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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 an <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> (full stop, plus, hyphen, colon) and should
2653 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> and <tt>.</tt> (plus and full stop) and is
2667 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.
2720 Then the initial part of the remainder of each string which
2721 consists entirely of digit characters is determined. The
2722 numerical values of these two parts are compared, and any
2723 difference found is returned as the result of the comparison.
2724 For these purposes an empty string (which can only occur at
2725 the end of one or both version strings being compared) counts
2730 These two steps (comparing and removing initial non-digit
2731 strings and initial digit strings) are repeated until a
2732 difference is found or both strings are exhausted.
2736 Note that the purpose of epochs is to allow us to leave behind
2737 mistakes in version numbering, and to cope with situations
2738 where the version numbering scheme changes. It is
2739 <em>not</em> intended to cope with version numbers containing
2740 strings of letters which the package management system cannot
2741 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
2742 silly orderings (the author of this manual has heard of a
2743 package whose versions went <tt>1.1</tt>, <tt>1.2</tt>,
2744 <tt>1.3</tt>, <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>,
2745 <tt>2</tt> and so forth).
2749 <sect1 id="f-Description">
2750 <heading><tt>Description</tt></heading>
2753 In a source or binary control file, the <tt>Description</tt>
2754 field contains a description of the binary package, consisting
2755 of two parts, the synopsis or the short description, and the
2756 long description. The field's format is as follows:
2761 Description: <single line synopsis>
2762 <extended description over several lines>
2767 The lines in the extended description can have these formats:
2773 Those starting with a single space are part of a paragraph.
2774 Successive lines of this form will be word-wrapped when
2775 displayed. The leading space will usually be stripped off.
2779 Those starting with two or more spaces. These will be
2780 displayed verbatim. If the display cannot be panned
2781 horizontally, the displaying program will line wrap them "hard"
2782 (i.e., without taking account of word breaks). If it can they
2783 will be allowed to trail off to the right. None, one or two
2784 initial spaces may be deleted, but the number of spaces
2785 deleted from each line will be the same (so that you can have
2786 indenting work correctly, for example).
2790 Those containing a single space followed by a single full stop
2791 character. These are rendered as blank lines. This is the
2792 <em>only</em> way to get a blank line<footnote>
2793 Completely empty lines will not be rendered as blank lines.
2794 Instead, they will cause the parser to think you're starting
2795 a whole new record in the control file, and will therefore
2796 likely abort with an error.
2801 Those containing a space, a full stop and some more characters.
2802 These are for future expansion. Do not use them.
2808 Do not use tab characters. Their effect is not predictable.
2812 See <ref id="descriptions"> for further information on this.
2816 In a <file>.changes</file> file, the <tt>Description</tt> field
2817 contains a summary of the descriptions for the packages being
2822 The part of the field before the first newline is empty;
2823 thereafter each line has the name of a binary package and
2824 the summary description line from that binary package.
2825 Each line is indented by one space.
2830 <sect1 id="f-Distribution">
2831 <heading><tt>Distribution</tt></heading>
2834 In a <file>.changes</file> file or parsed changelog output
2835 this contains the (space-separated) name(s) of the
2836 distribution(s) where this version of the package should
2837 be installed. Valid distributions are determined by the
2838 archive maintainers.<footnote>
2839 Current distribution names are:
2840 <taglist compact="compact">
2841 <tag><em>stable</em></tag>
2843 This is the current "released" version of Debian
2844 GNU/Linux. Once the distribution is
2845 <em>stable</em> only security fixes and other
2846 major bug fixes are allowed. When changes are
2847 made to this distribution, the release number is
2848 increased (for example: 2.2r1 becomes 2.2r2 then
2852 <tag><em>unstable</em></tag>
2854 This distribution value refers to the
2855 <em>developmental</em> part of the Debian
2856 distribution tree. New packages, new upstream
2857 versions of packages and bug fixes go into the
2858 <em>unstable</em> directory tree. Download from
2859 this distribution at your own risk.
2862 <tag><em>testing</em></tag>
2864 This distribution value refers to the
2865 <em>testing</em> part of the Debian distribution
2866 tree. It receives its packages from the
2867 unstable distribution after a short time lag to
2868 ensure that there are no major issues with the
2869 unstable packages. It is less prone to breakage
2870 than unstable, but still risky. It is not
2871 possible to upload packages directly to
2875 <tag><em>frozen</em></tag>
2877 From time to time, the <em>testing</em>
2878 distribution enters a state of "code-freeze" in
2879 anticipation of release as a <em>stable</em>
2880 version. During this period of testing only
2881 fixes for existing or newly-discovered bugs will
2882 be allowed. The exact details of this stage are
2883 determined by the Release Manager.
2886 <tag><em>experimental</em></tag>
2888 The packages with this distribution value are
2889 deemed by their maintainers to be high
2890 risk. Oftentimes they represent early beta or
2891 developmental packages from various sources that
2892 the maintainers want people to try, but are not
2893 ready to be a part of the other parts of the
2894 Debian distribution tree. Download at your own
2900 You should list <em>all</em> distributions that the
2901 package should be installed into.
2905 More information is available in the Debian Developer's
2906 Reference, section "The Debian archive".
2913 <heading><tt>Date</tt></heading>
2916 This field includes the date the package was built or last edited.
2920 The value of this field is usually extracted from the
2921 <file>debian/changelog</file> file - see
2922 <ref id="dpkgchangelog">).
2926 <sect1 id="f-Format">
2927 <heading><tt>Format</tt></heading>
2930 This field specifies a format revision for the file.
2931 The most current format described in the Policy Manual
2932 is version <strong>1.5</strong>. The syntax of the
2933 format value is the same as that of a package version
2934 number except that no epoch or Debian revision is allowed
2935 - see <ref id="f-Version">.
2939 <sect1 id="f-Urgency">
2940 <heading><tt>Urgency</tt></heading>
2943 This is a description of how important it is to upgrade to
2944 this version from previous ones. It consists of a single
2945 keyword usually taking one of the values <tt>low</tt>,
2946 <tt>medium</tt> or <tt>high</tt> (not case-sensitive)
2947 followed by an optional commentary (separated by a space)
2948 which is usually in parentheses. For example:
2951 Urgency: low (HIGH for users of diversions)
2957 The value of this field is usually extracted from the
2958 <file>debian/changelog</file> file - see
2959 <ref id="dpkgchangelog">.
2963 <sect1 id="f-Changes">
2964 <heading><tt>Changes</tt></heading>
2967 This field contains the human-readable changes data, describing
2968 the differences between the last version and the current one.
2972 There should be nothing in this field before the first
2973 newline; all the subsequent lines must be indented by at
2974 least one space; blank lines must be represented by a line
2975 consisting only of a space and a full stop.
2979 The value of this field is usually extracted from the
2980 <file>debian/changelog</file> file - see
2981 <ref id="dpkgchangelog">).
2985 Each version's change information should be preceded by a
2986 "title" line giving at least the version, distribution(s)
2987 and urgency, in a human-readable way.
2991 If data from several versions is being returned the entry
2992 for the most recent version should be returned first, and
2993 entries should be separated by the representation of a
2994 blank line (the "title" line may also be followed by the
2995 representation of blank line).
2999 <sect1 id="f-Binary">
3000 <heading><tt>Binary</tt></heading>
3003 This field is a list of binary packages.
3007 When it appears in the <file>.dsc</file> file it is the list
3008 of binary packages which a source package can produce. It
3009 does not necessarily produce all of these binary packages
3010 for every architecture. The source control file doesn't
3011 contain details of which architectures are appropriate for
3012 which of the binary packages.
3016 When it appears in a <file>.changes</file> file it lists the
3017 names of the binary packages actually being uploaded.
3021 The syntax is a list of binary packages separated by
3023 A space after each comma is conventional.
3024 </footnote>. Currently the packages must be separated using
3025 only spaces in the <file>.changes</file> file.
3029 <sect1 id="f-Installed-Size">
3030 <heading><tt>Installed-Size</tt></heading>
3033 This field appears in the control files of binary
3034 packages, and in the <file>Packages</file> files. It gives
3035 the total amount of disk space required to install the
3040 The disk space is represented in kilobytes as a simple
3045 <sect1 id="f-Files">
3046 <heading><tt>Files</tt></heading>
3049 This field contains a list of files with information about
3050 each one. The exact information and syntax varies with
3051 the context. In all cases the part of the field
3052 contents on the same line as the field name is empty. The
3053 remainder of the field is one line per file, each line
3054 being indented by one space and containing a number of
3055 sub-fields separated by spaces.
3059 In the <file>.dsc</file> file, each line contains the MD5
3060 checksum, size and filename of the tar file and (if applicable)
3061 diff file which make up the remainder of the source
3063 That is, the parts which are not the <tt>.dsc</tt>.
3065 The exact forms of the filenames are described
3066 in <ref id="pkg-sourcearchives">.
3070 In the <file>.changes</file> file this contains one line per
3071 file being uploaded. Each line contains the MD5 checksum,
3072 size, section and priority and the filename.
3073 The <qref id="f-Section">section</qref>
3074 and <qref id="f-Priority">priority</qref>
3075 are the values of the corresponding fields in
3076 the main source control file. If no section or priority is
3077 specified then <tt>-</tt> should be used, though section
3078 and priority values must be specified for new packages to
3079 be installed properly.
3083 The special value <tt>byhand</tt> for the section in a
3084 <tt>.changes</tt> file indicates that the file in question
3085 is not an ordinary package file and must by installed by
3086 hand by the distribution maintainers. If the section is
3087 <tt>byhand</tt> the priority should be <tt>-</tt>.
3091 If a new Debian revision of a package is being shipped and
3092 no new original source archive is being distributed the
3093 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3094 entry for the original source archive
3095 <file><var>package</var>-<var>upstream-version</var>.orig.tar.gz</file>,
3096 but the <file>.changes</file> file should leave it out. In
3097 this case the original source archive on the distribution
3098 site must match exactly, byte-for-byte, the original
3099 source archive which was used to generate the
3100 <file>.dsc</file> file and diff which are being uploaded.</p>
3103 <sect1 id="f-Closes">
3104 <heading><tt>Closes</tt></heading>
3107 A space-separated list of bug report numbers that the upload
3108 governed by the .changes file closes.
3115 <heading>User-defined fields</heading>
3118 Additional user-defined fields may be added to the
3119 source package control file. Such fields will be
3120 ignored, and not copied to (for example) binary or
3121 source package control files or upload control files.
3125 If you wish to add additional unsupported fields to
3126 these output files you should use the mechanism
3131 Fields in the main source control information file with
3132 names starting <tt>X</tt>, followed by one or more of
3133 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3134 be copied to the output files. Only the part of the
3135 field name after the hyphen will be used in the output
3136 file. Where the letter <tt>B</tt> is used the field
3137 will appear in binary package control files, where the
3138 letter <tt>S</tt> is used in source package control
3139 files and where <tt>C</tt> is used in upload control
3140 (<tt>.changes</tt>) files.
3144 For example, if the main source information control file
3147 XBS-Comment: I stand between the candle and the star.
3149 then the binary and source package control files will contain the
3152 Comment: I stand between the candle and the star.
3161 <chapt id="maintainerscripts">
3162 <heading>Package maintainer scripts and installation procedure</heading>
3165 <heading>Introduction to package maintainer scripts</heading>
3168 It is possible to supply scripts as part of a package which
3169 the package management system will run for you when your
3170 package is installed, upgraded or removed.
3174 These scripts are the files <prgn>preinst</prgn>,
3175 <prgn>postinst</prgn>, <prgn>prerm</prgn> and
3176 <prgn>postrm</prgn> in the control area of the package.
3177 They must be proper executable files; if they are scripts
3178 (which is recommended), they must start with the usual
3179 <tt>#!</tt> convention. They should be readable and
3180 executable by anyone, and must not be not world-writable.
3184 The package management system looks at the exit status from
3185 these scripts. It is important that they exit with a
3186 non-zero status if there is an error, so that the package
3187 management system can stop its processing. For shell
3188 scripts this means that you <em>almost always</em> need to
3189 use <tt>set -e</tt> (this is usually true when writing shell
3190 scripts, in fact). It is also important, of course, that
3191 they don't exit with a non-zero status if everything went
3196 Additionally, packages interacting with users using
3197 <tt>debconf</tt> in the <prgn>postinst</prgn> script should
3198 install a <prgn>config</prgn> script in the control area,
3199 see <ref id="maintscriptprompt"> for details.
3203 When a package is upgraded a combination of the scripts from
3204 the old and new packages is called during the upgrade
3205 procedure. If your scripts are going to be at all
3206 complicated you need to be aware of this, and may need to
3207 check the arguments to your scripts.
3211 Broadly speaking the <prgn>preinst</prgn> is called before
3212 (a particular version of) a package is installed, and the
3213 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3214 before (a version of) a package is removed and the
3215 <prgn>postrm</prgn> afterwards.
3219 Programs called from maintainer scripts should not normally
3220 have a path prepended to them. Before installation is
3221 started, the package management system checks to see if the
3222 programs <prgn>ldconfig</prgn>,
3223 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3224 and <prgn>update-rc.d</prgn> can be found via the
3225 <tt>PATH</tt> environment variable. Those programs, and any
3226 other program that one would expect to be on the
3227 <tt>PATH</tt>, should thus be invoked without an absolute
3228 pathname. Maintainer scripts should also not reset the
3229 <tt>PATH</tt>, though they might choose to modify it by
3230 prepending or appending package-specific directories. These
3231 considerations really apply to all shell scripts.</p>
3234 <sect id="idempotency">
3235 <heading>Maintainer scripts Idempotency</heading>
3238 It is necessary for the error recovery procedures that the
3239 scripts be idempotent. This means that if it is run
3240 successfully, and then it is called again, it doesn't bomb
3241 out or cause any harm, but just ensures that everything is
3242 the way it ought to be. If the first call failed, or
3243 aborted half way through for some reason, the second call
3244 should merely do the things that were left undone the first
3245 time, if any, and exit with a success status if everything
3247 This is so that if an error occurs, the user interrupts
3248 <prgn>dpkg</prgn> or some other unforeseen circumstance
3249 happens you don't leave the user with a badly-broken
3250 package when <prgn>dpkg</prgn> attempts to repeat the
3256 <sect id="controllingterminal">
3257 <heading>Controlling terminal for maintainer scripts</heading>
3260 The maintainer scripts are guaranteed to run with a
3261 controlling terminal and can interact with the user.
3262 Because these scripts may be executed with standard output
3263 redirected into a pipe for logging purposes, Perl scripts
3264 should set unbuffered output by setting <tt>$|=1</tt> so
3265 that the output is printed immediately rather than being
3269 <sect id="exitstatus">
3270 <heading>Exit status</heading>
3273 Each script must return a zero exit status for
3274 success, or a nonzero one for failure, since the package
3275 management system looks for the exit status of these scripts
3276 and determines what action to take next based on that datum.
3280 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3285 <list compact="compact">
3287 <var>new-preinst</var> <tt>install</tt>
3290 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3293 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3296 <var>old-preinst</var> <tt>abort-upgrade</tt>
3297 <var>new-version</var>
3302 <list compact="compact">
3304 <var>postinst</var> <tt>configure</tt>
3305 <var>most-recently-configured-version</var>
3308 <var>old-postinst</var> <tt>abort-upgrade</tt>
3309 <var>new-version</var>
3312 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3313 <tt>in-favour</tt> <var>package</var>
3314 <var>new-version</var>
3317 <var>postinst</var> <tt>abort-remove</tt>
3320 <var>deconfigured's-postinst</var>
3321 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3322 <var>failed-install-package</var> <var>version</var>
3323 <tt>removing</tt> <var>conflicting-package</var>
3329 <list compact="compact">
3331 <var>prerm</var> <tt>remove</tt>
3334 <var>old-prerm</var> <tt>upgrade</tt>
3335 <var>new-version</var>
3338 <var>new-prerm</var> <tt>failed-upgrade</tt>
3339 <var>old-version</var>
3342 <var>conflictor's-prerm</var> <tt>remove</tt>
3343 <tt>in-favour</tt> <var>package</var>
3344 <var>new-version</var>
3347 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3348 <tt>in-favour</tt> <var>package-being-installed</var>
3349 <var>version</var> <tt>removing</tt>
3350 <var>conflicting-package</var>
3356 <list compact="compact">
3358 <var>postrm</var> <tt>remove</tt>
3361 <var>postrm</var> <tt>purge</tt>
3364 <var>old-postrm</var> <tt>upgrade</tt>
3365 <var>new-version</var>
3368 <var>new-postrm</var> <tt>failed-upgrade</tt>
3369 <var>old-version</var>
3372 <var>new-postrm</var> <tt>abort-install</tt>
3375 <var>new-postrm</var> <tt>abort-install</tt>
3376 <var>old-version</var>
3379 <var>new-postrm</var> <tt>abort-upgrade</tt>
3380 <var>old-version</var>
3383 <var>disappearer's-postrm</var> <tt>disappear</tt>
3384 <var>overwriter</var>
3385 <var>overwriter-version</var>
3391 <sect id="unpackphase">
3392 <heading>Details of unpack phase of installation or upgrade</heading>
3395 The procedure on installation/upgrade/overwrite/disappear
3396 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3397 stage of <tt>dpkg --install</tt>) is as follows. In each
3398 case, if a major error occurs (unless listed below) the
3399 actions are, in general, run backwards - this means that the
3400 maintainer scripts are run with different arguments in
3401 reverse order. These are the "error unwind" calls listed
3408 If a version of the package is already installed, call
3409 <example compact="compact">
3410 <var>old-prerm</var> upgrade <var>new-version</var>
3414 If the script runs but exits with a non-zero
3415 exit status, <prgn>dpkg</prgn> will attempt:
3416 <example compact="compact">
3417 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3419 If this works, the upgrade continues. If this
3420 does not work, the error unwind:
3421 <example compact="compact">
3422 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3424 If this works, then the old-version is
3425 "Installed", if not, the old version is in a
3426 "Failed-Config" state.
3432 If a "conflicting" package is being removed at the same time:
3435 If any packages depended on that conflicting
3436 package and <tt>--auto-deconfigure</tt> is
3437 specified, call, for each such package:
3438 <example compact="compact">
3439 <var>deconfigured's-prerm</var> deconfigure \
3440 in-favour <var>package-being-installed</var> <var>version</var> \
3441 removing <var>conflicting-package</var> <var>version</var>
3444 <example compact="compact">
3445 <var>deconfigured's-postinst</var> abort-deconfigure \
3446 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3447 removing <var>conflicting-package</var> <var>version</var>
3449 The deconfigured packages are marked as
3450 requiring configuration, so that if
3451 <tt>--install</tt> is used they will be
3452 configured again if possible.
3455 To prepare for removal of the conflicting package, call:
3456 <example compact="compact">
3457 <var>conflictor's-prerm</var> remove \
3458 in-favour <var>package</var> <var>new-version</var>
3461 <example compact="compact">
3462 <var>conflictor's-postinst</var> abort-remove \
3463 in-favour <var>package</var> <var>new-version</var>
3472 If the package is being upgraded, call:
3473 <example compact="compact">
3474 <var>new-preinst</var> upgrade <var>old-version</var>
3476 If this fails, we call:
3478 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3485 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3487 is called. If this works, then the old version
3488 is in an "Installed" state, or else it is left
3489 in an "Unpacked" state.
3494 If it fails, then the old version is left
3495 in an "Half-Installed" state.
3502 Otherwise, if the package had some configuration
3503 files from a previous version installed (i.e., it
3504 is in the "configuration files only" state):
3505 <example compact="compact">
3506 <var>new-preinst</var> install <var>old-version</var>
3510 <var>new-postrm</var> abort-install <var>old-version</var>
3512 If this fails, the package is left in a
3513 "Half-Installed" state, which requires a
3514 reinstall. If it works, the packages is left in
3515 a "Config Files" state.
3518 Otherwise (i.e., the package was completely purged):
3519 <example compact="compact">
3520 <var>new-preinst</var> install
3523 <example compact="compact">
3524 <var>new-postrm</var> abort-install
3526 If the error-unwind fails, the package is in an
3527 "Half Installed" phase, and requires a
3528 reinstall. If the error unwind works, the
3529 package is in an not installed state.
3536 The new package's files are unpacked, overwriting any
3537 that may be on the system already, for example any
3538 from the old version of the same package or from
3539 another package. Backups of the old files are kept
3540 temporarily, and if anything goes wrong the package
3541 management system will attempt to put them back as
3542 part of the error unwind.
3546 It is an error for a package to contain files which
3547 are on the system in another package, unless
3548 <tt>Replaces</tt> is used (see <ref id="replaces">).
3550 The following paragraph is not currently the case:
3551 Currently the <tt>- - force-overwrite</tt> flag is
3552 enabled, downgrading it to a warning, but this may not
3558 It is a more serious error for a package to contain a
3559 plain file or other kind of non-directory where another
3560 package has a directory (again, unless
3561 <tt>Replaces</tt> is used). This error can be
3562 overridden if desired using
3563 <tt>--force-overwrite-dir</tt>, but this is not
3568 Packages which overwrite each other's files produce
3569 behavior which, though deterministic, is hard for the
3570 system administrator to understand. It can easily
3571 lead to "missing" programs if, for example, a package
3572 is installed which overwrites a file from another
3573 package, and is then removed again.<footnote>
3574 Part of the problem is due to what is arguably a
3575 bug in <prgn>dpkg</prgn>.
3580 A directory will never be replaced by a symbolic link
3581 to a directory or vice versa; instead, the existing
3582 state (symlink or not) will be left alone and
3583 <prgn>dpkg</prgn> will follow the symlink if there is
3592 If the package is being upgraded, call
3593 <example compact="compact">
3594 <var>old-postrm</var> upgrade <var>new-version</var>
3598 If this fails, <prgn>dpkg</prgn> will attempt:
3599 <example compact="compact">
3600 <var>new-postrm</var> failed-upgrade <var>old-version</var>
3602 If this works, installation continues. If not,
3604 <example compact="compact">
3605 <var>old-preinst</var> abort-upgrade <var>new-version</var>
3607 If this fails, the old version is left in an
3608 "Half Installed" state. If it works, dpkg now
3610 <example compact="compact">
3611 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3613 If this fails, the old version is left in an
3614 "Half Installed" state. If it works, dpkg now
3616 <example compact="compact">
3617 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3619 If this fails, the old version is in an
3626 This is the point of no return - if
3627 <prgn>dpkg</prgn> gets this far, it won't back off
3628 past this point if an error occurs. This will
3629 leave the package in a fairly bad state, which
3630 will require a successful re-installation to clear
3631 up, but it's when <prgn>dpkg</prgn> starts doing
3632 things that are irreversible.
3637 Any files which were in the old version of the package
3638 but not in the new are removed.
3642 The new file list replaces the old.
3646 The new maintainer scripts replace the old.
3650 Any packages all of whose files have been overwritten
3651 during the installation, and which aren't required for
3652 dependencies, are considered to have been removed.
3653 For each such package
3656 <prgn>dpkg</prgn> calls:
3657 <example compact="compact">
3658 <var>disappearer's-postrm</var> disappear \
3659 <var>overwriter</var> <var>overwriter-version</var>
3663 The package's maintainer scripts are removed.
3666 It is noted in the status database as being in a
3667 sane state, namely not installed (any conffiles
3668 it may have are ignored, rather than being
3669 removed by <prgn>dpkg</prgn>). Note that
3670 disappearing packages do not have their prerm
3671 called, because <prgn>dpkg</prgn> doesn't know
3672 in advance that the package is going to
3679 Any files in the package we're unpacking that are also
3680 listed in the file lists of other packages are removed
3681 from those lists. (This will lobotomize the file list
3682 of the "conflicting" package if there is one.)
3686 The backup files made during installation, above, are
3692 The new package's status is now sane, and recorded as
3697 Here is another point of no return - if the
3698 conflicting package's removal fails we do not unwind
3699 the rest of the installation; the conflicting package
3700 is left in a half-removed limbo.
3705 If there was a conflicting package we go and do the
3706 removal actions (described below), starting with the
3707 removal of the conflicting package's files (any that
3708 are also in the package being installed have already
3709 been removed from the conflicting package's file list,
3710 and so do not get removed now).
3716 <sect id="configdetails"><heading>Details of configuration</heading>
3719 When we configure a package (this happens with <tt>dpkg
3720 --install</tt> and <tt>dpkg --configure</tt>), we first
3721 update any <tt>conffile</tt>s and then call:
3722 <example compact="compact">
3723 <var>postinst</var> configure <var>most-recently-configured-version</var>
3728 No attempt is made to unwind after errors during
3729 configuration. If the configuration fails, the package is in
3730 a "Failed Config" state, and an error message is generated.
3734 If there is no most recently configured version
3735 <prgn>dpkg</prgn> will pass a null argument.
3738 Historical note: Truly ancient (pre-1997) versions of
3739 <prgn>dpkg</prgn> passed <tt><unknown></tt>
3740 (including the angle brackets) in this case. Even older
3741 ones did not pass a second argument at all, under any
3742 circumstance. Note that upgrades using such an old dpkg
3743 version are unlikely to work for other reasons, even if
3744 this old argument behavior is handled by your postinst script.
3750 <sect id="removedetails"><heading>Details of removal and/or
3751 configuration purging</heading>
3757 <example compact="compact">
3758 <var>prerm</var> remove
3762 If prerm fails during replacement due to conflict
3764 <var>conflictor's-postinst</var> abort-remove \
3765 in-favour <var>package</var> <var>new-version</var>
3769 <var>postinst</var> abort-remove
3773 If this fails, the package is in a "Failed-Config"
3774 state, or else it remains "Installed".
3778 The package's files are removed (except <tt>conffile</tt>s).
3781 <example compact="compact">
3782 <var>postrm</var> remove
3786 If it fails, there's no error unwind, and the package is in
3787 an "Half-Installed" state.
