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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>comm</em>,
644 <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>,
651 <em>otherosfs</em>, <em>perl</em>, <em>python</em>,
652 <em>science</em>, <em>shells</em>,
653 <em>sound</em>, <em>tex</em>, <em>text</em>,
654 <em>utils</em>, <em>web</em>, <em>x11</em>.
658 <sect id="priorities">
659 <heading>Priorities</heading>
662 Each package should have a <em>priority</em> value, which is
663 included in the package's <em>control record</em>
664 (see <ref id="f-Priority">).
665 This information is used by the Debian package management tools to
666 separate high-priority packages from less-important packages.
670 The following <em>priority levels</em> are recognized by the
671 Debian package management tools.
673 <tag><tt>required</tt></tag>
675 Packages which are necessary for the proper
676 functioning of the system (usually, this means that
677 dpkg functionality depends on these packages).
678 Removing a <tt>required</tt> package may cause your
679 system to become totally broken and you may not even
680 be able to use <prgn>dpkg</prgn> to put things back,
681 so only do so if you know what you are doing. Systems
682 with only the <tt>required</tt> packages are probably
683 unusable, but they do have enough functionality to
684 allow the sysadmin to boot and install more software.
686 <tag><tt>important</tt></tag>
688 Important programs, including those which one would
689 expect to find on any Unix-like system. If the
690 expectation is that an experienced Unix person who
691 found it missing would say "What on earth is going on,
692 where is <prgn>foo</prgn>?", it must be an
693 <tt>important</tt> package.<footnote>
694 This is an important criterion because we are
695 trying to produce, amongst other things, a free
698 Other packages without which the system will not run
699 well or be usable must also have priority
700 <tt>important</tt>. This does
701 <em>not</em> include Emacs, the X Window System, TeX
702 or any other large applications. The
703 <tt>important</tt> packages are just a bare minimum of
704 commonly-expected and necessary tools.
706 <tag><tt>standard</tt></tag>
708 These packages provide a reasonably small but not too
709 limited character-mode system. This is what will be
710 installed by default if the user doesn't select anything
711 else. It doesn't include many large applications.
713 <tag><tt>optional</tt></tag>
715 (In a sense everything that isn't required is
716 optional, but that's not what is meant here.) This is
717 all the software that you might reasonably want to
718 install if you didn't know what it was and don't have
719 specialized requirements. This is a much larger system
720 and includes the X Window System, a full TeX
721 distribution, and many applications. Note that
722 optional packages should not conflict with each other.
724 <tag><tt>extra</tt></tag>
726 This contains all packages that conflict with others
727 with required, important, standard or optional
728 priorities, or are only likely to be useful if you
729 already know what they are or have specialized
736 Packages must not depend on packages with lower priority
737 values (excluding build-time dependencies). In order to
738 ensure this, the priorities of one or more packages may need
747 <heading>Binary packages</heading>
750 The Debian GNU/Linux distribution is based on the Debian
751 package management system, called <prgn>dpkg</prgn>. Thus,
752 all packages in the Debian distribution must be provided
753 in the <tt>.deb</tt> file format.
757 <heading>The package name</heading>
760 Every package must have a name that's unique within the Debian
765 The package name is included in the control field
766 <tt>Package</tt>, the format of which is described
767 in <ref id="f-Package">.
768 The package name is also included as a part of the file name
769 of the <tt>.deb</tt> file.
774 <heading>The version of a package</heading>
777 Every package has a version number recorded in its
778 <tt>Version</tt> control file field, described in
779 <ref id="f-Version">.
783 The package management system imposes an ordering on version
784 numbers, so that it can tell whether packages are being up- or
785 downgraded and so that package system front end applications
786 can tell whether a package it finds available is newer than
787 the one installed on the system. The version number format
788 has the most significant parts (as far as comparison is
789 concerned) at the beginning.
793 If an upstream package has problematic version numbers they
794 should be converted to a sane form for use in the
795 <tt>Version</tt> field.
799 <heading>Version numbers based on dates</heading>
802 In general, Debian packages should use the same version
803 numbers as the upstream sources.
807 However, in some cases where the upstream version number is
808 based on a date (e.g., a development "snapshot" release) the
809 package management system cannot handle these version
810 numbers without epochs. For example, dpkg will consider
811 "96May01" to be greater than "96Dec24".
815 To prevent having to use epochs for every new upstream
816 version, the date based portion of the version number
817 should be changed to the following format in such cases:
818 "19960501", "19961224". It is up to the maintainer whether
819 they want to bother the upstream maintainer to change
820 the version numbers upstream, too.
824 Note that other version formats based on dates which are
825 parsed correctly by the package management system should
826 <em>not</em> be changed.
830 Native Debian packages (i.e., packages which have been
831 written especially for Debian) whose version numbers include
832 dates should always use the "YYYYMMDD" format.
839 <heading>The maintainer of a package</heading>
842 Every package must have a Debian maintainer (the
843 maintainer may be one person or a group of people
844 reachable from a common email address, such as a mailing
845 list). The maintainer is responsible for ensuring that
846 the package is placed in the appropriate distributions.
850 The maintainer must be specified in the
851 <tt>Maintainer</tt> control field with their correct name
852 and a working email address. If one person maintains
853 several packages, they should try to avoid having
854 different forms of their name and email address in
855 the <tt>Maintainer</tt> fields of those packages.
859 The format of the <tt>Maintainer</tt> control field is
860 described in <ref id="f-Maintainer">.
864 If the maintainer of a package quits from the Debian
865 project, "Debian QA Group"
866 <email>packages@qa.debian.org</email> takes over the
867 maintainer-ship of the package until someone else
868 volunteers for that task. These packages are called
869 <em>orphaned packages</em>.<footnote>
870 The detailed procedure for doing this gracefully can
871 be found in the Debian Developer's Reference,
872 see <ref id="related">.
877 <sect id="descriptions">
878 <heading>The description of a package</heading>
881 Every Debian package must have an extended description
882 stored in the appropriate field of the control record.
883 The technical information about the format of the
884 <tt>Description</tt> field is in <ref id="f-Description">.
888 The description should describe the package (the program) to a
889 user (system administrator) who has never met it before so that
890 they have enough information to decide whether they want to
891 install it. This description should not just be copied verbatim
892 from the program's documentation.
896 Put important information first, both in the synopsis and
897 extended description. Sometimes only the first part of the
898 synopsis or of the description will be displayed. You can
899 assume that there will usually be a way to see the whole
900 extended description.
904 The description should also give information about the
905 significant dependencies and conflicts between this package
906 and others, so that the user knows why these dependencies and
907 conflicts have been declared.
911 Instructions for configuring or using the package should
912 not be included (that is what installation scripts,
913 manual pages, info files, etc., are for). Copyright
914 statements and other administrivia should not be included
915 either (that is what the copyright file is for).
918 <sect1 id="synopsis"><heading>The single line synopsis</heading>
921 The single line synopsis should be kept brief - certainly
926 Do not include the package name in the synopsis line. The
927 display software knows how to display this already, and you
928 do not need to state it. Remember that in many situations
929 the user may only see the synopsis line - make it as
930 informative as you can.
935 <sect1 id="extendeddesc"><heading>The extended description</heading>
938 Do not try to continue the single line synopsis into the
939 extended description. This will not work correctly when
940 the full description is displayed, and makes no sense
941 where only the summary (the single line synopsis) is
946 The extended description should describe what the package
947 does and how it relates to the rest of the system (in terms
948 of, for example, which subsystem it is which part of).
952 The description field needs to make sense to anyone, even
953 people who have no idea about any of the things the
954 package deals with.<footnote>
955 The blurb that comes with a program in its
956 announcements and/or <prgn>README</prgn> files is
957 rarely suitable for use in a description. It is
958 usually aimed at people who are already in the
959 community where the package is used.
968 <heading>Dependencies</heading>
971 Every package must specify the dependency information
972 about other packages that are required for the first to
977 For example, a dependency entry must be provided for any
978 shared libraries required by a dynamically-linked executable
983 Packages are not required to declare any dependencies they
984 have on other packages which are marked <tt>Essential</tt>
985 (see below), and should not do so unless they depend on a
986 particular version of that package.<footnote>
988 Essential is defined as the minimal set of functionality
989 that must be available and usable on the system even
990 when packages are in an unconfigured (but unpacked)
991 state. This is needed to avoid unresolvable dependency
992 loops on upgrade. If packages add unnecessary
993 dependencies on packages in this set, the chances that
994 there <strong>will</strong> be an unresolvable
995 dependency loop caused by forcing these Essential
996 packages to be configured first before they need to be
997 is greatly increased. It also increases the chances
998 that frontends will be unable to
999 <strong>calculate</strong> an upgrade path, even if one
1003 Also, it's pretty unlikely that functionality from
1004 Essential shall ever be removed (which is one reason why
1005 care must be taken before adding to the Essential
1006 packages set), but <em>packages</em> have been removed
1007 from the Essential set when the functionality moved to a
1008 different package. So depending on these packages
1009 <em>just in case</em> they stop being essential does way
1010 more harm than good.
1016 Sometimes, a package requires another package to be installed
1017 <em>and</em> configured before it can be installed. In this
1018 case, you must specify a <tt>Pre-Depends</tt> entry for
1023 You should not specify a <tt>Pre-Depends</tt> entry for a
1024 package before this has been discussed on the
1025 <tt>debian-devel</tt> mailing list and a consensus about
1026 doing that has been reached.
1030 The format of the package interrelationship control fields is
1031 described in <ref id="relationships">.
1035 <sect id="virtual_pkg">
1036 <heading>Virtual packages</heading>
1039 Sometimes, there are several packages which offer
1040 more-or-less the same functionality. In this case, it's
1041 useful to define a <em>virtual package</em> whose name
1042 describes that common functionality. (The virtual
1043 packages only exist logically, not physically; that's why
1044 they are called <em>virtual</em>.) The packages with this
1045 particular function will then <em>provide</em> the virtual
1046 package. Thus, any other package requiring that function
1047 can simply depend on the virtual package without having to
1048 specify all possible packages individually.
1052 All packages should use virtual package names where
1053 appropriate, and arrange to create new ones if necessary.
1054 They should not use virtual package names (except privately,
1055 amongst a cooperating group of packages) unless they have
1056 been agreed upon and appear in the list of virtual package
1057 names. (See also <ref id="virtual">)
1061 The latest version of the authoritative list of virtual
1062 package names can be found in the <tt>debian-policy</tt> package.
1063 It is also available from the Debian web mirrors at
1064 <tt><url name="/doc/packaging-manuals/virtual-package-names-list.txt"
1065 id="http://www.debian.org/doc/packaging-manuals/virtual-package-names-list.txt"></tt>.
1069 The procedure for updating the list is described in the preface
1076 <heading>Base system</heading>
1079 The <tt>base system</tt> is a minimum subset of the Debian
1080 GNU/Linux system that is installed before everything else
1081 on a new system. Only very few packages are allowed to form
1082 part of the base system, in order to keep the required disk
1087 The base system consists of all those packages with priority
1088 <tt>required</tt> or <tt>important</tt>. Many of them will
1089 be tagged <tt>essential</tt> (see below).
1094 <heading>Essential packages</heading>
1097 Some packages are tagged <tt>essential</tt> for a system
1098 using the <tt>Essential</tt> control file field.
1099 The format of the <tt>Essential</tt> control field is
1100 described in <ref id="f-Essential">.
1104 Since these packages cannot be easily removed (one has to
1105 specify an extra <em>force option</em> to
1106 <prgn>dpkg</prgn> to do so), this flag must not be used
1107 unless absolutely necessary. A shared library package
1108 must not be tagged <tt>essential</tt>; dependencies will
1109 prevent its premature removal, and we need to be able to
1110 remove it when it has been superseded.
1114 Since dpkg will not prevent upgrading of other packages
1115 while an <tt>essential</tt> package is in an unconfigured
1116 state, all <tt>essential</tt> packages must supply all of
1117 their core functionality even when unconfigured. If the
1118 package cannot satisfy this requirement it must not be
1119 tagged as essential, and any packages depending on this
1120 package must instead have explicit dependency fields as
1125 You must not tag any packages <tt>essential</tt> before
1126 this has been discussed on the <tt>debian-devel</tt>
1127 mailing list and a consensus about doing that has been
1132 <sect id="maintscripts">
1133 <heading>Maintainer Scripts</heading>
1136 The package installation scripts should avoid producing
1137 output which is unnecessary for the user to see and
1138 should rely on <prgn>dpkg</prgn> to stave off boredom on
1139 the part of a user installing many packages. This means,
1140 amongst other things, using the <tt>--quiet</tt> option on
1141 <prgn>install-info</prgn>.
1145 Errors which occur during the execution of an installation
1146 script must be checked and the installation must not
1147 continue after an error.
1151 Note that in general <ref id="scripts"> applies to package
1152 maintainer scripts, too.
1156 You should not use <prgn>dpkg-divert</prgn> on a file
1157 belonging to another package without consulting the
1158 maintainer of that package first.
1162 All packages which supply an instance of a common command
1163 name (or, in general, filename) should generally use
1164 <prgn>update-alternatives</prgn>, so that they may be
1165 installed together. If <prgn>update-alternatives</prgn>
1166 is not used, then each package must use
1167 <tt>Conflicts</tt> to ensure that other packages are
1168 de-installed. (In this case, it may be appropriate to
1169 specify a conflict against earlier versions of something
1170 that previously did not use
1171 <prgn>update-alternatives</prgn>; this is an exception to
1172 the usual rule that versioned conflicts should be
1176 <sect1 id="maintscriptprompt">
1177 <heading>Prompting in maintainer scripts</heading>
1179 Package maintainer scripts may prompt the user if
1180 necessary. Prompting should be done by communicating
1181 through a program, such as <prgn>debconf</prgn>, which
1182 conforms to the Debian Configuration management
1183 specification, version 2 or higher. Prompting the user by
1184 other means, such as by hand<footnote>
1185 From the Jargon file: by hand 2. By extension,
1186 writing code which does something in an explicit or
1187 low-level way for which a presupplied library
1188 (<em>debconf, in this instance</em>) routine ought
1189 to have been available.
1190 </footnote>, is now deprecated.
1194 The Debian Configuration management specification is included
1195 in the <file>debconf_specification</file> files in the
1196 <package>debian-policy</package> package.
1197 It is also available from the Debian web mirrors at
1198 <tt><url name="/doc/packaging-manuals/debconf_specification.html"
1199 id="http://www.debian.org/doc/packaging-manuals/debconf_specification.html"></tt>.
1203 Packages which use the Debian Configuration management
1204 specification may contain an additional
1205 <prgn>config</prgn> script and a <tt>templates</tt>
1206 file in their control archive<footnote>
1207 The control.tar.gz inside the .deb.
1208 See <manref name="deb" section="5">.
1210 The <prgn>config</prgn> script might be run before the
1211 <prgn>preinst</prgn> script, and before the package is unpacked
1212 or any of its dependencies or pre-dependencies are satisfied.
1213 Therefore it must work using only the tools present in
1214 <em>essential</em> packages.<footnote>
1215 <package>Debconf</package> or another tool that
1216 implements the Debian Configuration management
1217 specification will also be installed, and any
1218 versioned dependencies on it will be satisfied
1219 before preconfiguration begins.
1224 Packages which use the Debian Configuration management
1225 specification must allow for translation of their messages
1226 by using a gettext-based system such as the one provided by
1227 the <package>po-debconf</package> package.
1231 Packages should try to minimize the amount of prompting
1232 they need to do, and they should ensure that the user
1233 will only ever be asked each question once. This means
1234 that packages should try to use appropriate shared
1235 configuration files (such as <file>/etc/papersize</file> and
1236 <file>/etc/news/server</file>), and shared
1237 <package>debconf</package> variables rather than each
1238 prompting for their own list of required pieces of
1243 It also means that an upgrade should not ask the same
1244 questions again, unless the user has used
1245 <tt>dpkg --purge</tt> to remove the package's configuration.
1246 The answers to configuration questions should be stored in an
1247 appropriate place in <file>/etc</file> so that the user can
1248 modify them, and how this has been done should be
1253 If a package has a vitally important piece of
1254 information to pass to the user (such as "don't run me
1255 as I am, you must edit the following configuration files
1256 first or you risk your system emitting badly-formatted
1257 messages"), it should display this in the
1258 <prgn>config</prgn> or <prgn>postinst</prgn> script and
1259 prompt the user to hit return to acknowledge the
1260 message. Copyright messages do not count as vitally
1261 important (they belong in
1262 <file>/usr/share/doc/<var>package</var>/copyright</file>);
1263 neither do instructions on how to use a program (these
1264 should be in on-line documentation, where all the users
1269 Any necessary prompting should almost always be confined
1270 to the <prgn>config</prgn> or <prgn>postinst</prgn>
1271 script. If it is done in the <prgn>postinst</prgn>, it
1272 should be protected with a conditional so that
1273 unnecessary prompting doesn't happen if a package's
1274 installation fails and the <prgn>postinst</prgn> is
1275 called with <tt>abort-upgrade</tt>,
1276 <tt>abort-remove</tt> or <tt>abort-deconfigure</tt>.
1286 <heading>Source packages</heading>
1288 <sect id="standardsversion">
1289 <heading>Standards conformance</heading>
1292 Source packages should specify the most recent version number
1293 of this policy document with which your package complied
1294 when it was last updated.
1298 This information may be used to file bug reports
1299 automatically if your package becomes too much out of date.
1303 The version is specified in the <tt>Standards-Version</tt>
1305 The format of the <tt>Standards-Version</tt> field is
1306 described in <ref id="f-Standards-Version">.
1310 You should regularly, and especially if your package has
1311 become out of date, check for the newest Policy Manual
1312 available and update your package, if necessary. When your
1313 package complies with the new standards you should update the
1314 <tt>Standards-Version</tt> source package field and
1315 release it.<footnote>
1316 See the file <file>upgrading-checklist</file> for
1317 information about policy which has changed between
1318 different versions of this document.
1324 <sect id="pkg-relations">
1325 <heading>Package relationships</heading>
1328 Source packages should specify which binary packages they
1329 require to be installed or not to be installed in order to
1330 build correctly. For example, if building a package
1331 requires a certain compiler, then the compiler should be
1332 specified as a build-time dependency.
1336 It is not necessary to explicitly specify build-time
1337 relationships on a minimal set of packages that are always
1338 needed to compile, link and put in a Debian package a
1339 standard "Hello World!" program written in C or C++. The
1340 required packages are called <em>build-essential</em>, and
1341 an informational list can be found in
1342 <file>/usr/share/doc/build-essential/list</file> (which is
1343 contained in the <tt>build-essential</tt>
1346 <list compact="compact">
1348 This allows maintaining the list separately
1349 from the policy documents (the list does not
1350 need the kind of control that the policy
1354 Having a separate package allows one to install
1355 the build-essential packages on a machine, as
1356 well as allowing other packages such as tasks to
1357 require installation of the build-essential
1358 packages using the depends relation.
1361 The separate package allows bug reports against
1362 the list to be categorized separately from
1363 the policy management process in the BTS.
1370 When specifying the set of build-time dependencies, one
1371 should list only those packages explicitly required by the
1372 build. It is not necessary to list packages which are
1373 required merely because some other package in the list of
1374 build-time dependencies depends on them.<footnote>
1375 The reason for this is that dependencies change, and
1376 you should list all those packages, and <em>only</em>
1377 those packages that <em>you</em> need directly. What
1378 others need is their business. For example, if you
1379 only link against <file>libimlib</file>, you will need to
1380 build-depend on <package>libimlib2-dev</package> but
1381 not against any <tt>libjpeg*</tt> packages, even
1382 though <tt>libimlib2-dev</tt> currently depends on
1383 them: installation of <package>libimlib2-dev</package>
1384 will automatically ensure that all of its run-time
1385 dependencies are satisfied.
1390 If build-time dependencies are specified, it must be
1391 possible to build the package and produce working binaries
1392 on a system with only essential and build-essential
1393 packages installed and also those required to satisfy the
1394 build-time relationships (including any implied
1395 relationships). In particular, this means that version
1396 clauses should be used rigorously in build-time
1397 relationships so that one cannot produce bad or
1398 inconsistently configured packages when the relationships
1399 are properly satisfied.
1403 <ref id="relationships"> explains the technical details.
1408 <heading>Changes to the upstream sources</heading>
1411 If changes to the source code are made that are not
1412 specific to the needs of the Debian system, they should be
1413 sent to the upstream authors in whatever form they prefer
1414 so as to be included in the upstream version of the
1419 If you need to configure the package differently for
1420 Debian or for Linux, and the upstream source doesn't
1421 provide a way to do so, you should add such configuration
1422 facilities (for example, a new <prgn>autoconf</prgn> test
1423 or <tt>#define</tt>) and send the patch to the upstream
1424 authors, with the default set to the way they originally
1425 had it. You can then easily override the default in your
1426 <file>debian/rules</file> or wherever is appropriate.
1430 You should make sure that the <prgn>configure</prgn> utility
1431 detects the correct architecture specification string
1432 (refer to <ref id="arch-spec"> for details).
1436 If you need to edit a <prgn>Makefile</prgn> where GNU-style
1437 <prgn>configure</prgn> scripts are used, you should edit the
1438 <file>.in</file> files rather than editing the
1439 <prgn>Makefile</prgn> directly. This allows the user to
1440 reconfigure the package if necessary. You should
1441 <em>not</em> configure the package and edit the generated
1442 <prgn>Makefile</prgn>! This makes it impossible for someone
1443 else to later reconfigure the package without losing the
1449 <sect id="dpkgchangelog">
1450 <heading>Debian changelog: <file>debian/changelog</file></heading>
1453 Changes in the Debian version of the package should be
1454 briefly explained in the Debian changelog file
1455 <file>debian/changelog</file>.<footnote>
1457 Mistakes in changelogs are usually best rectified by
1458 making a new changelog entry rather than "rewriting
1459 history" by editing old changelog entries.
1462 This includes modifications
1463 made in the Debian package compared to the upstream one
1464 as well as other changes and updates to the package.
1466 Although there is nothing stopping an author who is also
1467 the Debian maintainer from using this changelog for all
1468 their changes, it will have to be renamed if the Debian
1469 and upstream maintainers become different people. In such
1470 a case, however, it might be better to maintain the package
1471 as a non-native package.
1480 The format of the <file>debian/changelog</file> allows the
1481 package building tools to discover which version of the package
1482 is being built and find out other release-specific information.
1486 That format is a series of entries like this:
1488 <example compact="compact">
1489 <var>package</var> (<var>version</var>) <var>distribution(s)</var>; urgency=<var>urgency</var>
1491 [optional blank line(s), stripped]
1493 * <var>change details</var>
1494 <var>more change details</var>
1496 [blank line(s), included in output of dpkg-parsechangelog]
1498 * <var>even more change details</var>
1500 [optional blank line(s), stripped]
1502 -- <var>maintainer name</var> <<var>email address</var>><var>[two spaces]</var> <var>date</var>
1507 <var>package</var> and <var>version</var> are the source
1508 package name and version number.
1512 <var>distribution(s)</var> lists the distributions where
1513 this version should be installed when it is uploaded - it
1514 is copied to the <tt>Distribution</tt> field in the
1515 <file>.changes</file> file. See <ref id="f-Distribution">.
1519 <var>urgency</var> is the value for the <tt>Urgency</tt>
1520 field in the <file>.changes</file> file for the upload
1521 (see <ref id="f-Urgency">). It is not possible to specify
1522 an urgency containing commas; commas are used to separate
1523 <tt><var>keyword</var>=<var>value</var></tt> settings in the
1524 <prgn>dpkg</prgn> changelog format (though there is
1525 currently only one useful <var>keyword</var>,
1530 The change details may in fact be any series of lines
1531 starting with at least two spaces, but conventionally each
1532 change starts with an asterisk and a separating space and
1533 continuation lines are indented so as to bring them in
1534 line with the start of the text above. Blank lines may be
1535 used here to separate groups of changes, if desired.
1539 If this upload resolves bugs recorded in the Bug Tracking
1540 System (BTS), they may be automatically closed on the
1541 inclusion of this package into the Debian archive by
1542 including the string: <tt>closes: Bug#<var>nnnnn</var></tt>
1543 in the change details.<footnote>
1544 To be precise, the string should match the following
1545 Perl regular expression:
1547 /closes:\s*(?:bug)?\#?\s?\d+(?:,\s*(?:bug)?\#?\s?\d+)*/i
1549 Then all of the bug numbers listed will be closed by the
1550 archive maintenance script (<prgn>katie</prgn>), or in
1551 the case of an NMU, marked as fixed.
1553 This information is conveyed via the <tt>Closes</tt> field
1554 in the <tt>.changes</tt> file (see <ref id="f-Closes">).
1558 The maintainer name and email address used in the changelog
1559 should be the details of the person uploading <em>this</em>
1560 version. They are <em>not</em> necessarily those of the
1561 usual package maintainer. The information here will be
1562 copied to the <tt>Changed-By</tt> field in the
1563 <tt>.changes</tt> file (see <ref id="f-Changed-By">),
1564 and then later used to send an acknowledgement when the
1565 upload has been installed.
1569 The <var>date</var> should be in RFC822 format<footnote>
1570 This is generated by <tt>date -R</tt>.
1571 </footnote>; it should include the time zone specified
1572 numerically, with the time zone name or abbreviation
1573 optionally present as a comment in parentheses.
1577 The first "title" line with the package name should start
1578 at the left hand margin; the "trailer" line with the
1579 maintainer and date details should be preceded by exactly
1580 one space. The maintainer details and the date must be
1581 separated by exactly two spaces.
1585 For more information on placement of the changelog files
1586 within binary packages, please see <ref id="changelogs">.
1589 <sect1><heading>Alternative changelog formats</heading>
1592 In non-experimental packages you must use a format for
1593 <file>debian/changelog</file> which is supported by the most
1594 recent released version of <prgn>dpkg</prgn>.
1598 It is possible to use a format different from the standard
1599 one by providing a changelog parser for the format you wish
1600 to use. The parser must have an API compatible with that
1601 expected by <prgn>dpkg-genchanges</prgn> and
1602 <prgn>dpkg-gencontrol</prgn>, and it must not interact with
1605 If there is general interest in the new format, you should
1606 contact the <package>dpkg</package> maintainer to have the
1607 parser script for it included in the <prgn>dpkg</prgn>
1608 package. (You will need to agree that the parser and its
1609 man page may be distributed under the GNU GPL, just as the rest
1610 of <prgn>dpkg</prgn> is.)
1615 <sect id="dpkgcopyright">
1616 <heading>Copyright: <file>debian/copyright</file></heading>
1618 Every package must be accompanied by a verbatim copy of
1619 its copyright and distribution license in the file
1620 <file>/usr/share/doc/<var>package</var>/copyright</file>
1621 (see <ref id="copyrightfile"> for further details). Also see
1622 <ref id="pkgcopyright"> for further considerations relayed
1623 to copyrights for packages.
1627 <heading>Error trapping in makefiles</heading>
1630 When <prgn>make</prgn> invokes a command in a makefile
1631 (including your package's upstream makefiles and
1632 <file>debian/rules</file>), it does so using <prgn>sh</prgn>. This
1633 means that <prgn>sh</prgn>'s usual bad error handling
1634 properties apply: if you include a miniature script as one
1635 of the commands in your makefile you'll find that if you
1636 don't do anything about it then errors are not detected
1637 and <prgn>make</prgn> will blithely continue after
1642 Every time you put more than one shell command (this
1643 includes using a loop) in a makefile command you
1644 must make sure that errors are trapped. For
1645 simple compound commands, such as changing directory and
1646 then running a program, using <tt>&&</tt> rather
1647 than semicolon as a command separator is sufficient. For
1648 more complex commands including most loops and
1649 conditionals you should include a separate <tt>set -e</tt>
1650 command at the start of every makefile command that's
1651 actually one of these miniature shell scripts.
1655 <sect id="timestamps">
1656 <heading>Time Stamps</heading>
1658 Maintainers should preserve the modification times of the
1659 upstream source files in a package, as far as is reasonably
1661 The rationale is that there is some information conveyed
1662 by knowing the age of the file, for example, you could
1663 recognize that some documentation is very old by looking
1664 at the modification time, so it would be nice if the
1665 modification time of the upstream source would be
1671 <sect id="restrictions">
1672 <heading>Restrictions on objects in source packages</heading>
1675 The source package may not contain any hard links<footnote>
1677 This is not currently detected when building source
1678 packages, but only when extracting
1682 Hard links may be permitted at some point in the
1683 future, but would require a fair amount of
1686 </footnote>, device special files, sockets or setuid or
1687 setgid files.<footnote>
1688 Setgid directories are allowed.
1693 <sect id="debianrules">
1694 <heading>Main building script: <file>debian/rules</file></heading>
1697 This file must be an executable makefile, and contains the
1698 package-specific recipes for compiling the package and
1699 building binary package(s) from the source.
1703 It must start with the line <tt>#!/usr/bin/make -f</tt>,
1704 so that it can be invoked by saying its name rather than
1705 invoking <prgn>make</prgn> explicitly.
1709 Since an interactive <file>debian/rules</file> script makes it
1710 impossible to auto-compile that package and also makes it
1711 hard for other people to reproduce the same binary
1712 package, all <em>required targets</em> MUST be
1713 non-interactive. At a minimum, required targets are the
1714 ones called by <prgn>dpkg-buildpackage</prgn>, namely,
1715 <em>clean</em>, <em>binary</em>, <em>binary-arch</em>,
1716 <em>binary-indep</em>, and <em>build</em>. It also follows
1717 that any target that these targets depend on must also be
1722 The targets are as follows (required unless stated otherwise):
1724 <tag><tt>build</tt></tag>
1727 The <tt>build</tt> target should perform all the
1728 configuration and compilation of the package.
1729 If a package has an interactive pre-build
1730 configuration routine, the Debianized source package
1731 must either be built after this has taken place (so
1732 that the binary package can be built without rerunning
1733 the configuration) or the configuration routine
1734 modified to become non-interactive. (The latter is
1735 preferable if there are architecture-specific features
1736 detected by the configuration routine.)
1740 For some packages, notably ones where the same
1741 source tree is compiled in different ways to produce
1742 two binary packages, the <tt>build</tt> target
1743 does not make much sense. For these packages it is
1744 good enough to provide two (or more) targets
1745 (<tt>build-a</tt> and <tt>build-b</tt> or whatever)
1746 for each of the ways of building the package, and a
1747 <tt>build</tt> target that does nothing. The
1748 <tt>binary</tt> target will have to build the
1749 package in each of the possible ways and make the
1750 binary package out of each.
1754 The <tt>build</tt> target must not do anything
1755 that might require root privilege.
1759 The <tt>build</tt> target may need to run the
1760 <tt>clean</tt> target first - see below.
1764 When a package has a configuration and build routine
1765 which takes a long time, or when the makefiles are
1766 poorly designed, or when <tt>build</tt> needs to
1767 run <tt>clean</tt> first, it is a good idea to
1768 <tt>touch build</tt> when the build process is
1769 complete. This will ensure that if <tt>debian/rules
1770 build</tt> is run again it will not rebuild the whole
1772 Another common way to do this is for <tt>build</tt>
1773 to depend on <prgn>build-stamp</prgn> and to do
1774 nothing else, and for the <prgn>build-stamp</prgn>
1775 target to do the building and to <tt>touch
1776 build-stamp</tt> on completion. This is
1777 especially useful if the build routine creates a
1778 file or directory called <tt>build</tt>; in such a
1779 case, <tt>build</tt> will need to be listed as
1780 a phony target (i.e., as a dependency of the
1781 <tt>.PHONY</tt> target). See the documentation of
1782 <prgn>make</prgn> for more information on phony
1788 <tag><tt>build-arch</tt> (optional),
1789 <tt>build-indep</tt> (optional)
1793 A package may also provide both of the targets
1794 <tt>build-arch</tt> and <tt>build-indep</tt>.
1795 The <tt>build-arch</tt> target, if provided, should
1796 perform all the configuration and compilation required
1797 for producing all architecture-dependant binary packages
1798 (those packages for which the body of the
1799 <tt>Architecture</tt> field in <tt>debian/control</tt>
1800 is not <tt>all</tt>).
1801 Similarly, the <tt>build-indep</tt> target, if
1802 provided, should perform all the configuration and
1803 compilation required for producing all
1804 architecture-independent binary packages
1805 (those packages for which the body of the
1806 <tt>Architecture</tt> field in <tt>debian/control</tt>
1808 The <tt>build</tt> target should depend on those of the
1809 targets <tt>build-arch</tt> and <tt>build-indep</tt> that
1810 are provided in the rules file.
1814 If one or both of the targets <tt>build-arch</tt> and
1815 <tt>build-indep</tt> are not provided, then invoking
1816 <file>debian/rules</file> with one of the not-provided
1817 targets as arguments should produce a exit status code
1818 of 2. Usually this is provided automatically by make
1819 if the target is missing.
1823 The <tt>build-arch</tt> and <tt>build-indep</tt> targets
1824 must not do anything that might require root privilege.
1828 <tag><tt>binary</tt>, <tt>binary-arch</tt>,
1829 <tt>binary-indep</tt>
1833 The <tt>binary</tt> target must be all that is
1834 necessary for the user to build the binary package(s)
1835 produced from this source package. It is
1836 split into two parts: <prgn>binary-arch</prgn> builds
1837 the binary packages which are specific to a particular
1838 architecture, and <tt>binary-indep</tt> builds
1839 those which are not.
1842 <tt>binary</tt> may be (and commonly is) a target with
1843 no commands which simply depends on
1844 <tt>binary-arch</tt> and <tt>binary-indep</tt>.
1847 Both <tt>binary-*</tt> targets should depend on the
1848 <tt>build</tt> target, or on the appropriate
1849 <tt>build-arch</tt> or <tt>build-indep</tt> target, if
1850 provided, so that the package is built if it has not
1851 been already. It should then create the relevant
1852 binary package(s), using <prgn>dpkg-gencontrol</prgn> to
1853 make their control files and <prgn>dpkg-deb</prgn> to
1854 build them and place them in the parent of the top
1859 Both the <tt>binary-arch</tt> and
1860 <tt>binary-indep</tt> targets <em>must</em> exist.
1861 If one of them has nothing to do (which will always be
1862 the case if the source generates only a single binary
1863 package, whether architecture-dependent or not), it
1864 must still exist and must always succeed.
1868 The <tt>binary</tt> targets must be invoked as
1870 The <prgn>fakeroot</prgn> package often allows one
1871 to build a package correctly even without being
1877 <tag><tt>clean</tt></tag>
1880 This must undo any effects that the <tt>build</tt>
1881 and <tt>binary</tt> targets may have had, except
1882 that it should leave alone any output files created in
1883 the parent directory by a run of a <tt>binary</tt>
1888 If a <tt>build</tt> file is touched at the end of
1889 the <tt>build</tt> target, as suggested above, it
1890 should be removed as the first action that
1891 <tt>clean</tt> performs, so that running
1892 <tt>build</tt> again after an interrupted
1893 <tt>clean</tt> doesn't think that everything is
1898 The <tt>clean</tt> target may need to be
1899 invoked as root if <tt>binary</tt> has been
1900 invoked since the last <tt>clean</tt>, or if
1901 <tt>build</tt> has been invoked as root (since
1902 <tt>build</tt> may create directories, for
1907 <tag><tt>get-orig-source</tt> (optional)</tag>
1910 This target fetches the most recent version of the
1911 original source package from a canonical archive site
1912 (via FTP or WWW, for example), does any necessary
1913 rearrangement to turn it into the original source
1914 tar file format described below, and leaves it in the
1919 This target may be invoked in any directory, and
1920 should take care to clean up any temporary files it
1925 This target is optional, but providing it if
1926 possible is a good idea.
