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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 the <prgn>822-date</prgn>
1572 </footnote>; it should include the time zone specified
1573 numerically, with the time zone name or abbreviation
1574 optionally present as a comment in parentheses.
1578 The first "title" line with the package name should start
1579 at the left hand margin; the "trailer" line with the
1580 maintainer and date details should be preceded by exactly
1581 one space. The maintainer details and the date must be
1582 separated by exactly two spaces.
1586 For more information on placement of the changelog files
1587 within binary packages, please see <ref id="changelogs">.
1590 <sect1><heading>Alternative changelog formats</heading>
1593 In non-experimental packages you must use a format for
1594 <file>debian/changelog</file> which is supported by the most
1595 recent released version of <prgn>dpkg</prgn>.
1599 It is possible to use a format different from the standard
1600 one by providing a changelog parser for the format you wish
1601 to use. The parser must have an API compatible with that
1602 expected by <prgn>dpkg-genchanges</prgn> and
1603 <prgn>dpkg-gencontrol</prgn>, and it must not interact with
1606 If there is general interest in the new format, you should
1607 contact the <package>dpkg</package> maintainer to have the
1608 parser script for it included in the <prgn>dpkg</prgn>
1609 package. (You will need to agree that the parser and its
1610 man page may be distributed under the GNU GPL, just as the rest
1611 of <prgn>dpkg</prgn> is.)
1616 <sect id="dpkgcopyright">
1617 <heading>Copyright: <file>debian/copyright</file></heading>
1619 Every package must be accompanied by a verbatim copy of
1620 its copyright and distribution license in the file
1621 <file>/usr/share/doc/<var>package</var>/copyright</file>
1622 (see <ref id="copyrightfile"> for further details). Also see
1623 <ref id="pkgcopyright"> for further considerations relayed
1624 to copyrights for packages.
1628 <heading>Error trapping in makefiles</heading>
1631 When <prgn>make</prgn> invokes a command in a makefile
1632 (including your package's upstream makefiles and
1633 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1634 means that <prgn>sh</prgn>'s usual bad error handling
1635 properties apply: if you include a miniature script as one
1636 of the commands in your makefile you'll find that if you
1637 don't do anything about it then errors are not detected
1638 and <prgn>make</prgn> will blithely continue after
1643 Every time you put more than one shell command (this
1644 includes using a loop) in a makefile command you
1645 must make sure that errors are trapped. For
1646 simple compound commands, such as changing directory and
1647 then running a program, using <tt>&&</tt> rather
1648 than semicolon as a command separator is sufficient. For
1649 more complex commands including most loops and
1650 conditionals you should include a separate <tt>set -e</tt>
1651 command at the start of every makefile command that's
1652 actually one of these miniature shell scripts.
1656 <sect id="timestamps">
1657 <heading>Time Stamps</heading>
1659 Maintainers should preserve the modification times of the
1660 upstream source files in a package, as far as is reasonably
1662 The rationale is that there is some information conveyed
1663 by knowing the age of the file, for example, you could
1664 recognize that some documentation is very old by looking
1665 at the modification time, so it would be nice if the
1666 modification time of the upstream source would be
1672 <sect id="restrictions">
1673 <heading>Restrictions on objects in source packages</heading>
1676 The source package may not contain any hard links<footnote>
1678 This is not currently detected when building source
1679 packages, but only when extracting
1683 Hard links may be permitted at some point in the
1684 future, but would require a fair amount of
1687 </footnote>, device special files, sockets or setuid or
1688 setgid files.<footnote>
1689 Setgid directories are allowed.
1694 <sect id="debianrules">
1695 <heading>Main building script: <file>debian/rules</file></heading>
1698 This file must be an executable makefile, and contains the
1699 package-specific recipes for compiling the package and
1700 building binary package(s) from the source.
1704 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1705 so that it can be invoked by saying its name rather than
1706 invoking <prgn>make</prgn> explicitly.
1710 Since an interactive <file>debian/rules</file> script makes it
1711 impossible to auto-compile that package and also makes it
1712 hard for other people to reproduce the same binary
1713 package, all <em>required targets</em> MUST be
1714 non-interactive. At a minimum, required targets are the
1715 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1716 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1717 <em>binary-indep</em>, and <em>build</em>. It also follows
1718 that any target that these targets depend on must also be
1723 The targets are as follows (required unless stated otherwise):
1725 <tag><tt>build</tt></tag>
1728 The <tt>build</tt> target should perform all the
1729 configuration and compilation of the package.
1730 If a package has an interactive pre-build
1731 configuration routine, the Debianized source package
1732 must either be built after this has taken place (so
1733 that the binary package can be built without rerunning
1734 the configuration) or the configuration routine
1735 modified to become non-interactive. (The latter is
1736 preferable if there are architecture-specific features
1737 detected by the configuration routine.)
1741 For some packages, notably ones where the same
1742 source tree is compiled in different ways to produce
1743 two binary packages, the <tt>build</tt> target
1744 does not make much sense. For these packages it is
1745 good enough to provide two (or more) targets
1746 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1747 for each of the ways of building the package, and a
1748 <tt>build</tt> target that does nothing. The
1749 <tt>binary</tt> target will have to build the
1750 package in each of the possible ways and make the
1751 binary package out of each.
1755 The <tt>build</tt> target must not do anything
1756 that might require root privilege.
1760 The <tt>build</tt> target may need to run the
1761 <tt>clean</tt> target first - see below.
1765 When a package has a configuration and build routine
1766 which takes a long time, or when the makefiles are
1767 poorly designed, or when <tt>build</tt> needs to
1768 run <tt>clean</tt> first, it is a good idea to
1769 <tt>touch build</tt> when the build process is
1770 complete. This will ensure that if <tt>debian/rules
1771 build</tt> is run again it will not rebuild the whole
1773 Another common way to do this is for <tt>build</tt>
1774 to depend on <prgn>build-stamp</prgn> and to do
1775 nothing else, and for the <prgn>build-stamp</prgn>
1776 target to do the building and to <tt>touch
1777 build-stamp</tt> on completion. This is
1778 especially useful if the build routine creates a
1779 file or directory called <tt>build</tt>; in such a
1780 case, <tt>build</tt> will need to be listed as
1781 a phony target (i.e., as a dependency of the
1782 <tt>.PHONY</tt> target). See the documentation of
1783 <prgn>make</prgn> for more information on phony
1789 <tag><tt>build-arch</tt> (optional),
1790 <tt>build-indep</tt> (optional)
1794 A package may also provide both of the targets
1795 <tt>build-arch</tt> and <tt>build-indep</tt>.
1796 The <tt>build-arch</tt> target, if provided, should
1797 perform all the configuration and compilation required
1798 for producing all architecture-dependant binary packages
1799 (those packages for which the body of the
1800 <tt>Architecture</tt> field in <tt>debian/control</tt>
1801 is not <tt>all</tt>).
1802 Similarly, the <tt>build-indep</tt> target, if
1803 provided, should perform all the configuration and
1804 compilation required for producing all
1805 architecture-independent binary packages
1806 (those packages for which the body of the
1807 <tt>Architecture</tt> field in <tt>debian/control</tt>
1809 The <tt>build</tt> target should depend on those of the
1810 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1811 are provided in the rules file.
1815 If one or both of the targets <tt>build-arch</tt> and
1816 <tt>build-indep</tt> are not provided, then invoking
1817 <file>debian/rules</file> with one of the not-provided
1818 targets as arguments should produce a exit status code
1819 of 2. Usually this is provided automatically by make
1820 if the target is missing.
1824 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1825 must not do anything that might require root privilege.
1829 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1830 <tt>binary-indep</tt>
1834 The <tt>binary</tt> target must be all that is
1835 necessary for the user to build the binary package(s)
1836 produced from this source package. It is
1837 split into two parts: <prgn>binary-arch</prgn> builds
1838 the binary packages which are specific to a particular
1839 architecture, and <tt>binary-indep</tt> builds
1840 those which are not.
1843 <tt>binary</tt> may be (and commonly is) a target with
1844 no commands which simply depends on
1845 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1848 Both <tt>binary-*</tt> targets should depend on the
1849 <tt>build</tt> target, or on the appropriate
1850 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1851 provided, so that the package is built if it has not
1852 been already. It should then create the relevant
1853 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1854 make their control files and <prgn>dpkg-deb</prgn> to
1855 build them and place them in the parent of the top
1860 Both the <tt>binary-arch</tt> and
1861 <tt>binary-indep</tt> targets <em>must</em> exist.
1862 If one of them has nothing to do (which will always be
1863 the case if the source generates only a single binary
1864 package, whether architecture-dependent or not), it
1865 must still exist and must always succeed.
1869 The <tt>binary</tt> targets must be invoked as
1871 The <prgn>fakeroot</prgn> package often allows one
1872 to build a package correctly even without being
1878 <tag><tt>clean</tt></tag>
1881 This must undo any effects that the <tt>build</tt>
1882 and <tt>binary</tt> targets may have had, except
1883 that it should leave alone any output files created in
1884 the parent directory by a run of a <tt>binary</tt>
1889 If a <tt>build</tt> file is touched at the end of
1890 the <tt>build</tt> target, as suggested above, it
1891 should be removed as the first action that
1892 <tt>clean</tt> performs, so that running
1893 <tt>build</tt> again after an interrupted
1894 <tt>clean</tt> doesn't think that everything is
1899 The <tt>clean</tt> target may need to be
1900 invoked as root if <tt>binary</tt> has been
1901 invoked since the last <tt>clean</tt>, or if
1902 <tt>build</tt> has been invoked as root (since
1903 <tt>build</tt> may create directories, for
1908 <tag><tt>get-orig-source</tt> (optional)</tag>
1911 This target fetches the most recent version of the
1912 original source package from a canonical archive site
1913 (via FTP or WWW, for example), does any necessary
1914 rearrangement to turn it into the original source
1915 tar file format described below, and leaves it in the
1920 This target may be invoked in any directory, and
1921 should take care to clean up any temporary files it
1926 This target is optional, but providing it if
1927 possible is a good idea.
1933 The <tt>build</tt>, <tt>binary</tt> and
1934 <tt>clean</tt> targets must be invoked with the current
1935 directory being the package's top-level directory.
1940 Additional targets may exist in <file>debian/rules</file>,
1941 either as published or undocumented interfaces or for the
1942 package's internal use.
1946 The architectures we build on and build for are determined
1947 by <prgn>make</prgn> variables using the utility
1948 <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
1949 You can determine the
1950 Debian architecture and the GNU style architecture
1951 specification string for the build machine (the machine type
1952 we are building on) as well as for the host machine (the
1953 machine type we are building for). Here is a list of
1954 supported <prgn>make</prgn> variables:
1955 <list compact="compact">
1957 <tt>DEB_*_ARCH</tt> (the Debian architecture)
1960 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
1961 specification string)
1964 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
1965 <tt>DEB_*_GNU_TYPE</tt>)
1968 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
1969 <tt>DEB_*_GNU_TYPE</tt>)
1971 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
1972 the build machine or <tt>HOST</tt> for specification of the
1977 Backward compatibility can be provided in the rules file
1978 by setting the needed variables to suitable default
1979 values; please refer to the documentation of
1980 <prgn>dpkg-architecture</prgn> for details.
1984 It is important to understand that the <tt>DEB_*_ARCH</tt>
1985 string only determines which Debian architecture we are
1986 building on or for. It should not be used to get the CPU
1987 or system information; the GNU style variables should be
1992 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
1993 <sect id="substvars">
1994 <heading>Variable substitutions: <file>debian/substvars</file></heading>
1997 When <prgn>dpkg-gencontrol</prgn>,
1998 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
1999 generate control files they perform variable substitutions
2000 on their output just before writing it. Variable
2001 substitutions have the form <tt>${<var>variable</var>}</tt>.
2002 The optional file <file>debian/substvars</file> contains
2003 variable substitutions to be used; variables can also be set
2004 directly from <file>debian/rules</file> using the <tt>-V</tt>
2005 option to the source packaging commands, and certain
2006 predefined variables are also available.
2010 The <file>debian/substvars</file> file is usually generated and
2011 modified dynamically by <file>debian/rules</file> targets, in
2012 which case it must be removed by the <tt>clean</tt> target.
2016 See <manref name="dpkg-source" section="1"> for full
2017 details about source variable substitutions, including the
2018 format of <file>debian/substvars</file>.</p>
2021 <sect id="debianwatch">
2022 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2025 This is an optional, recommended control file for the
2026 <tt>uscan</tt> utility which defines how to automatically
2027 scan ftp or http sites for newly available updates of the
2028 package. This is used by <url id="
2029 http://dehs.alioth.debian.org/"> and other Debian QA tools
2030 to help with quality control and maintenance of the
2031 distribution as a whole.
2036 <sect id="debianfiles">
2037 <heading>Generated files list: <file>debian/files</file></heading>
2040 This file is not a permanent part of the source tree; it
2041 is used while building packages to record which files are
2042 being generated. <prgn>dpkg-genchanges</prgn> uses it
2043 when it generates a <file>.changes</file> file.
2047 It should not exist in a shipped source package, and so it
2048 (and any backup files or temporary files such as
2049 <file>files.new</file><footnote>
2050 <file>files.new</file> is used as a temporary file by
2051 <prgn>dpkg-gencontrol</prgn> and
2052 <prgn>dpkg-distaddfile</prgn> - they write a new
2053 version of <tt>files</tt> here before renaming it,
2054 to avoid leaving a corrupted copy if an error
2056 </footnote>) should be removed by the
2057 <tt>clean</tt> target. It may also be wise to
2058 ensure a fresh start by emptying or removing it at the
2059 start of the <tt>binary</tt> target.
2063 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2064 package, it adds an entry to <file>debian/files</file> for the
2065 <file>.deb</file> file that will be created when <tt>dpkg-deb
2066 --build</tt> is run for that binary package. So for most
2067 packages all that needs to be done with this file is to
2068 delete it in the <tt>clean</tt> target.
2072 If a package upload includes files besides the source
2073 package and any binary packages whose control files were
2074 made with <prgn>dpkg-gencontrol</prgn> then they should be
2075 placed in the parent of the package's top-level directory
2076 and <prgn>dpkg-distaddfile</prgn> should be called to add
2077 the file to the list in <file>debian/files</file>.</p>
2083 <chapt id="controlfields">
2084 <heading>Control files and their fields</heading>
2087 The package management system manipulates data represented in
2088 a common format, known as <em>control data</em>, stored in
2089 <em>control files</em>.
2090 Control files are used for source packages, binary packages and
2091 the <file>.changes</file> files which control the installation
2092 of uploaded files<footnote>
2093 <prgn>dpkg</prgn>'s internal databases are in a similar
2098 <sect id="controlsyntax">
2099 <heading>Syntax of control files</heading>
2102 A control file consists of one or more paragraphs of
2104 The paragraphs are also sometimes referred to as stanzas.
2106 The paragraphs are separated by blank lines. Some control
2107 files allow only one paragraph; others allow several, in
2108 which case each paragraph usually refers to a different
2109 package. (For example, in source packages, the first
2110 paragraph refers to the source package, and later paragraphs
2111 refer to binary packages generated from the source.)
2115 Each paragraph consists of a series of data fields; each
2116 field consists of the field name, followed by a colon and
2117 then the data/value associated with that field. It ends at
2118 the end of the (logical) line. Horizontal whitespace
2119 (spaces and tabs) may occur immediately before or after the
2120 value and is ignored there; it is conventional to put a
2121 single space after the colon. For example, a field might
2123 <example compact="compact">
2126 the field name is <tt>Package</tt> and the field value
2131 Many fields' values may span several lines; in this case
2132 each continuation line must start with a space or a tab.
2133 Any trailing spaces or tabs at the end of individual
2134 lines of a field value are ignored.
2138 In fields where it is specified that lines may not wrap,
2139 only a single line of data is allowed and whitespace is not
2140 significant in a field body. Whitespace must not appear
2141 inside names (of packages, architectures, files or anything
2142 else) or version numbers, or between the characters of
2143 multi-character version relationships.
2147 Field names are not case-sensitive, but it is usual to
2148 capitalize the field names using mixed case as shown below.
2152 Blank lines, or lines consisting only of spaces and tabs,
2153 are not allowed within field values or between fields - that
2154 would mean a new paragraph.
2159 <sect id="sourcecontrolfiles">
2160 <heading>Source package control files -- <file>debian/control</file></heading>
2163 The <file>debian/control</file> file contains the most vital
2164 (and version-independent) information about the source package
2165 and about the binary packages it creates.
2169 The first paragraph of the control file contains information about
2170 the source package in general. The subsequent sets each describe a
2171 binary package that the source tree builds.
2175 The fields in the general paragraph (the first one, for the source
2178 <list compact="compact">
2179 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2180 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2181 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2182 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2183 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2184 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2185 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2190 The fields in the binary package paragraphs are:
2192 <list compact="compact">
2193 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2194 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2195 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2196 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2197 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2198 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2199 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2204 The syntax and semantics of the fields are described below.
2210 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2211 generate control files for binary packages (see below), by
2212 <prgn>dpkg-genchanges</prgn> to generate the
2213 <tt>.changes</tt> file to accompany the upload, and by
2214 <prgn>dpkg-source</prgn> when it creates the
2215 <file>.dsc</file> source control file as part of a source
2216 archive. Many fields are permitted to span multiple lines in
2217 <file>debian/control</file> but not in any other control
2218 file. These tools are responsible for removing the line
2219 breaks from such fields when using fields from
2220 <file>debian/control</file> to generate other control files.
2224 The fields here may contain variable references - their
2225 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2226 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2227 when they generate output control files.
2228 See <ref id="substvars"> for details.
2233 <sect id="binarycontrolfiles">
2234 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2237 The <file>DEBIAN/control</file> file contains the most vital
2238 (and version-dependent) information about a binary package.
2242 The fields in this file are:
2244 <list compact="compact">
2245 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2246 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2247 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2248 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2249 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2250 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2251 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2252 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2253 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2254 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2255 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2260 <sect id="debiansourcecontrolfiles">
2261 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2264 This file contains a series of fields, identified and
2265 separated just like the fields in the control file of
2266 a binary package. The fields are listed below; their
2267 syntax is described above, in <ref id="pkg-controlfields">.
2269 <list compact="compact">
2270 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2271 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2272 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2273 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2274 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2275 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2276 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2277 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2278 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2279 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2284 The source package control file is generated by
2285 <prgn>dpkg-source</prgn> when it builds the source
2286 archive, from other files in the source package,
2287 described above. When unpacking, it is checked against
2288 the files and directories in the other parts of the
2294 <sect id="debianchangesfiles">
2295 <heading>Debian changes files -- <file>.changes</file></heading>
2298 The .changes files are used by the Debian archive maintenance
2299 software to process updates to packages. They contain one
2300 paragraph which contains information from the
2301 <tt>debian/control</tt> file and other data about the
2302 source package gathered via <tt>debian/changelog</tt>
2303 and <tt>debian/rules</tt>.
2307 The fields in this file are:
2309 <list compact="compact">
2310 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2311 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2312 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2313 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2314 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2315 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2316 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2317 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2318 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2319 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2320 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2321 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2322 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2323 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2328 <sect id="controlfieldslist">
2329 <heading>List of fields</heading>
2331 <sect1 id="f-Source">
2332 <heading><tt>Source</tt></heading>
2335 This field identifies the source package name.
2339 In a main source control information, a <file>.changes</file>
2340 or a <file>.dsc</file> file this may contain only the name
2341 of the source package.
2345 In the control file of a binary package it may be followed
2346 by a version number in parentheses<footnote>
2347 It is customary to leave a space after the package name
2348 if a version number is specified.
2350 This version number may be omitted (and is, by
2351 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2352 the <tt>Version</tt> field of the binary package in
2353 question. The field itself may be omitted from a binary
2354 package control file when the source package has the same
2355 name and version as the binary package.
2359 <sect1 id="f-Maintainer">
2360 <heading><tt>Maintainer</tt></heading>
2363 The package maintainer's name and email address. The name
2364 should come first, then the email address inside angle
2365 brackets <tt><></tt> (in RFC822 format).
2369 If the maintainer's name contains a full stop then the
2370 whole field will not work directly as an email address due
2371 to a misfeature in the syntax specified in RFC822; a
2372 program using this field as an address must check for this
2373 and correct the problem if necessary (for example by
2374 putting the name in round brackets and moving it to the
2375 end, and bringing the email address forward).
2379 <sect1 id="f-Uploaders">
2380 <heading><tt>Uploaders</tt></heading>
2383 List of the names and email addresses of co-maintainers of
2384 the package, if any. If the package has other maintainers
2385 beside the one named in the
2386 <qref id="f-Maintainer">Maintainer field</qref>, their
2387 names and email addresses should be listed here. The
2388 format is the same as that of the Maintainer tag, and
2389 multiple entries should be comma separated. Currently,
2390 this field is restricted to a single line of data. This
2391 is an optional field.
2394 Any parser that interprets the Uploaders field in
2395 <file>debian/control</file> should permit it to span multiple
2397 In the future, the Uploaders field in
2398 <file>debian/control</file> (but not other control files)
2399 will be permitted to span multiple lines and interpreting
2400 a multi-line Uploaders field shall be mandatory.
2401 </footnote>. Line breaks in an Uploaders field that spans
2402 multiple lines are not significant and the semantics of
2403 the field are the same as if the line breaks had not been
2408 <sect1 id="f-Changed-By">
2409 <heading><tt>Changed-By</tt></heading>
2412 The name and email address of the person who changed the
2413 said package. Usually the name of the maintainer.
2414 All the rules for the Maintainer field apply here, too.
2418 <sect1 id="f-Section">
2419 <heading><tt>Section</tt></heading>
2422 This field specifies an application area into which the package
2423 has been classified. See <ref id="subsections">.
2427 When it appears in the <file>debian/control</file> file,
2428 it gives the value for the subfield of the same name in
2429 the <tt>Files</tt> field of the <file>.changes</file> file.
2430 It also gives the default for the same field in the binary
2435 <sect1 id="f-Priority">
2436 <heading><tt>Priority</tt></heading>
2439 This field represents how important that it is that the user
2440 have the package installed. See <ref id="priorities">.
2444 When it appears in the <file>debian/control</file> file,
2445 it gives the value for the subfield of the same name in
2446 the <tt>Files</tt> field of the <file>.changes</file> file.
2447 It also gives the default for the same field in the binary
2452 <sect1 id="f-Package">
2453 <heading><tt>Package</tt></heading>
2456 The name of the binary package.
2460 Package names must consist only of lower case letters
2461 (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus (<tt>+</tt>)
2462 and minus (<tt>-</tt>) signs, and periods (<tt>.</tt>).
2463 They must be at least two characters long and must start
2464 with an alphanumeric character.
2468 <sect1 id="f-Architecture">
2469 <heading><tt>Architecture</tt></heading>
2472 Depending on context and the control file used, the
2473 <tt>Architecture</tt> field can include the following sets of
2476 <item>A unique single word identifying a Debian machine
2477 architecture, see <ref id="arch-spec">.
2478 <item><tt>all</tt>, which indicates an
2479 architecture-independent package.
2480 <item><tt>any</tt>, which indicates a package available
2481 for building on any architecture.
2482 <item><tt>source</tt>, which indicates a source package.
2487 In the main <file>debian/control</file> file in the source
2488 package, or in the source package control file
2489 <file>.dsc</file>, one may specify a list of architectures
2490 separated by spaces, or the special values <tt>any</tt> or
2495 Specifying <tt>any</tt> indicates that the source package
2496 isn't dependent on any particular architecture and should
2497 compile fine on any one. The produced binary package(s)
2498 will be specific to whatever the current build architecture
2500 This is the most often used setting, and is recommended
2501 for new packages that aren't <tt>Architecture: all</tt>.
2506 Specifying a list of architectures indicates that the source
2507 will build an architecture-dependent package, and will only
2508 work correctly on the listed architectures.<footnote>
2509 This is a setting used for a minority of cases where the
2510 program is not portable. Generally, it should not be used
2516 In a <file>.changes</file> file, the <tt>Architecture</tt>
2517 field lists the architecture(s) of the package(s)
2518 currently being uploaded. This will be a list; if the
2519 source for the package is also being uploaded, the special
2520 entry <tt>source</tt> is also present.
2524 See <ref id="debianrules"> for information how to get the
2525 architecture for the build process.
2529 <sect1 id="f-Essential">
2530 <heading><tt>Essential</tt></heading>
2533 This is a boolean field which may occur only in the
2534 control file of a binary package or in a per-package fields
2535 paragraph of a main source control data file.
2539 If set to <tt>yes</tt> then the package management system
2540 will refuse to remove the package (upgrading and replacing
2541 it is still possible). The other possible value is <tt>no</tt>,
2542 which is the same as not having the field at all.
2547 <heading>Package interrelationship fields:
2548 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2549 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Conflicts</tt>,
2550 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2554 These fields describe the package's relationships with
2555 other packages. Their syntax and semantics are described
2556 in <ref id="relationships">.</p>
2559 <sect1 id="f-Standards-Version">
2560 <heading><tt>Standards-Version</tt></heading>
2563 The most recent version of the standards (the policy
2564 manual and associated texts) with which the package
2569 The version number has four components: major and minor
2570 version number and major and minor patch level. When the
2571 standards change in a way that requires every package to
2572 change the major number will be changed. Significant
2573 changes that will require work in many packages will be
2574 signaled by a change to the minor number. The major patch
2575 level will be changed for any change to the meaning of the
2576 standards, however small; the minor patch level will be
2577 changed when only cosmetic, typographical or other edits
2578 are made which neither change the meaning of the document
2579 nor affect the contents of packages.
2583 Thus only the first three components of the policy version
2584 are significant in the <em>Standards-Version</em> control
2585 field, and so either these three components or the all
2586 four components may be specified.<footnote>
2587 In the past, people specified the full version number
2588 in the Standards-Version field, for example "2.3.0.0".
2589 Since minor patch-level changes don't introduce new
2590 policy, it was thought it would be better to relax
2591 policy and only require the first 3 components to be
2592 specified, in this example "2.3.0". All four
2593 components may still be used if someone wishes to do so.
2599 <sect1 id="f-Version">
2600 <heading><tt>Version</tt></heading>
2603 The version number of a package. The format is:
2604 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
2608 The three components here are:
2610 <tag><var>epoch</var></tag>
2613 This is a single (generally small) unsigned integer. It
2614 may be omitted, in which case zero is assumed. If it is
2615 omitted then the <var>upstream_version</var> may not
2620 It is provided to allow mistakes in the version numbers
2621 of older versions of a package, and also a package's
2622 previous version numbering schemes, to be left behind.
2626 <tag><var>upstream_version</var></tag>
2629 This is the main part of the version number. It is
2630 usually the version number of the original ("upstream")
2631 package from which the <file>.deb</file> file has been made,
2632 if this is applicable. Usually this will be in the same
2633 format as that specified by the upstream author(s);
2634 however, it may need to be reformatted to fit into the
2635 package management system's format and comparison
2640 The comparison behavior of the package management system
2641 with respect to the <var>upstream_version</var> is
2642 described below. The <var>upstream_version</var>
2643 portion of the version number is mandatory.
2647 The <var>upstream_version</var> may contain only
2648 alphanumerics<footnote>
2649 Alphanumerics are <tt>A-Za-z0-9</tt> only.
2651 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
2652 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
2653 tilde) and should start with a digit. If there is no
2654 <var>debian_revision</var> then hyphens are not allowed;
2655 if there is no <var>epoch</var> then colons are not
2660 <tag><var>debian_revision</var></tag>
2663 This part of the version number specifies the version of
2664 the Debian package based on the upstream version. It
2665 may contain only alphanumerics and the characters
2666 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
2667 tilde) and is compared in the same way as the
2668 <var>upstream_version</var> is.
2672 It is optional; if it isn't present then the
2673 <var>upstream_version</var> may not contain a hyphen.
2674 This format represents the case where a piece of
2675 software was written specifically to be turned into a
2676 Debian package, and so there is only one "debianisation"
2677 of it and therefore no revision indication is required.
2681 It is conventional to restart the
2682 <var>debian_revision</var> at <tt>1</tt> each time the
2683 <var>upstream_version</var> is increased.
2687 The package management system will break the version
2688 number apart at the last hyphen in the string (if there
2689 is one) to determine the <var>upstream_version</var> and
2690 <var>debian_revision</var>. The absence of a
2691 <var>debian_revision</var> compares earlier than the
2692 presence of one (but note that the
2693 <var>debian_revision</var> is the least significant part
2694 of the version number).
2701 The <var>upstream_version</var> and <var>debian_revision</var>
2702 parts are compared by the package management system using the
2707 The strings are compared from left to right.
2711 First the initial part of each string consisting entirely of
2712 non-digit characters is determined. These two parts (one of
2713 which may be empty) are compared lexically. If a difference
2714 is found it is returned. The lexical comparison is a
2715 comparison of ASCII values modified so that all the letters
2716 sort earlier than all the non-letters and so that a tilde
2717 sorts before anything, even the end of a part. For example,
2718 the following parts are in sorted order from earliest to
2719 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
2720 <tt>a</tt>.<footnote>
2721 One common use of <tt>~</tt> is for upstream pre-releases.
2722 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
2723 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
2728 Then the initial part of the remainder of each string which
2729 consists entirely of digit characters is determined. The
2730 numerical values of these two parts are compared, and any
2731 difference found is returned as the result of the comparison.
2732 For these purposes an empty string (which can only occur at
2733 the end of one or both version strings being compared) counts
2738 These two steps (comparing and removing initial non-digit
2739 strings and initial digit strings) are repeated until a
2740 difference is found or both strings are exhausted.
