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10 <title>Debian Policy Manual</title>
11 <author><qref id="authors">The Debian Policy Mailing List</qref></author>
12 <version>version &version;, &date;</version>
15 This manual describes the policy requirements for the Debian
16 GNU/Linux distribution. This includes the structure and
17 contents of the Debian archive and several design issues of
18 the operating system, as well as technical requirements that
19 each package must satisfy to be included in the distribution.
24 Copyright © 1996,1997,1998 Ian Jackson
25 and Christian Schwarz.
28 This manual is free software; you may redistribute it and/or
29 modify it under the terms of the GNU General Public License
30 as published by the Free Software Foundation; either version
31 2, or (at your option) any later version.
35 This is distributed in the hope that it will be useful, but
36 <em>without any warranty</em>; without even the implied
37 warranty of merchantability or fitness for a particular
38 purpose. See the GNU General Public License for more
43 A copy of the GNU General Public License is available as
44 <file>/usr/share/common-licenses/GPL</file> in the Debian GNU/Linux
45 distribution or on the World Wide Web at
46 <url id="http://www.gnu.org/copyleft/gpl.html"
47 name="the GNU General Public Licence">. You can also
48 obtain it by writing to the Free Software Foundation, Inc.,
49 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA.
57 <heading>About this manual</heading>
59 <heading>Scope</heading>
61 This manual describes the policy requirements for the Debian
62 GNU/Linux distribution. This includes the structure and
63 contents of the Debian archive and several design issues of the
64 operating system, as well as technical requirements that
65 each package must satisfy to be included in the
70 This manual also describes Debian policy as it relates to
71 creating Debian packages. It is not a tutorial on how to build
72 packages, nor is it exhaustive where it comes to describing
73 the behavior of the packaging system. Instead, this manual
74 attempts to define the interface to the package management
75 system that the developers have to be conversant with.<footnote>
76 Informally, the criteria used for inclusion is that the
77 material meet one of the following requirements:
78 <taglist compact="compact">
79 <tag>Standard interfaces</tag>
81 The material presented represents an interface to
82 the packaging system that is mandated for use, and
83 is used by, a significant number of packages, and
84 therefore should not be changed without peer
85 review. Package maintainers can then rely on this
86 interfaces not changing, and the package
87 management software authors need to ensure
88 compatibility with these interface
89 definitions. (Control file and changelog file
90 formats are examples.)
92 <tag>Chosen Convention</tag>
94 If there are a number of technically viable choices
95 that can be made, but one needs to select one of
96 these options for inter-operability. The version
97 number format is one example.
100 Please note that these are not mutually exclusive;
101 selected conventions often become parts of standard
107 The footnotes present in this manual are
108 merely informative, and are not part of Debian policy itself.
112 The appendices to this manual are not necessarily normative,
113 either. Please see <ref id="pkg-scope"> for more information.
117 In the normative part of this manual,
118 the words <em>must</em>, <em>should</em> and
119 <em>may</em>, and the adjectives <em>required</em>,
120 <em>recommended</em> and <em>optional</em>, are used to
121 distinguish the significance of the various guidelines in
122 this policy document. Packages that do not conform to the
123 guidelines denoted by <em>must</em> (or <em>required</em>)
124 will generally not be considered acceptable for the Debian
125 distribution. Non-conformance with guidelines denoted by
126 <em>should</em> (or <em>recommended</em>) will generally be
127 considered a bug, but will not necessarily render a package
128 unsuitable for distribution. Guidelines denoted by
129 <em>may</em> (or <em>optional</em>) are truly optional and
130 adherence is left to the maintainer's discretion.
134 These classifications are roughly equivalent to the bug
135 severities <em>serious</em> (for <em>must</em> or
136 <em>required</em> directive violations), <em>minor</em>,
137 <em>normal</em> or <em>important</em>
138 (for <em>should</em> or <em>recommended</em> directive
139 violations) and <em>wishlist</em> (for <em>optional</em>
142 Compare RFC 2119. Note, however, that these words are
143 used in a different way in this document.
148 Much of the information presented in this manual will be
149 useful even when building a package which is to be
150 distributed in some other way or is intended for local use
156 <heading>New versions of this document</heading>
159 This manual is distributed via the Debian package
160 <package><url name="debian-policy"
161 id="http://packages.debian.org/debian-policy"></package>
162 (<httpsite>packages.debian.org</httpsite>
163 <httppath>/debian-policy</httppath>).
167 The current version of this document is also available from
168 the Debian web mirrors at
169 <tt><url name="/doc/debian-policy/"
170 id="http://www.debian.org/doc/debian-policy/"></tt>.
172 <httpsite>www.debian.org</httpsite>
173 <httppath>/doc/debian-policy/</httppath>)
174 Also available from the same directory are several other
175 formats: <file>policy.html.tar.gz</file>
176 (<httppath>/doc/debian-policy/policy.html.tar.gz</httppath>),
177 <file>policy.pdf.gz</file>
178 (<httppath>/doc/debian-policy/policy.pdf.gz</httppath>)
179 and <file>policy.ps.gz</file>
180 (<httppath>/doc/debian-policy/policy.ps.gz</httppath>).
184 The <package>debian-policy</package> package also includes the file
185 <file>upgrading-checklist.txt.gz</file> which indicates policy
186 changes between versions of this document.
191 <heading>Authors and Maintainers</heading>
194 Originally called "Debian GNU/Linux Policy Manual", this
195 manual was initially written in 1996 by Ian Jackson.
196 It was revised on November 27th, 1996 by David A. Morris.
197 Christian Schwarz added new sections on March 15th, 1997,
198 and reworked/restructured it in April-July 1997.
199 Christoph Lameter contributed the "Web Standard".
200 Julian Gilbey largely restructured it in 2001.
204 Since September 1998, the responsibility for the contents of
205 this document lies on the <url name="debian-policy mailing list"
206 id="mailto:debian-policy@lists.debian.org">. Proposals
207 are discussed there and inserted into policy after a certain
208 consensus is established.
209 <!-- insert shameless policy-process plug here eventually -->
210 The actual editing is done by a group of maintainers that have
211 no editorial powers. These are the current maintainers:
214 <item>Julian Gilbey</item>
215 <item>Branden Robinson</item>
216 <item>Josip Rodin</item>
217 <item>Manoj Srivastava</item>
222 While the authors of this document have tried hard to avoid
223 typos and other errors, these do still occur. If you discover
224 an error in this manual or if you want to give any
225 comments, suggestions, or criticisms please send an email to
226 the Debian Policy List,
227 <email>debian-policy@lists.debian.org</email>, or submit a
228 bug report against the <tt>debian-policy</tt> package.
232 Please do not try to reach the individual authors or maintainers
233 of the Policy Manual regarding changes to the Policy.
238 <heading>Related documents</heading>
241 There are several other documents other than this Policy Manual
242 that are necessary to fully understand some Debian policies and
247 The external "sub-policy" documents are referred to in:
248 <list compact="compact">
249 <item><ref id="fhs"></item>
250 <item><ref id="virtual_pkg"></item>
251 <item><ref id="menus"></item>
252 <item><ref id="mime"></item>
253 <item><ref id="perl"></item>
254 <item><ref id="maintscriptprompt"></item>
255 <item><ref id="emacs"></item>
260 In addition to those, which carry the weight of policy, there
261 is the Debian Developer's Reference. This document describes
262 procedures and resources for Debian developers, but it is
263 <em>not</em> normative; rather, it includes things that don't
264 belong in the Policy, such as best practices for developers.
268 The Developer's Reference is available in the
269 <package>developers-reference</package> package.
270 It's also available from the Debian web mirrors at
271 <tt><url name="/doc/developers-reference/"
272 id="http://www.debian.org/doc/developers-reference/"></tt>.
280 <heading>The Debian Archive</heading>
283 The Debian GNU/Linux system is maintained and distributed as a
284 collection of <em>packages</em>. Since there are so many of
285 them (currently well over 15000), they are split into
286 <em>sections</em> and given <em>priorities</em> to simplify
287 the handling of them.
291 The effort of the Debian project is to build a free operating
292 system, but not every package we want to make accessible is
293 <em>free</em> in our sense (see the Debian Free Software
294 Guidelines, below), or may be imported/exported without
295 restrictions. Thus, the archive is split into the distribution
296 areas or categories based on their licenses and other restrictions.
300 The aims of this are:
302 <list compact="compact">
303 <item>to allow us to make as much software available as we can</item>
304 <item>to allow us to encourage everyone to write free software,
306 <item>to allow us to make it easy for people to produce
307 CD-ROMs of our system without violating any licenses,
308 import/export restrictions, or any other laws.</item>
313 The <em>main</em> category forms the
314 <em>Debian GNU/Linux distribution</em>.
318 Packages in the other distribution areas (<tt>contrib</tt>,
319 <tt>non-free</tt>) are not considered to be part of the Debian
320 distribution, although we support their use and provide
321 infrastructure for them (such as our bug-tracking system and
322 mailing lists). This Debian Policy Manual applies to these
327 <heading>The Debian Free Software Guidelines</heading>
329 The Debian Free Software Guidelines (DFSG) form our
330 definition of "free software". These are:
332 <tag>Free Redistribution
335 The license of a Debian component may not restrict any
336 party from selling or giving away the software as a
337 component of an aggregate software distribution
338 containing programs from several different
339 sources. The license may not require a royalty or
340 other fee for such sale.
345 The program must include source code, and must allow
346 distribution in source code as well as compiled form.
351 The license must allow modifications and derived
352 works, and must allow them to be distributed under the
353 same terms as the license of the original software.
355 <tag>Integrity of The Author's Source Code
358 The license may restrict source-code from being
359 distributed in modified form <em>only</em> if the
360 license allows the distribution of "patch files"
361 with the source code for the purpose of modifying the
362 program at build time. The license must explicitly
363 permit distribution of software built from modified
364 source code. The license may require derived works to
365 carry a different name or version number from the
366 original software. (This is a compromise. The Debian
367 Project encourages all authors to not restrict any
368 files, source or binary, from being modified.)
370 <tag>No Discrimination Against Persons or Groups
373 The license must not discriminate against any person
376 <tag>No Discrimination Against Fields of Endeavor
379 The license must not restrict anyone from making use
380 of the program in a specific field of endeavor. For
381 example, it may not restrict the program from being
382 used in a business, or from being used for genetic
385 <tag>Distribution of License
388 The rights attached to the program must apply to all
389 to whom the program is redistributed without the need
390 for execution of an additional license by those
393 <tag>License Must Not Be Specific to Debian
396 The rights attached to the program must not depend on
397 the program's being part of a Debian system. If the
398 program is extracted from Debian and used or
399 distributed without Debian but otherwise within the
400 terms of the program's license, all parties to whom
401 the program is redistributed must have the same
402 rights as those that are granted in conjunction with
405 <tag>License Must Not Contaminate Other Software
408 The license must not place restrictions on other
409 software that is distributed along with the licensed
410 software. For example, the license must not insist
411 that all other programs distributed on the same medium
412 must be free software.
414 <tag>Example Licenses
417 The "GPL," "BSD," and "Artistic" licenses are examples of
418 licenses that we consider <em>free</em>.
425 <heading>Categories</heading>
428 <heading>The main category</heading>
431 Every package in <em>main</em> must comply with the DFSG
432 (Debian Free Software Guidelines).
436 In addition, the packages in <em>main</em>
437 <list compact="compact">
439 must not require a package outside of <em>main</em>
440 for compilation or execution (thus, the package must
441 not declare a "Depends", "Recommends", or
442 "Build-Depends" relationship on a non-<em>main</em>
446 must not be so buggy that we refuse to support them,
450 must meet all policy requirements presented in this
459 <heading>The contrib category</heading>
462 Every package in <em>contrib</em> must comply with the DFSG.
466 In addition, the packages in <em>contrib</em>
467 <list compact="compact">
469 must not be so buggy that we refuse to support them,
473 must meet all policy requirements presented in this
481 Examples of packages which would be included in
482 <em>contrib</em> are:
483 <list compact="compact">
485 free packages which require <em>contrib</em>,
486 <em>non-free</em> packages or packages which are not
487 in our archive at all for compilation or execution,
491 wrapper packages or other sorts of free accessories for
498 <sect1 id="non-free">
499 <heading>The non-free category</heading>
502 Packages must be placed in <em>non-free</em> if they are
503 not compliant with the DFSG or are encumbered by patents
504 or other legal issues that make their distribution
509 In addition, the packages in <em>non-free</em>
510 <list compact="compact">
512 must not be so buggy that we refuse to support them,
516 must meet all policy requirements presented in this
517 manual that it is possible for them to meet.
519 It is possible that there are policy
520 requirements which the package is unable to
521 meet, for example, if the source is
522 unavailable. These situations will need to be
523 handled on a case-by-case basis.
532 <sect id="pkgcopyright">
533 <heading>Copyright considerations</heading>
536 Every package must be accompanied by a verbatim copy of
537 its copyright and distribution license in the file
538 <file>/usr/share/doc/<var>package</var>/copyright</file>
539 (see <ref id="copyrightfile"> for further details).
543 We reserve the right to restrict files from being included
544 anywhere in our archives if
545 <list compact="compact">
547 their use or distribution would break a law,
550 there is an ethical conflict in their distribution or
554 we would have to sign a license for them, or
557 their distribution would conflict with other project
564 Programs whose authors encourage the user to make
565 donations are fine for the main distribution, provided
566 that the authors do not claim that not donating is
567 immoral, unethical, illegal or something similar; in such
568 a case they must go in <em>non-free</em>.
572 Packages whose copyright permission notices (or patent
573 problems) do not even allow redistribution of binaries
574 only, and where no special permission has been obtained,
575 must not be placed on the Debian FTP site and its mirrors
580 Note that under international copyright law (this applies
581 in the United States, too), <em>no</em> distribution or
582 modification of a work is allowed without an explicit
583 notice saying so. Therefore a program without a copyright
584 notice <em>is</em> copyrighted and you may not do anything
585 to it without risking being sued! Likewise if a program
586 has a copyright notice but no statement saying what is
587 permitted then nothing is permitted.
591 Many authors are unaware of the problems that restrictive
592 copyrights (or lack of copyright notices) can cause for
593 the users of their supposedly-free software. It is often
594 worthwhile contacting such authors diplomatically to ask
595 them to modify their license terms. However, this can be a
596 politically difficult thing to do and you should ask for
597 advice on the <tt>debian-legal</tt> mailing list first, as
602 When in doubt about a copyright, send mail to
603 <email>debian-legal@lists.debian.org</email>. Be prepared
604 to provide us with the copyright statement. Software
605 covered by the GPL, public domain software and BSD-like
606 copyrights are safe; be wary of the phrases "commercial
607 use prohibited" and "distribution restricted".
611 <sect id="subsections">
612 <heading>Sections</heading>
615 The packages in the categories <em>main</em>,
616 <em>contrib</em> and <em>non-free</em> are grouped further
617 into <em>sections</em> to simplify handling.
621 The category and section for each package should be
622 specified in the package's <tt>Section</tt> control record
623 (see <ref id="f-Section">). However, the maintainer of the
624 Debian archive may override this selection to ensure the
625 consistency of the Debian distribution. The
626 <tt>Section</tt> field should be of the form:
627 <list compact="compact">
629 <em>section</em> if the package is in the
630 <em>main</em> category,
633 <em>segment/section</em> if the package is in
634 the <em>contrib</em> or <em>non-free</em>
641 The Debian archive maintainers provide the authoritative
642 list of sections. At present, they are:
643 <em>admin</em>, <em>base</em>, <em>comm</em>,
644 <em>contrib</em>, <em>devel</em>, <em>doc</em>,
645 <em>editors</em>, <em>electronics</em>, <em>embedded</em>,
646 <em>games</em>, <em>gnome</em>, <em>graphics</em>,
647 <em>hamradio</em>, <em>interpreters</em>, <em>kde</em>,
648 <em>libs</em>, <em>libdevel</em>, <em>mail</em>,
649 <em>math</em>, <em>misc</em>, <em>net</em>, <em>news</em>,
650 <em>non-free</em>, <em>oldlibs</em>,
651 <em>otherosfs</em>, <em>perl</em>, <em>python</em>,
652 <em>science</em>, <em>shells</em>,
653 <em>sound</em>, <em>tex</em>, <em>text</em>,
654 <em>utils</em>, <em>web</em>, <em>x11</em>.
658 <sect id="priorities">
659 <heading>Priorities</heading>
662 Each package should have a <em>priority</em> value, which is
663 included in the package's <em>control record</em>
664 (see <ref id="f-Priority">).
665 This information is used by the Debian package management tools to
666 separate high-priority packages from less-important packages.
670 The following <em>priority levels</em> are recognized by the
671 Debian package management tools.
673 <tag><tt>required</tt></tag>
675 Packages which are necessary for the proper
676 functioning of the system (usually, this means that
677 dpkg functionality depends on these packages).
678 Removing a <tt>required</tt> package may cause your
679 system to become totally broken and you may not even
680 be able to use <prgn>dpkg</prgn> to put things back,
681 so only do so if you know what you are doing. Systems
682 with only the <tt>required</tt> packages are probably
683 unusable, but they do have enough functionality to
684 allow the sysadmin to boot and install more software.
686 <tag><tt>important</tt></tag>
688 Important programs, including those which one would
689 expect to find on any Unix-like system. If the
690 expectation is that an experienced Unix person who
691 found it missing would say "What on earth is going on,
692 where is <prgn>foo</prgn>?", it must be an
693 <tt>important</tt> package.<footnote>
694 This is an important criterion because we are
695 trying to produce, amongst other things, a free
698 Other packages without which the system will not run
699 well or be usable must also have priority
700 <tt>important</tt>. This does
701 <em>not</em> include Emacs, the X Window System, TeX
702 or any other large applications. The
703 <tt>important</tt> packages are just a bare minimum of
704 commonly-expected and necessary tools.
706 <tag><tt>standard</tt></tag>
708 These packages provide a reasonably small but not too
709 limited character-mode system. This is what will be
710 installed by default if the user doesn't select anything
711 else. It doesn't include many large applications.
713 <tag><tt>optional</tt></tag>
715 (In a sense everything that isn't required is
716 optional, but that's not what is meant here.) This is
717 all the software that you might reasonably want to
718 install if you didn't know what it was and don't have
719 specialized requirements. This is a much larger system
720 and includes the X Window System, a full TeX
721 distribution, and many applications. Note that
722 optional packages should not conflict with each other.
724 <tag><tt>extra</tt></tag>
726 This contains all packages that conflict with others
727 with required, important, standard or optional
728 priorities, or are only likely to be useful if you
729 already know what they are or have specialized
736 Packages must not depend on packages with lower priority
737 values (excluding build-time dependencies). In order to
738 ensure this, the priorities of one or more packages may need
747 <heading>Binary packages</heading>
750 The Debian GNU/Linux distribution is based on the Debian
751 package management system, called <prgn>dpkg</prgn>. Thus,
752 all packages in the Debian distribution must be provided
753 in the <tt>.deb</tt> file format.
757 <heading>The package name</heading>
760 Every package must have a name that's unique within the Debian
765 The package name is included in the control field
766 <tt>Package</tt>, the format of which is described
767 in <ref id="f-Package">.
768 The package name is also included as a part of the file name
769 of the <tt>.deb</tt> file.
774 <heading>The version of a package</heading>
777 Every package has a version number recorded in its
778 <tt>Version</tt> control file field, described in
779 <ref id="f-Version">.
783 The package management system imposes an ordering on version
784 numbers, so that it can tell whether packages are being up- or
785 downgraded and so that package system front end applications
786 can tell whether a package it finds available is newer than
787 the one installed on the system. The version number format
788 has the most significant parts (as far as comparison is
789 concerned) at the beginning.
793 If an upstream package has problematic version numbers they
794 should be converted to a sane form for use in the
795 <tt>Version</tt> field.
799 <heading>Version numbers based on dates</heading>
802 In general, Debian packages should use the same version
803 numbers as the upstream sources.
807 However, in some cases where the upstream version number is
808 based on a date (e.g., a development "snapshot" release) the
809 package management system cannot handle these version
810 numbers without epochs. For example, dpkg will consider
811 "96May01" to be greater than "96Dec24".
815 To prevent having to use epochs for every new upstream
816 version, the date based portion of the version number
817 should be changed to the following format in such cases:
818 "19960501", "19961224". It is up to the maintainer whether
819 they want to bother the upstream maintainer to change
820 the version numbers upstream, too.
824 Note that other version formats based on dates which are
825 parsed correctly by the package management system should
826 <em>not</em> be changed.
830 Native Debian packages (i.e., packages which have been
831 written especially for Debian) whose version numbers include
832 dates should always use the "YYYYMMDD" format.
839 <heading>The maintainer of a package</heading>
842 Every package must have a Debian maintainer (the
843 maintainer may be one person or a group of people
844 reachable from a common email address, such as a mailing
845 list). The maintainer is responsible for ensuring that
846 the package is placed in the appropriate distributions.
850 The maintainer must be specified in the
851 <tt>Maintainer</tt> control field with their correct name
852 and a working email address. If one person maintains
853 several packages, they should try to avoid having
854 different forms of their name and email address in
855 the <tt>Maintainer</tt> fields of those packages.
859 The format of the <tt>Maintainer</tt> control field is
860 described in <ref id="f-Maintainer">.
864 If the maintainer of a package quits from the Debian
865 project, "Debian QA Group"
866 <email>packages@qa.debian.org</email> takes over the
867 maintainer-ship of the package until someone else
868 volunteers for that task. These packages are called
869 <em>orphaned packages</em>.<footnote>
870 The detailed procedure for doing this gracefully can
871 be found in the Debian Developer's Reference,
872 see <ref id="related">.
877 <sect id="descriptions">
878 <heading>The description of a package</heading>
881 Every Debian package must have an extended description
882 stored in the appropriate field of the control record.
883 The technical information about the format of the
884 <tt>Description</tt> field is in <ref id="f-Description">.
888 The description should describe the package (the program) to a
889 user (system administrator) who has never met it before so that
890 they have enough information to decide whether they want to
891 install it. This description should not just be copied verbatim
892 from the program's documentation.
896 Put important information first, both in the synopsis and
897 extended description. Sometimes only the first part of the
898 synopsis or of the description will be displayed. You can
899 assume that there will usually be a way to see the whole
900 extended description.
904 The description should also give information about the
905 significant dependencies and conflicts between this package
906 and others, so that the user knows why these dependencies and
907 conflicts have been declared.
911 Instructions for configuring or using the package should
912 not be included (that is what installation scripts,
913 manual pages, info files, etc., are for). Copyright
914 statements and other administrivia should not be included
915 either (that is what the copyright file is for).
918 <sect1 id="synopsis"><heading>The single line synopsis</heading>
921 The single line synopsis should be kept brief - certainly
926 Do not include the package name in the synopsis line. The
927 display software knows how to display this already, and you
928 do not need to state it. Remember that in many situations
929 the user may only see the synopsis line - make it as
930 informative as you can.
935 <sect1 id="extendeddesc"><heading>The extended description</heading>
938 Do not try to continue the single line synopsis into the
939 extended description. This will not work correctly when
940 the full description is displayed, and makes no sense
941 where only the summary (the single line synopsis) is
946 The extended description should describe what the package
947 does and how it relates to the rest of the system (in terms
948 of, for example, which subsystem it is which part of).
952 The description field needs to make sense to anyone, even
953 people who have no idea about any of the things the
954 package deals with.<footnote>
955 The blurb that comes with a program in its
956 announcements and/or <prgn>README</prgn> files is
957 rarely suitable for use in a description. It is
958 usually aimed at people who are already in the
959 community where the package is used.
968 <heading>Dependencies</heading>
971 Every package must specify the dependency information
972 about other packages that are required for the first to
977 For example, a dependency entry must be provided for any
978 shared libraries required by a dynamically-linked executable
983 Packages are not required to declare any dependencies they
984 have on other packages which are marked <tt>Essential</tt>
985 (see below), and should not do so unless they depend on a
986 particular version of that package.<footnote>
988 Essential is defined as the minimal set of functionality
989 that must be available and usable on the system even
990 when packages are in an unconfigured (but unpacked)
991 state. This is needed to avoid unresolvable dependency
992 loops on upgrade. If packages add unnecessary
993 dependencies on packages in this set, the chances that
994 there <strong>will</strong> be an unresolvable
995 dependency loop caused by forcing these Essential
996 packages to be configured first before they need to be
997 is greatly increased. It also increases the chances
998 that frontends will be unable to
999 <strong>calculate</strong> an upgrade path, even if one
1003 Also, it's pretty unlikely that functionality from
1004 Essential shall ever be removed (which is one reason why
1005 care must be taken before adding to the Essential
1006 packages set), but <em>packages</em> have been removed
1007 from the Essential set when the functionality moved to a
1008 different package. So depending on these packages
1009 <em>just in case</em> they stop being essential does way
1010 more harm than good.
1016 Sometimes, a package requires another package to be installed
1017 <em>and</em> configured before it can be installed. In this
1018 case, you must specify a <tt>Pre-Depends</tt> entry for
1023 You should not specify a <tt>Pre-Depends</tt> entry for a
1024 package before this has been discussed on the
1025 <tt>debian-devel</tt> mailing list and a consensus about
1026 doing that has been reached.
1030 The format of the package interrelationship control fields is
1031 described in <ref id="relationships">.
1035 <sect id="virtual_pkg">
1036 <heading>Virtual packages</heading>
1039 Sometimes, there are several packages which offer
1040 more-or-less the same functionality. In this case, it's
1041 useful to define a <em>virtual package</em> whose name
1042 describes that common functionality. (The virtual
1043 packages only exist logically, not physically; that's why
1044 they are called <em>virtual</em>.) The packages with this
1045 particular function will then <em>provide</em> the virtual
1046 package. Thus, any other package requiring that function
1047 can simply depend on the virtual package without having to
1048 specify all possible packages individually.
1052 All packages should use virtual package names where
1053 appropriate, and arrange to create new ones if necessary.
1054 They should not use virtual package names (except privately,
1055 amongst a cooperating group of packages) unless they have
1056 been agreed upon and appear in the list of virtual package
1057 names. (See also <ref id="virtual">)
1061 The latest version of the authoritative list of virtual
1062 package names can be found in the <tt>debian-policy</tt> package.
1063 It is also available from the Debian web mirrors at
1064 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1065 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1069 The procedure for updating the list is described in the preface
1076 <heading>Base system</heading>
1079 The <tt>base system</tt> is a minimum subset of the Debian
1080 GNU/Linux system that is installed before everything else
1081 on a new system. Thus, only very few packages are allowed
1082 to go into the <tt>base</tt> section to keep the required
1083 disk usage very small.
1087 Most of these packages will have the priority value
1088 <tt>required</tt> or at least <tt>important</tt>, and many
1089 of them will be tagged <tt>essential</tt> (see below).
1094 <heading>Essential packages</heading>
1097 Some packages are tagged <tt>essential</tt> for a system
1098 using the <tt>Essential</tt> control file field.
1099 The format of the <tt>Essential</tt> control field is
1100 described in <ref id="f-Essential">.
1104 Since these packages cannot be easily removed (one has to
1105 specify an extra <em>force option</em> to
1106 <prgn>dpkg</prgn> to do so), this flag must not be used
1107 unless absolutely necessary. A shared library package
1108 must not be tagged <tt>essential</tt>; dependencies will
1109 prevent its premature removal, and we need to be able to
1110 remove it when it has been superseded.
1114 Since dpkg will not prevent upgrading of other packages
1115 while an <tt>essential</tt> package is in an unconfigured
1116 state, all <tt>essential</tt> packages must supply all of
1117 their core functionality even when unconfigured. If the
1118 package cannot satisfy this requirement it must not be
1119 tagged as essential, and any packages depending on this
1120 package must instead have explicit dependency fields as
1125 You must not tag any packages <tt>essential</tt> before
1126 this has been discussed on the <tt>debian-devel</tt>
1127 mailing list and a consensus about doing that has been
1132 <sect id="maintscripts">
1133 <heading>Maintainer Scripts</heading>
1136 The package installation scripts should avoid producing
1137 output which is unnecessary for the user to see and
1138 should rely on <prgn>dpkg</prgn> to stave off boredom on
1139 the part of a user installing many packages. This means,
1140 amongst other things, using the <tt>--quiet</tt> option on
1141 <prgn>install-info</prgn>.
1145 Errors which occur during the execution of an installation
1146 script must be checked and the installation must not
1147 continue after an error.
1151 Note that in general <ref id="scripts"> applies to package
1152 maintainer scripts, too.
1156 You should not use <prgn>dpkg-divert</prgn> on a file
1157 belonging to another package without consulting the
1158 maintainer of that package first.
1162 All packages which supply an instance of a common command
1163 name (or, in general, filename) should generally use
1164 <prgn>update-alternatives</prgn>, so that they may be
1165 installed together. If <prgn>update-alternatives</prgn>
1166 is not used, then each package must use
1167 <tt>Conflicts</tt> to ensure that other packages are
1168 de-installed. (In this case, it may be appropriate to
1169 specify a conflict against earlier versions of something
1170 that previously did not use
1171 <prgn>update-alternatives</prgn>; this is an exception to
1172 the usual rule that versioned conflicts should be
1176 <sect1 id="maintscriptprompt">
1177 <heading>Prompting in maintainer scripts</heading>
1179 Package maintainer scripts may prompt the user if
1180 necessary. Prompting should be done by communicating
1181 through a program, such as <prgn>debconf</prgn>, which
1182 conforms to the Debian Configuration management
1183 specification, version 2 or higher. Prompting the user by
1184 other means, such as by hand<footnote>
1185 From the Jargon file: by hand 2. By extension,
1186 writing code which does something in an explicit or
1187 low-level way for which a presupplied library
1188 (<em>debconf, in this instance</em>) routine ought
1189 to have been available.
1190 </footnote>, is now deprecated.
1194 The Debian Configuration management specification is included
1195 in the <file>debconf_specification</file> files in the
1196 <package>debian-policy</package> package.
1197 It is also available from the Debian web mirrors at
1198 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1199 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1203 Packages which use the Debian Configuration management
1204 specification may contain an additional
1205 <prgn>config</prgn> script and a <tt>templates</tt>
1206 file in their control archive<footnote>
1207 The control.tar.gz inside the .deb.
1208 See <manref name="deb" section="5">.
1210 The <prgn>config</prgn> script might be run before the
1211 <prgn>preinst</prgn> script, and before the package is unpacked
1212 or any of its dependencies or pre-dependencies are satisfied.
1213 Therefore it must work using only the tools present in
1214 <em>essential</em> packages.<footnote>
1215 <package>Debconf</package> or another tool that
1216 implements the Debian Configuration management
1217 specification will also be installed, and any
1218 versioned dependencies on it will be satisfied
1219 before preconfiguration begins.
1224 Packages should try to minimize the amount of prompting
1225 they need to do, and they should ensure that the user
1226 will only ever be asked each question once. This means
1227 that packages should try to use appropriate shared
1228 configuration files (such as <file>/etc/papersize</file> and
1229 <file>/etc/news/server</file>), and shared
1230 <package>debconf</package> variables rather than each
1231 prompting for their own list of required pieces of
1236 It also means that an upgrade should not ask the same
1237 questions again, unless the user has used
1238 <tt>dpkg --purge</tt> to remove the package's configuration.
1239 The answers to configuration questions should be stored in an
1240 appropriate place in <file>/etc</file> so that the user can
1241 modify them, and how this has been done should be
1246 If a package has a vitally important piece of
1247 information to pass to the user (such as "don't run me
1248 as I am, you must edit the following configuration files
1249 first or you risk your system emitting badly-formatted
1250 messages"), it should display this in the
1251 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1252 prompt the user to hit return to acknowledge the
1253 message. Copyright messages do not count as vitally
1254 important (they belong in
1255 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1256 neither do instructions on how to use a program (these
1257 should be in on-line documentation, where all the users
1262 Any necessary prompting should almost always be confined
1263 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1264 script. If it is done in the <prgn>postinst</prgn>, it
1265 should be protected with a conditional so that
1266 unnecessary prompting doesn't happen if a package's
1267 installation fails and the <prgn>postinst</prgn> is
1268 called with <tt>abort-upgrade</tt>,
1269 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1279 <heading>Source packages</heading>
1281 <sect id="standardsversion">
1282 <heading>Standards conformance</heading>
1285 Source packages should specify the most recent version number
1286 of this policy document with which your package complied
1287 when it was last updated.
1291 This information may be used to file bug reports
1292 automatically if your package becomes too much out of date.
1296 The version is specified in the <tt>Standards-Version</tt>
1298 The format of the <tt>Standards-Version</tt> field is
1299 described in <ref id="f-Standards-Version">.
1303 You should regularly, and especially if your package has
1304 become out of date, check for the newest Policy Manual
1305 available and update your package, if necessary. When your
1306 package complies with the new standards you should update the
1307 <tt>Standards-Version</tt> source package field and
1308 release it.<footnote>
1309 See the file <file>upgrading-checklist</file> for
1310 information about policy which has changed between
1311 different versions of this document.
1317 <sect id="pkg-relations">
1318 <heading>Package relationships</heading>
1321 Source packages should specify which binary packages they
1322 require to be installed or not to be installed in order to
1323 build correctly. For example, if building a package
1324 requires a certain compiler, then the compiler should be
1325 specified as a build-time dependency.
1329 It is not necessary to explicitly specify build-time
1330 relationships on a minimal set of packages that are always
1331 needed to compile, link and put in a Debian package a
1332 standard "Hello World!" program written in C or C++. The
1333 required packages are called <em>build-essential</em>, and
1334 an informational list can be found in
1335 <file>/usr/share/doc/build-essential/list</file> (which is
1336 contained in the <tt>build-essential</tt>
1339 <list compact="compact">
1341 This allows maintaining the list separately
1342 from the policy documents (the list does not
1343 need the kind of control that the policy
1347 Having a separate package allows one to install
1348 the build-essential packages on a machine, as
1349 well as allowing other packages such as tasks to
1350 require installation of the build-essential
1351 packages using the depends relation.
1354 The separate package allows bug reports against
1355 the list to be categorized separately from
1356 the policy management process in the BTS.