1932 The <tt>build</tt>, <tt>binary</tt> and
1933 <tt>clean</tt> targets must be invoked with the current
1934 directory being the package's top-level directory.
1939 Additional targets may exist in <file>debian/rules</file>,
1940 either as published or undocumented interfaces or for the
1941 package's internal use.
1945 The architectures we build on and build for are determined
1946 by <prgn>make</prgn> variables using the utility
1947 <qref id="pkg-dpkg-architecture"><prgn>dpkg-architecture</prgn></qref>.
1948 You can determine the
1949 Debian architecture and the GNU style architecture
1950 specification string for the build machine (the machine type
1951 we are building on) as well as for the host machine (the
1952 machine type we are building for). Here is a list of
1953 supported <prgn>make</prgn> variables:
1954 <list compact="compact">
1956 <tt>DEB_*_ARCH</tt> (the Debian architecture)
1959 <tt>DEB_*_GNU_TYPE</tt> (the GNU style architecture
1960 specification string)
1963 <tt>DEB_*_GNU_CPU</tt> (the CPU part of
1964 <tt>DEB_*_GNU_TYPE</tt>)
1967 <tt>DEB_*_GNU_SYSTEM</tt> (the System part of
1968 <tt>DEB_*_GNU_TYPE</tt>)
1970 where <tt>*</tt> is either <tt>BUILD</tt> for specification of
1971 the build machine or <tt>HOST</tt> for specification of the
1976 Backward compatibility can be provided in the rules file
1977 by setting the needed variables to suitable default
1978 values; please refer to the documentation of
1979 <prgn>dpkg-architecture</prgn> for details.
1983 It is important to understand that the <tt>DEB_*_ARCH</tt>
1984 string only determines which Debian architecture we are
1985 building on or for. It should not be used to get the CPU
1986 or system information; the GNU style variables should be
1991 <!-- FIXME: section pkg-srcsubstvars is the same as substvars -->
1992 <sect id="substvars">
1993 <heading>Variable substitutions: <file>debian/substvars</file></heading>
1996 When <prgn>dpkg-gencontrol</prgn>,
1997 <prgn>dpkg-genchanges</prgn> and <prgn>dpkg-source</prgn>
1998 generate control files they perform variable substitutions
1999 on their output just before writing it. Variable
2000 substitutions have the form <tt>${<var>variable</var>}</tt>.
2001 The optional file <file>debian/substvars</file> contains
2002 variable substitutions to be used; variables can also be set
2003 directly from <file>debian/rules</file> using the <tt>-V</tt>
2004 option to the source packaging commands, and certain
2005 predefined variables are also available.
2009 The <file>debian/substvars</file> file is usually generated and
2010 modified dynamically by <file>debian/rules</file> targets, in
2011 which case it must be removed by the <tt>clean</tt> target.
2015 See <manref name="dpkg-source" section="1"> for full
2016 details about source variable substitutions, including the
2017 format of <file>debian/substvars</file>.</p>
2020 <sect id="debianwatch">
2021 <heading>Optional upstream source location: <file>debian/watch</file></heading>
2024 This is an optional, recommended control file for the
2025 <tt>uscan</tt> utility which defines how to automatically
2026 scan ftp or http sites for newly available updates of the
2027 package. This is used by <url id="
2028 http://dehs.alioth.debian.org/"> and other Debian QA tools
2029 to help with quality control and maintenance of the
2030 distribution as a whole.
2035 <sect id="debianfiles">
2036 <heading>Generated files list: <file>debian/files</file></heading>
2039 This file is not a permanent part of the source tree; it
2040 is used while building packages to record which files are
2041 being generated. <prgn>dpkg-genchanges</prgn> uses it
2042 when it generates a <file>.changes</file> file.
2046 It should not exist in a shipped source package, and so it
2047 (and any backup files or temporary files such as
2048 <file>files.new</file><footnote>
2049 <file>files.new</file> is used as a temporary file by
2050 <prgn>dpkg-gencontrol</prgn> and
2051 <prgn>dpkg-distaddfile</prgn> - they write a new
2052 version of <tt>files</tt> here before renaming it,
2053 to avoid leaving a corrupted copy if an error
2055 </footnote>) should be removed by the
2056 <tt>clean</tt> target. It may also be wise to
2057 ensure a fresh start by emptying or removing it at the
2058 start of the <tt>binary</tt> target.
2062 When <prgn>dpkg-gencontrol</prgn> is run for a binary
2063 package, it adds an entry to <file>debian/files</file> for the
2064 <file>.deb</file> file that will be created when <tt>dpkg-deb
2065 --build</tt> is run for that binary package. So for most
2066 packages all that needs to be done with this file is to
2067 delete it in the <tt>clean</tt> target.
2071 If a package upload includes files besides the source
2072 package and any binary packages whose control files were
2073 made with <prgn>dpkg-gencontrol</prgn> then they should be
2074 placed in the parent of the package's top-level directory
2075 and <prgn>dpkg-distaddfile</prgn> should be called to add
2076 the file to the list in <file>debian/files</file>.</p>
2079 <sect id="embeddedfiles">
2080 <heading>Convenience copies of code</heading>
2083 Some software packages include in their distribution convenience
2084 copies of code from other software packages, generally so that
2085 users compiling from source don't have to download multiple
2086 packages. Debian packages should not make use of these
2087 convenience copies unless the included package is explicitly
2088 intended to be used in this way.<footnote>
2089 For example, parts of the GNU build system work like this.
2091 If the included code is already in the Debian archive in the
2092 form of a library, the Debian packaging should ensure that
2093 binary packages reference the libraries already in Debian and
2094 the convenience copy is not used. If the included code is not
2095 already in Debian, it should be packaged separately as a
2096 prerequisite if possible.
2098 Having multiple copies of the same code in Debian is
2099 inefficient, often creates either static linking or shared
2100 library conflicts, and, most importantly, increases the
2101 difficulty of handling security vulnerabilities in the
2110 <chapt id="controlfields">
2111 <heading>Control files and their fields</heading>
2114 The package management system manipulates data represented in
2115 a common format, known as <em>control data</em>, stored in
2116 <em>control files</em>.
2117 Control files are used for source packages, binary packages and
2118 the <file>.changes</file> files which control the installation
2119 of uploaded files<footnote>
2120 <prgn>dpkg</prgn>'s internal databases are in a similar
2125 <sect id="controlsyntax">
2126 <heading>Syntax of control files</heading>
2129 A control file consists of one or more paragraphs of
2131 The paragraphs are also sometimes referred to as stanzas.
2133 The paragraphs are separated by blank lines. Some control
2134 files allow only one paragraph; others allow several, in
2135 which case each paragraph usually refers to a different
2136 package. (For example, in source packages, the first
2137 paragraph refers to the source package, and later paragraphs
2138 refer to binary packages generated from the source.)
2142 Each paragraph consists of a series of data fields; each
2143 field consists of the field name, followed by a colon and
2144 then the data/value associated with that field. It ends at
2145 the end of the (logical) line. Horizontal whitespace
2146 (spaces and tabs) may occur immediately before or after the
2147 value and is ignored there; it is conventional to put a
2148 single space after the colon. For example, a field might
2150 <example compact="compact">
2153 the field name is <tt>Package</tt> and the field value
2158 Many fields' values may span several lines; in this case
2159 each continuation line must start with a space or a tab.
2160 Any trailing spaces or tabs at the end of individual
2161 lines of a field value are ignored.
2165 In fields where it is specified that lines may not wrap,
2166 only a single line of data is allowed and whitespace is not
2167 significant in a field body. Whitespace must not appear
2168 inside names (of packages, architectures, files or anything
2169 else) or version numbers, or between the characters of
2170 multi-character version relationships.
2174 Field names are not case-sensitive, but it is usual to
2175 capitalize the field names using mixed case as shown below.
2179 Blank lines, or lines consisting only of spaces and tabs,
2180 are not allowed within field values or between fields - that
2181 would mean a new paragraph.
2186 <sect id="sourcecontrolfiles">
2187 <heading>Source package control files -- <file>debian/control</file></heading>
2190 The <file>debian/control</file> file contains the most vital
2191 (and version-independent) information about the source package
2192 and about the binary packages it creates.
2196 The first paragraph of the control file contains information about
2197 the source package in general. The subsequent sets each describe a
2198 binary package that the source tree builds.
2202 The fields in the general paragraph (the first one, for the source
2205 <list compact="compact">
2206 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2207 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2208 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2209 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2210 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2211 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2212 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2213 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2218 The fields in the binary package paragraphs are:
2220 <list compact="compact">
2221 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2222 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2223 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2224 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2225 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2226 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2227 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2228 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2233 The syntax and semantics of the fields are described below.
2239 These fields are used by <prgn>dpkg-gencontrol</prgn> to
2240 generate control files for binary packages (see below), by
2241 <prgn>dpkg-genchanges</prgn> to generate the
2242 <tt>.changes</tt> file to accompany the upload, and by
2243 <prgn>dpkg-source</prgn> when it creates the
2244 <file>.dsc</file> source control file as part of a source
2245 archive. Many fields are permitted to span multiple lines in
2246 <file>debian/control</file> but not in any other control
2247 file. These tools are responsible for removing the line
2248 breaks from such fields when using fields from
2249 <file>debian/control</file> to generate other control files.
2253 The fields here may contain variable references - their
2254 values will be substituted by <prgn>dpkg-gencontrol</prgn>,
2255 <prgn>dpkg-genchanges</prgn> or <prgn>dpkg-source</prgn>
2256 when they generate output control files.
2257 See <ref id="substvars"> for details.
2262 <sect id="binarycontrolfiles">
2263 <heading>Binary package control files -- <file>DEBIAN/control</file></heading>
2266 The <file>DEBIAN/control</file> file contains the most vital
2267 (and version-dependent) information about a binary package.
2271 The fields in this file are:
2273 <list compact="compact">
2274 <item><qref id="f-Package"><tt>Package</tt></qref> (mandatory)</item>
2275 <item><qref id="f-Source"><tt>Source</tt></qref></item>
2276 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2277 <item><qref id="f-Section"><tt>Section</tt></qref> (recommended)</item>
2278 <item><qref id="f-Priority"><tt>Priority</tt></qref> (recommended)</item>
2279 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2280 <item><qref id="f-Essential"><tt>Essential</tt></qref></item>
2281 <item><qref id="binarydeps"><tt>Depends</tt> et al</qref></item>
2282 <item><qref id="f-Installed-Size"><tt>Installed-Size</tt></qref></item>
2283 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2284 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2285 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2290 <sect id="debiansourcecontrolfiles">
2291 <heading>Debian source control files -- <tt>.dsc</tt></heading>
2294 This file contains a series of fields, identified and
2295 separated just like the fields in the control file of
2296 a binary package. The fields are listed below; their
2297 syntax is described above, in <ref id="pkg-controlfields">.
2299 <list compact="compact">
2300 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2301 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2302 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2303 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2304 <item><qref id="f-Uploaders"><tt>Uploaders</tt></qref></item>
2305 <item><qref id="f-Binary"><tt>Binary</tt></qref></item>
2306 <item><qref id="f-Architecture"><tt>Architecture</tt></qref></item>
2307 <item><qref id="sourcebinarydeps"><tt>Build-Depends</tt> et al</qref></item>
2308 <item><qref id="f-Standards-Version"><tt>Standards-Version</tt></qref> (recommended)</item>
2309 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2310 <item><qref id="f-Homepage"><tt>Homepage</tt></qref></item>
2315 The source package control file is generated by
2316 <prgn>dpkg-source</prgn> when it builds the source
2317 archive, from other files in the source package,
2318 described above. When unpacking, it is checked against
2319 the files and directories in the other parts of the
2325 <sect id="debianchangesfiles">
2326 <heading>Debian changes files -- <file>.changes</file></heading>
2329 The .changes files are used by the Debian archive maintenance
2330 software to process updates to packages. They contain one
2331 paragraph which contains information from the
2332 <tt>debian/control</tt> file and other data about the
2333 source package gathered via <tt>debian/changelog</tt>
2334 and <tt>debian/rules</tt>.
2338 The fields in this file are:
2340 <list compact="compact">
2341 <item><qref id="f-Format"><tt>Format</tt></qref> (mandatory)</item>
2342 <item><qref id="f-Date"><tt>Date</tt></qref> (mandatory)</item>
2343 <item><qref id="f-Source"><tt>Source</tt></qref> (mandatory)</item>
2344 <item><qref id="f-Binary"><tt>Binary</tt></qref> (mandatory)</item>
2345 <item><qref id="f-Architecture"><tt>Architecture</tt></qref> (mandatory)</item>
2346 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
2347 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
2348 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (recommended)</item>
2349 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
2350 <item><qref id="f-Changed-By"><tt>Changed-By</tt></qref></item>
2351 <item><qref id="f-Description"><tt>Description</tt></qref> (mandatory)</item>
2352 <item><qref id="f-Closes"><tt>Closes</tt></qref></item>
2353 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
2354 <item><qref id="f-Files"><tt>Files</tt></qref> (mandatory)</item>
2359 <sect id="controlfieldslist">
2360 <heading>List of fields</heading>
2362 <sect1 id="f-Source">
2363 <heading><tt>Source</tt></heading>
2366 This field identifies the source package name.
2370 In <file>debian/control</file> or a <file>.dsc</file> file,
2371 this field must contain only the name of the source package.
2375 In a binary package control file or a <file>.changes</file>
2376 file, the source package name may be followed by a version
2377 number in parentheses<footnote>
2378 It is customary to leave a space after the package name
2379 if a version number is specified.
2381 This version number may be omitted (and is, by
2382 <prgn>dpkg-gencontrol</prgn>) if it has the same value as
2383 the <tt>Version</tt> field of the binary package in
2384 question. The field itself may be omitted from a binary
2385 package control file when the source package has the same
2386 name and version as the binary package.
2390 <sect1 id="f-Maintainer">
2391 <heading><tt>Maintainer</tt></heading>
2394 The package maintainer's name and email address. The name
2395 should come first, then the email address inside angle
2396 brackets <tt><></tt> (in RFC822 format).
2400 If the maintainer's name contains a full stop then the
2401 whole field will not work directly as an email address due
2402 to a misfeature in the syntax specified in RFC822; a
2403 program using this field as an address must check for this
2404 and correct the problem if necessary (for example by
2405 putting the name in round brackets and moving it to the
2406 end, and bringing the email address forward).
2410 <sect1 id="f-Uploaders">
2411 <heading><tt>Uploaders</tt></heading>
2414 List of the names and email addresses of co-maintainers of
2415 the package, if any. If the package has other maintainers
2416 beside the one named in the
2417 <qref id="f-Maintainer">Maintainer field</qref>, their
2418 names and email addresses should be listed here. The
2419 format is the same as that of the Maintainer tag, and
2420 multiple entries should be comma separated. Currently,
2421 this field is restricted to a single line of data. This
2422 is an optional field.
2425 Any parser that interprets the Uploaders field in
2426 <file>debian/control</file> must permit it to span multiple
2427 lines. Line breaks in an Uploaders field that spans multiple
2428 lines are not significant and the semantics of the field are
2429 the same as if the line breaks had not been present.
2433 <sect1 id="f-Changed-By">
2434 <heading><tt>Changed-By</tt></heading>
2437 The name and email address of the person who changed the
2438 said package. Usually the name of the maintainer.
2439 All the rules for the Maintainer field apply here, too.
2443 <sect1 id="f-Section">
2444 <heading><tt>Section</tt></heading>
2447 This field specifies an application area into which the package
2448 has been classified. See <ref id="subsections">.
2452 When it appears in the <file>debian/control</file> file,
2453 it gives the value for the subfield of the same name in
2454 the <tt>Files</tt> field of the <file>.changes</file> file.
2455 It also gives the default for the same field in the binary
2460 <sect1 id="f-Priority">
2461 <heading><tt>Priority</tt></heading>
2464 This field represents how important that it is that the user
2465 have the package installed. See <ref id="priorities">.
2469 When it appears in the <file>debian/control</file> file,
2470 it gives the value for the subfield of the same name in
2471 the <tt>Files</tt> field of the <file>.changes</file> file.
2472 It also gives the default for the same field in the binary
2477 <sect1 id="f-Package">
2478 <heading><tt>Package</tt></heading>
2481 The name of the binary package.
2485 Package names must consist only of lower case letters
2486 (<tt>a-z</tt>), digits (<tt>0-9</tt>), plus (<tt>+</tt>)
2487 and minus (<tt>-</tt>) signs, and periods (<tt>.</tt>).
2488 They must be at least two characters long and must start
2489 with an alphanumeric character.
2493 <sect1 id="f-Architecture">
2494 <heading><tt>Architecture</tt></heading>
2497 Depending on context and the control file used, the
2498 <tt>Architecture</tt> field can include the following sets of
2501 <item>A unique single word identifying a Debian machine
2502 architecture, see <ref id="arch-spec">.
2503 <item><tt>all</tt>, which indicates an
2504 architecture-independent package.
2505 <item><tt>any</tt>, which indicates a package available
2506 for building on any architecture.
2507 <item><tt>source</tt>, which indicates a source package.
2512 In the main <file>debian/control</file> file in the source
2513 package, or in the source package control file
2514 <file>.dsc</file>, one may specify a list of architectures
2515 separated by spaces, or the special values <tt>any</tt> or
2520 Specifying <tt>any</tt> indicates that the source package
2521 isn't dependent on any particular architecture and should
2522 compile fine on any one. The produced binary package(s)
2523 will be specific to whatever the current build architecture
2525 This is the most often used setting, and is recommended
2526 for new packages that aren't <tt>Architecture: all</tt>.
2531 Specifying a list of architectures indicates that the source
2532 will build an architecture-dependent package, and will only
2533 work correctly on the listed architectures.<footnote>
2534 This is a setting used for a minority of cases where the
2535 program is not portable. Generally, it should not be used
2541 In a <file>.changes</file> file, the <tt>Architecture</tt>
2542 field lists the architecture(s) of the package(s)
2543 currently being uploaded. This will be a list; if the
2544 source for the package is also being uploaded, the special
2545 entry <tt>source</tt> is also present.
2549 See <ref id="debianrules"> for information how to get the
2550 architecture for the build process.
2554 <sect1 id="f-Essential">
2555 <heading><tt>Essential</tt></heading>
2558 This is a boolean field which may occur only in the
2559 control file of a binary package or in a per-package fields
2560 paragraph of a main source control data file.
2564 If set to <tt>yes</tt> then the package management system
2565 will refuse to remove the package (upgrading and replacing
2566 it is still possible). The other possible value is <tt>no</tt>,
2567 which is the same as not having the field at all.
2572 <heading>Package interrelationship fields:
2573 <tt>Depends</tt>, <tt>Pre-Depends</tt>,
2574 <tt>Recommends</tt>, <tt>Suggests</tt>,
2575 <tt>Breaks</tt>, <tt>Conflicts</tt>,
2576 <tt>Provides</tt>, <tt>Replaces</tt>, <tt>Enhances</tt>
2580 These fields describe the package's relationships with
2581 other packages. Their syntax and semantics are described
2582 in <ref id="relationships">.</p>
2585 <sect1 id="f-Standards-Version">
2586 <heading><tt>Standards-Version</tt></heading>
2589 The most recent version of the standards (the policy
2590 manual and associated texts) with which the package
2595 The version number has four components: major and minor
2596 version number and major and minor patch level. When the
2597 standards change in a way that requires every package to
2598 change the major number will be changed. Significant
2599 changes that will require work in many packages will be
2600 signaled by a change to the minor number. The major patch
2601 level will be changed for any change to the meaning of the
2602 standards, however small; the minor patch level will be
2603 changed when only cosmetic, typographical or other edits
2604 are made which neither change the meaning of the document
2605 nor affect the contents of packages.
2609 Thus only the first three components of the policy version
2610 are significant in the <em>Standards-Version</em> control
2611 field, and so either these three components or the all
2612 four components may be specified.<footnote>
2613 In the past, people specified the full version number
2614 in the Standards-Version field, for example "2.3.0.0".
2615 Since minor patch-level changes don't introduce new
2616 policy, it was thought it would be better to relax
2617 policy and only require the first 3 components to be
2618 specified, in this example "2.3.0". All four
2619 components may still be used if someone wishes to do so.
2625 <sect1 id="f-Version">
2626 <heading><tt>Version</tt></heading>
2629 The version number of a package. The format is:
2630 [<var>epoch</var><tt>:</tt>]<var>upstream_version</var>[<tt>-</tt><var>debian_revision</var>]
2634 The three components here are:
2636 <tag><var>epoch</var></tag>
2639 This is a single (generally small) unsigned integer. It
2640 may be omitted, in which case zero is assumed. If it is
2641 omitted then the <var>upstream_version</var> may not
2646 It is provided to allow mistakes in the version numbers
2647 of older versions of a package, and also a package's
2648 previous version numbering schemes, to be left behind.
2652 <tag><var>upstream_version</var></tag>
2655 This is the main part of the version number. It is
2656 usually the version number of the original ("upstream")
2657 package from which the <file>.deb</file> file has been made,
2658 if this is applicable. Usually this will be in the same
2659 format as that specified by the upstream author(s);
2660 however, it may need to be reformatted to fit into the
2661 package management system's format and comparison
2666 The comparison behavior of the package management system
2667 with respect to the <var>upstream_version</var> is
2668 described below. The <var>upstream_version</var>
2669 portion of the version number is mandatory.
2673 The <var>upstream_version</var> may contain only
2674 alphanumerics<footnote>
2675 Alphanumerics are <tt>A-Za-z0-9</tt> only.
2677 and the characters <tt>.</tt> <tt>+</tt> <tt>-</tt>
2678 <tt>:</tt> <tt>~</tt> (full stop, plus, hyphen, colon,
2679 tilde) and should start with a digit. If there is no
2680 <var>debian_revision</var> then hyphens are not allowed;
2681 if there is no <var>epoch</var> then colons are not
2686 <tag><var>debian_revision</var></tag>
2689 This part of the version number specifies the version of
2690 the Debian package based on the upstream version. It
2691 may contain only alphanumerics and the characters
2692 <tt>+</tt> <tt>.</tt> <tt>~</tt> (plus, full stop,
2693 tilde) and is compared in the same way as the
2694 <var>upstream_version</var> is.
2698 It is optional; if it isn't present then the
2699 <var>upstream_version</var> may not contain a hyphen.
2700 This format represents the case where a piece of
2701 software was written specifically to be turned into a
2702 Debian package, and so there is only one "debianisation"
2703 of it and therefore no revision indication is required.
2707 It is conventional to restart the
2708 <var>debian_revision</var> at <tt>1</tt> each time the
2709 <var>upstream_version</var> is increased.
2713 The package management system will break the version
2714 number apart at the last hyphen in the string (if there
2715 is one) to determine the <var>upstream_version</var> and
2716 <var>debian_revision</var>. The absence of a
2717 <var>debian_revision</var> compares earlier than the
2718 presence of one (but note that the
2719 <var>debian_revision</var> is the least significant part
2720 of the version number).
2727 The <var>upstream_version</var> and <var>debian_revision</var>
2728 parts are compared by the package management system using the
2733 The strings are compared from left to right.
2737 First the initial part of each string consisting entirely of
2738 non-digit characters is determined. These two parts (one of
2739 which may be empty) are compared lexically. If a difference
2740 is found it is returned. The lexical comparison is a
2741 comparison of ASCII values modified so that all the letters
2742 sort earlier than all the non-letters and so that a tilde
2743 sorts before anything, even the end of a part. For example,
2744 the following parts are in sorted order from earliest to
2745 latest: <tt>~~</tt>, <tt>~~a</tt>, <tt>~</tt>, the empty part,
2746 <tt>a</tt>.<footnote>
2747 One common use of <tt>~</tt> is for upstream pre-releases.
2748 For example, <tt>1.0~beta1~svn1245</tt> sorts earlier than
2749 <tt>1.0~beta1</tt>, which sorts earlier than <tt>1.0</tt>.
2754 Then the initial part of the remainder of each string which
2755 consists entirely of digit characters is determined. The
2756 numerical values of these two parts are compared, and any
2757 difference found is returned as the result of the comparison.
2758 For these purposes an empty string (which can only occur at
2759 the end of one or both version strings being compared) counts
2764 These two steps (comparing and removing initial non-digit
2765 strings and initial digit strings) are repeated until a
2766 difference is found or both strings are exhausted.
2770 Note that the purpose of epochs is to allow us to leave behind
2771 mistakes in version numbering, and to cope with situations
2772 where the version numbering scheme changes. It is
2773 <em>not</em> intended to cope with version numbers containing
2774 strings of letters which the package management system cannot
2775 interpret (such as <tt>ALPHA</tt> or <tt>pre-</tt>), or with
2776 silly orderings (the author of this manual has heard of a
2777 package whose versions went <tt>1.1</tt>, <tt>1.2</tt>,
2778 <tt>1.3</tt>, <tt>1</tt>, <tt>2.1</tt>, <tt>2.2</tt>,
2779 <tt>2</tt> and so forth).
2783 <sect1 id="f-Description">
2784 <heading><tt>Description</tt></heading>
2787 In a source or binary control file, the <tt>Description</tt>
2788 field contains a description of the binary package, consisting
2789 of two parts, the synopsis or the short description, and the
2790 long description. The field's format is as follows:
2795 Description: <single line synopsis>
2796 <extended description over several lines>
2801 The lines in the extended description can have these formats:
2807 Those starting with a single space are part of a paragraph.
2808 Successive lines of this form will be word-wrapped when
2809 displayed. The leading space will usually be stripped off.
2813 Those starting with two or more spaces. These will be
2814 displayed verbatim. If the display cannot be panned
2815 horizontally, the displaying program will line wrap them "hard"
2816 (i.e., without taking account of word breaks). If it can they
2817 will be allowed to trail off to the right. None, one or two
2818 initial spaces may be deleted, but the number of spaces
2819 deleted from each line will be the same (so that you can have
2820 indenting work correctly, for example).
2824 Those containing a single space followed by a single full stop
2825 character. These are rendered as blank lines. This is the
2826 <em>only</em> way to get a blank line<footnote>
2827 Completely empty lines will not be rendered as blank lines.
2828 Instead, they will cause the parser to think you're starting
2829 a whole new record in the control file, and will therefore
2830 likely abort with an error.
2835 Those containing a space, a full stop and some more characters.
2836 These are for future expansion. Do not use them.
2842 Do not use tab characters. Their effect is not predictable.
2846 See <ref id="descriptions"> for further information on this.
2850 In a <file>.changes</file> file, the <tt>Description</tt> field
2851 contains a summary of the descriptions for the packages being
2856 The part of the field before the first newline is empty;
2857 thereafter each line has the name of a binary package and
2858 the summary description line from that binary package.
2859 Each line is indented by one space.
2864 <sect1 id="f-Distribution">
2865 <heading><tt>Distribution</tt></heading>
2868 In a <file>.changes</file> file or parsed changelog output
2869 this contains the (space-separated) name(s) of the
2870 distribution(s) where this version of the package should
2871 be installed. Valid distributions are determined by the
2872 archive maintainers.<footnote>
2873 Current distribution names are:
2874 <taglist compact="compact">
2875 <tag><em>stable</em></tag>
2877 This is the current "released" version of Debian
2878 GNU/Linux. Once the distribution is
2879 <em>stable</em> only security fixes and other
2880 major bug fixes are allowed. When changes are
2881 made to this distribution, the release number is
2882 increased (for example: 2.2r1 becomes 2.2r2 then
2886 <tag><em>unstable</em></tag>
2888 This distribution value refers to the
2889 <em>developmental</em> part of the Debian
2890 distribution tree. New packages, new upstream
2891 versions of packages and bug fixes go into the
2892 <em>unstable</em> directory tree. Download from
2893 this distribution at your own risk.
2896 <tag><em>testing</em></tag>
2898 This distribution value refers to the
2899 <em>testing</em> part of the Debian distribution
2900 tree. It receives its packages from the
2901 unstable distribution after a short time lag to
2902 ensure that there are no major issues with the
2903 unstable packages. It is less prone to breakage
2904 than unstable, but still risky. It is not
2905 possible to upload packages directly to
2909 <tag><em>frozen</em></tag>
2911 From time to time, the <em>testing</em>
2912 distribution enters a state of "code-freeze" in
2913 anticipation of release as a <em>stable</em>
2914 version. During this period of testing only
2915 fixes for existing or newly-discovered bugs will
2916 be allowed. The exact details of this stage are
2917 determined by the Release Manager.
2920 <tag><em>experimental</em></tag>
2922 The packages with this distribution value are
2923 deemed by their maintainers to be high
2924 risk. Oftentimes they represent early beta or
2925 developmental packages from various sources that
2926 the maintainers want people to try, but are not
2927 ready to be a part of the other parts of the
2928 Debian distribution tree. Download at your own
2934 You should list <em>all</em> distributions that the
2935 package should be installed into.
2939 More information is available in the Debian Developer's
2940 Reference, section "The Debian archive".
2947 <heading><tt>Date</tt></heading>
2950 This field includes the date the package was built or last edited.
2954 The value of this field is usually extracted from the
2955 <file>debian/changelog</file> file - see
2956 <ref id="dpkgchangelog">).
2960 <sect1 id="f-Format">
2961 <heading><tt>Format</tt></heading>
2964 This field specifies a format revision for the file.
2965 The most current format described in the Policy Manual
2966 is version <strong>1.5</strong>. The syntax of the
2967 format value is the same as that of a package version
2968 number except that no epoch or Debian revision is allowed
2969 - see <ref id="f-Version">.
2973 <sect1 id="f-Urgency">
2974 <heading><tt>Urgency</tt></heading>
2977 This is a description of how important it is to upgrade to
2978 this version from previous ones. It consists of a single
2979 keyword taking one of the values <tt>low</tt>,
2980 <tt>medium</tt>, <tt>high</tt>, <tt>emergency</tt>, or
2981 <tt>critical</tt><footnote>
2982 Other urgency values are supported with configuration
2983 changes in the archive software but are not used in Debian.
2984 The urgency affects how quickly a package will be considered
2985 for inclusion into the <tt>testing</tt> distribution and
2986 gives an indication of the importance of any fixes included
2987 in the upload. <tt>Emergency</tt> and <tt>critical</tt> are
2988 treated as synonymous.
2989 </footnote> (not case-sensitive) followed by an optional
2990 commentary (separated by a space) which is usually in
2991 parentheses. For example:
2994 Urgency: low (HIGH for users of diversions)
3000 The value of this field is usually extracted from the
3001 <file>debian/changelog</file> file - see
3002 <ref id="dpkgchangelog">.
3006 <sect1 id="f-Changes">
3007 <heading><tt>Changes</tt></heading>
3010 This field contains the human-readable changes data, describing
3011 the differences between the last version and the current one.
3015 There should be nothing in this field before the first
3016 newline; all the subsequent lines must be indented by at
3017 least one space; blank lines must be represented by a line
3018 consisting only of a space and a full stop.
3022 The value of this field is usually extracted from the
3023 <file>debian/changelog</file> file - see
3024 <ref id="dpkgchangelog">).
3028 Each version's change information should be preceded by a
3029 "title" line giving at least the version, distribution(s)
3030 and urgency, in a human-readable way.
3034 If data from several versions is being returned the entry
3035 for the most recent version should be returned first, and
3036 entries should be separated by the representation of a
3037 blank line (the "title" line may also be followed by the
3038 representation of blank line).
3042 <sect1 id="f-Binary">
3043 <heading><tt>Binary</tt></heading>
3046 This field is a list of binary packages.
3050 When it appears in the <file>.dsc</file> file it is the list
3051 of binary packages which a source package can produce. It
3052 does not necessarily produce all of these binary packages
3053 for every architecture. The source control file doesn't
3054 contain details of which architectures are appropriate for
3055 which of the binary packages.
3059 When it appears in a <file>.changes</file> file it lists the
3060 names of the binary packages actually being uploaded.
3064 The syntax is a list of binary packages separated by
3066 A space after each comma is conventional.
3067 </footnote>. Currently the packages must be separated using
3068 only spaces in the <file>.changes</file> file.
3072 <sect1 id="f-Installed-Size">
3073 <heading><tt>Installed-Size</tt></heading>
3076 This field appears in the control files of binary
3077 packages, and in the <file>Packages</file> files. It gives
3078 the total amount of disk space required to install the
3083 The disk space is represented in kilobytes as a simple
3088 <sect1 id="f-Files">
3089 <heading><tt>Files</tt></heading>
3092 This field contains a list of files with information about
3093 each one. The exact information and syntax varies with
3094 the context. In all cases the part of the field
3095 contents on the same line as the field name is empty. The
3096 remainder of the field is one line per file, each line
3097 being indented by one space and containing a number of
3098 sub-fields separated by spaces.
3102 In the <file>.dsc</file> file, each line contains the MD5
3103 checksum, size and filename of the tar file and (if applicable)
3104 diff file which make up the remainder of the source
3106 That is, the parts which are not the <tt>.dsc</tt>.
3108 The exact forms of the filenames are described
3109 in <ref id="pkg-sourcearchives">.
3113 In the <file>.changes</file> file this contains one line per
3114 file being uploaded. Each line contains the MD5 checksum,
3115 size, section and priority and the filename.
3116 The <qref id="f-Section">section</qref>
3117 and <qref id="f-Priority">priority</qref>
3118 are the values of the corresponding fields in
3119 the main source control file. If no section or priority is
3120 specified then <tt>-</tt> should be used, though section
3121 and priority values must be specified for new packages to
3122 be installed properly.
3126 The special value <tt>byhand</tt> for the section in a
3127 <tt>.changes</tt> file indicates that the file in question
3128 is not an ordinary package file and must by installed by
3129 hand by the distribution maintainers. If the section is
3130 <tt>byhand</tt> the priority should be <tt>-</tt>.
3134 If a new Debian revision of a package is being shipped and
3135 no new original source archive is being distributed the
3136 <tt>.dsc</tt> must still contain the <tt>Files</tt> field
3137 entry for the original source archive
3138 <file><var>package</var>-<var>upstream-version</var>.orig.tar.gz</file>,
3139 but the <file>.changes</file> file should leave it out. In
3140 this case the original source archive on the distribution
3141 site must match exactly, byte-for-byte, the original
3142 source archive which was used to generate the
3143 <file>.dsc</file> file and diff which are being uploaded.</p>
3146 <sect1 id="f-Closes">
3147 <heading><tt>Closes</tt></heading>
3150 A space-separated list of bug report numbers that the upload
3151 governed by the .changes file closes.
3155 <sect1 id="f-Homepage">
3156 <heading><tt>Homepage</tt></heading>
3159 The URL of the web site for this package, preferably (when
3160 applicable) the site from which the original source can be
3161 obtained and any additional upstream documentation or
3162 information may be found. The content of this field is a
3163 simple URL without any surrounding characters such as
3171 <heading>User-defined fields</heading>
3174 Additional user-defined fields may be added to the
3175 source package control file. Such fields will be
3176 ignored, and not copied to (for example) binary or
3177 source package control files or upload control files.
3181 If you wish to add additional unsupported fields to
3182 these output files you should use the mechanism
3187 Fields in the main source control information file with
3188 names starting <tt>X</tt>, followed by one or more of
3189 the letters <tt>BCS</tt> and a hyphen <tt>-</tt>, will
3190 be copied to the output files. Only the part of the
3191 field name after the hyphen will be used in the output
3192 file. Where the letter <tt>B</tt> is used the field
3193 will appear in binary package control files, where the
3194 letter <tt>S</tt> is used in source package control
3195 files and where <tt>C</tt> is used in upload control
3196 (<tt>.changes</tt>) files.
