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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> must permit it to span multiple
2395 lines. Line breaks in an Uploaders field that spans multiple
2396 lines are not significant and the semantics of the field are
2397 the same as if the line breaks had not been present.
2401 <sect1 id="f-Changed-By">
2402 <heading><tt>Changed-By</tt></heading>
2405 The name and email address of the person who changed the
2406 said package. Usually the name of the maintainer.
2407 All the rules for the Maintainer field apply here, too.
2411 <sect1 id="f-Section">
2412 <heading><tt>Section</tt></heading>
2415 This field specifies an application area into which the package
2416 has been classified. See <ref id="subsections">.
2420 When it appears in the <file>debian/control</file> file,
2421 it gives the value for the subfield of the same name in
2422 the <tt>Files</tt> field of the <file>.changes</file> file.
2423 It also gives the default for the same field in the binary
2428 <sect1 id="f-Priority">
2429 <heading><tt>Priority</tt></heading>
2432 This field represents how important that it is that the user
2433 have the package installed. See <ref id="priorities">.
2437 When it appears in the <file>debian/control</file> file,
2438 it gives the value for the subfield of the same name in
2439 the <tt>Files</tt> field of the <file>.changes</file> file.
2440 It also gives the default for the same field in the binary
2445 <sect1 id="f-Package">
2446 <heading><tt>Package</tt></heading>
2449 The name of the binary package.
2453 Package names must consist only of lower case letters
2454 (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus (<tt>+</tt>)
2455 and minus (<tt>-</tt>) signs, and periods (<tt>.</tt>).
2456 They must be at least two characters long and must start
2457 with an alphanumeric character.
2461 <sect1 id="f-Architecture">
2462 <heading><tt>Architecture</tt></heading>
2465 Depending on context and the control file used, the
2466 <tt>Architecture</tt> field can include the following sets of
2469 <item>A unique single word identifying a Debian machine
2470 architecture, see <ref id="arch-spec">.
2471 <item><tt>all</tt>, which indicates an
2472 architecture-independent package.
2473 <item><tt>any</tt>, which indicates a package available
2474 for building on any architecture.
2475 <item><tt>source</tt>, which indicates a source package.
2480 In the main <file>debian/control</file> file in the source
2481 package, or in the source package control file
2482 <file>.dsc</file>, one may specify a list of architectures
2483 separated by spaces, or the special values <tt>any</tt> or
2488 Specifying <tt>any</tt> indicates that the source package
2489 isn't dependent on any particular architecture and should
2490 compile fine on any one. The produced binary package(s)
2491 will be specific to whatever the current build architecture
2493 This is the most often used setting, and is recommended
2494 for new packages that aren't <tt>Architecture: all</tt>.
2499 Specifying a list of architectures indicates that the source
2500 will build an architecture-dependent package, and will only
2501 work correctly on the listed architectures.<footnote>
2502 This is a setting used for a minority of cases where the
2503 program is not portable. Generally, it should not be used
2509 In a <file>.changes</file> file, the <tt>Architecture</tt>
2510 field lists the architecture(s) of the package(s)
2511 currently being uploaded. This will be a list; if the
2512 source for the package is also being uploaded, the special
2513 entry <tt>source</tt> is also present.
2517 See <ref id="debianrules"> for information how to get the
2518 architecture for the build process.
2522 <sect1 id="f-Essential">
2523 <heading><tt>Essential</tt></heading>
2526 This is a boolean field which may occur only in the
2527 control file of a binary package or in a per-package fields
2528 paragraph of a main source control data file.
2532 If set to <tt>yes</tt> then the package management system
2533 will refuse to remove the package (upgrading and replacing
2534 it is still possible). The other possible value is <tt>no</tt>,
2535 which is the same as not having the field at all.
2540 <heading>Package interrelationship fields:
2541 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2542 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Conflicts</tt>,
2543 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2547 These fields describe the package's relationships with
2548 other packages. Their syntax and semantics are described
2549 in <ref id="relationships">.</p>
2552 <sect1 id="f-Standards-Version">
2553 <heading><tt>Standards-Version</tt></heading>
2556 The most recent version of the standards (the policy
2557 manual and associated texts) with which the package
2562 The version number has four components: major and minor
2563 version number and major and minor patch level. When the
2564 standards change in a way that requires every package to
2565 change the major number will be changed. Significant
2566 changes that will require work in many packages will be
2567 signaled by a change to the minor number. The major patch
2568 level will be changed for any change to the meaning of the
2569 standards, however small; the minor patch level will be
2570 changed when only cosmetic, typographical or other edits
2571 are made which neither change the meaning of the document
2572 nor affect the contents of packages.
2576 Thus only the first three components of the policy version
2577 are significant in the <em>Standards-Version</em> control
2578 field, and so either these three components or the all
2579 four components may be specified.<footnote>
2580 In the past, people specified the full version number
2581 in the Standards-Version field, for example "2.3.0.0".
2582 Since minor patch-level changes don't introduce new
2583 policy, it was thought it would be better to relax
2584 policy and only require the first 3 components to be
2585 specified, in this example "2.3.0". All four
2586 components may still be used if someone wishes to do so.
2592 <sect1 id="f-Version">
2593 <heading><tt>Version</tt></heading>
2596 The version number of a package. The format is:
2597 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
2601 The three components here are:
2603 <tag><var>epoch</var></tag>
2606 This is a single (generally small) unsigned integer. It
2607 may be omitted, in which case zero is assumed. If it is
2608 omitted then the <var>upstream_version</var> may not
2613 It is provided to allow mistakes in the version numbers
2614 of older versions of a package, and also a package's
2615 previous version numbering schemes, to be left behind.
2619 <tag><var>upstream_version</var></tag>
2622 This is the main part of the version number. It is
2623 usually the version number of the original ("upstream")
2624 package from which the <file>.deb</file> file has been made,
2625 if this is applicable. Usually this will be in the same
2626 format as that specified by the upstream author(s);
2627 however, it may need to be reformatted to fit into the
2628 package management system's format and comparison
2633 The comparison behavior of the package management system
2634 with respect to the <var>upstream_version</var> is
2635 described below. The <var>upstream_version</var>
2636 portion of the version number is mandatory.
2640 The <var>upstream_version</var> may contain only
2641 alphanumerics<footnote>
2642 Alphanumerics are <tt>A-Za-z0-9</tt> only.
2644 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
2645 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
2646 tilde) and should start with a digit. If there is no
2647 <var>debian_revision</var> then hyphens are not allowed;
2648 if there is no <var>epoch</var> then colons are not
2653 <tag><var>debian_revision</var></tag>
2656 This part of the version number specifies the version of
2657 the Debian package based on the upstream version. It
2658 may contain only alphanumerics and the characters
2659 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
2660 tilde) and is compared in the same way as the
2661 <var>upstream_version</var> is.
2665 It is optional; if it isn't present then the
2666 <var>upstream_version</var> may not contain a hyphen.
2667 This format represents the case where a piece of
2668 software was written specifically to be turned into a
2669 Debian package, and so there is only one "debianisation"
2670 of it and therefore no revision indication is required.
2674 It is conventional to restart the
2675 <var>debian_revision</var> at <tt>1</tt> each time the
2676 <var>upstream_version</var> is increased.
2680 The package management system will break the version
2681 number apart at the last hyphen in the string (if there
2682 is one) to determine the <var>upstream_version</var> and
2683 <var>debian_revision</var>. The absence of a
2684 <var>debian_revision</var> compares earlier than the
2685 presence of one (but note that the
2686 <var>debian_revision</var> is the least significant part
2687 of the version number).
2694 The <var>upstream_version</var> and <var>debian_revision</var>
2695 parts are compared by the package management system using the
2700 The strings are compared from left to right.
2704 First the initial part of each string consisting entirely of
2705 non-digit characters is determined. These two parts (one of
2706 which may be empty) are compared lexically. If a difference
2707 is found it is returned. The lexical comparison is a
2708 comparison of ASCII values modified so that all the letters
2709 sort earlier than all the non-letters and so that a tilde
2710 sorts before anything, even the end of a part. For example,
2711 the following parts are in sorted order from earliest to
2712 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
2713 <tt>a</tt>.<footnote>
2714 One common use of <tt>~</tt> is for upstream pre-releases.
2715 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
2716 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
2721 Then the initial part of the remainder of each string which
2722 consists entirely of digit characters is determined. The
2723 numerical values of these two parts are compared, and any
2724 difference found is returned as the result of the comparison.
2725 For these purposes an empty string (which can only occur at
2726 the end of one or both version strings being compared) counts
2731 These two steps (comparing and removing initial non-digit
2732 strings and initial digit strings) are repeated until a
2733 difference is found or both strings are exhausted.
2737 Note that the purpose of epochs is to allow us to leave behind
2738 mistakes in version numbering, and to cope with situations
2739 where the version numbering scheme changes. It is
2740 <em>not</em> intended to cope with version numbers containing
2741 strings of letters which the package management system cannot
2742 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
2743 silly orderings (the author of this manual has heard of a
2744 package whose versions went <tt>1.1</tt>, <tt>1.2</tt>,
2745 <tt>1.3</tt>, <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>,
2746 <tt>2</tt> and so forth).
2750 <sect1 id="f-Description">
2751 <heading><tt>Description</tt></heading>
2754 In a source or binary control file, the <tt>Description</tt>
2755 field contains a description of the binary package, consisting
2756 of two parts, the synopsis or the short description, and the
2757 long description. The field's format is as follows:
2762 Description: <single line synopsis>
2763 <extended description over several lines>
2768 The lines in the extended description can have these formats:
2774 Those starting with a single space are part of a paragraph.
2775 Successive lines of this form will be word-wrapped when
2776 displayed. The leading space will usually be stripped off.
2780 Those starting with two or more spaces. These will be
2781 displayed verbatim. If the display cannot be panned
2782 horizontally, the displaying program will line wrap them "hard"
2783 (i.e., without taking account of word breaks). If it can they
2784 will be allowed to trail off to the right. None, one or two
2785 initial spaces may be deleted, but the number of spaces
2786 deleted from each line will be the same (so that you can have
2787 indenting work correctly, for example).
2791 Those containing a single space followed by a single full stop
2792 character. These are rendered as blank lines. This is the
2793 <em>only</em> way to get a blank line<footnote>
2794 Completely empty lines will not be rendered as blank lines.
2795 Instead, they will cause the parser to think you're starting
2796 a whole new record in the control file, and will therefore
2797 likely abort with an error.
2802 Those containing a space, a full stop and some more characters.
2803 These are for future expansion. Do not use them.
2809 Do not use tab characters. Their effect is not predictable.
2813 See <ref id="descriptions"> for further information on this.
2817 In a <file>.changes</file> file, the <tt>Description</tt> field
2818 contains a summary of the descriptions for the packages being
2823 The part of the field before the first newline is empty;
2824 thereafter each line has the name of a binary package and
2825 the summary description line from that binary package.
2826 Each line is indented by one space.
2831 <sect1 id="f-Distribution">
2832 <heading><tt>Distribution</tt></heading>
2835 In a <file>.changes</file> file or parsed changelog output
2836 this contains the (space-separated) name(s) of the
2837 distribution(s) where this version of the package should
2838 be installed. Valid distributions are determined by the
2839 archive maintainers.<footnote>
2840 Current distribution names are:
2841 <taglist compact="compact">
2842 <tag><em>stable</em></tag>
2844 This is the current "released" version of Debian
2845 GNU/Linux. Once the distribution is
2846 <em>stable</em> only security fixes and other
2847 major bug fixes are allowed. When changes are
2848 made to this distribution, the release number is
2849 increased (for example: 2.2r1 becomes 2.2r2 then
2853 <tag><em>unstable</em></tag>
2855 This distribution value refers to the
2856 <em>developmental</em> part of the Debian
2857 distribution tree. New packages, new upstream
2858 versions of packages and bug fixes go into the
2859 <em>unstable</em> directory tree. Download from
2860 this distribution at your own risk.
2863 <tag><em>testing</em></tag>
2865 This distribution value refers to the
2866 <em>testing</em> part of the Debian distribution
2867 tree. It receives its packages from the
2868 unstable distribution after a short time lag to
2869 ensure that there are no major issues with the
2870 unstable packages. It is less prone to breakage
2871 than unstable, but still risky. It is not
2872 possible to upload packages directly to
2876 <tag><em>frozen</em></tag>
2878 From time to time, the <em>testing</em>
2879 distribution enters a state of "code-freeze" in
2880 anticipation of release as a <em>stable</em>
2881 version. During this period of testing only
2882 fixes for existing or newly-discovered bugs will
2883 be allowed. The exact details of this stage are
2884 determined by the Release Manager.
2887 <tag><em>experimental</em></tag>
2889 The packages with this distribution value are
2890 deemed by their maintainers to be high
2891 risk. Oftentimes they represent early beta or
2892 developmental packages from various sources that
2893 the maintainers want people to try, but are not
2894 ready to be a part of the other parts of the
2895 Debian distribution tree. Download at your own
2901 You should list <em>all</em> distributions that the
2902 package should be installed into.
2906 More information is available in the Debian Developer's
2907 Reference, section "The Debian archive".
2914 <heading><tt>Date</tt></heading>
2917 This field includes the date the package was built or last edited.
2921 The value of this field is usually extracted from the
2922 <file>debian/changelog</file> file - see
2923 <ref id="dpkgchangelog">).
2927 <sect1 id="f-Format">
2928 <heading><tt>Format</tt></heading>
2931 This field specifies a format revision for the file.
2932 The most current format described in the Policy Manual
2933 is version <strong>1.5</strong>. The syntax of the
2934 format value is the same as that of a package version
2935 number except that no epoch or Debian revision is allowed
2936 - see <ref id="f-Version">.
2940 <sect1 id="f-Urgency">
2941 <heading><tt>Urgency</tt></heading>
2944 This is a description of how important it is to upgrade to
2945 this version from previous ones. It consists of a single
2946 keyword taking one of the values <tt>low</tt>,
2947 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
2948 <tt>critical</tt><footnote>
2949 Other urgency values are supported with configuration
2950 changes in the archive software but are not used in Debian.
2951 The urgency affects how quickly a package will be considered
2952 for inclusion into the <tt>testing</tt> distribution and
2953 gives an indication of the importance of any fixes included
2954 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
2955 treated as synonymous.
2956 </footnote> (not case-sensitive) followed by an optional
2957 commentary (separated by a space) which is usually in
2958 parentheses. For example:
2961 Urgency: low (HIGH for users of diversions)
2967 The value of this field is usually extracted from the
2968 <file>debian/changelog</file> file - see
2969 <ref id="dpkgchangelog">.
2973 <sect1 id="f-Changes">
2974 <heading><tt>Changes</tt></heading>
2977 This field contains the human-readable changes data, describing
2978 the differences between the last version and the current one.
2982 There should be nothing in this field before the first
2983 newline; all the subsequent lines must be indented by at
2984 least one space; blank lines must be represented by a line
2985 consisting only of a space and a full stop.
2989 The value of this field is usually extracted from the
2990 <file>debian/changelog</file> file - see
2991 <ref id="dpkgchangelog">).
2995 Each version's change information should be preceded by a
2996 "title" line giving at least the version, distribution(s)
2997 and urgency, in a human-readable way.
3001 If data from several versions is being returned the entry
3002 for the most recent version should be returned first, and
3003 entries should be separated by the representation of a
3004 blank line (the "title" line may also be followed by the
3005 representation of blank line).
3009 <sect1 id="f-Binary">
3010 <heading><tt>Binary</tt></heading>
3013 This field is a list of binary packages.
3017 When it appears in the <file>.dsc</file> file it is the list
3018 of binary packages which a source package can produce. It
3019 does not necessarily produce all of these binary packages
3020 for every architecture. The source control file doesn't
3021 contain details of which architectures are appropriate for
3022 which of the binary packages.
3026 When it appears in a <file>.changes</file> file it lists the
3027 names of the binary packages actually being uploaded.
3031 The syntax is a list of binary packages separated by
3033 A space after each comma is conventional.
3034 </footnote>. Currently the packages must be separated using
3035 only spaces in the <file>.changes</file> file.
3039 <sect1 id="f-Installed-Size">
3040 <heading><tt>Installed-Size</tt></heading>
3043 This field appears in the control files of binary
3044 packages, and in the <file>Packages</file> files. It gives
3045 the total amount of disk space required to install the
3050 The disk space is represented in kilobytes as a simple
3055 <sect1 id="f-Files">
3056 <heading><tt>Files</tt></heading>
3059 This field contains a list of files with information about
3060 each one. The exact information and syntax varies with
3061 the context. In all cases the part of the field
3062 contents on the same line as the field name is empty. The
3063 remainder of the field is one line per file, each line
3064 being indented by one space and containing a number of
3065 sub-fields separated by spaces.
3069 In the <file>.dsc</file> file, each line contains the MD5
3070 checksum, size and filename of the tar file and (if applicable)
3071 diff file which make up the remainder of the source
3073 That is, the parts which are not the <tt>.dsc</tt>.
3075 The exact forms of the filenames are described
3076 in <ref id="pkg-sourcearchives">.
3080 In the <file>.changes</file> file this contains one line per
3081 file being uploaded. Each line contains the MD5 checksum,
3082 size, section and priority and the filename.
3083 The <qref id="f-Section">section</qref>
3084 and <qref id="f-Priority">priority</qref>
3085 are the values of the corresponding fields in
3086 the main source control file. If no section or priority is
3087 specified then <tt>-</tt> should be used, though section
3088 and priority values must be specified for new packages to
3089 be installed properly.
3093 The special value <tt>byhand</tt> for the section in a
3094 <tt>.changes</tt> file indicates that the file in question
3095 is not an ordinary package file and must by installed by
3096 hand by the distribution maintainers. If the section is
3097 <tt>byhand</tt> the priority should be <tt>-</tt>.
3101 If a new Debian revision of a package is being shipped and
3102 no new original source archive is being distributed the
3103 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3104 entry for the original source archive
3105 <file><var>package</var>-<var>upstream-version</var>.orig.tar.gz</file>,
3106 but the <file>.changes</file> file should leave it out. In
3107 this case the original source archive on the distribution
3108 site must match exactly, byte-for-byte, the original
3109 source archive which was used to generate the
3110 <file>.dsc</file> file and diff which are being uploaded.</p>
3113 <sect1 id="f-Closes">
3114 <heading><tt>Closes</tt></heading>
3117 A space-separated list of bug report numbers that the upload
3118 governed by the .changes file closes.
3125 <heading>User-defined fields</heading>
3128 Additional user-defined fields may be added to the
3129 source package control file. Such fields will be
3130 ignored, and not copied to (for example) binary or
3131 source package control files or upload control files.
3135 If you wish to add additional unsupported fields to
3136 these output files you should use the mechanism
3141 Fields in the main source control information file with
3142 names starting <tt>X</tt>, followed by one or more of
3143 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3144 be copied to the output files. Only the part of the
3145 field name after the hyphen will be used in the output
3146 file. Where the letter <tt>B</tt> is used the field
3147 will appear in binary package control files, where the
3148 letter <tt>S</tt> is used in source package control
3149 files and where <tt>C</tt> is used in upload control
3150 (<tt>.changes</tt>) files.
3154 For example, if the main source information control file
3157 XBS-Comment: I stand between the candle and the star.
3159 then the binary and source package control files will contain the
3162 Comment: I stand between the candle and the star.
3171 <chapt id="maintainerscripts">
3172 <heading>Package maintainer scripts and installation procedure</heading>
3175 <heading>Introduction to package maintainer scripts</heading>
3178 It is possible to supply scripts as part of a package which
3179 the package management system will run for you when your
3180 package is installed, upgraded or removed.
3184 These scripts are the files <prgn>preinst</prgn>,
3185 <prgn>postinst</prgn>, <prgn>prerm</prgn> and
3186 <prgn>postrm</prgn> in the control area of the package.
3187 They must be proper executable files; if they are scripts
3188 (which is recommended), they must start with the usual
3189 <tt>#!</tt> convention. They should be readable and
3190 executable by anyone, and must not be world-writable.
3194 The package management system looks at the exit status from
3195 these scripts. It is important that they exit with a
3196 non-zero status if there is an error, so that the package
3197 management system can stop its processing. For shell
3198 scripts this means that you <em>almost always</em> need to
3199 use <tt>set -e</tt> (this is usually true when writing shell
3200 scripts, in fact). It is also important, of course, that
3201 they don't exit with a non-zero status if everything went
3206 Additionally, packages interacting with users using
3207 <tt>debconf</tt> in the <prgn>postinst</prgn> script should
3208 install a <prgn>config</prgn> script in the control area,
3209 see <ref id="maintscriptprompt"> for details.
3213 When a package is upgraded a combination of the scripts from
3214 the old and new packages is called during the upgrade
3215 procedure. If your scripts are going to be at all
3216 complicated you need to be aware of this, and may need to
3217 check the arguments to your scripts.
3221 Broadly speaking the <prgn>preinst</prgn> is called before
3222 (a particular version of) a package is installed, and the
3223 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3224 before (a version of) a package is removed and the
3225 <prgn>postrm</prgn> afterwards.
3229 Programs called from maintainer scripts should not normally
3230 have a path prepended to them. Before installation is
3231 started, the package management system checks to see if the
3232 programs <prgn>ldconfig</prgn>,
3233 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3234 and <prgn>update-rc.d</prgn> can be found via the
3235 <tt>PATH</tt> environment variable. Those programs, and any
3236 other program that one would expect to be in the
3237 <tt>PATH</tt>, should thus be invoked without an absolute
3238 pathname. Maintainer scripts should also not reset the
3239 <tt>PATH</tt>, though they might choose to modify it by
3240 prepending or appending package-specific directories. These
3241 considerations really apply to all shell scripts.</p>
3244 <sect id="idempotency">
3245 <heading>Maintainer scripts idempotency</heading>
3248 It is necessary for the error recovery procedures that the
3249 scripts be idempotent. This means that if it is run
3250 successfully, and then it is called again, it doesn't bomb
3251 out or cause any harm, but just ensures that everything is
3252 the way it ought to be. If the first call failed, or
3253 aborted half way through for some reason, the second call
3254 should merely do the things that were left undone the first
3255 time, if any, and exit with a success status if everything
3257 This is so that if an error occurs, the user interrupts
3258 <prgn>dpkg</prgn> or some other unforeseen circumstance
3259 happens you don't leave the user with a badly-broken
3260 package when <prgn>dpkg</prgn> attempts to repeat the
3266 <sect id="controllingterminal">
3267 <heading>Controlling terminal for maintainer scripts</heading>
3270 The maintainer scripts are guaranteed to run with a
3271 controlling terminal and can interact with the user.
3272 Because these scripts may be executed with standard output
3273 redirected into a pipe for logging purposes, Perl scripts
3274 should set unbuffered output by setting <tt>$|=1</tt> so
3275 that the output is printed immediately rather than being
3279 <sect id="exitstatus">
3280 <heading>Exit status</heading>
3283 Each script must return a zero exit status for
3284 success, or a nonzero one for failure, since the package
3285 management system looks for the exit status of these scripts
3286 and determines what action to take next based on that datum.
3290 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3295 <list compact="compact">
3297 <var>new-preinst</var> <tt>install</tt>
3300 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3303 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3306 <var>old-preinst</var> <tt>abort-upgrade</tt>
3307 <var>new-version</var>
3312 <list compact="compact">
3314 <var>postinst</var> <tt>configure</tt>
3315 <var>most-recently-configured-version</var>
3318 <var>old-postinst</var> <tt>abort-upgrade</tt>
3319 <var>new-version</var>
3322 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3323 <tt>in-favour</tt> <var>package</var>
3324 <var>new-version</var>
3327 <var>postinst</var> <tt>abort-remove</tt>
3330 <var>deconfigured's-postinst</var>
3331 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3332 <var>failed-install-package</var> <var>version</var>
3333 <tt>removing</tt> <var>conflicting-package</var>
3339 <list compact="compact">
3341 <var>prerm</var> <tt>remove</tt>
3344 <var>old-prerm</var> <tt>upgrade</tt>
3345 <var>new-version</var>
3348 <var>new-prerm</var> <tt>failed-upgrade</tt>
3349 <var>old-version</var>
3352 <var>conflictor's-prerm</var> <tt>remove</tt>
3353 <tt>in-favour</tt> <var>package</var>
3354 <var>new-version</var>
3357 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3358 <tt>in-favour</tt> <var>package-being-installed</var>
3359 <var>version</var> <tt>removing</tt>
3360 <var>conflicting-package</var>
3366 <list compact="compact">
3368 <var>postrm</var> <tt>remove</tt>
3371 <var>postrm</var> <tt>purge</tt>
3374 <var>old-postrm</var> <tt>upgrade</tt>
3375 <var>new-version</var>
3378 <var>new-postrm</var> <tt>failed-upgrade</tt>
3379 <var>old-version</var>
3382 <var>new-postrm</var> <tt>abort-install</tt>
3385 <var>new-postrm</var> <tt>abort-install</tt>
3386 <var>old-version</var>
3389 <var>new-postrm</var> <tt>abort-upgrade</tt>
3390 <var>old-version</var>
3393 <var>disappearer's-postrm</var> <tt>disappear</tt>
3394 <var>overwriter</var>
3395 <var>overwriter-version</var>
3401 <sect id="unpackphase">
3402 <heading>Details of unpack phase of installation or upgrade</heading>
3405 The procedure on installation/upgrade/overwrite/disappear
3406 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3407 stage of <tt>dpkg --install</tt>) is as follows. In each
3408 case, if a major error occurs (unless listed below) the
3409 actions are, in general, run backwards - this means that the
3410 maintainer scripts are run with different arguments in
3411 reverse order. These are the "error unwind" calls listed
3418 If a version of the package is already installed, call
3419 <example compact="compact">
3420 <var>old-prerm</var> upgrade <var>new-version</var>
3424 If the script runs but exits with a non-zero
3425 exit status, <prgn>dpkg</prgn> will attempt:
3426 <example compact="compact">
3427 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3429 If this works, the upgrade continues. If this
3430 does not work, the error unwind:
3431 <example compact="compact">
3432 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3434 If this works, then the old-version is
3435 "Installed", if not, the old version is in a
3436 "Failed-Config" state.
3442 If a "conflicting" package is being removed at the same time:
3445 If any packages depended on that conflicting
3446 package and <tt>--auto-deconfigure</tt> is
3447 specified, call, for each such package:
3448 <example compact="compact">
3449 <var>deconfigured's-prerm</var> deconfigure \
3450 in-favour <var>package-being-installed</var> <var>version</var> \
3451 removing <var>conflicting-package</var> <var>version</var>
3454 <example compact="compact">
3455 <var>deconfigured's-postinst</var> abort-deconfigure \
3456 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3457 removing <var>conflicting-package</var> <var>version</var>
3459 The deconfigured packages are marked as
3460 requiring configuration, so that if
3461 <tt>--install</tt> is used they will be
3462 configured again if possible.