2744 Note that the purpose of epochs is to allow us to leave behind
2745 mistakes in version numbering, and to cope with situations
2746 where the version numbering scheme changes. It is
2747 <em>not</em> intended to cope with version numbers containing
2748 strings of letters which the package management system cannot
2749 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
2750 silly orderings (the author of this manual has heard of a
2751 package whose versions went <tt>1.1</tt>, <tt>1.2</tt>,
2752 <tt>1.3</tt>, <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>,
2753 <tt>2</tt> and so forth).
2757 <sect1 id="f-Description">
2758 <heading><tt>Description</tt></heading>
2761 In a source or binary control file, the <tt>Description</tt>
2762 field contains a description of the binary package, consisting
2763 of two parts, the synopsis or the short description, and the
2764 long description. The field's format is as follows:
2769 Description: <single line synopsis>
2770 <extended description over several lines>
2775 The lines in the extended description can have these formats:
2781 Those starting with a single space are part of a paragraph.
2782 Successive lines of this form will be word-wrapped when
2783 displayed. The leading space will usually be stripped off.
2787 Those starting with two or more spaces. These will be
2788 displayed verbatim. If the display cannot be panned
2789 horizontally, the displaying program will line wrap them "hard"
2790 (i.e., without taking account of word breaks). If it can they
2791 will be allowed to trail off to the right. None, one or two
2792 initial spaces may be deleted, but the number of spaces
2793 deleted from each line will be the same (so that you can have
2794 indenting work correctly, for example).
2798 Those containing a single space followed by a single full stop
2799 character. These are rendered as blank lines. This is the
2800 <em>only</em> way to get a blank line<footnote>
2801 Completely empty lines will not be rendered as blank lines.
2802 Instead, they will cause the parser to think you're starting
2803 a whole new record in the control file, and will therefore
2804 likely abort with an error.
2809 Those containing a space, a full stop and some more characters.
2810 These are for future expansion. Do not use them.
2816 Do not use tab characters. Their effect is not predictable.
2820 See <ref id="descriptions"> for further information on this.
2824 In a <file>.changes</file> file, the <tt>Description</tt> field
2825 contains a summary of the descriptions for the packages being
2830 The part of the field before the first newline is empty;
2831 thereafter each line has the name of a binary package and
2832 the summary description line from that binary package.
2833 Each line is indented by one space.
2838 <sect1 id="f-Distribution">
2839 <heading><tt>Distribution</tt></heading>
2842 In a <file>.changes</file> file or parsed changelog output
2843 this contains the (space-separated) name(s) of the
2844 distribution(s) where this version of the package should
2845 be installed. Valid distributions are determined by the
2846 archive maintainers.<footnote>
2847 Current distribution names are:
2848 <taglist compact="compact">
2849 <tag><em>stable</em></tag>
2851 This is the current "released" version of Debian
2852 GNU/Linux. Once the distribution is
2853 <em>stable</em> only security fixes and other
2854 major bug fixes are allowed. When changes are
2855 made to this distribution, the release number is
2856 increased (for example: 2.2r1 becomes 2.2r2 then
2860 <tag><em>unstable</em></tag>
2862 This distribution value refers to the
2863 <em>developmental</em> part of the Debian
2864 distribution tree. New packages, new upstream
2865 versions of packages and bug fixes go into the
2866 <em>unstable</em> directory tree. Download from
2867 this distribution at your own risk.
2870 <tag><em>testing</em></tag>
2872 This distribution value refers to the
2873 <em>testing</em> part of the Debian distribution
2874 tree. It receives its packages from the
2875 unstable distribution after a short time lag to
2876 ensure that there are no major issues with the
2877 unstable packages. It is less prone to breakage
2878 than unstable, but still risky. It is not
2879 possible to upload packages directly to
2883 <tag><em>frozen</em></tag>
2885 From time to time, the <em>testing</em>
2886 distribution enters a state of "code-freeze" in
2887 anticipation of release as a <em>stable</em>
2888 version. During this period of testing only
2889 fixes for existing or newly-discovered bugs will
2890 be allowed. The exact details of this stage are
2891 determined by the Release Manager.
2894 <tag><em>experimental</em></tag>
2896 The packages with this distribution value are
2897 deemed by their maintainers to be high
2898 risk. Oftentimes they represent early beta or
2899 developmental packages from various sources that
2900 the maintainers want people to try, but are not
2901 ready to be a part of the other parts of the
2902 Debian distribution tree. Download at your own
2908 You should list <em>all</em> distributions that the
2909 package should be installed into.
2913 More information is available in the Debian Developer's
2914 Reference, section "The Debian archive".
2921 <heading><tt>Date</tt></heading>
2924 This field includes the date the package was built or last edited.
2928 The value of this field is usually extracted from the
2929 <file>debian/changelog</file> file - see
2930 <ref id="dpkgchangelog">).
2934 <sect1 id="f-Format">
2935 <heading><tt>Format</tt></heading>
2938 This field specifies a format revision for the file.
2939 The most current format described in the Policy Manual
2940 is version <strong>1.5</strong>. The syntax of the
2941 format value is the same as that of a package version
2942 number except that no epoch or Debian revision is allowed
2943 - see <ref id="f-Version">.
2947 <sect1 id="f-Urgency">
2948 <heading><tt>Urgency</tt></heading>
2951 This is a description of how important it is to upgrade to
2952 this version from previous ones. It consists of a single
2953 keyword usually taking one of the values <tt>low</tt>,
2954 <tt>medium</tt> or <tt>high</tt> (not case-sensitive)
2955 followed by an optional commentary (separated by a space)
2956 which is usually in parentheses. For example:
2959 Urgency: low (HIGH for users of diversions)
2965 The value of this field is usually extracted from the
2966 <file>debian/changelog</file> file - see
2967 <ref id="dpkgchangelog">.
2971 <sect1 id="f-Changes">
2972 <heading><tt>Changes</tt></heading>
2975 This field contains the human-readable changes data, describing
2976 the differences between the last version and the current one.
2980 There should be nothing in this field before the first
2981 newline; all the subsequent lines must be indented by at
2982 least one space; blank lines must be represented by a line
2983 consisting only of a space and a full stop.
2987 The value of this field is usually extracted from the
2988 <file>debian/changelog</file> file - see
2989 <ref id="dpkgchangelog">).
2993 Each version's change information should be preceded by a
2994 "title" line giving at least the version, distribution(s)
2995 and urgency, in a human-readable way.
2999 If data from several versions is being returned the entry
3000 for the most recent version should be returned first, and
3001 entries should be separated by the representation of a
3002 blank line (the "title" line may also be followed by the
3003 representation of blank line).
3007 <sect1 id="f-Binary">
3008 <heading><tt>Binary</tt></heading>
3011 This field is a list of binary packages.
3015 When it appears in the <file>.dsc</file> file it is the list
3016 of binary packages which a source package can produce. It
3017 does not necessarily produce all of these binary packages
3018 for every architecture. The source control file doesn't
3019 contain details of which architectures are appropriate for
3020 which of the binary packages.
3024 When it appears in a <file>.changes</file> file it lists the
3025 names of the binary packages actually being uploaded.
3029 The syntax is a list of binary packages separated by
3031 A space after each comma is conventional.
3032 </footnote>. Currently the packages must be separated using
3033 only spaces in the <file>.changes</file> file.
3037 <sect1 id="f-Installed-Size">
3038 <heading><tt>Installed-Size</tt></heading>
3041 This field appears in the control files of binary
3042 packages, and in the <file>Packages</file> files. It gives
3043 the total amount of disk space required to install the
3048 The disk space is represented in kilobytes as a simple
3053 <sect1 id="f-Files">
3054 <heading><tt>Files</tt></heading>
3057 This field contains a list of files with information about
3058 each one. The exact information and syntax varies with
3059 the context. In all cases the part of the field
3060 contents on the same line as the field name is empty. The
3061 remainder of the field is one line per file, each line
3062 being indented by one space and containing a number of
3063 sub-fields separated by spaces.
3067 In the <file>.dsc</file> file, each line contains the MD5
3068 checksum, size and filename of the tar file and (if applicable)
3069 diff file which make up the remainder of the source
3071 That is, the parts which are not the <tt>.dsc</tt>.
3073 The exact forms of the filenames are described
3074 in <ref id="pkg-sourcearchives">.
3078 In the <file>.changes</file> file this contains one line per
3079 file being uploaded. Each line contains the MD5 checksum,
3080 size, section and priority and the filename.
3081 The <qref id="f-Section">section</qref>
3082 and <qref id="f-Priority">priority</qref>
3083 are the values of the corresponding fields in
3084 the main source control file. If no section or priority is
3085 specified then <tt>-</tt> should be used, though section
3086 and priority values must be specified for new packages to
3087 be installed properly.
3091 The special value <tt>byhand</tt> for the section in a
3092 <tt>.changes</tt> file indicates that the file in question
3093 is not an ordinary package file and must by installed by
3094 hand by the distribution maintainers. If the section is
3095 <tt>byhand</tt> the priority should be <tt>-</tt>.
3099 If a new Debian revision of a package is being shipped and
3100 no new original source archive is being distributed the
3101 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3102 entry for the original source archive
3103 <file><var>package</var>-<var>upstream-version</var>.orig.tar.gz</file>,
3104 but the <file>.changes</file> file should leave it out. In
3105 this case the original source archive on the distribution
3106 site must match exactly, byte-for-byte, the original
3107 source archive which was used to generate the
3108 <file>.dsc</file> file and diff which are being uploaded.</p>
3111 <sect1 id="f-Closes">
3112 <heading><tt>Closes</tt></heading>
3115 A space-separated list of bug report numbers that the upload
3116 governed by the .changes file closes.
3123 <heading>User-defined fields</heading>
3126 Additional user-defined fields may be added to the
3127 source package control file. Such fields will be
3128 ignored, and not copied to (for example) binary or
3129 source package control files or upload control files.
3133 If you wish to add additional unsupported fields to
3134 these output files you should use the mechanism
3139 Fields in the main source control information file with
3140 names starting <tt>X</tt>, followed by one or more of
3141 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3142 be copied to the output files. Only the part of the
3143 field name after the hyphen will be used in the output
3144 file. Where the letter <tt>B</tt> is used the field
3145 will appear in binary package control files, where the
3146 letter <tt>S</tt> is used in source package control
3147 files and where <tt>C</tt> is used in upload control
3148 (<tt>.changes</tt>) files.
3152 For example, if the main source information control file
3155 XBS-Comment: I stand between the candle and the star.
3157 then the binary and source package control files will contain the
3160 Comment: I stand between the candle and the star.
3169 <chapt id="maintainerscripts">
3170 <heading>Package maintainer scripts and installation procedure</heading>
3173 <heading>Introduction to package maintainer scripts</heading>
3176 It is possible to supply scripts as part of a package which
3177 the package management system will run for you when your
3178 package is installed, upgraded or removed.
3182 These scripts are the files <prgn>preinst</prgn>,
3183 <prgn>postinst</prgn>, <prgn>prerm</prgn> and
3184 <prgn>postrm</prgn> in the control area of the package.
3185 They must be proper executable files; if they are scripts
3186 (which is recommended), they must start with the usual
3187 <tt>#!</tt> convention. They should be readable and
3188 executable by anyone, and must not be world-writable.
3192 The package management system looks at the exit status from
3193 these scripts. It is important that they exit with a
3194 non-zero status if there is an error, so that the package
3195 management system can stop its processing. For shell
3196 scripts this means that you <em>almost always</em> need to
3197 use <tt>set -e</tt> (this is usually true when writing shell
3198 scripts, in fact). It is also important, of course, that
3199 they don't exit with a non-zero status if everything went
3204 Additionally, packages interacting with users using
3205 <tt>debconf</tt> in the <prgn>postinst</prgn> script should
3206 install a <prgn>config</prgn> script in the control area,
3207 see <ref id="maintscriptprompt"> for details.
3211 When a package is upgraded a combination of the scripts from
3212 the old and new packages is called during the upgrade
3213 procedure. If your scripts are going to be at all
3214 complicated you need to be aware of this, and may need to
3215 check the arguments to your scripts.
3219 Broadly speaking the <prgn>preinst</prgn> is called before
3220 (a particular version of) a package is installed, and the
3221 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3222 before (a version of) a package is removed and the
3223 <prgn>postrm</prgn> afterwards.
3227 Programs called from maintainer scripts should not normally
3228 have a path prepended to them. Before installation is
3229 started, the package management system checks to see if the
3230 programs <prgn>ldconfig</prgn>,
3231 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3232 and <prgn>update-rc.d</prgn> can be found via the
3233 <tt>PATH</tt> environment variable. Those programs, and any
3234 other program that one would expect to be in the
3235 <tt>PATH</tt>, should thus be invoked without an absolute
3236 pathname. Maintainer scripts should also not reset the
3237 <tt>PATH</tt>, though they might choose to modify it by
3238 prepending or appending package-specific directories. These
3239 considerations really apply to all shell scripts.</p>
3242 <sect id="idempotency">
3243 <heading>Maintainer scripts Idempotency</heading>
3246 It is necessary for the error recovery procedures that the
3247 scripts be idempotent. This means that if it is run
3248 successfully, and then it is called again, it doesn't bomb
3249 out or cause any harm, but just ensures that everything is
3250 the way it ought to be. If the first call failed, or
3251 aborted half way through for some reason, the second call
3252 should merely do the things that were left undone the first
3253 time, if any, and exit with a success status if everything
3255 This is so that if an error occurs, the user interrupts
3256 <prgn>dpkg</prgn> or some other unforeseen circumstance
3257 happens you don't leave the user with a badly-broken
3258 package when <prgn>dpkg</prgn> attempts to repeat the
3264 <sect id="controllingterminal">
3265 <heading>Controlling terminal for maintainer scripts</heading>
3268 The maintainer scripts are guaranteed to run with a
3269 controlling terminal and can interact with the user.
3270 Because these scripts may be executed with standard output
3271 redirected into a pipe for logging purposes, Perl scripts
3272 should set unbuffered output by setting <tt>$|=1</tt> so
3273 that the output is printed immediately rather than being
3277 <sect id="exitstatus">
3278 <heading>Exit status</heading>
3281 Each script must return a zero exit status for
3282 success, or a nonzero one for failure, since the package
3283 management system looks for the exit status of these scripts
3284 and determines what action to take next based on that datum.
3288 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3293 <list compact="compact">
3295 <var>new-preinst</var> <tt>install</tt>
3298 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3301 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3304 <var>old-preinst</var> <tt>abort-upgrade</tt>
3305 <var>new-version</var>
3310 <list compact="compact">
3312 <var>postinst</var> <tt>configure</tt>
3313 <var>most-recently-configured-version</var>
3316 <var>old-postinst</var> <tt>abort-upgrade</tt>
3317 <var>new-version</var>
3320 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3321 <tt>in-favour</tt> <var>package</var>
3322 <var>new-version</var>
3325 <var>postinst</var> <tt>abort-remove</tt>
3328 <var>deconfigured's-postinst</var>
3329 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3330 <var>failed-install-package</var> <var>version</var>
3331 <tt>removing</tt> <var>conflicting-package</var>
3337 <list compact="compact">
3339 <var>prerm</var> <tt>remove</tt>
3342 <var>old-prerm</var> <tt>upgrade</tt>
3343 <var>new-version</var>
3346 <var>new-prerm</var> <tt>failed-upgrade</tt>
3347 <var>old-version</var>
3350 <var>conflictor's-prerm</var> <tt>remove</tt>
3351 <tt>in-favour</tt> <var>package</var>
3352 <var>new-version</var>
3355 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3356 <tt>in-favour</tt> <var>package-being-installed</var>
3357 <var>version</var> <tt>removing</tt>
3358 <var>conflicting-package</var>
3364 <list compact="compact">
3366 <var>postrm</var> <tt>remove</tt>
3369 <var>postrm</var> <tt>purge</tt>
3372 <var>old-postrm</var> <tt>upgrade</tt>
3373 <var>new-version</var>
3376 <var>new-postrm</var> <tt>failed-upgrade</tt>
3377 <var>old-version</var>
3380 <var>new-postrm</var> <tt>abort-install</tt>
3383 <var>new-postrm</var> <tt>abort-install</tt>
3384 <var>old-version</var>
3387 <var>new-postrm</var> <tt>abort-upgrade</tt>
3388 <var>old-version</var>
3391 <var>disappearer's-postrm</var> <tt>disappear</tt>
3392 <var>overwriter</var>
3393 <var>overwriter-version</var>
3399 <sect id="unpackphase">
3400 <heading>Details of unpack phase of installation or upgrade</heading>
3403 The procedure on installation/upgrade/overwrite/disappear
3404 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3405 stage of <tt>dpkg --install</tt>) is as follows. In each
3406 case, if a major error occurs (unless listed below) the
3407 actions are, in general, run backwards - this means that the
3408 maintainer scripts are run with different arguments in
3409 reverse order. These are the "error unwind" calls listed
3416 If a version of the package is already installed, call
3417 <example compact="compact">
3418 <var>old-prerm</var> upgrade <var>new-version</var>
3422 If the script runs but exits with a non-zero
3423 exit status, <prgn>dpkg</prgn> will attempt:
3424 <example compact="compact">
3425 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3427 If this works, the upgrade continues. If this
3428 does not work, the error unwind:
3429 <example compact="compact">
3430 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3432 If this works, then the old-version is
3433 "Installed", if not, the old version is in a
3434 "Failed-Config" state.
3440 If a "conflicting" package is being removed at the same time:
3443 If any packages depended on that conflicting
3444 package and <tt>--auto-deconfigure</tt> is
3445 specified, call, for each such package:
3446 <example compact="compact">
3447 <var>deconfigured's-prerm</var> deconfigure \
3448 in-favour <var>package-being-installed</var> <var>version</var> \
3449 removing <var>conflicting-package</var> <var>version</var>
3452 <example compact="compact">
3453 <var>deconfigured's-postinst</var> abort-deconfigure \
3454 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3455 removing <var>conflicting-package</var> <var>version</var>
3457 The deconfigured packages are marked as
3458 requiring configuration, so that if
3459 <tt>--install</tt> is used they will be
3460 configured again if possible.
3463 To prepare for removal of the conflicting package, call:
3464 <example compact="compact">
3465 <var>conflictor's-prerm</var> remove \
3466 in-favour <var>package</var> <var>new-version</var>
3469 <example compact="compact">
3470 <var>conflictor's-postinst</var> abort-remove \
3471 in-favour <var>package</var> <var>new-version</var>
3480 If the package is being upgraded, call:
3481 <example compact="compact">
3482 <var>new-preinst</var> upgrade <var>old-version</var>
3484 If this fails, we call:
3486 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3493 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3495 is called. If this works, then the old version
3496 is in an "Installed" state, or else it is left
3497 in an "Unpacked" state.
3502 If it fails, then the old version is left
3503 in an "Half-Installed" state.
3510 Otherwise, if the package had some configuration
3511 files from a previous version installed (i.e., it
3512 is in the "configuration files only" state):
3513 <example compact="compact">
3514 <var>new-preinst</var> install <var>old-version</var>
3518 <var>new-postrm</var> abort-install <var>old-version</var>
3520 If this fails, the package is left in a
3521 "Half-Installed" state, which requires a
3522 reinstall. If it works, the packages is left in
3523 a "Config Files" state.
3526 Otherwise (i.e., the package was completely purged):
3527 <example compact="compact">
3528 <var>new-preinst</var> install
3531 <example compact="compact">
3532 <var>new-postrm</var> abort-install
3534 If the error-unwind fails, the package is in a
3535 "Half Installed" phase, and requires a
3536 reinstall. If the error unwind works, the
3537 package is in a not installed state.
3544 The new package's files are unpacked, overwriting any
3545 that may be on the system already, for example any
3546 from the old version of the same package or from
3547 another package. Backups of the old files are kept
3548 temporarily, and if anything goes wrong the package
3549 management system will attempt to put them back as
3550 part of the error unwind.
3554 It is an error for a package to contain files which
3555 are on the system in another package, unless
3556 <tt>Replaces</tt> is used (see <ref id="replaces">).
3558 The following paragraph is not currently the case:
3559 Currently the <tt>- - force-overwrite</tt> flag is
3560 enabled, downgrading it to a warning, but this may not
3566 It is a more serious error for a package to contain a
3567 plain file or other kind of non-directory where another
3568 package has a directory (again, unless
3569 <tt>Replaces</tt> is used). This error can be
3570 overridden if desired using
3571 <tt>--force-overwrite-dir</tt>, but this is not
3576 Packages which overwrite each other's files produce
3577 behavior which, though deterministic, is hard for the
3578 system administrator to understand. It can easily
3579 lead to "missing" programs if, for example, a package
3580 is installed which overwrites a file from another
3581 package, and is then removed again.<footnote>
3582 Part of the problem is due to what is arguably a
3583 bug in <prgn>dpkg</prgn>.
3588 A directory will never be replaced by a symbolic link
3589 to a directory or vice versa; instead, the existing
3590 state (symlink or not) will be left alone and
3591 <prgn>dpkg</prgn> will follow the symlink if there is
3600 If the package is being upgraded, call
3601 <example compact="compact">
3602 <var>old-postrm</var> upgrade <var>new-version</var>
3606 If this fails, <prgn>dpkg</prgn> will attempt:
3607 <example compact="compact">
3608 <var>new-postrm</var> failed-upgrade <var>old-version</var>
3610 If this works, installation continues. If not,
3612 <example compact="compact">
3613 <var>old-preinst</var> abort-upgrade <var>new-version</var>
3615 If this fails, the old version is left in an
3616 "Half Installed" state. If it works, dpkg now
3618 <example compact="compact">
3619 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3621 If this fails, the old version is left in an
3622 "Half Installed" state. If it works, dpkg now
3624 <example compact="compact">
3625 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3627 If this fails, the old version is in an
3634 This is the point of no return - if
3635 <prgn>dpkg</prgn> gets this far, it won't back off
3636 past this point if an error occurs. This will
3637 leave the package in a fairly bad state, which
3638 will require a successful re-installation to clear
3639 up, but it's when <prgn>dpkg</prgn> starts doing
3640 things that are irreversible.
3645 Any files which were in the old version of the package
3646 but not in the new are removed.
3650 The new file list replaces the old.
3654 The new maintainer scripts replace the old.
3658 Any packages all of whose files have been overwritten
3659 during the installation, and which aren't required for
3660 dependencies, are considered to have been removed.
3661 For each such package
3664 <prgn>dpkg</prgn> calls:
3665 <example compact="compact">
3666 <var>disappearer's-postrm</var> disappear \
3667 <var>overwriter</var> <var>overwriter-version</var>
3671 The package's maintainer scripts are removed.
3674 It is noted in the status database as being in a
3675 sane state, namely not installed (any conffiles
3676 it may have are ignored, rather than being
3677 removed by <prgn>dpkg</prgn>). Note that
3678 disappearing packages do not have their prerm
3679 called, because <prgn>dpkg</prgn> doesn't know
3680 in advance that the package is going to
3687 Any files in the package we're unpacking that are also
3688 listed in the file lists of other packages are removed
3689 from those lists. (This will lobotomize the file list
3690 of the "conflicting" package if there is one.)
3694 The backup files made during installation, above, are
3700 The new package's status is now sane, and recorded as
3705 Here is another point of no return - if the
3706 conflicting package's removal fails we do not unwind
3707 the rest of the installation; the conflicting package
3708 is left in a half-removed limbo.
3713 If there was a conflicting package we go and do the
3714 removal actions (described below), starting with the
3715 removal of the conflicting package's files (any that
3716 are also in the package being installed have already
3717 been removed from the conflicting package's file list,
3718 and so do not get removed now).
3724 <sect id="configdetails"><heading>Details of configuration</heading>
3727 When we configure a package (this happens with <tt>dpkg
3728 --install</tt> and <tt>dpkg --configure</tt>), we first
3729 update any <tt>conffile</tt>s and then call:
3730 <example compact="compact">
3731 <var>postinst</var> configure <var>most-recently-configured-version</var>
3736 No attempt is made to unwind after errors during
3737 configuration. If the configuration fails, the package is in
3738 a "Failed Config" state, and an error message is generated.
3742 If there is no most recently configured version
3743 <prgn>dpkg</prgn> will pass a null argument.
3746 Historical note: Truly ancient (pre-1997) versions of
3747 <prgn>dpkg</prgn> passed <tt><unknown></tt>
3748 (including the angle brackets) in this case. Even older
3749 ones did not pass a second argument at all, under any
3750 circumstance. Note that upgrades using such an old dpkg
3751 version are unlikely to work for other reasons, even if
3752 this old argument behavior is handled by your postinst script.
3758 <sect id="removedetails"><heading>Details of removal and/or
3759 configuration purging</heading>
3765 <example compact="compact">
3766 <var>prerm</var> remove
3770 If prerm fails during replacement due to conflict
3772 <var>conflictor's-postinst</var> abort-remove \
3773 in-favour <var>package</var> <var>new-version</var>
3777 <var>postinst</var> abort-remove
3781 If this fails, the package is in a "Failed-Config"
3782 state, or else it remains "Installed".
3786 The package's files are removed (except <tt>conffile</tt>s).
3789 <example compact="compact">
3790 <var>postrm</var> remove
3794 If it fails, there's no error unwind, and the package is in
3795 an "Half-Installed" state.
3800 All the maintainer scripts except the <prgn>postrm</prgn>
3805 If we aren't purging the package we stop here. Note
3806 that packages which have no <prgn>postrm</prgn> and no
3807 <tt>conffile</tt>s are automatically purged when
3808 removed, as there is no difference except for the
3809 <prgn>dpkg</prgn> status.
3813 The <tt>conffile</tt>s and any backup files
3814 (<tt>~</tt>-files, <tt>#*#</tt> files,
3815 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
3820 <example compact="compact">
3821 <var>postrm</var> purge
3825 If this fails, the package remains in a "Config-Files"
3830 The package's file list is removed.
3839 <chapt id="relationships">
3840 <heading>Declaring relationships between packages</heading>
3842 <sect id="depsyntax">
3843 <heading>Syntax of relationship fields</heading>
3846 These fields all have a uniform syntax. They are a list of
3847 package names separated by commas.
3851 In the <tt>Depends</tt>, <tt>Recommends</tt>,
3852 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
3853 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
3854 control file fields of the package, which declare
3855 dependencies on other packages, the package names listed may
3856 also include lists of alternative package names, separated
3857 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
3858 if any one of the alternative packages is installed, that
3859 part of the dependency is considered to be satisfied.
3863 All of the fields except for <tt>Provides</tt> may restrict
3864 their applicability to particular versions of each named
3865 package. This is done in parentheses after each individual
3866 package name; the parentheses should contain a relation from
3867 the list below followed by a version number, in the format
3868 described in <ref id="f-Version">.
3872 The relations allowed are <tt><<</tt>, <tt><=</tt>,
3873 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
3874 strictly earlier, earlier or equal, exactly equal, later or
3875 equal and strictly later, respectively. The deprecated
3876 forms <tt><</tt> and <tt>></tt> were used to mean
3877 earlier/later or equal, rather than strictly earlier/later,
3878 so they should not appear in new packages (though
3879 <prgn>dpkg</prgn> still supports them).
3883 Whitespace may appear at any point in the version
3884 specification subject to the rules in <ref
3885 id="controlsyntax">, and must appear where it's necessary to
3886 disambiguate; it is not otherwise significant. For
3887 consistency and in case of future changes to
3888 <prgn>dpkg</prgn> it is recommended that a single space be
3889 used after a version relationship and before a version
3890 number; it is also conventional to put a single space after
3891 each comma, on either side of each vertical bar, and before
3892 each open parenthesis.
3896 For example, a list of dependencies might appear as:
3897 <example compact="compact">
3900 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
3905 All fields that specify build-time relationships
3906 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
3907 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>)
3908 may be restricted to a certain set of architectures. This
3909 is indicated in brackets after each individual package name and
3910 the optional version specification. The brackets enclose a
3911 list of Debian architecture names separated by whitespace.
3912 Exclamation marks may be prepended to each of the names.
3913 (It is not permitted for some names to be prepended with
3914 exclamation marks while others aren't.) If the current Debian
3915 host architecture is not in this list and there are no
3916 exclamation marks in the list, or it is in the list with a
3917 prepended exclamation mark, the package name and the
3918 associated version specification are ignored completely for
3919 the purposes of defining the relationships.
3924 <example compact="compact">
3926 Build-Depends-Indep: texinfo
3927 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
3928 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
3933 Note that the binary package relationship fields such as
3934 <tt>Depends</tt> appear in one of the binary package
3935 sections of the control file, whereas the build-time
3936 relationships such as <tt>Build-Depends</tt> appear in the
3937 source package section of the control file (which is the
3942 <sect id="binarydeps">
3943 <heading>Binary Dependencies - <tt>Depends</tt>,
3944 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
3945 <tt>Pre-Depends</tt>
3949 Packages can declare in their control file that they have
3950 certain relationships to other packages - for example, that
3951 they may not be installed at the same time as certain other
3952 packages, and/or that they depend on the presence of others.
3956 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
3957 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt> and
3958 <tt>Conflicts</tt> control file fields.
3962 These six fields are used to declare a dependency
3963 relationship by one package on another. Except for
3964 <tt>Enhances</tt>, they appear in the depending (binary)
3965 package's control file. (<tt>Enhances</tt> appears in the
3966 recommending package's control file.)