1363 When specifying the set of build-time dependencies, one
1364 should list only those packages explicitly required by the
1365 build. It is not necessary to list packages which are
1366 required merely because some other package in the list of
1367 build-time dependencies depends on them.<footnote>
1368 The reason for this is that dependencies change, and
1369 you should list all those packages, and <em>only</em>
1370 those packages that <em>you</em> need directly. What
1371 others need is their business. For example, if you
1372 only link against <file>libimlib</file>, you will need to
1373 build-depend on <package>libimlib2-dev</package> but
1374 not against any <tt>libjpeg*</tt> packages, even
1375 though <tt>libimlib2-dev</tt> currently depends on
1376 them: installation of <package>libimlib2-dev</package>
1377 will automatically ensure that all of its run-time
1378 dependencies are satisfied.
1383 If build-time dependencies are specified, it must be
1384 possible to build the package and produce working binaries
1385 on a system with only essential and build-essential
1386 packages installed and also those required to satisfy the
1387 build-time relationships (including any implied
1388 relationships). In particular, this means that version
1389 clauses should be used rigorously in build-time
1390 relationships so that one cannot produce bad or
1391 inconsistently configured packages when the relationships
1392 are properly satisfied.
1396 <ref id="relationships"> explains the technical details.
1401 <heading>Changes to the upstream sources</heading>
1404 If changes to the source code are made that are not
1405 specific to the needs of the Debian system, they should be
1406 sent to the upstream authors in whatever form they prefer
1407 so as to be included in the upstream version of the
1412 If you need to configure the package differently for
1413 Debian or for Linux, and the upstream source doesn't
1414 provide a way to do so, you should add such configuration
1415 facilities (for example, a new <prgn>autoconf</prgn> test
1416 or <tt>#define</tt>) and send the patch to the upstream
1417 authors, with the default set to the way they originally
1418 had it. You can then easily override the default in your
1419 <file>debian/rules</file> or wherever is appropriate.
1423 You should make sure that the <prgn>configure</prgn> utility
1424 detects the correct architecture specification string
1425 (refer to <ref id="arch-spec"> for details).
1429 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1430 <prgn>configure</prgn> scripts are used, you should edit the
1431 <file>.in</file> files rather than editing the
1432 <prgn>Makefile</prgn> directly. This allows the user to
1433 reconfigure the package if necessary. You should
1434 <em>not</em> configure the package and edit the generated
1435 <prgn>Makefile</prgn>! This makes it impossible for someone
1436 else to later reconfigure the package without losing the
1442 <sect id="dpkgchangelog">
1443 <heading>Debian changelog: <file>debian/changelog</file></heading>
1446 Changes in the Debian version of the package should be
1447 briefly explained in the Debian changelog file
1448 <file>debian/changelog</file>.<footnote>
1450 Mistakes in changelogs are usually best rectified by
1451 making a new changelog entry rather than "rewriting
1452 history" by editing old changelog entries.
1455 This includes modifications
1456 made in the Debian package compared to the upstream one
1457 as well as other changes and updates to the package.
1459 Although there is nothing stopping an author who is also
1460 the Debian maintainer from using this changelog for all
1461 their changes, it will have to be renamed if the Debian
1462 and upstream maintainers become different people. In such
1463 a case, however, it might be better to maintain the package
1464 as a non-native package.
1473 The format of the <file>debian/changelog</file> allows the
1474 package building tools to discover which version of the package
1475 is being built and find out other release-specific information.
1479 That format is a series of entries like this:
1481 <example compact="compact">
1482 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1484 [optional blank line(s), stripped]
1486 * <var>change details</var>
1487 <var>more change details</var>
1489 [blank line(s), included in output of dpkg-parsechangelog]
1491 * <var>even more change details</var>
1493 [optional blank line(s), stripped]
1495 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1500 <var>package</var> and <var>version</var> are the source
1501 package name and version number.
1505 <var>distribution(s)</var> lists the distributions where
1506 this version should be installed when it is uploaded - it
1507 is copied to the <tt>Distribution</tt> field in the
1508 <file>.changes</file> file. See <ref id="f-Distribution">.
1512 <var>urgency</var> is the value for the <tt>Urgency</tt>
1513 field in the <file>.changes</file> file for the upload
1514 (see <ref id="f-Urgency">). It is not possible to specify
1515 an urgency containing commas; commas are used to separate
1516 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1517 <prgn>dpkg</prgn> changelog format (though there is
1518 currently only one useful <var>keyword</var>,
1519 <tt>urgency</tt>).<footnote>
1520 Recognized urgency values are <tt>low</tt>,
1521 <tt>medium</tt>, <tt>high</tt> and <tt>emergency</tt>.
1522 They have an effect on how quickly a package will be
1523 considered for inclusion into the <tt>testing</tt>
1524 distribution, and give an indication of the importance
1525 of any fixes included in this upload.
1530 The change details may in fact be any series of lines
1531 starting with at least two spaces, but conventionally each
1532 change starts with an asterisk and a separating space and
1533 continuation lines are indented so as to bring them in
1534 line with the start of the text above. Blank lines may be
1535 used here to separate groups of changes, if desired.
1539 If this upload resolves bugs recorded in the Bug Tracking
1540 System (BTS), they may be automatically closed on the
1541 inclusion of this package into the Debian archive by
1542 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1543 in the change details.<footnote>
1544 To be precise, the string should match the following
1545 Perl regular expression:
1547 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1549 Then all of the bug numbers listed will be closed by the
1550 archive maintenance script (<prgn>katie</prgn>), or in
1551 the case of an NMU, marked as fixed.
1553 This information is conveyed via the <tt>Closes</tt> field
1554 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1558 The maintainer name and email address used in the changelog
1559 should be the details of the person uploading <em>this</em>
1560 version. They are <em>not</em> necessarily those of the
1561 usual package maintainer. The information here will be
1562 copied to the <tt>Changed-By</tt> field in the
1563 <tt>.changes</tt> file (see <ref id="f-Changed-By">),
1564 and then later used to send an acknowledgement when the
1565 upload has been installed.
1569 The <var>date</var> should be in RFC822 format<footnote>
1570 This is generated by <tt>date -R</tt>.
1571 </footnote>; it should include the time zone specified
1572 numerically, with the time zone name or abbreviation
1573 optionally present as a comment in parentheses.
1577 The first "title" line with the package name should start
1578 at the left hand margin; the "trailer" line with the
1579 maintainer and date details should be preceded by exactly
1580 one space. The maintainer details and the date must be
1581 separated by exactly two spaces.
1585 For more information on placement of the changelog files
1586 within binary packages, please see <ref id="changelogs">.
1589 <sect1><heading>Alternative changelog formats</heading>
1592 In non-experimental packages you must use a format for
1593 <file>debian/changelog</file> which is supported by the most
1594 recent released version of <prgn>dpkg</prgn>.
1598 It is possible to use a format different from the standard
1599 one by providing a changelog parser for the format you wish
1600 to use. The parser must have an API compatible with that
1601 expected by <prgn>dpkg-genchanges</prgn> and
1602 <prgn>dpkg-gencontrol</prgn>, and it must not interact with
1605 If there is general interest in the new format, you should
1606 contact the <package>dpkg</package> maintainer to have the
1607 parser script for it included in the <prgn>dpkg</prgn>
1608 package. (You will need to agree that the parser and its
1609 man page may be distributed under the GNU GPL, just as the rest
1610 of <prgn>dpkg</prgn> is.)
1615 <sect id="dpkgcopyright">
1616 <heading>Copyright: <file>debian/copyright</file></heading>
1618 Every package must be accompanied by a verbatim copy of
1619 its copyright and distribution license in the file
1620 <file>/usr/share/doc/<var>package</var>/copyright</file>
1621 (see <ref id="copyrightfile"> for further details). Also see
1622 <ref id="pkgcopyright"> for further considerations relayed
1623 to copyrights for packages.
1627 <heading>Error trapping in makefiles</heading>
1630 When <prgn>make</prgn> invokes a command in a makefile
1631 (including your package's upstream makefiles and
1632 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1633 means that <prgn>sh</prgn>'s usual bad error handling
1634 properties apply: if you include a miniature script as one
1635 of the commands in your makefile you'll find that if you
1636 don't do anything about it then errors are not detected
1637 and <prgn>make</prgn> will blithely continue after
1642 Every time you put more than one shell command (this
1643 includes using a loop) in a makefile command you
1644 must make sure that errors are trapped. For
1645 simple compound commands, such as changing directory and
1646 then running a program, using <tt>&&</tt> rather
1647 than semicolon as a command separator is sufficient. For
1648 more complex commands including most loops and
1649 conditionals you should include a separate <tt>set -e</tt>
1650 command at the start of every makefile command that's
1651 actually one of these miniature shell scripts.
1655 <sect id="timestamps">
1656 <heading>Time Stamps</heading>
1658 Maintainers should preserve the modification times of the
1659 upstream source files in a package, as far as is reasonably
1661 The rationale is that there is some information conveyed
1662 by knowing the age of the file, for example, you could
1663 recognize that some documentation is very old by looking
1664 at the modification time, so it would be nice if the
1665 modification time of the upstream source would be
1671 <sect id="restrictions">
1672 <heading>Restrictions on objects in source packages</heading>
1675 The source package may not contain any hard links<footnote>
1677 This is not currently detected when building source
1678 packages, but only when extracting
1682 Hard links may be permitted at some point in the
1683 future, but would require a fair amount of
1686 </footnote>, device special files, sockets or setuid or
1687 setgid files.<footnote>
1688 Setgid directories are allowed.
1693 <sect id="debianrules">
1694 <heading>Main building script: <file>debian/rules</file></heading>
1697 This file must be an executable makefile, and contains the
1698 package-specific recipes for compiling the package and
1699 building binary package(s) from the source.
1703 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1704 so that it can be invoked by saying its name rather than
1705 invoking <prgn>make</prgn> explicitly.
1709 Since an interactive <file>debian/rules</file> script makes it
1710 impossible to auto-compile that package and also makes it
1711 hard for other people to reproduce the same binary
1712 package, all <em>required targets</em> MUST be
1713 non-interactive. At a minimum, required targets are the
1714 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1715 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1716 <em>binary-indep</em>, and <em>build</em>. It also follows
1717 that any target that these targets depend on must also be
1722 The targets are as follows (required unless stated otherwise):
1724 <tag><tt>build</tt></tag>
1727 The <tt>build</tt> target should perform all the
1728 configuration and compilation of the package.
1729 If a package has an interactive pre-build
1730 configuration routine, the Debianized source package
1731 must either be built after this has taken place (so
1732 that the binary package can be built without rerunning
1733 the configuration) or the configuration routine
1734 modified to become non-interactive. (The latter is
1735 preferable if there are architecture-specific features
1736 detected by the configuration routine.)
1740 For some packages, notably ones where the same
1741 source tree is compiled in different ways to produce
1742 two binary packages, the <tt>build</tt> target
1743 does not make much sense. For these packages it is
1744 good enough to provide two (or more) targets
1745 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1746 for each of the ways of building the package, and a
1747 <tt>build</tt> target that does nothing. The
1748 <tt>binary</tt> target will have to build the
1749 package in each of the possible ways and make the
1750 binary package out of each.
1754 The <tt>build</tt> target must not do anything
1755 that might require root privilege.
1759 The <tt>build</tt> target may need to run the
1760 <tt>clean</tt> target first - see below.
1764 When a package has a configuration and build routine
1765 which takes a long time, or when the makefiles are
1766 poorly designed, or when <tt>build</tt> needs to
1767 run <tt>clean</tt> first, it is a good idea to
1768 <tt>touch build</tt> when the build process is
1769 complete. This will ensure that if <tt>debian/rules
1770 build</tt> is run again it will not rebuild the whole
1772 Another common way to do this is for <tt>build</tt>
1773 to depend on <prgn>build-stamp</prgn> and to do
1774 nothing else, and for the <prgn>build-stamp</prgn>
1775 target to do the building and to <tt>touch
1776 build-stamp</tt> on completion. This is
1777 especially useful if the build routine creates a
1778 file or directory called <tt>build</tt>; in such a
1779 case, <tt>build</tt> will need to be listed as
1780 a phony target (i.e., as a dependency of the
1781 <tt>.PHONY</tt> target). See the documentation of
1782 <prgn>make</prgn> for more information on phony
1788 <tag><tt>build-arch</tt> (optional),
1789 <tt>build-indep</tt> (optional)
1793 A package may also provide both of the targets
1794 <tt>build-arch</tt> and <tt>build-indep</tt>.
1795 The <tt>build-arch</tt> target, if provided, should
1796 perform all the configuration and compilation required
1797 for producing all architecture-dependant binary packages
1798 (those packages for which the body of the
1799 <tt>Architecture</tt> field in <tt>debian/control</tt>
1800 is not <tt>all</tt>).
1801 Similarly, the <tt>build-indep</tt> target, if
1802 provided, should perform all the configuration and
1803 compilation required for producing all
1804 architecture-independent binary packages
1805 (those packages for which the body of the
1806 <tt>Architecture</tt> field in <tt>debian/control</tt>
1808 The <tt>build</tt> target should depend on those of the
1809 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1810 are provided in the rules file.
1814 If one or both of the targets <tt>build-arch</tt> and
1815 <tt>build-indep</tt> are not provided, then invoking
1816 <file>debian/rules</file> with one of the not-provided
1817 targets as arguments should produce a exit status code
1818 of 2. Usually this is provided automatically by make
1819 if the target is missing.
1823 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1824 must not do anything that might require root privilege.
1828 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1829 <tt>binary-indep</tt>
1833 The <tt>binary</tt> target must be all that is
1834 necessary for the user to build the binary package(s)
1835 produced from this source package. It is
1836 split into two parts: <prgn>binary-arch</prgn> builds
1837 the binary packages which are specific to a particular
1838 architecture, and <tt>binary-indep</tt> builds
1839 those which are not.
1842 <tt>binary</tt> may be (and commonly is) a target with
1843 no commands which simply depends on
1844 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1847 Both <tt>binary-*</tt> targets should depend on the
1848 <tt>build</tt> target, or on the appropriate
1849 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1850 provided, so that the package is built if it has not
1851 been already. It should then create the relevant
1852 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1853 make their control files and <prgn>dpkg-deb</prgn> to
1854 build them and place them in the parent of the top
1859 Both the <tt>binary-arch</tt> and
1860 <tt>binary-indep</tt> targets <em>must</em> exist.
1861 If one of them has nothing to do (which will always be
1862 the case if the source generates only a single binary
1863 package, whether architecture-dependent or not), it
1864 must still exist and must always succeed.
1868 The <tt>binary</tt> targets must be invoked as
1870 The <prgn>fakeroot</prgn> package often allows one
1871 to build a package correctly even without being
1877 <tag><tt>clean</tt></tag>
1880 This must undo any effects that the <tt>build</tt>
1881 and <tt>binary</tt> targets may have had, except
1882 that it should leave alone any output files created in
1883 the parent directory by a run of a <tt>binary</tt>
1888 If a <tt>build</tt> file is touched at the end of
1889 the <tt>build</tt> target, as suggested above, it
1890 should be removed as the first action that
1891 <tt>clean</tt> performs, so that running
1892 <tt>build</tt> again after an interrupted
1893 <tt>clean</tt> doesn't think that everything is
1898 The <tt>clean</tt> target may need to be
1899 invoked as root if <tt>binary</tt> has been
1900 invoked since the last <tt>clean</tt>, or if
1901 <tt>build</tt> has been invoked as root (since
1902 <tt>build</tt> may create directories, for
1907 <tag><tt>get-orig-source</tt> (optional)</tag>
1910 This target fetches the most recent version of the
1911 original source package from a canonical archive site
1912 (via FTP or WWW, for example), does any necessary
1913 rearrangement to turn it into the original source
1914 tar file format described below, and leaves it in the
1919 This target may be invoked in any directory, and
1920 should take care to clean up any temporary files it
1925 This target is optional, but providing it if
1926 possible is a good idea.
1932 The <tt>build</tt>, <tt>binary</tt> and
1933 <tt>clean</tt> targets must be invoked with the current
1934 directory being the package's top-level directory.
1939 Additional targets may exist in <file>debian/rules</file>,
1940 either as published or undocumented interfaces or for the
1941 package's internal use.
1945 The architectures we build on and build for are determined
1946 by <prgn>make</prgn> variables using the utility
1947 <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
1948 You can determine the
1949 Debian architecture and the GNU style architecture
1950 specification string for the build machine (the machine type
1951 we are building on) as well as for the host machine (the
1952 machine type we are building for). Here is a list of
1953 supported <prgn>make</prgn> variables:
1954 <list compact="compact">
1956 <tt>DEB_*_ARCH</tt> (the Debian architecture)
1959 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
1960 specification string)
1963 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
1964 <tt>DEB_*_GNU_TYPE</tt>)
1967 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
1968 <tt>DEB_*_GNU_TYPE</tt>)
1970 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
1971 the build machine or <tt>HOST</tt> for specification of the
1976 Backward compatibility can be provided in the rules file
1977 by setting the needed variables to suitable default
1978 values; please refer to the documentation of
1979 <prgn>dpkg-architecture</prgn> for details.
1983 It is important to understand that the <tt>DEB_*_ARCH</tt>
1984 string only determines which Debian architecture we are
1985 building on or for. It should not be used to get the CPU
1986 or system information; the GNU style variables should be
1991 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
1992 <sect id="substvars">
1993 <heading>Variable substitutions: <file>debian/substvars</file></heading>
1996 When <prgn>dpkg-gencontrol</prgn>,
1997 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
1998 generate control files they perform variable substitutions
1999 on their output just before writing it. Variable
2000 substitutions have the form <tt>${<var>variable</var>}</tt>.
2001 The optional file <file>debian/substvars</file> contains
2002 variable substitutions to be used; variables can also be set
2003 directly from <file>debian/rules</file> using the <tt>-V</tt>
2004 option to the source packaging commands, and certain
2005 predefined variables are also available.
2009 The <file>debian/substvars</file> file is usually generated and
2010 modified dynamically by <file>debian/rules</file> targets, in
2011 which case it must be removed by the <tt>clean</tt> target.
2015 See <manref name="dpkg-source" section="1"> for full
2016 details about source variable substitutions, including the
2017 format of <file>debian/substvars</file>.</p>
2020 <sect id="debianwatch">
2021 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2024 This is an optional, recommended control file for the
2025 <tt>uscan</tt> utility which defines how to automatically
2026 scan ftp or http sites for newly available updates of the
2027 package. This is used by <url id="
2028 http://dehs.alioth.debian.org/"> and other Debian QA tools
2029 to help with quality control and maintenance of the
2030 distribution as a whole.
2035 <sect id="debianfiles">
2036 <heading>Generated files list: <file>debian/files</file></heading>
2039 This file is not a permanent part of the source tree; it
2040 is used while building packages to record which files are
2041 being generated. <prgn>dpkg-genchanges</prgn> uses it
2042 when it generates a <file>.changes</file> file.
2046 It should not exist in a shipped source package, and so it
2047 (and any backup files or temporary files such as
2048 <file>files.new</file><footnote>
2049 <file>files.new</file> is used as a temporary file by
2050 <prgn>dpkg-gencontrol</prgn> and
2051 <prgn>dpkg-distaddfile</prgn> - they write a new
2052 version of <tt>files</tt> here before renaming it,
2053 to avoid leaving a corrupted copy if an error
2055 </footnote>) should be removed by the
2056 <tt>clean</tt> target. It may also be wise to
2057 ensure a fresh start by emptying or removing it at the
2058 start of the <tt>binary</tt> target.
2062 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2063 package, it adds an entry to <file>debian/files</file> for the
2064 <file>.deb</file> file that will be created when <tt>dpkg-deb
2065 --build</tt> is run for that binary package. So for most
2066 packages all that needs to be done with this file is to
2067 delete it in the <tt>clean</tt> target.
2071 If a package upload includes files besides the source
2072 package and any binary packages whose control files were
2073 made with <prgn>dpkg-gencontrol</prgn> then they should be
2074 placed in the parent of the package's top-level directory
2075 and <prgn>dpkg-distaddfile</prgn> should be called to add
2076 the file to the list in <file>debian/files</file>.</p>
2082 <chapt id="controlfields">
2083 <heading>Control files and their fields</heading>
2086 The package management system manipulates data represented in
2087 a common format, known as <em>control data</em>, stored in
2088 <em>control files</em>.
2089 Control files are used for source packages, binary packages and
2090 the <file>.changes</file> files which control the installation
2091 of uploaded files<footnote>
2092 <prgn>dpkg</prgn>'s internal databases are in a similar
2097 <sect id="controlsyntax">
2098 <heading>Syntax of control files</heading>
2101 A control file consists of one or more paragraphs of
2103 The paragraphs are also sometimes referred to as stanzas.
2105 The paragraphs are separated by blank lines. Some control
2106 files allow only one paragraph; others allow several, in
2107 which case each paragraph usually refers to a different
2108 package. (For example, in source packages, the first
2109 paragraph refers to the source package, and later paragraphs
2110 refer to binary packages generated from the source.)
2114 Each paragraph consists of a series of data fields; each
2115 field consists of the field name, followed by a colon and
2116 then the data/value associated with that field. It ends at
2117 the end of the (logical) line. Horizontal whitespace
2118 (spaces and tabs) may occur immediately before or after the
2119 value and is ignored there; it is conventional to put a
2120 single space after the colon. For example, a field might
2122 <example compact="compact">
2125 the field name is <tt>Package</tt> and the field value
2130 Many fields' values may span several lines; in this case
2131 each continuation line must start with a space or a tab.
2132 Any trailing spaces or tabs at the end of individual
2133 lines of a field value are ignored.
2137 In fields where it is specified that lines may not wrap,
2138 only a single line of data is allowed and whitespace is not
2139 significant in a field body. Whitespace must not appear
2140 inside names (of packages, architectures, files or anything
2141 else) or version numbers, or between the characters of
2142 multi-character version relationships.
2146 Field names are not case-sensitive, but it is usual to
2147 capitalize the field names using mixed case as shown below.
2151 Blank lines, or lines consisting only of spaces and tabs,
2152 are not allowed within field values or between fields - that
2153 would mean a new paragraph.
2158 <sect id="sourcecontrolfiles">
2159 <heading>Source package control files -- <file>debian/control</file></heading>
2162 The <file>debian/control</file> file contains the most vital
2163 (and version-independent) information about the source package
2164 and about the binary packages it creates.
2168 The first paragraph of the control file contains information about
2169 the source package in general. The subsequent sets each describe a
2170 binary package that the source tree builds.
2174 The fields in the general paragraph (the first one, for the source
2177 <list compact="compact">
2178 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2179 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2180 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2181 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2182 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2183 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2184 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2189 The fields in the binary package paragraphs are:
2191 <list compact="compact">
2192 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2193 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2194 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2195 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2196 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2197 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2198 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2203 The syntax and semantics of the fields are described below.
2209 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2210 generate control files for binary packages (see below), by
2211 <prgn>dpkg-genchanges</prgn> to generate the
2212 <tt>.changes</tt> file to accompany the upload, and by
2213 <prgn>dpkg-source</prgn> when it creates the
2214 <file>.dsc</file> source control file as part of a source
2215 archive. Many fields are permitted to span multiple lines in
2216 <file>debian/control</file> but not in any other control
2217 file. These tools are responsible for removing the line
2218 breaks from such fields when using fields from
2219 <file>debian/control</file> to generate other control files.
2223 The fields here may contain variable references - their
2224 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2225 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2226 when they generate output control files.
2227 See <ref id="substvars"> for details.
2232 <sect id="binarycontrolfiles">
2233 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2236 The <file>DEBIAN/control</file> file contains the most vital
2237 (and version-dependent) information about a binary package.
2241 The fields in this file are:
2243 <list compact="compact">
2244 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2245 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2246 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2247 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2248 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2249 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2250 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2251 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2252 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2253 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2254 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2259 <sect id="debiansourcecontrolfiles">
2260 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2263 This file contains a series of fields, identified and
2264 separated just like the fields in the control file of
2265 a binary package. The fields are listed below; their
2266 syntax is described above, in <ref id="pkg-controlfields">.
2268 <list compact="compact">
2269 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2270 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2271 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2272 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2273 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2274 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2275 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2276 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2277 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2278 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2283 The source package control file is generated by
2284 <prgn>dpkg-source</prgn> when it builds the source
2285 archive, from other files in the source package,
2286 described above. When unpacking, it is checked against
2287 the files and directories in the other parts of the
2293 <sect id="debianchangesfiles">
2294 <heading>Debian changes files -- <file>.changes</file></heading>
2297 The .changes files are used by the Debian archive maintenance
2298 software to process updates to packages. They contain one
2299 paragraph which contains information from the
2300 <tt>debian/control</tt> file and other data about the
2301 source package gathered via <tt>debian/changelog</tt>
2302 and <tt>debian/rules</tt>.
2306 The fields in this file are:
2308 <list compact="compact">
2309 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2310 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2311 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2312 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2313 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2314 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2315 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2316 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2317 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2318 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2319 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2320 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2321 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2322 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2327 <sect id="controlfieldslist">
2328 <heading>List of fields</heading>
2330 <sect1 id="f-Source">
2331 <heading><tt>Source</tt></heading>
2334 This field identifies the source package name.
2338 In <file>debian/control</file> or a <file>.dsc</file> file,
2339 this field must contain only the name of the source package.
2343 In a binary package control file or a <file>.changes</file>
2344 file, the source package name may be followed by a version
2345 number in parentheses<footnote>
2346 It is customary to leave a space after the package name
2347 if a version number is specified.
2349 This version number may be omitted (and is, by
2350 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2351 the <tt>Version</tt> field of the binary package in
2352 question. The field itself may be omitted from a binary
2353 package control file when the source package has the same
2354 name and version as the binary package.
2358 <sect1 id="f-Maintainer">
2359 <heading><tt>Maintainer</tt></heading>
2362 The package maintainer's name and email address. The name
2363 should come first, then the email address inside angle
2364 brackets <tt><></tt> (in RFC822 format).
2368 If the maintainer's name contains a full stop then the
2369 whole field will not work directly as an email address due
2370 to a misfeature in the syntax specified in RFC822; a
2371 program using this field as an address must check for this
2372 and correct the problem if necessary (for example by
2373 putting the name in round brackets and moving it to the
2374 end, and bringing the email address forward).
2378 <sect1 id="f-Uploaders">
2379 <heading><tt>Uploaders</tt></heading>
2382 List of the names and email addresses of co-maintainers of
2383 the package, if any. If the package has other maintainers
2384 beside the one named in the
2385 <qref id="f-Maintainer">Maintainer field</qref>, their
2386 names and email addresses should be listed here. The
2387 format is the same as that of the Maintainer tag, and
2388 multiple entries should be comma separated. Currently,
2389 this field is restricted to a single line of data. This
2390 is an optional field.
2393 Any parser that interprets the Uploaders field in
2394 <file>debian/control</file> should permit it to span multiple
2396 In the future, the Uploaders field in
2397 <file>debian/control</file> (but not other control files)
2398 will be permitted to span multiple lines and interpreting
2399 a multi-line Uploaders field shall be mandatory.
2400 </footnote>. Line breaks in an Uploaders field that spans
2401 multiple lines are not significant and the semantics of
2402 the field are the same as if the line breaks had not been
2407 <sect1 id="f-Changed-By">
2408 <heading><tt>Changed-By</tt></heading>
2411 The name and email address of the person who changed the
2412 said package. Usually the name of the maintainer.
2413 All the rules for the Maintainer field apply here, too.
2417 <sect1 id="f-Section">
2418 <heading><tt>Section</tt></heading>
2421 This field specifies an application area into which the package
2422 has been classified. See <ref id="subsections">.
2426 When it appears in the <file>debian/control</file> file,
2427 it gives the value for the subfield of the same name in
2428 the <tt>Files</tt> field of the <file>.changes</file> file.
2429 It also gives the default for the same field in the binary
2434 <sect1 id="f-Priority">
2435 <heading><tt>Priority</tt></heading>
2438 This field represents how important that it is that the user
2439 have the package installed. See <ref id="priorities">.
2443 When it appears in the <file>debian/control</file> file,
2444 it gives the value for the subfield of the same name in
2445 the <tt>Files</tt> field of the <file>.changes</file> file.
2446 It also gives the default for the same field in the binary
2451 <sect1 id="f-Package">
2452 <heading><tt>Package</tt></heading>
2455 The name of the binary package.
2459 Package names must consist only of lower case letters
2460 (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus (<tt>+</tt>)
2461 and minus (<tt>-</tt>) signs, and periods (<tt>.</tt>).
2462 They must be at least two characters long and must start
2463 with an alphanumeric character.
2467 <sect1 id="f-Architecture">
2468 <heading><tt>Architecture</tt></heading>
2471 Depending on context and the control file used, the
2472 <tt>Architecture</tt> field can include the following sets of
2475 <item>A unique single word identifying a Debian machine
2476 architecture, see <ref id="arch-spec">.
2477 <item><tt>all</tt>, which indicates an
2478 architecture-independent package.
2479 <item><tt>any</tt>, which indicates a package available
2480 for building on any architecture.
2481 <item><tt>source</tt>, which indicates a source package.
2486 In the main <file>debian/control</file> file in the source
2487 package, or in the source package control file
2488 <file>.dsc</file>, one may specify a list of architectures
2489 separated by spaces, or the special values <tt>any</tt> or
2494 Specifying <tt>any</tt> indicates that the source package
2495 isn't dependent on any particular architecture and should
2496 compile fine on any one. The produced binary package(s)
2497 will be specific to whatever the current build architecture
2499 This is the most often used setting, and is recommended
2500 for new packages that aren't <tt>Architecture: all</tt>.
2505 Specifying a list of architectures indicates that the source
2506 will build an architecture-dependent package, and will only
2507 work correctly on the listed architectures.<footnote>
2508 This is a setting used for a minority of cases where the
2509 program is not portable. Generally, it should not be used
2515 In a <file>.changes</file> file, the <tt>Architecture</tt>
2516 field lists the architecture(s) of the package(s)
2517 currently being uploaded. This will be a list; if the
2518 source for the package is also being uploaded, the special
2519 entry <tt>source</tt> is also present.
2523 See <ref id="debianrules"> for information how to get the
2524 architecture for the build process.
2528 <sect1 id="f-Essential">
2529 <heading><tt>Essential</tt></heading>
2532 This is a boolean field which may occur only in the
2533 control file of a binary package or in a per-package fields
2534 paragraph of a main source control data file.
2538 If set to <tt>yes</tt> then the package management system
2539 will refuse to remove the package (upgrading and replacing
2540 it is still possible). The other possible value is <tt>no</tt>,
2541 which is the same as not having the field at all.
2546 <heading>Package interrelationship fields:
2547 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2548 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Conflicts</tt>,
2549 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2553 These fields describe the package's relationships with
2554 other packages. Their syntax and semantics are described
2555 in <ref id="relationships">.</p>
2558 <sect1 id="f-Standards-Version">
2559 <heading><tt>Standards-Version</tt></heading>
2562 The most recent version of the standards (the policy
2563 manual and associated texts) with which the package
2568 The version number has four components: major and minor
2569 version number and major and minor patch level. When the
2570 standards change in a way that requires every package to
2571 change the major number will be changed. Significant
2572 changes that will require work in many packages will be
2573 signaled by a change to the minor number. The major patch
2574 level will be changed for any change to the meaning of the
2575 standards, however small; the minor patch level will be
2576 changed when only cosmetic, typographical or other edits
2577 are made which neither change the meaning of the document
2578 nor affect the contents of packages.
2582 Thus only the first three components of the policy version
2583 are significant in the <em>Standards-Version</em> control
2584 field, and so either these three components or the all
2585 four components may be specified.<footnote>
2586 In the past, people specified the full version number
2587 in the Standards-Version field, for example "2.3.0.0".
2588 Since minor patch-level changes don't introduce new
2589 policy, it was thought it would be better to relax
2590 policy and only require the first 3 components to be
2591 specified, in this example "2.3.0". All four
2592 components may still be used if someone wishes to do so.
2598 <sect1 id="f-Version">
2599 <heading><tt>Version</tt></heading>
2602 The version number of a package. The format is:
2603 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
2607 The three components here are:
2609 <tag><var>epoch</var></tag>
2612 This is a single (generally small) unsigned integer. It
2613 may be omitted, in which case zero is assumed. If it is
2614 omitted then the <var>upstream_version</var> may not
2619 It is provided to allow mistakes in the version numbers
2620 of older versions of a package, and also a package's
2621 previous version numbering schemes, to be left behind.
2625 <tag><var>upstream_version</var></tag>
2628 This is the main part of the version number. It is
2629 usually the version number of the original ("upstream")
2630 package from which the <file>.deb</file> file has been made,
2631 if this is applicable. Usually this will be in the same
2632 format as that specified by the upstream author(s);
2633 however, it may need to be reformatted to fit into the
2634 package management system's format and comparison
2639 The comparison behavior of the package management system
2640 with respect to the <var>upstream_version</var> is
2641 described below. The <var>upstream_version</var>
2642 portion of the version number is mandatory.
2646 The <var>upstream_version</var> may contain only
2647 alphanumerics<footnote>
2648 Alphanumerics are <tt>A-Za-z0-9</tt> only.
2650 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
2651 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
2652 tilde) and should start with a digit. If there is no
2653 <var>debian_revision</var> then hyphens are not allowed;
2654 if there is no <var>epoch</var> then colons are not
2659 <tag><var>debian_revision</var></tag>
2662 This part of the version number specifies the version of
2663 the Debian package based on the upstream version. It
2664 may contain only alphanumerics and the characters
2665 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
2666 tilde) and is compared in the same way as the
2667 <var>upstream_version</var> is.
2671 It is optional; if it isn't present then the
2672 <var>upstream_version</var> may not contain a hyphen.
2673 This format represents the case where a piece of
2674 software was written specifically to be turned into a
2675 Debian package, and so there is only one "debianisation"
2676 of it and therefore no revision indication is required.
2680 It is conventional to restart the
2681 <var>debian_revision</var> at <tt>1</tt> each time the
2682 <var>upstream_version</var> is increased.
2686 The package management system will break the version
2687 number apart at the last hyphen in the string (if there
2688 is one) to determine the <var>upstream_version</var> and
2689 <var>debian_revision</var>. The absence of a
2690 <var>debian_revision</var> compares earlier than the
2691 presence of one (but note that the
2692 <var>debian_revision</var> is the least significant part
2693 of the version number).