3200 For example, if the main source information control file
3203 XBS-Comment: I stand between the candle and the star.
3205 then the binary and source package control files will contain the
3208 Comment: I stand between the candle and the star.
3217 <chapt id="maintainerscripts">
3218 <heading>Package maintainer scripts and installation procedure</heading>
3221 <heading>Introduction to package maintainer scripts</heading>
3224 It is possible to supply scripts as part of a package which
3225 the package management system will run for you when your
3226 package is installed, upgraded or removed.
3230 These scripts are the files <prgn>preinst</prgn>,
3231 <prgn>postinst</prgn>, <prgn>prerm</prgn> and
3232 <prgn>postrm</prgn> in the control area of the package.
3233 They must be proper executable files; if they are scripts
3234 (which is recommended), they must start with the usual
3235 <tt>#!</tt> convention. They should be readable and
3236 executable by anyone, and must not be world-writable.
3240 The package management system looks at the exit status from
3241 these scripts. It is important that they exit with a
3242 non-zero status if there is an error, so that the package
3243 management system can stop its processing. For shell
3244 scripts this means that you <em>almost always</em> need to
3245 use <tt>set -e</tt> (this is usually true when writing shell
3246 scripts, in fact). It is also important, of course, that
3247 they don't exit with a non-zero status if everything went
3252 Additionally, packages interacting with users using
3253 <tt>debconf</tt> in the <prgn>postinst</prgn> script should
3254 install a <prgn>config</prgn> script in the control area,
3255 see <ref id="maintscriptprompt"> for details.
3259 When a package is upgraded a combination of the scripts from
3260 the old and new packages is called during the upgrade
3261 procedure. If your scripts are going to be at all
3262 complicated you need to be aware of this, and may need to
3263 check the arguments to your scripts.
3267 Broadly speaking the <prgn>preinst</prgn> is called before
3268 (a particular version of) a package is installed, and the
3269 <prgn>postinst</prgn> afterwards; the <prgn>prerm</prgn>
3270 before (a version of) a package is removed and the
3271 <prgn>postrm</prgn> afterwards.
3275 Programs called from maintainer scripts should not normally
3276 have a path prepended to them. Before installation is
3277 started, the package management system checks to see if the
3278 programs <prgn>ldconfig</prgn>,
3279 <prgn>start-stop-daemon</prgn>, <prgn>install-info</prgn>,
3280 and <prgn>update-rc.d</prgn> can be found via the
3281 <tt>PATH</tt> environment variable. Those programs, and any
3282 other program that one would expect to be in the
3283 <tt>PATH</tt>, should thus be invoked without an absolute
3284 pathname. Maintainer scripts should also not reset the
3285 <tt>PATH</tt>, though they might choose to modify it by
3286 prepending or appending package-specific directories. These
3287 considerations really apply to all shell scripts.</p>
3290 <sect id="idempotency">
3291 <heading>Maintainer scripts idempotency</heading>
3294 It is necessary for the error recovery procedures that the
3295 scripts be idempotent. This means that if it is run
3296 successfully, and then it is called again, it doesn't bomb
3297 out or cause any harm, but just ensures that everything is
3298 the way it ought to be. If the first call failed, or
3299 aborted half way through for some reason, the second call
3300 should merely do the things that were left undone the first
3301 time, if any, and exit with a success status if everything
3303 This is so that if an error occurs, the user interrupts
3304 <prgn>dpkg</prgn> or some other unforeseen circumstance
3305 happens you don't leave the user with a badly-broken
3306 package when <prgn>dpkg</prgn> attempts to repeat the
3312 <sect id="controllingterminal">
3313 <heading>Controlling terminal for maintainer scripts</heading>
3316 The maintainer scripts are guaranteed to run with a
3317 controlling terminal and can interact with the user.
3318 Because these scripts may be executed with standard output
3319 redirected into a pipe for logging purposes, Perl scripts
3320 should set unbuffered output by setting <tt>$|=1</tt> so
3321 that the output is printed immediately rather than being
3325 <sect id="exitstatus">
3326 <heading>Exit status</heading>
3329 Each script must return a zero exit status for
3330 success, or a nonzero one for failure, since the package
3331 management system looks for the exit status of these scripts
3332 and determines what action to take next based on that datum.
3336 <sect id="mscriptsinstact"><heading>Summary of ways maintainer
3341 <list compact="compact">
3343 <var>new-preinst</var> <tt>install</tt>
3346 <var>new-preinst</var> <tt>install</tt> <var>old-version</var>
3349 <var>new-preinst</var> <tt>upgrade</tt> <var>old-version</var>
3352 <var>old-preinst</var> <tt>abort-upgrade</tt>
3353 <var>new-version</var>
3358 <list compact="compact">
3360 <var>postinst</var> <tt>configure</tt>
3361 <var>most-recently-configured-version</var>
3364 <var>old-postinst</var> <tt>abort-upgrade</tt>
3365 <var>new-version</var>
3368 <var>conflictor's-postinst</var> <tt>abort-remove</tt>
3369 <tt>in-favour</tt> <var>package</var>
3370 <var>new-version</var>
3373 <var>postinst</var> <tt>abort-remove</tt>
3376 <var>deconfigured's-postinst</var>
3377 <tt>abort-deconfigure</tt> <tt>in-favour</tt>
3378 <var>failed-install-package</var> <var>version</var>
3379 [<tt>removing</tt> <var>conflicting-package</var>
3385 <list compact="compact">
3387 <var>prerm</var> <tt>remove</tt>
3390 <var>old-prerm</var> <tt>upgrade</tt>
3391 <var>new-version</var>
3394 <var>new-prerm</var> <tt>failed-upgrade</tt>
3395 <var>old-version</var>
3398 <var>conflictor's-prerm</var> <tt>remove</tt>
3399 <tt>in-favour</tt> <var>package</var>
3400 <var>new-version</var>
3403 <var>deconfigured's-prerm</var> <tt>deconfigure</tt>
3404 <tt>in-favour</tt> <var>package-being-installed</var>
3405 <var>version</var> [<tt>removing</tt>
3406 <var>conflicting-package</var>
3412 <list compact="compact">
3414 <var>postrm</var> <tt>remove</tt>
3417 <var>postrm</var> <tt>purge</tt>
3420 <var>old-postrm</var> <tt>upgrade</tt>
3421 <var>new-version</var>
3424 <var>new-postrm</var> <tt>failed-upgrade</tt>
3425 <var>old-version</var>
3428 <var>new-postrm</var> <tt>abort-install</tt>
3431 <var>new-postrm</var> <tt>abort-install</tt>
3432 <var>old-version</var>
3435 <var>new-postrm</var> <tt>abort-upgrade</tt>
3436 <var>old-version</var>
3439 <var>disappearer's-postrm</var> <tt>disappear</tt>
3440 <var>overwriter</var>
3441 <var>overwriter-version</var>
3447 <sect id="unpackphase">
3448 <heading>Details of unpack phase of installation or upgrade</heading>
3451 The procedure on installation/upgrade/overwrite/disappear
3452 (i.e., when running <tt>dpkg --unpack</tt>, or the unpack
3453 stage of <tt>dpkg --install</tt>) is as follows. In each
3454 case, if a major error occurs (unless listed below) the
3455 actions are, in general, run backwards - this means that the
3456 maintainer scripts are run with different arguments in
3457 reverse order. These are the "error unwind" calls listed
3464 If a version of the package is already installed, call
3465 <example compact="compact">
3466 <var>old-prerm</var> upgrade <var>new-version</var>
3470 If the script runs but exits with a non-zero
3471 exit status, <prgn>dpkg</prgn> will attempt:
3472 <example compact="compact">
3473 <var>new-prerm</var> failed-upgrade <var>old-version</var>
3475 If this works, the upgrade continues. If this
3476 does not work, the error unwind:
3477 <example compact="compact">
3478 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3480 If this works, then the old-version is
3481 "Installed", if not, the old version is in a
3482 "Failed-Config" state.
3488 If a "conflicting" package is being removed at the same time,
3489 or if any package will be broken (due to <tt>Breaks</tt>):
3492 If <tt>--auto-deconfigure</tt> is
3493 specified, call, for each package to be deconfigured
3494 due to <tt>Breaks</tt>:
3495 <example compact="compact">
3496 <var>deconfigured's-prerm</var> deconfigure \
3497 in-favour <var>package-being-installed</var> <var>version</var>
3500 <example compact="compact">
3501 <var>deconfigured's-postinst</var> abort-deconfigure \
3502 in-favour <var>package-being-installed-but-failed</var> <var>version</var>
3504 The deconfigured packages are marked as
3505 requiring configuration, so that if
3506 <tt>--install</tt> is used they will be
3507 configured again if possible.
3510 If any packages depended on a conflicting
3511 package being removed and <tt>--auto-deconfigure</tt> is
3512 specified, call, for each such package:
3513 <example compact="compact">
3514 <var>deconfigured's-prerm</var> deconfigure \
3515 in-favour <var>package-being-installed</var> <var>version</var> \
3516 removing <var>conflicting-package</var> <var>version</var>
3519 <example compact="compact">
3520 <var>deconfigured's-postinst</var> abort-deconfigure \
3521 in-favour <var>package-being-installed-but-failed</var> <var>version</var> \
3522 removing <var>conflicting-package</var> <var>version</var>
3524 The deconfigured packages are marked as
3525 requiring configuration, so that if
3526 <tt>--install</tt> is used they will be
3527 configured again if possible.
3530 To prepare for removal of each conflicting package, call:
3531 <example compact="compact">
3532 <var>conflictor's-prerm</var> remove \
3533 in-favour <var>package</var> <var>new-version</var>
3536 <example compact="compact">
3537 <var>conflictor's-postinst</var> abort-remove \
3538 in-favour <var>package</var> <var>new-version</var>
3547 If the package is being upgraded, call:
3548 <example compact="compact">
3549 <var>new-preinst</var> upgrade <var>old-version</var>
3551 If this fails, we call:
3553 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3560 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3562 is called. If this works, then the old version
3563 is in an "Installed" state, or else it is left
3564 in an "Unpacked" state.
3569 If it fails, then the old version is left
3570 in an "Half-Installed" state.
3577 Otherwise, if the package had some configuration
3578 files from a previous version installed (i.e., it
3579 is in the "configuration files only" state):
3580 <example compact="compact">
3581 <var>new-preinst</var> install <var>old-version</var>
3585 <var>new-postrm</var> abort-install <var>old-version</var>
3587 If this fails, the package is left in a
3588 "Half-Installed" state, which requires a
3589 reinstall. If it works, the packages is left in
3590 a "Config Files" state.
3593 Otherwise (i.e., the package was completely purged):
3594 <example compact="compact">
3595 <var>new-preinst</var> install
3598 <example compact="compact">
3599 <var>new-postrm</var> abort-install
3601 If the error-unwind fails, the package is in a
3602 "Half Installed" phase, and requires a
3603 reinstall. If the error unwind works, the
3604 package is in a not installed state.
3611 The new package's files are unpacked, overwriting any
3612 that may be on the system already, for example any
3613 from the old version of the same package or from
3614 another package. Backups of the old files are kept
3615 temporarily, and if anything goes wrong the package
3616 management system will attempt to put them back as
3617 part of the error unwind.
3621 It is an error for a package to contain files which
3622 are on the system in another package, unless
3623 <tt>Replaces</tt> is used (see <ref id="replaces">).
3625 The following paragraph is not currently the case:
3626 Currently the <tt>- - force-overwrite</tt> flag is
3627 enabled, downgrading it to a warning, but this may not
3633 It is a more serious error for a package to contain a
3634 plain file or other kind of non-directory where another
3635 package has a directory (again, unless
3636 <tt>Replaces</tt> is used). This error can be
3637 overridden if desired using
3638 <tt>--force-overwrite-dir</tt>, but this is not
3643 Packages which overwrite each other's files produce
3644 behavior which, though deterministic, is hard for the
3645 system administrator to understand. It can easily
3646 lead to "missing" programs if, for example, a package
3647 is installed which overwrites a file from another
3648 package, and is then removed again.<footnote>
3649 Part of the problem is due to what is arguably a
3650 bug in <prgn>dpkg</prgn>.
3655 A directory will never be replaced by a symbolic link
3656 to a directory or vice versa; instead, the existing
3657 state (symlink or not) will be left alone and
3658 <prgn>dpkg</prgn> will follow the symlink if there is
3667 If the package is being upgraded, call
3668 <example compact="compact">
3669 <var>old-postrm</var> upgrade <var>new-version</var>
3673 If this fails, <prgn>dpkg</prgn> will attempt:
3674 <example compact="compact">
3675 <var>new-postrm</var> failed-upgrade <var>old-version</var>
3677 If this works, installation continues. If not,
3679 <example compact="compact">
3680 <var>old-preinst</var> abort-upgrade <var>new-version</var>
3682 If this fails, the old version is left in an
3683 "Half Installed" state. If it works, dpkg now
3685 <example compact="compact">
3686 <var>new-postrm</var> abort-upgrade <var>old-version</var>
3688 If this fails, the old version is left in an
3689 "Half Installed" state. If it works, dpkg now
3691 <example compact="compact">
3692 <var>old-postinst</var> abort-upgrade <var>new-version</var>
3694 If this fails, the old version is in an
3701 This is the point of no return - if
3702 <prgn>dpkg</prgn> gets this far, it won't back off
3703 past this point if an error occurs. This will
3704 leave the package in a fairly bad state, which
3705 will require a successful re-installation to clear
3706 up, but it's when <prgn>dpkg</prgn> starts doing
3707 things that are irreversible.
3712 Any files which were in the old version of the package
3713 but not in the new are removed.
3717 The new file list replaces the old.
3721 The new maintainer scripts replace the old.
3725 Any packages all of whose files have been overwritten
3726 during the installation, and which aren't required for
3727 dependencies, are considered to have been removed.
3728 For each such package
3731 <prgn>dpkg</prgn> calls:
3732 <example compact="compact">
3733 <var>disappearer's-postrm</var> disappear \
3734 <var>overwriter</var> <var>overwriter-version</var>
3738 The package's maintainer scripts are removed.
3741 It is noted in the status database as being in a
3742 sane state, namely not installed (any conffiles
3743 it may have are ignored, rather than being
3744 removed by <prgn>dpkg</prgn>). Note that
3745 disappearing packages do not have their prerm
3746 called, because <prgn>dpkg</prgn> doesn't know
3747 in advance that the package is going to
3754 Any files in the package we're unpacking that are also
3755 listed in the file lists of other packages are removed
3756 from those lists. (This will lobotomize the file list
3757 of the "conflicting" package if there is one.)
3761 The backup files made during installation, above, are
3767 The new package's status is now sane, and recorded as
3772 Here is another point of no return - if the
3773 conflicting package's removal fails we do not unwind
3774 the rest of the installation; the conflicting package
3775 is left in a half-removed limbo.
3780 If there was a conflicting package we go and do the
3781 removal actions (described below), starting with the
3782 removal of the conflicting package's files (any that
3783 are also in the package being installed have already
3784 been removed from the conflicting package's file list,
3785 and so do not get removed now).
3791 <sect id="configdetails"><heading>Details of configuration</heading>
3794 When we configure a package (this happens with <tt>dpkg
3795 --install</tt> and <tt>dpkg --configure</tt>), we first
3796 update any <tt>conffile</tt>s and then call:
3797 <example compact="compact">
3798 <var>postinst</var> configure <var>most-recently-configured-version</var>
3803 No attempt is made to unwind after errors during
3804 configuration. If the configuration fails, the package is in
3805 a "Failed Config" state, and an error message is generated.
3809 If there is no most recently configured version
3810 <prgn>dpkg</prgn> will pass a null argument.
3813 Historical note: Truly ancient (pre-1997) versions of
3814 <prgn>dpkg</prgn> passed <tt><unknown></tt>
3815 (including the angle brackets) in this case. Even older
3816 ones did not pass a second argument at all, under any
3817 circumstance. Note that upgrades using such an old dpkg
3818 version are unlikely to work for other reasons, even if
3819 this old argument behavior is handled by your postinst script.
3825 <sect id="removedetails"><heading>Details of removal and/or
3826 configuration purging</heading>
3832 <example compact="compact">
3833 <var>prerm</var> remove
3837 If prerm fails during replacement due to conflict
3839 <var>conflictor's-postinst</var> abort-remove \
3840 in-favour <var>package</var> <var>new-version</var>
3844 <var>postinst</var> abort-remove
3848 If this fails, the package is in a "Failed-Config"
3849 state, or else it remains "Installed".
3853 The package's files are removed (except <tt>conffile</tt>s).
3856 <example compact="compact">
3857 <var>postrm</var> remove
3861 If it fails, there's no error unwind, and the package is in
3862 an "Half-Installed" state.
3867 All the maintainer scripts except the <prgn>postrm</prgn>
3872 If we aren't purging the package we stop here. Note
3873 that packages which have no <prgn>postrm</prgn> and no
3874 <tt>conffile</tt>s are automatically purged when
3875 removed, as there is no difference except for the
3876 <prgn>dpkg</prgn> status.
3880 The <tt>conffile</tt>s and any backup files
3881 (<tt>~</tt>-files, <tt>#*#</tt> files,
3882 <tt>%</tt>-files, <tt>.dpkg-{old,new,tmp}</tt>, etc.)
3887 <example compact="compact">
3888 <var>postrm</var> purge
3892 If this fails, the package remains in a "Config-Files"
3897 The package's file list is removed.
3906 <chapt id="relationships">
3907 <heading>Declaring relationships between packages</heading>
3909 <sect id="depsyntax">
3910 <heading>Syntax of relationship fields</heading>
3913 These fields all have a uniform syntax. They are a list of
3914 package names separated by commas.
3918 In the <tt>Depends</tt>, <tt>Recommends</tt>,
3919 <tt>Suggests</tt>, <tt>Pre-Depends</tt>,
3920 <tt>Build-Depends</tt> and <tt>Build-Depends-Indep</tt>
3921 control file fields of the package, which declare
3922 dependencies on other packages, the package names listed may
3923 also include lists of alternative package names, separated
3924 by vertical bar (pipe) symbols <tt>|</tt>. In such a case,
3925 if any one of the alternative packages is installed, that
3926 part of the dependency is considered to be satisfied.
3930 All of the fields except for <tt>Provides</tt> may restrict
3931 their applicability to particular versions of each named
3932 package. This is done in parentheses after each individual
3933 package name; the parentheses should contain a relation from
3934 the list below followed by a version number, in the format
3935 described in <ref id="f-Version">.
3939 The relations allowed are <tt><<</tt>, <tt><=</tt>,
3940 <tt>=</tt>, <tt>>=</tt> and <tt>>></tt> for
3941 strictly earlier, earlier or equal, exactly equal, later or
3942 equal and strictly later, respectively. The deprecated
3943 forms <tt><</tt> and <tt>></tt> were used to mean
3944 earlier/later or equal, rather than strictly earlier/later,
3945 so they should not appear in new packages (though
3946 <prgn>dpkg</prgn> still supports them).
3950 Whitespace may appear at any point in the version
3951 specification subject to the rules in <ref
3952 id="controlsyntax">, and must appear where it's necessary to
3953 disambiguate; it is not otherwise significant. All of the
3954 relationship fields may span multiple lines. For
3955 consistency and in case of future changes to
3956 <prgn>dpkg</prgn> it is recommended that a single space be
3957 used after a version relationship and before a version
3958 number; it is also conventional to put a single space after
3959 each comma, on either side of each vertical bar, and before
3960 each open parenthesis. When wrapping a relationship field, it
3961 is conventional to do so after a comma and before the space
3962 following that comma.
3966 For example, a list of dependencies might appear as:
3967 <example compact="compact">
3970 Depends: libc6 (>= 2.2.1), exim | mail-transport-agent
3975 All fields that specify build-time relationships
3976 (<tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
3977 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>)
3978 may be restricted to a certain set of architectures. This
3979 is indicated in brackets after each individual package name and
3980 the optional version specification. The brackets enclose a
3981 list of Debian architecture names separated by whitespace.
3982 Exclamation marks may be prepended to each of the names.
3983 (It is not permitted for some names to be prepended with
3984 exclamation marks while others aren't.) If the current Debian
3985 host architecture is not in this list and there are no
3986 exclamation marks in the list, or it is in the list with a
3987 prepended exclamation mark, the package name and the
3988 associated version specification are ignored completely for
3989 the purposes of defining the relationships.
3994 <example compact="compact">
3996 Build-Depends-Indep: texinfo
3997 Build-Depends: kernel-headers-2.2.10 [!hurd-i386],
3998 hurd-dev [hurd-i386], gnumach-dev [hurd-i386]
4003 Note that the binary package relationship fields such as
4004 <tt>Depends</tt> appear in one of the binary package
4005 sections of the control file, whereas the build-time
4006 relationships such as <tt>Build-Depends</tt> appear in the
4007 source package section of the control file (which is the
4012 <sect id="binarydeps">
4013 <heading>Binary Dependencies - <tt>Depends</tt>,
4014 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4015 <tt>Pre-Depends</tt>
4019 Packages can declare in their control file that they have
4020 certain relationships to other packages - for example, that
4021 they may not be installed at the same time as certain other
4022 packages, and/or that they depend on the presence of others.
4026 This is done using the <tt>Depends</tt>, <tt>Pre-Depends</tt>,
4027 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4028 <tt>Breaks</tt> and <tt>Conflicts</tt> control file fields.
4032 These seven fields are used to declare a dependency
4033 relationship by one package on another. Except for
4034 <tt>Enhances</tt> and <tt>Breaks</tt>, they appear in the
4035 depending (binary) package's control file.
4036 (<tt>Enhances</tt> appears in the recommending package's
4037 control file, and <tt>Breaks</tt> appears in the version of
4038 depended-on package which causes the named package to
4043 A <tt>Depends</tt> field takes effect <em>only</em> when a
4044 package is to be configured. It does not prevent a package
4045 being on the system in an unconfigured state while its
4046 dependencies are unsatisfied, and it is possible to replace
4047 a package whose dependencies are satisfied and which is
4048 properly installed with a different version whose
4049 dependencies are not and cannot be satisfied; when this is
4050 done the depending package will be left unconfigured (since
4051 attempts to configure it will give errors) and will not
4052 function properly. If it is necessary, a
4053 <tt>Pre-Depends</tt> field can be used, which has a partial
4054 effect even when a package is being unpacked, as explained
4055 in detail below. (The other three dependency fields,
4056 <tt>Recommends</tt>, <tt>Suggests</tt> and
4057 <tt>Enhances</tt>, are only used by the various front-ends
4058 to <prgn>dpkg</prgn> such as <prgn>apt-get</prgn>,
4059 <prgn>aptitude</prgn>, and <prgn>dselect</prgn>.)
4063 For this reason packages in an installation run are usually
4064 all unpacked first and all configured later; this gives
4065 later versions of packages with dependencies on later
4066 versions of other packages the opportunity to have their
4067 dependencies satisfied.
4071 In case of circular dependencies, since installation or
4072 removal order honoring the dependency order can't be
4073 established, dependency loops are broken at some point
4074 (based on rules below), and some packages may not be able to
4075 rely on their dependencies being present when being
4076 installed or removed, depending on which side of the break
4077 of the circular dependency loop they happen to be on. If one
4078 of the packages in the loop has no postinst script, then the
4079 cycle will be broken at that package, so as to ensure that
4080 all postinst scripts run with the dependencies properly
4081 configured if this is possible. Otherwise the breaking point
4086 The <tt>Depends</tt> field thus allows package maintainers
4087 to impose an order in which packages should be configured.
4091 The meaning of the five dependency fields is as follows:
4093 <tag><tt>Depends</tt></tag>
4096 This declares an absolute dependency. A package will
4097 not be configured unless all of the packages listed in
4098 its <tt>Depends</tt> field have been correctly
4103 The <tt>Depends</tt> field should be used if the
4104 depended-on package is required for the depending
4105 package to provide a significant amount of
4110 The <tt>Depends</tt> field should also be used if the
4111 <prgn>postinst</prgn>, <prgn>prerm</prgn> or
4112 <prgn>postrm</prgn> scripts require the package to be
4113 present in order to run. Note, however, that the
4114 <prgn>postrm</prgn> cannot rely on any non-essential
4115 packages to be present during the <tt>purge</tt>
4119 <tag><tt>Recommends</tt></tag>
4122 This declares a strong, but not absolute, dependency.
4126 The <tt>Recommends</tt> field should list packages
4127 that would be found together with this one in all but
4128 unusual installations.
4132 <tag><tt>Suggests</tt></tag>
4134 This is used to declare that one package may be more
4135 useful with one or more others. Using this field
4136 tells the packaging system and the user that the
4137 listed packages are related to this one and can
4138 perhaps enhance its usefulness, but that installing
4139 this one without them is perfectly reasonable.
4142 <tag><tt>Enhances</tt></tag>
4144 This field is similar to Suggests but works in the
4145 opposite direction. It is used to declare that a
4146 package can enhance the functionality of another
4150 <tag><tt>Pre-Depends</tt></tag>
4153 This field is like <tt>Depends</tt>, except that it
4154 also forces <prgn>dpkg</prgn> to complete installation
4155 of the packages named before even starting the
4156 installation of the package which declares the
4157 pre-dependency, as follows:
4161 When a package declaring a pre-dependency is about to
4162 be <em>unpacked</em> the pre-dependency can be
4163 satisfied if the depended-on package is either fully
4164 configured, <em>or even if</em> the depended-on
4165 package(s) are only unpacked or half-configured,
4166 provided that they have been configured correctly at
4167 some point in the past (and not removed or partially
4168 removed since). In this case, both the
4169 previously-configured and currently unpacked or
4170 half-configured versions must satisfy any version
4171 clause in the <tt>Pre-Depends</tt> field.
4175 When the package declaring a pre-dependency is about
4176 to be <em>configured</em>, the pre-dependency will be
4177 treated as a normal <tt>Depends</tt>, that is, it will
4178 be considered satisfied only if the depended-on
4179 package has been correctly configured.
4183 <tt>Pre-Depends</tt> should be used sparingly,
4184 preferably only by packages whose premature upgrade or
4185 installation would hamper the ability of the system to
4186 continue with any upgrade that might be in progress.
4190 <tt>Pre-Depends</tt> are also required if the
4191 <prgn>preinst</prgn> script depends on the named
4192 package. It is best to avoid this situation if
4200 When selecting which level of dependency to use you should
4201 consider how important the depended-on package is to the
4202 functionality of the one declaring the dependency. Some
4203 packages are composed of components of varying degrees of
4204 importance. Such a package should list using
4205 <tt>Depends</tt> the package(s) which are required by the
4206 more important components. The other components'
4207 requirements may be mentioned as Suggestions or
4208 Recommendations, as appropriate to the components' relative
4214 <heading>Packages which break other packages - <tt>Breaks</tt></heading>
4217 Using <tt>Breaks</tt> may cause problems for upgrades from older
4218 versions of Debian and should not be used until the stable
4219 release of Debian supports <tt>Breaks</tt>.
4223 When one binary package declares that it breaks another,
4224 <prgn>dpkg</prgn> will refuse to allow the package which
4225 declares <tt>Breaks</tt> be installed unless the broken
4226 package is deconfigured first, and it will refuse to
4227 allow the broken package to be reconfigured.
4231 A package will not be regarded as causing breakage merely
4232 because its configuration files are still installed; it must
4233 be at least half-installed.
4237 A special exception is made for packages which declare that
4238 they break their own package name or a virtual package which
4239 they provide (see below): this does not count as a real
4244 Normally a <tt>Breaks</tt> entry will have an "earlier than"
4245 version clause; such a <tt>Breaks</tt> is introduced in the
4246 version of an (implicit or explicit) dependency which
4247 violates an assumption or reveals a bug in earlier versions
4248 of the broken package. This use of <tt>Breaks</tt> will
4249 inform higher-level package management tools that broken
4250 package must be upgraded before the new one.
4254 If the breaking package also overwrites some files from the
4255 older package, it should use <tt>Replaces</tt> (not
4256 <tt>Conflicts</tt>) to ensure this goes smoothly.
4260 <sect id="conflicts">
4261 <heading>Conflicting binary packages - <tt>Conflicts</tt></heading>
4264 When one binary package declares a conflict with another
4265 using a <tt>Conflicts</tt> field, <prgn>dpkg</prgn> will
4266 refuse to allow them to be installed on the system at the
4271 If one package is to be installed, the other must be removed
4272 first - if the package being installed is marked as
4273 replacing (see <ref id="replaces">) the one on the system,
4274 or the one on the system is marked as deselected, or both
4275 packages are marked <tt>Essential</tt>, then
4276 <prgn>dpkg</prgn> will automatically remove the package
4277 which is causing the conflict, otherwise it will halt the
4278 installation of the new package with an error. This
4279 mechanism is specifically designed to produce an error when
4280 the installed package is <tt>Essential</tt>, but the new
4285 A package will not cause a conflict merely because its
4286 configuration files are still installed; it must be at least
4291 A special exception is made for packages which declare a
4292 conflict with their own package name, or with a virtual
4293 package which they provide (see below): this does not
4294 prevent their installation, and allows a package to conflict
4295 with others providing a replacement for it. You use this
4296 feature when you want the package in question to be the only
4297 package providing some feature.
4301 A <tt>Conflicts</tt> entry should almost never have an
4302 "earlier than" version clause. This would prevent
4303 <prgn>dpkg</prgn> from upgrading or installing the package
4304 which declared such a conflict until the upgrade or removal
4305 of the conflicted-with package had been completed. Instead,
4306 <tt>Breaks</tt> may be used (once <tt>Breaks</tt> is supported
4307 by the stable release of Debian).
4311 <sect id="virtual"><heading>Virtual packages - <tt>Provides</tt>
4315 As well as the names of actual ("concrete") packages, the
4316 package relationship fields <tt>Depends</tt>,
4317 <tt>Recommends</tt>, <tt>Suggests</tt>, <tt>Enhances</tt>,
4318 <tt>Pre-Depends</tt>, <tt>Breaks</tt>, <tt>Conflicts</tt>,
4319 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4320 <tt>Build-Conflicts</tt> and <tt>Build-Conflicts-Indep</tt>
4321 may mention "virtual packages".
4325 A <em>virtual package</em> is one which appears in the
4326 <tt>Provides</tt> control file field of another package.
4327 The effect is as if the package(s) which provide a
4328 particular virtual package name had been listed by name
4329 everywhere the virtual package name appears. (See also <ref
4334 If there are both concrete and virtual packages of the same
4335 name, then the dependency may be satisfied (or the conflict
4336 caused) by either the concrete package with the name in
4337 question or any other concrete package which provides the
4338 virtual package with the name in question. This is so that,
4339 for example, supposing we have
4340 <example compact="compact">
4343 </example> and someone else releases an enhanced version of
4344 the <tt>bar</tt> package they can say:
4345 <example compact="compact">
4349 and the <tt>bar-plus</tt> package will now also satisfy the
4350 dependency for the <tt>foo</tt> package.
4354 If a relationship field has a version number attached
4355 then only real packages will be considered to see whether
4356 the relationship is satisfied (or the prohibition violated,
4357 for a conflict or breakage) - it is assumed that a real
4358 package which provides the virtual package is not of the
4359 "right" version. So, a <tt>Provides</tt> field may not
4360 contain version numbers, and the version number of the
4361 concrete package which provides a particular virtual package
4362 will not be looked at when considering a dependency on or
4363 conflict with the virtual package name.
4367 It is likely that the ability will be added in a future
4368 release of <prgn>dpkg</prgn> to specify a version number for
4369 each virtual package it provides. This feature is not yet
4370 present, however, and is expected to be used only
4375 If you want to specify which of a set of real packages
4376 should be the default to satisfy a particular dependency on
4377 a virtual package, you should list the real package as an
4378 alternative before the virtual one.
4383 <sect id="replaces"><heading>Overwriting files and replacing
4384 packages - <tt>Replaces</tt></heading>
4387 Packages can declare in their control file that they should
4388 overwrite files in certain other packages, or completely
4389 replace other packages. The <tt>Replaces</tt> control file
4390 field has these two distinct purposes.
4393 <sect1><heading>Overwriting files in other packages</heading>
4396 Firstly, as mentioned before, it is usually an error for a
4397 package to contain files which are on the system in
4402 However, if the overwriting package declares that it
4403 <tt>Replaces</tt> the one containing the file being
4404 overwritten, then <prgn>dpkg</prgn> will replace the file
4405 from the old package with that from the new. The file
4406 will no longer be listed as "owned" by the old package.
4410 If a package is completely replaced in this way, so that
4411 <prgn>dpkg</prgn> does not know of any files it still
4412 contains, it is considered to have "disappeared". It will
4413 be marked as not wanted on the system (selected for
4414 removal) and not installed. Any <tt>conffile</tt>s
4415 details noted for the package will be ignored, as they
4416 will have been taken over by the overwriting package. The
4417 package's <prgn>postrm</prgn> script will be run with a
4418 special argument to allow the package to do any final
4419 cleanup required. See <ref id="mscriptsinstact">.
4422 Replaces is a one way relationship -- you have to
4423 install the replacing package after the replaced
4430 For this usage of <tt>Replaces</tt>, virtual packages (see
4431 <ref id="virtual">) are not considered when looking at a
4432 <tt>Replaces</tt> field - the packages declared as being
4433 replaced must be mentioned by their real names.
4437 Furthermore, this usage of <tt>Replaces</tt> only takes
4438 effect when both packages are at least partially on the
4439 system at once, so that it can only happen if they do not
4440 conflict or if the conflict has been overridden.
4445 <sect1><heading>Replacing whole packages, forcing their
4449 Secondly, <tt>Replaces</tt> allows the packaging system to
4450 resolve which package should be removed when there is a
4451 conflict - see <ref id="conflicts">. This usage only
4452 takes effect when the two packages <em>do</em> conflict,
4453 so that the two usages of this field do not interfere with
4458 In this situation, the package declared as being replaced
4459 can be a virtual package, so for example, all mail
4460 transport agents (MTAs) would have the following fields in
4461 their control files:
4462 <example compact="compact">
4463 Provides: mail-transport-agent
4464 Conflicts: mail-transport-agent
4465 Replaces: mail-transport-agent
4467 ensuring that only one MTA can be installed at any one
4472 <sect id="sourcebinarydeps">
4473 <heading>Relationships between source and binary packages -
4474 <tt>Build-Depends</tt>, <tt>Build-Depends-Indep</tt>,
4475 <tt>Build-Conflicts</tt>, <tt>Build-Conflicts-Indep</tt>
4479 Source packages that require certain binary packages to be
4480 installed or absent at the time of building the package
4481 can declare relationships to those binary packages.
4485 This is done using the <tt>Build-Depends</tt>,
4486 <tt>Build-Depends-Indep</tt>, <tt>Build-Conflicts</tt> and
4487 <tt>Build-Conflicts-Indep</tt> control file fields.
4491 Build-dependencies on "build-essential" binary packages can be
4492 omitted. Please see <ref id="pkg-relations"> for more information.
4496 The dependencies and conflicts they define must be satisfied
4497 (as defined earlier for binary packages) in order to invoke
4498 the targets in <tt>debian/rules</tt>, as follows:<footnote>
4500 If you make "build-arch" or "binary-arch", you need
4501 Build-Depends. If you make "build-indep" or
4502 "binary-indep", you need Build-Depends and
4503 Build-Depends-Indep. If you make "build" or "binary",
4507 There is no Build-Depends-Arch; this role is essentially
4508 met with Build-Depends. Anyone building the
4509 <tt>build-indep</tt> and binary-indep<tt></tt> targets
4510 is basically assumed to be building the whole package
4511 anyway and so installs all build dependencies. The
4512 autobuilders use <tt>dpkg-buildpackage -B</tt>, which
4513 calls <tt>build</tt> (not <tt>build-arch</tt>, since it
4514 does not yet know how to check for its existence) and
4515 <tt>binary-arch</tt>.
