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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>apt</prgn>,
3994 <prgn>aptitutde</prgn>, and <prgn>dselect</prgn>.)
3998 For this reason packages in an installation run are usually
3999 all unpacked first and all configured later; this gives
4000 later versions of packages with dependencies on later
4001 versions of other packages the opportunity to have their
4002 dependencies satisfied.
4006 In case of circular dependencies, since installation or
4007 removal order honoring the dependency order can't be
4008 established, dependency loops are broken at some point
4009 (based on rules below), and some packages may not be able to
4010 rely on their dependencies being present when being
4011 installed or removed, depending on which side of the break
4012 of the circular dependcy loop they happen to be on. If one
4013 of the packages in the loop has no postinst script, then the
4014 cycle will be broken at that package, so as to ensure that
4015 all postinst scripts run with the dependencies properly
4016 configured if this is possible. Otherwise the breaking point
4021 The <tt>Depends</tt> field thus allows package maintainers
4022 to impose an order in which packages should be configured.
4026 The meaning of the five dependency fields is as follows:
4028 <tag><tt>Depends</tt></tag>
4031 This declares an absolute dependency. A package will
4032 not be configured unless all of the packages listed in
4033 its <tt>Depends</tt> field have been correctly
4038 The <tt>Depends</tt> field should be used if the
4039 depended-on package is required for the depending
4040 package to provide a significant amount of
4045 The <tt>Depends</tt> field should also be used if the
4046 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4047 <prgn>postrm</prgn> scripts require the package to be
4048 present in order to run. Note, however, that the
4049 <prgn>postrm</prgn> cannot rely on any non-essential
4050 packages to be present during the <tt>purge</tt>
4054 <tag><tt>Recommends</tt></tag>
4057 This declares a strong, but not absolute, dependency.
4061 The <tt>Recommends</tt> field should list packages
4062 that would be found together with this one in all but
4063 unusual installations.
4067 <tag><tt>Suggests</tt></tag>
4069 This is used to declare that one package may be more
4070 useful with one or more others. Using this field
4071 tells the packaging system and the user that the
4072 listed packages are related to this one and can
4073 perhaps enhance its usefulness, but that installing
4074 this one without them is perfectly reasonable.
4077 <tag><tt>Enhances</tt></tag>
4079 This field is similar to Suggests but works in the
4080 opposite direction. It is used to declare that a
4081 package can enhance the functionality of another
4085 <tag><tt>Pre-Depends</tt></tag>
4088 This field is like <tt>Depends</tt>, except that it
4089 also forces <prgn>dpkg</prgn> to complete installation
4090 of the packages named before even starting the
4091 installation of the package which declares the
4092 pre-dependency, as follows:
4096 When a package declaring a pre-dependency is about to
4097 be <em>unpacked</em> the pre-dependency can be
4098 satisfied if the depended-on package is either fully
4099 configured, <em>or even if</em> the depended-on
4100 package(s) are only unpacked or half-configured,
4101 provided that they have been configured correctly at
4102 some point in the past (and not removed or partially
4103 removed since). In this case, both the
4104 previously-configured and currently unpacked or
4105 half-configured versions must satisfy any version
4106 clause in the <tt>Pre-Depends</tt> field.
4110 When the package declaring a pre-dependency is about
4111 to be <em>configured</em>, the pre-dependency will be
4112 treated as a normal <tt>Depends</tt>, that is, it will
4113 be considered satisfied only if the depended-on
4114 package has been correctly configured.
4118 <tt>Pre-Depends</tt> should be used sparingly,
4119 preferably only by packages whose premature upgrade or
4120 installation would hamper the ability of the system to
4121 continue with any upgrade that might be in progress.
4125 <tt>Pre-Depends</tt> are also required if the
4126 <prgn>preinst</prgn> script depends on the named
4127 package. It is best to avoid this situation if
4135 When selecting which level of dependency to use you should
4136 consider how important the depended-on package is to the
4137 functionality of the one declaring the dependency. Some
4138 packages are composed of components of varying degrees of
4139 importance. Such a package should list using
4140 <tt>Depends</tt> the package(s) which are required by the
4141 more important components. The other components'
4142 requirements may be mentioned as Suggestions or
4143 Recommendations, as appropriate to the components' relative
4148 <sect id="conflicts">
4149 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4152 When one binary package declares a conflict with another
4153 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4154 refuse to allow them to be installed on the system at the
4159 If one package is to be installed, the other must be removed
4160 first - if the package being installed is marked as
4161 replacing (see <ref id="replaces">) the one on the system,
4162 or the one on the system is marked as deselected, or both
4163 packages are marked <tt>Essential</tt>, then
4164 <prgn>dpkg</prgn> will automatically remove the package
4165 which is causing the conflict, otherwise it will halt the
4166 installation of the new package with an error. This
4167 mechanism is specifically designed to produce an error when
4168 the installed package is <tt>Essential</tt>, but the new
4173 A package will not cause a conflict merely because its
4174 configuration files are still installed; it must be at least
4179 A special exception is made for packages which declare a
4180 conflict with their own package name, or with a virtual
4181 package which they provide (see below): this does not
4182 prevent their installation, and allows a package to conflict
4183 with others providing a replacement for it. You use this
4184 feature when you want the package in question to be the only
4185 package providing some feature.
4189 A <tt>Conflicts</tt> entry should almost never have an
4190 "earlier than" version clause. This would prevent
4191 <prgn>dpkg</prgn> from upgrading or installing the package
4192 which declared such a conflict until the upgrade or removal
4193 of the conflicted-with package had been completed.
4197 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4201 As well as the names of actual ("concrete") packages, the
4202 package relationship fields <tt>Depends</tt>,
4203 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4204 <tt>Pre-Depends</tt>, <tt>Conflicts</tt>,
4205 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4206 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4207 may mention "virtual packages".
4211 A <em>virtual package</em> is one which appears in the
4212 <tt>Provides</tt> control file field of another package.
4213 The effect is as if the package(s) which provide a
4214 particular virtual package name had been listed by name
4215 everywhere the virtual package name appears. (See also <ref
4220 If there are both concrete and virtual packages of the same
4221 name, then the dependency may be satisfied (or the conflict
4222 caused) by either the concrete package with the name in
4223 question or any other concrete package which provides the
4224 virtual package with the name in question. This is so that,
4225 for example, supposing we have
4226 <example compact="compact">
4229 </example> and someone else releases an enhanced version of
4230 the <tt>bar</tt> package they can say:
4231 <example compact="compact">
4235 and the <tt>bar-plus</tt> package will now also satisfy the
4236 dependency for the <tt>foo</tt> package.
4240 If a dependency or a conflict has a version number attached
4241 then only real packages will be considered to see whether
4242 the relationship is satisfied (or the prohibition violated,
4243 for a conflict) - it is assumed that a real package which
4244 provides the virtual package is not of the "right" version.
4245 So, a <tt>Provides</tt> field may not contain version
4246 numbers, and the version number of the concrete package
4247 which provides a particular virtual package will not be
4248 looked at when considering a dependency on or conflict with
4249 the virtual package name.
4253 It is likely that the ability will be added in a future
4254 release of <prgn>dpkg</prgn> to specify a version number for
4255 each virtual package it provides. This feature is not yet
4256 present, however, and is expected to be used only
4261 If you want to specify which of a set of real packages
4262 should be the default to satisfy a particular dependency on
4263 a virtual package, you should list the real package as an
4264 alternative before the virtual one.
4269 <sect id="replaces"><heading>Overwriting files and replacing
4270 packages - <tt>Replaces</tt></heading>
4273 Packages can declare in their control file that they should
4274 overwrite files in certain other packages, or completely
4275 replace other packages. The <tt>Replaces</tt> control file
4276 field has these two distinct purposes.
4279 <sect1><heading>Overwriting files in other packages</heading>
4282 Firstly, as mentioned before, it is usually an error for a
4283 package to contain files which are on the system in
4288 However, if the overwriting package declares that it
4289 <tt>Replaces</tt> the one containing the file being
4290 overwritten, then <prgn>dpkg</prgn> will replace the file
4291 from the old package with that from the new. The file
4292 will no longer be listed as "owned" by the old package.
4296 If a package is completely replaced in this way, so that
4297 <prgn>dpkg</prgn> does not know of any files it still
4298 contains, it is considered to have "disappeared". It will
4299 be marked as not wanted on the system (selected for
4300 removal) and not installed. Any <tt>conffile</tt>s
4301 details noted for the package will be ignored, as they
4302 will have been taken over by the overwriting package. The
4303 package's <prgn>postrm</prgn> script will be run with a
4304 special argument to allow the package to do any final
4305 cleanup required. See <ref id="mscriptsinstact">.
4308 Replaces is a one way relationship -- you have to
4309 install the replacing package after the replaced
4316 For this usage of <tt>Replaces</tt>, virtual packages (see
4317 <ref id="virtual">) are not considered when looking at a
4318 <tt>Replaces</tt> field - the packages declared as being
4319 replaced must be mentioned by their real names.
4323 Furthermore, this usage of <tt>Replaces</tt> only takes
4324 effect when both packages are at least partially on the
4325 system at once, so that it can only happen if they do not
4326 conflict or if the conflict has been overridden.
4331 <sect1><heading>Replacing whole packages, forcing their
4335 Secondly, <tt>Replaces</tt> allows the packaging system to
4336 resolve which package should be removed when there is a
4337 conflict - see <ref id="conflicts">. This usage only
4338 takes effect when the two packages <em>do</em> conflict,
4339 so that the two usages of this field do not interfere with
4344 In this situation, the package declared as being replaced
4345 can be a virtual package, so for example, all mail
4346 transport agents (MTAs) would have the following fields in
4347 their control files:
4348 <example compact="compact">
4349 Provides: mail-transport-agent
4350 Conflicts: mail-transport-agent
4351 Replaces: mail-transport-agent
4353 ensuring that only one MTA can be installed at any one
4358 <sect id="sourcebinarydeps">
4359 <heading>Relationships between source and binary packages -
4360 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4361 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
4365 Source packages that require certain binary packages to be
4366 installed or absent at the time of building the package
4367 can declare relationships to those binary packages.
4371 This is done using the <tt>Build-Depends</tt>,
4372 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
4373 <tt>Build-Conflicts-Indep</tt> control file fields.
4377 Build-dependencies on "build-essential" binary packages can be
4378 omitted. Please see <ref id="pkg-relations"> for more information.
4382 The dependencies and conflicts they define must be satisfied
4383 (as defined earlier for binary packages) in order to invoke
4384 the targets in <tt>debian/rules</tt>, as follows:<footnote>
4386 If you make "build-arch" or "binary-arch", you need
4387 Build-Depends. If you make "build-indep" or
4388 "binary-indep", you need Build-Depends and
4389 Build-Depends-Indep. If you make "build" or "binary",
4393 There is no Build-Depends-Arch; this role is essentially
4394 met with Build-Depends. Anyone building the
4395 <tt>build-indep</tt> and binary-indep<tt></tt> targets
4396 is basically assumed to be building the whole package
4397 anyway and so installs all build dependencies. The
4398 autobuilders use <tt>dpkg-buildpackage -B</tt>, which
4399 calls <tt>build</tt> (not <tt>build-arch</tt>, since it
4400 does not yet know how to check for its existence) and
4401 <tt>binary-arch</tt>.
4404 The purpose of the original split, I recall, was so that
4405 the autobuilders wouldn't need to install extra packages
4406 needed only for the binary-indep targets. But without a
4407 build-arch/build-indep split, this didn't work, since
4408 most of the work is done in the build target, not in the
4414 <tag><tt>Build-Depends</tt>, <tt>Build-Conflicts</tt></tag>
4416 The <tt>Build-Depends</tt> and
4417 <tt>Build-Conflicts</tt> fields must be satisfied when
4418 any of the following targets is invoked:
4419 <tt>build</tt>, <tt>clean</tt>, <tt>binary</tt>,
4420 <tt>binary-arch</tt>, <tt>build-arch</tt>,
4421 <tt>build-indep</tt> and <tt>binary-indep</tt>.
4423 <tag><tt>Build-Depends-Indep</tt>,
4424 <tt>Build-Conflicts-Indep</tt></tag>
4426 The <tt>Build-Depends-Indep</tt> and
4427 <tt>Build-Conflicts-Indep</tt> fields must be
4428 satisfied when any of the following targets is
4429 invoked: <tt>build</tt>, <tt>build-indep</tt>,
4430 <tt>binary</tt> and <tt>binary-indep</tt>.
4440 <chapt id="sharedlibs"><heading>Shared libraries</heading>
4443 Packages containing shared libraries must be constructed with
4444 a little care to make sure that the shared library is always
4445 available. This is especially important for packages whose
4446 shared libraries are vitally important, such as the C library
4447 (currently <tt>libc6</tt>).
4451 Packages involving shared libraries should be split up into
4452 several binary packages. This section mostly deals with how
4453 this separation is to be accomplished; rules for files within
4454 the shared library packages are in <ref id="libraries"> instead.
4457 <sect id="sharedlibs-runtime">
4458 <heading>Run-time shared libraries</heading>
4461 The run-time shared library needs to be placed in a package
4462 whose name changes whenever the shared object version
4465 Since it is common place to install several versions of a
4466 package that just provides shared libraries, it is a
4467 good idea that the library package should not
4468 contain any extraneous non-versioned files, unless they
4469 happen to be in versioned directories.</p>
4471 The most common mechanism is to place it in a package
4473 <package><var>libraryname</var><var>soversion</var></package>,
4474 where <file><var>soversion</var></file> is the version number
4475 in the soname of the shared library<footnote>
4476 The soname is the shared object name: it's the thing
4477 that has to match exactly between building an executable
4478 and running it for the dynamic linker to be able run the
4479 program. For example, if the soname of the library is
4480 <file>libfoo.so.6</file>, the library package would be
4481 called <file>libfoo6</file>.
4483 Alternatively, if it would be confusing to directly append
4484 <var>soversion</var> to <var>libraryname</var> (e.g. because
4485 <var>libraryname</var> itself ends in a number), you may use
4486 <package><var>libraryname</var>-<var>soversion</var></package> and
4487 <package><var>libraryname</var>-<var>soversion</var>-dev</package>
4492 If your package includes run-time support programs that
4493 do not need to be invoked manually by users, but are
4494 nevertheless required for the package to function, then it
4495 is recommended that these programs are placed
4496 (if they are binary) in a subdirectory of
4497 <file>/usr/lib</file>, preferably under
4498 <file>/usr/lib/</file><var>package-name</var>.
4499 If the program is architecture independent, the
4500 recommendation is for it to be placed in a subdirectory of
4501 <file>/usr/share</file> instead, preferably under
4502 <file>/usr/share/</file><var>package-name</var>.
4507 If you have several shared libraries built from the same
4508 source tree you may lump them all together into a single
4509 shared library package, provided that you change all of
4510 their sonames at once (so that you don't get filename
4511 clashes if you try to install different versions of the
4512 combined shared libraries package).
4516 The package should install the shared libraries under
4517 their normal names. For example, the <package>libgdbm3</package>
4518 package should install <file>libgdbm.so.3.0.0</file> as
4519 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
4520 renamed or re-linked by any <prgn>prerm</prgn> or
4521 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
4522 of renaming things safely without affecting running programs,
4523 and attempts to interfere with this are likely to lead to
4528 Shared libraries should not be installed executable, since
4529 the dynamic linker does not require this and trying to
4530 execute a shared library usually results in a core dump.
4534 The run-time library package should include the symbolic link that
4535 <prgn>ldconfig</prgn> would create for the shared libraries.
4536 For example, the <package>libgdbm3</package> package should include
4537 a symbolic link from <file>/usr/lib/libgdbm.so.3</file> to
4538 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
4539 linker (for example <prgn>ld.so</prgn> or
4540 <prgn>ld-linux.so.*</prgn>) can find the library between the
4541 time that <prgn>dpkg</prgn> installs it and the time that
4542 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
4544 The package management system requires the library to be
4545 placed before the symbolic link pointing to it in the
4546 <file>.deb</file> file. This is so that when
4547 <prgn>dpkg</prgn> comes to install the symlink
4548 (overwriting the previous symlink pointing at an older
4549 version of the library), the new shared library is already
4550 in place. In the past, this was achieved by creating the
4551 library in the temporary packaging directory before
4552 creating the symlink. Unfortunately, this was not always
4553 effective, since the building of the tar file in the
4554 <file>.deb</file> depended on the behavior of the underlying
4555 file system. Some file systems (such as reiserfs) reorder
4556 the files so that the order of creation is forgotten.
4557 Since version 1.7.0, <prgn>dpkg</prgn>
4558 reorders the files itself as necessary when building a
4559 package. Thus it is no longer important to concern
4560 oneself with the order of file creation.
4564 <sect1 id="ldconfig">
4565 <heading><tt>ldconfig</tt></heading>
4568 Any package installing shared libraries in one of the default
4569 library directories of the dynamic linker (which are currently
4570 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
4571 listed in <file>/etc/ld.so.conf</file><footnote>
4573 <list compact="compact">
4574 <item>/usr/local/lib</item>
4575 <item>/usr/lib/libc5-compat</item>
4576 <item>/lib/libc5-compat</item>
4579 must use <prgn>ldconfig</prgn> to update the shared library
4584 The package maintainer scripts must only call
4585 <prgn>ldconfig</prgn> under these circumstances:
4586 <list compact="compact">
4587 <item>When the <prgn>postinst</prgn> script is run with a
4588 first argument of <tt>configure</tt>, the script must call
4589 <prgn>ldconfig</prgn>, and may optionally invoke
4590 <prgn>ldconfig</prgn> at other times.
4592 <item>When the <prgn>postrm</prgn> script is run with a
4593 first argument of <tt>remove</tt>, the script should call
4594 <prgn>ldconfig</prgn>.
4599 During install or upgrade, the preinst is called before
4600 the new files are installed, so calling "ldconfig" is
4601 pointless. The preinst of an existing package can also be
4602 called if an upgrade fails. However, this happens during
4603 the critical time when a shared libs may exist on-disk
4604 under a temporary name. Thus, it is dangerous and
4605 forbidden by current policy to call "ldconfig" at this
4610 When a package is installed or upgraded, "postinst
4611 configure" runs after the new files are safely on-disk.
4612 Since it is perfectly safe to invoke ldconfig
4613 unconditionally in a postinst, it is OK for a package to
4614 simply put ldconfig in its postinst without checking the
4615 argument. The postinst can also be called to recover from
4616 a failed upgrade. This happens before any new files are
4617 unpacked, so there is no reason to call "ldconfig" at this
4622 For a package that is being removed, prerm is
4623 called with all the files intact, so calling ldconfig is
4624 useless. The other calls to "prerm" happen in the case of
4625 upgrade at a time when all the files of the old package
4626 are on-disk, so again calling "ldconfig" is pointless.
4630 postrm, on the other hand, is called with the "remove"
4631 argument just after the files are removed, so this is
4632 the proper time to call "ldconfig" to notify the system
4633 of the fact that the shared libraries from the package
4634 are removed. The postrm can be called at several other
4635 times. At the time of "postrm purge", "postrm
4636 abort-install", or "postrm abort-upgrade", calling
4637 "ldconfig" is useless because the shared lib files are
4638 not on-disk. However, when "postrm" is invoked with
4639 arguments "upgrade", "failed-upgrade", or "disappear", a
4640 shared lib may exist on-disk under a temporary filename.
4648 <sect id="sharedlibs-runtime-progs">
4649 <heading>Run-time support programs</heading>
4652 If your package has some run-time support programs which use
4653 the shared library you must not put them in the shared
4654 library package. If you do that then you won't be able to
4655 install several versions of the shared library without
4656 getting filename clashes.
4660 Instead, either create another package for the runtime binaries
4661 (this package might typically be named
4662 <package><var>libraryname</var>-runtime</package>; note the absence
4663 of the <var>soversion</var> in the package name), or if the
4664 development package is small, include them in there.
4668 <sect id="sharedlibs-static">
4669 <heading>Static libraries</heading>
4672 The static library (<file><var>libraryname.a</var></file>)
4673 is usually provided in addition to the shared version.
4674 It is placed into the development package (see below).
4678 In some cases, it is acceptable for a library to be
4679 available in static form only; these cases include:
4681 <item>libraries for languages whose shared library support
4682 is immature or unstable</item>
4683 <item>libraries whose interfaces are in flux or under
4684 development (commonly the case when the library's
4685 major version number is zero, or where the ABI breaks
4686 across patchlevels)</item>
4687 <item>libraries which are explicitly intended to be
4688 available only in static form by their upstream
4693 <sect id="sharedlibs-dev">
4694 <heading>Development files</heading>
4697 The development files associated to a shared library need to be
4698 placed in a package called
4699 <package><var>libraryname</var><var>soversion</var>-dev</package>,
4700 or if you prefer only to support one development version at a
4701 time, <package><var>libraryname</var>-dev</package>.
4705 In case several development versions of a library exist, you may
4706 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
4707 <ref id="conflicts">) to ensure that the user only installs one
4708 development version at a time (as different development versions are
4709 likely to have the same header files in them, which would cause a
4710 filename clash if both were installed).
4714 The development package should contain a symlink for the associated
4715 shared library without a version number. For example, the
4716 <package>libgdbm-dev</package> package should include a symlink
4717 from <file>/usr/lib/libgdbm.so</file> to
4718 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
4719 (<prgn>ld</prgn>) when compiling packages, as it will only look for
4720 <file>libgdbm.so</file> when compiling dynamically.
4724 <sect id="sharedlibs-intradeps">
4725 <heading>Dependencies between the packages of the same library</heading>
4728 Typically the development version should have an exact
4729 version dependency on the runtime library, to make sure that
4730 compilation and linking happens correctly. The
4731 <tt>${binary:Version}</tt> substitution variable can be
4732 useful for this purpose.
4734 Previously, <tt>${Source-Version}</tt> was used, but its name
4735 was confusing and it has been deprecated since dpkg 1.13.19.
