
3099 The special value <tt>byhand</tt> for the section in a
3100 <tt>.changes</tt> file indicates that the file in question
3101 is not an ordinary package file and must by installed by
3102 hand by the distribution maintainers. If the section is
3103 <tt>byhand</tt> the priority should be <tt>-</tt>.
3107 If a new Debian revision of a package is being shipped and
3108 no new original source archive is being distributed the
3109 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3110 entry for the original source archive
3111 <file><var>package</var>-<var>upstream-version</var>.orig.tar.gz</file>,
3112 but the <file>.changes</file> file should leave it out. In
3113 this case the original source archive on the distribution
3114 site must match exactly, byte-for-byte, the original
3115 source archive which was used to generate the
3116 <file>.dsc</file> file and diff which are being uploaded.</p>
3119 <sect1 id="f-Closes">
3120 <heading><tt>Closes</tt></heading>
3123 A space-separated list of bug report numbers that the upload
3124 governed by the .changes file closes.
3131 <heading>User-defined fields</heading>
3134 Additional user-defined fields may be added to the
3135 source package control file. Such fields will be
3136 ignored, and not copied to (for example) binary or
3137 source package control files or upload control files.
3141 If you wish to add additional unsupported fields to
3142 these output files you should use the mechanism
3147 Fields in the main source control information file with
3148 names starting <tt>X</tt>, followed by one or more of
3149 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3150 be copied to the output files. Only the part of the
3151 field name after the hyphen will be used in the output
3152 file. Where the letter <tt>B</tt> is used the field
3153 will appear in binary package control files, where the
3154 letter <tt>S</tt> is used in source package control
3155 files and where <tt>C</tt> is used in upload control
3156 (<tt>.changes</tt>) files.
3160 For example, if the main source information control file
3163 XBS-Comment: I stand between the candle and the star.
3165 then the binary and source package control files will contain the
3168 Comment: I stand between the candle and the star.
3177 <chapt id="maintainerscripts">
3178 <heading>Package maintainer scripts and installation procedure</heading>
3181 <heading>Introduction to package maintainer scripts</heading>
3184 It is possible to supply scripts as part of a package which
3185 the package management system will run for you when your
3186 package is installed, upgraded or removed.
3190 These scripts are the files <prgn>preinst</prgn>,
3191 <prgn>postinst</prgn>, <prgn>prerm</prgn> and
3192 <prgn>postrm</prgn> in the control area of the package.
3193 They must be proper executable files; if they are scripts
3194 (which is recommended), they must start with the usual
3195 <tt>#!</tt> convention. They should be readable and
3196 executable by anyone, and must not be world-writable.
3200 The package management system looks at the exit status from
3201 these scripts. It is important that they exit with a
3202 non-zero status if there is an error, so that the package
3203 management system can stop its processing. For shell
3204 scripts this means that you <em>almost always</em> need to
3205 use <tt>set -e</tt> (this is usually true when writing shell
3206 scripts, in fact). It is also important, of course, that
3207 they don't exit with a non-zero status if everything went
3212 Additionally, packages interacting with users using
3213 <tt>debconf</tt> in the <prgn>postinst</prgn> script should
3214 install a <prgn>config</prgn> script in the control area,
3215 see <ref id="maintscriptprompt"> for details.
3219 When a package is upgraded a combination of the scripts from
3220 the old and new packages is called during the upgrade
3221 procedure. If your scripts are going to be at all
3222 complicated you need to be aware of this, and may need to
3223 check the arguments to your scripts.
3227 Broadly speaking the <prgn>preinst</prgn> is called before
3228 (a particular version of) a package is installed, and the
3229 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3230 before (a version of) a package is removed and the
3231 <prgn>postrm</prgn> afterwards.
3235 Programs called from maintainer scripts should not normally
3236 have a path prepended to them. Before installation is
3237 started, the package management system checks to see if the
3238 programs <prgn>ldconfig</prgn>,
3239 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3240 and <prgn>update-rc.d</prgn> can be found via the
3241 <tt>PATH</tt> environment variable. Those programs, and any
3242 other program that one would expect to be in the
3243 <tt>PATH</tt>, should thus be invoked without an absolute
3244 pathname. Maintainer scripts should also not reset the
3245 <tt>PATH</tt>, though they might choose to modify it by
3246 prepending or appending package-specific directories. These
3247 considerations really apply to all shell scripts.</p>
3250 <sect id="idempotency">
3251 <heading>Maintainer scripts Idempotency</heading>
3254 It is necessary for the error recovery procedures that the
3255 scripts be idempotent. This means that if it is run
3256 successfully, and then it is called again, it doesn't bomb
3257 out or cause any harm, but just ensures that everything is
3258 the way it ought to be. If the first call failed, or
3259 aborted half way through for some reason, the second call
3260 should merely do the things that were left undone the first
3261 time, if any, and exit with a success status if everything
3263 This is so that if an error occurs, the user interrupts
3264 <prgn>dpkg</prgn> or some other unforeseen circumstance
3265 happens you don't leave the user with a badly-broken
3266 package when <prgn>dpkg</prgn> attempts to repeat the
3272 <sect id="controllingterminal">
3273 <heading>Controlling terminal for maintainer scripts</heading>
3276 The maintainer scripts are guaranteed to run with a
3277 controlling terminal and can interact with the user.
3278 Because these scripts may be executed with standard output
3279 redirected into a pipe for logging purposes, Perl scripts
3280 should set unbuffered output by setting <tt>$|=1</tt> so
3281 that the output is printed immediately rather than being
3285 <sect id="exitstatus">
3286 <heading>Exit status</heading>
3289 Each script must return a zero exit status for
3290 success, or a nonzero one for failure, since the package
3291 management system looks for the exit status of these scripts
3292 and determines what action to take next based on that datum.
3296 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3301 <list compact="compact">
3303 <var>new-preinst</var> <tt>install</tt>
3306 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3309 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3312 <var>old-preinst</var> <tt>abort-upgrade</tt>
3313 <var>new-version</var>
3318 <list compact="compact">
3320 <var>postinst</var> <tt>configure</tt>
3321 <var>most-recently-configured-version</var>
3324 <var>old-postinst</var> <tt>abort-upgrade</tt>
3325 <var>new-version</var>
3328 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3329 <tt>in-favour</tt> <var>package</var>
3330 <var>new-version</var>
3333 <var>postinst</var> <tt>abort-remove</tt>
3336 <var>deconfigured's-postinst</var>
3337 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3338 <var>failed-install-package</var> <var>version</var>
3339 <tt>removing</tt> <var>conflicting-package</var>
3345 <list compact="compact">
3347 <var>prerm</var> <tt>remove</tt>
3350 <var>old-prerm</var> <tt>upgrade</tt>
3351 <var>new-version</var>
3354 <var>new-prerm</var> <tt>failed-upgrade</tt>
3355 <var>old-version</var>
3358 <var>conflictor's-prerm</var> <tt>remove</tt>
3359 <tt>in-favour</tt> <var>package</var>
3360 <var>new-version</var>
3363 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3364 <tt>in-favour</tt> <var>package-being-installed</var>
3365 <var>version</var> <tt>removing</tt>
3366 <var>conflicting-package</var>
3372 <list compact="compact">
3374 <var>postrm</var> <tt>remove</tt>
3377 <var>postrm</var> <tt>purge</tt>
3380 <var>old-postrm</var> <tt>upgrade</tt>
3381 <var>new-version</var>
3384 <var>new-postrm</var> <tt>failed-upgrade</tt>
3385 <var>old-version</var>
3388 <var>new-postrm</var> <tt>abort-install</tt>
3391 <var>new-postrm</var> <tt>abort-install</tt>
3392 <var>old-version</var>
3395 <var>new-postrm</var> <tt>abort-upgrade</tt>
3396 <var>old-version</var>
3399 <var>disappearer's-postrm</var> <tt>disappear</tt>
3400 <var>overwriter</var>
3401 <var>overwriter-version</var>
3407 <sect id="unpackphase">
3408 <heading>Details of unpack phase of installation or upgrade</heading>
3411 The procedure on installation/upgrade/overwrite/disappear
3412 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3413 stage of <tt>dpkg --install</tt>) is as follows. In each
3414 case, if a major error occurs (unless listed below) the
3415 actions are, in general, run backwards - this means that the
3416 maintainer scripts are run with different arguments in
3417 reverse order. These are the "error unwind" calls listed
3424 If a version of the package is already installed, call
3425 <example compact="compact">
3426 <var>old-prerm</var> upgrade <var>new-version</var>
3430 If the script runs but exits with a non-zero
3431 exit status, <prgn>dpkg</prgn> will attempt:
3432 <example compact="compact">
3433 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3435 If this works, the upgrade continues. If this
3436 does not work, the error unwind:
3437 <example compact="compact">
3438 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3440 If this works, then the old-version is
3441 "Installed", if not, the old version is in a
3442 "Failed-Config" state.
3448 If a "conflicting" package is being removed at the same time:
3451 If any packages depended on that conflicting
3452 package and <tt>--auto-deconfigure</tt> is
3453 specified, call, for each such package:
3454 <example compact="compact">
3455 <var>deconfigured's-prerm</var> deconfigure \
3456 in-favour <var>package-being-installed</var> <var>version</var> \
3457 removing <var>conflicting-package</var> <var>version</var>
3460 <example compact="compact">
3461 <var>deconfigured's-postinst</var> abort-deconfigure \
3462 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3463 removing <var>conflicting-package</var> <var>version</var>
3465 The deconfigured packages are marked as
3466 requiring configuration, so that if
3467 <tt>--install</tt> is used they will be
3468 configured again if possible.
3471 To prepare for removal of the conflicting package, call:
3472 <example compact="compact">
3473 <var>conflictor's-prerm</var> remove \
3474 in-favour <var>package</var> <var>new-version</var>
3477 <example compact="compact">
3478 <var>conflictor's-postinst</var> abort-remove \
3479 in-favour <var>package</var> <var>new-version</var>
3488 If the package is being upgraded, call:
3489 <example compact="compact">
3490 <var>new-preinst</var> upgrade <var>old-version</var>
3492 If this fails, we call:
3494 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3501 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3503 is called. If this works, then the old version
3504 is in an "Installed" state, or else it is left
3505 in an "Unpacked" state.
3510 If it fails, then the old version is left
3511 in an "Half-Installed" state.
3518 Otherwise, if the package had some configuration
3519 files from a previous version installed (i.e., it
3520 is in the "configuration files only" state):
3521 <example compact="compact">
3522 <var>new-preinst</var> install <var>old-version</var>
3526 <var>new-postrm</var> abort-install <var>old-version</var>
3528 If this fails, the package is left in a
3529 "Half-Installed" state, which requires a
3530 reinstall. If it works, the packages is left in
3531 a "Config Files" state.
3534 Otherwise (i.e., the package was completely purged):
3535 <example compact="compact">
3536 <var>new-preinst</var> install
3539 <example compact="compact">
3540 <var>new-postrm</var> abort-install
3542 If the error-unwind fails, the package is in a
3543 "Half Installed" phase, and requires a
3544 reinstall. If the error unwind works, the
3545 package is in a not installed state.
3552 The new package's files are unpacked, overwriting any
3553 that may be on the system already, for example any
3554 from the old version of the same package or from
3555 another package. Backups of the old files are kept
3556 temporarily, and if anything goes wrong the package
3557 management system will attempt to put them back as
3558 part of the error unwind.
3562 It is an error for a package to contain files which
3563 are on the system in another package, unless
3564 <tt>Replaces</tt> is used (see <ref id="replaces">).
3566 The following paragraph is not currently the case:
3567 Currently the <tt>- - force-overwrite</tt> flag is
3568 enabled, downgrading it to a warning, but this may not
3574 It is a more serious error for a package to contain a
3575 plain file or other kind of non-directory where another
3576 package has a directory (again, unless
3577 <tt>Replaces</tt> is used). This error can be
3578 overridden if desired using
3579 <tt>--force-overwrite-dir</tt>, but this is not
3584 Packages which overwrite each other's files produce
3585 behavior which, though deterministic, is hard for the
3586 system administrator to understand. It can easily
3587 lead to "missing" programs if, for example, a package
3588 is installed which overwrites a file from another
3589 package, and is then removed again.<footnote>
3590 Part of the problem is due to what is arguably a
3591 bug in <prgn>dpkg</prgn>.
3596 A directory will never be replaced by a symbolic link
3597 to a directory or vice versa; instead, the existing
3598 state (symlink or not) will be left alone and
3599 <prgn>dpkg</prgn> will follow the symlink if there is
3608 If the package is being upgraded, call
3609 <example compact="compact">
3610 <var>old-postrm</var> upgrade <var>new-version</var>
3614 If this fails, <prgn>dpkg</prgn> will attempt:
3615 <example compact="compact">
3616 <var>new-postrm</var> failed-upgrade <var>old-version</var>
3618 If this works, installation continues. If not,
3620 <example compact="compact">
3621 <var>old-preinst</var> abort-upgrade <var>new-version</var>
3623 If this fails, the old version is left in an
3624 "Half Installed" state. If it works, dpkg now
3626 <example compact="compact">
3627 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3629 If this fails, the old version is left in an
3630 "Half Installed" state. If it works, dpkg now
3632 <example compact="compact">
3633 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3635 If this fails, the old version is in an
3642 This is the point of no return - if
3643 <prgn>dpkg</prgn> gets this far, it won't back off
3644 past this point if an error occurs. This will
3645 leave the package in a fairly bad state, which
3646 will require a successful re-installation to clear
3647 up, but it's when <prgn>dpkg</prgn> starts doing
3648 things that are irreversible.
3653 Any files which were in the old version of the package
3654 but not in the new are removed.
3658 The new file list replaces the old.
3662 The new maintainer scripts replace the old.
3666 Any packages all of whose files have been overwritten
3667 during the installation, and which aren't required for
3668 dependencies, are considered to have been removed.
3669 For each such package
3672 <prgn>dpkg</prgn> calls:
3673 <example compact="compact">
3674 <var>disappearer's-postrm</var> disappear \
3675 <var>overwriter</var> <var>overwriter-version</var>
3679 The package's maintainer scripts are removed.
3682 It is noted in the status database as being in a
3683 sane state, namely not installed (any conffiles
3684 it may have are ignored, rather than being
3685 removed by <prgn>dpkg</prgn>). Note that
3686 disappearing packages do not have their prerm
3687 called, because <prgn>dpkg</prgn> doesn't know
3688 in advance that the package is going to
3695 Any files in the package we're unpacking that are also
3696 listed in the file lists of other packages are removed
3697 from those lists. (This will lobotomize the file list
3698 of the "conflicting" package if there is one.)
3702 The backup files made during installation, above, are
3708 The new package's status is now sane, and recorded as
3713 Here is another point of no return - if the
3714 conflicting package's removal fails we do not unwind
3715 the rest of the installation; the conflicting package
3716 is left in a half-removed limbo.
3721 If there was a conflicting package we go and do the
3722 removal actions (described below), starting with the
3723 removal of the conflicting package's files (any that
3724 are also in the package being installed have already
3725 been removed from the conflicting package's file list,
3726 and so do not get removed now).
3732 <sect id="configdetails"><heading>Details of configuration</heading>
3735 When we configure a package (this happens with <tt>dpkg
3736 --install</tt> and <tt>dpkg --configure</tt>), we first
3737 update any <tt>conffile</tt>s and then call:
3738 <example compact="compact">
3739 <var>postinst</var> configure <var>most-recently-configured-version</var>
3744 No attempt is made to unwind after errors during
3745 configuration. If the configuration fails, the package is in
3746 a "Failed Config" state, and an error message is generated.
3750 If there is no most recently configured version
3751 <prgn>dpkg</prgn> will pass a null argument.
3754 Historical note: Truly ancient (pre-1997) versions of
3755 <prgn>dpkg</prgn> passed <tt><unknown></tt>
3756 (including the angle brackets) in this case. Even older
3757 ones did not pass a second argument at all, under any
3758 circumstance. Note that upgrades using such an old dpkg
3759 version are unlikely to work for other reasons, even if
3760 this old argument behavior is handled by your postinst script.
3766 <sect id="removedetails"><heading>Details of removal and/or
3767 configuration purging</heading>
3773 <example compact="compact">
3774 <var>prerm</var> remove
3778 If prerm fails during replacement due to conflict
3780 <var>conflictor's-postinst</var> abort-remove \
3781 in-favour <var>package</var> <var>new-version</var>
3785 <var>postinst</var> abort-remove
3789 If this fails, the package is in a "Failed-Config"
3790 state, or else it remains "Installed".
3794 The package's files are removed (except <tt>conffile</tt>s).
3797 <example compact="compact">
3798 <var>postrm</var> remove
3802 If it fails, there's no error unwind, and the package is in
3803 an "Half-Installed" state.
3808 All the maintainer scripts except the <prgn>postrm</prgn>
3813 If we aren't purging the package we stop here. Note
3814 that packages which have no <prgn>postrm</prgn> and no
3815 <tt>conffile</tt>s are automatically purged when
3816 removed, as there is no difference except for the
3817 <prgn>dpkg</prgn> status.
3821 The <tt>conffile</tt>s and any backup files
3822 (<tt>~</tt>-files, <tt>#*#</tt> files,
3823 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
3828 <example compact="compact">
3829 <var>postrm</var> purge
3833 If this fails, the package remains in a "Config-Files"
3838 The package's file list is removed.
3847 <chapt id="relationships">
3848 <heading>Declaring relationships between packages</heading>
3850 <sect id="depsyntax">
3851 <heading>Syntax of relationship fields</heading>
3854 These fields all have a uniform syntax. They are a list of
3855 package names separated by commas.
3859 In the <tt>Depends</tt>, <tt>Recommends</tt>,
3860 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
3861 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
3862 control file fields of the package, which declare
3863 dependencies on other packages, the package names listed may
3864 also include lists of alternative package names, separated
3865 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
3866 if any one of the alternative packages is installed, that
3867 part of the dependency is considered to be satisfied.
3871 All of the fields except for <tt>Provides</tt> may restrict
3872 their applicability to particular versions of each named
3873 package. This is done in parentheses after each individual
3874 package name; the parentheses should contain a relation from
3875 the list below followed by a version number, in the format
3876 described in <ref id="f-Version">.
3880 The relations allowed are <tt><<</tt>, <tt><=</tt>,
3881 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
3882 strictly earlier, earlier or equal, exactly equal, later or
3883 equal and strictly later, respectively. The deprecated
3884 forms <tt><</tt> and <tt>></tt> were used to mean
3885 earlier/later or equal, rather than strictly earlier/later,
3886 so they should not appear in new packages (though
3887 <prgn>dpkg</prgn> still supports them).
3891 Whitespace may appear at any point in the version
3892 specification subject to the rules in <ref
3893 id="controlsyntax">, and must appear where it's necessary to
3894 disambiguate; it is not otherwise significant. For
3895 consistency and in case of future changes to
3896 <prgn>dpkg</prgn> it is recommended that a single space be
3897 used after a version relationship and before a version
3898 number; it is also conventional to put a single space after
3899 each comma, on either side of each vertical bar, and before
3900 each open parenthesis.
3904 For example, a list of dependencies might appear as:
3905 <example compact="compact">
3908 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
3913 All fields that specify build-time relationships
3914 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
3915 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>)
3916 may be restricted to a certain set of architectures. This
3917 is indicated in brackets after each individual package name and
3918 the optional version specification. The brackets enclose a
3919 list of Debian architecture names separated by whitespace.
3920 Exclamation marks may be prepended to each of the names.
3921 (It is not permitted for some names to be prepended with
3922 exclamation marks while others aren't.) If the current Debian
3923 host architecture is not in this list and there are no
3924 exclamation marks in the list, or it is in the list with a
3925 prepended exclamation mark, the package name and the
3926 associated version specification are ignored completely for
3927 the purposes of defining the relationships.
3932 <example compact="compact">
3934 Build-Depends-Indep: texinfo
3935 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
3936 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
3941 Note that the binary package relationship fields such as
3942 <tt>Depends</tt> appear in one of the binary package
3943 sections of the control file, whereas the build-time
3944 relationships such as <tt>Build-Depends</tt> appear in the
3945 source package section of the control file (which is the
3950 <sect id="binarydeps">
3951 <heading>Binary Dependencies - <tt>Depends</tt>,
3952 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
3953 <tt>Pre-Depends</tt>
3957 Packages can declare in their control file that they have
3958 certain relationships to other packages - for example, that
3959 they may not be installed at the same time as certain other
3960 packages, and/or that they depend on the presence of others.
3964 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
3965 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt> and
3966 <tt>Conflicts</tt> control file fields.
3970 These six fields are used to declare a dependency
3971 relationship by one package on another. Except for
3972 <tt>Enhances</tt>, they appear in the depending (binary)
3973 package's control file. (<tt>Enhances</tt> appears in the
3974 recommending package's control file.)
3978 A <tt>Depends</tt> field takes effect <em>only</em> when a
3979 package is to be configured. It does not prevent a package
3980 being on the system in an unconfigured state while its
3981 dependencies are unsatisfied, and it is possible to replace
3982 a package whose dependencies are satisfied and which is
3983 properly installed with a different version whose
3984 dependencies are not and cannot be satisfied; when this is
3985 done the depending package will be left unconfigured (since
3986 attempts to configure it will give errors) and will not
3987 function properly. If it is necessary, a
3988 <tt>Pre-Depends</tt> field can be used, which has a partial
3989 effect even when a package is being unpacked, as explained
3990 in detail below. (The other three dependency fields,
3991 <tt>Recommends</tt>, <tt>Suggests</tt> and
3992 <tt>Enhances</tt>, are only used by the various front-ends
3993 to <prgn>dpkg</prgn> such as <prgn>dselect</prgn>.)
3997 For this reason packages in an installation run are usually
3998 all unpacked first and all configured later; this gives
3999 later versions of packages with dependencies on later
4000 versions of other packages the opportunity to have their
4001 dependencies satisfied.
4005 In case of circular dependencies, since installation or
4006 removal order honoring the dependency order can't be
4007 established, dependency loops are broken at some point
4008 (based on rules below), and some packages may not be able to
4009 rely on their dependencies being present when being
4010 installed or removed, depending on which side of the break
4011 of the circular dependcy loop they happen to be on. If one
4012 of the packages in the loop has no postinst script, then the
4013 cycle will be broken at that package, so as to ensure that
4014 all postinst scripts run with the dependencies properly
4015 configured if this is possible. Otherwise the breaking point
4020 The <tt>Depends</tt> field thus allows package maintainers
4021 to impose an order in which packages should be configured.
4025 The meaning of the five dependency fields is as follows:
4027 <tag><tt>Depends</tt></tag>
4030 This declares an absolute dependency. A package will
4031 not be configured unless all of the packages listed in
4032 its <tt>Depends</tt> field have been correctly
4037 The <tt>Depends</tt> field should be used if the
4038 depended-on package is required for the depending
4039 package to provide a significant amount of
4044 The <tt>Depends</tt> field should also be used if the
4045 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4046 <prgn>postrm</prgn> scripts require the package to be
4047 present in order to run. Note, however, that the
4048 <prgn>postrm</prgn> cannot rely on any non-essential
4049 packages to be present during the <tt>purge</tt>
4053 <tag><tt>Recommends</tt></tag>
4056 This declares a strong, but not absolute, dependency.
4060 The <tt>Recommends</tt> field should list packages
4061 that would be found together with this one in all but
4062 unusual installations.
4066 <tag><tt>Suggests</tt></tag>
4068 This is used to declare that one package may be more
4069 useful with one or more others. Using this field
4070 tells the packaging system and the user that the
4071 listed packages are related to this one and can
4072 perhaps enhance its usefulness, but that installing
4073 this one without them is perfectly reasonable.
4076 <tag><tt>Enhances</tt></tag>
4078 This field is similar to Suggests but works in the
4079 opposite direction. It is used to declare that a
4080 package can enhance the functionality of another
4084 <tag><tt>Pre-Depends</tt></tag>
4087 This field is like <tt>Depends</tt>, except that it
4088 also forces <prgn>dpkg</prgn> to complete installation
4089 of the packages named before even starting the
4090 installation of the package which declares the
4091 pre-dependency, as follows:
4095 When a package declaring a pre-dependency is about to
4096 be <em>unpacked</em> the pre-dependency can be
4097 satisfied if the depended-on package is either fully
4098 configured, <em>or even if</em> the depended-on
4099 package(s) are only unpacked or half-configured,
4100 provided that they have been configured correctly at
4101 some point in the past (and not removed or partially
4102 removed since). In this case, both the
4103 previously-configured and currently unpacked or
4104 half-configured versions must satisfy any version
4105 clause in the <tt>Pre-Depends</tt> field.
4109 When the package declaring a pre-dependency is about
4110 to be <em>configured</em>, the pre-dependency will be
4111 treated as a normal <tt>Depends</tt>, that is, it will
4112 be considered satisfied only if the depended-on
4113 package has been correctly configured.