3970 A <tt>Depends</tt> field takes effect <em>only</em> when a
3971 package is to be configured. It does not prevent a package
3972 being on the system in an unconfigured state while its
3973 dependencies are unsatisfied, and it is possible to replace
3974 a package whose dependencies are satisfied and which is
3975 properly installed with a different version whose
3976 dependencies are not and cannot be satisfied; when this is
3977 done the depending package will be left unconfigured (since
3978 attempts to configure it will give errors) and will not
3979 function properly. If it is necessary, a
3980 <tt>Pre-Depends</tt> field can be used, which has a partial
3981 effect even when a package is being unpacked, as explained
3982 in detail below. (The other three dependency fields,
3983 <tt>Recommends</tt>, <tt>Suggests</tt> and
3984 <tt>Enhances</tt>, are only used by the various front-ends
3985 to <prgn>dpkg</prgn> such as <prgn>dselect</prgn>.)
3989 For this reason packages in an installation run are usually
3990 all unpacked first and all configured later; this gives
3991 later versions of packages with dependencies on later
3992 versions of other packages the opportunity to have their
3993 dependencies satisfied.
3997 In case of circular dependencies, since installation or
3998 removal order honoring the dependency order can't be
3999 established, dependency loops are broken at some point
4000 (based on rules below), and some packages may not be able to
4001 rely on their dependencies being present when being
4002 installed or removed, depending on which side of the break
4003 of the circular dependcy loop they happen to be on. If one
4004 of the packages in the loop has no postinst script, then the
4005 cycle will be broken at that package, so as to ensure that
4006 all postinst scripts run with the dependencies properly
4007 configured if this is possible. Otherwise the breaking point
4012 The <tt>Depends</tt> field thus allows package maintainers
4013 to impose an order in which packages should be configured.
4017 The meaning of the five dependency fields is as follows:
4019 <tag><tt>Depends</tt></tag>
4022 This declares an absolute dependency. A package will
4023 not be configured unless all of the packages listed in
4024 its <tt>Depends</tt> field have been correctly
4029 The <tt>Depends</tt> field should be used if the
4030 depended-on package is required for the depending
4031 package to provide a significant amount of
4036 The <tt>Depends</tt> field should also be used if the
4037 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4038 <prgn>postrm</prgn> scripts require the package to be
4039 present in order to run. Note, however, that the
4040 <prgn>postrm</prgn> cannot rely on any non-essential
4041 packages to be present during the <tt>purge</tt>
4045 <tag><tt>Recommends</tt></tag>
4048 This declares a strong, but not absolute, dependency.
4052 The <tt>Recommends</tt> field should list packages
4053 that would be found together with this one in all but
4054 unusual installations.
4058 <tag><tt>Suggests</tt></tag>
4060 This is used to declare that one package may be more
4061 useful with one or more others. Using this field
4062 tells the packaging system and the user that the
4063 listed packages are related to this one and can
4064 perhaps enhance its usefulness, but that installing
4065 this one without them is perfectly reasonable.
4068 <tag><tt>Enhances</tt></tag>
4070 This field is similar to Suggests but works in the
4071 opposite direction. It is used to declare that a
4072 package can enhance the functionality of another
4076 <tag><tt>Pre-Depends</tt></tag>
4079 This field is like <tt>Depends</tt>, except that it
4080 also forces <prgn>dpkg</prgn> to complete installation
4081 of the packages named before even starting the
4082 installation of the package which declares the
4083 pre-dependency, as follows:
4087 When a package declaring a pre-dependency is about to
4088 be <em>unpacked</em> the pre-dependency can be
4089 satisfied if the depended-on package is either fully
4090 configured, <em>or even if</em> the depended-on
4091 package(s) are only unpacked or half-configured,
4092 provided that they have been configured correctly at
4093 some point in the past (and not removed or partially
4094 removed since). In this case, both the
4095 previously-configured and currently unpacked or
4096 half-configured versions must satisfy any version
4097 clause in the <tt>Pre-Depends</tt> field.
4101 When the package declaring a pre-dependency is about
4102 to be <em>configured</em>, the pre-dependency will be
4103 treated as a normal <tt>Depends</tt>, that is, it will
4104 be considered satisfied only if the depended-on
4105 package has been correctly configured.
4109 <tt>Pre-Depends</tt> should be used sparingly,
4110 preferably only by packages whose premature upgrade or
4111 installation would hamper the ability of the system to
4112 continue with any upgrade that might be in progress.
4116 <tt>Pre-Depends</tt> are also required if the
4117 <prgn>preinst</prgn> script depends on the named
4118 package. It is best to avoid this situation if
4126 When selecting which level of dependency to use you should
4127 consider how important the depended-on package is to the
4128 functionality of the one declaring the dependency. Some
4129 packages are composed of components of varying degrees of
4130 importance. Such a package should list using
4131 <tt>Depends</tt> the package(s) which are required by the
4132 more important components. The other components'
4133 requirements may be mentioned as Suggestions or
4134 Recommendations, as appropriate to the components' relative
4139 <sect id="conflicts">
4140 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4143 When one binary package declares a conflict with another
4144 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4145 refuse to allow them to be installed on the system at the
4150 If one package is to be installed, the other must be removed
4151 first - if the package being installed is marked as
4152 replacing (see <ref id="replaces">) the one on the system,
4153 or the one on the system is marked as deselected, or both
4154 packages are marked <tt>Essential</tt>, then
4155 <prgn>dpkg</prgn> will automatically remove the package
4156 which is causing the conflict, otherwise it will halt the
4157 installation of the new package with an error. This
4158 mechanism is specifically designed to produce an error when
4159 the installed package is <tt>Essential</tt>, but the new
4164 A package will not cause a conflict merely because its
4165 configuration files are still installed; it must be at least
4170 A special exception is made for packages which declare a
4171 conflict with their own package name, or with a virtual
4172 package which they provide (see below): this does not
4173 prevent their installation, and allows a package to conflict
4174 with others providing a replacement for it. You use this
4175 feature when you want the package in question to be the only
4176 package providing some feature.
4180 A <tt>Conflicts</tt> entry should almost never have an
4181 "earlier than" version clause. This would prevent
4182 <prgn>dpkg</prgn> from upgrading or installing the package
4183 which declared such a conflict until the upgrade or removal
4184 of the conflicted-with package had been completed.
4188 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4192 As well as the names of actual ("concrete") packages, the
4193 package relationship fields <tt>Depends</tt>,
4194 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4195 <tt>Pre-Depends</tt>, <tt>Conflicts</tt>,
4196 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4197 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4198 may mention "virtual packages".
4202 A <em>virtual package</em> is one which appears in the
4203 <tt>Provides</tt> control file field of another package.
4204 The effect is as if the package(s) which provide a
4205 particular virtual package name had been listed by name
4206 everywhere the virtual package name appears. (See also <ref
4211 If there are both concrete and virtual packages of the same
4212 name, then the dependency may be satisfied (or the conflict
4213 caused) by either the concrete package with the name in
4214 question or any other concrete package which provides the
4215 virtual package with the name in question. This is so that,
4216 for example, supposing we have
4217 <example compact="compact">
4220 </example> and someone else releases an enhanced version of
4221 the <tt>bar</tt> package they can say:
4222 <example compact="compact">
4226 and the <tt>bar-plus</tt> package will now also satisfy the
4227 dependency for the <tt>foo</tt> package.
4231 If a dependency or a conflict has a version number attached
4232 then only real packages will be considered to see whether
4233 the relationship is satisfied (or the prohibition violated,
4234 for a conflict) - it is assumed that a real package which
4235 provides the virtual package is not of the "right" version.
4236 So, a <tt>Provides</tt> field may not contain version
4237 numbers, and the version number of the concrete package
4238 which provides a particular virtual package will not be
4239 looked at when considering a dependency on or conflict with
4240 the virtual package name.
4244 It is likely that the ability will be added in a future
4245 release of <prgn>dpkg</prgn> to specify a version number for
4246 each virtual package it provides. This feature is not yet
4247 present, however, and is expected to be used only
4252 If you want to specify which of a set of real packages
4253 should be the default to satisfy a particular dependency on
4254 a virtual package, you should list the real package as an
4255 alternative before the virtual one.
4260 <sect id="replaces"><heading>Overwriting files and replacing
4261 packages - <tt>Replaces</tt></heading>
4264 Packages can declare in their control file that they should
4265 overwrite files in certain other packages, or completely
4266 replace other packages. The <tt>Replaces</tt> control file
4267 field has these two distinct purposes.
4270 <sect1><heading>Overwriting files in other packages</heading>
4273 Firstly, as mentioned before, it is usually an error for a
4274 package to contain files which are on the system in
4279 However, if the overwriting package declares that it
4280 <tt>Replaces</tt> the one containing the file being
4281 overwritten, then <prgn>dpkg</prgn> will replace the file
4282 from the old package with that from the new. The file
4283 will no longer be listed as "owned" by the old package.
4287 If a package is completely replaced in this way, so that
4288 <prgn>dpkg</prgn> does not know of any files it still
4289 contains, it is considered to have "disappeared". It will
4290 be marked as not wanted on the system (selected for
4291 removal) and not installed. Any <tt>conffile</tt>s
4292 details noted for the package will be ignored, as they
4293 will have been taken over by the overwriting package. The
4294 package's <prgn>postrm</prgn> script will be run with a
4295 special argument to allow the package to do any final
4296 cleanup required. See <ref id="mscriptsinstact">.
4299 Replaces is a one way relationship -- you have to
4300 install the replacing package after the replaced
4307 For this usage of <tt>Replaces</tt>, virtual packages (see
4308 <ref id="virtual">) are not considered when looking at a
4309 <tt>Replaces</tt> field - the packages declared as being
4310 replaced must be mentioned by their real names.
4314 Furthermore, this usage of <tt>Replaces</tt> only takes
4315 effect when both packages are at least partially on the
4316 system at once, so that it can only happen if they do not
4317 conflict or if the conflict has been overridden.
4322 <sect1><heading>Replacing whole packages, forcing their
4326 Secondly, <tt>Replaces</tt> allows the packaging system to
4327 resolve which package should be removed when there is a
4328 conflict - see <ref id="conflicts">. This usage only
4329 takes effect when the two packages <em>do</em> conflict,
4330 so that the two usages of this field do not interfere with
4335 In this situation, the package declared as being replaced
4336 can be a virtual package, so for example, all mail
4337 transport agents (MTAs) would have the following fields in
4338 their control files:
4339 <example compact="compact">
4340 Provides: mail-transport-agent
4341 Conflicts: mail-transport-agent
4342 Replaces: mail-transport-agent
4344 ensuring that only one MTA can be installed at any one
4349 <sect id="sourcebinarydeps">
4350 <heading>Relationships between source and binary packages -
4351 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4352 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
4356 Source packages that require certain binary packages to be
4357 installed or absent at the time of building the package
4358 can declare relationships to those binary packages.
4362 This is done using the <tt>Build-Depends</tt>,
4363 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
4364 <tt>Build-Conflicts-Indep</tt> control file fields.
4368 Build-dependencies on "build-essential" binary packages can be
4369 omitted. Please see <ref id="pkg-relations"> for more information.
4373 The dependencies and conflicts they define must be satisfied
4374 (as defined earlier for binary packages) in order to invoke
4375 the targets in <tt>debian/rules</tt>, as follows:<footnote>
4377 If you make "build-arch" or "binary-arch", you need
4378 Build-Depends. If you make "build-indep" or
4379 "binary-indep", you need Build-Depends and
4380 Build-Depends-Indep. If you make "build" or "binary",
4384 There is no Build-Depends-Arch; this role is essentially
4385 met with Build-Depends. Anyone building the
4386 <tt>build-indep</tt> and binary-indep<tt></tt> targets
4387 is basically assumed to be building the whole package
4388 anyway and so installs all build dependencies. The
4389 autobuilders use <tt>dpkg-buildpackage -B</tt>, which
4390 calls <tt>build</tt> (not <tt>build-arch</tt>, since it
4391 does not yet know how to check for its existence) and
4392 <tt>binary-arch</tt>.
4395 The purpose of the original split, I recall, was so that
4396 the autobuilders wouldn't need to install extra packages
4397 needed only for the binary-indep targets. But without a
4398 build-arch/build-indep split, this didn't work, since
4399 most of the work is done in the build target, not in the
4405 <tag><tt>Build-Depends</tt>, <tt>Build-Conflicts</tt></tag>
4407 The <tt>Build-Depends</tt> and
4408 <tt>Build-Conflicts</tt> fields must be satisfied when
4409 any of the following targets is invoked:
4410 <tt>build</tt>, <tt>clean</tt>, <tt>binary</tt>,
4411 <tt>binary-arch</tt>, <tt>build-arch</tt>,
4412 <tt>build-indep</tt> and <tt>binary-indep</tt>.
4414 <tag><tt>Build-Depends-Indep</tt>,
4415 <tt>Build-Conflicts-Indep</tt></tag>
4417 The <tt>Build-Depends-Indep</tt> and
4418 <tt>Build-Conflicts-Indep</tt> fields must be
4419 satisfied when any of the following targets is
4420 invoked: <tt>build</tt>, <tt>build-indep</tt>,
4421 <tt>binary</tt> and <tt>binary-indep</tt>.
4431 <chapt id="sharedlibs"><heading>Shared libraries</heading>
4434 Packages containing shared libraries must be constructed with
4435 a little care to make sure that the shared library is always
4436 available. This is especially important for packages whose
4437 shared libraries are vitally important, such as the C library
4438 (currently <tt>libc6</tt>).
4442 Packages involving shared libraries should be split up into
4443 several binary packages. This section mostly deals with how
4444 this separation is to be accomplished; rules for files within
4445 the shared library packages are in <ref id="libraries"> instead.
4448 <sect id="sharedlibs-runtime">
4449 <heading>Run-time shared libraries</heading>
4452 The run-time shared library needs to be placed in a package
4453 whose name changes whenever the shared object version
4456 Since it is common place to install several versions of a
4457 package that just provides shared libraries, it is a
4458 good idea that the library package should not
4459 contain any extraneous non-versioned files, unless they
4460 happen to be in versioned directories.</p>
4462 The most common mechanism is to place it in a package
4464 <package><var>libraryname</var><var>soversion</var></package>,
4465 where <file><var>soversion</var></file> is the version number
4466 in the soname of the shared library<footnote>
4467 The soname is the shared object name: it's the thing
4468 that has to match exactly between building an executable
4469 and running it for the dynamic linker to be able run the
4470 program. For example, if the soname of the library is
4471 <file>libfoo.so.6</file>, the library package would be
4472 called <file>libfoo6</file>.
4474 Alternatively, if it would be confusing to directly append
4475 <var>soversion</var> to <var>libraryname</var> (e.g. because
4476 <var>libraryname</var> itself ends in a number), you may use
4477 <package><var>libraryname</var>-<var>soversion</var></package> and
4478 <package><var>libraryname</var>-<var>soversion</var>-dev</package>
4483 If your package includes run-time support programs that
4484 do not need to be invoked manually by users, but are
4485 nevertheless required for the package to function, then it
4486 is recommended that these programs are placed
4487 (if they are binary) in a subdirectory of
4488 <file>/usr/lib</file>, preferably under
4489 <file>/usr/lib/</file><var>package-name</var>.
4490 If the program is architecture independent, the
4491 recommendation is for it to be placed in a subdirectory of
4492 <file>/usr/share</file> instead, preferably under
4493 <file>/usr/share/</file><var>package-name</var>.
4498 If you have several shared libraries built from the same
4499 source tree you may lump them all together into a single
4500 shared library package, provided that you change all of
4501 their sonames at once (so that you don't get filename
4502 clashes if you try to install different versions of the
4503 combined shared libraries package).
4507 The package should install the shared libraries under
4508 their normal names. For example, the <package>libgdbm3</package>
4509 package should install <file>libgdbm.so.3.0.0</file> as
4510 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
4511 renamed or re-linked by any <prgn>prerm</prgn> or
4512 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
4513 of renaming things safely without affecting running programs,
4514 and attempts to interfere with this are likely to lead to
4519 Shared libraries should not be installed executable, since
4520 the dynamic linker does not require this and trying to
4521 execute a shared library usually results in a core dump.
4525 The run-time library package should include the symbolic link that
4526 <prgn>ldconfig</prgn> would create for the shared libraries.
4527 For example, the <package>libgdbm3</package> package should include
4528 a symbolic link from <file>/usr/lib/libgdbm.so.3</file> to
4529 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
4530 linker (for example <prgn>ld.so</prgn> or
4531 <prgn>ld-linux.so.*</prgn>) can find the library between the
4532 time that <prgn>dpkg</prgn> installs it and the time that
4533 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
4535 The package management system requires the library to be
4536 placed before the symbolic link pointing to it in the
4537 <file>.deb</file> file. This is so that when
4538 <prgn>dpkg</prgn> comes to install the symlink
4539 (overwriting the previous symlink pointing at an older
4540 version of the library), the new shared library is already
4541 in place. In the past, this was achieved by creating the
4542 library in the temporary packaging directory before
4543 creating the symlink. Unfortunately, this was not always
4544 effective, since the building of the tar file in the
4545 <file>.deb</file> depended on the behavior of the underlying
4546 file system. Some file systems (such as reiserfs) reorder
4547 the files so that the order of creation is forgotten.
4548 Since version 1.7.0, <prgn>dpkg</prgn>
4549 reorders the files itself as necessary when building a
4550 package. Thus it is no longer important to concern
4551 oneself with the order of file creation.
4555 <sect1 id="ldconfig">
4556 <heading><tt>ldconfig</tt></heading>
4559 Any package installing shared libraries in one of the default
4560 library directories of the dynamic linker (which are currently
4561 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
4562 listed in <file>/etc/ld.so.conf</file><footnote>
4564 <list compact="compact">
4565 <item>/usr/local/lib</item>
4566 <item>/usr/lib/libc5-compat</item>
4567 <item>/lib/libc5-compat</item>
4570 must use <prgn>ldconfig</prgn> to update the shared library
4575 The package maintainer scripts must only call
4576 <prgn>ldconfig</prgn> under these circumstances:
4577 <list compact="compact">
4578 <item>When the <prgn>postinst</prgn> script is run with a
4579 first argument of <tt>configure</tt>, the script must call
4580 <prgn>ldconfig</prgn>, and may optionally invoke
4581 <prgn>ldconfig</prgn> at other times.
4583 <item>When the <prgn>postrm</prgn> script is run with a
4584 first argument of <tt>remove</tt>, the script should call
4585 <prgn>ldconfig</prgn>.
4590 During install or upgrade, the preinst is called before
4591 the new files are installed, so calling "ldconfig" is
4592 pointless. The preinst of an existing package can also be
4593 called if an upgrade fails. However, this happens during
4594 the critical time when a shared libs may exist on-disk
4595 under a temporary name. Thus, it is dangerous and
4596 forbidden by current policy to call "ldconfig" at this
4601 When a package is installed or upgraded, "postinst
4602 configure" runs after the new files are safely on-disk.
4603 Since it is perfectly safe to invoke ldconfig
4604 unconditionally in a postinst, it is OK for a package to
4605 simply put ldconfig in its postinst without checking the
4606 argument. The postinst can also be called to recover from
4607 a failed upgrade. This happens before any new files are
4608 unpacked, so there is no reason to call "ldconfig" at this
4613 For a package that is being removed, prerm is
4614 called with all the files intact, so calling ldconfig is
4615 useless. The other calls to "prerm" happen in the case of
4616 upgrade at a time when all the files of the old package
4617 are on-disk, so again calling "ldconfig" is pointless.
4621 postrm, on the other hand, is called with the "remove"
4622 argument just after the files are removed, so this is
4623 the proper time to call "ldconfig" to notify the system
4624 of the fact that the shared libraries from the package
4625 are removed. The postrm can be called at several other
4626 times. At the time of "postrm purge", "postrm
4627 abort-install", or "postrm abort-upgrade", calling
4628 "ldconfig" is useless because the shared lib files are
4629 not on-disk. However, when "postrm" is invoked with
4630 arguments "upgrade", "failed-upgrade", or "disappear", a
4631 shared lib may exist on-disk under a temporary filename.
4639 <sect id="sharedlibs-runtime-progs">
4640 <heading>Run-time support programs</heading>
4643 If your package has some run-time support programs which use
4644 the shared library you must not put them in the shared
4645 library package. If you do that then you won't be able to
4646 install several versions of the shared library without
4647 getting filename clashes.
4651 Instead, either create another package for the runtime binaries
4652 (this package might typically be named
4653 <package><var>libraryname</var>-runtime</package>; note the absence
4654 of the <var>soversion</var> in the package name), or if the
4655 development package is small, include them in there.
4659 <sect id="sharedlibs-static">
4660 <heading>Static libraries</heading>
4663 The static library (<file><var>libraryname.a</var></file>)
4664 is usually provided in addition to the shared version.
4665 It is placed into the development package (see below).
4669 In some cases, it is acceptable for a library to be
4670 available in static form only; these cases include:
4672 <item>libraries for languages whose shared library support
4673 is immature or unstable</item>
4674 <item>libraries whose interfaces are in flux or under
4675 development (commonly the case when the library's
4676 major version number is zero, or where the ABI breaks
4677 across patchlevels)</item>
4678 <item>libraries which are explicitly intended to be
4679 available only in static form by their upstream
4684 <sect id="sharedlibs-dev">
4685 <heading>Development files</heading>
4688 The development files associated to a shared library need to be
4689 placed in a package called
4690 <package><var>libraryname</var><var>soversion</var>-dev</package>,
4691 or if you prefer only to support one development version at a
4692 time, <package><var>libraryname</var>-dev</package>.
4696 In case several development versions of a library exist, you may
4697 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
4698 <ref id="conflicts">) to ensure that the user only installs one
4699 development version at a time (as different development versions are
4700 likely to have the same header files in them, which would cause a
4701 filename clash if both were installed).
4705 The development package should contain a symlink for the associated
4706 shared library without a version number. For example, the
4707 <package>libgdbm-dev</package> package should include a symlink
4708 from <file>/usr/lib/libgdbm.so</file> to
4709 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
4710 (<prgn>ld</prgn>) when compiling packages, as it will only look for
4711 <file>libgdbm.so</file> when compiling dynamically.
4715 <sect id="sharedlibs-intradeps">
4716 <heading>Dependencies between the packages of the same library</heading>
4719 Typically the development version should have an exact
4720 version dependency on the runtime library, to make sure that
4721 compilation and linking happens correctly. The
4722 <tt>${binary:Version}</tt> substitution variable can be
4723 useful for this purpose.
4725 Previously, <tt>${Source-Version}</tt> was used, but its name
4726 was confusing and it has been deprecated since dpkg 1.13.19.
4731 <sect id="sharedlibs-shlibdeps">
4732 <heading>Dependencies between the library and other packages -
4733 the <tt>shlibs</tt> system</heading>
4736 If a package contains a binary or library which links to a
4737 shared library, we must ensure that when the package is
4738 installed on the system, all of the libraries needed are
4739 also installed. This requirement led to the creation of the
4740 <tt>shlibs</tt> system, which is very simple in its design:
4741 any package which <em>provides</em> a shared library also
4742 provides information on the package dependencies required to
4743 ensure the presence of this library, and any package which
4744 <em>uses</em> a shared library uses this information to
4745 determine the dependencies it requires. The files which
4746 contain the mapping from shared libraries to the necessary
4747 dependency information are called <file>shlibs</file> files.
4751 Thus, when a package is built which contains any shared
4752 libraries, it must provide a <file>shlibs</file> file for other
4753 packages to use, and when a package is built which contains
4754 any shared libraries or compiled binaries, it must run
4755 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
4756 on these to determine the libraries used and hence the
4757 dependencies needed by this package.<footnote>
4759 In the past, the shared libraries linked to were
4760 determined by calling <prgn>ldd</prgn>, but now
4761 <prgn>objdump</prgn> is used to do this. The only
4762 change this makes to package building is that
4763 <prgn>dpkg-shlibdeps</prgn> must also be run on shared
4764 libraries, whereas in the past this was unnecessary.
4765 The rest of this footnote explains the advantage that
4770 We say that a binary <tt>foo</tt> <em>directly</em> uses
4771 a library <tt>libbar</tt> if it is explicitly linked
4772 with that library (that is, it uses the flag
4773 <tt>-lbar</tt> during the linking stage). Other
4774 libraries that are needed by <tt>libbar</tt> are linked
4775 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
4776 linker will load them automatically when it loads
4777 <tt>libbar</tt>. A package should depend on
4778 the libraries it directly uses, and the dependencies for
4779 those libraries should automatically pull in the other
4784 Unfortunately, the <prgn>ldd</prgn> program shows both
4785 the directly and indirectly used libraries, meaning that
4786 the dependencies determined included both direct and
4787 indirect dependencies. The use of <prgn>objdump</prgn>
4788 avoids this problem by determining only the directly
4793 A good example of where this helps is the following. We
4794 could update <tt>libimlib</tt> with a new version that
4795 supports a new graphics format called dgf (but retaining
4796 the same major version number). If we used the old
4797 <prgn>ldd</prgn> method, every package that uses
4798 <tt>libimlib</tt> would need to be recompiled so it
4799 would also depend on <tt>libdgf</tt> or it wouldn't run
4800 due to missing symbols. However with the new system,
4801 packages using <tt>libimlib</tt> can rely on
4802 <tt>libimlib</tt> itself having the dependency on
4803 <tt>libdgf</tt> and so they would not need rebuilding.
4809 In the following sections, we will first describe where the
4810 various <tt>shlibs</tt> files are to be found, then how to
4811 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
4812 file format and how to create them if your package contains a
4817 <heading>The <tt>shlibs</tt> files present on the system</heading>
4820 There are several places where <tt>shlibs</tt> files are
4821 found. The following list gives them in the order in which
4823 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
4824 (The first one which gives the required information is used.)
4830 <p><file>debian/shlibs.local</file></p>
4833 This lists overrides for this package. Its use is
4834 described below (see <ref id="shlibslocal">).
4839 <p><file>/etc/dpkg/shlibs.override</file></p>
4842 This lists global overrides. This list is normally
4843 empty. It is maintained by the local system
4849 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
4852 When packages are being built, any
4853 <file>debian/shlibs</file> files are copied into the
4854 control file area of the temporary build directory and
4855 given the name <file>shlibs</file>. These files give
4856 details of any shared libraries included in the
4858 An example may help here. Let us say that the
4859 source package <tt>foo</tt> generates two binary
4860 packages, <tt>libfoo2</tt> and
4861 <tt>foo-runtime</tt>. When building the binary
4862 packages, the two packages are created in the
4863 directories <file>debian/libfoo2</file> and
4864 <file>debian/foo-runtime</file> respectively.
4865 (<file>debian/tmp</file> could be used instead of one
4866 of these.) Since <tt>libfoo2</tt> provides the
4867 <tt>libfoo</tt> shared library, it will require a
4868 <tt>shlibs</tt> file, which will be installed in
4869 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually
4871 <file>/var/lib/dpkg/info/libfoo2.shlibs</file>. Then
4872 when <prgn>dpkg-shlibdeps</prgn> is run on the
4874 <file>debian/foo-runtime/usr/bin/foo-prog</file>, it
4876 <file>debian/libfoo2/DEBIAN/shlibs</file> file to
4877 determine whether <tt>foo-prog</tt>'s library
4878 dependencies are satisfied by any of the libraries
4879 provided by <tt>libfoo2</tt>. For this reason,
4880 <prgn>dpkg-shlibdeps</prgn> must only be run once
4881 all of the individual binary packages'
4882 <tt>shlibs</tt> files have been installed into the
4889 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
4892 These are the <file>shlibs</file> files corresponding to
4893 all of the packages installed on the system, and are
4894 maintained by the relevant package maintainers.
4899 <p><file>/etc/dpkg/shlibs.default</file></p>
4902 This file lists any shared libraries whose packages
4903 have failed to provide correct <file>shlibs</file> files.
4904 It was used when the <file>shlibs</file> setup was first
4905 introduced, but it is now normally empty. It is
4906 maintained by the <tt>dpkg</tt> maintainer.
4914 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
4915 <file>shlibs</file> files</heading>
4919 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
4920 into your <file>debian/rules</file> file. If your package
4921 contains only compiled binaries and libraries (but no scripts),
4922 you can use a command such as:
4923 <example compact="compact">
4924 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
4925 debian/tmp/usr/lib/*
4927 Otherwise, you will need to explicitly list the compiled
4928 binaries and libraries.<footnote>
4929 If you are using <tt>debhelper</tt>, the
4930 <prgn>dh_shlibdeps</prgn> program will do this work for
4931 you. It will also correctly handle multi-binary
4937 This command puts the dependency information into the
4938 <file>debian/substvars</file> file, which is then used by
4939 <prgn>dpkg-gencontrol</prgn>. You will need to place a
4940 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
4941 field in the control file for this to work.
4945 If <prgn>dpkg-shlibdeps</prgn> doesn't complain, you're
4946 done. If it does complain you might need to create your own
4947 <file>debian/shlibs.local</file> file, as explained below (see
4948 <ref id="shlibslocal">).
4952 If you have multiple binary packages, you will need to call
4953 <prgn>dpkg-shlibdeps</prgn> on each one which contains
4954 compiled libraries or binaries. In such a case, you will
4955 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
4956 utilities to specify a different <file>substvars</file> file.
4960 For more details on dpkg-shlibdeps, please see
4961 <ref id="pkg-dpkg-shlibdeps"> and
4962 <manref name="dpkg-shlibdeps" section="1">.