4740 <sect id="sharedlibs-shlibdeps">
4741 <heading>Dependencies between the library and other packages -
4742 the <tt>shlibs</tt> system</heading>
4745 If a package contains a binary or library which links to a
4746 shared library, we must ensure that when the package is
4747 installed on the system, all of the libraries needed are
4748 also installed. This requirement led to the creation of the
4749 <tt>shlibs</tt> system, which is very simple in its design:
4750 any package which <em>provides</em> a shared library also
4751 provides information on the package dependencies required to
4752 ensure the presence of this library, and any package which
4753 <em>uses</em> a shared library uses this information to
4754 determine the dependencies it requires. The files which
4755 contain the mapping from shared libraries to the necessary
4756 dependency information are called <file>shlibs</file> files.
4760 Thus, when a package is built which contains any shared
4761 libraries, it must provide a <file>shlibs</file> file for other
4762 packages to use, and when a package is built which contains
4763 any shared libraries or compiled binaries, it must run
4764 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
4765 on these to determine the libraries used and hence the
4766 dependencies needed by this package.<footnote>
4768 In the past, the shared libraries linked to were
4769 determined by calling <prgn>ldd</prgn>, but now
4770 <prgn>objdump</prgn> is used to do this. The only
4771 change this makes to package building is that
4772 <prgn>dpkg-shlibdeps</prgn> must also be run on shared
4773 libraries, whereas in the past this was unnecessary.
4774 The rest of this footnote explains the advantage that
4779 We say that a binary <tt>foo</tt> <em>directly</em> uses
4780 a library <tt>libbar</tt> if it is explicitly linked
4781 with that library (that is, it uses the flag
4782 <tt>-lbar</tt> during the linking stage). Other
4783 libraries that are needed by <tt>libbar</tt> are linked
4784 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
4785 linker will load them automatically when it loads
4786 <tt>libbar</tt>. A package should depend on
4787 the libraries it directly uses, and the dependencies for
4788 those libraries should automatically pull in the other
4793 Unfortunately, the <prgn>ldd</prgn> program shows both
4794 the directly and indirectly used libraries, meaning that
4795 the dependencies determined included both direct and
4796 indirect dependencies. The use of <prgn>objdump</prgn>
4797 avoids this problem by determining only the directly
4802 A good example of where this helps is the following. We
4803 could update <tt>libimlib</tt> with a new version that
4804 supports a new graphics format called dgf (but retaining
4805 the same major version number). If we used the old
4806 <prgn>ldd</prgn> method, every package that uses
4807 <tt>libimlib</tt> would need to be recompiled so it
4808 would also depend on <tt>libdgf</tt> or it wouldn't run
4809 due to missing symbols. However with the new system,
4810 packages using <tt>libimlib</tt> can rely on
4811 <tt>libimlib</tt> itself having the dependency on
4812 <tt>libdgf</tt> and so they would not need rebuilding.
4818 In the following sections, we will first describe where the
4819 various <tt>shlibs</tt> files are to be found, then how to
4820 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
4821 file format and how to create them if your package contains a
4826 <heading>The <tt>shlibs</tt> files present on the system</heading>
4829 There are several places where <tt>shlibs</tt> files are
4830 found. The following list gives them in the order in which
4832 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
4833 (The first one which gives the required information is used.)
4839 <p><file>debian/shlibs.local</file></p>
4842 This lists overrides for this package. Its use is
4843 described below (see <ref id="shlibslocal">).
4848 <p><file>/etc/dpkg/shlibs.override</file></p>
4851 This lists global overrides. This list is normally
4852 empty. It is maintained by the local system
4858 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
4861 When packages are being built, any
4862 <file>debian/shlibs</file> files are copied into the
4863 control file area of the temporary build directory and
4864 given the name <file>shlibs</file>. These files give
4865 details of any shared libraries included in the
4867 An example may help here. Let us say that the
4868 source package <tt>foo</tt> generates two binary
4869 packages, <tt>libfoo2</tt> and
4870 <tt>foo-runtime</tt>. When building the binary
4871 packages, the two packages are created in the
4872 directories <file>debian/libfoo2</file> and
4873 <file>debian/foo-runtime</file> respectively.
4874 (<file>debian/tmp</file> could be used instead of one
4875 of these.) Since <tt>libfoo2</tt> provides the
4876 <tt>libfoo</tt> shared library, it will require a
4877 <tt>shlibs</tt> file, which will be installed in
4878 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually
4880 <file>/var/lib/dpkg/info/libfoo2.shlibs</file>. Then
4881 when <prgn>dpkg-shlibdeps</prgn> is run on the
4883 <file>debian/foo-runtime/usr/bin/foo-prog</file>, it
4885 <file>debian/libfoo2/DEBIAN/shlibs</file> file to
4886 determine whether <tt>foo-prog</tt>'s library
4887 dependencies are satisfied by any of the libraries
4888 provided by <tt>libfoo2</tt>. For this reason,
4889 <prgn>dpkg-shlibdeps</prgn> must only be run once
4890 all of the individual binary packages'
4891 <tt>shlibs</tt> files have been installed into the
4898 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
4901 These are the <file>shlibs</file> files corresponding to
4902 all of the packages installed on the system, and are
4903 maintained by the relevant package maintainers.
4908 <p><file>/etc/dpkg/shlibs.default</file></p>
4911 This file lists any shared libraries whose packages
4912 have failed to provide correct <file>shlibs</file> files.
4913 It was used when the <file>shlibs</file> setup was first
4914 introduced, but it is now normally empty. It is
4915 maintained by the <tt>dpkg</tt> maintainer.
4923 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
4924 <file>shlibs</file> files</heading>
4928 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
4929 into your <file>debian/rules</file> file. If your package
4930 contains only compiled binaries and libraries (but no scripts),
4931 you can use a command such as:
4932 <example compact="compact">
4933 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
4934 debian/tmp/usr/lib/*
4936 Otherwise, you will need to explicitly list the compiled
4937 binaries and libraries.<footnote>
4938 If you are using <tt>debhelper</tt>, the
4939 <prgn>dh_shlibdeps</prgn> program will do this work for
4940 you. It will also correctly handle multi-binary
4946 This command puts the dependency information into the
4947 <file>debian/substvars</file> file, which is then used by
4948 <prgn>dpkg-gencontrol</prgn>. You will need to place a
4949 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
4950 field in the control file for this to work.
4954 If <prgn>dpkg-shlibdeps</prgn> doesn't complain, you're
4955 done. If it does complain you might need to create your own
4956 <file>debian/shlibs.local</file> file, as explained below (see
4957 <ref id="shlibslocal">).
4961 If you have multiple binary packages, you will need to call
4962 <prgn>dpkg-shlibdeps</prgn> on each one which contains
4963 compiled libraries or binaries. In such a case, you will
4964 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
4965 utilities to specify a different <file>substvars</file> file.
4969 If you are creating a udeb for use in the Debian Installer, you
4970 will need to specify that <prgn>dpkg-shlibdeps</prgn> should use
4971 the dependency line of type <tt>udeb</tt> by adding
4972 <tt>-tudeb</tt> as option<footnote>
4973 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
4974 will automatically add this option if it knows it is
4976 </footnote>. If there is no dependency line of type <tt>udeb</tt>
4977 in the <file>shlibs</file> file, <prgn>dpkg-shlibdeps</prgn> will
4978 fall back to the regular dependency line.
4982 For more details on dpkg-shlibdeps, please see
4983 <ref id="pkg-dpkg-shlibdeps"> and
4984 <manref name="dpkg-shlibdeps" section="1">.
4989 <heading>The <file>shlibs</file> File Format</heading>
4992 Each <file>shlibs</file> file has the same format. Lines
4993 beginning with <tt>#</tt> are considered to be comments and
4994 are ignored. Each line is of the form:
4995 <example compact="compact">
4996 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5001 We will explain this by reference to the example of the
5002 <tt>zlib1g</tt> package, which (at the time of writing)
5003 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5007 <var>type</var> is an optional element that indicates the type
5008 of package for which the line is valid. The only type currently
5009 in use is <tt>udeb</tt>. The colon and space after the type are
5014 <var>library-name</var> is the name of the shared library,
5015 in this case <tt>libz</tt>. (This must match the name part
5016 of the soname, see below.)
5020 <var>soname-version</var> is the version part of the soname of
5021 the library. The soname is the thing that must exactly match
5022 for the library to be recognized by the dynamic linker, and is
5024 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5025 example, <tt>libz.so.1</tt>.<footnote>
5026 This can be determined using the command
5027 <example compact="compact">
5028 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5031 The version part is the part which comes after
5032 <tt>.so.</tt>, so in our case, it is <tt>1</tt>.
5036 <var>dependencies</var> has the same syntax as a dependency
5037 field in a binary package control file. It should give
5038 details of which packages are required to satisfy a binary
5039 built against the version of the library contained in the
5040 package. See <ref id="depsyntax"> for details.
5044 In our example, if the first version of the <tt>zlib1g</tt>
5045 package which contained a minor number of at least
5046 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5047 <tt>shlibs</tt> entry for this library could say:
5048 <example compact="compact">
5049 libz 1 zlib1g (>= 1:1.1.3)
5051 The version-specific dependency is to avoid warnings from
5052 the dynamic linker about using older shared libraries with
5057 As zlib1g also provides a udeb containing the shared library,
5058 there would also be a second line:
5059 <example compact="compact">
5060 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5066 <heading>Providing a <file>shlibs</file> file</heading>
5069 If your package provides a shared library, you need to create
5070 a <file>shlibs</file> file following the format described above.
5071 It is usual to call this file <file>debian/shlibs</file> (but if
5072 you have multiple binary packages, you might want to call it
5073 <file>debian/shlibs.<var>package</var></file> instead). Then
5074 let <file>debian/rules</file> install it in the control area:
5075 <example compact="compact">
5076 install -m644 debian/shlibs debian/tmp/DEBIAN
5078 or, in the case of a multi-binary package:
5079 <example compact="compact">
5080 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5082 An alternative way of doing this is to create the
5083 <file>shlibs</file> file in the control area directly from
5084 <file>debian/rules</file> without using a <file>debian/shlibs</file>
5085 file at all,<footnote>
5086 This is what <prgn>dh_makeshlibs</prgn> in the
5087 <tt>debhelper</tt> suite does. If your package also has a udeb
5088 that provides a shared library, <prgn>dh_makeshlibs</prgn> can
5089 automatically generate the <tt>udeb:</tt> lines if you specify
5090 the name of the udeb with the <tt>--add-udeb</tt> option.
5092 since the <file>debian/shlibs</file> file itself is ignored by
5093 <prgn>dpkg-shlibdeps</prgn>.
5097 As <prgn>dpkg-shlibdeps</prgn> reads the
5098 <file>DEBIAN/shlibs</file> files in all of the binary packages
5099 being built from this source package, all of the
5100 <file>DEBIAN/shlibs</file> files should be installed before
5101 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5106 <sect1 id="shlibslocal">
5107 <heading>Writing the <file>debian/shlibs.local</file> file</heading>
5110 This file is intended only as a <em>temporary</em> fix if
5111 your binaries or libraries depend on a library whose package
5112 does not yet provide a correct <file>shlibs</file> file.
5116 We will assume that you are trying to package a binary
5117 <tt>foo</tt>. When you try running
5118 <prgn>dpkg-shlibdeps</prgn> you get the following error
5119 message (<tt>-O</tt> displays the dependency information on
5120 <tt>stdout</tt> instead of writing it to
5121 <tt>debian/substvars</tt>, and the lines have been wrapped
5122 for ease of reading):
5123 <example compact="compact">
5124 $ dpkg-shlibdeps -O debian/tmp/usr/bin/foo
5125 dpkg-shlibdeps: warning: unable to find dependency
5126 information for shared library libbar (soname 1,
5127 path /usr/lib/libbar.so.1, dependency field Depends)
5128 shlibs:Depends=libc6 (>= 2.2.2-2)
5130 You can then run <prgn>ldd</prgn> on the binary to find the
5131 full location of the library concerned:
5132 <example compact="compact">
5134 libbar.so.1 => /usr/lib/libbar.so.1 (0x4001e000)
5135 libc.so.6 => /lib/libc.so.6 (0x40032000)
5136 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
5138 So the <prgn>foo</prgn> binary depends on the
5139 <prgn>libbar</prgn> shared library, but no package seems to
5140 provide a <file>*.shlibs</file> file handling
5141 <file>libbar.so.1</file> in <file>/var/lib/dpkg/info/</file>. Let's
5142 determine the package responsible:
5143 <example compact="compact">
5144 $ dpkg -S /usr/lib/libbar.so.1
5145 bar1: /usr/lib/libbar.so.1
5146 $ dpkg -s bar1 | grep Version
5149 This tells us that the <tt>bar1</tt> package, version 1.0-1,
5150 is the one we are using. Now we can file a bug against the
5151 <tt>bar1</tt> package and create our own
5152 <file>debian/shlibs.local</file> to locally fix the problem.
5153 Including the following line into your
5154 <file>debian/shlibs.local</file> file:
5155 <example compact="compact">
5156 libbar 1 bar1 (>= 1.0-1)
5158 should allow the package build to work.
5162 As soon as the maintainer of <tt>bar1</tt> provides a
5163 correct <file>shlibs</file> file, you should remove this line
5164 from your <file>debian/shlibs.local</file> file. (You should
5165 probably also then have a versioned <tt>Build-Depends</tt>
5166 on <tt>bar1</tt> to help ensure that others do not have the
5167 same problem building your package.)
5176 <chapt id="opersys"><heading>The Operating System</heading>
5179 <heading>File system hierarchy</heading>
5183 <heading>File system Structure</heading>
5186 The location of all installed files and directories must
5187 comply with the File system Hierarchy Standard (FHS),
5188 version 2.3, with the exceptions noted below, and except
5189 where doing so would violate other terms of Debian
5190 Policy. The following exceptions to the FHS apply:
5195 Legacy XFree86 servers are permitted to retain the
5196 configuration file location
5197 <file>/etc/X11/XF86Config-4</file>.
5202 The optional rules related to user specific
5203 configuration files for applications are stored in
5204 the user's home directory are relaxed. It is
5205 recommended that such files start with the
5206 '<tt>.</tt>' character (a "dot file"), and if an
5207 application needs to create more than one dot file
5208 then the preferred placement is in a subdirectory
5209 with a name starting with a '.' character, (a "dot
5210 directory"). In this case it is recommended the
5211 configuration files not start with the '.'
5217 The requirement for amd64 to use <file>/lib64</file>
5218 for 64 bit binaries is removed.
5223 The requirement that
5224 <file>/usr/local/share/man</file> be "synonymous"
5225 with <file>/usr/local/man</file> is relaxed to a
5230 The requirement that windowmanagers with a single
5231 configuration file call it <file>system.*wmrc</file>
5232 is removed, as is the restriction that the window
5233 manager subdirectory be named identically to the
5234 window manager name itself.
5239 The requirement that boot manager configuration
5240 files live in <file>/etc</file>, or at least are
5241 symlinked there, is relaxed to a recommendation.
5248 The version of this document referred here can be
5249 found in the <tt>debian-policy</tt> package or on <url
5250 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5251 name="FHS (Debian copy)"> alongside this manual (or, if
5252 you have the <package>debian-policy</package> installed,
5254 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5255 (local copy)">). The
5256 latest version, which may be a more recent version, may
5258 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5259 Specific questions about following the standard may be
5260 asked on the <tt>debian-devel</tt> mailing list, or
5261 referred to the FHS mailing list (see the
5262 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
5268 <heading>Site-specific programs</heading>
5271 As mandated by the FHS, packages must not place any
5272 files in <file>/usr/local</file>, either by putting them in
5273 the file system archive to be unpacked by <prgn>dpkg</prgn>
5274 or by manipulating them in their maintainer scripts.
5278 However, the package may create empty directories below
5279 <file>/usr/local</file> so that the system administrator knows
5280 where to place site-specific files. These are not
5281 directories <em>in</em> <file>/usr/local</file>, but are
5282 children of directories in <file>/usr/local</file>. These
5283 directories (<file>/usr/local/*/dir/</file>)
5284 should be removed on package removal if they are
5289 Note, that this applies only to directories <em>below</em>
5290 <file>/usr/local</file>, not <em>in</em> <file>/usr/local</file>.
5291 Packages must not create sub-directories in the directory
5292 <file>/usr/local</file> itself, except those listed in FHS,
5293 section 4.5. However, you may create directories below
5294 them as you wish. You must not remove any of the
5295 directories listed in 4.5, even if you created them.
5299 Since <file>/usr/local</file> can be mounted read-only from a
5300 remote server, these directories must be created and
5301 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
5302 maintainer scripts and not be included in the
5303 <file>.deb</file> archive. These scripts must not fail if
5304 either of these operations fail.
5308 For example, the <tt>emacsen-common</tt> package could
5309 contain something like
5310 <example compact="compact">
5311 if [ ! -e /usr/local/share/emacs ]
5313 if mkdir /usr/local/share/emacs 2>/dev/null
5315 chown root:staff /usr/local/share/emacs
5316 chmod 2775 /usr/local/share/emacs
5320 in its <prgn>postinst</prgn> script, and
5321 <example compact="compact">
5322 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
5323 rmdir /usr/local/share/emacs 2>/dev/null || true
5325 in the <prgn>prerm</prgn> script. (Note that this form is
5326 used to ensure that if the script is interrupted, the
5327 directory <file>/usr/local/share/emacs</file> will still be
5332 If you do create a directory in <file>/usr/local</file> for
5333 local additions to a package, you should ensure that
5334 settings in <file>/usr/local</file> take precedence over the
5335 equivalents in <file>/usr</file>.
5339 However, because <file>/usr/local</file> and its contents are
5340 for exclusive use of the local administrator, a package
5341 must not rely on the presence or absence of files or
5342 directories in <file>/usr/local</file> for normal operation.
5346 The <file>/usr/local</file> directory itself and all the
5347 subdirectories created by the package should (by default) have
5348 permissions 2775 (group-writable and set-group-id) and be
5349 owned by <tt>root.staff</tt>.
5354 <heading>The system-wide mail directory</heading>
5356 The system-wide mail directory is <file>/var/mail</file>. This
5357 directory is part of the base system and should not owned
5358 by any particular mail agents. The use of the old
5359 location <file>/var/spool/mail</file> is deprecated, even
5360 though the spool may still be physically located there.
5361 To maintain partial upgrade compatibility for systems
5362 which have <file>/var/spool/mail</file> as their physical mail
5363 spool, packages using <file>/var/mail</file> must depend on
5364 either <package>libc6</package> (>= 2.1.3-13), or on
5365 <package>base-files</package> (>= 2.2.0), or on later
5366 versions of either one of these packages.
5372 <heading>Users and groups</heading>
5375 <heading>Introduction</heading>
5377 The Debian system can be configured to use either plain or
5382 Some user ids (UIDs) and group ids (GIDs) are reserved
5383 globally for use by certain packages. Because some
5384 packages need to include files which are owned by these
5385 users or groups, or need the ids compiled into binaries,
5386 these ids must be used on any Debian system only for the
5387 purpose for which they are allocated. This is a serious
5388 restriction, and we should avoid getting in the way of
5389 local administration policies. In particular, many sites
5390 allocate users and/or local system groups starting at 100.
5394 Apart from this we should have dynamically allocated ids,
5395 which should by default be arranged in some sensible
5396 order, but the behavior should be configurable.
5400 Packages other than <tt>base-passwd</tt> must not modify
5401 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
5402 <file>/etc/group</file> or <file>/etc/gshadow</file>.
5407 <heading>UID and GID classes</heading>
5409 The UID and GID numbers are divided into classes as
5415 Globally allocated by the Debian project, the same
5416 on every Debian system. These ids will appear in
5417 the <file>passwd</file> and <file>group</file> files of all
5418 Debian systems, new ids in this range being added
5419 automatically as the <tt>base-passwd</tt> package is
5424 Packages which need a single statically allocated
5425 uid or gid should use one of these; their
5426 maintainers should ask the <tt>base-passwd</tt>
5434 Dynamically allocated system users and groups.
5435 Packages which need a user or group, but can have
5436 this user or group allocated dynamically and
5437 differently on each system, should use <tt>adduser
5438 --system</tt> to create the group and/or user.
5439 <prgn>adduser</prgn> will check for the existence of
5440 the user or group, and if necessary choose an unused
5441 id based on the ranges specified in
5442 <file>adduser.conf</file>.
5446 <tag>1000-29999:</tag>
5449 Dynamically allocated user accounts. By default
5450 <prgn>adduser</prgn> will choose UIDs and GIDs for
5451 user accounts in this range, though
5452 <file>adduser.conf</file> may be used to modify this
5457 <tag>30000-59999:</tag>
5462 <tag>60000-64999:</tag>
5465 Globally allocated by the Debian project, but only
5466 created on demand. The ids are allocated centrally
5467 and statically, but the actual accounts are only
5468 created on users' systems on demand.
5472 These ids are for packages which are obscure or
5473 which require many statically-allocated ids. These
5474 packages should check for and create the accounts in
5475 <file>/etc/passwd</file> or <file>/etc/group</file> (using
5476 <prgn>adduser</prgn> if it has this facility) if
5477 necessary. Packages which are likely to require
5478 further allocations should have a "hole" left after
5479 them in the allocation, to give them room to
5484 <tag>65000-65533:</tag>
5492 User <tt>nobody</tt>. The corresponding gid refers
5493 to the group <tt>nogroup</tt>.
5500 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
5501 not</em> be used, because it is the error return
5510 <sect id="sysvinit">
5511 <heading>System run levels and <file>init.d</file> scripts</heading>
5513 <sect1 id="/etc/init.d">
5514 <heading>Introduction</heading>
5517 The <file>/etc/init.d</file> directory contains the scripts
5518 executed by <prgn>init</prgn> at boot time and when the
5519 init state (or "runlevel") is changed (see <manref
5520 name="init" section="8">).
5524 There are at least two different, yet functionally
5525 equivalent, ways of handling these scripts. For the sake
5526 of simplicity, this document describes only the symbolic
5527 link method. However, it must not be assumed by maintainer
5528 scripts that this method is being used, and any automated
5529 manipulation of the various runlevel behaviors by
5530 maintainer scripts must be performed using
5531 <prgn>update-rc.d</prgn> as described below and not by
5532 manually installing or removing symlinks. For information
5533 on the implementation details of the other method,
5534 implemented in the <tt>file-rc</tt> package, please refer
5535 to the documentation of that package.