3465 To prepare for removal of the conflicting package, call:
3466 <example compact="compact">
3467 <var>conflictor's-prerm</var> remove \
3468 in-favour <var>package</var> <var>new-version</var>
3471 <example compact="compact">
3472 <var>conflictor's-postinst</var> abort-remove \
3473 in-favour <var>package</var> <var>new-version</var>
3482 If the package is being upgraded, call:
3483 <example compact="compact">
3484 <var>new-preinst</var> upgrade <var>old-version</var>
3486 If this fails, we call:
3488 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3495 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3497 is called. If this works, then the old version
3498 is in an "Installed" state, or else it is left
3499 in an "Unpacked" state.
3504 If it fails, then the old version is left
3505 in an "Half-Installed" state.
3512 Otherwise, if the package had some configuration
3513 files from a previous version installed (i.e., it
3514 is in the "configuration files only" state):
3515 <example compact="compact">
3516 <var>new-preinst</var> install <var>old-version</var>
3520 <var>new-postrm</var> abort-install <var>old-version</var>
3522 If this fails, the package is left in a
3523 "Half-Installed" state, which requires a
3524 reinstall. If it works, the packages is left in
3525 a "Config Files" state.
3528 Otherwise (i.e., the package was completely purged):
3529 <example compact="compact">
3530 <var>new-preinst</var> install
3533 <example compact="compact">
3534 <var>new-postrm</var> abort-install
3536 If the error-unwind fails, the package is in a
3537 "Half Installed" phase, and requires a
3538 reinstall. If the error unwind works, the
3539 package is in a not installed state.
3546 The new package's files are unpacked, overwriting any
3547 that may be on the system already, for example any
3548 from the old version of the same package or from
3549 another package. Backups of the old files are kept
3550 temporarily, and if anything goes wrong the package
3551 management system will attempt to put them back as
3552 part of the error unwind.
3556 It is an error for a package to contain files which
3557 are on the system in another package, unless
3558 <tt>Replaces</tt> is used (see <ref id="replaces">).
3560 The following paragraph is not currently the case:
3561 Currently the <tt>- - force-overwrite</tt> flag is
3562 enabled, downgrading it to a warning, but this may not
3568 It is a more serious error for a package to contain a
3569 plain file or other kind of non-directory where another
3570 package has a directory (again, unless
3571 <tt>Replaces</tt> is used). This error can be
3572 overridden if desired using
3573 <tt>--force-overwrite-dir</tt>, but this is not
3578 Packages which overwrite each other's files produce
3579 behavior which, though deterministic, is hard for the
3580 system administrator to understand. It can easily
3581 lead to "missing" programs if, for example, a package
3582 is installed which overwrites a file from another
3583 package, and is then removed again.<footnote>
3584 Part of the problem is due to what is arguably a
3585 bug in <prgn>dpkg</prgn>.
3590 A directory will never be replaced by a symbolic link
3591 to a directory or vice versa; instead, the existing
3592 state (symlink or not) will be left alone and
3593 <prgn>dpkg</prgn> will follow the symlink if there is
3602 If the package is being upgraded, call
3603 <example compact="compact">
3604 <var>old-postrm</var> upgrade <var>new-version</var>
3608 If this fails, <prgn>dpkg</prgn> will attempt:
3609 <example compact="compact">
3610 <var>new-postrm</var> failed-upgrade <var>old-version</var>
3612 If this works, installation continues. If not,
3614 <example compact="compact">
3615 <var>old-preinst</var> abort-upgrade <var>new-version</var>
3617 If this fails, the old version is left in an
3618 "Half Installed" state. If it works, dpkg now
3620 <example compact="compact">
3621 <var>new-postrm</var> abort-upgrade <var>old-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>old-postinst</var> abort-upgrade <var>new-version</var>
3629 If this fails, the old version is in an
3636 This is the point of no return - if
3637 <prgn>dpkg</prgn> gets this far, it won't back off
3638 past this point if an error occurs. This will
3639 leave the package in a fairly bad state, which
3640 will require a successful re-installation to clear
3641 up, but it's when <prgn>dpkg</prgn> starts doing
3642 things that are irreversible.
3647 Any files which were in the old version of the package
3648 but not in the new are removed.
3652 The new file list replaces the old.
3656 The new maintainer scripts replace the old.
3660 Any packages all of whose files have been overwritten
3661 during the installation, and which aren't required for
3662 dependencies, are considered to have been removed.
3663 For each such package
3666 <prgn>dpkg</prgn> calls:
3667 <example compact="compact">
3668 <var>disappearer's-postrm</var> disappear \
3669 <var>overwriter</var> <var>overwriter-version</var>
3673 The package's maintainer scripts are removed.
3676 It is noted in the status database as being in a
3677 sane state, namely not installed (any conffiles
3678 it may have are ignored, rather than being
3679 removed by <prgn>dpkg</prgn>). Note that
3680 disappearing packages do not have their prerm
3681 called, because <prgn>dpkg</prgn> doesn't know
3682 in advance that the package is going to
3689 Any files in the package we're unpacking that are also
3690 listed in the file lists of other packages are removed
3691 from those lists. (This will lobotomize the file list
3692 of the "conflicting" package if there is one.)
3696 The backup files made during installation, above, are
3702 The new package's status is now sane, and recorded as
3707 Here is another point of no return - if the
3708 conflicting package's removal fails we do not unwind
3709 the rest of the installation; the conflicting package
3710 is left in a half-removed limbo.
3715 If there was a conflicting package we go and do the
3716 removal actions (described below), starting with the
3717 removal of the conflicting package's files (any that
3718 are also in the package being installed have already
3719 been removed from the conflicting package's file list,
3720 and so do not get removed now).
3726 <sect id="configdetails"><heading>Details of configuration</heading>
3729 When we configure a package (this happens with <tt>dpkg
3730 --install</tt> and <tt>dpkg --configure</tt>), we first
3731 update any <tt>conffile</tt>s and then call:
3732 <example compact="compact">
3733 <var>postinst</var> configure <var>most-recently-configured-version</var>
3738 No attempt is made to unwind after errors during
3739 configuration. If the configuration fails, the package is in
3740 a "Failed Config" state, and an error message is generated.
3744 If there is no most recently configured version
3745 <prgn>dpkg</prgn> will pass a null argument.
3748 Historical note: Truly ancient (pre-1997) versions of
3749 <prgn>dpkg</prgn> passed <tt><unknown></tt>
3750 (including the angle brackets) in this case. Even older
3751 ones did not pass a second argument at all, under any
3752 circumstance. Note that upgrades using such an old dpkg
3753 version are unlikely to work for other reasons, even if
3754 this old argument behavior is handled by your postinst script.
3760 <sect id="removedetails"><heading>Details of removal and/or
3761 configuration purging</heading>
3767 <example compact="compact">
3768 <var>prerm</var> remove
3772 If prerm fails during replacement due to conflict
3774 <var>conflictor's-postinst</var> abort-remove \
3775 in-favour <var>package</var> <var>new-version</var>
3779 <var>postinst</var> abort-remove
3783 If this fails, the package is in a "Failed-Config"
3784 state, or else it remains "Installed".
3788 The package's files are removed (except <tt>conffile</tt>s).
3791 <example compact="compact">
3792 <var>postrm</var> remove
3796 If it fails, there's no error unwind, and the package is in
3797 an "Half-Installed" state.
3802 All the maintainer scripts except the <prgn>postrm</prgn>
3807 If we aren't purging the package we stop here. Note
3808 that packages which have no <prgn>postrm</prgn> and no
3809 <tt>conffile</tt>s are automatically purged when
3810 removed, as there is no difference except for the
3811 <prgn>dpkg</prgn> status.
3815 The <tt>conffile</tt>s and any backup files
3816 (<tt>~</tt>-files, <tt>#*#</tt> files,
3817 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
3822 <example compact="compact">
3823 <var>postrm</var> purge
3827 If this fails, the package remains in a "Config-Files"
3832 The package's file list is removed.
3841 <chapt id="relationships">
3842 <heading>Declaring relationships between packages</heading>
3844 <sect id="depsyntax">
3845 <heading>Syntax of relationship fields</heading>
3848 These fields all have a uniform syntax. They are a list of
3849 package names separated by commas.
3853 In the <tt>Depends</tt>, <tt>Recommends</tt>,
3854 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
3855 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
3856 control file fields of the package, which declare
3857 dependencies on other packages, the package names listed may
3858 also include lists of alternative package names, separated
3859 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
3860 if any one of the alternative packages is installed, that
3861 part of the dependency is considered to be satisfied.
3865 All of the fields except for <tt>Provides</tt> may restrict
3866 their applicability to particular versions of each named
3867 package. This is done in parentheses after each individual
3868 package name; the parentheses should contain a relation from
3869 the list below followed by a version number, in the format
3870 described in <ref id="f-Version">.
3874 The relations allowed are <tt><<</tt>, <tt><=</tt>,
3875 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
3876 strictly earlier, earlier or equal, exactly equal, later or
3877 equal and strictly later, respectively. The deprecated
3878 forms <tt><</tt> and <tt>></tt> were used to mean
3879 earlier/later or equal, rather than strictly earlier/later,
3880 so they should not appear in new packages (though
3881 <prgn>dpkg</prgn> still supports them).
3885 Whitespace may appear at any point in the version
3886 specification subject to the rules in <ref
3887 id="controlsyntax">, and must appear where it's necessary to
3888 disambiguate; it is not otherwise significant. All of the
3889 relationship fields may span multiple lines. For
3890 consistency and in case of future changes to
3891 <prgn>dpkg</prgn> it is recommended that a single space be
3892 used after a version relationship and before a version
3893 number; it is also conventional to put a single space after
3894 each comma, on either side of each vertical bar, and before
3895 each open parenthesis. When wrapping a relationship field, it
3896 is conventional to do so after a comma and before the space
3897 following that comma.
3901 For example, a list of dependencies might appear as:
3902 <example compact="compact">
3905 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
3910 All fields that specify build-time relationships
3911 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
3912 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>)
3913 may be restricted to a certain set of architectures. This
3914 is indicated in brackets after each individual package name and
3915 the optional version specification. The brackets enclose a
3916 list of Debian architecture names separated by whitespace.
3917 Exclamation marks may be prepended to each of the names.
3918 (It is not permitted for some names to be prepended with
3919 exclamation marks while others aren't.) If the current Debian
3920 host architecture is not in this list and there are no
3921 exclamation marks in the list, or it is in the list with a
3922 prepended exclamation mark, the package name and the
3923 associated version specification are ignored completely for
3924 the purposes of defining the relationships.
3929 <example compact="compact">
3931 Build-Depends-Indep: texinfo
3932 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
3933 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
3938 Note that the binary package relationship fields such as
3939 <tt>Depends</tt> appear in one of the binary package
3940 sections of the control file, whereas the build-time
3941 relationships such as <tt>Build-Depends</tt> appear in the
3942 source package section of the control file (which is the
3947 <sect id="binarydeps">
3948 <heading>Binary Dependencies - <tt>Depends</tt>,
3949 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
3950 <tt>Pre-Depends</tt>
3954 Packages can declare in their control file that they have
3955 certain relationships to other packages - for example, that
3956 they may not be installed at the same time as certain other
3957 packages, and/or that they depend on the presence of others.
3961 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
3962 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt> and
3963 <tt>Conflicts</tt> control file fields.
3967 These six fields are used to declare a dependency
3968 relationship by one package on another. Except for
3969 <tt>Enhances</tt>, they appear in the depending (binary)
3970 package's control file. (<tt>Enhances</tt> appears in the
3971 recommending package's control file.)
3975 A <tt>Depends</tt> field takes effect <em>only</em> when a
3976 package is to be configured. It does not prevent a package
3977 being on the system in an unconfigured state while its
3978 dependencies are unsatisfied, and it is possible to replace
3979 a package whose dependencies are satisfied and which is
3980 properly installed with a different version whose
3981 dependencies are not and cannot be satisfied; when this is
3982 done the depending package will be left unconfigured (since
3983 attempts to configure it will give errors) and will not
3984 function properly. If it is necessary, a
3985 <tt>Pre-Depends</tt> field can be used, which has a partial
3986 effect even when a package is being unpacked, as explained
3987 in detail below. (The other three dependency fields,
3988 <tt>Recommends</tt>, <tt>Suggests</tt> and
3989 <tt>Enhances</tt>, are only used by the various front-ends
3990 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
3991 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
3995 For this reason packages in an installation run are usually
3996 all unpacked first and all configured later; this gives
3997 later versions of packages with dependencies on later
3998 versions of other packages the opportunity to have their
3999 dependencies satisfied.
4003 In case of circular dependencies, since installation or
4004 removal order honoring the dependency order can't be
4005 established, dependency loops are broken at some point
4006 (based on rules below), and some packages may not be able to
4007 rely on their dependencies being present when being
4008 installed or removed, depending on which side of the break
4009 of the circular dependcy loop they happen to be on. If one
4010 of the packages in the loop has no postinst script, then the
4011 cycle will be broken at that package, so as to ensure that
4012 all postinst scripts run with the dependencies properly
4013 configured if this is possible. Otherwise the breaking point
4018 The <tt>Depends</tt> field thus allows package maintainers
4019 to impose an order in which packages should be configured.
4023 The meaning of the five dependency fields is as follows:
4025 <tag><tt>Depends</tt></tag>
4028 This declares an absolute dependency. A package will
4029 not be configured unless all of the packages listed in
4030 its <tt>Depends</tt> field have been correctly
4035 The <tt>Depends</tt> field should be used if the
4036 depended-on package is required for the depending
4037 package to provide a significant amount of
4042 The <tt>Depends</tt> field should also be used if the
4043 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4044 <prgn>postrm</prgn> scripts require the package to be
4045 present in order to run. Note, however, that the
4046 <prgn>postrm</prgn> cannot rely on any non-essential
4047 packages to be present during the <tt>purge</tt>
4051 <tag><tt>Recommends</tt></tag>
4054 This declares a strong, but not absolute, dependency.
4058 The <tt>Recommends</tt> field should list packages
4059 that would be found together with this one in all but
4060 unusual installations.
4064 <tag><tt>Suggests</tt></tag>
4066 This is used to declare that one package may be more
4067 useful with one or more others. Using this field
4068 tells the packaging system and the user that the
4069 listed packages are related to this one and can
4070 perhaps enhance its usefulness, but that installing
4071 this one without them is perfectly reasonable.
4074 <tag><tt>Enhances</tt></tag>
4076 This field is similar to Suggests but works in the
4077 opposite direction. It is used to declare that a
4078 package can enhance the functionality of another
4082 <tag><tt>Pre-Depends</tt></tag>
4085 This field is like <tt>Depends</tt>, except that it
4086 also forces <prgn>dpkg</prgn> to complete installation
4087 of the packages named before even starting the
4088 installation of the package which declares the
4089 pre-dependency, as follows:
4093 When a package declaring a pre-dependency is about to
4094 be <em>unpacked</em> the pre-dependency can be
4095 satisfied if the depended-on package is either fully
4096 configured, <em>or even if</em> the depended-on
4097 package(s) are only unpacked or half-configured,
4098 provided that they have been configured correctly at
4099 some point in the past (and not removed or partially
4100 removed since). In this case, both the
4101 previously-configured and currently unpacked or
4102 half-configured versions must satisfy any version
4103 clause in the <tt>Pre-Depends</tt> field.
4107 When the package declaring a pre-dependency is about
4108 to be <em>configured</em>, the pre-dependency will be
4109 treated as a normal <tt>Depends</tt>, that is, it will
4110 be considered satisfied only if the depended-on
4111 package has been correctly configured.
4115 <tt>Pre-Depends</tt> should be used sparingly,
4116 preferably only by packages whose premature upgrade or
4117 installation would hamper the ability of the system to
4118 continue with any upgrade that might be in progress.
4122 <tt>Pre-Depends</tt> are also required if the
4123 <prgn>preinst</prgn> script depends on the named
4124 package. It is best to avoid this situation if
4132 When selecting which level of dependency to use you should
4133 consider how important the depended-on package is to the
4134 functionality of the one declaring the dependency. Some
4135 packages are composed of components of varying degrees of
4136 importance. Such a package should list using
4137 <tt>Depends</tt> the package(s) which are required by the
4138 more important components. The other components'
4139 requirements may be mentioned as Suggestions or
4140 Recommendations, as appropriate to the components' relative
4145 <sect id="conflicts">
4146 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4149 When one binary package declares a conflict with another
4150 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4151 refuse to allow them to be installed on the system at the
4156 If one package is to be installed, the other must be removed
4157 first - if the package being installed is marked as
4158 replacing (see <ref id="replaces">) the one on the system,
4159 or the one on the system is marked as deselected, or both
4160 packages are marked <tt>Essential</tt>, then
4161 <prgn>dpkg</prgn> will automatically remove the package
4162 which is causing the conflict, otherwise it will halt the
4163 installation of the new package with an error. This
4164 mechanism is specifically designed to produce an error when
4165 the installed package is <tt>Essential</tt>, but the new
4170 A package will not cause a conflict merely because its
4171 configuration files are still installed; it must be at least
4176 A special exception is made for packages which declare a
4177 conflict with their own package name, or with a virtual
4178 package which they provide (see below): this does not
4179 prevent their installation, and allows a package to conflict
4180 with others providing a replacement for it. You use this
4181 feature when you want the package in question to be the only
4182 package providing some feature.
4186 A <tt>Conflicts</tt> entry should almost never have an
4187 "earlier than" version clause. This would prevent
4188 <prgn>dpkg</prgn> from upgrading or installing the package
4189 which declared such a conflict until the upgrade or removal
4190 of the conflicted-with package had been completed.
4194 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4198 As well as the names of actual ("concrete") packages, the
4199 package relationship fields <tt>Depends</tt>,
4200 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4201 <tt>Pre-Depends</tt>, <tt>Conflicts</tt>,
4202 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4203 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4204 may mention "virtual packages".
4208 A <em>virtual package</em> is one which appears in the
4209 <tt>Provides</tt> control file field of another package.
4210 The effect is as if the package(s) which provide a
4211 particular virtual package name had been listed by name
4212 everywhere the virtual package name appears. (See also <ref
4217 If there are both concrete and virtual packages of the same
4218 name, then the dependency may be satisfied (or the conflict
4219 caused) by either the concrete package with the name in
4220 question or any other concrete package which provides the
4221 virtual package with the name in question. This is so that,
4222 for example, supposing we have
4223 <example compact="compact">
4226 </example> and someone else releases an enhanced version of
4227 the <tt>bar</tt> package they can say:
4228 <example compact="compact">
4232 and the <tt>bar-plus</tt> package will now also satisfy the
4233 dependency for the <tt>foo</tt> package.
4237 If a dependency or a conflict has a version number attached
4238 then only real packages will be considered to see whether
4239 the relationship is satisfied (or the prohibition violated,
4240 for a conflict) - it is assumed that a real package which
4241 provides the virtual package is not of the "right" version.
4242 So, a <tt>Provides</tt> field may not contain version
4243 numbers, and the version number of the concrete package
4244 which provides a particular virtual package will not be
4245 looked at when considering a dependency on or conflict with
4246 the virtual package name.
4250 It is likely that the ability will be added in a future
4251 release of <prgn>dpkg</prgn> to specify a version number for
4252 each virtual package it provides. This feature is not yet
4253 present, however, and is expected to be used only
4258 If you want to specify which of a set of real packages
4259 should be the default to satisfy a particular dependency on
4260 a virtual package, you should list the real package as an
4261 alternative before the virtual one.
4266 <sect id="replaces"><heading>Overwriting files and replacing
4267 packages - <tt>Replaces</tt></heading>
4270 Packages can declare in their control file that they should
4271 overwrite files in certain other packages, or completely
4272 replace other packages. The <tt>Replaces</tt> control file
4273 field has these two distinct purposes.
4276 <sect1><heading>Overwriting files in other packages</heading>
4279 Firstly, as mentioned before, it is usually an error for a
4280 package to contain files which are on the system in
4285 However, if the overwriting package declares that it
4286 <tt>Replaces</tt> the one containing the file being
4287 overwritten, then <prgn>dpkg</prgn> will replace the file
4288 from the old package with that from the new. The file
4289 will no longer be listed as "owned" by the old package.
4293 If a package is completely replaced in this way, so that
4294 <prgn>dpkg</prgn> does not know of any files it still
4295 contains, it is considered to have "disappeared". It will
4296 be marked as not wanted on the system (selected for
4297 removal) and not installed. Any <tt>conffile</tt>s
4298 details noted for the package will be ignored, as they
4299 will have been taken over by the overwriting package. The
4300 package's <prgn>postrm</prgn> script will be run with a
4301 special argument to allow the package to do any final
4302 cleanup required. See <ref id="mscriptsinstact">.
4305 Replaces is a one way relationship -- you have to
4306 install the replacing package after the replaced
4313 For this usage of <tt>Replaces</tt>, virtual packages (see
4314 <ref id="virtual">) are not considered when looking at a
4315 <tt>Replaces</tt> field - the packages declared as being
4316 replaced must be mentioned by their real names.
4320 Furthermore, this usage of <tt>Replaces</tt> only takes
4321 effect when both packages are at least partially on the
4322 system at once, so that it can only happen if they do not
4323 conflict or if the conflict has been overridden.
4328 <sect1><heading>Replacing whole packages, forcing their
4332 Secondly, <tt>Replaces</tt> allows the packaging system to
4333 resolve which package should be removed when there is a
4334 conflict - see <ref id="conflicts">. This usage only
4335 takes effect when the two packages <em>do</em> conflict,
4336 so that the two usages of this field do not interfere with
4341 In this situation, the package declared as being replaced
4342 can be a virtual package, so for example, all mail
4343 transport agents (MTAs) would have the following fields in
4344 their control files:
4345 <example compact="compact">
4346 Provides: mail-transport-agent
4347 Conflicts: mail-transport-agent
4348 Replaces: mail-transport-agent
4350 ensuring that only one MTA can be installed at any one
4355 <sect id="sourcebinarydeps">
4356 <heading>Relationships between source and binary packages -
4357 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4358 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
4362 Source packages that require certain binary packages to be
4363 installed or absent at the time of building the package
4364 can declare relationships to those binary packages.
4368 This is done using the <tt>Build-Depends</tt>,
4369 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
4370 <tt>Build-Conflicts-Indep</tt> control file fields.
4374 Build-dependencies on "build-essential" binary packages can be
4375 omitted. Please see <ref id="pkg-relations"> for more information.
4379 The dependencies and conflicts they define must be satisfied
4380 (as defined earlier for binary packages) in order to invoke
4381 the targets in <tt>debian/rules</tt>, as follows:<footnote>
4383 If you make "build-arch" or "binary-arch", you need
4384 Build-Depends. If you make "build-indep" or
4385 "binary-indep", you need Build-Depends and
4386 Build-Depends-Indep. If you make "build" or "binary",
4390 There is no Build-Depends-Arch; this role is essentially
4391 met with Build-Depends. Anyone building the
4392 <tt>build-indep</tt> and binary-indep<tt></tt> targets
4393 is basically assumed to be building the whole package
4394 anyway and so installs all build dependencies. The
4395 autobuilders use <tt>dpkg-buildpackage -B</tt>, which
4396 calls <tt>build</tt> (not <tt>build-arch</tt>, since it
4397 does not yet know how to check for its existence) and
4398 <tt>binary-arch</tt>.
4401 The purpose of the original split, I recall, was so that
4402 the autobuilders wouldn't need to install extra packages
4403 needed only for the binary-indep targets. But without a
4404 build-arch/build-indep split, this didn't work, since
4405 most of the work is done in the build target, not in the
4411 <tag><tt>Build-Depends</tt>, <tt>Build-Conflicts</tt></tag>
4413 The <tt>Build-Depends</tt> and
4414 <tt>Build-Conflicts</tt> fields must be satisfied when
4415 any of the following targets is invoked:
4416 <tt>build</tt>, <tt>clean</tt>, <tt>binary</tt>,
4417 <tt>binary-arch</tt>, <tt>build-arch</tt>,
4418 <tt>build-indep</tt> and <tt>binary-indep</tt>.
4420 <tag><tt>Build-Depends-Indep</tt>,
4421 <tt>Build-Conflicts-Indep</tt></tag>
4423 The <tt>Build-Depends-Indep</tt> and
4424 <tt>Build-Conflicts-Indep</tt> fields must be
4425 satisfied when any of the following targets is
4426 invoked: <tt>build</tt>, <tt>build-indep</tt>,
4427 <tt>binary</tt> and <tt>binary-indep</tt>.
4437 <chapt id="sharedlibs"><heading>Shared libraries</heading>
4440 Packages containing shared libraries must be constructed with
4441 a little care to make sure that the shared library is always
4442 available. This is especially important for packages whose
4443 shared libraries are vitally important, such as the C library
4444 (currently <tt>libc6</tt>).
4448 Packages involving shared libraries should be split up into
4449 several binary packages. This section mostly deals with how
4450 this separation is to be accomplished; rules for files within
4451 the shared library packages are in <ref id="libraries"> instead.
4454 <sect id="sharedlibs-runtime">
4455 <heading>Run-time shared libraries</heading>
4458 The run-time shared library needs to be placed in a package
4459 whose name changes whenever the shared object version
4462 Since it is common place to install several versions of a
4463 package that just provides shared libraries, it is a
4464 good idea that the library package should not
4465 contain any extraneous non-versioned files, unless they
4466 happen to be in versioned directories.</p>
4468 The most common mechanism is to place it in a package
4470 <package><var>libraryname</var><var>soversion</var></package>,
4471 where <file><var>soversion</var></file> is the version number
4472 in the soname of the shared library<footnote>
4473 The soname is the shared object name: it's the thing
4474 that has to match exactly between building an executable
4475 and running it for the dynamic linker to be able run the
4476 program. For example, if the soname of the library is
4477 <file>libfoo.so.6</file>, the library package would be
4478 called <file>libfoo6</file>.
4480 Alternatively, if it would be confusing to directly append
4481 <var>soversion</var> to <var>libraryname</var> (e.g. because
4482 <var>libraryname</var> itself ends in a number), you may use
4483 <package><var>libraryname</var>-<var>soversion</var></package> and
4484 <package><var>libraryname</var>-<var>soversion</var>-dev</package>
4489 If your package includes run-time support programs that
4490 do not need to be invoked manually by users, but are
4491 nevertheless required for the package to function, then it
4492 is recommended that these programs are placed
4493 (if they are binary) in a subdirectory of
4494 <file>/usr/lib</file>, preferably under
4495 <file>/usr/lib/</file><var>package-name</var>.
4496 If the program is architecture independent, the
4497 recommendation is for it to be placed in a subdirectory of
4498 <file>/usr/share</file> instead, preferably under
4499 <file>/usr/share/</file><var>package-name</var>.
4504 If you have several shared libraries built from the same
4505 source tree you may lump them all together into a single
4506 shared library package, provided that you change all of
4507 their sonames at once (so that you don't get filename
4508 clashes if you try to install different versions of the
4509 combined shared libraries package).