4117 <tt>Pre-Depends</tt> should be used sparingly,
4118 preferably only by packages whose premature upgrade or
4119 installation would hamper the ability of the system to
4120 continue with any upgrade that might be in progress.
4124 <tt>Pre-Depends</tt> are also required if the
4125 <prgn>preinst</prgn> script depends on the named
4126 package. It is best to avoid this situation if
4134 When selecting which level of dependency to use you should
4135 consider how important the depended-on package is to the
4136 functionality of the one declaring the dependency. Some
4137 packages are composed of components of varying degrees of
4138 importance. Such a package should list using
4139 <tt>Depends</tt> the package(s) which are required by the
4140 more important components. The other components'
4141 requirements may be mentioned as Suggestions or
4142 Recommendations, as appropriate to the components' relative
4147 <sect id="conflicts">
4148 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4151 When one binary package declares a conflict with another
4152 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4153 refuse to allow them to be installed on the system at the
4158 If one package is to be installed, the other must be removed
4159 first - if the package being installed is marked as
4160 replacing (see <ref id="replaces">) the one on the system,
4161 or the one on the system is marked as deselected, or both
4162 packages are marked <tt>Essential</tt>, then
4163 <prgn>dpkg</prgn> will automatically remove the package
4164 which is causing the conflict, otherwise it will halt the
4165 installation of the new package with an error. This
4166 mechanism is specifically designed to produce an error when
4167 the installed package is <tt>Essential</tt>, but the new
4172 A package will not cause a conflict merely because its
4173 configuration files are still installed; it must be at least
4178 A special exception is made for packages which declare a
4179 conflict with their own package name, or with a virtual
4180 package which they provide (see below): this does not
4181 prevent their installation, and allows a package to conflict
4182 with others providing a replacement for it. You use this
4183 feature when you want the package in question to be the only
4184 package providing some feature.
4188 A <tt>Conflicts</tt> entry should almost never have an
4189 "earlier than" version clause. This would prevent
4190 <prgn>dpkg</prgn> from upgrading or installing the package
4191 which declared such a conflict until the upgrade or removal
4192 of the conflicted-with package had been completed.
4196 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4200 As well as the names of actual ("concrete") packages, the
4201 package relationship fields <tt>Depends</tt>,
4202 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4203 <tt>Pre-Depends</tt>, <tt>Conflicts</tt>,
4204 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4205 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4206 may mention "virtual packages".
4210 A <em>virtual package</em> is one which appears in the
4211 <tt>Provides</tt> control file field of another package.
4212 The effect is as if the package(s) which provide a
4213 particular virtual package name had been listed by name
4214 everywhere the virtual package name appears. (See also <ref
4219 If there are both concrete and virtual packages of the same
4220 name, then the dependency may be satisfied (or the conflict
4221 caused) by either the concrete package with the name in
4222 question or any other concrete package which provides the
4223 virtual package with the name in question. This is so that,
4224 for example, supposing we have
4225 <example compact="compact">
4228 </example> and someone else releases an enhanced version of
4229 the <tt>bar</tt> package they can say:
4230 <example compact="compact">
4234 and the <tt>bar-plus</tt> package will now also satisfy the
4235 dependency for the <tt>foo</tt> package.
4239 If a dependency or a conflict has a version number attached
4240 then only real packages will be considered to see whether
4241 the relationship is satisfied (or the prohibition violated,
4242 for a conflict) - it is assumed that a real package which
4243 provides the virtual package is not of the "right" version.
4244 So, a <tt>Provides</tt> field may not contain version
4245 numbers, and the version number of the concrete package
4246 which provides a particular virtual package will not be
4247 looked at when considering a dependency on or conflict with
4248 the virtual package name.
4252 It is likely that the ability will be added in a future
4253 release of <prgn>dpkg</prgn> to specify a version number for
4254 each virtual package it provides. This feature is not yet
4255 present, however, and is expected to be used only
4260 If you want to specify which of a set of real packages
4261 should be the default to satisfy a particular dependency on
4262 a virtual package, you should list the real package as an
4263 alternative before the virtual one.
4268 <sect id="replaces"><heading>Overwriting files and replacing
4269 packages - <tt>Replaces</tt></heading>
4272 Packages can declare in their control file that they should
4273 overwrite files in certain other packages, or completely
4274 replace other packages. The <tt>Replaces</tt> control file
4275 field has these two distinct purposes.
4278 <sect1><heading>Overwriting files in other packages</heading>
4281 Firstly, as mentioned before, it is usually an error for a
4282 package to contain files which are on the system in
4287 However, if the overwriting package declares that it
4288 <tt>Replaces</tt> the one containing the file being
4289 overwritten, then <prgn>dpkg</prgn> will replace the file
4290 from the old package with that from the new. The file
4291 will no longer be listed as "owned" by the old package.
4295 If a package is completely replaced in this way, so that
4296 <prgn>dpkg</prgn> does not know of any files it still
4297 contains, it is considered to have "disappeared". It will
4298 be marked as not wanted on the system (selected for
4299 removal) and not installed. Any <tt>conffile</tt>s
4300 details noted for the package will be ignored, as they
4301 will have been taken over by the overwriting package. The
4302 package's <prgn>postrm</prgn> script will be run with a
4303 special argument to allow the package to do any final
4304 cleanup required. See <ref id="mscriptsinstact">.
4307 Replaces is a one way relationship -- you have to
4308 install the replacing package after the replaced
4315 For this usage of <tt>Replaces</tt>, virtual packages (see
4316 <ref id="virtual">) are not considered when looking at a
4317 <tt>Replaces</tt> field - the packages declared as being
4318 replaced must be mentioned by their real names.
4322 Furthermore, this usage of <tt>Replaces</tt> only takes
4323 effect when both packages are at least partially on the
4324 system at once, so that it can only happen if they do not
4325 conflict or if the conflict has been overridden.
4330 <sect1><heading>Replacing whole packages, forcing their
4334 Secondly, <tt>Replaces</tt> allows the packaging system to
4335 resolve which package should be removed when there is a
4336 conflict - see <ref id="conflicts">. This usage only
4337 takes effect when the two packages <em>do</em> conflict,
4338 so that the two usages of this field do not interfere with
4343 In this situation, the package declared as being replaced
4344 can be a virtual package, so for example, all mail
4345 transport agents (MTAs) would have the following fields in
4346 their control files:
4347 <example compact="compact">
4348 Provides: mail-transport-agent
4349 Conflicts: mail-transport-agent
4350 Replaces: mail-transport-agent
4352 ensuring that only one MTA can be installed at any one
4357 <sect id="sourcebinarydeps">
4358 <heading>Relationships between source and binary packages -
4359 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4360 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
4364 Source packages that require certain binary packages to be
4365 installed or absent at the time of building the package
4366 can declare relationships to those binary packages.
4370 This is done using the <tt>Build-Depends</tt>,
4371 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
4372 <tt>Build-Conflicts-Indep</tt> control file fields.
4376 Build-dependencies on "build-essential" binary packages can be
4377 omitted. Please see <ref id="pkg-relations"> for more information.
4381 The dependencies and conflicts they define must be satisfied
4382 (as defined earlier for binary packages) in order to invoke
4383 the targets in <tt>debian/rules</tt>, as follows:<footnote>
4385 If you make "build-arch" or "binary-arch", you need
4386 Build-Depends. If you make "build-indep" or
4387 "binary-indep", you need Build-Depends and
4388 Build-Depends-Indep. If you make "build" or "binary",
4392 There is no Build-Depends-Arch; this role is essentially
4393 met with Build-Depends. Anyone building the
4394 <tt>build-indep</tt> and binary-indep<tt></tt> targets
4395 is basically assumed to be building the whole package
4396 anyway and so installs all build dependencies. The
4397 autobuilders use <tt>dpkg-buildpackage -B</tt>, which
4398 calls <tt>build</tt> (not <tt>build-arch</tt>, since it
4399 does not yet know how to check for its existence) and
4400 <tt>binary-arch</tt>.
4403 The purpose of the original split, I recall, was so that
4404 the autobuilders wouldn't need to install extra packages
4405 needed only for the binary-indep targets. But without a
4406 build-arch/build-indep split, this didn't work, since
4407 most of the work is done in the build target, not in the
4413 <tag><tt>Build-Depends</tt>, <tt>Build-Conflicts</tt></tag>
4415 The <tt>Build-Depends</tt> and
4416 <tt>Build-Conflicts</tt> fields must be satisfied when
4417 any of the following targets is invoked:
4418 <tt>build</tt>, <tt>clean</tt>, <tt>binary</tt>,
4419 <tt>binary-arch</tt>, <tt>build-arch</tt>,
4420 <tt>build-indep</tt> and <tt>binary-indep</tt>.
4422 <tag><tt>Build-Depends-Indep</tt>,
4423 <tt>Build-Conflicts-Indep</tt></tag>
4425 The <tt>Build-Depends-Indep</tt> and
4426 <tt>Build-Conflicts-Indep</tt> fields must be
4427 satisfied when any of the following targets is
4428 invoked: <tt>build</tt>, <tt>build-indep</tt>,
4429 <tt>binary</tt> and <tt>binary-indep</tt>.
4439 <chapt id="sharedlibs"><heading>Shared libraries</heading>
4442 Packages containing shared libraries must be constructed with
4443 a little care to make sure that the shared library is always
4444 available. This is especially important for packages whose
4445 shared libraries are vitally important, such as the C library
4446 (currently <tt>libc6</tt>).
4450 Packages involving shared libraries should be split up into
4451 several binary packages. This section mostly deals with how
4452 this separation is to be accomplished; rules for files within
4453 the shared library packages are in <ref id="libraries"> instead.
4456 <sect id="sharedlibs-runtime">
4457 <heading>Run-time shared libraries</heading>
4460 The run-time shared library needs to be placed in a package
4461 whose name changes whenever the shared object version
4464 Since it is common place to install several versions of a
4465 package that just provides shared libraries, it is a
4466 good idea that the library package should not
4467 contain any extraneous non-versioned files, unless they
4468 happen to be in versioned directories.</p>
4470 The most common mechanism is to place it in a package
4472 <package><var>libraryname</var><var>soversion</var></package>,
4473 where <file><var>soversion</var></file> is the version number
4474 in the soname of the shared library<footnote>
4475 The soname is the shared object name: it's the thing
4476 that has to match exactly between building an executable
4477 and running it for the dynamic linker to be able run the
4478 program. For example, if the soname of the library is
4479 <file>libfoo.so.6</file>, the library package would be
4480 called <file>libfoo6</file>.
4482 Alternatively, if it would be confusing to directly append
4483 <var>soversion</var> to <var>libraryname</var> (e.g. because
4484 <var>libraryname</var> itself ends in a number), you may use
4485 <package><var>libraryname</var>-<var>soversion</var></package> and
4486 <package><var>libraryname</var>-<var>soversion</var>-dev</package>
4491 If your package includes run-time support programs that
4492 do not need to be invoked manually by users, but are
4493 nevertheless required for the package to function, then it
4494 is recommended that these programs are placed
4495 (if they are binary) in a subdirectory of
4496 <file>/usr/lib</file>, preferably under
4497 <file>/usr/lib/</file><var>package-name</var>.
4498 If the program is architecture independent, the
4499 recommendation is for it to be placed in a subdirectory of
4500 <file>/usr/share</file> instead, preferably under
4501 <file>/usr/share/</file><var>package-name</var>.
4506 If you have several shared libraries built from the same
4507 source tree you may lump them all together into a single
4508 shared library package, provided that you change all of
4509 their sonames at once (so that you don't get filename
4510 clashes if you try to install different versions of the
4511 combined shared libraries package).
4515 The package should install the shared libraries under
4516 their normal names. For example, the <package>libgdbm3</package>
4517 package should install <file>libgdbm.so.3.0.0</file> as
4518 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
4519 renamed or re-linked by any <prgn>prerm</prgn> or
4520 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
4521 of renaming things safely without affecting running programs,
4522 and attempts to interfere with this are likely to lead to
4527 Shared libraries should not be installed executable, since
4528 the dynamic linker does not require this and trying to
4529 execute a shared library usually results in a core dump.
4533 The run-time library package should include the symbolic link that
4534 <prgn>ldconfig</prgn> would create for the shared libraries.
4535 For example, the <package>libgdbm3</package> package should include
4536 a symbolic link from <file>/usr/lib/libgdbm.so.3</file> to
4537 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
4538 linker (for example <prgn>ld.so</prgn> or
4539 <prgn>ld-linux.so.*</prgn>) can find the library between the
4540 time that <prgn>dpkg</prgn> installs it and the time that
4541 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
4543 The package management system requires the library to be
4544 placed before the symbolic link pointing to it in the
4545 <file>.deb</file> file. This is so that when
4546 <prgn>dpkg</prgn> comes to install the symlink
4547 (overwriting the previous symlink pointing at an older
4548 version of the library), the new shared library is already
4549 in place. In the past, this was achieved by creating the
4550 library in the temporary packaging directory before
4551 creating the symlink. Unfortunately, this was not always
4552 effective, since the building of the tar file in the
4553 <file>.deb</file> depended on the behavior of the underlying
4554 file system. Some file systems (such as reiserfs) reorder
4555 the files so that the order of creation is forgotten.
4556 Since version 1.7.0, <prgn>dpkg</prgn>
4557 reorders the files itself as necessary when building a
4558 package. Thus it is no longer important to concern
4559 oneself with the order of file creation.
4563 <sect1 id="ldconfig">
4564 <heading><tt>ldconfig</tt></heading>
4567 Any package installing shared libraries in one of the default
4568 library directories of the dynamic linker (which are currently
4569 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
4570 listed in <file>/etc/ld.so.conf</file><footnote>
4572 <list compact="compact">
4573 <item>/usr/local/lib</item>
4574 <item>/usr/lib/libc5-compat</item>
4575 <item>/lib/libc5-compat</item>
4578 must use <prgn>ldconfig</prgn> to update the shared library
4583 The package maintainer scripts must only call
4584 <prgn>ldconfig</prgn> under these circumstances:
4585 <list compact="compact">
4586 <item>When the <prgn>postinst</prgn> script is run with a
4587 first argument of <tt>configure</tt>, the script must call
4588 <prgn>ldconfig</prgn>, and may optionally invoke
4589 <prgn>ldconfig</prgn> at other times.
4591 <item>When the <prgn>postrm</prgn> script is run with a
4592 first argument of <tt>remove</tt>, the script should call
4593 <prgn>ldconfig</prgn>.
4598 During install or upgrade, the preinst is called before
4599 the new files are installed, so calling "ldconfig" is
4600 pointless. The preinst of an existing package can also be
4601 called if an upgrade fails. However, this happens during
4602 the critical time when a shared libs may exist on-disk
4603 under a temporary name. Thus, it is dangerous and
4604 forbidden by current policy to call "ldconfig" at this
4609 When a package is installed or upgraded, "postinst
4610 configure" runs after the new files are safely on-disk.
4611 Since it is perfectly safe to invoke ldconfig
4612 unconditionally in a postinst, it is OK for a package to
4613 simply put ldconfig in its postinst without checking the
4614 argument. The postinst can also be called to recover from
4615 a failed upgrade. This happens before any new files are
4616 unpacked, so there is no reason to call "ldconfig" at this
4621 For a package that is being removed, prerm is
4622 called with all the files intact, so calling ldconfig is
4623 useless. The other calls to "prerm" happen in the case of
4624 upgrade at a time when all the files of the old package
4625 are on-disk, so again calling "ldconfig" is pointless.
4629 postrm, on the other hand, is called with the "remove"
4630 argument just after the files are removed, so this is
4631 the proper time to call "ldconfig" to notify the system
4632 of the fact that the shared libraries from the package
4633 are removed. The postrm can be called at several other
4634 times. At the time of "postrm purge", "postrm
4635 abort-install", or "postrm abort-upgrade", calling
4636 "ldconfig" is useless because the shared lib files are
4637 not on-disk. However, when "postrm" is invoked with
4638 arguments "upgrade", "failed-upgrade", or "disappear", a
4639 shared lib may exist on-disk under a temporary filename.
4647 <sect id="sharedlibs-runtime-progs">
4648 <heading>Run-time support programs</heading>
4651 If your package has some run-time support programs which use
4652 the shared library you must not put them in the shared
4653 library package. If you do that then you won't be able to
4654 install several versions of the shared library without
4655 getting filename clashes.
4659 Instead, either create another package for the runtime binaries
4660 (this package might typically be named
4661 <package><var>libraryname</var>-runtime</package>; note the absence
4662 of the <var>soversion</var> in the package name), or if the
4663 development package is small, include them in there.
4667 <sect id="sharedlibs-static">
4668 <heading>Static libraries</heading>
4671 The static library (<file><var>libraryname.a</var></file>)
4672 is usually provided in addition to the shared version.
4673 It is placed into the development package (see below).
4677 In some cases, it is acceptable for a library to be
4678 available in static form only; these cases include:
4680 <item>libraries for languages whose shared library support
4681 is immature or unstable</item>
4682 <item>libraries whose interfaces are in flux or under
4683 development (commonly the case when the library's
4684 major version number is zero, or where the ABI breaks
4685 across patchlevels)</item>
4686 <item>libraries which are explicitly intended to be
4687 available only in static form by their upstream
4692 <sect id="sharedlibs-dev">
4693 <heading>Development files</heading>
4696 The development files associated to a shared library need to be
4697 placed in a package called
4698 <package><var>libraryname</var><var>soversion</var>-dev</package>,
4699 or if you prefer only to support one development version at a
4700 time, <package><var>libraryname</var>-dev</package>.
4704 In case several development versions of a library exist, you may
4705 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
4706 <ref id="conflicts">) to ensure that the user only installs one
4707 development version at a time (as different development versions are
4708 likely to have the same header files in them, which would cause a
4709 filename clash if both were installed).
4713 The development package should contain a symlink for the associated
4714 shared library without a version number. For example, the
4715 <package>libgdbm-dev</package> package should include a symlink
4716 from <file>/usr/lib/libgdbm.so</file> to
4717 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
4718 (<prgn>ld</prgn>) when compiling packages, as it will only look for
4719 <file>libgdbm.so</file> when compiling dynamically.
4723 <sect id="sharedlibs-intradeps">
4724 <heading>Dependencies between the packages of the same library</heading>
4727 Typically the development version should have an exact
4728 version dependency on the runtime library, to make sure that
4729 compilation and linking happens correctly. The
4730 <tt>${binary:Version}</tt> substitution variable can be
4731 useful for this purpose.
4733 Previously, <tt>${Source-Version}</tt> was used, but its name
4734 was confusing and it has been deprecated since dpkg 1.13.19.
4739 <sect id="sharedlibs-shlibdeps">
4740 <heading>Dependencies between the library and other packages -
4741 the <tt>shlibs</tt> system</heading>
4744 If a package contains a binary or library which links to a
4745 shared library, we must ensure that when the package is
4746 installed on the system, all of the libraries needed are
4747 also installed. This requirement led to the creation of the
4748 <tt>shlibs</tt> system, which is very simple in its design:
4749 any package which <em>provides</em> a shared library also
4750 provides information on the package dependencies required to
4751 ensure the presence of this library, and any package which
4752 <em>uses</em> a shared library uses this information to
4753 determine the dependencies it requires. The files which
4754 contain the mapping from shared libraries to the necessary
4755 dependency information are called <file>shlibs</file> files.
4759 Thus, when a package is built which contains any shared
4760 libraries, it must provide a <file>shlibs</file> file for other
4761 packages to use, and when a package is built which contains
4762 any shared libraries or compiled binaries, it must run
4763 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
4764 on these to determine the libraries used and hence the
4765 dependencies needed by this package.<footnote>
4767 In the past, the shared libraries linked to were
4768 determined by calling <prgn>ldd</prgn>, but now
4769 <prgn>objdump</prgn> is used to do this. The only
4770 change this makes to package building is that
4771 <prgn>dpkg-shlibdeps</prgn> must also be run on shared
4772 libraries, whereas in the past this was unnecessary.
4773 The rest of this footnote explains the advantage that
4778 We say that a binary <tt>foo</tt> <em>directly</em> uses
4779 a library <tt>libbar</tt> if it is explicitly linked
4780 with that library (that is, it uses the flag
4781 <tt>-lbar</tt> during the linking stage). Other
4782 libraries that are needed by <tt>libbar</tt> are linked
4783 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
4784 linker will load them automatically when it loads
4785 <tt>libbar</tt>. A package should depend on
4786 the libraries it directly uses, and the dependencies for
4787 those libraries should automatically pull in the other
4792 Unfortunately, the <prgn>ldd</prgn> program shows both
4793 the directly and indirectly used libraries, meaning that
4794 the dependencies determined included both direct and
4795 indirect dependencies. The use of <prgn>objdump</prgn>
4796 avoids this problem by determining only the directly
4801 A good example of where this helps is the following. We
4802 could update <tt>libimlib</tt> with a new version that
4803 supports a new graphics format called dgf (but retaining
4804 the same major version number). If we used the old
4805 <prgn>ldd</prgn> method, every package that uses
4806 <tt>libimlib</tt> would need to be recompiled so it
4807 would also depend on <tt>libdgf</tt> or it wouldn't run
4808 due to missing symbols. However with the new system,
4809 packages using <tt>libimlib</tt> can rely on
4810 <tt>libimlib</tt> itself having the dependency on
4811 <tt>libdgf</tt> and so they would not need rebuilding.
4817 In the following sections, we will first describe where the
4818 various <tt>shlibs</tt> files are to be found, then how to
4819 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
4820 file format and how to create them if your package contains a
4825 <heading>The <tt>shlibs</tt> files present on the system</heading>
4828 There are several places where <tt>shlibs</tt> files are
4829 found. The following list gives them in the order in which
4831 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
4832 (The first one which gives the required information is used.)
4838 <p><file>debian/shlibs.local</file></p>
4841 This lists overrides for this package. Its use is
4842 described below (see <ref id="shlibslocal">).
4847 <p><file>/etc/dpkg/shlibs.override</file></p>
4850 This lists global overrides. This list is normally
4851 empty. It is maintained by the local system
4857 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
4860 When packages are being built, any
4861 <file>debian/shlibs</file> files are copied into the
4862 control file area of the temporary build directory and
4863 given the name <file>shlibs</file>. These files give
4864 details of any shared libraries included in the
4866 An example may help here. Let us say that the
4867 source package <tt>foo</tt> generates two binary
4868 packages, <tt>libfoo2</tt> and
4869 <tt>foo-runtime</tt>. When building the binary
4870 packages, the two packages are created in the
4871 directories <file>debian/libfoo2</file> and
4872 <file>debian/foo-runtime</file> respectively.
4873 (<file>debian/tmp</file> could be used instead of one
4874 of these.) Since <tt>libfoo2</tt> provides the
4875 <tt>libfoo</tt> shared library, it will require a
4876 <tt>shlibs</tt> file, which will be installed in
4877 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually
4879 <file>/var/lib/dpkg/info/libfoo2.shlibs</file>. Then
4880 when <prgn>dpkg-shlibdeps</prgn> is run on the
4882 <file>debian/foo-runtime/usr/bin/foo-prog</file>, it
4884 <file>debian/libfoo2/DEBIAN/shlibs</file> file to
4885 determine whether <tt>foo-prog</tt>'s library
4886 dependencies are satisfied by any of the libraries
4887 provided by <tt>libfoo2</tt>. For this reason,
4888 <prgn>dpkg-shlibdeps</prgn> must only be run once
4889 all of the individual binary packages'
4890 <tt>shlibs</tt> files have been installed into the
4897 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
4900 These are the <file>shlibs</file> files corresponding to
4901 all of the packages installed on the system, and are
4902 maintained by the relevant package maintainers.
4907 <p><file>/etc/dpkg/shlibs.default</file></p>
4910 This file lists any shared libraries whose packages
4911 have failed to provide correct <file>shlibs</file> files.
4912 It was used when the <file>shlibs</file> setup was first
4913 introduced, but it is now normally empty. It is
4914 maintained by the <tt>dpkg</tt> maintainer.
4922 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
4923 <file>shlibs</file> files</heading>
4927 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
4928 into your <file>debian/rules</file> file. If your package
4929 contains only compiled binaries and libraries (but no scripts),
4930 you can use a command such as:
4931 <example compact="compact">
4932 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
4933 debian/tmp/usr/lib/*
4935 Otherwise, you will need to explicitly list the compiled
4936 binaries and libraries.<footnote>
4937 If you are using <tt>debhelper</tt>, the
4938 <prgn>dh_shlibdeps</prgn> program will do this work for
4939 you. It will also correctly handle multi-binary
4945 This command puts the dependency information into the
4946 <file>debian/substvars</file> file, which is then used by
4947 <prgn>dpkg-gencontrol</prgn>. You will need to place a
4948 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
4949 field in the control file for this to work.