5539 These scripts are referenced by symbolic links in the
5540 <file>/etc/rc<var>n</var>.d</file> directories. When changing
5541 runlevels, <prgn>init</prgn> looks in the directory
5542 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
5543 execute, where <tt><var>n</var></tt> is the runlevel that
5544 is being changed to, or <tt>S</tt> for the boot-up
5549 The names of the links all have the form
5550 <file>S<var>mm</var><var>script</var></file> or
5551 <file>K<var>mm</var><var>script</var></file> where
5552 <var>mm</var> is a two-digit number and <var>script</var>
5553 is the name of the script (this should be the same as the
5554 name of the actual script in <file>/etc/init.d</file>).
5558 When <prgn>init</prgn> changes runlevel first the targets
5559 of the links whose names start with a <tt>K</tt> are
5560 executed, each with the single argument <tt>stop</tt>,
5561 followed by the scripts prefixed with an <tt>S</tt>, each
5562 with the single argument <tt>start</tt>. (The links are
5563 those in the <file>/etc/rc<var>n</var>.d</file> directory
5564 corresponding to the new runlevel.) The <tt>K</tt> links
5565 are responsible for killing services and the <tt>S</tt>
5566 link for starting services upon entering the runlevel.
5570 For example, if we are changing from runlevel 2 to
5571 runlevel 3, init will first execute all of the <tt>K</tt>
5572 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
5573 all of the <tt>S</tt> prefixed scripts in that directory.
5574 The links starting with <tt>K</tt> will cause the
5575 referred-to file to be executed with an argument of
5576 <tt>stop</tt>, and the <tt>S</tt> links with an argument
5581 The two-digit number <var>mm</var> is used to determine
5582 the order in which to run the scripts: low-numbered links
5583 have their scripts run first. For example, the
5584 <tt>K20</tt> scripts will be executed before the
5585 <tt>K30</tt> scripts. This is used when a certain service
5586 must be started before another. For example, the name
5587 server <prgn>bind</prgn> might need to be started before
5588 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
5589 can set up its access lists. In this case, the script
5590 that starts <prgn>bind</prgn> would have a lower number
5591 than the script that starts <prgn>inn</prgn> so that it
5593 <example compact="compact">
5600 The two runlevels 0 (halt) and 6 (reboot) are slightly
5601 different. In these runlevels, the links with an
5602 <tt>S</tt> prefix are still called after those with a
5603 <tt>K</tt> prefix, but they too are called with the single
5604 argument <tt>stop</tt>.
5608 Also, if the script name ends in <tt>.sh</tt>, the script
5609 will be sourced in runlevel <tt>S</tt> rather than being
5610 run in a forked subprocess, but will be explicitly run by
5611 <prgn>sh</prgn> in all other runlevels.
5616 <heading>Writing the scripts</heading>
5619 Packages that include daemons for system services should
5620 place scripts in <file>/etc/init.d</file> to start or stop
5621 services at boot time or during a change of runlevel.
5622 These scripts should be named
5623 <file>/etc/init.d/<var>package</var></file>, and they should
5624 accept one argument, saying what to do:
5627 <tag><tt>start</tt></tag>
5628 <item>start the service,</item>
5630 <tag><tt>stop</tt></tag>
5631 <item>stop the service,</item>
5633 <tag><tt>restart</tt></tag>
5634 <item>stop and restart the service if it's already running,
5635 otherwise start the service</item>
5637 <tag><tt>reload</tt></tag>
5638 <item><p>cause the configuration of the service to be
5639 reloaded without actually stopping and restarting
5642 <tag><tt>force-reload</tt></tag>
5643 <item>cause the configuration to be reloaded if the
5644 service supports this, otherwise restart the
5648 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
5649 <tt>force-reload</tt> options should be supported by all
5650 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
5655 The <file>init.d</file> scripts must ensure that they will
5656 behave sensibly if invoked with <tt>start</tt> when the
5657 service is already running, or with <tt>stop</tt> when it
5658 isn't, and that they don't kill unfortunately-named user
5659 processes. The best way to achieve this is usually to use
5660 <prgn>start-stop-daemon</prgn>.
5664 If a service reloads its configuration automatically (as
5665 in the case of <prgn>cron</prgn>, for example), the
5666 <tt>reload</tt> option of the <file>init.d</file> script
5667 should behave as if the configuration has been reloaded
5672 The <file>/etc/init.d</file> scripts must be treated as
5673 configuration files, either (if they are present in the
5674 package, that is, in the .deb file) by marking them as
5675 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
5676 by managing them correctly in the maintainer scripts (see
5677 <ref id="config-files">). This is important since we want
5678 to give the local system administrator the chance to adapt
5679 the scripts to the local system, e.g., to disable a
5680 service without de-installing the package, or to specify
5681 some special command line options when starting a service,
5682 while making sure their changes aren't lost during the next
5687 These scripts should not fail obscurely when the
5688 configuration files remain but the package has been
5689 removed, as configuration files remain on the system after
5690 the package has been removed. Only when <prgn>dpkg</prgn>
5691 is executed with the <tt>--purge</tt> option will
5692 configuration files be removed. In particular, as the
5693 <file>/etc/init.d/<var>package</var></file> script itself is
5694 usually a <tt>conffile</tt>, it will remain on the system
5695 if the package is removed but not purged. Therefore, you
5696 should include a <tt>test</tt> statement at the top of the
5698 <example compact="compact">
5699 test -f <var>program-executed-later-in-script</var> || exit 0
5704 Often there are some variables in the <file>init.d</file>
5705 scripts whose values control the behavior of the scripts,
5706 and which a system administrator is likely to want to
5707 change. As the scripts themselves are frequently
5708 <tt>conffile</tt>s, modifying them requires that the
5709 administrator merge in their changes each time the package
5710 is upgraded and the <tt>conffile</tt> changes. To ease
5711 the burden on the system administrator, such configurable
5712 values should not be placed directly in the script.
5713 Instead, they should be placed in a file in
5714 <file>/etc/default</file>, which typically will have the same
5715 base name as the <file>init.d</file> script. This extra file
5716 should be sourced by the script when the script runs. It
5717 must contain only variable settings and comments in SUSv3
5718 <prgn>sh</prgn> format. It may either be a
5719 <tt>conffile</tt> or a configuration file maintained by
5720 the package maintainer scripts. See <ref id="config-files">
5725 To ensure that vital configurable values are always
5726 available, the <file>init.d</file> script should set default
5727 values for each of the shell variables it uses, either
5728 before sourcing the <file>/etc/default/</file> file or
5729 afterwards using something like the <tt>:
5730 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
5731 script must behave sensibly and not fail if the
5732 <file>/etc/default</file> file is deleted.
5737 <heading>Interfacing with the initscript system</heading>
5740 Maintainers should use the abstraction layer provided by
5741 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
5742 programs to deal with initscripts in their packages'
5743 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
5744 and <prgn>postrm</prgn>.
5748 Directly managing the /etc/rc?.d links and directly
5749 invoking the <file>/etc/init.d/</file> initscripts should
5750 be done only by packages providing the initscript
5751 subsystem (such as <prgn>sysv-rc</prgn> and
5752 <prgn>file-rc</prgn>).
5756 <heading>Managing the links</heading>
5759 The program <prgn>update-rc.d</prgn> is provided for
5760 package maintainers to arrange for the proper creation and
5761 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
5762 or their functional equivalent if another method is being
5763 used. This may be used by maintainers in their packages'
5764 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
5768 You must not include any <file>/etc/rc<var>n</var>.d</file>
5769 symbolic links in the actual archive or manually create or
5770 remove the symbolic links in maintainer scripts; you must
5771 use the <prgn>update-rc.d</prgn> program instead. (The
5772 former will fail if an alternative method of maintaining
5773 runlevel information is being used.) You must not include
5774 the <file>/etc/rc<var>n</var>.d</file> directories themselves
5775 in the archive either. (Only the <tt>sysvinit</tt>
5780 By default <prgn>update-rc.d</prgn> will start services in
5781 each of the multi-user state runlevels (2, 3, 4, and 5)
5782 and stop them in the halt runlevel (0), the single-user
5783 runlevel (1) and the reboot runlevel (6). The system
5784 administrator will have the opportunity to customize
5785 runlevels by simply adding, moving, or removing the
5786 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
5787 symbolic links are being used, or by modifying
5788 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
5793 To get the default behavior for your package, put in your
5794 <prgn>postinst</prgn> script
5795 <example compact="compact">
5796 update-rc.d <var>package</var> defaults
5798 and in your <prgn>postrm</prgn>
5799 <example compact="compact">
5800 if [ "$1" = purge ]; then
5801 update-rc.d <var>package</var> remove
5803 </example>. Note that if your package changes runlevels
5804 or priority, you may have to remove and recreate the links,
5805 since otherwise the old links may persist. Refer to the
5806 documentation of <prgn>update-rc.d</prgn>.
5810 This will use a default sequence number of 20. If it does
5811 not matter when or in which order the <file>init.d</file>
5812 script is run, use this default. If it does, then you
5813 should talk to the maintainer of the <prgn>sysvinit</prgn>
5814 package or post to <tt>debian-devel</tt>, and they will
5815 help you choose a number.
5819 For more information about using <tt>update-rc.d</tt>,
5820 please consult its man page <manref name="update-rc.d"
5826 <heading>Running initscripts</heading>
5828 The program <prgn>invoke-rc.d</prgn> is provided to make
5829 it easier for package maintainers to properly invoke an
5830 initscript, obeying runlevel and other locally-defined
5831 constraints that might limit a package's right to start,
5832 stop and otherwise manage services. This program may be
5833 used by maintainers in their packages' scripts.
5837 The package maintainer scripts must use
5838 <prgn>invoke-rc.d</prgn> to invoke the
5839 <file>/etc/init.d/*</file> initscripts, instead of
5840 calling them directly.
5844 By default, <prgn>invoke-rc.d</prgn> will pass any
5845 action requests (start, stop, reload, restart...) to the
5846 <file>/etc/init.d</file> script, filtering out requests
5847 to start or restart a service out of its intended
5852 Most packages will simply need to change:
5853 <example compact="compact">/etc/init.d/<package>
5854 <action></example> in their <prgn>postinst</prgn>
5855 and <prgn>prerm</prgn> scripts to:
5856 <example compact="compact">
5857 if which invoke-rc.d >/dev/null 2>&1; then
5858 invoke-rc.d <var>package</var> <action>
5860 /etc/init.d/<var>package</var> <action>
5866 A package should register its initscript services using
5867 <prgn>update-rc.d</prgn> before it tries to invoke them
5868 using <prgn>invoke-rc.d</prgn>. Invocation of
5869 unregistered services may fail.
5873 For more information about using
5874 <prgn>invoke-rc.d</prgn>, please consult its man page
5875 <manref name="invoke-rc.d" section="8">.
5881 <heading>Boot-time initialization</heading>
5884 There used to be another directory, <file>/etc/rc.boot</file>,
5885 which contained scripts which were run once per machine
5886 boot. This has been deprecated in favour of links from
5887 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
5888 described in <ref id="/etc/init.d">. Packages must not
5889 place files in <file>/etc/rc.boot</file>.
5894 <heading>Example</heading>
5897 An example on which you can base your
5898 <file>/etc/init.d</file> scripts is found in
5899 <file>/etc/init.d/skeleton</file>.
5906 <heading>Console messages from <file>init.d</file> scripts</heading>
5909 This section describes the formats to be used for messages
5910 written to standard output by the <file>/etc/init.d</file>
5911 scripts. The intent is to improve the consistency of
5912 Debian's startup and shutdown look and feel. For this
5913 reason, please look very carefully at the details. We want
5914 the messages to have the same format in terms of wording,
5915 spaces, punctuation and case of letters.
5919 Here is a list of overall rules that should be used for
5920 messages generated by <file>/etc/init.d</file> scripts.
5926 The message should fit in one line (fewer than 80
5927 characters), start with a capital letter and end with
5928 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
5932 If the script is performing some time consuming task in
5933 the background (not merely starting or stopping a
5934 program, for instance), an ellipsis (three dots:
5935 <tt>...</tt>) should be output to the screen, with no
5936 leading or tailing whitespace or line feeds.
5940 The messages should appear as if the computer is telling
5941 the user what it is doing (politely :-), but should not
5942 mention "it" directly. For example, instead of:
5943 <example compact="compact">
5944 I'm starting network daemons: nfsd mountd.
5946 the message should say
5947 <example compact="compact">
5948 Starting network daemons: nfsd mountd.
5955 <tt>init.d</tt> script should use the following standard
5956 message formats for the situations enumerated below.
5962 <p>When daemons are started</p>
5965 If the script starts one or more daemons, the output
5966 should look like this (a single line, no leading
5968 <example compact="compact">
5969 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
5971 The <var>description</var> should describe the
5972 subsystem the daemon or set of daemons are part of,
5973 while <var>daemon-1</var> up to <var>daemon-n</var>
5974 denote each daemon's name (typically the file name of
5979 For example, the output of <file>/etc/init.d/lpd</file>
5981 <example compact="compact">
5982 Starting printer spooler: lpd.
5987 This can be achieved by saying
5988 <example compact="compact">
5989 echo -n "Starting printer spooler: lpd"
5990 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
5993 in the script. If there are more than one daemon to
5994 start, the output should look like this:
5995 <example compact="compact">
5996 echo -n "Starting remote file system services:"
5997 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
5998 echo -n " mountd"; start-stop-daemon --start --quiet mountd
5999 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6002 This makes it possible for the user to see what is
6003 happening and when the final daemon has been started.
6004 Care should be taken in the placement of white spaces:
6005 in the example above the system administrators can
6006 easily comment out a line if they don't want to start
6007 a specific daemon, while the displayed message still
6013 <p>When a system parameter is being set</p>
6016 If you have to set up different system parameters
6017 during the system boot, you should use this format:
6018 <example compact="compact">
6019 Setting <var>parameter</var> to "<var>value</var>".
6024 You can use a statement such as the following to get
6026 <example compact="compact">
6027 echo "Setting DNS domainname to \"$domainname\"."
6032 Note that the same symbol (<tt>"</tt>) is used for the left
6033 and right quotation marks. A grave accent (<tt>`</tt>) is
6034 not a quote character; neither is an apostrophe
6040 <p>When a daemon is stopped or restarted</p>
6043 When you stop or restart a daemon, you should issue a
6044 message identical to the startup message, except that
6045 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6046 or <tt>Restarting</tt> respectively.
6050 For example, stopping the printer daemon will look like
6052 <example compact="compact">
6053 Stopping printer spooler: lpd.
6059 <p>When something is executed</p>
6062 There are several examples where you have to run a
6063 program at system startup or shutdown to perform a
6064 specific task, for example, setting the system's clock
6065 using <prgn>netdate</prgn> or killing all processes
6066 when the system shuts down. Your message should look
6068 <example compact="compact">
6069 Doing something very useful...done.
6071 You should print the <tt>done.</tt> immediately after
6072 the job has been completed, so that the user is
6073 informed why they have to wait. You can get this
6075 <example compact="compact">
6076 echo -n "Doing something very useful..."
6085 <p>When the configuration is reloaded</p>
6088 When a daemon is forced to reload its configuration
6089 files you should use the following format:
6090 <example compact="compact">
6091 Reloading <var>description</var> configuration...done.
6093 where <var>description</var> is the same as in the
6094 daemon starting message.
6102 <heading>Cron jobs</heading>
6105 Packages must not modify the configuration file
6106 <file>/etc/crontab</file>, and they must not modify the files in
6107 <file>/var/spool/cron/crontabs</file>.</p>
6110 If a package wants to install a job that has to be executed
6111 via cron, it should place a file with the name of the
6112 package in one or more of the following directories:
6113 <example compact="compact">
6118 As these directory names imply, the files within them are
6119 executed on a daily, weekly, or monthly basis,
6120 respectively. The exact times are listed in
6121 <file>/etc/crontab</file>.</p>
6124 All files installed in any of these directories must be
6125 scripts (e.g., shell scripts or Perl scripts) so that they
6126 can easily be modified by the local system administrator.
6127 In addition, they should be treated as configuration
6132 If a certain job has to be executed more frequently than
6133 daily, the package should install a file
6134 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6135 same syntax as <file>/etc/crontab</file> and is processed by
6136 <prgn>cron</prgn> automatically. The file must also be
6137 treated as a configuration file. (Note that entries in the
6138 <file>/etc/cron.d</file> directory are not handled by
6139 <prgn>anacron</prgn>. Thus, you should only use this
6140 directory for jobs which may be skipped if the system is not
6144 The scripts or crontab entries in these directories should
6145 check if all necessary programs are installed before they
6146 try to execute them. Otherwise, problems will arise when a
6147 package was removed but not purged since configuration files
6148 are kept on the system in this situation.</p>
6152 <heading>Menus</heading>
6155 The Debian <tt>menu</tt> package provides a standard
6156 interface between packages providing applications and
6157 <em>menu programs</em> (either X window managers or
6158 text-based menu programs such as <prgn>pdmenu</prgn>).
6162 All packages that provide applications that need not be
6163 passed any special command line arguments for normal
6164 operation should register a menu entry for those
6165 applications, so that users of the <tt>menu</tt> package
6166 will automatically get menu entries in their window
6167 managers, as well in shells like <tt>pdmenu</tt>.
6171 Menu entries should follow the current menu policy.
6175 The menu policy can be found in the <tt>menu-policy</tt>
6176 files in the <tt>debian-policy</tt> package.
6177 It is also available from the Debian web mirrors at
6178 <tt><url name="/doc/packaging-manuals/menu-policy/"
6179 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6183 Please also refer to the <em>Debian Menu System</em>
6184 documentation that comes with the <package>menu</package>
6185 package for information about how to register your
6191 <heading>Multimedia handlers</heading>
6194 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6195 is a mechanism for encoding files and data streams and
6196 providing meta-information about them, in particular their
6197 type (e.g. audio or video) and format (e.g. PNG, HTML,
6202 Registration of MIME type handlers allows programs like mail
6203 user agents and web browsers to invoke these handlers to
6204 view, edit or display MIME types they don't support directly.
6208 Packages which provide the ability to view/show/play,
6209 compose, edit or print MIME types should register themselves
6210 as such following the current MIME support policy.
6214 The MIME support policy can be found in the <tt>mime-policy</tt>
6215 files in the <tt>debian-policy</tt> package.
6216 It is also available from the Debian web mirrors at
6217 <tt><url name="/doc/packaging-manuals/mime-policy/"
6218 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
6224 <heading>Keyboard configuration</heading>
6227 To achieve a consistent keyboard configuration so that all
6228 applications interpret a keyboard event the same way, all
6229 programs in the Debian distribution must be configured to
6230 comply with the following guidelines.
6234 The following keys must have the specified interpretations:
6237 <tag><tt><--</tt></tag>
6238 <item>delete the character to the left of the cursor</item>
6240 <tag><tt>Delete</tt></tag>
6241 <item>delete the character to the right of the cursor</item>
6243 <tag><tt>Control+H</tt></tag>
6244 <item>emacs: the help prefix</item>
6247 The interpretation of any keyboard events should be
6248 independent of the terminal that is used, be it a virtual
6249 console, an X terminal emulator, an rlogin/telnet session,
6254 The following list explains how the different programs
6255 should be set up to achieve this:
6261 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
6265 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
6269 X translations are set up to make
6270 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
6271 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
6272 is the vt220 escape code for the "delete character"
6273 key). This must be done by loading the X resources
6274 using <prgn>xrdb</prgn> on all local X displays, not
6275 using the application defaults, so that the
6276 translation resources used correspond to the
6277 <prgn>xmodmap</prgn> settings.
6281 The Linux console is configured to make
6282 <tt><--</tt> generate DEL, and <tt>Delete</tt>
6283 generate <tt>ESC [ 3 ~</tt>.
6287 X applications are configured so that <tt><</tt>
6288 deletes left, and <tt>Delete</tt> deletes right. Motif
6289 applications already work like this.
6293 Terminals should have <tt>stty erase ^?</tt> .
6297 The <tt>xterm</tt> terminfo entry should have <tt>ESC
6298 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
6299 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
6303 Emacs is programmed to map <tt>KB_Backspace</tt> or
6304 the <tt>stty erase</tt> character to
6305 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
6306 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
6307 <tt>^H</tt> to <tt>help</tt> as always.
6311 Other applications use the <tt>stty erase</tt>
6312 character and <tt>kdch1</tt> for the two delete keys,
6313 with ASCII DEL being "delete previous character" and
6314 <tt>kdch1</tt> being "delete character under
6322 This will solve the problem except for the following
6329 Some terminals have a <tt><--</tt> key that cannot
6330 be made to produce anything except <tt>^H</tt>. On
6331 these terminals Emacs help will be unavailable on
6332 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
6333 character takes precedence in Emacs, and has been set
6334 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
6335 available) can be used instead.
6339 Some operating systems use <tt>^H</tt> for <tt>stty
6340 erase</tt>. However, modern telnet versions and all
6341 rlogin versions propagate <tt>stty</tt> settings, and
6342 almost all UNIX versions honour <tt>stty erase</tt>.
6343 Where the <tt>stty</tt> settings are not propagated
6344 correctly, things can be made to work by using
6345 <tt>stty</tt> manually.
6349 Some systems (including previous Debian versions) use
6350 <prgn>xmodmap</prgn> to arrange for both
6351 <tt><--</tt> and <tt>Delete</tt> to generate
6352 <tt>KB_Delete</tt>. We can change the behavior of
6353 their X clients using the same X resources that we use
6354 to do it for our own clients, or configure our clients
6355 using their resources when things are the other way
6356 around. On displays configured like this
6357 <tt>Delete</tt> will not work, but <tt><--</tt>
6362 Some operating systems have different <tt>kdch1</tt>
6363 settings in their <tt>terminfo</tt> database for
6364 <tt>xterm</tt> and others. On these systems the
6365 <tt>Delete</tt> key will not work correctly when you
6366 log in from a system conforming to our policy, but
6367 <tt><--</tt> will.
6374 <heading>Environment variables</heading>
6377 A program must not depend on environment variables to get
6378 reasonable defaults. (That's because these environment
6379 variables would have to be set in a system-wide
6380 configuration file like <file>/etc/profile</file>, which is not
6381 supported by all shells.)