2700 The <var>upstream_version</var> and <var>debian_revision</var>
2701 parts are compared by the package management system using the
2706 The strings are compared from left to right.
2710 First the initial part of each string consisting entirely of
2711 non-digit characters is determined. These two parts (one of
2712 which may be empty) are compared lexically. If a difference
2713 is found it is returned. The lexical comparison is a
2714 comparison of ASCII values modified so that all the letters
2715 sort earlier than all the non-letters and so that a tilde
2716 sorts before anything, even the end of a part. For example,
2717 the following parts are in sorted order from earliest to
2718 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
2719 <tt>a</tt>.<footnote>
2720 One common use of <tt>~</tt> is for upstream pre-releases.
2721 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
2722 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
2727 Then the initial part of the remainder of each string which
2728 consists entirely of digit characters is determined. The
2729 numerical values of these two parts are compared, and any
2730 difference found is returned as the result of the comparison.
2731 For these purposes an empty string (which can only occur at
2732 the end of one or both version strings being compared) counts
2737 These two steps (comparing and removing initial non-digit
2738 strings and initial digit strings) are repeated until a
2739 difference is found or both strings are exhausted.
2743 Note that the purpose of epochs is to allow us to leave behind
2744 mistakes in version numbering, and to cope with situations
2745 where the version numbering scheme changes. It is
2746 <em>not</em> intended to cope with version numbers containing
2747 strings of letters which the package management system cannot
2748 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
2749 silly orderings (the author of this manual has heard of a
2750 package whose versions went <tt>1.1</tt>, <tt>1.2</tt>,
2751 <tt>1.3</tt>, <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>,
2752 <tt>2</tt> and so forth).
2756 <sect1 id="f-Description">
2757 <heading><tt>Description</tt></heading>
2760 In a source or binary control file, the <tt>Description</tt>
2761 field contains a description of the binary package, consisting
2762 of two parts, the synopsis or the short description, and the
2763 long description. The field's format is as follows:
2768 Description: <single line synopsis>
2769 <extended description over several lines>
2774 The lines in the extended description can have these formats:
2780 Those starting with a single space are part of a paragraph.
2781 Successive lines of this form will be word-wrapped when
2782 displayed. The leading space will usually be stripped off.
2786 Those starting with two or more spaces. These will be
2787 displayed verbatim. If the display cannot be panned
2788 horizontally, the displaying program will line wrap them "hard"
2789 (i.e., without taking account of word breaks). If it can they
2790 will be allowed to trail off to the right. None, one or two
2791 initial spaces may be deleted, but the number of spaces
2792 deleted from each line will be the same (so that you can have
2793 indenting work correctly, for example).
2797 Those containing a single space followed by a single full stop
2798 character. These are rendered as blank lines. This is the
2799 <em>only</em> way to get a blank line<footnote>
2800 Completely empty lines will not be rendered as blank lines.
2801 Instead, they will cause the parser to think you're starting
2802 a whole new record in the control file, and will therefore
2803 likely abort with an error.
2808 Those containing a space, a full stop and some more characters.
2809 These are for future expansion. Do not use them.
2815 Do not use tab characters. Their effect is not predictable.
2819 See <ref id="descriptions"> for further information on this.
2823 In a <file>.changes</file> file, the <tt>Description</tt> field
2824 contains a summary of the descriptions for the packages being
2829 The part of the field before the first newline is empty;
2830 thereafter each line has the name of a binary package and
2831 the summary description line from that binary package.
2832 Each line is indented by one space.
2837 <sect1 id="f-Distribution">
2838 <heading><tt>Distribution</tt></heading>
2841 In a <file>.changes</file> file or parsed changelog output
2842 this contains the (space-separated) name(s) of the
2843 distribution(s) where this version of the package should
2844 be installed. Valid distributions are determined by the
2845 archive maintainers.<footnote>
2846 Current distribution names are:
2847 <taglist compact="compact">
2848 <tag><em>stable</em></tag>
2850 This is the current "released" version of Debian
2851 GNU/Linux. Once the distribution is
2852 <em>stable</em> only security fixes and other
2853 major bug fixes are allowed. When changes are
2854 made to this distribution, the release number is
2855 increased (for example: 2.2r1 becomes 2.2r2 then
2859 <tag><em>unstable</em></tag>
2861 This distribution value refers to the
2862 <em>developmental</em> part of the Debian
2863 distribution tree. New packages, new upstream
2864 versions of packages and bug fixes go into the
2865 <em>unstable</em> directory tree. Download from
2866 this distribution at your own risk.
2869 <tag><em>testing</em></tag>
2871 This distribution value refers to the
2872 <em>testing</em> part of the Debian distribution
2873 tree. It receives its packages from the
2874 unstable distribution after a short time lag to
2875 ensure that there are no major issues with the
2876 unstable packages. It is less prone to breakage
2877 than unstable, but still risky. It is not
2878 possible to upload packages directly to
2882 <tag><em>frozen</em></tag>
2884 From time to time, the <em>testing</em>
2885 distribution enters a state of "code-freeze" in
2886 anticipation of release as a <em>stable</em>
2887 version. During this period of testing only
2888 fixes for existing or newly-discovered bugs will
2889 be allowed. The exact details of this stage are
2890 determined by the Release Manager.
2893 <tag><em>experimental</em></tag>
2895 The packages with this distribution value are
2896 deemed by their maintainers to be high
2897 risk. Oftentimes they represent early beta or
2898 developmental packages from various sources that
2899 the maintainers want people to try, but are not
2900 ready to be a part of the other parts of the
2901 Debian distribution tree. Download at your own
2907 You should list <em>all</em> distributions that the
2908 package should be installed into.
2912 More information is available in the Debian Developer's
2913 Reference, section "The Debian archive".
2920 <heading><tt>Date</tt></heading>
2923 This field includes the date the package was built or last edited.
2927 The value of this field is usually extracted from the
2928 <file>debian/changelog</file> file - see
2929 <ref id="dpkgchangelog">).
2933 <sect1 id="f-Format">
2934 <heading><tt>Format</tt></heading>
2937 This field specifies a format revision for the file.
2938 The most current format described in the Policy Manual
2939 is version <strong>1.5</strong>. The syntax of the
2940 format value is the same as that of a package version
2941 number except that no epoch or Debian revision is allowed
2942 - see <ref id="f-Version">.
2946 <sect1 id="f-Urgency">
2947 <heading><tt>Urgency</tt></heading>
2950 This is a description of how important it is to upgrade to
2951 this version from previous ones. It consists of a single
2952 keyword usually taking one of the values <tt>low</tt>,
2953 <tt>medium</tt> or <tt>high</tt> (not case-sensitive)
2954 followed by an optional commentary (separated by a space)
2955 which is usually in parentheses. For example:
2958 Urgency: low (HIGH for users of diversions)
2964 The value of this field is usually extracted from the
2965 <file>debian/changelog</file> file - see
2966 <ref id="dpkgchangelog">.
2970 <sect1 id="f-Changes">
2971 <heading><tt>Changes</tt></heading>
2974 This field contains the human-readable changes data, describing
2975 the differences between the last version and the current one.
2979 There should be nothing in this field before the first
2980 newline; all the subsequent lines must be indented by at
2981 least one space; blank lines must be represented by a line
2982 consisting only of a space and a full stop.
2986 The value of this field is usually extracted from the
2987 <file>debian/changelog</file> file - see
2988 <ref id="dpkgchangelog">).
2992 Each version's change information should be preceded by a
2993 "title" line giving at least the version, distribution(s)
2994 and urgency, in a human-readable way.
2998 If data from several versions is being returned the entry
2999 for the most recent version should be returned first, and
3000 entries should be separated by the representation of a
3001 blank line (the "title" line may also be followed by the
3002 representation of blank line).
3006 <sect1 id="f-Binary">
3007 <heading><tt>Binary</tt></heading>
3010 This field is a list of binary packages.
3014 When it appears in the <file>.dsc</file> file it is the list
3015 of binary packages which a source package can produce. It
3016 does not necessarily produce all of these binary packages
3017 for every architecture. The source control file doesn't
3018 contain details of which architectures are appropriate for
3019 which of the binary packages.
3023 When it appears in a <file>.changes</file> file it lists the
3024 names of the binary packages actually being uploaded.
3028 The syntax is a list of binary packages separated by
3030 A space after each comma is conventional.
3031 </footnote>. Currently the packages must be separated using
3032 only spaces in the <file>.changes</file> file.
3036 <sect1 id="f-Installed-Size">
3037 <heading><tt>Installed-Size</tt></heading>
3040 This field appears in the control files of binary
3041 packages, and in the <file>Packages</file> files. It gives
3042 the total amount of disk space required to install the
3047 The disk space is represented in kilobytes as a simple
3052 <sect1 id="f-Files">
3053 <heading><tt>Files</tt></heading>
3056 This field contains a list of files with information about
3057 each one. The exact information and syntax varies with
3058 the context. In all cases the part of the field
3059 contents on the same line as the field name is empty. The
3060 remainder of the field is one line per file, each line
3061 being indented by one space and containing a number of
3062 sub-fields separated by spaces.
3066 In the <file>.dsc</file> file, each line contains the MD5
3067 checksum, size and filename of the tar file and (if applicable)
3068 diff file which make up the remainder of the source
3070 That is, the parts which are not the <tt>.dsc</tt>.
3072 The exact forms of the filenames are described
3073 in <ref id="pkg-sourcearchives">.
3077 In the <file>.changes</file> file this contains one line per
3078 file being uploaded. Each line contains the MD5 checksum,
3079 size, section and priority and the filename.
3080 The <qref id="f-Section">section</qref>
3081 and <qref id="f-Priority">priority</qref>
3082 are the values of the corresponding fields in
3083 the main source control file. If no section or priority is
3084 specified then <tt>-</tt> should be used, though section
3085 and priority values must be specified for new packages to
3086 be installed properly.
3090 The special value <tt>byhand</tt> for the section in a
3091 <tt>.changes</tt> file indicates that the file in question
3092 is not an ordinary package file and must by installed by
3093 hand by the distribution maintainers. If the section is
3094 <tt>byhand</tt> the priority should be <tt>-</tt>.
3098 If a new Debian revision of a package is being shipped and
3099 no new original source archive is being distributed the
3100 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3101 entry for the original source archive
3102 <file><var>package</var>-<var>upstream-version</var>.orig.tar.gz</file>,
3103 but the <file>.changes</file> file should leave it out. In
3104 this case the original source archive on the distribution
3105 site must match exactly, byte-for-byte, the original
3106 source archive which was used to generate the
3107 <file>.dsc</file> file and diff which are being uploaded.</p>
3110 <sect1 id="f-Closes">
3111 <heading><tt>Closes</tt></heading>
3114 A space-separated list of bug report numbers that the upload
3115 governed by the .changes file closes.
3122 <heading>User-defined fields</heading>
3125 Additional user-defined fields may be added to the
3126 source package control file. Such fields will be
3127 ignored, and not copied to (for example) binary or
3128 source package control files or upload control files.
3132 If you wish to add additional unsupported fields to
3133 these output files you should use the mechanism
3138 Fields in the main source control information file with
3139 names starting <tt>X</tt>, followed by one or more of
3140 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3141 be copied to the output files. Only the part of the
3142 field name after the hyphen will be used in the output
3143 file. Where the letter <tt>B</tt> is used the field
3144 will appear in binary package control files, where the
3145 letter <tt>S</tt> is used in source package control
3146 files and where <tt>C</tt> is used in upload control
3147 (<tt>.changes</tt>) files.
3151 For example, if the main source information control file
3154 XBS-Comment: I stand between the candle and the star.
3156 then the binary and source package control files will contain the
3159 Comment: I stand between the candle and the star.
3168 <chapt id="maintainerscripts">
3169 <heading>Package maintainer scripts and installation procedure</heading>
3172 <heading>Introduction to package maintainer scripts</heading>
3175 It is possible to supply scripts as part of a package which
3176 the package management system will run for you when your
3177 package is installed, upgraded or removed.
3181 These scripts are the files <prgn>preinst</prgn>,
3182 <prgn>postinst</prgn>, <prgn>prerm</prgn> and
3183 <prgn>postrm</prgn> in the control area of the package.
3184 They must be proper executable files; if they are scripts
3185 (which is recommended), they must start with the usual
3186 <tt>#!</tt> convention. They should be readable and
3187 executable by anyone, and must not be world-writable.
3191 The package management system looks at the exit status from
3192 these scripts. It is important that they exit with a
3193 non-zero status if there is an error, so that the package
3194 management system can stop its processing. For shell
3195 scripts this means that you <em>almost always</em> need to
3196 use <tt>set -e</tt> (this is usually true when writing shell
3197 scripts, in fact). It is also important, of course, that
3198 they don't exit with a non-zero status if everything went
3203 Additionally, packages interacting with users using
3204 <tt>debconf</tt> in the <prgn>postinst</prgn> script should
3205 install a <prgn>config</prgn> script in the control area,
3206 see <ref id="maintscriptprompt"> for details.
3210 When a package is upgraded a combination of the scripts from
3211 the old and new packages is called during the upgrade
3212 procedure. If your scripts are going to be at all
3213 complicated you need to be aware of this, and may need to
3214 check the arguments to your scripts.
3218 Broadly speaking the <prgn>preinst</prgn> is called before
3219 (a particular version of) a package is installed, and the
3220 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3221 before (a version of) a package is removed and the
3222 <prgn>postrm</prgn> afterwards.
3226 Programs called from maintainer scripts should not normally
3227 have a path prepended to them. Before installation is
3228 started, the package management system checks to see if the
3229 programs <prgn>ldconfig</prgn>,
3230 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3231 and <prgn>update-rc.d</prgn> can be found via the
3232 <tt>PATH</tt> environment variable. Those programs, and any
3233 other program that one would expect to be in the
3234 <tt>PATH</tt>, should thus be invoked without an absolute
3235 pathname. Maintainer scripts should also not reset the
3236 <tt>PATH</tt>, though they might choose to modify it by
3237 prepending or appending package-specific directories. These
3238 considerations really apply to all shell scripts.</p>
3241 <sect id="idempotency">
3242 <heading>Maintainer scripts Idempotency</heading>
3245 It is necessary for the error recovery procedures that the
3246 scripts be idempotent. This means that if it is run
3247 successfully, and then it is called again, it doesn't bomb
3248 out or cause any harm, but just ensures that everything is
3249 the way it ought to be. If the first call failed, or
3250 aborted half way through for some reason, the second call
3251 should merely do the things that were left undone the first
3252 time, if any, and exit with a success status if everything
3254 This is so that if an error occurs, the user interrupts
3255 <prgn>dpkg</prgn> or some other unforeseen circumstance
3256 happens you don't leave the user with a badly-broken
3257 package when <prgn>dpkg</prgn> attempts to repeat the
3263 <sect id="controllingterminal">
3264 <heading>Controlling terminal for maintainer scripts</heading>
3267 The maintainer scripts are guaranteed to run with a
3268 controlling terminal and can interact with the user.
3269 Because these scripts may be executed with standard output
3270 redirected into a pipe for logging purposes, Perl scripts
3271 should set unbuffered output by setting <tt>$|=1</tt> so
3272 that the output is printed immediately rather than being
3276 <sect id="exitstatus">
3277 <heading>Exit status</heading>
3280 Each script must return a zero exit status for
3281 success, or a nonzero one for failure, since the package
3282 management system looks for the exit status of these scripts
3283 and determines what action to take next based on that datum.
3287 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3292 <list compact="compact">
3294 <var>new-preinst</var> <tt>install</tt>
3297 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3300 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3303 <var>old-preinst</var> <tt>abort-upgrade</tt>
3304 <var>new-version</var>
3309 <list compact="compact">
3311 <var>postinst</var> <tt>configure</tt>
3312 <var>most-recently-configured-version</var>
3315 <var>old-postinst</var> <tt>abort-upgrade</tt>
3316 <var>new-version</var>
3319 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3320 <tt>in-favour</tt> <var>package</var>
3321 <var>new-version</var>
3324 <var>postinst</var> <tt>abort-remove</tt>
3327 <var>deconfigured's-postinst</var>
3328 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3329 <var>failed-install-package</var> <var>version</var>
3330 <tt>removing</tt> <var>conflicting-package</var>
3336 <list compact="compact">
3338 <var>prerm</var> <tt>remove</tt>
3341 <var>old-prerm</var> <tt>upgrade</tt>
3342 <var>new-version</var>
3345 <var>new-prerm</var> <tt>failed-upgrade</tt>
3346 <var>old-version</var>
3349 <var>conflictor's-prerm</var> <tt>remove</tt>
3350 <tt>in-favour</tt> <var>package</var>
3351 <var>new-version</var>
3354 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3355 <tt>in-favour</tt> <var>package-being-installed</var>
3356 <var>version</var> <tt>removing</tt>
3357 <var>conflicting-package</var>
3363 <list compact="compact">
3365 <var>postrm</var> <tt>remove</tt>
3368 <var>postrm</var> <tt>purge</tt>
3371 <var>old-postrm</var> <tt>upgrade</tt>
3372 <var>new-version</var>
3375 <var>new-postrm</var> <tt>failed-upgrade</tt>
3376 <var>old-version</var>
3379 <var>new-postrm</var> <tt>abort-install</tt>
3382 <var>new-postrm</var> <tt>abort-install</tt>
3383 <var>old-version</var>
3386 <var>new-postrm</var> <tt>abort-upgrade</tt>
3387 <var>old-version</var>
3390 <var>disappearer's-postrm</var> <tt>disappear</tt>
3391 <var>overwriter</var>
3392 <var>overwriter-version</var>
3398 <sect id="unpackphase">
3399 <heading>Details of unpack phase of installation or upgrade</heading>
3402 The procedure on installation/upgrade/overwrite/disappear
3403 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3404 stage of <tt>dpkg --install</tt>) is as follows. In each
3405 case, if a major error occurs (unless listed below) the
3406 actions are, in general, run backwards - this means that the
3407 maintainer scripts are run with different arguments in
3408 reverse order. These are the "error unwind" calls listed
3415 If a version of the package is already installed, call
3416 <example compact="compact">
3417 <var>old-prerm</var> upgrade <var>new-version</var>
3421 If the script runs but exits with a non-zero
3422 exit status, <prgn>dpkg</prgn> will attempt:
3423 <example compact="compact">
3424 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3426 If this works, the upgrade continues. If this
3427 does not work, the error unwind:
3428 <example compact="compact">
3429 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3431 If this works, then the old-version is
3432 "Installed", if not, the old version is in a
3433 "Failed-Config" state.
3439 If a "conflicting" package is being removed at the same time:
3442 If any packages depended on that conflicting
3443 package and <tt>--auto-deconfigure</tt> is
3444 specified, call, for each such package:
3445 <example compact="compact">
3446 <var>deconfigured's-prerm</var> deconfigure \
3447 in-favour <var>package-being-installed</var> <var>version</var> \
3448 removing <var>conflicting-package</var> <var>version</var>
3451 <example compact="compact">
3452 <var>deconfigured's-postinst</var> abort-deconfigure \
3453 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3454 removing <var>conflicting-package</var> <var>version</var>
3456 The deconfigured packages are marked as
3457 requiring configuration, so that if
3458 <tt>--install</tt> is used they will be
3459 configured again if possible.
3462 To prepare for removal of the conflicting package, call:
3463 <example compact="compact">
3464 <var>conflictor's-prerm</var> remove \
3465 in-favour <var>package</var> <var>new-version</var>
3468 <example compact="compact">
3469 <var>conflictor's-postinst</var> abort-remove \
3470 in-favour <var>package</var> <var>new-version</var>
3479 If the package is being upgraded, call:
3480 <example compact="compact">
3481 <var>new-preinst</var> upgrade <var>old-version</var>
3483 If this fails, we call:
3485 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3492 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3494 is called. If this works, then the old version
3495 is in an "Installed" state, or else it is left
3496 in an "Unpacked" state.
3501 If it fails, then the old version is left
3502 in an "Half-Installed" state.
3509 Otherwise, if the package had some configuration
3510 files from a previous version installed (i.e., it
3511 is in the "configuration files only" state):
3512 <example compact="compact">
3513 <var>new-preinst</var> install <var>old-version</var>
3517 <var>new-postrm</var> abort-install <var>old-version</var>
3519 If this fails, the package is left in a
3520 "Half-Installed" state, which requires a
3521 reinstall. If it works, the packages is left in
3522 a "Config Files" state.
3525 Otherwise (i.e., the package was completely purged):
3526 <example compact="compact">
3527 <var>new-preinst</var> install
3530 <example compact="compact">
3531 <var>new-postrm</var> abort-install
3533 If the error-unwind fails, the package is in a
3534 "Half Installed" phase, and requires a
3535 reinstall. If the error unwind works, the
3536 package is in a not installed state.
3543 The new package's files are unpacked, overwriting any
3544 that may be on the system already, for example any
3545 from the old version of the same package or from
3546 another package. Backups of the old files are kept
3547 temporarily, and if anything goes wrong the package
3548 management system will attempt to put them back as
3549 part of the error unwind.
3553 It is an error for a package to contain files which
3554 are on the system in another package, unless
3555 <tt>Replaces</tt> is used (see <ref id="replaces">).
3557 The following paragraph is not currently the case:
3558 Currently the <tt>- - force-overwrite</tt> flag is
3559 enabled, downgrading it to a warning, but this may not
3565 It is a more serious error for a package to contain a
3566 plain file or other kind of non-directory where another
3567 package has a directory (again, unless
3568 <tt>Replaces</tt> is used). This error can be
3569 overridden if desired using
3570 <tt>--force-overwrite-dir</tt>, but this is not
3575 Packages which overwrite each other's files produce
3576 behavior which, though deterministic, is hard for the
3577 system administrator to understand. It can easily
3578 lead to "missing" programs if, for example, a package
3579 is installed which overwrites a file from another
3580 package, and is then removed again.<footnote>
3581 Part of the problem is due to what is arguably a
3582 bug in <prgn>dpkg</prgn>.
3587 A directory will never be replaced by a symbolic link
3588 to a directory or vice versa; instead, the existing
3589 state (symlink or not) will be left alone and
3590 <prgn>dpkg</prgn> will follow the symlink if there is
3599 If the package is being upgraded, call
3600 <example compact="compact">
3601 <var>old-postrm</var> upgrade <var>new-version</var>
3605 If this fails, <prgn>dpkg</prgn> will attempt:
3606 <example compact="compact">
3607 <var>new-postrm</var> failed-upgrade <var>old-version</var>
3609 If this works, installation continues. If not,
3611 <example compact="compact">
3612 <var>old-preinst</var> abort-upgrade <var>new-version</var>
3614 If this fails, the old version is left in an
3615 "Half Installed" state. If it works, dpkg now
3617 <example compact="compact">
3618 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3620 If this fails, the old version is left in an
3621 "Half Installed" state. If it works, dpkg now
3623 <example compact="compact">
3624 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3626 If this fails, the old version is in an
3633 This is the point of no return - if
3634 <prgn>dpkg</prgn> gets this far, it won't back off
3635 past this point if an error occurs. This will
3636 leave the package in a fairly bad state, which
3637 will require a successful re-installation to clear
3638 up, but it's when <prgn>dpkg</prgn> starts doing
3639 things that are irreversible.
3644 Any files which were in the old version of the package
3645 but not in the new are removed.
3649 The new file list replaces the old.
3653 The new maintainer scripts replace the old.
3657 Any packages all of whose files have been overwritten
3658 during the installation, and which aren't required for
3659 dependencies, are considered to have been removed.
3660 For each such package
3663 <prgn>dpkg</prgn> calls:
3664 <example compact="compact">
3665 <var>disappearer's-postrm</var> disappear \
3666 <var>overwriter</var> <var>overwriter-version</var>
3670 The package's maintainer scripts are removed.
3673 It is noted in the status database as being in a
3674 sane state, namely not installed (any conffiles
3675 it may have are ignored, rather than being
3676 removed by <prgn>dpkg</prgn>). Note that
3677 disappearing packages do not have their prerm
3678 called, because <prgn>dpkg</prgn> doesn't know
3679 in advance that the package is going to
3686 Any files in the package we're unpacking that are also
3687 listed in the file lists of other packages are removed
3688 from those lists. (This will lobotomize the file list
3689 of the "conflicting" package if there is one.)
3693 The backup files made during installation, above, are
3699 The new package's status is now sane, and recorded as
3704 Here is another point of no return - if the
3705 conflicting package's removal fails we do not unwind
3706 the rest of the installation; the conflicting package
3707 is left in a half-removed limbo.
3712 If there was a conflicting package we go and do the
3713 removal actions (described below), starting with the
3714 removal of the conflicting package's files (any that
3715 are also in the package being installed have already
3716 been removed from the conflicting package's file list,
3717 and so do not get removed now).
3723 <sect id="configdetails"><heading>Details of configuration</heading>
3726 When we configure a package (this happens with <tt>dpkg
3727 --install</tt> and <tt>dpkg --configure</tt>), we first
3728 update any <tt>conffile</tt>s and then call:
3729 <example compact="compact">
3730 <var>postinst</var> configure <var>most-recently-configured-version</var>
3735 No attempt is made to unwind after errors during
3736 configuration. If the configuration fails, the package is in
3737 a "Failed Config" state, and an error message is generated.
3741 If there is no most recently configured version
3742 <prgn>dpkg</prgn> will pass a null argument.
3745 Historical note: Truly ancient (pre-1997) versions of
3746 <prgn>dpkg</prgn> passed <tt><unknown></tt>
3747 (including the angle brackets) in this case. Even older
3748 ones did not pass a second argument at all, under any
3749 circumstance. Note that upgrades using such an old dpkg
3750 version are unlikely to work for other reasons, even if
3751 this old argument behavior is handled by your postinst script.
3757 <sect id="removedetails"><heading>Details of removal and/or
3758 configuration purging</heading>
3764 <example compact="compact">
3765 <var>prerm</var> remove
3769 If prerm fails during replacement due to conflict
3771 <var>conflictor's-postinst</var> abort-remove \
3772 in-favour <var>package</var> <var>new-version</var>
3776 <var>postinst</var> abort-remove
3780 If this fails, the package is in a "Failed-Config"
3781 state, or else it remains "Installed".
3785 The package's files are removed (except <tt>conffile</tt>s).
3788 <example compact="compact">
3789 <var>postrm</var> remove
3793 If it fails, there's no error unwind, and the package is in
3794 an "Half-Installed" state.
3799 All the maintainer scripts except the <prgn>postrm</prgn>
3804 If we aren't purging the package we stop here. Note
3805 that packages which have no <prgn>postrm</prgn> and no
3806 <tt>conffile</tt>s are automatically purged when
3807 removed, as there is no difference except for the
3808 <prgn>dpkg</prgn> status.
3812 The <tt>conffile</tt>s and any backup files
3813 (<tt>~</tt>-files, <tt>#*#</tt> files,
3814 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
3819 <example compact="compact">
3820 <var>postrm</var> purge
3824 If this fails, the package remains in a "Config-Files"
3829 The package's file list is removed.
3838 <chapt id="relationships">
3839 <heading>Declaring relationships between packages</heading>
3841 <sect id="depsyntax">
3842 <heading>Syntax of relationship fields</heading>
3845 These fields all have a uniform syntax. They are a list of
3846 package names separated by commas.
3850 In the <tt>Depends</tt>, <tt>Recommends</tt>,
3851 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
3852 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
3853 control file fields of the package, which declare
3854 dependencies on other packages, the package names listed may
3855 also include lists of alternative package names, separated
3856 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
3857 if any one of the alternative packages is installed, that
3858 part of the dependency is considered to be satisfied.
3862 All of the fields except for <tt>Provides</tt> may restrict
3863 their applicability to particular versions of each named
3864 package. This is done in parentheses after each individual
3865 package name; the parentheses should contain a relation from
3866 the list below followed by a version number, in the format
3867 described in <ref id="f-Version">.
3871 The relations allowed are <tt><<</tt>, <tt><=</tt>,
3872 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
3873 strictly earlier, earlier or equal, exactly equal, later or
3874 equal and strictly later, respectively. The deprecated
3875 forms <tt><</tt> and <tt>></tt> were used to mean
3876 earlier/later or equal, rather than strictly earlier/later,
3877 so they should not appear in new packages (though
3878 <prgn>dpkg</prgn> still supports them).
3882 Whitespace may appear at any point in the version
3883 specification subject to the rules in <ref
3884 id="controlsyntax">, and must appear where it's necessary to
3885 disambiguate; it is not otherwise significant. For
3886 consistency and in case of future changes to
3887 <prgn>dpkg</prgn> it is recommended that a single space be
3888 used after a version relationship and before a version
3889 number; it is also conventional to put a single space after
3890 each comma, on either side of each vertical bar, and before
3891 each open parenthesis.
3895 For example, a list of dependencies might appear as:
3896 <example compact="compact">
3899 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
3904 All fields that specify build-time relationships
3905 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
3906 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>)
3907 may be restricted to a certain set of architectures. This
3908 is indicated in brackets after each individual package name and
3909 the optional version specification. The brackets enclose a
3910 list of Debian architecture names separated by whitespace.
3911 Exclamation marks may be prepended to each of the names.
3912 (It is not permitted for some names to be prepended with
3913 exclamation marks while others aren't.) If the current Debian
3914 host architecture is not in this list and there are no
3915 exclamation marks in the list, or it is in the list with a
3916 prepended exclamation mark, the package name and the
3917 associated version specification are ignored completely for
3918 the purposes of defining the relationships.
3923 <example compact="compact">
3925 Build-Depends-Indep: texinfo
3926 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
3927 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
3932 Note that the binary package relationship fields such as
3933 <tt>Depends</tt> appear in one of the binary package
3934 sections of the control file, whereas the build-time
3935 relationships such as <tt>Build-Depends</tt> appear in the
3936 source package section of the control file (which is the
3941 <sect id="binarydeps">
3942 <heading>Binary Dependencies - <tt>Depends</tt>,
3943 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
3944 <tt>Pre-Depends</tt>
3948 Packages can declare in their control file that they have
3949 certain relationships to other packages - for example, that
3950 they may not be installed at the same time as certain other
3951 packages, and/or that they depend on the presence of others.
3955 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
3956 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt> and
3957 <tt>Conflicts</tt> control file fields.
3961 These six fields are used to declare a dependency
3962 relationship by one package on another. Except for
3963 <tt>Enhances</tt>, they appear in the depending (binary)
3964 package's control file. (<tt>Enhances</tt> appears in the
3965 recommending package's control file.)
3969 A <tt>Depends</tt> field takes effect <em>only</em> when a
3970 package is to be configured. It does not prevent a package
3971 being on the system in an unconfigured state while its
3972 dependencies are unsatisfied, and it is possible to replace
3973 a package whose dependencies are satisfied and which is
3974 properly installed with a different version whose
3975 dependencies are not and cannot be satisfied; when this is
3976 done the depending package will be left unconfigured (since
3977 attempts to configure it will give errors) and will not
3978 function properly. If it is necessary, a
3979 <tt>Pre-Depends</tt> field can be used, which has a partial
3980 effect even when a package is being unpacked, as explained
3981 in detail below. (The other three dependency fields,
3982 <tt>Recommends</tt>, <tt>Suggests</tt> and
3983 <tt>Enhances</tt>, are only used by the various front-ends
3984 to <prgn>dpkg</prgn> such as <prgn>dselect</prgn>.)
3988 For this reason packages in an installation run are usually
3989 all unpacked first and all configured later; this gives
3990 later versions of packages with dependencies on later
3991 versions of other packages the opportunity to have their
3992 dependencies satisfied.
3996 In case of circular dependencies, since installation or
3997 removal order honoring the dependency order can't be
3998 established, dependency loops are broken at some point
3999 (based on rules below), and some packages may not be able to
4000 rely on their dependencies being present when being
4001 installed or removed, depending on which side of the break
4002 of the circular dependcy loop they happen to be on. If one
4003 of the packages in the loop has no postinst script, then the
4004 cycle will be broken at that package, so as to ensure that
4005 all postinst scripts run with the dependencies properly
4006 configured if this is possible. Otherwise the breaking point
4011 The <tt>Depends</tt> field thus allows package maintainers
4012 to impose an order in which packages should be configured.
4016 The meaning of the five dependency fields is as follows:
4018 <tag><tt>Depends</tt></tag>
4021 This declares an absolute dependency. A package will
4022 not be configured unless all of the packages listed in
4023 its <tt>Depends</tt> field have been correctly
4028 The <tt>Depends</tt> field should be used if the
4029 depended-on package is required for the depending
4030 package to provide a significant amount of
4035 The <tt>Depends</tt> field should also be used if the
4036 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4037 <prgn>postrm</prgn> scripts require the package to be
4038 present in order to run. Note, however, that the
4039 <prgn>postrm</prgn> cannot rely on any non-essential
4040 packages to be present during the <tt>purge</tt>
4044 <tag><tt>Recommends</tt></tag>
4047 This declares a strong, but not absolute, dependency.
4051 The <tt>Recommends</tt> field should list packages
4052 that would be found together with this one in all but
4053 unusual installations.
4057 <tag><tt>Suggests</tt></tag>
4059 This is used to declare that one package may be more
4060 useful with one or more others. Using this field
4061 tells the packaging system and the user that the
4062 listed packages are related to this one and can
4063 perhaps enhance its usefulness, but that installing
4064 this one without them is perfectly reasonable.
4067 <tag><tt>Enhances</tt></tag>
4069 This field is similar to Suggests but works in the
4070 opposite direction. It is used to declare that a
4071 package can enhance the functionality of another
4075 <tag><tt>Pre-Depends</tt></tag>
4078 This field is like <tt>Depends</tt>, except that it
4079 also forces <prgn>dpkg</prgn> to complete installation
4080 of the packages named before even starting the
4081 installation of the package which declares the
4082 pre-dependency, as follows:
4086 When a package declaring a pre-dependency is about to
4087 be <em>unpacked</em> the pre-dependency can be
4088 satisfied if the depended-on package is either fully
4089 configured, <em>or even if</em> the depended-on
4090 package(s) are only unpacked or half-configured,
4091 provided that they have been configured correctly at
4092 some point in the past (and not removed or partially
4093 removed since). In this case, both the
4094 previously-configured and currently unpacked or
4095 half-configured versions must satisfy any version
4096 clause in the <tt>Pre-Depends</tt> field.
4100 When the package declaring a pre-dependency is about
4101 to be <em>configured</em>, the pre-dependency will be
4102 treated as a normal <tt>Depends</tt>, that is, it will
4103 be considered satisfied only if the depended-on
4104 package has been correctly configured.
4108 <tt>Pre-Depends</tt> should be used sparingly,
4109 preferably only by packages whose premature upgrade or
4110 installation would hamper the ability of the system to
4111 continue with any upgrade that might be in progress.