4953 If <prgn>dpkg-shlibdeps</prgn> doesn't complain, you're
4954 done. If it does complain you might need to create your own
4955 <file>debian/shlibs.local</file> file, as explained below (see
4956 <ref id="shlibslocal">).
4960 If you have multiple binary packages, you will need to call
4961 <prgn>dpkg-shlibdeps</prgn> on each one which contains
4962 compiled libraries or binaries. In such a case, you will
4963 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
4964 utilities to specify a different <file>substvars</file> file.
4968 If you are creating a udeb for use in the Debian Installer, you
4969 will need to specify that <prgn>dpkg-shlibdeps</prgn> should use
4970 the dependency line of type <tt>udeb</tt> by adding
4971 <tt>-tudeb</tt> as option<footnote>
4972 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
4973 will automatically add this option if it knows it is
4975 </footnote>. If there is no dependency line of type <tt>udeb</tt>
4976 in the <file>shlibs</file> file, <prgn>dpkg-shlibdeps</prgn> will
4977 fall back to the regular dependency line.
4981 For more details on dpkg-shlibdeps, please see
4982 <ref id="pkg-dpkg-shlibdeps"> and
4983 <manref name="dpkg-shlibdeps" section="1">.
4988 <heading>The <file>shlibs</file> File Format</heading>
4991 Each <file>shlibs</file> file has the same format. Lines
4992 beginning with <tt>#</tt> are considered to be comments and
4993 are ignored. Each line is of the form:
4994 <example compact="compact">
4995 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5000 We will explain this by reference to the example of the
5001 <tt>zlib1g</tt> package, which (at the time of writing)
5002 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5006 <var>type</var> is an optional element that indicates the type
5007 of package for which the line is valid. The only type currently
5008 in use is <tt>udeb</tt>. The colon and space after the type are
5013 <var>library-name</var> is the name of the shared library,
5014 in this case <tt>libz</tt>. (This must match the name part
5015 of the soname, see below.)
5019 <var>soname-version</var> is the version part of the soname of
5020 the library. The soname is the thing that must exactly match
5021 for the library to be recognized by the dynamic linker, and is
5023 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5024 example, <tt>libz.so.1</tt>.<footnote>
5025 This can be determined using the command
5026 <example compact="compact">
5027 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5030 The version part is the part which comes after
5031 <tt>.so.</tt>, so in our case, it is <tt>1</tt>.
5035 <var>dependencies</var> has the same syntax as a dependency
5036 field in a binary package control file. It should give
5037 details of which packages are required to satisfy a binary
5038 built against the version of the library contained in the
5039 package. See <ref id="depsyntax"> for details.
5043 In our example, if the first version of the <tt>zlib1g</tt>
5044 package which contained a minor number of at least
5045 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5046 <tt>shlibs</tt> entry for this library could say:
5047 <example compact="compact">
5048 libz 1 zlib1g (>= 1:1.1.3)
5050 The version-specific dependency is to avoid warnings from
5051 the dynamic linker about using older shared libraries with
5056 As zlib1g also provides a udeb containing the shared library,
5057 there would also be a second line:
5058 <example compact="compact">
5059 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5065 <heading>Providing a <file>shlibs</file> file</heading>
5068 If your package provides a shared library, you need to create
5069 a <file>shlibs</file> file following the format described above.
5070 It is usual to call this file <file>debian/shlibs</file> (but if
5071 you have multiple binary packages, you might want to call it
5072 <file>debian/shlibs.<var>package</var></file> instead). Then
5073 let <file>debian/rules</file> install it in the control area:
5074 <example compact="compact">
5075 install -m644 debian/shlibs debian/tmp/DEBIAN
5077 or, in the case of a multi-binary package:
5078 <example compact="compact">
5079 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5081 An alternative way of doing this is to create the
5082 <file>shlibs</file> file in the control area directly from
5083 <file>debian/rules</file> without using a <file>debian/shlibs</file>
5084 file at all,<footnote>
5085 This is what <prgn>dh_makeshlibs</prgn> in the
5086 <tt>debhelper</tt> suite does. If your package also has a udeb
5087 that provides a shared library, <prgn>dh_makeshlibs</prgn> can
5088 automatically generate the <tt>udeb:</tt> lines if you specify
5089 the name of the udeb with the <tt>--add-udeb</tt> option.
5091 since the <file>debian/shlibs</file> file itself is ignored by
5092 <prgn>dpkg-shlibdeps</prgn>.
5096 As <prgn>dpkg-shlibdeps</prgn> reads the
5097 <file>DEBIAN/shlibs</file> files in all of the binary packages
5098 being built from this source package, all of the
5099 <file>DEBIAN/shlibs</file> files should be installed before
5100 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5105 <sect1 id="shlibslocal">
5106 <heading>Writing the <file>debian/shlibs.local</file> file</heading>
5109 This file is intended only as a <em>temporary</em> fix if
5110 your binaries or libraries depend on a library whose package
5111 does not yet provide a correct <file>shlibs</file> file.
5115 We will assume that you are trying to package a binary
5116 <tt>foo</tt>. When you try running
5117 <prgn>dpkg-shlibdeps</prgn> you get the following error
5118 message (<tt>-O</tt> displays the dependency information on
5119 <tt>stdout</tt> instead of writing it to
5120 <tt>debian/substvars</tt>, and the lines have been wrapped
5121 for ease of reading):
5122 <example compact="compact">
5123 $ dpkg-shlibdeps -O debian/tmp/usr/bin/foo
5124 dpkg-shlibdeps: warning: unable to find dependency
5125 information for shared library libbar (soname 1,
5126 path /usr/lib/libbar.so.1, dependency field Depends)
5127 shlibs:Depends=libc6 (>= 2.2.2-2)
5129 You can then run <prgn>ldd</prgn> on the binary to find the
5130 full location of the library concerned:
5131 <example compact="compact">
5133 libbar.so.1 => /usr/lib/libbar.so.1 (0x4001e000)
5134 libc.so.6 => /lib/libc.so.6 (0x40032000)
5135 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
5137 So the <prgn>foo</prgn> binary depends on the
5138 <prgn>libbar</prgn> shared library, but no package seems to
5139 provide a <file>*.shlibs</file> file handling
5140 <file>libbar.so.1</file> in <file>/var/lib/dpkg/info/</file>. Let's
5141 determine the package responsible:
5142 <example compact="compact">
5143 $ dpkg -S /usr/lib/libbar.so.1
5144 bar1: /usr/lib/libbar.so.1
5145 $ dpkg -s bar1 | grep Version
5148 This tells us that the <tt>bar1</tt> package, version 1.0-1,
5149 is the one we are using. Now we can file a bug against the
5150 <tt>bar1</tt> package and create our own
5151 <file>debian/shlibs.local</file> to locally fix the problem.
5152 Including the following line into your
5153 <file>debian/shlibs.local</file> file:
5154 <example compact="compact">
5155 libbar 1 bar1 (>= 1.0-1)
5157 should allow the package build to work.
5161 As soon as the maintainer of <tt>bar1</tt> provides a
5162 correct <file>shlibs</file> file, you should remove this line
5163 from your <file>debian/shlibs.local</file> file. (You should
5164 probably also then have a versioned <tt>Build-Depends</tt>
5165 on <tt>bar1</tt> to help ensure that others do not have the
5166 same problem building your package.)
5175 <chapt id="opersys"><heading>The Operating System</heading>
5178 <heading>File system hierarchy</heading>
5182 <heading>File system Structure</heading>
5185 The location of all installed files and directories must
5186 comply with the File system Hierarchy Standard (FHS),
5187 version 2.3, with the exceptions noted below, and except
5188 where doing so would violate other terms of Debian
5189 Policy. The following exceptions to the FHS apply:
5194 Legacy XFree86 servers are permitted to retain the
5195 configuration file location
5196 <file>/etc/X11/XF86Config-4</file>.
5201 The optional rules related to user specific
5202 configuration files for applications are stored in
5203 the user's home directory are relaxed. It is
5204 recommended that such files start with the
5205 '<tt>.</tt>' character (a "dot file"), and if an
5206 application needs to create more than one dot file
5207 then the preferred placement is in a subdirectory
5208 with a name starting with a '.' character, (a "dot
5209 directory"). In this case it is recommended the
5210 configuration files not start with the '.'
5216 The requirement for amd64 to use <file>/lib64</file>
5217 for 64 bit binaries is removed.
5222 The requirement that
5223 <file>/usr/local/share/man</file> be "synonymous"
5224 with <file>/usr/local/man</file> is relaxed to a
5229 The requirement that windowmanagers with a single
5230 configuration file call it <file>system.*wmrc</file>
5231 is removed, as is the restriction that the window
5232 manager subdirectory be named identically to the
5233 window manager name itself.
5238 The requirement that boot manager configuration
5239 files live in <file>/etc</file>, or at least are
5240 symlinked there, is relaxed to a recommendation.
5247 The version of this document referred here can be
5248 found in the <tt>debian-policy</tt> package or on <url
5249 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5250 name="FHS (Debian copy)"> alongside this manual (or, if
5251 you have the <package>debian-policy</package> installed,
5253 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5254 (local copy)">). The
5255 latest version, which may be a more recent version, may
5257 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5258 Specific questions about following the standard may be
5259 asked on the <tt>debian-devel</tt> mailing list, or
5260 referred to the FHS mailing list (see the
5261 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
5267 <heading>Site-specific programs</heading>
5270 As mandated by the FHS, packages must not place any
5271 files in <file>/usr/local</file>, either by putting them in
5272 the file system archive to be unpacked by <prgn>dpkg</prgn>
5273 or by manipulating them in their maintainer scripts.
5277 However, the package may create empty directories below
5278 <file>/usr/local</file> so that the system administrator knows
5279 where to place site-specific files. These are not
5280 directories <em>in</em> <file>/usr/local</file>, but are
5281 children of directories in <file>/usr/local</file>. These
5282 directories (<file>/usr/local/*/dir/</file>)
5283 should be removed on package removal if they are
5288 Note, that this applies only to directories <em>below</em>
5289 <file>/usr/local</file>, not <em>in</em> <file>/usr/local</file>.
5290 Packages must not create sub-directories in the directory
5291 <file>/usr/local</file> itself, except those listed in FHS,
5292 section 4.5. However, you may create directories below
5293 them as you wish. You must not remove any of the
5294 directories listed in 4.5, even if you created them.
5298 Since <file>/usr/local</file> can be mounted read-only from a
5299 remote server, these directories must be created and
5300 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
5301 maintainer scripts and not be included in the
5302 <file>.deb</file> archive. These scripts must not fail if
5303 either of these operations fail.
5307 For example, the <tt>emacsen-common</tt> package could
5308 contain something like
5309 <example compact="compact">
5310 if [ ! -e /usr/local/share/emacs ]
5312 if mkdir /usr/local/share/emacs 2>/dev/null
5314 chown root:staff /usr/local/share/emacs
5315 chmod 2775 /usr/local/share/emacs
5319 in its <prgn>postinst</prgn> script, and
5320 <example compact="compact">
5321 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
5322 rmdir /usr/local/share/emacs 2>/dev/null || true
5324 in the <prgn>prerm</prgn> script. (Note that this form is
5325 used to ensure that if the script is interrupted, the
5326 directory <file>/usr/local/share/emacs</file> will still be
5331 If you do create a directory in <file>/usr/local</file> for
5332 local additions to a package, you should ensure that
5333 settings in <file>/usr/local</file> take precedence over the
5334 equivalents in <file>/usr</file>.
5338 However, because <file>/usr/local</file> and its contents are
5339 for exclusive use of the local administrator, a package
5340 must not rely on the presence or absence of files or
5341 directories in <file>/usr/local</file> for normal operation.
5345 The <file>/usr/local</file> directory itself and all the
5346 subdirectories created by the package should (by default) have
5347 permissions 2775 (group-writable and set-group-id) and be
5348 owned by <tt>root.staff</tt>.
5353 <heading>The system-wide mail directory</heading>
5355 The system-wide mail directory is <file>/var/mail</file>. This
5356 directory is part of the base system and should not owned
5357 by any particular mail agents. The use of the old
5358 location <file>/var/spool/mail</file> is deprecated, even
5359 though the spool may still be physically located there.
5360 To maintain partial upgrade compatibility for systems
5361 which have <file>/var/spool/mail</file> as their physical mail
5362 spool, packages using <file>/var/mail</file> must depend on
5363 either <package>libc6</package> (>= 2.1.3-13), or on
5364 <package>base-files</package> (>= 2.2.0), or on later
5365 versions of either one of these packages.
5371 <heading>Users and groups</heading>
5374 <heading>Introduction</heading>
5376 The Debian system can be configured to use either plain or
5381 Some user ids (UIDs) and group ids (GIDs) are reserved
5382 globally for use by certain packages. Because some
5383 packages need to include files which are owned by these
5384 users or groups, or need the ids compiled into binaries,
5385 these ids must be used on any Debian system only for the
5386 purpose for which they are allocated. This is a serious
5387 restriction, and we should avoid getting in the way of
5388 local administration policies. In particular, many sites
5389 allocate users and/or local system groups starting at 100.
5393 Apart from this we should have dynamically allocated ids,
5394 which should by default be arranged in some sensible
5395 order, but the behavior should be configurable.
5399 Packages other than <tt>base-passwd</tt> must not modify
5400 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
5401 <file>/etc/group</file> or <file>/etc/gshadow</file>.
5406 <heading>UID and GID classes</heading>
5408 The UID and GID numbers are divided into classes as
5414 Globally allocated by the Debian project, the same
5415 on every Debian system. These ids will appear in
5416 the <file>passwd</file> and <file>group</file> files of all
5417 Debian systems, new ids in this range being added
5418 automatically as the <tt>base-passwd</tt> package is
5423 Packages which need a single statically allocated
5424 uid or gid should use one of these; their
5425 maintainers should ask the <tt>base-passwd</tt>
5433 Dynamically allocated system users and groups.
5434 Packages which need a user or group, but can have
5435 this user or group allocated dynamically and
5436 differently on each system, should use <tt>adduser
5437 --system</tt> to create the group and/or user.
5438 <prgn>adduser</prgn> will check for the existence of
5439 the user or group, and if necessary choose an unused
5440 id based on the ranges specified in
5441 <file>adduser.conf</file>.
5445 <tag>1000-29999:</tag>
5448 Dynamically allocated user accounts. By default
5449 <prgn>adduser</prgn> will choose UIDs and GIDs for
5450 user accounts in this range, though
5451 <file>adduser.conf</file> may be used to modify this
5456 <tag>30000-59999:</tag>
5461 <tag>60000-64999:</tag>
5464 Globally allocated by the Debian project, but only
5465 created on demand. The ids are allocated centrally
5466 and statically, but the actual accounts are only
5467 created on users' systems on demand.
5471 These ids are for packages which are obscure or
5472 which require many statically-allocated ids. These
5473 packages should check for and create the accounts in
5474 <file>/etc/passwd</file> or <file>/etc/group</file> (using
5475 <prgn>adduser</prgn> if it has this facility) if
5476 necessary. Packages which are likely to require
5477 further allocations should have a "hole" left after
5478 them in the allocation, to give them room to
5483 <tag>65000-65533:</tag>
5491 User <tt>nobody</tt>. The corresponding gid refers
5492 to the group <tt>nogroup</tt>.
5499 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
5500 not</em> be used, because it is the error return
5509 <sect id="sysvinit">
5510 <heading>System run levels and <file>init.d</file> scripts</heading>
5512 <sect1 id="/etc/init.d">
5513 <heading>Introduction</heading>
5516 The <file>/etc/init.d</file> directory contains the scripts
5517 executed by <prgn>init</prgn> at boot time and when the
5518 init state (or "runlevel") is changed (see <manref
5519 name="init" section="8">).
5523 There are at least two different, yet functionally
5524 equivalent, ways of handling these scripts. For the sake
5525 of simplicity, this document describes only the symbolic
5526 link method. However, it must not be assumed by maintainer
5527 scripts that this method is being used, and any automated
5528 manipulation of the various runlevel behaviors by
5529 maintainer scripts must be performed using
5530 <prgn>update-rc.d</prgn> as described below and not by
5531 manually installing or removing symlinks. For information
5532 on the implementation details of the other method,
5533 implemented in the <tt>file-rc</tt> package, please refer
5534 to the documentation of that package.
5538 These scripts are referenced by symbolic links in the
5539 <file>/etc/rc<var>n</var>.d</file> directories. When changing
5540 runlevels, <prgn>init</prgn> looks in the directory
5541 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
5542 execute, where <tt><var>n</var></tt> is the runlevel that
5543 is being changed to, or <tt>S</tt> for the boot-up
5548 The names of the links all have the form
5549 <file>S<var>mm</var><var>script</var></file> or
5550 <file>K<var>mm</var><var>script</var></file> where
5551 <var>mm</var> is a two-digit number and <var>script</var>
5552 is the name of the script (this should be the same as the
5553 name of the actual script in <file>/etc/init.d</file>).
5557 When <prgn>init</prgn> changes runlevel first the targets
5558 of the links whose names start with a <tt>K</tt> are
5559 executed, each with the single argument <tt>stop</tt>,
5560 followed by the scripts prefixed with an <tt>S</tt>, each
5561 with the single argument <tt>start</tt>. (The links are
5562 those in the <file>/etc/rc<var>n</var>.d</file> directory
5563 corresponding to the new runlevel.) The <tt>K</tt> links
5564 are responsible for killing services and the <tt>S</tt>
5565 link for starting services upon entering the runlevel.
5569 For example, if we are changing from runlevel 2 to
5570 runlevel 3, init will first execute all of the <tt>K</tt>
5571 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
5572 all of the <tt>S</tt> prefixed scripts in that directory.
5573 The links starting with <tt>K</tt> will cause the
5574 referred-to file to be executed with an argument of
5575 <tt>stop</tt>, and the <tt>S</tt> links with an argument
5580 The two-digit number <var>mm</var> is used to determine
5581 the order in which to run the scripts: low-numbered links
5582 have their scripts run first. For example, the
5583 <tt>K20</tt> scripts will be executed before the
5584 <tt>K30</tt> scripts. This is used when a certain service
5585 must be started before another. For example, the name
5586 server <prgn>bind</prgn> might need to be started before
5587 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
5588 can set up its access lists. In this case, the script
5589 that starts <prgn>bind</prgn> would have a lower number
5590 than the script that starts <prgn>inn</prgn> so that it
5592 <example compact="compact">
5599 The two runlevels 0 (halt) and 6 (reboot) are slightly
5600 different. In these runlevels, the links with an
5601 <tt>S</tt> prefix are still called after those with a
5602 <tt>K</tt> prefix, but they too are called with the single
5603 argument <tt>stop</tt>.
5607 Also, if the script name ends in <tt>.sh</tt>, the script
5608 will be sourced in runlevel <tt>S</tt> rather than being
5609 run in a forked subprocess, but will be explicitly run by
5610 <prgn>sh</prgn> in all other runlevels.
5615 <heading>Writing the scripts</heading>
5618 Packages that include daemons for system services should
5619 place scripts in <file>/etc/init.d</file> to start or stop
5620 services at boot time or during a change of runlevel.
5621 These scripts should be named
5622 <file>/etc/init.d/<var>package</var></file>, and they should
5623 accept one argument, saying what to do:
5626 <tag><tt>start</tt></tag>
5627 <item>start the service,</item>
5629 <tag><tt>stop</tt></tag>
5630 <item>stop the service,</item>
5632 <tag><tt>restart</tt></tag>
5633 <item>stop and restart the service if it's already running,
5634 otherwise start the service</item>
5636 <tag><tt>reload</tt></tag>
5637 <item><p>cause the configuration of the service to be
5638 reloaded without actually stopping and restarting
5641 <tag><tt>force-reload</tt></tag>
5642 <item>cause the configuration to be reloaded if the
5643 service supports this, otherwise restart the
5647 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
5648 <tt>force-reload</tt> options should be supported by all
5649 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
5654 The <file>init.d</file> scripts must ensure that they will
5655 behave sensibly if invoked with <tt>start</tt> when the
5656 service is already running, or with <tt>stop</tt> when it
5657 isn't, and that they don't kill unfortunately-named user
5658 processes. The best way to achieve this is usually to use
5659 <prgn>start-stop-daemon</prgn>.
5663 If a service reloads its configuration automatically (as
5664 in the case of <prgn>cron</prgn>, for example), the
5665 <tt>reload</tt> option of the <file>init.d</file> script
5666 should behave as if the configuration has been reloaded
5671 The <file>/etc/init.d</file> scripts must be treated as
5672 configuration files, either (if they are present in the
5673 package, that is, in the .deb file) by marking them as
5674 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
5675 by managing them correctly in the maintainer scripts (see
5676 <ref id="config-files">). This is important since we want
5677 to give the local system administrator the chance to adapt
5678 the scripts to the local system, e.g., to disable a
5679 service without de-installing the package, or to specify
5680 some special command line options when starting a service,
5681 while making sure their changes aren't lost during the next
5686 These scripts should not fail obscurely when the
5687 configuration files remain but the package has been
5688 removed, as configuration files remain on the system after
5689 the package has been removed. Only when <prgn>dpkg</prgn>
5690 is executed with the <tt>--purge</tt> option will
5691 configuration files be removed. In particular, as the
5692 <file>/etc/init.d/<var>package</var></file> script itself is
5693 usually a <tt>conffile</tt>, it will remain on the system
5694 if the package is removed but not purged. Therefore, you
5695 should include a <tt>test</tt> statement at the top of the
5697 <example compact="compact">
5698 test -f <var>program-executed-later-in-script</var> || exit 0
5703 Often there are some variables in the <file>init.d</file>
5704 scripts whose values control the behavior of the scripts,
5705 and which a system administrator is likely to want to
5706 change. As the scripts themselves are frequently
5707 <tt>conffile</tt>s, modifying them requires that the
5708 administrator merge in their changes each time the package
5709 is upgraded and the <tt>conffile</tt> changes. To ease
5710 the burden on the system administrator, such configurable
5711 values should not be placed directly in the script.
5712 Instead, they should be placed in a file in
5713 <file>/etc/default</file>, which typically will have the same
5714 base name as the <file>init.d</file> script. This extra file
5715 should be sourced by the script when the script runs. It
5716 must contain only variable settings and comments in SUSv3
5717 <prgn>sh</prgn> format. It may either be a
5718 <tt>conffile</tt> or a configuration file maintained by
5719 the package maintainer scripts. See <ref id="config-files">
5724 To ensure that vital configurable values are always
5725 available, the <file>init.d</file> script should set default
5726 values for each of the shell variables it uses, either
5727 before sourcing the <file>/etc/default/</file> file or
5728 afterwards using something like the <tt>:
5729 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
5730 script must behave sensibly and not fail if the
5731 <file>/etc/default</file> file is deleted.
5736 <heading>Interfacing with the initscript system</heading>
5739 Maintainers should use the abstraction layer provided by
5740 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
5741 programs to deal with initscripts in their packages'
5742 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
5743 and <prgn>postrm</prgn>.
5747 Directly managing the /etc/rc?.d links and directly
5748 invoking the <file>/etc/init.d/</file> initscripts should
5749 be done only by packages providing the initscript
5750 subsystem (such as <prgn>sysv-rc</prgn> and
5751 <prgn>file-rc</prgn>).
5755 <heading>Managing the links</heading>
5758 The program <prgn>update-rc.d</prgn> is provided for
5759 package maintainers to arrange for the proper creation and
5760 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
5761 or their functional equivalent if another method is being
5762 used. This may be used by maintainers in their packages'
5763 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
5767 You must not include any <file>/etc/rc<var>n</var>.d</file>
5768 symbolic links in the actual archive or manually create or
5769 remove the symbolic links in maintainer scripts; you must
5770 use the <prgn>update-rc.d</prgn> program instead. (The
5771 former will fail if an alternative method of maintaining
5772 runlevel information is being used.) You must not include
5773 the <file>/etc/rc<var>n</var>.d</file> directories themselves
5774 in the archive either. (Only the <tt>sysvinit</tt>
5779 By default <prgn>update-rc.d</prgn> will start services in
5780 each of the multi-user state runlevels (2, 3, 4, and 5)
5781 and stop them in the halt runlevel (0), the single-user
5782 runlevel (1) and the reboot runlevel (6). The system
5783 administrator will have the opportunity to customize
5784 runlevels by simply adding, moving, or removing the
5785 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
5786 symbolic links are being used, or by modifying
5787 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
5792 To get the default behavior for your package, put in your
5793 <prgn>postinst</prgn> script
5794 <example compact="compact">
5795 update-rc.d <var>package</var> defaults
5797 and in your <prgn>postrm</prgn>
5798 <example compact="compact">
5799 if [ "$1" = purge ]; then
5800 update-rc.d <var>package</var> remove
5802 </example>. Note that if your package changes runlevels
5803 or priority, you may have to remove and recreate the links,
5804 since otherwise the old links may persist. Refer to the
5805 documentation of <prgn>update-rc.d</prgn>.