4513 The package should install the shared libraries under
4514 their normal names. For example, the <package>libgdbm3</package>
4515 package should install <file>libgdbm.so.3.0.0</file> as
4516 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
4517 renamed or re-linked by any <prgn>prerm</prgn> or
4518 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
4519 of renaming things safely without affecting running programs,
4520 and attempts to interfere with this are likely to lead to
4525 Shared libraries should not be installed executable, since
4526 the dynamic linker does not require this and trying to
4527 execute a shared library usually results in a core dump.
4531 The run-time library package should include the symbolic link that
4532 <prgn>ldconfig</prgn> would create for the shared libraries.
4533 For example, the <package>libgdbm3</package> package should include
4534 a symbolic link from <file>/usr/lib/libgdbm.so.3</file> to
4535 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
4536 linker (for example <prgn>ld.so</prgn> or
4537 <prgn>ld-linux.so.*</prgn>) can find the library between the
4538 time that <prgn>dpkg</prgn> installs it and the time that
4539 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
4541 The package management system requires the library to be
4542 placed before the symbolic link pointing to it in the
4543 <file>.deb</file> file. This is so that when
4544 <prgn>dpkg</prgn> comes to install the symlink
4545 (overwriting the previous symlink pointing at an older
4546 version of the library), the new shared library is already
4547 in place. In the past, this was achieved by creating the
4548 library in the temporary packaging directory before
4549 creating the symlink. Unfortunately, this was not always
4550 effective, since the building of the tar file in the
4551 <file>.deb</file> depended on the behavior of the underlying
4552 file system. Some file systems (such as reiserfs) reorder
4553 the files so that the order of creation is forgotten.
4554 Since version 1.7.0, <prgn>dpkg</prgn>
4555 reorders the files itself as necessary when building a
4556 package. Thus it is no longer important to concern
4557 oneself with the order of file creation.
4561 <sect1 id="ldconfig">
4562 <heading><tt>ldconfig</tt></heading>
4565 Any package installing shared libraries in one of the default
4566 library directories of the dynamic linker (which are currently
4567 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
4568 listed in <file>/etc/ld.so.conf</file><footnote>
4570 <list compact="compact">
4571 <item>/usr/local/lib</item>
4572 <item>/usr/lib/libc5-compat</item>
4573 <item>/lib/libc5-compat</item>
4576 must use <prgn>ldconfig</prgn> to update the shared library
4581 The package maintainer scripts must only call
4582 <prgn>ldconfig</prgn> under these circumstances:
4583 <list compact="compact">
4584 <item>When the <prgn>postinst</prgn> script is run with a
4585 first argument of <tt>configure</tt>, the script must call
4586 <prgn>ldconfig</prgn>, and may optionally invoke
4587 <prgn>ldconfig</prgn> at other times.
4589 <item>When the <prgn>postrm</prgn> script is run with a
4590 first argument of <tt>remove</tt>, the script should call
4591 <prgn>ldconfig</prgn>.
4596 During install or upgrade, the preinst is called before
4597 the new files are installed, so calling "ldconfig" is
4598 pointless. The preinst of an existing package can also be
4599 called if an upgrade fails. However, this happens during
4600 the critical time when a shared libs may exist on-disk
4601 under a temporary name. Thus, it is dangerous and
4602 forbidden by current policy to call "ldconfig" at this
4607 When a package is installed or upgraded, "postinst
4608 configure" runs after the new files are safely on-disk.
4609 Since it is perfectly safe to invoke ldconfig
4610 unconditionally in a postinst, it is OK for a package to
4611 simply put ldconfig in its postinst without checking the
4612 argument. The postinst can also be called to recover from
4613 a failed upgrade. This happens before any new files are
4614 unpacked, so there is no reason to call "ldconfig" at this
4619 For a package that is being removed, prerm is
4620 called with all the files intact, so calling ldconfig is
4621 useless. The other calls to "prerm" happen in the case of
4622 upgrade at a time when all the files of the old package
4623 are on-disk, so again calling "ldconfig" is pointless.
4627 postrm, on the other hand, is called with the "remove"
4628 argument just after the files are removed, so this is
4629 the proper time to call "ldconfig" to notify the system
4630 of the fact that the shared libraries from the package
4631 are removed. The postrm can be called at several other
4632 times. At the time of "postrm purge", "postrm
4633 abort-install", or "postrm abort-upgrade", calling
4634 "ldconfig" is useless because the shared lib files are
4635 not on-disk. However, when "postrm" is invoked with
4636 arguments "upgrade", "failed-upgrade", or "disappear", a
4637 shared lib may exist on-disk under a temporary filename.
4645 <sect id="sharedlibs-runtime-progs">
4646 <heading>Run-time support programs</heading>
4649 If your package has some run-time support programs which use
4650 the shared library you must not put them in the shared
4651 library package. If you do that then you won't be able to
4652 install several versions of the shared library without
4653 getting filename clashes.
4657 Instead, either create another package for the runtime binaries
4658 (this package might typically be named
4659 <package><var>libraryname</var>-runtime</package>; note the absence
4660 of the <var>soversion</var> in the package name), or if the
4661 development package is small, include them in there.
4665 <sect id="sharedlibs-static">
4666 <heading>Static libraries</heading>
4669 The static library (<file><var>libraryname.a</var></file>)
4670 is usually provided in addition to the shared version.
4671 It is placed into the development package (see below).
4675 In some cases, it is acceptable for a library to be
4676 available in static form only; these cases include:
4678 <item>libraries for languages whose shared library support
4679 is immature or unstable</item>
4680 <item>libraries whose interfaces are in flux or under
4681 development (commonly the case when the library's
4682 major version number is zero, or where the ABI breaks
4683 across patchlevels)</item>
4684 <item>libraries which are explicitly intended to be
4685 available only in static form by their upstream
4690 <sect id="sharedlibs-dev">
4691 <heading>Development files</heading>
4694 The development files associated to a shared library need to be
4695 placed in a package called
4696 <package><var>libraryname</var><var>soversion</var>-dev</package>,
4697 or if you prefer only to support one development version at a
4698 time, <package><var>libraryname</var>-dev</package>.
4702 In case several development versions of a library exist, you may
4703 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
4704 <ref id="conflicts">) to ensure that the user only installs one
4705 development version at a time (as different development versions are
4706 likely to have the same header files in them, which would cause a
4707 filename clash if both were installed).
4711 The development package should contain a symlink for the associated
4712 shared library without a version number. For example, the
4713 <package>libgdbm-dev</package> package should include a symlink
4714 from <file>/usr/lib/libgdbm.so</file> to
4715 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
4716 (<prgn>ld</prgn>) when compiling packages, as it will only look for
4717 <file>libgdbm.so</file> when compiling dynamically.
4721 <sect id="sharedlibs-intradeps">
4722 <heading>Dependencies between the packages of the same library</heading>
4725 Typically the development version should have an exact
4726 version dependency on the runtime library, to make sure that
4727 compilation and linking happens correctly. The
4728 <tt>${binary:Version}</tt> substitution variable can be
4729 useful for this purpose.
4731 Previously, <tt>${Source-Version}</tt> was used, but its name
4732 was confusing and it has been deprecated since dpkg 1.13.19.
4737 <sect id="sharedlibs-shlibdeps">
4738 <heading>Dependencies between the library and other packages -
4739 the <tt>shlibs</tt> system</heading>
4742 If a package contains a binary or library which links to a
4743 shared library, we must ensure that when the package is
4744 installed on the system, all of the libraries needed are
4745 also installed. This requirement led to the creation of the
4746 <tt>shlibs</tt> system, which is very simple in its design:
4747 any package which <em>provides</em> a shared library also
4748 provides information on the package dependencies required to
4749 ensure the presence of this library, and any package which
4750 <em>uses</em> a shared library uses this information to
4751 determine the dependencies it requires. The files which
4752 contain the mapping from shared libraries to the necessary
4753 dependency information are called <file>shlibs</file> files.
4757 Thus, when a package is built which contains any shared
4758 libraries, it must provide a <file>shlibs</file> file for other
4759 packages to use, and when a package is built which contains
4760 any shared libraries or compiled binaries, it must run
4761 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
4762 on these to determine the libraries used and hence the
4763 dependencies needed by this package.<footnote>
4765 In the past, the shared libraries linked to were
4766 determined by calling <prgn>ldd</prgn>, but now
4767 <prgn>objdump</prgn> is used to do this. The only
4768 change this makes to package building is that
4769 <prgn>dpkg-shlibdeps</prgn> must also be run on shared
4770 libraries, whereas in the past this was unnecessary.
4771 The rest of this footnote explains the advantage that
4776 We say that a binary <tt>foo</tt> <em>directly</em> uses
4777 a library <tt>libbar</tt> if it is explicitly linked
4778 with that library (that is, it uses the flag
4779 <tt>-lbar</tt> during the linking stage). Other
4780 libraries that are needed by <tt>libbar</tt> are linked
4781 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
4782 linker will load them automatically when it loads
4783 <tt>libbar</tt>. A package should depend on
4784 the libraries it directly uses, and the dependencies for
4785 those libraries should automatically pull in the other
4790 Unfortunately, the <prgn>ldd</prgn> program shows both
4791 the directly and indirectly used libraries, meaning that
4792 the dependencies determined included both direct and
4793 indirect dependencies. The use of <prgn>objdump</prgn>
4794 avoids this problem by determining only the directly
4799 A good example of where this helps is the following. We
4800 could update <tt>libimlib</tt> with a new version that
4801 supports a new graphics format called dgf (but retaining
4802 the same major version number). If we used the old
4803 <prgn>ldd</prgn> method, every package that uses
4804 <tt>libimlib</tt> would need to be recompiled so it
4805 would also depend on <tt>libdgf</tt> or it wouldn't run
4806 due to missing symbols. However with the new system,
4807 packages using <tt>libimlib</tt> can rely on
4808 <tt>libimlib</tt> itself having the dependency on
4809 <tt>libdgf</tt> and so they would not need rebuilding.
4815 In the following sections, we will first describe where the
4816 various <tt>shlibs</tt> files are to be found, then how to
4817 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
4818 file format and how to create them if your package contains a
4823 <heading>The <tt>shlibs</tt> files present on the system</heading>
4826 There are several places where <tt>shlibs</tt> files are
4827 found. The following list gives them in the order in which
4829 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
4830 (The first one which gives the required information is used.)
4836 <p><file>debian/shlibs.local</file></p>
4839 This lists overrides for this package. Its use is
4840 described below (see <ref id="shlibslocal">).
4845 <p><file>/etc/dpkg/shlibs.override</file></p>
4848 This lists global overrides. This list is normally
4849 empty. It is maintained by the local system
4855 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
4858 When packages are being built, any
4859 <file>debian/shlibs</file> files are copied into the
4860 control file area of the temporary build directory and
4861 given the name <file>shlibs</file>. These files give
4862 details of any shared libraries included in the
4864 An example may help here. Let us say that the
4865 source package <tt>foo</tt> generates two binary
4866 packages, <tt>libfoo2</tt> and
4867 <tt>foo-runtime</tt>. When building the binary
4868 packages, the two packages are created in the
4869 directories <file>debian/libfoo2</file> and
4870 <file>debian/foo-runtime</file> respectively.
4871 (<file>debian/tmp</file> could be used instead of one
4872 of these.) Since <tt>libfoo2</tt> provides the
4873 <tt>libfoo</tt> shared library, it will require a
4874 <tt>shlibs</tt> file, which will be installed in
4875 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually
4877 <file>/var/lib/dpkg/info/libfoo2.shlibs</file>. Then
4878 when <prgn>dpkg-shlibdeps</prgn> is run on the
4880 <file>debian/foo-runtime/usr/bin/foo-prog</file>, it
4882 <file>debian/libfoo2/DEBIAN/shlibs</file> file to
4883 determine whether <tt>foo-prog</tt>'s library
4884 dependencies are satisfied by any of the libraries
4885 provided by <tt>libfoo2</tt>. For this reason,
4886 <prgn>dpkg-shlibdeps</prgn> must only be run once
4887 all of the individual binary packages'
4888 <tt>shlibs</tt> files have been installed into the
4895 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
4898 These are the <file>shlibs</file> files corresponding to
4899 all of the packages installed on the system, and are
4900 maintained by the relevant package maintainers.
4905 <p><file>/etc/dpkg/shlibs.default</file></p>
4908 This file lists any shared libraries whose packages
4909 have failed to provide correct <file>shlibs</file> files.
4910 It was used when the <file>shlibs</file> setup was first
4911 introduced, but it is now normally empty. It is
4912 maintained by the <tt>dpkg</tt> maintainer.
4920 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
4921 <file>shlibs</file> files</heading>
4925 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
4926 into your <file>debian/rules</file> file. If your package
4927 contains only compiled binaries and libraries (but no scripts),
4928 you can use a command such as:
4929 <example compact="compact">
4930 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
4931 debian/tmp/usr/lib/*
4933 Otherwise, you will need to explicitly list the compiled
4934 binaries and libraries.<footnote>
4935 If you are using <tt>debhelper</tt>, the
4936 <prgn>dh_shlibdeps</prgn> program will do this work for
4937 you. It will also correctly handle multi-binary
4943 This command puts the dependency information into the
4944 <file>debian/substvars</file> file, which is then used by
4945 <prgn>dpkg-gencontrol</prgn>. You will need to place a
4946 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
4947 field in the control file for this to work.
4951 If <prgn>dpkg-shlibdeps</prgn> doesn't complain, you're
4952 done. If it does complain you might need to create your own
4953 <file>debian/shlibs.local</file> file, as explained below (see
4954 <ref id="shlibslocal">).
4958 If you have multiple binary packages, you will need to call
4959 <prgn>dpkg-shlibdeps</prgn> on each one which contains
4960 compiled libraries or binaries. In such a case, you will
4961 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
4962 utilities to specify a different <file>substvars</file> file.
4966 If you are creating a udeb for use in the Debian Installer, you
4967 will need to specify that <prgn>dpkg-shlibdeps</prgn> should use
4968 the dependency line of type <tt>udeb</tt> by adding
4969 <tt>-tudeb</tt> as option<footnote>
4970 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
4971 will automatically add this option if it knows it is
4973 </footnote>. If there is no dependency line of type <tt>udeb</tt>
4974 in the <file>shlibs</file> file, <prgn>dpkg-shlibdeps</prgn> will
4975 fall back to the regular dependency line.
4979 For more details on dpkg-shlibdeps, please see
4980 <ref id="pkg-dpkg-shlibdeps"> and
4981 <manref name="dpkg-shlibdeps" section="1">.
4986 <heading>The <file>shlibs</file> File Format</heading>
4989 Each <file>shlibs</file> file has the same format. Lines
4990 beginning with <tt>#</tt> are considered to be comments and
4991 are ignored. Each line is of the form:
4992 <example compact="compact">
4993 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
4998 We will explain this by reference to the example of the
4999 <tt>zlib1g</tt> package, which (at the time of writing)
5000 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5004 <var>type</var> is an optional element that indicates the type
5005 of package for which the line is valid. The only type currently
5006 in use is <tt>udeb</tt>. The colon and space after the type are
5011 <var>library-name</var> is the name of the shared library,
5012 in this case <tt>libz</tt>. (This must match the name part
5013 of the soname, see below.)
5017 <var>soname-version</var> is the version part of the soname of
5018 the library. The soname is the thing that must exactly match
5019 for the library to be recognized by the dynamic linker, and is
5021 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5022 example, <tt>libz.so.1</tt>.<footnote>
5023 This can be determined using the command
5024 <example compact="compact">
5025 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5028 The version part is the part which comes after
5029 <tt>.so.</tt>, so in our case, it is <tt>1</tt>.
5033 <var>dependencies</var> has the same syntax as a dependency
5034 field in a binary package control file. It should give
5035 details of which packages are required to satisfy a binary
5036 built against the version of the library contained in the
5037 package. See <ref id="depsyntax"> for details.
5041 In our example, if the first version of the <tt>zlib1g</tt>
5042 package which contained a minor number of at least
5043 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5044 <tt>shlibs</tt> entry for this library could say:
5045 <example compact="compact">
5046 libz 1 zlib1g (>= 1:1.1.3)
5048 The version-specific dependency is to avoid warnings from
5049 the dynamic linker about using older shared libraries with
5054 As zlib1g also provides a udeb containing the shared library,
5055 there would also be a second line:
5056 <example compact="compact">
5057 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5063 <heading>Providing a <file>shlibs</file> file</heading>
5066 If your package provides a shared library, you need to create
5067 a <file>shlibs</file> file following the format described above.
5068 It is usual to call this file <file>debian/shlibs</file> (but if
5069 you have multiple binary packages, you might want to call it
5070 <file>debian/shlibs.<var>package</var></file> instead). Then
5071 let <file>debian/rules</file> install it in the control area:
5072 <example compact="compact">
5073 install -m644 debian/shlibs debian/tmp/DEBIAN
5075 or, in the case of a multi-binary package:
5076 <example compact="compact">
5077 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5079 An alternative way of doing this is to create the
5080 <file>shlibs</file> file in the control area directly from
5081 <file>debian/rules</file> without using a <file>debian/shlibs</file>
5082 file at all,<footnote>
5083 This is what <prgn>dh_makeshlibs</prgn> in the
5084 <tt>debhelper</tt> suite does. If your package also has a udeb
5085 that provides a shared library, <prgn>dh_makeshlibs</prgn> can
5086 automatically generate the <tt>udeb:</tt> lines if you specify
5087 the name of the udeb with the <tt>--add-udeb</tt> option.
5089 since the <file>debian/shlibs</file> file itself is ignored by
5090 <prgn>dpkg-shlibdeps</prgn>.
5094 As <prgn>dpkg-shlibdeps</prgn> reads the
5095 <file>DEBIAN/shlibs</file> files in all of the binary packages
5096 being built from this source package, all of the
5097 <file>DEBIAN/shlibs</file> files should be installed before
5098 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5103 <sect1 id="shlibslocal">
5104 <heading>Writing the <file>debian/shlibs.local</file> file</heading>
5107 This file is intended only as a <em>temporary</em> fix if
5108 your binaries or libraries depend on a library whose package
5109 does not yet provide a correct <file>shlibs</file> file.
5113 We will assume that you are trying to package a binary
5114 <tt>foo</tt>. When you try running
5115 <prgn>dpkg-shlibdeps</prgn> you get the following error
5116 message (<tt>-O</tt> displays the dependency information on
5117 <tt>stdout</tt> instead of writing it to
5118 <tt>debian/substvars</tt>, and the lines have been wrapped
5119 for ease of reading):
5120 <example compact="compact">
5121 $ dpkg-shlibdeps -O debian/tmp/usr/bin/foo
5122 dpkg-shlibdeps: warning: unable to find dependency
5123 information for shared library libbar (soname 1,
5124 path /usr/lib/libbar.so.1, dependency field Depends)
5125 shlibs:Depends=libc6 (>= 2.2.2-2)
5127 You can then run <prgn>ldd</prgn> on the binary to find the
5128 full location of the library concerned:
5129 <example compact="compact">
5131 libbar.so.1 => /usr/lib/libbar.so.1 (0x4001e000)
5132 libc.so.6 => /lib/libc.so.6 (0x40032000)
5133 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
5135 So the <prgn>foo</prgn> binary depends on the
5136 <prgn>libbar</prgn> shared library, but no package seems to
5137 provide a <file>*.shlibs</file> file handling
5138 <file>libbar.so.1</file> in <file>/var/lib/dpkg/info/</file>. Let's
5139 determine the package responsible:
5140 <example compact="compact">
5141 $ dpkg -S /usr/lib/libbar.so.1
5142 bar1: /usr/lib/libbar.so.1
5143 $ dpkg -s bar1 | grep Version
5146 This tells us that the <tt>bar1</tt> package, version 1.0-1,
5147 is the one we are using. Now we can file a bug against the
5148 <tt>bar1</tt> package and create our own
5149 <file>debian/shlibs.local</file> to locally fix the problem.
5150 Including the following line into your
5151 <file>debian/shlibs.local</file> file:
5152 <example compact="compact">
5153 libbar 1 bar1 (>= 1.0-1)
5155 should allow the package build to work.
5159 As soon as the maintainer of <tt>bar1</tt> provides a
5160 correct <file>shlibs</file> file, you should remove this line
5161 from your <file>debian/shlibs.local</file> file. (You should
5162 probably also then have a versioned <tt>Build-Depends</tt>
5163 on <tt>bar1</tt> to help ensure that others do not have the
5164 same problem building your package.)
5173 <chapt id="opersys"><heading>The Operating System</heading>
5176 <heading>File system hierarchy</heading>
5180 <heading>File system Structure</heading>
5183 The location of all installed files and directories must
5184 comply with the File system Hierarchy Standard (FHS),
5185 version 2.3, with the exceptions noted below, and except
5186 where doing so would violate other terms of Debian
5187 Policy. The following exceptions to the FHS apply:
5192 Legacy XFree86 servers are permitted to retain the
5193 configuration file location
5194 <file>/etc/X11/XF86Config-4</file>.
5199 The optional rules related to user specific
5200 configuration files for applications are stored in
5201 the user's home directory are relaxed. It is
5202 recommended that such files start with the
5203 '<tt>.</tt>' character (a "dot file"), and if an
5204 application needs to create more than one dot file
5205 then the preferred placement is in a subdirectory
5206 with a name starting with a '.' character, (a "dot
5207 directory"). In this case it is recommended the
5208 configuration files not start with the '.'
5214 The requirement for amd64 to use <file>/lib64</file>
5215 for 64 bit binaries is removed.
5220 The requirement that
5221 <file>/usr/local/share/man</file> be "synonymous"
5222 with <file>/usr/local/man</file> is relaxed to a
5227 The requirement that windowmanagers with a single
5228 configuration file call it <file>system.*wmrc</file>
5229 is removed, as is the restriction that the window
5230 manager subdirectory be named identically to the
5231 window manager name itself.
5236 The requirement that boot manager configuration
5237 files live in <file>/etc</file>, or at least are
5238 symlinked there, is relaxed to a recommendation.
5245 The version of this document referred here can be
5246 found in the <tt>debian-policy</tt> package or on <url
5247 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5248 name="FHS (Debian copy)"> alongside this manual (or, if
5249 you have the <package>debian-policy</package> installed,
5251 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5252 (local copy)">). The
5253 latest version, which may be a more recent version, may
5255 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5256 Specific questions about following the standard may be
5257 asked on the <tt>debian-devel</tt> mailing list, or
5258 referred to the FHS mailing list (see the
5259 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
5265 <heading>Site-specific programs</heading>
5268 As mandated by the FHS, packages must not place any
5269 files in <file>/usr/local</file>, either by putting them in
5270 the file system archive to be unpacked by <prgn>dpkg</prgn>
5271 or by manipulating them in their maintainer scripts.
5275 However, the package may create empty directories below
5276 <file>/usr/local</file> so that the system administrator knows
5277 where to place site-specific files. These are not
5278 directories <em>in</em> <file>/usr/local</file>, but are
5279 children of directories in <file>/usr/local</file>. These
5280 directories (<file>/usr/local/*/dir/</file>)
5281 should be removed on package removal if they are
5286 Note, that this applies only to directories <em>below</em>
5287 <file>/usr/local</file>, not <em>in</em> <file>/usr/local</file>.
5288 Packages must not create sub-directories in the directory
5289 <file>/usr/local</file> itself, except those listed in FHS,
5290 section 4.5. However, you may create directories below
5291 them as you wish. You must not remove any of the
5292 directories listed in 4.5, even if you created them.
5296 Since <file>/usr/local</file> can be mounted read-only from a
5297 remote server, these directories must be created and
5298 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
5299 maintainer scripts and not be included in the
5300 <file>.deb</file> archive. These scripts must not fail if
5301 either of these operations fail.
5305 For example, the <tt>emacsen-common</tt> package could
5306 contain something like
5307 <example compact="compact">
5308 if [ ! -e /usr/local/share/emacs ]
5310 if mkdir /usr/local/share/emacs 2>/dev/null
5312 chown root:staff /usr/local/share/emacs
5313 chmod 2775 /usr/local/share/emacs
5317 in its <prgn>postinst</prgn> script, and
5318 <example compact="compact">
5319 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
5320 rmdir /usr/local/share/emacs 2>/dev/null || true
5322 in the <prgn>prerm</prgn> script. (Note that this form is
5323 used to ensure that if the script is interrupted, the
5324 directory <file>/usr/local/share/emacs</file> will still be
5329 If you do create a directory in <file>/usr/local</file> for
5330 local additions to a package, you should ensure that
5331 settings in <file>/usr/local</file> take precedence over the
5332 equivalents in <file>/usr</file>.
5336 However, because <file>/usr/local</file> and its contents are
5337 for exclusive use of the local administrator, a package
5338 must not rely on the presence or absence of files or
5339 directories in <file>/usr/local</file> for normal operation.
5343 The <file>/usr/local</file> directory itself and all the
5344 subdirectories created by the package should (by default) have
5345 permissions 2775 (group-writable and set-group-id) and be
5346 owned by <tt>root.staff</tt>.
5351 <heading>The system-wide mail directory</heading>
5353 The system-wide mail directory is <file>/var/mail</file>. This
5354 directory is part of the base system and should not owned
5355 by any particular mail agents. The use of the old
5356 location <file>/var/spool/mail</file> is deprecated, even
5357 though the spool may still be physically located there.
5358 To maintain partial upgrade compatibility for systems
5359 which have <file>/var/spool/mail</file> as their physical mail
5360 spool, packages using <file>/var/mail</file> must depend on
5361 either <package>libc6</package> (>= 2.1.3-13), or on
5362 <package>base-files</package> (>= 2.2.0), or on later
5363 versions of either one of these packages.
5369 <heading>Users and groups</heading>
5372 <heading>Introduction</heading>
5374 The Debian system can be configured to use either plain or
5379 Some user ids (UIDs) and group ids (GIDs) are reserved
5380 globally for use by certain packages. Because some
5381 packages need to include files which are owned by these
5382 users or groups, or need the ids compiled into binaries,
5383 these ids must be used on any Debian system only for the
5384 purpose for which they are allocated. This is a serious
5385 restriction, and we should avoid getting in the way of
5386 local administration policies. In particular, many sites
5387 allocate users and/or local system groups starting at 100.
5391 Apart from this we should have dynamically allocated ids,
5392 which should by default be arranged in some sensible
5393 order, but the behavior should be configurable.
5397 Packages other than <tt>base-passwd</tt> must not modify
5398 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
5399 <file>/etc/group</file> or <file>/etc/gshadow</file>.
5404 <heading>UID and GID classes</heading>
5406 The UID and GID numbers are divided into classes as
5412 Globally allocated by the Debian project, the same
5413 on every Debian system. These ids will appear in
5414 the <file>passwd</file> and <file>group</file> files of all
5415 Debian systems, new ids in this range being added
5416 automatically as the <tt>base-passwd</tt> package is
5421 Packages which need a single statically allocated
5422 uid or gid should use one of these; their
5423 maintainers should ask the <tt>base-passwd</tt>
5431 Dynamically allocated system users and groups.
5432 Packages which need a user or group, but can have
5433 this user or group allocated dynamically and
5434 differently on each system, should use <tt>adduser
5435 --system</tt> to create the group and/or user.