4967 <heading>The <file>shlibs</file> File Format</heading>
4970 Each <file>shlibs</file> file has the same format. Lines
4971 beginning with <tt>#</tt> are considered to be comments and
4972 are ignored. Each line is of the form:
4973 <example compact="compact">
4974 <var>library-name</var> <var>soname-version-number</var> <var>dependencies ...</var>
4979 We will explain this by reference to the example of the
4980 <tt>zlib1g</tt> package, which (at the time of writing)
4981 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
4985 <var>library-name</var> is the name of the shared library,
4986 in this case <tt>libz</tt>. (This must match the name part
4987 of the soname, see below.)
4991 <var>soname-version-number</var> is the version part of the
4992 soname of the library. The soname is the thing that must
4993 exactly match for the library to be recognized by the
4994 dynamic linker, and is usually of the form
4995 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
4996 example, <tt>libz.so.1</tt>.<footnote>
4997 This can be determined using the command
4998 <example compact="compact">
4999 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5002 The version part is the part which comes after
5003 <tt>.so.</tt>, so in our case, it is <tt>1</tt>.
5007 <var>dependencies</var> has the same syntax as a dependency
5008 field in a binary package control file. It should give
5009 details of which packages are required to satisfy a binary
5010 built against the version of the library contained in the
5011 package. See <ref id="depsyntax"> for details.
5015 In our example, if the first version of the <tt>zlib1g</tt>
5016 package which contained a minor number of at least
5017 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5018 <tt>shlibs</tt> entry for this library could say:
5019 <example compact="compact">
5020 libz 1 zlib1g (>= 1:1.1.3)
5022 The version-specific dependency is to avoid warnings from
5023 the dynamic linker about using older shared libraries with
5029 <heading>Providing a <file>shlibs</file> file</heading>
5032 If your package provides a shared library, you need to create
5033 a <file>shlibs</file> file following the format described above.
5034 It is usual to call this file <file>debian/shlibs</file> (but if
5035 you have multiple binary packages, you might want to call it
5036 <file>debian/shlibs.<var>package</var></file> instead). Then
5037 let <file>debian/rules</file> install it in the control area:
5038 <example compact="compact">
5039 install -m644 debian/shlibs debian/tmp/DEBIAN
5041 or, in the case of a multi-binary package:
5042 <example compact="compact">
5043 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5045 An alternative way of doing this is to create the
5046 <file>shlibs</file> file in the control area directly from
5047 <file>debian/rules</file> without using a <file>debian/shlibs</file>
5048 file at all,<footnote>
5049 This is what <prgn>dh_makeshlibs</prgn> in the
5050 <tt>debhelper</tt> suite does.
5052 since the <file>debian/shlibs</file> file itself is ignored by
5053 <prgn>dpkg-shlibdeps</prgn>.
5057 As <prgn>dpkg-shlibdeps</prgn> reads the
5058 <file>DEBIAN/shlibs</file> files in all of the binary packages
5059 being built from this source package, all of the
5060 <file>DEBIAN/shlibs</file> files should be installed before
5061 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5066 <sect1 id="shlibslocal">
5067 <heading>Writing the <file>debian/shlibs.local</file> file</heading>
5070 This file is intended only as a <em>temporary</em> fix if
5071 your binaries or libraries depend on a library whose package
5072 does not yet provide a correct <file>shlibs</file> file.
5076 We will assume that you are trying to package a binary
5077 <tt>foo</tt>. When you try running
5078 <prgn>dpkg-shlibdeps</prgn> you get the following error
5079 message (<tt>-O</tt> displays the dependency information on
5080 <tt>stdout</tt> instead of writing it to
5081 <tt>debian/substvars</tt>, and the lines have been wrapped
5082 for ease of reading):
5083 <example compact="compact">
5084 $ dpkg-shlibdeps -O debian/tmp/usr/bin/foo
5085 dpkg-shlibdeps: warning: unable to find dependency
5086 information for shared library libbar (soname 1,
5087 path /usr/lib/libbar.so.1, dependency field Depends)
5088 shlibs:Depends=libc6 (>= 2.2.2-2)
5090 You can then run <prgn>ldd</prgn> on the binary to find the
5091 full location of the library concerned:
5092 <example compact="compact">
5094 libbar.so.1 => /usr/lib/libbar.so.1 (0x4001e000)
5095 libc.so.6 => /lib/libc.so.6 (0x40032000)
5096 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
5098 So the <prgn>foo</prgn> binary depends on the
5099 <prgn>libbar</prgn> shared library, but no package seems to
5100 provide a <file>*.shlibs</file> file handling
5101 <file>libbar.so.1</file> in <file>/var/lib/dpkg/info/</file>. Let's
5102 determine the package responsible:
5103 <example compact="compact">
5104 $ dpkg -S /usr/lib/libbar.so.1
5105 bar1: /usr/lib/libbar.so.1
5106 $ dpkg -s bar1 | grep Version
5109 This tells us that the <tt>bar1</tt> package, version 1.0-1,
5110 is the one we are using. Now we can file a bug against the
5111 <tt>bar1</tt> package and create our own
5112 <file>debian/shlibs.local</file> to locally fix the problem.
5113 Including the following line into your
5114 <file>debian/shlibs.local</file> file:
5115 <example compact="compact">
5116 libbar 1 bar1 (>= 1.0-1)
5118 should allow the package build to work.
5122 As soon as the maintainer of <tt>bar1</tt> provides a
5123 correct <file>shlibs</file> file, you should remove this line
5124 from your <file>debian/shlibs.local</file> file. (You should
5125 probably also then have a versioned <tt>Build-Depends</tt>
5126 on <tt>bar1</tt> to help ensure that others do not have the
5127 same problem building your package.)
5136 <chapt id="opersys"><heading>The Operating System</heading>
5139 <heading>File system hierarchy</heading>
5143 <heading>File system Structure</heading>
5146 The location of all installed files and directories must
5147 comply with the File system Hierarchy Standard (FHS),
5148 version 2.3, with the exceptions noted below, and except
5149 where doing so would violate other terms of Debian
5150 Policy. The following exceptions to the FHS apply:
5155 Legacy XFree86 servers are permitted to retain the
5156 configuration file location
5157 <file>/etc/X11/XF86Config-4</file>.
5162 The optional rules related to user specific
5163 configuration files for applications are stored in
5164 the user's home directory are relaxed. It is
5165 recommended that such files start with the
5166 '<tt>.</tt>' character (a "dot file"), and if an
5167 application needs to create more than one dot file
5168 then the preferred placement is in a subdirectory
5169 with a name starting with a '.' character, (a "dot
5170 directory"). In this case it is recommended the
5171 configuration files not start with the '.'
5177 The requirement for amd64 to use <file>/lib64</file>
5178 for 64 bit binaries is removed.
5183 The requirement that
5184 <file>/usr/local/share/man</file> be "synonymous"
5185 with <file>/usr/local/man</file> is relaxed to a
5190 The requirement that windowmanagers with a single
5191 configuration file call it <file>system.*wmrc</file>
5192 is removed, as is the restriction that the window
5193 manager subdirectory be named identically to the
5194 window manager name itself.
5199 The requirement that boot manager configuration
5200 files live in <file>/etc</file>, or at least are
5201 symlinked there, is relaxed to a recommendation.
5208 The version of this document referred here can be
5209 found in the <tt>debian-policy</tt> package or on <url
5210 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5211 name="FHS (Debian copy)"> alongside this manual (or, if
5212 you have the <package>debian-policy</package> installed,
5214 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5215 (local copy)">). The
5216 latest version, which may be a more recent version, may
5218 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5219 Specific questions about following the standard may be
5220 asked on the <tt>debian-devel</tt> mailing list, or
5221 referred to the FHS mailing list (see the
5222 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
5228 <heading>Site-specific programs</heading>
5231 As mandated by the FHS, packages must not place any
5232 files in <file>/usr/local</file>, either by putting them in
5233 the file system archive to be unpacked by <prgn>dpkg</prgn>
5234 or by manipulating them in their maintainer scripts.
5238 However, the package may create empty directories below
5239 <file>/usr/local</file> so that the system administrator knows
5240 where to place site-specific files. These are not
5241 directories <em>in</em> <file>/usr/local</file>, but are
5242 children of directories in <file>/usr/local</file>. These
5243 directories (<file>/usr/local/*/dir/</file>)
5244 should be removed on package removal if they are
5249 Note, that this applies only to directories <em>below</em>
5250 <file>/usr/local</file>, not <em>in</em> <file>/usr/local</file>.
5251 Packages must not create sub-directories in the directory
5252 <file>/usr/local</file> itself, except those listed in FHS,
5253 section 4.5. However, you may create directories below
5254 them as you wish. You must not remove any of the
5255 directories listed in 4.5, even if you created them.
5259 Since <file>/usr/local</file> can be mounted read-only from a
5260 remote server, these directories must be created and
5261 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
5262 maintainer scripts and not be included in the
5263 <file>.deb</file> archive. These scripts must not fail if
5264 either of these operations fail.
5268 For example, the <tt>emacsen-common</tt> package could
5269 contain something like
5270 <example compact="compact">
5271 if [ ! -e /usr/local/share/emacs ]
5273 if mkdir /usr/local/share/emacs 2>/dev/null
5275 chown root:staff /usr/local/share/emacs
5276 chmod 2775 /usr/local/share/emacs
5280 in its <prgn>postinst</prgn> script, and
5281 <example compact="compact">
5282 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
5283 rmdir /usr/local/share/emacs 2>/dev/null || true
5285 in the <prgn>prerm</prgn> script. (Note that this form is
5286 used to ensure that if the script is interrupted, the
5287 directory <file>/usr/local/share/emacs</file> will still be
5292 If you do create a directory in <file>/usr/local</file> for
5293 local additions to a package, you should ensure that
5294 settings in <file>/usr/local</file> take precedence over the
5295 equivalents in <file>/usr</file>.
5299 However, because <file>/usr/local</file> and its contents are
5300 for exclusive use of the local administrator, a package
5301 must not rely on the presence or absence of files or
5302 directories in <file>/usr/local</file> for normal operation.
5306 The <file>/usr/local</file> directory itself and all the
5307 subdirectories created by the package should (by default) have
5308 permissions 2775 (group-writable and set-group-id) and be
5309 owned by <tt>root.staff</tt>.
5314 <heading>The system-wide mail directory</heading>
5316 The system-wide mail directory is <file>/var/mail</file>. This
5317 directory is part of the base system and should not owned
5318 by any particular mail agents. The use of the old
5319 location <file>/var/spool/mail</file> is deprecated, even
5320 though the spool may still be physically located there.
5321 To maintain partial upgrade compatibility for systems
5322 which have <file>/var/spool/mail</file> as their physical mail
5323 spool, packages using <file>/var/mail</file> must depend on
5324 either <package>libc6</package> (>= 2.1.3-13), or on
5325 <package>base-files</package> (>= 2.2.0), or on later
5326 versions of either one of these packages.
5332 <heading>Users and groups</heading>
5335 <heading>Introduction</heading>
5337 The Debian system can be configured to use either plain or
5342 Some user ids (UIDs) and group ids (GIDs) are reserved
5343 globally for use by certain packages. Because some
5344 packages need to include files which are owned by these
5345 users or groups, or need the ids compiled into binaries,
5346 these ids must be used on any Debian system only for the
5347 purpose for which they are allocated. This is a serious
5348 restriction, and we should avoid getting in the way of
5349 local administration policies. In particular, many sites
5350 allocate users and/or local system groups starting at 100.
5354 Apart from this we should have dynamically allocated ids,
5355 which should by default be arranged in some sensible
5356 order, but the behavior should be configurable.
5360 Packages other than <tt>base-passwd</tt> must not modify
5361 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
5362 <file>/etc/group</file> or <file>/etc/gshadow</file>.
5367 <heading>UID and GID classes</heading>
5369 The UID and GID numbers are divided into classes as
5375 Globally allocated by the Debian project, the same
5376 on every Debian system. These ids will appear in
5377 the <file>passwd</file> and <file>group</file> files of all
5378 Debian systems, new ids in this range being added
5379 automatically as the <tt>base-passwd</tt> package is
5384 Packages which need a single statically allocated
5385 uid or gid should use one of these; their
5386 maintainers should ask the <tt>base-passwd</tt>
5394 Dynamically allocated system users and groups.
5395 Packages which need a user or group, but can have
5396 this user or group allocated dynamically and
5397 differently on each system, should use <tt>adduser
5398 --system</tt> to create the group and/or user.
5399 <prgn>adduser</prgn> will check for the existence of
5400 the user or group, and if necessary choose an unused
5401 id based on the ranges specified in
5402 <file>adduser.conf</file>.
5406 <tag>1000-29999:</tag>
5409 Dynamically allocated user accounts. By default
5410 <prgn>adduser</prgn> will choose UIDs and GIDs for
5411 user accounts in this range, though
5412 <file>adduser.conf</file> may be used to modify this
5417 <tag>30000-59999:</tag>
5422 <tag>60000-64999:</tag>
5425 Globally allocated by the Debian project, but only
5426 created on demand. The ids are allocated centrally
5427 and statically, but the actual accounts are only
5428 created on users' systems on demand.
5432 These ids are for packages which are obscure or
5433 which require many statically-allocated ids. These
5434 packages should check for and create the accounts in
5435 <file>/etc/passwd</file> or <file>/etc/group</file> (using
5436 <prgn>adduser</prgn> if it has this facility) if
5437 necessary. Packages which are likely to require
5438 further allocations should have a "hole" left after
5439 them in the allocation, to give them room to
5444 <tag>65000-65533:</tag>
5452 User <tt>nobody</tt>. The corresponding gid refers
5453 to the group <tt>nogroup</tt>.
5460 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
5461 not</em> be used, because it is the error return
5470 <sect id="sysvinit">
5471 <heading>System run levels and <file>init.d</file> scripts</heading>
5473 <sect1 id="/etc/init.d">
5474 <heading>Introduction</heading>
5477 The <file>/etc/init.d</file> directory contains the scripts
5478 executed by <prgn>init</prgn> at boot time and when the
5479 init state (or "runlevel") is changed (see <manref
5480 name="init" section="8">).
5484 There are at least two different, yet functionally
5485 equivalent, ways of handling these scripts. For the sake
5486 of simplicity, this document describes only the symbolic
5487 link method. However, it must not be assumed by maintainer
5488 scripts that this method is being used, and any automated
5489 manipulation of the various runlevel behaviors by
5490 maintainer scripts must be performed using
5491 <prgn>update-rc.d</prgn> as described below and not by
5492 manually installing or removing symlinks. For information
5493 on the implementation details of the other method,
5494 implemented in the <tt>file-rc</tt> package, please refer
5495 to the documentation of that package.
5499 These scripts are referenced by symbolic links in the
5500 <file>/etc/rc<var>n</var>.d</file> directories. When changing
5501 runlevels, <prgn>init</prgn> looks in the directory
5502 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
5503 execute, where <tt><var>n</var></tt> is the runlevel that
5504 is being changed to, or <tt>S</tt> for the boot-up
5509 The names of the links all have the form
5510 <file>S<var>mm</var><var>script</var></file> or
5511 <file>K<var>mm</var><var>script</var></file> where
5512 <var>mm</var> is a two-digit number and <var>script</var>
5513 is the name of the script (this should be the same as the
5514 name of the actual script in <file>/etc/init.d</file>).
5518 When <prgn>init</prgn> changes runlevel first the targets
5519 of the links whose names start with a <tt>K</tt> are
5520 executed, each with the single argument <tt>stop</tt>,
5521 followed by the scripts prefixed with an <tt>S</tt>, each
5522 with the single argument <tt>start</tt>. (The links are
5523 those in the <file>/etc/rc<var>n</var>.d</file> directory
5524 corresponding to the new runlevel.) The <tt>K</tt> links
5525 are responsible for killing services and the <tt>S</tt>
5526 link for starting services upon entering the runlevel.
5530 For example, if we are changing from runlevel 2 to
5531 runlevel 3, init will first execute all of the <tt>K</tt>
5532 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
5533 all of the <tt>S</tt> prefixed scripts in that directory.
5534 The links starting with <tt>K</tt> will cause the
5535 referred-to file to be executed with an argument of
5536 <tt>stop</tt>, and the <tt>S</tt> links with an argument
5541 The two-digit number <var>mm</var> is used to determine
5542 the order in which to run the scripts: low-numbered links
5543 have their scripts run first. For example, the
5544 <tt>K20</tt> scripts will be executed before the
5545 <tt>K30</tt> scripts. This is used when a certain service
5546 must be started before another. For example, the name
5547 server <prgn>bind</prgn> might need to be started before
5548 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
5549 can set up its access lists. In this case, the script
5550 that starts <prgn>bind</prgn> would have a lower number
5551 than the script that starts <prgn>inn</prgn> so that it
5553 <example compact="compact">
5560 The two runlevels 0 (halt) and 6 (reboot) are slightly
5561 different. In these runlevels, the links with an
5562 <tt>S</tt> prefix are still called after those with a
5563 <tt>K</tt> prefix, but they too are called with the single
5564 argument <tt>stop</tt>.
5568 Also, if the script name ends in <tt>.sh</tt>, the script
5569 will be sourced in runlevel <tt>S</tt> rather than being
5570 run in a forked subprocess, but will be explicitly run by
5571 <prgn>sh</prgn> in all other runlevels.
5576 <heading>Writing the scripts</heading>
5579 Packages that include daemons for system services should
5580 place scripts in <file>/etc/init.d</file> to start or stop
5581 services at boot time or during a change of runlevel.
5582 These scripts should be named
5583 <file>/etc/init.d/<var>package</var></file>, and they should
5584 accept one argument, saying what to do:
5587 <tag><tt>start</tt></tag>
5588 <item>start the service,</item>
5590 <tag><tt>stop</tt></tag>
5591 <item>stop the service,</item>
5593 <tag><tt>restart</tt></tag>
5594 <item>stop and restart the service if it's already running,
5595 otherwise start the service</item>
5597 <tag><tt>reload</tt></tag>
5598 <item><p>cause the configuration of the service to be
5599 reloaded without actually stopping and restarting
5602 <tag><tt>force-reload</tt></tag>
5603 <item>cause the configuration to be reloaded if the
5604 service supports this, otherwise restart the
5608 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
5609 <tt>force-reload</tt> options should be supported by all
5610 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
5615 The <file>init.d</file> scripts must ensure that they will
5616 behave sensibly if invoked with <tt>start</tt> when the
5617 service is already running, or with <tt>stop</tt> when it
5618 isn't, and that they don't kill unfortunately-named user
5619 processes. The best way to achieve this is usually to use
5620 <prgn>start-stop-daemon</prgn>.
5624 If a service reloads its configuration automatically (as
5625 in the case of <prgn>cron</prgn>, for example), the
5626 <tt>reload</tt> option of the <file>init.d</file> script
5627 should behave as if the configuration has been reloaded
5632 The <file>/etc/init.d</file> scripts must be treated as
5633 configuration files, either (if they are present in the
5634 package, that is, in the .deb file) by marking them as
5635 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
5636 by managing them correctly in the maintainer scripts (see
5637 <ref id="config-files">). This is important since we want
5638 to give the local system administrator the chance to adapt
5639 the scripts to the local system, e.g., to disable a
5640 service without de-installing the package, or to specify
5641 some special command line options when starting a service,
5642 while making sure their changes aren't lost during the next
5647 These scripts should not fail obscurely when the
5648 configuration files remain but the package has been
5649 removed, as configuration files remain on the system after
5650 the package has been removed. Only when <prgn>dpkg</prgn>
5651 is executed with the <tt>--purge</tt> option will
5652 configuration files be removed. In particular, as the
5653 <file>/etc/init.d/<var>package</var></file> script itself is
5654 usually a <tt>conffile</tt>, it will remain on the system
5655 if the package is removed but not purged. Therefore, you
5656 should include a <tt>test</tt> statement at the top of the
5658 <example compact="compact">
5659 test -f <var>program-executed-later-in-script</var> || exit 0
5664 Often there are some variables in the <file>init.d</file>
5665 scripts whose values control the behavior of the scripts,
5666 and which a system administrator is likely to want to
5667 change. As the scripts themselves are frequently
5668 <tt>conffile</tt>s, modifying them requires that the
5669 administrator merge in their changes each time the package
5670 is upgraded and the <tt>conffile</tt> changes. To ease
5671 the burden on the system administrator, such configurable
5672 values should not be placed directly in the script.
5673 Instead, they should be placed in a file in
5674 <file>/etc/default</file>, which typically will have the same
5675 base name as the <file>init.d</file> script. This extra file
5676 should be sourced by the script when the script runs. It
5677 must contain only variable settings and comments in SUSv3
5678 <prgn>sh</prgn> format. It may either be a
5679 <tt>conffile</tt> or a configuration file maintained by
5680 the package maintainer scripts. See <ref id="config-files">
5685 To ensure that vital configurable values are always
5686 available, the <file>init.d</file> script should set default
5687 values for each of the shell variables it uses, either
5688 before sourcing the <file>/etc/default/</file> file or
5689 afterwards using something like the <tt>:
5690 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
5691 script must behave sensibly and not fail if the
5692 <file>/etc/default</file> file is deleted.
5697 <heading>Interfacing with the initscript system</heading>
5700 Maintainers should use the abstraction layer provided by
5701 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
5702 programs to deal with initscripts in their packages'
5703 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
5704 and <prgn>postrm</prgn>.
5708 Directly managing the /etc/rc?.d links and directly
5709 invoking the <file>/etc/init.d/</file> initscripts should
5710 be done only by packages providing the initscript
5711 subsystem (such as <prgn>sysv-rc</prgn> and
5712 <prgn>file-rc</prgn>).
5716 <heading>Managing the links</heading>
5719 The program <prgn>update-rc.d</prgn> is provided for
5720 package maintainers to arrange for the proper creation and
5721 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
5722 or their functional equivalent if another method is being
5723 used. This may be used by maintainers in their packages'
5724 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
5728 You must not include any <file>/etc/rc<var>n</var>.d</file>
5729 symbolic links in the actual archive or manually create or
5730 remove the symbolic links in maintainer scripts; you must
5731 use the <prgn>update-rc.d</prgn> program instead. (The
5732 former will fail if an alternative method of maintaining
5733 runlevel information is being used.) You must not include
5734 the <file>/etc/rc<var>n</var>.d</file> directories themselves
5735 in the archive either. (Only the <tt>sysvinit</tt>
5740 By default <prgn>update-rc.d</prgn> will start services in
5741 each of the multi-user state runlevels (2, 3, 4, and 5)
5742 and stop them in the halt runlevel (0), the single-user
5743 runlevel (1) and the reboot runlevel (6). The system
5744 administrator will have the opportunity to customize
5745 runlevels by simply adding, moving, or removing the
5746 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
5747 symbolic links are being used, or by modifying
5748 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
5753 To get the default behavior for your package, put in your
5754 <prgn>postinst</prgn> script
5755 <example compact="compact">
5756 update-rc.d <var>package</var> defaults
5758 and in your <prgn>postrm</prgn>
5759 <example compact="compact">
5760 if [ "$1" = purge ]; then
5761 update-rc.d <var>package</var> remove
5763 </example>. Note that if your package changes runlevels
5764 or priority, you may have to remove and recreate the links,
5765 since otherwise the old links may persist. Refer to the
5766 documentation of <prgn>update-rc.d</prgn>.
5770 This will use a default sequence number of 20. If it does
5771 not matter when or in which order the <file>init.d</file>
5772 script is run, use this default. If it does, then you
5773 should talk to the maintainer of the <prgn>sysvinit</prgn>
5774 package or post to <tt>debian-devel</tt>, and they will
5775 help you choose a number.
5779 For more information about using <tt>update-rc.d</tt>,
5780 please consult its man page <manref name="update-rc.d"
5786 <heading>Running initscripts</heading>
5788 The program <prgn>invoke-rc.d</prgn> is provided to make
5789 it easier for package maintainers to properly invoke an
5790 initscript, obeying runlevel and other locally-defined
5791 constraints that might limit a package's right to start,
5792 stop and otherwise manage services. This program may be
5793 used by maintainers in their packages' scripts.
5797 The package maintainer scripts must use
5798 <prgn>invoke-rc.d</prgn> to invoke the
5799 <file>/etc/init.d/*</file> initscripts, instead of
5800 calling them directly.
5804 By default, <prgn>invoke-rc.d</prgn> will pass any
5805 action requests (start, stop, reload, restart...) to the
5806 <file>/etc/init.d</file> script, filtering out requests
5807 to start or restart a service out of its intended
5812 Most packages will simply need to change:
5813 <example compact="compact">/etc/init.d/<package>
5814 <action></example> in their <prgn>postinst</prgn>
5815 and <prgn>prerm</prgn> scripts to:
5816 <example compact="compact">
5817 if which invoke-rc.d >/dev/null 2>&1; then
5818 invoke-rc.d <var>package</var> <action>
5820 /etc/init.d/<var>package</var> <action>
5826 A package should register its initscript services using
5827 <prgn>update-rc.d</prgn> before it tries to invoke them
5828 using <prgn>invoke-rc.d</prgn>. Invocation of
5829 unregistered services may fail.
5833 For more information about using
5834 <prgn>invoke-rc.d</prgn>, please consult its man page
5835 <manref name="invoke-rc.d" section="8">.
5841 <heading>Boot-time initialization</heading>
5844 There used to be another directory, <file>/etc/rc.boot</file>,
5845 which contained scripts which were run once per machine
5846 boot. This has been deprecated in favour of links from
5847 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
5848 described in <ref id="/etc/init.d">. Packages must not
5849 place files in <file>/etc/rc.boot</file>.
5854 <heading>Example</heading>
5857 An example on which you can base your
5858 <file>/etc/init.d</file> scripts is found in
5859 <file>/etc/init.d/skeleton</file>.
5866 <heading>Console messages from <file>init.d</file> scripts</heading>
5869 This section describes the formats to be used for messages
5870 written to standard output by the <file>/etc/init.d</file>
5871 scripts. The intent is to improve the consistency of
5872 Debian's startup and shutdown look and feel. For this
5873 reason, please look very carefully at the details. We want
5874 the messages to have the same format in terms of wording,
5875 spaces, punctuation and case of letters.
5879 Here is a list of overall rules that should be used for
5880 messages generated by <file>/etc/init.d</file> scripts.
5886 The message should fit in one line (fewer than 80
5887 characters), start with a capital letter and end with
5888 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
5892 If the script is performing some time consuming task in
5893 the background (not merely starting or stopping a
5894 program, for instance), an ellipsis (three dots:
5895 <tt>...</tt>) should be output to the screen, with no
5896 leading or tailing whitespace or line feeds.
5900 The messages should appear as if the computer is telling
5901 the user what it is doing (politely :-), but should not
5902 mention "it" directly. For example, instead of:
5903 <example compact="compact">
5904 I'm starting network daemons: nfsd mountd.
5906 the message should say
5907 <example compact="compact">
5908 Starting network daemons: nfsd mountd.
5915 <tt>init.d</tt> script should use the following standard
5916 message formats for the situations enumerated below.
5922 <p>When daemons are started</p>
5925 If the script starts one or more daemons, the output
5926 should look like this (a single line, no leading
5928 <example compact="compact">
5929 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
5931 The <var>description</var> should describe the
5932 subsystem the daemon or set of daemons are part of,
5933 while <var>daemon-1</var> up to <var>daemon-n</var>
5934 denote each daemon's name (typically the file name of
5939 For example, the output of <file>/etc/init.d/lpd</file>
5941 <example compact="compact">
5942 Starting printer spooler: lpd.
5947 This can be achieved by saying
5948 <example compact="compact">
5949 echo -n "Starting printer spooler: lpd"
5950 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
5953 in the script. If there are more than one daemon to
5954 start, the output should look like this:
5955 <example compact="compact">
5956 echo -n "Starting remote file system services:"
5957 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
5958 echo -n " mountd"; start-stop-daemon --start --quiet mountd
5959 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
5962 This makes it possible for the user to see what is
5963 happening and when the final daemon has been started.
5964 Care should be taken in the placement of white spaces:
5965 in the example above the system administrators can
5966 easily comment out a line if they don't want to start
5967 a specific daemon, while the displayed message still
5973 <p>When a system parameter is being set</p>
5976 If you have to set up different system parameters
5977 during the system boot, you should use this format:
5978 <example compact="compact">
5979 Setting <var>parameter</var> to "<var>value</var>".
5984 You can use a statement such as the following to get
5986 <example compact="compact">
5987 echo "Setting DNS domainname to \"$domainname\"."
5992 Note that the same symbol (<tt>"</tt>) is used for the left
5993 and right quotation marks. A grave accent (<tt>`</tt>) is
5994 not a quote character; neither is an apostrophe
6000 <p>When a daemon is stopped or restarted</p>
6003 When you stop or restart a daemon, you should issue a
6004 message identical to the startup message, except that
6005 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6006 or <tt>Restarting</tt> respectively.
6010 For example, stopping the printer daemon will look like
6012 <example compact="compact">
6013 Stopping printer spooler: lpd.
6019 <p>When something is executed</p>
6022 There are several examples where you have to run a
6023 program at system startup or shutdown to perform a
6024 specific task, for example, setting the system's clock
6025 using <prgn>netdate</prgn> or killing all processes
6026 when the system shuts down. Your message should look
6028 <example compact="compact">
6029 Doing something very useful...done.
6031 You should print the <tt>done.</tt> immediately after
6032 the job has been completed, so that the user is
6033 informed why they have to wait. You can get this
6035 <example compact="compact">
6036 echo -n "Doing something very useful..."