3792 All the maintainer scripts except the <prgn>postrm</prgn>
3797 If we aren't purging the package we stop here. Note
3798 that packages which have no <prgn>postrm</prgn> and no
3799 <tt>conffile</tt>s are automatically purged when
3800 removed, as there is no difference except for the
3801 <prgn>dpkg</prgn> status.
3805 The <tt>conffile</tt>s and any backup files
3806 (<tt>~</tt>-files, <tt>#*#</tt> files,
3807 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
3812 <example compact="compact">
3813 <var>postrm</var> purge
3817 If this fails, the package remains in a "Config-Files"
3822 The package's file list is removed.
3831 <chapt id="relationships">
3832 <heading>Declaring relationships between packages</heading>
3834 <sect id="depsyntax">
3835 <heading>Syntax of relationship fields</heading>
3838 These fields all have a uniform syntax. They are a list of
3839 package names separated by commas.
3843 In the <tt>Depends</tt>, <tt>Recommends</tt>,
3844 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
3845 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
3846 control file fields of the package, which declare
3847 dependencies on other packages, the package names listed may
3848 also include lists of alternative package names, separated
3849 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
3850 if any one of the alternative packages is installed, that
3851 part of the dependency is considered to be satisfied.
3855 All of the fields except for <tt>Provides</tt> may restrict
3856 their applicability to particular versions of each named
3857 package. This is done in parentheses after each individual
3858 package name; the parentheses should contain a relation from
3859 the list below followed by a version number, in the format
3860 described in <ref id="f-Version">.
3864 The relations allowed are <tt><<</tt>, <tt><=</tt>,
3865 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
3866 strictly earlier, earlier or equal, exactly equal, later or
3867 equal and strictly later, respectively. The deprecated
3868 forms <tt><</tt> and <tt>></tt> were used to mean
3869 earlier/later or equal, rather than strictly earlier/later,
3870 so they should not appear in new packages (though
3871 <prgn>dpkg</prgn> still supports them).
3875 Whitespace may appear at any point in the version
3876 specification subject to the rules in <ref
3877 id="controlsyntax">, and must appear where it's necessary to
3878 disambiguate; it is not otherwise significant. For
3879 consistency and in case of future changes to
3880 <prgn>dpkg</prgn> it is recommended that a single space be
3881 used after a version relationship and before a version
3882 number; it is also conventional to put a single space after
3883 each comma, on either side of each vertical bar, and before
3884 each open parenthesis.
3888 For example, a list of dependencies might appear as:
3889 <example compact="compact">
3892 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
3897 All fields that specify build-time relationships
3898 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
3899 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>)
3900 may be restricted to a certain set of architectures. This
3901 is indicated in brackets after each individual package name and
3902 the optional version specification. The brackets enclose a
3903 list of Debian architecture names separated by whitespace.
3904 Exclamation marks may be prepended to each of the names.
3905 (It is not permitted for some names to be prepended with
3906 exclamation marks and others not.) If the current Debian
3907 host architecture is not in this list and there are no
3908 exclamation marks in the list, or it is in the list with a
3909 prepended exclamation mark, the package name and the
3910 associated version specification are ignored completely for
3911 the purposes of defining the relationships.
3916 <example compact="compact">
3918 Build-Depends-Indep: texinfo
3919 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
3920 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
3925 Note that the binary package relationship fields such as
3926 <tt>Depends</tt> appear in one of the binary package
3927 sections of the control file, whereas the build-time
3928 relationships such as <tt>Build-Depends</tt> appear in the
3929 source package section of the control file (which is the
3934 <sect id="binarydeps">
3935 <heading>Binary Dependencies - <tt>Depends</tt>,
3936 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
3937 <tt>Pre-Depends</tt>
3941 Packages can declare in their control file that they have
3942 certain relationships to other packages - for example, that
3943 they may not be installed at the same time as certain other
3944 packages, and/or that they depend on the presence of others.
3948 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
3949 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt> and
3950 <tt>Conflicts</tt> control file fields.
3954 These six fields are used to declare a dependency
3955 relationship by one package on another. Except for
3956 <tt>Enhances</tt>, they appear in the depending (binary)
3957 package's control file. (<tt>Enhances</tt> appears in the
3958 recommending package's control file.)
3962 A <tt>Depends</tt> field takes effect <em>only</em> when a
3963 package is to be configured. It does not prevent a package
3964 being on the system in an unconfigured state while its
3965 dependencies are unsatisfied, and it is possible to replace
3966 a package whose dependencies are satisfied and which is
3967 properly installed with a different version whose
3968 dependencies are not and cannot be satisfied; when this is
3969 done the depending package will be left unconfigured (since
3970 attempts to configure it will give errors) and will not
3971 function properly. If it is necessary, a
3972 <tt>Pre-Depends</tt> field can be used, which has a partial
3973 effect even when a package is being unpacked, as explained
3974 in detail below. (The other three dependency fields,
3975 <tt>Recommends</tt>, <tt>Suggests</tt> and
3976 <tt>Enhances</tt>, are only used by the various front-ends
3977 to <prgn>dpkg</prgn> such as <prgn>dselect</prgn>.)
3981 For this reason packages in an installation run are usually
3982 all unpacked first and all configured later; this gives
3983 later versions of packages with dependencies on later
3984 versions of other packages the opportunity to have their
3985 dependencies satisfied.
3989 In case of circular dependencies, since installation or
3990 removal order honoring the dependency order can't be
3991 established, dependency loops are broken at some point
3992 (based on rules below), and some packages may not be able to
3993 rely on their dependencies being present when being
3994 installed or removed, depending on which side of the break
3995 of the circular dependcy loop they happen to be on. If one
3996 of the packages in the loop has no postinst script, then the
3997 cycle will be broken at that package, so as to ensure that
3998 all postinst scripts run with the dependencies properly
3999 configured if this is possible. Otherwise the breaking point
4004 The <tt>Depends</tt> field thus allows package maintainers
4005 to impose an order in which packages should be configured.
4009 The meaning of the five dependency fields is as follows:
4011 <tag><tt>Depends</tt></tag>
4014 This declares an absolute dependency. A package will
4015 not be configured unless all of the packages listed in
4016 its <tt>Depends</tt> field have been correctly
4021 The <tt>Depends</tt> field should be used if the
4022 depended-on package is required for the depending
4023 package to provide a significant amount of
4028 The <tt>Depends</tt> field should also be used if the
4029 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4030 <prgn>postrm</prgn> scripts require the package to be
4031 present in order to run. Note, however, that the
4032 <prgn>postrm</prgn> cannot rely on any non-essential
4033 packages to be present during the <tt>purge</tt>
4037 <tag><tt>Recommends</tt></tag>
4040 This declares a strong, but not absolute, dependency.
4044 The <tt>Recommends</tt> field should list packages
4045 that would be found together with this one in all but
4046 unusual installations.
4050 <tag><tt>Suggests</tt></tag>
4052 This is used to declare that one package may be more
4053 useful with one or more others. Using this field
4054 tells the packaging system and the user that the
4055 listed packages are related to this one and can
4056 perhaps enhance its usefulness, but that installing
4057 this one without them is perfectly reasonable.
4060 <tag><tt>Enhances</tt></tag>
4062 This field is similar to Suggests but works in the
4063 opposite direction. It is used to declare that a
4064 package can enhance the functionality of another
4068 <tag><tt>Pre-Depends</tt></tag>
4071 This field is like <tt>Depends</tt>, except that it
4072 also forces <prgn>dpkg</prgn> to complete installation
4073 of the packages named before even starting the
4074 installation of the package which declares the
4075 pre-dependency, as follows:
4079 When a package declaring a pre-dependency is about to
4080 be <em>unpacked</em> the pre-dependency can be
4081 satisfied if the depended-on package is either fully
4082 configured, <em>or even if</em> the depended-on
4083 package(s) are only unpacked or half-configured,
4084 provided that they have been configured correctly at
4085 some point in the past (and not removed or partially
4086 removed since). In this case, both the
4087 previously-configured and currently unpacked or
4088 half-configured versions must satisfy any version
4089 clause in the <tt>Pre-Depends</tt> field.
4093 When the package declaring a pre-dependency is about
4094 to be <em>configured</em>, the pre-dependency will be
4095 treated as a normal <tt>Depends</tt>, that is, it will
4096 be considered satisfied only if the depended-on
4097 package has been correctly configured.
4101 <tt>Pre-Depends</tt> should be used sparingly,
4102 preferably only by packages whose premature upgrade or
4103 installation would hamper the ability of the system to
4104 continue with any upgrade that might be in progress.
4108 <tt>Pre-Depends</tt> are also required if the
4109 <prgn>preinst</prgn> script depends on the named
4110 package. It is best to avoid this situation if
4118 When selecting which level of dependency to use you should
4119 consider how important the depended-on package is to the
4120 functionality of the one declaring the dependency. Some
4121 packages are composed of components of varying degrees of
4122 importance. Such a package should list using
4123 <tt>Depends</tt> the package(s) which are required by the
4124 more important components. The other components'
4125 requirements may be mentioned as Suggestions or
4126 Recommendations, as appropriate to the components' relative
4131 <sect id="conflicts">
4132 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4135 When one binary package declares a conflict with another
4136 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4137 refuse to allow them to be installed on the system at the
4142 If one package is to be installed, the other must be removed
4143 first - if the package being installed is marked as
4144 replacing (see <ref id="replaces">) the one on the system,
4145 or the one on the system is marked as deselected, or both
4146 packages are marked <tt>Essential</tt>, then
4147 <prgn>dpkg</prgn> will automatically remove the package
4148 which is causing the conflict, otherwise it will halt the
4149 installation of the new package with an error. This
4150 mechanism is specifically designed to produce an error when
4151 the installed package is <tt>Essential</tt>, but the new
4156 A package will not cause a conflict merely because its
4157 configuration files are still installed; it must be at least
4162 A special exception is made for packages which declare a
4163 conflict with their own package name, or with a virtual
4164 package which they provide (see below): this does not
4165 prevent their installation, and allows a package to conflict
4166 with others providing a replacement for it. You use this
4167 feature when you want the package in question to be the only
4168 package providing some feature.
4172 A <tt>Conflicts</tt> entry should almost never have an
4173 "earlier than" version clause. This would prevent
4174 <prgn>dpkg</prgn> from upgrading or installing the package
4175 which declared such a conflict until the upgrade or removal
4176 of the conflicted-with package had been completed.
4180 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4184 As well as the names of actual ("concrete") packages, the
4185 package relationship fields <tt>Depends</tt>,
4186 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4187 <tt>Pre-Depends</tt>, <tt>Conflicts</tt>,
4188 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4189 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4190 may mention "virtual packages".
4194 A <em>virtual package</em> is one which appears in the
4195 <tt>Provides</tt> control file field of another package.
4196 The effect is as if the package(s) which provide a
4197 particular virtual package name had been listed by name
4198 everywhere the virtual package name appears. (See also <ref
4203 If there are both concrete and virtual packages of the same
4204 name, then the dependency may be satisfied (or the conflict
4205 caused) by either the concrete package with the name in
4206 question or any other concrete package which provides the
4207 virtual package with the name in question. This is so that,
4208 for example, supposing we have
4209 <example compact="compact">
4212 </example> and someone else releases an enhanced version of
4213 the <tt>bar</tt> package they can say:
4214 <example compact="compact">
4218 and the <tt>bar-plus</tt> package will now also satisfy the
4219 dependency for the <tt>foo</tt> package.
4223 If a dependency or a conflict has a version number attached
4224 then only real packages will be considered to see whether
4225 the relationship is satisfied (or the prohibition violated,
4226 for a conflict) - it is assumed that a real package which
4227 provides the virtual package is not of the "right" version.
4228 So, a <tt>Provides</tt> field may not contain version
4229 numbers, and the version number of the concrete package
4230 which provides a particular virtual package will not be
4231 looked at when considering a dependency on or conflict with
4232 the virtual package name.
4236 It is likely that the ability will be added in a future
4237 release of <prgn>dpkg</prgn> to specify a version number for
4238 each virtual package it provides. This feature is not yet
4239 present, however, and is expected to be used only
4244 If you want to specify which of a set of real packages
4245 should be the default to satisfy a particular dependency on
4246 a virtual package, you should list the real package as an
4247 alternative before the virtual one.
4252 <sect id="replaces"><heading>Overwriting files and replacing
4253 packages - <tt>Replaces</tt></heading>
4256 Packages can declare in their control file that they should
4257 overwrite files in certain other packages, or completely
4258 replace other packages. The <tt>Replaces</tt> control file
4259 field has these two distinct purposes.
4262 <sect1><heading>Overwriting files in other packages</heading>
4265 Firstly, as mentioned before, it is usually an error for a
4266 package to contain files which are on the system in
4271 However, if the overwriting package declares that it
4272 <tt>Replaces</tt> the one containing the file being
4273 overwritten, then <prgn>dpkg</prgn> will replace the file
4274 from the old package with that from the new. The file
4275 will no longer be listed as "owned" by the old package.
4279 If a package is completely replaced in this way, so that
4280 <prgn>dpkg</prgn> does not know of any files it still
4281 contains, it is considered to have "disappeared". It will
4282 be marked as not wanted on the system (selected for
4283 removal) and not installed. Any <tt>conffile</tt>s
4284 details noted for the package will be ignored, as they
4285 will have been taken over by the overwriting package. The
4286 package's <prgn>postrm</prgn> script will be run with a
4287 special argument to allow the package to do any final
4288 cleanup required. See <ref id="mscriptsinstact">.
4291 Replaces is a one way relationship -- you have to
4292 install the replacing package after the replaced
4299 For this usage of <tt>Replaces</tt>, virtual packages (see
4300 <ref id="virtual">) are not considered when looking at a
4301 <tt>Replaces</tt> field - the packages declared as being
4302 replaced must be mentioned by their real names.
4306 Furthermore, this usage of <tt>Replaces</tt> only takes
4307 effect when both packages are at least partially on the
4308 system at once, so that it can only happen if they do not
4309 conflict or if the conflict has been overridden.
4314 <sect1><heading>Replacing whole packages, forcing their
4318 Secondly, <tt>Replaces</tt> allows the packaging system to
4319 resolve which package should be removed when there is a
4320 conflict - see <ref id="conflicts">. This usage only
4321 takes effect when the two packages <em>do</em> conflict,
4322 so that the two usages of this field do not interfere with
4327 In this situation, the package declared as being replaced
4328 can be a virtual package, so for example, all mail
4329 transport agents (MTAs) would have the following fields in
4330 their control files:
4331 <example compact="compact">
4332 Provides: mail-transport-agent
4333 Conflicts: mail-transport-agent
4334 Replaces: mail-transport-agent
4336 ensuring that only one MTA can be installed at any one
4341 <sect id="sourcebinarydeps">
4342 <heading>Relationships between source and binary packages -
4343 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4344 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
4348 Source packages that require certain binary packages to be
4349 installed or absent at the time of building the package
4350 can declare relationships to those binary packages.
4354 This is done using the <tt>Build-Depends</tt>,
4355 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
4356 <tt>Build-Conflicts-Indep</tt> control file fields.
4360 Build-dependencies on "build-essential" binary packages can be
4361 omitted. Please see <ref id="pkg-relations"> for more information.
4365 The dependencies and conflicts they define must be satisfied
4366 (as defined earlier for binary packages) in order to invoke
4367 the targets in <tt>debian/rules</tt>, as follows:<footnote>
4369 If you make "build-arch" or "binary-arch", you need
4370 Build-Depends. If you make "build-indep" or
4371 "binary-indep", you need Build-Depends and
4372 Build-Depends-Indep. If you make "build" or "binary",
4376 There is no Build-Depends-Arch; this role is essentially
4377 met with Build-Depends. Anyone building the
4378 <tt>build-indep</tt> and binary-indep<tt></tt> targets
4379 is basically assumed to be building the whole package
4380 anyway and so installs all build dependencies. The
4381 autobuilders use <tt>dpkg-buildpackage -B</tt>, which
4382 calls <tt>build</tt> (not <tt>build-arch</tt>, since it
4383 does not yet know how to check for its existence) and
4384 <tt>binary-arch</tt>.
4387 The purpose of the original split, I recall, was so that
4388 the autobuilders wouldn't need to install extra packages
4389 needed only for the binary-indep targets. But without a
4390 build-arch/build-indep split, this didn't work, since
4391 most of the work is done in the build target, not in the
4397 <tag><tt>Build-Depends</tt>, <tt>Build-Conflicts</tt></tag>
4399 The <tt>Build-Depends</tt> and
4400 <tt>Build-Conflicts</tt> fields must be satisfied when
4401 any of the following targets is invoked:
4402 <tt>build</tt>, <tt>clean</tt>, <tt>binary</tt>,
4403 <tt>binary-arch</tt>, <tt>build-arch</tt>,
4404 <tt>build-indep</tt> and <tt>binary-indep</tt>.
4406 <tag><tt>Build-Depends-Indep</tt>,
4407 <tt>Build-Conflicts-Indep</tt></tag>
4409 The <tt>Build-Depends-Indep</tt> and
4410 <tt>Build-Conflicts-Indep</tt> fields must be
4411 satisfied when any of the following targets is
4412 invoked: <tt>build</tt>, <tt>build-indep</tt>,
4413 <tt>binary</tt> and <tt>binary-indep</tt>.
4423 <chapt id="sharedlibs"><heading>Shared libraries</heading>
4426 Packages containing shared libraries must be constructed with
4427 a little care to make sure that the shared library is always
4428 available. This is especially important for packages whose
4429 shared libraries are vitally important, such as the C library
4430 (currently <tt>libc6</tt>).
4434 Packages involving shared libraries should be split up into
4435 several binary packages. This section mostly deals with how
4436 this separation is to be accomplished; rules for files within
4437 the shared library packages are in <ref id="libraries"> instead.
4440 <sect id="sharedlibs-runtime">
4441 <heading>Run-time shared libraries</heading>
4444 The run-time shared library needs to be placed in a package
4445 whose name changes whenever the shared object version
4448 Since it is common place to install several versions of a
4449 package that just provides shared libraries, it is a
4450 good idea that the library package should not
4451 contain any extraneous non-versioned files, unless they
4452 happen to be in versioned directories.</p>
4454 The most common mechanism is to place it in a package
4456 <package><var>libraryname</var><var>soversion</var></package>,
4457 where <file><var>soversion</var></file> is the version number
4458 in the soname of the shared library<footnote>
4459 The soname is the shared object name: it's the thing
4460 that has to match exactly between building an executable
4461 and running it for the dynamic linker to be able run the
4462 program. For example, if the soname of the library is
4463 <file>libfoo.so.6</file>, the library package would be
4464 called <file>libfoo6</file>.
4466 Alternatively, if it would be confusing to directly append
4467 <var>soversion</var> to <var>libraryname</var> (e.g. because
4468 <var>libraryname</var> itself ends in a number), you may use
4469 <package><var>libraryname</var>-<var>soversion</var></package> and
4470 <package><var>libraryname</var>-<var>soversion</var>-dev</package>
4475 If your package includes run-time support programs that
4476 do not need to be invoked manually by users, but are
4477 nevertheless required for the package to function, then it
4478 is recommended that these programs are placed
4479 (if they are binary) in a subdirectory of
4480 <file>/usr/lib</file>, preferably under
4481 <file>/usr/lib/</file><var>package-name</var>.
4482 If the program is architecture independent, the
4483 recommendation is for it to be placed in a subdirectory of
4484 <file>/usr/share</file> instead, preferably under
4485 <file>/usr/share/</file><var>package-name</var>.
4490 If you have several shared libraries built from the same
4491 source tree you may lump them all together into a single
4492 shared library package, provided that you change all of
4493 their sonames at once (so that you don't get filename
4494 clashes if you try to install different versions of the
4495 combined shared libraries package).
4499 The package should install the shared libraries under
4500 their normal names. For example, the <package>libgdbm3</package>
4501 package should install <file>libgdbm.so.3.0.0</file> as
4502 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
4503 renamed or re-linked by any <prgn>prerm</prgn> or
4504 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
4505 of renaming things safely without affecting running programs,
4506 and attempts to interfere with this are likely to lead to
4511 Shared libraries should not be installed executable, since
4512 the dynamic linker does not require this and trying to
4513 execute a shared library usually results in a core dump.
4517 The run-time library package should include the symbolic link that
4518 <prgn>ldconfig</prgn> would create for the shared libraries.
4519 For example, the <package>libgdbm3</package> package should include
4520 a symbolic link from <file>/usr/lib/libgdbm.so.3</file> to
4521 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
4522 linker (for example <prgn>ld.so</prgn> or
4523 <prgn>ld-linux.so.*</prgn>) can find the library between the
4524 time that <prgn>dpkg</prgn> installs it and the time that
4525 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
4527 The package management system requires the library to be
4528 placed before the symbolic link pointing to it in the
4529 <file>.deb</file> file. This is so that when
4530 <prgn>dpkg</prgn> comes to install the symlink
4531 (overwriting the previous symlink pointing at an older
4532 version of the library), the new shared library is already
4533 in place. In the past, this was achieved by creating the
4534 library in the temporary packaging directory before
4535 creating the symlink. Unfortunately, this was not always
4536 effective, since the building of the tar file in the
4537 <file>.deb</file> depended on the behavior of the underlying
4538 file system. Some file systems (such as reiserfs) reorder
4539 the files so that the order of creation is forgotten.
4540 Since version 1.7.0, <prgn>dpkg</prgn>
4541 reorders the files itself as necessary when building a
4542 package. Thus it is no longer important to concern
4543 oneself with the order of file creation.
4547 <sect1 id="ldconfig">
4548 <heading><tt>ldconfig</tt></heading>
4551 Any package installing shared libraries in one of the default
4552 library directories of the dynamic linker (which are currently
4553 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
4554 listed in <file>/etc/ld.so.conf</file><footnote>
4556 <list compact="compact">
4557 <item>/usr/local/lib</item>
4558 <item>/usr/lib/libc5-compat</item>
4559 <item>/lib/libc5-compat</item>
4562 must use <prgn>ldconfig</prgn> to update the shared library
4567 The package maintainer scripts must only call
4568 <prgn>ldconfig</prgn> under these circumstances:
4569 <list compact="compact">
4570 <item>When the <prgn>postinst</prgn> script is run with a
4571 first argument of <tt>configure</tt>, the script must call
4572 <prgn>ldconfig</prgn>, and may optionally invoke
4573 <prgn>ldconfig</prgn> at other times.
4575 <item>When the <prgn>postrm</prgn> script is run with a
4576 first argument of <tt>remove</tt>, the script should call
4577 <prgn>ldconfig</prgn>.
4582 During install or upgrade, the preinst is called before
4583 the new files are installed, so calling "ldconfig" is
4584 pointless. The preinst of an existing package can also be
4585 called if an upgrade fails. However, this happens during
4586 the critical time when a shared libs may exist on-disk
4587 under a temporary name. Thus, it is dangerous and
4588 forbidden by current policy to call "ldconfig" at this
4593 When a package is installed or upgraded, "postinst
4594 configure" runs after the new files are safely on-disk.
4595 Since it is perfectly safe to invoke ldconfig
4596 unconditionally in a postinst, it is OK for a package to
4597 simply put ldconfig in its postinst without checking the
4598 argument. The postinst can also be called to recover from
4599 a failed upgrade. This happens before any new files are
4600 unpacked, so there is no reason to call "ldconfig" at this
4605 For a package that is being removed, prerm is
4606 called with all the files intact, so calling ldconfig is
4607 useless. The other calls to "prerm" happen in the case of
4608 upgrade at a time when all the files of the old package
4609 are on-disk, so again calling "ldconfig" is pointless.
4613 postrm, on the other hand, is called with the "remove"
4614 argument just after the files are removed, so this is
4615 the proper time to call "ldconfig" to notify the system
4616 of the fact that the shared libraries from the package
4617 are removed. The postrm can be called at several other
4618 times. At the time of "postrm purge", "postrm
4619 abort-install", or "postrm abort-upgrade", calling
4620 "ldconfig" is useless because the shared lib files are
4621 not on-disk. However, when "postrm" is invoked with
4622 arguments "upgrade", "failed-upgrade", or "disappear", a
4623 shared lib may exist on-disk under a temporary filename.
4631 <sect id="sharedlibs-runtime-progs">
4632 <heading>Run-time support programs</heading>
4635 If your package has some run-time support programs which use
4636 the shared library you must not put them in the shared
4637 library package. If you do that then you won't be able to
4638 install several versions of the shared library without
4639 getting filename clashes.
4643 Instead, either create another package for the runtime binaries
4644 (this package might typically be named
4645 <package><var>libraryname</var>-runtime</package>; note the absence
4646 of the <var>soversion</var> in the package name), or if the
4647 development package is small, include them in there.
4651 <sect id="sharedlibs-static">
4652 <heading>Static libraries</heading>
4655 The static library (<file><var>libraryname.a</var></file>)
4656 is usually provided in addition to the shared version.
4657 It is placed into the development package (see below).
4661 In some cases, it is acceptable for a library to be
4662 available in static form only; these cases include:
4664 <item>libraries for languages whose shared library support
4665 is immature or unstable</item>
4666 <item>libraries whose interfaces are in flux or under
4667 development (commonly the case when the library's
4668 major version number is zero, or where the ABI breaks
4669 across patchlevels)</item>
4670 <item>libraries which are explicitly intended to be
4671 available only in static form by their upstream
4676 <sect id="sharedlibs-dev">
4677 <heading>Development files</heading>
4680 The development files associated to a shared library need to be
4681 placed in a package called
4682 <package><var>libraryname</var><var>soversion</var>-dev</package>,
4683 or if you prefer only to support one development version at a
4684 time, <package><var>libraryname</var>-dev</package>.