5436 <prgn>adduser</prgn> will check for the existence of
5437 the user or group, and if necessary choose an unused
5438 id based on the ranges specified in
5439 <file>adduser.conf</file>.
5443 <tag>1000-29999:</tag>
5446 Dynamically allocated user accounts. By default
5447 <prgn>adduser</prgn> will choose UIDs and GIDs for
5448 user accounts in this range, though
5449 <file>adduser.conf</file> may be used to modify this
5454 <tag>30000-59999:</tag>
5459 <tag>60000-64999:</tag>
5462 Globally allocated by the Debian project, but only
5463 created on demand. The ids are allocated centrally
5464 and statically, but the actual accounts are only
5465 created on users' systems on demand.
5469 These ids are for packages which are obscure or
5470 which require many statically-allocated ids. These
5471 packages should check for and create the accounts in
5472 <file>/etc/passwd</file> or <file>/etc/group</file> (using
5473 <prgn>adduser</prgn> if it has this facility) if
5474 necessary. Packages which are likely to require
5475 further allocations should have a "hole" left after
5476 them in the allocation, to give them room to
5481 <tag>65000-65533:</tag>
5489 User <tt>nobody</tt>. The corresponding gid refers
5490 to the group <tt>nogroup</tt>.
5497 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
5498 not</em> be used, because it is the error return
5507 <sect id="sysvinit">
5508 <heading>System run levels and <file>init.d</file> scripts</heading>
5510 <sect1 id="/etc/init.d">
5511 <heading>Introduction</heading>
5514 The <file>/etc/init.d</file> directory contains the scripts
5515 executed by <prgn>init</prgn> at boot time and when the
5516 init state (or "runlevel") is changed (see <manref
5517 name="init" section="8">).
5521 There are at least two different, yet functionally
5522 equivalent, ways of handling these scripts. For the sake
5523 of simplicity, this document describes only the symbolic
5524 link method. However, it must not be assumed by maintainer
5525 scripts that this method is being used, and any automated
5526 manipulation of the various runlevel behaviors by
5527 maintainer scripts must be performed using
5528 <prgn>update-rc.d</prgn> as described below and not by
5529 manually installing or removing symlinks. For information
5530 on the implementation details of the other method,
5531 implemented in the <tt>file-rc</tt> package, please refer
5532 to the documentation of that package.
5536 These scripts are referenced by symbolic links in the
5537 <file>/etc/rc<var>n</var>.d</file> directories. When changing
5538 runlevels, <prgn>init</prgn> looks in the directory
5539 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
5540 execute, where <tt><var>n</var></tt> is the runlevel that
5541 is being changed to, or <tt>S</tt> for the boot-up
5546 The names of the links all have the form
5547 <file>S<var>mm</var><var>script</var></file> or
5548 <file>K<var>mm</var><var>script</var></file> where
5549 <var>mm</var> is a two-digit number and <var>script</var>
5550 is the name of the script (this should be the same as the
5551 name of the actual script in <file>/etc/init.d</file>).
5555 When <prgn>init</prgn> changes runlevel first the targets
5556 of the links whose names start with a <tt>K</tt> are
5557 executed, each with the single argument <tt>stop</tt>,
5558 followed by the scripts prefixed with an <tt>S</tt>, each
5559 with the single argument <tt>start</tt>. (The links are
5560 those in the <file>/etc/rc<var>n</var>.d</file> directory
5561 corresponding to the new runlevel.) The <tt>K</tt> links
5562 are responsible for killing services and the <tt>S</tt>
5563 link for starting services upon entering the runlevel.
5567 For example, if we are changing from runlevel 2 to
5568 runlevel 3, init will first execute all of the <tt>K</tt>
5569 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
5570 all of the <tt>S</tt> prefixed scripts in that directory.
5571 The links starting with <tt>K</tt> will cause the
5572 referred-to file to be executed with an argument of
5573 <tt>stop</tt>, and the <tt>S</tt> links with an argument
5578 The two-digit number <var>mm</var> is used to determine
5579 the order in which to run the scripts: low-numbered links
5580 have their scripts run first. For example, the
5581 <tt>K20</tt> scripts will be executed before the
5582 <tt>K30</tt> scripts. This is used when a certain service
5583 must be started before another. For example, the name
5584 server <prgn>bind</prgn> might need to be started before
5585 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
5586 can set up its access lists. In this case, the script
5587 that starts <prgn>bind</prgn> would have a lower number
5588 than the script that starts <prgn>inn</prgn> so that it
5590 <example compact="compact">
5597 The two runlevels 0 (halt) and 6 (reboot) are slightly
5598 different. In these runlevels, the links with an
5599 <tt>S</tt> prefix are still called after those with a
5600 <tt>K</tt> prefix, but they too are called with the single
5601 argument <tt>stop</tt>.
5605 Also, if the script name ends in <tt>.sh</tt>, the script
5606 will be sourced in runlevel <tt>S</tt> rather than being
5607 run in a forked subprocess, but will be explicitly run by
5608 <prgn>sh</prgn> in all other runlevels.
5613 <heading>Writing the scripts</heading>
5616 Packages that include daemons for system services should
5617 place scripts in <file>/etc/init.d</file> to start or stop
5618 services at boot time or during a change of runlevel.
5619 These scripts should be named
5620 <file>/etc/init.d/<var>package</var></file>, and they should
5621 accept one argument, saying what to do:
5624 <tag><tt>start</tt></tag>
5625 <item>start the service,</item>
5627 <tag><tt>stop</tt></tag>
5628 <item>stop the service,</item>
5630 <tag><tt>restart</tt></tag>
5631 <item>stop and restart the service if it's already running,
5632 otherwise start the service</item>
5634 <tag><tt>reload</tt></tag>
5635 <item><p>cause the configuration of the service to be
5636 reloaded without actually stopping and restarting
5639 <tag><tt>force-reload</tt></tag>
5640 <item>cause the configuration to be reloaded if the
5641 service supports this, otherwise restart the
5645 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
5646 <tt>force-reload</tt> options should be supported by all
5647 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
5652 The <file>init.d</file> scripts must ensure that they will
5653 behave sensibly if invoked with <tt>start</tt> when the
5654 service is already running, or with <tt>stop</tt> when it
5655 isn't, and that they don't kill unfortunately-named user
5656 processes. The best way to achieve this is usually to use
5657 <prgn>start-stop-daemon</prgn>.
5661 If a service reloads its configuration automatically (as
5662 in the case of <prgn>cron</prgn>, for example), the
5663 <tt>reload</tt> option of the <file>init.d</file> script
5664 should behave as if the configuration has been reloaded
5669 The <file>/etc/init.d</file> scripts must be treated as
5670 configuration files, either (if they are present in the
5671 package, that is, in the .deb file) by marking them as
5672 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
5673 by managing them correctly in the maintainer scripts (see
5674 <ref id="config-files">). This is important since we want
5675 to give the local system administrator the chance to adapt
5676 the scripts to the local system, e.g., to disable a
5677 service without de-installing the package, or to specify
5678 some special command line options when starting a service,
5679 while making sure their changes aren't lost during the next
5684 These scripts should not fail obscurely when the
5685 configuration files remain but the package has been
5686 removed, as configuration files remain on the system after
5687 the package has been removed. Only when <prgn>dpkg</prgn>
5688 is executed with the <tt>--purge</tt> option will
5689 configuration files be removed. In particular, as the
5690 <file>/etc/init.d/<var>package</var></file> script itself is
5691 usually a <tt>conffile</tt>, it will remain on the system
5692 if the package is removed but not purged. Therefore, you
5693 should include a <tt>test</tt> statement at the top of the
5695 <example compact="compact">
5696 test -f <var>program-executed-later-in-script</var> || exit 0
5701 Often there are some variables in the <file>init.d</file>
5702 scripts whose values control the behavior of the scripts,
5703 and which a system administrator is likely to want to
5704 change. As the scripts themselves are frequently
5705 <tt>conffile</tt>s, modifying them requires that the
5706 administrator merge in their changes each time the package
5707 is upgraded and the <tt>conffile</tt> changes. To ease
5708 the burden on the system administrator, such configurable
5709 values should not be placed directly in the script.
5710 Instead, they should be placed in a file in
5711 <file>/etc/default</file>, which typically will have the same
5712 base name as the <file>init.d</file> script. This extra file
5713 should be sourced by the script when the script runs. It
5714 must contain only variable settings and comments in SUSv3
5715 <prgn>sh</prgn> format. It may either be a
5716 <tt>conffile</tt> or a configuration file maintained by
5717 the package maintainer scripts. See <ref id="config-files">
5722 To ensure that vital configurable values are always
5723 available, the <file>init.d</file> script should set default
5724 values for each of the shell variables it uses, either
5725 before sourcing the <file>/etc/default/</file> file or
5726 afterwards using something like the <tt>:
5727 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
5728 script must behave sensibly and not fail if the
5729 <file>/etc/default</file> file is deleted.
5734 <heading>Interfacing with the initscript system</heading>
5737 Maintainers should use the abstraction layer provided by
5738 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
5739 programs to deal with initscripts in their packages'
5740 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
5741 and <prgn>postrm</prgn>.
5745 Directly managing the /etc/rc?.d links and directly
5746 invoking the <file>/etc/init.d/</file> initscripts should
5747 be done only by packages providing the initscript
5748 subsystem (such as <prgn>sysv-rc</prgn> and
5749 <prgn>file-rc</prgn>).
5753 <heading>Managing the links</heading>
5756 The program <prgn>update-rc.d</prgn> is provided for
5757 package maintainers to arrange for the proper creation and
5758 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
5759 or their functional equivalent if another method is being
5760 used. This may be used by maintainers in their packages'
5761 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
5765 You must not include any <file>/etc/rc<var>n</var>.d</file>
5766 symbolic links in the actual archive or manually create or
5767 remove the symbolic links in maintainer scripts; you must
5768 use the <prgn>update-rc.d</prgn> program instead. (The
5769 former will fail if an alternative method of maintaining
5770 runlevel information is being used.) You must not include
5771 the <file>/etc/rc<var>n</var>.d</file> directories themselves
5772 in the archive either. (Only the <tt>sysvinit</tt>
5777 By default <prgn>update-rc.d</prgn> will start services in
5778 each of the multi-user state runlevels (2, 3, 4, and 5)
5779 and stop them in the halt runlevel (0), the single-user
5780 runlevel (1) and the reboot runlevel (6). The system
5781 administrator will have the opportunity to customize
5782 runlevels by simply adding, moving, or removing the
5783 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
5784 symbolic links are being used, or by modifying
5785 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
5790 To get the default behavior for your package, put in your
5791 <prgn>postinst</prgn> script
5792 <example compact="compact">
5793 update-rc.d <var>package</var> defaults
5795 and in your <prgn>postrm</prgn>
5796 <example compact="compact">
5797 if [ "$1" = purge ]; then
5798 update-rc.d <var>package</var> remove
5800 </example>. Note that if your package changes runlevels
5801 or priority, you may have to remove and recreate the links,
5802 since otherwise the old links may persist. Refer to the
5803 documentation of <prgn>update-rc.d</prgn>.
5807 This will use a default sequence number of 20. If it does
5808 not matter when or in which order the <file>init.d</file>
5809 script is run, use this default. If it does, then you
5810 should talk to the maintainer of the <prgn>sysvinit</prgn>
5811 package or post to <tt>debian-devel</tt>, and they will
5812 help you choose a number.
5816 For more information about using <tt>update-rc.d</tt>,
5817 please consult its man page <manref name="update-rc.d"
5823 <heading>Running initscripts</heading>
5825 The program <prgn>invoke-rc.d</prgn> is provided to make
5826 it easier for package maintainers to properly invoke an
5827 initscript, obeying runlevel and other locally-defined
5828 constraints that might limit a package's right to start,
5829 stop and otherwise manage services. This program may be
5830 used by maintainers in their packages' scripts.
5834 The package maintainer scripts must use
5835 <prgn>invoke-rc.d</prgn> to invoke the
5836 <file>/etc/init.d/*</file> initscripts, instead of
5837 calling them directly.
5841 By default, <prgn>invoke-rc.d</prgn> will pass any
5842 action requests (start, stop, reload, restart...) to the
5843 <file>/etc/init.d</file> script, filtering out requests
5844 to start or restart a service out of its intended
5849 Most packages will simply need to change:
5850 <example compact="compact">/etc/init.d/<package>
5851 <action></example> in their <prgn>postinst</prgn>
5852 and <prgn>prerm</prgn> scripts to:
5853 <example compact="compact">
5854 if which invoke-rc.d >/dev/null 2>&1; then
5855 invoke-rc.d <var>package</var> <action>
5857 /etc/init.d/<var>package</var> <action>
5863 A package should register its initscript services using
5864 <prgn>update-rc.d</prgn> before it tries to invoke them
5865 using <prgn>invoke-rc.d</prgn>. Invocation of
5866 unregistered services may fail.
5870 For more information about using
5871 <prgn>invoke-rc.d</prgn>, please consult its man page
5872 <manref name="invoke-rc.d" section="8">.
5878 <heading>Boot-time initialization</heading>
5881 There used to be another directory, <file>/etc/rc.boot</file>,
5882 which contained scripts which were run once per machine
5883 boot. This has been deprecated in favour of links from
5884 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
5885 described in <ref id="/etc/init.d">. Packages must not
5886 place files in <file>/etc/rc.boot</file>.
5891 <heading>Example</heading>
5894 An example on which you can base your
5895 <file>/etc/init.d</file> scripts is found in
5896 <file>/etc/init.d/skeleton</file>.
5903 <heading>Console messages from <file>init.d</file> scripts</heading>
5906 This section describes the formats to be used for messages
5907 written to standard output by the <file>/etc/init.d</file>
5908 scripts. The intent is to improve the consistency of
5909 Debian's startup and shutdown look and feel. For this
5910 reason, please look very carefully at the details. We want
5911 the messages to have the same format in terms of wording,
5912 spaces, punctuation and case of letters.
5916 Here is a list of overall rules that should be used for
5917 messages generated by <file>/etc/init.d</file> scripts.
5923 The message should fit in one line (fewer than 80
5924 characters), start with a capital letter and end with
5925 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
5929 If the script is performing some time consuming task in
5930 the background (not merely starting or stopping a
5931 program, for instance), an ellipsis (three dots:
5932 <tt>...</tt>) should be output to the screen, with no
5933 leading or tailing whitespace or line feeds.
5937 The messages should appear as if the computer is telling
5938 the user what it is doing (politely :-), but should not
5939 mention "it" directly. For example, instead of:
5940 <example compact="compact">
5941 I'm starting network daemons: nfsd mountd.
5943 the message should say
5944 <example compact="compact">
5945 Starting network daemons: nfsd mountd.
5952 <tt>init.d</tt> script should use the following standard
5953 message formats for the situations enumerated below.
5959 <p>When daemons are started</p>
5962 If the script starts one or more daemons, the output
5963 should look like this (a single line, no leading
5965 <example compact="compact">
5966 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
5968 The <var>description</var> should describe the
5969 subsystem the daemon or set of daemons are part of,
5970 while <var>daemon-1</var> up to <var>daemon-n</var>
5971 denote each daemon's name (typically the file name of
5976 For example, the output of <file>/etc/init.d/lpd</file>
5978 <example compact="compact">
5979 Starting printer spooler: lpd.
5984 This can be achieved by saying
5985 <example compact="compact">
5986 echo -n "Starting printer spooler: lpd"
5987 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
5990 in the script. If there are more than one daemon to
5991 start, the output should look like this:
5992 <example compact="compact">
5993 echo -n "Starting remote file system services:"
5994 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
5995 echo -n " mountd"; start-stop-daemon --start --quiet mountd
5996 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
5999 This makes it possible for the user to see what is
6000 happening and when the final daemon has been started.
6001 Care should be taken in the placement of white spaces:
6002 in the example above the system administrators can
6003 easily comment out a line if they don't want to start
6004 a specific daemon, while the displayed message still
6010 <p>When a system parameter is being set</p>
6013 If you have to set up different system parameters
6014 during the system boot, you should use this format:
6015 <example compact="compact">
6016 Setting <var>parameter</var> to "<var>value</var>".
6021 You can use a statement such as the following to get
6023 <example compact="compact">
6024 echo "Setting DNS domainname to \"$domainname\"."
6029 Note that the same symbol (<tt>"</tt>) is used for the left
6030 and right quotation marks. A grave accent (<tt>`</tt>) is
6031 not a quote character; neither is an apostrophe
6037 <p>When a daemon is stopped or restarted</p>
6040 When you stop or restart a daemon, you should issue a
6041 message identical to the startup message, except that
6042 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6043 or <tt>Restarting</tt> respectively.
6047 For example, stopping the printer daemon will look like
6049 <example compact="compact">
6050 Stopping printer spooler: lpd.
6056 <p>When something is executed</p>
6059 There are several examples where you have to run a
6060 program at system startup or shutdown to perform a
6061 specific task, for example, setting the system's clock
6062 using <prgn>netdate</prgn> or killing all processes
6063 when the system shuts down. Your message should look
6065 <example compact="compact">
6066 Doing something very useful...done.
6068 You should print the <tt>done.</tt> immediately after
6069 the job has been completed, so that the user is
6070 informed why they have to wait. You can get this
6072 <example compact="compact">
6073 echo -n "Doing something very useful..."
6082 <p>When the configuration is reloaded</p>
6085 When a daemon is forced to reload its configuration
6086 files you should use the following format:
6087 <example compact="compact">
6088 Reloading <var>description</var> configuration...done.
6090 where <var>description</var> is the same as in the
6091 daemon starting message.
6099 <heading>Cron jobs</heading>
6102 Packages must not modify the configuration file
6103 <file>/etc/crontab</file>, and they must not modify the files in
6104 <file>/var/spool/cron/crontabs</file>.</p>
6107 If a package wants to install a job that has to be executed
6108 via cron, it should place a file with the name of the
6109 package in one or more of the following directories:
6110 <example compact="compact">
6115 As these directory names imply, the files within them are
6116 executed on a daily, weekly, or monthly basis,
6117 respectively. The exact times are listed in
6118 <file>/etc/crontab</file>.</p>
6121 All files installed in any of these directories must be
6122 scripts (e.g., shell scripts or Perl scripts) so that they
6123 can easily be modified by the local system administrator.
6124 In addition, they should be treated as configuration
6129 If a certain job has to be executed more frequently than
6130 daily, the package should install a file
6131 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6132 same syntax as <file>/etc/crontab</file> and is processed by
6133 <prgn>cron</prgn> automatically. The file must also be
6134 treated as a configuration file. (Note that entries in the
6135 <file>/etc/cron.d</file> directory are not handled by
6136 <prgn>anacron</prgn>. Thus, you should only use this
6137 directory for jobs which may be skipped if the system is not
6141 The scripts or crontab entries in these directories should
6142 check if all necessary programs are installed before they
6143 try to execute them. Otherwise, problems will arise when a
6144 package was removed but not purged since configuration files
6145 are kept on the system in this situation.</p>
6149 <heading>Menus</heading>
6152 The Debian <tt>menu</tt> package provides a standard
6153 interface between packages providing applications and
6154 <em>menu programs</em> (either X window managers or
6155 text-based menu programs such as <prgn>pdmenu</prgn>).
6159 All packages that provide applications that need not be
6160 passed any special command line arguments for normal
6161 operation should register a menu entry for those
6162 applications, so that users of the <tt>menu</tt> package
6163 will automatically get menu entries in their window
6164 managers, as well in shells like <tt>pdmenu</tt>.
6168 Menu entries should follow the current menu policy.
6172 The menu policy can be found in the <tt>menu-policy</tt>
6173 files in the <tt>debian-policy</tt> package.
6174 It is also available from the Debian web mirrors at
6175 <tt><url name="/doc/packaging-manuals/menu-policy/"
6176 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6180 Please also refer to the <em>Debian Menu System</em>
6181 documentation that comes with the <package>menu</package>
6182 package for information about how to register your
6188 <heading>Multimedia handlers</heading>
6191 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6192 is a mechanism for encoding files and data streams and
6193 providing meta-information about them, in particular their
6194 type (e.g. audio or video) and format (e.g. PNG, HTML,
6199 Registration of MIME type handlers allows programs like mail
6200 user agents and web browsers to invoke these handlers to
6201 view, edit or display MIME types they don't support directly.
6205 Packages which provide the ability to view/show/play,
6206 compose, edit or print MIME types should register themselves
6207 as such following the current MIME support policy.
6211 The MIME support policy can be found in the <tt>mime-policy</tt>
6212 files in the <tt>debian-policy</tt> package.
6213 It is also available from the Debian web mirrors at
6214 <tt><url name="/doc/packaging-manuals/mime-policy/"
6215 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
6221 <heading>Keyboard configuration</heading>
6224 To achieve a consistent keyboard configuration so that all
6225 applications interpret a keyboard event the same way, all
6226 programs in the Debian distribution must be configured to
6227 comply with the following guidelines.
6231 The following keys must have the specified interpretations:
6234 <tag><tt><--</tt></tag>
6235 <item>delete the character to the left of the cursor</item>
6237 <tag><tt>Delete</tt></tag>
6238 <item>delete the character to the right of the cursor</item>
6240 <tag><tt>Control+H</tt></tag>
6241 <item>emacs: the help prefix</item>
6244 The interpretation of any keyboard events should be
6245 independent of the terminal that is used, be it a virtual
6246 console, an X terminal emulator, an rlogin/telnet session,
6251 The following list explains how the different programs
6252 should be set up to achieve this:
6258 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
6262 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
6266 X translations are set up to make
6267 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
6268 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
6269 is the vt220 escape code for the "delete character"
6270 key). This must be done by loading the X resources
6271 using <prgn>xrdb</prgn> on all local X displays, not
6272 using the application defaults, so that the
6273 translation resources used correspond to the
6274 <prgn>xmodmap</prgn> settings.
6278 The Linux console is configured to make
6279 <tt><--</tt> generate DEL, and <tt>Delete</tt>
6280 generate <tt>ESC [ 3 ~</tt>.
6284 X applications are configured so that <tt><</tt>
6285 deletes left, and <tt>Delete</tt> deletes right. Motif
6286 applications already work like this.
6290 Terminals should have <tt>stty erase ^?</tt> .
6294 The <tt>xterm</tt> terminfo entry should have <tt>ESC
6295 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
6296 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
6300 Emacs is programmed to map <tt>KB_Backspace</tt> or
6301 the <tt>stty erase</tt> character to
6302 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
6303 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
6304 <tt>^H</tt> to <tt>help</tt> as always.
6308 Other applications use the <tt>stty erase</tt>
6309 character and <tt>kdch1</tt> for the two delete keys,
6310 with ASCII DEL being "delete previous character" and
6311 <tt>kdch1</tt> being "delete character under
6319 This will solve the problem except for the following
6326 Some terminals have a <tt><--</tt> key that cannot
6327 be made to produce anything except <tt>^H</tt>. On
6328 these terminals Emacs help will be unavailable on
6329 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
6330 character takes precedence in Emacs, and has been set
6331 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
6332 available) can be used instead.
6336 Some operating systems use <tt>^H</tt> for <tt>stty
6337 erase</tt>. However, modern telnet versions and all
6338 rlogin versions propagate <tt>stty</tt> settings, and
6339 almost all UNIX versions honour <tt>stty erase</tt>.
6340 Where the <tt>stty</tt> settings are not propagated
6341 correctly, things can be made to work by using
6342 <tt>stty</tt> manually.
6346 Some systems (including previous Debian versions) use
6347 <prgn>xmodmap</prgn> to arrange for both
6348 <tt><--</tt> and <tt>Delete</tt> to generate
6349 <tt>KB_Delete</tt>. We can change the behavior of
6350 their X clients using the same X resources that we use
6351 to do it for our own clients, or configure our clients
6352 using their resources when things are the other way
6353 around. On displays configured like this
6354 <tt>Delete</tt> will not work, but <tt><--</tt>
6359 Some operating systems have different <tt>kdch1</tt>
6360 settings in their <tt>terminfo</tt> database for
6361 <tt>xterm</tt> and others. On these systems the
6362 <tt>Delete</tt> key will not work correctly when you
6363 log in from a system conforming to our policy, but
6364 <tt><--</tt> will.
6371 <heading>Environment variables</heading>
6374 A program must not depend on environment variables to get
6375 reasonable defaults. (That's because these environment
6376 variables would have to be set in a system-wide
6377 configuration file like <file>/etc/profile</file>, which is not
6378 supported by all shells.)
6382 If a program usually depends on environment variables for its
6383 configuration, the program should be changed to fall back to
6384 a reasonable default configuration if these environment
6385 variables are not present. If this cannot be done easily
6386 (e.g., if the source code of a non-free program is not
6387 available), the program must be replaced by a small
6388 "wrapper" shell script which sets the environment variables
6389 if they are not already defined, and calls the original program.
6393 Here is an example of a wrapper script for this purpose:
6395 <example compact="compact">
6397 BAR=${BAR:-/var/lib/fubar}
6399 exec /usr/lib/foo/foo "$@"
6404 Furthermore, as <file>/etc/profile</file> is a configuration
6405 file of the <prgn>base-files</prgn> package, other packages must
6406 not put any environment variables or other commands into that
6411 <sect id="doc-base">
6412 <heading>Registering Documents using doc-base</heading>
6415 The <package>doc-base</package> package implements a
6416 flexible mechanism for handling and presenting
6417 documentation. The recommended practice is for every Debian
6418 package that provides online documentation (other than just
6419 manual pages) to register these documents with
6420 <package>doc-base</package> by installing a
6421 <package>doc-base</package> control file via the
6422 <prgn/install-docs/ script at installation time and
6423 de-register the manuals again when the package is removed.
6426 Please refer to the documentation that comes with the
6427 <package>doc-base</package> package for information and
6436 <heading>Files</heading>
6439 <heading>Binaries</heading>
6442 Two different packages must not install programs with
6443 different functionality but with the same filenames. (The
6444 case of two programs having the same functionality but
6445 different implementations is handled via "alternatives" or
6446 the "Conflicts" mechanism. See <ref id="maintscripts"> and
6447 <ref id="conflicts"> respectively.) If this case happens,
6448 one of the programs must be renamed. The maintainers should
6449 report this to the <tt>debian-devel</tt> mailing list and
6450 try to find a consensus about which program will have to be
6451 renamed. If a consensus cannot be reached, <em>both</em>
6452 programs must be renamed.
6456 By default, when a package is being built, any binaries
6457 created should include debugging information, as well as
6458 being compiled with optimization. You should also turn on
6459 as many reasonable compilation warnings as possible; this
6460 makes life easier for porters, who can then look at build
6461 logs for possible problems. For the C programming language,
6462 this means the following compilation parameters should be
6464 <example compact="compact">
6466 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
6468 INSTALL = install -s # (or use strip on the files in debian/tmp)
6473 Note that by default all installed binaries should be stripped,
6474 either by using the <tt>-s</tt> flag to
6475 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
6476 the binaries after they have been copied into
6477 <file>debian/tmp</file> but before the tree is made into a
6482 Although binaries in the build tree should be compiled with
6483 debugging information by default, it can often be difficult
6484 to debug programs if they are also subjected to compiler
6485 optimization. For this reason, it is recommended to support
6486 the standardized environment
6487 variable <tt>DEB_BUILD_OPTIONS</tt>. This variable can
6488 contain several flags to change how a package is compiled
6496 The presence of this string means that the package
6497 should be compiled with a minimum of optimization.