6045 <p>When the configuration is reloaded</p>
6048 When a daemon is forced to reload its configuration
6049 files you should use the following format:
6050 <example compact="compact">
6051 Reloading <var>description</var> configuration...done.
6053 where <var>description</var> is the same as in the
6054 daemon starting message.
6062 <heading>Cron jobs</heading>
6065 Packages must not modify the configuration file
6066 <file>/etc/crontab</file>, and they must not modify the files in
6067 <file>/var/spool/cron/crontabs</file>.</p>
6070 If a package wants to install a job that has to be executed
6071 via cron, it should place a file with the name of the
6072 package in one or more of the following directories:
6073 <example compact="compact">
6078 As these directory names imply, the files within them are
6079 executed on a daily, weekly, or monthly basis,
6080 respectively. The exact times are listed in
6081 <file>/etc/crontab</file>.</p>
6084 All files installed in any of these directories must be
6085 scripts (e.g., shell scripts or Perl scripts) so that they
6086 can easily be modified by the local system administrator.
6087 In addition, they should be treated as configuration
6092 If a certain job has to be executed more frequently than
6093 daily, the package should install a file
6094 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6095 same syntax as <file>/etc/crontab</file> and is processed by
6096 <prgn>cron</prgn> automatically. The file must also be
6097 treated as a configuration file. (Note that entries in the
6098 <file>/etc/cron.d</file> directory are not handled by
6099 <prgn>anacron</prgn>. Thus, you should only use this
6100 directory for jobs which may be skipped if the system is not
6104 The scripts or crontab entries in these directories should
6105 check if all necessary programs are installed before they
6106 try to execute them. Otherwise, problems will arise when a
6107 package was removed but not purged since configuration files
6108 are kept on the system in this situation.</p>
6112 <heading>Menus</heading>
6115 The Debian <tt>menu</tt> package provides a standard
6116 interface between packages providing applications and
6117 <em>menu programs</em> (either X window managers or
6118 text-based menu programs such as <prgn>pdmenu</prgn>).
6122 All packages that provide applications that need not be
6123 passed any special command line arguments for normal
6124 operation should register a menu entry for those
6125 applications, so that users of the <tt>menu</tt> package
6126 will automatically get menu entries in their window
6127 managers, as well in shells like <tt>pdmenu</tt>.
6131 Menu entries should follow the current menu policy.
6135 The menu policy can be found in the <tt>menu-policy</tt>
6136 files in the <tt>debian-policy</tt> package.
6137 It is also available from the Debian web mirrors at
6138 <tt><url name="/doc/packaging-manuals/menu-policy/"
6139 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6143 Please also refer to the <em>Debian Menu System</em>
6144 documentation that comes with the <package>menu</package>
6145 package for information about how to register your
6151 <heading>Multimedia handlers</heading>
6154 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6155 is a mechanism for encoding files and data streams and
6156 providing meta-information about them, in particular their
6157 type (e.g. audio or video) and format (e.g. PNG, HTML,
6162 Registration of MIME type handlers allows programs like mail
6163 user agents and web browsers to invoke these handlers to
6164 view, edit or display MIME types they don't support directly.
6168 Packages which provide the ability to view/show/play,
6169 compose, edit or print MIME types should register themselves
6170 as such following the current MIME support policy.
6174 The MIME support policy can be found in the <tt>mime-policy</tt>
6175 files in the <tt>debian-policy</tt> package.
6176 It is also available from the Debian web mirrors at
6177 <tt><url name="/doc/packaging-manuals/mime-policy/"
6178 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
6184 <heading>Keyboard configuration</heading>
6187 To achieve a consistent keyboard configuration so that all
6188 applications interpret a keyboard event the same way, all
6189 programs in the Debian distribution must be configured to
6190 comply with the following guidelines.
6194 The following keys must have the specified interpretations:
6197 <tag><tt><--</tt></tag>
6198 <item>delete the character to the left of the cursor</item>
6200 <tag><tt>Delete</tt></tag>
6201 <item>delete the character to the right of the cursor</item>
6203 <tag><tt>Control+H</tt></tag>
6204 <item>emacs: the help prefix</item>
6207 The interpretation of any keyboard events should be
6208 independent of the terminal that is used, be it a virtual
6209 console, an X terminal emulator, an rlogin/telnet session,
6214 The following list explains how the different programs
6215 should be set up to achieve this:
6221 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
6225 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
6229 X translations are set up to make
6230 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
6231 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
6232 is the vt220 escape code for the "delete character"
6233 key). This must be done by loading the X resources
6234 using <prgn>xrdb</prgn> on all local X displays, not
6235 using the application defaults, so that the
6236 translation resources used correspond to the
6237 <prgn>xmodmap</prgn> settings.
6241 The Linux console is configured to make
6242 <tt><--</tt> generate DEL, and <tt>Delete</tt>
6243 generate <tt>ESC [ 3 ~</tt>.
6247 X applications are configured so that <tt><</tt>
6248 deletes left, and <tt>Delete</tt> deletes right. Motif
6249 applications already work like this.
6253 Terminals should have <tt>stty erase ^?</tt> .
6257 The <tt>xterm</tt> terminfo entry should have <tt>ESC
6258 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
6259 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
6263 Emacs is programmed to map <tt>KB_Backspace</tt> or
6264 the <tt>stty erase</tt> character to
6265 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
6266 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
6267 <tt>^H</tt> to <tt>help</tt> as always.
6271 Other applications use the <tt>stty erase</tt>
6272 character and <tt>kdch1</tt> for the two delete keys,
6273 with ASCII DEL being "delete previous character" and
6274 <tt>kdch1</tt> being "delete character under
6282 This will solve the problem except for the following
6289 Some terminals have a <tt><--</tt> key that cannot
6290 be made to produce anything except <tt>^H</tt>. On
6291 these terminals Emacs help will be unavailable on
6292 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
6293 character takes precedence in Emacs, and has been set
6294 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
6295 available) can be used instead.
6299 Some operating systems use <tt>^H</tt> for <tt>stty
6300 erase</tt>. However, modern telnet versions and all
6301 rlogin versions propagate <tt>stty</tt> settings, and
6302 almost all UNIX versions honour <tt>stty erase</tt>.
6303 Where the <tt>stty</tt> settings are not propagated
6304 correctly, things can be made to work by using
6305 <tt>stty</tt> manually.
6309 Some systems (including previous Debian versions) use
6310 <prgn>xmodmap</prgn> to arrange for both
6311 <tt><--</tt> and <tt>Delete</tt> to generate
6312 <tt>KB_Delete</tt>. We can change the behavior of
6313 their X clients using the same X resources that we use
6314 to do it for our own clients, or configure our clients
6315 using their resources when things are the other way
6316 around. On displays configured like this
6317 <tt>Delete</tt> will not work, but <tt><--</tt>
6322 Some operating systems have different <tt>kdch1</tt>
6323 settings in their <tt>terminfo</tt> database for
6324 <tt>xterm</tt> and others. On these systems the
6325 <tt>Delete</tt> key will not work correctly when you
6326 log in from a system conforming to our policy, but
6327 <tt><--</tt> will.
6334 <heading>Environment variables</heading>
6337 A program must not depend on environment variables to get
6338 reasonable defaults. (That's because these environment
6339 variables would have to be set in a system-wide
6340 configuration file like <file>/etc/profile</file>, which is not
6341 supported by all shells.)
6345 If a program usually depends on environment variables for its
6346 configuration, the program should be changed to fall back to
6347 a reasonable default configuration if these environment
6348 variables are not present. If this cannot be done easily
6349 (e.g., if the source code of a non-free program is not
6350 available), the program must be replaced by a small
6351 "wrapper" shell script which sets the environment variables
6352 if they are not already defined, and calls the original program.
6356 Here is an example of a wrapper script for this purpose:
6358 <example compact="compact">
6360 BAR=${BAR:-/var/lib/fubar}
6362 exec /usr/lib/foo/foo "$@"
6367 Furthermore, as <file>/etc/profile</file> is a configuration
6368 file of the <prgn>base-files</prgn> package, other packages must
6369 not put any environment variables or other commands into that
6374 <sect id="doc-base">
6375 <heading>Registering Documents using doc-base</heading>
6378 The <package>doc-base</package> package implements a
6379 flexible mechanism for handling and presenting
6380 documentation. The recommended practice is for every Debian
6381 package that provides online documentation (other than just
6382 manual pages) to register these documents with
6383 <package>doc-base</package> by installing a
6384 <package>doc-base</package> control file via the
6385 <prgn/install-docs/ script at installation time and
6386 de-register the manuals again when the package is removed.
6389 Please refer to the documentation that comes with the
6390 <package>doc-base</package> package for information and
6399 <heading>Files</heading>
6402 <heading>Binaries</heading>
6405 Two different packages must not install programs with
6406 different functionality but with the same filenames. (The
6407 case of two programs having the same functionality but
6408 different implementations is handled via "alternatives" or
6409 the "Conflicts" mechanism. See <ref id="maintscripts"> and
6410 <ref id="conflicts"> respectively.) If this case happens,
6411 one of the programs must be renamed. The maintainers should
6412 report this to the <tt>debian-devel</tt> mailing list and
6413 try to find a consensus about which program will have to be
6414 renamed. If a consensus cannot be reached, <em>both</em>
6415 programs must be renamed.
6419 By default, when a package is being built, any binaries
6420 created should include debugging information, as well as
6421 being compiled with optimization. You should also turn on
6422 as many reasonable compilation warnings as possible; this
6423 makes life easier for porters, who can then look at build
6424 logs for possible problems. For the C programming language,
6425 this means the following compilation parameters should be
6427 <example compact="compact">
6429 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
6431 INSTALL = install -s # (or use strip on the files in debian/tmp)
6436 Note that by default all installed binaries should be stripped,
6437 either by using the <tt>-s</tt> flag to
6438 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
6439 the binaries after they have been copied into
6440 <file>debian/tmp</file> but before the tree is made into a
6445 Although binaries in the build tree should be compiled with
6446 debugging information by default, it can often be difficult
6447 to debug programs if they are also subjected to compiler
6448 optimization. For this reason, it is recommended to support
6449 the standardized environment
6450 variable <tt>DEB_BUILD_OPTIONS</tt>. This variable can
6451 contain several flags to change how a package is compiled
6459 The presence of this string means that the package
6460 should be compiled with a minimum of optimization.
6461 For C programs, it is best to add <tt>-O0</tt>
6462 to <tt>CFLAGS</tt> (although this is usually the
6463 default). Some programs might fail to build or run at
6464 this level of optimization; it may be necessary to
6465 use <tt>-O1</tt>, for example.
6469 This string means that the debugging symbols should
6470 not be stripped from the binary during installation,
6471 so that debugging information may be included in the package.
6477 The following makefile snippet is an example of how one may
6478 implement the build options; you will probably have to
6479 massage this example in order to make it work for your
6481 <example compact="compact">
6484 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
6485 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
6486 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
6487 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
6489 ifneq (,$(findstring noopt,$(DEB_BUILD_OPTIONS)))
6494 ifeq (,$(findstring nostrip,$(DEB_BUILD_OPTIONS)))
6495 INSTALL_PROGRAM += -s
6501 It is up to the package maintainer to decide what
6502 compilation options are best for the package. Certain
6503 binaries (such as computationally-intensive programs) will
6504 function better with certain flags (<tt>-O3</tt>, for
6505 example); feel free to use them. Please use good judgment
6506 here. Don't use flags for the sake of it; only use them
6507 if there is good reason to do so. Feel free to override
6508 the upstream author's ideas about which compilation
6509 options are best: they are often inappropriate for our
6515 <sect id="libraries">
6516 <heading>Libraries</heading>
6519 If the package is <strong>architecture: any</strong>, then
6520 the shared library compilation and linking flags must have
6521 <tt>-fPIC</tt>, or the package shall not build on some of
6522 the supported architectures<footnote>
6524 If you are using GCC, <tt>-fPIC</tt> produces code with
6525 relocatable position independent code, which is required for
6526 most architectures to create a shared library, with i386 and
6527 perhaps some others where non position independent code is
6528 permitted in a shared library.
6531 Position independent code may have a performance penalty,
6532 especially on <tt>i386</tt>. However, in most cases the
6533 speed penalty must be measured against the memory wasted on
6534 the few architectures where non position independent code is
6537 </footnote>. Any exception to this rule must be discussed on
6538 the mailing list <em>debian-devel@lists.debian.org</em>, and
6539 a rough consensus obtained. The reasons for not compiling
6540 with <tt>-fPIC</tt> flag must be recorded in the file
6541 <tt>README.Debian</tt>, and care must be taken to either
6542 restrict the architecture or arrange for <tt>-fPIC</tt> to
6543 be used on architectures where it is required.<footnote>
6545 Some of the reasons why this might be required is if the
6546 library contains hand crafted assembly code that is not
6547 relocatable, the speed penalty is excessive for compute
6548 intensive libs, and similar reasons.
6553 As to the static libraries, the common case is not to have
6554 relocatable code, since there is no benefit, unless in specific
6555 cases; therefore the static version must not be compiled
6556 with the <tt>-fPIC</tt> flag. Any exception to this rule
6557 should be discussed on the mailing list
6558 <em>debian-devel@lists.debian.org</em>, and the reasons for
6559 compiling with the <tt>-fPIC</tt> flag must be recorded in
6560 the file <tt>README.Debian</tt>. <footnote>
6562 Some of the reasons for linking static libraries with
6563 the <tt>-fPIC</tt> flag are if, for example, one needs a
6564 Perl API for a library that is under rapid development,
6565 and has an unstable API, so shared libraries are
6566 pointless at this phase of the library's development. In
6567 that case, since Perl needs a library with relocatable
6568 code, it may make sense to create a static library with
6569 relocatable code. Another reason cited is if you are
6570 distilling various libraries into a common shared
6571 library, like <tt>mklibs</tt> does in the Debian
6577 In other words, if both a shared and a static library is
6578 being built, each source unit (<tt>*.c</tt>, for example,
6579 for C files) will need to be compiled twice, for the normal
6583 You must specify the gcc option <tt>-D_REENTRANT</tt>
6584 when building a library (either static or shared) to make
6585 the library compatible with LinuxThreads.
6589 Although not enforced by the build tools, shared libraries
6590 must be linked against all libraries that they use symbols from
6591 in the same way that binaries are. This ensures the correct
6592 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
6593 system and guarantees that all libraries can be safely opened
6594 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
6595 option <tt>-Wl,-z,defs</tt> when building a shared library.
6596 Since this option enforces symbol resolution at build time,
6597 a missing library reference will be caught early as a fatal
6602 All installed shared libraries should be stripped with
6603 <example compact="compact">
6604 strip --strip-unneeded <var>your-lib</var>
6606 (The option <tt>--strip-unneeded</tt> makes
6607 <prgn>strip</prgn> remove only the symbols which aren't
6608 needed for relocation processing.) Shared libraries can
6609 function perfectly well when stripped, since the symbols for
6610 dynamic linking are in a separate part of the ELF object
6612 You might also want to use the options
6613 <tt>--remove-section=.comment</tt> and
6614 <tt>--remove-section=.note</tt> on both shared libraries
6615 and executables, and <tt>--strip-debug</tt> on static
6621 Note that under some circumstances it may be useful to
6622 install a shared library unstripped, for example when
6623 building a separate package to support debugging.
6627 Shared object files (often <file>.so</file> files) that are not
6628 public libraries, that is, they are not meant to be linked
6629 to by third party executables (binaries of other packages),
6630 should be installed in subdirectories of the
6631 <file>/usr/lib</file> directory. Such files are exempt from the
6632 rules that govern ordinary shared libraries, except that
6633 they must not be installed executable and should be
6635 A common example are the so-called "plug-ins",
6636 internal shared objects that are dynamically loaded by
6637 programs using <manref name="dlopen" section="3">.
6642 Packages containing shared libraries that may be linked to
6643 by other packages' binaries, but which for some
6644 <em>compelling</em> reason can not be installed in
6645 <file>/usr/lib</file> directory, may install the shared library
6646 files in subdirectories of the <file>/usr/lib</file> directory,
6647 in which case they should arrange to add that directory in
6648 <file>/etc/ld.so.conf</file> in the package's post-installation
6649 script, and remove it in the package's post-removal script.
6653 An ever increasing number of packages are using
6654 <prgn>libtool</prgn> to do their linking. The latest GNU
6655 libtools (>= 1.3a) can take advantage of the metadata in the
6656 installed <prgn>libtool</prgn> archive files (<file>*.la</file>
6657 files). The main advantage of <prgn>libtool</prgn>'s
6658 <file>.la</file> files is that it allows <prgn>libtool</prgn> to
6659 store and subsequently access metadata with respect to the
6660 libraries it builds. <prgn>libtool</prgn> will search for
6661 those files, which contain a lot of useful information about
6662 a library (such as library dependency information for static
6663 linking). Also, they're <em>essential</em> for programs
6664 using <tt>libltdl</tt>.<footnote>
6665 Although <prgn>libtool</prgn> is fully capable of
6666 linking against shared libraries which don't have
6667 <tt>.la</tt> files, as it is a mere shell script it can
6668 add considerably to the build time of a
6669 <prgn>libtool</prgn>-using package if that shell script
6670 has to derive all this information from first principles
6671 for each library every time it is linked. With the
6672 advent of <prgn>libtool</prgn> version 1.4 (and to a
6673 lesser extent <prgn>libtool</prgn> version 1.3), the
6674 <file>.la</file> files also store information about
6675 inter-library dependencies which cannot necessarily be
6676 derived after the <file>.la</file> file is deleted.
6681 Packages that use <prgn>libtool</prgn> to create shared
6682 libraries should include the <file>.la</file> files in the
6683 <tt>-dev</tt> package, unless the package relies on
6684 <tt>libtool</tt>'s <tt>libltdl</tt> library, in which case
6685 the <tt>.la</tt> files must go in the run-time library
6690 You must make sure that you use only released versions of
6691 shared libraries to build your packages; otherwise other
6692 users will not be able to run your binaries
6693 properly. Producing source packages that depend on
6694 unreleased compilers is also usually a bad
6701 <heading>Shared libraries</heading>
6703 This section has moved to <ref id="sharedlibs">.
6709 <heading>Scripts</heading>
6712 All command scripts, including the package maintainer
6713 scripts inside the package and used by <prgn>dpkg</prgn>,
6714 should have a <tt>#!</tt> line naming the shell to be used
6719 In the case of Perl scripts this should be
6720 <tt>#!/usr/bin/perl</tt>.
6724 When scripts are installed into a directory in the system
6725 PATH, the script name should not include an extension such
6726 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
6727 language currently used to implement it.
6730 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>)
6731 should almost certainly start with <tt>set -e</tt> so that
6732 errors are detected. Every script should use
6733 <tt>set -e</tt> or check the exit status of <em>every</em>
6738 Scripts may assume that <file>/bin/sh</file> implements the
6739 SUSv3 Shell Command Language<footnote>
6740 Single UNIX Specification, version 3, which is also IEEE
6741 1003.1-2004 (POSIX), and is available on the World Wide Web
6742 from <url id="http://www.unix.org/version3/online.html"
6743 name="The Open Group"> after free
6744 registration.</footnote>
6745 plus the following additional features not mandated by
6747 These features are in widespread use in the Linux community
6748 and are implemented in all of bash, dash, and ksh, the most
6749 common shells users may wish to use as <file>/bin/sh</file>.
6752 <item><tt>echo -n</tt>, if implemented as a shell built-in,
6753 must not generate a newline.</item>
6754 <item><tt>test</tt>, if implemented as a shell built-in, must
6755 support <tt>-a</tt> and <tt>-o</tt> as binary logical
6757 <item><tt>local</tt> to create a scoped variable must be
6758 supported; however, <tt>local</tt> may or may not preserve
6759 the variable value from an outer scope and may or may not
6760 support arguments more complex than simple variables. Only
6772 If a shell script requires non-SUSv3 features from the shell
6773 interpreter other than those listed above, the appropriate shell
6774 must be specified in the first line of the script (e.g.,
6775 <tt>#!/bin/bash</tt>) and the package must depend on the package
6776 providing the shell (unless the shell package is marked
6777 "Essential", as in the case of <prgn>bash</prgn>).
6781 You may wish to restrict your script to SUSv3 features plus the
6782 above set when possible so that it may use <file>/bin/sh</file>
6783 as its interpreter. If your script works with <prgn>dash</prgn>
6784 (originally called <prgn>ash</prgn>), it probably complies with
6785 the above requirements, but if you are in doubt, use
6786 <file>/bin/bash</file>.
6790 Perl scripts should check for errors when making any
6791 system calls, including <tt>open</tt>, <tt>print</tt>,
6792 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
6796 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
6797 scripting languages. See <em>Csh Programming Considered
6798 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
6799 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
6800 If an upstream package comes with <prgn>csh</prgn> scripts
6801 then you must make sure that they start with
6802 <tt>#!/bin/csh</tt> and make your package depend on the
6803 <prgn>c-shell</prgn> virtual package.
6807 Any scripts which create files in world-writeable
6808 directories (e.g., in <file>/tmp</file>) must use a
6809 mechanism which will fail atomically if a file with the same
6810 name already exists.
6814 The Debian base system provides the <prgn>tempfile</prgn>
6815 and <prgn>mktemp</prgn> utilities for use by scripts for
6822 <heading>Symbolic links</heading>
6825 In general, symbolic links within a top-level directory
6826 should be relative, and symbolic links pointing from one
6827 top-level directory into another should be absolute. (A
6828 top-level directory is a sub-directory of the root
6829 directory <file>/</file>.)
6833 In addition, symbolic links should be specified as short as
6834 possible, i.e., link targets like <file>foo/../bar</file> are
6839 Note that when creating a relative link using
6840 <prgn>ln</prgn> it is not necessary for the target of the
6841 link to exist relative to the working directory you're
6842 running <prgn>ln</prgn> from, nor is it necessary to change
6843 directory to the directory where the link is to be made.
6844 Simply include the string that should appear as the target
6845 of the link (this will be a pathname relative to the
6846 directory in which the link resides) as the first argument
6851 For example, in your <prgn>Makefile</prgn> or
6852 <file>debian/rules</file>, you can do things like:
6853 <example compact="compact">
6854 ln -fs gcc $(prefix)/bin/cc
6855 ln -fs gcc debian/tmp/usr/bin/cc
6856 ln -fs ../sbin/sendmail $(prefix)/bin/runq
6857 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
6862 A symbolic link pointing to a compressed file should always
6863 have the same file extension as the referenced file. (For
6864 example, if a file <file>foo.gz</file> is referenced by a
6865 symbolic link, the filename of the link has to end with
6866 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
6871 <heading>Device files</heading>
6874 Packages must not include device files in the package file
6879 If a package needs any special device files that are not
6880 included in the base system, it must call
6881 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
6882 after notifying the user<footnote>
6883 This notification could be done via a (low-priority)
6884 debconf message, or an echo (printf) statement.
6889 Packages must not remove any device files in the
6890 <prgn>postrm</prgn> or any other script. This is left to the
6891 system administrator.
6895 Debian uses the serial devices
6896 <file>/dev/ttyS*</file>. Programs using the old
6897 <file>/dev/cu*</file> devices should be changed to use
6898 <file>/dev/ttyS*</file>.
6902 <sect id="config-files">
6903 <heading>Configuration files</heading>
6906 <heading>Definitions</heading>
6910 <tag>configuration file</tag>
6912 A file that affects the operation of a program, or
6913 provides site- or host-specific information, or
6914 otherwise customizes the behavior of a program.
6915 Typically, configuration files are intended to be
6916 modified by the system administrator (if needed or
6917 desired) to conform to local policy or to provide
6918 more useful site-specific behavior.
6921 <tag><tt>conffile</tt></tag>
6923 A file listed in a package's <tt>conffiles</tt>
6924 file, and is treated specially by <prgn>dpkg</prgn>
6925 (see <ref id="configdetails">).
6931 The distinction between these two is important; they are
6932 not interchangeable concepts. Almost all
6933 <tt>conffile</tt>s are configuration files, but many
6934 configuration files are not <tt>conffiles</tt>.
6938 Note that a script that embeds configuration information
6939 (such as most of the files in <file>/etc/default</file> and
6940 <file>/etc/cron.{daily,weekly,monthly}</file>) is de-facto a
6941 configuration file and should be treated as such.
6946 <heading>Location</heading>
6949 Any configuration files created or used by your package
6950 must reside in <file>/etc</file>. If there are several,
6951 consider creating a subdirectory of <file>/etc</file>
6952 named after your package.
6956 If your package creates or uses configuration files
6957 outside of <file>/etc</file>, and it is not feasible to modify
6958 the package to use <file>/etc</file> directly, put the files
6959 in <file>/etc</file> and create symbolic links to those files
6960 from the location that the package requires.
6965 <heading>Behavior</heading>
6968 Configuration file handling must conform to the following
6970 <list compact="compact">
6972 local changes must be preserved during a package
6976 configuration files must be preserved when the
6977 package is removed, and only deleted when the
6984 The easy way to achieve this behavior is to make the
6985 configuration file a <tt>conffile</tt>. This is
6986 appropriate only if it is possible to distribute a default
6987 version that will work for most installations, although
6988 some system administrators may choose to modify it. This
6989 implies that the default version will be part of the
6990 package distribution, and must not be modified by the
6991 maintainer scripts during installation (or at any other
6996 In order to ensure that local changes are preserved
6997 correctly, no package may contain or make hard links to
6998 conffiles.<footnote>
6999 Rationale: There are two problems with hard links.
7000 The first is that some editors break the link while
7001 editing one of the files, so that the two files may
7002 unwittingly become unlinked and different. The second
7003 is that <prgn>dpkg</prgn> might break the hard link
7004 while upgrading <tt>conffile</tt>s.
7009 The other way to do it is via the maintainer scripts. In
7010 this case, the configuration file must not be listed as a
7011 <tt>conffile</tt> and must not be part of the package
7012 distribution. If the existence of a file is required for
7013 the package to be sensibly configured it is the
7014 responsibility of the package maintainer to provide
7015 maintainer scripts which correctly create, update and
7016 maintain the file and remove it on purge. (See <ref
7017 id="maintainerscripts"> for more information.) These
7018 scripts must be idempotent (i.e., must work correctly if
7019 <prgn>dpkg</prgn> needs to re-run them due to errors
7020 during installation or removal), must cope with all the
7021 variety of ways <prgn>dpkg</prgn> can call maintainer
7022 scripts, must not overwrite or otherwise mangle the user's
7023 configuration without asking, must not ask unnecessary
7024 questions (particularly during upgrades), and must
7025 otherwise be good citizens.
7029 The scripts are not required to configure every possible
7030 option for the package, but only those necessary to get
7031 the package running on a given system. Ideally the
7032 sysadmin should not have to do any configuration other
7033 than that done (semi-)automatically by the
7034 <prgn>postinst</prgn> script.
7038 A common practice is to create a script called
7039 <file><var>package</var>-configure</file> and have the
7040 package's <prgn>postinst</prgn> call it if and only if the
7041 configuration file does not already exist. In certain
7042 cases it is useful for there to be an example or template
7043 file which the maintainer scripts use. Such files should
7044 be in <file>/usr/share/<var>package</var></file> or
7045 <file>/usr/lib/<var>package</var></file> (depending on whether
7046 they are architecture-independent or not). There should
7047 be symbolic links to them from
7048 <file>/usr/share/doc/<var>package</var>/examples</file> if
7049 they are examples, and should be perfectly ordinary
7050 <prgn>dpkg</prgn>-handled files (<em>not</em>
7051 configuration files).
7055 These two styles of configuration file handling must
7056 not be mixed, for that way lies madness:
7057 <prgn>dpkg</prgn> will ask about overwriting the file
7058 every time the package is upgraded.
7063 <heading>Sharing configuration files</heading>
7066 Packages which specify the same file as a
7067 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7068 with each other. (This is an instance of the general rule
7069 about not sharing files. Note that neither alternatives
7070 nor diversions are likely to be appropriate in this case;
7071 in particular, <prgn>dpkg</prgn> does not handle diverted
7072 <tt>conffile</tt>s well.)
7076 The maintainer scripts must not alter a <tt>conffile</tt>
7077 of <em>any</em> package, including the one the scripts
7082 If two or more packages use the same configuration file
7083 and it is reasonable for both to be installed at the same
7084 time, one of these packages must be defined as
7085 <em>owner</em> of the configuration file, i.e., it will be
7086 the package which handles that file as a configuration
7087 file. Other packages that use the configuration file must
7088 depend on the owning package if they require the
7089 configuration file to operate. If the other package will
7090 use the configuration file if present, but is capable of
7091 operating without it, no dependency need be declared.
7095 If it is desirable for two or more related packages to
7096 share a configuration file <em>and</em> for all of the
7097 related packages to be able to modify that configuration
7098 file, then the following should be done:
7099 <enumlist compact="compact">
7101 One of the related packages (the "owning" package)
7102 will manage the configuration file with maintainer
7103 scripts as described in the previous section.
7106 The owning package should also provide a program
7107 that the other packages may use to modify the
7111 The related packages must use the provided program
7112 to make any desired modifications to the
7113 configuration file. They should either depend on
7114 the core package to guarantee that the configuration
7115 modifier program is available or accept gracefully
7116 that they cannot modify the configuration file if it
7117 is not. (This is in addition to the fact that the
7118 configuration file may not even be present in the
7125 Sometimes it's appropriate to create a new package which
7126 provides the basic infrastructure for the other packages
7127 and which manages the shared configuration files. (The
7128 <tt>sgml-base</tt> package is a good example.)