4688 In case several development versions of a library exist, you may
4689 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
4690 <ref id="conflicts">) to ensure that the user only installs one
4691 development version at a time (as different development versions are
4692 likely to have the same header files in them, which would cause a
4693 filename clash if both were installed).
4697 The development package should contain a symlink for the associated
4698 shared library without a version number. For example, the
4699 <package>libgdbm-dev</package> package should include a symlink
4700 from <file>/usr/lib/libgdbm.so</file> to
4701 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
4702 (<prgn>ld</prgn>) when compiling packages, as it will only look for
4703 <file>libgdbm.so</file> when compiling dynamically.
4707 <sect id="sharedlibs-intradeps">
4708 <heading>Dependencies between the packages of the same library</heading>
4711 Typically the development version should have an exact
4712 version dependency on the runtime library, to make sure that
4713 compilation and linking happens correctly. The
4714 <tt>${Source-Version}</tt> substitution variable can be
4715 useful for this purpose.
4719 <sect id="sharedlibs-shlibdeps">
4720 <heading>Dependencies between the library and other packages -
4721 the <tt>shlibs</tt> system</heading>
4724 If a package contains a binary or library which links to a
4725 shared library, we must ensure that when the package is
4726 installed on the system, all of the libraries needed are
4727 also installed. This requirement led to the creation of the
4728 <tt>shlibs</tt> system, which is very simple in its design:
4729 any package which <em>provides</em> a shared library also
4730 provides information on the package dependencies required to
4731 ensure the presence of this library, and any package which
4732 <em>uses</em> a shared library uses this information to
4733 determine the dependencies it requires. The files which
4734 contain the mapping from shared libraries to the necessary
4735 dependency information are called <file>shlibs</file> files.
4739 Thus, when a package is built which contains any shared
4740 libraries, it must provide a <file>shlibs</file> file for other
4741 packages to use, and when a package is built which contains
4742 any shared libraries or compiled binaries, it must run
4743 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
4744 on these to determine the libraries used and hence the
4745 dependencies needed by this package.<footnote>
4747 In the past, the shared libraries linked to were
4748 determined by calling <prgn>ldd</prgn>, but now
4749 <prgn>objdump</prgn> is used to do this. The only
4750 change this makes to package building is that
4751 <prgn>dpkg-shlibdeps</prgn> must also be run on shared
4752 libraries, whereas in the past this was unnecessary.
4753 The rest of this footnote explains the advantage that
4758 We say that a binary <tt>foo</tt> <em>directly</em> uses
4759 a library <tt>libbar</tt> if it is explicitly linked
4760 with that library (that is, it uses the flag
4761 <tt>-lbar</tt> during the linking stage). Other
4762 libraries that are needed by <tt>libbar</tt> are linked
4763 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
4764 linker will load them automatically when it loads
4765 <tt>libbar</tt>. A package should depend on
4766 the libraries it directly uses, and the dependencies for
4767 those libraries should automatically pull in the other
4772 Unfortunately, the <prgn>ldd</prgn> program shows both
4773 the directly and indirectly used libraries, meaning that
4774 the dependencies determined included both direct and
4775 indirect dependencies. The use of <prgn>objdump</prgn>
4776 avoids this problem by determining only the directly
4781 A good example of where this helps is the following. We
4782 could update <tt>libimlib</tt> with a new version that
4783 supports a new graphics format called dgf (but retaining
4784 the same major version number). If we used the old
4785 <prgn>ldd</prgn> method, every package that uses
4786 <tt>libimlib</tt> would need to be recompiled so it
4787 would also depend on <tt>libdgf</tt> or it wouldn't run
4788 due to missing symbols. However with the new system,
4789 packages using <tt>libimlib</tt> can rely on
4790 <tt>libimlib</tt> itself having the dependency on
4791 <tt>libdgf</tt> and so they would not need rebuilding.
4797 In the following sections, we will first describe where the
4798 various <tt>shlibs</tt> files are to be found, then how to
4799 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
4800 file format and how to create them if your package contains a
4805 <heading>The <tt>shlibs</tt> files present on the system</heading>
4808 There are several places where <tt>shlibs</tt> files are
4809 found. The following list gives them in the order in which
4811 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
4812 (The first one which gives the required information is used.)
4818 <p><file>debian/shlibs.local</file></p>
4821 This lists overrides for this package. Its use is
4822 described below (see <ref id="shlibslocal">).
4827 <p><file>/etc/dpkg/shlibs.override</file></p>
4830 This lists global overrides. This list is normally
4831 empty. It is maintained by the local system
4837 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
4840 When packages are being built, any
4841 <file>debian/shlibs</file> files are copied into the
4842 control file area of the temporary build directory and
4843 given the name <file>shlibs</file>. These files give
4844 details of any shared libraries included in the
4846 An example may help here. Let us say that the
4847 source package <tt>foo</tt> generates two binary
4848 packages, <tt>libfoo2</tt> and
4849 <tt>foo-runtime</tt>. When building the binary
4850 packages, the two packages are created in the
4851 directories <file>debian/libfoo2</file> and
4852 <file>debian/foo-runtime</file> respectively.
4853 (<file>debian/tmp</file> could be used instead of one
4854 of these.) Since <tt>libfoo2</tt> provides the
4855 <tt>libfoo</tt> shared library, it will require a
4856 <tt>shlibs</tt> file, which will be installed in
4857 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually
4859 <file>/var/lib/dpkg/info/libfoo2.shlibs</file>. Then
4860 when <prgn>dpkg-shlibdeps</prgn> is run on the
4862 <file>debian/foo-runtime/usr/bin/foo-prog</file>, it
4864 <file>debian/libfoo2/DEBIAN/shlibs</file> file to
4865 determine whether <tt>foo-prog</tt>'s library
4866 dependencies are satisfied by any of the libraries
4867 provided by <tt>libfoo2</tt>. For this reason,
4868 <prgn>dpkg-shlibdeps</prgn> must only be run once
4869 all of the individual binary packages'
4870 <tt>shlibs</tt> files have been installed into the
4877 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
4880 These are the <file>shlibs</file> files corresponding to
4881 all of the packages installed on the system, and are
4882 maintained by the relevant package maintainers.
4887 <p><file>/etc/dpkg/shlibs.default</file></p>
4890 This file lists any shared libraries whose packages
4891 have failed to provide correct <file>shlibs</file> files.
4892 It was used when the <file>shlibs</file> setup was first
4893 introduced, but it is now normally empty. It is
4894 maintained by the <tt>dpkg</tt> maintainer.
4902 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
4903 <file>shlibs</file> files</heading>
4907 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
4908 into your <file>debian/rules</file> file. If your package
4909 contains only compiled binaries and libraries (but no scripts),
4910 you can use a command such as:
4911 <example compact="compact">
4912 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
4913 debian/tmp/usr/lib/*
4915 Otherwise, you will need to explicitly list the compiled
4916 binaries and libraries.<footnote>
4917 If you are using <tt>debhelper</tt>, the
4918 <prgn>dh_shlibdeps</prgn> program will do this work for
4919 you. It will also correctly handle multi-binary
4925 This command puts the dependency information into the
4926 <file>debian/substvars</file> file, which is then used by
4927 <prgn>dpkg-gencontrol</prgn>. You will need to place a
4928 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
4929 field in the control file for this to work.
4933 If <prgn>dpkg-shlibdeps</prgn> doesn't complain, you're
4934 done. If it does complain you might need to create your own
4935 <file>debian/shlibs.local</file> file, as explained below (see
4936 <ref id="shlibslocal">).
4940 If you have multiple binary packages, you will need to call
4941 <prgn>dpkg-shlibdeps</prgn> on each one which contains
4942 compiled libraries or binaries. In such a case, you will
4943 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
4944 utilities to specify a different <file>substvars</file> file.
4948 For more details on dpkg-shlibdeps, please see
4949 <ref id="pkg-dpkg-shlibdeps"> and
4950 <manref name="dpkg-shlibdeps" section="1">.
4955 <heading>The <file>shlibs</file> File Format</heading>
4958 Each <file>shlibs</file> file has the same format. Lines
4959 beginning with <tt>#</tt> are considered to be comments and
4960 are ignored. Each line is of the form:
4961 <example compact="compact">
4962 <var>library-name</var> <var>soname-version-number</var> <var>dependencies ...</var>
4967 We will explain this by reference to the example of the
4968 <tt>zlib1g</tt> package, which (at the time of writing)
4969 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
4973 <var>library-name</var> is the name of the shared library,
4974 in this case <tt>libz</tt>. (This must match the name part
4975 of the soname, see below.)
4979 <var>soname-version-number</var> is the version part of the
4980 soname of the library. The soname is the thing that must
4981 exactly match for the library to be recognized by the
4982 dynamic linker, and is usually of the form
4983 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
4984 example, <tt>libz.so.1</tt>.<footnote>
4985 This can be determined using the command
4986 <example compact="compact">
4987 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
4990 The version part is the part which comes after
4991 <tt>.so.</tt>, so in our case, it is <tt>1</tt>.
4995 <var>dependencies</var> has the same syntax as a dependency
4996 field in a binary package control file. It should give
4997 details of which packages are required to satisfy a binary
4998 built against the version of the library contained in the
4999 package. See <ref id="depsyntax"> for details.
5003 In our example, if the first version of the <tt>zlib1g</tt>
5004 package which contained a minor number of at least
5005 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5006 <tt>shlibs</tt> entry for this library could say:
5007 <example compact="compact">
5008 libz 1 zlib1g (>= 1:1.1.3)
5010 The version-specific dependency is to avoid warnings from
5011 the dynamic linker about using older shared libraries with
5017 <heading>Providing a <file>shlibs</file> file</heading>
5020 If your package provides a shared library, you need to create
5021 a <file>shlibs</file> file following the format described above.
5022 It is usual to call this file <file>debian/shlibs</file> (but if
5023 you have multiple binary packages, you might want to call it
5024 <file>debian/shlibs.<var>package</var></file> instead). Then
5025 let <file>debian/rules</file> install it in the control area:
5026 <example compact="compact">
5027 install -m644 debian/shlibs debian/tmp/DEBIAN
5029 or, in the case of a multi-binary package:
5030 <example compact="compact">
5031 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5033 An alternative way of doing this is to create the
5034 <file>shlibs</file> file in the control area directly from
5035 <file>debian/rules</file> without using a <file>debian/shlibs</file>
5036 file at all,<footnote>
5037 This is what <prgn>dh_makeshlibs</prgn> in the
5038 <tt>debhelper</tt> suite does.
5040 since the <file>debian/shlibs</file> file itself is ignored by
5041 <prgn>dpkg-shlibdeps</prgn>.
5045 As <prgn>dpkg-shlibdeps</prgn> reads the
5046 <file>DEBIAN/shlibs</file> files in all of the binary packages
5047 being built from this source package, all of the
5048 <file>DEBIAN/shlibs</file> files should be installed before
5049 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5054 <sect1 id="shlibslocal">
5055 <heading>Writing the <file>debian/shlibs.local</file> file</heading>
5058 This file is intended only as a <em>temporary</em> fix if
5059 your binaries or libraries depend on a library whose package
5060 does not yet provide a correct <file>shlibs</file> file.
5064 We will assume that you are trying to package a binary
5065 <tt>foo</tt>. When you try running
5066 <prgn>dpkg-shlibdeps</prgn> you get the following error
5067 message (<tt>-O</tt> displays the dependency information on
5068 <tt>stdout</tt> instead of writing it to
5069 <tt>debian/substvars</tt>, and the lines have been wrapped
5070 for ease of reading):
5071 <example compact="compact">
5072 $ dpkg-shlibdeps -O debian/tmp/usr/bin/foo
5073 dpkg-shlibdeps: warning: unable to find dependency
5074 information for shared library libbar (soname 1,
5075 path /usr/lib/libbar.so.1, dependency field Depends)
5076 shlibs:Depends=libc6 (>= 2.2.2-2)
5078 You can then run <prgn>ldd</prgn> on the binary to find the
5079 full location of the library concerned:
5080 <example compact="compact">
5082 libbar.so.1 => /usr/lib/libbar.so.1 (0x4001e000)
5083 libc.so.6 => /lib/libc.so.6 (0x40032000)
5084 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
5086 So the <prgn>foo</prgn> binary depends on the
5087 <prgn>libbar</prgn> shared library, but no package seems to
5088 provide a <file>*.shlibs</file> file handling
5089 <file>libbar.so.1</file> in <file>/var/lib/dpkg/info/</file>. Let's
5090 determine the package responsible:
5091 <example compact="compact">
5092 $ dpkg -S /usr/lib/libbar.so.1
5093 bar1: /usr/lib/libbar.so.1
5094 $ dpkg -s bar1 | grep Version
5097 This tells us that the <tt>bar1</tt> package, version 1.0-1,
5098 is the one we are using. Now we can file a bug against the
5099 <tt>bar1</tt> package and create our own
5100 <file>debian/shlibs.local</file> to locally fix the problem.
5101 Including the following line into your
5102 <file>debian/shlibs.local</file> file:
5103 <example compact="compact">
5104 libbar 1 bar1 (>= 1.0-1)
5106 should allow the package build to work.
5110 As soon as the maintainer of <tt>bar1</tt> provides a
5111 correct <file>shlibs</file> file, you should remove this line
5112 from your <file>debian/shlibs.local</file> file. (You should
5113 probably also then have a versioned <tt>Build-Depends</tt>
5114 on <tt>bar1</tt> to help ensure that others do not have the
5115 same problem building your package.)
5124 <chapt id="opersys"><heading>The Operating System</heading>
5127 <heading>File system hierarchy</heading>
5131 <heading>File system Structure</heading>
5134 The location of all installed files and directories must
5135 comply with the File system Hierarchy Standard (FHS),
5136 version 2.3, with the exceptions noted below, and except
5137 where doing so would violate other terms of Debian
5138 Policy. The following exceptions to the FHS apply:
5143 Legacy XFree86 servers are permitted to retain the
5144 configuration file location
5145 <file>/etc/X11/XF86Config-4</file>.
5150 The optional rules related to user specific
5151 configuration files for applications are stored in
5152 the user's home directory are relaxed. It is
5153 recommended that such files start with the
5154 '<tt>.</tt>' character (a "dot file"), and if an
5155 application needs to create more than one dot file
5156 then the preferred placement is in a subdirectory
5157 with a name starting with a '.' character, (a "dot
5158 directory"). In this case it is recommended the
5159 configuration files not start with the '.'
5165 The requirement for amd64 to use <file>/lib64</file>
5166 for 64 bit binaries is removed.
5171 The requirement that
5172 <file>/usr/local/share/man</file> be "synonymous"
5173 with <file>/usr/local/man</file> is relaxed to a
5178 The requirement that windowmanagers with a single
5179 configuration file call it <file>system.*wmrc</file>
5180 is removed, as is the restriction that the window
5181 manager subdirectory be named identically to the
5182 window manager name itself.
5187 The requirement that boot manager configuration
5188 files live in <file>/etc</file>, or at least are
5189 symlinked there, is relaxed to a recommendation.
5196 The version of this document referred here can be
5197 found in the <tt>debian-policy</tt> package or on <url
5198 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5199 name="FHS (Debian copy)"> alongside this manual (or, if
5200 you have the <package>debian-policy</package> installed,
5202 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5203 (local copy)">). The
5204 latest version, which may be a more recent version, may
5206 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5207 Specific questions about following the standard may be
5208 asked on the <tt>debian-devel</tt> mailing list, or
5209 referred to the FHS mailing list (see the
5210 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
5216 <heading>Site-specific programs</heading>
5219 As mandated by the FHS, packages must not place any
5220 files in <file>/usr/local</file>, either by putting them in
5221 the file system archive to be unpacked by <prgn>dpkg</prgn>
5222 or by manipulating them in their maintainer scripts.
5226 However, the package may create empty directories below
5227 <file>/usr/local</file> so that the system administrator knows
5228 where to place site-specific files. These are not
5229 directories <em>in</em> <file>/usr/local</file>, but are
5230 children of directories in <file>/usr/local</file>. These
5231 directories (<file>/usr/local/*/dir/</file>)
5232 should be removed on package removal if they are
5237 Note, that this applies only to directories <em>below</em>
5238 <file>/usr/local</file>, not <em>in</em> <file>/usr/local</file>.
5239 Packages must not create sub-directories in the directory
5240 <file>/usr/local</file> itself, except those listed in FHS,
5241 section 4.5. However, you may create directories below
5242 them as you wish. You must not remove any of the
5243 directories listed in 4.5, even if you created them.
5247 Since <file>/usr/local</file> can be mounted read-only from a
5248 remote server, these directories must be created and
5249 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
5250 maintainer scripts and not be included in the
5251 <file>.deb</file> archive. These scripts must not fail if
5252 either of these operations fail.
5256 For example, the <tt>emacsen-common</tt> package could
5257 contain something like
5258 <example compact="compact">
5259 if [ ! -e /usr/local/share/emacs ]
5261 if mkdir /usr/local/share/emacs 2>/dev/null
5263 chown root:staff /usr/local/share/emacs
5264 chmod 2775 /usr/local/share/emacs
5268 in its <prgn>postinst</prgn> script, and
5269 <example compact="compact">
5270 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
5271 rmdir /usr/local/share/emacs 2>/dev/null || true
5273 in the <prgn>prerm</prgn> script. (Note that this form is
5274 used to ensure that if the script is interrupted, the
5275 directory <file>/usr/local/share/emacs</file> will still be
5280 If you do create a directory in <file>/usr/local</file> for
5281 local additions to a package, you should ensure that
5282 settings in <file>/usr/local</file> take precedence over the
5283 equivalents in <file>/usr</file>.
5287 However, because <file>/usr/local</file> and its contents are
5288 for exclusive use of the local administrator, a package
5289 must not rely on the presence or absence of files or
5290 directories in <file>/usr/local</file> for normal operation.
5294 The <file>/usr/local</file> directory itself and all the
5295 subdirectories created by the package should (by default) have
5296 permissions 2775 (group-writable and set-group-id) and be
5297 owned by <tt>root.staff</tt>.
5302 <heading>The system-wide mail directory</heading>
5304 The system-wide mail directory is <file>/var/mail</file>. This
5305 directory is part of the base system and should not owned
5306 by any particular mail agents. The use of the old
5307 location <file>/var/spool/mail</file> is deprecated, even
5308 though the spool may still be physically located there.
5309 To maintain partial upgrade compatibility for systems
5310 which have <file>/var/spool/mail</file> as their physical mail
5311 spool, packages using <file>/var/mail</file> must depend on
5312 either <package>libc6</package> (>= 2.1.3-13), or on
5313 <package>base-files</package> (>= 2.2.0), or on later
5314 versions of either one of these packages.
5320 <heading>Users and groups</heading>
5323 <heading>Introduction</heading>
5325 The Debian system can be configured to use either plain or
5330 Some user ids (UIDs) and group ids (GIDs) are reserved
5331 globally for use by certain packages. Because some
5332 packages need to include files which are owned by these
5333 users or groups, or need the ids compiled into binaries,
5334 these ids must be used on any Debian system only for the
5335 purpose for which they are allocated. This is a serious
5336 restriction, and we should avoid getting in the way of
5337 local administration policies. In particular, many sites
5338 allocate users and/or local system groups starting at 100.
5342 Apart from this we should have dynamically allocated ids,
5343 which should by default be arranged in some sensible
5344 order, but the behavior should be configurable.
5348 Packages other than <tt>base-passwd</tt> must not modify
5349 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
5350 <file>/etc/group</file> or <file>/etc/gshadow</file>.
5355 <heading>UID and GID classes</heading>
5357 The UID and GID numbers are divided into classes as
5363 Globally allocated by the Debian project, the same
5364 on every Debian system. These ids will appear in
5365 the <file>passwd</file> and <file>group</file> files of all
5366 Debian systems, new ids in this range being added
5367 automatically as the <tt>base-passwd</tt> package is
5372 Packages which need a single statically allocated
5373 uid or gid should use one of these; their
5374 maintainers should ask the <tt>base-passwd</tt>
5382 Dynamically allocated system users and groups.
5383 Packages which need a user or group, but can have
5384 this user or group allocated dynamically and
5385 differently on each system, should use <tt>adduser
5386 --system</tt> to create the group and/or user.
5387 <prgn>adduser</prgn> will check for the existence of
5388 the user or group, and if necessary choose an unused
5389 id based on the ranges specified in
5390 <file>adduser.conf</file>.
5394 <tag>1000-29999:</tag>
5397 Dynamically allocated user accounts. By default
5398 <prgn>adduser</prgn> will choose UIDs and GIDs for
5399 user accounts in this range, though
5400 <file>adduser.conf</file> may be used to modify this
5405 <tag>30000-59999:</tag>
5410 <tag>60000-64999:</tag>
5413 Globally allocated by the Debian project, but only
5414 created on demand. The ids are allocated centrally
5415 and statically, but the actual accounts are only
5416 created on users' systems on demand.
5420 These ids are for packages which are obscure or
5421 which require many statically-allocated ids. These
5422 packages should check for and create the accounts in
5423 <file>/etc/passwd</file> or <file>/etc/group</file> (using
5424 <prgn>adduser</prgn> if it has this facility) if
5425 necessary. Packages which are likely to require
5426 further allocations should have a "hole" left after
5427 them in the allocation, to give them room to
5432 <tag>65000-65533:</tag>
5440 User <tt>nobody</tt>. The corresponding gid refers
5441 to the group <tt>nogroup</tt>.
5448 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
5449 not</em> be used, because it is the error return
5458 <sect id="sysvinit">
5459 <heading>System run levels and <file>init.d</file> scripts</heading>
5461 <sect1 id="/etc/init.d">
5462 <heading>Introduction</heading>
5465 The <file>/etc/init.d</file> directory contains the scripts
5466 executed by <prgn>init</prgn> at boot time and when the
5467 init state (or "runlevel") is changed (see <manref
5468 name="init" section="8">).
5472 There are at least two different, yet functionally
5473 equivalent, ways of handling these scripts. For the sake
5474 of simplicity, this document describes only the symbolic
5475 link method. However, it must not be assumed by maintainer
5476 scripts that this method is being used, and any automated
5477 manipulation of the various runlevel behaviors by
5478 maintainer scripts must be performed using
5479 <prgn>update-rc.d</prgn> as described below and not by
5480 manually installing or removing symlinks. For information
5481 on the implementation details of the other method,
5482 implemented in the <tt>file-rc</tt> package, please refer
5483 to the documentation of that package.
5487 These scripts are referenced by symbolic links in the
5488 <file>/etc/rc<var>n</var>.d</file> directories. When changing
5489 runlevels, <prgn>init</prgn> looks in the directory
5490 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
5491 execute, where <tt><var>n</var></tt> is the runlevel that
5492 is being changed to, or <tt>S</tt> for the boot-up
5497 The names of the links all have the form
5498 <file>S<var>mm</var><var>script</var></file> or
5499 <file>K<var>mm</var><var>script</var></file> where
5500 <var>mm</var> is a two-digit number and <var>script</var>
5501 is the name of the script (this should be the same as the
5502 name of the actual script in <file>/etc/init.d</file>).
5506 When <prgn>init</prgn> changes runlevel first the targets
5507 of the links whose names start with a <tt>K</tt> are
5508 executed, each with the single argument <tt>stop</tt>,
5509 followed by the scripts prefixed with an <tt>S</tt>, each
5510 with the single argument <tt>start</tt>. (The links are
5511 those in the <file>/etc/rc<var>n</var>.d</file> directory
5512 corresponding to the new runlevel.) The <tt>K</tt> links
5513 are responsible for killing services and the <tt>S</tt>
5514 link for starting services upon entering the runlevel.
5518 For example, if we are changing from runlevel 2 to
5519 runlevel 3, init will first execute all of the <tt>K</tt>
5520 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
5521 all of the <tt>S</tt> prefixed scripts in that directory.
5522 The links starting with <tt>K</tt> will cause the
5523 referred-to file to be executed with an argument of
5524 <tt>stop</tt>, and the <tt>S</tt> links with an argument
5529 The two-digit number <var>mm</var> is used to determine
5530 the order in which to run the scripts: low-numbered links
5531 have their scripts run first. For example, the
5532 <tt>K20</tt> scripts will be executed before the
5533 <tt>K30</tt> scripts. This is used when a certain service
5534 must be started before another. For example, the name
5535 server <prgn>bind</prgn> might need to be started before
5536 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
5537 can set up its access lists. In this case, the script
5538 that starts <prgn>bind</prgn> would have a lower number
5539 than the script that starts <prgn>inn</prgn> so that it
5541 <example compact="compact">
5548 The two runlevels 0 (halt) and 6 (reboot) are slightly
5549 different. In these runlevels, the links with an
5550 <tt>S</tt> prefix are still called after those with a
5551 <tt>K</tt> prefix, but they too are called with the single
5552 argument <tt>stop</tt>.
5556 Also, if the script name ends in <tt>.sh</tt>, the script
5557 will be sourced in runlevel <tt>S</tt> rather than being
5558 run in a forked subprocess, but will be explicitly run by
5559 <prgn>sh</prgn> in all other runlevels.
5564 <heading>Writing the scripts</heading>
5567 Packages that include daemons for system services should
5568 place scripts in <file>/etc/init.d</file> to start or stop
5569 services at boot time or during a change of runlevel.
5570 These scripts should be named
5571 <file>/etc/init.d/<var>package</var></file>, and they should
5572 accept one argument, saying what to do:
5575 <tag><tt>start</tt></tag>
5576 <item>start the service,</item>
5578 <tag><tt>stop</tt></tag>
5579 <item>stop the service,</item>
5581 <tag><tt>restart</tt></tag>
5582 <item>stop and restart the service if it's already running,
5583 otherwise start the service</item>
5585 <tag><tt>reload</tt></tag>
5586 <item><p>cause the configuration of the service to be
5587 reloaded without actually stopping and restarting
5590 <tag><tt>force-reload</tt></tag>
5591 <item>cause the configuration to be reloaded if the
5592 service supports this, otherwise restart the
5596 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
5597 <tt>force-reload</tt> options should be supported by all
5598 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
5603 The <file>init.d</file> scripts must ensure that they will
5604 behave sensibly if invoked with <tt>start</tt> when the
5605 service is already running, or with <tt>stop</tt> when it
5606 isn't, and that they don't kill unfortunately-named user
5607 processes. The best way to achieve this is usually to use
5608 <prgn>start-stop-daemon</prgn>.