4115 <tt>Pre-Depends</tt> are also required if the
4116 <prgn>preinst</prgn> script depends on the named
4117 package. It is best to avoid this situation if
4125 When selecting which level of dependency to use you should
4126 consider how important the depended-on package is to the
4127 functionality of the one declaring the dependency. Some
4128 packages are composed of components of varying degrees of
4129 importance. Such a package should list using
4130 <tt>Depends</tt> the package(s) which are required by the
4131 more important components. The other components'
4132 requirements may be mentioned as Suggestions or
4133 Recommendations, as appropriate to the components' relative
4138 <sect id="conflicts">
4139 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4142 When one binary package declares a conflict with another
4143 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4144 refuse to allow them to be installed on the system at the
4149 If one package is to be installed, the other must be removed
4150 first - if the package being installed is marked as
4151 replacing (see <ref id="replaces">) the one on the system,
4152 or the one on the system is marked as deselected, or both
4153 packages are marked <tt>Essential</tt>, then
4154 <prgn>dpkg</prgn> will automatically remove the package
4155 which is causing the conflict, otherwise it will halt the
4156 installation of the new package with an error. This
4157 mechanism is specifically designed to produce an error when
4158 the installed package is <tt>Essential</tt>, but the new
4163 A package will not cause a conflict merely because its
4164 configuration files are still installed; it must be at least
4169 A special exception is made for packages which declare a
4170 conflict with their own package name, or with a virtual
4171 package which they provide (see below): this does not
4172 prevent their installation, and allows a package to conflict
4173 with others providing a replacement for it. You use this
4174 feature when you want the package in question to be the only
4175 package providing some feature.
4179 A <tt>Conflicts</tt> entry should almost never have an
4180 "earlier than" version clause. This would prevent
4181 <prgn>dpkg</prgn> from upgrading or installing the package
4182 which declared such a conflict until the upgrade or removal
4183 of the conflicted-with package had been completed.
4187 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4191 As well as the names of actual ("concrete") packages, the
4192 package relationship fields <tt>Depends</tt>,
4193 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4194 <tt>Pre-Depends</tt>, <tt>Conflicts</tt>,
4195 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4196 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4197 may mention "virtual packages".
4201 A <em>virtual package</em> is one which appears in the
4202 <tt>Provides</tt> control file field of another package.
4203 The effect is as if the package(s) which provide a
4204 particular virtual package name had been listed by name
4205 everywhere the virtual package name appears. (See also <ref
4210 If there are both concrete and virtual packages of the same
4211 name, then the dependency may be satisfied (or the conflict
4212 caused) by either the concrete package with the name in
4213 question or any other concrete package which provides the
4214 virtual package with the name in question. This is so that,
4215 for example, supposing we have
4216 <example compact="compact">
4219 </example> and someone else releases an enhanced version of
4220 the <tt>bar</tt> package they can say:
4221 <example compact="compact">
4225 and the <tt>bar-plus</tt> package will now also satisfy the
4226 dependency for the <tt>foo</tt> package.
4230 If a dependency or a conflict has a version number attached
4231 then only real packages will be considered to see whether
4232 the relationship is satisfied (or the prohibition violated,
4233 for a conflict) - it is assumed that a real package which
4234 provides the virtual package is not of the "right" version.
4235 So, a <tt>Provides</tt> field may not contain version
4236 numbers, and the version number of the concrete package
4237 which provides a particular virtual package will not be
4238 looked at when considering a dependency on or conflict with
4239 the virtual package name.
4243 It is likely that the ability will be added in a future
4244 release of <prgn>dpkg</prgn> to specify a version number for
4245 each virtual package it provides. This feature is not yet
4246 present, however, and is expected to be used only
4251 If you want to specify which of a set of real packages
4252 should be the default to satisfy a particular dependency on
4253 a virtual package, you should list the real package as an
4254 alternative before the virtual one.
4259 <sect id="replaces"><heading>Overwriting files and replacing
4260 packages - <tt>Replaces</tt></heading>
4263 Packages can declare in their control file that they should
4264 overwrite files in certain other packages, or completely
4265 replace other packages. The <tt>Replaces</tt> control file
4266 field has these two distinct purposes.
4269 <sect1><heading>Overwriting files in other packages</heading>
4272 Firstly, as mentioned before, it is usually an error for a
4273 package to contain files which are on the system in
4278 However, if the overwriting package declares that it
4279 <tt>Replaces</tt> the one containing the file being
4280 overwritten, then <prgn>dpkg</prgn> will replace the file
4281 from the old package with that from the new. The file
4282 will no longer be listed as "owned" by the old package.
4286 If a package is completely replaced in this way, so that
4287 <prgn>dpkg</prgn> does not know of any files it still
4288 contains, it is considered to have "disappeared". It will
4289 be marked as not wanted on the system (selected for
4290 removal) and not installed. Any <tt>conffile</tt>s
4291 details noted for the package will be ignored, as they
4292 will have been taken over by the overwriting package. The
4293 package's <prgn>postrm</prgn> script will be run with a
4294 special argument to allow the package to do any final
4295 cleanup required. See <ref id="mscriptsinstact">.
4298 Replaces is a one way relationship -- you have to
4299 install the replacing package after the replaced
4306 For this usage of <tt>Replaces</tt>, virtual packages (see
4307 <ref id="virtual">) are not considered when looking at a
4308 <tt>Replaces</tt> field - the packages declared as being
4309 replaced must be mentioned by their real names.
4313 Furthermore, this usage of <tt>Replaces</tt> only takes
4314 effect when both packages are at least partially on the
4315 system at once, so that it can only happen if they do not
4316 conflict or if the conflict has been overridden.
4321 <sect1><heading>Replacing whole packages, forcing their
4325 Secondly, <tt>Replaces</tt> allows the packaging system to
4326 resolve which package should be removed when there is a
4327 conflict - see <ref id="conflicts">. This usage only
4328 takes effect when the two packages <em>do</em> conflict,
4329 so that the two usages of this field do not interfere with
4334 In this situation, the package declared as being replaced
4335 can be a virtual package, so for example, all mail
4336 transport agents (MTAs) would have the following fields in
4337 their control files:
4338 <example compact="compact">
4339 Provides: mail-transport-agent
4340 Conflicts: mail-transport-agent
4341 Replaces: mail-transport-agent
4343 ensuring that only one MTA can be installed at any one
4348 <sect id="sourcebinarydeps">
4349 <heading>Relationships between source and binary packages -
4350 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4351 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
4355 Source packages that require certain binary packages to be
4356 installed or absent at the time of building the package
4357 can declare relationships to those binary packages.
4361 This is done using the <tt>Build-Depends</tt>,
4362 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
4363 <tt>Build-Conflicts-Indep</tt> control file fields.
4367 Build-dependencies on "build-essential" binary packages can be
4368 omitted. Please see <ref id="pkg-relations"> for more information.
4372 The dependencies and conflicts they define must be satisfied
4373 (as defined earlier for binary packages) in order to invoke
4374 the targets in <tt>debian/rules</tt>, as follows:<footnote>
4376 If you make "build-arch" or "binary-arch", you need
4377 Build-Depends. If you make "build-indep" or
4378 "binary-indep", you need Build-Depends and
4379 Build-Depends-Indep. If you make "build" or "binary",
4383 There is no Build-Depends-Arch; this role is essentially
4384 met with Build-Depends. Anyone building the
4385 <tt>build-indep</tt> and binary-indep<tt></tt> targets
4386 is basically assumed to be building the whole package
4387 anyway and so installs all build dependencies. The
4388 autobuilders use <tt>dpkg-buildpackage -B</tt>, which
4389 calls <tt>build</tt> (not <tt>build-arch</tt>, since it
4390 does not yet know how to check for its existence) and
4391 <tt>binary-arch</tt>.
4394 The purpose of the original split, I recall, was so that
4395 the autobuilders wouldn't need to install extra packages
4396 needed only for the binary-indep targets. But without a
4397 build-arch/build-indep split, this didn't work, since
4398 most of the work is done in the build target, not in the
4404 <tag><tt>Build-Depends</tt>, <tt>Build-Conflicts</tt></tag>
4406 The <tt>Build-Depends</tt> and
4407 <tt>Build-Conflicts</tt> fields must be satisfied when
4408 any of the following targets is invoked:
4409 <tt>build</tt>, <tt>clean</tt>, <tt>binary</tt>,
4410 <tt>binary-arch</tt>, <tt>build-arch</tt>,
4411 <tt>build-indep</tt> and <tt>binary-indep</tt>.
4413 <tag><tt>Build-Depends-Indep</tt>,
4414 <tt>Build-Conflicts-Indep</tt></tag>
4416 The <tt>Build-Depends-Indep</tt> and
4417 <tt>Build-Conflicts-Indep</tt> fields must be
4418 satisfied when any of the following targets is
4419 invoked: <tt>build</tt>, <tt>build-indep</tt>,
4420 <tt>binary</tt> and <tt>binary-indep</tt>.
4430 <chapt id="sharedlibs"><heading>Shared libraries</heading>
4433 Packages containing shared libraries must be constructed with
4434 a little care to make sure that the shared library is always
4435 available. This is especially important for packages whose
4436 shared libraries are vitally important, such as the C library
4437 (currently <tt>libc6</tt>).
4441 Packages involving shared libraries should be split up into
4442 several binary packages. This section mostly deals with how
4443 this separation is to be accomplished; rules for files within
4444 the shared library packages are in <ref id="libraries"> instead.
4447 <sect id="sharedlibs-runtime">
4448 <heading>Run-time shared libraries</heading>
4451 The run-time shared library needs to be placed in a package
4452 whose name changes whenever the shared object version
4455 Since it is common place to install several versions of a
4456 package that just provides shared libraries, it is a
4457 good idea that the library package should not
4458 contain any extraneous non-versioned files, unless they
4459 happen to be in versioned directories.</p>
4461 The most common mechanism is to place it in a package
4463 <package><var>libraryname</var><var>soversion</var></package>,
4464 where <file><var>soversion</var></file> is the version number
4465 in the soname of the shared library<footnote>
4466 The soname is the shared object name: it's the thing
4467 that has to match exactly between building an executable
4468 and running it for the dynamic linker to be able run the
4469 program. For example, if the soname of the library is
4470 <file>libfoo.so.6</file>, the library package would be
4471 called <file>libfoo6</file>.
4473 Alternatively, if it would be confusing to directly append
4474 <var>soversion</var> to <var>libraryname</var> (e.g. because
4475 <var>libraryname</var> itself ends in a number), you may use
4476 <package><var>libraryname</var>-<var>soversion</var></package> and
4477 <package><var>libraryname</var>-<var>soversion</var>-dev</package>
4482 If your package includes run-time support programs that
4483 do not need to be invoked manually by users, but are
4484 nevertheless required for the package to function, then it
4485 is recommended that these programs are placed
4486 (if they are binary) in a subdirectory of
4487 <file>/usr/lib</file>, preferably under
4488 <file>/usr/lib/</file><var>package-name</var>.
4489 If the program is architecture independent, the
4490 recommendation is for it to be placed in a subdirectory of
4491 <file>/usr/share</file> instead, preferably under
4492 <file>/usr/share/</file><var>package-name</var>.
4497 If you have several shared libraries built from the same
4498 source tree you may lump them all together into a single
4499 shared library package, provided that you change all of
4500 their sonames at once (so that you don't get filename
4501 clashes if you try to install different versions of the
4502 combined shared libraries package).
4506 The package should install the shared libraries under
4507 their normal names. For example, the <package>libgdbm3</package>
4508 package should install <file>libgdbm.so.3.0.0</file> as
4509 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
4510 renamed or re-linked by any <prgn>prerm</prgn> or
4511 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
4512 of renaming things safely without affecting running programs,
4513 and attempts to interfere with this are likely to lead to
4518 Shared libraries should not be installed executable, since
4519 the dynamic linker does not require this and trying to
4520 execute a shared library usually results in a core dump.
4524 The run-time library package should include the symbolic link that
4525 <prgn>ldconfig</prgn> would create for the shared libraries.
4526 For example, the <package>libgdbm3</package> package should include
4527 a symbolic link from <file>/usr/lib/libgdbm.so.3</file> to
4528 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
4529 linker (for example <prgn>ld.so</prgn> or
4530 <prgn>ld-linux.so.*</prgn>) can find the library between the
4531 time that <prgn>dpkg</prgn> installs it and the time that
4532 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
4534 The package management system requires the library to be
4535 placed before the symbolic link pointing to it in the
4536 <file>.deb</file> file. This is so that when
4537 <prgn>dpkg</prgn> comes to install the symlink
4538 (overwriting the previous symlink pointing at an older
4539 version of the library), the new shared library is already
4540 in place. In the past, this was achieved by creating the
4541 library in the temporary packaging directory before
4542 creating the symlink. Unfortunately, this was not always
4543 effective, since the building of the tar file in the
4544 <file>.deb</file> depended on the behavior of the underlying
4545 file system. Some file systems (such as reiserfs) reorder
4546 the files so that the order of creation is forgotten.
4547 Since version 1.7.0, <prgn>dpkg</prgn>
4548 reorders the files itself as necessary when building a
4549 package. Thus it is no longer important to concern
4550 oneself with the order of file creation.
4554 <sect1 id="ldconfig">
4555 <heading><tt>ldconfig</tt></heading>
4558 Any package installing shared libraries in one of the default
4559 library directories of the dynamic linker (which are currently
4560 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
4561 listed in <file>/etc/ld.so.conf</file><footnote>
4563 <list compact="compact">
4564 <item>/usr/local/lib</item>
4565 <item>/usr/lib/libc5-compat</item>
4566 <item>/lib/libc5-compat</item>
4569 must use <prgn>ldconfig</prgn> to update the shared library
4574 The package maintainer scripts must only call
4575 <prgn>ldconfig</prgn> under these circumstances:
4576 <list compact="compact">
4577 <item>When the <prgn>postinst</prgn> script is run with a
4578 first argument of <tt>configure</tt>, the script must call
4579 <prgn>ldconfig</prgn>, and may optionally invoke
4580 <prgn>ldconfig</prgn> at other times.
4582 <item>When the <prgn>postrm</prgn> script is run with a
4583 first argument of <tt>remove</tt>, the script should call
4584 <prgn>ldconfig</prgn>.
4589 During install or upgrade, the preinst is called before
4590 the new files are installed, so calling "ldconfig" is
4591 pointless. The preinst of an existing package can also be
4592 called if an upgrade fails. However, this happens during
4593 the critical time when a shared libs may exist on-disk
4594 under a temporary name. Thus, it is dangerous and
4595 forbidden by current policy to call "ldconfig" at this
4600 When a package is installed or upgraded, "postinst
4601 configure" runs after the new files are safely on-disk.
4602 Since it is perfectly safe to invoke ldconfig
4603 unconditionally in a postinst, it is OK for a package to
4604 simply put ldconfig in its postinst without checking the
4605 argument. The postinst can also be called to recover from
4606 a failed upgrade. This happens before any new files are
4607 unpacked, so there is no reason to call "ldconfig" at this
4612 For a package that is being removed, prerm is
4613 called with all the files intact, so calling ldconfig is
4614 useless. The other calls to "prerm" happen in the case of
4615 upgrade at a time when all the files of the old package
4616 are on-disk, so again calling "ldconfig" is pointless.
4620 postrm, on the other hand, is called with the "remove"
4621 argument just after the files are removed, so this is
4622 the proper time to call "ldconfig" to notify the system
4623 of the fact that the shared libraries from the package
4624 are removed. The postrm can be called at several other
4625 times. At the time of "postrm purge", "postrm
4626 abort-install", or "postrm abort-upgrade", calling
4627 "ldconfig" is useless because the shared lib files are
4628 not on-disk. However, when "postrm" is invoked with
4629 arguments "upgrade", "failed-upgrade", or "disappear", a
4630 shared lib may exist on-disk under a temporary filename.
4638 <sect id="sharedlibs-runtime-progs">
4639 <heading>Run-time support programs</heading>
4642 If your package has some run-time support programs which use
4643 the shared library you must not put them in the shared
4644 library package. If you do that then you won't be able to
4645 install several versions of the shared library without
4646 getting filename clashes.
4650 Instead, either create another package for the runtime binaries
4651 (this package might typically be named
4652 <package><var>libraryname</var>-runtime</package>; note the absence
4653 of the <var>soversion</var> in the package name), or if the
4654 development package is small, include them in there.
4658 <sect id="sharedlibs-static">
4659 <heading>Static libraries</heading>
4662 The static library (<file><var>libraryname.a</var></file>)
4663 is usually provided in addition to the shared version.
4664 It is placed into the development package (see below).
4668 In some cases, it is acceptable for a library to be
4669 available in static form only; these cases include:
4671 <item>libraries for languages whose shared library support
4672 is immature or unstable</item>
4673 <item>libraries whose interfaces are in flux or under
4674 development (commonly the case when the library's
4675 major version number is zero, or where the ABI breaks
4676 across patchlevels)</item>
4677 <item>libraries which are explicitly intended to be
4678 available only in static form by their upstream
4683 <sect id="sharedlibs-dev">
4684 <heading>Development files</heading>
4687 The development files associated to a shared library need to be
4688 placed in a package called
4689 <package><var>libraryname</var><var>soversion</var>-dev</package>,
4690 or if you prefer only to support one development version at a
4691 time, <package><var>libraryname</var>-dev</package>.
4695 In case several development versions of a library exist, you may
4696 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
4697 <ref id="conflicts">) to ensure that the user only installs one
4698 development version at a time (as different development versions are
4699 likely to have the same header files in them, which would cause a
4700 filename clash if both were installed).
4704 The development package should contain a symlink for the associated
4705 shared library without a version number. For example, the
4706 <package>libgdbm-dev</package> package should include a symlink
4707 from <file>/usr/lib/libgdbm.so</file> to
4708 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
4709 (<prgn>ld</prgn>) when compiling packages, as it will only look for
4710 <file>libgdbm.so</file> when compiling dynamically.
4714 <sect id="sharedlibs-intradeps">
4715 <heading>Dependencies between the packages of the same library</heading>
4718 Typically the development version should have an exact
4719 version dependency on the runtime library, to make sure that
4720 compilation and linking happens correctly. The
4721 <tt>${binary:Version}</tt> substitution variable can be
4722 useful for this purpose.
4724 Previously, <tt>${Source-Version}</tt> was used, but its name
4725 was confusing and it has been deprecated since dpkg 1.13.19.
4730 <sect id="sharedlibs-shlibdeps">
4731 <heading>Dependencies between the library and other packages -
4732 the <tt>shlibs</tt> system</heading>
4735 If a package contains a binary or library which links to a
4736 shared library, we must ensure that when the package is
4737 installed on the system, all of the libraries needed are
4738 also installed. This requirement led to the creation of the
4739 <tt>shlibs</tt> system, which is very simple in its design:
4740 any package which <em>provides</em> a shared library also
4741 provides information on the package dependencies required to
4742 ensure the presence of this library, and any package which
4743 <em>uses</em> a shared library uses this information to
4744 determine the dependencies it requires. The files which
4745 contain the mapping from shared libraries to the necessary
4746 dependency information are called <file>shlibs</file> files.
4750 Thus, when a package is built which contains any shared
4751 libraries, it must provide a <file>shlibs</file> file for other
4752 packages to use, and when a package is built which contains
4753 any shared libraries or compiled binaries, it must run
4754 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
4755 on these to determine the libraries used and hence the
4756 dependencies needed by this package.<footnote>
4758 In the past, the shared libraries linked to were
4759 determined by calling <prgn>ldd</prgn>, but now
4760 <prgn>objdump</prgn> is used to do this. The only
4761 change this makes to package building is that
4762 <prgn>dpkg-shlibdeps</prgn> must also be run on shared
4763 libraries, whereas in the past this was unnecessary.
4764 The rest of this footnote explains the advantage that
4769 We say that a binary <tt>foo</tt> <em>directly</em> uses
4770 a library <tt>libbar</tt> if it is explicitly linked
4771 with that library (that is, it uses the flag
4772 <tt>-lbar</tt> during the linking stage). Other
4773 libraries that are needed by <tt>libbar</tt> are linked
4774 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
4775 linker will load them automatically when it loads
4776 <tt>libbar</tt>. A package should depend on
4777 the libraries it directly uses, and the dependencies for
4778 those libraries should automatically pull in the other
4783 Unfortunately, the <prgn>ldd</prgn> program shows both
4784 the directly and indirectly used libraries, meaning that
4785 the dependencies determined included both direct and
4786 indirect dependencies. The use of <prgn>objdump</prgn>
4787 avoids this problem by determining only the directly
4792 A good example of where this helps is the following. We
4793 could update <tt>libimlib</tt> with a new version that
4794 supports a new graphics format called dgf (but retaining
4795 the same major version number). If we used the old
4796 <prgn>ldd</prgn> method, every package that uses
4797 <tt>libimlib</tt> would need to be recompiled so it
4798 would also depend on <tt>libdgf</tt> or it wouldn't run
4799 due to missing symbols. However with the new system,
4800 packages using <tt>libimlib</tt> can rely on
4801 <tt>libimlib</tt> itself having the dependency on
4802 <tt>libdgf</tt> and so they would not need rebuilding.
4808 In the following sections, we will first describe where the
4809 various <tt>shlibs</tt> files are to be found, then how to
4810 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
4811 file format and how to create them if your package contains a
4816 <heading>The <tt>shlibs</tt> files present on the system</heading>
4819 There are several places where <tt>shlibs</tt> files are
4820 found. The following list gives them in the order in which
4822 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
4823 (The first one which gives the required information is used.)
4829 <p><file>debian/shlibs.local</file></p>
4832 This lists overrides for this package. Its use is
4833 described below (see <ref id="shlibslocal">).
4838 <p><file>/etc/dpkg/shlibs.override</file></p>
4841 This lists global overrides. This list is normally
4842 empty. It is maintained by the local system
4848 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
4851 When packages are being built, any
4852 <file>debian/shlibs</file> files are copied into the
4853 control file area of the temporary build directory and
4854 given the name <file>shlibs</file>. These files give
4855 details of any shared libraries included in the
4857 An example may help here. Let us say that the
4858 source package <tt>foo</tt> generates two binary
4859 packages, <tt>libfoo2</tt> and
4860 <tt>foo-runtime</tt>. When building the binary
4861 packages, the two packages are created in the
4862 directories <file>debian/libfoo2</file> and
4863 <file>debian/foo-runtime</file> respectively.
4864 (<file>debian/tmp</file> could be used instead of one
4865 of these.) Since <tt>libfoo2</tt> provides the
4866 <tt>libfoo</tt> shared library, it will require a
4867 <tt>shlibs</tt> file, which will be installed in
4868 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually
4870 <file>/var/lib/dpkg/info/libfoo2.shlibs</file>. Then
4871 when <prgn>dpkg-shlibdeps</prgn> is run on the
4873 <file>debian/foo-runtime/usr/bin/foo-prog</file>, it
4875 <file>debian/libfoo2/DEBIAN/shlibs</file> file to
4876 determine whether <tt>foo-prog</tt>'s library
4877 dependencies are satisfied by any of the libraries
4878 provided by <tt>libfoo2</tt>. For this reason,
4879 <prgn>dpkg-shlibdeps</prgn> must only be run once
4880 all of the individual binary packages'
4881 <tt>shlibs</tt> files have been installed into the
4888 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
4891 These are the <file>shlibs</file> files corresponding to
4892 all of the packages installed on the system, and are
4893 maintained by the relevant package maintainers.
4898 <p><file>/etc/dpkg/shlibs.default</file></p>
4901 This file lists any shared libraries whose packages
4902 have failed to provide correct <file>shlibs</file> files.
4903 It was used when the <file>shlibs</file> setup was first
4904 introduced, but it is now normally empty. It is
4905 maintained by the <tt>dpkg</tt> maintainer.
4913 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
4914 <file>shlibs</file> files</heading>
4918 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
4919 into your <file>debian/rules</file> file. If your package
4920 contains only compiled binaries and libraries (but no scripts),
4921 you can use a command such as:
4922 <example compact="compact">
4923 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
4924 debian/tmp/usr/lib/*
4926 Otherwise, you will need to explicitly list the compiled
4927 binaries and libraries.<footnote>
4928 If you are using <tt>debhelper</tt>, the
4929 <prgn>dh_shlibdeps</prgn> program will do this work for
4930 you. It will also correctly handle multi-binary
4936 This command puts the dependency information into the
4937 <file>debian/substvars</file> file, which is then used by
4938 <prgn>dpkg-gencontrol</prgn>. You will need to place a
4939 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
4940 field in the control file for this to work.
4944 If <prgn>dpkg-shlibdeps</prgn> doesn't complain, you're
4945 done. If it does complain you might need to create your own
4946 <file>debian/shlibs.local</file> file, as explained below (see
4947 <ref id="shlibslocal">).
4951 If you have multiple binary packages, you will need to call
4952 <prgn>dpkg-shlibdeps</prgn> on each one which contains
4953 compiled libraries or binaries. In such a case, you will
4954 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
4955 utilities to specify a different <file>substvars</file> file.
4959 For more details on dpkg-shlibdeps, please see
4960 <ref id="pkg-dpkg-shlibdeps"> and
4961 <manref name="dpkg-shlibdeps" section="1">.
4966 <heading>The <file>shlibs</file> File Format</heading>
4969 Each <file>shlibs</file> file has the same format. Lines
4970 beginning with <tt>#</tt> are considered to be comments and
4971 are ignored. Each line is of the form:
4972 <example compact="compact">
4973 <var>library-name</var> <var>soname-version-number</var> <var>dependencies ...</var>
4978 We will explain this by reference to the example of the
4979 <tt>zlib1g</tt> package, which (at the time of writing)
4980 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
4984 <var>library-name</var> is the name of the shared library,
4985 in this case <tt>libz</tt>. (This must match the name part
4986 of the soname, see below.)
4990 <var>soname-version-number</var> is the version part of the
4991 soname of the library. The soname is the thing that must
4992 exactly match for the library to be recognized by the
4993 dynamic linker, and is usually of the form
4994 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
4995 example, <tt>libz.so.1</tt>.<footnote>
4996 This can be determined using the command
4997 <example compact="compact">
4998 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5001 The version part is the part which comes after
5002 <tt>.so.</tt>, so in our case, it is <tt>1</tt>.
5006 <var>dependencies</var> has the same syntax as a dependency
5007 field in a binary package control file. It should give
5008 details of which packages are required to satisfy a binary
5009 built against the version of the library contained in the
5010 package. See <ref id="depsyntax"> for details.
5014 In our example, if the first version of the <tt>zlib1g</tt>
5015 package which contained a minor number of at least
5016 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5017 <tt>shlibs</tt> entry for this library could say:
5018 <example compact="compact">
5019 libz 1 zlib1g (>= 1:1.1.3)
5021 The version-specific dependency is to avoid warnings from
5022 the dynamic linker about using older shared libraries with
5028 <heading>Providing a <file>shlibs</file> file</heading>
5031 If your package provides a shared library, you need to create
5032 a <file>shlibs</file> file following the format described above.
5033 It is usual to call this file <file>debian/shlibs</file> (but if
5034 you have multiple binary packages, you might want to call it
5035 <file>debian/shlibs.<var>package</var></file> instead). Then
5036 let <file>debian/rules</file> install it in the control area:
5037 <example compact="compact">
5038 install -m644 debian/shlibs debian/tmp/DEBIAN
5040 or, in the case of a multi-binary package:
5041 <example compact="compact">
5042 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5044 An alternative way of doing this is to create the
5045 <file>shlibs</file> file in the control area directly from
5046 <file>debian/rules</file> without using a <file>debian/shlibs</file>
5047 file at all,<footnote>
5048 This is what <prgn>dh_makeshlibs</prgn> in the
5049 <tt>debhelper</tt> suite does.
5051 since the <file>debian/shlibs</file> file itself is ignored by
5052 <prgn>dpkg-shlibdeps</prgn>.
5056 As <prgn>dpkg-shlibdeps</prgn> reads the
5057 <file>DEBIAN/shlibs</file> files in all of the binary packages
5058 being built from this source package, all of the
5059 <file>DEBIAN/shlibs</file> files should be installed before
5060 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5065 <sect1 id="shlibslocal">
5066 <heading>Writing the <file>debian/shlibs.local</file> file</heading>
5069 This file is intended only as a <em>temporary</em> fix if
5070 your binaries or libraries depend on a library whose package
5071 does not yet provide a correct <file>shlibs</file> file.
5075 We will assume that you are trying to package a binary
5076 <tt>foo</tt>. When you try running
5077 <prgn>dpkg-shlibdeps</prgn> you get the following error
5078 message (<tt>-O</tt> displays the dependency information on
5079 <tt>stdout</tt> instead of writing it to
5080 <tt>debian/substvars</tt>, and the lines have been wrapped
5081 for ease of reading):
5082 <example compact="compact">
5083 $ dpkg-shlibdeps -O debian/tmp/usr/bin/foo
5084 dpkg-shlibdeps: warning: unable to find dependency
5085 information for shared library libbar (soname 1,
5086 path /usr/lib/libbar.so.1, dependency field Depends)
5087 shlibs:Depends=libc6 (>= 2.2.2-2)
5089 You can then run <prgn>ldd</prgn> on the binary to find the
5090 full location of the library concerned:
5091 <example compact="compact">
5093 libbar.so.1 => /usr/lib/libbar.so.1 (0x4001e000)
5094 libc.so.6 => /lib/libc.so.6 (0x40032000)
5095 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
5097 So the <prgn>foo</prgn> binary depends on the
5098 <prgn>libbar</prgn> shared library, but no package seems to
5099 provide a <file>*.shlibs</file> file handling
5100 <file>libbar.so.1</file> in <file>/var/lib/dpkg/info/</file>. Let's
5101 determine the package responsible:
5102 <example compact="compact">
5103 $ dpkg -S /usr/lib/libbar.so.1
5104 bar1: /usr/lib/libbar.so.1
5105 $ dpkg -s bar1 | grep Version
5108 This tells us that the <tt>bar1</tt> package, version 1.0-1,
5109 is the one we are using. Now we can file a bug against the
5110 <tt>bar1</tt> package and create our own
5111 <file>debian/shlibs.local</file> to locally fix the problem.
5112 Including the following line into your
5113 <file>debian/shlibs.local</file> file:
5114 <example compact="compact">
5115 libbar 1 bar1 (>= 1.0-1)
5117 should allow the package build to work.
5121 As soon as the maintainer of <tt>bar1</tt> provides a
5122 correct <file>shlibs</file> file, you should remove this line
5123 from your <file>debian/shlibs.local</file> file. (You should
5124 probably also then have a versioned <tt>Build-Depends</tt>
5125 on <tt>bar1</tt> to help ensure that others do not have the
5126 same problem building your package.)
5135 <chapt id="opersys"><heading>The Operating System</heading>
5138 <heading>File system hierarchy</heading>
5142 <heading>File system Structure</heading>
5145 The location of all installed files and directories must
5146 comply with the File system Hierarchy Standard (FHS),
5147 version 2.3, with the exceptions noted below, and except
5148 where doing so would violate other terms of Debian
5149 Policy. The following exceptions to the FHS apply:
5154 Legacy XFree86 servers are permitted to retain the
5155 configuration file location
5156 <file>/etc/X11/XF86Config-4</file>.
5161 The optional rules related to user specific
5162 configuration files for applications are stored in
5163 the user's home directory are relaxed. It is
5164 recommended that such files start with the
5165 '<tt>.</tt>' character (a "dot file"), and if an
5166 application needs to create more than one dot file
5167 then the preferred placement is in a subdirectory
5168 with a name starting with a '.' character, (a "dot
5169 directory"). In this case it is recommended the
5170 configuration files not start with the '.'
5176 The requirement for amd64 to use <file>/lib64</file>
5177 for 64 bit binaries is removed.
5182 The requirement that
5183 <file>/usr/local/share/man</file> be "synonymous"
5184 with <file>/usr/local/man</file> is relaxed to a
5189 The requirement that windowmanagers with a single
5190 configuration file call it <file>system.*wmrc</file>
5191 is removed, as is the restriction that the window
5192 manager subdirectory be named identically to the
5193 window manager name itself.
5198 The requirement that boot manager configuration
5199 files live in <file>/etc</file>, or at least are
5200 symlinked there, is relaxed to a recommendation.
5207 The version of this document referred here can be
5208 found in the <tt>debian-policy</tt> package or on <url
5209 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5210 name="FHS (Debian copy)"> alongside this manual (or, if
5211 you have the <package>debian-policy</package> installed,
5213 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5214 (local copy)">). The
5215 latest version, which may be a more recent version, may
5217 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5218 Specific questions about following the standard may be
5219 asked on the <tt>debian-devel</tt> mailing list, or
5220 referred to the FHS mailing list (see the
5221 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
5227 <heading>Site-specific programs</heading>
5230 As mandated by the FHS, packages must not place any
5231 files in <file>/usr/local</file>, either by putting them in
5232 the file system archive to be unpacked by <prgn>dpkg</prgn>
5233 or by manipulating them in their maintainer scripts.
5237 However, the package may create empty directories below
5238 <file>/usr/local</file> so that the system administrator knows
5239 where to place site-specific files. These are not
5240 directories <em>in</em> <file>/usr/local</file>, but are
5241 children of directories in <file>/usr/local</file>. These
5242 directories (<file>/usr/local/*/dir/</file>)
5243 should be removed on package removal if they are
5248 Note, that this applies only to directories <em>below</em>
5249 <file>/usr/local</file>, not <em>in</em> <file>/usr/local</file>.
5250 Packages must not create sub-directories in the directory
5251 <file>/usr/local</file> itself, except those listed in FHS,
5252 section 4.5. However, you may create directories below
5253 them as you wish. You must not remove any of the
5254 directories listed in 4.5, even if you created them.
5258 Since <file>/usr/local</file> can be mounted read-only from a
5259 remote server, these directories must be created and
5260 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
5261 maintainer scripts and not be included in the
5262 <file>.deb</file> archive. These scripts must not fail if
5263 either of these operations fail.
5267 For example, the <tt>emacsen-common</tt> package could
5268 contain something like
5269 <example compact="compact">
5270 if [ ! -e /usr/local/share/emacs ]
5272 if mkdir /usr/local/share/emacs 2>/dev/null
5274 chown root:staff /usr/local/share/emacs
5275 chmod 2775 /usr/local/share/emacs
5279 in its <prgn>postinst</prgn> script, and
5280 <example compact="compact">
5281 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
5282 rmdir /usr/local/share/emacs 2>/dev/null || true
5284 in the <prgn>prerm</prgn> script. (Note that this form is
5285 used to ensure that if the script is interrupted, the
5286 directory <file>/usr/local/share/emacs</file> will still be
5291 If you do create a directory in <file>/usr/local</file> for
5292 local additions to a package, you should ensure that
5293 settings in <file>/usr/local</file> take precedence over the
5294 equivalents in <file>/usr</file>.