7133 <heading>User configuration files ("dotfiles")</heading>
7136 The files in <file>/etc/skel</file> will automatically be
7137 copied into new user accounts by <prgn>adduser</prgn>.
7138 No other program should reference the files in
7139 <file>/etc/skel</file>.
7143 Therefore, if a program needs a dotfile to exist in
7144 advance in <file>$HOME</file> to work sensibly, that dotfile
7145 should be installed in <file>/etc/skel</file> and treated as a
7150 However, programs that require dotfiles in order to
7151 operate sensibly are a bad thing, unless they do create
7152 the dotfiles themselves automatically.
7156 Furthermore, programs should be configured by the Debian
7157 default installation to behave as closely to the upstream
7158 default behavior as possible.
7162 Therefore, if a program in a Debian package needs to be
7163 configured in some way in order to operate sensibly, that
7164 should be done using a site-wide configuration file placed
7165 in <file>/etc</file>. Only if the program doesn't support a
7166 site-wide default configuration and the package maintainer
7167 doesn't have time to add it may a default per-user file be
7168 placed in <file>/etc/skel</file>.
7172 <file>/etc/skel</file> should be as empty as we can make it.
7173 This is particularly true because there is no easy (or
7174 necessarily desirable) mechanism for ensuring that the
7175 appropriate dotfiles are copied into the accounts of
7176 existing users when a package is installed.
7182 <heading>Log files</heading>
7184 Log files should usually be named
7185 <file>/var/log/<var>package</var>.log</file>. If you have many
7186 log files, or need a separate directory for permission
7187 reasons (<file>/var/log</file> is writable only by
7188 <file>root</file>), you should usually create a directory named
7189 <file>/var/log/<var>package</var></file> and place your log
7194 Log files must be rotated occasionally so that they don't
7195 grow indefinitely; the best way to do this is to drop a log
7196 rotation configuration file into the directory
7197 <file>/etc/logrotate.d</file> and use the facilities provided by
7198 logrotate.<footnote>
7200 The traditional approach to log files has been to set up
7201 <em>ad hoc</em> log rotation schemes using simple shell
7202 scripts and cron. While this approach is highly
7203 customizable, it requires quite a lot of sysadmin work.
7204 Even though the original Debian system helped a little
7205 by automatically installing a system which can be used
7206 as a template, this was deemed not enough.
7210 The use of <prgn>logrotate</prgn>, a program developed
7211 by Red Hat, is better, as it centralizes log management.
7212 It has both a configuration file
7213 (<file>/etc/logrotate.conf</file>) and a directory where
7214 packages can drop their individual log rotation
7215 configurations (<file>/etc/logrotate.d</file>).
7218 Here is a good example for a logrotate config
7219 file (for more information see <manref name="logrotate"
7221 <example compact="compact">
7222 /var/log/foo/*.log {
7227 /etc/init.d/foo force-reload
7231 This rotates all files under <file>/var/log/foo</file>, saves 12
7232 compressed generations, and forces the daemon to reload its
7233 configuration information after the log rotation.
7237 Log files should be removed when the package is
7238 purged (but not when it is only removed). This should be
7239 done by the <prgn>postrm</prgn> script when it is called
7240 with the argument <tt>purge</tt> (see <ref
7241 id="removedetails">).
7246 <heading>Permissions and owners</heading>
7249 The rules in this section are guidelines for general use.
7250 If necessary you may deviate from the details below.
7251 However, if you do so you must make sure that what is done
7252 is secure and you should try to be as consistent as possible
7253 with the rest of the system. You should probably also
7254 discuss it on <prgn>debian-devel</prgn> first.
7258 Files should be owned by <tt>root.root</tt>, and made
7259 writable only by the owner and universally readable (and
7260 executable, if appropriate), that is mode 644 or 755.
7264 Directories should be mode 755 or (for group-writability)
7265 mode 2775. The ownership of the directory should be
7266 consistent with its mode: if a directory is mode 2775, it
7267 should be owned by the group that needs write access to
7270 When a package is upgraded, and the owner or permissions
7271 of a file included in the package has changed, dpkg
7272 arranges for the ownership and permissions to be
7273 correctly set upon installation. However, this does not
7274 extend to directories; the permissions and ownership of
7275 directories already on the system does not change on
7276 install or upgrade of packages. This makes sense, since
7277 otherwise common directories like <tt>/usr</tt> would
7278 always be in flux. To correctly change permissions of a
7279 directory the package owns, explicit action is required,
7280 usually in the <tt>postinst</tt> script. Care must be
7281 taken to handle downgrades as well, in that case.
7288 Setuid and setgid executables should be mode 4755 or 2755
7289 respectively, and owned by the appropriate user or group.
7290 They should not be made unreadable (modes like 4711 or
7291 2711 or even 4111); doing so achieves no extra security,
7292 because anyone can find the binary in the freely available
7293 Debian package; it is merely inconvenient. For the same
7294 reason you should not restrict read or execute permissions
7295 on non-set-id executables.
7299 Some setuid programs need to be restricted to particular
7300 sets of users, using file permissions. In this case they
7301 should be owned by the uid to which they are set-id, and by
7302 the group which should be allowed to execute them. They
7303 should have mode 4754; again there is no point in making
7304 them unreadable to those users who must not be allowed to
7309 It is possible to arrange that the system administrator can
7310 reconfigure the package to correspond to their local
7311 security policy by changing the permissions on a binary:
7312 they can do this by using <prgn>dpkg-statoverride</prgn>, as
7313 described below.<footnote>
7314 Ordinary files installed by <prgn>dpkg</prgn> (as
7315 opposed to <tt>conffile</tt>s and other similar objects)
7316 normally have their permissions reset to the distributed
7317 permissions when the package is reinstalled. However,
7318 the use of <prgn>dpkg-statoverride</prgn> overrides this
7319 default behavior. If you use this method, you should
7320 remember to describe <prgn>dpkg-statoverride</prgn> in
7321 the package documentation; being a relatively new
7322 addition to Debian, it is probably not yet well-known.
7324 Another method you should consider is to create a group for
7325 people allowed to use the program(s) and make any setuid
7326 executables executable only by that group.
7330 If you need to create a new user or group for your package
7331 there are two possibilities. Firstly, you may need to
7332 make some files in the binary package be owned by this
7333 user or group, or you may need to compile the user or
7334 group id (rather than just the name) into the binary
7335 (though this latter should be avoided if possible, as in
7336 this case you need a statically allocated id).</p>
7339 If you need a statically allocated id, you must ask for a
7340 user or group id from the <tt>base-passwd</tt> maintainer,
7341 and must not release the package until you have been
7342 allocated one. Once you have been allocated one you must
7343 either make the package depend on a version of the
7344 <tt>base-passwd</tt> package with the id present in
7345 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
7346 your package to create the user or group itself with the
7347 correct id (using <tt>adduser</tt>) in its
7348 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
7349 the <prgn>postinst</prgn> is to be preferred if it is
7350 possible, otherwise a pre-dependency will be needed on the
7351 <tt>adduser</tt> package.)
7355 On the other hand, the program might be able to determine
7356 the uid or gid from the user or group name at runtime, so
7357 that a dynamically allocated id can be used. In this case
7358 you should choose an appropriate user or group name,
7359 discussing this on <prgn>debian-devel</prgn> and checking
7360 with the <package/base-passwd/ maintainer that it is unique and that
7361 they do not wish you to use a statically allocated id
7362 instead. When this has been checked you must arrange for
7363 your package to create the user or group if necessary using
7364 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
7365 <prgn>postinst</prgn> script (again, the latter is to be
7366 preferred if it is possible).
7370 Note that changing the numeric value of an id associated
7371 with a name is very difficult, and involves searching the
7372 file system for all appropriate files. You need to think
7373 carefully whether a static or dynamic id is required, since
7374 changing your mind later will cause problems.
7377 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
7379 This section is not intended as policy, but as a
7380 description of the use of <prgn>dpkg-statoverride</prgn>.
7384 <prgn>dpkg-statoverride</prgn> is a replacement for the
7385 deprecated <tt>suidmanager</tt> package. Packages which
7386 previously used <tt>suidmanager</tt> should have a
7387 <tt>Conflicts: suidmanager (<< 0.50)</tt> entry (or even
7388 <tt>(<< 0.52)</tt>), and calls to <tt>suidregister</tt>
7389 and <tt>suidunregister</tt> should now be simply removed
7390 from the maintainer scripts.
7394 If a system administrator wishes to have a file (or
7395 directory or other such thing) installed with owner and
7396 permissions different from those in the distributed Debian
7397 package, they can use the <prgn>dpkg-statoverride</prgn>
7398 program to instruct <prgn>dpkg</prgn> to use the different
7399 settings every time the file is installed. Thus the
7400 package maintainer should distribute the files with their
7401 normal permissions, and leave it for the system
7402 administrator to make any desired changes. For example, a
7403 daemon which is normally required to be setuid root, but
7404 in certain situations could be used without being setuid,
7405 should be installed setuid in the <tt>.deb</tt>. Then the
7406 local system administrator can change this if they wish.
7407 If there are two standard ways of doing it, the package
7408 maintainer can use <tt>debconf</tt> to find out the
7409 preference, and call <prgn>dpkg-statoverride</prgn> in the
7410 maintainer script if necessary to accommodate the system
7411 administrator's choice. Care must be taken during
7412 upgrades to not override an existing setting.
7416 Given the above, <prgn>dpkg-statoverride</prgn> is
7417 essentially a tool for system administrators and would not
7418 normally be needed in the maintainer scripts. There is
7419 one type of situation, though, where calls to
7420 <prgn>dpkg-statoverride</prgn> would be needed in the
7421 maintainer scripts, and that involves packages which use
7422 dynamically allocated user or group ids. In such a
7423 situation, something like the following idiom can be very
7424 helpful in the package's <prgn>postinst</prgn>, where
7425 <tt>sysuser</tt> is a dynamically allocated id:
7427 for i in /usr/bin/foo /usr/sbin/bar
7429 # only do something when no setting exists
7430 if ! dpkg-statoverride --list $i >/dev/null 2>&1
7432 #include: debconf processing, question about foo and bar
7433 if [ "$RET" = "true" ] ; then
7434 dpkg-statoverride --update --add sysuser root 4755 $i
7439 The corresponding <tt>dpkg-statoverride --remove</tt>
7440 calls can then be made unconditionally when the package is
7448 <chapt id="customized-programs">
7449 <heading>Customized programs</heading>
7451 <sect id="arch-spec">
7452 <heading>Architecture specification strings</heading>
7455 If a program needs to specify an <em>architecture specification
7456 string</em> in some place, it should select one of the
7457 strings provided by <tt>dpkg-architecture -L</tt>. The
7458 strings are in the format
7459 <tt><var>os</var>-<var>arch</var></tt>, though the OS part
7460 is sometimes elided, as when the OS is Linux.<footnote>
7461 <p>Currently, the strings are:
7462 i386 ia64 alpha amd64 armeb arm hppa m32r m68k mips
7463 mipsel powerpc ppc64 s390 s390x sh3 sh3eb sh4 sh4eb
7464 sparc darwin-i386 darwin-ia64 darwin-alpha darwin-amd64
7465 darwin-armeb darwin-arm darwin-hppa darwin-m32r
7466 darwin-m68k darwin-mips darwin-mipsel darwin-powerpc
7467 darwin-ppc64 darwin-s390 darwin-s390x darwin-sh3
7468 darwin-sh3eb darwin-sh4 darwin-sh4eb darwin-sparc
7469 freebsd-i386 freebsd-ia64 freebsd-alpha freebsd-amd64
7470 freebsd-armeb freebsd-arm freebsd-hppa freebsd-m32r
7471 freebsd-m68k freebsd-mips freebsd-mipsel freebsd-powerpc
7472 freebsd-ppc64 freebsd-s390 freebsd-s390x freebsd-sh3
7473 freebsd-sh3eb freebsd-sh4 freebsd-sh4eb freebsd-sparc
7474 kfreebsd-i386 kfreebsd-ia64 kfreebsd-alpha
7475 kfreebsd-amd64 kfreebsd-armeb kfreebsd-arm kfreebsd-hppa
7476 kfreebsd-m32r kfreebsd-m68k kfreebsd-mips
7477 kfreebsd-mipsel kfreebsd-powerpc kfreebsd-ppc64
7478 kfreebsd-s390 kfreebsd-s390x kfreebsd-sh3 kfreebsd-sh3eb
7479 kfreebsd-sh4 kfreebsd-sh4eb kfreebsd-sparc knetbsd-i386
7480 knetbsd-ia64 knetbsd-alpha knetbsd-amd64 knetbsd-armeb
7481 knetbsd-arm knetbsd-hppa knetbsd-m32r knetbsd-m68k
7482 knetbsd-mips knetbsd-mipsel knetbsd-powerpc
7483 knetbsd-ppc64 knetbsd-s390 knetbsd-s390x knetbsd-sh3
7484 knetbsd-sh3eb knetbsd-sh4 knetbsd-sh4eb knetbsd-sparc
7485 netbsd-i386 netbsd-ia64 netbsd-alpha netbsd-amd64
7486 netbsd-armeb netbsd-arm netbsd-hppa netbsd-m32r
7487 netbsd-m68k netbsd-mips netbsd-mipsel netbsd-powerpc
7488 netbsd-ppc64 netbsd-s390 netbsd-s390x netbsd-sh3
7489 netbsd-sh3eb netbsd-sh4 netbsd-sh4eb netbsd-sparc
7490 openbsd-i386 openbsd-ia64 openbsd-alpha openbsd-amd64
7491 openbsd-armeb openbsd-arm openbsd-hppa openbsd-m32r
7492 openbsd-m68k openbsd-mips openbsd-mipsel openbsd-powerpc
7493 openbsd-ppc64 openbsd-s390 openbsd-s390x openbsd-sh3
7494 openbsd-sh3eb openbsd-sh4 openbsd-sh4eb openbsd-sparc
7495 hurd-i386 hurd-ia64 hurd-alpha hurd-amd64 hurd-armeb
7496 hurd-arm hurd-hppa hurd-m32r hurd-m68k hurd-mips
7497 hurd-mipsel hurd-powerpc hurd-ppc64 hurd-s390 hurd-s390x
7498 hurd-sh3 hurd-sh3eb hurd-sh4 hurd-sh4eb hurd-sparc
7504 Note that we don't want to use
7505 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
7506 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
7507 since this would make our programs incompatible with other
7508 Linux distributions. We also don't use something like
7509 <tt><var>arch</var>-unknown-linux</tt>, since the
7510 <tt>unknown</tt> does not look very good.
7515 <heading>Daemons</heading>
7518 The configuration files <file>/etc/services</file>,
7519 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
7520 by the <prgn>netbase</prgn> package and must not be modified
7525 If a package requires a new entry in one of these files, the
7526 maintainer should get in contact with the
7527 <prgn>netbase</prgn> maintainer, who will add the entries
7528 and release a new version of the <prgn>netbase</prgn>
7533 The configuration file <file>/etc/inetd.conf</file> must not be
7534 modified by the package's scripts except via the
7535 <prgn>update-inetd</prgn> script or the
7536 <file>DebianNet.pm</file> Perl module. See their documentation
7537 for details on how to add entries.
7541 If a package wants to install an example entry into
7542 <file>/etc/inetd.conf</file>, the entry must be preceded with
7543 exactly one hash character (<tt>#</tt>). Such lines are
7544 treated as "commented out by user" by the
7545 <prgn>update-inetd</prgn> script and are not changed or
7546 activated during package updates.
7551 <heading>Using pseudo-ttys and modifying wtmp, utmp and
7555 Some programs need to create pseudo-ttys. This should be done
7556 using Unix98 ptys if the C library supports it. The resulting
7557 program must not be installed setuid root, unless that
7558 is required for other functionality.
7562 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
7563 <file>/var/log/lastlog</file> must be installed writable by
7564 group <tt>utmp</tt>. Programs which need to modify those
7565 files must be installed setgid <tt>utmp</tt>.
7570 <heading>Editors and pagers</heading>
7573 Some programs have the ability to launch an editor or pager
7574 program to edit or display a text document. Since there are
7575 lots of different editors and pagers available in the Debian
7576 distribution, the system administrator and each user should
7577 have the possibility to choose their preferred editor and
7582 In addition, every program should choose a good default
7583 editor/pager if none is selected by the user or system
7588 Thus, every program that launches an editor or pager must
7589 use the EDITOR or PAGER environment variable to determine
7590 the editor or pager the user wishes to use. If these
7591 variables are not set, the programs <file>/usr/bin/editor</file>
7592 and <file>/usr/bin/pager</file> should be used, respectively.
7596 These two files are managed through the <prgn>dpkg</prgn>
7597 "alternatives" mechanism. Thus every package providing an
7598 editor or pager must call the
7599 <prgn>update-alternatives</prgn> script to register these
7604 If it is very hard to adapt a program to make use of the
7605 EDITOR or PAGER variables, that program may be configured to
7606 use <file>/usr/bin/sensible-editor</file> and
7607 <file>/usr/bin/sensible-pager</file> as the editor or pager
7608 program respectively. These are two scripts provided in the
7609 Debian base system that check the EDITOR and PAGER variables
7610 and launch the appropriate program, and fall back to
7611 <file>/usr/bin/editor</file> and <file>/usr/bin/pager</file> if the
7612 variable is not set.
7616 A program may also use the VISUAL environment variable to
7617 determine the user's choice of editor. If it exists, it
7618 should take precedence over EDITOR. This is in fact what
7619 <file>/usr/bin/sensible-editor</file> does.
7623 It is not required for a package to depend on
7624 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
7625 package to provide such virtual packages.<footnote>
7626 The Debian base system already provides an editor and a
7632 <sect id="web-appl">
7633 <heading>Web servers and applications</heading>
7636 This section describes the locations and URLs that should
7637 be used by all web servers and web applications in the
7644 Cgi-bin executable files are installed in the
7646 <example compact="compact">
7647 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
7649 and should be referred to as
7650 <example compact="compact">
7651 http://localhost/cgi-bin/<var>cgi-bin-name</var>
7657 <p>Access to HTML documents</p>
7660 HTML documents for a package are stored in
7661 <file>/usr/share/doc/<var>package</var></file>
7662 and can be referred to as
7663 <example compact="compact">
7664 http://localhost/doc/<var>package</var>/<var>filename</var>
7669 The web server should restrict access to the document
7670 tree so that only clients on the same host can read
7671 the documents. If the web server does not support such
7672 access controls, then it should not provide access at
7673 all, or ask about providing access during installation.
7678 <p>Access to images</p>
7680 It is recommended that images for a package be stored
7681 in <tt>/usr/share/images/<var>package</var></tt> and
7682 may be referred to through an alias <tt>/images/</tt>
7685 http://localhost/images/<package>/<filename>
7692 <p>Web Document Root</p>
7695 Web Applications should try to avoid storing files in
7696 the Web Document Root. Instead they should use the
7697 /usr/share/doc/<var>package</var> directory for
7698 documents and register the Web Application via the
7699 <package>doc-base</package> package. If access to the
7700 web document root is unavoidable then use
7701 <example compact="compact">
7704 as the Document Root. This might be just a symbolic
7705 link to the location where the system administrator
7706 has put the real document root.
7709 <item><p>Providing httpd and/or httpd-cgi</p>
7711 All web servers should provide the virtual package
7712 <tt>httpd</tt>. If a web server has CGI support it should
7713 provide <tt>httpd-cgi</tt> additionally.
7716 All web applications which do not contain CGI scripts should
7717 depend on <tt>httpd</tt>, all those web applications which
7718 <tt>do</tt> contain CGI scripts, should depend on
7726 <sect id="mail-transport-agents">
7727 <heading>Mail transport, delivery and user agents</heading>
7730 Debian packages which process electronic mail, whether mail
7731 user agents (MUAs) or mail transport agents (MTAs), must
7732 ensure that they are compatible with the configuration
7733 decisions below. Failure to do this may result in lost
7734 mail, broken <tt>From:</tt> lines, and other serious brain
7739 The mail spool is <file>/var/mail</file> and the interface to
7740 send a mail message is <file>/usr/sbin/sendmail</file> (as per
7741 the FHS). On older systems, the mail spool may be
7742 physically located in <file>/var/spool/mail</file>, but all
7743 access to the mail spool should be via the
7744 <file>/var/mail</file> symlink. The mail spool is part of the
7745 base system and not part of the MTA package.
7749 All Debian MUAs, MTAs, MDAs and other mailbox accessing
7750 programs (such as IMAP daemons) must lock the mailbox in an
7751 NFS-safe way. This means that <tt>fcntl()</tt> locking must
7752 be combined with dot locking. To avoid deadlocks, a program
7753 should use <tt>fcntl()</tt> first and dot locking after
7754 this, or alternatively implement the two locking methods in
7755 a non blocking way<footnote>
7756 If it is not possible to establish both locks, the
7757 system shouldn't wait for the second lock to be
7758 established, but remove the first lock, wait a (random)
7759 time, and start over locking again.
7760 </footnote>. Using the functions <tt>maillock</tt> and
7761 <tt>mailunlock</tt> provided by the
7762 <tt>liblockfile*</tt><footnote>
7763 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
7764 to use these functions.
7765 </footnote> packages is the recommended way to realize this.
7769 Mailboxes are generally mode 660
7770 <tt><var>user</var>.mail</tt> unless the system
7771 administrator has chosen otherwise. A MUA may remove a
7772 mailbox (unless it has nonstandard permissions) in which
7773 case the MTA or another MUA must recreate it if needed.
7774 Mailboxes must be writable by group mail.
7778 The mail spool is 2775 <tt>root.mail</tt>, and MUAs should
7779 be setgid mail to do the locking mentioned above (and
7780 must obviously avoid accessing other users' mailboxes
7781 using this privilege).</p>
7784 <file>/etc/aliases</file> is the source file for the system mail
7785 aliases (e.g., postmaster, usenet, etc.), it is the one
7786 which the sysadmin and <prgn>postinst</prgn> scripts may
7787 edit. After <file>/etc/aliases</file> is edited the program or
7788 human editing it must call <prgn>newaliases</prgn>. All MTA
7789 packages must come with a <prgn>newaliases</prgn> program,
7790 even if it does nothing, but older MTA packages did not do
7791 this so programs should not fail if <prgn>newaliases</prgn>
7792 cannot be found. Note that because of this, all MTA
7793 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
7794 <tt>Replaces: mail-transport-agent</tt> control file
7799 The convention of writing <tt>forward to
7800 <var>address</var></tt> in the mailbox itself is not
7801 supported. Use a <tt>.forward</tt> file instead.</p>
7804 The <prgn>rmail</prgn> program used by UUCP
7805 for incoming mail should be <file>/usr/sbin/rmail</file>.
7806 Likewise, <prgn>rsmtp</prgn>, for receiving
7807 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
7811 If your package needs to know what hostname to use on (for
7812 example) outgoing news and mail messages which are generated
7813 locally, you should use the file <file>/etc/mailname</file>. It
7814 will contain the portion after the username and <tt>@</tt>
7815 (at) sign for email addresses of users on the machine
7816 (followed by a newline).
7820 Such a package should check for the existence of this file
7821 when it is being configured. If it exists, it should be
7822 used without comment, although an MTA's configuration script
7823 may wish to prompt the user even if it finds that this file
7824 exists. If the file does not exist, the package should
7825 prompt the user for the value (preferably using
7826 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
7827 as well as using it in the package's configuration. The
7828 prompt should make it clear that the name will not just be
7829 used by that package. For example, in this situation the
7830 <tt>inn</tt> package could say something like:
7831 <example compact="compact">
7832 Please enter the "mail name" of your system. This is the
7833 hostname portion of the address to be shown on outgoing
7834 news and mail messages. The default is
7835 <var>syshostname</var>, your system's host name. Mail
7836 name ["<var>syshostname</var>"]:
7838 where <var>syshostname</var> is the output of <tt>hostname
7844 <heading>News system configuration</heading>
7847 All the configuration files related to the NNTP (news)
7848 servers and clients should be located under
7849 <file>/etc/news</file>.</p>
7852 There are some configuration issues that apply to a number
7853 of news clients and server packages on the machine. These
7857 <tag><file>/etc/news/organization</file></tag>
7859 A string which should appear as the
7860 organization header for all messages posted
7861 by NNTP clients on the machine
7864 <tag><file>/etc/news/server</file></tag>
7866 Contains the FQDN of the upstream NNTP
7867 server, or localhost if the local machine is
7872 Other global files may be added as required for cross-package news
7879 <heading>Programs for the X Window System</heading>
7882 <heading>Providing X support and package priorities</heading>
7885 Programs that can be configured with support for the X
7886 Window System must be configured to do so and must declare
7887 any package dependencies necessary to satisfy their
7888 runtime requirements when using the X Window System. If
7889 such a package is of higher priority than the X packages
7890 on which it depends, it is required that either the
7891 X-specific components be split into a separate package, or
7892 that an alternative version of the package, which includes
7893 X support, be provided, or that the package's priority be
7899 <heading>Packages providing an X server</heading>
7902 Packages that provide an X server that, directly or
7903 indirectly, communicates with real input and display
7904 hardware should declare in their control data that they
7905 provide the virtual package <tt>xserver</tt>.<footnote>
7906 This implements current practice, and provides an
7907 actual policy for usage of the <tt>xserver</tt>
7908 virtual package which appears in the virtual packages
7909 list. In a nutshell, X servers that interface
7910 directly with the display and input hardware or via
7911 another subsystem (e.g., GGI) should provide
7912 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
7913 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
7919 <heading>Packages providing a terminal emulator</heading>
7922 Packages that provide a terminal emulator for the X Window
7923 System which meet the criteria listed below should declare
7924 in their control data that they provide the virtual
7925 package <tt>x-terminal-emulator</tt>. They should also
7926 register themselves as an alternative for
7927 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
7932 To be an <tt>x-terminal-emulator</tt>, a program must:
7933 <list compact="compact">
7935 Be able to emulate a DEC VT100 terminal, or a
7936 compatible terminal.
7940 Support the command-line option <tt>-e
7941 <var>command</var></tt>, which creates a new
7942 terminal window<footnote>
7943 "New terminal window" does not necessarily mean
7944 a new top-level X window directly parented by
7945 the window manager; it could, if the terminal
7946 emulator application were so coded, be a new
7947 "view" in a multiple-document interface (MDI).
7949 and runs the specified <var>command</var>,
7950 interpreting the entirety of the rest of the command
7951 line as a command to pass straight to exec, in the
7952 manner that <tt>xterm</tt> does.
7956 Support the command-line option <tt>-T
7957 <var>title</var></tt>, which creates a new terminal
7958 window with the window title <var>title</var>.
7965 <heading>Packages providing a window manager</heading>
7968 Packages that provide a window manager should declare in
7969 their control data that they provide the virtual package
7970 <tt>x-window-manager</tt>. They should also register
7971 themselves as an alternative for
7972 <file>/usr/bin/x-window-manager</file>, with a priority
7973 calculated as follows:
7974 <list compact="compact">
7976 Start with a priority of 20.
7980 If the window manager supports the Debian menu
7981 system, add 20 points if this support is available
7982 in the package's default configuration (i.e., no
7983 configuration files belonging to the system or user
7984 have to be edited to activate the feature); if
7985 configuration files must be modified, add only 10
7991 If the window manager complies with <url
7992 id="http://www.freedesktop.org/Standards/wm-spec"
7993 name="The Window Manager Specification Project">,
7994 written by the <url id="http://www.freedesktop.org/"
7995 name="Free Desktop Group">, add 40 points.
7999 If the window manager permits the X session to be
8000 restarted using a <em>different</em> window manager
8001 (without killing the X server) in its default
8002 configuration, add 10 points; otherwise add none.
8009 <heading>Packages providing fonts</heading>
8012 Packages that provide fonts for the X Window
8014 For the purposes of Debian Policy, a "font for the X
8015 Window System" is one which is accessed via X protocol
8016 requests. Fonts for the Linux console, for PostScript
8017 renderer, or any other purpose, do not fit this
8018 definition. Any tool which makes such fonts available
8019 to the X Window System, however, must abide by this
8022 must do a number of things to ensure that they are both
8023 available without modification of the X or font server
8024 configuration, and that they do not corrupt files used by
8025 other font packages to register information about
8029 Fonts of any type supported by the X Window System
8030 must be in a separate binary package from any
8031 executables, libraries, or documentation (except
8032 that specific to the fonts shipped, such as their
8033 license information). If one or more of the fonts
8034 so packaged are necessary for proper operation of
8035 the package with which they are associated the font
8036 package may be Recommended; if the fonts merely
8037 provide an enhancement, a Suggests relationship may
8038 be used. Packages must not Depend on font
8040 This is because the X server may retrieve fonts
8041 from the local file system or over the network
8042 from an X font server; the Debian package system
8043 is empowered to deal only with the local
8049 BDF fonts must be converted to PCF fonts with the
8050 <prgn>bdftopcf</prgn> utility (available in the
8051 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8052 placed in a directory that corresponds to their
8054 <list compact="compact">
8056 100 dpi fonts must be placed in
8057 <file>/usr/share/fonts/X11/100dpi/</file>.
8061 75 dpi fonts must be placed in
8062 <file>/usr/share/fonts/X11/75dpi/</file>.
8066 Character-cell fonts, cursor fonts, and other
8067 low-resolution fonts must be placed in
8068 <file>/usr/share/fonts/X11/misc/</file>.