5612 If a service reloads its configuration automatically (as
5613 in the case of <prgn>cron</prgn>, for example), the
5614 <tt>reload</tt> option of the <file>init.d</file> script
5615 should behave as if the configuration has been reloaded
5620 The <file>/etc/init.d</file> scripts must be treated as
5621 configuration files, either (if they are present in the
5622 package, that is, in the .deb file) by marking them as
5623 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
5624 by managing them correctly in the maintainer scripts (see
5625 <ref id="config-files">). This is important since we want
5626 to give the local system administrator the chance to adapt
5627 the scripts to the local system, e.g., to disable a
5628 service without de-installing the package, or to specify
5629 some special command line options when starting a service,
5630 while making sure their changes aren't lost during the next
5635 These scripts should not fail obscurely when the
5636 configuration files remain but the package has been
5637 removed, as configuration files remain on the system after
5638 the package has been removed. Only when <prgn>dpkg</prgn>
5639 is executed with the <tt>--purge</tt> option will
5640 configuration files be removed. In particular, as the
5641 <file>/etc/init.d/<var>package</var></file> script itself is
5642 usually a <tt>conffile</tt>, it will remain on the system
5643 if the package is removed but not purged. Therefore, you
5644 should include a <tt>test</tt> statement at the top of the
5646 <example compact="compact">
5647 test -f <var>program-executed-later-in-script</var> || exit 0
5652 Often there are some variables in the <file>init.d</file>
5653 scripts whose values control the behavior of the scripts,
5654 and which a system administrator is likely to want to
5655 change. As the scripts themselves are frequently
5656 <tt>conffile</tt>s, modifying them requires that the
5657 administrator merge in their changes each time the package
5658 is upgraded and the <tt>conffile</tt> changes. To ease
5659 the burden on the system administrator, such configurable
5660 values should not be placed directly in the script.
5661 Instead, they should be placed in a file in
5662 <file>/etc/default</file>, which typically will have the same
5663 base name as the <file>init.d</file> script. This extra file
5664 should be sourced by the script when the script runs. It
5665 must contain only variable settings and comments in POSIX
5666 <prgn>sh</prgn> format. It may either be a
5667 <tt>conffile</tt> or a configuration file maintained by
5668 the package maintainer scripts. See <ref id="config-files">
5673 To ensure that vital configurable values are always
5674 available, the <file>init.d</file> script should set default
5675 values for each of the shell variables it uses, either
5676 before sourcing the <file>/etc/default/</file> file or
5677 afterwards using something like the <tt>:
5678 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
5679 script must behave sensibly and not fail if the
5680 <file>/etc/default</file> file is deleted.
5685 <heading>Interfacing with the initscript system</heading>
5688 Maintainers should use the abstraction layer provided by
5689 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
5690 programs to deal with initscripts in their packages'
5691 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
5692 and <prgn>postrm</prgn>.
5696 Directly managing the /etc/rc?.d links and directly
5697 invoking the <file>/etc/init.d/</file> initscripts should
5698 be done only by packages providing the initscript
5699 subsystem (such as <prgn>sysv-rc</prgn> and
5700 <prgn>file-rc</prgn>).
5704 <heading>Managing the links</heading>
5707 The program <prgn>update-rc.d</prgn> is provided for
5708 package maintainers to arrange for the proper creation and
5709 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
5710 or their functional equivalent if another method is being
5711 used. This may be used by maintainers in their packages'
5712 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
5716 You must not include any <file>/etc/rc<var>n</var>.d</file>
5717 symbolic links in the actual archive or manually create or
5718 remove the symbolic links in maintainer scripts; you must
5719 use the <prgn>update-rc.d</prgn> program instead. (The
5720 former will fail if an alternative method of maintaining
5721 runlevel information is being used.) You must not include
5722 the <file>/etc/rc<var>n</var>.d</file> directories themselves
5723 in the archive either. (Only the <tt>sysvinit</tt>
5728 By default <prgn>update-rc.d</prgn> will start services in
5729 each of the multi-user state runlevels (2, 3, 4, and 5)
5730 and stop them in the halt runlevel (0), the single-user
5731 runlevel (1) and the reboot runlevel (6). The system
5732 administrator will have the opportunity to customize
5733 runlevels by simply adding, moving, or removing the
5734 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
5735 symbolic links are being used, or by modifying
5736 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
5741 To get the default behavior for your package, put in your
5742 <prgn>postinst</prgn> script
5743 <example compact="compact">
5744 update-rc.d <var>package</var> defaults
5746 and in your <prgn>postrm</prgn>
5747 <example compact="compact">
5748 if [ "$1" = purge ]; then
5749 update-rc.d <var>package</var> remove
5751 </example>. Note that if your package changes runlevels
5752 or priority, you may have to remove and recreate the links,
5753 since otherwise the old links may persist. Refer to the
5754 documentation of <prgn>update-rc.d</prgn>.
5758 This will use a default sequence number of 20. If it does
5759 not matter when or in which order the <file>init.d</file>
5760 script is run, use this default. If it does, then you
5761 should talk to the maintainer of the <prgn>sysvinit</prgn>
5762 package or post to <tt>debian-devel</tt>, and they will
5763 help you choose a number.
5767 For more information about using <tt>update-rc.d</tt>,
5768 please consult its man page <manref name="update-rc.d"
5774 <heading>Running initscripts</heading>
5776 The program <prgn>invoke-rc.d</prgn> is provided to make
5777 it easier for package maintainers to properly invoke an
5778 initscript, obeying runlevel and other locally-defined
5779 constraints that might limit a package's right to start,
5780 stop and otherwise manage services. This program may be
5781 used by maintainers in their packages' scripts.
5785 The package maintainer scripts must use
5786 <prgn>invoke-rc.d</prgn> to invoke the
5787 <file>/etc/init.d/*</file> initscripts, instead of
5788 calling them directly.
5792 By default, <prgn>invoke-rc.d</prgn> will pass any
5793 action requests (start, stop, reload, restart...) to the
5794 <file>/etc/init.d</file> script, filtering out requests
5795 to start or restart a service out of its intended
5800 Most packages will simply need to change:
5801 <example compact="compact">/etc/init.d/<package>
5802 <action></example> in their <prgn>postinst</prgn>
5803 and <prgn>prerm</prgn> scripts to:
5804 <example compact="compact">
5805 if which invoke-rc.d >/dev/null 2>&1; then
5806 invoke-rc.d <var>package</var> <action>
5808 /etc/init.d/<var>package</var> <action>
5814 A package should register its initscript services using
5815 <prgn>update-rc.d</prgn> before it tries to invoke them
5816 using <prgn>invoke-rc.d</prgn>. Invocation of
5817 unregistered services may fail.
5821 For more information about using
5822 <prgn>invoke-rc.d</prgn>, please consult its man page
5823 <manref name="invoke-rc.d" section="8">.
5829 <heading>Boot-time initialization</heading>
5832 There used to be another directory, <file>/etc/rc.boot</file>,
5833 which contained scripts which were run once per machine
5834 boot. This has been deprecated in favour of links from
5835 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
5836 described in <ref id="/etc/init.d">. Packages must not
5837 place files in <file>/etc/rc.boot</file>.
5842 <heading>Example</heading>
5845 An example on which you can base your
5846 <file>/etc/init.d</file> scripts is found in
5847 <file>/etc/init.d/skeleton</file>.
5854 <heading>Console messages from <file>init.d</file> scripts</heading>
5857 This section describes the formats to be used for messages
5858 written to standard output by the <file>/etc/init.d</file>
5859 scripts. The intent is to improve the consistency of
5860 Debian's startup and shutdown look and feel. For this
5861 reason, please look very carefully at the details. We want
5862 the messages to have the same format in terms of wording,
5863 spaces, punctuation and case of letters.
5867 Here is a list of overall rules that should be used for
5868 messages generated by <file>/etc/init.d</file> scripts.
5874 The message should fit in one line (fewer than 80
5875 characters), start with a capital letter and end with
5876 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
5880 If the script is performing some time consuming task in
5881 the background (not merely starting or stopping a
5882 program, for instance), an ellipsis (three dots:
5883 <tt>...</tt>) should be output to the screen, with no
5884 leading or tailing whitespace or line feeds.
5888 The messages should appear as if the computer is telling
5889 the user what it is doing (politely :-), but should not
5890 mention "it" directly. For example, instead of:
5891 <example compact="compact">
5892 I'm starting network daemons: nfsd mountd.
5894 the message should say
5895 <example compact="compact">
5896 Starting network daemons: nfsd mountd.
5903 <tt>init.d</tt> script should use the following standard
5904 message formats for the situations enumerated below.
5910 <p>When daemons are started</p>
5913 If the script starts one or more daemons, the output
5914 should look like this (a single line, no leading
5916 <example compact="compact">
5917 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
5919 The <var>description</var> should describe the
5920 subsystem the daemon or set of daemons are part of,
5921 while <var>daemon-1</var> up to <var>daemon-n</var>
5922 denote each daemon's name (typically the file name of
5927 For example, the output of <file>/etc/init.d/lpd</file>
5929 <example compact="compact">
5930 Starting printer spooler: lpd.
5935 This can be achieved by saying
5936 <example compact="compact">
5937 echo -n "Starting printer spooler: lpd"
5938 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
5941 in the script. If there are more than one daemon to
5942 start, the output should look like this:
5943 <example compact="compact">
5944 echo -n "Starting remote file system services:"
5945 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
5946 echo -n " mountd"; start-stop-daemon --start --quiet mountd
5947 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
5950 This makes it possible for the user to see what is
5951 happening and when the final daemon has been started.
5952 Care should be taken in the placement of white spaces:
5953 in the example above the system administrators can
5954 easily comment out a line if they don't want to start
5955 a specific daemon, while the displayed message still
5961 <p>When a system parameter is being set</p>
5964 If you have to set up different system parameters
5965 during the system boot, you should use this format:
5966 <example compact="compact">
5967 Setting <var>parameter</var> to "<var>value</var>".
5972 You can use a statement such as the following to get
5974 <example compact="compact">
5975 echo "Setting DNS domainname to \"$domainname\"."
5980 Note that the same symbol (<tt>"</tt>) is used for the left
5981 and right quotation marks. A grave accent (<tt>`</tt>) is
5982 not a quote character; neither is an apostrophe
5988 <p>When a daemon is stopped or restarted</p>
5991 When you stop or restart a daemon, you should issue a
5992 message identical to the startup message, except that
5993 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
5994 or <tt>Restarting</tt> respectively.
5998 For example, stopping the printer daemon will look like
6000 <example compact="compact">
6001 Stopping printer spooler: lpd.
6007 <p>When something is executed</p>
6010 There are several examples where you have to run a
6011 program at system startup or shutdown to perform a
6012 specific task, for example, setting the system's clock
6013 using <prgn>netdate</prgn> or killing all processes
6014 when the system shuts down. Your message should look
6016 <example compact="compact">
6017 Doing something very useful...done.
6019 You should print the <tt>done.</tt> immediately after
6020 the job has been completed, so that the user is
6021 informed why they have to wait. You can get this
6023 <example compact="compact">
6024 echo -n "Doing something very useful..."
6033 <p>When the configuration is reloaded</p>
6036 When a daemon is forced to reload its configuration
6037 files you should use the following format:
6038 <example compact="compact">
6039 Reloading <var>description</var> configuration...done.
6041 where <var>description</var> is the same as in the
6042 daemon starting message.
6050 <heading>Cron jobs</heading>
6053 Packages must not modify the configuration file
6054 <file>/etc/crontab</file>, and they must not modify the files in
6055 <file>/var/spool/cron/crontabs</file>.</p>
6058 If a package wants to install a job that has to be executed
6059 via cron, it should place a file with the name of the
6060 package in one or more of the following directories:
6061 <example compact="compact">
6066 As these directory names imply, the files within them are
6067 executed on a daily, weekly, or monthly basis,
6068 respectively. The exact times are listed in
6069 <file>/etc/crontab</file>.</p>
6072 All files installed in any of these directories must be
6073 scripts (e.g., shell scripts or Perl scripts) so that they
6074 can easily be modified by the local system administrator.
6075 In addition, they should be treated as configuration
6080 If a certain job has to be executed more frequently than
6081 daily, the package should install a file
6082 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6083 same syntax as <file>/etc/crontab</file> and is processed by
6084 <prgn>cron</prgn> automatically. The file must also be
6085 treated as a configuration file. (Note that entries in the
6086 <file>/etc/cron.d</file> directory are not handled by
6087 <prgn>anacron</prgn>. Thus, you should only use this
6088 directory for jobs which may be skipped if the system is not
6092 The scripts or crontab entries in these directories should
6093 check if all necessary programs are installed before they
6094 try to execute them. Otherwise, problems will arise when a
6095 package was removed but not purged since configuration files
6096 are kept on the system in this situation.</p>
6100 <heading>Menus</heading>
6103 The Debian <tt>menu</tt> package provides a standard
6104 interface between packages providing applications and
6105 <em>menu programs</em> (either X window managers or
6106 text-based menu programs such as <prgn>pdmenu</prgn>).
6110 All packages that provide applications that need not be
6111 passed any special command line arguments for normal
6112 operation should register a menu entry for those
6113 applications, so that users of the <tt>menu</tt> package
6114 will automatically get menu entries in their window
6115 managers, as well in shells like <tt>pdmenu</tt>.
6119 Menu entries should follow the current menu policy.
6123 The menu policy can be found in the <tt>menu-policy</tt>
6124 files in the <tt>debian-policy</tt> package.
6125 It is also available from the Debian web mirrors at
6126 <tt><url name="/doc/packaging-manuals/menu-policy/"
6127 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6131 Please also refer to the <em>Debian Menu System</em>
6132 documentation that comes with the <package>menu</package>
6133 package for information about how to register your
6139 <heading>Multimedia handlers</heading>
6142 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6143 is a mechanism for encoding files and data streams and
6144 providing meta-information about them, in particular their
6145 type (e.g. audio or video) and format (e.g. PNG, HTML,
6150 Registration of MIME type handlers allows programs like mail
6151 user agents and web browsers to invoke these handlers to
6152 view, edit or display MIME types they don't support directly.
6156 Packages which provide the ability to view/show/play,
6157 compose, edit or print MIME types should register themselves
6158 as such following the current MIME support policy.
6162 The MIME support policy can be found in the <tt>mime-policy</tt>
6163 files in the <tt>debian-policy</tt> package.
6164 It is also available from the Debian web mirrors at
6165 <tt><url name="/doc/packaging-manuals/mime-policy/"
6166 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
6172 <heading>Keyboard configuration</heading>
6175 To achieve a consistent keyboard configuration so that all
6176 applications interpret a keyboard event the same way, all
6177 programs in the Debian distribution must be configured to
6178 comply with the following guidelines.
6182 The following keys must have the specified interpretations:
6185 <tag><tt><--</tt></tag>
6186 <item>delete the character to the left of the cursor</item>
6188 <tag><tt>Delete</tt></tag>
6189 <item>delete the character to the right of the cursor</item>
6191 <tag><tt>Control+H</tt></tag>
6192 <item>emacs: the help prefix</item>
6195 The interpretation of any keyboard events should be
6196 independent of the terminal that is used, be it a virtual
6197 console, an X terminal emulator, an rlogin/telnet session,
6202 The following list explains how the different programs
6203 should be set up to achieve this:
6209 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
6213 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
6217 X translations are set up to make
6218 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
6219 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
6220 is the vt220 escape code for the "delete character"
6221 key). This must be done by loading the X resources
6222 using <prgn>xrdb</prgn> on all local X displays, not
6223 using the application defaults, so that the
6224 translation resources used correspond to the
6225 <prgn>xmodmap</prgn> settings.
6229 The Linux console is configured to make
6230 <tt><--</tt> generate DEL, and <tt>Delete</tt>
6231 generate <tt>ESC [ 3 ~</tt>.
6235 X applications are configured so that <tt><</tt>
6236 deletes left, and <tt>Delete</tt> deletes right. Motif
6237 applications already work like this.
6241 Terminals should have <tt>stty erase ^?</tt> .
6245 The <tt>xterm</tt> terminfo entry should have <tt>ESC
6246 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
6247 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
6251 Emacs is programmed to map <tt>KB_Backspace</tt> or
6252 the <tt>stty erase</tt> character to
6253 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
6254 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
6255 <tt>^H</tt> to <tt>help</tt> as always.
6259 Other applications use the <tt>stty erase</tt>
6260 character and <tt>kdch1</tt> for the two delete keys,
6261 with ASCII DEL being "delete previous character" and
6262 <tt>kdch1</tt> being "delete character under
6270 This will solve the problem except for the following
6277 Some terminals have a <tt><--</tt> key that cannot
6278 be made to produce anything except <tt>^H</tt>. On
6279 these terminals Emacs help will be unavailable on
6280 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
6281 character takes precedence in Emacs, and has been set
6282 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
6283 available) can be used instead.
6287 Some operating systems use <tt>^H</tt> for <tt>stty
6288 erase</tt>. However, modern telnet versions and all
6289 rlogin versions propagate <tt>stty</tt> settings, and
6290 almost all UNIX versions honour <tt>stty erase</tt>.
6291 Where the <tt>stty</tt> settings are not propagated
6292 correctly, things can be made to work by using
6293 <tt>stty</tt> manually.
6297 Some systems (including previous Debian versions) use
6298 <prgn>xmodmap</prgn> to arrange for both
6299 <tt><--</tt> and <tt>Delete</tt> to generate
6300 <tt>KB_Delete</tt>. We can change the behavior of
6301 their X clients using the same X resources that we use
6302 to do it for our own clients, or configure our clients
6303 using their resources when things are the other way
6304 around. On displays configured like this
6305 <tt>Delete</tt> will not work, but <tt><--</tt>
6310 Some operating systems have different <tt>kdch1</tt>
6311 settings in their <tt>terminfo</tt> database for
6312 <tt>xterm</tt> and others. On these systems the
6313 <tt>Delete</tt> key will not work correctly when you
6314 log in from a system conforming to our policy, but
6315 <tt><--</tt> will.
6322 <heading>Environment variables</heading>
6325 A program must not depend on environment variables to get
6326 reasonable defaults. (That's because these environment
6327 variables would have to be set in a system-wide
6328 configuration file like <file>/etc/profile</file>, which is not
6329 supported by all shells.)
6333 If a program usually depends on environment variables for its
6334 configuration, the program should be changed to fall back to
6335 a reasonable default configuration if these environment
6336 variables are not present. If this cannot be done easily
6337 (e.g., if the source code of a non-free program is not
6338 available), the program must be replaced by a small
6339 "wrapper" shell script which sets the environment variables
6340 if they are not already defined, and calls the original program.
6344 Here is an example of a wrapper script for this purpose:
6346 <example compact="compact">
6348 BAR=${BAR:-/var/lib/fubar}
6350 exec /usr/lib/foo/foo "$@"
6355 Furthermore, as <file>/etc/profile</file> is a configuration
6356 file of the <prgn>base-files</prgn> package, other packages must
6357 not put any environment variables or other commands into that
6362 <sect id="doc-base">
6363 <heading>Registering Documents using doc-base</heading>
6366 The <package>doc-base</package> package implements a
6367 flexible mechanism for handling and presenting
6368 documentation. The recommended practice is for every Debian
6369 package that provides online documentation (other than just
6370 manual pages) to register these documents with
6371 <package>doc-base</package> by installing a
6372 <package>doc-base</package> control file via the
6373 <prgn/install-docs/ script at installation time and
6374 de-register the manuals again when the package is removed.
6377 Please refer to the documentation that comes with the
6378 <package>doc-base</package> package for information and
6387 <heading>Files</heading>
6390 <heading>Binaries</heading>
6393 Two different packages must not install programs with
6394 different functionality but with the same filenames. (The
6395 case of two programs having the same functionality but
6396 different implementations is handled via "alternatives" or
6397 the "Conflicts" mechanism. See <ref id="maintscripts"> and
6398 <ref id="conflicts"> respectively.) If this case happens,
6399 one of the programs must be renamed. The maintainers should
6400 report this to the <tt>debian-devel</tt> mailing list and
6401 try to find a consensus about which program will have to be
6402 renamed. If a consensus cannot be reached, <em>both</em>
6403 programs must be renamed.
6407 By default, when a package is being built, any binaries
6408 created should include debugging information, as well as
6409 being compiled with optimization. You should also turn on
6410 as many reasonable compilation warnings as possible; this
6411 makes life easier for porters, who can then look at build
6412 logs for possible problems. For the C programming language,
6413 this means the following compilation parameters should be
6415 <example compact="compact">
6417 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
6419 INSTALL = install -s # (or use strip on the files in debian/tmp)
6424 Note that by default all installed binaries should be stripped,
6425 either by using the <tt>-s</tt> flag to
6426 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
6427 the binaries after they have been copied into
6428 <file>debian/tmp</file> but before the tree is made into a
6433 Although binaries in the build tree should be compiled with
6434 debugging information by default, it can often be difficult
6435 to debug programs if they are also subjected to compiler
6436 optimization. For this reason, it is recommended to support
6437 the standardized environment
6438 variable <tt>DEB_BUILD_OPTIONS</tt>. This variable can
6439 contain several flags to change how a package is compiled
6447 The presence of this string means that the package
6448 should be compiled with a minimum of optimization.
6449 For C programs, it is best to add <tt>-O0</tt>
6450 to <tt>CFLAGS</tt> (although this is usually the
6451 default). Some programs might fail to build or run at
6452 this level of optimization; it may be necessary to
6453 use <tt>-O1</tt>, for example.
6457 This string means that the debugging symbols should
6458 not be stripped from the binary during installation,
6459 so that debugging information may be included in the package.
6465 The following makefile snippet is an example of how one may
6466 implement the build options; you will probably have to
6467 massage this example in order to make it work for your
6469 <example compact="compact">
6472 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
6473 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
6474 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
6475 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
6477 ifneq (,$(findstring noopt,$(DEB_BUILD_OPTIONS)))
6482 ifeq (,$(findstring nostrip,$(DEB_BUILD_OPTIONS)))
6483 INSTALL_PROGRAM += -s
6489 It is up to the package maintainer to decide what
6490 compilation options are best for the package. Certain
6491 binaries (such as computationally-intensive programs) will
6492 function better with certain flags (<tt>-O3</tt>, for
6493 example); feel free to use them. Please use good judgment
6494 here. Don't use flags for the sake of it; only use them
6495 if there is good reason to do so. Feel free to override
6496 the upstream author's ideas about which compilation
6497 options are best: they are often inappropriate for our
6503 <sect id="libraries">
6504 <heading>Libraries</heading>
6507 If the package is <strong>architecture: any</strong>, then
6508 the shared library compilation and linking flags must have
6509 <tt>-fPIC</tt>, or the package shall not build on some of
6510 the supported architectures<footnote>
6512 If you are using GCC, <tt>-fPIC</tt> produces code with
6513 relocatable position independent code, which is required for
6514 most architectures to create a shared library, with i386 and
6515 perhaps some others where non position independent code is
6516 permitted in a shared library.
6519 Position independent code may have a performance penalty,
6520 especially on <tt>i386</tt>. However, in most cases the
6521 speed penalty must be measured against the memory wasted on
6522 the few architectures where non position independent code is
6525 </footnote>. Any exception to this rule must be discussed on
6526 the mailing list <em>debian-devel@lists.debian.org</em>, and
6527 a rough consensus obtained. The reasons for not compiling
6528 with <tt>-fPIC</tt> flag must be recorded in the file
6529 <tt>README.Debian</tt>, and care must be taken to either
6530 restrict the architecture or arrange for <tt>-fPIC</tt> to
6531 be used on architectures where it is required.<footnote>
6533 Some of the reasons why this might be required is if the
6534 library contains hand crafted assembly code that is not
6535 relocatable, the speed penalty is excessive for compute
6536 intensive libs, and similar reasons.
6541 As to the static libraries, the common case is not to have
6542 relocatable code, since there is no benefit, unless in specific
6543 cases; therefore the static version must not be compiled
6544 with the <tt>-fPIC</tt> flag. Any exception to this rule
6545 should be discussed on the mailing list
6546 <em>debian-devel@lists.debian.org</em>, and the reasons for
6547 compiling with the <tt>-fPIC</tt> flag must be recorded in
6548 the file <tt>README.Debian</tt>. <footnote>
6550 Some of the reasons for linking static libraries with
6551 the <tt>-fPIC</tt> flag are if, for example, one needs a
6552 Perl API for a library that is under rapid development,
6553 and has an unstable API, so shared libraries are
6554 pointless at this phase of the library's development. In
6555 that case, since Perl needs a library with relocatable
6556 code, it may make sense to create a static library with
6557 relocatable code. Another reason cited is if you are
6558 distilling various libraries into a common shared
6559 library, like <tt>mklibs</tt> does in the Debian
6565 In other words, if both a shared and a static library is
6566 being built, each source unit (<tt>*.c</tt>, for example,
6567 for C files) will need to be compiled twice, for the normal
6571 You must specify the gcc option <tt>-D_REENTRANT</tt>
6572 when building a library (either static or shared) to make
6573 the library compatible with LinuxThreads.
6577 Although not enforced by the build tools, shared libraries
6578 must be linked against all libraries that they use symbols from
6579 in the same way that binaries are. This ensures the correct
6580 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
6581 system and guarantees that all libraries can be safely opened
6582 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
6583 option <tt>-Wl,-z,defs</tt> when building a shared library.