5298 However, because <file>/usr/local</file> and its contents are
5299 for exclusive use of the local administrator, a package
5300 must not rely on the presence or absence of files or
5301 directories in <file>/usr/local</file> for normal operation.
5305 The <file>/usr/local</file> directory itself and all the
5306 subdirectories created by the package should (by default) have
5307 permissions 2775 (group-writable and set-group-id) and be
5308 owned by <tt>root.staff</tt>.
5313 <heading>The system-wide mail directory</heading>
5315 The system-wide mail directory is <file>/var/mail</file>. This
5316 directory is part of the base system and should not owned
5317 by any particular mail agents. The use of the old
5318 location <file>/var/spool/mail</file> is deprecated, even
5319 though the spool may still be physically located there.
5320 To maintain partial upgrade compatibility for systems
5321 which have <file>/var/spool/mail</file> as their physical mail
5322 spool, packages using <file>/var/mail</file> must depend on
5323 either <package>libc6</package> (>= 2.1.3-13), or on
5324 <package>base-files</package> (>= 2.2.0), or on later
5325 versions of either one of these packages.
5331 <heading>Users and groups</heading>
5334 <heading>Introduction</heading>
5336 The Debian system can be configured to use either plain or
5341 Some user ids (UIDs) and group ids (GIDs) are reserved
5342 globally for use by certain packages. Because some
5343 packages need to include files which are owned by these
5344 users or groups, or need the ids compiled into binaries,
5345 these ids must be used on any Debian system only for the
5346 purpose for which they are allocated. This is a serious
5347 restriction, and we should avoid getting in the way of
5348 local administration policies. In particular, many sites
5349 allocate users and/or local system groups starting at 100.
5353 Apart from this we should have dynamically allocated ids,
5354 which should by default be arranged in some sensible
5355 order, but the behavior should be configurable.
5359 Packages other than <tt>base-passwd</tt> must not modify
5360 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
5361 <file>/etc/group</file> or <file>/etc/gshadow</file>.
5366 <heading>UID and GID classes</heading>
5368 The UID and GID numbers are divided into classes as
5374 Globally allocated by the Debian project, the same
5375 on every Debian system. These ids will appear in
5376 the <file>passwd</file> and <file>group</file> files of all
5377 Debian systems, new ids in this range being added
5378 automatically as the <tt>base-passwd</tt> package is
5383 Packages which need a single statically allocated
5384 uid or gid should use one of these; their
5385 maintainers should ask the <tt>base-passwd</tt>
5393 Dynamically allocated system users and groups.
5394 Packages which need a user or group, but can have
5395 this user or group allocated dynamically and
5396 differently on each system, should use <tt>adduser
5397 --system</tt> to create the group and/or user.
5398 <prgn>adduser</prgn> will check for the existence of
5399 the user or group, and if necessary choose an unused
5400 id based on the ranges specified in
5401 <file>adduser.conf</file>.
5405 <tag>1000-29999:</tag>
5408 Dynamically allocated user accounts. By default
5409 <prgn>adduser</prgn> will choose UIDs and GIDs for
5410 user accounts in this range, though
5411 <file>adduser.conf</file> may be used to modify this
5416 <tag>30000-59999:</tag>
5421 <tag>60000-64999:</tag>
5424 Globally allocated by the Debian project, but only
5425 created on demand. The ids are allocated centrally
5426 and statically, but the actual accounts are only
5427 created on users' systems on demand.
5431 These ids are for packages which are obscure or
5432 which require many statically-allocated ids. These
5433 packages should check for and create the accounts in
5434 <file>/etc/passwd</file> or <file>/etc/group</file> (using
5435 <prgn>adduser</prgn> if it has this facility) if
5436 necessary. Packages which are likely to require
5437 further allocations should have a "hole" left after
5438 them in the allocation, to give them room to
5443 <tag>65000-65533:</tag>
5451 User <tt>nobody</tt>. The corresponding gid refers
5452 to the group <tt>nogroup</tt>.
5459 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
5460 not</em> be used, because it is the error return
5469 <sect id="sysvinit">
5470 <heading>System run levels and <file>init.d</file> scripts</heading>
5472 <sect1 id="/etc/init.d">
5473 <heading>Introduction</heading>
5476 The <file>/etc/init.d</file> directory contains the scripts
5477 executed by <prgn>init</prgn> at boot time and when the
5478 init state (or "runlevel") is changed (see <manref
5479 name="init" section="8">).
5483 There are at least two different, yet functionally
5484 equivalent, ways of handling these scripts. For the sake
5485 of simplicity, this document describes only the symbolic
5486 link method. However, it must not be assumed by maintainer
5487 scripts that this method is being used, and any automated
5488 manipulation of the various runlevel behaviors by
5489 maintainer scripts must be performed using
5490 <prgn>update-rc.d</prgn> as described below and not by
5491 manually installing or removing symlinks. For information
5492 on the implementation details of the other method,
5493 implemented in the <tt>file-rc</tt> package, please refer
5494 to the documentation of that package.
5498 These scripts are referenced by symbolic links in the
5499 <file>/etc/rc<var>n</var>.d</file> directories. When changing
5500 runlevels, <prgn>init</prgn> looks in the directory
5501 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
5502 execute, where <tt><var>n</var></tt> is the runlevel that
5503 is being changed to, or <tt>S</tt> for the boot-up
5508 The names of the links all have the form
5509 <file>S<var>mm</var><var>script</var></file> or
5510 <file>K<var>mm</var><var>script</var></file> where
5511 <var>mm</var> is a two-digit number and <var>script</var>
5512 is the name of the script (this should be the same as the
5513 name of the actual script in <file>/etc/init.d</file>).
5517 When <prgn>init</prgn> changes runlevel first the targets
5518 of the links whose names start with a <tt>K</tt> are
5519 executed, each with the single argument <tt>stop</tt>,
5520 followed by the scripts prefixed with an <tt>S</tt>, each
5521 with the single argument <tt>start</tt>. (The links are
5522 those in the <file>/etc/rc<var>n</var>.d</file> directory
5523 corresponding to the new runlevel.) The <tt>K</tt> links
5524 are responsible for killing services and the <tt>S</tt>
5525 link for starting services upon entering the runlevel.
5529 For example, if we are changing from runlevel 2 to
5530 runlevel 3, init will first execute all of the <tt>K</tt>
5531 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
5532 all of the <tt>S</tt> prefixed scripts in that directory.
5533 The links starting with <tt>K</tt> will cause the
5534 referred-to file to be executed with an argument of
5535 <tt>stop</tt>, and the <tt>S</tt> links with an argument
5540 The two-digit number <var>mm</var> is used to determine
5541 the order in which to run the scripts: low-numbered links
5542 have their scripts run first. For example, the
5543 <tt>K20</tt> scripts will be executed before the
5544 <tt>K30</tt> scripts. This is used when a certain service
5545 must be started before another. For example, the name
5546 server <prgn>bind</prgn> might need to be started before
5547 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
5548 can set up its access lists. In this case, the script
5549 that starts <prgn>bind</prgn> would have a lower number
5550 than the script that starts <prgn>inn</prgn> so that it
5552 <example compact="compact">
5559 The two runlevels 0 (halt) and 6 (reboot) are slightly
5560 different. In these runlevels, the links with an
5561 <tt>S</tt> prefix are still called after those with a
5562 <tt>K</tt> prefix, but they too are called with the single
5563 argument <tt>stop</tt>.
5567 Also, if the script name ends in <tt>.sh</tt>, the script
5568 will be sourced in runlevel <tt>S</tt> rather than being
5569 run in a forked subprocess, but will be explicitly run by
5570 <prgn>sh</prgn> in all other runlevels.
5575 <heading>Writing the scripts</heading>
5578 Packages that include daemons for system services should
5579 place scripts in <file>/etc/init.d</file> to start or stop
5580 services at boot time or during a change of runlevel.
5581 These scripts should be named
5582 <file>/etc/init.d/<var>package</var></file>, and they should
5583 accept one argument, saying what to do:
5586 <tag><tt>start</tt></tag>
5587 <item>start the service,</item>
5589 <tag><tt>stop</tt></tag>
5590 <item>stop the service,</item>
5592 <tag><tt>restart</tt></tag>
5593 <item>stop and restart the service if it's already running,
5594 otherwise start the service</item>
5596 <tag><tt>reload</tt></tag>
5597 <item><p>cause the configuration of the service to be
5598 reloaded without actually stopping and restarting
5601 <tag><tt>force-reload</tt></tag>
5602 <item>cause the configuration to be reloaded if the
5603 service supports this, otherwise restart the
5607 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
5608 <tt>force-reload</tt> options should be supported by all
5609 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
5614 The <file>init.d</file> scripts must ensure that they will
5615 behave sensibly if invoked with <tt>start</tt> when the
5616 service is already running, or with <tt>stop</tt> when it
5617 isn't, and that they don't kill unfortunately-named user
5618 processes. The best way to achieve this is usually to use
5619 <prgn>start-stop-daemon</prgn>.
5623 If a service reloads its configuration automatically (as
5624 in the case of <prgn>cron</prgn>, for example), the
5625 <tt>reload</tt> option of the <file>init.d</file> script
5626 should behave as if the configuration has been reloaded
5631 The <file>/etc/init.d</file> scripts must be treated as
5632 configuration files, either (if they are present in the
5633 package, that is, in the .deb file) by marking them as
5634 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
5635 by managing them correctly in the maintainer scripts (see
5636 <ref id="config-files">). This is important since we want
5637 to give the local system administrator the chance to adapt
5638 the scripts to the local system, e.g., to disable a
5639 service without de-installing the package, or to specify
5640 some special command line options when starting a service,
5641 while making sure their changes aren't lost during the next
5646 These scripts should not fail obscurely when the
5647 configuration files remain but the package has been
5648 removed, as configuration files remain on the system after
5649 the package has been removed. Only when <prgn>dpkg</prgn>
5650 is executed with the <tt>--purge</tt> option will
5651 configuration files be removed. In particular, as the
5652 <file>/etc/init.d/<var>package</var></file> script itself is
5653 usually a <tt>conffile</tt>, it will remain on the system
5654 if the package is removed but not purged. Therefore, you
5655 should include a <tt>test</tt> statement at the top of the
5657 <example compact="compact">
5658 test -f <var>program-executed-later-in-script</var> || exit 0
5663 Often there are some variables in the <file>init.d</file>
5664 scripts whose values control the behavior of the scripts,
5665 and which a system administrator is likely to want to
5666 change. As the scripts themselves are frequently
5667 <tt>conffile</tt>s, modifying them requires that the
5668 administrator merge in their changes each time the package
5669 is upgraded and the <tt>conffile</tt> changes. To ease
5670 the burden on the system administrator, such configurable
5671 values should not be placed directly in the script.
5672 Instead, they should be placed in a file in
5673 <file>/etc/default</file>, which typically will have the same
5674 base name as the <file>init.d</file> script. This extra file
5675 should be sourced by the script when the script runs. It
5676 must contain only variable settings and comments in SUSv3
5677 <prgn>sh</prgn> format. It may either be a
5678 <tt>conffile</tt> or a configuration file maintained by
5679 the package maintainer scripts. See <ref id="config-files">
5684 To ensure that vital configurable values are always
5685 available, the <file>init.d</file> script should set default
5686 values for each of the shell variables it uses, either
5687 before sourcing the <file>/etc/default/</file> file or
5688 afterwards using something like the <tt>:
5689 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
5690 script must behave sensibly and not fail if the
5691 <file>/etc/default</file> file is deleted.
5696 <heading>Interfacing with the initscript system</heading>
5699 Maintainers should use the abstraction layer provided by
5700 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
5701 programs to deal with initscripts in their packages'
5702 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
5703 and <prgn>postrm</prgn>.
5707 Directly managing the /etc/rc?.d links and directly
5708 invoking the <file>/etc/init.d/</file> initscripts should
5709 be done only by packages providing the initscript
5710 subsystem (such as <prgn>sysv-rc</prgn> and
5711 <prgn>file-rc</prgn>).
5715 <heading>Managing the links</heading>
5718 The program <prgn>update-rc.d</prgn> is provided for
5719 package maintainers to arrange for the proper creation and
5720 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
5721 or their functional equivalent if another method is being
5722 used. This may be used by maintainers in their packages'
5723 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
5727 You must not include any <file>/etc/rc<var>n</var>.d</file>
5728 symbolic links in the actual archive or manually create or
5729 remove the symbolic links in maintainer scripts; you must
5730 use the <prgn>update-rc.d</prgn> program instead. (The
5731 former will fail if an alternative method of maintaining
5732 runlevel information is being used.) You must not include
5733 the <file>/etc/rc<var>n</var>.d</file> directories themselves
5734 in the archive either. (Only the <tt>sysvinit</tt>
5739 By default <prgn>update-rc.d</prgn> will start services in
5740 each of the multi-user state runlevels (2, 3, 4, and 5)
5741 and stop them in the halt runlevel (0), the single-user
5742 runlevel (1) and the reboot runlevel (6). The system
5743 administrator will have the opportunity to customize
5744 runlevels by simply adding, moving, or removing the
5745 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
5746 symbolic links are being used, or by modifying
5747 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
5752 To get the default behavior for your package, put in your
5753 <prgn>postinst</prgn> script
5754 <example compact="compact">
5755 update-rc.d <var>package</var> defaults
5757 and in your <prgn>postrm</prgn>
5758 <example compact="compact">
5759 if [ "$1" = purge ]; then
5760 update-rc.d <var>package</var> remove
5762 </example>. Note that if your package changes runlevels
5763 or priority, you may have to remove and recreate the links,
5764 since otherwise the old links may persist. Refer to the
5765 documentation of <prgn>update-rc.d</prgn>.
5769 This will use a default sequence number of 20. If it does
5770 not matter when or in which order the <file>init.d</file>
5771 script is run, use this default. If it does, then you
5772 should talk to the maintainer of the <prgn>sysvinit</prgn>
5773 package or post to <tt>debian-devel</tt>, and they will
5774 help you choose a number.
5778 For more information about using <tt>update-rc.d</tt>,
5779 please consult its man page <manref name="update-rc.d"
5785 <heading>Running initscripts</heading>
5787 The program <prgn>invoke-rc.d</prgn> is provided to make
5788 it easier for package maintainers to properly invoke an
5789 initscript, obeying runlevel and other locally-defined
5790 constraints that might limit a package's right to start,
5791 stop and otherwise manage services. This program may be
5792 used by maintainers in their packages' scripts.
5796 The package maintainer scripts must use
5797 <prgn>invoke-rc.d</prgn> to invoke the
5798 <file>/etc/init.d/*</file> initscripts, instead of
5799 calling them directly.
5803 By default, <prgn>invoke-rc.d</prgn> will pass any
5804 action requests (start, stop, reload, restart...) to the
5805 <file>/etc/init.d</file> script, filtering out requests
5806 to start or restart a service out of its intended
5811 Most packages will simply need to change:
5812 <example compact="compact">/etc/init.d/<package>
5813 <action></example> in their <prgn>postinst</prgn>
5814 and <prgn>prerm</prgn> scripts to:
5815 <example compact="compact">
5816 if which invoke-rc.d >/dev/null 2>&1; then
5817 invoke-rc.d <var>package</var> <action>
5819 /etc/init.d/<var>package</var> <action>
5825 A package should register its initscript services using
5826 <prgn>update-rc.d</prgn> before it tries to invoke them
5827 using <prgn>invoke-rc.d</prgn>. Invocation of
5828 unregistered services may fail.
5832 For more information about using
5833 <prgn>invoke-rc.d</prgn>, please consult its man page
5834 <manref name="invoke-rc.d" section="8">.
5840 <heading>Boot-time initialization</heading>
5843 There used to be another directory, <file>/etc/rc.boot</file>,
5844 which contained scripts which were run once per machine
5845 boot. This has been deprecated in favour of links from
5846 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
5847 described in <ref id="/etc/init.d">. Packages must not
5848 place files in <file>/etc/rc.boot</file>.
5853 <heading>Example</heading>
5856 An example on which you can base your
5857 <file>/etc/init.d</file> scripts is found in
5858 <file>/etc/init.d/skeleton</file>.
5865 <heading>Console messages from <file>init.d</file> scripts</heading>
5868 This section describes the formats to be used for messages
5869 written to standard output by the <file>/etc/init.d</file>
5870 scripts. The intent is to improve the consistency of
5871 Debian's startup and shutdown look and feel. For this
5872 reason, please look very carefully at the details. We want
5873 the messages to have the same format in terms of wording,
5874 spaces, punctuation and case of letters.
5878 Here is a list of overall rules that should be used for
5879 messages generated by <file>/etc/init.d</file> scripts.
5885 The message should fit in one line (fewer than 80
5886 characters), start with a capital letter and end with
5887 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
5891 If the script is performing some time consuming task in
5892 the background (not merely starting or stopping a
5893 program, for instance), an ellipsis (three dots:
5894 <tt>...</tt>) should be output to the screen, with no
5895 leading or tailing whitespace or line feeds.
5899 The messages should appear as if the computer is telling
5900 the user what it is doing (politely :-), but should not
5901 mention "it" directly. For example, instead of:
5902 <example compact="compact">
5903 I'm starting network daemons: nfsd mountd.
5905 the message should say
5906 <example compact="compact">
5907 Starting network daemons: nfsd mountd.
5914 <tt>init.d</tt> script should use the following standard
5915 message formats for the situations enumerated below.
5921 <p>When daemons are started</p>
5924 If the script starts one or more daemons, the output
5925 should look like this (a single line, no leading
5927 <example compact="compact">
5928 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
5930 The <var>description</var> should describe the
5931 subsystem the daemon or set of daemons are part of,
5932 while <var>daemon-1</var> up to <var>daemon-n</var>
5933 denote each daemon's name (typically the file name of
5938 For example, the output of <file>/etc/init.d/lpd</file>
5940 <example compact="compact">
5941 Starting printer spooler: lpd.
5946 This can be achieved by saying
5947 <example compact="compact">
5948 echo -n "Starting printer spooler: lpd"
5949 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
5952 in the script. If there are more than one daemon to
5953 start, the output should look like this:
5954 <example compact="compact">
5955 echo -n "Starting remote file system services:"
5956 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
5957 echo -n " mountd"; start-stop-daemon --start --quiet mountd
5958 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
5961 This makes it possible for the user to see what is
5962 happening and when the final daemon has been started.
5963 Care should be taken in the placement of white spaces:
5964 in the example above the system administrators can
5965 easily comment out a line if they don't want to start
5966 a specific daemon, while the displayed message still
5972 <p>When a system parameter is being set</p>
5975 If you have to set up different system parameters
5976 during the system boot, you should use this format:
5977 <example compact="compact">
5978 Setting <var>parameter</var> to "<var>value</var>".
5983 You can use a statement such as the following to get
5985 <example compact="compact">
5986 echo "Setting DNS domainname to \"$domainname\"."
5991 Note that the same symbol (<tt>"</tt>) is used for the left
5992 and right quotation marks. A grave accent (<tt>`</tt>) is
5993 not a quote character; neither is an apostrophe
5999 <p>When a daemon is stopped or restarted</p>
6002 When you stop or restart a daemon, you should issue a
6003 message identical to the startup message, except that
6004 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6005 or <tt>Restarting</tt> respectively.
6009 For example, stopping the printer daemon will look like
6011 <example compact="compact">
6012 Stopping printer spooler: lpd.
6018 <p>When something is executed</p>
6021 There are several examples where you have to run a
6022 program at system startup or shutdown to perform a
6023 specific task, for example, setting the system's clock
6024 using <prgn>netdate</prgn> or killing all processes
6025 when the system shuts down. Your message should look
6027 <example compact="compact">
6028 Doing something very useful...done.
6030 You should print the <tt>done.</tt> immediately after
6031 the job has been completed, so that the user is
6032 informed why they have to wait. You can get this
6034 <example compact="compact">
6035 echo -n "Doing something very useful..."
6044 <p>When the configuration is reloaded</p>
6047 When a daemon is forced to reload its configuration
6048 files you should use the following format:
6049 <example compact="compact">
6050 Reloading <var>description</var> configuration...done.
6052 where <var>description</var> is the same as in the
6053 daemon starting message.
6061 <heading>Cron jobs</heading>
6064 Packages must not modify the configuration file
6065 <file>/etc/crontab</file>, and they must not modify the files in
6066 <file>/var/spool/cron/crontabs</file>.</p>
6069 If a package wants to install a job that has to be executed
6070 via cron, it should place a file with the name of the
6071 package in one or more of the following directories:
6072 <example compact="compact">
6077 As these directory names imply, the files within them are
6078 executed on a daily, weekly, or monthly basis,
6079 respectively. The exact times are listed in
6080 <file>/etc/crontab</file>.</p>
6083 All files installed in any of these directories must be
6084 scripts (e.g., shell scripts or Perl scripts) so that they
6085 can easily be modified by the local system administrator.
6086 In addition, they should be treated as configuration
6091 If a certain job has to be executed more frequently than
6092 daily, the package should install a file
6093 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6094 same syntax as <file>/etc/crontab</file> and is processed by
6095 <prgn>cron</prgn> automatically. The file must also be
6096 treated as a configuration file. (Note that entries in the
6097 <file>/etc/cron.d</file> directory are not handled by
6098 <prgn>anacron</prgn>. Thus, you should only use this
6099 directory for jobs which may be skipped if the system is not
6103 The scripts or crontab entries in these directories should
6104 check if all necessary programs are installed before they
6105 try to execute them. Otherwise, problems will arise when a
6106 package was removed but not purged since configuration files
6107 are kept on the system in this situation.</p>
6111 <heading>Menus</heading>
6114 The Debian <tt>menu</tt> package provides a standard
6115 interface between packages providing applications and
6116 <em>menu programs</em> (either X window managers or
6117 text-based menu programs such as <prgn>pdmenu</prgn>).
6121 All packages that provide applications that need not be
6122 passed any special command line arguments for normal
6123 operation should register a menu entry for those
6124 applications, so that users of the <tt>menu</tt> package
6125 will automatically get menu entries in their window
6126 managers, as well in shells like <tt>pdmenu</tt>.
6130 Menu entries should follow the current menu policy.
6134 The menu policy can be found in the <tt>menu-policy</tt>
6135 files in the <tt>debian-policy</tt> package.
6136 It is also available from the Debian web mirrors at
6137 <tt><url name="/doc/packaging-manuals/menu-policy/"
6138 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6142 Please also refer to the <em>Debian Menu System</em>
6143 documentation that comes with the <package>menu</package>
6144 package for information about how to register your
6150 <heading>Multimedia handlers</heading>
6153 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6154 is a mechanism for encoding files and data streams and
6155 providing meta-information about them, in particular their
6156 type (e.g. audio or video) and format (e.g. PNG, HTML,
6161 Registration of MIME type handlers allows programs like mail
6162 user agents and web browsers to invoke these handlers to
6163 view, edit or display MIME types they don't support directly.
6167 Packages which provide the ability to view/show/play,
6168 compose, edit or print MIME types should register themselves
6169 as such following the current MIME support policy.
6173 The MIME support policy can be found in the <tt>mime-policy</tt>
6174 files in the <tt>debian-policy</tt> package.
6175 It is also available from the Debian web mirrors at
6176 <tt><url name="/doc/packaging-manuals/mime-policy/"
6177 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
6183 <heading>Keyboard configuration</heading>
6186 To achieve a consistent keyboard configuration so that all
6187 applications interpret a keyboard event the same way, all
6188 programs in the Debian distribution must be configured to
6189 comply with the following guidelines.
6193 The following keys must have the specified interpretations:
6196 <tag><tt><--</tt></tag>
6197 <item>delete the character to the left of the cursor</item>
6199 <tag><tt>Delete</tt></tag>
6200 <item>delete the character to the right of the cursor</item>
6202 <tag><tt>Control+H</tt></tag>
6203 <item>emacs: the help prefix</item>
6206 The interpretation of any keyboard events should be
6207 independent of the terminal that is used, be it a virtual
6208 console, an X terminal emulator, an rlogin/telnet session,
6213 The following list explains how the different programs
6214 should be set up to achieve this:
6220 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
6224 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
6228 X translations are set up to make
6229 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
6230 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
6231 is the vt220 escape code for the "delete character"
6232 key). This must be done by loading the X resources
6233 using <prgn>xrdb</prgn> on all local X displays, not
6234 using the application defaults, so that the
6235 translation resources used correspond to the
6236 <prgn>xmodmap</prgn> settings.
6240 The Linux console is configured to make
6241 <tt><--</tt> generate DEL, and <tt>Delete</tt>
6242 generate <tt>ESC [ 3 ~</tt>.
6246 X applications are configured so that <tt><</tt>
6247 deletes left, and <tt>Delete</tt> deletes right. Motif
6248 applications already work like this.
6252 Terminals should have <tt>stty erase ^?</tt> .
6256 The <tt>xterm</tt> terminfo entry should have <tt>ESC
6257 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
6258 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
6262 Emacs is programmed to map <tt>KB_Backspace</tt> or
6263 the <tt>stty erase</tt> character to
6264 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
6265 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
6266 <tt>^H</tt> to <tt>help</tt> as always.
6270 Other applications use the <tt>stty erase</tt>
6271 character and <tt>kdch1</tt> for the two delete keys,
6272 with ASCII DEL being "delete previous character" and
6273 <tt>kdch1</tt> being "delete character under
6281 This will solve the problem except for the following
6288 Some terminals have a <tt><--</tt> key that cannot
6289 be made to produce anything except <tt>^H</tt>. On
6290 these terminals Emacs help will be unavailable on
6291 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
6292 character takes precedence in Emacs, and has been set
6293 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
6294 available) can be used instead.
6298 Some operating systems use <tt>^H</tt> for <tt>stty
6299 erase</tt>. However, modern telnet versions and all
6300 rlogin versions propagate <tt>stty</tt> settings, and
6301 almost all UNIX versions honour <tt>stty erase</tt>.
6302 Where the <tt>stty</tt> settings are not propagated
6303 correctly, things can be made to work by using
6304 <tt>stty</tt> manually.
6308 Some systems (including previous Debian versions) use
6309 <prgn>xmodmap</prgn> to arrange for both
6310 <tt><--</tt> and <tt>Delete</tt> to generate
6311 <tt>KB_Delete</tt>. We can change the behavior of
6312 their X clients using the same X resources that we use
6313 to do it for our own clients, or configure our clients
6314 using their resources when things are the other way
6315 around. On displays configured like this
6316 <tt>Delete</tt> will not work, but <tt><--</tt>
6321 Some operating systems have different <tt>kdch1</tt>
6322 settings in their <tt>terminfo</tt> database for
6323 <tt>xterm</tt> and others. On these systems the
6324 <tt>Delete</tt> key will not work correctly when you
6325 log in from a system conforming to our policy, but
6326 <tt><--</tt> will.
6333 <heading>Environment variables</heading>
6336 A program must not depend on environment variables to get
6337 reasonable defaults. (That's because these environment
6338 variables would have to be set in a system-wide
6339 configuration file like <file>/etc/profile</file>, which is not
6340 supported by all shells.)
6344 If a program usually depends on environment variables for its
6345 configuration, the program should be changed to fall back to
6346 a reasonable default configuration if these environment
6347 variables are not present. If this cannot be done easily
6348 (e.g., if the source code of a non-free program is not
6349 available), the program must be replaced by a small
6350 "wrapper" shell script which sets the environment variables
6351 if they are not already defined, and calls the original program.
6355 Here is an example of a wrapper script for this purpose:
6357 <example compact="compact">
6359 BAR=${BAR:-/var/lib/fubar}
6361 exec /usr/lib/foo/foo "$@"
6366 Furthermore, as <file>/etc/profile</file> is a configuration
6367 file of the <prgn>base-files</prgn> package, other packages must
6368 not put any environment variables or other commands into that
6373 <sect id="doc-base">
6374 <heading>Registering Documents using doc-base</heading>
6377 The <package>doc-base</package> package implements a
6378 flexible mechanism for handling and presenting
6379 documentation. The recommended practice is for every Debian
6380 package that provides online documentation (other than just
6381 manual pages) to register these documents with
6382 <package>doc-base</package> by installing a
6383 <package>doc-base</package> control file via the
6384 <prgn/install-docs/ script at installation time and
6385 de-register the manuals again when the package is removed.
6388 Please refer to the documentation that comes with the
6389 <package>doc-base</package> package for information and
6398 <heading>Files</heading>
6401 <heading>Binaries</heading>
6404 Two different packages must not install programs with
6405 different functionality but with the same filenames. (The
6406 case of two programs having the same functionality but
6407 different implementations is handled via "alternatives" or
6408 the "Conflicts" mechanism. See <ref id="maintscripts"> and
6409 <ref id="conflicts"> respectively.) If this case happens,
6410 one of the programs must be renamed. The maintainers should
6411 report this to the <tt>debian-devel</tt> mailing list and
6412 try to find a consensus about which program will have to be
6413 renamed. If a consensus cannot be reached, <em>both</em>
6414 programs must be renamed.
6418 By default, when a package is being built, any binaries
6419 created should include debugging information, as well as
6420 being compiled with optimization. You should also turn on
6421 as many reasonable compilation warnings as possible; this
6422 makes life easier for porters, who can then look at build
6423 logs for possible problems. For the C programming language,
6424 this means the following compilation parameters should be
6426 <example compact="compact">
6428 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
6430 INSTALL = install -s # (or use strip on the files in debian/tmp)
6435 Note that by default all installed binaries should be stripped,
6436 either by using the <tt>-s</tt> flag to
6437 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
6438 the binaries after they have been copied into
6439 <file>debian/tmp</file> but before the tree is made into a
6444 Although binaries in the build tree should be compiled with
6445 debugging information by default, it can often be difficult
6446 to debug programs if they are also subjected to compiler
6447 optimization. For this reason, it is recommended to support
6448 the standardized environment
6449 variable <tt>DEB_BUILD_OPTIONS</tt>. This variable can
6450 contain several flags to change how a package is compiled
6458 The presence of this string means that the package
6459 should be compiled with a minimum of optimization.
6460 For C programs, it is best to add <tt>-O0</tt>
6461 to <tt>CFLAGS</tt> (although this is usually the
6462 default). Some programs might fail to build or run at
6463 this level of optimization; it may be necessary to
6464 use <tt>-O1</tt>, for example.
6468 This string means that the debugging symbols should
6469 not be stripped from the binary during installation,
6470 so that debugging information may be included in the package.
6476 The following makefile snippet is an example of how one may
6477 implement the build options; you will probably have to
6478 massage this example in order to make it work for your
6480 <example compact="compact">
6483 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
6484 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
6485 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
6486 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
6488 ifneq (,$(findstring noopt,$(DEB_BUILD_OPTIONS)))
6493 ifeq (,$(findstring nostrip,$(DEB_BUILD_OPTIONS)))
6494 INSTALL_PROGRAM += -s
6500 It is up to the package maintainer to decide what
6501 compilation options are best for the package. Certain
6502 binaries (such as computationally-intensive programs) will
6503 function better with certain flags (<tt>-O3</tt>, for
6504 example); feel free to use them. Please use good judgment
6505 here. Don't use flags for the sake of it; only use them
6506 if there is good reason to do so. Feel free to override
6507 the upstream author's ideas about which compilation
6508 options are best: they are often inappropriate for our
6514 <sect id="libraries">
6515 <heading>Libraries</heading>
6518 If the package is <strong>architecture: any</strong>, then
6519 the shared library compilation and linking flags must have
6520 <tt>-fPIC</tt>, or the package shall not build on some of
6521 the supported architectures<footnote>
6523 If you are using GCC, <tt>-fPIC</tt> produces code with
6524 relocatable position independent code, which is required for
6525 most architectures to create a shared library, with i386 and
6526 perhaps some others where non position independent code is
6527 permitted in a shared library.
6530 Position independent code may have a performance penalty,
6531 especially on <tt>i386</tt>. However, in most cases the
6532 speed penalty must be measured against the memory wasted on
6533 the few architectures where non position independent code is
6536 </footnote>. Any exception to this rule must be discussed on
6537 the mailing list <em>debian-devel@lists.debian.org</em>, and
6538 a rough consensus obtained. The reasons for not compiling
6539 with <tt>-fPIC</tt> flag must be recorded in the file
6540 <tt>README.Debian</tt>, and care must be taken to either
6541 restrict the architecture or arrange for <tt>-fPIC</tt> to
6542 be used on architectures where it is required.<footnote>
6544 Some of the reasons why this might be required is if the
6545 library contains hand crafted assembly code that is not
6546 relocatable, the speed penalty is excessive for compute
6547 intensive libs, and similar reasons.
6552 As to the static libraries, the common case is not to have
6553 relocatable code, since there is no benefit, unless in specific
6554 cases; therefore the static version must not be compiled
6555 with the <tt>-fPIC</tt> flag. Any exception to this rule
6556 should be discussed on the mailing list
6557 <em>debian-devel@lists.debian.org</em>, and the reasons for
6558 compiling with the <tt>-fPIC</tt> flag must be recorded in
6559 the file <tt>README.Debian</tt>. <footnote>
6561 Some of the reasons for linking static libraries with
6562 the <tt>-fPIC</tt> flag are if, for example, one needs a
6563 Perl API for a library that is under rapid development,
6564 and has an unstable API, so shared libraries are
6565 pointless at this phase of the library's development. In
6566 that case, since Perl needs a library with relocatable
6567 code, it may make sense to create a static library with
6568 relocatable code. Another reason cited is if you are
6569 distilling various libraries into a common shared
6570 library, like <tt>mklibs</tt> does in the Debian
6576 In other words, if both a shared and a static library is
6577 being built, each source unit (<tt>*.c</tt>, for example,
6578 for C files) will need to be compiled twice, for the normal
6582 You must specify the gcc option <tt>-D_REENTRANT</tt>
6583 when building a library (either static or shared) to make
6584 the library compatible with LinuxThreads.
6588 Although not enforced by the build tools, shared libraries
6589 must be linked against all libraries that they use symbols from
6590 in the same way that binaries are. This ensures the correct
6591 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
6592 system and guarantees that all libraries can be safely opened
6593 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
6594 option <tt>-Wl,-z,defs</tt> when building a shared library.