8074 Speedo fonts must be placed in
8075 <file>/usr/share/fonts/X11/Speedo/</file>.
8079 Type 1 fonts must be placed in
8080 <file>/usr/share/fonts/X11/Type1/</file>. If font
8081 metric files are available, they must be placed here
8086 Subdirectories of <file>/usr/share/fonts/X11/</file>
8087 other than those listed above must be neither
8088 created nor used. (The <file>PEX</file>, <file>CID</file>,
8089 and <file>cyrillic</file> directories are excepted for
8090 historical reasons, but installation of files into
8091 these directories remains discouraged.)
8095 Font packages may, instead of placing files directly
8096 in the X font directories listed above, provide
8097 symbolic links in that font directory pointing to
8098 the files' actual location in the filesystem. Such
8099 a location must comply with the FHS.
8103 Font packages should not contain both 75dpi and
8104 100dpi versions of a font. If both are available,
8105 they should be provided in separate binary packages
8106 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8107 the names of the packages containing the
8108 corresponding fonts.
8112 Fonts destined for the <file>misc</file> subdirectory
8113 should not be included in the same package as 75dpi
8114 or 100dpi fonts; instead, they should be provided in
8115 a separate package with <tt>-misc</tt> appended to
8120 Font packages must not provide the files
8121 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8122 <file>fonts.scale</file> in a font directory:
8125 <file>fonts.dir</file> files must not be provided at all.
8129 <file>fonts.alias</file> and <file>fonts.scale</file>
8130 files, if needed, should be provided in the
8132 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8133 where <var>fontdir</var> is the name of the
8135 <file>/usr/share/fonts/X11/</file> where the
8136 package's corresponding fonts are stored
8137 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8138 <var>package</var> is the name of the package
8139 that provides these fonts, and
8140 <var>extension</var> is either <tt>scale</tt>
8141 or <tt>alias</tt>, whichever corresponds to
8148 Font packages must declare a dependency on
8149 <tt>xfonts-utils</tt> in their control
8154 Font packages that provide one or more
8155 <file>fonts.scale</file> files as described above must
8156 invoke <prgn>update-fonts-scale</prgn> on each
8157 directory into which they installed fonts
8158 <em>before</em> invoking
8159 <prgn>update-fonts-dir</prgn> on that directory.
8160 This invocation must occur in both the
8161 <prgn>postinst</prgn> (for all arguments) and
8162 <prgn>postrm</prgn> (for all arguments except
8163 <tt>upgrade</tt>) scripts.
8167 Font packages that provide one or more
8168 <file>fonts.alias</file> files as described above must
8169 invoke <prgn>update-fonts-alias</prgn> on each
8170 directory into which they installed fonts. This
8171 invocation must occur in both the
8172 <prgn>postinst</prgn> (for all arguments) and
8173 <prgn>postrm</prgn> (for all arguments except
8174 <tt>upgrade</tt>) scripts.
8178 Font packages must invoke
8179 <prgn>update-fonts-dir</prgn> on each directory into
8180 which they installed fonts. This invocation must
8181 occur in both the <prgn>postinst</prgn> (for all
8182 arguments) and <prgn>postrm</prgn> (for all
8183 arguments except <tt>upgrade</tt>) scripts.
8187 Font packages must not provide alias names for the
8188 fonts they include which collide with alias names
8189 already in use by fonts already packaged.
8193 Font packages must not provide fonts with the same
8194 XLFD registry name as another font already packaged.
8201 <heading>Application defaults files</heading>
8204 Application defaults files must be installed in the
8205 directory <file>/etc/X11/app-defaults/</file> (use of a
8206 localized subdirectory of <file>/etc/X11/</file> as described
8207 in the <em>X Toolkit Intrinsics - C Language
8208 Interface</em> manual is also permitted). They must be
8209 registered as <tt>conffile</tt>s or handled as
8210 configuration files. Packages must not provide the
8211 directory <file>/usr/X11R6/lib/X11/app-defaults/</file>.
8215 Customization of programs' X resources may also be
8216 supported with the provision of a file with the same name
8217 as that of the package placed in the
8218 <file>/etc/X11/Xresources/</file> directory, which must
8219 registered as a <tt>conffile</tt> or handled as a
8220 configuration file.<footnote>
8221 Note that this mechanism is not the same as using
8222 app-defaults; app-defaults are tied to the client
8223 binary on the local file system, whereas X resources
8224 are stored in the X server and affect all connecting
8227 <em>Important:</em> packages that install files into the
8228 <file>/etc/X11/Xresources/</file> directory must conflict with
8229 <tt>xbase (<< 3.3.2.3a-2)</tt>; if this is not done
8230 it is possible for the installing package to destroy a
8231 previously-existing <file>/etc/X11/Xresources</file> file
8232 which had been customized by the system administrator.
8237 <heading>Installation directory issues</heading>
8240 Packages using the X Window System should not be
8241 configured to install files under the
8242 <file>/usr/X11R6/</file> directory. The
8243 <file>/usr/X11R6/</file> directory hierarchy should be
8244 regarded as obsolete.
8248 Programs that use GNU <prgn>autoconf</prgn> and
8249 <prgn>automake</prgn> are usually easily configured at
8250 compile time to use <file>/usr/</file> instead of
8251 <file>/usr/X11R6/</file>, and this should be done whenever
8252 possible. Configuration files for window managers and
8253 display managers should be placed in a subdirectory of
8254 <file>/etc/X11/</file> corresponding to the package name due
8255 to these programs' tight integration with the mechanisms
8256 of the X Window System. Application-level programs should
8257 use the <file>/etc/</file> directory unless otherwise mandated
8262 The installation of files into subdirectories
8263 of <file>/usr/X11R6/include/X11/</file> and
8264 <file>/usr/X11R6/lib/X11/</file> is now prohibited;
8265 package maintainers should determine if subdirectories of
8266 <file>/usr/lib/</file> and <file>/usr/share/</file> can be used
8271 Packages should install any relevant files into the
8272 directories <file>/usr/include/X11/</file> and
8273 <file>/usr/lib/X11/</file>, but if they do so, they must
8274 pre-depend on <tt>x11-common (>=
8275 1:7.0.0)</tt><footnote>
8277 These libraries used to be all symbolic
8278 links. However, with <tt>X11R7</tt>,
8279 <tt>/usr/include/X11</tt> and <tt>/usr/lib/X11</tt>
8280 are now real directories, and packages
8281 <strong>should</strong> ship their files here instead
8282 of in <tt>/usr/X11R6/{include,lib}/X11</tt>.
8283 <tt>x11-common (>= 1:7.0.0) </tt> is the package
8284 responsible for converting these symlinks into
8292 <heading>The OSF/Motif and OpenMotif libraries</heading>
8295 <em>Programs that require the non-DFSG-compliant OSF/Motif or
8296 OpenMotif libraries</em><footnote>
8297 OSF/Motif and OpenMotif are collectively referred to as
8298 "Motif" in this policy document.
8300 should be compiled against and tested with LessTif (a free
8301 re-implementation of Motif) instead. If the maintainer
8302 judges that the program or programs do not work
8303 sufficiently well with LessTif to be distributed and
8304 supported, but do so when compiled against Motif, then two
8305 versions of the package should be created; one linked
8306 statically against Motif and with <tt>-smotif</tt>
8307 appended to the package name, and one linked dynamically
8308 against Motif and with <tt>-dmotif</tt> appended to the
8313 Both Motif-linked versions are dependent
8314 upon non-DFSG-compliant software and thus cannot be
8315 uploaded to the <em>main</em> distribution; if the
8316 software is itself DFSG-compliant it may be uploaded to
8317 the <em>contrib</em> distribution. While known existing
8318 versions of Motif permit unlimited redistribution of
8319 binaries linked against the library (whether statically or
8320 dynamically), it is the package maintainer's
8321 responsibility to determine whether this is permitted by
8322 the license of the copy of Motif in their possession.
8328 <heading>Perl programs and modules</heading>
8331 Perl programs and modules should follow the current Perl policy.
8335 The Perl policy can be found in the <tt>perl-policy</tt>
8336 files in the <tt>debian-policy</tt> package.
8337 It is also available from the Debian web mirrors at
8338 <tt><url name="/doc/packaging-manuals/perl-policy/"
8339 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
8344 <heading>Emacs lisp programs</heading>
8347 Please refer to the "Debian Emacs Policy" for details of how to
8348 package emacs lisp programs.
8352 The Emacs policy is available in
8353 <file>debian-emacs-policy.gz</file> of the
8354 <package>emacsen-common</package> package.
8355 It is also available from the Debian web mirrors at
8356 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
8357 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
8362 <heading>Games</heading>
8365 The permissions on <file>/var/games</file> are mode 755, owner
8366 <tt>root</tt> and group <tt>root</tt>.
8370 Each game decides on its own security policy.</p>
8373 Games which require protected, privileged access to
8374 high-score files, saved games, etc., may be made
8375 set-<em>group</em>-id (mode 2755) and owned by
8376 <tt>root.games</tt>, and use files and directories with
8377 appropriate permissions (770 <tt>root.games</tt>, for
8378 example). They must not be made
8379 set-<em>user</em>-id, as this causes security problems. (If
8380 an attacker can subvert any set-user-id game they can
8381 overwrite the executable of any other, causing other players
8382 of these games to run a Trojan horse program. With a
8383 set-group-id game the attacker only gets access to less
8384 important game data, and if they can get at the other
8385 players' accounts at all it will take considerably more
8389 Some packages, for example some fortune cookie programs, are
8390 configured by the upstream authors to install with their
8391 data files or other static information made unreadable so
8392 that they can only be accessed through set-id programs
8393 provided. You should not do this in a Debian package: anyone can
8394 download the <file>.deb</file> file and read the data from it,
8395 so there is no point making the files unreadable. Not
8396 making the files unreadable also means that you don't have
8397 to make so many programs set-id, which reduces the risk of a
8401 As described in the FHS, binaries of games should be
8402 installed in the directory <file>/usr/games</file>. This also
8403 applies to games that use the X Window System. Manual pages
8404 for games (X and non-X games) should be installed in
8405 <file>/usr/share/man/man6</file>.</p>
8411 <heading>Documentation</heading>
8414 <heading>Manual pages</heading>
8417 You should install manual pages in <prgn>nroff</prgn> source
8418 form, in appropriate places under <file>/usr/share/man</file>.
8419 You should only use sections 1 to 9 (see the FHS for more
8420 details). You must not install a pre-formatted "cat page".
8424 Each program, utility, and function should have an
8425 associated manual page included in the same package. It is
8426 suggested that all configuration files also have a manual
8427 page included as well. Manual pages for protocols and other
8428 auxiliary things are optional.
8432 If no manual page is available, this is considered as a bug
8433 and should be reported to the Debian Bug Tracking System (the
8434 maintainer of the package is allowed to write this bug report
8435 themselves, if they so desire). Do not close the bug report
8436 until a proper man page is available.<footnote>
8437 It is not very hard to write a man page. See the
8438 <url id="http://www.schweikhardt.net/man_page_howto.html"
8439 name="Man-Page-HOWTO">,
8440 <manref name="man" section="7">, the examples
8441 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
8442 the helper programs <prgn>help2man</prgn>, or the
8443 directory <file>/usr/share/doc/man-db/examples</file>.
8448 You may forward a complaint about a missing man page to the
8449 upstream authors, and mark the bug as forwarded in the
8450 Debian bug tracking system. Even though the GNU Project do
8451 not in general consider the lack of a man page to be a bug,
8452 we do; if they tell you that they don't consider it a bug
8453 you should leave the bug in our bug tracking system open
8458 Manual pages should be installed compressed using <tt>gzip -9</tt>.
8462 If one man page needs to be accessible via several names it
8463 is better to use a symbolic link than the <file>.so</file>
8464 feature, but there is no need to fiddle with the relevant
8465 parts of the upstream source to change from <file>.so</file> to
8466 symlinks: don't do it unless it's easy. You should not
8467 create hard links in the manual page directories, nor put
8468 absolute filenames in <file>.so</file> directives. The filename
8469 in a <file>.so</file> in a man page should be relative to the
8470 base of the man page tree (usually
8471 <file>/usr/share/man</file>). If you do not create any links
8472 (whether symlinks, hard links, or <tt>.so</tt> directives)
8473 in the file system to the alternate names of the man page,
8474 then you should not rely on <prgn>man</prgn> finding your
8475 man page under those names based solely on the information in
8476 the man page's header.<footnote>
8477 Supporting this in <prgn>man</prgn> often requires
8478 unreasonable processing time to find a manual page or to
8479 report that none exists, and moves knowledge into man's
8480 database that would be better left in the file system.
8481 This support is therefore deprecated and will cease to
8482 be present in the future.
8488 <heading>Info documents</heading>
8491 Info documents should be installed in <file>/usr/share/info</file>.
8492 They should be compressed with <tt>gzip -9</tt>.
8496 Your package should call <prgn>install-info</prgn> to update
8497 the Info <file>dir</file> file in its <prgn>postinst</prgn>
8498 script when called with a <tt>configure</tt> argument, for
8500 <example compact="compact">
8501 install-info --quiet --section Development Development \
8502 /usr/share/info/foobar.info
8506 It is a good idea to specify a section for the location of
8507 your program; this is done with the <tt>--section</tt>
8508 switch. To determine which section to use, you should look
8509 at <file>/usr/share/info/dir</file> on your system and choose the most
8510 relevant (or create a new section if none of the current
8511 sections are relevant). Note that the <tt>--section</tt>
8512 flag takes two arguments; the first is a regular expression
8513 to match (case-insensitively) against an existing section,
8514 the second is used when creating a new one.</p>
8517 You should remove the entries in the <prgn>prerm</prgn>
8518 script when called with a <tt>remove</tt> argument:
8519 <example compact="compact">
8520 install-info --quiet --remove /usr/share/info/foobar.info
8524 If <prgn>install-info</prgn> cannot find a description entry
8525 in the Info file you must supply one. See <manref
8526 name="install-info" section="8"> for details.</p>
8530 <heading>Additional documentation</heading>
8533 Any additional documentation that comes with the package may
8534 be installed at the discretion of the package maintainer.
8535 Plain text documentation should be installed in the directory
8536 <file>/usr/share/doc/<var>package</var></file>, where
8537 <var>package</var> is the name of the package, and
8538 compressed with <tt>gzip -9</tt> unless it is small.
8542 If a package comes with large amounts of documentation which
8543 many users of the package will not require you should create
8544 a separate binary package to contain it, so that it does not
8545 take up disk space on the machines of users who do not need
8546 or want it installed.</p>
8549 It is often a good idea to put text information files
8550 (<file>README</file>s, changelogs, and so forth) that come with
8551 the source package in <file>/usr/share/doc/<var>package</var></file>
8552 in the binary package. However, you don't need to install
8553 the instructions for building and installing the package, of
8557 Packages must not require the existence of any files in
8558 <file>/usr/share/doc/</file> in order to function
8560 The system administrator should be able to
8561 delete files in <file>/usr/share/doc/</file> without causing
8562 any programs to break.
8564 Any files that are referenced by programs but are also
8565 useful as stand alone documentation should be installed under
8566 <file>/usr/share/<var>package</var>/</file> with symbolic links from
8567 <file>/usr/share/doc/<var>package</var></file>.
8571 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8572 link to another directory in <file>/usr/share/doc</file> only if
8573 the two packages both come from the same source and the
8574 first package Depends on the second.<footnote>
8576 Please note that this does not override the section on
8577 changelog files below, so the file
8578 <file>/usr/share/<var>package</var>/changelog.Debian.gz</file>
8579 must refer to the changelog for the current version of
8580 <var>package</var> in question. In practice, this means
8581 that the sources of the target and the destination of the
8582 symlink must be the same (same source package and
8589 Former Debian releases placed all additional documentation
8590 in <file>/usr/doc/<var>package</var></file>. This has been
8591 changed to <file>/usr/share/doc/<var>package</var></file>,
8592 and packages must not put documentation in the directory
8593 <file>/usr/doc/<var>package</var></file>. <footnote>
8594 At this phase of the transition, we no longer require a
8595 symbolic link in <file>/usr/doc/</file>. At a later point,
8596 policy shall change to make the symbolic links a bug.
8602 <heading>Preferred documentation formats</heading>
8605 The unification of Debian documentation is being carried out
8609 If your package comes with extensive documentation in a
8610 markup format that can be converted to various other formats
8611 you should if possible ship HTML versions in a binary
8612 package, in the directory
8613 <file>/usr/share/doc/<var>appropriate-package</var></file> or
8614 its subdirectories.<footnote>
8615 The rationale: The important thing here is that HTML
8616 docs should be available in <em>some</em> package, not
8617 necessarily in the main binary package.
8622 Other formats such as PostScript may be provided at the
8623 package maintainer's discretion.
8627 <sect id="copyrightfile">
8628 <heading>Copyright information</heading>
8631 Every package must be accompanied by a verbatim copy of its
8632 copyright and distribution license in the file
8633 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
8634 file must neither be compressed nor be a symbolic link.
8638 In addition, the copyright file must say where the upstream
8639 sources (if any) were obtained. It should name the original
8640 authors of the package and the Debian maintainer(s) who were
8641 involved with its creation.</p>
8644 A copy of the file which will be installed in
8645 <file>/usr/share/doc/<var>package</var>/copyright</file> should
8646 be in <file>debian/copyright</file> in the source package.
8650 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8651 link to another directory in <file>/usr/share/doc</file> only if
8652 the two packages both come from the same source and the
8653 first package Depends on the second. These rules are
8654 important because copyrights must be extractable by
8659 Packages distributed under the UCB BSD license, the Artistic
8660 license, the GNU GPL, and the GNU LGPL, should refer to the
8661 corresponding files under
8662 <file>/usr/share/common-licenses</file>,<footnote>
8665 <file>/usr/share/common-licenses/Artistic</file>,
8666 <file>/usr/share/common-licenses/BSD</file>,
8667 <file>/usr/share/common-licenses/GPL</file>,
8668 <file>/usr/share/common-licenses/LGPL</file>,
8669 <file>/usr/share/common-licenses/GFDL</file>,
8670 <file>/usr/share/common-licenses/GPL-2</file>, and
8671 <file>/usr/share/common-licenses/LGPL-2.1</file>, and so
8672 on. Note that the GFDL is new here, and the license file
8673 may not yet be in place in
8674 <file>/usr/share/common-licenses/GFDL</file>.
8676 </footnote> rather than quoting them in the copyright
8681 You should not use the copyright file as a general <file>README</file>
8682 file. If your package has such a file it should be
8683 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
8684 <file>README.Debian</file> or some other appropriate place.</p>
8688 <heading>Examples</heading>
8691 Any examples (configurations, source files, whatever),
8692 should be installed in a directory
8693 <file>/usr/share/doc/<var>package</var>/examples</file>. These
8694 files should not be referenced by any program: they're there
8695 for the benefit of the system administrator and users as
8696 documentation only. Architecture-specific example files
8697 should be installed in a directory
8698 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
8700 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
8701 latter directory itself may be a symbolic link to the
8706 If the purpose of a package is to provide examples, then the
8707 example files may be installed into
8708 <file>/usr/share/doc/<var>package</var></file>.
8712 <sect id="changelogs">
8713 <heading>Changelog files</heading>
8716 Packages that are not Debian-native must contain a
8717 compressed copy of the <file>debian/changelog</file> file from
8718 the Debian source tree in
8719 <file>/usr/share/doc/<var>package</var></file> with the name
8720 <file>changelog.Debian.gz</file>.
8724 If an upstream changelog is available, it should be accessible as
8725 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
8726 plain text. If the upstream changelog is distributed in
8727 HTML, it should be made available in that form as
8728 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
8729 and a plain text <file>changelog.gz</file> should be generated
8730 from it using, for example, <tt>lynx -dump -nolist</tt>. If
8731 the upstream changelog files do not already conform to this
8732 naming convention, then this may be achieved either by
8733 renaming the files, or by adding a symbolic link, at the
8734 maintainer's discretion.<footnote>
8735 Rationale: People should not have to look in places for
8736 upstream changelogs merely because they are given
8737 different names or are distributed in HTML format.
8742 All of these files should be installed compressed using
8743 <tt>gzip -9</tt>, as they will become large with time even
8744 if they start out small.
8748 If the package has only one changelog which is used both as
8749 the Debian changelog and the upstream one because there is
8750 no separate upstream maintainer then that changelog should
8751 usually be installed as
8752 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
8753 there is a separate upstream maintainer, but no upstream
8754 changelog, then the Debian changelog should still be called
8755 <file>changelog.Debian.gz</file>.
8759 For details about the format and contents of the Debian
8760 changelog file, please see <ref id="dpkgchangelog">.
8765 <appendix id="pkg-scope">
8766 <heading>Introduction and scope of these appendices</heading>
8769 These appendices are taken essentially verbatim from the
8770 now-deprecated Packaging Manual, version 3.2.1.0. They are
8771 the chapters which are likely to be of use to package
8772 maintainers and which have not already been included in the
8773 policy document itself. Most of these sections are very likely
8774 not relevant to policy; they should be treated as
8775 documentation for the packaging system. Please note that these
8776 appendices are included for convenience, and for historical
8777 reasons: they used to be part of policy package, and they have
8778 not yet been incorporated into dpkg documentation. However,
8779 they still have value, and hence they are presented here.
8783 They have not yet been checked to ensure that they are
8784 compatible with the contents of policy, and if there are any
8785 contradictions, the version in the main policy document takes
8786 precedence. The remaining chapters of the old Packaging
8787 Manual have also not been read in detail to ensure that there
8788 are not parts which have been left out. Both of these will be
8793 Certain parts of the Packaging manual were integrated into the
8794 Policy Manual proper, and removed from the appendices. Links
8795 have been placed from the old locations to the new ones.
8799 <prgn>dpkg</prgn> is a suite of programs for creating binary
8800 package files and installing and removing them on Unix
8802 <prgn>dpkg</prgn> is targeted primarily at Debian
8803 GNU/Linux, but may work on or be ported to other
8809 The binary packages are designed for the management of
8810 installed executable programs (usually compiled binaries) and
8811 their associated data, though source code examples and
8812 documentation are provided as part of some packages.</p>
8815 This manual describes the technical aspects of creating Debian
8816 binary packages (<file>.deb</file> files). It documents the
8817 behavior of the package management programs
8818 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
8819 they interact with packages.</p>
8822 It also documents the interaction between
8823 <prgn>dselect</prgn>'s core and the access method scripts it
8824 uses to actually install the selected packages, and describes
8825 how to create a new access method.</p>
8828 This manual does not go into detail about the options and
8829 usage of the package building and installation tools. It
8830 should therefore be read in conjunction with those programs'
8835 The utility programs which are provided with <prgn>dpkg</prgn>
8836 for managing various system configuration and similar issues,
8837 such as <prgn>update-rc.d</prgn> and
8838 <prgn>install-info</prgn>, are not described in detail here -
8839 please see their man pages.
8843 It is assumed that the reader is reasonably familiar with the
8844 <prgn>dpkg</prgn> System Administrators' manual.
8845 Unfortunately this manual does not yet exist.
8849 The Debian version of the FSF's GNU hello program is provided
8850 as an example for people wishing to create Debian
8851 packages. The Debian <prgn>debmake</prgn> package is
8852 recommended as a very helpful tool in creating and maintaining
8853 Debian packages. However, while the tools and examples are
8854 helpful, they do not replace the need to read and follow the
8855 Policy and Programmer's Manual.</p>
8858 <appendix id="pkg-binarypkg">
8859 <heading>Binary packages (from old Packaging Manual)</heading>
8862 The binary package has two main sections. The first part
8863 consists of various control information files and scripts used
8864 by <prgn>dpkg</prgn> when installing and removing. See <ref
8865 id="pkg-controlarea">.
8869 The second part is an archive containing the files and
8870 directories to be installed.
8874 In the future binary packages may also contain other
8875 components, such as checksums and digital signatures. The
8876 format for the archive is described in full in the
8877 <file>deb(5)</file> man page.
8881 <sect id="pkg-bincreating"><heading>Creating package files -
8882 <prgn>dpkg-deb</prgn>
8886 All manipulation of binary package files is done by
8887 <prgn>dpkg-deb</prgn>; it's the only program that has
8888 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
8889 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
8890 will spot that the options requested are appropriate to
8891 <prgn>dpkg-deb</prgn> and invoke that instead with the same
8896 In order to create a binary package you must make a
8897 directory tree which contains all the files and directories
8898 you want to have in the file system data part of the package.
8899 In Debian-format source packages this directory is usually
8900 <file>debian/tmp</file>, relative to the top of the package's
8905 They should have the locations (relative to the root of the
8906 directory tree you're constructing) ownerships and
8907 permissions which you want them to have on the system when
8912 With current versions of <prgn>dpkg</prgn> the uid/username
8913 and gid/groupname mappings for the users and groups being
8914 used should be the same on the system where the package is
8915 built and the one where it is installed.
8919 You need to add one special directory to the root of the
8920 miniature file system tree you're creating:
8921 <prgn>DEBIAN</prgn>. It should contain the control
8922 information files, notably the binary package control file
8923 (see <ref id="pkg-controlfile">).
8927 The <prgn>DEBIAN</prgn> directory will not appear in the
8928 file system archive of the package, and so won't be installed
8929 by <prgn>dpkg</prgn> when the package is installed.
8933 When you've prepared the package, you should invoke:
8935 dpkg --build <var>directory</var>
8940 This will build the package in
8941 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
8942 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
8943 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
8948 See the man page <manref name="dpkg-deb" section="8"> for details of how
8949 to examine the contents of this newly-created file. You may find the
8950 output of following commands enlightening:
8952 dpkg-deb --info <var>filename</var>.deb
8953 dpkg-deb --contents <var>filename</var>.deb
8954 dpkg --contents <var>filename</var>.deb
8956 To view the copyright file for a package you could use this command:
8958 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - \*/copyright | pager
8963 <sect id="pkg-controlarea">
8964 <heading>Package control information files</heading>
8967 The control information portion of a binary package is a
8968 collection of files with names known to <prgn>dpkg</prgn>.
8969 It will treat the contents of these files specially - some
8970 of them contain information used by <prgn>dpkg</prgn> when
8971 installing or removing the package; others are scripts which
8972 the package maintainer wants <prgn>dpkg</prgn> to run.
8976 It is possible to put other files in the package control
8977 area, but this is not generally a good idea (though they
8978 will largely be ignored).
8982 Here is a brief list of the control info files supported by
8983 <prgn>dpkg</prgn> and a summary of what they're used for.
8988 <tag><tt>control</tt>
8991 This is the key description file used by
8992 <prgn>dpkg</prgn>. It specifies the package's name
8993 and version, gives its description for the user,
8994 states its relationships with other packages, and so
8995 forth. See <ref id="sourcecontrolfiles"> and
8996 <ref id="binarycontrolfiles">.
9000 It is usually generated automatically from information
9001 in the source package by the
9002 <prgn>dpkg-gencontrol</prgn> program, and with
9003 assistance from <prgn>dpkg-shlibdeps</prgn>.
9004 See <ref id="pkg-sourcetools">.
9008 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9013 These are executable files (usually scripts) which
9014 <prgn>dpkg</prgn> runs during installation, upgrade
9015 and removal of packages. They allow the package to
9016 deal with matters which are particular to that package
9017 or require more complicated processing than that
9018 provided by <prgn>dpkg</prgn>. Details of when and
9019 how they are called are in <ref id="maintainerscripts">.
9023 It is very important to make these scripts idempotent.
9024 See <ref id="idempotency">.
9028 The maintainer scripts are guaranteed to run with a
9029 controlling terminal and can interact with the user.
9030 See <ref id="controllingterminal">.
9034 <tag><tt>conffiles</tt>
9037 This file contains a list of configuration files which
9038 are to be handled automatically by <prgn>dpkg</prgn>
9039 (see <ref id="pkg-conffiles">). Note that not necessarily
9040 every configuration file should be listed here.
9043 <tag><tt>shlibs</tt>
9046 This file contains a list of the shared libraries
9047 supplied by the package, with dependency details for
9048 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9049 when it determines what dependencies are required in a
9050 package control file. The <tt>shlibs</tt> file format
9051 is described on <ref id="shlibs">.
9056 <sect id="pkg-controlfile">
9057 <heading>The main control information file: <tt>control</tt></heading>
9060 The most important control information file used by
9061 <prgn>dpkg</prgn> when it installs a package is
9062 <tt>control</tt>. It contains all the package's "vital
9067 The binary package control files of packages built from
9068 Debian sources are made by a special tool,
9069 <prgn>dpkg-gencontrol</prgn>, which reads
9070 <file>debian/control</file> and <file>debian/changelog</file> to
9071 find the information it needs. See <ref id="pkg-sourcepkg"> for
9076 The fields in binary package control files are listed in
9077 <ref id="binarycontrolfiles">.
9081 A description of the syntax of control files and the purpose
9082 of the fields is available in <ref id="controlfields">.
9087 <heading>Time Stamps</heading>
9090 See <ref id="timestamps">.
9095 <appendix id="pkg-sourcepkg">
9096 <heading>Source packages (from old Packaging Manual) </heading>
9099 The Debian binary packages in the distribution are generated
9100 from Debian sources, which are in a special format to assist
9101 the easy and automatic building of binaries.
9104 <sect id="pkg-sourcetools">
9105 <heading>Tools for processing source packages</heading>
9108 Various tools are provided for manipulating source packages;
9109 they pack and unpack sources and help build of binary
9110 packages and help manage the distribution of new versions.