6498 For C programs, it is best to add <tt>-O0</tt>
6499 to <tt>CFLAGS</tt> (although this is usually the
6500 default). Some programs might fail to build or run at
6501 this level of optimization; it may be necessary to
6502 use <tt>-O1</tt>, for example.
6506 This string means that the debugging symbols should
6507 not be stripped from the binary during installation,
6508 so that debugging information may be included in the package.
6514 The following makefile snippet is an example of how one may
6515 implement the build options; you will probably have to
6516 massage this example in order to make it work for your
6518 <example compact="compact">
6521 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
6522 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
6523 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
6524 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
6526 ifneq (,$(findstring noopt,$(DEB_BUILD_OPTIONS)))
6531 ifeq (,$(findstring nostrip,$(DEB_BUILD_OPTIONS)))
6532 INSTALL_PROGRAM += -s
6538 It is up to the package maintainer to decide what
6539 compilation options are best for the package. Certain
6540 binaries (such as computationally-intensive programs) will
6541 function better with certain flags (<tt>-O3</tt>, for
6542 example); feel free to use them. Please use good judgment
6543 here. Don't use flags for the sake of it; only use them
6544 if there is good reason to do so. Feel free to override
6545 the upstream author's ideas about which compilation
6546 options are best: they are often inappropriate for our
6552 <sect id="libraries">
6553 <heading>Libraries</heading>
6556 If the package is <strong>architecture: any</strong>, then
6557 the shared library compilation and linking flags must have
6558 <tt>-fPIC</tt>, or the package shall not build on some of
6559 the supported architectures<footnote>
6561 If you are using GCC, <tt>-fPIC</tt> produces code with
6562 relocatable position independent code, which is required for
6563 most architectures to create a shared library, with i386 and
6564 perhaps some others where non position independent code is
6565 permitted in a shared library.
6568 Position independent code may have a performance penalty,
6569 especially on <tt>i386</tt>. However, in most cases the
6570 speed penalty must be measured against the memory wasted on
6571 the few architectures where non position independent code is
6574 </footnote>. Any exception to this rule must be discussed on
6575 the mailing list <em>debian-devel@lists.debian.org</em>, and
6576 a rough consensus obtained. The reasons for not compiling
6577 with <tt>-fPIC</tt> flag must be recorded in the file
6578 <tt>README.Debian</tt>, and care must be taken to either
6579 restrict the architecture or arrange for <tt>-fPIC</tt> to
6580 be used on architectures where it is required.<footnote>
6582 Some of the reasons why this might be required is if the
6583 library contains hand crafted assembly code that is not
6584 relocatable, the speed penalty is excessive for compute
6585 intensive libs, and similar reasons.
6590 As to the static libraries, the common case is not to have
6591 relocatable code, since there is no benefit, unless in specific
6592 cases; therefore the static version must not be compiled
6593 with the <tt>-fPIC</tt> flag. Any exception to this rule
6594 should be discussed on the mailing list
6595 <em>debian-devel@lists.debian.org</em>, and the reasons for
6596 compiling with the <tt>-fPIC</tt> flag must be recorded in
6597 the file <tt>README.Debian</tt>. <footnote>
6599 Some of the reasons for linking static libraries with
6600 the <tt>-fPIC</tt> flag are if, for example, one needs a
6601 Perl API for a library that is under rapid development,
6602 and has an unstable API, so shared libraries are
6603 pointless at this phase of the library's development. In
6604 that case, since Perl needs a library with relocatable
6605 code, it may make sense to create a static library with
6606 relocatable code. Another reason cited is if you are
6607 distilling various libraries into a common shared
6608 library, like <tt>mklibs</tt> does in the Debian
6614 In other words, if both a shared and a static library is
6615 being built, each source unit (<tt>*.c</tt>, for example,
6616 for C files) will need to be compiled twice, for the normal
6620 You must specify the gcc option <tt>-D_REENTRANT</tt>
6621 when building a library (either static or shared) to make
6622 the library compatible with LinuxThreads.
6626 Although not enforced by the build tools, shared libraries
6627 must be linked against all libraries that they use symbols from
6628 in the same way that binaries are. This ensures the correct
6629 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
6630 system and guarantees that all libraries can be safely opened
6631 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
6632 option <tt>-Wl,-z,defs</tt> when building a shared library.
6633 Since this option enforces symbol resolution at build time,
6634 a missing library reference will be caught early as a fatal
6639 All installed shared libraries should be stripped with
6640 <example compact="compact">
6641 strip --strip-unneeded <var>your-lib</var>
6643 (The option <tt>--strip-unneeded</tt> makes
6644 <prgn>strip</prgn> remove only the symbols which aren't
6645 needed for relocation processing.) Shared libraries can
6646 function perfectly well when stripped, since the symbols for
6647 dynamic linking are in a separate part of the ELF object
6649 You might also want to use the options
6650 <tt>--remove-section=.comment</tt> and
6651 <tt>--remove-section=.note</tt> on both shared libraries
6652 and executables, and <tt>--strip-debug</tt> on static
6658 Note that under some circumstances it may be useful to
6659 install a shared library unstripped, for example when
6660 building a separate package to support debugging.
6664 Shared object files (often <file>.so</file> files) that are not
6665 public libraries, that is, they are not meant to be linked
6666 to by third party executables (binaries of other packages),
6667 should be installed in subdirectories of the
6668 <file>/usr/lib</file> directory. Such files are exempt from the
6669 rules that govern ordinary shared libraries, except that
6670 they must not be installed executable and should be
6672 A common example are the so-called "plug-ins",
6673 internal shared objects that are dynamically loaded by
6674 programs using <manref name="dlopen" section="3">.
6679 Packages containing shared libraries that may be linked to
6680 by other packages' binaries, but which for some
6681 <em>compelling</em> reason can not be installed in
6682 <file>/usr/lib</file> directory, may install the shared library
6683 files in subdirectories of the <file>/usr/lib</file> directory,
6684 in which case they should arrange to add that directory in
6685 <file>/etc/ld.so.conf</file> in the package's post-installation
6686 script, and remove it in the package's post-removal script.
6690 An ever increasing number of packages are using
6691 <prgn>libtool</prgn> to do their linking. The latest GNU
6692 libtools (>= 1.3a) can take advantage of the metadata in the
6693 installed <prgn>libtool</prgn> archive files (<file>*.la</file>
6694 files). The main advantage of <prgn>libtool</prgn>'s
6695 <file>.la</file> files is that it allows <prgn>libtool</prgn> to
6696 store and subsequently access metadata with respect to the
6697 libraries it builds. <prgn>libtool</prgn> will search for
6698 those files, which contain a lot of useful information about
6699 a library (such as library dependency information for static
6700 linking). Also, they're <em>essential</em> for programs
6701 using <tt>libltdl</tt>.<footnote>
6702 Although <prgn>libtool</prgn> is fully capable of
6703 linking against shared libraries which don't have
6704 <tt>.la</tt> files, as it is a mere shell script it can
6705 add considerably to the build time of a
6706 <prgn>libtool</prgn>-using package if that shell script
6707 has to derive all this information from first principles
6708 for each library every time it is linked. With the
6709 advent of <prgn>libtool</prgn> version 1.4 (and to a
6710 lesser extent <prgn>libtool</prgn> version 1.3), the
6711 <file>.la</file> files also store information about
6712 inter-library dependencies which cannot necessarily be
6713 derived after the <file>.la</file> file is deleted.
6718 Packages that use <prgn>libtool</prgn> to create shared
6719 libraries should include the <file>.la</file> files in the
6720 <tt>-dev</tt> package, unless the package relies on
6721 <tt>libtool</tt>'s <tt>libltdl</tt> library, in which case
6722 the <tt>.la</tt> files must go in the run-time library
6727 You must make sure that you use only released versions of
6728 shared libraries to build your packages; otherwise other
6729 users will not be able to run your binaries
6730 properly. Producing source packages that depend on
6731 unreleased compilers is also usually a bad
6738 <heading>Shared libraries</heading>
6740 This section has moved to <ref id="sharedlibs">.
6746 <heading>Scripts</heading>
6749 All command scripts, including the package maintainer
6750 scripts inside the package and used by <prgn>dpkg</prgn>,
6751 should have a <tt>#!</tt> line naming the shell to be used
6756 In the case of Perl scripts this should be
6757 <tt>#!/usr/bin/perl</tt>.
6761 When scripts are installed into a directory in the system
6762 PATH, the script name should not include an extension such
6763 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
6764 language currently used to implement it.
6767 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>)
6768 should almost certainly start with <tt>set -e</tt> so that
6769 errors are detected. Every script should use
6770 <tt>set -e</tt> or check the exit status of <em>every</em>
6775 Scripts may assume that <file>/bin/sh</file> implements the
6776 SUSv3 Shell Command Language<footnote>
6777 Single UNIX Specification, version 3, which is also IEEE
6778 1003.1-2004 (POSIX), and is available on the World Wide Web
6779 from <url id="http://www.unix.org/version3/online.html"
6780 name="The Open Group"> after free
6781 registration.</footnote>
6782 plus the following additional features not mandated by
6784 These features are in widespread use in the Linux community
6785 and are implemented in all of bash, dash, and ksh, the most
6786 common shells users may wish to use as <file>/bin/sh</file>.
6789 <item><tt>echo -n</tt>, if implemented as a shell built-in,
6790 must not generate a newline.</item>
6791 <item><tt>test</tt>, if implemented as a shell built-in, must
6792 support <tt>-a</tt> and <tt>-o</tt> as binary logical
6794 <item><tt>local</tt> to create a scoped variable must be
6795 supported; however, <tt>local</tt> may or may not preserve
6796 the variable value from an outer scope and may or may not
6797 support arguments more complex than simple variables. Only
6809 If a shell script requires non-SUSv3 features from the shell
6810 interpreter other than those listed above, the appropriate shell
6811 must be specified in the first line of the script (e.g.,
6812 <tt>#!/bin/bash</tt>) and the package must depend on the package
6813 providing the shell (unless the shell package is marked
6814 "Essential", as in the case of <prgn>bash</prgn>).
6818 You may wish to restrict your script to SUSv3 features plus the
6819 above set when possible so that it may use <file>/bin/sh</file>
6820 as its interpreter. If your script works with <prgn>dash</prgn>
6821 (originally called <prgn>ash</prgn>), it probably complies with
6822 the above requirements, but if you are in doubt, use
6823 <file>/bin/bash</file>.
6827 Perl scripts should check for errors when making any
6828 system calls, including <tt>open</tt>, <tt>print</tt>,
6829 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
6833 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
6834 scripting languages. See <em>Csh Programming Considered
6835 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
6836 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
6837 If an upstream package comes with <prgn>csh</prgn> scripts
6838 then you must make sure that they start with
6839 <tt>#!/bin/csh</tt> and make your package depend on the
6840 <prgn>c-shell</prgn> virtual package.
6844 Any scripts which create files in world-writeable
6845 directories (e.g., in <file>/tmp</file>) must use a
6846 mechanism which will fail atomically if a file with the same
6847 name already exists.
6851 The Debian base system provides the <prgn>tempfile</prgn>
6852 and <prgn>mktemp</prgn> utilities for use by scripts for
6859 <heading>Symbolic links</heading>
6862 In general, symbolic links within a top-level directory
6863 should be relative, and symbolic links pointing from one
6864 top-level directory into another should be absolute. (A
6865 top-level directory is a sub-directory of the root
6866 directory <file>/</file>.)
6870 In addition, symbolic links should be specified as short as
6871 possible, i.e., link targets like <file>foo/../bar</file> are
6876 Note that when creating a relative link using
6877 <prgn>ln</prgn> it is not necessary for the target of the
6878 link to exist relative to the working directory you're
6879 running <prgn>ln</prgn> from, nor is it necessary to change
6880 directory to the directory where the link is to be made.
6881 Simply include the string that should appear as the target
6882 of the link (this will be a pathname relative to the
6883 directory in which the link resides) as the first argument
6888 For example, in your <prgn>Makefile</prgn> or
6889 <file>debian/rules</file>, you can do things like:
6890 <example compact="compact">
6891 ln -fs gcc $(prefix)/bin/cc
6892 ln -fs gcc debian/tmp/usr/bin/cc
6893 ln -fs ../sbin/sendmail $(prefix)/bin/runq
6894 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
6899 A symbolic link pointing to a compressed file should always
6900 have the same file extension as the referenced file. (For
6901 example, if a file <file>foo.gz</file> is referenced by a
6902 symbolic link, the filename of the link has to end with
6903 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
6908 <heading>Device files</heading>
6911 Packages must not include device files in the package file
6916 If a package needs any special device files that are not
6917 included in the base system, it must call
6918 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
6919 after notifying the user<footnote>
6920 This notification could be done via a (low-priority)
6921 debconf message, or an echo (printf) statement.
6926 Packages must not remove any device files in the
6927 <prgn>postrm</prgn> or any other script. This is left to the
6928 system administrator.
6932 Debian uses the serial devices
6933 <file>/dev/ttyS*</file>. Programs using the old
6934 <file>/dev/cu*</file> devices should be changed to use
6935 <file>/dev/ttyS*</file>.
6939 <sect id="config-files">
6940 <heading>Configuration files</heading>
6943 <heading>Definitions</heading>
6947 <tag>configuration file</tag>
6949 A file that affects the operation of a program, or
6950 provides site- or host-specific information, or
6951 otherwise customizes the behavior of a program.
6952 Typically, configuration files are intended to be
6953 modified by the system administrator (if needed or
6954 desired) to conform to local policy or to provide
6955 more useful site-specific behavior.
6958 <tag><tt>conffile</tt></tag>
6960 A file listed in a package's <tt>conffiles</tt>
6961 file, and is treated specially by <prgn>dpkg</prgn>
6962 (see <ref id="configdetails">).
6968 The distinction between these two is important; they are
6969 not interchangeable concepts. Almost all
6970 <tt>conffile</tt>s are configuration files, but many
6971 configuration files are not <tt>conffiles</tt>.
6975 Note that a script that embeds configuration information
6976 (such as most of the files in <file>/etc/default</file> and
6977 <file>/etc/cron.{daily,weekly,monthly}</file>) is de-facto a
6978 configuration file and should be treated as such.
6983 <heading>Location</heading>
6986 Any configuration files created or used by your package
6987 must reside in <file>/etc</file>. If there are several,
6988 consider creating a subdirectory of <file>/etc</file>
6989 named after your package.
6993 If your package creates or uses configuration files
6994 outside of <file>/etc</file>, and it is not feasible to modify
6995 the package to use <file>/etc</file> directly, put the files
6996 in <file>/etc</file> and create symbolic links to those files
6997 from the location that the package requires.
7002 <heading>Behavior</heading>
7005 Configuration file handling must conform to the following
7007 <list compact="compact">
7009 local changes must be preserved during a package
7013 configuration files must be preserved when the
7014 package is removed, and only deleted when the
7021 The easy way to achieve this behavior is to make the
7022 configuration file a <tt>conffile</tt>. This is
7023 appropriate only if it is possible to distribute a default
7024 version that will work for most installations, although
7025 some system administrators may choose to modify it. This
7026 implies that the default version will be part of the
7027 package distribution, and must not be modified by the
7028 maintainer scripts during installation (or at any other
7033 In order to ensure that local changes are preserved
7034 correctly, no package may contain or make hard links to
7035 conffiles.<footnote>
7036 Rationale: There are two problems with hard links.
7037 The first is that some editors break the link while
7038 editing one of the files, so that the two files may
7039 unwittingly become unlinked and different. The second
7040 is that <prgn>dpkg</prgn> might break the hard link
7041 while upgrading <tt>conffile</tt>s.
7046 The other way to do it is via the maintainer scripts. In
7047 this case, the configuration file must not be listed as a
7048 <tt>conffile</tt> and must not be part of the package
7049 distribution. If the existence of a file is required for
7050 the package to be sensibly configured it is the
7051 responsibility of the package maintainer to provide
7052 maintainer scripts which correctly create, update and
7053 maintain the file and remove it on purge. (See <ref
7054 id="maintainerscripts"> for more information.) These
7055 scripts must be idempotent (i.e., must work correctly if
7056 <prgn>dpkg</prgn> needs to re-run them due to errors
7057 during installation or removal), must cope with all the
7058 variety of ways <prgn>dpkg</prgn> can call maintainer
7059 scripts, must not overwrite or otherwise mangle the user's
7060 configuration without asking, must not ask unnecessary
7061 questions (particularly during upgrades), and must
7062 otherwise be good citizens.
7066 The scripts are not required to configure every possible
7067 option for the package, but only those necessary to get
7068 the package running on a given system. Ideally the
7069 sysadmin should not have to do any configuration other
7070 than that done (semi-)automatically by the
7071 <prgn>postinst</prgn> script.
7075 A common practice is to create a script called
7076 <file><var>package</var>-configure</file> and have the
7077 package's <prgn>postinst</prgn> call it if and only if the
7078 configuration file does not already exist. In certain
7079 cases it is useful for there to be an example or template
7080 file which the maintainer scripts use. Such files should
7081 be in <file>/usr/share/<var>package</var></file> or
7082 <file>/usr/lib/<var>package</var></file> (depending on whether
7083 they are architecture-independent or not). There should
7084 be symbolic links to them from
7085 <file>/usr/share/doc/<var>package</var>/examples</file> if
7086 they are examples, and should be perfectly ordinary
7087 <prgn>dpkg</prgn>-handled files (<em>not</em>
7088 configuration files).
7092 These two styles of configuration file handling must
7093 not be mixed, for that way lies madness:
7094 <prgn>dpkg</prgn> will ask about overwriting the file
7095 every time the package is upgraded.
7100 <heading>Sharing configuration files</heading>
7103 Packages which specify the same file as a
7104 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7105 with each other. (This is an instance of the general rule
7106 about not sharing files. Note that neither alternatives
7107 nor diversions are likely to be appropriate in this case;
7108 in particular, <prgn>dpkg</prgn> does not handle diverted
7109 <tt>conffile</tt>s well.)
7113 The maintainer scripts must not alter a <tt>conffile</tt>
7114 of <em>any</em> package, including the one the scripts
7119 If two or more packages use the same configuration file
7120 and it is reasonable for both to be installed at the same
7121 time, one of these packages must be defined as
7122 <em>owner</em> of the configuration file, i.e., it will be
7123 the package which handles that file as a configuration
7124 file. Other packages that use the configuration file must
7125 depend on the owning package if they require the
7126 configuration file to operate. If the other package will
7127 use the configuration file if present, but is capable of
7128 operating without it, no dependency need be declared.
7132 If it is desirable for two or more related packages to
7133 share a configuration file <em>and</em> for all of the
7134 related packages to be able to modify that configuration
7135 file, then the following should be done:
7136 <enumlist compact="compact">
7138 One of the related packages (the "owning" package)
7139 will manage the configuration file with maintainer
7140 scripts as described in the previous section.
7143 The owning package should also provide a program
7144 that the other packages may use to modify the
7148 The related packages must use the provided program
7149 to make any desired modifications to the
7150 configuration file. They should either depend on
7151 the core package to guarantee that the configuration
7152 modifier program is available or accept gracefully
7153 that they cannot modify the configuration file if it
7154 is not. (This is in addition to the fact that the
7155 configuration file may not even be present in the
7162 Sometimes it's appropriate to create a new package which
7163 provides the basic infrastructure for the other packages
7164 and which manages the shared configuration files. (The
7165 <tt>sgml-base</tt> package is a good example.)
7170 <heading>User configuration files ("dotfiles")</heading>
7173 The files in <file>/etc/skel</file> will automatically be
7174 copied into new user accounts by <prgn>adduser</prgn>.
7175 No other program should reference the files in
7176 <file>/etc/skel</file>.
7180 Therefore, if a program needs a dotfile to exist in
7181 advance in <file>$HOME</file> to work sensibly, that dotfile
7182 should be installed in <file>/etc/skel</file> and treated as a
7187 However, programs that require dotfiles in order to
7188 operate sensibly are a bad thing, unless they do create
7189 the dotfiles themselves automatically.
7193 Furthermore, programs should be configured by the Debian
7194 default installation to behave as closely to the upstream
7195 default behavior as possible.
7199 Therefore, if a program in a Debian package needs to be
7200 configured in some way in order to operate sensibly, that
7201 should be done using a site-wide configuration file placed
7202 in <file>/etc</file>. Only if the program doesn't support a
7203 site-wide default configuration and the package maintainer
7204 doesn't have time to add it may a default per-user file be
7205 placed in <file>/etc/skel</file>.
7209 <file>/etc/skel</file> should be as empty as we can make it.
7210 This is particularly true because there is no easy (or
7211 necessarily desirable) mechanism for ensuring that the
7212 appropriate dotfiles are copied into the accounts of
7213 existing users when a package is installed.
7219 <heading>Log files</heading>
7221 Log files should usually be named
7222 <file>/var/log/<var>package</var>.log</file>. If you have many
7223 log files, or need a separate directory for permission
7224 reasons (<file>/var/log</file> is writable only by
7225 <file>root</file>), you should usually create a directory named
7226 <file>/var/log/<var>package</var></file> and place your log
7231 Log files must be rotated occasionally so that they don't
7232 grow indefinitely; the best way to do this is to drop a log
7233 rotation configuration file into the directory
7234 <file>/etc/logrotate.d</file> and use the facilities provided by
7235 logrotate.<footnote>
7237 The traditional approach to log files has been to set up
7238 <em>ad hoc</em> log rotation schemes using simple shell
7239 scripts and cron. While this approach is highly
7240 customizable, it requires quite a lot of sysadmin work.
7241 Even though the original Debian system helped a little
7242 by automatically installing a system which can be used
7243 as a template, this was deemed not enough.
7247 The use of <prgn>logrotate</prgn>, a program developed
7248 by Red Hat, is better, as it centralizes log management.
7249 It has both a configuration file
7250 (<file>/etc/logrotate.conf</file>) and a directory where
7251 packages can drop their individual log rotation
7252 configurations (<file>/etc/logrotate.d</file>).
7255 Here is a good example for a logrotate config
7256 file (for more information see <manref name="logrotate"
7258 <example compact="compact">
7259 /var/log/foo/*.log {
7264 /etc/init.d/foo force-reload
7268 This rotates all files under <file>/var/log/foo</file>, saves 12
7269 compressed generations, and forces the daemon to reload its
7270 configuration information after the log rotation.
7274 Log files should be removed when the package is
7275 purged (but not when it is only removed). This should be
7276 done by the <prgn>postrm</prgn> script when it is called
7277 with the argument <tt>purge</tt> (see <ref
7278 id="removedetails">).
7283 <heading>Permissions and owners</heading>
7286 The rules in this section are guidelines for general use.
7287 If necessary you may deviate from the details below.
7288 However, if you do so you must make sure that what is done
7289 is secure and you should try to be as consistent as possible
7290 with the rest of the system. You should probably also
7291 discuss it on <prgn>debian-devel</prgn> first.
7295 Files should be owned by <tt>root.root</tt>, and made
7296 writable only by the owner and universally readable (and
7297 executable, if appropriate), that is mode 644 or 755.
7301 Directories should be mode 755 or (for group-writability)
7302 mode 2775. The ownership of the directory should be
7303 consistent with its mode: if a directory is mode 2775, it
7304 should be owned by the group that needs write access to
7307 When a package is upgraded, and the owner or permissions
7308 of a file included in the package has changed, dpkg
7309 arranges for the ownership and permissions to be
7310 correctly set upon installation. However, this does not
7311 extend to directories; the permissions and ownership of
7312 directories already on the system does not change on
7313 install or upgrade of packages. This makes sense, since
7314 otherwise common directories like <tt>/usr</tt> would
7315 always be in flux. To correctly change permissions of a
7316 directory the package owns, explicit action is required,
7317 usually in the <tt>postinst</tt> script. Care must be
7318 taken to handle downgrades as well, in that case.
7325 Setuid and setgid executables should be mode 4755 or 2755
7326 respectively, and owned by the appropriate user or group.
7327 They should not be made unreadable (modes like 4711 or
7328 2711 or even 4111); doing so achieves no extra security,
7329 because anyone can find the binary in the freely available
7330 Debian package; it is merely inconvenient. For the same
7331 reason you should not restrict read or execute permissions
7332 on non-set-id executables.
7336 Some setuid programs need to be restricted to particular
7337 sets of users, using file permissions. In this case they
7338 should be owned by the uid to which they are set-id, and by
7339 the group which should be allowed to execute them. They
7340 should have mode 4754; again there is no point in making
7341 them unreadable to those users who must not be allowed to
7346 It is possible to arrange that the system administrator can
7347 reconfigure the package to correspond to their local
7348 security policy by changing the permissions on a binary:
7349 they can do this by using <prgn>dpkg-statoverride</prgn>, as
7350 described below.<footnote>
7351 Ordinary files installed by <prgn>dpkg</prgn> (as
7352 opposed to <tt>conffile</tt>s and other similar objects)
7353 normally have their permissions reset to the distributed
7354 permissions when the package is reinstalled. However,
7355 the use of <prgn>dpkg-statoverride</prgn> overrides this
7356 default behavior. If you use this method, you should
7357 remember to describe <prgn>dpkg-statoverride</prgn> in
7358 the package documentation; being a relatively new
7359 addition to Debian, it is probably not yet well-known.
7361 Another method you should consider is to create a group for
7362 people allowed to use the program(s) and make any setuid
7363 executables executable only by that group.
7367 If you need to create a new user or group for your package
7368 there are two possibilities. Firstly, you may need to
7369 make some files in the binary package be owned by this
7370 user or group, or you may need to compile the user or
7371 group id (rather than just the name) into the binary
7372 (though this latter should be avoided if possible, as in
7373 this case you need a statically allocated id).</p>
7376 If you need a statically allocated id, you must ask for a
7377 user or group id from the <tt>base-passwd</tt> maintainer,
7378 and must not release the package until you have been
7379 allocated one. Once you have been allocated one you must
7380 either make the package depend on a version of the
7381 <tt>base-passwd</tt> package with the id present in
7382 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
7383 your package to create the user or group itself with the
7384 correct id (using <tt>adduser</tt>) in its
7385 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
7386 the <prgn>postinst</prgn> is to be preferred if it is
7387 possible, otherwise a pre-dependency will be needed on the
7388 <tt>adduser</tt> package.)
7392 On the other hand, the program might be able to determine
7393 the uid or gid from the user or group name at runtime, so
7394 that a dynamically allocated id can be used. In this case
7395 you should choose an appropriate user or group name,
7396 discussing this on <prgn>debian-devel</prgn> and checking
7397 with the <package/base-passwd/ maintainer that it is unique and that
7398 they do not wish you to use a statically allocated id
7399 instead. When this has been checked you must arrange for
7400 your package to create the user or group if necessary using
7401 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
7402 <prgn>postinst</prgn> script (again, the latter is to be
7403 preferred if it is possible).