6385 If a program usually depends on environment variables for its
6386 configuration, the program should be changed to fall back to
6387 a reasonable default configuration if these environment
6388 variables are not present. If this cannot be done easily
6389 (e.g., if the source code of a non-free program is not
6390 available), the program must be replaced by a small
6391 "wrapper" shell script which sets the environment variables
6392 if they are not already defined, and calls the original program.
6396 Here is an example of a wrapper script for this purpose:
6398 <example compact="compact">
6400 BAR=${BAR:-/var/lib/fubar}
6402 exec /usr/lib/foo/foo "$@"
6407 Furthermore, as <file>/etc/profile</file> is a configuration
6408 file of the <prgn>base-files</prgn> package, other packages must
6409 not put any environment variables or other commands into that
6414 <sect id="doc-base">
6415 <heading>Registering Documents using doc-base</heading>
6418 The <package>doc-base</package> package implements a
6419 flexible mechanism for handling and presenting
6420 documentation. The recommended practice is for every Debian
6421 package that provides online documentation (other than just
6422 manual pages) to register these documents with
6423 <package>doc-base</package> by installing a
6424 <package>doc-base</package> control file via the
6425 <prgn/install-docs/ script at installation time and
6426 de-register the manuals again when the package is removed.
6429 Please refer to the documentation that comes with the
6430 <package>doc-base</package> package for information and
6439 <heading>Files</heading>
6442 <heading>Binaries</heading>
6445 Two different packages must not install programs with
6446 different functionality but with the same filenames. (The
6447 case of two programs having the same functionality but
6448 different implementations is handled via "alternatives" or
6449 the "Conflicts" mechanism. See <ref id="maintscripts"> and
6450 <ref id="conflicts"> respectively.) If this case happens,
6451 one of the programs must be renamed. The maintainers should
6452 report this to the <tt>debian-devel</tt> mailing list and
6453 try to find a consensus about which program will have to be
6454 renamed. If a consensus cannot be reached, <em>both</em>
6455 programs must be renamed.
6459 By default, when a package is being built, any binaries
6460 created should include debugging information, as well as
6461 being compiled with optimization. You should also turn on
6462 as many reasonable compilation warnings as possible; this
6463 makes life easier for porters, who can then look at build
6464 logs for possible problems. For the C programming language,
6465 this means the following compilation parameters should be
6467 <example compact="compact">
6469 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
6471 INSTALL = install -s # (or use strip on the files in debian/tmp)
6476 Note that by default all installed binaries should be stripped,
6477 either by using the <tt>-s</tt> flag to
6478 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
6479 the binaries after they have been copied into
6480 <file>debian/tmp</file> but before the tree is made into a
6485 Although binaries in the build tree should be compiled with
6486 debugging information by default, it can often be difficult
6487 to debug programs if they are also subjected to compiler
6488 optimization. For this reason, it is recommended to support
6489 the standardized environment
6490 variable <tt>DEB_BUILD_OPTIONS</tt>. This variable can
6491 contain several flags to change how a package is compiled
6499 The presence of this string means that the package
6500 should be compiled with a minimum of optimization.
6501 For C programs, it is best to add <tt>-O0</tt>
6502 to <tt>CFLAGS</tt> (although this is usually the
6503 default). Some programs might fail to build or run at
6504 this level of optimization; it may be necessary to
6505 use <tt>-O1</tt>, for example.
6509 This string means that the debugging symbols should
6510 not be stripped from the binary during installation,
6511 so that debugging information may be included in the package.
6517 The following makefile snippet is an example of how one may
6518 implement the build options; you will probably have to
6519 massage this example in order to make it work for your
6521 <example compact="compact">
6524 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
6525 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
6526 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
6527 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
6529 ifneq (,$(findstring noopt,$(DEB_BUILD_OPTIONS)))
6534 ifeq (,$(findstring nostrip,$(DEB_BUILD_OPTIONS)))
6535 INSTALL_PROGRAM += -s
6541 It is up to the package maintainer to decide what
6542 compilation options are best for the package. Certain
6543 binaries (such as computationally-intensive programs) will
6544 function better with certain flags (<tt>-O3</tt>, for
6545 example); feel free to use them. Please use good judgment
6546 here. Don't use flags for the sake of it; only use them
6547 if there is good reason to do so. Feel free to override
6548 the upstream author's ideas about which compilation
6549 options are best: they are often inappropriate for our
6555 <sect id="libraries">
6556 <heading>Libraries</heading>
6559 If the package is <strong>architecture: any</strong>, then
6560 the shared library compilation and linking flags must have
6561 <tt>-fPIC</tt>, or the package shall not build on some of
6562 the supported architectures<footnote>
6564 If you are using GCC, <tt>-fPIC</tt> produces code with
6565 relocatable position independent code, which is required for
6566 most architectures to create a shared library, with i386 and
6567 perhaps some others where non position independent code is
6568 permitted in a shared library.
6571 Position independent code may have a performance penalty,
6572 especially on <tt>i386</tt>. However, in most cases the
6573 speed penalty must be measured against the memory wasted on
6574 the few architectures where non position independent code is
6577 </footnote>. Any exception to this rule must be discussed on
6578 the mailing list <em>debian-devel@lists.debian.org</em>, and
6579 a rough consensus obtained. The reasons for not compiling
6580 with <tt>-fPIC</tt> flag must be recorded in the file
6581 <tt>README.Debian</tt>, and care must be taken to either
6582 restrict the architecture or arrange for <tt>-fPIC</tt> to
6583 be used on architectures where it is required.<footnote>
6585 Some of the reasons why this might be required is if the
6586 library contains hand crafted assembly code that is not
6587 relocatable, the speed penalty is excessive for compute
6588 intensive libs, and similar reasons.
6593 As to the static libraries, the common case is not to have
6594 relocatable code, since there is no benefit, unless in specific
6595 cases; therefore the static version must not be compiled
6596 with the <tt>-fPIC</tt> flag. Any exception to this rule
6597 should be discussed on the mailing list
6598 <em>debian-devel@lists.debian.org</em>, and the reasons for
6599 compiling with the <tt>-fPIC</tt> flag must be recorded in
6600 the file <tt>README.Debian</tt>. <footnote>
6602 Some of the reasons for linking static libraries with
6603 the <tt>-fPIC</tt> flag are if, for example, one needs a
6604 Perl API for a library that is under rapid development,
6605 and has an unstable API, so shared libraries are
6606 pointless at this phase of the library's development. In
6607 that case, since Perl needs a library with relocatable
6608 code, it may make sense to create a static library with
6609 relocatable code. Another reason cited is if you are
6610 distilling various libraries into a common shared
6611 library, like <tt>mklibs</tt> does in the Debian
6617 In other words, if both a shared and a static library is
6618 being built, each source unit (<tt>*.c</tt>, for example,
6619 for C files) will need to be compiled twice, for the normal
6623 You must specify the gcc option <tt>-D_REENTRANT</tt>
6624 when building a library (either static or shared) to make
6625 the library compatible with LinuxThreads.
6629 Although not enforced by the build tools, shared libraries
6630 must be linked against all libraries that they use symbols from
6631 in the same way that binaries are. This ensures the correct
6632 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
6633 system and guarantees that all libraries can be safely opened
6634 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
6635 option <tt>-Wl,-z,defs</tt> when building a shared library.
6636 Since this option enforces symbol resolution at build time,
6637 a missing library reference will be caught early as a fatal
6642 All installed shared libraries should be stripped with
6643 <example compact="compact">
6644 strip --strip-unneeded <var>your-lib</var>
6646 (The option <tt>--strip-unneeded</tt> makes
6647 <prgn>strip</prgn> remove only the symbols which aren't
6648 needed for relocation processing.) Shared libraries can
6649 function perfectly well when stripped, since the symbols for
6650 dynamic linking are in a separate part of the ELF object
6652 You might also want to use the options
6653 <tt>--remove-section=.comment</tt> and
6654 <tt>--remove-section=.note</tt> on both shared libraries
6655 and executables, and <tt>--strip-debug</tt> on static
6661 Note that under some circumstances it may be useful to
6662 install a shared library unstripped, for example when
6663 building a separate package to support debugging.
6667 Shared object files (often <file>.so</file> files) that are not
6668 public libraries, that is, they are not meant to be linked
6669 to by third party executables (binaries of other packages),
6670 should be installed in subdirectories of the
6671 <file>/usr/lib</file> directory. Such files are exempt from the
6672 rules that govern ordinary shared libraries, except that
6673 they must not be installed executable and should be
6675 A common example are the so-called "plug-ins",
6676 internal shared objects that are dynamically loaded by
6677 programs using <manref name="dlopen" section="3">.
6682 Packages containing shared libraries that may be linked to
6683 by other packages' binaries, but which for some
6684 <em>compelling</em> reason can not be installed in
6685 <file>/usr/lib</file> directory, may install the shared library
6686 files in subdirectories of the <file>/usr/lib</file> directory,
6687 in which case they should arrange to add that directory in
6688 <file>/etc/ld.so.conf</file> in the package's post-installation
6689 script, and remove it in the package's post-removal script.
6693 An ever increasing number of packages are using
6694 <prgn>libtool</prgn> to do their linking. The latest GNU
6695 libtools (>= 1.3a) can take advantage of the metadata in the
6696 installed <prgn>libtool</prgn> archive files (<file>*.la</file>
6697 files). The main advantage of <prgn>libtool</prgn>'s
6698 <file>.la</file> files is that it allows <prgn>libtool</prgn> to
6699 store and subsequently access metadata with respect to the
6700 libraries it builds. <prgn>libtool</prgn> will search for
6701 those files, which contain a lot of useful information about
6702 a library (such as library dependency information for static
6703 linking). Also, they're <em>essential</em> for programs
6704 using <tt>libltdl</tt>.<footnote>
6705 Although <prgn>libtool</prgn> is fully capable of
6706 linking against shared libraries which don't have
6707 <tt>.la</tt> files, as it is a mere shell script it can
6708 add considerably to the build time of a
6709 <prgn>libtool</prgn>-using package if that shell script
6710 has to derive all this information from first principles
6711 for each library every time it is linked. With the
6712 advent of <prgn>libtool</prgn> version 1.4 (and to a
6713 lesser extent <prgn>libtool</prgn> version 1.3), the
6714 <file>.la</file> files also store information about
6715 inter-library dependencies which cannot necessarily be
6716 derived after the <file>.la</file> file is deleted.
6721 Packages that use <prgn>libtool</prgn> to create shared
6722 libraries should include the <file>.la</file> files in the
6723 <tt>-dev</tt> package, unless the package relies on
6724 <tt>libtool</tt>'s <tt>libltdl</tt> library, in which case
6725 the <tt>.la</tt> files must go in the run-time library
6730 You must make sure that you use only released versions of
6731 shared libraries to build your packages; otherwise other
6732 users will not be able to run your binaries
6733 properly. Producing source packages that depend on
6734 unreleased compilers is also usually a bad
6741 <heading>Shared libraries</heading>
6743 This section has moved to <ref id="sharedlibs">.
6749 <heading>Scripts</heading>
6752 All command scripts, including the package maintainer
6753 scripts inside the package and used by <prgn>dpkg</prgn>,
6754 should have a <tt>#!</tt> line naming the shell to be used
6759 In the case of Perl scripts this should be
6760 <tt>#!/usr/bin/perl</tt>.
6764 When scripts are installed into a directory in the system
6765 PATH, the script name should not include an extension such
6766 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
6767 language currently used to implement it.
6770 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>)
6771 should almost certainly start with <tt>set -e</tt> so that
6772 errors are detected. Every script should use
6773 <tt>set -e</tt> or check the exit status of <em>every</em>
6778 Scripts may assume that <file>/bin/sh</file> implements the
6779 SUSv3 Shell Command Language<footnote>
6780 Single UNIX Specification, version 3, which is also IEEE
6781 1003.1-2004 (POSIX), and is available on the World Wide Web
6782 from <url id="http://www.unix.org/version3/online.html"
6783 name="The Open Group"> after free
6784 registration.</footnote>
6785 plus the following additional features not mandated by
6787 These features are in widespread use in the Linux community
6788 and are implemented in all of bash, dash, and ksh, the most
6789 common shells users may wish to use as <file>/bin/sh</file>.
6792 <item><tt>echo -n</tt>, if implemented as a shell built-in,
6793 must not generate a newline.</item>
6794 <item><tt>test</tt>, if implemented as a shell built-in, must
6795 support <tt>-a</tt> and <tt>-o</tt> as binary logical
6797 <item><tt>local</tt> to create a scoped variable must be
6798 supported; however, <tt>local</tt> may or may not preserve
6799 the variable value from an outer scope and may or may not
6800 support arguments more complex than simple variables. Only
6812 If a shell script requires non-SUSv3 features from the shell
6813 interpreter other than those listed above, the appropriate shell
6814 must be specified in the first line of the script (e.g.,
6815 <tt>#!/bin/bash</tt>) and the package must depend on the package
6816 providing the shell (unless the shell package is marked
6817 "Essential", as in the case of <prgn>bash</prgn>).
6821 You may wish to restrict your script to SUSv3 features plus the
6822 above set when possible so that it may use <file>/bin/sh</file>
6823 as its interpreter. If your script works with <prgn>dash</prgn>
6824 (originally called <prgn>ash</prgn>), it probably complies with
6825 the above requirements, but if you are in doubt, use
6826 <file>/bin/bash</file>.
6830 Perl scripts should check for errors when making any
6831 system calls, including <tt>open</tt>, <tt>print</tt>,
6832 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
6836 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
6837 scripting languages. See <em>Csh Programming Considered
6838 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
6839 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
6840 If an upstream package comes with <prgn>csh</prgn> scripts
6841 then you must make sure that they start with
6842 <tt>#!/bin/csh</tt> and make your package depend on the
6843 <prgn>c-shell</prgn> virtual package.
6847 Any scripts which create files in world-writeable
6848 directories (e.g., in <file>/tmp</file>) must use a
6849 mechanism which will fail atomically if a file with the same
6850 name already exists.
6854 The Debian base system provides the <prgn>tempfile</prgn>
6855 and <prgn>mktemp</prgn> utilities for use by scripts for
6862 <heading>Symbolic links</heading>
6865 In general, symbolic links within a top-level directory
6866 should be relative, and symbolic links pointing from one
6867 top-level directory into another should be absolute. (A
6868 top-level directory is a sub-directory of the root
6869 directory <file>/</file>.)
6873 In addition, symbolic links should be specified as short as
6874 possible, i.e., link targets like <file>foo/../bar</file> are
6879 Note that when creating a relative link using
6880 <prgn>ln</prgn> it is not necessary for the target of the
6881 link to exist relative to the working directory you're
6882 running <prgn>ln</prgn> from, nor is it necessary to change
6883 directory to the directory where the link is to be made.
6884 Simply include the string that should appear as the target
6885 of the link (this will be a pathname relative to the
6886 directory in which the link resides) as the first argument
6891 For example, in your <prgn>Makefile</prgn> or
6892 <file>debian/rules</file>, you can do things like:
6893 <example compact="compact">
6894 ln -fs gcc $(prefix)/bin/cc
6895 ln -fs gcc debian/tmp/usr/bin/cc
6896 ln -fs ../sbin/sendmail $(prefix)/bin/runq
6897 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
6902 A symbolic link pointing to a compressed file should always
6903 have the same file extension as the referenced file. (For
6904 example, if a file <file>foo.gz</file> is referenced by a
6905 symbolic link, the filename of the link has to end with
6906 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
6911 <heading>Device files</heading>
6914 Packages must not include device files in the package file
6919 If a package needs any special device files that are not
6920 included in the base system, it must call
6921 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
6922 after notifying the user<footnote>
6923 This notification could be done via a (low-priority)
6924 debconf message, or an echo (printf) statement.
6929 Packages must not remove any device files in the
6930 <prgn>postrm</prgn> or any other script. This is left to the
6931 system administrator.
6935 Debian uses the serial devices
6936 <file>/dev/ttyS*</file>. Programs using the old
6937 <file>/dev/cu*</file> devices should be changed to use
6938 <file>/dev/ttyS*</file>.
6942 <sect id="config-files">
6943 <heading>Configuration files</heading>
6946 <heading>Definitions</heading>
6950 <tag>configuration file</tag>
6952 A file that affects the operation of a program, or
6953 provides site- or host-specific information, or
6954 otherwise customizes the behavior of a program.
6955 Typically, configuration files are intended to be
6956 modified by the system administrator (if needed or
6957 desired) to conform to local policy or to provide
6958 more useful site-specific behavior.
6961 <tag><tt>conffile</tt></tag>
6963 A file listed in a package's <tt>conffiles</tt>
6964 file, and is treated specially by <prgn>dpkg</prgn>
6965 (see <ref id="configdetails">).
6971 The distinction between these two is important; they are
6972 not interchangeable concepts. Almost all
6973 <tt>conffile</tt>s are configuration files, but many
6974 configuration files are not <tt>conffiles</tt>.
6978 Note that a script that embeds configuration information
6979 (such as most of the files in <file>/etc/default</file> and
6980 <file>/etc/cron.{daily,weekly,monthly}</file>) is de-facto a
6981 configuration file and should be treated as such.
6986 <heading>Location</heading>
6989 Any configuration files created or used by your package
6990 must reside in <file>/etc</file>. If there are several,
6991 consider creating a subdirectory of <file>/etc</file>
6992 named after your package.
6996 If your package creates or uses configuration files
6997 outside of <file>/etc</file>, and it is not feasible to modify
6998 the package to use <file>/etc</file> directly, put the files
6999 in <file>/etc</file> and create symbolic links to those files
7000 from the location that the package requires.
7005 <heading>Behavior</heading>
7008 Configuration file handling must conform to the following
7010 <list compact="compact">
7012 local changes must be preserved during a package
7016 configuration files must be preserved when the
7017 package is removed, and only deleted when the
7024 The easy way to achieve this behavior is to make the
7025 configuration file a <tt>conffile</tt>. This is
7026 appropriate only if it is possible to distribute a default
7027 version that will work for most installations, although
7028 some system administrators may choose to modify it. This
7029 implies that the default version will be part of the
7030 package distribution, and must not be modified by the
7031 maintainer scripts during installation (or at any other
7036 In order to ensure that local changes are preserved
7037 correctly, no package may contain or make hard links to
7038 conffiles.<footnote>
7039 Rationale: There are two problems with hard links.
7040 The first is that some editors break the link while
7041 editing one of the files, so that the two files may
7042 unwittingly become unlinked and different. The second
7043 is that <prgn>dpkg</prgn> might break the hard link
7044 while upgrading <tt>conffile</tt>s.
7049 The other way to do it is via the maintainer scripts. In
7050 this case, the configuration file must not be listed as a
7051 <tt>conffile</tt> and must not be part of the package
7052 distribution. If the existence of a file is required for
7053 the package to be sensibly configured it is the
7054 responsibility of the package maintainer to provide
7055 maintainer scripts which correctly create, update and
7056 maintain the file and remove it on purge. (See <ref
7057 id="maintainerscripts"> for more information.) These
7058 scripts must be idempotent (i.e., must work correctly if
7059 <prgn>dpkg</prgn> needs to re-run them due to errors
7060 during installation or removal), must cope with all the
7061 variety of ways <prgn>dpkg</prgn> can call maintainer
7062 scripts, must not overwrite or otherwise mangle the user's
7063 configuration without asking, must not ask unnecessary
7064 questions (particularly during upgrades), and must
7065 otherwise be good citizens.
7069 The scripts are not required to configure every possible
7070 option for the package, but only those necessary to get
7071 the package running on a given system. Ideally the
7072 sysadmin should not have to do any configuration other
7073 than that done (semi-)automatically by the
7074 <prgn>postinst</prgn> script.
7078 A common practice is to create a script called
7079 <file><var>package</var>-configure</file> and have the
7080 package's <prgn>postinst</prgn> call it if and only if the
7081 configuration file does not already exist. In certain
7082 cases it is useful for there to be an example or template
7083 file which the maintainer scripts use. Such files should
7084 be in <file>/usr/share/<var>package</var></file> or
7085 <file>/usr/lib/<var>package</var></file> (depending on whether
7086 they are architecture-independent or not). There should
7087 be symbolic links to them from
7088 <file>/usr/share/doc/<var>package</var>/examples</file> if
7089 they are examples, and should be perfectly ordinary
7090 <prgn>dpkg</prgn>-handled files (<em>not</em>
7091 configuration files).
7095 These two styles of configuration file handling must
7096 not be mixed, for that way lies madness:
7097 <prgn>dpkg</prgn> will ask about overwriting the file
7098 every time the package is upgraded.
7103 <heading>Sharing configuration files</heading>
7106 Packages which specify the same file as a
7107 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7108 with each other. (This is an instance of the general rule
7109 about not sharing files. Note that neither alternatives
7110 nor diversions are likely to be appropriate in this case;
7111 in particular, <prgn>dpkg</prgn> does not handle diverted
7112 <tt>conffile</tt>s well.)
7116 The maintainer scripts must not alter a <tt>conffile</tt>
7117 of <em>any</em> package, including the one the scripts
7122 If two or more packages use the same configuration file
7123 and it is reasonable for both to be installed at the same
7124 time, one of these packages must be defined as
7125 <em>owner</em> of the configuration file, i.e., it will be
7126 the package which handles that file as a configuration
7127 file. Other packages that use the configuration file must
7128 depend on the owning package if they require the
7129 configuration file to operate. If the other package will
7130 use the configuration file if present, but is capable of
7131 operating without it, no dependency need be declared.
7135 If it is desirable for two or more related packages to
7136 share a configuration file <em>and</em> for all of the
7137 related packages to be able to modify that configuration
7138 file, then the following should be done:
7139 <enumlist compact="compact">
7141 One of the related packages (the "owning" package)
7142 will manage the configuration file with maintainer
7143 scripts as described in the previous section.
7146 The owning package should also provide a program
7147 that the other packages may use to modify the
7151 The related packages must use the provided program
7152 to make any desired modifications to the
7153 configuration file. They should either depend on
7154 the core package to guarantee that the configuration
7155 modifier program is available or accept gracefully
7156 that they cannot modify the configuration file if it
7157 is not. (This is in addition to the fact that the
7158 configuration file may not even be present in the
7165 Sometimes it's appropriate to create a new package which
7166 provides the basic infrastructure for the other packages
7167 and which manages the shared configuration files. (The
7168 <tt>sgml-base</tt> package is a good example.)