5809 This will use a default sequence number of 20. If it does
5810 not matter when or in which order the <file>init.d</file>
5811 script is run, use this default. If it does, then you
5812 should talk to the maintainer of the <prgn>sysvinit</prgn>
5813 package or post to <tt>debian-devel</tt>, and they will
5814 help you choose a number.
5818 For more information about using <tt>update-rc.d</tt>,
5819 please consult its man page <manref name="update-rc.d"
5825 <heading>Running initscripts</heading>
5827 The program <prgn>invoke-rc.d</prgn> is provided to make
5828 it easier for package maintainers to properly invoke an
5829 initscript, obeying runlevel and other locally-defined
5830 constraints that might limit a package's right to start,
5831 stop and otherwise manage services. This program may be
5832 used by maintainers in their packages' scripts.
5836 The package maintainer scripts must use
5837 <prgn>invoke-rc.d</prgn> to invoke the
5838 <file>/etc/init.d/*</file> initscripts, instead of
5839 calling them directly.
5843 By default, <prgn>invoke-rc.d</prgn> will pass any
5844 action requests (start, stop, reload, restart...) to the
5845 <file>/etc/init.d</file> script, filtering out requests
5846 to start or restart a service out of its intended
5851 Most packages will simply need to change:
5852 <example compact="compact">/etc/init.d/<package>
5853 <action></example> in their <prgn>postinst</prgn>
5854 and <prgn>prerm</prgn> scripts to:
5855 <example compact="compact">
5856 if which invoke-rc.d >/dev/null 2>&1; then
5857 invoke-rc.d <var>package</var> <action>
5859 /etc/init.d/<var>package</var> <action>
5865 A package should register its initscript services using
5866 <prgn>update-rc.d</prgn> before it tries to invoke them
5867 using <prgn>invoke-rc.d</prgn>. Invocation of
5868 unregistered services may fail.
5872 For more information about using
5873 <prgn>invoke-rc.d</prgn>, please consult its man page
5874 <manref name="invoke-rc.d" section="8">.
5880 <heading>Boot-time initialization</heading>
5883 There used to be another directory, <file>/etc/rc.boot</file>,
5884 which contained scripts which were run once per machine
5885 boot. This has been deprecated in favour of links from
5886 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
5887 described in <ref id="/etc/init.d">. Packages must not
5888 place files in <file>/etc/rc.boot</file>.
5893 <heading>Example</heading>
5896 An example on which you can base your
5897 <file>/etc/init.d</file> scripts is found in
5898 <file>/etc/init.d/skeleton</file>.
5905 <heading>Console messages from <file>init.d</file> scripts</heading>
5908 This section describes the formats to be used for messages
5909 written to standard output by the <file>/etc/init.d</file>
5910 scripts. The intent is to improve the consistency of
5911 Debian's startup and shutdown look and feel. For this
5912 reason, please look very carefully at the details. We want
5913 the messages to have the same format in terms of wording,
5914 spaces, punctuation and case of letters.
5918 Here is a list of overall rules that should be used for
5919 messages generated by <file>/etc/init.d</file> scripts.
5925 The message should fit in one line (fewer than 80
5926 characters), start with a capital letter and end with
5927 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
5931 If the script is performing some time consuming task in
5932 the background (not merely starting or stopping a
5933 program, for instance), an ellipsis (three dots:
5934 <tt>...</tt>) should be output to the screen, with no
5935 leading or tailing whitespace or line feeds.
5939 The messages should appear as if the computer is telling
5940 the user what it is doing (politely :-), but should not
5941 mention "it" directly. For example, instead of:
5942 <example compact="compact">
5943 I'm starting network daemons: nfsd mountd.
5945 the message should say
5946 <example compact="compact">
5947 Starting network daemons: nfsd mountd.
5954 <tt>init.d</tt> script should use the following standard
5955 message formats for the situations enumerated below.
5961 <p>When daemons are started</p>
5964 If the script starts one or more daemons, the output
5965 should look like this (a single line, no leading
5967 <example compact="compact">
5968 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
5970 The <var>description</var> should describe the
5971 subsystem the daemon or set of daemons are part of,
5972 while <var>daemon-1</var> up to <var>daemon-n</var>
5973 denote each daemon's name (typically the file name of
5978 For example, the output of <file>/etc/init.d/lpd</file>
5980 <example compact="compact">
5981 Starting printer spooler: lpd.
5986 This can be achieved by saying
5987 <example compact="compact">
5988 echo -n "Starting printer spooler: lpd"
5989 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
5992 in the script. If there are more than one daemon to
5993 start, the output should look like this:
5994 <example compact="compact">
5995 echo -n "Starting remote file system services:"
5996 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
5997 echo -n " mountd"; start-stop-daemon --start --quiet mountd
5998 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6001 This makes it possible for the user to see what is
6002 happening and when the final daemon has been started.
6003 Care should be taken in the placement of white spaces:
6004 in the example above the system administrators can
6005 easily comment out a line if they don't want to start
6006 a specific daemon, while the displayed message still
6012 <p>When a system parameter is being set</p>
6015 If you have to set up different system parameters
6016 during the system boot, you should use this format:
6017 <example compact="compact">
6018 Setting <var>parameter</var> to "<var>value</var>".
6023 You can use a statement such as the following to get
6025 <example compact="compact">
6026 echo "Setting DNS domainname to \"$domainname\"."
6031 Note that the same symbol (<tt>"</tt>) is used for the left
6032 and right quotation marks. A grave accent (<tt>`</tt>) is
6033 not a quote character; neither is an apostrophe
6039 <p>When a daemon is stopped or restarted</p>
6042 When you stop or restart a daemon, you should issue a
6043 message identical to the startup message, except that
6044 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6045 or <tt>Restarting</tt> respectively.
6049 For example, stopping the printer daemon will look like
6051 <example compact="compact">
6052 Stopping printer spooler: lpd.
6058 <p>When something is executed</p>
6061 There are several examples where you have to run a
6062 program at system startup or shutdown to perform a
6063 specific task, for example, setting the system's clock
6064 using <prgn>netdate</prgn> or killing all processes
6065 when the system shuts down. Your message should look
6067 <example compact="compact">
6068 Doing something very useful...done.
6070 You should print the <tt>done.</tt> immediately after
6071 the job has been completed, so that the user is
6072 informed why they have to wait. You can get this
6074 <example compact="compact">
6075 echo -n "Doing something very useful..."
6084 <p>When the configuration is reloaded</p>
6087 When a daemon is forced to reload its configuration
6088 files you should use the following format:
6089 <example compact="compact">
6090 Reloading <var>description</var> configuration...done.
6092 where <var>description</var> is the same as in the
6093 daemon starting message.
6101 <heading>Cron jobs</heading>
6104 Packages must not modify the configuration file
6105 <file>/etc/crontab</file>, and they must not modify the files in
6106 <file>/var/spool/cron/crontabs</file>.</p>
6109 If a package wants to install a job that has to be executed
6110 via cron, it should place a file with the name of the
6111 package in one or more of the following directories:
6112 <example compact="compact">
6117 As these directory names imply, the files within them are
6118 executed on a daily, weekly, or monthly basis,
6119 respectively. The exact times are listed in
6120 <file>/etc/crontab</file>.</p>
6123 All files installed in any of these directories must be
6124 scripts (e.g., shell scripts or Perl scripts) so that they
6125 can easily be modified by the local system administrator.
6126 In addition, they should be treated as configuration
6131 If a certain job has to be executed more frequently than
6132 daily, the package should install a file
6133 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6134 same syntax as <file>/etc/crontab</file> and is processed by
6135 <prgn>cron</prgn> automatically. The file must also be
6136 treated as a configuration file. (Note that entries in the
6137 <file>/etc/cron.d</file> directory are not handled by
6138 <prgn>anacron</prgn>. Thus, you should only use this
6139 directory for jobs which may be skipped if the system is not
6143 The scripts or crontab entries in these directories should
6144 check if all necessary programs are installed before they
6145 try to execute them. Otherwise, problems will arise when a
6146 package was removed but not purged since configuration files
6147 are kept on the system in this situation.</p>
6151 <heading>Menus</heading>
6154 The Debian <tt>menu</tt> package provides a standard
6155 interface between packages providing applications and
6156 <em>menu programs</em> (either X window managers or
6157 text-based menu programs such as <prgn>pdmenu</prgn>).
6161 All packages that provide applications that need not be
6162 passed any special command line arguments for normal
6163 operation should register a menu entry for those
6164 applications, so that users of the <tt>menu</tt> package
6165 will automatically get menu entries in their window
6166 managers, as well in shells like <tt>pdmenu</tt>.
6170 Menu entries should follow the current menu policy.
6174 The menu policy can be found in the <tt>menu-policy</tt>
6175 files in the <tt>debian-policy</tt> package.
6176 It is also available from the Debian web mirrors at
6177 <tt><url name="/doc/packaging-manuals/menu-policy/"
6178 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6182 Please also refer to the <em>Debian Menu System</em>
6183 documentation that comes with the <package>menu</package>
6184 package for information about how to register your
6190 <heading>Multimedia handlers</heading>
6193 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6194 is a mechanism for encoding files and data streams and
6195 providing meta-information about them, in particular their
6196 type (e.g. audio or video) and format (e.g. PNG, HTML,
6201 Registration of MIME type handlers allows programs like mail
6202 user agents and web browsers to invoke these handlers to
6203 view, edit or display MIME types they don't support directly.
6207 Packages which provide the ability to view/show/play,
6208 compose, edit or print MIME types should register themselves
6209 as such following the current MIME support policy.
6213 The MIME support policy can be found in the <tt>mime-policy</tt>
6214 files in the <tt>debian-policy</tt> package.
6215 It is also available from the Debian web mirrors at
6216 <tt><url name="/doc/packaging-manuals/mime-policy/"
6217 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
6223 <heading>Keyboard configuration</heading>
6226 To achieve a consistent keyboard configuration so that all
6227 applications interpret a keyboard event the same way, all
6228 programs in the Debian distribution must be configured to
6229 comply with the following guidelines.
6233 The following keys must have the specified interpretations:
6236 <tag><tt><--</tt></tag>
6237 <item>delete the character to the left of the cursor</item>
6239 <tag><tt>Delete</tt></tag>
6240 <item>delete the character to the right of the cursor</item>
6242 <tag><tt>Control+H</tt></tag>
6243 <item>emacs: the help prefix</item>
6246 The interpretation of any keyboard events should be
6247 independent of the terminal that is used, be it a virtual
6248 console, an X terminal emulator, an rlogin/telnet session,
6253 The following list explains how the different programs
6254 should be set up to achieve this:
6260 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
6264 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
6268 X translations are set up to make
6269 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
6270 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
6271 is the vt220 escape code for the "delete character"
6272 key). This must be done by loading the X resources
6273 using <prgn>xrdb</prgn> on all local X displays, not
6274 using the application defaults, so that the
6275 translation resources used correspond to the
6276 <prgn>xmodmap</prgn> settings.
6280 The Linux console is configured to make
6281 <tt><--</tt> generate DEL, and <tt>Delete</tt>
6282 generate <tt>ESC [ 3 ~</tt>.
6286 X applications are configured so that <tt><</tt>
6287 deletes left, and <tt>Delete</tt> deletes right. Motif
6288 applications already work like this.
6292 Terminals should have <tt>stty erase ^?</tt> .
6296 The <tt>xterm</tt> terminfo entry should have <tt>ESC
6297 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
6298 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
6302 Emacs is programmed to map <tt>KB_Backspace</tt> or
6303 the <tt>stty erase</tt> character to
6304 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
6305 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
6306 <tt>^H</tt> to <tt>help</tt> as always.
6310 Other applications use the <tt>stty erase</tt>
6311 character and <tt>kdch1</tt> for the two delete keys,
6312 with ASCII DEL being "delete previous character" and
6313 <tt>kdch1</tt> being "delete character under
6321 This will solve the problem except for the following
6328 Some terminals have a <tt><--</tt> key that cannot
6329 be made to produce anything except <tt>^H</tt>. On
6330 these terminals Emacs help will be unavailable on
6331 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
6332 character takes precedence in Emacs, and has been set
6333 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
6334 available) can be used instead.
6338 Some operating systems use <tt>^H</tt> for <tt>stty
6339 erase</tt>. However, modern telnet versions and all
6340 rlogin versions propagate <tt>stty</tt> settings, and
6341 almost all UNIX versions honour <tt>stty erase</tt>.
6342 Where the <tt>stty</tt> settings are not propagated
6343 correctly, things can be made to work by using
6344 <tt>stty</tt> manually.
6348 Some systems (including previous Debian versions) use
6349 <prgn>xmodmap</prgn> to arrange for both
6350 <tt><--</tt> and <tt>Delete</tt> to generate
6351 <tt>KB_Delete</tt>. We can change the behavior of
6352 their X clients using the same X resources that we use
6353 to do it for our own clients, or configure our clients
6354 using their resources when things are the other way
6355 around. On displays configured like this
6356 <tt>Delete</tt> will not work, but <tt><--</tt>
6361 Some operating systems have different <tt>kdch1</tt>
6362 settings in their <tt>terminfo</tt> database for
6363 <tt>xterm</tt> and others. On these systems the
6364 <tt>Delete</tt> key will not work correctly when you
6365 log in from a system conforming to our policy, but
6366 <tt><--</tt> will.
6373 <heading>Environment variables</heading>
6376 A program must not depend on environment variables to get
6377 reasonable defaults. (That's because these environment
6378 variables would have to be set in a system-wide
6379 configuration file like <file>/etc/profile</file>, which is not
6380 supported by all shells.)
6384 If a program usually depends on environment variables for its
6385 configuration, the program should be changed to fall back to
6386 a reasonable default configuration if these environment
6387 variables are not present. If this cannot be done easily
6388 (e.g., if the source code of a non-free program is not
6389 available), the program must be replaced by a small
6390 "wrapper" shell script which sets the environment variables
6391 if they are not already defined, and calls the original program.
6395 Here is an example of a wrapper script for this purpose:
6397 <example compact="compact">
6399 BAR=${BAR:-/var/lib/fubar}
6401 exec /usr/lib/foo/foo "$@"
6406 Furthermore, as <file>/etc/profile</file> is a configuration
6407 file of the <prgn>base-files</prgn> package, other packages must
6408 not put any environment variables or other commands into that
6413 <sect id="doc-base">
6414 <heading>Registering Documents using doc-base</heading>
6417 The <package>doc-base</package> package implements a
6418 flexible mechanism for handling and presenting
6419 documentation. The recommended practice is for every Debian
6420 package that provides online documentation (other than just
6421 manual pages) to register these documents with
6422 <package>doc-base</package> by installing a
6423 <package>doc-base</package> control file via the
6424 <prgn/install-docs/ script at installation time and
6425 de-register the manuals again when the package is removed.
6428 Please refer to the documentation that comes with the
6429 <package>doc-base</package> package for information and
6438 <heading>Files</heading>
6441 <heading>Binaries</heading>
6444 Two different packages must not install programs with
6445 different functionality but with the same filenames. (The
6446 case of two programs having the same functionality but
6447 different implementations is handled via "alternatives" or
6448 the "Conflicts" mechanism. See <ref id="maintscripts"> and
6449 <ref id="conflicts"> respectively.) If this case happens,
6450 one of the programs must be renamed. The maintainers should
6451 report this to the <tt>debian-devel</tt> mailing list and
6452 try to find a consensus about which program will have to be
6453 renamed. If a consensus cannot be reached, <em>both</em>
6454 programs must be renamed.
6458 By default, when a package is being built, any binaries
6459 created should include debugging information, as well as
6460 being compiled with optimization. You should also turn on
6461 as many reasonable compilation warnings as possible; this
6462 makes life easier for porters, who can then look at build
6463 logs for possible problems. For the C programming language,
6464 this means the following compilation parameters should be
6466 <example compact="compact">
6468 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
6470 INSTALL = install -s # (or use strip on the files in debian/tmp)
6475 Note that by default all installed binaries should be stripped,
6476 either by using the <tt>-s</tt> flag to
6477 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
6478 the binaries after they have been copied into
6479 <file>debian/tmp</file> but before the tree is made into a
6484 Although binaries in the build tree should be compiled with
6485 debugging information by default, it can often be difficult
6486 to debug programs if they are also subjected to compiler
6487 optimization. For this reason, it is recommended to support
6488 the standardized environment
6489 variable <tt>DEB_BUILD_OPTIONS</tt>. This variable can
6490 contain several flags to change how a package is compiled
6498 The presence of this string means that the package
6499 should be compiled with a minimum of optimization.
6500 For C programs, it is best to add <tt>-O0</tt>
6501 to <tt>CFLAGS</tt> (although this is usually the
6502 default). Some programs might fail to build or run at
6503 this level of optimization; it may be necessary to
6504 use <tt>-O1</tt>, for example.
6508 This string means that the debugging symbols should
6509 not be stripped from the binary during installation,
6510 so that debugging information may be included in the package.
6516 The following makefile snippet is an example of how one may
6517 implement the build options; you will probably have to
6518 massage this example in order to make it work for your
6520 <example compact="compact">
6523 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
6524 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
6525 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
6526 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
6528 ifneq (,$(findstring noopt,$(DEB_BUILD_OPTIONS)))
6533 ifeq (,$(findstring nostrip,$(DEB_BUILD_OPTIONS)))
6534 INSTALL_PROGRAM += -s
6540 It is up to the package maintainer to decide what
6541 compilation options are best for the package. Certain
6542 binaries (such as computationally-intensive programs) will
6543 function better with certain flags (<tt>-O3</tt>, for
6544 example); feel free to use them. Please use good judgment
6545 here. Don't use flags for the sake of it; only use them
6546 if there is good reason to do so. Feel free to override
6547 the upstream author's ideas about which compilation
6548 options are best: they are often inappropriate for our
6554 <sect id="libraries">
6555 <heading>Libraries</heading>
6558 If the package is <strong>architecture: any</strong>, then
6559 the shared library compilation and linking flags must have
6560 <tt>-fPIC</tt>, or the package shall not build on some of
6561 the supported architectures<footnote>
6563 If you are using GCC, <tt>-fPIC</tt> produces code with
6564 relocatable position independent code, which is required for
6565 most architectures to create a shared library, with i386 and
6566 perhaps some others where non position independent code is
6567 permitted in a shared library.
6570 Position independent code may have a performance penalty,
6571 especially on <tt>i386</tt>. However, in most cases the
6572 speed penalty must be measured against the memory wasted on
6573 the few architectures where non position independent code is
6576 </footnote>. Any exception to this rule must be discussed on
6577 the mailing list <em>debian-devel@lists.debian.org</em>, and
6578 a rough consensus obtained. The reasons for not compiling
6579 with <tt>-fPIC</tt> flag must be recorded in the file
6580 <tt>README.Debian</tt>, and care must be taken to either
6581 restrict the architecture or arrange for <tt>-fPIC</tt> to
6582 be used on architectures where it is required.<footnote>
6584 Some of the reasons why this might be required is if the
6585 library contains hand crafted assembly code that is not
6586 relocatable, the speed penalty is excessive for compute
6587 intensive libs, and similar reasons.
6592 As to the static libraries, the common case is not to have
6593 relocatable code, since there is no benefit, unless in specific
6594 cases; therefore the static version must not be compiled
6595 with the <tt>-fPIC</tt> flag. Any exception to this rule
6596 should be discussed on the mailing list
6597 <em>debian-devel@lists.debian.org</em>, and the reasons for
6598 compiling with the <tt>-fPIC</tt> flag must be recorded in
6599 the file <tt>README.Debian</tt>. <footnote>
6601 Some of the reasons for linking static libraries with
6602 the <tt>-fPIC</tt> flag are if, for example, one needs a
6603 Perl API for a library that is under rapid development,
6604 and has an unstable API, so shared libraries are
6605 pointless at this phase of the library's development. In
6606 that case, since Perl needs a library with relocatable
6607 code, it may make sense to create a static library with
6608 relocatable code. Another reason cited is if you are
6609 distilling various libraries into a common shared
6610 library, like <tt>mklibs</tt> does in the Debian
6616 In other words, if both a shared and a static library is
6617 being built, each source unit (<tt>*.c</tt>, for example,
6618 for C files) will need to be compiled twice, for the normal
6622 You must specify the gcc option <tt>-D_REENTRANT</tt>
6623 when building a library (either static or shared) to make
6624 the library compatible with LinuxThreads.
6628 Although not enforced by the build tools, shared libraries
6629 must be linked against all libraries that they use symbols from
6630 in the same way that binaries are. This ensures the correct
6631 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
6632 system and guarantees that all libraries can be safely opened
6633 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
6634 option <tt>-Wl,-z,defs</tt> when building a shared library.
6635 Since this option enforces symbol resolution at build time,
6636 a missing library reference will be caught early as a fatal
6641 All installed shared libraries should be stripped with
6642 <example compact="compact">
6643 strip --strip-unneeded <var>your-lib</var>
6645 (The option <tt>--strip-unneeded</tt> makes
6646 <prgn>strip</prgn> remove only the symbols which aren't
6647 needed for relocation processing.) Shared libraries can
6648 function perfectly well when stripped, since the symbols for
6649 dynamic linking are in a separate part of the ELF object
6651 You might also want to use the options
6652 <tt>--remove-section=.comment</tt> and
6653 <tt>--remove-section=.note</tt> on both shared libraries
6654 and executables, and <tt>--strip-debug</tt> on static
6660 Note that under some circumstances it may be useful to
6661 install a shared library unstripped, for example when
6662 building a separate package to support debugging.
6666 Shared object files (often <file>.so</file> files) that are not
6667 public libraries, that is, they are not meant to be linked
6668 to by third party executables (binaries of other packages),
6669 should be installed in subdirectories of the
6670 <file>/usr/lib</file> directory. Such files are exempt from the
6671 rules that govern ordinary shared libraries, except that
6672 they must not be installed executable and should be
6674 A common example are the so-called "plug-ins",
6675 internal shared objects that are dynamically loaded by
6676 programs using <manref name="dlopen" section="3">.
6681 Packages containing shared libraries that may be linked to
6682 by other packages' binaries, but which for some
6683 <em>compelling</em> reason can not be installed in
6684 <file>/usr/lib</file> directory, may install the shared library
6685 files in subdirectories of the <file>/usr/lib</file> directory,
6686 in which case they should arrange to add that directory in
6687 <file>/etc/ld.so.conf</file> in the package's post-installation
6688 script, and remove it in the package's post-removal script.
6692 An ever increasing number of packages are using
6693 <prgn>libtool</prgn> to do their linking. The latest GNU
6694 libtools (>= 1.3a) can take advantage of the metadata in the
6695 installed <prgn>libtool</prgn> archive files (<file>*.la</file>
6696 files). The main advantage of <prgn>libtool</prgn>'s
6697 <file>.la</file> files is that it allows <prgn>libtool</prgn> to
6698 store and subsequently access metadata with respect to the
6699 libraries it builds. <prgn>libtool</prgn> will search for
6700 those files, which contain a lot of useful information about
6701 a library (such as library dependency information for static
6702 linking). Also, they're <em>essential</em> for programs
6703 using <tt>libltdl</tt>.<footnote>
6704 Although <prgn>libtool</prgn> is fully capable of
6705 linking against shared libraries which don't have
6706 <tt>.la</tt> files, as it is a mere shell script it can
6707 add considerably to the build time of a
6708 <prgn>libtool</prgn>-using package if that shell script
6709 has to derive all this information from first principles
6710 for each library every time it is linked. With the
6711 advent of <prgn>libtool</prgn> version 1.4 (and to a
6712 lesser extent <prgn>libtool</prgn> version 1.3), the
6713 <file>.la</file> files also store information about
6714 inter-library dependencies which cannot necessarily be
6715 derived after the <file>.la</file> file is deleted.
6720 Packages that use <prgn>libtool</prgn> to create shared
6721 libraries should include the <file>.la</file> files in the
6722 <tt>-dev</tt> package, unless the package relies on
6723 <tt>libtool</tt>'s <tt>libltdl</tt> library, in which case
6724 the <tt>.la</tt> files must go in the run-time library
6729 You must make sure that you use only released versions of
6730 shared libraries to build your packages; otherwise other
6731 users will not be able to run your binaries
6732 properly. Producing source packages that depend on
6733 unreleased compilers is also usually a bad
6740 <heading>Shared libraries</heading>
6742 This section has moved to <ref id="sharedlibs">.
6748 <heading>Scripts</heading>
6751 All command scripts, including the package maintainer
6752 scripts inside the package and used by <prgn>dpkg</prgn>,
6753 should have a <tt>#!</tt> line naming the shell to be used
6758 In the case of Perl scripts this should be
6759 <tt>#!/usr/bin/perl</tt>.
6763 When scripts are installed into a directory in the system
6764 PATH, the script name should not include an extension such
6765 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
6766 language currently used to implement it.