4518 The purpose of the original split, I recall, was so that
4519 the autobuilders wouldn't need to install extra packages
4520 needed only for the binary-indep targets. But without a
4521 build-arch/build-indep split, this didn't work, since
4522 most of the work is done in the build target, not in the
4528 <tag><tt>Build-Depends</tt>, <tt>Build-Conflicts</tt></tag>
4530 The <tt>Build-Depends</tt> and
4531 <tt>Build-Conflicts</tt> fields must be satisfied when
4532 any of the following targets is invoked:
4533 <tt>build</tt>, <tt>clean</tt>, <tt>binary</tt>,
4534 <tt>binary-arch</tt>, <tt>build-arch</tt>,
4535 <tt>build-indep</tt> and <tt>binary-indep</tt>.
4537 <tag><tt>Build-Depends-Indep</tt>,
4538 <tt>Build-Conflicts-Indep</tt></tag>
4540 The <tt>Build-Depends-Indep</tt> and
4541 <tt>Build-Conflicts-Indep</tt> fields must be
4542 satisfied when any of the following targets is
4543 invoked: <tt>build</tt>, <tt>build-indep</tt>,
4544 <tt>binary</tt> and <tt>binary-indep</tt>.
4554 <chapt id="sharedlibs"><heading>Shared libraries</heading>
4557 Packages containing shared libraries must be constructed with
4558 a little care to make sure that the shared library is always
4559 available. This is especially important for packages whose
4560 shared libraries are vitally important, such as the C library
4561 (currently <tt>libc6</tt>).
4565 Packages involving shared libraries should be split up into
4566 several binary packages. This section mostly deals with how
4567 this separation is to be accomplished; rules for files within
4568 the shared library packages are in <ref id="libraries"> instead.
4571 <sect id="sharedlibs-runtime">
4572 <heading>Run-time shared libraries</heading>
4575 The run-time shared library needs to be placed in a package
4576 whose name changes whenever the shared object version
4579 Since it is common place to install several versions of a
4580 package that just provides shared libraries, it is a
4581 good idea that the library package should not
4582 contain any extraneous non-versioned files, unless they
4583 happen to be in versioned directories.</p>
4585 The most common mechanism is to place it in a package
4587 <package><var>libraryname</var><var>soversion</var></package>,
4588 where <file><var>soversion</var></file> is the version number
4589 in the soname of the shared library<footnote>
4590 The soname is the shared object name: it's the thing
4591 that has to match exactly between building an executable
4592 and running it for the dynamic linker to be able run the
4593 program. For example, if the soname of the library is
4594 <file>libfoo.so.6</file>, the library package would be
4595 called <file>libfoo6</file>.
4597 Alternatively, if it would be confusing to directly append
4598 <var>soversion</var> to <var>libraryname</var> (e.g. because
4599 <var>libraryname</var> itself ends in a number), you may use
4600 <package><var>libraryname</var>-<var>soversion</var></package> and
4601 <package><var>libraryname</var>-<var>soversion</var>-dev</package>
4606 If your package includes run-time support programs that
4607 do not need to be invoked manually by users, but are
4608 nevertheless required for the package to function, then it
4609 is recommended that these programs are placed
4610 (if they are binary) in a subdirectory of
4611 <file>/usr/lib</file>, preferably under
4612 <file>/usr/lib/</file><var>package-name</var>.
4613 If the program is architecture independent, the
4614 recommendation is for it to be placed in a subdirectory of
4615 <file>/usr/share</file> instead, preferably under
4616 <file>/usr/share/</file><var>package-name</var>.
4621 If you have several shared libraries built from the same
4622 source tree you may lump them all together into a single
4623 shared library package, provided that you change all of
4624 their sonames at once (so that you don't get filename
4625 clashes if you try to install different versions of the
4626 combined shared libraries package).
4630 The package should install the shared libraries under
4631 their normal names. For example, the <package>libgdbm3</package>
4632 package should install <file>libgdbm.so.3.0.0</file> as
4633 <file>/usr/lib/libgdbm.so.3.0.0</file>. The files should not be
4634 renamed or re-linked by any <prgn>prerm</prgn> or
4635 <prgn>postrm</prgn> scripts; <prgn>dpkg</prgn> will take care
4636 of renaming things safely without affecting running programs,
4637 and attempts to interfere with this are likely to lead to
4642 Shared libraries should not be installed executable, since
4643 the dynamic linker does not require this and trying to
4644 execute a shared library usually results in a core dump.
4648 The run-time library package should include the symbolic link that
4649 <prgn>ldconfig</prgn> would create for the shared libraries.
4650 For example, the <package>libgdbm3</package> package should include
4651 a symbolic link from <file>/usr/lib/libgdbm.so.3</file> to
4652 <file>libgdbm.so.3.0.0</file>. This is needed so that the dynamic
4653 linker (for example <prgn>ld.so</prgn> or
4654 <prgn>ld-linux.so.*</prgn>) can find the library between the
4655 time that <prgn>dpkg</prgn> installs it and the time that
4656 <prgn>ldconfig</prgn> is run in the <prgn>postinst</prgn>
4658 The package management system requires the library to be
4659 placed before the symbolic link pointing to it in the
4660 <file>.deb</file> file. This is so that when
4661 <prgn>dpkg</prgn> comes to install the symlink
4662 (overwriting the previous symlink pointing at an older
4663 version of the library), the new shared library is already
4664 in place. In the past, this was achieved by creating the
4665 library in the temporary packaging directory before
4666 creating the symlink. Unfortunately, this was not always
4667 effective, since the building of the tar file in the
4668 <file>.deb</file> depended on the behavior of the underlying
4669 file system. Some file systems (such as reiserfs) reorder
4670 the files so that the order of creation is forgotten.
4671 Since version 1.7.0, <prgn>dpkg</prgn>
4672 reorders the files itself as necessary when building a
4673 package. Thus it is no longer important to concern
4674 oneself with the order of file creation.
4678 <sect1 id="ldconfig">
4679 <heading><tt>ldconfig</tt></heading>
4682 Any package installing shared libraries in one of the default
4683 library directories of the dynamic linker (which are currently
4684 <file>/usr/lib</file> and <file>/lib</file>) or a directory that is
4685 listed in <file>/etc/ld.so.conf</file><footnote>
4687 <list compact="compact">
4688 <item>/usr/local/lib</item>
4689 <item>/usr/lib/libc5-compat</item>
4690 <item>/lib/libc5-compat</item>
4693 must use <prgn>ldconfig</prgn> to update the shared library
4698 The package maintainer scripts must only call
4699 <prgn>ldconfig</prgn> under these circumstances:
4700 <list compact="compact">
4701 <item>When the <prgn>postinst</prgn> script is run with a
4702 first argument of <tt>configure</tt>, the script must call
4703 <prgn>ldconfig</prgn>, and may optionally invoke
4704 <prgn>ldconfig</prgn> at other times.
4706 <item>When the <prgn>postrm</prgn> script is run with a
4707 first argument of <tt>remove</tt>, the script should call
4708 <prgn>ldconfig</prgn>.
4713 During install or upgrade, the preinst is called before
4714 the new files are installed, so calling "ldconfig" is
4715 pointless. The preinst of an existing package can also be
4716 called if an upgrade fails. However, this happens during
4717 the critical time when a shared libs may exist on-disk
4718 under a temporary name. Thus, it is dangerous and
4719 forbidden by current policy to call "ldconfig" at this
4724 When a package is installed or upgraded, "postinst
4725 configure" runs after the new files are safely on-disk.
4726 Since it is perfectly safe to invoke ldconfig
4727 unconditionally in a postinst, it is OK for a package to
4728 simply put ldconfig in its postinst without checking the
4729 argument. The postinst can also be called to recover from
4730 a failed upgrade. This happens before any new files are
4731 unpacked, so there is no reason to call "ldconfig" at this
4736 For a package that is being removed, prerm is
4737 called with all the files intact, so calling ldconfig is
4738 useless. The other calls to "prerm" happen in the case of
4739 upgrade at a time when all the files of the old package
4740 are on-disk, so again calling "ldconfig" is pointless.
4744 postrm, on the other hand, is called with the "remove"
4745 argument just after the files are removed, so this is
4746 the proper time to call "ldconfig" to notify the system
4747 of the fact that the shared libraries from the package
4748 are removed. The postrm can be called at several other
4749 times. At the time of "postrm purge", "postrm
4750 abort-install", or "postrm abort-upgrade", calling
4751 "ldconfig" is useless because the shared lib files are
4752 not on-disk. However, when "postrm" is invoked with
4753 arguments "upgrade", "failed-upgrade", or "disappear", a
4754 shared lib may exist on-disk under a temporary filename.
4762 <sect id="sharedlibs-runtime-progs">
4763 <heading>Run-time support programs</heading>
4766 If your package has some run-time support programs which use
4767 the shared library you must not put them in the shared
4768 library package. If you do that then you won't be able to
4769 install several versions of the shared library without
4770 getting filename clashes.
4774 Instead, either create another package for the runtime binaries
4775 (this package might typically be named
4776 <package><var>libraryname</var>-runtime</package>; note the absence
4777 of the <var>soversion</var> in the package name), or if the
4778 development package is small, include them in there.
4782 <sect id="sharedlibs-static">
4783 <heading>Static libraries</heading>
4786 The static library (<file><var>libraryname.a</var></file>)
4787 is usually provided in addition to the shared version.
4788 It is placed into the development package (see below).
4792 In some cases, it is acceptable for a library to be
4793 available in static form only; these cases include:
4795 <item>libraries for languages whose shared library support
4796 is immature or unstable</item>
4797 <item>libraries whose interfaces are in flux or under
4798 development (commonly the case when the library's
4799 major version number is zero, or where the ABI breaks
4800 across patchlevels)</item>
4801 <item>libraries which are explicitly intended to be
4802 available only in static form by their upstream
4807 <sect id="sharedlibs-dev">
4808 <heading>Development files</heading>
4811 The development files associated to a shared library need to be
4812 placed in a package called
4813 <package><var>libraryname</var><var>soversion</var>-dev</package>,
4814 or if you prefer only to support one development version at a
4815 time, <package><var>libraryname</var>-dev</package>.
4819 In case several development versions of a library exist, you may
4820 need to use <prgn>dpkg</prgn>'s Conflicts mechanism (see
4821 <ref id="conflicts">) to ensure that the user only installs one
4822 development version at a time (as different development versions are
4823 likely to have the same header files in them, which would cause a
4824 filename clash if both were installed).
4828 The development package should contain a symlink for the associated
4829 shared library without a version number. For example, the
4830 <package>libgdbm-dev</package> package should include a symlink
4831 from <file>/usr/lib/libgdbm.so</file> to
4832 <file>libgdbm.so.3.0.0</file>. This symlink is needed by the linker
4833 (<prgn>ld</prgn>) when compiling packages, as it will only look for
4834 <file>libgdbm.so</file> when compiling dynamically.
4838 <sect id="sharedlibs-intradeps">
4839 <heading>Dependencies between the packages of the same library</heading>
4842 Typically the development version should have an exact
4843 version dependency on the runtime library, to make sure that
4844 compilation and linking happens correctly. The
4845 <tt>${binary:Version}</tt> substitution variable can be
4846 useful for this purpose.
4848 Previously, <tt>${Source-Version}</tt> was used, but its name
4849 was confusing and it has been deprecated since dpkg 1.13.19.
4854 <sect id="sharedlibs-shlibdeps">
4855 <heading>Dependencies between the library and other packages -
4856 the <tt>shlibs</tt> system</heading>
4859 If a package contains a binary or library which links to a
4860 shared library, we must ensure that when the package is
4861 installed on the system, all of the libraries needed are
4862 also installed. This requirement led to the creation of the
4863 <tt>shlibs</tt> system, which is very simple in its design:
4864 any package which <em>provides</em> a shared library also
4865 provides information on the package dependencies required to
4866 ensure the presence of this library, and any package which
4867 <em>uses</em> a shared library uses this information to
4868 determine the dependencies it requires. The files which
4869 contain the mapping from shared libraries to the necessary
4870 dependency information are called <file>shlibs</file> files.
4874 Thus, when a package is built which contains any shared
4875 libraries, it must provide a <file>shlibs</file> file for other
4876 packages to use, and when a package is built which contains
4877 any shared libraries or compiled binaries, it must run
4878 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
4879 on these to determine the libraries used and hence the
4880 dependencies needed by this package.<footnote>
4882 In the past, the shared libraries linked to were
4883 determined by calling <prgn>ldd</prgn>, but now
4884 <prgn>objdump</prgn> is used to do this. The only
4885 change this makes to package building is that
4886 <prgn>dpkg-shlibdeps</prgn> must also be run on shared
4887 libraries, whereas in the past this was unnecessary.
4888 The rest of this footnote explains the advantage that
4893 We say that a binary <tt>foo</tt> <em>directly</em> uses
4894 a library <tt>libbar</tt> if it is explicitly linked
4895 with that library (that is, it uses the flag
4896 <tt>-lbar</tt> during the linking stage). Other
4897 libraries that are needed by <tt>libbar</tt> are linked
4898 <em>indirectly</em> to <tt>foo</tt>, and the dynamic
4899 linker will load them automatically when it loads
4900 <tt>libbar</tt>. A package should depend on
4901 the libraries it directly uses, and the dependencies for
4902 those libraries should automatically pull in the other
4907 Unfortunately, the <prgn>ldd</prgn> program shows both
4908 the directly and indirectly used libraries, meaning that
4909 the dependencies determined included both direct and
4910 indirect dependencies. The use of <prgn>objdump</prgn>
4911 avoids this problem by determining only the directly
4916 A good example of where this helps is the following. We
4917 could update <tt>libimlib</tt> with a new version that
4918 supports a new graphics format called dgf (but retaining
4919 the same major version number). If we used the old
4920 <prgn>ldd</prgn> method, every package that uses
4921 <tt>libimlib</tt> would need to be recompiled so it
4922 would also depend on <tt>libdgf</tt> or it wouldn't run
4923 due to missing symbols. However with the new system,
4924 packages using <tt>libimlib</tt> can rely on
4925 <tt>libimlib</tt> itself having the dependency on
4926 <tt>libdgf</tt> and so they would not need rebuilding.
4932 In the following sections, we will first describe where the
4933 various <tt>shlibs</tt> files are to be found, then how to
4934 use <prgn>dpkg-shlibdeps</prgn>, and finally the <tt>shlibs</tt>
4935 file format and how to create them if your package contains a
4940 <heading>The <tt>shlibs</tt> files present on the system</heading>
4943 There are several places where <tt>shlibs</tt> files are
4944 found. The following list gives them in the order in which
4946 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>.
4947 (The first one which gives the required information is used.)
4953 <p><file>debian/shlibs.local</file></p>
4956 This lists overrides for this package. Its use is
4957 described below (see <ref id="shlibslocal">).
4962 <p><file>/etc/dpkg/shlibs.override</file></p>
4965 This lists global overrides. This list is normally
4966 empty. It is maintained by the local system
4972 <p><file>DEBIAN/shlibs</file> files in the "build directory"</p>
4975 When packages are being built, any
4976 <file>debian/shlibs</file> files are copied into the
4977 control file area of the temporary build directory and
4978 given the name <file>shlibs</file>. These files give
4979 details of any shared libraries included in the
4981 An example may help here. Let us say that the
4982 source package <tt>foo</tt> generates two binary
4983 packages, <tt>libfoo2</tt> and
4984 <tt>foo-runtime</tt>. When building the binary
4985 packages, the two packages are created in the
4986 directories <file>debian/libfoo2</file> and
4987 <file>debian/foo-runtime</file> respectively.
4988 (<file>debian/tmp</file> could be used instead of one
4989 of these.) Since <tt>libfoo2</tt> provides the
4990 <tt>libfoo</tt> shared library, it will require a
4991 <tt>shlibs</tt> file, which will be installed in
4992 <file>debian/libfoo2/DEBIAN/shlibs</file>, eventually
4994 <file>/var/lib/dpkg/info/libfoo2.shlibs</file>. Then
4995 when <prgn>dpkg-shlibdeps</prgn> is run on the
4997 <file>debian/foo-runtime/usr/bin/foo-prog</file>, it
4999 <file>debian/libfoo2/DEBIAN/shlibs</file> file to
5000 determine whether <tt>foo-prog</tt>'s library
5001 dependencies are satisfied by any of the libraries
5002 provided by <tt>libfoo2</tt>. For this reason,
5003 <prgn>dpkg-shlibdeps</prgn> must only be run once
5004 all of the individual binary packages'
5005 <tt>shlibs</tt> files have been installed into the
5012 <p><file>/var/lib/dpkg/info/*.shlibs</file></p>
5015 These are the <file>shlibs</file> files corresponding to
5016 all of the packages installed on the system, and are
5017 maintained by the relevant package maintainers.
5022 <p><file>/etc/dpkg/shlibs.default</file></p>
5025 This file lists any shared libraries whose packages
5026 have failed to provide correct <file>shlibs</file> files.
5027 It was used when the <file>shlibs</file> setup was first
5028 introduced, but it is now normally empty. It is
5029 maintained by the <tt>dpkg</tt> maintainer.
5037 <heading>How to use <prgn>dpkg-shlibdeps</prgn> and the
5038 <file>shlibs</file> files</heading>
5042 <qref id="pkg-dpkg-shlibdeps"><prgn>dpkg-shlibdeps</prgn></qref>
5043 into your <file>debian/rules</file> file. If your package
5044 contains only compiled binaries and libraries (but no scripts),
5045 you can use a command such as:
5046 <example compact="compact">
5047 dpkg-shlibdeps debian/tmp/usr/bin/* debian/tmp/usr/sbin/* \
5048 debian/tmp/usr/lib/*
5050 Otherwise, you will need to explicitly list the compiled
5051 binaries and libraries.<footnote>
5052 If you are using <tt>debhelper</tt>, the
5053 <prgn>dh_shlibdeps</prgn> program will do this work for
5054 you. It will also correctly handle multi-binary
5060 This command puts the dependency information into the
5061 <file>debian/substvars</file> file, which is then used by
5062 <prgn>dpkg-gencontrol</prgn>. You will need to place a
5063 <tt>${shlibs:Depends}</tt> variable in the <tt>Depends</tt>
5064 field in the control file for this to work.
5068 If <prgn>dpkg-shlibdeps</prgn> doesn't complain, you're
5069 done. If it does complain you might need to create your own
5070 <file>debian/shlibs.local</file> file, as explained below (see
5071 <ref id="shlibslocal">).
5075 If you have multiple binary packages, you will need to call
5076 <prgn>dpkg-shlibdeps</prgn> on each one which contains
5077 compiled libraries or binaries. In such a case, you will
5078 need to use the <tt>-T</tt> option to the <tt>dpkg</tt>
5079 utilities to specify a different <file>substvars</file> file.
5083 If you are creating a udeb for use in the Debian Installer, you
5084 will need to specify that <prgn>dpkg-shlibdeps</prgn> should use
5085 the dependency line of type <tt>udeb</tt> by adding
5086 <tt>-tudeb</tt> as option<footnote>
5087 <prgn>dh_shlibdeps</prgn> from the <tt>debhelper</tt> suite
5088 will automatically add this option if it knows it is
5090 </footnote>. If there is no dependency line of type <tt>udeb</tt>
5091 in the <file>shlibs</file> file, <prgn>dpkg-shlibdeps</prgn> will
5092 fall back to the regular dependency line.
5096 For more details on dpkg-shlibdeps, please see
5097 <ref id="pkg-dpkg-shlibdeps"> and
5098 <manref name="dpkg-shlibdeps" section="1">.
5103 <heading>The <file>shlibs</file> File Format</heading>
5106 Each <file>shlibs</file> file has the same format. Lines
5107 beginning with <tt>#</tt> are considered to be comments and
5108 are ignored. Each line is of the form:
5109 <example compact="compact">
5110 [<var>type</var>: ]<var>library-name</var> <var>soname-version</var> <var>dependencies ...</var>
5115 We will explain this by reference to the example of the
5116 <tt>zlib1g</tt> package, which (at the time of writing)
5117 installs the shared library <file>/usr/lib/libz.so.1.1.3</file>.
5121 <var>type</var> is an optional element that indicates the type
5122 of package for which the line is valid. The only type currently
5123 in use is <tt>udeb</tt>. The colon and space after the type are
5128 <var>library-name</var> is the name of the shared library,
5129 in this case <tt>libz</tt>. (This must match the name part
5130 of the soname, see below.)
5134 <var>soname-version</var> is the version part of the soname of
5135 the library. The soname is the thing that must exactly match
5136 for the library to be recognized by the dynamic linker, and is
5138 <tt><var>name</var>.so.<var>major-version</var></tt>, in our
5139 example, <tt>libz.so.1</tt>.<footnote>
5140 This can be determined using the command
5141 <example compact="compact">
5142 objdump -p /usr/lib/libz.so.1.1.3 | grep SONAME
5145 The version part is the part which comes after
5146 <tt>.so.</tt>, so in our case, it is <tt>1</tt>.
5150 <var>dependencies</var> has the same syntax as a dependency
5151 field in a binary package control file. It should give
5152 details of which packages are required to satisfy a binary
5153 built against the version of the library contained in the
5154 package. See <ref id="depsyntax"> for details.
5158 In our example, if the first version of the <tt>zlib1g</tt>
5159 package which contained a minor number of at least
5160 <tt>1.3</tt> was <var>1:1.1.3-1</var>, then the
5161 <tt>shlibs</tt> entry for this library could say:
5162 <example compact="compact">
5163 libz 1 zlib1g (>= 1:1.1.3)
5165 The version-specific dependency is to avoid warnings from
5166 the dynamic linker about using older shared libraries with
5171 As zlib1g also provides a udeb containing the shared library,
5172 there would also be a second line:
5173 <example compact="compact">
5174 udeb: libz 1 zlib1g-udeb (>= 1:1.1.3)
5180 <heading>Providing a <file>shlibs</file> file</heading>
5183 If your package provides a shared library, you need to create
5184 a <file>shlibs</file> file following the format described above.
5185 It is usual to call this file <file>debian/shlibs</file> (but if
5186 you have multiple binary packages, you might want to call it
5187 <file>debian/shlibs.<var>package</var></file> instead). Then
5188 let <file>debian/rules</file> install it in the control area:
5189 <example compact="compact">
5190 install -m644 debian/shlibs debian/tmp/DEBIAN
5192 or, in the case of a multi-binary package:
5193 <example compact="compact">
5194 install -m644 debian/shlibs.<var>package</var> debian/<var>package</var>/DEBIAN/shlibs
5196 An alternative way of doing this is to create the
5197 <file>shlibs</file> file in the control area directly from
5198 <file>debian/rules</file> without using a <file>debian/shlibs</file>
5199 file at all,<footnote>
5200 This is what <prgn>dh_makeshlibs</prgn> in the
5201 <tt>debhelper</tt> suite does. If your package also has a udeb
5202 that provides a shared library, <prgn>dh_makeshlibs</prgn> can
5203 automatically generate the <tt>udeb:</tt> lines if you specify
5204 the name of the udeb with the <tt>--add-udeb</tt> option.
5206 since the <file>debian/shlibs</file> file itself is ignored by
5207 <prgn>dpkg-shlibdeps</prgn>.
5211 As <prgn>dpkg-shlibdeps</prgn> reads the
5212 <file>DEBIAN/shlibs</file> files in all of the binary packages
5213 being built from this source package, all of the
5214 <file>DEBIAN/shlibs</file> files should be installed before
5215 <prgn>dpkg-shlibdeps</prgn> is called on any of the binary
5220 <sect1 id="shlibslocal">
5221 <heading>Writing the <file>debian/shlibs.local</file> file</heading>
5224 This file is intended only as a <em>temporary</em> fix if
5225 your binaries or libraries depend on a library whose package
5226 does not yet provide a correct <file>shlibs</file> file.
5230 We will assume that you are trying to package a binary
5231 <tt>foo</tt>. When you try running
5232 <prgn>dpkg-shlibdeps</prgn> you get the following error
5233 message (<tt>-O</tt> displays the dependency information on
5234 <tt>stdout</tt> instead of writing it to
5235 <tt>debian/substvars</tt>, and the lines have been wrapped
5236 for ease of reading):
5237 <example compact="compact">
5238 $ dpkg-shlibdeps -O debian/tmp/usr/bin/foo
5239 dpkg-shlibdeps: warning: unable to find dependency
5240 information for shared library libbar (soname 1,
5241 path /usr/lib/libbar.so.1, dependency field Depends)
5242 shlibs:Depends=libc6 (>= 2.2.2-2)
5244 You can then run <prgn>ldd</prgn> on the binary to find the
5245 full location of the library concerned:
5246 <example compact="compact">
5248 libbar.so.1 => /usr/lib/libbar.so.1 (0x4001e000)
5249 libc.so.6 => /lib/libc.so.6 (0x40032000)
5250 /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)
5252 So the <prgn>foo</prgn> binary depends on the
5253 <prgn>libbar</prgn> shared library, but no package seems to
5254 provide a <file>*.shlibs</file> file handling
5255 <file>libbar.so.1</file> in <file>/var/lib/dpkg/info/</file>. Let's
5256 determine the package responsible:
5257 <example compact="compact">
5258 $ dpkg -S /usr/lib/libbar.so.1
5259 bar1: /usr/lib/libbar.so.1
5260 $ dpkg -s bar1 | grep Version
5263 This tells us that the <tt>bar1</tt> package, version 1.0-1,
5264 is the one we are using. Now we can file a bug against the
5265 <tt>bar1</tt> package and create our own
5266 <file>debian/shlibs.local</file> to locally fix the problem.
5267 Including the following line into your
5268 <file>debian/shlibs.local</file> file:
5269 <example compact="compact">
5270 libbar 1 bar1 (>= 1.0-1)
5272 should allow the package build to work.
5276 As soon as the maintainer of <tt>bar1</tt> provides a
5277 correct <file>shlibs</file> file, you should remove this line
5278 from your <file>debian/shlibs.local</file> file. (You should
5279 probably also then have a versioned <tt>Build-Depends</tt>
5280 on <tt>bar1</tt> to help ensure that others do not have the
5281 same problem building your package.)
5290 <chapt id="opersys"><heading>The Operating System</heading>
5293 <heading>File system hierarchy</heading>
5297 <heading>File system Structure</heading>
5300 The location of all installed files and directories must
5301 comply with the File system Hierarchy Standard (FHS),
5302 version 2.3, with the exceptions noted below, and except
5303 where doing so would violate other terms of Debian
5304 Policy. The following exceptions to the FHS apply:
5309 Legacy XFree86 servers are permitted to retain the
5310 configuration file location
5311 <file>/etc/X11/XF86Config-4</file>.
5316 The optional rules related to user specific
5317 configuration files for applications are stored in
5318 the user's home directory are relaxed. It is
5319 recommended that such files start with the
5320 '<tt>.</tt>' character (a "dot file"), and if an
5321 application needs to create more than one dot file
5322 then the preferred placement is in a subdirectory
5323 with a name starting with a '.' character, (a "dot
5324 directory"). In this case it is recommended the
5325 configuration files not start with the '.'
5331 The requirement for amd64 to use <file>/lib64</file>
5332 for 64 bit binaries is removed.
5337 The requirement that
5338 <file>/usr/local/share/man</file> be "synonymous"
5339 with <file>/usr/local/man</file> is relaxed to a
5344 The requirement that windowmanagers with a single
5345 configuration file call it <file>system.*wmrc</file>
5346 is removed, as is the restriction that the window
5347 manager subdirectory be named identically to the
5348 window manager name itself.
5353 The requirement that boot manager configuration
5354 files live in <file>/etc</file>, or at least are
5355 symlinked there, is relaxed to a recommendation.
5362 The version of this document referred here can be
5363 found in the <tt>debian-policy</tt> package or on <url
5364 id="http://www.debian.org/doc/packaging-manuals/fhs/"
5365 name="FHS (Debian copy)"> alongside this manual (or, if
5366 you have the <package>debian-policy</package> installed,
5368 id="file:///usr/share/doc/debian-policy/fhs/" name="FHS
5369 (local copy)">). The
5370 latest version, which may be a more recent version, may
5372 <url id="http://www.pathname.com/fhs/" name="FHS (upstream)">.
5373 Specific questions about following the standard may be
5374 asked on the <tt>debian-devel</tt> mailing list, or
5375 referred to the FHS mailing list (see the
5376 <url id="http://www.pathname.com/fhs/" name="FHS web site"> for
5382 <heading>Site-specific programs</heading>
5385 As mandated by the FHS, packages must not place any
5386 files in <file>/usr/local</file>, either by putting them in
5387 the file system archive to be unpacked by <prgn>dpkg</prgn>
5388 or by manipulating them in their maintainer scripts.
5392 However, the package may create empty directories below
5393 <file>/usr/local</file> so that the system administrator knows
5394 where to place site-specific files. These are not
5395 directories <em>in</em> <file>/usr/local</file>, but are
5396 children of directories in <file>/usr/local</file>. These
5397 directories (<file>/usr/local/*/dir/</file>)
5398 should be removed on package removal if they are
5403 Note, that this applies only to directories <em>below</em>
5404 <file>/usr/local</file>, not <em>in</em> <file>/usr/local</file>.
5405 Packages must not create sub-directories in the directory
5406 <file>/usr/local</file> itself, except those listed in FHS,
5407 section 4.5. However, you may create directories below
5408 them as you wish. You must not remove any of the
5409 directories listed in 4.5, even if you created them.
5413 Since <file>/usr/local</file> can be mounted read-only from a
5414 remote server, these directories must be created and
5415 removed by the <prgn>postinst</prgn> and <prgn>prerm</prgn>
5416 maintainer scripts and not be included in the
5417 <file>.deb</file> archive. These scripts must not fail if
5418 either of these operations fail.
5422 For example, the <tt>emacsen-common</tt> package could
5423 contain something like
5424 <example compact="compact">
5425 if [ ! -e /usr/local/share/emacs ]
5427 if mkdir /usr/local/share/emacs 2>/dev/null
5429 chown root:staff /usr/local/share/emacs
5430 chmod 2775 /usr/local/share/emacs
5434 in its <prgn>postinst</prgn> script, and
5435 <example compact="compact">
5436 rmdir /usr/local/share/emacs/site-lisp 2>/dev/null || true
5437 rmdir /usr/local/share/emacs 2>/dev/null || true
5439 in the <prgn>prerm</prgn> script. (Note that this form is
5440 used to ensure that if the script is interrupted, the
5441 directory <file>/usr/local/share/emacs</file> will still be
5446 If you do create a directory in <file>/usr/local</file> for
5447 local additions to a package, you should ensure that
5448 settings in <file>/usr/local</file> take precedence over the
5449 equivalents in <file>/usr</file>.
5453 However, because <file>/usr/local</file> and its contents are
5454 for exclusive use of the local administrator, a package
5455 must not rely on the presence or absence of files or
5456 directories in <file>/usr/local</file> for normal operation.
5460 The <file>/usr/local</file> directory itself and all the
5461 subdirectories created by the package should (by default) have
5462 permissions 2775 (group-writable and set-group-id) and be
5463 owned by <tt>root.staff</tt>.
5468 <heading>The system-wide mail directory</heading>
5470 The system-wide mail directory is <file>/var/mail</file>. This
5471 directory is part of the base system and should not owned
5472 by any particular mail agents. The use of the old
5473 location <file>/var/spool/mail</file> is deprecated, even
5474 though the spool may still be physically located there.
5475 To maintain partial upgrade compatibility for systems
5476 which have <file>/var/spool/mail</file> as their physical mail
5477 spool, packages using <file>/var/mail</file> must depend on
5478 either <package>libc6</package> (>= 2.1.3-13), or on
5479 <package>base-files</package> (>= 2.2.0), or on later
5480 versions of either one of these packages.
5486 <heading>Users and groups</heading>
5489 <heading>Introduction</heading>
5491 The Debian system can be configured to use either plain or
5496 Some user ids (UIDs) and group ids (GIDs) are reserved
5497 globally for use by certain packages. Because some
5498 packages need to include files which are owned by these
5499 users or groups, or need the ids compiled into binaries,
5500 these ids must be used on any Debian system only for the
5501 purpose for which they are allocated. This is a serious
5502 restriction, and we should avoid getting in the way of
5503 local administration policies. In particular, many sites
5504 allocate users and/or local system groups starting at 100.
5508 Apart from this we should have dynamically allocated ids,
5509 which should by default be arranged in some sensible
5510 order, but the behavior should be configurable.
5514 Packages other than <tt>base-passwd</tt> must not modify
5515 <file>/etc/passwd</file>, <file>/etc/shadow</file>,
5516 <file>/etc/group</file> or <file>/etc/gshadow</file>.
5521 <heading>UID and GID classes</heading>
5523 The UID and GID numbers are divided into classes as
5529 Globally allocated by the Debian project, the same
5530 on every Debian system. These ids will appear in
5531 the <file>passwd</file> and <file>group</file> files of all
5532 Debian systems, new ids in this range being added
5533 automatically as the <tt>base-passwd</tt> package is
5538 Packages which need a single statically allocated
5539 uid or gid should use one of these; their
5540 maintainers should ask the <tt>base-passwd</tt>
5548 Dynamically allocated system users and groups.
5549 Packages which need a user or group, but can have
5550 this user or group allocated dynamically and
5551 differently on each system, should use <tt>adduser
5552 --system</tt> to create the group and/or user.
5553 <prgn>adduser</prgn> will check for the existence of
5554 the user or group, and if necessary choose an unused
5555 id based on the ranges specified in
5556 <file>adduser.conf</file>.
5560 <tag>1000-29999:</tag>
5563 Dynamically allocated user accounts. By default
5564 <prgn>adduser</prgn> will choose UIDs and GIDs for
5565 user accounts in this range, though
5566 <file>adduser.conf</file> may be used to modify this
5571 <tag>30000-59999:</tag>
5576 <tag>60000-64999:</tag>
5579 Globally allocated by the Debian project, but only
5580 created on demand. The ids are allocated centrally
5581 and statically, but the actual accounts are only
5582 created on users' systems on demand.
5586 These ids are for packages which are obscure or
5587 which require many statically-allocated ids. These
5588 packages should check for and create the accounts in
5589 <file>/etc/passwd</file> or <file>/etc/group</file> (using
5590 <prgn>adduser</prgn> if it has this facility) if
5591 necessary. Packages which are likely to require
5592 further allocations should have a "hole" left after
5593 them in the allocation, to give them room to
5598 <tag>65000-65533:</tag>
5606 User <tt>nobody</tt>. The corresponding gid refers
5607 to the group <tt>nogroup</tt>.
5614 <tt>(uid_t)(-1) == (gid_t)(-1)</tt> <em>must
5615 not</em> be used, because it is the error return
5624 <sect id="sysvinit">
5625 <heading>System run levels and <file>init.d</file> scripts</heading>
5627 <sect1 id="/etc/init.d">
5628 <heading>Introduction</heading>
5631 The <file>/etc/init.d</file> directory contains the scripts
5632 executed by <prgn>init</prgn> at boot time and when the
5633 init state (or "runlevel") is changed (see <manref
5634 name="init" section="8">).
5638 There are at least two different, yet functionally
5639 equivalent, ways of handling these scripts. For the sake
5640 of simplicity, this document describes only the symbolic
5641 link method. However, it must not be assumed by maintainer
5642 scripts that this method is being used, and any automated
5643 manipulation of the various runlevel behaviors by
5644 maintainer scripts must be performed using
5645 <prgn>update-rc.d</prgn> as described below and not by
5646 manually installing or removing symlinks. For information
5647 on the implementation details of the other method,
5648 implemented in the <tt>file-rc</tt> package, please refer
5649 to the documentation of that package.