6595 Since this option enforces symbol resolution at build time,
6596 a missing library reference will be caught early as a fatal
6601 All installed shared libraries should be stripped with
6602 <example compact="compact">
6603 strip --strip-unneeded <var>your-lib</var>
6605 (The option <tt>--strip-unneeded</tt> makes
6606 <prgn>strip</prgn> remove only the symbols which aren't
6607 needed for relocation processing.) Shared libraries can
6608 function perfectly well when stripped, since the symbols for
6609 dynamic linking are in a separate part of the ELF object
6611 You might also want to use the options
6612 <tt>--remove-section=.comment</tt> and
6613 <tt>--remove-section=.note</tt> on both shared libraries
6614 and executables, and <tt>--strip-debug</tt> on static
6620 Note that under some circumstances it may be useful to
6621 install a shared library unstripped, for example when
6622 building a separate package to support debugging.
6626 Shared object files (often <file>.so</file> files) that are not
6627 public libraries, that is, they are not meant to be linked
6628 to by third party executables (binaries of other packages),
6629 should be installed in subdirectories of the
6630 <file>/usr/lib</file> directory. Such files are exempt from the
6631 rules that govern ordinary shared libraries, except that
6632 they must not be installed executable and should be
6634 A common example are the so-called "plug-ins",
6635 internal shared objects that are dynamically loaded by
6636 programs using <manref name="dlopen" section="3">.
6641 Packages containing shared libraries that may be linked to
6642 by other packages' binaries, but which for some
6643 <em>compelling</em> reason can not be installed in
6644 <file>/usr/lib</file> directory, may install the shared library
6645 files in subdirectories of the <file>/usr/lib</file> directory,
6646 in which case they should arrange to add that directory in
6647 <file>/etc/ld.so.conf</file> in the package's post-installation
6648 script, and remove it in the package's post-removal script.
6652 An ever increasing number of packages are using
6653 <prgn>libtool</prgn> to do their linking. The latest GNU
6654 libtools (>= 1.3a) can take advantage of the metadata in the
6655 installed <prgn>libtool</prgn> archive files (<file>*.la</file>
6656 files). The main advantage of <prgn>libtool</prgn>'s
6657 <file>.la</file> files is that it allows <prgn>libtool</prgn> to
6658 store and subsequently access metadata with respect to the
6659 libraries it builds. <prgn>libtool</prgn> will search for
6660 those files, which contain a lot of useful information about
6661 a library (such as library dependency information for static
6662 linking). Also, they're <em>essential</em> for programs
6663 using <tt>libltdl</tt>.<footnote>
6664 Although <prgn>libtool</prgn> is fully capable of
6665 linking against shared libraries which don't have
6666 <tt>.la</tt> files, as it is a mere shell script it can
6667 add considerably to the build time of a
6668 <prgn>libtool</prgn>-using package if that shell script
6669 has to derive all this information from first principles
6670 for each library every time it is linked. With the
6671 advent of <prgn>libtool</prgn> version 1.4 (and to a
6672 lesser extent <prgn>libtool</prgn> version 1.3), the
6673 <file>.la</file> files also store information about
6674 inter-library dependencies which cannot necessarily be
6675 derived after the <file>.la</file> file is deleted.
6680 Packages that use <prgn>libtool</prgn> to create shared
6681 libraries should include the <file>.la</file> files in the
6682 <tt>-dev</tt> package, unless the package relies on
6683 <tt>libtool</tt>'s <tt>libltdl</tt> library, in which case
6684 the <tt>.la</tt> files must go in the run-time library
6689 You must make sure that you use only released versions of
6690 shared libraries to build your packages; otherwise other
6691 users will not be able to run your binaries
6692 properly. Producing source packages that depend on
6693 unreleased compilers is also usually a bad
6700 <heading>Shared libraries</heading>
6702 This section has moved to <ref id="sharedlibs">.
6708 <heading>Scripts</heading>
6711 All command scripts, including the package maintainer
6712 scripts inside the package and used by <prgn>dpkg</prgn>,
6713 should have a <tt>#!</tt> line naming the shell to be used
6718 In the case of Perl scripts this should be
6719 <tt>#!/usr/bin/perl</tt>.
6723 When scripts are installed into a directory in the system
6724 PATH, the script name should not include an extension such
6725 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
6726 language currently used to implement it.
6729 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>)
6730 should almost certainly start with <tt>set -e</tt> so that
6731 errors are detected. Every script should use
6732 <tt>set -e</tt> or check the exit status of <em>every</em>
6737 Scripts may assume that <file>/bin/sh</file> implements the
6738 SUSv3 Shell Command Language<footnote>
6739 Single UNIX Specification, version 3, which is also IEEE
6740 1003.1-2004 (POSIX), and is available on the World Wide Web
6741 from <url id="http://www.unix.org/version3/online.html"
6742 name="The Open Group"> after free
6743 registration.</footnote>
6744 plus the following additional features not mandated by
6746 These features are in widespread use in the Linux community
6747 and are implemented in all of bash, dash, and ksh, the most
6748 common shells users may wish to use as <file>/bin/sh</file>.
6751 <item><tt>echo -n</tt>, if implemented as a shell built-in,
6752 must not generate a newline.</item>
6753 <item><tt>test</tt>, if implemented as a shell built-in, must
6754 support <tt>-a</tt> and <tt>-o</tt> as binary logical
6756 <item><tt>local</tt> to create a scoped variable must be
6757 supported; however, <tt>local</tt> may or may not preserve
6758 the variable value from an outer scope and may or may not
6759 support arguments more complex than simple variables. Only
6771 If a shell script requires non-SUSv3 features from the shell
6772 interpreter other than those listed above, the appropriate shell
6773 must be specified in the first line of the script (e.g.,
6774 <tt>#!/bin/bash</tt>) and the package must depend on the package
6775 providing the shell (unless the shell package is marked
6776 "Essential", as in the case of <prgn>bash</prgn>).
6780 You may wish to restrict your script to SUSv3 features plus the
6781 above set when possible so that it may use <file>/bin/sh</file>
6782 as its interpreter. If your script works with <prgn>dash</prgn>
6783 (originally called <prgn>ash</prgn>), it probably complies with
6784 the above requirements, but if you are in doubt, use
6785 <file>/bin/bash</file>.
6789 Perl scripts should check for errors when making any
6790 system calls, including <tt>open</tt>, <tt>print</tt>,
6791 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
6795 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
6796 scripting languages. See <em>Csh Programming Considered
6797 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
6798 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
6799 If an upstream package comes with <prgn>csh</prgn> scripts
6800 then you must make sure that they start with
6801 <tt>#!/bin/csh</tt> and make your package depend on the
6802 <prgn>c-shell</prgn> virtual package.
6806 Any scripts which create files in world-writeable
6807 directories (e.g., in <file>/tmp</file>) must use a
6808 mechanism which will fail atomically if a file with the same
6809 name already exists.
6813 The Debian base system provides the <prgn>tempfile</prgn>
6814 and <prgn>mktemp</prgn> utilities for use by scripts for
6821 <heading>Symbolic links</heading>
6824 In general, symbolic links within a top-level directory
6825 should be relative, and symbolic links pointing from one
6826 top-level directory into another should be absolute. (A
6827 top-level directory is a sub-directory of the root
6828 directory <file>/</file>.)
6832 In addition, symbolic links should be specified as short as
6833 possible, i.e., link targets like <file>foo/../bar</file> are
6838 Note that when creating a relative link using
6839 <prgn>ln</prgn> it is not necessary for the target of the
6840 link to exist relative to the working directory you're
6841 running <prgn>ln</prgn> from, nor is it necessary to change
6842 directory to the directory where the link is to be made.
6843 Simply include the string that should appear as the target
6844 of the link (this will be a pathname relative to the
6845 directory in which the link resides) as the first argument
6850 For example, in your <prgn>Makefile</prgn> or
6851 <file>debian/rules</file>, you can do things like:
6852 <example compact="compact">
6853 ln -fs gcc $(prefix)/bin/cc
6854 ln -fs gcc debian/tmp/usr/bin/cc
6855 ln -fs ../sbin/sendmail $(prefix)/bin/runq
6856 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
6861 A symbolic link pointing to a compressed file should always
6862 have the same file extension as the referenced file. (For
6863 example, if a file <file>foo.gz</file> is referenced by a
6864 symbolic link, the filename of the link has to end with
6865 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
6870 <heading>Device files</heading>
6873 Packages must not include device files in the package file
6878 If a package needs any special device files that are not
6879 included in the base system, it must call
6880 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
6881 after notifying the user<footnote>
6882 This notification could be done via a (low-priority)
6883 debconf message, or an echo (printf) statement.
6888 Packages must not remove any device files in the
6889 <prgn>postrm</prgn> or any other script. This is left to the
6890 system administrator.
6894 Debian uses the serial devices
6895 <file>/dev/ttyS*</file>. Programs using the old
6896 <file>/dev/cu*</file> devices should be changed to use
6897 <file>/dev/ttyS*</file>.
6901 <sect id="config-files">
6902 <heading>Configuration files</heading>
6905 <heading>Definitions</heading>
6909 <tag>configuration file</tag>
6911 A file that affects the operation of a program, or
6912 provides site- or host-specific information, or
6913 otherwise customizes the behavior of a program.
6914 Typically, configuration files are intended to be
6915 modified by the system administrator (if needed or
6916 desired) to conform to local policy or to provide
6917 more useful site-specific behavior.
6920 <tag><tt>conffile</tt></tag>
6922 A file listed in a package's <tt>conffiles</tt>
6923 file, and is treated specially by <prgn>dpkg</prgn>
6924 (see <ref id="configdetails">).
6930 The distinction between these two is important; they are
6931 not interchangeable concepts. Almost all
6932 <tt>conffile</tt>s are configuration files, but many
6933 configuration files are not <tt>conffiles</tt>.
6937 Note that a script that embeds configuration information
6938 (such as most of the files in <file>/etc/default</file> and
6939 <file>/etc/cron.{daily,weekly,monthly}</file>) is de-facto a
6940 configuration file and should be treated as such.
6945 <heading>Location</heading>
6948 Any configuration files created or used by your package
6949 must reside in <file>/etc</file>. If there are several,
6950 consider creating a subdirectory of <file>/etc</file>
6951 named after your package.
6955 If your package creates or uses configuration files
6956 outside of <file>/etc</file>, and it is not feasible to modify
6957 the package to use <file>/etc</file> directly, put the files
6958 in <file>/etc</file> and create symbolic links to those files
6959 from the location that the package requires.
6964 <heading>Behavior</heading>
6967 Configuration file handling must conform to the following
6969 <list compact="compact">
6971 local changes must be preserved during a package
6975 configuration files must be preserved when the
6976 package is removed, and only deleted when the
6983 The easy way to achieve this behavior is to make the
6984 configuration file a <tt>conffile</tt>. This is
6985 appropriate only if it is possible to distribute a default
6986 version that will work for most installations, although
6987 some system administrators may choose to modify it. This
6988 implies that the default version will be part of the
6989 package distribution, and must not be modified by the
6990 maintainer scripts during installation (or at any other
6995 In order to ensure that local changes are preserved
6996 correctly, no package may contain or make hard links to
6997 conffiles.<footnote>
6998 Rationale: There are two problems with hard links.
6999 The first is that some editors break the link while
7000 editing one of the files, so that the two files may
7001 unwittingly become unlinked and different. The second
7002 is that <prgn>dpkg</prgn> might break the hard link
7003 while upgrading <tt>conffile</tt>s.
7008 The other way to do it is via the maintainer scripts. In
7009 this case, the configuration file must not be listed as a
7010 <tt>conffile</tt> and must not be part of the package
7011 distribution. If the existence of a file is required for
7012 the package to be sensibly configured it is the
7013 responsibility of the package maintainer to provide
7014 maintainer scripts which correctly create, update and
7015 maintain the file and remove it on purge. (See <ref
7016 id="maintainerscripts"> for more information.) These
7017 scripts must be idempotent (i.e., must work correctly if
7018 <prgn>dpkg</prgn> needs to re-run them due to errors
7019 during installation or removal), must cope with all the
7020 variety of ways <prgn>dpkg</prgn> can call maintainer
7021 scripts, must not overwrite or otherwise mangle the user's
7022 configuration without asking, must not ask unnecessary
7023 questions (particularly during upgrades), and must
7024 otherwise be good citizens.
7028 The scripts are not required to configure every possible
7029 option for the package, but only those necessary to get
7030 the package running on a given system. Ideally the
7031 sysadmin should not have to do any configuration other
7032 than that done (semi-)automatically by the
7033 <prgn>postinst</prgn> script.
7037 A common practice is to create a script called
7038 <file><var>package</var>-configure</file> and have the
7039 package's <prgn>postinst</prgn> call it if and only if the
7040 configuration file does not already exist. In certain
7041 cases it is useful for there to be an example or template
7042 file which the maintainer scripts use. Such files should
7043 be in <file>/usr/share/<var>package</var></file> or
7044 <file>/usr/lib/<var>package</var></file> (depending on whether
7045 they are architecture-independent or not). There should
7046 be symbolic links to them from
7047 <file>/usr/share/doc/<var>package</var>/examples</file> if
7048 they are examples, and should be perfectly ordinary
7049 <prgn>dpkg</prgn>-handled files (<em>not</em>
7050 configuration files).
7054 These two styles of configuration file handling must
7055 not be mixed, for that way lies madness:
7056 <prgn>dpkg</prgn> will ask about overwriting the file
7057 every time the package is upgraded.
7062 <heading>Sharing configuration files</heading>
7065 Packages which specify the same file as a
7066 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7067 with each other. (This is an instance of the general rule
7068 about not sharing files. Note that neither alternatives
7069 nor diversions are likely to be appropriate in this case;
7070 in particular, <prgn>dpkg</prgn> does not handle diverted
7071 <tt>conffile</tt>s well.)
7075 The maintainer scripts must not alter a <tt>conffile</tt>
7076 of <em>any</em> package, including the one the scripts
7081 If two or more packages use the same configuration file
7082 and it is reasonable for both to be installed at the same
7083 time, one of these packages must be defined as
7084 <em>owner</em> of the configuration file, i.e., it will be
7085 the package which handles that file as a configuration
7086 file. Other packages that use the configuration file must
7087 depend on the owning package if they require the
7088 configuration file to operate. If the other package will
7089 use the configuration file if present, but is capable of
7090 operating without it, no dependency need be declared.
7094 If it is desirable for two or more related packages to
7095 share a configuration file <em>and</em> for all of the
7096 related packages to be able to modify that configuration
7097 file, then the following should be done:
7098 <enumlist compact="compact">
7100 One of the related packages (the "owning" package)
7101 will manage the configuration file with maintainer
7102 scripts as described in the previous section.
7105 The owning package should also provide a program
7106 that the other packages may use to modify the
7110 The related packages must use the provided program
7111 to make any desired modifications to the
7112 configuration file. They should either depend on
7113 the core package to guarantee that the configuration
7114 modifier program is available or accept gracefully
7115 that they cannot modify the configuration file if it
7116 is not. (This is in addition to the fact that the
7117 configuration file may not even be present in the
7124 Sometimes it's appropriate to create a new package which
7125 provides the basic infrastructure for the other packages
7126 and which manages the shared configuration files. (The
7127 <tt>sgml-base</tt> package is a good example.)
7132 <heading>User configuration files ("dotfiles")</heading>
7135 The files in <file>/etc/skel</file> will automatically be
7136 copied into new user accounts by <prgn>adduser</prgn>.
7137 No other program should reference the files in
7138 <file>/etc/skel</file>.
7142 Therefore, if a program needs a dotfile to exist in
7143 advance in <file>$HOME</file> to work sensibly, that dotfile
7144 should be installed in <file>/etc/skel</file> and treated as a
7149 However, programs that require dotfiles in order to
7150 operate sensibly are a bad thing, unless they do create
7151 the dotfiles themselves automatically.
7155 Furthermore, programs should be configured by the Debian
7156 default installation to behave as closely to the upstream
7157 default behavior as possible.
7161 Therefore, if a program in a Debian package needs to be
7162 configured in some way in order to operate sensibly, that
7163 should be done using a site-wide configuration file placed
7164 in <file>/etc</file>. Only if the program doesn't support a
7165 site-wide default configuration and the package maintainer
7166 doesn't have time to add it may a default per-user file be
7167 placed in <file>/etc/skel</file>.
7171 <file>/etc/skel</file> should be as empty as we can make it.
7172 This is particularly true because there is no easy (or
7173 necessarily desirable) mechanism for ensuring that the
7174 appropriate dotfiles are copied into the accounts of
7175 existing users when a package is installed.
7181 <heading>Log files</heading>
7183 Log files should usually be named
7184 <file>/var/log/<var>package</var>.log</file>. If you have many
7185 log files, or need a separate directory for permission
7186 reasons (<file>/var/log</file> is writable only by
7187 <file>root</file>), you should usually create a directory named
7188 <file>/var/log/<var>package</var></file> and place your log
7193 Log files must be rotated occasionally so that they don't
7194 grow indefinitely; the best way to do this is to drop a log
7195 rotation configuration file into the directory
7196 <file>/etc/logrotate.d</file> and use the facilities provided by
7197 logrotate.<footnote>
7199 The traditional approach to log files has been to set up
7200 <em>ad hoc</em> log rotation schemes using simple shell
7201 scripts and cron. While this approach is highly
7202 customizable, it requires quite a lot of sysadmin work.
7203 Even though the original Debian system helped a little
7204 by automatically installing a system which can be used
7205 as a template, this was deemed not enough.
7209 The use of <prgn>logrotate</prgn>, a program developed
7210 by Red Hat, is better, as it centralizes log management.
7211 It has both a configuration file
7212 (<file>/etc/logrotate.conf</file>) and a directory where
7213 packages can drop their individual log rotation
7214 configurations (<file>/etc/logrotate.d</file>).
7217 Here is a good example for a logrotate config
7218 file (for more information see <manref name="logrotate"
7220 <example compact="compact">
7221 /var/log/foo/*.log {
7226 /etc/init.d/foo force-reload
7230 This rotates all files under <file>/var/log/foo</file>, saves 12
7231 compressed generations, and forces the daemon to reload its
7232 configuration information after the log rotation.
7236 Log files should be removed when the package is
7237 purged (but not when it is only removed). This should be
7238 done by the <prgn>postrm</prgn> script when it is called
7239 with the argument <tt>purge</tt> (see <ref
7240 id="removedetails">).
7245 <heading>Permissions and owners</heading>
7248 The rules in this section are guidelines for general use.
7249 If necessary you may deviate from the details below.
7250 However, if you do so you must make sure that what is done
7251 is secure and you should try to be as consistent as possible
7252 with the rest of the system. You should probably also
7253 discuss it on <prgn>debian-devel</prgn> first.
7257 Files should be owned by <tt>root.root</tt>, and made
7258 writable only by the owner and universally readable (and
7259 executable, if appropriate), that is mode 644 or 755.
7263 Directories should be mode 755 or (for group-writability)
7264 mode 2775. The ownership of the directory should be
7265 consistent with its mode: if a directory is mode 2775, it
7266 should be owned by the group that needs write access to
7269 When a package is upgraded, and the owner or permissions
7270 of a file included in the package has changed, dpkg
7271 arranges for the ownership and permissions to be
7272 correctly set upon installation. However, this does not
7273 extend to directories; the permissions and ownership of
7274 directories already on the system does not change on
7275 install or upgrade of packages. This makes sense, since
7276 otherwise common directories like <tt>/usr</tt> would
7277 always be in flux. To correctly change permissions of a
7278 directory the package owns, explicit action is required,
7279 usually in the <tt>postinst</tt> script. Care must be
7280 taken to handle downgrades as well, in that case.
7287 Setuid and setgid executables should be mode 4755 or 2755
7288 respectively, and owned by the appropriate user or group.
7289 They should not be made unreadable (modes like 4711 or
7290 2711 or even 4111); doing so achieves no extra security,
7291 because anyone can find the binary in the freely available
7292 Debian package; it is merely inconvenient. For the same
7293 reason you should not restrict read or execute permissions
7294 on non-set-id executables.
7298 Some setuid programs need to be restricted to particular
7299 sets of users, using file permissions. In this case they
7300 should be owned by the uid to which they are set-id, and by
7301 the group which should be allowed to execute them. They
7302 should have mode 4754; again there is no point in making
7303 them unreadable to those users who must not be allowed to
7308 It is possible to arrange that the system administrator can
7309 reconfigure the package to correspond to their local
7310 security policy by changing the permissions on a binary:
7311 they can do this by using <prgn>dpkg-statoverride</prgn>, as
7312 described below.<footnote>
7313 Ordinary files installed by <prgn>dpkg</prgn> (as
7314 opposed to <tt>conffile</tt>s and other similar objects)
7315 normally have their permissions reset to the distributed
7316 permissions when the package is reinstalled. However,
7317 the use of <prgn>dpkg-statoverride</prgn> overrides this
7318 default behavior. If you use this method, you should
7319 remember to describe <prgn>dpkg-statoverride</prgn> in
7320 the package documentation; being a relatively new
7321 addition to Debian, it is probably not yet well-known.
7323 Another method you should consider is to create a group for
7324 people allowed to use the program(s) and make any setuid
7325 executables executable only by that group.
7329 If you need to create a new user or group for your package
7330 there are two possibilities. Firstly, you may need to
7331 make some files in the binary package be owned by this
7332 user or group, or you may need to compile the user or
7333 group id (rather than just the name) into the binary
7334 (though this latter should be avoided if possible, as in
7335 this case you need a statically allocated id).</p>
7338 If you need a statically allocated id, you must ask for a
7339 user or group id from the <tt>base-passwd</tt> maintainer,
7340 and must not release the package until you have been
7341 allocated one. Once you have been allocated one you must
7342 either make the package depend on a version of the
7343 <tt>base-passwd</tt> package with the id present in
7344 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
7345 your package to create the user or group itself with the
7346 correct id (using <tt>adduser</tt>) in its
7347 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
7348 the <prgn>postinst</prgn> is to be preferred if it is
7349 possible, otherwise a pre-dependency will be needed on the
7350 <tt>adduser</tt> package.)
7354 On the other hand, the program might be able to determine
7355 the uid or gid from the user or group name at runtime, so
7356 that a dynamically allocated id can be used. In this case
7357 you should choose an appropriate user or group name,
7358 discussing this on <prgn>debian-devel</prgn> and checking
7359 with the <package/base-passwd/ maintainer that it is unique and that
7360 they do not wish you to use a statically allocated id
7361 instead. When this has been checked you must arrange for
7362 your package to create the user or group if necessary using
7363 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
7364 <prgn>postinst</prgn> script (again, the latter is to be
7365 preferred if it is possible).
7369 Note that changing the numeric value of an id associated
7370 with a name is very difficult, and involves searching the
7371 file system for all appropriate files. You need to think
7372 carefully whether a static or dynamic id is required, since
7373 changing your mind later will cause problems.
7376 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
7378 This section is not intended as policy, but as a
7379 description of the use of <prgn>dpkg-statoverride</prgn>.
7383 <prgn>dpkg-statoverride</prgn> is a replacement for the
7384 deprecated <tt>suidmanager</tt> package. Packages which
7385 previously used <tt>suidmanager</tt> should have a
7386 <tt>Conflicts: suidmanager (<< 0.50)</tt> entry (or even
7387 <tt>(<< 0.52)</tt>), and calls to <tt>suidregister</tt>
7388 and <tt>suidunregister</tt> should now be simply removed
7389 from the maintainer scripts.
7393 If a system administrator wishes to have a file (or
7394 directory or other such thing) installed with owner and
7395 permissions different from those in the distributed Debian
7396 package, they can use the <prgn>dpkg-statoverride</prgn>
7397 program to instruct <prgn>dpkg</prgn> to use the different
7398 settings every time the file is installed. Thus the
7399 package maintainer should distribute the files with their
7400 normal permissions, and leave it for the system
7401 administrator to make any desired changes. For example, a
7402 daemon which is normally required to be setuid root, but
7403 in certain situations could be used without being setuid,
7404 should be installed setuid in the <tt>.deb</tt>. Then the
7405 local system administrator can change this if they wish.
7406 If there are two standard ways of doing it, the package
7407 maintainer can use <tt>debconf</tt> to find out the
7408 preference, and call <prgn>dpkg-statoverride</prgn> in the
7409 maintainer script if necessary to accommodate the system
7410 administrator's choice. Care must be taken during
7411 upgrades to not override an existing setting.
7415 Given the above, <prgn>dpkg-statoverride</prgn> is
7416 essentially a tool for system administrators and would not
7417 normally be needed in the maintainer scripts. There is
7418 one type of situation, though, where calls to
7419 <prgn>dpkg-statoverride</prgn> would be needed in the
7420 maintainer scripts, and that involves packages which use
7421 dynamically allocated user or group ids. In such a
7422 situation, something like the following idiom can be very
7423 helpful in the package's <prgn>postinst</prgn>, where
7424 <tt>sysuser</tt> is a dynamically allocated id:
7426 for i in /usr/bin/foo /usr/sbin/bar
7428 # only do something when no setting exists
7429 if ! dpkg-statoverride --list $i >/dev/null 2>&1
7431 #include: debconf processing, question about foo and bar
7432 if [ "$RET" = "true" ] ; then
7433 dpkg-statoverride --update --add sysuser root 4755 $i
7438 The corresponding <tt>dpkg-statoverride --remove</tt>
7439 calls can then be made unconditionally when the package is
7447 <chapt id="customized-programs">
7448 <heading>Customized programs</heading>
7450 <sect id="arch-spec">
7451 <heading>Architecture specification strings</heading>
7454 If a program needs to specify an <em>architecture specification
7455 string</em> in some place, it should select one of the
7456 strings provided by <tt>dpkg-architecture -L</tt>. The
7457 strings are in the format
7458 <tt><var>os</var>-<var>arch</var></tt>, though the OS part
7459 is sometimes elided, as when the OS is Linux.<footnote>
7460 <p>Currently, the strings are:
7461 i386 ia64 alpha amd64 armeb arm hppa m32r m68k mips
7462 mipsel powerpc ppc64 s390 s390x sh3 sh3eb sh4 sh4eb
7463 sparc darwin-i386 darwin-ia64 darwin-alpha darwin-amd64
7464 darwin-armeb darwin-arm darwin-hppa darwin-m32r
7465 darwin-m68k darwin-mips darwin-mipsel darwin-powerpc
7466 darwin-ppc64 darwin-s390 darwin-s390x darwin-sh3
7467 darwin-sh3eb darwin-sh4 darwin-sh4eb darwin-sparc
7468 freebsd-i386 freebsd-ia64 freebsd-alpha freebsd-amd64
7469 freebsd-armeb freebsd-arm freebsd-hppa freebsd-m32r
7470 freebsd-m68k freebsd-mips freebsd-mipsel freebsd-powerpc
7471 freebsd-ppc64 freebsd-s390 freebsd-s390x freebsd-sh3
7472 freebsd-sh3eb freebsd-sh4 freebsd-sh4eb freebsd-sparc
7473 kfreebsd-i386 kfreebsd-ia64 kfreebsd-alpha
7474 kfreebsd-amd64 kfreebsd-armeb kfreebsd-arm kfreebsd-hppa
7475 kfreebsd-m32r kfreebsd-m68k kfreebsd-mips
7476 kfreebsd-mipsel kfreebsd-powerpc kfreebsd-ppc64
7477 kfreebsd-s390 kfreebsd-s390x kfreebsd-sh3 kfreebsd-sh3eb
7478 kfreebsd-sh4 kfreebsd-sh4eb kfreebsd-sparc knetbsd-i386
7479 knetbsd-ia64 knetbsd-alpha knetbsd-amd64 knetbsd-armeb
7480 knetbsd-arm knetbsd-hppa knetbsd-m32r knetbsd-m68k
7481 knetbsd-mips knetbsd-mipsel knetbsd-powerpc
7482 knetbsd-ppc64 knetbsd-s390 knetbsd-s390x knetbsd-sh3
7483 knetbsd-sh3eb knetbsd-sh4 knetbsd-sh4eb knetbsd-sparc
7484 netbsd-i386 netbsd-ia64 netbsd-alpha netbsd-amd64
7485 netbsd-armeb netbsd-arm netbsd-hppa netbsd-m32r
7486 netbsd-m68k netbsd-mips netbsd-mipsel netbsd-powerpc
7487 netbsd-ppc64 netbsd-s390 netbsd-s390x netbsd-sh3
7488 netbsd-sh3eb netbsd-sh4 netbsd-sh4eb netbsd-sparc
7489 openbsd-i386 openbsd-ia64 openbsd-alpha openbsd-amd64
7490 openbsd-armeb openbsd-arm openbsd-hppa openbsd-m32r
7491 openbsd-m68k openbsd-mips openbsd-mipsel openbsd-powerpc
7492 openbsd-ppc64 openbsd-s390 openbsd-s390x openbsd-sh3
7493 openbsd-sh3eb openbsd-sh4 openbsd-sh4eb openbsd-sparc
7494 hurd-i386 hurd-ia64 hurd-alpha hurd-amd64 hurd-armeb
7495 hurd-arm hurd-hppa hurd-m32r hurd-m68k hurd-mips
7496 hurd-mipsel hurd-powerpc hurd-ppc64 hurd-s390 hurd-s390x
7497 hurd-sh3 hurd-sh3eb hurd-sh4 hurd-sh4eb hurd-sparc
7503 Note that we don't want to use
7504 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
7505 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
7506 since this would make our programs incompatible with other
7507 Linux distributions. We also don't use something like
7508 <tt><var>arch</var>-unknown-linux</tt>, since the
7509 <tt>unknown</tt> does not look very good.
7514 <heading>Daemons</heading>
7517 The configuration files <file>/etc/services</file>,
7518 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
7519 by the <prgn>netbase</prgn> package and must not be modified
7524 If a package requires a new entry in one of these files, the
7525 maintainer should get in contact with the
7526 <prgn>netbase</prgn> maintainer, who will add the entries
7527 and release a new version of the <prgn>netbase</prgn>
7532 The configuration file <file>/etc/inetd.conf</file> must not be
7533 modified by the package's scripts except via the
7534 <prgn>update-inetd</prgn> script or the
7535 <file>DebianNet.pm</file> Perl module. See their documentation
7536 for details on how to add entries.
7540 If a package wants to install an example entry into
7541 <file>/etc/inetd.conf</file>, the entry must be preceded with
7542 exactly one hash character (<tt>#</tt>). Such lines are
7543 treated as "commented out by user" by the
7544 <prgn>update-inetd</prgn> script and are not changed or
7545 activated during package updates.
7550 <heading>Using pseudo-ttys and modifying wtmp, utmp and
7554 Some programs need to create pseudo-ttys. This should be done
7555 using Unix98 ptys if the C library supports it. The resulting
7556 program must not be installed setuid root, unless that
7557 is required for other functionality.
7561 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
7562 <file>/var/log/lastlog</file> must be installed writable by
7563 group <tt>utmp</tt>. Programs which need to modify those
7564 files must be installed setgid <tt>utmp</tt>.
7569 <heading>Editors and pagers</heading>
7572 Some programs have the ability to launch an editor or pager
7573 program to edit or display a text document. Since there are
7574 lots of different editors and pagers available in the Debian
7575 distribution, the system administrator and each user should
7576 have the possibility to choose their preferred editor and
7581 In addition, every program should choose a good default
7582 editor/pager if none is selected by the user or system
7587 Thus, every program that launches an editor or pager must
7588 use the EDITOR or PAGER environment variable to determine
7589 the editor or pager the user wishes to use. If these
7590 variables are not set, the programs <file>/usr/bin/editor</file>
7591 and <file>/usr/bin/pager</file> should be used, respectively.
7595 These two files are managed through the <prgn>dpkg</prgn>
7596 "alternatives" mechanism. Thus every package providing an
7597 editor or pager must call the
7598 <prgn>update-alternatives</prgn> script to register these
7603 If it is very hard to adapt a program to make use of the
7604 EDITOR or PAGER variables, that program may be configured to
7605 use <file>/usr/bin/sensible-editor</file> and
7606 <file>/usr/bin/sensible-pager</file> as the editor or pager
7607 program respectively. These are two scripts provided in the
7608 Debian base system that check the EDITOR and PAGER variables
7609 and launch the appropriate program, and fall back to
7610 <file>/usr/bin/editor</file> and <file>/usr/bin/pager</file> if the
7611 variable is not set.
7615 A program may also use the VISUAL environment variable to
7616 determine the user's choice of editor. If it exists, it
7617 should take precedence over EDITOR. This is in fact what
7618 <file>/usr/bin/sensible-editor</file> does.
7622 It is not required for a package to depend on
7623 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
7624 package to provide such virtual packages.<footnote>
7625 The Debian base system already provides an editor and a
7631 <sect id="web-appl">
7632 <heading>Web servers and applications</heading>
7635 This section describes the locations and URLs that should
7636 be used by all web servers and web applications in the
7643 Cgi-bin executable files are installed in the
7645 <example compact="compact">
7646 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
7648 and should be referred to as
7649 <example compact="compact">
7650 http://localhost/cgi-bin/<var>cgi-bin-name</var>
7656 <p>Access to HTML documents</p>
7659 HTML documents for a package are stored in
7660 <file>/usr/share/doc/<var>package</var></file>
7661 and can be referred to as
7662 <example compact="compact">
7663 http://localhost/doc/<var>package</var>/<var>filename</var>
7668 The web server should restrict access to the document
7669 tree so that only clients on the same host can read
7670 the documents. If the web server does not support such
7671 access controls, then it should not provide access at
7672 all, or ask about providing access during installation.
7677 <p>Access to images</p>
7679 It is recommended that images for a package be stored
7680 in <tt>/usr/share/images/<var>package</var></tt> and
7681 may be referred to through an alias <tt>/images/</tt>
7684 http://localhost/images/<package>/<filename>
7691 <p>Web Document Root</p>
7694 Web Applications should try to avoid storing files in
7695 the Web Document Root. Instead they should use the
7696 /usr/share/doc/<var>package</var> directory for
7697 documents and register the Web Application via the
7698 <package>doc-base</package> package. If access to the
7699 web document root is unavoidable then use
7700 <example compact="compact">
7703 as the Document Root. This might be just a symbolic
7704 link to the location where the system administrator
7705 has put the real document root.
7708 <item><p>Providing httpd and/or httpd-cgi</p>
7710 All web servers should provide the virtual package
7711 <tt>httpd</tt>. If a web server has CGI support it should
7712 provide <tt>httpd-cgi</tt> additionally.