7407 Note that changing the numeric value of an id associated
7408 with a name is very difficult, and involves searching the
7409 file system for all appropriate files. You need to think
7410 carefully whether a static or dynamic id is required, since
7411 changing your mind later will cause problems.
7414 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
7416 This section is not intended as policy, but as a
7417 description of the use of <prgn>dpkg-statoverride</prgn>.
7421 <prgn>dpkg-statoverride</prgn> is a replacement for the
7422 deprecated <tt>suidmanager</tt> package. Packages which
7423 previously used <tt>suidmanager</tt> should have a
7424 <tt>Conflicts: suidmanager (<< 0.50)</tt> entry (or even
7425 <tt>(<< 0.52)</tt>), and calls to <tt>suidregister</tt>
7426 and <tt>suidunregister</tt> should now be simply removed
7427 from the maintainer scripts.
7431 If a system administrator wishes to have a file (or
7432 directory or other such thing) installed with owner and
7433 permissions different from those in the distributed Debian
7434 package, they can use the <prgn>dpkg-statoverride</prgn>
7435 program to instruct <prgn>dpkg</prgn> to use the different
7436 settings every time the file is installed. Thus the
7437 package maintainer should distribute the files with their
7438 normal permissions, and leave it for the system
7439 administrator to make any desired changes. For example, a
7440 daemon which is normally required to be setuid root, but
7441 in certain situations could be used without being setuid,
7442 should be installed setuid in the <tt>.deb</tt>. Then the
7443 local system administrator can change this if they wish.
7444 If there are two standard ways of doing it, the package
7445 maintainer can use <tt>debconf</tt> to find out the
7446 preference, and call <prgn>dpkg-statoverride</prgn> in the
7447 maintainer script if necessary to accommodate the system
7448 administrator's choice. Care must be taken during
7449 upgrades to not override an existing setting.
7453 Given the above, <prgn>dpkg-statoverride</prgn> is
7454 essentially a tool for system administrators and would not
7455 normally be needed in the maintainer scripts. There is
7456 one type of situation, though, where calls to
7457 <prgn>dpkg-statoverride</prgn> would be needed in the
7458 maintainer scripts, and that involves packages which use
7459 dynamically allocated user or group ids. In such a
7460 situation, something like the following idiom can be very
7461 helpful in the package's <prgn>postinst</prgn>, where
7462 <tt>sysuser</tt> is a dynamically allocated id:
7464 for i in /usr/bin/foo /usr/sbin/bar
7466 # only do something when no setting exists
7467 if ! dpkg-statoverride --list $i >/dev/null 2>&1
7469 #include: debconf processing, question about foo and bar
7470 if [ "$RET" = "true" ] ; then
7471 dpkg-statoverride --update --add sysuser root 4755 $i
7476 The corresponding <tt>dpkg-statoverride --remove</tt>
7477 calls can then be made unconditionally when the package is
7485 <chapt id="customized-programs">
7486 <heading>Customized programs</heading>
7488 <sect id="arch-spec">
7489 <heading>Architecture specification strings</heading>
7492 If a program needs to specify an <em>architecture specification
7493 string</em> in some place, it should select one of the
7494 strings provided by <tt>dpkg-architecture -L</tt>. The
7495 strings are in the format
7496 <tt><var>os</var>-<var>arch</var></tt>, though the OS part
7497 is sometimes elided, as when the OS is Linux.<footnote>
7498 <p>Currently, the strings are:
7499 i386 ia64 alpha amd64 armeb arm hppa m32r m68k mips
7500 mipsel powerpc ppc64 s390 s390x sh3 sh3eb sh4 sh4eb
7501 sparc darwin-i386 darwin-ia64 darwin-alpha darwin-amd64
7502 darwin-armeb darwin-arm darwin-hppa darwin-m32r
7503 darwin-m68k darwin-mips darwin-mipsel darwin-powerpc
7504 darwin-ppc64 darwin-s390 darwin-s390x darwin-sh3
7505 darwin-sh3eb darwin-sh4 darwin-sh4eb darwin-sparc
7506 freebsd-i386 freebsd-ia64 freebsd-alpha freebsd-amd64
7507 freebsd-armeb freebsd-arm freebsd-hppa freebsd-m32r
7508 freebsd-m68k freebsd-mips freebsd-mipsel freebsd-powerpc
7509 freebsd-ppc64 freebsd-s390 freebsd-s390x freebsd-sh3
7510 freebsd-sh3eb freebsd-sh4 freebsd-sh4eb freebsd-sparc
7511 kfreebsd-i386 kfreebsd-ia64 kfreebsd-alpha
7512 kfreebsd-amd64 kfreebsd-armeb kfreebsd-arm kfreebsd-hppa
7513 kfreebsd-m32r kfreebsd-m68k kfreebsd-mips
7514 kfreebsd-mipsel kfreebsd-powerpc kfreebsd-ppc64
7515 kfreebsd-s390 kfreebsd-s390x kfreebsd-sh3 kfreebsd-sh3eb
7516 kfreebsd-sh4 kfreebsd-sh4eb kfreebsd-sparc knetbsd-i386
7517 knetbsd-ia64 knetbsd-alpha knetbsd-amd64 knetbsd-armeb
7518 knetbsd-arm knetbsd-hppa knetbsd-m32r knetbsd-m68k
7519 knetbsd-mips knetbsd-mipsel knetbsd-powerpc
7520 knetbsd-ppc64 knetbsd-s390 knetbsd-s390x knetbsd-sh3
7521 knetbsd-sh3eb knetbsd-sh4 knetbsd-sh4eb knetbsd-sparc
7522 netbsd-i386 netbsd-ia64 netbsd-alpha netbsd-amd64
7523 netbsd-armeb netbsd-arm netbsd-hppa netbsd-m32r
7524 netbsd-m68k netbsd-mips netbsd-mipsel netbsd-powerpc
7525 netbsd-ppc64 netbsd-s390 netbsd-s390x netbsd-sh3
7526 netbsd-sh3eb netbsd-sh4 netbsd-sh4eb netbsd-sparc
7527 openbsd-i386 openbsd-ia64 openbsd-alpha openbsd-amd64
7528 openbsd-armeb openbsd-arm openbsd-hppa openbsd-m32r
7529 openbsd-m68k openbsd-mips openbsd-mipsel openbsd-powerpc
7530 openbsd-ppc64 openbsd-s390 openbsd-s390x openbsd-sh3
7531 openbsd-sh3eb openbsd-sh4 openbsd-sh4eb openbsd-sparc
7532 hurd-i386 hurd-ia64 hurd-alpha hurd-amd64 hurd-armeb
7533 hurd-arm hurd-hppa hurd-m32r hurd-m68k hurd-mips
7534 hurd-mipsel hurd-powerpc hurd-ppc64 hurd-s390 hurd-s390x
7535 hurd-sh3 hurd-sh3eb hurd-sh4 hurd-sh4eb hurd-sparc
7541 Note that we don't want to use
7542 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
7543 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
7544 since this would make our programs incompatible with other
7545 Linux distributions. We also don't use something like
7546 <tt><var>arch</var>-unknown-linux</tt>, since the
7547 <tt>unknown</tt> does not look very good.
7552 <heading>Daemons</heading>
7555 The configuration files <file>/etc/services</file>,
7556 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
7557 by the <prgn>netbase</prgn> package and must not be modified
7562 If a package requires a new entry in one of these files, the
7563 maintainer should get in contact with the
7564 <prgn>netbase</prgn> maintainer, who will add the entries
7565 and release a new version of the <prgn>netbase</prgn>
7570 The configuration file <file>/etc/inetd.conf</file> must not be
7571 modified by the package's scripts except via the
7572 <prgn>update-inetd</prgn> script or the
7573 <file>DebianNet.pm</file> Perl module. See their documentation
7574 for details on how to add entries.
7578 If a package wants to install an example entry into
7579 <file>/etc/inetd.conf</file>, the entry must be preceded with
7580 exactly one hash character (<tt>#</tt>). Such lines are
7581 treated as "commented out by user" by the
7582 <prgn>update-inetd</prgn> script and are not changed or
7583 activated during package updates.
7588 <heading>Using pseudo-ttys and modifying wtmp, utmp and
7592 Some programs need to create pseudo-ttys. This should be done
7593 using Unix98 ptys if the C library supports it. The resulting
7594 program must not be installed setuid root, unless that
7595 is required for other functionality.
7599 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
7600 <file>/var/log/lastlog</file> must be installed writable by
7601 group <tt>utmp</tt>. Programs which need to modify those
7602 files must be installed setgid <tt>utmp</tt>.
7607 <heading>Editors and pagers</heading>
7610 Some programs have the ability to launch an editor or pager
7611 program to edit or display a text document. Since there are
7612 lots of different editors and pagers available in the Debian
7613 distribution, the system administrator and each user should
7614 have the possibility to choose their preferred editor and
7619 In addition, every program should choose a good default
7620 editor/pager if none is selected by the user or system
7625 Thus, every program that launches an editor or pager must
7626 use the EDITOR or PAGER environment variable to determine
7627 the editor or pager the user wishes to use. If these
7628 variables are not set, the programs <file>/usr/bin/editor</file>
7629 and <file>/usr/bin/pager</file> should be used, respectively.
7633 These two files are managed through the <prgn>dpkg</prgn>
7634 "alternatives" mechanism. Thus every package providing an
7635 editor or pager must call the
7636 <prgn>update-alternatives</prgn> script to register these
7641 If it is very hard to adapt a program to make use of the
7642 EDITOR or PAGER variables, that program may be configured to
7643 use <file>/usr/bin/sensible-editor</file> and
7644 <file>/usr/bin/sensible-pager</file> as the editor or pager
7645 program respectively. These are two scripts provided in the
7646 Debian base system that check the EDITOR and PAGER variables
7647 and launch the appropriate program, and fall back to
7648 <file>/usr/bin/editor</file> and <file>/usr/bin/pager</file> if the
7649 variable is not set.
7653 A program may also use the VISUAL environment variable to
7654 determine the user's choice of editor. If it exists, it
7655 should take precedence over EDITOR. This is in fact what
7656 <file>/usr/bin/sensible-editor</file> does.
7660 It is not required for a package to depend on
7661 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
7662 package to provide such virtual packages.<footnote>
7663 The Debian base system already provides an editor and a
7669 <sect id="web-appl">
7670 <heading>Web servers and applications</heading>
7673 This section describes the locations and URLs that should
7674 be used by all web servers and web applications in the
7681 Cgi-bin executable files are installed in the
7683 <example compact="compact">
7684 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
7686 and should be referred to as
7687 <example compact="compact">
7688 http://localhost/cgi-bin/<var>cgi-bin-name</var>
7694 <p>Access to HTML documents</p>
7697 HTML documents for a package are stored in
7698 <file>/usr/share/doc/<var>package</var></file>
7699 and can be referred to as
7700 <example compact="compact">
7701 http://localhost/doc/<var>package</var>/<var>filename</var>
7706 The web server should restrict access to the document
7707 tree so that only clients on the same host can read
7708 the documents. If the web server does not support such
7709 access controls, then it should not provide access at
7710 all, or ask about providing access during installation.
7715 <p>Access to images</p>
7717 It is recommended that images for a package be stored
7718 in <tt>/usr/share/images/<var>package</var></tt> and
7719 may be referred to through an alias <tt>/images/</tt>
7722 http://localhost/images/<package>/<filename>
7729 <p>Web Document Root</p>
7732 Web Applications should try to avoid storing files in
7733 the Web Document Root. Instead they should use the
7734 /usr/share/doc/<var>package</var> directory for
7735 documents and register the Web Application via the
7736 <package>doc-base</package> package. If access to the
7737 web document root is unavoidable then use
7738 <example compact="compact">
7741 as the Document Root. This might be just a symbolic
7742 link to the location where the system administrator
7743 has put the real document root.
7746 <item><p>Providing httpd and/or httpd-cgi</p>
7748 All web servers should provide the virtual package
7749 <tt>httpd</tt>. If a web server has CGI support it should
7750 provide <tt>httpd-cgi</tt> additionally.
7753 All web applications which do not contain CGI scripts should
7754 depend on <tt>httpd</tt>, all those web applications which
7755 <tt>do</tt> contain CGI scripts, should depend on
7763 <sect id="mail-transport-agents">
7764 <heading>Mail transport, delivery and user agents</heading>
7767 Debian packages which process electronic mail, whether mail
7768 user agents (MUAs) or mail transport agents (MTAs), must
7769 ensure that they are compatible with the configuration
7770 decisions below. Failure to do this may result in lost
7771 mail, broken <tt>From:</tt> lines, and other serious brain
7776 The mail spool is <file>/var/mail</file> and the interface to
7777 send a mail message is <file>/usr/sbin/sendmail</file> (as per
7778 the FHS). On older systems, the mail spool may be
7779 physically located in <file>/var/spool/mail</file>, but all
7780 access to the mail spool should be via the
7781 <file>/var/mail</file> symlink. The mail spool is part of the
7782 base system and not part of the MTA package.
7786 All Debian MUAs, MTAs, MDAs and other mailbox accessing
7787 programs (such as IMAP daemons) must lock the mailbox in an
7788 NFS-safe way. This means that <tt>fcntl()</tt> locking must
7789 be combined with dot locking. To avoid deadlocks, a program
7790 should use <tt>fcntl()</tt> first and dot locking after
7791 this, or alternatively implement the two locking methods in
7792 a non blocking way<footnote>
7793 If it is not possible to establish both locks, the
7794 system shouldn't wait for the second lock to be
7795 established, but remove the first lock, wait a (random)
7796 time, and start over locking again.
7797 </footnote>. Using the functions <tt>maillock</tt> and
7798 <tt>mailunlock</tt> provided by the
7799 <tt>liblockfile*</tt><footnote>
7800 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
7801 to use these functions.
7802 </footnote> packages is the recommended way to realize this.
7806 Mailboxes are generally mode 660
7807 <tt><var>user</var>.mail</tt> unless the system
7808 administrator has chosen otherwise. A MUA may remove a
7809 mailbox (unless it has nonstandard permissions) in which
7810 case the MTA or another MUA must recreate it if needed.
7811 Mailboxes must be writable by group mail.
7815 The mail spool is 2775 <tt>root.mail</tt>, and MUAs should
7816 be setgid mail to do the locking mentioned above (and
7817 must obviously avoid accessing other users' mailboxes
7818 using this privilege).</p>
7821 <file>/etc/aliases</file> is the source file for the system mail
7822 aliases (e.g., postmaster, usenet, etc.), it is the one
7823 which the sysadmin and <prgn>postinst</prgn> scripts may
7824 edit. After <file>/etc/aliases</file> is edited the program or
7825 human editing it must call <prgn>newaliases</prgn>. All MTA
7826 packages must come with a <prgn>newaliases</prgn> program,
7827 even if it does nothing, but older MTA packages did not do
7828 this so programs should not fail if <prgn>newaliases</prgn>
7829 cannot be found. Note that because of this, all MTA
7830 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
7831 <tt>Replaces: mail-transport-agent</tt> control file
7836 The convention of writing <tt>forward to
7837 <var>address</var></tt> in the mailbox itself is not
7838 supported. Use a <tt>.forward</tt> file instead.</p>
7841 The <prgn>rmail</prgn> program used by UUCP
7842 for incoming mail should be <file>/usr/sbin/rmail</file>.
7843 Likewise, <prgn>rsmtp</prgn>, for receiving
7844 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
7848 If your package needs to know what hostname to use on (for
7849 example) outgoing news and mail messages which are generated
7850 locally, you should use the file <file>/etc/mailname</file>. It
7851 will contain the portion after the username and <tt>@</tt>
7852 (at) sign for email addresses of users on the machine
7853 (followed by a newline).
7857 Such a package should check for the existence of this file
7858 when it is being configured. If it exists, it should be
7859 used without comment, although an MTA's configuration script
7860 may wish to prompt the user even if it finds that this file
7861 exists. If the file does not exist, the package should
7862 prompt the user for the value (preferably using
7863 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
7864 as well as using it in the package's configuration. The
7865 prompt should make it clear that the name will not just be
7866 used by that package. For example, in this situation the
7867 <tt>inn</tt> package could say something like:
7868 <example compact="compact">
7869 Please enter the "mail name" of your system. This is the
7870 hostname portion of the address to be shown on outgoing
7871 news and mail messages. The default is
7872 <var>syshostname</var>, your system's host name. Mail
7873 name ["<var>syshostname</var>"]:
7875 where <var>syshostname</var> is the output of <tt>hostname
7881 <heading>News system configuration</heading>
7884 All the configuration files related to the NNTP (news)
7885 servers and clients should be located under
7886 <file>/etc/news</file>.</p>
7889 There are some configuration issues that apply to a number
7890 of news clients and server packages on the machine. These
7894 <tag><file>/etc/news/organization</file></tag>
7896 A string which should appear as the
7897 organization header for all messages posted
7898 by NNTP clients on the machine
7901 <tag><file>/etc/news/server</file></tag>
7903 Contains the FQDN of the upstream NNTP
7904 server, or localhost if the local machine is
7909 Other global files may be added as required for cross-package news
7916 <heading>Programs for the X Window System</heading>
7919 <heading>Providing X support and package priorities</heading>
7922 Programs that can be configured with support for the X
7923 Window System must be configured to do so and must declare
7924 any package dependencies necessary to satisfy their
7925 runtime requirements when using the X Window System. If
7926 such a package is of higher priority than the X packages
7927 on which it depends, it is required that either the
7928 X-specific components be split into a separate package, or
7929 that an alternative version of the package, which includes
7930 X support, be provided, or that the package's priority be
7936 <heading>Packages providing an X server</heading>
7939 Packages that provide an X server that, directly or
7940 indirectly, communicates with real input and display
7941 hardware should declare in their control data that they
7942 provide the virtual package <tt>xserver</tt>.<footnote>
7943 This implements current practice, and provides an
7944 actual policy for usage of the <tt>xserver</tt>
7945 virtual package which appears in the virtual packages
7946 list. In a nutshell, X servers that interface
7947 directly with the display and input hardware or via
7948 another subsystem (e.g., GGI) should provide
7949 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
7950 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
7956 <heading>Packages providing a terminal emulator</heading>
7959 Packages that provide a terminal emulator for the X Window
7960 System which meet the criteria listed below should declare
7961 in their control data that they provide the virtual
7962 package <tt>x-terminal-emulator</tt>. They should also
7963 register themselves as an alternative for
7964 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
7969 To be an <tt>x-terminal-emulator</tt>, a program must:
7970 <list compact="compact">
7972 Be able to emulate a DEC VT100 terminal, or a
7973 compatible terminal.
7977 Support the command-line option <tt>-e
7978 <var>command</var></tt>, which creates a new
7979 terminal window<footnote>
7980 "New terminal window" does not necessarily mean
7981 a new top-level X window directly parented by
7982 the window manager; it could, if the terminal
7983 emulator application were so coded, be a new
7984 "view" in a multiple-document interface (MDI).
7986 and runs the specified <var>command</var>,
7987 interpreting the entirety of the rest of the command
7988 line as a command to pass straight to exec, in the
7989 manner that <tt>xterm</tt> does.
7993 Support the command-line option <tt>-T
7994 <var>title</var></tt>, which creates a new terminal
7995 window with the window title <var>title</var>.
8002 <heading>Packages providing a window manager</heading>
8005 Packages that provide a window manager should declare in
8006 their control data that they provide the virtual package
8007 <tt>x-window-manager</tt>. They should also register
8008 themselves as an alternative for
8009 <file>/usr/bin/x-window-manager</file>, with a priority
8010 calculated as follows:
8011 <list compact="compact">
8013 Start with a priority of 20.
8017 If the window manager supports the Debian menu
8018 system, add 20 points if this support is available
8019 in the package's default configuration (i.e., no
8020 configuration files belonging to the system or user
8021 have to be edited to activate the feature); if
8022 configuration files must be modified, add only 10
8028 If the window manager complies with <url
8029 id="http://www.freedesktop.org/Standards/wm-spec"
8030 name="The Window Manager Specification Project">,
8031 written by the <url id="http://www.freedesktop.org/"
8032 name="Free Desktop Group">, add 40 points.
8036 If the window manager permits the X session to be
8037 restarted using a <em>different</em> window manager
8038 (without killing the X server) in its default
8039 configuration, add 10 points; otherwise add none.
8046 <heading>Packages providing fonts</heading>
8049 Packages that provide fonts for the X Window
8051 For the purposes of Debian Policy, a "font for the X
8052 Window System" is one which is accessed via X protocol
8053 requests. Fonts for the Linux console, for PostScript
8054 renderer, or any other purpose, do not fit this
8055 definition. Any tool which makes such fonts available
8056 to the X Window System, however, must abide by this
8059 must do a number of things to ensure that they are both
8060 available without modification of the X or font server
8061 configuration, and that they do not corrupt files used by
8062 other font packages to register information about
8066 Fonts of any type supported by the X Window System
8067 must be in a separate binary package from any
8068 executables, libraries, or documentation (except
8069 that specific to the fonts shipped, such as their
8070 license information). If one or more of the fonts
8071 so packaged are necessary for proper operation of
8072 the package with which they are associated the font
8073 package may be Recommended; if the fonts merely
8074 provide an enhancement, a Suggests relationship may
8075 be used. Packages must not Depend on font
8077 This is because the X server may retrieve fonts
8078 from the local file system or over the network
8079 from an X font server; the Debian package system
8080 is empowered to deal only with the local
8086 BDF fonts must be converted to PCF fonts with the
8087 <prgn>bdftopcf</prgn> utility (available in the
8088 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8089 placed in a directory that corresponds to their
8091 <list compact="compact">
8093 100 dpi fonts must be placed in
8094 <file>/usr/share/fonts/X11/100dpi/</file>.
8098 75 dpi fonts must be placed in
8099 <file>/usr/share/fonts/X11/75dpi/</file>.
8103 Character-cell fonts, cursor fonts, and other
8104 low-resolution fonts must be placed in
8105 <file>/usr/share/fonts/X11/misc/</file>.
8111 Speedo fonts must be placed in
8112 <file>/usr/share/fonts/X11/Speedo/</file>.
8116 Type 1 fonts must be placed in
8117 <file>/usr/share/fonts/X11/Type1/</file>. If font
8118 metric files are available, they must be placed here
8123 Subdirectories of <file>/usr/share/fonts/X11/</file>
8124 other than those listed above must be neither
8125 created nor used. (The <file>PEX</file>, <file>CID</file>,
8126 and <file>cyrillic</file> directories are excepted for
8127 historical reasons, but installation of files into
8128 these directories remains discouraged.)
8132 Font packages may, instead of placing files directly
8133 in the X font directories listed above, provide
8134 symbolic links in that font directory pointing to
8135 the files' actual location in the filesystem. Such
8136 a location must comply with the FHS.
8140 Font packages should not contain both 75dpi and
8141 100dpi versions of a font. If both are available,
8142 they should be provided in separate binary packages
8143 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8144 the names of the packages containing the
8145 corresponding fonts.
8149 Fonts destined for the <file>misc</file> subdirectory
8150 should not be included in the same package as 75dpi
8151 or 100dpi fonts; instead, they should be provided in
8152 a separate package with <tt>-misc</tt> appended to
8157 Font packages must not provide the files
8158 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8159 <file>fonts.scale</file> in a font directory:
8162 <file>fonts.dir</file> files must not be provided at all.
8166 <file>fonts.alias</file> and <file>fonts.scale</file>
8167 files, if needed, should be provided in the
8169 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8170 where <var>fontdir</var> is the name of the
8172 <file>/usr/share/fonts/X11/</file> where the
8173 package's corresponding fonts are stored
8174 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8175 <var>package</var> is the name of the package
8176 that provides these fonts, and
8177 <var>extension</var> is either <tt>scale</tt>
8178 or <tt>alias</tt>, whichever corresponds to
8185 Font packages must declare a dependency on
8186 <tt>xfonts-utils</tt> in their control
8191 Font packages that provide one or more
8192 <file>fonts.scale</file> files as described above must
8193 invoke <prgn>update-fonts-scale</prgn> on each
8194 directory into which they installed fonts
8195 <em>before</em> invoking
8196 <prgn>update-fonts-dir</prgn> on that directory.
8197 This invocation must occur in both the
8198 <prgn>postinst</prgn> (for all arguments) and
8199 <prgn>postrm</prgn> (for all arguments except
8200 <tt>upgrade</tt>) scripts.
8204 Font packages that provide one or more
8205 <file>fonts.alias</file> files as described above must
8206 invoke <prgn>update-fonts-alias</prgn> on each
8207 directory into which they installed fonts. This
8208 invocation must occur in both the
8209 <prgn>postinst</prgn> (for all arguments) and
8210 <prgn>postrm</prgn> (for all arguments except
8211 <tt>upgrade</tt>) scripts.
8215 Font packages must invoke
8216 <prgn>update-fonts-dir</prgn> on each directory into
8217 which they installed fonts. This invocation must
8218 occur in both the <prgn>postinst</prgn> (for all
8219 arguments) and <prgn>postrm</prgn> (for all
8220 arguments except <tt>upgrade</tt>) scripts.
8224 Font packages must not provide alias names for the
8225 fonts they include which collide with alias names
8226 already in use by fonts already packaged.
8230 Font packages must not provide fonts with the same
8231 XLFD registry name as another font already packaged.
8238 <heading>Application defaults files</heading>
8241 Application defaults files must be installed in the
8242 directory <file>/etc/X11/app-defaults/</file> (use of a
8243 localized subdirectory of <file>/etc/X11/</file> as described
8244 in the <em>X Toolkit Intrinsics - C Language
8245 Interface</em> manual is also permitted). They must be
8246 registered as <tt>conffile</tt>s or handled as
8247 configuration files. Packages must not provide the
8248 directory <file>/usr/X11R6/lib/X11/app-defaults/</file>.
8252 Customization of programs' X resources may also be
8253 supported with the provision of a file with the same name
8254 as that of the package placed in the
8255 <file>/etc/X11/Xresources/</file> directory, which must
8256 registered as a <tt>conffile</tt> or handled as a
8257 configuration file.<footnote>
8258 Note that this mechanism is not the same as using
8259 app-defaults; app-defaults are tied to the client
8260 binary on the local file system, whereas X resources
8261 are stored in the X server and affect all connecting
8264 <em>Important:</em> packages that install files into the
8265 <file>/etc/X11/Xresources/</file> directory must conflict with
8266 <tt>xbase (<< 3.3.2.3a-2)</tt>; if this is not done
8267 it is possible for the installing package to destroy a
8268 previously-existing <file>/etc/X11/Xresources</file> file
8269 which had been customized by the system administrator.
8274 <heading>Installation directory issues</heading>
8277 Packages using the X Window System should not be
8278 configured to install files under the
8279 <file>/usr/X11R6/</file> directory. The
8280 <file>/usr/X11R6/</file> directory hierarchy should be
8281 regarded as obsolete.