5653 These scripts are referenced by symbolic links in the
5654 <file>/etc/rc<var>n</var>.d</file> directories. When changing
5655 runlevels, <prgn>init</prgn> looks in the directory
5656 <file>/etc/rc<var>n</var>.d</file> for the scripts it should
5657 execute, where <tt><var>n</var></tt> is the runlevel that
5658 is being changed to, or <tt>S</tt> for the boot-up
5663 The names of the links all have the form
5664 <file>S<var>mm</var><var>script</var></file> or
5665 <file>K<var>mm</var><var>script</var></file> where
5666 <var>mm</var> is a two-digit number and <var>script</var>
5667 is the name of the script (this should be the same as the
5668 name of the actual script in <file>/etc/init.d</file>).
5672 When <prgn>init</prgn> changes runlevel first the targets
5673 of the links whose names start with a <tt>K</tt> are
5674 executed, each with the single argument <tt>stop</tt>,
5675 followed by the scripts prefixed with an <tt>S</tt>, each
5676 with the single argument <tt>start</tt>. (The links are
5677 those in the <file>/etc/rc<var>n</var>.d</file> directory
5678 corresponding to the new runlevel.) The <tt>K</tt> links
5679 are responsible for killing services and the <tt>S</tt>
5680 link for starting services upon entering the runlevel.
5684 For example, if we are changing from runlevel 2 to
5685 runlevel 3, init will first execute all of the <tt>K</tt>
5686 prefixed scripts it finds in <file>/etc/rc3.d</file>, and then
5687 all of the <tt>S</tt> prefixed scripts in that directory.
5688 The links starting with <tt>K</tt> will cause the
5689 referred-to file to be executed with an argument of
5690 <tt>stop</tt>, and the <tt>S</tt> links with an argument
5695 The two-digit number <var>mm</var> is used to determine
5696 the order in which to run the scripts: low-numbered links
5697 have their scripts run first. For example, the
5698 <tt>K20</tt> scripts will be executed before the
5699 <tt>K30</tt> scripts. This is used when a certain service
5700 must be started before another. For example, the name
5701 server <prgn>bind</prgn> might need to be started before
5702 the news server <prgn>inn</prgn> so that <prgn>inn</prgn>
5703 can set up its access lists. In this case, the script
5704 that starts <prgn>bind</prgn> would have a lower number
5705 than the script that starts <prgn>inn</prgn> so that it
5707 <example compact="compact">
5714 The two runlevels 0 (halt) and 6 (reboot) are slightly
5715 different. In these runlevels, the links with an
5716 <tt>S</tt> prefix are still called after those with a
5717 <tt>K</tt> prefix, but they too are called with the single
5718 argument <tt>stop</tt>.
5722 Also, if the script name ends in <tt>.sh</tt>, the script
5723 will be sourced in runlevel <tt>S</tt> rather than being
5724 run in a forked subprocess, but will be explicitly run by
5725 <prgn>sh</prgn> in all other runlevels.
5730 <heading>Writing the scripts</heading>
5733 Packages that include daemons for system services should
5734 place scripts in <file>/etc/init.d</file> to start or stop
5735 services at boot time or during a change of runlevel.
5736 These scripts should be named
5737 <file>/etc/init.d/<var>package</var></file>, and they should
5738 accept one argument, saying what to do:
5741 <tag><tt>start</tt></tag>
5742 <item>start the service,</item>
5744 <tag><tt>stop</tt></tag>
5745 <item>stop the service,</item>
5747 <tag><tt>restart</tt></tag>
5748 <item>stop and restart the service if it's already running,
5749 otherwise start the service</item>
5751 <tag><tt>reload</tt></tag>
5752 <item><p>cause the configuration of the service to be
5753 reloaded without actually stopping and restarting
5756 <tag><tt>force-reload</tt></tag>
5757 <item>cause the configuration to be reloaded if the
5758 service supports this, otherwise restart the
5762 The <tt>start</tt>, <tt>stop</tt>, <tt>restart</tt>, and
5763 <tt>force-reload</tt> options should be supported by all
5764 scripts in <file>/etc/init.d</file>, the <tt>reload</tt>
5769 The <file>init.d</file> scripts must ensure that they will
5770 behave sensibly if invoked with <tt>start</tt> when the
5771 service is already running, or with <tt>stop</tt> when it
5772 isn't, and that they don't kill unfortunately-named user
5773 processes. The best way to achieve this is usually to use
5774 <prgn>start-stop-daemon</prgn>.
5778 If a service reloads its configuration automatically (as
5779 in the case of <prgn>cron</prgn>, for example), the
5780 <tt>reload</tt> option of the <file>init.d</file> script
5781 should behave as if the configuration has been reloaded
5786 The <file>/etc/init.d</file> scripts must be treated as
5787 configuration files, either (if they are present in the
5788 package, that is, in the .deb file) by marking them as
5789 <tt>conffile</tt>s, or, (if they do not exist in the .deb)
5790 by managing them correctly in the maintainer scripts (see
5791 <ref id="config-files">). This is important since we want
5792 to give the local system administrator the chance to adapt
5793 the scripts to the local system, e.g., to disable a
5794 service without de-installing the package, or to specify
5795 some special command line options when starting a service,
5796 while making sure their changes aren't lost during the next
5801 These scripts should not fail obscurely when the
5802 configuration files remain but the package has been
5803 removed, as configuration files remain on the system after
5804 the package has been removed. Only when <prgn>dpkg</prgn>
5805 is executed with the <tt>--purge</tt> option will
5806 configuration files be removed. In particular, as the
5807 <file>/etc/init.d/<var>package</var></file> script itself is
5808 usually a <tt>conffile</tt>, it will remain on the system
5809 if the package is removed but not purged. Therefore, you
5810 should include a <tt>test</tt> statement at the top of the
5812 <example compact="compact">
5813 test -f <var>program-executed-later-in-script</var> || exit 0
5818 Often there are some variables in the <file>init.d</file>
5819 scripts whose values control the behavior of the scripts,
5820 and which a system administrator is likely to want to
5821 change. As the scripts themselves are frequently
5822 <tt>conffile</tt>s, modifying them requires that the
5823 administrator merge in their changes each time the package
5824 is upgraded and the <tt>conffile</tt> changes. To ease
5825 the burden on the system administrator, such configurable
5826 values should not be placed directly in the script.
5827 Instead, they should be placed in a file in
5828 <file>/etc/default</file>, which typically will have the same
5829 base name as the <file>init.d</file> script. This extra file
5830 should be sourced by the script when the script runs. It
5831 must contain only variable settings and comments in SUSv3
5832 <prgn>sh</prgn> format. It may either be a
5833 <tt>conffile</tt> or a configuration file maintained by
5834 the package maintainer scripts. See <ref id="config-files">
5839 To ensure that vital configurable values are always
5840 available, the <file>init.d</file> script should set default
5841 values for each of the shell variables it uses, either
5842 before sourcing the <file>/etc/default/</file> file or
5843 afterwards using something like the <tt>:
5844 ${VAR:=default}</tt> syntax. Also, the <file>init.d</file>
5845 script must behave sensibly and not fail if the
5846 <file>/etc/default</file> file is deleted.
5851 <heading>Interfacing with the initscript system</heading>
5854 Maintainers should use the abstraction layer provided by
5855 the <prgn>update-rc.d</prgn> and <prgn>invoke-rc.d</prgn>
5856 programs to deal with initscripts in their packages'
5857 scripts such as <prgn>postinst</prgn>, <prgn>prerm</prgn>
5858 and <prgn>postrm</prgn>.
5862 Directly managing the /etc/rc?.d links and directly
5863 invoking the <file>/etc/init.d/</file> initscripts should
5864 be done only by packages providing the initscript
5865 subsystem (such as <prgn>sysv-rc</prgn> and
5866 <prgn>file-rc</prgn>).
5870 <heading>Managing the links</heading>
5873 The program <prgn>update-rc.d</prgn> is provided for
5874 package maintainers to arrange for the proper creation and
5875 removal of <file>/etc/rc<var>n</var>.d</file> symbolic links,
5876 or their functional equivalent if another method is being
5877 used. This may be used by maintainers in their packages'
5878 <prgn>postinst</prgn> and <prgn>postrm</prgn> scripts.
5882 You must not include any <file>/etc/rc<var>n</var>.d</file>
5883 symbolic links in the actual archive or manually create or
5884 remove the symbolic links in maintainer scripts; you must
5885 use the <prgn>update-rc.d</prgn> program instead. (The
5886 former will fail if an alternative method of maintaining
5887 runlevel information is being used.) You must not include
5888 the <file>/etc/rc<var>n</var>.d</file> directories themselves
5889 in the archive either. (Only the <tt>sysvinit</tt>
5894 By default <prgn>update-rc.d</prgn> will start services in
5895 each of the multi-user state runlevels (2, 3, 4, and 5)
5896 and stop them in the halt runlevel (0), the single-user
5897 runlevel (1) and the reboot runlevel (6). The system
5898 administrator will have the opportunity to customize
5899 runlevels by simply adding, moving, or removing the
5900 symbolic links in <file>/etc/rc<var>n</var>.d</file> if
5901 symbolic links are being used, or by modifying
5902 <file>/etc/runlevel.conf</file> if the <tt>file-rc</tt> method
5907 To get the default behavior for your package, put in your
5908 <prgn>postinst</prgn> script
5909 <example compact="compact">
5910 update-rc.d <var>package</var> defaults
5912 and in your <prgn>postrm</prgn>
5913 <example compact="compact">
5914 if [ "$1" = purge ]; then
5915 update-rc.d <var>package</var> remove
5917 </example>. Note that if your package changes runlevels
5918 or priority, you may have to remove and recreate the links,
5919 since otherwise the old links may persist. Refer to the
5920 documentation of <prgn>update-rc.d</prgn>.
5924 This will use a default sequence number of 20. If it does
5925 not matter when or in which order the <file>init.d</file>
5926 script is run, use this default. If it does, then you
5927 should talk to the maintainer of the <prgn>sysvinit</prgn>
5928 package or post to <tt>debian-devel</tt>, and they will
5929 help you choose a number.
5933 For more information about using <tt>update-rc.d</tt>,
5934 please consult its man page <manref name="update-rc.d"
5940 <heading>Running initscripts</heading>
5942 The program <prgn>invoke-rc.d</prgn> is provided to make
5943 it easier for package maintainers to properly invoke an
5944 initscript, obeying runlevel and other locally-defined
5945 constraints that might limit a package's right to start,
5946 stop and otherwise manage services. This program may be
5947 used by maintainers in their packages' scripts.
5951 The package maintainer scripts must use
5952 <prgn>invoke-rc.d</prgn> to invoke the
5953 <file>/etc/init.d/*</file> initscripts, instead of
5954 calling them directly.
5958 By default, <prgn>invoke-rc.d</prgn> will pass any
5959 action requests (start, stop, reload, restart...) to the
5960 <file>/etc/init.d</file> script, filtering out requests
5961 to start or restart a service out of its intended
5966 Most packages will simply need to change:
5967 <example compact="compact">/etc/init.d/<package>
5968 <action></example> in their <prgn>postinst</prgn>
5969 and <prgn>prerm</prgn> scripts to:
5970 <example compact="compact">
5971 if which invoke-rc.d >/dev/null 2>&1; then
5972 invoke-rc.d <var>package</var> <action>
5974 /etc/init.d/<var>package</var> <action>
5980 A package should register its initscript services using
5981 <prgn>update-rc.d</prgn> before it tries to invoke them
5982 using <prgn>invoke-rc.d</prgn>. Invocation of
5983 unregistered services may fail.
5987 For more information about using
5988 <prgn>invoke-rc.d</prgn>, please consult its man page
5989 <manref name="invoke-rc.d" section="8">.
5995 <heading>Boot-time initialization</heading>
5998 There used to be another directory, <file>/etc/rc.boot</file>,
5999 which contained scripts which were run once per machine
6000 boot. This has been deprecated in favour of links from
6001 <file>/etc/rcS.d</file> to files in <file>/etc/init.d</file> as
6002 described in <ref id="/etc/init.d">. Packages must not
6003 place files in <file>/etc/rc.boot</file>.
6008 <heading>Example</heading>
6011 An example on which you can base your
6012 <file>/etc/init.d</file> scripts is found in
6013 <file>/etc/init.d/skeleton</file>.
6020 <heading>Console messages from <file>init.d</file> scripts</heading>
6023 This section describes the formats to be used for messages
6024 written to standard output by the <file>/etc/init.d</file>
6025 scripts. The intent is to improve the consistency of
6026 Debian's startup and shutdown look and feel. For this
6027 reason, please look very carefully at the details. We want
6028 the messages to have the same format in terms of wording,
6029 spaces, punctuation and case of letters.
6033 Here is a list of overall rules that should be used for
6034 messages generated by <file>/etc/init.d</file> scripts.
6040 The message should fit in one line (fewer than 80
6041 characters), start with a capital letter and end with
6042 a period (<tt>.</tt>) and line feed (<tt>"\n"</tt>).
6046 If the script is performing some time consuming task in
6047 the background (not merely starting or stopping a
6048 program, for instance), an ellipsis (three dots:
6049 <tt>...</tt>) should be output to the screen, with no
6050 leading or tailing whitespace or line feeds.
6054 The messages should appear as if the computer is telling
6055 the user what it is doing (politely :-), but should not
6056 mention "it" directly. For example, instead of:
6057 <example compact="compact">
6058 I'm starting network daemons: nfsd mountd.
6060 the message should say
6061 <example compact="compact">
6062 Starting network daemons: nfsd mountd.
6069 <tt>init.d</tt> script should use the following standard
6070 message formats for the situations enumerated below.
6076 <p>When daemons are started</p>
6079 If the script starts one or more daemons, the output
6080 should look like this (a single line, no leading
6082 <example compact="compact">
6083 Starting <var>description</var>: <var>daemon-1</var> ... <var>daemon-n</var>.
6085 The <var>description</var> should describe the
6086 subsystem the daemon or set of daemons are part of,
6087 while <var>daemon-1</var> up to <var>daemon-n</var>
6088 denote each daemon's name (typically the file name of
6093 For example, the output of <file>/etc/init.d/lpd</file>
6095 <example compact="compact">
6096 Starting printer spooler: lpd.
6101 This can be achieved by saying
6102 <example compact="compact">
6103 echo -n "Starting printer spooler: lpd"
6104 start-stop-daemon --start --quiet --exec /usr/sbin/lpd
6107 in the script. If there are more than one daemon to
6108 start, the output should look like this:
6109 <example compact="compact">
6110 echo -n "Starting remote file system services:"
6111 echo -n " nfsd"; start-stop-daemon --start --quiet nfsd
6112 echo -n " mountd"; start-stop-daemon --start --quiet mountd
6113 echo -n " ugidd"; start-stop-daemon --start --quiet ugidd
6116 This makes it possible for the user to see what is
6117 happening and when the final daemon has been started.
6118 Care should be taken in the placement of white spaces:
6119 in the example above the system administrators can
6120 easily comment out a line if they don't want to start
6121 a specific daemon, while the displayed message still
6127 <p>When a system parameter is being set</p>
6130 If you have to set up different system parameters
6131 during the system boot, you should use this format:
6132 <example compact="compact">
6133 Setting <var>parameter</var> to "<var>value</var>".
6138 You can use a statement such as the following to get
6140 <example compact="compact">
6141 echo "Setting DNS domainname to \"$domainname\"."
6146 Note that the same symbol (<tt>"</tt>) is used for the left
6147 and right quotation marks. A grave accent (<tt>`</tt>) is
6148 not a quote character; neither is an apostrophe
6154 <p>When a daemon is stopped or restarted</p>
6157 When you stop or restart a daemon, you should issue a
6158 message identical to the startup message, except that
6159 <tt>Starting</tt> is replaced with <tt>Stopping</tt>
6160 or <tt>Restarting</tt> respectively.
6164 For example, stopping the printer daemon will look like
6166 <example compact="compact">
6167 Stopping printer spooler: lpd.
6173 <p>When something is executed</p>
6176 There are several examples where you have to run a
6177 program at system startup or shutdown to perform a
6178 specific task, for example, setting the system's clock
6179 using <prgn>netdate</prgn> or killing all processes
6180 when the system shuts down. Your message should look
6182 <example compact="compact">
6183 Doing something very useful...done.
6185 You should print the <tt>done.</tt> immediately after
6186 the job has been completed, so that the user is
6187 informed why they have to wait. You can get this
6189 <example compact="compact">
6190 echo -n "Doing something very useful..."
6199 <p>When the configuration is reloaded</p>
6202 When a daemon is forced to reload its configuration
6203 files you should use the following format:
6204 <example compact="compact">
6205 Reloading <var>description</var> configuration...done.
6207 where <var>description</var> is the same as in the
6208 daemon starting message.
6216 <heading>Cron jobs</heading>
6219 Packages must not modify the configuration file
6220 <file>/etc/crontab</file>, and they must not modify the files in
6221 <file>/var/spool/cron/crontabs</file>.</p>
6224 If a package wants to install a job that has to be executed
6225 via cron, it should place a file with the name of the
6226 package in one or more of the following directories:
6227 <example compact="compact">
6232 As these directory names imply, the files within them are
6233 executed on a daily, weekly, or monthly basis,
6234 respectively. The exact times are listed in
6235 <file>/etc/crontab</file>.</p>
6238 All files installed in any of these directories must be
6239 scripts (e.g., shell scripts or Perl scripts) so that they
6240 can easily be modified by the local system administrator.
6241 In addition, they should be treated as configuration
6246 If a certain job has to be executed more frequently than
6247 daily, the package should install a file
6248 <file>/etc/cron.d/<var>package</var></file>. This file uses the
6249 same syntax as <file>/etc/crontab</file> and is processed by
6250 <prgn>cron</prgn> automatically. The file must also be
6251 treated as a configuration file. (Note that entries in the
6252 <file>/etc/cron.d</file> directory are not handled by
6253 <prgn>anacron</prgn>. Thus, you should only use this
6254 directory for jobs which may be skipped if the system is not
6258 The scripts or crontab entries in these directories should
6259 check if all necessary programs are installed before they
6260 try to execute them. Otherwise, problems will arise when a
6261 package was removed but not purged since configuration files
6262 are kept on the system in this situation.</p>
6266 <heading>Menus</heading>
6269 The Debian <tt>menu</tt> package provides a standard
6270 interface between packages providing applications and
6271 <em>menu programs</em> (either X window managers or
6272 text-based menu programs such as <prgn>pdmenu</prgn>).
6276 All packages that provide applications that need not be
6277 passed any special command line arguments for normal
6278 operation should register a menu entry for those
6279 applications, so that users of the <tt>menu</tt> package
6280 will automatically get menu entries in their window
6281 managers, as well in shells like <tt>pdmenu</tt>.
6285 Menu entries should follow the current menu policy.
6289 The menu policy can be found in the <tt>menu-policy</tt>
6290 files in the <tt>debian-policy</tt> package.
6291 It is also available from the Debian web mirrors at
6292 <tt><url name="/doc/packaging-manuals/menu-policy/"
6293 id="http://www.debian.org/doc/packaging-manuals/menu-policy/"></tt>.
6297 Please also refer to the <em>Debian Menu System</em>
6298 documentation that comes with the <package>menu</package>
6299 package for information about how to register your
6305 <heading>Multimedia handlers</heading>
6308 MIME (Multipurpose Internet Mail Extensions, RFCs 2045-2049)
6309 is a mechanism for encoding files and data streams and
6310 providing meta-information about them, in particular their
6311 type (e.g. audio or video) and format (e.g. PNG, HTML,
6316 Registration of MIME type handlers allows programs like mail
6317 user agents and web browsers to invoke these handlers to
6318 view, edit or display MIME types they don't support directly.
6322 Packages which provide the ability to view/show/play,
6323 compose, edit or print MIME types should register themselves
6324 as such following the current MIME support policy.
6328 The MIME support policy can be found in the <tt>mime-policy</tt>
6329 files in the <tt>debian-policy</tt> package.
6330 It is also available from the Debian web mirrors at
6331 <tt><url name="/doc/packaging-manuals/mime-policy/"
6332 id="http://www.debian.org/doc/packaging-manuals/mime-policy/"></tt>.
6338 <heading>Keyboard configuration</heading>
6341 To achieve a consistent keyboard configuration so that all
6342 applications interpret a keyboard event the same way, all
6343 programs in the Debian distribution must be configured to
6344 comply with the following guidelines.
6348 The following keys must have the specified interpretations:
6351 <tag><tt><--</tt></tag>
6352 <item>delete the character to the left of the cursor</item>
6354 <tag><tt>Delete</tt></tag>
6355 <item>delete the character to the right of the cursor</item>
6357 <tag><tt>Control+H</tt></tag>
6358 <item>emacs: the help prefix</item>
6361 The interpretation of any keyboard events should be
6362 independent of the terminal that is used, be it a virtual
6363 console, an X terminal emulator, an rlogin/telnet session,
6368 The following list explains how the different programs
6369 should be set up to achieve this:
6375 <tt><--</tt> generates <tt>KB_BackSpace</tt> in X.
6379 <tt>Delete</tt> generates <tt>KB_Delete</tt> in X.
6383 X translations are set up to make
6384 <tt>KB_Backspace</tt> generate ASCII DEL, and to make
6385 <tt>KB_Delete</tt> generate <tt>ESC [ 3 ~</tt> (this
6386 is the vt220 escape code for the "delete character"
6387 key). This must be done by loading the X resources
6388 using <prgn>xrdb</prgn> on all local X displays, not
6389 using the application defaults, so that the
6390 translation resources used correspond to the
6391 <prgn>xmodmap</prgn> settings.
6395 The Linux console is configured to make
6396 <tt><--</tt> generate DEL, and <tt>Delete</tt>
6397 generate <tt>ESC [ 3 ~</tt>.
6401 X applications are configured so that <tt><</tt>
6402 deletes left, and <tt>Delete</tt> deletes right. Motif
6403 applications already work like this.
6407 Terminals should have <tt>stty erase ^?</tt> .
6411 The <tt>xterm</tt> terminfo entry should have <tt>ESC
6412 [ 3 ~</tt> for <tt>kdch1</tt>, just as for
6413 <tt>TERM=linux</tt> and <tt>TERM=vt220</tt>.
6417 Emacs is programmed to map <tt>KB_Backspace</tt> or
6418 the <tt>stty erase</tt> character to
6419 <tt>delete-backward-char</tt>, and <tt>KB_Delete</tt>
6420 or <tt>kdch1</tt> to <tt>delete-forward-char</tt>, and
6421 <tt>^H</tt> to <tt>help</tt> as always.
6425 Other applications use the <tt>stty erase</tt>
6426 character and <tt>kdch1</tt> for the two delete keys,
6427 with ASCII DEL being "delete previous character" and
6428 <tt>kdch1</tt> being "delete character under
6436 This will solve the problem except for the following
6443 Some terminals have a <tt><--</tt> key that cannot
6444 be made to produce anything except <tt>^H</tt>. On
6445 these terminals Emacs help will be unavailable on
6446 <tt>^H</tt> (assuming that the <tt>stty erase</tt>
6447 character takes precedence in Emacs, and has been set
6448 correctly). <tt>M-x help</tt> or <tt>F1</tt> (if
6449 available) can be used instead.
6453 Some operating systems use <tt>^H</tt> for <tt>stty
6454 erase</tt>. However, modern telnet versions and all
6455 rlogin versions propagate <tt>stty</tt> settings, and
6456 almost all UNIX versions honour <tt>stty erase</tt>.
6457 Where the <tt>stty</tt> settings are not propagated
6458 correctly, things can be made to work by using
6459 <tt>stty</tt> manually.
6463 Some systems (including previous Debian versions) use
6464 <prgn>xmodmap</prgn> to arrange for both
6465 <tt><--</tt> and <tt>Delete</tt> to generate
6466 <tt>KB_Delete</tt>. We can change the behavior of
6467 their X clients using the same X resources that we use
6468 to do it for our own clients, or configure our clients
6469 using their resources when things are the other way
6470 around. On displays configured like this
6471 <tt>Delete</tt> will not work, but <tt><--</tt>
6476 Some operating systems have different <tt>kdch1</tt>
6477 settings in their <tt>terminfo</tt> database for
6478 <tt>xterm</tt> and others. On these systems the
6479 <tt>Delete</tt> key will not work correctly when you
6480 log in from a system conforming to our policy, but
6481 <tt><--</tt> will.
6488 <heading>Environment variables</heading>
6491 A program must not depend on environment variables to get
6492 reasonable defaults. (That's because these environment
6493 variables would have to be set in a system-wide
6494 configuration file like <file>/etc/profile</file>, which is not
6495 supported by all shells.)
6499 If a program usually depends on environment variables for its
6500 configuration, the program should be changed to fall back to
6501 a reasonable default configuration if these environment
6502 variables are not present. If this cannot be done easily
6503 (e.g., if the source code of a non-free program is not
6504 available), the program must be replaced by a small
6505 "wrapper" shell script which sets the environment variables
6506 if they are not already defined, and calls the original program.
6510 Here is an example of a wrapper script for this purpose:
6512 <example compact="compact">
6514 BAR=${BAR:-/var/lib/fubar}
6516 exec /usr/lib/foo/foo "$@"
6521 Furthermore, as <file>/etc/profile</file> is a configuration
6522 file of the <prgn>base-files</prgn> package, other packages must
6523 not put any environment variables or other commands into that
6528 <sect id="doc-base">
6529 <heading>Registering Documents using doc-base</heading>
6532 The <package>doc-base</package> package implements a
6533 flexible mechanism for handling and presenting
6534 documentation. The recommended practice is for every Debian
6535 package that provides online documentation (other than just
6536 manual pages) to register these documents with
6537 <package>doc-base</package> by installing a
6538 <package>doc-base</package> control file via the
6539 <prgn/install-docs/ script at installation time and
6540 de-register the manuals again when the package is removed.
6543 Please refer to the documentation that comes with the
6544 <package>doc-base</package> package for information and
6553 <heading>Files</heading>
6556 <heading>Binaries</heading>
6559 Two different packages must not install programs with
6560 different functionality but with the same filenames. (The
6561 case of two programs having the same functionality but
6562 different implementations is handled via "alternatives" or
6563 the "Conflicts" mechanism. See <ref id="maintscripts"> and
6564 <ref id="conflicts"> respectively.) If this case happens,
6565 one of the programs must be renamed. The maintainers should
6566 report this to the <tt>debian-devel</tt> mailing list and
6567 try to find a consensus about which program will have to be
6568 renamed. If a consensus cannot be reached, <em>both</em>
6569 programs must be renamed.
6573 By default, when a package is being built, any binaries
6574 created should include debugging information, as well as
6575 being compiled with optimization. You should also turn on
6576 as many reasonable compilation warnings as possible; this
6577 makes life easier for porters, who can then look at build
6578 logs for possible problems. For the C programming language,
6579 this means the following compilation parameters should be
6581 <example compact="compact">
6583 CFLAGS = -O2 -g -Wall # sane warning options vary between programs
6585 INSTALL = install -s # (or use strip on the files in debian/tmp)
6590 Note that by default all installed binaries should be stripped,
6591 either by using the <tt>-s</tt> flag to
6592 <prgn>install</prgn>, or by calling <prgn>strip</prgn> on
6593 the binaries after they have been copied into
6594 <file>debian/tmp</file> but before the tree is made into a
6599 Although binaries in the build tree should be compiled with
6600 debugging information by default, it can often be difficult
6601 to debug programs if they are also subjected to compiler
6602 optimization. For this reason, it is recommended to support
6603 the standardized environment
6604 variable <tt>DEB_BUILD_OPTIONS</tt>. This variable can
6605 contain several flags to change how a package is compiled
6613 The presence of this string means that the package
6614 should be compiled with a minimum of optimization.
6615 For C programs, it is best to add <tt>-O0</tt>
6616 to <tt>CFLAGS</tt> (although this is usually the
6617 default). Some programs might fail to build or run at
6618 this level of optimization; it may be necessary to
6619 use <tt>-O1</tt>, for example.
6623 This string means that the debugging symbols should
6624 not be stripped from the binary during installation,
6625 so that debugging information may be included in the package.
6631 The following makefile snippet is an example of how one may
6632 implement the build options; you will probably have to
6633 massage this example in order to make it work for your
6635 <example compact="compact">
6638 INSTALL_FILE = $(INSTALL) -p -o root -g root -m 644
6639 INSTALL_PROGRAM = $(INSTALL) -p -o root -g root -m 755
6640 INSTALL_SCRIPT = $(INSTALL) -p -o root -g root -m 755
6641 INSTALL_DIR = $(INSTALL) -p -d -o root -g root -m 755
6643 ifneq (,$(findstring noopt,$(DEB_BUILD_OPTIONS)))
6648 ifeq (,$(findstring nostrip,$(DEB_BUILD_OPTIONS)))
6649 INSTALL_PROGRAM += -s
6655 It is up to the package maintainer to decide what
6656 compilation options are best for the package. Certain
6657 binaries (such as computationally-intensive programs) will
6658 function better with certain flags (<tt>-O3</tt>, for
6659 example); feel free to use them. Please use good judgment
6660 here. Don't use flags for the sake of it; only use them
6661 if there is good reason to do so. Feel free to override
6662 the upstream author's ideas about which compilation
6663 options are best: they are often inappropriate for our
6669 <sect id="libraries">
6670 <heading>Libraries</heading>
6673 If the package is <strong>architecture: any</strong>, then
6674 the shared library compilation and linking flags must have
6675 <tt>-fPIC</tt>, or the package shall not build on some of
6676 the supported architectures<footnote>
6678 If you are using GCC, <tt>-fPIC</tt> produces code with
6679 relocatable position independent code, which is required for
6680 most architectures to create a shared library, with i386 and
6681 perhaps some others where non position independent code is
6682 permitted in a shared library.
6685 Position independent code may have a performance penalty,
6686 especially on <tt>i386</tt>. However, in most cases the
6687 speed penalty must be measured against the memory wasted on
6688 the few architectures where non position independent code is
6691 </footnote>. Any exception to this rule must be discussed on
6692 the mailing list <em>debian-devel@lists.debian.org</em>, and
6693 a rough consensus obtained. The reasons for not compiling
6694 with <tt>-fPIC</tt> flag must be recorded in the file
6695 <tt>README.Debian</tt>, and care must be taken to either
6696 restrict the architecture or arrange for <tt>-fPIC</tt> to
6697 be used on architectures where it is required.<footnote>
6699 Some of the reasons why this might be required is if the
6700 library contains hand crafted assembly code that is not
6701 relocatable, the speed penalty is excessive for compute
6702 intensive libs, and similar reasons.
6707 As to the static libraries, the common case is not to have
6708 relocatable code, since there is no benefit, unless in specific
6709 cases; therefore the static version must not be compiled
6710 with the <tt>-fPIC</tt> flag. Any exception to this rule
6711 should be discussed on the mailing list
6712 <em>debian-devel@lists.debian.org</em>, and the reasons for
6713 compiling with the <tt>-fPIC</tt> flag must be recorded in
6714 the file <tt>README.Debian</tt>. <footnote>
6716 Some of the reasons for linking static libraries with
6717 the <tt>-fPIC</tt> flag are if, for example, one needs a
6718 Perl API for a library that is under rapid development,
6719 and has an unstable API, so shared libraries are
6720 pointless at this phase of the library's development. In
6721 that case, since Perl needs a library with relocatable
6722 code, it may make sense to create a static library with
6723 relocatable code. Another reason cited is if you are
6724 distilling various libraries into a common shared
6725 library, like <tt>mklibs</tt> does in the Debian
6731 In other words, if both a shared and a static library is
6732 being built, each source unit (<tt>*.c</tt>, for example,
6733 for C files) will need to be compiled twice, for the normal
6737 You must specify the gcc option <tt>-D_REENTRANT</tt>
6738 when building a library (either static or shared) to make
6739 the library compatible with LinuxThreads.
6743 Although not enforced by the build tools, shared libraries
6744 must be linked against all libraries that they use symbols from
6745 in the same way that binaries are. This ensures the correct
6746 functioning of the <qref id="sharedlibs-shlibdeps">shlibs</qref>
6747 system and guarantees that all libraries can be safely opened
6748 with <tt>dlopen()</tt>. Packagers may wish to use the gcc
6749 option <tt>-Wl,-z,defs</tt> when building a shared library.
6750 Since this option enforces symbol resolution at build time,
6751 a missing library reference will be caught early as a fatal
6756 All installed shared libraries should be stripped with
6757 <example compact="compact">
6758 strip --strip-unneeded <var>your-lib</var>
6760 (The option <tt>--strip-unneeded</tt> makes
6761 <prgn>strip</prgn> remove only the symbols which aren't
6762 needed for relocation processing.) Shared libraries can
6763 function perfectly well when stripped, since the symbols for
6764 dynamic linking are in a separate part of the ELF object
6766 You might also want to use the options
6767 <tt>--remove-section=.comment</tt> and
6768 <tt>--remove-section=.note</tt> on both shared libraries
6769 and executables, and <tt>--strip-debug</tt> on static
6775 Note that under some circumstances it may be useful to
6776 install a shared library unstripped, for example when
6777 building a separate package to support debugging.
6781 Shared object files (often <file>.so</file> files) that are not
6782 public libraries, that is, they are not meant to be linked
6783 to by third party executables (binaries of other packages),
6784 should be installed in subdirectories of the
6785 <file>/usr/lib</file> directory. Such files are exempt from the
6786 rules that govern ordinary shared libraries, except that
6787 they must not be installed executable and should be
6789 A common example are the so-called "plug-ins",
6790 internal shared objects that are dynamically loaded by
6791 programs using <manref name="dlopen" section="3">.
6796 Packages containing shared libraries that may be linked to
6797 by other packages' binaries, but which for some
6798 <em>compelling</em> reason can not be installed in
6799 <file>/usr/lib</file> directory, may install the shared library
6800 files in subdirectories of the <file>/usr/lib</file> directory,
6801 in which case they should arrange to add that directory in
6802 <file>/etc/ld.so.conf</file> in the package's post-installation
6803 script, and remove it in the package's post-removal script.
6807 An ever increasing number of packages are using
6808 <prgn>libtool</prgn> to do their linking. The latest GNU
6809 libtools (>= 1.3a) can take advantage of the metadata in the
6810 installed <prgn>libtool</prgn> archive files (<file>*.la</file>
6811 files). The main advantage of <prgn>libtool</prgn>'s
6812 <file>.la</file> files is that it allows <prgn>libtool</prgn> to
6813 store and subsequently access metadata with respect to the
6814 libraries it builds. <prgn>libtool</prgn> will search for
6815 those files, which contain a lot of useful information about
6816 a library (such as library dependency information for static
6817 linking). Also, they're <em>essential</em> for programs
6818 using <tt>libltdl</tt>.<footnote>
6819 Although <prgn>libtool</prgn> is fully capable of
6820 linking against shared libraries which don't have
6821 <tt>.la</tt> files, as it is a mere shell script it can
6822 add considerably to the build time of a
6823 <prgn>libtool</prgn>-using package if that shell script
6824 has to derive all this information from first principles
6825 for each library every time it is linked. With the
6826 advent of <prgn>libtool</prgn> version 1.4 (and to a
6827 lesser extent <prgn>libtool</prgn> version 1.3), the
6828 <file>.la</file> files also store information about
6829 inter-library dependencies which cannot necessarily be
6830 derived after the <file>.la</file> file is deleted.
6835 Packages that use <prgn>libtool</prgn> to create shared
6836 libraries should include the <file>.la</file> files in the
6837 <tt>-dev</tt> package, unless the package relies on
6838 <tt>libtool</tt>'s <tt>libltdl</tt> library, in which case
6839 the <tt>.la</tt> files must go in the run-time library
6844 You must make sure that you use only released versions of
6845 shared libraries to build your packages; otherwise other
6846 users will not be able to run your binaries
6847 properly. Producing source packages that depend on
6848 unreleased compilers is also usually a bad
6855 <heading>Shared libraries</heading>
6857 This section has moved to <ref id="sharedlibs">.
6863 <heading>Scripts</heading>
6866 All command scripts, including the package maintainer
6867 scripts inside the package and used by <prgn>dpkg</prgn>,
6868 should have a <tt>#!</tt> line naming the shell to be used
6873 In the case of Perl scripts this should be
6874 <tt>#!/usr/bin/perl</tt>.