7173 <heading>User configuration files ("dotfiles")</heading>
7176 The files in <file>/etc/skel</file> will automatically be
7177 copied into new user accounts by <prgn>adduser</prgn>.
7178 No other program should reference the files in
7179 <file>/etc/skel</file>.
7183 Therefore, if a program needs a dotfile to exist in
7184 advance in <file>$HOME</file> to work sensibly, that dotfile
7185 should be installed in <file>/etc/skel</file> and treated as a
7190 However, programs that require dotfiles in order to
7191 operate sensibly are a bad thing, unless they do create
7192 the dotfiles themselves automatically.
7196 Furthermore, programs should be configured by the Debian
7197 default installation to behave as closely to the upstream
7198 default behavior as possible.
7202 Therefore, if a program in a Debian package needs to be
7203 configured in some way in order to operate sensibly, that
7204 should be done using a site-wide configuration file placed
7205 in <file>/etc</file>. Only if the program doesn't support a
7206 site-wide default configuration and the package maintainer
7207 doesn't have time to add it may a default per-user file be
7208 placed in <file>/etc/skel</file>.
7212 <file>/etc/skel</file> should be as empty as we can make it.
7213 This is particularly true because there is no easy (or
7214 necessarily desirable) mechanism for ensuring that the
7215 appropriate dotfiles are copied into the accounts of
7216 existing users when a package is installed.
7222 <heading>Log files</heading>
7224 Log files should usually be named
7225 <file>/var/log/<var>package</var>.log</file>. If you have many
7226 log files, or need a separate directory for permission
7227 reasons (<file>/var/log</file> is writable only by
7228 <file>root</file>), you should usually create a directory named
7229 <file>/var/log/<var>package</var></file> and place your log
7234 Log files must be rotated occasionally so that they don't
7235 grow indefinitely; the best way to do this is to drop a log
7236 rotation configuration file into the directory
7237 <file>/etc/logrotate.d</file> and use the facilities provided by
7238 logrotate.<footnote>
7240 The traditional approach to log files has been to set up
7241 <em>ad hoc</em> log rotation schemes using simple shell
7242 scripts and cron. While this approach is highly
7243 customizable, it requires quite a lot of sysadmin work.
7244 Even though the original Debian system helped a little
7245 by automatically installing a system which can be used
7246 as a template, this was deemed not enough.
7250 The use of <prgn>logrotate</prgn>, a program developed
7251 by Red Hat, is better, as it centralizes log management.
7252 It has both a configuration file
7253 (<file>/etc/logrotate.conf</file>) and a directory where
7254 packages can drop their individual log rotation
7255 configurations (<file>/etc/logrotate.d</file>).
7258 Here is a good example for a logrotate config
7259 file (for more information see <manref name="logrotate"
7261 <example compact="compact">
7262 /var/log/foo/*.log {
7267 /etc/init.d/foo force-reload
7271 This rotates all files under <file>/var/log/foo</file>, saves 12
7272 compressed generations, and forces the daemon to reload its
7273 configuration information after the log rotation.
7277 Log files should be removed when the package is
7278 purged (but not when it is only removed). This should be
7279 done by the <prgn>postrm</prgn> script when it is called
7280 with the argument <tt>purge</tt> (see <ref
7281 id="removedetails">).
7286 <heading>Permissions and owners</heading>
7289 The rules in this section are guidelines for general use.
7290 If necessary you may deviate from the details below.
7291 However, if you do so you must make sure that what is done
7292 is secure and you should try to be as consistent as possible
7293 with the rest of the system. You should probably also
7294 discuss it on <prgn>debian-devel</prgn> first.
7298 Files should be owned by <tt>root.root</tt>, and made
7299 writable only by the owner and universally readable (and
7300 executable, if appropriate), that is mode 644 or 755.
7304 Directories should be mode 755 or (for group-writability)
7305 mode 2775. The ownership of the directory should be
7306 consistent with its mode: if a directory is mode 2775, it
7307 should be owned by the group that needs write access to
7310 When a package is upgraded, and the owner or permissions
7311 of a file included in the package has changed, dpkg
7312 arranges for the ownership and permissions to be
7313 correctly set upon installation. However, this does not
7314 extend to directories; the permissions and ownership of
7315 directories already on the system does not change on
7316 install or upgrade of packages. This makes sense, since
7317 otherwise common directories like <tt>/usr</tt> would
7318 always be in flux. To correctly change permissions of a
7319 directory the package owns, explicit action is required,
7320 usually in the <tt>postinst</tt> script. Care must be
7321 taken to handle downgrades as well, in that case.
7328 Setuid and setgid executables should be mode 4755 or 2755
7329 respectively, and owned by the appropriate user or group.
7330 They should not be made unreadable (modes like 4711 or
7331 2711 or even 4111); doing so achieves no extra security,
7332 because anyone can find the binary in the freely available
7333 Debian package; it is merely inconvenient. For the same
7334 reason you should not restrict read or execute permissions
7335 on non-set-id executables.
7339 Some setuid programs need to be restricted to particular
7340 sets of users, using file permissions. In this case they
7341 should be owned by the uid to which they are set-id, and by
7342 the group which should be allowed to execute them. They
7343 should have mode 4754; again there is no point in making
7344 them unreadable to those users who must not be allowed to
7349 It is possible to arrange that the system administrator can
7350 reconfigure the package to correspond to their local
7351 security policy by changing the permissions on a binary:
7352 they can do this by using <prgn>dpkg-statoverride</prgn>, as
7353 described below.<footnote>
7354 Ordinary files installed by <prgn>dpkg</prgn> (as
7355 opposed to <tt>conffile</tt>s and other similar objects)
7356 normally have their permissions reset to the distributed
7357 permissions when the package is reinstalled. However,
7358 the use of <prgn>dpkg-statoverride</prgn> overrides this
7359 default behavior. If you use this method, you should
7360 remember to describe <prgn>dpkg-statoverride</prgn> in
7361 the package documentation; being a relatively new
7362 addition to Debian, it is probably not yet well-known.
7364 Another method you should consider is to create a group for
7365 people allowed to use the program(s) and make any setuid
7366 executables executable only by that group.
7370 If you need to create a new user or group for your package
7371 there are two possibilities. Firstly, you may need to
7372 make some files in the binary package be owned by this
7373 user or group, or you may need to compile the user or
7374 group id (rather than just the name) into the binary
7375 (though this latter should be avoided if possible, as in
7376 this case you need a statically allocated id).</p>
7379 If you need a statically allocated id, you must ask for a
7380 user or group id from the <tt>base-passwd</tt> maintainer,
7381 and must not release the package until you have been
7382 allocated one. Once you have been allocated one you must
7383 either make the package depend on a version of the
7384 <tt>base-passwd</tt> package with the id present in
7385 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
7386 your package to create the user or group itself with the
7387 correct id (using <tt>adduser</tt>) in its
7388 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
7389 the <prgn>postinst</prgn> is to be preferred if it is
7390 possible, otherwise a pre-dependency will be needed on the
7391 <tt>adduser</tt> package.)
7395 On the other hand, the program might be able to determine
7396 the uid or gid from the user or group name at runtime, so
7397 that a dynamically allocated id can be used. In this case
7398 you should choose an appropriate user or group name,
7399 discussing this on <prgn>debian-devel</prgn> and checking
7400 with the <package/base-passwd/ maintainer that it is unique and that
7401 they do not wish you to use a statically allocated id
7402 instead. When this has been checked you must arrange for
7403 your package to create the user or group if necessary using
7404 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
7405 <prgn>postinst</prgn> script (again, the latter is to be
7406 preferred if it is possible).
7410 Note that changing the numeric value of an id associated
7411 with a name is very difficult, and involves searching the
7412 file system for all appropriate files. You need to think
7413 carefully whether a static or dynamic id is required, since
7414 changing your mind later will cause problems.
7417 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
7419 This section is not intended as policy, but as a
7420 description of the use of <prgn>dpkg-statoverride</prgn>.
7424 <prgn>dpkg-statoverride</prgn> is a replacement for the
7425 deprecated <tt>suidmanager</tt> package. Packages which
7426 previously used <tt>suidmanager</tt> should have a
7427 <tt>Conflicts: suidmanager (<< 0.50)</tt> entry (or even
7428 <tt>(<< 0.52)</tt>), and calls to <tt>suidregister</tt>
7429 and <tt>suidunregister</tt> should now be simply removed
7430 from the maintainer scripts.
7434 If a system administrator wishes to have a file (or
7435 directory or other such thing) installed with owner and
7436 permissions different from those in the distributed Debian
7437 package, they can use the <prgn>dpkg-statoverride</prgn>
7438 program to instruct <prgn>dpkg</prgn> to use the different
7439 settings every time the file is installed. Thus the
7440 package maintainer should distribute the files with their
7441 normal permissions, and leave it for the system
7442 administrator to make any desired changes. For example, a
7443 daemon which is normally required to be setuid root, but
7444 in certain situations could be used without being setuid,
7445 should be installed setuid in the <tt>.deb</tt>. Then the
7446 local system administrator can change this if they wish.
7447 If there are two standard ways of doing it, the package
7448 maintainer can use <tt>debconf</tt> to find out the
7449 preference, and call <prgn>dpkg-statoverride</prgn> in the
7450 maintainer script if necessary to accommodate the system
7451 administrator's choice. Care must be taken during
7452 upgrades to not override an existing setting.
7456 Given the above, <prgn>dpkg-statoverride</prgn> is
7457 essentially a tool for system administrators and would not
7458 normally be needed in the maintainer scripts. There is
7459 one type of situation, though, where calls to
7460 <prgn>dpkg-statoverride</prgn> would be needed in the
7461 maintainer scripts, and that involves packages which use
7462 dynamically allocated user or group ids. In such a
7463 situation, something like the following idiom can be very
7464 helpful in the package's <prgn>postinst</prgn>, where
7465 <tt>sysuser</tt> is a dynamically allocated id:
7467 for i in /usr/bin/foo /usr/sbin/bar
7469 # only do something when no setting exists
7470 if ! dpkg-statoverride --list $i >/dev/null 2>&1
7472 #include: debconf processing, question about foo and bar
7473 if [ "$RET" = "true" ] ; then
7474 dpkg-statoverride --update --add sysuser root 4755 $i
7479 The corresponding <tt>dpkg-statoverride --remove</tt>
7480 calls can then be made unconditionally when the package is
7488 <chapt id="customized-programs">
7489 <heading>Customized programs</heading>
7491 <sect id="arch-spec">
7492 <heading>Architecture specification strings</heading>
7495 If a program needs to specify an <em>architecture specification
7496 string</em> in some place, it should select one of the
7497 strings provided by <tt>dpkg-architecture -L</tt>. The
7498 strings are in the format
7499 <tt><var>os</var>-<var>arch</var></tt>, though the OS part
7500 is sometimes elided, as when the OS is Linux.<footnote>
7501 <p>Currently, the strings are:
7502 i386 ia64 alpha amd64 armeb arm hppa m32r m68k mips
7503 mipsel powerpc ppc64 s390 s390x sh3 sh3eb sh4 sh4eb
7504 sparc darwin-i386 darwin-ia64 darwin-alpha darwin-amd64
7505 darwin-armeb darwin-arm darwin-hppa darwin-m32r
7506 darwin-m68k darwin-mips darwin-mipsel darwin-powerpc
7507 darwin-ppc64 darwin-s390 darwin-s390x darwin-sh3
7508 darwin-sh3eb darwin-sh4 darwin-sh4eb darwin-sparc
7509 freebsd-i386 freebsd-ia64 freebsd-alpha freebsd-amd64
7510 freebsd-armeb freebsd-arm freebsd-hppa freebsd-m32r
7511 freebsd-m68k freebsd-mips freebsd-mipsel freebsd-powerpc
7512 freebsd-ppc64 freebsd-s390 freebsd-s390x freebsd-sh3
7513 freebsd-sh3eb freebsd-sh4 freebsd-sh4eb freebsd-sparc
7514 kfreebsd-i386 kfreebsd-ia64 kfreebsd-alpha
7515 kfreebsd-amd64 kfreebsd-armeb kfreebsd-arm kfreebsd-hppa
7516 kfreebsd-m32r kfreebsd-m68k kfreebsd-mips
7517 kfreebsd-mipsel kfreebsd-powerpc kfreebsd-ppc64
7518 kfreebsd-s390 kfreebsd-s390x kfreebsd-sh3 kfreebsd-sh3eb
7519 kfreebsd-sh4 kfreebsd-sh4eb kfreebsd-sparc knetbsd-i386
7520 knetbsd-ia64 knetbsd-alpha knetbsd-amd64 knetbsd-armeb
7521 knetbsd-arm knetbsd-hppa knetbsd-m32r knetbsd-m68k
7522 knetbsd-mips knetbsd-mipsel knetbsd-powerpc
7523 knetbsd-ppc64 knetbsd-s390 knetbsd-s390x knetbsd-sh3
7524 knetbsd-sh3eb knetbsd-sh4 knetbsd-sh4eb knetbsd-sparc
7525 netbsd-i386 netbsd-ia64 netbsd-alpha netbsd-amd64
7526 netbsd-armeb netbsd-arm netbsd-hppa netbsd-m32r
7527 netbsd-m68k netbsd-mips netbsd-mipsel netbsd-powerpc
7528 netbsd-ppc64 netbsd-s390 netbsd-s390x netbsd-sh3
7529 netbsd-sh3eb netbsd-sh4 netbsd-sh4eb netbsd-sparc
7530 openbsd-i386 openbsd-ia64 openbsd-alpha openbsd-amd64
7531 openbsd-armeb openbsd-arm openbsd-hppa openbsd-m32r
7532 openbsd-m68k openbsd-mips openbsd-mipsel openbsd-powerpc
7533 openbsd-ppc64 openbsd-s390 openbsd-s390x openbsd-sh3
7534 openbsd-sh3eb openbsd-sh4 openbsd-sh4eb openbsd-sparc
7535 hurd-i386 hurd-ia64 hurd-alpha hurd-amd64 hurd-armeb
7536 hurd-arm hurd-hppa hurd-m32r hurd-m68k hurd-mips
7537 hurd-mipsel hurd-powerpc hurd-ppc64 hurd-s390 hurd-s390x
7538 hurd-sh3 hurd-sh3eb hurd-sh4 hurd-sh4eb hurd-sparc
7544 Note that we don't want to use
7545 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
7546 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
7547 since this would make our programs incompatible with other
7548 Linux distributions. We also don't use something like
7549 <tt><var>arch</var>-unknown-linux</tt>, since the
7550 <tt>unknown</tt> does not look very good.
7555 <heading>Daemons</heading>
7558 The configuration files <file>/etc/services</file>,
7559 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
7560 by the <prgn>netbase</prgn> package and must not be modified
7565 If a package requires a new entry in one of these files, the
7566 maintainer should get in contact with the
7567 <prgn>netbase</prgn> maintainer, who will add the entries
7568 and release a new version of the <prgn>netbase</prgn>
7573 The configuration file <file>/etc/inetd.conf</file> must not be
7574 modified by the package's scripts except via the
7575 <prgn>update-inetd</prgn> script or the
7576 <file>DebianNet.pm</file> Perl module. See their documentation
7577 for details on how to add entries.
7581 If a package wants to install an example entry into
7582 <file>/etc/inetd.conf</file>, the entry must be preceded with
7583 exactly one hash character (<tt>#</tt>). Such lines are
7584 treated as "commented out by user" by the
7585 <prgn>update-inetd</prgn> script and are not changed or
7586 activated during package updates.
7591 <heading>Using pseudo-ttys and modifying wtmp, utmp and
7595 Some programs need to create pseudo-ttys. This should be done
7596 using Unix98 ptys if the C library supports it. The resulting
7597 program must not be installed setuid root, unless that
7598 is required for other functionality.
7602 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
7603 <file>/var/log/lastlog</file> must be installed writable by
7604 group <tt>utmp</tt>. Programs which need to modify those
7605 files must be installed setgid <tt>utmp</tt>.
7610 <heading>Editors and pagers</heading>
7613 Some programs have the ability to launch an editor or pager
7614 program to edit or display a text document. Since there are
7615 lots of different editors and pagers available in the Debian
7616 distribution, the system administrator and each user should
7617 have the possibility to choose their preferred editor and
7622 In addition, every program should choose a good default
7623 editor/pager if none is selected by the user or system
7628 Thus, every program that launches an editor or pager must
7629 use the EDITOR or PAGER environment variable to determine
7630 the editor or pager the user wishes to use. If these
7631 variables are not set, the programs <file>/usr/bin/editor</file>
7632 and <file>/usr/bin/pager</file> should be used, respectively.
7636 These two files are managed through the <prgn>dpkg</prgn>
7637 "alternatives" mechanism. Thus every package providing an
7638 editor or pager must call the
7639 <prgn>update-alternatives</prgn> script to register these
7644 If it is very hard to adapt a program to make use of the
7645 EDITOR or PAGER variables, that program may be configured to
7646 use <file>/usr/bin/sensible-editor</file> and
7647 <file>/usr/bin/sensible-pager</file> as the editor or pager
7648 program respectively. These are two scripts provided in the
7649 Debian base system that check the EDITOR and PAGER variables
7650 and launch the appropriate program, and fall back to
7651 <file>/usr/bin/editor</file> and <file>/usr/bin/pager</file> if the
7652 variable is not set.
7656 A program may also use the VISUAL environment variable to
7657 determine the user's choice of editor. If it exists, it
7658 should take precedence over EDITOR. This is in fact what
7659 <file>/usr/bin/sensible-editor</file> does.
7663 It is not required for a package to depend on
7664 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
7665 package to provide such virtual packages.<footnote>
7666 The Debian base system already provides an editor and a
7672 <sect id="web-appl">
7673 <heading>Web servers and applications</heading>
7676 This section describes the locations and URLs that should
7677 be used by all web servers and web applications in the
7684 Cgi-bin executable files are installed in the
7686 <example compact="compact">
7687 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
7689 and should be referred to as
7690 <example compact="compact">
7691 http://localhost/cgi-bin/<var>cgi-bin-name</var>
7697 <p>Access to HTML documents</p>
7700 HTML documents for a package are stored in
7701 <file>/usr/share/doc/<var>package</var></file>
7702 and can be referred to as
7703 <example compact="compact">
7704 http://localhost/doc/<var>package</var>/<var>filename</var>
7709 The web server should restrict access to the document
7710 tree so that only clients on the same host can read
7711 the documents. If the web server does not support such
7712 access controls, then it should not provide access at
7713 all, or ask about providing access during installation.
7718 <p>Access to images</p>
7720 It is recommended that images for a package be stored
7721 in <tt>/usr/share/images/<var>package</var></tt> and
7722 may be referred to through an alias <tt>/images/</tt>
7725 http://localhost/images/<package>/<filename>
7732 <p>Web Document Root</p>
7735 Web Applications should try to avoid storing files in
7736 the Web Document Root. Instead they should use the
7737 /usr/share/doc/<var>package</var> directory for
7738 documents and register the Web Application via the
7739 <package>doc-base</package> package. If access to the
7740 web document root is unavoidable then use
7741 <example compact="compact">
7744 as the Document Root. This might be just a symbolic
7745 link to the location where the system administrator
7746 has put the real document root.
7749 <item><p>Providing httpd and/or httpd-cgi</p>
7751 All web servers should provide the virtual package
7752 <tt>httpd</tt>. If a web server has CGI support it should
7753 provide <tt>httpd-cgi</tt> additionally.
7756 All web applications which do not contain CGI scripts should
7757 depend on <tt>httpd</tt>, all those web applications which
7758 <tt>do</tt> contain CGI scripts, should depend on
7766 <sect id="mail-transport-agents">
7767 <heading>Mail transport, delivery and user agents</heading>
7770 Debian packages which process electronic mail, whether mail
7771 user agents (MUAs) or mail transport agents (MTAs), must
7772 ensure that they are compatible with the configuration
7773 decisions below. Failure to do this may result in lost
7774 mail, broken <tt>From:</tt> lines, and other serious brain
7779 The mail spool is <file>/var/mail</file> and the interface to
7780 send a mail message is <file>/usr/sbin/sendmail</file> (as per
7781 the FHS). On older systems, the mail spool may be
7782 physically located in <file>/var/spool/mail</file>, but all
7783 access to the mail spool should be via the
7784 <file>/var/mail</file> symlink. The mail spool is part of the
7785 base system and not part of the MTA package.
7789 All Debian MUAs, MTAs, MDAs and other mailbox accessing
7790 programs (such as IMAP daemons) must lock the mailbox in an
7791 NFS-safe way. This means that <tt>fcntl()</tt> locking must
7792 be combined with dot locking. To avoid deadlocks, a program
7793 should use <tt>fcntl()</tt> first and dot locking after
7794 this, or alternatively implement the two locking methods in
7795 a non blocking way<footnote>
7796 If it is not possible to establish both locks, the
7797 system shouldn't wait for the second lock to be
7798 established, but remove the first lock, wait a (random)
7799 time, and start over locking again.
7800 </footnote>. Using the functions <tt>maillock</tt> and
7801 <tt>mailunlock</tt> provided by the
7802 <tt>liblockfile*</tt><footnote>
7803 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
7804 to use these functions.
7805 </footnote> packages is the recommended way to realize this.
7809 Mailboxes are generally mode 660
7810 <tt><var>user</var>.mail</tt> unless the system
7811 administrator has chosen otherwise. A MUA may remove a
7812 mailbox (unless it has nonstandard permissions) in which
7813 case the MTA or another MUA must recreate it if needed.