6584 Since this option enforces symbol resolution at build time,
6585 a missing library reference will be caught early as a fatal
6590 All installed shared libraries should be stripped with
6591 <example compact="compact">
6592 strip --strip-unneeded <var>your-lib</var>
6594 (The option <tt>--strip-unneeded</tt> makes
6595 <prgn>strip</prgn> remove only the symbols which aren't
6596 needed for relocation processing.) Shared libraries can
6597 function perfectly well when stripped, since the symbols for
6598 dynamic linking are in a separate part of the ELF object
6600 You might also want to use the options
6601 <tt>--remove-section=.comment</tt> and
6602 <tt>--remove-section=.note</tt> on both shared libraries
6603 and executables, and <tt>--strip-debug</tt> on static
6609 Note that under some circumstances it may be useful to
6610 install a shared library unstripped, for example when
6611 building a separate package to support debugging.
6615 Shared object files (often <file>.so</file> files) that are not
6616 public libraries, that is, they are not meant to be linked
6617 to by third party executables (binaries of other packages),
6618 should be installed in subdirectories of the
6619 <file>/usr/lib</file> directory. Such files are exempt from the
6620 rules that govern ordinary shared libraries, except that
6621 they must not be installed executable and should be
6623 A common example are the so-called "plug-ins",
6624 internal shared objects that are dynamically loaded by
6625 programs using <manref name="dlopen" section="3">.
6630 Packages containing shared libraries that may be linked to
6631 by other packages' binaries, but which for some
6632 <em>compelling</em> reason can not be installed in
6633 <file>/usr/lib</file> directory, may install the shared library
6634 files in subdirectories of the <file>/usr/lib</file> directory,
6635 in which case they should arrange to add that directory in
6636 <file>/etc/ld.so.conf</file> in the package's post-installation
6637 script, and remove it in the package's post-removal script.
6641 An ever increasing number of packages are using
6642 <prgn>libtool</prgn> to do their linking. The latest GNU
6643 libtools (>= 1.3a) can take advantage of the metadata in the
6644 installed <prgn>libtool</prgn> archive files (<file>*.la</file>
6645 files). The main advantage of <prgn>libtool</prgn>'s
6646 <file>.la</file> files is that it allows <prgn>libtool</prgn> to
6647 store and subsequently access metadata with respect to the
6648 libraries it builds. <prgn>libtool</prgn> will search for
6649 those files, which contain a lot of useful information about
6650 a library (such as library dependency information for static
6651 linking). Also, they're <em>essential</em> for programs
6652 using <tt>libltdl</tt>.<footnote>
6653 Although <prgn>libtool</prgn> is fully capable of
6654 linking against shared libraries which don't have
6655 <tt>.la</tt> files, as it is a mere shell script it can
6656 add considerably to the build time of a
6657 <prgn>libtool</prgn>-using package if that shell script
6658 has to derive all this information from first principles
6659 for each library every time it is linked. With the
6660 advent of <prgn>libtool</prgn> version 1.4 (and to a
6661 lesser extent <prgn>libtool</prgn> version 1.3), the
6662 <file>.la</file> files also store information about
6663 inter-library dependencies which cannot necessarily be
6664 derived after the <file>.la</file> file is deleted.
6669 Packages that use <prgn>libtool</prgn> to create shared
6670 libraries should include the <file>.la</file> files in the
6671 <tt>-dev</tt> package, unless the package relies on
6672 <tt>libtool</tt>'s <tt>libltdl</tt> library, in which case
6673 the <tt>.la</tt> files must go in the run-time library
6678 You must make sure that you use only released versions of
6679 shared libraries to build your packages; otherwise other
6680 users will not be able to run your binaries
6681 properly. Producing source packages that depend on
6682 unreleased compilers is also usually a bad
6689 <heading>Shared libraries</heading>
6691 This section has moved to <ref id="sharedlibs">.
6697 <heading>Scripts</heading>
6700 All command scripts, including the package maintainer
6701 scripts inside the package and used by <prgn>dpkg</prgn>,
6702 should have a <tt>#!</tt> line naming the shell to be used
6707 In the case of Perl scripts this should be
6708 <tt>#!/usr/bin/perl</tt>.
6712 When scripts are installed into a directory in the system
6713 PATH, the script name should not include an extension such
6714 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
6715 language currently used to implement it.
6718 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>)
6719 should almost certainly start with <tt>set -e</tt> so that
6720 errors are detected. Every script should use
6721 <tt>set -e</tt> or check the exit status of <em>every</em>
6726 The standard shell interpreter <file>/bin/sh</file> can be a
6727 symbolic link to any POSIX compatible shell, if <tt>echo
6728 -n</tt> does not generate a newline.<footnote>
6729 Debian policy specifies POSIX behavior for
6730 <file>/bin/sh</file>, but <tt>echo -n</tt> has widespread
6731 use in the Linux community (in particular including this
6732 policy, the Linux kernel source, many Debian scripts,
6733 etc.). This <tt>echo -n</tt> mechanism is valid but not
6734 required under POSIX, hence this explicit addition.
6735 Also, rumour has it that this shall be mandated under
6738 Thus, shell scripts specifying <file>/bin/sh</file> as
6739 interpreter must only use POSIX features. If a script
6740 requires non-POSIX features from the shell interpreter, the
6741 appropriate shell must be specified in the first line of the
6742 script (e.g., <tt>#!/bin/bash</tt>) and the package must
6743 depend on the package providing the shell (unless the shell
6744 package is marked "Essential", as in the case of
6749 You may wish to restrict your script to POSIX features when
6750 possible so that it may use <file>/bin/sh</file> as its
6751 interpreter. If your script works with <prgn>dash</prgn>
6752 (originally called <prgn>ash</prgn>), it's probably POSIX
6753 compliant, but if you are in doubt, use
6754 <file>/bin/bash</file>.
6758 Perl scripts should check for errors when making any
6759 system calls, including <tt>open</tt>, <tt>print</tt>,
6760 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
6764 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
6765 scripting languages. See <em>Csh Programming Considered
6766 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
6767 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
6768 If an upstream package comes with <prgn>csh</prgn> scripts
6769 then you must make sure that they start with
6770 <tt>#!/bin/csh</tt> and make your package depend on the
6771 <prgn>c-shell</prgn> virtual package.
6775 Any scripts which create files in world-writeable
6776 directories (e.g., in <file>/tmp</file>) must use a
6777 mechanism which will fail atomically if a file with the same
6778 name already exists.
6782 The Debian base system provides the <prgn>tempfile</prgn>
6783 and <prgn>mktemp</prgn> utilities for use by scripts for
6790 <heading>Symbolic links</heading>
6793 In general, symbolic links within a top-level directory
6794 should be relative, and symbolic links pointing from one
6795 top-level directory into another should be absolute. (A
6796 top-level directory is a sub-directory of the root
6797 directory <file>/</file>.)
6801 In addition, symbolic links should be specified as short as
6802 possible, i.e., link targets like <file>foo/../bar</file> are
6807 Note that when creating a relative link using
6808 <prgn>ln</prgn> it is not necessary for the target of the
6809 link to exist relative to the working directory you're
6810 running <prgn>ln</prgn> from, nor is it necessary to change
6811 directory to the directory where the link is to be made.
6812 Simply include the string that should appear as the target
6813 of the link (this will be a pathname relative to the
6814 directory in which the link resides) as the first argument
6819 For example, in your <prgn>Makefile</prgn> or
6820 <file>debian/rules</file>, you can do things like:
6821 <example compact="compact">
6822 ln -fs gcc $(prefix)/bin/cc
6823 ln -fs gcc debian/tmp/usr/bin/cc
6824 ln -fs ../sbin/sendmail $(prefix)/bin/runq
6825 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
6830 A symbolic link pointing to a compressed file should always
6831 have the same file extension as the referenced file. (For
6832 example, if a file <file>foo.gz</file> is referenced by a
6833 symbolic link, the filename of the link has to end with
6834 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
6839 <heading>Device files</heading>
6842 Packages must not include device files in the package file
6847 If a package needs any special device files that are not
6848 included in the base system, it must call
6849 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
6850 after notifying the user<footnote>
6851 This notification could be done via a (low-priority)
6852 debconf message, or an echo (printf) statement.
6857 Packages must not remove any device files in the
6858 <prgn>postrm</prgn> or any other script. This is left to the
6859 system administrator.
6863 Debian uses the serial devices
6864 <file>/dev/ttyS*</file>. Programs using the old
6865 <file>/dev/cu*</file> devices should be changed to use
6866 <file>/dev/ttyS*</file>.
6870 <sect id="config-files">
6871 <heading>Configuration files</heading>
6874 <heading>Definitions</heading>
6878 <tag>configuration file</tag>
6880 A file that affects the operation of a program, or
6881 provides site- or host-specific information, or
6882 otherwise customizes the behavior of a program.
6883 Typically, configuration files are intended to be
6884 modified by the system administrator (if needed or
6885 desired) to conform to local policy or to provide
6886 more useful site-specific behavior.
6889 <tag><tt>conffile</tt></tag>
6891 A file listed in a package's <tt>conffiles</tt>
6892 file, and is treated specially by <prgn>dpkg</prgn>
6893 (see <ref id="configdetails">).
6899 The distinction between these two is important; they are
6900 not interchangeable concepts. Almost all
6901 <tt>conffile</tt>s are configuration files, but many
6902 configuration files are not <tt>conffiles</tt>.
6906 Note that a script that embeds configuration information
6907 (such as most of the files in <file>/etc/default</file> and
6908 <file>/etc/cron.{daily,weekly,monthly}</file>) is de-facto a
6909 configuration file and should be treated as such.
6914 <heading>Location</heading>
6917 Any configuration files created or used by your package
6918 must reside in <file>/etc</file>. If there are several,
6919 consider creating a subdirectory of <file>/etc</file>
6920 named after your package.
6924 If your package creates or uses configuration files
6925 outside of <file>/etc</file>, and it is not feasible to modify
6926 the package to use <file>/etc</file> directly, put the files
6927 in <file>/etc</file> and create symbolic links to those files
6928 from the location that the package requires.
6933 <heading>Behavior</heading>
6936 Configuration file handling must conform to the following
6938 <list compact="compact">
6940 local changes must be preserved during a package
6944 configuration files must be preserved when the
6945 package is removed, and only deleted when the
6952 The easy way to achieve this behavior is to make the
6953 configuration file a <tt>conffile</tt>. This is
6954 appropriate only if it is possible to distribute a default
6955 version that will work for most installations, although
6956 some system administrators may choose to modify it. This
6957 implies that the default version will be part of the
6958 package distribution, and must not be modified by the
6959 maintainer scripts during installation (or at any other
6964 In order to ensure that local changes are preserved
6965 correctly, no package may contain or make hard links to
6966 conffiles.<footnote>
6967 Rationale: There are two problems with hard links.
6968 The first is that some editors break the link while
6969 editing one of the files, so that the two files may
6970 unwittingly become unlinked and different. The second
6971 is that <prgn>dpkg</prgn> might break the hard link
6972 while upgrading <tt>conffile</tt>s.
6977 The other way to do it is via the maintainer scripts. In
6978 this case, the configuration file must not be listed as a
6979 <tt>conffile</tt> and must not be part of the package
6980 distribution. If the existence of a file is required for
6981 the package to be sensibly configured it is the
6982 responsibility of the package maintainer to provide
6983 maintainer scripts which correctly create, update and
6984 maintain the file and remove it on purge. (See <ref
6985 id="maintainerscripts"> for more information.) These
6986 scripts must be idempotent (i.e., must work correctly if
6987 <prgn>dpkg</prgn> needs to re-run them due to errors
6988 during installation or removal), must cope with all the
6989 variety of ways <prgn>dpkg</prgn> can call maintainer
6990 scripts, must not overwrite or otherwise mangle the user's
6991 configuration without asking, must not ask unnecessary
6992 questions (particularly during upgrades), and must
6993 otherwise be good citizens.
6997 The scripts are not required to configure every possible
6998 option for the package, but only those necessary to get
6999 the package running on a given system. Ideally the
7000 sysadmin should not have to do any configuration other
7001 than that done (semi-)automatically by the
7002 <prgn>postinst</prgn> script.
7006 A common practice is to create a script called
7007 <file><var>package</var>-configure</file> and have the
7008 package's <prgn>postinst</prgn> call it if and only if the
7009 configuration file does not already exist. In certain
7010 cases it is useful for there to be an example or template
7011 file which the maintainer scripts use. Such files should
7012 be in <file>/usr/share/<var>package</var></file> or
7013 <file>/usr/lib/<var>package</var></file> (depending on whether
7014 they are architecture-independent or not). There should
7015 be symbolic links to them from
7016 <file>/usr/share/doc/<var>package</var>/examples</file> if
7017 they are examples, and should be perfectly ordinary
7018 <prgn>dpkg</prgn>-handled files (<em>not</em>
7019 configuration files).
7023 These two styles of configuration file handling must
7024 not be mixed, for that way lies madness:
7025 <prgn>dpkg</prgn> will ask about overwriting the file
7026 every time the package is upgraded.
7031 <heading>Sharing configuration files</heading>
7034 Packages which specify the same file as a
7035 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7036 with each other. (This is an instance of the general rule
7037 about not sharing files. Note that neither alternatives
7038 nor diversions are likely to be appropriate in this case;
7039 in particular, <prgn>dpkg</prgn> does not handle diverted
7040 <tt>conffile</tt>s well.)
7044 The maintainer scripts must not alter a <tt>conffile</tt>
7045 of <em>any</em> package, including the one the scripts
7050 If two or more packages use the same configuration file
7051 and it is reasonable for both to be installed at the same
7052 time, one of these packages must be defined as
7053 <em>owner</em> of the configuration file, i.e., it will be
7054 the package which handles that file as a configuration
7055 file. Other packages that use the configuration file must
7056 depend on the owning package if they require the
7057 configuration file to operate. If the other package will
7058 use the configuration file if present, but is capable of
7059 operating without it, no dependency need be declared.
7063 If it is desirable for two or more related packages to
7064 share a configuration file <em>and</em> for all of the
7065 related packages to be able to modify that configuration
7066 file, then the following should be done:
7067 <enumlist compact="compact">
7069 One of the related packages (the "owning" package)
7070 will manage the configuration file with maintainer
7071 scripts as described in the previous section.
7074 The owning package should also provide a program
7075 that the other packages may use to modify the
7079 The related packages must use the provided program
7080 to make any desired modifications to the
7081 configuration file. They should either depend on
7082 the core package to guarantee that the configuration
7083 modifier program is available or accept gracefully
7084 that they cannot modify the configuration file if it
7085 is not. (This is in addition to the fact that the
7086 configuration file may not even be present in the
7093 Sometimes it's appropriate to create a new package which
7094 provides the basic infrastructure for the other packages
7095 and which manages the shared configuration files. (The
7096 <tt>sgml-base</tt> package is a good example.)
7101 <heading>User configuration files ("dotfiles")</heading>
7104 The files in <file>/etc/skel</file> will automatically be
7105 copied into new user accounts by <prgn>adduser</prgn>.
7106 No other program should reference the files in
7107 <file>/etc/skel</file>.
7111 Therefore, if a program needs a dotfile to exist in
7112 advance in <file>$HOME</file> to work sensibly, that dotfile
7113 should be installed in <file>/etc/skel</file> and treated as a
7118 However, programs that require dotfiles in order to
7119 operate sensibly are a bad thing, unless they do create
7120 the dotfiles themselves automatically.
7124 Furthermore, programs should be configured by the Debian
7125 default installation to behave as closely to the upstream
7126 default behavior as possible.
7130 Therefore, if a program in a Debian package needs to be
7131 configured in some way in order to operate sensibly, that
7132 should be done using a site-wide configuration file placed
7133 in <file>/etc</file>. Only if the program doesn't support a
7134 site-wide default configuration and the package maintainer
7135 doesn't have time to add it may a default per-user file be
7136 placed in <file>/etc/skel</file>.
7140 <file>/etc/skel</file> should be as empty as we can make it.
7141 This is particularly true because there is no easy (or
7142 necessarily desirable) mechanism for ensuring that the
7143 appropriate dotfiles are copied into the accounts of
7144 existing users when a package is installed.
7150 <heading>Log files</heading>
7152 Log files should usually be named
7153 <file>/var/log/<var>package</var>.log</file>. If you have many
7154 log files, or need a separate directory for permission
7155 reasons (<file>/var/log</file> is writable only by
7156 <file>root</file>), you should usually create a directory named
7157 <file>/var/log/<var>package</var></file> and place your log
7162 Log files must be rotated occasionally so that they don't
7163 grow indefinitely; the best way to do this is to drop a log
7164 rotation configuration file into the directory
7165 <file>/etc/logrotate.d</file> and use the facilities provided by
7166 logrotate.<footnote>
7168 The traditional approach to log files has been to set up
7169 <em>ad hoc</em> log rotation schemes using simple shell
7170 scripts and cron. While this approach is highly
7171 customizable, it requires quite a lot of sysadmin work.
7172 Even though the original Debian system helped a little
7173 by automatically installing a system which can be used
7174 as a template, this was deemed not enough.
7178 The use of <prgn>logrotate</prgn>, a program developed
7179 by Red Hat, is better, as it centralizes log management.
7180 It has both a configuration file
7181 (<file>/etc/logrotate.conf</file>) and a directory where
7182 packages can drop their individual log rotation
7183 configurations (<file>/etc/logrotate.d</file>).
7186 Here is a good example for a logrotate config
7187 file (for more information see <manref name="logrotate"
7189 <example compact="compact">
7190 /var/log/foo/*.log {
7195 /etc/init.d/foo force-reload
7199 This rotates all files under <file>/var/log/foo</file>, saves 12
7200 compressed generations, and forces the daemon to reload its
7201 configuration information after the log rotation.
7205 Log files should be removed when the package is
7206 purged (but not when it is only removed). This should be
7207 done by the <prgn>postrm</prgn> script when it is called
7208 with the argument <tt>purge</tt> (see <ref
7209 id="removedetails">).
7214 <heading>Permissions and owners</heading>
7217 The rules in this section are guidelines for general use.
7218 If necessary you may deviate from the details below.
7219 However, if you do so you must make sure that what is done
7220 is secure and you should try to be as consistent as possible
7221 with the rest of the system. You should probably also
7222 discuss it on <prgn>debian-devel</prgn> first.
7226 Files should be owned by <tt>root.root</tt>, and made
7227 writable only by the owner and universally readable (and
7228 executable, if appropriate), that is mode 644 or 755.
7232 Directories should be mode 755 or (for group-writability)
7233 mode 2775. The ownership of the directory should be
7234 consistent with its mode: if a directory is mode 2775, it
7235 should be owned by the group that needs write access to
7238 When a package is upgraded, and the owner or permissions
7239 of a file included in the package has changed, dpkg
7240 arranges for the ownership and permissions to be
7241 correctly set upon installation. However, this does not
7242 extend to directories; the permissions and ownership of
7243 directories already on the system does not change on
7244 install or upgrade of packages. This makes sense, since
7245 otherwise common directories like <tt>/usr</tt> would
7246 always be in flux. To correctly change permissions of a
7247 directory the package owns, explicit action is required,
7248 usually in the <tt>postinst</tt> script. Care must be
7249 taken to handle downgrades as well, in that case.
7256 Setuid and setgid executables should be mode 4755 or 2755
7257 respectively, and owned by the appropriate user or group.
7258 They should not be made unreadable (modes like 4711 or
7259 2711 or even 4111); doing so achieves no extra security,
7260 because anyone can find the binary in the freely available
7261 Debian package; it is merely inconvenient. For the same
7262 reason you should not restrict read or execute permissions
7263 on non-set-id executables.
7267 Some setuid programs need to be restricted to particular
7268 sets of users, using file permissions. In this case they
7269 should be owned by the uid to which they are set-id, and by
7270 the group which should be allowed to execute them. They
7271 should have mode 4754; again there is no point in making
7272 them unreadable to those users who must not be allowed to
7277 It is possible to arrange that the system administrator can
7278 reconfigure the package to correspond to their local
7279 security policy by changing the permissions on a binary:
7280 they can do this by using <prgn>dpkg-statoverride</prgn>, as
7281 described below.<footnote>
7282 Ordinary files installed by <prgn>dpkg</prgn> (as
7283 opposed to <tt>conffile</tt>s and other similar objects)
7284 normally have their permissions reset to the distributed
7285 permissions when the package is reinstalled. However,
7286 the use of <prgn>dpkg-statoverride</prgn> overrides this
7287 default behavior. If you use this method, you should
7288 remember to describe <prgn>dpkg-statoverride</prgn> in
7289 the package documentation; being a relatively new
7290 addition to Debian, it is probably not yet well-known.
7292 Another method you should consider is to create a group for
7293 people allowed to use the program(s) and make any setuid
7294 executables executable only by that group.
7298 If you need to create a new user or group for your package
7299 there are two possibilities. Firstly, you may need to
7300 make some files in the binary package be owned by this
7301 user or group, or you may need to compile the user or
7302 group id (rather than just the name) into the binary
7303 (though this latter should be avoided if possible, as in
7304 this case you need a statically allocated id).</p>
7307 If you need a statically allocated id, you must ask for a
7308 user or group id from the <tt>base-passwd</tt> maintainer,
7309 and must not release the package until you have been
7310 allocated one. Once you have been allocated one you must
7311 either make the package depend on a version of the
7312 <tt>base-passwd</tt> package with the id present in
7313 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
7314 your package to create the user or group itself with the
7315 correct id (using <tt>adduser</tt>) in its
7316 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
7317 the <prgn>postinst</prgn> is to be preferred if it is
7318 possible, otherwise a pre-dependency will be needed on the
7319 <tt>adduser</tt> package.)
7323 On the other hand, the program might be able to determine
7324 the uid or gid from the user or group name at runtime, so
7325 that a dynamically allocated id can be used. In this case
7326 you should choose an appropriate user or group name,
7327 discussing this on <prgn>debian-devel</prgn> and checking
7328 with the <package/base-passwd/ maintainer that it is unique and that
7329 they do not wish you to use a statically allocated id
7330 instead. When this has been checked you must arrange for
7331 your package to create the user or group if necessary using
7332 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
7333 <prgn>postinst</prgn> script (again, the latter is to be
7334 preferred if it is possible).
7338 Note that changing the numeric value of an id associated
7339 with a name is very difficult, and involves searching the
7340 file system for all appropriate files. You need to think
7341 carefully whether a static or dynamic id is required, since
7342 changing your mind later will cause problems.
7345 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
7347 This section is not intended as policy, but as a
7348 description of the use of <prgn>dpkg-statoverride</prgn>.
7352 <prgn>dpkg-statoverride</prgn> is a replacement for the
7353 deprecated <tt>suidmanager</tt> package. Packages which
7354 previously used <tt>suidmanager</tt> should have a
7355 <tt>Conflicts: suidmanager (<< 0.50)</tt> entry (or even
7356 <tt>(<< 0.52)</tt>), and calls to <tt>suidregister</tt>
7357 and <tt>suidunregister</tt> should now be simply removed
7358 from the maintainer scripts.
7362 If a system administrator wishes to have a file (or
7363 directory or other such thing) installed with owner and
7364 permissions different from those in the distributed Debian
7365 package, they can use the <prgn>dpkg-statoverride</prgn>
7366 program to instruct <prgn>dpkg</prgn> to use the different
7367 settings every time the file is installed. Thus the
7368 package maintainer should distribute the files with their
7369 normal permissions, and leave it for the system
7370 administrator to make any desired changes. For example, a
7371 daemon which is normally required to be setuid root, but
7372 in certain situations could be used without being setuid,
7373 should be installed setuid in the <tt>.deb</tt>. Then the
7374 local system administrator can change this if they wish.
7375 If there are two standard ways of doing it, the package
7376 maintainer can use <tt>debconf</tt> to find out the
7377 preference, and call <prgn>dpkg-statoverride</prgn> in the
7378 maintainer script if necessary to accommodate the system
7379 administrator's choice. Care must be taken during
7380 upgrades to not override an existing setting.