6769 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>)
6770 should almost certainly start with <tt>set -e</tt> so that
6771 errors are detected. Every script should use
6772 <tt>set -e</tt> or check the exit status of <em>every</em>
6777 Scripts may assume that <file>/bin/sh</file> implements the
6778 SUSv3 Shell Command Language<footnote>
6779 Single UNIX Specification, version 3, which is also IEEE
6780 1003.1-2004 (POSIX), and is available on the World Wide Web
6781 from <url id="http://www.unix.org/version3/online.html"
6782 name="The Open Group"> after free
6783 registration.</footnote>
6784 plus the following additional features not mandated by
6786 These features are in widespread use in the Linux community
6787 and are implemented in all of bash, dash, and ksh, the most
6788 common shells users may wish to use as <file>/bin/sh</file>.
6791 <item><tt>echo -n</tt>, if implemented as a shell built-in,
6792 must not generate a newline.</item>
6793 <item><tt>test</tt>, if implemented as a shell built-in, must
6794 support <tt>-a</tt> and <tt>-o</tt> as binary logical
6796 <item><tt>local</tt> to create a scoped variable must be
6797 supported; however, <tt>local</tt> may or may not preserve
6798 the variable value from an outer scope and may or may not
6799 support arguments more complex than simple variables. Only
6811 If a shell script requires non-SUSv3 features from the shell
6812 interpreter other than those listed above, the appropriate shell
6813 must be specified in the first line of the script (e.g.,
6814 <tt>#!/bin/bash</tt>) and the package must depend on the package
6815 providing the shell (unless the shell package is marked
6816 "Essential", as in the case of <prgn>bash</prgn>).
6820 You may wish to restrict your script to SUSv3 features plus the
6821 above set when possible so that it may use <file>/bin/sh</file>
6822 as its interpreter. If your script works with <prgn>dash</prgn>
6823 (originally called <prgn>ash</prgn>), it probably complies with
6824 the above requirements, but if you are in doubt, use
6825 <file>/bin/bash</file>.
6829 Perl scripts should check for errors when making any
6830 system calls, including <tt>open</tt>, <tt>print</tt>,
6831 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
6835 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
6836 scripting languages. See <em>Csh Programming Considered
6837 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
6838 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
6839 If an upstream package comes with <prgn>csh</prgn> scripts
6840 then you must make sure that they start with
6841 <tt>#!/bin/csh</tt> and make your package depend on the
6842 <prgn>c-shell</prgn> virtual package.
6846 Any scripts which create files in world-writeable
6847 directories (e.g., in <file>/tmp</file>) must use a
6848 mechanism which will fail atomically if a file with the same
6849 name already exists.
6853 The Debian base system provides the <prgn>tempfile</prgn>
6854 and <prgn>mktemp</prgn> utilities for use by scripts for
6861 <heading>Symbolic links</heading>
6864 In general, symbolic links within a top-level directory
6865 should be relative, and symbolic links pointing from one
6866 top-level directory into another should be absolute. (A
6867 top-level directory is a sub-directory of the root
6868 directory <file>/</file>.)
6872 In addition, symbolic links should be specified as short as
6873 possible, i.e., link targets like <file>foo/../bar</file> are
6878 Note that when creating a relative link using
6879 <prgn>ln</prgn> it is not necessary for the target of the
6880 link to exist relative to the working directory you're
6881 running <prgn>ln</prgn> from, nor is it necessary to change
6882 directory to the directory where the link is to be made.
6883 Simply include the string that should appear as the target
6884 of the link (this will be a pathname relative to the
6885 directory in which the link resides) as the first argument
6890 For example, in your <prgn>Makefile</prgn> or
6891 <file>debian/rules</file>, you can do things like:
6892 <example compact="compact">
6893 ln -fs gcc $(prefix)/bin/cc
6894 ln -fs gcc debian/tmp/usr/bin/cc
6895 ln -fs ../sbin/sendmail $(prefix)/bin/runq
6896 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
6901 A symbolic link pointing to a compressed file should always
6902 have the same file extension as the referenced file. (For
6903 example, if a file <file>foo.gz</file> is referenced by a
6904 symbolic link, the filename of the link has to end with
6905 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
6910 <heading>Device files</heading>
6913 Packages must not include device files in the package file
6918 If a package needs any special device files that are not
6919 included in the base system, it must call
6920 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
6921 after notifying the user<footnote>
6922 This notification could be done via a (low-priority)
6923 debconf message, or an echo (printf) statement.
6928 Packages must not remove any device files in the
6929 <prgn>postrm</prgn> or any other script. This is left to the
6930 system administrator.
6934 Debian uses the serial devices
6935 <file>/dev/ttyS*</file>. Programs using the old
6936 <file>/dev/cu*</file> devices should be changed to use
6937 <file>/dev/ttyS*</file>.
6941 <sect id="config-files">
6942 <heading>Configuration files</heading>
6945 <heading>Definitions</heading>
6949 <tag>configuration file</tag>
6951 A file that affects the operation of a program, or
6952 provides site- or host-specific information, or
6953 otherwise customizes the behavior of a program.
6954 Typically, configuration files are intended to be
6955 modified by the system administrator (if needed or
6956 desired) to conform to local policy or to provide
6957 more useful site-specific behavior.
6960 <tag><tt>conffile</tt></tag>
6962 A file listed in a package's <tt>conffiles</tt>
6963 file, and is treated specially by <prgn>dpkg</prgn>
6964 (see <ref id="configdetails">).
6970 The distinction between these two is important; they are
6971 not interchangeable concepts. Almost all
6972 <tt>conffile</tt>s are configuration files, but many
6973 configuration files are not <tt>conffiles</tt>.
6977 Note that a script that embeds configuration information
6978 (such as most of the files in <file>/etc/default</file> and
6979 <file>/etc/cron.{daily,weekly,monthly}</file>) is de-facto a
6980 configuration file and should be treated as such.
6985 <heading>Location</heading>
6988 Any configuration files created or used by your package
6989 must reside in <file>/etc</file>. If there are several,
6990 consider creating a subdirectory of <file>/etc</file>
6991 named after your package.
6995 If your package creates or uses configuration files
6996 outside of <file>/etc</file>, and it is not feasible to modify
6997 the package to use <file>/etc</file> directly, put the files
6998 in <file>/etc</file> and create symbolic links to those files
6999 from the location that the package requires.
7004 <heading>Behavior</heading>
7007 Configuration file handling must conform to the following
7009 <list compact="compact">
7011 local changes must be preserved during a package
7015 configuration files must be preserved when the
7016 package is removed, and only deleted when the
7023 The easy way to achieve this behavior is to make the
7024 configuration file a <tt>conffile</tt>. This is
7025 appropriate only if it is possible to distribute a default
7026 version that will work for most installations, although
7027 some system administrators may choose to modify it. This
7028 implies that the default version will be part of the
7029 package distribution, and must not be modified by the
7030 maintainer scripts during installation (or at any other
7035 In order to ensure that local changes are preserved
7036 correctly, no package may contain or make hard links to
7037 conffiles.<footnote>
7038 Rationale: There are two problems with hard links.
7039 The first is that some editors break the link while
7040 editing one of the files, so that the two files may
7041 unwittingly become unlinked and different. The second
7042 is that <prgn>dpkg</prgn> might break the hard link
7043 while upgrading <tt>conffile</tt>s.
7048 The other way to do it is via the maintainer scripts. In
7049 this case, the configuration file must not be listed as a
7050 <tt>conffile</tt> and must not be part of the package
7051 distribution. If the existence of a file is required for
7052 the package to be sensibly configured it is the
7053 responsibility of the package maintainer to provide
7054 maintainer scripts which correctly create, update and
7055 maintain the file and remove it on purge. (See <ref
7056 id="maintainerscripts"> for more information.) These
7057 scripts must be idempotent (i.e., must work correctly if
7058 <prgn>dpkg</prgn> needs to re-run them due to errors
7059 during installation or removal), must cope with all the
7060 variety of ways <prgn>dpkg</prgn> can call maintainer
7061 scripts, must not overwrite or otherwise mangle the user's
7062 configuration without asking, must not ask unnecessary
7063 questions (particularly during upgrades), and must
7064 otherwise be good citizens.
7068 The scripts are not required to configure every possible
7069 option for the package, but only those necessary to get
7070 the package running on a given system. Ideally the
7071 sysadmin should not have to do any configuration other
7072 than that done (semi-)automatically by the
7073 <prgn>postinst</prgn> script.
7077 A common practice is to create a script called
7078 <file><var>package</var>-configure</file> and have the
7079 package's <prgn>postinst</prgn> call it if and only if the
7080 configuration file does not already exist. In certain
7081 cases it is useful for there to be an example or template
7082 file which the maintainer scripts use. Such files should
7083 be in <file>/usr/share/<var>package</var></file> or
7084 <file>/usr/lib/<var>package</var></file> (depending on whether
7085 they are architecture-independent or not). There should
7086 be symbolic links to them from
7087 <file>/usr/share/doc/<var>package</var>/examples</file> if
7088 they are examples, and should be perfectly ordinary
7089 <prgn>dpkg</prgn>-handled files (<em>not</em>
7090 configuration files).
7094 These two styles of configuration file handling must
7095 not be mixed, for that way lies madness:
7096 <prgn>dpkg</prgn> will ask about overwriting the file
7097 every time the package is upgraded.
7102 <heading>Sharing configuration files</heading>
7105 Packages which specify the same file as a
7106 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7107 with each other. (This is an instance of the general rule
7108 about not sharing files. Note that neither alternatives
7109 nor diversions are likely to be appropriate in this case;
7110 in particular, <prgn>dpkg</prgn> does not handle diverted
7111 <tt>conffile</tt>s well.)
7115 The maintainer scripts must not alter a <tt>conffile</tt>
7116 of <em>any</em> package, including the one the scripts
7121 If two or more packages use the same configuration file
7122 and it is reasonable for both to be installed at the same
7123 time, one of these packages must be defined as
7124 <em>owner</em> of the configuration file, i.e., it will be
7125 the package which handles that file as a configuration
7126 file. Other packages that use the configuration file must
7127 depend on the owning package if they require the
7128 configuration file to operate. If the other package will
7129 use the configuration file if present, but is capable of
7130 operating without it, no dependency need be declared.
7134 If it is desirable for two or more related packages to
7135 share a configuration file <em>and</em> for all of the
7136 related packages to be able to modify that configuration
7137 file, then the following should be done:
7138 <enumlist compact="compact">
7140 One of the related packages (the "owning" package)
7141 will manage the configuration file with maintainer
7142 scripts as described in the previous section.
7145 The owning package should also provide a program
7146 that the other packages may use to modify the
7150 The related packages must use the provided program
7151 to make any desired modifications to the
7152 configuration file. They should either depend on
7153 the core package to guarantee that the configuration
7154 modifier program is available or accept gracefully
7155 that they cannot modify the configuration file if it
7156 is not. (This is in addition to the fact that the
7157 configuration file may not even be present in the
7164 Sometimes it's appropriate to create a new package which
7165 provides the basic infrastructure for the other packages
7166 and which manages the shared configuration files. (The
7167 <tt>sgml-base</tt> package is a good example.)
7172 <heading>User configuration files ("dotfiles")</heading>
7175 The files in <file>/etc/skel</file> will automatically be
7176 copied into new user accounts by <prgn>adduser</prgn>.
7177 No other program should reference the files in
7178 <file>/etc/skel</file>.
7182 Therefore, if a program needs a dotfile to exist in
7183 advance in <file>$HOME</file> to work sensibly, that dotfile
7184 should be installed in <file>/etc/skel</file> and treated as a
7189 However, programs that require dotfiles in order to
7190 operate sensibly are a bad thing, unless they do create
7191 the dotfiles themselves automatically.
7195 Furthermore, programs should be configured by the Debian
7196 default installation to behave as closely to the upstream
7197 default behavior as possible.
7201 Therefore, if a program in a Debian package needs to be
7202 configured in some way in order to operate sensibly, that
7203 should be done using a site-wide configuration file placed
7204 in <file>/etc</file>. Only if the program doesn't support a
7205 site-wide default configuration and the package maintainer
7206 doesn't have time to add it may a default per-user file be
7207 placed in <file>/etc/skel</file>.
7211 <file>/etc/skel</file> should be as empty as we can make it.
7212 This is particularly true because there is no easy (or
7213 necessarily desirable) mechanism for ensuring that the
7214 appropriate dotfiles are copied into the accounts of
7215 existing users when a package is installed.
7221 <heading>Log files</heading>
7223 Log files should usually be named
7224 <file>/var/log/<var>package</var>.log</file>. If you have many
7225 log files, or need a separate directory for permission
7226 reasons (<file>/var/log</file> is writable only by
7227 <file>root</file>), you should usually create a directory named
7228 <file>/var/log/<var>package</var></file> and place your log
7233 Log files must be rotated occasionally so that they don't
7234 grow indefinitely; the best way to do this is to drop a log
7235 rotation configuration file into the directory
7236 <file>/etc/logrotate.d</file> and use the facilities provided by
7237 logrotate.<footnote>
7239 The traditional approach to log files has been to set up
7240 <em>ad hoc</em> log rotation schemes using simple shell
7241 scripts and cron. While this approach is highly
7242 customizable, it requires quite a lot of sysadmin work.
7243 Even though the original Debian system helped a little
7244 by automatically installing a system which can be used
7245 as a template, this was deemed not enough.
7249 The use of <prgn>logrotate</prgn>, a program developed
7250 by Red Hat, is better, as it centralizes log management.
7251 It has both a configuration file
7252 (<file>/etc/logrotate.conf</file>) and a directory where
7253 packages can drop their individual log rotation
7254 configurations (<file>/etc/logrotate.d</file>).
7257 Here is a good example for a logrotate config
7258 file (for more information see <manref name="logrotate"
7260 <example compact="compact">
7261 /var/log/foo/*.log {
7266 /etc/init.d/foo force-reload
7270 This rotates all files under <file>/var/log/foo</file>, saves 12
7271 compressed generations, and forces the daemon to reload its
7272 configuration information after the log rotation.
7276 Log files should be removed when the package is
7277 purged (but not when it is only removed). This should be
7278 done by the <prgn>postrm</prgn> script when it is called
7279 with the argument <tt>purge</tt> (see <ref
7280 id="removedetails">).
7285 <heading>Permissions and owners</heading>
7288 The rules in this section are guidelines for general use.
7289 If necessary you may deviate from the details below.
7290 However, if you do so you must make sure that what is done
7291 is secure and you should try to be as consistent as possible
7292 with the rest of the system. You should probably also
7293 discuss it on <prgn>debian-devel</prgn> first.
7297 Files should be owned by <tt>root.root</tt>, and made
7298 writable only by the owner and universally readable (and
7299 executable, if appropriate), that is mode 644 or 755.
7303 Directories should be mode 755 or (for group-writability)
7304 mode 2775. The ownership of the directory should be
7305 consistent with its mode: if a directory is mode 2775, it
7306 should be owned by the group that needs write access to
7309 When a package is upgraded, and the owner or permissions
7310 of a file included in the package has changed, dpkg
7311 arranges for the ownership and permissions to be
7312 correctly set upon installation. However, this does not
7313 extend to directories; the permissions and ownership of
7314 directories already on the system does not change on
7315 install or upgrade of packages. This makes sense, since
7316 otherwise common directories like <tt>/usr</tt> would
7317 always be in flux. To correctly change permissions of a
7318 directory the package owns, explicit action is required,
7319 usually in the <tt>postinst</tt> script. Care must be
7320 taken to handle downgrades as well, in that case.
7327 Setuid and setgid executables should be mode 4755 or 2755
7328 respectively, and owned by the appropriate user or group.
7329 They should not be made unreadable (modes like 4711 or
7330 2711 or even 4111); doing so achieves no extra security,
7331 because anyone can find the binary in the freely available
7332 Debian package; it is merely inconvenient. For the same
7333 reason you should not restrict read or execute permissions
7334 on non-set-id executables.
7338 Some setuid programs need to be restricted to particular
7339 sets of users, using file permissions. In this case they
7340 should be owned by the uid to which they are set-id, and by
7341 the group which should be allowed to execute them. They
7342 should have mode 4754; again there is no point in making
7343 them unreadable to those users who must not be allowed to
7348 It is possible to arrange that the system administrator can
7349 reconfigure the package to correspond to their local
7350 security policy by changing the permissions on a binary:
7351 they can do this by using <prgn>dpkg-statoverride</prgn>, as
7352 described below.<footnote>
7353 Ordinary files installed by <prgn>dpkg</prgn> (as
7354 opposed to <tt>conffile</tt>s and other similar objects)
7355 normally have their permissions reset to the distributed
7356 permissions when the package is reinstalled. However,
7357 the use of <prgn>dpkg-statoverride</prgn> overrides this
7358 default behavior. If you use this method, you should
7359 remember to describe <prgn>dpkg-statoverride</prgn> in
7360 the package documentation; being a relatively new
7361 addition to Debian, it is probably not yet well-known.
7363 Another method you should consider is to create a group for
7364 people allowed to use the program(s) and make any setuid
7365 executables executable only by that group.
7369 If you need to create a new user or group for your package
7370 there are two possibilities. Firstly, you may need to
7371 make some files in the binary package be owned by this
7372 user or group, or you may need to compile the user or
7373 group id (rather than just the name) into the binary
7374 (though this latter should be avoided if possible, as in
7375 this case you need a statically allocated id).</p>
7378 If you need a statically allocated id, you must ask for a
7379 user or group id from the <tt>base-passwd</tt> maintainer,
7380 and must not release the package until you have been
7381 allocated one. Once you have been allocated one you must
7382 either make the package depend on a version of the
7383 <tt>base-passwd</tt> package with the id present in
7384 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
7385 your package to create the user or group itself with the
7386 correct id (using <tt>adduser</tt>) in its
7387 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
7388 the <prgn>postinst</prgn> is to be preferred if it is
7389 possible, otherwise a pre-dependency will be needed on the
7390 <tt>adduser</tt> package.)
7394 On the other hand, the program might be able to determine
7395 the uid or gid from the user or group name at runtime, so
7396 that a dynamically allocated id can be used. In this case
7397 you should choose an appropriate user or group name,
7398 discussing this on <prgn>debian-devel</prgn> and checking
7399 with the <package/base-passwd/ maintainer that it is unique and that
7400 they do not wish you to use a statically allocated id
7401 instead. When this has been checked you must arrange for
7402 your package to create the user or group if necessary using
7403 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
7404 <prgn>postinst</prgn> script (again, the latter is to be
7405 preferred if it is possible).
7409 Note that changing the numeric value of an id associated
7410 with a name is very difficult, and involves searching the
7411 file system for all appropriate files. You need to think
7412 carefully whether a static or dynamic id is required, since
7413 changing your mind later will cause problems.
7416 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
7418 This section is not intended as policy, but as a
7419 description of the use of <prgn>dpkg-statoverride</prgn>.
7423 <prgn>dpkg-statoverride</prgn> is a replacement for the
7424 deprecated <tt>suidmanager</tt> package. Packages which
7425 previously used <tt>suidmanager</tt> should have a
7426 <tt>Conflicts: suidmanager (<< 0.50)</tt> entry (or even
7427 <tt>(<< 0.52)</tt>), and calls to <tt>suidregister</tt>
7428 and <tt>suidunregister</tt> should now be simply removed
7429 from the maintainer scripts.
7433 If a system administrator wishes to have a file (or
7434 directory or other such thing) installed with owner and
7435 permissions different from those in the distributed Debian
7436 package, they can use the <prgn>dpkg-statoverride</prgn>
7437 program to instruct <prgn>dpkg</prgn> to use the different
7438 settings every time the file is installed. Thus the
7439 package maintainer should distribute the files with their
7440 normal permissions, and leave it for the system
7441 administrator to make any desired changes. For example, a
7442 daemon which is normally required to be setuid root, but
7443 in certain situations could be used without being setuid,
7444 should be installed setuid in the <tt>.deb</tt>. Then the
7445 local system administrator can change this if they wish.
7446 If there are two standard ways of doing it, the package
7447 maintainer can use <tt>debconf</tt> to find out the
7448 preference, and call <prgn>dpkg-statoverride</prgn> in the
7449 maintainer script if necessary to accommodate the system
7450 administrator's choice. Care must be taken during
7451 upgrades to not override an existing setting.
7455 Given the above, <prgn>dpkg-statoverride</prgn> is
7456 essentially a tool for system administrators and would not
7457 normally be needed in the maintainer scripts. There is
7458 one type of situation, though, where calls to
7459 <prgn>dpkg-statoverride</prgn> would be needed in the
7460 maintainer scripts, and that involves packages which use
7461 dynamically allocated user or group ids. In such a
7462 situation, something like the following idiom can be very
7463 helpful in the package's <prgn>postinst</prgn>, where
7464 <tt>sysuser</tt> is a dynamically allocated id:
7466 for i in /usr/bin/foo /usr/sbin/bar
7468 # only do something when no setting exists
7469 if ! dpkg-statoverride --list $i >/dev/null 2>&1
7471 #include: debconf processing, question about foo and bar
7472 if [ "$RET" = "true" ] ; then
7473 dpkg-statoverride --update --add sysuser root 4755 $i
7478 The corresponding <tt>dpkg-statoverride --remove</tt>
7479 calls can then be made unconditionally when the package is
7487 <chapt id="customized-programs">
7488 <heading>Customized programs</heading>
7490 <sect id="arch-spec">
7491 <heading>Architecture specification strings</heading>
7494 If a program needs to specify an <em>architecture specification
7495 string</em> in some place, it should select one of the
7496 strings provided by <tt>dpkg-architecture -L</tt>. The
7497 strings are in the format
7498 <tt><var>os</var>-<var>arch</var></tt>, though the OS part
7499 is sometimes elided, as when the OS is Linux.<footnote>
7500 <p>Currently, the strings are:
7501 i386 ia64 alpha amd64 armeb arm hppa m32r m68k mips
7502 mipsel powerpc ppc64 s390 s390x sh3 sh3eb sh4 sh4eb
7503 sparc darwin-i386 darwin-ia64 darwin-alpha darwin-amd64
7504 darwin-armeb darwin-arm darwin-hppa darwin-m32r
7505 darwin-m68k darwin-mips darwin-mipsel darwin-powerpc
7506 darwin-ppc64 darwin-s390 darwin-s390x darwin-sh3
7507 darwin-sh3eb darwin-sh4 darwin-sh4eb darwin-sparc
7508 freebsd-i386 freebsd-ia64 freebsd-alpha freebsd-amd64
7509 freebsd-armeb freebsd-arm freebsd-hppa freebsd-m32r
7510 freebsd-m68k freebsd-mips freebsd-mipsel freebsd-powerpc
7511 freebsd-ppc64 freebsd-s390 freebsd-s390x freebsd-sh3
7512 freebsd-sh3eb freebsd-sh4 freebsd-sh4eb freebsd-sparc
7513 kfreebsd-i386 kfreebsd-ia64 kfreebsd-alpha
7514 kfreebsd-amd64 kfreebsd-armeb kfreebsd-arm kfreebsd-hppa
7515 kfreebsd-m32r kfreebsd-m68k kfreebsd-mips
7516 kfreebsd-mipsel kfreebsd-powerpc kfreebsd-ppc64
7517 kfreebsd-s390 kfreebsd-s390x kfreebsd-sh3 kfreebsd-sh3eb
7518 kfreebsd-sh4 kfreebsd-sh4eb kfreebsd-sparc knetbsd-i386
7519 knetbsd-ia64 knetbsd-alpha knetbsd-amd64 knetbsd-armeb
7520 knetbsd-arm knetbsd-hppa knetbsd-m32r knetbsd-m68k
7521 knetbsd-mips knetbsd-mipsel knetbsd-powerpc
7522 knetbsd-ppc64 knetbsd-s390 knetbsd-s390x knetbsd-sh3
7523 knetbsd-sh3eb knetbsd-sh4 knetbsd-sh4eb knetbsd-sparc
7524 netbsd-i386 netbsd-ia64 netbsd-alpha netbsd-amd64
7525 netbsd-armeb netbsd-arm netbsd-hppa netbsd-m32r
7526 netbsd-m68k netbsd-mips netbsd-mipsel netbsd-powerpc
7527 netbsd-ppc64 netbsd-s390 netbsd-s390x netbsd-sh3
7528 netbsd-sh3eb netbsd-sh4 netbsd-sh4eb netbsd-sparc
7529 openbsd-i386 openbsd-ia64 openbsd-alpha openbsd-amd64
7530 openbsd-armeb openbsd-arm openbsd-hppa openbsd-m32r
7531 openbsd-m68k openbsd-mips openbsd-mipsel openbsd-powerpc
7532 openbsd-ppc64 openbsd-s390 openbsd-s390x openbsd-sh3
7533 openbsd-sh3eb openbsd-sh4 openbsd-sh4eb openbsd-sparc
7534 hurd-i386 hurd-ia64 hurd-alpha hurd-amd64 hurd-armeb
7535 hurd-arm hurd-hppa hurd-m32r hurd-m68k hurd-mips
7536 hurd-mipsel hurd-powerpc hurd-ppc64 hurd-s390 hurd-s390x
7537 hurd-sh3 hurd-sh3eb hurd-sh4 hurd-sh4eb hurd-sparc
7543 Note that we don't want to use
7544 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
7545 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
7546 since this would make our programs incompatible with other
7547 Linux distributions. We also don't use something like
7548 <tt><var>arch</var>-unknown-linux</tt>, since the
7549 <tt>unknown</tt> does not look very good.