8285 Programs that use GNU <prgn>autoconf</prgn> and
8286 <prgn>automake</prgn> are usually easily configured at
8287 compile time to use <file>/usr/</file> instead of
8288 <file>/usr/X11R6/</file>, and this should be done whenever
8289 possible. Configuration files for window managers and
8290 display managers should be placed in a subdirectory of
8291 <file>/etc/X11/</file> corresponding to the package name due
8292 to these programs' tight integration with the mechanisms
8293 of the X Window System. Application-level programs should
8294 use the <file>/etc/</file> directory unless otherwise mandated
8299 The installation of files into subdirectories
8300 of <file>/usr/X11R6/include/X11/</file> and
8301 <file>/usr/X11R6/lib/X11/</file> is now prohibited;
8302 package maintainers should determine if subdirectories of
8303 <file>/usr/lib/</file> and <file>/usr/share/</file> can be used
8308 Packages should install any relevant files into the
8309 directories <file>/usr/include/X11/</file> and
8310 <file>/usr/lib/X11/</file>, but if they do so, they must
8311 pre-depend on <tt>x11-common (>=
8312 1:7.0.0)</tt><footnote>
8314 These libraries used to be all symbolic
8315 links. However, with <tt>X11R7</tt>,
8316 <tt>/usr/include/X11</tt> and <tt>/usr/lib/X11</tt>
8317 are now real directories, and packages
8318 <strong>should</strong> ship their files here instead
8319 of in <tt>/usr/X11R6/{include,lib}/X11</tt>.
8320 <tt>x11-common (>= 1:7.0.0) </tt> is the package
8321 responsible for converting these symlinks into
8329 <heading>The OSF/Motif and OpenMotif libraries</heading>
8332 <em>Programs that require the non-DFSG-compliant OSF/Motif or
8333 OpenMotif libraries</em><footnote>
8334 OSF/Motif and OpenMotif are collectively referred to as
8335 "Motif" in this policy document.
8337 should be compiled against and tested with LessTif (a free
8338 re-implementation of Motif) instead. If the maintainer
8339 judges that the program or programs do not work
8340 sufficiently well with LessTif to be distributed and
8341 supported, but do so when compiled against Motif, then two
8342 versions of the package should be created; one linked
8343 statically against Motif and with <tt>-smotif</tt>
8344 appended to the package name, and one linked dynamically
8345 against Motif and with <tt>-dmotif</tt> appended to the
8350 Both Motif-linked versions are dependent
8351 upon non-DFSG-compliant software and thus cannot be
8352 uploaded to the <em>main</em> distribution; if the
8353 software is itself DFSG-compliant it may be uploaded to
8354 the <em>contrib</em> distribution. While known existing
8355 versions of Motif permit unlimited redistribution of
8356 binaries linked against the library (whether statically or
8357 dynamically), it is the package maintainer's
8358 responsibility to determine whether this is permitted by
8359 the license of the copy of Motif in their possession.
8365 <heading>Perl programs and modules</heading>
8368 Perl programs and modules should follow the current Perl policy.
8372 The Perl policy can be found in the <tt>perl-policy</tt>
8373 files in the <tt>debian-policy</tt> package.
8374 It is also available from the Debian web mirrors at
8375 <tt><url name="/doc/packaging-manuals/perl-policy/"
8376 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
8381 <heading>Emacs lisp programs</heading>
8384 Please refer to the "Debian Emacs Policy" for details of how to
8385 package emacs lisp programs.
8389 The Emacs policy is available in
8390 <file>debian-emacs-policy.gz</file> of the
8391 <package>emacsen-common</package> package.
8392 It is also available from the Debian web mirrors at
8393 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
8394 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
8399 <heading>Games</heading>
8402 The permissions on <file>/var/games</file> are mode 755, owner
8403 <tt>root</tt> and group <tt>root</tt>.
8407 Each game decides on its own security policy.</p>
8410 Games which require protected, privileged access to
8411 high-score files, saved games, etc., may be made
8412 set-<em>group</em>-id (mode 2755) and owned by
8413 <tt>root.games</tt>, and use files and directories with
8414 appropriate permissions (770 <tt>root.games</tt>, for
8415 example). They must not be made
8416 set-<em>user</em>-id, as this causes security problems. (If
8417 an attacker can subvert any set-user-id game they can
8418 overwrite the executable of any other, causing other players
8419 of these games to run a Trojan horse program. With a
8420 set-group-id game the attacker only gets access to less
8421 important game data, and if they can get at the other
8422 players' accounts at all it will take considerably more
8426 Some packages, for example some fortune cookie programs, are
8427 configured by the upstream authors to install with their
8428 data files or other static information made unreadable so
8429 that they can only be accessed through set-id programs
8430 provided. You should not do this in a Debian package: anyone can
8431 download the <file>.deb</file> file and read the data from it,
8432 so there is no point making the files unreadable. Not
8433 making the files unreadable also means that you don't have
8434 to make so many programs set-id, which reduces the risk of a
8438 As described in the FHS, binaries of games should be
8439 installed in the directory <file>/usr/games</file>. This also
8440 applies to games that use the X Window System. Manual pages
8441 for games (X and non-X games) should be installed in
8442 <file>/usr/share/man/man6</file>.</p>
8448 <heading>Documentation</heading>
8451 <heading>Manual pages</heading>
8454 You should install manual pages in <prgn>nroff</prgn> source
8455 form, in appropriate places under <file>/usr/share/man</file>.
8456 You should only use sections 1 to 9 (see the FHS for more
8457 details). You must not install a pre-formatted "cat page".
8461 Each program, utility, and function should have an
8462 associated manual page included in the same package. It is
8463 suggested that all configuration files also have a manual
8464 page included as well. Manual pages for protocols and other
8465 auxiliary things are optional.
8469 If no manual page is available, this is considered as a bug
8470 and should be reported to the Debian Bug Tracking System (the
8471 maintainer of the package is allowed to write this bug report
8472 themselves, if they so desire). Do not close the bug report
8473 until a proper man page is available.<footnote>
8474 It is not very hard to write a man page. See the
8475 <url id="http://www.schweikhardt.net/man_page_howto.html"
8476 name="Man-Page-HOWTO">,
8477 <manref name="man" section="7">, the examples
8478 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
8479 the helper programs <prgn>help2man</prgn>, or the
8480 directory <file>/usr/share/doc/man-db/examples</file>.
8485 You may forward a complaint about a missing man page to the
8486 upstream authors, and mark the bug as forwarded in the
8487 Debian bug tracking system. Even though the GNU Project do
8488 not in general consider the lack of a man page to be a bug,
8489 we do; if they tell you that they don't consider it a bug
8490 you should leave the bug in our bug tracking system open
8495 Manual pages should be installed compressed using <tt>gzip -9</tt>.
8499 If one man page needs to be accessible via several names it
8500 is better to use a symbolic link than the <file>.so</file>
8501 feature, but there is no need to fiddle with the relevant
8502 parts of the upstream source to change from <file>.so</file> to
8503 symlinks: don't do it unless it's easy. You should not
8504 create hard links in the manual page directories, nor put
8505 absolute filenames in <file>.so</file> directives. The filename
8506 in a <file>.so</file> in a man page should be relative to the
8507 base of the man page tree (usually
8508 <file>/usr/share/man</file>). If you do not create any links
8509 (whether symlinks, hard links, or <tt>.so</tt> directives)
8510 in the file system to the alternate names of the man page,
8511 then you should not rely on <prgn>man</prgn> finding your
8512 man page under those names based solely on the information in
8513 the man page's header.<footnote>
8514 Supporting this in <prgn>man</prgn> often requires
8515 unreasonable processing time to find a manual page or to
8516 report that none exists, and moves knowledge into man's
8517 database that would be better left in the file system.
8518 This support is therefore deprecated and will cease to
8519 be present in the future.
8525 <heading>Info documents</heading>
8528 Info documents should be installed in <file>/usr/share/info</file>.
8529 They should be compressed with <tt>gzip -9</tt>.
8533 Your package should call <prgn>install-info</prgn> to update
8534 the Info <file>dir</file> file in its <prgn>postinst</prgn>
8535 script when called with a <tt>configure</tt> argument, for
8537 <example compact="compact">
8538 install-info --quiet --section Development Development \
8539 /usr/share/info/foobar.info
8543 It is a good idea to specify a section for the location of
8544 your program; this is done with the <tt>--section</tt>
8545 switch. To determine which section to use, you should look
8546 at <file>/usr/share/info/dir</file> on your system and choose the most
8547 relevant (or create a new section if none of the current
8548 sections are relevant). Note that the <tt>--section</tt>
8549 flag takes two arguments; the first is a regular expression
8550 to match (case-insensitively) against an existing section,
8551 the second is used when creating a new one.</p>
8554 You should remove the entries in the <prgn>prerm</prgn>
8555 script when called with a <tt>remove</tt> argument:
8556 <example compact="compact">
8557 install-info --quiet --remove /usr/share/info/foobar.info
8561 If <prgn>install-info</prgn> cannot find a description entry
8562 in the Info file you must supply one. See <manref
8563 name="install-info" section="8"> for details.</p>
8567 <heading>Additional documentation</heading>
8570 Any additional documentation that comes with the package may
8571 be installed at the discretion of the package maintainer.
8572 Plain text documentation should be installed in the directory
8573 <file>/usr/share/doc/<var>package</var></file>, where
8574 <var>package</var> is the name of the package, and
8575 compressed with <tt>gzip -9</tt> unless it is small.
8579 If a package comes with large amounts of documentation which
8580 many users of the package will not require you should create
8581 a separate binary package to contain it, so that it does not
8582 take up disk space on the machines of users who do not need
8583 or want it installed.</p>
8586 It is often a good idea to put text information files
8587 (<file>README</file>s, changelogs, and so forth) that come with
8588 the source package in <file>/usr/share/doc/<var>package</var></file>
8589 in the binary package. However, you don't need to install
8590 the instructions for building and installing the package, of
8594 Packages must not require the existence of any files in
8595 <file>/usr/share/doc/</file> in order to function
8597 The system administrator should be able to
8598 delete files in <file>/usr/share/doc/</file> without causing
8599 any programs to break.
8601 Any files that are referenced by programs but are also
8602 useful as stand alone documentation should be installed under
8603 <file>/usr/share/<var>package</var>/</file> with symbolic links from
8604 <file>/usr/share/doc/<var>package</var></file>.
8608 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8609 link to another directory in <file>/usr/share/doc</file> only if
8610 the two packages both come from the same source and the
8611 first package Depends on the second.<footnote>
8613 Please note that this does not override the section on
8614 changelog files below, so the file
8615 <file>/usr/share/<var>package</var>/changelog.Debian.gz</file>
8616 must refer to the changelog for the current version of
8617 <var>package</var> in question. In practice, this means
8618 that the sources of the target and the destination of the
8619 symlink must be the same (same source package and
8626 Former Debian releases placed all additional documentation
8627 in <file>/usr/doc/<var>package</var></file>. This has been
8628 changed to <file>/usr/share/doc/<var>package</var></file>,
8629 and packages must not put documentation in the directory
8630 <file>/usr/doc/<var>package</var></file>. <footnote>
8631 At this phase of the transition, we no longer require a
8632 symbolic link in <file>/usr/doc/</file>. At a later point,
8633 policy shall change to make the symbolic links a bug.
8639 <heading>Preferred documentation formats</heading>
8642 The unification of Debian documentation is being carried out
8646 If your package comes with extensive documentation in a
8647 markup format that can be converted to various other formats
8648 you should if possible ship HTML versions in a binary
8649 package, in the directory
8650 <file>/usr/share/doc/<var>appropriate-package</var></file> or
8651 its subdirectories.<footnote>
8652 The rationale: The important thing here is that HTML
8653 docs should be available in <em>some</em> package, not
8654 necessarily in the main binary package.
8659 Other formats such as PostScript may be provided at the
8660 package maintainer's discretion.
8664 <sect id="copyrightfile">
8665 <heading>Copyright information</heading>
8668 Every package must be accompanied by a verbatim copy of its
8669 copyright and distribution license in the file
8670 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
8671 file must neither be compressed nor be a symbolic link.
8675 In addition, the copyright file must say where the upstream
8676 sources (if any) were obtained. It should name the original
8677 authors of the package and the Debian maintainer(s) who were
8678 involved with its creation.</p>
8681 A copy of the file which will be installed in
8682 <file>/usr/share/doc/<var>package</var>/copyright</file> should
8683 be in <file>debian/copyright</file> in the source package.
8687 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8688 link to another directory in <file>/usr/share/doc</file> only if
8689 the two packages both come from the same source and the
8690 first package Depends on the second. These rules are
8691 important because copyrights must be extractable by
8696 Packages distributed under the UCB BSD license, the Artistic
8697 license, the GNU GPL (version 2 or 3), the GNU LGPL (versions
8698 2, 2.1, or 3), and the GNU FDL (version 1.2) should refer to
8699 the corresponding files under
8700 <file>/usr/share/common-licenses</file>,<footnote>
8703 <file>/usr/share/common-licenses/BSD</file>,
8704 <file>/usr/share/common-licenses/Artistic</file>,
8705 <file>/usr/share/common-licenses/GPL-2</file>,
8706 <file>/usr/share/common-licenses/GPL-3</file>,
8707 <file>/usr/share/common-licenses/LGPL-2</file>,
8708 <file>/usr/share/common-licenses/LGPL-2.1</file>,
8709 <file>/usr/share/common-licenses/LGPL-3</file>, and
8710 <file>/usr/share/common-licenses/GFDL-1.2</file>,
8713 </footnote> rather than quoting them in the copyright
8718 You should not use the copyright file as a general <file>README</file>
8719 file. If your package has such a file it should be
8720 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
8721 <file>README.Debian</file> or some other appropriate place.</p>
8725 <heading>Examples</heading>
8728 Any examples (configurations, source files, whatever),
8729 should be installed in a directory
8730 <file>/usr/share/doc/<var>package</var>/examples</file>. These
8731 files should not be referenced by any program: they're there
8732 for the benefit of the system administrator and users as
8733 documentation only. Architecture-specific example files
8734 should be installed in a directory
8735 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
8737 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
8738 latter directory itself may be a symbolic link to the
8743 If the purpose of a package is to provide examples, then the
8744 example files may be installed into
8745 <file>/usr/share/doc/<var>package</var></file>.
8749 <sect id="changelogs">
8750 <heading>Changelog files</heading>
8753 Packages that are not Debian-native must contain a
8754 compressed copy of the <file>debian/changelog</file> file from
8755 the Debian source tree in
8756 <file>/usr/share/doc/<var>package</var></file> with the name
8757 <file>changelog.Debian.gz</file>.
8761 If an upstream changelog is available, it should be accessible as
8762 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
8763 plain text. If the upstream changelog is distributed in
8764 HTML, it should be made available in that form as
8765 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
8766 and a plain text <file>changelog.gz</file> should be generated
8767 from it using, for example, <tt>lynx -dump -nolist</tt>. If
8768 the upstream changelog files do not already conform to this
8769 naming convention, then this may be achieved either by
8770 renaming the files, or by adding a symbolic link, at the
8771 maintainer's discretion.<footnote>
8772 Rationale: People should not have to look in places for
8773 upstream changelogs merely because they are given
8774 different names or are distributed in HTML format.
8779 All of these files should be installed compressed using
8780 <tt>gzip -9</tt>, as they will become large with time even
8781 if they start out small.
8785 If the package has only one changelog which is used both as
8786 the Debian changelog and the upstream one because there is
8787 no separate upstream maintainer then that changelog should
8788 usually be installed as
8789 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
8790 there is a separate upstream maintainer, but no upstream
8791 changelog, then the Debian changelog should still be called
8792 <file>changelog.Debian.gz</file>.
8796 For details about the format and contents of the Debian
8797 changelog file, please see <ref id="dpkgchangelog">.
8802 <appendix id="pkg-scope">
8803 <heading>Introduction and scope of these appendices</heading>
8806 These appendices are taken essentially verbatim from the
8807 now-deprecated Packaging Manual, version 3.2.1.0. They are
8808 the chapters which are likely to be of use to package
8809 maintainers and which have not already been included in the
8810 policy document itself. Most of these sections are very likely
8811 not relevant to policy; they should be treated as
8812 documentation for the packaging system. Please note that these
8813 appendices are included for convenience, and for historical
8814 reasons: they used to be part of policy package, and they have
8815 not yet been incorporated into dpkg documentation. However,
8816 they still have value, and hence they are presented here.
8820 They have not yet been checked to ensure that they are
8821 compatible with the contents of policy, and if there are any
8822 contradictions, the version in the main policy document takes
8823 precedence. The remaining chapters of the old Packaging
8824 Manual have also not been read in detail to ensure that there
8825 are not parts which have been left out. Both of these will be
8830 Certain parts of the Packaging manual were integrated into the
8831 Policy Manual proper, and removed from the appendices. Links
8832 have been placed from the old locations to the new ones.
8836 <prgn>dpkg</prgn> is a suite of programs for creating binary
8837 package files and installing and removing them on Unix
8839 <prgn>dpkg</prgn> is targeted primarily at Debian
8840 GNU/Linux, but may work on or be ported to other
8846 The binary packages are designed for the management of
8847 installed executable programs (usually compiled binaries) and
8848 their associated data, though source code examples and
8849 documentation are provided as part of some packages.</p>
8852 This manual describes the technical aspects of creating Debian
8853 binary packages (<file>.deb</file> files). It documents the
8854 behavior of the package management programs
8855 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
8856 they interact with packages.</p>
8859 It also documents the interaction between
8860 <prgn>dselect</prgn>'s core and the access method scripts it
8861 uses to actually install the selected packages, and describes
8862 how to create a new access method.</p>
8865 This manual does not go into detail about the options and
8866 usage of the package building and installation tools. It
8867 should therefore be read in conjunction with those programs'
8872 The utility programs which are provided with <prgn>dpkg</prgn>
8873 for managing various system configuration and similar issues,
8874 such as <prgn>update-rc.d</prgn> and
8875 <prgn>install-info</prgn>, are not described in detail here -
8876 please see their man pages.
8880 It is assumed that the reader is reasonably familiar with the
8881 <prgn>dpkg</prgn> System Administrators' manual.
8882 Unfortunately this manual does not yet exist.
8886 The Debian version of the FSF's GNU hello program is provided
8887 as an example for people wishing to create Debian
8888 packages. The Debian <prgn>debmake</prgn> package is
8889 recommended as a very helpful tool in creating and maintaining
8890 Debian packages. However, while the tools and examples are
8891 helpful, they do not replace the need to read and follow the
8892 Policy and Programmer's Manual.</p>
8895 <appendix id="pkg-binarypkg">
8896 <heading>Binary packages (from old Packaging Manual)</heading>
8899 The binary package has two main sections. The first part
8900 consists of various control information files and scripts used
8901 by <prgn>dpkg</prgn> when installing and removing. See <ref
8902 id="pkg-controlarea">.
8906 The second part is an archive containing the files and
8907 directories to be installed.
8911 In the future binary packages may also contain other
8912 components, such as checksums and digital signatures. The
8913 format for the archive is described in full in the
8914 <file>deb(5)</file> man page.
8918 <sect id="pkg-bincreating"><heading>Creating package files -
8919 <prgn>dpkg-deb</prgn>
8923 All manipulation of binary package files is done by
8924 <prgn>dpkg-deb</prgn>; it's the only program that has
8925 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
8926 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
8927 will spot that the options requested are appropriate to
8928 <prgn>dpkg-deb</prgn> and invoke that instead with the same
8933 In order to create a binary package you must make a
8934 directory tree which contains all the files and directories
8935 you want to have in the file system data part of the package.
8936 In Debian-format source packages this directory is usually
8937 <file>debian/tmp</file>, relative to the top of the package's
8942 They should have the locations (relative to the root of the
8943 directory tree you're constructing) ownerships and
8944 permissions which you want them to have on the system when
8949 With current versions of <prgn>dpkg</prgn> the uid/username
8950 and gid/groupname mappings for the users and groups being
8951 used should be the same on the system where the package is
8952 built and the one where it is installed.
8956 You need to add one special directory to the root of the
8957 miniature file system tree you're creating:
8958 <prgn>DEBIAN</prgn>. It should contain the control
8959 information files, notably the binary package control file
8960 (see <ref id="pkg-controlfile">).
8964 The <prgn>DEBIAN</prgn> directory will not appear in the
8965 file system archive of the package, and so won't be installed
8966 by <prgn>dpkg</prgn> when the package is installed.
8970 When you've prepared the package, you should invoke:
8972 dpkg --build <var>directory</var>
8977 This will build the package in
8978 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
8979 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
8980 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
8985 See the man page <manref name="dpkg-deb" section="8"> for details of how
8986 to examine the contents of this newly-created file. You may find the
8987 output of following commands enlightening:
8989 dpkg-deb --info <var>filename</var>.deb
8990 dpkg-deb --contents <var>filename</var>.deb
8991 dpkg --contents <var>filename</var>.deb
8993 To view the copyright file for a package you could use this command:
8995 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - \*/copyright | pager
9000 <sect id="pkg-controlarea">
9001 <heading>Package control information files</heading>
9004 The control information portion of a binary package is a
9005 collection of files with names known to <prgn>dpkg</prgn>.
9006 It will treat the contents of these files specially - some
9007 of them contain information used by <prgn>dpkg</prgn> when
9008 installing or removing the package; others are scripts which
9009 the package maintainer wants <prgn>dpkg</prgn> to run.
9013 It is possible to put other files in the package control
9014 area, but this is not generally a good idea (though they
9015 will largely be ignored).
9019 Here is a brief list of the control info files supported by
9020 <prgn>dpkg</prgn> and a summary of what they're used for.
9025 <tag><tt>control</tt>
9028 This is the key description file used by
9029 <prgn>dpkg</prgn>. It specifies the package's name
9030 and version, gives its description for the user,
9031 states its relationships with other packages, and so
9032 forth. See <ref id="sourcecontrolfiles"> and
9033 <ref id="binarycontrolfiles">.
9037 It is usually generated automatically from information
9038 in the source package by the
9039 <prgn>dpkg-gencontrol</prgn> program, and with
9040 assistance from <prgn>dpkg-shlibdeps</prgn>.
9041 See <ref id="pkg-sourcetools">.
9045 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9050 These are executable files (usually scripts) which
9051 <prgn>dpkg</prgn> runs during installation, upgrade
9052 and removal of packages. They allow the package to
9053 deal with matters which are particular to that package
9054 or require more complicated processing than that
9055 provided by <prgn>dpkg</prgn>. Details of when and
9056 how they are called are in <ref id="maintainerscripts">.
9060 It is very important to make these scripts idempotent.
9061 See <ref id="idempotency">.
9065 The maintainer scripts are guaranteed to run with a
9066 controlling terminal and can interact with the user.
9067 See <ref id="controllingterminal">.
9071 <tag><tt>conffiles</tt>
9074 This file contains a list of configuration files which
9075 are to be handled automatically by <prgn>dpkg</prgn>
9076 (see <ref id="pkg-conffiles">). Note that not necessarily
9077 every configuration file should be listed here.
9080 <tag><tt>shlibs</tt>
9083 This file contains a list of the shared libraries
9084 supplied by the package, with dependency details for
9085 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9086 when it determines what dependencies are required in a
9087 package control file. The <tt>shlibs</tt> file format
9088 is described on <ref id="shlibs">.
9093 <sect id="pkg-controlfile">
9094 <heading>The main control information file: <tt>control</tt></heading>
9097 The most important control information file used by
9098 <prgn>dpkg</prgn> when it installs a package is
9099 <tt>control</tt>. It contains all the package's "vital
9104 The binary package control files of packages built from
9105 Debian sources are made by a special tool,
9106 <prgn>dpkg-gencontrol</prgn>, which reads
9107 <file>debian/control</file> and <file>debian/changelog</file> to
9108 find the information it needs. See <ref id="pkg-sourcepkg"> for
9113 The fields in binary package control files are listed in
9114 <ref id="binarycontrolfiles">.
9118 A description of the syntax of control files and the purpose
9119 of the fields is available in <ref id="controlfields">.
9124 <heading>Time Stamps</heading>
9127 See <ref id="timestamps">.
9132 <appendix id="pkg-sourcepkg">
9133 <heading>Source packages (from old Packaging Manual) </heading>
9136 The Debian binary packages in the distribution are generated
9137 from Debian sources, which are in a special format to assist
9138 the easy and automatic building of binaries.
9141 <sect id="pkg-sourcetools">
9142 <heading>Tools for processing source packages</heading>
9145 Various tools are provided for manipulating source packages;
9146 they pack and unpack sources and help build of binary
9147 packages and help manage the distribution of new versions.
9151 They are introduced and typical uses described here; see
9152 <manref name="dpkg-source" section="1"> for full
9153 documentation about their arguments and operation.
9157 For examples of how to construct a Debian source package,
9158 and how to use those utilities that are used by Debian
9159 source packages, please see the <prgn>hello</prgn> example
9163 <sect1 id="pkg-dpkg-source">
9165 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9170 This program is frequently used by hand, and is also
9171 called from package-independent automated building scripts
9172 such as <prgn>dpkg-buildpackage</prgn>.
9176 To unpack a package it is typically invoked with
9178 dpkg-source -x <var>.../path/to/filename</var>.dsc
9183 with the <file><var>filename</var>.tar.gz</file> and
9184 <file><var>filename</var>.diff.gz</file> (if applicable) in
9185 the same directory. It unpacks into
9186 <file><var>package</var>-<var>version</var></file>, and if
9188 <file><var>package</var>-<var>version</var>.orig</file>, in
9189 the current directory.
9193 To create a packed source archive it is typically invoked:
9195 dpkg-source -b <var>package</var>-<var>version</var>
9200 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
9201 <file>.diff.gz</file> (if appropriate) in the current
9202 directory. <prgn>dpkg-source</prgn> does not clean the
9203 source tree first - this must be done separately if it is
9208 See also <ref id="pkg-sourcearchives">.</p>
9212 <sect1 id="pkg-dpkg-buildpackage">
9214 <prgn>dpkg-buildpackage</prgn> - overall package-building
9219 <prgn>dpkg-buildpackage</prgn> is a script which invokes
9220 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
9221 targets <tt>clean</tt>, <tt>build</tt> and
9222 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
9223 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
9224 source and binary package upload.
9228 It is usually invoked by hand from the top level of the
9229 built or unbuilt source directory. It may be invoked with
9230 no arguments; useful arguments include:
9231 <taglist compact="compact">
9232 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
9235 Do not sign the <tt>.changes</tt> file or the
9236 source package <tt>.dsc</tt> file, respectively.</p>
9238 <tag><tt>-p<var>sign-command</var></tt></tag>
9241 Invoke <var>sign-command</var> instead of finding
9242 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
9243 <var>sign-command</var> must behave just like
9244 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
9246 <tag><tt>-r<var>root-command</var></tt></tag>
9249 When root privilege is required, invoke the command
9250 <var>root-command</var>. <var>root-command</var>
9251 should invoke its first argument as a command, from
9252 the <prgn>PATH</prgn> if necessary, and pass its
9253 second and subsequent arguments to the command it
9254 calls. If no <var>root-command</var> is supplied
9255 then <var>dpkg-buildpackage</var> will take no
9256 special action to gain root privilege, so that for
9257 most packages it will have to be invoked as root to
9260 <tag><tt>-b</tt>, <tt>-B</tt></tag>
9263 Two types of binary-only build and upload - see
9264 <manref name="dpkg-source" section="1">.