7384 Given the above, <prgn>dpkg-statoverride</prgn> is
7385 essentially a tool for system administrators and would not
7386 normally be needed in the maintainer scripts. There is
7387 one type of situation, though, where calls to
7388 <prgn>dpkg-statoverride</prgn> would be needed in the
7389 maintainer scripts, and that involves packages which use
7390 dynamically allocated user or group ids. In such a
7391 situation, something like the following idiom can be very
7392 helpful in the package's <prgn>postinst</prgn>, where
7393 <tt>sysuser</tt> is a dynamically allocated id:
7395 for i in /usr/bin/foo /usr/sbin/bar
7397 # only do something when no setting exists
7398 if ! dpkg-statoverride --list $i >/dev/null 2>&1
7400 #include: debconf processing, question about foo and bar
7401 if [ "$RET" = "true" ] ; then
7402 dpkg-statoverride --update --add sysuser root 4755 $i
7407 The corresponding <tt>dpkg-statoverride --remove</tt>
7408 calls can then be made unconditionally when the package is
7416 <chapt id="customized-programs">
7417 <heading>Customized programs</heading>
7419 <sect id="arch-spec">
7420 <heading>Architecture specification strings</heading>
7423 If a program needs to specify an <em>architecture specification
7424 string</em> in some place, it should select one of the
7425 strings provided by <tt>dpkg-architecture -L</tt>. The
7426 strings are in the format
7427 <tt><var>os</var>-<var>arch</var></tt>, though the OS part
7428 is sometimes elided, as when the OS is Linux.<footnote>
7429 <p>Currently, the strings are:
7430 i386 ia64 alpha amd64 armeb arm hppa m32r m68k mips
7431 mipsel powerpc ppc64 s390 s390x sh3 sh3eb sh4 sh4eb
7432 sparc darwin-i386 darwin-ia64 darwin-alpha darwin-amd64
7433 darwin-armeb darwin-arm darwin-hppa darwin-m32r
7434 darwin-m68k darwin-mips darwin-mipsel darwin-powerpc
7435 darwin-ppc64 darwin-s390 darwin-s390x darwin-sh3
7436 darwin-sh3eb darwin-sh4 darwin-sh4eb darwin-sparc
7437 freebsd-i386 freebsd-ia64 freebsd-alpha freebsd-amd64
7438 freebsd-armeb freebsd-arm freebsd-hppa freebsd-m32r
7439 freebsd-m68k freebsd-mips freebsd-mipsel freebsd-powerpc
7440 freebsd-ppc64 freebsd-s390 freebsd-s390x freebsd-sh3
7441 freebsd-sh3eb freebsd-sh4 freebsd-sh4eb freebsd-sparc
7442 kfreebsd-i386 kfreebsd-ia64 kfreebsd-alpha
7443 kfreebsd-amd64 kfreebsd-armeb kfreebsd-arm kfreebsd-hppa
7444 kfreebsd-m32r kfreebsd-m68k kfreebsd-mips
7445 kfreebsd-mipsel kfreebsd-powerpc kfreebsd-ppc64
7446 kfreebsd-s390 kfreebsd-s390x kfreebsd-sh3 kfreebsd-sh3eb
7447 kfreebsd-sh4 kfreebsd-sh4eb kfreebsd-sparc knetbsd-i386
7448 knetbsd-ia64 knetbsd-alpha knetbsd-amd64 knetbsd-armeb
7449 knetbsd-arm knetbsd-hppa knetbsd-m32r knetbsd-m68k
7450 knetbsd-mips knetbsd-mipsel knetbsd-powerpc
7451 knetbsd-ppc64 knetbsd-s390 knetbsd-s390x knetbsd-sh3
7452 knetbsd-sh3eb knetbsd-sh4 knetbsd-sh4eb knetbsd-sparc
7453 netbsd-i386 netbsd-ia64 netbsd-alpha netbsd-amd64
7454 netbsd-armeb netbsd-arm netbsd-hppa netbsd-m32r
7455 netbsd-m68k netbsd-mips netbsd-mipsel netbsd-powerpc
7456 netbsd-ppc64 netbsd-s390 netbsd-s390x netbsd-sh3
7457 netbsd-sh3eb netbsd-sh4 netbsd-sh4eb netbsd-sparc
7458 openbsd-i386 openbsd-ia64 openbsd-alpha openbsd-amd64
7459 openbsd-armeb openbsd-arm openbsd-hppa openbsd-m32r
7460 openbsd-m68k openbsd-mips openbsd-mipsel openbsd-powerpc
7461 openbsd-ppc64 openbsd-s390 openbsd-s390x openbsd-sh3
7462 openbsd-sh3eb openbsd-sh4 openbsd-sh4eb openbsd-sparc
7463 hurd-i386 hurd-ia64 hurd-alpha hurd-amd64 hurd-armeb
7464 hurd-arm hurd-hppa hurd-m32r hurd-m68k hurd-mips
7465 hurd-mipsel hurd-powerpc hurd-ppc64 hurd-s390 hurd-s390x
7466 hurd-sh3 hurd-sh3eb hurd-sh4 hurd-sh4eb hurd-sparc
7472 Note that we don't want to use
7473 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
7474 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
7475 since this would make our programs incompatible with other
7476 Linux distributions. We also don't use something like
7477 <tt><var>arch</var>-unknown-linux</tt>, since the
7478 <tt>unknown</tt> does not look very good.
7483 <heading>Daemons</heading>
7486 The configuration files <file>/etc/services</file>,
7487 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
7488 by the <prgn>netbase</prgn> package and must not be modified
7493 If a package requires a new entry in one of these files, the
7494 maintainer should get in contact with the
7495 <prgn>netbase</prgn> maintainer, who will add the entries
7496 and release a new version of the <prgn>netbase</prgn>
7501 The configuration file <file>/etc/inetd.conf</file> must not be
7502 modified by the package's scripts except via the
7503 <prgn>update-inetd</prgn> script or the
7504 <file>DebianNet.pm</file> Perl module. See their documentation
7505 for details on how to add entries.
7509 If a package wants to install an example entry into
7510 <file>/etc/inetd.conf</file>, the entry must be preceded with
7511 exactly one hash character (<tt>#</tt>). Such lines are
7512 treated as "commented out by user" by the
7513 <prgn>update-inetd</prgn> script and are not changed or
7514 activated during package updates.
7519 <heading>Using pseudo-ttys and modifying wtmp, utmp and
7523 Some programs need to create pseudo-ttys. This should be done
7524 using Unix98 ptys if the C library supports it. The resulting
7525 program must not be installed setuid root, unless that
7526 is required for other functionality.
7530 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
7531 <file>/var/log/lastlog</file> must be installed writable by
7532 group <tt>utmp</tt>. Programs which need to modify those
7533 files must be installed setgid <tt>utmp</tt>.
7538 <heading>Editors and pagers</heading>
7541 Some programs have the ability to launch an editor or pager
7542 program to edit or display a text document. Since there are
7543 lots of different editors and pagers available in the Debian
7544 distribution, the system administrator and each user should
7545 have the possibility to choose their preferred editor and
7550 In addition, every program should choose a good default
7551 editor/pager if none is selected by the user or system
7556 Thus, every program that launches an editor or pager must
7557 use the EDITOR or PAGER environment variable to determine
7558 the editor or pager the user wishes to use. If these
7559 variables are not set, the programs <file>/usr/bin/editor</file>
7560 and <file>/usr/bin/pager</file> should be used, respectively.
7564 These two files are managed through the <prgn>dpkg</prgn>
7565 "alternatives" mechanism. Thus every package providing an
7566 editor or pager must call the
7567 <prgn>update-alternatives</prgn> script to register these
7572 If it is very hard to adapt a program to make use of the
7573 EDITOR or PAGER variables, that program may be configured to
7574 use <file>/usr/bin/sensible-editor</file> and
7575 <file>/usr/bin/sensible-pager</file> as the editor or pager
7576 program respectively. These are two scripts provided in the
7577 Debian base system that check the EDITOR and PAGER variables
7578 and launch the appropriate program, and fall back to
7579 <file>/usr/bin/editor</file> and <file>/usr/bin/pager</file> if the
7580 variable is not set.
7584 A program may also use the VISUAL environment variable to
7585 determine the user's choice of editor. If it exists, it
7586 should take precedence over EDITOR. This is in fact what
7587 <file>/usr/bin/sensible-editor</file> does.
7591 It is not required for a package to depend on
7592 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
7593 package to provide such virtual packages.<footnote>
7594 The Debian base system already provides an editor and a
7600 <sect id="web-appl">
7601 <heading>Web servers and applications</heading>
7604 This section describes the locations and URLs that should
7605 be used by all web servers and web applications in the
7612 Cgi-bin executable files are installed in the
7614 <example compact="compact">
7615 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
7617 and should be referred to as
7618 <example compact="compact">
7619 http://localhost/cgi-bin/<var>cgi-bin-name</var>
7625 <p>Access to HTML documents</p>
7628 HTML documents for a package are stored in
7629 <file>/usr/share/doc/<var>package</var></file>
7630 and can be referred to as
7631 <example compact="compact">
7632 http://localhost/doc/<var>package</var>/<var>filename</var>
7637 The web server should restrict access to the document
7638 tree so that only clients on the same host can read
7639 the documents. If the web server does not support such
7640 access controls, then it should not provide access at
7641 all, or ask about providing access during installation.
7646 <p>Access to images</p>
7648 It is recommended that images for a package be stored
7649 in <tt>/usr/share/images/<var>package</var></tt> and
7650 may be referred to through an alias <tt>/images/</tt>
7653 http://localhost/images/<package>/<filename>
7660 <p>Web Document Root</p>
7663 Web Applications should try to avoid storing files in
7664 the Web Document Root. Instead they should use the
7665 /usr/share/doc/<var>package</var> directory for
7666 documents and register the Web Application via the
7667 <package>doc-base</package> package. If access to the
7668 web document root is unavoidable then use
7669 <example compact="compact">
7672 as the Document Root. This might be just a symbolic
7673 link to the location where the system administrator
7674 has put the real document root.
7677 <item><p>Providing httpd and/or httpd-cgi</p>
7679 All web servers should provide the virtual package
7680 <tt>httpd</tt>. If a web server has CGI support it should
7681 provide <tt>httpd-cgi</tt> additionally.
7684 All web applications which do not contain CGI scripts should
7685 depend on <tt>httpd</tt>, all those web applications which
7686 <tt>do</tt> contain CGI scripts, should depend on
7694 <sect id="mail-transport-agents">
7695 <heading>Mail transport, delivery and user agents</heading>
7698 Debian packages which process electronic mail, whether mail
7699 user agents (MUAs) or mail transport agents (MTAs), must
7700 ensure that they are compatible with the configuration
7701 decisions below. Failure to do this may result in lost
7702 mail, broken <tt>From:</tt> lines, and other serious brain
7707 The mail spool is <file>/var/mail</file> and the interface to
7708 send a mail message is <file>/usr/sbin/sendmail</file> (as per
7709 the FHS). On older systems, the mail spool may be
7710 physically located in <file>/var/spool/mail</file>, but all
7711 access to the mail spool should be via the
7712 <file>/var/mail</file> symlink. The mail spool is part of the
7713 base system and not part of the MTA package.
7717 All Debian MUAs, MTAs, MDAs and other mailbox accessing
7718 programs (such as IMAP daemons) must lock the mailbox in an
7719 NFS-safe way. This means that <tt>fcntl()</tt> locking must
7720 be combined with dot locking. To avoid deadlocks, a program
7721 should use <tt>fcntl()</tt> first and dot locking after
7722 this, or alternatively implement the two locking methods in
7723 a non blocking way<footnote>
7724 If it is not possible to establish both locks, the
7725 system shouldn't wait for the second lock to be
7726 established, but remove the first lock, wait a (random)
7727 time, and start over locking again.
7728 </footnote>. Using the functions <tt>maillock</tt> and
7729 <tt>mailunlock</tt> provided by the
7730 <tt>liblockfile*</tt><footnote>
7731 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
7732 to use these functions.
7733 </footnote> packages is the recommended way to realize this.
7737 Mailboxes are generally mode 660
7738 <tt><var>user</var>.mail</tt> unless the system
7739 administrator has chosen otherwise. A MUA may remove a
7740 mailbox (unless it has nonstandard permissions) in which
7741 case the MTA or another MUA must recreate it if needed.
7742 Mailboxes must be writable by group mail.
7746 The mail spool is 2775 <tt>root.mail</tt>, and MUAs should
7747 be setgid mail to do the locking mentioned above (and
7748 must obviously avoid accessing other users' mailboxes
7749 using this privilege).</p>
7752 <file>/etc/aliases</file> is the source file for the system mail
7753 aliases (e.g., postmaster, usenet, etc.), it is the one
7754 which the sysadmin and <prgn>postinst</prgn> scripts may
7755 edit. After <file>/etc/aliases</file> is edited the program or
7756 human editing it must call <prgn>newaliases</prgn>. All MTA
7757 packages must come with a <prgn>newaliases</prgn> program,
7758 even if it does nothing, but older MTA packages did not do
7759 this so programs should not fail if <prgn>newaliases</prgn>
7760 cannot be found. Note that because of this, all MTA
7761 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
7762 <tt>Replaces: mail-transport-agent</tt> control file
7767 The convention of writing <tt>forward to
7768 <var>address</var></tt> in the mailbox itself is not
7769 supported. Use a <tt>.forward</tt> file instead.</p>
7772 The <prgn>rmail</prgn> program used by UUCP
7773 for incoming mail should be <file>/usr/sbin/rmail</file>.
7774 Likewise, <prgn>rsmtp</prgn>, for receiving
7775 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
7779 If your package needs to know what hostname to use on (for
7780 example) outgoing news and mail messages which are generated
7781 locally, you should use the file <file>/etc/mailname</file>. It
7782 will contain the portion after the username and <tt>@</tt>
7783 (at) sign for email addresses of users on the machine
7784 (followed by a newline).
7788 Such package should check for the existence of this file
7789 when it is being configured. If it exists, it should be
7790 used without comment, although an MTA's configuration script
7791 may wish to prompt the user even if it finds that this file
7792 exists. If the file does not exist, the package should
7793 prompt the user for the value (preferably using
7794 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
7795 as well as using it in the package's configuration. The
7796 prompt should make it clear that the name will not just be
7797 used by that package. For example, in this situation the
7798 <tt>inn</tt> package could say something like:
7799 <example compact="compact">
7800 Please enter the "mail name" of your system. This is the
7801 hostname portion of the address to be shown on outgoing
7802 news and mail messages. The default is
7803 <var>syshostname</var>, your system's host name. Mail
7804 name ["<var>syshostname</var>"]:
7806 where <var>syshostname</var> is the output of <tt>hostname
7812 <heading>News system configuration</heading>
7815 All the configuration files related to the NNTP (news)
7816 servers and clients should be located under
7817 <file>/etc/news</file>.</p>
7820 There are some configuration issues that apply to a number
7821 of news clients and server packages on the machine. These
7825 <tag><file>/etc/news/organization</file></tag>
7827 A string which should appear as the
7828 organization header for all messages posted
7829 by NNTP clients on the machine
7832 <tag><file>/etc/news/server</file></tag>
7834 Contains the FQDN of the upstream NNTP
7835 server, or localhost if the local machine is
7840 Other global files may be added as required for cross-package news
7847 <heading>Programs for the X Window System</heading>
7850 <heading>Providing X support and package priorities</heading>
7853 Programs that can be configured with support for the X
7854 Window System must be configured to do so and must declare
7855 any package dependencies necessary to satisfy their
7856 runtime requirements when using the X Window System. If
7857 such a package is of higher priority than the X packages
7858 on which it depends, it is required that either the
7859 X-specific components be split into a separate package, or
7860 that an alternative version of the package, which includes
7861 X support, be provided, or that the package's priority be
7867 <heading>Packages providing an X server</heading>
7870 Packages that provide an X server that, directly or
7871 indirectly, communicates with real input and display
7872 hardware should declare in their control data that they
7873 provide the virtual package <tt>xserver</tt>.<footnote>
7874 This implements current practice, and provides an
7875 actual policy for usage of the <tt>xserver</tt>
7876 virtual package which appears in the virtual packages
7877 list. In a nutshell, X servers that interface
7878 directly with the display and input hardware or via
7879 another subsystem (e.g., GGI) should provide
7880 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
7881 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
7887 <heading>Packages providing a terminal emulator</heading>
7890 Packages that provide a terminal emulator for the X Window
7891 System which meet the criteria listed below should declare
7892 in their control data that they provide the virtual
7893 package <tt>x-terminal-emulator</tt>. They should also
7894 register themselves as an alternative for
7895 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
7900 To be an <tt>x-terminal-emulator</tt>, a program must:
7901 <list compact="compact">
7903 Be able to emulate a DEC VT100 terminal, or a
7904 compatible terminal.
7908 Support the command-line option <tt>-e
7909 <var>command</var></tt>, which creates a new
7910 terminal window<footnote>
7911 "New terminal window" does not necessarily mean
7912 a new top-level X window directly parented by
7913 the window manager; it could, if the terminal
7914 emulator application were so coded, be a new
7915 "view" in a multiple-document interface (MDI).
7917 and runs the specified <var>command</var>,
7918 interpreting the entirety of the rest of the command
7919 line as a command to pass straight to exec, in the
7920 manner that <tt>xterm</tt> does.
7924 Support the command-line option <tt>-T
7925 <var>title</var></tt>, which creates a new terminal
7926 window with the window title <var>title</var>.
7933 <heading>Packages providing a window manager</heading>
7936 Packages that provide a window manager should declare in
7937 their control data that they provide the virtual package
7938 <tt>x-window-manager</tt>. They should also register
7939 themselves as an alternative for
7940 <file>/usr/bin/x-window-manager</file>, with a priority
7941 calculated as follows:
7942 <list compact="compact">
7944 Start with a priority of 20.
7948 If the window manager supports the Debian menu
7949 system, add 20 points if this support is available
7950 in the package's default configuration (i.e., no
7951 configuration files belonging to the system or user
7952 have to be edited to activate the feature); if
7953 configuration files must be modified, add only 10
7959 If the window manager complies with <url
7960 id="http://www.freedesktop.org/Standards/wm-spec"
7961 name="The Window Manager Specification Project">,
7962 written by the <url id="http://www.freedesktop.org/"
7963 name="Free Desktop Group">, add 40 points.
7967 If the window manager permits the X session to be
7968 restarted using a <em>different</em> window manager
7969 (without killing the X server) in its default
7970 configuration, add 10 points; otherwise add none.
7977 <heading>Packages providing fonts</heading>
7980 Packages that provide fonts for the X Window
7982 For the purposes of Debian Policy, a "font for the X
7983 Window System" is one which is accessed via X protocol
7984 requests. Fonts for the Linux console, for PostScript
7985 renderer, or any other purpose, do not fit this
7986 definition. Any tool which makes such fonts available
7987 to the X Window System, however, must abide by this
7990 must do a number of things to ensure that they are both
7991 available without modification of the X or font server
7992 configuration, and that they do not corrupt files used by
7993 other font packages to register information about
7997 Fonts of any type supported by the X Window System
7998 must be in a separate binary package from any
7999 executables, libraries, or documentation (except
8000 that specific to the fonts shipped, such as their
8001 license information). If one or more of the fonts
8002 so packaged are necessary for proper operation of
8003 the package with which they are associated the font
8004 package may be Recommended; if the fonts merely
8005 provide an enhancement, a Suggests relationship may
8006 be used. Packages must not Depend on font
8008 This is because the X server may retrieve fonts
8009 from the local file system or over the network
8010 from an X font server; the Debian package system
8011 is empowered to deal only with the local
8017 BDF fonts must be converted to PCF fonts with the
8018 <prgn>bdftopcf</prgn> utility (available in the
8019 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8020 placed in a directory that corresponds to their
8022 <list compact="compact">
8024 100 dpi fonts must be placed in
8025 <file>/usr/share/fonts/X11/100dpi/</file>.
8029 75 dpi fonts must be placed in
8030 <file>/usr/share/fonts/X11/75dpi/</file>.
8034 Character-cell fonts, cursor fonts, and other
8035 low-resolution fonts must be placed in
8036 <file>/usr/share/fonts/X11/misc/</file>.
8042 Speedo fonts must be placed in
8043 <file>/usr/share/fonts/X11/Speedo/</file>.
8047 Type 1 fonts must be placed in
8048 <file>/usr/share/fonts/X11/Type1/</file>. If font
8049 metric files are available, they must be placed here
8054 Subdirectories of <file>/usr/share/fonts/X11/</file>
8055 other than those listed above must be neither
8056 created nor used. (The <file>PEX</file>, <file>CID</file>,
8057 and <file>cyrillic</file> directories are excepted for
8058 historical reasons, but installation of files into
8059 these directories remains discouraged.)
8063 Font packages may, instead of placing files directly
8064 in the X font directories listed above, provide
8065 symbolic links in that font directory pointing to
8066 the files' actual location in the filesystem. Such
8067 a location must comply with the FHS.
8071 Font packages should not contain both 75dpi and
8072 100dpi versions of a font. If both are available,
8073 they should be provided in separate binary packages
8074 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8075 the names of the packages containing the
8076 corresponding fonts.
8080 Fonts destined for the <file>misc</file> subdirectory
8081 should not be included in the same package as 75dpi
8082 or 100dpi fonts; instead, they should be provided in
8083 a separate package with <tt>-misc</tt> appended to
8088 Font packages must not provide the files
8089 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8090 <file>fonts.scale</file> in a font directory:
8093 <file>fonts.dir</file> files must not be provided at all.
8097 <file>fonts.alias</file> and <file>fonts.scale</file>
8098 files, if needed, should be provided in the
8100 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8101 where <var>fontdir</var> is the name of the
8103 <file>/usr/share/fonts/X11/</file> where the
8104 package's corresponding fonts are stored
8105 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8106 <var>package</var> is the name of the package
8107 that provides these fonts, and
8108 <var>extension</var> is either <tt>scale</tt>
8109 or <tt>alias</tt>, whichever corresponds to
8116 Font packages must declare a dependency on
8117 <tt>xfonts-utils</tt> in their control
8122 Font packages that provide one or more
8123 <file>fonts.scale</file> files as described above must
8124 invoke <prgn>update-fonts-scale</prgn> on each
8125 directory into which they installed fonts
8126 <em>before</em> invoking
8127 <prgn>update-fonts-dir</prgn> on that directory.
8128 This invocation must occur in both the
8129 <prgn>postinst</prgn> (for all arguments) and
8130 <prgn>postrm</prgn> (for all arguments except
8131 <tt>upgrade</tt>) scripts.
8135 Font packages that provide one or more
8136 <file>fonts.alias</file> files as described above must
8137 invoke <prgn>update-fonts-alias</prgn> on each
8138 directory into which they installed fonts. This
8139 invocation must occur in both the
8140 <prgn>postinst</prgn> (for all arguments) and
8141 <prgn>postrm</prgn> (for all arguments except
8142 <tt>upgrade</tt>) scripts.
8146 Font packages must invoke
8147 <prgn>update-fonts-dir</prgn> on each directory into
8148 which they installed fonts. This invocation must
8149 occur in both the <prgn>postinst</prgn> (for all
8150 arguments) and <prgn>postrm</prgn> (for all
8151 arguments except <tt>upgrade</tt>) scripts.
8155 Font packages must not provide alias names for the
8156 fonts they include which collide with alias names
8157 already in use by fonts already packaged.
8161 Font packages must not provide fonts with the same
8162 XLFD registry name as another font already packaged.
8169 <heading>Application defaults files</heading>
8172 Application defaults files must be installed in the
8173 directory <file>/etc/X11/app-defaults/</file> (use of a
8174 localized subdirectory of <file>/etc/X11/</file> as described
8175 in the <em>X Toolkit Intrinsics - C Language
8176 Interface</em> manual is also permitted). They must be
8177 registered as <tt>conffile</tt>s or handled as
8178 configuration files. Packages must not provide the
8179 directory <file>/usr/X11R6/lib/X11/app-defaults/</file>.
8183 Customization of programs' X resources may also be
8184 supported with the provision of a file with the same name
8185 as that of the package placed in the
8186 <file>/etc/X11/Xresources/</file> directory, which must
8187 registered as a <tt>conffile</tt> or handled as a
8188 configuration file.<footnote>
8189 Note that this mechanism is not the same as using
8190 app-defaults; app-defaults are tied to the client
8191 binary on the local file system, whereas X resources
8192 are stored in the X server and affect all connecting
8195 <em>Important:</em> packages that install files into the
8196 <file>/etc/X11/Xresources/</file> directory must conflict with
8197 <tt>xbase (<< 3.3.2.3a-2)</tt>; if this is not done
8198 it is possible for the installing package to destroy a
8199 previously-existing <file>/etc/X11/Xresources</file> file
8200 which had been customized by the system administrator.
8205 <heading>Installation directory issues</heading>
8208 Packages using the X Window System should not be
8209 configured to install files under the
8210 <file>/usr/X11R6/</file> directory. The
8211 <file>/usr/X11R6/</file> directory hierarchy should be
8212 regarded as obsolete.
8216 Programs that use GNU <prgn>autoconf</prgn> and
8217 <prgn>automake</prgn> are usually easily configured at
8218 compile time to use <file>/usr/</file> instead of
8219 <file>/usr/X11R6/</file>, and this should be done whenever
8220 possible. Configuration files for window managers and
8221 display managers should be placed in a subdirectory of
8222 <file>/etc/X11/</file> corresponding to the package name due
8223 to these programs' tight integration with the mechanisms
8224 of the X Window System. Application-level programs should
8225 use the <file>/etc/</file> directory unless otherwise mandated
8230 The installation of files into subdirectories
8231 of <file>/usr/X11R6/include/X11/</file> and
8232 <file>/usr/X11R6/lib/X11/</file> is now prohibited;
8233 package maintainers should determine if subdirectories of
8234 <file>/usr/lib/</file> and <file>/usr/share/</file> can be used
8239 Packages should install any relevant files into the
8240 directories <file>/usr/include/X11/</file> and
8241 <file>/usr/lib/X11/</file>, but if they do so, they must
8242 pre-depend on <tt>x11-common (>=
8243 1:7.0.0)</tt><footnote>
8245 These libraries used to be all symbolic
8246 links. However, with <tt>X11R7</tt>,
8247 <tt>/usr/include/X11</tt> and <tt>/usr/lib/X11</tt>
8248 are now real directories, and packages
8249 <strong>should</strong> ship their files here instead
8250 of in <tt>/usr/X11R6/{include,lib}/X11</tt>.
8251 <tt>x11-common (>= 1:7.0.0) </tt> is the package
8252 responsible for converting these symlinks into
8260 <heading>The OSF/Motif and OpenMotif libraries</heading>
8263 <em>Programs that require the non-DFSG-compliant OSF/Motif or
8264 OpenMotif libraries</em><footnote>
8265 OSF/Motif and OpenMotif are collectively referred to as
8266 "Motif" in this policy document.
8268 should be compiled against and tested with LessTif (a free
8269 re-implementation of Motif) instead. If the maintainer
8270 judges that the program or programs do not work
8271 sufficiently well with LessTif to be distributed and
8272 supported, but do so when compiled against Motif, then two
8273 versions of the package should be created; one linked
8274 statically against Motif and with <tt>-smotif</tt>
8275 appended to the package name, and one linked dynamically
8276 against Motif and with <tt>-dmotif</tt> appended to the
8281 Both Motif-linked versions are dependent
8282 upon non-DFSG-compliant software and thus cannot be
8283 uploaded to the <em>main</em> distribution; if the
8284 software is itself DFSG-compliant it may be uploaded to
8285 the <em>contrib</em> distribution. While known existing
8286 versions of Motif permit unlimited redistribution of
8287 binaries linked against the library (whether statically or
8288 dynamically), it is the package maintainer's
8289 responsibility to determine whether this is permitted by
8290 the license of the copy of Motif in their possession.