7554 <heading>Daemons</heading>
7557 The configuration files <file>/etc/services</file>,
7558 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
7559 by the <prgn>netbase</prgn> package and must not be modified
7564 If a package requires a new entry in one of these files, the
7565 maintainer should get in contact with the
7566 <prgn>netbase</prgn> maintainer, who will add the entries
7567 and release a new version of the <prgn>netbase</prgn>
7572 The configuration file <file>/etc/inetd.conf</file> must not be
7573 modified by the package's scripts except via the
7574 <prgn>update-inetd</prgn> script or the
7575 <file>DebianNet.pm</file> Perl module. See their documentation
7576 for details on how to add entries.
7580 If a package wants to install an example entry into
7581 <file>/etc/inetd.conf</file>, the entry must be preceded with
7582 exactly one hash character (<tt>#</tt>). Such lines are
7583 treated as "commented out by user" by the
7584 <prgn>update-inetd</prgn> script and are not changed or
7585 activated during package updates.
7590 <heading>Using pseudo-ttys and modifying wtmp, utmp and
7594 Some programs need to create pseudo-ttys. This should be done
7595 using Unix98 ptys if the C library supports it. The resulting
7596 program must not be installed setuid root, unless that
7597 is required for other functionality.
7601 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
7602 <file>/var/log/lastlog</file> must be installed writable by
7603 group <tt>utmp</tt>. Programs which need to modify those
7604 files must be installed setgid <tt>utmp</tt>.
7609 <heading>Editors and pagers</heading>
7612 Some programs have the ability to launch an editor or pager
7613 program to edit or display a text document. Since there are
7614 lots of different editors and pagers available in the Debian
7615 distribution, the system administrator and each user should
7616 have the possibility to choose their preferred editor and
7621 In addition, every program should choose a good default
7622 editor/pager if none is selected by the user or system
7627 Thus, every program that launches an editor or pager must
7628 use the EDITOR or PAGER environment variable to determine
7629 the editor or pager the user wishes to use. If these
7630 variables are not set, the programs <file>/usr/bin/editor</file>
7631 and <file>/usr/bin/pager</file> should be used, respectively.
7635 These two files are managed through the <prgn>dpkg</prgn>
7636 "alternatives" mechanism. Thus every package providing an
7637 editor or pager must call the
7638 <prgn>update-alternatives</prgn> script to register these
7643 If it is very hard to adapt a program to make use of the
7644 EDITOR or PAGER variables, that program may be configured to
7645 use <file>/usr/bin/sensible-editor</file> and
7646 <file>/usr/bin/sensible-pager</file> as the editor or pager
7647 program respectively. These are two scripts provided in the
7648 Debian base system that check the EDITOR and PAGER variables
7649 and launch the appropriate program, and fall back to
7650 <file>/usr/bin/editor</file> and <file>/usr/bin/pager</file> if the
7651 variable is not set.
7655 A program may also use the VISUAL environment variable to
7656 determine the user's choice of editor. If it exists, it
7657 should take precedence over EDITOR. This is in fact what
7658 <file>/usr/bin/sensible-editor</file> does.
7662 It is not required for a package to depend on
7663 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
7664 package to provide such virtual packages.<footnote>
7665 The Debian base system already provides an editor and a
7671 <sect id="web-appl">
7672 <heading>Web servers and applications</heading>
7675 This section describes the locations and URLs that should
7676 be used by all web servers and web applications in the
7683 Cgi-bin executable files are installed in the
7685 <example compact="compact">
7686 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
7688 and should be referred to as
7689 <example compact="compact">
7690 http://localhost/cgi-bin/<var>cgi-bin-name</var>
7696 <p>Access to HTML documents</p>
7699 HTML documents for a package are stored in
7700 <file>/usr/share/doc/<var>package</var></file>
7701 and can be referred to as
7702 <example compact="compact">
7703 http://localhost/doc/<var>package</var>/<var>filename</var>
7708 The web server should restrict access to the document
7709 tree so that only clients on the same host can read
7710 the documents. If the web server does not support such
7711 access controls, then it should not provide access at
7712 all, or ask about providing access during installation.
7717 <p>Access to images</p>
7719 It is recommended that images for a package be stored
7720 in <tt>/usr/share/images/<var>package</var></tt> and
7721 may be referred to through an alias <tt>/images/</tt>
7724 http://localhost/images/<package>/<filename>
7731 <p>Web Document Root</p>
7734 Web Applications should try to avoid storing files in
7735 the Web Document Root. Instead they should use the
7736 /usr/share/doc/<var>package</var> directory for
7737 documents and register the Web Application via the
7738 <package>doc-base</package> package. If access to the
7739 web document root is unavoidable then use
7740 <example compact="compact">
7743 as the Document Root. This might be just a symbolic
7744 link to the location where the system administrator
7745 has put the real document root.
7748 <item><p>Providing httpd and/or httpd-cgi</p>
7750 All web servers should provide the virtual package
7751 <tt>httpd</tt>. If a web server has CGI support it should
7752 provide <tt>httpd-cgi</tt> additionally.
7755 All web applications which do not contain CGI scripts should
7756 depend on <tt>httpd</tt>, all those web applications which
7757 <tt>do</tt> contain CGI scripts, should depend on
7765 <sect id="mail-transport-agents">
7766 <heading>Mail transport, delivery and user agents</heading>
7769 Debian packages which process electronic mail, whether mail
7770 user agents (MUAs) or mail transport agents (MTAs), must
7771 ensure that they are compatible with the configuration
7772 decisions below. Failure to do this may result in lost
7773 mail, broken <tt>From:</tt> lines, and other serious brain
7778 The mail spool is <file>/var/mail</file> and the interface to
7779 send a mail message is <file>/usr/sbin/sendmail</file> (as per
7780 the FHS). On older systems, the mail spool may be
7781 physically located in <file>/var/spool/mail</file>, but all
7782 access to the mail spool should be via the
7783 <file>/var/mail</file> symlink. The mail spool is part of the
7784 base system and not part of the MTA package.
7788 All Debian MUAs, MTAs, MDAs and other mailbox accessing
7789 programs (such as IMAP daemons) must lock the mailbox in an
7790 NFS-safe way. This means that <tt>fcntl()</tt> locking must
7791 be combined with dot locking. To avoid deadlocks, a program
7792 should use <tt>fcntl()</tt> first and dot locking after
7793 this, or alternatively implement the two locking methods in
7794 a non blocking way<footnote>
7795 If it is not possible to establish both locks, the
7796 system shouldn't wait for the second lock to be
7797 established, but remove the first lock, wait a (random)
7798 time, and start over locking again.
7799 </footnote>. Using the functions <tt>maillock</tt> and
7800 <tt>mailunlock</tt> provided by the
7801 <tt>liblockfile*</tt><footnote>
7802 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
7803 to use these functions.
7804 </footnote> packages is the recommended way to realize this.
7808 Mailboxes are generally mode 660
7809 <tt><var>user</var>.mail</tt> unless the system
7810 administrator has chosen otherwise. A MUA may remove a
7811 mailbox (unless it has nonstandard permissions) in which
7812 case the MTA or another MUA must recreate it if needed.
7813 Mailboxes must be writable by group mail.
7817 The mail spool is 2775 <tt>root.mail</tt>, and MUAs should
7818 be setgid mail to do the locking mentioned above (and
7819 must obviously avoid accessing other users' mailboxes
7820 using this privilege).</p>
7823 <file>/etc/aliases</file> is the source file for the system mail
7824 aliases (e.g., postmaster, usenet, etc.), it is the one
7825 which the sysadmin and <prgn>postinst</prgn> scripts may
7826 edit. After <file>/etc/aliases</file> is edited the program or
7827 human editing it must call <prgn>newaliases</prgn>. All MTA
7828 packages must come with a <prgn>newaliases</prgn> program,
7829 even if it does nothing, but older MTA packages did not do
7830 this so programs should not fail if <prgn>newaliases</prgn>
7831 cannot be found. Note that because of this, all MTA
7832 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
7833 <tt>Replaces: mail-transport-agent</tt> control file
7838 The convention of writing <tt>forward to
7839 <var>address</var></tt> in the mailbox itself is not
7840 supported. Use a <tt>.forward</tt> file instead.</p>
7843 The <prgn>rmail</prgn> program used by UUCP
7844 for incoming mail should be <file>/usr/sbin/rmail</file>.
7845 Likewise, <prgn>rsmtp</prgn>, for receiving
7846 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
7850 If your package needs to know what hostname to use on (for
7851 example) outgoing news and mail messages which are generated
7852 locally, you should use the file <file>/etc/mailname</file>. It
7853 will contain the portion after the username and <tt>@</tt>
7854 (at) sign for email addresses of users on the machine
7855 (followed by a newline).
7859 Such a package should check for the existence of this file
7860 when it is being configured. If it exists, it should be
7861 used without comment, although an MTA's configuration script
7862 may wish to prompt the user even if it finds that this file
7863 exists. If the file does not exist, the package should
7864 prompt the user for the value (preferably using
7865 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
7866 as well as using it in the package's configuration. The
7867 prompt should make it clear that the name will not just be
7868 used by that package. For example, in this situation the
7869 <tt>inn</tt> package could say something like:
7870 <example compact="compact">
7871 Please enter the "mail name" of your system. This is the
7872 hostname portion of the address to be shown on outgoing
7873 news and mail messages. The default is
7874 <var>syshostname</var>, your system's host name. Mail
7875 name ["<var>syshostname</var>"]:
7877 where <var>syshostname</var> is the output of <tt>hostname
7883 <heading>News system configuration</heading>
7886 All the configuration files related to the NNTP (news)
7887 servers and clients should be located under
7888 <file>/etc/news</file>.</p>
7891 There are some configuration issues that apply to a number
7892 of news clients and server packages on the machine. These
7896 <tag><file>/etc/news/organization</file></tag>
7898 A string which should appear as the
7899 organization header for all messages posted
7900 by NNTP clients on the machine
7903 <tag><file>/etc/news/server</file></tag>
7905 Contains the FQDN of the upstream NNTP
7906 server, or localhost if the local machine is
7911 Other global files may be added as required for cross-package news
7918 <heading>Programs for the X Window System</heading>
7921 <heading>Providing X support and package priorities</heading>
7924 Programs that can be configured with support for the X
7925 Window System must be configured to do so and must declare
7926 any package dependencies necessary to satisfy their
7927 runtime requirements when using the X Window System. If
7928 such a package is of higher priority than the X packages
7929 on which it depends, it is required that either the
7930 X-specific components be split into a separate package, or
7931 that an alternative version of the package, which includes
7932 X support, be provided, or that the package's priority be
7938 <heading>Packages providing an X server</heading>
7941 Packages that provide an X server that, directly or
7942 indirectly, communicates with real input and display
7943 hardware should declare in their control data that they
7944 provide the virtual package <tt>xserver</tt>.<footnote>
7945 This implements current practice, and provides an
7946 actual policy for usage of the <tt>xserver</tt>
7947 virtual package which appears in the virtual packages
7948 list. In a nutshell, X servers that interface
7949 directly with the display and input hardware or via
7950 another subsystem (e.g., GGI) should provide
7951 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
7952 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
7958 <heading>Packages providing a terminal emulator</heading>
7961 Packages that provide a terminal emulator for the X Window
7962 System which meet the criteria listed below should declare
7963 in their control data that they provide the virtual
7964 package <tt>x-terminal-emulator</tt>. They should also
7965 register themselves as an alternative for
7966 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
7971 To be an <tt>x-terminal-emulator</tt>, a program must:
7972 <list compact="compact">
7974 Be able to emulate a DEC VT100 terminal, or a
7975 compatible terminal.
7979 Support the command-line option <tt>-e
7980 <var>command</var></tt>, which creates a new
7981 terminal window<footnote>
7982 "New terminal window" does not necessarily mean
7983 a new top-level X window directly parented by
7984 the window manager; it could, if the terminal
7985 emulator application were so coded, be a new
7986 "view" in a multiple-document interface (MDI).
7988 and runs the specified <var>command</var>,
7989 interpreting the entirety of the rest of the command
7990 line as a command to pass straight to exec, in the
7991 manner that <tt>xterm</tt> does.
7995 Support the command-line option <tt>-T
7996 <var>title</var></tt>, which creates a new terminal
7997 window with the window title <var>title</var>.
8004 <heading>Packages providing a window manager</heading>
8007 Packages that provide a window manager should declare in
8008 their control data that they provide the virtual package
8009 <tt>x-window-manager</tt>. They should also register
8010 themselves as an alternative for
8011 <file>/usr/bin/x-window-manager</file>, with a priority
8012 calculated as follows:
8013 <list compact="compact">
8015 Start with a priority of 20.
8019 If the window manager supports the Debian menu
8020 system, add 20 points if this support is available
8021 in the package's default configuration (i.e., no
8022 configuration files belonging to the system or user
8023 have to be edited to activate the feature); if
8024 configuration files must be modified, add only 10
8030 If the window manager complies with <url
8031 id="http://www.freedesktop.org/Standards/wm-spec"
8032 name="The Window Manager Specification Project">,
8033 written by the <url id="http://www.freedesktop.org/"
8034 name="Free Desktop Group">, add 40 points.
8038 If the window manager permits the X session to be
8039 restarted using a <em>different</em> window manager
8040 (without killing the X server) in its default
8041 configuration, add 10 points; otherwise add none.
8048 <heading>Packages providing fonts</heading>
8051 Packages that provide fonts for the X Window
8053 For the purposes of Debian Policy, a "font for the X
8054 Window System" is one which is accessed via X protocol
8055 requests. Fonts for the Linux console, for PostScript
8056 renderer, or any other purpose, do not fit this
8057 definition. Any tool which makes such fonts available
8058 to the X Window System, however, must abide by this
8061 must do a number of things to ensure that they are both
8062 available without modification of the X or font server
8063 configuration, and that they do not corrupt files used by
8064 other font packages to register information about
8068 Fonts of any type supported by the X Window System
8069 must be in a separate binary package from any
8070 executables, libraries, or documentation (except
8071 that specific to the fonts shipped, such as their
8072 license information). If one or more of the fonts
8073 so packaged are necessary for proper operation of
8074 the package with which they are associated the font
8075 package may be Recommended; if the fonts merely
8076 provide an enhancement, a Suggests relationship may
8077 be used. Packages must not Depend on font
8079 This is because the X server may retrieve fonts
8080 from the local file system or over the network
8081 from an X font server; the Debian package system
8082 is empowered to deal only with the local
8088 BDF fonts must be converted to PCF fonts with the
8089 <prgn>bdftopcf</prgn> utility (available in the
8090 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8091 placed in a directory that corresponds to their
8093 <list compact="compact">
8095 100 dpi fonts must be placed in
8096 <file>/usr/share/fonts/X11/100dpi/</file>.
8100 75 dpi fonts must be placed in
8101 <file>/usr/share/fonts/X11/75dpi/</file>.
8105 Character-cell fonts, cursor fonts, and other
8106 low-resolution fonts must be placed in
8107 <file>/usr/share/fonts/X11/misc/</file>.
8113 Speedo fonts must be placed in
8114 <file>/usr/share/fonts/X11/Speedo/</file>.
8118 Type 1 fonts must be placed in
8119 <file>/usr/share/fonts/X11/Type1/</file>. If font
8120 metric files are available, they must be placed here
8125 Subdirectories of <file>/usr/share/fonts/X11/</file>
8126 other than those listed above must be neither
8127 created nor used. (The <file>PEX</file>, <file>CID</file>,
8128 and <file>cyrillic</file> directories are excepted for
8129 historical reasons, but installation of files into
8130 these directories remains discouraged.)
8134 Font packages may, instead of placing files directly
8135 in the X font directories listed above, provide
8136 symbolic links in that font directory pointing to
8137 the files' actual location in the filesystem. Such
8138 a location must comply with the FHS.
8142 Font packages should not contain both 75dpi and
8143 100dpi versions of a font. If both are available,
8144 they should be provided in separate binary packages
8145 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8146 the names of the packages containing the
8147 corresponding fonts.
8151 Fonts destined for the <file>misc</file> subdirectory
8152 should not be included in the same package as 75dpi
8153 or 100dpi fonts; instead, they should be provided in
8154 a separate package with <tt>-misc</tt> appended to
8159 Font packages must not provide the files
8160 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8161 <file>fonts.scale</file> in a font directory:
8164 <file>fonts.dir</file> files must not be provided at all.
8168 <file>fonts.alias</file> and <file>fonts.scale</file>
8169 files, if needed, should be provided in the
8171 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8172 where <var>fontdir</var> is the name of the
8174 <file>/usr/share/fonts/X11/</file> where the
8175 package's corresponding fonts are stored
8176 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8177 <var>package</var> is the name of the package
8178 that provides these fonts, and
8179 <var>extension</var> is either <tt>scale</tt>
8180 or <tt>alias</tt>, whichever corresponds to
8187 Font packages must declare a dependency on
8188 <tt>xfonts-utils</tt> in their control
8193 Font packages that provide one or more
8194 <file>fonts.scale</file> files as described above must
8195 invoke <prgn>update-fonts-scale</prgn> on each
8196 directory into which they installed fonts
8197 <em>before</em> invoking
8198 <prgn>update-fonts-dir</prgn> on that directory.
8199 This invocation must occur in both the
8200 <prgn>postinst</prgn> (for all arguments) and
8201 <prgn>postrm</prgn> (for all arguments except
8202 <tt>upgrade</tt>) scripts.
8206 Font packages that provide one or more
8207 <file>fonts.alias</file> files as described above must
8208 invoke <prgn>update-fonts-alias</prgn> on each
8209 directory into which they installed fonts. This
8210 invocation must occur in both the
8211 <prgn>postinst</prgn> (for all arguments) and
8212 <prgn>postrm</prgn> (for all arguments except
8213 <tt>upgrade</tt>) scripts.
8217 Font packages must invoke
8218 <prgn>update-fonts-dir</prgn> on each directory into
8219 which they installed fonts. This invocation must
8220 occur in both the <prgn>postinst</prgn> (for all
8221 arguments) and <prgn>postrm</prgn> (for all
8222 arguments except <tt>upgrade</tt>) scripts.
8226 Font packages must not provide alias names for the
8227 fonts they include which collide with alias names
8228 already in use by fonts already packaged.
8232 Font packages must not provide fonts with the same
8233 XLFD registry name as another font already packaged.
8240 <heading>Application defaults files</heading>
8243 Application defaults files must be installed in the
8244 directory <file>/etc/X11/app-defaults/</file> (use of a
8245 localized subdirectory of <file>/etc/X11/</file> as described
8246 in the <em>X Toolkit Intrinsics - C Language
8247 Interface</em> manual is also permitted). They must be
8248 registered as <tt>conffile</tt>s or handled as
8249 configuration files. Packages must not provide the
8250 directory <file>/usr/X11R6/lib/X11/app-defaults/</file>.
8254 Customization of programs' X resources may also be
8255 supported with the provision of a file with the same name
8256 as that of the package placed in the
8257 <file>/etc/X11/Xresources/</file> directory, which must
8258 registered as a <tt>conffile</tt> or handled as a
8259 configuration file.<footnote>
8260 Note that this mechanism is not the same as using
8261 app-defaults; app-defaults are tied to the client
8262 binary on the local file system, whereas X resources
8263 are stored in the X server and affect all connecting
8266 <em>Important:</em> packages that install files into the
8267 <file>/etc/X11/Xresources/</file> directory must conflict with
8268 <tt>xbase (<< 3.3.2.3a-2)</tt>; if this is not done
8269 it is possible for the installing package to destroy a
8270 previously-existing <file>/etc/X11/Xresources</file> file
8271 which had been customized by the system administrator.
8276 <heading>Installation directory issues</heading>
8279 Packages using the X Window System should not be
8280 configured to install files under the
8281 <file>/usr/X11R6/</file> directory. The
8282 <file>/usr/X11R6/</file> directory hierarchy should be
8283 regarded as obsolete.
8287 Programs that use GNU <prgn>autoconf</prgn> and
8288 <prgn>automake</prgn> are usually easily configured at
8289 compile time to use <file>/usr/</file> instead of
8290 <file>/usr/X11R6/</file>, and this should be done whenever
8291 possible. Configuration files for window managers and
8292 display managers should be placed in a subdirectory of
8293 <file>/etc/X11/</file> corresponding to the package name due
8294 to these programs' tight integration with the mechanisms
8295 of the X Window System. Application-level programs should
8296 use the <file>/etc/</file> directory unless otherwise mandated
8301 The installation of files into subdirectories
8302 of <file>/usr/X11R6/include/X11/</file> and
8303 <file>/usr/X11R6/lib/X11/</file> is now prohibited;
8304 package maintainers should determine if subdirectories of
8305 <file>/usr/lib/</file> and <file>/usr/share/</file> can be used
8310 Packages should install any relevant files into the
8311 directories <file>/usr/include/X11/</file> and
8312 <file>/usr/lib/X11/</file>, but if they do so, they must
8313 pre-depend on <tt>x11-common (>=
8314 1:7.0.0)</tt><footnote>
8316 These libraries used to be all symbolic
8317 links. However, with <tt>X11R7</tt>,
8318 <tt>/usr/include/X11</tt> and <tt>/usr/lib/X11</tt>
8319 are now real directories, and packages
8320 <strong>should</strong> ship their files here instead
8321 of in <tt>/usr/X11R6/{include,lib}/X11</tt>.
8322 <tt>x11-common (>= 1:7.0.0) </tt> is the package
8323 responsible for converting these symlinks into
8331 <heading>The OSF/Motif and OpenMotif libraries</heading>
8334 <em>Programs that require the non-DFSG-compliant OSF/Motif or
8335 OpenMotif libraries</em><footnote>
8336 OSF/Motif and OpenMotif are collectively referred to as
8337 "Motif" in this policy document.
8339 should be compiled against and tested with LessTif (a free
8340 re-implementation of Motif) instead. If the maintainer
8341 judges that the program or programs do not work
8342 sufficiently well with LessTif to be distributed and
8343 supported, but do so when compiled against Motif, then two
8344 versions of the package should be created; one linked
8345 statically against Motif and with <tt>-smotif</tt>
8346 appended to the package name, and one linked dynamically
8347 against Motif and with <tt>-dmotif</tt> appended to the
8352 Both Motif-linked versions are dependent
8353 upon non-DFSG-compliant software and thus cannot be
8354 uploaded to the <em>main</em> distribution; if the
8355 software is itself DFSG-compliant it may be uploaded to
8356 the <em>contrib</em> distribution. While known existing
8357 versions of Motif permit unlimited redistribution of
8358 binaries linked against the library (whether statically or
8359 dynamically), it is the package maintainer's
8360 responsibility to determine whether this is permitted by
8361 the license of the copy of Motif in their possession.
8367 <heading>Perl programs and modules</heading>
8370 Perl programs and modules should follow the current Perl policy.
8374 The Perl policy can be found in the <tt>perl-policy</tt>
8375 files in the <tt>debian-policy</tt> package.
8376 It is also available from the Debian web mirrors at
8377 <tt><url name="/doc/packaging-manuals/perl-policy/"
8378 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
8383 <heading>Emacs lisp programs</heading>
8386 Please refer to the "Debian Emacs Policy" for details of how to
8387 package emacs lisp programs.
8391 The Emacs policy is available in
8392 <file>debian-emacs-policy.gz</file> of the
8393 <package>emacsen-common</package> package.
8394 It is also available from the Debian web mirrors at
8395 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
8396 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
8401 <heading>Games</heading>
8404 The permissions on <file>/var/games</file> are mode 755, owner
8405 <tt>root</tt> and group <tt>root</tt>.