7814 Mailboxes must be writable by group mail.
7818 The mail spool is 2775 <tt>root.mail</tt>, and MUAs should
7819 be setgid mail to do the locking mentioned above (and
7820 must obviously avoid accessing other users' mailboxes
7821 using this privilege).</p>
7824 <file>/etc/aliases</file> is the source file for the system mail
7825 aliases (e.g., postmaster, usenet, etc.), it is the one
7826 which the sysadmin and <prgn>postinst</prgn> scripts may
7827 edit. After <file>/etc/aliases</file> is edited the program or
7828 human editing it must call <prgn>newaliases</prgn>. All MTA
7829 packages must come with a <prgn>newaliases</prgn> program,
7830 even if it does nothing, but older MTA packages did not do
7831 this so programs should not fail if <prgn>newaliases</prgn>
7832 cannot be found. Note that because of this, all MTA
7833 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
7834 <tt>Replaces: mail-transport-agent</tt> control file
7839 The convention of writing <tt>forward to
7840 <var>address</var></tt> in the mailbox itself is not
7841 supported. Use a <tt>.forward</tt> file instead.</p>
7844 The <prgn>rmail</prgn> program used by UUCP
7845 for incoming mail should be <file>/usr/sbin/rmail</file>.
7846 Likewise, <prgn>rsmtp</prgn>, for receiving
7847 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
7851 If your package needs to know what hostname to use on (for
7852 example) outgoing news and mail messages which are generated
7853 locally, you should use the file <file>/etc/mailname</file>. It
7854 will contain the portion after the username and <tt>@</tt>
7855 (at) sign for email addresses of users on the machine
7856 (followed by a newline).
7860 Such a package should check for the existence of this file
7861 when it is being configured. If it exists, it should be
7862 used without comment, although an MTA's configuration script
7863 may wish to prompt the user even if it finds that this file
7864 exists. If the file does not exist, the package should
7865 prompt the user for the value (preferably using
7866 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
7867 as well as using it in the package's configuration. The
7868 prompt should make it clear that the name will not just be
7869 used by that package. For example, in this situation the
7870 <tt>inn</tt> package could say something like:
7871 <example compact="compact">
7872 Please enter the "mail name" of your system. This is the
7873 hostname portion of the address to be shown on outgoing
7874 news and mail messages. The default is
7875 <var>syshostname</var>, your system's host name. Mail
7876 name ["<var>syshostname</var>"]:
7878 where <var>syshostname</var> is the output of <tt>hostname
7884 <heading>News system configuration</heading>
7887 All the configuration files related to the NNTP (news)
7888 servers and clients should be located under
7889 <file>/etc/news</file>.</p>
7892 There are some configuration issues that apply to a number
7893 of news clients and server packages on the machine. These
7897 <tag><file>/etc/news/organization</file></tag>
7899 A string which should appear as the
7900 organization header for all messages posted
7901 by NNTP clients on the machine
7904 <tag><file>/etc/news/server</file></tag>
7906 Contains the FQDN of the upstream NNTP
7907 server, or localhost if the local machine is
7912 Other global files may be added as required for cross-package news
7919 <heading>Programs for the X Window System</heading>
7922 <heading>Providing X support and package priorities</heading>
7925 Programs that can be configured with support for the X
7926 Window System must be configured to do so and must declare
7927 any package dependencies necessary to satisfy their
7928 runtime requirements when using the X Window System. If
7929 such a package is of higher priority than the X packages
7930 on which it depends, it is required that either the
7931 X-specific components be split into a separate package, or
7932 that an alternative version of the package, which includes
7933 X support, be provided, or that the package's priority be
7939 <heading>Packages providing an X server</heading>
7942 Packages that provide an X server that, directly or
7943 indirectly, communicates with real input and display
7944 hardware should declare in their control data that they
7945 provide the virtual package <tt>xserver</tt>.<footnote>
7946 This implements current practice, and provides an
7947 actual policy for usage of the <tt>xserver</tt>
7948 virtual package which appears in the virtual packages
7949 list. In a nutshell, X servers that interface
7950 directly with the display and input hardware or via
7951 another subsystem (e.g., GGI) should provide
7952 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
7953 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
7959 <heading>Packages providing a terminal emulator</heading>
7962 Packages that provide a terminal emulator for the X Window
7963 System which meet the criteria listed below should declare
7964 in their control data that they provide the virtual
7965 package <tt>x-terminal-emulator</tt>. They should also
7966 register themselves as an alternative for
7967 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
7972 To be an <tt>x-terminal-emulator</tt>, a program must:
7973 <list compact="compact">
7975 Be able to emulate a DEC VT100 terminal, or a
7976 compatible terminal.
7980 Support the command-line option <tt>-e
7981 <var>command</var></tt>, which creates a new
7982 terminal window<footnote>
7983 "New terminal window" does not necessarily mean
7984 a new top-level X window directly parented by
7985 the window manager; it could, if the terminal
7986 emulator application were so coded, be a new
7987 "view" in a multiple-document interface (MDI).
7989 and runs the specified <var>command</var>,
7990 interpreting the entirety of the rest of the command
7991 line as a command to pass straight to exec, in the
7992 manner that <tt>xterm</tt> does.
7996 Support the command-line option <tt>-T
7997 <var>title</var></tt>, which creates a new terminal
7998 window with the window title <var>title</var>.
8005 <heading>Packages providing a window manager</heading>
8008 Packages that provide a window manager should declare in
8009 their control data that they provide the virtual package
8010 <tt>x-window-manager</tt>. They should also register
8011 themselves as an alternative for
8012 <file>/usr/bin/x-window-manager</file>, with a priority
8013 calculated as follows:
8014 <list compact="compact">
8016 Start with a priority of 20.
8020 If the window manager supports the Debian menu
8021 system, add 20 points if this support is available
8022 in the package's default configuration (i.e., no
8023 configuration files belonging to the system or user
8024 have to be edited to activate the feature); if
8025 configuration files must be modified, add only 10
8031 If the window manager complies with <url
8032 id="http://www.freedesktop.org/Standards/wm-spec"
8033 name="The Window Manager Specification Project">,
8034 written by the <url id="http://www.freedesktop.org/"
8035 name="Free Desktop Group">, add 40 points.
8039 If the window manager permits the X session to be
8040 restarted using a <em>different</em> window manager
8041 (without killing the X server) in its default
8042 configuration, add 10 points; otherwise add none.
8049 <heading>Packages providing fonts</heading>
8052 Packages that provide fonts for the X Window
8054 For the purposes of Debian Policy, a "font for the X
8055 Window System" is one which is accessed via X protocol
8056 requests. Fonts for the Linux console, for PostScript
8057 renderer, or any other purpose, do not fit this
8058 definition. Any tool which makes such fonts available
8059 to the X Window System, however, must abide by this
8062 must do a number of things to ensure that they are both
8063 available without modification of the X or font server
8064 configuration, and that they do not corrupt files used by
8065 other font packages to register information about
8069 Fonts of any type supported by the X Window System
8070 must be in a separate binary package from any
8071 executables, libraries, or documentation (except
8072 that specific to the fonts shipped, such as their
8073 license information). If one or more of the fonts
8074 so packaged are necessary for proper operation of
8075 the package with which they are associated the font
8076 package may be Recommended; if the fonts merely
8077 provide an enhancement, a Suggests relationship may
8078 be used. Packages must not Depend on font
8080 This is because the X server may retrieve fonts
8081 from the local file system or over the network
8082 from an X font server; the Debian package system
8083 is empowered to deal only with the local
8089 BDF fonts must be converted to PCF fonts with the
8090 <prgn>bdftopcf</prgn> utility (available in the
8091 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8092 placed in a directory that corresponds to their
8094 <list compact="compact">
8096 100 dpi fonts must be placed in
8097 <file>/usr/share/fonts/X11/100dpi/</file>.
8101 75 dpi fonts must be placed in
8102 <file>/usr/share/fonts/X11/75dpi/</file>.
8106 Character-cell fonts, cursor fonts, and other
8107 low-resolution fonts must be placed in
8108 <file>/usr/share/fonts/X11/misc/</file>.
8114 Speedo fonts must be placed in
8115 <file>/usr/share/fonts/X11/Speedo/</file>.
8119 Type 1 fonts must be placed in
8120 <file>/usr/share/fonts/X11/Type1/</file>. If font
8121 metric files are available, they must be placed here
8126 Subdirectories of <file>/usr/share/fonts/X11/</file>
8127 other than those listed above must be neither
8128 created nor used. (The <file>PEX</file>, <file>CID</file>,
8129 and <file>cyrillic</file> directories are excepted for
8130 historical reasons, but installation of files into
8131 these directories remains discouraged.)
8135 Font packages may, instead of placing files directly
8136 in the X font directories listed above, provide
8137 symbolic links in that font directory pointing to
8138 the files' actual location in the filesystem. Such
8139 a location must comply with the FHS.
8143 Font packages should not contain both 75dpi and
8144 100dpi versions of a font. If both are available,
8145 they should be provided in separate binary packages
8146 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8147 the names of the packages containing the
8148 corresponding fonts.
8152 Fonts destined for the <file>misc</file> subdirectory
8153 should not be included in the same package as 75dpi
8154 or 100dpi fonts; instead, they should be provided in
8155 a separate package with <tt>-misc</tt> appended to
8160 Font packages must not provide the files
8161 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8162 <file>fonts.scale</file> in a font directory:
8165 <file>fonts.dir</file> files must not be provided at all.
8169 <file>fonts.alias</file> and <file>fonts.scale</file>
8170 files, if needed, should be provided in the
8172 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8173 where <var>fontdir</var> is the name of the
8175 <file>/usr/share/fonts/X11/</file> where the
8176 package's corresponding fonts are stored
8177 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8178 <var>package</var> is the name of the package
8179 that provides these fonts, and
8180 <var>extension</var> is either <tt>scale</tt>
8181 or <tt>alias</tt>, whichever corresponds to
8188 Font packages must declare a dependency on
8189 <tt>xfonts-utils</tt> in their control
8194 Font packages that provide one or more
8195 <file>fonts.scale</file> files as described above must
8196 invoke <prgn>update-fonts-scale</prgn> on each
8197 directory into which they installed fonts
8198 <em>before</em> invoking
8199 <prgn>update-fonts-dir</prgn> on that directory.
8200 This invocation must occur in both the
8201 <prgn>postinst</prgn> (for all arguments) and
8202 <prgn>postrm</prgn> (for all arguments except
8203 <tt>upgrade</tt>) scripts.
8207 Font packages that provide one or more
8208 <file>fonts.alias</file> files as described above must
8209 invoke <prgn>update-fonts-alias</prgn> on each
8210 directory into which they installed fonts. This
8211 invocation must occur in both the
8212 <prgn>postinst</prgn> (for all arguments) and
8213 <prgn>postrm</prgn> (for all arguments except
8214 <tt>upgrade</tt>) scripts.
8218 Font packages must invoke
8219 <prgn>update-fonts-dir</prgn> on each directory into
8220 which they installed fonts. This invocation must
8221 occur in both the <prgn>postinst</prgn> (for all
8222 arguments) and <prgn>postrm</prgn> (for all
8223 arguments except <tt>upgrade</tt>) scripts.
8227 Font packages must not provide alias names for the
8228 fonts they include which collide with alias names
8229 already in use by fonts already packaged.
8233 Font packages must not provide fonts with the same
8234 XLFD registry name as another font already packaged.
8241 <heading>Application defaults files</heading>
8244 Application defaults files must be installed in the
8245 directory <file>/etc/X11/app-defaults/</file> (use of a
8246 localized subdirectory of <file>/etc/X11/</file> as described
8247 in the <em>X Toolkit Intrinsics - C Language
8248 Interface</em> manual is also permitted). They must be
8249 registered as <tt>conffile</tt>s or handled as
8250 configuration files. Packages must not provide the
8251 directory <file>/usr/X11R6/lib/X11/app-defaults/</file>.
8255 Customization of programs' X resources may also be
8256 supported with the provision of a file with the same name
8257 as that of the package placed in the
8258 <file>/etc/X11/Xresources/</file> directory, which must
8259 registered as a <tt>conffile</tt> or handled as a
8260 configuration file.<footnote>
8261 Note that this mechanism is not the same as using
8262 app-defaults; app-defaults are tied to the client
8263 binary on the local file system, whereas X resources
8264 are stored in the X server and affect all connecting
8267 <em>Important:</em> packages that install files into the
8268 <file>/etc/X11/Xresources/</file> directory must conflict with
8269 <tt>xbase (<< 3.3.2.3a-2)</tt>; if this is not done
8270 it is possible for the installing package to destroy a
8271 previously-existing <file>/etc/X11/Xresources</file> file
8272 which had been customized by the system administrator.
8277 <heading>Installation directory issues</heading>
8280 Packages using the X Window System should not be
8281 configured to install files under the
8282 <file>/usr/X11R6/</file> directory. The
8283 <file>/usr/X11R6/</file> directory hierarchy should be
8284 regarded as obsolete.
8288 Programs that use GNU <prgn>autoconf</prgn> and
8289 <prgn>automake</prgn> are usually easily configured at
8290 compile time to use <file>/usr/</file> instead of
8291 <file>/usr/X11R6/</file>, and this should be done whenever
8292 possible. Configuration files for window managers and
8293 display managers should be placed in a subdirectory of
8294 <file>/etc/X11/</file> corresponding to the package name due
8295 to these programs' tight integration with the mechanisms
8296 of the X Window System. Application-level programs should
8297 use the <file>/etc/</file> directory unless otherwise mandated
8302 The installation of files into subdirectories
8303 of <file>/usr/X11R6/include/X11/</file> and
8304 <file>/usr/X11R6/lib/X11/</file> is now prohibited;
8305 package maintainers should determine if subdirectories of
8306 <file>/usr/lib/</file> and <file>/usr/share/</file> can be used
8311 Packages should install any relevant files into the
8312 directories <file>/usr/include/X11/</file> and
8313 <file>/usr/lib/X11/</file>, but if they do so, they must
8314 pre-depend on <tt>x11-common (>=
8315 1:7.0.0)</tt><footnote>
8317 These libraries used to be all symbolic
8318 links. However, with <tt>X11R7</tt>,
8319 <tt>/usr/include/X11</tt> and <tt>/usr/lib/X11</tt>
8320 are now real directories, and packages
8321 <strong>should</strong> ship their files here instead
8322 of in <tt>/usr/X11R6/{include,lib}/X11</tt>.
8323 <tt>x11-common (>= 1:7.0.0) </tt> is the package
8324 responsible for converting these symlinks into
8332 <heading>The OSF/Motif and OpenMotif libraries</heading>
8335 <em>Programs that require the non-DFSG-compliant OSF/Motif or
8336 OpenMotif libraries</em><footnote>
8337 OSF/Motif and OpenMotif are collectively referred to as
8338 "Motif" in this policy document.
8340 should be compiled against and tested with LessTif (a free
8341 re-implementation of Motif) instead. If the maintainer
8342 judges that the program or programs do not work
8343 sufficiently well with LessTif to be distributed and
8344 supported, but do so when compiled against Motif, then two
8345 versions of the package should be created; one linked
8346 statically against Motif and with <tt>-smotif</tt>
8347 appended to the package name, and one linked dynamically
8348 against Motif and with <tt>-dmotif</tt> appended to the
8353 Both Motif-linked versions are dependent
8354 upon non-DFSG-compliant software and thus cannot be
8355 uploaded to the <em>main</em> distribution; if the
8356 software is itself DFSG-compliant it may be uploaded to
8357 the <em>contrib</em> distribution. While known existing
8358 versions of Motif permit unlimited redistribution of
8359 binaries linked against the library (whether statically or
8360 dynamically), it is the package maintainer's
8361 responsibility to determine whether this is permitted by
8362 the license of the copy of Motif in their possession.
8368 <heading>Perl programs and modules</heading>
8371 Perl programs and modules should follow the current Perl policy.
8375 The Perl policy can be found in the <tt>perl-policy</tt>
8376 files in the <tt>debian-policy</tt> package.
8377 It is also available from the Debian web mirrors at
8378 <tt><url name="/doc/packaging-manuals/perl-policy/"
8379 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
8384 <heading>Emacs lisp programs</heading>
8387 Please refer to the "Debian Emacs Policy" for details of how to
8388 package emacs lisp programs.
8392 The Emacs policy is available in
8393 <file>debian-emacs-policy.gz</file> of the
8394 <package>emacsen-common</package> package.
8395 It is also available from the Debian web mirrors at
8396 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
8397 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
8402 <heading>Games</heading>
8405 The permissions on <file>/var/games</file> are mode 755, owner
8406 <tt>root</tt> and group <tt>root</tt>.
8410 Each game decides on its own security policy.</p>
8413 Games which require protected, privileged access to
8414 high-score files, saved games, etc., may be made
8415 set-<em>group</em>-id (mode 2755) and owned by
8416 <tt>root.games</tt>, and use files and directories with
8417 appropriate permissions (770 <tt>root.games</tt>, for
8418 example). They must not be made
8419 set-<em>user</em>-id, as this causes security problems. (If
8420 an attacker can subvert any set-user-id game they can
8421 overwrite the executable of any other, causing other players
8422 of these games to run a Trojan horse program. With a
8423 set-group-id game the attacker only gets access to less
8424 important game data, and if they can get at the other
8425 players' accounts at all it will take considerably more
8429 Some packages, for example some fortune cookie programs, are
8430 configured by the upstream authors to install with their
8431 data files or other static information made unreadable so
8432 that they can only be accessed through set-id programs
8433 provided. You should not do this in a Debian package: anyone can
8434 download the <file>.deb</file> file and read the data from it,
8435 so there is no point making the files unreadable. Not
8436 making the files unreadable also means that you don't have
8437 to make so many programs set-id, which reduces the risk of a
8441 As described in the FHS, binaries of games should be
8442 installed in the directory <file>/usr/games</file>. This also
8443 applies to games that use the X Window System. Manual pages
8444 for games (X and non-X games) should be installed in
8445 <file>/usr/share/man/man6</file>.</p>
8451 <heading>Documentation</heading>
8454 <heading>Manual pages</heading>
8457 You should install manual pages in <prgn>nroff</prgn> source
8458 form, in appropriate places under <file>/usr/share/man</file>.
8459 You should only use sections 1 to 9 (see the FHS for more
8460 details). You must not install a pre-formatted "cat page".
8464 Each program, utility, and function should have an
8465 associated manual page included in the same package. It is
8466 suggested that all configuration files also have a manual
8467 page included as well. Manual pages for protocols and other
8468 auxiliary things are optional.
8472 If no manual page is available, this is considered as a bug
8473 and should be reported to the Debian Bug Tracking System (the
8474 maintainer of the package is allowed to write this bug report
8475 themselves, if they so desire). Do not close the bug report
8476 until a proper man page is available.<footnote>
8477 It is not very hard to write a man page. See the
8478 <url id="http://www.schweikhardt.net/man_page_howto.html"
8479 name="Man-Page-HOWTO">,
8480 <manref name="man" section="7">, the examples
8481 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
8482 the helper programs <prgn>help2man</prgn>, or the
8483 directory <file>/usr/share/doc/man-db/examples</file>.
8488 You may forward a complaint about a missing man page to the
8489 upstream authors, and mark the bug as forwarded in the
8490 Debian bug tracking system. Even though the GNU Project do
8491 not in general consider the lack of a man page to be a bug,
8492 we do; if they tell you that they don't consider it a bug
8493 you should leave the bug in our bug tracking system open
8498 Manual pages should be installed compressed using <tt>gzip -9</tt>.
8502 If one man page needs to be accessible via several names it
8503 is better to use a symbolic link than the <file>.so</file>
8504 feature, but there is no need to fiddle with the relevant
8505 parts of the upstream source to change from <file>.so</file> to
8506 symlinks: don't do it unless it's easy. You should not
8507 create hard links in the manual page directories, nor put
8508 absolute filenames in <file>.so</file> directives. The filename
8509 in a <file>.so</file> in a man page should be relative to the
8510 base of the man page tree (usually
8511 <file>/usr/share/man</file>). If you do not create any links
8512 (whether symlinks, hard links, or <tt>.so</tt> directives)
8513 in the file system to the alternate names of the man page,
8514 then you should not rely on <prgn>man</prgn> finding your
8515 man page under those names based solely on the information in
8516 the man page's header.<footnote>
8517 Supporting this in <prgn>man</prgn> often requires
8518 unreasonable processing time to find a manual page or to
8519 report that none exists, and moves knowledge into man's
8520 database that would be better left in the file system.
8521 This support is therefore deprecated and will cease to
8522 be present in the future.
8528 <heading>Info documents</heading>
8531 Info documents should be installed in <file>/usr/share/info</file>.
8532 They should be compressed with <tt>gzip -9</tt>.
8536 Your package should call <prgn>install-info</prgn> to update
8537 the Info <file>dir</file> file in its <prgn>postinst</prgn>
8538 script when called with a <tt>configure</tt> argument, for
8540 <example compact="compact">
8541 install-info --quiet --section Development Development \
8542 /usr/share/info/foobar.info
8546 It is a good idea to specify a section for the location of
8547 your program; this is done with the <tt>--section</tt>
8548 switch. To determine which section to use, you should look
8549 at <file>/usr/share/info/dir</file> on your system and choose the most
8550 relevant (or create a new section if none of the current
8551 sections are relevant). Note that the <tt>--section</tt>
8552 flag takes two arguments; the first is a regular expression
8553 to match (case-insensitively) against an existing section,
8554 the second is used when creating a new one.</p>
8557 You should remove the entries in the <prgn>prerm</prgn>
8558 script when called with a <tt>remove</tt> argument:
8559 <example compact="compact">
8560 install-info --quiet --remove /usr/share/info/foobar.info
8564 If <prgn>install-info</prgn> cannot find a description entry
8565 in the Info file you must supply one. See <manref
8566 name="install-info" section="8"> for details.</p>
8570 <heading>Additional documentation</heading>
8573 Any additional documentation that comes with the package may
8574 be installed at the discretion of the package maintainer.
8575 Plain text documentation should be installed in the directory
8576 <file>/usr/share/doc/<var>package</var></file>, where
8577 <var>package</var> is the name of the package, and
8578 compressed with <tt>gzip -9</tt> unless it is small.
8582 If a package comes with large amounts of documentation which
8583 many users of the package will not require you should create
8584 a separate binary package to contain it, so that it does not
8585 take up disk space on the machines of users who do not need
8586 or want it installed.</p>
8589 It is often a good idea to put text information files
8590 (<file>README</file>s, changelogs, and so forth) that come with
8591 the source package in <file>/usr/share/doc/<var>package</var></file>
8592 in the binary package. However, you don't need to install
8593 the instructions for building and installing the package, of
8597 Packages must not require the existence of any files in
8598 <file>/usr/share/doc/</file> in order to function
8600 The system administrator should be able to
8601 delete files in <file>/usr/share/doc/</file> without causing
8602 any programs to break.