8296 <heading>Perl programs and modules</heading>
8299 Perl programs and modules should follow the current Perl policy.
8303 The Perl policy can be found in the <tt>perl-policy</tt>
8304 files in the <tt>debian-policy</tt> package.
8305 It is also available from the Debian web mirrors at
8306 <tt><url name="/doc/packaging-manuals/perl-policy/"
8307 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
8312 <heading>Emacs lisp programs</heading>
8315 Please refer to the "Debian Emacs Policy" for details of how to
8316 package emacs lisp programs.
8320 The Emacs policy is available in
8321 <file>debian-emacs-policy.gz</file> of the
8322 <package>emacsen-common</package> package.
8323 It is also available from the Debian web mirrors at
8324 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
8325 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
8330 <heading>Games</heading>
8333 The permissions on <file>/var/games</file> are mode 755, owner
8334 <tt>root</tt> and group <tt>root</tt>.
8338 Each game decides on its own security policy.</p>
8341 Games which require protected, privileged access to
8342 high-score files, saved games, etc., may be made
8343 set-<em>group</em>-id (mode 2755) and owned by
8344 <tt>root.games</tt>, and use files and directories with
8345 appropriate permissions (770 <tt>root.games</tt>, for
8346 example). They must not be made
8347 set-<em>user</em>-id, as this causes security problems. (If
8348 an attacker can subvert any set-user-id game they can
8349 overwrite the executable of any other, causing other players
8350 of these games to run a Trojan horse program. With a
8351 set-group-id game the attacker only gets access to less
8352 important game data, and if they can get at the other
8353 players' accounts at all it will take considerably more
8357 Some packages, for example some fortune cookie programs, are
8358 configured by the upstream authors to install with their
8359 data files or other static information made unreadable so
8360 that they can only be accessed through set-id programs
8361 provided. You should not do this in a Debian package: anyone can
8362 download the <file>.deb</file> file and read the data from it,
8363 so there is no point making the files unreadable. Not
8364 making the files unreadable also means that you don't have
8365 to make so many programs set-id, which reduces the risk of a
8369 As described in the FHS, binaries of games should be
8370 installed in the directory <file>/usr/games</file>. This also
8371 applies to games that use the X Window System. Manual pages
8372 for games (X and non-X games) should be installed in
8373 <file>/usr/share/man/man6</file>.</p>
8379 <heading>Documentation</heading>
8382 <heading>Manual pages</heading>
8385 You should install manual pages in <prgn>nroff</prgn> source
8386 form, in appropriate places under <file>/usr/share/man</file>.
8387 You should only use sections 1 to 9 (see the FHS for more
8388 details). You must not install a pre-formatted "cat page".
8392 Each program, utility, and function should have an
8393 associated manual page included in the same package. It is
8394 suggested that all configuration files also have a manual
8395 page included as well. Manual pages for protocols and other
8396 auxiliary things are optional.
8400 If no manual page is available, this is considered as a bug
8401 and should be reported to the Debian Bug Tracking System (the
8402 maintainer of the package is allowed to write this bug report
8403 themselves, if they so desire). Do not close the bug report
8404 until a proper man page is available.<footnote>
8405 It is not very hard to write a man page. See the
8406 <url id="http://www.schweikhardt.net/man_page_howto.html"
8407 name="Man-Page-HOWTO">,
8408 <manref name="man" section="7">, the examples
8409 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
8410 the helper programs <prgn>help2man</prgn>, or the
8411 directory <file>/usr/share/doc/man-db/examples</file>.
8416 You may forward a complaint about a missing man page to the
8417 upstream authors, and mark the bug as forwarded in the
8418 Debian bug tracking system. Even though the GNU Project do
8419 not in general consider the lack of a man page to be a bug,
8420 we do; if they tell you that they don't consider it a bug
8421 you should leave the bug in our bug tracking system open
8426 Manual pages should be installed compressed using <tt>gzip -9</tt>.
8430 If one man page needs to be accessible via several names it
8431 is better to use a symbolic link than the <file>.so</file>
8432 feature, but there is no need to fiddle with the relevant
8433 parts of the upstream source to change from <file>.so</file> to
8434 symlinks: don't do it unless it's easy. You should not
8435 create hard links in the manual page directories, nor put
8436 absolute filenames in <file>.so</file> directives. The filename
8437 in a <file>.so</file> in a man page should be relative to the
8438 base of the man page tree (usually
8439 <file>/usr/share/man</file>). If you do not create any links
8440 (whether symlinks, hard links, or <tt>.so</tt> directives)
8441 in the file system to the alternate names of the man page,
8442 then you should not rely on <prgn>man</prgn> finding your
8443 man page under those names based solely on the information in
8444 the man page's header.<footnote>
8445 Supporting this in <prgn>man</prgn> often requires
8446 unreasonable processing time to find a manual page or to
8447 report that none exists, and moves knowledge into man's
8448 database that would be better left in the file system.
8449 This support is therefore deprecated and will cease to
8450 be present in the future.
8456 <heading>Info documents</heading>
8459 Info documents should be installed in <file>/usr/share/info</file>.
8460 They should be compressed with <tt>gzip -9</tt>.
8464 Your package should call <prgn>install-info</prgn> to update
8465 the Info <file>dir</file> file in its <prgn>postinst</prgn>
8466 script when called with a <tt>configure</tt> argument, for
8468 <example compact="compact">
8469 install-info --quiet --section Development Development \
8470 /usr/share/info/foobar.info
8474 It is a good idea to specify a section for the location of
8475 your program; this is done with the <tt>--section</tt>
8476 switch. To determine which section to use, you should look
8477 at <file>/usr/share/info/dir</file> on your system and choose the most
8478 relevant (or create a new section if none of the current
8479 sections are relevant). Note that the <tt>--section</tt>
8480 flag takes two arguments; the first is a regular expression
8481 to match (case-insensitively) against an existing section,
8482 the second is used when creating a new one.</p>
8485 You should remove the entries in the <prgn>prerm</prgn>
8486 script when called with a <tt>remove</tt> argument:
8487 <example compact="compact">
8488 install-info --quiet --remove /usr/share/info/foobar.info
8492 If <prgn>install-info</prgn> cannot find a description entry
8493 in the Info file you must supply one. See <manref
8494 name="install-info" section="8"> for details.</p>
8498 <heading>Additional documentation</heading>
8501 Any additional documentation that comes with the package may
8502 be installed at the discretion of the package maintainer.
8503 Plain text documentation should be installed in the directory
8504 <file>/usr/share/doc/<var>package</var></file>, where
8505 <var>package</var> is the name of the package, and
8506 compressed with <tt>gzip -9</tt> unless it is small.
8510 If a package comes with large amounts of documentation which
8511 many users of the package will not require you should create
8512 a separate binary package to contain it, so that it does not
8513 take up disk space on the machines of users who do not need
8514 or want it installed.</p>
8517 It is often a good idea to put text information files
8518 (<file>README</file>s, changelogs, and so forth) that come with
8519 the source package in <file>/usr/share/doc/<var>package</var></file>
8520 in the binary package. However, you don't need to install
8521 the instructions for building and installing the package, of
8525 Packages must not require the existence of any files in
8526 <file>/usr/share/doc/</file> in order to function
8528 The system administrator should be able to
8529 delete files in <file>/usr/share/doc/</file> without causing
8530 any programs to break.
8532 Any files that are referenced by programs but are also
8533 useful as stand alone documentation should be installed under
8534 <file>/usr/share/<var>package</var>/</file> with symbolic links from
8535 <file>/usr/share/doc/<var>package</var></file>.
8539 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8540 link to another directory in <file>/usr/share/doc</file> only if
8541 the two packages both come from the same source and the
8542 first package Depends on the second.<footnote>
8544 Please note that this does not override the section on
8545 changelog files below, so the file
8546 <file>/usr/share/<var>package</var>/changelog.Debian.gz</file>
8547 must refer to the changelog for the current version of
8548 <var>package</var> in question. In practice, this means
8549 that the sources of the target and the destination of the
8550 symlink must be the same (same source package and
8557 Former Debian releases placed all additional documentation
8558 in <file>/usr/doc/<var>package</var></file>. This has been
8559 changed to <file>/usr/share/doc/<var>package</var></file>,
8560 and packages must not put documentation in the directory
8561 <file>/usr/doc/<var>package</var></file>. <footnote>
8562 At this phase of the transition, we no longer require a
8563 symbolic link in <file>/usr/doc/</file>. At a later point,
8564 policy shall change to make the symbolic links a bug.
8570 <heading>Preferred documentation formats</heading>
8573 The unification of Debian documentation is being carried out
8577 If your package comes with extensive documentation in a
8578 markup format that can be converted to various other formats
8579 you should if possible ship HTML versions in a binary
8580 package, in the directory
8581 <file>/usr/share/doc/<var>appropriate-package</var></file> or
8582 its subdirectories.<footnote>
8583 The rationale: The important thing here is that HTML
8584 docs should be available in <em>some</em> package, not
8585 necessarily in the main binary package.
8590 Other formats such as PostScript may be provided at the
8591 package maintainer's discretion.
8595 <sect id="copyrightfile">
8596 <heading>Copyright information</heading>
8599 Every package must be accompanied by a verbatim copy of its
8600 copyright and distribution license in the file
8601 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
8602 file must neither be compressed nor be a symbolic link.
8606 In addition, the copyright file must say where the upstream
8607 sources (if any) were obtained. It should name the original
8608 authors of the package and the Debian maintainer(s) who were
8609 involved with its creation.</p>
8612 A copy of the file which will be installed in
8613 <file>/usr/share/doc/<var>package</var>/copyright</file> should
8614 be in <file>debian/copyright</file> in the source package.
8618 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8619 link to another directory in <file>/usr/share/doc</file> only if
8620 the two packages both come from the same source and the
8621 first package Depends on the second. These rules are
8622 important because copyrights must be extractable by
8627 Packages distributed under the UCB BSD license, the Artistic
8628 license, the GNU GPL, and the GNU LGPL, should refer to the
8629 corresponding files under
8630 <file>/usr/share/common-licenses</file>,<footnote>
8633 <file>/usr/share/common-licenses/Artistic</file>,
8634 <file>/usr/share/common-licenses/BSD</file>,
8635 <file>/usr/share/common-licenses/GPL</file>,
8636 <file>/usr/share/common-licenses/LGPL</file>,
8637 <file>/usr/share/common-licenses/GFDL</file>,
8638 <file>/usr/share/common-licenses/GPL-2</file>, and
8639 <file>/usr/share/common-licenses/LGPL-2.1</file>, and so
8640 on. Note that the GFDL is new here, and the license file
8641 may not yet be in place in
8642 <file>/usr/share/common-licenses/GFDL</file>.
8644 </footnote> rather than quoting them in the copyright
8649 You should not use the copyright file as a general <file>README</file>
8650 file. If your package has such a file it should be
8651 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
8652 <file>README.Debian</file> or some other appropriate place.</p>
8656 <heading>Examples</heading>
8659 Any examples (configurations, source files, whatever),
8660 should be installed in a directory
8661 <file>/usr/share/doc/<var>package</var>/examples</file>. These
8662 files should not be referenced by any program: they're there
8663 for the benefit of the system administrator and users as
8664 documentation only. Architecture-specific example files
8665 should be installed in a directory
8666 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
8668 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
8669 latter directory itself may be a symbolic link to the
8674 If the purpose of a package is to provide examples, then the
8675 example files may be installed into
8676 <file>/usr/share/doc/<var>package</var></file>.
8680 <sect id="changelogs">
8681 <heading>Changelog files</heading>
8684 Packages that are not Debian-native must contain a
8685 compressed copy of the <file>debian/changelog</file> file from
8686 the Debian source tree in
8687 <file>/usr/share/doc/<var>package</var></file> with the name
8688 <file>changelog.Debian.gz</file>.
8692 If an upstream changelog is available, it should be accessible as
8693 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
8694 plain text. If the upstream changelog is distributed in
8695 HTML, it should be made available in that form as
8696 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
8697 and a plain text <file>changelog.gz</file> should be generated
8698 from it using, for example, <tt>lynx -dump -nolist</tt>. If
8699 the upstream changelog files do not already conform to this
8700 naming convention, then this may be achieved either by
8701 renaming the files, or by adding a symbolic link, at the
8702 maintainer's discretion.<footnote>
8703 Rationale: People should not have to look in places for
8704 upstream changelogs merely because they are given
8705 different names or are distributed in HTML format.
8710 All of these files should be installed compressed using
8711 <tt>gzip -9</tt>, as they will become large with time even
8712 if they start out small.
8716 If the package has only one changelog which is used both as
8717 the Debian changelog and the upstream one because there is
8718 no separate upstream maintainer then that changelog should
8719 usually be installed as
8720 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
8721 there is a separate upstream maintainer, but no upstream
8722 changelog, then the Debian changelog should still be called
8723 <file>changelog.Debian.gz</file>.
8727 For details about the format and contents of the Debian
8728 changelog file, please see <ref id="dpkgchangelog">.
8733 <appendix id="pkg-scope">
8734 <heading>Introduction and scope of these appendices</heading>
8737 These appendices are taken essentially verbatim from the
8738 now-deprecated Packaging Manual, version 3.2.1.0. They are
8739 the chapters which are likely to be of use to package
8740 maintainers and which have not already been included in the
8741 policy document itself. Most of these sections are very likely
8742 not relevant to policy; they should be treated as
8743 documentation for the packaging system. Please note that these
8744 appendices are included for convenience, and for historical
8745 reasons: they used to be part of policy package, and they have
8746 not yet been incorporated into dpkg documentation. However,
8747 they still have value, and hence they are presented here.
8751 They have not yet been checked to ensure that they are
8752 compatible with the contents of policy, and if there are any
8753 contradictions, the version in the main policy document takes
8754 precedence. The remaining chapters of the old Packaging
8755 Manual have also not been read in detail to ensure that there
8756 are not parts which have been left out. Both of these will be
8761 Certain parts of the Packaging manual were integrated into the
8762 Policy Manual proper, and removed from the appendices. Links
8763 have been placed from the old locations to the new ones.
8767 <prgn>dpkg</prgn> is a suite of programs for creating binary
8768 package files and installing and removing them on Unix
8770 <prgn>dpkg</prgn> is targeted primarily at Debian
8771 GNU/Linux, but may work on or be ported to other
8777 The binary packages are designed for the management of
8778 installed executable programs (usually compiled binaries) and
8779 their associated data, though source code examples and
8780 documentation are provided as part of some packages.</p>
8783 This manual describes the technical aspects of creating Debian
8784 binary packages (<file>.deb</file> files). It documents the
8785 behavior of the package management programs
8786 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
8787 they interact with packages.</p>
8790 It also documents the interaction between
8791 <prgn>dselect</prgn>'s core and the access method scripts it
8792 uses to actually install the selected packages, and describes
8793 how to create a new access method.</p>
8796 This manual does not go into detail about the options and
8797 usage of the package building and installation tools. It
8798 should therefore be read in conjunction with those programs'
8803 The utility programs which are provided with <prgn>dpkg</prgn>
8804 for managing various system configuration and similar issues,
8805 such as <prgn>update-rc.d</prgn> and
8806 <prgn>install-info</prgn>, are not described in detail here -
8807 please see their man pages.
8811 It is assumed that the reader is reasonably familiar with the
8812 <prgn>dpkg</prgn> System Administrators' manual.
8813 Unfortunately this manual does not yet exist.
8817 The Debian version of the FSF's GNU hello program is provided
8818 as an example for people wishing to create Debian
8819 packages. The Debian <prgn>debmake</prgn> package is
8820 recommended as a very helpful tool in creating and maintaining
8821 Debian packages. However, while the tools and examples are
8822 helpful, they do not replace the need to read and follow the
8823 Policy and Programmer's Manual.</p>
8826 <appendix id="pkg-binarypkg">
8827 <heading>Binary packages (from old Packaging Manual)</heading>
8830 The binary package has two main sections. The first part
8831 consists of various control information files and scripts used
8832 by <prgn>dpkg</prgn> when installing and removing. See <ref
8833 id="pkg-controlarea">.
8837 The second part is an archive containing the files and
8838 directories to be installed.
8842 In the future binary packages may also contain other
8843 components, such as checksums and digital signatures. The
8844 format for the archive is described in full in the
8845 <file>deb(5)</file> man page.
8849 <sect id="pkg-bincreating"><heading>Creating package files -
8850 <prgn>dpkg-deb</prgn>
8854 All manipulation of binary package files is done by
8855 <prgn>dpkg-deb</prgn>; it's the only program that has
8856 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
8857 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
8858 will spot that the options requested are appropriate to
8859 <prgn>dpkg-deb</prgn> and invoke that instead with the same
8864 In order to create a binary package you must make a
8865 directory tree which contains all the files and directories
8866 you want to have in the file system data part of the package.
8867 In Debian-format source packages this directory is usually
8868 <file>debian/tmp</file>, relative to the top of the package's
8873 They should have the locations (relative to the root of the
8874 directory tree you're constructing) ownerships and
8875 permissions which you want them to have on the system when
8880 With current versions of <prgn>dpkg</prgn> the uid/username
8881 and gid/groupname mappings for the users and groups being
8882 used should be the same on the system where the package is
8883 built and the one where it is installed.
8887 You need to add one special directory to the root of the
8888 miniature file system tree you're creating:
8889 <prgn>DEBIAN</prgn>. It should contain the control
8890 information files, notably the binary package control file
8891 (see <ref id="pkg-controlfile">).
8895 The <prgn>DEBIAN</prgn> directory will not appear in the
8896 file system archive of the package, and so won't be installed
8897 by <prgn>dpkg</prgn> when the package is installed.
8901 When you've prepared the package, you should invoke:
8903 dpkg --build <var>directory</var>
8908 This will build the package in
8909 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
8910 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
8911 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
8916 See the man page <manref name="dpkg-deb" section="8"> for details of how
8917 to examine the contents of this newly-created file. You may find the
8918 output of following commands enlightening:
8920 dpkg-deb --info <var>filename</var>.deb
8921 dpkg-deb --contents <var>filename</var>.deb
8922 dpkg --contents <var>filename</var>.deb
8924 To view the copyright file for a package you could use this command:
8926 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - \*/copyright | pager
8931 <sect id="pkg-controlarea">
8932 <heading>Package control information files</heading>
8935 The control information portion of a binary package is a
8936 collection of files with names known to <prgn>dpkg</prgn>.
8937 It will treat the contents of these files specially - some
8938 of them contain information used by <prgn>dpkg</prgn> when
8939 installing or removing the package; others are scripts which
8940 the package maintainer wants <prgn>dpkg</prgn> to run.
8944 It is possible to put other files in the package control
8945 area, but this is not generally a good idea (though they
8946 will largely be ignored).
8950 Here is a brief list of the control info files supported by
8951 <prgn>dpkg</prgn> and a summary of what they're used for.
8956 <tag><tt>control</tt>
8959 This is the key description file used by
8960 <prgn>dpkg</prgn>. It specifies the package's name
8961 and version, gives its description for the user,
8962 states its relationships with other packages, and so
8963 forth. See <ref id="sourcecontrolfiles"> and
8964 <ref id="binarycontrolfiles">.
8968 It is usually generated automatically from information
8969 in the source package by the
8970 <prgn>dpkg-gencontrol</prgn> program, and with
8971 assistance from <prgn>dpkg-shlibdeps</prgn>.
8972 See <ref id="pkg-sourcetools">.
8976 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
8981 These are executable files (usually scripts) which
8982 <prgn>dpkg</prgn> runs during installation, upgrade
8983 and removal of packages. They allow the package to
8984 deal with matters which are particular to that package
8985 or require more complicated processing than that
8986 provided by <prgn>dpkg</prgn>. Details of when and
8987 how they are called are in <ref id="maintainerscripts">.
8991 It is very important to make these scripts idempotent.
8992 See <ref id="idempotency">.
8996 The maintainer scripts are guaranteed to run with a
8997 controlling terminal and can interact with the user.
8998 See <ref id="controllingterminal">.
9002 <tag><tt>conffiles</tt>
9005 This file contains a list of configuration files which
9006 are to be handled automatically by <prgn>dpkg</prgn>
9007 (see <ref id="pkg-conffiles">). Note that not necessarily
9008 every configuration file should be listed here.
9011 <tag><tt>shlibs</tt>
9014 This file contains a list of the shared libraries
9015 supplied by the package, with dependency details for
9016 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9017 when it determines what dependencies are required in a
9018 package control file. The <tt>shlibs</tt> file format
9019 is described on <ref id="shlibs">.
9024 <sect id="pkg-controlfile">
9025 <heading>The main control information file: <tt>control</tt></heading>
9028 The most important control information file used by
9029 <prgn>dpkg</prgn> when it installs a package is
9030 <tt>control</tt>. It contains all the package's "vital
9035 The binary package control files of packages built from
9036 Debian sources are made by a special tool,
9037 <prgn>dpkg-gencontrol</prgn>, which reads
9038 <file>debian/control</file> and <file>debian/changelog</file> to
9039 find the information it needs. See <ref id="pkg-sourcepkg"> for
9044 The fields in binary package control files are listed in
9045 <ref id="binarycontrolfiles">.
9049 A description of the syntax of control files and the purpose
9050 of the fields is available in <ref id="controlfields">.
9055 <heading>Time Stamps</heading>
9058 See <ref id="timestamps">.
9063 <appendix id="pkg-sourcepkg">
9064 <heading>Source packages (from old Packaging Manual) </heading>
9067 The Debian binary packages in the distribution are generated
9068 from Debian sources, which are in a special format to assist
9069 the easy and automatic building of binaries.
9072 <sect id="pkg-sourcetools">
9073 <heading>Tools for processing source packages</heading>
9076 Various tools are provided for manipulating source packages;
9077 they pack and unpack sources and help build of binary
9078 packages and help manage the distribution of new versions.
9082 They are introduced and typical uses described here; see
9083 <manref name="dpkg-source" section="1"> for full
9084 documentation about their arguments and operation.
9088 For examples of how to construct a Debian source package,
9089 and how to use those utilities that are used by Debian
9090 source packages, please see the <prgn>hello</prgn> example
9094 <sect1 id="pkg-dpkg-source">
9096 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9101 This program is frequently used by hand, and is also
9102 called from package-independent automated building scripts
9103 such as <prgn>dpkg-buildpackage</prgn>.
9107 To unpack a package it is typically invoked with
9109 dpkg-source -x <var>.../path/to/filename</var>.dsc
9114 with the <file><var>filename</var>.tar.gz</file> and
9115 <file><var>filename</var>.diff.gz</file> (if applicable) in
9116 the same directory. It unpacks into
9117 <file><var>package</var>-<var>version</var></file>, and if
9119 <file><var>package</var>-<var>version</var>.orig</file>, in
9120 the current directory.
9124 To create a packed source archive it is typically invoked:
9126 dpkg-source -b <var>package</var>-<var>version</var>
9131 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
9132 <file>.diff.gz</file> (if appropriate) in the current
9133 directory. <prgn>dpkg-source</prgn> does not clean the
9134 source tree first - this must be done separately if it is
9139 See also <ref id="pkg-sourcearchives">.</p>
9143 <sect1 id="pkg-dpkg-buildpackage">
9145 <prgn>dpkg-buildpackage</prgn> - overall package-building
9150 <prgn>dpkg-buildpackage</prgn> is a script which invokes
9151 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
9152 targets <tt>clean</tt>, <tt>build</tt> and
9153 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
9154 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
9155 source and binary package upload.
9159 It is usually invoked by hand from the top level of the
9160 built or unbuilt source directory. It may be invoked with
9161 no arguments; useful arguments include:
9162 <taglist compact="compact">
9163 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
9166 Do not sign the <tt>.changes</tt> file or the
9167 source package <tt>.dsc</tt> file, respectively.</p>
9169 <tag><tt>-p<var>sign-command</var></tt></tag>
9172 Invoke <var>sign-command</var> instead of finding
9173 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
9174 <var>sign-command</var> must behave just like
9175 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
9177 <tag><tt>-r<var>root-command</var></tt></tag>
9180 When root privilege is required, invoke the command
9181 <var>root-command</var>. <var>root-command</var>
9182 should invoke its first argument as a command, from
9183 the <prgn>PATH</prgn> if necessary, and pass its
9184 second and subsequent arguments to the command it
9185 calls. If no <var>root-command</var> is supplied
9186 then <var>dpkg-buildpackage</var> will take no
9187 special action to gain root privilege, so that for
9188 most packages it will have to be invoked as root to
9191 <tag><tt>-b</tt>, <tt>-B</tt></tag>
9194 Two types of binary-only build and upload - see
9195 <manref name="dpkg-source" section="1">.
9202 <sect1 id="pkg-dpkg-gencontrol">
9204 <prgn>dpkg-gencontrol</prgn> - generates binary package
9209 This program is usually called from <file>debian/rules</file>
9210 (see <ref id="pkg-sourcetree">) in the top level of the source
9215 This is usually done just before the files and directories in the
9216 temporary directory tree where the package is being built have their
9217 permissions and ownerships set and the package is constructed using
9218 <prgn>dpkg-deb/</prgn>
9220 This is so that the control file which is produced has
9221 the right permissions
9226 <prgn>dpkg-gencontrol</prgn> must be called after all the
9227 files which are to go into the package have been placed in
9228 the temporary build directory, so that its calculation of
9229 the installed size of a package is correct.
9233 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
9234 be run after <prgn>dpkg-shlibdeps</prgn> so that the
9235 variable substitutions created by
9236 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
9241 For a package which generates only one binary package, and
9242 which builds it in <file>debian/tmp</file> relative to the top
9243 of the source package, it is usually sufficient to call
9244 <prgn>dpkg-gencontrol</prgn>.