6878 When scripts are installed into a directory in the system
6879 PATH, the script name should not include an extension such
6880 as <tt>.sh</tt> or <tt>.pl</tt> that denotes the scripting
6881 language currently used to implement it.
6884 Shell scripts (<prgn>sh</prgn> and <prgn>bash</prgn>)
6885 should almost certainly start with <tt>set -e</tt> so that
6886 errors are detected. Every script should use
6887 <tt>set -e</tt> or check the exit status of <em>every</em>
6892 Scripts may assume that <file>/bin/sh</file> implements the
6893 SUSv3 Shell Command Language<footnote>
6894 Single UNIX Specification, version 3, which is also IEEE
6895 1003.1-2004 (POSIX), and is available on the World Wide Web
6896 from <url id="http://www.unix.org/version3/online.html"
6897 name="The Open Group"> after free
6898 registration.</footnote>
6899 plus the following additional features not mandated by
6901 These features are in widespread use in the Linux community
6902 and are implemented in all of bash, dash, and ksh, the most
6903 common shells users may wish to use as <file>/bin/sh</file>.
6906 <item><tt>echo -n</tt>, if implemented as a shell built-in,
6907 must not generate a newline.</item>
6908 <item><tt>test</tt>, if implemented as a shell built-in, must
6909 support <tt>-a</tt> and <tt>-o</tt> as binary logical
6911 <item><tt>local</tt> to create a scoped variable must be
6912 supported; however, <tt>local</tt> may or may not preserve
6913 the variable value from an outer scope and may or may not
6914 support arguments more complex than simple variables. Only
6926 If a shell script requires non-SUSv3 features from the shell
6927 interpreter other than those listed above, the appropriate shell
6928 must be specified in the first line of the script (e.g.,
6929 <tt>#!/bin/bash</tt>) and the package must depend on the package
6930 providing the shell (unless the shell package is marked
6931 "Essential", as in the case of <prgn>bash</prgn>).
6935 You may wish to restrict your script to SUSv3 features plus the
6936 above set when possible so that it may use <file>/bin/sh</file>
6937 as its interpreter. If your script works with <prgn>dash</prgn>
6938 (originally called <prgn>ash</prgn>), it probably complies with
6939 the above requirements, but if you are in doubt, use
6940 <file>/bin/bash</file>.
6944 Perl scripts should check for errors when making any
6945 system calls, including <tt>open</tt>, <tt>print</tt>,
6946 <tt>close</tt>, <tt>rename</tt> and <tt>system</tt>.
6950 <prgn>csh</prgn> and <prgn>tcsh</prgn> should be avoided as
6951 scripting languages. See <em>Csh Programming Considered
6952 Harmful</em>, one of the <tt>comp.unix.*</tt> FAQs, which
6953 can be found at <url id="http://www.faqs.org/faqs/unix-faq/shell/csh-whynot/">.
6954 If an upstream package comes with <prgn>csh</prgn> scripts
6955 then you must make sure that they start with
6956 <tt>#!/bin/csh</tt> and make your package depend on the
6957 <prgn>c-shell</prgn> virtual package.
6961 Any scripts which create files in world-writeable
6962 directories (e.g., in <file>/tmp</file>) must use a
6963 mechanism which will fail atomically if a file with the same
6964 name already exists.
6968 The Debian base system provides the <prgn>tempfile</prgn>
6969 and <prgn>mktemp</prgn> utilities for use by scripts for
6976 <heading>Symbolic links</heading>
6979 In general, symbolic links within a top-level directory
6980 should be relative, and symbolic links pointing from one
6981 top-level directory into another should be absolute. (A
6982 top-level directory is a sub-directory of the root
6983 directory <file>/</file>.)
6987 In addition, symbolic links should be specified as short as
6988 possible, i.e., link targets like <file>foo/../bar</file> are
6993 Note that when creating a relative link using
6994 <prgn>ln</prgn> it is not necessary for the target of the
6995 link to exist relative to the working directory you're
6996 running <prgn>ln</prgn> from, nor is it necessary to change
6997 directory to the directory where the link is to be made.
6998 Simply include the string that should appear as the target
6999 of the link (this will be a pathname relative to the
7000 directory in which the link resides) as the first argument
7005 For example, in your <prgn>Makefile</prgn> or
7006 <file>debian/rules</file>, you can do things like:
7007 <example compact="compact">
7008 ln -fs gcc $(prefix)/bin/cc
7009 ln -fs gcc debian/tmp/usr/bin/cc
7010 ln -fs ../sbin/sendmail $(prefix)/bin/runq
7011 ln -fs ../sbin/sendmail debian/tmp/usr/bin/runq
7016 A symbolic link pointing to a compressed file should always
7017 have the same file extension as the referenced file. (For
7018 example, if a file <file>foo.gz</file> is referenced by a
7019 symbolic link, the filename of the link has to end with
7020 "<file>.gz</file>" too, as in <file>bar.gz</file>.)
7025 <heading>Device files</heading>
7028 Packages must not include device files in the package file
7033 If a package needs any special device files that are not
7034 included in the base system, it must call
7035 <prgn>MAKEDEV</prgn> in the <prgn>postinst</prgn> script,
7036 after notifying the user<footnote>
7037 This notification could be done via a (low-priority)
7038 debconf message, or an echo (printf) statement.
7043 Packages must not remove any device files in the
7044 <prgn>postrm</prgn> or any other script. This is left to the
7045 system administrator.
7049 Debian uses the serial devices
7050 <file>/dev/ttyS*</file>. Programs using the old
7051 <file>/dev/cu*</file> devices should be changed to use
7052 <file>/dev/ttyS*</file>.
7056 <sect id="config-files">
7057 <heading>Configuration files</heading>
7060 <heading>Definitions</heading>
7064 <tag>configuration file</tag>
7066 A file that affects the operation of a program, or
7067 provides site- or host-specific information, or
7068 otherwise customizes the behavior of a program.
7069 Typically, configuration files are intended to be
7070 modified by the system administrator (if needed or
7071 desired) to conform to local policy or to provide
7072 more useful site-specific behavior.
7075 <tag><tt>conffile</tt></tag>
7077 A file listed in a package's <tt>conffiles</tt>
7078 file, and is treated specially by <prgn>dpkg</prgn>
7079 (see <ref id="configdetails">).
7085 The distinction between these two is important; they are
7086 not interchangeable concepts. Almost all
7087 <tt>conffile</tt>s are configuration files, but many
7088 configuration files are not <tt>conffiles</tt>.
7092 Note that a script that embeds configuration information
7093 (such as most of the files in <file>/etc/default</file> and
7094 <file>/etc/cron.{daily,weekly,monthly}</file>) is de-facto a
7095 configuration file and should be treated as such.
7100 <heading>Location</heading>
7103 Any configuration files created or used by your package
7104 must reside in <file>/etc</file>. If there are several,
7105 consider creating a subdirectory of <file>/etc</file>
7106 named after your package.
7110 If your package creates or uses configuration files
7111 outside of <file>/etc</file>, and it is not feasible to modify
7112 the package to use <file>/etc</file> directly, put the files
7113 in <file>/etc</file> and create symbolic links to those files
7114 from the location that the package requires.
7119 <heading>Behavior</heading>
7122 Configuration file handling must conform to the following
7124 <list compact="compact">
7126 local changes must be preserved during a package
7130 configuration files must be preserved when the
7131 package is removed, and only deleted when the
7138 The easy way to achieve this behavior is to make the
7139 configuration file a <tt>conffile</tt>. This is
7140 appropriate only if it is possible to distribute a default
7141 version that will work for most installations, although
7142 some system administrators may choose to modify it. This
7143 implies that the default version will be part of the
7144 package distribution, and must not be modified by the
7145 maintainer scripts during installation (or at any other
7150 In order to ensure that local changes are preserved
7151 correctly, no package may contain or make hard links to
7152 conffiles.<footnote>
7153 Rationale: There are two problems with hard links.
7154 The first is that some editors break the link while
7155 editing one of the files, so that the two files may
7156 unwittingly become unlinked and different. The second
7157 is that <prgn>dpkg</prgn> might break the hard link
7158 while upgrading <tt>conffile</tt>s.
7163 The other way to do it is via the maintainer scripts. In
7164 this case, the configuration file must not be listed as a
7165 <tt>conffile</tt> and must not be part of the package
7166 distribution. If the existence of a file is required for
7167 the package to be sensibly configured it is the
7168 responsibility of the package maintainer to provide
7169 maintainer scripts which correctly create, update and
7170 maintain the file and remove it on purge. (See <ref
7171 id="maintainerscripts"> for more information.) These
7172 scripts must be idempotent (i.e., must work correctly if
7173 <prgn>dpkg</prgn> needs to re-run them due to errors
7174 during installation or removal), must cope with all the
7175 variety of ways <prgn>dpkg</prgn> can call maintainer
7176 scripts, must not overwrite or otherwise mangle the user's
7177 configuration without asking, must not ask unnecessary
7178 questions (particularly during upgrades), and must
7179 otherwise be good citizens.
7183 The scripts are not required to configure every possible
7184 option for the package, but only those necessary to get
7185 the package running on a given system. Ideally the
7186 sysadmin should not have to do any configuration other
7187 than that done (semi-)automatically by the
7188 <prgn>postinst</prgn> script.
7192 A common practice is to create a script called
7193 <file><var>package</var>-configure</file> and have the
7194 package's <prgn>postinst</prgn> call it if and only if the
7195 configuration file does not already exist. In certain
7196 cases it is useful for there to be an example or template
7197 file which the maintainer scripts use. Such files should
7198 be in <file>/usr/share/<var>package</var></file> or
7199 <file>/usr/lib/<var>package</var></file> (depending on whether
7200 they are architecture-independent or not). There should
7201 be symbolic links to them from
7202 <file>/usr/share/doc/<var>package</var>/examples</file> if
7203 they are examples, and should be perfectly ordinary
7204 <prgn>dpkg</prgn>-handled files (<em>not</em>
7205 configuration files).
7209 These two styles of configuration file handling must
7210 not be mixed, for that way lies madness:
7211 <prgn>dpkg</prgn> will ask about overwriting the file
7212 every time the package is upgraded.
7217 <heading>Sharing configuration files</heading>
7220 Packages which specify the same file as a
7221 <tt>conffile</tt> must be tagged as <em>conflicting</em>
7222 with each other. (This is an instance of the general rule
7223 about not sharing files. Note that neither alternatives
7224 nor diversions are likely to be appropriate in this case;
7225 in particular, <prgn>dpkg</prgn> does not handle diverted
7226 <tt>conffile</tt>s well.)
7230 The maintainer scripts must not alter a <tt>conffile</tt>
7231 of <em>any</em> package, including the one the scripts
7236 If two or more packages use the same configuration file
7237 and it is reasonable for both to be installed at the same
7238 time, one of these packages must be defined as
7239 <em>owner</em> of the configuration file, i.e., it will be
7240 the package which handles that file as a configuration
7241 file. Other packages that use the configuration file must
7242 depend on the owning package if they require the
7243 configuration file to operate. If the other package will
7244 use the configuration file if present, but is capable of
7245 operating without it, no dependency need be declared.
7249 If it is desirable for two or more related packages to
7250 share a configuration file <em>and</em> for all of the
7251 related packages to be able to modify that configuration
7252 file, then the following should be done:
7253 <enumlist compact="compact">
7255 One of the related packages (the "owning" package)
7256 will manage the configuration file with maintainer
7257 scripts as described in the previous section.
7260 The owning package should also provide a program
7261 that the other packages may use to modify the
7265 The related packages must use the provided program
7266 to make any desired modifications to the
7267 configuration file. They should either depend on
7268 the core package to guarantee that the configuration
7269 modifier program is available or accept gracefully
7270 that they cannot modify the configuration file if it
7271 is not. (This is in addition to the fact that the
7272 configuration file may not even be present in the
7279 Sometimes it's appropriate to create a new package which
7280 provides the basic infrastructure for the other packages
7281 and which manages the shared configuration files. (The
7282 <tt>sgml-base</tt> package is a good example.)
7287 <heading>User configuration files ("dotfiles")</heading>
7290 The files in <file>/etc/skel</file> will automatically be
7291 copied into new user accounts by <prgn>adduser</prgn>.
7292 No other program should reference the files in
7293 <file>/etc/skel</file>.
7297 Therefore, if a program needs a dotfile to exist in
7298 advance in <file>$HOME</file> to work sensibly, that dotfile
7299 should be installed in <file>/etc/skel</file> and treated as a
7304 However, programs that require dotfiles in order to
7305 operate sensibly are a bad thing, unless they do create
7306 the dotfiles themselves automatically.
7310 Furthermore, programs should be configured by the Debian
7311 default installation to behave as closely to the upstream
7312 default behavior as possible.
7316 Therefore, if a program in a Debian package needs to be
7317 configured in some way in order to operate sensibly, that
7318 should be done using a site-wide configuration file placed
7319 in <file>/etc</file>. Only if the program doesn't support a
7320 site-wide default configuration and the package maintainer
7321 doesn't have time to add it may a default per-user file be
7322 placed in <file>/etc/skel</file>.
7326 <file>/etc/skel</file> should be as empty as we can make it.
7327 This is particularly true because there is no easy (or
7328 necessarily desirable) mechanism for ensuring that the
7329 appropriate dotfiles are copied into the accounts of
7330 existing users when a package is installed.
7336 <heading>Log files</heading>
7338 Log files should usually be named
7339 <file>/var/log/<var>package</var>.log</file>. If you have many
7340 log files, or need a separate directory for permission
7341 reasons (<file>/var/log</file> is writable only by
7342 <file>root</file>), you should usually create a directory named
7343 <file>/var/log/<var>package</var></file> and place your log
7348 Log files must be rotated occasionally so that they don't
7349 grow indefinitely; the best way to do this is to drop a log
7350 rotation configuration file into the directory
7351 <file>/etc/logrotate.d</file> and use the facilities provided by
7352 logrotate.<footnote>
7354 The traditional approach to log files has been to set up
7355 <em>ad hoc</em> log rotation schemes using simple shell
7356 scripts and cron. While this approach is highly
7357 customizable, it requires quite a lot of sysadmin work.
7358 Even though the original Debian system helped a little
7359 by automatically installing a system which can be used
7360 as a template, this was deemed not enough.
7364 The use of <prgn>logrotate</prgn>, a program developed
7365 by Red Hat, is better, as it centralizes log management.
7366 It has both a configuration file
7367 (<file>/etc/logrotate.conf</file>) and a directory where
7368 packages can drop their individual log rotation
7369 configurations (<file>/etc/logrotate.d</file>).
7372 Here is a good example for a logrotate config
7373 file (for more information see <manref name="logrotate"
7375 <example compact="compact">
7376 /var/log/foo/*.log {
7381 /etc/init.d/foo force-reload
7385 This rotates all files under <file>/var/log/foo</file>, saves 12
7386 compressed generations, and forces the daemon to reload its
7387 configuration information after the log rotation.
7391 Log files should be removed when the package is
7392 purged (but not when it is only removed). This should be
7393 done by the <prgn>postrm</prgn> script when it is called
7394 with the argument <tt>purge</tt> (see <ref
7395 id="removedetails">).
7400 <heading>Permissions and owners</heading>
7403 The rules in this section are guidelines for general use.
7404 If necessary you may deviate from the details below.
7405 However, if you do so you must make sure that what is done
7406 is secure and you should try to be as consistent as possible
7407 with the rest of the system. You should probably also
7408 discuss it on <prgn>debian-devel</prgn> first.
7412 Files should be owned by <tt>root.root</tt>, and made
7413 writable only by the owner and universally readable (and
7414 executable, if appropriate), that is mode 644 or 755.
7418 Directories should be mode 755 or (for group-writability)
7419 mode 2775. The ownership of the directory should be
7420 consistent with its mode: if a directory is mode 2775, it
7421 should be owned by the group that needs write access to
7424 When a package is upgraded, and the owner or permissions
7425 of a file included in the package has changed, dpkg
7426 arranges for the ownership and permissions to be
7427 correctly set upon installation. However, this does not
7428 extend to directories; the permissions and ownership of
7429 directories already on the system does not change on
7430 install or upgrade of packages. This makes sense, since
7431 otherwise common directories like <tt>/usr</tt> would
7432 always be in flux. To correctly change permissions of a
7433 directory the package owns, explicit action is required,
7434 usually in the <tt>postinst</tt> script. Care must be
7435 taken to handle downgrades as well, in that case.
7442 Setuid and setgid executables should be mode 4755 or 2755
7443 respectively, and owned by the appropriate user or group.
7444 They should not be made unreadable (modes like 4711 or
7445 2711 or even 4111); doing so achieves no extra security,
7446 because anyone can find the binary in the freely available
7447 Debian package; it is merely inconvenient. For the same
7448 reason you should not restrict read or execute permissions
7449 on non-set-id executables.
7453 Some setuid programs need to be restricted to particular
7454 sets of users, using file permissions. In this case they
7455 should be owned by the uid to which they are set-id, and by
7456 the group which should be allowed to execute them. They
7457 should have mode 4754; again there is no point in making
7458 them unreadable to those users who must not be allowed to
7463 It is possible to arrange that the system administrator can
7464 reconfigure the package to correspond to their local
7465 security policy by changing the permissions on a binary:
7466 they can do this by using <prgn>dpkg-statoverride</prgn>, as
7467 described below.<footnote>
7468 Ordinary files installed by <prgn>dpkg</prgn> (as
7469 opposed to <tt>conffile</tt>s and other similar objects)
7470 normally have their permissions reset to the distributed
7471 permissions when the package is reinstalled. However,
7472 the use of <prgn>dpkg-statoverride</prgn> overrides this
7473 default behavior. If you use this method, you should
7474 remember to describe <prgn>dpkg-statoverride</prgn> in
7475 the package documentation; being a relatively new
7476 addition to Debian, it is probably not yet well-known.
7478 Another method you should consider is to create a group for
7479 people allowed to use the program(s) and make any setuid
7480 executables executable only by that group.
7484 If you need to create a new user or group for your package
7485 there are two possibilities. Firstly, you may need to
7486 make some files in the binary package be owned by this
7487 user or group, or you may need to compile the user or
7488 group id (rather than just the name) into the binary
7489 (though this latter should be avoided if possible, as in
7490 this case you need a statically allocated id).</p>
7493 If you need a statically allocated id, you must ask for a
7494 user or group id from the <tt>base-passwd</tt> maintainer,
7495 and must not release the package until you have been
7496 allocated one. Once you have been allocated one you must
7497 either make the package depend on a version of the
7498 <tt>base-passwd</tt> package with the id present in
7499 <file>/etc/passwd</file> or <file>/etc/group</file>, or arrange for
7500 your package to create the user or group itself with the
7501 correct id (using <tt>adduser</tt>) in its
7502 <prgn>preinst</prgn> or <prgn>postinst</prgn>. (Doing it in
7503 the <prgn>postinst</prgn> is to be preferred if it is
7504 possible, otherwise a pre-dependency will be needed on the
7505 <tt>adduser</tt> package.)
7509 On the other hand, the program might be able to determine
7510 the uid or gid from the user or group name at runtime, so
7511 that a dynamically allocated id can be used. In this case
7512 you should choose an appropriate user or group name,
7513 discussing this on <prgn>debian-devel</prgn> and checking
7514 with the <package/base-passwd/ maintainer that it is unique and that
7515 they do not wish you to use a statically allocated id
7516 instead. When this has been checked you must arrange for
7517 your package to create the user or group if necessary using
7518 <prgn>adduser</prgn> in the <prgn>preinst</prgn> or
7519 <prgn>postinst</prgn> script (again, the latter is to be
7520 preferred if it is possible).
7524 Note that changing the numeric value of an id associated
7525 with a name is very difficult, and involves searching the
7526 file system for all appropriate files. You need to think
7527 carefully whether a static or dynamic id is required, since
7528 changing your mind later will cause problems.
7531 <sect1><heading>The use of <prgn>dpkg-statoverride</prgn></heading>
7533 This section is not intended as policy, but as a
7534 description of the use of <prgn>dpkg-statoverride</prgn>.
7538 If a system administrator wishes to have a file (or
7539 directory or other such thing) installed with owner and
7540 permissions different from those in the distributed Debian
7541 package, they can use the <prgn>dpkg-statoverride</prgn>
7542 program to instruct <prgn>dpkg</prgn> to use the different
7543 settings every time the file is installed. Thus the
7544 package maintainer should distribute the files with their
7545 normal permissions, and leave it for the system
7546 administrator to make any desired changes. For example, a
7547 daemon which is normally required to be setuid root, but
7548 in certain situations could be used without being setuid,
7549 should be installed setuid in the <tt>.deb</tt>. Then the
7550 local system administrator can change this if they wish.
7551 If there are two standard ways of doing it, the package
7552 maintainer can use <tt>debconf</tt> to find out the
7553 preference, and call <prgn>dpkg-statoverride</prgn> in the
7554 maintainer script if necessary to accommodate the system
7555 administrator's choice. Care must be taken during
7556 upgrades to not override an existing setting.
7560 Given the above, <prgn>dpkg-statoverride</prgn> is
7561 essentially a tool for system administrators and would not
7562 normally be needed in the maintainer scripts. There is
7563 one type of situation, though, where calls to
7564 <prgn>dpkg-statoverride</prgn> would be needed in the
7565 maintainer scripts, and that involves packages which use
7566 dynamically allocated user or group ids. In such a
7567 situation, something like the following idiom can be very
7568 helpful in the package's <prgn>postinst</prgn>, where
7569 <tt>sysuser</tt> is a dynamically allocated id:
7571 for i in /usr/bin/foo /usr/sbin/bar
7573 # only do something when no setting exists
7574 if ! dpkg-statoverride --list $i >/dev/null 2>&1
7576 #include: debconf processing, question about foo and bar
7577 if [ "$RET" = "true" ] ; then
7578 dpkg-statoverride --update --add sysuser root 4755 $i
7583 The corresponding <tt>dpkg-statoverride --remove</tt>
7584 calls can then be made unconditionally when the package is
7592 <chapt id="customized-programs">
7593 <heading>Customized programs</heading>
7595 <sect id="arch-spec">
7596 <heading>Architecture specification strings</heading>
7599 If a program needs to specify an <em>architecture specification
7600 string</em> in some place, it should select one of the
7601 strings provided by <tt>dpkg-architecture -L</tt>. The
7602 strings are in the format
7603 <tt><var>os</var>-<var>arch</var></tt>, though the OS part
7604 is sometimes elided, as when the OS is Linux.<footnote>
7605 <p>Currently, the strings are:
7606 i386 ia64 alpha amd64 armeb arm hppa m32r m68k mips
7607 mipsel powerpc ppc64 s390 s390x sh3 sh3eb sh4 sh4eb
7608 sparc darwin-i386 darwin-ia64 darwin-alpha darwin-amd64
7609 darwin-armeb darwin-arm darwin-hppa darwin-m32r
7610 darwin-m68k darwin-mips darwin-mipsel darwin-powerpc
7611 darwin-ppc64 darwin-s390 darwin-s390x darwin-sh3
7612 darwin-sh3eb darwin-sh4 darwin-sh4eb darwin-sparc
7613 freebsd-i386 freebsd-ia64 freebsd-alpha freebsd-amd64
7614 freebsd-armeb freebsd-arm freebsd-hppa freebsd-m32r
7615 freebsd-m68k freebsd-mips freebsd-mipsel freebsd-powerpc
7616 freebsd-ppc64 freebsd-s390 freebsd-s390x freebsd-sh3
7617 freebsd-sh3eb freebsd-sh4 freebsd-sh4eb freebsd-sparc
7618 kfreebsd-i386 kfreebsd-ia64 kfreebsd-alpha
7619 kfreebsd-amd64 kfreebsd-armeb kfreebsd-arm kfreebsd-hppa
7620 kfreebsd-m32r kfreebsd-m68k kfreebsd-mips
7621 kfreebsd-mipsel kfreebsd-powerpc kfreebsd-ppc64
7622 kfreebsd-s390 kfreebsd-s390x kfreebsd-sh3 kfreebsd-sh3eb
7623 kfreebsd-sh4 kfreebsd-sh4eb kfreebsd-sparc knetbsd-i386
7624 knetbsd-ia64 knetbsd-alpha knetbsd-amd64 knetbsd-armeb
7625 knetbsd-arm knetbsd-hppa knetbsd-m32r knetbsd-m68k
7626 knetbsd-mips knetbsd-mipsel knetbsd-powerpc
7627 knetbsd-ppc64 knetbsd-s390 knetbsd-s390x knetbsd-sh3
7628 knetbsd-sh3eb knetbsd-sh4 knetbsd-sh4eb knetbsd-sparc
7629 netbsd-i386 netbsd-ia64 netbsd-alpha netbsd-amd64
7630 netbsd-armeb netbsd-arm netbsd-hppa netbsd-m32r
7631 netbsd-m68k netbsd-mips netbsd-mipsel netbsd-powerpc
7632 netbsd-ppc64 netbsd-s390 netbsd-s390x netbsd-sh3
7633 netbsd-sh3eb netbsd-sh4 netbsd-sh4eb netbsd-sparc
7634 openbsd-i386 openbsd-ia64 openbsd-alpha openbsd-amd64
7635 openbsd-armeb openbsd-arm openbsd-hppa openbsd-m32r
7636 openbsd-m68k openbsd-mips openbsd-mipsel openbsd-powerpc
7637 openbsd-ppc64 openbsd-s390 openbsd-s390x openbsd-sh3
7638 openbsd-sh3eb openbsd-sh4 openbsd-sh4eb openbsd-sparc
7639 hurd-i386 hurd-ia64 hurd-alpha hurd-amd64 hurd-armeb
7640 hurd-arm hurd-hppa hurd-m32r hurd-m68k hurd-mips
7641 hurd-mipsel hurd-powerpc hurd-ppc64 hurd-s390 hurd-s390x
7642 hurd-sh3 hurd-sh3eb hurd-sh4 hurd-sh4eb hurd-sparc
7648 Note that we don't want to use
7649 <tt><var>arch</var>-debian-linux</tt> to apply to the rule
7650 <tt><var>architecture</var>-<var>vendor</var>-<var>os</var></tt>
7651 since this would make our programs incompatible with other
7652 Linux distributions. We also don't use something like
7653 <tt><var>arch</var>-unknown-linux</tt>, since the
7654 <tt>unknown</tt> does not look very good.
7659 <heading>Daemons</heading>
7662 The configuration files <file>/etc/services</file>,
7663 <file>/etc/protocols</file>, and <file>/etc/rpc</file> are managed
7664 by the <prgn>netbase</prgn> package and must not be modified
7669 If a package requires a new entry in one of these files, the
7670 maintainer should get in contact with the
7671 <prgn>netbase</prgn> maintainer, who will add the entries
7672 and release a new version of the <prgn>netbase</prgn>
7677 The configuration file <file>/etc/inetd.conf</file> must not be
7678 modified by the package's scripts except via the
7679 <prgn>update-inetd</prgn> script or the
7680 <file>DebianNet.pm</file> Perl module. See their documentation
7681 for details on how to add entries.
7685 If a package wants to install an example entry into
7686 <file>/etc/inetd.conf</file>, the entry must be preceded with
7687 exactly one hash character (<tt>#</tt>). Such lines are
7688 treated as "commented out by user" by the
7689 <prgn>update-inetd</prgn> script and are not changed or
7690 activated during package updates.
7695 <heading>Using pseudo-ttys and modifying wtmp, utmp and
7699 Some programs need to create pseudo-ttys. This should be done
7700 using Unix98 ptys if the C library supports it. The resulting
7701 program must not be installed setuid root, unless that
7702 is required for other functionality.
7706 The files <file>/var/run/utmp</file>, <file>/var/log/wtmp</file> and
7707 <file>/var/log/lastlog</file> must be installed writable by
7708 group <tt>utmp</tt>. Programs which need to modify those
7709 files must be installed setgid <tt>utmp</tt>.
7714 <heading>Editors and pagers</heading>
7717 Some programs have the ability to launch an editor or pager
7718 program to edit or display a text document. Since there are
7719 lots of different editors and pagers available in the Debian
7720 distribution, the system administrator and each user should
7721 have the possibility to choose their preferred editor and
7726 In addition, every program should choose a good default
7727 editor/pager if none is selected by the user or system
7732 Thus, every program that launches an editor or pager must
7733 use the EDITOR or PAGER environment variable to determine
7734 the editor or pager the user wishes to use. If these
7735 variables are not set, the programs <file>/usr/bin/editor</file>
7736 and <file>/usr/bin/pager</file> should be used, respectively.
7740 These two files are managed through the <prgn>dpkg</prgn>
7741 "alternatives" mechanism. Thus every package providing an
7742 editor or pager must call the
7743 <prgn>update-alternatives</prgn> script to register these
7748 If it is very hard to adapt a program to make use of the
7749 EDITOR or PAGER variables, that program may be configured to
7750 use <file>/usr/bin/sensible-editor</file> and
7751 <file>/usr/bin/sensible-pager</file> as the editor or pager
7752 program respectively. These are two scripts provided in the
7753 Debian base system that check the EDITOR and PAGER variables
7754 and launch the appropriate program, and fall back to
7755 <file>/usr/bin/editor</file> and <file>/usr/bin/pager</file> if the
7756 variable is not set.
7760 A program may also use the VISUAL environment variable to
7761 determine the user's choice of editor. If it exists, it
7762 should take precedence over EDITOR. This is in fact what
7763 <file>/usr/bin/sensible-editor</file> does.
7767 It is not required for a package to depend on
7768 <tt>editor</tt> and <tt>pager</tt>, nor is it required for a
7769 package to provide such virtual packages.<footnote>
7770 The Debian base system already provides an editor and a
7776 <sect id="web-appl">
7777 <heading>Web servers and applications</heading>
7780 This section describes the locations and URLs that should
7781 be used by all web servers and web applications in the
7788 Cgi-bin executable files are installed in the
7790 <example compact="compact">
7791 /usr/lib/cgi-bin/<var>cgi-bin-name</var>
7793 and should be referred to as
7794 <example compact="compact">
7795 http://localhost/cgi-bin/<var>cgi-bin-name</var>
7801 <p>Access to HTML documents</p>
7804 HTML documents for a package are stored in
7805 <file>/usr/share/doc/<var>package</var></file>
7806 and can be referred to as
7807 <example compact="compact">
7808 http://localhost/doc/<var>package</var>/<var>filename</var>
7813 The web server should restrict access to the document
7814 tree so that only clients on the same host can read
7815 the documents. If the web server does not support such
7816 access controls, then it should not provide access at
7817 all, or ask about providing access during installation.
7822 <p>Access to images</p>
7824 It is recommended that images for a package be stored
7825 in <tt>/usr/share/images/<var>package</var></tt> and
7826 may be referred to through an alias <tt>/images/</tt>
7829 http://localhost/images/<package>/<filename>
7836 <p>Web Document Root</p>
7839 Web Applications should try to avoid storing files in
7840 the Web Document Root. Instead they should use the
7841 /usr/share/doc/<var>package</var> directory for
7842 documents and register the Web Application via the
7843 <package>doc-base</package> package. If access to the
7844 web document root is unavoidable then use
7845 <example compact="compact">
7848 as the Document Root. This might be just a symbolic
7849 link to the location where the system administrator
7850 has put the real document root.
7853 <item><p>Providing httpd and/or httpd-cgi</p>
7855 All web servers should provide the virtual package
7856 <tt>httpd</tt>. If a web server has CGI support it should
7857 provide <tt>httpd-cgi</tt> additionally.
7860 All web applications which do not contain CGI scripts should
7861 depend on <tt>httpd</tt>, all those web applications which
7862 <tt>do</tt> contain CGI scripts, should depend on
7870 <sect id="mail-transport-agents">
7871 <heading>Mail transport, delivery and user agents</heading>
7874 Debian packages which process electronic mail, whether mail
7875 user agents (MUAs) or mail transport agents (MTAs), must
7876 ensure that they are compatible with the configuration
7877 decisions below. Failure to do this may result in lost
7878 mail, broken <tt>From:</tt> lines, and other serious brain
7883 The mail spool is <file>/var/mail</file> and the interface to
7884 send a mail message is <file>/usr/sbin/sendmail</file> (as per
7885 the FHS). On older systems, the mail spool may be
7886 physically located in <file>/var/spool/mail</file>, but all
7887 access to the mail spool should be via the
7888 <file>/var/mail</file> symlink. The mail spool is part of the
7889 base system and not part of the MTA package.
7893 All Debian MUAs, MTAs, MDAs and other mailbox accessing
7894 programs (such as IMAP daemons) must lock the mailbox in an
7895 NFS-safe way. This means that <tt>fcntl()</tt> locking must
7896 be combined with dot locking. To avoid deadlocks, a program
7897 should use <tt>fcntl()</tt> first and dot locking after
7898 this, or alternatively implement the two locking methods in
7899 a non blocking way<footnote>
7900 If it is not possible to establish both locks, the
7901 system shouldn't wait for the second lock to be
7902 established, but remove the first lock, wait a (random)
7903 time, and start over locking again.
7904 </footnote>. Using the functions <tt>maillock</tt> and
7905 <tt>mailunlock</tt> provided by the
7906 <tt>liblockfile*</tt><footnote>
7907 You will need to depend on <tt>liblockfile1 (>>1.01)</tt>
7908 to use these functions.
7909 </footnote> packages is the recommended way to realize this.
7913 Mailboxes are generally mode 660
7914 <tt><var>user</var>.mail</tt> unless the system
7915 administrator has chosen otherwise. A MUA may remove a
7916 mailbox (unless it has nonstandard permissions) in which
7917 case the MTA or another MUA must recreate it if needed.
7918 Mailboxes must be writable by group mail.
7922 The mail spool is 2775 <tt>root.mail</tt>, and MUAs should
7923 be setgid mail to do the locking mentioned above (and
7924 must obviously avoid accessing other users' mailboxes
7925 using this privilege).</p>
7928 <file>/etc/aliases</file> is the source file for the system mail
7929 aliases (e.g., postmaster, usenet, etc.), it is the one
7930 which the sysadmin and <prgn>postinst</prgn> scripts may
7931 edit. After <file>/etc/aliases</file> is edited the program or
7932 human editing it must call <prgn>newaliases</prgn>. All MTA
7933 packages must come with a <prgn>newaliases</prgn> program,
7934 even if it does nothing, but older MTA packages did not do
7935 this so programs should not fail if <prgn>newaliases</prgn>
7936 cannot be found. Note that because of this, all MTA
7937 packages must have <tt>Provides</tt>, <tt>Conflicts</tt> and
7938 <tt>Replaces: mail-transport-agent</tt> control file
7943 The convention of writing <tt>forward to
7944 <var>address</var></tt> in the mailbox itself is not
7945 supported. Use a <tt>.forward</tt> file instead.</p>
7948 The <prgn>rmail</prgn> program used by UUCP
7949 for incoming mail should be <file>/usr/sbin/rmail</file>.
7950 Likewise, <prgn>rsmtp</prgn>, for receiving
7951 batch-SMTP-over-UUCP, should be <file>/usr/sbin/rsmtp</file> if it
7955 If your package needs to know what hostname to use on (for
7956 example) outgoing news and mail messages which are generated
7957 locally, you should use the file <file>/etc/mailname</file>. It
7958 will contain the portion after the username and <tt>@</tt>
7959 (at) sign for email addresses of users on the machine
7960 (followed by a newline).