9114 They are introduced and typical uses described here; see
9115 <manref name="dpkg-source" section="1"> for full
9116 documentation about their arguments and operation.
9120 For examples of how to construct a Debian source package,
9121 and how to use those utilities that are used by Debian
9122 source packages, please see the <prgn>hello</prgn> example
9126 <sect1 id="pkg-dpkg-source">
9128 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9133 This program is frequently used by hand, and is also
9134 called from package-independent automated building scripts
9135 such as <prgn>dpkg-buildpackage</prgn>.
9139 To unpack a package it is typically invoked with
9141 dpkg-source -x <var>.../path/to/filename</var>.dsc
9146 with the <file><var>filename</var>.tar.gz</file> and
9147 <file><var>filename</var>.diff.gz</file> (if applicable) in
9148 the same directory. It unpacks into
9149 <file><var>package</var>-<var>version</var></file>, and if
9151 <file><var>package</var>-<var>version</var>.orig</file>, in
9152 the current directory.
9156 To create a packed source archive it is typically invoked:
9158 dpkg-source -b <var>package</var>-<var>version</var>
9163 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
9164 <file>.diff.gz</file> (if appropriate) in the current
9165 directory. <prgn>dpkg-source</prgn> does not clean the
9166 source tree first - this must be done separately if it is
9171 See also <ref id="pkg-sourcearchives">.</p>
9175 <sect1 id="pkg-dpkg-buildpackage">
9177 <prgn>dpkg-buildpackage</prgn> - overall package-building
9182 <prgn>dpkg-buildpackage</prgn> is a script which invokes
9183 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
9184 targets <tt>clean</tt>, <tt>build</tt> and
9185 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
9186 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
9187 source and binary package upload.
9191 It is usually invoked by hand from the top level of the
9192 built or unbuilt source directory. It may be invoked with
9193 no arguments; useful arguments include:
9194 <taglist compact="compact">
9195 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
9198 Do not sign the <tt>.changes</tt> file or the
9199 source package <tt>.dsc</tt> file, respectively.</p>
9201 <tag><tt>-p<var>sign-command</var></tt></tag>
9204 Invoke <var>sign-command</var> instead of finding
9205 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
9206 <var>sign-command</var> must behave just like
9207 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
9209 <tag><tt>-r<var>root-command</var></tt></tag>
9212 When root privilege is required, invoke the command
9213 <var>root-command</var>. <var>root-command</var>
9214 should invoke its first argument as a command, from
9215 the <prgn>PATH</prgn> if necessary, and pass its
9216 second and subsequent arguments to the command it
9217 calls. If no <var>root-command</var> is supplied
9218 then <var>dpkg-buildpackage</var> will take no
9219 special action to gain root privilege, so that for
9220 most packages it will have to be invoked as root to
9223 <tag><tt>-b</tt>, <tt>-B</tt></tag>
9226 Two types of binary-only build and upload - see
9227 <manref name="dpkg-source" section="1">.
9234 <sect1 id="pkg-dpkg-gencontrol">
9236 <prgn>dpkg-gencontrol</prgn> - generates binary package
9241 This program is usually called from <file>debian/rules</file>
9242 (see <ref id="pkg-sourcetree">) in the top level of the source
9247 This is usually done just before the files and directories in the
9248 temporary directory tree where the package is being built have their
9249 permissions and ownerships set and the package is constructed using
9250 <prgn>dpkg-deb/</prgn>
9252 This is so that the control file which is produced has
9253 the right permissions
9258 <prgn>dpkg-gencontrol</prgn> must be called after all the
9259 files which are to go into the package have been placed in
9260 the temporary build directory, so that its calculation of
9261 the installed size of a package is correct.
9265 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
9266 be run after <prgn>dpkg-shlibdeps</prgn> so that the
9267 variable substitutions created by
9268 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
9273 For a package which generates only one binary package, and
9274 which builds it in <file>debian/tmp</file> relative to the top
9275 of the source package, it is usually sufficient to call
9276 <prgn>dpkg-gencontrol</prgn>.
9280 Sources which build several binaries will typically need
9283 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
9284 </example> The <tt>-P</tt> tells
9285 <prgn>dpkg-gencontrol</prgn> that the package is being
9286 built in a non-default directory, and the <tt>-p</tt>
9287 tells it which package's control file should be generated.
9291 <prgn>dpkg-gencontrol</prgn> also adds information to the
9292 list of files in <file>debian/files</file>, for the benefit of
9293 (for example) a future invocation of
9294 <prgn>dpkg-genchanges</prgn>.</p>
9297 <sect1 id="pkg-dpkg-shlibdeps">
9299 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
9304 This program is usually called from <file>debian/rules</file>
9305 just before <prgn>dpkg-gencontrol</prgn> (see <ref
9306 id="pkg-sourcetree">), in the top level of the source tree.
9310 Its arguments are executables.
9313 In a forthcoming dpkg version,
9314 <prgn>dpkg-shlibdeps</prgn> would be required to be
9315 called on shared libraries as well.
9318 They may be specified either in the locations in the
9319 source tree where they are created or in the locations
9320 in the temporary build tree where they are installed
9321 prior to binary package creation.
9323 </footnote> for which shared library dependencies should
9324 be included in the binary package's control file.
9328 If some of the found shared libraries should only
9329 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
9330 some warrant a <tt>Pre-Depends</tt>, this can be achieved
9331 by using the <tt>-d<var>dependency-field</var></tt> option
9332 before those executable(s). (Each <tt>-d</tt> option
9333 takes effect until the next <tt>-d</tt>.)
9337 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
9338 output control file to be modified. Instead by default it
9339 adds to the <file>debian/substvars</file> file variable
9340 settings like <tt>shlibs:Depends</tt>. These variable
9341 settings must be referenced in dependency fields in the
9342 appropriate per-binary-package sections of the source
9347 For example, a package that generates an essential part
9348 which requires dependencies, and optional parts that
9349 which only require a recommendation, would separate those
9350 two sets of dependencies into two different fields.<footnote>
9351 At the time of writing, an example for this was the
9352 <package/xmms/ package, with Depends used for the xmms
9353 executable, Recommends for the plug-ins and Suggests for
9354 even more optional features provided by unzip.
9356 It can say in its <file>debian/rules</file>:
9358 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
9359 -dRecommends <var>optionalpart anotheroptionalpart</var>
9361 and then in its main control file <file>debian/control</file>:
9364 Depends: ${shlibs:Pre-Depends}
9365 Recommends: ${shlibs:Recommends}
9371 Sources which produce several binary packages with
9372 different shared library dependency requirements can use
9373 the <tt>-p<var>varnameprefix</var></tt> option to override
9374 the default <tt>shlibs:</tt> prefix (one invocation of
9375 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
9376 They can thus produce several sets of dependency
9377 variables, each of the form
9378 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
9379 which can be referred to in the appropriate parts of the
9380 binary package control files.
9385 <sect1 id="pkg-dpkg-distaddfile">
9387 <prgn>dpkg-distaddfile</prgn> - adds a file to
9388 <file>debian/files</file>
9392 Some packages' uploads need to include files other than
9393 the source and binary package files.
9397 <prgn>dpkg-distaddfile</prgn> adds a file to the
9398 <file>debian/files</file> file so that it will be included in
9399 the <file>.changes</file> file when
9400 <prgn>dpkg-genchanges</prgn> is run.
9404 It is usually invoked from the <tt>binary</tt> target of
9405 <file>debian/rules</file>:
9407 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
9409 The <var>filename</var> is relative to the directory where
9410 <prgn>dpkg-genchanges</prgn> will expect to find it - this
9411 is usually the directory above the top level of the source
9412 tree. The <file>debian/rules</file> target should put the
9413 file there just before or just after calling
9414 <prgn>dpkg-distaddfile</prgn>.
9418 The <var>section</var> and <var>priority</var> are passed
9419 unchanged into the resulting <file>.changes</file> file.
9424 <sect1 id="pkg-dpkg-genchanges">
9426 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
9431 This program is usually called by package-independent
9432 automatic building scripts such as
9433 <prgn>dpkg-buildpackage</prgn>, but it may also be called
9438 It is usually called in the top level of a built source
9439 tree, and when invoked with no arguments will print out a
9440 straightforward <file>.changes</file> file based on the
9441 information in the source package's changelog and control
9442 file and the binary and source packages which should have
9448 <sect1 id="pkg-dpkg-parsechangelog">
9450 <prgn>dpkg-parsechangelog</prgn> - produces parsed
9451 representation of a changelog
9455 This program is used internally by
9456 <prgn>dpkg-source</prgn> et al. It may also occasionally
9457 be useful in <file>debian/rules</file> and elsewhere. It
9458 parses a changelog, <file>debian/changelog</file> by default,
9459 and prints a control-file format representation of the
9460 information in it to standard output.
9464 <sect1 id="pkg-dpkg-architecture">
9466 <prgn>dpkg-architecture</prgn> - information about the build and
9471 This program can be used manually, but is also invoked by
9472 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
9473 to set environment or make variables which specify the build and
9474 host architecture for the package building process.
9479 <sect id="pkg-sourcetree">
9480 <heading>The Debianised source tree</heading>
9483 The source archive scheme described later is intended to
9484 allow a Debianised source tree with some associated control
9485 information to be reproduced and transported easily. The
9486 Debianised source tree is a version of the original program
9487 with certain files added for the benefit of the
9488 Debianisation process, and with any other changes required
9489 made to the rest of the source code and installation
9494 The extra files created for Debian are in the subdirectory
9495 <file>debian</file> of the top level of the Debianised source
9496 tree. They are described below.
9499 <sect1 id="pkg-debianrules">
9500 <heading><file>debian/rules</file> - the main building script</heading>
9503 See <ref id="debianrules">.
9508 <sect1 id="pkg-dpkgchangelog">
9509 <heading><file>debian/changelog</file></heading>
9512 See <ref id="dpkgchangelog">.
9516 It is recommended that the entire changelog be encoded in the
9517 <url id="http://www.cis.ohio-state.edu/cgi-bin/rfc/rfc2279.html" name="UTF-8">
9519 <url id="http://www.unicode.org/"
9520 name="Unicode">.<footnote>
9522 I think it is fairly obvious that we need to
9523 eventually transition to UTF-8 for our package
9524 infrastructure; it is really the only sane char-set in
9525 an international environment. Now, we can't switch to
9526 using UTF-8 for package control fields and the like
9527 until dpkg has better support, but one thing we can
9528 start doing today is requesting that Debian changelogs
9529 are UTF-8 encoded. At some point in time, we can start
9530 requiring them to do so.
9533 Checking for non-UTF8 characters in a changelog is
9534 trivial. Dump the file through
9535 <example>iconv -f utf-8 -t ucs-4</example>
9536 discard the output, and check the return
9537 value. If there are any characters in the stream
9538 which are invalid UTF-8 sequences, iconv will exit
9539 with an error code; and this will be the case for the
9540 vast majority of other character sets.
9545 <sect2><heading>Defining alternative changelog formats
9549 It is possible to use a different format to the standard
9550 one, by providing a parser for the format you wish to
9555 In order to have <tt>dpkg-parsechangelog</tt> run your
9556 parser, you must include a line within the last 40 lines
9557 of your file matching the Perl regular expression:
9558 <tt>\schangelog-format:\s+([0-9a-z]+)\W</tt> The part in
9559 parentheses should be the name of the format. For
9560 example, you might say:
9562 @@@ changelog-format: joebloggs @@@
9564 Changelog format names are non-empty strings of alphanumerics.
9568 If such a line exists then <tt>dpkg-parsechangelog</tt>
9569 will look for the parser as
9570 <file>/usr/lib/dpkg/parsechangelog/<var>format-name</var></file>
9572 <file>/usr/local/lib/dpkg/parsechangelog/<var>format-name</var></file>;
9573 it is an error for it not to find it, or for it not to
9574 be an executable program. The default changelog format
9575 is <tt>dpkg</tt>, and a parser for it is provided with
9576 the <tt>dpkg</tt> package.
9580 The parser will be invoked with the changelog open on
9581 standard input at the start of the file. It should read
9582 the file (it may seek if it wishes) to determine the
9583 information required and return the parsed information
9584 to standard output in the form of a series of control
9585 fields in the standard format. By default it should
9586 return information about only the most recent version in
9587 the changelog; it should accept a
9588 <tt>-v<var>version</var></tt> option to return changes
9589 information from all versions present <em>strictly
9590 after</em> <var>version</var>, and it should then be an
9591 error for <var>version</var> not to be present in the
9597 <list compact="compact">
9598 <item><qref id="f-Source"><tt>Source</tt></qref></item>
9599 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
9600 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
9601 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (mandatory)</item>
9602 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
9603 <item><qref id="f-Date"><tt>Date</tt></qref></item>
9604 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
9609 If several versions are being returned (due to the use
9610 of <tt>-v</tt>), the urgency value should be of the
9611 highest urgency code listed at the start of any of the
9612 versions requested followed by the concatenated
9613 (space-separated) comments from all the versions
9614 requested; the maintainer, version, distribution and
9615 date should always be from the most recent version.
9619 For the format of the <tt>Changes</tt> field see
9620 <ref id="f-Changes">.
9624 If the changelog format which is being parsed always or
9625 almost always leaves a blank line between individual
9626 change notes these blank lines should be stripped out,
9627 so as to make the resulting output compact.
9631 If the changelog format does not contain date or package
9632 name information this information should be omitted from
9633 the output. The parser should not attempt to synthesize
9634 it or find it from other sources.
9638 If the changelog does not have the expected format the
9639 parser should exit with a nonzero exit status, rather
9640 than trying to muddle through and possibly generating
9645 A changelog parser may not interact with the user at
9651 <sect1 id="pkg-srcsubstvars">
9652 <heading><file>debian/substvars</file> and variable substitutions</heading>
9655 See <ref id="substvars">.
9661 <heading><file>debian/files</file></heading>
9664 See <ref id="debianfiles">.
9668 <sect1><heading><file>debian/tmp</file>
9672 This is the canonical temporary location for the
9673 construction of binary packages by the <tt>binary</tt>
9674 target. The directory <file>tmp</file> serves as the root of
9675 the file system tree as it is being constructed (for
9676 example, by using the package's upstream makefiles install
9677 targets and redirecting the output there), and it also
9678 contains the <tt>DEBIAN</tt> subdirectory. See <ref
9679 id="pkg-bincreating">.
9683 If several binary packages are generated from the same
9684 source tree it is usual to use several
9685 <file>debian/tmp<var>something</var></file> directories, for
9686 example <file>tmp-a</file> or <file>tmp-doc</file>.
9690 Whatever <file>tmp</file> directories are created and used by
9691 <tt>binary</tt> must of course be removed by the
9692 <tt>clean</tt> target.</p></sect1>
9696 <sect id="pkg-sourcearchives"><heading>Source packages as archives
9700 As it exists on the FTP site, a Debian source package
9701 consists of three related files. You must have the right
9702 versions of all three to be able to use them.
9707 <tag>Debian source control file - <tt>.dsc</tt></tag>
9709 This file is a control file used by <prgn>dpkg-source</prgn>
9710 to extract a source package.
9711 See <ref id="debiansourcecontrolfiles">.
9715 Original source archive -
9717 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
9723 This is a compressed (with <tt>gzip -9</tt>)
9724 <prgn>tar</prgn> file containing the source code from
9725 the upstream authors of the program.
9730 Debianisation diff -
9732 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
9738 This is a unified context diff (<tt>diff -u</tt>)
9739 giving the changes which are required to turn the
9740 original source into the Debian source. These changes
9741 may only include editing and creating plain files.
9742 The permissions of files, the targets of symbolic
9743 links and the characteristics of special files or
9744 pipes may not be changed and no files may be removed
9749 All the directories in the diff must exist, except the
9750 <file>debian</file> subdirectory of the top of the source
9751 tree, which will be created by
9752 <prgn>dpkg-source</prgn> if necessary when unpacking.
9756 The <prgn>dpkg-source</prgn> program will
9757 automatically make the <file>debian/rules</file> file
9758 executable (see below).</p></item>
9763 If there is no original source code - for example, if the
9764 package is specially prepared for Debian or the Debian
9765 maintainer is the same as the upstream maintainer - the
9766 format is slightly different: then there is no diff, and the
9768 <file><var>package</var>_<var>version</var>.tar.gz</file>,
9769 and preferably contains a directory named
9770 <file><var>package</var>-<var>version</var></file>.
9775 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
9778 <tt>dpkg-source -x</tt> is the recommended way to unpack a
9779 Debian source package. However, if it is not available it
9780 is possible to unpack a Debian source archive as follows:
9781 <enumlist compact="compact">
9784 Untar the tarfile, which will create a <file>.orig</file>
9788 <p>Rename the <file>.orig</file> directory to
9789 <file><var>package</var>-<var>version</var></file>.</p>
9793 Create the subdirectory <file>debian</file> at the top of
9794 the source tree.</p>
9796 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
9798 <item><p>Untar the tarfile again if you want a copy of the original
9799 source code alongside the Debianised version.</p>
9804 It is not possible to generate a valid Debian source archive
9805 without using <prgn>dpkg-source</prgn>. In particular,
9806 attempting to use <prgn>diff</prgn> directly to generate the
9807 <file>.diff.gz</file> file will not work.
9811 <heading>Restrictions on objects in source packages</heading>
9814 The source package may not contain any hard links
9816 This is not currently detected when building source
9817 packages, but only when extracting
9821 Hard links may be permitted at some point in the
9822 future, but would require a fair amount of
9824 </footnote>, device special files, sockets or setuid or
9827 Setgid directories are allowed.
9832 The source packaging tools manage the changes between the
9833 original and Debianised source using <prgn>diff</prgn> and
9834 <prgn>patch</prgn>. Turning the original source tree as
9835 included in the <file>.orig.tar.gz</file> into the debianised
9836 source must not involve any changes which cannot be
9837 handled by these tools. Problematic changes which cause
9838 <prgn>dpkg-source</prgn> to halt with an error when
9839 building the source package are:
9840 <list compact="compact">
9841 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
9843 <item><p>Changing the targets of symbolic links.</p>
9845 <item><p>Creating directories, other than <file>debian</file>.</p>
9847 <item><p>Changes to the contents of binary files.</p></item>
9848 </list> Changes which cause <prgn>dpkg-source</prgn> to
9849 print a warning but continue anyway are:
9850 <list compact="compact">
9853 Removing files, directories or symlinks.
9855 Renaming a file is not treated specially - it is
9856 seen as the removal of the old file (which
9857 generates a warning, but is otherwise ignored),
9858 and the creation of the new one.
9864 Changed text files which are missing the usual final
9865 newline (either in the original or the modified
9870 Changes which are not represented, but which are not detected by
9871 <prgn>dpkg-source</prgn>, are:
9872 <list compact="compact">
9873 <item><p>Changing the permissions of files (other than
9874 <file>debian/rules</file>) and directories.</p></item>
9879 The <file>debian</file> directory and <file>debian/rules</file>
9880 are handled specially by <prgn>dpkg-source</prgn> - before
9881 applying the changes it will create the <file>debian</file>
9882 directory, and afterwards it will make
9883 <file>debian/rules</file> world-executable.
9889 <appendix id="pkg-controlfields">
9890 <heading>Control files and their fields (from old Packaging Manual)</heading>
9893 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
9894 data in a common format, known as control files. Binary and
9895 source packages have control data as do the <file>.changes</file>
9896 files which control the installation of uploaded files, and
9897 <prgn>dpkg</prgn>'s internal databases are in a similar
9902 <heading>Syntax of control files</heading>
9905 See <ref id="controlsyntax">.
9909 It is important to note that there are several fields which
9910 are optional as far as <prgn>dpkg</prgn> and the related
9911 tools are concerned, but which must appear in every Debian
9912 package, or whose omission may cause problems.
9917 <heading>List of fields</heading>
9920 See <ref id="controlfieldslist">.
9924 This section now contains only the fields that didn't belong
9925 to the Policy manual.
9928 <sect1 id="pkg-f-Filename">
9929 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
9932 These fields in <tt>Packages</tt> files give the
9933 filename(s) of (the parts of) a package in the
9934 distribution directories, relative to the root of the
9935 Debian hierarchy. If the package has been split into
9936 several parts the parts are all listed in order, separated
9941 <sect1 id="pkg-f-Size">
9942 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
9945 These fields in <file>Packages</file> files give the size (in
9946 bytes, expressed in decimal) and MD5 checksum of the
9947 file(s) which make(s) up a binary package in the
9948 distribution. If the package is split into several parts
9949 the values for the parts are listed in order, separated by
9954 <sect1 id="pkg-f-Status">
9955 <heading><tt>Status</tt></heading>
9958 This field in <prgn>dpkg</prgn>'s status file records
9959 whether the user wants a package installed, removed or
9960 left alone, whether it is broken (requiring
9961 re-installation) or not and what its current state on the
9962 system is. Each of these pieces of information is a
9967 <sect1 id="pkg-f-Config-Version">
9968 <heading><tt>Config-Version</tt></heading>
9971 If a package is not installed or not configured, this
9972 field in <prgn>dpkg</prgn>'s status file records the last
9973 version of the package which was successfully
9978 <sect1 id="pkg-f-Conffiles">
9979 <heading><tt>Conffiles</tt></heading>
9982 This field in <prgn>dpkg</prgn>'s status file contains
9983 information about the automatically-managed configuration
9984 files held by a package. This field should <em>not</em>
9985 appear anywhere in a package!
9990 <heading>Obsolete fields</heading>
9993 These are still recognized by <prgn>dpkg</prgn> but should
9994 not appear anywhere any more.
9996 <taglist compact="compact">
9998 <tag><tt>Revision</tt></tag>
9999 <tag><tt>Package-Revision</tt></tag>
10000 <tag><tt>Package_Revision</tt></tag>
10002 The Debian revision part of the package version was
10003 at one point in a separate control file field. This
10004 field went through several names.
10007 <tag><tt>Recommended</tt></tag>
10008 <item>Old name for <tt>Recommends</tt>.</item>
10010 <tag><tt>Optional</tt></tag>
10011 <item>Old name for <tt>Suggests</tt>.</item>
10013 <tag><tt>Class</tt></tag>
10014 <item>Old name for <tt>Priority</tt>.</item>
10023 <appendix id="pkg-conffiles">
10024 <heading>Configuration file handling (from old Packaging Manual)</heading>
10027 <prgn>dpkg</prgn> can do a certain amount of automatic
10028 handling of package configuration files.
10032 Whether this mechanism is appropriate depends on a number of
10033 factors, but basically there are two approaches to any
10034 particular configuration file.
10038 The easy method is to ship a best-effort configuration in the
10039 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10040 handle updates. If the user is unlikely to want to edit the
10041 file, but you need them to be able to without losing their
10042 changes, and a new package with a changed version of the file
10043 is only released infrequently, this is a good approach.
10047 The hard method is to build the configuration file from
10048 scratch in the <prgn>postinst</prgn> script, and to take the
10049 responsibility for fixing any mistakes made in earlier
10050 versions of the package automatically. This will be
10051 appropriate if the file is likely to need to be different on
10055 <sect><heading>Automatic handling of configuration files by
10060 A package may contain a control area file called
10061 <tt>conffiles</tt>. This file should be a list of filenames
10062 of configuration files needing automatic handling, separated
10063 by newlines. The filenames should be absolute pathnames,
10064 and the files referred to should actually exist in the
10069 When a package is upgraded <prgn>dpkg</prgn> will process
10070 the configuration files during the configuration stage,
10071 shortly before it runs the package's <prgn>postinst</prgn>
10076 For each file it checks to see whether the version of the
10077 file included in the package is the same as the one that was
10078 included in the last version of the package (the one that is
10079 being upgraded from); it also compares the version currently
10080 installed on the system with the one shipped with the last
10085 If neither the user nor the package maintainer has changed
10086 the file, it is left alone. If one or the other has changed
10087 their version, then the changed version is preferred - i.e.,
10088 if the user edits their file, but the package maintainer
10089 doesn't ship a different version, the user's changes will
10090 stay, silently, but if the maintainer ships a new version
10091 and the user hasn't edited it the new version will be
10092 installed (with an informative message). If both have
10093 changed their version the user is prompted about the problem
10094 and must resolve the differences themselves.
10098 The comparisons are done by calculating the MD5 message
10099 digests of the files, and storing the MD5 of the file as it
10100 was included in the most recent version of the package.
10104 When a package is installed for the first time
10105 <prgn>dpkg</prgn> will install the file that comes with it,
10106 unless that would mean overwriting a file already on the
10111 However, note that <prgn>dpkg</prgn> will <em>not</em>
10112 replace a conffile that was removed by the user (or by a
10113 script). This is necessary because with some programs a
10114 missing file produces an effect hard or impossible to
10115 achieve in another way, so that a missing file needs to be
10116 kept that way if the user did it.
10120 Note that a package should <em>not</em> modify a
10121 <prgn>dpkg</prgn>-handled conffile in its maintainer
10122 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10123 the user confusing and possibly dangerous options for
10124 conffile update when the package is upgraded.</p>
10127 <sect><heading>Fully-featured maintainer script configuration
10132 For files which contain site-specific information such as
10133 the hostname and networking details and so forth, it is
10134 better to create the file in the package's
10135 <prgn>postinst</prgn> script.
10139 This will typically involve examining the state of the rest
10140 of the system to determine values and other information, and
10141 may involve prompting the user for some information which
10142 can't be obtained some other way.
10146 When using this method there are a couple of important
10147 issues which should be considered:
10151 If you discover a bug in the program which generates the
10152 configuration file, or if the format of the file changes
10153 from one version to the next, you will have to arrange for
10154 the postinst script to do something sensible - usually this
10155 will mean editing the installed configuration file to remove
10156 the problem or change the syntax. You will have to do this
10157 very carefully, since the user may have changed the file,
10158 perhaps to fix the very problem that your script is trying
10159 to deal with - you will have to detect these situations and
10160 deal with them correctly.
10164 If you do go down this route it's probably a good idea to
10165 make the program that generates the configuration file(s) a
10166 separate program in <file>/usr/sbin</file>, by convention called
10167 <file><var>package</var>config</file> and then run that if
10168 appropriate from the post-installation script. The
10169 <tt><var>package</var>config</tt> program should not
10170 unquestioningly overwrite an existing configuration - if its
10171 mode of operation is geared towards setting up a package for
10172 the first time (rather than any arbitrary reconfiguration
10173 later) you should have it check whether the configuration
10174 already exists, and require a <tt>--force</tt> flag to
10175 overwrite it.</p></sect>
10178 <appendix id="pkg-alternatives"><heading>Alternative versions of
10179 an interface - <prgn>update-alternatives</prgn> (from old
10184 When several packages all provide different versions of the
10185 same program or file it is useful to have the system select a
10186 default, but to allow the system administrator to change it
10187 and have their decisions respected.
10191 For example, there are several versions of the <prgn>vi</prgn>
10192 editor, and there is no reason to prevent all of them from
10193 being installed at once, each under their own name
10194 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10195 Nevertheless it is desirable to have the name <tt>vi</tt>
10196 refer to something, at least by default.
10200 If all the packages involved cooperate, this can be done with
10201 <prgn>update-alternatives</prgn>.
10205 Each package provides its own version under its own name, and
10206 calls <prgn>update-alternatives</prgn> in its postinst to
10207 register its version (and again in its prerm to deregister
10212 See the man page <manref name="update-alternatives"
10213 section="8"> for details.
10217 If <prgn>update-alternatives</prgn> does not seem appropriate
10218 you may wish to consider using diversions instead.</p>
10221 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10222 package's version of a file (from old Packaging Manual)
10226 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10227 when it reinstalls the package it belongs to, and to have it
10228 put the file from the package somewhere else instead.
10232 This can be used locally to override a package's version of a
10233 file, or by one package to override another's version (or
10234 provide a wrapper for it).
10238 Before deciding to use a diversion, read <ref
10239 id="pkg-alternatives"> to see if you really want a diversion
10240 rather than several alternative versions of a program.
10244 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10245 and updated by a special program <prgn>dpkg-divert</prgn>.
10246 Please see <manref name="dpkg-divert" section="8"> for full
10247 details of its operation.
10251 When a package wishes to divert a file from another, it should
10252 call <prgn>dpkg-divert</prgn> in its preinst to add the
10253 diversion and rename the existing file. For example,
10254 supposing that a <prgn>smailwrapper</prgn> package wishes to
10255 install a wrapper around <file>/usr/sbin/smail</file>:
10257 if [ install = "$1" ]; then
10258 dpkg-divert --package smailwrapper --add --rename \
10259 --divert /usr/sbin/smail.real /usr/sbin/smail
10261 </example> Testing <tt>$1</tt> is necessary so that the script
10262 doesn't try to add the diversion again when
10263 <prgn>smailwrapper</prgn> is upgraded. The <tt>--package
10264 smailwrapper</tt> ensures that <prgn>smailwrapper</prgn>'s
10265 copy of <file>/usr/sbin/smail</file> can bypass the diversion and
10266 get installed as the true version.
10270 The postrm has to do the reverse:
10272 if [ remove = "$1" ]; then
10273 dpkg-divert --package smailwrapper --remove --rename \
10274 --divert /usr/sbin/smail.real /usr/sbin/smail
10280 Do not attempt to divert a file which is vitally important for
10281 the system's operation - when using <prgn>dpkg-divert</prgn>
10282 there is a time, after it has been diverted but before
10283 <prgn>dpkg</prgn> has installed the new version, when the file
10284 does not exist.</p>
10289 <!-- vim:set ai et sts=2 sw=2 tw=76: -->