9248 Sources which build several binaries will typically need
9251 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
9252 </example> The <tt>-P</tt> tells
9253 <prgn>dpkg-gencontrol</prgn> that the package is being
9254 built in a non-default directory, and the <tt>-p</tt>
9255 tells it which package's control file should be generated.
9259 <prgn>dpkg-gencontrol</prgn> also adds information to the
9260 list of files in <file>debian/files</file>, for the benefit of
9261 (for example) a future invocation of
9262 <prgn>dpkg-genchanges</prgn>.</p>
9265 <sect1 id="pkg-dpkg-shlibdeps">
9267 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
9272 This program is usually called from <file>debian/rules</file>
9273 just before <prgn>dpkg-gencontrol</prgn> (see <ref
9274 id="pkg-sourcetree">), in the top level of the source tree.
9278 Its arguments are executables.
9281 In a forthcoming dpkg version,
9282 <prgn>dpkg-shlibdeps</prgn> would be required to be
9283 called on shared libraries as well.
9286 They may be specified either in the locations in the
9287 source tree where they are created or in the locations
9288 in the temporary build tree where they are installed
9289 prior to binary package creation.
9291 </footnote> for which shared library dependencies should
9292 be included in the binary package's control file.
9296 If some of the found shared libraries should only
9297 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
9298 some warrant a <tt>Pre-Depends</tt>, this can be achieved
9299 by using the <tt>-d<var>dependency-field</var></tt> option
9300 before those executable(s). (Each <tt>-d</tt> option
9301 takes effect until the next <tt>-d</tt>.)
9305 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
9306 output control file to be modified. Instead by default it
9307 adds to the <file>debian/substvars</file> file variable
9308 settings like <tt>shlibs:Depends</tt>. These variable
9309 settings must be referenced in dependency fields in the
9310 appropriate per-binary-package sections of the source
9315 For example, a package that generates an essential part
9316 which requires dependencies, and optional parts that
9317 which only require a recommendation, would separate those
9318 two sets of dependencies into two different fields.<footnote>
9319 At the time of writing, an example for this was the
9320 <package/xmms/ package, with Depends used for the xmms
9321 executable, Recommends for the plug-ins and Suggests for
9322 even more optional features provided by unzip.
9324 It can say in its <file>debian/rules</file>:
9326 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
9327 -dRecommends <var>optionalpart anotheroptionalpart</var>
9329 and then in its main control file <file>debian/control</file>:
9332 Depends: ${shlibs:Pre-Depends}
9333 Recommends: ${shlibs:Recommends}
9339 Sources which produce several binary packages with
9340 different shared library dependency requirements can use
9341 the <tt>-p<var>varnameprefix</var></tt> option to override
9342 the default <tt>shlibs:</tt> prefix (one invocation of
9343 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
9344 They can thus produce several sets of dependency
9345 variables, each of the form
9346 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
9347 which can be referred to in the appropriate parts of the
9348 binary package control files.
9353 <sect1 id="pkg-dpkg-distaddfile">
9355 <prgn>dpkg-distaddfile</prgn> - adds a file to
9356 <file>debian/files</file>
9360 Some packages' uploads need to include files other than
9361 the source and binary package files.
9365 <prgn>dpkg-distaddfile</prgn> adds a file to the
9366 <file>debian/files</file> file so that it will be included in
9367 the <file>.changes</file> file when
9368 <prgn>dpkg-genchanges</prgn> is run.
9372 It is usually invoked from the <tt>binary</tt> target of
9373 <file>debian/rules</file>:
9375 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
9377 The <var>filename</var> is relative to the directory where
9378 <prgn>dpkg-genchanges</prgn> will expect to find it - this
9379 is usually the directory above the top level of the source
9380 tree. The <file>debian/rules</file> target should put the
9381 file there just before or just after calling
9382 <prgn>dpkg-distaddfile</prgn>.
9386 The <var>section</var> and <var>priority</var> are passed
9387 unchanged into the resulting <file>.changes</file> file.
9392 <sect1 id="pkg-dpkg-genchanges">
9394 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
9399 This program is usually called by package-independent
9400 automatic building scripts such as
9401 <prgn>dpkg-buildpackage</prgn>, but it may also be called
9406 It is usually called in the top level of a built source
9407 tree, and when invoked with no arguments will print out a
9408 straightforward <file>.changes</file> file based on the
9409 information in the source package's changelog and control
9410 file and the binary and source packages which should have
9416 <sect1 id="pkg-dpkg-parsechangelog">
9418 <prgn>dpkg-parsechangelog</prgn> - produces parsed
9419 representation of a changelog
9423 This program is used internally by
9424 <prgn>dpkg-source</prgn> et al. It may also occasionally
9425 be useful in <file>debian/rules</file> and elsewhere. It
9426 parses a changelog, <file>debian/changelog</file> by default,
9427 and prints a control-file format representation of the
9428 information in it to standard output.
9432 <sect1 id="pkg-dpkg-architecture">
9434 <prgn>dpkg-architecture</prgn> - information about the build and
9439 This program can be used manually, but is also invoked by
9440 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
9441 to set environment or make variables which specify the build and
9442 host architecture for the package building process.
9447 <sect id="pkg-sourcetree">
9448 <heading>The Debianised source tree</heading>
9451 The source archive scheme described later is intended to
9452 allow a Debianised source tree with some associated control
9453 information to be reproduced and transported easily. The
9454 Debianised source tree is a version of the original program
9455 with certain files added for the benefit of the
9456 Debianisation process, and with any other changes required
9457 made to the rest of the source code and installation
9462 The extra files created for Debian are in the subdirectory
9463 <file>debian</file> of the top level of the Debianised source
9464 tree. They are described below.
9467 <sect1 id="pkg-debianrules">
9468 <heading><file>debian/rules</file> - the main building script</heading>
9471 See <ref id="debianrules">.
9476 <sect1 id="pkg-dpkgchangelog">
9477 <heading><file>debian/changelog</file></heading>
9480 See <ref id="dpkgchangelog">.
9484 It is recommended that the entire changelog be encoded in the
9485 <url id="http://www.cis.ohio-state.edu/cgi-bin/rfc/rfc2279.html" name="UTF-8">
9487 <url id="http://www.unicode.org/"
9488 name="Unicode">.<footnote>
9490 I think it is fairly obvious that we need to
9491 eventually transition to UTF-8 for our package
9492 infrastructure; it is really the only sane char-set in
9493 an international environment. Now, we can't switch to
9494 using UTF-8 for package control fields and the like
9495 until dpkg has better support, but one thing we can
9496 start doing today is requesting that Debian changelogs
9497 are UTF-8 encoded. At some point in time, we can start
9498 requiring them to do so.
9501 Checking for non-UTF8 characters in a changelog is
9502 trivial. Dump the file through
9503 <example>iconv -f utf-8 -t ucs-4</example>
9504 discard the output, and check the return
9505 value. If there are any characters in the stream
9506 which are invalid UTF-8 sequences, iconv will exit
9507 with an error code; and this will be the case for the
9508 vast majority of other character sets.
9513 <sect2><heading>Defining alternative changelog formats
9517 It is possible to use a different format to the standard
9518 one, by providing a parser for the format you wish to
9523 In order to have <tt>dpkg-parsechangelog</tt> run your
9524 parser, you must include a line within the last 40 lines
9525 of your file matching the Perl regular expression:
9526 <tt>\schangelog-format:\s+([0-9a-z]+)\W</tt> The part in
9527 parentheses should be the name of the format. For
9528 example, you might say:
9530 @@@ changelog-format: joebloggs @@@
9532 Changelog format names are non-empty strings of alphanumerics.
9536 If such a line exists then <tt>dpkg-parsechangelog</tt>
9537 will look for the parser as
9538 <file>/usr/lib/dpkg/parsechangelog/<var>format-name</var></file>
9540 <file>/usr/local/lib/dpkg/parsechangelog/<var>format-name</var></file>;
9541 it is an error for it not to find it, or for it not to
9542 be an executable program. The default changelog format
9543 is <tt>dpkg</tt>, and a parser for it is provided with
9544 the <tt>dpkg</tt> package.
9548 The parser will be invoked with the changelog open on
9549 standard input at the start of the file. It should read
9550 the file (it may seek if it wishes) to determine the
9551 information required and return the parsed information
9552 to standard output in the form of a series of control
9553 fields in the standard format. By default it should
9554 return information about only the most recent version in
9555 the changelog; it should accept a
9556 <tt>-v<var>version</var></tt> option to return changes
9557 information from all versions present <em>strictly
9558 after</em> <var>version</var>, and it should then be an
9559 error for <var>version</var> not to be present in the
9565 <list compact="compact">
9566 <item><qref id="f-Source"><tt>Source</tt></qref></item>
9567 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
9568 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
9569 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (mandatory)</item>
9570 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
9571 <item><qref id="f-Date"><tt>Date</tt></qref></item>
9572 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
9577 If several versions are being returned (due to the use
9578 of <tt>-v</tt>), the urgency value should be of the
9579 highest urgency code listed at the start of any of the
9580 versions requested followed by the concatenated
9581 (space-separated) comments from all the versions
9582 requested; the maintainer, version, distribution and
9583 date should always be from the most recent version.
9587 For the format of the <tt>Changes</tt> field see
9588 <ref id="f-Changes">.
9592 If the changelog format which is being parsed always or
9593 almost always leaves a blank line between individual
9594 change notes these blank lines should be stripped out,
9595 so as to make the resulting output compact.
9599 If the changelog format does not contain date or package
9600 name information this information should be omitted from
9601 the output. The parser should not attempt to synthesize
9602 it or find it from other sources.
9606 If the changelog does not have the expected format the
9607 parser should exit with a nonzero exit status, rather
9608 than trying to muddle through and possibly generating
9613 A changelog parser may not interact with the user at
9619 <sect1 id="pkg-srcsubstvars">
9620 <heading><file>debian/substvars</file> and variable substitutions</heading>
9623 See <ref id="substvars">.
9629 <heading><file>debian/files</file></heading>
9632 See <ref id="debianfiles">.
9636 <sect1><heading><file>debian/tmp</file>
9640 This is the canonical temporary location for the
9641 construction of binary packages by the <tt>binary</tt>
9642 target. The directory <file>tmp</file> serves as the root of
9643 the file system tree as it is being constructed (for
9644 example, by using the package's upstream makefiles install
9645 targets and redirecting the output there), and it also
9646 contains the <tt>DEBIAN</tt> subdirectory. See <ref
9647 id="pkg-bincreating">.
9651 If several binary packages are generated from the same
9652 source tree it is usual to use several
9653 <file>debian/tmp<var>something</var></file> directories, for
9654 example <file>tmp-a</file> or <file>tmp-doc</file>.
9658 Whatever <file>tmp</file> directories are created and used by
9659 <tt>binary</tt> must of course be removed by the
9660 <tt>clean</tt> target.</p></sect1>
9664 <sect id="pkg-sourcearchives"><heading>Source packages as archives
9668 As it exists on the FTP site, a Debian source package
9669 consists of three related files. You must have the right
9670 versions of all three to be able to use them.
9675 <tag>Debian source control file - <tt>.dsc</tt></tag>
9677 This file is a control file used by <prgn>dpkg-source</prgn>
9678 to extract a source package.
9679 See <ref id="debiansourcecontrolfiles">.
9683 Original source archive -
9685 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
9691 This is a compressed (with <tt>gzip -9</tt>)
9692 <prgn>tar</prgn> file containing the source code from
9693 the upstream authors of the program.
9698 Debianisation diff -
9700 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
9706 This is a unified context diff (<tt>diff -u</tt>)
9707 giving the changes which are required to turn the
9708 original source into the Debian source. These changes
9709 may only include editing and creating plain files.
9710 The permissions of files, the targets of symbolic
9711 links and the characteristics of special files or
9712 pipes may not be changed and no files may be removed
9717 All the directories in the diff must exist, except the
9718 <file>debian</file> subdirectory of the top of the source
9719 tree, which will be created by
9720 <prgn>dpkg-source</prgn> if necessary when unpacking.
9724 The <prgn>dpkg-source</prgn> program will
9725 automatically make the <file>debian/rules</file> file
9726 executable (see below).</p></item>
9731 If there is no original source code - for example, if the
9732 package is specially prepared for Debian or the Debian
9733 maintainer is the same as the upstream maintainer - the
9734 format is slightly different: then there is no diff, and the
9736 <file><var>package</var>_<var>version</var>.tar.gz</file>,
9737 and preferably contains a directory named
9738 <file><var>package</var>-<var>version</var></file>.
9743 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
9746 <tt>dpkg-source -x</tt> is the recommended way to unpack a
9747 Debian source package. However, if it is not available it
9748 is possible to unpack a Debian source archive as follows:
9749 <enumlist compact="compact">
9752 Untar the tarfile, which will create a <file>.orig</file>
9756 <p>Rename the <file>.orig</file> directory to
9757 <file><var>package</var>-<var>version</var></file>.</p>
9761 Create the subdirectory <file>debian</file> at the top of
9762 the source tree.</p>
9764 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
9766 <item><p>Untar the tarfile again if you want a copy of the original
9767 source code alongside the Debianised version.</p>
9772 It is not possible to generate a valid Debian source archive
9773 without using <prgn>dpkg-source</prgn>. In particular,
9774 attempting to use <prgn>diff</prgn> directly to generate the
9775 <file>.diff.gz</file> file will not work.
9779 <heading>Restrictions on objects in source packages</heading>
9782 The source package may not contain any hard links
9784 This is not currently detected when building source
9785 packages, but only when extracting
9789 Hard links may be permitted at some point in the
9790 future, but would require a fair amount of
9792 </footnote>, device special files, sockets or setuid or
9795 Setgid directories are allowed.
9800 The source packaging tools manage the changes between the
9801 original and Debianised source using <prgn>diff</prgn> and
9802 <prgn>patch</prgn>. Turning the original source tree as
9803 included in the <file>.orig.tar.gz</file> into the debianised
9804 source must not involve any changes which cannot be
9805 handled by these tools. Problematic changes which cause
9806 <prgn>dpkg-source</prgn> to halt with an error when
9807 building the source package are:
9808 <list compact="compact">
9809 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
9811 <item><p>Changing the targets of symbolic links.</p>
9813 <item><p>Creating directories, other than <file>debian</file>.</p>
9815 <item><p>Changes to the contents of binary files.</p></item>
9816 </list> Changes which cause <prgn>dpkg-source</prgn> to
9817 print a warning but continue anyway are:
9818 <list compact="compact">
9821 Removing files, directories or symlinks.
9823 Renaming a file is not treated specially - it is
9824 seen as the removal of the old file (which
9825 generates a warning, but is otherwise ignored),
9826 and the creation of the new one.
9832 Changed text files which are missing the usual final
9833 newline (either in the original or the modified
9838 Changes which are not represented, but which are not detected by
9839 <prgn>dpkg-source</prgn>, are:
9840 <list compact="compact">
9841 <item><p>Changing the permissions of files (other than
9842 <file>debian/rules</file>) and directories.</p></item>
9847 The <file>debian</file> directory and <file>debian/rules</file>
9848 are handled specially by <prgn>dpkg-source</prgn> - before
9849 applying the changes it will create the <file>debian</file>
9850 directory, and afterwards it will make
9851 <file>debian/rules</file> world-executable.
9857 <appendix id="pkg-controlfields">
9858 <heading>Control files and their fields (from old Packaging Manual)</heading>
9861 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
9862 data in a common format, known as control files. Binary and
9863 source packages have control data as do the <file>.changes</file>
9864 files which control the installation of uploaded files, and
9865 <prgn>dpkg</prgn>'s internal databases are in a similar
9870 <heading>Syntax of control files</heading>
9873 See <ref id="controlsyntax">.
9877 It is important to note that there are several fields which
9878 are optional as far as <prgn>dpkg</prgn> and the related
9879 tools are concerned, but which must appear in every Debian
9880 package, or whose omission may cause problems.
9885 <heading>List of fields</heading>
9888 See <ref id="controlfieldslist">.
9892 This section now contains only the fields that didn't belong
9893 to the Policy manual.
9896 <sect1 id="pkg-f-Filename">
9897 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
9900 These fields in <tt>Packages</tt> files give the
9901 filename(s) of (the parts of) a package in the
9902 distribution directories, relative to the root of the
9903 Debian hierarchy. If the package has been split into
9904 several parts the parts are all listed in order, separated
9909 <sect1 id="pkg-f-Size">
9910 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
9913 These fields in <file>Packages</file> files give the size (in
9914 bytes, expressed in decimal) and MD5 checksum of the
9915 file(s) which make(s) up a binary package in the
9916 distribution. If the package is split into several parts
9917 the values for the parts are listed in order, separated by
9922 <sect1 id="pkg-f-Status">
9923 <heading><tt>Status</tt></heading>
9926 This field in <prgn>dpkg</prgn>'s status file records
9927 whether the user wants a package installed, removed or
9928 left alone, whether it is broken (requiring
9929 re-installation) or not and what its current state on the
9930 system is. Each of these pieces of information is a
9935 <sect1 id="pkg-f-Config-Version">
9936 <heading><tt>Config-Version</tt></heading>
9939 If a package is not installed or not configured, this
9940 field in <prgn>dpkg</prgn>'s status file records the last
9941 version of the package which was successfully
9946 <sect1 id="pkg-f-Conffiles">
9947 <heading><tt>Conffiles</tt></heading>
9950 This field in <prgn>dpkg</prgn>'s status file contains
9951 information about the automatically-managed configuration
9952 files held by a package. This field should <em>not</em>
9953 appear anywhere in a package!
9958 <heading>Obsolete fields</heading>
9961 These are still recognized by <prgn>dpkg</prgn> but should
9962 not appear anywhere any more.
9964 <taglist compact="compact">
9966 <tag><tt>Revision</tt></tag>
9967 <tag><tt>Package-Revision</tt></tag>
9968 <tag><tt>Package_Revision</tt></tag>
9970 The Debian revision part of the package version was
9971 at one point in a separate control file field. This
9972 field went through several names.
9975 <tag><tt>Recommended</tt></tag>
9976 <item>Old name for <tt>Recommends</tt>.</item>
9978 <tag><tt>Optional</tt></tag>
9979 <item>Old name for <tt>Suggests</tt>.</item>
9981 <tag><tt>Class</tt></tag>
9982 <item>Old name for <tt>Priority</tt>.</item>
9991 <appendix id="pkg-conffiles">
9992 <heading>Configuration file handling (from old Packaging Manual)</heading>
9995 <prgn>dpkg</prgn> can do a certain amount of automatic
9996 handling of package configuration files.
10000 Whether this mechanism is appropriate depends on a number of
10001 factors, but basically there are two approaches to any
10002 particular configuration file.
10006 The easy method is to ship a best-effort configuration in the
10007 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10008 handle updates. If the user is unlikely to want to edit the
10009 file, but you need them to be able to without losing their
10010 changes, and a new package with a changed version of the file
10011 is only released infrequently, this is a good approach.
10015 The hard method is to build the configuration file from
10016 scratch in the <prgn>postinst</prgn> script, and to take the
10017 responsibility for fixing any mistakes made in earlier
10018 versions of the package automatically. This will be
10019 appropriate if the file is likely to need to be different on
10023 <sect><heading>Automatic handling of configuration files by
10028 A package may contain a control area file called
10029 <tt>conffiles</tt>. This file should be a list of filenames
10030 of configuration files needing automatic handling, separated
10031 by newlines. The filenames should be absolute pathnames,
10032 and the files referred to should actually exist in the
10037 When a package is upgraded <prgn>dpkg</prgn> will process
10038 the configuration files during the configuration stage,
10039 shortly before it runs the package's <prgn>postinst</prgn>
10044 For each file it checks to see whether the version of the
10045 file included in the package is the same as the one that was
10046 included in the last version of the package (the one that is
10047 being upgraded from); it also compares the version currently
10048 installed on the system with the one shipped with the last
10053 If neither the user nor the package maintainer has changed
10054 the file, it is left alone. If one or the other has changed
10055 their version, then the changed version is preferred - i.e.,
10056 if the user edits their file, but the package maintainer
10057 doesn't ship a different version, the user's changes will
10058 stay, silently, but if the maintainer ships a new version
10059 and the user hasn't edited it the new version will be
10060 installed (with an informative message). If both have
10061 changed their version the user is prompted about the problem
10062 and must resolve the differences themselves.
10066 The comparisons are done by calculating the MD5 message
10067 digests of the files, and storing the MD5 of the file as it
10068 was included in the most recent version of the package.
10072 When a package is installed for the first time
10073 <prgn>dpkg</prgn> will install the file that comes with it,
10074 unless that would mean overwriting a file already on the
10079 However, note that <prgn>dpkg</prgn> will <em>not</em>
10080 replace a conffile that was removed by the user (or by a
10081 script). This is necessary because with some programs a
10082 missing file produces an effect hard or impossible to
10083 achieve in another way, so that a missing file needs to be
10084 kept that way if the user did it.
10088 Note that a package should <em>not</em> modify a
10089 <prgn>dpkg</prgn>-handled conffile in its maintainer
10090 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10091 the user confusing and possibly dangerous options for
10092 conffile update when the package is upgraded.</p>
10095 <sect><heading>Fully-featured maintainer script configuration
10100 For files which contain site-specific information such as
10101 the hostname and networking details and so forth, it is
10102 better to create the file in the package's
10103 <prgn>postinst</prgn> script.
10107 This will typically involve examining the state of the rest
10108 of the system to determine values and other information, and
10109 may involve prompting the user for some information which
10110 can't be obtained some other way.
10114 When using this method there are a couple of important
10115 issues which should be considered:
10119 If you discover a bug in the program which generates the
10120 configuration file, or if the format of the file changes
10121 from one version to the next, you will have to arrange for
10122 the postinst script to do something sensible - usually this
10123 will mean editing the installed configuration file to remove
10124 the problem or change the syntax. You will have to do this
10125 very carefully, since the user may have changed the file,
10126 perhaps to fix the very problem that your script is trying
10127 to deal with - you will have to detect these situations and
10128 deal with them correctly.
10132 If you do go down this route it's probably a good idea to
10133 make the program that generates the configuration file(s) a
10134 separate program in <file>/usr/sbin</file>, by convention called
10135 <file><var>package</var>config</file> and then run that if
10136 appropriate from the post-installation script. The
10137 <tt><var>package</var>config</tt> program should not
10138 unquestioningly overwrite an existing configuration - if its
10139 mode of operation is geared towards setting up a package for
10140 the first time (rather than any arbitrary reconfiguration
10141 later) you should have it check whether the configuration
10142 already exists, and require a <tt>--force</tt> flag to
10143 overwrite it.</p></sect>
10146 <appendix id="pkg-alternatives"><heading>Alternative versions of
10147 an interface - <prgn>update-alternatives</prgn> (from old
10152 When several packages all provide different versions of the
10153 same program or file it is useful to have the system select a
10154 default, but to allow the system administrator to change it
10155 and have their decisions respected.
10159 For example, there are several versions of the <prgn>vi</prgn>
10160 editor, and there is no reason to prevent all of them from
10161 being installed at once, each under their own name
10162 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10163 Nevertheless it is desirable to have the name <tt>vi</tt>
10164 refer to something, at least by default.
10168 If all the packages involved cooperate, this can be done with
10169 <prgn>update-alternatives</prgn>.
10173 Each package provides its own version under its own name, and
10174 calls <prgn>update-alternatives</prgn> in its postinst to
10175 register its version (and again in its prerm to deregister
10180 See the man page <manref name="update-alternatives"
10181 section="8"> for details.
10185 If <prgn>update-alternatives</prgn> does not seem appropriate
10186 you may wish to consider using diversions instead.</p>
10189 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10190 package's version of a file (from old Packaging Manual)
10194 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10195 when it reinstalls the package it belongs to, and to have it
10196 put the file from the package somewhere else instead.
10200 This can be used locally to override a package's version of a
10201 file, or by one package to override another's version (or
10202 provide a wrapper for it).
10206 Before deciding to use a diversion, read <ref
10207 id="pkg-alternatives"> to see if you really want a diversion
10208 rather than several alternative versions of a program.
10212 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10213 and updated by a special program <prgn>dpkg-divert</prgn>.
10214 Please see <manref name="dpkg-divert" section="8"> for full
10215 details of its operation.
10219 When a package wishes to divert a file from another, it should
10220 call <prgn>dpkg-divert</prgn> in its preinst to add the
10221 diversion and rename the existing file. For example,
10222 supposing that a <prgn>smailwrapper</prgn> package wishes to
10223 install a wrapper around <file>/usr/sbin/smail</file>:
10225 if [ install = "$1" ]; then
10226 dpkg-divert --package smailwrapper --add --rename \
10227 --divert /usr/sbin/smail.real /usr/sbin/smail
10229 </example> Testing <tt>$1</tt> is necessary so that the script
10230 doesn't try to add the diversion again when
10231 <prgn>smailwrapper</prgn> is upgraded. The <tt>--package
10232 smailwrapper</tt> ensures that <prgn>smailwrapper</prgn>'s
10233 copy of <file>/usr/sbin/smail</file> can bypass the diversion and
10234 get installed as the true version.
10238 The postrm has to do the reverse:
10240 if [ remove = "$1" ]; then
10241 dpkg-divert --package smailwrapper --remove --rename \
10242 --divert /usr/sbin/smail.real /usr/sbin/smail
10248 Do not attempt to divert a file which is vitally important for
10249 the system's operation - when using <prgn>dpkg-divert</prgn>
10250 there is a time, after it has been diverted but before
10251 <prgn>dpkg</prgn> has installed the new version, when the file
10252 does not exist.</p>
10257 <!-- vim:set ai et sts=2 sw=2 tw=76: -->