8604 Any files that are referenced by programs but are also
8605 useful as stand alone documentation should be installed under
8606 <file>/usr/share/<var>package</var>/</file> with symbolic links from
8607 <file>/usr/share/doc/<var>package</var></file>.
8611 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8612 link to another directory in <file>/usr/share/doc</file> only if
8613 the two packages both come from the same source and the
8614 first package Depends on the second.<footnote>
8616 Please note that this does not override the section on
8617 changelog files below, so the file
8618 <file>/usr/share/<var>package</var>/changelog.Debian.gz</file>
8619 must refer to the changelog for the current version of
8620 <var>package</var> in question. In practice, this means
8621 that the sources of the target and the destination of the
8622 symlink must be the same (same source package and
8629 Former Debian releases placed all additional documentation
8630 in <file>/usr/doc/<var>package</var></file>. This has been
8631 changed to <file>/usr/share/doc/<var>package</var></file>,
8632 and packages must not put documentation in the directory
8633 <file>/usr/doc/<var>package</var></file>. <footnote>
8634 At this phase of the transition, we no longer require a
8635 symbolic link in <file>/usr/doc/</file>. At a later point,
8636 policy shall change to make the symbolic links a bug.
8642 <heading>Preferred documentation formats</heading>
8645 The unification of Debian documentation is being carried out
8649 If your package comes with extensive documentation in a
8650 markup format that can be converted to various other formats
8651 you should if possible ship HTML versions in a binary
8652 package, in the directory
8653 <file>/usr/share/doc/<var>appropriate-package</var></file> or
8654 its subdirectories.<footnote>
8655 The rationale: The important thing here is that HTML
8656 docs should be available in <em>some</em> package, not
8657 necessarily in the main binary package.
8662 Other formats such as PostScript may be provided at the
8663 package maintainer's discretion.
8667 <sect id="copyrightfile">
8668 <heading>Copyright information</heading>
8671 Every package must be accompanied by a verbatim copy of its
8672 copyright and distribution license in the file
8673 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
8674 file must neither be compressed nor be a symbolic link.
8678 In addition, the copyright file must say where the upstream
8679 sources (if any) were obtained. It should name the original
8680 authors of the package and the Debian maintainer(s) who were
8681 involved with its creation.</p>
8684 A copy of the file which will be installed in
8685 <file>/usr/share/doc/<var>package</var>/copyright</file> should
8686 be in <file>debian/copyright</file> in the source package.
8690 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8691 link to another directory in <file>/usr/share/doc</file> only if
8692 the two packages both come from the same source and the
8693 first package Depends on the second. These rules are
8694 important because copyrights must be extractable by
8699 Packages distributed under the UCB BSD license, the Artistic
8700 license, the GNU GPL (version 2 or 3), the GNU LGPL (versions
8701 2, 2.1, or 3), and the GNU FDL (version 1.2) should refer to
8702 the corresponding files under
8703 <file>/usr/share/common-licenses</file>,<footnote>
8706 <file>/usr/share/common-licenses/BSD</file>,
8707 <file>/usr/share/common-licenses/Artistic</file>,
8708 <file>/usr/share/common-licenses/GPL-2</file>,
8709 <file>/usr/share/common-licenses/GPL-3</file>,
8710 <file>/usr/share/common-licenses/LGPL-2</file>,
8711 <file>/usr/share/common-licenses/LGPL-2.1</file>,
8712 <file>/usr/share/common-licenses/LGPL-3</file>, and
8713 <file>/usr/share/common-licenses/GFDL-1.2</file>,
8716 </footnote> rather than quoting them in the copyright
8721 You should not use the copyright file as a general <file>README</file>
8722 file. If your package has such a file it should be
8723 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
8724 <file>README.Debian</file> or some other appropriate place.</p>
8728 <heading>Examples</heading>
8731 Any examples (configurations, source files, whatever),
8732 should be installed in a directory
8733 <file>/usr/share/doc/<var>package</var>/examples</file>. These
8734 files should not be referenced by any program: they're there
8735 for the benefit of the system administrator and users as
8736 documentation only. Architecture-specific example files
8737 should be installed in a directory
8738 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
8740 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
8741 latter directory itself may be a symbolic link to the
8746 If the purpose of a package is to provide examples, then the
8747 example files may be installed into
8748 <file>/usr/share/doc/<var>package</var></file>.
8752 <sect id="changelogs">
8753 <heading>Changelog files</heading>
8756 Packages that are not Debian-native must contain a
8757 compressed copy of the <file>debian/changelog</file> file from
8758 the Debian source tree in
8759 <file>/usr/share/doc/<var>package</var></file> with the name
8760 <file>changelog.Debian.gz</file>.
8764 If an upstream changelog is available, it should be accessible as
8765 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
8766 plain text. If the upstream changelog is distributed in
8767 HTML, it should be made available in that form as
8768 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
8769 and a plain text <file>changelog.gz</file> should be generated
8770 from it using, for example, <tt>lynx -dump -nolist</tt>. If
8771 the upstream changelog files do not already conform to this
8772 naming convention, then this may be achieved either by
8773 renaming the files, or by adding a symbolic link, at the
8774 maintainer's discretion.<footnote>
8775 Rationale: People should not have to look in places for
8776 upstream changelogs merely because they are given
8777 different names or are distributed in HTML format.
8782 All of these files should be installed compressed using
8783 <tt>gzip -9</tt>, as they will become large with time even
8784 if they start out small.
8788 If the package has only one changelog which is used both as
8789 the Debian changelog and the upstream one because there is
8790 no separate upstream maintainer then that changelog should
8791 usually be installed as
8792 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
8793 there is a separate upstream maintainer, but no upstream
8794 changelog, then the Debian changelog should still be called
8795 <file>changelog.Debian.gz</file>.
8799 For details about the format and contents of the Debian
8800 changelog file, please see <ref id="dpkgchangelog">.
8805 <appendix id="pkg-scope">
8806 <heading>Introduction and scope of these appendices</heading>
8809 These appendices are taken essentially verbatim from the
8810 now-deprecated Packaging Manual, version 3.2.1.0. They are
8811 the chapters which are likely to be of use to package
8812 maintainers and which have not already been included in the
8813 policy document itself. Most of these sections are very likely
8814 not relevant to policy; they should be treated as
8815 documentation for the packaging system. Please note that these
8816 appendices are included for convenience, and for historical
8817 reasons: they used to be part of policy package, and they have
8818 not yet been incorporated into dpkg documentation. However,
8819 they still have value, and hence they are presented here.
8823 They have not yet been checked to ensure that they are
8824 compatible with the contents of policy, and if there are any
8825 contradictions, the version in the main policy document takes
8826 precedence. The remaining chapters of the old Packaging
8827 Manual have also not been read in detail to ensure that there
8828 are not parts which have been left out. Both of these will be
8833 Certain parts of the Packaging manual were integrated into the
8834 Policy Manual proper, and removed from the appendices. Links
8835 have been placed from the old locations to the new ones.
8839 <prgn>dpkg</prgn> is a suite of programs for creating binary
8840 package files and installing and removing them on Unix
8842 <prgn>dpkg</prgn> is targeted primarily at Debian
8843 GNU/Linux, but may work on or be ported to other
8849 The binary packages are designed for the management of
8850 installed executable programs (usually compiled binaries) and
8851 their associated data, though source code examples and
8852 documentation are provided as part of some packages.</p>
8855 This manual describes the technical aspects of creating Debian
8856 binary packages (<file>.deb</file> files). It documents the
8857 behavior of the package management programs
8858 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
8859 they interact with packages.</p>
8862 It also documents the interaction between
8863 <prgn>dselect</prgn>'s core and the access method scripts it
8864 uses to actually install the selected packages, and describes
8865 how to create a new access method.</p>
8868 This manual does not go into detail about the options and
8869 usage of the package building and installation tools. It
8870 should therefore be read in conjunction with those programs'
8875 The utility programs which are provided with <prgn>dpkg</prgn>
8876 for managing various system configuration and similar issues,
8877 such as <prgn>update-rc.d</prgn> and
8878 <prgn>install-info</prgn>, are not described in detail here -
8879 please see their man pages.
8883 It is assumed that the reader is reasonably familiar with the
8884 <prgn>dpkg</prgn> System Administrators' manual.
8885 Unfortunately this manual does not yet exist.
8889 The Debian version of the FSF's GNU hello program is provided
8890 as an example for people wishing to create Debian
8891 packages. The Debian <prgn>debmake</prgn> package is
8892 recommended as a very helpful tool in creating and maintaining
8893 Debian packages. However, while the tools and examples are
8894 helpful, they do not replace the need to read and follow the
8895 Policy and Programmer's Manual.</p>
8898 <appendix id="pkg-binarypkg">
8899 <heading>Binary packages (from old Packaging Manual)</heading>
8902 The binary package has two main sections. The first part
8903 consists of various control information files and scripts used
8904 by <prgn>dpkg</prgn> when installing and removing. See <ref
8905 id="pkg-controlarea">.
8909 The second part is an archive containing the files and
8910 directories to be installed.
8914 In the future binary packages may also contain other
8915 components, such as checksums and digital signatures. The
8916 format for the archive is described in full in the
8917 <file>deb(5)</file> man page.
8921 <sect id="pkg-bincreating"><heading>Creating package files -
8922 <prgn>dpkg-deb</prgn>
8926 All manipulation of binary package files is done by
8927 <prgn>dpkg-deb</prgn>; it's the only program that has
8928 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
8929 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
8930 will spot that the options requested are appropriate to
8931 <prgn>dpkg-deb</prgn> and invoke that instead with the same
8936 In order to create a binary package you must make a
8937 directory tree which contains all the files and directories
8938 you want to have in the file system data part of the package.
8939 In Debian-format source packages this directory is usually
8940 <file>debian/tmp</file>, relative to the top of the package's
8945 They should have the locations (relative to the root of the
8946 directory tree you're constructing) ownerships and
8947 permissions which you want them to have on the system when
8952 With current versions of <prgn>dpkg</prgn> the uid/username
8953 and gid/groupname mappings for the users and groups being
8954 used should be the same on the system where the package is
8955 built and the one where it is installed.
8959 You need to add one special directory to the root of the
8960 miniature file system tree you're creating:
8961 <prgn>DEBIAN</prgn>. It should contain the control
8962 information files, notably the binary package control file
8963 (see <ref id="pkg-controlfile">).
8967 The <prgn>DEBIAN</prgn> directory will not appear in the
8968 file system archive of the package, and so won't be installed
8969 by <prgn>dpkg</prgn> when the package is installed.
8973 When you've prepared the package, you should invoke:
8975 dpkg --build <var>directory</var>
8980 This will build the package in
8981 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
8982 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
8983 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
8988 See the man page <manref name="dpkg-deb" section="8"> for details of how
8989 to examine the contents of this newly-created file. You may find the
8990 output of following commands enlightening:
8992 dpkg-deb --info <var>filename</var>.deb
8993 dpkg-deb --contents <var>filename</var>.deb
8994 dpkg --contents <var>filename</var>.deb
8996 To view the copyright file for a package you could use this command:
8998 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - \*/copyright | pager
9003 <sect id="pkg-controlarea">
9004 <heading>Package control information files</heading>
9007 The control information portion of a binary package is a
9008 collection of files with names known to <prgn>dpkg</prgn>.
9009 It will treat the contents of these files specially - some
9010 of them contain information used by <prgn>dpkg</prgn> when
9011 installing or removing the package; others are scripts which
9012 the package maintainer wants <prgn>dpkg</prgn> to run.
9016 It is possible to put other files in the package control
9017 area, but this is not generally a good idea (though they
9018 will largely be ignored).
9022 Here is a brief list of the control info files supported by
9023 <prgn>dpkg</prgn> and a summary of what they're used for.
9028 <tag><tt>control</tt>
9031 This is the key description file used by
9032 <prgn>dpkg</prgn>. It specifies the package's name
9033 and version, gives its description for the user,
9034 states its relationships with other packages, and so
9035 forth. See <ref id="sourcecontrolfiles"> and
9036 <ref id="binarycontrolfiles">.
9040 It is usually generated automatically from information
9041 in the source package by the
9042 <prgn>dpkg-gencontrol</prgn> program, and with
9043 assistance from <prgn>dpkg-shlibdeps</prgn>.
9044 See <ref id="pkg-sourcetools">.
9048 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9053 These are executable files (usually scripts) which
9054 <prgn>dpkg</prgn> runs during installation, upgrade
9055 and removal of packages. They allow the package to
9056 deal with matters which are particular to that package
9057 or require more complicated processing than that
9058 provided by <prgn>dpkg</prgn>. Details of when and
9059 how they are called are in <ref id="maintainerscripts">.
9063 It is very important to make these scripts idempotent.
9064 See <ref id="idempotency">.
9068 The maintainer scripts are guaranteed to run with a
9069 controlling terminal and can interact with the user.
9070 See <ref id="controllingterminal">.
9074 <tag><tt>conffiles</tt>
9077 This file contains a list of configuration files which
9078 are to be handled automatically by <prgn>dpkg</prgn>
9079 (see <ref id="pkg-conffiles">). Note that not necessarily
9080 every configuration file should be listed here.
9083 <tag><tt>shlibs</tt>
9086 This file contains a list of the shared libraries
9087 supplied by the package, with dependency details for
9088 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9089 when it determines what dependencies are required in a
9090 package control file. The <tt>shlibs</tt> file format
9091 is described on <ref id="shlibs">.
9096 <sect id="pkg-controlfile">
9097 <heading>The main control information file: <tt>control</tt></heading>
9100 The most important control information file used by
9101 <prgn>dpkg</prgn> when it installs a package is
9102 <tt>control</tt>. It contains all the package's "vital
9107 The binary package control files of packages built from
9108 Debian sources are made by a special tool,
9109 <prgn>dpkg-gencontrol</prgn>, which reads
9110 <file>debian/control</file> and <file>debian/changelog</file> to
9111 find the information it needs. See <ref id="pkg-sourcepkg"> for
9116 The fields in binary package control files are listed in
9117 <ref id="binarycontrolfiles">.
9121 A description of the syntax of control files and the purpose
9122 of the fields is available in <ref id="controlfields">.
9127 <heading>Time Stamps</heading>
9130 See <ref id="timestamps">.
9135 <appendix id="pkg-sourcepkg">
9136 <heading>Source packages (from old Packaging Manual) </heading>
9139 The Debian binary packages in the distribution are generated
9140 from Debian sources, which are in a special format to assist
9141 the easy and automatic building of binaries.
9144 <sect id="pkg-sourcetools">
9145 <heading>Tools for processing source packages</heading>
9148 Various tools are provided for manipulating source packages;
9149 they pack and unpack sources and help build of binary
9150 packages and help manage the distribution of new versions.
9154 They are introduced and typical uses described here; see
9155 <manref name="dpkg-source" section="1"> for full
9156 documentation about their arguments and operation.
9160 For examples of how to construct a Debian source package,
9161 and how to use those utilities that are used by Debian
9162 source packages, please see the <prgn>hello</prgn> example
9166 <sect1 id="pkg-dpkg-source">
9168 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9173 This program is frequently used by hand, and is also
9174 called from package-independent automated building scripts
9175 such as <prgn>dpkg-buildpackage</prgn>.
9179 To unpack a package it is typically invoked with
9181 dpkg-source -x <var>.../path/to/filename</var>.dsc
9186 with the <file><var>filename</var>.tar.gz</file> and
9187 <file><var>filename</var>.diff.gz</file> (if applicable) in
9188 the same directory. It unpacks into
9189 <file><var>package</var>-<var>version</var></file>, and if
9191 <file><var>package</var>-<var>version</var>.orig</file>, in
9192 the current directory.
9196 To create a packed source archive it is typically invoked:
9198 dpkg-source -b <var>package</var>-<var>version</var>
9203 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
9204 <file>.diff.gz</file> (if appropriate) in the current
9205 directory. <prgn>dpkg-source</prgn> does not clean the
9206 source tree first - this must be done separately if it is
9211 See also <ref id="pkg-sourcearchives">.</p>
9215 <sect1 id="pkg-dpkg-buildpackage">
9217 <prgn>dpkg-buildpackage</prgn> - overall package-building
9222 <prgn>dpkg-buildpackage</prgn> is a script which invokes
9223 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
9224 targets <tt>clean</tt>, <tt>build</tt> and
9225 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
9226 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
9227 source and binary package upload.
9231 It is usually invoked by hand from the top level of the
9232 built or unbuilt source directory. It may be invoked with
9233 no arguments; useful arguments include:
9234 <taglist compact="compact">
9235 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
9238 Do not sign the <tt>.changes</tt> file or the
9239 source package <tt>.dsc</tt> file, respectively.</p>
9241 <tag><tt>-p<var>sign-command</var></tt></tag>
9244 Invoke <var>sign-command</var> instead of finding
9245 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
9246 <var>sign-command</var> must behave just like
9247 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
9249 <tag><tt>-r<var>root-command</var></tt></tag>
9252 When root privilege is required, invoke the command
9253 <var>root-command</var>. <var>root-command</var>
9254 should invoke its first argument as a command, from
9255 the <prgn>PATH</prgn> if necessary, and pass its
9256 second and subsequent arguments to the command it
9257 calls. If no <var>root-command</var> is supplied
9258 then <var>dpkg-buildpackage</var> will take no
9259 special action to gain root privilege, so that for
9260 most packages it will have to be invoked as root to
9263 <tag><tt>-b</tt>, <tt>-B</tt></tag>
9266 Two types of binary-only build and upload - see
9267 <manref name="dpkg-source" section="1">.
9274 <sect1 id="pkg-dpkg-gencontrol">
9276 <prgn>dpkg-gencontrol</prgn> - generates binary package
9281 This program is usually called from <file>debian/rules</file>
9282 (see <ref id="pkg-sourcetree">) in the top level of the source
9287 This is usually done just before the files and directories in the
9288 temporary directory tree where the package is being built have their
9289 permissions and ownerships set and the package is constructed using
9290 <prgn>dpkg-deb/</prgn>
9292 This is so that the control file which is produced has
9293 the right permissions
9298 <prgn>dpkg-gencontrol</prgn> must be called after all the
9299 files which are to go into the package have been placed in
9300 the temporary build directory, so that its calculation of
9301 the installed size of a package is correct.
9305 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
9306 be run after <prgn>dpkg-shlibdeps</prgn> so that the
9307 variable substitutions created by
9308 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
9313 For a package which generates only one binary package, and
9314 which builds it in <file>debian/tmp</file> relative to the top
9315 of the source package, it is usually sufficient to call
9316 <prgn>dpkg-gencontrol</prgn>.
9320 Sources which build several binaries will typically need
9323 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
9324 </example> The <tt>-P</tt> tells
9325 <prgn>dpkg-gencontrol</prgn> that the package is being
9326 built in a non-default directory, and the <tt>-p</tt>
9327 tells it which package's control file should be generated.
9331 <prgn>dpkg-gencontrol</prgn> also adds information to the
9332 list of files in <file>debian/files</file>, for the benefit of
9333 (for example) a future invocation of
9334 <prgn>dpkg-genchanges</prgn>.</p>
9337 <sect1 id="pkg-dpkg-shlibdeps">
9339 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
9344 This program is usually called from <file>debian/rules</file>
9345 just before <prgn>dpkg-gencontrol</prgn> (see <ref
9346 id="pkg-sourcetree">), in the top level of the source tree.
9350 Its arguments are executables.
9353 In a forthcoming dpkg version,
9354 <prgn>dpkg-shlibdeps</prgn> would be required to be
9355 called on shared libraries as well.
9358 They may be specified either in the locations in the
9359 source tree where they are created or in the locations
9360 in the temporary build tree where they are installed
9361 prior to binary package creation.
9363 </footnote> for which shared library dependencies should
9364 be included in the binary package's control file.
9368 If some of the found shared libraries should only
9369 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
9370 some warrant a <tt>Pre-Depends</tt>, this can be achieved
9371 by using the <tt>-d<var>dependency-field</var></tt> option
9372 before those executable(s). (Each <tt>-d</tt> option
9373 takes effect until the next <tt>-d</tt>.)
9377 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
9378 output control file to be modified. Instead by default it
9379 adds to the <file>debian/substvars</file> file variable
9380 settings like <tt>shlibs:Depends</tt>. These variable
9381 settings must be referenced in dependency fields in the
9382 appropriate per-binary-package sections of the source
9387 For example, a package that generates an essential part
9388 which requires dependencies, and optional parts that
9389 which only require a recommendation, would separate those
9390 two sets of dependencies into two different fields.<footnote>
9391 At the time of writing, an example for this was the
9392 <package/xmms/ package, with Depends used for the xmms
9393 executable, Recommends for the plug-ins and Suggests for
9394 even more optional features provided by unzip.
9396 It can say in its <file>debian/rules</file>:
9398 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
9399 -dRecommends <var>optionalpart anotheroptionalpart</var>
9401 and then in its main control file <file>debian/control</file>:
9404 Depends: ${shlibs:Pre-Depends}
9405 Recommends: ${shlibs:Recommends}
9411 Sources which produce several binary packages with
9412 different shared library dependency requirements can use
9413 the <tt>-p<var>varnameprefix</var></tt> option to override
9414 the default <tt>shlibs:</tt> prefix (one invocation of
9415 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
9416 They can thus produce several sets of dependency
9417 variables, each of the form
9418 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
9419 which can be referred to in the appropriate parts of the
9420 binary package control files.
9425 <sect1 id="pkg-dpkg-distaddfile">
9427 <prgn>dpkg-distaddfile</prgn> - adds a file to
9428 <file>debian/files</file>
9432 Some packages' uploads need to include files other than
9433 the source and binary package files.
9437 <prgn>dpkg-distaddfile</prgn> adds a file to the
9438 <file>debian/files</file> file so that it will be included in
9439 the <file>.changes</file> file when
9440 <prgn>dpkg-genchanges</prgn> is run.