7964 Such a package should check for the existence of this file
7965 when it is being configured. If it exists, it should be
7966 used without comment, although an MTA's configuration script
7967 may wish to prompt the user even if it finds that this file
7968 exists. If the file does not exist, the package should
7969 prompt the user for the value (preferably using
7970 <prgn>debconf</prgn>) and store it in <file>/etc/mailname</file>
7971 as well as using it in the package's configuration. The
7972 prompt should make it clear that the name will not just be
7973 used by that package. For example, in this situation the
7974 <tt>inn</tt> package could say something like:
7975 <example compact="compact">
7976 Please enter the "mail name" of your system. This is the
7977 hostname portion of the address to be shown on outgoing
7978 news and mail messages. The default is
7979 <var>syshostname</var>, your system's host name. Mail
7980 name ["<var>syshostname</var>"]:
7982 where <var>syshostname</var> is the output of <tt>hostname
7988 <heading>News system configuration</heading>
7991 All the configuration files related to the NNTP (news)
7992 servers and clients should be located under
7993 <file>/etc/news</file>.</p>
7996 There are some configuration issues that apply to a number
7997 of news clients and server packages on the machine. These
8001 <tag><file>/etc/news/organization</file></tag>
8003 A string which should appear as the
8004 organization header for all messages posted
8005 by NNTP clients on the machine
8008 <tag><file>/etc/news/server</file></tag>
8010 Contains the FQDN of the upstream NNTP
8011 server, or localhost if the local machine is
8016 Other global files may be added as required for cross-package news
8023 <heading>Programs for the X Window System</heading>
8026 <heading>Providing X support and package priorities</heading>
8029 Programs that can be configured with support for the X
8030 Window System must be configured to do so and must declare
8031 any package dependencies necessary to satisfy their
8032 runtime requirements when using the X Window System. If
8033 such a package is of higher priority than the X packages
8034 on which it depends, it is required that either the
8035 X-specific components be split into a separate package, or
8036 that an alternative version of the package, which includes
8037 X support, be provided, or that the package's priority be
8043 <heading>Packages providing an X server</heading>
8046 Packages that provide an X server that, directly or
8047 indirectly, communicates with real input and display
8048 hardware should declare in their control data that they
8049 provide the virtual package <tt>xserver</tt>.<footnote>
8050 This implements current practice, and provides an
8051 actual policy for usage of the <tt>xserver</tt>
8052 virtual package which appears in the virtual packages
8053 list. In a nutshell, X servers that interface
8054 directly with the display and input hardware or via
8055 another subsystem (e.g., GGI) should provide
8056 <tt>xserver</tt>. Things like <tt>Xvfb</tt>,
8057 <tt>Xnest</tt>, and <tt>Xprt</tt> should not.
8063 <heading>Packages providing a terminal emulator</heading>
8066 Packages that provide a terminal emulator for the X Window
8067 System which meet the criteria listed below should declare
8068 in their control data that they provide the virtual
8069 package <tt>x-terminal-emulator</tt>. They should also
8070 register themselves as an alternative for
8071 <file>/usr/bin/x-terminal-emulator</file>, with a priority of
8076 To be an <tt>x-terminal-emulator</tt>, a program must:
8077 <list compact="compact">
8079 Be able to emulate a DEC VT100 terminal, or a
8080 compatible terminal.
8084 Support the command-line option <tt>-e
8085 <var>command</var></tt>, which creates a new
8086 terminal window<footnote>
8087 "New terminal window" does not necessarily mean
8088 a new top-level X window directly parented by
8089 the window manager; it could, if the terminal
8090 emulator application were so coded, be a new
8091 "view" in a multiple-document interface (MDI).
8093 and runs the specified <var>command</var>,
8094 interpreting the entirety of the rest of the command
8095 line as a command to pass straight to exec, in the
8096 manner that <tt>xterm</tt> does.
8100 Support the command-line option <tt>-T
8101 <var>title</var></tt>, which creates a new terminal
8102 window with the window title <var>title</var>.
8109 <heading>Packages providing a window manager</heading>
8112 Packages that provide a window manager should declare in
8113 their control data that they provide the virtual package
8114 <tt>x-window-manager</tt>. They should also register
8115 themselves as an alternative for
8116 <file>/usr/bin/x-window-manager</file>, with a priority
8117 calculated as follows:
8118 <list compact="compact">
8120 Start with a priority of 20.
8124 If the window manager supports the Debian menu
8125 system, add 20 points if this support is available
8126 in the package's default configuration (i.e., no
8127 configuration files belonging to the system or user
8128 have to be edited to activate the feature); if
8129 configuration files must be modified, add only 10
8135 If the window manager complies with <url
8136 id="http://www.freedesktop.org/Standards/wm-spec"
8137 name="The Window Manager Specification Project">,
8138 written by the <url id="http://www.freedesktop.org/"
8139 name="Free Desktop Group">, add 40 points.
8143 If the window manager permits the X session to be
8144 restarted using a <em>different</em> window manager
8145 (without killing the X server) in its default
8146 configuration, add 10 points; otherwise add none.
8153 <heading>Packages providing fonts</heading>
8156 Packages that provide fonts for the X Window
8158 For the purposes of Debian Policy, a "font for the X
8159 Window System" is one which is accessed via X protocol
8160 requests. Fonts for the Linux console, for PostScript
8161 renderer, or any other purpose, do not fit this
8162 definition. Any tool which makes such fonts available
8163 to the X Window System, however, must abide by this
8166 must do a number of things to ensure that they are both
8167 available without modification of the X or font server
8168 configuration, and that they do not corrupt files used by
8169 other font packages to register information about
8173 Fonts of any type supported by the X Window System
8174 must be in a separate binary package from any
8175 executables, libraries, or documentation (except
8176 that specific to the fonts shipped, such as their
8177 license information). If one or more of the fonts
8178 so packaged are necessary for proper operation of
8179 the package with which they are associated the font
8180 package may be Recommended; if the fonts merely
8181 provide an enhancement, a Suggests relationship may
8182 be used. Packages must not Depend on font
8184 This is because the X server may retrieve fonts
8185 from the local file system or over the network
8186 from an X font server; the Debian package system
8187 is empowered to deal only with the local
8193 BDF fonts must be converted to PCF fonts with the
8194 <prgn>bdftopcf</prgn> utility (available in the
8195 <tt>xfonts-utils</tt> package, <prgn>gzip</prgn>ped, and
8196 placed in a directory that corresponds to their
8198 <list compact="compact">
8200 100 dpi fonts must be placed in
8201 <file>/usr/share/fonts/X11/100dpi/</file>.
8205 75 dpi fonts must be placed in
8206 <file>/usr/share/fonts/X11/75dpi/</file>.
8210 Character-cell fonts, cursor fonts, and other
8211 low-resolution fonts must be placed in
8212 <file>/usr/share/fonts/X11/misc/</file>.
8218 Speedo fonts must be placed in
8219 <file>/usr/share/fonts/X11/Speedo/</file>.
8223 Type 1 fonts must be placed in
8224 <file>/usr/share/fonts/X11/Type1/</file>. If font
8225 metric files are available, they must be placed here
8230 Subdirectories of <file>/usr/share/fonts/X11/</file>
8231 other than those listed above must be neither
8232 created nor used. (The <file>PEX</file>, <file>CID</file>,
8233 and <file>cyrillic</file> directories are excepted for
8234 historical reasons, but installation of files into
8235 these directories remains discouraged.)
8239 Font packages may, instead of placing files directly
8240 in the X font directories listed above, provide
8241 symbolic links in that font directory pointing to
8242 the files' actual location in the filesystem. Such
8243 a location must comply with the FHS.
8247 Font packages should not contain both 75dpi and
8248 100dpi versions of a font. If both are available,
8249 they should be provided in separate binary packages
8250 with <tt>-75dpi</tt> or <tt>-100dpi</tt> appended to
8251 the names of the packages containing the
8252 corresponding fonts.
8256 Fonts destined for the <file>misc</file> subdirectory
8257 should not be included in the same package as 75dpi
8258 or 100dpi fonts; instead, they should be provided in
8259 a separate package with <tt>-misc</tt> appended to
8264 Font packages must not provide the files
8265 <file>fonts.dir</file>, <file>fonts.alias</file>, or
8266 <file>fonts.scale</file> in a font directory:
8269 <file>fonts.dir</file> files must not be provided at all.
8273 <file>fonts.alias</file> and <file>fonts.scale</file>
8274 files, if needed, should be provided in the
8276 <file>/etc/X11/fonts/<var>fontdir</var>/<var>package</var>.<var>extension</var></file>,
8277 where <var>fontdir</var> is the name of the
8279 <file>/usr/share/fonts/X11/</file> where the
8280 package's corresponding fonts are stored
8281 (e.g., <tt>75dpi</tt> or <tt>misc</tt>),
8282 <var>package</var> is the name of the package
8283 that provides these fonts, and
8284 <var>extension</var> is either <tt>scale</tt>
8285 or <tt>alias</tt>, whichever corresponds to
8292 Font packages must declare a dependency on
8293 <tt>xfonts-utils</tt> in their control
8298 Font packages that provide one or more
8299 <file>fonts.scale</file> files as described above must
8300 invoke <prgn>update-fonts-scale</prgn> on each
8301 directory into which they installed fonts
8302 <em>before</em> invoking
8303 <prgn>update-fonts-dir</prgn> on that directory.
8304 This invocation must occur in both the
8305 <prgn>postinst</prgn> (for all arguments) and
8306 <prgn>postrm</prgn> (for all arguments except
8307 <tt>upgrade</tt>) scripts.
8311 Font packages that provide one or more
8312 <file>fonts.alias</file> files as described above must
8313 invoke <prgn>update-fonts-alias</prgn> on each
8314 directory into which they installed fonts. This
8315 invocation must occur in both the
8316 <prgn>postinst</prgn> (for all arguments) and
8317 <prgn>postrm</prgn> (for all arguments except
8318 <tt>upgrade</tt>) scripts.
8322 Font packages must invoke
8323 <prgn>update-fonts-dir</prgn> on each directory into
8324 which they installed fonts. This invocation must
8325 occur in both the <prgn>postinst</prgn> (for all
8326 arguments) and <prgn>postrm</prgn> (for all
8327 arguments except <tt>upgrade</tt>) scripts.
8331 Font packages must not provide alias names for the
8332 fonts they include which collide with alias names
8333 already in use by fonts already packaged.
8337 Font packages must not provide fonts with the same
8338 XLFD registry name as another font already packaged.
8345 <heading>Application defaults files</heading>
8348 Application defaults files must be installed in the
8349 directory <file>/etc/X11/app-defaults/</file> (use of a
8350 localized subdirectory of <file>/etc/X11/</file> as described
8351 in the <em>X Toolkit Intrinsics - C Language
8352 Interface</em> manual is also permitted). They must be
8353 registered as <tt>conffile</tt>s or handled as
8354 configuration files. Packages must not provide the
8355 directory <file>/usr/X11R6/lib/X11/app-defaults/</file>.
8359 Customization of programs' X resources may also be
8360 supported with the provision of a file with the same name
8361 as that of the package placed in the
8362 <file>/etc/X11/Xresources/</file> directory, which must
8363 registered as a <tt>conffile</tt> or handled as a
8364 configuration file.<footnote>
8365 Note that this mechanism is not the same as using
8366 app-defaults; app-defaults are tied to the client
8367 binary on the local file system, whereas X resources
8368 are stored in the X server and affect all connecting
8371 <em>Important:</em> packages that install files into the
8372 <file>/etc/X11/Xresources/</file> directory must conflict with
8373 <tt>xbase (<< 3.3.2.3a-2)</tt>; if this is not done
8374 it is possible for the installing package to destroy a
8375 previously-existing <file>/etc/X11/Xresources</file> file
8376 which had been customized by the system administrator.
8381 <heading>Installation directory issues</heading>
8384 Packages using the X Window System should not be
8385 configured to install files under the
8386 <file>/usr/X11R6/</file> directory. The
8387 <file>/usr/X11R6/</file> directory hierarchy should be
8388 regarded as obsolete.
8392 Programs that use GNU <prgn>autoconf</prgn> and
8393 <prgn>automake</prgn> are usually easily configured at
8394 compile time to use <file>/usr/</file> instead of
8395 <file>/usr/X11R6/</file>, and this should be done whenever
8396 possible. Configuration files for window managers and
8397 display managers should be placed in a subdirectory of
8398 <file>/etc/X11/</file> corresponding to the package name due
8399 to these programs' tight integration with the mechanisms
8400 of the X Window System. Application-level programs should
8401 use the <file>/etc/</file> directory unless otherwise mandated
8406 The installation of files into subdirectories
8407 of <file>/usr/X11R6/include/X11/</file> and
8408 <file>/usr/X11R6/lib/X11/</file> is now prohibited;
8409 package maintainers should determine if subdirectories of
8410 <file>/usr/lib/</file> and <file>/usr/share/</file> can be used
8415 Packages should install any relevant files into the
8416 directories <file>/usr/include/X11/</file> and
8417 <file>/usr/lib/X11/</file>, but if they do so, they must
8418 pre-depend on <tt>x11-common (>=
8419 1:7.0.0)</tt><footnote>
8421 These libraries used to be all symbolic
8422 links. However, with <tt>X11R7</tt>,
8423 <tt>/usr/include/X11</tt> and <tt>/usr/lib/X11</tt>
8424 are now real directories, and packages
8425 <strong>should</strong> ship their files here instead
8426 of in <tt>/usr/X11R6/{include,lib}/X11</tt>.
8427 <tt>x11-common (>= 1:7.0.0) </tt> is the package
8428 responsible for converting these symlinks into
8436 <heading>The OSF/Motif and OpenMotif libraries</heading>
8439 <em>Programs that require the non-DFSG-compliant OSF/Motif or
8440 OpenMotif libraries</em><footnote>
8441 OSF/Motif and OpenMotif are collectively referred to as
8442 "Motif" in this policy document.
8444 should be compiled against and tested with LessTif (a free
8445 re-implementation of Motif) instead. If the maintainer
8446 judges that the program or programs do not work
8447 sufficiently well with LessTif to be distributed and
8448 supported, but do so when compiled against Motif, then two
8449 versions of the package should be created; one linked
8450 statically against Motif and with <tt>-smotif</tt>
8451 appended to the package name, and one linked dynamically
8452 against Motif and with <tt>-dmotif</tt> appended to the
8457 Both Motif-linked versions are dependent
8458 upon non-DFSG-compliant software and thus cannot be
8459 uploaded to the <em>main</em> distribution; if the
8460 software is itself DFSG-compliant it may be uploaded to
8461 the <em>contrib</em> distribution. While known existing
8462 versions of Motif permit unlimited redistribution of
8463 binaries linked against the library (whether statically or
8464 dynamically), it is the package maintainer's
8465 responsibility to determine whether this is permitted by
8466 the license of the copy of Motif in their possession.
8472 <heading>Perl programs and modules</heading>
8475 Perl programs and modules should follow the current Perl policy.
8479 The Perl policy can be found in the <tt>perl-policy</tt>
8480 files in the <tt>debian-policy</tt> package.
8481 It is also available from the Debian web mirrors at
8482 <tt><url name="/doc/packaging-manuals/perl-policy/"
8483 id="http://www.debian.org/doc/packaging-manuals/perl-policy/"></tt>.
8488 <heading>Emacs lisp programs</heading>
8491 Please refer to the "Debian Emacs Policy" for details of how to
8492 package emacs lisp programs.
8496 The Emacs policy is available in
8497 <file>debian-emacs-policy.gz</file> of the
8498 <package>emacsen-common</package> package.
8499 It is also available from the Debian web mirrors at
8500 <tt><url name="/doc/packaging-manuals/debian-emacs-policy"
8501 id="http://www.debian.org/doc/packaging-manuals/debian-emacs-policy"></tt>.
8506 <heading>Games</heading>
8509 The permissions on <file>/var/games</file> are mode 755, owner
8510 <tt>root</tt> and group <tt>root</tt>.
8514 Each game decides on its own security policy.</p>
8517 Games which require protected, privileged access to
8518 high-score files, saved games, etc., may be made
8519 set-<em>group</em>-id (mode 2755) and owned by
8520 <tt>root.games</tt>, and use files and directories with
8521 appropriate permissions (770 <tt>root.games</tt>, for
8522 example). They must not be made
8523 set-<em>user</em>-id, as this causes security problems. (If
8524 an attacker can subvert any set-user-id game they can
8525 overwrite the executable of any other, causing other players
8526 of these games to run a Trojan horse program. With a
8527 set-group-id game the attacker only gets access to less
8528 important game data, and if they can get at the other
8529 players' accounts at all it will take considerably more
8533 Some packages, for example some fortune cookie programs, are
8534 configured by the upstream authors to install with their
8535 data files or other static information made unreadable so
8536 that they can only be accessed through set-id programs
8537 provided. You should not do this in a Debian package: anyone can
8538 download the <file>.deb</file> file and read the data from it,
8539 so there is no point making the files unreadable. Not
8540 making the files unreadable also means that you don't have
8541 to make so many programs set-id, which reduces the risk of a
8545 As described in the FHS, binaries of games should be
8546 installed in the directory <file>/usr/games</file>. This also
8547 applies to games that use the X Window System. Manual pages
8548 for games (X and non-X games) should be installed in
8549 <file>/usr/share/man/man6</file>.</p>
8555 <heading>Documentation</heading>
8558 <heading>Manual pages</heading>
8561 You should install manual pages in <prgn>nroff</prgn> source
8562 form, in appropriate places under <file>/usr/share/man</file>.
8563 You should only use sections 1 to 9 (see the FHS for more
8564 details). You must not install a pre-formatted "cat page".
8568 Each program, utility, and function should have an
8569 associated manual page included in the same package. It is
8570 suggested that all configuration files also have a manual
8571 page included as well. Manual pages for protocols and other
8572 auxiliary things are optional.
8576 If no manual page is available, this is considered as a bug
8577 and should be reported to the Debian Bug Tracking System (the
8578 maintainer of the package is allowed to write this bug report
8579 themselves, if they so desire). Do not close the bug report
8580 until a proper man page is available.<footnote>
8581 It is not very hard to write a man page. See the
8582 <url id="http://www.schweikhardt.net/man_page_howto.html"
8583 name="Man-Page-HOWTO">,
8584 <manref name="man" section="7">, the examples
8585 created by <prgn>debmake</prgn> or <prgn>dh_make</prgn>,
8586 the helper programs <prgn>help2man</prgn>, or the
8587 directory <file>/usr/share/doc/man-db/examples</file>.
8592 You may forward a complaint about a missing man page to the
8593 upstream authors, and mark the bug as forwarded in the
8594 Debian bug tracking system. Even though the GNU Project do
8595 not in general consider the lack of a man page to be a bug,
8596 we do; if they tell you that they don't consider it a bug
8597 you should leave the bug in our bug tracking system open
8602 Manual pages should be installed compressed using <tt>gzip -9</tt>.
8606 If one man page needs to be accessible via several names it
8607 is better to use a symbolic link than the <file>.so</file>
8608 feature, but there is no need to fiddle with the relevant
8609 parts of the upstream source to change from <file>.so</file> to
8610 symlinks: don't do it unless it's easy. You should not
8611 create hard links in the manual page directories, nor put
8612 absolute filenames in <file>.so</file> directives. The filename
8613 in a <file>.so</file> in a man page should be relative to the
8614 base of the man page tree (usually
8615 <file>/usr/share/man</file>). If you do not create any links
8616 (whether symlinks, hard links, or <tt>.so</tt> directives)
8617 in the file system to the alternate names of the man page,
8618 then you should not rely on <prgn>man</prgn> finding your
8619 man page under those names based solely on the information in
8620 the man page's header.<footnote>
8621 Supporting this in <prgn>man</prgn> often requires
8622 unreasonable processing time to find a manual page or to
8623 report that none exists, and moves knowledge into man's
8624 database that would be better left in the file system.
8625 This support is therefore deprecated and will cease to
8626 be present in the future.
8631 Manual pages in locale-specific subdirectories of
8632 <file>/usr/share/man</file> should use either UTF-8 or the usual
8633 legacy encoding for that language (normally the one corresponding
8634 to the shortest relevant locale name in
8635 <file>/usr/share/i18n/SUPPORTED</file>). For example, pages under
8636 <file>/usr/share/man/fr</file> should use either UTF-8 or
8637 ISO-8859-1.<footnote>
8638 <prgn>man</prgn> will automatically detect whether UTF-8 is in
8639 use. In future, all manual pages will be required to use
8645 A country name (the <tt>DE</tt> in <tt>de_DE</tt>) should not be
8646 included in the subdirectory name unless it indicates a
8647 significant difference in the language, as this excludes
8648 speakers of the language in other countries.<footnote>
8649 At the time of writing, Chinese and Portuguese are the main
8650 languages with such differences, so <file>pt_BR</file>,
8651 <file>zh_CN</file>, and <file>zh_TW</file> are all allowed.
8656 Due to limitations in current implementations, all characters
8657 in the manual page source should be representable in the usual
8658 legacy encoding for that language, even if the file is
8659 actually encoded in UTF-8. Safe alternative ways to write many
8660 characters outside that range may be found in
8661 <manref name="groff_char" section="7">.
8666 <heading>Info documents</heading>
8669 Info documents should be installed in <file>/usr/share/info</file>.
8670 They should be compressed with <tt>gzip -9</tt>.
8674 Your package should call <prgn>install-info</prgn> to update
8675 the Info <file>dir</file> file in its <prgn>postinst</prgn>
8676 script when called with a <tt>configure</tt> argument, for
8678 <example compact="compact">
8679 install-info --quiet --section Development Development \
8680 /usr/share/info/foobar.info
8684 It is a good idea to specify a section for the location of
8685 your program; this is done with the <tt>--section</tt>
8686 switch. To determine which section to use, you should look
8687 at <file>/usr/share/info/dir</file> on your system and choose the most
8688 relevant (or create a new section if none of the current
8689 sections are relevant). Note that the <tt>--section</tt>
8690 flag takes two arguments; the first is a regular expression
8691 to match (case-insensitively) against an existing section,
8692 the second is used when creating a new one.</p>
8695 You should remove the entries in the <prgn>prerm</prgn>
8696 script when called with a <tt>remove</tt> argument:
8697 <example compact="compact">
8698 install-info --quiet --remove /usr/share/info/foobar.info
8702 If <prgn>install-info</prgn> cannot find a description entry
8703 in the Info file you must supply one. See <manref
8704 name="install-info" section="8"> for details.</p>
8708 <heading>Additional documentation</heading>
8711 Any additional documentation that comes with the package may
8712 be installed at the discretion of the package maintainer.
8713 Plain text documentation should be installed in the directory
8714 <file>/usr/share/doc/<var>package</var></file>, where
8715 <var>package</var> is the name of the package, and
8716 compressed with <tt>gzip -9</tt> unless it is small.
8720 If a package comes with large amounts of documentation which
8721 many users of the package will not require you should create
8722 a separate binary package to contain it, so that it does not
8723 take up disk space on the machines of users who do not need
8724 or want it installed.</p>
8727 It is often a good idea to put text information files
8728 (<file>README</file>s, changelogs, and so forth) that come with
8729 the source package in <file>/usr/share/doc/<var>package</var></file>
8730 in the binary package. However, you don't need to install
8731 the instructions for building and installing the package, of
8735 Packages must not require the existence of any files in
8736 <file>/usr/share/doc/</file> in order to function
8738 The system administrator should be able to
8739 delete files in <file>/usr/share/doc/</file> without causing
8740 any programs to break.
8742 Any files that are referenced by programs but are also
8743 useful as stand alone documentation should be installed under
8744 <file>/usr/share/<var>package</var>/</file> with symbolic links from
8745 <file>/usr/share/doc/<var>package</var></file>.
8749 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8750 link to another directory in <file>/usr/share/doc</file> only if
8751 the two packages both come from the same source and the
8752 first package Depends on the second.<footnote>
8754 Please note that this does not override the section on
8755 changelog files below, so the file
8756 <file>/usr/share/<var>package</var>/changelog.Debian.gz</file>
8757 must refer to the changelog for the current version of
8758 <var>package</var> in question. In practice, this means
8759 that the sources of the target and the destination of the
8760 symlink must be the same (same source package and
8767 Former Debian releases placed all additional documentation
8768 in <file>/usr/doc/<var>package</var></file>. This has been
8769 changed to <file>/usr/share/doc/<var>package</var></file>,
8770 and packages must not put documentation in the directory
8771 <file>/usr/doc/<var>package</var></file>. <footnote>
8772 At this phase of the transition, we no longer require a
8773 symbolic link in <file>/usr/doc/</file>. At a later point,
8774 policy shall change to make the symbolic links a bug.
8780 <heading>Preferred documentation formats</heading>
8783 The unification of Debian documentation is being carried out
8787 If your package comes with extensive documentation in a
8788 markup format that can be converted to various other formats
8789 you should if possible ship HTML versions in a binary
8790 package, in the directory
8791 <file>/usr/share/doc/<var>appropriate-package</var></file> or
8792 its subdirectories.<footnote>
8793 The rationale: The important thing here is that HTML
8794 docs should be available in <em>some</em> package, not
8795 necessarily in the main binary package.
8800 Other formats such as PostScript may be provided at the
8801 package maintainer's discretion.
8805 <sect id="copyrightfile">
8806 <heading>Copyright information</heading>
8809 Every package must be accompanied by a verbatim copy of its
8810 copyright and distribution license in the file
8811 <file>/usr/share/doc/<var>package</var>/copyright</file>. This
8812 file must neither be compressed nor be a symbolic link.
8816 In addition, the copyright file must say where the upstream
8817 sources (if any) were obtained. It should name the original
8818 authors of the package and the Debian maintainer(s) who were
8819 involved with its creation.</p>
8822 A copy of the file which will be installed in
8823 <file>/usr/share/doc/<var>package</var>/copyright</file> should
8824 be in <file>debian/copyright</file> in the source package.
8828 <file>/usr/share/doc/<var>package</var></file> may be a symbolic
8829 link to another directory in <file>/usr/share/doc</file> only if
8830 the two packages both come from the same source and the
8831 first package Depends on the second. These rules are
8832 important because copyrights must be extractable by
8837 Packages distributed under the UCB BSD license, the Apache
8838 license (version 2.0), the Artistic license, the GNU GPL
8839 (version 2 or 3), the GNU LGPL (versions 2, 2.1, or 3), and
8840 the GNU FDL (version 1.2) should refer to the corresponding
8841 files under <file>/usr/share/common-licenses</file>,<footnote>
8844 <file>/usr/share/common-licenses/BSD</file>,
8845 <file>/usr/share/common-licenses/Apache-2.0</file>,
8846 <file>/usr/share/common-licenses/Artistic</file>,
8847 <file>/usr/share/common-licenses/GPL-2</file>,
8848 <file>/usr/share/common-licenses/GPL-3</file>,
8849 <file>/usr/share/common-licenses/LGPL-2</file>,
8850 <file>/usr/share/common-licenses/LGPL-2.1</file>,
8851 <file>/usr/share/common-licenses/LGPL-3</file>, and
8852 <file>/usr/share/common-licenses/GFDL-1.2</file>
8855 </footnote> rather than quoting them in the copyright
8860 You should not use the copyright file as a general <file>README</file>
8861 file. If your package has such a file it should be
8862 installed in <file>/usr/share/doc/<var>package</var>/README</file> or
8863 <file>README.Debian</file> or some other appropriate place.</p>
8867 <heading>Examples</heading>
8870 Any examples (configurations, source files, whatever),
8871 should be installed in a directory
8872 <file>/usr/share/doc/<var>package</var>/examples</file>. These
8873 files should not be referenced by any program: they're there
8874 for the benefit of the system administrator and users as
8875 documentation only. Architecture-specific example files
8876 should be installed in a directory
8877 <file>/usr/lib/<var>package</var>/examples</file> with symbolic
8879 <file>/usr/share/doc/<var>package</var>/examples</file>, or the
8880 latter directory itself may be a symbolic link to the
8885 If the purpose of a package is to provide examples, then the
8886 example files may be installed into
8887 <file>/usr/share/doc/<var>package</var></file>.
8891 <sect id="changelogs">
8892 <heading>Changelog files</heading>
8895 Packages that are not Debian-native must contain a
8896 compressed copy of the <file>debian/changelog</file> file from
8897 the Debian source tree in
8898 <file>/usr/share/doc/<var>package</var></file> with the name
8899 <file>changelog.Debian.gz</file>.
8903 If an upstream changelog is available, it should be accessible as
8904 <file>/usr/share/doc/<var>package</var>/changelog.gz</file> in
8905 plain text. If the upstream changelog is distributed in
8906 HTML, it should be made available in that form as
8907 <file>/usr/share/doc/<var>package</var>/changelog.html.gz</file>
8908 and a plain text <file>changelog.gz</file> should be generated
8909 from it using, for example, <tt>lynx -dump -nolist</tt>. If
8910 the upstream changelog files do not already conform to this
8911 naming convention, then this may be achieved either by
8912 renaming the files, or by adding a symbolic link, at the
8913 maintainer's discretion.<footnote>
8914 Rationale: People should not have to look in places for
8915 upstream changelogs merely because they are given
8916 different names or are distributed in HTML format.
8921 All of these files should be installed compressed using
8922 <tt>gzip -9</tt>, as they will become large with time even
8923 if they start out small.
8927 If the package has only one changelog which is used both as
8928 the Debian changelog and the upstream one because there is
8929 no separate upstream maintainer then that changelog should
8930 usually be installed as
8931 <file>/usr/share/doc/<var>package</var>/changelog.gz</file>; if
8932 there is a separate upstream maintainer, but no upstream
8933 changelog, then the Debian changelog should still be called
8934 <file>changelog.Debian.gz</file>.
8938 For details about the format and contents of the Debian
8939 changelog file, please see <ref id="dpkgchangelog">.
8944 <appendix id="pkg-scope">
8945 <heading>Introduction and scope of these appendices</heading>
8948 These appendices are taken essentially verbatim from the
8949 now-deprecated Packaging Manual, version 3.2.1.0. They are
8950 the chapters which are likely to be of use to package
8951 maintainers and which have not already been included in the
8952 policy document itself. Most of these sections are very likely
8953 not relevant to policy; they should be treated as
8954 documentation for the packaging system. Please note that these
8955 appendices are included for convenience, and for historical
8956 reasons: they used to be part of policy package, and they have
8957 not yet been incorporated into dpkg documentation. However,
8958 they still have value, and hence they are presented here.
8962 They have not yet been checked to ensure that they are
8963 compatible with the contents of policy, and if there are any
8964 contradictions, the version in the main policy document takes
8965 precedence. The remaining chapters of the old Packaging
8966 Manual have also not been read in detail to ensure that there
8967 are not parts which have been left out. Both of these will be
8972 Certain parts of the Packaging manual were integrated into the
8973 Policy Manual proper, and removed from the appendices. Links
8974 have been placed from the old locations to the new ones.
8978 <prgn>dpkg</prgn> is a suite of programs for creating binary
8979 package files and installing and removing them on Unix
8981 <prgn>dpkg</prgn> is targeted primarily at Debian
8982 GNU/Linux, but may work on or be ported to other
8988 The binary packages are designed for the management of
8989 installed executable programs (usually compiled binaries) and
8990 their associated data, though source code examples and
8991 documentation are provided as part of some packages.</p>
8994 This manual describes the technical aspects of creating Debian
8995 binary packages (<file>.deb</file> files). It documents the
8996 behavior of the package management programs
8997 <prgn>dpkg</prgn>, <prgn>dselect</prgn> et al. and the way
8998 they interact with packages.</p>
9001 It also documents the interaction between
9002 <prgn>dselect</prgn>'s core and the access method scripts it
9003 uses to actually install the selected packages, and describes
9004 how to create a new access method.</p>
9007 This manual does not go into detail about the options and
9008 usage of the package building and installation tools. It
9009 should therefore be read in conjunction with those programs'
9014 The utility programs which are provided with <prgn>dpkg</prgn>
9015 for managing various system configuration and similar issues,
9016 such as <prgn>update-rc.d</prgn> and
9017 <prgn>install-info</prgn>, are not described in detail here -
9018 please see their man pages.
9022 It is assumed that the reader is reasonably familiar with the
9023 <prgn>dpkg</prgn> System Administrators' manual.
9024 Unfortunately this manual does not yet exist.
9028 The Debian version of the FSF's GNU hello program is provided
9029 as an example for people wishing to create Debian
9030 packages. The Debian <prgn>debmake</prgn> package is
9031 recommended as a very helpful tool in creating and maintaining
9032 Debian packages. However, while the tools and examples are
9033 helpful, they do not replace the need to read and follow the
9034 Policy and Programmer's Manual.</p>
9037 <appendix id="pkg-binarypkg">
9038 <heading>Binary packages (from old Packaging Manual)</heading>
9041 The binary package has two main sections. The first part
9042 consists of various control information files and scripts used
9043 by <prgn>dpkg</prgn> when installing and removing. See <ref
9044 id="pkg-controlarea">.
9048 The second part is an archive containing the files and
9049 directories to be installed.
9053 In the future binary packages may also contain other
9054 components, such as checksums and digital signatures. The
9055 format for the archive is described in full in the
9056 <file>deb(5)</file> man page.
9060 <sect id="pkg-bincreating"><heading>Creating package files -
9061 <prgn>dpkg-deb</prgn>
9065 All manipulation of binary package files is done by
9066 <prgn>dpkg-deb</prgn>; it's the only program that has
9067 knowledge of the format. (<prgn>dpkg-deb</prgn> may be
9068 invoked by calling <prgn>dpkg</prgn>, as <prgn>dpkg</prgn>
9069 will spot that the options requested are appropriate to
9070 <prgn>dpkg-deb</prgn> and invoke that instead with the same
9075 In order to create a binary package you must make a
9076 directory tree which contains all the files and directories
9077 you want to have in the file system data part of the package.
9078 In Debian-format source packages this directory is usually
9079 <file>debian/tmp</file>, relative to the top of the package's
9084 They should have the locations (relative to the root of the
9085 directory tree you're constructing) ownerships and
9086 permissions which you want them to have on the system when
9091 With current versions of <prgn>dpkg</prgn> the uid/username
9092 and gid/groupname mappings for the users and groups being
9093 used should be the same on the system where the package is
9094 built and the one where it is installed.
9098 You need to add one special directory to the root of the
9099 miniature file system tree you're creating:
9100 <prgn>DEBIAN</prgn>. It should contain the control
9101 information files, notably the binary package control file
9102 (see <ref id="pkg-controlfile">).
9106 The <prgn>DEBIAN</prgn> directory will not appear in the
9107 file system archive of the package, and so won't be installed
9108 by <prgn>dpkg</prgn> when the package is installed.
9112 When you've prepared the package, you should invoke:
9114 dpkg --build <var>directory</var>
9119 This will build the package in
9120 <file><var>directory</var>.deb</file>. (<prgn>dpkg</prgn> knows
9121 that <tt>--build</tt> is a <prgn>dpkg-deb</prgn> option, so
9122 it invokes <prgn>dpkg-deb</prgn> with the same arguments to
9127 See the man page <manref name="dpkg-deb" section="8"> for details of how
9128 to examine the contents of this newly-created file. You may find the
9129 output of following commands enlightening:
9131 dpkg-deb --info <var>filename</var>.deb
9132 dpkg-deb --contents <var>filename</var>.deb
9133 dpkg --contents <var>filename</var>.deb
9135 To view the copyright file for a package you could use this command:
9137 dpkg --fsys-tarfile <var>filename</var>.deb | tar xOf - \*/copyright | pager
9142 <sect id="pkg-controlarea">
9143 <heading>Package control information files</heading>
9146 The control information portion of a binary package is a
9147 collection of files with names known to <prgn>dpkg</prgn>.