9271 <sect1 id="pkg-dpkg-gencontrol">
9273 <prgn>dpkg-gencontrol</prgn> - generates binary package
9278 This program is usually called from <file>debian/rules</file>
9279 (see <ref id="pkg-sourcetree">) in the top level of the source
9284 This is usually done just before the files and directories in the
9285 temporary directory tree where the package is being built have their
9286 permissions and ownerships set and the package is constructed using
9287 <prgn>dpkg-deb/</prgn>
9289 This is so that the control file which is produced has
9290 the right permissions
9295 <prgn>dpkg-gencontrol</prgn> must be called after all the
9296 files which are to go into the package have been placed in
9297 the temporary build directory, so that its calculation of
9298 the installed size of a package is correct.
9302 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
9303 be run after <prgn>dpkg-shlibdeps</prgn> so that the
9304 variable substitutions created by
9305 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
9310 For a package which generates only one binary package, and
9311 which builds it in <file>debian/tmp</file> relative to the top
9312 of the source package, it is usually sufficient to call
9313 <prgn>dpkg-gencontrol</prgn>.
9317 Sources which build several binaries will typically need
9320 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
9321 </example> The <tt>-P</tt> tells
9322 <prgn>dpkg-gencontrol</prgn> that the package is being
9323 built in a non-default directory, and the <tt>-p</tt>
9324 tells it which package's control file should be generated.
9328 <prgn>dpkg-gencontrol</prgn> also adds information to the
9329 list of files in <file>debian/files</file>, for the benefit of
9330 (for example) a future invocation of
9331 <prgn>dpkg-genchanges</prgn>.</p>
9334 <sect1 id="pkg-dpkg-shlibdeps">
9336 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
9341 This program is usually called from <file>debian/rules</file>
9342 just before <prgn>dpkg-gencontrol</prgn> (see <ref
9343 id="pkg-sourcetree">), in the top level of the source tree.
9347 Its arguments are executables.
9350 In a forthcoming dpkg version,
9351 <prgn>dpkg-shlibdeps</prgn> would be required to be
9352 called on shared libraries as well.
9355 They may be specified either in the locations in the
9356 source tree where they are created or in the locations
9357 in the temporary build tree where they are installed
9358 prior to binary package creation.
9360 </footnote> for which shared library dependencies should
9361 be included in the binary package's control file.
9365 If some of the found shared libraries should only
9366 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
9367 some warrant a <tt>Pre-Depends</tt>, this can be achieved
9368 by using the <tt>-d<var>dependency-field</var></tt> option
9369 before those executable(s). (Each <tt>-d</tt> option
9370 takes effect until the next <tt>-d</tt>.)
9374 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
9375 output control file to be modified. Instead by default it
9376 adds to the <file>debian/substvars</file> file variable
9377 settings like <tt>shlibs:Depends</tt>. These variable
9378 settings must be referenced in dependency fields in the
9379 appropriate per-binary-package sections of the source
9384 For example, a package that generates an essential part
9385 which requires dependencies, and optional parts that
9386 which only require a recommendation, would separate those
9387 two sets of dependencies into two different fields.<footnote>
9388 At the time of writing, an example for this was the
9389 <package/xmms/ package, with Depends used for the xmms
9390 executable, Recommends for the plug-ins and Suggests for
9391 even more optional features provided by unzip.
9393 It can say in its <file>debian/rules</file>:
9395 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
9396 -dRecommends <var>optionalpart anotheroptionalpart</var>
9398 and then in its main control file <file>debian/control</file>:
9401 Depends: ${shlibs:Pre-Depends}
9402 Recommends: ${shlibs:Recommends}
9408 Sources which produce several binary packages with
9409 different shared library dependency requirements can use
9410 the <tt>-p<var>varnameprefix</var></tt> option to override
9411 the default <tt>shlibs:</tt> prefix (one invocation of
9412 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
9413 They can thus produce several sets of dependency
9414 variables, each of the form
9415 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
9416 which can be referred to in the appropriate parts of the
9417 binary package control files.
9422 <sect1 id="pkg-dpkg-distaddfile">
9424 <prgn>dpkg-distaddfile</prgn> - adds a file to
9425 <file>debian/files</file>
9429 Some packages' uploads need to include files other than
9430 the source and binary package files.
9434 <prgn>dpkg-distaddfile</prgn> adds a file to the
9435 <file>debian/files</file> file so that it will be included in
9436 the <file>.changes</file> file when
9437 <prgn>dpkg-genchanges</prgn> is run.
9441 It is usually invoked from the <tt>binary</tt> target of
9442 <file>debian/rules</file>:
9444 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
9446 The <var>filename</var> is relative to the directory where
9447 <prgn>dpkg-genchanges</prgn> will expect to find it - this
9448 is usually the directory above the top level of the source
9449 tree. The <file>debian/rules</file> target should put the
9450 file there just before or just after calling
9451 <prgn>dpkg-distaddfile</prgn>.
9455 The <var>section</var> and <var>priority</var> are passed
9456 unchanged into the resulting <file>.changes</file> file.
9461 <sect1 id="pkg-dpkg-genchanges">
9463 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
9468 This program is usually called by package-independent
9469 automatic building scripts such as
9470 <prgn>dpkg-buildpackage</prgn>, but it may also be called
9475 It is usually called in the top level of a built source
9476 tree, and when invoked with no arguments will print out a
9477 straightforward <file>.changes</file> file based on the
9478 information in the source package's changelog and control
9479 file and the binary and source packages which should have
9485 <sect1 id="pkg-dpkg-parsechangelog">
9487 <prgn>dpkg-parsechangelog</prgn> - produces parsed
9488 representation of a changelog
9492 This program is used internally by
9493 <prgn>dpkg-source</prgn> et al. It may also occasionally
9494 be useful in <file>debian/rules</file> and elsewhere. It
9495 parses a changelog, <file>debian/changelog</file> by default,
9496 and prints a control-file format representation of the
9497 information in it to standard output.
9501 <sect1 id="pkg-dpkg-architecture">
9503 <prgn>dpkg-architecture</prgn> - information about the build and
9508 This program can be used manually, but is also invoked by
9509 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
9510 to set environment or make variables which specify the build and
9511 host architecture for the package building process.
9516 <sect id="pkg-sourcetree">
9517 <heading>The Debianised source tree</heading>
9520 The source archive scheme described later is intended to
9521 allow a Debianised source tree with some associated control
9522 information to be reproduced and transported easily. The
9523 Debianised source tree is a version of the original program
9524 with certain files added for the benefit of the
9525 Debianisation process, and with any other changes required
9526 made to the rest of the source code and installation
9531 The extra files created for Debian are in the subdirectory
9532 <file>debian</file> of the top level of the Debianised source
9533 tree. They are described below.
9536 <sect1 id="pkg-debianrules">
9537 <heading><file>debian/rules</file> - the main building script</heading>
9540 See <ref id="debianrules">.
9545 <sect1 id="pkg-dpkgchangelog">
9546 <heading><file>debian/changelog</file></heading>
9549 See <ref id="dpkgchangelog">.
9553 It is recommended that the entire changelog be encoded in the
9554 <url id="http://www.cis.ohio-state.edu/cgi-bin/rfc/rfc2279.html" name="UTF-8">
9556 <url id="http://www.unicode.org/"
9557 name="Unicode">.<footnote>
9559 I think it is fairly obvious that we need to
9560 eventually transition to UTF-8 for our package
9561 infrastructure; it is really the only sane char-set in
9562 an international environment. Now, we can't switch to
9563 using UTF-8 for package control fields and the like
9564 until dpkg has better support, but one thing we can
9565 start doing today is requesting that Debian changelogs
9566 are UTF-8 encoded. At some point in time, we can start
9567 requiring them to do so.
9570 Checking for non-UTF8 characters in a changelog is
9571 trivial. Dump the file through
9572 <example>iconv -f utf-8 -t ucs-4</example>
9573 discard the output, and check the return
9574 value. If there are any characters in the stream
9575 which are invalid UTF-8 sequences, iconv will exit
9576 with an error code; and this will be the case for the
9577 vast majority of other character sets.
9582 <sect2><heading>Defining alternative changelog formats
9586 It is possible to use a different format to the standard
9587 one, by providing a parser for the format you wish to
9592 In order to have <tt>dpkg-parsechangelog</tt> run your
9593 parser, you must include a line within the last 40 lines
9594 of your file matching the Perl regular expression:
9595 <tt>\schangelog-format:\s+([0-9a-z]+)\W</tt> The part in
9596 parentheses should be the name of the format. For
9597 example, you might say:
9599 @@@ changelog-format: joebloggs @@@
9601 Changelog format names are non-empty strings of alphanumerics.
9605 If such a line exists then <tt>dpkg-parsechangelog</tt>
9606 will look for the parser as
9607 <file>/usr/lib/dpkg/parsechangelog/<var>format-name</var></file>
9609 <file>/usr/local/lib/dpkg/parsechangelog/<var>format-name</var></file>;
9610 it is an error for it not to find it, or for it not to
9611 be an executable program. The default changelog format
9612 is <tt>dpkg</tt>, and a parser for it is provided with
9613 the <tt>dpkg</tt> package.
9617 The parser will be invoked with the changelog open on
9618 standard input at the start of the file. It should read
9619 the file (it may seek if it wishes) to determine the
9620 information required and return the parsed information
9621 to standard output in the form of a series of control
9622 fields in the standard format. By default it should
9623 return information about only the most recent version in
9624 the changelog; it should accept a
9625 <tt>-v<var>version</var></tt> option to return changes
9626 information from all versions present <em>strictly
9627 after</em> <var>version</var>, and it should then be an
9628 error for <var>version</var> not to be present in the
9634 <list compact="compact">
9635 <item><qref id="f-Source"><tt>Source</tt></qref></item>
9636 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
9637 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
9638 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (mandatory)</item>
9639 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
9640 <item><qref id="f-Date"><tt>Date</tt></qref></item>
9641 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
9646 If several versions are being returned (due to the use
9647 of <tt>-v</tt>), the urgency value should be of the
9648 highest urgency code listed at the start of any of the
9649 versions requested followed by the concatenated
9650 (space-separated) comments from all the versions
9651 requested; the maintainer, version, distribution and
9652 date should always be from the most recent version.
9656 For the format of the <tt>Changes</tt> field see
9657 <ref id="f-Changes">.
9661 If the changelog format which is being parsed always or
9662 almost always leaves a blank line between individual
9663 change notes these blank lines should be stripped out,
9664 so as to make the resulting output compact.
9668 If the changelog format does not contain date or package
9669 name information this information should be omitted from
9670 the output. The parser should not attempt to synthesize
9671 it or find it from other sources.
9675 If the changelog does not have the expected format the
9676 parser should exit with a nonzero exit status, rather
9677 than trying to muddle through and possibly generating
9682 A changelog parser may not interact with the user at
9688 <sect1 id="pkg-srcsubstvars">
9689 <heading><file>debian/substvars</file> and variable substitutions</heading>
9692 See <ref id="substvars">.
9698 <heading><file>debian/files</file></heading>
9701 See <ref id="debianfiles">.
9705 <sect1><heading><file>debian/tmp</file>
9709 This is the canonical temporary location for the
9710 construction of binary packages by the <tt>binary</tt>
9711 target. The directory <file>tmp</file> serves as the root of
9712 the file system tree as it is being constructed (for
9713 example, by using the package's upstream makefiles install
9714 targets and redirecting the output there), and it also
9715 contains the <tt>DEBIAN</tt> subdirectory. See <ref
9716 id="pkg-bincreating">.
9720 If several binary packages are generated from the same
9721 source tree it is usual to use several
9722 <file>debian/tmp<var>something</var></file> directories, for
9723 example <file>tmp-a</file> or <file>tmp-doc</file>.
9727 Whatever <file>tmp</file> directories are created and used by
9728 <tt>binary</tt> must of course be removed by the
9729 <tt>clean</tt> target.</p></sect1>
9733 <sect id="pkg-sourcearchives"><heading>Source packages as archives
9737 As it exists on the FTP site, a Debian source package
9738 consists of three related files. You must have the right
9739 versions of all three to be able to use them.
9744 <tag>Debian source control file - <tt>.dsc</tt></tag>
9746 This file is a control file used by <prgn>dpkg-source</prgn>
9747 to extract a source package.
9748 See <ref id="debiansourcecontrolfiles">.
9752 Original source archive -
9754 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
9760 This is a compressed (with <tt>gzip -9</tt>)
9761 <prgn>tar</prgn> file containing the source code from
9762 the upstream authors of the program.
9767 Debianisation diff -
9769 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
9775 This is a unified context diff (<tt>diff -u</tt>)
9776 giving the changes which are required to turn the
9777 original source into the Debian source. These changes
9778 may only include editing and creating plain files.
9779 The permissions of files, the targets of symbolic
9780 links and the characteristics of special files or
9781 pipes may not be changed and no files may be removed
9786 All the directories in the diff must exist, except the
9787 <file>debian</file> subdirectory of the top of the source
9788 tree, which will be created by
9789 <prgn>dpkg-source</prgn> if necessary when unpacking.
9793 The <prgn>dpkg-source</prgn> program will
9794 automatically make the <file>debian/rules</file> file
9795 executable (see below).</p></item>
9800 If there is no original source code - for example, if the
9801 package is specially prepared for Debian or the Debian
9802 maintainer is the same as the upstream maintainer - the
9803 format is slightly different: then there is no diff, and the
9805 <file><var>package</var>_<var>version</var>.tar.gz</file>,
9806 and preferably contains a directory named
9807 <file><var>package</var>-<var>version</var></file>.
9812 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
9815 <tt>dpkg-source -x</tt> is the recommended way to unpack a
9816 Debian source package. However, if it is not available it
9817 is possible to unpack a Debian source archive as follows:
9818 <enumlist compact="compact">
9821 Untar the tarfile, which will create a <file>.orig</file>
9825 <p>Rename the <file>.orig</file> directory to
9826 <file><var>package</var>-<var>version</var></file>.</p>
9830 Create the subdirectory <file>debian</file> at the top of
9831 the source tree.</p>
9833 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
9835 <item><p>Untar the tarfile again if you want a copy of the original
9836 source code alongside the Debianised version.</p>
9841 It is not possible to generate a valid Debian source archive
9842 without using <prgn>dpkg-source</prgn>. In particular,
9843 attempting to use <prgn>diff</prgn> directly to generate the
9844 <file>.diff.gz</file> file will not work.
9848 <heading>Restrictions on objects in source packages</heading>
9851 The source package may not contain any hard links
9853 This is not currently detected when building source
9854 packages, but only when extracting
9858 Hard links may be permitted at some point in the
9859 future, but would require a fair amount of
9861 </footnote>, device special files, sockets or setuid or
9864 Setgid directories are allowed.
9869 The source packaging tools manage the changes between the
9870 original and Debianised source using <prgn>diff</prgn> and
9871 <prgn>patch</prgn>. Turning the original source tree as
9872 included in the <file>.orig.tar.gz</file> into the debianised
9873 source must not involve any changes which cannot be
9874 handled by these tools. Problematic changes which cause
9875 <prgn>dpkg-source</prgn> to halt with an error when
9876 building the source package are:
9877 <list compact="compact">
9878 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
9880 <item><p>Changing the targets of symbolic links.</p>
9882 <item><p>Creating directories, other than <file>debian</file>.</p>
9884 <item><p>Changes to the contents of binary files.</p></item>
9885 </list> Changes which cause <prgn>dpkg-source</prgn> to
9886 print a warning but continue anyway are:
9887 <list compact="compact">
9890 Removing files, directories or symlinks.
9892 Renaming a file is not treated specially - it is
9893 seen as the removal of the old file (which
9894 generates a warning, but is otherwise ignored),
9895 and the creation of the new one.
9901 Changed text files which are missing the usual final
9902 newline (either in the original or the modified
9907 Changes which are not represented, but which are not detected by
9908 <prgn>dpkg-source</prgn>, are:
9909 <list compact="compact">
9910 <item><p>Changing the permissions of files (other than
9911 <file>debian/rules</file>) and directories.</p></item>
9916 The <file>debian</file> directory and <file>debian/rules</file>
9917 are handled specially by <prgn>dpkg-source</prgn> - before
9918 applying the changes it will create the <file>debian</file>
9919 directory, and afterwards it will make
9920 <file>debian/rules</file> world-executable.
9926 <appendix id="pkg-controlfields">
9927 <heading>Control files and their fields (from old Packaging Manual)</heading>
9930 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
9931 data in a common format, known as control files. Binary and
9932 source packages have control data as do the <file>.changes</file>
9933 files which control the installation of uploaded files, and
9934 <prgn>dpkg</prgn>'s internal databases are in a similar
9939 <heading>Syntax of control files</heading>
9942 See <ref id="controlsyntax">.
9946 It is important to note that there are several fields which
9947 are optional as far as <prgn>dpkg</prgn> and the related
9948 tools are concerned, but which must appear in every Debian
9949 package, or whose omission may cause problems.
9954 <heading>List of fields</heading>
9957 See <ref id="controlfieldslist">.
9961 This section now contains only the fields that didn't belong
9962 to the Policy manual.
9965 <sect1 id="pkg-f-Filename">
9966 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
9969 These fields in <tt>Packages</tt> files give the
9970 filename(s) of (the parts of) a package in the
9971 distribution directories, relative to the root of the
9972 Debian hierarchy. If the package has been split into
9973 several parts the parts are all listed in order, separated
9978 <sect1 id="pkg-f-Size">
9979 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
9982 These fields in <file>Packages</file> files give the size (in
9983 bytes, expressed in decimal) and MD5 checksum of the
9984 file(s) which make(s) up a binary package in the
9985 distribution. If the package is split into several parts
9986 the values for the parts are listed in order, separated by
9991 <sect1 id="pkg-f-Status">
9992 <heading><tt>Status</tt></heading>
9995 This field in <prgn>dpkg</prgn>'s status file records
9996 whether the user wants a package installed, removed or
9997 left alone, whether it is broken (requiring
9998 re-installation) or not and what its current state on the
9999 system is. Each of these pieces of information is a
10004 <sect1 id="pkg-f-Config-Version">
10005 <heading><tt>Config-Version</tt></heading>
10008 If a package is not installed or not configured, this
10009 field in <prgn>dpkg</prgn>'s status file records the last
10010 version of the package which was successfully
10015 <sect1 id="pkg-f-Conffiles">
10016 <heading><tt>Conffiles</tt></heading>
10019 This field in <prgn>dpkg</prgn>'s status file contains
10020 information about the automatically-managed configuration
10021 files held by a package. This field should <em>not</em>
10022 appear anywhere in a package!
10027 <heading>Obsolete fields</heading>
10030 These are still recognized by <prgn>dpkg</prgn> but should
10031 not appear anywhere any more.
10033 <taglist compact="compact">
10035 <tag><tt>Revision</tt></tag>
10036 <tag><tt>Package-Revision</tt></tag>
10037 <tag><tt>Package_Revision</tt></tag>
10039 The Debian revision part of the package version was
10040 at one point in a separate control file field. This
10041 field went through several names.
10044 <tag><tt>Recommended</tt></tag>
10045 <item>Old name for <tt>Recommends</tt>.</item>
10047 <tag><tt>Optional</tt></tag>
10048 <item>Old name for <tt>Suggests</tt>.</item>
10050 <tag><tt>Class</tt></tag>
10051 <item>Old name for <tt>Priority</tt>.</item>
10060 <appendix id="pkg-conffiles">
10061 <heading>Configuration file handling (from old Packaging Manual)</heading>
10064 <prgn>dpkg</prgn> can do a certain amount of automatic
10065 handling of package configuration files.
10069 Whether this mechanism is appropriate depends on a number of
10070 factors, but basically there are two approaches to any
10071 particular configuration file.
10075 The easy method is to ship a best-effort configuration in the
10076 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10077 handle updates. If the user is unlikely to want to edit the
10078 file, but you need them to be able to without losing their
10079 changes, and a new package with a changed version of the file
10080 is only released infrequently, this is a good approach.
10084 The hard method is to build the configuration file from
10085 scratch in the <prgn>postinst</prgn> script, and to take the
10086 responsibility for fixing any mistakes made in earlier
10087 versions of the package automatically. This will be
10088 appropriate if the file is likely to need to be different on
10092 <sect><heading>Automatic handling of configuration files by
10097 A package may contain a control area file called
10098 <tt>conffiles</tt>. This file should be a list of filenames
10099 of configuration files needing automatic handling, separated
10100 by newlines. The filenames should be absolute pathnames,
10101 and the files referred to should actually exist in the
10106 When a package is upgraded <prgn>dpkg</prgn> will process
10107 the configuration files during the configuration stage,
10108 shortly before it runs the package's <prgn>postinst</prgn>
10113 For each file it checks to see whether the version of the
10114 file included in the package is the same as the one that was
10115 included in the last version of the package (the one that is
10116 being upgraded from); it also compares the version currently
10117 installed on the system with the one shipped with the last
10122 If neither the user nor the package maintainer has changed
10123 the file, it is left alone. If one or the other has changed
10124 their version, then the changed version is preferred - i.e.,
10125 if the user edits their file, but the package maintainer
10126 doesn't ship a different version, the user's changes will
10127 stay, silently, but if the maintainer ships a new version
10128 and the user hasn't edited it the new version will be
10129 installed (with an informative message). If both have
10130 changed their version the user is prompted about the problem
10131 and must resolve the differences themselves.
10135 The comparisons are done by calculating the MD5 message
10136 digests of the files, and storing the MD5 of the file as it
10137 was included in the most recent version of the package.
10141 When a package is installed for the first time
10142 <prgn>dpkg</prgn> will install the file that comes with it,
10143 unless that would mean overwriting a file already on the
10148 However, note that <prgn>dpkg</prgn> will <em>not</em>
10149 replace a conffile that was removed by the user (or by a
10150 script). This is necessary because with some programs a
10151 missing file produces an effect hard or impossible to
10152 achieve in another way, so that a missing file needs to be
10153 kept that way if the user did it.
10157 Note that a package should <em>not</em> modify a
10158 <prgn>dpkg</prgn>-handled conffile in its maintainer
10159 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10160 the user confusing and possibly dangerous options for
10161 conffile update when the package is upgraded.</p>
10164 <sect><heading>Fully-featured maintainer script configuration
10169 For files which contain site-specific information such as
10170 the hostname and networking details and so forth, it is
10171 better to create the file in the package's
10172 <prgn>postinst</prgn> script.
10176 This will typically involve examining the state of the rest
10177 of the system to determine values and other information, and
10178 may involve prompting the user for some information which
10179 can't be obtained some other way.
10183 When using this method there are a couple of important
10184 issues which should be considered:
10188 If you discover a bug in the program which generates the
10189 configuration file, or if the format of the file changes
10190 from one version to the next, you will have to arrange for
10191 the postinst script to do something sensible - usually this
10192 will mean editing the installed configuration file to remove
10193 the problem or change the syntax. You will have to do this
10194 very carefully, since the user may have changed the file,
10195 perhaps to fix the very problem that your script is trying
10196 to deal with - you will have to detect these situations and
10197 deal with them correctly.
10201 If you do go down this route it's probably a good idea to
10202 make the program that generates the configuration file(s) a
10203 separate program in <file>/usr/sbin</file>, by convention called
10204 <file><var>package</var>config</file> and then run that if
10205 appropriate from the post-installation script. The
10206 <tt><var>package</var>config</tt> program should not
10207 unquestioningly overwrite an existing configuration - if its
10208 mode of operation is geared towards setting up a package for
10209 the first time (rather than any arbitrary reconfiguration
10210 later) you should have it check whether the configuration
10211 already exists, and require a <tt>--force</tt> flag to
10212 overwrite it.</p></sect>
10215 <appendix id="pkg-alternatives"><heading>Alternative versions of
10216 an interface - <prgn>update-alternatives</prgn> (from old
10221 When several packages all provide different versions of the
10222 same program or file it is useful to have the system select a
10223 default, but to allow the system administrator to change it
10224 and have their decisions respected.
10228 For example, there are several versions of the <prgn>vi</prgn>
10229 editor, and there is no reason to prevent all of them from
10230 being installed at once, each under their own name
10231 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10232 Nevertheless it is desirable to have the name <tt>vi</tt>
10233 refer to something, at least by default.
10237 If all the packages involved cooperate, this can be done with
10238 <prgn>update-alternatives</prgn>.
10242 Each package provides its own version under its own name, and
10243 calls <prgn>update-alternatives</prgn> in its postinst to
10244 register its version (and again in its prerm to deregister
10249 See the man page <manref name="update-alternatives"
10250 section="8"> for details.
10254 If <prgn>update-alternatives</prgn> does not seem appropriate
10255 you may wish to consider using diversions instead.</p>
10258 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10259 package's version of a file (from old Packaging Manual)
10263 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10264 when it reinstalls the package it belongs to, and to have it
10265 put the file from the package somewhere else instead.
10269 This can be used locally to override a package's version of a
10270 file, or by one package to override another's version (or
10271 provide a wrapper for it).
10275 Before deciding to use a diversion, read <ref
10276 id="pkg-alternatives"> to see if you really want a diversion
10277 rather than several alternative versions of a program.
10281 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10282 and updated by a special program <prgn>dpkg-divert</prgn>.
10283 Please see <manref name="dpkg-divert" section="8"> for full
10284 details of its operation.
10288 When a package wishes to divert a file from another, it should
10289 call <prgn>dpkg-divert</prgn> in its preinst to add the
10290 diversion and rename the existing file. For example,
10291 supposing that a <prgn>smailwrapper</prgn> package wishes to
10292 install a wrapper around <file>/usr/sbin/smail</file>:
10294 if [ install = "$1" ]; then
10295 dpkg-divert --package smailwrapper --add --rename \
10296 --divert /usr/sbin/smail.real /usr/sbin/smail
10298 </example> Testing <tt>$1</tt> is necessary so that the script
10299 doesn't try to add the diversion again when
10300 <prgn>smailwrapper</prgn> is upgraded. The <tt>--package
10301 smailwrapper</tt> ensures that <prgn>smailwrapper</prgn>'s
10302 copy of <file>/usr/sbin/smail</file> can bypass the diversion and
10303 get installed as the true version.
10307 The postrm has to do the reverse:
10309 if [ remove = "$1" ]; then
10310 dpkg-divert --package smailwrapper --remove --rename \
10311 --divert /usr/sbin/smail.real /usr/sbin/smail
10317 Do not attempt to divert a file which is vitally important for
10318 the system's operation - when using <prgn>dpkg-divert</prgn>
10319 there is a time, after it has been diverted but before
10320 <prgn>dpkg</prgn> has installed the new version, when the file
10321 does not exist.</p>
10326 <!-- Local variables: -->
10327 <!-- indent-tabs-mode: t -->
10329 <!-- vim:set ai et sts=2 sw=2 tw=76: -->