7715 All web applications which do not contain CGI scripts should
7716 depend on <tt>httpd</tt>, all those web applications which
7717 <tt>do</tt> contain CGI scripts, should depend on
7725 <sect id="mail-transport-agents">
7726 <heading>Mail transport, delivery and user agents</heading>
7729 Debian packages which process electronic mail, whether mail
7730 user agents (MUAs) or mail transport agents (MTAs), must
7731 ensure that they are compatible with the configuration
7732 decisions below. Failure to do this may result in lost
7733 mail, broken <tt>From:</tt> lines, and other serious brain
7738 The mail spool is <file>/var/mail</file> and the interface to
7739 send a mail message is <file>/usr/sbin/sendmail</file> (as per
7740 the FHS). On older systems, the mail spool may be
7741 physically located in <file>/var/spool/mail</file>, but all
7742 access to the mail spool should be via the
7743 <file>/var/mail</file> symlink. The mail spool is part of the
7744 base system and not part of the MTA package.
7748 All Debian MUAs, MTAs, MDAs and other mailbox accessing
7749 programs (such as IMAP daemons) must lock the mailbox in an
7750 NFS-safe way. This means that <tt>fcntl()</tt> locking must
7751 be combined with dot locking. To avoid deadlocks, a program
7752 should use <tt>fcntl()</tt> first and dot locking after
7753 this, or alternatively implement the two locking methods in
7754 a non blocking way<footnote>
7755 If it is not possible to establish both locks, the
7756 system shouldn't wait for the second lock to be
7757 established, but remove the first lock, wait a (random)
7758 time, and start over locking again.
7759 </footnote>. Using the functions <tt>maillock</tt> and
7760 <tt>mailunlock</tt> provided by the
7761 <tt>liblockfile*</tt><footnote>
7762 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
7763 to use these functions.
7764 </footnote> packages is the recommended way to realize this.
7768 Mailboxes are generally mode 660
7769 <tt><var>user</var>.mail</tt> unless the system
7770 administrator has chosen otherwise. A MUA may remove a
7771 mailbox (unless it has nonstandard permissions) in which
7772 case the MTA or another MUA must recreate it if needed.
7773 Mailboxes must be writable by group mail.
7777 The mail spool is 2775 <tt>root.mail</tt>, and MUAs should
7778 be setgid mail to do the locking mentioned above (and
7779 must obviously avoid accessing other users' mailboxes
7780 using this privilege).</p>
7783 <file>/etc/aliases</file> is the source file for the system mail
7784 aliases (e.g., postmaster, usenet, etc.), it is the one
7785 which the sysadmin and <prgn>postinst</prgn> scripts may
7786 edit. After <file>/etc/aliases</file> is edited the program or
7787 human editing it must call <prgn>newaliases</prgn>. All MTA
7788 packages must come with a <prgn>newaliases</prgn> program,
7789 even if it does nothing, but older MTA packages did not do
7790 this so programs should not fail if <prgn>newaliases</prgn>
7791 cannot be found. Note that because of this, all MTA
7792 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
7793 <tt>Replaces: mail-transport-agent</tt> control file
7798 The convention of writing <tt>forward to
7799 <var>address</var></tt> in the mailbox itself is not
7800 supported. Use a <tt>.forward</tt> file instead.</p>
7803 The <prgn>rmail</prgn> program used by UUCP
7804 for incoming mail should be <file>/usr/sbin/rmail</file>.
7805 Likewise, <prgn>rsmtp</prgn>, for receiving
7806 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
7810 If your package needs to know what hostname to use on (for
7811 example) outgoing news and mail messages which are generated
7812 locally, you should use the file <file>/etc/mailname</file>. It
7813 will contain the portion after the username and <tt>@</tt>
7814 (at) sign for email addresses of users on the machine
7815 (followed by a newline).
7819 Such a package should check for the existence of this file
7820 when it is being configured. If it exists, it should be
7821 used without comment, although an MTA's configuration script
7822 may wish to prompt the user even if it finds that this file
7823 exists. If the file does not exist, the package should
7824 prompt the user for the value (preferably using
7825 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
7826 as well as using it in the package's configuration. The
7827 prompt should make it clear that the name will not just be
7828 used by that package. For example, in this situation the
7829 <tt>inn</tt> package could say something like:
7830 <example compact="compact">
7831 Please enter the "mail name" of your system. This is the
7832 hostname portion of the address to be shown on outgoing
7833 news and mail messages. The default is
7834 <var>syshostname</var>, your system's host name. Mail
7835 name ["<var>syshostname</var>"]:
7837 where <var>syshostname</var> is the output of <tt>hostname
7843 <heading>News system configuration</heading>
7846 All the configuration files related to the NNTP (news)
7847 servers and clients should be located under
7848 <file>/etc/news</file>.</p>
7851 There are some configuration issues that apply to a number
7852 of news clients and server packages on the machine. These
7856 <tag><file>/etc/news/organization</file></tag>
7858 A string which should appear as the
7859 organization header for all messages posted
7860 by NNTP clients on the machine
7863 <tag><file>/etc/news/server</file></tag>
7865 Contains the FQDN of the upstream NNTP
7866 server, or localhost if the local machine is
7871 Other global files may be added as required for cross-package news
7878 <heading>Programs for the X Window System</heading>
7881 <heading>Providing X support and package priorities</heading>
7884 Programs that can be configured with support for the X
7885 Window System must be configured to do so and must declare
7886 any package dependencies necessary to satisfy their
7887 runtime requirements when using the X Window System. If
7888 such a package is of higher priority than the X packages
7889 on which it depends, it is required that either the
7890 X-specific components be split into a separate package, or
7891 that an alternative version of the package, which includes
7892 X support, be provided, or that the package's priority be
7898 <heading>Packages providing an X server</heading>
7901 Packages that provide an X server that, directly or
7902 indirectly, communicates with real input and display
7903 hardware should declare in their control data that they
7904 provide the virtual package <tt>xserver</tt>.<footnote>
7905 This implements current practice, and provides an
7906 actual policy for usage of the <tt>xserver</tt>
7907 virtual package which appears in the virtual packages
7908 list. In a nutshell, X servers that interface
7909 directly with the display and input hardware or via
7910 another subsystem (e.g., GGI) should provide
7911 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
7912 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
7918 <heading>Packages providing a terminal emulator</heading>
7921 Packages that provide a terminal emulator for the X Window
7922 System which meet the criteria listed below should declare
7923 in their control data that they provide the virtual
7924 package <tt>x-terminal-emulator</tt>. They should also
7925 register themselves as an alternative for
7926 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
7931 To be an <tt>x-terminal-emulator</tt>, a program must:
7932 <list compact="compact">
7934 Be able to emulate a DEC VT100 terminal, or a
7935 compatible terminal.
7939 Support the command-line option <tt>-e
7940 <var>command</var></tt>, which creates a new
7941 terminal window<footnote>
7942 "New terminal window" does not necessarily mean
7943 a new top-level X window directly parented by
7944 the window manager; it could, if the terminal
7945 emulator application were so coded, be a new
7946 "view" in a multiple-document interface (MDI).
7948 and runs the specified <var>command</var>,
7949 interpreting the entirety of the rest of the command
7950 line as a command to pass straight to exec, in the
7951 manner that <tt>xterm</tt> does.
7955 Support the command-line option <tt>-T
7956 <var>title</var></tt>, which creates a new terminal
7957 window with the window title <var>title</var>.
7964 <heading>Packages providing a window manager</heading>
7967 Packages that provide a window manager should declare in
7968 their control data that they provide the virtual package
7969 <tt>x-window-manager</tt>. They should also register
7970 themselves as an alternative for
7971 <file>/usr/bin/x-window-manager</file>, with a priority
7972 calculated as follows:
7973 <list compact="compact">
7975 Start with a priority of 20.
7979 If the window manager supports the Debian menu
7980 system, add 20 points if this support is available
7981 in the package's default configuration (i.e., no
7982 configuration files belonging to the system or user
7983 have to be edited to activate the feature); if
7984 configuration files must be modified, add only 10
7990 If the window manager complies with <url
7991 id="http://www.freedesktop.org/Standards/wm-spec"
7992 name="The Window Manager Specification Project">,
7993 written by the <url id="http://www.freedesktop.org/"
7994 name="Free Desktop Group">, add 40 points.
7998 If the window manager permits the X session to be
7999 restarted using a <em>different</em> window manager
8000 (without killing the X server) in its default
8001 configuration, add 10 points; otherwise add none.
8008 <heading>Packages providing fonts</heading>
8011 Packages that provide fonts for the X Window
8013 For the purposes of Debian Policy, a "font for the X
8014 Window System" is one which is accessed via X protocol
8015 requests. Fonts for the Linux console, for PostScript
8016 renderer, or any other purpose, do not fit this
8017 definition. Any tool which makes such fonts available
8018 to the X Window System, however, must abide by this
8021 must do a number of things to ensure that they are both
8022 available without modification of the X or font server
8023 configuration, and that they do not corrupt files used by
8024 other font packages to register information about
8028 Fonts of any type supported by the X Window System
8029 must be in a separate binary package from any
8030 executables, libraries, or documentation (except
8031 that specific to the fonts shipped, such as their
8032 license information). If one or more of the fonts
8033 so packaged are necessary for proper operation of
8034 the package with which they are associated the font
8035 package may be Recommended; if the fonts merely
8036 provide an enhancement, a Suggests relationship may
8037 be used. Packages must not Depend on font
8039 This is because the X server may retrieve fonts
8040 from the local file system or over the network
8041 from an X font server; the Debian package system
8042 is empowered to deal only with the local
8048 BDF fonts must be converted to PCF fonts with the
8049 <prgn>bdftopcf</prgn> utility (available in the
8050 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8051 placed in a directory that corresponds to their
8053 <list compact="compact">
8055 100 dpi fonts must be placed in
8056 <file>/usr/share/fonts/X11/100dpi/</file>.
8060 75 dpi fonts must be placed in
8061 <file>/usr/share/fonts/X11/75dpi/</file>.
8065 Character-cell fonts, cursor fonts, and other
8066 low-resolution fonts must be placed in
8067 <file>/usr/share/fonts/X11/misc/</file>.
8073 Speedo fonts must be placed in
8074 <file>/usr/share/fonts/X11/Speedo/</file>.
8078 Type 1 fonts must be placed in
8079 <file>/usr/share/fonts/X11/Type1/</file>. If font
8080 metric files are available, they must be placed here
8085 Subdirectories of <file>/usr/share/fonts/X11/</file>
8086 other than those listed above must be neither
8087 created nor used. (The <file>PEX</file>, <file>CID</file>,
8088 and <file>cyrillic</file> directories are excepted for
8089 historical reasons, but installation of files into
8090 these directories remains discouraged.)
8094 Font packages may, instead of placing files directly
8095 in the X font directories listed above, provide
8096 symbolic links in that font directory pointing to
8097 the files' actual location in the filesystem. Such
8098 a location must comply with the FHS.
8102 Font packages should not contain both 75dpi and
8103 100dpi versions of a font. If both are available,
8104 they should be provided in separate binary packages
8105 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8106 the names of the packages containing the
8107 corresponding fonts.
8111 Fonts destined for the <file>misc</file> subdirectory
8112 should not be included in the same package as 75dpi
8113 or 100dpi fonts; instead, they should be provided in
8114 a separate package with <tt>-misc</tt> appended to
8119 Font packages must not provide the files
8120 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8121 <file>fonts.scale</file> in a font directory:
8124 <file>fonts.dir</file> files must not be provided at all.
8128 <file>fonts.alias</file> and <file>fonts.scale</file>
8129 files, if needed, should be provided in the
8131 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8132 where <var>fontdir</var> is the name of the
8134 <file>/usr/share/fonts/X11/</file> where the
8135 package's corresponding fonts are stored
8136 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8137 <var>package</var> is the name of the package
8138 that provides these fonts, and
8139 <var>extension</var> is either <tt>scale</tt>
8140 or <tt>alias</tt>, whichever corresponds to
8147 Font packages must declare a dependency on
8148 <tt>xfonts-utils</tt> in their control
8153 Font packages that provide one or more
8154 <file>fonts.scale</file> files as described above must
8155 invoke <prgn>update-fonts-scale</prgn> on each
8156 directory into which they installed fonts
8157 <em>before</em> invoking
8158 <prgn>update-fonts-dir</prgn> on that directory.
8159 This invocation must occur in both the
8160 <prgn>postinst</prgn> (for all arguments) and
8161 <prgn>postrm</prgn> (for all arguments except
8162 <tt>upgrade</tt>) scripts.
8166 Font packages that provide one or more
8167 <file>fonts.alias</file> files as described above must
8168 invoke <prgn>update-fonts-alias</prgn> on each
8169 directory into which they installed fonts. This
8170 invocation must occur in both the
8171 <prgn>postinst</prgn> (for all arguments) and
8172 <prgn>postrm</prgn> (for all arguments except
8173 <tt>upgrade</tt>) scripts.
8177 Font packages must invoke
8178 <prgn>update-fonts-dir</prgn> on each directory into
8179 which they installed fonts. This invocation must
8180 occur in both the <prgn>postinst</prgn> (for all
8181 arguments) and <prgn>postrm</prgn> (for all
8182 arguments except <tt>upgrade</tt>) scripts.
8186 Font packages must not provide alias names for the
8187 fonts they include which collide with alias names
8188 already in use by fonts already packaged.
8192 Font packages must not provide fonts with the same
8193 XLFD registry name as another font already packaged.
8200 <heading>Application defaults files</heading>
8203 Application defaults files must be installed in the
8204 directory <file>/etc/X11/app-defaults/</file> (use of a
8205 localized subdirectory of <file>/etc/X11/</file> as described
8206 in the <em>X Toolkit Intrinsics - C Language
8207 Interface</em> manual is also permitted). They must be
8208 registered as <tt>conffile</tt>s or handled as
8209 configuration files. Packages must not provide the
8210 directory <file>/usr/X11R6/lib/X11/app-defaults/</file>.
8214 Customization of programs' X resources may also be
8215 supported with the provision of a file with the same name
8216 as that of the package placed in the
8217 <file>/etc/X11/Xresources/</file> directory, which must
8218 registered as a <tt>conffile</tt> or handled as a
8219 configuration file.<footnote>
8220 Note that this mechanism is not the same as using
8221 app-defaults; app-defaults are tied to the client
8222 binary on the local file system, whereas X resources
8223 are stored in the X server and affect all connecting
8226 <em>Important:</em> packages that install files into the
8227 <file>/etc/X11/Xresources/</file> directory must conflict with
8228 <tt>xbase (<< 3.3.2.3a-2)</tt>; if this is not done
8229 it is possible for the installing package to destroy a
8230 previously-existing <file>/etc/X11/Xresources</file> file
8231 which had been customized by the system administrator.
8236 <heading>Installation directory issues</heading>
8239 Packages using the X Window System should not be
8240 configured to install files under the
8241 <file>/usr/X11R6/</file> directory. The
8242 <file>/usr/X11R6/</file> directory hierarchy should be
8243 regarded as obsolete.
8247 Programs that use GNU <prgn>autoconf</prgn> and
8248 <prgn>automake</prgn> are usually easily configured at
8249 compile time to use <file>/usr/</file> instead of
8250 <file>/usr/X11R6/</file>, and this should be done whenever
8251 possible. Configuration files for window managers and
8252 display managers should be placed in a subdirectory of
8253 <file>/etc/X11/</file> corresponding to the package name due
8254 to these programs' tight integration with the mechanisms
8255 of the X Window System. Application-level programs should
8256 use the <file>/etc/</file> directory unless otherwise mandated
8261 The installation of files into subdirectories
8262 of <file>/usr/X11R6/include/X11/</file> and
8263 <file>/usr/X11R6/lib/X11/</file> is now prohibited;
8264 package maintainers should determine if subdirectories of
8265 <file>/usr/lib/</file> and <file>/usr/share/</file> can be used
8270 Packages should install any relevant files into the
8271 directories <file>/usr/include/X11/</file> and
8272 <file>/usr/lib/X11/</file>, but if they do so, they must
8273 pre-depend on <tt>x11-common (>=
8274 1:7.0.0)</tt><footnote>
8276 These libraries used to be all symbolic
8277 links. However, with <tt>X11R7</tt>,
8278 <tt>/usr/include/X11</tt> and <tt>/usr/lib/X11</tt>
8279 are now real directories, and packages
8280 <strong>should</strong> ship their files here instead
8281 of in <tt>/usr/X11R6/{include,lib}/X11</tt>.
8282 <tt>x11-common (>= 1:7.0.0) </tt> is the package
8283 responsible for converting these symlinks into
8291 <heading>The OSF/Motif and OpenMotif libraries</heading>
8294 <em>Programs that require the non-DFSG-compliant OSF/Motif or
8295 OpenMotif libraries</em><footnote>
8296 OSF/Motif and OpenMotif are collectively referred to as
8297 "Motif" in this policy document.
8299 should be compiled against and tested with LessTif (a free
8300 re-implementation of Motif) instead. If the maintainer
8301 judges that the program or programs do not work
8302 sufficiently well with LessTif to be distributed and
8303 supported, but do so when compiled against Motif, then two
8304 versions of the package should be created; one linked
8305 statically against Motif and with <tt>-smotif</tt>
8306 appended to the package name, and one linked dynamically
8307 against Motif and with <tt>-dmotif</tt> appended to the
8312 Both Motif-linked versions are dependent
8313 upon non-DFSG-compliant software and thus cannot be
8314 uploaded to the <em>main</em> distribution; if the
8315 software is itself DFSG-compliant it may be uploaded to
8316 the <em>contrib</em> distribution. While known existing
8317 versions of Motif permit unlimited redistribution of
8318 binaries linked against the library (whether statically or
8319 dynamically), it is the package maintainer's
8320 responsibility to determine whether this is permitted by
8321 the license of the copy of Motif in their possession.
8327 <heading>Perl programs and modules</heading>
8330 Perl programs and modules should follow the current Perl policy.
8334 The Perl policy can be found in the <tt>perl-policy</tt>
8335 files in the <tt>debian-policy</tt> package.
8336 It is also available from the Debian web mirrors at
8337 <tt><url name="/doc/packaging-manuals/perl-policy/"
8338 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
8343 <heading>Emacs lisp programs</heading>
8346 Please refer to the "Debian Emacs Policy" for details of how to
8347 package emacs lisp programs.
8351 The Emacs policy is available in
8352 <file>debian-emacs-policy.gz</file> of the
8353 <package>emacsen-common</package> package.
8354 It is also available from the Debian web mirrors at
8355 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
8356 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
8361 <heading>Games</heading>
8364 The permissions on <file>/var/games</file> are mode 755, owner
8365 <tt>root</tt> and group <tt>root</tt>.
8369 Each game decides on its own security policy.</p>
8372 Games which require protected, privileged access to
8373 high-score files, saved games, etc., may be made
8374 set-<em>group</em>-id (mode 2755) and owned by
8375 <tt>root.games</tt>, and use files and directories with
8376 appropriate permissions (770 <tt>root.games</tt>, for
8377 example). They must not be made
8378 set-<em>user</em>-id, as this causes security problems. (If
8379 an attacker can subvert any set-user-id game they can
8380 overwrite the executable of any other, causing other players
8381 of these games to run a Trojan horse program. With a
8382 set-group-id game the attacker only gets access to less
8383 important game data, and if they can get at the other
8384 players' accounts at all it will take considerably more
8388 Some packages, for example some fortune cookie programs, are
8389 configured by the upstream authors to install with their
8390 data files or other static information made unreadable so
8391 that they can only be accessed through set-id programs
8392 provided. You should not do this in a Debian package: anyone can
8393 download the <file>.deb</file> file and read the data from it,
8394 so there is no point making the files unreadable. Not
8395 making the files unreadable also means that you don't have
8396 to make so many programs set-id, which reduces the risk of a
8400 As described in the FHS, binaries of games should be
8401 installed in the directory <file>/usr/games</file>. This also
8402 applies to games that use the X Window System. Manual pages
8403 for games (X and non-X games) should be installed in
8404 <file>/usr/share/man/man6</file>.</p>
8410 <heading>Documentation</heading>
8413 <heading>Manual pages</heading>
8416 You should install manual pages in <prgn>nroff</prgn> source
8417 form, in appropriate places under <file>/usr/share/man</file>.
8418 You should only use sections 1 to 9 (see the FHS for more
8419 details). You must not install a pre-formatted "cat page".
8423 Each program, utility, and function should have an
8424 associated manual page included in the same package. It is
8425 suggested that all configuration files also have a manual
8426 page included as well. Manual pages for protocols and other
8427 auxiliary things are optional.
8431 If no manual page is available, this is considered as a bug
8432 and should be reported to the Debian Bug Tracking System (the
8433 maintainer of the package is allowed to write this bug report
8434 themselves, if they so desire). Do not close the bug report
8435 until a proper man page is available.<footnote>
8436 It is not very hard to write a man page. See the
8437 <url id="http://www.schweikhardt.net/man_page_howto.html"
8438 name="Man-Page-HOWTO">,
8439 <manref name="man" section="7">, the examples
8440 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
8441 the helper programs <prgn>help2man</prgn>, or the
8442 directory <file>/usr/share/doc/man-db/examples</file>.
8447 You may forward a complaint about a missing man page to the
8448 upstream authors, and mark the bug as forwarded in the
8449 Debian bug tracking system. Even though the GNU Project do
8450 not in general consider the lack of a man page to be a bug,
8451 we do; if they tell you that they don't consider it a bug
8452 you should leave the bug in our bug tracking system open
8457 Manual pages should be installed compressed using <tt>gzip -9</tt>.
8461 If one man page needs to be accessible via several names it
8462 is better to use a symbolic link than the <file>.so</file>
8463 feature, but there is no need to fiddle with the relevant
8464 parts of the upstream source to change from <file>.so</file> to
8465 symlinks: don't do it unless it's easy. You should not
8466 create hard links in the manual page directories, nor put
8467 absolute filenames in <file>.so</file> directives. The filename
8468 in a <file>.so</file> in a man page should be relative to the
8469 base of the man page tree (usually
8470 <file>/usr/share/man</file>). If you do not create any links
8471 (whether symlinks, hard links, or <tt>.so</tt> directives)
8472 in the file system to the alternate names of the man page,
8473 then you should not rely on <prgn>man</prgn> finding your
8474 man page under those names based solely on the information in
8475 the man page's header.<footnote>
8476 Supporting this in <prgn>man</prgn> often requires
8477 unreasonable processing time to find a manual page or to
8478 report that none exists, and moves knowledge into man's
8479 database that would be better left in the file system.
8480 This support is therefore deprecated and will cease to
8481 be present in the future.
8487 <heading>Info documents</heading>
8490 Info documents should be installed in <file>/usr/share/info</file>.
8491 They should be compressed with <tt>gzip -9</tt>.
8495 Your package should call <prgn>install-info</prgn> to update
8496 the Info <file>dir</file> file in its <prgn>postinst</prgn>
8497 script when called with a <tt>configure</tt> argument, for
8499 <example compact="compact">
8500 install-info --quiet --section Development Development \
8501 /usr/share/info/foobar.info
8505 It is a good idea to specify a section for the location of
8506 your program; this is done with the <tt>--section</tt>
8507 switch. To determine which section to use, you should look
8508 at <file>/usr/share/info/dir</file> on your system and choose the most
8509 relevant (or create a new section if none of the current
8510 sections are relevant). Note that the <tt>--section</tt>
8511 flag takes two arguments; the first is a regular expression
8512 to match (case-insensitively) against an existing section,
8513 the second is used when creating a new one.</p>
8516 You should remove the entries in the <prgn>prerm</prgn>
8517 script when called with a <tt>remove</tt> argument:
8518 <example compact="compact">
8519 install-info --quiet --remove /usr/share/info/foobar.info
8523 If <prgn>install-info</prgn> cannot find a description entry
8524 in the Info file you must supply one. See <manref
8525 name="install-info" section="8"> for details.</p>
8529 <heading>Additional documentation</heading>
8532 Any additional documentation that comes with the package may
8533 be installed at the discretion of the package maintainer.
8534 Plain text documentation should be installed in the directory
8535 <file>/usr/share/doc/<var>package</var></file>, where
8536 <var>package</var> is the name of the package, and
8537 compressed with <tt>gzip -9</tt> unless it is small.
8541 If a package comes with large amounts of documentation which
8542 many users of the package will not require you should create
8543 a separate binary package to contain it, so that it does not
8544 take up disk space on the machines of users who do not need
8545 or want it installed.</p>
8548 It is often a good idea to put text information files
8549 (<file>README</file>s, changelogs, and so forth) that come with
8550 the source package in <file>/usr/share/doc/<var>package</var></file>
8551 in the binary package. However, you don't need to install
8552 the instructions for building and installing the package, of
8556 Packages must not require the existence of any files in
8557 <file>/usr/share/doc/</file> in order to function
8559 The system administrator should be able to
8560 delete files in <file>/usr/share/doc/</file> without causing
8561 any programs to break.
8563 Any files that are referenced by programs but are also
8564 useful as stand alone documentation should be installed under
8565 <file>/usr/share/<var>package</var>/</file> with symbolic links from
8566 <file>/usr/share/doc/<var>package</var></file>.
8570 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8571 link to another directory in <file>/usr/share/doc</file> only if
8572 the two packages both come from the same source and the
8573 first package Depends on the second.<footnote>
8575 Please note that this does not override the section on
8576 changelog files below, so the file
8577 <file>/usr/share/<var>package</var>/changelog.Debian.gz</file>
8578 must refer to the changelog for the current version of
8579 <var>package</var> in question. In practice, this means
8580 that the sources of the target and the destination of the
8581 symlink must be the same (same source package and
8588 Former Debian releases placed all additional documentation
8589 in <file>/usr/doc/<var>package</var></file>. This has been
8590 changed to <file>/usr/share/doc/<var>package</var></file>,
8591 and packages must not put documentation in the directory
8592 <file>/usr/doc/<var>package</var></file>. <footnote>
8593 At this phase of the transition, we no longer require a
8594 symbolic link in <file>/usr/doc/</file>. At a later point,
8595 policy shall change to make the symbolic links a bug.
8601 <heading>Preferred documentation formats</heading>
8604 The unification of Debian documentation is being carried out
8608 If your package comes with extensive documentation in a
8609 markup format that can be converted to various other formats
8610 you should if possible ship HTML versions in a binary
8611 package, in the directory
8612 <file>/usr/share/doc/<var>appropriate-package</var></file> or
8613 its subdirectories.<footnote>
8614 The rationale: The important thing here is that HTML
8615 docs should be available in <em>some</em> package, not
8616 necessarily in the main binary package.
8621 Other formats such as PostScript may be provided at the
8622 package maintainer's discretion.
8626 <sect id="copyrightfile">
8627 <heading>Copyright information</heading>
8630 Every package must be accompanied by a verbatim copy of its
8631 copyright and distribution license in the file
8632 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
8633 file must neither be compressed nor be a symbolic link.
8637 In addition, the copyright file must say where the upstream
8638 sources (if any) were obtained. It should name the original
8639 authors of the package and the Debian maintainer(s) who were
8640 involved with its creation.</p>
8643 A copy of the file which will be installed in
8644 <file>/usr/share/doc/<var>package</var>/copyright</file> should
8645 be in <file>debian/copyright</file> in the source package.
8649 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8650 link to another directory in <file>/usr/share/doc</file> only if
8651 the two packages both come from the same source and the
8652 first package Depends on the second. These rules are
8653 important because copyrights must be extractable by
8658 Packages distributed under the UCB BSD license, the Artistic
8659 license, the GNU GPL, and the GNU LGPL, should refer to the
8660 corresponding files under
8661 <file>/usr/share/common-licenses</file>,<footnote>
8664 <file>/usr/share/common-licenses/Artistic</file>,
8665 <file>/usr/share/common-licenses/BSD</file>,
8666 <file>/usr/share/common-licenses/GPL</file>,
8667 <file>/usr/share/common-licenses/LGPL</file>,
8668 <file>/usr/share/common-licenses/GFDL</file>,
8669 <file>/usr/share/common-licenses/GPL-2</file>, and
8670 <file>/usr/share/common-licenses/LGPL-2.1</file>, and so
8671 on. Note that the GFDL is new here, and the license file
8672 may not yet be in place in
8673 <file>/usr/share/common-licenses/GFDL</file>.
8675 </footnote> rather than quoting them in the copyright
8680 You should not use the copyright file as a general <file>README</file>
8681 file. If your package has such a file it should be
8682 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
8683 <file>README.Debian</file> or some other appropriate place.</p>
8687 <heading>Examples</heading>
8690 Any examples (configurations, source files, whatever),
8691 should be installed in a directory
8692 <file>/usr/share/doc/<var>package</var>/examples</file>. These
8693 files should not be referenced by any program: they're there
8694 for the benefit of the system administrator and users as
8695 documentation only. Architecture-specific example files
8696 should be installed in a directory
8697 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
8699 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
8700 latter directory itself may be a symbolic link to the
8705 If the purpose of a package is to provide examples, then the
8706 example files may be installed into
8707 <file>/usr/share/doc/<var>package</var></file>.
8711 <sect id="changelogs">
8712 <heading>Changelog files</heading>
8715 Packages that are not Debian-native must contain a
8716 compressed copy of the <file>debian/changelog</file> file from
8717 the Debian source tree in
8718 <file>/usr/share/doc/<var>package</var></file> with the name
8719 <file>changelog.Debian.gz</file>.
8723 If an upstream changelog is available, it should be accessible as
8724 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
8725 plain text. If the upstream changelog is distributed in
8726 HTML, it should be made available in that form as
8727 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
8728 and a plain text <file>changelog.gz</file> should be generated
8729 from it using, for example, <tt>lynx -dump -nolist</tt>. If
8730 the upstream changelog files do not already conform to this
8731 naming convention, then this may be achieved either by
8732 renaming the files, or by adding a symbolic link, at the
8733 maintainer's discretion.<footnote>
8734 Rationale: People should not have to look in places for
8735 upstream changelogs merely because they are given
8736 different names or are distributed in HTML format.
8741 All of these files should be installed compressed using
8742 <tt>gzip -9</tt>, as they will become large with time even
8743 if they start out small.
8747 If the package has only one changelog which is used both as
8748 the Debian changelog and the upstream one because there is
8749 no separate upstream maintainer then that changelog should
8750 usually be installed as
8751 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
8752 there is a separate upstream maintainer, but no upstream
8753 changelog, then the Debian changelog should still be called
8754 <file>changelog.Debian.gz</file>.
8758 For details about the format and contents of the Debian
8759 changelog file, please see <ref id="dpkgchangelog">.
8764 <appendix id="pkg-scope">
8765 <heading>Introduction and scope of these appendices</heading>
8768 These appendices are taken essentially verbatim from the
8769 now-deprecated Packaging Manual, version 3.2.1.0. They are
8770 the chapters which are likely to be of use to package
8771 maintainers and which have not already been included in the
8772 policy document itself. Most of these sections are very likely
8773 not relevant to policy; they should be treated as
8774 documentation for the packaging system. Please note that these
8775 appendices are included for convenience, and for historical
8776 reasons: they used to be part of policy package, and they have
8777 not yet been incorporated into dpkg documentation. However,
8778 they still have value, and hence they are presented here.
8782 They have not yet been checked to ensure that they are
8783 compatible with the contents of policy, and if there are any
8784 contradictions, the version in the main policy document takes
8785 precedence. The remaining chapters of the old Packaging
8786 Manual have also not been read in detail to ensure that there
8787 are not parts which have been left out. Both of these will be
8792 Certain parts of the Packaging manual were integrated into the
8793 Policy Manual proper, and removed from the appendices. Links
8794 have been placed from the old locations to the new ones.
8798 <prgn>dpkg</prgn> is a suite of programs for creating binary
8799 package files and installing and removing them on Unix
8801 <prgn>dpkg</prgn> is targeted primarily at Debian
8802 GNU/Linux, but may work on or be ported to other
8808 The binary packages are designed for the management of
8809 installed executable programs (usually compiled binaries) and
8810 their associated data, though source code examples and
8811 documentation are provided as part of some packages.</p>
8814 This manual describes the technical aspects of creating Debian
8815 binary packages (<file>.deb</file> files). It documents the
8816 behavior of the package management programs
8817 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
8818 they interact with packages.</p>
8821 It also documents the interaction between
8822 <prgn>dselect</prgn>'s core and the access method scripts it
8823 uses to actually install the selected packages, and describes
8824 how to create a new access method.</p>
8827 This manual does not go into detail about the options and
8828 usage of the package building and installation tools. It
8829 should therefore be read in conjunction with those programs'
8834 The utility programs which are provided with <prgn>dpkg</prgn>
8835 for managing various system configuration and similar issues,
8836 such as <prgn>update-rc.d</prgn> and
8837 <prgn>install-info</prgn>, are not described in detail here -
8838 please see their man pages.
8842 It is assumed that the reader is reasonably familiar with the
8843 <prgn>dpkg</prgn> System Administrators' manual.
8844 Unfortunately this manual does not yet exist.
8848 The Debian version of the FSF's GNU hello program is provided
8849 as an example for people wishing to create Debian
8850 packages. The Debian <prgn>debmake</prgn> package is
8851 recommended as a very helpful tool in creating and maintaining
8852 Debian packages. However, while the tools and examples are
8853 helpful, they do not replace the need to read and follow the
8854 Policy and Programmer's Manual.</p>
8857 <appendix id="pkg-binarypkg">
8858 <heading>Binary packages (from old Packaging Manual)</heading>
8861 The binary package has two main sections. The first part
8862 consists of various control information files and scripts used
8863 by <prgn>dpkg</prgn> when installing and removing. See <ref
8864 id="pkg-controlarea">.
8868 The second part is an archive containing the files and
8869 directories to be installed.
8873 In the future binary packages may also contain other
8874 components, such as checksums and digital signatures. The
8875 format for the archive is described in full in the
8876 <file>deb(5)</file> man page.
8880 <sect id="pkg-bincreating"><heading>Creating package files -
8881 <prgn>dpkg-deb</prgn>
8885 All manipulation of binary package files is done by
8886 <prgn>dpkg-deb</prgn>; it's the only program that has
8887 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
8888 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
8889 will spot that the options requested are appropriate to
8890 <prgn>dpkg-deb</prgn> and invoke that instead with the same
8895 In order to create a binary package you must make a
8896 directory tree which contains all the files and directories
8897 you want to have in the file system data part of the package.