9148 It will treat the contents of these files specially - some
9149 of them contain information used by <prgn>dpkg</prgn> when
9150 installing or removing the package; others are scripts which
9151 the package maintainer wants <prgn>dpkg</prgn> to run.
9155 It is possible to put other files in the package control
9156 area, but this is not generally a good idea (though they
9157 will largely be ignored).
9161 Here is a brief list of the control info files supported by
9162 <prgn>dpkg</prgn> and a summary of what they're used for.
9167 <tag><tt>control</tt>
9170 This is the key description file used by
9171 <prgn>dpkg</prgn>. It specifies the package's name
9172 and version, gives its description for the user,
9173 states its relationships with other packages, and so
9174 forth. See <ref id="sourcecontrolfiles"> and
9175 <ref id="binarycontrolfiles">.
9179 It is usually generated automatically from information
9180 in the source package by the
9181 <prgn>dpkg-gencontrol</prgn> program, and with
9182 assistance from <prgn>dpkg-shlibdeps</prgn>.
9183 See <ref id="pkg-sourcetools">.
9187 <tag><tt>postinst</tt>, <tt>preinst</tt>, <tt>postrm</tt>,
9192 These are executable files (usually scripts) which
9193 <prgn>dpkg</prgn> runs during installation, upgrade
9194 and removal of packages. They allow the package to
9195 deal with matters which are particular to that package
9196 or require more complicated processing than that
9197 provided by <prgn>dpkg</prgn>. Details of when and
9198 how they are called are in <ref id="maintainerscripts">.
9202 It is very important to make these scripts idempotent.
9203 See <ref id="idempotency">.
9207 The maintainer scripts are guaranteed to run with a
9208 controlling terminal and can interact with the user.
9209 See <ref id="controllingterminal">.
9213 <tag><tt>conffiles</tt>
9216 This file contains a list of configuration files which
9217 are to be handled automatically by <prgn>dpkg</prgn>
9218 (see <ref id="pkg-conffiles">). Note that not necessarily
9219 every configuration file should be listed here.
9222 <tag><tt>shlibs</tt>
9225 This file contains a list of the shared libraries
9226 supplied by the package, with dependency details for
9227 each. This is used by <prgn>dpkg-shlibdeps</prgn>
9228 when it determines what dependencies are required in a
9229 package control file. The <tt>shlibs</tt> file format
9230 is described on <ref id="shlibs">.
9235 <sect id="pkg-controlfile">
9236 <heading>The main control information file: <tt>control</tt></heading>
9239 The most important control information file used by
9240 <prgn>dpkg</prgn> when it installs a package is
9241 <tt>control</tt>. It contains all the package's "vital
9246 The binary package control files of packages built from
9247 Debian sources are made by a special tool,
9248 <prgn>dpkg-gencontrol</prgn>, which reads
9249 <file>debian/control</file> and <file>debian/changelog</file> to
9250 find the information it needs. See <ref id="pkg-sourcepkg"> for
9255 The fields in binary package control files are listed in
9256 <ref id="binarycontrolfiles">.
9260 A description of the syntax of control files and the purpose
9261 of the fields is available in <ref id="controlfields">.
9266 <heading>Time Stamps</heading>
9269 See <ref id="timestamps">.
9274 <appendix id="pkg-sourcepkg">
9275 <heading>Source packages (from old Packaging Manual) </heading>
9278 The Debian binary packages in the distribution are generated
9279 from Debian sources, which are in a special format to assist
9280 the easy and automatic building of binaries.
9283 <sect id="pkg-sourcetools">
9284 <heading>Tools for processing source packages</heading>
9287 Various tools are provided for manipulating source packages;
9288 they pack and unpack sources and help build of binary
9289 packages and help manage the distribution of new versions.
9293 They are introduced and typical uses described here; see
9294 <manref name="dpkg-source" section="1"> for full
9295 documentation about their arguments and operation.
9299 For examples of how to construct a Debian source package,
9300 and how to use those utilities that are used by Debian
9301 source packages, please see the <prgn>hello</prgn> example
9305 <sect1 id="pkg-dpkg-source">
9307 <prgn>dpkg-source</prgn> - packs and unpacks Debian source
9312 This program is frequently used by hand, and is also
9313 called from package-independent automated building scripts
9314 such as <prgn>dpkg-buildpackage</prgn>.
9318 To unpack a package it is typically invoked with
9320 dpkg-source -x <var>.../path/to/filename</var>.dsc
9325 with the <file><var>filename</var>.tar.gz</file> and
9326 <file><var>filename</var>.diff.gz</file> (if applicable) in
9327 the same directory. It unpacks into
9328 <file><var>package</var>-<var>version</var></file>, and if
9330 <file><var>package</var>-<var>version</var>.orig</file>, in
9331 the current directory.
9335 To create a packed source archive it is typically invoked:
9337 dpkg-source -b <var>package</var>-<var>version</var>
9342 This will create the <file>.dsc</file>, <file>.tar.gz</file> and
9343 <file>.diff.gz</file> (if appropriate) in the current
9344 directory. <prgn>dpkg-source</prgn> does not clean the
9345 source tree first - this must be done separately if it is
9350 See also <ref id="pkg-sourcearchives">.</p>
9354 <sect1 id="pkg-dpkg-buildpackage">
9356 <prgn>dpkg-buildpackage</prgn> - overall package-building
9361 <prgn>dpkg-buildpackage</prgn> is a script which invokes
9362 <prgn>dpkg-source</prgn>, the <file>debian/rules</file>
9363 targets <tt>clean</tt>, <tt>build</tt> and
9364 <tt>binary</tt>, <prgn>dpkg-genchanges</prgn> and
9365 <prgn>gpg</prgn> (or <prgn>pgp</prgn>) to build a signed
9366 source and binary package upload.
9370 It is usually invoked by hand from the top level of the
9371 built or unbuilt source directory. It may be invoked with
9372 no arguments; useful arguments include:
9373 <taglist compact="compact">
9374 <tag><tt>-uc</tt>, <tt>-us</tt></tag>
9377 Do not sign the <tt>.changes</tt> file or the
9378 source package <tt>.dsc</tt> file, respectively.</p>
9380 <tag><tt>-p<var>sign-command</var></tt></tag>
9383 Invoke <var>sign-command</var> instead of finding
9384 <tt>gpg</tt> or <tt>pgp</tt> on the <prgn>PATH</prgn>.
9385 <var>sign-command</var> must behave just like
9386 <prgn>gpg</prgn> or <tt>pgp</tt>.</p>
9388 <tag><tt>-r<var>root-command</var></tt></tag>
9391 When root privilege is required, invoke the command
9392 <var>root-command</var>. <var>root-command</var>
9393 should invoke its first argument as a command, from
9394 the <prgn>PATH</prgn> if necessary, and pass its
9395 second and subsequent arguments to the command it
9396 calls. If no <var>root-command</var> is supplied
9397 then <var>dpkg-buildpackage</var> will take no
9398 special action to gain root privilege, so that for
9399 most packages it will have to be invoked as root to
9402 <tag><tt>-b</tt>, <tt>-B</tt></tag>
9405 Two types of binary-only build and upload - see
9406 <manref name="dpkg-source" section="1">.
9413 <sect1 id="pkg-dpkg-gencontrol">
9415 <prgn>dpkg-gencontrol</prgn> - generates binary package
9420 This program is usually called from <file>debian/rules</file>
9421 (see <ref id="pkg-sourcetree">) in the top level of the source
9426 This is usually done just before the files and directories in the
9427 temporary directory tree where the package is being built have their
9428 permissions and ownerships set and the package is constructed using
9429 <prgn>dpkg-deb/</prgn>
9431 This is so that the control file which is produced has
9432 the right permissions
9437 <prgn>dpkg-gencontrol</prgn> must be called after all the
9438 files which are to go into the package have been placed in
9439 the temporary build directory, so that its calculation of
9440 the installed size of a package is correct.
9444 It is also necessary for <prgn>dpkg-gencontrol</prgn> to
9445 be run after <prgn>dpkg-shlibdeps</prgn> so that the
9446 variable substitutions created by
9447 <prgn>dpkg-shlibdeps</prgn> in <file>debian/substvars</file>
9452 For a package which generates only one binary package, and
9453 which builds it in <file>debian/tmp</file> relative to the top
9454 of the source package, it is usually sufficient to call
9455 <prgn>dpkg-gencontrol</prgn>.
9459 Sources which build several binaries will typically need
9462 dpkg-gencontrol -Pdebian/tmp-<var>pkg</var> -p<var>package</var>
9463 </example> The <tt>-P</tt> tells
9464 <prgn>dpkg-gencontrol</prgn> that the package is being
9465 built in a non-default directory, and the <tt>-p</tt>
9466 tells it which package's control file should be generated.
9470 <prgn>dpkg-gencontrol</prgn> also adds information to the
9471 list of files in <file>debian/files</file>, for the benefit of
9472 (for example) a future invocation of
9473 <prgn>dpkg-genchanges</prgn>.</p>
9476 <sect1 id="pkg-dpkg-shlibdeps">
9478 <prgn>dpkg-shlibdeps</prgn> - calculates shared library
9483 This program is usually called from <file>debian/rules</file>
9484 just before <prgn>dpkg-gencontrol</prgn> (see <ref
9485 id="pkg-sourcetree">), in the top level of the source tree.
9489 Its arguments are executables.
9492 In a forthcoming dpkg version,
9493 <prgn>dpkg-shlibdeps</prgn> would be required to be
9494 called on shared libraries as well.
9497 They may be specified either in the locations in the
9498 source tree where they are created or in the locations
9499 in the temporary build tree where they are installed
9500 prior to binary package creation.
9502 </footnote> for which shared library dependencies should
9503 be included in the binary package's control file.
9507 If some of the found shared libraries should only
9508 warrant a <tt>Recommends</tt> or <tt>Suggests</tt>, or if
9509 some warrant a <tt>Pre-Depends</tt>, this can be achieved
9510 by using the <tt>-d<var>dependency-field</var></tt> option
9511 before those executable(s). (Each <tt>-d</tt> option
9512 takes effect until the next <tt>-d</tt>.)
9516 <prgn>dpkg-shlibdeps</prgn> does not directly cause the
9517 output control file to be modified. Instead by default it
9518 adds to the <file>debian/substvars</file> file variable
9519 settings like <tt>shlibs:Depends</tt>. These variable
9520 settings must be referenced in dependency fields in the
9521 appropriate per-binary-package sections of the source
9526 For example, a package that generates an essential part
9527 which requires dependencies, and optional parts that
9528 which only require a recommendation, would separate those
9529 two sets of dependencies into two different fields.<footnote>
9530 At the time of writing, an example for this was the
9531 <package/xmms/ package, with Depends used for the xmms
9532 executable, Recommends for the plug-ins and Suggests for
9533 even more optional features provided by unzip.
9535 It can say in its <file>debian/rules</file>:
9537 dpkg-shlibdeps -dDepends <var>program anotherprogram ...</var> \
9538 -dRecommends <var>optionalpart anotheroptionalpart</var>
9540 and then in its main control file <file>debian/control</file>:
9543 Depends: ${shlibs:Pre-Depends}
9544 Recommends: ${shlibs:Recommends}
9550 Sources which produce several binary packages with
9551 different shared library dependency requirements can use
9552 the <tt>-p<var>varnameprefix</var></tt> option to override
9553 the default <tt>shlibs:</tt> prefix (one invocation of
9554 <prgn>dpkg-shlibdeps</prgn> per setting of this option).
9555 They can thus produce several sets of dependency
9556 variables, each of the form
9557 <tt><var>varnameprefix</var>:<var>dependencyfield</var></tt>,
9558 which can be referred to in the appropriate parts of the
9559 binary package control files.
9564 <sect1 id="pkg-dpkg-distaddfile">
9566 <prgn>dpkg-distaddfile</prgn> - adds a file to
9567 <file>debian/files</file>
9571 Some packages' uploads need to include files other than
9572 the source and binary package files.
9576 <prgn>dpkg-distaddfile</prgn> adds a file to the
9577 <file>debian/files</file> file so that it will be included in
9578 the <file>.changes</file> file when
9579 <prgn>dpkg-genchanges</prgn> is run.
9583 It is usually invoked from the <tt>binary</tt> target of
9584 <file>debian/rules</file>:
9586 dpkg-distaddfile <var>filename</var> <var>section</var> <var>priority</var>
9588 The <var>filename</var> is relative to the directory where
9589 <prgn>dpkg-genchanges</prgn> will expect to find it - this
9590 is usually the directory above the top level of the source
9591 tree. The <file>debian/rules</file> target should put the
9592 file there just before or just after calling
9593 <prgn>dpkg-distaddfile</prgn>.
9597 The <var>section</var> and <var>priority</var> are passed
9598 unchanged into the resulting <file>.changes</file> file.
9603 <sect1 id="pkg-dpkg-genchanges">
9605 <prgn>dpkg-genchanges</prgn> - generates a <file>.changes</file>
9610 This program is usually called by package-independent
9611 automatic building scripts such as
9612 <prgn>dpkg-buildpackage</prgn>, but it may also be called
9617 It is usually called in the top level of a built source
9618 tree, and when invoked with no arguments will print out a
9619 straightforward <file>.changes</file> file based on the
9620 information in the source package's changelog and control
9621 file and the binary and source packages which should have
9627 <sect1 id="pkg-dpkg-parsechangelog">
9629 <prgn>dpkg-parsechangelog</prgn> - produces parsed
9630 representation of a changelog
9634 This program is used internally by
9635 <prgn>dpkg-source</prgn> et al. It may also occasionally
9636 be useful in <file>debian/rules</file> and elsewhere. It
9637 parses a changelog, <file>debian/changelog</file> by default,
9638 and prints a control-file format representation of the
9639 information in it to standard output.
9643 <sect1 id="pkg-dpkg-architecture">
9645 <prgn>dpkg-architecture</prgn> - information about the build and
9650 This program can be used manually, but is also invoked by
9651 <tt>dpkg-buildpackage</tt> or <file>debian/rules</file> to set
9652 to set environment or make variables which specify the build and
9653 host architecture for the package building process.
9658 <sect id="pkg-sourcetree">
9659 <heading>The Debianised source tree</heading>
9662 The source archive scheme described later is intended to
9663 allow a Debianised source tree with some associated control
9664 information to be reproduced and transported easily. The
9665 Debianised source tree is a version of the original program
9666 with certain files added for the benefit of the
9667 Debianisation process, and with any other changes required
9668 made to the rest of the source code and installation
9673 The extra files created for Debian are in the subdirectory
9674 <file>debian</file> of the top level of the Debianised source
9675 tree. They are described below.
9678 <sect1 id="pkg-debianrules">
9679 <heading><file>debian/rules</file> - the main building script</heading>
9682 See <ref id="debianrules">.
9687 <sect1 id="pkg-dpkgchangelog">
9688 <heading><file>debian/changelog</file></heading>
9691 See <ref id="dpkgchangelog">.
9695 It is recommended that the entire changelog be encoded in the
9696 <url id="http://www.cis.ohio-state.edu/cgi-bin/rfc/rfc2279.html" name="UTF-8">
9698 <url id="http://www.unicode.org/"
9699 name="Unicode">.<footnote>
9701 I think it is fairly obvious that we need to
9702 eventually transition to UTF-8 for our package
9703 infrastructure; it is really the only sane char-set in
9704 an international environment. Now, we can't switch to
9705 using UTF-8 for package control fields and the like
9706 until dpkg has better support, but one thing we can
9707 start doing today is requesting that Debian changelogs
9708 are UTF-8 encoded. At some point in time, we can start
9709 requiring them to do so.
9712 Checking for non-UTF8 characters in a changelog is
9713 trivial. Dump the file through
9714 <example>iconv -f utf-8 -t ucs-4</example>
9715 discard the output, and check the return
9716 value. If there are any characters in the stream
9717 which are invalid UTF-8 sequences, iconv will exit
9718 with an error code; and this will be the case for the
9719 vast majority of other character sets.
9724 <sect2><heading>Defining alternative changelog formats
9728 It is possible to use a different format to the standard
9729 one, by providing a parser for the format you wish to
9734 In order to have <tt>dpkg-parsechangelog</tt> run your
9735 parser, you must include a line within the last 40 lines
9736 of your file matching the Perl regular expression:
9737 <tt>\schangelog-format:\s+([0-9a-z]+)\W</tt> The part in
9738 parentheses should be the name of the format. For
9739 example, you might say:
9741 @@@ changelog-format: joebloggs @@@
9743 Changelog format names are non-empty strings of alphanumerics.
9747 If such a line exists then <tt>dpkg-parsechangelog</tt>
9748 will look for the parser as
9749 <file>/usr/lib/dpkg/parsechangelog/<var>format-name</var></file>
9751 <file>/usr/local/lib/dpkg/parsechangelog/<var>format-name</var></file>;
9752 it is an error for it not to find it, or for it not to
9753 be an executable program. The default changelog format
9754 is <tt>dpkg</tt>, and a parser for it is provided with
9755 the <tt>dpkg</tt> package.
9759 The parser will be invoked with the changelog open on
9760 standard input at the start of the file. It should read
9761 the file (it may seek if it wishes) to determine the
9762 information required and return the parsed information
9763 to standard output in the form of a series of control
9764 fields in the standard format. By default it should
9765 return information about only the most recent version in
9766 the changelog; it should accept a
9767 <tt>-v<var>version</var></tt> option to return changes
9768 information from all versions present <em>strictly
9769 after</em> <var>version</var>, and it should then be an
9770 error for <var>version</var> not to be present in the
9776 <list compact="compact">
9777 <item><qref id="f-Source"><tt>Source</tt></qref></item>
9778 <item><qref id="f-Version"><tt>Version</tt></qref> (mandatory)</item>
9779 <item><qref id="f-Distribution"><tt>Distribution</tt></qref> (mandatory)</item>
9780 <item><qref id="f-Urgency"><tt>Urgency</tt></qref> (mandatory)</item>
9781 <item><qref id="f-Maintainer"><tt>Maintainer</tt></qref> (mandatory)</item>
9782 <item><qref id="f-Date"><tt>Date</tt></qref></item>
9783 <item><qref id="f-Changes"><tt>Changes</tt></qref> (mandatory)</item>
9788 If several versions are being returned (due to the use
9789 of <tt>-v</tt>), the urgency value should be of the
9790 highest urgency code listed at the start of any of the
9791 versions requested followed by the concatenated
9792 (space-separated) comments from all the versions
9793 requested; the maintainer, version, distribution and
9794 date should always be from the most recent version.
9798 For the format of the <tt>Changes</tt> field see
9799 <ref id="f-Changes">.
9803 If the changelog format which is being parsed always or
9804 almost always leaves a blank line between individual
9805 change notes these blank lines should be stripped out,
9806 so as to make the resulting output compact.
9810 If the changelog format does not contain date or package
9811 name information this information should be omitted from
9812 the output. The parser should not attempt to synthesize
9813 it or find it from other sources.
9817 If the changelog does not have the expected format the
9818 parser should exit with a nonzero exit status, rather
9819 than trying to muddle through and possibly generating
9824 A changelog parser may not interact with the user at
9830 <sect1 id="pkg-srcsubstvars">
9831 <heading><file>debian/substvars</file> and variable substitutions</heading>
9834 See <ref id="substvars">.
9840 <heading><file>debian/files</file></heading>
9843 See <ref id="debianfiles">.
9847 <sect1><heading><file>debian/tmp</file>
9851 This is the canonical temporary location for the
9852 construction of binary packages by the <tt>binary</tt>
9853 target. The directory <file>tmp</file> serves as the root of
9854 the file system tree as it is being constructed (for
9855 example, by using the package's upstream makefiles install
9856 targets and redirecting the output there), and it also
9857 contains the <tt>DEBIAN</tt> subdirectory. See <ref
9858 id="pkg-bincreating">.
9862 If several binary packages are generated from the same
9863 source tree it is usual to use several
9864 <file>debian/tmp<var>something</var></file> directories, for
9865 example <file>tmp-a</file> or <file>tmp-doc</file>.
9869 Whatever <file>tmp</file> directories are created and used by
9870 <tt>binary</tt> must of course be removed by the
9871 <tt>clean</tt> target.</p></sect1>
9875 <sect id="pkg-sourcearchives"><heading>Source packages as archives
9879 As it exists on the FTP site, a Debian source package
9880 consists of three related files. You must have the right
9881 versions of all three to be able to use them.
9886 <tag>Debian source control file - <tt>.dsc</tt></tag>
9888 This file is a control file used by <prgn>dpkg-source</prgn>
9889 to extract a source package.
9890 See <ref id="debiansourcecontrolfiles">.
9894 Original source archive -
9896 <var>package</var>_<var>upstream-version</var>.orig.tar.gz
9902 This is a compressed (with <tt>gzip -9</tt>)
9903 <prgn>tar</prgn> file containing the source code from
9904 the upstream authors of the program.
9909 Debianisation diff -
9911 <var>package</var>_<var>upstream_version-revision</var>.diff.gz
9917 This is a unified context diff (<tt>diff -u</tt>)
9918 giving the changes which are required to turn the
9919 original source into the Debian source. These changes
9920 may only include editing and creating plain files.
9921 The permissions of files, the targets of symbolic
9922 links and the characteristics of special files or
9923 pipes may not be changed and no files may be removed
9928 All the directories in the diff must exist, except the
9929 <file>debian</file> subdirectory of the top of the source
9930 tree, which will be created by
9931 <prgn>dpkg-source</prgn> if necessary when unpacking.
9935 The <prgn>dpkg-source</prgn> program will
9936 automatically make the <file>debian/rules</file> file
9937 executable (see below).</p></item>
9942 If there is no original source code - for example, if the
9943 package is specially prepared for Debian or the Debian
9944 maintainer is the same as the upstream maintainer - the
9945 format is slightly different: then there is no diff, and the
9947 <file><var>package</var>_<var>version</var>.tar.gz</file>,
9948 and preferably contains a directory named
9949 <file><var>package</var>-<var>version</var></file>.
9954 <heading>Unpacking a Debian source package without <prgn>dpkg-source</prgn></heading>
9957 <tt>dpkg-source -x</tt> is the recommended way to unpack a
9958 Debian source package. However, if it is not available it
9959 is possible to unpack a Debian source archive as follows:
9960 <enumlist compact="compact">
9963 Untar the tarfile, which will create a <file>.orig</file>
9967 <p>Rename the <file>.orig</file> directory to
9968 <file><var>package</var>-<var>version</var></file>.</p>
9972 Create the subdirectory <file>debian</file> at the top of
9973 the source tree.</p>
9975 <item><p>Apply the diff using <tt>patch -p0</tt>.</p>
9977 <item><p>Untar the tarfile again if you want a copy of the original
9978 source code alongside the Debianised version.</p>
9983 It is not possible to generate a valid Debian source archive
9984 without using <prgn>dpkg-source</prgn>. In particular,
9985 attempting to use <prgn>diff</prgn> directly to generate the
9986 <file>.diff.gz</file> file will not work.
9990 <heading>Restrictions on objects in source packages</heading>
9993 The source package may not contain any hard links
9995 This is not currently detected when building source
9996 packages, but only when extracting
10000 Hard links may be permitted at some point in the
10001 future, but would require a fair amount of
10003 </footnote>, device special files, sockets or setuid or
10006 Setgid directories are allowed.
10011 The source packaging tools manage the changes between the
10012 original and Debianised source using <prgn>diff</prgn> and
10013 <prgn>patch</prgn>. Turning the original source tree as
10014 included in the <file>.orig.tar.gz</file> into the debianised
10015 source must not involve any changes which cannot be
10016 handled by these tools. Problematic changes which cause
10017 <prgn>dpkg-source</prgn> to halt with an error when
10018 building the source package are:
10019 <list compact="compact">
10020 <item><p>Adding or removing symbolic links, sockets or pipes.</p>
10022 <item><p>Changing the targets of symbolic links.</p>
10024 <item><p>Creating directories, other than <file>debian</file>.</p>
10026 <item><p>Changes to the contents of binary files.</p></item>
10027 </list> Changes which cause <prgn>dpkg-source</prgn> to
10028 print a warning but continue anyway are:
10029 <list compact="compact">
10032 Removing files, directories or symlinks.
10034 Renaming a file is not treated specially - it is
10035 seen as the removal of the old file (which
10036 generates a warning, but is otherwise ignored),
10037 and the creation of the new one.
10043 Changed text files which are missing the usual final
10044 newline (either in the original or the modified
10049 Changes which are not represented, but which are not detected by
10050 <prgn>dpkg-source</prgn>, are:
10051 <list compact="compact">
10052 <item><p>Changing the permissions of files (other than
10053 <file>debian/rules</file>) and directories.</p></item>
10058 The <file>debian</file> directory and <file>debian/rules</file>
10059 are handled specially by <prgn>dpkg-source</prgn> - before
10060 applying the changes it will create the <file>debian</file>
10061 directory, and afterwards it will make
10062 <file>debian/rules</file> world-executable.
10068 <appendix id="pkg-controlfields">
10069 <heading>Control files and their fields (from old Packaging Manual)</heading>
10072 Many of the tools in the <prgn>dpkg</prgn> suite manipulate
10073 data in a common format, known as control files. Binary and
10074 source packages have control data as do the <file>.changes</file>
10075 files which control the installation of uploaded files, and
10076 <prgn>dpkg</prgn>'s internal databases are in a similar
10081 <heading>Syntax of control files</heading>
10084 See <ref id="controlsyntax">.
10088 It is important to note that there are several fields which
10089 are optional as far as <prgn>dpkg</prgn> and the related
10090 tools are concerned, but which must appear in every Debian
10091 package, or whose omission may cause problems.
10096 <heading>List of fields</heading>
10099 See <ref id="controlfieldslist">.
10103 This section now contains only the fields that didn't belong
10104 to the Policy manual.
10107 <sect1 id="pkg-f-Filename">
10108 <heading><tt>Filename</tt> and <tt>MSDOS-Filename</tt></heading>
10111 These fields in <tt>Packages</tt> files give the
10112 filename(s) of (the parts of) a package in the
10113 distribution directories, relative to the root of the
10114 Debian hierarchy. If the package has been split into
10115 several parts the parts are all listed in order, separated
10120 <sect1 id="pkg-f-Size">
10121 <heading><tt>Size</tt> and <tt>MD5sum</tt></heading>
10124 These fields in <file>Packages</file> files give the size (in
10125 bytes, expressed in decimal) and MD5 checksum of the
10126 file(s) which make(s) up a binary package in the
10127 distribution. If the package is split into several parts
10128 the values for the parts are listed in order, separated by
10133 <sect1 id="pkg-f-Status">
10134 <heading><tt>Status</tt></heading>
10137 This field in <prgn>dpkg</prgn>'s status file records
10138 whether the user wants a package installed, removed or
10139 left alone, whether it is broken (requiring
10140 re-installation) or not and what its current state on the
10141 system is. Each of these pieces of information is a
10146 <sect1 id="pkg-f-Config-Version">
10147 <heading><tt>Config-Version</tt></heading>
10150 If a package is not installed or not configured, this
10151 field in <prgn>dpkg</prgn>'s status file records the last
10152 version of the package which was successfully
10157 <sect1 id="pkg-f-Conffiles">
10158 <heading><tt>Conffiles</tt></heading>
10161 This field in <prgn>dpkg</prgn>'s status file contains
10162 information about the automatically-managed configuration
10163 files held by a package. This field should <em>not</em>
10164 appear anywhere in a package!
10169 <heading>Obsolete fields</heading>
10172 These are still recognized by <prgn>dpkg</prgn> but should
10173 not appear anywhere any more.
10175 <taglist compact="compact">
10177 <tag><tt>Revision</tt></tag>
10178 <tag><tt>Package-Revision</tt></tag>
10179 <tag><tt>Package_Revision</tt></tag>
10181 The Debian revision part of the package version was
10182 at one point in a separate control file field. This
10183 field went through several names.
10186 <tag><tt>Recommended</tt></tag>
10187 <item>Old name for <tt>Recommends</tt>.</item>
10189 <tag><tt>Optional</tt></tag>
10190 <item>Old name for <tt>Suggests</tt>.</item>
10192 <tag><tt>Class</tt></tag>
10193 <item>Old name for <tt>Priority</tt>.</item>
10202 <appendix id="pkg-conffiles">
10203 <heading>Configuration file handling (from old Packaging Manual)</heading>
10206 <prgn>dpkg</prgn> can do a certain amount of automatic
10207 handling of package configuration files.
10211 Whether this mechanism is appropriate depends on a number of
10212 factors, but basically there are two approaches to any
10213 particular configuration file.
10217 The easy method is to ship a best-effort configuration in the
10218 package, and use <prgn>dpkg</prgn>'s conffile mechanism to
10219 handle updates. If the user is unlikely to want to edit the
10220 file, but you need them to be able to without losing their
10221 changes, and a new package with a changed version of the file
10222 is only released infrequently, this is a good approach.
10226 The hard method is to build the configuration file from
10227 scratch in the <prgn>postinst</prgn> script, and to take the
10228 responsibility for fixing any mistakes made in earlier
10229 versions of the package automatically. This will be
10230 appropriate if the file is likely to need to be different on
10234 <sect><heading>Automatic handling of configuration files by
10239 A package may contain a control area file called
10240 <tt>conffiles</tt>. This file should be a list of filenames
10241 of configuration files needing automatic handling, separated
10242 by newlines. The filenames should be absolute pathnames,
10243 and the files referred to should actually exist in the
10248 When a package is upgraded <prgn>dpkg</prgn> will process
10249 the configuration files during the configuration stage,
10250 shortly before it runs the package's <prgn>postinst</prgn>
10255 For each file it checks to see whether the version of the
10256 file included in the package is the same as the one that was
10257 included in the last version of the package (the one that is
10258 being upgraded from); it also compares the version currently
10259 installed on the system with the one shipped with the last
10264 If neither the user nor the package maintainer has changed
10265 the file, it is left alone. If one or the other has changed
10266 their version, then the changed version is preferred - i.e.,
10267 if the user edits their file, but the package maintainer
10268 doesn't ship a different version, the user's changes will
10269 stay, silently, but if the maintainer ships a new version
10270 and the user hasn't edited it the new version will be
10271 installed (with an informative message). If both have
10272 changed their version the user is prompted about the problem
10273 and must resolve the differences themselves.
10277 The comparisons are done by calculating the MD5 message
10278 digests of the files, and storing the MD5 of the file as it
10279 was included in the most recent version of the package.
10283 When a package is installed for the first time
10284 <prgn>dpkg</prgn> will install the file that comes with it,
10285 unless that would mean overwriting a file already on the
10290 However, note that <prgn>dpkg</prgn> will <em>not</em>
10291 replace a conffile that was removed by the user (or by a
10292 script). This is necessary because with some programs a
10293 missing file produces an effect hard or impossible to
10294 achieve in another way, so that a missing file needs to be
10295 kept that way if the user did it.
10299 Note that a package should <em>not</em> modify a
10300 <prgn>dpkg</prgn>-handled conffile in its maintainer
10301 scripts. Doing this will lead to <prgn>dpkg</prgn> giving
10302 the user confusing and possibly dangerous options for
10303 conffile update when the package is upgraded.</p>
10306 <sect><heading>Fully-featured maintainer script configuration
10311 For files which contain site-specific information such as
10312 the hostname and networking details and so forth, it is
10313 better to create the file in the package's
10314 <prgn>postinst</prgn> script.
10318 This will typically involve examining the state of the rest
10319 of the system to determine values and other information, and
10320 may involve prompting the user for some information which
10321 can't be obtained some other way.
10325 When using this method there are a couple of important
10326 issues which should be considered:
10330 If you discover a bug in the program which generates the
10331 configuration file, or if the format of the file changes
10332 from one version to the next, you will have to arrange for
10333 the postinst script to do something sensible - usually this
10334 will mean editing the installed configuration file to remove
10335 the problem or change the syntax. You will have to do this
10336 very carefully, since the user may have changed the file,
10337 perhaps to fix the very problem that your script is trying
10338 to deal with - you will have to detect these situations and
10339 deal with them correctly.
10343 If you do go down this route it's probably a good idea to
10344 make the program that generates the configuration file(s) a
10345 separate program in <file>/usr/sbin</file>, by convention called
10346 <file><var>package</var>config</file> and then run that if
10347 appropriate from the post-installation script. The
10348 <tt><var>package</var>config</tt> program should not
10349 unquestioningly overwrite an existing configuration - if its
10350 mode of operation is geared towards setting up a package for
10351 the first time (rather than any arbitrary reconfiguration
10352 later) you should have it check whether the configuration
10353 already exists, and require a <tt>--force</tt> flag to
10354 overwrite it.</p></sect>
10357 <appendix id="pkg-alternatives"><heading>Alternative versions of
10358 an interface - <prgn>update-alternatives</prgn> (from old
10363 When several packages all provide different versions of the
10364 same program or file it is useful to have the system select a
10365 default, but to allow the system administrator to change it
10366 and have their decisions respected.
10370 For example, there are several versions of the <prgn>vi</prgn>
10371 editor, and there is no reason to prevent all of them from
10372 being installed at once, each under their own name
10373 (<prgn>nvi</prgn>, <prgn>vim</prgn> or whatever).
10374 Nevertheless it is desirable to have the name <tt>vi</tt>
10375 refer to something, at least by default.
10379 If all the packages involved cooperate, this can be done with
10380 <prgn>update-alternatives</prgn>.
10384 Each package provides its own version under its own name, and
10385 calls <prgn>update-alternatives</prgn> in its postinst to
10386 register its version (and again in its prerm to deregister
10391 See the man page <manref name="update-alternatives"
10392 section="8"> for details.
10396 If <prgn>update-alternatives</prgn> does not seem appropriate
10397 you may wish to consider using diversions instead.</p>
10400 <appendix id="pkg-diversions"><heading>Diversions - overriding a
10401 package's version of a file (from old Packaging Manual)
10405 It is possible to have <prgn>dpkg</prgn> not overwrite a file
10406 when it reinstalls the package it belongs to, and to have it
10407 put the file from the package somewhere else instead.
10411 This can be used locally to override a package's version of a
10412 file, or by one package to override another's version (or
10413 provide a wrapper for it).
10417 Before deciding to use a diversion, read <ref
10418 id="pkg-alternatives"> to see if you really want a diversion
10419 rather than several alternative versions of a program.
10423 There is a diversion list, which is read by <prgn>dpkg</prgn>,
10424 and updated by a special program <prgn>dpkg-divert</prgn>.
10425 Please see <manref name="dpkg-divert" section="8"> for full
10426 details of its operation.
10430 When a package wishes to divert a file from another, it should
10431 call <prgn>dpkg-divert</prgn> in its preinst to add the
10432 diversion and rename the existing file. For example,
10433 supposing that a <prgn>smailwrapper</prgn> package wishes to
10434 install a wrapper around <file>/usr/sbin/smail</file>:
10436 if [ install = "$1" ]; then
10437 dpkg-divert --package smailwrapper --add --rename \
10438 --divert /usr/sbin/smail.real /usr/sbin/smail
10440 </example> Testing <tt>$1</tt> is necessary so that the script
10441 doesn't try to add the diversion again when
10442 <prgn>smailwrapper</prgn> is upgraded. The <tt>--package
10443 smailwrapper</tt> ensures that <prgn>smailwrapper</prgn>'s
10444 copy of <file>/usr/sbin/smail</file> can bypass the diversion and
10445 get installed as the true version.
10449 The postrm has to do the reverse:
10451 if [ remove = "$1" ]; then
10452 dpkg-divert --package smailwrapper --remove --rename \
10453 --divert /usr/sbin/smail.real /usr/sbin/smail
10459 Do not attempt to divert a file which is vitally important for
10460 the system's operation - when using <prgn>dpkg-divert</prgn>
10461 there is a time, after it has been diverted but before
10462 <prgn>dpkg</prgn> has installed the new version, when the file
10463 does not exist.</p>
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