8409 Each game decides on its own security policy.</p>
8412 Games which require protected, privileged access to
8413 high-score files, saved games, etc., may be made
8414 set-<em>group</em>-id (mode 2755) and owned by
8415 <tt>root.games</tt>, and use files and directories with
8416 appropriate permissions (770 <tt>root.games</tt>, for
8417 example). They must not be made
8418 set-<em>user</em>-id, as this causes security problems. (If
8419 an attacker can subvert any set-user-id game they can
8420 overwrite the executable of any other, causing other players
8421 of these games to run a Trojan horse program. With a
8422 set-group-id game the attacker only gets access to less
8423 important game data, and if they can get at the other
8424 players' accounts at all it will take considerably more
8428 Some packages, for example some fortune cookie programs, are
8429 configured by the upstream authors to install with their
8430 data files or other static information made unreadable so
8431 that they can only be accessed through set-id programs
8432 provided. You should not do this in a Debian package: anyone can
8433 download the <file>.deb</file> file and read the data from it,
8434 so there is no point making the files unreadable. Not
8435 making the files unreadable also means that you don't have
8436 to make so many programs set-id, which reduces the risk of a
8440 As described in the FHS, binaries of games should be
8441 installed in the directory <file>/usr/games</file>. This also
8442 applies to games that use the X Window System. Manual pages
8443 for games (X and non-X games) should be installed in
8444 <file>/usr/share/man/man6</file>.</p>
8450 <heading>Documentation</heading>
8453 <heading>Manual pages</heading>
8456 You should install manual pages in <prgn>nroff</prgn> source
8457 form, in appropriate places under <file>/usr/share/man</file>.
8458 You should only use sections 1 to 9 (see the FHS for more
8459 details). You must not install a pre-formatted "cat page".
8463 Each program, utility, and function should have an
8464 associated manual page included in the same package. It is
8465 suggested that all configuration files also have a manual
8466 page included as well. Manual pages for protocols and other
8467 auxiliary things are optional.
8471 If no manual page is available, this is considered as a bug
8472 and should be reported to the Debian Bug Tracking System (the
8473 maintainer of the package is allowed to write this bug report
8474 themselves, if they so desire). Do not close the bug report
8475 until a proper man page is available.<footnote>
8476 It is not very hard to write a man page. See the
8477 <url id="http://www.schweikhardt.net/man_page_howto.html"
8478 name="Man-Page-HOWTO">,
8479 <manref name="man" section="7">, the examples
8480 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
8481 the helper programs <prgn>help2man</prgn>, or the
8482 directory <file>/usr/share/doc/man-db/examples</file>.
8487 You may forward a complaint about a missing man page to the
8488 upstream authors, and mark the bug as forwarded in the
8489 Debian bug tracking system. Even though the GNU Project do
8490 not in general consider the lack of a man page to be a bug,
8491 we do; if they tell you that they don't consider it a bug
8492 you should leave the bug in our bug tracking system open
8497 Manual pages should be installed compressed using <tt>gzip -9</tt>.
8501 If one man page needs to be accessible via several names it
8502 is better to use a symbolic link than the <file>.so</file>
8503 feature, but there is no need to fiddle with the relevant
8504 parts of the upstream source to change from <file>.so</file> to
8505 symlinks: don't do it unless it's easy. You should not
8506 create hard links in the manual page directories, nor put
8507 absolute filenames in <file>.so</file> directives. The filename
8508 in a <file>.so</file> in a man page should be relative to the
8509 base of the man page tree (usually
8510 <file>/usr/share/man</file>). If you do not create any links
8511 (whether symlinks, hard links, or <tt>.so</tt> directives)
8512 in the file system to the alternate names of the man page,
8513 then you should not rely on <prgn>man</prgn> finding your
8514 man page under those names based solely on the information in
8515 the man page's header.<footnote>
8516 Supporting this in <prgn>man</prgn> often requires
8517 unreasonable processing time to find a manual page or to
8518 report that none exists, and moves knowledge into man's
8519 database that would be better left in the file system.
8520 This support is therefore deprecated and will cease to
8521 be present in the future.
8527 <heading>Info documents</heading>
8530 Info documents should be installed in <file>/usr/share/info</file>.
8531 They should be compressed with <tt>gzip -9</tt>.
8535 Your package should call <prgn>install-info</prgn> to update
8536 the Info <file>dir</file> file in its <prgn>postinst</prgn>
8537 script when called with a <tt>configure</tt> argument, for
8539 <example compact="compact">
8540 install-info --quiet --section Development Development \
8541 /usr/share/info/foobar.info
8545 It is a good idea to specify a section for the location of
8546 your program; this is done with the <tt>--section</tt>
8547 switch. To determine which section to use, you should look
8548 at <file>/usr/share/info/dir</file> on your system and choose the most
8549 relevant (or create a new section if none of the current
8550 sections are relevant). Note that the <tt>--section</tt>
8551 flag takes two arguments; the first is a regular expression
8552 to match (case-insensitively) against an existing section,
8553 the second is used when creating a new one.</p>
8556 You should remove the entries in the <prgn>prerm</prgn>
8557 script when called with a <tt>remove</tt> argument:
8558 <example compact="compact">
8559 install-info --quiet --remove /usr/share/info/foobar.info
8563 If <prgn>install-info</prgn> cannot find a description entry
8564 in the Info file you must supply one. See <manref
8565 name="install-info" section="8"> for details.</p>
8569 <heading>Additional documentation</heading>
8572 Any additional documentation that comes with the package may
8573 be installed at the discretion of the package maintainer.
8574 Plain text documentation should be installed in the directory
8575 <file>/usr/share/doc/<var>package</var></file>, where
8576 <var>package</var> is the name of the package, and
8577 compressed with <tt>gzip -9</tt> unless it is small.
8581 If a package comes with large amounts of documentation which
8582 many users of the package will not require you should create
8583 a separate binary package to contain it, so that it does not
8584 take up disk space on the machines of users who do not need
8585 or want it installed.</p>
8588 It is often a good idea to put text information files
8589 (<file>README</file>s, changelogs, and so forth) that come with
8590 the source package in <file>/usr/share/doc/<var>package</var></file>
8591 in the binary package. However, you don't need to install
8592 the instructions for building and installing the package, of
8596 Packages must not require the existence of any files in
8597 <file>/usr/share/doc/</file> in order to function
8599 The system administrator should be able to
8600 delete files in <file>/usr/share/doc/</file> without causing
8601 any programs to break.
8603 Any files that are referenced by programs but are also
8604 useful as stand alone documentation should be installed under
8605 <file>/usr/share/<var>package</var>/</file> with symbolic links from
8606 <file>/usr/share/doc/<var>package</var></file>.
8610 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8611 link to another directory in <file>/usr/share/doc</file> only if
8612 the two packages both come from the same source and the
8613 first package Depends on the second.<footnote>
8615 Please note that this does not override the section on
8616 changelog files below, so the file
8617 <file>/usr/share/<var>package</var>/changelog.Debian.gz</file>
8618 must refer to the changelog for the current version of
8619 <var>package</var> in question. In practice, this means
8620 that the sources of the target and the destination of the
8621 symlink must be the same (same source package and
8628 Former Debian releases placed all additional documentation
8629 in <file>/usr/doc/<var>package</var></file>. This has been
8630 changed to <file>/usr/share/doc/<var>package</var></file>,
8631 and packages must not put documentation in the directory
8632 <file>/usr/doc/<var>package</var></file>. <footnote>
8633 At this phase of the transition, we no longer require a
8634 symbolic link in <file>/usr/doc/</file>. At a later point,
8635 policy shall change to make the symbolic links a bug.
8641 <heading>Preferred documentation formats</heading>
8644 The unification of Debian documentation is being carried out
8648 If your package comes with extensive documentation in a
8649 markup format that can be converted to various other formats
8650 you should if possible ship HTML versions in a binary
8651 package, in the directory
8652 <file>/usr/share/doc/<var>appropriate-package</var></file> or
8653 its subdirectories.<footnote>
8654 The rationale: The important thing here is that HTML
8655 docs should be available in <em>some</em> package, not
8656 necessarily in the main binary package.
8661 Other formats such as PostScript may be provided at the
8662 package maintainer's discretion.
8666 <sect id="copyrightfile">
8667 <heading>Copyright information</heading>
8670 Every package must be accompanied by a verbatim copy of its
8671 copyright and distribution license in the file
8672 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
8673 file must neither be compressed nor be a symbolic link.
8677 In addition, the copyright file must say where the upstream
8678 sources (if any) were obtained. It should name the original
8679 authors of the package and the Debian maintainer(s) who were
8680 involved with its creation.</p>
8683 A copy of the file which will be installed in
8684 <file>/usr/share/doc/<var>package</var>/copyright</file> should
8685 be in <file>debian/copyright</file> in the source package.
8689 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8690 link to another directory in <file>/usr/share/doc</file> only if
8691 the two packages both come from the same source and the
8692 first package Depends on the second. These rules are
8693 important because copyrights must be extractable by
8698 Packages distributed under the UCB BSD license, the Artistic
8699 license, the GNU GPL (version 2 or 3), the GNU LGPL (versions
8700 2, 2.1, or 3), and the GNU FDL (version 1.2) should refer to
8701 the corresponding files under
8702 <file>/usr/share/common-licenses</file>,<footnote>
8705 <file>/usr/share/common-licenses/BSD</file>,
8706 <file>/usr/share/common-licenses/Artistic</file>,
8707 <file>/usr/share/common-licenses/GPL-2</file>,
8708 <file>/usr/share/common-licenses/GPL-3</file>,
8709 <file>/usr/share/common-licenses/LGPL-2</file>,
8710 <file>/usr/share/common-licenses/LGPL-2.1</file>,
8711 <file>/usr/share/common-licenses/LGPL-3</file>, and
8712 <file>/usr/share/common-licenses/GFDL-1.2</file>,
8715 </footnote> rather than quoting them in the copyright
8720 You should not use the copyright file as a general <file>README</file>
8721 file. If your package has such a file it should be
8722 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
8723 <file>README.Debian</file> or some other appropriate place.</p>
8727 <heading>Examples</heading>
8730 Any examples (configurations, source files, whatever),
8731 should be installed in a directory
8732 <file>/usr/share/doc/<var>package</var>/examples</file>. These
8733 files should not be referenced by any program: they're there
8734 for the benefit of the system administrator and users as
8735 documentation only. Architecture-specific example files
8736 should be installed in a directory
8737 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
8739 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
8740 latter directory itself may be a symbolic link to the
8745 If the purpose of a package is to provide examples, then the
8746 example files may be installed into
8747 <file>/usr/share/doc/<var>package</var></file>.
8751 <sect id="changelogs">
8752 <heading>Changelog files</heading>
8755 Packages that are not Debian-native must contain a
8756 compressed copy of the <file>debian/changelog</file> file from
8757 the Debian source tree in
8758 <file>/usr/share/doc/<var>package</var></file> with the name
8759 <file>changelog.Debian.gz</file>.
8763 If an upstream changelog is available, it should be accessible as
8764 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
8765 plain text. If the upstream changelog is distributed in
8766 HTML, it should be made available in that form as
8767 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
8768 and a plain text <file>changelog.gz</file> should be generated
8769 from it using, for example, <tt>lynx -dump -nolist</tt>. If
8770 the upstream changelog files do not already conform to this
8771 naming convention, then this may be achieved either by
8772 renaming the files, or by adding a symbolic link, at the
8773 maintainer's discretion.<footnote>
8774 Rationale: People should not have to look in places for
8775 upstream changelogs merely because they are given
8776 different names or are distributed in HTML format.
8781 All of these files should be installed compressed using
8782 <tt>gzip -9</tt>, as they will become large with time even
8783 if they start out small.
8787 If the package has only one changelog which is used both as
8788 the Debian changelog and the upstream one because there is
8789 no separate upstream maintainer then that changelog should
8790 usually be installed as
8791 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
8792 there is a separate upstream maintainer, but no upstream
8793 changelog, then the Debian changelog should still be called
8794 <file>changelog.Debian.gz</file>.
8798 For details about the format and contents of the Debian
8799 changelog file, please see <ref id="dpkgchangelog">.
8804 <appendix id="pkg-scope">
8805 <heading>Introduction and scope of these appendices</heading>
8808 These appendices are taken essentially verbatim from the
8809 now-deprecated Packaging Manual, version 3.2.1.0. They are
8810 the chapters which are likely to be of use to package
8811 maintainers and which have not already been included in the
8812 policy document itself. Most of these sections are very likely
8813 not relevant to policy; they should be treated as
8814 documentation for the packaging system. Please note that these
8815 appendices are included for convenience, and for historical
8816 reasons: they used to be part of policy package, and they have
8817 not yet been incorporated into dpkg documentation. However,
8818 they still have value, and hence they are presented here.
8822 They have not yet been checked to ensure that they are
8823 compatible with the contents of policy, and if there are any
8824 contradictions, the version in the main policy document takes
8825 precedence. The remaining chapters of the old Packaging
8826 Manual have also not been read in detail to ensure that there
8827 are not parts which have been left out. Both of these will be
8832 Certain parts of the Packaging manual were integrated into the
8833 Policy Manual proper, and removed from the appendices. Links
8834 have been placed from the old locations to the new ones.
8838 <prgn>dpkg</prgn> is a suite of programs for creating binary
8839 package files and installing and removing them on Unix
8841 <prgn>dpkg</prgn> is targeted primarily at Debian
8842 GNU/Linux, but may work on or be ported to other
8848 The binary packages are designed for the management of
8849 installed executable programs (usually compiled binaries) and
8850 their associated data, though source code examples and
8851 documentation are provided as part of some packages.</p>
8854 This manual describes the technical aspects of creating Debian
8855 binary packages (<file>.deb</file> files). It documents the
8856 behavior of the package management programs
8857 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
8858 they interact with packages.</p>
8861 It also documents the interaction between
8862 <prgn>dselect</prgn>'s core and the access method scripts it
8863 uses to actually install the selected packages, and describes
8864 how to create a new access method.</p>
8867 This manual does not go into detail about the options and
8868 usage of the package building and installation tools. It
8869 should therefore be read in conjunction with those programs'
8874 The utility programs which are provided with <prgn>dpkg</prgn>
8875 for managing various system configuration and similar issues,
8876 such as <prgn>update-rc.d</prgn> and
8877 <prgn>install-info</prgn>, are not described in detail here -
8878 please see their man pages.
8882 It is assumed that the reader is reasonably familiar with the
8883 <prgn>dpkg</prgn> System Administrators' manual.
8884 Unfortunately this manual does not yet exist.
8888 The Debian version of the FSF's GNU hello program is provided
8889 as an example for people wishing to create Debian
8890 packages. The Debian <prgn>debmake</prgn> package is
8891 recommended as a very helpful tool in creating and maintaining
8892 Debian packages. However, while the tools and examples are
8893 helpful, they do not replace the need to read and follow the
8894 Policy and Programmer's Manual.</p>
8897 <appendix id="pkg-binarypkg">
8898 <heading>Binary packages (from old Packaging Manual)</heading>
8901 The binary package has two main sections. The first part
8902 consists of various control information files and scripts used
8903 by <prgn>dpkg</prgn> when installing and removing. See <ref
8904 id="pkg-controlarea">.
8908 The second part is an archive containing the files and
8909 directories to be installed.
8913 In the future binary packages may also contain other
8914 components, such as checksums and digital signatures. The
8915 format for the archive is described in full in the
8916 <file>deb(5)</file> man page.
8920 <sect id="pkg-bincreating"><heading>Creating package files -
8921 <prgn>dpkg-deb</prgn>
8925 All manipulation of binary package files is done by
8926 <prgn>dpkg-deb</prgn>; it's the only program that has
8927 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
8928 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
8929 will spot that the options requested are appropriate to
8930 <prgn>dpkg-deb</prgn> and invoke that instead with the same
8935 In order to create a binary package you must make a
8936 directory tree which contains all the files and directories
8937 you want to have in the file system data part of the package.
8938 In Debian-format source packages this directory is usually
8939 <file>debian/tmp</file>, relative to the top of the package's
8944 They should have the locations (relative to the root of the
8945 directory tree you're constructing) ownerships and
8946 permissions which you want them to have on the system when
8951 With current versions of <prgn>dpkg</prgn> the uid/username
8952 and gid/groupname mappings for the users and groups being
8953 used should be the same on the system where the package is
8954 built and the one where it is installed.
8958 You need to add one special directory to the root of the
8959 miniature file system tree you're creating:
8960 <prgn>DEBIAN</prgn>. It should contain the control
8961 information files, notably the binary package control file
8962 (see <ref id="pkg-controlfile">).
8966 The <prgn>DEBIAN</prgn> directory will not appear in the
8967 file system archive of the package, and so won't be installed
8968 by <prgn>dpkg</prgn> when the package is installed.
8972 When you've prepared the package, you should invoke:
8974 dpkg --build <var>directory</var>
8979 This will build the package in
8980 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
8981 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
8982 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
8987 See the man page <manref name="dpkg-deb" section="8"> for details of how
8988 to examine the contents of this newly-created file. You may find the
8989 output of following commands enlightening:
8991 dpkg-deb --info <var>filename</var>.deb
8992 dpkg-deb --contents <var>filename</var>.deb
8993 dpkg --contents <var>filename</var>.deb
8995 To view the copyright file for a package you could use this command:
8997 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - \*/copyright | pager
9002 <sect id="pkg-controlarea">
9003 <heading>Package control information files</heading>
9006 The control information portion of a binary package is a
9007 collection of files with names known to <prgn>dpkg</prgn>.
9008 It will treat the contents of these files specially - some
9009 of them contain information used by <prgn>dpkg</prgn> when
9010 installing or removing the package; others are scripts which
9011 the package maintainer wants <prgn>dpkg</prgn> to run.
9015 It is possible to put other files in the package control
9016 area, but this is not generally a good idea (though they
9017 will largely be ignored).
9021 Here is a brief list of the control info files supported by
9022 <prgn>dpkg</prgn> and a summary of what they're used for.
9027 <tag><tt>control</tt>
9030 This is the key description file used by
9031 <prgn>dpkg</prgn>. It specifies the package's name
9032 and version, gives its description for the user,
9033 states its relationships with other packages, and so
9034 forth. See <ref id="sourcecontrolfiles"> and
9035 <ref id="binarycontrolfiles">.
9039 It is usually generated automatically from information
9040 in the source package by the
9041 <prgn>dpkg-gencontrol</prgn> program, and with
9042 assistance from <prgn>dpkg-shlibdeps</prgn>.
9043 See <ref id="pkg-sourcetools">.
9047 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9052 These are executable files (usually scripts) which
9053 <prgn>dpkg</prgn> runs during installation, upgrade
9054 and removal of packages. They allow the package to
9055 deal with matters which are particular to that package
9056 or require more complicated processing than that
9057 provided by <prgn>dpkg</prgn>. Details of when and
9058 how they are called are in <ref id="maintainerscripts">.
9062 It is very important to make these scripts idempotent.
9063 See <ref id="idempotency">.
9067 The maintainer scripts are guaranteed to run with a
9068 controlling terminal and can interact with the user.
9069 See <ref id="controllingterminal">.
9073 <tag><tt>conffiles</tt>
9076 This file contains a list of configuration files which
9077 are to be handled automatically by <prgn>dpkg</prgn>
9078 (see <ref id="pkg-conffiles">). Note that not necessarily
9079 every configuration file should be listed here.
9082 <tag><tt>shlibs</tt>
9085 This file contains a list of the shared libraries
9086 supplied by the package, with dependency details for
9087 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9088 when it determines what dependencies are required in a
9089 package control file. The <tt>shlibs</tt> file format
9090 is described on <ref id="shlibs">.
9095 <sect id="pkg-controlfile">
9096 <heading>The main control information file: <tt>control</tt></heading>
9099 The most important control information file used by
9100 <prgn>dpkg</prgn> when it installs a package is
9101 <tt>control</tt>. It contains all the package's "vital
9106 The binary package control files of packages built from
9107 Debian sources are made by a special tool,
9108 <prgn>dpkg-gencontrol</prgn>, which reads
9109 <file>debian/control</file> and <file>debian/changelog</file> to
9110 find the information it needs. See <ref id="pkg-sourcepkg"> for
9115 The fields in binary package control files are listed in
9116 <ref id="binarycontrolfiles">.
9120 A description of the syntax of control files and the purpose
9121 of the fields is available in <ref id="controlfields">.
9126 <heading>Time Stamps</heading>
9129 See <ref id="timestamps">.
9134 <appendix id="pkg-sourcepkg">
9135 <heading>Source packages (from old Packaging Manual) </heading>
9138 The Debian binary packages in the distribution are generated
9139 from Debian sources, which are in a special format to assist
9140 the easy and automatic building of binaries.
9143 <sect id="pkg-sourcetools">
9144 <heading>Tools for processing source packages</heading>
9147 Various tools are provided for manipulating source packages;
9148 they pack and unpack sources and help build of binary
9149 packages and help manage the distribution of new versions.
9153 They are introduced and typical uses described here; see
9154 <manref name="dpkg-source" section="1"> for full
9155 documentation about their arguments and operation.
9159 For examples of how to construct a Debian source package,
9160 and how to use those utilities that are used by Debian
9161 source packages, please see the <prgn>hello</prgn> example
9165 <sect1 id="pkg-dpkg-source">
9167 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9172 This program is frequently used by hand, and is also
9173 called from package-independent automated building scripts
9174 such as <prgn>dpkg-buildpackage</prgn>.
9178 To unpack a package it is typically invoked with
9180 dpkg-source -x <var>.../path/to/filename</var>.dsc
9185 with the <file><var>filename</var>.tar.gz</file> and
9186 <file><var>filename</var>.diff.gz</file> (if applicable) in
9187 the same directory. It unpacks into
9188 <file><var>package</var>-<var>version</var></file>, and if
9190 <file><var>package</var>-<var>version</var>.orig</file>, in
9191 the current directory.
9195 To create a packed source archive it is typically invoked:
9197 dpkg-source -b <var>package</var>-<var>version</var>
9202 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
9203 <file>.diff.gz</file> (if appropriate) in the current
9204 directory. <prgn>dpkg-source</prgn> does not clean the
9205 source tree first - this must be done separately if it is
9210 See also <ref id="pkg-sourcearchives">.</p>
9214 <sect1 id="pkg-dpkg-buildpackage">
9216 <prgn>dpkg-buildpackage</prgn> - overall package-building
9221 <prgn>dpkg-buildpackage</prgn> is a script which invokes
9222 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
9223 targets <tt>clean</tt>, <tt>build</tt> and
9224 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
9225 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
9226 source and binary package upload.
9230 It is usually invoked by hand from the top level of the
9231 built or unbuilt source directory. It may be invoked with
9232 no arguments; useful arguments include:
9233 <taglist compact="compact">
9234 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
9237 Do not sign the <tt>.changes</tt> file or the
9238 source package <tt>.dsc</tt> file, respectively.</p>
9240 <tag><tt>-p<var>sign-command</var></tt></tag>
9243 Invoke <var>sign-command</var> instead of finding
9244 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
9245 <var>sign-command</var> must behave just like
9246 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
9248 <tag><tt>-r<var>root-command</var></tt></tag>
9251 When root privilege is required, invoke the command
9252 <var>root-command</var>. <var>root-command</var>
9253 should invoke its first argument as a command, from
9254 the <prgn>PATH</prgn> if necessary, and pass its
9255 second and subsequent arguments to the command it
9256 calls. If no <var>root-command</var> is supplied
9257 then <var>dpkg-buildpackage</var> will take no
9258 special action to gain root privilege, so that for
9259 most packages it will have to be invoked as root to
9262 <tag><tt>-b</tt>, <tt>-B</tt></tag>
9265 Two types of binary-only build and upload - see
9266 <manref name="dpkg-source" section="1">.
9273 <sect1 id="pkg-dpkg-gencontrol">
9275 <prgn>dpkg-gencontrol</prgn> - generates binary package
9280 This program is usually called from <file>debian/rules</file>
9281 (see <ref id="pkg-sourcetree">) in the top level of the source
9286 This is usually done just before the files and directories in the
9287 temporary directory tree where the package is being built have their
9288 permissions and ownerships set and the package is constructed using
9289 <prgn>dpkg-deb/</prgn>
9291 This is so that the control file which is produced has
9292 the right permissions
9297 <prgn>dpkg-gencontrol</prgn> must be called after all the
9298 files which are to go into the package have been placed in
9299 the temporary build directory, so that its calculation of
9300 the installed size of a package is correct.
9304 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
9305 be run after <prgn>dpkg-shlibdeps</prgn> so that the
9306 variable substitutions created by
9307 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
9312 For a package which generates only one binary package, and
9313 which builds it in <file>debian/tmp</file> relative to the top
9314 of the source package, it is usually sufficient to call
9315 <prgn>dpkg-gencontrol</prgn>.
9319 Sources which build several binaries will typically need
9322 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
9323 </example> The <tt>-P</tt> tells
9324 <prgn>dpkg-gencontrol</prgn> that the package is being
9325 built in a non-default directory, and the <tt>-p</tt>
9326 tells it which package's control file should be generated.
9330 <prgn>dpkg-gencontrol</prgn> also adds information to the
9331 list of files in <file>debian/files</file>, for the benefit of
9332 (for example) a future invocation of
9333 <prgn>dpkg-genchanges</prgn>.</p>
9336 <sect1 id="pkg-dpkg-shlibdeps">
9338 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
9343 This program is usually called from <file>debian/rules</file>
9344 just before <prgn>dpkg-gencontrol</prgn> (see <ref
9345 id="pkg-sourcetree">), in the top level of the source tree.