8898 In Debian-format source packages this directory is usually
8899 <file>debian/tmp</file>, relative to the top of the package's
8904 They should have the locations (relative to the root of the
8905 directory tree you're constructing) ownerships and
8906 permissions which you want them to have on the system when
8911 With current versions of <prgn>dpkg</prgn> the uid/username
8912 and gid/groupname mappings for the users and groups being
8913 used should be the same on the system where the package is
8914 built and the one where it is installed.
8918 You need to add one special directory to the root of the
8919 miniature file system tree you're creating:
8920 <prgn>DEBIAN</prgn>. It should contain the control
8921 information files, notably the binary package control file
8922 (see <ref id="pkg-controlfile">).
8926 The <prgn>DEBIAN</prgn> directory will not appear in the
8927 file system archive of the package, and so won't be installed
8928 by <prgn>dpkg</prgn> when the package is installed.
8932 When you've prepared the package, you should invoke:
8934 dpkg --build <var>directory</var>
8939 This will build the package in
8940 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
8941 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
8942 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
8947 See the man page <manref name="dpkg-deb" section="8"> for details of how
8948 to examine the contents of this newly-created file. You may find the
8949 output of following commands enlightening:
8951 dpkg-deb --info <var>filename</var>.deb
8952 dpkg-deb --contents <var>filename</var>.deb
8953 dpkg --contents <var>filename</var>.deb
8955 To view the copyright file for a package you could use this command:
8957 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - \*/copyright | pager
8962 <sect id="pkg-controlarea">
8963 <heading>Package control information files</heading>
8966 The control information portion of a binary package is a
8967 collection of files with names known to <prgn>dpkg</prgn>.
8968 It will treat the contents of these files specially - some
8969 of them contain information used by <prgn>dpkg</prgn> when
8970 installing or removing the package; others are scripts which
8971 the package maintainer wants <prgn>dpkg</prgn> to run.
8975 It is possible to put other files in the package control
8976 area, but this is not generally a good idea (though they
8977 will largely be ignored).
8981 Here is a brief list of the control info files supported by
8982 <prgn>dpkg</prgn> and a summary of what they're used for.
8987 <tag><tt>control</tt>
8990 This is the key description file used by
8991 <prgn>dpkg</prgn>. It specifies the package's name
8992 and version, gives its description for the user,
8993 states its relationships with other packages, and so
8994 forth. See <ref id="sourcecontrolfiles"> and
8995 <ref id="binarycontrolfiles">.
8999 It is usually generated automatically from information
9000 in the source package by the
9001 <prgn>dpkg-gencontrol</prgn> program, and with
9002 assistance from <prgn>dpkg-shlibdeps</prgn>.
9003 See <ref id="pkg-sourcetools">.
9007 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9012 These are executable files (usually scripts) which
9013 <prgn>dpkg</prgn> runs during installation, upgrade
9014 and removal of packages. They allow the package to
9015 deal with matters which are particular to that package
9016 or require more complicated processing than that
9017 provided by <prgn>dpkg</prgn>. Details of when and
9018 how they are called are in <ref id="maintainerscripts">.
9022 It is very important to make these scripts idempotent.
9023 See <ref id="idempotency">.
9027 The maintainer scripts are guaranteed to run with a
9028 controlling terminal and can interact with the user.
9029 See <ref id="controllingterminal">.
9033 <tag><tt>conffiles</tt>
9036 This file contains a list of configuration files which
9037 are to be handled automatically by <prgn>dpkg</prgn>
9038 (see <ref id="pkg-conffiles">). Note that not necessarily
9039 every configuration file should be listed here.
9042 <tag><tt>shlibs</tt>
9045 This file contains a list of the shared libraries
9046 supplied by the package, with dependency details for
9047 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9048 when it determines what dependencies are required in a
9049 package control file. The <tt>shlibs</tt> file format
9050 is described on <ref id="shlibs">.
9055 <sect id="pkg-controlfile">
9056 <heading>The main control information file: <tt>control</tt></heading>
9059 The most important control information file used by
9060 <prgn>dpkg</prgn> when it installs a package is
9061 <tt>control</tt>. It contains all the package's "vital
9066 The binary package control files of packages built from
9067 Debian sources are made by a special tool,
9068 <prgn>dpkg-gencontrol</prgn>, which reads
9069 <file>debian/control</file> and <file>debian/changelog</file> to
9070 find the information it needs. See <ref id="pkg-sourcepkg"> for
9075 The fields in binary package control files are listed in
9076 <ref id="binarycontrolfiles">.
9080 A description of the syntax of control files and the purpose
9081 of the fields is available in <ref id="controlfields">.
9086 <heading>Time Stamps</heading>
9089 See <ref id="timestamps">.
9094 <appendix id="pkg-sourcepkg">
9095 <heading>Source packages (from old Packaging Manual) </heading>
9098 The Debian binary packages in the distribution are generated
9099 from Debian sources, which are in a special format to assist
9100 the easy and automatic building of binaries.
9103 <sect id="pkg-sourcetools">
9104 <heading>Tools for processing source packages</heading>
9107 Various tools are provided for manipulating source packages;
9108 they pack and unpack sources and help build of binary
9109 packages and help manage the distribution of new versions.
9113 They are introduced and typical uses described here; see
9114 <manref name="dpkg-source" section="1"> for full
9115 documentation about their arguments and operation.
9119 For examples of how to construct a Debian source package,
9120 and how to use those utilities that are used by Debian
9121 source packages, please see the <prgn>hello</prgn> example
9125 <sect1 id="pkg-dpkg-source">
9127 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9132 This program is frequently used by hand, and is also
9133 called from package-independent automated building scripts
9134 such as <prgn>dpkg-buildpackage</prgn>.
9138 To unpack a package it is typically invoked with
9140 dpkg-source -x <var>.../path/to/filename</var>.dsc
9145 with the <file><var>filename</var>.tar.gz</file> and
9146 <file><var>filename</var>.diff.gz</file> (if applicable) in
9147 the same directory. It unpacks into
9148 <file><var>package</var>-<var>version</var></file>, and if
9150 <file><var>package</var>-<var>version</var>.orig</file>, in
9151 the current directory.
9155 To create a packed source archive it is typically invoked:
9157 dpkg-source -b <var>package</var>-<var>version</var>
9162 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
9163 <file>.diff.gz</file> (if appropriate) in the current
9164 directory. <prgn>dpkg-source</prgn> does not clean the
9165 source tree first - this must be done separately if it is
9170 See also <ref id="pkg-sourcearchives">.</p>
9174 <sect1 id="pkg-dpkg-buildpackage">
9176 <prgn>dpkg-buildpackage</prgn> - overall package-building
9181 <prgn>dpkg-buildpackage</prgn> is a script which invokes
9182 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
9183 targets <tt>clean</tt>, <tt>build</tt> and
9184 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
9185 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
9186 source and binary package upload.
9190 It is usually invoked by hand from the top level of the
9191 built or unbuilt source directory. It may be invoked with
9192 no arguments; useful arguments include:
9193 <taglist compact="compact">
9194 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
9197 Do not sign the <tt>.changes</tt> file or the
9198 source package <tt>.dsc</tt> file, respectively.</p>
9200 <tag><tt>-p<var>sign-command</var></tt></tag>
9203 Invoke <var>sign-command</var> instead of finding
9204 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
9205 <var>sign-command</var> must behave just like
9206 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
9208 <tag><tt>-r<var>root-command</var></tt></tag>
9211 When root privilege is required, invoke the command
9212 <var>root-command</var>. <var>root-command</var>
9213 should invoke its first argument as a command, from
9214 the <prgn>PATH</prgn> if necessary, and pass its
9215 second and subsequent arguments to the command it
9216 calls. If no <var>root-command</var> is supplied
9217 then <var>dpkg-buildpackage</var> will take no
9218 special action to gain root privilege, so that for
9219 most packages it will have to be invoked as root to
9222 <tag><tt>-b</tt>, <tt>-B</tt></tag>
9225 Two types of binary-only build and upload - see
9226 <manref name="dpkg-source" section="1">.
9233 <sect1 id="pkg-dpkg-gencontrol">
9235 <prgn>dpkg-gencontrol</prgn> - generates binary package
9240 This program is usually called from <file>debian/rules</file>
9241 (see <ref id="pkg-sourcetree">) in the top level of the source
9246 This is usually done just before the files and directories in the
9247 temporary directory tree where the package is being built have their
9248 permissions and ownerships set and the package is constructed using
9249 <prgn>dpkg-deb/</prgn>
9251 This is so that the control file which is produced has
9252 the right permissions
9257 <prgn>dpkg-gencontrol</prgn> must be called after all the
9258 files which are to go into the package have been placed in
9259 the temporary build directory, so that its calculation of
9260 the installed size of a package is correct.
9264 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
9265 be run after <prgn>dpkg-shlibdeps</prgn> so that the
9266 variable substitutions created by
9267 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
9272 For a package which generates only one binary package, and
9273 which builds it in <file>debian/tmp</file> relative to the top
9274 of the source package, it is usually sufficient to call
9275 <prgn>dpkg-gencontrol</prgn>.
9279 Sources which build several binaries will typically need
9282 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
9283 </example> The <tt>-P</tt> tells
9284 <prgn>dpkg-gencontrol</prgn> that the package is being
9285 built in a non-default directory, and the <tt>-p</tt>
9286 tells it which package's control file should be generated.
9290 <prgn>dpkg-gencontrol</prgn> also adds information to the
9291 list of files in <file>debian/files</file>, for the benefit of
9292 (for example) a future invocation of
9293 <prgn>dpkg-genchanges</prgn>.</p>
9296 <sect1 id="pkg-dpkg-shlibdeps">
9298 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
9303 This program is usually called from <file>debian/rules</file>
9304 just before <prgn>dpkg-gencontrol</prgn> (see <ref
9305 id="pkg-sourcetree">), in the top level of the source tree.
9309 Its arguments are executables.
9312 In a forthcoming dpkg version,
9313 <prgn>dpkg-shlibdeps</prgn> would be required to be
9314 called on shared libraries as well.
9317 They may be specified either in the locations in the
9318 source tree where they are created or in the locations
9319 in the temporary build tree where they are installed
9320 prior to binary package creation.
9322 </footnote> for which shared library dependencies should
9323 be included in the binary package's control file.
9327 If some of the found shared libraries should only
9328 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
9329 some warrant a <tt>Pre-Depends</tt>, this can be achieved
9330 by using the <tt>-d<var>dependency-field</var></tt> option
9331 before those executable(s). (Each <tt>-d</tt> option
9332 takes effect until the next <tt>-d</tt>.)
9336 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
9337 output control file to be modified. Instead by default it
9338 adds to the <file>debian/substvars</file> file variable
9339 settings like <tt>shlibs:Depends</tt>. These variable
9340 settings must be referenced in dependency fields in the
9341 appropriate per-binary-package sections of the source
9346 For example, a package that generates an essential part
9347 which requires dependencies, and optional parts that
9348 which only require a recommendation, would separate those
9349 two sets of dependencies into two different fields.<footnote>
9350 At the time of writing, an example for this was the
9351 <package/xmms/ package, with Depends used for the xmms
9352 executable, Recommends for the plug-ins and Suggests for
9353 even more optional features provided by unzip.
9355 It can say in its <file>debian/rules</file>:
9357 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
9358 -dRecommends <var>optionalpart anotheroptionalpart</var>
9360 and then in its main control file <file>debian/control</file>:
9363 Depends: ${shlibs:Pre-Depends}
9364 Recommends: ${shlibs:Recommends}
9370 Sources which produce several binary packages with
9371 different shared library dependency requirements can use
9372 the <tt>-p<var>varnameprefix</var></tt> option to override
9373 the default <tt>shlibs:</tt> prefix (one invocation of
9374 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
9375 They can thus produce several sets of dependency
9376 variables, each of the form
9377 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
9378 which can be referred to in the appropriate parts of the
9379 binary package control files.
9384 <sect1 id="pkg-dpkg-distaddfile">
9386 <prgn>dpkg-distaddfile</prgn> - adds a file to
9387 <file>debian/files</file>
9391 Some packages' uploads need to include files other than
9392 the source and binary package files.
9396 <prgn>dpkg-distaddfile</prgn> adds a file to the
9397 <file>debian/files</file> file so that it will be included in
9398 the <file>.changes</file> file when
9399 <prgn>dpkg-genchanges</prgn> is run.
9403 It is usually invoked from the <tt>binary</tt> target of
9404 <file>debian/rules</file>:
9406 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
9408 The <var>filename</var> is relative to the directory where
9409 <prgn>dpkg-genchanges</prgn> will expect to find it - this
9410 is usually the directory above the top level of the source
9411 tree. The <file>debian/rules</file> target should put the
9412 file there just before or just after calling
9413 <prgn>dpkg-distaddfile</prgn>.
9417 The <var>section</var> and <var>priority</var> are passed
9418 unchanged into the resulting <file>.changes</file> file.
9423 <sect1 id="pkg-dpkg-genchanges">
9425 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
9430 This program is usually called by package-independent
9431 automatic building scripts such as
9432 <prgn>dpkg-buildpackage</prgn>, but it may also be called
9437 It is usually called in the top level of a built source
9438 tree, and when invoked with no arguments will print out a
9439 straightforward <file>.changes</file> file based on the
9440 information in the source package's changelog and control
9441 file and the binary and source packages which should have
9447 <sect1 id="pkg-dpkg-parsechangelog">
9449 <prgn>dpkg-parsechangelog</prgn> - produces parsed
9450 representation of a changelog
9454 This program is used internally by
9455 <prgn>dpkg-source</prgn> et al. It may also occasionally
9456 be useful in <file>debian/rules</file> and elsewhere. It
9457 parses a changelog, <file>debian/changelog</file> by default,
9458 and prints a control-file format representation of the
9459 information in it to standard output.
9463 <sect1 id="pkg-dpkg-architecture">
9465 <prgn>dpkg-architecture</prgn> - information about the build and
9470 This program can be used manually, but is also invoked by
9471 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
9472 to set environment or make variables which specify the build and
9473 host architecture for the package building process.
9478 <sect id="pkg-sourcetree">
9479 <heading>The Debianised source tree</heading>
9482 The source archive scheme described later is intended to
9483 allow a Debianised source tree with some associated control
9484 information to be reproduced and transported easily. The
9485 Debianised source tree is a version of the original program
9486 with certain files added for the benefit of the
9487 Debianisation process, and with any other changes required
9488 made to the rest of the source code and installation
9493 The extra files created for Debian are in the subdirectory
9494 <file>debian</file> of the top level of the Debianised source
9495 tree. They are described below.
9498 <sect1 id="pkg-debianrules">
9499 <heading><file>debian/rules</file> - the main building script</heading>
9502 See <ref id="debianrules">.
9507 <sect1 id="pkg-dpkgchangelog">
9508 <heading><file>debian/changelog</file></heading>
9511 See <ref id="dpkgchangelog">.
9515 It is recommended that the entire changelog be encoded in the
9516 <url id="http://www.cis.ohio-state.edu/cgi-bin/rfc/rfc2279.html" name="UTF-8">
9518 <url id="http://www.unicode.org/"
9519 name="Unicode">.<footnote>
9521 I think it is fairly obvious that we need to
9522 eventually transition to UTF-8 for our package
9523 infrastructure; it is really the only sane char-set in
9524 an international environment. Now, we can't switch to
9525 using UTF-8 for package control fields and the like
9526 until dpkg has better support, but one thing we can
9527 start doing today is requesting that Debian changelogs
9528 are UTF-8 encoded. At some point in time, we can start
9529 requiring them to do so.
9532 Checking for non-UTF8 characters in a changelog is
9533 trivial. Dump the file through
9534 <example>iconv -f utf-8 -t ucs-4</example>
9535 discard the output, and check the return
9536 value. If there are any characters in the stream
9537 which are invalid UTF-8 sequences, iconv will exit
9538 with an error code; and this will be the case for the
9539 vast majority of other character sets.
9544 <sect2><heading>Defining alternative changelog formats
9548 It is possible to use a different format to the standard
9549 one, by providing a parser for the format you wish to
9554 In order to have <tt>dpkg-parsechangelog</tt> run your
9555 parser, you must include a line within the last 40 lines
9556 of your file matching the Perl regular expression:
9557 <tt>\schangelog-format:\s+([0-9a-z]+)\W</tt> The part in
9558 parentheses should be the name of the format. For
9559 example, you might say:
9561 @@@ changelog-format: joebloggs @@@
9563 Changelog format names are non-empty strings of alphanumerics.
9567 If such a line exists then <tt>dpkg-parsechangelog</tt>
9568 will look for the parser as
9569 <file>/usr/lib/dpkg/parsechangelog/<var>format-name</var></file>
9571 <file>/usr/local/lib/dpkg/parsechangelog/<var>format-name</var></file>;
9572 it is an error for it not to find it, or for it not to
9573 be an executable program. The default changelog format
9574 is <tt>dpkg</tt>, and a parser for it is provided with
9575 the <tt>dpkg</tt> package.
9579 The parser will be invoked with the changelog open on
9580 standard input at the start of the file. It should read
9581 the file (it may seek if it wishes) to determine the
9582 information required and return the parsed information
9583 to standard output in the form of a series of control
9584 fields in the standard format. By default it should
9585 return information about only the most recent version in
9586 the changelog; it should accept a
9587 <tt>-v<var>version</var></tt> option to return changes
9588 information from all versions present <em>strictly
9589 after</em> <var>version</var>, and it should then be an
9590 error for <var>version</var> not to be present in the
9596 <list compact="compact">
9597 <item><qref id="f-Source"><tt>Source</tt></qref></item>
9598 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
9599 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
9600 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (mandatory)</item>
9601 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
9602 <item><qref id="f-Date"><tt>Date</tt></qref></item>
9603 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
9608 If several versions are being returned (due to the use
9609 of <tt>-v</tt>), the urgency value should be of the
9610 highest urgency code listed at the start of any of the
9611 versions requested followed by the concatenated
9612 (space-separated) comments from all the versions
9613 requested; the maintainer, version, distribution and
9614 date should always be from the most recent version.
9618 For the format of the <tt>Changes</tt> field see
9619 <ref id="f-Changes">.
9623 If the changelog format which is being parsed always or
9624 almost always leaves a blank line between individual
9625 change notes these blank lines should be stripped out,
9626 so as to make the resulting output compact.
9630 If the changelog format does not contain date or package
9631 name information this information should be omitted from
9632 the output. The parser should not attempt to synthesize
9633 it or find it from other sources.
9637 If the changelog does not have the expected format the
9638 parser should exit with a nonzero exit status, rather
9639 than trying to muddle through and possibly generating
9644 A changelog parser may not interact with the user at
9650 <sect1 id="pkg-srcsubstvars">
9651 <heading><file>debian/substvars</file> and variable substitutions</heading>
9654 See <ref id="substvars">.
9660 <heading><file>debian/files</file></heading>
9663 See <ref id="debianfiles">.
9667 <sect1><heading><file>debian/tmp</file>
9671 This is the canonical temporary location for the
9672 construction of binary packages by the <tt>binary</tt>
9673 target. The directory <file>tmp</file> serves as the root of
9674 the file system tree as it is being constructed (for
9675 example, by using the package's upstream makefiles install
9676 targets and redirecting the output there), and it also
9677 contains the <tt>DEBIAN</tt> subdirectory. See <ref
9678 id="pkg-bincreating">.
9682 If several binary packages are generated from the same
9683 source tree it is usual to use several
9684 <file>debian/tmp<var>something</var></file> directories, for
9685 example <file>tmp-a</file> or <file>tmp-doc</file>.
9689 Whatever <file>tmp</file> directories are created and used by
9690 <tt>binary</tt> must of course be removed by the
9691 <tt>clean</tt> target.</p></sect1>
9695 <sect id="pkg-sourcearchives"><heading>Source packages as archives
9699 As it exists on the FTP site, a Debian source package
9700 consists of three related files. You must have the right
9701 versions of all three to be able to use them.
9706 <tag>Debian source control file - <tt>.dsc</tt></tag>
9708 This file is a control file used by <prgn>dpkg-source</prgn>
9709 to extract a source package.
9710 See <ref id="debiansourcecontrolfiles">.
9714 Original source archive -
9716 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
9722 This is a compressed (with <tt>gzip -9</tt>)
9723 <prgn>tar</prgn> file containing the source code from
9724 the upstream authors of the program.
9729 Debianisation diff -
9731 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
9737 This is a unified context diff (<tt>diff -u</tt>)
9738 giving the changes which are required to turn the
9739 original source into the Debian source. These changes
9740 may only include editing and creating plain files.
9741 The permissions of files, the targets of symbolic
9742 links and the characteristics of special files or
9743 pipes may not be changed and no files may be removed
9748 All the directories in the diff must exist, except the
9749 <file>debian</file> subdirectory of the top of the source
9750 tree, which will be created by
9751 <prgn>dpkg-source</prgn> if necessary when unpacking.
9755 The <prgn>dpkg-source</prgn> program will
9756 automatically make the <file>debian/rules</file> file
9757 executable (see below).</p></item>
9762 If there is no original source code - for example, if the
9763 package is specially prepared for Debian or the Debian
9764 maintainer is the same as the upstream maintainer - the
9765 format is slightly different: then there is no diff, and the
9767 <file><var>package</var>_<var>version</var>.tar.gz</file>,
9768 and preferably contains a directory named
9769 <file><var>package</var>-<var>version</var></file>.
9774 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
9777 <tt>dpkg-source -x</tt> is the recommended way to unpack a
9778 Debian source package. However, if it is not available it
9779 is possible to unpack a Debian source archive as follows:
9780 <enumlist compact="compact">
9783 Untar the tarfile, which will create a <file>.orig</file>
9787 <p>Rename the <file>.orig</file> directory to
9788 <file><var>package</var>-<var>version</var></file>.</p>
9792 Create the subdirectory <file>debian</file> at the top of
9793 the source tree.</p>
9795 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
9797 <item><p>Untar the tarfile again if you want a copy of the original
9798 source code alongside the Debianised version.</p>
9803 It is not possible to generate a valid Debian source archive
9804 without using <prgn>dpkg-source</prgn>. In particular,
9805 attempting to use <prgn>diff</prgn> directly to generate the
9806 <file>.diff.gz</file> file will not work.
9810 <heading>Restrictions on objects in source packages</heading>
9813 The source package may not contain any hard links
9815 This is not currently detected when building source
9816 packages, but only when extracting
9820 Hard links may be permitted at some point in the
9821 future, but would require a fair amount of
9823 </footnote>, device special files, sockets or setuid or
9826 Setgid directories are allowed.
9831 The source packaging tools manage the changes between the
9832 original and Debianised source using <prgn>diff</prgn> and
9833 <prgn>patch</prgn>. Turning the original source tree as
9834 included in the <file>.orig.tar.gz</file> into the debianised
9835 source must not involve any changes which cannot be
9836 handled by these tools. Problematic changes which cause
9837 <prgn>dpkg-source</prgn> to halt with an error when
9838 building the source package are:
9839 <list compact="compact">
9840 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
9842 <item><p>Changing the targets of symbolic links.</p>
9844 <item><p>Creating directories, other than <file>debian</file>.</p>
9846 <item><p>Changes to the contents of binary files.</p></item>
9847 </list> Changes which cause <prgn>dpkg-source</prgn> to
9848 print a warning but continue anyway are:
9849 <list compact="compact">
9852 Removing files, directories or symlinks.
9854 Renaming a file is not treated specially - it is
9855 seen as the removal of the old file (which
9856 generates a warning, but is otherwise ignored),
9857 and the creation of the new one.
9863 Changed text files which are missing the usual final
9864 newline (either in the original or the modified
9869 Changes which are not represented, but which are not detected by
9870 <prgn>dpkg-source</prgn>, are:
9871 <list compact="compact">
9872 <item><p>Changing the permissions of files (other than
9873 <file>debian/rules</file>) and directories.</p></item>
9878 The <file>debian</file> directory and <file>debian/rules</file>
9879 are handled specially by <prgn>dpkg-source</prgn> - before
9880 applying the changes it will create the <file>debian</file>
9881 directory, and afterwards it will make
9882 <file>debian/rules</file> world-executable.
9888 <appendix id="pkg-controlfields">
9889 <heading>Control files and their fields (from old Packaging Manual)</heading>
9892 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
9893 data in a common format, known as control files. Binary and
9894 source packages have control data as do the <file>.changes</file>
9895 files which control the installation of uploaded files, and
9896 <prgn>dpkg</prgn>'s internal databases are in a similar
9901 <heading>Syntax of control files</heading>
9904 See <ref id="controlsyntax">.
9908 It is important to note that there are several fields which
9909 are optional as far as <prgn>dpkg</prgn> and the related
9910 tools are concerned, but which must appear in every Debian
9911 package, or whose omission may cause problems.
9916 <heading>List of fields</heading>
9919 See <ref id="controlfieldslist">.
9923 This section now contains only the fields that didn't belong
9924 to the Policy manual.
9927 <sect1 id="pkg-f-Filename">
9928 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
9931 These fields in <tt>Packages</tt> files give the
9932 filename(s) of (the parts of) a package in the
9933 distribution directories, relative to the root of the
9934 Debian hierarchy. If the package has been split into
9935 several parts the parts are all listed in order, separated
9940 <sect1 id="pkg-f-Size">
9941 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
9944 These fields in <file>Packages</file> files give the size (in
9945 bytes, expressed in decimal) and MD5 checksum of the
9946 file(s) which make(s) up a binary package in the
9947 distribution. If the package is split into several parts
9948 the values for the parts are listed in order, separated by
9953 <sect1 id="pkg-f-Status">
9954 <heading><tt>Status</tt></heading>
9957 This field in <prgn>dpkg</prgn>'s status file records
9958 whether the user wants a package installed, removed or
9959 left alone, whether it is broken (requiring
9960 re-installation) or not and what its current state on the
9961 system is. Each of these pieces of information is a
9966 <sect1 id="pkg-f-Config-Version">
9967 <heading><tt>Config-Version</tt></heading>
9970 If a package is not installed or not configured, this
9971 field in <prgn>dpkg</prgn>'s status file records the last
9972 version of the package which was successfully
9977 <sect1 id="pkg-f-Conffiles">
9978 <heading><tt>Conffiles</tt></heading>
9981 This field in <prgn>dpkg</prgn>'s status file contains
9982 information about the automatically-managed configuration
9983 files held by a package. This field should <em>not</em>
9984 appear anywhere in a package!
9989 <heading>Obsolete fields</heading>
9992 These are still recognized by <prgn>dpkg</prgn> but should
9993 not appear anywhere any more.
9995 <taglist compact="compact">
9997 <tag><tt>Revision</tt></tag>
9998 <tag><tt>Package-Revision</tt></tag>
9999 <tag><tt>Package_Revision</tt></tag>
10001 The Debian revision part of the package version was
10002 at one point in a separate control file field. This
10003 field went through several names.
10006 <tag><tt>Recommended</tt></tag>
10007 <item>Old name for <tt>Recommends</tt>.</item>
10009 <tag><tt>Optional</tt></tag>
10010 <item>Old name for <tt>Suggests</tt>.</item>
10012 <tag><tt>Class</tt></tag>
10013 <item>Old name for <tt>Priority</tt>.</item>
10022 <appendix id="pkg-conffiles">
10023 <heading>Configuration file handling (from old Packaging Manual)</heading>
10026 <prgn>dpkg</prgn> can do a certain amount of automatic
10027 handling of package configuration files.
10031 Whether this mechanism is appropriate depends on a number of
10032 factors, but basically there are two approaches to any
10033 particular configuration file.
10037 The easy method is to ship a best-effort configuration in the
10038 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10039 handle updates. If the user is unlikely to want to edit the
10040 file, but you need them to be able to without losing their
10041 changes, and a new package with a changed version of the file
10042 is only released infrequently, this is a good approach.
10046 The hard method is to build the configuration file from
10047 scratch in the <prgn>postinst</prgn> script, and to take the
10048 responsibility for fixing any mistakes made in earlier
10049 versions of the package automatically. This will be
10050 appropriate if the file is likely to need to be different on
10054 <sect><heading>Automatic handling of configuration files by
10059 A package may contain a control area file called
10060 <tt>conffiles</tt>. This file should be a list of filenames
10061 of configuration files needing automatic handling, separated
10062 by newlines. The filenames should be absolute pathnames,
10063 and the files referred to should actually exist in the
10068 When a package is upgraded <prgn>dpkg</prgn> will process
10069 the configuration files during the configuration stage,
10070 shortly before it runs the package's <prgn>postinst</prgn>
10075 For each file it checks to see whether the version of the
10076 file included in the package is the same as the one that was
10077 included in the last version of the package (the one that is
10078 being upgraded from); it also compares the version currently
10079 installed on the system with the one shipped with the last
10084 If neither the user nor the package maintainer has changed
10085 the file, it is left alone. If one or the other has changed
10086 their version, then the changed version is preferred - i.e.,
10087 if the user edits their file, but the package maintainer
10088 doesn't ship a different version, the user's changes will
10089 stay, silently, but if the maintainer ships a new version
10090 and the user hasn't edited it the new version will be
10091 installed (with an informative message). If both have
10092 changed their version the user is prompted about the problem
10093 and must resolve the differences themselves.
10097 The comparisons are done by calculating the MD5 message
10098 digests of the files, and storing the MD5 of the file as it
10099 was included in the most recent version of the package.
10103 When a package is installed for the first time
10104 <prgn>dpkg</prgn> will install the file that comes with it,
10105 unless that would mean overwriting a file already on the
10110 However, note that <prgn>dpkg</prgn> will <em>not</em>
10111 replace a conffile that was removed by the user (or by a
10112 script). This is necessary because with some programs a
10113 missing file produces an effect hard or impossible to
10114 achieve in another way, so that a missing file needs to be
10115 kept that way if the user did it.
10119 Note that a package should <em>not</em> modify a
10120 <prgn>dpkg</prgn>-handled conffile in its maintainer
10121 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10122 the user confusing and possibly dangerous options for
10123 conffile update when the package is upgraded.</p>
10126 <sect><heading>Fully-featured maintainer script configuration
10131 For files which contain site-specific information such as
10132 the hostname and networking details and so forth, it is
10133 better to create the file in the package's
10134 <prgn>postinst</prgn> script.
10138 This will typically involve examining the state of the rest
10139 of the system to determine values and other information, and
10140 may involve prompting the user for some information which
10141 can't be obtained some other way.
10145 When using this method there are a couple of important
10146 issues which should be considered:
10150 If you discover a bug in the program which generates the
10151 configuration file, or if the format of the file changes
10152 from one version to the next, you will have to arrange for
10153 the postinst script to do something sensible - usually this
10154 will mean editing the installed configuration file to remove
10155 the problem or change the syntax. You will have to do this
10156 very carefully, since the user may have changed the file,
10157 perhaps to fix the very problem that your script is trying
10158 to deal with - you will have to detect these situations and
10159 deal with them correctly.
10163 If you do go down this route it's probably a good idea to
10164 make the program that generates the configuration file(s) a
10165 separate program in <file>/usr/sbin</file>, by convention called
10166 <file><var>package</var>config</file> and then run that if
10167 appropriate from the post-installation script. The
10168 <tt><var>package</var>config</tt> program should not
10169 unquestioningly overwrite an existing configuration - if its
10170 mode of operation is geared towards setting up a package for
10171 the first time (rather than any arbitrary reconfiguration
10172 later) you should have it check whether the configuration
10173 already exists, and require a <tt>--force</tt> flag to
10174 overwrite it.</p></sect>
10177 <appendix id="pkg-alternatives"><heading>Alternative versions of
10178 an interface - <prgn>update-alternatives</prgn> (from old
10183 When several packages all provide different versions of the
10184 same program or file it is useful to have the system select a
10185 default, but to allow the system administrator to change it
10186 and have their decisions respected.
10190 For example, there are several versions of the <prgn>vi</prgn>
10191 editor, and there is no reason to prevent all of them from
10192 being installed at once, each under their own name
10193 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10194 Nevertheless it is desirable to have the name <tt>vi</tt>
10195 refer to something, at least by default.
10199 If all the packages involved cooperate, this can be done with
10200 <prgn>update-alternatives</prgn>.
10204 Each package provides its own version under its own name, and
10205 calls <prgn>update-alternatives</prgn> in its postinst to
10206 register its version (and again in its prerm to deregister
10211 See the man page <manref name="update-alternatives"
10212 section="8"> for details.
10216 If <prgn>update-alternatives</prgn> does not seem appropriate
10217 you may wish to consider using diversions instead.</p>
10220 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10221 package's version of a file (from old Packaging Manual)
10225 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10226 when it reinstalls the package it belongs to, and to have it
10227 put the file from the package somewhere else instead.
10231 This can be used locally to override a package's version of a
10232 file, or by one package to override another's version (or
10233 provide a wrapper for it).
10237 Before deciding to use a diversion, read <ref
10238 id="pkg-alternatives"> to see if you really want a diversion
10239 rather than several alternative versions of a program.
10243 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10244 and updated by a special program <prgn>dpkg-divert</prgn>.
10245 Please see <manref name="dpkg-divert" section="8"> for full
10246 details of its operation.
10250 When a package wishes to divert a file from another, it should
10251 call <prgn>dpkg-divert</prgn> in its preinst to add the
10252 diversion and rename the existing file. For example,
10253 supposing that a <prgn>smailwrapper</prgn> package wishes to
10254 install a wrapper around <file>/usr/sbin/smail</file>:
10256 if [ install = "$1" ]; then
10257 dpkg-divert --package smailwrapper --add --rename \
10258 --divert /usr/sbin/smail.real /usr/sbin/smail
10260 </example> Testing <tt>$1</tt> is necessary so that the script
10261 doesn't try to add the diversion again when
10262 <prgn>smailwrapper</prgn> is upgraded. The <tt>--package
10263 smailwrapper</tt> ensures that <prgn>smailwrapper</prgn>'s
10264 copy of <file>/usr/sbin/smail</file> can bypass the diversion and
10265 get installed as the true version.
10269 The postrm has to do the reverse:
10271 if [ remove = "$1" ]; then
10272 dpkg-divert --package smailwrapper --remove --rename \
10273 --divert /usr/sbin/smail.real /usr/sbin/smail
10279 Do not attempt to divert a file which is vitally important for
10280 the system's operation - when using <prgn>dpkg-divert</prgn>
10281 there is a time, after it has been diverted but before
10282 <prgn>dpkg</prgn> has installed the new version, when the file
10283 does not exist.</p>
10288 <!-- vim:set ai et sts=2 sw=2 tw=76: -->