9444 It is usually invoked from the <tt>binary</tt> target of
9445 <file>debian/rules</file>:
9447 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
9449 The <var>filename</var> is relative to the directory where
9450 <prgn>dpkg-genchanges</prgn> will expect to find it - this
9451 is usually the directory above the top level of the source
9452 tree. The <file>debian/rules</file> target should put the
9453 file there just before or just after calling
9454 <prgn>dpkg-distaddfile</prgn>.
9458 The <var>section</var> and <var>priority</var> are passed
9459 unchanged into the resulting <file>.changes</file> file.
9464 <sect1 id="pkg-dpkg-genchanges">
9466 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
9471 This program is usually called by package-independent
9472 automatic building scripts such as
9473 <prgn>dpkg-buildpackage</prgn>, but it may also be called
9478 It is usually called in the top level of a built source
9479 tree, and when invoked with no arguments will print out a
9480 straightforward <file>.changes</file> file based on the
9481 information in the source package's changelog and control
9482 file and the binary and source packages which should have
9488 <sect1 id="pkg-dpkg-parsechangelog">
9490 <prgn>dpkg-parsechangelog</prgn> - produces parsed
9491 representation of a changelog
9495 This program is used internally by
9496 <prgn>dpkg-source</prgn> et al. It may also occasionally
9497 be useful in <file>debian/rules</file> and elsewhere. It
9498 parses a changelog, <file>debian/changelog</file> by default,
9499 and prints a control-file format representation of the
9500 information in it to standard output.
9504 <sect1 id="pkg-dpkg-architecture">
9506 <prgn>dpkg-architecture</prgn> - information about the build and
9511 This program can be used manually, but is also invoked by
9512 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
9513 to set environment or make variables which specify the build and
9514 host architecture for the package building process.
9519 <sect id="pkg-sourcetree">
9520 <heading>The Debianised source tree</heading>
9523 The source archive scheme described later is intended to
9524 allow a Debianised source tree with some associated control
9525 information to be reproduced and transported easily. The
9526 Debianised source tree is a version of the original program
9527 with certain files added for the benefit of the
9528 Debianisation process, and with any other changes required
9529 made to the rest of the source code and installation
9534 The extra files created for Debian are in the subdirectory
9535 <file>debian</file> of the top level of the Debianised source
9536 tree. They are described below.
9539 <sect1 id="pkg-debianrules">
9540 <heading><file>debian/rules</file> - the main building script</heading>
9543 See <ref id="debianrules">.
9548 <sect1 id="pkg-dpkgchangelog">
9549 <heading><file>debian/changelog</file></heading>
9552 See <ref id="dpkgchangelog">.
9556 It is recommended that the entire changelog be encoded in the
9557 <url id="http://www.cis.ohio-state.edu/cgi-bin/rfc/rfc2279.html" name="UTF-8">
9559 <url id="http://www.unicode.org/"
9560 name="Unicode">.<footnote>
9562 I think it is fairly obvious that we need to
9563 eventually transition to UTF-8 for our package
9564 infrastructure; it is really the only sane char-set in
9565 an international environment. Now, we can't switch to
9566 using UTF-8 for package control fields and the like
9567 until dpkg has better support, but one thing we can
9568 start doing today is requesting that Debian changelogs
9569 are UTF-8 encoded. At some point in time, we can start
9570 requiring them to do so.
9573 Checking for non-UTF8 characters in a changelog is
9574 trivial. Dump the file through
9575 <example>iconv -f utf-8 -t ucs-4</example>
9576 discard the output, and check the return
9577 value. If there are any characters in the stream
9578 which are invalid UTF-8 sequences, iconv will exit
9579 with an error code; and this will be the case for the
9580 vast majority of other character sets.
9585 <sect2><heading>Defining alternative changelog formats
9589 It is possible to use a different format to the standard
9590 one, by providing a parser for the format you wish to
9595 In order to have <tt>dpkg-parsechangelog</tt> run your
9596 parser, you must include a line within the last 40 lines
9597 of your file matching the Perl regular expression:
9598 <tt>\schangelog-format:\s+([0-9a-z]+)\W</tt> The part in
9599 parentheses should be the name of the format. For
9600 example, you might say:
9602 @@@ changelog-format: joebloggs @@@
9604 Changelog format names are non-empty strings of alphanumerics.
9608 If such a line exists then <tt>dpkg-parsechangelog</tt>
9609 will look for the parser as
9610 <file>/usr/lib/dpkg/parsechangelog/<var>format-name</var></file>
9612 <file>/usr/local/lib/dpkg/parsechangelog/<var>format-name</var></file>;
9613 it is an error for it not to find it, or for it not to
9614 be an executable program. The default changelog format
9615 is <tt>dpkg</tt>, and a parser for it is provided with
9616 the <tt>dpkg</tt> package.
9620 The parser will be invoked with the changelog open on
9621 standard input at the start of the file. It should read
9622 the file (it may seek if it wishes) to determine the
9623 information required and return the parsed information
9624 to standard output in the form of a series of control
9625 fields in the standard format. By default it should
9626 return information about only the most recent version in
9627 the changelog; it should accept a
9628 <tt>-v<var>version</var></tt> option to return changes
9629 information from all versions present <em>strictly
9630 after</em> <var>version</var>, and it should then be an
9631 error for <var>version</var> not to be present in the
9637 <list compact="compact">
9638 <item><qref id="f-Source"><tt>Source</tt></qref></item>
9639 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
9640 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
9641 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (mandatory)</item>
9642 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
9643 <item><qref id="f-Date"><tt>Date</tt></qref></item>
9644 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
9649 If several versions are being returned (due to the use
9650 of <tt>-v</tt>), the urgency value should be of the
9651 highest urgency code listed at the start of any of the
9652 versions requested followed by the concatenated
9653 (space-separated) comments from all the versions
9654 requested; the maintainer, version, distribution and
9655 date should always be from the most recent version.
9659 For the format of the <tt>Changes</tt> field see
9660 <ref id="f-Changes">.
9664 If the changelog format which is being parsed always or
9665 almost always leaves a blank line between individual
9666 change notes these blank lines should be stripped out,
9667 so as to make the resulting output compact.
9671 If the changelog format does not contain date or package
9672 name information this information should be omitted from
9673 the output. The parser should not attempt to synthesize
9674 it or find it from other sources.
9678 If the changelog does not have the expected format the
9679 parser should exit with a nonzero exit status, rather
9680 than trying to muddle through and possibly generating
9685 A changelog parser may not interact with the user at
9691 <sect1 id="pkg-srcsubstvars">
9692 <heading><file>debian/substvars</file> and variable substitutions</heading>
9695 See <ref id="substvars">.
9701 <heading><file>debian/files</file></heading>
9704 See <ref id="debianfiles">.
9708 <sect1><heading><file>debian/tmp</file>
9712 This is the canonical temporary location for the
9713 construction of binary packages by the <tt>binary</tt>
9714 target. The directory <file>tmp</file> serves as the root of
9715 the file system tree as it is being constructed (for
9716 example, by using the package's upstream makefiles install
9717 targets and redirecting the output there), and it also
9718 contains the <tt>DEBIAN</tt> subdirectory. See <ref
9719 id="pkg-bincreating">.
9723 If several binary packages are generated from the same
9724 source tree it is usual to use several
9725 <file>debian/tmp<var>something</var></file> directories, for
9726 example <file>tmp-a</file> or <file>tmp-doc</file>.
9730 Whatever <file>tmp</file> directories are created and used by
9731 <tt>binary</tt> must of course be removed by the
9732 <tt>clean</tt> target.</p></sect1>
9736 <sect id="pkg-sourcearchives"><heading>Source packages as archives
9740 As it exists on the FTP site, a Debian source package
9741 consists of three related files. You must have the right
9742 versions of all three to be able to use them.
9747 <tag>Debian source control file - <tt>.dsc</tt></tag>
9749 This file is a control file used by <prgn>dpkg-source</prgn>
9750 to extract a source package.
9751 See <ref id="debiansourcecontrolfiles">.
9755 Original source archive -
9757 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
9763 This is a compressed (with <tt>gzip -9</tt>)
9764 <prgn>tar</prgn> file containing the source code from
9765 the upstream authors of the program.
9770 Debianisation diff -
9772 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
9778 This is a unified context diff (<tt>diff -u</tt>)
9779 giving the changes which are required to turn the
9780 original source into the Debian source. These changes
9781 may only include editing and creating plain files.
9782 The permissions of files, the targets of symbolic
9783 links and the characteristics of special files or
9784 pipes may not be changed and no files may be removed
9789 All the directories in the diff must exist, except the
9790 <file>debian</file> subdirectory of the top of the source
9791 tree, which will be created by
9792 <prgn>dpkg-source</prgn> if necessary when unpacking.
9796 The <prgn>dpkg-source</prgn> program will
9797 automatically make the <file>debian/rules</file> file
9798 executable (see below).</p></item>
9803 If there is no original source code - for example, if the
9804 package is specially prepared for Debian or the Debian
9805 maintainer is the same as the upstream maintainer - the
9806 format is slightly different: then there is no diff, and the
9808 <file><var>package</var>_<var>version</var>.tar.gz</file>,
9809 and preferably contains a directory named
9810 <file><var>package</var>-<var>version</var></file>.
9815 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
9818 <tt>dpkg-source -x</tt> is the recommended way to unpack a
9819 Debian source package. However, if it is not available it
9820 is possible to unpack a Debian source archive as follows:
9821 <enumlist compact="compact">
9824 Untar the tarfile, which will create a <file>.orig</file>
9828 <p>Rename the <file>.orig</file> directory to
9829 <file><var>package</var>-<var>version</var></file>.</p>
9833 Create the subdirectory <file>debian</file> at the top of
9834 the source tree.</p>
9836 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
9838 <item><p>Untar the tarfile again if you want a copy of the original
9839 source code alongside the Debianised version.</p>
9844 It is not possible to generate a valid Debian source archive
9845 without using <prgn>dpkg-source</prgn>. In particular,
9846 attempting to use <prgn>diff</prgn> directly to generate the
9847 <file>.diff.gz</file> file will not work.
9851 <heading>Restrictions on objects in source packages</heading>
9854 The source package may not contain any hard links
9856 This is not currently detected when building source
9857 packages, but only when extracting
9861 Hard links may be permitted at some point in the
9862 future, but would require a fair amount of
9864 </footnote>, device special files, sockets or setuid or
9867 Setgid directories are allowed.
9872 The source packaging tools manage the changes between the
9873 original and Debianised source using <prgn>diff</prgn> and
9874 <prgn>patch</prgn>. Turning the original source tree as
9875 included in the <file>.orig.tar.gz</file> into the debianised
9876 source must not involve any changes which cannot be
9877 handled by these tools. Problematic changes which cause
9878 <prgn>dpkg-source</prgn> to halt with an error when
9879 building the source package are:
9880 <list compact="compact">
9881 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
9883 <item><p>Changing the targets of symbolic links.</p>
9885 <item><p>Creating directories, other than <file>debian</file>.</p>
9887 <item><p>Changes to the contents of binary files.</p></item>
9888 </list> Changes which cause <prgn>dpkg-source</prgn> to
9889 print a warning but continue anyway are:
9890 <list compact="compact">
9893 Removing files, directories or symlinks.
9895 Renaming a file is not treated specially - it is
9896 seen as the removal of the old file (which
9897 generates a warning, but is otherwise ignored),
9898 and the creation of the new one.
9904 Changed text files which are missing the usual final
9905 newline (either in the original or the modified
9910 Changes which are not represented, but which are not detected by
9911 <prgn>dpkg-source</prgn>, are:
9912 <list compact="compact">
9913 <item><p>Changing the permissions of files (other than
9914 <file>debian/rules</file>) and directories.</p></item>
9919 The <file>debian</file> directory and <file>debian/rules</file>
9920 are handled specially by <prgn>dpkg-source</prgn> - before
9921 applying the changes it will create the <file>debian</file>
9922 directory, and afterwards it will make
9923 <file>debian/rules</file> world-executable.
9929 <appendix id="pkg-controlfields">
9930 <heading>Control files and their fields (from old Packaging Manual)</heading>
9933 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
9934 data in a common format, known as control files. Binary and
9935 source packages have control data as do the <file>.changes</file>
9936 files which control the installation of uploaded files, and
9937 <prgn>dpkg</prgn>'s internal databases are in a similar
9942 <heading>Syntax of control files</heading>
9945 See <ref id="controlsyntax">.
9949 It is important to note that there are several fields which
9950 are optional as far as <prgn>dpkg</prgn> and the related
9951 tools are concerned, but which must appear in every Debian
9952 package, or whose omission may cause problems.
9957 <heading>List of fields</heading>
9960 See <ref id="controlfieldslist">.
9964 This section now contains only the fields that didn't belong
9965 to the Policy manual.
9968 <sect1 id="pkg-f-Filename">
9969 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
9972 These fields in <tt>Packages</tt> files give the
9973 filename(s) of (the parts of) a package in the
9974 distribution directories, relative to the root of the
9975 Debian hierarchy. If the package has been split into
9976 several parts the parts are all listed in order, separated
9981 <sect1 id="pkg-f-Size">
9982 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
9985 These fields in <file>Packages</file> files give the size (in
9986 bytes, expressed in decimal) and MD5 checksum of the
9987 file(s) which make(s) up a binary package in the
9988 distribution. If the package is split into several parts
9989 the values for the parts are listed in order, separated by
9994 <sect1 id="pkg-f-Status">
9995 <heading><tt>Status</tt></heading>
9998 This field in <prgn>dpkg</prgn>'s status file records
9999 whether the user wants a package installed, removed or
10000 left alone, whether it is broken (requiring
10001 re-installation) or not and what its current state on the
10002 system is. Each of these pieces of information is a
10007 <sect1 id="pkg-f-Config-Version">
10008 <heading><tt>Config-Version</tt></heading>
10011 If a package is not installed or not configured, this
10012 field in <prgn>dpkg</prgn>'s status file records the last
10013 version of the package which was successfully
10018 <sect1 id="pkg-f-Conffiles">
10019 <heading><tt>Conffiles</tt></heading>
10022 This field in <prgn>dpkg</prgn>'s status file contains
10023 information about the automatically-managed configuration
10024 files held by a package. This field should <em>not</em>
10025 appear anywhere in a package!
10030 <heading>Obsolete fields</heading>
10033 These are still recognized by <prgn>dpkg</prgn> but should
10034 not appear anywhere any more.
10036 <taglist compact="compact">
10038 <tag><tt>Revision</tt></tag>
10039 <tag><tt>Package-Revision</tt></tag>
10040 <tag><tt>Package_Revision</tt></tag>
10042 The Debian revision part of the package version was
10043 at one point in a separate control file field. This
10044 field went through several names.
10047 <tag><tt>Recommended</tt></tag>
10048 <item>Old name for <tt>Recommends</tt>.</item>
10050 <tag><tt>Optional</tt></tag>
10051 <item>Old name for <tt>Suggests</tt>.</item>
10053 <tag><tt>Class</tt></tag>
10054 <item>Old name for <tt>Priority</tt>.</item>
10063 <appendix id="pkg-conffiles">
10064 <heading>Configuration file handling (from old Packaging Manual)</heading>
10067 <prgn>dpkg</prgn> can do a certain amount of automatic
10068 handling of package configuration files.
10072 Whether this mechanism is appropriate depends on a number of
10073 factors, but basically there are two approaches to any
10074 particular configuration file.
10078 The easy method is to ship a best-effort configuration in the
10079 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10080 handle updates. If the user is unlikely to want to edit the
10081 file, but you need them to be able to without losing their
10082 changes, and a new package with a changed version of the file
10083 is only released infrequently, this is a good approach.
10087 The hard method is to build the configuration file from
10088 scratch in the <prgn>postinst</prgn> script, and to take the
10089 responsibility for fixing any mistakes made in earlier
10090 versions of the package automatically. This will be
10091 appropriate if the file is likely to need to be different on
10095 <sect><heading>Automatic handling of configuration files by
10100 A package may contain a control area file called
10101 <tt>conffiles</tt>. This file should be a list of filenames
10102 of configuration files needing automatic handling, separated
10103 by newlines. The filenames should be absolute pathnames,
10104 and the files referred to should actually exist in the
10109 When a package is upgraded <prgn>dpkg</prgn> will process
10110 the configuration files during the configuration stage,
10111 shortly before it runs the package's <prgn>postinst</prgn>
10116 For each file it checks to see whether the version of the
10117 file included in the package is the same as the one that was
10118 included in the last version of the package (the one that is
10119 being upgraded from); it also compares the version currently
10120 installed on the system with the one shipped with the last
10125 If neither the user nor the package maintainer has changed
10126 the file, it is left alone. If one or the other has changed
10127 their version, then the changed version is preferred - i.e.,
10128 if the user edits their file, but the package maintainer
10129 doesn't ship a different version, the user's changes will
10130 stay, silently, but if the maintainer ships a new version
10131 and the user hasn't edited it the new version will be
10132 installed (with an informative message). If both have
10133 changed their version the user is prompted about the problem
10134 and must resolve the differences themselves.
10138 The comparisons are done by calculating the MD5 message
10139 digests of the files, and storing the MD5 of the file as it
10140 was included in the most recent version of the package.
10144 When a package is installed for the first time
10145 <prgn>dpkg</prgn> will install the file that comes with it,
10146 unless that would mean overwriting a file already on the
10151 However, note that <prgn>dpkg</prgn> will <em>not</em>
10152 replace a conffile that was removed by the user (or by a
10153 script). This is necessary because with some programs a
10154 missing file produces an effect hard or impossible to
10155 achieve in another way, so that a missing file needs to be
10156 kept that way if the user did it.
10160 Note that a package should <em>not</em> modify a
10161 <prgn>dpkg</prgn>-handled conffile in its maintainer
10162 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10163 the user confusing and possibly dangerous options for
10164 conffile update when the package is upgraded.</p>
10167 <sect><heading>Fully-featured maintainer script configuration
10172 For files which contain site-specific information such as
10173 the hostname and networking details and so forth, it is
10174 better to create the file in the package's
10175 <prgn>postinst</prgn> script.
10179 This will typically involve examining the state of the rest
10180 of the system to determine values and other information, and
10181 may involve prompting the user for some information which
10182 can't be obtained some other way.
10186 When using this method there are a couple of important
10187 issues which should be considered:
10191 If you discover a bug in the program which generates the
10192 configuration file, or if the format of the file changes
10193 from one version to the next, you will have to arrange for
10194 the postinst script to do something sensible - usually this
10195 will mean editing the installed configuration file to remove
10196 the problem or change the syntax. You will have to do this
10197 very carefully, since the user may have changed the file,
10198 perhaps to fix the very problem that your script is trying
10199 to deal with - you will have to detect these situations and
10200 deal with them correctly.
10204 If you do go down this route it's probably a good idea to
10205 make the program that generates the configuration file(s) a
10206 separate program in <file>/usr/sbin</file>, by convention called
10207 <file><var>package</var>config</file> and then run that if
10208 appropriate from the post-installation script. The
10209 <tt><var>package</var>config</tt> program should not
10210 unquestioningly overwrite an existing configuration - if its
10211 mode of operation is geared towards setting up a package for
10212 the first time (rather than any arbitrary reconfiguration
10213 later) you should have it check whether the configuration
10214 already exists, and require a <tt>--force</tt> flag to
10215 overwrite it.</p></sect>
10218 <appendix id="pkg-alternatives"><heading>Alternative versions of
10219 an interface - <prgn>update-alternatives</prgn> (from old
10224 When several packages all provide different versions of the
10225 same program or file it is useful to have the system select a
10226 default, but to allow the system administrator to change it
10227 and have their decisions respected.
10231 For example, there are several versions of the <prgn>vi</prgn>
10232 editor, and there is no reason to prevent all of them from
10233 being installed at once, each under their own name
10234 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10235 Nevertheless it is desirable to have the name <tt>vi</tt>
10236 refer to something, at least by default.
10240 If all the packages involved cooperate, this can be done with
10241 <prgn>update-alternatives</prgn>.
10245 Each package provides its own version under its own name, and
10246 calls <prgn>update-alternatives</prgn> in its postinst to
10247 register its version (and again in its prerm to deregister
10252 See the man page <manref name="update-alternatives"
10253 section="8"> for details.
10257 If <prgn>update-alternatives</prgn> does not seem appropriate
10258 you may wish to consider using diversions instead.</p>
10261 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10262 package's version of a file (from old Packaging Manual)
10266 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10267 when it reinstalls the package it belongs to, and to have it
10268 put the file from the package somewhere else instead.
10272 This can be used locally to override a package's version of a
10273 file, or by one package to override another's version (or
10274 provide a wrapper for it).
10278 Before deciding to use a diversion, read <ref
10279 id="pkg-alternatives"> to see if you really want a diversion
10280 rather than several alternative versions of a program.
10284 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10285 and updated by a special program <prgn>dpkg-divert</prgn>.
10286 Please see <manref name="dpkg-divert" section="8"> for full
10287 details of its operation.
10291 When a package wishes to divert a file from another, it should
10292 call <prgn>dpkg-divert</prgn> in its preinst to add the
10293 diversion and rename the existing file. For example,
10294 supposing that a <prgn>smailwrapper</prgn> package wishes to
10295 install a wrapper around <file>/usr/sbin/smail</file>:
10297 if [ install = "$1" ]; then
10298 dpkg-divert --package smailwrapper --add --rename \
10299 --divert /usr/sbin/smail.real /usr/sbin/smail
10301 </example> Testing <tt>$1</tt> is necessary so that the script
10302 doesn't try to add the diversion again when
10303 <prgn>smailwrapper</prgn> is upgraded. The <tt>--package
10304 smailwrapper</tt> ensures that <prgn>smailwrapper</prgn>'s
10305 copy of <file>/usr/sbin/smail</file> can bypass the diversion and
10306 get installed as the true version.
10310 The postrm has to do the reverse:
10312 if [ remove = "$1" ]; then
10313 dpkg-divert --package smailwrapper --remove --rename \
10314 --divert /usr/sbin/smail.real /usr/sbin/smail
10320 Do not attempt to divert a file which is vitally important for
10321 the system's operation - when using <prgn>dpkg-divert</prgn>
10322 there is a time, after it has been diverted but before
10323 <prgn>dpkg</prgn> has installed the new version, when the file
10324 does not exist.</p>
10329 <!-- vim:set ai et sts=2 sw=2 tw=76: -->