9349 Its arguments are executables.
9352 In a forthcoming dpkg version,
9353 <prgn>dpkg-shlibdeps</prgn> would be required to be
9354 called on shared libraries as well.
9357 They may be specified either in the locations in the
9358 source tree where they are created or in the locations
9359 in the temporary build tree where they are installed
9360 prior to binary package creation.
9362 </footnote> for which shared library dependencies should
9363 be included in the binary package's control file.
9367 If some of the found shared libraries should only
9368 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
9369 some warrant a <tt>Pre-Depends</tt>, this can be achieved
9370 by using the <tt>-d<var>dependency-field</var></tt> option
9371 before those executable(s). (Each <tt>-d</tt> option
9372 takes effect until the next <tt>-d</tt>.)
9376 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
9377 output control file to be modified. Instead by default it
9378 adds to the <file>debian/substvars</file> file variable
9379 settings like <tt>shlibs:Depends</tt>. These variable
9380 settings must be referenced in dependency fields in the
9381 appropriate per-binary-package sections of the source
9386 For example, a package that generates an essential part
9387 which requires dependencies, and optional parts that
9388 which only require a recommendation, would separate those
9389 two sets of dependencies into two different fields.<footnote>
9390 At the time of writing, an example for this was the
9391 <package/xmms/ package, with Depends used for the xmms
9392 executable, Recommends for the plug-ins and Suggests for
9393 even more optional features provided by unzip.
9395 It can say in its <file>debian/rules</file>:
9397 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
9398 -dRecommends <var>optionalpart anotheroptionalpart</var>
9400 and then in its main control file <file>debian/control</file>:
9403 Depends: ${shlibs:Pre-Depends}
9404 Recommends: ${shlibs:Recommends}
9410 Sources which produce several binary packages with
9411 different shared library dependency requirements can use
9412 the <tt>-p<var>varnameprefix</var></tt> option to override
9413 the default <tt>shlibs:</tt> prefix (one invocation of
9414 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
9415 They can thus produce several sets of dependency
9416 variables, each of the form
9417 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
9418 which can be referred to in the appropriate parts of the
9419 binary package control files.
9424 <sect1 id="pkg-dpkg-distaddfile">
9426 <prgn>dpkg-distaddfile</prgn> - adds a file to
9427 <file>debian/files</file>
9431 Some packages' uploads need to include files other than
9432 the source and binary package files.
9436 <prgn>dpkg-distaddfile</prgn> adds a file to the
9437 <file>debian/files</file> file so that it will be included in
9438 the <file>.changes</file> file when
9439 <prgn>dpkg-genchanges</prgn> is run.
9443 It is usually invoked from the <tt>binary</tt> target of
9444 <file>debian/rules</file>:
9446 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
9448 The <var>filename</var> is relative to the directory where
9449 <prgn>dpkg-genchanges</prgn> will expect to find it - this
9450 is usually the directory above the top level of the source
9451 tree. The <file>debian/rules</file> target should put the
9452 file there just before or just after calling
9453 <prgn>dpkg-distaddfile</prgn>.
9457 The <var>section</var> and <var>priority</var> are passed
9458 unchanged into the resulting <file>.changes</file> file.
9463 <sect1 id="pkg-dpkg-genchanges">
9465 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
9470 This program is usually called by package-independent
9471 automatic building scripts such as
9472 <prgn>dpkg-buildpackage</prgn>, but it may also be called
9477 It is usually called in the top level of a built source
9478 tree, and when invoked with no arguments will print out a
9479 straightforward <file>.changes</file> file based on the
9480 information in the source package's changelog and control
9481 file and the binary and source packages which should have
9487 <sect1 id="pkg-dpkg-parsechangelog">
9489 <prgn>dpkg-parsechangelog</prgn> - produces parsed
9490 representation of a changelog
9494 This program is used internally by
9495 <prgn>dpkg-source</prgn> et al. It may also occasionally
9496 be useful in <file>debian/rules</file> and elsewhere. It
9497 parses a changelog, <file>debian/changelog</file> by default,
9498 and prints a control-file format representation of the
9499 information in it to standard output.
9503 <sect1 id="pkg-dpkg-architecture">
9505 <prgn>dpkg-architecture</prgn> - information about the build and
9510 This program can be used manually, but is also invoked by
9511 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
9512 to set environment or make variables which specify the build and
9513 host architecture for the package building process.
9518 <sect id="pkg-sourcetree">
9519 <heading>The Debianised source tree</heading>
9522 The source archive scheme described later is intended to
9523 allow a Debianised source tree with some associated control
9524 information to be reproduced and transported easily. The
9525 Debianised source tree is a version of the original program
9526 with certain files added for the benefit of the
9527 Debianisation process, and with any other changes required
9528 made to the rest of the source code and installation
9533 The extra files created for Debian are in the subdirectory
9534 <file>debian</file> of the top level of the Debianised source
9535 tree. They are described below.
9538 <sect1 id="pkg-debianrules">
9539 <heading><file>debian/rules</file> - the main building script</heading>
9542 See <ref id="debianrules">.
9547 <sect1 id="pkg-dpkgchangelog">
9548 <heading><file>debian/changelog</file></heading>
9551 See <ref id="dpkgchangelog">.
9555 It is recommended that the entire changelog be encoded in the
9556 <url id="http://www.cis.ohio-state.edu/cgi-bin/rfc/rfc2279.html" name="UTF-8">
9558 <url id="http://www.unicode.org/"
9559 name="Unicode">.<footnote>
9561 I think it is fairly obvious that we need to
9562 eventually transition to UTF-8 for our package
9563 infrastructure; it is really the only sane char-set in
9564 an international environment. Now, we can't switch to
9565 using UTF-8 for package control fields and the like
9566 until dpkg has better support, but one thing we can
9567 start doing today is requesting that Debian changelogs
9568 are UTF-8 encoded. At some point in time, we can start
9569 requiring them to do so.
9572 Checking for non-UTF8 characters in a changelog is
9573 trivial. Dump the file through
9574 <example>iconv -f utf-8 -t ucs-4</example>
9575 discard the output, and check the return
9576 value. If there are any characters in the stream
9577 which are invalid UTF-8 sequences, iconv will exit
9578 with an error code; and this will be the case for the
9579 vast majority of other character sets.
9584 <sect2><heading>Defining alternative changelog formats
9588 It is possible to use a different format to the standard
9589 one, by providing a parser for the format you wish to
9594 In order to have <tt>dpkg-parsechangelog</tt> run your
9595 parser, you must include a line within the last 40 lines
9596 of your file matching the Perl regular expression:
9597 <tt>\schangelog-format:\s+([0-9a-z]+)\W</tt> The part in
9598 parentheses should be the name of the format. For
9599 example, you might say:
9601 @@@ changelog-format: joebloggs @@@
9603 Changelog format names are non-empty strings of alphanumerics.
9607 If such a line exists then <tt>dpkg-parsechangelog</tt>
9608 will look for the parser as
9609 <file>/usr/lib/dpkg/parsechangelog/<var>format-name</var></file>
9611 <file>/usr/local/lib/dpkg/parsechangelog/<var>format-name</var></file>;
9612 it is an error for it not to find it, or for it not to
9613 be an executable program. The default changelog format
9614 is <tt>dpkg</tt>, and a parser for it is provided with
9615 the <tt>dpkg</tt> package.
9619 The parser will be invoked with the changelog open on
9620 standard input at the start of the file. It should read
9621 the file (it may seek if it wishes) to determine the
9622 information required and return the parsed information
9623 to standard output in the form of a series of control
9624 fields in the standard format. By default it should
9625 return information about only the most recent version in
9626 the changelog; it should accept a
9627 <tt>-v<var>version</var></tt> option to return changes
9628 information from all versions present <em>strictly
9629 after</em> <var>version</var>, and it should then be an
9630 error for <var>version</var> not to be present in the
9636 <list compact="compact">
9637 <item><qref id="f-Source"><tt>Source</tt></qref></item>
9638 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
9639 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
9640 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (mandatory)</item>
9641 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
9642 <item><qref id="f-Date"><tt>Date</tt></qref></item>
9643 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
9648 If several versions are being returned (due to the use
9649 of <tt>-v</tt>), the urgency value should be of the
9650 highest urgency code listed at the start of any of the
9651 versions requested followed by the concatenated
9652 (space-separated) comments from all the versions
9653 requested; the maintainer, version, distribution and
9654 date should always be from the most recent version.
9658 For the format of the <tt>Changes</tt> field see
9659 <ref id="f-Changes">.
9663 If the changelog format which is being parsed always or
9664 almost always leaves a blank line between individual
9665 change notes these blank lines should be stripped out,
9666 so as to make the resulting output compact.
9670 If the changelog format does not contain date or package
9671 name information this information should be omitted from
9672 the output. The parser should not attempt to synthesize
9673 it or find it from other sources.
9677 If the changelog does not have the expected format the
9678 parser should exit with a nonzero exit status, rather
9679 than trying to muddle through and possibly generating
9684 A changelog parser may not interact with the user at
9690 <sect1 id="pkg-srcsubstvars">
9691 <heading><file>debian/substvars</file> and variable substitutions</heading>
9694 See <ref id="substvars">.
9700 <heading><file>debian/files</file></heading>
9703 See <ref id="debianfiles">.
9707 <sect1><heading><file>debian/tmp</file>
9711 This is the canonical temporary location for the
9712 construction of binary packages by the <tt>binary</tt>
9713 target. The directory <file>tmp</file> serves as the root of
9714 the file system tree as it is being constructed (for
9715 example, by using the package's upstream makefiles install
9716 targets and redirecting the output there), and it also
9717 contains the <tt>DEBIAN</tt> subdirectory. See <ref
9718 id="pkg-bincreating">.
9722 If several binary packages are generated from the same
9723 source tree it is usual to use several
9724 <file>debian/tmp<var>something</var></file> directories, for
9725 example <file>tmp-a</file> or <file>tmp-doc</file>.
9729 Whatever <file>tmp</file> directories are created and used by
9730 <tt>binary</tt> must of course be removed by the
9731 <tt>clean</tt> target.</p></sect1>
9735 <sect id="pkg-sourcearchives"><heading>Source packages as archives
9739 As it exists on the FTP site, a Debian source package
9740 consists of three related files. You must have the right
9741 versions of all three to be able to use them.
9746 <tag>Debian source control file - <tt>.dsc</tt></tag>
9748 This file is a control file used by <prgn>dpkg-source</prgn>
9749 to extract a source package.
9750 See <ref id="debiansourcecontrolfiles">.
9754 Original source archive -
9756 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
9762 This is a compressed (with <tt>gzip -9</tt>)
9763 <prgn>tar</prgn> file containing the source code from
9764 the upstream authors of the program.
9769 Debianisation diff -
9771 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
9777 This is a unified context diff (<tt>diff -u</tt>)
9778 giving the changes which are required to turn the
9779 original source into the Debian source. These changes
9780 may only include editing and creating plain files.
9781 The permissions of files, the targets of symbolic
9782 links and the characteristics of special files or
9783 pipes may not be changed and no files may be removed
9788 All the directories in the diff must exist, except the
9789 <file>debian</file> subdirectory of the top of the source
9790 tree, which will be created by
9791 <prgn>dpkg-source</prgn> if necessary when unpacking.
9795 The <prgn>dpkg-source</prgn> program will
9796 automatically make the <file>debian/rules</file> file
9797 executable (see below).</p></item>
9802 If there is no original source code - for example, if the
9803 package is specially prepared for Debian or the Debian
9804 maintainer is the same as the upstream maintainer - the
9805 format is slightly different: then there is no diff, and the
9807 <file><var>package</var>_<var>version</var>.tar.gz</file>,
9808 and preferably contains a directory named
9809 <file><var>package</var>-<var>version</var></file>.
9814 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
9817 <tt>dpkg-source -x</tt> is the recommended way to unpack a
9818 Debian source package. However, if it is not available it
9819 is possible to unpack a Debian source archive as follows:
9820 <enumlist compact="compact">
9823 Untar the tarfile, which will create a <file>.orig</file>
9827 <p>Rename the <file>.orig</file> directory to
9828 <file><var>package</var>-<var>version</var></file>.</p>
9832 Create the subdirectory <file>debian</file> at the top of
9833 the source tree.</p>
9835 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
9837 <item><p>Untar the tarfile again if you want a copy of the original
9838 source code alongside the Debianised version.</p>
9843 It is not possible to generate a valid Debian source archive
9844 without using <prgn>dpkg-source</prgn>. In particular,
9845 attempting to use <prgn>diff</prgn> directly to generate the
9846 <file>.diff.gz</file> file will not work.
9850 <heading>Restrictions on objects in source packages</heading>
9853 The source package may not contain any hard links
9855 This is not currently detected when building source
9856 packages, but only when extracting
9860 Hard links may be permitted at some point in the
9861 future, but would require a fair amount of
9863 </footnote>, device special files, sockets or setuid or
9866 Setgid directories are allowed.
9871 The source packaging tools manage the changes between the
9872 original and Debianised source using <prgn>diff</prgn> and
9873 <prgn>patch</prgn>. Turning the original source tree as
9874 included in the <file>.orig.tar.gz</file> into the debianised
9875 source must not involve any changes which cannot be
9876 handled by these tools. Problematic changes which cause
9877 <prgn>dpkg-source</prgn> to halt with an error when
9878 building the source package are:
9879 <list compact="compact">
9880 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
9882 <item><p>Changing the targets of symbolic links.</p>
9884 <item><p>Creating directories, other than <file>debian</file>.</p>
9886 <item><p>Changes to the contents of binary files.</p></item>
9887 </list> Changes which cause <prgn>dpkg-source</prgn> to
9888 print a warning but continue anyway are:
9889 <list compact="compact">
9892 Removing files, directories or symlinks.
9894 Renaming a file is not treated specially - it is
9895 seen as the removal of the old file (which
9896 generates a warning, but is otherwise ignored),
9897 and the creation of the new one.
9903 Changed text files which are missing the usual final
9904 newline (either in the original or the modified
9909 Changes which are not represented, but which are not detected by
9910 <prgn>dpkg-source</prgn>, are:
9911 <list compact="compact">
9912 <item><p>Changing the permissions of files (other than
9913 <file>debian/rules</file>) and directories.</p></item>
9918 The <file>debian</file> directory and <file>debian/rules</file>
9919 are handled specially by <prgn>dpkg-source</prgn> - before
9920 applying the changes it will create the <file>debian</file>
9921 directory, and afterwards it will make
9922 <file>debian/rules</file> world-executable.
9928 <appendix id="pkg-controlfields">
9929 <heading>Control files and their fields (from old Packaging Manual)</heading>
9932 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
9933 data in a common format, known as control files. Binary and
9934 source packages have control data as do the <file>.changes</file>
9935 files which control the installation of uploaded files, and
9936 <prgn>dpkg</prgn>'s internal databases are in a similar
9941 <heading>Syntax of control files</heading>
9944 See <ref id="controlsyntax">.
9948 It is important to note that there are several fields which
9949 are optional as far as <prgn>dpkg</prgn> and the related
9950 tools are concerned, but which must appear in every Debian
9951 package, or whose omission may cause problems.
9956 <heading>List of fields</heading>
9959 See <ref id="controlfieldslist">.
9963 This section now contains only the fields that didn't belong
9964 to the Policy manual.
9967 <sect1 id="pkg-f-Filename">
9968 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
9971 These fields in <tt>Packages</tt> files give the
9972 filename(s) of (the parts of) a package in the
9973 distribution directories, relative to the root of the
9974 Debian hierarchy. If the package has been split into
9975 several parts the parts are all listed in order, separated
9980 <sect1 id="pkg-f-Size">
9981 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
9984 These fields in <file>Packages</file> files give the size (in
9985 bytes, expressed in decimal) and MD5 checksum of the
9986 file(s) which make(s) up a binary package in the
9987 distribution. If the package is split into several parts
9988 the values for the parts are listed in order, separated by
9993 <sect1 id="pkg-f-Status">
9994 <heading><tt>Status</tt></heading>
9997 This field in <prgn>dpkg</prgn>'s status file records
9998 whether the user wants a package installed, removed or
9999 left alone, whether it is broken (requiring
10000 re-installation) or not and what its current state on the
10001 system is. Each of these pieces of information is a
10006 <sect1 id="pkg-f-Config-Version">
10007 <heading><tt>Config-Version</tt></heading>
10010 If a package is not installed or not configured, this
10011 field in <prgn>dpkg</prgn>'s status file records the last
10012 version of the package which was successfully
10017 <sect1 id="pkg-f-Conffiles">
10018 <heading><tt>Conffiles</tt></heading>
10021 This field in <prgn>dpkg</prgn>'s status file contains
10022 information about the automatically-managed configuration
10023 files held by a package. This field should <em>not</em>
10024 appear anywhere in a package!
10029 <heading>Obsolete fields</heading>
10032 These are still recognized by <prgn>dpkg</prgn> but should
10033 not appear anywhere any more.
10035 <taglist compact="compact">
10037 <tag><tt>Revision</tt></tag>
10038 <tag><tt>Package-Revision</tt></tag>
10039 <tag><tt>Package_Revision</tt></tag>
10041 The Debian revision part of the package version was
10042 at one point in a separate control file field. This
10043 field went through several names.
10046 <tag><tt>Recommended</tt></tag>
10047 <item>Old name for <tt>Recommends</tt>.</item>
10049 <tag><tt>Optional</tt></tag>
10050 <item>Old name for <tt>Suggests</tt>.</item>
10052 <tag><tt>Class</tt></tag>
10053 <item>Old name for <tt>Priority</tt>.</item>
10062 <appendix id="pkg-conffiles">
10063 <heading>Configuration file handling (from old Packaging Manual)</heading>
10066 <prgn>dpkg</prgn> can do a certain amount of automatic
10067 handling of package configuration files.
10071 Whether this mechanism is appropriate depends on a number of
10072 factors, but basically there are two approaches to any
10073 particular configuration file.
10077 The easy method is to ship a best-effort configuration in the
10078 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10079 handle updates. If the user is unlikely to want to edit the
10080 file, but you need them to be able to without losing their
10081 changes, and a new package with a changed version of the file
10082 is only released infrequently, this is a good approach.
10086 The hard method is to build the configuration file from
10087 scratch in the <prgn>postinst</prgn> script, and to take the
10088 responsibility for fixing any mistakes made in earlier
10089 versions of the package automatically. This will be
10090 appropriate if the file is likely to need to be different on
10094 <sect><heading>Automatic handling of configuration files by
10099 A package may contain a control area file called
10100 <tt>conffiles</tt>. This file should be a list of filenames
10101 of configuration files needing automatic handling, separated
10102 by newlines. The filenames should be absolute pathnames,
10103 and the files referred to should actually exist in the
10108 When a package is upgraded <prgn>dpkg</prgn> will process
10109 the configuration files during the configuration stage,
10110 shortly before it runs the package's <prgn>postinst</prgn>
10115 For each file it checks to see whether the version of the
10116 file included in the package is the same as the one that was
10117 included in the last version of the package (the one that is
10118 being upgraded from); it also compares the version currently
10119 installed on the system with the one shipped with the last
10124 If neither the user nor the package maintainer has changed
10125 the file, it is left alone. If one or the other has changed
10126 their version, then the changed version is preferred - i.e.,
10127 if the user edits their file, but the package maintainer
10128 doesn't ship a different version, the user's changes will
10129 stay, silently, but if the maintainer ships a new version
10130 and the user hasn't edited it the new version will be
10131 installed (with an informative message). If both have
10132 changed their version the user is prompted about the problem
10133 and must resolve the differences themselves.
10137 The comparisons are done by calculating the MD5 message
10138 digests of the files, and storing the MD5 of the file as it
10139 was included in the most recent version of the package.
10143 When a package is installed for the first time
10144 <prgn>dpkg</prgn> will install the file that comes with it,
10145 unless that would mean overwriting a file already on the
10150 However, note that <prgn>dpkg</prgn> will <em>not</em>
10151 replace a conffile that was removed by the user (or by a
10152 script). This is necessary because with some programs a
10153 missing file produces an effect hard or impossible to
10154 achieve in another way, so that a missing file needs to be
10155 kept that way if the user did it.
10159 Note that a package should <em>not</em> modify a
10160 <prgn>dpkg</prgn>-handled conffile in its maintainer
10161 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10162 the user confusing and possibly dangerous options for
10163 conffile update when the package is upgraded.</p>
10166 <sect><heading>Fully-featured maintainer script configuration
10171 For files which contain site-specific information such as
10172 the hostname and networking details and so forth, it is
10173 better to create the file in the package's
10174 <prgn>postinst</prgn> script.
10178 This will typically involve examining the state of the rest
10179 of the system to determine values and other information, and
10180 may involve prompting the user for some information which
10181 can't be obtained some other way.
10185 When using this method there are a couple of important
10186 issues which should be considered:
10190 If you discover a bug in the program which generates the
10191 configuration file, or if the format of the file changes
10192 from one version to the next, you will have to arrange for
10193 the postinst script to do something sensible - usually this
10194 will mean editing the installed configuration file to remove
10195 the problem or change the syntax. You will have to do this
10196 very carefully, since the user may have changed the file,
10197 perhaps to fix the very problem that your script is trying
10198 to deal with - you will have to detect these situations and
10199 deal with them correctly.
10203 If you do go down this route it's probably a good idea to
10204 make the program that generates the configuration file(s) a
10205 separate program in <file>/usr/sbin</file>, by convention called
10206 <file><var>package</var>config</file> and then run that if
10207 appropriate from the post-installation script. The
10208 <tt><var>package</var>config</tt> program should not
10209 unquestioningly overwrite an existing configuration - if its
10210 mode of operation is geared towards setting up a package for
10211 the first time (rather than any arbitrary reconfiguration
10212 later) you should have it check whether the configuration
10213 already exists, and require a <tt>--force</tt> flag to
10214 overwrite it.</p></sect>
10217 <appendix id="pkg-alternatives"><heading>Alternative versions of
10218 an interface - <prgn>update-alternatives</prgn> (from old
10223 When several packages all provide different versions of the
10224 same program or file it is useful to have the system select a
10225 default, but to allow the system administrator to change it
10226 and have their decisions respected.
10230 For example, there are several versions of the <prgn>vi</prgn>
10231 editor, and there is no reason to prevent all of them from
10232 being installed at once, each under their own name
10233 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10234 Nevertheless it is desirable to have the name <tt>vi</tt>
10235 refer to something, at least by default.
10239 If all the packages involved cooperate, this can be done with
10240 <prgn>update-alternatives</prgn>.
10244 Each package provides its own version under its own name, and
10245 calls <prgn>update-alternatives</prgn> in its postinst to
10246 register its version (and again in its prerm to deregister
10251 See the man page <manref name="update-alternatives"
10252 section="8"> for details.
10256 If <prgn>update-alternatives</prgn> does not seem appropriate
10257 you may wish to consider using diversions instead.</p>
10260 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10261 package's version of a file (from old Packaging Manual)
10265 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10266 when it reinstalls the package it belongs to, and to have it
10267 put the file from the package somewhere else instead.
10271 This can be used locally to override a package's version of a
10272 file, or by one package to override another's version (or
10273 provide a wrapper for it).
10277 Before deciding to use a diversion, read <ref
10278 id="pkg-alternatives"> to see if you really want a diversion
10279 rather than several alternative versions of a program.
10283 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10284 and updated by a special program <prgn>dpkg-divert</prgn>.
10285 Please see <manref name="dpkg-divert" section="8"> for full
10286 details of its operation.
10290 When a package wishes to divert a file from another, it should
10291 call <prgn>dpkg-divert</prgn> in its preinst to add the
10292 diversion and rename the existing file. For example,
10293 supposing that a <prgn>smailwrapper</prgn> package wishes to
10294 install a wrapper around <file>/usr/sbin/smail</file>:
10296 if [ install = "$1" ]; then
10297 dpkg-divert --package smailwrapper --add --rename \
10298 --divert /usr/sbin/smail.real /usr/sbin/smail
10300 </example> Testing <tt>$1</tt> is necessary so that the script
10301 doesn't try to add the diversion again when
10302 <prgn>smailwrapper</prgn> is upgraded. The <tt>--package
10303 smailwrapper</tt> ensures that <prgn>smailwrapper</prgn>'s
10304 copy of <file>/usr/sbin/smail</file> can bypass the diversion and
10305 get installed as the true version.
10309 The postrm has to do the reverse:
10311 if [ remove = "$1" ]; then
10312 dpkg-divert --package smailwrapper --remove --rename \
10313 --divert /usr/sbin/smail.real /usr/sbin/smail
10319 Do not attempt to divert a file which is vitally important for
10320 the system's operation - when using <prgn>dpkg-divert</prgn>
10321 there is a time, after it has been diverted but before
10322 <prgn>dpkg</prgn> has installed the new version, when the file
10323 does not exist.</p>
10328 <!-- vim:set ai et sts=2 sw=2 tw=76: -->